KR100662196B1 - Electrophoretic display and manufacturing method thereof - Google Patents

Abstract

An electrophoretic display and a method of fabricating the electrophoretic display are provided to reduce the driving voltage of the electrophoretic display by forming fine protrusions on upper and lower electrodes coming into contact with electrophoretic particles. An electrophoretic display includes an upper structure, a lower structure, barriers(14), and electrophoretic particles(12). The upper structure includes an upper substrate(20), an upper electrode(21) and upper fine protrusions(30a). The lower structure is located opposite to the upper structure having a predetermined distance from the upper structure and includes a lower substrate(10), a lower electrode(11) and lower fine protrusions(30b). The barriers are formed between the upper structure and the lower structure to form pixel spaces. The electrophoretic particles are filled in the pixel spaces.

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,

3 is a partial cross-sectional view showing a state of contact between the electrophoretic particles and the electrode of the conventional dry electrophoretic display,

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

5 is a partial cross-sectional view showing a contact state of the electrophoretic particles and the micro-projection of the electrophoretic display according to an embodiment of the present invention,

6a to 6c are enlarged cross-sectional views of the microprojection of the electrophoretic display according to an embodiment of the present invention;

7a to 7d is a partial flow chart of the electrophoretic display manufacturing method according to an embodiment of the present invention,

8a to 8c is a partial flow chart of the electrophoretic display manufacturing method according to an embodiment of the present invention,

9 is a cross-sectional view of an electrophoretic display according to an example of a variant of the invention.

※ Explanation of the main symbols in the drawing

10: lower substrate 11: lower electrode

12: electrophoretic particles 14: bulkhead

15: insulating layer 20: upper substrate

21: upper electrode 30: fine protrusion

The present invention relates to an electrophoretic display and a method of manufacturing the same, and more particularly, to an electrophoretic display having a microprojection for reducing the contact area with the electrophoretic particles and a method of manufacturing the same.

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 electronic papers in a wide range of applications, including paper-like faces and e-books with moving illustrations, self-renewable newspapers, reusable paper displays for mobile phones, disposable TV screens and electronic wallpaper. It has a huge potential market, which is accelerating the development of electronic paper technology and entering the commercial development stage.

The technical approach to the electronic paper implementation is largely liquid crystal method, organic EL, reflective film reflective display, electrophoresis, twist ball, electrochromic, mechanical reflective indicator, the most attention Paper implementation technology is an electrophoretic display using electrophoresis.

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

1 is a diagram illustrating an electrophoretic display using a microcapsule proposed by E-Ink, which is separated from a representative MIT Media Lab and a MIT Media Lab in a wet manner (US Patent No. 5961804, etc.). 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 is slow in response time by about 100ms due to the viscous resistance of the liquid, and there are many problems in the implementation of the video.In addition, a large part of the upper part of the capsule is shielded by a binder or partially consumed so that the light efficiency is relatively low. have. 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 insulating layer 117 may be further included to effectively prevent the discharge of charged electrophoretic particles.

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 order to realize the commercialization of the dry electrophoretic display, research is being actively conducted to lower the driving voltage, in particular, to realize portability.

3 is a partial cross-sectional view of the dry electrophoretic display, in which dry electrophoretic particles are in contact with an upper or lower electrode. Dry electrophoretic particles are mainly manufactured in the form of beads, but since the polymer base material is a component, as shown, the surface of the electrophoretic particles is embedded by the van der Waals force and / or coulomb force. It has a contact area and comes into contact with the upper or lower electrode. In particular, the contact area is further increased because the electrode or the insulating layer has a flat structure.

When contacted with a high contact force with a large contact area as described above, the van der Waals force increases, so even if a very high voltage is applied to each other, a phenomenon occurs that the driving voltage increases.

This problem is hampering the practical use and portability of the electrophoretic display is urgent solution.

The present invention is to solve the above problems, by having an upper structure and a lower structure having a microprojection formed on the upper and lower electrodes in contact with the electrophoretic particles, the contact area of the electrophoretic particles and the upper structure and the lower structure The purpose of the present invention is to provide an electrophoretic display and a method of manufacturing the same, which can reduce the driving voltage by reducing the van der Waals force, thereby allowing the electrophoretic particles to easily escape from the upper structure and the lower structure even at a low voltage. It is done.

