KR101258464B1 - Electrophoretic particle and method for fabricating the same - Google Patents

Abstract

The present invention relates to electrophoretic particles and methods for their preparation. Electrophoretic particles according to an embodiment of the present invention, the core structure including a charged mother particles and a plurality of magnetic particles on the surface of the mother particles; And a polymerization dispersion layer on the core structure.

Description

Electrophoretic particle and method for fabricating the same

FIELD OF THE INVENTION The present invention relates to display technology, and more particularly, to electrophoretic particles and methods for their preparation.

As an information display device for replacing a liquid crystal display device, a display device using an electrophoresis method, an electro-chromic method, and a dichroic particles rotary method has been proposed. These technologies are in demand as next generation display devices that can replace liquid crystal display devices due to advantages such as wide viewing angle, low power consumption and memory effect in proximity to conventional print media such as paper.

Among these display devices, an electrophoretic display device uses a phenomenon in which charged particles move by an electric field applied between two electrodes. The wet electrophoretic display device uses a particle dispersion solution in which the charged particles are dispersed in an insulating liquid fluid.

The particles may have one kind of color or may include different kinds of particles having two or more kinds of colors. When two or more kinds of color particles are used, the electrical polarities of these particles are generally opposite to each other, but may be independently controlled by the difference in electrophoretic mobility even though they have the same polarity.

As such, since the electrophoretic display device displays information by particles having electrical polarity, dispersion characteristics must be maintained while the electrical properties of the particles are maintained in various environments in which the product is used. In recent years, with regard to the intelligence of automobiles, various display devices have been combined with vehicle information systems. In order for an electrophoretic display device to be used in an information system of such a vehicle, it is necessary to maintain the electrical and dispersion characteristics of the particles in a harsher temperature range, for example, a high temperature environment of 70 ° C, unlike room temperature. Such high temperature durability is also important in general user environments such as outdoors.

The technical problem to be achieved by the present invention is to provide electrophoretic particles having excellent display quality and bistable stability in a wide operating temperature range by having excellent dispersion characteristics at room temperature as well as at high temperature.

In addition, another technical problem to be achieved by the present invention is to provide a method for producing electrophoretic particles having the aforementioned advantages.

Electrophoretic particles according to an embodiment of the present invention for solving the technical problem, the charged mother particles; And a core structure including a plurality of magnetic particles externally attached to the surface of the mother particle. And a polymerization dispersion layer on the core structure.

In some embodiments, the polymerization dispersion layer may be formed on the surface of the plurality of magnetic particles. The mother particle may include a charged polymeric binder and a colorant dispersed in the polymeric binder.

In some embodiments, the diameter of the parent particles is in the range of 400 nm to 3 μm, the diameter of the plurality of magnetic particles is in the range of 10 nm to 300 nm, and the plurality of magnetic particles are the mother particles It can be externalized to have a coverage of less than 100% on the surface. In this case, the ratio of the average diameter of the mother particles to the average diameter of the plurality of magnetic particles may be in the range of 1/300 to 1/10.

In some embodiments, the plurality of magnetic particles may include metal oxides, metal salts, or monoatomic metals or alloys. In another embodiment, the plurality of magnetic particles may include a polymer of polyester, styrene-acrylic, methyl methacrylate series. The polymerization dispersion layer may include a styrene or an acrylate polymer.

Electrophoretic particles according to an embodiment of the present invention for solving the other technical problem, providing a charged mother particle; Externalizing a plurality of magnetic particles on the charged mother particles to expand the surface area of the charged mother particles; And forming a polymerization dispersion layer on a surface of the plurality of magnetic particles. In some embodiments, the plurality of magnetic particles may be externalized to have a coverage of less than 100% on the charged parent particles.

The polymerization dispersion layer may include a styrene or an acrylate polymer. In addition, externalizing the plurality of magnetic particles on the charged mother particles may be performed by bead milling.

