Adhesive sheet and peeling method

Abstract

The present invention enables an object held by an adhesive sheet to be picked up using a milder operation.　This adhesive sheet comprises: a base material; and an adhesive layer that has protrusions / recessions on the front surface thereof. The adhesive layer includes a base portion and a projection section provided on the base portion, and satisfies relational expression (1), the base portion being formed from a portion extending in the thickness direction of the adhesive layer from a recess section at which the thickness of the adhesive layer is at a minimum to the surface on the opposite side from the front surface on which the protrusions / recesses are provided. Relational expression (1): 0.25<S<4.75 (in relational expression (1), S indicates the thickness of the base portion, and H indicates the height of the projections.)

Description

Adhesive sheet and peeling method

[0001] The present invention relates to a pressure-sensitive adhesive sheet and a peeling method.

[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 object temporarily held by the adhesive sheet is peeled off (picked up) from the adhesive sheet in a subsequent process. In particular, when holding an object that is weak against external forces, such as a semiconductor element, it is desirable that the sheet's holding force for the object not be too strong in order to prevent the object from being damaged when peeled off.

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

[0007] After extensive research, the inventors discovered that by providing irregularities on the surface of the adhesive layer of the adhesive sheet, the pickup force required to pick up an object from the adhesive sheet can be reduced, 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 a substrate and a pressure-sensitive adhesive layer having an uneven surface, wherein the pressure-sensitive adhesive layer has a base portion configured from a portion extending in the thickness direction of the pressure-sensitive adhesive layer from a recess where the thickness of the pressure-sensitive adhesive layer is smallest to a surface opposite the uneven surface, and convex portions provided on the base portion, and wherein the pressure-sensitive adhesive sheet is characterized by satisfying the following relational expression (1): Relational expression (1): 0.25<S / H<4.75 (In relational expression (1), S represents the thickness of the base portion, and H represents the height of the convex portions.) [2] The pressure-sensitive adhesive sheet according to [1], wherein the base portion has a uniform thickness. [3] The pressure-sensitive adhesive sheet according to any one of [1] to [2], wherein the pressure-sensitive adhesive layer has a plurality of convex portions, and the height of the plurality of convex portions is uniform. [4] The pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the height of the convex portions is 1 μm to 15 μm. [5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], characterized in that the thickness of the base portion is 1 μm or more and 50 μm or less. [6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], characterized in that the base portion and the protrusions are integral. [7] The pressure-sensitive adhesive sheet according to any one of [1] to [6], characterized in that the pressure-sensitive adhesive layer has a plurality of protrusions spaced apart from one another and defined by recesses, the pitch of the plurality of protrusions being 1 μm or more and 100 μm or less. [8] The pressure-sensitive adhesive sheet according to any one of [1] to [7], characterized in that the shear storage modulus of the pressure-sensitive adhesive layer is 0.001 MPa or more and 100 MPa or less. [9] The pressure-sensitive adhesive sheet according to any one of [1] to [8], characterized in that the tensile modulus of the substrate is 2500 MPa or less.

[10] The pressure-sensitive adhesive sheet according to any one of [1] to [9], characterized in that it is a sheet for fixing an element.

[11] The pressure-sensitive adhesive sheet according to any one of [1] to [9], characterized in that it is a sheet for transferring an element.

[12] The adhesive sheet described in any one of [1] to

[11] , characterized in that the adhesive sheet is expandable in the planar direction and the holding force of an object on the adhesive sheet after expansion is reduced compared to before expansion.

[13] A method for peeling an element from an adhesive sheet, comprising: an expansion step of expanding the adhesive sheet according to any one of [1] to

[12] in a plane direction, the adhesive sheet holding an element on an adhesive layer; and a peeling step of peeling the element from the adhesive layer of the adhesive sheet expanded in the plane direction.

[14] The peeling method according to

[13] , further comprising a step of forming a plurality of elements by dicing the element held on the adhesive layer before the expansion step.

