Method for preparing high-stability electrophoretic display particles by miniemulsion polymerization method

Abstract

The invention discloses a method for preparing high-stability electrophoretic display particles through a miniemulsion polymerization method, and belongs to the technical field of material surface engineering and emulsion polymerization. The preparation method comprises the following steps: coating the surfaces of pigment particles with silicon dioxide through a hydrolytic deposition method to form a stable inorganic coating layer; then, a silane coupling agent is used for graft modification, so that the lipophilicity and hydrophobicity of the pigment are further improved. Then, the modified pigment, a polymer monomer and a polymerizable charge control agent are subjected to ball milling dispersion, stable emulsion is formed under the action of an emulsifier, emulsion polymerization is initiated through an initiator, and polymer-coated pigment particles with uniform particle size and controllable surface charge quantity are obtained. The obtained particles can be widely applied to the fields of electronic ink, coatings and high-performance composite materials, the problems that pigments are prone to agglomeration, uneven in charge density, poor in dispersion stability and the like are solved, and the functional performance and the application effect of the pigment particles are further improved.

Description

Technical Field

[0001] The present invention relates to the technical fields of material surface engineering and emulsion polymerization, and in particular to a method for preparing highly stable electrophoretic display particles by miniemulsion polymerization. Background Art

[0002] Due to the advantages of high contrast, wide viewing angle, low power consumption, and strong visibility in sunlight, electrophoretic display technology has been widely used in display fields such as electronic paper, electronic tags, and wearable devices. In the existing electrophoretic display system, the display of black-and-white or color images is mainly achieved by controlling the movement of charged black-and-white particles. Among them, the charge characteristics and dispersion stability of electrophoretic particles are the key factors affecting the display effect. Traditional electrophoretic display systems often use inorganic particles as electrophoretic particles and use non-polar dispersion media and charge control agents to adjust the charge properties of the particles to achieve stable image display. However, due to the limitations of inorganic particles in terms of dispersion stability, color richness, and material diversity, in recent years, the application demand for high-performance organic pigment particles in electrophoretic display has been increasing.

[0003] In order to achieve more rich color display and improve the stability of the display system, researchers have continuously explored the modification technologies of new electrophoretic particles, including chemical modification of the particle surface, optimization of charge regulation methods, and selection of dispersion media. Based on this, the present invention proposes a solution that uses the Isopar series as the dispersion medium, combines the silica deposition modification process and charge control agent to regulate the charge amount, realizes the charge controllability and dispersion stability of organic pigment electrophoretic particles, and provides a new solution for color electrophoretic display. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing highly stable electrophoretic display particles by miniemulsion polymerization. By depositing silica on the surface and modifying with silane coupling agent, the dispersion stability of the particles is improved. By adjusting the content of the charge control agent in the emulsion polymerization particles, the effective control of the surface charge amount is realized. The system uses the Isopar series as the dispersion medium and the organic pigment particles coated by emulsion polymerization as the color electrophoretic display particles. The electrophoretic display liquid shows excellent display effect and stability, is suitable for the preparation of electrophoretic display devices, and provides a stable and controllable solution for color electrophoretic display.

[0005] To achieve the above purpose, the present invention discloses a method for preparing highly stable electrophoretic display particles by miniemulsion polymerization, including the following steps:

[0006] S1. Pretreatment of raw material particles: Add organic raw material particles and a surfactant into an ethanol solvent, add zirconium beads, adjust the pH of the mixed solvent, after ball milling in a ball mill, remove the zirconium beads, centrifuge and wash the ball milling liquid, and dry it in a vacuum environment to obtain pretreated organic pigment particles;

