Thermosetting adhesive composition, cured product thereof, and bonded body

Abstract

To provide a thermosetting adhesive composition which can achieve both high curability and excellent storage stability.SOLUTION: A thermosetting adhesive composition contains (A) an epoxy resin, (B) a curing agent, and (C) a latent curing agent. The (B) curing agent contains (B1) secondary thiol. The (C) latent curing agent contains two or more latent curing agents having mutually different exothermic peak top temperatures by reaction of an epoxy resin and secondary thiol determined by differential scanning calorimetry at a rate of temperature rise of 10°C / min by 10°C or more. A molar ratio of a sulfanyl group of (B) the curing agent to an epoxy group of (A) the epoxy resin is 0.8 or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a thermosetting adhesive composition, a cured product of this thermosetting adhesive composition, and a bonded body, and more particularly to a thermosetting adhesive composition containing an epoxy resin, a curing agent, and a latent curing agent, a cured product of this thermosetting adhesive composition, and a bonded body produced using this thermosetting adhesive composition. [Background technology]

[0002] In electronic devices, a thermosetting adhesive composition used for adhesion in the manufacture of a bonded body, such as the assembly of a module such as a camera module or lamination to a housing, is required to be able to achieve a high curing rate in a relatively low temperature and short time, such as 80°C for 60 minutes, and thereby to increase the adhesive strength of the cured product to copper, liquid crystal polymer (LCP), etc. In addition, such a thermosetting adhesive composition is also required to have good storage stability. In order to achieve both good curability and storage stability, a curable one-liquid epoxy resin composition containing (a) an epoxy component, (b) a latent curing agent component, (c) a thixotropy-imparting component, (d) a polythiol component containing a polythiol having a secondary or tertiary thiol group, and (e) a stabilizing component containing a solid organic acid has been studied (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2014-500895 Summary of the Invention [Problem to be solved by the invention]

[0004] However, recently, the demand for curability and storage stability for thermosetting adhesive compositions has been increasing, and in addition to high curability that can achieve a high cure rate at a lower temperature in a shorter time, such as at 60°C for 30 minutes, there is a demand for excellent storage stability that can suppress deterioration not only at room temperature but also in a relatively high temperature environment of about 45°C, such as during transportation in summer, etc. The conventional compositions described above have not been able to achieve both high curability and excellent storage stability.

[0005] An object of the present disclosure is to provide a thermosetting adhesive composition that can achieve both high curability and excellent storage stability, a cured product of this thermosetting adhesive composition, and a bonded body produced using this thermosetting adhesive composition. [Means for solving the problem]

[0006] A thermosetting adhesive composition according to one embodiment of the present disclosure contains an epoxy resin (A), a curing agent (B), and a latent curing agent (C). The curing agent (B) contains a secondary thiol (B1). The latent curing agent (C) contains two or more latent curing agents having exothermic peak top temperatures that differ from each other by 10°C or more in a reaction with an epoxy resin and a secondary thiol, as determined by differential scanning calorimetry at a heating rate of 10°C / min. The molar ratio of sulfanyl groups in the curing agent (B) to epoxy groups in the epoxy resin (A) is 0.8 or more.

[0007] A cured product according to one embodiment of the present disclosure is a cured product of the thermosetting adhesive composition.

[0008] A bonded structure according to one embodiment of the present disclosure includes a first member, a second member, and a bonding layer. The bonding layer is interposed between the first member and the second member to bond the first member and the second member. The bonding layer includes a cured product of the thermosetting adhesive composition. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a thermosetting adhesive composition that can achieve both high curability and excellent storage stability, a cured product of this thermosetting adhesive composition, and a bonded body produced using this thermosetting adhesive composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 1. Overview The thermosetting adhesive composition according to this embodiment (hereinafter also referred to as composition (X)) contains (A) an epoxy resin, (B) a curing agent, and (C) a latent curing agent. The (B) curing agent contains (B1) a secondary thiol. The (C) latent curing agent contains two or more latent curing agents whose exothermic peak top temperatures in the reaction with the epoxy resin and the secondary thiol differ by 10°C or more as determined by differential scanning calorimetry at a heating rate of 10°C / min. The molar ratio of sulfanyl groups in the (B) curing agent to epoxy groups in the (A) epoxy resin is 0.8 or more.

[0011] The inventors conducted extensive research to solve the problem of achieving both high curability that can achieve a high curing rate at a relatively low temperature in a short time and storage stability at room temperature and at a relatively high temperature. As a result, they discovered that in a thermosetting adhesive composition containing an epoxy resin (A), a secondary thiol is used as the curing agent (B) and multiple latent curing agents having specific temperature characteristics are used as the latent curing agent (C), thereby more appropriately controlling the curing reaction during heat curing and achieving both high curability and excellent storage stability, and thus completed the present disclosure.

