Conductive ink for pressure sensitive sensor and pressure sensitive sensor

Abstract

The present invention relates to the technical fields of novel ink and sensor production, and provides a conductive ink for a pressure-sensitive sensor and a pressure-sensitive sensor. The conductive ink comprises the following components: a resin, which is an ink resin and accounts for 40-60 wt% of the total weight of the conductive ink; conductive particles, which include carbon powder, carbon nanotubes and silver powder, and the conductive particles are mixed with the resin at a ratio of 5-30 wt%; a dispersant, which accounts for 0.5-2 wt% of the total weight of the conductive ink; a flexible additive, which accounts for 1-8 wt% of the total weight of the conductive ink; a cross-linking agent, which accounts for 0.1-1 wt% of the total weight of the conductive ink; and a solvent, which accounts for 10-30 wt% of the total weight of the conductive ink. The flexibility, conductivity and reliability of the conductive ink are improved, and when used to produce a pressure-sensitive sensor, the stability of the pressure-sensitive sensor can be improved.

Description

Technical Field

[0001] The present invention relates to the technical fields of novel inks, sensor production, and the like, and in particular to a conductive ink for a pressure-sensitive sensor and a pressure-sensitive sensor. Background Art

[0002] A pressure-sensitive sensor is a sensor device used to sense changes in pressure, and is commonly used on objects such as cars, mattresses, pillows, and musical instruments. For example, a car's seat cushion sensor can be used to detect whether a passenger is sitting on the seat, the passenger's weight distribution, and the seat's occupancy status. Pressure-sensitive sensors usually use a flexible substrate, and a conductive path is formed by printing conductive ink on the flexible substrate (such as PET conductive cloth). The conductive path can adapt to the bending and deformation of the vehicle seat and detect the status of the passenger on the seat. Therefore, the flexibility, conductivity, and reliability of the conductive ink are very critical in the production of pressure-sensitive sensors. In the prior art, the conductive inks used in the production of pressure-sensitive sensors vary in composition and ratio, and many conductive inks need to be improved in terms of flexibility, conductivity, reliability and other performance.

[0003] In summary, the conductive ink used in the production of existing pressure-sensitive sensors has technical problems such as flexibility, conductivity and reliability that need to be improved. Summary of the invention

[0004] In view of the deficiencies in the above-mentioned prior art, the present invention provides a conductive ink for a pressure-sensitive sensor and a pressure-sensitive sensor, so as to improve the flexibility, conductivity and reliability of the conductive ink, and further improve the stability of the pressure-sensitive sensor.

[0005] In a first aspect, the present invention provides a conductive ink for a pressure-sensitive sensor, wherein the conductive ink comprises the following components:

[0006] Resin, the resin is ink resin, accounting for 40-60 wt% of the total weight of the conductive ink;

[0007] Conductive particles, the conductive particles comprising carbon powder, carbon nanotubes and silver powder, the conductive particles being mixed with the resin at a ratio of 5-30 wt%;

[0008] A dispersant, accounting for 0.5-2 wt% of the total weight of the conductive ink, is used to improve the uniform distribution of the conductive particles in the resin;

[0009] A flexible additive, accounting for 1-8 wt% of the total weight of the conductive ink, is used to enhance the flexibility of the conductive ink so that it can adapt to the bending and deformation of the pressure-sensitive sensor;

[0010] A cross-linking agent, accounting for 0.1-1 wt% of the total weight of the conductive ink, is used to improve the adhesion and durability of the conductive ink;

[0011] The solvent, accounting for 10-30 wt% of the total weight of the conductive ink, is used to adjust the viscosity and printing performance of the ink.

[0012] In a second aspect, the present invention provides a pressure-sensitive sensor, the production of which is applied to the above-mentioned conductive ink for pressure-sensitive sensors.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The present invention provides a conductive ink for a pressure-sensitive sensor and a pressure-sensitive sensor, wherein the conductive ink comprises the following components: a resin, which is an ink resin and accounts for 40-60 wt% of the total weight of the conductive ink; conductive particles, which include carbon powder, carbon nanotubes and silver powder, and are mixed with the resin at a ratio of 5-30 wt%; a dispersant, which accounts for 0.5-2 wt% of the total weight of the conductive ink and is used to improve the uniform distribution of the conductive particles in the resin; a flexible additive, which accounts for 1-8 wt% of the total weight of the conductive ink and is used to enhance the flexibility of the conductive ink so that it can adapt to the bending and deformation of the pressure-sensitive sensor; a cross-linking agent, which accounts for 0.1-1 wt% of the total weight of the conductive ink and is used to improve the adhesion and durability of the conductive ink; and a solvent, which accounts for 10-30 wt% of the total weight of the conductive ink and is used to adjust the viscosity and printing performance of the ink. The flexibility, conductivity and reliability of the conductive ink are improved, and when used to produce a pressure-sensitive sensor, the stability of the pressure-sensitive sensor can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. Some specific embodiments of the present invention will be described in detail in an exemplary and non-restrictive manner with reference to the drawings. The same reference numerals in the drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the drawings:

