Nano jet printing character ink and preparation method thereof

Abstract

The invention provides nano jet printing character ink and a preparation method thereof, and the preparation method comprises the following steps: separating a water-based acrylate dispersion into a first part and a second part, mixing the first part, a dispersing agent and a pigment, uniformly stirring, adding an inorganic grinding material, grinding, and filtering to obtain nano color paste; the preparation method comprises the following steps: mixing metal nanoparticles and a high-branch polymer in an organic solvent to obtain a metal nano dispersion liquid, mixing a gallium-indium-tin alloy and an inorganic filler, stirring, and filtering to obtain mixed guniting; and sequentially adding the nano color paste, the second component, polyester acrylate, silane-terminated polyurethane, the metal nano dispersion liquid and the mixed guniting into a reaction kettle, uniformly stirring, adding the functional additive, stirring and mixing, and curing at room temperature to obtain the nano jet printing character ink. Therefore, the heat dissipation capability, the electromagnetic shielding effect and the mechanical strength of the cable for the new energy vehicle are improved. Therefore, a continuous and stable fine line and stable sheet resistance are obtained.

Description

Technical Field

[0001] This invention belongs to the field of ink material technology, and in particular relates to a nano-printing character ink and its preparation method. Background Technology

[0002] Inkjet printing ink is a specialized functional ink used by inkjet printers to create clear text, barcodes, QR codes, and icons on various substrate surfaces (such as PET, PC, metal, glass, and paper). Unlike traditional coatings, it must complete the entire process of spraying, spreading, setting, and curing in an extremely short time, enabling high-speed production lines to achieve instant drying and high-contrast imaging, ensuring fine line widths and sharp edges for easy machine vision recognition and traceability management. Functionally, inkjet printing ink plays a core role in identification and traceability. In scenarios such as food and pharmaceuticals, electronics, automotive parts, medical devices, lithium batteries, and photovoltaics, it is responsible for the online printing of batch numbers, production dates, serial numbers, barcodes / QR codes, and other information. The characters must be clear, durable, non-fading, and non-migrating, and compatible with subsequent coating, packaging, and sterilization processes.

[0003] In related technologies, the formulation relies solely on pigments and UV resins. After ink is sprayed, it is affected by high surface tension, making it difficult for ink droplets to spread continuously on low surface energy substrates. If a metallic conductive phase is present, agglomeration is likely to occur, leading to interruption of the conductive path. This ultimately manifests as micro-discontinuities in fine lines, discontinuous current paths, and significant fluctuations in sheet resistance depending on location and batch. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a nano-printing character ink and its preparation method, which aims to solve the problem of unstable sheet resistance caused by easy line breakage of nano-printing character ink.

[0005] To address the above problems, this invention proposes a method for preparing nano-printing character ink, comprising the following steps: S1. Separate the aqueous acrylate dispersion into a first part and a second part. Mix the first part, dispersant and pigment, stir evenly, add inorganic abrasive for grinding, and filter to obtain nano-color paste. S2. Metal nanoparticles and highly branched polymers are mixed in an organic solvent to obtain a metal nanoparticle dispersion. Gallium indium tin alloy and inorganic filler are mixed, stirred, and then filtered to obtain a mixed spray. S3. Add the nano-color paste, the second component, polyester acrylate, silane-terminated polyurethane, metal nano-dispersion, and mixed spray paste to the reaction vessel in sequence, stir evenly, then add functional additives and stir to mix. Allow to mature at room temperature to obtain nano-printing character ink.

[0006] In some embodiments, step S1 includes: S1.1 The acrylic dispersion is divided into a first part and a second part by mass, each part accounting for 45-55%, and the first part and the second part may have the same or different mass. The first part is adjusted to a solid content of 18-22 wt% with deionized water. S1.2. Add the first component, dispersant and pigment to the mixing tank in sequence, stir at 1000~1500 rpm for 15~20 min and control the temperature to ≤25℃ to obtain a pre-dispersed slurry; S1.3. The pre-dispersed slurry is circulated into a sand mill, inorganic abrasive is added, and ball milling is carried out for 4~8 hours to obtain a grinding slurry. The grinding slurry is transferred into a vacuum degassing tank and stirred at a rotation speed of 100~200rpm for 10~15 minutes under the conditions of -0.06~-0.08MPa and 25℃ to obtain a color paste. S1.4. The pigment paste is filtered through a three-stage filter system consisting of a 5µm bag filter, a 1µm filter, and a 0.45µm pleated filter under a nitrogen pressure of 0.05~0.1MPa to obtain nano pigment paste.

[0007] In some embodiments, the dispersant includes at least one of BYK-190, polycarboxylate dispersant, polyvinylpyrrolidone, and TEGODispers755W; the pigment includes at least one of phthalocyanine blue, phthalocyanine green, and coated iron oxide black; the inorganic abrasive includes at least one of zirconia beads, silica microspheres, and alumina ceramic beads; and the particle size of the inorganic abrasive is 0.3~0.5 mm.

[0008] In some embodiments, step S2 includes: S2.1 Weigh the metal nanoparticles and highly branched polymer, add organic solvent, and stir magnetically at 500 rpm for 20 min in a reaction vessel. Then reduce the rotation speed to 300~400 rpm and stir for 10 min. Place in an ultrasonic water bath with a frequency of 40 kHz and a power of ≤120 W for 5~8 min and keep warm at 20~25℃ to obtain a metal nanoparticle dispersion. S2.2 Weigh gallium indium tin alloy and inorganic filler, add them to the mixer at a mass ratio of metal:filler = 10:1, stir at 400~600 rpm, stir at room temperature for 30 min, and then pass the mixture through a 1μm filter to obtain the mixed spray slurry.

