Magnetoelectric dual-drive microcapsule capable of stably displaying written image, preparation method and display panel comprising magnetoelectric dual-drive microcapsule

Abstract

The invention relates to the field of display, in particular to a magnetoelectric double-drive microcapsule capable of stably displaying a written image, a preparation method and a display panel comprising the magnetoelectric double-drive microcapsule. According to the magnetoelectric dual-drive microcapsule capable of stably displaying the writing image, a core material is a dispersion liquid of a carbon-coated magnetic particle mixture, white particles, a charge control agent and a stability control agent, and a wall material is a gelatin-anionic polymer; the carbon-coated magnetic particle mixture is formed by mixing low-coercivity carbon-coated magnetic particles and high-coercivity carbon-coated magnetic particles with different morphologies. The display panel made of the magneto-electric double-drive microcapsule has the advantages that writing is fine and distortionless, a written image is stable and does not fade, local erasing is easy, and one-key clearing can be achieved.

Description

Technical Field

[0001] The present application relates to the field of displays, and particularly to a magnetoelectric dual-drive microcapsule for stably displaying a written image, a preparation method thereof, and a display panel including the same. Background Art

[0002] In the field of microcapsule display methods, magnetophoresis technology, electrophoresis technology, etc. are well known in the industry. In the magnetophoresis display method, a dispersion liquid of fine magnetic particles and white particles is encapsulated in microcapsules, and the magnetic particles swim toward the display panel under the action of a magnetic field for display. For example, Patent CN100411884C discloses a microcapsule magnetophoresis display panel that can be written and erased, in which a dispersion liquid, white pigment, additives, and magnetic particles of different diameters are encapsulated in microcapsules, and a good erasing effect is achieved by selecting magnetic particles of different diameters. In the electrophoresis display method, for example, the electronic ink screen produced by Eink company is well known. It encapsulates dispersion liquids of black and white particles with different charges in microcapsules. When an electric field in a certain direction is applied, the corresponding pigment particles are pushed to the top, and the microcapsules will display different colors. The black particles are usually modified carbon black.

[0003] The magnetoelectric dual-drive display technology innovatively combines electrophoresis display and magnetophoresis display technologies. It can not only highly restore the real touch when writing with a pen and paper, but also has the convenient function of one-key erasing. Among traditional materials, black magnetic particles such as magnetite have too high a density and too low a blackness, which do not meet the requirements of electrophoresis display. Magnetic particles suitable for magnetoelectric dual-drive display technology generally undergo carbon coating treatment. One is to effectively reduce the density of the particles, and the other is to significantly improve the blackness of the particles. Through these two improvements, the stability of the panel is greatly improved and the blackness of the handwriting is enhanced, thus greatly improving the visual perception and making the writing experience closer to the real feeling of writing on white paper. However, carbon coating treatment of the particles will reduce the magnetism and coercivity of the particles, resulting in slower movement of the magnetic particles and the inability to display the handwriting for a long time, that is, the written image cannot be stably displayed. Patent CN 112147830A discloses a microcapsule magnetophoresis display that can be erased from the surface. By adding hard ferrite particles with an average particle size of less than 1.0 μm to form apparent large particles, but there will be obvious disconnection in the handwriting. Based on the above analysis, it is very necessary to prepare a magnetoelectric dual-drive microcapsule that can stably display a written image. Summary of the Invention

[0004] Embodiments of the present application provide a magnetoelectric dual-drive microcapsule for stably displaying a written image, so as to solve the problems that the written image cannot be stably displayed and is easily erased after the carbon coating treatment of magnetic particles in the related art.

[0005] In a first aspect, the present application provides a magnetoelectrically driven microcapsule for stably displaying a written image. The core material thereof is a dispersion liquid of a carbon-coated magnetic particle mixture, white particles, a charge control agent, and a stability control agent, and the wall material is gelatin-anionic polymer; the carbon-coated magnetic particle mixture is composed of a mixture of low-coercivity carbon-coated magnetic particles and high-coercivity carbon-coated magnetic particles with different morphologies. The compounding of magnetic particles with different coercivities can not only stably display the written image but also effectively ensure local erasability.

[0006] In some embodiments, the morphology of the carbon-coated magnetic particles is at least two of spherical, cubic, and octahedral, and at least one of them is spherical.

