Transparent conductive ink for touch display screen as well as preparation method and application of transparent conductive ink

Abstract

The invention provides transparent conductive ink for a touch display screen and a preparation method and application of the transparent conductive ink, and belongs to the technical field of ink, the transparent conductive ink comprises conductive filler, and the conductive filler comprises silver nanowires and a conductive metal organic framework layer coating the surfaces of the silver nanowires; a polymer binder, wherein the polymer binder comprises a furan functionalized polyurethane prepolymer and a bismaleimide cross-linking agent; and an organic solvent; wherein the conductive metal organic framework layer comprises a hexaaminotriphenyl-nickel coordination polymer. According to the invention, the silver nanowire is coated in situ by adopting the hexaaminotriphenyl-nickel coordination polymer, so that the problems of micro short circuit caused by silver ion migration and haze increase caused by high contact resistance are effectively avoided, the conductivity of the display module is improved, and the service life of the display module is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of ink technology, specifically relating to a transparent conductive ink for touch displays, its preparation method, and its application. Background Technology

[0002] Transparent conductive materials, as core components of touch display modules, are widely used in smartphones, automotive displays, and human-computer interaction terminals due to their excellent photoelectric transmission performance. Currently, the industry mainly uses magnetron sputtering of indium tin oxide (ITO) for production. This process utilizes the high transmittance and low sheet resistance of ITO materials to fabricate transparent electrodes. Compared to other conductive polymers, the ITO solution has significant advantages in terms of industry chain maturity and photoelectric performance. However, this process is highly susceptible to limitations imposed by the inherent brittleness of the material and processing technology when fabricating next-generation flexible and foldable displays, leading to product yield bottlenecks. As a ceramic material, ITO has extremely low elongation at break and will fracture brittlely when the bending radius is less than 5mm, failing to meet the mechanical performance requirements of foldable screens.

[0003] As the most promising alternative to ITO, silver nanowires (AgNW) possess excellent flexibility and conductivity. However, the process of constructing their conductive network is essentially a physical contact process based on random stacking. This "point contact" mechanism between wires creates a significant contact barrier for carrier transport within the percolation network, resulting in high contact resistance. Increasing the silver wire density to reduce resistance inevitably leads to a sharp increase in film haze, making it difficult to meet the stringent optical transparency requirements of high-end displays. More importantly, silver nanowires have high chemical activity and specific surface area at the microscale. Under the high temperature, high humidity, and voltage bias environments of actual industrial applications, elemental silver is highly susceptible to oxidation, releasing silver ions. These free metal ions, driven by an electric field, undergo electrochemical migration across the insulating layer and are reduced at the cathode to form dendrites, ultimately causing irreversible micro-short circuits. Even trace amounts of sulfidation or oxidation reactions in the system can lead to localized open circuits in the conductive network, severely shortening the lifespan of the display module.

[0004] To address the contact resistance and stability issues of silver nanowires, the industry currently employs methods such as simply increasing the thickness of the protective layer or introducing conventional polymer binders. However, this traditional modification strategy has significant inherent drawbacks: limited by the electrical properties of the insulating polymer, an excessively thick coating, while blocking water and oxygen, will sever the conductive pathways between nanowires, leading to a substantial increase in sheet resistance; and conventional binders lack the ability to chemically complex or passivate silver ions, failing to fundamentally inhibit the lattice ionization and migration of silver ions, resulting in rapid performance degradation of the conductive film under harsh weathering tests. Therefore, there is a need to develop a novel conductive ink system that can reduce silver ion migration through chemical means and is compatible with low-cost printing processes to solve the problems of high contact resistance and poor electrochemical stability in existing technologies. Summary of the Invention

[0005] In view of the above situation and to overcome the defects of the prior art, the purpose of the present invention is to provide a transparent conductive ink for touch screens, a method for preparing the ink and its application, so as to at least partially solve the problems mentioned in the background art.

[0006] The technical solution adopted in this invention is as follows: The first aspect of this invention provides a transparent conductive ink for touch displays, comprising the following steps: The conductive filler includes silver nanowires and a conductive metal-organic framework layer coated on the surface of the silver nanowires. A polymeric adhesive, comprising a furan-functionalized polyurethane prepolymer and a bismaleimide crosslinking agent; and Organic solvents; The conductive metal-organic framework layer comprises a hexaaminotriphenyl-nickel coordination polymer.

