KR20240137586A - Adhesive sheet - Google Patents

Abstract

An adhesive sheet that can be used when transporting electronic components, and which can contribute to improving production costs, has excellent positional accuracy of electronic components, fixation properties and peelability of electronic components to the adhesive sheet, and enables prevention of contamination of electronic components and prevention of damage to electronic components. The adhesive sheet of the present invention is an adhesive sheet having an adhesive layer composed of an active energy ray-curable adhesive, wherein the active energy ray-curable adhesive contains an ultraviolet absorber and/or a photopolymerization initiator, and the adhesive layer has an initial indentation elasticity at 23°C of 4 MPa or less, and the adhesive layer is a layer whose indentation elasticity at 23°C is 150 MPa or more after irradiation with ultraviolet rays of 460 mJ/cm2, and the adhesive sheet has a light transmittance at a wavelength of 355 nm of 50% or less.

Description

Adhesive sheet

The present invention relates to an adhesive sheet.

Conventionally, when transferring an electronic component placed on a predetermined member to another member, the electronic component is received with an adhesive sheet, and then the electronic component is transferred to the other member. For example, when incorporating an LED chip into a device, the LED chip formed on the member is first transferred and received on an adhesive sheet, and then the LED chip is transferred from the adhesive sheet to a predetermined device or member, thereby transferring the LED chip.

In the transport of electronic components as described above, it is required to improve production costs (reduce required materials, shorten required time and number of processes, etc.), ensure positional accuracy of electronic components, ensure both fixation and peelability of electronic components to adhesive sheets, prevent contamination of electronic components, and prevent damage to electronic components.

Japanese Patent No. 5875850 Japanese Patent No. 6053756

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to provide an adhesive sheet that can be used when transporting electronic components, and that can contribute to improving production costs, has excellent positional accuracy of electronic components, fixation properties of electronic components to the adhesive sheet, and peelability, and enables prevention of contamination of electronic components and prevention of damage to electronic components.

[1] The adhesive sheet of the present invention is an adhesive sheet having an adhesive layer composed of an active energy ray-curable adhesive, wherein the active energy ray-curable adhesive contains an ultraviolet absorber and/or a photopolymerization initiator, the adhesive layer has an initial indentation elasticity at 23°C of 4 MPa or less, the adhesive layer is a layer whose indentation elasticity at 23°C is 150 MPa or more after irradiation with ultraviolet light of 460 mJ/cm2, and the adhesive sheet has a light transmittance at a wavelength of 355 nm of 50% or less.

[2] In one embodiment, the adhesive sheet does not include a substrate.

[3] In the adhesive sheet of [1] or [2], the stress relaxation rate of the adhesive layer after 600 seconds may be 10% or more.

[4] In the adhesive sheets of [1] to [3] above, the thickness of the adhesive layer may be 20 ㎛ or less.

[5] In the adhesive sheet of the above [1] to [4], the active energy ray-curable adhesive may contain a photopolymerization initiator, and the photopolymerization initiator may have two or more photodecomposable groups.

[6] In the adhesive sheet of [1] to [5] above, the active energy ray-curable adhesive may contain a photopolymerization initiator, and the photopolymerization initiator may be a compound containing a phosphorus atom and/or a nitrogen atom.

[7] In the adhesive sheet of the above [1] to [6], the active energy ray-curable adhesive may contain an active energy ray-reactive compound, and the active energy ray-reactive compound may be a multifunctional (meth)acrylate having five or more functional groups.

[8] The adhesive sheets of [1] to [7] above may be used for transferring electronic components.

[9] In the adhesive sheet of the above [1] to [8], it may be used for transferring electronic components, including catching of electronic components by a laser lift-off process, and subsequent peeling of the electronic components by laser light irradiation.

[10] In the adhesive sheets of [8] to [9], the electronic component may be a mini LED or a micro LED.

[11] According to another aspect of the present invention, a method for transporting electronic components is provided. This method for transporting electronic components is a method for transporting electronic components using the adhesive sheet.

[12] In one embodiment, the method for transferring electronic components includes a first step of transferring a plurality of electronic components arranged on a substrate onto the adhesive layer of the adhesive sheet; and a second step of transferring the electronic components on the adhesive sheet to another member.

[13] In one embodiment, the same adhesive sheet is used in the first process and the second process.

According to the present invention, an adhesive sheet that can be used when transporting electronic components can be provided, which can contribute to improving production costs, has excellent positional accuracy of electronic components, fixation properties and peelability of electronic components to the adhesive sheet, and enables prevention of contamination of electronic components and prevention of damage to electronic components.

Fig. 1 (a) is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. (b) is a schematic cross-sectional view of an adhesive sheet according to another embodiment of the present invention.

A. Overview of the adhesive sheet

Fig. 1 (a) is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. An adhesive sheet (100) according to this embodiment has an adhesive layer (10). The adhesive layer (10) is composed of an active energy ray-curable adhesive. The active energy ray-curable adhesive contains an ultraviolet absorber and/or a photopolymerization initiator. Fig. 1 (b) is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. An adhesive sheet (200) according to this embodiment further has a substrate (20), and an adhesive layer (10) is arranged on at least one side of the substrate (20). Although not shown, the adhesive sheet of the present invention may have a release liner provided on the outer side of the adhesive layer for the purpose of protecting the adhesive surface until it is put into use. In addition, the adhesive sheet may further include any other appropriate layer as long as the effects of the present invention are obtained. In addition, in the present invention, since it is possible to satisfactorily separate an adherend by the occurrence of deformation accompanying the decrease in adhesive strength and the increase in elasticity of the adhesive layer as described later, it is possible to configure an adhesive sheet without forming a layer other than an adhesive layer (so-called separation layer) for separating an adherend from the adhesive sheet. In one embodiment, the adhesive sheet is used for transferring electronic components. More specifically, the adhesive sheet can be used for transferring electronic components, including receiving electronic components by a laser lift-off process and subsequent peeling of the electronic components by laser light irradiation. Examples of the electronic components include mini LEDs and micro LEDs.

In one embodiment, the adhesive sheet does not include a substrate. In one embodiment, the adhesive sheet of the present invention is composed of only an adhesive layer (1), as shown in Fig. 1 (a). An adhesive sheet composed without including a substrate is preferable in that it has excellent energy utilization efficiency when peeling an adherend by laser light irradiation. In another embodiment, the adhesive sheet of the present invention includes a substrate and an adhesive layer, as shown in Fig. 1 (b), and the adhesive layer is arranged directly on the substrate (i.e., without intervening any other layer).

The above-mentioned adhesive layer has an initial indentation elastic modulus of 4 MPa or less at 23°C. In the present invention, since the adhesive layer has such indentation elastic modulus, when bonding an electronic component, a part of the electronic component can be preferably filled with the adhesive layer, and the electronic component can be temporarily fixed with good fixation. For example, as described below, when transferring an electronic component from a rigid substrate to an adhesive sheet, misalignment of the adherend, tilting of the adherend, and the like are prevented when the rigid substrate is removed. The indentation elastic modulus can be measured by a single indentation method at 23°C, at a indentation speed of 10 nm/s, and a indentation depth of 100 nm.

In one embodiment, the adhesive sheet can be used to transfer a plurality of electronic components (e.g., LED chips) arranged on a substrate (e.g., a hard substrate such as a sapphire substrate) to the adhesive sheet; and to transfer the electronic components on the adhesive sheet to another member. In one embodiment, the transfer of the electronic components from the substrate to the adhesive sheet can be performed by a process including irradiating a portion of the substrate/electronic component interface with laser light, i.e., a laser lift-off process. According to the present invention, since the electronic components can be arranged on the adhesive sheet in a desirable state, such as preventing the tilting of the electronic components as adherends, as described above, it becomes possible to preferably perform receiving of the electronic components by, for example, the laser lift-off process. In addition, in the case where the laser lift-off process is employed, it is possible to prevent contaminants generated from the adhesive layer due to the influence of the laser light irradiation from attaching to the electronic components as adherends.