[0009] Objects held on the adhesive sheet can be picked up with a gentler operation.

[0010] 1 is a cross-sectional view of a sheet according to an embodiment; 2 is a cross-sectional view showing an example of unevenness on a sheet; 3 is a cross-sectional view showing an example of unevenness on a sheet; 4 is a top view showing an example of unevenness on a sheet; 5 is a top view showing an example of unevenness on a sheet; 6 is a cross-sectional view showing an example of unevenness on a sheet; 7 is a cross-sectional view showing an example of unevenness on a sheet; 8 is a cross-sectional view showing an example of unevenness on a sheet; 9 is a cross-sectional view showing an example of unevenness on a sheet; 10 is a diagram for explaining a method of expanding a sheet; 11 is a diagram for explaining a method of expanding a sheet; 12 is a flowchart of an element peeling method and a transfer method according to an embodiment;

[0011] 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.

[0012] (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.

[0013] 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.

[0014] (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 is used to temporarily hold an element and transfer it to a destination. For example, the adhesive sheet can be used to receive an element held on another holding substrate, temporarily hold the element, and transfer the element to a desired position on the destination. The substrate 120 can support the adhesive layer 110. The structure of such a sheet will be described below with reference to FIG. 1, which is a schematic diagram of a sheet according to one embodiment. In this specification, the adhesive sheet may be simply referred to as a sheet.

[0015] (Base material)

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

[0017] As will be described later, the 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 elements, facilitate stacking of sheets, or form the sheet into a roll. For example, a resin film can be used as the substrate 120. The resin film is a film in which a resin-based material is used as the main material, and may be made of a resin material or may contain an additive in addition to the resin material. The resin film may be laser light transmissive.

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

[0019] From the viewpoint of facilitating sheet expansion, 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-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 also contain other resin components or additives.

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

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

[0022] Similarly, to facilitate expansion of the sheet, the breaking elongation of the substrate 120 is preferably 105% or more, more preferably 150% or more, and even more preferably 250% or more. In this specification, the breaking elongation is measured in accordance with JIS K 7127:1999.

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

[0024] (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.

[0025] 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.

[0026] 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.

[0027] The shear 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 shear storage modulus of the adhesive layer 110 is preferable in that it can suppress positional displacement when holding an element. From this viewpoint, the shear 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 shear storage modulus is measured in accordance with JIS K7244-1:1998. Specifically, the shear 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 shear storage modulus of the sample using a viscoelasticity measuring device by a torsional shear method at 1 Hz and 23°C.

[0028] 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.

[0029] 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.

[0030] (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.

[0031] 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.

[0032] 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.

[0033] 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. The alkyl group constituting the alkyl ester has a chain structure having 1 to 18 carbon atoms (methacrylate), such as acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, myristyl (meth)acrylate, pentadecyl (meth)acrylate, palmityl (meth)acrylate, heptadecyl (meth)acrylate, and stearyl (meth)acrylate. (meth)acrylic acid alkyl esters; (meth)acrylic acid cycloalkyl esters such as isobornyl (meth)acrylate and dicyclopentanyl (meth)acrylate; (meth)acrylic acid aralkyl esters such as benzyl (meth)acrylate; (meth)acrylic acid cycloalkenyl esters such as dicyclopentenyl (meth)acrylate; (meth)acrylic acid cycloalkenyloxyalkyl esters such as dicyclopentenyloxyethyl (meth)acrylate; imide (meth)acrylates; glycidyl (meth)acrylate and other glycidyl (meth)acrylates. Examples of the acrylate include ricidyl group-containing (meth)acrylic acid esters; hydroxyl group-containing (meth)acrylic acid esters such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and substituted amino group-containing (meth)acrylic acid esters such as N-methylaminoethyl (meth)acrylate.Here, the term "substituted amino group" refers to a group having a structure in which one or two hydrogen atoms of an amino group are substituted with a group other than a hydrogen atom.

