UV-curable resin composition, cured product thereof, substrate containing the cured product, and method for manufacturing a display device.

Abstract

The present invention provides an ultraviolet (UV) curable resin composition that can be used in the manufacture of display devices, wherein the cured product has appropriate tackiness, adheres well to a substrate, and can be peeled off the substrate with an organic solvent. The present invention also provides a cured product of this UV curable resin composition, a substrate containing the cured product, and a method for manufacturing a display device using the UV curable resin composition. [Solution] The present invention relates to an ultraviolet-curable resin composition comprising a cyclopolymerizable monomer, a monofunctional (meth)acrylamide monomer, and a compound having a polybutadiene skeleton, a cured product thereof, a substrate containing the cured product, and a method for manufacturing a display device using the ultraviolet-curable resin composition.

Description

[Technical Field]

[0001] The present invention relates to an ultraviolet-curable resin composition used in the manufacture of a display device, a cured product thereof, a substrate containing the cured product, and a method for manufacturing a display device using the ultraviolet-curable resin composition. [Background technology]

[0002] In recent years, display devices using microLEDs have been attracting attention as display devices that can display high-brightness, high-definition images with low power consumption, without the need for fast response speeds or image burn-in. In the manufacturing of this display device, micro-light-emitting elements are bonded to a drive substrate at a predetermined array pitch. To reduce the number of defective micro-light-emitting elements after bonding to the drive substrate, a method has been proposed in which the micro-light-emitting elements are first held on an intermediate substrate, defective elements are detected, and the remaining micro-light-emitting elements are bonded to the drive substrate after removing these defective elements (Patent Document 1). Patent Document 1 describes a method in which a silicone resin (polydimethylsiloxane (PDMS) resin) is coated onto an intermediate substrate and heated to form a rubber film, micro-light-emitting elements (chips) are attached to the film and held on the intermediate substrate, and then these chips are transferred onto the drive substrate.

[0003] However, in Patent Document 1, the polydimethylsiloxane (PDMS) resin is a two-component type and requires thermosetting, so there was room for further improvement in terms of productivity. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-110875 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a UV-curable resin composition (hereinafter sometimes referred to as "UV-curable resin composition") that can be used in the manufacture of the above-mentioned display device, wherein the cured product has appropriate tackiness, adheres well to a substrate, and can be peeled off the substrate with an organic solvent. Furthermore, the present invention also aims to provide a cured product of the UV-curable resin composition, a substrate containing the cured product, and a method for manufacturing a display device using the UV-curable resin composition. [Means for solving the problem]

[0006] The inventors, through diligent research to solve the above problems, have found that a UV-curable resin composition containing a cyclopolymerizable monomer, a monofunctional (meth)acrylamide monomer, and a compound having a polybutadiene skeleton can solve the above problems. Based on this finding, further research has led to the completion of the present invention.

[0007] In other words, the present invention provides an ultraviolet-curable resin composition used in the manufacture of the following display devices, a cured product thereof, a substrate containing the cured product, and a method for manufacturing a display device using the ultraviolet-curable resin composition. Item 1. An ultraviolet-curable resin composition comprising a cyclopolymerizable monomer, a monofunctional (meth)acrylamide monomer, and a compound having a polybutadiene skeleton. Item 2. The ultraviolet-curable resin composition according to Item 1, wherein the cyclopolymerizable monomer is 2-(allyloxymethyl)acrylic acid ester. Item 3. The UV-curable resin composition according to item 1 or 2, wherein the monofunctional (meth)acrylamide monomer is acryloylmorpholine. Item 4. The ultraviolet-curable resin composition according to any one of items 1 to 3, wherein the compound having a polybutadiene skeleton is at least one selected from the group consisting of polybutadiene homopolymer, hydrogenated polybutadiene homopolymer, hydroxide of polybutadiene polymer, carboxylated polybutadiene polymer, and acrylic-modified polybutadiene polymer. Item 5. The ultraviolet-curable resin composition according to any one of items 1 to 4, wherein the compound having a polybutadiene skeleton is polybutadiene urethane (meth)acrylate. Item 6. The UV-curable resin composition according to Item 5, wherein the polybutadiene urethane (meth)acrylate is a compound having (meth)acrylic groups at both ends of a polybutadiene skeleton via urethane bonds. Item 7. The ultraviolet-curable resin composition according to Item 5, wherein the polybutadiene urethane (meth)acrylate comprises a compound represented by formula (1-1). [ka] (In the formula, R is the same or different group represented by formula (1A), [ka] (In the formula, R 1 R indicates a divalent hydrocarbon group, 2 R indicates an alkylene group, 3 represents a hydrogen atom or a methyl group. (n represents a number greater than or equal to 2.) Item 8. A substrate having the ultraviolet-curable resin composition described in any of Items 1 to 7. Item 9. A substrate having a cured product of an ultraviolet-curable resin composition according to any one of Items 1 to 7. Item 10. The substrate according to Item 9, wherein the tack value of the surface of the cured product is 100 to 200 gf. Item 11. A method for manufacturing a display device including a micro-luminescent element having an element-side electrode, A step of applying an ultraviolet-curable resin composition described in any of items 1 to 7 onto a relay substrate and forming a cured product by ultraviolet irradiation, A step of holding a micro-light-emitting element on a cured material formed on a relay substrate such that the element-side electrodes are exposed, and A process of transferring a micro-luminescent element from a relay substrate onto a drive substrate having drive substrate side electrodes, and joining the element side electrodes to the drive substrate side electrodes. A manufacturing method that includes this. Item 12. The manufacturing method according to Item 11, wherein the relay substrate is a wafer.

[0008] In this specification, "(meth)acrylate" means acrylate (acrylic acid ester) and / or methacrylate (methacrylic acid ester), and "(meth)acrylamide" means acrylamide and / or methacrylamide. Also, when a numerical range is expressed using "~" as in "A~B", unless otherwise specified, this means "A or more and B or less".

Advantages of the Invention

[0009] The UV-curable resin composition of the present invention is a low-viscosity liquid composition, so it has excellent handleability. The composition can be cured by ultraviolet rays on a substrate, and the obtained cured product has high adhesion to the substrate. In addition, the surface of the cured product has appropriate tackiness (adhesiveness), and further, the cured product can be easily peeled off from the substrate by an organic solvent. Due to these characteristics, the UV-curable resin composition can be suitably used in the manufacturing process of a display device including a micro light-emitting element (chip).

