WO2013120369A1

WO2013120369A1 - Nanometer pigment composition, preparation method therefor, electronic ink microcapsules and electrophoretic display device

Info

Publication number: WO2013120369A1
Application number: PCT/CN2012/085125
Authority: WO
Inventors: 孙雯雯; 薛建设; 徐传祥
Original assignee: 京东方科技集团股份有限公司
Priority date: 2012-02-14
Filing date: 2012-11-23
Publication date: 2013-08-22
Also published as: CN102649880A; CN102649880B

Abstract

A nanometer pigment composition, a preparation method therefor, electronic ink microcapsules and an electrophoretic display device. The nanometer pigment composition comprises a pigment. A surfactant is grafted to the surface of the pigment and is a silane coupling agent or an anionic surfactant. Because of the surfactant on the surface of the pigment, the fluidity, the dispersibility and the stability of the nanometer pigment composition are improved.

Description

Nano pigment composition and preparation method thereof, electronic ink microcapsule and electrophoretic display device

The present invention relates to a nanopigment composition and a method of preparing the same, an electronic ink microcapsule and an electrophoretic display device. Background technique

The electronic ink micro-adhesive technology is a technique in which charged particles and a dispersion solution are encapsulated in a microcapsule, and electrophoretic display is realized in a microcapsule by an electrophoretic display principle. The micro-gelled electrophoretic display device prepared by the electronic ink micro-adhesive technology not only has the advantages of high contrast, low energy consumption, and no need for a backlight, but also has flexibility. Therefore, the electrophoretic display device is favored by the market.

In recent years, in order to realize the colorization of the electrophoretic display device and to avoid the influence of the color filter film on the image color saturation, the electronic ink microgel has gradually developed into a color electronic ink microcapsule. It is well known that the performance of color electronic ink microcapsules directly affects the display effect of color electrophoretic display devices. For example, the fluidity and dispersibility of nanopigment (electrophoretic particles) as a core dispersion will directly affect the contrast and response time of the electrophoretic display device, and its stability indirectly affects the contrast and response time of the electrophoretic display device, and also affects the electrophoretic display. The service life of the device. The nanopigment is generally a smaller particle pigment after the process is refined for the pigment, and the average particle size of the refined nanopigment is usually less than 100 nm. For the existing nano pigments, the display performance of the electrophoretic display device is poor due to poor fluidity, dispersibility, and stability.

Further, Chinese Patent Publication No. CN1687252 discloses a surface modification method using a polymer-coated nano pigment particle, which is a coating of a nano pigment particle with a polymer, and then an electronic ink microcapsule. The method requires a separate polymer coating process before preparing the electronic ink microcapsule, and requires separation of the solvent used and drying of the nanopigment powder, which not only increases the preparation process of the electronic ink microcapsule, but also Energy is wasted in the process of separating and drying the nanopigment powder, increasing production costs. Summary of the invention

The technical problem to be solved by the present invention is to provide the above-mentioned defects existing in the prior art. A nano pigment composition and a preparation method thereof, the nanopigment composition has good fluidity, dispersibility, and excellent stability.

Further, the present invention provides an electronic ink microcapsule which has high stability and good electric field responsiveness at a low voltage.

Further, the present invention provides an electrophoretic display device which has good contrast and response time and has a long service life.

A technical solution to solve the above technical problems is to provide a nanopigment composition comprising a pigment, the surface of which is grafted with a surfactant, the surfactant being a silane coupling agent or an anionic surface active Agent.

Preferably, the surface of the pigment has a reactive group through which the surfactant is grafted.

Preferably, the nanopigment composition has a viscosity of 1.8 to 2.2 mPa_s, and the nanopigment composition has a particle size of 65 to 72.

Preferably, the anionic surfactant is a multi-branched anionic surfactant or a single-branched anionic surfactant.

Preferably, the multi-branched anionic surfactant comprises stearic acid or dodecyl benzene cross-acid).

Preferably, the single-branched anionic surfactant comprises a carboxylate, a sulfate or a cross-acid.

The present invention also provides a method for preparing a nanopigment composition, comprising the steps of: providing a mixed solvent;

Adding a pigment, a dye, and a charge control agent to the mixed solvent to form a mixture;

Adding a surfactant to the mixture, and uniformly mixing the surfactant and the mixture, the surfactant being a silane coupling agent or an anionic surfactant;

The mixture in which the surfactant is added is dispersed and ground so that the surface of the pigment is grafted with the surfactant.