[0034] The acrylic resin may be, for example, a resin obtained by copolymerizing one or more monomers selected from the group consisting of itaconic acid, vinyl acetate, acrylonitrile, styrene, and N-methylolacrylamide in addition to a (meth)acrylic acid ester or (meth)acrylic acid.

[0035] The acrylic resin may be made up 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.

[0036] In one embodiment, the acrylic resin contains a monomer having a hydroxyl group as a constituent unit. The acrylic resin may also have functional groups capable of bonding to other compounds, such as vinyl groups, (meth)acryloyl groups, amino groups, carboxy groups, and isocyanate groups, in addition to the hydroxyl groups. These functional groups, including the hydroxyl groups 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).

[0037] 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 80% by mass or less, even more preferably 60% by mass or less.

[0038] (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.

[0039] 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.

[0040] 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.

[0041] 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 unevenness in the resin.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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 30% by mass or less, and more preferably 25% by mass or less.

[0050] Furthermore, when the adhesive layer 110 contains an acrylic resin (A) and an energy reactive resin (B), 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, particularly preferably 10 parts by mass or more, and preferably 30 parts by mass or less, more preferably 25 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 are based on the mass of the solid content, and hereinafter also based on mass unless otherwise specified.

[0051] (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), and other additives.

[0052] 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.

[0053] 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 polyvalent isocyanate compound, a biuret modified product obtained by reacting the polyvalent isocyanate compound with water, and an isocyanurate modified product containing an isocyanurate ring.

[0054] 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 mass% or more, more preferably 0.1 mass% or more, even more preferably 0.5 mass% or more, particularly preferably 0.8 mass% or more, and preferably 5 mass% or less, more preferably 4 mass% or less, even more preferably 2 mass% or less.

[0055] For example, the crosslinking agent may be a crosslinking agent for the acrylic resin (A). For example, an isocyanate-based crosslinking agent of an isocyanurate-type modified compound 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 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 0.5 parts by mass or more, particularly preferably 1.0 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.

[0056] 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.

[0057] 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.

[0058] 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, and is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less.

[0059] Other additives that may be contained in the adhesive layer 110 are not particularly limited, but include, for example, 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; antioxidants such as phenol-based compounds such as hindered phenol-based compounds, aromatic amine-based compounds, sulfur-based compounds, or phosphorus-based compounds such as phosphate ester-based compounds, fillers, pigments, extenders, and softeners.

[0060] When the adhesive layer 110 contains these additives, the content of the additives in the adhesive layer 110 is preferably 0.0001% by mass or more, more preferably 0.01% by mass or more, particularly preferably 0.1% by mass or more, even more preferably 1% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less.

[0061] (Shape of Adhesive Layer) The surface of the adhesive layer 110 according to this embodiment has projections and recesses. More specifically, the adhesive layer 110 has a base portion 113 and protrusions 111 provided on the base portion 113. FIG. 4A shows a cross-sectional view of the adhesive layer 110 according to one embodiment, passing through the protrusions 111 and perpendicular to the surface of the adhesive layer 110. As shown in FIG. 4A, the protrusions 111 and the base portion 113 may be integral. That is, the protrusions 111 and the base portion 113 may be formed from the same material. Alternatively, the protrusions 111 and the base portion 113 may be formed integrally.

[0062] As shown in FIG. 4A , the adhesive layer 110 can have a protrusion 111 and a recess 112. The recess 112 is the portion of the adhesive layer 110 where the thickness is the smallest, for example, the portion where the thickness of the adhesive layer 110 is minimal. In this case, the base portion 113 can be defined as the portion in the thickness direction of the adhesive layer 110 from the recess 112 to the surface opposite the uneven surface (in the example of FIG. 4A , the surface in contact with the substrate 120). As shown in FIG. 4A , the adhesive layer 110 can have, on its surface, a plurality of protrusions 111 that are separated from one another and bounded by the base portion 113. Furthermore, each of the plurality of protrusions 111 may be separated by the base portion 113 that is continuous throughout the entire adhesive layer 110.