[0007] In some embodiments of the present invention, the furan-functionalized polyurethane prepolymer comprises a soft segment composed of polytetrahydrofuran ether diol and a hard segment composed of isophorone diisocyanate.

[0008] In some embodiments of the present invention, the transparent conductive ink further includes a rheology modifier, a wetting agent, and a defoamer; Based on the total weight of the conductive ink, the mass percentage content of each component is as follows: conductive filler 3.5wt%-4.5wt%; polymer binder 15.0wt%-20.0wt%; rheology modifier 0.5wt%-1.5wt%; wetting agent 0.1wt%-0.5wt%; defoamer 0.05wt%-0.3wt%; the balance is organic solvent; The rheology modifier is selected from hydroxypropyl methylcellulose or fumed silica; the organic solvent includes diethylene glycol butyl ether and terpineol.

[0009] A second aspect of this invention provides a method for preparing a transparent conductive ink for a touch display screen, comprising the following steps: S1. Under a nitrogen atmosphere, copper chloride is added to ethylene glycol and heated to the reaction temperature. Then, silver nitrate and polyvinylpyrrolidone are added to carry out a reduction growth reaction to obtain silver nanowires. S2. Add nickel chloride and 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride to water, add the silver nanowires and stir evenly, then adjust the pH value to 8.5-9 and carry out in-situ coordination polymerization reaction to obtain conductive filler; S3. Polytetrahydrofuran ether diol and isophorone diisocyanate are mixed and heated to obtain a prepolymer. Then, furfuryl alcohol is added to carry out an end-capping reaction to obtain a furan-functionalized polyurethane prepolymer. Bismaleimide is dissolved in a solvent and added to the polyurethane prepolymer and mixed evenly to obtain a mixture. S4. Add the conductive filler, rheology modifier, wetting agent and defoamer to the mixture obtained in step S3, and mix and disperse to obtain the transparent conductive ink.

[0010] In some embodiments of the present invention, in step S1, the reaction temperature is 145°C to 155°C; The molar ratio of copper chloride to silver nitrate is 0.01:1 to 0.03:1, and the molar ratio of polyvinylpyrrolidone to silver nitrate is 2.5:1 to 3.5:1.

[0011] In some embodiments of the present invention, in step S2, the molar ratio of nickel chloride to 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride is 1.4:1 to 1.6:1, and the mass ratio of silver nanowires to 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride is 8:1 to 15:1. The in-situ coordination polymerization reaction is carried out at a temperature of 55°C to 65°C and for a reaction time of 2.5 hours to 3.5 hours.

[0012] In some embodiments of the present invention, in step S3, the polytetrahydrofuran ether diol and isophorone diisocyanate are mixed and heated to a temperature of 75°C to 85°C, and the reaction is carried out in the presence of a catalyst. The catalyst is dibutyltin dilaurate, and its addition amount is 0.03% to 0.08% of the total mass of the reactants.

[0013] In some embodiments of the present invention, in step S3, the end-capping reaction is carried out under constant temperature conditions of 75°C to 85°C for a reaction time of 30 to 60 minutes.

[0014] A third aspect of this invention provides a method for preparing a transparent conductive film for a touch display screen, comprising the following steps: (1) Print the transparent conductive ink onto a substrate; (2) Dry the printed substrate at 75°C-85°C for 5 to 15 minutes; (3) The dried coating is sintered; (4) The sintered coating is heated at 80°C-90°C for 30 to 60 minutes to cure, thereby obtaining the transparent conductive film.

[0015] A fourth aspect of the present invention provides a touch display module, comprising a display panel and a transparent conductive film disposed on the display panel, wherein the transparent conductive film is prepared by the above-described preparation method.

[0016] The beneficial effects achieved by this invention are as follows: This invention employs a hexaaminotriphenyl-nickel coordination polymer to in-situ coat silver nanowires, effectively avoiding micro-short circuits caused by silver ion migration and haze increases due to high contact resistance, thereby improving conductivity and the lifespan of the display module. Simultaneously, the thermally reversible polyurethane constructed from a furan-functionalized polyurethane prepolymer and a bismaleimide crosslinking agent avoids irreversible fracture failure caused by stress concentration during processing, thus significantly improving the yield of the touch display module. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0019] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0020] To address the problems raised in the background art, the first aspect of the present invention provides a transparent conductive ink for touch displays, comprising the following steps: The conductive filler includes silver nanowires and a conductive metal-organic framework layer coated on the surface of the silver nanowires. A polymeric adhesive, comprising a furan-functionalized polyurethane prepolymer and a bismaleimide crosslinking agent; and Organic solvents; The conductive metal-organic framework layer comprises a hexaaminotriphenyl-nickel coordination polymer.

