Colorful fluorescent particles for electrophoretic display and preparation method thereof

Abstract

The invention discloses a colored fluorescent particle for electrophoretic display, and relates to the field of photoelectric display, the colored fluorescent particle is of a core-shell structure, and the colored fluorescent particle sequentially comprises a core, a middle layer and a shell layer from inside to outside; the core is a pigment unit, the middle layer is a quantum dot layer coating the surfaces of pigment particles, the shell layer comprises one or more high-molecular polymers selected from polylauryl methacrylate and polymethyl methacrylate, and the surface of the middle layer is coated with the shell layer; the color fluorescent particles comprise intrinsic primary colors presented by the pigment units and compensation fluorescence excited by the quantum dot layer under light; and the compensation fluorescence is matched with the intrinsic primary color. In addition, the invention also provides a preparation process of the colored fluorescent particles. The colored fluorescent electrophoretic particle provided by the invention is pure and full in color and luster, and is more gorgeous in color under the excitation of ultraviolet rays.

Description

Technical Field

[0001] The invention relates to the field of optoelectronic display, and in particular to a color fluorescent particle used for electrophoretic display and a preparation method thereof. Background Art

[0002] Electrophoretic display is a new display technology. Compared with traditional liquid crystal display and light-emitting diode display, electrophoretic display has the advantages of wide viewing angle, bistable, low energy consumption, and flexible display. Electrophoretic display uses an external electric field to drive the movement of electrophoretic particles to display letters, images, and videos. Electrophoretic display technology has a wide range of applications, such as billboards in shopping malls, bus stops, luggage labels, thermos cup temperature screens, etc., and is deeply loved by consumers. Currently, commercial electrophoretic display products are mainly black and white displays, which can no longer meet the huge market prospects. In order to expand the application field of electrophoretic display and enhance the consumer experience, colored electrophoretic particles have become a research hotspot.

[0003] In recent years, color electrophoretic display usually adopts the filter solution or the color dual-particle solution. The filter solution covers a layer of filter on the traditional black and white electrophoretic display to achieve colorization; while the color dual-particle solution uses two colored electrophoretic particles to achieve color display, and controls the electric field strength of each pixel to achieve color display. However, the use of filters will reduce the saturation and brightness of the electrophoretic display, and the dual-particle electrophoretic display requires complex technology to accurately control the color change and charge value, which is not easy to operate and the process is complicated, resulting in reduced brightness. Summary of the invention

[0004] In view of the shortcomings of the prior art, the primary purpose of the present invention is to make up for the shortcomings of the prior art and provide a color fluorescent particle for electrophoretic display, breaking the disadvantage of insufficient display brightness caused by the use of filters or two-color particle solutions. On the basis of the original total internal reflection display of pigment particles, a color fluorescent electrophoretic particle with quantum dots coated with pigment particles is provided, which improves the display brightness. The present invention also provides a method for preparing color fluorescent electrophoretic particles for electrophoretic display, which has a simple preparation process, can increase the -OH content of active groups on the surface of nanocomposite particles, effectively improve the ζ-potential, and accelerate the response speed of composite particles.

[0005] To achieve the above-mentioned purpose, in a first aspect of the present invention, a color fluorescent particle for electrophoretic display is provided, wherein the color fluorescent particle is a core-shell structure, and the color fluorescent particle comprises, from the inside to the outside, a core, an intermediate layer and a shell layer; the core is a pigment unit, the intermediate layer is a quantum dot layer coated on the surface of the pigment particle, the shell layer comprises a high molecular polymer, and the shell layer is coated on the surface of the intermediate layer; the color fluorescent particle contains an intrinsic primary color presented by the pigment unit and a compensating fluorescence excited by light from the quantum dot layer; the compensating fluorescence is adapted to the color of the intrinsic primary color.

