KR100473807B1 - Organic compound coated particles for electrophoretic displays and method for forming the same - Google Patents

Abstract

Disclosed are charged particles for an electrophoretic display uniformly coated with an organic compound having a substituent bonded to the terminal so as to have high mobility and reflectance and excellent bistable stability, and a method of manufacturing the same. The charged particles for electrophoretic display according to the present invention consists of a core made of inorganic oxide particles and a core shell made of an organic compound coated so as to spherically surround the core. In order to produce charged particles for electrophoretic displays having such a structure, a colloidal solution in which inorganic oxide particles are dispersed in a solvent is formed. A homogeneous mixture of the organic compound having a functional group and the colloidal solution is formed. The temperature of the mixture is lowered to form crystals coated with organic compounds on the surface of the inorganic oxide particles.

Description

Charged particles for electrophoretic displays coated with organic compounds and manufacturing method thereof {Organic compound coated particles for electrophoretic displays and method for forming the same}

TECHNICAL FIELD The present invention relates to electrophoretic displays (electronic paper), and more particularly, to charged particles, which are an important element of an electronic ink required for constructing an electrophoretic display, and a manufacturing method thereof.

The electrophoretic display using the electrophoresis phenomenon is an electronic display that applies the phenomenon that charged particles move when an electric field is applied between anodes, and is an electronic book, an electronic newspaper, an electronic magazine, an electronic book, and a mobile. It can be applied to a display such as an information display medium of a communication device.

The electrophoretic phenomenon refers to a phenomenon in which charged particles move when an electric field is applied. When electrophoresis occurs in a fluid, charged particles are determined by viscous drag, charge, dielectric properties of the fluid, and magnitude of applied electric field. It will move at the velocity it becomes.

Such electrophoretic displays determine color using particles with one or more colors dispersed in dielectric liquids of different colors. That is, when an electric field is applied to particles having one or more colors, the charged particles move toward the electrode having the opposite sign as the electric field. The result is a visual observation of the change in color.

Displays using electrophoresis have bistable. That is, even after the applied electric field is removed, the color before the electric field is removed is maintained. However, the display using the electrophoresis phenomenon has a problem in stability. That is, by making the density of the charged particles in the fluid and the density of the fluid the same, the precipitation of the charged particles can be prevented, but the problem caused by the agglomeration of the charged particles for a long time cannot be solved. In particular, the movement of two particles of more than one color by electrophoresis causes more serious problems. This problem causes the display to deteriorate.

To solve this problem, E-ink of the United States proposed a display using electrophoretic phenomena by placing charged particles and fluid in a capsule. Electrophoretic displays in the form of capsules require the proper interaction of several different types of materials and methods. That is, materials such as polymerizable binders, capsule films, charged particles, and fluids must all be chemically compatible.

However, in the conventional electrophoretic display, in order to form charged particles operating in the microcapsule, the specific gravity between the charged particles of two colors and the dielectric fluid must be kept the same, and the aggregation between the two charged particles is prevented, Physical and chemical treatments for charge attachment are required to have electrophoretic mobility. This involves a complex process of two or three steps to introduce a functional group that introduces white after chemical, physical polymer coating or polymer ball formation and facilitates the attachment of charge control agents.

An object of the present invention is to solve the above problems in the prior art, having the same specific gravity as dielectric fluid, at the same time having a high mobility and bi-stable, charging for electrophoretic display that can solve the problem of aggregation between two charged particles To provide particles.

Another object of the present invention is to provide a method for producing a charged particle for an electrophoretic display, which can produce a charged particle having high mobility and bistable stability as an inexpensive and simple process as a charged particle for constituting an electrophoretic display.

In order to achieve the above object, the electrophoretic display charging particles according to the present invention is a core composed of inorganic oxide particles, coated with a spherical shape around the core and an organic compound having a substituent bonded to the terminal It consists of a core shell. The charged particles for electrophoretic display according to the present invention have a uniform mobility of 100 µm ² / V · sec or more under an electric field.

