U.S. patent application number 10/886147 was filed with the patent office on 2006-01-12 for encapsulated bichromal gyricon display.
This patent application is currently assigned to Xerox Corporation. Invention is credited to Man-Chung Tam.
Application Number | 20060007523 10/886147 |
Document ID | / |
Family ID | 35482631 |
Filed Date | 2006-01-12 |
United States Patent
Application |
20060007523 |
Kind Code |
A1 |
Tam; Man-Chung |
January 12, 2006 |
ENCAPSULATED BICHROMAL GYRICON DISPLAY
Abstract
Various layered arrays utilizing encapsulated bichromal balls
are disclosed that can be used in display applications. Also
disclosed are related methods for manufacturing the layered arrays,
and forming displays. The methods are particularly well-suited for
forming displays having one or more monolayer(s) of closely-packed
encapsulated bichromal balls.
Inventors: |
Tam; Man-Chung;
(Mississauga, CA) |
Correspondence
Address: |
Richard M. Klein, Esq.;FAY, SHARPE, FAGAN, MINNICH & McKEE, LLP
SEVENTH FLOOR
1100 SUPERIOR AVENUE
CLEVELAND
OH
44114-2579
US
|
Assignee: |
Xerox Corporation
|
Family ID: |
35482631 |
Appl. No.: |
10/886147 |
Filed: |
July 7, 2004 |
Current U.S.
Class: |
359/296 |
Current CPC
Class: |
G02B 26/026
20130101 |
Class at
Publication: |
359/296 |
International
Class: |
G02B 26/00 20060101
G02B026/00 |
Claims
1. A display member comprising: a substrate; a layer of an adhesive
disposed on said substrate; and a monolayer of closely-packed
encapsulated bichromal balls disposed on said adhesive to produce a
display member having a transmission optical density contrast of
from about 0.40 to about 0.70.
2. The display member of claim 1, further comprising: an addressing
electrode disposed between said substrate and said adhesive
layer.
3. The display member of claim 1, further comprising: a first
addressing electrode disposed between said substrate and said
adhesive layer; a second layer of an adhesive disposed on and
contacting said monolayer of encapsulated bichromal balls; a
protective layer disposed on said second adhesive layer; and a
second addressing electrode disposed between said second adhesive
layer and said protective layer.
4. The display member of claim 1, wherein said substrate is
electrically conductive and includes a material selected from the
group consisting of copper, brass, nickel, zinc, chromium,
stainless steel, conductive plastics, conductive rubbers, aluminum,
semitransparent aluminum, steel, cadmium, silver, gold, indium,
tin, metal oxides, and combinations thereof.
5. The display member of claim 1, wherein said substrate is
electrically insulative and includes a material selected from the
group consisting of paper, glass, plastics, and combinations
thereof.
6. The display member of claim 1, wherein said adhesive is selected
from the group consisting of copolymers of styrene and acrylate,
polyester resins, copolymers of acrylonitrile and vinylidene
chloride, polyvinyl acetate, polyvinyl butyral, polyolefins,
cyanacrylates, silicone, epoxy and combinations thereof.
7. The display member of claim 1, wherein said substrate has a
thickness of from about 25 microns to about 2000 microns.
8. The display member of claim 1, wherein said adhesive layer has a
thickness in the range of from about 0.01 micron to about 20
microns.
9. The display member of claim 1, wherein said capsule of the
encapsulated bichromal balls have a diameter of from about 30
microns to about 300 microns.
10. The display member of claim 9, Wherein said bichromal balls
have a diameter of about 70% to about 90% of the diameter of the
capsules.
11. A display assembly comprising: a supporting substrate; a first
addressing electrode disposed on said supporting substrate; a first
adhesive layer disposed on said first electrode; a first monolayer
of closely-packed encapsulated bichromal balls disposed on said
first adhesive layer; a second monolayer of closely-packed
bichromal balls disposed on said first monolayer of bichromal
balls; a second adhesive layer disposed on said second monolayer of
bichromal balls; a second addressing electrode disposed on said
second adhesive layer; and a protective cover disposed on said
second electrode and generally encapsulating the resulting
assembly.
12. The display assembly of claim 11, wherein said substrate is
electrically conductive and includes a material selected from the
group consisting of copper, brass, nickel, zinc, chromium,
stainless steel, conductive plastics, conductive rubbers, aluminum,
semitransparent aluminum, steel, cadmium, silver, gold, indium,
tin, metal oxides, and combinations thereof.
13. The display assembly of claim 11, wherein said substrate is
electrically insulative and includes a material selected from the
group consisting of paper, glass, plastics, and combinations
thereof.
