Process for curing cationically polymerizable epoxy resin compositions

Abstract

The present invention relates to a method of curing a cationically polymerizable epoxy resin composition, the method comprising: irradiating a cationically polymerizable epoxy resin composition with an ultraviolet, visible or infrared laser, and maintaining a temperature of the cationically polymerizable epoxy resin composition between a temperature 25 DEG C higher than a curing reaction peak temperature of the cationically polymerizable epoxy resin composition measured by differential scanning calorimetry to 275 DEG C, wherein the cationically polymerizable epoxy resin composition comprises: (A) an epoxy resin; and (B) an acid generator.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for curing a cationically polymerizable epoxy resin composition. BACKGROUND

[0002] Bonding techniques are increasingly used for bonding of components of optical devices such as camera modules and LiDAR (Light Detection and Ranging) modules. For example, US 2015 / 0124098 A discloses a dual-curable epoxy adhesive for bonding lens components of automotive camera modules, which is temporarily cured by ultraviolet irradiation so that it does not immediately shift after adjustment of the lens optical axis, and then firmly cured by heating. However, this technique requires a long time curing process using heat, which is problematic in terms of production efficiency. In addition, JP 2022-136720 A discloses the use of a laser beam to cure a cationically polymerizable epoxy adhesive composition, which process can be completed in a short time. However, when the adhesive is irradiated with a laser, the temperature of the adhesive continues to rise rapidly, and the adhesive can decompose before a sufficient curing strength is obtained. SUMMARY

[0003] PROBLEMS The present inventors found that conventional methods for curing a cationically polymerizable epoxy resin composition have the following problems. Specifically, in these conventional methods, the curing process with ultraviolet irradiation requires a long time, or in the process using a laser beam, the adhesive is irradiated with a laser, the temperature of the adhesive continues to rise rapidly, and the adhesive can decompose before a sufficient curing strength is obtained.

[0004] An object of the present application is to provide a method for curing a cationically polymerizable epoxy resin composition, which firmly cures the adhesive composition in a short time without decomposing the adhesive.

[0005] [Solution to the problem] To achieve the above object, the present inventors conducted extensive research and found that the object can be achieved by a method comprising: irradiating the cationically polymerizable epoxy resin composition with ultraviolet, visible or infrared laser, and maintaining the surface temperature of the cationically polymerizable epoxy resin composition at a temperature of 25°C higher than the peak temperature of the curing reaction of the cationically polymerizable epoxy resin composition measured by differential scanning calorimetry to 275°C, wherein the cationically polymerizable epoxy resin composition comprises: (A) an epoxy resin; and (B) an acid generator. The present application was completed based on this finding and further research. The present application includes the following embodiments.

[0006] Item 1 A method of curing a cationically polymerizable epoxy resin composition, the method comprising: 1) irradiating the cationically polymerizable epoxy resin composition with an ultraviolet, visible, or infrared laser, and 2) maintaining the surface temperature of the cationically polymerizable epoxy resin composition at a temperature between 25°C higher than the peak temperature of the curing reaction of the cationically polymerizable epoxy resin composition measured by differential scanning calorimetry to 275°C, wherein the cationically polymerizable epoxy resin composition comprises: (A) an epoxy resin; and (B) an acid generator.

[0007] Item 2 The method of curing a cationically polymerizable epoxy resin composition according to item 1, wherein the epoxy resin (A) comprises an alicyclic epoxy resin.

[0008] Item 3 The method of curing a cationically polymerizable epoxy resin composition according to item 2, wherein the epoxy resin (A) further comprises a glycidyl ether epoxy resin.

[0009] Item 4 The method of curing a cationically polymerizable epoxy resin composition according to any one of items 1 to 3, wherein the surface temperature of the cationically polymerizable epoxy resin composition is maintained at a temperature between 30°C higher than the peak temperature of the curing reaction of the cationically polymerizable epoxy resin composition measured by differential scanning calorimetry to 250°C.

[0010] Item 5 The method of curing a cationically polymerizable epoxy resin composition according to any one of items 1 to 4, wherein the cationically polymerizable epoxy resin composition further comprises (C) an oxetane resin.

[0011] Item 6 The method of curing a cationically polymerizable epoxy resin composition according to any one of items 1 to 5, wherein the cationically polymerizable epoxy resin composition further comprises (D) an inorganic filler.

