A method for preparing nanoflower-shaped defective particles capable of realizing high-contrast electrophoresis display

Abstract

The present application belongs to the technical field of electronic display devices, and in particular, relates to a method for preparing nano-flower-shaped defective particles that can achieve high-contrast electrophoretic display. In the method for preparing defective electrophoretic particles provided by the present application, nano-flower-shaped defective particles are prepared by carbonizing a bimetallic organic framework material for coupling and grafting, which is beneficial for introducing more acidic or basic groups during the coupling and grafting process, thereby increasing the charge on the surface of the electrophoretic particles, and the nano-flower-shaped defective particles have high absorbance, thereby solving the technical problem in the prior art that spherical pigment particles cannot effectively introduce acidic or basic groups, the prepared electrophoretic particles have a low charge, and the color itself is not black enough, resulting in insufficient response speed and contrast of the electrophoretic display device.

Description

Technical Field

[0001] The present application belongs to the technical field of electronic display devices, and in particular, relates to a method for preparing nano-flower-shaped defective particles capable of realizing high-contrast electrophoretic display. Background Art

[0002] The main method for preparing electrophoretic particles is to introduce acidic or basic functional groups such as amino, carboxyl, and ester groups into electrophoretic pigment particles, so that the electrophoretic pigment particles are negatively or positively charged to obtain electrophoretic particles, so that the electronic ink containing the electrophoretic particles has a higher response speed.

[0003] However, currently electrophoretic pigment particles are mainly spherical electrophoretic pigment particles. The spherical electrophoretic pigment particles have regular morphology and low specific surface area. The limited specific surface area of ​​the spherical electrophoretic pigment particles results in a low number of sites where functional groups can be introduced during the subsequent introduction of acidic or basic groups. The spherical electrophoretic pigment particles cannot effectively introduce acidic or basic groups, which ultimately results in a low number of surface charges on the particles. In addition, the contrast of the electrophoretic ink is mainly related to the color of the material of the electrophoretic particles themselves, as well as the thickness and charge of the coating layer. The spherical electrophoretic particles have low absorbance, their own color is not black enough, and their charge is not high, so the contrast is not high enough in the electrophoretic display device. Summary of the invention

[0004] In view of this, the present application provides a method for preparing nanoflower-shaped defective particles that can achieve high-contrast electrophoretic display, which is used to solve the technical problem in the prior art that spherical pigment particles cannot effectively introduce acidic or basic groups, the prepared electrophoretic particles have a low charge, and the color itself is not black enough, which leads to the electrophoretic display device having insufficient response speed and contrast.

[0005] The first aspect of the present application provides a method for preparing nanoflower-shaped defective particles capable of realizing high-contrast electrophoretic display, the preparation method comprising the steps of:

[0006] Step S1, carbonizing the bimetallic organic framework material to prepare nano-flower-shaped defective particles;

[0007] Step S2, dispersing the pigment particles with nanoflower structure, the silane coupling agent containing unsaturated bonds and the silane coupling agent containing acidic or basic groups in a first solvent, and coupling them to obtain acidic or basic modified nanoflower-shaped defect-state modified particles;

[0008] Step S3, dispersing the acidic or alkaline modified pigment particles, the polymer monomer containing the acidic or alkaline group and the initiator in the second solvent, and performing grafting to obtain nano-flower-shaped defective electrophoretic particles.

[0009] Preferably, in step S1, the method for preparing the bimetallic organic framework material comprises the steps of:

[0010] Step S1-1, dissolving ferrous perchlorate, pyrazine and polyvinyl pyrrolidone in an alcohol aqueous solution to prepare a bimetallic organic framework material precursor solution;

[0011] Step S1-2, adding the potassium tetracyanonickelite solution dropwise to the bimetallic organic framework material precursor solution and stirring to obtain a bimetallic organic framework material precursor gel;

[0012] Step S1-3, washing and drying the bimetallic organic framework material precursor gel in sequence to obtain the bimetallic organic framework material.

[0013] Preferably, in step S1, the carbonization comprises the steps of: placing the bimetallic organic framework material in a high temperature furnace for carbonization in an inert atmosphere;

[0014] The carbonization temperature is 300-900° C. and the time is 1-10 hours.

[0015] Preferably, in step S1-1, the concentration of ferrous perchlorate in the bimetallic organic framework material precursor solution is 2.5-10 mmol / L, the concentration of pyrazine is 2.5-10 mmol / L, and the concentration of polyvinyl pyrrolidone is 2.5-7.5 g / L;

[0016] In step S1-2, the concentration of the potassium tetracyanonitric acid solution is 5-50 mmol / L.