[0009] In some embodiments, in step S2, the metal nanoparticles include at least one of silver nanowires, copper nanowires, and gold nanoparticles; the highly branched polymer includes at least one of hyperbranched polyethyleneimine, hyperbranched polyurethane, and hyperbranched polyester; the organic solvent includes at least one of isopropanol, ethanol, propylene glycol methyl ether, and ethyl acetate; and the inorganic filler includes at least one of silica, alumina, zirconium oxide, and titanium dioxide, with a particle size of 20-100 nm.

[0010] In some embodiments, the functional additives include photoinitiators, reactive diluents, defoamers, thixotropic agents, leveling agents, and antioxidant polymerization inhibitors; Step S3 includes: S3.1 Add the second part to the mixing vessel, adjust the temperature to 23~25℃, and stir at 400~600rpm for 5~10min. Then add polyester acrylate and silane-terminated polyurethane in sequence, and continue stirring for 10~15min. S3.2. Maintain stirring speed and temperature, add nano pigment and stir for 10-15 minutes, adjust stirring speed to 300-400 rpm, add metal nano dispersion and stir for 10 minutes, add mixed spraying at a volume ratio of metal nano dispersion to mixed spraying slurry of 1:2, and stir for another 10-15 minutes to obtain mixed slurry. S3.3 Add reactive diluent to the mixed slurry and mix at a stirring speed of 500~800 rpm for 30~40 min. Then add defoamer at a stirring speed of 300~400 rpm and stir for 10~15 min. Next, slowly add thixotropic agent and mix at a stirring speed of 800~1000 rpm for 20~30 min. Then, add leveling agent and antioxidant polymerization inhibitor in sequence at a stirring speed of 300~400 rpm and stir for 15~20 min. Finally, add photoinitiator in a light-protected environment at a stirring speed of 100~200 rpm and stir for 30~40 min. Allow to stand at room temperature for 12~24 h to mature. After three-stage filtration, obtain nano-printing character ink.

[0011] In some embodiments, in step S3, the photoinitiator includes at least one of TPO-L, 819, and 1173; the reactive diluent includes at least one of trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and isoborneol acrylate; the defoamer includes at least one of BYK-024, BYK-022, BYK-028, and TEGOFoamex N / 810; the thixotropic agent includes at least one of fumed silica, organobentonite, and polyamide wax rheology modifier; the leveling agent includes one of BYK-348, SF-6500, and Tego-450; and the antioxidant polymerization inhibitor includes at least one of BYK-3510, 2,6-di-tert-butyl-4-methylphenol, and ethyl dimethylaminobenzoate.

[0012] This invention proposes a nano-printing character ink, which is prepared by the method described above.

[0013] Compared with existing technologies, the nano-printing ink and its preparation method in this invention have the following advantages: S1 involves phase separation of an aqueous acrylate dispersion, followed by grinding and filtration with a dispersant and pigment to obtain a nano-paste with narrow particle size distribution, controllable rheology, and significantly reduced impurities and coarse particles. This results in more uniform spreading and more stable boundaries after inkjet printing, reducing the necking and voids in lines caused by agglomeration and coarse particle size distribution from the source. Secondly, S2 pre-stabilizes metal nanoparticles and highly branched polymers in an organic solvent to form a metal nano-dispersion, inhibiting re-agglomeration of the metal phase during batching and printing, ensuring continuous network formation of the conductive framework within the fine lines. Simultaneously, it mixes gallium indium tin alloy with inorganic fillers and filters them to form a mixed spray paste, making the liquid... The metal achieves stable distribution and good wetting at the interface of the inorganic filler, thereby forming effective bridging and compensation at weak points in the conductive framework. Finally, S3 is batched in the order of nano-pigment paste, second component, polyester acrylate, silane-terminated polyurethane, metal nano-dispersion and mixed spray paste, and cured at room temperature after the addition of functional additives. This allows the pigment phase, resin continuous phase, metal nano-framework and liquid metal mixed spray paste to achieve uniform distribution and compatibility in the same matrix. The conductive path is formed by the synergistic effect of framework penetration and local bridging. Micro-defects in the line are effectively filled, and finally, continuous and stable fine lines and low resistance fluctuations are obtained without changing the printing window. Attached Figure Description

[0014] Figure 1 This is a schematic flowchart of a method for preparing nano-printing character ink in one embodiment of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0016] Please refer to Figure 1 This invention proposes a method for preparing nano-printing character ink, the steps of which include: S1. Separate the aqueous acrylate dispersion into a first part and a second part. Mix the first part, dispersant, and pigment, stir evenly, add inorganic abrasive, and grind. After filtration, obtain nano-color paste. The dispersant includes at least one of BYK-190, polycarboxylate dispersant, polyvinylpyrrolidone, and TEGODispers 755W. The pigment includes at least one of phthalocyanine blue, phthalocyanine green, and coated iron oxide black. The inorganic abrasive includes at least one of zirconia beads, silica microspheres, and alumina ceramic beads. The particle size of the inorganic abrasive is 0.3~0.5mm.

[0017] Step S1 includes: S1.1 The acrylic dispersion is divided into a first part and a second part by mass, with each part accounting for 45-55%. The first part and the second part may have the same or different mass. The first part is adjusted to a solid content of 18-22 wt% with deionized water.

[0018] The aqueous acrylate dispersion was divided into a first part and a second part. The first part was adjusted with deionized water to a solid content of 18-22 wt%. This reduced the initial viscosity and internal friction of the system without sacrificing the film-forming properties of the resin, and significantly improved the subsequent wetting and shear transfer efficiency. Stirring was maintained at 300-500 rpm and the temperature was controlled at room temperature, which helped to suppress the mechanical shearing and thermal agglomeration of acrylic latex particles, thereby maintaining a stable particle size distribution. This phase separation and solid content window made it easier for the dispersant in the pre-dispersion stage to spread and occupy pigment surface sites, reducing the energy required for subsequent grinding, achieving a reduction in unit energy consumption and heat load, while retaining an independent adjustment margin for rheology and surface tension when introducing metal nanophases into the pigment paste.

