Phthalo-cyanine blue composite electrophoretic particles, method for preparing same and use thereof

Abstract

This invention relates to phthalocyanine blue composite electrophoretic particles, their preparation method, and applications, belonging to the field of electrophoretic display materials technology. It aims to solve the problems of poor dispersibility, insufficient electrophoretic charge, and dependence on charge control agents for phthalocyanine blue pigment in non-polar media. This invention uses phthalocyanine blue as the core and styrene and divinylbenzene as coating monomers. Primary coated particles are formed through oil-in-water emulsion polymerization. In the later stage of polymerization, a monomer solution containing styrene, nitrogen-containing vinyl functional monomers (such as 4-vinylaniline), and an initiator is slowly added dropwise, allowing the functional monomers to participate in the outer layer polymerization regulation of the particles. After demulsification and washing, composite particles are obtained. The particles obtained by this invention can be well dispersed in Isopar G, exhibiting a significant negative electrophoretic response without the addition of charge control agents, with an apparent zeta potential reaching 60.8 mV, and possess reversible electrophoretic migration capability, making them suitable for color electronic inks and electrophoretic displays.

Description

Technical Field

[0001] This invention belongs to the field of electrophoretic display materials technology, and relates to phthalocyanine blue composite electrophoretic particles, their preparation methods and applications. Background Technology

[0002] Electrophoretic display technology is a typical reflective low-power display technology. Its basic principle involves dispersing charged pigment particles in a non-polar insulating medium. Under the influence of an applied electric field, the particles migrate in a specific direction, switching between colors or brightness levels to display patterns and text. Due to its low power consumption, good readability under ambient light, and bistable operation, electrophoretic displays are widely used in e-book readers, electronic tags, and smart signage.

[0003] As electronic paper technology evolves towards color, the preparation of colored electrophoretic particles has become an important direction in the research of electrophoretic display materials. Compared with traditional black and white particles, colored electrophoretic particles not only need to have good color performance, but also need to possess suitable particle size, density, non-polar medium dispersibility, and stable and controllable electrophoretic charging behavior. Among them, blue electrophoretic particles are an important component in the construction of colored electronic inks.

[0004] Phthalocyanine blue is a common blue organic pigment with advantages such as bright color, strong tinting strength, good heat resistance, and good chemical stability. However, unmodified phthalocyanine blue pigment usually exhibits an irregular crystalline aggregate morphology, has poor compatibility with nonpolar media such as Isopar G hydrocarbons, and lacks a stable charge regulation structure on the particle surface. When used directly in electrophoretic display systems, it is prone to problems such as insufficient dispersibility, weak charge, and unstable migration.

[0005] Current methods for electrifying particles in color electrophoresis typically rely on the addition of charge control agents, such as polyisobutylene succinimide, metal soaps, quaternary ammonium salts, or other additives that can form reverse micelles or interfacial adsorption layers in nonpolar media. While these charge control agents can improve the electrophoretic charge of particles to some extent, the particle charge is often quite sensitive to the type and amount of charge control agent, the composition of the medium, and the adsorption state. When the amount of charge control agent changes, the apparent potential and migration behavior of the particles are prone to fluctuations, and even charge shielding or interfacial rearrangement may occur.

[0006] On the other hand, while polymer coating can improve the morphology and dispersibility of pigments, it does not necessarily endow particles with sufficiently strong and reproducible electrophoretic charging behavior. Therefore, if the structure of the outer layer or near-surface region of the particles can be controlled by adding functional monomers after the particle preparation stage, enabling the particles to exhibit a clear negative electrophoretic response without the need for additional charge control agents, it will help reduce the dependence of the electrophoretic dispersion on external charge control agents and improve the controllability and practical value of the blue electrophoretic particle preparation scheme. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a phthalocyanine blue composite electrophoretic particle, its preparation method and application.

[0008] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a method for preparing phthalocyanine blue composite electrophoretic particles, comprising the following steps: S1: Phthalocyanine blue, styrene, divinylbenzene, stabilizer and oil-soluble emulsifier are mixed and dispersed, and an oil-soluble initiator is added to obtain the oil phase; S2: Dissolve the anionic surfactant in water and adjust the pH to 9.0–9.5 to obtain the aqueous phase; S3: The oil phase and the water phase are mixed and emulsified at high speed to obtain an oil-in-water emulsion; the oil-in-water emulsion is polymerized under an inert atmosphere to form phthalocyanine blue primary coated particles; S4: Add a monomer liquid containing styrene, nitrogen-containing vinyl functional monomers and oil-soluble initiators dropwise to the reaction system, and continue the polymerization reaction to obtain a polymer-coated phthalocyanine blue composite electrophoretic particle emulsion. S5: The obtained emulsion is demulsified, centrifuged, washed and solvent replaced to obtain the phthalocyanine blue composite electrophoretic particles; Preferably, in step S1, the phthalocyanine blue is CI Pigment Blue 15; the stabilizer is liquid paraffin; the oil-soluble emulsifier is Span 80; the oil-soluble initiator is N,N-azobisisobutyronitrile; the anionic surfactant is sodium dodecyl sulfate; and the nitrogen-containing vinyl functional monomer is selected from one or more of 4-vinylaniline, 2-vinylaniline, 3-vinylaniline, 4-vinylbenzylamine, N-methyl-4-vinylaniline, N,N-dimethyl-4-vinylaniline, 4-vinylpyridine, 2-vinylpyridine, N-vinylimidazolium, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, and allylamine. Preferably, the mass ratio of phthalocyanine blue, styrene, divinylbenzene, stabilizer, oil-soluble emulsifier, anionic surfactant and oil-soluble initiator is 10:80:3:4:4:3:2; Preferably, in step S3, the high-speed emulsification rotation speed is 10000–15000 rpm, the emulsification time is 10–20 min, the polymerization temperature is 70–80 ℃, the polymerization time is 4–6 h, and the stirring speed is 400–800 rpm. Preferably, in step S4, the mass ratio of styrene, nitrogen-containing vinyl functional monomer and oil-soluble initiator is (30–80):(5–40):(0.5–2), the dropping time is 10–120 min, and the polymerization time is 4–12 h; Preferably, in step S5, anhydrous ethanol is used for demulsification, and the particles are collected by centrifugation at 10,000 rpm for 5 min after demulsification; then the particles are washed with anhydrous ethanol and n-hexane, and centrifuged at 8,000 rpm for 5 min after each wash; the phthalocyanine blue composite electrophoretic particles are obtained. Furthermore, the phthalocyanine blue composite electrophoretic particles prepared by the aforementioned preparation method; The present invention also discloses a blue electrophoretic dispersion, comprising the aforementioned phthalocyanine blue composite electrophoretic particles and a nonpolar dispersion medium, wherein the nonpolar dispersion medium is at least one selected from Isopar G, isoalkanes, isododecane, n-hexane, cyclohexane, and toluene; Preferably, the blue electrophoretic dispersion further includes a charge control agent, which is 0–40 wt% of the mass of the phthalocyanine blue composite electrophoretic particles.

[0009] Furthermore, the application of the phthalocyanine blue composite electrophoretic particles, or the blue electrophoretic dispersion, in the preparation of electronic paper, electrophoretic displays, color electronic inks, electronic tags, or reflective display materials.

[0010] The beneficial effects of this invention are as follows: 1. Improve pigment morphology and dispersibility Polymer coating of phthalocyanine blue pigment was achieved through oil-in-water emulsion polymerization, which improved the irregular aggregate morphology of the original phthalocyanine blue and facilitated its redispersion in non-polar media (such as Isopar G).

[0011] 2. Achieve negative electrophoresis behavior without the need for external charge control agents. By adding 4-vinylaniline or similar nitrogen-containing vinyl functional monomers dropwise, the functional monomers participate in the interface regulation of the outer layer or near-surface region of the particles. The resulting composite electrophoretic particles can exhibit a significant negative electrophoretic response without the addition of charge control agents.

[0012] 3. Flexible control and adjustable electrophoretic performance. By changing the type and amount of the added functional monomer, the negative electrophoretic charge of the particles can be effectively controlled. Examples show that when the amount of 4-vinylaniline added is in the range of 0.05 g to 0.20 g, the absolute value of the negative potential of the particles increases with increasing amount; further increases result in a decrease in negative potential, indicating that non-monotonic control can be achieved through the amount added, facilitating optimization.

[0013] 4. The preparation process is simple and the raw materials are readily available. The raw materials used (phthalocyanine blue, styrene, divinylbenzene, 4-vinylaniline, etc.) are all common chemicals, and the polymerization process is conventional emulsion polymerization, which is simple to operate and suitable for large-scale preparation.

[0014] 5. The resulting particles exhibit a reversible electrophoretic response. When a 30 V DC voltage is applied, the particles migrate toward the positive electrode; when the voltage is applied in the opposite direction, the particles migrate in the opposite direction, indicating that the composite electrophoretic particles have a reversible electrophoretic response capability, which is suitable for electrophoretic display devices.

