Underfill material for micro LED display element, underfill film, method for producing underfill film, and micro LED display element

Abstract

A purpose of the present invention is to provide an underfill material for making it possible to improve the efficiency of mass transfer and metal bonding of an LED element and improve the quality of an LED display element, the underfill material having a flux function, sufficient adhesive force at room temperature, and thermal yellowing resistance during high-temperature processes, and enabling film formation in only a specific area. Another purpose of the present invention is to provide: an underfill film that is patterned on an array substrate, uses the underfill material, and can improve the efficiency of mass transfer and metal bonding of an LED element; a method for producing the underfill film; and a micro-LED display element provided with the underfill film. A thermosetting adhesive composition contains the following component (A), component (B), component (C), and component (D).　Component (A): an alkali-soluble resin which has a phenolic hydroxyl group and in which the glass transition temperature (Tg) of the polymer is 60°C or less　Component (B): a compound which has an isocyanurate skeleton　Component (C): an aliphatic or alicyclic epoxy compound　Component (D): a solvent.

Description

[Technical field]

[0001] The present invention relates to an underfill material for micro LED display elements, an underfill film, a method for manufacturing an underfill film, and a micro LED display element, and in particular to an underfill material used in micro LED display elements, a method for manufacturing an underfill film, an underfill film obtained by the manufacturing method, and a micro LED display element using the underfill film. [Background technology]

[0002] Currently, liquid crystal display elements (LCDs) and organic light-emitting diode display elements (OLEDs) are mainly used for flat panel displays used in mobile phones, monitors, and TVs. LCDs have already been fully mass-produced, and are inexpensive and can be made large. However, they are inferior in form factor and flexibility because they require a backlight for display. OLEDs are also excellent in flexibility, but they have the problem that their lifespan shortens when the brightness of the display element is increased. As a display element that can solve these shortcomings, micro LED display elements have been developed in recent years, which display by arranging inorganic light-emitting diodes on each pixel of an array substrate. Micro LED display elements use micrometer-sized inorganic light-emitting diodes as the light source, so they can achieve higher brightness, higher color purity, and a longer lifespan than LCDs and OLEDs. In addition, because LEDs are arranged for each pixel, each pixel can be made independent, and they are also excellent in flexibility.

[0003] The LED elements that are the light source are supplied as small pieces by epitaxially growing a semiconductor layer on a sapphire substrate, forming electrodes, and then dicing the substrate. Micro LED display elements require LED elements manufactured in this way to be arranged on an array substrate with high precision. Until now, the pick and place method, in which each LED element is installed one by one, has been considered as a method for arranging LED elements on an array substrate. However, this method requires a huge amount of time to install the LEDs, making it unsuitable for mass production.

[0004] In response to this, a stamp method has been proposed in recent years, in which a large number of LED elements are picked up from a sapphire substrate at once using an adhesive base material (stamp), mass-transferred to an array substrate, and then the LED elements are bonded to the electrodes of the array substrate by thermocompression bonding using a bonding head or by metal bonding using laser heating (Non-Patent Documents 1 and 2). Using this method, a large number of LED elements can be arranged on the array substrate at once and bonded to the array substrate, and it is expected to significantly improve throughput compared to the Pick & Place method. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Adv.Optical Mater.2015,3,1313-1335 [Non-Patent Document 2] SID 2017 DIGEST, 257 Summary of the Invention [Problem to be solved by the invention]

[0006] In this stamp-based mass transfer method, the LED elements are mass-transferred from the sapphire substrate to the array substrate due to the difference in adhesion between the array substrate and the LED elements and between the stamp and the LED elements, so an adhesive component is required on the array substrate. The adhesive component often serves to bond the LED elements to the substrate electrodes, so solder paste or conductive paste is usually used. However, in this case, a space is created around the electrodes of the LED elements, which can cause problems such as peeling and corrosion of the electrodes due to external stress applied to the panel, such as vibration, or moisture.

[0007] Among the adhesive components, the non-conductive paste and film are expected to alleviate the problems described above, as they are expelled from between the LED electrode and the array substrate electrode and remain as a permanent film around the electrodes when the LED element is bonded onto the paste or film and the LED element is joined to the substrate electrode. This function as an underfill material that protects the area around the electrodes from moisture and external stress.

[0008] Another issue specific to micro LED display elements is the prevention of heat-induced yellowing of the materials surrounding the LED elements. Since light emitted from the LED elements spreads in all directions, not just perpendicular to the substrate, the surrounding materials must be transparent to maintain the color purity of the LED elements. Furthermore, as mentioned above, high-temperature processes such as thermocompression bonding and laser heating are used to metal-bond the electrodes of the LED elements and array substrate. For this reason, the materials surrounding the LED elements must be heat-resistant and yellowing-resistant to maintain high transparency even after this high-temperature process.

[0009] Next, a common issue for semiconductor mounted devices, but not specific to micro LED display elements, is the flux treatment process for removing the oxide film on the electrodes. In micro LED display elements, if an oxide film is formed on the electrodes of the array substrate or LED elements, metal bonding cannot be achieved and poor electrical continuity occurs. Normally, this oxide film is removed using a flux agent containing volatile low molecules, but if these volatile low molecules remain between the electrodes after flux treatment, it can cause electrode corrosion.

[0010] Furthermore, once a functional film is formed over the entire surface of an array substrate or wafer, there is the issue that it is difficult to remove the wiring thereafter. Therefore, there is a demand for an underfill material that is non-volatile and has flux functionality, and that can be used to form a film only in specific areas by patterning using photolithography, inkjet coating, or pattern application using a film sheet.

