Adhesive sheet and method for handling object

Abstract

The present invention makes it possible for an object held on an adhesive sheet provided with an adhesive layer having a relief pattern on the surface thereof to be picked up by means of a milder operation.　This adhesive sheet comprises an adhesive layer having a relief pattern on the surface thereof. The tensile breaking stress of the adhesive layer at 23°C is 20 MPa or higher.

Description

Adhesive sheet and method for handling objects

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

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

[0003] Pressure-sensitive adhesive sheets come in various shapes depending on their intended use. For example, Patent Document 1 describes providing grooves on the surface of a pressure-sensitive adhesive layer so that air bubbles can be removed after application.

[0004] Japanese Patent Application Laid-Open No. 2021-147418

[0005] The present inventors have investigated the provision of irregularities on the surface of the adhesive layer of an adhesive sheet. Such a 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 reduce damage to the object during pick-up.

[0006] An object of the present invention is to enable an object held on an adhesive sheet having an adhesive layer with an uneven surface to be picked up with a milder operation.

[0007] After extensive research, the inventors discovered that by appropriately adjusting the tensile breaking stress of the adhesive layer of the adhesive sheet, it becomes easier to pick up objects, thereby solving the above-mentioned problem. After further research, they completed the present invention.

[0008] That is, the present invention relates to the following items [1] to

[14] . [1] A pressure-sensitive adhesive sheet comprising an adhesive layer having an uneven surface, wherein the adhesive layer has a tensile stress at break of 20 MPa or more at 23°C. [2] The pressure-sensitive adhesive sheet according to [1], wherein the tensile stress at break is 100 MPa or less. [3] The pressure-sensitive adhesive sheet according to any one of [1] to [2], further comprising a release layer having an uneven surface complementary to the uneven surface of the adhesive layer. [4] The pressure-sensitive adhesive sheet according to any one of [1] to [3], which is expandable in the plane direction by 1% or more. [5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein the adhesive layer has a plurality of convex portions spaced apart from one another and defined by concave portions, the pitch of the plurality of convex portions being 1 μm or more and 100 μm or less. [6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], wherein the adhesive layer has a plurality of convex portions, the height of the plurality of convex portions being uniform. [7] The pressure-sensitive adhesive sheet according to any one of [1] to [6], wherein the adhesive layer contains an acrylic resin and an energy ray-curable resin. [8] The pressure-sensitive adhesive sheet according to [7], wherein the energy ray-curable resin contains a polyvalent (meth)acrylate as a structural unit. [9] The pressure-sensitive adhesive sheet according to any one of [7] to [8], wherein the amount of the energy ray-curable resin per 100 parts by mass of the acrylic resin is 8 parts by mass or more.

[10] The pressure-sensitive adhesive sheet according to any one of [7] to [9], wherein the adhesive layer further contains a crosslinking agent for the acrylic resin, and wherein the amount of the crosslinking agent per 100 parts by mass of the acrylic resin is 0.05 parts by mass or more.

[11] A method for handling an object, comprising: a holding step of holding an object with the adhesive layer of the pressure-sensitive adhesive sheet according to any one of [1] to

[10] , and a peeling step of peeling the object from the adhesive layer of the pressure-sensitive adhesive sheet.

[12] The method for handling an object according to

[11] , further comprising: a step of expanding the adhesive sheet holding the object in a planar direction; and a step of peeling the object from the adhesive layer of the adhesive sheet expanded in the planar direction.

[13] The method for handling an object according to any one of

[11] to

[12] , further comprising a step of peeling the object from the adhesive layer of the adhesive sheet using an adsorption member in the peeling step.

[14] The method for handling an object described in any one of

[11] to

[13] , wherein in the peeling step, the object is peeled from the adhesive layer of the adhesive sheet without applying a physical stimulus from the opposite side of the adhesive layer of the adhesive sheet.

[0009] To enable an object held on an adhesive sheet having an adhesive layer with an uneven surface to be picked up with a milder operation.

[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 in 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 a sheet according to one embodiment. A cross-sectional view showing an example of unevenness on a sheet. A cross-sectional view showing an example of unevenness on a sheet. A top view showing an example of unevenness on a sheet. A top view showing an example of unevenness on a sheet. A cross-sectional view showing an example of unevenness on a sheet. A cross-sectional view showing an example of unevenness on a sheet. A cross-sectional view showing an example of unevenness on a sheet. A cross-sectional view showing an example of unevenness on a sheet. A diagram for explaining a sheet expanding method. A diagram for explaining a sheet expanding method. A flowchart of an object transfer 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 the lower limit and upper limit therein is described. For example, the description "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 or more to 9 or less, 1 or more to 8 or less, 1 or more to 7 or less, 2 or more to 9 or less, 2 or more to 8 or less, 2 or more to 7 or less, 3 or more to 9 or less, 3 or more to 8 or less, and 3 or more to 7 or less.

