TW201346416A - Electrophoretic particle, method for preparing electrophoretic particle, electrophoretic slurry composition and electrophoretic display device including the same - Google Patents

Abstract

This disclosure relates to electrophoretic particles including white inorganic particles and a polymer resin layer formed on the surface of the inorganic particles, a method for preparing the electrophoretic particles, an electrophoretic slurry composition including the electrophoretic particles, and an electrophoretic display device using the electrophoretic slurry.

Description

Electrophoretic particle, electrophoretic particle preparation method, electrophoretic slurry composition and composition containing the same Electrophoretic display device

The present invention relates to electrophoretic particles, a method for preparing electrophoretic particles, an electrophoretic slurry composition, and an electrophoretic display device. The present invention relates to an electrophoretic particle capable of achieving high contrast and response reaction rate, and having high bistability and dispersion stability, a method for preparing the electrophoretic particle, an electrophoretic slurry composition, and An electrophoretic display device containing the composition of the electrophoretic slurry.

Electronic paper (digital paper), called E-paper, is an electronic device that can be easily carried and easily brought out when needed, like paper books, traditional newspapers or paper. Magazines can be recorded on top of them, and the function is like paper.

Electronic paper can be a type of electronic display that is flexible and bendable. Compared to existing flat-panel displays, the production cost is lower, and there is no need to distinguish between background lights, so energy efficiency is much higher than that of flat-panel displays.

Electronic paper has high resolution or sharpness and a wide viewing angle, and has a memory function when the text has not completely disappeared or even when no power is supplied.

Due to these advantages, electronic paper can be applied to a wide range of applications, such as e-books and mobile pictures that are thin like paper on the side, self-renewable newspapers, environmentally-friendly paper displays for mobile phones, and disposable TV screens. Electronic wallpapers and the like, so e-paper has great potential in the market.

The electronic paper can be representatively classified into an electrophoretic type, a liquid crystal type, a toner type (QR-LPD), a micro electro mechanical system (MEMS) type, or the like.

In the above version, the electrophoretic pattern is based on electrophoresis in which charged pigment particles float in a dielectric solvent, wherein if a voltage difference is applied between the electrodes facing each other, the charged pigment particles will move toward the opposite electrode by attraction to express Colored or dark.

In electrophoretic displays, commercial technology types include microcapsule-type electrophoretic displays and microcup-type electrophoretic displays that use particles as colored display devices.

A microcapsule electrophoretic display is a display device in which a dispersion containing charged particles, a flowing fluid, and the like are positioned between two electrodes facing each other; and a microcup type electrophoretic display is a display device, A concave unit defined as a partition wall is formed between two electrodes opposed to each other and having charged particles or a charged particle slurry is placed in the concave unit.

It has been previously known that electronic display devices do not have sufficient color rendering performance or contrast to be practically applied in various fields, and cannot ensure the ability to properly maintain an afterimage or for a driving voltage when the driving voltage is eliminated. Reactivity.

Further, in an electrophoretic display device, electrophoretic particles generally used in a flowing fluid are dispersed, however, it has been previously known that they may have significantly different densities depending on the kind of electrophoretic particles, and therefore, if applied together, it may be difficult to ensure electrophoresis. The particles are bi-stable and cannot be stably dispersed in the flowing fluid, and thus aggregation may occur.

Further, it has been previously known that the preparation method of the electrophoretic particles involves a complicated process or a polymerization which requires a long time, and thus is not economically practicable, and its reproducibility is low due to various process conditions or various factors.

It is an object of the present invention to provide electrophoretic particles which have high bistability and dispersion stability in an electrophoretic slurry, and which can achieve high contrast and response rate.

Another object of the present invention is to provide a method for preparing such electrophoretic particles. law.

Still another object of the present invention is to provide an electrophoretic slurry composition comprising the electrophoretic particles.

It is still another object of the present invention to provide an electrophoretic display device that exhibits high contrast and improved visibility to produce high definition text.

The present invention provides an electrophoretic particle comprising a white inorganic particle and a polymer resin layer formed on a surface of the white inorganic particle, the polymer resin layer comprising an aromatic diamine compound residue and An aromatic acyl halide residue.

The present invention also provides a method for preparing an electrophoretic particle, comprising: mixing an aromatic hydrazine-containing organic solvent with a white inorganic particle; and recovering the white inorganic particle from the organic solvent, and recovering the recovered The white inorganic particles are mixed with an aqueous solution containing an aromatic diamine compound.

The invention also provides an electrophoretic slurry composition comprising the electrophoretic particles and a flowing fluid.

