Magnetoelectric dual-drive microcapsule as well as preparation method and application thereof

Abstract

The invention discloses a magnetoelectric double-drive microcapsule as well as a preparation method and application thereof. A core material of the microcapsule is a dispersion liquid containing a modified carbon-coated magnetic particle cluster body, white particles and a charge control agent, and a wall material is prepared from gelatin and an anionic polymer; wherein the modified carbon-coated magnetic particle cluster body is a carbon-coated magnetic particle cluster body subjected to surface modification by a silane coupling agent; the magnetic particles are ferroferric oxide. The magneto-electric dual-drive microcapsule provided by the invention can be used for preparing a display panel, and the display panel has the characteristics of high contrast, low delay and one-key clearing.

Description

Technical Field

[0001] The present invention belongs to the technical field of microcapsules, and particularly relates to a magnetoelectrically driven microcapsule, a preparation method thereof, and an application thereof. Background Art

[0002] Magnetophoresis and electrophoresis are two common methods for microcapsule display, which utilize different physical principles to achieve image display. Among them, magnetophoretic display utilizes the movement of magnetic particles in a magnetic field. Specifically, a dispersion of fine magnetic particles and white particles is encapsulated in microcapsules. By applying an external magnetic field, the magnetic particles will move towards one end of the display panel surface; when the magnetic particles approach the display panel, they will change the local light reflection or absorption characteristics, thereby forming a visible image. For example, Patent CN105730082A discloses a microcapsule magnetic writing board. The microcapsules adopted in this technical solution encapsulate magnetic microparticles, white color fillers, a dispersion medium, an oil-phase interface monomer, and an auxiliary agent. The magnetic microparticles are one or several of iron tetroxide powder, ferrite powder, and alloy magnetic powder with a particle size of 0.1 - 3 μm. Electrophoretic display utilizes the movement of charged particles in an electric field. Specifically, charged black and white particles are dispersed in an insulating liquid and then encapsulated in microcapsules; by applying a voltage, the charged particles move towards the corresponding electrodes under the action of the electric field. When they move to a specific position, they change the local light reflection or absorption characteristics, thereby forming a visible image. For example, the electronic ink screen produced by Eink company is well-known. It encapsulates a dispersion of black and white particles with different charges in microcapsules. After applying an electric field in a certain direction, the corresponding pigment particles are pushed to the top, and the microcapsules will display different colors.

[0003] In the magnetophoretic display method, an external magnetic field is used to directly move the black particles, and there is no obvious lag between writing and the appearance of the image. In addition, since there is no need for a relatively thick glass layer to separate the stylus from the active layer, the parallax shift between the stylus tip and the writing line can be ignored. Therefore, the writing experience of the magnetic stylus is very similar to writing on paper with a pen, and it can be mass-produced in a roll-to-roll manner with relatively low cost. However, magnetophoretic display panels mostly use magnetic iron tetroxide, and the contrast is relatively low, and the handwriting display is not clear enough. In addition, in large-size panels, due to the difficulty in preparing a large-size integrated strong magnet, it is difficult to erase the large-area magnetophoretic display handwriting. Although electrophoretic display has a high panel contrast and the displayed handwriting can be cleared with one key, there is a writing delay, the writing feeling of a pen and paper cannot be restored, and the cost is high. Summary of the Invention

[0004] In view of the above technical problems, the present invention provides a magnetoelectric dual-drive microcapsule, its preparation method and application, to solve the problems of low contrast, unclear handwriting display, inability to clear with one key in the existing magnetophoresis display panel, and delay and high cost in writing of the electrophoretic display panel.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] On the one hand, the present invention provides a magnetoelectric dual-drive microcapsule. The core material of the microcapsule is a dispersion liquid containing modified carbon-coated magnetic particle clusters, white particles and a charge control agent, and the wall material is prepared from gelatin and an anionic polymer; wherein, the modified carbon-coated magnetic particle clusters are carbon-coated magnetic particle clusters surface-modified by a silane coupling agent; the magnetic particles are magnetite.

[0007] In the technical solution of the present invention, by mass, the core material of the microcapsule includes: 1-3 parts of modified carbon-coated magnetic particle clusters, 10-20 parts of white particles, 0.05-0.5 part of a dispersant, 0.05-0.5 part of a stability control agent, 0.25-2.5 parts of a charge control agent, and 25-35 parts of a dispersion medium.

[0008] In the technical solution of the present invention, the mass ratio of gelatin to the anionic polymer is 0.2-5:1.

