Electroconductive adhesive

Abstract

[Problem] To provide an electroconductive adhesive capable of achieving good storage stability and / or workability in the uncured state, and further good electrical conductivity, adhesiveness and / or durability after being cured. [Solution] In an electroconductive adhesive according to the present invention, a main agent (A) 72 containing a dispersed first electroconductive filler (C1) 72a and a curing agent (B) 74 containing a dispersed second electroconductive filler (C2) 74a are simultaneously fed to a single mixing unit 80, together with a plurality of liquid epoxy resins (D) having different molecular structures, a fatty acid-modified epoxy resin (E), and a reactive diluent (H), and mixed in the mixing unit 80.

Description

Conductive adhesive

[0001] The present invention relates to a conductive adhesive that can be used, for example, for electrical connection or adhesion in electronic components, circuits and the like.

[0002] Conventionally, conductive adhesives obtained by mixing metal powder with high conductivity into resin-based adhesives have been employed to obtain electrical connections. For example, epoxy resins used as adhesives may provide high adhesiveness and durability when used together with a curing agent. Epoxy resin-based adhesives include a one-component type, in which a base resin and a curing agent are premixed before use, and a two-component type, in which the base resin and the curing agent are stored in separate containers respectively and mixed when actually used.

[0003] The above-mentioned one-component adhesive has the features that since the base resin and the curing agent are uniformly blended in predetermined amounts in advance, stable curing performance can be obtained, and there is no need for mixing during use. However, when a one-component type is employed, since the base resin and the curing agent are in a mixed state from the beginning, there is a technical problem that the curing reaction proceeds spontaneously unless stored at a low temperature. In particular, for adhesives that can be cured at room temperature, the problem of progression of the curing reaction during storage becomes more serious not only at room temperature but also at low temperatures. Furthermore, once opened and started to be used, there is a problem that it cannot be used for a long time due to the progression of curing. On the other hand, if the adhesive can be stored at room temperature, the curing speed will be slowed down, so there are restrictions such as that it must be heated to a relatively high temperature for use.

[0004] On the other hand, when a two-component adhesive is employed, the above-mentioned problems caused by one-component adhesives are solved. However, since the base resin and the curing agent are mixed and cured, it is necessary to highly uniformly blend these two types of materials in an appropriate mixing ratio before mixing and use. As a result, the two-component adhesive has the disadvantages that the work for obtaining the required blending takes time and effort, and curing starts once mixed, leading to unused leftover material. In order to solve the above-mentioned problems, a plurality of adhesive supply devices that develop adhesive force by mixing multiple types of chemical substances have been disclosed so far (Patent Documents 1 to 3).

[0005] The various usage problems and technical challenges of one-component and two-component adhesives, such as storage stability, usage constraints, usage stability, workability, and stable performance, as described above, are extremely difficult to solve in conductive adhesives that use conductive particles with high conductivity and significantly different specific gravities from the resin, particularly conductive adhesives that can cure at room temperature, as shown in Patent Document 4, for example. This has been a long-standing challenge in the industry. For example, even in two-component adhesives, development is underway to reduce costs by reducing the content of expensive metals responsible for conductivity (for example, Reference Document 1). However, it is not easy to ensure that the dispensed main component and curing agent are properly mixed and that the desired conductivity is reliably achieved in the mixed, uncured adhesive (Patent Document 5).

[0006] Japanese Patent Publication No. 2007-303086, Japanese Patent Publication No. 2005-146753, Japanese Patent Publication No. 2008-105739, Japanese Patent Publication No. 38-16317, Japanese Patent Publication No. 2009-541572

[0007] As described above, when using a two-component adhesive, in order to ensure that the uncured adhesive can be cured at room temperature (hereinafter collectively referred to as "room temperature") without requiring special heating equipment such as a heating furnace after the main component and curing agent have been dispensed, and that the desired conductivity is reliably achieved, several special considerations and ingenuity are preferably required. Specifically, not only is optimization of the main component and curing agent constituting the uncured adhesive required, but also consideration and ingenuity regarding the type or shape of the conductive material (for example, a conductive material consisting of metal powder, etc.) that may be contained in the main component and / or curing agent, or the manner in which the conductive material is contained in the main component and / or curing agent. In particular, optimizing the manner in which the conductive material is contained in the main component and / or curing agent (for example, the state in which the conductive material is present in the main component and / or curing agent) is an important technical challenge for achieving good storage stability and / or workability of the final uncured adhesive, and consequently good conductivity, adhesion and / or durability after curing.

[0008] However, the development and realization of a two-component, room-temperature curable conductive adhesive that incorporates features to solve at least one of the following technical challenges (TC1) to (TC3) is still only halfway complete.

[0009] (TC1) A method for easily and uniformly mixing predetermined amounts of multiple types of chemical substances, such as the main agent and the curing agent described above, in a state in which uneven conductivity is less likely to occur when trying to give the adhesive good conductivity. (TC2) A method for forming and maintaining a stable dispersion state of the conductive material over a long period of time in a mixture containing the main agent or curing agent and metal powder, etc. (conductive material) having a specific gravity difference with respect to the main agent or curing agent, unlike simple adhesives. (TC3) A method for achieving a curing speed that is acceptable in this field, while maintaining workability that allows for application over a large area and / or time-consuming correction after application, and which can be stored at room temperature without requiring cooling or heating.

