An ink for inkjet printing and a preparation method thereof

Abstract

An ink for inkjet printing and a preparation method thereof. The present invention belongs to the field of inkjet printing technology. The present invention aims to solve the problems that existing nano-silver conductive inks cannot achieve low-temperature curing, high conductivity, and at the same time have uniform dispersion and stable storage. The ink is composed of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, absolute ethanol, isopropanol, dispersion solvent, surface-modified nano-silver powder, polyvinylpyrrolidone, deionized water, glycerol, surfactant, binder and defoaming agent; the method includes weighing, stirring, mixing, dispersing and filtering in sequence. The present invention relates to an ink for inkjet printing and its preparation.

Description

Technical Field

[0001] The present invention belongs to the field of inkjet printing technology. Background Art

[0002] With the rapid development of the electronics manufacturing industry, electronic products such as smart phones, tablet computers, e-books, and wearable watches have completely changed the way of human life, which poses a huge challenge to traditional electronics production. As is well known, microfabrication through lithography or electroplating etching technology is a rather cumbersome and expensive process. Inkjet printing technology is a non-contact microscale printing process that can be achieved by directly jetting nano-sized solutions onto flexible or rigid substrates. Since the inkjet printing process can directly form a patterned thin film without a mask, it is considered a highly promising printing process. In addition, the use of printing ink media with functional materials such as polymer materials and metal nanoparticles enables the inkjet printing technology to provide a wide range of application options in photovoltaics, transistors, displays, batteries, antennas, and flexible electronic devices.

[0003] The key and core part of the inkjet printing technology is the preparation of conductive ink, that is, a suspension system for dispersing conductive particles. Conductive ink is mainly composed of conductive particles, solvents (water or alcohol), surfactants, dispersion stabilizers, and other additives. Silver nanoparticles have attracted the most extensive attention due to their excellent electrical conductivity, low melting point, high antioxidant stability, and feasible processing methods, showing a wide range of industrial applications, such as radio frequency identification (RFID), thin film transistors, solar cells, organic light-emitting diodes (OLEDs), printed circuit boards (PCBs), etc.

[0004] Nano silver conductive ink mainly refers to silver particles at the nanoscale level as the conductive component. Since the metal particle size is at the nanoscale level, it has physical and chemical properties different from those of conventional scales. Specifically, the metal particles can be melted at a lower temperature, enabling the conductive ink to achieve better conductive performance through low-temperature treatment. Nano silver particles will agglomerate and settle due to factors such as adsorption, charge, and van der Waals force, reducing the application effect of the conductive ink. Therefore, some polymer dispersants need to be added. The dispersant prevents the agglomeration of nano particles through steric hindrance, and makes the polymers on adjacent particles repel each other due to volume effects, ultimately effectively maintaining the suspension stability of the system. However, these polymers usually require high temperatures to form sintering necks between nano silver particles and finally form a conductive path.

[0005] Therefore, how to achieve low-temperature curing of nano silver conductive ink, with uniform dispersion, high conductivity, and a low-temperature ink that can be stably stored is an urgent problem to be solved in the prior art. Summary of the Invention

[0006] The present invention aims to solve the problem that existing nano - silver conductive inks cannot achieve low - temperature curing, high conductivity, and at the same time have uniform dispersion and stable storage, and further provides an ink for inkjet printing and its preparation method.

[0007] An ink for inkjet printing, by mass fraction, is composed of 2 parts - 20 parts of polyoxyethylene - polyoxypropylene - polyoxyethylene triblock copolymer, 0.5 parts - 20 parts of absolute ethanol, 1 part - 24 parts of isopropanol, 40 parts - 70 parts of dispersion solvent, 10 parts - 30 parts of surface - modified nano - silver powder, 0.85 parts - 10 parts of polyvinylpyrrolidone, 0.1 parts - 2 parts of deionized water, 0.2 parts - 5 parts of glycerol, 0.1 parts - 3 parts of surfactant, 0.1 parts - 1.3 parts of binder, and 0.1 parts - 1 part of defoamer.

[0008] The surface - modified nano - silver powder is obtained by modifying nano - silver powder with sodium bis(2 - ethylhexyl)sulfosuccinate.

[0009] A preparation method of an ink for inkjet printing is carried out according to the following steps:

[0010] I. Weighing:

[0011] Weigh 2 parts - 20 parts of polyoxyethylene - polyoxypropylene - polyoxyethylene triblock copolymer, 0.5 parts - 20 parts of absolute ethanol, 1 part - 24 parts of isopropanol, 40 parts - 70 parts of dispersion solvent, 10 parts - 30 parts of surface - modified nano - silver powder, 0.85 parts - 10 parts of polyvinylpyrrolidone, 0.1 parts - 2 parts of deionized water, 0.2 parts - 5 parts of glycerol, 0.1 parts - 3 parts of surfactant, 0.1 parts - 1.3 parts of binder, and 0.1 parts - 1 part of defoamer by mass fraction;

[0012] The surface - modified nano - silver powder is obtained by modifying nano - silver powder with sodium bis(2 - ethylhexyl)sulfosuccinate;