[0009] In the technical solution of the present invention, the preparation method of the modified carbon-coated magnetic particle clusters includes the following steps: by mass, add 5-10 parts of carbon-coated magnetic particle clusters to an isopropanol-aqueous solution containing 1-2 parts of a silane coupling agent, adjust the pH to 3-5, and react for 5-10 h; in the technical solution of the present invention, surface modification of the carbon-coated magnetic particle clusters with silane coupling agents having different organic groups can further increase the electrophoretic mobility. Among them, coupling agents with electron-withdrawing functional groups such as methacrylic acid groups make the carbon-coated magnetic particles negatively charged, while coupling agents with electron-donating functional groups such as amino groups make the carbon-coated magnetic particles positively charged.

[0010] In the technical solution of the present invention, the silane coupling agent is selected from any one of positively charged amino silanes and negatively charged methacryloxy silanes, and different coupling agents can be selected according to the particle charge requirements.

[0011] Furthermore, the white particles are selected from at least one of titanium dioxide, lithopone and zinc white powder, and more preferably rutile titanium dioxide with a particle size of 200-400 nm.

[0012] Further, the charge control agent is selected from any one of organic amines, sorbitan esters, and sulfonic acids; in the technical solution of the present invention, the charge control agent is a surfactant or a low-molecular polymer with a low molecular weight, which can act on the particle surface by chemical reaction or physical adsorption, and the charge control agent is used to improve the particle stability or electrophoretic mobility.

[0013] Specifically, examples of the organic amine-based charge control agent include polyisobutylene succinimide, N-cyclohexyl propylenediamine, polyacrylamide, etc.

[0014] Specifically, examples of the sorbitan ester-based control agent include sorbitan oleate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monolaurate, etc.

[0015] Specifically, examples of the sulfonic acid-based control agent include sodium bis(2-ethylhexyl) sulfosuccinate, sodium fatty alcohol polyoxyethylene ether sulfate, sodium dodecylbenzenesulfonate, etc.

[0016] Further, the charge control agent is selected from any one of polyisobutylene succinimide, sorbitan oleate, and sodium bis(2-ethylhexyl) sulfosuccinate.

[0017] Further, the dispersant is a hyperdispersant; the hyperdispersant contains one or more anchoring functional groups and a soluble polymer long-chain segment, and examples include Lubrizol 17000, Lubrizol 13940, BYK190, BYK164, BYK184, CH-1A, CH-2C, CH-3, CH-5, and the above examples can be used alone or in any mixture.

[0018] Further, the stability control agent is selected from at least one of fumed silica, castor oil derivatives, polyolefin waxes, modified hydrogenated castor oil, polyisobutylene, and polyisoprene; in the technical solution of the present invention, the stability control agent can adjust the viscosity of the dispersion to form a network structure, further increase the suspension stability of the core material, and contribute to the redispersibility of the precipitated and aggregated particles.

[0019] Further, the dispersion medium is a non-polar organic solvent, selected from at least one of aliphatic hydrocarbons, fluorocarbons, and halogenated hydrocarbons, such as isoparaffin, n-paraffin, cycloalkane, carbon tetrachloride, tetrachloroethylene, etc.

[0020] Furthermore, the anionic polymer is at least one of natural anionic polymers, semi-synthetic anionic polymers or synthetic anionic polymers; examples of the natural anionic polymers include gum arabic, gum, pectin, sodium alginate, etc.; examples of the semi-synthetic anionic polymers include sodium carboxymethyl cellulose, methyl cellulose, carboxymethyl cellulose, etc.; examples of the synthetic anionic polymers include sodium polystyrene maleic anhydride, sodium polyacrylate, etc.

[0021] As a preferred embodiment, the carbon-coated magnetic particle cluster is prepared from a ferric salt precursor and an organic carbon source by ultrasonic spray pyrolysis or solvothermal pyrolysis; in the technical solution of the present invention, the surface of the carbon-coated magnetic particle cluster has a loose submicron structure formed by close packing of ultra-small nanocrystals, the particle size of the ultra-small nanocrystals is 10-30 nm, and the size of the cluster is 200-500 nm; the density of the cluster can be regulated by adjusting the thickness of the carbon layer, considering the smoothness of magnetic pen writing, the thickness of the carbon layer is controlled within 10 nm, and further preferably between 4-8 nm.

[0022] Furthermore, the ultrasonic spray pyrolysis includes the following steps: an aqueous solution containing a ferric salt precursor and an organic carbon source is ultrasonically atomized into droplets and then subjected to high-temperature pyrolysis in an inert atmosphere.

[0023] Furthermore, the solvothermal pyrolysis includes the following steps: a ferric salt precursor and an organic carbon source are subjected to a solvothermal reaction in an alcohol solvent and then subjected to high-temperature pyrolysis in an inert atmosphere.

[0024] Furthermore, the ferric salt precursor is selected from any one of ferric chloride and ferric nitrate.