Preferably, the silane coupling agent is added in an amount of 0.1 to 2% by weight of the mixture. Preferably, the multi-branched anionic surfactant or the single-branched anionic surfactant The amount added is 0.2 to 10% by weight of the mixture.

Preferably, the mixed solvent is a mixed solvent of tetrachloroethylene and dinonylbenzene.

Preferably, in the mixture, the content of the pigment is 10-20% by weight, the content of the dye is 5-10% by weight, and the content of the charge control agent is 0.1-0.3% by weight, and the balance is Mixed solvent.

Preferably, the dispersing comprises dispersing in a sand mill at a rotation speed of 100 to 300 r/min for 1 to 5 hours; and the grinding comprises grinding the ball 20 to 30 at a rotation speed of 200 to 500 r/min by a ball mill and/or an emulsifier. hour.

The present invention also provides an electronic ink microcapsule comprising a nanopigment composition as the nanopigment composition for use in the nanopigment composition provided by the present invention.

The present invention also provides an electrophoretic display device comprising an electronic ink microcapsule, and the electronic ink microcapsule provided by the present invention as the electronic ink microcapsule.

The invention has the following beneficial effects:

The nanopigment composition provided by the invention has a silane coupling agent or an anionic surfactant grafted on the surface of the pigment, wherein the surface of the pigment and the surfactant are linked by a covalent bond or an ionic bond. In a preferred case, the surface of the pigment has a reactive group through which the surface of the pigment is grafted with a silane coupling agent or an anionic surfactant. The surfactant on the surface of the pigment not only improves the fluidity and dispersibility of the nanopigment, but also makes the viscosity and particle size of the nanopigment composition reach 1.8 to 2.2 mPa.s and 65 to 72 nm, respectively, and can improve the stability of the nanopigment. For example, after 6 months of placement in the air, the viscosity and particle size change of the nanopigment is 10-11% and 0.043~0.077%, respectively. a silane coupling agent or an anionic surfactant is added, and after dispersion and grinding, a reactive group on the surface of the pigment or preferably a surface thereof is grafted with a silane coupling agent or an anionic surfactant, on the surface of the pigment or on the surface thereof. The reactive group and the surfactant are linked by a covalent bond or an ionic bond. Surfactants on the surface of the pigment not only improve the flowability and dispersibility of the nanopigment composition, but also make the nano The viscosity and particle size of the pigment composition are 1.8 to 2.2 mPa-s and 65 to 72 nm, respectively, and the stability of the nanopigment composition can be improved. For example, after the nanopigment composition is placed in the air for 6 months, the viscosity and particle size change rates are 10 to 11% and 0.043 to 0.077%, respectively. In addition, the method for preparing the nanopigment composition does not require a special preparation environment, and the nanopigment composition can be prepared in the preparation process of the microcapsule, thereby improving process efficiency, saving energy, and reducing cost.

The electronic ink microcapsule provided by the invention uses the nanopigment composition provided by the invention, and the stability of the nanopigment composition is high, the stability of the microcapsule is high; and the microcapsule can be made at a low voltage. Good electric field responsiveness.

The electrophoretic display device provided by the invention uses the electronic ink microcapsule provided by the invention to make the electrophoretic display device have good contrast and response time, and has a long service life. DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below. It is obvious that the drawings in the following description relate only to some embodiments of the present invention, and are not intended to limit the present invention. .

1 is a flow chart of a method for preparing a nanopigment composition provided by the present invention. detailed description

The technical solutions of the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings of the embodiments of the present invention. It is apparent that the described embodiments are part of the embodiments of the invention, rather than all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the described embodiments of the present invention without departing from the scope of the invention are within the scope of the invention.

The pigments used herein are generally insoluble in water or poorly soluble or sparingly soluble in water. The pigment can be classified into an organic pigment or an inorganic pigment. For example, color pigments such as red, green, and blue can be used.

Organic pigments are preferably used in the present invention. Preferred pigments are selected from the group consisting of benzidines, phthalocyanines, anthraquinone pigments, and the like.