[0019] S1.2. Add the first component, dispersant and pigment to the mixing tank in sequence, stir at 1000~1500rpm for 15~20min and control the temperature to ≤25℃ to obtain a pre-dispersed slurry.

[0020] By adding the first component first, followed by the dispersant and pigment, and forming a pre-dispersed slurry at 1000-1500 rpm and ≤25℃, the dispersant, such as BYK-190, polycarboxylate dispersant, polyvinylpyrrolidone, or TEGODispers755W, can be rapidly adsorbed onto the surfaces of phthalocyanine blue, phthalocyanine green, and coated iron oxide black. A primary stable layer is established through multi-point anchoring and electrostatic / steric hindrance dual mechanisms. Temperature control in the low-temperature range can reduce the surface energy of the pigment and slow down the secondary agglomeration caused by brown movement, while avoiding the coagulation caused by the softening of latex particles. This results in a uniform pre-dispersed system without obvious dry powder cores, laying a uniform starting interface for the efficient refinement of subsequent bead milling.

[0021] S1.3. The pre-dispersed slurry is circulated into a sand mill, inorganic abrasive is added, and ball milling is carried out for 4~8 hours to obtain a grinding slurry. The grinding slurry is transferred into a vacuum degassing tank and stirred at a rotation speed of 100~200 rpm for 10~15 minutes under the conditions of -0.06~-0.08MPa and 25℃ to obtain a color paste.

[0022] The pre-dispersed slurry is circulated into a sand mill and ball-milled for 4-8 hours with zirconia beads, silica microspheres, or alumina ceramic beads with a particle size of 0.3-0.5 mm. This process achieves deagglomeration and refinement of pigments under high specific surface area and controllable impact frequency, continuously shearing and breaking down coarse agglomerates and stabilizing them into nanoscale monodisperse particles under the protection of a dispersant. The inorganic abrasive in this particle size range balances momentum and contact frequency, increasing energy input per unit time while avoiding excessive impact and temperature rise caused by excessively large bead diameters, thereby reducing the risk of lattice defects and hue drift. Subsequently, vacuum degassing at -0.06 to -0.08 MPa, 25°C, and 100-200 rpm effectively removes microbubbles introduced by grinding, reduces voids and satellite droplets during the spraying process, and prevents bubbles from forming shrinkage cavities and pinhole defects in the film formation. The final product is a color paste with a dense structure, narrow particle size distribution, and saturated interface coating.

[0023] S1.4. The pigment paste is filtered through a three-stage filter system consisting of a 5µm bag filter, a 1µm filter, and a 0.45µm pleated filter under a nitrogen pressure of 0.05~0.1MPa to obtain nano pigment paste.

[0024] Under a nitrogen pressure of 0.05~0.1MPa, the ink is filtered through a three-stage process using 5µm bag filters, 1µm filters, and 0.45µm pleated filter cartridges. This process progressively removes residual large particles, soft gels, and foreign matter, significantly reducing the risk of nozzle clogging and substrate scratches. The nitrogen pressure also prevents air re-introduction and reduces interfacial oxidation caused by dissolved oxygen, ensuring the cleanliness and stability of the ink paste. The resulting nano-ink paste possesses comprehensive characteristics such as D50 nanometer scale, narrow distribution, and controllable viscosity and surface tension. It can achieve stable filamentation, clear edges, and low coffee rings during the printing process. At the same time, it provides a highly compatible optical and rheological basis for subsequent synergistic integration with the resin continuous phase, metal nano-dispersion, and mixed ink paste.

[0025] S2. Metal nanoparticles and highly branched polymers are mixed in an organic solvent to obtain a metal nanoparticle dispersion. Gallium indium tin alloy and inorganic filler are mixed, stirred, and then filtered to obtain a mixed spray. The metal nanoparticles include at least one of silver nanowires, copper nanowires, and gold nanoparticles. The highly branched polymers include at least one of hyperbranched polyethyleneimine, hyperbranched polyurethane, and hyperbranched polyester. The organic solvents include at least one of isopropanol, ethanol, propylene glycol methyl ether, and ethyl acetate. The inorganic fillers include at least one of silica, alumina, zirconium oxide, and titanium dioxide. The particle size of the inorganic filler is 20-100 nm.

[0026] Step S2 includes: S2.1 Weigh the metal nanoparticles and highly branched polymer, add organic solvent, and stir magnetically at 500 rpm for 20 min in a reaction vessel. Then reduce the rotation speed to 300~400 rpm and stir for 10 min. Place in an ultrasonic water bath with a frequency of 40 kHz and a power of ≤120 W for 5~8 min and keep warm at 20~25℃ to obtain a metal nanoparticle dispersion.

[0027] In moderately polar, low-surface-tension organic solvents such as isopropanol, ethanol, propylene glycol methyl ether, or ethyl acetate, silver nanowires, copper nanowires, or gold nanoparticles are co-mixed with hyperbranched polyethyleneimine, hyperbranched polyurethane, or hyperbranched polyester. A dispersion path combining high-to-low shear with low-power ultrasound is employed, allowing the end groups of the highly branched polymer to undergo multi-point coordination and adsorption with the metal surface (amine, carboxyl, and thiol groups form coordination bonds with the electron cloud on the metal surface or establish potential repulsion through van der Waals forces and electrostatic interactions). This constructs a dual stabilizing layer of steric hindrance and charge around the particles or nanowires, thereby inhibiting aggregation and sedimentation. The polyamine sites of the hyperbranched polyethyleneimine exhibit stronger complexation capabilities for silver and copper surfaces, while also inhibiting the initial oxidation of the copper surface. With certain complexing shielding and antioxidant buffering effects, hyperbranched polyurethane and hyperbranched polyester provide a flexible molecular shell to maintain rheological stability and compatibility with subsequent film formation. Under these conditions, the polarity and evaporation rate of the organic solvent can effectively reduce the surface tension of the system and match the spray window, allowing the nanowires to maintain their aspect ratio integrity under low shear and achieve uniform dispersion and fine particle size distribution during the gentle de-agglomeration process of ultrasonic cavitation. Finally, a metal nano-dispersion with viscosity and surface tension within the controllable range of printing at 25 degrees Celsius is obtained. This dispersion can form a through-conductive framework with a low addition amount in subsequent film formation, improving the continuity of fine lines, reducing breakpoint sensitivity, and mitigating the coffee ring effect, thus providing a foundation for high-resolution characters and isotopic electrical functions.