[0025] Furthermore, the organic carbon source is selected from any one of glucose, sucrose, polyethylene glycol and cyclodextrin.

[0026] Furthermore, the mass ratio of the ferric salt precursor to the organic carbon source is 1-5:1.

[0027] Furthermore, in the ultrasonic spray pyrolysis, the temperature of the high-temperature pyrolysis is 200-250 °C, and the time of the high-temperature pyrolysis is 4-6 h.

[0028] Furthermore, in the solvothermal pyrolysis, the temperature of the solvothermal reaction is 180-240 °C, the reaction time of the solvothermal reaction is 5-15 h; the temperature of the high-temperature pyrolysis is 200-250 °C, and the time of the high-temperature pyrolysis is 4-6 h; before the high-temperature pyrolysis, it also includes a treatment process of centrifuging, magnetic separation and drying of the reactants of the solvothermal reaction; the alcohol solvent is selected from at least one of ethanol, ethylene glycol and propanol.

[0029] In the technical solution of the present invention, the surface of the carbon-coated magnetic particle clusters obtained by the above preparation method contains =C-H, C=O and C-H groups, and shows good affinity in dielectric solvents.

[0030] In another aspect, the present invention provides a method for preparing the above magnetoelectric dual-drive microcapsules, comprising the following steps:

[0031] Prepare a white particle suspension and a magnetic particle suspension respectively, mix them and add a stability control agent to obtain a core material dispersion; the white particle suspension contains a dispersant, a dispersion medium and white particles; the magnetic particle suspension contains a charge control agent, a dispersion medium and modified carbon-coated magnetic particle clusters;

[0032] Prepare an aqueous solution containing gelatin and an anionic polymer;

[0033] Add the core material dispersion to the aqueous solution and stir for emulsification;

[0034] Adjust the pH of the emulsion to ≤4.5, cool down to ≤10°C; add a curing agent, adjust the pH to 7-10; stir and react at 35-45°C for 2-4 h.

[0035] In the technical solution of the present invention, an acid is added to adjust the pH of the emulsion to ≤4.5, and the acid is at least one of inorganic acids or organic acids, such as hydrochloric acid, sulfuric acid, acetic acid, citric acid, etc.

[0036] In the technical solution of the present invention, a base is added to adjust the pH to 7-10, and the base is an inorganic base, such as sodium hydroxide and potassium hydroxide.

[0037] As a preferred embodiment, the curing agent is selected from any one of glutaraldehyde, tannic acid and transglutaminase.

[0038] Furthermore, the mass fraction of the curing agent is 0.1-1 part.

[0039] In another aspect, the present invention provides the application of the above magnetoelectric dual-drive microcapsules in the preparation of display panels.

[0040] In another aspect, the present invention provides a display panel comprising the above magnetoelectric dual-drive microcapsules.

[0041] In the technical solution of the present invention, the preparation method of the display panel comprises the following steps: after mixing the magnetoelectric dual-drive microcapsules and a binder, coat them on a PET-ITO substrate transparent film, and form a coating after drying; after further drying, the coating is bonded and compounded with a PET layer to obtain the display panel.

[0042] Specifically, the binder is any one of silicone-based binders, polyurethane-based binders, and acrylic-based binders, preferably self-crosslinking polyurethane. By self-crosslinking during the film-forming process, the crosslinking density is increased, thereby enhancing the adhesion and barrier properties. For example, Takelac of Mitsui Chemicals and Turboset series resins of Lubrizol.

[0043] The beneficial effects of the present invention include:

[0044] 1. In the present invention, magnetic particles are prepared into carbon-coated clusters, which not only improve the blackness of the particles but also reduce the density. Only the black particles need to be charged, and the dispersion is further encapsulated into microcapsules, so that the fabricated magnetoelectric dual-drive display panel combines magnetophoretic display and electrophoretic display, with the characteristics of high contrast, low latency, and one-key clearing. Moreover, the display panel has a relatively low cost and can be prepared on a large scale;

[0045] 2. In common electrophoretic displays, usually all particles are charged or can obtain charges, and the particles need to be surface-treated or organically coated to improve chargeability or dispersion stability. In fact, the charging of particles is a very complex process, involving ion adsorption, acid-base proton exchange, reverse micelles, etc. It becomes very difficult to charge all particles and maintain long-term stability. In the present invention, only the carbon-coated magnetic particles need to be charged, and the suspension stability of the white particles is ensured, thus greatly simplifying the process complexity of particle charging. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a micrograph of the carbon-coated magnetic particle clusters prepared in Example 1 of the present invention;

[0047] Figure 2 It is a micrograph of the display panel prepared in Example 1 of the present invention under magnetic field driving;

[0048] Figure 3 It is a micrograph of the display panel prepared in Comparative Example 1 of the present invention under electric field driving. DETAILED DESCRIPTION OF THE INVENTION

[0049] The following embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0050] In the present invention, unless otherwise specified, all devices, raw materials, etc. can be purchased from the market or are commonly used in this industry. The methods in the following examples are all conventional methods in this field unless otherwise specified.