[0010] In particular, in conductive adhesives, which consist of a resin-based adhesive such as epoxy resin that can serve as the main component, a curing agent that hardens the main component, and a material with high conductivity (for example, metal powder such as silver or gold), there is a strong demand in the field for the realization of a two-component conductive adhesive that can harden at room temperature and solve the aforementioned technical problems.

[0011] By solving the above-mentioned technical problems, the present invention can greatly contribute to the realization of a two-component conductive adhesive that can cure at room temperature and solve at least some of the above-mentioned problems (TC1) to (TC3).

[0012] In order to solve at least one of the above-mentioned technical problems, the inventors first diligently conducted research and analysis to optimize the form of the conductive material to be mixed (or introduced) with the main component and / or curing agent containing epoxy resin, while also ensuring that it can be cured at room temperature. This is because even if the conductive material itself is optimized, if it becomes localized when mixed with the main component and / or curing agent, the possibility of uneven storage stability and / or workability of the resulting uncured adhesive, and consequently uneven conductivity of the cured adhesive, becomes very high.

[0013] Therefore, the inventors considered that it was necessary to devise a way for the conductive material in the main component and / or curing agent to remain stable for a long period of time without localizing within the main component and / or curing agent. In addition, in order to achieve good storage stability and / or workability of the final uncured adhesive, and consequently good conductivity, adhesion and / or durability after curing, the inventors also investigated and analyzed whether the conductive material should be mixed into only one of the main component or the curing agent, or into both the main component and the curing agent.

[0014] Furthermore, as mentioned above, with consideration for user convenience and ease of use, we diligently studied and analyzed the selection of materials for the main component and / or curing agent, as well as the optimization of their mixing ratios, so that even conductive adhesives can cure at room temperature.

[0015] As a result, from the viewpoint of suppressing the localization of the conductive material in the main component and / or curing agent, it was found that it is preferable to optimize the viscosity of the main component and curing agent, which serve as dispersion media, and to mix the conductive material with both the main component and the curing agent in order to suppress localization and achieve as uniform a mixture as possible. Furthermore, from the viewpoint of improving the feasibility of curing at room temperature, it was found that it is preferable to use a curing agent and / or reactive diluent with appropriate reactive activity in order to cure the epoxy resin that can constitute the main component at room temperature and to ensure an appropriate working time in mounting or repairing electronic components, etc.

[0016] Furthermore, as a result of their extensive research, the inventors have found that, for example, adjusting the particle size and shape of the conductive material, the specific gravity difference with the main component or the curing agent, and / or adding a dispersant adapted to the material of the conductive material to prevent aggregation of the conductive material can contribute to the highly reliable suppression of aggregation and localization of the conductive material.

[0017] In addition, the inventors have found that when using a two-component adhesive, by devising the form of the conductive material in the main component and the curing agent, and by appropriately mixing the main component containing the conductive material and the curing agent containing the conductive material, that is, in a state in which aggregation and / or localization of the conductive material is suppressed, and then dispensing the mixture, it is possible to dispense an uncured adhesive that is less likely to produce unevenness or bias in the properties of conductivity, adhesion, and / or durability (hereinafter collectively referred to as "conductivity unevenness," "adhesion unevenness," and "durability unevenness"). Furthermore, the inventors have found that in order to achieve this, preferably a structure is provided that can simultaneously supply the main component containing the conductive material and the curing agent containing the conductive material to a single mixing section, and by dispensing the uncured adhesive from a single discharge port via the mixing section, at least one of the above technical problems can be solved. The present invention was created from the above perspectives.

[0018] Another conductive adhesive of the present invention comprises a main component (A) containing a dispersed first conductive filler (C1) along with a plurality of liquid epoxy resins (D) having different molecular structures, a fatty acid-modified epoxy resin (E), and a reactive diluent (H), and a curing agent (B) containing a dispersed second conductive filler (C2), which are supplied to a single mixing section, and the viscosity of the mixture mixed in the mixing section at 25°C is 1,000 mPa·s or more and 1,000,000 mPa·s or less.

[0019] This conductive adhesive contains a first conductive filler (C1) in which the main component (A) is dispersed, and a second conductive filler (C2) in which the curing agent (B) is dispersed. In addition, for example, immediately after manufacture, or during the second or subsequent use after the first use, when the aforementioned main component (A), first conductive filler (C1), curing agent (B), and second conductive filler (C2) are supplied to one of the above-mentioned mixing parts, the conductive adhesive has a viscosity within the above-mentioned numerical range, so that good conductivity, adhesion, and / or durability can be achieved after curing.

[0020] Furthermore, regarding the viscosity mentioned above, from the viewpoints described above, it is more preferable that the viscosity at 25°C be 1,000 mPa·s (even more preferably 5,000 mPa·s) or more and 100,000 mPa·s or less (even more preferably 50,000 mPa·s) or less.

[0021] Furthermore, in another conductive adhesive of the present invention, a main component (A) containing a dispersed first conductive filler (C1) along with a plurality of liquid epoxy resins (D) having different molecular structures, a fatty acid-modified epoxy resin (E), and a reactive diluent (H), and a curing agent (B) containing a dispersed second conductive filler (C2) are simultaneously supplied to a single mixing section and mixed within the mixing section.