In addition, transfer from the adhesive sheet to another member can be performed by laser light irradiation. In the present invention, since the adhesive layer contains an ultraviolet absorber or a photopolymerization initiator, peeling of the adherend (electronic component) by laser light irradiation becomes possible. More specifically, by irradiating the adhesive layer with laser light, the ultraviolet absorber or the photopolymerization initiator is heated, causing deformation in the adhesive layer, and as a result, peelability is expressed in the portion irradiated with the laser light. According to the present invention, since deformation can be caused in the adhesive layer in a minute range as described above, even when processing a small electronic component (for example, a square with one side measuring 50 μm), the electronic component can be satisfactorily peeled. Using such an adhesive sheet can omit cleaning of the electronic component after peeling. In addition, even when small electronic components requiring peeling and small electronic components not requiring peeling are temporarily fixed adjacent to each other, only the small electronic components requiring peeling can be peeled, thereby preventing unnecessary detachment of the small electronic components.

As described above, the adhesive sheet of the present invention exhibits excellent properties in both receiving of electronic components by the laser lift-off process and peeling of electronic components by laser light irradiation. Therefore, according to the present invention, when transferring electronic components by a method including receiving of electronic components by the laser lift-off process and peeling of electronic components by laser light irradiation, the transfer can be completed using only the adhesive sheet. Since a plurality of adhesive sheets are not required, the number of transfer processes can be reduced, and as a result, electronic components can be transferred with high positional accuracy. In addition, production costs can be reduced.

The above-described adhesive layer is composed of an active energy ray-curable adhesive. An adhesive sheet including an active energy ray-curable adhesive has the adhesive strength of the entire adhesive layer reduced by irradiating the adhesive sheet with an active energy ray. By irradiating the entire adhesive layer of the adhesive sheet to which an adherend (electronic component) is adhered with an active energy ray to reduce the adhesive strength, and then irradiating the laser light as described above, adhesive residue after peeling can be prevented. By using such an adhesive sheet, cleaning of the electronic component after peeling can be omitted. In addition, by forming the adhesive layer including an active energy ray-curable adhesive, the laser output at the time of peeling can be lowered. Since the adhesive sheet of the present invention exhibits peelability with a low-output laser light, by using the adhesive sheet, damage to the electronic component as an adherend at the time of peeling can be reduced, and breakage of the electronic component can be prevented. In addition, since the peelability can be expressed by laser light of an output level that does not cause decomposition (thermal decomposition) of the adhesive layer itself, contamination of electronic components, which are adherends, by decomposed products of the adhesive layer can be prevented. Examples of the active energy rays include gamma rays, ultraviolet rays, visible light, infrared rays (heat rays), radio waves, alpha rays, beta rays, electron rays, plasmas, ionizing rays, and particle rays. Ultraviolet rays are preferable.

The above adhesive layer is a layer having an indentation elastic modulus of 150 MPa or more at 23°C after being irradiated with ultraviolet rays of 460 mJ/cm2. If an adhesive layer capable of having such an indentation elastic modulus after irradiation with ultraviolet rays is provided, deformation occurs in the adhesive layer by irradiation with laser light at low energy, and as a result, the adherend (electronic component) can be peeled off satisfactorily. In addition, contamination of the electronic component during peeling can be prevented.

The light transmittance of the adhesive sheet of the present invention at a wavelength of 355 nm is 50% or less. In the present invention, by lowering the light transmittance, the laser output at the time of peeling can be lowered. Since the adhesive sheet of the present invention exhibits peelability with low-output laser light, when the adhesive sheet is used, damage to an electronic component as an adherend at the time of peeling can be reduced, and breakage of the electronic component can be prevented. The light transmittance of the adhesive sheet of the present invention at a wavelength of 355 nm is preferably 40% or less, and more preferably 30% or less. Within this range, the above-described effect becomes more remarkable. In addition, the light transmittance of the adhesive sheet is the light transmittance in the thickness direction of the adhesive sheet, and is the light transmittance measured for the entire constituent layer of the adhesive sheet. In the present invention, the light transmittance of the adhesive sheet at a wavelength of 355 nm can be controlled by adjusting the content ratio of the ultraviolet absorber contained in the adhesive layer. In addition, the light transmittance at a wavelength of 355 nm of the adhesive sheet can also be controlled by the composition of the base polymer and photopolymerization initiator constituting the adhesive layer. For example, the light transmittance at a wavelength of 355 nm of the adhesive sheet can be controlled by the type and amount of the photopolymerization initiator included in the adhesive layer, and particularly by the compatibility between the photopolymerization initiator and the base polymer.

The visible light transmittance of the above adhesive sheet is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. Within this range, an adhesive sheet can be obtained in which the adherend to be peeled can be well-visible through the adhesive sheet when peeling the adherend by laser light irradiation. The higher the visible light transmittance of the adhesive sheet, the more preferable it is, but the upper limit thereof is, for example, 95% (preferably 100%).

The haze value of the adhesive sheet is preferably 70% or less, more preferably 65% or less. Within this range, an adhesive sheet can be obtained in which the adherend to be peeled can be clearly seen through the adhesive sheet when peeling the adherend by laser light irradiation. The lower the haze value of the adhesive sheet, the more preferable it is, but the lower limit thereof is, for example, 0.1%.

The initial adhesive strength A at 23°C immediately after the adhesive sheet is adhered to a stainless steel plate is preferably 0.1 N/20 mm to 15 N/20 mm, more preferably 0.5 N/20 mm to 10 N/20 mm. Within this range, an adhesive sheet capable of holding and supporting an adherend well can be obtained. The adhesive strength is measured in accordance with JIS Z 0237:2000. Specifically, the adhesive sheet is adhered to a stainless steel plate (arithmetic mean surface roughness Ra: 50±25 nm) by one reciprocation of a 2 kg roller, left for 30 minutes under 23°C, and then the adhesive sheet is peeled off and measured under the conditions of a peeling angle of 180° and a peeling speed (tensile speed) of 300 mm/min. The adhesive layer changes its adhesive strength by irradiating with active energy rays and laser light, but in this specification, “initial adhesive strength” means the adhesive strength before irradiating with active energy rays and laser light.

In one embodiment, the adhesive strength B at 23°C (also referred to as the adhesive strength B after curing) after the adhesive sheet is adhered to a stainless steel plate and irradiated with ultraviolet rays of 300 mJ/cm2 is preferably 0.2 N/20 mm or less, more preferably 0.01 N/20 mm to 0.2 N/20 mm, and even more preferably 0.02 N/20 mm to 0.15 N/20 mm. Within this range, an adhesive sheet with little adhesive residue can be obtained. The ultraviolet irradiation is performed, for example, by irradiating the adhesive layer with ultraviolet rays of a high-pressure mercury lamp (characteristic wavelength: 365 nm, accumulated light intensity: 300 mJ/cm2) using an ultraviolet irradiation device (manufactured by Nitto Seiki Co., Ltd., product name "UM-810").

The reduction rate of the adhesive strength B after curing with respect to the initial adhesive strength A is preferably 90% or more, and more preferably 95% or more. Within this range, an adhesive sheet having excellent peelability can be obtained. In addition, the reduction rate (%) can be obtained by the formula (initial adhesive strength A - adhesive strength B after curing) / initial adhesive strength A × 100.