[0007] S2. Deposition of silicon dioxide and grafting of silane coupling agent: Take the pretreated organic pigment particles, add sodium silicate and water, place them in a four-necked flask, heat to 70 - 90 °C by mechanical stirring, at the same time add an appropriate amount of hydrochloric acid to adjust the pH of the mixed solution, and keep the temperature constant for 4 h; after the reaction is completed, cool the system to room temperature; dissolve the silane coupling agent in an organic solvent to form a solution, uniformly drip it into the reaction flask, the dripping time is 50 - 70 min, then heat up to 70 - 90 °C again, and keep the temperature constant for 3 - 5 h under mechanical stirring; after the reaction is completed, centrifuge and wash the obtained material until the conductivity is stable, and dry it in a vacuum at 90 - 120 °C to obtain organic pigment particles grafted with a silane coupling agent;

[0008] S3. Emulsion polymerization: Ball mill the organic pigment particles grafted with a silane coupling agent together with a polymerizable charge control agent, polymer monomers and zirconium beads for 2 - 12 h, after ball milling is completed, obtain a ball milling liquid, mix water, sodium dodecylbenzenesulfonate and the ball milling liquid, and use ultrasonic or high-shear stirring for 25 - 35 min to form a stable emulsion; transfer the emulsion to a four-necked flask, under the protection of an inert gas, heat it by mechanical stirring to 50 - 60 °C, add an appropriate amount of initiator, and continue to heat up to 70 - 90 °C under the protection of a nitrogen environment, keep the temperature constant for 10 - 15 h, after the reaction is completed, centrifuge and wash the obtained product until the conductivity is stable, and dry it in a vacuum at 60 °C to finally obtain high-stability polymer spheres containing organic pigment particles, a charge control agent and a polymer matrix, that is, high-stability electrophoretic display particles.

[0009] Preferably, in step S1, by mass, it includes 10 - 20 parts of ethanol solvent, 1 part of organic raw material particles, 0.1 - 0.5 part of surfactant, 5 - 20 parts of zirconium beads;

[0010] The pH of the mixed solvent is 7 - 10, the ball milling time is 5 - 12 h, and the vacuum drying temperature is 100 °C.

[0011] Preferably, in step S2, by mass, it includes 1 part of pretreated organic pigment particles, 0.1 - 0.5 part of sodium silicate, 5 - 20 parts of water, 0.1 - 0.5 part of silane coupling agent, 10 - 20 parts of organic solvent;

[0012] The rotation speed of mechanical stirring is 200 - 400 rpm, and the pH of the mixed solution is 9 - 10.

[0013] Preferably, in step S3, by mass parts, it includes 1 part of organic pigment particles grafted with silane coupling agent, 10 - 20 parts of zirconium beads, 5 - 20 parts of polymer monomer, 0.1 - 0.5 part of polymerizable charge control agent, 100 parts of water and 0.05 - 0.1 part of sodium dodecylbenzenesulfonate;

[0014] The rotation speed of mechanical stirring is 200 - 500 rpm, the mechanical stirring time is 4 - 12 h, and the product is vacuum dried at 60 °C for 5 - 12 h;

[0015] The mass of the initiator is 0.01 - 0.5% of the total mass of the polymer monomer.

[0016] Preferably, in step S1, the organic raw material particles are colored organic pigment particles, which are any one of Pigment Red 254, Pigment Red 202, Pigment Red 48:2, Pigment Red 49:2, Pigment Red 57:1.

[0017] Preferably, in step S1, the surfactant is any one or more of polyvinyl alcohol, polyethylene glycol, cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, and sodium dodecyl sulfate.

[0018] Preferably, the silane coupling agent in step S2 is any one of γ-(methacryloyloxy)propyltrimethoxysilane, trimethoxy(7-octen-1-yl)silane, 10-undecenyltrichlorosilane, [3-(triethoxysilyl)propyl] propargylcarbamate, or aminopropyltriethoxysilane;

[0019] The organic solvent in step S2 is any one of ethanol, isopropanol, toluene, cyclohexane, Isopar L, and Isopar G.

