Fluorescent electrophoretic inks and display devices

Abstract

This invention discloses a fluorescent electrophoretic ink and a display device, relating to the field of electrophoretic display technology. The fluorescent electrophoretic ink includes an electrophoretic medium and first, second, and third electrophoretic particles dispersed in the electrophoretic medium. The first electrophoretic particle has a first charge polarity, the second electrophoretic particle has a second charge polarity, and the third electrophoretic particle has either a first or a second charge polarity. The first electrophoretic particle exhibits a first color under visible light irradiation, the second electrophoretic particle exhibits a second color under visible light irradiation, and the third electrophoretic particle exhibits a colorless transparent or semi-transparent state under visible light irradiation, and exhibits fluorescence of a third color under non-visible light irradiation of a preset wavelength. This invention improves the display effect of fluorescent electrophoretic displays.

Description

Technical Field

[0001] This invention relates to the field of electrophoretic display technology, and more particularly to a fluorescent electrophoretic ink and display device. Background Technology

[0002] Traditional electrophoretic display devices can usually only be used under white light illumination, displaying black and white colors, such as sunlight and white light, and have a certain dependence on light source. In order to expand the application scenarios of electrophoretic display devices, fluorescent electrophoretic particles are introduced to enable them to emit light under non-visible light (infrared light, ultraviolet light, etc.), thereby enabling them to display fluorescently, which is expected to be applied to fields such as anti-counterfeiting and display.

[0003] In current fluorescence electrophoresis displays, fluorescent electrophoretic particles are usually used to replace one of the two-color electrophoretic particles. Fluorescent electrophoretic particles play both the role of reflection and fluorescence. However, the optical reflection performance of fluorescent electrophoretic particles is very poor, and the display effect of the device is very poor under visible light. The color difference between the fluorescent state and the reflected state, as well as the color difference between the excitation light source and the fluorescent state of the device, does not have a significant impact on the display effect of the device. Summary of the Invention

[0004] This invention provides a fluorescent electrophoretic ink and a display device, aiming to improve the display effect of fluorescent electrophoretic displays.

[0005] The fluorescent electrophoretic ink proposed in this invention includes an electrophoretic medium and a first electrophoretic particle and a second electrophoretic particle dispersed in the electrophoretic medium. The first electrophoretic particle has a first charge polarity and exhibits a first color under visible light irradiation, and the second electrophoretic particle has a second charge polarity and exhibits a second color under visible light irradiation.

[0006] The fluorescent electrophoretic ink is characterized in that it further includes third electrophoretic particles dispersed in the electrophoretic medium;

[0007] The third electrophoretic particle has a first charge polarity or a second charge polarity;

[0008] The third electrophoretic particle appears colorless and transparent or semi-transparent under visible light irradiation, and exhibits fluorescence of a third color under non-visible light irradiation of a preset wavelength.

[0009] Optionally, the particle size of the third electrophoretic particle is smaller than the particle size of the first electrophoretic particle and the particle size of the second electrophoretic particle.

[0010] Optionally, the particle size of the third electrophoretic particle is 10-200 nm.

[0011] Optionally, the first color and the second color are different, and the first color and the second color are any two of white, black, red, orange, yellow, green, cyan, blue, purple or other colors.

[0012] Optionally, the third electrophoretic particle contains a fluorescent pigment, which is at least one of inorganic / organic upconversion fluorescent pigment, inorganic / organic ultraviolet downconversion fluorescent pigment, and composite fluorescent pigment.

[0013] Optionally, the third electrophoretic particle includes a fluorescent pigment layer and a polymer layer surrounding the fluorescent pigment layer.

[0014] Optionally, the fluorescent pigment is an upconversion fluorescent pigment, and the third electrophoretic particle is prepared through the following steps:

[0015] Step 1: Ball mill the upconversion fluorescent pigment to the preset particle size;

[0016] Step 2: The ball-milled fluorescent pigment, tetraethyl silicate, and silane coupling agent are added to a polar solvent and stirred to carry out a coupling reaction, thereby obtaining coupled fluorescent pigment particles.