[0007] In some embodiments, the average particle size of the carbon-coated magnetic particles is 0.3 μm. The low-coercivity carbon-coated magnetic particles are spherical particles with a coercivity of 40-60 Oe, and the high-coercivity carbon-coated magnetic particles are cubic or octahedral particles with a coercivity of 80-130 Oe. When a magnetic field is applied, the magnetic particles are magnetized, and the remanence of the particles attracts the surrounding particles and continuously magnetizes and aggregates to form black aggregates with a larger particle size, thereby displaying an image. During the migration of the magnetic field, particles with a relatively smaller particle size are more likely to move, and the handwriting displayed after magnetization and aggregation will be more delicate and real; magnetic particles with a relatively larger particle size are more likely to attract fine particles around them to aggregate into large particles, and high-blackness points will be formed at different places during writing. Macroscopically, the handwriting appears to be in a state of broken lines. In particular, when the magnetic particles are carbon-coated, their residual magnetic field strength is significantly reduced and the coercivity is lower. On the one hand, only a lower strong magnetic field is required for erasure, and on the other hand, the displayed image cannot exist stably, that is, the handwriting easily fades. However, after particles with too high coercivity aggregate, the erasability is poor, and a higher magnetic field or multiple erasures are required to eliminate the displayed handwriting.

[0008] In some embodiments, the thickness of the carbon coating layer of the carbon-coated magnetic particles is 10-20 nm. When the carbon coating layer is less than 10 nm, the improvement of blackness is not obvious, and when it is higher than 20 nm, it will significantly affect the remanence and coercivity of the particles.

[0009] In some embodiments, the stability control agent is selected from free radical scavengers. Traditional stability control agents, such as fumed silica, castor oil derivatives, polyolefin waxes, modified hydrogenated castor oil, polyisobutylene, polyisoprene, etc., can control the suspension state of particles in the initial stage, but will cause the formation of local networks in the later stage. Especially in outdoor situations, the mobility of particles is significantly restricted. The present application finds that using a stability control agent such as a free radical scavenger can avoid the occurrence of such problems.

[0010] In some preferred embodiments, the stability control agent is selected from UV-400 or UV 384-2.

[0011] In some embodiments, the white particles are TiO2 particles coated with inorganic substances, and the inorganic substances are one or several mixtures of aluminum oxide, silicon oxide, and zirconium oxide. In this application, the TiO2 particles coated with inorganic substances are prepared by the sol-gel method or the precipitation method.

[0012] In some embodiments, the charge control agent is any one of organic amines, sorbitan esters, and sulfonic acids.

[0013] In some preferred embodiments, the charge control agent is selected from any one of polyisobutylene succinimide (commercial OLOA series), sorbitan oleate (commercial Span series), and sodium bis(2-ethylhexyl) sulfosuccinate (AOT).

[0014] In a second aspect, the present application also provides a method for preparing the above-mentioned magnetoelectric dual-drive microcapsules, including the following steps:

[0015] Step S101: Add the charge control agent to the dispersion medium, and then add carbon-coated magnetic particles, white particles, and a stability control agent, and ultrasonically mix evenly to obtain a core material dispersion liquid;

[0016] Step S102: Add gelatin and an anionic polymer to water to obtain an aqueous phase;

[0017] Step S103: Add the core material dispersion liquid to the aqueous phase and stir to obtain an emulsion;

[0018] Step S104: Add an acid to adjust the pH value of the emulsion, cool it to below 10°C, add a curing agent, add an alkali solution to adjust the pH value, and then carry out a reaction. After the reaction is completed, sieve and filter by suction to obtain the magnetoelectric dual-drive microcapsules.

[0019] In some embodiments, the carbon-coated magnetic particles are prepared through the following process: Mix magnetic particles, an organic carbon source, and water evenly, then ball mill for 2 - 5 h and separate. Pyrolyze the separated product at high temperature in a nitrogen atmosphere, and then wash with alcohol and separate by magnetic field to obtain the carbon-coated magnetic particles.

[0020] In some embodiments, the organic carbon source is selected from any one of glucose, sucrose, polyethylene glycol, and cyclodextrin.