[0020] Preferably, the polymer monomer in step S3 is any one or more of styrene, methyl acrylate, methyl methacrylate, butyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, acrylic acid, acrylamide, oleic acid, and oleylamine.

[0021] Preferably, the initiator in step S3 is any one of benzoyl peroxide, potassium persulfate (KPS), azobisisobutyronitrile, and dimethyl 2,2'-azobis(2-methylpropionate).

[0022] Preferably, the charge control agent in step S3 is an anionic charge control agent or a cationic charge control agent. The anionic charge control agent is SE-10, and the cationic charge control agent is polyethyleneimine (PEI).

[0023] The silica deposition method used in the present invention is the sodium silicate water glass method. By hydrolyzing the sodium silicate solution, a uniform silica layer is formed on the surface of organic pigment particles to enhance the stability of the particles. The silane coupling agents used on the particle surface are 3-aminopropyltriethoxysilane (APTES) or 3-methacryloxypropyltrimethoxysilane (Kh570). These coupling agents can provide good charge characteristics and chemical stability for the pigment particles by binding to the hydroxyl groups on the silica layer.

[0024] The present invention uses the miniemulsion polymerization method to coat organic pigment particles to form polymer spheres with uniform and stable structures. In this method, monomers, modified organic pigment particles, charge control agents, emulsifiers, and water are fully mixed by ultrasonic or high-shear stirring to generate fine emulsion droplets. Subsequently, an initiator is introduced into the emulsion system to cause the monomers to polymerize within the emulsion droplets, thereby coating a layer of polymer on the surface of the organic pigment particles to form a stable polymer sphere structure. The application of the miniemulsion polymerization method can precisely control the particle size distribution, and the coating layer has a uniform structure, ensuring the high dispersibility and stability of the coated organic pigment particles in the electrophoretic display liquid.

[0025] During the emulsion polymerization process of the present invention, the added charge control agents are anionic and cationic polymerizable charge control agents. The polymerizable charge control agents can participate in the polymerization together with the monomers during the polymerization reaction and firmly embed into the polymer network, thereby realizing the stable regulation of the surface charge of the polymer spheres. In this way, the charge control agents are not easily lost in the solution, ensuring that the coated organic pigment particles have persistent charge stability and uniform electrophoretic behavior, which helps to improve the dispersion stability and display performance of the electrophoretic display liquid.

[0026] Therefore, the present invention has the following beneficial effects:

[0027] The present invention explores the influence of the concentration of the charge control agent on the surface charge amount of electrophoretic particles during the deposition and modification process on the particle surface. By precisely controlling the dosage of the charge control agent, the charge distribution of the particles can be effectively adjusted, the electrophoretic performance can be improved, and the clarity and contrast of the electrophoretic display image can be ensured; through the emulsion polymerization technology, the particle size of the particles can be precisely controlled to reach the required particle size range (for example, 500 nm), so that the electrophoretic display particles show excellent performance in different application scenarios.

[0028] The technical solution of the present invention will be further described in detail below through the accompanying drawings and embodiments. Description of the Drawings

[0029] Figure 1 SEM photograph of Particle A prepared in Example 1 of the present invention;

[0030] Figure 2TEM photograph of particle A prepared in Example 1 of the present invention;

[0031] Figure 3 SEM photograph of particle B prepared in Example 1 of the present invention;

[0032] Figure 4 TEM photograph of particle B prepared in Example 1 of the present invention;

[0033] Figure 5 Charge curves of particles SE-10 with different concentrations of charge control agent added on the surface in Isopar L in the examples of the preparation method of a highly stable electrophoretic display particle of the present invention;

[0034] Figure 6 Steady-state curve of the prototype device prepared with particle E in the examples of the preparation method of a highly stable electrophoretic display particle of the present invention. Detailed implementation mode

[0035] The technical solutions of the present invention will be further described below with reference to the drawings and examples.

[0036] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those of ordinary skill in the field to which the present invention pertains.

