A method for preparing a particle-free conductive ink

Abstract

This invention discloses a method for preparing a particle-free conductive ink, belonging to the field of electronic information functional materials technology. The particle-free conductive ink comprises, by mass percentage, silver benzoate powder precursor, organic solvent, impurity remover, and compounding agent. The specific preparation steps are as follows: Silver benzoate powder is prepared; the impurity remover is fully dissolved in the organic solvent, and silver benzoate powder is added as a precursor and an organic amine as a ligand, controlling the silver content in the ink to be 2.5%–15%; the ink is stirred under ice-water bath conditions until it becomes clear and transparent, indicating successful preparation; the prepared particle-free conductive ink is spin-coated onto a PI film, with the spin coater speed set to 50–400 RPM, divided into 2–4 sections, each section spin-coating for 5–20 seconds, and sintered at 120℃–230℃ for 15–45 minutes to obtain a silver film.

Description

Technical Field

[0001] This invention relates to a method for preparing a particle-free conductive ink, belonging to the field of electronic information functional materials technology. Background Technology

[0002] As flexible electronic materials begin to enter more and more everyday life scenarios, researchers of electronic information materials are paying increasing attention to how to expand production scale by simplifying the production process, optimizing production technology, and controlling raw material costs, so as to further reduce production costs through the scale effect of the electronics industry.

[0003] Compared to traditional electronic material manufacturing technologies that require sophisticated equipment, complex processes, and are prone to producing toxic and harmful byproducts, such as etching, chemical plating, or vacuum deposition, printed electronics offers a more convenient production process that allows for large-scale production. Furthermore, because printed electronics does not require the same level of equipment as traditional manufacturing technologies and offers flexible production methods, it reduces production costs. Printed electronics technology mainly includes functional conductive inks and printing processes, with functional conductive inks being the core of printed electronics.

[0004] In the printing process of particulate conductive ink, clusters of particles need to be sintered under certain conditions (thermal sintering, plasma sintering, or chemical reaction) to form conductive pathways between the particle clusters, and the continuous solid structure ensures that it has a certain material strength. In contrast, particulate conductive ink does not contain solid particles, but is prepared by mixing various precursors (such as metal salts, ligands, reducing agents, and solvents). It also needs to have good transport stability to meet storage and transportation requirements. Under certain conditions (such as heat treatment, UV light, or laser), the conductive functional phase is deposited on the substrate to achieve the printing of conductive patterns. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a process for preparing a particle-free conductive ink. The particle-free conductive ink comprises, by weight percentage, 10%–40% silver benzoate precursor, 10%–50% organic solvent, 15%–30% impurity remover, and 15%–30% compounding agent, wherein the total weight percentage of the silver benzoate precursor, organic solvent, impurity remover, and compounding agent is 100%. The specific preparation steps are as follows:

[0006] (1) Silver nitrate and sodium benzoate are fully dissolved in deionized water, and silver benzoate precipitate is prepared by ion exchange method. Silver benzoate powder is obtained by vacuum drying.

[0007] (2) Mix the organic solvent and the impurity remover evenly.

[0008] (3) Continue to add the silver benzoate powder obtained in step (1) and stir thoroughly.

[0009] (4) Continue to add the compounding agent under ice bath conditions and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0010] Preferably, in step (1), the molar ratio of silver nitrate to sodium benzoate is silver nitrate:sodium benzoate aqueous solution = 1:1 to 1:3.

[0011] Preferably, the organic solvent in step (2) includes one or more of the following: 4-7 parts by mass of acetone, 4-7 parts by mass of methanol, 4-7 parts by mass of ethanol, 2-6 parts by mass of ethylene glycol, 2-6 parts by mass of propylene glycol, 2-6 parts by mass of n-butanol, 2-6 parts by mass of isobutanol, 2-6 parts by mass of n-pentanol, and 2-6 parts by mass of cyclohexanol.

[0012] Preferably, the impurity removal additive in step (2) includes one of sodium dodecylbenzenesulfonate (LAS), methyl diethanolamine (MDEA), diethanolamine (DEA), diisopropanolamine (DIPA), phenyl dimethyl ketone (BHT), and ethanolamine (MEA).

[0013] Preferably, the complexing agent in step (4) includes one or two of the following: 1-4 parts by weight of ethylamine, 1-4 parts by weight of n-butylamine, 2-5 parts by weight of ethanolamine, 2-5 parts by weight of ethylenediamine, 2-6 parts by weight of diethanolamine, 1-4 parts by weight of isopropanolamine, and 1-4 parts by weight of aniline.

[0014] Preferably, the particle-free conductive ink is spin-coated onto a PI film and fired at 120℃-230℃ for 15min-45min to obtain a silver film.

[0015] Beneficial effects of the present invention

[0016] (1) This invention is the first to successfully prepare a novel particle-free conductive ink using silver benzoate powder as a precursor. It also solves the shortcomings of other particle-free conductive inks, such as difficulty in preservation during preparation and production, high cost due to high silver content, and the generation of toxic byproducts during production. It provides a simple, convenient, and low-cost preparation process that greatly reduces the silver content while ensuring the excellent storage properties and conductivity of the prepared ink. The resistivity after sintering is only 1.5 times that of pure silver, and the ink has stable writing properties.

[0017] (2) Based on the successful preparation of a novel particle-free conductive ink, this invention studies the most suitable sintering conditions for the ink, explores the influence of sintering temperature and sintering time on the conductive pattern performance, and determines the suitable sintering condition range for the ink.

[0018] (3) Since the organic impurities remaining during the sintering process of particle-free conductive ink will hinder the formation of conductive pathways between precipitated nanoparticles, thus affecting the performance of conductive ink, the present invention solves the problem of organic impurities remaining during the ink sintering process by adding a decontaminant, which greatly improves the performance of the new particle-free conductive ink. Attached Figure Description

[0019] Figure 1 Resistance test of ink after sintering in Example 1;

[0020] Figure 2 The image shows the ink prepared in Example 1 and its UV-VIS spectrum after six months of storage.

[0021] Figure 3 This is a test of the ink direct writing performance in Example 1;

[0022] Figure 4 For Comparative Example 2, scanning electron microscope images and energy dispersive spectroscopy (EDS) images of the ink after sintering were obtained using silver terephthalate precursor. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0024] Example 1

[0025] This embodiment prepares a novel particle-free conductive ink. In this embodiment, the novel particle-free conductive ink comprises 30% silver benzoate powder, 30% organic solvent, 15% impurity remover and 25% compounding agent by mass percentage, wherein the total mass percentage of silver benzoate precursor, organic solvent, impurity remover and compounding agent is 100%.

[0026] The specific preparation steps are as follows:

[0027] (1) Dissolve equimolar amounts of silver nitrate and sodium benzoate in water and mix them evenly. Prepare silver benzoate precipitate by ion exchange method and obtain silver benzoate powder by vacuum drying.

[0028] (2) Mix 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol and 2 parts by weight of cyclohexanol to form an organic solvent and mix it with the impurity remover diisopropanolamine (DIPA) until the diisopropanolamine is fully dissolved to obtain a mixed solvent.

[0029] (3) Add the silver benzoate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver nitrate powder fully by magnetic stirring.

[0030] (4) Continue to add a compounding agent consisting of 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine under ice bath conditions, and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0031] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 225 RPM, divided into 3 sections, with each section having a spin coating time of 15 seconds. The film was then sintered at 225°C for 30 minutes to obtain a silver film deposited after ink sintering.

[0032] Sheet resistance and film thickness were tested on the silver film after sintering of particle-free conductive ink. The results showed that the thickness of the silver film deposited on the PI film surface ranged from 1 to 3 μm, and the sheet resistance results were as follows: Figure 1 As shown in the figure, the film thickness is uniform after ink sintering, and the resistance of each part is not much different. The resistivity of the silver film after sintering is calculated to be only 2.43 μΩ·cm.

[0033] The prepared ink was stored at 1–10°C for six months. Afterward, the ink was removed and its temperature was gradually increased to room temperature. Characterization was performed using UV-Vis spectroscopy to determine whether the ink deteriorated due to silver precipitation. The results are as follows: Figure 2 As shown, no characteristic peaks appeared in the wavelength range of 380nm-450nm, indicating that the ink did not precipitate silver nanoparticles after being stored for half a year, is not prone to deterioration, and has excellent storage properties.

[0034] The prepared ink was poured into a cleaned ballpoint pen refill to test its direct writing performance and the conductive pattern performance after sintering. The results are as follows: Figure 3 As shown in the figure, the ink has excellent direct writing performance, can be used for writing complex patterns, and maintains good conductivity after sintering.

[0035] In summary, the silver benzoate particle-free conductive ink prepared using the above process exhibits excellent performance. Unlike other conductive inks, which often require the addition of more than 25% silver by mass to ensure the conductivity of the sintered silver film, the improved conductive ink in this study has a silver content of only 15%, and the resistivity of the sintered silver film is only 2.43 μΩ·cm, which is very close to the resistivity of elemental silver (only 1.5 times the resistivity of silver).

[0036] Example 2

[0037] This embodiment prepares a novel particle-free conductive ink. In this embodiment, the novel particle-free conductive ink comprises 20% silver benzoate powder, 40% organic solvent, 25% impurity remover and 15% compounding agent by mass percentage, wherein the total mass percentage of silver benzoate precursor, organic solvent, impurity remover and compounding agent is 100%.

[0038] The specific preparation steps are as follows:

[0039] (1) Dissolve silver nitrate and sodium benzoate in water with a molar ratio of silver nitrate:sodium benzoate = 1:3 and mix them evenly. Prepare silver benzoate precipitate by ion exchange method and obtain silver benzoate powder by vacuum drying.

[0040] (2) Mix 4 parts by weight of acetone, 4 parts by weight of methanol and 4 parts by weight of ethanol into an organic solvent and a cleansing agent sodium dodecylbenzenesulfonate (LAS) until homogeneous.

[0041] (3) Add the silver benzoate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver nitrate powder fully by magnetic stirring.

[0042] (4) Continue to add a compounding agent consisting of 4 parts by weight of ethylamine and 2 parts by weight of ethanolamine under ice bath conditions, and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0043] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 50 RPM, divided into two sections, with each section having a spin coating time of 20 s. The film was then sintered at 120℃ for 45 min to obtain a silver film deposited on the surface of the PI film. The resistivity of the silver film after sintering was calculated to be 117.4 μΩ·cm.

[0044] Example 3

[0045] This embodiment prepares a novel particle-free conductive ink. In this embodiment, the novel particle-free conductive ink comprises 10% silver benzoate powder, 50% organic solvent, 20% impurity remover and 20% compounding agent by mass percentage, wherein the total mass percentage of silver benzoate precursor, organic solvent, impurity remover and compounding agent is 100%.

[0046] The specific preparation steps are as follows:

[0047] (1) Dissolve equimolar amounts of silver nitrate and sodium benzoate in water and mix them evenly. Prepare silver benzoate precipitate by ion exchange method and obtain silver benzoate powder by vacuum drying.

[0048] (2) Mix 2 parts by weight of ethylene glycol, 2 parts by weight of propylene glycol and 2 parts by weight of isobutanol into an organic solvent and a purifying agent methyl diethanolamine (MDEA) until homogeneous.

[0049] (3) Add the silver benzoate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver nitrate powder fully by magnetic stirring.

[0050] (4) Continue to add a compounding agent consisting of 1 part by weight of n-butylamine and 6 parts by weight of diethanolamine under ice bath conditions, and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0051] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 400 RPM, divided into 4 sections, with each section having a spin coating time of 5 seconds. The film was then sintered at 230℃ for 15 minutes to obtain a silver film deposited on the surface of the PI film. The resistivity of the silver film after sintering was calculated to be only 152.8 μΩ·cm.

[0052] Example 4

[0053] This embodiment prepares a novel particle-free conductive ink. In this embodiment, the novel particle-free conductive ink comprises 40% silver benzoate powder, 10% organic solvent, 30% impurity remover and 20% compounding agent by mass percentage, wherein the total mass percentage of silver benzoate precursor, organic solvent, impurity remover and compounding agent is 100%.

[0054] The specific preparation steps are as follows:

[0055] (1) Dissolve equimolar amounts of silver nitrate and sodium benzoate in water and mix them evenly. Prepare silver benzoate precipitate by ion exchange method and obtain silver benzoate powder by vacuum drying.

[0056] (2) Mix 6 parts by weight of ethylene glycol and 6 parts by weight of isobutanol to form an organic solvent and diisopropanolamine (DIPA) as a purifying agent.

[0057] (3) Add the silver benzoate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver nitrate powder fully by magnetic stirring.

[0058] (4) Continue to add 5 parts by weight of a compounding agent consisting of ethanolamine and 4 parts by weight of isopropanolamine under ice bath conditions, and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0059] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 50 RPM, divided into 4 sections, with each section having a spin coating time of 5 seconds. The film was then sintered at 230℃ for 15 minutes to obtain a silver film deposited on the surface of the PI film. The resistivity of the sintered silver film was calculated to be only 8.38 μΩ·cm.

[0060] Example 5

[0061] This embodiment prepares a novel particle-free conductive ink. In this embodiment, the novel particle-free conductive ink comprises 10% silver benzoate powder, 30% organic solvent, 30% impurity remover and 30% compounding agent by mass percentage, wherein the total mass percentage of silver benzoate precursor, organic solvent, impurity remover and compounding agent is 100%.

[0062] The specific preparation steps are as follows:

[0063] (1) Dissolve equimolar amounts of silver nitrate and sodium benzoate in water and mix them evenly. Prepare silver benzoate precipitate by ion exchange method and obtain silver benzoate powder by vacuum drying.

[0064] (2) Mix 6 parts by mass of cyclohexanol and 2 parts by mass of isobutanol into an organic solvent and a purifying agent phenyl dimethyl ketone (BHT) until homogeneous.

[0065] (3) Add the silver benzoate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver nitrate powder fully by magnetic stirring.

[0066] (4) Continue to add a compounding agent consisting of 1 part by weight of ethylamine and 5 parts by weight of ethylenediamine under ice bath conditions, and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0067] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 50 RPM, divided into 4 sections, with each section having a spin coating time of 5 seconds. The film was then sintered at 230℃ for 15 minutes to obtain a silver film deposited on the surface of the PI film. The resistivity of the sintered silver film was calculated to be only 7.14 μΩ·cm.

[0068] Example 6

[0069] This embodiment prepares a novel particle-free conductive ink. In this embodiment, the novel particle-free conductive ink comprises, by mass percentage, 35% silver benzoate powder, 25% organic solvent, 10% impurity remover, and 30% compounding agent, wherein the total mass percentage of silver benzoate precursor, organic solvent, impurity remover, and compounding agent is 100%. The specific preparation steps are as follows:

[0070] (1) Dissolve equimolar amounts of silver nitrate and sodium benzoate in water and mix them evenly. Prepare silver benzoate precipitate by ion exchange method and obtain silver benzoate powder by vacuum drying.

[0071] (2) Mix the organic solvent isobutanol with the impurity remover ethanolamine (MEA) until homogeneous.

[0072] (3) Add the silver benzoate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver nitrate powder fully by magnetic stirring.

[0073] (4) Continue to add a compounding agent consisting of 2 parts by weight of ethylenediamine and 4 parts by weight of aniline under ice bath conditions, and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0074] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 50 RPM, divided into 4 sections, with each section having a spin coating time of 5 seconds. The film was then sintered at 230℃ for 15 minutes to obtain a silver film deposited on the surface of the PI film. The resistivity of the sintered silver film was calculated to be only 3.74 μΩ·cm.

[0075] Example 7

[0076] This embodiment prepares a novel particle-free conductive ink. In this embodiment, the novel particle-free conductive ink comprises, by mass percentage, 10% silver benzoate powder, 40% organic solvent, 30% impurity remover, and 20% compounding agent, wherein the total mass percentage of silver benzoate precursor, organic solvent, impurity remover, and compounding agent is 100%. The specific preparation steps are as follows:

[0077] (1) Dissolve equimolar amounts of silver nitrate and sodium benzoate in water and mix them evenly. Prepare silver benzoate precipitate by ion exchange method and obtain silver benzoate powder by vacuum drying.

[0078] (2) Mix 6 parts by mass of n-butanol, 6 parts by mass of n-pentanol, 2 parts by mass of cyclohexanol and 7 parts by mass of methanol into an organic solvent and diethanolamine (DEA) as a purifying agent.

[0079] (3) Add the silver benzoate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver nitrate powder fully by magnetic stirring.

[0080] (4) Continue to add aniline as a complexing agent under ice bath conditions and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0081] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 225 RPM, divided into 3 sections, with each section having a spin coating time of 15 s. The film was then sintered at 275℃ for 30 min to obtain a silver film deposited on the surface of the PI film. The resistivity of the silver film after sintering was calculated to be only 11.6 μΩ·cm.