[0012] The reason why the composition (X) has the above-mentioned configuration and thus exhibits the above-mentioned effect is not necessarily clear, but can be inferred, for example, as follows. That is, by using a plurality of latent curing agents (C) whose exothermic peak temperatures are different from each other by a certain value or more, curing occurs stepwise during heat curing, and it is possible to efficiently react the (A) epoxy resin with the (B) curing agent within a limited time, and to significantly reduce the amount of unreacted (A) epoxy resin remaining after heat treatment, and it is considered that the curing property is improved. In addition, by using a secondary thiol having a relatively low reactivity with the (A) epoxy resin as the (B) curing agent, it is possible to improve the storage stability, and even in this case, it is considered that the molar ratio of the sulfanyl group of the (B) curing agent to the epoxy group of the (A) epoxy resin is set to a specific value or more, and the unreacted epoxy resin is further reduced, and the curing property can be further improved. As a result of these, the composition (X) can achieve both high curability and excellent storage stability. In addition, due to this high curability, the cured product of the composition (X) can exhibit high adhesive strength to copper, LCP, etc.

[0013] 2.Details <Thermosetting adhesive composition> The composition (X) according to the present embodiment contains an epoxy resin (A), a curing agent (B), and a latent curing agent (C). The composition (X) preferably contains a stabilizer (D), and may contain other components (E) other than the components (A) to (D) within a range that does not impair the effects of the present disclosure. Each component will be described below.

[0014] [(A) Epoxy resin] The epoxy resin (A) is not particularly limited as long as it is a compound having one or more epoxy groups in one molecule. The epoxy resin (A) preferably includes one having two or more epoxy groups in one molecule.

[0015] Examples of the (A) epoxy resin include bisphenol type epoxy resins such as bisphenol A type epoxy resins and bisphenol F type epoxy resins; hydrogenated bisphenol type epoxy resins such as hydrogenated bisphenol A type epoxy resins and hydrogenated bisphenol F type epoxy resins; biphenyl type epoxy resins, naphthalene ring-containing epoxy resins, alicyclic epoxy resins, dicyclopentadiene type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, triphenylmethane type epoxy resins, aliphatic epoxy resins, triglycidyl isocyanurate, glycidyl group-containing silicone resins, and glycidylamine type epoxy resins.

[0016] The epoxy resin (A) is preferably liquid at room temperature (25° C.). By using an epoxy resin (A) that is liquid at room temperature, the viscosity of the composition (X) can be appropriately reduced, and as a result, the coatability can be further improved.

[0017] The ratio of the epoxy resin (A) to the entire composition (X) is preferably 10% by mass or more and 70% by mass or less. In this case, the curability and storage stability of the composition (X) can be further improved. This ratio is more preferably 20% by mass or more and 60% by mass or less, and even more preferably 30% by mass or more and 45% by mass or less.

[0018] [(B) Hardener] (B) Curing agent is a compound capable of undergoing a curing reaction with (A) epoxy resin. It is important that (B) curing agent contains (B1) secondary thiol. "Secondary thiol" refers to a compound having at least one secondary sulfanyl group (-SH group) and no primary sulfanyl group. "Secondary sulfanyl group" refers to a sulfanyl group bonded to a secondary carbon atom. "Primary sulfanyl group" refers to a sulfanyl group bonded to a primary carbon atom.

[0019] (B1) Examples of secondary thiols include monofunctional thiols such as 2-octanethiol, 2-decanethiol, cyclopentanethiol, cyclohexanethiol, and 3-mercaptohexyl acetate; bifunctional thiols such as 1,4-bis(3-mercaptobutyryloxy)butane (commercially available product: Karenz MT BD1 manufactured by Showa Denko K.K.); and 2,7-octanedithiol; 1,3,5-tris(2-(3-mercaptobutyryloxy)ethyl)-1,3,5-triazine-2,4,6(1H,2H,5H)-trione (commercially available product: Karenz MT NR1 manufactured by Showa Denko K.K.); trimethylolpropane tris(3-mercaptobutyrate) (commercially available product: Karenz MT Examples of the thiol include trifunctional thiols such as pentaerythritol tetrakis(3-mercaptobutyrate) (commercially available product: "KarenzMT PE1" manufactured by Showa Denko K.K.); tetrafunctional thiols such as pentaerythritol tetrakis(3-mercaptobutyrate) (commercially available product: "KarenzMT PE1" manufactured by Showa Denko K.K.); and hexafunctional thiols such as dipentaerythritol hexakis(3-mercaptobutyrate).