The present invention for achieving the above object,

An upper structure including an upper substrate, an upper electrode, and an upper microprojection, and a lower structure, the lower structure including a lower substrate, a lower electrode, and a lower microprojection, disposed to face each other at a predetermined interval, and the upper structure and the lower structure; It provides an electrophoretic display comprising a partition wall formed to form a pixel space between the structures and electrophoretic particles enclosed in the pixel space.

The microprojection may be made of an insulating material, and may further include a lower insulation layer between the upper electrode and the upper microprojection and / or between the lower electrode and the lower microprojection.

In addition, the upper and lower fine protrusions may be formed limited to the pixel space. The microprojections may be made by applying microparticles having a size of 0.1 to 0.01 times the electrophoretic particles, and the microprojections may be made by applying microparticles having a size of 10 nm to 10 μm.

The thickness of the microprojection is preferably in the range of 10nm ~ 10㎛, the microprojection may be made of a polymer or an inorganic oxide. The polymer may be, in particular, polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyimide (PI) or polystyrene (PS), and the inorganic oxide may be silica (SiO ₂ ), Titanium oxide (TiO ₂ ), alumina (Al ₂ O ₃ ), or zinc oxide (ZnO).

In addition, the protruding shape of the microprojections may be hemispherical, pyramid, cone, prismatic or cylindrical, or a combination thereof.

In another aspect of the present invention for achieving the above object,

Forming an upper electrode on the upper substrate and forming an upper microprojection on the upper electrode, manufacturing an upper structure, forming a lower electrode on the lower substrate, and forming a lower microprojection on the lower electrode; Manufacturing a lower structure, manufacturing a partition for forming a pixel space on the lower structure, injecting electrophoretic particles into the pixel space for image representation, and the upper structure; It provides a method of manufacturing an electrophoretic display comprising the step of laminating the bottom structure formed with the partition wall.

The method may further include forming an upper insulating layer between the upper electrode and the upper microprojection, and further comprising forming a lower insulating layer between the lower electrode and the lower microprojection.

In addition, the process of forming the micro-projection, characterized in that for applying a material containing an organic polymer or inorganic oxide fine particles of 0.1 ~ 0.01 times the size of the electrophoretic particles, or after applying the organic polymer or inorganic oxide Photolithography may be used, or a mold having predetermined microgrooves may be used after applying an organic polymer or an inorganic oxide.

In addition, the protruding shape of the microprojections may be hemispherical, pyramid, cone, prismatic or cylindrical, or a combination thereof.

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, the upper structure comprising the upper substrate 20, the upper electrode 21 formed under the upper substrate 20 and the upper micro-projection portion 30a formed below the upper electrode 21, the upper It is disposed to face the structure at a predetermined interval, and includes a lower substrate 10, a lower electrode 11 formed on the lower substrate 10 and a lower microprojection portion 30b formed on the lower electrode 11. And a partition 14 formed to form a pixel space between the upper structure and the lower structure, and electrophoretic particles 12 encapsulated in the pixel space.

In particular, by forming a micro-projection as described above, it is possible to reduce the contact area between the electrophoretic particles 12 and the upper and lower electrodes (11, 21), so that the electrophoretic particles (12) at a lower driving voltage It can be separated from the electrode.

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

The micro-projection 30 is one of the great features of the present invention, the material is not limited but preferably comprises a polymer or an inorganic oxide. In particular, the polymer may be selected from polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyimide (PI) or polystyrene (PS), the inorganic oxide is silica ( SiO ₂ ), titanium oxide (TiO ₂ ), alumina (Al ₂ O ₃ ) or zinc oxide (ZnO) may be preferably selected.

The upper and lower fine protrusions 30 may be formed to cover all of the upper or lower electrodes 11. More preferably, since the electrophoretic particles 12 exist only in the pixel space, the microprojections 12 are more preferably formed only in the pixel space. The thickness of the microprojection is not limited but is preferably in the range of 10 nm to 10 μm.

In addition, the micro-projection 30 may be made of an insulating material such as a polymer or an insulating inorganic oxide, and may also be configured to serve as an insulating layer. In this case, the charged electrophoretic particles 12 may be prevented from being discharged in contact with the electrode.