[0012] Item 7 The method of curing a cationically polymerizable epoxy resin composition according to any one of items 1 to 6, wherein the acid generator (B) is a photoacid generator or a thermal acid generator.

[0013] Item 8 The method of curing a cationically polymerizable epoxy resin composition according to any one of items 1 to 7, wherein the cationically polymerizable epoxy resin composition is curable under visible or infrared laser light having a wavelength of 300 to 1200 nm.

[0014] Item 9 The method of curing a cationically polymerizable epoxy resin composition according to any one of items 1 to 8, wherein the laser irradiation is controlled so that the time from the start of the laser irradiation to the attainment of the surface temperature of the cationically polymerizable epoxy resin composition is 0.1 to 30 seconds.

[0015] Item 10 The method of curing a cationically polymerizable epoxy resin composition according to any one of items 1 to 9, wherein the laser irradiation is controlled so that the time from the start of the laser irradiation to the attainment of the surface temperature of the cationically polymerizable epoxy resin composition is 1 to 25 seconds.

[0016] Item 11 The method of curing a cationically polymerizable epoxy resin composition according to any one of items 1 to 10, which is used for at least one application selected from the group consisting of metal bonding, camera module assembly, and electronic sensor assembly.

[0017] Advantages of the present invention The method of curing a cationically polymerizable epoxy resin composition of the present invention ensures the curing of an epoxy adhesive composition in a shorter time without decomposing the cured epoxy adhesive.

[0018] Specific embodiments The method of curing a cationically polymerizable epoxy resin composition of the present invention comprises at least two steps: 1) irradiating a cationically polymerizable epoxy resin composition comprising (A) an epoxy resin and (B) an acid generator with ultraviolet, visible, or infrared laser light; and 2) maintaining the surface temperature of the cationically polymerizable epoxy resin composition at a temperature between 25°C higher than the peak temperature of the curing reaction of the cationically polymerizable epoxy resin composition measured by differential scanning calorimetry and 275°C.

[0019] In one embodiment, the curing method further comprises the step of applying the cationically polymerizable epoxy resin composition to a first substrate and / or a second substrate.

[0020] The first substrate and / or the second substrate can be a single material and a single layer, or can comprise multiple layers of the same or different materials. The layers can be continuous or discontinuous.

[0021] The substrates described herein can have various properties, including rigidity (e.g., rigid substrates, i.e., substrates that cannot be bent using both hands or that will break if an attempt is made to bend the substrate using both hands), flexibility (e.g., flexible substrates, i.e., substrates that can be bent using less than both hands), porosity, electrical conductivity, non-electrical conductivity, and combinations thereof.

[0022] The substrates of the articles can be in various forms, including, for example, fibers, threads, yarns, woven fabrics, nonwoven fabrics, films (e.g., polymeric films, metallized polymeric films, continuous films, discontinuous films, and combinations thereof), foils (e.g., metal foils), sheets (e.g., metal sheets, polymeric sheets, continuous sheets, discontinuous sheets, and combinations thereof), and combinations thereof.

[0023] In preferred embodiments, the at least one substrate can be selected from metals, such as metal firing pastes, aluminum, tin, molybdenum, silver, electrically conductive metal oxides such as indium tin oxide (ITO), fluorine-doped tin oxide, aluminum-doped zinc oxide, and the like; glasses, such as inked glass, bare glass; resins, such as polycarbonates, polybutylene terephthalate, polyethylene terephthalate, and polyamides. Other suitable metals include copper, gold, palladium, platinum, aluminum, indium, silver-coated copper, silver-coated aluminum, tin, and tin-coated copper. Preferably, both substrates are selected from one of the above materials. More preferably, both substrates are glass.

[0024] The cationically polymerizable epoxy resin composition can be applied to the first and / or second substrates by using any suitable application method, including, for example, automatic thread distribution, spray distribution, slot die coating, roll coating, gravure coating, transfer coating, pattern coating, screen printing, spray coating, filament coating, by extrusion, air knife, doctor blade, brush coating, dip coating, knife coating, offset gravure coating, rotogravure coating, and combinations thereof. The cationically polymerizable epoxy resin composition can be applied in continuous or discontinuous coatings, in a single layer or multiple layers, and combinations thereof.

[0025] In the present invention, the ultraviolet, visible, or infrared laser used to irradiate the cationically polymerizable epoxy resin composition specifically refers to a laser having a wavelength of 300 to 1200 nm. The cationically polymerizable epoxy resin composition of the present invention can be used for curing using a laser having a preferred wavelength of 350 to 1100 nm, more preferably a wavelength of 400 to 1100 nm.