[0021] First, this invention employs a hexaaminotriphenyl-nickel coordination polymer (Ni-HITP) to in-situ coat silver nanowires, constructing a core-shell structured conductive filler. Ni-HITP, as a two-dimensional conductive metal-organic framework, combines a dense lattice structure with excellent conductivity. On one hand, this coating layer can block the penetration of sulfur ions and water oxygen from the environment, inhibiting the lattice ionization and electrochemical migration of silver ions under high temperature, high humidity, and electric field conditions, thereby preventing micro-short circuits caused by silver dendrite growth and improving the lifespan of the display module. On the other hand, this conductive layer increases the effective electrical contact area at the nanowire overlap, reducing the contact barrier, enabling the conductive film to achieve low sheet resistance with a relatively low silver wire packing density. This results in excellent conductivity while ensuring high light transmittance and low haze.

[0022] Secondly, this invention constructs a thermally reversible dynamic covalent bond bonding system based on the Diels-Alder reaction by introducing a furan-functionalized polyurethane prepolymer and a bismaleimide crosslinking agent. Specifically, by utilizing the temperature-responsive characteristics of this dynamic covalent bond, the microstructure of the conductive coating can be controlled. This means maintaining a stable crosslinked network at room temperature to provide sufficient surface hardness and adhesion, while undergoing reverse dissociation at high temperatures (>110℃) to restore the fluidity of the polymer chains. This enables automatic filling and healing of microcracks or indentations, thus avoiding irreversible fracture failures caused by stress concentration during processing of traditional brittle electrode materials or thermosetting resins, effectively improving the yield of touch display modules.

[0023] In summary, this invention effectively avoids the problems of micro-short circuits caused by silver ion migration and haze increase caused by high contact resistance by using a hexaaminotriphenyl-nickel coordination polymer to in situ coat silver nanowires, thereby improving its conductivity and the service life of the display module. At the same time, the thermally reversible polyurethane constructed by furan-functionalized polyurethane prepolymer and bismaleimide crosslinking agent avoids irreversible fracture failure caused by stress concentration during processing, thereby significantly improving the yield of touch display modules.

[0024] In some embodiments, the furan-functionalized polyurethane prepolymer comprises soft segments composed of polytetrahydrofuran ether diol and hard segments composed of isophorone diisocyanate. Polytetrahydrofuran ether diol, as a polyether-type soft segment, imparts excellent low-temperature flexibility and hydrolytic stability to the material, enabling the conductive film to effectively absorb and dissipate stress during small-radius bending, preventing physical damage to the conductive network due to matrix brittleness. The alicyclic hard segment composed of isophorone diisocyanate possesses moderate reactivity and good photochemical stability, and its hydrogen-bonded crosslinking enhances the cohesive strength and surface hardness of the coating.

[0025] In some embodiments, the transparent conductive ink further includes a rheology modifier, a wetting agent, and a defoamer; Based on the total weight of the conductive ink, the mass percentage content of each component is as follows: conductive filler 3.5wt%-4.5wt%; polymer binder 15.0wt%-20.0wt%; rheology modifier 0.5wt%-1.5wt%; wetting agent 0.1wt%-0.5wt%; defoamer 0.05wt%-0.3wt%; the balance is organic solvent; The rheology modifier is selected from hydroxypropyl methylcellulose or fumed silica; the organic solvent includes diethylene glycol butyl ether and terpineol. A conductive filler content of 3.5wt%-4.5wt% keeps the ink system above the percolation threshold, minimizing haze while ensuring conductivity. The introduction of the rheology modifier endows the ink with significant pseudoplastic fluid characteristics, meaning it can smoothly pass through the screen during high-shear printing and maintain its linear shape without collapsing during low-shear leveling. Combined with the synergistic effect of wetting agents and defoamers, pinholes and craters on the printed surface are effectively eliminated, ensuring uniformity and surface integrity of coating on large-area flexible substrates.

