Adhesive sheet and method for peeling object from adhesive sheet

Abstract

The present invention facilitates the pick up of an object held on an adhesive sheet having an adhesive layer comprising protrusions and recesses on the surface thereof.　This adhesive sheet comprises a base material, and an adhesive layer that has protrusions and recesses on the surface thereof. The adhesive sheet can be extended in the surface direction. When the adhesive sheet is attached to an object, the bonding area ratio of the adhesive sheet to the object is 4%-60%.

Description

Adhesive sheet and method for peeling an object from the adhesive sheet

[0001] The present invention relates to an adhesive sheet and a method for peeling an object from an adhesive sheet.

[0002] Adhesive sheets can be used to temporarily hold an object, for example, to transfer an object to a desired location.

[0003] On the other hand, in order to improve production efficiency, it is also necessary to make it easier to peel objects from adhesive sheets. For example, Patent Document 1 discloses a configuration in which an electronic component is attached to a smooth first adhesive film and the film is irradiated with ultraviolet light to reduce the adhesive strength of the film. In the method described in Patent Document 1, the electronic component is further pressure-bonded to a second adhesive film, and then the first adhesive film is peeled off, thereby transferring the electronic component from the first adhesive film to the second adhesive film.

[0004] Japanese Patent Application Laid-Open No. 2020-61529

[0005] The present inventors have investigated the creation of irregularities on the surface of the adhesive layer of an adhesive sheet. This configuration reduces the sheet's ability to hold an object, making it easier to pick up the object from the sheet for transfer. However, there is a need for a gentler method of picking up the object to enable the peeling of more fragile objects, such as thin semiconductor chips.

[0006] An embodiment of the present invention can facilitate the pickup of an object held on an adhesive sheet having an adhesive layer with an uneven surface.

[0007] As a result of extensive research, the inventors have found that by providing an adhesive layer having an uneven surface so that the contact area between the adhesive layer and an object when the object is attached to the adhesive layer is smaller, it becomes easier to pick up the object, thereby solving the above-mentioned problem. After further research, they have completed the present invention.

[0008] That is, embodiments of the present invention relate to the following [1] to

[12] . [1] A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer having an uneven surface, wherein the pressure-sensitive adhesive sheet is expandable in a plane direction, and when the pressure-sensitive adhesive sheet is attached to an article, the ratio of the adhesive area of ​​the pressure-sensitive adhesive sheet to the article is 4% to 60%. [2] The pressure-sensitive adhesive sheet according to [1], wherein the pressure-sensitive adhesive layer comprises a cross-linked polymer, and the content of the cross-linked polymer relative to the total amount of components constituting the pressure-sensitive adhesive layer is 70 to 100% by mass. [3] The pressure-sensitive adhesive sheet according to any one of [1] to [2], wherein the pressure-sensitive adhesive layer comprises a polymer, and the polymer is an acrylic resin cross-linked with an isocyanate-based cross-linking agent. [4] The pressure-sensitive adhesive sheet according to [3], wherein the amount of the isocyanate-based cross-linking agent relative to 100 parts by mass of the polymer is 2 parts by mass or more. [5] The pressure-sensitive adhesive sheet according to any one of [3] to [4], wherein the acrylic resin further comprises an energy ray-curable group. [6] The pressure-sensitive adhesive sheet according to any one of [2] to [5], wherein the polymer has a mass-average molecular weight of 10,000 or more. [7] The pressure-sensitive adhesive sheet according to any one of [1] to [6], wherein the substrate has a tensile modulus of 2,500 MPa or less. [8] The pressure-sensitive adhesive sheet according to any one of [1] to [7], wherein the pressure-sensitive adhesive layer has a plurality of convex portions spaced apart from one another and defined by concave portions, the plurality of convex portions having a pitch of 1 μm or more and 100 μm or less. [9] The pressure-sensitive adhesive sheet according to any one of [1] to [8], wherein the pressure-sensitive adhesive layer has a plurality of convex portions, the height of the plurality of convex portions being uniform.

[10] The pressure-sensitive adhesive sheet according to any one of [1] to [9], wherein the height of the convex portions of the pressure-sensitive adhesive layer is 1 μm or more.

[11] The pressure-sensitive adhesive sheet according to any one of [1] to

[10] , further comprising a release layer having an uneven surface complementary to the uneven surface of the pressure-sensitive adhesive layer.

[12] A method for peeling an object from an adhesive sheet according to any one of [1] to

[11] , in which the object is held on an adhesive layer, the peeling method comprising: an expansion step of expanding the adhesive layer in a planar direction; and a peeling step of peeling the object from the adhesive layer of the adhesive sheet.

[0009] An embodiment of the present invention can facilitate the pickup of an object held on an adhesive sheet having an adhesive layer with an uneven surface.

[0010] Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which the same or similar elements are designated by the same reference numerals.

[0011] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments of the present invention, and together with the description are used to explain the principles of the present invention. A cross-sectional view of an adhesive sheet according to one embodiment. A cross-sectional view showing an example of the irregularities of an adhesive layer before expansion. A cross-sectional view showing an example of the irregularities of an adhesive layer after expansion. A top view showing an example of the irregularities of an adhesive layer before expansion. A top view showing an example of the irregularities of an adhesive layer after expansion. A top view showing another example of the irregularities of an adhesive layer. A cross-sectional view showing an example of the irregularities of an adhesive layer. A cross-sectional view showing an example of the irregularities of an adhesive layer. A cross-sectional view showing an example of the irregularities of an adhesive layer. A cross-sectional view showing an example of the irregularities of an adhesive layer. A diagram explaining a method for expanding an adhesive sheet. A diagram explaining a method for expanding an adhesive sheet. A flowchart of a method for manufacturing an adhesive sheet according to one embodiment. A flowchart of a peeling method according to one embodiment.

[0012] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be combined in any desired manner. Furthermore, the same reference numerals are used to designate identical or similar components, and redundant descriptions will be omitted.

[0013] (Definitions) In this specification, the mass average molecular weight (Mw) and number average molecular weight (Mn) are values ​​measured by size exclusion chromatography in terms of standard polystyrene, specifically, values ​​measured in accordance with JIS K7252-1: 2016. In addition, in this specification, "(meth)acrylic acid" is a term that refers to both "acrylic acid" and "methacrylic acid," and the same applies to other similar terms.

[0014] In this specification, when one or more lower limits and one or more upper limits of a numerical range (e.g., a range of content, etc.) are described, it can be understood that any combination of lower and upper limits therein is described. For example, a description such as "preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and preferably 9 or less, more preferably 8 or less, even more preferably 7 or less" clearly means that the numerical range may be any of 1 to 9, 1 to 8, 1 to 7, 2 to 9, 2 to 8, 2 to 7, 3 to 9, 3 to 8, and 3 to 7. Furthermore, in this specification, parts by mass and % by mass indicate proportions based on the mass of the solid content, unless otherwise specified.

[0015] (Configuration of Adhesive Sheet) An adhesive sheet according to one embodiment of the present invention comprises a substrate 120 and an adhesive layer 110 having an uneven surface. The adhesive sheet can be used as a transfer sheet for temporarily holding an object and transferring it to a destination. For example, the adhesive sheet can be used to receive an object held on another holding substrate, temporarily hold the object, and transfer the object to a desired position on the destination. The substrate 120 can support the adhesive layer 110. The configuration of such an adhesive sheet will be described below with reference to FIG. 1, which is a schematic diagram of an adhesive sheet according to one embodiment.

[0016] (Substrate) The substrate 120 functions as a support for supporting the adhesive layer 110. The substrate 120 is located on the surface of the adhesive layer 110 opposite to the surface having the irregularities.

[0017] In one embodiment, the adhesive sheet is expandable in the planar direction. From this perspective, a flexible substrate can be used as the substrate 120. Furthermore, by using a flexible substrate as the substrate 120, it is possible to improve cushioning properties when holding an object, facilitate stacking of the adhesive sheet, or form the adhesive sheet into a roll. For example, a resin film can be used as the substrate 120. The resin film is a film in which a resin-based material is used as the main material, and may be made of a resin material or may contain an additive in addition to the resin material. The resin film may be laser light transmissive.

[0018] Specific examples of resin films include polyethylene films such as low-density polyethylene (LDPE) film, linear low-density polyethylene (LLDPE) film, and high-density polyethylene (HDPE) film; polyolefin films such as polypropylene film, polybutene film, polybutadiene film, poly(4-methyl-1-pentene) film, ethylene-norbornene copolymer film, and norbornene resin film; ethylene copolymer films such as ethylene-vinyl acetate copolymer film, ethylene-(meth)acrylic acid copolymer film, and ethylene-(meth)acrylic acid ester copolymer film; polyvinyl chloride films such as polyvinyl chloride film and vinyl chloride copolymer film; polyester films such as polyethylene terephthalate film and polybutylene terephthalate film; polyurethane film; polyimide film; polystyrene film; polycarbonate film; and fluororesin films. Films containing a mixture of two or more materials, crosslinked films in which the resins forming these films are crosslinked, and modified films such as ionomer films may also be used. Furthermore, the substrate 120 may be a laminate film in which two or more resin films are laminated.

