Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2000-04-14
2002-12-24
Ben, Loha (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
C345S084000, C345S107000, C264S001360, C264S004100, C264S008000, C264S429000
Reexamination Certificate
active
06498674
ABSTRACT:
I. FIELD OF INVENTION
The present invention relates to the preparation and use of rotating element sheet material with a generalized containment structure. Specifically, the present invention relates to the preparation and use of rotating element sheet material with a matrix substrate, or a substrate derived from a matrix structure.
II. BACKGROUND OF THE INVENTION
Rotating element sheet material has been disclosed in U.S. Pat. Nos. 4,126,854 and 4,143,103, both herein incorporated by reference, and generally comprises a substrate, an enabling fluid, and a class of rotatable elements. As discussed more below, rotating element sheet material has found a use as “reusable electric paper.”
FIG. 1
depicts an enlarged section of rotating element sheet material
18
, including rotatable element
10
, enabling fluid
12
, cavity
14
, and substrate
16
. Observer
28
is also shown. Although
FIG. 1
depicts a spherically shaped rotatable element and cavity, many other shapes will work and are consistent with the present invention. As disclosed in U.S. Pat. No. 5,389,945, herein incorporated by reference, the thickness of substrate
16
may be of the order of hundreds of microns, and the dimensions of rotatable element
10
and cavity
14
may be of the order of 10 to 100 microns.
In
FIG. 1
, substrate
16
is an elastomer material, such as silicone rubber, that accommodates both enabling fluid
12
and the class of rotatable elements within a cavity or cavities disposed throughout substrate
16
. The cavity or cavities contain both enabling fluid
12
and the class of rotatable elements such that rotatable element
10
is in contact with enabling fluid
12
and at least one translational degree of freedom of rotatable element
10
is restricted. The contact between enabling fluid
12
and rotatable element
10
breaks a symmetry of rotatable element
10
and allows rotatable element
10
to be addressed. The state of broken symmetry of rotatable element
10
, or addressing polarity, can be the establishment of an electric dipole about an axis of rotation. For example, it is well known that small particles in a dielectric liquid acquire an electrical charge that is related to the Zeta potential of the surface coating. Thus, an electric dipole can be established on a rotatable element in a dielectric liquid by the suitable choice of coatings applied to opposing surfaces of the rotatable element.
The use of rotating element sheet material as “reusable electric paper” is due to that fact that the rotatable elements are typically given a second broken symmetry, a multivalued aspect, correlated with the addressing polarity discussed above. That is, the above mentioned coatings may be chosen so as to respond to incident electromagnetic energy in distinguishable ways. Thus, the aspect of rotatable element
10
to observer
28
favorably situated can be controlled by an applied vector field.
For example, as disclosed in U.S. Pat. No. 4,126,854, hereinabove incorporated by reference, rotatable element
10
may comprise a black polyethylene generally spherical body with titanium oxide sputtered on one hemisphere, where the titanium oxide provides a light-colored aspect in one orientation. Such a rotatable element in a transparent dielectric liquid will exhibit the desired addressing polarity as well as the desired aspect.
II.A. Rotatable elements with two-valued aspects
A multivalued aspect in its simplest form is a two-valued aspect. When the aspect is the chromatic response to visible light, a rotatable element with a two-valued aspect can be referred to as a bichromal rotatable element. Such a rotatable element is generally fabricated by the union of two layers of material as described in U.S. Pat. No. 5,262,098, herein incorporated by reference.
FIGS. 2-5
depict rotatable element
10
with a two-valued aspect and an exemplary system that use such rotatable elements from the prior art. In
FIG. 2
, rotatable element
10
is composed of first layer
20
and second layer
22
and is, by way of example again, a generally spherical body. The surface of first layer
20
has first coating
91
at a first Zeta potential, and the surface of second layer
22
has second coating
93
at a second Zeta potential. First coating
91
and second coating
93
are chosen such that, when in contact with a dielectric fluid (not shown), first coating
91
has a net positive electric charge with respect to second coating
93
. This is depicted in
FIG. 2
by the “+” and “−” symbols respectively. Furthermore, the combination of first coating
91
and the surface of first layer
20
is non-white-colored, indicated in
FIG. 2
by hatching, and the combination of second coating
93
and the surface of second layer
22
is white-colored. One skilled in the art will appreciate that the material associated with first layer
20
and first coating
91
may be the same. Likewise, the material associated with second layer
22
and second coating
93
may be the same.
FIG. 3
depicts no-field set
30
. No-field set
30
is a subset of randomly oriented rotatable elements in the vicinity of vector field
24
when vector field
24
has zero magnitude. Vector field
24
is an electric field. No-field set
30
, thus, contains rotatable elements with arbitrary orientations with respect to each other. Therefore, observer
28
in the case of no-field set
30
registers views of the combination of second coating
93
and the surface of second layer
22
, and first coating
91
and the surface of first layer
20
(as depicted in
FIG. 2
) in an unordered sequence. Infralayer
26
forms the backdrop of aspect
34
. Infralayer
26
can consist of any type of material, including but not limited to other rotatable elements, or some material that presents a given aspect to observer
28
.
FIGS. 4 and 5
depict first aspect set
32
. First aspect set
32
is a subset of rotatable elements in the vicinity of vector field
24
when the magnitude of vector field
24
is nonzero and has the orientation indicated by arrow
25
. In first aspect set
32
, all of the rotatable elements orient themselves with respect to arrow
25
due to the electrostatic dipole present on each rotatable element
10
. In contrast to no-field set
30
, observer
28
in the case of first aspect set
32
registers a view of a set of rotatable elements ordered with the non-white-colored side up (the combination of first coating
91
and the surface of first layer
20
as depicted in FIG.
2
). Again, infralayer
26
forms the backdrop of the aspect. In
FIGS. 4 and 5
, rotatable element
10
, under the influence of applied vector field
24
, orients itself with respect to vector field
24
due to the electric charges present as a result of first coating
91
and second coating
93
.
FIG. 4
is a side view indicating the relative positions of observer
28
, first aspect set
32
, and infralayer
26
.
FIG. 5
is an alternate view of first aspect set
32
from a top perspective. In
FIG. 5
, the symbol &THgr; indicates an arrow directed out of the plane of the figure.
One skilled in the art will appreciate that first aspect set
32
will maintain its aspect after applied vector field
24
is removed, in part due to the energy associated with the attraction between rotatable element
10
and the substrate structure, as, for example, cavity walls (not shown). This energy contributes, in part, to the switching characteristics and the memory capability of rotating element sheet material
18
, as disclosed in U.S. Pat. No. 4,126,854, hereinabove incorporated by reference, and discussed in more detail below.
II.B. Rotatable elements with multivalued aspect
A rotatable element with multivalued aspect is generally fabricated as disclosed in U.S. Pat. No. 5,919,409, herein incorporated by reference. An exemplary rotatable element
10
with multivalued aspect of the prior art is depicted in FIG.
6
. Rotatable element
10
in
FIG. 6
is composed of first layer
36
, second layer
37
and third layer
38
. The surface of third layer
38
has third coating
95
at a
Ben Loha
Xerox Corporation
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