[0015] (Structure of the Sheet) The 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 structure 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] (Base material)

[0017] 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.

[0018] As will be described later, the adhesive sheet according to this embodiment can be expanded. 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] (Adhesive Layer) The adhesive layer 110 is a layer having adhesive properties and may contain a resin. As described above, the adhesive layer 110 has an uneven 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.

[0025] (Composition of Adhesive Layer) 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.

[0026] The resin contained in the adhesive layer 110 is preferably an adhesive resin that exhibits adhesiveness by itself. The resin is preferably a polymer having a mass average molecular weight (Mw) of 10,000 or more. From the viewpoint of improving retention, 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, the mass average molecular weight (Mw) of the resin is preferably 2,000,000 or less, and even more preferably 1,200,000 or less. From the viewpoint of improving retention, 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, the number average molecular weight (Mn) of the resin is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,200,000 or less. 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. 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 Tg is within this range, the retention properties and storage modulus of the obtained adhesive layer 110 can be easily set within the ranges described below.

[0027] The amount of resin contained in the adhesive layer 110 relative to the total amount of components constituting the adhesive layer 110 can be set appropriately depending on the desired retention and storage modulus of the 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.

[0028] 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.

[0029] In one embodiment, the resin contained in the adhesive composition forming 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 and softening the resin, 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.

[0030] 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.

[0031] (Acrylic Resin (A)) In one embodiment, the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer 110 contains an acrylic resin. The acrylic resin is a resin containing (meth)acrylic acid or a (meth)acrylic acid ester as a monomer. From the viewpoint of improving adhesive strength, the mass average molecular weight (Mw) of the acrylic resin is preferably 10,000 or more, more preferably 100,000 or more, and even more preferably 500,000 or more. Furthermore, from the viewpoint of suppressing the storage modulus to a predetermined value or less, the mass average molecular weight (Mw) is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,200,000 or less.

[0032] The glass transition temperature (Tg) of the acrylic 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 Tg is within this range, it becomes easier to obtain adhesive layer 110 having the above-mentioned storage modulus.

[0033] When an acrylic resin has two or more structural units, the glass transition temperature (Tg) of the acrylic resin can be calculated using the Fox equation. The Tg of the monomer from which the structural unit is derived can be calculated using the value listed in the Polymer Data Handbook or the Adhesive Handbook.

[0034] Examples of (meth)acrylic acid esters constituting acrylic resins 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. (Meth)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, stearyl (meth)acrylate, and the like, in which the alkyl group constituting the alkyl ester has a chain structure having 1 to 18 carbon atoms. 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 Examples of the hydroxyl group-containing (meth)acrylic acid ester include: a hydroxyl group-containing (meth)acrylic acid ester 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 a substituted amino group-containing (meth)acrylic acid ester 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.

[0035] 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.

[0036] The acrylic resin may be composed of one kind of monomer or two or more kinds of monomers, and when two or more kinds of monomers are used, the combination and ratio thereof can be selected arbitrarily.

[0037] In one embodiment, the acrylic resin contains a monomer having a hydroxy group as a constituent unit. The acrylic resin may have, in addition to the hydroxy group, a functional group capable of bonding to other compounds, such as a vinyl group, a (meth)acryloyl group, an amino group, a carboxy group, or an isocyanate group. These functional groups, including the hydroxy group of the acrylic resin, may bond to other compounds via a crosslinking agent (C) described below, or may bond directly to other compounds without the crosslinking agent (C).

[0038] The amount of acrylic resin in the total amount of resin in the adhesive composition can be set appropriately depending on the desired adhesive strength and storage modulus of the adhesive layer 110, but is preferably 0% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, even more preferably 50% by mass or more, and is preferably 100% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, even more preferably 80% by mass or less.

[0039] (Energy Reactive Resin (B)) In one embodiment, the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer 110 contains an energy reactive resin (B). The energy reactive resin (B) refers to a resin whose elastic modulus improves upon application of energy. The energy reactive resin may be a resin derived from an energy-reactive monomer. In this case, the energy reactive resin is a resin obtained by polymerizing the energy-reactive monomer by application of energy.

[0040] Examples of energy reactive resins include energy ray reactive resins and heat reactive resins. Energy ray reactive resins refer to resins whose elastic modulus improves when irradiated with energy rays. For example, energy reactive resins can be energy ray curable resins. Heat reactive resins refer to resins whose elastic modulus improves when heated. The resin contained in the adhesive layer 110 is more preferably derived from a thermoplastic energy reactive resin, and even more preferably derived from a thermoplastic energy ray reactive resin. The type of energy ray is not particularly limited, and examples include ultraviolet rays, electron beams, and ionizing radiation. Preferred energy rays are ultraviolet rays, i.e., the resin is preferably an ultraviolet reactive resin.