[0020] From the viewpoint of further improving the reactivity of the composition (X) and the glass transition temperature and strength of the cured product, the secondary thiol (B1) preferably contains a polyfunctional thiol having 2 to 6 functional groups, and more preferably contains a tetrafunctional to hexafunctional thiol.

[0021] The (B) curing agent may contain a (B2) primary thiol in addition to the (B1) secondary thiol. The "primary thiol" refers to a compound having at least one primary sulfanyl group. When the (B) curing agent contains the (B2) primary thiol, the curability of the composition (X) can be further improved. The (B) curing agent may contain a (B3) tertiary thiol in addition to the (B1) secondary thiol. The "tertiary thiol" refers to a compound having only a tertiary sulfanyl group as a sulfanyl group. The "tertiary sulfanyl group" refers to a sulfanyl group bonded to a tertiary carbon atom.

[0022] (B2) Primary thiols include, for example, monofunctional thiols such as 1-pentanethiol, 1-decanethiol, 1-dodecanethiol (commercially available product: "Thiocalcol 20" manufactured by Kao Corporation), 1-hexadecanethiol, 1-octadecanethiol, 2-ethylhexyl-3-mercaptopropionate (commercially available product: "EHMP" manufactured by SC Organic Chemicals Co., Ltd.), n-octyl-3-mercaptopropionate (commercially available product: "NOMP" manufactured by SC Organic Chemicals Co., Ltd.), and stearyl-3-mercaptopropionate (commercially available product: "STMP" manufactured by SC Organic Chemicals Co., Ltd.); tetraethylene glycol bis(3-mercaptopropionate) (commercially available product: "DPMP" manufactured by SC Organic Chemicals Co., Ltd.). and 1,6-hexanediol bis(thioglycolate); trifunctional thiols such as trimethylolpropane tris(3-mercaptopropionate) (commercially available product: "TMMP" manufactured by SC Organic Chemical Industry Co., Ltd.) and tris-[(3-mercaptopropionyloxy)ethyl]-isocyanurate (commercially available product: "TEMPIC" manufactured by SC Organic Chemical Industry Co., Ltd.); tetrafunctional thiols such as pentaerythritol tetrakis(3-mercaptopropionate) (commercially available product: "PEMP" manufactured by SC Organic Chemical Industry Co., Ltd.); and hexafunctional thiols such as dipentaerythritol hexakis(3-mercaptopropionate) (commercially available product: "DPMP" manufactured by SC Organic Chemical Industry Co., Ltd.).

[0023] When the (B) curing agent contains a (B2) primary thiol, from the viewpoint of further improving the reactivity of the composition (X) and the glass transition temperature and strength of the cured product, the (B2) primary thiol preferably contains a polyfunctional thiol having 2 to 6 functional groups, and more preferably contains a tetrafunctional to hexafunctional thiol.

[0024] (B3) Examples of tertiary thiols include t-butyl thiol and 3-mercapto-3-methylbutanol.

[0025] The (B) curing agent may contain (B4) other curing agents other than (B1) secondary thiol, (B2) primary thiol, and (B3) tertiary thiol. (B4) Other curing agents include, for example, phenolic curing agents such as phenol novolac resins, acid anhydrides, amines, imidazoles or salts thereof, hydrazides, polymercaptans, Lewis acid-amine complexes, and the like.

[0026] The ratio of the (B1) secondary thiol in the (B) curing agent is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The ratio of the (B1) secondary thiol may be 100% by mass. In these cases, the storage stability of the composition (X) can be further improved.

[0027] The ratio of the (B) curing agent to the entire composition (X) is preferably 10% by mass or more and 60% by mass or less, more preferably 20% by mass or more and 50% by mass or less, and even more preferably 30% by mass or more and 40% by mass or less, in which case the curability of the composition (X) can be further improved.

[0028] It is important that the molar ratio of sulfanyl groups of the (B) curing agent to epoxy groups of the (A) epoxy resin (moles of sulfanyl groups / moles of epoxy groups) is 0.8 or more. This molar ratio is preferably 0.85 or more, more preferably 0.9 or more. The upper limit of this molar ratio is, for example, 1.2 or less, preferably 1.1 or less, more preferably 1.05 or less, and even more preferably 1.0 or less. In these cases, the curability and storage stability of the composition (X) can be further improved. The sulfanyl groups of the (B) curing agent refer to the sum of the secondary sulfanyl groups, primary sulfanyl groups, and tertiary sulfanyl groups of the (B) curing agent.