[0010] Specifically, after applying the UV-curable resin composition of the present invention on an intermediate substrate, a cured product can be obtained by ultraviolet irradiation. The cured product has high adhesion to the intermediate substrate, and the surface of the cured product has appropriate tackiness, so the chip can be reliably held or fixed on the intermediate substrate. Then, in the process of transferring the chip on the intermediate substrate onto a driving substrate, the chip can also be separated from the cured product on the intermediate substrate. Also, even if defective portions due to peeling, bubbles, or foreign matters occur in the cured product formation process, the cured product can be easily peeled off with an organic solvent, so the cured product can be re-formed after peeling. This does not waste an expensive intermediate substrate. By using the UV-curable resin composition of the present invention, it becomes possible to manufacture a display device more efficiently and with excellent cost-effectiveness.

Brief Description of the Drawings

[0011] [Figure 1] It is a schematic cross-sectional view of an intermediate substrate having a cured product. [Figure 2] This is a schematic cross-sectional view of a chip held on a holding substrate. [Figure 3] This is a schematic cross-sectional view illustrating the process of transferring a chip from a holding substrate to a relay substrate. [Figure 4] This is a schematic cross-sectional view showing the chip held on the relay substrate. [Figure 5] This is a schematic cross-sectional view illustrating the transfer of a chip from a relay board to a drive board. [Figure 6] This is a schematic cross-sectional view showing the chip bonded to the drive substrate. [Figure 7] This is a schematic cross-sectional view showing the drive board after reflow. [Modes for carrying out the invention]

[0012] The following describes a UV-curable resin composition according to this embodiment, its cured product, a substrate containing the cured product, and a method for manufacturing a display device using the UV-curable resin composition.

[0013] 1.UV curable resin composition The UV-curable resin composition of the present invention is characterized by comprising a cyclizable monomer, a monofunctional (meth)acrylamide monomer, and a compound having a polybutadiene skeleton. It may optionally contain polymerization initiators and other components.

[0014] [Cycloplastic monomers] The UV-curable resin composition of the present invention contains a cyclizable monomer. The cyclizable monomer means a monomer having two or more (particularly two) polymerizable unsaturated groups in its molecule, and capable of undergoing an intramolecular cyclization reaction during polymerization to produce a cyclic compound.

[0015] Typical examples of cyclopolymerizable monomers include 2-(allyloxymethyl)acrylic acid esters, specifically methyl 2-(allyloxymethyl)acrylate, ethyl 2-(allyloxymethyl)acrylate, n-propyl 2-(allyloxymethyl)acrylate, isopropyl 2-(allyloxymethyl)acrylate, n-butyl 2-(allyloxymethyl)acrylate, s-butyl 2-(allyloxymethyl)acrylate, t-butyl 2-(allyloxymethyl)acrylate, etc. Examples of esters include 2-(allyloxymethyl)acrylate ring structure esters having a ring structure, such as 2-(allyloxymethyl)cyclopentanyl acrylate, 2-(allyloxymethyl)adamantyl acrylate, 2-(allyloxymethyl)dicyclopetanyl acrylate, 2-(allyloxymethyl)dicyclopentenyl acrylate, 2-(allyloxymethyl)isobornyl acrylate, 2-(allyloxymethyl)benzyl acrylate, 2-(allyloxymethyl)naphthyl acrylate, and 2-(methyl)biphenyl acrylate. Of these, methyl 2-(allyloxymethyl)acrylate, 2-(allyloxymethyl)dicyclopentenyl acrylate, 2-(allyloxymethyl)naphthyl acrylate, and 2-(allyloxymethyl)biphenyl acrylate are preferred from the viewpoint of further improving hydrophobicity, providing high moisture resistance, and having an excellent viscosity reduction effect. Cyclopolymerizable monomers can be used individually or in combination of two or more of these.

[0016] Cyclopolymerizable monomers have low viscosity, excellent dilution properties for oligomers and the like, and exhibit high radical polymerizability, thus functioning effectively as reactive diluents. Furthermore, these cyclopolymerizable monomers undergo cyclization through polymerization to form polymers with a ring structure in the main chain, i.e., polymers having a structure in which tetrahydrofuran rings are linked by carbon chains (dimethylene groups). Because the cured product of the UV-curable resin composition of the present invention contains such polymers, it exhibits good flexibility and high adhesion to the substrate.

[0017] Cyclopolymerizable monomers can be commercially available. Specific examples include AOMA® (manufactured by Nippon Shokubai Co., Ltd.).

[0018] The content of cyclizable monomers in the UV-curable resin composition of the present invention is typically 10 to 60% by mass, preferably 15 to 50% by mass, and more preferably 20 to 40% by mass, based on the total amount of the UV-curable resin composition.

[0019] [Monofunctional (meth)acrylamide monomer] The UV-curable resin composition of the present invention contains a monofunctional (meth)acrylamide monomer. Monofunctional (meth)acrylamide monomers include (meth)acrylamide and those having substituents on the nitrogen atom of the (meth)acrylamide.

[0020] The monofunctional (meth)acrylamide monomer is not particularly limited, but examples include (meth)acrylamide, (meth)acrylamide with one or two alkyl groups bonded to the nitrogen atom, (meth)acrylamide with one or two aryl groups bonded to the nitrogen atom, (meth)acrylamide with one or two hydroxyalkyl groups bonded to the nitrogen atom, (meth)acrylamide with one or two alkoxyalkyl groups bonded to the nitrogen atom, (meth)acrylamide with one or two aryloxyalkyl groups bonded to the nitrogen atom, and (meth)acrylamide in which two groups bonded to the nitrogen atom form a nitrogen-containing ring together with the nitrogen atom.

[0021] Specific examples of (meth)acrylamides in which one or two alkyl groups are bonded to the nitrogen atom include N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-tert-butyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, and N,N-dibutyl(meth)acrylamide. Specific examples of (meth)acrylamides in which one or two aryl groups are bonded to a nitrogen atom include N-phenyl(meth)acrylamide. Specific examples of (meth)acrylamides in which one or two hydroxyalkyl groups are bonded to the nitrogen atom include hydroxyethyl(meth)acrylamide and N-methylol(meth)acrylamide. Specific examples of (meth)acrylamides in which one or two alkoxyalkyl groups are bonded to a nitrogen atom include N-methoxymethyl(meth)acrylamide and N-ethoxymethyl(meth)acrylamide. Specific examples of (meth)acrylamides in which one or two aryloxyalkyl groups are bonded to the nitrogen atom include N-phenoxymethyl(meth)acrylamide. Specific examples of (meth)acrylamides in which two groups are bonded to the nitrogen atom and form a nitrogen-containing ring together with the nitrogen atom include (meth)acryloylmorpholine and (meth)acryloylpiperidine.

