Epoxy resin composition, cured product, and bond

Abstract

The present invention provides an epoxy resin composition that, when used as an adhesive to bond components together, can suppress misalignment between components and inhibit thermal degradation of the components. [Solution] An epoxy resin composition comprising an epoxy resin, a polythiol, a photobase generator, and a sensitizer, wherein the epoxy resin composition comprises one or more types of epoxy resins, at least one of which has two or more epoxy groups in one molecule, and the polythiol contains an ester bond and has five or more mercapto groups, or the polythiol contains a nitrogen atom and the mercapto group is bonded to the nitrogen atom via an alkylene group.

Description

Technical Field

[0001] The present invention relates to an epoxy resin composition, a cured product, and a bonded body.

Background Art

[0002] Generally, an electronic device typified by an inkjet head is formed by adhering a plurality of members constituting it with an adhesive. The adhesive used for an inkjet head needs to be excellent in ink resistance, adhesiveness, etc. Therefore, an epoxy resin composition is used as the adhesive. The epoxy resin composition contains an epoxy resin, a curing agent, etc., and polymerizes and cures by heat or light.

[0003] When adhering the members of an inkjet head using an epoxy resin composition as an adhesive, there is a method of temporarily fixing in the first stage to suppress misalignment and performing final curing in the second stage. And the temporary fixing in the first stage may be performed by curing the adhesive by light and heat. Further, the final curing in the second stage may be performed by further curing the adhesive by heat. Thus, an epoxy resin composition containing an epoxy resin, a photo-base generator, a specific polythiol, etc. has been proposed as an adhesive for adhering members in two stages (for example, refer to Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Furthermore, when bonding the components of the inkjet head together, it is necessary to prevent misalignment, where the components shift out of place. In addition, when bonding the components together, it is necessary to prevent the components from degrading due to the heat generated during curing.

[0006] The epoxy resin composition described in Patent Document 1 above aims to achieve effects such as enabling rapid temporary fixing in the first stage, but further improvements were needed in terms of suppressing misalignment and deterioration of the components.

[0007] The present invention has been made in view of the above-mentioned problems and circumstances. The problem to be solved by the present invention is to provide an epoxy resin composition that, when used as an adhesive to bond components of an inkjet head together, can suppress misalignment between components and suppress thermal degradation of the components. [Means for solving the problem]

[0008] To solve the above problems, the inventors focused on the structure of epoxy resins and curing agents and conducted thorough research. As a result, they discovered that by using a bifunctional or more epoxy resin and a polythiol with a specific structure as a curing agent, displacement and deterioration of the components can be suppressed, leading to the present invention. In other words, the above problems according to the present invention are solved by the following means.

[0009] 1. An epoxy resin composition comprising epoxy resin, polythiol, photobase generator and sensitizer, The epoxy resin comprises one or more types, At least one of the epoxy resins has two or more epoxy groups in one molecule, An epoxy resin composition characterized in that the polythiol contains an ester bond and has five or more mercapto groups, or the polythiol contains a nitrogen atom and the mercapto groups are bonded to the nitrogen atom via alkylene groups.

[0010] 2. The epoxy resin composition according to claim 1, characterized in that the polythiol, in which the mercapto group is bonded to the nitrogen atom via an alkylene group, has a glycoluryl skeleton.

[0011] 3. The epoxy resin composition according to paragraph 1, characterized in that at least one of the epoxy resins has three or more epoxy groups in its molecule.

[0012] 4. The epoxy resin composition according to paragraph 1, characterized in that the epoxy resin is glycidylamine-based.

[0013] 5. The photobase generating agent comprises one or more types, The epoxy resin composition according to claim 1, characterized in that at least one of the photobase generators has a borate salt.

[0014] 6. The epoxy resin composition according to paragraph 1, characterized in that the amount of the photobase generator is in a ratio of 3 to 10 equivalents per 100 equivalents of epoxy resin.

[0015] 7. Containing one or more of the above-mentioned sensitizers, The epoxy resin composition according to claim 1, wherein at least one of the sensitizers is 2-isopropylthioxanthone or 2-ethylanthraquinone.

[0016] 8. The epoxy resin composition according to item 1, comprising a silane coupling agent.

[0017] 9. The epoxy resin composition according to item 8, wherein the silane coupling agent is a compound having an epoxy group or an amine group, or an isocyanate.

[0018] 10. A cured product which is a reaction product of an epoxy resin composition described in any one of paragraphs 1 to 9.

[0019] 11. A cured product according to item 10, wherein the nitrogen content is 7.5 to 11% by mass and the sulfur content is 10 to 17% by mass.

