KR20080071250A - Electrowetting display - Google Patents

Abstract

An electrowetting display device is provided to represent a clear image with vivid colors by arranging a color filter on a lower substrate. An electrowetting display device includes an upper substrate(1), a transparent electrode(2), a pixel wall(4), a water layer(3), a black oil layer(5), a hydrophobic insulator(6), RGB color filter regions(7,8,9), a reflective electrode(10), and a lower substrate(11). The plane type transparent electrode is arranged under the upper substrate. The pixel wall surrounds the water and oil layers under the transparent electrode. The water layer is arranged between the upper and lower substrates. The black oil layer is arranged under the water layer. The hydrophobic insulator is arranged under the black oil layer. The RGB color filter regions are arranged under the insulator. The reflective electrode is patterned in a straight line on respective pixels under the color filter regions. The lower substrate is arranged under the reflective electrode.

Description

Electro Wetting Display {Electrowetting Display}

1 is a structure of an electrowetting display using a conventionally proposed color filter.

2 is a cross-sectional view of an electrowetting display of R, G, and B pixel structures using a color filter according to a first embodiment.

3 is a cross-sectional view of a linear R, G, B, W pixel structure electrowetting display using a color filter according to the first embodiment;

Fig. 4 is a sectional view of an electrowetting display having a " 田 " shape R, G, B, W pixel structure using a color filter according to the second embodiment.

5 is a cross-sectional view of an electrowetting display in which each pixel is isolated according to the third embodiment.

6 is a cross-sectional view of a transmissive electrowetting display according to a fourth embodiment;

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrowetting display, and more particularly, by using a color filter located on a lower substrate in one pixel wall by using an electrowetting method, water pushes oil according to an applied voltage. The present invention relates to an electrowetting display that implements color while incident light reflects or transmits in the color filter region. This creates a perfect dark state when black oil is covered in front of one pixel, and the light that passes the color filter in each pixel represents water as water pushes the oil out. Conventionally, color is expressed by using an oil containing dye or by placing a color filter on an upper glass substrate to express color.

Electrowetting technology refers to the surface tension of a conductive fluid by coating a hydrophobic insulator on the electrode and applying a voltage to the electrode and the conductive fluid from the outside when the conductive fluid (water) and the non-conductive fluid (oil) contact it. By controlling it is meant to change the contact angle of the conductive fluid and the shape of the interface of the two fluids. Therefore, when a voltage is applied to water and oil, the hydrophobic interface of the water changes to hydrophilicity, the contact angle of water decreases, and water pushes the oil to reflect light while reflecting light. Recently, electrowetting technology and reflective displays using water and oil show fast response time and high reflectance. These advantages are comparable to existing electronic paper products and liquid crystal displays. In addition, it is possible to realize better image quality with fast response speed and low driving voltage to realize video image.

The electrowetting display that has been proposed previously uses a small amount of dye oil and water in each pixel and an insulator that can be converted from hydrophobic to hydrophilic to realize color by emitting light from the dye oil. In such a structure using dye oil, there is a problem that the contrast ratio is reduced than using a color filter, and it is difficult to realize a perfect dark state. In addition, the electrowetting display using the conventional color filter, when the color filter is present on the upper substrate, the poor quality of the image in the dark due to the light reflected from the color filter.

1 shows a structure of an electrowetting display using a color filter proposed in the related art. 1 (a) shows the dark state before the voltage is applied in the structure of the electrowetting display using the conventionally proposed color filter, Figure 1 (b) is a structure showing the bright state after the voltage is applied. As shown in FIG. 1 (a), the upper substrate has a plane-shaped upper transparent electrode 2 under the upper glass substrate or plastic substrate 1, and R under the upper transparent electrode 2 (red), G (green) and B (blue) color filters. The lower substrate has a reflective electrode 8 patterned in a straight line shape for each pixel on the lower glass substrate or plastic substrate 9, and a hydrophobic insulator 7 is coated on the front surface of the reflective electrode 8. On the hydrophobic insulator 7, a pixel wall 5 is formed which divides the R, G, and B pixels, and in each pixel, a black oil 6 is placed on the hydrophobic insulator 7, 4) is covered.

Therefore, in order to solve this problem, unlike the structure of the electrowetting display using the previously proposed color filter on the upper substrate, the color filter is placed on the lower glass substrate to show perfect color and vivid color.

The present invention has been studied based on the above-described technology, and uses a color filter and has a R, G, B pixel structure or a R, G, B, W (white) pixel structure, and a color filter on the lower substrate. Its purpose is to produce an electrowetting display that can be present to produce vivid colors.

In recent years, research on electrowetting displays has been actively conducted, and has been in the spotlight for ultra-thin displays and curved displays having high-speed response characteristics. Therefore, in terms of how to implement color, cost reduction, high aperture ratio, and vivid and perfect color are emerging as important issues.

However, in conventional electrowetting displays, there are various problems in color implementation, and in the case of oil with dye, the vividness of color is very different according to the amount of dye, and if the color filter is present on the upper glass substrate, The sharpness is lowered and it is difficult to realize the dark state, so it is difficult to flexibly respond to the vivid color.

