阅读说明：本技术 一种用于柔性印刷电子的导电油墨及声化学合成方法 (Conductive ink for flexible printed electronics and phonochemical synthesis method ) 是由 计红军 张文武 修子进 马秋晨 曹依琛 潘浩 张琳 李明雨 于 2020-05-09 设计创作，主要内容包括：本发明公开了一种用于柔性印刷电子的导电油墨及声化学合成方法,该制备方法包括：首先,利用高强度超声场来高效获得铜纳米颗粒前驱体,然后利用低能量均匀分散的超声场来实现银置换铜原子的过程,从而得到银包铜纳米颗粒分散液；其次,从银包铜纳米颗粒分散液分离得到纯净抗氧化银包铜纳米颗粒,重复洗涤后加入各种有机溶剂混合得到纳米银包铜导电油墨。该导电油墨的制备方法操作简单、效率高、产率高、环境友好、成本低廉,且适用于大规模生产,并克服了成本高昂的纳米银油墨和易氧化的纳米铜油墨的缺点,在柔性印刷电子领域中有着广泛的应用前景。(The invention discloses a conductive ink for flexible printing electronics and a sonochemical synthesis method, wherein the preparation method comprises the following steps: firstly, a copper nanoparticle precursor is efficiently obtained by using a high-intensity ultrasonic field, and then the process of replacing copper atoms by silver is realized by using a low-energy uniformly-dispersed ultrasonic field, so that a silver-coated copper nanoparticle dispersion liquid is obtained; and secondly, separating the silver-coated copper nanoparticle dispersion liquid to obtain pure antioxidant silver-coated copper nanoparticles, repeatedly washing, and adding various organic solvents to mix to obtain the nano silver-coated copper conductive ink. The preparation method of the conductive ink is simple to operate, high in efficiency, high in yield, environment-friendly, low in cost and suitable for large-scale production, overcomes the defects of high-cost nano silver ink and easily-oxidized nano copper ink, and has a wide application prospect in the field of flexible printed electronics.)

1. A sonochemical synthesis method of conductive ink for flexible printed electronics, characterized in that:

step one, preparing copper nanoparticles: preparing copper nanoparticles under the action of ultrasonic sonochemistry by adopting a mixture of a copper source, a reducing agent, a dispersing agent and one or more solvents;

step two, preparing silver-coated copper nanoparticles: mixing the obtained copper nanoparticles, a silver source, a reducing agent, a dispersing agent and one or more solvents, quickly synthesizing silver-coated copper nanoparticle dispersion liquid under the efficient action of ultrasonic sonochemistry, separating the silver-coated copper nanoparticles from the silver-coated copper nanoparticle dispersion liquid, and washing to obtain pure antioxidant silver-coated copper nanoparticles;

step three, preparing the conductive ink: and adding a proper amount of various organic solvents, and uniformly mixing to obtain the nano silver-coated copper conductive ink.

2. The sonochemical synthesis method of the conductive ink for the flexible printed electronics as claimed in claim 1, wherein the copper nanoparticles are prepared by adding a copper source into a solvent A according to a ratio of 0.1-1 mol/L, stirring uniformly, heating to 60-160 ℃ to obtain a solution a, adding a reducing agent into the solvent A according to a ratio of 0.1-1 mol/L, adding a certain amount of a dispersing agent, stirring uniformly to obtain a solution b, placing the solution b in a customized ultrasonic device at 60-160 ℃, rapidly dissolving the solution b according to preset ultrasonic parameters, after the solution b is mixed uniformly, rapidly pouring the solution a into the solution b, continuing ultrasonic for 0.2-3h, cooling to room temperature, and repeatedly centrifuging for multiple times to obtain the precipitated copper nanoparticles.

3. The sonochemical synthesis method of conductive ink for flexible printed electronics according to claim 2, characterized in that the ultrasound parameters are set as: the ultrasonic power is 200-800W, the ultrasonic frequency is 20-80kHz, and the ultrasonic intermittent pulse ratio is 1: 1-4: 1.

4. the sonochemical synthesis method of conductive ink for flexible printed electronics according to claim 2, wherein the solvent a is selected from one or a mixture of at least two of deionized water, ethanol, ethylene glycol, diethylene glycol, -dipropylene glycol, and glycerol;

the reducing agent is selected from one or a mixture of at least two of hydrazine hydrate, potassium borohydride, sodium hypophosphite, ascorbic acid and methylamine;

the dispersing agent is selected from one or a mixture of at least two of sodium dodecyl sulfate, polyacrylamide, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG) and span.

