Isocyanate curing agent, conductive silver paste and preparation method

Abstract

The invention provides an isocyanate curing agent, conductive silver paste, a preparation method of the isocyanate curing agent and a preparation method of the conductive silver paste, and relates to the technical field of conductive paste. The preparation method of the isocyanate curing agent comprises the following steps: preparing an isocyanate solution and a sealing agent solution; wherein the sealing agent solution is an imidazole sealing agent solution or an imidazole derivative sealing agent solution, and the molar ratio of hydrogen atoms in secondary amino groups on an imidazole ring to-NCO groups is 1.2-1.5; mixing the isocyanate solution with the sealing agent solution in a solution dropwise adding manner to obtain a mixed solution; and removing the solvent in the mixed solution to obtain the isocyanate curing agent. The storage stability of the conductive silver paste can be improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of conductive pastes, and in particular to an isocyanate curing agent, a conductive silver paste, a method for preparing isocyanate curing, and a method for preparing conductive silver paste. Background Art

[0002] In recent years, low-temperature curing electronic paste has been increasingly valued in the electronics industry. Taking low-temperature curing silver paste as an example, it can be cured in the temperature range of 80°C to 150°C. In the manufacturing process of electronic equipment, this feature can effectively prevent high temperatures from damaging fragile electronic components and plastic parts while ensuring good conductive connection performance. Therefore, low-temperature curing silver paste has been widely used in many fields such as electronic component manufacturing, semiconductor chip packaging, and solar cells.

[0003] Currently, the curing agent contained in the conductive silver paste has poor performance, resulting in the conductive silver paste having poor storage stability.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] The purpose of the present disclosure is to provide an isocyanate curing agent, a conductive silver paste, a preparation method of isocyanate curing, and a preparation method of conductive silver paste, thereby overcoming the problem of poor storage stability of the conductive silver paste at least to a certain extent.

[0006] According to a first aspect of the present disclosure, a method for preparing an isocyanate curing agent is provided, comprising: preparing an isocyanate solution and a blocking agent solution; wherein the blocking agent solution is an imidazole blocking agent solution or an imidazole derivative blocking agent solution, and the molar ratio of the hydrogen atom in the secondary amino group on the imidazole ring to the -NCO group is 1.2 to 1.5; mixing the isocyanate solution and the blocking agent solution by dropwise addition to obtain a mixed solution; and removing the solvent from the mixed solution to obtain the isocyanate curing agent.

[0007] Optionally, the isocyanate solution and the blocking agent solution are mixed by solution dropwise addition to obtain a mixed solution, including: adding the blocking agent solution into a flask, and adding the isocyanate solution into a dropping funnel, and completing the dropwise addition within a predetermined time to obtain an intermediate solution; stirring the intermediate solution at a temperature of 60° C. to 80° C. for 1 h to 2 h to obtain a mixed solution.

[0008] Optionally, the isocyanate in the isocyanate solution is one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and naphthalene diisocyanate.

[0009] Optionally, the blocking agent in the blocking agent solution is one or more of imidazole, dimethylimidazole, diethylimidazole, 2-ethyl-4-methylimidazole, benzimidazole, and nitroimidazole.

[0010] Optionally, the solvent of the isocyanate solution and / or the blocking agent solution is one or more of methanol, ethanol, xylene, acetone, ethyl acetate, chloroform, dimethylformamide, tetrahydrofuran, and chloroform.

[0011] According to a second aspect of the present disclosure, an isocyanate curing agent is provided, wherein the isocyanate curing agent is prepared by any of the above-mentioned methods for preparing the isocyanate curing agent.

[0012] According to a third aspect of the present disclosure, a method for preparing a conductive silver paste is provided, comprising: adding epoxy resin, micron-sized flaky silver powder, nano-sized silver particles, a coupling agent, a dispersant, a thixotropic agent and an isocyanate curing agent into a solvent to obtain a first intermediate paste; wherein the isocyanate curing agent is prepared by any of the above-mentioned methods for preparing the isocyanate curing agent; stirring the first intermediate paste to obtain a second intermediate paste; and grinding the second intermediate paste for 3 to 5 times to obtain a conductive silver paste.

[0013] Optionally, by weight, the solvent is 80 to 110 parts, the epoxy resin is 50 to 80 parts, the micron-sized flaky silver powder is 1000 to 2000 parts, the nano-sized silver particles are 100 to 1000 parts, the coupling agent is 10 to 20 parts, the dispersant is 3 to 10 parts, the thixotropic agent is 2 to 8 parts, and the isocyanate curing agent is 10 to 30 parts.

[0014] Optionally, the epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin.