Electrophoretic particles according to another embodiment of the present invention for solving the other technical problem, providing a charged mother particle; Providing a plurality of magnetic particles having a polymerization dispersion layer formed on a surface thereof; And externally enlarging a plurality of magnetic particles having the polymerization dispersion layer formed on the charged mother particles, thereby expanding the surface area of the charged mother particles.

The plurality of magnetic particles may be externally attached to have a coverage of less than 100% on the charged mother particles, and the polymerization dispersion layer may include a styrene or an acrylate polymer. Also, externalizing the plurality of magnetic particles on the charged mother particles is preferably performed by bead milling.

According to embodiments of the present invention, the effective surface area may be extended by a plurality of magnetic particles externally attached to the charged mother particle, and a polymer dispersion layer may be formed on the extended effective surface area. As a result, the bonding area of the polymerization dispersion layer may be maximized, and the dispersion stability of the electrophoretic particles in the wet electrophoretic display pixel may be improved, and excellent display quality and bistable stability may be obtained at room temperature as well as at high temperature. In addition, the immersion density of the electrophoretic particles is reduced by the polymerization dispersion layer in the insulating fluid, so that the electrical mobility is increased, thereby obtaining the electrophoretic particles having improved driving speed.

1 is a cross-sectional view schematically showing the structure of electrophoretic particles in one embodiment of the present invention.
2 is a view schematically showing an electrophoretic pixel according to an embodiment of the present invention.
3 is a cross-sectional view showing an electrophoretic display device according to an embodiment of the present invention.

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

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art.

In the drawings, the thickness and size of each layer are exaggerated for convenience and clarity of description, and the same reference numerals refer to the same elements in the drawings. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. Also, as used herein, "comprise" and / or "comprising" specifies the presence of the mentioned shapes, numbers, steps, actions, members, elements and / or groups of these. It is not intended to exclude the presence or the addition of one or more other shapes, numbers, acts, members, elements and / or groups.

Although the terms first, second, etc. are used herein to describe various members, parts, regions, and / or parts, these members, parts, regions, and / or parts should not be limited by these terms. Is self-explanatory. These terms are only used to distinguish one member, part, region or part from another region or part. Thus, the first member, part, region, or portion, which will be described below, may refer to the second member, component, region, or portion without departing from the teachings of the present invention.

Embodiments of the present invention will now be described with reference to the drawings, which schematically illustrate ideal embodiments of the present invention. In the drawings, for example, the size and shape of the members may be exaggerated for convenience and clarity of description, and in actual implementation, variations of the illustrated shape may be expected. Accordingly, embodiments of the present invention should not be construed as limited to the specific shapes of the regions shown herein.

1 is a cross-sectional view schematically showing the structure of an electrophoretic particle 100 according to an embodiment of the present invention.

Referring to FIG. 1, the electrophoretic particle 100 includes a core structure 15. The core structure 15 may include the mother particle 10 and a plurality of magnetic particles 20 on the surface of the mother particle 10. The parent particle 10 may be charged to have a positive or negative charge for electrophoresis. In addition, the parent particles 10 may include a polymeric resin material colored by pigments and / dyes for information display. The diameter of the designed mother particle 10 is 400 nm to 3 ㎛, it is possible to ensure a suitable electric mobility within the above range.

The polymer resin material may be, for example, urethane resin, urea resin, acrylic resin, polyester resin, acrylic urethane resin, acrylic urethane Acrylic resins, acryl urethane fluoro-carbon polymers, acryl fluorocarbon polymers, silicone resins, acrylic silicone resins, polystyrene Polystyrene resin, styrene acrylic resin, polyolefin resin, butyral resin, vinylydinene chloride resin, melamine resin, phenol Phenolic resins, fluorocarbon polymers, polycarbonate resins, polysulfon resins, polyether resins polymeric resin materials such as esin), polyethylene resins, and polyamide resins, and these materials may be used in combination of two or more materials. However, this is exemplary and the present invention is not limited thereto. For example, the polymer resin material may be gelatin, alginic acid, latex polymer, polystyrene, polyvinyl formal, polyvinyl butyral, polymethyl acrylate, polybutyl acrylate, poly It may also be formed from any one of methyl methacrylate, polybutyl methacrylate or in combination with those described above.

