Method for preparing particle-free silver ink by reducing silver acetate with formic acid

Abstract

The invention provides a method for preparing particle-free silver ink by reducing silver acetate through formic acid. Raw materials adopted by the method comprise a silver precursor, a complexing agent, a solvent, a reducing agent and an auxiliary. The viscosity of the produced particle-free silver ink can adapt to all printers adopting an ink jet technology in the market. The adhesive has good adhesion performance on all printing substrates, and after low-temperature sintering, no effective material layer falls off within the application range through a bending test on the substrate. The ink has a good printing effect, and is free of excessive dispersion, annular cavities and conductive layer circuit disconnection phenomena after sintering.

Description

Technical Field

[0001] The invention relates to the preparation and production of conductive particle-free silver ink, and in particular to a preparation method for preparing a silver precursor by reducing silver acetate with formic acid. Background Art

[0002] Conductive particle-free silver ink (also known as nanosilver conductive ink) exhibits significant advantages in high-precision electronic printing, optoelectronics, and specialty applications due to its unique particle-free properties. Key advantages include: After sintering at relatively low temperatures (100-120°C), it forms effective microcircuits with strong adhesion, low resistance, high conductivity, and resistance to detachment of active ingredients. The specific content of the silver precursor can be flexibly adjusted to achieve varying degrees of conductive properties for different application scenarios.

[0003] The basic manufacturing process for existing silver conductive inks is based on a silver precursor, a complexing agent, a solvent, and additives. This process involves using a strong acid to produce a weak acid, and a strong base to produce a weak base, to convert the ionic silver in the silver salt into free elemental silver (or a readily decomposable silver salt). The addition of additives such as dispersants, surfactants, and stabilizers prevents premature aggregation of the elemental silver before sintering and reduction, resulting in a stable, particle-free ink in solution.

[0004] However, while existing processes can achieve normal inkjet printing and form circuits after sintering, if silver is directly reduced during the production process, it can even cause visible stratification, or microscopic aggregation (or sedimentation) of the silver element, especially after 20-30 days of storage. Furthermore, during the preparation of the silver precursor, there is a risk of excessive impurity groups, leading to a decrease in the overall stability of the solution.

[0005] On the other hand, in the current mainstream conductive silver ink, if the content of silver precursor in the overall composition is less than 10%, it is easy to cause spot-like vacancies during the sintering process after inkjet printing due to the evaporation of solvent or water in the ink, or large-scale conductive silver ink can be produced by reducing silver acetate with formic acid.

[0006] Particle-free silver ink method

[0007] Effective silver circuit disconnection phenomenon. Most silver inks use organic alcohol solvents, which often have a lower boiling point than water, making it difficult to separate the water molecules in the ink. Summary of the Invention

[0008] The object of the present invention is to provide a method for preparing a particle-free silver ink by reducing silver acetate with formic acid, characterized in that:

[0009] The raw materials used include:

[0010]

[0011] The silver precursor is silver acetate;

[0012] The complexing agent is one or a mixture of several selected from ethylenediamine, triethanolamine, propanolamine, and isopropanolamine;

[0013] The reducing agent is formic acid;

[0014] The solvent is selected from one or a mixture of several of liquid alcohol compounds, ether compounds, and aldehyde compounds;

[0015] The auxiliary agent is an ethanol solution of a dispersant, ethylene glycol, or an ethanol solution of a surfactant.

[0016] The preparation includes the following steps:

[0017] (1) Weigh the corresponding raw materials according to the raw material ratio;

[0018] (2) Add the complexing agent and part of the solvent to the reaction vessel and stir to ensure the mixing of the complexing agent and the solvent;

[0019] (3) Add a sufficient amount of the silver precursor to the mixture obtained in step (2);

[0020] (4) After the silver precursor is completely dissolved, add the auxiliary agent solution dropwise into the reaction mixture system;

[0021] (5) After all the auxiliary agents are added, add the reducing agent dropwise to the mixing system;

[0022] (6) Add the remaining part of the solvent to the reaction system;

[0023] (7) Continuously stir the mixing system and then filter to obtain particle-free silver ink.

[0024] Furthermore, in the auxiliary agent:

[0025] The dispersant is selected from one or a mixture of several of polyvinylpyrrolidone, polyvinyl alcohol, polyacrylic acid, and lecithin;

[0026] The surfactant is selected from one of PVP, ammonium polyacrylate, polymethacrylic acid, ammonium citrate, polyethylene glycol, or polyvinyl alcohol.