[0026] A second aspect of this invention provides a method for preparing a transparent conductive ink for a touch display screen, comprising the following steps: S1. Under a nitrogen atmosphere, copper chloride is added to ethylene glycol and heated to the reaction temperature. Then, silver nitrate and polyvinylpyrrolidone are added to carry out a reduction growth reaction to obtain silver nanowires. S2. Add nickel chloride and 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride to water, add the silver nanowires and stir evenly, then adjust the pH value to 8.5-9 and carry out in-situ coordination polymerization reaction to obtain conductive filler; S3. Polytetrahydrofuran ether diol and isophorone diisocyanate are mixed and heated to obtain a prepolymer. Then, furfuryl alcohol is added to carry out an end-capping reaction to obtain a furan-functionalized polyurethane prepolymer. Bismaleimide is dissolved in a solvent and added to the polyurethane prepolymer and mixed evenly to obtain a mixture. S4. Add the conductive filler, rheology modifier, wetting agent and defoamer to the mixture obtained in step S3, and mix and disperse to obtain the transparent conductive ink.

[0027] In the preparation of the conductive filler, polyvinylpyrrolidone (PVP) on the surface of silver nanowires is used as a bridge. Its carbonyl functional groups coordinate with nickel ions, inducing local enrichment of the reaction precursor at the silver wire interface. This heterogeneous nucleation mechanism ensures that the conductive MOF shell can tightly and uniformly coat the silver wire surface, constructing a core-shell heterojunction with electrochemical shielding capabilities. In the binder system, a thermoreversible chemical system based on the Diels-Alder reaction is constructed using furan-functionalized polyurethane and bismaleimide. The principle lies in the dynamic covalent bonds formed through the [4+2] cycloaddition reaction, which allow the material to maintain a stable cross-linked network at room temperature, while reversibly dissociating the chemical bonds and restoring fluidity upon heating. This mechanism allows the material to repair physical damage through the recombination of micro-segments, thereby ensuring the integrity and reliability of the conductive network during complex deformation and bonding processes.

[0028] In some embodiments, in step S1, the reaction temperature is 145°C to 155°C; the molar ratio of copper chloride to silver nitrate is 0.01:1 to 0.03:1, and the molar ratio of polyvinylpyrrolidone to silver nitrate is 2.5:1 to 3.5:1. The temperature range of 145°C to 155°C, combined with a specific concentration of copper chloride, utilizes the oxygen scavenging effect and seed-inducing effect of copper ions to suppress the isotropic aggregation of silver atoms. The specific molar ratio of polyvinylpyrrolidone to silver nitrate ensures the differentiated adsorption of surfactants on different crystal planes, promoting the directional growth of crystals along a one-dimensional direction, thereby obtaining silver nanowires with a high aspect ratio.

[0029] In some embodiments, in step S2, the molar ratio of nickel chloride to 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride is 1.4:1 to 1.6:1, and the mass ratio of silver nanowires to 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride is 8:1 to 15:1; the reaction temperature of the in-situ coordination polymerization reaction is 55°C to 65°C, and the reaction time is 2.5 hours to 3.5 hours. Limiting the molar ratio of nickel ions to ligands ensures the structural regularity of the complex; controlling the pH value within the range of 8.5-9 initiates the deprotonation process of the ligands while avoiding oxidative damage to the surface of the silver nanowires in a strongly alkaline environment. The reaction time of 2.5-3.5 hours ensures that the MOF shell has sufficient density to block ion permeation, effectively suppressing the electrochemical migration of silver ions in an electric field and water-oxygen environment, thus improving the reliability of the conductive film.

[0030] In some embodiments, in step S3, the polytetrahydrofuran ether diol and isophorone diisocyanate are mixed and heated to a temperature of 75°C to 85°C, and the reaction is carried out in the presence of a catalyst; the catalyst is dibutyltin dilaurate, and its addition amount is 0.03% to 0.08% of the total mass of the reactants. The reaction temperature of 75°C-85°C, combined with the catalytic effect of dibutyltin dilaurate, promotes the addition reaction of isocyanate groups with hydroxyl groups while reducing the probability of side reactions such as biuret. This highly linear main-chain structure retains the mechanical flexibility of the material and ensures the accurate positioning of isocyanate groups at the ends of the molecular chain, providing stoichiometrically accurate active sites for subsequent end-capping reactions.