[0017] Preferably, in step S2, the silane coupling agent containing an unsaturated bond includes vinyltrimethoxysilane or vinyltriethoxysilane;

[0018] Among the silane coupling agents containing acidic or basic groups, the silane coupling agents containing acidic groups include silane coupling agents containing ester groups and / or carboxyl groups, and the silane coupling agents containing basic groups include silane coupling agents containing amino groups.

[0019] Preferably, in step S3, the acidic group-containing polymer monomers in the acidic or basic group-containing polymer monomers include monomers of acrylic acid, methacrylic acid, sulfonic acid or ether bond groups, and the basic group-containing polymer monomers include polymer monomers containing amino groups.

[0020] Preferably, the silane coupling agent containing an acidic group includes γ-methacryloxypropyltrimethoxysilane, and the silane coupling agent containing a basic group includes γ-aminopropyltriethoxysilane or 3-aminopropyltrimethoxysilane;

[0021] The polymer monomer containing an acidic group includes acrylate, and the polymer monomer containing a basic group includes aminostyrene.

[0022] Preferably, in step S2, the first solvent includes anhydrous ethanol;

[0023] In step S3, the second solvent includes toluene, benzene, xylene, chloroform or tetrachloroethylene;

[0024] The initiator includes azobisisocyanate, azobisisoheptanenitrile, dibenzoyl peroxide or dicumyl peroxide.

[0025] A second aspect of the present application provides an electronic ink, comprising an electrophoretic medium and the above-mentioned defective electrophoretic particles and the electrophoretic medium;

[0026] The electrophoretic medium includes a non-polar solution and a charge control agent.

[0027] It should be noted that the electronic ink described in the present application contains defective electrophoretic particles, which can effectively introduce acidic groups or basic groups so that the electrophoretic particles carry high charges, thereby enabling the electronic ink to have a high response speed. In addition, the coupling effect between the iron-nickel metal and the carbon matrix in the defective electrophoretic particles helps to enhance the site activity, so that the electrophoretic particles can leave more charges on the particle surface to the maximum extent during the interaction with the charge control agent reverse micelles in the electrophoretic liquid, thereby further improving the response speed of the electronic ink.

[0028] A third aspect of the present application provides an electrophoretic display device, comprising a microcavity encapsulating the above-mentioned electronic ink.

[0029] It should be noted that the structure of the electrophoretic display device described in the present application is the structure of an existing conventional electrophoretic display device. Since the microcavity attached to the surface of the electrophoretic display device in the present application that performs the display function encapsulates electronic ink containing defective electrophoretic particles, the defective electrophoretic particles have a high charge, which is beneficial to improving the refresh rate of the electrophoretic display device and obtaining an electrophoretic display device with low power consumption and fast refresh display; and since the defective electrophoretic particles can also affect the absorbance of the electrophoretic particles, the higher the defect concentration, the darker the particle color, thereby making the electrophoretic display device have a good black state display effect; the electrophoretic display device provided in the present application can be used as an e-book, bus stop sign, shelf label or smart wearable application.

[0030] In summary, the present application provides a method for preparing nanoflower-shaped defective particles that can achieve high-contrast electrophoretic display. The method for preparing defective electrophoretic particles includes carbonizing a bimetallic organic framework material to prepare pigment particles with a nanoflower structure, and then sequentially coupling and grafting the pigment particles with a silane coupling agent containing an acidic group or a basic group, a silane coupling agent containing an unsaturated bond, and a polymer monomer containing an acidic or basic group to obtain defective electrophoretic particles. Compared with the coupling and grafting of conventional spherical pigment particles, the bimetallic organic framework material has a high-contrast electrophoretic display. The pigment particles with nanoflower structure prepared by carbonization have a large number of active sites, so that during the coupling and grafting process, more acidic or basic groups can be chemically bonded to the surface of the pigment particles, thereby increasing the charge on the surface of the electrophoretic pigment particles. The nanoflower-like defective particles have a higher absorbance, making the electrophoretic particles provided in the present application darker in color, thereby solving the technical problem in the prior art that spherical pigment particles cannot effectively introduce acidic or basic groups, the prepared electrophoretic particles have a low charge, and the color itself is not black enough, which leads to insufficient response speed and contrast of the electrophoretic display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 A schematic diagram of a process for preparing defective electrophoretic particles provided in Example 1 of the present application;