[0027] The ratio of the dispersant to the surfactant is 1:1

[0028] All the ethanol solution auxiliary agents need to be prepared into saturated or unsaturated ethanol solutions with solvent ethanol before being added to the reaction vessel.

[0029] Further, in step (2), the stirring temperature is 2 - 5°C, the stirring speed is 200 rpm, and after 10 minutes, it is increased to 1000 rpm.

[0030] Further, in step (3), when adding the silver precursor to the mixed system, it is added in sufficient batches.

[0031] Further, in step (4), when dropping the additive solution, the silver precursor has been completely dissolved, the dropping speed is 1 drop / second, and each drop is about 0.03 - 0.05 mL.

[0032] Further, in step (5), the dropping speed of the reducing agent is 1 drop / 10 seconds, and each drop is about 0.03 - 0.05 mL.

[0033] Further, the mass ratio of the solvent added in step (2) to the solvent added in step (6) is 1∶1.1 - 1.3.

[0034] Further, in step (7), the stirring time is 30 - 90 min; filtration is carried out using a microporous membrane (22 nm organic microporous filter).

[0035] A method for preparing -3-

[0036] particle-free silver ink using formic acid to reduce silver acetate

[0037] The present invention also claims the particle-free silver ink obtained by the above method. The particle-free silver ink is a light yellow transparent solution. After experiments, the particle-free silver ink does not contain any visible particles to the naked eye, and can be stored for 6 months without any color change and precipitation of silver particles under low temperature and light-proof environment. The viscosity of the particle-free silver ink is 3 - 800 mPa·s, the contact angle is 15 - 70°, and the surface tension is 25 - 65 mN / m.

[0038] The beneficial effects of a particle-free silver ink and its preparation method of the present invention compared with the prior art are as follows:

[0039] 1. The viscosity of the produced particle-free silver ink can adapt to all printers using inkjet technology on the market.

[0040] 2. The ink can be applied to most printing substrates on the market and has good adhesion performance on all available printing substrates. After low-temperature sintering, the substrate is bent and tested for 1H for a total of 6000 times, and no effective material layer falls off.

[0041] 3. No harmful gases and environmental pollution gases are generated under low-temperature sintering.

[0042] 4. The generated conductive circuit has good conductivity, and the conductivity can reach 2*103 - 6*103 μS / cm.

[0043] 5. The ink has good printing effect, without excessive dispersion, annular voids and disconnection of the conductive layer circuit after sintering. Description of the Drawings

[0044] Figure 1 Comparison of the printing effects of the ink produced in Example 1 with other inks of the same type on the market on the same substrate. (The right side is the particle-free silver ink produced in the example)

[0045] Figure 2 Comparison of the printing effects of the ink produced in Example 2 with other inks of the same type on the market on the same substrate. (The right side is the particle-free silver ink produced in the example). Detailed Implementation Modes

[0046] The present invention will be further described below in conjunction with embodiments, but it should not be understood that the above-mentioned subject scope of the present invention is limited to the following embodiments. Without departing from the above technical idea of the present invention, various substitutions and changes made according to the common general knowledge and conventional means in the art should be included in the protection scope of the present invention.

[0047] Method for preparing particle-free silver ink

[0048] Under the following embodiments, a Shanghai Zhongbin Technology Co., Ltd. CCIPHS-3DW intelligent desktop laboratory pH meter is used to measure the pH value range of the particle-free silver ink, a Shanghai Zhongbin Technology Co., Ltd. T series touch screen viscometer is used to test the viscosity of the particle-free silver ink, a Shanghai Zhongbin Technology Co., Ltd. CCIDD-810D Chinese desktop conductivity meter is used to test the conductivity of the ink, and a Shanghai Zhongbin Technology Co., Ltd. CCIST-2665 type four-probe sheet resistance resistivity tester is used to test the resistance and sheet resistance of the conductive circuit after printing and sintering.