The thickness of the adhesive sheet is preferably 1 µm to 300 µm, more preferably 5 µm to 200 µm.

B. Adhesive layer

The thickness of the adhesive layer is preferably 20 ㎛ or less. In this range, it is possible to lower the laser output at the time of peeling, and an adhesive sheet with excellent peeling performance can be obtained. The thickness of the adhesive layer is more preferably 15 ㎛ or less, further preferably 10 ㎛ or less, and still more preferably 1 ㎛ to 10 ㎛. In this range, the above effect becomes remarkable.

As described above, the adhesive layer has an initial indentation elastic modulus of 4 MPa or less at 23°C. The initial indentation elastic modulus of the adhesive layer at 23°C is preferably 3 MPa or less, more preferably 2 MPa or less. Within this range, the effects of the present invention become remarkable. In addition, the initial indentation elastic modulus of the adhesive layer at 23°C is preferably 0.1 MPa or more, more preferably 0.2 MPa or more, even more preferably 0.3 MPa or more, and particularly preferably 0.7 MPa or more. Within this range, it is difficult to contaminate an adherend, and an adhesive sheet having excellent peelability can be obtained.

As described above, the adhesive layer is a layer whose indentation elastic modulus at 23°C is 150 MPa or more after irradiation with ultraviolet rays of 460 mJ/cm2. The adhesive layer is preferably a layer whose indentation elastic modulus at 23°C is 200 MPa or more after irradiation with ultraviolet rays of 460 mJ/cm2, more preferably a layer whose indentation elastic modulus is 300 MPa or more, still more preferably a layer whose indentation elastic modulus is 400 MPa or more, particularly preferably a layer whose indentation elastic modulus is 500 MPa or more, and most preferably a layer whose indentation elastic modulus is 800 MPa or more. Within this range, the above effect becomes remarkable. The upper limit of the indentation elastic modulus of the adhesive layer after irradiation with ultraviolet rays of 460 mJ/cm2 is, for example, 8000 MPa (preferably 5000 MPa, more preferably 4000 MPa).

The adhesive layer preferably has a stress relaxation rate of 10% or more after 600 seconds, more preferably 15% or more, and even more preferably 20% or more. Within this range, an adhesive sheet having excellent chip retention properties can be obtained. Specifically, an adhesive sheet in which the adherend (electronic component) is unlikely to tilt on the adhesive layer even after the passage of time after the adherend (electronic component) is placed can be obtained. Using such an adhesive sheet, electronic components can be transported with high positional accuracy. The upper limit of the stress relaxation rate of the adhesive layer after 600 seconds is, for example, 100% (preferably 80%). The stress relaxation rate of the adhesive layer after 600 seconds can be obtained from the stress value A (MPa) immediately after elongation by 50% in the longitudinal direction at an environmental temperature of 23°C for a sample in which the adhesive layer is rounded into a cylindrical shape, and the stress value B (MPa) after 600 seconds in the 50% elongated state, by the formula (stress relaxation rate (%) = (A-B)/A × 100).

As described above, the adhesive layer is composed of an active energy ray-curable adhesive. The active energy ray-curable adhesive may include the ultraviolet absorber and/or the photopolymerization initiator.

(Active energy ray curing adhesive)

In one embodiment, an active energy ray-curable pressure-sensitive adhesive (A1) is used which comprises a base polymer as a parent material and an active energy ray-reactive compound (monomer or oligomer) which can be bonded to the base polymer. In another embodiment, an active energy ray-curable pressure-sensitive adhesive (A2) which comprises an active energy ray-reactive polymer as a base polymer is used. Preferably, the base polymer has a functional group which can react with a photopolymerization initiator. Examples of the functional group include a hydroxyl group, a carboxyl group, and the like.

As the base polymer used in the above adhesive (A1), examples thereof include rubber polymers such as natural rubber, polyisobutylene rubber, styrene-butadiene rubber, styrene-isoprene-styrene block copolymer rubber, regenerated rubber, butyl rubber, polyisobutylene rubber, and nitrile rubber (NBR); silicone polymers; and acrylic polymers. These polymers may be used alone or in combination of two or more. Among them, acrylic polymers are preferable.

As acrylic polymers, examples thereof include homopolymers or copolymers of hydrocarbon group-containing (meth)acrylic acid esters such as (meth)acrylic acid alkyl esters, (meth)acrylic acid cycloalkyl esters, and (meth)acrylic acid aryl esters; copolymers of the hydrocarbon group-containing (meth)acrylic acid esters and other copolymerizable monomers; and the like. As (meth)acrylic acid alkyl esters, examples thereof include methyl ester, ethyl ester, propyl ester, isopropyl ester, butyl ester, isobutyl ester, s-butyl ester, t-butyl ester, pentyl ester, isopentyl ester, hexyl ester, heptyl ester, octyl ester, 2-ethylhexyl ester, isooctyl ester, nonyl ester, decyl ester, isodecyl ester, undecyl ester, dodecyl ester, i.e. lauryl ester, tridecyl ester, tetradecyl ester, hexadecyl ester, octadecyl ester, and eicosyl ester of (meth)acrylic acid. As the (meth)acrylic acid cycloalkyl ester, examples thereof include cyclopentyl ester and cyclohexyl ester of (meth)acrylic acid. As the (meth)acrylic acid aryl ester, examples thereof include phenyl (meth)acrylate and benzyl (meth)acrylate. The content ratio of the structural unit derived from the hydrocarbon group-containing (meth)acrylic acid ester is preferably 40 parts by weight or more, and more preferably 60 parts by weight or more, with respect to 100 parts by weight of the base polymer.

Examples of the other copolymerizable monomers include carboxyl group-containing monomers, acid anhydride monomers, hydroxyl group-containing monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, acrylamide, and functional group-containing monomers such as acrylonitrile. Examples of the carboxyl group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of the acid anhydride monomers include maleic anhydride and itaconic anhydride. Examples of the hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. Examples of the glycidyl group-containing monomers include glycidyl (meth)acrylate and methyl glycidyl (meth)acrylate. Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl(meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid. Examples of the phosphoric acid group-containing monomer include 2-hydroxyethylacryloylphosphate. Examples of the acrylamide include N-acryloylmorpholine. These may be used singly or in combination of two or more. The content ratio of the structural unit derived from the copolymerizable monomer is preferably 60 parts by weight or less, and more preferably 40 parts by weight or less, with respect to 100 parts by weight of the base polymer.

Acrylic polymers may include structural units derived from polyfunctional monomers to form crosslinked structures in their polymer backbones. Examples of the polyfunctional monomers include hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy(meth)acrylate (i.e., polyglycidyl(meth)acrylate), polyester(meth)acrylate, and urethane(meth)acrylate. These may be used alone or in combination of two or more. The content ratio of the structural unit derived from the above-mentioned multifunctional monomer is preferably 40 parts by weight or less, and more preferably 30 parts by weight or less, with respect to 100 parts by weight of the base polymer.

The weight average molecular weight of the above acrylic polymer is preferably 100,000 to 3 million, more preferably 200,000 to 2 million. The weight average molecular weight can be measured by GPC (solvent: THF).