[0026] Techniques for generating lasers in this wavelength range are known in the art. Preferably, the laser is provided by a laser diode device. Examples of commercially available products of such devices include CB series products from Panasonic Corporation, such as CB1F, CB3, CB5, CB20.

[0027] In the second step, the surface temperature of the cationically polymerizable epoxy resin composition is maintained at a temperature higher than the peak temperature of the curing reaction of the cationically polymerizable epoxy resin composition measured by differential scanning calorimetry by 25°C to 275°C.

[0028] Preferably, the surface temperature of the cationically polymerizable epoxy resin composition is maintained at a temperature higher than the peak temperature of the curing reaction of the cationically polymerizable epoxy resin composition measured by differential scanning calorimetry by 30°C to 250°C. If the temperature is too high, the cured adhesive can have a poor appearance due to burning since the decomposition temperature of the cured product of such a cationically polymerizable epoxy resin composition is about 275°C. If the temperature is too low, the adhesive composition can not be fully cured and can not obtain sufficient adhesive properties. By controlling the surface temperature to be stabilized at a preset temperature in a short time by laser output, the cured adhesive can obtain a good appearance and sufficient adhesive properties.

[0029] The peak temperature of the curing reaction of the cationically polymerizable epoxy resin composition can be measured using a differential scanning calorimeter (e.g., DSC 6000 of Seiko Instruments Inc.) under a nitrogen atmosphere at a temperature of 25°C to 200°C at a temperature increase rate of 10°C / minute.

[0030] The laser irradiation is controlled so that the time from the start of the laser irradiation to the surface temperature of the cationically polymerizable epoxy resin composition reaches is 0.5 to 30 seconds, preferably 1 to 25 seconds, more preferably 1 to 20 seconds. Preferably, the total irradiation time is 1 to 60 seconds, preferably 2 to 30 seconds, and the maintenance time, which is the difference between the total irradiation time and the time required to reach the surface temperature, is 0.5 to 30 seconds, preferably 1 to 20 seconds. If the irradiation and maintenance times are controlled within this range, the appearance and / or curability of the cured adhesive can be improved.

[0031] The surface temperature of the cationically polymerizable epoxy resin composition can be measured by a method known in the art. Preferably, the measurement is non-contact with respect to the surface of the cationically polymerizable epoxy resin composition. The means for non-contact measurement of the surface temperature of the adhesive is not particularly limited, but for example, there is a configuration that combines a temperature sensor for detecting radiated infrared rays from the adhesive composition and a calculation unit for calculating the temperature of the adhesive composition. Although the output control means is not particularly limited, for example, by connecting the calculation unit and the laser in a controllable manner, the output of the laser can be adjusted according to the calculation result of the calculation unit. By this configuration, by detecting the surface temperature of the adhesive composition, if the temperature exceeds a preset temperature, a command signal can be sent to the laser to control the output so as to become appropriate. Preferably, the laser diode device for generating ultraviolet, visible, or infrared laser includes a radiation thermometer having such a configuration to control the operating temperature.

[0032] The epoxy resin composition in the curing method is cationically polymerizable and comprises (A) an epoxy resin; and (B) an acid generator.

[0033] The epoxy resin used in the present application is not particularly limited as long as the epoxy resin is capable of undergoing cationic polymerization. The mechanism of cationic polymerization of epoxy resins is well known. Specifically, the epoxy resin used in the present application can be any polymerization system in which the growing chain is a carbo cation or a carbocation. The epoxy resin used in the present application forms a carbo cation by reacting with the acid generated from the acid generator. A growing reaction occurs between the carbo cation and the epoxy resin used in the present application, thereby ultimately providing a cured product.

[0034] If desired, the epoxy resin used in the present application can be a single epoxy resin or a combination of two or more epoxy resins.

[0035] In terms of excellent curability, the epoxy resin used in the present application preferably comprises an alicyclic epoxy resin. The alicyclic epoxy resin refers to an epoxy resin having an alicyclic ring in the molecule thereof and the portion of the carbon-carbon bond forming the alicyclic ring is shared with the epoxy ring. The alicyclic epoxy resin used can be a known alicyclic epoxy resin.