[0049] Under the following embodiments, a Shanghai Zhongbin Technology Co., Ltd. CCIPHS-3DW intelligent desktop laboratory pH meter is used to measure the pH value range of the particle-free silver ink, a Shanghai Zhongbin Technology Co., Ltd. T series touch screen viscometer is used to test the viscosity of the particle-free silver ink, a Shanghai Zhongbin Technology Co., Ltd. CCIDD-810D Chinese desktop conductivity meter is used to test the conductivity of the ink, and a Shanghai Zhongbin Technology Co., Ltd. CCIST-2665 type four-probe sheet resistance resistivity tester is used to test the resistance and sheet resistance of the conductive circuit after printing and sintering.

[0050] Example 1

[0051] A particle-free silver ink, the main raw materials are silver acetate, isopropanolamine, absolute ethanol, formic acid, FS8500 surfactant, ethylene glycol and polyvinylpyrrolidone.

[0052] The specific mass ratio of each component is:

[0053] Silver precursor - silver acetate: 12.55%

[0054] Complexing agent - isopropanolamine: 22%

[0055] Solvent - absolute ethanol: 30%

[0056] Reducing agent - formic acid: 35%

[0057] Auxiliary agent - FS8500 surfactant (ethanol solution): 0.15%; Ethylene glycol: 0.15%; Polyvinylpyrrolidone (ethanol solution): 0.15%.

[0058] A preparation method of particle - free silver ink specifically includes the following steps:

[0059] (1) Connect and start all the instruments required for the reaction environment to ensure that the reaction environment meets the standards;

[0060] (2) Use solvent ethanol to prepare the corresponding auxiliary agents into corresponding ethanol solutions;

[0061] (3) Mix a part of absolute ethanol and isopropanolamine as the base liquid;

[0062] (4) Add sufficient silver acetate into the base liquid in batches. After mixing evenly, add various auxiliary agents at a speed of 1 drop / second;

[0063] A method for preparing - 5 - particle - free silver ink by reducing silver acetate with formic acid

[0064] particle - free silver ink

[0065] (5) After the auxiliary agents are well - dispersed, add formic acid at a strictly controlled speed of 1 drop / 10 seconds. After the dropping is completed, supplement the absolute ethanol in the remaining amount used in steps 2 and 3 to the system (note: in steps 2 and 3, just add ethanol to dissolve the complexing agent and auxiliary agents);

[0066] (6) After maintaining stirring for 60 min, filter with a 22 - nm organic filter to obtain particle - free silver ink.

[0067] The control of the above - mentioned entire reaction process is at 2 - 5°C.

[0068] The obtained particle - free silver ink is a light - yellow transparent solution, does not contain any visible particles to the naked eye, and can be stored for 6 months without discoloration, precipitation, or stratification under low - temperature and light - avoiding conditions. The overall viscosity of the ink is 4.5 mPa·S, pH value: 9.7, conductivity: 2.479×10 3 μS / cm, and the sheet resistance of the conductive circuit formed after printing: 8.24 Ω / □.

[0069] The printing effect is good during on - machine testing. After sintering, the adhesion performance of the ink is tested. It can be bent 6000 times in 60 minutes without any effective material falling off.

[0070] Example 2

[0071] A particle - free silver ink is prepared from silver acetate, isopropanolamine, absolute ethanol, formic acid, FS8500 surfactant, ethylene glycol, and polyvinylpyrrolidone as the main raw materials.

[0072] The mass percentage of each specific component is as follows:

[0073] Silver precursor - silver acetate: 13.5%

[0074] Complexing agent - isopropanolamine: 21.5%

[0075] Solvent - absolute ethanol: 30%

[0076] Reducing agent - formic acid: 34.55%

[0077] Auxiliary agent - FS8500 surfactant (ethanol solution): 0.15%, ethylene glycol: 0.15%, polyvinylpyrrolidone (ethanol solution): 0.15%.

[0078] A method for preparing a particle-free silver ink specifically includes the following steps:

[0079] (1) Connect and start all the instruments required for the reaction environment, and ensure that the reaction environment reaches a standard for preparing particle-free silver ink by reducing silver acetate with formic acid -

[0080] method

[0081] standard

[0082] (2) Using the solvent ethanol, prepare the corresponding auxiliary agents into the corresponding ethanol solutions;

[0083] (3) Mix a part of absolute ethanol and isopropanolamine as the base liquid;

[0084] (4) Add a sufficient amount of silver acetate into the base liquid in batches. After mixing evenly, add each auxiliary agent at a rate of 1 drop / second;

[0085] (5) After the auxiliary agents are well dispersed, add formic acid at a strictly controlled rate of 1 drop / 10 seconds. After the dropping is completed, add the remaining amount of absolute ethanol used in steps 2 and 3 to the system (Note: In steps 2 and 3, only add ethanol to dissolve the complexing agent and auxiliary agents);

[0086] (6) After maintaining stirring for 60 minutes, filter using a 22 nm organic filter to obtain the particle-free silver ink.