[0041] A thermoplastic energy reactive resin refers to an energy reactive resin that has thermoplastic properties at least before energy is applied. Furthermore, a resin derived from an energy reactive resin means that the resin is obtained from an energy reactive resin. For example, a resin derived from an energy reactive resin is a crosslinked energy reactive resin.

[0042] When such an energy reactive resin is used, the formed uneven shape can be easily maintained by providing energy (for example, by irradiating with energy rays) after forming the uneven shape in the resin.

[0043] Such energy reactive resins can be polymers having polymerizable functional groups introduced therein. The polymerizable functional groups are functional groups that are crosslinked by the application of energy (e.g., irradiation with energy rays). Examples of such polymerizable functional groups include alkenyl groups such as vinyl groups and allyl groups, (meth)acryloyl groups, oxetanyl groups, and epoxy groups.

[0044] For example, a diene rubber composed of a polymer having a polymerizable functional group at the end of the main chain and / or at a side chain can be used as the energy reactive resin. Diene rubber refers to a rubbery polymer having a double bond in the polymer main chain. Specific examples of diene rubber include polymers using butadiene or isoprene as a monomer (i.e., having butenediyl groups or pentenediyl groups as structural units). Preferred examples of the energy reactive resin include polybutadiene resin (PB resin), styrene-butadiene-styrene block copolymer (SBS resin), and styrene-isoprene-styrene block copolymer. These resins can be used as ultraviolet-reactive resins.

[0045] The average number of polymerizable functional groups per molecule in these energy reactive resins is preferably 1.5 or more, more preferably 2 or more, from the viewpoint of easily maintaining the uneven shape of the adhesive layer 110. On the other hand, from the viewpoint of improving the adhesiveness and flexibility of the adhesive layer 110, this average value is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less.

[0046] The adhesive layer 110 may contain one type of resin or two or more types of resins. In one embodiment, the adhesive layer 110 contains a liquid resin, a resin derived from an energy-reactive liquid resin, or a resin derived from an energy-reactive monomer, in addition to a thermoplastic resin or a resin derived from a thermoplastic energy-reactive resin. The liquid resin refers to a resin that is liquid at room temperature (25°C) before mixing. The energy-reactive liquid resin refers to an energy-reactive resin that is liquid at room temperature (25°C) before mixing and before energy is applied. The resin derived from an energy-reactive monomer refers to a resin obtained by polymerizing an energy-reactive monomer by applying energy. Adding such a liquid resin or monomer makes it easier to control the retention and storage modulus of the adhesive layer 110.

[0047] It is preferable that adhesive layer 110 according to an embodiment contains a resin derived from an energy reactive liquid resin, since it is easy to maintain the uneven shape of adhesive layer 110. An example of such a liquid resin is a diene rubber, and a specific example is a polybutadiene resin in which butadiene is used as a monomer.

[0048] According to another embodiment, the adhesive layer 110 includes a combination of any resin and an energy-reactive liquid resin or a resin derived from an energy-reactive monomer. For example, the adhesive layer 110 may include an acrylic resin (A) and an energy-reactive liquid resin or a resin derived from an energy-reactive monomer. Even with this combination, by forming irregularities on a film of a mixture of the acrylic resin (A) and the energy-reactive liquid resin or the energy-reactive monomer and then applying energy (e.g., irradiating with energy rays), the energy-reactive liquid resin or the energy-reactive monomer is polymerized, making it easy to maintain the irregularities that have been formed.

[0049] Examples of energy-reactive monomers include bifunctional or polyfunctional compounds incorporating polymerizable functional groups such as alkenyl groups (e.g., vinyl groups and allyl groups), (meth)acryloyl groups, oxetanyl groups, and epoxy groups. Preferred examples of energy-reactive monomers include polyvalent (meth)acrylates, such as difunctional (meth)acrylates. Thus, the adhesive layer 110 can include an energy-ray-curable resin containing a polyvalent (meth)acrylate as a structural unit. Specific examples of polyvalent (meth)acrylates include cycloalkyl di(meth)acrylates, such as tricyclodecane dimethanol diacrylate.

[0050] Furthermore, the ratio of the energy reactive resin (B) to the total amount of components constituting the adhesive layer 110 can be selected depending on the desired retention and storage modulus of the adhesive layer 110. For example, this ratio is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 8% by mass or more, and even more preferably 10% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

[0051] As described above, the adhesive layer 110 may contain an acrylic resin (A) and an energy reactive resin (B). In this case, the amount of the energy reactive resin relative to the acrylic resin can be selected depending on the desired retention and storage modulus of the adhesive layer 110. For example, the amount of the energy reactive resin relative to 100 parts by mass of the acrylic resin is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 8 parts by mass or more, and particularly preferably 10 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 75 parts by mass or less, and even more preferably 50 parts by mass or less. In this case, the energy reactive resin is, for example, an energy ray-curable resin, such as a resin derived from an energy ray-curable monomer. Here, parts by mass refers to the mass of the solid content, and hereinafter also refers to the mass basis unless otherwise specified.

