Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-03-25
2001-06-05
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S085000
Reexamination Certificate
active
06243058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to the field of visual displays. More particularly, the invention relates to a gyricon or twisting ball visual display having a controlled response to triboelectric charge effects.
2. Description of Related Art
Paper has traditionally been a preferred medium for the presentation and display of text and images. Paper has several characteristics that make it a desirable display medium, including the fact that it is lightweight, thin, portable, flexible, foldable, high-contrast, low-cost, relatively permanent, and readily configured into a myriad of shapes. It can maintain its displayed images without using any electricity. Paper can also be read in ambient light and can be written or marked upon with a pen, pencil, paintbrush, or any number of other implements, including a computer printer.
Unfortunately, paper is not well suited for real-time display purposes. Real-time imagery from computer, video, or other sources cannot be displayed directly with paper, but must be displayed by other means, such as by a cathode-ray tube (CRT) display or a liquid-crystal display (LCD). However, Teal-time display media lack many of the desirable qualities of paper, such as physical flexibility and stable retention of the displayed image in the absence of an electric power source.
Electric paper combines the desirable qualities of paper with those of real-time display media. Like ordinary paper, electric paper can be written and erased, can be read in ambient light and can retain imposed information in the absence of an electric field or other external retaining force. Also like ordinary paper, electric paper can be made in the form of a light-weight, flexible, durable sheet that can be folded or rolled into a tubular form about any axis and placed into a shirt or coat pocket, and then later retrieved, re-straightened, and read without loss of information. Yet unlike ordinary paper, electric paper can be used to display fall-motion and other real-time imagery as well as still images and text. Thus, electric paper can be used in a computer system display screen or a television.
The gyricon, also called the twisting-ball display, rotary ball display, particle display, dipolar particle light valve, etc., provides a technology for making electric paper. A gyricon display is a display that can be altered or addressed. A gyricon display is made up of a multiplicity of optically anisotropic balls which can be selectively rotated to present a desired surface to an observer.
The optical anisotropy of the gyricon balls is provided by dividing the surface of each gyricon ball into two or more portions. One portion of the surface of each gyricon ball has a first light reflectance or color. At least one other portion of the surface of the gyricon ball has a different color or a different light reflectance. For example, a gyricon ball can have two distinct hemispheres, one black and the other white. Additionally, each hemisphere can have a distinct electrical characteristic, e.g., a zeta potential with respect to a dielectric fluid. Accordingly, the gyricon balls are electrically as well as optically anisotropic. It is conventionally known that when particles are dispersed in a dielectric liquid, the particles acquire an electric charge related to the zeta potential of their surface coating.
The black-and-white gyricon balls are embedded in a sheet of optically transparent material, such as an elastomer layer, that contains a multiplicity of spheroidal cavities. Each of the spheroidal cavities is permeated by a transparent dielectric fluid, such as a plasticizer. The fluid-filled cavities accommodate the gyricon balls, one gyricon ball per cavity, to prevent the balls from migrating within the sheet. Each cavity is slightly larger than the size of the gyricon ball so that each gyricon ball can rotate or move slightly within its cavity.
A gyricon ball can be selectively rotated within its respective fluid-filled cavity by applying an electric field, so that either the black or white hemisphere of the gyricon ball is exposed to an observer viewing the surface of the sheet. By applying an electric field in two dimensions, for example, using a matrix addressing scheme, the black and white sides of the balls can be caused to appear as the image elements, e.g., pixels or subpixels, of a displayed image.
Gyricon displays are described further in U.S. Pat. No. 5,389,945 to Sheridon, incorporated herein by reference in its entirety. The 945 patent discloses that gyricon displays can be made that have many of the desirable qualities of paper, such as flexibility and stable retention of a displayed image in the absence of power, that are not found in CRTs, LCDs, or other conventional display media. Gyricon displays can also be made that are not paper-like, for example, in the form of rigid display screens for flat-panel displays.
SUMMARY OF THE INVENTION
Conventional gyricon displays, as described in U.S. Pat. Nos. 4,126,854, 4,143,103 and 5,739,801, each incorporated herein by reference in its entirety, require a source of electrical power. Gyricon materials respond to the application of high electric fields. However, the electric current requirements can be very low. Basically, the energy required to change the state of the display is the same as that needed to charge the capacitance of the display structure.
As a result, according to this invention, tribo-electrically generated charges can be used to write, re-write or erase a gyricon sheet.
This invention provides a gyricon sheet encapsulated between a conducting plate, and a thin, insulating film.
The invention separately provides a gyricon display addressable by a tribo-electric charge.
The invention separately provides for erasing an image formed on a gyricon display using a tribo-electric charge.
The invention separately provides a gyricon display that does not require an external electric power source to form or erase an image from the gyricon display.
The invention separately provides a gyricon display having a substrate that is sufficiently conductive to dissipate the small amounts of charge generated by tribo-electric effects.
According to one exemplary embodiment of the electric paper of this invention, a tribo-electric charge induced on the surface of an insulating film generates a sufficient electric field to change the state of one or more gyricon balls of the electric paper.
According to a second exemplary embodiment of the electric paper of this invention, the tribo-electrically addressable electric paper can be used to form a whiteboard that does not require chalk, solvent based pens or, in fact, any type of pen.
In the exemplary embodiment of the tribo-electrically addressable electric paper of this invention, sufficient electric energy to produce an image is provided by tribo-electric charges stored and dissipated on a surface of the display.
Gyricon displays designed to be addressed by a stylus can sometimes be adversely affected by tribo-electric effects. For example, in the case of gyricon displays typically addressed by an electrically driven stylus, inadvertently contacting of the gyricon sheet with the user's finger rather than with the writing stylus can, under certain conditions, cause rotation of the gyricon balls due to tribo-electric effects.
In another exemplary embodiment of the electric paper of this invention, the insulative layer of the electric paper is sufficiently conductive to dissipate small amounts of tribo-electrically generated charge. That is, the elastomer layer effectively discharges the tribo electrically generated charge in a time that is less than that required to cause ball rotation. Intentionally applied voltage, as from a powered voltage source such as a writing stylus, has an effectively infinite supply of charge and will deliver a sustained voltage until the desired writing occurs.
REFERENCES:
patent: 4126854 (1978-11-01), Sheridon
patent: 4143103 (1979-03-01), Sheridon
patent: 5389945 (1995-02-01), Sheridon
patent: 5739801 (1998-04-01
Mikkelsen James C.
Richley Edward A.
Sheridon Nicholas K.
Kumar Srilakshmi
Oliff & Berridg,e PLC
Saras Steven
Xerox Coporation
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