[0028] In one embodiment, after step S2.1, an amino-terminated hyperbranched polymer and a thiol-terminated hyperbranched polymer are added to the metal nano-dispersion. The mass ratio of the amino-terminated hyperbranched polymer to the thiol-terminated hyperbranched polymer is 1:1, and the amino-terminated hyperbranched polymer and the thiol-terminated hyperbranched polymer account for 0.2 wt% of the metal nano-dispersion. The mixture is stirred at a speed of 300–400 rpm for 10 min. After stirring, the mixture is allowed to stand for 30 min to allow the end groups to fully occupy the metal surface sites. Then, pulsed ultrasound at a frequency of 40 kHz and a power of 120 W is performed, with the pulses on for 30 s and off for 30 s, for 6 cycles, with the temperature controlled at 20–25 °C throughout.

[0029] This improvement, without altering the formulation, achieves stronger interfacial anchoring and a more uniform aspect ratio distribution in the metal nanoparticle dispersion through a sequence of end-group pre-complexation, static saturation, and pulsed ultrasound. After incorporating amino-terminated hyperbranched polymers and thiol-terminated hyperbranched polymers at a 1:1 ratio (0.2 wt% total), the –NH2 / –SH end groups fully occupy the metal surface sites during gentle stirring at 300–400 rpm and static 30 min, forming a dual stable layer of coordination / chemisorption and steric hindrance. Subsequent 40 kHz, 120 W pulsed ultrasound (30 s on / 30 s off × 6) at 20–25 °C provides gentle cavitation de-agglomeration without cutting the nanowires, thereby significantly inhibiting secondary agglomeration and shortening, maintaining the nanowire aspect ratio and interconnectivity, and improving low-dose network formation capability and rheological reversibility of the jetting process. Its direct effects are: reduced probability of breakage in the printed fine lines, reduced initial sheet resistance and point-to-point fluctuations, easier formation of stable bridging at nodes when combined with mixed spraying, further reduction of the relative resistance change rate after bending, and improved consistency between storage period and multiple batches prepared.

[0030] S2.2 Weigh gallium indium tin alloy and inorganic filler, add them to the mixer at a mass ratio of metal:filler = 10:1, stir at 400~600 rpm, stir at room temperature for 30 min, and then pass the mixture through a 1μm filter to obtain the mixed spray slurry.

[0031] A gallium-indium-tin alloy is uniformly stirred with silicon dioxide, alumina, zirconium oxide, or titanium dioxide with a particle size of 20 to 100 nanometers at a mass ratio of 10:1, and the stirring intensity is maintained at room temperature in air. This promotes the formation of an extremely thin gallium oxide film on the alloy surface, which intercalates and adsorbs with inorganic fillers, constructing a three-phase interface structure of particles, oxide layer, and liquid metal. Silica, with its surface hydroxyl groups and high specific surface area, can significantly reduce the surface tension of the liquid metal, inhibit bead formation, and improve wetting and spreading on low surface energy substrates, while also imparting thixotropic anti-sagging properties to the system. Alumina has high hardness, which can improve the scratch resistance and wear resistance of the lines. Zirconia has good toughness. It can maintain linear stability under repeated bending and thermal shock conditions; the surface polarity of titanium dioxide is strong, which makes it easy to form stable adsorption sites on the oxide layer, which is conducive to the initial spreading of microdroplets on the substrate and the bridging and healing under subsequent micro-thermal treatment; the primary filtration after stirring removes large agglomerates and foreign matter, which can significantly reduce the risk of nozzle clogging and stabilize the spray particle spectrum, and finally obtain a rheologically tunable, spreading, and compatible hybrid spray with conductive skeleton. In the subsequent low-temperature short-time heat treatment stage, the spray can form liquid metal bridging micro-regions at the conductive network nodes, realize the self-healing of fine lines and the reduction of resistance, while maintaining good compatibility with the gentle ethanol wiping and dilute acid metal recovery process.

[0032] In one embodiment, in step S2.2, after the gallium indium tin alloy and inorganic filler are added to the mixer, air at a flow rate of 0.10 L / min is introduced for 5 minutes before stirring begins. Stirring then commences, followed by a 5-minute settling period, and finally 1 μm filtration before proceeding to step S3. This step does not alter the formulation; it merely achieves rapid generation of ultrathin Ga2O3 on the liquid metal surface through controlled oxidation. This allows for more stable adsorption and intercalation of 20–100 nm SiO2 / Al2O3 / ZrO2 / TiO2, pre-constructing a three-phase interface between particles, oxide layer, and liquid metal. Compared to conventional simple mechanical mixing followed by filtration, this pulsed oxidation and pause significantly improves the initial wetting and distribution uniformity of the mixed spray when it contacts the metal framework in step S3, thereby achieving low-temperature bridging at micro-defects. This represents a process innovation in interface engineering, rather than a simple material superposition.

[0033] S3. Add the nano-color paste, the second component, polyester acrylate, silane-terminated polyurethane, metal nano-dispersion, and mixed spray paste to the reaction vessel in sequence, stir evenly, then add functional additives and stir to mix. Allow to mature at room temperature to obtain nano-printing character ink.