According to the present invention, the silane coupling agent or the anionic surfactant may be grafted onto the surface of the pigment by a chemical reaction or by chemical bond induction or ionic electrostatic adsorption. As described above, the pigment surface of the present invention may have and preferably have a reactive group. The reactive group will be specific The pigment to be used may vary, and it may be such that it can be grafted with a silane coupling agent or an anionic surfactant. Preferably, the reactive group may be a group capable of matching an anionic surfactant, including but not limited to, -S0 ₂ C1 and tt, and the like.

The dyes used herein differ from pigments in that the dye is generally soluble in water.

The charge control agent which can be used herein is a charge control machine conventionally used in the related art, including but not limited to: an amine type charge control agent such as o-nonanoyl benzene lateral imide or polybutylene succinamide.

In one embodiment, the provided nanopigment composition comprises a pigment, a dye, and a charge control agent, wherein the pigment is benzidine yellow, the dye is disperse blue, and the charge control agent is polybutylene succinamide. The surfactant is grafted with a surfactant by a reactive group on the surface of the pigment, and the surfactant is a silane coupling agent or an anionic surfactant.

In the present embodiment, the anionic surfactant is a multi-branched anionic surfactant or a single-branched anionic surfactant. Multi-branched anionic surfactants include stearic acid or sodium dodecyl benzoate. Single-branched anionic surfactants include carboxylates, sulfates or sulfonates.

In the nanopigment composition provided in this embodiment, a silane coupling agent or an anionic surfactant is grafted on the surface of the pigment through a reactive group, and the active group on the surface of the pigment is linked with a surfactant by a covalent bond or an ionic bond. The surfactant on the surface of the pigment not only improves the fluidity and dispersibility of the nanopigment, but also makes the viscosity and particle size of the nanopigment composition reach 1.8 ~ 2.2mpa.s and 65 ~ 72nm, respectively, and can improve the nano pigment composition. stability. When the nanopigment was placed in air for 6 months, the viscosity and particle size change rates were 10-11% and 0.043~0.077%, respectively.

1 is a flow chart of a method for preparing a nanopigment provided by the present invention. Referring to Figure 1, the schematic preparation method of the nano pigment includes the following steps:

Step s10, providing a mixed solvent. Solvents, for example: diethylene glycol alkyl ether, propylene glycol monoalkyl ether acetate, alkyl alkoxypropionate, acetates, aromatic hydrocarbons, halogenated hydrocarbons, and the like. These solvents may be used singly or in combination of two or more kinds in any ratio. Commonly used solvents include propylene glycol monoterpene ether acetate, diethylene glycol dioxime ether, ethyl 3-ethoxypropionate, tetrachloro One or more of ethylene and diphenylbenzene are preferably a mixed solvent of two or more of them. In the present invention, it is particularly preferable to use tetrachloroethylene and diphenylbenzene to obtain a mixed solvent. In the case of using a mixed solvent of tetrachloroethylene and diphenylbenzene, it is preferred that tetrachloroethylene and diphenylbenzene are mixed in a mass ratio of (1 to 2):1, particularly preferably 3:2. The quality ratio.

In step s20, a pigment, a dye, and a charge control agent are added to the mixed solvent to form a mixture. In the step s20, the pigment is preferably benzidine yellow, the dye is preferably disperse blue, and the charge control agent is preferably polybutylene succinamide. Further, in the mixture, the weight percentage of benzidine yellow, disperse blue, and polybutylene succinamide may be 10 to 20%, 5 - 10%, and 0.1 to 0.3%, respectively, and the remainder is a mixed solvent. The benzidine yellow, the disperse blue, and the charge control agent are added to the mixed solvent and uniformly mixed to form a mixture.

In step s30, a surfactant is added to the mixture, and the surfactant and the mixture are uniformly mixed.

A surfactant is added to the mixture obtained in the step s20, and the surfactant is a silane coupling agent or an anionic surfactant. The amount of the silane coupling agent to be added is preferably 0.1 to 2% by weight of the mixture, and the amount of the multi-branched anionic surfactant or the single-branched anionic surfactant is from 0.2 to 10% by weight based on the weight of the mixture. Multi-branched anionic surfactants include stearic acid or sodium dodecylbenzene sulfonate. Single-branched anionic surfactants include carboxylates, sulfates or sulfonates.

Step s40, dispersing and grinding the mixture to which the surfactant is added, so that the active group on the surface of the pigment is grafted with a surfactant.

In step s40, the basket sander can be used for dispersion. The speed of the sand mill is 100 ~ 300r/min (rev / min), and the dispersion time can be 1 ~ 5 hours. It can be ground by a ball mill or an emulsifier, or mixed by a ball mill and an emulsifier. For example, first grind with a ball mill and then with an emulsifier; or first grind with an emulsifier and then with a ball mill. Ball mills and emulsifiers typically have a speed of 200 to 500 r/min and a grinding time of 20 to 30 hours. The preparation process of the nanopigment composition of the present invention is described in detail below in seven examples.

Embodiment 1

a. Mixing tetrachloroethylene and diphenylbenzene in a mass ratio of 1:1 to obtain a mixed solvent.

b. 79.9 parts by weight of a mixed solvent, then 10 parts by weight of benzidine yellow, 10 parts by weight of disperse blue, and 0.1 part by weight of polybutylene succinamide were added, and uniformly mixed to form a mixture.

c. 0.1 part by weight of a silane coupling agent was added to the mixture and uniformly mixed.

d. The mixture containing the silane coupling agent was dispersed and mixed by a basket mill, and the speed of the basket mill was 100 r/min, and the dispersion time was 1 hour. e. Grinding with a ball mill, the ball mill was rotated at 200 r/min, and the grinding time was 20 hours, thereby obtaining a nanopigment composition. Embodiment 2

a. Mixing tetrachloroethylene and diphenylbenzene in a mass ratio of 1.2:1 to obtain a mixed solvent.

b. 78.85 parts by weight of a mixed solvent, then 12 parts by weight of benzidine yellow, 9 parts by weight of disperse blue and 0.15 parts by weight of polybutylene succinamide were added, and uniformly mixed to form a mixture.

c. 1 part by weight of a silane coupling agent was added to the mixture and uniformly mixed.

d. The mixture containing the silane coupling agent was dispersed and mixed by a basket mill. The speed of the basket mill was 150 r/min and the dispersion time was 1.5 hours.

e. Grinding with a ball mill, the ball mill speed was 260 r/min, and the grinding time was 25 hours, thereby obtaining a nanopigment composition. Embodiment 3

a. Mixing tetrachloroethylene and diphenylbenzene in a mass ratio of 1.5:1 to obtain a mixed solvent.

b. 76.8 parts by weight of a mixed solvent, then 15 parts by weight of benzidine yellow, 8 parts by weight of disperse blue, and 0.2 part by weight of polybutylene succinamide were added, and uniformly mixed to form a mixture.

c. 2 parts by weight of a silane coupling agent was added to the mixture and uniformly mixed.

d. Disperse and mix the mixture containing the silane coupling agent using a basket mill. The basket mill has a rotation speed of 200 r/min and a dispersion time of 2.5 hours.

e. Grinding with a ball mill, the ball mill was rotated at 300 r/min, and the grinding time was 28 hours, thereby obtaining a nanopigment composition.

Embodiment 4

a. Mixing tetrachloroethylene and diphenylbenzene in a mass ratio of 1.8:1 to obtain a mixed solvent.

b. 74.7 parts by weight of a mixed solvent, and then 18 parts by weight of benzidine yellow, 7 parts by weight of disperse blue, and 0.3 part by weight of polybutylene succinamide were added, and uniformly mixed to form a mixture.

c. 0.2 parts by weight of stearic acid was added to the mixture and uniformly mixed.

d. The mixture containing the silane coupling agent was dispersed and mixed by a basket mill, and the basket mill was rotated at 250 r/min for a dispersion time of 3 hours.

e. Grinding with a ball mill, the ball mill speed is 350r/min, and the grinding time is 24 hours. f. Grinding with an emulsifier, the speed of the emulsifier was 350 r/min, and the grinding time was 2 hours, thereby obtaining a nanopigment composition. Embodiment 5

a. Mixing tetrachloroethylene and diphenylbenzene in a mass ratio of 2:1 to obtain a mixed solvent.

b. 73.75 parts by weight of a mixed solvent, then 20 parts by weight of benzidine yellow, 6 parts by weight of disperse blue and 0.25 parts by weight of polybutylene succinamide were added, and uniformly mixed to form a mixture.

c. 1 part by weight of sodium dodecylbenzenesulfonate was added to the mixture and uniformly mixed.

d. Disperse and mix the mixture containing the silane coupling agent using a basket mill. The basket mill has a rotation speed of 300 r/min and a dispersion time of 4 hours.

e. Grinding with a ball mill, the ball mill rotates at 400 r/min and the grinding time is 25 hours. f. Grinding with an emulsifier, the speed of the emulsifier was 400 r/min, and the grinding time was 3 hours, thereby obtaining a nanopigment composition. Embodiment 6

a. Mixing tetrachloroethylene and diphenylbenzene in a mass ratio of 1.7:1 to obtain a mixed solvent.

b. 78.79 parts by weight of a mixed solvent, then 16 parts by weight of benzidine yellow, 5 parts by weight of disperse blue, and 0.21 part by weight of polybutylene succinamide were added, and uniformly mixed to form a mixture.

c. 5 parts by weight of sodium dodecylbenzenesulfonate was added to the mixture and uniformly mixed.

d. The mixture containing the silane coupling agent was dispersed and mixed by a basket mill. The speed of the basket mill was 300 r/min, and the dispersion time was 5 hours.

e. Grinding with a ball mill, the ball mill has a speed of 450 r/min and a grinding time of 18 hours. f. Grinding with an emulsifier, the speed of the emulsifier was 450 r/min, and the grinding time was 4 hours, thereby obtaining a nanopigment composition. Example 7

a. Mixing tetrachloroethylene and diphenylbenzene in a mass ratio of 1.3:1 to obtain a mixed solvent.

b. 80.32 parts by weight of a mixed solvent, then 14 parts by weight of benzidine yellow, 5.5 parts by weight of disperse blue and 0.18 parts by weight of polybutylene succinamide were added, and uniformly mixed to form a mixture.

c. 10 parts by weight of sodium carboxylate was added to the mixture and uniformly mixed. d. The mixture containing the silane coupling agent was dispersed and mixed by a basket mill. The speed of the basket mill was 200 r/min, and the dispersion time was 5 hours.

e. Grinding with a ball mill, the ball mill rotates at 500r/min and the grinding time is 20 hours. f. Grinding with an emulsifier, the speed of the emulsifier was 500 r/min, and the grinding time was 3 hours, thereby obtaining a nanopigment composition.

The nano pigments obtained were subjected to the following tests for the above examples: the viscosity was measured using a BROOKFIELD DV-C digital viscometer, and the viscosity unit was mPa's; the particle size was measured by a Nano ZS particle size analyzer, and the unit of particle size was nm; the nanopigment composition was in the air. After standing for 6 months, the viscosity and particle size were again measured, and the change rate of viscosity and particle size was obtained, thereby obtaining the stability of the nanopigment. The specific test results are shown in Table 1. Comparative Example 1 and Comparative Example 2 are also given in Table 1, the experimental steps of which correspond to Examples 1 and 2, respectively, but the pigments used in Comparative Examples 1 and 2 are Pigment Red 254 of Ciba Corporation, and the surface thereof is not The surfactant is grafted, and other formulations and conditions are the same as in the embodiment of the present invention. Table 1

Mr^a^日会

A silane coupling agent or an anionic surfactant is added in the process, and after dispersion and grinding, the reactive groups on the surface of the pigment are grafted with a silane coupling agent or an anionic surfactant, and the active groups and surfactants on the surface of the pigment are added. By covalent bond or ionic bond, the surfactant on the surface of the pigment not only improves the fluidity and dispersibility of the nanopigment composition, but also makes the viscosity and particle size of the nanopigment composition reach 1.8 ~ 2.2 mPa-s and 65, respectively. ~ 72nm, and can improve the stability of the nano-pigment composition. When the nano-pigment composition is placed in the air for 6 months, the viscosity and particle size change rate are respectively 10 ~ 11% and 0.043 ~ 0.077%. In addition, the method for preparing the nanopigment composition does not require a special preparation environment, and the nanopigment composition can be prepared in the preparation process of the microcapsule, thereby improving process efficiency, saving energy, and reducing cost.

The embodiment further provides an electronic ink microcapsule comprising a crucible wall and a crucible core, and the nano pigment provided by the embodiment is used.