[0011] Therefore, an object of the present invention is to provide an underfill material having the following functions in order to improve the efficiency of mass transfer and metal bonding of LED elements and to enable high quality LED display elements. (1) Having flux function (2) It has sufficient adhesive strength at room temperature. (3) Prevents heat yellowing during high-temperature processes (4) Film formation only in specific areas Another object of the present invention is to provide an underfill film patterned on an array substrate, which uses the underfill material and enables efficient mass transfer and metal bonding of LED elements.

[0012] It is yet another object of the present invention to provide a method for producing an underfill film using the underfill material, which enables efficient mass transfer and metal bonding of LED elements.

[0013] And, an object of the present invention is to provide a micro LED display element having an underfill film that enables efficient mass transfer and metal bonding of the LED element. [Means for solving the problem]

[0014] The present inventors have conducted intensive research to solve the above problems and have come up with the present invention. 1. An adhesive composition comprising the following components (A), (B), (C), and (D): Component (A): an alkali-soluble resin having a phenolic hydroxyl group and a glass transition temperature (Tg) of the polymer of 60° C. or lower Component (B): Compound having an isocyanurate skeleton (C) Component: Aliphatic or alicyclic epoxy compound (D) Component: Solvent 2. The adhesive composition according to 1, wherein the component (A) is a polymer containing a structural unit derived from a monomer (A2) that gives a homopolymer Tg of 0° C. or lower. 3. The adhesive composition according to 2, wherein the component (A) is an acrylic polymer containing, as constituent components, constituent units derived from a monomer (A1) having a phenolic hydroxyl group and a polymerizable unsaturated group, and a monomer (A2) having a homopolymer Tg of 0°C or lower. 4. The adhesive composition according to 3, wherein the monomer (A1) having a phenolic hydroxyl group and a polymerizable unsaturated group is selected from the group consisting of p-hydroxystyrene, m-hydroxystyrene, α-methyl-p-hydroxystyrene, and compounds represented by the following formula (1):

[0015] [ka] In the formula, P represents a (meth)acrylic group, a (meth)acrylamide group, an N-methyl(meth)acrylamide group, or a maleimide group; b1 represents a single bond, or a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, or a combination thereof; c1 represents a single bond, -O-, -COO-, or -OCO-; and d1 represents a substituted or unsubstituted hydroxyphenyl group. 5. The monomer (A2) that gives a homopolymer having a Tg of 0° C. or less is a compound represented by the following formula (2): 3 to The adhesive composition described herein.

[0016] [ka] In the formula, R2 represents a hydrogen atom or a methyl group, a2 represents an oxygen atom or a sulfur atom, b2 represents a linear, branched or cyclic alkylene group having 2 to 20 carbon atoms or a combination thereof, and -CH2- in the alkylene group may be replaced with an oxygen atom provided that they are not adjacent to each other, c2 represents a single bond, -O-, -COO- or -OCO-, and d2 represents a hydrogen atom or a hydroxyl group. 6. The adhesive composition according to any one of 1 to 5, wherein the amount of the (B) component is 20 to 100 parts by mass per 100 parts by mass of the (A) component (optimum amount of isocyanurate component) 7. A composition comprising 10 to 100 parts by mass of component (C) per 100 parts by mass of component (A). 5 (Optimum amount of other epoxy components) 8. The composition further contains, as the component (E), 0.01 to 1.0 parts by mass of a surfactant per 100 parts by mass of the component (A), 5 13. The adhesive composition according to claim 12, 9. 1 to 1, further comprising an inorganic filler as component (F). 5 13. The adhesive composition according to claim 12, 10.1~ 5 The adhesive composition according to any one of claims 1 to 5 is peeled off from both sides. Base material An adhesive sheet laminated with. 11.1~ 5 2. A cured film obtained by curing the adhesive composition according to any one of claims 1 to 11. 12. An LED display element having the cured film according to 11 as an underfill material. Effect of the Invention

[0017] The adhesive composition of the present invention has excellent flux properties, adhesion, and heat-resistant yellowing, and has excellent film transparency, and can form an underfill material that can improve the efficiency of mass transfer and metal bonding of LED elements. Furthermore, in the form of a film sheet, it is possible to form an underfill film only on the necessary parts of an array substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The adhesive composition of the present invention contains the following components (A), (B), (C), and (D). (A) component: having a phenolic hydroxyl group, G Resin with a glass transition temperature (Tg) of 60°C or less Component (B): Compound having an isocyanurate skeleton Component (C): an epoxy compound having an aliphatic or alicyclic skeleton (D) Component: Solvent

[0019] Each component will be described in detail below. <Component (A)> The component (A) has a phenolic hydroxyl group, G The resin has a glass transition temperature (Tg) of 60° C. or less, and specifically is an alkali-soluble resin. The alkali-soluble resin is preferably an acrylic polymer.

[0020] In the present invention, the acrylic polymer refers to a polymer obtained by using a monomer having a polymerizable unsaturated group such as an acrylic acid ester, a methacrylic acid ester, styrene, or maleimide, that is, a polymerizable group containing a carbon-carbon double bond in the structure.

[0021] The resin of component (A) is not particularly limited with respect to the type of the main chain skeleton and the side chain of the polymer constituting the acrylic polymer.

[0022] If the weight average molecular weight of the resin of component (A) is too small, less than 20,000, peeling may occur during the production of the sheet. Base material On the other hand, if the weight average molecular weight is too large, exceeding 150,000, the flexibility of the film is impaired, and the resin repulsion during flip chip bonding is deteriorated. From these viewpoints, the weight average molecular weight of the resin is preferably in the range of 20,000 to 150,000, and more preferably in the range of 30,000 to 100,000.