[0034] The functional additives include photoinitiators, reactive diluents, defoamers, thixotropic agents, leveling agents, and antioxidant polymerization inhibitors; the photoinitiators include at least one of TPO-L, 819, and 1173; the reactive diluents include at least one of trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and isoborneol acrylate; the defoamers include at least one of BYK-024, BYK-022, BYK-028, and TEGOFoamex N / 810; the thixotropic agents include at least one of fumed silica, organobentonite, and polyamide wax rheology modifiers; the leveling agents include one of BYK-348, SF-6500, and Tego-450; and the antioxidant polymerization inhibitors include at least one of BYK-3510, 2,6-di-tert-butyl-4-methylphenol, and ethyl dimethylaminobenzoate.

[0035] Step S3 includes: S3.1 Add the second part to the mixing vessel, adjust the temperature to 23~25℃, and stir at 400~600rpm for 5~10min. Then add polyester acrylate and silane-terminated polyurethane in sequence, and continue stirring for 10~15min.

[0036] First, a continuous resin phase is established using the second component. Then, under mild shear conditions of 23-25 ​​degrees Celsius and 400-600 rpm, polyester acrylate and silane-terminated polyurethane are added sequentially. This allows for the simultaneous construction of the base of two key networks: First, the polyester acrylate provides a highly reactive and dense cross-linked framework for subsequent photocuring, imparting initial shape retention and surface scratch resistance to the film. Second, the silane end groups in the silane-terminated polyurethane can gradually hydrolyze and condense to form silicon-oxygen bonds in the presence of watermarks and hydroxyl groups on the substrate surface. These bonds then form silicon-oxygen-metal bonds with polar sites on the surfaces of glass, metal, and engineering plastics, significantly improving adhesion and flexible buffering without increasing the curing temperature. This sequential establishment of a continuous phase allows for the uniform dispersion of subsequent functional components without shearing and damaging the latex particles. It avoids interfacial competitive adsorption, reduces the risk of viscosity spikes and phase separation when the conductive phase is subsequently incorporated, and lays a structural and chemical foundation for printing stability and post-curing durability.

[0037] S3.2. Maintain stirring speed and temperature, add nano pigment and stir for 10-15 minutes, adjust stirring speed to 300-400 rpm, add metal nano dispersion and stir for 10 minutes, add mixed spraying at a volume ratio of metal nano dispersion to mixed spraying slurry of 1:2, and stir for another 10-15 minutes to obtain mixed slurry.

[0038] By adding nano-pigment paste under constant temperature and shear, coated iron oxide black or phthalocyanine pigments maintain a nanoscale particle size distribution under the steric hindrance and electrostatic synergy of the dispersant, thereby obtaining high-contrast characters with clear edges and low coffee rings. Subsequently, the shear is reduced and a metal nano-dispersion is incorporated, which allows silver nanowires, copper nanowires, or gold nanoparticles to maintain their aspect ratio and dispersion stability under the end-group coordination protection of hyperbranched polyethyleneimine, hyperbranched polyurethane, or hyperbranched polyester, forming micro-framework pathways that can be connected with low addition amounts. Then, a mixed spray containing gallium indium tin alloy is introduced at a volume ratio of 1:2. Under the interfacial interlocking effect of silica, alumina, zirconium oxide, or titanium dioxide nanofillers, the liquid metal localizes and wets the framework nodes in the resin microenvironment, forming bridging micro-regions. The grid-connected strategy of prioritizing the framework and then bridging stems from the synergistic mechanism of the highly branched polymer-stabilized metal nanonetwork and the three-phase interface of particles, oxide layer, and liquid metal: the former ensures the continuity of fine lines and low discontinuity sensitivity, while the latter achieves micro-region self-healing and reduced contact resistance under low-temperature short-time thermal excitation, thereby obtaining lower sheet resistance and higher repeated bending stability under the same linewidth conditions, while maintaining material compatibility with ethanol wiping and dilute acid recovery processes.

[0039] In one embodiment, between steps S3.2 and S3.3, a rotational viscometer is used to monitor whether the viscosity of the mixed slurry at 25°C is between 18 and 28 mPa·s; if the viscosity is greater than 28 mPa·s, 1 to 3 vol% ethanol / IPA or ACMO / TMPTA is added for dilution; if the viscosity is less than 28 mPa·s, 0.1 to 0.2 wt% inorganic filler is added.

[0040] S3.3. After adding the reactive diluent to the mixed slurry and mixing at a stirring speed of 500-800 rpm for 30-40 minutes, add the defoamer at a stirring speed of 300-400 rpm and stir for 10-15 minutes. Then, slowly add the thixotropic agent and mix at a stirring speed of 800-1000 rpm for 20-30 minutes. Next, add the leveling agent and antioxidant / polymerization inhibitor sequentially at a stirring speed of 300-400 rpm and stir for 15-20 minutes. Finally, add the photoinitiator in a light-protected environment at a stirring speed of 100-200 rpm and stir for 30-40 minutes. Allow the mixture to stand at room temperature for 12-24 hours to mature. After three-stage filtration, the nano-printing character ink is obtained.