[0051] Example 1:

[0052] (1) Preparation of modified carbon-coated magnetic particle clusters:

[0053] Dissolve 5 g of glucose and 15 g of ferric trichloride in 30 g of water. Atomize the solution into microdroplets by an ultrasonic generator and carry out a pyrolysis reaction at 200 °C for 4 h in a high-temperature furnace with the aid of nitrogen; wash and dry to obtain carbon-coated magnetic particle clusters with a particle size of 200 - 400 nm and a density of 3.0 g / cm 3 ;

[0054] Add 5 g of carbon-coated magnetic particle clusters to a mixed solution of 5 g of isopropanol, 95 g of water, and 1 g of positively charged 3-aminopropyltriethoxysilane; slowly adjust the pH to 3 and react for 8 h; centrifuge, wash, and dry to obtain modified carbon-coated magnetic particle clusters.

[0055] The microscopic morphology diagram of the carbon-coated magnetic particle clusters before modification prepared in this example is shown in Figure 1 From Figure 1 it can be seen that the carbon-coated magnetic particle clusters are composed of nanoparticle accumulations and have a non-smooth surface.

[0056] (2) Preparation of magneto-electrically driven microcapsules:

[0057] (1) Weigh 0.4 g of Lubrizol 17000 and dissolve it in 20 g of tetrachloroethylene. Add 15 g of rutile titanium dioxide with a particle size of 300 nm and disperse it evenly by ultrasonic treatment to obtain a white particle suspension;

[0058] (2) Add 0.25 g of polyisobutylene succinimide to 12.75 g of tetrachloroethylene and disperse it evenly by ultrasonic treatment; add 1.5 g of modified carbon-coated magnetic particle clusters, mix and stir for 3 h, and centrifuge to remove bubbles to obtain a magnetic particle suspension;

[0059] (3) Mix the white particle suspension and the magnetic particle suspension evenly, add 0.1 g of fumed silica, and disperse it evenly by ultrasonic treatment to obtain a core material dispersion;

[0060] (4) Weigh 2 g of gelatin and 2 g of gum arabic and dissolve them in 150 g of water at 45 °C, and stir evenly to obtain an aqueous solution;

[0061] (5) Add the core material dispersion to the aqueous solution and stir at 200 rpm in a reaction kettle for 10 min to obtain an emulsion with an average particle size of about 100 μm;

[0062] (6) Add citric acid to adjust the pH of the emulsion to ≤ 4.5, cool down to within 10 °C; add 1 g of glutaraldehyde solution with a mass concentration of 50%; adjust the pH to 8 with potassium hydroxide; stir and react at 40 °C for 2 h; wash, sieve, and filter the completely reacted mixture to obtain magnetoelectric dual-drive microcapsules.

[0063] (III) Preparation of display panel:

[0064] Mix aqueous polyurethane resin Turboset TM 5000HS and magnetoelectric dual-drive microcapsules in a mass ratio of 1:10, coat the mixture on a PET-ITO substrate transparent film, and form a coating after drying; further dry and bond the coating with the PET layer to obtain the display panel.

[0065] The microscopic morphology diagram of the display panel prepared in this example after being driven by a magnetic field is shown in Figure 2 , and the microscopic morphology diagram after being driven by an electric field is shown in Figure 3 , Figure 2 and Figure 3 It shows that the display panel made of the magnetoelectric dual-drive microcapsules of the present invention can be driven by a magnetic field and an electric field.

[0066] Example 2:

[0067] (I) Preparation of modified carbon-coated magnetic particle clusters:

[0068] Dissolve 5 g of glucose and 15 g of iron nitrate in 30 g of water, atomize the solution into microdroplets by an ultrasonic generator, and carry out a pyrolysis reaction at 220 °C for 5 h in a high-temperature furnace with the aid of nitrogen; wash and dry to obtain carbon-coated magnetic particle clusters with a particle size of 200 - 400 nm and a density of 3.0 g / cm 3 ;

[0069] Add 5 g of carbon-coated magnetic particle clusters to a mixed solution of 5 g of isopropanol, 95 g of water, and 1 g of positively charged methacryloyloxy silane; slowly adjust the pH to 4 and react for 6 h; centrifuge, wash, and dry to obtain modified carbon-coated magnetic particle clusters.