Accordingly, an object of the present invention is to use a color filter and to implement a color while the color filter is present on the lower glass substrate, thereby making it possible to flexibly cope with implementing a vivid color.

In order to achieve the above object, the present invention has a color filter R, G, B or R, G, B, W pixel structure and position the color filter on the lower glass substrate. A color filter is placed on the lower electrode and a hydrophobic insulator is coated on which the interfacial properties can be changed from hydrophobic to hydrophilic according to the application of a voltage thereon. Black oil is spread over the coated insulation and water is present on it. When the voltage is applied, the characteristics of the insulator change to hydrophilicity, and the contact angle between the water and the interface becomes small, so that the water pushes the oil out, and the light incident on the color filter is reflected or transmitted to express the color. Therefore, when the black oil is covered before the voltage is applied, the oil is pushed out when the voltage is applied, and light is incident from the outside to the color filter area and reflected back from the reflective electrode, or the internal light source passes through the transparent electrode to express the color. As a result, water pushes oil out according to the voltage applied to each pixel electrode, and the intensity and time of black oil covering the color filter are controlled to express the contrast of color. Therefore, the present invention is characterized by an electrowetting display that can use a color filter and the color filter is present on the lower glass substrate, the color can be clearly realized.

Example 1

Embodiment 1 relates to an electrowetting display using a color filter, having an R, G, and B pixel structure, wherein the color filter is present on a lower glass substrate, and the oil is pushed to the pixel wall according to an applied voltage to implement colors. will be. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 2 is a plan view of an electrowetting display having an R, G, and B pixel structure using a color filter according to a first embodiment of the present invention.

As shown, Fig. 2 shows a cross-sectional view of the off and on states of the electrowetting display of the R, G, and B pixel structures using the color filter under the glass substrate. FIG. 2A shows the dark state when the black oil covers all the color filters of each pixel as the off state. FIG. 2 (b) shows the bright state in which the black oil is pushed to the pixel wall and all the light passing through the color filter is reflected when voltage is applied to all pixel electrodes R, G, and B. In the upper substrate, an upper glass substrate or a plastic substrate 1 is present, and a transparent electrode 2 having a plane shape is disposed under the glass substrate 1. The lower substrate is provided with a lower glass substrate or a plastic substrate 11, and a reflective electrode 10 having a pattern in the form of a line for each pixel is placed on the glass substrate 11 to prevent distortion of the reflected image. Very small protrusions may be formed on the reflective electrode. A color filter of R (7), G (8), and B (9) exists on the reflective electrode 10, and a hydrophobic insulator 6 is coated on the entire surface of the color filter. The black oil 5 covers the entire surface of the hydrophobic insulator 6, and the water 3 is present on the black oil 5. In each pixel, the pixel wall 4 surrounding the oil and water layers is spaced apart from the upper substrate by a predetermined distance.

3 illustrates a cross-sectional view of an electrowetting display having a linear R, G, B, W pixel structure by adding a white region to improve transmittance and color to the R, G, B pixel structures. In the upper substrate, an upper glass substrate or a plastic substrate 1 is present, and a transparent electrode 2 having a plane shape is disposed under the glass substrate 1. The lower substrate is provided with a lower glass substrate or a plastic substrate 12 and a reflective electrode 11 patterned in a linear form for each pixel on the glass substrate, and has a very small protrusion to prevent distortion of the reflected image. Can be formed over the reflective electrode. On the reflective electrode 11, color filters of R (7), G (8), B (9), and W (10) regions exist, and the white region is coated with an insulator. The hydrophobic insulator 6 is coated on the front surface of the color filter. On top of the hydrophobic insulator 6 a black oil 5 covers the entire surface and there is a water layer 3 on top of the black oil 5. In each pixel, the pixel wall 4 surrounding the oil and water layers is spaced apart from the upper substrate by a predetermined distance.

In the conventional electrowetting display, the color clarity is very different depending on the amount of dye in the color-added oil in the color implementation, and the color clarity in the dark state due to reflection from the color filter when the color filter is present on the upper glass substrate. There was a problem of implementing the color due to the poor state of the dark state, in the present invention, by using the color filter as described above and the color filter is present on the lower glass substrate can implement a vivid color. In addition, it has a linear R, G, B, W pixel structure, it is possible to improve the transmittance and realize a better color than conventional.

Example 2

Unlike the linear R, G, B, and W pixel structures in the first embodiment, the second embodiment of the present invention relates to an electrowetting display having an R, G, B, W pixel structure in which the pixel wall is in the form of "田". will be. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 4 shows a plan view of the electrowetting display of the R, G, B, W pixel structure of the pixel wall of the "田" shape. A pixel wall 1 surrounds each of the R (2), G (3), B (4), and W (5) regions, and the color filter is present on the electrode on the lower substrate.

In the conventional electrowetting display, there is a problem that the transmittance is low in the bright state while using the color filter on the upper substrate, in the present invention, as described above, it is possible to implement the advantages of increasing the transmittance by adding a white region and an excellent color sense than the conventional one. .