The upper and lower substrates 10 and 20 are made of a flexible material. Flexible materials, such as flexible glass substrates or flexible plastics, 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 11 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 made as wide as possible in consideration of the required adhesive strength of the upper and lower plates, but since the opening ratio may be lowered, the thickness of the partition wall 14 is preferably about 10 to 500 μm. .

The electrophoretic particles 12 are intended for image representation, all of the electrophoretic particles used for image representation in the art may be used. 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.

5 is a partial cross-sectional view of the electrophoretic display according to the present invention, showing a contact state between the microprojection 30 and the electrophoretic particles 12 formed by the method of applying the microparticles in the method of manufacturing a microprojection to be described later. to be.

As shown, the contact area of the electrophoretic particles is reduced and the van der Waals forces are reduced by the minute protrusions of the microprojections 30 naturally formed by applying the fine particles. Therefore, the electrophoretic particles 12 are easily separated from the upper and lower structures, thereby reducing the driving voltage.

6a to 6c are cross-sectional views and plan views showing the projecting shape of the micro-projection portion 30 of the electrophoretic display according to the present invention.

The protruding shape of the fine protrusions 30 is not limited and may protrude in various shapes. Preferably it may have a hemispherical protruding shape (Fig. 7a), it may have a protruding shape of a pyramid such as a cone or pyramid (Fig. 7b), it may have a protruding shape of a cylinder or a prismatic, the combination of the Can have

Hereinafter, a manufacturing method of the electrophoretic display of the present invention will be described with reference to FIGS. 4, 7A to 7D, and 8A to 8C.

The manufacturing method of the electrophoretic display of the present invention includes the process of forming the upper electrode 21 on the upper substrate 20 and the upper micro-projection portion 30a on the upper electrode 21 to manufacture the upper structure. Manufacturing a lower structure, including forming a lower electrode 11 on the lower substrate 10 and forming a lower microprojection part 30b on the lower electrode 11. Manufacturing a partition wall 14 for forming a pixel space in the pixel space, injecting electrophoretic particles 12 into the pixel space for image representation, and stacking the upper structure and a lower structure on which the partition wall 14 is formed. It characterized in that it comprises a step of bonding.

First, the method of forming the upper and lower electrodes 11 and 21 on the upper and lower substrates 10 and 20 is well known in the art, and accordingly, the conventional method is used. 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, fine projections 30 are formed on the upper and lower electrodes 11 and 21, respectively, to complete the upper structure and the lower structure.

The fine protrusions 30 may be used without limitation as long as the method of forming the fine protrusions is included in the scope of the present invention. Preferably, the microprojection 30 is formed using an addition method, a photolithography method, or a molding method.

The addition method is a method of naturally forming fine protrusions by applying fine particles on the electrode. In order to apply the fine particles to the electrode more effectively, a binder such as a polymer resin and the like may be mixed and applied. Or after apply | coating a binder or adhesive agent, such as a polymeric resin, on an electrode, you may apply a fine particle on it. The shape of the microparticles is not limited and it is preferable to have a spherical shape, a prismatic shape or a cylindrical shape, and particularly preferably a spherical shape. The size of the microparticles preferably has a size of 0.1 ~ 0.01 times the size of the electrophoretic particles (12). In particular, the size of the fine particles is preferably in the range of 10nm ~ 10㎛.

It is preferable that the microparticles comprise a polymer or an inorganic oxide. In particular, the polymer may be selected from polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyimide (PI) or polystyrene (PS), the inorganic oxide is silica ( SiO ₂ ), titanium oxide (TiO ₂ ), alumina (Al ₂ O ₃ ) or zinc oxide (ZnO) may be preferably selected.

7A to 7D are flowcharts of a photolithography method of forming the microprojection 30. As shown, after forming the above-described material for forming the microprojection 30 on the electrode evenly (Figs. 7a, 7b), and using the photoresist PR on the top to form a pattern mask ( Fig. 7c), dry or wet etching to complete the microprojection (Fig. 7d). Protruding shapes of various microprojections may be implemented according to the pattern shape of the photoresist. The photolithography method has an advantage that high precision can be achieved.