[0013] II. Mix 1 part - 24 parts of isopropanol and 0.5 parts - 20 parts of absolute ethanol evenly, then add 2 parts - 20 parts of polyoxyethylene - polyoxypropylene - polyoxyethylene triblock copolymer, heat and stir until the polyoxyethylene - polyoxypropylene - polyoxyethylene triblock copolymer is completely dissolved to obtain an F127 solution;

[0014] III. Heat and stir 40 parts - 70 parts of dispersion solvent, 0.1 parts - 2 parts of deionized water and 0.85 parts - 10 parts of polyvinylpyrrolidone until the polyvinylpyrrolidone is completely dissolved to obtain a polyvinylpyrrolidone solution;

[0015] IV. Add 10 to 30 parts of surface-modified nano silver powder into the polyvinylpyrrolidone solution, then conduct vacuum degassing and stirring in sequence, and then conduct magnetic stirring at room temperature. Finally, add the F127 solution and continue magnetic stirring at room temperature to obtain reaction system A;

[0016] V. Add 0.2 to 5 parts of glycerol and 0.1 to 3 parts of surfactant into reaction system A and mix evenly. Then add 0.1 to 1.3 parts of binder and 0.1 to 1 part of defoamer, and conduct magnetic stirring at room temperature to obtain reaction system B;

[0017] VI. Under the condition of 60 to 90 times gravitational acceleration, use an acoustic resonance mixer to disperse and process reaction system B for 10 to 30 minutes to obtain a suspension of nano silver powder;

[0018] VII. Filter the suspension of nano silver powder to obtain the ink for inkjet printing.

[0019] The beneficial effects of the present invention are as follows:

[0020] The inkjet printing ink of the present invention uses poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (F127) + PVPK30 as the dispersion system, uses bis(2-ethylhexyl)sulfosuccinate (AOT) to modify the surface of nano silver powder, and combines the acoustic resonance mixer dispersion technology, so that the inkjet printing ink has the characteristics of stable dispersion, low curing temperature (F127 can be decomposed at low temperature), and high conductivity, expanding the scope of use of inkjet printing substrates. Moreover, when F127 is combined with ethanol and isopropanol, at room temperature, after printing, the solvent will dry quickly, which is beneficial to maintaining the pattern accuracy. After low-temperature sintering treatment, the conductivity can reach the seventh order of magnitude.

[0021] The present invention uses poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer (F127). The micelles can encapsulate the hydrophobic Ag nanoparticles in their PPO cores, and at the same time, the surface of the encapsulated nanoparticles is essentially covered by a layer of free PEO chains, which makes the Ag particles colloidal stable. The melting temperature of small particles is low. When sintered at 200 °C, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) will decompose, and the silver particles will melt to form large particles. Some silver particles with small particle sizes will melt to form bridges connecting large particles, thus forming a conductive network. Polyvinylpyrrolidone is mainly adsorbed on the surface of silver particles by forming coordination bonds through the lone pair electrons provided by N atoms and O atoms in the molecular structure, resulting in a volume effect between Ag nanoparticles. To a certain extent, the particles lose the space for free movement, correspondingly reducing their entropy value, and at the same time increasing the mutual repulsion between particles, so that the contact of dispersed particles is hindered by spatial obstacles, maintaining the stability of the dispersion system.

[0022] The present invention relates to an ink for inkjet printing and a preparation method thereof. Description of the Drawings

[0023] Figure 1 Dispersion morphology diagram of the ink drop prepared for Comparative Experiment 1 after drying at 60 degrees on a silicon wafer;

[0024] Figure 2 Dispersion morphology diagram of the ink drop prepared for Comparative Experiment 2 after drying at 60 °C on a silicon wafer;

[0025] Figure 3 Scanning electron microscope image of the ink prepared for Comparative Experiment 1 printed on a ceramic substrate after curing and sintering at 200 °C for 1 h;

[0026] Figure 4 Scanning electron microscope image of the ink prepared for Comparative Experiment 2 printed on a ceramic substrate after curing and sintering at 200 °C for 1 h;

[0027] Figure 5 Scanning electron microscope image of the ink prepared in Example 1 printed on a ceramic substrate after sintering at 200 °C for 2 h;

[0028] Figure 6 Physical diagram of the circuit after inkjet printing and sintering of the ink prepared in Example 1;

[0029] Figure 7 Rheological curve diagram of the ink, where 1 in the abscissa is Example 1, 2 is Example 2, 3 is Example 3, 4 is Example 4, 5 is Example 5, 6 is Comparative Experiment 1, and 7 is Comparative Experiment 2. Detailed Embodiments

[0030] The technical solution of the present invention is not limited to the following specific embodiments listed, but also includes any combination between the specific embodiments.