[0016] Figure 1 It is a flow chart of a method for producing conductive ink for pressure-sensitive sensors according to an embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0018] Embodiment 1

[0019] This embodiment provides a conductive ink for a pressure-sensitive sensor, wherein the conductive ink comprises the following components:

[0020] Resin, the resin is ink resin, accounting for 40-60 wt% of the total weight of the conductive ink;

[0021] Conductive particles, the conductive particles comprising carbon powder, carbon nanotubes and silver powder, the conductive particles being mixed with the resin at a ratio of 5-30 wt%;

[0022] A dispersant, accounting for 0.5-2 wt% of the total weight of the conductive ink, is used to improve the uniform distribution of the conductive particles in the resin;

[0023] A flexible additive, accounting for 1-8 wt% of the total weight of the conductive ink, is used to enhance the flexibility of the conductive ink so that it can adapt to the bending and deformation of the pressure-sensitive sensor;

[0024] A cross-linking agent, accounting for 0.1-1 wt% of the total weight of the conductive ink, is used to improve the adhesion and durability of the conductive ink;

[0025] The solvent, accounting for 10-30 wt% of the total weight of the conductive ink, is used to adjust the viscosity and printing performance of the ink.

[0026] It should be noted that in this embodiment, the conductive ink comprises the following components: resin, which is ink resin and accounts for 40-60 wt% of the total weight of the conductive ink; conductive particles, which include carbon powder, carbon nanotubes and silver powder, and the conductive particles are mixed with the resin at a ratio of 5-30 wt%; dispersant, which accounts for 0.5-2 wt% of the total weight of the conductive ink and is used to improve the uniform distribution of the conductive particles in the resin; flexible additives, which account for 1-8 wt% of the total weight of the conductive ink and are used to enhance the flexibility of the conductive ink so that it can adapt to the bending and deformation of the pressure-sensitive sensor; cross-linking agents, which account for 0.1-1 wt% of the total weight of the conductive ink and are used to improve the adhesion and durability of the conductive ink; solvents, which account for 10-30 wt% of the total weight of the conductive ink and are used to adjust the viscosity and printing performance of the ink. The flexibility, conductivity and reliability of the conductive ink are improved, and when used to produce pressure-sensitive sensors, the stability of the pressure-sensitive sensors can be improved.

[0027] It should be noted that the following are some experiments and data that demonstrate the performance improvement of conductive ink for pressure-sensitive sensors in terms of flexibility, conductivity and reliability.

[0028] Experiment 1: The components and proportions of the conductive ink are selected as follows: ink resin: 50 wt%; conductive particles (mixed with carbon powder, carbon nanotubes and silver powder): 20 wt%; dispersant: 1 wt%; flexible additive: 7 wt%; crosslinker: 0.5 wt%; solvent: 21.5 wt%. The selected components are mixed and stirred to prepare a conductive ink. Alternatively, the components and proportions of the conductive ink are selected as follows: ink resin: 45 wt%; conductive particles (mixed with carbon powder, carbon nanotubes and silver powder): 15 wt%; dispersant: 0.5 wt%; flexible additive: 5 wt%; crosslinker: 0.7 wt%; solvent: 34.8 wt%; the selected components are combined and stirred to prepare a conductive ink. The conductive ink prepared is printed on a flexible substrate (such as polyester film), and a 180° bending test is performed to record whether cracks or breaks appear on the ink surface. In the experimental data, the initial state: the ink surface is smooth and crack-free. After 180° bending 5 times: the ink has no cracks and maintains integrity. After bending 180° 100 times: the ink has no cracks and the surface is intact. Experiment 1 proves that the conductive ink exhibits extremely high flexibility and can adapt to the repeated bending and deformation of the pressure-sensitive sensor. It should be noted that in Experiment 1, the ink resin can be polyurethane resin, the carbon powder in the conductive particles can be ultrafine carbon black, the carbon nanotubes in the conductive particles can be multi-walled carbon nanotubes, the silver powder in the conductive particles can be nano-scale spherical silver powder, the dispersant can be a polyoxyethylene non-ionic dispersant, the flexible additive can be dioctyl phthalate, the cross-linking agent can be hexamethylene diisocyanate, and the solvent can be dimethylformamide.