[0021] In some embodiments, in step S101, the mass parts of each raw material in the core material dispersion liquid are: 20 - 40 parts of white particles, 2 - 5 parts of carbon-coated magnetic particles, 0.1 - 0.5 part of stability control agent, 2 - 5 parts of charge control agent, and 50 - 70 parts of dispersion medium.

[0022] In some embodiments, in step S102, the mass part of gelatin is 1 - 5 parts, and the mass part of the anionic polymer is 1 - 5 parts.

[0023] In some embodiments, the mass parts of the curing agent are 0.1 to 1 part.

[0024] In some embodiments, the dispersion medium is a non-polar solvent.

[0025] In some preferred embodiments, the non-polar solvent is selected from any one or a mixture of n-alkanes, isoparaffins, and naphthenes.

[0026] In some embodiments, the acid solution is selected from any one of hydrochloric acid, sulfuric acid, acetic acid, and citric acid; the alkali solution is selected from sodium hydroxide or potassium hydroxide; the curing agent is selected from any one of glutaraldehyde, tannic acid, or transglutaminase.

[0027] In some embodiments, the anionic polymer is selected from any one of natural polymers, semi-synthetic polymers, or synthetic polymers.

[0028] In some preferred embodiments, the natural polymer is a mixture of any one or more of gum arabic, gum, pectin, and sodium alginate; the semi-synthetic polymer is a mixture of any one or more of sodium carboxymethyl cellulose, methyl cellulose, and carboxymethyl cellulose; the synthetic polymer is a mixture of any one or more of sodium polystyrene maleic anhydride and sodium polyacrylate.

[0029] In a third aspect, the present application also provides a display panel including the above-mentioned magnetoelectric dual-drive microcapsules.

[0030] In a fourth aspect, the present application also provides a method for preparing the above-mentioned display panel, including the following steps: mixing the magnetoelectric dual-drive microcapsules and a binder, coating them on a PET-ITO (Indium Tin Oxides) substrate transparent film, drying to form a coating, and further drying and bonding and laminating with a PET layer to obtain the display panel.

[0031] In some embodiments, the binder is one of silicone-based, polyurethane-based, and acrylic-based, preferably a self-crosslinking polyurethane, which increases the crosslinking density during film formation to improve adhesion and barrier properties, such as Takelac of Mitsui Chemicals and Turboset series resins of Lubrizol.

[0032] The beneficial effects brought by the technical solution provided by the present application include:

[0033] After carbon coating magnetic particles with the same particle size but different coercive forces in the present application, the particles are charged through a charge control agent, and the dispersion liquid is further wrapped into microcapsules, so that the magnetoelectric dual-drive display panel has the characteristics of delicate and distortion-free writing, stable and non-fading writing images, easy local erasure, and one-key clearing. The manufacturing process of the display panel is simple and can be mass-produced. Brief Description of the Drawings

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0035] Figure 1 Photograph of the display panel prepared in Example 1 of the present application showing an image after writing for 5 minutes;

[0036] Figure 2 Photograph of the display panel prepared in Comparative Example 1 of the present application showing an image after writing for 5 minutes. Detailed Description of the Embodiments

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0038] The embodiments of the present application provide a magnetoelectrically dual-driven microcapsule that can stably display a written image, which can solve the problems in the related art that the carbon-coated magnetic particles cannot stably display a written image and are easily erased after carbon coating treatment.

[0039] Example 1:

[0040] Prepare low coercivity carbon-coated magnetic particles: Mix 5 g of spherical magnetite with a coercivity of 55 Oe, 1 g of glucose, and 10 g of water evenly. After ball milling for 3 h, separate the zirconium beads and place them in an 80 °C oven to dry. Place the mixture in a nitrogen atmosphere and slowly heat it from room temperature to 600 °C, and keep it warm for 2 h. After washing the product with alcohol and separating it by magnetic field, carbon-coated magnetic particles with an average particle size of 0.3 μm and a coercivity of 45 Oe are obtained, and the thickness of the carbon coating layer is 15 nm;

[0041] Prepare high coercivity carbon-coated magnetic particles: Mix 5 g of octahedral magnetite with a coercivity of 130 Oe, 1 g of glucose, and 10 g of water evenly. After ball milling for 3 h, separate the zirconium beads and place them in an 80 °C oven to dry. Place the mixture in a nitrogen atmosphere and slowly heat it from room temperature to 600 °C, and keep it warm for 2 h. After washing the product with alcohol and separating it by magnetic field, carbon-coated magnetic particles with an average particle size of 0.3 μm and a coercivity of 125 Oe are obtained, and the thickness of the carbon coating layer is 12 nm;