5. The sonochemical synthesis method of conductive ink for flexible printed electronics according to any one of claims 1 to 4, wherein the preparation method of the silver-coated copper nanoparticles comprises the steps of adding a silver source into a solvent B according to 0.025-0.25 mol/L, stirring uniformly to obtain a solution c, adding prepared fresh copper nanoparticles into the solvent B, adding the prepared fresh copper nanoparticles into the solution c according to 0.05-0.5 mol/L, mixing uniformly to obtain a solution d, placing the solution d in a customized ultrasonic device at 20-50 ℃, quickly dissolving the solution d according to preset ultrasonic parameters, slowly dropping the solution c into the solution d after the solution d is mixed uniformly, cooling to room temperature after ultrasonic lasts for 0.2-3h, and repeatedly centrifuging for multiple times to obtain the precipitated silver-coated copper nanoparticles.

6. The sonochemical synthesis method of conductive ink for flexible printed electronics according to claim 5, characterized in that the ultrasound parameters are set as: the ultrasonic power is 20-100W, the ultrasonic frequency is 20-80kHz, and the ultrasonic intermittent pulse ratio is 1: 1-4: 1.

7. the sonochemical synthesis method of conductive ink for flexible printed electronics according to claim 5, characterized in that the silver source is selected from at least one of silver nitrate, silver sulfate, silver acetate; the solvent B is one or a mixture of at least two of deionized water, ethanol, glycol, diethylene glycol and glycerol.

8. The conductive ink and the sonochemical synthesis method for flexible printed electronics according to claim 1, wherein the preparation method of the conductive ink comprises: mixing freshly prepared silver-coated copper nanoparticles, a solvent C, a binder D, a foaming agent E and the like according to a certain mass ratio, and then putting the mixture into a special paste mixing machine to stir uniformly, thereby finally obtaining the required nano-silver-coated copper conductive ink.

9. The conductive ink and sonochemical synthesis method for flexible printed electronics according to claim 8, wherein the solvent C is selected from one or a mixture of at least two of deionized water, ethanol, ethylene glycol, and glycerol;

the binder D is one or a mixture of at least two of glycerol, terpineol, ethyl cellulose, polyethylene, alcohol polyurethane and polyacrylate;

blowing agent E is selected from one or a mixture of at least two of N-nitroso compound, azodicarbonamide, ethylene glycol and amine nitrite.

10. A conductive ink for flexible printed electronics prepared by the method of any one of claims 1-9, wherein the silver-coated copper nanoparticles have a solids content of preferably 50% to 90%.

Technical Field

The invention belongs to the technology of conductive ink preparation, relates to conductive ink for flexible printed electronics and a sonochemical synthesis method, and particularly relates to a preparation method taking nano silver-coated copper particles as conductive fillers, which is mainly applied to processing and manufacturing of various components in the flexible printed electronics.

Background

Human beings have entered the new century and a great deal of research progress has been made in developing the next generation of flexible, low-cost and environmentally friendly printed electronics. With the continuous and intensive research on printed electronics in recent years, people have developed wide applications in the fields of flexible electronic devices, printed circuit boards, light emitting diodes, radio frequency identification tags, electromagnetic shielding, chip packaging, and the like. The printed electronic technology is an electronic preparation technology based on a printing principle, and mainly prints and patterns some liquid materials with good dispersibility or soluble materials so as to realize the preparation of electronic components. Compared with the traditional PCB manufacturing method, the printed electronic technology is more convenient, the traditional PCB manufacturing method needs 8 steps of film coating, gluing, baking and the like, and the printed electronic only needs two steps, namely printing and sintering. And the printed electronics also have the inherent advantages of independence of substrate materials, mass production, low cost, environmental protection and the like. One of the key technologies is to prepare the novel conductive ink with environmental protection and low cost.