[0029] Experiment 2: The components and proportions of the conductive ink are selected as follows: ink resin: 50 wt%; conductive particles (mixed with carbon powder, carbon nanotubes and silver powder): 20 wt%; dispersant: 1 wt%; flexible additive: 7 wt%; cross-linking agent: 0.5 wt%; solvent: 21.5 wt%; the selected components are mixed and stirred to prepare a conductive ink. Alternatively, the components and proportions of the conductive ink are selected as follows: ink resin: 45 wt%; conductive particles (mixed with carbon powder, carbon nanotubes and silver powder): 15 wt%; dispersant: 0.5 wt%; flexible additive: 5 wt%; cross-linking agent: 0.7 wt%; solvent: 34.8 wt%; the selected components are mixed and stirred to prepare a conductive ink. The prepared conductive ink is printed on a substrate, and its initial conductivity is measured, and the conductivity is measured again after 1000 bending cycles. In the experimental data, the initial conductivity: 1.5 × 10 3 S / m. Conductivity after 1000 bending cycles: 1.45 × 10 3S / m (decreased by about 3%). Experiment 2 proves that the conductivity of the conductive ink remains stable after repeated bending, indicating that the ink has good conductivity and reliability. It should be noted that in Experiment 2, the ink resin can be polyurethane resin, the carbon powder in the conductive particles can be ultrafine carbon black, the carbon nanotubes in the conductive particles can be multi-walled carbon nanotubes, the silver powder in the conductive particles can be nano-scale spherical silver powder, the dispersant can be a polyoxyethylene non-ionic dispersant, the flexible additive can be dioctyl phthalate, the cross-linking agent can be hexamethylene diisocyanate, and the solvent can be dimethylformamide.

[0030] Experiment 3: The components and proportions of the conductive ink are selected as follows: ink resin: 50 wt%; conductive particles (mixed with carbon powder, carbon nanotubes and silver powder): 20 wt%; dispersant: 1 wt%; flexible additive: 7 wt%; cross-linking agent: 0.5 wt%; solvent: 21.5 wt%; the selected components are mixed and stirred to prepare a conductive ink. Alternatively, the components and proportions of the conductive ink are selected as follows: ink resin: 45 wt%; conductive particles (mixed with carbon powder, carbon nanotubes and silver powder): 15 wt%; dispersant: 0.5 wt%; flexible additive: 5 wt%; cross-linking agent: 0.7 wt%; solvent: 34.8 wt%; the selected components are mixed and stirred to prepare a conductive ink. The prepared conductive ink samples are placed under different environmental conditions (such as high temperature and high humidity), and the conductivity changes are measured regularly for 1000 hours. In the experimental data, after 500 hours at high temperature (85°C): the conductivity decreases by less than 5%, and the ink does not show obvious degradation. After 500 hours at high humidity (90% RH): the conductivity decreased by less than 4%, and the ink remained stable. Experiment 3 proved that the conductive ink showed good stability under high temperature and high humidity conditions and had excellent reliability. It should be noted that in Experiment 3, the ink resin can be polyurethane resin, the carbon powder in the conductive particles can be ultrafine carbon black, the carbon nanotubes in the conductive particles can be multi-walled carbon nanotubes, the silver powder in the conductive particles can be nano-scale spherical silver powder, the dispersant can be a polyoxyethylene non-ionic dispersant, the flexible additive can be dioctyl phthalate, the cross-linking agent can be hexamethylene diisocyanate, and the solvent can be dimethylformamide.

[0031] In some preferred embodiments, the ink resin is a polyurethane resin, the basic molecular structure of which is formed by the reaction of polyisocyanate and polyol, and the molecular formula is:

[0032] ;Wherein, R is hexamethylene, R' is p-phenylenediamine, and R'' is an ethylene glycol group.