The present invention also provides an electrophoretic display comprising two substrates facing each other, an electrophoretic element formed between the two substrates, and the above-described electrophoretic paste composition positioned in the electrophoretic element.

Specific embodiments of the electrophoretic particles, the method for producing the electrophoretic particles, the electrophoretic paste composition, and the electrophoretic display device according to the present invention will be described in detail below.

According to an embodiment of the present invention, there is provided an electrophoretic particle comprising a white inorganic particle and a polymer resin layer formed on a surface of the white inorganic particle, the polymer resin layer comprising an aromatic diamine compound And an aromatic hydrazine halide residue.

Through experiments, the inventors confirmed that the electrophoretic particles obtained by the specific preparation method described below have a lower density, and thus have high bi-stability and dispersion stability in the electrophoretic display slurry, and can be applied to electrophoresis. The present invention has been accomplished by a display device to achieve high contrast and response to reaction rates.

In particular, since the electrophoretic particles comprise a polymer resin layer having the above specific chemical structure, it can have a low density compared to those of electrophoretic particles containing only white inorganic particles. a value, therefore, even if mixed with other kinds of electrophoretic particles, for example, colored particles such as iron oxide, chrome copper (CrCu), carbon black, and the like, according to The density is different, the double stability is not greatly reduced in the electrophoretic slurry, and the particles can be stably dispersed in the flowing fluid without causing aggregation of the particles.

As used herein, "electrophoretic particles" refers to particles capable of having charging characteristics, and by supplying an attractive force of a specific voltage between the electrodes, the electrophoretic particles can move toward the opposite charged electrode, thereby exhibiting color or dark color.

The white inorganic particles refer to inorganic particles having a colored or dark color, which are white or can be visually divided into white, and in a specific example, may include titanium oxide (TiO ₂ ), magnesium oxide (MgO) ), zinc oxide (ZnO), calcium oxide (CaO), zirconium oxide (ZrO ₂ ) or a mixture thereof.

Further, the white inorganic particles may have a maximum diameter of 10 nm to 10 μm, preferably 30 nm to 1 μm, and more preferably 100 nm to 800 nm.

If the maximum diameter of the white inorganic particles is too large, the particle flow rate may be lowered, or the pixel of the display device using the electrophoretic particles may be reduced; if the diameter of the white inorganic particles is too small, the contrast may be greatly lowered.

At the same time, the polymer resin layer is formed on the surface of the white inorganic particles, and more particularly, it may surround the surface of the white inorganic particles.

Further, the polymer resin layer may contain an aromatic diamine compound residue and an aromatic hydrazine halide residue.

As used herein, "residue" refers to a particular moiety or element that is included in a resulting product of the chemical reaction formula when a particular compound is involved in a chemical reaction, and which is derived from a particular compound.

For example, the "aromatic diamine compound residue" and the "aromatic hydrazine halide residue" respectively mean an aromatic diamine compound or an aromatic hydrazine halide group used in the formation process of the polymer resin layer. Partial or repeating components.

As described in the preparation method, after an aromatic oxime halide compound is bonded to the surface of the white inorganic particles, an aromatic diamine compound is reacted therein to provide electrophoretic particles, and thus the aromatic diamine in the polymer resin layer Compound residues and aromatic oxime halide residues can be A guanamine bond.

The aromatic oxime halide group may comprise an aromatic ring substituted with at least two fluorenyl halide groups, which may be a C6-20 aromatic ring substituted with at least two fluorenyl halide groups.

Specific examples of the aromatic hydrazine halide compound may include the compound of the following Chemical Formula 2.

In Chemical Formula 2, Ar ₁ is an C6-20 arylene group, and HaI is a halogen atom such as Chlorine (Cl), Bromine (Br), and Iodine (Idine, I). ).

Further, n is an integer from 2 to 10, and it may be determined according to the number of substituents of Ar ₁ .

The aromatic diamine compound means an aromatic ring substituted with two amine groups, which may contain a compound of the following Chemical Formula 1.

Chemical formula 1 H ₂ NR ₁ -NH ₂

In Chemical Formula 1, R ₁ is an C6-20 arylene group.

Meanwhile, the polymer resin layer may have a thickness of from 1 nm to 50 μm, and preferably from 10 nm to 1 μm.

If the polymer resin layer is too thick, the contrast of the electrophoretic display device using the electrophoretic particles may be lowered; if the polymer resin layer is too thin, the bistableness cannot be maintained due to the high particle density.

As described above, the electrophoretic particles containing the white inorganic particles and the polymer resin layer may have a lower density, for example, a density of 3.9 g/cm ² or less, and preferably 3.0 g/cm ² to A density of 3.8 g/cm ² .