[0006] In a second aspect of the present invention, a method for preparing colored fluorescent particles is provided, the method comprising:

[0007] Step S1, color paste preparation: dispersing pigment particles in a first dispersing solvent to prepare a color paste with a pigment particle content of 5 to 20 wt %;

[0008] Step S2, coating quantum dots: coating the surface of the pigment particles in step S1 with quantum dots by chemical precipitation method or sol-gel method to prepare first composite pigment particles with the surface coated with the quantum dots;

[0009] Step S3, coupling high molecular polymer: dispersing the first composite pigment particles obtained in step S2 in water or an aqueous solution of ethanol to form a first mixture, wherein the content of the first composite pigment particles in the first mixture is 10 to 60 wt%, adjusting the pH value of the mixture to 6 to 8, adding 1 to 15 wt % of the total mass of a silane coupling agent to the first mixture, reacting at 30 to 60° C. for 1 to 20 h, then centrifuging and washing to obtain second composite pigment particles grafted with a silane coupling agent;

[0010] Step S4, dispersing the second composite pigment particles obtained in step S3 in an organic solvent so that the second composite pigment particles contained therein are 10-60wt%, heating to 50-60°C, adding 0.01-0.06wt% initiator, and continuing the reaction for 10-20h to obtain electrophoretic display particles.

[0011] In a specific embodiment, when the first dispersing solvent is water, the step S2 uses the chemical precipitation method to wrap the quantum dots; the chemical precipitation method includes: at 20 to 50° C., simultaneously adding a prepared 0.1 to 5 mol / L quantum dot solution to the color paste of step S1, controlling the dropping speed so that the pH value of the reaction system is constant at 5 to 7, and continuing the dropping for 30 to 120 minutes; then aging for 120 to 300 minutes, cooling to room temperature, and after centrifugation and washing, obtaining the first composite pigment particles with quantum dots coated on the surface.

[0012] In a specific embodiment, when the first dispersing solvent is one or a combination of organic alcohol, organic benzene, and water, the step S2 uses the sol-gel method to coat the quantum dots; the sol-gel method includes: adding 0.1-5 mol / L quantum dot solution to the color paste of step S1, wherein the volume ratio of the added amount of quantum dots to the first dispersing solution is 1:100-20:100, stirring evenly, adding a mixed solution consisting of water and isopropanol in a volume ratio of 1-5:5-10, adjusting the pH value of the reaction system to 6-7, and ultrasonically reacting for 5-30 minutes, then heating to 40-60°C, stirring and aging, and cooling the reaction system to room temperature; centrifuging and washing to obtain the first composite pigment particles coated with quantum dots.

[0013] In a specific embodiment, the pigment particles are one or a combination of two or more of carbon black, copper chrome black, copper iron manganese black, iron black, titanium dioxide, zinc white, barium sulfate, red iron oxide, yellow iron oxide, ultramarine blue, chrome yellow, cadmium red, manganese violet, chrome green, iron blue, and cobalt blue.

[0014] In a specific embodiment, the average particle size of the electrophoretic display particles is 300nm-600nm, the content of quantum dots coated on the surface of the pigment particles is 1wt%-5wt%, and the content of high molecular polymer coated on the surface of the display particles is 5wt%-10wt%.

[0015] In a specific embodiment, the shell layer is one or a combination of two or more of Y-mercaptopropyltrimethoxysilane (KH580), N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane) (KH792), vinylbenzylaminoethylaminopropyltrimethoxysilane (VAPMS), and isopropyltrioleyltitanate.

[0016] In a specific embodiment, the silane coupling agent is selected from one or more of 3-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), and γ-(methacryloyloxy)propyltrimethoxysilane (KH570).

[0017] In a specific embodiment, the initiator is one or a combination of two or more of lauroyl peroxide, tert-butyl perbenzoate or cyclohexanone peroxide.

[0018] In a third aspect of the present invention, a display device based on the first aspect is provided, characterized in that the device comprises an upper substrate, a lower substrate and a receiving space pixel array arranged between the upper substrate and the lower substrate, and the colored fluorescent particles are arranged in the receiving space pixel array.