[0052] (Other Components of Adhesive Layer) The adhesive composition forming the adhesive layer 110 may contain components other than the resin. For example, the adhesive composition may contain one or more of a crosslinking agent (C), a photopolymerization initiator (D), an antioxidant (E), and other additives.

[0053] Examples of the crosslinking agent (C) include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, a metal chelate-based crosslinking agent, etc. These crosslinking agents may be used alone or in combination of two or more.

[0054] Among these crosslinking agents, isocyanate-based crosslinking agents are preferred from the viewpoints of increasing cohesive strength and improving adhesive strength, 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.

[0055] The pressure-sensitive adhesive composition 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 pressure-sensitive adhesive composition 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, particularly preferably 0.3% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less.

[0056] For example, the crosslinking agent may be a crosslinking agent for the acrylic resin (A). For example, an isocyanurate-type modified isocyanate crosslinking agent can be used as a crosslinking agent for an acrylic resin containing a monomer having a hydroxy group as a constituent unit. In this case, the amount of crosslinking agent relative to the acrylic resin can be selected so that the crosslinking reaction can be carried out appropriately. For example, the amount of crosslinking agent relative to 100 parts by mass of the acrylic resin is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 0.2 parts by mass or more, particularly preferably 0.4 parts by mass or more, and preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 2 parts by mass or less.

[0057] The photopolymerization initiator (D) initiates a crosslinking reaction in response to the application of energy (e.g., irradiation with energy rays). When the pressure-sensitive adhesive composition contains the energy reactive resin (B), the pressure-sensitive adhesive layer 110 further contains the photopolymerization initiator (D), and thus the crosslinking reaction proceeds even when a relatively low amount of energy is applied.

[0058] Examples of the photopolymerization initiator (D) 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.

[0059] The pressure-sensitive adhesive composition may contain one type of polymerization initiator or two or more types of polymerization initiators. The content of the photopolymerization initiator in the pressure-sensitive adhesive composition 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 1% by mass or less.

[0060] Examples of the antioxidant (E) 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.

[0061] 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.

[0062] 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 10% by mass or less, even more preferably 5% by mass or less.

[0063] (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.

[0064] 2A and 2B are side views showing the shape of the adhesive layer 110, and FIGS. 3A, 3B, and 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 element 140 held by the convex portions 111 of the adhesive layer 110, FIGS. 3A, 3B, and 3C omit the element 140 held by the convex portions 111.

[0065] 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.

[0066] 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.

[0067] In this embodiment, the adhesive sheet is expanded, and the adhesive layer 110 shown in FIGS. 2A and 3A is transformed into the adhesive layer 110' shown in FIGS. 2B and 3B. Comparing the adhesive layer 110 and the adhesive layer 110', the pitch P of each convex portion 111 in the adhesive layer 110' is increased due to the expansion, and the number of convex portions 111 that hold one element 140 is reduced. As a result, the adhesive layer 110' has a lower force for holding the element 140 by the convex portions 111 compared to the adhesive layer 110. Furthermore, the expansion of the adhesive sheet causes shear stress to act between the convex portions 111 and the element 140. The inventors of the present application believe that this also leads to a decrease in the holding force of the element 140 by the convex portions 111.

[0068] 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.

[0069] The specific shape of the protrusions 111 is not particularly limited. For example, the protrusions 111 may have a pillar (column) shape. As a specific example, the protrusions 111 may have a cylindrical shape or a prismatic shape. Furthermore, as described above, the protrusions 111 may extend in a line shape, or may extend in a curved shape such as a wavy shape. Furthermore, these protrusions 111 may be tapered.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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 D in FIG. 4A ) between two parallel lines that contact the protrusion 111 from both sides on the surface of the recess.

[0074] 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 D in the case of FIG. 4A).

[0075] 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 improving ease of peeling of the object. On the other hand, from the viewpoint of improving dimensional stability, 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 the 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.

[0076] 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.