[0063] In this embodiment, the thickness (S) of the base portion 113 and the height (H) of the convex portion 111 satisfy the following relational expression (1): 0.25<S / H<4.75

[0064] According to the inventors' studies, forming unevenness on the adhesive layer 110 can reduce the pickup force required to pick up an object from the adhesive sheet. In particular, forming unevenness on the adhesive layer 110 so as to satisfy the relational expression (1) can further reduce the pickup force required to pick up an object from the adhesive sheet. The inventors believe that the reason for this is that the depressions 112 also contribute to the retention of the object due to deformation of the surface of the adhesive layer 110, and that when the height (H) of the protrusions 111 is relatively large, the object is more likely to peel off from the depressions 112. The inventors also believe that the reason for this is that when the thickness (S) of the base portion 113 is relatively small, the surface of the adhesive layer 110 is less likely to deform, which also contributes to the object being more likely to peel off from the depressions 112.

[0065] Thus, from the viewpoint of reducing the pickup force required to pick up an object from the pressure-sensitive adhesive sheet, the S / H value is less than 4.75, preferably less than 4.25, more preferably less than 3.50, even more preferably less than 3.00, even more preferably less than 2.50, even more preferably less than 2.00, and even more preferably less than 1.75. On the other hand, from the viewpoint of increasing the holding power, the S / H value is greater than 0.25, preferably greater than 0.50, more preferably greater than 0.75, and even more preferably greater than 1.00.

[0066] In one embodiment, the height (H) of the protrusions 111 is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more from the viewpoint of reducing the pick-up force, while the height (H) of the protrusions 111 is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less from the viewpoint of improving the shape stability.

[0067] Furthermore, from the viewpoint of reducing the pick-up force, the thickness (S) of the base portion 113 is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, and even more preferably 20 μm or less. From the viewpoint of increasing the holding force, the thickness (S) of the base portion 113 is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.

[0068] In one embodiment, the base portion 113 has a uniform thickness. For example, the thickness of the adhesive layer 110 may be uniform in each of the multiple recesses 112 that the adhesive layer 110 has. Also, in one embodiment, the heights of the multiple protrusions 111 that the adhesive layer 110 has are uniform. On the other hand, the thickness of the base portion 113 does not need to be uniform, and the heights of the protrusions 111 do not need to be uniform. In such cases, the height (H) of the protrusions 111, the thickness (S) of the base portion 113, or the above-mentioned S / H value falls within the above-mentioned ranges in at least a portion of the adhesive layer 110, at least half of the adhesive layer 110, or the entire adhesive layer 110.

[0069] As one example, the adhesive layer 110 may have a first plurality of convex portions having a first uniform height and a second plurality of convex portions having different heights. Here, the second plurality of convex portions may have a second uniform height. For example, the convex portions 111 may be composed of such first convex portions and second convex portions. As another example, the adhesive layer 110 may have a plurality of convex portions 111 having random heights.

[0070] 2A to 2C are side views showing the shape of the adhesive layer 110, and FIGS. 3A to 3C are top views showing the shape of the adhesive layer 110. FIGS. 2A and 3A show an example of the adhesive layer 110 before expansion, and FIGS. 2B and 3B show an example of the adhesive layer 110 after expansion. In addition, while FIGS. 2A to 2C depict the element 140 held by the convex portions 111 of the adhesive layer 110, FIGS. 3A to 3C omit the element 140 held by the convex portions 111.

[0071] As shown in Figures 2A and 3A, the protrusions 111 may be regularly arranged on the surface of the adhesive layer 110. Regularly arranging the protrusions means that the protrusions are lined up in a straight line at regular intervals. On the other hand, the protrusions 111 may be arranged so that the intervals between them vary regularly. For example, the intervals between the protrusions may be short in the center of the sheet and long in the peripheral area of ​​the sheet. Furthermore, the protrusions may be arranged irregularly.

[0072] 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.