Moreover, the electrophoretic particles may comprise at least two layers of the polymer resin layer as described above.

According to another embodiment of the present invention, there is provided a method for producing an electrophoretic particle, comprising: mixing an organic solvent containing an aromatic hydrazine halide group with a white inorganic particle; and removing the white inorganic particle from the The organic solvent is recovered and the recovered white inorganic particles are mixed with an aqueous solution containing an aromatic diamine compound.

In the step of mixing an organic solvent containing an aromatic fluorenyl halide with a white inorganic particle, an aromatic hydrazine halide compound may be bonded to the surface of the white inorganic particle, and the white inorganic particle is recovered and contains one The aqueous solution of the aromatic diamine compound is mixed, and thus a polymer resin layer is formed on the surface of the white inorganic particles via interfacial polymerization.

According to an embodiment of the present invention, the detailed description of the polymer resin layer is as described above with respect to the electrophoretic particles.

In the preparation method, in particular, the hydrophobic white inorganic particles are reacted with an aromatic sulfonium halide group in an organic solvent, and the white inorganic particles obtained by the reaction are reacted with an aromatic diamine compound contained in an aqueous solvent, and then occur. The interfacial polymerization acts to form a highly reproducible polymer resin layer on the surface of the white inorganic particles in a relatively short period of time.

Specifically, the aromatic cerium halide group in the organic solvent does not mix with the two liquid phases of the aromatic diamine compound in the aqueous solvent, thereby forming an interface, and the aromatic diamine compound and the aromatic diamine compound are The interface reacts to form a polymer, and thus a polymer resin layer is formed on the surface of the white inorganic particles.

Interfacial polymerization is a reversible reaction between two liquid phases, wherein the equivalency between the reaction groups is as important as in the equilibrium polycondensation and is higher. The weight average molecular weight polymer compound can be composed in a short time.

Further, the step of mixing the aromatic hydrazine-containing organic solvent with the white inorganic particles and mixing the recovered white inorganic particles with an aromatic diamine compound can be carried out in an hour at 20 ° C to 40 ° C, respectively. .

Mixing the aromatic solvent-containing organic solvent with the white inorganic particles The step can be carried out by adding an aromatic hydrazine halide to the organic solvent and stirring.

The apparatus and method which can be used for stirring are not particularly limited, and for example, the stirring can be carried out at a rate of 100 rpm to 1,000 rpm at 20 ° C to 40 ° C for 10 minutes to 1 hour.

The organic solvent which can be used in the present invention is not particularly limited, and specific examples thereof may include, for example, benzene, chloroform, diethylether, toluene, hexane, carbon tetrachloride. An organic solvent of (carbon tetrachloride) and the like; and, for example, decahydronaphthalene (DECLIN), 5-ethylidene-2-norbornene, fatty oils Hydrocarbons compounds of paraffin oil (trade name Isopar G, Isopar L, Isopar M and the like) and analogues thereof; for example, toluene, xylene, phenyl xylyl Aromatic hydrocarbons of phenylxylylethane, dodecylbenzene, alkylnaphthalene and the like; for example, perfluorodecalin, perfluorotoluene (perfluorodecalin) Perfluorotoluene), perfluoroxylene, dichlorobenzotrifuoride, 3,4,5-trichlorobenzotrifuoride, chloropentafluoro-benzene Dichloropurine (dichlorononane), a halogenated solvent of pentachlororbenzene and the like; a perfluoro solvent; for example, a perfluoropolyalkylether-containing low molecular weight halogen solvent containing a polymer, and Its analogues.

The concentration of the aromatic sulfonium halide group in the organic solvent can be controlled depending on the conditions of the reaction, stirring, and the like, and for example, it may be between 0.1% by weight and 20% by weight.

Meanwhile, the step of mixing the recovered white inorganic particles with an aqueous solution containing an aromatic diamine compound can be carried out by adding an aromatic diamine compound to an aqueous solution and stirring.

The apparatus and method which can be used for stirring are not particularly limited, and for example, the stirring can be carried out at a rate of 100 rpm to 1,000 rpm at 20 ° C to 40 ° C for 10 minutes to 1 hour.

An aqueous solution means water (H ₂ O) or a solution containing water and a water-soluble substance.

The example of the solution of the water-soluble substance is not particularly limited, and it may contain various water-soluble salts or water-soluble substances which do not change the characteristics of the aromatic diamine compound.

Moreover, in the interfacial polymerization reaction, hydrochloric acid can be produced by a polycondensation reaction. Hydrochloric acid, and hydrochloric acid can be reacted with a Lewis base such as a diamine compound and the like to lower the reaction rate.