[0033] It should be noted that polyurethane resin has excellent elasticity and flexibility, which can effectively cope with repeated bending and deformation of vehicle seats during use. This means that under repeated mechanical stress, the coating of conductive ink will not easily crack or break, maintaining the continuity of the conductive path. Moreover, the molecular structure of polyurethane resin contains flexible segments that can be extended under external forces, so that the ink can still maintain stable mechanical properties under various dynamic conditions. At the same time, the good rheological properties and viscosity adjustment ability of polyurethane resin enable conductive particles (such as carbon nanotubes and silver powder) to be evenly distributed in the ink and are not prone to agglomeration. This uniform distribution helps to form a continuous conductive network and improve conductivity. In addition, the good interface compatibility between polyurethane resin and conductive fillers such as carbon nanotubes and silver powder can reduce interface resistance and further improve conductive performance. In addition, polyurethane resin can form good adhesion on the substrate to prevent the conductive ink from falling off during use, thereby improving the reliability of the ink.

[0034] It should also be noted that the hexamethylene group is a long-chain aliphatic group with good flexibility and ductility. This group can increase the flexibility of the polyurethane resin, so that the conductive ink can maintain structural integrity under repeated bending and stretching, avoiding cracks and breaks. The hexamethylene segment can also provide a certain mechanical strength, which helps to provide sufficient strength to resist external forces while maintaining flexibility. The p-xylyl group is a rigid aromatic group that can enhance the compatibility of the polyurethane resin with conductive particles (such as carbon nanotubes and silver powder). This compatibility helps to reduce interfacial resistance and ensure that the conductive particles form a stable conductive network in the resin matrix, thereby improving the conductivity of the conductive ink. The ethylene glycol group is a flexible segment that can provide good adhesion of the polyurethane resin to the substrate. This adhesion can ensure that the conductive ink will not peel or fall off during long-term use, improving the reliability of the conductive ink. The ethylene glycol group can also enhance the environmental tolerance of the polyurethane, allowing the conductive ink to maintain its physical and electrical properties under humidity changes and chemical exposure.

[0035] In some preferred embodiments, after the conductive particles are mixed with the resin, a dispersant, a flexible additive, a cross-linking agent and a solvent are added to obtain a conductive ink mixed solution; an ultrasonic vibrator is inserted into a container containing the conductive ink mixed solution, and the ultrasonic vibrator is started to perform ultrasonic treatment on the mixed solution in the container containing the conductive ink mixed solution, and the power and frequency of the ultrasonic wave are adjusted so that the ultrasonic frequency range is 20 kHz to 40 kHz, the ultrasonic treatment time is controlled to be 30 minutes to 60 minutes, and the temperature of the mixed solution in the container is controlled to be 20°C to 30°C.

[0036] It should be noted that, in this embodiment, within the frequency range of 20 kHz to 40 kHz, ultrasound can produce a strong cavitation effect, generate a large number of tiny bubbles and cause them to burst rapidly, releasing enough energy to effectively disperse the conductive particles. Ultrasonic waves in this frequency range can break the agglomeration between the conductive particles, ensure that the particles are evenly distributed in the resin, and form a stable conductive network, which can not only maximize the dispersion effect, but also avoid excessive wear on the equipment. It can be understood that by performing ultrasonic treatment within the frequency range of 20 kHz to 40 kHz, the conductive particles can be more evenly distributed, forming a continuous conductive path, significantly improving the conductivity of the conductive ink. At the same time, the evenly dispersed conductive particles reduce stress concentration points, thereby improving the flexibility of the conductive ink and maintaining stable mechanical properties during repeated bending and compression.

[0037] It should be noted that, in this embodiment, the ultrasonic treatment time of 30 minutes to 60 minutes is usually sufficient to allow the conductive particles to be completely dispersed in the resin, eliminate agglomeration, and form a uniform distribution in the resin matrix. Ultrasonic treatment for more than 60 minutes may cause overheating or degradation of the resin and the conductive particles, while the treatment time of 30 minutes to 60 minutes can ensure sufficient dispersion while avoiding unnecessary negative effects. It is understandable that within 30 minutes to 60 minutes, the conductive particles can be completely dispersed to form a stable and uniform conductive network, improve the overall conductive performance of the conductive ink, and will not cause material degradation, thereby ensuring the long-term reliability and stability of the conductive ink.