[0037] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered by the protection scope of the present invention.

[0038] Example 1

[0039] Take 1 g of organic pigment red 254, 0.1 g of CTAB, and 15 ml of ethanol. Mix the three and add 10 g of zirconium beads and ball mill for 12 h. After the ball milling is completed, remove the zirconium beads, transfer the ball milling liquid to a four-necked flask, heat to 50 °C at 300 rpm, add 0.4 g of sodium silicate and 100 ml of water, adjust the reaction pH to 8, raise the temperature to 70 °C, react for 4 h, then add 0.2 g of Kh570, continue the constant temperature reaction for 3 h, centrifuge, wash, and vacuum dry to obtain organic pigment particles A grafted with silane coupling agent.

[0040] Take 1 g of organic pigment particles A grafted with silane coupling agent, take 0.5 g of SE-10, take 10 g of styrene monomer, add 10 g of zirconium beads and ball mill for 2 - 12 h. Take 100 g of water and 0.1 g of sodium dodecylbenzenesulfonate and mix with the ball milled liquid, then ultrasonicate for 30 min. Transfer the formed emulsion to a four-necked flask, mechanically stir at 400 rpm until the temperature rises to 50 °C, add 0.2 g of KPS as the initiator, heat to 70 °C under a nitrogen atmosphere, then carry out a constant temperature reaction for 12 h, centrifuge and wash until the conductivity is stable, and vacuum dry at 60 °C to obtain polymer spherical particles B.

[0041] Example Two

[0042] Take 1 g of organic pigment particles A grafted with silane coupling agent prepared in Example One, take 0.2 g of SE-10, take 10 g of styrene monomer, add 10 g of zirconium beads and ball mill for 12 h. Take 100 g of water and 0.1 g of sodium dodecylbenzenesulfonate and mix with the ball milled liquid, then ultrasonicate for 30 min. Transfer the formed emulsion to a four-necked flask, mechanically stir at 400 rpm until the temperature rises to 50 °C, add 0.2 g of KPS as the initiator, heat to 70 °C under a nitrogen atmosphere, then carry out a constant temperature reaction for 12 h, centrifuge and wash until the conductivity is stable, and vacuum dry at 60 °C to obtain polymer spherical particles C.

[0043] Example Three

[0044] Take 1 g of organic pigment particles A grafted with silane coupling agent prepared in Example One, take 0.3 g of SE-10, take 10 g of styrene monomer, add 10 g of zirconium beads and ball mill for 12 h. Take 100 g of water and 0.1 g of sodium dodecylbenzenesulfonate and mix with the ball milled liquid, then ultrasonicate for 30 min. Transfer the formed emulsion to a four-necked flask, mechanically stir at 400 rpm until the temperature rises to 50 °C, add 0.2 g of KPS as the initiator, heat to 70 °C under a nitrogen atmosphere, then carry out a constant temperature reaction for 12 h, centrifuge and wash until the conductivity is stable, and vacuum dry at 60 °C to obtain polymer spherical particles D.

[0045] Example Four

[0046] Take 1 g of organic pigment particles A grafted with silane coupling agent prepared in Example One, take 0.4 g of SE-10, take 10 g of styrene monomer, add 10 g of zirconium beads and ball mill for 12 h. Take 100 g of water and 0.1 g of sodium dodecylbenzenesulfonate and mix with the ball milled liquid, then ultrasonicate for 30 min. Transfer the formed emulsion to a four-necked flask, mechanically stir at 400 rpm until the temperature rises to 50 °C, add 0.2 g of KPS as the initiator, heat to 90 °C under a nitrogen atmosphere, then carry out a constant temperature reaction for 12 h, centrifuge and wash until the conductivity is stable, and vacuum dry at 60 °C to obtain polymer spherical particles E.