[0020] A bonded body comprising the cured product according to claim 10.

Effects of the Invention

[0021] The epoxy resin composition of the present invention is such that the polythiol contains an ester bond and has five or more mercapto groups, or the polythiol contains a nitrogen atom and the mercapto group is bonded to the nitrogen atom via an alkylene group. Therefore, the epoxy resin composition of the present invention has a very high reaction rate when cured. As a result, when used as an adhesive for bonding members of an inkjet head, displacement of the members can be suppressed. Further, since the epoxy resin composition of the present invention has a high reaction rate, it can be cured at a low temperature. Thus, when used as an adhesive for bonding members of an inkjet head, deterioration of the members due to heat can be suppressed. That is, when bonding members of an inkjet head, it is preferable to use an adhesive containing the epoxy resin composition of the present invention for bonding.

[0022] Although the mechanism of expression or the mechanism of action of the effects of the present invention has not been clearly understood, it is speculated as follows.

[0023] When the polythiol contains an ester bond and has five or more mercapto groups, there are appropriately many mercapto groups which are reaction points. Therefore, it is presumed that the reaction rate becomes high and displacement suppression and low-temperature reaction become possible.

[0024] Also, when the polythiol contains a nitrogen atom and the mercapto group is bonded to the nitrogen atom via an alkylene group, it is presumed that this special structure of the polythiol contributes to an improvement in the reaction rate.

Brief Description of the Drawings

[0025] [Figure 1] It is a schematic diagram schematically showing an embodiment of the bonded body of the present invention. [Figure 2]This is a schematic diagram illustrating another embodiment of the joint of the present invention. [Modes for carrying out the invention]

[0026] One embodiment of the epoxy resin composition of the present invention is an epoxy resin composition comprising an epoxy resin, a polythiol, a photobase generator, and a sensitizer. The epoxy resin composition of this embodiment comprises one or more types of the epoxy resin, and at least one of the epoxy resins has two or more epoxy groups in one molecule. The epoxy resin composition of this embodiment comprises either the following first polythiol or the following second polythiol. The first polythiol is a polythiol that contains an ester bond and has five or more mercapto groups. The second polythiol is a polythiol that contains a nitrogen atom and in which the mercapto group is bonded to the nitrogen atom via an alkylene group. In this specification, when we refer to "the first polythiol or the second polythiol," we mean the first polythiol, the second polythiol, or "both the first polythiol and the second polythiol." In the case of "both the first polythiol and the second polythiol," the ratio of these two is not particularly limited. Furthermore, in the epoxy resin composition of this embodiment, the alkylene group is linear, and is a group structure in which one hydrogen atom is removed from each carbon atom located at both ends of the linear alkane and bonded to other atoms. A mercapto group is bonded to one of the carbon atoms at each end of the linear alkylene group, and a nitrogen atom is bonded to the other end. The above features are technical features common to or corresponding to each of the embodiments described below.

[0027] It is preferable that the polythiol, in which the mercapto group is bonded to the nitrogen atom via an alkylene group, has a glycoluryl skeleton. In this embodiment, the epoxy resin composition has a faster reaction rate during curing because the polythiol has a glycoluryl skeleton, thereby suppressing displacement of the component. Furthermore, as described above, a faster reaction rate during curing makes it possible to lower the curing temperature, thereby suppressing thermal degradation of the component.

[0028] Preferably, at least one of the above epoxy resins has three or more epoxy groups in its molecule. Having three or more epoxy groups in the molecule increases the number of reaction sites when the epoxy resin composition is polymerized and cured, thus increasing the crosslinking density and improving ink resistance. In this specification, polymerizing and curing the epoxy resin composition with light is also referred to as curing reaction.

[0029] It is preferable that the epoxy resin described above is glycidylamine-based. Using a glycidylamine-based epoxy resin allows for a faster reaction rate during the curing reaction, and further improves ink resistance by increasing the crosslinking density.

[0030] The epoxy resin composition of this embodiment preferably contains one or more of the above-mentioned photobase generators, and at least one of the photobase generators is a borate salt. By having at least one of the photobase generators be a borate salt, the reaction can be advanced by UV curing.

[0031] The amount of the above-mentioned photobase generator is preferably 3 to 10 equivalents per 100 equivalents of epoxy resin. In other words, the amount of the above-mentioned photobase generator is preferably 3 / 100 to 10 / 100 gram equivalents per 1 gram equivalent of epoxy resin.

[0032] The epoxy resin composition of this embodiment contains one or more of the above-mentioned sensitizers. Preferably, at least one of the sensitizers is 2-isopropylthioxanthone or 2-ethylanthraquinone. This allows the photobase generator to exhibit photosensitivity in the long-wavelength region (around 365 nm) and accelerate the reaction.