[0015] In the scheme of the exemplary embodiment of the present disclosure, on the one hand, a blocked isocyanate curing agent is prepared by reacting an imidazole or imidazole derivative blocking agent with an isocyanate, and the nitrogen atom with a lone pair of electrons on the imidazole ring will attack the carbon atom in the isocyanate-NCO group, causing the carbon-nitrogen double bond of the isocyanate group to open, and the nitrogen atom and the carbon atom form a new covalent bond. This covalent bond will break under heating or the action of a catalyst, so that the imidazole-isocyanate structure decomposes, and the imidazole and isocyanate groups will restore the original structure and reactivity. The preparation process conditions of this blocked isocyanate curing agent are mild and easy to control, and it can be stably stored for a long time at room temperature. It can also be directly mixed with an epoxy resin monomer to prepare a single-component epoxy resin, which has high stability during storage and transportation. At the same time, this curing agent can be quickly unblocked at the unblocking temperature to release the active isocyanate group, and efficiently cross-linked and cured with the epoxy resin. On the other hand, the conductive silver paste prepared by the present disclosure of the epoxy resin-blocked isocyanate system has excellent conductivity and storage stability. The synergistic effect of micron-sized flaky silver powder and nano-silver particles can ensure that the cured silver paste forms a more dense and uniform conductive network and obtains high conductivity. The use of blocked isocyanate curing agent effectively avoids the premature reaction of the curing agent and epoxy resin, so the paste has stable rheological properties and printing properties.

[0016] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0018] Figure 1 A flow chart of a method for preparing an isocyanate curing agent according to an exemplary embodiment of the present disclosure is schematically shown.

[0019] Figure 2 A flow chart of a method for preparing a conductive silver paste according to an exemplary embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0020] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the example embodiments are fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or other methods, processes, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0021] In addition, the accompanying drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated descriptions will be omitted. The flowcharts shown in the accompanying drawings are only exemplary illustrations and do not necessarily include all the steps. For example, some steps can also be decomposed, while some steps can be combined or partially combined, so the actual execution order may change according to actual conditions. In addition, all the terms "first", "second", etc. below are only for the purpose of distinction and should not be used as limitations of the present disclosure.

[0022] Epoxy resin is the most commonly used organic binder in low-temperature curing electronic paste. Low-temperature curing conductive silver paste of epoxy resin system has good conductivity and adhesion. Commonly used curing agents include amine curing agents and acid anhydride curing agents. Amine curing agents have high reactivity and can undergo a slow curing reaction with epoxy resin at room temperature, resulting in poor storage stability of the paste. Acid anhydride curing agents have low toxicity and good heat resistance, but the curing speed is relatively slow, which limits its application range. In order to obtain higher storage stability and faster curing speed, it is very important to optimize the existing low-temperature curing agent system of epoxy resin.

[0023] Isocyanate is a class of organic compounds containing -NCO functional groups. -NCO groups have high reactivity and can undergo addition reactions with hydroxyl groups in epoxy resins to achieve curing and crosslinking. The activity of the -NCO group can be temporarily blocked by reacting isocyanate with specific blocking agents (such as ethanol, propanol, phenol, etc.). In application, the blocked product only needs to be heated to a specific temperature to decompose and release the -NCO group to participate in subsequent reactions. Blocked isocyanate curing agents can be directly mixed with epoxy resins to form slurry, which can be stored for a long time in an environment below the unblocking temperature and has stable rheological and chemical properties. At the same time, the selection of isocyanate blocking agents plays a crucial role in the unblocking temperature and reactivity.

[0024] In order to at least improve the performance of the curing agent to improve the storage stability of the conductive silver paste, the present disclosure provides a novel preparation scheme of an isocyanate curing agent.

[0025] Figure 1 The flowchart of the method for preparing the isocyanate curing agent according to the exemplary embodiment of the present disclosure is schematically shown. Figure 1 The preparation method of the isocyanate curing agent according to the embodiment of the present disclosure comprises the following steps:

[0026] S12. Prepare an isocyanate solution and a blocking agent solution; wherein the blocking agent solution is an imidazole blocking agent solution or an imidazole derivative blocking agent solution, and the molar ratio of the hydrogen atom in the secondary amino group on the imidazole ring to the -NCO group is 1.2 to 1.5.

[0027] According to some embodiments of the present disclosure, for the isocyanate solution, the isocyanate may be one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and naphthalene diisocyanate (NDI). The solvent may be one or more of methanol, ethanol, xylene, acetone, ethyl acetate, chloroform, dimethylformamide, tetrahydrofuran, and chloroform.