[0038] It should be noted that excessively high temperature can cause degradation of the resin matrix or oxidation of the surface of the conductive particles, thereby affecting the performance of the conductive ink. Controlling the temperature within the range of 20°C to 30°C can effectively avoid these problems and ensure that the components of the conductive ink maintain chemical and physical stability during ultrasonic treatment. In the temperature range of 20°C to 30°C, the cavitation effect is most significant, which can effectively promote the dispersion of the conductive particles while maintaining the stability of the system. In this embodiment, by controlling the temperature within the range of 20°C to 30°C, it can be ensured that the viscosity of the resin and the surface structure of the conductive particles are not affected, thereby maintaining the flexibility, conductivity and adhesion of the conductive ink. The interaction between the conductive particles and the resin matrix can be optimized to form an efficient and stable conductive network, thereby improving the long-term reliability of the conductive ink.

[0039] In some preferred embodiments, the carbon powder is selected from micron-sized graphite powder or ultrafine carbon black, and the particle size range is 1-5 microns. It should be noted that micron-sized graphite powder has high conductivity and can form a stable conductive network, which is particularly suitable for highly filled conductive inks. Ultrafine carbon black can provide better conductivity and improve the dispersion stability of the ink. Carbon powder with smaller particle size can be better compatible with the resin matrix, reduce the risk of fracture of the conductive path, and enhance the flexibility of the ink. The particle size range of 1-5 microns allows the carbon powder to be evenly distributed in the resin, forming a uniform conductive network while maintaining the printing performance and viscosity of the ink.

[0040] In some preferred embodiments, the carbon nanotubes are multi-walled carbon nanotubes (MWCNTs) that have been surface functionally treated, and the length of the multi-walled carbon nanotubes ranges from 5 to 15 microns and the diameter is 10 to 20 nanometers; the surface functional treatment of the multi-walled carbon nanotubes includes: the multi-walled carbon nanotubes are treated with carboxylation to generate carboxylated carbon nanotubes, and the carboxylated carbon nanotubes are treated with amination to generate amination carbon nanotubes. It should be noted that multi-walled carbon nanotubes (MWCNTs) have extremely high conductivity and a high aspect ratio, which helps to form a continuous conductive path and significantly improve the conductivity of the conductive ink. Due to the high aspect ratio of multi-walled carbon nanotubes, carbon nanotubes can effectively improve the mechanical strength and flexibility of the composite material in the resin matrix, so that the conductive ink can better adapt to the bending and deformation of the substrate. Through carboxylation and amination treatment, the surface of the carbon nanotubes carries active groups, which can better combine with the resin matrix, further enhance the dispersibility and compatibility, and thus improve the uniformity and reliability of the ink. Further, the carboxylation treatment includes: immersing the multi-walled carbon nanotubes (MWCNTs) in a mixed solution of concentrated nitric acid and concentrated sulfuric acid, and reacting for several hours under heating conditions (preferably 70-100°C). After the reaction, the sample is repeatedly washed to neutrality to obtain carboxylated carbon nanotubes (MWCNTs-COOH). Among them, the carboxyl group increases the hydrophilicity and polarity of the surface of the carbon nanotubes, making it easier to disperse evenly in the resin matrix and avoid agglomeration. The carboxyl group can form hydrogen bonds or covalent bonds with functional groups (such as hydroxyl groups, amino groups, etc.) in the resin matrix, further enhancing the interface bonding between the carbon nanotubes and the resin, and ensuring the mechanical strength and flexibility of the conductive ink during use. Further, the amination treatment includes: reacting the carboxylated carbon nanotubes with ethylenediamine in dimethylformamide, and causing the carboxyl group and the amino group to undergo a condensation reaction by heating and refluxing to generate aminated carbon nanotubes (MWCNTs-NH2). It should be noted that the amino (-NH2) group can react chemically with the carboxyl or other reactive groups in the resin matrix to form a stronger chemical bond, further improving the interfacial bonding between the carbon nanotubes and the resin matrix. This enhanced interfacial bonding helps to improve the mechanical properties and flexibility of the conductive ink. The amination treatment can improve the chemical stability of the carbon nanotubes, prevent them from undergoing adverse chemical reactions in the environment, and maintain the long-term stability and reliability of the conductive ink. The carbon nanotubes after the amination treatment have better dispersibility and compatibility, and can form a more uniform and stable conductive network, significantly improving the conductive properties of the conductive ink.

