KR20120012155A - Electrophoretic display device - Google Patents

Abstract

PURPOSE: An electrophoretic display device is provided to implement all colors of each pixel by using the interference layer of electrophoresis materials. CONSTITUTION: An upper electrode(11) and a lower electrode(21) are faced with each other. A plurality of electrophoresis materials(12) and solvent(13) have a surface charge. The surface charge is injected between electrodes. A plurality of electrophoresis materials moves to the surface of the electrode by voltage of the electrode. A plurality of electrophoresis materials forms an interference layer.

Description

Electrophoretic Display Device {ELECTROPHORETIC DISPLAY DEVICE}

The present invention relates to an electrophoretic display device including an electrophoretic material and a solvent having a surface charge between electrodes, and more particularly to a plurality of electrophoretic materials and a solvent having a surface charge between a pair of electrodes facing each other. The present invention relates to an electrophoretic display device in which a plurality of electrophoretic materials form an interference layer by implantation, and a voltage applied between electrodes to display a desired color.

The electrophoretic display device has the ability to store images without any additional energy due to the high bisability that maintains the original image without applying an external electric field, and has excellent flexibility, portability, and durability. And a type of flat panel display using electrophoresis (a phenomenon in which a colloidal particle having a charge moves to an anode or a cathode) in an electric field.

The electrophoretic display device has the characteristics closest to the paper texture, and has a light reflection efficiency of about 40% or even higher than that of a newspaper having a light reflection efficiency of about 40%, and an excellent contrast ratio. Reflective display that drives Electrophoretic Suspension by applying electrode to base film. Device.

The electrophoretic display device includes an electrophoretic display device using microcapsules. The electrophoretic display device is a transparent microcapsule containing pigment particles with charge and a dielectric medium mixed with a binder and placed between the upper and lower electrodes, and the voltage is lowered. Applying this will display text or images. However, this method has a problem in that a large portion of the upper portion of the capsule is shielded or partially consumed by the binder, so that the light efficiency is relatively low, and the response speed is slow, and thus, the video is weak. In addition, in order to manufacture such microcapsules, a complicated step occurs and a problem arises in that the cost of the product increases.

Another type of electrophoretic display apparatus is an apparatus for displaying an image using two kinds of electrophoretic particles having different charging characteristics between electrodes without using microcapsules. In such an electrophoretic display device, two types of electrophoretic particles having different charging characteristics are enclosed between substrates having electrodes formed on one surface thereof, and a voltage is applied to the electrodes of the upper and lower plates so that the electrophoretic particles collide with each other to display an image. . Such an electrophoretic display device is a reflective display, and generally displays a color image using a color filter. When the color filter is used, not only the color filter has to be aligned with each electrode for color implementation, but additional cost is generated due to the color filter production, and thus, a method of implementing color without using the color filter is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide an electrophoretic display device which can display a desired color by making an interference layer with a plurality of electrophoretic materials having surface charges without using a color filter. .

In addition, the present invention by expressing all the colors in one pixel using the interference layer of the plurality of electrophoretic material, the light efficiency is higher than the display using the color filter, the thickness is thin, low power, can be used as a flexible display The purpose is to provide a phoretic display device.

In order to achieve the above object, the present invention comprises an upper electrode and a lower electrode facing each other; And a plurality of electrophoretic materials and solvents having surface charges injected between the electrodes, wherein the plurality of electrophoretic materials move to the surface of the electrode by a voltage applied between the electrodes to form an interference layer. It provides an electrophoretic display device, characterized in that.

In addition, the present invention in order to achieve the above object, the upper substrate and the lower substrate facing each other; Electrodes formed on the upper substrate and the lower substrate, respectively; A plurality of partition walls formed to have a plurality of cells between the upper substrate and the following substrate; And it provides a electrophoretic display device comprising a plurality of electrophoretic material and a solvent having a surface charge injected into the plurality of cells.

The electrophoretic display device according to the present invention expresses all colors in one pixel by using an interference layer of a plurality of electrophoretic materials having a surface charge, so that the light efficiency is higher than the display using the color filter, and the thickness is thin. It is low power and can be used as a flexible display.

1 is a view showing a state when no voltage is applied between the electrodes in the electrophoretic display device according to an embodiment of the present invention.
2 is a view showing a state when a voltage is applied between the electrodes in the electrophoretic display device according to an embodiment of the present invention.
3 is a view showing a state in which the red, green, blue color in the electrophoretic display device according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

1 and 2 are cross-sectional views of an electrophoretic display apparatus according to an embodiment of the present invention.

As shown, the electrophoretic display device according to an embodiment of the present invention includes an upper substrate 10 and a lower substrate 20 facing each other; Electrodes 11 and 21 formed on the upper substrate and the lower substrate, respectively; A plurality of partition walls 14 formed to have a plurality of cells between the upper substrate and the lower substrate; And a plurality of electrophoretic materials 12 and a solvent 13 having surface charges injected into the plurality of cells.