The parent particles 10 colored by the pigment and / or dye may have any one of red, green and blue, one of magenta, cyan and yellow, or white, or black. If necessary, the parent particles 10 may be transparent without including pigments and / or dyes so as not to have color. The pigments and dyes may be commercially suitable materials. For example, the pigment may be inorganic fine particles having a particle diameter of about 0.05 μm to several μm and dispersed in the polymer resin. In addition, the dyes may be commercial acid dyes, oil-soluble dyes, disperse dyes, reactive dyes, direct dyes, and the like.

In addition, in order to actively control the charge amount of the mother particle 10, a positive or negative charge control agent may be combined with the polymer resin material. The positive charge control agent may be, for example, a nigrosine dye, a trih-enylmethane compound, the fourth grade ammonium salt-based compound, It may be any one or combination of polyamine resins and imidazole derivatives. The negative charge control agent may be, for example, a salicylic acid metal complex, a metal containing azo dye, an oil-soluble dye of metal-containing, a quaternary The fourth grade ammonium salt-based compound, calixarene compound, boron-containing compound such as the benzyl acid boron complex, and nitroimi Nitroimidazole derivatives The materials described above are exemplary and the present invention is not limited thereby, and other known suitable materials may be used.

The plurality of magnetic particles 20 may be organic particulates, inorganic particulates, or a combination thereof. The magnetic particles 20 may be designed to be smaller than the parent particles, and have a diameter in the range of 10 nm to 300 nm. When the size of the magnetic particles 20 is less than 10 nm, not only is it difficult to form a polymerization dispersion layer to be described later, but it is also difficult to obtain the effect of reducing the particle density of the particles.

The organic fine particles may be, for example, a polymer of polyester, styrene-acrylic or methyl methacrylate series. The organic fine particles may be formed by a pulverization or polymerization reaction, and preferably may be formed by a polymerization reaction in which the particle size distribution is easily controlled. The polymerization reaction can be carried out by emulsion polymerization / aggregation or suspension polymerization.

The inorganic fine particles may include, for example, metal oxides such as titanium oxide, zinc sulfide, cerium oxide, aluminum oxide, barium titanium oxide, or metal salts such as calcium carbonate, calcium oxide, and kaolin, or monoatomic metals or alloys. Can be. However, these materials are illustrative only and the present invention is not limited thereto. For example, the inorganic fine particles include other metal particles such as Si, Ti, Sr, Al, Zn, Ba, Sb, Ce, Pd, oxides thereof, nitrides thereof, oxygen nitrides thereof, salts thereof, or Other suitable materials, including combinations thereof.

The fine particles described above may be externalized on the surface of the parent particle 10. For this purpose, a bead milling method or a graft polymerization method by a chemical method may be used to fix the fine particles to the surface of the parent particle 10 by a mechanical method. Preferably, the plurality of magnetic particles 20 may be externalized by bead milling. In the bead milling, the mother particle 10 and the child particle 20 are put together in the chamber together with the zirconia beads, and then the milling process is performed while controlling the milling time and the amount of the bead. The core structure 15 is obtained. After the milling process, the beads may simply be removed via a filtration process. Such bead milling has an advantage of high recovery rate because the process is simpler than the graft polymerization method by the chemical method, and the process of removing the residual monomer after the graft polymerization is unnecessary.

The plurality of magnetic particles 20 externally attached to the parent particle 10 serves to three-dimensionally expand the entire surface area of the core structure 15. That is, the effective surface area (= surface area / volume) of the core structure 15 may be increased by the plurality of magnetic particles 20. The ratio of the average diameter of the parent particle 10 to the average diameter of the plurality of magnetic particles 20 may be in the range of 1/300 to 1/10. When the average diameter of the magnetic particles 20 is less than 1/300 of the average diameter of the mother particles 10, the surface coverage of the mother particles by the plurality of magnetic particles may be rapidly increased, so that the effective surface area may be rather reduced. Dispersion stability may be impaired. In addition, when the average diameter of the magnetic particles 20 is less than 10 nm, it is difficult to provide a polymerization dispersion layer to be described later on the plurality of magnetic particles 20. When the average diameter of the magnetic particles 20 exceeds 1/10 of the average diameter of the mother particles 10, for example, the magnetic particles exceeding 300 nm with respect to the mother particles 10 having a 3 μm average diameter. In the case of (20), there is a problem that the adhesion stability of the magnetic particles 20 is reduced after the above-mentioned external addition process.