[0023] The resin of component (A) can be synthesized simply by copolymerizing a monomer mixture containing monomer (A1) having a phenolic hydroxyl group and a polymerizable unsaturated group, and monomer (A2) having a homopolymer Tg of 0° C. or less. Here, the homopolymer refers to a polymer of monomer (A2) alone, and is a polymer having a weight average molecular weight of 3000 or more obtained by polymerization reaction at a temperature of 50 to 110° C. in a solvent optionally containing a polymerization initiator, etc., or by polymerization reaction by irradiation with ultraviolet light in the coexistence of monomer (A2) and a photoradical generator, etc.

[0024] The constituent monomers of component (A) are described in detail below.

[0025] Monomer (A1) is a monomer having a phenolic hydroxyl group and a polymerizable unsaturated group, and is preferably at least one monomer selected from p-hydroxystyrene, m-hydroxystyrene, α-methyl-p-hydroxystyrene, and a compound represented by the following formula (1).

[0026] [ka] In formula (1), P represents a (meth)acrylic group, a (meth)acrylamide group, an N-methyl(meth)acrylamide group, or a maleimide group, and is preferably a (meth)acrylic group. b1 represents a single bond, or a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, or a combination thereof, and is preferably a single bond or a linear alkylene group having 1 to 6 carbon atoms. c1 represents a single bond, -O-, -COO-, or -OCO-, and is preferably a single bond or -O-. d1 represents a substituted or unsubstituted hydroxyphenyl group, and is preferably a p-hydroxyphenyl group. Examples of the substituent on the hydroxyphenyl group include a halogen atom, an alkyl group having 1 to 3 carbon atoms, an alkenyl group having 2 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluoroalkyl group having 1 to 3 carbon atoms, a fluoroalkenyl group having 2 to 3 carbon atoms, a fluoroalkoxy group having 1 to 3 carbon atoms, an alkyloxycarbonyl group having 2 to 3 carbon atoms, a cyano group, a nitro group, etc. By having these hydroxyphenyl groups, component (A) exhibits flux properties.

[0027] Examples of the monomer (A1) include p-hydroxystyrene, α-methyl-p-hydroxystyrene, N-(p-hydroxyphenyl)maleimide, N-(p-hydroxyphenyl)acrylamide, N-(p-hydroxyphenyl)methacrylamide, p-hydroxyphenylacrylate, p-hydroxyphenylmethacrylate, etc., which can be used alone or in combination of two or more. Among them, the monomer selected from p-hydroxyphenylacrylate and p-hydroxyphenylmethacrylate is preferred.

[0028] The monomer (A2) is a monomer that gives a homopolymer having a Tg of 0° C. or lower, and is preferably a compound represented by the following formula (2).

[0029] [ka] In formula (2), R2 represents a hydrogen atom or a methyl group. a2 represents an oxygen atom or a sulfur atom, preferably an oxygen atom. b2 represents a linear, branched, or cyclic alkylene group having 2 to 20 carbon atoms, or a combination thereof, preferably a linear, branched, or cyclic alkylene group having 2 to 12 carbon atoms, or a combination thereof, more preferably a linear or branched alkylene group having 2 to 12 carbon atoms. In addition, -CH2- in the alkylene group of b2 may be replaced with an oxygen atom, provided that they are not adjacent to each other. c2 represents a single bond, -O-, -COO-, or -OCO-, preferably a single bond or -O-. d2 represents a hydrogen atom or a hydroxyl group.

[0030] Specific examples of the monomer (A2) include ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-hexyl methacrylate, n-heptyl acrylate, n-heptyl methacrylate, n-octyl acrylate, n-octyl methacrylate, nonyl acrylate, nonyl methacrylate, isononyl acrylate, isononyl methacrylate, lauryl acrylate, lauryl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl acrylate, 3-hydroxypropyl ... Examples of the acrylates include propyl acrylate, 4-hydroxybutyl acrylate, ethyl carbitol acrylate, glycidyl acrylate, methoxytriethylene glycol acrylate, methoxytriethylene glycol methacrylate, 2-methoxyethyl acrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl acrylate, 2-ethoxyethyl methacrylate, tetrahydrofurfuryl acrylate, 3-methoxybutyl acrylate, 3-methoxybutyl methacrylate, diethylene glycol monoacrylate, and diethylene glycol monomethacrylate, which may be used alone or in combination of two or more, but are not limited to these.

[0031] From the viewpoint of suitably obtaining the effects of the present invention, the constituent units derived from monomer (A1) in component (A) preferably account for 10 to 50 mass% of the total of the constituent units derived from monomer (A1) and the constituent units derived from monomer (A2), and the constituent units derived from monomer (A2) in component (A) preferably account for 50 to 90 mass% of the total of the constituent units derived from monomer (A1) and the constituent units derived from monomer (A2).

[0032] In the present invention, when obtaining the acrylic polymer of the component (A), other monomers copolymerizable with the monomers (A1) to (A2) can be used in combination. Specific examples of the other monomers include acrylic acid ester compounds, methacrylic acid ester compounds, maleimides, acrylamide compounds, acrylonitrile, styrene compounds, and vinyl compounds. Specific examples of the other monomers are listed below, but are not limited thereto.