[0041] In some preferred embodiments, the silver powder is selected from nano-scale spherical silver powder or flaky silver powder, with a particle size range of 50-200 nanometers, and is surface treated by coating a polymer layer. It should be noted that silver powder is the main conductive component in conductive ink. Nano-scale silver powder has a large specific surface area and a short electron transmission path, which can significantly improve the conductivity of the conductive ink. Spherical silver powder has good fluidity and filling properties, and can form a dense conductive network in the resin, while flaky silver powder is easier to form a stable conductive layer due to its special two-dimensional structure, further enhancing the conductivity. At the same time, by coating the surface with a polymer layer, the agglomeration of silver powder can be reduced, and the oxidation of silver powder in high temperature or high humidity environments can be prevented, ensuring its long-term stability and conductivity. Furthermore, the silver powder is subjected to surface treatment after being coated with a polymer layer, including: selecting any one of the polymer materials selected from polystyrene (PS), polyacrylic acid (PAA), polyvinyl pyrrolidone (PVP), and polydimethylsiloxane (PDMS); before coating the polymer layer, cleaning and deoxidizing the silver powder to ensure that the surface of the silver powder is clean and free of oxides or impurities, for example, by acid washing or ultrasonic cleaning; using plasma treatment to generate active groups on the surface of the silver powder, the active groups can react with polymer monomers so that the polymer layer is uniformly coated on the surface of the silver powder; dispersing the silver powder in a solution of the polymer monomer, and then initiating a polymerization reaction so that the polymer chain grows on the surface of the silver powder to form a coating layer, or dispersing the silver powder in a polymer solution, depositing the polymer on the surface of the silver powder by physical adsorption, and then obtaining a stable polymer coating layer by solvent volatilization or heat treatment; after coating the polymer layer, drying and curing the silver powder to ensure that the polymer layer is firmly attached to the surface of the silver powder and there is no residual solvent or unreacted monomer. It should be noted that the coating of the polymer layer can enhance the bonding force and flexibility between the silver powder particles, reduce the particle breakage or conductive path breakage caused by stress during use, and thus improve the overall flexibility of the conductive ink. Appropriate polymer layer coating can effectively prevent the oxidation of silver powder and maintain the high conductivity of silver powder. In addition, the thickness and uniformity of the coating layer can also be controlled by process, so as to ensure that the conductivity is not significantly reduced while maintaining the continuity of the conductive path. At the same time, the polymer layer can improve the dispersibility of the silver powder in the resin matrix and prevent the silver powder from agglomerating into agglomerates and causing a decrease in conductive performance. In addition, the polymer layer can also protect the stability of the silver powder in harsh environments, reduce the performance degradation of the silver powder due to environmental changes, and enhance the durability and stability of the ink.

[0042] In some preferred embodiments, the dispersant is a polycarboxylate dispersant (such as polyacrylate) or a polyoxyethylene nonionic dispersant. It should be noted that the polycarboxylate dispersant can effectively adsorb on the surface of the conductive particles through its anionic group, provide electrostatic repulsion, prevent particle agglomeration, and ensure that the particles are evenly dispersed in the resin matrix. The polyoxyethylene nonionic dispersant stabilizes the dispersion of the conductive particles by forming a steric hindrance, and can show good dispersibility in both polar and non-polar media.

[0043] In some preferred embodiments, the flexible additive is a plasticizer (such as dioctyl phthalate, DOP) or a polyether flexible segment (such as polyethylene glycol, PEG). As a plasticizer, dioctyl phthalate (DOP) can be inserted between resin segments to reduce the interaction between the segments, significantly improve the flexibility and ductility of the material, and enhance the flexibility of the conductive ink. Polyethylene glycol (PEG) is a water-soluble polymer with good flexibility and low temperature resistance. It can provide long-chain flexible segments, so that the ink maintains excellent flexibility and ductility at low temperatures or repeated bending.