[0073] The sheet according to this embodiment can be expanded. For example, the adhesive layer 110 shown in FIGS. 2A and 3A is transformed into the adhesive layer 110' shown in FIGS. 2B and 3B by expansion. Comparing the adhesive layer 110 and the adhesive layer 110', the pitch P of the convex portions 111 in the adhesive layer 110' is increased by expansion, and the number of convex portions 111 that hold one element 140 is reduced. As a result, the force of the convex portions 111 holding the element 140 is reduced in the adhesive layer 110' compared to the adhesive layer 110.

[0074] 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 element 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 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 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.

[0075] 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.

[0076] 4A shows a cross-sectional view of an adhesive layer 110 according to one embodiment, taken perpendicular to the surface of the adhesive layer 110 and passing through a protruding portion 111. The protruding portion 111 shown in FIG. 4A is tapered, i.e., the protruding portion 111 is tapered. Furthermore, as shown in FIG. 4B, the tip of the protruding portion 111 may be curved. This configuration further reduces the impact when the adhesive layer 110 holds the element, making it easier for the adhesive layer 110 to hold the element without slipping. Alternatively, the tip of the protruding portion may be flat.

[0077] 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.

[0078] 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 element. On the other hand, from the viewpoint of improving the ease of peeling the element, 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 base portion 113, respectively.

[0079] In addition, the area of ​​each of the protrusions 111 is preferably 10 μm from the viewpoint of maintaining the holding force of the element. 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 element, it is preferable that the thickness is 2000 μm. ２ Less than 1000 μm, more preferably ２ More preferably, 500 μm or less ２Here, the area of ​​the convex portion 111 means the area of ​​the portion protruding from the surface of the base portion 113 (the area of ​​a circle with a diameter D in the case of FIG. 4A).

[0080] 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 force of the element. 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 element.

[0081] The unevenness of the adhesive layer 110 may be designed according to the shape of the element held by the sheet. For example, the ratio of the adhesive area between the adhesive layer 110 and one element to the area of ​​one element 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 the area of ​​one element (100%), from the viewpoint of maintaining the holding force of the element. On the other hand, the ratio of the adhesive area between the adhesive layer 110 and one element to the area of ​​one element 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 improving the ease of peeling the element. 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 element on the 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 workpiece.

[0082] (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.

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

[0084] The release sheet 150 may have a substrate 170 on the surface that does not contact the adhesive layer 110. This substrate 170 can be designed similarly to the substrate 120, but does not need to have the same composition or structure as the substrate 120. 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.

[0085] (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.

[0086] (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.

[0087] 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).

[0088] 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.

[0089] 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.

[0090] (Method of Using the Adhesive Sheet) The sheet according to this embodiment can be used to fix, hold, or transfer an object. The type of object is not particularly limited, and may be, for example, an element, as described below. For example, the sheet according to one embodiment is an element fixing sheet that can be used to fix an element to the adhesive layer. Furthermore, the sheet according to one embodiment is an element transfer sheet that can be used to temporarily hold an element on the adhesive layer and transfer the held element to a desired position. As a specific example, the sheet according to this embodiment can be used to transfer a semiconductor chip obtained by dicing to a desired position. A method for peeling and transferring an element using the sheet according to this embodiment will be described with reference to the flowchart of FIG. 6.

[0091] (S10: Holding of Element) In S10, an element is held in the adhesive layer of the adhesive sheet according to this embodiment. The type of element is not particularly limited. The element may be, for example, a semiconductor chip such as an LED chip, a semiconductor chip with a protective film, or a semiconductor chip with a die attach film (DAF). The element may also be a micro light-emitting diode, a mini light-emitting diode, a power device, a MEMS (Micro Electro Mechanical Systems), or a controller chip, or a component thereof. The element may also be a singulated object such as a wafer, panel, or substrate. The element may have a circuit surface on which an integrated circuit having circuit elements such as transistors, resistors, and capacitors is formed. The element is not necessarily limited to a singulated object, and may also be various unsingulated wafers or various substrates.