Example 3

According to the third and second embodiments of the present invention, the pixel wall and the upper substrate are separated from each other by a predetermined distance in the first and second embodiments, and the pixel walls and the upper substrate are attached so that each pixel is completely isolated. . Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

5 is a cross-sectional view of an electrowetting display in which each pixel is isolated according to a third embodiment. In the upper substrate, an upper glass substrate or a plastic substrate 1 exists, and a transparent transparent electrode 2 in a plane form is disposed under the glass substrate 1. The lower substrate is provided with a lower glass substrate or a plastic substrate 11 and a reflective electrode 10 having a straight pattern on the glass substrate. A very small protrusion is formed on the reflective electrode to prevent distortion of the reflected image. Can be. R (7), G (8), and B (9) color filters are present on the reflective electrode 10, and a hydrophobic insulator 6 is coated on the front surface of the color filter. On top of the hydrophobic insulator 6 a black oil 5 covers the entire surface and there is a water layer 3 on top of the black oil 5. Each pixel is attached to the pixel wall 4 surrounding the oil and water layers without being spaced apart from the upper substrate to isolate each pixel.

Example 4

Example 4 relates to a transmissive electrowetting display using a color filter, wherein the color filter is present on the lower glass substrate and uses an internal light source rather than an external light source. Instead of the reflective electrode on the lower glass substrate, a transparent electrode can be used for the transmissive electrowetting display. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

6 is a cross-sectional view of a transmissive electrowetting display using a color filter according to a fourth embodiment of the present invention. In the upper substrate, an upper glass substrate or a plastic substrate 1 exists, and a transparent transparent electrode 2 in a plane form is disposed under the glass substrate 1. The lower substrate has a lower glass substrate or a plastic substrate 11, and a transparent electrode 10 having a pattern for each pixel is placed on the glass substrate, and the transparent electrode is made of indium tin oxide (ITO) or indium zinc oxide (IZO). This can be used. R (7), G (8), and B (9) color filters are present on the transparent electrode 10, and a hydrophobic insulator 6 is coated on the front surface of the color filter. On top of the hydrophobic insulator 6 a black oil 5 covers the entire surface and there is a water layer 3 on top of the black oil 5. An internal light source exists under the lower glass substrate. In addition, in the first and second electrowetting displays having the linear R, G, B, W pixel structures and the "田" shaped R, G, B, W pixel structures, transparent electrodes are placed instead of the lower reflective electrodes. It can be used as a transmissive electrowetting display.

In the conventional electrowetting display, it was used as a reflective display. In the present invention, as described above, the color filter may be positioned on the lower substrate and a transparent electrowetting display using an internal light source may be manufactured using a transparent electrode.

This invention has an overall useful effect on electrowetting displays using color filters produced in production processes. In addition, although specific embodiments of the present invention have been described and illustrated, it will be apparent that various modifications may be made by those skilled in the art.

As described in detail above, by using the electrowetting display according to the present invention, the color filter is present on the lower substrate to implement an electrowetting display capable of expressing color clearly and easily.

Claims (6)

An upper glass substrate or a plastic substrate; A plane transparent electrode positioned below the upper glass substrate; A pixel wall disposed under the transparent electrode and surrounding the water and oil layers; A water layer filled between the upper substrate and the lower substrate; A black oil layer located below the water layer; A hydrophobic insulator beneath the black oil layer; An R, G, B color filter area under the insulator; A reflective electrode patterned in a linear shape for each pixel under the color filter area; And a color filter comprising a lower glass substrate or a plastic substrate positioned below the reflective electrode, on the lower substrate. The method of claim 1, A reflective electrowetting display having a linear R, G, B, W pixel structure in which a white pixel region is added to the pixel structure. The method according to claim 1 and 2, A reflective electrowetting display wherein small protrusions are present on the reflective electrode. An upper glass substrate or a plastic substrate; A plane transparent electrode positioned below the upper glass substrate; A pixel wall of a “田” shape positioned under the transparent electrode and surrounding the water and oil layers; A water layer filled between the upper substrate and the lower substrate; A black oil layer located below the water layer; A hydrophobic insulator beneath the black oil layer; An R, G, B, W color filter area under the insulator; A reflective electrode patterned in a linear shape for each pixel under the color filter area; A lower glass substrate or a plastic substrate positioned below the reflective electrode; Reflective electrowetting display with a color filter placed on the lower substrate. The method of claim 1, 2 and 4, A reflective electrowetting display, wherein the pixel wall is attached to an upper substrate. An upper glass substrate or a plastic substrate; A plane transparent electrode positioned below the upper glass substrate; A pixel wall disposed under the transparent electrode and surrounding the water and oil layers; A water layer filled between the upper substrate and the lower substrate; A black oil layer located below the water layer; A hydrophobic insulator beneath the black oil layer; A color filter area under the insulator; A transparent electrode having a pattern formed in a linear shape for each pixel under the color filter area; And a color filter comprising a lower glass substrate or a plastic substrate positioned below the transparent electrode.

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