[0017] Step 3: The coupled fluorescent pigment particles are polymerized with polymer monomers to obtain polymer-coated fluorescent electrophoretic particles.

[0018] Optionally, the third electrophoretic particle includes nanoparticles with hydroxyl groups on their surface, a quantum dot luminescent layer disposed on the nanoparticles, and a polymer layer wrapped around the quantum dot luminescent layer.

[0019] Optionally, the third electrophoretic particle is prepared by the following steps:

[0020] Step 1: The nanoparticles with hydroxyl groups on the surface are mixed with silane coupling agent, non-polar solvent and acetic acid in a preset ratio and then ball-milled. The mixture is then dispersed in a non-polar solvent to obtain a nanoparticle solution.

[0021] Step 2: Drop the perovskite quantum dot precursor solution into the nanoparticle solution and stir for a preset time to obtain nanoparticles loaded with perovskite quantum dots.

[0022] Step 3: The nanoparticles loaded with perovskite quantum dots are polymerized with polymer monomers to obtain polymer-coated fluorescent electrophoretic particles.

[0023] The display device proposed in this invention includes an upper electrode and a lower electrode, which are used to connect the positive and negative terminals of a power supply.

[0024] A cavity is formed between the upper electrode and the lower electrode, and the cavity is filled with the fluorescent electrophoretic ink described above.

[0025] The present invention has the following beneficial effects:

[0026] This invention introduces a small-diameter, colorless, transparent or translucent third electrophoretic particle into a two-color electrophoretic ink comprising first and second electrophoretic particles to create a fluorescent electrophoretic ink. The third electrophoretic particle does not affect the reflected light display of the first and second electrophoretic particles under visible light irradiation, and can achieve good fluorescence display under non-visible light irradiation. At the same time, the small-diameter charged third electrophoretic particle can promote the separation of the first and second electrophoretic particles, ensuring high contrast and fast response speed of the display device under ambient light, while making the fluorescence color distinction more obvious. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 These are schematic diagrams illustrating the structure of some embodiments of the display device of the present invention;

[0029] Figure 2 This is a schematic diagram of the interaction between electrophoretic particles in the fluorescent electrophoretic ink of the present invention;

[0030] Figure 3 These are schematic diagrams illustrating the structures of some embodiments of the fluorescent electrophoretic particles of the present invention;

[0031] Figure 4 This is a schematic diagram of the preparation process of some embodiments of the fluorescent electrophoretic particles of the present invention;

[0032] Figure 5 This is a schematic diagram of the preparation process of some other embodiments of the fluorescent electrophoretic particles of the present invention;

[0033] Figure 6 These are schematic diagrams illustrating the operation of some embodiments of the display device of the present invention;

[0034] Figure 7 for Figure 6 The image shown is a physical diagram of the display device in operation.

[0035] Figure 8 These are schematic diagrams illustrating the operation of other embodiments of the display device of the present invention;

[0036] Figure 9 for Figure 8 The image shown is a physical diagram of the display device in operation.

[0037] Explanation of reference numerals in the attached figures:

[0038] 1. Substrate; 21. Upper electrode; 22. Lower electrode; 31. White electrophoretic particles; 32. Black electrophoretic particles; 33. Fluorescent electrophoretic particles. Detailed Implementation

[0039] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] The English technical terms involved in this invention are explained below:

[0041] UCNP: Upconversion nanoparticles; TEOS: Tetraethyl silicate; LMA: Dodecyl methacrylate; AIBN: Azobisisobutyronitrile; Span 80: Span 80; SDBS: Sodium dodecylbenzenesulfonate; ABVN: Azobisisoheptanenitrile; NaYF4 (Yb 3+ Er 3+ ):Yb 3+ Er 3+ Doped NaYF4; DMF: N,N-dimethylformamide.

[0042] In electrophoretic electronic display technology, pigment particles of different colors with different amounts of charge are placed in a non-polar solvent. By controlling the directional movement of the charged pigment particles with an applied voltage, different colors can be displayed, thereby realizing the display of patterns.