[0042] Preparation of core material dispersion: Add 5 g of sodium bis(2-ethylhexyl)sulfosuccinate to 56.9 g of n-decane, then add 2 g of carbon-coated magnetic particles with a coercivity of 45 Oe, 1 g of carbon-coated magnetic particles with a coercivity of 125 Oe, 35 g of alumina-coated titanium dioxide, and 0.1 g of UV-400, and mix evenly by ultrasonic treatment to obtain the core material dispersion;

[0043] Preparation of magnetoelectric dual-drive microcapsules: Weigh 2.5 g of gelatin and 2.5 g of gum arabic, dissolve them in 150 g of water at 45 °C, and stir evenly to obtain an aqueous solution; add 50 g of the core material dispersion to the aqueous solution, stir in a reaction kettle at 200 rpm for 10 min to obtain an emulsion with a suitable particle size; add citric acid to adjust the pH value of the emulsion to within 4.5, cool it to within 10 °C, add 1.5 g of 50% glutaraldehyde solution, add sodium hydroxide to adjust the pH of the mixed solution to 9, and raise the temperature to 40 °C and stir for 5 h; after the reaction, wash and sieve to obtain the magnetoelectric dual-drive microcapsules.

[0044] Preparation of display panel: Mix aqueous polyurethane resin Turboset TM 5000HS and the magnetoelectric dual-drive microcapsules in a ratio of 1:6, coat them on a PET-ITO substrate transparent film, form a coating after drying, and further dry and bond and compound with a PET layer to obtain a magnetoelectric dual-drive display panel.

[0045] The photo of the display panel prepared in Example 1 showing an image after writing for 5 min is shown in Figure 1 .

[0046] Example 2:

[0047] Preparation of low coercivity carbon-coated magnetic particles: Mix 5 g of spherical Fe₃O₄ with a coercivity of 60 Oe, 1 g of glucose, and 10 g of water evenly, after ball milling for 3 h, separate the zirconia beads and place them in an 80 °C oven to dry, place the mixture in a nitrogen atmosphere and slowly raise the temperature from room temperature to 600 °C, and keep it warm for 2 h, wash the product with alcohol and then separate it by magnetic field to obtain carbon-coated magnetic particles with an average particle size of 0.3 μm and a coercivity of 55 Oe, and the thickness of the carbon coating layer is 12 nm;

[0048] Preparation of high coercivity carbon-coated magnetic particles: Mix 5 g of cubic Fe₃O₄ with a coercivity of 90 Oe, 1 g of glucose, and 10 g of water evenly, after ball milling for 3 h, separate the zirconia beads and place them in an 80 °C oven to dry, place the mixture in a nitrogen atmosphere and slowly raise the temperature from room temperature to 600 °C, and keep it warm for 2 h, wash the product with alcohol and then separate it by magnetic field to obtain carbon-coated magnetic particles with an average particle size of 0.3 μm and a coercivity of 86 Oe, and the thickness of the carbon coating layer is 10 nm;

[0049] Preparation of core material dispersion: Add 4 g of sorbitan oleate (Span80) to a mixture of 54.8 g of isomeric tridecane and cyclohexane, then add 1.5 g of carbon-coated magnetic particles with a coercivity of 55 Oe, 1.5 g of carbon-coated magnetic particles with a coercivity of 86 Oe, 38 g of silica-coated titanium dioxide, and 0.2 g of UV 384-2, and mix evenly by ultrasonic treatment to obtain the core material dispersion;

[0050] Preparation of magnetoelectric dual-drive microcapsules: Weigh 2.5 g of gelatin and 2.5 g of gum arabic, dissolve them in 150 g of water at 45 °C, and stir evenly to obtain an aqueous solution; add 50 g of the core material dispersion to the aqueous solution, stir in a reaction kettle at 200 rpm for 10 min to obtain an emulsion with a suitable particle size; add acetic acid to adjust the pH value of the emulsion to within 4.5, cool down to within 10 °C, add 1.5 g of 50% glutaraldehyde solution, add sodium hydroxide to adjust the pH of the mixed solution to 7, and raise the temperature to 40 °C and stir and react for 5 h; after the reaction is completed, wash and sieve to obtain the magnetoelectric dual-drive microcapsules.

