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-curable resin composition that can be used in the manufacture of display devices, wherein the cured product is used as an adhesive possessing appropriate tackiness, adhesion to a substrate, and release properties with water or organic solvents. [Solution] An ultraviolet-curable resin composition for easily removable adhesives, comprising 2-(allyloxymethyl)acrylic acid ester (A), acryloylmorpholine (B), and a photopolymerization initiator (C).

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 including the cured product, and a method for manufacturing a display device.

Background Art

[0002] In recent years, display devices using micro LEDs have attracted attention as display devices that can display high-brightness and high-definition images with low power consumption without causing image sticking and having a high response speed.

[0003] In the manufacture of this display device, micro light-emitting elements are bonded onto a driving substrate at a predetermined array pitch. In order to reduce defective micro light-emitting elements after bonding to this driving substrate, a method has been proposed in which the micro light-emitting elements are once held on an intermediate substrate, defective elements are detected, and then the micro light-emitting elements after removing the defective elements are bonded to the driving substrate (Patent Document 1).

[0004] In the method described in Patent Document 1, a silicone resin (polydimethylsiloxane (PDMS) resin) is coated on an intermediate substrate and heated to form a rubber film, and a micro light-emitting element (chip) is attached onto the film and held on the intermediate substrate, and then this chip is transferred onto the driving substrate.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the method described in Patent Document 1, PDMS resin is used to attach the chips to the intermediate substrate. Therefore, it is not easy to remove the PDMS resin from the intermediate substrate, and there is a problem that the intermediate substrate is wasted if defects such as repulsion, air bubbles, or foreign matter occur during the curing process.

[0007] The present invention aims to provide an ultraviolet-curable resin composition that can be used in the manufacture of the above-mentioned display device, wherein the cured product is used as an adhesive possessing appropriate tackiness, adhesion to a substrate, and peelability with water or organic solvents. The present invention also aims to provide a cured product of the ultraviolet-curable resin composition, a substrate containing the cured product, and a method for manufacturing a display device using the ultraviolet-curable resin composition. [Means for solving the problem]

[0008] In order to solve the above problems, the inventors conducted extensive research and found that by using an ultraviolet-curable resin composition containing 2-(allyloxymethyl)acrylic acid ester, (meth)acryloylmorpholine, and a photopolymerization initiator, an adhesive can be obtained that possesses appropriate tackiness, adhesion to the substrate, and solvent-based release properties.

[0009] This invention was completed based on these findings and includes the following broad embodiments of the invention. [Section 1] A UV-curable resin composition for easily removable adhesives, comprising 2-(allyloxymethyl)acrylic acid ester (A), (meth)acryloylmorpholine (B), and a photopolymerization initiator (C). [Section 2] The ultraviolet-curable resin composition for easily peelable adhesives according to item 1, wherein the content ratio of 2-(allyloxymethyl)acrylic acid ester (A) and (meth)acryloylmorpholin (B) is (A):(B) = 1:9 to 5:5 by mass ratio. [Section 3] The ultraviolet-curable resin composition for easily peelable adhesives according to claim 1 or 2, wherein the content of (meth)acryloylmorpholin (B) is 65 to 90 parts by mass per 100 parts by mass of the ultraviolet-curable resin composition for easily peelable adhesives. [Section 4] The ultraviolet-curable resin composition for easily peelable adhesives according to any one of claims 1 to 3, wherein the content of 2-(allyloxymethyl)acrylic acid ester (A) is 8 to 60 parts by mass per 100 parts by mass of the ultraviolet-curable resin composition for easily peelable adhesives. [Section 5] A substrate having a cured product of an ultraviolet-curable resin composition for easily peelable adhesives as described in any one of items 1 to 4. [Section 6] The substrate according to item 5, wherein the tack value of the surface of the cured product is 30 to 70 gf. [Section 7] A method for manufacturing a display device including a micro-luminescent element having an element-side electrode, (i) A step of applying an ultraviolet-curable resin composition for easily peelable adhesives described in any one of items 1 to 4 onto a relay substrate and forming a cured product by ultraviolet irradiation, (ii) 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, (iii) A step of transferring the micro-luminescent element from the relay substrate onto a drive substrate having a drive substrate side electrode, and joining the element side electrode and the drive substrate side electrode. A manufacturing method that includes this. [Section 8] The manufacturing method according to item 7, wherein the relay substrate is a wafer. [Effects of the Invention]