As the active energy ray reactive compound that can be used in the above adhesive (A1), examples thereof include a photoreactive monomer or oligomer having a functional group having a polymerizable carbon-carbon multiple bond, such as an acryloyl group, a methacryloyl group, a vinyl group, an allyl group, an acetylene group, etc. Specific examples of the photoreactive monomer include esters of (meth)acrylic acid and polyhydric alcohols, such as trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and polyethylene glycol di(meth)acrylate; polyfunctional urethane (meth)acrylate; epoxy (meth)acrylate; and oligoester (meth)acrylate. In addition, monomers such as methacryloisocyanate, 2-methacryloyloxyethyl isocyanate (2-isocyanatoethyl methacrylate), m-isopropenyl-α,α-dimethylbenzyl isocyanate, etc. may be used. Specific examples of the photoreactive oligomer include dimers to pentamers of the above monomers. The molecular weight of the photoreactive oligomer is preferably 100 to 3000.

In one embodiment, as the active energy ray reactive compound, a polyfunctional (meth)acrylate having five or more functional groups, or an oligomer of a polyfunctional (meth)acrylate having five or more functional groups, is used. By using such an active energy ray reactive compound, an adhesive layer that can be made highly elastic by irradiation with an active energy ray (for example, ultraviolet ray) can be formed. If the adhesive layer can be made highly elastic, the above-described peeling operation can be performed by a low-power laser light.

In addition, as the above-mentioned active energy ray reactive compound, a monomer such as epoxidized butadiene, glycidyl methacrylate, acrylamide, vinyl siloxane, or an oligomer composed of the monomer may be used.

In addition, as the above-mentioned active energy ray reactive compound, a mixture of an organic salt such as an onium salt and a compound having multiple heterocycles in the molecule may be used. In the above-mentioned mixture, the organic salt is cleaved by irradiation with an active energy ray (e.g., ultraviolet ray, electron beam) to generate an ion, which becomes an initiating species and causes a ring-opening reaction of a heterocycle to form a three-dimensional network structure. Examples of the above-mentioned organic salt include iodonium salts, phosphonium salts, antimonium salts, sulfonium salts, borate salts, and the like. Examples of the heterocycle in the compound having multiple heterocycles in the molecule include oxirane, oxetane, oxolane, thiirane, aziridine, and the like.

In the above adhesive (A1), the content ratio of the active energy ray reactive compound is preferably 0.1 to 500 parts by weight, more preferably 5 to 300 parts by weight, and even more preferably 40 to 150 parts by weight, relative to 100 parts by weight of the base polymer.

As the active energy ray reactive polymer (base polymer) included in the above adhesive (A2), for example, a polymer having a functional group having a carbon-carbon multiple bond such as an acryloyl group, a methacryloyl group, a vinyl group, an allyl group, an acetylene group, etc. can be mentioned. Specific examples of the active energy ray reactive polymer include a polymer composed of a multifunctional (meth)acrylate; a photocationically polymerizable polymer; a polymer containing a cinnamoyl group such as polyvinyl cinnamate; a diazotized aminonovolac resin; a polyacrylamide; etc.

In one embodiment, an active energy ray-reactive polymer is used, which is configured by introducing an active energy ray-polymerizable carbon-carbon multiple bond into the side chain, main chain and/or main chain terminal of the acrylic polymer (precursor resin). As a method for introducing a radiation polymerizable carbon-carbon double bond into the acrylic polymer (precursor resin), an example of which is a method in which a raw material monomer including a monomer having a predetermined functional group (first functional group) is copolymerized to obtain an acrylic polymer (precursor resin), and then a compound having a predetermined functional group (second functional group) capable of reacting and bonding with the first functional group and a radiation polymerizable carbon-carbon double bond (hereinafter, also simply referred to as a compound having a carbon double bond) is subjected to a condensation reaction or addition reaction with the acrylic polymer while maintaining the radiation polymerizability of the carbon-carbon double bond.

The amount of the compound having the above-mentioned carbon double bond to be introduced is preferably 10 parts by weight or more, more preferably 12 parts by weight or more, and even more preferably 15 parts by weight or more, relative to 100 parts by weight of the acrylic polymer (precursor resin) solid content. Within this range, a low-polarity, active energy ray-reactive polymer (base polymer) can be obtained, and when the base polymer is used, even if the adhesive layer has a relatively low elastic modulus after ultraviolet irradiation, peeling of the adherend by low-energy laser irradiation can be preferably performed. The upper limit of the amount of the compound having the above-mentioned carbon double bond to be introduced is, for example, 80 parts by weight (preferably 60 parts by weight, more preferably 50 parts by weight) relative to 100 parts by weight of the acrylic polymer (precursor resin) solid content.

As a combination of the first functional group and the second functional group, examples thereof include a carboxyl group and an epoxy group, an epoxy group and a carboxyl group, a carboxyl group and an aziridyl group, an aziridyl group and a carboxyl group, a hydroxyl group and an isocyanate group, and an isocyanate group and a hydroxyl group. Among these combinations, from the viewpoint of the ease of tracking the reaction, a combination of a hydroxyl group and an isocyanate group or a combination of an isocyanate group and a hydroxyl group is preferable. In addition, since the technical difficulty of producing a polymer having a highly reactive isocyanate group is high, from the viewpoint of the ease of producing or obtaining an acrylic polymer, it is more preferable when the first functional group on the acrylic polymer side is a hydroxyl group and the second functional group is an isocyanate group. In this case, as the isocyanate compound having both a radiation polymerizable carbon-carbon double bond and an isocyanate group as the second functional group, examples thereof include methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, and m-isopropenyl-α,α-dimethylbenzyl isocyanate. In addition, as the acrylic polymer having the first functional group, it is preferable that it contains a structural unit derived from the above-mentioned hydroxyl group-containing monomer, and it is also preferable that it contains a structural unit derived from an ether compound such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, or diethylene glycol monovinyl ether.

The glass transition temperature Tg of the above-mentioned active energy ray reactive polymer (base polymer) is preferably -60°C or higher, more preferably -50°C or higher, and even more preferably -40°C or higher. Within this range, a low-polar active energy ray reactive polymer (base polymer) can be obtained, and when the base polymer is used, even if the adhesive layer has a relatively low elastic modulus after ultraviolet irradiation, peeling of the adherend by irradiation with laser light at low energy can be preferably performed. The upper limit of the glass transition temperature Tg of the active energy ray reactive polymer (base polymer) is preferably 0°C, and more preferably -20°C. The Tg of the base polymer refers to a value obtained from Fox's formula based on the Tg of the homopolymer (homopolymer) of each monomer constituting the base polymer and the weight fraction (copolymerization ratio on a weight basis) of the monomer. Fox's equation is, as shown below, a relationship between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer.

In the above Fox equation, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K). As the Tg of the homopolymer, a value described in a known material is adopted.

The above adhesive (A2) may further contain the above active energy ray reactive compound (monomer or oligomer).

The above-mentioned active energy ray-curable adhesive may contain an ultraviolet absorber and/or a photopolymerization initiator. Details of the ultraviolet absorber and photopolymerization initiator used are as described above.

In one embodiment, the active energy ray curable adhesive may include a photosensitizer.

In one embodiment, the photosensitizer can be used in combination with the photopolymerization initiator. Since the photosensitizer can generate radicals from the photopolymerization initiator by transferring energy obtained by absorbing light itself to the photopolymerization initiator, the polymerization can proceed with light on the long-wavelength side that does not have an absorption peak of the photopolymerization initiator itself. Therefore, by containing the photosensitizer, it becomes possible to increase the difference between the absorption wavelength of the ultraviolet absorber and the wavelength at which radicals can be generated from the photopolymerization initiator. As a result, the photopolymerization of the adhesive layer and the peeling by the ultraviolet absorber can be performed without affecting each other. In one embodiment, 2,2-dimethoxy-1,2-diphenylethane-1-one (for example, manufactured by BASF, trade name “Irgacure 651”) as a photopolymerization initiator and the photosensitizer are used in combination. Examples of such photosensitizers include Kawasaki Chemical Industry Co., Ltd.'s product name "UVS-581" and 9,10-diethoxyanthracene (e.g., Kawasaki Chemical Industry Co., Ltd.'s product name "UVS1101").