[0043] Traditional electrophoretic displays are mainly black and white dual-color displays, which can hardly meet people's needs. In order to expand the application scenarios of electrophoretic display devices, fluorescent electrophoretic particles are introduced so that they can emit light under non-visible light (infrared light, ultraviolet light, etc.), thus enabling them to display fluorescently and making them widely used in anti-counterfeiting and display fields.

[0044] The inventors of this application have made a keen research discovery that in current fluorescent electrophoretic displays, fluorescent electrophoretic particles are usually used to replace one of the two-color electrophoretic particles. Fluorescent electrophoretic particles play both the role of reflection and fluorescence. However, the optical reflection performance of fluorescent electrophoretic particles is very poor, and the display effect of the display device is very poor under visible light. The color difference between the fluorescent state and the reflective state, as well as the color difference between the excitation light source and the fluorescent state of the device, does not have a significant impact on the display effect of the device.

[0045] This invention proposes a fluorescent electrophoretic ink and a display device, aiming to solve the above-mentioned problems.

[0046] In embodiments of the present invention, the fluorescent electrophoretic ink includes an electrophoretic medium and first electrophoretic particles, second electrophoretic particles and third electrophoretic particles dispersed in the electrophoretic medium.

[0047] The electrophoretic medium consists of a transparent nonpolar solvent and a charge control agent. The nonpolar solvent is selected from one or more of halogenated hydrocarbons, paraffin wax, silicone oil, alkane compounds, epoxy compounds, aromatic hydrocarbons, and vinyl ethers. The charge control agent is selected from one or more of organic sulfonates, organic sulfates, organic phosphates, organic phosphate esters, polyesters, polyolefins, and polyacrylates.

[0048] The first electrophoretic particle has a first charge polarity, the second electrophoretic particle has a second charge polarity, and the third electrophoretic particle has either a first charge polarity or a second charge polarity; the first electrophoretic particle exhibits a first color under visible light irradiation, the second electrophoretic particle exhibits a second color under visible light irradiation, and the third electrophoretic particle is colorless under visible light irradiation, but exhibits a third color of fluorescence under non-visible light irradiation of a preset wavelength.

[0049] Optionally, the first color and the second color are colors that can form a strong contrast between the first electrophoretic particle and the second electrophoretic particle under visible light, such as any two of white, black, red, orange, yellow, green, cyan, blue, purple, or other colors; the first electrophoretic particle and the second electrophoretic particle are dispersed in the electrophoretic medium with opposite charges, and when an external voltage is applied, the first electrophoretic particle and the second electrophoretic particle will move in opposite directions in the electrophoretic medium, and the color corresponding to one of the two electrophoretic particles will be displayed on the light-emitting surface or the viewing side of the display device.

[0050] Alternatively, the first electrophoretic particle and the second electrophoretic particle can be any combination of two particles with opposite charge properties and opposite colors, selected from black positively charged particles, white negatively charged particles, black negatively charged particles, and white positively charged particles.

[0051] In an embodiment of the present invention, the third electrophoretic particle appears colorless and transparent or semi-transparent under visible light irradiation, and its reflection effect on visible light is zero or extremely low. That is, under normal observation conditions, it does not show obvious color and will not affect the color presentation of the first and second electrophoretic particles.

[0052] The third electrophoretic particle has the same charge property as the first or second electrophoretic particle. When an external voltage is applied, the first or second electrophoretic particle moves together with the third electrophoretic particle to the electrophoretic medium near the light-emitting surface or observation side of the display device. Under visible light, it presents the corresponding color of the electrophoretic particle at that location. Under non-visible light, the third electrophoretic particle fluoresces and can present a third color.

[0053] The third electrophoretic particle exhibits fluorescence in a third color under non-visible light, including infrared and ultraviolet light. The third color is any one of white, black, red, orange, yellow, green, cyan, blue, purple, or other colors, and is different from the first and second colors.