[0010] According to the present invention, an ultraviolet curable resin composition can be provided which is used as an adhesive having appropriate tackiness, adhesion to a substrate, and peelability by water, organic solvents, etc. The ultraviolet curable resin composition of the present invention can be suitably used in the manufacturing process of a display device including a micro light emitting element (chip). By using the ultraviolet 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] It is a schematic cross-sectional view of a chip held on a holding substrate. [Figure 3] It is a schematic cross-sectional view for explaining the process of transferring a chip from a holding substrate to an intermediate substrate. [Figure 4] It is a schematic cross-sectional view showing a state where a chip is held on an intermediate substrate. [Figure 5] It is a schematic cross-sectional view for explaining the transfer of a chip from an intermediate substrate to a driving substrate. [Figure 6] It is a schematic cross-sectional view showing a state where a chip is bonded to a driving substrate. [Figure 7] It is a schematic cross-sectional view showing a driving substrate after reflow.

Embodiments for Carrying Out the Invention

[0012] In this specification, the “easily peelable adhesive” means an adhesive that has appropriate adhesiveness and can be easily peeled from an intermediate substrate by using water, organic solvents, etc.

[0013] In this specification, (meth)acrylate means at least one selected from the group consisting of acrylate (acrylic acid ester) and methacrylate (methacrylic acid ester). Also, when a numerical range is expressed using “~” as in “A~B”, unless otherwise specified, this means “A or more and B or less”.

[0014] 1. UV-curable resin composition for easily removable adhesives The UV-curable resin composition for easily peelable adhesives of the present invention (hereinafter sometimes simply referred to as "the UV-curable resin composition of the present invention") comprises 2-(allyloxymethyl)acrylic acid ester (A), (meth)acryloylmorpholine (B), and a photopolymerization initiator (C).

[0015] <(A)2-(allyloxymethyl)acrylate> Examples of 2-(allyloxymethyl)acrylate esters (A) include alkyl esters of 2-(allyloxymethyl)acrylate such as 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, and t-butyl 2-(allyloxymethyl)acrylate; 2-( Examples include 2-(allyloxy)acrylic acid ring structure esters having a ring structure, such as cyclopentanyl acrylate (allyloxymethyl), adamantyl acrylate (2-(allyloxymethyl), dicyclopetanyl acrylate (2-(allyloxymethyl), dicyclopentenyl acrylate (2-(allyloxymethyl), isobornyl acrylate (2-(allyloxymethyl), benzyl acrylate (2-(allyloxymethyl), naphthyl acrylate (2-(allyloxymethyl), biphenyl acrylate (2-(methyl), acrylate (biphenyl)). These may be used individually or in combination of two or more.

[0016] As the 2-(allyloxymethyl)acrylic acid ester (A) used in the UV-curable resin composition of the present invention, 2-(allyloxymethyl)acrylate is preferred from the viewpoint of dilutability and adhesion to the substrate.

[0017] 2-(allyloxymethyl)acrylic acid ester (A) undergoes polymerization to form a polymer with a ring structure in its main chain, i.e., a polymer having a structure in which tetrahydrofuran rings are linked by carbon chains (dimethylene groups). The cured product of the UV-curable resin composition for easily peelable adhesives of the present invention contains such a polymer, and therefore has good flexibility and high adhesion to the substrate.

[0018] 2-(allyloxymethyl)acrylic acid ester (A) can be a commercially available product. Examples of commercially available products include AOMA® (manufactured by Nippon Shokubai Co., Ltd.).