[0022] Of these, (meth)acrylamide is preferred, (meth)acryloylmorpholine is more preferred, and acryloylmorpholine is even more preferred, in which two groups on the nitrogen atom are bonded together to form a nitrogen-containing ring with the nitrogen atom. Monofunctional (meth)acrylamide monomers can be used individually or in combination of two or more.

[0023] The content of monofunctional (meth)acrylamide monomer in the UV-curable resin composition of the present invention is typically 10 to 60% by mass, preferably 15 to 50% by mass, and more preferably 20 to 40% by mass, based on the total amount of the UV-curable resin composition.

[0024] [Compounds containing a polybutadiene skeleton] The UV-curable resin composition of the present invention contains a compound having a polybutadiene skeleton. The term "polybutadiene skeleton" is used to mean a skeleton formed by polymerization of butadiene, and a skeleton in which all or part of the unsaturated bonds contained in that skeleton are hydrogenated. Here, the modes of polymerization of butadiene include modes in which the 1,2 positions of butadiene are polymerized, modes in which the 1,4 positions are polymerized, and modes including both.

[0025] Specific examples of polybutadiene skeletons include skeletons having two or more repeating units (hereinafter also referred to as constituent units) represented by the following formula (1a) or formula (1b). Preferably, the skeleton has two or more constituent units represented by formula (1a). [ka]

[0026] Compounds having a polybutadiene skeleton may also contain repeating units (constituent units) having epoxy groups represented by the following formula (1c), in addition to the repeating units represented by formula (1a) or formula (1b). [ka]

[0027] Examples of compounds having a polybutadiene skeleton include polybutadiene homopolymers, hydrogenated polybutadiene homopolymers, hydroxides of polybutadiene polymers, carboxylated polybutadiene polymers, and acrylic-modified polybutadiene polymers. Preferably, the compound is an acrylic-modified polybutadiene polymer, and more preferably, polybutadiene urethane (meth)acrylate.

[0028] The polybutadiene urethane (meth)acrylate is preferably a bifunctional (meth)acrylate compound having (meth)acrylic groups at both ends of a polybutadiene skeleton via urethane bonds, and is usually a chain-like oligomeric molecule.

[0029] Specific examples of compounds having a polybutadiene skeleton include the compound represented by the following formula (1). [ka] (In the formula, R is the same or different hydrogen atom, hydroxyl group, or group represented by formula (1A),

[0030] [ka] (In the formula, R 1 R indicates a divalent hydrocarbon group, 2 R indicates an alkylene group, 3 (This represents a hydrogen atom or a methyl group.) Alk indicates an alkylene group. m represents 0 or 1. n represents a number greater than or equal to 2.

[0031] R is the same or different hydrogen atom, hydroxyl group, or group represented by formula (1A), preferably two Rs are groups represented by formula (1A).

[0032] In equation (1A), R 1 Examples of divalent hydrocarbon groups shown include divalent groups obtained by removing two hydrogen atoms from acyclic hydrocarbons, cyclic hydrocarbons (including alicyclic hydrocarbons, aromatic hydrocarbons, etc.), etc. Examples of divalent groups obtained by removing two hydrogen atoms from acyclic hydrocarbons include linear or branched alkylene groups having 1 to 10 carbon atoms, specifically the methylene group (-CH2-), dimethylene group (-CH2-CH2-), trimethylene group, tetramethylene group, dimethylmethylene group, and the like.

[0033] Examples of the divalent group obtained by removing two hydrogen atoms from an alicyclic hydrocarbon include divalent groups obtained by removing two hydrogen atoms from a monocyclic or polycondensed alicyclic hydrocarbon. Specifically, examples include a cyclopropanediyl group, a cyclobutanediyl group, a cyclopentanediyl group, a cyclohexanediyl, a cycloheptanediyl group, and the like. Examples of the divalent group obtained by removing two hydrogen atoms from an aromatic hydrocarbon include divalent groups obtained by removing two hydrogen atoms from a monocyclic or polycondensed aromatic hydrocarbon. Specifically, examples include a benzenediyl group, a toluenediyl group, a xylenediyl group, a naphthalenediyl group, and the like.

[0034] Among these, R 1 is preferably a divalent group obtained by removing two hydrogen atoms from a monocyclic aromatic hydrocarbon, more preferably a benzenediyl group or a toluenediyl group, and particularly preferably a toluenediyl group.

[0035] In formula (1A), examples of the alkylene group represented by R 2 include linear or branched alkylene groups having 1 to 10 carbon atoms (preferably 2 to 6 carbon atoms). Specifically, examples include a methylene group (-CH2-), a dimethylene group (-CH2-CH2-), a trimethylene group, a tetramethylene group, a dimethylmethylene group, and the like, and a dimethylene group is preferred.

[0036] R 3 is a hydrogen atom or a methyl group, and preferably a hydrogen atom.

[0037] In formula (1A), examples of the alkylene group represented by Alk include linear or branched alkylene groups having 1 to 10 carbon atoms (preferably 2 to 6 carbon atoms). Specifically, examples include a methylene group (-CH2-), a dimethylene group (-CH2-CH2-), a trimethylene group, a tetramethylene group, a dimethylmethylene group, and the like, and a dimethylene group is preferred. m is 0 or 1, and preferably 1.

[0038] Among the compounds represented by formula (1), the compound represented by formula (1-1) is preferred. [ka] (In the formula, R and n are the same as above.)

[0039] R is preferably a group represented by formula (1A). Furthermore, in formula (1A), R 1 The preferred group is a divalent group obtained by removing two hydrogen atoms from a monocyclic aromatic hydrocarbon (particularly a benzenediyl group or a toluenediyl group), and R 2 A chain or branched alkylene group having 2 to 6 carbon atoms is preferred (particularly a dimethylene group (-CH2-CH2-), a trimethylene group, a tetramethylene group, or a dimethylmethylene group), R 3 A hydrogen atom is preferred.

[0040] In formula (1), n ​​represents the degree of polymerization of butadiene (the number of repeating units represented by formula (1a)), and is a number of 2 or more. n can be set arbitrarily within the range in which the UV-curable resin composition of the present invention having a compound having a polybutadiene skeleton has the desired properties. For example, n can be set so that the compound having a polybutadiene skeleton has the following number-average molecular weight (Mn).