[0019] From the viewpoint of facilitating expansion of the PSA sheet, the substrate 120 is preferably a polyolefin film or a vinyl chloride copolymer film. Examples of polyolefin films include polyethylene films, polypropylene films, and copolymers containing unsubstituted olefins such as ethylene or propylene as structural units, such as ethylene copolymers containing ethylene-methacrylic acid copolymer (EMAA). Examples of vinyl chloride copolymer films include vinyl chloride-vinylidene chloride copolymer films, vinyl chloride-vinyl acetate copolymer films, and vinyl chloride-ethylene copolymer films. The form of such copolymers is not particularly limited and may be any of block copolymers, random copolymers, alternating copolymers, and graft copolymers. These films may also contain other resin components or additives.

[0020] The thickness of the substrate 120 is not particularly limited, but from the viewpoint of achieving both supportability and roll winding properties, it is preferably 10 μm or more, more preferably 25 μm or more, and even more preferably 40 μm or more, while it is preferably 500 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, still more preferably 150 μm or less, even more preferably 120 μm or less, and particularly preferably 90 μm or less.

[0021] To facilitate uniform expansion of the PSA sheet, the tensile modulus of the substrate 120 is preferably 50 MPa or more, more preferably 80 MPa or more, even more preferably 120 MPa or more, and is preferably 2500 MPa or less, more preferably 1000 MPa or less, even more preferably 500 MPa or less. In this specification, the tensile modulus is measured in accordance with JIS K7161-1:2014.

[0022] Similarly, to facilitate expansion of the PSA sheet, the breaking elongation of the substrate 120 is preferably 105% or more, more preferably 110% or more, and even more preferably 115% or more. In this specification, the breaking elongation is measured in accordance with JIS K 7127:1999.

[0023] (Adhesive Layer) The adhesive layer 110 is a layer having adhesive properties. As described above, the adhesive layer 110 has unevenness on its surface. The adhesive sheet may have two or more adhesive layers 110. For example, the adhesive sheet may have a laminate of one type or two or more types of adhesive layers 110.

[0024] In one embodiment, the adhesive layer 110 is energy responsive. In this specification, energy responsiveness means that the elastic modulus is improved by the application of energy. For example, the adhesive layer 110 may be energy ray responsive or heat responsive. The type of energy ray is not particularly limited, and examples include ultraviolet rays, electron beams, and ionizing radiation. The energy ray is preferably ultraviolet rays, and therefore the adhesive layer 110 is preferably ultraviolet responsive.

[0025] The following describes examples of the composition of the adhesive layer 110. However, the composition of the adhesive layer 110 is not limited to the following.

[0026] (Resin) The adhesive layer 110 may contain a resin. The adhesive layer 110 may contain one type of resin, or two or more types of resins. Examples of resins contained in the adhesive layer 110 include rubber-based resins such as polyisobutylene-based resins, polybutadiene-based resins, and styrene-butadiene-based resins, acrylic-based resins, urethane-based resins, polyester-based resins, olefin-based resins, silicone-based resins, and polyvinyl ether-based resins. The adhesive layer may be heat-resistant, and examples of materials for the adhesive layer 110 that have such heat resistance include polyimide-based resins and silicone-based resins. The adhesive layer 110 may contain a copolymer having two or more types of structural units. The form of such a copolymer is not particularly limited, and may be any of a block copolymer, a random copolymer, an alternating copolymer, and a graft copolymer.

[0027] The resin contained in the adhesive layer 110 is preferably an adhesive resin that exhibits adhesiveness by itself. In one embodiment, the resin is a polymer having a mass average molecular weight (Mw) of 10,000 or more. From the viewpoint of improving holding power, the mass average molecular weight (Mw) of the resin is preferably 10,000 or more, more preferably 70,000 or more, and even more preferably 140,000 or more. From the viewpoint of suppressing the storage modulus to a predetermined value or less, it is preferably 2,000,000 or less, and more preferably 1,200,000 or less. From the viewpoint of improving holding power, the number average molecular weight (Mn) of the resin is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more. From the viewpoint of suppressing the storage modulus to a predetermined value or less, it is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,200,000 or less. Note that, as described below, when the adhesive layer 110 contains a resin derived from an energy reactive resin, the mass average molecular weight (Mw) and number average molecular weight (Mn) refer to the mass average molecular weight (Mw) and number average molecular weight (Mn) before the crosslinking reaction due to energy application.

[0028] Furthermore, from the viewpoint of improving the holding power of the adhesive layer 110, the glass transition temperature (Tg) of the resin is preferably −75° C. or higher, more preferably −70° C. or higher, and preferably 5° C. or lower, more preferably −20° C. or lower. When the resin has two or more types of structural units, the glass transition temperature (Tg) of the resin can be calculated using Fox's formula. The Tg of the monomer from which the structural unit is derived can be any value listed in the Polymer Data Handbook or the Adhesive Handbook.

[0029] The amount of resin contained in adhesive layer 110 relative to the total amount of components constituting adhesive layer 110 can be set appropriately depending on the desired adhesive strength of adhesive layer 110, but is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and is preferably 99.99% by mass or less, more preferably 99.95% by mass or less, even more preferably 99.90% by mass or less, even more preferably 99.80% by mass or less, and even more preferably 99.50% by mass or less.

[0030] The storage modulus of the adhesive layer 110 is preferably 0.001 MPa or more, more preferably 0.01 MPa or more, even more preferably 0.03 MPa or more, and even more preferably 0.07 MPa or more, from the viewpoint of morphological stability of the uneven shape of the adhesive layer surface. On the other hand, a low storage modulus of the adhesive layer 110 is preferable in that it can suppress positional displacement when holding an object. From this viewpoint, the storage modulus of the adhesive layer 110 is preferably 100 MPa or less, more preferably 50 MPa or less, even more preferably 20 MPa or less, and particularly preferably 5 MPa or less. In this specification, the storage modulus is measured in accordance with JIS K7244-1:1998. Specifically, the storage modulus of the adhesive layer 110 can be measured by preparing a cylindrical sample having a thickness of 3 mm and a diameter of 8 mm, and measuring the storage modulus of the sample using a viscoelasticity measuring device by a torsional shear method at 1 Hz and 23°C.

[0031] In one embodiment, the resin contained in the adhesive layer 110 may include a thermoplastic resin. That is, the adhesive layer 110 may be formed from a thermoplastic resin. When a thermoplastic resin is used, it becomes easy to form irregularities in the adhesive layer 110 by heating the resin to soften it, and it also becomes easy to maintain the irregular shape formed by cooling. Examples of thermoplastic resins include rubber-based resins, acrylic-based resins, urethane-based resins, and olefin-based resins. Examples include polybutadiene-based thermoplastic elastomers using butadiene as a monomer, styrene-based thermoplastic elastomers using styrene as a monomer, and acrylic-based thermoplastic elastomers using (meth)acrylic acid or a (meth)acrylic acid ester as a monomer.

[0032] (Energy-Reactive Component) As described above, the adhesive layer 110 may be energy-reactive. To this end, the adhesive layer 110 may contain an energy-reactive component. The energy-reactive component may be a compound into which a polymerizable functional group has been introduced. The polymerizable functional group is a functional group that crosslinks upon the application of energy. Examples of this polymerizable functional group include multiple bond-containing groups, oxetanyl groups, and epoxy groups. Examples of multiple bond-containing groups include alkenyl groups such as vinyl groups and allyl groups, and double bond-containing groups such as (meth)acryloyl groups. Crosslinking of such polymerizable functional groups proceeds in the presence of an appropriate polymerization initiator or crosslinking agent.

[0033] The energy-reactive component may be a difunctional or polyfunctional monomer having a polymerizable functional group as described above. Examples of such monomers include polyfunctional (meth)acrylates such as difunctional (meth)acrylates. Specific examples of polyfunctional (meth)acrylates include cycloalkyl di(meth)acrylates such as tricyclodecane dimethanol diacrylate.

[0034] (Energy Reactive Resin (A)) In one embodiment, the resin contained in the adhesive layer 110 has energy reactivity. That is, as described above, the adhesive layer 110 may contain an energy reactive resin. Examples of the energy reactive resin include an energy ray reactive resin and a heat reactive resin. The energy reactive resin may be an energy ray curable resin. The heat reactive resin may be a thermosetting resin. In this specification, the energy reactive resin refers to a resin whose elastic modulus improves when energy is applied thereto. On the other hand, a resin whose elastic modulus has already been improved by the application of energy and whose elastic modulus does not improve even when further energy is applied thereto (for example, an ultraviolet curable resin after curing is complete) is not included in the energy reactive resin in this specification.