In order to achieve the above another object, in the method for producing charged particles for an electrophoretic display according to the present invention, a colloidal solution in which inorganic oxide particles are dispersed in a solvent is formed. A homogeneous mixture of an organic compound having a substituent bonded to the terminal and the colloidal solution is formed. The temperature of the mixture is lowered to form crystals coated with the organic compound on the surface of the inorganic oxide particles.

The colloidal solution may include the inorganic oxide particles added in an amount of 1 to 20% by weight based on the total weight of the solvent. In addition, the colloidal solution may further include a dispersant added in an amount of 0.1 to 10% by weight based on the total weight of the inorganic oxide particles.

Preferably, the inorganic oxide particles may be made of Ti oxide, Zn oxide, Mg oxide, Zr oxide, Br oxide, Al oxide, Si oxide, Cr oxide, Co oxide, Cu oxide, Fe oxide and the like. For example, the inorganic oxide particles may be formed of TiO ₂ , ZnO, MgO, ZrO, BaO, Al ₂ O ₃ , SiO ₂ , Cr ₂ O ₃ , Co ₃ O ₄ , CuO, and Fe ₂ O ₃ . Can be selected.

The inorganic oxide particles may be hydrophilic or lipophilic. When the inorganic oxide particles are hydrophilic, a water-soluble solvent having a solubility parameter of 20 to 40 δ (SI) is used as the solvent, and when the inorganic oxide particles are lipophilic, the dissolution constant is 14 to 20 as the solvent. A water-insoluble solvent having δ (SI) is used. Preferably, the inorganic oxide particles may be made of hydrophilic titanium oxide or lipophilic titanium oxide. When the said inorganic oxide particle consists of hydrophilic titanium oxide, it is preferable to use the water-soluble solvent chosen from the group which consists of water, alcohols, ethylene glycol, and mixtures thereof as a solvent, for example. In addition, when the inorganic oxide particles are made of lipophilic titanium oxide, as a solvent, for example, halogenated hydrocarbons, halogenated hydrocarbon oil (trade name "halocarbon", product of Halogenated hydrocarbon Inc.), galden (Galden, Ausimont company), It is preferable to use a water-insoluble solvent selected from the group consisting of isopar (manufactured by Exxon Co.) series materials and mixtures thereof.

In the method for producing charged particles for an electrophoretic display according to the present invention, the method includes dispersing the inorganic oxide particles in the solvent using ultrasonic waves to form the colloidal solution.

In addition, in the method for producing charged particles for an electrophoretic display according to the present invention, in order to form a uniform mixture of the organic compound and the colloidal solution, first, the colloidal solution is at a temperature above the melting point of the organic compound, preferably 70 Heat to a temperature of ˜130 ° C. The organic compound is added to the heated colloidal solution. Thereafter, the colloidal solution to which the organic compound is added is stirred.

The organic compound may be added in an amount of 10 to 100% by weight based on the total weight of the inorganic oxide particles.

Preferably, the organic compound is a carboxylic acid (-COOH), amide (-CONH ₂ ), amine (-NH ₂ ), alcohol (-OH), aldehyde (-CHO), ester which can react with a charge control agent at the end (-COOR), nitrile (-CN), thiol (-SH), sulfonic acid and less than (-SO ₃ H) and the substituents, such as are partially bonded to, a melting point of 60 ℃ comprises a body of organic compounds.

Examples of those organic compounds usable for producing positively charged particles include montan-based natural waxes, carboxylic acid-based synthetic waxes, polyethylene-based synthetic waxes, polypropylene-based synthetic waxes, and carboxylic acids partially bonded to terminals; Polymer wax. Among these, S-wax, PE wax, ethylene-acrylic acid wax, ethylene-vinylacetate and the like are particularly preferably used.

Further examples of the organic compound that can be used to prepare negative charged particles include synthetic waxes having basic functional groups partially bonded to amides or amines at the terminals.

In addition, the method for preparing charged particles for an electrophoretic display according to the present invention may further include separating and purifying the crystal, and attaching a charge control agent to the crystal surface.