[0041] The number-average molecular weight (Mn) of compounds having a polybutadiene skeleton is typically 1500 to 4000, preferably 2000 to 3000, and more preferably 2300 to 2700. This number-average molecular weight can be measured using gel permeation chromatography (standard polymer: polystyrene equivalent, eluent: THF).

[0042] The viscosity of compounds containing a polybutadiene skeleton is typically 500–4000 poise / 45°C, and more specifically 1000–3000 poise / 45°C. Viscosity can be measured using a cone-plate viscometer. Their acrylic equivalent is typically 1000–3000 g / eq, and more specifically 1600–2300 g / eq. Their glass transition temperature (Tg) is typically -20–0°C, and more specifically -15–-5°C.

[0043] Compounds having a polybutadiene skeleton can be used individually or in combination of two or more.

[0044] The UV-curable resin composition of the present invention contains a compound having a polybutadiene skeleton. Therefore, the cured product obtained by curing the composition exhibits excellent adhesion to the substrate, and its surface has appropriate tackiness.

[0045] Compounds having a polybutadiene skeleton can be commercially available. Specific examples include B-1000, B-2100, B-3000, G-1000, G-2000, G-3000, BI-2000, BI-3000, GI-1000, GI-2000, GI-3000, JP-100, JP-200, TEAI-1000, and TE-2000 (all manufactured by Nippon Soda Co., Ltd.).

[0046] The content of the compound having a polybutadiene skeleton in the UV-curable resin composition of the present invention is typically 20 to 80% by mass, preferably 30 to 70% by mass, and more preferably 40 to 60% by mass, based on the total amount of the UV-curable resin composition.

[0047] [Polymerization initiator] The UV-curable resin composition of the present invention may contain a polymerization initiator. The polymerization initiator is not particularly limited as long as it can disclose a radical polymerization reaction, and examples include oxime compounds, alkylphenone compounds, acylphosphine oxide compounds, aromatic onium salt compounds, organic peroxides, thioxanthone compounds, hexaarylbisimidazole compounds, borate compounds, azinium compounds, titanocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamines.

[0048] Of these, from the viewpoint of UV curability, it is preferable that the polymerization initiator includes at least one selected from the group consisting of alkylphenone compounds, acylphosphine oxide compounds, and thioxanthone compounds.

[0049] Examples of alkylphenone compounds include α-hydroxyalkylphenone compounds, α-aminoalkylphenone compounds, and benzylketal alkylphenone compounds.

[0050] Examples of α-hydroxyalkylphenone compounds include 2,2'-dihydroxy-2,2'-dimethyl-1,1'-[methylenebis(4,1-phenylene)]bis(propan-1-one), 1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-2-hydroxy-1-propanone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and 1-hydroxycyclohexylphenyl ketone.

[0051] Examples of α-aminoalkylphenone compounds include 2-methyl-1-phenyl-2-morpholinopropan-1-one, 2-methyl-1-[4-(hexyl)phenyl]-2-morpholinopropan-1-one, 2-ethyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, and 2-dimethylamino-2-(4-methylbenzyl Examples include 2-(dimethylamino)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-(dimethylamino)-2-(4-methylbenzyl)-1-(4-morpholinophenyl)-butan-1-one, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-butan-1-one.

[0052] Examples of benzyl ketal alkylphenone compounds include 2,2-dimethoxy-2-phenylacetophenone.

[0053] Examples of commercially available alkylphenone compounds include Omnirad 651, Omnirad 184, Omnirad 1173, Omnirad 2959, Omnirad 127, Omnirad 907, Omnirad 369, Omnirad 369E, and Omnirad 379 (manufactured by IGM Resins BV).

[0054] Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0055] A commercially available acylphosphine oxide compound is Omnirad 819 (manufactured by IGM Resins BV).

[0056] Examples of thioxanthone compounds include thioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, and 2,4-dichlorothioxanthone.

[0057] The polymerization initiator can be used by using only one of these, or by using a combination of two or more.

[0058] When the UV-curable resin composition of the present invention contains a polymerization initiator, the content of the polymerization initiator in the composition is usually 0.2 to 8.0% by mass, preferably 0.5 to 6.0% by mass, and more preferably 1.0 to 5.0% by mass, based on the total amount of the UV-curable resin composition.

[0059] [Other ingredients] The UV-curable resin composition of the present invention may, as necessary, further contain components (additives) such as polymerization inhibitors, surfactants, organic solvents, co-sensitizers, ultraviolet absorbers, antioxidants, non-cyclizable monomers, ion catchers, coupling agents, tackifiers, surface modifiers, leveling agents, defoamers, and rheology control agents, to the extent that the effects of the present invention are exhibited.

[0060] The polymerization inhibitor is not particularly limited, but for example, at least one of naphthalene derivatives, naphthoquinone, and naphthoquinone derivatives can be used. Stable resolution can be obtained by including a polymerization inhibitor. Specific examples of naphthalene derivatives include ammonium 1,4-dihydroxy-2-naphthalenesulfonate and 4-methoxy-1-naphthol. Specific examples of naphthoquinone and naphthoquinone derivatives include 1,4-naphthoquinone, 2-hydroxy-1,4-naphthoquinone, and anthrone. Examples of commercially available naphthalene derivatives include Kinopower® QS-30, WSI, and Kinopower MNT (manufactured by Air Water Performance Chemical Co., Ltd.). Examples of commercially available naphthoquinone and naphthoquinone derivatives include Kinopower® NQI, Kinopower LSN, Kinopower ATR (manufactured by Air Water Performance Chemical Co., Ltd.), 1,4-naphthoquinone, 2-hydroxy-1,4-naphthoquinone, and Anthrone (all manufactured by Tokyo Chemical Industry Co., Ltd.). Examples of defoaming agents, leveling agents, and surface modifiers include the BYK series, such as BYK-3550, manufactured by BYChemie Japan.

[0061] [Preparation of UV-curable resin composition] The UV-curable resin composition of the present invention is prepared as a homogeneous liquid composition by mixing the above-mentioned cyclizable monomer, monofunctional (meth)acrylamide monomer, and compound having a polybutadiene skeleton, and optionally a polymerization initiator and other components. It is preferable that the liquid composition is miscible and free of solids. Typically, it can be prepared by mixing the components.

[0062] The UV-curable resin composition of the present invention is typically a liquid composition, and its viscosity is, for example, 1.0 to 15 poises / 25°C, preferably 2.0 to 13 poises / 25°C, and more preferably 5.0 to 10 poises / 25°C. The viscosity can be measured in accordance with JIS Z 8803:2011, section 10, "Method for measuring viscosity using a cone-plate rotational viscometer," at 25°C, 50 rpm, and 10 seconds, using a cone rotor of 3°×R14 or 1°34'×R24, and a cone-plate viscometer (manufactured by Toki Sangyo Co., Ltd., TVE-33H).