[0035] In this way, by including an energy reactive resin in the adhesive layer 110, the elastic modulus of the adhesive layer 110 is more likely to be improved when energy is applied. Also, it becomes easier to achieve both the object-holding force of the adhesive layer 110 before energy application and the object-easy peelability of the adhesive layer 110 after energy application. Also, by including an energy reactive resin in the adhesive layer 110, it becomes easier to maintain high adhesive strength before energy application while increasing the ability of the adhesive layer 110 to retain the uneven shape.

[0036] The adhesive layer 110 according to one embodiment includes an energy ray reactive resin, and this energy ray reactive resin is a polymer having an energy ray curable group. This polymer may be a copolymer. Furthermore, this polymer may have a side chain having an energy ray curable group. Examples of the energy ray curable group include the above-mentioned multiple bond-containing groups, an oxetanyl group, and an epoxy group. Preferred examples of the energy ray curable group include alkenyl groups such as a vinyl group and an allyl group, and carbon-carbon double bond-containing groups such as a (meth)acryloyl group. In one embodiment, the energy ray curable group is an ultraviolet ray curable group. When the adhesive layer 110 includes a polymer having an ultraviolet ray curable group, the energy ray curable groups of the polymer can be crosslinked to each other by irradiating the adhesive layer 110 with ultraviolet light.

[0037] In one embodiment, the main component of the adhesive layer 110 is an energy ray reactive resin. From the viewpoint of reducing adhesive strength after curing, the content of the polymer having an energy ray curable group relative to the total amount of components constituting the adhesive layer 110 is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, and on the other hand, is 100% by mass or less, more preferably 99% by mass or more, and even more preferably 98% by mass or less.

[0038] The number of energy ray curable groups in the energy ray reactive resin can be appropriately set depending on the application of the pressure-sensitive adhesive sheet. In one embodiment, from the viewpoint of reducing the adhesive strength after curing, the proportion of the structural units having energy ray curable groups among the structural units constituting the polymer that is the energy ray reactive resin is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 15 mol% or more. Furthermore, from the viewpoint of maintaining the adhesiveness after curing, the proportion of the structural units having energy ray curable groups among the structural units constituting the polymer that is the energy ray reactive resin is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 30 mol% or less.

[0039] On the other hand, as described above, the adhesive layer 110 has an uneven surface. Therefore, it is desirable that the adhesive layer 110 have a degree of elasticity sufficient to maintain the uneven surface even before energy is applied. From this perspective, in one embodiment, the adhesive layer 110 includes a crosslinked polymer. The adhesive layer 110 may also include a crosslinked polymer as a main component. For example, from the perspective of maintaining the uneven surface, the content of the crosslinked polymer relative to the total amount of components constituting the adhesive layer 110 is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, while being 100% by mass or less, more preferably 99% by mass or more, and even more preferably 98% by mass or less. The type of crosslinking is not particularly limited. For example, functional groups such as hydroxyl groups, vinyl groups, (meth)acryloyl groups, amino groups, carboxy groups, or isocyanate groups contained in the polymer may form crosslinks via a crosslinking agent (B) described below, or may form crosslinks directly without the crosslinking agent (B). For example, the polymer may include urethane crosslinks. Urethane crosslinking refers to crosslinking via urethane bonds.

[0040] The crosslinked polymer in the adhesive layer 110 may be a polymer having the above-mentioned energy ray-curable group. That is, the polymer having the energy ray-curable group in the adhesive layer 110 may be crosslinked. For example, the polymer having the energy ray-curable group may have both a side chain having an energy ray-curable group and a crosslinked side chain. Such a polymer can be produced, for example, by preparing a polymer having a side chain having an energy ray-curable group and a side chain having thermal reactivity, and crosslinking the thermally reactive side chains using a crosslinking agent. The specific crosslinking method is not particularly limited. For example, the crosslinking agent may be an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, or a metal chelate-based crosslinking agent. Specifically, the thermally reactive side chain may have a hydroxyl group. In this case, the thermally reactive side chains can be crosslinked using an isocyanate-based crosslinking agent to form a urethane crosslink.

[0041] The number of crosslinks possessed by the energy ray reactive resin can be appropriately set depending on the application of the pressure-sensitive adhesive sheet. In one embodiment, from the viewpoint of maintaining the uneven shape of the surface, the proportion of crosslinked structural units among the structural units constituting the polymer that is the energy ray reactive resin is preferably 0.5 mol% or more, more preferably 1 mol% or more, and even more preferably 1.5 mol% or more. Furthermore, from the viewpoint of increasing adhesive strength, the proportion of structural units having energy ray curable groups among the structural units constituting the polymer that is the energy ray reactive resin is preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less.

[0042] As a more specific example, a polymer having an energy ray-curable group can be prepared by modifying a polymer (including a copolymer) having a first type of structural unit. The first type of structural unit of this polymer has, for example, a hydroxyl group. In the polymer having an energy ray-curable group, the hydroxyl groups of some of the first type of structural units are modified to have a carbon-carbon double bond-containing group via a urethane bond. Furthermore, the hydroxyl groups of another portion of the first type of structural units are modified to form a urethane crosslink.

[0043] Such a polymer can be prepared, for example, by the following method. First, the hydroxyl groups of some of the first type of structural units can be modified using a carbon-carbon double bond-containing compound having an isocyanate group in an equivalent amount less than the hydroxyl groups of the first type of structural units contained in the polymer. Furthermore, urethane crosslinking can be performed between the hydroxyl groups of the remaining part of the first type of structural units using an isocyanate crosslinking agent such as a polyisocyanate compound. In this case, from the viewpoint of reducing adhesive strength after curing while maintaining the surface irregularities, the amount of the carbon-carbon double bond-containing compound having an isocyanate group used is preferably 25% equivalent or more, more preferably 50% equivalent or more, and even more preferably 80% equivalent or more, relative to the hydroxyl groups of the first type of structural units contained in the polymer, while being preferably 99% equivalent or less, more preferably 98% equivalent or less, and even more preferably 95% equivalent or less. Furthermore, the amount of the isocyanate crosslinking agent used may be in excess of the hydroxyl groups of the first type of structural units contained in the polymer.

[0044] (Energy Ray-Curable Acrylic Resin) In one embodiment, the polymer contained in the adhesive layer 110 is an acrylic resin. The adhesive layer 110 may contain an acrylic resin as an energy-reactive resin. The acrylic resin is a resin containing (meth)acrylic acid or a (meth)acrylic acid ester as a monomer.

[0045] Examples of (meth)acrylic acid esters constituting the acrylic resin include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isooctyl (meth)acrylate. The alkyl group constituting the alkyl ester has a chain structure having 1 to 18 carbon atoms (methacrylate), such as acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, myristyl (meth)acrylate, pentadecyl (meth)acrylate, palmityl (meth)acrylate, heptadecyl (meth)acrylate, and stearyl (meth)acrylate. (meth)acrylic acid alkyl esters; (meth)acrylic acid cycloalkyl esters such as isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate; (meth)acrylic acid aralkyl esters such as benzyl (meth)acrylate; (meth)acrylic acid cycloalkenyl esters such as dicyclopentenyl (meth)acrylate; (meth)acrylic acid cycloalkenyloxyalkyl esters such as dicyclopentenyloxyethyl (meth)acrylate; imide (meth)acrylates; glycidyl (meth)acrylate and other glycidyl (meth)acrylates. Examples of the acrylate include ricidyl group-containing (meth)acrylic acid esters; hydroxyl group-containing (meth)acrylic acid esters such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and substituted amino group-containing (meth)acrylic acid esters such as N-methylaminoethyl (meth)acrylate.Here, the term "substituted amino group" refers to a group having a structure in which one or two hydrogen atoms of an amino group are substituted with a group other than a hydrogen atom.

[0046] The acrylic resin may be, for example, a resin obtained by copolymerizing one or more monomers selected from the group consisting of (meth)acrylic acid esters or (meth)acrylic acid, itaconic acid, vinyl acetate, acrylonitrile, styrene, and N-methylolacrylamide.

[0047] The acrylic resin may be a homopolymer or a copolymer. That is, the monomer constituting the acrylic resin may be one type or two or more types, and when two or more types are used, the combination and ratio thereof can be selected arbitrarily.

[0048] As described above, the acrylic resin may have energy reactivity. For example, the acrylic resin may have an energy ray-curable group. Specifically, the acrylic resin may have a side chain having an energy ray-curable group. Such an acrylic resin can be obtained by a polymerization reaction using a monomer having an energy ray-curable group. Alternatively, such an acrylic resin can be obtained by modifying a polymer to introduce an energy ray-curable group. For example, the acrylic resin may contain a hydroxyl group-containing (meth)acrylic acid ester as a structural unit. The energy ray-curable group can be introduced by reacting the hydroxyl group of such an acrylic resin with a compound having an isocyanate group and an energy ray-curable group, such as 2-isocyanatoethyl methacrylate.