[0070] (II) Preparation of magnetoelectric dual-drive microcapsules:

[0071] (1) Weigh 0.4 g of Lubrizol 13940 and dissolve it in 20 g of tetrachloroethylene, add 15 g of rutile titanium dioxide with a particle size of 300 nm, and disperse it evenly by ultrasonic to obtain a white particle suspension;

[0072] (2) Add 1 g of sorbitan oleate to 12 g of tetrachloroethylene, disperse it evenly by ultrasonic; add 1.5 g of modified carbon-coated magnetic particle clusters, mix and stir for 3 h, and centrifuge to defoam to obtain a magnetic particle suspension;

[0073] (3) The white particle suspension and the magnetic particle suspension were mixed evenly, 0.1 g of polyisobutylene was added, and ultrasonic dispersion was performed to obtain a core material dispersion;

[0074] (4) Weigh 2 g of gelatin and 2 g of sodium alginate and dissolve them in 150 g of 45°C water. Stir well to obtain an aqueous solution.

[0075] (5) adding the core material dispersion to the aqueous phase solution and stirring in a reactor at 200 rpm for 10 min to obtain an emulsion with an average particle size of about 100 μm;

[0076] (6) Add citric acid to adjust the pH of the emulsion to ≤4.5, and cool it to less than 10°C; add 1g of tannic acid solution with a mass concentration of 40%; adjust the pH to 8 with potassium hydroxide; stir and react at 40°C for 2h; wash the mixed solution after the reaction is complete, sieve it, and filter it to obtain magnetic and electric dual-drive microcapsules.

[0077] (3) Preparation of display panel:

[0078] Turboset waterborne polyurethane resin TM 5000HS and magnetoelectric dual-drive microcapsules are mixed in a mass ratio of 1:10, coated on a PET-ITO substrate transparent film, and dried to form a coating; after further drying, the coating is bonded and composited with the PET layer to obtain a display panel.

[0079] Example 3:

[0080] (1) Preparation of modified carbon-coated magnetic particle clusters:

[0081] 5 g of polyethylene glycol and 15 g of ferric chloride were dissolved in 30 g of ethylene glycol and mixed evenly; the mixture was reacted in an autoclave at 200 ° C for 10 h; the mixture was centrifuged and dried, and the obtained product was pyrolyzed at 210 ° C for 6 h under a nitrogen atmosphere to obtain carbon-coated magnetic particle clusters with a particle size of 200-400 nm and a density of 3.0 g / cm 3 ;

[0082] 5 g of carbon-coated magnetic particle clusters were added to a mixed solution of 5 g of isopropanol, 95 g of water, and 1 g of positively charged 3-aminopropyltriethoxysilane; the pH was slowly adjusted to 5 and the reaction was carried out for 6 h; the modified carbon-coated magnetic particle clusters were obtained by centrifugation, washing, and drying.

[0083] (2) Preparation of electromagnetic dual-drive microcapsules:

[0084] (1) Weigh 0.4 g of dispersant BYK190 and dissolve it in 15 g of dodecylbenzene. Add 14 g of zinc white powder with a particle size of about 150 to 250 nm and disperse it evenly by ultrasonication to obtain a white particle suspension.

[0085] (2) Add 1.5 g of sorbitan oleate to 17 g of tetrachloroethylene, and disperse it evenly by ultrasonic treatment; add 2 g of modified carbon-coated magnetic particle clusters, mix and stir for 3 h, and centrifuge to remove bubbles to obtain a magnetic particle suspension;

[0086] (3) Mix the white particle suspension and the magnetic particle suspension evenly, add 0.1 g of polyamide-modified hydrogenated castor oil, and disperse it evenly by ultrasonic treatment to obtain a core material dispersion;

[0087] (4) Weigh 2 g of gelatin and 2 g of sodium carboxymethyl cellulose, dissolve them in 150 g of water at 45 °C, and stir evenly to obtain an aqueous solution;

[0088] (5) Add the core material dispersion to the aqueous solution, stir at 200 rpm in a reaction kettle for 10 min to obtain an emulsion with an average particle size of 100 μm;

[0089] (6) Add hydrochloric acid to adjust the pH of the emulsion ≤ 4.5, and cool it to within 10 °C; add 1 g of a glutamine transaminase solution with a mass concentration of 50%; adjust the pH to 8 with sodium hydroxide; stir and react at 40 °C for 2 h; wash, sieve, and filter the completely reacted mixed solution to obtain magnetoelectrically dual-driven microcapsules.

[0090] (III) Preparation of a display panel:

[0091] Mix the aqueous polyurethane resin Turboset TM 5000HS and the magnetoelectrically dual-driven microcapsules in a mass ratio of 1:10, coat them on a PET-ITO substrate transparent film, and form a coating after drying; further dry and bond the coating to the PET layer to obtain a display panel.

