Method for preparing conductive pattern through vacuum filtration

Abstract

The invention discloses a method for preparing a conductive pattern through vacuum filtration, and relates to the field of flexible electronic technology and micro-nano processing. Comprising the following steps that firstly, a nanometer liquid metal particle solution is obtained; 2, polyvinylpyrrolidone is added into the nanometer liquid metal particle solution, solvent dilution and ultrasonic treatment are carried out, and liquid metal conductive ink is obtained; 3, printing a powdered ink pattern on the filter membrane by using a laser printer, and then forming a patterned thin film with a conductive pattern on the filter membrane through vacuum filtration of the liquid metal conductive ink; 4, the patterned thin film and the low-viscosity transfer printing thin film are subjected to cold pressing attachment and further subjected to hot pressing transfer printing to a target base material, and a finished product is obtained. The method has the beneficial effects that the laser printing technology is used for achieving accurate patterning, the liquid metal conductive ink forms a uniform patterned thin film on the filter membrane through the vacuum filtration technology, the manufacturing process is optimized, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of flexible electronic technology and micro-nano processing, and in particular to a method for preparing a conductive pattern by vacuum filtration. Background Art

[0002] In today's microelectronics and wearable devices, the demand for thin films with good conductivity and high stretchability is experiencing unprecedented growth. Liquid metal, due to its extraordinary conductive properties, is widely considered to be an ideal material for making such films. Compared with traditional methods based on raw bulk liquid metal, the application potential of liquid metal in the manufacture of flexible printed electronics can be significantly improved by processing it into nanodroplets. The surface tension of such liquid metal nanodroplets is significantly reduced, making it easier to accurately form high-resolution circuit patterns through a variety of printing techniques. Inks composed of liquid metal nanodroplets can not only be printed into conductive circuits with complex routing, but also provide better flexibility and stretchability, which is difficult to achieve with traditional bulk metals.

[0003] At present, due to the high surface tension and low viscosity of traditional liquid metal ink, it is difficult to control during the printing process and cannot achieve precise patterning; and liquid metal nanoparticles are easy to settle in the ink due to gravity, which makes it difficult to store the ink for a long time, severely limiting the printing resolution. In addition, in practical applications, the lack of rheological properties and printing difficulty of liquid metal ink limit its widespread application in the manufacture of high-performance electronic devices. In addition, existing conductive materials often have limitations in stretchability and flexibility, making it difficult to meet the needs of wearable devices for stretchable conductive connection lines.

[0004] Therefore, in order to solve the above problems, the present invention designs a method for preparing a conductive pattern by vacuum filtration. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a conductive pattern by vacuum filtration to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a conductive pattern by vacuum filtration comprises the following steps:

[0008] Step 1: placing liquid metal in a solvent and subjecting it to ultrasonic treatment to obtain a nano-liquid metal particle solution;

[0009] Step 2: adding polyvinyl pyrrolidone to the nano liquid metal particle solution, diluting with solvent, and ultrasonic treatment to obtain liquid metal conductive ink;

[0010] Step 3: Printing a toner pattern on the filter membrane using a laser printer, and then forming a patterned film with a conductive pattern on the filter membrane by vacuum filtration of the liquid metal conductive ink;

[0011] Step 4: cold-press the patterned film and the low-viscosity transfer film, and further hot-press transfer the patterned film to the target substrate to obtain a finished product.

[0012] More optimally: the pH of the liquid metal conductive ink is 3.5-6.5, and the viscosity is 100-1000 Pa.s; the liquid metal includes one of gallium-indium alloy and mercury.

[0013] More optimally: in the liquid metal conductive ink, the concentration of liquid metal is 1-3 g / mL, and the concentration of polyvinyl pyrrolidone is 0.03-0.06 g / mL.