8A to 8C are flowcharts of a molding method of forming the microprotrusions 30. As shown, after uniformly forming the above-described material for forming the microprotrusions on the electrode (FIG. 8A), pressing and pressing the mold 50 with a predetermined groove (FIG. 8B), By removing 50), it is possible to implement protrusion shapes of various microprojections. It may be further heated when pressing into a mold. Alternatively, the microprojection material may be put in a mold to form a predetermined shape and then adhered to the upper electrode 21 or the lower electrode 11.

Next, when the fine protrusions 30 are completed, the partition wall 14 for forming the pixel space on the lower structure is formed. The partition 14 may be formed by photolithography or the like, and the partition 14 may be formed by uniformly applying a film of the partition 14 material and then pressing and molding 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 attached to the lower electrode 11 after the partition wall 14 is formed. Through the compression molding method, the bulkhead can be mass-produced, thereby simplifying the manufacturing process and reducing the manufacturing cost.

Next, the electrophoretic particles 12 for image expression are injected and applied to the pixel space. That is, the electrophoretic particles 12 may be injected and applied by spraying, screen printing, roll coating or spin coating, but are not limited thereto, and the electrophoretic particles 12 may be injected into the pixel space. All methods are 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, the electrophoretic particles 12 are enclosed in the pixel.

In the case where the injected electrophoretic particles 12 are collision-charged electrophoretic particles, they are generally injected into the pixel space in an uncharged state. The electrophoretic particles 12 are applied to each other so that they are charged with the collision to form the electrophoretic particles 12 to complete 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.

9 is a cross-sectional view of an electrophoretic display further including an insulating layer 15 as an example of a modification of the present invention. That is, the insulating layer 15 may be formed between the upper electrode 21 and / or the lower electrode 11 and the micro-projection to prevent discharge of the charged electrophoretic particles 12.

The insulating layer 15 is formed by a method such as sputtering, chemical vapor deposition (CVD), vacuum deposition, coating, or printing. The thickness is not limited, but is formed to a thickness of 0.01 ~ 10㎛. 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 15b may be naturally formed when the partition wall 14 is formed. 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.

As described above, in the conventional electronic paper display, when the electrophoretic particles come into contact with a large contact area, the van der Waals force increases, thereby strongly adhering to the upper or lower structure. Therefore, even if a very high voltage is applied, a phenomenon occurs that does not fall apart, resulting in a problem that the driving voltage is increased.

The present invention forms a micro-projection on the electrode or insulating layer that the electrophoretic particles contact, thereby preventing the electrophoretic particles from sticking to the upper or lower structure with high adhesion to improve the quality of the image, increase the contrast ratio of the image It provides the effect of reducing the driving voltage.

Claims (21)

An upper structure including an upper substrate and an upper electrode formed below the upper substrate; A lower structure disposed to face the upper structure at a predetermined interval, the lower structure including a lower substrate and a lower electrode formed on the lower substrate; Barrier ribs formed to form a pixel space between the upper structure and the lower structure; And Electrophoretic particles encapsulated in the pixel space and electrophoretic up and down; Electrophoretic display having a micro-projection portion is formed in the upper electrode lower and the lower electrode upper portion to reduce the driving voltage by reducing the adhesion with the electrophoretic particles. The electrophoretic display of claim 1, wherein the microprojection is made of an insulating material. The electrophoretic display of claim 1, further comprising an upper insulating layer between the upper electrode and the upper microprojection. The electrophoretic display of claim 1 or 3, further comprising a lower insulating layer between the lower electrode and the lower microprojection. The electrophoretic display of claim 1, wherein the upper and lower microprojections are defined in a pixel space. delete The electrophoretic display of claim 1, wherein the microprojections are coated with fine particles having a size of 10 nm to 10 µm. The electrophoretic display of claim 1, wherein the thickness of the microprojections is in the range of 10 nm to 10 μm. The electrophoretic display of claim 1, wherein the microprojections comprise a polymer or an inorganic oxide. The electrophoretic display according to claim 9, wherein the polymer is polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene terephthalate (PET), polyimide (PI) or polystyrene (PS). The electrophoretic display of claim 9, wherein the inorganic oxide is silica (SiO ₂ ), titanium oxide (TiO ₂ ), alumina (Al ₂ O ₃ ) or zinc oxide (ZnO). The electrophoretic display of claim 1, wherein the protruding shape of the microprojections is hemispherical, pyramid, cone, prismatic or cylindrical, or a combination thereof. delete delete delete delete delete delete delete delete delete

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