[0047] Example Five

[0048] Take 1 g of the pretreated organic pigment particle A prepared in Example 1, take 0.5 g of SE-10, take 10 g of styrene monomer, add 10 g of zirconium beads and ball mill for 12 h. Take 100 g of water and 0.1 g of sodium dodecylbenzenesulfonate and mix with the ball mill liquor, and ultrasonicate for 30 min. Transfer the formed emulsion to a four-necked flask, mechanically stir at 400 rpm until the temperature rises to 50 °C, add 0.2 g of KPS as an initiator, heat to 90 °C under a nitrogen atmosphere, and then carry out a constant temperature reaction for 12 h. Centrifuge and wash until the conductivity is stable, and vacuum dry at 60 °C to obtain polymer sphere particles F.

[0049] Example Six

[0050] Take 1 g of the pretreated organic pigment particle A prepared in Example 1, take 0.6 g of SE-10, take 10 g of styrene monomer, add 10 g of zirconium beads and ball mill for 12 h. Take 100 g of water and 0.1 g of sodium dodecylbenzenesulfonate and mix with the ball mill liquor, and ultrasonicate for 30 min. Transfer the formed emulsion to a four-necked flask, mechanically stir at 400 rpm until the temperature rises to 50 °C, add 0.2 g of KPS as an initiator, heat to 90 °C under a nitrogen atmosphere, and then carry out a constant temperature reaction for 12 h. Centrifuge and wash until the conductivity is stable, and vacuum dry at 60 °C to obtain polymer sphere particles G.

[0051] Example Seven

[0052] Take 1 g of the pretreated organic pigment particle A prepared in Example 1, take 0.5 g of SE-10, take a mixture of 7 g of styrene monomer and 3 g of methyl methacrylate monomer, add 10 g of zirconium beads and ball mill for 12 h. Take 100 g of water and 0.1 g of sodium dodecylbenzenesulfonate and mix with the ball mill liquor, ultrasonicate for 30 min. Transfer the formed emulsion to a four-necked flask, mechanically stir at 400 rpm until the temperature rises to 50 °C, add 0.2 g of KPS as an initiator, heat to 70 °C under a nitrogen atmosphere, and then carry out a constant temperature reaction for 12 h. Centrifuge and wash until the conductivity is stable, and vacuum dry at 60 °C to obtain polymer sphere particles H.

[0053] Example Eight

[0054] Take 1 g of organic pigment red 202, take 0.1 g of polyethylene glycol, take 20 ml of ethanol, mix the three and add 10 g of zirconium beads and ball mill for 12 h. After ball milling, remove the zirconium beads, transfer the ball mill liquor to a four-necked flask, heat to 50 °C at 300 rpm, add 0.4 g of sodium silicate and 100 ml of water, adjust the reaction pH to 8, heat to 70 °C, react for 4 h, then add 0.2 g of trimethoxy(7-octen-1-yl)silane, continue the constant temperature reaction for 3 h, centrifuge, wash and vacuum dry to obtain organic pigment particles I grafted with silane coupling agent.

[0055] Take 1 g of grafted silane coupling agent organic pigment particles I, take 0.2 g of polyethyleneimine, take 10 g of styrene monomer, add 10 g of zirconium beads and ball mill for 12 h. Take 100 g of water and 0.1 g of sodium dodecylbenzenesulfonate and mix with the ball milled liquid, then ultrasonicate for 30 min. Transfer the formed emulsion to a four-necked flask, mechanically stir at 400 rpm until the temperature rises to 50 °C, add 0.2 g of KPS as the initiator, heat to 70 °C under a nitrogen atmosphere, and then react at a constant temperature for 12 h. Centrifuge and wash until the conductivity is stable, and vacuum dry at 60 °C to obtain polymer sphere particles J.