14. The display assembly of claim 11, wherein said adhesive is
selected from the group consisting of copolymers of styrene and
acrylate, polyester resins, copolymers of acrylonitrile and
vinylidene chloride, polyvinyl acetate, polyvinyl butyral,
polyolefins, cyanacrylates, silicone, epoxy and combinations
thereof.
15. The display assembly of claim 11, wherein said substrate has a
thickness of from about 25 microns to about 2000 microns, said
adhesive layer has a thickness of from about 0.01 micron to about
20 microns, and said encapsulated bichromal balls have a diameter
of from about 100 microns to about 150 microns.
16. A process for forming a layered array having a monolayer of
closely-packed encapsulated bichromal balls, said process
comprising: providing a substrate having an exposed adhesive
surface; depositing a plurality of encapsulated bichromal balls on
said exposed adhesive surface of said substrate such that a
monolayer of encapsulated bichromal balls is formed by a cascading
application process whereby each said encapsulated bichromal ball
contacts said exposed adhesive face of said substrate and is
thereby retained on said substrate, wherein the array exhibits a
transmission optical contrast density of from about 0.40 to about
0.70.
17. The process of claim 16, further comprising: positioning said
substrate at an inclined orientation.
18. The process of claim 16, wherein the depositing step is
repeated a plurality of times to provide a substantially uniform
monolayer.
19. The process of claim 17, wherein the amount of incident light
that can transmit through the monolayer produced is 40% or
less.
20. The process of claim 16, wherein during said depositing step, a
portion of said encapsulated bichromal balls deposited on said
substrate are not retained thereon and instead are collected in a
container.
21. The process of claim 16, wherein during said depositing step,
said substrate is moving.
22. The layered array produced according to the process of claim
16.
Description
BACKGROUND
[0001] The present disclosure relates to displays based upon
encapsulated bichromal balls and methods of manufacturing such
displays. It finds particular application in conjunction with
display technology, and "electric paper" and will be described with
particular reference thereto. However, it is to be appreciated that
the present exemplary embodiment is also amenable to other like
applications.
[0002] Bichromal balls or beads as sometimes referred to in the
art, are small spherical balls which have an optical and an
electrical anisotropy. These characteristics generally result from
each hemisphere surface having a different color and electrical
charge.
[0003] These spherical particles are imbedded in a solid substrate
and a slight space between each ball and the substrate is filled
with an oil so that the balls are free to rotate, and migrate in an
oil-filled cavity, in a changing electrical field. If one
hemisphere is black and the other is white, each pixel can be
turned on and off by the electrical field applied to that location.
Each pixel can be individually addressed, and a full page image can
thus be generated.
[0004] Numerous patents describe bichromal balls, their
manufacture, incorporation in display systems or substrates, and
related uses and applications. Exemplary patents include, but are
not limited to: U.S. Pat. Nos. 5,262,098; 5,344,594; 5,604,027
reissued as Re 37,085; U.S. Pat. Nos. 5,708,525; 5,717,514;
5,739,801; 5,754,332; 5,815,306; 5,900,192; 5,976,428; 6,054,071;
5,989,629; 6,235,395; 6,419,982; 6,235,395; 6,419,982; 6,445,490;
and 6,703,074; all of which are hereby incorporated by reference.
In addition, disclosure is provided by U.S. Pat. Nos. 4,126,854;
and 5,825,529; and N. K. Sheridon et al., "The Gyricon--A twisting
ball display", Proc. SID, Boston, Mass., 289, 1977; T. Pham et al.,
"Electro-optical characteristics of the Gyricon display", SID '02
Digest, 199, 2002; all of which are hereby incorporated by
reference.
[0005] Gyricon display technology is currently being developed for
commercial signage application. The Gyricon display devices are
often produced by the "swollen sheet" method. In this method, the
Gyricon display sheets are made by mixing or dispersing bare
bichromal balls, which are approximately 75 .mu.m to 150 .mu.m in
diameter, into an uncured silicone elastomer to yield a viscous
paste. The elastomeric gel is then spread into a thin layer by a
doctor blade on a supporting substrate and cured to form a solid
flexible sheet. The sheet is then soaked in a dielectric oil that
causes the elastomer to swell and form an oil-filled cavity around
each ball. The balls are free to rotate in each swollen cavity. The
swollen sheets are sandwiched between substrates carrying arrays of
addressing electrodes to form a display.
[0006] Fabrication of the Gyricon display sheet involves many
complicated steps. The material into which the balls are disposed
or embedded is largely limited to the class of elastomeric
materials chosen for their large capacity to swell. This material
is costly. To prevent the loss of dielectric oil, which would
render the display inoperative, the display needs to be sealed. The
produced Gyricon sheet is relatively thick, about 300 .mu.m to
about 700 .mu.m, and includes a dispersion of bichromal balls of
many layers. The disadvantage of the multi-layered structure is
that it degrades the contrast, i.e. reflectance, degrades the
resolution, increases the switching voltage, and increases the
complexity and cost of the driver electronics of the display. These
add to the complexity and cost of the resulting Gyricon
display.