[0049] As described above, the acrylic resin may be a crosslinked polymer. For example, the acrylic resin may be crosslinked with an isocyanate-based crosslinking agent. Such an acrylic resin can be obtained by a crosslinking reaction of a polymer. As described above, the acrylic resin may contain a hydroxyl group-containing (meth)acrylic acid ester as a structural unit. By reacting such an acrylic resin with an isocyanate-based crosslinking agent such as a polyisocyanate compound, urethane crosslinking can be performed between the hydroxyl groups of the acrylic resin. The amount of the isocyanate-based crosslinking agent used is not particularly limited. For example, an excess amount of the crosslinking agent relative to the hydroxyl groups of the acrylic resin may be used. In one embodiment, the amount of the isocyanate-based crosslinking agent relative to 100 parts by mass of the polymer is preferably 1.5 parts by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, from the viewpoint of maintaining the uneven shape of the surface of the adhesive layer 110. From the viewpoint of increasing the object retention force of the adhesive layer 110, the amount is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less.

[0050] As described above, the adhesive layer 110 may include an acrylic resin having an energy ray-curable group and crosslinked with an isocyanate-based crosslinking agent. The acrylic resin according to one embodiment includes a hydroxyl group-containing (meth)acrylic ester as a structural unit, some of which have hydroxyl groups modified to have a carbon-carbon double bond-containing group via a urethane bond. The remaining hydroxyl groups are modified to form a urethane crosslink.

[0051] (Other Components of Adhesive Layer) The adhesive layer 110 may contain components other than resin. For example, the adhesive layer 110 may contain one or more of a crosslinking agent (B), a photopolymerization initiator (C), an antioxidant, and other additives.

[0052] Examples of the crosslinking agent (B) include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, and a metal chelate-based crosslinking agent. These crosslinking agents may be used alone or in combination of two or more. The crosslinking agent can be selected according to the resin contained in the adhesive layer 110. The crosslinking agent may be a crosslinking agent for the resin contained in the adhesive layer 110. For example, the crosslinking agent may be a crosslinking agent for an acrylic resin.

[0053] Among these crosslinking agents, isocyanate-based crosslinking agents are preferred from the viewpoints of increasing cohesive force and maintaining the uneven shape, ease of availability, etc. Examples of the isocyanate-based crosslinking agent include polyvalent isocyanate compounds such as aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; alicyclic polyisocyanates such as dicyclohexylmethane-4,4'-diisocyanate, bicycloheptane triisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, methylenebis(cyclohexyl isocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, and hydrogenated xylylene diisocyanate; and acyclic aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. Further, examples of the isocyanate crosslinking agent include a trimethylolpropane adduct modified product of the polyisocyanate compound, a biuret modified product obtained by reacting the polyisocyanate compound with water, and an isocyanurate modified product containing an isocyanurate ring.

[0054] The adhesive layer 110 may contain one type of crosslinking agent, or may contain two or more types of crosslinking agents. From the viewpoint of appropriately carrying out the crosslinking reaction, the content of the crosslinking agent in the adhesive layer 110 is preferably 1% by mass or more, more preferably 1.5% by mass or more, even more preferably 2% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less. Here, the content of the crosslinking agent in the adhesive layer 110 includes the amount of crosslinking agent that has formed crosslinks, in addition to the amount of unreacted crosslinking agent.

[0055] The photopolymerization initiator (C) initiates a crosslinking reaction in response to the application of energy (for example, irradiation with an energy ray such as ultraviolet light). When the adhesive layer 110 contains the energy reactive resin (A), the adhesive layer 110 further contains the photopolymerization initiator (C), and thus the crosslinking reaction proceeds even when a relatively low amount of energy is applied.

[0056] Examples of the photopolymerization initiator (C) include 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0057] The adhesive layer 110 may contain one type of polymerization initiator or may contain two or more types of polymerization initiators. The content of the photopolymerization initiator in the adhesive layer 110 is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less.

[0058] Examples of antioxidants include phenol-based antioxidants such as hindered phenol-based compounds, aromatic amine-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants such as phosphate ester-based compounds.

[0059] Other additives that may be contained in the adhesive layer 110 are not particularly limited, but examples thereof include ultraviolet absorbers such as benzotriazole-based compounds, oxazolic acid amide compounds, or benzophenone-based compounds; light stabilizers such as hindered amine-based, benzophenone-based, or benzotriazole-based compounds; resin stabilizers such as imidazole-based resin stabilizers, dithiocarbamate-based resin stabilizers, phosphorus-based resin stabilizers, or sulfur ester-based resin stabilizers; fillers, pigments, extenders, and softeners.

[0060] When the adhesive layer 110 contains these additives, the content of the additives in the adhesive layer 110 is preferably 0.0001% by mass or more, more preferably 0.01% by mass or more, particularly preferably 0.1% by mass or more, even more preferably 1% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less.

[0061] (Shape of Adhesive Layer) The surface of the adhesive layer 110 according to this embodiment has projections and depressions. In one embodiment, the adhesive layer 110 has a plurality of projections on its surface that are spaced apart and bounded by depressions. Each of the projections may be spaced apart by a depression that is continuous across the entire adhesive layer 110.

[0062] 2A and 2B are side views showing the shape of the adhesive layer 110, and FIGS. 3A to 3C are top views showing the shape of the adhesive layer 110. FIGS. 2A and 3A show an example of the adhesive layer 110 before expansion, and FIGS. 2B and 3B show an example of the adhesive layer 110 after expansion. In addition, while FIGS. 2A and 2B depict the object 140 held by the convex portions 111 of the adhesive layer 110, FIGS. 3A to 3C omit the object 140 held by the convex portions 111.

[0063] As shown in Figures 2A and 3A, the convex portions 111 may be regularly arranged on the surface of the adhesive layer 110. Regularly arranged convex portions means that the convex portions are lined up in a straight line at regular intervals. On the other hand, the convex portions 111 may be arranged so that the intervals between them vary regularly. For example, the intervals between the convex portions may be short in the center of the adhesive sheet and long in the peripheral portion of the adhesive sheet. Furthermore, the convex portions may be arranged irregularly.

[0064] 3C is a top view showing another shape of the adhesive layer 110. As shown in FIG. 3C, stripe-shaped convex portions 111 may be provided on the surface of the adhesive layer 110. In FIG. 3C, linear convex portions 111 having a constant width are arranged at regular intervals. The width or interval of these linear convex portions 111 may vary regularly, or the linear convex portions 111 may be arranged irregularly.

[0065] The pitch P of the convex portions 111 before expansion is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and even more preferably 15 μm or more, from the viewpoint of adjusting the holding force. On the other hand, from the viewpoint of increasing the contact area between the adhesive layer 110 and the object and thereby increasing the holding force, this pitch P is preferably 100 μm or less, more preferably 75 μm or less, even more preferably 50 μm or less, even more preferably 35 μm or less, and even more preferably 25 μm or less. Here, the pitch P of the convex portions 111 refers to the distance between the center point of an arbitrarily selected convex portion 111 and the center point of another convex portion 111 closest to that convex portion 111. For example, in the case of FIG. 2A, the pitch P of the convex portions 111 represents the distance between the center point of the convex portion 111 on a straight line on which the convex portions 111 are arranged at regular intervals and the center point of another convex portion 111 closest to that convex portion 111. When the convex portions 111 are arranged on a plurality of straight lines, the pitch P represents the distance between the center points of the convex portions on the straight line on which the convex portions 111 are arranged at the shortest pitch. In this specification, the spacing between the convex portions 111 means the spacing between the centers of the convex portions.

[0066] The specific shape of the protrusions 111 is not particularly limited. For example, the protrusions 111 may have a pillar shape. Specific examples of the protrusions 111 include a cylindrical shape, a prismatic shape, a conical shape, a pyramidal shape, a spherical shape, and a hemispherical shape. Furthermore, as described above, the protrusions 111 may extend in a linear shape, or may extend in a curved shape such as a wavy shape. Furthermore, the protrusions 111 may be tapered or inverted tapered.

[0067] Fig. 4A shows a cross-sectional view of an adhesive layer 110 according to one embodiment, passing through a protrusion 111 and perpendicular to the surface of the adhesive layer 110. The protrusion 111 shown in Fig. 4A is tapered, i.e., the protrusion 111 is tapered. Furthermore, as shown in Fig. 4B, the tip of the protrusion 111 may be curved. With this configuration, the impact when holding an object with the adhesive layer 110 is further alleviated, making it easier for the adhesive layer 110 to hold the object without slipping. On the other hand, the tip of the protrusion may be flat.