[0092] The size of the element is not particularly limited. For example, the size of the element 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 element is preferably 100 mm ２ Less than 25 mm, more preferably ２ Less than 1 mm, more preferably ２ It may be the following:

[0093] 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.

[0094] 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.

[0095] The substrate may be a glass substrate, a sapphire substrate, or a compound semiconductor substrate.

[0096] 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. The adhesive strength between the wafer substrate and the elements can then be reduced by applying an external stimulus such as laser light. This process allows elements to be transferred from the wafer substrate to a semiconductor transfer 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.

[0097] 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, the element comes into contact with the adhesive layer 110 of the sheet, causing the element to be separated from the holding substrate and captured by the 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, thereby separating the element 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 sheet.

[0098] In a further embodiment, a plurality of elements can be formed by dicing an element held on the adhesive layer 110 of the adhesive sheet. For example, a semiconductor wafer is attached to the adhesive layer 110. Then, a plurality of elements are formed by dicing the semiconductor wafer on the adhesive layer 110. This method also allows the adhesive sheet to hold elements. This dicing step can be performed before the adhesive sheet expansion step (S20) described below.

[0099] (S20: Expanding the adhesive sheet) Thereafter, the element held on the adhesive layer 110 of the adhesive sheet is peeled off. By using the adhesive sheet according to this embodiment, the element can be peeled off from the adhesive layer 110 with a small pick-up force. On the other hand, in order to peel off the element from the adhesive layer 110 with an even smaller pick-up force, in S20, the adhesive sheet holding the element on the adhesive layer 110 can be expanded in the planar direction. By expanding the sheet, the holding force of the element is reduced, making it easier to peel off the element in the next step.

[0100] The method of expanding the sheet is not particularly limited. For example, the sheet may be expanded in one direction, two directions, or multiple directions.

[0101] The expansion rate of the pressure-sensitive adhesive sheet is 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 rates 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.

[0102] As a specific example, the sheet can be expanded by fixing the sheet to a frame and pressing a base against the 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 sheet holds elements 140a to 140d. As shown in FIG. 5A, the outer periphery of the 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 sheet to be expanded in all directions.

[0103] The sheet fixed to the frame 320 can be expanded by contacting the base 310 with the base and then displacing (pulling down) the frame 320 toward the base 310 as shown in FIG. 5B . 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.

[0104] (S30: Peeling of Element) In S30, the element is peeled from the adhesive layer 110 of the adhesive sheet. In this embodiment, the element is peeled from the adhesive layer 110 of the adhesive sheet expanded in the planar direction. The method for peeling the element is not particularly limited. For example, the method described above can be used to transfer an element attached to a holding substrate to an adhesive sheet. Specifically, the element can be moved to the destination by bringing the destination substrate or sheet close to the surface of the element and pressing the surface of the sheet opposite the element using a pin or the like. As another method, specifically, the element can be peeled from the adhesive layer 110 of the sheet using an adsorption member such as a vacuum chuck and moved to the desired position of the destination. If the holding force of the adhesive layer 110 is reduced by expanding the sheet, the element may be peeled from the adhesive layer 110 of the sheet without applying a physical stimulus from the opposite surface of the adhesive layer 110 of the sheet. Furthermore, the adhesion between the element and the adhesive sheet may be reduced by bringing the element held by the adhesive sheet into close contact with the destination substrate or sheet and then applying an external stimulus such as laser light. This method also allows elements to be transferred from the adhesive sheet to the transfer destination. In this case, the relative arrangement of the elements at the transfer destination changes from the relative arrangement of the elements before the adhesive sheet was expanded.

[0105] By this procedure, the element can be transferred to any desired destination using the adhesive sheet. Furthermore, by using this transfer method, electronic components or semiconductor devices having the element can be manufactured. The element held by the adhesive sheet may be subjected to treatment or processing.

[0106] 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.

[0107] 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.