[0031] In some embodiments, in step S3, the end-capping reaction is carried out at a constant temperature of 75°C to 85°C for 30 to 60 minutes. The constant temperature environment of 75°C-85°C promotes the complete reaction between furfuryl alcohol and residual isocyanate groups, eliminating the moisture absorption and gelation problems that may be caused by free isocyanate groups in the system, and improving the storage stability of the conductive ink.

[0032] A third aspect of this invention provides a method for preparing a transparent conductive film for a touch display screen, comprising the following steps: (1) Print the transparent conductive ink onto a substrate; (2) Dry the printed substrate at 75°C-85°C for 5 to 15 minutes; (3) The dried coating is sintered; (4) The sintered coating is heated at 80°C-90°C for 30 to 60 minutes to cure, thereby obtaining the transparent conductive film.

[0033] By setting the curing temperature to 80°C-90°C within the forward range of the Diels-Alder reaction, the matrix is ​​fully cross-linked while retaining the thermal responsiveness of the dynamic covalent bonds in subsequent processing steps.

[0034] A fourth aspect of the present invention provides a touch display module, including a display panel and a transparent conductive film disposed on the display panel, wherein the transparent conductive film is prepared by the above-described preparation method.

[0035] The present invention will be further described below by way of specific embodiments.

[0036] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods already existing in the art; unless otherwise specified, the experimental materials used in the following embodiments are all purchased from commercial channels.

[0037] Example 1: S1. Under a nitrogen protective atmosphere, ethylene glycol was added to a reaction vessel and preheated to a constant temperature of 150°C. A copper chloride ethylene glycol solution was then added. Subsequently, a silver nitrate ethylene glycol solution and a polyvinylpyrrolidone ethylene glycol solution were added dropwise to the reaction vessel. The molar ratio of copper chloride, polyvinylpyrrolidone, and silver nitrate was controlled at 0.02:3:1. After the addition was complete, the reaction was maintained at 150°C for 90 minutes. After the reaction was completed, the product was purified by replacing the solvent with deionized water to obtain a silver nanowire dispersion.

[0038] S2. Nickel chloride hexahydrate and 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride were dissolved in deionized water at a molar ratio of 1.5:1. The silver nanowire dispersion obtained in step S1 was slowly added to the above solution and stirred until homogeneous. The mass ratio of silver nanowires to 2,3,6,7,10,11-hexaaminotriphenylhexahydrochloride ligand was 10:1. Subsequently, dilute ammonia was slowly added dropwise to adjust the pH of the system to 8.5-9, and a trace amount of air was introduced. The system was heated to 60°C and in-situ coordination polymerization was carried out for 3 hours. After the reaction was completed, the mixture was centrifuged, washed, and solvent-replaced with ethanol to obtain the conductive filler.

[0039] S3. Polytetrahydrofuran ether diol was dehydrated under vacuum and added to a reaction flask. Isophorone diisocyanate and dibutyltin dilaurate catalyst were added (0.05% of the total mass of the reactants). The mixture was heated to 80°C and reacted for 3 hours under nitrogen protection. When the isocyanate group content reached the theoretical value, the temperature was lowered to 60°C, and furfuryl alcohol was added for end-capping. The mixture was then kept at 80°C for 45 minutes until the characteristic peak of the isocyanate group disappeared in the infrared spectrum, yielding a furan-functionalized polyurethane prepolymer. Bismaleimide was dissolved in dimethylacetamide and added to the prepolymer solution at room temperature according to the stoichiometric ratio. The mixture was stirred until homogeneous, yielding a homogeneous solution.

[0040] S4. Weigh the following components by mass percentage: conductive filler: 4.0 wt%, polymer binder (solids): 17.5 wt%, rheology modifier (hydroxypropyl methylcellulose): 1.0 wt%, wetting agent (BYK-346): 0.3 wt%, defoamer (Tego 900): 0.1 wt%, and the balance 77.1 wt% is organic solvent (diethylene glycol butyl ether and terpineol volume ratio 4:1). Add the conductive filler, rheology modifier, wetting agent, and defoamer to the mixture obtained in step S3. First, disperse at high speed (1500 rpm, 15 min), then grind and disperse. Finally, filter through a 400-mesh nylon screen to obtain the finished transparent conductive ink.