[0031] Specific Embodiment 1: An ink for inkjet printing in this embodiment is composed of 2 to 20 parts by mass of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, 0.5 to 20 parts by mass of absolute ethanol, 1 to 24 parts by mass of isopropanol, 40 to 70 parts by mass of dispersion solvent, 10 to 30 parts by mass of surface-modified nano silver powder, 0.85 to 10 parts by mass of polyvinylpyrrolidone, 0.1 to 2 parts by mass of deionized water, 0.2 to 5 parts by mass of glycerol, 0.1 to 3 parts by mass of surfactant, 0.1 to 1.3 parts by mass of binder, and 0.1 to 1 part by mass of defoaming agent;

[0032] The surface-modified nano silver powder is obtained by modifying nano silver powder with sodium bis(2-ethylhexyl)sulfosuccinate.

[0033] The polyoxyethylene-polyoxypropylene-polyoxyethylene is F127.

[0034] The beneficial effects of this embodiment are as follows:

[0035] The inkjet printing ink of this embodiment uses poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (F127) + PVP K30 as the dispersion system, and uses bis(2-ethylhexyl)sulfosuccinate (AOT) to modify the surface of silver nanoparticles. Combining with the dispersion technology of an acoustic resonance mixer, the inkjet printing ink has the characteristics of stable dispersion, low curing temperature (F127 can decompose at low temperature), and high conductivity, expanding the scope of use of inkjet printing substrates. Moreover, when F127 is combined with ethanol and isopropanol, at room temperature, after printing, the solvent will dry quickly, which is beneficial to maintaining the pattern accuracy. After treatment at a low sintering temperature, the conductivity can reach the order of magnitude of the seventh power.

[0036] This embodiment uses poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymer (F127). The micelles can encapsulate the hydrophobic Ag nanoparticles in their PPO cores, and at the same time, the surface of the encapsulated nanoparticles is essentially covered by a layer of free PEO chains, which makes the Ag particles colloidally stable. The melting temperature of small particles is low. When sintered at 200 °C, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) will decompose, and the silver particles will melt to form large particles. Some silver particles with small particle sizes will melt to form bridges connecting the large particles, thus forming a conductive network. Polyvinylpyrrolidone mainly adsorbs on the surface of silver particles by forming coordination bonds through the lone pair electrons provided by N atoms and O atoms in the molecular structure, resulting in a volume effect between Ag nanoparticles. To a certain extent, the particles lose the space for free movement, correspondingly reducing their entropy value, while increasing the mutual repulsion between the particles, making the contact of the dispersed particles subject to spatial obstacles and maintaining the stability of the dispersion system.

[0037] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that the total mass fraction of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, absolute ethanol, isopropanol, dispersion solvent, surface-modified silver nanoparticles, polyvinylpyrrolidone, deionized water, glycerol, surfactant, binder, and defoamer is 100 parts. Others are the same as Specific Embodiment 1.

[0038] Embodiment 3: The difference between this embodiment and one of Embodiment 1 or 2 is that: the dispersion solvent is triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, diethylene glycol monobutyl ether or propylene glycol monomethyl ether; the surfactant is Pluronic P-123, polyoxyethylene sorbitan monolaurate, sodium dodecylbenzenesulfonate, octylphenol polyoxyethylene ether, laureth-10, (Z)-sorbitan monooleate, tetradecyldimethylbetaine or isomeric tridecyl alcohol; the binder is polyvinyl butyral, polyamide resin, chlorinated polypropylene, sodium dioctyl sulfosuccinate, bisphenol A epoxy resin or phenolic resin; the defoaming agent is polyoxypropylene oxyethylene glycerol ether, polyoxypropylene glycerol ether, coconut oil fatty acid diethanolamide, dialkyl phosphate, K155 defoaming agent or palmitic acid. Others are the same as Embodiment 1 or 2.

[0039] Embodiment 4: A method for preparing ink for inkjet printing according to this embodiment is carried out according to the following steps:

[0040] I. Weighing:

[0041] Weigh 2 to 20 parts by mass of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, 0.5 to 20 parts of absolute ethanol, 1 to 24 parts of isopropanol, 40 to 70 parts of dispersion solvent, 10 to 30 parts of surface-modified nano silver powder, 0.85 to 10 parts of polyvinylpyrrolidone, 0.1 to 2 parts of deionized water, 0.2 to 5 parts of glycerol, 0.1 to 3 parts of surfactant, 0.1 to 1.3 parts of binder and 0.1 to 1 part of defoaming agent;

[0042] The surface-modified nano silver powder is obtained by modifying nano silver powder with sodium bis(2-ethylhexyl)sulfosuccinate;

[0043] II. Mix 1 to 24 parts of isopropanol and 0.5 to 20 parts of absolute ethanol evenly, then add 2 to 20 parts of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, heat and stir until the polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer is completely dissolved to obtain an F127 solution;

[0044] III. Heat and stir 40 to 70 parts of dispersion solvent, 0.1 to 2 parts of deionized water and 0.85 to 10 parts of polyvinylpyrrolidone until the polyvinylpyrrolidone is completely dissolved to obtain a polyvinylpyrrolidone solution;

[0045] IV. Add 10 to 30 parts of surface-modified nano silver powder to the polyvinylpyrrolidone solution, then carry out vacuum defoaming stirring and normal-temperature magnetic stirring in sequence, and finally add the F127 solution and continue normal-temperature magnetic stirring to obtain a reaction system A;

[0046] V. Add 0.2 to 5 parts of glycerol and 0.1 to 3 parts of surfactant into reaction system A and mix evenly, then add 0.1 to 1.3 parts of binder and 0.1 to 1 part of defoamer, and stir magnetically at room temperature to obtain reaction system B;

[0047] VI. Under the condition of 60 to 90 times of gravitational acceleration, use an acoustic resonance mixer to disperse reaction system B for 10 to 30 minutes to obtain a suspension of silver nanopowder;

[0048] VII. Filter the suspension of silver nanopowder to obtain ink for inkjet printing.