[0041] First, an active diluent is added and thoroughly mixed under high shear. The reactive dilution effect of trimethylolpropane triacrylate, hexanediol diacrylate, tripropylene glycol diacrylate, or isoborneol acrylate simultaneously achieves viscosity reduction and adjustable crosslinking density, resulting in stable ink filaments within the printhead and a crosslinked network that balances hardness and toughness after curing. Then, defoamers such as BYK-024, BYK-022, BYK-028, or TEGOFoamex N / 810 are added at a reduced rate to quickly remove microbubbles without disrupting the established dispersion structure, reducing jet satellite droplets and film-forming pores. Next, fumed silica, organobentonite, or polyamide wax rheology modifiers are slowly added and dispersed under high shear for a short time to form a reversible thixotropic network. This network increases the storage modulus when stationary to prevent sagging and thins under shear during movement to ensure continuous jetting, balancing fine line morphology with uniform large-area spreading. Finally, BYK-348 is added at low shear. Leveling agents such as SF-6500 or Tego-450 rapidly homogenize the surface tension gradient, thereby suppressing Bénal convection and edge burrs, and improving character boundary sharpness. Then, antioxidant polymerization inhibitor systems such as BYK-3510, 2,6-di-tert-butyl-4-methylphenol, or ethyl dimethylaminobenzoate are incorporated. The former stabilizes storage time by capturing free radicals and peroxides through hindered phenols, while the latter, as an amine, synergistically alleviates oxygen polymerization inhibition at the photocuring interface, improving surface drying integrity and curing depth. Finally, photoinitiators such as TPO-L, 819, and 1173 are added and fully homogenized under light-protected and low-shear conditions, giving both the bulk and surface phases high absorption and high quantum efficiency initiation capabilities. Combined with room temperature curing, this promotes microscale rearrangement and minimizes interfacial energy. Finally, after three-stage filtration to remove occasional agglomerates, a print-ready ink is obtained, possessing high-definition readability, low sheet resistance, strong adhesion, excellent rheology, and reversible removal and metal recovery throughout the entire manufacturing process.

[0042] This invention proposes a nano-printing character ink, which is prepared by a method for preparing nano-printing character ink.

[0043] Example 1.

[0044] S1. Nano-color paste is prepared according to the established steps: BYK-190 is selected as the dispersant, coated iron oxide black is selected as the pigment, and zirconia beads with a particle size of 0.4 mm are selected as the inorganic abrasive. The batch size is set to 500g. S1.1 The aqueous acrylate dispersion is divided into a first part (250g) and a second part (250g). Deionized water is added to the first part to adjust the solid content to 20wt%. The stirring speed is 400rpm, the temperature is 24℃, and the time is 12min. S1.2 The first part (250g), BYK-190 (10.0g), and coated iron oxide black (50.0g) are added to the stirred tank in sequence. The stirring speed is 1200rpm, the time is 18min, and the temperature is ≤25℃ to obtain a pre-dispersed paste. S1.3 The pre-dispersed slurry was circulated into a sand mill, filled with 1.2 L of 0.4 mm zirconium oxide beads, and ball-milled at a linear velocity of 10 m / s for 6 h; then transferred to a vacuum degassing tank and degassed at -0.07 MPa, 25 °C, and 150 rpm for 12 min to obtain the color paste. S1.4 The slurry was then filtered sequentially through a 5 μm bag filter, a 1 μm filter, and a 0.45 μm pleated filter under nitrogen pressure of 0.08 MPa to obtain the nano-color paste. S2 Two slurries were prepared: the metal nano-dispersion used silver nanowires and hyperbranched polyethyleneimine, with isopropanol / ethanol (volume fraction 70 / 30) as the solvent. 10.0 g of silver nanowires, 2.0 g of hyperbranched polyethyleneimine, 280 g of isopropanol, and 120 g of ethanol were weighed and placed in a reactor. The mixture was stirred at 500 rpm for 20 min, then at 350 rpm for 10 min. The mixture was then transferred to an ultrasonic water bath (40 kHz, 120 W) and sonicated for 6 min at a constant temperature of 22 °C to obtain a metal nanoparticle dispersion. The mixed spray slurry was prepared using a gallium indium tin alloy and silicon dioxide (50 nm) at a mass ratio of metal:filler = 10:1. 110.0 g of gallium indium tin alloy and 11.0 g of silicon dioxide were weighed and stirred at 500 rpm for 30 min using a planetary mixer at room temperature of 22 °C. The mixture was then filtered through a 1 μm filter to obtain the mixed spray slurry.S3 batch: Add 250g of the second component to the mixing tank, maintain the temperature at 23–25℃ (24℃), and stir at 500rpm for 8 minutes. Then, add 105.0g of polyester acrylate and 28.0g of silane-terminated polyurethane sequentially, and continue stirring for 12 minutes. Add 200.0g of nano-pigment and stir for 12 minutes. Adjust the speed to 350rpm, add 30.0g of metal nano-dispersion and stir for 10 minutes. Then, add 60.0mL of mixed spray at a volume ratio of 1:2 and stir for 12 minutes. Add a total of 70.0g of reactive diluent (42.0g of 1,6-hexanediol diacrylate and 28.0g of tripropylene glycol diacrylate), and mix at 700rpm for 35 minutes. Add defoamer at 300rpm. Add 2.0g of agent BYK-028 and stir for 12 min; slowly add 5.0g of thixotropic agent fumed silica and mix at 900 rpm for 25 min; add 1.2g of leveling agent BYK-348 and 3.6g of antioxidant polymerization inhibitor (2.4g of BYK-3510 and 1.2g of 2,6-di-tert-butyl-4-methylphenol) sequentially at 300 rpm and stir for 18 min; under light-protected conditions, add a total of 33.0g of photoinitiator (20.0g of TPO-L, 8.0g of 819, and 35.0g of 117) at 150 rpm and stir for 35 min; allow to stand and mature at room temperature (23℃) for 18 h, and filter through 5μm, 1μm, and 0.45μm filters to obtain nano-printing character ink.

[0045] Example 2.

[0046] S1 was performed according to Example 1, except that the dispersant was replaced with TEGODispers 755W (10.0g), the pigment was replaced with phthalocyanine blue (50.0g), and the inorganic abrasive remained zirconia beads (0.4mm). S2 used copper nanowires and hyperbranched polyurethane as the metal nanodispersion, with ethanol / propylene glycol methyl ether (80 / 20 volume fraction) as the solvent. 10.0g of copper nanowires, 3.0g of hyperbranched polyurethane, 288g of ethanol, and 72g of propylene glycol methyl ether were weighed, stirred at 500rpm for 20min, stirred at 350rpm for 10min, and ultrasonically heated in a water bath (40kHz, 100W) for 6min at a constant temperature of 23℃ to obtain the metal nanodispersion. The mixed spray slurry used gallium indium tin alloy and alumina (60nm), with a metal:filler ratio of 10:1. 110.0g of gallium indium tin alloy and 11.0g of alumina were weighed, stirred at 500rpm for 30min, and filtered through a 1μm filter to obtain the mixed spray slurry. The dosage and order of S3 are the same as in Example 1, except that the reactive diluent is replaced with 35.0g of trimethylolpropane triacrylate and 35.0g of isoborneol acrylate, the defoamer is BYK-024, 2.0g, the leveling agent is SF-6500, 1.2g, and the antioxidant and polymerization inhibitor is BYK-3510, 2.4g and 2,6-di-tert-butyl-4-methylphenol, 1.2g.

