WO2025063124A1 - Adhesive sheet and method for handling object - Google Patents

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. After the mirror surface of a silicon chip having a size of 5.0 mm × 5.0 mm is pressed against the adhesive layer of the adhesive sheet at a contact pressure of 0.3 MPa, the workload when peeling the silicon chip from the adhesive layer is 25 μJ or less.

Description

Adhesive sheet and method for handling objects

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

Adhesive sheets can be used to temporarily hold an object. For example, such adhesive sheets can be used to transfer an object to a desired location.

Adhesive sheets come in a variety of shapes depending on their applications. For example, Patent Document 1 describes providing grooves on the surface of the adhesive layer so that air bubbles can be removed after application.

JP 2021-147418 A

The inventors of the present application have investigated providing irregularities on the surface of the adhesive layer of an adhesive sheet. Such a configuration reduces the force with which the sheet holds an object, making it easier to pick up the object from the sheet for transfer. On the other hand, there is a demand for picking up the object with a gentler operation in order to reduce damage to the object when picking it up.

The present invention aims to make it possible to pick up an object held on an adhesive sheet with an adhesive layer having an uneven surface with a milder operation.

After extensive research, the inventors discovered that the above-mentioned problem could be solved by appropriately adjusting the amount of work required to peel an object from the adhesive layer of an adhesive sheet, making it easier to pick up the object. After further research, the inventors have completed the present invention.

That is, the present invention relates to the following [1] to [14].
[1] An adhesive sheet having an adhesive layer with an uneven surface, wherein the amount of work required to peel off a silicon chip from the adhesive layer after pressing a mirror surface of the silicon chip having a size of 5.0 mm x 5.0 mm against the adhesive layer of the adhesive sheet at a contact pressure of 0.3 MPa is 25 μJ or less.
[2] The pressure-sensitive adhesive sheet according to [1], wherein the workload is 0.1 μJ or more.
[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 pressure-sensitive adhesive layer.
[4] The pressure-sensitive adhesive sheet according to any one of [1] to [3], which is expandable by 1% or more in the planar direction.
[5] The 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 bounded by concave portions, and the pitch of the plurality of convex portions is 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 pressure-sensitive adhesive layer has a plurality of convex portions, and the height of the plurality of convex portions is uniform.
[7] The pressure-sensitive adhesive sheet according to any one of [1] to [6], wherein the pressure-sensitive 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 constituent 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 adhesive sheet according to any one of [7] to [9], 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 an adhesive layer of the adhesive sheet described in any one of [1] to [10]; and a peeling step of peeling the object from the adhesive layer of the adhesive sheet.
[12] The method for handling an object described in [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 any one of [11] to [12], 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 any one of [11] to [13], wherein in the peeling step, the object is peeled off 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.

This allows objects held on an adhesive sheet with an uneven surface to be picked up with a gentler operation.

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 components are designated by the same reference numerals.

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
FIG. 2 is a cross-sectional view of a sheet according to an embodiment. FIG. 4 is a cross-sectional view showing an example of projections and recesses on a sheet. FIG. 4 is a cross-sectional view showing an example of projections and recesses on a sheet. FIG. 4 is a top view showing an example of unevenness of a sheet. FIG. 4 is a top view showing an example of unevenness of a sheet. FIG. 4 is a top view showing an example of unevenness of a sheet. FIG. 4 is a cross-sectional view showing an example of projections and recesses on a sheet. FIG. 4 is a cross-sectional view showing an example of projections and recesses on a sheet. FIG. 4 is a cross-sectional view showing an example of projections and recesses on a sheet. 11A and 11B are diagrams for explaining a sheet expansion method. 11A and 11B are diagrams for explaining a sheet expansion method. 1 is a flowchart of an object transfer method according to an embodiment.

Below, the embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit 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 multiple features described in the embodiments may be combined in any desired manner. Furthermore, the same reference numbers are used for the same or similar configurations, and duplicate descriptions will be omitted.

(Definition)
In this specification, the mass average molecular weight (Mw) and the number average molecular weight (Mn) are values calculated in terms of standard polystyrene measured by size exclusion chromatography, specifically, values measured based on 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.

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, a description that is 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 and 9 or less, 1 or more and 8 or less, 1 or more and 7 or less, 2 or more and 9 or less, 2 or more and 8 or less, 2 or more and 7 or less, 3 or more and 9 or less, 3 or more and 8 or less, and 3 or more and 7 or less.