[0041] The above ink was applied to a polyethylene terephthalate substrate by screen printing and dried at 80°C for 10 min; photonic sintering was performed using a pulsed light device; and finally, thermal crosslinking and curing were carried out at 85°C for 40 min to obtain a transparent conductive film.

[0042] Example 2: The only difference from Example 1 is: In step S1, the reaction temperature is set to 145°C; the molar ratio of copper chloride to silver nitrate is 0.01:1; and the molar ratio of polyvinylpyrrolidone to silver nitrate is 2.5:1.

[0043] In step S2: When preparing the conductive filler, the molar ratio of nickel chloride to ligand is 1.4:1; the mass ratio of silver nanowires to ligand is 8:1; the reaction temperature is 55°C and the reaction time is 2.5h.

[0044] In the ink formulation of step S4, the conductive filler has a mass percentage of 3.5 wt%; the polymer binder has a mass percentage of 15.0 wt%; and the rheology modifier has a mass percentage of 0.5 wt%.

[0045] Example 3: The only difference from Example 1 is: In step S1, the reaction temperature is set to 155°C; the molar ratio of copper chloride to silver nitrate is 0.03:1; and the molar ratio of polyvinylpyrrolidone to silver nitrate is 3.5:1.

[0046] In step S2, during the preparation of the conductive filler, the molar ratio of nickel chloride to ligand is 1.6:1; the mass ratio of silver nanowires to ligand is 15:1; the reaction temperature is 65°C; and the reaction time is 3.5 h.

[0047] In the ink formulation of step S4, the conductive filler has a mass percentage of 4.5 wt%; the polymer binder has a mass percentage of 20.0 wt%; and the rheology modifier has a mass percentage of 1.5 wt%.

[0048] Example 4: The only difference from Example 1 is: In step S3, the amount of catalyst dibutyltin dilaurate added is 0.03% of the total mass of the reactants.

[0049] In step S4, the rheology modifier is fumed silica, and the amount added is 1.2 wt%.

[0050] Example 5: The only difference from Example 1 is: In step S3, the reaction temperature of polytetrahydrofuran ether diol and isophorone diisocyanate is 75°C; the end-capping reaction temperature is 75°C, the reaction time is 60 min, and the amount of catalyst dibutyltin dilaurate added is 0.08% of the total mass of the reactants.

[0051] Example 6: In the film preparation step, the drying conditions are drying at 75℃ for 15 min, and the final curing conditions are heating at 90℃ for 30 min.

[0052] Comparative Example 1: The difference from Example 1 is that in step S2, the in-situ coating of the hexaaminotriphenyl-nickel coordination polymer was not performed; instead, pure silver nanowires were used directly as the conductive filler. That is, step S2 was omitted, and the silver nanowire dispersion purified in step S1 was directly solvent-replaced and mixed with a polymer binder according to the formulation ratio of Example 1 to prepare the ink.

[0053] Comparative Example 2: The only difference from Example 1 is that step S3 uses ordinary thermosetting polyurethane without introducing furan and bismaleimide structures. That is, ordinary hydroxyl acrylic resin and isocyanate curing agent are used as the binder system, which does not have thermally reversible bonds.

[0054] Comparative Example 3: The only difference from Example 1 is that in step S2, in-situ growth is not performed; instead, silver nanowires and hexaaminotriphenyl-nickel coordination polymer powders are prepared separately and then physically mixed. That is, hexaaminotriphenyl-nickel coordination polymer particles are first synthesized separately, and then directly physically blended with silver nanowires at the same mass ratio and added to the ink, thus preventing the formation of a core-shell coating structure.

[0055] To verify the beneficial effects of the present invention, performance tests were conducted on the conductive films prepared in the above embodiments and comparative examples.

[0056] Test method: 1. Initial sheet resistance test: A four-probe sheet resistance tester (model: RTS-9) was used to perform multi-point contact tests on the surface of the cured conductive film at room temperature of 25°C (5 points were randomly selected), and the values ​​were read and averaged.

[0057] 2. Haze test: The optical haze of the conductive film (including the substrate) was tested using a transmittance haze meter (model: WGT-S) in accordance with ASTM D1003 standard.

