A composite carbon-based conductive ink based on interface modification and a preparation method and application thereof

Abstract

The application belongs to the technical field of conductive ink, and particularly relates to a composite carbon-based conductive ink based on interface modification and a preparation method and application thereof. The preparation method comprises the following steps: S1, modifying ternary carbon fillers using a modifier to obtain modified carbon powder, wherein the modifier is composed of polyvinylpyrrolidone and silane coupling agent; S2, preparing a composite resin base: mixing water-based acrylic resin, water-based polyurethane, ethylene glycol butyl ether and polydimethylsiloxane to obtain the composite resin base; S3, grading feeding and dispersing: adding the modified carbon powder into the composite resin base in batches, and performing three-stage ladder type dispersion treatment to obtain a pre-dispersed slurry; S4, adding a film forming agent, a defoaming agent, a dispersing agent, a leveling agent and an adhesion promoter into the pre-dispersed slurry in sequence, and mixing; vacuum degassing, filtering and constant temperature curing. The composite carbon-based conductive ink has excellent comprehensive performance, and improves the dispersion particle size, storage stability, conductivity, bending resistance and adhesion.

Description

Technical Field

[0001] This invention belongs to the field of conductive ink technology, specifically relating to a composite carbon-based conductive ink based on interface modification, its preparation method, and its application. Background Technology

[0002] The rapid development of flexible electronic devices has led to a surge in demand for low-temperature curing carbon-based conductive inks. Since the heat resistance of existing PET / PI substrates is less than 100℃, and the curing temperature of traditional carbon-based inks is generally between 120 and 150℃, this easily leads to substrate deformation, shrinkage, and aging. Furthermore, the cured inks exhibit poor continuity of the conductive network, high sheet resistance, weak adhesion, and poor bending resistance, limiting their application in flexible devices.

[0003] Commercially available ternary carbon-based conductive inks still have some problems in actual production and application: First, graphene sheets are prone to π-π stacking, carbon nanotubes are entangled and agglomerated, and conductive carbon black particles are also prone to secondary flocculation. The three types of carbon fillers are difficult to disperse evenly, making it difficult to build continuous and interconnected conductive pathways inside the formed coating film. Second, most of the industry only uses a single surfactant or silane reagent for modification treatment, which has limited effect on the coating and isolation of carbon materials. After the finished ink has been standing for a period of time, it is easy to experience stratification and sedimentation, resulting in a general effective storage period of less than 30 days for conventional products. In addition, the carbon fillers are distributed randomly in the resin matrix, and the conductive skeleton is irregularly arranged with many breaks in the conductive pathway, resulting in a higher sheet resistance value of the final coating film. The conductivity parameters fluctuate significantly after long-term storage or bending. Finally, the resins used in conventional inks are difficult to simultaneously ensure the coating's adhesion to the substrate and the film flexibility required for repeated bending.

[0004] Chinese patent CN116904067A discloses a graphene electrothermal ink, its preparation method, and its uses. The electrothermal ink prepared by this disclosure has a highly elastic three-dimensional spatial conductive network structure, excellent stretchability and bending performance, low resistance change rate under high deformation tensile limit, and high adhesion. It can radiate far-infrared spectrum when voltage is applied, has stable electrothermal performance, and the preparation process is simple and easy to mass-produce.

[0005] Chinese patent CN117903631A discloses a high-performance water-based carbon-based conductive ink and its preparation method. Through simple dispersion and ball milling processes, an effective three-dimensional structure of "carbon black-few-carbon black" is constructed, resulting in an ink with low cost, high stability, high conductivity, excellent mechanical flexibility, and green environmental protection, showing great potential in the field of flexible electronics.

[0006] However, for conductive inks used in flexible electronic printing, the particle size directly determines the fineness of the printed lines and the density of the film; storage stability affects batch consistency and shelf life in continuous industrial production; conductivity is a core parameter determining device power consumption and signal transmission efficiency; bending resistance directly relates to the reliability of flexible devices under repeated deformation conditions; and adhesion is a key indicator of the durability of the coating-substrate bond. Therefore, achieving simultaneous improvement in these five properties is a crucial technology that carbon-based conductive inks must address for industrial applications in flexible electronics. However, current technologies still need to address the challenge of simultaneously improving the particle size, storage stability, conductivity, bending resistance, and adhesion of conductive inks. Summary of the Invention

[0007] The purpose of this invention is to provide a composite carbon-based conductive ink based on interface modification, its preparation method and application. The composite carbon-based conductive ink of this invention simultaneously improves the dispersion particle size, storage stability, conductivity, bending resistance and adhesion.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a composite carbon-based conductive ink based on interface modification includes the following steps: S1. The ternary carbon filler is modified with a modifier to obtain modified carbon powder. The modifier is composed of polyvinylpyrrolidone and silane coupling agent. S2. Preparation of composite resin base material: Waterborne acrylic resin, waterborne polyurethane, ethylene glycol butyl ether, and polydimethylsiloxane are mixed to obtain composite resin base material. S3. Graded feeding and dispersion: Modified carbon powder is added to the composite resin base in batches and a three-stage step dispersion treatment is carried out to obtain a pre-dispersed slurry.