[0077] The unevenness of the adhesive layer 110 may be designed according to the shape of the object to be held by the adhesive sheet. For example, the ratio of the adhesive area between the adhesive layer 110 and an object to the area of ​​the object is preferably 1% or more, more preferably 2% or more, even more preferably 3% or more, even more preferably 4% or more, even more preferably 5% or more, even more preferably 7% or more, and even more preferably 10% or more, relative to 100% of the area of ​​the object, from the viewpoint of maintaining the holding force of the object. On the other hand, the ratio of the adhesive area between the adhesive layer 110 and an object to the area of ​​the object is preferably 95% or less, more preferably 70% or less, even more preferably 50% or less, and even more preferably 30% or less, from the viewpoint of increasing the ease of peeling the object. In the case of FIG. 4A , the adhesive area corresponds to the area of ​​a circle with a diameter T. Note that the adhesive area may change if the holding position of the object on the adhesive sheet is shifted. In this case, it is preferable that the adhesive area ratio falls within the above range, regardless of the position of the object to be treated.

[0078] (Characteristics of the adhesive layer) In an adhesive sheet according to one embodiment, the amount of work required to peel an object from the adhesive layer 110 is adjusted. For example, in order to enable picking up of an object under milder conditions, the mirror surface of a silicon chip having a size of 5.0 mm x 5.0 mm is pressed against the adhesive layer of the adhesive sheet at a contact pressure of 0.3 MPa, and then the amount of work required to peel the silicon chip from the adhesive layer is 25 μJ or less, preferably 15 μJ or less, more preferably 10 μJ or less, and even more preferably 7 μJ or less. On the other hand, in order to ensure the holding force of the object, the amount of work required to peel the silicon chip from the adhesive layer under the same conditions is 0.1 μJ or more, more preferably 0.3 μJ or more, and even more preferably 0.7 μJ or more.

[0079] This workload can be evaluated by performing a probe tack measurement under a contact load of 8 N in an environment of 23°C. Specifically, a probe with a silicon chip measuring 5.0 mm x 5.0 mm fixed to its tip is used. The chip is then pressed against the adhesive layer of the adhesive sheet at a contact pressure of 0.3 MPa so that the mirror surface of the silicon chip contacts the adhesive layer, and the probe tack at the interface between the chip and the adhesive layer can then be measured. The workload is represented by the area under a graph showing the relationship between the probe travel distance and tack force.

[0080] Such workload can be adjusted, for example, by controlling the composition of the adhesive layer 110. For example, the workload can be reduced by increasing the proportion of the energy reactive resin that constitutes the adhesive layer 110 or by increasing the proportion of the crosslinking agent.

[0081] The present inventors have investigated controlling the force required to peel an object from the adhesive layer 110, but have found that the force required to peel an object from the adhesive layer 110 is not constant depending on the pulling position on the silicon chip, etc. On the other hand, the present inventors' investigations have found that controlling the workload as described above makes it possible to stably pick up an object from the adhesive layer 110 under mild conditions. In one embodiment, an object is peeled from the adhesive layer 110 after the adhesive sheet is expanded, but adjusting the workload before expansion as described above can make it easier to peel the object from the expanded adhesive sheet.

[0082] In an adhesive sheet according to one embodiment, the tensile stress at break of the adhesive layer 110 is adjusted. For example, from the viewpoint of enabling pickup of an object under milder conditions, the tensile stress at break of the adhesive layer 110 at 23° C. is 20 MPa or more, preferably 22 MPa or more, and more preferably 23 MPa or more. On the other hand, from the viewpoint of ensuring the holding power of an object, the tensile stress at break of the adhesive layer 110 at 23° C. is 100 MPa or less, preferably 50 MPa or less, more preferably 40 MPa or less, and even more preferably 30 MPa or less.

[0083] The tensile breaking stress of the adhesive layer 110 can be measured by uniaxial extensional viscosity measurement using a viscoelasticity measuring device at a test temperature of 23°C and a strain rate of 0.1 / sec. The sample used for the measurement can be prepared by cutting it out from an adhesive sheet, for example. The size of the sample is not particularly limited, but for example, a sample with a width of 5 mm, a length of 30 mm, and a thickness of 0.1 mm can be used.

[0084] Such a tensile breaking stress can be adjusted, for example, by controlling the composition of the adhesive layer 110. For example, the tensile breaking stress can be increased by increasing the proportion of the energy reactive resin constituting the adhesive layer 110 or by increasing the proportion of the crosslinking agent.

[0085] The inventors of the present application believe that by controlling the tensile breaking stress of the adhesive layer 110 as described above, when the adhesive sheet is expanded, the adhesive layer 110 is more likely to stretch in accordance with the substrate 120, making it easier to apply shear stress between the object and the adhesive layer 110, and therefore making it easier to pick up the object.

[0086] In an adhesive sheet according to one embodiment, the adhesive strength of the adhesive layer 110 is adjusted. For example, from the viewpoint of enabling pickup of an object under milder conditions, the adhesive strength of the adhesive layer 110 to a silicon mirror surface measured at a peel angle of 180 degrees and a peel speed of 300 mm / min is 35 mN / 50 mm or less, preferably 30 mN / 50 mm or less, and more preferably 28 mN / 50 mm or less. On the other hand, from the viewpoint of ensuring the holding power of an object, the adhesive strength of the adhesive layer 110 measured under the same conditions is 1 mN / 50 mm or more, preferably 3 mN / 50 mm or more, more preferably 10 mN / 50 mm or more, and even more preferably 15 mN / 50 mm or more.