[0049] Specific Embodiment 5: The difference between this embodiment and Specific Embodiment 4 is that the surface-modified silver nanopowder described in Step I is specifically prepared according to the following steps: Dissolve sodium bis(2-ethylhexyl)sulfosuccinate in deionized water, add silver nanopowder, and stir magnetically for 12 to 24 hours at room temperature and a stirring speed of 300 to 800 r / min. Then, under the conditions of a temperature ≤ 40°C and an ultrasonic power of 360 to 600 W, ultrasonicate for not less than 30 minutes. Then, centrifuge for 5 to 20 minutes at a rotation speed of 3000 to 6000 r / min to obtain a precipitate of silver nanoparticles. Finally, dry the precipitate of silver nanoparticles in a vacuum environment at a temperature of 40 to 60°C for 30 to 90 minutes to obtain surface-modified silver nanopowder; the mass ratio of sodium bis(2-ethylhexyl)sulfosuccinate to silver nanopowder is (10 to 15):1; the mass ratio of sodium bis(2-ethylhexyl)sulfosuccinate to the volume of deionized water is 1 g:(10 to 20) mL. Others are the same as Specific Embodiment 4.

[0050] Specific Embodiment 6: The difference between this embodiment and one of Specific Embodiments 4 or 5 is that the particle size of the silver nanopowder is 20 nm to 80 nm. Others are the same as Specific Embodiment 4 or 5.

[0051] Specific Embodiment 7: The difference between this embodiment and one of Specific Embodiments 4 to 6 is that the heating and stirring described in Step II and Step III are specifically carried out under the conditions of a temperature of 30 to 40°C and a stirring speed of 300 to 500 r / min. Others are the same as Specific Embodiments 4 to 6.

[0052] Embodiment 8: The difference between this embodiment and one of Embodiments 4 to 7 is that: in Step 4, 10 to 30 parts of surface-modified nano silver powder are added to the polyvinylpyrrolidone solution, and under the conditions of room temperature and a rotation speed of 500 r / min to 2000 r / min, vacuum degassing and stirring are carried out for 1 min to 10 min, and then under the conditions of a rotation speed of 300 r / min to 800 r / min, magnetic stirring is carried out at room temperature for 1 h to 3 h. Finally, an F127 solution is added, and under the conditions of a rotation speed of 300 r / min to 800 r / min, magnetic stirring is continued at room temperature for 0.5 h to 1.5 h to obtain reaction system A. Others are the same as those in Embodiments 4 to 7.

[0053] Embodiment 9: The difference between this embodiment and one of Embodiments 4 to 8 is that: the room temperature magnetic stirring described in Step 5 is specifically carried out under the conditions of a rotation speed of 360 r / min to 800 r / min and room temperature magnetic stirring for 0.5 h to 1 h. Others are the same as those in Embodiments 4 to 8.

[0054] Embodiment 10: The difference between this embodiment and one of Embodiments 4 to 9 is that: in Step 7, a filter screen with a pore size of 0.22 μm to 0.45 μm is used to filter the suspension of nano silver powder. Others are the same as those in Embodiments 4 to 9.

[0055] The following examples are used to verify the beneficial effects of the present invention:

[0056] Example 1:

[0057] A method for preparing an ink for inkjet printing is carried out according to the following steps:

[0058] I. Weighing:

[0059] Weigh 10 parts of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer (F127), 1 part of absolute ethanol, 9 parts of isopropanol, 42.8 parts of a dispersion solvent, 30 parts of surface-modified nano silver powder, 4.5 parts of polyvinylpyrrolidone, 0.3 part of deionized water, 2 parts of glycerol, 0.1 part of a surfactant, 0.1 part of a binder, and 0.2 part of an antifoaming agent by mass;

[0060] The surface-modified nano silver powder is obtained by modifying nano silver powder with sodium bis(2-ethylhexyl)sulfosuccinate;

[0061] II. Mix 9 parts of isopropanol and 1 part of absolute ethanol evenly, and then add 10 parts of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, and heat and stir under the conditions of a temperature of 35°C and a stirring speed of 800 r / min until the polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer is completely dissolved to obtain an F127 solution;