The upper and lower substrates 10 and 20 may be made of a flexible material, and a flexible material such as a flexible glass substrate or a flexible plastic may be selected. Preferably, it may be selected from polycarbonate (PC), polyethylene terephthalate (PET), polyethersulfone (PES) or polyimide film (Kapton, Upilex), but is not limited thereto. The thickness of the upper and lower substrates 10 and 20 is preferably about 0.05 to 0.5 mm in order to realize thinning while giving a predetermined strength.

The upper and lower electrodes 11 and 21 formed on the upper and lower substrates, respectively, may be made of a conductive material, and electrode materials commonly used in the art may be used. For example, printed conductors, graphite or conductive carbon materials, such as conductive polymers such as polythiopine, polyaniline or polyethylenedioxythiophene, polymer films containing metal particles such as silver or nickel, or tin oxide or indium Printed conductors, such as polymer films containing conductive oxides, such as tin oxide, may be included, and indium tin oxide (ITO) may be selected. The transparent electrode may be more preferably selected. The electrode used in the present invention does not have a change in resistance even when the strain is about 1.5% when it is bent, and preferably has a thickness of 50 to 500 nm so that the adhesion to the substrate is good.

As the material of the partition 14, a material such as a substrate may be used, and a photoresist for thick film or a photosensitive material in the form of a film may also be used to manufacture an accurate shape. Flexible materials are preferred, and polymers such as polycarbonate (PC), polyethylene terephthalate (PET), polyethersulfone (PES) or polyimide films (Kapton, Upilex) may be selected. The thickness of the partition wall 14 is advantageous if the contact area is made as wide as possible in consideration of the required adhesive strength of the upper and lower plates, but the thickness of the partition wall 14 is preferably about 0.01 to 0.5 mm because of the disadvantage of lowering the opening ratio. .

The electrophoretic material 12 having the surface charge is injected together with the solvent 13 between the electrodes 11 and 21. Specifically, the plurality of electrophoretic materials 12 having the surface charges are injected together with the solvent 13 into the cells formed by the substrates 10 and 20 and the plurality of partitions 14.

The electrophoretic material 12 moves to the surfaces of the electrodes 11 and 21 by an electric field inside the cell to form an interference layer, and reinforces and interfers optically calculated wavelengths according to its thickness and refractive index to produce a desired color. It is a substance that can be expressed. The electrophoretic material 12 can be used in any material or any form as long as it has surface charge. The electrophoretic material 12 preferably uses one kind of nanoparticles. 1 to 3 illustrate nanoparticles as electrophoretic materials having surface charges.

As the material of the nanoparticles, both organic and inorganic materials may be used. As the organic material, organic pigments including azo (azo), cyanine based phthalocyanine pigments and anthraquinone series may be used. As inorganic materials, antimony-doped tin oxide, antimony oxide, zinc oxide, tin oxide, indium tin oxide, Cerium oxide, aluminum oxide, titanium dioxide (TiO ₂ ), zirconium oxide particles, calcium carbonate, talc, black iron oxide, cadmium red, molybdenum red, cadmium yellow, cobalt green, cobalt blue, manganese violet, cobalt violet, carbon black, etc. Can be used. Preferably, particles having a refractive index of 0.1 or more larger than the solvent are used, and more preferably particles having a refractive index of 0.3 or more larger than the solvent are used. To this end, antimony-doped tin oxide, antimony oxide, zinc oxide, tin oxide, indium tin oxide, cerium oxide, aluminum oxide, titanium dioxide (TiO ₂ ), and zirconium oxide particles, which can easily produce a difference in solvent and refractive index, can be used. .

The diameter of the nanoparticles should be smaller than the thickness of the interference layer formed by the electric field between the electrodes, preferably between 3 and 300 nm, more preferably between 5 and 100 nm. If the diameter of the nanoparticles is smaller than 5nm, it is difficult to manufacture the nanoparticles, if larger than 100nm there is a fear of haze generation by fine scattering.

In addition, the electrophoretic material 12 may use micelles or aggregates of oligomers or polymer resins, which are not in the form of particles. The oligomer or the polymer resin is not limited, but urethane, nylon, fluorine, silicone, melamine, phenol, styrene, styrene acryl, urethane acryl, etc. may be used, and preferably polymethyl methacrylate or polyethylene tere. Phthalates, polystyrenes, polyethylenes, polypropylenes, phenol resins, ethylene-vinyl acetate copolymers, polyesters, polyacrylates, polymethacrylates, ethyleneacrylic acid or ethylenemethacrylic acid copolymers and the like can be used.

The electrophoretic material 12 preferably has a refractive index difference of 0.1 or more in order to form an interference layer due to an electric field between the electrodes. If the refractive index difference is 0.1 or less, even if the layers are separated, the reflectance of the interface is low, and the utility as a display is inferior.