[0014] More optimally: the parameters of the ultrasonic treatment are: power 280-320W, time 25-30min, temperature 18-22℃; this ultrasonic treatment method can effectively break the liquid metal into fine nano-scale particles with high size uniformity, which is not only conducive to improving the rheological properties of the ink, but also improves the electrical and mechanical properties of the final product. At the same time, during the ultrasonic treatment process, a layer of gallium oxide protective film will naturally form on the surface of the particles, which is crucial for the subsequent stabilization treatment.

[0015] More optimally: the molecular weight of the polyvinyl pyrrolidone is 10000-360000Da, and the polymer can form a coating layer outside the liquid metal particles, thereby obtaining a stable dispersed liquid metal particle ink system in ethanol; the solvent includes any one of ethanol or ethanol aqueous solution; when the solvent is ethanol aqueous solution, the deionized water in the liquid metal conductive ink does not exceed 20% of the total solvent.

[0016] More optimally: during the vacuum filtration process, the pore size of the filter membrane is 0.22-5μm, and the filtration time is 3-10min. This method can ensure the high consistency of the thickness and distribution of the patterned film formed, and significantly reduce the holes and unevenness. In addition, the high-precision patterning process makes this technology particularly suitable for the manufacture of high-performance electronic devices that require fine circuits and complex patterns. The thickness of the patterned film is 50-500μm.

[0017] More optimally: The vacuum filtration method can not only quickly spread the liquid metal into a film, but also the whole process is efficient and fast, which is very suitable for mass production. Compared with other precision pattern production technologies, such as photolithography, the equipment involved in the present invention is simpler, and the operation and maintenance costs are low, which provides a significant advantage in reducing the overall production cost. In addition, the present invention avoids the use of harmful chemicals, such as acid, alkali and other etching agents, which not only reduces environmental pollution, but also simplifies the operation process and reduces the safety risks in the operation.

[0018] More optimally: a predetermined toner pattern is printed on the filter membrane using a high-resolution laser printer, and precise patterning can be achieved on the filter membrane through the selective shielding effect of the toner and the application of vacuum filtration technology; this step not only improves the processing accuracy, but also greatly broadens the application range of the product; the resolution of the toner pattern is at least 600dpi; the toner is a self-thermofusible toner or a UV-curable toner.

[0019] More optimally: the low-viscosity film is a heat-sensitive foaming adhesive of a polyurethane system, which is similar to a low-viscosity pressure-sensitive adhesive at room temperature and foams and loses its adhesiveness after heating.

[0020] More optimally: the liquid metal conductive ink also includes modified carbon nanotubes, and the concentration of the modified carbon nanotubes is 0.05-0.1 g / mL.

[0021] More optimally: the preparation process of the modified carbon nanotubes is:

[0022] S1: add octylamine to ethanol, add formic acid dropwise at 60-70°C, stir for 30-40 minutes, heat to 80-90°C, add 25-30wt% formaldehyde aqueous solution, react for 2-3 hours; cool and distill under reduced pressure to obtain intermediate A;

[0023] S2: Add intermediate A and epichlorohydrin to ethanol, heat to 60-70°C, react for 3-4h, cool, and distill under reduced pressure to obtain intermediate B;

[0024] S3: adding hydroxylated carbon nanotubes and γ-aminopropyltriethoxysilane to a 20-25 wt % ethanol aqueous solution, mixing, ultrasonically treating for 2-3 h, stirring at 40-50° C. for 5-6 h, washing, filtering, drying, and grinding to obtain amino carbon nanotubes;

[0025] S4: adding the aminated carbon nanotubes and the intermediate B into ethanol and mixing, heating to 80-90° C., reacting for 4-5 hours, filtering, washing and drying to obtain modified carbon nanotubes.