[0092] Example 4:

[0093] (I) Preparation of modified carbon-coated magnetic particle clusters:

[0094] Dissolve 5 g of polyethylene glycol and 15 g of ferric chloride in 30 g of ethylene glycol; react in a high-pressure autoclave at 200 °C for 10 h; centrifuge, separate, and dry, and pyrolyze the obtained product in a nitrogen atmosphere at 200 °C for 5 h to obtain carbon-coated magnetic particle clusters with a particle size of 200 - 400 nm and a density of 3.0 g / cm 3 ;

[0095] Add 5 g of carbon-coated magnetic particle clusters to a mixed solution of 5 g of isopropanol, 95 g of water, and 1 g of negatively charged methacryloyloxy silane; slowly adjust the pH to 3 and react for 8 h; centrifuge, wash, and dry to obtain modified carbon-coated magnetic particle clusters.

[0096] (II) Preparation of electromagnetic dual-driven microcapsules:

[0097] (1) Weigh 0.4 g of dispersant BYK184 and dissolve it in 15 g of dodecylbenzene. Add 14 g of rutile titanium dioxide with a particle size of 300 nm and disperse it evenly by ultrasonic wave to obtain a white particle suspension;

[0098] (2) Add 0.5 g of polyisobutylene succinimide to a mixed solution of 18 g of dodecylbenzene and isomeric tridecane with a mass ratio of 3:1, and disperse it evenly by ultrasonic wave; add 2 g of modified carbon-coated magnetic particle clusters, mix and stir for 3 h, and centrifuge to defoam to obtain a magnetic particle suspension;

[0099] (3) Mix the white particle suspension and the magnetic particle suspension evenly, add 0.1 g of polyisoprene, and disperse it evenly by ultrasonic wave to obtain a core material dispersion;

[0100] (4) Weigh 2 g of gelatin and 2 g of pectin, dissolve them in 150 g of water at 45 °C, and stir evenly to obtain an aqueous solution;

[0101] (5) Add the core material dispersion to the aqueous solution, stir at 200 rpm in a reaction kettle for 10 min to obtain an emulsion with an average particle size of 100 μm;

[0102] (6) Add acetic acid to adjust the pH value of the emulsion ≤ 4.5, cool it down to within 10 °C; add 1 g of glutaraldehyde solution with a mass concentration of 50%; adjust the pH to 8 with potassium hydroxide; stir and react at 40 °C for 2 h; wash, sieve, and filter the completely reacted mixed solution to obtain magnetoelectric dual-drive microcapsules.

[0103] (III) Preparation of a display panel:

[0104] Mix the aqueous polyurethane resin Turboset TM 5000HS and the magnetoelectric dual-drive microcapsules in a mass ratio of 1:10, coat them on a PET-ITO substrate transparent film, and form a coating after drying; after further drying, the coating is bonded and compounded with the PET layer to obtain a display panel.

[0105] The display panels prepared in Examples 1 to 5 can stably display writing, there is no delay in writing, and the displayed handwriting can be cleared in one key over a large area.

[0106] Comparative Example 1:

[0107] (I) Preparation of microcapsules:

[0108] (1) Weigh 0.4 g of Lubrizol 17000 and dissolve it in 20 g of tetrachloroethylene. Add 15 g of rutile titanium dioxide with a particle size of 300 nm and disperse it evenly by ultrasonic wave to obtain a white particle suspension;

[0109] (2) Add 0.25 g of polyisobutylene succinimide to 12.75 g of tetrachloroethylene and disperse uniformly by ultrasonication; add 1.5 g of black ferroferric oxide magnetic particles with a particle size of 200 to 400 nm, mix and stir for 3 h, and centrifuge to degas to obtain a magnetic particle suspension;

[0110] (3) The white particle suspension and the magnetic particle suspension were mixed evenly, 0.1 g of fumed silica was added, and ultrasonic dispersion was performed to obtain a core material dispersion;

[0111] (4) Weigh 2 g of gelatin and 2 g of gum arabic and dissolve them in 150 g of water at 45°C. Stir well to obtain an aqueous solution.

[0112] (5) adding the core material dispersion to the aqueous phase solution and stirring in a reactor at 200 rpm for 10 min to obtain an emulsion with an average particle size of 100 μm;

[0113] (6) Add citric acid to adjust the pH value of the emulsion to ≤4.5, and cool it to less than 10°C; add 1 g of 50% glutaraldehyde solution; adjust the pH to 8 with potassium hydroxide; stir and react at 40°C for 2 h, and wash, sieve, and filter the mixture after the reaction is complete to obtain microcapsules.

