Twisting-cylinder display

Details Twisting-cylinder display Twisting-cylinder display

2001-10-02

2002-12-24

Dixon, Merrick (Department: 1774)

Stock material or miscellaneous articles

Structurally defined web or sheet

Discontinuous or differential coating, impregnation or bond

C428S040200, C428S038000, C345S107000, C345S108000, C359S296000

Reexamination Certificate

active

06497942

ABSTRACT:

INCORPORATION BY REFERENCE
The following U.S. patents are fully incorporated herein by reference: U.S. Pat. No. 4,126,854, (Sheridon, “TWISTING BALL PANEL DISPLAY”); U.S. Pat. No. 4,143,103 (Sheridon, “METHOD OF MAKING A TWISTING BALL PANEL DISPLAY”); U.S. Pat. No. 5,262,098 (Crowley et al., “METHOD AND APPARATUS FOR FABRICATING BICHROMAL BALLS FOR A TWISTING BALL DISPLAY”); U.S. Pat. No. 5,344,594 (Sheridon, “METHOD FOR THE FABRICATION OF MULTICOLORED BALLS FOR A TWISTING BALL DISPLAY”); and U.S. Pat. No. 5,389,945 (Sheridon, “WRITING SYSTEM INCLUDING PAPER-LIKE DIGITALLY ADDRESSED MEDIA AND ADDRESSING DEVICE THEREFOR”), U.S. patent application Ser. No. 08/572,779 entitled “POLYCHROMAL SEGMENTED BALLS FOR A TWISTING BALL DISPLAY”; U.S. patent application Ser. No. 08/572,778, entitled “APPLICATIONS OF A TRANSMISSIVE TWISTING BALL DISPLAY”; U.S. patent application Ser. No. 08/572,819, entitled “CANTED ELECTRIC FIELDS FOR ADDRESSING A TWISTING BALL DISPLAY”; U.S. patent application Ser. No. 08/572,927, entitled “HIGHLIGHT COLOR TWISTING BALL DISPLAY”; U.S. patent application Ser. No. 08/572,912, entitled “PSEUDO-FOUR COLOR TWISTING BALL DISPLAY”; U.S. patent application Ser. No. 08/572,820, entitled “ADDITIVE COLOR TRANSMISSIVE TWISTING BALL DISPLAY”; U.S. patent application Ser. No. 08/572,780, entitled “SUBTRACTIVE COLOR TWISTING BALL DISPLAY”; U.S. patent application Ser. No. 08/572,775, entitled “MULTITHRESHOLD ADDRESSING OF A TWISTING BALL DISPLAY”; U.S. patent application Ser. No. 08/572,777, entitled “FABRICATION OF A TWISTING BALL DISPLAY HAVING TWO OR MORE DIFFERENT KINDS OF BALLS”; and U.S. patent application Ser. No. 08/573,922, entitled “ADDITIVE COLOR TRISTATE LIGHT VALVE TWISTING BALL DISPLAY.” All filed concurrently on Dec. 15
th
, 1995, and two divisional applications from U.S. patent application Ser. No. 08/572,779, entitled “POLYCHROMAL SEGMENTED BALLS FOR A TWISTING BALL DISPLAY”, “POLYCHROMAL SEGMENTED BALLS FOR A TWISTING BALL DISPLAY” now U.S. Pat. No. 5,919,409, U.S. patent application Ser. No. 08/889,762, entitled “APPARATUS FOR FABRICATING POLYCHROMAL SEGMENTED BALLS FOR A TWISTING BALL DISPLAY” filed on Jul. 10
th
, 1997.
RELATED PATENT APPLICATIONS
The following copending, coassigned U.S. Patent Applications are related to this case: U.S. patent application Ser. No. 08/713935, entitled “MONOLAYER GYRICON DISPLAY”; U.S. patent application Ser. No. 08713,936, entitled “HIGH REFLECTANCE GYRICON DISPLAY”; U.S. patent application Ser. No. 081716,675,entitled “GYRICON DISPLAY WITH INTERSTITIALLY PACKED PARTICLE ARRAYS”; and U.S. patent application Ser. No. 08/713,325, entitled “GYRICON DISPLAY WITH NO ELASTOMER SUBSTRATE.”
BACKGROUND OF THE INVENTION
The invention pertains to visual displays and more particularly to twisting-ball displays, such as gyricon displays and the like.
Gyricon displays, also known by other names such as electrical twisting-ball displays or rotary ball displays, were first developed over twenty years ago. See U.S. Pat. Nos. 4,126,854 and 4,143,103, incorporated by reference hereinabove.
An exemplary gyricon display
10
is shown in side view in
FIG. 1A
(PRIOR ART). Bichromal balls
1
are disposed in an elastomer substrate
2
that is swelled by a dielectric fluid creating cavities
3
in which the balls
1
are free to rotate. The balls
1
are electrically dipolar in the presence of the fluid and so are subject to rotation upon application of an electric field, as by matrix-addressable electrodes
4
a
,
4
b
. The electrode
4
a
closest to upper surface
5
is preferably transparent. An observer at I sees an image formed by the black and white pattern of the balls
1
as rotated to expose their black or white faces (hemispheres) to the upper surface
5
of substrate
2
.
A single one of bichromal balls