[0063] A preferred embodiment of the UV-curable resin composition of the present invention includes a composition comprising methyl 2-(allyloxymethyl)acrylate as a cyclizable monomer, acryloylmorpholine as a monofunctional (meth)acrylamide monomer, polybutadiene urethane (meth)acrylate (furthermore, a compound represented by formula (1), particularly a compound represented by formula (1-1)) as a compound having a polybutadiene skeleton, and an alkylphenone compound as a polymerization initiator.

[0064] 2. Applications of UV-curable resin compositions The UV-curable resin composition of the present invention is a low-viscosity liquid composition that, when cured with ultraviolet light, yields a cured product with appropriate tackiness (adhesion) on its surface. Furthermore, the cured product exhibits excellent adhesion to a substrate, while also being easily peeled off from the substrate using a solvent (organic solvent). Therefore, the UV-curable resin composition can be used in a variety of applications. As an example of a typical embodiment, an example of its use in the manufacturing process of a display device including a micro-light-emitting element (chip) is described below.

[0065] (Manufacturing of display devices) A display device including a micro-light-emitting element can be manufactured using the UV-curable resin composition of the present invention. Specifically, it can be manufactured by a method comprising the following steps.

[0066] A display device including a micro-light-emitting element having an element-side electrode, The process involves applying the UV-curable resin composition of the present invention onto a relay substrate and curing it with ultraviolet light to form a cured product (hereinafter also referred to as the cured product formation process), A step of holding a micro-light-emitting element on a cured material formed on a relay substrate so that the element-side electrodes are exposed (hereinafter also referred to as the chip holding step), and The process involves transferring a micro-luminescent element from a relay substrate onto a drive substrate having drive substrate side electrodes, and joining the element-side electrodes of the micro-luminescent element to the drive substrate side electrodes on the drive substrate (hereinafter also referred to as the chip transfer process). It can be manufactured by a method that includes [the following].

[0067] In the chip transfer process described above, the element-side electrode of the micro-light-emitting element and the drive-side electrode on the drive substrate are temporarily bonded together. Then, the relay substrate is separated (removed) from the micro-light-emitting element, and the micro-light-emitting element and the drive-side electrode are firmly bonded together by heat treatment (reflow).

[0068] By repeating the above series of steps, a display device including a micro-light-emitting element can be manufactured efficiently and at low cost. Furthermore, the manufacturing method of the present invention is not limited to cases where the above steps are performed in order, but also includes cases where each step is performed in any order. In addition, even if each step cannot be clearly distinguished from the others, if each step achieves its intended purpose, it is included in the manufacturing method of the present invention.

[0069] [Cured product formation process] In this process, the UV-curable resin composition of the present invention is applied to the relay substrate 14 and cured by ultraviolet irradiation to form a cured product 31.

[0070] The UV-curable resin composition of the present invention is applied to the relay substrate 14 to form a coating film with a uniform thickness, for example, by spin coating, slit coating, molding, etc. Spin coating is preferred.

[0071] Examples of materials for the relay substrate 14 include quartz glass, alkali-free glass, silicon (Si), silicon carbide (SiC), and sapphire. The surface of the relay substrate 14 is preferably smooth with a small thickness tolerance, from the viewpoint of forming a hardened material 31 with uniform thickness and ensuring stable chip adhesion. Specific examples of the relay substrate include wafers made of silicon (Si), silicon carbide (SiC), sapphire, etc.

[0072] Subsequently, the coating film on the relay substrate 14 can be irradiated with ultraviolet (UV) light to form a cured product 31 on the relay substrate 14. The peak wavelength of the irradiated ultraviolet light is usually 200 to 450 nm, preferably 250 to 420 nm, and more preferably 300 to 405 nm. Examples of light sources for ultraviolet irradiation include UV-LEDs (light-emitting diodes), UV-LDs (laser diodes), mercury lamps, metal halide lamps, and ultraviolet fluorescent lamps. Of these, UV-LEDs and UV-LDs are preferred from the viewpoint of small size, long lifespan, and high efficiency. The integrated UV light amount (UV exposure amount) is usually 300 to 2000 mJ / cm². 2 The concentration is preferably 500 to 1500 mJ / cm². 2 Figure 1 shows an embodiment of the relay substrate 14 having the cured product 31. Typical examples of the cured product include the cured film form shown in Figure 1.

[0073] The surface of the cured material has moderate tackiness. The tack value of the surface of the cured material is usually 50 to 200 gf, preferably 100 to 200 gf, and more preferably 130 to 170 gf. A tack value within this range is suitable for adhering, holding, or fixing the chip to the surface of the cured material, and is also suitable for separating the relay substrate and the chip in the process of transferring the chip to the drive substrate described later.

[0074] The thickness of the cured material on the intermediate substrate after UV crosslinking should be sufficient to allow the chip to adhere, for example, about 1 μm to 1 mm. This thickness ensures that the chip adheres securely to the cured material. This thickness can be measured using a micrometer. Furthermore, if the thickness of the cured material is about 1 μm to 1 mm, sufficient light will pass through the cured material when the LED is illuminated during the electrical inspection described later.

[0075] In the cured product formation process described above, if defects such as bleeds, air bubbles, or foreign matter occur in the cured product 31, the cured product 31 can be peeled off from the intermediate substrate 14 using a solvent. This allows the intermediate substrate 14 to be subjected to the cured product formation process again, thereby reducing waste of the intermediate substrate.

[0076] One method for peeling the cured material from the intermediate substrate is to contact the intermediate substrate 14 having the cured material 31 with a solvent to dissolve or swell the cured material 31 and peel it off from the intermediate substrate 14. Methods for contacting with the solvent include immersing the intermediate substrate 14 in the solvent or spraying the solvent onto the intermediate substrate 14. The temperature at contact is, for example, about 10 to 40°C, preferably 20 to 30°C. The contact time is, for example, about 30 seconds to 20 minutes, preferably 1 to 10 minutes.

[0077] Examples of solvents include organic solvents, such as glycol ether solvents, glycol ester solvents, ketone solvents, ester solvents, carbonate ester solvents, and amide solvents.