[0044] In some preferred embodiments, the crosslinking agent is an isocyanate crosslinking agent (such as hexamethylene diisocyanate, HDI) or ethylene glycol diglycidyl ether (such as polyether epoxy resin). Isocyanate crosslinking agents (HDI) have extremely high reactivity and can undergo crosslinking reactions with hydroxyl groups, amine groups and other groups in the resin matrix to form a stable polymer network structure. This crosslinking reaction can significantly enhance the adhesion and chemical resistance of the ink, and is suitable for application scenarios requiring high adhesion and durability. Ethylene glycol diglycidyl ether can react with active hydrogen in the resin matrix to form a stable three-dimensional network structure. The use of ethylene glycol diglycidyl ether can significantly improve the heat resistance and aging resistance of the conductive ink, while improving its adhesion on the substrate. The solvents are isopropyl alcohol (IPA), ethanol and dimethylformamide (DMF). Isopropyl alcohol (IPA) is a medium-volatile solvent with good solubility, which can effectively reduce the viscosity of the conductive ink and ensure good fluidity and coating properties in processes such as screen printing and inkjet printing. In addition, isopropyl alcohol has moderate volatility, which helps control the curing speed of the ink. Ethanol, as a commonly used low-viscosity solvent, has a fast evaporation rate and is suitable for use in printing processes that require fast drying. It can help adjust the viscosity of the ink to adapt it to different printing requirements without adversely affecting the chemical properties of the ink. Dimethylformamide (DMF) is a highly polar solvent with excellent solubility. It can fully mix the conductive particles with the resin matrix to ensure the fluidity and printing performance of the ink under high filling. It is suitable for conductive inks that require high conductivity and uniformity.

[0045] Embodiment 2

[0046] See also Figure 1 This embodiment provides some methods for producing conductive ink for pressure-sensitive sensors, as follows.

[0047] Production method 1: Select the components and proportions of the conductive ink for pressure-sensitive sensors: resin (epoxy resin): 50wt%; conductive particles (carbon powder: 10wt%, carbon nanotubes: 5wt%, silver powder: 5wt%); dispersant (polyethylene glycol): 1wt%; flexible additive (polydimethylsiloxane, PDMS): 6wt%; cross-linking agent (isocyanate): 0.5wt%; solvent (ethyl acetate): 22.5wt%; dissolve the epoxy resin in ethyl acetate and stir evenly; gradually add carbon powder, carbon nanotubes and silver powder, and add the dispersant, and continue stirring until evenly dispersed; add the flexible additive PDMS and continue stirring; finally add the cross-linking agent and stir evenly to obtain the conductive ink.

[0048] It should be noted that the conductive ink obtained by production method 1 has no cracks and maintains integrity in the 180° bending test. The conductivity reaches 1.5 × 10 3 S / m. After 1000 bending cycles, the conductivity dropped by less than 5%.

[0049] Production method 2: Select the components and proportions of the conductive ink for pressure-sensitive sensors: resin (epoxy resin): 45wt%; conductive particles (carbon powder: 10wt%; carbon nanotubes: 6wt%; silver powder: 8wt%; dispersant (polyethylene glycol): 1.5wt%; flexible additive (polydimethylsiloxane, PDMS): 7wt%; crosslinker (isocyanate): 0.5wt%; solvent (ethyl acetate): 22wt%; dissolve 45wt% of epoxy resin in 22wt% of ethyl acetate and stir evenly; gradually add 10wt% of carbon powder, 6wt% of carbon nanotubes and 8wt% of silver powder, and add 1.5wt% of dispersant, continue to stir until evenly dispersed; add 7wt% of flexible additive PDMS, continue to stir evenly; finally add 0.5wt% of crosslinker, stir evenly, and obtain conductive ink.

[0050] It should be noted that the conductive ink obtained by production method 2 has no cracks in the 180° bending test, maintains integrity, and has slightly improved flexibility compared to the conductive ink produced by production method 1. The conductivity can reach 1.7 × 10 3 S / m (due to the increased proportion of conductive particles). After 1000 bending cycles, the conductivity drop is expected to be within 3%, showing higher reliability than the conductive ink produced by production method 1.

[0051] Embodiment 3

[0052] This embodiment provides a pressure-sensitive sensor, and the production of the pressure-sensitive sensor is applied to the conductive ink for pressure-sensitive sensors described in any of the above embodiments. The conductive ink comprises the following components: resin, the resin is ink resin, accounting for 40-60 wt% of the total weight of the conductive ink; conductive particles, the conductive particles include carbon powder, carbon nanotubes and silver powder, and the conductive particles are mixed with the resin at a ratio of 5-30 wt%; dispersant, accounting for 0.5-2 wt% of the total weight of the conductive ink, used to improve the uniform distribution of the conductive particles in the resin; flexible additive, accounting for 1-8 wt% of the total weight of the conductive ink, used to enhance the flexibility of the conductive ink so that it can adapt to the bending and deformation of the pressure-sensitive sensor; cross-linking agent, accounting for 0.1-1 wt% of the total weight of the conductive ink, used to improve the adhesion and durability of the conductive ink; solvent, accounting for 10-30 wt% of the total weight of the conductive ink, used to adjust the viscosity and printing performance of the ink. The flexibility, conductivity and reliability of the conductive ink are improved, and when used to produce a pressure-sensitive sensor, the stability of the pressure-sensitive sensor can be improved.