[0026] More optimally, the intermediate A comprises the following components: by weight, 20-30 parts of octylamine, 200-250 parts of ethanol, 8-10 parts of formic acid, and 8-10 parts of formaldehyde aqueous solution; the intermediate B comprises the following components: by weight, 8-10 parts of intermediate A, 100-120 parts of ethanol, and 4.5-6 parts of epichlorohydrin; the amination carbon nanotubes comprise the following components: by weight, 2-5 parts of hydroxylated carbon nanotubes, 10-15 parts of γ-aminopropyltriethoxysilane, and 60-70 parts of ethanol aqueous solution; the modified carbon nanotubes comprise the following components: by weight, 10-12 parts of amination carbon nanotubes, 60-80 parts of ethanol, and 5-8 parts of intermediate B.

[0027] Furthermore, the power of the ultrasonic treatment device in the present invention is adjustable and is equipped with a temperature control module to maintain a stable temperature during the treatment process; the vacuum filtration system includes a digital control unit for accurately controlling the filtration time and pressure; the filter membrane device is replaceable to meet the needs of filter membranes of different specifications and sizes; the laser printer has high-resolution printing capabilities and is compatible with the use of hot-melt or ultraviolet curing toners; the curing device is selected from a heat treatment furnace, an ultraviolet lamp or other appropriate devices to improve the performance of the patterned film.

[0028] The present invention uses laser printing technology to achieve precise patterning, and uses vacuum filtration technology to form a uniform patterned film of liquid metal conductive ink on the filter membrane, which not only optimizes the manufacturing process but also improves production efficiency. The details are as follows:

[0029] First, in order to improve the rheology and printability of liquid metal ink, the present invention ultrasonically crushes the liquid metal in ethanol to form fine liquid metal particles, increases its surface area, thereby reducing surface tension and improving rheology. A gallium oxide protective film is naturally formed on its surface to prevent further oxidation of the liquid metal particles in ethanol and maintain its stability. Polyvinyl polypyrrolidone is used as a dispersant to wrap the liquid metal particles, which not only provides steric hindrance to prevent particle agglomeration, but also helps the particles to form a stable colloidal state in ethanol, thereby improving the stability and printability of the ink.

[0030] Second: In order to ensure the uniformity and consistency of the patterned film, the present invention controls the flow rate and pressure of the ink through vacuum filtration technology to achieve uniform deposition and obtain a film of consistent thickness; and through patterning steps such as toner masking, complex circuit design can be achieved to meet the needs of stretchable conductive connection circuits.

[0031] In a further scheme, in order to improve the tensile properties of the finished product and enhance the dispersibility of nano liquid metal particles in conductive ink, the present invention introduces carbon nanotubes as a reinforcing material and chemically modifies its surface. The grafted longer carbon molecular chains enhance its dispersibility. The amphoteric surfactant segments can work synergistically with polyvinyl polypyrrolidone to avoid agglomeration of liquid metal particles and improve the stability and printability of the ink. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The microscopic morphology of the liquid metal after ultrasonic crushing of the present invention;

[0033] Figure 2 The vacuum filtration membrane forming device of the present invention;

[0034] Figure 3 It is a schematic diagram of the process flow of the present invention;

[0035] Figure 4 It is the finished product prepared by the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] It should be noted that there is no special restriction on the purchase manufacturers of all raw materials involved in the present invention. In the following examples, the liquid metal is gallium-indium alloy.

[0038] Example 1: A method for preparing a conductive pattern by vacuum filtration, the specific preparation method is as follows:

[0039] Step 1: Place the liquid metal in ethanol and treat it with ultrasound at a power of 300 W and a temperature of 20°C for 28 minutes to obtain a nano-liquid metal particle solution;

[0040] Step 2: Add polyvinyl pyrrolidone to the nano liquid metal particle solution, and then dilute it with a solvent to a suitable concentration (the concentration of liquid metal is 2 g / mL, and the concentration of polyvinyl pyrrolidone is 0.04 g / mL) to obtain liquid metal conductive ink;

[0041] Step 3: Printing a toner pattern on the filter membrane using a laser printer, and then forming a patterned film with a conductive pattern on the filter membrane by vacuum filtration of the liquid metal conductive ink;

[0042] Step 4: cold-press the patterned film and the low-viscosity transfer film, and further hot-press transfer the patterned film to the target substrate to obtain a finished product.