[0009] S4. Additive preparation: Film-forming agent, defoamer, dispersant, leveling agent and thickener are added to the pre-dispersed slurry in sequence and mixed; vacuum degassing, filtration, and constant temperature curing are performed to obtain composite carbon-based conductive ink based on interface modification.

[0010] This invention utilizes both PVP and KH550 as amphiphilic synergistic modifiers to construct a multidimensional hybrid interface layer on the surface of composite carbon nanofillers, characterized by physical coating, chemical anchoring, and hydrogen bonding. This completely solves the common technical challenge of easy secondary aggregation of carbon nanotubes and graphene in aqueous / polar systems. Through in-depth research, the applicant discovered that the two are not simply physically superimposed, but exhibit a significant synergistic effect. First, PVP provides a strong steric hindrance effect, initially breaking the physical aggregation of carbon materials. Second, KH550 achieves chemical anchoring. More importantly, a high-density intermolecular hydrogen bond network is formed between the highly polar carbonyl groups in the PVP molecular chain and the silanol groups and free amino groups of KH550. Simultaneously, the self-crosslinking siloxane network formed by KH550 on the carbon material surface firmly locks the PVP macromolecules onto the carbon framework surface. This unique interpenetrating locking mechanism effectively prevents the modifier from desorbing and failing from the carbon material surface during long-term storage or under high shear stress, thus endowing the conductive ink of this invention with unexpectedly long suspension stability and an extremely narrow submicron particle size distribution. Simultaneously, the highly active amino groups epitaxially bound to KH550 crosslink with the resin matrix during the film-forming and curing stage, achieving a perfect bridging between the inorganic conductive network and the organic resin matrix, giving the coating excellent adhesion.

[0011] Preferably, the waterborne acrylic resin includes waterborne acrylic resin I, waterborne acrylic resin II, and waterborne acrylic resin III; waterborne acrylic resin I has a viscosity of 200~300 mPa·s and a glass transition temperature of 95~99℃; waterborne acrylic resin II has a viscosity of 1000~2000 mPa·s and a glass transition temperature of 5~10℃; and waterborne acrylic resin III has a viscosity of 2500~3000 mPa·s and a glass transition temperature of -20℃~-25℃.

[0012] Preferably, the viscosity of waterborne acrylic resin I is 250 mPa.s at 23°C and the glass transition temperature is 98°C.

[0013] The viscosity of waterborne acrylic resin II is 1400 mPa.s at 23℃, and the glass transition temperature is 7℃.

[0014] The viscosity of waterborne acrylic resin III is 2700 mPa.s at 23℃, and the glass transition temperature is -23℃.

[0015] The waterborne polyurethane is model number Refober@HYR-4760. Longnan Haoyu New Material Technology Co., Ltd.

[0016] Preferably, the waterborne acrylic resin comprises waterborne acrylic resin I, waterborne acrylic resin II, and waterborne acrylic resin III in a mass ratio of 1:(1.4~1.7):(0.3~0.5).

[0017] This invention selects three water-based acrylic resins with different glass transition temperatures, and blends them in a specific mass ratio to form a gradient structure from hard to soft. During the curing process, it can ensure rapid surface drying and promote the rearrangement of carbon fillers through soft segments, thus constructing a denser three-dimensional conductive pathway. At the same time, the different viscosities not only ensure the long-term suspension stability of the three carbon fillers in the liquid slurry, but also provide the best rheological environment for the orderly stacking of conductive particles during the curing stage. This achieves synergistic effect from two dimensions, ensuring that the ink is simultaneously improved in terms of ultra-fine dispersion, ultra-long storage stability, and ultra-low resistance.

[0018] Preferably, the three-stage step dispersion treatment specifically includes the following steps: the modified toner is divided into three equal parts; after adding the first part of modified toner, it is sheared at 2000~2500r / min for 15~20min; the second part of modified toner is added, and grinding media is added and sand milled at 1500~1800r / min for 30~40min; finally, the third part of modified toner is added and ultrasonicated at 400~600W for 15~20min.

[0019] The three-stage stepped dispersion process of "high-speed shearing-grinding-ultrasound" used in this invention is perfectly matched with the reaction kinetics of the PVP / KH550 amphiphilic synergistic modifier: In the first stage of high-speed shearing, the fluid shear force initially tears apart the macroscopically aggregated carbon nanotubes and graphene, and the PVP macromolecules quickly capture and wrap around the exposed carbon material surface, using steric hindrance to prevent rapid regeneration; In the second stage of high-speed shearing, micron-sized zirconium beads strongly peel off the graphene sheets and cut off some of the dead knots in the carbon nanotubes, exposing a large number of fresh oxygen-containing active edges. At this time, KH550 in the system quickly undergoes a grafting reaction at these highly active sites, completing chemical anchoring; In the third stage of high-speed shearing, the microjets generated by the ultrasonic cavitation effect further straighten the overlapping configuration of carbon nanotubes and graphene, and promote the carbonyl groups of PVP and the functional groups of KH550 to fully collide and form a dense hydrogen bond network, completing the final microscopic locking of the composite conductive filler. With the synergy of this process and formulation, zero-dimensional carbon black, one-dimensional carbon nanotubes and two-dimensional graphene exhibit a highly extended discrete state in the system. After the ink is cured, they naturally assemble into a dense, gradient-interpenetrating three-dimensional conductive network, which can reduce the sheet resistance with a relatively low amount of carbon filler added.