[0019] Beneficial effects of the present invention: 1) The electrophoretic display particles provided by the present invention have a structure with pigment as the core, quantum dots as the middle layer, and high molecular polymer as the shell layer. Such electrophoretic display particles have a high charge and a high ζ-potential, which can reach ±60-80mV; such electrophoretic display particles are applied to electrophoretic display equipment, which not only have good dispersion stability, but also show good electrophoretic rate and short response time, and can prepare electrophoretic display devices with excellent display performance. 2) When preparing electrophoretic display particles, the present invention first coats a layer of quantum dots on the surface of the pigment particles, so that light (including ultraviolet rays) can be used to excite the quantum dots to emit colored light, thereby improving the brightness of the electrophoretic particles. There are a large number of charged groups in the molecular structure of the silane coupling agent, such as amino, carboxyl, siloxy, etc., which provide more activation groups for the organic modification of the electrophoretic particles. The preparation process of the present invention can increase the luminous intensity of the surface of the electrophoretic particles and make more bonds, which can greatly enhance the charge of the electrophoretic particles, and have a high ζ-potential, which can reach ±60-80mV. The preparation process of the present invention can further improve the reflective brightness of the electrophoretic particles and reduce the response time of the electrophoretic particles. 3) The method for preparing electrophoretic display particles of the present invention is simple and environmentally friendly, easy to operate, and the core of the prepared electrophoretic particles is tightly combined with the polymer shell layer through the quantum dot intermediate layer, and the intermediate layer and the shell layer are very uniformly coated on the surface of the pigment particles. The formed electrophoretic display particles have good stability and strong charge. The electrophoretic display particles prepared by the preparation method of the present invention can be grafted with 1 to 15 wt% of coupling agent, and the surface of the display particles can be coated with 5 to 10 wt% of polymer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the preparation process of the color fluorescent electrophoretic particles provided in Example 1;

[0021] Figure 2 is a cross-sectional schematic diagram of an electrophoretic display device;

[0022] Figure 3 It is a cross-sectional schematic diagram of an electrophoretic display device under ultraviolet light excitation.

[0023] Explanation of the reference numerals: 1. upper substrate; 2. negatively charged electrophoretic particles; 3. transparent microcup; 4. positively charged electrophoretic particles; 5. lower substrate. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0025] like Figure 1-Figure 3 As shown, an embodiment of the present invention provides a color fluorescent particle for electrophoretic display, characterized in that the color fluorescent particle is a core-shell structure, and the color fluorescent particle includes, from the inside to the outside, a core, an intermediate layer and a shell layer; the core is a pigment unit, the intermediate layer is a quantum dot layer coated on the surface of the pigment particle, the shell layer includes a high molecular polymer, and the shell layer is coated on the surface of the intermediate layer; the color fluorescent particle contains an intrinsic primary color presented by the pigment unit and a compensating fluorescence excited by light on the quantum dot layer; the compensating fluorescence is adapted to the color of the intrinsic primary color.

[0026] In other embodiments, a method for preparing colored fluorescent particles for electrophoretic display is provided.

[0027] Example 1

[0028] In a first embodiment of the present invention, a method for preparing color fluorescent particles for electrophoretic display is provided, and the preparation steps are as follows:

[0029] 1) Preparation of color paste: Weigh an appropriate amount of red iron oxide, add it to 500 mL of water, and stir and disperse it at 500 rpm for 20 min to prepare an original color paste with a pigment particle content of 8 wt%;

[0030] 2) Coating quantum dots: keep the temperature of the reaction system constant at 40°C, and simultaneously add 0.5 mol / L cesium lead iodine to the color paste of step 1); adjust the dropping speed of the cesium lead iodine solution to maintain the pH value of the reaction system at 6-8; continue to add for 40 minutes, age for 180 minutes, cool to room temperature, centrifuge, and wash to obtain composite pigment particles A coated with cesium lead iodine quantum dots.

