KR20070009901A - Electrophoretic display and manufacturing method thereof - Google Patents

Abstract

An electrophoretic display and a manufacturing method thereof is provided to prevent electrophoretic particles from adhering to a partition wall with a high adhesive force by forming a lubricant layer at a side surface of the partition wall or the like. A lower substrate(10) and an upper substrate(20) face each other with a predetermined gap therebetween. A lower electrode(11) and an upper electrode(21) are formed on inner surfaces of the lower substrate and the upper substrate, respectively. A partition wall(14) is formed between the lower electrode and the upper electrode to divide a pixel and form a pixel space. A lubricant layer(15) is formed at a side surface of the partition wall. Electrophoretic particles are encapsulated within the pixel space.

Description

Electrophoretic Display and Manufacturing Method Thereof}

1 is a cross-sectional view of a wet electrophoretic display using a conventional microcapsule,

2 is a cross-sectional view of a conventional dry electrophoretic display,

3A and 3B are views of agglomeration of conventional dry electrophoretic displays;

4 is a cross-sectional view of an electrophoretic display according to an embodiment of the present invention;

5 is a cross-sectional view of the electrophoretic display electrophoretic particles according to the present invention,

6 is a diagram illustrating a method of forming a lubricating layer of an electrophoretic display according to the present invention.

※ Explanation of the main symbols in the drawing

1: lubricant 2: polymer resin

3: dye or pigment 4: charge control agent

10: lower substrate 11: lower electrode

12: electrophoretic particles 14: bulkhead

15: lubricating layer 20: upper substrate

21: upper electrode

The present invention relates to an electrophoretic display and a method for manufacturing the same, in particular, by forming a lubrication layer on the side of the partition wall, to prevent the electrophoretic particles from sticking to the partition wall with high adhesion to improve the quality of the image, the driving voltage is increased The present invention relates to an electrophoretic display and a method of manufacturing the same, which can prevent an increase in power consumption.

Today, the need for a transformation into a way of communicating and sharing information that corresponds to an information society that requires a new paradigm is accelerating technological development of electronic paper that can be bent as a flexible display and entering the commercial development stage. .

Electronic paper, which has the advantage of being flexible as a flexible display, is much cheaper to produce than a conventional flat panel display panel and can be driven with very little energy because it does not require background lighting or continuous recharging like a liquid crystal display device. Far ahead In addition, the electronic paper is very sharp, has a wide viewing angle, and has a memory function that does not completely disappear even in the absence of power.

These great advantages make it possible for electronic paper to be used in a wide range of applications, such as e-books with paper-like sides and moving illustrations, self-renewable newspapers, reusable paper displays for mobile phones, disposable TV screens and electronic wallpaper. It has a huge potential market.

The technical approach for the electronic paper implementation is largely liquid crystal method, organic EL, reflective film reflective display, electrophoresis, twist ball, electrochromic method, mechanical reflective indicator, and double twist ball method. In the phase change of, there is no voltage threshold and it has a critical defect.Electrochromic devices also have low chemical stability when the colored layer is exposed to air and moisture, and the response speed is high due to the diffusion rate of ions in the electrolyte. Due to the slow drawback, the electronic paper implementation technology currently attracting the most attention is an electrophoretic display using electrophoresis.

The electrophoretic phenomena can be divided into wet and dry methods.

A typical wet method is a display device using a microcapsule proposed by E-Ink, which was established separately from MIT Media Lab and MIT Media Lab (US Patent No. 5961804, etc.).

1 is a cross-sectional view showing the schematic structure. As shown, 200-300 μm in diameter containing ink particles of a specific color with specific charge (103a) and ink particles of different colors (or colored dielectric fluid, 103b) and transparent dielectric fluid 104 having opposite charges. The transparent microcapsules 100 were prepared. These microcapsules are mixed with the binder 107 to be positioned between the upper and lower transparent electrodes 105 and 106 and a voltage is applied to display characters or images by the method described above.

However, this wet method has a problem in realizing a video due to the slow response speed of about 100ms due to the viscous resistance of the liquid, and also has a problem in that a large portion of the upper part of the capsule is shielded by a binder or partially consumed so that the light efficiency is relatively low. . In addition, the specific gravity between the two charged electrophoretic particles and the dielectric fluid should be kept the same, and the physical and chemical treatments for charge attachment to prevent aggregation between the two charged electrophoretic particles and to have electrophoretic mobility Additionally required. In other words, a chemical or physical polymer coating or a polymer ball is produced, followed by a complex process of two or three steps for introducing white and introducing functional groups that facilitate the attachment of charge control agents.