[0082] Example 8

[0083] This embodiment prepares a novel particle-free conductive ink. In this embodiment, the novel particle-free conductive ink comprises, by mass percentage, 25% silver benzoate powder, 50% organic solvent, 15% impurity remover, and 10% compounding agent, wherein the total mass percentage of silver benzoate precursor, organic solvent, impurity remover, and compounding agent is 100%. The specific preparation steps are as follows:

[0084] (1) Dissolve equimolar amounts of silver nitrate and sodium benzoate in water and mix them evenly. Prepare silver benzoate precipitate by ion exchange method and obtain silver benzoate powder by vacuum drying.

[0085] (2) Mix 7 parts by mass of acetone and 7 parts by mass of ethanol to form an organic solvent and methyl diethanolamine (MDEA) as a purifying agent.

[0086] (3) Add the silver benzoate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver nitrate powder fully by magnetic stirring.

[0087] (4) Continue to add 4 parts by weight of aniline and 2 parts by weight of diethanolamine complexing agent aniline under ice bath conditions, and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0088] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 225 RPM, divided into 3 sections, with each section having a spin coating time of 15 s. The film was then sintered at 275℃ for 30 min to obtain a silver film deposited on the surface of the PI film. The resistivity of the silver film after sintering was calculated to be only 158.2 μΩ·cm.

[0089] Example 9

[0090] This embodiment prepares a novel particle-free conductive ink. In this embodiment, the novel particle-free conductive ink comprises, by mass percentage, 25% silver benzoate powder, 50% organic solvent, 15% impurity remover, and 10% compounding agent, wherein the total mass percentage of silver benzoate precursor, organic solvent, impurity remover, and compounding agent is 100%. The specific preparation steps are as follows:

[0091] (1) Dissolve equimolar amounts of silver nitrate and sodium benzoate in water and mix them evenly. Prepare silver benzoate precipitate by ion exchange method and obtain silver benzoate powder by vacuum drying.

[0092] (2) Mix 6 parts by mass of propylene glycol and 4 parts by mass of ethanol to form an organic solvent and mix it evenly with the impurity remover methyl diethanolamine (MDEA).

[0093] (3) Add the silver benzoate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver nitrate powder fully by magnetic stirring.

[0094] (4) Continue to add 1 part by weight of aniline and 2 parts by weight of diethanolamine complexing agent aniline under ice bath conditions, and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0095] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 225 RPM, divided into 3 sections, with each section having a spin coating time of 15 s. The film was then sintered at 275℃ for 30 min to obtain a silver film deposited on the surface of the PI film. The resistivity of the silver film after sintering was calculated to be only 163.7 μΩ·cm.

[0096] Comparative Example 1

[0097] The only difference between this embodiment and Example 1 is that silver oxalate is used instead of silver benzoate in Example 1. In this embodiment, the novel particle-free conductive ink comprises 30% silver oxalate powder, 30% organic solvent, 15% impurity remover and 25% compounding agent by mass percentage, wherein the total mass percentage of silver oxalate precursor, organic solvent, impurity remover and compounding agent is 100%.

[0098] The specific preparation steps are as follows:

[0099] (1) Dissolve equal molar amounts of silver nitrate and sodium oxalate in water and mix them evenly. Prepare silver oxalate precipitate by ion exchange method and obtain silver oxalate powder by vacuum drying.

[0100] (2) Mix 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol and 2 parts by weight of cyclohexanol into an organic solvent and a purification agent diisopropanolamine, and stir until the diisopropanolamine is fully dissolved in the mixed solvent.

[0101] (3) Add the silver oxalate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver oxalate powder fully by magnetic stirring.

[0102] (4) Continue to add a compounding agent consisting of 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine under ice bath conditions, and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0103] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 225 RPM, divided into 3 sections, with each section spin-coating for 15 seconds. The film was then sintered at 225°C for 30 minutes. A silver film was obtained after the ink was sintered.

[0104] Comparative Example 2

[0105] The only difference between this embodiment and Example 1 is that silver terephthalate is used instead of silver benzoate in Example 1. In this embodiment, the novel particle-free conductive ink comprises 30% terephthalic acid powder, 30% organic solvent, 15% impurity remover, and 25% compounding agent by mass percentage, wherein the total mass percentage of silver terephthalate precursor, organic solvent, impurity remover, and compounding agent is 100%. The specific operating steps are as follows:

[0106] (1) Mix 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol and 2 parts by weight of cyclohexanol into an organic solvent and a purification agent diisopropanolamine, and stir until the diisopropanolamine is fully dissolved in the mixed solvent.