[0033] Examples of the acrylic acid ester compound include methyl acrylate, cyclohexyl acrylate, isobornyl acrylate, 2-methyl-2-adamantyl acrylate, anthryl acrylate, anthryl methyl acrylate, 2,2,2-trifluoroethyl acrylate, 2-aminoethyl acrylate, 2-propyl-2-adamantyl acrylate, caprolactone 2-(acryloyloxy)ethyl ester, and poly(ethylene glycol) ethyl ether acrylate.

[0034] Examples of the methacrylic acid ester compound include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, 2-methyl-2-adamantyl methacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, anthryl methacrylate, anthryl methyl methacrylate, 2,2,2-trifluoroethyl methacrylate, 2-aminomethyl methacrylate, γ-butyrolactone methacrylate, 2-propyl-2-adamantyl methacrylate, caprolactone 2-(methacryloyloxy)ethyl ester, and poly(ethylene glycol) ethyl ether methacrylate.

[0035] Examples of the acrylamide compound include N-methylacrylamide, N-methylmethacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-butoxymethylacrylamide, and N-butoxymethylmethacrylamide.

[0036] Examples of the vinyl compound include methyl vinyl ether, benzyl vinyl ether, cyclohexyl vinyl ether, vinyl naphthalene, vinyl anthracene, vinyl carbazole, allyl glycidyl ether, 3-ethenyl-7-oxabicyclo[4.1.0]heptane, 1,2-epoxy-5-hexene, and 1,7-octadiene monoepoxide.

[0037] Examples of the styrene compound include styrenes having no hydroxy group, such as styrene, α-methylstyrene, chlorostyrene, and bromostyrene.

[0038] The method for obtaining the alkali-soluble resin used in the present invention is not particularly limited, but for example, the resin can be obtained by polymerization reaction at a temperature of 50 to 110°C in a solvent in which the monomer (A1), the monomer (A2), the above-mentioned other monomers, and optionally a polymerization initiator are present. The solvent used at that time is not particularly limited as long as it dissolves the monomers constituting the resin and the resin. Specific examples include the solvents described in the (D) solvent described later.

[0039] The resin thus obtained (hereinafter also referred to as the specific copolymer) is usually in the state of a solution dissolved in a solvent.

[0040] The solution of the specific copolymer obtained as described above can be reprecipitated by adding diethyl ether or water under stirring, and the resulting precipitate can be filtered and washed, and then dried at room temperature or by heating under normal or reduced pressure to obtain a powder of the specific copolymer. By such an operation, the polymerization initiator and unreacted monomers coexisting with the specific copolymer can be removed, and as a result, a powder of the purified specific copolymer can be obtained. If the specific copolymer cannot be sufficiently purified by a single operation, the obtained powder can be redissolved in a solvent and the above operation can be repeated.

[0041] In the present invention, the powder of the specific copolymer may be used as it is, or the powder may be redissolved in, for example, the solvent (D) described below and used in the form of a solution.

[0042] In the present invention, the resin of component (A) may be a mixture of multiple types of specific copolymers.

[0043] <(B) component> The component (B) of the present invention is a compound having an isocyanurate skeleton. By including an isocyanurate skeleton in the composition, high adhesion to metals at room temperature can be achieved. From the viewpoint of curability, a compound having two or more polymerizable unsaturated double bonds in the isocyanurate skeleton is preferred. Preferred skeletons of the component (B) are exemplified by formula (4A) and formula (4B) (also simply referred to as formula (4)).

[0044] [ka]

[0045] [ka]

[0046] The content of the component (B) in the composition of the present invention is preferably 20 to 100 parts by mass, and more preferably 30 to 90 parts by mass, per 100 parts by mass of the component (A).

[0047] <(C) component> Component (C) is an epoxy compound having an aliphatic or alicyclic skeleton. When the epoxy compound serving as the crosslinking component in the composition has an aromatic or aminoglycidyl group, the film is easily yellowed by high-temperature heating, so an aliphatic or alicyclic skeleton is preferred.

[0048] A preferred skeleton of the component (C) is represented by formula (5) or formula (6).

[0049] [ka] (In formula (5), k is an integer of 2 to 10, m is an integer of 0 to 4, and X5 represents a k-valent organic group not containing an aromatic ring. Multiple m's may be the same or different.)

[0050] [ka] (In formula (6), k is an integer of 2 to 10, and X6 represents a k-valent organic group not containing an aromatic ring.)

[0051] Specific examples of compounds having a cycloalkene oxide structure represented by formula (5) include Epolead GT-401, GT-403, GT-301, GT-302, PB4700, Celloxide 2021, Celloxide 2081, Celloxide 3000 (trade names, manufactured by Daicel Corporation), Epocalic DE-102, DE-103 (all manufactured by ENEOS Corporation), and the like.

[0052] Specific examples of the compound represented by formula (6) include alicyclic epoxy compound EHPE3150 (trade name, manufactured by Daicel Corporation), hydrogenated glycidyl ether epoxy compound Denacol EX-252 (trade name, manufactured by Nagase Chemtex Corporation), ST-3000, ST-4000D (trade name, manufactured by Nippon Steel Chemical & Material Corporation), EPOTEC YDH184, EPOTEC YDH3000 (trade name, manufactured by Tomoe Engineering Co., Ltd.), Rikaresin HBE-100 (trade name, manufactured by New Japan Chemical Co., Ltd.), aliphatic ester structure EPOTEC RD107, RD111, RD114, RD130, RD113, RD129 (trade name, manufactured by Tomoe Engineering Co., Ltd.), and Showfree PETG (trade name, manufactured by Resonac Corporation).