[0022] This conductive adhesive contains a first conductive filler (C1) in which the above-mentioned main component (A) is dispersed, and a second conductive filler (C2) in which the above-mentioned curing agent (B) is dispersed. In addition, the main component (A), the first conductive filler (C1), the curing agent (B), and the second conductive filler (C2) are all simultaneously supplied to a single mixing section and mixed within the mixing section. As a result, this conductive adhesive allows for obtaining a predetermined mixing ratio and good uniformity of components in the final uncured adhesive, as well as stable discharge from the dispensing section, and consequently, can reliably suppress the occurrence of inconsistencies in the conductivity, adhesion, and / or durability properties of the cured adhesive.

[0023] In the above inventions, the term "dispersed" means a state that satisfies either (DF1) or (DF2) below. (DF1) A state in which the localization of the first conductive filler (C1) or the second conductive filler (C2) is suppressed in the main agent (A) or the curing agent (B) described above, or more narrowly, a state in which the size (maximum diameter) of the substantially spherical or amorphous aggregates of the first conductive filler (C1) or the second conductive filler (C2) is 30 μm or less. (DF2) A state in which the surface resistance value of the conductive adhesive after curing is 1.0 × 10⁻⁶. －２ It must be less than or equal to Ωcm.

[0024] According to one conductive adhesive of the present invention, at least some of the following effects (TE1) to (TE4) can be achieved. (TE1) In the final uncured adhesive, predetermined amounts of multiple types of chemical substances, such as the main agent and curing agent described above, can be mixed easily and substantially uniformly, thereby enabling highly reliable suppression of inconsistencies in the conductivity, adhesion, and / or durability properties of the cured adhesive. (TE2) It is possible to cure at room temperature and achieve a dense structure, thereby obtaining sufficient or good conductivity, adhesion, and / or durability for conductive bonding of electronic components. (TE3) It is possible to cure at room temperature and achieve a practically acceptable curing speed while maintaining workability that allows for application over large areas and time-consuming corrections after application. (TE4) It is possible to highly reliable suppress aggregation and sedimentation of the resins and / or conductive fillers that can constitute the main agent and curing agent described above, and enable stable storage at room temperature for a long period of time.

[0025] This is a partial cross-sectional view showing the configuration of the supply device 100 of the first embodiment, in which the main component (A) containing dispersed first conductive filler (C1) and the curing agent (B) containing dispersed second conductive filler (C2) are contained. This is an exploded assembly drawing including a partial cross-sectional view showing the configuration of the supply device 100 of the first embodiment. This is a partial cross-sectional view showing the configuration of the supply device 100 of the first embodiment, in which the main component (A) containing dispersed first conductive filler (C1) and the curing agent (B) containing dispersed second conductive filler (C2) have all been pushed out from the containment section. This is a partial cross-sectional view showing the configuration of the supply device 100 of the first embodiment when it is stored, in which the main component (A) containing dispersed first conductive filler (C1) and the curing agent (B) containing dispersed second conductive filler (C2) are contained. This is an exploded assembly diagram, including a partial cross-sectional view, showing the configuration of the supply device 100 of the first embodiment when it is stored, without containing the main component (A) containing dispersed first conductive filler (C1) and the curing agent (B) containing dispersed second conductive filler (C2).

[0026] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In this description, common reference numerals are used throughout the drawings unless otherwise specified. Furthermore, the elements of this embodiment are not necessarily shown to scale in the drawings. Also, some reference numerals and shapes may be omitted in order to improve clarity in each drawing.

[0027] <First Embodiment> [Regarding the Conductive Adhesive] The following describes in detail each chemical substance that constitutes the conductive adhesive of this embodiment. The conductive adhesive of this embodiment is composed of chemical substances belonging to the following two groups. When describing the conductive adhesive of this embodiment, the reference numerals for each component will be those shown in the supply device 100, which is an example suitable for using the conductive adhesive of this embodiment and will be described in detail later, as shown in Figures 1 to 5.

[0028] One group of chemicals comprises a main component (A) containing a dispersed first conductive filler (C1) along with multiple liquid epoxy resins (D) with different molecular structures, a fatty acid-modified epoxy resin (E), and a reactive diluent (H). The other group of chemicals comprises a curing agent (B) containing a dispersed second conductive filler (C2).

[0029] In this embodiment of the conductive adhesive, a main component (A) 72 containing dispersed first conductive filler (C1) 72a, which constitutes one group, is contained in a first syringe 12a. A curing agent (B) 74 containing dispersed second conductive filler (C2) 74a, which constitutes the other group, is contained in a second syringe 12b integrated with the first syringe 12a. Therefore, the main component (A) 72 and the curing agent (B) 74 are each contained in separate syringes. In this embodiment, the main component (A) 72 includes a plurality of liquid epoxy resins (D), fatty acid-modified epoxy resins (E), and reactive diluents (H) with different molecular structures. In this embodiment, to simplify the following explanation, "main component (A)" means a chemical substance containing a plurality of liquid epoxy resins (D), fatty acid-modified epoxy resins (E), and reactive diluents (H) with different molecular structures.