[0020] Preferably, the ternary carbon filler includes large-diameter graphene, long multi-walled carbon nanotubes, and nano-conductive carbon black in a mass ratio of (15~25):(8~12):(30~40).

[0021] Preferably, the large-diameter graphene sheet has a diameter of 5~10μm; the long multi-walled carbon nanotube has a length of 10~30μm; and the nano-conductive carbon black has a particle size of 20~30nm.

[0022] This invention constructs a three-dimensional interpenetrating network by defining a specific physical size gradient: micron-micron-tens of micron-nano carbon black, thereby creating a continuous and dense three-dimensional conductive pathway within the resin. This reduces the sheet resistance of the cured film and lowers the resistivity compared to ordinary composite carbon black.

[0023] Preferably, the mass ratio of the waterborne acrylic resin to the waterborne polyurethane is (3~4):1.

[0024] This invention uses a specific ratio of waterborne acrylic resin and waterborne polyurethane as a composite resin base. The introduction of waterborne polyurethane not only provides high elasticity and internal toughening effect, but also improves the adhesion of the coating to the PET / PI substrate. At the same time, the flexible segments of polyurethane effectively absorb bending stress, preventing the conductive network from breaking.

[0025] Preferably, the film-forming agent is one or more of ethylene glycol butyl ether, propylene glycol methyl ether, dodecyl alcohol ester, and dipropylene glycol methyl ether; Preferably, the defoamer is one or more of polydimethylsiloxane, polyether-modified siloxane, mineral defoamer, and acrylic resin ester defoamer; Preferably, the dispersant is one or more of sodium hexametaphosphate, polyacrylate resin salt, and carboxylic acid copolymer; Preferably, the leveling agent is one or more of silicone-based and acrylic resin-based leveling agents; Preferably, the tackifier is one or more of rosin resin, terpene resin, petroleum resin, and waterborne polyurethane tackifying resin.

[0026] A composite carbon-based conductive ink based on interface modification is prepared by the above-described preparation method.

[0027] The application of the interface-modified composite carbon-based conductive ink prepared by the aforementioned method is that the composite carbon-based conductive ink is used to prepare flexible electronic devices.

[0028] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention uses PVP and KH550 as amphiphilic synergistic modifiers, which endows the conductive ink of this invention with unexpected ultra-long suspension stability and extremely narrow submicron particle size distribution, giving the coating excellent adhesion.

[0029] 2. This invention uses a specific ratio of waterborne acrylic resin and waterborne polyurethane as the composite resin base. The introduction of waterborne polyurethane not only provides high elasticity and internal toughening effect, but also improves the adhesion of the coating to the PET / PI substrate. At the same time, the flexible segments of polyurethane effectively absorb bending stress, preventing the conductive network from breaking.

[0030] 3. This invention selects three water-based acrylic resins with different glass transition temperatures, and the three are compounded in a specific mass ratio to achieve synergistic effect from two dimensions, ensuring that the ink is simultaneously improved in terms of ultra-fine dispersion, ultra-long storage stability and ultra-low resistance.

[0031] 4. The three-stage step dispersion process of "high-speed shearing-sand milling-ultrasound" used in this invention is perfectly matched with the reaction kinetics of PVP / KH550 amphiphilic synergistic modifier, which can reduce sheet resistance with a low amount of carbon filler added.

[0032] 5. This invention constructs a three-dimensional interpenetrating network by defining a specific physical size gradient: micron-micron-tens of micron-nano carbon black, thereby constructing a continuous and dense three-dimensional conductive pathway inside the resin. This reduces the sheet resistance of the cured film and significantly lowers the resistivity compared to ordinary composite carbon black. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the preparation process of the amphiphilic, hydrophobic interface modified gradient three-dimensional network composite carbon-based conductive ink of the present invention.

[0034] Figure 2 This is a graph showing the change in D90 particle size of the ink during the three-stage dispersion process in Example 1.

[0035] Figure 3 The graph shows the changes in block resistance and system viscosity in the three-stage dispersion process of Example 1. Detailed Implementation

[0036] 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.

[0037] All raw materials used in the following embodiments of the present invention are commercially available products: Polyvinylpyrrolidone: PVPK30, industrial grade.

[0038] Silane coupling agent KH550, industrial grade.

[0039] Example 1 Please see Figure 1 This embodiment provides a composite carbon-based conductive ink based on interface modification, the preparation method of which includes the following steps: S1. Preparation of modified toner: (1) Weigh 20 parts of large-diameter graphene, 10 parts of long multi-walled carbon nanotubes and 35 parts of nano-conductive carbon black by mass and mix them evenly to obtain a composite carbon-based filler; the diameter of the large-diameter graphene is 5~10μm; the length of the long multi-walled carbon nanotubes is 10~30μm; and the particle size of the nano-conductive carbon black is 20~30nm.