[0036] When the epoxy resin used in the present application comprises an alicyclic epoxy resin, in terms of curability, the content of the alicyclic epoxy resin in the epoxy resin is preferably 3% by weight or more, more preferably 5% by weight or more, and still more preferably 10% by weight or more, based on the entire epoxy resin.

[0037] The alicyclic epoxy resin used in the present application has an epoxy equivalent weight of, for example, 100 to 500, preferably 100 to 400, more preferably 100 to 300.

[0038] Examples of the alicyclic epoxy resin used in the present application include, but are not limited to, 3',4'-epoxycyclohexane methyl-3,4-epoxycyclohexylmethyl ester (Celloxide 2021P (CEL2021P) produced by Daicel Corporation), 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane methyl ester modified ε-caprolactone (Celloxide 2081 (CEL2081) produced by Daicel Corporation), 1,2-epoxy-4-vinylcyclohexane (Celloxide 2000 (CEL2000) produced by Daicel Corporation, Celloxide 8010 (CEL8010) produced by Daicel Corporation, KR-470 produced by Shin-Etsu Chemical Co., Ltd., and the like.

[0039] In terms of imparting flexibility to the cured product, the epoxy resin used in the present application preferably contains at least one epoxy resin selected from the group consisting of glycidyl ether epoxy resins and glycidyl ester epoxy resins. These epoxy resins have slower growth reactions than alicyclic epoxy resins, so the curing reaction continues to proceed after laser irradiation, and the molecular weight grows only to about several thousand. Therefore, these epoxy resins can impart preferred flexibility to the final cured product.

[0040] The glycidyl ether epoxy resin and the glycidyl ester epoxy resin each used in the present application has an epoxy equivalent weight of, for example, 100 to 1000, preferably 100 to 800, more preferably 100 to 600.

[0041] The glycidyl ether epoxy resin and the glycidyl ester epoxy resin used in the present application are preferably liquid or semi-solid at room temperature (about 23°C), but if they are solid, they can be used dissolved.

[0042] The glycidyl ether epoxy resin and the glycidyl ester epoxy resin are preferably those having an aromatic structure in the main chain. The glycidyl ether epoxy resin and the glycidyl ester epoxy resin can have a polycyclic aromatic structure (naphthalene, anthracene, etc.) in the main chain.

[0043] The epoxy resin added in order to impart flexibility to the cured product is preferably a glycidyl ether epoxy resin. Examples of the glycidyl ether epoxy resin include bisphenol-type glycidyl ethers and the like.

[0044] Bisphenol-type glycidyl ethers include bisphenol A glycidyl ether, bisphenol F glycidyl ether, bisphenol AP glycidyl ether, bisphenol B glycidyl ether, bisphenol C glycidyl ether, bisphenol E glycidyl ether, bisphenol G glycidyl ether, and the like.

[0045] Preferred bisphenol A glycidyl ethers include EPICLON 840 produced by DIC Corporation, EPICLON 840S produced by DIC Corporation, EPICLON 850 produced by DIC Corporation, EPICLON 850S produced by DIC Corporation, EXA-850CRP produced by DIC Corporation, EXA-850LC produced by DIC Corporation, EXA-860 produced by DIC Corporation, EXA-1050 produced by DIC Corporation, EXA-1055 produced by DIC Corporation, 825 produced by Mitsubishi Chemical Corporation, 827 produced by Mitsubishi Chemical Corporation, 828 produced by Mitsubishi Chemical Corporation, 1001 produced by Mitsubishi Chemical Corporation, 1002 produced by Mitsubishi Chemical Corporation, RE-310S produced by Nippon Kayaku Co., Ltd., and the like.

[0046] Preferred bisphenol F glycidyl ethers include EXA-830 produced by DIC Corporation, EXA-830S produced by DIC Corporation, EXA-835 produced by DIC Corporation, EXA-830CRP produced by DIC Corporation, EXA830LVP produced by DIC Corporation, EXA835LV produced by DIC Corporation, 806 produced by Mitsubishi Chemical Corporation, 806H produced by Mitsubishi Chemical Corporation, 807 produced by Mitsubishi Chemical Corporation, and RE-303SL produced by Nippon Kayaku Co., Ltd.; phenol aralkyl epoxy resins include NC3000L produced by Nippon Kayaku Co., Ltd., NC2000L produced by Nippon Kayaku Co., Ltd., and the like.