In this embodiment, the plurality of magnetic particles 20 externally attached on the surface of the parent particle 10 is preferably separated from each other. When the plurality of magnetic particles 20 are attached to each other to form a continuous surface, the weight of the core particles is increased as compared with the effect of increasing the surface area, thereby reducing the mobility of the electrophoretic particles. Therefore, in order to increase the mobility while maximizing the effective surface area of the core structure 10, the plurality of magnetic particles 20 are discontinuously or discretely so that the plurality of magnetic particles 20 have a coverage of less than 100% on the surface of the mother particle 10. It is preferable to externally add.

The polymeric dispersion layer 30 is provided on the core structure 15 having an effective surface area extended three-dimensionally by the plurality of magnetic particles 20. Compared with providing the polymer dispersion layer 30 on the parent particles 10, when providing the polymer dispersion layer 30 on the core structure 15 having an extended effective surface area, more polymer dispersion layer ( 30) may be combined to reduce the particle density of the particles, thereby improving particle mobility and bistable stability.

When the plurality of magnetic particles 20 are organic fine particles, the polymerization dispersant constituting the polymerization dispersion layer 30 may be chemically bonded to the organic fine particles. For example, the organic fine particles and the polymeric dispersant may be bonded to each other through acid base reactions, ionic bonds, covalent bonds, hydrogen bonds, π electron bonds, or a combination thereof between suitable functional groups. When the plurality of magnetic particles 20 are formed of inorganic fine particles, the polymerization dispersant may be physically coated or adsorbed on the inorganic fine particles.

The polymerization dispersant may be prepared by free radical polymerization of one or more types of monomers which are not saturated. Suitable free radical polymerization reactions may include suspensions, emulsions, dispersions and preferably solution polymerizations. The manufacturing methods listed are exemplary and the present invention is not limited thereto.

The polymerization dispersant is a polymer having at least one monomer repeating step, and may be, for example, a styrene or an acrylate polymer. The polymer for the polymeric dispersant may have suitable functional groups that can chemically interact with the surface of the magnetic particles as described above. For example, when the surface of the magnetic particles and the polymerization dispersant are hydrogen bonded, the surface of the magnetic particles may be formed of a pyridinium group, an imidazorium group, and a quaternary ammonium group. The same may include a hydrogen donor, and the polymerization dispersant may include a hydrogen upsector, such as a ketone group, a sulfonate group, a pyridinine group, or a carboxykate group. . In another embodiment, the polymerization dispersant may have a functional group capable of performing a suitable crosslinking reaction when coated on the inorganic fine particles.

The above-described polymerization dispersion layer 30 may be first formed on the surfaces of the magnetic particles 20 before externally attaching the magnetic particles 20 to the mother particles 10. In another embodiment, the core structure 15 is first formed by externally attaching the magnetic particles 20 to the mother particle 10, and then, on the magnetic particles 20 of the core structure 15, a polymerization dispersion layer ( 30) may be formed. In addition, the polymerization dispersion layer 30 may be further formed by the above-described mechanism on the surface of the parent particle 10 which is not covered with the plurality of magnetic particles 20.

Preparation of White and Black Electrophoretic Particles

≪ Example 1 >

To prepare the black mother particles, cationic polyester was used as the binder resin, carbon black was used as the black pigment, and the mother particles having positive charge were prepared using Bontron E84 available from Orient Co. as the charge control agent. It was. Specifically, about 1.0 g of cationic polyester is dissolved in 20 ml of methyl ethyl ketone, which is an organic solvent, and about 0.4 g of carbon black is added thereto and mixed to prepare a dispersion. Subsequently, after dissolving Bontron NO7 as a charge control agent in the dispersion, a polymer compound was induced to prepare a mother particle.