[0053] The content of the component (C) in the composition of the present invention is preferably 10 to 100 parts by mass, and more preferably 30 to 90 parts by mass, per 100 parts by mass of the component (A).

[0054] <(D) component> The (D) solvent used in the present invention dissolves the (A), (B), and (C) components, and also dissolves various components that are added as desired. As long as the solvent has such dissolving ability, there are no particular limitations on the type or structure of the solvent.

[0055] Examples of such (D) solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol propyl ether acetate, toluene, xylene, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-butanone, 3-methyl-2-pentanone, 2 ... Examples of the alkyl ester include pentanone, 2-heptanone, γ-butyrolactone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone.

[0056] Among these (D) solvents, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, 2-heptanone, propylene glycol propyl ether, propylene glycol propyl ether acetate, ethyl lactate, butyl lactate, and the like are preferred from the viewpoints of good film-forming properties and high safety.

[0057] Furthermore, for the purpose of improving the wettability to the substrate, adjusting the surface tension of the solvent, adjusting the polarity, adjusting the boiling point, etc., other solvents can be mixed in an amount of 1 to 90 mass %, preferably 1 to 50 mass %, of the total solvents used in the varnish.

[0058] Examples of such solvents include, but are not limited to, methanol, ethanol, isopropyl alcohol, diisoamyl ether, methyl salicylate, etc. These solvents can be used alone or in combination of two or more.

[0059] <(E) component> Component (E) is a surfactant. The composition of the present invention may further contain a surfactant for the purpose of improving the coating properties, as long as the effect of the present invention is not impaired.

[0060] The surfactant of component (E) is not particularly limited, but examples thereof include fluorine-based surfactants, silicone-based surfactants, and nonionic surfactants. As this type of surfactant, for example, commercially available products manufactured by 3M Japan Co., Ltd., DIC Corporation, AGC Seimi Chemical Co., Ltd., etc. can be used. These commercially available products are convenient because they are easily available. Specific examples thereof include Polyfox PF-136A, 151, 156A, 154N, 159, 636, 6320, 656, 6520 (manufactured by Omnova), Megafac R30, R08, R40, R41, R43, F251, F477, F552, F553, F554, F555, F556, F557, F558, F559, F560, F56 1, F562, F563, F565, F567, F570 (DIC Corporation), FC4430, FC4432 (3M Japan Ltd.), Asahiguard AG710, Surflon S-386, S-611, S-651, (AGC Seimi Chemical Co., Ltd.), Futergent FTX-218, DFX-18, 220P, 251, 212M, 215M Fluorosurfactants such as BYK-300, 302, 306, 307, 310, 313, 315, 320, 322, 323, 325, 330, 331, 333, 342, 345, 346, 347, 348, 349, 370, 377, 378, 3455 (manufactured by BYK Japan Co., Ltd.), SH3746, SH3749, SH377 1, SH8400, SH8410, SH8700, SF8428 (manufactured by Dow Corning Toray Silicones Co., Ltd.), KF-351, KF-352, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-618, KF-6011, KF-6015 (manufactured by Shin-Etsu Chemical Co., Ltd.), and other silicone surfactants.

[0061] The surfactant of component (E) can use either a single type alone or a combination of two or more types.

[0062] When a surfactant is used, its content is usually 0.01 to 1.0 part by mass, and preferably 0.02 to 0.8 part by mass, based on 100 parts by mass of the component (A).

[0063] <(F) Component> Component (F) is an inorganic filler. The composition of the present invention may further contain an inorganic filler for the purpose of improving the transparency of the film and the hardness of the cured film, as long as the effect of the present invention is not impaired.

[0064] (F) Component Inorganic Filler Examples of the inorganic filler include, but are not limited to, sols of silica, aluminum nitride, boron nitride, zirconia, alumina, etc., each having a particle diameter of 1 nm or more and 700 nm or less. The particles contained in the inorganic filler may be surface-treated with a silane coupling agent or the like.

[0065] When an inorganic filler is used, the content thereof is usually 10 to 90 parts by mass, and preferably 20 to 80 parts by mass, per 100 parts by mass of the total solid content.

[0066] <Adhesive sheet> A peeling adhesive using the adhesive composition of the present invention as a base film Base material The coating film can be formed by coating the composition on a substrate (e.g., a PET film coated with a silicone release layer) by bar coating, slit coating, inkjet coating, or the like, and then pre-drying the substrate in an oven or the like.

[0067] The conditions for this heat treatment are, for example, a heating temperature and a heating time appropriately selected from the ranges of 70 to 160° C. and 0.3 to 60 minutes, respectively. The heating temperature and heating time are preferably 80 to 140° C. and 0.5 to 10 minutes.

[0068] Then, a protective film is applied to the coating of the composition. Base material An adhesive sheet is obtained by laminating the two films together. Using a manual or automatic laminating roller, the coating film and the protective film are pressed together in a certain direction while taking care not to trap air bubbles between them, and an adhesive sheet is obtained.

[0069] By processing the adhesive sheet to a desired size, the adhesive composition can be formed into a film only at the required location on the array substrate. After processing to a desired size, the protective film is peeled off, the peeled surface is attached to a desired location, and the base film is peeled off, so that the adhesive composition film is transferred onto the substrate. In order to increase the adhesion between the composition film and the substrate, it is also effective to transfer the film under pressure.

[0070] In order to peel the protective film well from the coating surface, it is necessary that the peel strength of the protective film is small and that of the base film is large. The peel strength of the protective film is preferably 80 N / 25 mm or less, and the peel strength of the base film is preferably 160 N / 25 mm or more.