[0043] Example 2: A method for preparing a conductive pattern by vacuum filtration, the specific preparation method is as follows:

[0044] Pre-preparation: The preparation process of modified carbon nanotubes is as follows: S1: 25 parts of octylamine are added to 220 parts of ethanol, 9 parts of formic acid are added dropwise at 65°C, stirred for 35 minutes, heated to 85°C, 9 parts of formaldehyde aqueous solution are added, reacted for 2.5 hours, cooled, and distilled under reduced pressure to obtain intermediate A;

[0045] S2: Add 9 parts of intermediate A and 5 parts of epichlorohydrin to 110 parts of ethanol, heat to 65°C, react for 3.5 hours, and distill under reduced pressure to obtain intermediate B;

[0046] S3: adding 3 parts of hydroxylated carbon nanotubes and 12 parts of γ-aminopropyltriethoxysilane to a 20 wt% ethanol aqueous solution, ultrasonically treating for 2.5 h, stirring at 45° C. for 5.5 h, washing, filtering, drying, and grinding to obtain amino carbon nanotubes;

[0047] S4: adding 11 parts of amino carbon nanotubes and 6 parts of intermediate B to 70 parts of ethanol, heating to 85°C, reacting for 4.5 hours, filtering, washing with ethanol, and vacuum drying to obtain modified carbon nanotubes;

[0048] Step 1: Place the liquid metal in ethanol and treat it with ultrasound at a power of 300 W and a temperature of 20°C for 28 minutes to obtain a nano-liquid metal particle solution;

[0049] Step 2: Add polyvinyl pyrrolidone and modified carbon nanotubes to the nano liquid metal particle solution, and then dilute it with a solvent to an appropriate concentration (the concentration of liquid metal is 2 g / mL, the concentration of polyvinyl pyrrolidone is 0.04 g / mL, and the concentration of modified carbon nanotubes is 0.05 g / mL) to obtain liquid metal conductive ink;

[0050] Step 3: Printing a toner pattern on the filter membrane using a laser printer, and then forming a patterned film with a conductive pattern on the filter membrane by vacuum filtration of the liquid metal conductive ink;

[0051] Step 4: cold-press the patterned film and the low-viscosity transfer film, and further hot-press transfer the patterned film to the target substrate to obtain a finished product.

[0052] Comparative Example 1: Aminated carbon nanotubes were added, and the rest was the same as Example 2, specifically as follows:

[0053] Pre-preparation: 3 parts of hydroxylated carbon nanotubes and 12 parts of γ-aminopropyltriethoxysilane were added to a 20 wt% ethanol aqueous solution, ultrasonically treated for 2.5 h, stirred at 45 °C for 5.5 h, washed, filtered, dried, and ground to obtain amino carbon nanotubes;

[0054] Step 1: Place the liquid metal in ethanol and treat it with ultrasound at a power of 300 W and a temperature of 20°C for 28 minutes to obtain a nano-liquid metal particle solution;

[0055] Step 2: Adding aminated carbon nanotubes to the nano liquid metal particle solution, and then diluting it with a solvent to a suitable concentration (the concentration of liquid metal is 2 g / mL, and the concentration of aminated carbon nanotubes is 0.05 g / mL) to obtain liquid metal conductive ink;

[0056] Step 3: Printing a toner pattern on the filter membrane using a laser printer, and then forming a patterned film with a conductive pattern on the filter membrane by vacuum filtration of the liquid metal conductive ink;

[0057] Step 4: cold-press the patterned film and the low-viscosity transfer film, and further hot-press transfer the patterned film to the target substrate to obtain a finished product.

