Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2000-07-21
2002-06-18
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C345S107000, C347S153000, C359S296000
Reexamination Certificate
active
06407763
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image display medium, an image-forming method, and an image-forming apparatus. More specifically, it relates to an image display medium capable of repetitive rewriting, an image-forming method in which an image is formed on the image display medium, and an image-forming apparatus.
DESCRIPTION OF THE RELATED ART
As an image display technology capable of repetitive rewriting, which is called electronic paper, technologies such as twisting of color particles (twisting ball display), electrophoresis, a thermal rewritable medium, a liquid crystal having a memory property and electrochromy have been so far known. Of these display technologies, a thermal rewritable medium and a liquid crystal having a memory property are excellent in the image memory property, but no satisfactory white display as in paper can be applied to the display surface. Accordingly, when an image is displayed, an image display portion can hardly be distinguished visually from an image non-display portion. That is, there has been a problem that the image quality is decreased.
Further, the twisting ball display has a display memory property, and oil is present only in cavities around particles inside an image display medium. However, particles are almost solid to conduct sheeting relatively easily. Even when semispherical surfaces colored in white are completely arrayed on the display side, rays entered between gaps of spheres are not reflected, and lost thereinside. Accordingly, white display with 100% coverage is theoretically impossible, and slightly grayish display is provided. Further, since a particle size is required to be smaller than a pixel size, fine particles colored in different tints have to be produced for high-resolution display, and a high-level production technology is needed.
In these technologies, as an image display medium in which an image is displayed with a toner, there is an image display medium in which a conductive color toner and white particles are contained between a display substrate and a non-display substrate that are facing each other using air as a medium to form a charge transfer layer and an electrode within both substrates (Toner Display, Nippon Gazoh Gakkai, Japan Hardcopy '99
Ronbunshu,
pp. 249-251 and Japan Hardcopy '99 Fall
Yokohshu pp.
10-13). In such an image display medium, charge is injected into the conductive color toner through the charge transfer layer, and the conductive color toner in which charge has been injected is moved by an electric field between substrates formed according to the image with an electrode, and is adhered to the display substrate. As a result, the image as a contrast between the conductive color toner and the white particles is displayed on the display substrate side.
Further, as an image display medium capable of repetitive rewriting, an image display medium using electrophoresis has been known (Kawai, Development of Electrophoresis Display Using Microcapsules, Nippon Gazoh Gakkai,
Electronic Imaging Kenkyukai,
p. 32, 1999).
However, in the image display technology using the toner, the contrast between black and white is low, and excellent results are not obtained in comparison with other image display technologies. Reporters of this technology presume that a conductive color toner not contacted with a charge transfer layer mounted on an inner surface of an electrode of a non-display substrate and isolated from other conductive color particles is present and charge is not injected in these isolated conductive color particles, so that the particles are not moved by an electric field but randomly remain in the substrates and the contrast is therefore low. Further, a high-speed response is also problematic.
Moreover, since the electrode is employed in the image display medium using the toner, the medium cannot directly be applied to an ordinary image-forming apparatus in which an image is formed by developing an electrostatic latent image formed on an image carrier with a toner and transferring the same onto recording paper, such as a copier or a printer.
Meanwhile, a display technology using electrophoresis or magnetic migration is a technology which provides an image memory property and in which color particles are dispersed in a white liquid. Thus, it is excellent in white display. However, since a white liquid is always incorporated into a gap between color particles in a black display portion, a grayish color is provided to decrease a contrast.
SUMMARY OF THE INVENTION
Under these circumstances, the invention has been made, and provides an image display medium which satisfies a high contrast, a safety and a high-speed response and which is capable of repetitive rewriting, an image-forming method in which an image can be formed on the image display medium, and an image-forming apparatus, and further to provide an image-forming method which can be used in a copier or a printer in which an image is formed on recording paper and an image-forming apparatus at low costs.
The image display medium includes a pair of substrates, and plural types of particle groups contained between the substrates to be movable between the substrates by an electric field applied and which are different in color and charging properties.
According to an aspect of the invention, plural types of particles different in color and charging properties are contained between substrates such that the respective particles are movable between the substrates by the electric field applied. At this time, the plural types of particles have charging properties, and the respective particles are moved according to the strength and the polarity of the electric field applied. As the particles, insulating particles to be charged through frictional charging or conductive particles to be charged by injecting charge through an electrode may be used.
Incidentally, during studies for making the invention, the present inventors have presumed the following with respect to the problems of the display medium using the toner. That is, the image display medium using the toner is so adapted that white particles are treated as a stationary medium unreactive with an electric field and conductive black particles are caused to migrate therein. For this reason, it is only one (conductive black particles) of the two particle groups that can be moved between the substrates. Specifically, white particles can be fixed in nearly stationary state by a structure that the white particles are packed well between the substrates. Nevertheless, in this construction, conductive black particles have to be moved in high-density white particles. Further, the conductive black particles hardly exclude the white particles remaining near the surface of the substrate. Thus, only grayish display is conducted to decrease the contrast.
Moreover, in case of using conductive particles, particles that are not directly contacted with a charge injection electrode have no chance of charge injection unless they are contacted with other charged conductive particles. Thus, such particles cannot be reacted with an electric field. That is, it is presumed that when conductive black particles having good charging properties are used but stationary white particles are present, almost all of conductive black particles cannot be moved and contributed to image display.
In the invention, therefore, the image display medium is so constructed that the particles belonging to the different particle groups can be moved between substrates in mutually opposite directions by the electric field applied. Further, since charging properties of these particles are different depending on the particle group, the moving characteristics by the electric field are also varied.
In case of using insulating particles of reverse polarities, the particles are in the mixed state by the Coulomb force between the substrates just before being contained, and the particles of reverse polarities are separated by applying electric fields stronger than the Coulomb force between these particles, moved i
Kakinuma Takeo
Koshimizu Minoru
Machida Yoshinori
Nakayama Nobuyuki
Oba Shota
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
Pendegrass Joan
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