The charge control agent may be made of metal soap, OLOA-based, Ganex-based, or a mixture thereof.

Preferable examples of the charge control agent consisting of metal soap include Co-naphthenate, Ca-naphthenate, Cu-naphthenate, Mn-naphthenate, Zn-naphthenate, Fe-naphthenate, Ba -Stearate, Al-Stearate, Zn-Stearate, Cu-Stearate, Pb-Stearate, Cr-Stearate, Fe-Stearate, Ba-Octoate, Al-Octoate, Ca-Octoate, Co -Octoate, Mn-octoate, Pb-octoate, Zr-octoate, Zn-octoate and the like.

In the colloidal solution formation step and the charge control agent attachment step, a surfactant having a hydrophile lipophile balance (HLB) of 3 or more may be used as a dispersant and a stabilizer. For example, when using a hydrophilic solvent, byk-190, -183 or Tween-based surfactant is used as the dispersant and stabilizer. In the case of using a lipophilic solvent, byk-110, -161, -183, or Tween, Span, OLOA series (manufactured by Chevron Oronite Inc.), Ganex series ( Surfactant from ISP Inc. is used.

According to the present invention, after coating the inorganic oxide particles with an organic compound having a partially bonded organic compound having a substituent capable of reacting with the charge control agent at the end to facilitate the attachment of the charge control agent, a charge control agent having an ionic charge such as metal soap is applied. Adheres to the coated particles. By adjusting the amount of the organic compound added, it is possible to produce particles dispersed in a uniform size, thereby providing uniform mobility, and uniformly coating the organic compound on the inorganic particles, thereby providing charged particles having high reflectance and bistable stability. It can be manufactured cheaply and simply.

Next, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing the main configuration of the microcapsule-type electrophoretic display to which the charged particles produced by the method according to the invention is applied.

Referring to FIG. 1, the microcapsule type electrophoretic display consists of millions of microcapsules 1, each microcapsule 1 being capable of responding to an applied voltage to represent an image. The charged particles 3 are included. The charged particles 3 consist of a core made of inorganic oxide particles and a core shell made of an organic compound coated so as to spherically surround the core. The charged particles 3 for electrophoretic display according to the present invention have a uniform mobility of 100 µm ² / V · sec or more under an electric field. The optical contrast ratio consists mainly of the movement of charged particles in the dye fluid 2. For example, when the charged particles move toward the viewer, the charged particles scatter the incident light to show the color of the particles. At this time, white is shown when the charged particles are white particles, and black when it is black particles. As the charged particles move away from the viewer, the incident light is scattered or absorbed by the dye fluid. At this time, if the dye fluid is black, it absorbs all the light and becomes black. If the dye fluid is blue, the blue light is reflected by reflecting blue light. Thus, a visual contrast ratio can be achieved.

In order to use inorganic oxide particles in an electrophoretic display, the following functionality must be imparted. In other words, in order to maintain phase stability in the absence of a power source, the dye fluid and particle density must be the same, and in order to respond to an applied voltage, a charge control agent must be attached to the particles, and the reaction between the particles and the dye fluid is prevented. Inorganic oxide particles should be coated with suitable organic materials that may be used. Therefore, such organic coatings are one of the important process elements for producing electrophoretic displays.

In order to satisfy the above conditions, the electrophoretic display charging particles according to the present invention is coated with a core made of inorganic oxide particles as described above, spherical surrounding the core and attached with a charge control agent. It consists of a core shell made of organic compounds. In the production of charged particles having such a configuration, in the method for producing a charged particle for electrophoretic display according to the present invention, in order to use a cheaper and simpler process than the existing process, a functional group for introducing a charge control agent, that is, a charge control agent An organic compound having a substituent which can be reacted with a terminal already bonded to the terminal is used as a physical coating agent. In addition, metal soaps having an ionic charge are used as charge control agents to increase the mobility and stability of the particles under an electric field.