The conductive ink mainly comprises conductive filler, a regulator, a solvent and various auxiliaries, and can be divided into the following components according to different functional components: a metal-based conductive ink, a carbon-based conductive ink, and an organic polymer-based conductive ink. The selection of the conductive ink is very limited, the dispersibility of the organic conductive ink in the preparation process is difficult to solve, so that the printability of the organic conductive ink is poor in the use process, and the conductive performance of the organic conductive ink is inferior to that of the inorganic conductive ink, so that the use of the organic conductive ink is greatly challenged. Although the conductive performance of carbon-based conductive ink is slightly lower than that of metal conductive ink, the greatest difficulty is that the purification is difficult, so that the manufacturing cost is too high, and the application of the carbon-based conductive ink to printed electronics is limited. At present, the conductivity of silver is relatively good, the stability is also good, and the price is much cheaper than that of gold, platinum and the like. However, the silver content in conductive inks is low, and the overall cost of the ink is acceptable, but the conductivity is poor. The copper-based ink has the advantages of low cost and good conductivity, but the problems of instability and easy oxidation bring great trouble to researchers. Therefore, in the scheme of coating a stable substance on the surface of copper to improve the oxidation resistance, silver-shell-coated copper core-shell structure nanoparticles (Cu @ Ag NPs) formed by coating a copper core with a silver shell are most studied. Such as: chinese patent 201610154292.3 discloses a method for preparing silver-coated copper nanoparticle conductive ink which is simple to operate, high in purity, low in cost, high in yield, environment-friendly and suitable for mass production. Chinese patent 201711241749.5 discloses a conductive nano silver-coated copper material for RFID antenna conductive patterns, which has simple preparation process, environment-friendly and renewable ink solvent, and has great application prospect in the field of conductive ink for RFID antennas.

At present, the preparation method of the conductive nano silver-coated copper ink which has the advantages of particle size within 100nm, simple process, no need of protective gas, greenness, no pollution and suitability for mass production is not disclosed.

Disclosure of Invention

In view of the problems of the prior art, the invention aims to provide a conductive ink for flexible printing electronics and a sonochemical preparation method. The method has the advantages of simple preparation process, low cost, environmental friendliness, high efficiency, energy conservation and suitability for large-scale production.

The technical scheme adopted by the invention is as follows:

a sonochemical synthesis method of conductive ink for flexible printed electronics, comprising the steps of:

step one, preparing copper nanoparticles: preparing copper nanoparticles under the action of ultrasonic sonochemistry by adopting a mixture of a copper source, a reducing agent, a dispersing agent and one or more solvents;

step two, preparing silver-coated copper nanoparticles: mixing the obtained copper nanoparticles, a silver source, a reducing agent, a dispersing agent and one or more solvents, quickly synthesizing silver-coated copper nanoparticle dispersion liquid under the efficient action of ultrasonic sonochemistry, separating the silver-coated copper nanoparticles from the silver-coated copper nanoparticle dispersion liquid, and washing to obtain pure antioxidant silver-coated copper nanoparticles;

step three, preparing the conductive ink: and adding a proper amount of various organic solvents, and uniformly mixing to obtain the nano silver-coated copper conductive ink.

More specifically, a sonochemical synthesis method of conductive ink for flexible printed electronics, comprising the steps of:

step one, preparing copper nanoparticles:

adding a copper source into a solvent A according to the proportion of 0.1-1 mol/L, uniformly stirring, heating to 60-160 ℃ to obtain a solution a, adding a reducing agent into the solvent A according to the proportion of 0.1-1 mol/L, then adding a certain amount of dispersing agent, uniformly stirring to obtain a solution b, placing the solution b into a customized ultrasonic device at the temperature of 60-160 ℃, rapidly dissolving the solution b according to preset ultrasonic parameters, rapidly pouring the solution a into the solution b after the solution b is uniformly mixed, carrying out ultrasonic treatment for 0.2-3h, cooling to room temperature, and repeatedly centrifuging for multiple times to obtain precipitated copper nanoparticles.

The copper source is preferably at least one of copper hydroxide, copper nitrate, copper acetylacetonate, copper sulfate or copper chloride.

The solvent A is preferably one or a mixture of at least two of deionized water, ethanol, ethylene glycol, diethylene glycol, -dipropylene glycol and glycerol.

The reducing agent is preferably one or a mixture of at least two of hydrazine hydrate, potassium borohydride, sodium hypophosphite, ascorbic acid and methylamine.

The dispersing agent is preferably one or a mixture of at least two of sodium dodecyl sulfate, polyacrylamide, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG) and span.

The ultrasonic parameters are preferably as follows: the ultrasonic power is 200-800W, the ultrasonic frequency is 20-80kHz, and the ultrasonic intermittent pulse ratio is 1: 1-4: 1.

preferably, the temperature of the solution a and the solution b is the same.

Preferably, the centrifugation condition is centrifugation washing at 3000-.

Preferably, the number of centrifugal washing times is 4.

Step two, preparing silver-coated copper nanoparticles:

adding a silver source into a solvent B according to the proportion of 0.025-0.25 mol/L, uniformly stirring to obtain a solution c, adding the prepared fresh copper nanoparticles into the solvent B, adding the prepared fresh copper nanoparticles into the solution c according to the proportion of 0.05-0.5 mol/L, uniformly mixing to obtain a solution d, placing the solution d into a customized ultrasonic device at the temperature of 20-50 ℃, rapidly dissolving the solution d according to preset ultrasonic parameters, slowly dropping the solution c into the solution d after the solution d is uniformly mixed, carrying out ultrasonic treatment for 0.2-3h, cooling to room temperature, and repeatedly centrifuging for multiple times to obtain the precipitated silver-coated copper nanoparticles.

