Preparation method of nano-silver transparent conductive film

Abstract

The invention discloses a preparation method of a nano-silver transparent conductive film, and relates to the technical field of conductive films, and the preparation method specifically comprises the following operation steps: S1, substrate pretreatment and photoresist coating; s2, exposing and drying again; s3, developing and hardening; s4, preparing modified nano-silver particles; s5, preparing conductive silver paste; s6, silver paste filling and surface cleaning; and S7, pulsed light sintering and finished product treatment. According to the preparation method of the nano-silver transparent conductive film, an epoxy resin matrix is modified through polyurethane, so that silver paste is endowed with good rheological property and flexibility, and excellent adhesive force and bending resistance are achieved between a conductive grid and a substrate; the forming effect is ensured and residual silver paste in a non-groove area is removed through blade coating processing and plasma cleaning, so that short circuit between grids is effectively prevented, and the product yield is improved; by adopting a pulsed light sintering technology, silver particles are welded under instantaneous high-energy pulses; ascorbic acid is used as a reducing agent, and the process is environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of conductive film technology, specifically to a method for preparing a nano-silver transparent conductive film. Background Technology

[0002] Transparent conductive films are core materials for optoelectronic devices such as flexible displays and touch panels. Due to their high conductivity and flexibility, metal mesh transparent conductive films have become one of the mainstream alternatives to traditional ITO. Their typical preparation process includes: forming mesh grooves on the surface of a transparent substrate by photolithography, filling the grooves with conductive silver paste, and then sintering and curing to form a conductive mesh.

[0003] Currently, in the silver paste filling process, scraping is one of the commonly used methods. In the existing technology, the scraper device is used in conjunction with the conveyor belt and is fixedly set above the conveyor belt. It is at a certain angle to the substrate surface and maintains contact pressure. The substrate is carried by the conveyor belt and moves at a uniform speed in a preset direction. The silver paste is pre-applied to the substrate surface. When the substrate passes under the scraper, the scraper presses the silver paste into the grid groove and scrapes off the excess silver paste on the surface. By adjusting parameters such as the scraper angle, pressure and substrate travel speed, the filling effect can be controlled.

[0004] However, in reality, due to the lack of integrated methods for silver paste filling and surface cleaning, a thin layer of silver paste remains on the substrate surface after scraping. When exposed to air, the solvent continues to evaporate, causing the paste to form a skin. If the residual silver paste is not completely removed, it will form a conductive path during subsequent sintering, causing short circuits between the grids and directly affecting the product yield.

[0005] Secondly, existing scraper devices lack continuous operation conditions. Most existing solutions do not consider the problem of silver paste drying and adhering on the blade surface during continuous production. As production progresses, the material on the blade surface gradually thickens, changing the preset contact state between the scraper and the substrate, resulting in uneven coating thickness or even scratching the substrate. Therefore, it is necessary to stop the machine regularly for cleaning, which also leads to a decrease in production efficiency. Summary of the Invention

[0006] This invention provides a method for preparing a transparent conductive film of nano-silver, which solves the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides a method for preparing a nano-silver transparent conductive film, comprising the following steps:

[0008] S1. Substrate pretreatment and photoresist coating

[0009] Take a flexible transparent substrate, clean and dry it; coat the substrate surface with SU-8 3025 negative photoresist with a coating thickness of 4-5 μm, and then perform a two-stage drying process.

[0010] S2, Exposure and Re-drying

[0011] Exposure was performed using an ultraviolet light source in conjunction with a chromium mask, with an exposure energy of 90–110 mJ / cm². Then, a two-stage drying process was carried out again.

[0012] S3, Development and Hardening

[0013] The film was developed using propylene glycol methyl ether acetate to form a grid groove with a line width of 3-5 μm, a depth of 4-5 μm, and an aspect ratio of ≥1:1. Then, it was hardened and baked at 100℃-120℃ for 20-25 minutes.

[0014] S4. Preparation of modified silver nanoparticles

[0015] Silver powder was prepared using ascorbic acid as a reducing agent and ball-milled to obtain silver powder with a particle size of 50-70 nm. After ozone oxidation, the silver powder was reacted with pyrrole in the presence of ferric chloride hexahydrate and sodium dodecylbenzenesulfonate to obtain modified silver nanoparticles with a polypyrrole / silver chloride / silver monoxide composite shell, wherein the mass fraction of polypyrrole was 13.5-14.5 wt%.