2 is a flowchart for explaining a method for producing charged particles for an electrophoretic display according to a preferred embodiment of the present invention.

Referring to FIG. 2, first, a colloidal solution in which inorganic oxide particles are dispersed in a solvent is formed (step 10). The colloidal solution is formed to contain the inorganic oxide particles in an amount of 1 to 20% by weight based on the total weight of the solvent. In addition, a dispersant may be used in forming the colloidal solution in order to increase the concentration of the inorganic oxide particles in the solvent. The dispersant in the colloidal solution may be included in an amount of 0.1 to 10% by weight based on the total weight of the inorganic oxide particles.

As the inorganic oxide particles, Ti oxide, Zn oxide, Mg oxide, Zr oxide, Br oxide, Al oxide, Si oxide, Cr oxide, Co oxide, Cu oxide, Fe oxide, etc. may be used. Specific examples thereof include TiO ₂ , ZnO, MgO, ZrO, BaO, Al ₂ O ₃ , SiO ₂ , Cr ₂ O ₃ , Co ₃ O ₄ , CuO, Fe ₂ O ₃ and the like can be used, but is not limited to those illustrated above.

Titanium oxide (TiO ₂ ), which is one of examples suitable for use as the inorganic oxide particles, is largely divided into hydrophilic titanium oxide and lipophilic titanium oxide. Mainly used as hydrophilic titanium oxide is Rutile R-902, 900, 706 from Dupont or RGX-150 from Precolor. Mainly used as lipophilic titanium oxide is Rutile R-104 from Dupont or RGX-300 from Precolor. The hydrophilic particles are dispersed in a water-soluble solvent having a solubility parameter of 20 to 40 δ (SI), for example, a water-soluble solvent composed of water, alcohols, ethylene glycol, or a mixture thereof. Non-aqueous solvent having a value of 14 to 20 δ (SI), for example, halogenated hydrocarbons such as dichloromethane or derivatives thereof, halogenated hydrocarbon oils, galden, isopar-based materials, or mixtures thereof It is used by dispersing in a water-insoluble solvent.

In order to produce charged particles having high refractive index, reflectance and bistable stability, inorganic oxide particles should be uniformly coated with an organic compound, and in order to be uniformly dispersed in a solvent. In the present invention, as described above, a dispersant and a stabilizer are selectively used depending on the type and amount of the inorganic oxide particles or the type and amount of the solvent. That is, dispersants and stabilizers may not be used, and dispersants and stabilizers may be used to increase the concentration of inorganic oxide particles in the solvent.

Suitable dispersants for use in the present invention are surfactants having a hydrophile lipophile balance (HLB) of at least 3. Preferably, when using a hydrophilic solvent byk-190, -183 or Tween-based surfactant as the dispersant, when using a lipophilic solvent byk-110, -161 as the dispersant , -183, or Tween, Span, OLOA series (manufactured by Chevron Oronite Inc.), Ganex series (manufactured by ISP Inc.) may be used. They show different degrees of dispersion depending on the particle concentration, the amount of dispersant, and the dielectric constant of the solvent. The degree of dispersion can be determined by measuring the change in size of the dispersed particles over time using a Malvern Metasizer. have.

In step 10, in order to form the colloidal solution, a certain proportion of inorganic oxide particles are added to the solvent in an amount of about 1 to 20% by weight based on the total weight of the solvent, and further, as necessary, the dispersant Is added in an amount of about 0.1 to 10% by weight based on the total weight of the inorganic oxide particles, and then dispersed for about 20 minutes using an ultrasonic sonicator.

Thereafter, a homogeneous mixture of the colloidal solution and the organic compound having a substituent bonded to the terminal to react with the charge control agent is formed (step 20).

The organic compound may be added in an amount of 10 to 100% by weight based on the total weight of the inorganic oxide particles.