(Seat configuration)
The adhesive sheet according to one embodiment of the present invention includes 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 transfer 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 transfer destination. The substrate 120 can support the adhesive layer 110. Hereinafter, the configuration of such an adhesive sheet will be described with reference to FIG. 1, which is a schematic diagram of an adhesive sheet according to one embodiment.

(Substrate)

The substrate 120 functions as a support for the adhesive layer 110. The substrate 120 is located on the side opposite the uneven surface of the adhesive layer 110.

As 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 when holding an object, facilitate lamination 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 transparent.

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 film. In addition, 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 be used. In addition, the substrate 120 may be a laminate film in which two or more resin films are laminated.

From the viewpoint of facilitating the expansion of the adhesive sheet, the substrate 120 is preferably a polyolefin-based film or a vinyl chloride copolymer film. Examples of polyolefin-based films include polyethylene films, polypropylene films, and copolymers containing unsubstituted olefins such as ethylene or propylene as constituent units, such as ethylene-based 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 contain other resin components or additives.

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, even more preferably 150 μm or less, even more preferably 120 μm or less, and particularly preferably 90 μm or less.

To facilitate uniform expansion of the adhesive 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.

Similarly, to facilitate expansion of the adhesive 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.

(Adhesive layer)
The adhesive layer 110 is a layer having adhesiveness 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.

(Composition of Adhesive Layer)
Examples of the resin contained in the adhesive layer 110 include rubber-based resins such as polyisobutylene-based resins, polybutadiene-based resins, and styrene-butadiene-based resins, acrylic resins, urethane-based resins, polyester-based resins, olefin-based resins, silicone-based resins, and polyvinyl ether-based resins. The adhesive layer may have heat resistance, and examples of the material of the adhesive layer 110 having 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 constituent 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.

The resin contained in the adhesive layer 110 is preferably an adhesive resin that has 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, it is preferably 2 million or less, and more preferably 1.2 million 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, it is preferably 2 million or less, more preferably 1.5 million or less, and even more preferably 1.2 million or less. In addition, when the adhesive layer 110 contains a resin derived from an energy reactive resin as described later, 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 the application of energy. In addition, 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. By having the Tg within this range, it becomes easier to keep the retention and storage modulus of the resulting adhesive layer 110 within the ranges described below.

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, even more preferably 99.50% by mass or less.

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 the 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 deviation 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 with a thickness of 3 mm and a diameter of 8 mm, and measuring the storage modulus of the sample by a torsional shear method using a viscoelasticity measuring device under an environment of 1 Hz and 23°C.

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 unevenness in the adhesive layer 110 by heating and softening the resin, and it becomes easy to maintain the uneven 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 (meth)acrylic acid esters as monomers.

Below, examples of the composition of the adhesive layer 110 are described. However, the composition of the adhesive layer 110 is not limited to those shown below.

(Acrylic Resin (A))
In one embodiment, the adhesive composition forming the 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. Moreover, 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.

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. By having the Tg within this range, it becomes easier to obtain an adhesive layer 110 having the above-mentioned storage modulus.

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

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, 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, or 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 (meth)acrylates. Examples of the hydroxyl group-containing (meth)acrylic acid ester include 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.

The acrylic resin may be, for example, a resin obtained by copolymerizing one or more monomers selected from (meth)acrylic acid esters or (meth)acrylic acid, such as itaconic acid, vinyl acetate, acrylonitrile, styrene, and N-methylolacrylamide.

The acrylic resin may be made up of one type of monomer or two or more types, and if there are two or more types, the combination and ratio of these can be selected arbitrarily.

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

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.

(Energy Reactive Resin (B))
In one embodiment, the adhesive composition forming the adhesive layer 110 contains an energy reactive resin (B). The energy reactive resin (B) refers to a resin whose elastic modulus is improved by the 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 the application of energy.

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. The energy ray is preferably ultraviolet rays, that is, the resin is preferably an ultraviolet-reactive resin.

Thermoplastic energy reactive resin refers to an energy reactive resin that has thermoplastic properties at least before energy is applied. In addition, 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.

When using such energy reactive resins, it becomes easy to maintain the uneven shape that was formed by applying energy (e.g., irradiating with energy rays) after forming the unevenness in the resin.