Figure 2 is a cross-sectional view of a dry electrophoretic display to solve this problem. As shown, the dry electrophoretic display encapsulates two types of electrophoretic particles 116 having different colors and charging characteristics between the transparent substrates 111 and 112 having the electrodes 114 and 115 formed on one surface thereof, and the upper and lower electrodes. Electrophoretic charged from the electrodes 114 and 115 of the upper and lower plates having different electric potentials after forming a electrophoretic particle by applying a voltage to (114, 115) and causing the electrophoretic particles to strike each other to give an electric charge due to a collision. It comprises one or more pixels separated from each other by the partition wall 113 which gives an electric field to the particle group and moves to display an image.

The dry electrophoretic display does not have a material with high viscosity such as liquid in the pixel space, so the response speed is considerably fast, which is suitable for the implementation of a video.

In the method of manufacturing such a dry electrophoretic display, it is very important to prevent the electrophoretic particles from sticking together. In other words, when the particles are agglomerated with each other, the fluidity of the particles deteriorates, thereby degrading the stability and uniformity of the image. Development to prevent such agglomeration of particles is urgent.

In addition, in the case of a dry type electronic paper device, when the electrophoretic particles cling to the upper and lower electrodes and the partition wall with high adhesion force, a phenomenon occurs that no matter how high a voltage is applied from the outside, they do not fall apart. Particularly, the partition wall is made of an insulating material, and when charges accumulate, it becomes more unfavorable and the electrophoretic particles stick to the partition wall.

3A and 3B are cross-sectional views and optical photographs of specimens in which the above-mentioned problems appear, as shown in the drawing, resulting in a lower contrast ratio and uneven image quality.

The present invention has been made to solve the above problems, by forming a lubrication layer on the outside of the electrophoretic particles and the side of the partition wall, thereby preventing the electrophoretic particles from agglomerating or sticking to the partition wall with a high adhesion to improve the quality of the image. It is an object of the present invention to provide an electrophoretic display and a method of manufacturing the same, which can improve and prevent the power consumption from being increased by increasing the driving voltage.

The present invention for achieving the above object,

A lower substrate and an upper substrate disposed to face each other at a predetermined interval; A lower electrode and an upper electrode inscribed on the substrate, respectively; A partition wall which contacts the lower electrode and the upper electrode and divides the pixel to form a pixel space; A lubrication layer formed on a side surface of the partition wall; It provides an electrophoretic display comprising electrophoretic particles enclosed in the pixel space.

The apparatus may further include an upper insulating layer and a lower insulating layer inscribed to the upper electrode and the lower electrode, or further include a lubrication layer inscribed in the pixel space region of the upper electrode or the lower electrode. It provides an electrophoretic display further comprising a lubrication layer inscribed in the pixel space region of the insulating layer.

In addition, the electrophoretic particles are formed by including a lubricant on the outside, the lubricating layer is made of the same material as the material of the lubricant formed on the outside of the electrophoretic particles, the lubricating layer comprises silica particles (silica) particles It comprises, and the silica particles provide an electrophoretic display, characterized in that the nano-size.

The method may further include forming upper and lower electrodes on one surface of the upper and lower substrates, respectively; Forming a partition on the lower electrode to provide a plurality of pixel spaces; Forming a lubrication layer on the side surface of the partition wall; Injecting electrophoretic particles into the pixel space for image representation; And stacking and bonding the upper substrate on which the upper electrode is formed to the upper surface of the partition wall.

The method may further include forming a lubricating layer in the pixel space region of the lower electrode or the upper electrode, wherein the lubricating layer is formed by pressurizing and spraying a lubricant on the partition wall, and the lubricating layer is silica. It comprises a particle, the silica particle provides a method for producing an electrophoretic display, characterized in that the nano-size.

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

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

As shown in the drawing, the lower substrate 10 and the upper substrate 20 which are disposed to face each other at a predetermined interval, and the lower electrode 11 and the upper electrode 21 in contact with the substrate, respectively, the lower electrode 11 and A partition wall 14 which contacts the upper electrode 21 and divides the pixel to form a pixel space, a lubrication layer 15 formed on the side surface of the partition wall 14, and a plurality of electrophoretic particles 12a enclosed in the pixel space. , An electrophoretic display comprising 12b).

Referring to the configuration of the electrophoretic display of the present invention in more detail as follows.