[0029] [(C) Latent hardener] A "latent curing agent" refers to a curing agent that does not exhibit curing properties in an epoxy resin under room temperature conditions, but exhibits curing properties when subjected to external stimuli such as heat or pressure. The (C) latent curing agent contained in composition (X) exhibits curing properties when heated to a specified temperature or higher.

[0030] It is important that composition (X) contains two or more latent curing agents as latent curing agent (C), and that the exothermic peak top temperatures of these two or more latent curing agents differ from each other by 10° C. or more. When the latent curing agent (C) contains three or more latent curing agents, "the exothermic peak top temperatures differ from each other by 10° C. or more" means that the difference in the exothermic peak top temperatures of any two of the three or more latent curing agents is 10° C. or more.

[0031] When the temperature of a latent curing agent is raised by heating or the like, when a certain temperature is reached, a curing agent and / or catalyst is generated from the latent curing agent, and the action of this curing agent and / or catalyst causes a reaction with the epoxy resin and secondary thiol, which generates heat. This heat generation can be observed by differential scanning calorimetry (DSC), and the temperature at which the peak top of the obtained exothermic curve gives the maximum amount of heat generation in the exothermic peak is called the "exothermic peak top temperature." In addition, the temperature corresponding to the intersection of the tangent at the inflection point with the maximum gradient and the baseline in the rise of the exothermic peak of the exothermic curve is called the "onset temperature."

[0032] The temperature at which the DSC exothermic peak occurs varies depending not only on the type of latent curing agent, but also on the ratio of the latent curing agent in the DSC measurement sample, the types and ratios of the epoxy resin and curing agent, and the heating rate in the DSC measurement. In this embodiment, the exothermic peak top temperature and onset temperature are values ​​determined by the measurement method and measurement conditions described in the Examples below.

[0033] The difference in exothermic peak top temperature between two or more latent curing agents is preferably 13°C or more, more preferably 15°C or more, even more preferably 18°C ​​or more, particularly preferably 30°C or more, even more particularly preferably 50°C or more, and most preferably 80°C or more. In this case, the curability and storage stability of the composition (X) can be further improved. The upper limit of the difference in exothermic peak top is not particularly limited, but is, for example, 100°C or less.

[0034] The difference in onset temperature between the two or more latent curing agents is preferably 10° C. or more, more preferably 13° C. or more, further preferably 20° C. or more, and particularly preferably 70° C. or more. In this case, the curability and storage stability of the composition (X) can be further improved.

[0035] Among the two or more latent curing agents in the (C) latent curing agent, the one with the lowest exothermic peak top temperature is designated as the (CA) latent curing agent, and the one with the second lowest exothermic peak top temperature is designated as the (CB) latent curing agent. In this case, the exothermic peak top temperature of the (CA) latent curing agent is preferably 60°C or higher and 90°C or lower, more preferably 65°C or higher and 80°C or lower, and even more preferably 70°C or higher and 75°C or lower. The onset temperature of the (CA) latent curing agent is preferably 45°C or higher and 75°C or lower, more preferably 50°C or higher and 65°C or lower, and even more preferably 55°C or higher and 60°C or lower. The exothermic peak top temperature of the (CB) latent curing agent is preferably 75°C or higher and 200°C or lower, more preferably 80°C or higher and 180°C or lower, even more preferably 85°C or higher and 175°C or lower, and particularly preferably 120°C or higher and 170°C or lower. The onset temperature of the latent curing agent (CB) is preferably 60°C or more and 160°C or less, more preferably 65°C or more and 155°C or less, even more preferably 70°C or more and 150°C or less, and particularly preferably 100°C or more and 145°C or less.

[0036] Examples of the (C) latent curing agent include (C1) a microcapsule type latent curing agent, (C2) a solid dispersion type latent curing agent, (C3) a reactive group block type latent curing agent, (C4) a dissolution type latent curing agent, and (C5) an ion type latent curing agent.

[0037] (C1) A microcapsule-type latent curing agent usually has a shell portion that constitutes the outer shell and a core portion that is enveloped by the shell portion, and is a latent curing agent in which the core portion contains a curing agent such as an amine-based curing agent. When the core portion is heated to a predetermined temperature or higher by heating or the like, the shell portion is destroyed and the curing agent is released, thereby accelerating the curing reaction.

[0038] Commercially available microcapsule-type latent curing agents (C1) include, for example, Novacure HX-3722, HX-3748, HX-3088, HX-3741, HX-3742, HX-5945HP, and HX-9322HP manufactured by Asahi Kasei Corporation.