As such an energy reactive resin, a polymer into which a polymerizable functional group has been introduced can be used. A polymerizable functional group is a functional group that is crosslinked by the application of energy (for example, by 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.

For example, diene rubber composed of a polymer having a polymerizable functional group at the end of the main chain and/or at the 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 or pentenediyl groups as structural units). Preferred examples of energy reactive resins 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.

The average number of polymerizable functional groups per molecule in these energy reactive resins is preferably 1.5 or more, and more preferably 2 or more, from the viewpoint of making it easier to maintain the uneven shape of the adhesive layer 110. On the other hand, this average value is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less, from the viewpoint of increasing the adhesion and flexibility of the adhesive layer 110.

The adhesive layer 110 may contain one type of resin, or may contain two or more types of resin. 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 resin derived from a thermoplastic resin or 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. By adding such a liquid resin or monomer, it becomes easier to control the retention and storage modulus of the adhesive layer 110.

In one embodiment, the adhesive layer 110 preferably contains a resin derived from an energy reactive liquid resin, since this makes it easier to maintain the uneven shape of the adhesive layer 110. An example of such a liquid resin is a diene-based rubber, and a specific example is a polybutadiene-based resin in which butadiene is used as a monomer.

The adhesive layer 110 according to another embodiment includes a combination of any resin and a resin derived from an energy reactive liquid resin or an energy reactive monomer. For example, the adhesive layer 110 may include an acrylic resin (A) and a resin derived from an energy reactive liquid resin or an energy reactive monomer. Even with such a combination, by forming irregularities in 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 irregular shape that has been formed.

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

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

Also, 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 according to the required 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, 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, for example, a resin derived from an energy ray curable monomer. Here, the parts by mass are based on the mass of the solid content, and hereinafter, unless otherwise specified, are also based on the mass.

(Other components of the 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.

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

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 isocyanate-based crosslinking agents include 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, methylene bis(cyclohexyl isocyanate), 3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate, and hydrogenated xylylene diisocyanate; and acyclic aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate; and other polyvalent isocyanate compounds. Further, examples of isocyanate-based crosslinking agents include trimethylolpropane adduct-type modified products of the polyisocyanate compound, biuret-type modified products reacted with water, and isocyanurate-type modified products containing an isocyanurate ring.

The adhesive composition may contain one type of crosslinking agent, or may contain two or more types of crosslinking agents. From the viewpoint of carrying out a suitable crosslinking reaction, the content of the crosslinking agent in the adhesive composition is preferably 0.01 mass% or more, more preferably 0.1 mass% or more, even more preferably 0.2 mass% or more, particularly preferably 0.3 mass% or more, and is preferably 5 mass% or less, more preferably 3 mass% or less, and even more preferably 1 mass% or less.

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 hydroxyl group as a constituent unit. In this case, the amount of the 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 the 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 is 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.

The photopolymerization initiator (D) initiates a crosslinking reaction in response to the application of energy (e.g., irradiation with energy rays). When the adhesive composition contains an energy reactive resin (B), the adhesive layer 110 further contains a photopolymerization initiator (D), so that the crosslinking reaction proceeds even with the application of relatively low energy.

Examples of photopolymerization initiators (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.

The adhesive composition 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 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.

Examples of antioxidants (E) include phenol-based, such as hindered phenol-based compounds, aromatic amine-based, sulfur-based, and phosphorus-based, such as phosphate ester-based compounds.

Other additives that may be contained in the adhesive layer 110 include, but are not limited to, 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; 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.

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.

(Shape of adhesive layer)
The surface of the adhesive layer 110 according to the present embodiment has projections and recesses. In one embodiment, the adhesive layer 110 has a surface including a plurality of projections spaced apart from one another and bounded by recesses. Each of the projections may be separated by a recess that is continuous throughout the adhesive layer 110.

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. Also, Figs. 2A and 2B depict the element 140 held by the convex portion 111 of the adhesive layer 110, while Figs. 3A, 3B, and 3C omit the element 140 held by the convex portion 111.

As shown in Figures 2A and 3A, the convex portions 111 may be regularly arranged on the surface of the adhesive layer 110. Regular arrangement of the 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 irregularly arranged.