[0058] Comparative Example 2: The amount of modified carbon nanotubes introduced is too much, and the rest is the same as Example 2, specifically as follows:

[0059] Pre-preparation: The preparation process of modified carbon nanotubes is:

[0060] S1: Add 25 parts of octylamine to 220 parts of ethanol, add 9 parts of formic acid dropwise at 65°C, stir for 35 minutes, heat to 85°C, add 9 parts of formaldehyde aqueous solution, react for 2.5 hours, cool, and distill under reduced pressure to obtain intermediate A;

[0061] S2: Add 9 parts of intermediate A and 5 parts of epichlorohydrin to 110 parts of ethanol, heat to 65°C, react for 3.5 hours, and distill under reduced pressure to obtain intermediate B;

[0062] S3: adding 3 parts of hydroxylated carbon nanotubes and 12 parts of γ-aminopropyltriethoxysilane to a 20 wt% ethanol aqueous solution, ultrasonically treating for 2.5 h, stirring at 45° C. for 5.5 h, washing, filtering, drying, and grinding to obtain amino carbon nanotubes;

[0063] S4: adding 11 parts of amino carbon nanotubes and 6 parts of intermediate B to 70 parts of ethanol, heating to 85°C, reacting for 4.5 hours, filtering, washing with ethanol, and vacuum drying to obtain modified carbon nanotubes;

[0064] Step 1: Place the liquid metal in ethanol and treat it with ultrasound at a power of 300 W and a temperature of 20°C for 28 minutes to obtain a nano-liquid metal particle solution;

[0065] Step 2: Add polyvinyl pyrrolidone and modified carbon nanotubes to the nano liquid metal particle solution, and then dilute it with a solvent to an appropriate concentration (the concentration of liquid metal is 2 g / mL, the concentration of polyvinyl pyrrolidone is 0.04 g / mL, and the concentration of modified carbon nanotubes is 0.1 g / mL) to obtain liquid metal conductive ink;

[0066] Step 3: Printing a toner pattern on the filter membrane using a laser printer, and then forming a patterned film with a conductive pattern on the filter membrane by vacuum filtration of the liquid metal conductive ink;

[0067] Step 4: cold-press the patterned film and the low-viscosity transfer film, and further hot-press transfer the patterned film to the target substrate to obtain a finished product.

[0068] Test experiment: (1) The liquid metal conductive ink obtained in Example 1-2 and Comparative Example 1-2 was placed at room temperature for settling, and its sedimentation rate was observed after 4 months. The sedimentation rate was determined according to the following method: after settling for 4 months, the ratio of the volume of the supernatant to the total volume of the sample was taken and multiplied by 100%, which was the sedimentation rate. The obtained data is shown in the following table:

[0069] project Example 1 Example 2 Comparative Example 1 Comparative Example 2 Sedimentation rate / % 8.6 6.8 7.5 8.1

[0070] Table 1

[0071] Conclusion: Example 1 uses laser printing technology to achieve precise patterning, and forms a uniform patterned film of liquid metal conductive ink on the filter membrane through vacuum filtration technology, which not only optimizes the manufacturing process, but also improves production efficiency. At the same time, in order to further improve the tensile properties of the obtained finished product, enhance the dispersibility of nano liquid metal particles in the conductive ink, and reduce the sedimentation rate of nano liquid metal particles, Example 2 introduces the reinforcement material carbon nanotubes on this basis, and chemically modifies its surface so that it can work synergistically with polyvinyl pyrrolidone.

[0072] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a conductive pattern by vacuum filtration, characterized in that: The following steps are involved: Step 1: placing liquid metal in a solvent and subjecting it to ultrasonic treatment to obtain a nano-liquid metal particle solution; Step 2: adding polyvinyl pyrrolidone to the nano liquid metal particle solution, diluting with solvent, and ultrasonic treatment to obtain liquid metal conductive ink; Step 3: Printing a toner pattern on the filter membrane using a laser printer, and then forming a patterned film with a conductive pattern on the filter membrane by vacuum filtration of the liquid metal conductive ink; Step 4: cold-press the patterned film and the low-viscosity transfer film, and further hot-press transfer the patterned film to the target substrate to obtain a finished product.