[0108] <Component (B): Energy Reactive Resin> Tricyclodecane dimethanol diacrylate was used as the energy reactive resin.

[0109] <Component (C): Crosslinking Agent> As the crosslinking agent, an isocyanurate type polyisocyanate derived from hexamethylene diisocyanate was used.

[0110] <Component (D): Photopolymerization Initiator> As the photopolymerization initiator, 2,4,6-trimethylbenzoyldiphenylphosphine oxide was used.

[0111] <Thickness Measurement> The thickness of each layer and each portion was measured at 23° C. using a constant pressure thickness gauge manufactured by Teclock Corporation (model number: PG-02J, standard specifications: compliant with JIS K6783, Z1702, and Z1709).

[0112] <Pick-up force evaluation> The pick-up force of the sheet obtained in each example was evaluated as follows: First, the adhesive layer of the sheet obtained in each example was attached to a ring frame (made of stainless steel, inner diameter 194 mm), and the sheet was cut to fit the outer diameter of the ring frame.

[0113] 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 10 mm x 10 mm squares to obtain multiple elements (silicon chips, element size 10 mm x 10 mm x 150 μm). The multiple elements obtained were attached to the adhesive layer of the 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 laminating at room temperature (23°C). The dicing tape was then peeled off to transfer the multiple elements from the dicing tape to the sheet. In this way, a sheet on which multiple elements were placed and supported by a ring frame was obtained as an evaluation sample. Furthermore, hook-shaped hooks were fixed to the multiple elements of the obtained evaluation sample using an adhesive.

[0114] An evaluation sample having a hook-shaped hook fixed to an element was placed in the expanding device shown in FIG. 5A. With the element supported by base 310 over the sheet, ring frame 320 was pushed down at a speed of 1 mm / sec. The push-down distance (pull-down amount) was 0 mm, 5 mm, or 10 mm. The measurement terminal of a push-pull gauge (manufactured by Aiko Engineering Co., Ltd., product name "RX-5") was then connected to the hook-shaped hook, and the push-pull gauge was used to measure the pickup force required to pick up the element from the adhesive sheet.

[0115] Example 1 A pressure-sensitive adhesive composition was prepared by dissolving 100 parts by solids by mass of an acrylic resin (A), 25 parts by solids by mass of an energy-reactive resin (B), 1.25 parts by solids by mass of a crosslinking agent (C), and 0.75 parts by solids by mass of a photopolymerization initiator (D) in toluene. This pressure-sensitive adhesive composition was applied to 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. The shear storage modulus of the resulting pressure-sensitive adhesive layer was 2.04 MPa.

[0116] 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.

[0117] 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 200 mW / cm. ２ , light intensity 800mJ / cm ２ A sheet having a textured surface was produced by irradiating ultraviolet light onto the sheet. The textured shape of the adhesive layer of the sheet was a grid-like arrangement of pillars, similar to that shown in FIG. 2A. The pitch P between pillars in the sheet was 20 μm. As shown in FIG. 4A, the diameter (T) of the tip of each pillar 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 sheet was approximately 12.6%. Furthermore, the height (H) of each pillar (convex portion) and the thickness (S) of the base portion shown in FIG. 4A were as shown in Table 1. The replica mold used had a surface shape complementary to the textured shape.

[0118] The pick-up force of the sheet thus obtained was evaluated as described above. The measured pick-up force is shown in Table 1.

[0119] (Examples 2 to 5) Sheets were produced and evaluated in the same manner as in Example 1, except that the adhesive layer was formed so as to have the height (H) of the pillar (protrusion) and the thickness (S) of the base portion shown in Table 1.

[0120] (Comparative Examples 1 to 3) Sheets were produced and evaluated in the same manner as in Example 1, except that the adhesive layer was formed so as to have the height (H) of the pillars (protrusions) and the thickness (S) of the base portion shown in Table 1. In Comparative Example 1, the adhesive layer had a flat surface and did not have protrusions.