[0062] III. Heat and stir 42.8 parts of a dispersion solvent, 0.3 part of deionized water, and 4.5 parts of polyvinylpyrrolidone at a temperature of 40 °C and a stirring speed of 800 r / min until the polyvinylpyrrolidone is completely dissolved to obtain a polyvinylpyrrolidone solution;

[0063] IV. Add 30 parts of surface-modified silver nanoparticles to the polyvinylpyrrolidone solution. Under room temperature conditions, first perform vacuum degassing and stirring for 60 s at a rotation speed of 500 r / min, then perform vacuum degassing and stirring for 90 s at a rotation speed of 1500 r / min, then perform vacuum degassing and stirring for 120 s at a rotation speed of 2000 r / min, and then perform magnetic stirring at room temperature for 3 h at a rotation speed of 800 r / min. Finally, add the F127 solution and continue magnetic stirring at room temperature for 1 h at a rotation speed of 800 r / min to obtain reaction system A;

[0064] V. Add 2 parts of glycerol and 0.1 part of a surfactant to reaction system A and mix evenly, then add 0.1 part of a binder and 0.2 part of an antifoaming agent, and perform magnetic stirring at room temperature for 1 h at a rotation speed of 800 r / min to obtain reaction system B;

[0065] VI. Under the condition of 90 times the gravitational acceleration, use an acoustic resonance mixer to disperse and process reaction system B for 30 min to obtain a suspension of silver nanoparticles;

[0066] VII. Filter the suspension of silver nanoparticles using a filter screen with a pore size of 0.45 μm to obtain the ink.

[0067] The surface-modified silver nanoparticles described in Step I are specifically prepared according to the following steps: Dissolve sodium bis(2-ethylhexyl)sulfosuccinate in deionized water, add silver nanoparticles, and perform magnetic stirring for 24 h at room temperature and a stirring speed of 600 r / min. Then, perform ultrasonic treatment for 30 min at a temperature of 30 °C and an ultrasonic power of 600 W. Then, centrifuge for 20 min at a rotation speed of 5000 r / min to obtain a precipitate of silver nanoparticles. Finally, dry the precipitate of silver nanoparticles in a vacuum environment at a temperature of 50 °C for 90 min to obtain the surface-modified silver nanoparticles; the mass ratio of sodium bis(2-ethylhexyl)sulfosuccinate to silver nanoparticles is 15:1; the mass ratio of sodium bis(2-ethylhexyl)sulfosuccinate to the volume of deionized water is 1 g:10 mL; the particle size of the silver nanoparticles is 50 nm.

[0068] The dispersion solvent described in Step 1 is triethylene glycol monomethyl ether; the surfactant described in Step 1 is Pluronic P-123; the binder described in Step 1 is polyvinyl butyral (PVB); the defoamer described in Step 1 is polyoxypropylene glycerol ether; the polyvinylpyrrolidone described in Step 1 is PVPK30.

[0069] Example 2: The difference between this example and Example 1 is that in Step 1, 7.88 parts by mass of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer (F127), 2 parts of absolute ethanol, 8 parts of isopropanol, 47.57 parts of dispersion solvent, 28 parts of surface-modified nano silver powder, 2.8 parts of polyvinylpyrrolidone, 0.3 part of deionized water, 3 parts of glycerol, 0.15 part of surfactant, 0.1 part of binder, and 0.2 part of defoamer are weighed by mass; the dispersion solvent described in Step 1 is triethylene glycol ethyl ether, and the surfactant described in Step 1 is octylphenol polyoxyethylene ether. Others are the same as in Example 1.

[0070] Example 3: The difference between this example and Example 1 is that in Step 1, 6.5 parts by mass of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer (F127), 7.1 parts of absolute ethanol, 5 parts of isopropanol, 51 parts of dispersion solvent, 24 parts of surface-modified nano silver powder, 2.4 parts of polyvinylpyrrolidone, 0.2 part of deionized water, 3 parts of glycerol, 0.5 part of surfactant, 0.2 part of binder, and 0.1 part of defoamer are weighed by mass; the surfactant described in Step 1 is isomeric tridecyl alcohol. Others are the same as in Example 1.

[0071] Example 4: The difference between this example and Example 1 is that in Step 1, 4.4 parts by mass of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer (F127), 6.8 parts of absolute ethanol, 12 parts of isopropanol, 50.8 parts of dispersion solvent, 20 parts of surface-modified nano silver powder, 1.6 parts of polyvinylpyrrolidone, 0.2 part of deionized water, 3.3 parts of glycerol, 0.5 part of surfactant, 0.2 part of binder, and 0.2 part of defoamer are weighed by mass; the binder described in Step 1 is chlorinated polypropylene, and the defoamer described in Step 1 is K155 defoamer. Others are the same as in Example 1.

[0072] Example 5: The difference between this example and Example 1 is as follows: In step one, 2.33 parts by mass of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer (F127), 6.15 parts of absolute ethanol, 18.2 parts of isopropanol, 51.27 parts of dispersion solvent, 17 parts of surface-modified nano silver powder, 0.85 part of polyvinylpyrrolidone, 0.3 part of deionized water, 3 parts of glycerol, 0.5 part of surfactant, 0.2 part of binder and 0.2 part of defoamer are weighed by mass; the dispersion solvent described in step one is triethylene glycol ethyl ether, and the defoamer described in step one is palmitic acid. Others are the same as in Example 1.