Examples of organic compounds that can be used to prepare positively charged particles in the process according to the invention include, for example, montan-based natural waxes, polyethylene-based synthetic waxes, polypropylene-based, and partially carboxylic acid-bonded terminals. Synthetic waxes, and polymer waxes. Preferably, S-wax, PE wax, ethylene-acrylic acid wax, ethylene-vinylacetate and the like are used. Examples of organic compounds that can be used to prepare negative charge particles are synthetic waxes having basic functional groups such as amides and amines. The reactivity and the shape of the coated particle surface vary depending on the physical properties such as the acidity or basicity of the wax, molecular weight, and the like.

In order for the density of the coated charged particles to correspond to the density (1.5 to 1.7 g / mL) of the fluid used in preparing the microcapsules, the coating thickness and size of the organic compound should be adjusted. It mainly depends on the ratio of the organic compound to the inorganic oxide particles and the stirring speed.

In order to form a homogeneous mixture of the organic compound and the colloidal solution in step 20, the temperature of the mixture is first changed to a temperature above the melting point of the organic compound, for example, while rapidly stirring the colloidal solution at about 700 to 1000 rpm. For example, it is heated to a temperature selected in the range of about 70 ~ 130 ℃. In this case, ultrasonic waves may be simultaneously applied for effective dispersion of the particles. Thereafter, a predetermined amount of the organic compound is added to the heated colloidal solution. As already described, the organic compound is preferably added in an amount of 10 to 100% by weight based on the total weight of the inorganic oxide particles. The organic compound may be added in a solid state or dissolved in a small amount of solvent. Thereafter, the colloidal solution to which the organic compound is added is stirred for about 30 minutes so that the organic compound can be uniformly distributed between the solvent and the inorganic oxide particles. At this time, the mixture is rapidly stirred at about 700 to 1000 rpm while maintaining the temperature at about 70 ~ 130 ℃. At this time, ultrasonic waves may be applied at the same time for effective particle dispersion.

If a homogeneous mixture of the organic compound and the colloidal solution is obtained in step 20, the temperature of the mixture is lowered while stirring the mixture for about 1 hour so that the organic compound is crystallized and adsorbed onto the surface of the inorganic oxide particles. (Step 30). At this time, the temperature of the mixture may be lowered slowly or quenched. As a result, crystals obtained by coating an organic compound on the inorganic oxide particles are obtained.

Thereafter, the inorganic oxide particles are separated and purified with crystals coated with an organic compound (step 40). When halogenated hydrocarbon oil (Halocarbon), galden or isopar are used as the fluid used in the subsequent encapsulation process, the reaction mixture obtained in step 30 can be used as it is without the need for separate purification. However, in the case of using a solvent other than the solvents exemplified above, the solvent was removed from the reaction mixture obtained in step 30 under reduced pressure, washed with water, dried with a lyophilizer, and the inorganic oxide particles were coated with an organic compound. A white powder is obtained.

After forming a dispersion in which the white powder is dispersed again in a fluid, a charge control agent is attached to the crystal surface (step 50).

As the charge control agent usable in the present invention, there are OLOA series, metal soap, or Ganex series, and these may be mixed and used.

Representative examples of metal soaps suitable for use as the charge control agent include Co-naphthenate, Ca-naphthenate, Cu-naphthenate, Mn-naphthenate, Zn-naphthenate, Fe-naphthenate, Ba-Stearate, Al-Stearate, Zn-Stearate, Cu-Stearate, Pb-Stearate, Cr-Stearate, Fe-Stearate, Ba-Octoate, Al-Octoate, Ca-Octoate, Co-octoate, Mn-octoate, Pb-octoate, Zr-octoate, Zn-octoate and the like.

In order to attach the charge control agent to the crystal surface, the charge control agent is added to the dispersion together with a span, Ganex or OLOA-based dispersion stabilizer, and the temperature is maintained at a temperature of about 40 to 50 ° C. for about 30 minutes to 1 hour. Stir or react with ultrasonic waves. The reacted solution is dispersed by ultrasonication again and then the zeta potential and mobility of the charged particles are measured.

The zeta potential value for the same particle is highly dependent on the type and concentration of the charge control agent and the degree of dispersion. Applicants obtained zeta potentials in the range of about 90-140 mV and mobility values in the range of about 700-1060 μm ² / V · sec under various conditions. This is about seven times the mobility reported in the literature.