[0056] Example Nine

[0057] Take 1 g of organic pigment red 57:1, take 0.3 g of sodium dodecyl sulfate, take 15 ml of ethanol, mix the three and add 10 g of zirconium beads and ball mill for 12 h. After ball milling, remove the zirconium beads, transfer the ball milled liquid to a four-necked flask, heat to 50 °C at 300 rpm, add 0.4 g of sodium silicate and 100 ml of water, adjust the reaction pH to 8, heat to 70 °C, after reacting for 4 h, add 0.2 g of trimethoxy(7-octen-1-yl)silane, continue to react at a constant temperature for 3 h, centrifuge, wash and vacuum dry to obtain grafted silane coupling agent organic pigment particles K.

[0058] Take 1 g of grafted silane coupling agent organic pigment particles K, take 0.2 g of SE-10, take 10 g of styrene monomer, add 10 g of zirconium beads and ball mill for 12 h. Take 100 g of water and 0.1 g of sodium dodecylbenzenesulfonate and mix with the ball milled liquid, then ultrasonicate for 30 min. Transfer the formed emulsion to a four-necked flask, mechanically stir at 400 rpm until the temperature rises to 50 °C, add 0.2 g of azobisisobutyronitrile as the initiator, heat to 70 °C under a nitrogen atmosphere, and then react at a constant temperature for 12 h. Centrifuge and wash until the conductivity is stable, and vacuum dry at 60 °C to obtain polymer sphere particles L.

[0059] Experimental Test

[0060] Take about 25 mg each of a small amount of grafted silane coupling agent organic pigment particles A and polymer sphere particles B, disperse them separately in a small amount of anhydrous ethanol (12 ml), and use ultrasonic oscillation for 30 minutes to ensure uniform dispersion of the particles. Drop a small amount of the dispersion liquid on a clean silicon wafer or copper sheet, let it stand and volatilize to dryness to ensure that the sample adheres uniformly to the surface of the silicon wafer or copper sheet. Use an ion plating machine to perform gold or platinum plating on the sample to improve the conductivity of the sample surface. Subsequently, use a scanning electron microscope (SEM), model Regulus 8100, to take morphological photos of the particles, observe their surface structure and uniformity. The results of the grafted silane coupling agent organic pigment particles A are as Figure 1 and the results of the polymer sphere particles B are as Figure 3 shown.

[0061] Use a micropipette to take an appropriate amount of the dispersion (about 10 μl), and drop it onto a carbon film copper grid (200 mesh or 300 mesh), and let it stand until it is completely naturally dried. Use a transmission electron microscope (TEM), with the instrument model JEM-F200, to take the morphology photos of the particles. The results of the organic pigment particles A grafted with silane coupling agent are as Figure 2 shown, and the results of the polymer sphere particles B are as Figure 4 shown.

[0062] From Figure 1 , Figure 2 it can be seen that the surface of the organic pigment particles A grafted with silane coupling agent is coated with a uniform silica layer, forming a continuous and dense inorganic protective layer, which effectively prevents the aggregation of pigment particles and provides active sites for subsequent reactions at the same time.

[0063] From Figure 3 , Figure 4 it can be seen that after emulsion polymerization coating of the pigment particles treated with KH570, polymer microspheres composed of pigment particles, polymers and charge control agents are successfully prepared. From the morphology, these particles show a spherical structure, in which the pigment particles are firmly embedded in the polymer matrix, forming composite particles with coexistence of multiple components. This structure not only effectively improves the charge uniformity and stability of the particles, but also further optimizes the dispersion performance of the particles through the polymer coating layer.

[0064] Take about 10 mg of particles C, D, E, G and F, and add them to their respective clean glass vials containing 10 mL of Isopar L solvent. Use an ultrasonic oscillator to ultrasonically disperse the samples for 30 minutes to ensure uniform dispersion of the particles. Use a dynamic light scattering (DLS) device (such as the Malvern Zetasizer Nano series) to measure the dispersed particle size. Use the same device (such as the Malvern Zetasizer) to measure the zeta potential.