[0047] Example 3.

[0048] S1 was performed according to Example 1, except that the dispersant was replaced with 10.0 g of polycarboxylate dispersant, the pigment was replaced with 50.0 g of phthalocyanine green, and the inorganic abrasive was replaced with 1.2 L of 0.4 mm alumina ceramic beads. S2's metal nano-dispersion used gold nanoparticles and hyperbranched polyester, with isopropanol / ethyl acetate (volume fraction 60 / 40) as the solvent. 10.0 g of gold nanoparticles, 2.5 g of hyperbranched polyester, 240 g of isopropanol, and 160 g of ethyl acetate were weighed, stirred at 500 rpm for 20 min, stirred at 350 rpm for 10 min, and ultrasonically heated in a water bath (40 kHz, 80 W) for 6 min at a constant temperature of 22°C to obtain the metal nano-dispersion. The mixed spray slurry used gallium indium tin alloy and titanium dioxide (40 nm), with a metal:filler ratio of 10:1. 110.0 g of gallium indium tin alloy and 11.0 g of titanium dioxide were weighed, stirred at 500 rpm for 30 min, and filtered through a 1 μm filter to obtain the mixed spray slurry. The dosage and order of S3 are the same as in Example 1, except that the reactive diluent is 35.0g of 1,6-hexanediol diacrylate and 35.0g of tripropylene glycol diacrylate, the defoamer is TEGOFoamex N / 810, 2.0g, the leveling agent is Tego-450, 1.2g, and the antioxidant and polymerization inhibitor is BYK-3510, 2.4g and ethyl dimethylaminobenzoate, 1.2g.

[0049] Comparative Example 1.

[0050] Comparative Example 1 completely follows the same dosage and process as Example 1 in S1 and S2, with the dosage and order of the second component 250g, polyester acrylate 105.0g, silane-terminated polyurethane 28.0g, nano pigment 200.0g, metal nano dispersion 30.0g, reactive diluent 70.0g, thixotropic agent 5.0g, defoamer 2.0g, leveling agent 1.2g, antioxidant polymerization inhibitor 3.6g, and photoinitiator 33.0g remaining unchanged in S3, but without adding the mixed spraying slurry, and all other conditions are the same.

[0051] Comparative Example 2.

[0052] Comparative Example 2 maintained all conditions and amounts of Example 1, except that the silica particle size was changed from 50 nm to 200 nm when preparing the mixed spray in S2. The metal, filler, stirring and filtration parameters remained unchanged.

[0053] Experimental procedures for performance parameters.

[0054] All samples were spray-coated onto a PET substrate using a 21μm nozzle, a single drop volume of 6pL, a printing resolution of 400dpi, and a line speed of 1.2m / s. Curing was performed using LED-UV 395–405nm with a pre-curing temperature of 150mJ / cm².2 Fully cured 1000mJ / cm 2 The sample was then heated to 70°C for 2 minutes. A bending test was performed on a 5mm bending radius fixture for 10,000 cycles, and the relative resistance change rate ΔR / R0 was recorded. For erasability, anhydrous ethanol was applied for 60 seconds, followed by wiping three times with a lint-free cloth, and the residue rate was measured. Sheet resistance was measured at 10 points using the four-probe method, and the average was calculated; the relative standard deviation was recorded.

[0055] The experimental data are shown in Table 1.

[0056] Table 1: The results show that, under the same linewidth and curing conditions, the relative resistance change rate after bending in the examples (Examples 1–3) with the introduction of metal nano-dispersion liquid, gallium indium tin alloy and inorganic filler mixed spraying is significantly lower than that in the comparative examples. This indicates that, in addition to being connected by the metal nano-skeleton, the conductive path of the fine line is also supported by the bridging nodes formed by the liquid metal in the mixed spraying at the interface of the inorganic filler, thus maintaining the resistance stability under mechanical stress. In the comparative example 1 without mixed spraying, the current path is easily interrupted at micro-defects due to the lack of bridging and low-temperature self-healing, resulting in a surge in resistance after bending. Although the comparative example 2 with enlarged inorganic filler particle size can still maintain the initial conductivity, the bridging uniformity and linear integrity decrease, and the bending resistance is significantly deteriorated. Regarding sheet resistance, all three sets of examples remained stable at the order of 10^5 Ω / sq, while Comparative Example 1 was significantly higher (1.2 × 10^6 Ω / sq), further confirming that the lack of bridging amplifies the impact of breakage at fine lines. The sheet resistance of Comparative Example 2 was close to that of the examples, reflecting that the initial DC resistance was still mainly determined by the metal nanoframework, but its bending degradation indicated insufficient bridging efficiency. The ethanol removal residue rate did not differ much among the samples, indicating that erasability was mainly determined by the resin / pigment system and the degree of curing, rather than by the mixed spraying. In summary, the three-step method effectively solved the problems of easy breakage and large sheet resistance fluctuations under fine linewidths through stable spreading of nano-pigment, low-dose network formation of the metal framework, and synergistic bridging by liquid metal particles, while maintaining the established ethanol erasability characteristics.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing nano-printing character ink, characterized in that the steps include... include: S1. Separate the aqueous acrylate dispersion into a first part and a second part. Mix the first part, dispersant and pigment, stir evenly, add inorganic abrasive for grinding, and filter to obtain nano-color paste. S2. Metal nanoparticles and highly branched polymers are mixed in an organic solvent to obtain a metal nanoparticle dispersion. Gallium indium tin alloy and inorganic filler are mixed, stirred, and then filtered to obtain a mixed spray. S3. Add the nano-color paste, the second component, polyester acrylate, silane-terminated polyurethane, metal nano-dispersion, and mixed spray paste to the reaction vessel in sequence, stir evenly, then add functional additives and stir to mix. Allow to mature at room temperature to obtain nano-printing character ink.