[0030] In this embodiment, when a mixture is formed by simultaneously supplying and mixing all the chemical substances belonging to the two groups described above into a single mixing unit (e.g., a container) either by the two groups separately, the viscosity of the mixture at 25°C is adjusted to be 1 million mPa·s (in other words, 1,000 Pa·s) or less.

[0031] Looking more closely at one of the groups mentioned above, the multiple liquid epoxy resins (D) with different molecular structures are selected primarily to suppress aggregation and crystallization of epoxy resin components by utilizing molecular structural factors such as steric hindrance, thereby ensuring the long-term stability of the uncured adhesive. The fatty acid-modified epoxy resin (E) is selected primarily to ensure the long-term stability of the epoxy resin components due to the differences in molecular structure mentioned above, while also utilizing the physical and / or chemical surface adsorption properties of the fatty acid components to metals, etc., to improve the dispersibility of conductive fillers, and as a result, to ensure the good and stable conductivity, adhesion, and durability of the final cured product. The reactive diluent (H) is selected primarily to adjust the viscosity of the main component, prevent sedimentation of conductive fillers, and accurately control the reactivity when mixed with the curing agent. Furthermore, the first conductive filler (C1) is selected primarily to facilitate easy and uniform mixing in a two-component epoxy conductive adhesive, and as a result, to reliably achieve good and stable conductivity in the final cured product. The main component (A) is selected primarily to reliably achieve good and stable conductivity, adhesion, and durability in the final cured product.

[0032] Next, looking more closely at the other group mentioned above, the second conductive filler (C2) is selected primarily to facilitate easy and uniform mixing in two-component epoxy conductive adhesives, and as a result, to reliably achieve good and stable conductivity in the final cured product, by incorporating a conductive filler in the curing agent as well as the main component, in conjunction with the effect of the first conductive filler (C1) mentioned above. Furthermore, the curing agent (B) is selected primarily to promote curing at room temperature by designing its reactivity with the main component, and to ensure sufficient working time after mixing with the main component before use, and to reliably achieve good and stable conductivity, adhesion, and durability in the final cured product.

[0033] Furthermore, by adjusting the viscosity of the above-mentioned mixture to within the above-mentioned numerical range and employing the conductive adhesive of this embodiment, at least some of the following effects (aII) to (cII) can be achieved. (aII) The main component (A) and the hardener (B), which have an appropriate component composition and physical properties to prevent sedimentation and aggregation, are housed in separate containers and are further mixed upon use, allowing the adhesive to cure at room temperature while also being able to be stored and used reliably for a long period of time even in a room temperature environment. (i.e., highly reliable long-term usability) (bII) The main component and hardener, with an appropriate component composition designed to ensure uniform mixing and a constant mixing ratio, are mechanically mixed within a predetermined area, resulting in highly reliable, good, and uniform conductivity, adhesion, and durability (i.e., highly reliable high functionality and homogeneity). (cII) The main component and hardener, with a component composition and physical properties that allow for storage in a syringe or discharge from a nozzle, are housed in separate containers. Furthermore, by using a supply device in which only the supply part containing the mixed main component and adhesive can be replaced, it can be used repeatedly, and can be applied to narrow areas, used in poor working positions, and even with automatic dispenser machines with high reliability. (i.e., highly reliable workability)

[0034] Furthermore, regarding the viscosity mentioned above, from the viewpoints described above, it is more preferable that the viscosity at 25°C be 1,000 mPa·s (even more preferably 5,000 mPa·s) or more and 100,000 mPa·s or less (even more preferably 50,000 mPa·s) or less.

[0035] To further elaborate on the chemical substances described above, the main component (A) 72 of this embodiment contains a dispersed first conductive filler (C1) 72a together with a plurality of liquid epoxy resins (D) having different molecular structures, a fatty acid-modified epoxy resin (E), and a reactive diluent (H), as described above. More specifically, a preferred example of the liquid epoxy resins (D) having different molecular structures is a chemical substance that combines two or more epoxy resins selected from the group consisting of bisphenol A type, bisphenol F type, cresol novolac type, and hydroxyphenyl type. A preferred example of the fatty acid-modified epoxy resin (E) is a long-chain unsaturated fatty acid glycidyl ester. A preferred example of the reactive diluent (H) is a glycol ether.

[0036] Furthermore, the type of curing agent (B) 74 described above is not limited as long as the effects of this embodiment can be achieved, but preferred examples of curing agent (B) 74 are amine-based, imidazole-based, or an amine-based curing agent (I) and a cationic polymer dispersant (J). In particular, the curing agent (B) containing an amine-based curing agent (I) and a cationic polymer dispersant (J) is a preferred embodiment from the viewpoint of enabling curing at room temperature and achieving an acceptable curing speed at use with greater certainty. In particular, the amine-based curing agent (I) being a polyamine with an active hydrogen equivalent of 150 to 250 is a preferred embodiment from the viewpoint of enabling curing at room temperature and obtaining good adhesion and / or durability after curing with greater certainty. Also, the cationic polymer dispersant (J) being an amine with a molecular weight of 10,000 to 30,000 is a preferred embodiment from the viewpoint of enabling curing at room temperature and improving the dispersibility of the conductive filler with greater certainty.