[0068] 4A, the surface of the adhesive layer 110 may have flat recesses and protruding portions 111 protruding from the recesses. In this manner, the adhesive layer 110 has a plurality of protruding portions 111 that are spaced apart from one another and may be bounded by the recesses.

[0069] As another example, the convex portions may be hemispherical or partial spheres as shown in Figure 4B. Furthermore, the convex portions 111 may be T-shaped as shown in Figure 4C. As yet another example, the convex portions 111 may have a shape of a collection of particles, a mushroom shape, the surface of a lotus leaf, or a needle shape. As yet another example, the surface of the adhesive layer 110 may be rough or fibrous, and such a surface may also be said to have irregularities.

[0070] The width or diameter of each protrusion 111 is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 5 μm or more, and even more preferably 10 μm or more, from the viewpoint of maintaining the holding force of the object. On the other hand, from the viewpoint of improving the ease of peeling the object, it is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, and even more preferably 20 μm or less. Here, the width and diameter of the protrusion 111 refer to the minimum distance and maximum distance (represented by W in FIG. 4A ) between two parallel lines that contact the protrusion 111 from both sides on the surface of the recess.

[0071] In addition, the area of ​​each of the protrusions 111 is preferably 10 μm from the viewpoint of maintaining the holding force of the object. ２ More preferably, 20 μm or more ２ More preferably, 30 μm or more ２ On the other hand, from the viewpoint of increasing the ease of peeling off the object, it is preferable that the thickness is 2000 μm. ２ Less than 1000 μm, more preferably ２ More preferably, 500 μm or less ２ Here, the area of ​​the convex portion 111 means the area of ​​the portion protruding from the surface of the concave portion (the area of ​​a circle with a diameter W in the case of FIG. 4A).

[0072] In one embodiment, the height of each protrusion 111 is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more, from the viewpoint of increasing the ease of peeling an object. On the other hand, from the viewpoint of increasing the holding power of an object, the height of each protrusion 111 is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. This allows the holding power of an object to be changed. Here, the height of the protrusion 111 is represented by H in FIG. 4A. Also, in one embodiment, the heights of the multiple protrusions in the adhesive layer 110 are uniform. In another embodiment, the adhesive layer 110 may have a first multiple protrusions having a first uniform height and a second multiple protrusions having a different height. Here, the second multiple protrusions may have a second uniform height. For example, the protrusions 111 may be composed of such first protrusions and second protrusions. In a further embodiment, the adhesive layer 110 may have multiple protrusions of random heights.

[0073] Furthermore, the total area of ​​the protrusions 111 relative to the area of ​​the adhesive layer 110 is preferably 1% or more, more preferably 5% or more, even more preferably 10% or more, even more preferably 18% or more, and even more preferably 40% or more, from the viewpoint of maintaining the holding power of the object. On the other hand, the total area of ​​the protrusions relative to the area of ​​the adhesive layer 110 is preferably 95% or less, more preferably 75% or less, and even more preferably 60% or less, from the viewpoint of improving the ease of peeling the object.

[0074] (Characteristics of Adhesive Layer) As described above, in one embodiment, the adhesive layer 110 is energy responsive. Therefore, by applying energy to the adhesive layer 110 (for example, by irradiating it with energy rays), the elastic modulus of the adhesive layer 110 increases. Furthermore, by applying energy to the adhesive layer 110, the adhesive force of the adhesive layer 110 decreases.

[0075] In one embodiment, from the viewpoint of improving the holding power of an object, the adhesive strength of the adhesive layer before energy application (e.g., before energy ray irradiation) is preferably 2000 mN / 25 mm or more, more preferably 2200 mN / 25 mm or more, and even more preferably 2500 mN / 25 mm or more, or may be 6000 mN / 25 mm or less. Furthermore, from the viewpoint of facilitating peeling of an object, the adhesive strength of the adhesive layer after energy application (e.g., after energy ray irradiation) is preferably 100 mN / 25 mm or less, more preferably 70 mN / 25 mm or less, and even more preferably 50 mN / 25 mm or less, or may be 25 mN / 25 mm or more.

[0076] The adhesive strength of the adhesive layer 110 can be measured using a tensile tester under an environment of 23°C and 50% RH (relative humidity) in accordance with JIS Z0237:2000. Such adhesive strength can be adjusted by controlling the composition of the adhesive layer 110. For example, increasing the amount of crosslinking agent (B) used in the adhesive layer 110 tends to decrease the adhesive strength before and after energy application. Furthermore, in order to decrease the adhesive strength after energy application, the number of energy ray-curable groups contained in the adhesive layer 110 can be increased.

[0077] In one embodiment, the adhesive area ratio of the adhesive sheet to the object when the adhesive sheet is attached to the object is preferably 60% or less, more preferably 30% or less, even more preferably 15% or less, and particularly preferably 10% or less, from the viewpoint of facilitating picking up of the object from the adhesive sheet, and this adhesive area ratio is preferably 4% or more, and more preferably 5% or more, from the viewpoint of improving the holding power of the object.

[0078] This adhesion area ratio refers to the ratio of the area of ​​the contact surface between the adhesive sheet and the object to the area of ​​the adhesive sheet itself. This adhesion area ratio can be calculated based on the area of ​​the contact surface between the adhesive sheet and the silicon wafer, which is evaluated by pressing the adhesive sheet onto a silicon wafer using a laminator, leaving it to stand for 10 minutes, and then observing the resulting sample under a microscope. This adhesion area ratio refers to a value evaluated before applying energy to the adhesive layer 110. This adhesion area ratio can be adjusted by controlling the composition of the adhesive layer 110. For example, increasing the amount of crosslinking agent (B) used in the adhesive layer 110 tends to decrease the adhesion area ratio. Furthermore, to reduce the adhesion area ratio, a resin with a lower elastic modulus can be used as the material for the adhesive layer 110.

[0079] In one embodiment, the gel fraction of the adhesive layer 110 is preferably 90% or more, more preferably 92% or more, and even more preferably 94% or more, from the viewpoint of easily maintaining the uneven shape of the adhesive layer 110. The gel fraction of the adhesive layer 110 is 100% or less, and from the viewpoint of increasing the holding power of an object, it is preferably 98% or less, and more preferably 96% or less. This gel fraction refers to a value evaluated before applying energy to the adhesive layer 110.

[0080] The gel fraction is evaluated based on the mass before and after the solvent immersion and drying treatments. Specifically, the gel fraction represents the ratio of the mass after the treatment to the mass before the treatment. In the immersion treatment, the test sample is immersed in toluene at room temperature (23°C) for 168 hours. In the drying treatment, the sample is dried at 100°C for 2 hours. Such a gel fraction can be adjusted by controlling the composition of the adhesive layer 110. For example, the gel fraction tends to increase by increasing the amount of crosslinking agent (B) used in the adhesive layer 110.

[0081] Furthermore, the adhesive sheet according to one embodiment is expandable in the planar direction. The adhesive layer 110 shown in FIGS. 2A and 3A is transformed into the adhesive layer 110' shown in FIGS. 2B and 3B by expanding the adhesive sheet. Comparing the adhesive layer 110 and the adhesive layer 110', the pitch P per convex portion 111 is enlarged in the adhesive layer 110' due to expansion, and the number of convex portions 111 that hold one object 140 is reduced. This reduces the force with which the convex portions 111 hold the object 140 in the adhesive layer 110' compared to the adhesive layer 110. Furthermore, shear stress acts between the convex portions 111 and the object 140 due to expansion of the adhesive sheet. The inventors of the present application believe that this also leads to a reduction in the holding force of the convex portions 111 to the object 140. The adhesive sheet according to one embodiment may be expandable by 1% or more in the planar direction (e.g., one direction or two orthogonal directions) or by 5% or more, from the viewpoint of sufficiently reducing the holding force of the object.

[0082] (Release Layer) Furthermore, the pressure-sensitive adhesive sheet according to this embodiment may have a release sheet 150 in contact with the pressure-sensitive adhesive layer 110, as shown in Fig. 1. For the sake of explanation, Fig. 1 shows a state in which the pressure-sensitive adhesive layer 110 and the release sheet 150 are separated. As shown in Fig. 1, the release sheet 150 has an uneven surface that is complementary to the uneven surface of the pressure-sensitive adhesive layer 110.

[0083] The release sheet 150 has a release layer 160. The release layer 160 is a layer that is easily peelable from the adhesive layer 110. The release layer 160 may have an uneven surface that is complementary to the uneven surface of the adhesive layer 110. That is, the release layer 160 has recesses 161, and the recesses 161 have a shape that is complementary to the protrusions 111. However, it is not essential that the recesses 161 have a shape that is complementary to the protrusions 111.

[0084] The release sheet 150 may have a substrate 170 on the surface that does not contact the adhesive layer 110. This substrate 170 can be designed similarly to the substrate 120, but does not need to have the same composition or structure as the substrate 120. In addition, the release sheet 150 may have an undercoat layer (not shown) between the release layer 160 and the substrate 170.