The electrophoretic material 12 is injected into the cell at 5 parts by weight to 200 parts by weight with respect to 100 parts by weight of the solvent, preferably 10 parts by weight to 100 parts by weight into the cell. When the electrophoretic material is injected less than 10 parts by weight or more than 200 parts by weight with respect to 100 parts by weight of the solvent, the thickness of the interference layer that can be formed by the electric field is formed in a range that is too thin or too thick to a variety of desired It is difficult to express color. Therefore, in order to express various colors desired by the interference layer of the electrophoretic material, it is preferable to include the electrophoretic material within the above range.

The solvent 13 injected into the cell between the electrodes together with the electrophoretic material 12 causes the electrophoretic material to move fluidly in the electric field when a voltage is applied between the electrodes, and electrophoresis when the voltage is not applied. It is a medium that maintains a vice-table state where material does not move. The solvent 13 has a refractive index difference from that of the electrophoretic material having a surface charge, and the wavelength of the constructive interference is determined by the difference.

If the solvent is a solvent that electrophoretic material is well dispersed there is no limitation to use. Alcohol solvents such as, but not limited to, methanol, ethanol, propanol, isopropanol, butanol and PGME; Epoxide solvents such as decane epoxide and dodecane epoxide; Ether solvents such as vinyl ether and cyclohexyl vinyl ether; Ketone solvents such as MEK and MIBK; Aromatic hydrocarbons such as toluene and naphthalene; Alicyclic hydrocarbons such as dodecane and tetradecane; Halogenated organic solvents such as trifluoroethylene, tetrafluorodibromoethylene, tetrachloroethylene, trifluorochloroethylene, 1,2,4-trichlorobenzene and carbon tetrachloride; Amides such as dimethylacetamide and dimethylformamide; Dimethyl sulfoxide; Tetrahydrofuran; Silicone oils such as octamethyl cyclosiloxane and high molecular weight cyclic siloxane, poly (methyl phenyl siloxane), hexamethyldisiloxane, and polydimethylsiloxane can be used.

The solvent, in order to more smoothly move the electrophoretic material when the electric field is applied to the cell, preferably a polar solvent can be used, and the electrolyte can be injected together with the solvent in the cell. Although there is no restriction | limiting in the kind of electrolyte, It is a polyhydroxy compound containing a hydroxyl group, Ethylene glycol, 2,4,7,9-tetramethyl-decine-4,7-diol, poly (propylene glycol), pentaethylene glycol , Tripropylene glycol, triethylene glycol, glycerol, pentaerythritol, glycerol-tri-12-hydroxystearate, propyleneglycerol monohydroxystearate, ethylene glycol monohydroxystearate, trifluoroethanol can be used. . In addition, aminoalcohol compounds containing at least one alcohol function and at least one amine function in the same molecule include triisopropanolamine, triethanolamine, ethanolamine, 3-amino-1-propanol, o-aminophenol, 5-amino-1- Pentanol and tetra (2-hydroxyethyl) ethylenediamine can be used.

1 is a view showing a state when no voltage is applied between the electrodes in the electrophoretic display device according to an embodiment of the present invention. In the cell between the electrodes 11 and 21, a plurality of nanoparticles 12 are contained in the solvent 13 in the sol state. When no voltage is applied between the electrodes, the nanoparticles 12 are homogeneously dispersed in the solvent 13 inside the cell, and the nanoparticles 12 are in a vice-table state in which the nanoparticles 12 do not move. . The vice-table state refers to a state in which particles are not moved in the state immediately before the electric field is removed even when the external electric field is removed.

2 is a view showing a state when a voltage is applied between the electrodes in the electrophoretic display device according to an embodiment of the present invention. When a voltage is applied between the electrodes 11 and 21, an electric field is generated in the cell, thereby moving the plurality of nanoparticles 12 to the surface of the electrode to form an interference layer. In FIG. 2, although the plurality of nanoparticles 12 move to the surface of the upper electrode 11 to form an interference layer, the plurality of nanoparticles 12 move to the surface of the lower electrode 21 according to the direction of the electric field. To form an interference layer.

As shown in FIG. 2, the plurality of nanoparticles 12 form an interference layer by an electric field inside the cell, and as a result, the cell interior forms a layer separation structure in which the interference layer and the solvent layer of the nanoparticles are separated. As such, when an electric field is applied between the electrodes in the electrophoretic display device of the present invention, a layer-separated structure having different refractive indices is formed inside the cell, and due to such a structure, the desired wavelength range is reinforced and reflected to exhibit a desired color.