[0065] The test results are as Figure 5As shown, in the embodiment of the method for preparing high-stability electrophoretic display particles of the present invention, with the change of the addition concentration of the charge control agent SE-10, the surface charge distribution of the particles in the Isopar L solvent. It can be seen from the curve that as the addition concentration of SE-10 increases, the surface charge density of the particles gradually increases. When the concentration of SE-10 is lower than a certain threshold, the surface charge density is relatively low, and increasing the addition amount of SE-10 can significantly increase the surface charge amount of the particles; while when the concentration of SE-10 exceeds a certain threshold, the surface charge density tends to be saturated, and the improvement effect of increasing the addition amount on the charge density gradually weakens, and further increasing the amount of SE-10 will result in a decrease in the charge density. This indicates that the concentration of SE-10 directly affects the controllability of the surface charge amount of the particles, thereby affecting the dispersibility and display performance of the electrophoretic particles. Appropriate addition of SE-10 can achieve the best particle charge performance and dispersion stability.

[0066] Take 0.5 g of particle E and add it to 4.5 g of Isopar L, place it in a clean glass vial, and use an ultrasonic oscillator to ultrasonically disperse for 30 minutes to ensure uniform dispersion of the particles, and finally obtain a red electrophoretic solution with a particle solid content of 10%. Take the self-made white electrophoretic solution in the laboratory. According to the mass ratio of red to white particles of 1:2, take 0.5 g of the red electrophoretic solution and 1 g of the white electrophoretic solution respectively and mix them, and use ultrasonic oscillation to treat for 15 minutes to ensure uniform distribution of the two types of particles in the mixed solution, and obtain the final red-white electrophoretic solution. In the experimental device, under the conditions of an electrode spacing of 25 μm and an applied voltage of ±15 V, test the electrophoretic performance and display effect of the obtained red-white electrophoretic solution. As Figure 6 shown, in the long-term test, the L value of the white surface of the device decreased by 2% within the first 6 hours and then remained stable, indicating that the red-white electrophoretic solution has good display performance and system stability.

[0067] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing highly stable electrophoretic display particles by miniemulsion polymerization, characterized in that, It includes the following steps: S1. Pretreatment of raw material particles: Add organic raw material particles and a surfactant into an ethanol solvent, add zirconium beads, adjust the pH of the mixed solvent, after ball milling in a ball mill, remove the zirconium beads, centrifuge and wash the ball milling liquid, and dry it in a vacuum environment to obtain pretreated organic pigment particles; S2. Deposition of silica and grafting of silane coupling agent: Take the pretreated organic pigment particles, add sodium silicate and water, place them in a four-necked flask, heat to 70 - 90 °C with mechanical stirring, at the same time add an appropriate amount of hydrochloric acid to adjust the pH of the mixed solution, and react at a constant temperature for 4 h; after the reaction is completed, cool the system to room temperature; dissolve the silane coupling agent in an organic solvent to form a solution, uniformly add it dropwise to the reaction flask, the dropping time is 50 - 70 min, then heat up to 70 - 90 °C again, and react at a constant temperature for 3 - 5 h under mechanical stirring; after the reaction is completed, centrifuge and wash the obtained material until the conductivity is stable, and dry it in a vacuum at 90 - 120 °C to obtain organic pigment particles grafted with a silane coupling agent; S3. Emulsion polymerization: Ball mill the organic pigment particles grafted with a silane coupling agent, a polymerizable charge control agent, a polymer monomer and zirconium beads together for 2 - 12 h, after ball milling is completed, obtain a ball milling liquid, mix water, sodium dodecylbenzenesulfonate and the ball milling liquid, and use ultrasonic or high-shear stirring for 25 - 35 min to form a stable emulsion; transfer the emulsion to a four-necked flask, under the protection of an inert gas, heat with mechanical stirring to 50 - 60 °C, add an appropriate amount of initiator, and continue to heat up to 70 - 90 °C under the protection of a nitrogen environment, react at a constant temperature for 10 - 15 h, after the reaction is completed, centrifuge and wash the obtained product until the conductivity is stable, and dry it in a vacuum at 60 °C to finally obtain high-stability polymer spheres containing organic pigment particles, a charge control agent and a polymer matrix, that is, high-stability electrophoretic display particles.