[0078] Glycol ether solvents refer to compounds (organic solvents) in which at least one of the two hydroxyl groups of a glycol forms an ether. Here, glycol is interpreted to include both diol compounds in which two hydrogen atoms on two carbon atoms of an aliphatic hydrocarbon are each replaced by hydroxyl groups (e.g., alkylene glycols), and diol compounds having ether bonds obtained by dehydration condensation of two or more such diol compounds (e.g., polyalkylene glycols). The same applies hereafter.

[0079] Examples of glycol ether-based solvents include alkylene glycol monoalkyl ethers, polyalkylene glycol monoalkyl ethers, and alkylene glycol monoaryl ethers.

[0080] As the alkylene glycol monoalkyl ether, for example, (C2-C3) alkylene glycol mono(C1-C6) alkyl ethers are preferred, and specific examples include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether.

[0081] As the polyalkylene glycol monoalkyl ether, for example, poly(C2-C3)alkylene glycol mono(C1-C6) alkyl ether is preferred, and specific examples include diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and tripropylene glycol monoethyl ether.

[0082] As the alkylene glycol monoaryl ether, for example, poly(C2-C3)alkylene glycol monoaryl ether is preferred, and specific examples include ethylene glycol monophenyl ether and propylene glycol monophenyl ether.

[0083] Glycol ester solvents refer to compounds (organic solvents) in which at least one of the two hydroxyl groups of the glycol forms an ester. Furthermore, compounds (organic solvents) in which one of the two hydroxyl groups of the glycol forms an ester and the other forms an ether are preferred.

[0084] Examples of glycol ester solvents include alkylene glycol monoalkyl ether acylate, polyalkylene glycol monoalkyl ether acylate, alkylene glycol monoaryl ether acylate, and polyalkylene glycol monoaryl ether acylate.

[0085] As the alkylene glycol monoalkyl ether acylate, for example, (C2-C3)alkylene glycol mono(C1-C6)alkyl ether (C1-C4) acylates are preferred, and specific examples include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether propionate, ethylene glycol monopropyl ether propionate, ethylene glycol monobutyl ether propionate, propylene glycol monomethyl ether propionate, propylene glycol monoethyl ether propionate, propylene glycol monopropyl ether propionate, and propylene glycol monobutyl ether propionate.

[0086] As polyalkylene glycol monoalkyl ether acylates, for example, poly(C2-C3)alkylene glycol mono(C1-C6)alkyl ether(C1-C4) acylates are preferred, and specific examples include diethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, triethylene glycol monoethyl ether acetate, diethylene glycol monopropyl ether acetate, diethylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, tripropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, and tripropylene glycol monoethyl ether acetate.

[0087] Ketone solvents refer to organic solvents that contain a ketone group in their structure. Specific examples of ketone solvents include acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, cyclohexanone, diacetone alcohol, isophorone, and γ-butyrolactone.

[0088] Ester solvents refer to organic solvents that contain an ester group in their structure but do not contain an ether group. Specific examples of ester solvents include ethyl acetate, butyl acetate, sec-butyl acetate, methoxybutyl acetate, methyl acetate, amyl acetate, n-propyl acetate, isopropyl acetate, methyl lactate, ethyl lactate, butyl lactate, triacetin, γ-butyrolactone, and dimethyl glutarate.

[0089] Carbonate ester solvents refer to organic solvents that contain a carbonate group in their structure. Specific examples of carbonate ester solvents include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0090] Amide solvents are organic solvents that have an amide group in their structure. Specific examples of amide solvents include N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0091] Among the organic solvents mentioned above, glycol ether solvents, glycol ester solvents, and ketone solvents are preferred, glycol ether solvents and glycol ester solvents are more preferred, and alkylene glycol monoalkyl ethers and alkylene glycol monoalkyl ether acylates are even more preferred. Propylene glycol monomethyl ether acetate (PMA, CAS: 108-65-6) is particularly preferred due to its low toxicity.

[0092] The solvent can be one of these, or a combination of two or more.

[0093] Furthermore, the solvent may include other solvents in addition to the above-mentioned solvent, as long as they do not adversely affect the effects of the present invention.

[0094] [Chip holding process] In this process, the micro-light-emitting element (chip) is held on a cured material formed on a relay substrate so that the element-side electrodes are exposed.

[0095] A micro-light-emitting element (chip) has a chip-side electrode 12 (element-side electrode) formed on a semiconductor layer 11, and further microbumps made of solder 13 (metal material) are formed on the element-side electrode 12. In other words, a micro-light-emitting element (chip) includes the semiconductor layer 11, the chip-side electrode 12, and the solder 13.

[0096] The semiconductor layer 11 is an emissive layer that emits light with a predetermined emission spectrum. In this embodiment, for example, a three-color microLED can be used. The three colors are red (R), green (G), and blue (B). The chip-side electrodes 12 formed on the semiconductor layer 11 are formed in accordance with the arrangement pitch of the chips placed on the drive substrate 20, which will be described later. The chip-side electrodes 12 are formed using, for example, one of the following metals: Au, Ag, Cu, Al, Pt, Ni, Cr, Ti, ITO, or graphene. Among these, Au, Ag, and Cu are preferred.

[0097] The chip used in this process is attached by a resin layer 111 such that, as shown in Figure 2, the surface on which the chip-side electrode 12 is formed faces the holding substrate 112, and the bottom surface of the side opposite to the chip-side electrode 12 is exposed. For the holding substrate 112, for example, alkali-free glass or quartz glass substrate can be used. The resin layer 111 can be made of resin such as polyimide resin, acrylic resin, epoxy resin, polypropylene resin, polycarbonate resin, or ABS resin. This embodiment can be prepared, for example, in accordance with or in accordance with the description in Patent Document 1 (for example, Figures 1 to 4, etc.).

[0098] Next, the chip is transferred from the holding substrate 112 to the surface of the cured material 31 on the relay substrate 14 manufactured in the cured material formation process described above. Figure 3 is a schematic cross-sectional view illustrating the process of transferring the chip from the holding substrate 112 to the relay substrate 14.

[0099] Transferring the chip from the holding substrate 112 to the surface of the cured material 31 on the relay substrate 14 involves attaching the chip to the relay substrate 14 from the bottom side. As shown in Figure 3, the chip is first pressed together with the holding substrate 112 onto the cured material 31. The chip adheres to the cured material 31 due to its appropriate tackiness. When transferring the chip onto the relay substrate 14, after pressing the chip onto the cured material 31, the chip may be further pressed towards the relay substrate 14 to ensure a stronger bond.

[0100] After transfer, the chip is held or fixed by the moderate tackiness of the cured material 31, so it does not easily change position or fall off the relay substrate 14 even if the side with the chip is facing downwards.