[0087] The adhesive strength of 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. In one embodiment, an object is peeled from adhesive layer 110 after the adhesive sheet is expanded, and adjusting the adhesive strength before expansion as described above can make it easier to peel the object from the expanded adhesive sheet.

[0088] Such adhesive strength can be adjusted, for example, by controlling the composition of adhesive layer 110. For example, increasing the proportion of the energy reactive resin constituting adhesive layer 110 or increasing the proportion of the crosslinking agent tends to decrease the adhesive strength.

[0089] (Release Sheet) Furthermore, as shown in Fig. 1, the pressure-sensitive adhesive sheet according to this embodiment may include a release sheet 150 that is in contact with the pressure-sensitive adhesive layer 110 and has an uneven surface that is complementary to the uneven surface of the pressure-sensitive adhesive layer 110. 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.

[0090] 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.

[0091] 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. For example, the material of the substrate 120 may be EMAA, and the material of the substrate 170 may be polyethylene terephthalate. Furthermore, the release sheet 150 may have an undercoat layer (not shown) between the release layer 160 and the substrate 170.

[0092] (Other Layers) The above sheet may have layers other than the substrate and the adhesive layer. For example, an additional adhesive layer may be provided on the surface of the substrate opposite to the adhesive layer. 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 for example, the additional adhesive layer can be formed using a general adhesive.

[0093] (Method for manufacturing adhesive layer and sheet) There are no particular limitations on the method for manufacturing the adhesive layer and sheet. For example, a sheet having an adhesive layer 110 provided on a substrate 120 can be produced as follows. First, an organic solvent is added to a raw material composition containing each of the components of the adhesive layer 110 described above to prepare a solution of the raw material composition. This solution is then applied to the substrate 120 to form a coating film, which is then dried, thereby providing an adhesive layer on the substrate 120. Furthermore, by performing a process to provide irregularities on the surface of this adhesive layer, an adhesive layer 110 having irregularities can be formed.

[0094] Examples of organic solvents used to prepare the solution of the raw material 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).

[0095] There are no particular limitations on the process for providing the surface of the adhesive layer 110 with irregularities. For example, irregularities can be provided on the surface of the adhesive layer 110 using an imprinting method. In the imprinting method, a mold having a surface shape complementary to the irregularities to be provided can be used. Specifically, irregularities can be provided on the surface of the adhesive layer by heating the adhesive layer while pressing the adhesive layer provided on the substrate with the mold. A more specific method involves pressing the adhesive layer with the mold, heating the adhesive layer, and maintaining the temperature for a predetermined period of time, after which the adhesive layer is cooled and the mold is removed. When heating the adhesive layer, for example, the adhesive layer can be heated to a temperature higher than the softening point of the adhesive layer. The time for maintaining the adhesive layer in the heated state is also not particularly limited, and may be maintained for, for example, 10 seconds or more or 10 minutes or less. A specific method for heating the adhesive layer while pressing the adhesive layer with the mold includes vacuum laminating the adhesive layer provided on the substrate and the mold. Instead of performing the two-step process of forming the adhesive layer and forming the irregularities, an adhesive layer having irregularities on its surface may be formed on the substrate in a single step. Also, the release sheet 150 having the release layer 160 having irregularities as described above may be used as the mold.

[0096] As another method, the adhesive layer 110 having a rough surface can be provided by spray-coating a solution of the raw material composition. Furthermore, the adhesive layer 110 having a rough or fibrous surface can be provided by adding a filler to the solution of the raw material 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 coating the solution of the raw material composition according to a desired pattern using a printing method such as an inkjet method.

[0097] (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. A method of handling an object using the adhesive sheet according to this embodiment will be described with reference to the flowchart of FIG. 6.

[0098] (S10: Holding of Object) In S10, an object is held by 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 objects 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.

[0099] 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 It may be the following:

[0100] 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.

[0101] 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.

[0102] The substrate may be a glass substrate, a sapphire substrate, or a compound semiconductor substrate.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] (S20: Expanding the adhesive sheet) In an object handling method according to one embodiment, the adhesive sheet holding the object is expanded in the planar direction. In the flowchart shown in FIG. 6, the adhesive sheet is expanded in the planar direction in S20. As described above with reference to FIGS. 2A, 2B, 3A, 3B, and 3C, expanding the adhesive sheet reduces the holding force of the object, making it easier to peel off the object in the next step. 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) from the viewpoint of sufficiently reducing the holding force of the object.