[0019] In the UV-curable resin composition of the present invention, the content of 2-(allyloxymethyl)acrylic acid ester (A) is preferably 5 to 90 parts by mass, more preferably 8 to 60 parts by mass, even more preferably 10 to 50 parts by mass, particularly preferably 10 to 40 parts by mass, and most preferably 15 to 30 parts by mass, per 100 parts by mass of the UV-curable resin composition of the present invention.

[0020] <(B)(meth)acryloylmorpholin> (Meth)acryloylmorpholine (B) polymerizes to form a polymer that is highly soluble in water and organic solvents. The cured product of the UV-curable resin composition of the present invention contains such a polymer and therefore exhibits excellent peelability using water or organic solvents.

[0021] (Meth)acryloylmorpholine (B) can be a commercially available product. Examples of commercially available products include ACMO® (manufactured by KJ Chemicals Co., Ltd.).

[0022] The content of (meth)acryloylmorpholin (B) in the ultraviolet-curable resin composition of the present invention is preferably 5 to 95 parts by mass, more preferably 35 to 92 parts by mass, even more preferably 45 to 90 parts by mass, particularly preferably 55 to 90 parts by mass, and most preferably 65 to 85 parts by mass, per 100 parts by mass of the ultraviolet-curable resin composition of the present invention.

[0023] Furthermore, in the ultraviolet-curable resin composition of the present invention, the content ratio of 2-(allyloxymethyl)acrylic acid ester (A) and (meth)acryloylmorpholin (B) is preferably (A):(B) = 1:9 to 9:1 by mass ratio, more preferably 1:9 to 6:4, even more preferably 1:9 to 5:5, particularly preferably 1:9 to 4:6, and most preferably 1:9 to 3:7.

[0024] <(C) Photopolymerization initiator> As the photopolymerization initiator (C) used in the UV-curable resin composition, any known and commonly used one can be used without particular limitation.

[0025] Examples of photopolymerization initiators include α-aminoacetophenone-based photopolymerization initiators such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, N,N-dimethylaminoacetophenone, 1-hydroxycyclohexylphenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl] Hydroxyacetophenone-based photopolymerization initiators such as -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]phenyl}-2-methylpropan-1-one, and 2-hydroxy-2-methyl-1-phenylpropan-1-one; bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, and bis-(2,6-dichlorobenzoyl)-4-propylphenyl Phosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenyl Acylphosphine oxide-based photopolymerization initiators such as ylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphinate methyl ester, 2-methylbenzoyldiphenylphosphine oxide, pivaloylphenylphosphinate isopropyl ester, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; benzoin-based photopolymerization initiators such as benzoin, benzyl, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, and benzoin n-butyl ether;Benzoin alkyl ether photopolymerization initiators; Benzophenone-based photopolymerization initiators such as benzophenone, p-methylbenzophenone, Michla's ketone, methylbenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone; Acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[ Acetophenone-based photopolymerization initiators such as 4-(methylthio)phenyl]-2-morpholino-1-propanone; thioxanthone-based photopolymerization initiators such as thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone; anthraquinone, chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butyl Anthraquinone-based photopolymerization initiators such as anthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, and 2-aminoanthraquinone; ketal-based photopolymerization initiators such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzoic acid ester-based photopolymerization initiators such as ethyl-4-dimethylaminobenzoate, 2-(dimethylamino)ethyl benzoate, and p-dimethylbenzoate ethyl ester; 2-(O-benzoyloxime)-1-[4-(phenylthio)phenyl]-1,2-o Oxime ester-based photopolymerization initiators such as ctanedione and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]ethanone 1-(O-acetyloxime); titanocene-based photopolymerization initiators such as bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)phenyl)titanium and bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyr-1-yl)ethyl)phenyl]titanium;Examples include the following. Among these, α-aminoacetophenone-based photopolymerization initiators, anthraquinone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, and oxime-based initiators are preferred. These may be used individually or in combination of two or more.