Since the electronic ink microcapsule provided by the embodiment uses the nanopigment composition provided by the present invention, since the stability of the nanopigment composition is high, the stability of the microcapsule is high; and, since the nanopigment composition has good The fluidity and dispersibility, so the electronic ink microcapsule has good electric field responsiveness at low voltage.

In addition, the embodiment further provides an electrophoretic display device, which comprises an electronic ink microcapsule, and the electronic ink microcapsule provided by the embodiment.

The electrophoretic display device provided in this embodiment has good contrast and response time and long service life because the electronic ink microcapsule provided by the embodiment is used.

The above is only an exemplary embodiment of the present invention, and is not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims.

Claims

Claim

A nanopigment composition comprising a pigment, wherein a surface of the pigment is grafted with a surfactant, and the surfactant is a silane coupling agent or an anionic surfactant.

The nanopigment composition according to claim 1, wherein the pigment surface has a reactive group, and the surfactant is grafted by the reactive group.

The nanopigment composition according to claim 1 or 2, wherein the nanopigment composition has a viscosity of 1.8 to 2.2 mPa*s, and the nanopigment composition has a particle size of 65 to 72 nm.

The nanopigment composition according to any one of claims 1 to 3, wherein the anionic surfactant is a multi-branched anionic surfactant or a monobranched anionic surfactant.

The nanopigment composition according to claim 4, wherein the multi-branched anionic surfactant comprises stearic acid or sodium dodecylbenzenesulfonate.

The nanopigment composition according to claim 4, wherein the mono-branched anionic surfactant comprises a carboxylate, a sulfate or a sulfonate.

The nanopigment composition according to any one of claims 1 to 6, which further comprises a dye and a charge control agent.

8. A method of preparing a nanopigment composition, wherein the method comprises the steps of: providing a mixed solvent;

Adding a pigment, a dye, and a charge control agent to the mixed solvent to form a mixture; adding a surfactant to the mixture, and uniformly mixing the surfactant and the mixture, the surfactant being a silane coupling Or an anionic surfactant; dispersing, grinding, adding the mixture of the surfactant such that the surface of the pigment is grafted with the surfactant.

The method of producing a nanopigment composition according to claim 8, wherein the surface of the pigment has a reactive group, and the surfactant is grafted by the reactive group.

The method for producing a nanopigment composition according to claim 8 or 9, wherein the silane coupling agent is added in an amount of 0.1 to 2% by weight based on the mixture.

The method for producing a nanopigment composition according to any one of claims 8 to 10, wherein the anionic surfactant is a multi-branched anionic surfactant or Single-branched anionic surfactant.

The method for producing a nanopigment composition according to claim 11, wherein the multi-branched anionic surfactant or the single-branched anionic surfactant is added in an amount of 0.2 by weight of the mixture. ~ 10%.

The method for producing a nanopigment composition according to claim 11 or 12, wherein the multi-branched anionic surfactant comprises stearic acid or dodecylbenzenesulfonic acid).

The method for producing a nanopigment composition according to claim 11 or 12, wherein the monobranched anionic surfactant comprises a carboxylate, a sulfate or a sulfonate.

The method for producing a nanopigment composition according to any one of claims 8 to 14, wherein the mixed solvent is selected from the group consisting of propylene glycol monoterpene ether acetate, diethylene glycol dioxime ether, 3-ethoxy A mixed solvent of two or more of ethyl propyl propionate, tetrachloroethylene and diphenyl benzene, preferably a mixed solvent of tetrachloroethylene and diterpene benzene.

The method for producing a nanopigment composition according to any one of claims 8 to 15, wherein, in the mixture, the content of the pigment is 10 to 20% by weight, and the content of the dye is 5 -10%, the charge control agent is contained in an amount of from 0.1 to 0.3% by weight, with the balance being a mixed solvent.

The method for preparing a nanopigment composition according to any one of claims 8 to 16, wherein the dispersing comprises dispersing in a sand mill at a rotation speed of 100 to 300 r/min for 1 to 5 hours; This includes grinding with a ball mill and/or emulsifier at 200 ~ 500r/min for 20 ~ 30 hours.

An electronic ink microcapsule comprising a nanopigment composition, wherein the nanopigment composition according to any one of claims 1 to 7 is used as the nanopigment composition.

An electrophoretic display device comprising an electronic ink microcapsule, wherein the electronic ink microcapsule is used as the electronic ink microcapsule according to claim 18.