[0051] Preparation of display panel: Mix the aqueous polyurethane resin Turboset TM 5000HS and the magnetoelectric dual-drive microcapsules in a ratio of 1:6, coat them on a PET-ITO substrate transparent film, dry to form a coating, and further dry and bond and compound with a PET layer to obtain the magnetoelectric dual-drive display panel.

[0052] Example 3:

[0053] Preparation of low coercivity carbon-coated magnetic particles: Mix 5 g of spherical magnetite with a coercivity of 55 Oe, 1 g of polyethylene glycol, and 10 g of water evenly, after ball milling for 3 h, separate the zirconium beads and place them in an 80 °C oven to dry, place the mixture in a nitrogen atmosphere and slowly raise the temperature from room temperature to 600 °C, and keep it warm for 2 h, wash the product with alcohol and then separate it by magnetic field to obtain carbon-coated magnetic particles with an average particle size of 0.3 μm and a coercivity of 50 Oe, and the thickness of the carbon coating layer is 12 nm;

[0054] Preparation of high coercivity carbon-coated magnetic particles: Mix 5 g of octahedral magnetite with a coercivity of 100 Oe, 1 g of polyethylene glycol, and 10 g of water evenly, after ball milling for 3 h, separate the zirconium beads and place them in an 80 °C oven to dry, place the mixture in a nitrogen atmosphere and slowly raise the temperature from room temperature to 600 °C, and keep it warm for 2 h, wash the product with alcohol and then separate it by magnetic field to obtain carbon-coated magnetic particles with an average particle size of 0.3 μm and a coercivity of 95 Oe, and the thickness of the carbon coating layer is 12 nm;

[0055] Preparation of core material dispersion: Add 3.5 g of polyisobutylene succinimide into 58.6 g of n-octane, then add 1.5 g of carbon-coated magnetic particles with 50 Oe, 2 g of carbon-coated magnetic particles with coercivity of 95 Oe, 34 g of silica-coated titanium dioxide and 0.4 g of UV 384-2, and mix evenly by ultrasonic to obtain the core material dispersion;

[0056] Preparation of magnetoelectric double-drive microcapsules: Weigh 2.5 g of gelatin and 2.5 g of pectin, dissolve them in 150 g of water at 45 °C, and stir evenly to obtain an aqueous solution; add 50 g of the core material dispersion to the aqueous solution, stir in a reaction kettle at 200 rpm for 10 min to obtain an emulsion with appropriate particle size; add acetic acid to adjust the pH value of the emulsion to less than 4.5, cool down to within 10 °C, add 1.5 g of tannic acid solution, add potassium hydroxide to adjust the pH of the mixed solution to 8, and heat up to 40 °C and stir and react for 5 h; after the reaction is completed, wash and sieve to obtain the magnetoelectric double-drive microcapsules.

[0057] Preparation of display panel: Mix the aqueous polyurethane resin Turboset TM 5000HS and the magnetoelectric double-drive microcapsules in a ratio of 1:6, coat them on a PET-ITO substrate transparent film, dry to form a coating, and further dry and bond and compound with the PET layer to obtain the magnetoelectric double-drive display panel.

[0058] In Examples 1 to 3, particles with different coercivities were compounded, and the prepared display panel could not only stably display writing, but also maintain the local erasability within 3 times.

[0059] Comparative Example 1:

[0060] Preparation of low coercivity carbon-coated magnetic particles: Mix 5 g of spherical magnetite with a coercivity of 55 Oe, 1 g of glucose, and 10 g of water evenly, after ball milling for 3 h, separate the zirconium beads and place them in an oven at 80 °C for drying, place the mixture in a nitrogen atmosphere and slowly heat from room temperature to 600 °C, and keep it warm for 2 h, wash the product with alcohol and then separate it by magnetic field to obtain carbon-coated magnetic particles with an average particle size of 0.3 μm and a coercivity of 45 Oe, and the thickness of the carbon coating layer is 15 nm;

[0061] Preparation of core material dispersion: Add 5 g of bis(2-ethylhexyl)sulfosuccinate into 56.9 g of n-hexane, then add 3 g of carbon-coated magnetic particles with a coercivity of 45 Oe, 35 g of alumina-coated titanium dioxide and 0.1 g of UV-400, and mix evenly by ultrasonic to obtain the core material dispersion;

[0062] The processes of preparing the magnetoelectric double-drive microcapsules and the display panel are the same as those in Example 1.

