Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-12-14
2004-06-22
Lao, Lun-Yi (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C359S296000
Reexamination Certificate
active
06753844
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image display devices and display drive methods and, more particularly, to an image display device which is rewritable repeatedly and display drive method thereof.
2. Description of the Related Art
Conventionally, there have been proposed, as repeatedly rewritable display mediums, twisting ball displays (display with rotation of two-colored particles), electrophoretic display mediums, magnetophoretic display mediums, thermal-rewritable display mediums, storable liquid crystal display mediums.
Among these display mediums, the thermal-rewritable and storable liquid crystal display mediums are excellent in storing images but cannot display sufficient paper-like whiteness in the background. Therefore, in displaying images, the imaging and non-imaging regions have insufficient contrast, thus making it difficult to display a clear image.
Moreover, in the display medium utilizing electrophoresis or magnetophresis, for example, coloring particles which can move under electric or magnetic field are dispersed in a white liquid. In the imaging region, the color of coloring particles is displayed by putting the coloring particles on the display surface. In the non-imaging region, the coloring particles are removed from the display surface to display white with the white liquid. Thus, an image is formed. The coloring particles do not move unless an electric or magnetic field is applied thereto, thus making it possible to store the image displayed.
In these display mediums, white which is displayed with the white liquid is clear. However, when displaying the color of coloring particles, white liquid intrudes in the gap between coloring particles, thereby lowering the density of image. This, accordingly, lowers the contrast between the imaging region and the non-imaging region, making it difficult to display a clear image. Also, because the display medium is filled with the white liquid, when the display medium is removed from the image display apparatus and is roughly handled, the white liquid may leak out of the display medium.
Moreover, in the twisting ball display, spherical particles painted white on a half surface and black on the remaining half are rotated under the action of an electric field. Display is conducted such that, for example, in the imaging region the black surface is directed toward the display surface while in the non-imaging region the white surface is directed toward the display surface. Since the particles are not rotated if an electric-field is not applied to the particles, an image can be stored. Oil exists only in the cavity around the particles. However, because the interior of the display medium is mainly solid, the display medium is comparatively easily made in a sheet form.
In this display medium, however, it is difficult to perfectly rotate the particles. The contrast is lowered by the particles not perfectly rotated, making it difficult to form a vivid display image. Further, even if the white-painted hemisphere be perfectly directed toward the display side, it is still difficult to display paper-like white because of light absorption and scatter in the cavity region and it is difficult to display a vivid image. Furthermore, because the particles are required to have a size smaller than a size of the pixel, fine spherical particles must be produced for displaying images with high resolution, which requires high-level manufacturing technology.
Moreover, there are recent proposals, as completely-solid display medium, of the display mediums in which coloring particles, such as a powder toner, are enclosed in a space between a pair of substrates. For example, these are the display mediums described in Japan Hardcopy, '99 theses, pp. 249-252. Japan Hardcopy, '99 Fall Proceedings, pp. 10-13, JP A No. 2000-347483, and the display mediums or the like described in JP-A No. 2001-33833.
These display mediums have a structure having a conductive coloring toner (e.g., black toner) and an insulating coloring toner (e.g., white particle) in a space between a transparent front substrate and a rear substrate. Electrodes are formed on the front and rear substrates. The inner surfaces of the substrates are coated with a charge-transport material to transport only one charge polarity (e.g., holes).
If a voltage is applied to the substrates, holes are injected only to the conductive black toner. The black toner, electrified positive, moves between the substrates while pushing away the white particles according to an electric field formed between the substrates. Herein, black is displayed by moving the black toner toward the front substrate while white of the white particles is displayed by moving the black toner toward the rear substrate. Accordingly, a black and white image can be displayed by applying a voltage to the Substrate to desirably move the black toner according to image information.
The above display medium using coloring particles can store images because the particles do not move if an electric field is not applied thereto. Also, liquid spill does not occur because the display medium is solid. The use of two kinds of coloring particles (e.g., white and black particles) results in image display with high contrast.
Further, the display medium described in Japanese Patent Application No. 2000-165138 proposed by the present inventors has a structure in which two kinds of coloring particles different in color and electrifying characteristics are enclosed in a space between a transparent front substrate and a rear substrate. As the two kinds of coloring particles, particles having different polarities are selected. Consequently, if an electric field is formed between the substrates of the display medium, the two kinds of coloring particles respectively move toward the different substrates. If a voltage is applied to the substrates according to image information, a clear image with high contrast can be displayed.
However, in the display medium enclosing the coloring particles in a space between a pair of substrates, adhesion and coagulation gradually occur as images are displayed repeatedly. Thus, there has been a problem of raising defective display in a dot-like form.
Moreover, in the structure having a gap member to keep a gap between substrates and divide the space between the substrates into a plurality of cells, the particles gradually adhere onto the gap member. Thus, there have been problems in that display contrast is lowered due to a decrease in the number of particles which can actually move or defective display is caused by particles adhering to the gap member.
Also, when the display medium is disposed vertically and used as such and the coloring particles move toward the substrate according to an electric field formed between the substrates, the coloring particles move slightly downward from their previous height due to the action of gravity. Accordingly, change of display if repeated causes the coloring particles to gradually fall, ultimately causing a serious problem of impossible display.
Incidentally, in the structure having a gap member to keep a gap between the substrates and divide the space between the substrates into a plurality of cells, if the cell size is reduced, the movement of coloring particle in the gravity direction can be suppressed within a practical level. However, if the cell size is reduced, there is increase in the ratio of a gap member area to the actual display area on the display surface (area of the region enclosing coloring particles to effect actual display), resulting in lowered contrast of display.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above fact, and it is a first object to provide an image display device having coloring particles in a space between a pair of substrates and display drive method thereof capable of preventing the coloring particles from coagulating even when display is repeatedly conducted, and, if the display medium comprises cells, preventing the coloring particles from adheri
Machida Yoshinori
Matsunaga Takeshi
Sakamaki Motohiko
Shigehiro Kiyoshi
Suwabe Yasufumi
Fuji 'Xerox Co., Ltd.
Lao Lun-Yi
Oliff & Berridg,e PLC
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