[0039] The (C2) solid-dispersed latent curing agent is usually a solid that is insoluble in epoxy resins at room temperature (25°C), and is a latent curing agent that can accelerate the curing reaction by being heated to a predetermined temperature or higher and then melted or solubilized. Examples of the (C2) solid-dispersed latent curing agent include ureas, amine adducts, organic acid hydrazides, imidazole derivatives, dicyandiamide and its derivatives, diaminomaleonitrile and its derivatives, melamine and its derivatives, polyamides, and BF3 complexes.

[0040] Examples of commercially available solid dispersion type latent curing agents (C2) include Fujicure FXR-1020, FXR-1030, FXR-1032, FXR-1081, FXR-1121, and FXR-1131 manufactured by T&K TOKA Corporation; Amicure PN-23, PN-H, PN-F, VDH, UDH, AH-123, and AH-154 manufactured by Ajinomoto Fine-Techno Co., Ltd.; and U-CAT3512T and U-CAT3513N manufactured by San-Apro Ltd.

[0041] (C3) The reactive group block type latent curing agent is a latent curing agent in which, when heated to a certain temperature or higher by heating or the like, the compound blocking the reactive group is eliminated to generate a curing agent having a reactive group, thereby accelerating the curing reaction.

[0042] Examples of the (C3) reactive group blocked latent curing agent include a reaction product between an amine compound and an epoxy compound (amine-epoxy adduct system), and a reaction product between an amine compound and an isocyanate compound or a urea compound (urea adduct system).

[0043] Commercially available reactive group-blocked latent curing agents (C3) include, for example, Fujicure 7000, 7001, and 7002 manufactured by T&K Toka Corporation.

[0044] (C4) The elution type latent curing agent is a latent curing agent in which a curing agent such as an amine-based curing agent is encapsulated in a porous material, and when heated to a predetermined temperature or higher, the curing agent is released, thereby accelerating the curing reaction.

[0045] (C4) Examples of the elution type latent hardener include molecular sieve encapsulated hardeners.

[0046] (C5) The ionic latent curing agent contains an ionic compound of an ammonium cation and an organic acid anion, and is a latent curing agent that accelerates the curing reaction by generating a curing agent such as an amine-based curing agent at a predetermined temperature or higher by heating or the like.

[0047] Commercially available ionic latent curing agents (C5) include, for example, U-CAT SA1 and U-CAT1102 manufactured by San-Apro Co., Ltd.

[0048] The two or more latent curing agents in the latent curing agent (C) preferably include two or more latent curing agents selected from the group consisting of a microcapsule-type latent curing agent (C1), a solid dispersion-type latent curing agent (C2), and a reactive group block-type latent curing agent (C3), and more preferably include two latent curing agents selected from the group consisting of (C1) to (C3). By using different types of these latent curing agents in combination as the multiple latent curing agents in the latent curing agent (C), the composition (X) can further improve the curability while maintaining the storage stability.

[0049] When the (C) latent curing agent contains two latent curing agents, the two latent curing agents are preferably a combination of a (C1) microcapsule-type latent curing agent and a (C2) solid dispersion-type latent curing agent, a combination of a (C1) microcapsule-type latent curing agent and a (C3) reactive group block-type latent curing agent, or a combination of two latent curing agents among the (C1) microcapsule-type latent curing agent. By adopting these combinations as the two latent curing agents in the (C) latent curing agent, the composition (X) can further improve the curing property while maintaining the storage stability.

[0050] The proportion of the (CA) latent curing agent is preferably from 10 to 60 parts by mass, and more preferably from 30 to 50 parts by mass, relative to 100 parts by mass of the (A) epoxy resin. The proportion of the (CB) latent curing agent is preferably from 5 to 50 parts by mass, and more preferably from 10 to 30 parts by mass, relative to 100 parts by mass of the (A) epoxy resin.

[0051] The proportion of the latent curing agent (CA) is preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 30% by mass or less, based on the entire composition (X). The proportion of the latent curing agent (CB) is preferably 1% by mass or more and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less, based on the entire composition (X).

[0052] By setting the ratio of the latent curing agent (CA) and the latent curing agent (CB) within the above range, the curability and storage stability of the composition (X) can be further improved.

[0053] The total amount of the (C) latent curing agent is preferably from 50 to 200 parts by mass, and more preferably from 70 to 100 parts by mass, relative to 100 parts by mass of the (A) epoxy resin. The total amount of the (C) latent curing agent is preferably from 10 to 60% by mass, and more preferably from 20 to 50% by mass, relative to the entire composition (X).