[0040] (2) Add the composite carbon-based filler to a mixed solvent of ethanol-deionized water at a volume ratio of 4:1, control the solid-liquid ratio of the composite carbon-based filler to the mixed solvent to be 1g:10mL, and stir at room temperature for 30min to prepare a suspension.

[0041] (3) Add modifier to suspension. Modifier is prepared by mixing polyvinylpyrrolidone and silane coupling agent KH550 at a mass ratio of 2.5:1. The total amount of modifier added is 6% of the total mass of composite carbon-based filler. Sonicate at 45℃ and 400W for 50 minutes. (4) Subsequently, the modified carbon powder was obtained by vacuum filtration, washing with anhydrous ethanol 4 times, vacuum drying at 65°C for 15 hours, pulverizing and sieving through a 200-mesh sieve.

[0042] S2. Preparation of Composite Resin Base Material: Weigh 45 parts by weight of waterborne acrylic resin, 12 parts by weight of waterborne polyurethane (ratio 3.75:1), 4 parts by weight of ethylene glycol butyl ether, and 0.8 parts by weight of polydimethylsiloxane. Mix and stir at 900 rpm for 18 minutes to obtain the composite resin base material. The waterborne acrylic resin includes waterborne acrylic resin I, waterborne acrylic resin II, and waterborne acrylic resin III in a mass ratio of 1:1.5:0.4. Waterborne acrylic resin I has a viscosity of 250 mPa·s at 23℃ and a glass transition temperature of 98℃; model: Covestro Neocryl waterborne acrylic resin A1091. Waterborne acrylic resin II has a viscosity of 1400 mPa·s at 23℃ and a glass transition temperature of 7℃; model: 8027. Zhongshan Huamingtai Technology Co., Ltd. Waterborne acrylic resin III has a viscosity of 2700 mPa·s at 23℃ and a glass transition temperature of -23℃. Model: 8050. Zhongshan Huamingtai Technology Co., Ltd. The waterborne polyurethane model is Refober@HYR-4760. Longnan Haoyu New Material Technology Co., Ltd.

[0043] S3. Graded feeding and dispersion: Weigh the modified toner and composite resin base material at a mass ratio of 1.44:1. Divide the modified toner into three equal parts. After adding the first part of modified toner, perform high-speed shearing at 2200r / min for 20min. After standing for 10min, add the second part of modified toner and add 0.5mm zirconia beads at 1.5 times the mass of the slurry. Perform sand milling at 1600r / min for 35min. After filtering out the zirconia beads and transferring them to an ultrasonic device, add the third part of modified toner and perform ultrasonic homogenization at 500W for 18min to obtain a pre-dispersed slurry.

[0044] S4. Additive preparation: According to the mass percentage, add 2 parts of 12-ol ester, 0.5 parts of polyether-modified polysiloxane, 1.5 parts of sodium hexametaphosphate, 1 part of TEGO450 leveling agent, and 2.5 parts of rosin resin to 100 parts of pre-dispersed slurry in sequence, mix, stir at 700 r / min for 28 min; degas under vacuum at -0.07 MPa for 12 min, filter through a 100-mesh filter, and cure at 28℃ for 24 h to obtain the finished ink.

[0045] Figure 2 The graph shows the change curve of ink D90 particle size during the three-stage dispersion process of Example 1. It can be seen that D90 gradually decreases as high-speed shearing, sand milling and ultrasonic homogenization progress. Figure 3 The figure shows the viscosity and sheet resistance curves of the composite carbon-based conductive ink in Example 1 during a three-stage feeding and dispersion process. It can be seen that with the progression of high-speed shearing, sand milling and ultrasonic homogenization, the three-dimensional network of carbon-based filler is gradually improved, and the sheet resistance drops rapidly from the initial extremely high value and stabilizes at 9 Ω / sq after the ultrasonic stage. At the same time, the viscosity of the system drops from 5000 to about 2500, which proves that the amphiphilic modifier and the carbon-based filler achieve good rheological matching.

[0046] Example 2 This embodiment provides a composite carbon-based conductive ink based on interface modification, the preparation method of which includes the following steps: S1. Preparation of modified toner: (1) Weigh 15 parts of large-diameter graphene, 8 parts of long multi-walled carbon nanotubes and 30 parts of nano-conductive carbon black by mass and mix them evenly to obtain a composite carbon-based filler; the diameter of the large-diameter graphene is 5~10μm; the length of the long multi-walled carbon nanotubes is 10~30μm; and the particle size of the nano-conductive carbon black is 20~30nm.

[0047] (2) Add the composite carbon-based filler to a mixed solvent of ethanol-deionized water at a volume ratio of 3:1, control the solid-liquid ratio of the composite carbon-based filler to the mixed solvent to be 1g:10mL, and stir at room temperature for 30min to prepare a suspension.