[0026] Commercially available α-aminoacetophenone-based photopolymerization initiators include Omnirad 907, 369, 369E, and 379 from IGM Resins. Commercially available anthraquinone-based photopolymerization initiators include 2-ethyl AQ from Mitsui & Co. Chemicals, Ltd. Commercially available acylphosphine oxide-based photopolymerization initiators include TPO from Kusumoto Chemicals, Ltd. and Omnirad 819 from IGM Resins. Commercially available oxime ester-based photopolymerization initiators include Irgacure OXE01 and OXE02 from BASF Japan Ltd., N-1919 from ADEKA Corporation, ADEKA Arclus NCI-831 and NCI-831E, and TR-PBG-304 from Changzhou Strong Electronic New Materials Co., Ltd.

[0027] The content of the photopolymerization initiator (C) in the ultraviolet-curable resin composition of the present invention is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and particularly preferably 1 to 5 parts by mass, per 100 parts by mass of the ultraviolet-curable resin composition of the present invention, from the viewpoint of photocurability and the physical properties of the cured coating film.

[0028] <Other photopolymerizable compounds> The UV-curable resin composition of the present invention may contain photopolymerizable compounds other than 2-(allyloxymethyl)acrylic acid ester (A) and (meth)acryloylmorpholine (B), to the extent that the effects of the present invention can be exhibited.

[0029] Other photopolymerizable compounds include, for example, monofunctional (meth)acrylates such as ethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid, 2-acryloyloxyethylhexahydrophthalic acid, and 2-acryloyloxyethyl succinic acid; ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate. Examples include, but are not limited to, polyfunctional (meth)acrylates such as acrylate, ethoxylated bisphenol A di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane triacrylate, and ethoxylated glycerin triacrylate; acrylamides such as 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; photopolymerizable oligomers such as epoxy(meth)acrylate, urethane(meth)acrylate, polyether(meth)acrylate, and polyester(meth)acrylate; and vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, styrene, and methylstyrene. Other photopolymerizable compounds may be used individually or in combination of two or more.

[0030] The content of other photopolymerizable compounds in the UV-curable resin composition of the present invention is preferably 0 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and particularly preferably 1 to 5 parts by mass, per 100 parts by mass of the UV-curable resin composition of the present invention.

[0031] <Additives> 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, UV 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.

[0032] 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.

[0033] 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.).

[0034] Examples of defoaming agents, leveling agents, and surface modifiers include the BYK series, such as BYK-3550, manufactured by BIC Chemie Japan Co., Ltd.

[0035] The amount of additive in the UV-curable resin composition of the present invention is preferably 0.1 to 10 parts by mass, and more preferably 1 to 5 parts by mass, per 100 parts by mass of the UV-curable resin composition of the present invention.

[0036] <Preparation of UV-curable resin composition for easily removable adhesives> The UV-curable resin composition of the present invention is prepared as a homogeneous liquid composition by mixing 2-(allyloxymethyl)acrylic acid ester (A), (meth)acryloylmorpholine (B), a photopolymerization initiator (C), and, if necessary, other photopolymerizable compounds and other components.

[0037] The viscosity of the UV-curable resin composition of the present invention at 25°C is preferably 100 to 1500 mPa·s, more preferably 200 to 1300 mPa·s, and particularly preferably 500 to 1000 mPa·s. This viscosity range facilitates application using a spin coater. The viscosity can be measured in accordance with JIS Z 8803:2011, item 10, "Method for measuring viscosity using a cone-plate type rotational viscometer," at 25°C, 50 rpm, and 30 seconds, using a cone rotor of 1°34' × R24 and a cone-plate type viscometer (Toki Sangyo Co., Ltd., TVE-33H).