[0054] [(D) Stabilizer] The stabilizer (D) is a compound capable of reacting with a basic substance such as an amine. Even if the latent curing agent (C) contains a basic substance such as an amine generated by decomposition before heat curing, the composition (X) can maintain excellent storage stability by including the stabilizer (D).

[0055] Examples of the (D) stabilizer include borate esters, etc. Examples of the borate esters include alkyl borate esters such as trimethyl borate, triethyl borate, tributyl borate, tri-n-octyl borate, tri(triethylene glycol methyl ether) borate ester, tricyclohexyl borate, and trimenthyl borate, aromatic borate esters such as tri-o-cresyl borate, tri-m-cresyl borate, tri-p-cresyl borate, and triphenyl borate, tri(1,3-butanediol) biborate, tri(2-methyl-2,4-pentanediol) biborate, and trioctylene glycol diborate.

[0056] When the composition (X) contains the stabilizer (D), the proportion of the stabilizer (D) is preferably 0.1 parts by mass or more and 100 parts by mass or less, and more preferably 1 part by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the total amount of the latent curing agent (C). The proportion of the stabilizer (D) is preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.1% by mass or more and 3% by mass or less, relative to the entire composition (X).

[0057] [(E) Other ingredients] Examples of the (E) other components include inorganic fillers, thixotropy agents, coupling agents, release agents, flame retardants, flame retardant assistants, ion trapping agents, pigments such as carbon black, colorants, stress reducing agents, adhesion imparting agents, silicone flexibilizers, etc. When the composition (X) contains the (E) other components, the proportion of the (E) other components is, for example, 0.001% by mass or more and 20% by mass or less with respect to the entire composition (X).

[0058] Composition (X) can achieve both high curability and excellent storage stability, and therefore can be suitably used, for example, as an adhesive for use in assembling modules such as camera modules in electronic devices, or for bonding to housings.

[0059] The curing rate of the composition (X) when heated at 60°C for 30 minutes is preferably 90% or more, more preferably 92% or more, even more preferably 95% or more, and particularly preferably 97% or more. This curing rate may be 100%. This curing rate is a value determined by the measurement method described in the examples below.

[0060] <Cured product> The cured product according to this embodiment is obtained by curing the above-mentioned composition (X). The cured product according to this embodiment can be obtained, for example, by heating the composition (X). The heating conditions are appropriately selected depending on the type of the latent curing agent (C) contained in the composition (X). The heating temperature is, for example, 50°C or more and 200°C or less, preferably 55°C or more and 80°C or less, and more preferably 60°C or more and 65°C or less. The heating time is, for example, 10 seconds or more and 5 hours or less, preferably 10 minutes or more and 1 hour or less, and more preferably 20 minutes or more and 40 minutes or less. According to the composition (X), a cured product can be obtained by heating at a relatively low temperature for a short time, for example, 60°C for 30 minutes.

[0061] The cured product of the present embodiment can be suitably used, for example, as a bonding layer that is placed between components in the manufacture of equipment to bond the components together, and can also be suitably used as a sealant for sealing electronic components.

[0062] <zygote> The bonded body according to this embodiment (hereinafter also referred to as bonded body (Y)) includes a first member (hereinafter also referred to as member (1)), a second member (hereinafter also referred to as member (2)), and a bonding layer (hereinafter also referred to as bonding layer (h)). The bonding layer (h) is interposed between the member (1) and the member (2) to bond the member (1) and the member (2). The bonding layer (h) contains a cured product of the composition (X).

[0063] The bonded body (Y) is produced using the composition (X) that has both high curability and excellent storage stability, and therefore can be produced simply and reliably, with an increased yield.

[0064] The bonded body (Y) is composed of a member (1), a member (2), and a bonding layer (h) interposed between them and produced by curing a composition (X). The number of members to be bonded is not limited to 2, and may be 3 or more. The number of members included in the bonded body (Y) is not limited to 2, and may be 3 or more.

[0065] The member (1) and the member (2) are not particularly limited, and examples thereof include substrates in electronic devices, electronic devices, etc. The bonded body (Y) is not particularly limited as long as it is produced by bonding a plurality of members with the composition (X), and examples thereof include various electronic devices, electric devices, etc.

[0066] The above-mentioned bonded body (Y) can be produced, for example, by interposing the composition (X) between the member (1) and the member (2) and heating the composition (X) to form a bonding layer (h).

[0067] In producing the bonded body (Y), first, the composition (X) is interposed between the member (1) and the member (2). The method for interposing the composition (X) is not particularly limited, but examples thereof include a method in which the members are brought into close contact with each other and then the composition (X) is applied to the contacted portions, and a method in which the composition (X) is applied to each member and then the applied portions are brought into close contact with each other.