[0048] (3) Add modifier to suspension. Modifier is prepared by mixing polyvinylpyrrolidone and silane coupling agent KH550 at a mass ratio of 2.5:1. The total amount of modifier added is 5% of the total mass of carbon filler. Sonicate at 40℃ and 300W for 45 minutes. (4) Subsequently, the modified carbon powder was obtained by vacuum filtration, washing with anhydrous ethanol 4 times, vacuum drying at 60°C for 18 hours, and pulverizing and sieving through a 200-mesh sieve.

[0049] S2. Preparation of Composite Resin Base Material: Weigh out 40 parts by weight of waterborne acrylic resin, 10 parts by weight of waterborne polyurethane (ratio 4:1), 3 parts by weight of ethylene glycol butyl ether, and 0.5 parts by weight of polydimethylsiloxane. Stir at 800 rpm for 20 minutes to obtain the composite resin base material. The waterborne acrylic resin includes waterborne acrylic resin I, waterborne acrylic resin II, and waterborne acrylic resin III in a mass ratio of 1:1.4:0.5. Waterborne acrylic resin I has a viscosity of 250 mPa·s at 23℃ and a glass transition temperature of 98℃; model: Covestro Neocryl waterborne acrylic resin A1091. Waterborne acrylic resin II has a viscosity of 1400 mPa·s at 23℃ and a glass transition temperature of 7℃; model: 8027. Zhongshan Huamingtai Technology Co., Ltd. Waterborne acrylic resin III has a viscosity of 2700 mPa·s at 23℃ and a glass transition temperature of -23℃; model: 8050. Zhongshan Huamingtai Technology Co., Ltd. The waterborne polyurethane model is Refober@HYR-4760. Longnan Haoyu New Material Technology Co., Ltd.

[0050] S3. Graded feeding and dispersion: Weigh the modified filler and composite resin at a mass ratio of 1.33:1. Divide the modified toner into three equal parts. After adding the first part of modified toner, perform the first feeding at 2000r / min high-speed shearing for 20min. After standing for 10min, add the second part of modified toner and add 0.5mm zirconia beads at 1.5 times the mass of the slurry. Perform sand milling at 1500r / min for 30min. After filtering out the zirconia beads and transferring them to an ultrasonic device, add the third part of modified toner and perform ultrasonic homogenization at 400W for 15min to obtain the pre-dispersed slurry.

[0051] S4. Additive preparation: According to the mass fraction, add 1.5 parts of propylene glycol methyl ether, 0.3 parts of mineral oil defoamer, 1 part of sodium hexametaphosphate, 0.8 parts of TEGO450 leveling agent, and 2 parts of rosin resin to 100 parts of pre-dispersed slurry in sequence, stir at 600 r / min for 30 min; defoam under vacuum at -0.08 MPa for 15 min, filter through a 100-mesh filter, and cure at a constant temperature of 25℃ for 24 h to obtain the finished ink.

[0052] Example 3 This embodiment provides a composite carbon-based conductive ink based on interface modification, the preparation method of which includes the following steps: S1. Preparation of modified toner: (1) Weigh 25 parts of large-diameter graphene, 12 parts of long multi-walled carbon nanotubes and 40 parts of nano-conductive carbon black by mass and mix them evenly to obtain a composite carbon-based filler; the diameter of the large-diameter graphene is 5~10μm; the length of the long multi-walled carbon nanotubes is 10~30μm; and the particle size of the nano-conductive carbon black is 20~30nm.

[0053] (2) Add the composite carbon-based filler to a mixed solvent of ethanol-deionized water at a volume ratio of 5:1, control the solid-liquid ratio of the composite carbon-based filler to the mixed solvent to be 1g:10mL, and stir at room temperature for 30min to prepare a suspension.

[0054] (3) Add modifier to suspension. Modifier is prepared by mixing polyvinylpyrrolidone and silane coupling agent KH550 at a mass ratio of 3:1. The total amount of modifier added is 8% of the total mass of carbon filler. Sonicate at 50°C and 500W for 60 minutes. (4) Subsequently, the modified carbon powder was obtained by vacuum filtration, washing with anhydrous ethanol 4 times, vacuum drying at 70℃ for 12h, pulverizing and sieving through a 200-mesh sieve.

[0055] S2. Preparation of Composite Resin Base Material: Weigh 50 parts by weight of waterborne acrylic resin, 13 parts by weight of waterborne polyurethane (ratio 3.85:1), 5 parts by weight of ethylene glycol butyl ether, and 1 part by weight of polydimethylsiloxane. Stir at 1000 r / min for 15 min to obtain the composite resin base material. The waterborne acrylic resin includes waterborne acrylic resin I, waterborne acrylic resin II, and waterborne acrylic resin III in a mass ratio of 1:1.7:0.3. Waterborne acrylic resin I has a viscosity of 250 mPa.s at 23℃ and a glass transition temperature of 98℃; model: Covestro Neocryl waterborne acrylic resin A1091. Waterborne acrylic resin II has a viscosity of 1400 mPa.s at 23℃ and a glass transition temperature of 7℃; model: 8027. Zhongshan Huamingtai Technology Co., Ltd. Waterborne acrylic resin III has a viscosity of 2700 mPa.s at 23℃ and a glass transition temperature of -23℃; model: 8050. Zhongshan Huamingtai Technology Co., Ltd. The waterborne polyurethane model is Refober@HYR-4760. Longnan Haoyu New Material Technology Co., Ltd.