[0071] <Cured film> Subsequently, the pattern-forming film is post-baked for thermal curing, specifically by heating using a hot plate, oven, or the like, to obtain a film having excellent heat resistance, transparency, flattening properties, low water absorption, chemical resistance, and the like, and having a good pattern.

[0072] The post-bake is generally performed at a heating temperature selected from the range of 140 to 270° C. for 5 to 30 minutes on a hot plate or for 30 to 90 minutes in an oven.

[0073] Thus, by such post-baking, a cured film having a desired good pattern shape can be obtained.

[0074] The film obtained from the adhesive composition of the present invention has flux properties and adhesive properties, and the film can be processed as desired to form a film only in required locations on an array substrate.

[0075] After mass-transferring the LED elements onto an array substrate having an adhesive composition film, the array electrodes and the LED element electrodes are bonded by thermocompression bonding using a flip-chip bonder (the heating temperature is usually in the range of 250 to 350°C to melt the solder electrodes). During thermocompression bonding, the composition film is in an uncured state, so it melts when heated, and when pressure is applied, the composition film is expelled from between the array electrodes and the LED element electrodes, so that it does not impede the bonding between the electrodes. After that, the composition film expelled around the electrodes is thermally cured, so that it functions as an underfill material that protects the area around the electrodes from air and moisture.

[0076] Furthermore, since the adhesive composition of the present invention is resistant to yellowing even during high-temperature processes such as flip-chip bonding and has high transparency, it is unlikely to impair the color purity of LED elements. EXAMPLES

[0077] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The abbreviations of the compounds used, the release substrates, and the methods for measuring the various physical properties are as follows.

[0078] (monomer) HQMA: p-hydroxyphenyl methacrylate HEMA: 2-hydroxyethyl methacrylate BA: n-butyl acrylate (Radical polymerization initiator) AIBN: α,α'-azobisisobutyronitrile (Isocyanurate Compounds) I1: NK Ester A-9300 (manufactured by Shin-Nakamura Chemical Co., Ltd.) I2: TEPIC-VL (Nissan Chemical Co., Ltd.) (Epoxy compounds) E1: Epochalic DE-102 (manufactured by ENEOS Corporation) E2: EHPE 3150 (manufactured by Daicel Corporation) E3: jER152 (Mitsubishi Chemical Corporation) E4: Epolead GT-401 (butanetetracarboxylic acid tetra(3,4-epoxycyclohexylmethyl) modified ε-caprolactone, manufactured by Daicel Corporation) E5: Celoxide 2021P (manufactured by Daicel Corporation) E6: Denacol EX-851 (Nagase ChemteX Corporation) E7: Showfree BATG (manufactured by Resonac Co., Ltd.) (Inorganic filler) F1: Organosilica sol MEK-AC-5140Z (Nissan Chemical Co., Ltd.) (solvent) PGME: Propylene glycol monomethyl ether IPA: Isopropyl alcohol (Release substrate) Base film: PET film coated with a silicone release layer with a peel strength of 380N / 25mm (Nippa Corporation) Protective film: PET film coated with a silicone release layer, with a peel strength of 40N / 25mm (manufactured by Nippa Corporation)

[0079] <Molecular weight measurement> The molecular weight of the polymer was measured using a room temperature gel permeation chromatography (GPC) apparatus (GPC-101) (Showa Denko KK) and columns (KD-803, KD-805 in series) (Showa Denko KK) as follows. Column temperature: 50℃ Eluent: N,N-dimethylformamide (additives: lithium bromide monohydrate (LiBr·H2O) 30 mmol / L, phosphoric acid anhydrous crystal (o-phosphoric acid) 30 mmol / L, tetrahydrofuran (THF) 10 mL / L) Flow rate: 1.0ml / min Standard samples for preparing a calibration curve: TSK standard polyethylene oxide (molecular weight: approximately 900,000, 150,000, 100,000, and 30,000) (manufactured by Tosoh Corporation) and polyethylene glycol (molecular weight: approximately 12,000, 4,000, and 1,000) (manufactured by Polymer Laboratory Co., Ltd.).

[0080] <Measurement of glass transition temperature (Tg)> The Tg of the polymer obtained in the synthesis examples was measured under the following conditions using a differential scanning calorimeter (DSC) DSC1 (manufactured by METTLER TOREDO). Heating rate: 10℃ / min Measurement temperature: -20℃~200℃ Number of measurements: 2. Tg was calculated from the results of the second heating.

[0081] <Synthesis of acrylic polymer> (Synthesis Example 1) As monomer components constituting the acrylic polymer, HQMA (6.0 g), HEMA (4.0 g), and BA (10.0 g) were used, and AIBN (0.2 g) was used as a radical polymerization initiator. These were polymerized in a solvent PGME (47.1 g) at a temperature of 60°C to obtain a solution P1 (acrylic polymer concentration: 30.0 mass%) of an acrylic polymer component having Mn (number average molecular weight): 24,700 and Mw (weight average molecular weight): 111,900. This solution P1 was applied to a 5 cm x 5 cm glass substrate using a spin coater, and then prebaked on a hot plate at a temperature of 100°C for 120 seconds to obtain a dried film of the acrylic polymer. The Tg of the obtained acrylic polymer was 31°C. (Synthesis Example 2) HQMA (10.0 g) and BA (10.0 g) were used as monomer components constituting the acrylic polymer, and AIBN (0.06 g) was used as a radical polymerization initiator. These were subjected to a polymerization reaction in a solvent PGME (46.8 g) at a temperature of 60° C., to obtain an acrylic polymer P2 (acrylic polymer concentration: 30.0 mass%) having a molecular weight and Tg shown in Table 1. (Synthesis Example 3) HQMA (14.0 g) and BA (6.0 g) were used as monomer components constituting the acrylic polymer, and AIBN (0.2 g) was used as a radical polymerization initiator. These were subjected to a polymerization reaction in a solvent PGME (37.5 g) at a temperature of 60° C., to obtain an acrylic polymer P3 (acrylic polymer concentration: 35.0 mass%) having a molecular weight and Tg shown in Table 1.