[0054] In this embodiment of the invention, a fluorescent electrophoretic particle (i.e., a third electrophoretic particle) that is colorless and transparent or translucent under visible light irradiation is introduced into a two-color electrophoretic ink comprising a first electrophoretic particle and a second electrophoretic particle to form a fluorescent electrophoretic ink. The colorless fluorescent electrophoretic particle does not affect the reflected light display of the first and second electrophoretic particles under visible light irradiation, and can achieve good fluorescence display under non-visible light irradiation.

[0055] Optionally, the third electrophoretic particle contains a fluorescent pigment, which is at least one of inorganic / organic upconversion fluorescent pigment, inorganic / organic ultraviolet downconversion fluorescent pigment, and composite fluorescent pigment.

[0056] Among them, upconversion fluorescent pigments achieve upconversion luminescence, that is, they absorb two or more low-energy photons and radiate one high-energy photon, converting long-wave radiation into short-wave radiation, thereby producing fluorescence.

[0057] When a UV downconversion fluorescent pigment absorbs UV light, its internal molecular structure changes, causing electrons to transition from the ground state to an excited state. When the electrons return from the excited state to the ground state, they release energy and are emitted in the form of visible light, thus producing fluorescence.

[0058] Composite fluorescent pigments are fluorescent pigments composed of fluorescent substances and inorganic / organic carriers. For example, quantum dots with unique optical properties can be combined with other materials to form pigments with fluorescent properties.

[0059] See Figure 3 and Figure 4 In some embodiments, the third electrophoretic particle includes a fluorescent pigment layer and a polymer layer wrapped around the fluorescent pigment layer. The fluorescent pigment layer is used for fluorescence emission, and the polymer layer is used to improve the dispersibility of the electrophoretic particle.

[0060] Specifically, fluorescent pigment particles can be grafted by hydrolysis of tetraethyl silicate and silane coupling agents. The coupled fluorescent pigment is then polymerized with polymer monomers to obtain polymer-coated fluorescent electrophoretic particles. This process may include the following steps:

[0061] Step 1: Grind the fluorescent pigment to the preset particle size;

[0062] Step 2: The ball-milled fluorescent pigment, tetraethyl silicate, and silane coupling agent are added to a polar solvent and stirred to carry out a coupling reaction, thereby obtaining coupled fluorescent pigment particles.

[0063] Step 3: The coupled fluorescent pigment particles are polymerized with polymer monomers to obtain polymer-coated fluorescent electrophoretic particles.

[0064] See Figure 5 In some other embodiments, the third electrophoretic particle includes nanoparticles with hydroxyl groups on their surface, a quantum dot luminescent layer disposed on the nanoparticles, and a polymer layer wrapped around the quantum dot luminescent layer.

[0065] Nanoparticles containing hydroxyl groups on their surface include, but are not limited to, silicon dioxide, zinc oxide, or aluminum oxide nanoparticles.

[0066] Quantum dots are low-dimensional semiconductor materials, typically spherical or near-spherical in shape, with diameters ranging from 2 to 20 nm. When these nano-semiconductor materials are excited by external light, they emit fluorescence at specific frequencies. The size of the quantum dots also affects their emission color.

[0067] Specifically, after grafting nanoparticles containing hydroxyl groups on their surface with a silane coupling agent, a perovskite quantum dot precursor solution is dropped into the nanoparticle solution to form perovskite quantum dot-loaded nanoparticles. These nanoparticles are then polymerized with polymer monomers to obtain polymer-coated fluorescent electrophoretic particles. The process may include the following steps:

[0068] Step 1: The nanoparticles with hydroxyl groups on the surface are mixed with silane coupling agent, non-polar solvent and acetic acid in a preset ratio and then ball-milled. The mixture is then dispersed in a non-polar solvent to obtain a nanoparticle solution.

[0069] Step 2: Drop the perovskite quantum dot precursor solution into the nanoparticle solution and stir for a preset time to obtain nanoparticles loaded with perovskite quantum dots.