[0056] S3. Graded feeding and dispersion: The modified filler and composite resin are weighed at a mass ratio of 1.54:1. The modified toner is divided into three equal parts. After adding the first part of modified toner, it is subjected to high-speed shearing at 2200r / min for 20min. After standing for 10min, the second part of modified toner is added. Then, 0.5mm zirconia beads are added at 1.5 times the mass of the slurry. The mixture is then sand-milled at 1600r / min for 35min. After filtering out the zirconia beads and transferring the mixture to an ultrasonic device, the third part of modified toner is added. The mixture is then ultrasonically homogenized at 500W for 18min to obtain a pre-dispersed slurry.

[0057] S4. Additive preparation: According to the mass percentage, add 2.5 parts of dipropylene glycol methyl ether, 0.6 parts of acrylic resin ester defoamer, 2 parts of sodium hexametaphosphate, 1.5 parts of TEGO450 leveling agent, and 3 parts of rosin resin to 100 parts of pre-dispersed slurry in sequence, stir at 800 r / min for 25 min; degas under vacuum at -0.06 MPa for 10 min, filter through a 100-mesh filter, and cure at 30℃ for 24 h to obtain the finished ink.

[0058] Comparative Example 1 The difference between this comparative example and Example 1 is that: large-diameter graphene of 5~10μm is replaced with ordinary graphene of 1~3μm small-diameter; long multi-walled carbon nanotubes of 10~30μm are replaced with short multi-walled carbon nanotubes of 1~5μm; and nano-conductive carbon black of 20~30nm is replaced with ordinary carbon black of 100~500nm. The proportions are the same as in Example 1.

[0059] Comparative Example 2 The difference between this comparative example and Example 1 is that the modifier is polyvinylpyrrolidone.

[0060] Comparative Example 3 The difference between this comparative example and Example 1 is that all the resin was replaced with an equal mass of waterborne acrylic resin, and no polyurethane was added. The remaining parameters for carbon filler, modification, dispersion, and additives were exactly the same as in Example 1. That is, by mass, 57 parts of waterborne acrylic resin, 4 parts of ethylene glycol butyl ether, and 0.8 parts of polydimethylsiloxane were weighed, mixed, and stirred at 900 r / min for 18 min to obtain a composite resin base.

[0061] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: S3, graded feeding and dispersion: the modified toner and the composite resin base are weighed at a mass ratio of 1.44:1. The modified toner is added to the composite resin base in two equal portions, with an interval of 10 minutes between each addition. The first addition is a high-speed shearing at 2200 r / min for 29 minutes. The second addition is 0.5 mm zirconia beads and sand milling at 1600 r / min for 44 minutes to obtain a pre-dispersed slurry.

[0062] Comparative Example 5 The difference between this comparative example and Example 1 is that 45 parts of waterborne acrylic resin and 12 parts of waterborne polyurethane (ratio 3.75:1) are replaced with 47.5 parts of waterborne acrylic resin and 9.5 parts of waterborne polyurethane (ratio 5:1).

[0063] Comparative Example 6 The difference between this comparative example and Example 1 is that the waterborne acrylic resin includes waterborne acrylic resin I, waterborne acrylic resin II, and waterborne acrylic resin III in a mass ratio of 0.8:1:0.7.

[0064] Waterborne acrylic resin I has a viscosity of 250 mPa·s at 23°C and a glass transition temperature of 98°C. Model: Covestro Neocryl Waterborne Acrylic Resin A1091. Waterborne acrylic resin II has a viscosity of 1400 mPa·s at 23°C and a glass transition temperature of 7°C. Model: 8027. Zhongshan Huamingtai Technology Co., Ltd. Waterborne acrylic resin III has a viscosity of 2700 mPa·s at 23°C and a glass transition temperature of -23°C. Model: 8050. Zhongshan Huamingtai Technology Co., Ltd.

[0065] Comparative Example 7 The difference between this comparative example and Example 1 is that the waterborne acrylic resin includes waterborne acrylic resin I and waterborne acrylic resin III in a mass ratio of 1:0.4. Waterborne acrylic resin I has a viscosity of 250 mPa·s at 23°C and a glass transition temperature of 98°C; its model number is Covestro Neocryl waterborne acrylic resin A1091. Waterborne acrylic resin III has a viscosity of 2700 mPa·s at 23°C and a glass transition temperature of -23°C; its model number is 8050. Zhongshan Huamingtai Technology Co., Ltd.

[0066] Performance testing The performance of the composite carbon-based conductive inks prepared in Examples 1-3 and Comparative Examples 1-7 was tested. The performance testing methods are as follows: (1) Dispersed particle size (D90): The particle size was determined using a Malvern Mastersizer 3000 laser particle size analyzer with deionized water as the dispersion medium.