[0082] [Table 1]

[0083] <Preparation of Adhesive Composition> (Example 1-1) As a resin solution, isocyanurate compound I1 (0.375 g), epoxy compound E1 (0.375 g), and solvents PGME (2.683 g) and IPA (2.400 g) were added to the acrylic polymer solution (P1) (4.167 g) obtained in Synthesis Example 1 above, and the mixture was stirred at room temperature for 2 hours to prepare adhesive composition V1 having the composition shown in Table 2.

[0084] (Examples 1-2 to 1-5) and (Comparative Examples 1-1 to 1-4) The resin solution, isocyanurate compound, epoxy compound, and solvent types and amounts were changed as shown in Table 2 and then added, followed by stirring at room temperature for 2 hours to prepare positive-type photosensitive adhesive compositions V2 to V5 and RV1 to RV4 having the compositions shown in Table 2.

[0085] (Examples 1 to 6) To the acrylic polymer resin solution (P2) (2.857 g), isocyanurate compound I2 (0.623 g), epoxy compound E2 (0.623 g), inorganic filler F1 (2.144 g) and solvent PGME (3.752 g) were added, and the mixture was stirred at room temperature for 2 hours to prepare adhesive composition V6 having the composition shown in Table 2.

[0086] [Table 2]

[0087] (Example 2-1) <Adhesion strength evaluation> The adhesive composition V1 prepared in Example 1-1 was applied to a 5 cm x 5 cm glass substrate using a spin coater, and then prebaked on a hot plate at a temperature of 100°C for 120 seconds to form a prebaked film with a thickness of 3 μm. Thereafter, the peel strength of the coating surface was measured at room temperature (23°C) using a texture analyzer manufactured by Stable Micro Systems, using a probe ball (diameter: 25 mm, material: SUS), compression speed: 1 mm / sec, tensile speed: 1 mm / sec, compression load: 200 g, and compression holding time: 2 sec. If the peel strength was 1.0 g or more, the adhesion was judged to be good, and if it was less than 1.0 g, the adhesion was judged to be poor. The results are shown in Table 3.

[0088] <Transmittance evaluation> The adhesive composition V1 prepared in Example 1-1 was applied to a quartz substrate of 4 cm x 4 cm using a spin coater, and then prebaked on a hot plate at a temperature of 100 ° C for 120 seconds to form a prebaked film with a thickness of 3 μm. The prebaked film was heated on a hot plate at a temperature of 300 ° C for 60 seconds, assuming the heat given to the organic film during flip chip bonding. Then, postbaked on a hot plate at a temperature of 230 ° C for 30 minutes to form a cured film. The transmittance of the obtained cured film was measured, and a film with an average value of 95% or more in the visible range (wavelength 400 nm to 800 nm) was evaluated as having good transparency, and a film with an average value of less than 95% was evaluated as having poor transparency. The results are shown in Table 3.

[0089] (Examples 2-2 to 2-6 and Comparative Examples 2-1 to 2-4) Example 1-2 1 The adhesive compositions V2 to V6 and RV1 to RV4 prepared in Comparative Examples 1-6 and 1-1 to 1-4 were used to evaluate the adhesiveness and transparency in the same manner as in Example 2-1. Note that the pre-baking conditions were appropriately changed to a temperature of 100 to 140°C and a time of 2 to 10 minutes.

[0090] The results are shown in Table 3.

[0091] [Table 3]

[0092] As shown in Table 3, all of the adhesive compositions of the Examples showed good adhesion and transparency. In contrast, when an adhesive composition using an acrylic polymer with a glass transition temperature (Tg) of 100°C or higher was used (Comparative Example 2-3), or when no isocyanurate compound was used (Comparative Example 2-2), the adhesion was insufficient. In addition, when the epoxy compound used had an aromatic ring (Comparative Examples 2-1 and 2-4), the transparency was insufficient.

[0093] (Example 3-1) <Production and evaluation of film sheets> The adhesive composition V1 prepared in Example 1-1 was applied onto an A4-sized base film using a bar coater, and then prebaked in an oven at a temperature of 100° C. for 120 seconds to form a prebaked film with a thickness of 3 μm. The protective film was then laminated onto the prebaked film using a roller to prepare an adhesive sheet S1. The peelability of the protective film was then evaluated. After the protective film was peeled off, it was judged to be good if there was no film remaining on the protective film side, and bad if a part of the adhesive composition remained on the protective film side. Next, the transferability from the base film to the substrate was evaluated. A glass substrate with a size of 5 cm×5 cm and a thickness of 1 mm was used as the substrate. After the base film was peeled off, it was judged to be good if there was no film remaining on the base film side and the adhesive sheet was transferred to the substrate without wrinkles, and bad if a part of the adhesive composition remained on the base film side or wrinkles occurred on the adhesive sheet after transfer. Finally, the peel strength of the coating surface was measured at room temperature (23°C) using a texture analyzer manufactured by Stable Micro Systems, with a probe ball (diameter: 25 mm, material: SUS), compression speed: 1 mm / sec, tensile speed: 1 mm / sec, compression load: 200 g, and compression hold time: 2 sec. A peel strength of 1.0 g or more was judged to indicate good adhesion, and a peel strength of less than 1.0 g was judged to be poor. The results are shown in Table 4.