[0047] If the epoxy resin used in the present application contains a glycidyl ether epoxy resin and / or a glycidyl ester epoxy resin, the epoxy resin contains the glycidyl ether epoxy resin and the glycidyl ester epoxy resin in a total amount of preferably 3% by weight or more, more preferably 5% by weight or more, still more preferably 10% by weight or more, based on the entire epoxy resin, in terms of imparting flexibility to the cured product.

[0048] The acid generator used in the present application is not particularly limited as long as it directly or indirectly generates an acid by using visible or infrared laser light, and as long as the acid reacts with the epoxy resin (A) to produce a carbocation.

[0049] Examples of the above-mentioned acid generator that directly or indirectly generates an acid by using visible or infrared laser light include a photoacid generator and the like. A photoacid generator is a compound that generates an acid by being irradiated with light. The photoacid generator has a portion that absorbs light and a portion that serves as an acid source in the molecule. Examples include, but are not particularly limited to, onium salts and the like having a cationic portion and an anionic portion. In these onium salts, the cationic portion corresponds to the portion that absorbs light, and the anionic portion serves as the acid source.

[0050] As the cationic portion, the above-mentioned onium salts can contain a sulfonium ion, an iodonium ion, a phosphonium ion, a quaternary ammonium ion, or a diazonium ion, and the like. The sulfonium ion used can be, for example, a triaryl sulfonium ion.

[0051] As the anionic portion, the onium salts can contain PF6 - , SbF6 -, BF4 - , etc.

[0052] Examples of the photoacid generator include CPI-100P, CPI-101A, CPI-200K, CPI-210S, CPI-310B, CPI-310FG, CPI-410S, and IK-1, all of which are produced by San-Apro Ltd.; IRGACURE 250 and IRGACURE 270, all of which are produced by Ciba Specialty Chemicals Inc.; BLUESIL PI 2074, all of which are produced by Elkem, etc.

[0053] Examples of the above-mentioned acid generators that directly or indirectly generate an acid by using visible or infrared laser light include a thermal acid generator, etc. A thermal acid generator is a compound that generates an acid by absorbing heat. The heat generated by visible or infrared laser light can cause the thermal acid generator to generate an acid. If necessary, for example, an inorganic filler, etc. can be appropriately incorporated into the cationically polymerizable epoxy resin composition of the present application, thereby more easily generating heat by visible or infrared laser light irradiation, and more easily generating an acid from the thermal acid generator.

[0054] Examples of the thermal acid generator include TGA CXC1612 and TGA CXC1821, all of which are produced by King Industries, Inc.; San-aid SI-B2A, produced by Sanshin Chemical Industry Co., Ltd.; San-aid SI-B7, produced by Sanshin Chemical Industry Co., Ltd.; San-aid SI-B3A, produced by Sanshin Chemical Industry Co., Ltd.; San-aid SI-B3, produced by Sanshin Chemical Industry Co., Ltd.; San-aid SI-B5, produced by Sanshin Chemical Industry Co., Ltd., etc.

[0055] If necessary, the acid generator used in the present application can be a single acid generator or a combination of two or more acid generators.

[0056] The cationically polymerizable epoxy resin composition of the present application contains the acid generator in an amount of, for example, 0.01 to 10% by weight, preferably 0.1 to 8% by weight, more preferably 0.1 to 5% by weight, still more preferably 0.1 to 3% by weight, based on the entire cationically polymerizable epoxy resin composition.

[0057] The cationically polymerizable epoxy resin composition of the present application preferably contains an oxetane resin.

[0058] The oxetane resin is not particularly limited as long as it is a resin having an oxetane ring in the molecule thereof. Preferably, the oxetane compound has a 3-oxetanyl group, and if desired, another functional group. The oxetane compound has at least one oxetane ring in the molecule thereof, but preferably has two or more oxetane rings. The oxetane equivalent of the multifunctional monomer having two or more oxetane groups is not particularly limited, but is preferably 400 or less, more preferably 300 or less, and preferably 100 or more.

[0059] The oxetane compound is not particularly limited, and examples thereof include bis[l-ethyl(3-oxetanyl)]methyl ether [(3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane)] represented by the following formula (al-1); xylylene bisoxetane represented by the following formula (al-2); 4,4'-bis[3-ethyl-(3-oxetanyl)methoxymethyl]biphenyl; 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane; 3-ethyl-3-hydroxymethyloxetane; 3-ethyl-3-(4-hydroxybutyl)oxymethyloxetane; 1,4-bis(3-ethyl-3-oxetanylmethoxy)methylbenzene; (3-ethyloxetan-3-yl)methyl methacrylate; and m-phthalic acid bis[(3-ethyl-3-oxetanyl)methyl ester], etc.