[0033] The epoxy resin composition of this embodiment preferably contains a silane coupling agent. This improves adhesion.

[0034] The silane coupling agent is preferably a compound having an epoxy group or an amine group, or an isocyanate. This improves adhesion and extends the pot life.

[0035] One embodiment of the cured product of the present invention is a reaction product of the epoxy resin composition described above. Since the cured product of this embodiment is a reaction product of the epoxy resin composition of this embodiment, degradation during the reaction is suppressed, resulting in a cured product with a low degree of degradation. Furthermore, degradation due to solvents and the like is suppressed in the cured product of this embodiment.

[0036] The cured product of this embodiment preferably has a nitrogen content of 7.5 to 11% by mass. Furthermore, the cured product of this embodiment preferably has a sulfur content of 10 to 17% by mass. The cured product of this embodiment has a nitrogen content of 7.5 to 11% by mass. Since the cured product of this embodiment has a sulfur content of 10 to 17% by mass, it can be seen that the polythiol content in the epoxy resin composition before curing is the preferred content in the epoxy resin composition of this embodiment.

[0037] One embodiment of the joint of the present invention includes the cured product of this embodiment. Because the joint of this embodiment includes the cured product of this embodiment, misalignment of the members constituting the joint is suppressed. Furthermore, because the cured product of this embodiment is a cured product with a low degree of deterioration, the joint of this embodiment also has suppressed deterioration and is a cured product with a low degree of deterioration.

[0038] The present invention, its components, and embodiments and models for carrying out the present invention will be described in detail below. In this specification, the "~" symbol indicating a numerical range is used to mean that the numbers before and after it are included as the lower and upper limits.

[0039] 1. Epoxy resin composition <Epoxy resin> The epoxy resin composition of this embodiment contains one or more epoxy resins. The epoxy resins may be one or more types. At least one of the epoxy resins has two or more epoxy groups per molecule. Examples of epoxy resins having two epoxy groups per molecule include bisphenol F type epoxy resins and bisphenol A type epoxy resins.

[0040] Preferably, at least one of the above epoxy resins has three or more epoxy groups in its molecule. Examples of epoxy resins having three epoxy groups in one molecule include triglycidyl-p-aminophenol, triglycidyl isocyanurate, triglycidylurazole, triglycidylaminocresol, and lycerol triglycidyl ether. Examples of epoxy resins having four epoxy groups in one molecule include tetraglycidyldiaminodiphenylmethane and tetraglycidyl-1,3-diaminomethylcyclohexane. Furthermore, examples of epoxy resins having three or more epoxy groups in their molecule include phenol novolac type epoxy resins and cresol novolac type epoxy resins. Among the above epoxy resins, it is preferable that the epoxy resin is glycidylamine-based. In particular, triglycidyl-p-aminophenol is a preferred embodiment. Because at least one of the epoxy resins has three or more epoxy groups in its molecule, when the epoxy resin composition is cured by polymerization, the number of reaction sites increases, resulting in a higher crosslinking density and improved ink resistance.

[0041] <Polythiol> The epoxy resin composition of this embodiment contains a polythiol as a curing agent. The polythiol is a polythiol containing an ester bond and having five or more mercapto groups, or a polythiol containing a nitrogen atom and in which the mercapto groups are bonded to the nitrogen atom via alkylene groups. A polythiol containing an ester bond and having five or more mercapto groups may be referred to as the first polythiol as described above. A polythiol containing a nitrogen atom and in which the mercapto groups are bonded to the nitrogen atom via alkylene groups may be referred to as the second polythiol as described above.

[0042] In the epoxy resin composition of this embodiment, the alkylene group is a structural unit represented by the following formula (1).

[0043] [ka]

[0044] In equation (1) above, n is an integer between 2 and 3.

[0045] As described above, the epoxy resin composition of this embodiment contains either a first polythiol or a second polythiol. As a result, the epoxy resin composition of this embodiment has a very fast reaction rate when curing. Therefore, when used as an adhesive to bond components of an inkjet head, misalignment of the components can be suppressed. Furthermore, because the epoxy resin of the present invention has a fast reaction rate, it can cure at low temperatures. Therefore, when used as an adhesive to bond components of an inkjet head, deterioration of the components can be suppressed.

[0046] When a polythiol contains an ester bond and has five or more mercapto groups, it is presumed that the reaction rate increases due to the moderate number of mercapto groups, which are the reaction sites, thus suppressing displacement and enabling low-temperature reactions. Furthermore, when a polythiol contains a nitrogen atom and the mercapto groups are bonded to the nitrogen atom via alkylene groups, it is presumed that this special structure of the polythiol contributes to the improvement of the reaction rate.