[0028] The blocking agent solution may be an imidazole blocking agent solution or an imidazole derivative blocking agent solution. Specifically, the blocking agent in the blocking agent solution is one or more of imidazole, dimethylimidazole, diethylimidazole, 2-ethyl-4-methylimidazole, benzimidazole, and nitroimidazole. The solvent may be one or more of methanol, ethanol, xylene, acetone, ethyl acetate, chloroform, dimethylformamide, tetrahydrofuran, and chloroform.

[0029] It should be understood that the solvents used in the isocyanate solution and the blocking agent solution may be the same or different, and the present disclosure does not impose any limitation on this.

[0030] In an exemplary embodiment of the present disclosure, the molar ratio of hydrogen atoms in the secondary amino group on the imidazole ring to -NCO groups is controlled to be 1.2 to 1.5, thereby ensuring that all -NCO groups undergo addition reaction.

[0031] S14. Mix the isocyanate solution and the blocking agent solution by adding the solution dropwise to obtain a mixed solution.

[0032] According to some embodiments of the present disclosure, first, the blocking agent solution can be added to a flask, and the isocyanate solution can be added to a dropping funnel, and the addition can be completed within a predetermined time to obtain an intermediate solution. Specifically, the addition time can be controlled to regulate the reaction rate, and the predetermined time can be controlled to be 1 hour to 1.5 hours.

[0033] Next, the intermediate solution may be stirred at a temperature of 60° C. to 80° C. for 1 h to 2 h to obtain a mixed solution.

[0034] According to other embodiments of the present disclosure, first, the isocyanate solution can be added to a flask, and the blocking agent solution can be added to a dropping funnel, and the addition can be completed within a predetermined time to obtain an intermediate solution. Specifically, the addition time can be controlled to regulate the reaction rate, and the predetermined time can be controlled to be 1 hour to 1.5 hours.

[0035] Next, the intermediate solution may be stirred at a temperature of 60° C. to 80° C. for 1 h to 2 h to obtain a mixed solution.

[0036] S16. removing the solvent from the mixed solution to obtain an isocyanate curing agent.

[0037] According to some embodiments of the present disclosure, a rotary evaporator may be used to remove the solvent in the mixed solution. However, the present disclosure is not limited thereto, and the solvent may also be removed by heating, drying, or the like.

[0038] The blocked isocyanate curing agent is prepared by reacting imidazole or imidazole derivative blocking agent with isocyanate. The nitrogen atom with lone pair of electrons on the imidazole ring will attack the carbon atom in the isocyanate-NCO group, causing the carbon-nitrogen double bond of the isocyanate group to open, and the nitrogen atom and the carbon atom to form a new covalent bond. This covalent bond will break under heating or catalyst action, causing the imidazole-isocyanate structure to decompose, and the imidazole and isocyanate groups will restore their original structure and reactivity. The preparation process conditions of this blocked isocyanate curing agent are mild and easy to control, and it can be stably stored for a long time at room temperature. It can also be directly mixed with epoxy resin monomers to prepare single-component epoxy resins, which have high stability during storage and transportation. At the same time, this curing agent can be quickly unblocked at the unblocking temperature to release active isocyanate groups, and efficiently cross-link and cure with epoxy resins.

[0039] Furthermore, the embodiment of the present disclosure also provides an isocyanate curing agent, which is prepared by the method of the above steps S12 to S16.

[0040] Furthermore, the embodiments of the present disclosure also provide a method for preparing a conductive silver paste.

[0041] Figure 2 The flowchart of the method for preparing the conductive silver paste according to the exemplary embodiment of the present disclosure is schematically shown. Figure 2 The method for preparing the conductive silver paste according to the embodiment of the present disclosure comprises the following steps:

[0042] S22. Add epoxy resin, micron-sized flaky silver powder, nano-sized silver particles, coupling agent, dispersant, thixotropic agent and isocyanate curing agent into the solvent to obtain a first intermediate slurry.

[0043] The isocyanate curing agent is prepared by the method of steps S12 to S16 above.

[0044] The epoxy resin may be one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin.

[0045] The present disclosure does not limit the coupling agent, dispersant and thixotropic agent. For example, the coupling agent may be KH-550, KH-560, KH-570, etc., the dispersant may be BYK-111, Span-85, Tego Dispers-655, etc., and the thixotropic agent may be polyamide wax, hydrogenated castor oil, BYK-405, BYK-410, etc.

[0046] In addition, the solvent in step S22 may be, for example, a diethylene glycol butyl ether solvent, but the present disclosure is not limited thereto, and the solvent may also be methanol, ethanol, xylene, acetone, ethyl acetate, and the like.