[0060] The oxetane compound can be used alone or in combination of two or more.

[0061] In one aspect of the present embodiment, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane represented by the following formula (al-1) is preferably contained as the component (al). The amount of the compound represented by formula (al-1) is preferably 80 mass% or more, and can be 100 mass%, based on the total amount of the component (al).

[0062] .

[0063] Examples of commercially available products of the compound represented by formula (a1-1) include OXT-221 (trade name, manufactured by Toagosei Co., Ltd.). Furthermore, examples of commercially available products of the oxetane compound include OXT-212, OXT-101, and OXT-121 manufactured by Toagosei Co., and EHO, OXMA, OXBP, HBOX, and OXIPA manufactured by Ube Industries, Ltd.

[0064] The cationically polymerizable epoxy resin composition of the present application can further contain an inorganic filler.

[0065] The inorganic filler used in the present application can be a single inorganic filler or a combination of two or more inorganic fillers, if desired.

[0066] Examples of the inorganic filler used in the present application include a silica filler such as colloidal silica, hydrophobic silica, fine powder silica, and nano silica, and an acrylic bead, a glass bead, a polyurethane bead, bentonite, acetylene black, Ketjen black, and the like.

[0067] The volume average particle diameter (the largest weight average diameter thereof if the filler is not particulate) of the inorganic filler used in the present application can be, for example, 0.01 to 50 μm, preferably 0.1 to 40 μm, and more preferably 1 to 30 μm. In the present specification, the volume average particle diameter of the inorganic filler is specifically measured by a dynamic light scattering nanoparticle size analyzer.

[0068] Examples of commercially available products of the inorganic filler include high-purity synthetic spherical silica (SO-E5 produced by Admatechs, average particle diameter: 2 μm; SO-E2, average particle diameter: 0.6 μm), silica (FB7SDX produced by Tatsumori Ltd., average particle diameter: 10 μm), silica (TS-10-034P produced by Micron, average particle diameter: 20 μm), and the like.

[0069] The cationically polymerizable epoxy resin composition of the present application contains the inorganic filler in an amount of, for example, 40 to 80% by weight, and preferably 50 to 70% by weight, based on the entire cationically polymerizable epoxy resin composition.

[0070] The cationically polymerizable epoxy resin composition of the present application can further contain one or more other components, if desired.

[0071] Specific examples of the other component include an oxetane resin. In particular, in terms of imparting flexibility to the cured product, the cationically polymerizable epoxy resin composition of the present application preferably further contains an oxetane resin after the curing of the glycidyl ether epoxy resin or glycidyl ester epoxy resin is promoted by an acid generator when the epoxy resin is contained.

[0072] The cationically polymerizable epoxy resin composition of the present application contains the oxetane resin in an amount of, for example, 3 to 60% by weight, preferably 5 to 50% by weight, based on the entire cationically polymerizable epoxy resin composition.

[0073] Examples of the other component also include adhesion aids (e.g., silane), coupling agents (e.g., titanate), rheology modifiers (e.g., fumed silica), and the like.

[0074] The cationically polymerizable epoxy resin composition of the present application can be effectively cured by visible or infrared laser even if it does not contain a pigment. If necessary, the cationically polymerizable epoxy resin composition of the present application can contain a pigment.

[0075] The method of curing the cationically polymerizable epoxy resin composition of the present application is preferably used for camera module assembly. More specifically, in camera module assembly, the curing of the cationically polymerizable epoxy resin composition of the present application is preferably used to bond a lens holder and a substrate on which an imaging element is fixed. In the above, the camera module is not particularly limited, and is, for example, a small camera module for a smartphone or the like.

[0076] Furthermore, the method of curing the cationically polymerizable epoxy resin composition of the present application is also preferably used for electronic sensor assembly.

[0077] Examples The resin composition of all examples was prepared by mixing 100 mg of 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanemethyl ester ("Celloxide 2021P" produced by Daicel Corporation), 100 mg of bisphenol A type epoxy resin ("EPICLON 840" produced by DIC Corporation), 100 mg of 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane ("OXT 221" produced by Toagosei Co., Ltd.), 3 mg of thermal acid generator ("TGA CXC1821" produced by King Industries), and 500 mg of high-purity synthetic spherical silica (SO-E5 produced by Admatechs, average particle diameter: 2 μm). Specifically, the above components were blended, kneaded, and dispersed using a three-roll mill, and further vacuum defoamed to obtain the resin composition.