The upper and lower substrates 10 and 20 are made of a flexible material. Flexible materials of the general glass substrate or flexible plastic type can 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 substrates 10 and 20 is most preferably about 0.05 to 0.5 mm in order to achieve a thin film while giving a predetermined strength.

The upper and lower electrodes 11 and 21 formed on the substrates 10 and 20 are conductive materials, and electrode materials commonly used in the art of the present invention may be used, and conductive polymers such as polythiopin or polyaniline, Printed conductors such as polymer films containing metal particles such as silver or nickel, printed conductors such as graphite or conductive carbon materials, or polymer films containing conductive oxides such as tin oxide or indium tin oxide, etc. Indium tin oxide (ITO) may be selected. The transparent electrode may be more preferably selected. When bent, the strain is about 1.5% and there is no change in resistance, and it is preferable to have a thickness of 50 to 500 nm so that the adhesion to the substrate is good. The upper and lower electrodes are arranged to perpendicularly cross each other.

As the material of the barrier rib 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 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 10 to 500 μm because of the disadvantage of lowering the opening ratio.

The electrophoretic particles 12 are intended for image representation, all of the electrophoretic particles used for image representation in the art may be used. Among them, dry particles may be preferably selected. Electrophoretic particles having different colors and charging characteristics are selected, and in order to display monochrome, it is preferable to use carbon black as black particles and titanium oxide as white particles. The charged particles may be injected, or may be applied while charging by using a corona discharge at the time of coating.

Preferably, after injecting uncharged particles, a dry charging collision-type electrophoretic particle is injected, by applying a voltage to the upper and lower electrodes to collide the particles with each other to form an electrophoretic particle by causing a charge due to a collision. Good to do.

The lubrication layer 15 is used to prevent the electrophoretic particles from adhering to the partition wall in manufacturing an electrophoretic display having a high contrast ratio, thereby improving the fluidity of the electrophoretic particles and preventing the electrophoretic particles from agglomerating into the partition wall. Is applied to. In FIG. 4, the lubrication layer is formed only on the partition wall, but is not limited thereto. A lubrication layer may also be formed on the pixel region portions of the upper electrode and the lower electrode to prevent the electrophoretic particles from sticking to the electrode and falling off. In addition, when the insulating layer is inscribed on the upper electrode and the lower electrode, a lubricating layer may be formed on the insulating layer.

It is preferable to use the same material as the lubricant applied to the electrophoretic display electrophoretic particles, which will be described later, for more effective lubrication. In addition, the material of the lubricating layer is preferably used nano-size. This is to ensure that even if the material of the lubricating layer is slightly separated from the partition wall, it is nano-sized so that it is invisible to the human eye so as not to drop the contrast ratio. Lubricants of the preferred material is barium titanate (BaTiO _3), strontium titanate (SrTiO _3), calcium titanate (CaTiO _3), lead titanate (PbTiO _3), titanium dioxide (TiO _2), tin dioxide (SnO ₂ ), calcium oxide (CaO), magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), gamma iron oxide, magnesium silicate (MgSiO ₃ ), magnetite (Fe ₃ O ₄ ), Zirconia (ZrO ₂ ), boron oxide (B ₂ O ₃ ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), nickel ferrite, zinc ferrite, nickel zinc ferrite and barium ferrite (BaFe ₂ O ₄ At least one selected from the group consisting of), most preferably silica (SiO ₂ ) is suitable.

Although not shown in FIG. 4, the insulating layer may be formed by in contact with the upper electrode and the lower electrode, respectively. The insulating layer may be formed to prevent the electrophoretic particles are attached to the electrode and discharged.

In forming the insulating layer, it is formed to a thickness of 0.01 to 10 탆 by a method such as sputtering, chemical vapor deposition (CVD), or vacuum deposition. The material is preferably a transparent material, and silicon oxide, silicon nitride, silicon carbide, aluminum oxide, tantalum oxide (Ta ₂ O ₃ ), and the like may be selected, and a polymer resin may be selected.

The lower insulating layer may be naturally formed when forming the partition 14. That is, when pressing the mold to form the partition wall 14, the lower surface of the pixel space may have a predetermined thickness so that the insulating layer may be integrated with the partition wall to perform an insulating role.

5 shows a preferred embodiment of a dry electrophoretic display electrophoretic particle 12 according to the present invention.

As shown in the figure, it is preferable that the lubricant 1 is coated on the outer shell of the polymer resin 2 including the charge control agent 4 and the pigment or the dye 3. The lubricant may be physically coated or coated with a chemical bond.

The lubricant (1) is to improve the fluidity of the electrophoretic particles and to prevent agglomeration between the electrophoretic particles, preferred materials of the lubricant is barium titanate (BaTiO ₃ ), strontium titanate (SrTiO ₃ ), calcium Titanate (CaTiO ₃ ), lead titanate (PbTiO ₃ ), titanium dioxide (TiO ₂ ), tin dioxide (SnO ₂ ), calcium oxide (CaO), magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ), Iron oxide (Fe ₂ O ₃ ), gamma iron oxide, magnesium silicate (MgSiO ₃ ), magnetite (Fe ₃ O ₄ ), zirconia (ZrO ₂ ), boron oxide (B ₂ O ₃ ), silicon carbide (SiC), silicon At least one selected from the group consisting of nitride (Si ₃ N ₄ ), nickel ferrite, zinc ferrite, nickel zinc ferrite and barium ferrite (BaFe ₂ O ₄ ), most preferably silica (SiO ₂ ) is suitable. .

The polymer resin (2) is, but not limited to, polymethyl methcrylate (PMMA), polyethylene terephthalate (PETE), polystyrene (PS), polyethylene, polypropylene, phenol resin, Du Pont Elvax resin (Ethylene-vinyl acetate copolymer), polyester, polyacrylate, polymethacrylate, ethylene acrylic acid or methacrylic acid copolymer (Nucrel Resins-Dupont, Primacor Resins-Dow Chemical) acrylic acid copolymer and trimer (Elvacite Resins) , DuPont). In addition, as these copolymers, materials useful for high shear melting homopolymers and / or pigment phase separation include, but are not limited to, polyethylene, polypropylene, polymethylmethacrylate, polyisobutylmethacrylate, polystyrene, Polybutadiene, polyisoprene, polyisobutylene, polylauryl methacrylate, polystearyl methacrylate, polyisobornyl methacrylate, poly-t-butyl methacrylate, polyethyl methacrylate, polymethyl Acrylate, polyethyl acrylate, polyacrylonitrile and copolymers of two or more such materials.

The pigments or dyes (3) may be pigments, polymers, laked pigments or some combination thereof which are commonly used. Pure pigments can be any pigment, and pigments such as rutile (titania), anatase (titania), barium sulfate, kaolin or zinc oxide are generally useful for pale particles. Some typical particles have high refractive index, high scattering coefficient and low absorption coefficient. Other particles are absorbent, such as carbon black or colored pigments used in paints and inks. In addition, the pigment should be insoluble in the suspension fluid. Yellow pigments such as diarylide yellow, Hansa yellow and benzidine yellow are also used in similar displays. Any other reflective material can be used for the pale particles, including non-pigment materials such as metallic particles. Carbon black may be preferably selected for black expression and titanium oxide for white expression.

The charge control agent 4 is used to provide good electrophoretic mobility to the electrophoretic particles. The charge control agent is not limited, but may be made of metal soap, OLOA series, Ganex series, or mixtures thereof. Preferable examples of the charge control agent 4 made of metal soap include preferred examples of the charge control agent made of metal soap, such as Co-naphthenate, Ca-naphthenate, Cu-naphthenate and Mn-naphthene. Acid, 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.

Hereinafter, a method of manufacturing the electrophoretic display of the present invention will be described.

First, a method of forming the electrodes 11 and 21 on the substrates 10 and 20 is well known in the art, and accordingly, the conventional method. Preferably, screen printing, photolithography or the like can be used. In particular, if the resolution is not large, it can be formed by screen printing liquid ITO.

Next, the partition wall 14 is formed on the lower electrode 11 of the lower substrate 10 to form a pixel space. First, the partition 14 material film is evenly applied and then crimped into a predetermined mold to form the partition 14. In the mold, it is preferable to use a mold in which a plurality of molds are spaced apart at predetermined intervals so that a plurality of barrier ribs are formed at the time of pressing molding. The partition wall 14 may be formed directly by forming a material film on the lower electrode 11 by compression molding, or may be separately bonded to the lower electrode after the partition wall 14 is formed. Through the crimping molding method, bulkheads can be mass-produced to simplify the manufacturing process and reduce manufacturing costs.

Next, the lubricant is injected to the side surface of the partition wall 14 to form the lubrication layer 15 on the side surface.