[0007] Additionally, U.S. Pat. No. 6,445,496, which is incorporated
herein by reference in its entirety, describes a method of
encapsulating the bichromal balls within an oil-filled capsule. The
capsule is formed by chemical means. Encapsulation of the Gyricon
beads may eliminate the need for a costly elastomer and the sealing
steps.
[0008] Furthermore, U.S. Pat. No. 6,492,025, incorporated herein by
reference in its entirety, describes an example of microcapsule
composition. U.S. Pat. No. 6,488,870, also incorporated herein by
reference in its entirety, describes examples of additional
encapsulation processes.
[0009] Monolayers of encapsulated bichromal balls can also be
produced. The balls are generally randomly dispersed within the
resin. However, such randomly dispersed balls are not
closely-packed and produce a large amount of open space. This
results in decreased optical contrast.
[0010] Accordingly, there is a need for a display member of one or
more monolayers of closely-packed bichromal balls, and a technique
for producing such a display member.
BRIEF DESCRIPTION
[0011] The present disclosure relates to methods and compositions
for producing a closely-packed bichromal Gyricon display. The
resulting Gyricon display exhibits enhanced optical
characteristics.
[0012] In accordance with one aspect of the present exemplary
embodiment, a display member is provided comprising a substrate, a
layer of an adhesive on the substrate, and a monolayer of
encapsulated bichromal balls disposed within the adhesive on the
substrate. Preferably, the monolayer of encapsulated bichromal
balls is applied to the adhesive by a cascading application
process. This results in improved uniformity and close-packing of
the coated monolayer, critical factors for achieving maximum
optical performance of a display member.
[0013] In accordance with yet another aspect of the present
exemplary embodiment, a process for forming a layered array having
a monolayer of encapsulated bichromal balls is provided. The
process comprises providing a substrate having an exposed adhesive
surface. The process also comprises a step of depositing, such as
by a cascading application process, a plurality of encapsulated
bichromal balls on the exposed adhesive surface of the substrate
such that a monolayer of closely-packed encapsulated bichromal
balls is formed whereby each of the encapsulated bichromal balls of
the resulting monolayer contacts the exposed adhesive face of the
substrate and is thereby retained on the substrate.
[0014] In another aspect of the present exemplary embodiment, a
display assembly is provided comprising a supporting substrate, a
first addressing electrode disposed on the supporting substrate, a
first adhesive layer disposed on the first electrode, a first
monolayer of encapsulated bichromal balls disposed within the
adhesive on the first adhesive layer, a second monolayer of
bichromal balls disposed on the first monolayer of bichromal balls,
a second adhesive layer disposed on the second monolayer of
bichromal balls, a second addressing electrode disposed on the
second adhesive layer, and a protective cover disposed on the
second electrode and generally encapsulating the resulting
assembly. The encapsulated bichromal balls are applied through the
use of a cascading application process to produce layer(s) of
closely-packed bichromal balls.
[0015] The transmission optical contrasts obtained by the
monolayer(s) of the closely-packed bichromal balls produced by the
processes disclosed herein are from about 0.40 to about 0.70. This
allows only from about 20% to about 40% of incident light to
transmit through the monolayer(s). Preferably, only less than 30%
of incident light is allowed to transmit. Displays produced
utilizing such closely-packed bichromal balls exhibit enhanced
optical contrast, among other characteristics.
[0016] These and other non-limiting aspects and/or objects of the
exemplary embodiment of the present disclosure are more
particularly described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The following is a brief description of the drawings, which
are presented for the purposes of illustrating the development
disclosed herein and not for the purposes of limiting the same.
[0018] FIG. 1 is a schematic cross-sectional diagram of a display
member having a monolayered structure in accordance with one of the
exemplary embodiments.
[0019] FIG. 2 shows a schematic cross section of another display
member having a dual-layered structure in accordance with another
of the exemplary embodiments.
[0020] FIG. 3 illustrates schematically yet another display member
having a monolayered structure and coated on a substrate in
accordance with a further exemplary embodiment.
[0021] FIG. 4 shows schematically a coating process suitable for
making a sheet or display member in accordance with one of the
exemplary embodiments.
[0022] FIG. 5 illustrates schematically another coating process
suitable for making a continuous roll of display member in
accordance with a further embodiment.
[0023] FIG. 6 shows schematically a further coating process for
making a sheet or display member in accordance to another exemplary
embodiment.