[0068] Next, the composition (X) interposed between the member (1) and the member (2) is heated. This causes the composition (X) to be thermally cured, and the bonding layer (h) is produced. By producing the bonding layer (h), the members (1) and (2) of the bonded body (Y) are more firmly bonded to each other. The heating conditions are appropriately selected depending on the type of the latent curing agent (C) contained in the composition (X). The heating temperature is, for example, 50°C or more and 200°C or less, preferably 55°C or more and 80°C or less, and more preferably 60°C or more and 65°C or less. The heating time is, for example, 10 seconds or more and 5 hours or less, preferably 10 minutes or more and 1 hour or less, and more preferably 20 minutes or more and 40 minutes or less. In this manner, the bonded body (Y) is produced. EXAMPLES

[0069] Hereinafter, the present disclosure will be specifically described with reference to examples, but the present disclosure is not limited to only these examples.

[0070] <Preparation of Thermosetting Adhesive Composition> A thermosetting adhesive composition was prepared by mixing the raw materials shown in Table 2. Details of the raw materials shown in Table 2 are as follows. -(A) Epoxy resin (A1) Liquid bisphenol A type epoxy resin: “YD8125” manufactured by Nippon Steel Chemical & Material Co., Ltd. -(B) Hardener (B1) Secondary thiol: Karenz MT PE1 manufactured by Showa Denko Co., Ltd. Pentaerythritol tetrakis(3-mercaptobutyrate). (B2) Primary thiol: "PEMP" manufactured by SC Organic Chemicals. Pentaerythritol tetrakis(3-mercaptopropionate). -(C) Latent hardener (C1-1) Microcapsule type latent hardener: “Novacure HXA5945HP” manufactured by Asahi Kasei Corporation. (C1-2) Microcapsule type latent hardener: “Novacure HXA9322HP” manufactured by Asahi Kasei Corporation. (C1-1) and (C1-2) are masterbatches having a core / shell mass ratio of about 1 / 2, and contain an amine derivative, an imidazole derivative, or a mixture thereof as a core, and the liquid epoxy resin is a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or a mixture thereof. (C2-1) Solid dispersion type latent hardener: “Fujicure FXR-1081” manufactured by T&K TOKA. (C3-1) Reactive group block type latent hardener: “Fujicure 7002” manufactured by T&K TOKA. -(D) Stabilizer (D1) Tributyl borate, manufactured by Tokyo Chemical Industry Co., Ltd.

[0071] [Measurement of exothermic peak temperature of latent hardener] The types and amounts of each component shown in Table 1 below were mixed to prepare DSC measurement samples (S-1) to (S-4). In these DSC measurement samples, the types and ratios of the epoxy resin and curing agent contained, and the ratio of the curing agent component contained in the latent curing agent were all the same. In these DSC measurement samples, a liquid bisphenol A type epoxy resin ("YD8125" manufactured by Nippon Steel Chemical & Material Co., Ltd.) was used as the epoxy resin, and its ratio to the entire sample was 40 mass%. A secondary thiol ("Karens MT PE1" manufactured by Showa Denko KK) was used as the curing agent, and its ratio to the entire sample was 42 mass%. The molar ratio of the sulfanyl group of the curing agent to the epoxy group of the epoxy resin (moles of sulfanyl group / moles of epoxy group) was 1.0. The ratio of the curing agent component contained in the latent curing agent was 6.1 mass parts per 100 mass parts of epoxy resin.

[0072] The prepared DSC measurement sample was measured using a differential scanning calorimeter (DSC) (Diamond DSC, manufactured by PerkinElmer Japan) under a nitrogen atmosphere at a temperature rise rate of 10°C / min to obtain a DSC chart. From the obtained DSC chart, the onset temperature (°C) of the exothermic peak and the top temperature (°C) of the exothermic peak were determined. The measured values ​​of the onset temperature and the peak top temperature are shown in Table 1 below.

[0073] [Table 1]

[0074] <Evaluation> [Curing rate] The thermosetting adhesive composition was cured in a dryer at 60° C. for 30 minutes. About 2 mg of each of the composition before and after curing was placed in a measurement pan, and the heat generation amount was measured using a differential scanning calorimeter (DSC) measuring device ("Diamond DSC" manufactured by PerkinElmer Japan Co., Ltd.), and the cure rate was calculated according to the following formula (1). Curing rate (%)=(Ho-Ht)×100 / Ho ···(1) (In formula (1), Ho is the amount of heat generated by the composition before curing. Ht is the amount of heat generated by the composition after curing.) A cure rate of 90% or more can be evaluated as "good", and a cure rate of less than 90% can be evaluated as "poor".