[0085] (Other Layers) The above sheet may have layers other than the substrate 120 and the adhesive layer 110. For example, an additional adhesive layer may be provided on the surface of the substrate 120 opposite the adhesive layer 110. The sheet can be attached to another object via such an adhesive layer. The type of the additional adhesive layer is not particularly limited, and the additional adhesive layer can be formed using, for example, a general adhesive.

[0086] (Method for Manufacturing Adhesive Sheet) There are no particular limitations on the method for manufacturing the adhesive sheet and the adhesive layer 110. An example of a method for manufacturing an adhesive sheet will be described below with reference to FIG.

[0087] In S610, a material layer containing the material of the adhesive layer 110 is formed on the substrate 120. First, an adhesive composition is prepared by adding an organic solvent to a raw material composition containing the above-mentioned components of the adhesive layer 110. Then, this solution is applied to the substrate 120 to form a coating film, which is then dried, thereby providing a material layer on the substrate 120.

[0088] When forming the adhesive layer 110 containing a polymer having an energy ray-curable group, the adhesive composition may contain a polymer having an energy ray-curable group. In this case, a material layer containing a polymer having an energy ray-curable group is formed. Furthermore, when the adhesive layer 110 contains a crosslinked polymer (e.g., a polymer having a crosslinked energy ray-curable group), the adhesive composition may contain a polymer before crosslinking. Furthermore, the adhesive composition may contain a crosslinking agent. In this case, a material layer containing the polymer before crosslinking and the crosslinking agent is formed.

[0089] Examples of organic solvents used to prepare the pressure-sensitive adhesive composition include toluene, ethyl acetate, methyl ethyl ketone, etc. Examples of methods for applying the solution include spin coating, spray coating, bar coating, knife coating, roll coating, roll knife coating, blade coating, die coating, gravure coating, and printing methods (e.g., screen printing and inkjet printing).

[0090] In S620, irregularities are formed on the surface of the material layer thus formed. There are no particular limitations on the process for forming irregularities on the surface of the material layer. For example, irregularities can be formed on the surface of the material layer using an imprinting method. In the imprinting method, a mold having an irregular surface complementary to the irregularities to be formed can be used. In this way, an adhesive layer 110 having an irregular surface is formed. Specifically, the material layer is pressed with the mold, heated and maintained for a predetermined period of time, and then cooled and the mold is removed. When heating the material layer, for example, the material layer can be heated to a temperature higher than the softening point of the material layer. A specific method for heating the material layer while pressing it with the mold includes vacuum laminating the material layer provided on the substrate 120 and the mold. Alternatively, a release sheet 150 having a release layer 160 having irregularities as described above may be used as the mold.

[0091] On the other hand, to improve the retention of the uneven shape, energy may be applied to the material layer when forming the unevenness on the surface of the material layer. By promoting a curing reaction in the material layer through the application of energy, the elastic modulus of the adhesive layer 110 can be increased, thereby improving the retention of the uneven shape. As a specific example, the adhesive layer 110 having an uneven surface can be formed by thermally curing the material layer while bringing a mold having an uneven surface complementary to the unevenness into contact with the material layer. In one embodiment, a crosslinking reaction is used as the curing reaction. As described above, when the material layer contains a pre-crosslinked polymer and a crosslinking agent, the crosslinking reaction proceeds by heating the material layer while pressing it with the mold, and an adhesive layer 110 containing a crosslinked polymer is formed. In particular, when the adhesive composition contains a polymer having energy ray-curable groups before crosslinking, the crosslinking reaction by heating can leave unreacted energy ray-curable groups in the adhesive layer 110.

[0092] As another method, the adhesive layer 110 having a rough surface can be provided by spray-coating the adhesive composition. Furthermore, the adhesive layer 110 having a rough or fibrous surface can be provided by adding a filler to the adhesive composition and coating such a solution. As yet another method, the adhesive layer 110 having a textured shape can be directly provided on the substrate 120 by applying the adhesive composition according to a desired pattern using a printing method such as an inkjet method.

[0093] (Method of Using the Adhesive Sheet) The adhesive sheet according to this embodiment can be used to handle an object. For example, the adhesive sheet according to this embodiment can be used to temporarily hold an object. The adhesive sheet according to this embodiment can also be used to transfer an object. As a specific example, the adhesive sheet according to this embodiment can be used to transfer a semiconductor chip obtained by dicing to a desired position.

[0094] The method for handling an object using the adhesive sheet according to this embodiment will be described with reference to the flowchart of FIG.

[0095] (S710: Holding an Object) In S710, an object is held on the adhesive layer of the adhesive sheet according to this embodiment. The type of object is not particularly limited. The object may be, for example, an element. Examples of elements include semiconductor chips such as LED chips, semiconductor chips with protective films, and semiconductor chips with die attach films (DAFs). The element may also be a micro light-emitting diode, a mini light-emitting diode, a power device, a MEMS (Micro Electro Mechanical Systems), or a controller chip, or a component thereof. The element may also be a singulated object such as a wafer, panel, or substrate. The element may have a circuit surface on which an integrated circuit having circuit elements such as transistors, resistors, and capacitors is formed. The element is not necessarily limited to a singulated object, and may also be various unsingulated wafers or substrates.

[0096] The size of the object is not particularly limited. For example, the size of the object is preferably 100 μm. ２ More preferably, 500 μm or more ２ More preferably, 1000 μm or more ２ On the other hand, the size of the object is preferably 100 mm or more. ２ Less than 25 mm, more preferably ２ Less than 1 mm, more preferably ２ The following is the result.

[0097] Examples of wafers include semiconductor wafers such as silicon wafers, silicon carbide (SiC) wafers, and compound semiconductor wafers (e.g., gallium phosphide (GaP) wafers, gallium arsenide (GaAs) wafers, indium phosphide (InP) wafers, and gallium nitride (GaN) wafers). The size of the wafer is not particularly limited, but is preferably 6 inches (diameter approximately 150 mm) or larger, and more preferably 12 inches (diameter approximately 300 mm) or larger. The shape of the wafer is not limited to a circle, and may be an angular shape such as a square or rectangle.

[0098] The panel may be a fan-out type semiconductor package (e.g., FOWLP or FOPLP). That is, the workpiece may be a semiconductor package before or after singulation in a fan-out type semiconductor package manufacturing technique. The size of the panel is not particularly limited, but may be, for example, a rectangular substrate of about 300 to 700 mm.

[0099] The substrate may be a glass substrate, a sapphire substrate, or a compound semiconductor substrate.

[0100] In one embodiment, elements are transferred from a holding substrate to an adhesive sheet, and the adhesive sheet holds the transferred elements. For example, a semiconductor wafer can be attached to a wafer substrate, and the semiconductor wafer can then be diced. The elements on the wafer substrate obtained by dicing can then be brought into close contact with the adhesive layer 110 of the adhesive sheet. Thereafter, the adhesion between the wafer substrate and the elements can be reduced by applying an external stimulus such as laser light. This process allows the elements to be transferred from the wafer substrate to the adhesive sheet. Alternatively, elements obtained by dicing a semiconductor wafer can be transferred to a holding substrate to obtain a holding substrate with elements attached thereto. The elements attached to the holding substrate can then be transferred to the adhesive layer 110 of the adhesive sheet in a similar manner.

[0101] In another embodiment, an external stimulus may be used to separate an element attached to a holding substrate from the holding substrate. Specifically, the element moves away from the holding substrate relative to the holding substrate. Alternatively, the element moves closer to the adhesive sheet relative to the holding substrate. Then, when the element comes into contact with the adhesive layer 110 of the adhesive sheet, the element is separated from the holding substrate and captured by the adhesive sheet. The type of external stimulus is not particularly limited, but examples include application of energy, cooling, expansion of the holding substrate, and physical stimulation (e.g., pressing the back surface of the holding substrate with a pin, etc.). By using one or more of these external stimuli, the bonding force between the holding substrate and the element can be reduced and the element can be separated from the holding substrate. For example, the element can be separated from the holding substrate by irradiation with laser light (laser lift-off method). In such an embodiment, pressure is generated between the element and the adhesive layer 110 as the separated element approaches the adhesive layer 110. However, the uneven surface of the adhesive layer 110 reduces the pressure generated between the element and the adhesive layer 110, making it easier to capture the element at the desired position on the adhesive sheet.

[0102] In a further embodiment, a semiconductor wafer is attached to the adhesive layer 110 of the adhesive sheet. Then, elements are formed by dicing the semiconductor wafer on the adhesive layer 110. This method also allows the adhesive sheet to hold elements.

