KR20080006036A - Eletrophoretic display apparatus - Google Patents

Abstract

An EPD(Electrophoretic Display) is provided to increase reaction velocity as protrusion parts limit the path of pigment particles so that friction can be diminished between the pigment particles. An EPD comprises a lower substrate and an upper substrate(200). The lower substrate comprises gate lines, data lines(130), thin film transistors, a planarized film(150), partition walls(160), protrusion parts(180) and pixel electrodes(170). The gate lines and the data lines(130), crossing one another, define pixel regions. The thin film transistors are electrically connected with the gate lines and the data lines(130). The planarized film(150) covers the thin film transistors. The partition walls(160), formed on the planarized film(150), respectively enclose the pixel regions. Each of the protrusion parts(180) is formed at each of the pixel regions. The pixel electrodes(170), respectively formed between the partition walls(160) and the protrusion parts(180), are electrically connected with the thin film transistors. The upper substrate(200), combined with the lower substrate, contains an electrophoretic medium(300), and comprises a common electrode(220).

Description

Electrophoretic display {ELETROPHORETIC DISPLAY APPARATUS}

1 is a plan view illustrating a lower substrate of an electrophoretic display device according to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line II ′ of FIG. 1.

3 is another plan view illustrating a lower substrate of an electrophoretic display device according to an exemplary embodiment of the present invention.

4 and 5 are conceptual cross-sectional views for describing an operation of an electrophoretic display device according to an exemplary embodiment of the present invention.

6 is a plan view illustrating a lower substrate of an electrophoretic display device according to another exemplary embodiment.

      * Description of the symbols for the main parts of the drawings

100: lower substrate 110: lower base substrate

120: gate line 130: data line

TFT: thin film transistor 150: planarization film

160: partition wall 170: pixel electrode

180: protrusion 200: upper substrate

300: electrophoretic medium 310: fluid

320: pigment particles

The present invention relates to an electrophoretic display device, and more particularly, to an electrophoretic display device capable of increasing the reaction rate.

An electrophoretic display (EPD) is one of the flat panel display devices used in an e-book. In general, an electrophoretic display (EPD) is formed between two display panels on which electric field generating electrodes are formed and between the display panels, respectively, and is white in color. And microcapsules comprising an electronic ink that is black and has positive and negatively charged pigment particles.

The electrophoretic display displays an image by applying a voltage to two opposite electrodes to generate a potential difference across the electrodes to move charged pigment particles having black and white colors to electrodes having opposite polarities, respectively.

The electrophoretic display has a high reflectance and contrast, and unlike the liquid crystal display, has no dependence on viewing angle, and thus has an advantage of displaying an image with a comfortable feeling like paper. In addition, it has a bistable characteristic of black and white color, so that an image can be maintained without applying a constant voltage, and power consumption is small. In addition, unlike a liquid crystal display device, a polarizing plate, an alignment film, a liquid crystal layer, and the like are not required, which has advantages in terms of price competitiveness. In addition, since the opposing display panel is attached to the thin film transistor array panel using a laminator, the manufacturing process is simple.

However, in order to manufacture the electrophoretic display including the microcapsule, a process of manufacturing the microcapsule is required, and a film including the microcapsule must be manufactured, so that manufacturing cost is high and various applications are difficult.

Accordingly, the technical problem of the present invention is to solve such a conventional problem, and to provide an electrophoretic display device capable of increasing a reaction speed.

An electrophoretic display device according to an aspect of the present invention includes a lower substrate and an upper substrate. The lower substrate includes a plurality of gate lines and a plurality of data lines crossing each other to define a pixel region, a plurality of thin film transistors electrically connected to the gate lines and the data lines, a planarization film covering the thin film transistors, and the planarization. And a partition wall formed on the film and surrounding each pixel area, a protrusion formed in each pixel area, and a pixel electrode formed between the partition wall and the protrusion and electrically connected to the thin film transistor. The upper substrate is combined with the lower substrate to receive an electrophoretic medium and includes a common electrode.

The electrophoretic medium may comprise a fluid and pigment particles dispersed in the fluid. For example, the fluid may be black, the pigment particles may be white, on the contrary, the fluid may be white, and the pigment particles may be black. The pigment particles are either positively or negatively charged. In addition, the fluid and the pigment particles may have a color of any one of red, green and blue, respectively.