[0121]

[0122] As can be seen from a comparison between Examples 1 to 5 and Comparative Example 1, by providing irregularities on the surface of the adhesive portion, the effect of reducing the pick-up force when the sheet was expanded was obtained. Furthermore, as can be seen from a comparison between Examples 1 to 5 and Comparative Examples 2 and 3, by setting the ratio represented by the thickness (S) of the base portion to the height (H) of the protrusions to less than 4.75, the effect of reducing the pick-up force was obtained, and in particular, the pick-up force was able to be further reduced when the sheet was expanded. In particular, as can be seen from a comparison between Examples 2, 3, and Comparative Example 3, it was confirmed that, in general, the pick-up force tended to be further reduced by reducing the ratio represented by the thickness (S) of the base portion to the height (H) of the protrusions.

[0123] 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.

[0124] This application claims priority based on Japanese Patent Application No. 2022-151756 filed on September 22, 2022, Japanese Patent Application No. 2022-151757 filed on September 22, 2022, Japanese Patent Application No. 2023-058459 filed on March 31, 2023, Japanese Patent Application No. 2023-058460 filed on March 31, 2023, Japanese Patent Application No. 2023-058462 filed on March 31, 2023, and Japanese Patent Application No. 2023-058463 filed on March 31, 2023, the entire contents of which are incorporated herein by reference.

[0125] 110: adhesive layer, 111: convex portion, 112: concave portion, 113: base portion, 120: substrate, 140: element, 150: release sheet, 160: release layer, 161: concave portion, 170: substrate, P: pitch, S: thickness of base portion, H: height of convex portion

Claims

Claim 1 An adhesive sheet comprising a base material and an adhesive layer having irregularities on its surface, wherein the adhesive layer includes a base portion formed by a portion from a concave portion having the smallest thickness in the thickness direction of the adhesive layer to the surface opposite to the surface having irregularities, and a convex portion provided on the base portion, The adhesive sheet is characterized by satisfying the following relational expression (1). Relational expression (1): 0.25 < S / H < 4.75 (In relational expression (1), S represents the thickness of the base portion, and H represents the height of the convex portion.) Claim 2 The adhesive sheet according to claim 1, wherein the base portion has a uniform thickness. Claim 3 The adhesive sheet according to claim 1, wherein the adhesive layer has a plurality of convex portions, and the heights of the plurality of convex portions are uniform. Claim 4 The adhesive sheet according to claim 1, wherein the height of the convex portion is 1 μm or more and 15 μm or less. Claim 5 The adhesive sheet according to claim 1, wherein the thickness of the base portion is 1 μm or more and 50 μm or less. Claim 6 The adhesive sheet according to claim 1, wherein the base portion and the convex portion are integral. Claim 7 The adhesive sheet according to claim 1, wherein the adhesive layer has a plurality of convex portions defined by concave portions and spaced apart from each other, and the pitch of the plurality of convex portions is 1 μm or more and 100 μm or less. Claim 8 The adhesive sheet according to claim 1, wherein the shear storage modulus of the adhesive layer is 0.001 MPa or more and 100 MPa or less. Claim 9 The adhesive sheet according to claim 1, wherein the tensile modulus of the base material is 2500 MPa or less. Claim 10 The adhesive sheet according to claim 1, which is a sheet for fixing an element. Claim 11 The adhesive sheet according to claim 1, which is a sheet for transferring an element. Claim 12 The adhesive sheet according to claim 1, wherein the adhesive sheet is expandable in the plane direction, and the holding force of an object on the expanded adhesive sheet is reduced as compared with that before expansion. Claim 13 An expanding step of expanding in the plane direction the adhesive sheet according to any one of claims 1 to 12, which holds an element in the adhesive layer, A peeling step of peeling the element from the adhesive layer of the adhesive sheet expanded in the plane direction, A method for peeling an element from an adhesive sheet, including the above steps. Claim 14 The peeling method according to claim 13, further comprising a step of forming a plurality of elements by dicing the elements held by the adhesive layer before the extension step.