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

In this embodiment, the adhesive sheet is expanded, and the adhesive layer 110 shown in FIG. 2A and FIG. 3A is transformed into the adhesive layer 110' shown in FIG. 2B and FIG. 3B. Comparing the adhesive layer 110 and the adhesive layer 110', the pitch P of each convex portion 111 is enlarged due to the expansion in the adhesive layer 110', and the number of convex portions 111 that hold one element 140 is reduced. As a result, in the adhesive layer 110', the force with which the convex portions 111 hold the element 140 is reduced compared to the adhesive layer 110. In addition, shear stress acts between the convex portions 111 and the element 140 due to the expansion of the adhesive sheet. The inventors of the present application consider that this also leads to a decrease in the holding force of the element 140 by the convex portions 111.

The pitch P of the convex portion 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 increasing the holding force, the 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 portion 111 means the distance between the center point of one 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 portion 111 represents the distance between the center point of the convex portion 111 on the 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 multiple 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.

The specific shape of the convex portion 111 is not particularly limited. For example, the convex portion 111 may have a pillar shape. As a specific example, the convex portion 111 may have a cylindrical shape or a rectangular prism shape. As described above, the convex portion 111 may extend in a line shape, or may extend in a curved shape such as a wave shape. Furthermore, these convex portions 111 may be tapered.

FIG. 4A shows a cross-sectional view of an adhesive layer 110 according to one embodiment, passing through a convex portion 111 and perpendicular to the surface of the adhesive layer 110. The convex portion 111 shown in FIG. 4A is tapered, that is, the convex portion 111 is tapered. Also, as shown in FIG. 4B, the tip of the convex portion 111 may be curved. With this configuration, the impact when an object is held by the adhesive layer 110 is further mitigated, making it easier for the adhesive layer 110 to hold the object without it slipping. On the other hand, the tip of the convex portion may be flat.

As shown in FIG. 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.

As another example, the convex portion may be hemispherical or part of a sphere as shown in FIG. 4B. The convex portion 111 may also be T-shaped as shown in FIG. 4C. As yet another example, the convex portion 111 may have a shape of a collection of multiple grains, 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 unevenness.

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 power of the object. On the other hand, from the viewpoint of increasing 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 respectively 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.

Moreover, the area of each of the convex portions 111 is preferably 10 μm ² or more, more preferably 20 μm ² or more, and even more preferably 30 μm ² or more, from the viewpoint of maintaining the holding force of the object. On the other hand, from the viewpoint of increasing the ease of peeling the object, it is preferably 2000 μm ² or less, more preferably 1000 μm ² or less, and even more preferably 500 μm ² or less. 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).

In one embodiment, the height of each of the convex portions 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 of the object. On the other hand, from the viewpoint of increasing the dimensional stability, the height of each of the convex portions 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 force of the object to be changed. Here, the height of the convex portion 111 is represented by H in FIG. 4A. Also, in one embodiment, the height of the multiple convex portions of the adhesive layer 110 is uniform. In another embodiment, the adhesive layer 110 may have a first multiple convex portion having a first uniform height and a second multiple convex portion having a different height. Here, the second multiple convex portions may have a second uniform height. For example, the convex portion 111 may be composed of such a first convex portion and a second convex portion. In a further embodiment, the adhesive layer 110 may have multiple convex portions of random heights.

The total area of the convex portions 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 convex portions 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 increasing the ease of peeling the object.

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

(Characteristics of the adhesive layer)
In the adhesive sheet according to one embodiment, the work required to peel off an object from the adhesive layer 110 is adjusted. For example, from the viewpoint of enabling picking up an object under milder conditions, the work required to peel off the silicon chip from the adhesive layer after pressing the mirror surface of a silicon chip having a size of 5.0 mm x 5.0 mm against the adhesive layer of the adhesive sheet at a contact pressure of 0.3 MPa 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, from the viewpoint of ensuring the holding force of the object, the work required to peel off 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.

This workload can be evaluated by performing a probe tack measurement under conditions of a contact load of 8 N in an environment of 23°C. Specifically, a probe is used with a silicon chip measuring 5.0 mm x 5.0 mm fixed to its tip. Then, the silicon chip is pressed against the adhesive layer of the adhesive sheet with a contact pressure of 0.3 MPa so that the mirror surface of the silicon chip comes into contact with 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 the tack force.

This 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.

The inventors of the present application 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 inventors' investigation has found that by controlling the workload as described above, it is 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 by adjusting the workload before expansion as described above, it is possible to easily peel the object from the adhesive sheet after expansion.