The pixel electrode may be symmetrical with respect to the protrusion, and the pixel electrode may include a plurality of sub pixel electrodes facing each other with the protrusion interposed therebetween. In addition, the pixel electrode may be formed to surround the protrusion.

The height of the protrusion may be lower than the height of the partition wall and spaced apart from the partition wall by a predetermined distance.

The upper substrate may further include a sealing material coupling the upper substrate and the lower substrate.

As described above, the image quality and the response speed of the electrophoretic display device having the protrusion may be improved.

Hereinafter, an electrophoretic display device according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a plan view illustrating a lower substrate of an electrophoretic display device according to an exemplary embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II ′ of FIG. 1. 3 is another plan view illustrating a lower substrate of an electrophoretic display device according to an exemplary embodiment of the present invention.

1 to 3, an electrophoretic display device includes a lower substrate 100 and an upper substrate 200. The lower substrate 100 includes a lower base substrate 110, a plurality of gate lines 120, a plurality of data lines 130, a plurality of thin film transistors (TFTs), barrier ribs 160, and a plurality of protrusions 180. And a plurality of pixel electrodes 170. The lower base substrate 110 is, for example, glass, polyester, polyacrylate, polycarbonate, polyether ketone, steel foil Or the like. The gate lines 120 are formed on the lower base substrate 110 and extend in the first direction D1. The gate line 120 may be formed of a single film made of silver (Ag) or silver alloy (Ag) or aluminum (Al) or aluminum alloy (Al alloy) having a low resistivity. It may be made of a multilayer film including other films made of materials such as chromium (Cr), titanium (Ti), and tantalum (Ta) having good physical and electrical contact properties. A portion of each gate line 120 forms a gate electrode 122 of the thin film transistor TFT. The side of the gate line 120 is inclined, the inclination angle is in the range of 20-80 degrees from the horizontal plane.

A gate insulating layer 124 is formed on the gate lines 120. The gate insulating layer 124 is made of silicon nitride (SiNx), silicon oxide (SiOx), or the like.

The data lines 130 are formed on the insulating layer 124 and extend in a second direction D2.

A plurality of active layers 126 are formed on the gate insulating layer. The active layer 126 overlaps the gate electrode 124 to form a channel layer of the thin film transistor TFT. The active layer 126 may be made of, for example, hydrogenated amorphous silicon.

An ohmic contact layer 128 is formed on each of the active layers 126. The ohmic contact layer 128 reduces contact resistance between the active layer 126 and the source electrode 132 and between the active layer 126 and the drain electrode 134. For example, the ohmic contact layer 128 may be made of amorphous silicon doped with a high concentration of silicide or n ⁺ type impurities. A center portion of the ohmic contact layer 128 is removed to expose a portion of the active 126 layer.

The source electrode 132 is formed on the ohmic contact layer 128. The source electrode 132 extends from each of the data lines 130. In addition, a drain electrode 134 is formed on the ohmic contact layer 128. The drain electrode 134 is spaced apart from the source electrode 132.

The passivation layer 140 is formed on the source electrode 132, the drain electrode 134, and the exposed active layer 126. The passivation layer 140 protects the source electrode 132, the drain electrode 134, and the exposed active layer 126. The planarization layer 150 is formed on the passivation layer 140. The passivation layer 140 and the planarization layer 150 may be made of an insulating material.

In the passivation layer 140 and the planarization layer 150, a via hole 152 exposing a part of the drain electrode 134 is formed. The partition wall 160 is formed on the planarization layer 150. The partition wall 160 surrounds each pixel area to distinguish each pixel. That is, the partition 160 is formed in a matrix form. For example, the partition wall 160 may be formed by photolithography, softlithography, micro-contact printing, or the like.

Protrusions 180 are formed in each pixel space surrounded by the partition wall 160. For example, as shown in FIG. 3, the protrusion 180 may have an island shape surrounded by the partition wall 160. The protrusion 180 has a height lower than that of the partition wall 160. The protrusion 180 may be formed by, for example, photolithography, softlithography, micro-contact printing, or the like, and may be simultaneously formed with the barrier 160. have.