[0037] Furthermore, the specific gravity of the main component (A) 72 being 0.07 or more and 0.4 or less when the specific gravity of the first conductive filler (C1) 72a is set to 1, and the specific gravity of the hardener (B) 74 being 0.07 or more and 0.4 or less when the specific gravity of the second conductive filler (C2) 74a is set to 1, is a preferred embodiment from the viewpoint of more reliably suppressing the sedimentation and uneven distribution of the aforementioned conductive fillers 72a and 74a during storage, and more reliably achieving long-term storage stability.

[0038] Furthermore, when the viscosity of the main component (A) 72 (excluding the first conductive filler (C1) 72a) at 25°C is set to 1, the viscosity of the curing agent (B) 74 (excluding the second conductive filler (C2) 74a) at 25°C is 0.5 or more and 3.0 or less, and when the viscosity of the main component (A) 72 containing the dispersed first conductive filler (C1) 72a at 25°C is set to 1, the viscosity of the curing agent (B) 74 containing the dispersed second conductive filler (C2) 74a at 25°C is 0.5 or more and 3.0 or less, as described above, is a preferred embodiment from the viewpoint of more reliably suppressing the sedimentation and uneven distribution of the filler during storage and more reliably ensuring long-term storage stability.

[0039] Furthermore, in order to achieve the effects of this embodiment with greater certainty, it is a preferred alternative embodiment that the total volume of the first conductive filler (C1) 72a and the second conductive filler (C2) 74a is 0.4 to 1.5 when the total volume of the main component (A) 72 and the curing agent (B) 74 is set to 1. This is from the viewpoint of obtaining a more reliable and uniform mixture of the main component (A) 72 and the curing agent (B) 74 when using the adhesive, such as by dispensing the uncured conductive adhesive.

[0040] Furthermore, the fact that the first conductive filler (C1) 72a consists of flake-shaped silver powder and spherical silver powder, and the second conductive filler (C2) 74a consists of flake-shaped silver powder and spherical silver powder, is a preferred embodiment from the viewpoint of achieving appropriate viscosity in the main component (A) 72 containing the first conductive filler (C1) 72a, the curing agent (B) 74 containing the second conductive filler (C1) 74a, and the mixed uncured conductive adhesive, and / or from the viewpoint of achieving acceptable conductivity in conductive bonding and repair of electronic components, etc. The mixing ratio of flake-shaped silver powder to spherical silver powder in the first conductive filler (C1) 72a and the second conductive filler (C2) 74a is not particularly limited. For example, the mixing ratio is selected according to the conductivity to be obtained after curing, and / or the viscosity and other workability when using the uncured conductive adhesive.

[0041] In addition, when the average primary particle diameter of the first conductive filler (C1) 72a and the second conductive filler (C2) 74a is 0.1 µm or more and 20 µm or less, and the maximum particle diameter of the first conductive filler (C1) 72a and the second conductive filler (C2) 74a is 60 µm or less, this is a preferred embodiment from the viewpoint of achieving appropriate viscosity in the main agent (A) 72 containing each of the aforementioned conductive fillers 72a and 74a, the curing agent (B), and the mixed uncured conductive adhesive. In addition, having the maximum particle diameter of 60 µm or less as described above can achieve acceptable conductivity in conductive bonding and repair of electronic components and the like, and can ensure uniformity of the constituent components when an appropriate supply device is used, which is also a preferred embodiment from the viewpoint of convenience when performing high-precision coating and automation of industrial coating work using an automatic dispenser machine.

[0042] In addition, that the aforementioned fatty acid-modified epoxy resin (E) is a long-chain unsaturated fatty acid ester with a molecular weight of 400 or more and 1200 or less is a preferred embodiment from the viewpoint of maintaining the main agent at an appropriate viscosity and achieving good adhesion after curing.

[0043] In addition, that the aforementioned reactive diluent (H) is a glycol ether with a molecular weight of 150 or more and 350 or less is a preferred embodiment from the viewpoint of maintaining the main agent at an appropriate viscosity and achieving an acceptable curing rate.

[0044] As described above, an example of the respective preparation method for the main agent (A) 72 containing the first conductive filler (C1) 72a and the curing agent (B) 74 containing the second conductive filler (C2) 74a has been described, but the preparation method is not limited to the above example. For example, the aforementioned respective constituent components can be mixed by using a known mixing and stirring device such as a kneader mixer or a planetary mixer, and then a substantially uniform mixture can be obtained by a known dispersion and mixing device such as a three-roll mill.

[0045] [Supply Device 100 as an Example Suitable for Use of the Conductive Adhesive of the Present Embodiment and Embodiment Thereof] Next, the supply device 100 as an example suitable for use of the conductive adhesive of the present embodiment and an embodiment thereof will be described.

[0046] Figure 1 shows the state in which the main component (A) 72 containing dispersed first conductive filler (C1) 72a and the curing agent (B) 74 containing dispersed second conductive filler (C2) 74a (hereinafter, in this embodiment and the embodiments and examples described later, the four materials are collectively referred to as "four types of chemical substances") are contained in separate syringe containers 12a and 12b in the supply device 100 of this embodiment. Figure 2 is an exploded assembly diagram including a partial cross-sectional view showing the configuration of the supply device 100 of this embodiment. Figure 3 is a partial cross-sectional view showing the configuration of the supply device 100 of this embodiment after all of the four types of chemical substances have been pushed out from the storage section 10. Figure 4 is a partial cross-sectional view showing the configuration of the supply device 100 of this embodiment when it is stored with the four types of chemical substances contained inside. In addition, Figure 5 is an exploded assembly diagram including a partial cross-sectional view showing the configuration of the supply device 100 of this embodiment when it is stored without the four types of chemical substances contained inside.