[0016] S5, Preparation of conductive silver paste

[0017] Modified silver nanoparticles are mixed with polyurethane-modified epoxy resin matrix, solvent, and additives to obtain a silver paste with a viscosity of 700-900 cps, wherein the content of modified silver nanoparticles is 70-72 wt%.

[0018] S6, Silver paste filling and surface cleaning

[0019] The silver paste is applied to the grid grooves using a scraper mechanism, while excess silver paste is scraped off simultaneously. Plasma cleaning is then used to remove surface residue.

[0020] S7, pulsed light sintering and finished product processing

[0021] Sintering is performed using a pulsed xenon lamp with a single pulse energy of 6–7 J / cm², a pulse width of 450–550 μs, and at least two pulses. After natural cooling, the finished product is obtained.

[0022] Preferably, in step S1, the flexible transparent substrate is an optical-grade PET film, a COP film, or a transparent polyimide film. The temperature change range of the two-stage drying process in step S1 is the same as that of the two-stage drying process in step S2, which is 65℃ / 5min followed by heating to 95℃ / 10min.

[0023] Preferably, the ultraviolet light source in step S3 is specifically an i-line ultraviolet light source, and in step S4, the mass ratio of pyrrole to silver powder is 1:13 to 1:15, and the molar ratio of ferric chloride hexahydrate to pyrrole is 2.3:1.

[0024] Preferably, in step S5, the polyurethane modified epoxy resin matrix is ​​prepared by the following method: isophorone diisocyanate and palmitol are reacted at 80°C for 4 hours under the catalysis of dibutyltin dilaurate, and then polytetrahydrofuran diol with a number average molecular weight of 1000 is added and reacted at 110°C for 5 hours. The resulting polyurethane prepolymer is mixed with bisphenol A type epoxy resin E-51 at a mass ratio of 1:1.

[0025] Preferably, in step S7, the instantaneous peak temperature of the substrate during the pulsed light sintering process does not exceed 75°C, and step S7 also includes the step of coating a transparent protective coating on the surface of the conductive film.

[0026] A scraper mechanism is used in a method for preparing a nano-silver transparent conductive film. The scraper mechanism includes a composite hollow scraper and a feed slot opened on the top of one side of the composite hollow scraper. A conveyor belt assembly is fitted inside the composite hollow scraper, and a return space communicating with the feed slot is formed between the top of the conveyor belt assembly and the top inner wall of the composite hollow scraper. A power assembly and a spiral blade shaft are respectively arranged on the top inner side of the other side of the composite hollow scraper, and the two ends of the spiral blade shaft pass through the front and rear ends of the top of the other side of the composite hollow scraper. The power assembly includes a motor assembly, a first gear, a second gear, and a third gear installed on the top of the other side of the composite hollow scraper. The two sides of the second gear are respectively meshed with the first gear and the third gear, and the first gear is driven by the output structure of the motor assembly. The second gear and the third gear are driven by the conveyor belt assembly and the spiral blade shaft, respectively.

[0027] Preferably, the conveyor belt assembly includes a conveyor belt body and two drive shafts. The two drive shafts are respectively fitted inside the two sides of the conveyor belt body, and the ends of the two drive shafts are fitted through the corresponding side wall structure of the composite hollow scraper via sealing rings. One end of one drive shaft is fitted into the middle of the second gear. The surfaces of the two sides of the conveyor belt body are respectively attached to the inner walls of the two sides of the composite hollow scraper, and a C-shaped scraper that can be attached to and contacted with one side surface of the conveyor belt body is fitted inside the top of the other side of the composite hollow scraper.

[0028] Preferably, the motor assembly includes a reducer and a servo motor, both mounted on the top surface of the other side of the composite hollow scraper. The input end of the reducer is connected to the output end of the servo motor, and the output end of the reducer is fitted inside the middle of the first gear.

[0029] Preferably, both ends of the spiral blade shaft are configured as smooth rod structures, and one end of the spiral blade shaft is fitted through a sealing ring to the rear end structure of the top of the other side of the composite hollow scraper. One end of the spiral blade shaft is fitted to the inner side of the middle of the third gear, and the other end of the spiral blade shaft is fitted with a guide tube installed at the front end of the top of the other side of the composite hollow scraper. The surface of the guide tube away from the composite hollow scraper is provided with external threads.

[0030] Preferably, the top of the composite hollow scraper is fixed with a support frame, and the inner walls of the front and rear ends of the composite hollow scraper are both fixed with limiting partitions that are in close contact with the top surface of the conveyor belt body.

[0031] The present invention has the following beneficial effects:

[0032] 1. The preparation method of this nano-silver transparent conductive film involves using a polyurethane-modified epoxy resin matrix to impart good rheological properties and flexibility to the silver paste, resulting in excellent adhesion and bending resistance between the conductive mesh and the substrate. The coating process and plasma cleaning ensure the molding effect and remove residual silver paste in non-grooved areas, effectively preventing short circuits between meshes and improving product yield.

[0033] 2. The preparation method of this transparent conductive nano-silver film employs pulsed light sintering technology to fuse silver particles under instantaneous high-energy pulses, while avoiding thermal damage to temperature-sensitive flexible substrates such as PET; ascorbic acid is used as a reducing agent, making the process green and environmentally friendly; modified silver nanoparticles coated with a polypyrrole / silver chloride / silver monoxide composite shell utilize the light absorption properties of polypyrrole to reduce visible light reflection of the conductive mesh while maintaining good conductivity.

[0034] 3. The scraper mechanism of the preparation method of the nano-silver transparent conductive film, through the linkage of the conveyor belt assembly, the power assembly and the spiral blade shaft, can simultaneously move the conveyor belt assembly and the spiral blade shaft upward and collect the excess silver paste scraped out by the composite hollow scraper without delaying the composite hollow scraper coating process. This meets the use requirements of continuous scraping and coating of composite hollow scraper and related structures, while reducing the number of downtime cleaning and ensuring the efficient operation of the overall process.

[0035] 4. The scraper mechanism of the preparation method of the nano-silver transparent conductive film, through the set guide tube as an extension conveying channel of the spiral blade shaft, can be detachably installed with the designated collection container, further improving the continuous use effect of the scraper mechanism. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the process of the present invention;

[0037] Figure 2This is a cross-sectional schematic diagram of the composite hollow scraper in this invention;

[0038] Figure 3 This is a rear view schematic diagram of the composite hollow scraper in this invention;

[0039] Figure 4 This is a three-dimensional schematic diagram of the composite hollow scraper in this invention;

[0040] Figure 5 This is a left-side schematic diagram of the composite hollow scraper in this invention;

[0041] Figure 6 This is an enlarged schematic diagram of the C-shaped scraper in this invention;

[0042] Figure 7 This is a top view of the limiting partition in this invention.

[0043] In the diagram: 1. Composite hollow scraper; 2. Feed trough; 3. Conveyor belt body; 4. Drive shaft; 5. Spiral blade shaft; 6. Reducer; 7. Servo motor; 8. First gear; 9. Second gear; 10. Third gear; 11. Support frame; 12. Guide pipe; 13. C-shaped scraper; 14. Limiting partition. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Please see Figure 1 A method for preparing a transparent conductive nanofilm of silver nanoparticles includes the following steps.

[0046] S1. Substrate pretreatment and photoresist coating

[0047] Take a flexible transparent substrate, and ultrasonically clean it sequentially with acetone, isopropanol, and deionized water. After drying with nitrogen, dry it in an oven at 110°C for 30 minutes. The flexible transparent substrate can be optical-grade PET film, COP film, or transparent polyimide film.

[0048] A layer of negative photoresist, SU-83025, was coated onto a clean substrate surface using a slit-coating process, with the coating thickness controlled at 4–5 μm.

[0049] After coating, place the substrate on a hot plate for a two-stage pre-baking process: first bake at 65°C for 5 minutes, then increase the temperature to 95°C and bake for 10 minutes, followed by natural cooling to room temperature.

[0050] S2, Exposure and Re-drying

[0051] Exposure was performed using an i-line (365nm) ultraviolet light source and a chromium mask with a target grid pattern, employing a proximity exposure method with exposure energy controlled between 90 and 110 mJ / cm².

[0052] Immediately after exposure, a two-stage post-baking process is performed: the substrate is placed on a hot plate and baked at 65°C for 2 minutes, followed by baking at 95°C for 5 minutes to promote the crosslinking reaction, and then allowed to cool naturally.

[0053] S3, Development and Hardening

[0054] The post-baked substrate was immersed in propylene glycol methyl ether acetate developer at a temperature controlled at 25±0.5℃ for 3–4 minutes, with ultrasonic stirring to form patterned grid grooves. After development, the substrate was rinsed with isopropanol and dried with nitrogen.

[0055] The developed substrate was baked at 120°C for 20 minutes to form a hard film. The line width of the grid grooves was 3-5 μm, the depth was 4-5 μm, the aspect ratio was ≥1:1, and the sidewall angle was greater than 85°.

[0056] S4. Preparation of modified silver nanoparticles

[0057] S4-1. Preparation of nano-silver powder: Prepare silver nitrate solution and sodium carbonate solution, mix to form silver carbonate precipitate; after filtration and washing, disperse the precipitate in deionized water and adjust the pH to 8.2-8.8; under stirring, add ascorbic acid aqueous solution dropwise as a reducing agent, and react at 40℃ for 2 hours; after centrifugation and washing, add polyvinylpyrrolidone as a dispersant, vacuum dry, and ball mill for 110-120 hours to obtain silver powder with an average particle size of 50-70 nm.

[0058] S4-2, Surface Oxidation and Polypyrrole Coating: The above-mentioned silver powder is placed in an ozone atmosphere and treated for 65-75 minutes at a relative humidity of 15-25% and a temperature of 18-22℃, so that silver monoxide and silver oxide are generated in situ on the surface of the silver powder.

[0059] Under nitrogen protection, treated silver powder, ferric chloride hexahydrate, and sodium dodecylbenzenesulfonate were added to deionized water and ultrasonically dispersed for 30 minutes. Pyrrole monomer was slowly added under ice bath stirring, with a pyrrole to silver powder mass ratio of 1:13–1:15 and a ferric chloride to pyrrole molar ratio of 2.3:1. After reacting for 8 hours, the mixture was washed, filtered, and vacuum dried at 60°C for 12 hours to obtain modified silver nanoparticles coated with a polypyrrole / silver chloride / silver monoxide composite shell; the mass fraction of polypyrrole was 13.5–14.5 wt%.

[0060] S5, Preparation of conductive silver paste

[0061] S5-1, Preparation of Flexible Resin: Under nitrogen protection, isophorone diisocyanate was dissolved in N,N-dimethylformamide, and dibutyltin dilaurate was added; the temperature was raised to 80℃, and palmitol was slowly added dropwise, reacting for 4 hours; then polytetrahydrofuran diol with a number average molecular weight of 1000 was added, and the reaction was continued at 110℃ for 5 hours; after cooling, precipitation, washing, and drying, a polyurethane prepolymer was obtained; this prepolymer was mixed with bisphenol A type epoxy resin E-51 at a mass ratio of 1:1 to obtain the resin matrix.

[0062] S5-2, Silver Paste Preparation: The modified silver nanoparticles obtained in S4, the resin matrix obtained in S5-1, diethylene glycol butyl ether acetate, leveling agent, and defoamer are blended together; wherein the modified silver nanoparticle content is 70-72 wt%, and the resin matrix content is 20-22 wt%; after high-speed dispersion and three-roll milling, a uniform conductive silver paste with a viscosity of 700-900 cps is obtained. Wetting and dispersing agents can be further added to the silver paste to delay surface drying, and high-boiling-point solvents and thixotropy are used to adjust its viscosity to maintain a high viscosity during standing to prevent sedimentation, and the viscosity decreases under the shearing action of scraping to facilitate filling.

[0063] S6, Silver paste filling and surface cleaning

[0064] The conductive silver paste prepared in S5 is applied by scraping into the grid grooves formed in S3. After filling, excess silver paste is scraped off. Subsequently, the substrate surface is treated with plasma cleaning for 30–60 seconds to remove residual silver paste from the photoresist surface and ensure insulation between the grids.

[0065] S7, pulsed light sintering and finished product processing

[0066] The substrate treated with S6 was placed in a pulsed light sintering equipment and sintered using a pulsed xenon lamp. The sintering parameters were: single pulse energy 6-7 J / cm², pulse width 450-550 μs, number of pulses 2, and pulse interval 1 second. Through the instantaneous high-energy pulse, the surface of the nano-silver particles in the groove was fused to form a dense conductive mesh, and the instantaneous peak temperature of the substrate did not exceed 75℃.

[0067] After the finished product is sintered, it is naturally cooled to obtain a low-reflection flexible transparent conductive film. Optionally, a transparent protective coating can be applied to the surface of the conductive film.

[0068] Please see Figures 2-7A scraper mechanism is used in a method for preparing a nano-silver transparent conductive film. The scraper mechanism includes a composite hollow scraper 1 and a feed slot 2 opened on the top of one side of the composite hollow scraper 1. A conveyor belt assembly is fitted inside the composite hollow scraper 1, and a return space communicating with the feed slot 2 is formed between the top of the conveyor belt assembly and the top inner wall of the composite hollow scraper 1.

[0069] The conveyor belt assembly includes a conveyor belt body 3 and two drive shafts 4. The two drive shafts 4 are respectively fitted inside both sides of the conveyor belt body 3, and the ends of both drive shafts 4 are threaded through and fitted into the corresponding sidewall structure of the composite hollow scraper 1 via sealing rings. This not only provides transmission support to the conveyor belt body 3, but also maintains a sealed connection between the drive shafts 4 and the composite hollow scraper 1 during rotation, preventing leakage of the recovered silver paste material. One end of one drive shaft 4 is fitted into the middle of the second gear 9. The two sides of the conveyor belt body 3... The surfaces are respectively attached to the inner walls on both sides of the composite hollow scraper 1, which not only improves the stability of the conveyor belt body 3, but also can scrape and clean or block the silver paste material on the surface of the conveyor belt body 3. In addition, a C-shaped scraper 13 is installed inside the top of the other side of the composite hollow scraper 1, which can be attached to and contact one side of the surface of the conveyor belt body 3. The C-shaped scraper 13 can passively scrape and clean the silver paste material conveyed on the surface of the conveyor belt body 3 and concentrate the silver paste material conveyed by the conveyor belt body 3 in the top space on the other side of the composite hollow scraper 1.

[0070] The top inner side of the other side of the composite hollow scraper 1 is provided with a power assembly and a spiral blade shaft 5. The two ends of the spiral blade shaft 5 pass through the front and rear ends of the top of the other side of the composite hollow scraper 1. The power assembly includes a motor assembly, a first gear 8, a second gear 9 and a third gear 10 installed on the top of the other side of the composite hollow scraper 1. The two sides of the second gear 9 are meshed with the first gear 8 and the third gear 10 respectively. The first gear 8 is connected to the output structure of the motor assembly. The second gear 9 and the third gear 10 are connected to the conveyor belt assembly and the spiral blade shaft 5 respectively.

[0071] The motor assembly includes a reducer 6 and a servo motor 7, both mounted on the top surface of the other side of the composite hollow scraper 1. The input end of the reducer 6 is connected to the output end of the servo motor 7, and the output end of the reducer 6 is fitted inside the middle of the first gear 8. Both ends of the spiral blade shaft 5 are set as smooth rod structures, and one end of the spiral blade shaft 5 is fitted through a sealing ring to the rear end structure of the top of the other side of the composite hollow scraper 1, improving the sealing effect after the spiral blade shaft 5 and the composite hollow scraper 1 are fitted together. One end of the spiral blade shaft 5 is fitted inside the middle of the third gear 10, and the other end of the spiral blade shaft 5 is fitted with a guide pipe 12 installed at the front end of the top of the other side of the composite hollow scraper 1. The surface of the guide pipe 12 away from the composite hollow scraper 1 has an external thread, thereby collecting and guiding the silver paste material spirally output by the spiral blade shaft 5, meeting the need for the continuous recycling container to give way to the composite hollow scraper 1.

[0072] The top of the composite hollow scraper 1 is fixed with a support frame 11, which provides structural conditions for subsequent positioning and installation. The inner walls of the front and rear ends of the composite hollow scraper 1 are fixed with limiting partitions 14 that are in close contact with the top surface of the conveyor belt body 3. This further constrains and guides the output channel at the top of the conveyor belt body 3, maintaining the continuous and smooth recycling and conveying effect of the conveyor belt body 3.

[0073] In use, in step S6 above, for the requirements of scraping coating, the scraper mechanism set above is used in conjunction with the existing conveyor belt equipment for conveying the substrate and is fixedly set above the conveyor belt equipment, forming a certain angle with the substrate surface and maintaining contact pressure;

[0074] The substrate is carried by a conveyor belt and moves at a constant speed along a preset direction. Silver paste is pre-applied to the substrate surface. When the substrate passes under the composite hollow scraper 1, the scraper presses the silver paste into the grid grooves and simultaneously scrapes off excess silver paste from the surface. The scraped-off excess silver paste enters the feed trough 2 due to inertia and then falls onto the top surface of the conveyor belt body 3. Simultaneously, the servo motor 7 is activated, driving the corresponding first gear 8 to rotate synchronously via the reducer 6. Then, the second gear 9 and third gear 10, which mesh with the first gear 8, also rotate synchronously. Therefore, under the drive of the second gear 9 and two drive shafts 4, the conveyor belt body 3 automatically moves the silver paste falling onto its top surface upward and transports it to the top of the other side of the composite hollow scraper 1. The spiral blade shaft 5, driven by the third gear 10, spirally transports the silver paste material concentrated in the top of the other side of the composite hollow scraper 1 to the inside of the guide pipe 12. Then, it is collected and stored in a collection container that is threadedly connected to the guide pipe 12. After a certain amount is collected, it is replaced. This satisfies the continuous scraping and coating requirements of the composite hollow scraper 1 and related structures, reduces the number of downtime cleanings, and ensures the efficient operation of the overall process.

[0075] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Moreover, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a transparent conductive nanofilm of silver nanoparticles, characterized in that: The following steps are included: S1. Substrate pretreatment and photoresist coating Take a flexible transparent substrate, clean and dry it; coat the substrate surface with SU-8 3025 negative photoresist with a coating thickness of 4-5 μm, and then perform a two-stage drying process. S2, Exposure and Re-drying Exposure was performed using an ultraviolet light source in conjunction with a chromium mask, with an exposure energy of 90–110 mJ / cm². Then, a two-stage drying process was carried out again. S3, Development and Hardening The film was developed using propylene glycol methyl ether acetate to form a grid groove with a line width of 3-5 μm, a depth of 4-5 μm, and an aspect ratio of ≥1:

1. Then, it was hardened and baked at 100℃-120℃ for 20-25 minutes. S4. Preparation of modified silver nanoparticles Silver powder was prepared using ascorbic acid as a reducing agent and ball-milled to obtain silver powder with a particle size of 50-70 nm. After ozone oxidation, the silver powder was reacted with pyrrole in the presence of ferric chloride hexahydrate and sodium dodecylbenzenesulfonate to obtain modified silver nanoparticles with a polypyrrole / silver chloride / silver monoxide composite shell, wherein the mass fraction of polypyrrole was 13.5-14.5 wt%. S5, Preparation of conductive silver paste Modified silver nanoparticles are mixed with polyurethane-modified epoxy resin matrix, solvent and additives to obtain silver paste with a viscosity of 700-900 cps, wherein the content of modified silver nanoparticles is 70-72 wt%. S6, Silver paste filling and surface cleaning The silver paste is applied to the grid grooves using a scraper mechanism, while excess silver paste is scraped off simultaneously. Plasma cleaning is then used to remove surface residue. S7, pulsed light sintering and finished product processing Pulsed xenon lamp sintering is used, with a single pulse energy of 6-7 J / cm², a pulse width of 450-550 μs, and at least 2 pulses. After natural cooling, the finished product is obtained.

2. The method for preparing a transparent conductive nanofilm of silver according to claim 1, characterized in that: In step S1, the flexible transparent substrate is an optical-grade PET film, a COP film, or a transparent polyimide film. The temperature change range of the two-stage drying process in step S1 is the same as that of the two-stage drying process in step S2, which is 65℃ / 5min followed by a temperature increase to 95℃ / 10min.