[0058] 3. Bending Resistance Test: A fully automatic flexural tester (model: ZH-T205) was used. The conductive film was cut into standard strips and fixed on the test fixture. The bending radius R = 1 mm and the bending frequency was 1 Hz, and 200,000 continuous dynamic bends were performed. The resistance change before and after bending was recorded using an online resistance testing system, and the resistance change rate ΔR / R0 = (R after bending - R initial) / R initial × 100%.

[0059] 4. Silver Migration Resistance Test (ECM): The conductive thin film sample was placed in a programmable temperature and humidity chamber, with environmental conditions set at 85°C and 85% RH. A 10V DC bias voltage (source meter model: Keithley 2400) was applied to the electrodes at both ends of the thin film, and the test was conducted continuously for 500 hours. The presence of dendrite formation was observed under a microscope, and the occurrence of short circuits was monitored.

[0060] 5. Self-healing efficiency test: Microscopic scratches with a depth of 5-10 μm are created on the surface of the conductive film using a precision scratch tester to simulate physical damage, and the resistance value after scratching is measured. The sample is then placed on a 120°C heating stage and heated for 5 minutes. After cooling, the resistance value at the scratch site is measured again. Self-healing efficiency = (Rafter scratch - Rafter repair) / (Rafter scratch - Rinitial) × 100%.

[0061] The data from the above tests were statistically analyzed, and the results are shown in Tables 1 and 2.

[0062] Table 1

[0063] Table 2

[0064] Analysis of the test results in Tables 1 and 2 shows that the initial sheet resistance of Example 1 was significantly lower than that of Comparative Example 1. This is because the hexaaminotriphenyl-nickel coordination polymer shell acts as a "conductive solder" between the silver nanowires, increasing the line contact area and reducing the interfacial contact resistance. Example 3 further reduced the sheet resistance to 18 Ω / sq by increasing the conductive filler content to 4.5%, but the haze slightly increased to 0.9%, still meeting the display requirements. Compared to Comparative Example 3, although the same substance was added, the conductive metal-organic framework particles were prone to agglomeration due to physical blending, resulting in a haze as high as 2.1%, severely affecting optical transparency and failing to effectively improve contact resistance (sheet resistance as high as 45 Ω / sq). Example 4 used fumed silica as a rheology modifier, and the haze (1.1%) was slightly higher than that of Example 1 (using hydroxypropyl methylcellulose), indicating that the choice of rheology modifier has a slight impact on optical performance, but it is still within an acceptable range.

[0065] Example 1 exhibited a resistance change rate of less than 5% after 200,000 bends, while Comparative Example 2, using ordinary thermosetting polyurethane, experienced an open circuit during the test. This is attributed to the furan-maleimide system employed in this invention, whose polytetrahydrofuran soft segments provide excellent flexibility. More importantly, Comparative Example 2 completely lacked self-healing capabilities, while Example 1 was able to repair scratch damage after heating, achieving a repair efficiency of 95%. In Example 5, the increased catalyst dosage and crosslinking density, although potentially increasing mechanical strength, restricted chain segment movement, resulting in a slight decrease in self-healing efficiency to 91% and a slight decrease in bending resistance (<7%). This illustrates the importance of controlling crosslinking density.

[0066] Under stringent 85°C / 85%RH / 10V bias testing, Comparative Example 1 (pure silver wire) short-circuited after only 48 hours, indicating severe electrochemical migration of silver ions. Example 1, however, remained normal for over 500 hours, demonstrating that the dense, in-situ grown hexaaminotriphenyl-nickel coordination polymer shell effectively blocked the corrosion of the silver wire by water, oxygen, and the electric field. Although Example 3 reduced the shell thickness to achieve higher conductivity, resulting in a slightly shorter anti-migration time (>450h) compared to Example 1 (>500h), it was still far superior to the comparative example. Comparative Example 3, due to the inability to form a continuous, dense coating layer through physical stacking, exhibited a protective vulnerability, resulting in a localized short circuit after only 120 hours. This further demonstrates the microscopic design advantages of the core-shell structure of this invention.

[0067] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A transparent conductive ink for a touch display panel, characterized by, The transparent conductive ink comprises: a conductive filler, including silver nanowires and a conductive metal organic framework layer coated on surfaces of the silver nanowires; a high-molecular binder, including a furan-functionalized polyurethane prepolymer and a bismaleimide crosslinking agent; and an organic solvent; wherein the conductive metal organic framework layer comprises a hexaamino-triphenyl-nickel coordination polymer.