[0067] (2) Storage stability: The prepared conductive ink was sealed in a glass bottle and placed in a constant temperature chamber at 25°C. The presence of stratification or precipitation was observed periodically, and the viscosity change was tested using a rotational viscometer. The storage stability period was defined as the number of days with a viscosity change rate ≤5% and no obvious sedimentation.

[0068] (3) Sheet resistance: Conductive ink was printed onto a PET substrate through a 200-mesh screen and cured at 80°C for 30 minutes to obtain a conductive film with a thickness of 15 μm. The film surface was tested at multiple points using a four-probe tester at room temperature, and the average value was taken.

[0069] (4) Bending resistance (bending rise rate): Using a flexible circuit bending tester, the above-mentioned PET substrate with conductive film is fixed and continuously bent 1000 times under the conditions of bending radius of 2mm and bending angle of 180°. The resistance value before and after bending is tested, and the resistance rise rate (ΔR / R0×100%) is calculated.

[0070] (5) Adhesion test: Use a cross-cutting tool (1mm spacing) to make a grid on the surface of the conductive film, apply 3M 600 test tape tightly and then quickly tear it off. The grade is evaluated according to ASTM D3359 standard, with grade 0 being the highest (no peeling).

[0071] The specific results are shown in Table 1 below.

[0072] Table 1 Performance Test Results

[0073] As shown in Table 1, the conductive inks prepared in Examples 1-3 have a dispersion particle size D90 of 1.0~1.4μm, a storage stability of 90~98 days, a sheet resistance of 8~11Ω / sq, and an adhesion grade of 0.

[0074] A comparative analysis of the measured data of each group of samples in Table 1 clearly shows that, with the gradient particle size compounded carbon filler system, the combined use of PVP and KH550 amphiphilic modification process, the acrylic resin-polyurethane blended resin matrix, and the three-stage graded dispersion preparation process, the dispersion uniformity of the carbon filler in the system is greatly improved, the static stability time of the ink is significantly extended, and the conductivity of the cured film is far superior to that of the comparative example. Especially in terms of adhesion, thanks to the chemical bridging effect of KH550 between the filler and the resin and the internal toughening effect of polyurethane, the adhesion of Examples 1 to 3 all reached the highest level of 0, while the comparative examples lacking key components showed varying degrees of coating peeling. This fully demonstrates that the entire preparation scheme of this invention has outstanding innovative advantages and high industrial application value. In Comparative Example 4, the lack of a third-stage ultrasonic homogenization resulted in a chaotic state of coiled and entangled carbon nanotubes and two-dimensional graphene within the system. This led to a significant increase in resistance, an incomplete hydrogen bond network, and easy desorption of the modifier during subsequent storage. The carbon filler re-agglomerated, resulting in a sharp decrease in storage stability and an increase in particle size. The irregular entanglement of carbon nanotubes and graphene easily caused localized stress concentration during bending, leading to the breakage of conductive pathways and thus poor bending resistance. In Comparative Example 6, the altered resin blending ratio of the three waterborne acrylic resins disrupted the hard-soft gradient rheological equilibrium. This resulted in insufficient depolymerization shear force being transferred to the carbon filler during high-speed shearing and milling stages. The carbon filler was difficult to fully open, leading to a significant increase in particle size. During film formation, the carbon filler could not form a tight, dense, ordered stack, resulting in sparse conductive pathways and increased sheet resistance. An excessively high proportion of soft segments altered the overall polar environment of the resin, weakening the chemical cross-linking efficiency between the KH550 modified layer and the resin matrix, thereby impairing adhesion and long-term storage suspension stability. In Comparative Example 7, the medium-Tg acrylic resin acts as a transition bridge between the high-Tg hard segments and the low-Tg soft segments in the system. Its absence leads to severe microscopic phase separation between the hard and soft segments, resulting in a distinct microphase interface within the resin matrix. This causes a large amount of carbon filler to be repelled and agglomerated at the phase interface during mixing, preventing uniform dispersion. The severe agglomeration of carbon filler prevents the formation of a through-conductive path, resulting in a sheet resistance as high as 38 Ω / sq. The incompatibility between the hard and soft segments generates significant internal stress after curing, making it prone to cracking during bending. Furthermore, the interface between the coating and the substrate rapidly peels off under stress, leading to decreased adhesion.