[0101] Next, the retaining substrate 112 is removed from the chip. Figure 4 is a schematic cross-sectional view showing the relay substrate 14 after the retaining substrate 112 has been removed. There are no particular limitations on how the retaining substrate 112 is removed. For example, laser lift-off technology can be used.

[0102] [Chip transfer process] In this process, the micro-luminescent element (chip) is transferred from the relay substrate onto a drive substrate having electrodes on the drive substrate side, and the element-side electrodes and the drive substrate-side electrodes are joined together.

[0103] The chip is transferred from the relay substrate 14 to the drive substrate 20. The drive substrate 20 has electrodes formed on it for joining with the chip-side electrodes 12, along with wiring and TFTs (thin-film-transistors) necessary for supplying power to each micro-LED chip. In this embodiment, the electrodes provided on the drive substrate 20 are referred to as drive substrate-side electrodes 21. The drive substrate-side electrodes 21 are made of the same metal as the chip-side electrodes 12 described above. The surface of the drive substrate-side electrodes 21 can be left as is, but microbumps of solder 13 may be formed on it.

[0104] Figure 5 is a schematic cross-sectional view illustrating the transfer of a chip from the relay substrate 14 to the drive substrate 20. The transfer of the chip from the relay substrate 14 to the drive substrate 20 is performed by fluxless temporary bonding (temporary bonding stage). As shown in Figure 5, the temporary bonding is performed by overlapping the relay substrate 14 and the drive substrate 20 so that the chip-side electrode 12 of the chip attached to the relay substrate 14 and the drive substrate-side electrode 21 formed on the drive substrate 20 are in contact. Then, while applying pressure to bring the relay substrate 14 and the drive substrate 20 closer together, the entire structure is heated to a temperature above room temperature but below the solder melting temperature. This bonds the chip-side electrode 12 and the drive substrate-side electrode 21. Even at a temperature below the solder melting temperature, the chip-side electrode 12 and the drive substrate-side electrode 21 are bonded with a certain degree of force.

[0105] This is because, even below the solder melting point, pressure causes the metal atoms of tin (Sn), the main component of solder 13, to diffuse and join with the electrode materials such as gold (Au), copper (Cu), and aluminum (Al). Regarding this diffusion bonding, JIS standard Z3001-2, section 22702, defines it as "a method of bonding by bringing the base materials into close contact, applying pressure at a temperature below the melting point of the base materials to the extent that plastic deformation is minimized, and utilizing the diffusion of atoms that occurs between the bonding surfaces."

[0106] The heating temperature and applied pressure vary depending on the material of the solder 13 used for the microbumps on the chip-side electrode 12. For example, in the case of SAC (Sn 96.5%, Ag 3.0%, Cu 0.5%), the melting point is 217-220°C. Therefore, when performing temporary bonding, it is preferable to heat the solder to a temperature of 200-216°C, and to apply a pressure of 0.5-1.0 MPa to press the relay substrate 14 against the drive substrate-side electrode 21.

[0107] By using this temperature and pressure range, the chip and the drive substrate 20 can be joined without the solder 13 melting. Furthermore, within this temperature range, the cured material 31 will not deteriorate.

[0108] Flux is not used for the temporary bonding of the chip and the drive substrate 20. Therefore, bonding can be achieved at the interface between the solder 13 of the chip-side electrode 12 and the drive substrate-side electrode 21 without the presence of any non-metallic components.

[0109] Subsequently, the relay substrate is separated from the micro-luminescent element (separation stage). In other words, the relay substrate 14 is removed from the chip. Figure 6 is a schematic cross-sectional view showing the drive substrate 20 after the relay substrate 14 has been removed from the chip.

[0110] To remove the relay substrate 14 from the chip, the relay substrate 14 is peeled off (separated) from the chip. As already explained, the chip on the relay substrate 14 is held or fixed to the cured material 31, but only adheres to it. Therefore, the force with which the chip on the relay substrate 14 adheres to the cured material 31 is weaker than the force with which it is temporarily bonded to the drive substrate 20. Consequently, the relay substrate 14 can be easily peeled off the chip, resulting in the chip being temporarily bonded to the drive substrate 20, as shown in Figure 6.

[0111] Subsequently, the drive substrate 20 is heated (reflowed) to a temperature above the solder melting temperature to firmly bond the chip and the drive substrate side electrode 21 (bonding stage). Figure 7 is a schematic cross-sectional view showing the drive substrate 20 after reflow.

[0112] In reflow soldering, flux is applied to the surface of the drive substrate 20 on which the chip is mounted before heating. In this reflow process, since the interface between the solder 13 and the drive substrate side electrode 21 is already bonded, the applied flux does not penetrate the interface between the solder 13 and the drive substrate side electrode 21. When reflow soldering is performed in this state, as shown in Figure 7, the self-alignment effect when the solder 13 solidifies (eutectic metallization) after melting allows the chip to be mounted in a well-aligned state. Furthermore, in this embodiment, since the reflow soldering is performed after applying flux, the solder 13 also flows around the electrodes that protrude slightly from the substrate surface, resulting in a stronger bond between the chip side electrode 12 and the drive substrate side electrode 21.

[0113] In this embodiment, the solder 13, which is a microbump formed on the chip-side electrode 12, and the drive substrate-side electrode 21 become a eutectic metal through reflow soldering and are firmly bonded together. Furthermore, in this embodiment, the bond between the chip-side electrode 12 and the drive substrate-side electrode 21 is achieved solely by the presence of solder 13 (metal material), without the presence of flux components.

[0114] In reflow soldering, reflow may be performed without applying flux. Even without applying flux, the solder 13 and the drive substrate side electrode 21 can be strongly bonded by eutectic metallization when heated above the melting point of the solder 13. [Examples]

[0115] The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0116] Examples 1-5 and Comparative Examples 1-6 (1) Preparation of UV-curable resin composition The UV-curable resin compositions of Examples 1-5 and Comparative Examples 1-6 were prepared by mixing each component in the proportions and compositions shown in Table 1 below, then finely dispersing the initiator and other components using a disperser such as a three-roll mill or bead mill, filtering the resulting composition through a 10 μm aperture filter, and finally degassing it using a centrifugal degasser at 1800 rpm for 2 minutes. Unless otherwise specified, the values ​​in Table 1 refer to "parts by mass".