2. The transparent conductive ink for a touch display screen according to claim 1, characterized by, The furan-functionalized polyurethane prepolymer includes soft segments composed of polytetrahydrofuran ether diol and hard segments composed of isophorone diisocyanate.

3. The transparent conductive ink for a touch display screen according to claim 1, characterized by, The transparent conductive ink further comprises a rheological aid, a wetting agent and a defoaming agent; The mass percentage of each component is as follows: the conductive filler is 3.5wt%-4.5wt%, the high-molecular binder is 15.0wt%-20.0wt%, the rheological aid is 0.5wt%-1.5wt%, the wetting agent is 0.1wt%-0.5wt%, the defoaming agent is 0.05wt%-0.3wt%, and the rest is the organic solvent, based on the total weight of the conductive ink. The rheological aid is selected from hydroxypropyl methyl cellulose or fumed silica; and the organic solvent includes diethylene glycol butyl ether and terpineol.

4. A method for producing the transparent conductive ink for a touch display panel according to any one of claims 1 to 3, characterized by, The method comprises the following steps: S1. Under a nitrogen atmosphere, copper chloride is added to ethylene glycol, heated to a reaction temperature, and then silver nitrate and polyvinylpyrrolidone are added to perform a reduction growth reaction to obtain silver nanowires; S2. Nickel chloride and 2,3,6,7,10,11-hexaamino-triphenyl hexa-hydrochloride are added to water, the silver nanowires are added and stirred until uniform, and then the pH value is adjusted to 8.5-9 to perform an in-situ coordination polymerization reaction to obtain a conductive filler; S3. Polytetrahydrofuran ether diol and isophorone diisocyanate are mixed and heated to react to obtain a prepolymer, and then furfuryl alcohol is added to perform a capping reaction to obtain a furan-functionalized polyurethane prepolymer; bismaleimide is dissolved in a solvent and added to the polyurethane prepolymer to mix uniformly to obtain a mixed solution; S4. The conductive filler, rheological aid, wetting agent and defoaming agent are added to the mixed solution obtained in step S3 to perform mixing and dispersion to obtain the transparent conductive ink.

5. The preparation method according to claim 4, characterized in that, In step S1, the reaction temperature is 145°C to 155°C; The molar ratio of the copper chloride to the silver nitrate is 0.01:1 to 0.03:1, and the molar ratio of the polyvinylpyrrolidone to the silver nitrate is 2.5:1 to 3.5:

1.

6. The preparation method according to claim 4, characterized in that, In step S2, the molar ratio of the nickel chloride to the 2,3,6,7,10,11-hexaamino-triphenyl hexa-hydrochloride is 1.4:1 to 1.6:1, and the mass ratio of the silver nanowires to the 2,3,6,7,10,11-hexaamino-triphenyl hexa-hydrochloride is 8:1 to 15:1; The reaction temperature of the in-situ coordination polymerization reaction is 55°C to 65°C, and the reaction time is 2.5 hours to 3.5 hours.

7. The preparation method according to claim 4, characterized in that, In step S3, the polytetrahydrofuran ether diol and isophorone diisocyanate are mixed and heated to react at a temperature of 75°C to 85°C, and the reaction is performed in the presence of a catalyst; The catalyst is dibutyltin dilaurate, and the addition amount of the catalyst is 0.03% to 0.08% of the total mass of the reactants.

8. The preparation method according to claim 4, characterized in that, In step S3, the end-capping reaction is carried out at a constant temperature of 75°C to 85°C, and the reaction time is 30 minutes to 60 minutes.

9. A method for producing a transparent conductive film for a touch display panel, characterized by, The transparent conductive ink as claimed in any one of claims 1-3, comprising the following steps: (1) printing the transparent conductive ink on a substrate; (2) drying the printed substrate at 75°C-85°C for 5 minutes to 15 minutes; (3) sintering the dried coating layer; (4) curing the sintered coating layer at 80°C-90°C for 30 minutes to 60 minutes to obtain the transparent conductive film.

10. A touch display module, comprising: A display panel and a transparent conductive film disposed on the display panel, wherein the transparent conductive film is prepared by the preparation method of claim 9.

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