[0103] (S720: Adhesive Strength Reduction Process) In S720, the adhesive strength of the adhesive layer 110 holding the object is reduced. To reduce the adhesive strength, one or both of a processing step of applying energy to the adhesive sheet and an expansion step of expanding the adhesive sheet in the planar direction can be performed. By applying energy to the energy-reactive adhesive layer 110, the elastic modulus of the adhesive layer 110 increases, and the adhesive strength is reduced. Furthermore, by expanding the adhesive sheet in the planar direction, the holding force of the adhesive layer 110 to the object is reduced, as described above.

[0104] In the treatment step, energy can be applied according to the type of adhesive layer 110. For example, if the adhesive layer 110 is energy ray reactive, the adhesive sheet can be irradiated with energy rays in the treatment step.

[0105] The amount of energy applied in the treatment step can be set depending on the type of adhesive layer 110 and the desired adhesive strength. For example, when irradiating with ultraviolet light, the amount of ultraviolet light is set to 20 mJ / cm from the viewpoint of sufficiently reducing the adhesive strength. ２ It is preferable that the concentration is 100 mJ / cm or more. ２ From the viewpoint of shortening the treatment time, the amount of ultraviolet light is more preferably 1000 mJ / cm. ２ Preferably, it is 500 mJ / cm or less. ２ More preferably, it is:

[0106] Furthermore, in the treatment step, it is possible to irradiate an amount of energy rays that reduces the adhesive strength of the adhesive layer 110. For example, from the viewpoint of facilitating peeling of the object, it is possible to irradiate an amount of energy rays that makes the adhesive strength of the adhesive layer 110 preferably 100 mN / 25 mm or less, more preferably 70 mN / 25 mm or less, and even more preferably 50 mN / 25 mm or less. Furthermore, in the treatment step, it is possible to irradiate an amount of energy rays that increases the elastic modulus of the adhesive layer 110.

[0107] In the expansion step, the pressure-sensitive adhesive sheet is expanded in the planar direction. The expansion method of the pressure-sensitive adhesive sheet is not particularly limited. For example, the pressure-sensitive adhesive sheet may be expanded in one direction, two directions, or multiple other directions. The expansion rate of the pressure-sensitive adhesive sheet is also not particularly limited. For example, from the viewpoint of sufficiently reducing the holding force of an object, the expansion rate of the pressure-sensitive adhesive sheet in one direction may be 1% or more, or may be 5% or more. Furthermore, from the viewpoint of preventing breakage of the pressure-sensitive adhesive sheet, the expansion rate of the pressure-sensitive adhesive sheet in one direction may be 50% or less, or may be 20% or less. From the same viewpoint, the expansion rate of the pressure-sensitive adhesive sheet in two mutually perpendicular directions may be 1% or more, or may be 5% or more, or may be 50% or less, or may be 20% or less.

[0108] As a specific example, the adhesive sheet can be expanded by fixing the adhesive sheet to a frame and pressing a base against the adhesive sheet inside the frame. Such an example will be described with reference to FIGS. 5A and 5B. FIG. 5A shows a state in which the adhesive sheet holds objects 140a to 140d. As shown in FIG. 5A, the outer periphery of the adhesive sheet can be fixed to a frame 320. The shape of the frame 320 is not particularly limited. For example, the frame 320 may be a circular or rectangular frame-shaped member having an opening. In one embodiment, a circular ring frame is used as the frame. Using a ring frame allows the adhesive sheet to expand in all directions.

[0109] The adhesive sheet fixed to the frame 320 is then brought into contact with the base 310, and the frame 320 is then displaced (pulled down) toward the base 310 as shown in FIG. 5B , thereby expanding the adhesive sheet. The configuration of the base 310 is not particularly limited, and may be, for example, cylindrical or rectangular. The base 310 may also be mesh-shaped or ring-shaped. The frame 320 may be displaced relative to the base 310 at a speed of, for example, 0.1 mm / sec or more, or 1 mm / sec or more. In this case, the displacement amount of the frame 320, i.e., the pull-down amount, may be, for example, 1 mm or more or 5 mm or more, from the viewpoint of sufficiently reducing the holding force of the object. On the other hand, the displacement amount of the frame 320 may be 30 mm or less or 20 mm or less, from the viewpoint of suppressing damage to the adhesive sheet.

[0110] (S730: Peeling Off the Object) After reducing the adhesive force of the adhesive layer 110, in S730, the object is peeled off from the adhesive layer 110 of the adhesive sheet. For example, after the treatment process and the expansion process have been performed, the object can be peeled off from the adhesive layer 110 of the adhesive sheet. The method for peeling off the object is not particularly limited. For example, the method described above can be used to transfer an object attached to a holding substrate to an adhesive sheet. As an example, the object can be peeled off from the adhesive layer 110 of the adhesive sheet using an adsorption member such as a vacuum collet. The adsorbed object can then be moved to a desired transfer location. By reducing the holding force of the adhesive layer 110 as in this embodiment, the object can be peeled off from the adhesive layer 110 of the adhesive sheet without applying a physical stimulus, such as pressure from the opposite side of the adhesive layer 110 using a pin or the like. However, the object may also be peeled off from the adhesive layer 110 of the adhesive sheet while applying a physical stimulus from the opposite side of the adhesive layer 110 of the adhesive sheet.

[0111] According to the inventors' investigations, when attempting to peel an object from the adhesive layer 110, increasing the suction force in accordance with the holding strength of the adhesive layer 110 makes the object, such as a device, more likely to be damaged. In particular, when peeling a thin object, such as a device, increasing the suction force makes the object more likely to be damaged. On the other hand, decreasing the adhesive strength of the adhesive layer 110 reduces the holding strength of the object in the adhesive layer 110. For example, when transferring a device obtained by dicing from a wafer substrate to an adhesive sheet, if the adhesive strength of the adhesive layer 110 is low, part of the device may remain on the wafer substrate. In this embodiment, by using a process to reduce the adhesive strength, it is possible to achieve both high holding strength of the adhesive layer 110 when holding an object on the adhesive sheet and low holding strength of the adhesive layer 110 when peeling the object from the adhesive sheet. From this perspective, the handling method and adhesive sheet of this embodiment are suitable for handling thin objects. For example, the thickness of the object held by the adhesive sheet is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less.

[0112] According to the above-described procedure, an object can be transferred to any desired destination using the adhesive sheet. Also, one embodiment of the present invention relates to a method for peeling an object from an adhesive sheet holding the object on the adhesive layer. Such a peeling method can include a step of reducing adhesive strength as in S720 and a step of peeling the object as in S730.

[0113] Furthermore, such a peeling method can be used to manufacture electronic components or semiconductor devices having elements. For example, a method for manufacturing an article according to one embodiment of the present invention can include, in addition to the step of peeling an object from a pressure-sensitive adhesive sheet according to the above-described peeling method, a step of manufacturing the article by performing post-processing on the object. In the example of Figure 7, in S740, a post-processing step is performed on the object. The type of post-processing is not particularly limited. For example, processes such as wiring formation, backmetal formation, cleaning, plating, singulation, thinning, and encapsulation can be performed.

[0114] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0115] The following compounds were used in the examples and comparative examples. <Component (A): Acrylic Ester Copolymer> The following acrylic ester copolymer was used: (A1) An acrylic copolymer (monomer mass ratio: butyl acrylate / methyl methacrylate / 2-hydroxyethyl acrylate = 52 / 20 / 28) was reacted with 90% equivalent of 2-isocyanatoethyl methacrylate relative to the 2-hydroxyethyl acrylate, thereby introducing energy ray reactive groups into the polymer side chains via hydroxyl groups (mass average molecular weight (Mw): 520,000, number average molecular weight (Mn): 155,000).

[0116] <Component (B): Crosslinking Agent> As the crosslinking agent, an isocyanurate type polyisocyanate derived from hexamethylene diisocyanate was used.

[0117] <Component (C): Photopolymerization Initiator> The following photopolymerization initiator was used: (C1) 1-hydroxycyclohexyl phenyl ketone

[0118] Examples 1 to 4 Pressure-sensitive adhesive compositions were prepared by dissolving in toluene the acrylic acid ester copolymer (A1), crosslinking agent (B), and photopolymerization initiator (C1) in the amounts shown in Table 1. Table 1 shows the solid content parts by mass of each material.

[0119] This pressure-sensitive adhesive composition was applied to the release-treated surface of a release sheet (finely embossed release sheet) with a concave pattern, and the resulting coating was dried at 100°C for 2 minutes to form a 25 μm thick adhesive layer. The concave-convex pattern on the surface of the formed adhesive layer was a grid-like arrangement of pillars, similar to that shown in Figure 2A. The pitch P between pillars on the adhesive sheet was 20 μm. Furthermore, as shown in Figure 4A, each pillar had a height (H) of 8 μm, a tip diameter (T) of 8 μm, and a base diameter (W) of 16 μm. The release sheet used had a concave pattern on its surface that was complementary to the concave-convex pattern.