[0075] This invention characterizes the carbon filler before and after modification using Fourier transform infrared spectroscopy (FTIR). The results show that the surface area of ​​the unmodified composite carbon material is only at 3400 cm⁻¹. -1 A weak -OH stretching vibration peak is present nearby; however, the infrared spectrum of the carbon filler modified by the three-stage dispersion process of this invention shows significant changes: firstly, at 1085 cm⁻¹... -1 and 1120cm -1A strong asymmetric stretching vibration peak appeared nearby, which is attributed to Si-OC and Si-O-Si bonds, strongly confirming that the silanol groups of KH550 underwent dehydration condensation with oxygen-containing defects on the carbon material surface, successfully achieving chemical anchoring; secondly, at 2925 cm⁻¹... -1 and 2855cm -1 The presence of distinct -CH2- asymmetric and symmetric stretching vibration peaks at this point proves that the long-chain organic compounds (the carbon skeleton of PVP and the coupling agent) have been successfully coated onto the surface of the carbon material. Most importantly, the characteristic lactam carbonyl (C=O) stretching vibration peak in the PVP molecule, which should have been located at 1680 cm⁻¹, was unexpectedly found. -1 However, in the spectrum of the modified carbon material of this invention, this peak shows a significant red shift (moving to a lower wavenumber) to 1655 cm⁻¹. -1 The peak width increases significantly. This significant redshift provides conclusive microscopic evidence that a high density of strong intermolecular hydrogen bonds is formed between the highly polar carbonyl group of PVP and the silanol or amino (-NH2) group of KH550. The above characterization results demonstrate the formation mechanism of the 'physical coating-chemical anchoring-hydrogen bond locking' multidimensional hybrid interface layer of this invention.

[0076] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite carbon-based conductive ink based on interface modification, characterized in that, Includes the following steps: S1. The ternary carbon filler is modified with a modifier to obtain modified carbon powder. The modifier is composed of polyvinylpyrrolidone and silane coupling agent. S2. Preparation of composite resin base material: Waterborne acrylic resin, waterborne polyurethane, ethylene glycol butyl ether, and polydimethylsiloxane are mixed to obtain composite resin base material; S3. Graded feeding and dispersion: Modified carbon powder is added to the composite resin base in batches and a three-stage step dispersion treatment is carried out to obtain a pre-dispersed slurry. S4. Additive preparation: Add film-forming agent, defoamer, dispersant, leveling agent and thickener to the pre-dispersed slurry in sequence, and mix; Vacuum degassing, filtration, and constant-temperature curing yield a composite carbon-based conductive ink based on interface modification.

2. The method for preparing composite carbon-based conductive ink based on interface modification according to claim 1, characterized in that, Waterborne acrylic resins include waterborne acrylic resin I, waterborne acrylic resin II, and waterborne acrylic resin III; waterborne acrylic resin I has a viscosity of 200~300 mPa·s and a glass transition temperature of 95~99℃; waterborne acrylic resin II has a viscosity of 1000~2000 mPa·s and a glass transition temperature of 5~10℃; and waterborne acrylic resin III has a viscosity of 2500~3000 mPa·s and a glass transition temperature of -20℃~-25℃.

3. The method for preparing composite carbon-based conductive ink based on interface modification according to claim 1, characterized in that, Waterborne acrylic resins include waterborne acrylic resin I, waterborne acrylic resin II, and waterborne acrylic resin III in a mass ratio of 1:(1.4~1.7):(0.3~0.5).

4. The method for preparing composite carbon-based conductive ink based on interface modification according to claim 1, characterized in that, The three-stage step dispersion process includes the following steps: Divide the modified toner into three equal parts. After adding the first part of modified toner, shear at 2000~2500r / min for 15~20min. Then add the second part of modified toner, add grinding media, and sand mill at 1500~1800r / min for 30~40min. Finally, add the third part of modified toner and sonicate at 400~600W for 15~20min.

5. The method for preparing composite carbon-based conductive ink based on interface modification according to claim 1, characterized in that, Ternary carbon fillers include large-diameter graphene, long multi-walled carbon nanotubes, and nano-conductive carbon black in a mass ratio of (15~25):(8~12):(30~40).

6. The method for preparing composite carbon-based conductive ink based on interface modification according to claim 5, characterized in that, The large-diameter graphene sheets have a diameter of 5~10μm; the long multi-walled carbon nanotubes have a length of 10~30μm; and the nano-conductive carbon black has a particle size of 20~30nm.

7. The method for preparing composite carbon-based conductive ink based on interface modification according to claim 1, characterized in that, The mass ratio of the waterborne acrylic resin to the waterborne polyurethane is (3~4):

1.

8. The method for preparing composite carbon-based conductive ink based on interface modification according to claim 1, characterized in that, The film-forming agent is one or more of ethylene glycol butyl ether, propylene glycol methyl ether, dodecyl alcohol ester, and dipropylene glycol methyl ether; the defoamer is one or more of polydimethylsiloxane, polyether-modified siloxane, mineral defoamer, and acrylic resin ester defoamer; the dispersant is one or more of sodium hexametaphosphate, polyacrylate resin salt, and carboxylic acid copolymer; the leveling agent is one or more of organosilicon and acrylic resin leveling agents; and the tackifier is one or more of rosin resin, terpene resin, petroleum resin, and waterborne polyurethane tackifying resin.

9. A composite carbon-based conductive ink based on interface modification, characterized in that, The interface-modified composite carbon-based conductive ink is prepared by the preparation method described in any one of claims 1 to 8.

10. The application of an interface-modified composite carbon-based conductive ink prepared by the preparation method according to any one of claims 1 to 8, characterized in that, Composite carbon-based conductive inks are used to prepare flexible electronic devices.

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