[0117] (2) Formation of hardened material The UV-curable resin compositions of Examples 1-5 and Comparative Examples 1-6 were applied by spin coating to achieve a cured film thickness of 30 μm, and exposed to a UV-LED light source (wavelength: 365 nm) (manufactured by Phoseon Technology) at an exposure dose of 1000 mJ / cm². 2 By exposure, cured products of Examples 1-5 and Comparative Examples 1-6 were formed on a 6-inch diameter JEIDA-standard silicon wafer to prepare evaluation samples.

[0118] (3) Evaluation of the cured product [Tack measurement of the surface of hardened material] Probe tack tests were performed on the cured materials of Examples 1-5 and Comparative Examples 1-6 formed on wafers using a probe tack measuring instrument (TAC-1000, RHESCA). Specifically, under conditions of a measurement temperature of 23°C, a 5 mm diameter stainless steel probe (SUS304) was brought into contact with the surface of the cured material of the evaluation sample with a contact load of 1000 gf, and the load on the probe was measured over time as it was pulled away at a speed of 1 mm / s. The maximum load required to peel it off was defined as the tack value.

[0119] [Evaluation of the release properties of the cured material] The solvent-based peelability of the cured products of Examples 1-5 and Comparative Examples 1-6, formed on wafers, was evaluated. At room temperature, a 6 L container was filled to a depth of approximately 5 cm with solvent (propylene glycol monomethyl ether acetate; PMA). The evaluation samples (wafers with cured products) were placed upright in the solvent and a portion of the cured product was immersed in the solvent and left to stand. After immersion, the cured product was observed visually until it lifted off the wafer. The state in which the cured product lifted off was defined as the swollen state, and the time from the start of immersion to swelling was defined as the peeling (swelling) time. <Evaluation Method> ○: Peeling time within 10 minutes ×: Peeling time exceeding 10 minutes

[0120] [Table 1]

[0121] *1 AOMA (2-(allyloxymethyl)methyl acrylate: cyclizable monomer) (manufactured by Nippon Shokubai Co., Ltd.) *2 Acryloylmorpholine (manufactured by KJ Chemicals Co., Ltd.): Monofunctional *3 1,6-Hexanediol diacrylate (manufactured by Daicel Ornex Co., Ltd.): bifunctional *4 Dipropylene glycol diacrylate (manufactured by Daicel Ornex Co., Ltd.): bifunctional *5 Trimethylolpropane triacrylate (manufactured by Daicel Ornex Co., Ltd.): bifunctional *6 Polybutadiene dimethacrylate (a polybutadiene methacrylate resin having methacrylate groups at both ends of polybutadiene via urethane bonds) (manufactured by Nippon Soda Co., Ltd.) *7 1,2-Polybutadiene homopolymer (manufactured by Nippon Soda Co., Ltd.) *8 Epoxy-modified polybutadiene (manufactured by Daicel Corporation) *9 Omnirad 379 (2-(dimethylamino)-2-(4-methylbenzyl)-1-(4-morpholinophenyl)-butan-1-one) (manufactured by IGM Resins BV)

[0122] The results in Table 1 confirm that the cured products of the UV-curable resin compositions of Examples 1 to 5 exhibit excellent adhesion to the substrate, have a suitable surface tackiness, and also have excellent peelability. Therefore, these UV-curable resin compositions can be suitably used in the manufacture of display devices including micro-luminescent elements.

[0123] On the other hand, in Comparative Example 1, it was found that the tackiness of the cured product was too high because a cyclizable monomer was not used. In Comparative Examples 2-5, a cured product that satisfied both tack value and peelability could not be obtained because a monofunctional acrylamide monomer was not used, and in Comparative Example 6, a compound having a polybutadiene skeleton was not used. [Industrial applicability]

[0124] The UV-curable resin composition of the present invention has a cured product that exhibits appropriate tackiness and high adhesion to a substrate, and can be easily peeled off the substrate with an organic solvent. Therefore, it can be suitably used, for example, in the manufacture of display devices including micro-luminescent elements. [Explanation of Symbols]

[0125] 11 (Chip) Semiconductor layer 12. Chip-side electrodes 13 Solder 14 Relay board 20 Drive board 21 Drive board side electrode 31 Cured product 101 Sapphire substrate 102 Semiconductor layer 111 Resin layer 112 Holding board

Claims

1. A UV-curable resin composition comprising a cyclopolymerizable monomer, a monofunctional (meth)acrylamide monomer, and a compound having a polybutadiene skeleton.

2. The ultraviolet-curable resin composition according to claim 1, wherein the cyclizable monomer is 2-(allyloxymethyl)acrylic acid ester.

3. The UV-curable resin composition according to claim 1, wherein the monofunctional (meth)acrylamide monomer is acryloylmorpholine.

4. The ultraviolet-curable resin composition according to claim 1, wherein the compound having a polybutadiene skeleton is at least one selected from the group consisting of polybutadiene homopolymer, hydrogenated polybutadiene homopolymer, hydroxide of polybutadiene polymer, carboxylated polybutadiene polymer, and acrylic-modified polybutadiene polymer.

5. The UV-curable resin composition according to claim 1, wherein the compound having a polybutadiene skeleton is polybutadiene urethane (meth)acrylate.

6. The ultraviolet-curable resin composition according to claim 5, wherein the polybutadiene urethane (meth)acrylate is a compound having (meth)acrylic groups at both ends of a polybutadiene skeleton via urethane bonds.

7. The ultraviolet-curable resin composition according to claim 5, wherein the polybutadiene urethane (meth)acrylate comprises a compound represented by formula (1-1). 【Chemistry 1】 (In the formula, R is the same or different group represented by formula (1A), 【Chemistry 2】 (In the formula, R １ R indicates a divalent hydrocarbon group. ２ R indicates an alkylene group, ３ (where n represents a hydrogen atom or a methyl group; where n represents a number greater than or equal to 2.)

8. A substrate having the ultraviolet-curable resin composition according to any one of claims 1 to 7.

9. A substrate having a cured product of an ultraviolet-curable resin composition according to any one of claims 1 to 7.

10. The substrate according to claim 9, wherein the tack value of the surface of the cured product is 100 to 200 gf.

11. A method for manufacturing a display device including a micro-luminescent element having an element-side electrode, A step of applying the ultraviolet-curable resin composition described in claim 1 onto a relay substrate and forming a cured product by ultraviolet irradiation, A step of holding a micro-light-emitting element on a cured material formed on a relay substrate such that the element-side electrodes are exposed, and A process of transferring a micro-luminescent element from a relay substrate onto a drive substrate having drive substrate side electrodes, and joining the element side electrodes to the drive substrate side electrodes. A manufacturing method that includes this.

12. The manufacturing method according to claim 11, wherein the relay substrate is a wafer.

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