[0114] (2) Preparation of display panel:

[0115] Turboset waterborne polyurethane resin TM 5000HS and magnetoelectric dual-drive microcapsules are mixed in a mass ratio of 1:10, coated on a PET-ITO substrate transparent film, and dried to form a coating; after further drying, the coating is bonded and composited with the PET layer to obtain a display panel.

[0116] Comparative Example 1 differs from Example 1 in that the modified carbon-coated magnetic particle clusters are replaced with magnetic particles of the same particle size. The display panel prepared in Comparative Example 1 exhibits significantly lower blackness than that of Example 1. The black particles migrate very slowly under the action of an electric field and lack dual-drive efficiency.

[0117] The display panel prepared in Comparative Example 1 requires six magnetic erasing cycles with the same magnetic field strength to erase a large area of displayed characters, while Example 1 only requires one cycle.

[0118] Comparative Example 2:

[0119] (1) Preparation of modified carbon-coated magnetic particle clusters:

[0120] Dissolve 5 g of glucose and 15 g of ferric chloride in 30 g of water. Atomize the solution into microdroplets using an ultrasonic generator, and carry out a pyrolysis reaction at 200 °C for 4 h in a high-temperature furnace with the aid of nitrogen to obtain carbon-coated magnetic particle clusters with a particle size of 200 - 400 nm and a density of 3.0 g / cm 3 ;

[0121] Add 5 g of the carbon-coated magnetic particle clusters to a mixed solution of 5 g of isopropanol, 95 g of water, and 1 g of positively charged 3-aminopropyltriethoxysilane; slowly adjust the pH to 3 and react for 8 h; centrifuge, wash, and dry to obtain modified carbon-coated magnetic particle clusters.

[0122] (II) Preparation of microcapsules:

[0123] (1) Weigh 0.4 g of Lubrizol 17000 and dissolve it in 20 g of tetrachloroethylene. Add 15 g of rutile titanium dioxide with a particle size of 300 nm, and disperse it evenly by ultrasonic treatment to obtain a white particle suspension;

[0124] (2) Add 0.25 g of Lubrizol 17000 to 12.75 g of tetrachloroethylene and disperse it evenly by ultrasonic treatment; add 1.5 g of the modified carbon-coated magnetic particle clusters, mix and stir for 3 h, and centrifuge to remove bubbles to obtain a magnetic particle suspension;

[0125] (3) Mix the white particle suspension and the magnetic particle suspension evenly, add 0.1 g of fumed silica, and disperse it evenly by ultrasonic treatment to obtain a core material dispersion;

[0126] (4) Weigh 2 g of gelatin and 2 g of gum arabic, dissolve them in 150 g of water at 45 °C, and stir evenly to obtain an aqueous solution;

[0127] (5) Add the core material dispersion to the aqueous solution, and stir at 200 rpm in a reaction kettle for 10 min;

[0128] (6) Add citric acid to adjust the pH of the emulsion ≤ 4.5, cool it to within 10 °C; add 1 g of a 50% glutaraldehyde solution by mass; adjust the pH to 8 with potassium hydroxide; stir and react at 40 °C for 2 h; wash, sieve, and filter the completely reacted mixture to obtain microcapsules.

[0129] (III) Preparation of a display panel:

[0130] Mix aqueous polyurethane resin Turboset TM 5000HS and the magnetoelectrically dual-driven microcapsules in a mass ratio of 1:10, coat them on a PET-ITO substrate transparent film, and form a coating after drying; further dry and bond the coating to the PET layer to obtain a display panel.

[0131] Comparative Example 2 differs from Example 1 in that the charge control agent (polyisobutylene succinimide) used in step (2) is replaced with a dispersant (Lubrizol 17000) of equal mass. The display panel prepared in Comparative Example 2 exhibits slightly lower blackness than Example 1, but the black particles migrate very slowly under the action of an electric field, failing to demonstrate the practical efficacy of dual-drive technology.

[0132] The display panel prepared in Comparative Example 2 requires five magnetic erasing cycles with the same magnetic field strength to erase a large area of displayed characters, while Example 1 only requires one cycle.

[0133] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A magnetoelectrically dual-driven microcapsule, characterized in that, The core material of the microcapsule is a dispersion liquid containing modified carbon-coated magnetic particle clusters, white particles and a charge control agent, and the wall material is prepared from gelatin and an anionic polymer; wherein, the modified carbon-coated magnetic particle clusters are carbon-coated magnetic particle clusters surface-modified by a silane coupling agent; the magnetic particles are magnetite.