Figure 6 illustrates a method of forming a lubrication layer 15 of an electrophoretic display according to the present invention. It is preferable to form a lubricating layer by pressure spraying as shown. The partition wall and the pressure injector may be sprayed closer than shown, and the distance may be arbitrarily adjusted.

The pressurized spray is preferably sprayed by air pressure and is controlled to be less than the pneumatic pressure used in the sand blasting process so that the partition wall is not etched. Since the degree of pneumatic pressure can be arbitrarily adjusted by those skilled in the art, a detailed description thereof will be omitted.

When the lubrication layer 15 is formed only on the side surfaces of the partition wall, a method of forming a lubrication layer on the partition wall separately manufactured by the above method and then attaching the lower electrode may be used. The lubricating layer may also be formed on the upper and / or lower electrodes (not shown), and the method may be formed by the above-described method of forming the electrode or may be formed by the pressure spraying method.

Next, the electrophoretic particles 12 for image expression are injected and applied to the pixel space. That is, the electrophoretic particles may be injected and applied by spraying, screen printing, roll coating or spin coating, but the present invention is not limited thereto. Any method may be used as long as the electrophoretic particles 12 may be injected into the pixel space. Everything is possible.

Next, when all of the electrophoretic particles 12 are injected, the UV curable adhesive is applied to the upper surface of the partition 14, the upper substrate 20 on which the upper electrode 21 is formed is laminated, and the upper substrate 20 is irradiated with ultraviolet rays. )). As a result, electrophoretic particles are enclosed in the pixel.

In the case where the injected electrophoretic particles 14 are collision-charged electrophoretic particles, they are generally injected into the pixel space in an uncharged state, so that the voltages are applied to the upper and lower electrodes 11 and 21 after the upper substrate 20 is bonded. The electrophoretic particles are applied to each other so that the electrophoretic particles are charged with each other to form electrophoretic particles, thereby completing the electrophoretic display of the present invention.

The above embodiments are described in detail to make the present invention easier to understand and are not intended to limit the present invention. Thus, modified electrophoretic displays that are typically applicable are also included in the present invention.

As described above, the present invention prevents agglomeration between the electrophoretic particles by forming a lubricant on the outside of the electrophoretic particles to greatly improve the fluidity of the electrophoretic particles, and also electrophoresis through a structure in which a lubrication layer is formed on the side of the partition wall. Prevents particles from sticking to the partition walls with high adhesion to improve image quality, increases the contrast ratio of the images, and increases the driving voltage to achieve particle quality by agglomerating particles and sticking to the partition walls. This prevents the power consumption from being lowered.

Claims (13)

A lower substrate and an upper substrate disposed to face each other at a predetermined interval; A lower electrode and an upper electrode inscribed to each of the lower substrate and the upper substrate; Barrier ribs formed between the lower electrode and the upper electrode to divide the pixel to form a pixel space; A lubrication layer formed on a side surface of the partition wall; And An electrophoretic display comprising electrophoretic particles enclosed in the pixel space. The electrophoretic display of claim 1, further comprising an upper insulating layer and a lower insulating layer inscribed to the upper electrode and the lower electrode, respectively. The electrophoretic display of claim 1, further comprising a lubrication layer inscribed on the pixel space region side of the upper electrode or the lower electrode. The electrophoretic display of claim 2, further comprising a lubrication layer inscribed on the pixel space region side of the upper or lower insulating layer. The electrophoretic display according to claim 1, wherein the electrophoretic particles are formed by including a lubricant on the outside. The electrophoretic display of claim 5, wherein the lubricating layer comprises the same material as that of the lubricant formed on the outside of the electrophoretic particles. The electrophoretic display according to any one of claims 1 to 6, wherein the lubricating layer comprises silica particles. The electrophoretic display of claim 7, wherein the silica particles are nanoscale. Forming upper and lower electrodes on one surface of the upper and lower substrates, respectively; Forming a partition on the lower electrode to provide a plurality of pixel spaces; Forming a lubrication layer on the side surface of the partition wall; Injecting electrophoretic particles into the pixel space for image representation; And And an upper substrate on which the upper electrode is formed is laminated and bonded to an upper surface of the partition wall. The method of claim 9, further comprising the step of forming a lubrication layer on the pixel space region side of the lower electrode or the upper electrode. 10. The method of claim 9, wherein the lubricating layer is formed by pressurizing a lubricant to the partition wall. 10. The method of claim 9, wherein the lubricating layer comprises silica particles. The method of claim 12, wherein the silica particles are nano-sized.

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