[0047] As for the first polythiol mentioned above, dipentaerythritol hexakis(3-mercaptopropionate) can be cited due to its rapid reaction rate.

[0048] Examples of the second polythiol mentioned above include 1,3,4,6-tetrakis(2-mercaptopropyl) glycoluryl and 1,3,4,6-tetrakis(2-mercaptoethyl) glycoluryl. Among these, 1,3,4,6-tetrakis(2-mercaptopropyl) glycoluryl or 1,3,4,6-tetrakis(2-mercaptoethyl) glycoluryl are preferred due to their faster reaction rate. Furthermore, among these, 1,3,4,6-tetrakis(2-mercaptoethyl) glycoluryl is even more preferred due to its even faster reaction rate.

[0049] By curing the epoxy resin composition using the first or second polythiol described above, the curing temperature can be lowered. When curing the epoxy resin composition of this embodiment, a cured product is obtained by first curing by light irradiation, and then curing by heating. The temperature during light irradiation is preferably 20 to 40°C. The subsequent heating is preferably carried out at 50 to 100°C. Both the curing reaction with the first and second polythiol has a fast reaction rate. Therefore, the epoxy resin can be cured at a low temperature in this way. In this way, because the epoxy resin composition of this embodiment can be cured at a low temperature, when used as an adhesive for bonding components of an inkjet head, the deterioration of the components can be suppressed.

[0050] It is preferable that the polythiol is contained in an amount of 60 to 100 parts by mass per 100 parts by mass of epoxy resin. It is even more preferable that the polythiol is contained in an amount of 60 to 75 parts by mass per 100 parts by mass of epoxy resin. If the polythiol content is less than 60 parts by mass, the crosslinking density will decrease and the solvent resistance may deteriorate.

[0051] <Photobase Generator> The epoxy resin composition of this embodiment contains a photobase generator. The photobase generator is a compound that generates a base upon irradiation with UV light. In the epoxy resin composition of this embodiment, it is preferable that the photobase generator is a compound that generates an organic base upon irradiation with UV light suitable for base generation.

[0052] The epoxy resin composition of this embodiment contains one or more of the above-mentioned photobase generators. Preferably, at least one of the photobase generators has a borate salt. Having at least one of the photobase generators has a borate salt allows the reaction rate during curing to be increased. Examples of photobase generators include "1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium n-butyltriphenylborate" and "(Z)-{[bis(dimethylamino)methylidene]amino}-N-cyclohexyl(cyclohexylamino)methaneiminium tetrakis(3-fluorophenyl)borate". Commercially available products include WPBG-300 (trade name, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and WPBG-345 (trade name, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0053] The photobase generator is preferably contained in the epoxy resin composition in a ratio of 3 to 10 equivalents per 100 equivalents of epoxy resin. More preferably, the photobase generator is contained in a ratio of 5 to 10 equivalents per 100 equivalents of epoxy resin. This speeds up the reaction of the epoxy resin composition. Furthermore, it improves the rate of thickening after UV irradiation. If the content of the photobase generator in the epoxy resin is less than 3 equivalents per 100 equivalents of epoxy resin, the reaction of the epoxy resin composition may be slow. If the content of the photobase generator in the epoxy resin exceeds 10 equivalents per 100 equivalents of epoxy resin, the storage stability of the epoxy resin composition may decrease.

[0054] <Sensitizer> The epoxy resin composition of this embodiment contains a sensitizer. By including a sensitizer together with the photobase generator, the epoxy resin composition of this embodiment can further promote the generation of bases. By including a sensitizer, it is possible to generate bases from the photobase generator with shorter light irradiation times. Furthermore, it is possible to generate bases from the photobase generator with longer wavelength light irradiation. Photobase generators usually have a maximum absorption around 345 nm, but by adding a sensitizer, the photobase generator has the advantage of exhibiting photosensitivity in the longer wavelength region (around 365 nm).

[0055] While not particularly limited, examples of sensitizers include 1-chloroanthraquinone, 2-ethylanthraquinone, and 2-isopropylthioxanthone. Among these, 2-ethylanthraquinone and 2-isopropylthioxanthone are preferred, and 2-isopropylthioxanthone is even more preferred. Adding a sensitizer has the advantage that the photobase generator exhibits photosensitivity in the long-wavelength region (around 365 nm).

[0056] The sensitizer is preferably contained in an amount of 0.5 to 5 parts by mass per 100 parts by mass of epoxy resin. More preferably, the sensitizer is contained in an amount of 1 to 3 parts by mass per 100 parts by mass of epoxy resin.