[0087] The control of the above entire reaction process is at 2 - 5 °C.

[0088] The obtained particle-free silver ink is a light yellow transparent solution, does not contain any visible particles to the naked eye, and can be stored for 6 months without discoloration, precipitation, or stratification under low temperature and light-proof conditions. The overall viscosity of the ink is 5.27 mPa·S, pH value: 9.0, conductivity: 4.015*10 3μS / cm, sheet resistance of the formed conductive circuit after printing: 2.01 Ω / sq.

Claims

1. A method for preparing particle-free silver ink by reducing silver acetate with formic acid, characterized in that: The raw materials used include: The silver precursor is silver acetate; The complexing agent is one or a mixture of several selected from ethylenediamine, triethanolamine, propanolamine, and isopropanolamine; The reducing agent is formic acid; The solvent is selected from one or a mixture of several of liquid alcohol, ether, and aldehyde compounds; The auxiliary agent is an ethanol solution of a dispersant, ethylene glycol, or an ethanol solution of a surfactant. The preparation includes the following steps: (1) Weigh the corresponding raw materials according to the raw material ratio; (2) Add the complexing agent and part of the solvent to the reaction vessel and stir to ensure the mixing of the complexing agent and the solvent; (3) Add a sufficient amount of silver precursor to the mixture obtained in step (2); (4) After the silver precursor is completely dissolved, add the auxiliary agent solution dropwise into the reaction mixture system; (5) After all the auxiliary agents are added, add the reducing agent dropwise to the mixing system; (6) Add the remaining part of the solvent to the reaction system; (7) Continuously stir the mixing system and then filter to obtain particle-free silver ink.

2. The method for preparing particle-free silver ink by reducing silver acetate with formic acid according to claim 1, characterized in that: Among the auxiliary agents: The dispersant is selected from one or a mixture of several of polyvinylpyrrolidone, polyvinyl alcohol, polyacrylic acid, and lecithin; The surfactant is selected from one of PVP, ammonium polyacrylate, polymethacrylic acid, ammonium citrate, polyethylene glycol, or polyvinyl alcohol. The ratio of the dispersant to the surfactant is 1:0.75 - 1.25 All the ethanol solution auxiliary agents should be prepared into saturated or unsaturated ethanol solutions with solvent ethanol before being added to the reaction vessel.

3. The method for preparing particle-free silver ink by reducing silver acetate with formic acid according to claim 1, characterized in that: In step (2), the stirring temperature is 2 - 5°C, the stirring speed is 200 rpm, and it is increased to 1000 rpm after 10 minutes. The stirring speed in steps (4) and (5) is in the range of 1100 - 1400 rpm.

4. A method for preparing particle-free silver ink by reducing silver acetate with formic acid according to claim 1, characterized in that: In step (3), when adding the silver precursor to the mixing system, add a sufficient amount.

5. A method for preparing particle-free silver ink by reducing silver acetate with formic acid according to claim 1, characterized in that: In step (4), when adding the auxiliary agent solution dropwise, the silver precursor has been completely dissolved, the dropping speed is 1 drop / second, and each drop is about 0.03 - 0.05 mL 6. A method for preparing particle-free silver ink by reducing silver acetate with formic acid according to claim 1, characterized in that: In step (5), the dropping speed of the reducing agent is 1 drop / 10 seconds.

7. A method for preparing particle-free silver ink by reducing silver acetate with formic acid according to claim 1, characterized in that: The mass ratio of the solvent added in step (2) to the solvent added in step (6) is 1:1.1 - 1.3 8. A method for preparing particle-free silver ink by reducing silver acetate with formic acid according to claim 1, characterized in that: In step (7), the stirring time is 30 - 90 min; filtration is carried out using a microporous filter membrane.

9. A particle-free silver ink obtained by the method according to claims 1 - 8.

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