[0078] The curing test was conducted as follows. Table 1 shows the evaluation results.

[0079] Curing test method The curing reaction peak of the epoxy resin composition was determined using a Seiko Instruments Inc. DSC6000 differential scanning calorimeter in a nitrogen atmosphere at a temperature range of 25°C to 200°C and a heating rate of 10°C / min. The peak curing temperature was observed at 80°C.

[0080] A 0.01 cubic centimeter cc amount of epoxy resin composition was applied to a glass slide. The slide was irradiated with a 980 nm laser at a 90-degree angle using a laser diode device (CB1F, Panasonic Corporation) including a radiation thermometer. The controlled temperature on the surface of the resin composition, the time to reach the controlled temperature, and the total irradiation time are shown in Table 1. The appearance and curability of the cured product were then evaluated by touch with a bamboo stick, and the curing quality was further evaluated.

[0081] Table 1 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Control temperature 175℃ 125℃ 225℃ 80℃ 300℃ Time to control temperature 3 seconds 3 seconds 3 seconds 3 seconds 3 seconds Total exposure time 10 seconds 15 seconds 5 seconds 15 seconds 5 seconds Appearance Good Good Good Good Burnt Curability Fully cured Fully cured Fully cured Partially cured Fully cured When the cationic polymerizable epoxy resin compositions of Examples 1, 2, and 3 were irradiated with a laser to maintain the surface temperature within an appropriate range, they were fully cured and had a good appearance. Conversely, when a lower temperature was applied in Comparative Example 1, the cationic polymerizable epoxy resin compositions only partially cured. Furthermore, when a higher temperature was applied in Comparative Example 2, although the compositions were fully cured, decomposition of the cured adhesive occurred.

Claims

1. A method for curing a cationic polymerizable epoxy resin composition, the method comprising: 1) Irradiation of cationic polymerizable epoxy resin compositions with ultraviolet, visible, or infrared lasers, and 2) The surface temperature of the cationic polymerizable epoxy resin composition is maintained between 25°C and 275°C, which is 25°C higher than the peak curing temperature of the cationic polymerizable epoxy resin composition as determined by differential scanning calorimetry. The cationic polymerizable epoxy resin composition comprises: (A) Epoxy resin; and (B) Acid generating agent.

2. The method for curing a cationic polymerizable epoxy resin composition according to claim 1, wherein the epoxy resin (A) comprises an alicyclic epoxy resin.

3. The method for curing a cationic polymerizable epoxy resin composition according to claim 2, wherein the epoxy resin (A) further comprises glycidyl ether epoxy resin.

4. The method for curing a cationic polymerizable epoxy resin composition according to any one of claims 1 to 3, wherein the surface temperature of the cationic polymerizable epoxy resin composition is maintained between 30°C and 250°C above the peak curing reaction temperature of the cationic polymerizable epoxy resin composition as determined by differential scanning calorimetry.

5. A method for curing a cationic polymerizable epoxy resin composition according to any one of claims 1 to 4, wherein the cationic polymerizable epoxy resin composition further comprises (C) oxetane resin.

6. A method for curing a cationic polymerizable epoxy resin composition according to any one of claims 1 to 5, wherein the cationic polymerizable epoxy resin composition further comprises (D) an inorganic filler.

7. The method for curing a cationic polymerizable epoxy resin composition according to any one of claims 1 to 6, wherein the acid generating agent (B) is a photoacid generating agent or a thermal acid generating agent.

8. A method for curing a cationic polymerizable epoxy resin composition according to any one of claims 1 to 7, wherein the cationic polymerizable epoxy resin composition is curable under ultraviolet, visible, or infrared laser light with a wavelength of 300 to 1200 nm.

9. The method for curing a cationic polymerizable epoxy resin composition according to any one of claims 1 to 8, wherein laser irradiation is controlled such that the time from the start of laser irradiation to reaching the surface temperature of the cationic polymerizable epoxy resin composition is 0.1 to 30 seconds, preferably 1 to 25 seconds.

10. A method for curing a cationic polymerizable epoxy resin composition according to any one of claims 1 to 9, for use in at least one application selected from metal bonding, camera module assembly, and electronic sensor assembly.

Images