[0057] <Silane coupling agent> The epoxy resin composition of this embodiment preferably contains a silane coupling agent. By containing a silane coupling agent, the epoxy resin composition of this embodiment improves adhesion when used as an adhesive for bonding components of an inkjet head.

[0058] The silane coupling agent is not particularly limited, but is preferably a compound having an epoxy group or an amine group, or an isocyanate. Examples of compounds having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane. Examples of compounds having an amine group include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine. Examples of isocyanates include 3-isocyanatepropyltriethoxysilane. Among these, 3-glycidoxypropyltrimethoxysilane is even more preferred from the viewpoint of improving adhesion.

[0059] The silane coupling agent is preferably contained in an amount of 0.2 to 10 parts by mass per 100 parts by mass of epoxy resin. More preferably, the silane coupling agent is contained in an amount of 0.2 to 2 parts by mass per 100 parts by mass of epoxy resin. Adhesion is improved when the silane coupling agent content in the epoxy resin composition is within this range. If the silane coupling agent content exceeds 10 parts by mass, adhesion may decrease due to aggregation of the silane coupling agent.

[0060] <Other additives> The epoxy resin composition of this embodiment may also contain thixotropic agents, viscosity modifiers, and the like, in addition to the above-mentioned components.

[0061] <Method for producing epoxy resin composition> The method for producing the epoxy resin of this embodiment is not particularly limited, and it can be produced by mixing each component contained in the epoxy resin composition of this embodiment described above.

[0062] 2.Cured product One embodiment of the cured product of the present invention is a reactant of the epoxy resin composition of this embodiment. This reactant is obtained by curing the epoxy resin composition of this embodiment with light, and this reactant is the cured product of this embodiment.

[0063] The cured product of this embodiment is obtained by photocuring the epoxy resin composition of this embodiment, and is therefore formed at low temperature and in a short time. When the components of the inkjet head are bonded together, the cured product of this embodiment preferably exhibits excellent ink resistance and sealing properties. The epoxy resin composition of this embodiment exhibits particularly excellent ink resistance and sealing properties if it contains an epoxy resin having three or more epoxy groups per molecule.

[0064] The cured product of this embodiment preferably has a nitrogen content of 7.5 to 11% by mass and a sulfur content of 10 to 17% by mass.

[0065] The nitrogen and sulfur content in the cured product of this embodiment can be measured, for example, by the following method. The apparatus can be a fully automated elemental analyzer, Vario EL cube, manufactured by Elementar. Preferably, the measurement conditions are set to CHNS measurement mode, with a combustion temperature of 1150°C and a reduction temperature of 850°C. Preferably, a tin boat is used, the combustion time is 150 seconds, and a thermal conduction detector (TCD) is used as the detector.

[0066] The method for manufacturing the cured product of this embodiment will be explained in the section describing the method for manufacturing the joined body of this embodiment below.

[0067] 3.Zygote <zygote> One embodiment of the joint of the present invention includes the cured product of the above embodiment. Preferably, the joint of this embodiment is formed by joining multiple members together using the epoxy resin composition of this embodiment as an adhesive. Furthermore, preferably, the joint of this embodiment is an inkjet head, camera module, etc., formed by joining in the manner described above. In this case, the inkjet head, camera module, etc., comprises multiple members and a cured product which is a reaction product obtained by reacting the epoxy resin composition of this embodiment. In particular, an inkjet head is preferred as the joint of this embodiment.

[0068] The joint of this embodiment is formed by joining multiple members together using the epoxy resin composition of this embodiment as an adhesive, thereby suppressing misalignment of the members. Furthermore, for the same reason, deterioration of the members is suppressed in the joint of this embodiment. The above effect is particularly noticeable when multiple members constituting an inkjet head are joined together using the epoxy resin composition of this embodiment as an adhesive. Figure 1 is a schematic diagram illustrating one embodiment of the joint of the present invention. The joint of this embodiment is an inkjet head 1. The inkjet head 1 of this embodiment comprises a substrate 4, a cured epoxy resin composition 5 located on one side of the substrate 4, and a nozzle plate 2 disposed on the side of the cured epoxy resin composition 5 opposite to the side on which the substrate 4 is disposed. Nozzle holes 3 are formed in the nozzle plate 2. This is because the substrate 4 and the nozzle plate 2 are joined together using the epoxy resin composition of this embodiment as an adhesive. Figure 2 is a schematic diagram illustrating another embodiment of the joint of the present invention. The joint of this embodiment is a part 1 of a camera module. A part 1 of the camera module of this embodiment comprises a substrate 8, a cured epoxy resin composition 9 located on one side of the substrate 8, and a PC chip 7 disposed on the side of the cured epoxy resin composition 9 opposite to the side on which the substrate 8 is disposed. In this case, the substrate 4 and the PC chip 7 are joined together using the epoxy resin composition of this embodiment as an adhesive.