The silver source is preferably at least one of silver nitrate, silver sulfate and silver acetate.

The solvent B is preferably one or a mixture of at least two of deionized water, ethanol, glycol, diethylene glycol and glycerol.

The ultrasonic parameters are preferably as follows: the ultrasonic power is 20-100W, the ultrasonic frequency is 20-80kHz, and the ultrasonic intermittent pulse ratio is 1: 1-4: 1.

preferably, the temperature of the solution c is the same as that of the solution d.

Preferably, the centrifugation condition is centrifugation washing at 3000-.

Preferably, the centrifugal washing times are 3-6.

Step three, preparing the conductive ink:

mixing freshly prepared silver-coated copper nanoparticles, a solvent C, a binder D, a foaming agent E and the like according to a certain mass ratio, and then putting the mixture into a special paste mixing machine to stir uniformly, thereby finally obtaining the required nano-silver-coated copper conductive ink.

The solvent C is preferably one or a mixture of at least two of deionized water, ethanol, glycol and glycerol.

The binder D is preferably one or a mixture of at least two of glycerol, terpineol, ethyl cellulose, polyethylene, alcohol polyurethane and polyacrylate.

The foaming agent E is preferably one or a mixture of at least two of N-nitroso compound, azodicarbonamide, glycol and amine nitrite

The mass ratio of the nano particles to the solvent is 4: 1-8: 1.

the mass ratio of the nano particles to the binder is 10: 1-20: 1.

the mass ratio of the nano particles to the foaming agent is 20: 1-30: 1

Preferably, the rotating speed of the paste mixing machine is 200-1000 r/min.

Preferably, the paste mixing times are 3-6.

The invention provides conductive ink for flexible printed electronics, which is prepared by any one of the methods, wherein the particle size of silver-coated copper nanoparticles is less than 100nm, the average particle size is about 55-60 nm, and the solid content of the silver-coated copper nanoparticles is preferably 50-90%.

Compared with the prior art, the invention has the advantages that:

(1) the invention introduces the ultrasonic action, the ultrasonic chemical synthesis accelerates the collision and contact of reaction ions in the solution by means of special effects (acoustic flow, cavitation, acoustic gradient and the like) of ultrasonic waves in the liquid state, further improves the chemical reaction process, and greatly shortens the reaction time by utilizing the unique effect of an ultrasonic field in the liquid state, thereby obtaining nanoparticles with better dispersibility.

(2) The method is characterized in that the ultrasonic parameters of the silver-coated copper nanoparticles prepared by the two-step method are accurately regulated, wherein the copper nanoparticles are prepared by adopting high-power and high-frequency short pulse ultrasonic waves, and the generated high-energy ultrasonic field greatly accelerates the reaction process and shortens the reaction time; and the silver-copper replacement needs to adopt ultrasonic waves with small power, low frequency and long pulse, the uniform ultrasonic field generated by the ultrasonic waves is favorable for generating a silver coating layer, and the silver layer thickness of the silver-copper replacement is controlled to protect the copper nanoparticles.

(3) The silver-coated copper nanoparticles prepared by the method have good oxidation resistance and conductivity, and the double defects of high-price silver and easy-oxidation copper are overcome; the conductive ink prepared by the invention has the characteristics of about 55-60 nm of average particle size, low sintering temperature and excellent conductivity, and has wide application prospect in the field of printed electronics.

(4) The invention does not need protective gas, has easily obtained raw materials, simple process, environmental protection and ultrahigh efficiency, and is suitable for mass production.

Drawings

FIG. 1 is a schematic representation of an ultrasonic sonochemical reaction during example 1 of the present invention;

FIG. 2 is an XRD pattern of nano-silver coated copper particles obtained in example 1 of the present invention;

FIGS. 3a to 3b are SEM images and particle size distribution histograms of the nano-silver coated copper particles obtained in example 1 of the present invention;

FIG. 4 is a graph showing UV contrast in the process of preparing nano silver-coated copper particles obtained in example 1 of the present invention;

FIG. 5 is a TEM image of nano-silver coated copper particles obtained in example 1 of the present invention;

FIG. 6 is a pictorial view of a printed electronic circuit obtained in example 1 of the present invention.

Detailed Description

The invention will be described in further detail below with reference to the following figures and specific examples, but the invention is not limited thereto: