Function-oriented Knowledge Base \ Electronic paper \ Improve image quality of paper-like display
Bichromal cylinders obtain improved brightness of gyricon display
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Introduction A gyricon display is based upon the use of optically
anisotropic bichromal balls rotatable in an external electric
field. A bichromal ball is located in a transparent elastomer
layer within a cavity filled with a dielectric fluid. In a
monolayer gyricon display, the bichromal balls cover 90 percent
of the working display surface. Such coverage ensures high
reflectance, so the display exhibits perfect contrast and
brightness characteristics. However, dark portions present
in the reflected light between bichromal balls imply a possible
further increase in the display reflectance. Thus, the brightness
characteristic of the surface in the reflected light may also
be improved. Interstices between the balls may be filled with
bichromal balls of smaller diameter. Such a configuration,
however, complicates display fabrication and results in a
tradeoff between light losses due to unfilled interstices
and light losses due to absorption by the black hemispheres
of the smaller interstitial balls. It is necessary to obtain
an improved brightness for a gyricon display.
Description Using nonspheroidal bichromal particles instead
of bichromal balls to improve the brightness of a monolayer
gyricon display is proposed. Such nonspheroidal particles
may be (for example) bichromal cylindrical particles. The
bichromal cylinders are closely packed in a monolayer in parallel
with one another. In the display, light is reflected from
the monolayer of the closely packed cylinders of uniform diameter.
A rectangular planar closely packed monolayer array of cylinders
entirely or almost entirely (approaching 100 percent coverage)
covers the plane. In the case of closely packed cylindrical
particles, there is no need for adding interstitial particles
of a smaller diameter between the particles of larger diameter.
With the white faces of the cylinders exposed to an observer,
little if any light can pass through the layer. For the closely
packed cylinders, the portion of reflected light is maximized.
Correspondingly, the display brightness is increased, or in
other words, the brightness characteristic is improved. Therefore,
a closely packed monolayer of bichromal cylinders makes it
possible to improve the brightness of a gyricon display.
Additional information With an improved display surface brightness,
the brightness difference between black and white image portions
in ambient light is greater. Correspondingly, the brightness
and contrast characteristics may be improved. The fabrication
of the proposed display is relatively easy with respect to
other gyricon displays exhibiting high brightness. The cavities
for accommodating the cylinders are made as small as possible
with respect to the cylinders.