2. The method for preparing a nano-printing character ink according to claim 1, characterized in that, Step S1 includes: S1.1 The acrylic dispersion is divided into a first part and a second part by mass, each part accounting for 45-55%, and the first part and the second part may have the same or different mass. The first part is adjusted to a solid content of 18-22 wt% with deionized water. S1.

2. Add the first part, dispersant and pigment to the mixing tank in sequence, stir at 1000~1500rpm for 15~20min and control the temperature to ≤25℃ to obtain a pre-dispersed slurry; S1.

3. The pre-dispersed slurry is circulated into a sand mill, inorganic abrasive is added, and ball milling is carried out for 4~8 hours to obtain a grinding slurry. The grinding slurry is transferred into a vacuum degassing tank and stirred at a rotation speed of 100~200rpm for 10~15 minutes under the conditions of -0.06~-0.08MPa and 25℃ to obtain a color paste. S1.

4. The pigment paste is filtered through a three-stage filter system consisting of a 5µm bag filter, a 1µm filter, and a 0.45µm pleated filter under a nitrogen pressure of 0.05~0.1MPa to obtain nano pigment paste.

3. A method for preparing a nano-printing character ink according to claim 1 or 2, characterized in that, The dispersant includes at least one of BYK-190, polycarboxylate dispersant, polyvinylpyrrolidone, and TEGODispers755W; the pigment includes at least one of phthalocyanine blue, phthalocyanine green, and coated iron oxide black; the inorganic abrasive includes at least one of zirconia beads, silica microspheres, and alumina ceramic beads; and the particle size of the inorganic abrasive is 0.3~0.5 mm.

4. The method for preparing a nano-printing character ink according to claim 1, characterized in that, Step S2 includes: S2.1 Weigh the metal nanoparticles and highly branched polymer, add organic solvent, and stir magnetically at 500 rpm for 20 min in a reaction vessel. Then reduce the rotation speed to 300~400 rpm and stir for 10 min. Place in an ultrasonic water bath with a frequency of 40 kHz and a power of ≤120 W for 5~8 min and keep warm at 20~25℃ to obtain a metal nanoparticle dispersion. S2.2 Weigh gallium indium tin alloy and inorganic filler, add them to the mixer at a mass ratio of metal:filler = 10:1, stir at 400~600 rpm, stir at room temperature for 30 min, and then pass the mixture through a 1μm filter to obtain the mixed spray slurry.

5. A method for preparing a nano-printing character ink according to claim 1 or 4, characterized in that, In step S2, the metal nanoparticles include at least one of silver nanowires, copper nanowires, and gold nanoparticles; the highly branched polymer includes at least one of hyperbranched polyethyleneimine, hyperbranched polyurethane, and hyperbranched polyester; the organic solvent includes at least one of isopropanol, ethanol, propylene glycol methyl ether, and ethyl acetate; and the inorganic filler includes at least one of silica, alumina, zirconium oxide, and titanium dioxide. The particle size of the inorganic filler is 20-100 nm.

6. The method for preparing a nano-printing character ink according to claim 1, characterized in that, Functional additives include photoinitiators, reactive diluents, defoamers, thixotropic agents, leveling agents, and antioxidant polymerization inhibitors; Step S3 includes: S3.1 Add the second part to the mixing vessel, adjust the temperature to 23~25℃, and stir at 400~600rpm for 5~10min. Then add polyester acrylate and silane-terminated polyurethane in sequence, and continue stirring for 10~15min. S3.

2. Maintain stirring speed and temperature, add nano pigment and stir for 10-15 minutes, adjust stirring speed to 300-400 rpm, add metal nano dispersion and stir for 10 minutes, add mixed spraying at a volume ratio of metal nano dispersion to mixed spraying slurry of 1:2, and stir for another 10-15 minutes to obtain mixed slurry. S3.3 Add reactive diluent to the mixed slurry and mix at a stirring speed of 500~800 rpm for 30~40 min. Then add defoamer at a stirring speed of 300~400 rpm and stir for 10~15 min. Next, slowly add thixotropic agent and mix at a stirring speed of 800~1000 rpm for 20~30 min. Then, add leveling agent and antioxidant polymerization inhibitor in sequence at a stirring speed of 300~400 rpm and stir for 15~20 min. Finally, add photoinitiator in a light-protected environment at a stirring speed of 100~200 rpm and stir for 30~40 min. Allow to stand at room temperature for 12~24 h to mature. After three-stage filtration, obtain nano-printing character ink.

7. The method for preparing a nano-printing character ink according to claim 6, characterized in that, In step S3, the photoinitiator includes at least one of TPO-L, 819, and 1173; the reactive diluent includes at least one of trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and isoborneol acrylate; the defoamer includes at least one of BYK-024, BYK-022, BYK-028, and TEGOFoamex N / 810; the thixotropic agent includes at least one of fumed silica, organobentonite, and polyamide wax rheology modifier; the leveling agent includes one of BYK-348, SF-6500, and Tego-450; and the antioxidant polymerization inhibitor includes at least one of BYK-3510, 2,6-di-tert-butyl-4-methylphenol, and ethyl dimethylaminobenzoate.

8. A nano-printing character ink, characterized in that, It is prepared by the method of preparing a nano-printing character ink as described in any one of claims 1-7.

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