2. The magnetoelectric dual-drive microcapsule according to claim 1, wherein By mass, the core material of the microcapsule includes: 1-3 parts of modified carbon-coated magnetic particle clusters, 10-20 parts of white particles, 0.05-0.5 parts of a dispersant, 0.05-0.5 parts of a stability control agent, 0.25-2.5 parts of a charge control agent, and 25-35 parts of a dispersion medium; and / or, the mass ratio of the gelatin to the anionic polymer is 0.2-5:

1.

3. The magnetoelectrically driven microcapsule according to claim 1, wherein The preparation method of the modified carbon-coated magnetic particle clusters includes the following steps: By mass, add 5-10 parts of carbon-coated magnetic particle clusters to an isopropanol-aqueous solution containing 1-2 parts of a silane coupling agent, adjust the pH to 3-5, and react for 5-10 h.

4. The magnetoelectrically driven microcapsule according to claim 2, wherein, The silane coupling agent is selected from any one of positively charged amino silanes and negatively charged methacryloxy silanes; and / or, the white particles are selected from at least one of titanium dioxide, lithopone and zinc white powder, and more preferably rutile titanium dioxide with a particle size of 200-400 nm; and / or, the charge control agent is selected from any one of organic amines, sorbitan esters and sulfonic acids; and / or, the charge control agent is selected from any one of polyisobutylene succinimide, sorbitan oleate, and sodium bis(2-ethylhexyl)sulfosuccinate; and / or, the dispersant is a hyperdispersant; and / or, the stability control agent is selected from at least one of fumed silica, castor oil derivatives, polyolefin wax, modified hydrogenated castor oil, polyisobutylene, and polyisoprene; and / or, the dispersion medium is a non-polar organic solvent, selected from at least one of aliphatic hydrocarbons, fluorocarbons and halogenated hydrocarbons; and / or, the anionic polymer is at least one of natural anionic polymers, semi-synthetic anionic polymers or synthetic anionic polymers.

5. The magnetoelectrically dual-driven microcapsule according to claim 1, wherein The carbon-coated magnetic particle clusters are prepared by an ultrasonic spray pyrolysis method or a solvothermal pyrolysis method using a trivalent iron salt precursor and an organic carbon source; The ultrasonic spray pyrolysis method includes the following steps: After ultrasonic atomizing an aqueous solution containing a trivalent iron salt precursor and an organic carbon source into droplets, perform high-temperature pyrolysis in an inert atmosphere; The solvothermal pyrolysis method includes the following steps: Perform a solvothermal reaction on a trivalent iron salt precursor and an organic carbon source in an alcohol solvent, and then perform high-temperature pyrolysis in an inert atmosphere.

6. The magnetoelectrically dual-driven microcapsule according to claim 5, characterized in that, The trivalent iron salt precursor is selected from any one of ferric chloride and ferric nitrate; and / or, the organic carbon source is selected from any one of glucose, sucrose, polyethylene glycol and cyclodextrin; and / or, the mass ratio of the trivalent iron salt precursor to the organic carbon source is 1-5:1; and / or, in the ultrasonic spray pyrolysis method, the temperature of the high-temperature pyrolysis is 200-250 °C, and the time of the high-temperature pyrolysis is 4-6 h; And / or, in the solvothermal-pyrolysis method, the temperature of solvothermal treatment is 180 - 240 °C, and the reaction time of solvothermal treatment is 5 - 15 h; the temperature of high-temperature pyrolysis is 200 - 250 °C, and the time of high-temperature pyrolysis is 4 - 6 h; the alcohol solvent is selected from at least one of ethanol, ethylene glycol and propanol.

7. The preparation method of the magnetoelectric dual-drive microcapsule according to any one of claims 1-6, characterized in that, Comprising the following steps: Preparing a white particle suspension and a magnetic particle suspension respectively, mixing them and adding a stability control agent to obtain a core material dispersion; the white particle suspension contains a dispersant, a dispersion medium and white particles; the magnetic particle suspension contains a charge control agent, a dispersion medium and a modified carbon-coated magnetic particle cluster. Preparing an aqueous solution containing gelatin and an anionic polymer. Adding the core material dispersion to the aqueous solution and stirring for emulsification. Adjusting the pH of the emulsion to ≤ 4.5, cooling it to ≤ 10 °C; adding a curing agent, adjusting the pH to 7 - 10; stirring and reacting at 35 - 45 °C for 2 - 4 h.

8. The preparation method according to claim 7, wherein The curing agent is selected from any one of glutaraldehyde, tannic acid and transglutaminase. The mass fraction of the curing agent is 0.1 - 1 part.

9. Use of the magnetoelectric dual-drive microcapsule according to any one of claims 1 - 6 in the preparation of a display panel.

10. A display panel comprising the magnetoelectric dual-drive microcapsule according to any one of claims 1 - 6.

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