[0033] Figure 2 This is a scanning electron microscope image of the defective electrophoretic particle provided in Example 1 of the present application; Figure 1 In the figure, 11 is a nanoflower structured pigment particle, 12 is a pre-treated nanoflower structured pigment particle, 13 is a nanoflower structured pigment particle coupled with a silane coupling agent, and 12 is a nanoflower structured pigment particle grafted with a polymer monomer. DETAILED DESCRIPTION

[0034] The present application provides a method for preparing nanoflower-shaped defective particles that can achieve high-contrast electrophoretic display, which is used to solve the technical problem in the prior art that spherical pigment particles cannot effectively introduce acidic or basic groups, the prepared electrophoretic particles have a low charge, and the color itself is not black enough, which leads to insufficient response speed and contrast of electrophoretic display devices.

[0035] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0036] Example 1

[0037] In view of the fact that in the process of introducing acidic groups or basic groups to prepare electrophoretic particles in the prior art, the number of sites where functional groups can be introduced into spherical electrophoretic pigment particles is low, resulting in the inability to effectively introduce acidic groups or basic groups, and the defect of the prepared electrophoretic particles having a low charge; Example 1 of the present application provides a nanoflower-shaped defective electrophoretic particle, and the preparation method includes the steps of carbonizing a bimetallic organic framework material, coupling a silane coupling agent containing an acidic group, and grafting a polymer monomer containing an acidic group.

[0038] The step of carbonizing the bimetallic organic framework material comprises first preparing the bimetallic organic framework material by a sol-gel method, and then carbonizing the bimetallic organic framework material; the sol-gel method for preparing the bimetallic organic framework material comprises dissolving ferrous perchlorate hydrate in a mixture of anhydrous methanol and water in a volume ratio of 1:1 to 1:5 to obtain an alcohol aqueous solution of ferrous perchlorate with a concentration of 2.5 to 10 mM, and then dissolving pyrazine and polyvinyl pyrrolidone (PVP, Mw=8000-700000) therein, wherein the pyrazine and ferrous perchlorate hydrate are of equal mass, and the amount of polyvinyl pyrrolidone added is 2.5 to 10 mM. 7.5g / L, then a Ni-containing organic precursor potassium tetracyanonickelate solution (the concentration of potassium tetracyanonickelate is 2 to 5 times the concentration of ferrous perchlorate hydrate solution) is added dropwise into the above-mentioned mixed solution, stirred for 1 to 12 hours, the obtained precipitate is washed with deionized water several times, washed with ethanol several times, and dried at room temperature for 12 to 48 hours to obtain an iron-nickel bimetallic organic framework material precursor; the carbide iron-nickel bimetallic organic framework material comprises placing the obtained dry powder in a tubular furnace, and keeping it warm at 300 to 900°C for 1 to 10 hours under a N2 atmosphere, and the obtained black powder is a pigment particle with a nanoflower structure, and the microscopic picture is shown in FIG. Figure 2 Compared with the particle morphology of traditional spherical particles, the nano-flower-shaped defective electrophoretic particles synthesized in this patent greatly increase the specific surface area to increase the charge, improve the site activity and promote the subsequent charging process of introducing functional groups. This application first proposed and prepared a black electrophoretic particle ink with high charge and high absorbance based on defect state regulation;

[0039] At the same time, in the preparation process of the carbonized bimetallic organic framework material provided by the present application, the carbon matrix is ​​an organic carbon-containing mesh structure. When bimetallic materials such as nickel and iron are introduced by chemical precipitation, the bimetallic materials will naturally bond with the carbon matrix to obtain a bimetallic organic framework material. Then, the organic components in the obtained bimetallic organic framework material are removed by calcination to obtain nano-flower-shaped defective particles, providing a new preparation process for nano-flower-shaped defective particles.

[0040] The step of coupling the silane coupling agent containing an acidic group comprises dispersing the pigment particles of the nanoflower structure in 20 to 30 times the mass of anhydrous ethanol, adding 0.5 to 2 times the mass of γ-methacryloxypropyltrimethoxysilane thereto, and adding vinyltrimethoxysilane of the same mass as the γ-methacryloxypropyltrimethoxysilane thereto, adding additives such as SDBS during stirring, wherein the amount of the additives is 0.015 to 0.025 times the amount of the particles, stirring for 12 to 36 hours, centrifuging, washing for multiple times and drying to obtain acid-modified pigment particles.