[0073] Comparative Experiment 1: The difference between this comparative experiment and Example 1 is as follows: In step one, 1.76 parts by mass of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer (F127), 2.6 parts of absolute ethanol, 15.56 parts of isopropanol, 60.1 parts of dispersion solvent, 15 parts of surface-modified nano silver powder, 0.75 part of polyvinylpyrrolidone, 0.3 part of deionized water, 3 parts of glycerol, 0.48 part of surfactant, 0.2 part of binder and 0.25 part of defoamer are weighed by mass; the binder described in step one is polyamide resin HY-108; in step two, 1.76 parts of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer are added to 15.56 parts of isopropanol; in step five, 0.2 part of binder is dissolved in 2.6 parts of absolute ethanol, added to reaction system A and mixed evenly, then 3 parts of glycerol, 0.48 part of surfactant and 0.25 part of defoamer are added, and under the condition of a rotation speed of 800 r / min, magnetic stirring is carried out at room temperature for 1 h to obtain reaction system B. Others are the same as in Example 1.

[0074] Comparative Experiment 2: The difference between this comparative experiment and Example 1 is as follows: In step one, 4.36 parts of absolute ethanol, 15.56 parts of isopropanol, 60.4 parts of dispersion solvent, 15 parts of surface-modified nano silver powder, 0.75 part of polyvinylpyrrolidone, 3 parts of glycerol, 0.48 part of surfactant, 0.2 part of binder and 0.25 part of defoamer are weighed by mass; the binder is polyamide resin HY-108; step two is cancelled; in step three, 60.4 parts of dispersion solvent, 15.56 parts of isopropanol and 0.75 part of polyvinylpyrrolidone are heated and stirred under the conditions of a temperature of 40 °C and a stirring speed of 800 r / min; in step five, 0.48 part of binder is dissolved in 4.36 parts of absolute ethanol, added to reaction system A and mixed evenly, then 3 parts of glycerol, 0.48 part of surfactant and 0.25 part of defoamer are added, and under the conditions of room temperature and a rotation speed of 800 r / min, magnetic stirring is carried out for 1 h to obtain reaction system B. Others are the same as in Example 1.

[0075] Figure 1This is a dispersion morphology of the ink drop prepared in the comparative experiment 1 after being dried at 60 degrees on a silicon wafer; as can be seen from the figure, using F127+PVP K30 as a dispersant, a clear dispersion morphology of small silver particles mixed with large silver particles is presented.

[0076] Figure 2 This is the dispersion morphology of the ink drop prepared in Experiment 2 after being dried at 60°C on a silicon wafer; as can be seen from the figure, when PVPK30 is used alone as a dispersant, the silver particles do not show an obvious morphology of large silver particles sandwiched between small silver particles.

[0077] pass Figure 1 and Figure 2 Verify the difference in the dispersion morphology of F127 and PVP. The melting temperature of nano silver particles with small particle size is lower. Comparative experiment 1 shows the dispersion of small silver particles sandwiched between large particles. When treated at 200°C, the small silver particles in contact with each other melt into large particles, and the small particles dispersed between the large silver particles melt to form a bridge connecting the large particles. Comparative experiment 2 is a pure PVP dispersion, which does not show the morphology of small silver particles mixed with large silver particles.

[0078] The morphology verification after printing and sintering is shown in the figure below. The printing parameters are as follows: at room temperature, the ink is inkjet printed on the ceramic substrate. The inkjet printer uses a piezoelectric nozzle. 16 nozzles with an aperture of 22μm are arranged in sequence at the nozzle. The resolution of inkjet printing is 5760×1440dpi, the printing diameter is about φ8cm, the printing speed is set to 70mm / s, the printing voltage is 40V, the printing interval is 15s, and the dot spacing is set to 1 / 2~2 / 3 of the value of the single ink droplet diameter.

[0079] Figure 3 The ink prepared in comparative experiment 1 was printed on a ceramic substrate and the scanning electron microscope image was taken after curing and sintering at 200°C for 1 hour. As can be seen from the image, at 200°C, connections were formed between the molten silver particles, showing a morphology of small silver particles connecting large silver particles, and a conductive network was formed.

[0080] Figure 4 For comparison, the ink prepared in Experiment 2 was printed on a ceramic substrate and the SEM image was taken after curing and sintering at 200°C for 1 hour. As can be seen from the figure, after the particles using PVP alone as a dispersant were cured at 200°C, the particles were still in a dispersed state and no network connection was formed.

[0081] Figure 5 The ink prepared in Example 1 is printed on a ceramic substrate and the scanning electron microscope image is taken after sintering at 200°C for 2 hours. As can be seen from the figure, after the curing treatment at 200°C, the silver particles are all connected together, and the dispersion morphology of small-sized silver particles connected to large-sized silver particles is more obvious.