[0031] 3) Coupling with ethylaminopropyltrimethoxysilane: Take an appropriate amount of the composite pigment particles A prepared in step 2) and mix with 500 mL of ethanol and 500 mL of water to form a mixture with a composite pigment particle A content of 10 wt%, stir and disperse at 400 rpm for 20 min, keep the temperature of the reaction system constant at 30° C., adjust the pH value of the mixture to 7-9, add 1 wt% of the total mass of ethylaminopropyltrimethoxysilane to the mixture, and react at 30° C. for 15 h; then centrifuge and wash to obtain composite pigment particles B grafted with a silane coupling agent;

[0032] 4) Take an appropriate amount of the composite pigment particles B prepared in step (3) and mix with 500 mL of toluene and 500 mL of ethanol to form a mixture with a mass concentration of 10 wt% of the composite pigment particles B, stir and disperse at 400 rpm for 20 min, add 0.02 wt% of azobisisobutyronitrile as an initiator, and continue the reaction for 8 h to obtain red electrophoresis display particles coated with a polymer. The grafting amount of the coupling agent is 1 wt%, the content of the quantum dot solution coated on the particle surface is 1 wt%, and the content of the polymer coated on the particle surface is 8 wt%. The preparation mechanism of this embodiment can be found in the attached Figure 1 .

[0033] 5) Testing the zeta potential of the electrophoretic particles: The electrophoretic particles prepared in step (4) were mixed with 50 g of tetrachloroethylene and 5 g of Span-80, and ultrasonically dispersed for 60 min; stirred at a speed of 400 rpm for 24 h to obtain a test sample, and 10 g of the test sample was taken to test the potential. The test was performed five times using a Zeta potential tester, and the average value was 56 mV.

[0034] Example 2

[0035] In a second embodiment of the present invention, a color fluorescent particle for electrophoretic display is provided, and the preparation steps are as follows:

[0036] 1) Preparation of color paste: Weigh an appropriate amount of cobalt blue, add it to 1000 mL of water, and stir and disperse it at 400 rpm for 20 min to prepare a color paste with a pigment particle content of 15 wt%;

[0037] 2) Coating quantum dots: keep the temperature of the reaction system constant at 50° C., and simultaneously add 0.5 mol / L cesium lead bromine solution to the color paste of step 1); adjust the dropping speed of the cesium lead bromine solution to maintain the pH value of the reaction system at 5 to 6; continue to add for 180 minutes, age for 240 minutes, cool to room temperature, centrifuge, and wash to obtain composite pigment particles A coated with cesium lead bromine.

[0038] 3) Coupling: Take an appropriate amount of the composite pigment particles A prepared in step 2) and mix with 500 mL of ethanol and 500 mL of water to form a mixture with a composite pigment particle A content of 10 wt%, stir and disperse at 400 rpm for 20 min, keep the temperature of the reaction system constant at 30° C., adjust the pH value of the mixture to 7-9, add 10 wt % of the total mass of γ-(methacryloyloxy)propyltrimethoxysilane to the mixture, and react at 50° C. for 2 h; then centrifuge and wash to obtain composite pigment particles B grafted with a silane coupling agent;

[0039] 4) The composite pigment particles B prepared in step 3) are mixed with 500 mL of toluene to form a mixture with a composite pigment particle B content of 50 wt%, and the mixture is stirred and dispersed at 400 rpm for 20 min, and 0.05 wt% of azobisisobutyronitrile is added, and the reaction is continued for 20 h to obtain blue electrophoretic display particles coated with a polymer. The obtained electrophoretic display particles have a particle size of about 500 nm, a grafting amount of the coupling agent is 2 wt%, a cesium lead bromine content coated on the particle surface is 3 wt%, and a content of the polymer coated on the particle surface is 8 wt%.

[0040] 5) Test ζ-potential: The electrophoretic particles prepared in step (4) were mixed with 50 g of tetrachloroethylene and 2 g of Span-80, and ultrasonically dispersed for 60 min; stirred at 400 rpm for 24 h to obtain a test sample, and 10 g of the test sample was taken to test the ζ-potential. The test was performed five times using a Zeta potential tester, and the average value was -69 mV.