[0063] The photo of the display image after writing for 5 min on the display panel prepared in Comparative Example 1 is shown inFigure 2 , from Figure 2 It can be seen that the clarity of the image after writing on the display panel made entirely of carbon-coated magnetic particles with a coercivity of 45 Oe is inferior to that of Example 1, indicating that the image clarity of the display panel made entirely of low-coercivity carbon-coated magnetic particles is poor.

[0064] Comparative Example 2:

[0065] Prepare high-coercivity carbon-coated magnetic particles: Mix 5 g of octahedral magnetite with a coercivity of 130 Oe, 1 g of glucose, and 10 g of water evenly. After ball milling for 3 h, separate the zirconia beads and place them in an 80 °C oven to dry. Place the mixture in a nitrogen atmosphere and slowly raise the temperature from room temperature to 600 °C, and keep it warm for 2 h. After alcohol washing the product, separate it by magnetic field to obtain carbon-coated magnetic particles with an average particle size of 0.3 μm and a coercivity of 125 Oe. The thickness of the carbon coating layer is 12 nm;

[0066] Prepare the core material dispersion liquid: Add 5 g of bis(2-ethylhexyl)sulfosuccinate to 56.9 g of n-hexane, then add 3 g of carbon-coated magnetic particles with a coercivity of 125 Oe, 35 g of alumina-coated titanium dioxide, and 0.1 g of UV-400, and mix them evenly by ultrasonic treatment to obtain the core material dispersion liquid;

[0067] The processes of preparing the magnetoelectric dual-drive microcapsules and the display panel are the same as those in Example 1. The clarity of the image displayed on the display panel prepared in Comparative Example 2 is close to that of Example 1 after writing for 5 min, but it takes 8 times of magnetic erasure with the same magnetic field intensity to erase the handwriting, while only 2 times are needed in Example 1, indicating that the display panel obtained entirely with high-coercivity carbon-coated magnetic particles is not easy to erase.

[0068] Comparative Example 3:

[0069] Prepare high-coercivity carbon-coated magnetic particles: Mix 5 g of cubic magnetite with a coercivity of 90 Oe, 1 g of glucose, and 10 g of water evenly. After ball milling for 3 h, separate the zirconia beads and place them in an 80 °C oven to dry. Place the mixture in a nitrogen atmosphere and slowly raise the temperature from room temperature to 600 °C, and keep it warm for 2 h. After alcohol washing the product, separate it by magnetic field to obtain carbon-coated magnetic particles with an average particle size of 0.3 μm and a coercivity of 86 Oe. The thickness of the carbon coating layer is 10 nm;

[0070] Mix 5 g of octahedral magnetite with a coercivity of 100 Oe, 1 g of polyethylene glycol, and 10 g of water evenly. After ball milling for 3 h, separate the zirconia beads and place them in an 80 °C oven to dry. Place the mixture in a nitrogen atmosphere and slowly raise the temperature from room temperature to 600 °C, and keep it warm for 2 h. After alcohol washing the product, separate it by magnetic field to obtain carbon-coated magnetic particles with an average particle size of 0.3 μm and a coercivity of 95 Oe. The thickness of the carbon coating layer is 12 nm;

[0071] Preparation of core material dispersion liquid: Add 5 g of sodium bis(2-ethylhexyl)sulfosuccinate to 56.9 g of n-hexane, then add 2 g of carbon-coated magnetic particles with a coercivity of 86 Oe, 1 g of carbon-coated magnetic particles with a coercivity of 95 Oe, 35 g of alumina-coated titanium dioxide, and 0.1 g of UV-400, and mix evenly by ultrasonic treatment to obtain the core material dispersion liquid;

[0072] The processes of preparing magnetoelectric dual-drive microcapsules and preparing a display panel are the same as those in Example 1. After writing for 5 minutes, the image clarity of the display panel prepared in Comparative Example 3 is close to that in Example 1, but it requires 5 times of magnetic erasure with the same magnetic field intensity to erase the handwriting; it shows that the use of high-coercivity carbon-coated magnetic particles in different forms has little effect on the image clarity of the display panel, but the erasability of the prepared display panel is poor.

