Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2000-10-24
2004-11-23
Dang, Hung (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C345S107000, C264S004000, C264S007000
Reexamination Certificate
active
06822781
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to gyricon displays and display systems. The present invention, more particularly, relates to gyricon displays and display systems, using particles, such as pigments, which improve the display.
U.S. Pat. Nos. 5,961,804 and 5,930,026, for instance, describe electrophoretic displays using microcapsules which contain a suspension of particles in a dielectric fluid. Through the use of two electrodes which are located on opposite sides of the microcapsule arrangement, a potential difference can cause the particles to migrate toward one of the electrodes thus forming images or text on a display which is located on one of the electrodes since one of the electrodes is transparent. The electrophoretic displays form images and text through the use of a potential difference between two electrodes and a quantity of charged particles. If these charged particles agglomerate they would not remain suspended in the dielectric fluid, and the ability to form a reusable display of images or text can be greatly diminished if not made problematic.
U.S. Pat. No. 5,604,027 describes electric paper using bichromal balls having two hemispheres where one is typically black and the other is white. Each of the hemispheres has different electrical properties and the balls are enclosed within a spherical shell wherein the shell is filled with liquid to form a microsphere so that the ball is free to rotate in response to an electrical field. These microspheres can then be mixed into a substrate which can be formed into sheets or can be applied to any kind of surface. This can then be used to form an image from an applied electrical field.
For this system to work properly, each hemisphere of the bichromal balls must have different electrical properties. To achieve this difference in electrical properties for the two hemispheres, for example, U.S. Pat. No. 4,143,103 describes a sphere comprised of black polyethylene with a light reflective material such as titanium dioxide sputtered on the one hemisphere. U.S. Pat. No. 4,438,160 describes a ball prepared by coating white glass balls with an inorganic colorant by evaporation. In a similar process (“The Gyricon—A Twisting Ball Display” published in the proceedings of the S.I.D., Vol. 18/3 and 4 (1977)), the material used to form the bichromal ball was conductive such as glass containing a heavy loading of titanium dioxide and half of this ball was coated with a dense layer of a non-conductive black material. Further, U.S. Pat. Nos. 5,262,098 and 5,344,594 describe a method of forming bichromal balls by bringing together streams of differently colored hardenable liquids. Unfortunately, with this current type of technology, the ability to achieve a diverse combination of colors is quite limited and further, the clarity of the image formed when an electrical field is applied can be improved.
U.S. Patents, like U.S. Pat. No. 5,717,514, relate to multi-segmented balls for the electrical twisting ball display device wherein the ball is composed of segments arrayed substantially parallel to one another. Each segment can be a different color and have a difference in electrical properties. Put another way, each segment would have a different optical modulation characteristic and be anisotropic in order to provide an electrical dipole moment. As before, the ball is rotatably disposed in a non-oscillating electric field. As described in these patents, polymeric material, such as plastics, are used to create the various segments which can contain a dispersion of pigments to create the various colors. In addition, some of these patents emphasize the need to make smaller and size consistent multi-segmented or polychromal balls in order to create images which are more defined. Essentially, the technology is going toward smaller and smaller particles to obtain high pixel resolution in order to create sharper and more defined images and text. As a result, there is an increasing need to have a defined amount of pigment or other colorant in each polychromal or bichromal ball. Thus, there is a need to ensure that pigment is adequately and uniformly dispersed in the various materials used to form the polychromal or bichromal balls. Furthermore, since there is an increasing demand on the level of pigment that must exist in each polychromal ball, again, there would be a need to ensure that large amounts of pigment can be introduced into the polymer used to form the polychromal balls. This can be a problem since large amounts of pigments in polymeric materials lead to agglomeration or non-uniform dispersion of the pigment in the polymer. Accordingly, there is a need to improve upon the display technology in order to ensure that clear and visually sharp images can be obtained using display technology and pigment particles. Each of the above cited patents and publications are incorporated in their entirety herein by reference.
SUMMARY OF THE PRESENT INVENTION
A feature of the present invention is to provide gyricon displays which provide sharp and clear images on the display.
Another feature of the present invention is to provide a gyricon display having a variety of different color combinations that can be displayed.
A further feature of the present invention is to provide a gyricon display having bichromal or polychromal balls that have uniform and high concentrations of pigment in each ball.
An additional feature of the present invention is to provide methods of making polychromal or bichromal balls wherein each ball contains a uniform distribution of pigment and/or high concentration of pigment.
Additional features and advantages of the present invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the description and appended claims.
To achieve these and other advantages, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention relates to a gyricon display having an arrangement of bichromal balls and first and second electrodes disposed on and covering opposite sides of the arrangement. One of the electrodes is substantially visually transparent. The display also has means for creating a potential difference between the two electrodes. Also, each bichromal ball has two hemispheres, wherein one of the hemispheres includes a modified colored pigment having attached at least one organic group and the other hemisphere has at least a surface with a different color and different electrical properties than the first hemisphere. Each ball is enclosed within a shell to form a capsule wherein a liquid is present between the shell and the ball, so that the ball is free to rotate in response to an electric field. The organic group preferably contains an ionic and/or ionizable group wherein the organic group preferably on the surface contributes to the rotation of the ball towards one of the electrodes when there is a potential difference created between the two electrodes.
The present invention further relates to bichromal balls having two hemispheres, wherein one of the hemispheres has a surface comprising a modified colored pigment having attached at least one organic group and the other hemisphere having a surface with a different color and different electrical properties than the first hemisphere. Each ball is enclosed within a shell to form a capsule wherein a liquid is present between the shell and the ball, so that the ball is free to rotate in response to an electrical field. The organic group contains an ionic and/or ionizable group. The organic group on the surface causes the ball to rotate in response to an electrical field.
The present invention also relates to bichromal balls having two hemispheres as described above, wherein a modified colored pigment having attached at least on
Amici Robert M.
Dalton Dennis M.
Galloway Collin P.
Cabot Corporation
Dang Hung
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