2. A method for preparing a conductive pattern by vacuum filtration according to claim 1, characterized in that: The pH of the liquid metal conductive ink is 3.5-6.5, and the viscosity is 100-1000 Pa.s; the liquid metal includes one of gallium-indium alloy and mercury.

3. The method for preparing a conductive pattern by vacuum filtration according to claim 1, characterized in that: In the liquid metal conductive ink, the concentration of the liquid metal is 1-3 g / mL, and the concentration of the polyvinyl pyrrolidone is 0.03-0.06 g / mL.

4. The method for preparing a conductive pattern by vacuum filtration according to claim 1, characterized in that: The parameters of the ultrasonic treatment are: power 280-320W, time 25-30min, temperature 18-22°C.

5. The method for preparing a conductive pattern by vacuum filtration according to claim 1, characterized in that: The molecular weight of the polyvinyl pyrrolidone is 10000-360000Da; the solvent includes any one of ethanol or ethanol aqueous solution; when the solvent is ethanol aqueous solution, the deionized water in the liquid metal conductive ink does not exceed 20% of the total solvent amount.

6. The method for preparing a conductive pattern by vacuum filtration according to claim 1, characterized in that: During the vacuum filtration process, the pore size of the filter membrane is 0.22-5 μm, and the filtration time is 3-10 min; the thickness of the patterned film is 50-500 μm.

7. The method for preparing a conductive pattern by vacuum filtration according to claim 1, characterized in that: The resolution of the toner pattern is at least 600 dpi; the toner is a self-thermal melting toner or an ultraviolet curing toner; and the low-viscosity film is a thermosensitive foaming adhesive of a polyurethane system.

8. The method for preparing a conductive pattern by vacuum filtration according to claim 1, characterized in that: The liquid metal conductive ink also includes modified carbon nanotubes, and the concentration of the modified carbon nanotubes is 0.05-0.1 g / mL.

9. The method for preparing a conductive pattern by vacuum filtration according to claim 8, characterized in that: The preparation process of the modified carbon nanotubes is as follows: S1: add octylamine to ethanol, add formic acid dropwise at 60-70°C, stir for 30-40 minutes, heat to 80-90°C, add formaldehyde aqueous solution, react for 2-3 hours; cool, and distill under reduced pressure to obtain intermediate A; S2: Add intermediate A and epichlorohydrin to ethanol, heat to 60-70°C, react for 3-4h, cool, and distill under reduced pressure to obtain intermediate B; S3: adding hydroxylated carbon nanotubes and γ-aminopropyltriethoxysilane to a 20-25 wt % ethanol aqueous solution, mixing, ultrasonically treating for 2-3 h, stirring at 40-50° C. for 5-6 h, washing, filtering, drying, and grinding to obtain amino carbon nanotubes; S4: adding the aminated carbon nanotubes and the intermediate B into ethanol and mixing, heating to 80-90° C., reacting for 4-5 hours, filtering, washing and drying to obtain modified carbon nanotubes.

10. The method for preparing a conductive pattern by vacuum filtration according to claim 9, characterized in that: The intermediate A comprises the following components: by weight, 20-30 parts of octylamine, 200-250 parts of ethanol, 8-10 parts of formic acid, and 8-10 parts of formaldehyde aqueous solution; the intermediate B comprises the following components: by weight, 8-10 parts of intermediate A, 100-120 parts of ethanol, and 4.5-6 parts of epichlorohydrin; the amination carbon nanotube comprises the following components: by weight, 2-5 parts of hydroxylated carbon nanotubes, 10-15 parts of γ-aminopropyltriethoxysilane, and 60-70 parts of ethanol aqueous solution; The modified carbon nanotubes include the following components: 10-12 parts of amino carbon nanotubes, 60-80 parts of ethanol, and 5-8 parts of intermediate B, by weight.

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