3A to 3C are scanning electron micrographs of charged particles for electrophoretic displays, respectively, prepared by the method according to the preferred embodiment of the present invention. In the examples of FIGS. 3A to 3C, titanium oxide was used as white inorganic oxide particles, respectively.

More specifically, Figure 3a is a scanning electron micrograph of particles coated with titanium oxide R-900 with an organic compound of 50% by weight based on the total weight of the titanium oxide, the particle size of about 1 to 25 ㎛ Not uniform

3B and 3C are results obtained by adjusting the amount of the organic compound to be relatively low at 15 wt% based on the total weight of titanium oxide, and increasing the stirring speed higher than that of FIG. 3A. As can be seen in Figures 3b and 3c, it was possible to obtain particles of uniform size of about 0.5 ㎛ or less by increasing the stirring speed and adjusting the amount of the organic compound added.

Particles dispersed in uniform size have uniform mobility. Therefore, it becomes an important basic condition that can solve the problem of difference in reaction time between charged particles when an electric field is applied.

4 is a thermal gravity analysis graph of the particles shown in FIG. 3A. In Figure 4, the average mass ratio of the coated organic compound and inorganic oxide particles to the particles can be seen, indirectly infer the coating thickness and specific gravity.

FIG. 5 is a Fourier Transfer Infrared Spectrometer (FTIR) spectrum of the particle shown in FIG. 3A. FIG. Characteristic peaks of Ti-O bonds near 686 cm ⁻¹ and characteristic peaks of C═O bonds at 1708 cm ⁻¹ . From this, it can be seen that an organic compound having a COOH functional group is coated.

6 is based on the degree of whiteness of ZnO, by measuring the reflectance of each of the white particles and used titanium oxide (TiO ₂ ) at 15% by weight 50% by weight of the organic compound content in Figures 3a to 3c It is a graph comparing. From FIG. 6, it can be seen that the particles obtained according to the present invention have a reflectance almost similar to that of titanium oxide in the visible region even after coating of the organic compound.

Next, specific production examples of the method for producing charged particles for an electrophoretic display according to the present invention will be described. These are merely examples, and do not limit or limit the scope of the present invention. Those skilled in the art may make various modifications and changes therefrom.

Production Example  One

Oxide 500 mL of solvent mixed with 4: 1 or 9: 1 ethylene glycol and water in 1 liter flask, 1-20 g of titanium oxide (R-900), and dispersant (byk-190 or Tween series) It is added in an amount of 0.1 to 10% by weight based on the total weight of titanium and dispersed for 20 minutes using ultrasonic waves. The mixture is stirred at a speed of 700-1000 rpm while raising the temperature of the mixture to 70-130 ° C. S-wax (montane series natural wax bonded with carboxylic acid) is added in an amount of 10 to 100% by weight based on titanium oxide and stirred for 30 minutes. The temperature is gradually lowered or quenched with stirring for about 1 hour to precipitate the crystals. The solvent is removed under reduced pressure, washed with water and dried with a freeze dryer to obtain a white powder.

Production Example  2

In a 1 liter flask, 500 mL of halogenated hydrocarbon oil, 1 to 10 g of titanium oxide (RGX-300), and a dispersant (byk-based or span-based) are added in an amount of 0.1 to 10% by weight based on the total weight of titanium oxide and ultrasonic waves are applied. Dispersion for 20 minutes. While stirring the temperature of the mixture to 70 ~ 130 ℃ at a speed of 700 ~ 1000 rpm. S-wax (Montan series natural wax conjugated with carboxylic acid) is added in an amount of 10 to 100% by weight based on the total weight of titanium oxide and stirred for 30 minutes. The temperature is gradually lowered or quenched with stirring over about 1 hour to precipitate the crystals. The reaction mixture is used as is in the next step.