In the adhesive sheet according to one embodiment, the tensile breaking stress of the adhesive layer 110 is adjusted. For example, from the viewpoint of enabling picking up of an object under milder conditions, the tensile breaking stress 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 force of an object, the tensile breaking stress 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.

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. Samples used for the measurement can be prepared by cutting them out from an adhesive sheet or other methods. There are no particular limitations on the size of the sample, but for example, a sample with a width of 5 mm, length of 30 mm, and thickness of 0.1 mm can be used.

Such tensile stress at break can be adjusted, for example, by controlling the composition of the adhesive layer 110. For example, the tensile stress at break can be increased by increasing the proportion of the energy reactive resin that constitutes the adhesive layer 110 or by increasing the proportion of the crosslinking agent.

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.

In the adhesive sheet according to one embodiment, the adhesive strength of the adhesive layer 110 is adjusted. For example, from the viewpoint of enabling picking up 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 force 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.

The adhesive strength of the adhesive layer 110 can be measured using a tensile tester in an environment of 23°C and 50% RH (relative humidity) based on JIS Z0237:2000. In one embodiment, the object is peeled off from the adhesive layer 110 after the adhesive sheet is expanded, and by adjusting the adhesive strength before expansion as described above, it is possible to easily peel off the object from the adhesive sheet after expansion.

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

(Release sheet)
As shown in Fig. 1, the adhesive sheet according to the present embodiment may include a release sheet 150 that is in contact with the adhesive layer 110 and has an uneven surface complementary to the uneven surface of the adhesive layer 110. For the sake of explanation, Fig. 1 shows a state in which the adhesive layer 110 and the release sheet 150 are separated from each other.

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 a recess 161, and the recess 161 has a shape that is complementary to the protrusion 111. However, it is not essential that the recess 161 has a shape that is complementary to the protrusion 111.

The release sheet 150 may have a substrate 170 on the surface that is not in contact with the adhesive layer 110. The substrate 170 may 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 substrate 120 may be made of EMAA, and the substrate 170 may be made of polyethylene terephthalate. The release sheet 150 may also have an undercoat layer (not shown) between the release layer 160 and the substrate 170.

(Other layers)
The above-mentioned sheet may have a layer 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.

(Method of manufacturing adhesive layer and sheet)
There is no particular limitation on the manufacturing method of the adhesive layer and the sheet. For example, a sheet having an adhesive layer 110 on a substrate 120 can be manufactured as follows. First, an organic solvent is added to a raw material composition containing each component of the adhesive layer 110 described above to prepare a solution of the raw material composition. Then, this solution is applied onto the substrate 120 to form a coating film, and then the solution is dried to provide an adhesive layer on the substrate 120. Furthermore, a treatment is performed to provide irregularities on the surface of the adhesive layer, thereby forming an adhesive layer 110 having irregularities.

Examples of organic solvents used to prepare the solution of the raw material composition include toluene, ethyl acetate, and methyl ethyl ketone. 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 (e.g., screen printing and inkjet printing).

There is no particular limit to the process for providing the unevenness on the surface of the adhesive layer 110. For example, the unevenness 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 unevenness to be provided can be used. Specifically, the unevenness 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 a mold. As a more specific method, the adhesive layer can be pressed with a mold, heated and maintained for a predetermined time, and then cooled and the mold can be 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. In addition, the time for maintaining the adhesive layer in a heated state is not particularly limited, but may be maintained for 10 seconds or more, or may be maintained for 10 minutes or less. As a specific method for heating the adhesive layer while pressing the adhesive layer with a mold, a method of vacuum laminating the adhesive layer provided on the substrate and the mold can be mentioned. Instead of performing the two-step process of forming the adhesive layer and forming the unevenness, an adhesive layer having an uneven surface may be formed on the substrate in a single step. Also, a release sheet 150 having a release layer 160 having unevenness as described above may be used as the mold.

Alternatively, a solution of the raw material composition can be sprayed to provide an adhesive layer 110 having a rough surface. Furthermore, a filler can be added to the solution of the raw material composition and the solution can be applied to provide an adhesive layer 110 having a rough or fibrous surface. As yet another method, an adhesive layer 110 having a concave-convex shape can be directly provided on the substrate 120 by applying the solution of the raw material composition according to a desired pattern using a printing method such as an inkjet method.