In order to prepare a magnetic particle having a polymerization dispersion layer, a dispersion of SiO ₂ having a hydrophilic surface before surface treatment was prepared, and an alkoxyamine terminated with triethoxyl in -OH group on the surface of SiO ₂ was used. Terminated Alkoxyamine) is grafted. Thereafter, when the styrene-based monomer is put into the dispersion and subjected to a polymerization reaction, SiO ₂ particles obtained by grafting the styrene-based dispersion polymerization layer may be obtained.

SiO ₂ magnetic particles in which the styrene-based dispersion polymerization layer was formed were mixed by 0.5 wt% based on the packing weight of the mother particles and the magnetic particles, and a bead milling process using zirconia beads was performed to carry out the bead milling process according to Example 1 of the present invention. Black electrophoretic particles were prepared. The prepared electrophoretic particles have a core structure in which parent particles having an average size of 800 nm are externally attached to the mother particle surface with a coverage of 40% to less than 60% of the magnetic particles having a size of 10 nm to 30 nm.

<Example 2>

As described in Example 1, after preparing the mother particles containing carbon black-containing mother particles and the styrene-based dispersion polymerization layer, 10 wt% of the magnetic particles were added to the mother particles and the weight of the magnetic particles. After mixing, the bead milling process was performed to prepare black electrophoretic particles according to Example 2 of the present invention. The prepared electrophoretic particles have a core structure in which the parent particles having an average size of 800 nm are externally attached to the mother particle surface with a coverage of less than 60% to 80% of the magnetic particles having a size of 10 nm to 30 nm.

&Lt; Comparative Example 1 &

For performance comparison with the above-described examples, positively charged black electrophoretic particles were prepared in which the dispersant was directly bonded to the above-described parent particles.

Comparative Example 2

In order to compare the performance with the above-described embodiments, as shown in Example 1, after preparing the mother particles having the carbon black-impregnated mother particles and the styrene-based dispersion polymerization layer, the mother particles and the particles The black electrophoretic particles according to Example 2 of the present invention were prepared by mixing 25 wt% of the magnetic particles with respect to the packed weight and performing a bead milling process. The prepared electrophoretic particles have a core structure in which parent particles having an average size of 800 nm are externally attached to the surface of the mother particles with a coverage of 100% or more.

White electrophoretic particles are prepared to be dispersed together with the black electrophoretic particles according to Examples 1 and 2 and Comparative Examples described above to constitute a two-particle wet electrophoretic pixel. The white electrophoretic particles, like the aforementioned black electrophoretic particles, used anionic polyester as a binder resin, TiO ₂ as a white pigment, and negatively using Bontron P84 available from Orient as a charge control agent. Charged.

The electrophoretic particle dispersion was prepared by dispersing the above-mentioned black electrophoretic particles and white electrophoretic particles in Isopar G (specific gravity 0.75), which is an electrically insulating fluid, and then charged into an experimental electrophoretic display pixel to display contrast, Bistable and high temperature stability were evaluated. Table 1 below shows the evaluation results of Examples 1 and 2 and Comparative Examples 1 and 2.

In Table 1, the contrast ratio is the ratio (% W /% K) of the reflectance observed when white electrophoretic particles float to the front of the pixel and the reflectance (% K) observed when black electrophoretic particles float to the front of the pixel. )to be. The reflectance measurement was carried out to produce an experimental electrophoretic pixel, irradiated with halogen light as a light source in the dark room and evaluated the luminance of the reflected light using a luminance measuring device (CS-200) of Konica Minolta Co. (Konica Minolta Co.). A standard white reflector (SRS-99) from Labspher Co. was used.