[0038] 2. Applications of UV-curable resin compositions for easily removable adhesives The UV-curable resin composition of the present invention can be cured with appropriate tackiness (adhesion) on its surface by UV curing. Furthermore, the cured product exhibits excellent adhesion to a substrate, while also being easily peeled off from the substrate using water or organic solvents. Therefore, the UV-curable resin composition of the present invention 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.

[0039] (Manufacturing of display devices) A display device including a micro-light-emitting element can be manufactured using the ultraviolet-curable resin composition of the present invention. Specifically, it can be manufactured by a method comprising the following steps.

[0040] A display device including a micro-light-emitting element having an element-side electrode, (i) A step of applying the ultraviolet-curable resin composition of the present invention onto a relay substrate and forming a cured product by ultraviolet irradiation (hereinafter also referred to as the cured product formation step), (ii) A step of holding the micro-light-emitting element on a cured material formed on a relay substrate such that the element-side electrodes are exposed (hereinafter also referred to as the chip holding step), and (iii) A step of transferring the micro-luminescent element from the relay substrate onto a drive substrate having the drive substrate side electrode, and joining the element side electrode and the drive substrate side electrode (hereinafter also referred to as the chip transfer step). It can be manufactured by a method that includes [the following].

[0041] By repeating the above series of steps, a display device including a micro-light-emitting element can be manufactured efficiently and at low cost.

[0042] 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.

[0043] [Cured product formation process] In this process, the ultraviolet-curable resin composition of the present invention is applied to the relay substrate 14 and irradiated with ultraviolet light to form a cured product 31.

[0044] The ultraviolet-curable resin composition of the present invention is applied to the relay substrate 14 to form a coating film with a uniform thickness by, for example, spin coating, slit coating, molding, etc. Spin coating is preferred.

[0045] 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.

[0046] Subsequently, the coating film on the relay substrate 14 can be irradiated with ultraviolet light to form a cured product 31 on the relay substrate 14. The peak wavelength of the ultraviolet light to be irradiated 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.

[0047] The surface of the cured material has appropriate tackiness. The tack value of the surface of the cured material is preferably 30 to 70 gf, and more preferably 40 to 70 gf. A tack value within this range is suitable for attaching, holding, or fixing the chip to the surface of the cured material, and is also suitable for separating the intermediate substrate and the chip in the process of transferring the chip to the drive substrate described later. The tack value can be measured in an environment with a measurement temperature of 25°C, by pressing a 10 mm diameter stainless steel probe (SUS304) against the surface of the cured material at a speed of 0.5 mm / s with a contact load of 800 gf, maintaining contact for 5 seconds, and then pulling it away at a speed of 10 mm / s, as the maximum load applied to the probe.

[0048] The thickness of the cured material on the intermediate substrate after UV curing 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.

[0049] In the cured product formation process described above, if defects such as blemishes, air bubbles, or foreign matter occur in the cured product 31, the cured product 31 can be peeled off the intermediate substrate 14 using water or an organic solvent. This allows the intermediate substrate 14 to be subjected to the cured product formation process again, thereby reducing waste of the intermediate substrate.

[0050] One method for peeling the cured material from the intermediate substrate is to contact the intermediate substrate 14 having the cured material 31 with water or an organic solvent to dissolve or swell the cured material 31 and peel it off from the intermediate substrate 14. Methods for contacting with water or an organic solvent include immersing the intermediate substrate 14 in water or an organic solvent, or spraying water or an organic 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.

[0051] Examples of water and organic solvents include water, organic solvents, and mixtures of water and organic solvents. Examples of organic solvents include glycol ether solvents, glycol ester solvents, ketone solvents, ester solvents, carbonate ester solvents, and amide solvents. These may be used individually or in combination of two or more.

[0052] Examples of glycol ether-based solvents include alkylene glycol monoalkyl ethers, polyalkylene glycol monoalkyl ethers, and alkylene glycol monoaryl ethers.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] Examples of ketone-based solvents include acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, cyclopentanone, cyclohexanone, diacetone alcohol, isophorone, and γ-butyrolactone.