[0073] In the description of this specification, the descriptions with reference to terms such as "one embodiment / way", "some embodiments / ways", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment / way or example are included in at least one embodiment / way or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment / way or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments / ways or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments / ways or examples described in this specification and the features of different embodiments / ways or examples.

[0074] It should be noted that in the present application, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, the element defined by the statement "comprising one..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element. In the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0075] The above description is only a specific implementation manner of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A magnetoelectrically dual-driven microcapsule for stably displaying a written image, characterized in that, Its core material is a dispersion of carbon-coated magnetic particle mixture, white particles, charge control agent and stability control agent, and the wall material is gelatin-anionic polymer; the carbon-coated magnetic particle mixture is composed of a mixture of low coercivity carbon-coated magnetic particles and high coercivity carbon-coated magnetic particles with different morphologies.

2. The magnetoelectrically driven microcapsule for stably displaying a written image according to claim 1, wherein The morphologies of the carbon-coated magnetic particles are at least two of spherical, cubic and octahedral, and at least one of them is spherical.

3. The magnetoelectrically driven microcapsule for stably displaying a written image according to claim 1, wherein The coercivity of the low coercivity carbon-coated magnetic particles is 40-60 Oe, and the coercivity of the high coercivity carbon-coated magnetic particles is 80-130 Oe.

4. The magnetoelectrically driven microcapsule for stably displaying a written image according to claim 1, wherein The stability control agent is selected from radical trapping types; the white particles are TiO2 particles coated with inorganic substances; the charge control agent is any one of organic amines, sorbitan esters, and sulfonic acids.

5. The preparation method of the magnetoelectrically dual-driven microcapsules for stably displaying a written image according to any one of claims 1-4, characterized in that, It includes the following steps: S101, adding the charge control agent into the dispersion medium, then adding the carbon-coated magnetic particles, white particles and stability control agent, and ultrasonically mixing evenly to obtain the core material dispersion liquid; S102, adding gelatin and anionic polymer into water to obtain an aqueous phase; S103, adding the core material dispersion liquid into the aqueous phase and stirring to obtain an emulsion; S104, adding an acid to adjust the pH value of the emulsion, cooling to below 10 °C, adding a curing agent, adding an alkali solution to adjust the pH value and then reacting. After the reaction is completed, sieving and suction filtration are carried out to obtain the magnetoelectric dual-drive microcapsules.

6. The preparation method of the magnetoelectrically dual-driven microcapsules for stably displaying a writing image according to claim 5, wherein The carbon-coated magnetic particles are prepared through the following process: mixing magnetic particles, organic carbon source and water evenly, ball milling for 2-5 h and then separating, pyrolyzing the separated product at high temperature under a nitrogen atmosphere, and then washing with alcohol and separating by magnetic field to obtain the carbon-coated magnetic particles.

7. The preparation method of the magnetoelectrically dual-driven microcapsules for stably displaying a written image according to claim 5, wherein, In step S101, the mass parts of each raw material in the core material dispersion liquid are: 20-40 parts of white particles, 2-5 parts of carbon-coated magnetic particles, 0.1-0.5 part of stability control agent, 2-5 parts of charge control agent, and 50-70 parts of solvent; the dispersion medium is a non-polar solvent.

8. The preparation method of the magnetoelectrically dual-driven microcapsules for stably displaying a written image according to claim 5, wherein, The anionic polymer is selected from any one of natural polymers, semi-synthetic polymers or synthetic polymers.

9. The preparation method of the magnetoelectrically dual-driven microcapsules for stably displaying a written image according to claim 5, characterized in that, The acid solution is selected from any one of hydrochloric acid, sulfuric acid, acetic acid, and citric acid; the alkali solution is selected from sodium hydroxide or potassium hydroxide; the curing agent is selected from any one of glutaraldehyde, tannic acid or transglutaminase.

10. A display panel, characterized in that, It includes the magnetoelectric dual-drive microcapsules according to any one of claims 1-4 or the magnetoelectric dual-drive microcapsules prepared by using the preparation method according to any one of claims 5-9.

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