[0070] Step 3: The nanoparticles loaded with perovskite quantum dots are polymerized with polymer monomers to obtain polymer-coated fluorescent electrophoretic particles.

[0071] Furthermore, in some embodiments, the polymer on the surface of the fluorescent electrophoretic particles can interact with some surfactants in an acid-base manner, resulting in proton transfer and thus acquiring the corresponding positive or negative charge; the surfactant can be one or more of the following: organic sulfonates, organic sulfates, organic phosphates, organic phosphate esters, polyesters, polyolefins, and polyacrylates.

[0072] In embodiments of the present invention, the types of silane coupling agents include, but are not limited to, KH570, KH560, and KH550, and the types of polymer monomers include, but are not limited to, acrylic, epoxy, styrene, alcohol, and acid anhydride.

[0073] In an embodiment of the present invention, the particle size of the third electrophoretic particle is smaller than that of the first electrophoretic particle and the second electrophoretic particle.

[0074] See Figure 2 In an embodiment of the present invention, the charge of the third electrophoretic particle is less than that of the first and second electrophoretic particles. The small-diameter and low-charge third electrophoretic particle will preferentially adsorb with particles with opposite charges, thereby promoting the separation of the first and second electrophoretic particles, ensuring the high contrast and fast response speed of the display device under ambient light, and making the fluorescence color distinction more obvious.

[0075] Since the particle size of the electrophoretic particles used in traditional electrophoretic displays that reflect visible light is usually above 200 nm, in the embodiments of the present invention, the particle size of the third electrophoretic particle can be selected as 10-200 nm.

[0076] As can be seen from the above embodiments, the present invention introduces small-diameter colorless transparent or translucent fluorescent electrophoretic particles (i.e., third electrophoretic particles) into a two-color electrophoretic ink comprising first and second electrophoretic particles to produce fluorescent electrophoretic ink. The colorless transparent or translucent fluorescent electrophoretic particles do not affect the reflected light display of the first and second electrophoretic particles under visible light irradiation, and can achieve good fluorescence display under non-visible light irradiation. At the same time, the small-diameter charged fluorescent electrophoretic particles can promote the separation of the first and second electrophoretic particles, ensuring high contrast and fast response speed of the display device under ambient light, while making the fluorescence color distinction more obvious.

[0077] Therefore, the present invention can effectively improve the display effect of fluorescence electrophoresis display devices.

[0078] Based on the above-described embodiments of fluorescent electrophoretic ink, the present invention also proposes a display device.

[0079] See Figure 1 In some embodiments, the display device proposed in this invention includes an upper electrode 21 and a lower electrode 22. A substrate 1 is provided on the outer side of the upper electrode 21 and the lower electrode 22 to provide structural support. The upper electrode 21 and the lower electrode 22 are used to connect the positive and negative poles of the power supply. The upper electrode 21 is the light-emitting surface / observation side. The substrate on the outer side of the upper electrode 21 can be made of a transparent material. A receiving cavity is formed between the upper electrode 21 and the lower electrode 22. The receiving cavity is filled with the fluorescent electrophoretic ink provided in the above embodiments.

[0080] See Figure 1In some embodiments, the fluorescent electrophoretic ink infused into the display device includes an electrophoretic medium and white electrophoretic particles 31, black electrophoretic particles 32 and fluorescent electrophoretic particles 33 dispersed in the electrophoretic medium.

[0081] In embodiments of the present invention, depending on the substrate and electrode materials, the display device can be a rigid display device based on conductive glass, or a flexible display device such as electronic paper based on a flexible substrate.

[0082] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the following specific embodiments are not intended to limit the present invention, and those skilled in the art can make various changes within the scope of the claims of the present invention.

[0083] Example 1

[0084] Longitudinal-driven electrophoretic display device based on upconversion fluorescent electrophoretic particles.