1
, with black and white hemispheres
1
a
and
1
b
, is shown in
FIG. 1B
(PRIOR ART).
Gyricon displays have numerous advantages over conventional electrically addressable visual displays, such as LCD and CRT displays. In particular, they are suitable for viewing in ambient light, retain an image indefinitely in the absence of an applied electric field, and can be made lightweight, flexible, foldable, and with many other familiar and useful characteristics of ordinary writing paper. Thus, at least in principle, they are suitable both for display applications and for so-called electric paper or interactive paper applications, in which they serve as an electrically addressable, reuseable (and thus environmentally friendly) substitute for ordinary paper. For further advantages of the gyricon, see U.S. Pat. No. 5,389,945, incorporated by reference hereinabove.
Known gyricon displays employ spherical particles (e.g., bichromal balls) as their fundamental display elements. There are good reasons for using spherical particles. In particular:
Spherical bichromal balls can be readily manufactured by a number of techniques. See the '098 and '594 patents, incorporated by reference hereinabove, in this regard.
Spheres are symmetrical in three dimensions. This means that fabrication of a gyricon display sheet from spherical particles is straightforward. It is only necessary to disperse the balls throughout an elastomer substrate, which is then swelled with dielectric fluid to form spherical cavities around the balls. The spherical balls can be placed anywhere within the substrate, and at any orientation with respect to each other and with respect to the substrate surface. There is no need to align the balls with one another or with the substrate surface. Once in place, a ball is free to rotate about any axis within its cavity.
“In the ‘white’ state, the gyricon display reflects almost entirely from the topmost layer of bichromal balls and, more particularly, from the white hemispherical upper surfaces of the topmost layer of balls. In a preferred embodiment, the inventive display is constructed with a single close-packed monolayer of bichromal balls.”
Ideally, a close-packing arrangement would entirely cover the plane with the monolayer of gyricon elements. However,. Inasmuch as a planar array of spheres cannot fully cover the plane, but must necessarily contain interstices, the best that can be achieved with a single population of uniform-diameter spherical elements is about 90.7 percent areal coverage, which is obtained with a hexagonal packing geometry. A second population of smaller balls can be added to fill in the gaps somewhat, but this 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.
Therefore, it would be desirable to provide a close-packed monolayer gyricon display in which areal coverage surpasses 90.7 percent or approaches 100 percent, without any need for interstitial particles. This can be done by using cylindrical rather than spherical elements. For example, a rectangular planar monolayer array of cylinders can be constructed that entirely or almost entirely covers the plane. With the white faces of the cylinders exposed to an observer, little if any light can get through the layer.
SUMMARY OF THE INVENTION
The invention provides a gyricon display having cylindrical, rather than spherical, rotating elements. The elements can be bichromal or polychromal cylinders, preferably aligned parallel to one another and packed close together in a monolayer. The close-packed monolayer configuration provides excellent brightness characteristics and relative ease of manufacture as compared with certain other high-brightness gyricon displays. The cylinders can be fabricated by techniques that will be disclosed. The substrate containing the cylinders can be fabricated with the swelled-elastomer techniques known from spherical-particle gyricon displays, with a simple agitation process step being used to align the cylinders within the sheeting material.
Further, the invention is well-suited to providing a gyricon display having superior reflectance characteristics comparing favorabl

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