[0075] [Storage stability] (45℃3 hours) Approximately 1 g of the thermosetting adhesive composition was placed in a sample bottle and left for 3 hours in a water bath at 45° C. After 3 hours, the fluidity of the composition was observed, and the storage stability at 45° C. for 3 hours was evaluated according to the following evaluation criteria. 〇: Did not solidify ×: Solidified

[0076] (25℃72 hours) 80 g of the thermosetting adhesive composition was placed in a 100 cc plastic sample bottle and left for 72 hours in a thermostatic chamber at 25° C. The viscosity of the composition after 72 hours was measured with an E-type viscometer, and the storage stability at 25° C. for 72 hours was evaluated based on the increase in viscosity due to being left for 72 hours (the viscosity value after being left when the viscosity before being left is taken as 100%) according to the following evaluation criteria. ○: Viscosity increase was within 120% ×: Viscosity increase was more than 120%

[0077] [Adhesive strength] (Adhesive strength to copper) The composition was applied onto an adherend made of copper plate (manufactured by Hirai Seimitsu Kogyo Co., Ltd., material: KFC-1 / 2H, unplated) to produce a coating film 5 mm in diameter and 0.5 mm thick. This coating film was heated at 60°C for 30 minutes to heat cure and form a cured product. The shear adhesive strength of the cured product to the adherend was measured using a shear tester. Adhesive strength to copper can be evaluated as "good" if it is 8.5 MPa or more, and "poor" if it is less than 8.5 MPa.

[0078] (Adhesive strength to LCP) The composition was applied onto an adherend made of liquid crystal polymer ("E463i" manufactured by Polyplastics Co., Ltd.) to produce a coating film 5 mm in diameter and 0.5 mm thick. This coating film was thermally cured by heating at 60°C for 30 minutes to form a cured product. The shear adhesive strength of the cured product to the adherend was measured using a shear tester. Adhesive strength to LCP is evaluated as "good" when it is 9.4 MPa or more, and "poor" when it is less than 9.4 MPa.

[0079] Table 2 below shows the cure rate (%), the evaluation results of storage stability (45°C for 3 hours), the viscosity increase (%) and evaluation results (25°C for 72 hours), and the adhesive strength (Cu, LCP) value (MPa).

[0080] [Table 2]

[0081] The results in Table 2 show that the thermosetting adhesive compositions of Examples 1 to 6 had both high curability and excellent storage stability, and also had high adhesive strength. On the other hand, the thermosetting adhesive compositions of Comparative Examples 1 to 6 had insufficient curability, low adhesive strength, and some of them had insufficient storage stability.

Claims

1. A thermosetting adhesive composition comprising (A) an epoxy resin, (B) a curing agent, and (C) a latent curing agent, The (B) curing agent contains (B1) a secondary thiol, The latent curing agent (C) includes two or more latent curing agents having exothermic peak top temperatures that differ from each other by 10° C. or more in a reaction with an epoxy resin and a secondary thiol as determined by differential scanning calorimetry at a heating rate of 10° C. / min, Among the two or more latent curing agents in the (C) latent curing agent, the latent curing agent (CA) having the lowest exothermic peak top temperature has an onset temperature in a reaction with an epoxy resin and a secondary thiol, which is determined by differential scanning calorimetry at a heating rate of 10° C. / min, of 45° C. or more and 75° C. or less; the ratio of the latent curing agent (CA) is 10 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the epoxy resin (A), a molar ratio of sulfanyl groups in the (B) curing agent to epoxy groups in the (A) epoxy resin is 0.8 or more; The thermosetting adhesive composition has a cure rate of 90% or more and 100% or less when heated at 60° C. for 30 minutes.

2. 2. The thermosetting adhesive composition according to claim 1, wherein the two or more latent curing agents comprise two or more types of latent curing agents selected from the group consisting of (C1) a microcapsule-type latent curing agent, (C2) a solid dispersion-type latent curing agent, and (C3) a reactive group block-type latent curing agent.

3. The thermosetting adhesive composition according to claim 1 or 2, further comprising (D) a stabilizer.

4. A cured product of the thermosetting adhesive composition according to any one of claims 1 to 3.

5. a first member, a second member, and a bonding layer interposed between the first member and the second member to bond the first member and the second member; A bonded structure, wherein the bonding layer comprises a cured product of the thermosetting adhesive composition according to claim 1 .

Images