Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-09-20
2003-12-02
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
06657612
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a driving method for an image display medium and to an image display device, and relates more specifically to a driving method and to an image display device for an image display medium having unit cells disposed between plural substrates and at least two types of particles of different charge characteristics and color sealed inside the unit cells.
2. Description of Related Art
Twisting ball displays (dichroic twisting ball displays), electrophoretic image displays, magnetophoretic image displays, thermal rewritable image displays, and liquid crystals with memory have been proposed as display media capable of repeating image display.
Thermal rewritable display media and liquid crystals with memory stand out amongst these rewritable display media because of their excellent image memory characteristics.
Electrophoretic and magnetophoretic display media apply an electrical or magnetic field to disperse movable colored particles in a white fluid medium, and form images from the color of the colored particles and the color of the white medium. Images are formed, for example, by making the color particles adhere to the display surface in the image area to display the color of the color particles while removing the color particles from the display surface in the non-image areas to display the white of the white fluid. Furthermore, these types of displays have memory because the color particles do not move unless an electrical or magnetic field is applied.
Twisting ball displays produce an image by applying an electric field to spheric particles (balls), half of each ball being white and the other half black, to selectively reverse ball orientation. For example, the balls are driven to produce the black side to the surface of the display in the image areas, and produce the white side to the display surface in the non-image areas.
This type of display can also store an image because the balls do not change orientation unless a field is applied. This type of display medium can also be manufactured in sheets relatively easily because the inside of the display medium contains substantially solid particles, although oil is present only in the cavities around the particles.
A common problem of thermal rewritable display media and liquid crystals having memory is that a truly paper white display cannot be achieved. This means that contrast between image and non-image areas is not sufficient, and it is therefore difficult to achieve a sharp image display.
Furthermore, while the white fluid medium used in electrophoretic and magnetophoretic display media makes it possible to produce a clear white display like a paper, intrusion of the white fluid between color particles when displaying the color of the color particles causes a drop in display density. Contrast between the image and non-image areas is thus low, and it is difficult to achieve a sharp image display.
If the display medium is removed from the image display device and handled roughly like paper, there is the possibility of the white fluid sealed inside the display medium leaking.
Even when a twisting ball display is driven to produce the white spheric side of every particle to the display surface, it is not possible in principle to produce a 100% white display because ambient light rays penetrating the gaps between the balls are not reflected and are lost inside the display medium. In addition, light absorption and diffusion by the cavities mean that only a gray tinged white display can be achieved. It is also difficult to completely reverse the particles, leading to a drop in contrast and, as a result, making it difficult to produce a sharp image. Moreover, because particle size must be smaller than the pixel size, minute particles coated different colors must be manufactured in order to achieve a high resolution display. This requires sophisticated manufacturing technology.
A number of display media using toner (particles) have been proposed as a novel display medium resolving the above problems (see Japan Hardcopy L99, pp. 249-252; and Japan Hardcopy L99 fall (scheduled publication), pp. 10-13).
These display media have a transparent display substrate and a facing back substrate with a small gap therebetween, and two types of particles (toner) with different color and charge characteristics sealed in this substrate gap. When a field is applied between these substrates according to the image information, the desired color particles are made to adhere to the display substrate to form and produce an image display.
This type of particle display medium using toner also has memory because the toner does not move unless a field is applied. Such display media are also free from leakage problems because the image display medium contains nothing but solids. Furthermore, a nearly 100% reversal between white and black is in principle possible, and high contrast, sharp images can be displayed. It is also possible to display high contrast two color (such as black and white) images by using high opacity particles. It should be noted that display media using toner are referred to below as simply an image display medium.
To display multiple colors on a conventional image display medium, it is necessary, as shown in
FIG. 19
, to form plural unit cells inside the display medium, seal a different color of particle into each unit cell, and group a number of adjacent unit cells in order to display one color.
As shown in
FIG. 19
, for example, three types of unit cells, respectively containing sealed therein white and magenta particles, white and yellow particles, and white and cyan particles, are disposed in regular sequential order, and three adjacent unit cells are driven as a unit to display a particular pixel color as shown in FIG.
20
.
To achieve a full color image display using this type of display medium, the white particles in each of the unit cells are collected at the display surface side to display white as shown in FIG.
20
. Black is displayed by collecting the color particles in each of the unit cells to the display surface side. Magenta, yellow, and cyan are displayed by collecting the color particles to the display surface side in each unit cell containing the corresponding color particles while displaying white in the other unit cells. Red, blue, and green are displayed by driving the color particles in each unit cell so that the color particles combine appropriately as shown in FIG.
20
. Note that in
FIG. 20
W indicates white, M magenta, C cyan, and Y yellow.
By using plural cells to represent one pixel, this driving method leads to a drop in resolution, which is particularly apparent as a drop in text quality. It is therefore necessary to use microcells with a small surface display area per unit cell in order to maintain the resolution of display. However, it is difficult to manufacture such microcells, and when production is successful, production efficiency is poor and a rise in production cost is unavoidable.
The load on the drive circuit driving the individual cells is also high because a large number of unit cells are formed in the same display area. A high capacity drive circuit is therefore needed. An increase in drive circuit cost is therefore also unavoidable.
A further problem with a display as shown in FIG.
19
and
FIG. 20
is that there is a grayish tinge to the black display, and there is a resulting drop in display quality.
It will be noted that changing the color combinations of the enclosed color particles will not change the fundamental problems of degraded text quality due to a drop in resolution, and degraded display quality due to lower contrast between black and white.
Conventional image display media are also completely reflection display media. Viewability thus drops sharply at night and in the dark, making lighting necessary. The particles used in such image display media must be highly opaque, however, and backlighting such as used with liquid crystal displays cannot be used. Such image display media mus
Machida Yoshinori
Matsunaga Takeshi
Sakamaki Motohiko
Shigehiro Kiyoshi
Yamaguchi Yoshiro
Fuji 'Xerox Co., Ltd.
Lao Lun-Yi
Oliff & Berridg,e PLC
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