[0120] An adhesive sheet was produced by laminating the non-embossed surface of a substrate (ethylene methacrylic acid copolymer (EMAA) film, acid content 9% by mass, one surface embossed to give a matte finish, thickness 80 μm, tensile modulus 160 MPa) onto the adhesive layer thus obtained.

[0121] Comparative Example 1 A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the amount of crosslinking agent (B) shown in Table 1 was used, and a pressure-sensitive adhesive sheet was produced.

[0122] (Comparative Example 2) When forming the adhesive layer, in addition to heat drying, an ultraviolet irradiator (manufactured by Heraeus) was used to irradiate the adhesive layer with an illuminance of 130 mW / cm ２ , light intensity 210mJ / cm ２ A pressure-sensitive adhesive composition was prepared and a pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the ultraviolet light was irradiated at 1000 kJ / cm 2 .

[0123] <Evaluation of Pickup Property> The pickup property of an object held by the pressure-sensitive adhesive sheet obtained in each Example and Comparative Example was evaluated as follows: First, the adhesive layer of the pressure-sensitive adhesive sheet obtained in each Example and Comparative Example was attached to a ring frame (made of stainless steel, inner diameter 194 mm), and the pressure-sensitive adhesive sheet was cut to fit the outer diameter of the ring frame.

[0124] Next, a wafer substrate (ground silicon wafer, 6 inches, 50 μm thick) was fixed to a separately prepared dicing tape. The wafer substrate was then diced into 8 mm x 8 mm squares to obtain multiple elements (silicon chips, element size 8 mm x 8 mm x 50 μm). The multiple elements obtained were attached to the adhesive layer of the adhesive sheet at the center of the inner side of the ring frame so that the ground surface was attached to the adhesive layer. The attachment was performed by lamination at room temperature (23°C). The dicing tape was then peeled off to transfer the multiple elements from the dicing tape to the adhesive sheet. In this way, an adhesive sheet on which multiple elements were placed and supported by a ring frame was obtained as an evaluation sample.

[0125] The obtained evaluation sample was irradiated with an ultraviolet irradiator (manufactured by Heraeus) at an illuminance of 130 mW / cm ２ , light intensity 210mJ / cm２ UV light was irradiated.

[0126] The evaluation sample after UV irradiation was set in a pickup device (Canon Machinery Inc., product name "BESTEM-D510"). After expanding the adhesive sheet, an attempt was made to pick up the element using a vacuum suction collet. The adhesive sheet was expanded as shown in FIGS. 5A to 5B. That is, with the element supported by the base 310 over the adhesive sheet, the ring frame 320 was pulled down 10 mm relative to the base 310, thereby expanding the adhesive sheet. This evaluation also evaluated whether the element could be picked up without poking the surface (substrate) of the adhesive sheet opposite the element to be adsorbed with a needle. If the element could be picked up without damage, it was evaluated as "pickup possible" (A). If the element was damaged during pickup, the element could not be picked up, or transfer of the element from the wafer substrate to the adhesive sheet failed, it was evaluated as "pickup impossible" (F).

[0127] <Evaluation of Adhesion Area> Evaluation of the adhesion area when an object was attached to the pressure-sensitive adhesive sheet obtained in each Example and Comparative Example was performed as follows. First, the pressure-sensitive adhesive sheet obtained in each Example and Comparative Example was cut into a width of 200 mm x 50 mm. The cut pressure-sensitive adhesive sheet was attached to a 6-inch silicon wafer using a laminator and left to stand for 10 minutes after attachment.

[0128] The obtained sample was observed through the substrate using a digital microscope (Keyence Corporation, VHX-5000). Then, the ratio of the area of ​​the contact portion between the pressure-sensitive adhesive sheet and the wafer shown in the observed image to the wafer area (adhesion area ratio) was calculated. Note that when the adhesion state was pillar contact (i.e., when the pillars were not in contact with each other and each pillar was in individual contact with the wafer), the center and diameter of the circle indicating the contact surface between the pillar and the wafer were measured. The adhesion area ratio was calculated by dividing the area of ​​the circle obtained based on the diameter by the square of the center-to-center distance between the circles indicating the contact surfaces of adjacent pillars (i.e., the area of ​​a square whose side length is the center-to-center distance). In addition, when the adhesion state was not pillar contact (i.e., when adjacent pillars were in contact with each other and multiple pillars were in contact with each other and in contact with the wafer), the observation image was subjected to image binarization processing using MATLAB (registered trademark), and the area of ​​each region after binarization was calculated to calculate the adhesion area ratio.

[0129] The evaluation results are shown in Table 1.

[0130] As shown in Table 1, the adhesion area when an object was attached to the pressure-sensitive adhesive sheets according to Examples 1 to 4 was 4% or more and 60% or less. Furthermore, evaluation of the pickup properties of the pressure-sensitive adhesive sheets according to Examples 1 to 4 confirmed that it was possible to pick up an element from the pressure-sensitive adhesive sheet.

[0131] On the other hand, when an object was attached to the pressure-sensitive adhesive sheet according to Comparative Example 1, the adhesion area exceeded 60%. When a pickup property evaluation was performed on the pressure-sensitive adhesive sheet according to Comparative Example 1, it was not possible to pick up the object from the pressure-sensitive adhesive sheet. One reason for this is thought to be that when the adhesion area exceeds 60%, as in the case of the pressure-sensitive adhesive sheet according to Comparative Example 1, the adhesive strength becomes too high due to the excessive adhesion area. In order to pick up easily breakable objects (e.g., thin elements) such as those used in the above pickup property evaluation, it was thought that it was necessary to reduce the adhesion area so that the adhesive strength of the adhesive layer would be lower.

[0132] Furthermore, when an object was attached to the pressure-sensitive adhesive sheet according to Comparative Example 2, the adhesion area was less than 4%. An attempt was made to evaluate the pickup property of the pressure-sensitive adhesive sheet according to Comparative Example 2, but it was not possible to transfer the element from the dicing tape to the pressure-sensitive adhesive sheet. One reason for this is thought to be that when the adhesion area is less than 4%, as in the case of the pressure-sensitive adhesive sheet according to Comparative Example 2, the adhesive strength becomes insufficient due to the insufficient adhesion area.

[0133] As described above, by setting the adhesive sheet's adhesion area ratio to the article to be 4% or more and 60% or less when the adhesive sheet is attached to the article, it is possible to easily pick up an object held on the adhesive sheet.

[0134] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention.

[0135] This application claims priority based on Japanese Patent Application No. 2024-046979 filed on March 22, 2024, Japanese Patent Application No. 2024-046980 filed on March 22, 2024, Japanese Patent Application No. 2024-046981 filed on March 22, 2024, Japanese Patent Application No. 2024-046982 filed on March 22, 2024, Japanese Patent Application No. 2024-170363 filed on September 30, 2024, and Japanese Patent Application No. 2024-170369 filed on September 30, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. An adhesive sheet comprising a substrate and an adhesive layer having an uneven surface, wherein the adhesive sheet is expandable in the planar direction, and when the adhesive sheet is attached to an article, the adhesive area ratio of the adhesive sheet to the article is 4% or more and 60% or less.

2. The adhesive sheet according to claim 1, wherein the adhesive layer comprises a crosslinked polymer, and the content of the crosslinked polymer relative to the total amount of components constituting the adhesive layer is 70 to 100 mass %.

3. The adhesive sheet according to claim 1, wherein the adhesive layer comprises a polymer, and the polymer is an acrylic resin crosslinked with an isocyanate-based crosslinking agent.

4. The pressure-sensitive adhesive sheet according to claim 3, wherein the amount of said isocyanate-based crosslinking agent is 2 parts by mass or more per 100 parts by mass of said polymer.

5. The pressure-sensitive adhesive sheet according to claim 3, wherein the acrylic resin further has an energy ray-curable group.

6. The pressure-sensitive adhesive sheet according to claim 2, wherein the polymer has a mass average molecular weight of 10,000 or more.

7. The pressure-sensitive adhesive sheet according to claim 1, wherein the tensile modulus of the substrate is 2500 MPa or less.

8. The adhesive sheet of claim 1, wherein the adhesive layer has a plurality of protrusions spaced apart from one another and bounded by recesses, the pitch of the plurality of protrusions being between 1 μm and 100 μm.

9. The adhesive sheet according to claim 1, wherein the adhesive layer has a plurality of protrusions, the heights of the plurality of protrusions being uniform.

10. The adhesive sheet according to claim 1, wherein the height of the convex portions of the adhesive layer is 1 μm or more.

11. The adhesive sheet according to claim 1, further comprising a release layer having a textured surface complementary to the textured surface of the adhesive layer.

12. A method for peeling an object from an adhesive sheet according to claim 1, in which the object is held on an adhesive layer, comprising: an expansion step of expanding the adhesive layer in a planar direction; and a peeling step of peeling the object from the adhesive layer of the adhesive sheet.