(How to use the adhesive sheet)
The adhesive sheet according to the present embodiment can be used to handle an object. For example, the adhesive sheet according to the present embodiment can be used to temporarily hold an object. The adhesive sheet according to the present embodiment can also be used to transfer an object. As a specific example, the adhesive sheet according to the present embodiment can be used to transfer a semiconductor chip obtained by dicing to a desired position. The method for handling an object using the adhesive sheet according to the present embodiment will be described with reference to the flow chart of FIG. 6.

(S10: Holding an object)
In S10, an object is held in the adhesive layer of the adhesive sheet according to the present 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 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 may be a component thereof. The element may be an individualized object such as a wafer, a panel, or a 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 an individualized object, and may be various wafers or various substrates that are not individualized.

The size of the object is not particularly limited. The size of the object may be, for example, preferably 100 μm ² or more, more preferably 500 μm ² or more, and even more preferably 1000 μm ² or more. On the other hand, the size of the object may be preferably 100 mm ² or less, more preferably 25 mm ² or less, and even more preferably 1 mm ² or less.

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 more, and more preferably 12 inches (diameter approximately 300 mm) or more. The shape of the wafer is not limited to a circle, and may be an angular shape such as a square or rectangle.

The panel may be a fan-out type semiconductor package (e.g., FOWLP or FOPLP). In other words, 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 square substrate of about 300 to 700 mm.

Examples of substrates include glass substrates, sapphire substrates, and compound semiconductor substrates.

In one embodiment, the elements are transferred from the holding substrate to the adhesive sheet, and the adhesive sheet holds the transferred elements. For example, a semiconductor wafer can be attached onto a wafer substrate, and the semiconductor wafer can 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, an external stimulus such as laser light can be applied to reduce the adhesiveness between the wafer substrate and the elements. Through such a process, the elements can be transferred from the wafer substrate to the adhesive sheet. As another method, the elements obtained by dicing the semiconductor wafer can be transferred to a holding substrate to obtain a holding substrate to which the elements are attached. The elements attached to the holding substrate can then be transferred to the adhesive layer 110 of the adhesive sheet in a similar manner.

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. Also, the element moves closer to the adhesive sheet relative to the adhesive sheet. Then, the element comes into contact with the adhesive layer 110 of the adhesive sheet, and 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 energy application, cooling, expansion of the holding substrate, and physical stimulus (e.g., pressing the rear 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, when the separated element approaches the adhesive layer 110, pressure is generated between the element and the adhesive layer 110. However, since the surface of the adhesive layer 110 has unevenness, the pressure generated between the element and the adhesive layer 110 is alleviated, making it easier to capture the element at a desired position on the adhesive sheet.

In a further embodiment, a semiconductor wafer is attached to the adhesive layer 110 of the adhesive sheet. The semiconductor wafer on the adhesive layer 110 is then diced to form elements. This method also allows the adhesive sheet to hold elements.

(S20: Expanding the adhesive sheet)
In the method for handling an object according to an embodiment, the adhesive sheet holding the object is expanded in a surface direction. In the flow chart shown in FIG. 6, the adhesive sheet is expanded in a surface direction in S20. As described above with reference to FIGS. 2A, 2B, 3A, 3B, and 3C, the holding force of the object is reduced by expanding the adhesive sheet, which makes it easier to peel off the object in the next step. The adhesive sheet according to an embodiment may be expandable by 1% or more in a surface direction (for example, in one direction or two orthogonal directions) from the viewpoint of sufficiently reducing the holding force of the object.

The method of expanding the adhesive sheet is not particularly limited. For example, the adhesive sheet may be expanded in one direction, two directions, or multiple other directions. The expansion rate of the adhesive sheet is also not particularly limited. For example, from the viewpoint of sufficiently reducing the holding force of the object, the expansion rate of the adhesive sheet in one direction may be 1% or more, or may be 5% or more. Furthermore, from the viewpoint of preventing the adhesive sheet from breaking, the expansion rate of the 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 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.

As a specific example, the adhesive sheet can be expanded by fixing the adhesive sheet to a frame and pressing a seat against the adhesive sheet inside the frame. Such an example will be described with reference to Figures 5A and 5B. Figure 5A shows a state in which the adhesive sheet holds elements 140a to 140d. As shown in Figure 5A, the outer periphery of the adhesive sheet can be fixed to frame 320. The shape of frame 320 is not particularly limited. For example, 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. By using a ring frame, the adhesive sheet can be expanded in all directions.