The pixel electrode 170 is formed between the barrier rib 160 and the protrusion 180. In more detail, the pixel electrode 170 is formed on the planarization layer 150 between the barrier rib 160 and the protrusion 180. The pixel electrode 170 may be made of, for example, a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The pixel electrode 170 is electrically connected to the drain electrode 134 through the via hole 152 formed in the passivation layer 140 and the planarization layer 150. The pixel electrode 170 may have a symmetrical shape with respect to the protrusion 180, and may be formed to surround the protrusion 180. In addition, a portion of the pixel electrode 170 may be formed on the side surface of the barrier rib 160 or the protrusion 180.

The upper substrate 200 includes an upper base substrate 210, a common electrode 220, and a sealant 230. The upper base substrate 210 may include, for example, glass, polyester, polyacrylate, polycarbonate, polyether ketone, and steel foil. Or the like. The common electrode 220 may be made of, for example, a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO).

The lower substrate 100 and the upper substrate 200 are coupled through a lamination method. In more detail, a sealing material 230 is formed on the common electrode 220, and the lower substrate 100 and the upper substrate 200 are compressed and laminated.

An electrophoretic medium 300 is positioned in a space between the lower substrate 100 and the upper substrate 200. The electrophoretic medium 300 includes a fluid 310 and pigment particles 320 dispersed in the fluid 310. The electrophoretic medium 300 may be filled in each pixel area by, for example, an ink jet method.

The fluid 310 is a dielectric solvent, and may further include additives such as charge control agents, dispersants, and surfactants. In addition, the fluid 310 may have a color of white, black or other chromatic colors. For example, the fluid 310 may have any one color of red, green, and blue.

The pigment particles 320 are positively or negatively charged. In addition, the pigment particle 320 may be an organic pigment or an inorganic pigment such as titanium oxide, and may have a color of white, black or other chromatic colors. More specifically, the pigment particles 320 are, for example, phthalocyanine blue, phthalocyanine green, diarylide yellow, diarylide AAOT yellow, Rhodamine or perylene pigment series manufactured by Sun Chemical, Hansa yellow manufactured by Kanto Chemical. It can be formed from organic or inorganic pigments, such as G particles and Fisher Lamp's Carbon Lampblack. The size of the pigment particles 320 is preferably in the range of about 0.01 to 5 microns, more preferably in the range of 0.05 to 2 microns. The pigment particles 320 should not be swollen or softened by a dielectric solvent, but should be chemically stable.

  The pigment particles 320 can exhibit the original charge or can be charged using a charge control agent. The charge control agent may be ionic or nonionic, aerosol OT, sodium dodecylbenzenesulfonate, metal soap, polybutenesuccinimide, maleic anhydride copolymer, vinylpyridine copolymer, vinylpyrrolidone copolymer, (Meth) acrylic acid copolymer, N, N-dimethylaminoethyl (meth) acrylate copolymer, etc. are mentioned.

The electrophoretic display device according to the exemplary embodiment of the present invention does not need to manufacture a microcapsule including pigment particles, which is advantageous in the manufacturing process.

Hereinafter, an operation of the electrophoretic display device will be described with reference to the drawings.

4 and 5 are conceptual cross-sectional views for describing an operation of an electrophoretic display device according to an exemplary embodiment of the present invention.

2, 4, and 5, the pigment particles 320 are positively or negatively charged and dispersed in the fluid 310. When a predetermined voltage is applied to the common electrode 220 and the pixel electrode 170, an electric field is formed between the common electrode 220 and the pixel electrode 170, and the pigment particles 320 move. .

For example, when the negatively charged voltage is applied to the common electrode 220, and the positively charged voltage is applied to the pixel electrode 170, the common electrode 220 is positively charged. Go to near. Thus, the color of the pigment particles 320 is displayed on the screen.

On the other hand, when a positive voltage is applied to the common electrode 220 and a negative voltage is applied to the pixel electrode 170, the positively charged pigment particles 320 move near the pixel electrode 220. do. Therefore, the color of the fluid 310 is displayed on the screen.

The protrusion 180 serves to support the pigment particle 320. Therefore, it is possible to reduce the scattering of the pigment particles 320 moved near the common electrode 220 or the pixel electrode 170 by disordered voltage due to electric noise.