[0053] It should be pointed out that the above embodiments are only preferred specific implementation modes of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. The protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A conductive ink for a pressure-sensitive sensor, characterized in that: The conductive ink comprises the following components: a resin, which is an ink resin and accounts for 40-60wt% of the total weight of the conductive ink; conductive particles, which include carbon powder, carbon nanotubes and silver powder, and are mixed with the resin at a ratio of 5-30wt%; a dispersant, which accounts for 0.5-2wt% of the total weight of the conductive ink and is used to improve the uniform distribution of the conductive particles in the resin; a flexible additive, which accounts for 1-8wt% of the total weight of the conductive ink and is used to enhance the flexibility of the conductive ink so that it can adapt to the bending and deformation of the pressure-sensitive sensor; a cross-linking agent, which accounts for 0.1-1wt% of the total weight of the conductive ink and is used to improve the adhesion and durability of the conductive ink; a solvent, which accounts for 10-30wt% of the total weight of the conductive ink and is used to adjust the viscosity and printing performance of the ink; the carbon nanotubes are multi-walled carbon nanotubes that have been surface-functionalized, and the length of the multi-walled carbon nanotubes ranges from 5 to 15 microns and the diameter is 10 to 20 nanometers; The surface functional treatment of the multi-walled carbon nanotubes includes: the multi-walled carbon nanotubes are subjected to carboxylation treatment to generate carboxylated carbon nanotubes, and the carboxylated carbon nanotubes are subjected to amination treatment to generate amination carbon nanotubes; The carboxylation treatment includes: immersing the multi-walled carbon nanotubes in a mixed solution of concentrated nitric acid and concentrated sulfuric acid, reacting for several hours under heating conditions, and after the reaction, repeatedly washing the sample until it is neutral to obtain carboxylated carbon nanotubes; the amination treatment includes: reacting the carboxylated carbon nanotubes with ethylenediamine in dimethylformamide, and causing the carboxyl group and the amino group to undergo a condensation reaction by heating and refluxing to generate aminated carbon nanotubes.

2. The conductive ink for pressure sensitive sensor according to claim 1, characterized in that: The ink resin is a polyurethane resin, the basic molecular structure of which is formed by the reaction of polyisocyanate and polyol, and the molecular formula is: -[-R-NH-COO-R′-O-CO-NH-R″]-; wherein R is hexamethylene, R′ is p-xylylene, and R″ is an ethylene glycol group.

3. The conductive ink for pressure sensitive sensor according to claim 1, characterized in that: After the conductive particles are mixed with the resin, a dispersant, a flexible additive, a cross-linking agent and a solvent are added to obtain a conductive ink mixed solution; an ultrasonic vibrator is inserted into a container containing the conductive ink mixed solution, and the ultrasonic vibrator is started to perform ultrasonic treatment on the mixed solution in the container containing the conductive ink mixed solution.

4. The conductive ink for pressure sensitive sensor according to claim 3, characterized in that: When performing ultrasonic treatment, the frequency of the ultrasonic wave is adjusted so that the ultrasonic wave frequency ranges from 20 kHz to 40 kHz.

5. The conductive ink for pressure sensitive sensor according to claim 3, characterized in that: During the ultrasonic treatment, the ultrasonic treatment time is controlled to be between 30 minutes and 60 minutes, and the temperature of the mixed solution in the container is controlled to be between 20° C. and 30° C.

6. The conductive ink for pressure sensitive sensor according to claim 1, characterized in that: The carbon powder is selected from micron-grade graphite powder or ultrafine carbon black, and the particle size range is 1-5 microns.

7. The conductive ink for pressure sensitive sensor according to claim 1, characterized in that: The silver powder is selected from nano-scale spherical silver powder or flaky silver powder, with a particle size ranging from 50 to 200 nanometers, and is surface-treated by coating a polymer layer.

8. A pressure-sensitive sensor, characterized in that: The production of the pressure-sensitive sensor is applied to the conductive ink for the pressure-sensitive sensor as described in any one of claims 1-7.

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