[0094] (Example 3-2) Using the adhesive composition V2 prepared in Example 1-2, an adhesive sheet S2 was prepared in the same manner as in Example 3-1, and the peelability of the protective film, the transferability to the substrate, and the adhesiveness of the sheet were evaluated. The results are shown in Table 4.

[0095] [Table 4]

[0096] (Examples 4-1 and 4-2) <Flip chip bonding test> As a mounting sample, a TEG (Test Element Group) chip (5.1 mm x 5.1 mm x 700 μm thick) having 1700 electrodes with an electrode area of ​​20 μm x 20 μm and an electrode height of 5.5 μm (the height of the SnAg solder is 2.3 μm, and the height of the copper post electrode is 3.2 μm) and a TEG substrate (15 mm x 15 mm x 700 μm thick) in which copper electrodes were wired to form a daisy chain with the electrodes of the TEG chip were prepared. The adhesive sheets prepared in Examples 3-1 and 3-2 were transferred onto the TEG substrate, respectively, to form an underfill film. Next, using a Panasonic Corporation flip chip bonder, the TEG chip was flip chip bonded to the TEG substrate having the underfill film at a stage temperature of 60° C., a head temperature of 370° C. for 60 seconds, and a head pressure of 150 N. After that, post-baking (post-curing) was performed at 230° C. for 30 minutes to obtain a bonded body. The obtained bonded body was evaluated for the presence or absence of peeling of the TEG chip (no peeling: ◯, peeling: ×) and the conductive resistance value (less than 100 Ω: ◯, 100 Ω or more: ×). The results are shown in Table 5.

[0097] (Comparative Example 4-1) Instead of using an adhesive sheet as an underfill film, the TEG chip and the TEG substrate were washed with a 5% by mass sulfuric acid aqueous solution before flip chip bonding to remove the surface oxide film, and a bonded body was formed in the same manner as in Example 4-1, and the presence or absence of peeling of the TEG chip was confirmed and the conductive resistance value was measured. The results are shown in Table 5.

[0098] [Table 5]

[0099] As shown in Table 5, the TEG assembly using the adhesive sheet of the embodiment as the underfill film did not peel off the TEG chip and had a good conductive resistance value. In contrast, when no underfill film was used, the peeling of the TEG chip increased significantly and the resistance value could not be measured reproducibly (Comparative Example 4-1).

Claims

1. An adhesive composition comprising the following components (A), (B), (C), and (D): Component (A): an alkali-soluble resin having a phenolic hydroxyl group and a glass transition temperature (Tg) of 60° C. or lower, the acrylic polymer containing, as constituent components, a constituent unit derived from a monomer (A1) having a phenolic hydroxyl group and a polymerizable unsaturated group, and a constituent unit derived from a monomer (A2) having a homopolymer with a Tg of 0° C. or lower. Component (B): A compound having a (meth)acrylic group or an epoxy group and an isocyanurate skeleton Component (C): Polyfunctional aliphatic or alicyclic epoxy compound Component (D): Solvent

2. 2. The adhesive composition according to claim 1, wherein the monomer (A1) having a phenolic hydroxyl group and a polymerizable unsaturated group is selected from the group consisting of p-hydroxystyrene, m-hydroxystyrene, α-methyl-p-hydroxystyrene, and a compound represented by the following formula (1): 【Chemistry 1】 In formula (1), P represents a (meth)acrylic group, a (meth)acrylamide group, an N-methyl(meth)acrylamide group, or a maleimide group; b １ represents a single bond, or a linear, branched, or cyclic alkylene group having 1 to 12 carbon atoms, or a combination thereof; １ represents a single bond, -O-, -COO-, or -OCO-; d １ represents a substituted or unsubstituted hydroxyphenyl group.

3. 2. The adhesive composition according to claim 1, wherein the monomer (A2) which gives a homopolymer having a Tg of 0° C. or lower is a compound represented by the following formula (2): 【Chemistry 2】 (In formula (2), R ２ represents a hydrogen atom or a methyl group; ２ represents an oxygen atom or a sulfur atom, b ２ represents a linear, branched, or cyclic alkylene group having 2 to 20 carbon atoms, or a combination thereof, and —CH ２ - may be replaced with an oxygen atom, provided that they are not adjacent to each other. ２ represents a single bond, -O-, -COO-, or -OCO-; d ２ represents a hydrogen atom or a hydroxyl group.)

4. 4. The adhesive composition according to claim 1, wherein the amount of the component (B) is 20 to 100 parts by mass per 100 parts by mass of the component (A).

5. 4. The adhesive composition according to claim 1, wherein the amount of the component (C) is 10 to 100 parts by mass per 100 parts by mass of the component (A).

6. The adhesive composition according to any one of claims 1 to 3, further comprising a surfactant as component (E) in an amount of 0.01 to 1.0 part by mass per 100 parts by mass of component (A).

7. The adhesive composition according to any one of claims 1 to 3, further comprising an inorganic filler as a component (F).

8. An adhesive sheet comprising the adhesive composition according to any one of claims 1 to 3 laminated on both sides with a release substrate.

9. A cured film obtained by curing the adhesive composition according to any one of claims 1 to 3.

10. An LED display element comprising the cured film according to claim 9 as an underfill material.

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