In addition, the movement path of the pigment particles 320 is limited by the protrusions 180, thereby reducing friction between the pigment particles 320. Therefore, when a predetermined voltage is applied to the common electrode 220 and the pixel electrode 170, the pigment particles 320 may move quickly, and thus the reaction speed of the electrophoretic display may increase. In addition, since the amount of the electrophoretic medium 300 can be reduced by the volume occupied by the protrusion 180, it is economically advantageous.

The cross section of the protrusion 180 may have various shapes such as a quadrangle, a triangle, and a semicircle.

6 is a plan view illustrating a lower substrate of an electrophoretic display device according to another exemplary embodiment.

Referring to FIG. 6, the electrophoretic display device includes a lower substrate 300 and an upper substrate (not shown). The lower substrate 300 includes a lower base substrate, a plurality of gate lines, a plurality of data lines, a plurality of thin film transistors, a partition wall 360, a plurality of protrusions 380, and a plurality of pixel electrodes 370. The upper substrate includes an upper base substrate, a common electrode and a sealing material. The upper substrate includes an upper base substrate, a common electrode, and a sealing material and is combined with the lower substrate to receive an electrophoretic medium. Except for the protrusion 380 and the pixel electrode 370, the lower substrate 300, the upper substrate, and the electrophoretic medium may be substantially the same as the upper substrate, the lower substrate, and the electrophoretic medium shown in FIGS. 1 and 2. Same as

The pixel electrode 370 is formed near the partition wall 360 formed in a matrix. In detail, the pixel electrode 370 is formed between the partition wall 360 and the protrusion 380. The pixel electrode 370 may include a first sub pixel electrode 370a and a second sub pixel electrode 370b, and the first and second sub pixel electrodes 370a and 370b face each other.

According to the present invention, the lower substrate of the electrophoretic display device includes a partition wall surrounding each pixel area, a protrusion formed in the pixel area, and a pixel electrode formed between the partition wall and the protrusion. The protruding portion may support the pigment particles of the electrophoretic medium to reduce the scattering of the pigment particles migrating in the vicinity of the common electrode or the pixel electrode by disordered voltage drop due to electrical noise. Therefore, the image quality of the electrophoretic display device may be improved.

In addition, the path between the pigment particles is limited by the protrusions, so that the friction between the pigment particles is reduced. Therefore, the reaction speed of the electrophoretic display device may increase.

In the detailed description of the present invention described above with reference to a preferred embodiment of the present invention, those skilled in the art or those skilled in the art having ordinary knowledge in the scope of the invention described in the claims to be described later It will be understood that various modifications and variations can be made in the present invention without departing from the scope of the present invention.

Claims (13)

A plurality of gate lines and a plurality of data lines crossing each other to define pixel regions, a plurality of thin film transistors electrically connected to the gate lines and the data lines, a planarization film covering the thin film transistors, and a planarization film formed on the planarization film. A lower substrate including a partition wall surrounding each pixel area, a protrusion formed in each pixel area, and a pixel electrode formed between the partition wall and the protrusion and electrically connected to the thin film transistor; And And an upper substrate coupled to the lower substrate to receive an electrophoretic medium and including a common electrode. The electrophoretic display of claim 1, wherein the electrophoretic medium comprises a fluid and pigment particles dispersed in the fluid. The electrophoretic display of claim 2, wherein the fluid is black and the pigment particles are white indices. The electrophoretic display of claim 2, wherein the fluid is white and the pigment particles are black indices. The electrophoretic display of claim 2, wherein the pigment particles are positively or negatively charged. The electrophoretic display of claim 2, wherein the fluid has one of red, green, and blue colors. The electrophoretic display of claim 2, wherein the pigment particles have any one of red, green, and blue colors. The electrophoretic display of claim 1, wherein the pixel electrode is symmetric about the protrusion. The electrophoretic display of claim 8, wherein the pixel electrode includes a plurality of sub pixel electrodes facing each other with the protrusion interposed therebetween. The electrophoretic display of claim 8, wherein the pixel electrode surrounds the protrusion. The electrophoretic display of claim 1, wherein a height of the protrusion is lower than a height of the barrier rib. The electrophoretic display of claim 11, wherein the protrusion is spaced apart from the partition by a predetermined distance. 2. The electrophoretic display of claim 1, wherein the upper substrate further comprises a sealing material for bonding the upper substrate and the lower substrate.

Images