[0060] 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.

[0061] Examples of carbonate ester solvents include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0062] Examples of amide solvents include N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0063] When used as a mixture of water and an organic solvent, any of the organic solvents listed above that can be uniformly miscible with water can be used without particular limitation. The mixing ratio of water to organic solvent is not particularly limited, but for example, water:organic solvent = 4:6 to 10:0 is preferred, 5:5 to 9:1 is more preferred, and 6:4 to 9:1 is particularly preferred.

[0064] The water and organic solvents are preferably water, a mixture of water and an organic solvent, a glycol ether solvent, a glycol ester solvent, or a ketone solvent. More preferably, the water is a mixture of water and a glycol ether solvent, a mixture of water and a glycol ester solvent, or a mixture of water and a ketone solvent. Particularly preferred are water, a mixture of water and an alkylene glycol monoalkyl ether, or a mixture of water and an alkylene glycol monoalkyl ether acylate.

[0065] [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.

[0066] 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.

[0067] 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).

[0068] 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.

[0069] 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 Japanese Patent Application Publication No. 2021-1108755 (for example, Figures 1 to 4).

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] [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.

[0075] In this process, the element-side electrode of the micro-light-emitting element and the drive-side electrode on the drive substrate are temporarily joined 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 joined by heat treatment (reflow).

[0076] 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.

[0077] 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.

[0078] 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."

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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]

[0088] The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

[0089] <Materials used> • AOMA: Manufactured by Nippon Shokubai Co., Ltd., methyl 2-(allyloxymethyl)acrylate • ACMO: Acryloylmorphine, manufactured by KJ Chemicals Co., Ltd. • Omnirad379: Manufactured by IGM Resins, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone TPO: 2,4,6-trimethylbenzoyldipenylphosphine oxide, manufactured by Kusumoto Chemical Co., Ltd., photopolymerization initiator. • DPM: Dipropylene glycol monomethyl ether • PM: Propylene glycol monomethyl ether

[0090] <Manufacturing Examples 1-11> A UV-curable resin composition was prepared by pre-mixing each component according to the composition and proportions shown in Table 1 below, and then kneading the mixture using a three-roll mill.

[0091] <Examples 1-9, Comparative Examples 1, 2> The prepared UV-curable resin composition was coated onto a 6-inch diameter JEIDA-standard silicon wafer by spin coating to achieve a cured film thickness of 20 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 A cured material (coating) was formed by exposure. Subsequently, peel tests and tack value measurements were performed on the cured material using organic solvents DPM and PM. The results are shown in Table 1.

[0092] (Organic solvent stripping test) The wafers with the cured material formed on them were immersed in an organic solvent (DPM or PM) at 25°C for 2 minutes. After that, the wafers were removed, dried, and the state of the cured material was visually observed. ○: Wrinkles due to lifting are visible across the entire surface of the hardened material. △: Part of the hardened material is not floating. ×: Most of the hardened material is not floating.

[0093] (Tack value measurement) A probe tack test was performed on the cured material formed on the wafer using a probe tack measuring instrument (TAC-1000, manufactured by RHESCA). Specifically, under conditions of 25°C, a 10 mm diameter stainless steel probe (SUS304) was pressed against the surface of the cured material at a speed of 0.5 mm / s with a contact load of 800 gf. After maintaining contact for 5 seconds, the probe was pulled away at a speed of 10 mm / s, and the load on the probe was measured over time. The maximum load required to peel it off was defined as the tack value. ◎: Tack value is between 40gf and 70gf. ○: Tack value is 30gf or more and less than 40gf. ×: Tack value is less than 30gf or greater than 70gf.