[0069] In the joint of this embodiment, the material of the member is preferably metal, glass, ceramics, resin, etc.

[0070] <Method for manufacturing a jointed body> Next, a method for manufacturing the joint of this embodiment will be described. The joint of this embodiment is formed by joining multiple members together using the epoxy resin of this embodiment as an adhesive. Therefore, the multiple members are joined with the cured product of this embodiment sandwiched between them. Accordingly, the method for manufacturing the joint of this embodiment is a method for creating a state in which multiple members are joined with the cured product of this embodiment sandwiched between them, and includes a method for manufacturing the cured product of this embodiment.

[0071] The joint of this embodiment is a joint comprising two plate-like members and a cured product of this embodiment that is sandwiched between the two plate-like members and bonded together. This joint is made by bonding the two plate-like members using the epoxy resin composition of this embodiment as an adhesive. The method for manufacturing a joint of this structure will be described below.

[0072] First, the epoxy resin composition of this embodiment is applied to the surface of a single plate-shaped member at room temperature. The method of applying the epoxy resin composition is not particularly limited.

[0073] Next, the epoxy resin composition applied to the surface of the plate-shaped member is irradiated with UV light to perform partial curing. Partial curing is preferably performed at room temperature. In this specification, room temperature refers to a temperature in the range of 20 to 30°C. Since UV irradiation during the manufacture of the bonded body in this embodiment does not need to be performed at high temperatures, deterioration of the member can be suppressed.

[0074] Here, UV light refers to light containing ultraviolet rays that can generate a base when irradiated onto a composition containing a photobase generator and a sensitizer. The UV light used for irradiation is preferably one that can effectively generate a base using the photobase generator and sensitizer contained in the epoxy resin composition. For example, the UV light is preferably one with a peak wavelength in the range of 340-380 nm, and an integrated light intensity of 100-200 J / cm². 2 A range of [this] is preferred.

[0075] Next, one side of one plate-shaped member is placed on the surface of the plate-shaped member coated with the epoxy resin composition, thereby obtaining an assembly in which the UV-cured epoxy resin composition is sandwiched between the two plate-shaped members. The assembly is then heated to 50-100°C to perform the final curing and obtain a joint. At this time, the epoxy resin composition sandwiched between the plate-shaped members has also cured, so the joint and the cured material are obtained simultaneously. Because the epoxy resin composition of this embodiment reacts quickly, final curing can be achieved even when heated at a low temperature of 50-100°C. Furthermore, because the final curing temperature is low, deterioration of the members can be suppressed. In addition, because the epoxy resin composition of this embodiment reacts quickly, misalignment can be suppressed when joining the two plate-shaped members. [Examples]

[0076] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, the operations were carried out at room temperature (25°C).

[0077] (Examples 1-13, Comparative Examples 1-3) (Epoxy resin composition) An epoxy resin composition was prepared by mixing epoxy resin, polythiol, photobase generator, sensitizer, and silane coupling agent in the formulations shown in Tables 1 and 2. The units of the formulations shown in Tables 1 and 2 are parts by mass. In Tables 1 and 2, the "Name" column indicates the trade name or compound name.

[0078] The mixture of each component was prepared by stirring the epoxy resin, photobase generator, and sensitizer, heating at 110°C for 30 minutes, and then adding polythiol after cooling. The mixture was then stirred for 1 minute using a Synky Co., Ltd. product name: Awatori Rentaro (model number: AR-250).

[0079] The components contained in the epoxy resin composition are as follows:

[0080] (Epoxy resin) jER828 (product name): Bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 184-194 jER630 (product name): Multifunctional epoxy resin, manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 90-106

[0081] (Polythiol) PE-1 (Kalenz MT PE-1; trade name): Ester-type polythiol, manufactured by Resonaq, compound name: pentaerythritol tetrakis(3-mercaptobutyrate) DPMP (trade name): Ester-type polythiol, manufactured by Sakai Chemical Industry Co., Ltd., compound name: 3-mercaptopropionate of dipentaerythritol C3TS-G (trade name): Glycoluryl-type polythiol, manufactured by Shikoku Chemicals Co., Ltd., compound name: 1,3,4,6-tetrakis(3-mercaptopropyl)glycoluryl PEPT: Pentaerythritol tripropanechol, manufactured by SC Organic Chemicals Co., Ltd.