[0047] As described above, in this embodiment, the conductive adhesive contains a main component (A) 72 containing dispersed first conductive filler (C1) 72a in an uncured conductive adhesive state, which is contained in the first syringe 12a of the supply device 100 shown in Figure 1. In addition, a curing agent (B) 74 containing dispersed second conductive filler (C2) 74a is contained in the second syringe 12b shown in Figure 1, which is integrated with the first syringe 12a. Therefore, in the supply device 100, the main component (A) 72 and the curing agent (B) 74 are each contained in separate syringes.

[0048] A supply device 100, which is an example suitable for use with the conductive adhesive of this embodiment, consists of the following five main components when in use, as shown in Figures 1 to 3. Specifically, the supply device 100 comprises a housing section 10 having a first syringe 12a and a second syringe 12b integrated by mold molding or the like, a pressing member 40 in which a first piston 42a and a second piston 42b are integrated by a connecting section 46, a mixing section 80 having a discharge port 82, and viscoelastic bodies 20a and 20b arranged in the first syringe 12a and the second syringe 12b, respectively, and plungers 30a and 30b in contact with the viscoelastic bodies 20a and 20b, respectively.

[0049] Furthermore, the supply device 100, which is an example suitable for use with the conductive adhesive of this embodiment, consists of the following five main components when stored, as shown in Figures 4 and 5. Specifically, the supply device 100 includes a housing section 10 having a first syringe 12a and a second syringe 12b integrated by mold molding or the like, a pressing member 40 in which a first piston 42a and a second piston 42b are integrated by a connecting section 46, a stopper 60 having a lid 50, and viscoelastic bodies 20a and 20b arranged inside the first syringe 12a and the second syringe 12b, respectively, and plungers 30a and 30b that abut against the viscoelastic bodies 20a and 20b, respectively.

[0050] When the supply device 100 is in use, as shown in Figure 3, when force (pressing force) is applied to the pressing member 40, the pressing force is transmitted to the pistons 42a and 42b inserted into the syringes 12a and 12b using the openings 18a and 18b provided in the housing 10, and to the plungers 30a and 30b and viscoelastic bodies 20a and 20b that are in contact with the pistons 42a and 42b. As a result, the four types of chemical substances in the housing 10 receive the pressing force directly from the viscoelastic bodies 20a and 20b. Consequently, the four types of chemical substances are supplied from the discharge ports 14a and 14b provided at the ends of the syringes 12a and 12b towards the mixing port 80 (more specifically, the introduction ports 84a and 84b). Each plunger 30a, 30b is provided with a non-through hole (not shown) on the side opposite to the contact surface of each viscoelastic body 20a, 20b. The connecting portions (protrusions) 44a, 44b of each piston 42a, 42b of the pressing member 40 are fitted into these non-through holes, thereby enabling the pressing force when the pressing member 40 is pressed to be transmitted to each viscoelastic body 20a, 20b with high accuracy.

[0051] In the mixing section 80, the four chemical substances supplied from the containment section 10 are mixed. After being uniformly mixed by a static mixer or the like pre-installed in the mixing section 80, the uncured conductive adhesive is discharged from the discharge port 82 and supplied to the object to be coated. In this embodiment, the main component (A) 72 and the curing agent (B) 74 of the conductive adhesive satisfy the viscosity and total volume relationship described above. This is a particularly preferred embodiment because, as in the containment section 10 of this embodiment, the main component (A) 72 and the curing agent (B) 74 are contained in separate syringes 12a and 12b, and the pressing member 40 delivers the main component (A) 72 and the curing agent (B) 74 to the mixing section 80 substantially "simultaneously," resulting in a mixture with high uniformity / homogeny that can be obtained simply and with greater accuracy.

[0052] Here, it is optional whether or not to use the viscoelastic bodies 20a, 20b and plungers 30a, 30b of this embodiment. However, from the viewpoint of accurately transmitting the pressure applied to the pressing member 40 to the four chemical substances in the syringes 12a, 12b through the pistons 42a, 42b, employing the viscoelastic bodies 20a, 20b and plungers 30a, 30b of this embodiment is a preferred configuration.

[0053] Furthermore, it is particularly preferable to use viscoelastic bodies 20a and 20b that have appropriate viscoelastic properties to extrude the relatively high viscosity conductive adhesive without being defeated by its resistance, and to deform according to the shape of the tip of each syringe 12a and 12b, thereby ensuring that the four types of chemical substances are almost completely used up with high accuracy. In addition, from the viewpoint of reliably preventing leakage of the four types of chemical substances from the openings 18a and 18b provided in each syringe 12a and 12b when pressed by the pressing member 40, it is even more preferable to use plungers 30a and 30b that are manufactured using a mold molding machine or the like from a resin material (for example, polyethylene) that has an appropriate shape and airtight function and appropriate rigidity.