[0047] Specifically, by weight, the solvent is 80 to 110 parts, the epoxy resin is 50 to 80 parts, the micron-sized flaky silver powder is 1000 to 2000 parts, the nano-sized silver particles are 100 to 1000 parts, the coupling agent is 10 to 20 parts, the dispersant is 3 to 10 parts, the thixotropic agent is 2 to 8 parts, and the isocyanate curing agent is 10 to 30 parts.

[0048] S24. Stir the first intermediate slurry to obtain a second intermediate slurry.

[0049] The present disclosure does not limit the stirring method of the first intermediate slurry. For example, a planetary mixer may be used to stir the first intermediate slurry for 30 to 60 minutes to fully mix the above substances.

[0050] S26. Grind the second intermediate slurry 3 to 5 times to obtain a conductive silver paste.

[0051] The present disclosure does not limit the grinding method of the second intermediate slurry. For example, the second intermediate slurry can be added to a three-roll grinder and ground for 3 to 5 times to obtain the conductive silver paste.

[0052] The conductive silver paste of the epoxy resin-blocked isocyanate system prepared by the present invention has excellent conductive properties and storage stability. The synergistic effect of the micron-sized flaky silver powder and the nano silver particles can ensure that the silver paste after curing forms a more dense and uniform conductive network to obtain high conductivity. The use of a blocked isocyanate curing agent effectively avoids the premature reaction of the curing agent and the epoxy resin, so the paste has stable rheological properties and printing properties.

[0053] Furthermore, the embodiment of the present disclosure also provides a conductive silver paste, which is prepared by the method of the above steps S22 to S26.

[0054] The preparation scheme of the conductive silver paste disclosed in the present invention is described below through examples.

[0055] Example 1

[0056] First, 50 ml of a 1.0 mol / L hexamethylene diisocyanate acetone solution and 50 ml of a 2.4 mol / L dimethylimidazole chloroform solution were prepared. The two were mixed by dropwise addition of the solution to obtain an intermediate solution. During the dropwise addition of the solution, the dropwise addition speed was controlled and the dropwise addition was completed in about 1 h to avoid a violent reaction.

[0057] Next, the intermediate solution was magnetically stirred for 2 hours, and the reaction temperature was controlled at 60° C. After the reaction was completed, the solvent was removed by a rotary evaporator to obtain a solid powder, which was a blocked hexamethylene diisocyanate curing agent.

[0058] Then, 60 parts of bisphenol A epoxy resin, 20 parts of the above-mentioned blocked hexamethylene diisocyanate curing agent, 1500 parts of micron-grade flaky silver powder, 500 parts of nano silver particles, 10 parts of silane coupling agent KH-550, 5 parts of BYK-111, and 4 parts of polyamide wax were added to 100 parts of diethylene glycol butyl ether solvent by weight, and mixed for 30 minutes using a planetary mixer. The mixed slurry was added to a three-roll mill and ground for 3 times to finally obtain a conductive silver paste.

[0059] Example 2

[0060] The preparation steps are the same as those in Example 1, except that 50 ml of a 1.0 mol / L tetrahydrofuran solution of toluene diisocyanate and 50 ml of a 2.4 mol / L trichloroethanol solution of 2-ethyl-4-methylimidazole are used to prepare the isocyanate curing agent, and the reaction temperature is controlled at 70°C.

[0061] Example 3

[0062] The preparation steps are the same as those in Example 1, except that 50 ml of a 0.8 ml / L methanol solution of diphenylmethane diisocyanate and 50 ml of a 2.4 mol / L ethanol solution of diethylimidazole are used to prepare the isocyanate curing agent, and the reaction temperature is controlled at 80°C.

[0063] Table 1 shows the differences in raw materials and preparation conditions used in preparing isocyanate curing agents among Example 1, Example 2 and Example 3.

[0064] Table 1

[0065]

[0066] The conductive silver pastes prepared in Example 1, Example 2, and Example 3 can all be stored at 0°C to 5°C, and the viscosity change of the paste during a storage period of 0 to 6 months is tested. At the same time, the square resistance of the cured film tape after the paste is dried at 90°C for 30 minutes is tested. All tests are performed in accordance with the non-ferrous metal industry standard YS / T606-2006 "Curing Silver Conductive Paste".

[0067] Table 2 shows the test results, where @ means under certain conditions, for example, @5rpm means that the viscosity test is carried out under the condition of a rotation speed of 5rpm, and @25μm means that the slurry is tested for square resistance under the condition of a thickness of 25μm.