[0082] (Photobase Generator) WPBG-300 (product name): Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., compound name: 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium n-butyltriphenylborate WPBG-345 (product name): Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., compound name: (Z)-{[bis(dimethylamino)methylidene]amino}-N-cyclohexyl(cyclohexylamino)methaniminium tetrakis(3-fluorophenyl)borate

[0083] (Sensitizer) 2-Isopropylthioxanthone: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., Compound name: 2-Isopropylthioxanthone 2-Ethylanthraquinone, manufactured by Tokyo Chemical Industry Co., Ltd., compound name: 2-ethylanthraquinone

[0084] (Silane coupling agent) KBM-403 (product name): Manufactured by Shin-Etsu Chemical Co., Ltd., compound name: 3-glycidoxypropyltrimethoxysilane

[0085] The obtained epoxy resin compositions (Examples 1-13, Comparative Examples 1-3) were evaluated as follows. The results are shown in Tables 1 and 2.

[0086] (Position misalignment) The epoxy resin composition has an integrated light intensity of 182 J / cm². 2 The epoxy resin composition is irradiated with ultraviolet (UV) light to achieve the desired result. The epoxy resin composition gels upon UV irradiation. It is then heated to 100°C. During heating, the viscosity after the start of heating is measured using a rheometer. The viscosity reduction rate is then calculated using the following formula: The viscosity reduction rate is the initial viscosity minus the minimum viscosity after the start of heating, divided by the initial viscosity, and multiplied by 100. Viscosity reduction rate = {(Initial viscosity - Minimum viscosity after heating begins) / Initial viscosity} × 100 [%]

[0087] Ultraviolet irradiation should be performed at room temperature. Initial viscosity should be measured immediately after heating begins. Viscosity after heating should be measured every second thereafter.

[0088] The evaluation criteria for viscosity reduction rate are as follows: A and B are acceptable, while C and D are unacceptable. A: Less than 5% B: 5% or more, less than 10% C: 10% or more, less than 20% D: 20% or more

[0089] (Low temperature curing) The residual heat generation of the obtained epoxy resin composition is measured using a differential scanning calorimeter (DSC). Low-temperature curability is determined as the unreacted rate according to the following formula for determining the unreacted rate. The unreacted rate is the ratio of the amount of unreacted components remaining as unreacted components when the epoxy resin composition is cured at low temperature to the amount of epoxy resin composition before curing. The more advanced the low-temperature curing, the smaller the residual heat generation will be, as the reaction has progressed when left at 100°C for 1 hour. Here, "heat generation in the uncured state" is the amount of heat generated when the epoxy resin composition is cured before curing. "Heat generation of the cured product" is the amount of heat generated when the epoxy resin composition is left at 100°C for 1 hour. Unreacted rate = (1 - (Heat generation of cured material / Heat generation when uncured)) × 100 [%]

[0090] The evaluation criteria for low-temperature curing properties are as follows: A and B are acceptable, while C and D are unacceptable. A: Less than 10% B: 10% or more but less than 15% C: 15% or more, less than 20% D: 20% or more

[0091] For the obtained epoxy resin compositions (Examples 1-13, Comparative Examples 1-3), the cumulative light intensity at 23°C was 182 J / cm². 2 Ultraviolet (UV) light was irradiated to achieve the following result. The epoxy resin composition gelled upon UV irradiation. Subsequently, it was heated to 100°C and cured at 100°C for 1 hour to obtain a cured product. The amount of epoxy resin composition used for curing was 0.2 g each. The obtained cured product is the cured product of the present invention. The swelling rate of the obtained cured product was determined by the following method.

[0092] (swelling rate) The mass of each cured material is measured. Then, each cured material is immersed in anisole, a solvent, and left at 60°C for 7 days. After 7 days, each swollen cured material is removed from the solvent and its mass is measured. The swelling rate is calculated using the following formula. Swelling rate = {(Mass of hardened material after swelling - Mass of hardened material before swelling) / Mass of hardened material before swelling} × 100 [%]

[0093] The evaluation criteria for swelling rate are as follows: A and B are acceptable, while C and D are unacceptable. A: Less than 5% B: 5% or more, less than 10% C: 10% or more, less than 20% D: 20% or more

[0094] The obtained epoxy resin composition was used as an adhesive to join two components to create a joint. The components used were a plate-shaped glass and a film-shaped polyimide. The resulting joint is a structure in which the plate-shaped glass and the film-shaped polyimide are joined with a cured product (a reaction product of the epoxy resin composition) in between. The resulting joint is the joint of the present invention.