[0082] Method for measuring conductivity: Select a ceramic substrate as the base. First, stick two tapes parallel to each other on the ceramic substrate at a distance of 1 cm, with a height difference between the height of the tapes and the base. At room temperature, use a dropper to suck the ink and drop it between the two tapes, and then scrape it with a glass rod against the tape paper until a uniformly coated film is obtained. Place the ceramic substrate with the ink applied into a vacuum drying oven, take it out after drying at 200 °C, then tear off the tape paper on the ceramic substrate to obtain an ink coating. Use a thickness gauge to measure the thickness of the ceramic substrate before dropping the solution, and then measure the thickness of the sintered layer + ceramic substrate to calculate the thickness of the layer, which is controlled at about 20 μm. Then, combine a four-probe resistance meter to measure the sheet resistance value and calculate the conductivity.

[0083] Sheet resistance: Rs = ρ / t (where ρ is the resistivity of the material, unit: Ω·mm; t is the thickness of the material, unit: mm);

[0084] R = R S ×t (R is the resistance, unit: Ω, t is the thickness of the material, unit: mm);

[0085] Conductivity = 1 / R (conductivity unit: s / m), and thus verify the conductivity of the solution.

[0086] After the ink prepared in Example 1 is sintered at 200 °C for 2 h, the conductivity is 2.2×10 7 s / m, and the surface tension is 30 dyn / cm;

[0087] After the ink prepared in Example 2 is sintered at 200 °C for 1.5 h, the conductivity is 8.8×10 6 s / m, and the surface tension is 30 dyn / cm;

[0088] After the ink prepared in Example 3 is sintered at 200 °C for 1.5 h, the conductivity is 6.37×10 6 s / m, and the surface tension is 29 dyn / cm;

[0089] After the ink prepared in Example 4 is sintered at 200 °C for 1 h, the conductivity is 4.71×10 6 s / m, and the surface tension is 26 dyn / cm;

[0090] After the ink prepared in Example 5 is sintered at 200 °C for 1 h, the conductivity is 3.05×10 6 s / m, and the surface tension is 25 dyn / cm;

[0091] After the ink prepared in Comparative Experiment 1 is sintered at 200 °C for 1 h, the conductivity is 2.9×10 6 s / m, and the surface tension is 26 dyn / cm.

[0092] After the ink prepared in Comparative Experiment 2 was sintered at 200 °C for 1 h, the conductivity was 6.5×10 5 S / m, and the surface tension was 27 dyn / cm.

[0093] The change in the curing treatment time depends on the content of F127. The decomposition amount of F127 affects the conductivity to a certain extent. The more thoroughly F127 decomposes, the more silver is exposed, and the higher the probability of forming a conductive network by melting.

[0094] Under room temperature conditions, the ink prepared in Example 1 was inkjet printed on a ceramic substrate. The inkjet printer used a piezoelectric nozzle. 16 nozzles with a pore diameter of 22 μm were arranged in sequence at the nozzle. The resolution of the inkjet printing was 5760×1440 dpi, the printing diameter was about φ8 cm, the printing speed was set at 70 mm / s, the printing voltage was 40 V, the printing interval was 15 s, the dot pitch was set to 1 / 2 to 2 / 3 of the value of the single ink droplet diameter, and after printing, it was sintered at 200 °C for 2 h to obtain a ceramic substrate with a printed circuit; Figure 6 is the physical diagram of the circuit after inkjet printing and sintering for the ink prepared in Example 1; as can be seen from the figure, after printing and sintering, there are no defects such as coffee rings. The length of the ceramic substrate is 100 mm×100 mm, the printing length of the large square design is 4.6 cm, and the length after printing and curing is 4.242 cm.

[0095] The cross-cut test was carried out. Using the ink prepared in Example 1, a 3×3 cm surface was first printed on the ceramic substrate, and an AREPO QFH-A three-purpose cross-cut tool was used to cut the coating through to the substrate in a right-angle grid pattern to evaluate the resistance of the coating to detachment from the substrate. The evaluation method of the result was to evaluate through the coating peeling area. The cutting spacing depends on the coating thickness and the substrate type. Common standard: GB / T 9286-98. Inspection result: The cutting was smooth and flat, and there was no peeling at the grid edges. This printed circuit sample met the experimental result of Grade 5B (ASTM grade).

[0096] For the verification of the dispersion stability, taking Example 1 as the verification target, the prepared ink was left standing for one week, and the supernatant was taken and dried for solid content testing. The results of the three solid content tests were 28.79%, 29.11%, and 29.54% respectively. It was close to the designed 30% of the components. Therefore, the dispersant combination of F127+PVP can make the ink stable.

[0097] Figure 7 is the rheological curve diagram of the ink. In the abscissa, 1 is Example 1, 2 is Example 2, 3 is Example 3, 4 is Example 4, 5 is Example 5, 6 is Comparative Experiment 1, and 7 is Comparative Experiment 2; as can be seen from the figure, the viscosity of the ink is less than or equal to 4 mPa·s, meeting the viscosity requirements of the inkjet printing ink.