3. The method for preparing a nano-silver transparent conductive film according to claim 1, characterized in that: In step S3, the ultraviolet light source is specifically selected as an i-line ultraviolet light source. In step S4, the mass ratio of pyrrole to silver powder is 1:13 to 1:15, and the molar ratio of ferric chloride hexahydrate to pyrrole is 2.3:

1.

4. The method for preparing a nano-silver transparent conductive film according to claim 1, characterized in that: In step S5, the polyurethane modified epoxy resin matrix is ​​prepared by the following method: isophorone diisocyanate and palmitol are reacted at 80°C for 4 hours under the catalysis of dibutyltin dilaurate, and then polytetrahydrofuran diol with a number average molecular weight of 1000 is added and reacted at 110°C for 5 hours. The resulting polyurethane prepolymer is mixed with bisphenol A type epoxy resin E-51 at a mass ratio of 1:

1.

5. The method for preparing a nano-silver transparent conductive film according to claim 1, characterized in that: In step S7, the instantaneous peak temperature of the substrate during the pulsed light sintering process does not exceed 75°C. Step S7 also includes the step of coating a transparent protective coating on the surface of the conductive film.

6. A scraper mechanism used in the preparation method of the nano-silver transparent conductive film as described in claim 1, characterized in that, The scraper mechanism includes a composite hollow scraper (1) and a feed chute (2) opened on the top of one side of the composite hollow scraper (1). The composite hollow scraper (1) is fitted with a conveyor belt assembly, and a return space communicating with the feed chute (2) is formed between the top of the conveyor belt assembly and the top inner wall of the composite hollow scraper (1). The top inner side of the other side of the composite hollow scraper (1) is provided with a power assembly and a spiral blade shaft (5) respectively. The two ends of the spiral blade shaft (5) pass through the front and rear ends of the top of the other side of the composite hollow scraper (1). The power assembly includes a motor assembly installed on the top of the other side of the composite hollow scraper (1), a first gear (8), a second gear (9) and a third gear (10). The two sides of the second gear (9) are meshed with the first gear (8) and the third gear (10) respectively. The first gear (8) is connected to the output structure of the motor assembly. The second gear (9) and the third gear (10) are connected to the conveyor belt assembly and the spiral blade shaft (5) respectively.

7. The scraper mechanism used in the method for preparing a nano-silver transparent conductive film according to claim 6, characterized in that: The conveyor belt assembly includes a conveyor belt body (3) and two drive shafts (4). The two drive shafts (4) are respectively fitted inside the two sides of the conveyor belt body (3), and the ends of the two drive shafts (4) are fitted through the corresponding side wall structure of the composite hollow scraper (1) by sealing rings. One end of one drive shaft (4) is fitted to the middle of the second gear (9). The surfaces on both sides of the conveyor belt body (3) are respectively attached to the inner walls on both sides of the composite hollow scraper (1), and a C-shaped scraper (13) that can be attached to one side of the surface of the conveyor belt body (3) is fitted inside the top of the other side of the composite hollow scraper (1).

8. The scraper mechanism used in the method for preparing a nano-silver transparent conductive film according to claim 6, characterized in that: The motor assembly includes a reducer (6) and a servo motor (7) both mounted on the top surface of the other side of the composite hollow scraper (1). The input end of the reducer (6) is connected to the output end of the servo motor (7), and the output end of the reducer (6) is fitted inside the middle of the first gear (8).

9. The scraper mechanism used in the method for preparing a nano-silver transparent conductive film according to claim 6, characterized in that: Both ends of the spiral blade shaft (5) are set as smooth rod structures, and one end of the spiral blade shaft (5) is fitted through a sealing ring to the rear end structure of the top of the other side of the composite hollow scraper (1). One end of the spiral blade shaft (5) is fitted to the inner side of the middle of the third gear (10), and the other end of the spiral blade shaft (5) is fitted with a guide tube (12) installed at the front end of the top of the other side of the composite hollow scraper (1). The guide tube (12) has an external thread on the surface of the end away from the composite hollow scraper (1).

10. The scraper mechanism used in the method for preparing a nano-silver transparent conductive film according to claim 7, characterized in that: The top of the composite hollow scraper (1) is fixed with a support frame (11), and the inner walls of the front and rear ends of the composite hollow scraper (1) are fixed with limiting partitions (14) that are in contact with the top surface of the conveyor belt body (3).

Images