[0095] [Table 1]

[0096] [Table 2]

[0097] The evaluation results for Examples 3 and 4, and Examples 9, 10, and 11, show that increasing the amount of photobase generator leads to a greater suppression of positional displacement.

[0098] From the evaluation results of Example 8 and Comparative Example 1, it can be seen that incorporating glycoluryl type polythiol yields better results in terms of displacement, ink resistance, and low-temperature curing compared to incorporating ether type polythiol. This is thought to be because the epoxy resin composition of Comparative Example 1, being a combination of a bifunctional epoxy resin and an ether-based thiol, had a reaction temperature of 100°C that was too low, leaving unreacted components.

[0099] The epoxy resin composition of Comparative Example 2, being a combination of a trifunctional epoxy resin and an ether-based thiol, had a reaction temperature of 100°C which was too low, resulting in unreacted components remaining. This is thought to have led to poor evaluation results for displacement and low-temperature curing properties. Similarly, the epoxy resin composition of Comparative Example 3, being a combination of a bifunctional epoxy resin and a tetrafunctional ester-type thiol, had a low crosslinking density, which is thought to have led to poor evaluation results for ink resistance.

[0100] The epoxy resin composition of Example 3 was obtained by adding 2 parts by mass of a silane coupling agent to the epoxy resin composition of Example 2. The epoxy resin composition of Example 3 had stronger adhesive strength than the epoxy resin composition of Example 2. This indicates that the adhesive strength can be further improved with a silane coupling agent. The adhesive strength was confirmed by the following method. First, a joint was prepared by bonding a polyimide film and a glass plate with the epoxy resin composition. Then, the adhesive strength of the obtained joint was confirmed by a 90-degree peel test (JIS K6854-1).

[0101] The nitrogen and sulfur content of the cured epoxy resin composition of Example 10 was measured, and it was found that the nitrogen content was 8.2% by mass and the sulfur content was 11.3% by mass. The nitrogen and sulfur content in the cured product was measured by the following method. The measuring device used was a fully automated elemental analyzer, Vario EL cube, manufactured by Elementar. The measurement conditions were set to CHNS measurement mode, with a combustion temperature of 1150°C and a reduction temperature of 850°C. A tin boat was used, the combustion time was 150 seconds, and a thermal conduction detector (TCD) was used. [Industrial applicability]

[0102] According to the present invention, when used as an adhesive to bond components of an inkjet head together, it is possible to provide an epoxy resin composition that can suppress misalignment between components and suppress thermal degradation of the components. [Explanation of Symbols]

[0103] 1. Inkjet head 2 Nozzle Plates 3 nozzle holes 4. Foundation 5. Cured product of epoxy resin composition 6. Part of the camera module 7 PC chips 8 bases 9. Cured product of epoxy resin composition

Claims

1. An epoxy resin composition comprising epoxy resin, polythiol, photobase generator and sensitizer, The epoxy resin comprises one or more types, At least one of the epoxy resins has two or more epoxy groups in one molecule, An epoxy resin composition characterized in that the polythiol contains an ester bond and has five or more mercapto groups, or the polythiol contains a nitrogen atom and the mercapto groups are bonded to the nitrogen atom via alkylene groups.

2. The epoxy resin composition according to claim 1, characterized in that the polythiol, in which the mercapto group is bonded to the nitrogen atom via an alkylene group, has a glycoluryl skeleton.

3. The epoxy resin composition according to claim 1, characterized in that at least one of the epoxy resins has three or more epoxy groups in its molecule.

4. The epoxy resin composition according to claim 1, characterized in that the epoxy resin is glycidylamine-based.

5. The above-mentioned photobase generator comprises one or more types, The epoxy resin composition according to claim 1, characterized in that at least one of the photobase generators has a borate salt.

6. The epoxy resin composition according to claim 1, characterized in that the amount of the photobase generator is in a ratio of 3 to 10 equivalents per 100 equivalents of epoxy resin.

7. The above-mentioned sensitizer comprises one or more types, The epoxy resin composition according to claim 1, wherein at least one of the sensitizers is 2-isopropylthioxanthone or 2-ethylanthraquinone.

8. The epoxy resin composition according to claim 1, comprising a silane coupling agent.

9. The epoxy resin composition according to claim 8, wherein the silane coupling agent is a compound having an epoxy group or an amine group, or an isocyanate.

10. A cured product which is a reactant of the epoxy resin composition according to any one of claims 1 to 9.

11. The cured product according to claim 10, wherein the nitrogen content is 7.5 to 11% by mass and the sulfur content is 10 to 17% by mass.

12. A joint characterized by containing the cured product described in claim 10.

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