Therefore, the aqueous solution may further contain an alkali compound such as sodium carbonate (Na ₂ CO ₃ ), sodium cyanide (NaCN), sodium hydroxide (NaOH), and the like.

The concentration of the aromatic diamine compound in the aqueous solution can be appropriately controlled depending on the conditions of the reaction, stirring, and the like, and for example, it may be between 0.1% by weight and 20% by weight.

The details of the white inorganic particles, the aromatic diamine compound, the aromatic oxime halide group, and the polymer resin layer are as described above.

After the aromatic hydrazine halide-containing organic solvent is mixed with the white inorganic particles, the mixed solution may be filtered to recover white inorganic particles having an aromatic hydrazine halide group attached to the surface.

Furthermore, after the recovered white inorganic particles are mixed with an aqueous solution containing an aromatic diamine compound, the recovered white inorganic particles are white inorganic particles having an aromatic hydrazine halide group attached to the surface thereof, and the mixed aqueous solution can be passed through. It is filtered to obtain electrophoretic particles in which a specific polymer resin layer is formed on the surface of the white charged particles.

Meanwhile, the method of preparing the electrophoretic particles may further comprise the steps of recovering white inorganic particles from the aqueous solution, and neutralizing the recovered white inorganic particles.

During the interfacial polymerization, a specific polymer resin layer is formed on the surface of the white charged particles, and hydrochloric acid may be generated. If the electrophoretic particles contain hydrochloric acid, the stability of the electrophoretic slurry or the electrophoretic display device Performance may be reduced.

Thus, the preparation of the electrophoretic particles can be neutralized using a base compound such as sodium carbonate (Na ₂ CO ₃ ), sodium cyanide (NaCN), sodium hydroxide (NaOH), and the like.

Specifically, the neutralization step of the recovered inorganic particles may comprise mixing the recovered white inorganic particles with an aqueous solution comprising at least one selected from the group consisting of sodium carbonate (Na ₂ CO ₃ ) and sodium cyanide (NaCN). And a compound of the group consisting of sodium hydroxide (NaOH).

Further, the method of preparing the electrophoretic particles may further comprise drying the obtained electrophoretic particles.

The organic solvent or aqueous solution contained in the electrophoretic particles can be removed through the drying step.

The specific method and apparatus which can be used for drying are not particularly limited, and apparatuses and methods generally used in the preparation method of electrophoretic particles can be used, for example, drying by hot air or heat source or freeze drying and the like can be used. method.

Further, in the method for producing an electrophoretic particle, the step of mixing an organic solvent containing an aromatic fluorene halide group with white inorganic particles and the step of recovering white inorganic particles from an organic solvent, and the recovered inorganic particles are repeated When the aromatic diamine compound is mixed at least twice, a polymer resin layer of two or more layers which is clearly distinguishable is provided on the electrophoretic particles, and the polymer resin layer is formed on the surface of the white inorganic particles as described above.

Meanwhile, according to another embodiment of the present invention, the present invention provides an electrophoretic slurry composition comprising the electrophoretic particles described above and a flowing fluid.

As shown in the results of the study, the inventors have determined that the electrophoretic slurry containing the electrophoretic particles having the above structure can have high bi-stability and dispersion stability, and the electrophoretic slurry can be applied to an electrophoretic display device to achieve high contrast and response. reaction speed.

As used herein, "electrophoretic slurry" means a dispersed phase material containing a flowing fluid, electrophoretic particles, and optionally other components such as additives such as dyes, stabilizers, dispersants, or the like. Wherein the component can be reacted or driven at a particular drive voltage.

The flowing fluid may be a solvent having a viscosity of 20 cP or less, more preferably a hydrocarbon-baesd solvent having a viscosity of 20 cP or less, but is not limited thereto.

A solvent having a dielectric constant of 2 to 30 can be used as the flowing fluid.

Examples of the flowing fluid may include: hydrocarbon compounds such as decahydronaphthalene (DECLIN), 5-ethylidene-2-norbornene, and fatty acids ( Fatty acids), paraffin oil (trade name Isopar G, Isopar L, Isopar M and the like); aromatic hydrocarbons such as toluene, xylene, phenyl xylene Phenyllylethane, dodecylbenzene, alkylnaphthalene And analogs thereof; halogenated solvents such as perfluorodecalin, perfluorotoluene, perfluoroxylene, dichlorobenzotrifuoride, 3, 4, 5 - 3,4,5-trichlorobenzotrifuoride, chloropentafluoro-benzene, dichlorononane, pentachlororbenzene and the like; perfluoro Solvent; a low molecular weight halogen solvent containing a polymer such as perfluoropolyalkylether and the like, but is not limited thereto.