[0054] Furthermore, when using the supply device 100, the mixing unit 80 is configured as a lid with inlets 84a and 84b positioned opposite the discharge units 14a and 14b provided in the housing unit 10, as shown in Figure 2, thereby preventing liquid leakage from the inlets. The mixing unit 80 is engaged with an engagement unit 16 having a key-shaped locking mechanism provided at the end of the housing unit 10, and can maintain a state in which the mixing unit 80 (more specifically, the inlets 84a and 84b) can rotate relative to the discharge units 14a and 14b while connected to them. In this embodiment, when the mixing unit 80 is rotated to a predetermined position, the mixing unit 80 locks to the housing unit 10, preventing it from being removed from the housing unit 10. The mixing unit 80 is detachable from the housing unit 10, and can be removed from the housing unit 10 by rotating the mixing unit 80 in the opposite direction to the aforementioned rotation direction.

[0055] When storing the supply device 100 before and after use, as described above, the mixing unit 80 is removed from the housing unit 10, and then, using the key-shaped locking mechanism of the housing unit 10, a stopper 60 is attached, which is not a through-type but has sealing protrusions 52a and 52b, as shown in Figure 5. As a result, the dispensing ports 14a and 14b of each syringe 12a and 12b of the housing unit 10 are sealed using the sealing protrusions 52a and 52b, enabling long-term storage of the conductive adhesive and reuse of the four unused chemical substances.

[0056] To give a typical example, as mentioned above, the fact that the aforementioned conductive adhesive does not substantially harden at the first temperature, which can be considered room temperature, between -20°C and 50°C, and allows for long-term storage or maintenance of adhesive performance for at least one year at temperatures ranging from frozen to around 25°C, and that it can harden at the second temperature, which can be considered low in industries such as electronic component mounting, where leaded or lead-free solder is used for electrical joining, is particularly noteworthy.

[0057] Furthermore, for example, after being stored at room temperature for a certain period of time, the stopper 60 can be replaced with the mixing unit 80 again, and the main component (A) 72 containing the scattered first conductive filler (C1) 72a and the hardener (B) 74 containing the second conductive filler (C2) 74a remaining in the storage unit 10 can be mixed again and used as a conductive adhesive.

[0058] As described above, the conductive adhesive of this embodiment allows for room-temperature curing while providing storage stability, usage stability, workability, and stable high-performance characteristics, and overcomes the limitations imposed by conventional one-component and two-component adhesives.

[0059] [Examples and Comparative Examples] The embodiments described above will be explained in more detail below with reference to examples and comparative examples. However, these examples are illustrative of the embodiments described above and are not limiting to the embodiments described above. The numerical values ​​indicated by "parts" for each component shown in the examples and comparative examples refer to parts by mass.

[0060] (Performance Evaluation) 1. Workability (Handling) The need for weighing and mixing before application, the ease of removing the contents from the container and applying them to the object to be coated, and the homogeneity of the components and performance of the coated material were comprehensively evaluated. ○: No problems ×: Separation and sedimentation occurred during storage, or thorough mixing is required before use, or the viscosity is high and difficult to mix / apply, or homogeneity cannot be guaranteed.

[0061] 2. Conductive adhesive was printed onto a glass plate using a stencil mask approximately 35 mm long, 22 mm wide, and 0.2 mm thick. After sufficient drying or curing at room temperature, the volume resistivity at room temperature was measured using the four-terminal method. ○:10 －４ Lower resistance than Ωcm △: 10 －４ Ωcm~10 －２ Ωcm ×: 10 －２ Higher resistance than Ωcm

[0062] 3. Adhesive aluminum and copper plates were bonded together, coated, and allowed to dry or harden completely at room temperature. The shear bond strength was then measured using an autograph tensile test. ○: Shear bond strength of 3 MPa ×: Shear bond strength of less than 1 MPa, or no adhesion even after being kept at room temperature for one week after bonding.

[0063] 4. After allowing the durable coating to dry or harden completely at room temperature, the coating was evaluated for peeling, detachment, or dissolution by scratching with an iron pen and wiping with a solvent (thinner). ○: No peeling or dissolution occurred. △: Peeling or dissolution occurred. ×: Peeling and dissolution occurred.

[0064] [Example] In this example, 5 parts of liquid bisphenol A type epoxy resin, 5 parts of liquid bisphenol F type, 1 part of unsaturated fatty acid glycidyl ester, 1 part of glycol ether, 30 parts of flake silver powder with an average primary particle size of 10 μm, and 23 parts of spherical silver powder with an average primary particle size of 1.0 μm were used as the main component (corresponding to the example of main component (A)). In addition, 11 parts of amine-based curing agent, 1 part of cationic polymer dispersant, 22 parts of flake silver powder with an average primary particle size of 10 μm, and 10 parts of spherical silver powder with an average primary particle size of 1.0 μm were used as the curing agent (corresponding to the example of curing agent (B)).

[0065] The main agent and hardener described above were mixed together with silver powder in a planetary mixer, and then the silver powder was further dispersed in a nearly uniform manner using a three-roll mixer (hereinafter referred to as the "mixing and dispersion process") to obtain the raw materials for the conductive adhesive.

[0066] The viscosity of the main component obtained after the mixing and dispersion treatment described above was approximately 20 Pa·s, and the viscosity of the curing agent was approximately 30 Pa·s. Furthermore, the main component and the curing agent obtained after the mixing and dispersion treatment were filled into the syringes 12a and 12b of the supply device 100 described in the first embodiment in a mass ratio of 5:4 (volume ratio of approximately 1:1), and used as a supply device 100 for uncured conductive adhesive.