[0041] The step of grafting the polymer monomer containing an acidic group includes dispersing the acid-modified pigment particles in 5 to 15 times the mass of a low-polarity dispersion solvent toluene, adding 0.5 to 2 times the mass of a carboxyl-containing polymer monomer acrylate to the solution, and adding additives such as SDBS thereto, and raising the temperature to 70°C to 110°C. After stirring for 15 to 30 minutes, a low-polarity solvent toluene containing 0.05 times the mass of an AIBN initiator is added dropwise, and the mixture is stirred for 5 to 24 hours with a stirrer. The reaction is carried out in an inert atmosphere throughout the process. After the temperature of the reactant container is reduced to room temperature, the reaction mixture is filtered and washed several times with a low-polarity solvent to obtain defective electrophoretic particles.

[0042] In the preparation process of defective electrophoretic particles provided in Example 1 of the present application, since the carbonized bimetallic organic framework material obtains nanoflower-shaped electrophoretic particles, the number of sites that can be introduced is greatly increased, which is conducive to coupling and grafting more acidic groups, and improves the technical problem of low charge of electrophoretic particles prepared by spherical electrophoretic pigment particles in the traditional preparation method; before coupling the silane coupling agent containing acidic groups, the pigment particles of the nanoflower structure need to be pretreated, and the pigment particles of the nanoflower structure are dispersed in anhydrous ethanol, the mass of anhydrous ethanol is 20 to 50 times the amount of pigment particles used in the nanoflower structure, and a small amount of ammonia water (about 1 to 2 times the amount of pigment particles) is added during stirring, and the reaction is carried out for 1 to 5 hours; tetraethyl orthosilicate (about 0.25 to 0.75 times the amount of pigment particles) is added, and the reaction is continued for 3 to 6 hours; centrifugation and washing are performed several times, and after drying, the pigment particles of the nanoflower structure containing a silicon layer are obtained, and the pigment particles of the nanoflower structure are pretreated by silicon layer coating, and a large number of hydroxyl groups can be produced on the surface of the particles, which is convenient for the implementation of subsequent modification steps

[0043] Preferably, Example 1 of the present application also provides an alternative technical solution, wherein the coupled silane coupling and the grafted polymer monomer are silane couplings containing basic groups, and the grafted polymer monomer is a polymer monomer containing basic groups.

[0044] Example 2

[0045] This embodiment 2 provides a method for preparing electrophoretic particles. The difference between the preparation method and the embodiment 1 is that the step of preparing nano-flower-shaped defective particles by carbonizing the bimetallic organic framework material is not included, and the electrophoretic particles are directly prepared from spherical particles.

[0046] Example 3

[0047] This embodiment 3 provides an electronic ink, which includes the defective electrophoretic particles described in embodiment 1, a non-polar solution and a charge control agent; the non-polar solution and the charge control agent are conventional charge control agents. Since the bimetallic organic framework material provided in this embodiment 1 is an iron-nickel metal-organic framework material, the coupling effect between the iron-nickel metal and the carbon matrix helps to enhance the site activity, so that the particles can leave more charges on the particle surface to the maximum extent during the interaction with the charge control agent reverse micelles in the electrophoretic liquid, thereby further improving the charge amount of the electrophoretic particles, which is beneficial to improving the response speed of the electronic ink.

[0048] Example 4

[0049] This embodiment 3 provides an electrophoretic display device, the microcavity of the electrophoretic display device encapsulates the electronic ink described in embodiment 3, and since the electronic ink provided in this embodiment 2 is an electronic ink with a high charge, the electrophoretic display device has a high refresh rate, and the nanoflower-shaped defective electrophoretic particles contained in the electronic ink have high absorbance, so that the darker the color of the electrophoretic particles, the better the black state display effect of the electronic ink, thereby improving the display effect of the electrophoretic display device. As shown in Table 1,

[0050] sample Chromaticity Y value Spherical black particles provided in Example 2 0.53 Nano flower-shaped black particles provided in Example 1 0.42

[0051] Table 1

[0052] It can be seen from Table 1 that the electrophoretic particles prepared from the nano flower-shaped black particles described in Example 1 have a higher blackness than traditional spherical black electrophoretic particles and can achieve high-contrast electrophoretic display.

[0053] Experimental Example 1

[0054] Experimental Example 1 of the present application is used to test the defective electrophoretic particles and the charge of the electrophoretic particles prepared in Examples 1-2. The test solutions are all Isopar-G containing 3.0% AOT. The test results are shown in Table 2.