Claims

1. A method for preparing ink for inkjet printing, characterized in that It is carried out according to the following steps: I. Weighing: Weigh 7.88 to 10 parts by mass of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, 1 to 2 parts of absolute ethanol, 8 to 9 parts of isopropanol, 42.8 to 47.57 parts of dispersion solvent, 28 to 30 parts of surface-modified nano silver powder, 2.8 to 4.5 parts of polyvinylpyrrolidone, 0.3 part of deionized water, 2 to 3 parts of glycerol, 0.1 to 0.15 part of surfactant, 0.1 part of binder and 0.2 part of defoamer; the total mass parts of the polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, absolute ethanol, isopropanol, dispersion solvent, surface-modified nano silver powder, polyvinylpyrrolidone, deionized water, glycerol, surfactant, binder and defoamer are 100 parts; The dispersion solvent is triethylene glycol monomethyl ether, triethylene glycol ethyl ether, diethylene glycol butyl ether or propylene glycol methyl ether; The surface-modified nano silver powder is obtained by modifying nano silver powder with sodium bis(2-ethylhexyl)sulfosuccinate; The surface-modified nano silver powder is specifically prepared according to the following steps: dissolve sodium bis(2-ethylhexyl)sulfosuccinate in deionized water, add nano silver powder, under the conditions of room temperature and a stirring speed of 300 r / min to 800 r / min, magnetically stir for 12 h to 24 h, then under the conditions of a temperature ≤ 40 °C and an ultrasonic power of 360 W to 600 W, ultrasonicate for not less than 30 min, and then under the conditions of a rotation speed of 3000 r / min to 6000 r / min, centrifuge for 5 min to 20 min to obtain nano silver particle precipitate, and finally under the conditions of a vacuum environment and a temperature of 40 °C to 60 °C, dry the nano silver particle precipitate for 30 min to 90 min to obtain the surface-modified nano silver powder; the mass ratio of sodium bis(2-ethylhexyl)sulfosuccinate to nano silver powder is (10 to 15):1; the mass ratio of sodium bis(2-ethylhexyl)sulfosuccinate to the volume of deionized water is 1 g:(10 to 20) mL; the particle size of the nano silver powder is 20 nm to 80 nm; II. Mix 8 to 9 parts of isopropanol and 1 to 2 parts of absolute ethanol evenly, then add 7.88 to 10 parts of polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer, and heat and stir under the conditions of a temperature of 30 °C to 40 °C and a stirring speed of 300 r / min to 500 r / min until the polyoxyethylene-polyoxypropylene-polyoxyethylene triblock copolymer is completely dissolved to obtain an F127 solution; III. Under the conditions of a temperature of 30 °C to 40 °C and a stirring speed of 300 r / min to 500 r / min, heat and stir 42.8 to 47.57 parts of dispersion solvent, 0.3 part of deionized water and 2.8 to 4.5 parts of polyvinylpyrrolidone until the polyvinylpyrrolidone is completely dissolved to obtain a polyvinylpyrrolidone solution; IV. Add 28 to 30 parts of surface-modified nano silver powder into the polyvinylpyrrolidone solution. Under the conditions of room temperature and a rotation speed of 500 r / min to 2000 r / min, perform vacuum degassing and stirring for 1 min to 10 min. Then, under the condition of a rotation speed of 300 r / min to 800 r / min, perform magnetic stirring at room temperature for 1 h to 3 h. Finally, add the F127 solution and continue magnetic stirring at room temperature for 0.5 h to 1.5 h under the condition of a rotation speed of 300 r / min to 800 r / min to obtain reaction system A; V. Add 2 to 3 parts of glycerol and 0.1 to 0.15 parts of surfactant into reaction system A and mix evenly. Then add 0.1 part of binder and 0.2 part of defoamer, and perform magnetic stirring at room temperature for 0.5 h to 1 h under the condition of a rotation speed of 360 r / min to 800 r / min to obtain reaction system B; VI. Under the condition of 60 to 90 times the gravitational acceleration, use an acoustic resonance mixer to disperse and treat reaction system B for 10 min to 30 min to obtain a suspension of nano silver powder; VII. Use a filter screen with a pore size of 0.22 μm to 0.45 μm to filter the suspension of nano silver powder to obtain the ink for inkjet printing.

2. The method for preparing ink for inkjet printing according to claim 1, wherein The surfactant is Pluronic P-123, polyoxyethylene sorbitan monolaurate, sodium dodecylbenzenesulfonate, octylphenol polyoxyethylene ether, laureth-10, (Z)-sorbitan mono-9-octadecenoate, tetradecyldimethylbetaine or isomeric tridecyl alcohol; the binder is polyvinyl butyral, polyamide resin, chlorinated polypropylene, sodium dioctyl sulfosuccinate, bisphenol A epoxy resin or phenolic resin; the defoamer is polyoxypropylene oxyethylene glycerol ether, polyoxypropylene glycerol ether, coconut oil fatty acid diethanolamide, dialkyl phosphate, K155 defoamer or palmitic acid.

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