Other examples of the photosensitizer include 9,10-dibutoxyanthracene (e.g., manufactured by Kawasaki Kasei Kogyo Co., Ltd., trade name “UVS-1331”), 2-isopropylthioxanthone, benzophenone, thioxanthone derivatives, 4,4'-bis(dimethylamino)benzophenone, etc. Examples of the thioxanthone derivatives include ethoxycarbonylthioxanthone, isopropylthioxanthone, etc.

The content ratio of the above-mentioned photosensitizer is preferably 0.01 to 2 parts by weight, and more preferably 0.5 to 2 parts by weight, with respect to 100 parts by weight of the base polymer.

Preferably, the active energy ray-curable pressure-sensitive adhesive contains a crosslinking agent. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, a melamine-based crosslinking agent, a peroxide-based crosslinking agent, a urea-based crosslinking agent, a metal alkoxide-based crosslinking agent, a metal chelate-based crosslinking agent, a metal salt-based crosslinking agent, a carbodiimide-based crosslinking agent, and an amine-based crosslinking agent.

The content ratio of the crosslinking agent is preferably 0.5 to 10 parts by weight, and more preferably 1 to 8 parts by weight, relative to 100 parts by weight of the base polymer of the adhesive.

In one embodiment, an isocyanate-based crosslinking agent is preferably used. An isocyanate-based crosslinking agent is preferable because it can react with various functional groups. Specific examples of the isocyanate-based crosslinking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate and xylylene diisocyanate; Isocyanate adducts such as trimethylolpropane/tolylene diisocyanate terpolymer adduct (manufactured by Nippon Polyurethane Industries, Ltd., trade name “Coronate L”), trimethylolpropane/hexamethylene diisocyanate terpolymer adduct (manufactured by Nippon Polyurethane Industries, Ltd., trade name “Coronate HL”), and isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industries, Ltd., trade name “Coronate HX”); etc. A crosslinking agent having three or more isocyanate groups is preferably used.

The active energy ray-curable pressure-sensitive adhesive may further contain any suitable additives as needed. Examples of the additives include an active energy ray polymerization accelerator, a radical scavenger, a tackifier, a plasticizer (for example, a trimellitic acid ester plasticizer, a pyromellitic acid ester plasticizer, etc.), a pigment, a dye, a filler, an anti-aging agent, a conductive agent, an antistatic agent, an ultraviolet absorber, a light stabilizer, a peeling regulator, a softener, a surfactant, a flame retardant, an antioxidant, and the like.

(UV absorber)

As the ultraviolet absorber, any appropriate ultraviolet absorber can be used as long as it is a compound that absorbs ultraviolet rays (for example, having a wavelength of 355 nm). Examples of the ultraviolet absorber include a benzotriazole-based ultraviolet absorber, a benzophenone-based ultraviolet absorber, a triazine-based ultraviolet absorber, a salicylate-based ultraviolet absorber, and a cyanoacrylate-based ultraviolet absorber. Among these, a triazine-based ultraviolet absorber or a benzotriazole-based ultraviolet absorber is preferable, and a triazine-based ultraviolet absorber is particularly preferable. In particular, when an acrylic adhesive is used as the adhesive, a triazine-based ultraviolet absorber can be preferably used because of its high compatibility with the base polymer of the acrylic adhesive. The triazine-based ultraviolet absorber is more preferably composed of a compound having a hydroxyl group, and is particularly preferable an ultraviolet absorber composed of a hydroxyphenyltriazine-based compound (hydroxyphenyltriazine-based ultraviolet absorber).

As hydroxyphenyl triazine-based ultraviolet absorbers, for example, the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl and [(C10-C16 (mainly C12-C13) alkyloxy)methyl]oxirane (trade name "TINUVIN 400", manufactured by BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol), the reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidic acid ester (trade name "TINUVIN 405", BASF Corporation), 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibuthoxyphenyl)-1,3,5-triazine (trade name "TINUVIN 460", BASF Corporation), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (trade name "TINUVIN 1577", BASF Corporation), 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]-phenol (trade name "ADEKASTAP LA-46", ADEKA Corporation), Examples include 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (trade name “TINUVIN 479”, manufactured by BASF), and BASF’s trade name “TINUVIN 477”.

As benzotriazole-based UV absorbers (benzotriazole-based compounds), for example, 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (trade name "TINUVIN PS", manufactured by BASF), ester compounds of benzenepropanoic acid and 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy (C7-9 branched and straight-chain alkyl) (trade name "TINUVIN 384-2", manufactured by BASF), octyl 3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl]propionate, and Mixture of 2-ethylhexyl-3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-yl)phenyl]propionate (trade name "TINUVIN 109", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN 900", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN 928", manufactured by BASF), methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate/polyethylene glycol 300 Product (trade name "TINUVIN 1130", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (trade name "TINUVIN P", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (trade name "TINUVIN 234", manufactured by BASF), 2-[5-chloro-2H-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (trade name "TINUVIN 326", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (trade name "TINUVIN 328", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol (trade name "TINUVIN 329", manufactured by BASF), 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol] (trade name "TINUVIN 360", manufactured by BASF), reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate and polyethylene glycol 300 (trade name "TINUVIN 213", manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (trade name "TINUVIN 571", manufactured by BASF), 2-[2-Hydroxy-3-(3,4,5,6-tetrahydrophthalimide-methyl)-5-methylphenyl]benzotriazole (trade name "Sumisorb 250", manufactured by Sumitomo Chemical Co., Ltd.), 2-(3-tert-butyl-2-hydroxy-5-methylphenyl)-5-chloro-2H-benzotriazole (trade name "SEESORB 703", manufactured by Cipro Kasei Co., Ltd.), 2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl)phenol (trade name "SEESORB 706", manufactured by Cipro Kasei Co., Ltd.), 2-(4-Benzoyloxy-2-hydroxyphenyl)-5-chloro-2H-benzotriazole (trade name "SEESORB", manufactured by Cipro Kasei Co., Ltd.) Examples thereof include 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol (trade name "KEMISORB 73", manufactured by Chemipro Kasei Co., Ltd.), 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol] (trade name "ADEKA STAP LA-31", manufactured by ADEKA Co., Ltd.), 2-(2H-benzotriazol-2-yl)-p-cellulose (trade name "ADEKA STAP LA-32", manufactured by ADEKA Co., Ltd.), 2-(5-chloro-2H-benzotriazol-2-yl)-6-tert-butyl-4-methylphenol (trade name "ADEKA STAP LA-36", manufactured by ADEKA Co., Ltd.).

The above ultraviolet absorber may be a dye or a pigment. Examples of the pigment include azo pigments, phthalocyanine pigments, anthraquinone pigments, lake pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, dioxanzine pigments, isoindolinone pigments, and quinophthalone pigments. Examples of the dye include azo pigments, phthalocyanine pigments, anthraquinone pigments, carbonyl pigments, indigo pigments, quinone imines, methine pigments, quinoline pigments, and nitro pigments.

The molecular weight of the compound constituting the above ultraviolet absorber is preferably 1000 or less, more preferably 800 or less, and even more preferably 600 or less. Since the ultraviolet absorber having a molecular weight in the above range has excellent compatibility with the base polymer, when the ultraviolet absorber is used, deformation occurs only at the laser irradiation location when irradiated with laser light, so that peeling with extremely low laser energy becomes possible. As a result, thermal decomposition of the adhesive layer can be prevented. When such an adhesive layer is formed, an adhesive sheet that is difficult to contaminate an adherend can be obtained. The lower limit of the molecular weight of the compound constituting the ultraviolet absorber is, for example, 100.

The maximum absorption wavelength of the above ultraviolet absorbent is preferably 300 nm to 450 nm, more preferably 320 nm to 400 nm, and even more preferably 330 nm to 380 nm. The difference between the maximum absorption wavelength of the ultraviolet absorbent and the maximum absorption wavelength of the photopolymerization initiator is preferably 10 nm or more, and more preferably 25 nm or more.

The content ratio of the above ultraviolet absorber is preferably 1 to 50 parts by weight, more preferably 2 to 30 parts by weight, and even more preferably 3 to 25 parts by weight, relative to 100 parts by weight of the base polymer in the adhesive layer. Within this range, when the adhesive strength of the entire adhesive layer is satisfactorily reduced by irradiation with an active energy ray, curing of the adhesive layer progresses satisfactorily, and furthermore, an adhesive sheet exhibiting good peelability can be obtained by irradiation with a laser light.

(photopolymerization initiator)

As the photopolymerization initiator, any appropriate initiator can be used. As the photopolymerization initiator, for example, α-ketol compounds such as 4-(2-hydroxyethoxy)phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α,α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and 1-hydroxycyclohexylphenyl ketone; acetophenone compounds such as methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxyacetophenone, and 2-methyl-1-[4-(methylthio)-phenyl]-2-morpholinopropane-1; benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether; ketal compounds such as benzyl dimethyl ketal; Examples thereof include aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; photoactive oxime compounds such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid, and 3,3'-dimethyl-4-methoxybenzophenone; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, and 2,4-diisopropylthioxanthone; camphorquinone; halogenated ketones; acylphosphine oxides; and acylphosphonates. The amount of the photopolymerization initiator to be used can be set to any appropriate amount.

In one embodiment, as the photopolymerization initiator, a photopolymerization initiator having two or more photodecomposable groups (preferably 2 to 5) is used. When such a photopolymerization initiator is used, an adhesive layer that can be made highly elastic by irradiation with an active energy ray (e.g., ultraviolet ray) can be formed. If the adhesive layer can be made highly elastic, the peeling operation described above can be performed by a low-power laser light. The photodecomposable group means a functional group that absorbs an irradiated active energy ray and generates a radical, and specific examples thereof include a ketone group, a halogenated alkyl group, an ester group, a sulfone group, a peroxy group, and the like.

Examples of the photopolymerization initiator having two or more photolytic groups include 2-hydroxy-1-[4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl]-2-methyl-propan-1-one (trade name: Omnirad 127, manufactured by BASF Japan), 1-[4-(4-benzoicylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one (trade name: ESURE1001M), methyl benzoyl formate (trade name: SPEEDCURE MBF manufactured by LAMBSON), O-ethoxyimino-1-phenylpropan-1-one (trade name: SPEEDCURE PDO manufactured by LAMBSON), and oligo[2-hydroxy-2-methyl-4-(1-methylvinyl)phenyl]propanone (trade name: ESCURE KIPI50 manufactured by LAMBERTI).

In one embodiment, a compound containing a phosphorus atom and/or a nitrogen atom is used as the photopolymerization initiator. Examples of such photopolymerization initiators include 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (trade name Omnirad 907, manufactured by BASF Japan), 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone (trade name Omnirad 369, manufactured by BASF Japan), 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)butan-1-one (trade name Omnirad 379, manufactured by BASF Japan), bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide (trade name Omnirad 819, manufactured by BASF Japan), 2,4,6-trimethylbenzoyl-diphenylphosphineoxide (trade name Omnirad TPO, manufactured by BASF Japan), Examples thereof include 1,2-octanedione-1-[4-(phenylthio)phenyl-2-(O-benzoyloxime)] (trade name: Omnirad OXE01, manufactured by BASF Japan), ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime) (trade name: Omnirad OXE02, manufactured by BASF Japan). When such a photopolymerization initiator is used, an adhesive layer that can be made highly elastic by irradiation with an active energy ray (e.g., ultraviolet ray) can be formed. If the adhesive layer can be made highly elastic, the above-mentioned peeling operation can be performed by a low-output laser light.

The content ratio of the above photopolymerization initiator is preferably 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and even more preferably 3 to 15 parts by weight, relative to 100 parts by weight of the base polymer in the adhesive layer. In this range, when the adhesive strength of the entire adhesive layer is satisfactorily reduced by irradiation with an active energy ray, curing of the adhesive layer progresses satisfactorily, and furthermore, the amount of deformation of the adhesive layer due to irradiation with a laser light is large, so that an adhesive sheet exhibiting good peelability can be obtained.

C. Description

The above-mentioned description may be composed of any suitable resin. Examples of the resin include polyolefin resins such as polyethylene resins, polypropylene resins, polybutene resins, and polymethylpentene resins, polyurethane resins, polyester resins, polyimide resins, polyetherketone resins, polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, fluorine resins, silicone resins, cellulose resins, and ionomer resins. Among them, a polyolefin resin is preferable.

The thickness of the above-mentioned substrate is preferably 2 µm to 300 µm, more preferably 2 µm to 100 µm, and even more preferably 2 µm to 50 µm.

The light transmittance of the substrate at a wavelength of 355 nm is preferably 70% or more, more preferably 80% or more, still more preferably 90% or more, and particularly preferably 95% or more. The upper limit of the total light transmittance of the substrate is, for example, 98% (preferably 99%).

D. Method for manufacturing adhesive sheet

The above-mentioned adhesive sheet can be manufactured by any suitable method. The adhesive sheet can be obtained, for example, by coating the adhesive on a substrate or a release liner. Various methods such as bar coater coating, air knife coating, gravure coating, gravure reverse coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexographic printing, and screen printing can be adopted as the coating method. In addition, a method of separately forming an adhesive layer on a release liner and then bonding it to a substrate, etc. can also be adopted.

E. Method of transporting electronic components

In one embodiment, a method for transferring electronic components using the adhesive sheet is provided. The transfer method includes, for example, a first step of transferring a plurality of electronic components arranged on a substrate onto an adhesive layer of the adhesive sheet; and a second step of transferring the electronic components on the adhesive sheet to another member. Preferably, the same adhesive sheet is used in the first step and the second step. That is, in the transfer method, the electronic components can be transferred without including an additional transfer step.

In the first process, the transfer of the electronic component from the substrate to the adhesive sheet can be performed by a process including irradiating a laser light to a portion of the substrate/electronic component interface, i.e., a laser lift-off process. Various conditions of the laser lift-off process can be any suitable conditions.

As the above substrate, a hard substrate such as a sapphire substrate can be used, for example.

In one embodiment, the second process includes the following operations, namely, the second process includes (i) irradiating the adhesive sheet with an active energy ray (e.g., ultraviolet ray) to reduce the adhesive strength of the adhesive layer of the adhesive sheet, and (ii) irradiating a location where peelability is desired with laser light to cause deformation in the adhesive layer to further reduce the adhesive strength. According to the method, electronic components can be peeled only at the location where the laser light has been irradiated. Since the adhesive sheet of the present invention can reduce the adhesive strength to the extent that it naturally falls off, even very small electronic components (e.g., a square with a side of 50 µm) can be peeled separately.

The active energy ray in the above (i) can be irradiated to the entire surface of the adhesive layer. In one embodiment, ultraviolet rays having an accumulated light amount of 200 mJ/cm2 to 600 mJ/cm2 are irradiated.

As the laser light in the above (ii), for example, a laser light having a wavelength of 200 nm to 360 nm (preferably 355 nm) is used. The laser light output is, for example, 100 mJ/cm2 to 1200 mJ/cm2.

In one embodiment, the electronic component is a mini LED or micro LED.

Example

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited to these examples. The test and evaluation methods in the examples are as follows. In addition, unless specifically stated, "part" and "%" are based on weight.

(1) Adhesion

The PET release liner of the adhesive sheet was peeled, and a PET (Lumilar S10 manufactured by Toray) having a thickness of 25 ㎛ was bonded. Thereafter, the PET release liner on the other side was peeled, and the sheet was bonded to SUS304 by one reciprocation of a 2 kg roller, and the adhesive strength was measured by a method according to JIS Z 0237:2000 (peel angle 180°, peel speed (tensile speed) 300 mm/min, measurement temperature: 23°C), and this was used as the initial adhesive strength.

In the same way, after bonding an adhesive sheet to SUS304, an ultraviolet irradiation device (product name "UM-810" manufactured by Nitto Seiki) was used from the adhesive sheet side, and ultraviolet rays (specific wavelength: 365 nm, accumulated light intensity: 300 mJ/cm2) from a high-pressure mercury lamp were irradiated to the entire surface, and the adhesive strength was measured in the same way, which was taken as the adhesive strength after curing.

(2) Light transmittance at wavelength 355 nm

The PET release liner of the adhesive sheet was peeled off, and the sheet was bonded to a large slide glass (product name "S9111" manufactured by Matsunami Glass) using a hand roller, and measurements were made while the PET release liner on one side was peeled off. Specifically, a spectrophotometer (product name "Spectrophotometer U-4100" manufactured by Hitachi High-Tech Science) was used to measure the transmittance at a wavelength of 355 nm of the adhesive sheet itself on the large slide glass.

(3) Compression elastic modulus

The PET release liner of the adhesive sheet was peeled off, and it was bonded to a large slide glass (Matsunami Glass, product name "S9111") using a hand roller. The entire surface of the obtained sample was irradiated with ultraviolet rays (specific wavelength: 365 nm, accumulated light intensity: 460 mJ/cm2) of a high-pressure mercury lamp from the slide glass side using an ultraviolet irradiation device (Nitto Seiki, product name "UM-810"). Thereafter, the other PET release liner was peeled off to expose the adhesive layer, and the indentation elastic modulus was measured using a tribo indenter TI-950 manufactured by Hysitron. The measurement was performed by a single indentation method at 23°C, at an indentation speed of 10 nm/s, and an indentation depth of 100 nm.

(4) Stress relaxation rate after 600 seconds

The adhesive layer was cut to a size of 50 mm in length × 40 mm in width to obtain a round, cylindrical test piece (diameter: 0.5643 mm, length: 40 mm). This test piece was stretched (elongated) to an elongation of 50% using a tensile tester (product name "AFX-50NX", manufactured by Shimadzu Seisakusho Co., Ltd.) at an initial chuck distance of 20 mm and a tensile speed of 50 mm/min in an atmosphere of 23°C and 50% RH, then stopped, and the stress value A (MPa) was measured. Thereafter, the stress value B (MPa) when 600 seconds had elapsed from the stop was measured. The stress relaxation rate was obtained from the stress values A and B by the following formula.

Stress relaxation rate (%) = (A-B)/A × 100

(5) Laser lift-off (LLO) evaluation

After bonding the adhesive on a quartz glass surface with one side measuring 4 inches, a sapphire substrate was bonded so that the LED chip was on the adhesive surface. Bonding was performed using a protective tape bonding device equipped with a vacuum + press mechanism (trade name: “DV 3000”, manufactured by Nitto Seiki Co., Ltd.), with the vacuum time: 90 seconds, the pressing conditions: 0.25 MPa, and the pressing time: 0 seconds.

After the pressing was completed, a laser (excimer laser manufactured by M-Rayze) was irradiated from the sapphire surface to perform LLO. The LLO conditions were wavelength: 248 nm, energy density: 900 mJ/cm2. After the LLO, the sapphire glass was removed and the yield was confirmed. Yield: 90% or more was considered good (○), 80% or more and less than 90% was considered possible (△), and less than 80% was considered unacceptable (×).

The LED chips on the adhesive tape were observed using a confocal microscope (product name: “OLS 5100”, manufactured by Shimadzu Corporation), the inclination angles of 100 chips were measured, and the average value was calculated. When the average inclination value was 0.15° or less, it was rated as excellent (◎), when it was greater than 0.15° and less than 0.25°, it was rated as good (○), and when it was greater than 0.25°, it was rated as unacceptable (×).

(6) Laser Transfer Evaluation

After LLO, the adhesive was photo-cured from the quartz glass side of the obtained sample under a nitrogen atmosphere using an ultraviolet irradiation device (trade name “UM 810”, manufactured by Nitto Seiki Co., Ltd.). The curing conditions were ultraviolet rays from a high-pressure mercury lamp, wavelength: 365 nm (equivalent to 460 mJ/cm2).

Thereafter, laser (wavelength: 355 nm, pulse width: 5 ns) was irradiated only to the target chip position from the quartz glass side to perform Laser Transfer. Laser light was irradiated at 100 mJ/cm2 intervals from 100 mJ/cm2 to 1200 mJ/cm2, and the energy with the best positional accuracy was set as the Energy value. A case of 500 mJ/cm2 or less was rated as Excellent (◎), a case of more than 500 mJ/cm2 and less than or equal to 1000 mJ/cm2 was rated as Good (○), and a case of more than 1000 mJ/cm2 and a case where transfer was not possible at 1200 mJ/cm2 was rated as Unable (×).

The chips after transcription were observed using a digital microscope (product name: "VHX2000", manufactured by Keyence Co., Ltd.) and the positional accuracy was evaluated. When the misalignment distance in the long side of the chip was 2 ㎛ or less, it was rated as excellent (◎), when it was greater than 2 ㎛ and less than 5 ㎛, it was rated as good (○), and when it was greater than 5 ㎛, it was rated as unacceptable (×).

[Manufacturing Example 1] Adjustment of acrylic polymer A

A monomer composition was prepared by mixing 100 parts by weight of 2-methoxyethyl acrylate, 27 parts by weight of acryloylmorpholine, and 22 parts by weight of 2-hydroxyethyl acrylate.

Next, nitrogen was introduced into a reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirrer, and under a nitrogen atmosphere, 500 parts by weight of toluene, 149 parts by weight of the above monomer composition, and 0.3 parts by weight of benzoyl peroxide (BPO) were charged and stirred at 60°C for 5 hours. Thereafter, the mixture was cooled to room temperature, and 24 parts by weight of 2-methacryloyloxyethyl isocyanate was added and reacted to obtain an acrylic polymer solution A containing an acrylic polymer A having a carbon-carbon double bond at the terminal by adding an NCO group to the side chain terminal OH group of 2-hydroxyethyl acrylate in the copolymer.

[Manufacturing Example 2] Adjustment of Acrylic Polymer B

A monomer composition was prepared by mixing 100 parts by weight of 2-ethylhexyl acrylate, 25.5 parts by weight of acryloylmorpholine, and 18.5 parts by weight of hydroxyethyl acrylate.