[0067] [Comparative Examples] Conductive paints or adhesives with room-temperature curing properties available on the market were used as comparative examples. <Comparative Example 1> One-component, Chinese-made syringe type <Comparative Example 2> One-component, Japanese-made tube type <Comparative Example 3> Two-component, American-made syringe type

[0068] Table 1 below shows the results of the performance evaluation described above for this embodiment and each comparative example. This embodiment can solve the problems of conventional room-temperature curing conductive adhesives.

[0069]

[0070] The embodiments and examples described above are provided for illustrative purposes only and are not intended to limit the invention. In addition, other modifications within the scope of the invention, including other combinations of the embodiments and examples, are also included in the claims.

[0071] The conductive adhesive supply device of the present invention can be widely applied in various industrial fields.

[0072] 10 Containing section 12a First syringe 12b Second syringe 14a, 14b Discharge section 16 Engaging section 18a, 18b Opening 20a, 20b Viscoelastic body 30a, 30b Plunger 40 Pressing member 42a First piston 42b Second piston 44a, 44b Joint section 46 Connecting section 50 Cover 52a, 52b Sealing protrusion 60 Stopper 72 Main component 72a First conductive filler 74 Hardener 74a Second conductive filler 80 Mixing section 82 Discharge port 84a, 84b Inlet section 100 Conductive adhesive supply device

Claims

1. A conductive adhesive comprising a main component (A) containing a dispersed first conductive filler (C1) together with a plurality of liquid epoxy resins (D) having different molecular structures, a fatty acid-modified epoxy resin (E), and a reactive diluent (H), and a curing agent (B) containing a dispersed second conductive filler (C2), which are supplied to a single mixing section, and the viscosity of the mixture mixed in the mixing section at 25°C is 1,000 mPa·s or more and 1,000,000 mPa·s or less.

2. A conductive adhesive comprising a main component (A) containing a dispersed first conductive filler (C1) along with multiple liquid epoxy resins (D) having different molecular structures, a fatty acid-modified epoxy resin (E), and a reactive diluent (H), and a curing agent (B) containing a dispersed second conductive filler (C2), which are simultaneously supplied to a single mixing section and mixed within the mixing section.

3. The conductive adhesive according to claim 1 or claim 2, wherein the specific gravity of the main component (A) is 0.07 or more and 0.4 or less when the specific gravity of the first conductive filler (C1) is set to 1, and the specific gravity of the curing agent (B) is 0.07 or more and 0.4 or less when the specific gravity of the second conductive filler (C2) is set to 1.

4. The conductive adhesive according to claim 1 or claim 2, wherein the viscosity of the curing agent (B) (excluding the second conductive filler (C2)) at 25°C is 0.5 or more and 3.0 or less, with the viscosity of the main component (A) (excluding the first conductive filler (C1)) at 25°C being set to 1, and the viscosity of the curing agent (B) (excluding the second conductive filler (C2)) at 25°C being 0.5 or more and 3.0 or less, with the viscosity of the main component (A) (containing the dispersed first conductive filler (C1)) at 25°C being set to 1, 5. The conductive adhesive according to claim 1 or claim 2, wherein the total volume of the first conductive filler (C1) and the second conductive filler (C2) is 0.4 or more and 1.5 or less, when the total volume of the main component (A) and the curing agent (B) is 1.

6. The conductive adhesive according to claim 1 or claim 2, wherein the first conductive filler (C1) consists of flake-shaped silver powder and spherical silver powder, and the second conductive filler (C2) consists of the flake-shaped silver powder and the spherical silver powder.

7. The conductive adhesive according to claim 1 or claim 2, wherein the average particle diameter of the primary particles of the first conductive filler (C1) and the second conductive filler (C2) is 0.1 μm or more and 20 μm or less, and the maximum particle diameter of the first conductive filler (C1) and the second conductive filler (C2) is 60 μm or less.

8. The conductive adhesive according to claim 1 or claim 2, wherein the fatty acid-modified epoxy resin (E) is a long-chain unsaturated fatty acid ester having a molecular weight of 400 or more and 1200 or less.

9. The conductive adhesive according to claim 1 or claim 2, wherein the reactive diluent (H) is a glycol ether having a molecular weight of 150 or more and 350 or less.

10. The conductive adhesive according to claim 1 or claim 2, wherein the curing agent (B) comprises an amine-based curing agent (I) and a cationic polymer dispersant (J).

11. The conductive adhesive according to claim 10, wherein the amine-based curing agent (I) is a polyamine having an active hydrogen equivalent of 150 or more and 250 or less.

12. The conductive adhesive according to claim 10, wherein the cationic polymer dispersant (J) is an amine with a molecular weight of 10,000 or more and 30,000 or less.

13. The conductive adhesive according to claim 1, wherein the main component (A) is contained in a first syringe, the curing agent (B) is contained in a second syringe, the first syringe and the second syringe are integrated, the first syringe, the second syringe and the mixing unit are all maintained at a first temperature of -20°C to 50°C, and the adhesive can be cured at a second temperature of 5°C to 100°C.

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