[0068] Table 2

[0069]

[0070] It can be seen from Table 2 that the conductive silver paste prepared by Examples 1 to 3 of the present disclosure exhibits good storage stability and conductivity over time.

[0071] In summary, the embodiments of the present disclosure can prepare a storage-resistant low-temperature curing conductive silver paste. First, a blocked isocyanate curing agent is prepared by reacting a blocking agent containing an imidazole group with an isocyanate. The selection of the blocking agent and the isocyanate is based on whether the product after the addition reaction has a more stable chemical bond and a lower steric hindrance. Both factors are conducive to increasing the unblocking temperature of the product. Compared with common amine and anhydride epoxy resin low-temperature curing agents, the blocked isocyanate curing agent has higher chemical stability at room temperature, and the conductive silver paste prepared after mixing with epoxy resin and silver powder has excellent storage stability. During long-term storage, the silver paste can not only maintain a relatively stable viscosity, but also has a smaller decrease in conductivity. This storage-resistant characteristic greatly reduces the risk of performance degradation due to environmental factors and time factors, and provides convenience for the production and application of silver paste.

[0072] It should be noted that although the steps of the method in the present disclosure are described in a specific order in the drawings, this does not require or imply that the steps must be performed in this specific order, or that all the steps shown must be performed to achieve the desired results. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step, and / or one step may be decomposed into multiple steps, etc.

[0073] In addition, the above-mentioned figures are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present disclosure, and are not intended to be limiting. It is easy to understand that the processes shown in the above-mentioned figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0074] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing what is disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary technical means in the art that are not disclosed in the present disclosure. The specification and embodiments are to be considered merely as exemplary, and the true scope and spirit of the present disclosure are indicated by the claims.

[0075] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for preparing an isocyanate curing agent, characterized in that: include: Prepare an isocyanate solution and a blocking agent solution; wherein the blocking agent solution is an imidazole blocking agent solution or an imidazole derivative blocking agent solution, and the molar ratio of the hydrogen atom in the secondary amino group on the imidazole ring to the -NCO group is 1.2 to 1.5; Mixing the isocyanate solution and the blocking agent solution by solution dropwise addition to obtain a mixed solution; The solvent in the mixed solution is removed to obtain an isocyanate curing agent.

2. The preparation method according to claim 1, characterized in that: The isocyanate solution and the blocking agent solution are mixed by solution dropwise addition to obtain a mixed solution, comprising: Add the blocking agent solution into a flask, and add the isocyanate solution into a dropping funnel, and complete the addition within a predetermined time to obtain an intermediate solution; The intermediate solution is stirred at 60° C. to 80° C. for 1 h to 2 h to obtain a mixed solution.

3. The preparation method according to claim 1, characterized in that: The isocyanate in the isocyanate solution is one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and naphthalene diisocyanate.

4. The preparation method according to claim 1, characterized in that: The blocking agent in the blocking agent solution is one or more of imidazole, dimethylimidazole, diethylimidazole, 2-ethyl-4-methylimidazole, benzimidazole, and nitroimidazole.

5. The preparation method according to claim 3 or 4, characterized in that: The solvent of the isocyanate solution and / or the blocking agent solution is one or more of methanol, ethanol, xylene, acetone, ethyl acetate, chloroform, dimethylformamide, tetrahydrofuran, and chloroform.

6. An isocyanate curing agent, characterized in that The isocyanate curing agent is prepared by the preparation method of any one of claims 1 to 5.

7. A method for preparing a conductive silver paste, characterized in that: include: Adding epoxy resin, micron-sized flaky silver powder, nano-sized silver particles, coupling agent, dispersant, thixotropic agent and isocyanate curing agent into a solvent to obtain a first intermediate slurry; wherein the isocyanate curing agent is prepared by the preparation method of the isocyanate curing agent according to any one of claims 1 to 5; Stirring the first intermediate slurry to obtain a second intermediate slurry; The second intermediate slurry is ground 3 to 5 times to obtain a conductive silver paste.

8. The preparation method according to claim 7, characterized in that: In parts by weight, the solvent is 80 to 110 parts, the epoxy resin is 50 to 80 parts, the micron-sized flaky silver powder is 1000 to 2000 parts, the nano-sized silver particles are 100 to 1000 parts, the coupling agent is 10 to 20 parts, the dispersant is 3 to 10 parts, the thixotropic agent is 2 to 8 parts, and the isocyanate curing agent is 10 to 30 parts.

9. The preparation method according to claim 7 or 8, characterized in that: The epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin and bisphenol S epoxy resin.

10. A conductive silver paste, characterized in that: The conductive silver paste is prepared by the preparation method of any one of claims 7 to 9.

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