The bistableness measures the initial reflectance of the white electrophoretic particles and the black electrophoretic particles, and then measures the reflectance after storage for 24 hours in a dispersed state maintained with the power off, thereby evaluating the difference in reflectance (ΔL ^* ). It is. Thermal stability measures the reflectance by the same method as the above after 240 hours passed at 70 degreeC, and evaluates the difference (ΔL ^* ) between the initial reflectance and the reflectance after 240 hours.

reflectivity Contrast Bistable (ΔL ^* ) Thermal Stability (ΔL ^* )
[70 ℃, 240 hours] % W % K White Black White Black Example 1 40.8% 4.1% 9.95 -3.5 1.7 -1.8 1.5 Example 2 39.5% 3.7% 10.68 -2.8 0.9 - 1.5 1.3 Comparative Example 1 41.5% 4.2% 9.89 -6.5 2.1 -10.3 5.4 Comparative Example 2 35% 5% 7 -10 3 -11.3 5.8

Referring to Table 1, in Example 1 in which 5 wt% of the particles are attached and Example 2 in which 10 wt% of the particles are attached, the external coverage of the particles is less than 100%, and as the amount of the particles increases, The contrast ratio increases, and the bistable and thermal stability tend to improve. This is because, as the amount of the magnetic particles on which the polymer dispersion layer is formed increases, the immersion density of the electrophoretic particles decreases, and the dispersion stability increases.

In the case of the electrophoretic particles according to Comparative Example 1 in which the polymer dispersion layer was directly formed on the surface of the mother particles, there was no significant difference in display quality, but it was time-lapsed compared to the particle structures according to Examples 1 and 2 in both white and black driving of pixels. It can be seen that the change is large and the bistable stability of the particles is reduced. In particular, it is assumed that the decrease in the reflectivity during the white driving of the pixel is large, which is because the dispersion stability of the black electrophoretic particles is reduced, thus affecting the dispersion state of the white electrophoretic particles.

In the case of the particles according to Comparative Example 2, like the particles of Comparative Example 1, the reflectance rapidly deteriorates in both the white and black driving of the pixel, and the change over time is large, so that both bistable and thermal stability are reduced. In practice, the dispersion solution according to Comparative Example 2 had a degree of contrast that was difficult to be commercialized, and although not indicated, a continuous magnetic particle coating layer of one to two or more layers was formed on the surface of the mother particle by addition of excess magnetic particles. The haptic density was also shown to decrease the driving speed.

In the above embodiments, the parent particles have an average particle diameter of 800 nm, but this is exemplary and, as described above, exhibits bistable and thermal stability while having optimal display quality and driving characteristics in a wet electrophoretic display device. The diameter of the mother particles is in the range of 400 nm to 3 μm, and the diameter of the magnetic particles forming the core structure of the particles is in the range of 10 nm to 30 nm and is smaller than the diameter of the mother particles from 10 nm to 300 nm. It may be in the range of.

Electrophoretic display pixels and devices

2 is a diagram schematically showing an electrophoretic pixel 200 according to an embodiment of the present invention.

Referring to FIG. 2, the electrophoretic pixel 200 may include two or more subpixels adjacent to each other. In some embodiments, in order to implement a multi-color display device, the electrophoretic pixel 200 may include a plurality of color subpixels 200Y, 200M, and 200C. The color subpixels 200Y, 200M, and 200C may be yellow, magenta, and cyan subpixels, respectively. The particle dispersion solution DU may be provided in the color sub pixels 200Y, 200M, and 200C.

The particle dispersion solution DU is dispersed in the electrically insulating fluid 31 and the color electrophoretic particles 100Y, 100M, and 100C having the core structure described above and having a corresponding color, for example, yellow, magenta, and cyan. ) And black electrophoretic particles 100K. In another embodiment, the color sub pixels 200Y, 200M, 200C may be red, green and blue sub pixels, for example. In this case, the color subpixels 200Y, 200M, 200C are colored electrophoretic particles 100Y, 100M having the corresponding color, for example, red, green, and blue, together with the aforementioned black electrophoretic particles 100K. , 100C). In the two particle system shown in FIG. 2, only one kind of particles of the color electrophoretic particles 100Y, 100M, 100C and the black electrophoretic particles 100K in each sub-pixel may have a core structure.