[0041] Example 3

[0042] In a third embodiment of the present invention, the steps for preparing color fluorescent particles for electrophoretic display are as follows:

[0043] 1) Preparation of color paste: Weigh an appropriate amount of yellow iron oxide, add it to 1000 mL of water, and stir and disperse it at 400 rpm for 20 minutes to prepare a color paste with a pigment particle content of 15 wt%;

[0044] 2) Coating quantum dots: keep the temperature of the reaction system constant at 50° C., and simultaneously add 0.5 mol / L cesium lead chloride solution to the color paste of step 1); adjust the dropping speed of the cesium lead chloride solution to maintain the pH value of the reaction system at 6 to 8; continue to add for 120 min, age for 240 min, cool to room temperature, centrifuge, and wash to obtain composite pigment particles A coated with cesium lead chloride quantum dots.

[0045] 3) Coupling with ethylaminopropyltrimethoxysilane: the composite pigment particles A prepared in step (2) are mixed with 500 mL of ethanol and 500 mL of water to form a mixture containing 50 wt% of the composite pigment particles A, and the mixture is stirred and dispersed at 400 rpm for 20 min. The temperature of the reaction system is kept constant at 30° C., and the pH value of the mixture is adjusted to 8-10. 6 wt% of the total mass of ethylaminopropyltrimethoxysilane is added to the mixture, and the mixture is reacted at 50° C. for 10 h. Thereafter, the mixture is centrifuged and washed to obtain composite pigment particles B grafted with a silane coupling agent.

[0046] 4) The composite pigment particles B prepared in step 3) are mixed with 500 mL of toluene to form a mixture with a composite pigment particle B content of 50 wt%, 0.03 wt% of azobisisobutyronitrile is added, and the reaction is continued for 15 hours to obtain electrophoretic display particles coated with a polymer. The obtained electrophoretic display particles have a particle size of about 600 nm, a grafting amount of the coupling agent is 3 wt%, a content of quantum dots coated on the particle surface is 2.11 wt%, and a content of the polymer coated on the particle surface is 6 wt%.

[0047] 5) Testing ζ-potential: The electrophoretic particles prepared in step 4) were mixed with 50g of tetrachloroethylene and 5g of Span-80, and ultrasonically dispersed for 60min; stirred at 400rpm for 24h to obtain a test sample, and 10g of the test sample was taken to test the ζ-potential. The test was performed five times using a Zeta potential tester, and the average value was 62mV.

[0048] The above examples 1-3 are only examples for explaining the technical solution of the present invention. The pigment particles, silane coupling agents, and initiators in Examples 1-3 are not limited to the substances listed. Among them, the pigment particles can be selected from one or more combinations of carbon black, copper chrome black, copper iron manganese black, iron black, titanium dioxide, zinc white, barium sulfate, iron oxide red, iron oxide yellow, ultramarine, chrome yellow, cadmium red, fierce purple, chrome green, iron blue, and cobalt blue; the silane coupling agent can be selected from one or more combinations of γ-mercaptopropyl trimethoxysilane, N-β-(aminoethyl)-γ-aminopropyl trimethoxysilane, vinylbenzylaminoethylaminopropyl trimethoxysilane, and isopropyl trioleyl titanate; the initiator can be selected from one or more combinations of azobisisobutyronitrile, azobisisoheptonitrile, benzoyl peroxide, lauroyl peroxide, tert-butyl perbenzoate, or cyclohexanone peroxide. The quantum dots in Examples 1 to 3 are also not limited to the quantum dots listed.

[0049] Finally, in other embodiments, a display device is provided, the device comprising an upper substrate, a lower substrate, and a receiving space pixel array disposed between the upper substrate and the lower substrate, the color fluorescent particles being disposed in the receiving space pixel array.

[0050] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A color fluorescent particle for electrophoretic display, characterized in that: The colored fluorescent particles are of a core-shell structure, and the colored fluorescent particles include, from the inside out, a core, an intermediate layer, and a shell layer; the core is a pigment unit, the intermediate layer is a quantum dot layer coated on the surface of the pigment particle, the shell layer includes a high molecular polymer, and the shell layer is coated on the surface of the intermediate layer; the colored fluorescent particles include an intrinsic primary color presented by the pigment unit and a compensating fluorescence excited by light on the quantum dot layer; the compensating fluorescence is adapted to the color of the intrinsic primary color.