The electrophoretic paste composition may further comprise at least one colored particle selected from the group consisting of iron oxide, chrome copper (CrCu), and carbon black.

The flowing fluid can be used in a suitable content that takes into account the amount of electrophoretic particles, and the electrophoretic particles can be suitably adjusted depending on the additional additives used.

Further, the preparation method of the electrophoretic slurry composition is not particularly limited, and a known method of preparing a generally charged particle slurry can be used without particular limitation.

For example, the electrophoretic particles and the flowing fluid can be mixed by a general method to form a uniformly dispersed electrophoretic slurry, such as: grinding, milling, attating, microfluidizing, or Ultrasonification and similar methods.

The electrophoretic slurry may further comprise at least one additive selected from the group consisting of a charge control agent and a dispersion stabilizer.

Meanwhile, according to still another embodiment of the present invention, an electrophoretic display includes: two substrates facing each other; an electrophoretic element formed between the two substrates; and positioning in the electrophoretic element as described above Electrophoretic slurry composition.

Due to the high stability and reactivity of the electrophoretic slurry containing special electrophoretic particles, the electrophoretic display device can achieve good reactivity and bi-stability when supplied with a driving voltage, and can exhibit high contrast and improved Visibility to produce high definition text and images.

The "substrate" refers to both sides of an electrophoretic display device containing an electrophoretic element, for example, a base side constituting upper/lower sides.

Various layers or structures, or electrodes for electrophoresis and the like can be formed on one side of the substrate or included in the substrate.

Thus, the substrate can comprise a base layer, a conductive substrate layer, an electrode layer, and the like.

The base layer is not particularly limited as long as it can be used as a substrate or a substrate of a display device, for example, a thermoplastic resin or a thermosetting resin, or a polyethylene terephthalate (PET) or a polypropylene eye can be used. (polyacrylonitrile, PAN), polyimide (PI), glass and the like.

The conductive underlayer may comprise a conductive material generally used in display devices, and is not particularly limited, and for example, a carbon nanotube (CNT), a conductive polymer, and the like may be used.

In the electrode layer, there is no particular limitation in the known electrode materials which can be used in the display device, but it is preferable that at least one of the electrode materials contained in the two substrates is a transparent electrode material such as indium oxide. Tin (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), indium zinc oxide (IZO), and the like.

The electrophoretic element refers to an element in which charged particles are moved to an electrode by attraction force to exhibit color or darkness if a voltage difference is applied between the electrodes opposed to each other.

The electrophoresis element may comprise the electrophoretic slurry described above.

The shape or structure of the electrophoretic element is not particularly limited, and for example, it may comprise a microcapsule or a microcup structure.

The "microcup" refers to a cup-shaped recess formed in an electrophoretic display device, for example, it may be a space surrounded by two electrodes opposed to each other, and a partition wall formed between the electrodes.

"Microcapsule" means a spherical or elliptical closed container formed in an electrophoretic display device and having a diameter of micrometer (μm).

The size and shape of the microcup can be defined by the partition wall formed in the electrophoretic element, and can be appropriately controlled according to the characteristics, size, and the like of the electrophoretic display device to be manufactured.

For example, the partition wall may have a height of 10 μm to 100 μm, 5 μm A thickness of up to 50 μm, as well as cross-sections of various shapes, such as rectangles, squares, trapezoids, and the like, are not limited thereto.

The microcups may have a planar shape such as a circle, a triangle, a quadrangle, an ellipse or various polygons.

The size and material of the microcapsules can be controlled according to the characteristics of the display device to be manufactured, for example, each of the microcapsules may have a circular or elliptical shape having a longest diameter of 10 μm to 200 μm.

The microcapsule may be combined with a substrate by an adhesive or an organic solvent to form an electrophoretic element, but is not limited thereto, and may be used for any shape of electrophoresis element known to microcapsule electrophoretic display devices. There are no specific restrictions.

The electrophoretic plasma composition as described above is positioned in the electrophoretic element, that is, the flow of electrophoretic particles may be included in the particular flowing fluid.

The volume ratio of the fluid flowing in the electrophoretic slurry may be 40% to 95%.

According to the present invention, an electrophoretic particle is provided, which can achieve high contrast and response rate, and has high bistable stability and dispersion stability in an electrophoretic slurry, a method for preparing the electrophoretic particles, and a method for preparing the electrophoretic particles. An electrophoretic slurry composition, and an electrophoretic display device comprising the electrophoretic slurry composition.

1 shows a scanning electron microscope (SEM) image of the electrophoretic particles obtained in Example 1, and FIG. 2 shows a scanning electron microscope image of the electrophoretic particles obtained in Example 2; 3 shows a scanning electron microscope image of the electrophoretic particles obtained in Example 3; FIG. 4 shows a scanning electron microscope image of the electrophoretic particles obtained in the comparative example; FIG. 5 shows Example 1 and comparison A graph of the results of the bi-stability evaluation of the electrophoretic particles of the sexual example, such as the measurement method of Experimental Example 2; and Figure 6 shows the supply voltage to the use of Examples 1 to 3 and the comparative examples. A picture of a unit of an electrophoretic display device manufactured by electrophoretic particles.

The invention is described in detail with reference to the following examples. However, the examples are only intended to illustrate the invention and are not intended to limit the invention.

Example: Preparation of Electrophoretic Particles Example 1

Trimesoyl chloride (TMC) was dissolved in paraffin oil Isopar G at a concentration of 1% by weight, and the solution was stirred at 250 rpm at room temperature.

30 g of titanium oxide (TiO ₂ ) was added to the above-mentioned paraffin oil Isopar G solution containing TMC dissolved therein, and the mixture was stirred at 400 rpm for 30 minutes at room temperature.

After the completion of the stirring, the paraffin oil Isopar G solution was filtered to recover TiO ₂ .

Next, m-phenylene diamine (MPD) was dissolved in pure water (H ₂ O) at a concentration of 1% by weight, and the mixture was stirred at room temperature at 250 rpm.

The filtered recovered TiO _{2 was} added to an aqueous solution in which the MPD was dissolved, and the mixture was stirred at 400 rpm for 30 minutes at room temperature.

After the completion of the stirring, the aqueous solution was filtered to recover TiO ₂ .

The recovered TiO _{2 was} then introduced into an aqueous solution of sodium carbonate (Na ₂ CO ₃ ) (concentration: 0.5% by weight), and the mixture was stirred at 400 rpm for 30 minutes at room temperature.

After the completion of the stirring, the aqueous Na ₂ CO ₃ solution was filtered to recover TiO ₂ , and the recovered TiO _{2 was} freeze-dried to obtain electrophoretic particles.

Example 2

The method of obtaining electrophoretic particles in Example 2 was the same as in Example 1 except that the concentration of TMC dissolved in the paraffin oil Isopar G was changed to 3% by weight, and the concentration of the MPD dissolved in the aqueous solution was changed to 3% by weight.

Example 3

Example 3 obtained electrophoresis except that the concentration of TMC dissolved in paraffin oil Isopar G was changed to 5% by weight, and the concentration of MPD dissolved in aqueous solution was changed to 5% by weight. The method of particles is the same as in Example 1.

Comparative example: preparation of electrophoretic particles

M-phenylene diamine (MPD) was dissolved in pure water at a concentration of 1% by weight, and the mixture was stirred at room temperature at 250 rpm.

30 g of titanium oxide (TiO ₂ ) was added to the aqueous solution in which the MPD was dissolved, and the mixture was stirred at 400 rpm for 30 minutes at room temperature.

After the completion of the stirring, the aqueous solution was filtered to recover TiO ₂ .

Next, Trimesoyl chloride (TMC) was dissolved in paraffin oil Isopar G at a concentration of 1% by weight, and the mixture was stirred at room temperature at 250 rpm.

The filtered recovered TiO _{2 was} added to a paraffin oil ISOPAR G solution containing TMC dissolved therein, and the mixture was stirred at 400 rpm for 30 minutes at room temperature.

After the completion of the stirring, the paraffin oil Isopar G solution was filtered to recover TiO ₂ .

Then, the filtered TiO _{2 was} introduced into an aqueous solution of sodium carbonate (Na ₂ CO ₃ ) (concentration: 0.5% by weight), and the mixture was stirred at 400 rpm for 30 minutes at room temperature.

After the completion of the stirring, the aqueous Na ₂ CO ₃ solution was filtered to recover TiO ₂ , and the recovered TiO _{2 was} freeze-dried to obtain electrophoretic particles.

Experimental example Experimental Example 1: Measurement of characteristics of electrophoretic particles

The electrophoretic particles obtained by the examples and the comparative examples were observed by a scanning electron microscope (SEM) in the following manner, and their zeta potential and specific gravity were measured.

(1) Scanning electron microscope observation

The electrophoretic particles obtained by the examples and comparative examples were observed using a scanning electron microscope instrument (Model S-4300, Hitachi, Japan) at a magnification of 40,000 times.

As shown in FIGS. 1 to 3, it was confirmed that the polymer resin layers of Examples 1 to 3 were formed on the surface of the electrophoretic particles.

On the contrary, the polymer resin layer is not formed in the comparative example electrophoretic particles. On the surface, it is therefore confirmed that the electrophoretic particles of the comparative example are not different from the general cerium oxide.

(2) Measurement of specific gravity

The true specific gravity of the electrophoretic particles obtained from the examples and comparative examples was measured using a true pycnometer (Micromeritics Instruments, Inc., USA).

(3) Measurement of the boundary potential

The surface charge was measured using ELS-8000 (Otsuka Electronics Co., Ltd., Japan) to calculate the boundary potential of the electrophoretic particles.

The measurement results of true specific gravity and bound potential are summarized in Table 1 below.

As shown in Table 1, the results confirmed that the electrophoretic particles of Examples 1 to 3 have lower specific gravity and higher boundary potential than the electrophoretic particles of the comparative example.

The results of formation of the polymer resin layer on the surface of the electrophoretic particles from Examples 1 to 3 are shown in the SEM image. When the polymer resin layer is formed, the specific gravity of the electrophoretic particles becomes lower due to the thickness of the polymer resin layer, and the boundary potential becomes higher.

In the comparative example, the results confirmed that the polymer resin layer was not formed on the surface of the titanium dioxide, possibly because the hydrophobic titanium dioxide surface did not react with the aromatic mercapto compound dissolved in the hydrophilic solution, and the interfacial polymerization was not Will occur on the surface of titanium dioxide.

Experimental Example 2: Evaluation of Bi-stability of Electrophoretic Slurry

The electrophoretic particles obtained in the examples and comparative examples were dispersed in a hydrocarbon-based solvent at a ratio of 5 to 1, to prepare an electrophoretic particle slurry, the hydrocarbon-based solvent paraffin oil Isopar G A 1 to 1 solution relative to the organic halide (Halocarbon) system.

The electrophoretic slurry was injected into an indium tin oxide (ITO) unit (width 40 mm × length) 45 mm × height 80 μm), in which current flows from the upper/lower plate, a voltage of +15 V is supplied to the upper/lower portions to maximize whiteness, and then the level of whiteness reduction is measured, thereby evaluating the bistable stability.

As shown in Fig. 5, the results confirmed that the bistable stability between the case of using the electrophoretic particles of Examples 1, 2, and 3 and the case of using the electrophoretic particles of the comparative example was significantly different.

In particular, as a result, it was confirmed that the whiteness of the electrophoretic particles using the example 1 in the ITO unit was stably maintained for 2 minutes, and in the examples 2 and 3, the whiteness was decreased after 1 minute.

On the contrary, in the ITO unit using the electrophoretic particles of the comparative example, although the initial luminance (L*) value was high, it gradually began to decrease after 20 seconds, and became black after 2 minutes.

This result is considered to be because the electrophoretic particles of the comparative example have lower dispersion and bi-stability in the ITO unit, so it can be confirmed that the white inorganic particles having the polymer resin layer on the surface can exhibit compared with the general electrophoretic particles. Good performance.

Experimental Example 3: Performance Measurement of Electrophoretic Display Devices

The driving characteristics of the electrophoretic display device containing the electrophoretic slurry obtained by using the electrophoretic particles of the examples and comparative examples were evaluated below.

(1) Measurement of contrast

The electrophoretic particles obtained in the examples and comparative examples were dissolved in a hydrocarbon-based solvent at a ratio of 5 to 1 to prepare an electrophoretic particle slurry in which Isopar G was compared with an organic halide (Halocarbon). It is a 1 to 1 solution.

The electrophoretic slurry was injected into an indium tin oxide (ITO) unit (width: 40 mm × length 45 mm × height: 80 μm), in which current flowed from the upper/lower plate, and voltages of +15 V and -15 V were supplied to the upper/lower portions, and then white was measured. The absolute value of the maximum value of the reflectance and the absolute value of the minimum value of the black reflectance are divided and converted into a ratio to determine the contrast.

In particular, the black color exhibited by the ITO unit was measured using a Chroma Meter CS-100A luminance meter (Kodak Minolta, Japan) to obtain a luminance (L) value, which is relative to A standard white plate (100 cd/m ² ) made of barium sulfate was used to calculate the L* value.

(2) Measurement of response rate

By the same method as the contrast, the electrophoretic slurry was injected between the upper/lower plates of the ITO, supplied with voltages of +15 V and -15 V, and the time taken to reach the minimum of white luminosity and the minimum of black luminosity was measured.

The measured contrast and response rates are summarized in Table 2 below.

As shown in Table 2, it was confirmed that the ITO unit fabricated using the electrophoretic particles of Examples 1 to 3 and the comparative examples exhibited a contrast and a response rate exceeding a certain degree.

However, as described above, when the electrophoretic particles of the comparative example are used, it is difficult to sufficiently ensure dispersion stability and bi-stability, and thus an electrophoretic display using the exemplary electrophoretic particles can exhibit better performance.

Claims (20)

An electrophoretic particle comprising: a white inorganic particle; and a polymer resin layer formed on a surface of the white inorganic particle, wherein the polymer resin layer comprises an aromatic diamine compound residue and a Aromatic acyl halide residue. The electrophoretic particle according to claim 1, wherein the white inorganic particle comprises at least one selected from the group consisting of titanium oxide (TiO ₂ ), magnesium oxide (MgO), zinc oxide (zinc) Oxide, ZnO), calcium oxide (CaO), and zirconium oxide (ZrO ₂ ). The electrophoretic particle according to claim 1, wherein the white inorganic particle has a maximum diameter of 10 nm to 10 μm. The electrophoretic particle according to claim 1, wherein the aromatic diamine compound residue and the aromatic hydrazine halide residue are linked via a guanamine bond. The electrophoretic particle according to claim 1, wherein the aromatic diamine compound comprises a compound of the formula 1: Chemical formula 1 H ₂ NR ₁ -NH ₂ wherein, in the chemical formula 1, R ₁ is C6-20 Arylene group. The electrophoretic particle of claim 1, wherein the aromatic fluorenyl halide comprises a C6-20 aromatic ring substituted with at least two fluorenyl halides. The electrophoretic particle according to claim 1, wherein the polymer resin layer has a thickness of from 1 nm to 50 μm. The electrophoretic particle according to claim 1, wherein the electrophoretic particle has a density of 3.9 g/cm ² or less. A method for preparing an electrophoretic particle, comprising: mixing an organic solvent containing an aromatic cerium halide group with a white inorganic particle; and recovering the white inorganic particle from the organic solvent, and recovering the recovered white inorganic particle It is mixed with an aqueous solution containing an aromatic diamine compound. The method for producing an electrophoretic particle according to claim 9, wherein the organic solvent containing the aromatic fluorenyl halide is mixed with the white inorganic particles and the recovered white inorganic particles are contained in one The step of mixing the aqueous solution of the aromatic diamine compound is carried out at 20 ° C to 40 ° C for 1 hour, respectively. The method for producing an electrophoretic particle according to claim 9, further comprising recovering the white inorganic particles from the aqueous solution, and neutralizing the recovered white inorganic particles. The method for preparing an electrophoretic particle according to claim 11, wherein the step of neutralizing the recovered white inorganic particles comprises mixing the recovered white inorganic particles with an aqueous solution, and the aqueous solution comprises At least one compound selected from the group consisting of sodium carbonate (Na ₂ CO ₃ ), sodium cyanide (NaCN), and sodium hydroxide (NaOH). An electrophoretic slurry composition comprising the electrophoretic particles as described in claim 1 and a flowing fluid. The electrophoretic slurry composition according to claim 13, further comprising at least one selected from the group consisting of iron oxide, chrome copper (CrCu) and carbon black. Colored particles. The electrophoretic slurry composition of claim 13, wherein the flowing fluid has a viscosity of 20 cP or less. The electrophoretic slurry composition of claim 13, wherein the flowing fluid comprises a dielectric constant of from 2 to 30. The electrophoretic slurry composition according to claim 13, wherein the flowing flow system comprises at least one selected from the group consisting of decahydronaphthalene (DECLI N) and 5-ethylidene-2-norborene (5). -ethylidene-2-norbornene), fatty oils, paraffin oil, toluene, xylene, phenylxylylethane, dodecylbenzene Dodecylbenzene, alkylnaphthalene, perfluorodecalin, perfluorotoluene, perfluoroxylene, dichlorobenzotrifuoride, 3,4,5-trichloro Trifluorotoluene (3,4,5-trichlorobenzotrifuoride), chloropentafluoro-benzene, dichlorononane, pentachlororbenzene, perfluoro solvent, and perfluoropolyalkyl Dissolution of a group consisting of perfluoropolyalkylether Agent. The electrophoretic slurry composition according to claim 13, further comprising at least one additive selected from the group consisting of a charge control agent and a dispersion stabilizer. An electrophoretic display device comprising: two substrates facing each other; an electrophoretic element formed between the two substrates; and an electrophoretic paste composition as claimed in claim 13 in the electrophoretic element. The electrophoretic display device of claim 19, wherein the electrophoretic element comprises a microcell or a microcup.