2. The method for preparing highly stable electrophoretic display particles by miniemulsion polymerization according to claim 1, wherein In step S1, by mass, it includes 10 - 20 parts of ethanol solvent, 1 part of organic raw material particles, 0.1 - 0.5 part of surfactant, and 5 - 20 parts of zirconium beads; The pH of the mixed solvent is 7 - 10, the ball milling time is 5 - 12 h, and the vacuum drying temperature is 100 °C.

3. A method for preparing highly stable electrophoretic display particles by miniemulsion polymerization according to claim 1, characterized in that, In step S2, by mass, it includes 1 part of pretreated organic pigment particles, 0.1 - 0.5 part of sodium silicate, 5 - 20 parts of water, 0.1 - 0.5 part of silane coupling agent, and 10 - 20 parts of organic solvent; The rotation speed of mechanical stirring is 200 - 400 rpm, and the pH of the mixed solution is 9 - 10.

4. A method for preparing highly stable electrophoretic display particles by miniemulsion polymerization according to claim 2, characterized in that, In step S3, by mass, it includes 1 part of organic pigment particles grafted with a silane coupling agent, 10 - 20 parts of zirconium beads, 5 - 20 parts of polymer monomer, 0.1 - 0.5 part of polymerizable charge control agent, 100 parts of water and 0.05 - 0.1 part of sodium dodecylbenzenesulfonate; The rotation speed of mechanical stirring is 200 - 500 rpm, the mechanical stirring time is 4 - 12 h, and the product is vacuum dried at 60 °C for 5 - 12 h; The mass of the initiator is 0.01 - 0.5% of the total mass of the polymer monomer.

5. A method for preparing highly stable electrophoretic display particles by miniemulsion polymerization according to claim 2, characterized in that, In step S1, the organic raw material particles are colored organic pigment particles, which are any one of pigment red 254, pigment red 202, pigment red 48:2, pigment red 49:2, and pigment red 57:

1.

6. A method for preparing highly stable electrophoretic display particles by miniemulsion polymerization according to claim 1, characterized in that, In step S1, the surfactant is any one or more of polyvinyl alcohol, polyethylene glycol, cetyltrimethylammonium bromide, dodecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, and sodium dodecyl sulfate.

7. A method for preparing highly stable electrophoretic display particles by miniemulsion polymerization according to claim 1, characterized in that, In step S2, the silane coupling agent is any one of γ-(methacryloyloxy)propyltrimethoxysilane, trimethoxy(7-octen-1-yl)silane, 10-undecenyltrichlorosilane, 2-propynyl [3-(triethoxysilyl)propyl]carbamate, or aminopropyltriethoxysilane; In step S2, the organic solvent is any one of ethanol, isopropanol, toluene, cyclohexane, Isopar L, and Isopar G.

8. A method for preparing highly stable electrophoretic display particles by miniemulsion polymerization according to claim 1, characterized in that, In step S3, the polymer monomer is any one or more of styrene, methyl acrylate, methyl methacrylate, butyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, acrylic acid, acrylamide, oleic acid, and oleylamine.

9. A method for preparing highly stable electrophoretic display particles by miniemulsion polymerization according to claim 1, characterized in that, In step S3, the initiator is any one of benzoyl peroxide, potassium persulfate, azobisisobutyronitrile, and dimethyl azobisisobutyrate.

10. A method for preparing highly stable electrophoretic display particles by miniemulsion polymerization according to claim 1, characterized in that: In step S3, the charge control agent is an anionic charge control agent or a cationic charge control agent. The anionic charge control agent is SE-10, and the cationic charge control agent is polyethyleneimine.

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