2. The method for preparing the colored fluorescent particles according to claim 1, characterized in that: The method comprises: Step S1, color paste preparation: dispersing pigment particles in a first dispersing solvent to prepare a color paste with a pigment particle content of 5 to 20 wt %; Step S2, coating quantum dots: coating the surface of the pigment particles in step S1 with quantum dots by chemical precipitation method or sol-gel method to prepare first composite pigment particles with the surface coated with the quantum dots; Step S3, coupling high molecular polymer: dispersing the first composite pigment particles obtained in step S2 in water or an aqueous solution of ethanol to form a first mixture, wherein the content of the first composite pigment particles in the first mixture is 10 to 60 wt%, adjusting the pH value of the mixture to 6 to 8, adding 1 to 15 wt % of the total mass of a silane coupling agent to the first mixture, reacting at 30 to 60° C. for 1 to 20 h, then centrifuging and washing to obtain second composite pigment particles grafted with a silane coupling agent; Step S4, dispersing the second composite pigment particles obtained in step S3 in an organic solvent so that the second composite pigment particles contained therein are 10-60wt%, heating to 50-60°C, adding 0.01-0.06wt% initiator, and continuing the reaction for 10-20h to obtain electrophoretic display particles.

3. The preparation method according to claim 2, characterized in that: When the first dispersing solvent is water, the step S2 uses the chemical precipitation method to encapsulate the quantum dots; the chemical precipitation method comprises: at 20 to 50° C., simultaneously adding a prepared 0.1 to 5 mol / L quantum dot solution to the color paste of the step S1, controlling the dropping speed so that the pH value of the reaction system is constant at 5 to 7, and continuing the dropping for 30 to 120 minutes; then aging for 120 to 300 minutes, cooling to room temperature, and after centrifugation and washing, obtaining first composite pigment particles with quantum dots coated on the surface.

4. The preparation method according to claim 2, characterized in that: When the first dispersing solvent is one of organic alcohol, organic benzene, water or a combination of several thereof, the step S2 adopts the sol-gel method to coat the quantum dots; the sol-gel method comprises: adding 0.1-5 mol / L quantum dot solution to the color paste of step S1, wherein the volume ratio of the added quantum dots to the first dispersing solution is 1:100-20:100, stirring evenly, adding dropwise a mixed solution consisting of water and isopropanol in a volume ratio of 1-5:5-10, adjusting the pH value of the reaction system to 6-7, and ultrasonically reacting for 5-30 minutes, then heating to 40-60°C, stirring and aging, and then cooling the reaction system to room temperature; centrifuging and washing to obtain the first composite pigment particles coated with quantum dots.

5. The preparation method according to claim 2, characterized in that: The pigment particles are one or a combination of two or more of carbon black, copper chrome black, copper iron manganese black, iron black, titanium dioxide, zinc white, barium sulfate, red iron oxide, yellow iron oxide, ultramarine blue, chrome yellow, cadmium red, manganese violet, chrome green, iron blue, and cobalt blue.

6. The preparation method according to claim 2, characterized in that: The average particle size of the electrophoretic display particles is 300nm-600nm, the content of quantum dots coated on the surface of the pigment particles is 1wt%-5wt%, and the content of high molecular polymer coated on the surface of the display particles is 5wt%-10wt%.

7. The preparation method according to claim 1, characterized in that: The shell layer is one or a combination of two or more of Y-mercaptopropyltrimethoxysilane (KH580), N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane) (KH792), vinylbenzylaminoethylaminopropyltrimethoxysilane (VAPMS), and isopropyltrioleyltitanate.

8. The preparation method according to claim 2, characterized in that: The silane coupling agent is selected from one or more of 3-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), and γ-(methacryloyloxy)propyltrimethoxysilane (KH570).

9. The preparation method according to claim 2, characterized in that: The initiator is one or a combination of two or more of lauroyl peroxide, tert-butyl perbenzoate or cyclohexanone peroxide.

10. A display device based on the color fluorescent particles according to claim 1, characterized in that: The device comprises an upper substrate, a lower substrate and a receiving space pixel array arranged between the upper substrate and the lower substrate, wherein the color fluorescent particles are arranged in the receiving space pixel array.

Images