The adhesive sheet fixed to the frame 320 is then brought into contact with the base 310, and the frame 320 is 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 at a speed of 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.

(S30: Peeling off object)
In S30, the object is peeled off from the adhesive layer 110 of the adhesive sheet. In the flow chart of FIG. 6, the object is peeled off from the adhesive layer 110 of the adhesive sheet expanded in the surface direction. The method of peeling off the object is not particularly limited. For example, the above-mentioned method can be used as a method of transferring an object attached to a holding substrate to an 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. Then, the adsorbed object can be moved to a desired position of the transfer destination. When 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.

In addition, according to the research of the present inventors, when attempting to peel an object from the adhesive layer 110 using an adhesive member without physical stimulation, if the adhesive force is increased in accordance with the strength of 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.

By using such a procedure, an object can be transferred to any desired destination using the adhesive sheet. Furthermore, such a transfer method can be used to manufacture electronic components or semiconductor devices having elements. The object held by the adhesive sheet may be treated or processed.

The present invention will be described in more detail below with reference to examples. However, the present invention is in no way limited to the following examples. Parts and percentages in each example are based on the mass of the solid content unless otherwise specified.

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): 1.1 million) was used.

<Component (B): Energy Reactive Resin>
The following energy reactive resins were used:
(B1) Tricyclodecane dimethanol diacrylate (A-DCP)
(B2) SBS having vinyl groups in the side chains: styrene-butadiene-styrene block copolymer (SBS) having 1,2-vinyl groups in the side chains [having a branched structure and a radial structure with a branch point as a central nucleus, number average molecular weight (Mn) 160,000, mass average molecular weight (Mw) 180,000, styrene block content 20 mass%, butadiene block content 80 mass%, content of structural units having 1,2-vinyl groups in the side chains among all structural units constituting the butadiene block is 42 mol%, melt flow rate measured under conditions of temperature 200° C. and load 5 kg is 5 g/10 min]
(B3) PB having vinyl groups in the side chains: polybutadiene copolymer (PB) having 1,2-vinyl groups in the side chains [mass average molecular weight (Mw) 5,500, glass transition temperature: -49°C, liquid at room temperature]

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

<Component (D): Photopolymerization initiator>
As the photopolymerization initiator, the following was used.
(D1) 2,4,6-trimethylbenzoyldiphenylphosphine oxide (D2) bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide

<Component (E): Antioxidant>
As the antioxidant, a composition in which a hindered phenol-based antioxidant and a phosphorus-based antioxidant were mixed in a mass ratio of 1:1 was used.

<Workload evaluation>
The amount of work required to peel an object held by the adhesive sheet obtained in each example from the adhesive layer was measured as follows. A sample for measuring the amount of work was prepared by bonding the substrate side of the adhesive sheet obtained in each example to glass (manufactured by Corning, product name "Eagle XG") using double-sided tape. A roll laminator was used for bonding.

The probe tack measurement was performed on the prepared work measurement sample at 23°C using a probe tack measurement device (product name "TA-XT plus Texture Analyser" manufactured by Stable Micro Systems) under a contact load of 8N. A silicon chip (mirror silicon wafer, 6 inches, 150 μm thick, diced to a size of 5 mm x 5 mm) was fixed to the tip of the probe using double-sided tape. The chip was then pressed against the adhesive layer of the adhesive sheet with a contact pressure of 0.3 MPa so that the silicon mirror surface was in contact with the adhesive layer, and the probe tack at the interface between the chip and the adhesive layer was measured. Measurement data was obtained in which the tack force was plotted every 0.2 μm of the probe's travel distance. The work amount was calculated by integrating the obtained measurement data. The work amount is represented by the area under the graph showing the relationship between the probe's travel distance and the tack force.

<Pickup evaluation>
The pickup evaluation of the object held by the adhesive sheet obtained in each Example was carried out as follows: First, the adhesive layer of the adhesive sheet obtained in each Example was attached to a ring frame (made of stainless steel, inner diameter 194 mm), and the adhesive sheet was cut to fit the outer diameter of the ring frame.