[0107] The method of expanding 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 the pressure-sensitive adhesive sheet from breaking, 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 the elements 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] (S30: Peeling off the object) In S30, the object is peeled off from the adhesive layer 110 of the adhesive sheet. In the flowchart of FIG. 6 , the object is peeled off from the adhesive layer 110 of the adhesive sheet expanded in the planar direction. The method for peeling off the object is not particularly limited. For example, the method described above can be used as a method for transferring an object attached to a holding substrate to the adhesive sheet. Specifically, 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 destination position. If the holding force of the adhesive layer 110 is reduced by expanding the adhesive sheet, the object can be peeled off from the adhesive layer 110 of the adhesive sheet without applying a physical stimulus such as pressing with a pin or the like from the opposite surface of the adhesive layer 110 of the adhesive sheet.

[0111] According to the study by the inventors of the present application, when an object is to be peeled off from the adhesive layer 110 using an adsorption member without physical stimulation, if the adsorption force is increased in accordance with the holding power of the adhesive layer 110, the object, such as an element, becomes more likely to be damaged. For this reason, in this embodiment, the adhesive force of the adhesive layer 110 is adjusted.

[0112] By this procedure, an object can be transferred to any desired destination using the adhesive sheet. Furthermore, this transfer method can be used to manufacture electronic components or semiconductor devices having elements. The object held by the adhesive sheet may be subjected to processing or treatment.

[0113] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples. In each example, parts and percentages are based on the mass of the solid content unless otherwise specified.

[0114] The following compounds were used in the examples and comparative examples. <Component (A): Acrylic Resin> As the acrylic resin, an acrylic copolymer (monomer mass ratio: 2-ethylhexyl acrylate / 2-hydroxyethyl acrylate / acrylic acid = 92.8 / 7.0 / 0.2, mass average molecular weight (Mw): 1,100,000) was used.

[0115] <Component (B): Energy Reactive Resin> Tricyclodecane dimethanol diacrylate was used as the energy reactive resin.

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

[0117] <Component (D): Photopolymerization Initiator> As the photopolymerization initiator, 2,4,6-trimethylbenzoyldiphenylphosphine oxide was used.

[0118] <Evaluation of Tensile Breaking Stress> The tensile breaking stress of the adhesive layer used in each Example was measured as follows. An adhesive layer having a thickness of 0.1 mm was prepared from the adhesive composition obtained in each Example. The obtained adhesive layer was cut into a width of 5 mm and a length of 30 mm, and the tensile breaking stress of the adhesive layer at 23°C was measured by uniaxial extensional viscosity measurement using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR302") under conditions of a test temperature of 23°C and a strain rate of 0.1 / sec.

[0119] <Pickup Evaluation> The pickup evaluation of the elements held on the pressure-sensitive adhesive sheets obtained in each Example was carried out as follows: First, the adhesive layer of the pressure-sensitive adhesive sheet obtained in each 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.

[0120] Next, a wafer substrate (mirror silicon wafer, 6 inches, 150 μm thick) was fixed to a separately prepared dicing tape. The wafer substrate was then diced into 8.2 mm x 8.2 mm squares to obtain multiple elements (silicon chips, element size 8.2 mm x 8.2 mm x 150 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 mirror 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. Thus, an adhesive sheet on which multiple elements were mounted and supported by a ring frame was obtained as an evaluation sample.

[0121] The obtained evaluation sample 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 FIG. 6. 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.

[0122] (Example 1) A pressure-sensitive adhesive composition was prepared by dissolving in toluene the acrylic resin (A), energy reactive resin (B), crosslinking agent (C), and photopolymerization initiator (D) in the amounts shown in Table 1. Table 1 shows the solid content parts by mass of each material.

[0123] This pressure-sensitive adhesive composition was applied onto the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name: SP-PET382150, a polyethylene terephthalate film laminated with a silicone-based release agent, thickness 38 μm), and the resulting coating was dried at 100°C for 2 minutes to form a pressure-sensitive adhesive layer with a thickness of 25 μm.

[0124] An EMAA film (ethylene-methacrylic acid copolymer film, acid content 9% by mass, one surface embossed to give a matte finish, thickness 80 μm) was used as a substrate on this adhesive layer, and the non-embossed surface of the EMAA film was bonded to the adhesive layer.

[0125] After the release sheet was peeled off, the adhesive layer was attached to a replica mold on which a concave shape had been formed in advance, and vacuum laminated at 60° C. for 300 seconds. Next, 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 An adhesive sheet having a textured surface was produced by irradiating ultraviolet light at 1000 kJ / cm2 with the adhesive layer of the adhesive sheet. The textured shape of the adhesive layer of the adhesive sheet was a grid-like arrangement of pillars, similar to that shown in FIG. 2A. The pitch P between the pillars in the adhesive sheet was 20 μm. As shown in FIG. 4A, the height (H) of each pillar was 8 μm, the diameter (T) of the tip was 8 μm, and the diameter (D) of the base was 16 μm. The ratio of the area of ​​the adhesive portion between the adhesive layer and the captured element (i.e., the area of ​​the tip surface of the convex portion) to the area of ​​the adhesive sheet was approximately 12.6%. The replica mold used had a surface shape complementary to the textured shape.