In some embodiments, the electrophoretic pixel 200 further adds a white subpixel 200W adjacent to the aforementioned color subpixels 200Y, 200M, 200C to increase the white and black saturation to further enhance the contrast ratio. It may include. The white subpixel 200W may include white electrophoretic particles 100W together with the black electrophoretic particles 100K as described above. The electrophoretic pixel 200 may further include transparent particles having no color along with the color electrophoretic particles and the black electrophoretic particles.

The subpixels constituting the electrophoretic pixel 200 may be arranged in a quadrangular shape, as shown in FIG. 2, but this is exemplary. For example, the sub-pixels constituting the electrophoretic pixel 200 may be arranged in a line shape, or may have polygons such as hexagons and octagons, concentric circles, or a combination thereof, but the present invention is not limited thereto. . In addition, although FIG. 2 illustrates the microcapsule 200S as a means for storing the particle dispersion solution DU, this is exemplary, and the cavity is defined by a partition structure as described below between each pixel or subpixel. The microcapsules 200S may be defined within the cavity, or the particle dispersion solution may be stored directly in the cavity without the microcapsules 200S. In another embodiment, the particle dispersion solution may be stored in a known microcup structure or other various types of cavity structures, polymer dispersed structures, but the present invention is not limited thereto.

3 is a cross-sectional view of an electrophoretic display apparatus 300 according to an embodiment of the present invention.

Referring to FIG. 3, at least one cavity V1 and V2 between a first substrate 310 (which may be a lower substrate in this drawing) and a second substrate 320 (which may be an upper substrate in this drawing) facing each other. , A light conversion layer 70 comprising V3) may be provided. At least one of the lower substrate 310 and the upper substrate 320, for example, the upper substrate 320 on the observer side may be formed of a transparent material such as glass and a transparent resin.

Cavities V1, V2, and V3 may be defined by partition 300R, which is a separating member, as shown. However, this is exemplary and the cavities V1, V2, V3 may be defined by other separating members such as microcup structures or microcapsules as is well known in the art. The cavities V1, V2, V3, alone or in combination with other adjacent one or more cavities, may constitute one sub-pixel or pixel.

In one embodiment, the electrophoretic display device 300 may include electrodes 341; 342Y, 342M, and 342C for driving the electrophoretic particles 100K; 100Y, 100M, and 100C. The electrodes 341 and 342 may have a configuration opposite to each other so as to generate an electric field perpendicular to the main surfaces of the substrates 310 and 320, as shown. The electrodes 342Y, 342M, and 342C disposed on the lower substrate 310 may be individual electrodes that can be independently addressed for each pixel by a suitable switching element such as a transistor, and an electrode 341 on the upper substrate 320. ) May be a common electrode opposite the individual electrodes. However, the above-described electrode configuration is exemplary and the present invention is not limited thereto. For example, it may have a known in-plane configuration or a combination thereof. In addition, at least one of these electrodes 341 and 342, for example, the common electrode, may be a transparent electrode formed of Indium-Tin-Oxide (ITO) or another transparent conductor.

Individual electrodes 342Y, 342M, 342C may be driven by an active matrix that includes transistors 350 as switching elements. However, this is only illustrative, and those skilled in the art will appreciate that a passive matrix type electrode configuration, or a segment type electrode configuration and wiring structure for static driving are also included in the embodiments of the present invention.

The cavity V1, V2, V3 is filled with an electrically insulating fluid U, and at least one kind of particles 100Y, 100M, 100C, 100K having the aforementioned core structure is dispersed. According to an embodiment of the present invention, an effective surface area is extended by a plurality of magnetic particles externally charged on a charged mother particle, and a polymer dispersion layer is formed on the extended effective surface area, so that the bonding area of the polymer dispersion layer is increased. Is maximized. Accordingly, the dispersion stability of the electrophoretic particles in the wet electrophoretic display pixel can be improved, and excellent display quality and bi-stability can be secured at room temperature as well as at high temperature. In addition, the immersion density of the electrophoretic particles is reduced by the polymerization dispersion layer in the electrically insulating fluid, thereby increasing the electrical mobility, thereby obtaining an electrophoretic display device having improved driving speed.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be clear to those who have knowledge.