Next, nitrogen was introduced into a reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirrer, and under a nitrogen atmosphere, 60 parts by weight of toluene, 144 parts by weight of the above monomer composition, and 0.3 parts by weight of benzoyl peroxide (BPO) were charged and stirred at 60°C for 4 hours. Thereafter, the mixture was cooled to room temperature, and 12 parts by weight of 2-methacryloyloxyethyl isocyanate was added and reacted to obtain an acrylic polymer solution B containing an acrylic polymer B having a carbon-carbon double bond at the terminal by adding an NCO group to the side chain terminal OH group of 2-hydroxyethyl acrylate in the copolymer.

[Manufacturing Example 3] Adjustment of acrylic polymer C

The monomer composition was adjusted by mixing 100 parts by weight of isononyl acrylate and 32 parts by weight of hydroxyethyl acrylate.

Next, nitrogen was introduced into a reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirrer, and under a nitrogen atmosphere, 280 parts by weight of ethyl acetate, 132 parts by weight of the above monomer composition, and 0.3 parts by weight of benzoyl peroxide (BPO) were charged and stirred at 60°C for 4 hours. Thereafter, the mixture was cooled to room temperature, and 56 parts by weight of 2-methacryloyloxyethyl isocyanate was added and reacted to obtain an acrylic polymer solution C containing an acrylic polymer C having a carbon-carbon double bond at the terminal by adding an NCO group to the side chain terminal OH group of 2-hydroxyethyl acrylate in the copolymer.

[Manufacturing Example 4] Adjustment of Acrylic Polymer D

The monomer composition was adjusted by mixing 88.8 parts by weight of 2-ethylhexyl acrylate and 11.2 parts by weight of hydroxyethyl acrylate.

Next, nitrogen was introduced into a reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirrer, and under a nitrogen atmosphere, 150 parts by weight of toluene, 100 parts by weight of the above monomer composition, and 0.3 parts by weight of benzoyl peroxide (BPO) were charged and stirred at 60°C for 4 hours. Thereafter, the mixture was cooled to room temperature, and 12 parts by weight of 2-methacryloyloxyethyl isocyanate was added and reacted to obtain an acrylic polymer solution D containing an acrylic polymer D having a carbon-carbon double bond at the terminal by adding an NCO group to the side chain terminal OH group of 2-hydroxyethyl acrylate in the copolymer.

[Example 1]

(Preparation of adhesive)

To an acrylic polymer solution A containing 100 parts by weight of acrylic polymer A, 3 parts by weight of a crosslinking agent (manufactured by Mitsui Chemical Co., Ltd., trade name “Takenate D-101A”), 5 parts by weight of an ultraviolet absorber (manufactured by BASF Co., Ltd., trade name “Tinuvin PS”), and 3 parts by weight of a photopolymerization initiator (manufactured by BASF Co., Ltd., trade name “Omnirad TPO”) were added, thereby obtaining an adhesive (1).

(Adhesive sheet)

The adhesive (1) was applied to the silicone-treated surface of a PET release liner (thickness: 38 μm), and then heated at 130°C for 2 minutes to form an adhesive layer with a thickness of 5 μm.

Using a hand roller, a PET release liner was bonded onto the adhesive layer, and an adhesive sheet provided with a release liner was obtained.

The obtained adhesive sheet equipped with a peeling liner was subjected to the above evaluation. The results are shown in Table 1.

[Examples 2 to 14, Comparative Examples 1 to 5]

An adhesive sheet was obtained in the same manner as in Example 1, except that the acrylic polymer solution, crosslinking agent, ultraviolet absorber, active energy ray reactive compound (oligomer), and photopolymerization initiator shown in Table 1 were used in the blending amounts shown in Table 1. The obtained adhesive sheet was subjected to the above evaluation. The results are shown in Table 1.

In an experimental example using an active energy ray reactive compound (oligomer), the oligomer was added during the production of the adhesive to obtain the adhesive.

The compounds used in the examples and comparative examples are as follows.

(Bridger)

·D-101A: Isocyanate crosslinking agent, manufactured by Mitsui Chemical Co., Ltd., trade name "Takenate D-101A"

·Coronate HX: Isocyanate crosslinking agent, ·Manufactured by Tososa Corporation, trade name "Coronate/HX"

(UV absorber)

·Tinuvin PS: BASF, trade name "Tinuvin PS", 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole

·Tinuvin 405: BASF, trade name "Tinuvin 405", reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidic acid ester

·Tinuvin 460: BASF, trade name "Tinuvin 460", 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibuthoxyphenyl)-1,3,5-triazine

·Tinuvin 477: BASF, trade name "Tinuvin 460", hydroxyphenyltriazine compound

·KEMISORB 111: Chemipro Gassei, product name "KEMISORB 111"

·KEMISORB 71: Chemipro Gassei, product name 「KEMISORB 71」,

(Active energy ray reactive compound (oligomer))

·UV-1700TL: Urethane acrylate multifunctional oligomer, manufactured by Nippon Gosei Chemical Co., Ltd., product name "UV-1700TL"

·DPHA: Dipentaerythritol hexaacrylate

(photopolymerization initiator)

·Omni 127D: BASF, trade name 「Omnirad 127D」, chemical compound name: 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one

·Omni TPO: manufactured by BASF, trade name "Omnirad TPO", compound name: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide

·Omni 379: BASF, trade name 「Omnirad 379」, chemical name: 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one

·Omni 369: BASF, trade name 「Omnirad 369」, chemical name: 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone

10: Adhesive layer
20: Description
100, 200: Adhesive sheet

Claims (13)

An adhesive sheet having an adhesive layer composed of an active energy ray curable adhesive,
The active energy ray curable adhesive comprises an ultraviolet absorber and/or a photopolymerization initiator,
The initial indentation elastic modulus of the adhesive layer at 23°C is 4 MPa or less,
The adhesive layer is a layer having an indentation elastic modulus of 150 MPa or more at 23°C after being irradiated with 460 mJ/cm2 of ultraviolet rays.
The light transmittance of the adhesive sheet at a wavelength of 355 nm is 50% or less.
Adhesive sheet. In the first paragraph,
Adhesive sheet, not including substrate. In the first paragraph,
An adhesive sheet, wherein the stress relaxation rate of the adhesive layer after 600 seconds is 10% or more. In the first paragraph,
An adhesive sheet having a thickness of the adhesive layer of 20㎛ or less. In the first paragraph,
The above active energy ray curable adhesive contains a photopolymerization initiator,
The photopolymerization initiator has two or more photolytic groups,
Adhesive sheet. In the first paragraph,
The above active energy ray curable adhesive contains a photopolymerization initiator,
The photopolymerization initiator is a compound containing a phosphorus atom and/or a nitrogen atom,
Adhesive sheet. In the first paragraph,
The above active energy ray curable adhesive comprises an active energy ray reactive compound,
The active energy ray reactive compound is a polyfunctional (meth)acrylate having five or more functional groups.
Adhesive sheet. In the first paragraph,
An adhesive sheet used for transferring electronic components. In the first paragraph,
An adhesive sheet used for transferring electronic components, including catching electronic components by a laser lift-off process and then peeling off the electronic components by laser light irradiation. In clause 8 or 9,
An adhesive sheet wherein the electronic component is a mini LED or micro LED. A method for transporting electronic components using an adhesive sheet according to any one of claims 1 to 7. In Article 11,
A first process of transferring a plurality of electronic components arranged on a substrate onto the adhesive layer of the adhesive sheet; and
A second process comprising transferring the electronic component on the adhesive sheet to another member;
Method of transporting electronic components. In Article 12,
A method for transporting electronic components, wherein the same adhesive sheet is used in the first process and the second process.