[0085] First, upconversion fluorescent electrophoresis particles are prepared; the preparation process is described in [reference needed]. Figure 4 It includes the following steps:

[0086] Add 5g NaYF4 (Yb) 3+ Er 3+ 5g TEOS, 10g KH570, 100ml ethanol and 5mL ammonia were stirred for 4h, and then centrifuged and washed multiple times to obtain well-coupled fluorescent electrophoretic particles.

[0087] 5g of coupled fluorescent electrophoretic particles, 1g of hexadecyltrimethylammonium bromide, 100ml of toluene and 10g of LMA were mechanically stirred at 600rpm for 1h at 40°C and under a nitrogen atmosphere. Then, 1g of AIBN was added and polymerized at 70°C for 12h to obtain fluorescent electrophoretic particles.

[0088] The fabrication of a display device includes the following steps:

[0089] A simple display device is formed by bonding two ITO electrodes together with OCA adhesive, and then filling it with fluorescent electrophoretic ink composed of negatively charged white electrophoretic particles, negatively charged fluorescent electrophoretic particles, and positively charged black electrophoretic particles to form an electrophoretic display device.

[0090] See Figure 6In this embodiment, the display device is initially gray when filled with fluorescent electrophoretic ink. When a +15V voltage is applied to the upper electrode, the positive and negative charged particles separate, and the negatively charged white particles and the fluorescent electrophoretic particles are driven together to the upper electrode, at which point the display device appears white. When the display device is white, applying infrared light causes the fluorescent electrophoretic particles to emit green light, making the display device green. Conversely, applying a negative voltage to the upper electrode drives the positively charged black electrophoretic particles to the upper electrode, making the display device black. Therefore, this embodiment, through positive and negative voltage regulation and the application of infrared light, enables the longitudinally driven electrophoretic display device based on upconversion fluorescent electrophoretic particles to achieve black, white, and green three-state display. Figure 7 As shown.

[0091] Example 2

[0092] A longitudinally driven electrophoretic display device based on silica-loaded quantum dot fluorescent particles.

[0093] First, silica-loaded quantum dot fluorescent particles are prepared; the preparation process is described in [reference needed]. Figure 5 It includes the following steps:

[0094] 50g of silica, 20g of silane coupling agent (KH550+KH570), 200ml of toluene and 5ml of acetic acid were ball-milled for 12h, then centrifuged multiple times and dispersed in 200ml of toluene solution to obtain silica-toluene solution.

[0095] Dissolve 3.15 g of cesium bromide and 5.48 g of lead bromide in 100 ml of DMF, and add 10 ml of oleic acid and 10 ml of oleylamine to the DMF solution to obtain a precursor solution of perovskite quantum dots.

[0096] 30 ml of perovskite quantum dot precursor solution was added dropwise to 200 ml of silica toluene solution and stirred at 500 rpm for 5 h to obtain perovskite quantum dot-loaded SiO2 (SiO2 / CsPbBr3).

[0097] 10g SiO2 / CsPbBr3, 1g SDBS, 100ml toluene, 5g LMA and 1g ABVN were mechanically stirred at 40°C and 600rpm for 12h to obtain fluorescent electrophoretic particles.

[0098] The fabrication of a display device includes the following steps:

[0099] A simple display device is formed by bonding two ITO electrodes together with OCA adhesive, and then filling it with fluorescent electrophoretic ink composed of negatively charged white electrophoretic particles, positively charged fluorescent electrophoretic particles, and positively charged black electrophoretic particles to form an electrophoretic display device.

[0100] See Figure 8In this embodiment, the display device is initially gray when filled with fluorescent electrophoretic ink. When a -15V voltage is applied to the upper electrode, the positive and negative charged particles separate, and the positively charged black particles and the fluorescent electrophoretic particles are driven together to the upper electrode, at which point the display device appears black. When the display device is black, applying ultraviolet light can cause the fluorescent electrophoretic particles to emit green light, making the display device green. Conversely, applying a positive voltage to the upper electrode drives the negatively charged white particles to the upper electrode, making the display device white. Therefore, this embodiment, through positive and negative voltage regulation and ultraviolet light illumination, enables the longitudinally driven electrophoretic display device based on fluorescent electrophoretic particles to achieve black, white, and green three-state display. Figure 9 As shown.