Claims (17)

Charged parent particles; And a core structure including a plurality of magnetic particles externally attached on the surface of the mother particle, wherein the plurality of magnetic particles include inorganic fine particles; And
Styrene or acrylate-based polymerization dispersion layer bonded to the inorganic fine particles to improve the feel density of the core structure,
The polymerized dispersion layer is electrophoretic particles that are polymerized and bonded through a grafted initiator formed on the surface of the inorganic fine particles. delete The method of claim 1,
The polymerized dispersion layer is electrophoretic particles, characterized in that the magnetic particles are further formed on the surface is not added. The method of claim 1,
Wherein said mother particle comprises a charged polymeric binder and a colorant dispersed in said polymeric binder. The method of claim 1,
The diameter of the parent particles is in the range of 400 nm to 3 ㎛,
The diameter of the plurality of magnetic particles is in the range of 10 nm to 300 nm,
And said plurality of magnetic particles are externalized to have a coverage of 40% to less than 80% on the surface of the mother particle. The method of claim 5, wherein
The ratio of the average diameter of the parent particles to the average diameter of the plurality of magnetic particles is in the range of 1/300 to 1/10 electrophoretic particles. The method of claim 1,
The said inorganic fine particle contains a metal oxide, a metal salt, or monoatomic metal or an alloy, The electrophoretic particle characterized by the above-mentioned. The method of claim 7, wherein
Wherein said inorganic particulate is a metal oxide and said grafted initiator comprises an alkoxyamine initiator. The method of claim 1,
The plurality of magnetic particles are electrophoretic particles, characterized in that the externally added to have a coverage of less than 40% to 80% of the surface of the parent particles. Providing a charged parent particle;
Externalizing a plurality of magnetic particles on the charged mother particles to expand the surface area of the charged mother particles; And
Forming a styrene or acrylate-based polymer dispersion layer on a surface of the plurality of magnetic particles;
The plurality of magnetic particles include inorganic fine particles,
The polymerized dispersion layer is bonded to the inorganic fine particles to improve the feel density of the core structure including the charged mother particles and the plurality of magnetic particles,
And the polymerization dispersion layer is polymerized and bonded through a grafted initiator formed on the surface of the inorganic fine particles. 11. The method of claim 10,
The inorganic fine particles include a metal oxide, a metal salt, or a monoatomic metal or an alloy, wherein the electrophoretic particles are produced. 11. The method of claim 10,
Wherein said inorganic fine particles are metal oxides and said grafted initiator comprises an alkoxyamine initiator. 11. The method of claim 10,
The plurality of magnetic particles are externally attached to the surface of the parent particles to have a coverage of less than 40% to 80%. Providing a charged parent particle;
Providing a plurality of magnetic particles having a polymerization dispersion layer formed on a surface thereof; And
Sintering a plurality of magnetic particles in which the styrene or acrylate-based polymer dispersion layer is formed on the charged mother particles to expand the surface area of the charged mother particles,
The plurality of magnetic particles include inorganic fine particles,
The polymerized dispersion layer is bonded to the inorganic fine particles to improve the feel density of the core structure including the charged mother particles and the plurality of magnetic particles,
And the polymerization dispersion layer is polymerized and bonded through a grafted initiator formed on the surface of the inorganic fine particles. 15. The method of claim 14,
The inorganic fine particles include a metal oxide, a metal salt, or a monoatomic metal or an alloy, wherein the electrophoretic particles are produced. 15. The method of claim 14,
Wherein said inorganic fine particles are metal oxides and said grafted initiator comprises an alkoxyamine initiator. 15. The method of claim 14,
The plurality of magnetic particles are externally attached to the surface of the parent particles to have a coverage of less than 40% to 80%.

Images