[0094] [Table 1]

[0095] <Examples 10-15, Comparative Example 3> The prepared UV-curable resin composition was coated onto a 6-inch diameter JEIDA-standard silicon wafer by spin coating to achieve a cured film thickness of 20 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 A cured product (coating) was formed by exposure. Subsequently, peel tests were performed on the cured product using a mixture of DPM and water (40% DPM aqueous solution) and a mixture of PM and water (40% PM aqueous solution). The results are shown in Table 2.

[0096] (Peeling test using a mixture of organic solvent and water) A wafer with a cured material formed on it was immersed in an organic solvent aqueous solution (40% DPM aqueous solution or 40% PM aqueous solution) at 25°C for 2 minutes. After that, the wafer was removed, dried, and the state of the cured material was visually observed. ○: Wrinkles due to lifting are visible across the entire surface of the hardened material. △: Part of the hardened material is not floating. ×: Most of the hardened material is not floating.

[0097] [Table 2]

[0098] <Examples 16-19, Comparative Example 4> The prepared UV-curable resin composition was coated onto a 6-inch diameter JEIDA-standard silicon wafer by spin coating to achieve a cured film thickness of 20 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 A cured material (coating) was formed by exposure to light. Subsequently, a peel test using water was performed on the cured material. The results are shown in Table 3.

[0099] (Water peel test) The cured material on the wafer was sprayed with 30°C deionized water at a spray pressure of 0.2 MPa using a flat nozzle for 2 to 5 minutes. After drying the wafer, its surface was visually inspected to check for any remaining cured material. ○: The hardened material peeled off within 2 minutes. △: The hardened material peels off between 2 and 5 minutes. ×: Even after running for more than 5 minutes, the hardened material could not be removed.

[0100] [Table 3]

[0101] The cured products of the UV-curable resin compositions in Production Examples 2-10 (Examples 1-19) were confirmed to have excellent adhesion to the substrate, a surface with appropriate tackiness, and excellent peelability. On the other hand, the cured products of the UV-curable resin compositions in Production Examples 1 and 11 (Comparative Examples 1-4) were outside the scope of the present invention, and therefore showed inferiority compared to the present invention in at least one of the following aspects, such as insufficient tackiness or poor peelability. [Explanation of symbols]

[0102] 11 (Chip) Semiconductor layer 12. Chip-side electrodes 13 Solder 14. Intermediate 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 for easily removable adhesives, comprising 2-(allyloxymethyl)acrylic acid ester (A), (meth)acryloylmorpholine (B), and a photopolymerization initiator (C).

2. The ultraviolet-curable resin composition for easily peelable adhesives according to claim 1, wherein the content ratio of 2-(allyloxymethyl)acrylic acid ester (A) and (meth)acryloylmorpholin (B) is (A):(B) = 1:9 to 5:5 by mass ratio.

3. The ultraviolet-curable resin composition for easily peelable adhesives according to claim 1, wherein the content of (meth)acryloylmorpholin (B) is 65 to 90 parts by mass per 100 parts by mass of the ultraviolet-curable resin composition for easily peelable adhesives.

4. The ultraviolet-curable resin composition for easily peelable adhesives according to claim 1, wherein the content of 2-(allyloxymethyl)acrylic acid ester (A) is 8 to 60 parts by mass per 100 parts by mass of the ultraviolet-curable resin composition for easily peelable adhesives.

5. A substrate having a cured product of an ultraviolet-curable resin composition for easily peelable adhesives according to any one of claims 1 to 4.

6. The substrate according to claim 5, wherein the tack value of the surface of the cured product is 30 to 70 gf.

7. A method for manufacturing a display device including a micro-luminescent element having an element-side electrode, (i) A step of applying the UV-curable resin composition for easily peelable adhesives described in claim 1 onto a relay substrate and forming a cured product by UV irradiation, (ii) 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, (iii) A step of transferring the micro-luminescent element from the relay substrate onto a drive substrate having a drive substrate side electrode, and joining the element side electrode and the drive substrate side electrode. A manufacturing method that includes this.

8. The manufacturing method according to claim 7, wherein the relay substrate is a wafer.

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