In the method for producing charged particles for an electrophoretic display according to the present invention, an organic compound in which a substituent capable of reacting with a charge control agent is already bonded to the terminal is used as a physical coating agent for the charged particles for an electrophoretic display.

According to the present invention, in the formation of charged particles for electrophoretic display using inorganic oxide particles with a charge control agent having an ionic charge such as metal soap, the particles dispersed in a uniform size through the addition amount control of the organic compound Since manufacturing is possible, uniform mobility can be provided, and organic compounds can be uniformly coated on inorganic particles, thereby easily preparing charged particles having high reflectance and bistable stability. In addition, by controlling the coating thickness of the organic compound on the surface of the particles, the specific gravity of the particles and the dielectric fluid can be equalized, and the charged particles for the electrophoretic display can be manufactured at low cost.

The present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made by those skilled in the art within the scope of the technical idea of the present invention. Do.

1 is a view showing the main configuration of the microcapsule-type electrophoretic display to which the charged particles produced by the method according to the invention is applied.

2 is a flowchart for explaining a method for producing charged particles for an electrophoretic display according to a preferred embodiment of the present invention.

3A to 3C are scanning electron micrographs of charged particles for electrophoretic displays, respectively, prepared by the method according to the preferred embodiment of the present invention.

4 is a graph of a thermal gravity analysis of charged particles for an electrophoretic display prepared by the method according to a preferred embodiment of the present invention.

5 is a Fourier Transfer Infrared Spectrometer (FTIR) spectrum of charged particles for an electrophoretic display prepared by a method according to a preferred embodiment of the present invention.

6 is a graph comparing the reflectance of the charged particles for electrophoretic display prepared by the method according to a preferred embodiment of the present invention with the reflectance of titanium oxide (TiO ₂ ) itself.

<Explanation of symbols for the main parts of the drawings>

1: microcapsules, 2: dye fluids, 3: charged particles.

Claims (23)

A core made of inorganic oxide particles, Charged particles for an electrophoretic display, characterized in that it consists of a core shell made of an organic compound coated so as to surround the core around the sphere and the substituent is bonded to the end. The method of claim 1, The inorganic oxide particles are electrophoretic, characterized in that selected from the group consisting of Ti oxide, Zn oxide, Mg oxide, Zr oxide, Br oxide, Al oxide, Si oxide, Cr oxide, Co oxide, Cu oxide, and Fe oxide. Charged particles for display. The method of claim 2, The inorganic oxide particles are selected from the group consisting of TiO ₂ , ZnO, MgO, ZrO, BaO, Al ₂ O ₃ , SiO ₂ , Cr ₂ O ₃ , Co ₃ O ₄ , CuO, and Fe ₂ O ₃ . Charged particles for electrophoretic display. The method of claim 1, The organic compound has carboxylic acid (-COOH), amide (-CONH ₂ ), amine (-NH ₂ ), alcohol (-OH), aldehyde (-CHO), ester (-COOR), nitrile (-CN) , Particles for which a thiol (-SH) or sulfonic acid (-SO3H) substituent is partially conjugated. The method of claim 4, wherein The organic compound is a charged particle for electrophoretic display, characterized in that consisting of montan-based natural wax, polyethylene-based synthetic wax, polypropylene-based synthetic wax, polymer wax, or synthetic wax having a basic functional group. Forming a colloidal solution in which inorganic oxide particles are dispersed in a solvent, Forming a homogeneous mixture of the organic compound having a substituent bonded to the terminal and the colloidal solution, Reducing the temperature of the mixture to form crystals coated with the organic compound on the surface of the inorganic oxide particles. The method of claim 6, The colloidal solution is a method for producing charged particles for electrophoretic display, characterized in that the inorganic oxide particles are added in an amount of 1 to 20% by weight based on the total weight of the solvent. The method of claim 7, wherein The colloidal solution further comprises a dispersing agent added in an amount of 0.1 to 10% by weight based on the total weight of the inorganic oxide particles, the electrophoretic display charging particle manufacturing method. The method of claim 6, The inorganic oxide particles are electrophoretic display, characterized in that selected from the group consisting of Ti oxide, Zn oxide, Mg oxide, Zr oxide, Br oxide, Al oxide, Si oxide, Cr oxide, Co oxide, Cu oxide, Fe oxide. Method for producing charged particles for dragon. The method of claim 9, The inorganic oxide particles are selected from the group consisting of TiO ₂ , ZnO, MgO, ZrO, BaO, Al ₂ O ₃ , SiO ₂ , Cr ₂ O ₃ , Co ₃ O ₄ , CuO, and Fe ₂ O ₃ . Method for producing charged particles for an electrophoretic display. The method of claim 6, The inorganic oxide particle is a method for producing charged particles for electrophoretic display, characterized in that it has a hydrophilic or lipophilic. The method of claim 6, The inorganic oxide particles are made of hydrophilic titanium oxide, The solvent comprises a water-soluble solvent selected from the group consisting of water, alcohols, ethylene glycol, and mixtures thereof. The method of claim 6, The inorganic oxide particles are made of lipophilic titanium oxide, The solvent consists of a halogenated hydrocarbon, halogenated hydrocarbon oil (trade name "halocarbon", manufactured by Halogenated hydrocarbon Inc.), galden (Galden, Ausimont), isopa (Isopar, Exxon) -based materials, and mixtures thereof A method for producing charged particles for an electrophoretic display, comprising a water-insoluble solvent selected from the group. The method of claim 6, Dispersing the inorganic oxide particles in the solvent using ultrasonic waves to form the colloidal solution. The method of claim 6, Forming a uniform mixture of the organic compound and the colloidal solution Heating the colloidal solution to a first temperature that is equal to or higher than the melting point of the organic compound; Adding the organic compound to the heated colloidal solution, Method for producing a charged particle for an electrophoretic display, characterized in that it comprises the step of stirring the colloidal solution to which the organic compound is added. The method of claim 15, The first temperature is selected from the range of 70 ~ 130 ℃ elective particles for electrophoretic display, characterized in that the. The method of claim 15, The organic compound is a method for producing charged particles for electrophoretic display, characterized in that added in an amount of 10 to 100% by weight based on the total weight of the inorganic oxide particles. The method according to claim 6, 15 or 17, The organic compound has carboxylic acid (-COOH), amide (-CONH ₂ ), amine (-NH ₂ ), alcohol (-OH), aldehyde (-CHO), ester (-COOR), nitrile (-CN) The thiol (-SH) or sulfonic acid (-SO3H) substituent is partially bonded, the melting point of the electrophoretic display, characterized in that it has a solid form of 60 ℃ or more. The method of claim 18, The organic compound may be a montan-based natural wax, a polyethylene-based synthetic wax, a polypropylene-based synthetic wax, a polymer wax, or a amide or amine partially bonded to a terminal, in which a carboxylic acid is partially conjugated to a terminal. A method for producing charged particles for an electrophoretic display, comprising a wax selected from the group consisting of synthetic waxes having groups. The method of claim 6, The method for producing charged particles for an electrophoretic display, characterized in that it further comprises the step of separating and purifying the crystal. The method of claim 6 or 20, The method for producing charged particles for an electrophoretic display further comprising the step of attaching a charge control agent to the crystal surface. The method of claim 21, The charge control agent is a method for producing charged particles for electrophoretic display, characterized in that the metal soap, OLOA-based, or Ganex-based material. The method of claim 22, The charge control agents include Co-naphthenate, Ca-naphthenate, Cu-naphthenate, Mn-naphthenate, Zn-naphthenate and Fe-naphthenate; Ba-Stearate, Al-Stearate, Zn-Stearate, Cu-Stearate, Pb-Stearate, Cr-Stearate and Fe-Stearate, Ba-Octoate, Al-Octoate, Ca-Octoate, A method for producing charged particles for electrophoretic displays, comprising a metal soap selected from the group consisting of Co-octoate, Mn-octoate, Pb-octoate, Zr-octoate, and Zn-octoate.