3 is a view showing a state in which the red, green, blue color in the electrophoretic display device according to an embodiment of the present invention. The interference layers of the plurality of nanoparticles vary in the degree of surface movement of the particles according to the intensity of the electric field, and thus, the thickness (d) of the moved particle layer is changed, and the density of the particles is also changed, resulting in a refractive index in the interference layer. In view of the average refractive index of the solvent and the particles, the refractive index n changes as the ratio of the particles changes. The constructive interference of the interference layer can be expressed as follows.

(1) mλ = 2nd (when n is smaller than the refractive index of the substrate)

(2) (m + 1/2) λ = 2nd (when n is larger than the refractive index of the substrate)

(Wherein m is an integer, λ is a wavelength, n is the refractive index of the interference layer, and d is the thickness of the interference layer.)

In the present invention, in order to increase the amount of reflected light, the refractive index of the interference layer uses a refractive index higher than that of the substrate. In this case, when m is 1, the basic tricolor (red, green, blue) can be implemented by satisfying the following conditions.

Red: λ = 630nm = (4/3) n _red d _red

Green: λ = 530nm = (4/3) n _green d _green

Blue: λ = 440 nm = (4/3) n _blue d _blue

That is, when the product of the refractive index n and the thickness d of the interference layer coincides with the wavelength of the color, the light of the color is subjected to constructive interference reflection.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but the following examples are merely to illustrate the present invention and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention.

Experimental Example

After bonding two sheets of ITO glass with a gap of 15 μm, TiO ₂ sol (catalyzed yarn, 1330-TIV: solvent MIBK, solid content of 30% by weight) was injected and the glass was sealed. A voltage was applied to the upper and lower ITO to form TiO ₂ as an interference layer between the glasses. After that, the back side of the lower ITO glass was painted black, the reflection color was measured on the opposite side, and the applied voltage in each case and the refractive index and thickness of the interference layer were checked. The results are shown in Table 1 below.

Example 1 Example 2 Example 3 Applied voltage (V) 3 4 5 TiO ₂ interference layer refractive index 2.0 2.1 2.2 TiO ₂ interference layer thickness (nm) 236 189 150 Reflective colors Red green blue

Examples 1 to 3 in Table 1 correspond to cells expressing red, green, and blue in FIG. 3. As such, the electrophoretic display device of the present invention can express all colors in one cell by adjusting the intensity of the electric field in the cell.

10: upper substrate 11: upper electrode
12: electrophoretic material 13: solvent
14: partition 20: lower substrate
21: lower electrode

Claims (15)

An upper electrode and a lower electrode facing each other; And
A plurality of electrophoretic materials and solvents having a surface charge injected between the electrodes,
The plurality of electrophoretic material is moved to the surface of the electrode by a voltage applied between the electrodes to form an electrophoretic display device.
The electrophoretic display device according to claim 1, wherein the electrophoretic material is one kind of nanoparticles.
The electrophoretic display device according to claim 2, wherein the outflow particles are TiO ₂ particles.
The electrophoretic display device according to claim 2, wherein the nanoparticles have a diameter of 3 nm or more and 300 nm or less.
The electrophoretic display device according to claim 1, wherein the electrophoretic material has a refractive index difference of 0.1 or more from the solvent.
The electrophoretic display device according to claim 1, wherein an electrolyte is further injected between the electrodes.
The electrophoretic display device of claim 1, wherein the plurality of electrophoretic materials move to a surface of one of the upper and lower electrodes by a voltage applied between the electrodes to form an interference layer.
The electrophoretic display device of claim 1, wherein the interference layer is subjected to constructive interference by the following equation.
(1) mλ = 2nd (when n is smaller than the refractive index of the substrate)
(2) (m + 1/2) λ = 2nd (when n is larger than the refractive index of the substrate)
(Wherein m is an integer, λ is a wavelength, n is the refractive index of the interference layer, and d is the thickness of the interference layer.)
The electrophoretic display device of claim 1, wherein the interference layer is subjected to constructive interference by the following equation.
λ = (4/3) nd
Where λ is the wavelength, n is the refractive index of the interference layer, and d is the thickness of the interference layer.
An upper substrate and a lower substrate facing each other;
Electrodes formed on the upper substrate and the lower substrate, respectively;
A plurality of partition walls formed to have a plurality of cells between the upper substrate and the lower substrate; And
An electrophoretic display device comprising a plurality of electrophoretic material and a solvent having a surface charge injected into the plurality of cells.
The electrophoretic display device according to claim 10, wherein the electrophoretic material is one kind of nanoparticles.
The electrophoretic display device according to claim 11, wherein the outflow particles are TiO ₂ particles.
The electrophoretic display apparatus of claim 11, wherein the nanoparticles have a diameter of 3 nm or more and 300 nm or less.
The electrophoretic display of claim 10, wherein the electrophoretic material has a refractive index difference of 0.1 or more from the solvent.
The electrophoretic display device according to claim 10, wherein an electrolyte is further injected into the cell.

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