[0015] 6. The composite electrophoretic particles of the present invention can be applied to fields such as blue electronic ink, color electrophoretic display materials, electronic paper, electrophoretic displays, electronic tags, and reflective display materials.

[0016] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0017] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 is a scanning electron micrograph of phthalocyanine blue pigment; Figure 2 shows a transmission electron micrograph of phthalocyanine blue pigment; Figure 3 is a scanning electron micrograph of the phthalocyanine blue composite electrophoretic particles obtained in Example 1; Figure 4 is a transmission electron micrograph of the phthalocyanine blue composite electrophoretic particles obtained in Example 1; Figure 5 is a schematic diagram of the electrophoretic response of the blue negative electrophoretic composite electrophoretic particles obtained in Example 1; Figure 6 is a flowchart of the preparation process of negative electrophoretic phthalocyanine blue composite electrophoretic particles; Figure 7 is a schematic diagram of the structure of the negative electrophoretic phthalocyanine blue composite electrophoretic particles. Detailed Implementation

[0018] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0019] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0020] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0021] Example 1: Preparation of VA-0.20 negative electrophoretic phthalocyanine blue composite electrophoretic particles Weigh out 0.50 g phthalocyanine blue, 4.00 g styrene, 0.15 g divinylbenzene, 0.20 g liquid paraffin, and 0.20 g Span 80, mix them, and then ultrasonically disperse them to obtain an oil phase. After the oil phase cools, add 0.10 g AIBN and allow it to dissolve completely.

[0022] Weigh 0.15 g SDS, dissolve it in 40 mL of deionized water, and adjust the pH of the aqueous phase to 9.0–9.5 using NaOH solution to obtain the aqueous phase. Add the oil phase to the aqueous phase and emulsify at 10,000 rpm for 10 min under ice bath conditions to obtain an oil-in-water emulsion.

[0023] The resulting emulsion was transferred to a three-necked flask, which was then placed in a magnetically stirred water bath for heating. Nitrogen gas was continuously introduced during the reaction to purge oxygen. The temperature was raised to 70 °C under magnetic stirring at 400 rpm for 4 h to carry out the first stage of polymerization.

[0024] After the first stage reaction was completed, a second-stage monomer solution containing 0.50 g styrene, 0.20 g 4-vinylaniline, and 0.01 g AIBN was prepared. Using a small syringe inserted through the rubber stopper of a three-necked flask, the second-stage monomer solution was slowly added dropwise to the reaction system over approximately 30 minutes to minimize oxygen ingress.

[0025] After the addition was complete, the reaction was continued for 8 h at 70 ℃, 400 rpm and nitrogen protection to obtain a polymer-coated phthalocyanine blue composite electrophoretic particle emulsion.

[0026] After the reaction was complete, the emulsion was allowed to cool naturally to room temperature. Anhydrous ethanol was added to the emulsion to break the emulsion, and the mixture was centrifuged at 10,000 rpm for 5 min to collect the blue composite electrophoretic particles. The obtained particles were washed three times with anhydrous ethanol and twice with n-hexane, centrifuged at 8,000 rpm for 5 min after each wash. The washed particles were not dried, but the n-hexane was allowed to evaporate naturally in centrifuge tubes at room temperature. After the n-hexane had largely evaporated, the resulting blue composite electrophoretic particles were dispersed in Isopar G to obtain a blue electrophoretic dispersion.

[0027] The obtained particles were dispersed in Isopar G at a particle mass concentration of approximately 2 mg / mL. The apparent zeta potential was measured using a zeta potential meter, and the result was -60.8 mV, indicating that the VA-0.20 sample exhibited a significant negative electrophoretic response.

[0028] Example 2: Preparation of VA-0 composite electrophoretic particles Phthalocyanine blue composite electrophoretic particles were prepared according to the method of Example 1, except that the amount of 4-vinylaniline added to the monomer solution in the second stage was adjusted to 0 g. All other parameters, including the oil phase formulation, aqueous phase formulation, emulsification conditions, first-stage polymerization conditions, second-stage dropping time, continued polymerization time, demulsification, and washing conditions, were the same as in Example 1. The resulting sample was designated VA-0.

[0029] The obtained particles were dispersed in Isopar G at a particle mass concentration of approximately 2 mg / mL. The apparent zeta potential was measured using a zeta potential meter, and the result was -11.6 mV.