[0055]

[0056] Table 2

[0057] It can be seen from Table 2 that the charge of the electrophoretic particles prepared by the spherical pigment particles in Example 2 is -12mV, which is lower than the charge of the electrophoretic particles prepared by the nano flower-like black particles in Example 1, which is -18mV. The experimental data in Table 2 show that the carbonized bimetallic organic framework material provided in Example 1 of the present application for preparing the nano flower-like pigment particles introduces more acidic groups, thereby increasing the charge of the electrophoretic particles. Moreover, since the bimetallic organic framework material is an iron-nickel bimetallic organic framework material, the coupling effect between the iron-nickel metal and the carbon matrix helps to enhance the site activity, so that the particles can leave more charge on the particle surface to the maximum extent during the interaction with the reverse micelles in the electrophoretic solution, thereby greatly improving the charging capacity of the electrophoretic particles.

[0058] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing nanoflower-shaped defective particles capable of achieving high-contrast electrophoretic display, characterized in that: Includes steps: Step S1, carbonizing the bimetallic organic framework material to prepare nano-flower-shaped defective particles; Step S2, dispersing the nanoflower-shaped defective particles, the silane coupling agent containing an unsaturated bond, and the silane coupling agent containing an acidic or basic group in a first solvent, and performing coupling to obtain acidic or basic modified nanoflower-shaped defective modified particles; Step S3, dispersing the acidic or alkaline modified pigment particles, the polymer monomer containing the acidic or alkaline group and the initiator in the second solvent, and performing grafting to obtain nano-flower-shaped defective electrophoretic particles; In step S1, the method for preparing the bimetallic organic framework material comprises the steps of: Step S1-1, dissolving ferrous perchlorate, pyrazine and polyvinyl pyrrolidone in an alcohol aqueous solution to prepare a bimetallic organic framework material precursor solution; Step S1-2, adding the potassium tetracyanonickelite solution dropwise to the bimetallic organic framework material precursor solution and stirring to obtain a bimetallic organic framework material precursor gel; Step S1-3, washing and drying the bimetallic organic framework material precursor gel in sequence to obtain the bimetallic organic framework material.

2. The method for preparing nano flower-shaped defective particles according to claim 1, characterized in that: In step S1, the carbonization comprises the steps of: placing the bimetallic organic framework material in a high temperature furnace for carbonization in an inert atmosphere; The carbonization temperature is 300-900°C, and the time is 1-10 h.

3. The method for preparing nano flower-shaped defective particles according to claim 1, characterized in that: In step S1-1, the concentration of ferrous perchlorate in the bimetallic organic framework material precursor solution is 2.5-10 mmol / L, the concentration of pyrazine is 2.5-10 mmol / L, and the concentration of polyvinyl pyrrolidone is 2.5-7.5 g / L; In step S1-2, the concentration of the potassium tetracyanonitric acid solution is 5-50 mmol / L.

4. The method for preparing nano flower-shaped defective particles according to claim 1, characterized in that: In step S2, the silane coupling agent containing an unsaturated bond includes vinyl trimethoxy silane or vinyl triethoxy silane; The silane coupling agent containing an acidic group in the silane coupling agent containing an acidic or basic group includes a silane coupling agent containing an ester group and / or a carboxyl group, and the silane coupling agent containing a basic group includes a silane coupling agent containing an amino group; In step S3, among the polymer monomers containing acidic or basic groups, the polymer monomers containing acidic groups include polymer monomers containing acrylic acid, methacrylic acid or sulfonic acid groups, and the polymer monomers containing basic groups include polymer monomers containing amino groups.

5. The method for preparing nano flower-shaped defective particles according to claim 4, characterized in that: The silane coupling agent containing an acidic group includes γ-methacryloxypropyltrimethoxysilane, and the silane coupling agent containing a basic group includes γ-aminopropyltriethoxysilane or 3-aminopropyltrimethoxysilane; The polymer monomer containing an acidic group includes acrylate, and the polymer monomer containing a basic group includes aminostyrene.

6. The method for preparing nano flower-shaped defective particles according to claim 5, characterized in that: In step S2, the first solvent includes anhydrous ethanol; In step S3, the second solvent includes toluene, benzene, xylene, chloroform or tetrachloroethylene; The initiator includes azobisisocyanate, azobisisoheptanenitrile, dibenzoyl peroxide or dicumyl peroxide.

7. An electronic ink, characterized in that: The invention comprises a method for preparing the nano flower-shaped defective particles as described in any one of claims 1 to 6.

8. An electrophoretic display device, characterized in that: The invention comprises a preparation method for encapsulating the nano flower-shaped defective particles described in any one of claims 1 to 6.

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