Next, a wafer substrate (mirror silicon wafer, 6 inches, 150 μm thick) was fixed to a dicing tape prepared separately. 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. In this way, an adhesive sheet on which multiple elements were placed and supported by a ring frame was obtained as an evaluation sample.

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 Figure 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 to expand the adhesive sheet. This evaluation also assessed whether the element could be picked up without poking the surface (base material) of the adhesive sheet opposite the element to be adsorbed with a needle.

Example 1
A pressure-sensitive adhesive composition was prepared by dissolving in toluene the acrylic resin (A), the energy reactive resin (B1), the crosslinking agent (C), and the photopolymerization initiator (D1) in the amounts shown in Table 1. Table 1 shows the solid content parts by mass of each material.

This 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 an adhesive layer 25 μm thick.

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

After peeling off the release sheet, the adhesive layer was attached to a replica mold in 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 ultraviolet light at an illuminance of 130 mW/ ^cm2 and a light amount of 210 mJ/ ^cm2 to produce an adhesive sheet having an uneven surface. The uneven shape of the adhesive layer of the adhesive sheet was a shape in which pillars were arranged in a lattice shape, similar to FIG. 2A. The pitch P between the pillars in the adhesive sheet was 20 μm. In addition, the height (H) of each pillar shown in FIG. 4A was 8 μm, the diameter (T) of the tip was 8 μm, and the diameter (D) of the base was 16 μm. In addition, the ratio of the area of the adhesive layer and the captured element to the area of the adhesive sheet (i.e., the area of the tip surface of the convex portion) was approximately 12.6%. In addition, as the replica mold, one having a surface shape complementary to such an uneven shape was used.

The adhesive strength of the adhesive layer was evaluated using the prepared adhesive composition according to the method described above. In addition, a pickup evaluation of the object held by 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 the object was picked up, and "F" indicates that the object was not picked up.

(Examples 2 to 3)
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 amounts of energy reactive resin (B1) and photopolymerization initiator (D1) shown in Table 1 were used.

(Comparative Examples 1 to 3)
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 amounts of energy reactive resin (B1), crosslinking agent (C), and photopolymerization initiator (D1) shown in Table 1 were used.

(Comparative Example 4)
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the pressure-sensitive adhesive composition was prepared by dissolving the energy reactive resins (B2) and (B3) and the photopolymerization initiator (D2) in the amounts shown in Table 1 in toluene, and a pressure-sensitive adhesive sheet was produced.

As can be seen from a comparison between Examples 1 to 3 and Comparative Examples 1 to 4, it was confirmed that an object can be picked up using a collet when the amount of work required to peel the silicon chip from the adhesive layer is 25 μJ or less.

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

This application claims priority based on Japanese Patent Application No. 2023-156492, filed on September 21, 2023, the entire contents of which are incorporated herein by reference.

Claims (14)

An adhesive sheet having an adhesive layer with an uneven surface,
An adhesive sheet, in which the amount of work required to peel off a silicon chip having a size of 5.0 mm x 5.0 mm from an adhesive layer of the adhesive sheet after pressing the mirror surface of the silicon chip against the adhesive layer at a contact pressure of 0.3 MPa is 25 μJ or less. The adhesive sheet according to claim 1, wherein the workload is 0.1 μJ or more. The adhesive sheet of claim 1, further comprising a release layer having an uneven surface complementary to the uneven surface of the adhesive layer. The adhesive sheet according to claim 1, which is expandable in the planar direction by 1% or more. The adhesive sheet of claim 1, wherein the adhesive layer has a plurality of convex portions spaced apart from one another and bounded by concave portions, and the pitch of the plurality of convex portions is 1 μm or more and 100 μm or less. 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. The adhesive sheet according to claim 1, wherein the adhesive layer contains an acrylic resin and an energy ray curable resin. The adhesive sheet according to claim 7, wherein the energy ray curable resin contains a polyvalent (meth)acrylate as a constituent unit. The 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. 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. A holding step of holding an object on the adhesive layer of the adhesive sheet according to any one of claims 1 to 10;
a peeling step of peeling the object from the adhesive layer of the adhesive sheet;
(c) a method of handling an object, The method further includes a step of expanding the adhesive sheet holding the object in a planar direction,
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 expanded in a planar direction. 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. 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 without applying a physical stimulus from the opposite side of the adhesive layer of the adhesive sheet.

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