[0126] The adhesive strength of the adhesive layer was evaluated using the prepared adhesive composition according to the method described above. Furthermore, the pickup evaluation of the element held on the obtained adhesive sheet was performed according to the method described above. The evaluation results are shown in Table 1. In the pickup evaluation, "A" indicates that pickup was possible, and "F" indicates that pickup was not possible.

[0127] Examples 2 and 3 Pressure-sensitive adhesive compositions were prepared and pressure-sensitive adhesive sheets were produced in the same manner as in Example 1, except that the amounts of energy reactive resin (B) and photopolymerization initiator (D) shown in Table 1 were used.

[0128] Comparative Examples 1 to 3 Pressure-sensitive adhesive compositions were prepared and pressure-sensitive adhesive sheets were fabricated in the same manner as in Example 1, except that the amounts of energy reactive resin (B), crosslinking agent (C), and photopolymerization initiator (D) shown in Table 1 were used.

[0129]

[0130] As can be seen from the comparison between Examples 1 to 3 and Comparative Examples 1 to 3, it was confirmed that when the tensile breaking stress of the adhesive layer was 20 MPa or more, the element could be picked up using a collet.

[0131] Examples 4 to 6 A pressure-sensitive adhesive composition was prepared by dissolving the energy-reactive resin (B'), crosslinking agent (C), and photopolymerization initiator (D') in the amounts shown in Table 2 in toluene. Then, using this pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet was produced in the same manner as in Example 1. The following components (B') and (D') were used. <Component (B'): Energy-Reactive Resin> The energy-reactive resin was an acrylic copolymer (monomer mass ratio: butyl acrylate / methyl methacrylate / 2-hydroxyethyl acrylate = 52 / 20 / 28) reacted with 90% equivalent of 2-isocyanatoethyl methacrylate relative to the 2-hydroxyethyl acrylate, thereby introducing an energy ray-reactive group into the polymer side chain via the hydroxy group (mass average molecular weight (Mw): 520,000, number average molecular weight (Mn): 155,000). <Component (D'): Photopolymerization Initiator> 1-Hydroxycyclohexyl phenyl ketone was used as the photopolymerization initiator.

[0132]

[0133] In Examples 4 to 6, it was also confirmed that when the tensile breaking stress of the adhesive layer was 20 MPa or more, the element could be picked up using a collet.

[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. 2023-156493, filed September 21, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. An adhesive sheet having an adhesive layer with an uneven surface, wherein the tensile breaking stress of the adhesive layer at 23°C is 20 MPa or more.

2. The adhesive sheet according to claim 1, wherein the tensile breaking stress is 100 MPa or less.

3. 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.

4. The pressure-sensitive adhesive sheet according to claim 1, which is expandable in the planar direction by 1% or more.

5. 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 plurality of protrusions having a pitch of at least 1 μm and no greater than 100 μm.

6. 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.

7. The adhesive sheet according to claim 1, wherein the adhesive layer contains an acrylic resin and an energy ray curable resin.

8. The pressure-sensitive adhesive sheet according to claim 7, wherein the energy ray-curable resin contains a polyvalent (meth)acrylate as a constituent unit.

9. The pressure-sensitive adhesive sheet according to claim 7, wherein the amount of the energy ray-curable resin per 100 parts by mass of the acrylic resin is 8 parts by mass or more.

10. The adhesive sheet according to claim 7, wherein the adhesive layer further contains a crosslinking agent for the acrylic resin, and the amount of the crosslinking agent per 100 parts by mass of the acrylic resin is 0.05 parts by mass or more.

11. A method for handling an object, comprising: a holding step of holding an object in the adhesive layer of the adhesive sheet according to any one of claims 1 to 10; and a peeling step of peeling the object from the adhesive layer of the adhesive sheet.

12. A method for handling an object as described in claim 11, further comprising an expansion step of expanding the adhesive sheet holding the object in a planar direction, and in the peeling step, peeling the object from the adhesive layer of the adhesive sheet expanded in the planar direction.

13. The method for handling an object according to claim 11, wherein in the peeling step, the object is peeled off from the adhesive layer of the adhesive sheet using an adsorption member.

14. The method for handling an object described in claim 11, wherein in the peeling step, the object is peeled off from the adhesive layer of the adhesive sheet without applying a physical stimulus to the opposite surface of the adhesive layer of the adhesive sheet.

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