[0107] (2) Add terephthalic acid powder to the mixed solvent obtained in step (1) and use magnetic stirring to fully disperse the terephthalic acid powder.

[0108] (3) Continue to add aniline as a complexing agent under ice bath conditions and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0109] (4) Spin-coat the particle-free conductive ink obtained in step (3) onto the PI film. Set the spin coater speed to 225 RPM, divide it into 3 sections, and spin coat for 15 seconds for each section. Sinter at 225°C for 30 minutes to obtain the silver film deposited after ink sintering.

[0110] After relevant testing, the conductivity of the silver film obtained after sintering the inks prepared in Comparative Examples 1 and 2 was not as good as that in Example 1. The resistivity of the silver film after sintering the ink prepared in Comparative Example 1 was calculated to be 19.68 μΩ·cm, approximately 10 times that of Example 1, thus excluding the aliphatic carboxylic acid silver precursor. The resistivity of the silver film after sintering the ink prepared in Comparative Example 2 was calculated to be 286 μΩ·cm, two orders of magnitude higher than that in Example 1. This is attributed to excessive impurities remaining on the surface of the silver film after sintering. The surface morphology photographs and energy dispersive spectroscopy (EDS) are shown below. Figure 4 As shown.

[0111] Comparative Example 3

[0112] The only difference between this embodiment and Example 1 is that no impurity remover is added. In this embodiment, the novel particle-free conductive ink comprises 35% silver benzoate powder, 35% organic solvent and 30% compounding agent by mass percentage, wherein the total mass percentage of silver benzoate precursor, organic solvent and compounding agent is 100%.

[0113] The specific preparation steps are as follows:

[0114] (1) Dissolve equimolar amounts of silver nitrate and sodium benzoate in water and mix them evenly. Prepare silver benzoate precipitate by ion exchange method and obtain silver benzoate powder by vacuum drying.

[0115] (2) Mix 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol and 2 parts by weight of cyclohexanol evenly, add silver benzoate powder, and stir until silver benzoate is fully dispersed in the mixed solvent.

[0116] (3) Add the silver benzoate powder obtained in step (1) to the mixed solvent obtained in step (2), and disperse the silver nitrate powder fully by magnetic stirring.

[0117] (3) Continue to add the compounding agent isopropanolamine under ice bath conditions, and stir thoroughly until the solution is clear and transparent to obtain particle-free conductive ink.

[0118] The obtained particle-free conductive ink was spin-coated onto a PI film. The spin coater was set to a speed of 225 RPM, divided into 3 sections, with each section spin-coating for 15 seconds. The film was then sintered at 225°C for 30 minutes. A silver film was obtained after the ink was sintered.

[0119] After relevant testing, the ink prepared in Comparative Example 3 did not perform as well as the ink prepared in Example 1. The reason is that carbonaceous organic impurities could not be volatilized and removed in time during the ink sintering process, which hindered the formation of conductive pathways between the precipitated silver nanoparticles, thus greatly reducing the conductivity of the silver film.

Claims

1. A method of making a particle-free conductive ink, characterized by: The particle-free conductive ink comprises 30% silver benzoate powder, 30% organic solvent, 15% impurity removing agent and 25% complexing agent by mass percentage, wherein the total mass percentage of silver benzoate powder, organic solvent, impurity removing agent and complexing agent is 100%; the specific preparation steps are as follows: (1) Dissolve equal molar amount of silver nitrate and sodium benzoate in water and mix uniformly to obtain silver benzoate precipitate by ion exchange method, and vacuum dry to obtain silver benzoate powder; (2) Mix 2 parts by weight of n-butanol, 2 parts by weight of n-pentanol and 2 parts by weight of cyclohexanol to obtain an organic solvent, and mix the organic solvent with the impurity removing agent diisopropanolamine uniformly to obtain a mixed solvent by stirring until the diisopropanolamine is fully dissolved; (3) Add the silver benzoate powder obtained in step (1) into the mixed solvent obtained in step (2), and fully disperse the silver benzoate powder by magnetic stirring; (4) Continue to add the complexing agent obtained by mixing 1 part by weight of isopropanolamine and 4 parts by weight of n-butylamine under ice bath condition, and fully stir until the solution is clear and transparent to obtain the particle-free conductive ink.

2. The particle-free conductive ink prepared according to the method of claim 1, characterized in that: The particle-free conductive ink can be spin-coated on a PI film, and sintered at 120-230℃ for 15-45 min to obtain a silver film.

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