[0030] Example 3: Preparation of VA-0.05 composite electrophoretic particles Phthalocyanine blue composite electrophoretic particles were prepared according to the method in Example 1, except that the amount of 4-vinylaniline added to the monomer solution in the second stage was adjusted to 0.05 g. The remaining oil phase formulation, aqueous phase formulation, emulsification conditions, first-stage polymerization conditions, second-stage dropping time, continued polymerization time, demulsification, and washing conditions were the same as in Example 1. The resulting sample was denoted as VA-0.05.

[0031] The obtained particles were dispersed in Isopar G at a particle mass concentration of approximately 2 mg / mL. The apparent zeta potential was measured using a zeta potential meter, and the result was -23.7 mV.

[0032] Example 4: Preparation of VA-0.10 composite electrophoretic particles Phthalocyanine blue composite electrophoretic particles were prepared according to the method in Example 1, except that the amount of 4-vinylaniline added to the monomer solution in the second stage was adjusted to 0.10 g. The remaining oil phase formulation, aqueous phase formulation, emulsification conditions, first-stage polymerization conditions, second-stage dropping time, continued polymerization time, demulsification, and washing conditions were the same as in Example 1. The resulting sample was denoted as VA-0.10.

[0033] The obtained particles were dispersed in Isopar G at a particle mass concentration of approximately 2 mg / mL. The apparent zeta potential was measured using a zeta potential meter, and the result was -41.6 mV.

[0034] Example 5: Preparation of VA-0.30 composite electrophoretic particles Phthalocyanine blue composite electrophoretic particles were prepared according to the method of Example 1, except that the amount of 4-vinylaniline added to the monomer solution in the second stage was adjusted to 0.30 g. The remaining oil phase formulation, aqueous phase formulation, emulsification conditions, first-stage polymerization conditions, second-stage dropping time, continued polymerization time, demulsification, and washing conditions were the same as in Example 1. The resulting sample was denoted as VA-0.30.

[0035] The obtained particles were dispersed in Isopar G at a particle mass concentration of approximately 2 mg / mL. The apparent zeta potential was measured using a zeta potential meter, and the result was -19.5 mV.

[0036] Example 6: Preparation of VA-0.40 composite electrophoretic particles Phthalocyanine blue composite electrophoretic particles were prepared according to the method of Example 1, except that the amount of 4-vinylaniline added to the monomer solution in the second stage was adjusted to 0.40 g. The remaining oil phase formulation, aqueous phase formulation, emulsification conditions, first-stage polymerization conditions, second-stage dropping time, continued polymerization time, demulsification, and washing conditions were the same as in Example 1. The resulting sample was denoted as VA-0.40.

[0037] The obtained particles were dispersed in Isopar G at a particle mass concentration of approximately 2 mg / mL. The apparent zeta potential was measured using a zeta potential meter, and the result was -6.5 mV.

[0038] The test results of Examples 1–6 are summarized in Table 1. The results show that as the amount of 4-vinylaniline added increased from 0.05 g to 0.20 g, the absolute value of the negative electrophoretic potential of the particles gradually increased; when the amount of 4-vinylaniline added was 0.20 g, the particles exhibited the strongest negative electrophoretic response; after further increasing the amount of 4-vinylaniline added to 0.30 g and 0.40 g, the absolute value of the negative potential decreased. These results indicate that the amount of 4-vinylaniline added has a non-monotonic regulatory effect on the negative electrophoretic behavior of the particles, and appropriate addition is beneficial for forming strongly negative electrophoretic composite electrophoretic particles.

[0039] Table 1. Effect of different amounts of 4-vinylaniline added on the apparent zeta potential of particles.

[0040] The above results indicate that VA-0.20 is the superior sample.

[0041] Example 7: Effect of T151 on the apparent charge of VA-0.20 composite electrophoretic particles The VA-0.20 composite electrophoretic particles obtained in Example 1 were dispersed in Isopar G, with a particle mass concentration of approximately 2 mg / mL. Different mass fractions of T151 were added to the dispersion, with the amounts of T151 added based on particle mass being 0, 1 wt%, 2 wt%, 5 wt%, 10 wt%, 20 wt%, and 40 wt%.

[0042] Test results show that without the addition of T151, the VA-0.20 particles exhibit the highest negative apparent zeta potential; after the addition of T151, the absolute value of the negative potential of the particles decreases and fluctuates within a lower negative range.

[0043] Table 2 Effect of T151 addition amount on apparent zeta potential of VA-0.20 composite electrophoretic particles

[0044] The results indicate that T151 is not the main source of the strong negative electrophoretic response of VA-0.20 composite electrophoretic particles, and the strong negative electrophoretic behavior of VA-0.20 particles is mainly related to the particle interface structure induced by the subsequent addition of 4-vinylaniline.