[0101] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A fluorescent electrophoretic ink, comprising an electrophoretic medium and a first electrophoretic particle and a second electrophoretic particle dispersed in the electrophoretic medium, wherein the first electrophoretic particle has a first charge polarity and exhibits a first color under visible light irradiation, and the second electrophoretic particle has a second charge polarity and exhibits a second color under visible light irradiation; Its features are, The fluorescent electrophoretic ink also includes third electrophoretic particles dispersed in the electrophoretic medium; The third electrophoretic particle has a first charge polarity or a second charge polarity; The third electrophoretic particle appears colorless and transparent or semi-transparent under visible light irradiation, and exhibits fluorescence of a third color under non-visible light irradiation of a preset wavelength; The third electrophoretic particle comprises a fluorescent pigment layer and a polymer layer surrounding the fluorescent pigment layer; the third electrophoretic particle is prepared by the following steps: Step 1: Grind the fluorescent pigment to the preset particle size; Step 2: The ball-milled fluorescent pigment, tetraethyl silicate, and silane coupling agent are added to a polar solvent and stirred to carry out a coupling reaction, thereby obtaining coupled fluorescent pigment particles. Step 3: The coupled fluorescent pigment particles are polymerized with polymer monomers to obtain polymer-coated fluorescent electrophoretic particles. The fluorescent pigment is at least one of inorganic / organic upconversion fluorescent pigment, inorganic / organic ultraviolet downconversion fluorescent pigment, and composite fluorescent pigment.

2. A fluorescent electrophoretic ink, comprising an electrophoretic medium and a first electrophoretic particle and a second electrophoretic particle dispersed in the electrophoretic medium, wherein the first electrophoretic particle has a first charge polarity and exhibits a first color under visible light irradiation, and the second electrophoretic particle has a second charge polarity and exhibits a second color under visible light irradiation; Its features are, The fluorescent electrophoretic ink also includes third electrophoretic particles dispersed in the electrophoretic medium; The third electrophoretic particle has a first charge polarity or a second charge polarity; The third electrophoretic particle appears colorless and transparent or semi-transparent under visible light irradiation, and exhibits fluorescence of a third color under non-visible light irradiation of a preset wavelength; The third electrophoretic particle comprises nanoparticles with hydroxyl groups on their surface, a quantum dot luminescent layer disposed on the nanoparticles, and a polymer layer encapsulating the quantum dot luminescent layer; the third electrophoretic particle is prepared by the following steps: Step 1: The nanoparticles with hydroxyl groups on the surface are mixed with silane coupling agent, non-polar solvent and acetic acid in a preset ratio and then ball-milled. The mixture is then dispersed in a non-polar solvent to obtain a nanoparticle solution. Step 2: Drop the perovskite quantum dot precursor solution into the nanoparticle solution and stir for a preset time to obtain nanoparticles loaded with perovskite quantum dots. Step 3: The nanoparticles loaded with perovskite quantum dots are polymerized with polymer monomers to obtain polymer-coated fluorescent electrophoretic particles.

3. The fluorescent electrophoretic ink according to claim 1 or 2, characterized in that, The particle size of the third electrophoretic particle is smaller than that of the first electrophoretic particle and the second electrophoretic particle.

4. The fluorescent electrophoretic ink according to claim 3, characterized in that, The particle size of the third electrophoretic particle is 10-200 nm.

5. The fluorescent electrophoretic ink according to claim 1 or 2, characterized in that, The first color and the second color are different, and the first color and the second color are any two of white, black, red, orange, yellow, green, cyan, blue, purple or other colors.

6. A display device, characterized in that, It includes an upper electrode and a lower electrode, which are used to connect the positive and negative terminals of the power supply; A receiving cavity is formed between the upper electrode and the lower electrode, and the receiving cavity is filled with the fluorescent electrophoretic ink according to any one of claims 1-5.

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