[0045] Example 8: Electrophoretic response of VA-0.20 composite electrophoretic particles The VA-0.20 composite electrophoretic particles obtained in Example 1 were dispersed in Isopar G and injected into a simple electrophoretic test cell made of ITO glass. After applying a DC voltage of 30 V, blue composite electrophoretic particles were observed to migrate towards the positive electrode, indicating that the obtained composite electrophoretic particles behave as negative electrophoretic particles in Isopar G. After applying a voltage in the opposite direction, the particles can migrate in the reverse direction, indicating that the composite electrophoretic particles have reversible electrophoretic response capability.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing phthalocyanine blue composite electrophoretic particles, characterized in that, Includes the following steps: S1: Phthalocyanine blue, styrene, divinylbenzene, stabilizer and oil-soluble emulsifier are mixed and dispersed, and an oil-soluble initiator is added to obtain the oil phase; S2: Dissolve the anionic surfactant in water and adjust the pH to 9.0–9.5 to obtain the aqueous phase; S3: The oil phase and the water phase are mixed and emulsified at high speed to obtain an oil-in-water emulsion; the oil-in-water emulsion is polymerized under an inert atmosphere to form phthalocyanine blue primary coated particles; S4: Add monomer liquid containing styrene, nitrogen-containing vinyl functional monomer and oil-soluble initiator dropwise to the reaction system, and continue the polymerization reaction to obtain polymer-coated phthalocyanine blue composite electrophoretic particle emulsion; S5: The obtained emulsion is demulsified, centrifuged, washed, and solvent replaced to obtain the phthalocyanine blue composite electrophoretic particles.

2. The preparation method according to claim 1, characterized in that: The phthalocyanine blue in S1 is CI PigmentBlue 15; the stabilizer is liquid paraffin; the oil-soluble emulsifier is Span 80; the oil-soluble initiator is N,N-azobisisobutyronitrile; the anionic surfactant is sodium dodecyl sulfate; and the nitrogen-containing vinyl functional monomer is selected from one or more of 4-vinylaniline, 2-vinylaniline, 3-vinylaniline, 4-vinylbenzylamine, N-methyl-4-vinylaniline, N,N-dimethyl-4-vinylaniline, 4-vinylpyridine, 2-vinylpyridine, N-vinylimidazolium, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, and allylamine.

3. The preparation method according to claim 1, characterized in that: The mass ratio of phthalocyanine blue, styrene, divinylbenzene, stabilizer, oil-soluble emulsifier, anionic surfactant, and oil-soluble initiator is 10:80:3:4:4:3:

2.

4. The preparation method according to claim 1, characterized in that: In step S3, the high-speed emulsification speed is 10,000–15,000 rpm, the emulsification time is 10–20 min, the polymerization temperature is 70–80 ℃, the polymerization time is 4–6 h, and the stirring speed is 400–800 rpm.

5. The preparation method according to claim 1, characterized in that: In step S4, the mass ratio of styrene, nitrogen-containing vinyl functional monomer and oil-soluble initiator is (30–80):(5–40):(0.5–2), the dropping time is 10–120 min, and the polymerization time is 4–12 h.

6. The preparation method according to claim 1, characterized in that: In step S5, anhydrous ethanol was used for demulsification, and the particles were collected by centrifugation at 10,000 rpm for 5 min after demulsification; then the particles were washed with anhydrous ethanol and n-hexane, and centrifuged at 8,000 rpm for 5 min after each wash; the phthalocyanine blue composite electrophoretic particles were obtained.

7. Phthalocyanine blue composite electrophoretic particles prepared by the preparation method according to claims 1-6.

8. A blue electrophoretic dispersion, characterized in that: The invention includes the phthalocyanine blue composite electrophoretic particles and the nonpolar dispersion medium as described in claim 7, wherein the nonpolar dispersion medium is at least one of Isopar G, isoalkanes, isododecane, n-hexane, cyclohexane, and toluene.

9. The blue electrophoretic dispersion according to claim 8, characterized in that: It also includes a charge control agent, which is 0–40 wt% of the mass of the phthalocyanine blue composite electrophoretic particles.

10. The application of the phthalocyanine blue composite electrophoretic particles of claim 7, or the blue electrophoretic dispersion of claim 8 or 9, in the preparation of electronic paper, electrophoretic displays, color electronic inks, electronic tags, or reflective display materials.

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