DETAILED DESCRIPTION
[0024] Recent work has shown the feasibility of encapsulating
bichromal balls within an oil-filled gelatin-polyphosphate shell by
chemical means. The shell can be produced from a variety of
materials such as those conventionally described and include
gelatin/polyphosphate as well as gelatin/gum arabic. Encapsulation
eliminates the need for the costly elastomer and the swelling step.
Also, there is no need to form a seal to prevent the loss of
oil.
[0025] The present exemplary embodiment provides an improved
display member utilizing a monolayer of closely-packed encapsulated
bichromal balls. The embodiment also provides an improved display
member exhibiting some of the optical and tactile properties of
paper. Furthermore, the embodiment provides an improved display
including two or more layers of bichromal balls. The embodiment
also provides a manufacturing process of fabricating the improved
display members. The manufacturing process is applicable for making
display members having planar and non-planar surfaces.
[0026] The monolayer structure of the exemplary display members in
accordance with the present discovery has the advantage of a
smaller thickness which reduces the switching voltage and improves
resolution, results in higher contrast, provides for a simplified
manufacturing process and lower cost. The discovery also finds
application in electrical paper.
[0027] In this regard, when Gyricon displays are prepared from
bichromal balls arranged in a monolayer, it is important that the
balls are packed as closely to each other as possible. Otherwise
the optical contrast will be degraded.
[0028] The packing efficiency can be assessed by coating a
monolayer of bichromal balls on an adhesive transparent substrate
such as polyester and measuring the transmission optical contrast
density. Transmission optical density can be experimentally
measured by a commercially available densitometer such as Model
TR927 made by GretagMacbeth.
[0029] Transmission optical density DT is represented by the
formula: DT=log.sub.10(I.sub.0/I) where I is the transmitted light
intensity and I.sub.0 is the incident light intensity.
[0030] Transmission optical contrast density is given by the
difference between the optical densities of the monolayer of
bichromal balls coated on the polyester substrate and that of the
polyester substrate alone.
[0031] The transmission optical contrast density obtained by
coating a monolayer of bichromal balls on an adhesive polyester
substrate in accordance with the present disclosure is in the range
of 0.40-0.70, allowing only 20-40% of incident light to transmit
through the monolayer. Preferably, only less than 30% of incident
light is allowed to transmit.
[0032] For bichromal balls encapsulated inside capsules, the amount
of light that can transmit through the monolayer is preferably less
than 40%
[0033] The various display members comprising closely-packed
monolayers described herein generally comprise a supporting
substrate or paper on which is disposed a layer of an adhesive.
Typically, an addressing electrode is disposed between the adhesive
layer and the supporting substrate. Disposed on the first adhesive
layer are one or more layers of encapsulated bichromal balls. For
layered arrays, a second adhesive layer is disposed on the one or
more layers of bichromal balls such that the bichromal balls are
positioned between the two adhesive layers. In another embodiment,
a monolayer of bichromal balls is produced and then joined
face-to-face. Disposed adjacent to the second adhesive layer, and
on a side of that layer opposite the layers of bichromal balls, is
a second addressing electrode. And, a protective cover or layer is
positioned along the exposed second addressing electrode. Details
of each of these components are as follows.
[0034] The supporting substrate can be either electrically
conductive or insulative. The substrate can be opaque,
semi-transparent or transparent. In addition, the substrate can
comprise an insulative layer with an electrically conductive
coating such as vacuum-deposited aluminized or titanized polyester.
The substrate can have any thickness typically in the range of from
about 25 to about 2000 microns depending on the end-use
application.
[0035] The commonly used supporting substrate includes indium tin
oxide coated on glass or on polyester. Both are commercially
available. Also potentially included are printed circuit
boards.
[0036] More specifically, the substrate can be either electrically
conductive or electrically insulating. When conductive, the
substrate can be opaque, translucent, semitransparent, or
transparent, and can be of any suitable conductive material,
including, but not limited to, copper, brass, nickel, zinc,
chromium, stainless steel, conductive plastics and rubbers,
aluminum, semitransparent aluminum, steel, cadmium, silver, gold,
indium, tin, metal oxides, including tin oxide and indium tin
oxide, and the like. For electric paper applications, the paper can
be rendered conductive by the inclusion of a suitable material
therein or through conditioning in a humid atmosphere to ensure the
presence of sufficient water content to render the material
conductive. When insulative, the substrate can be opaque,
translucent, semitransparent, or transparent, and can be of any
suitable insulative material, such as paper, glass, plastic,
polyesters such as Mylar.RTM. (available from Du Pont) or
Melinex.RTM. 442, (available from ICI Americas, Inc.), and the
like. In addition, the substrate can comprise an insulative layer
with a conductive coating, such as vacuum-deposited metallized
plastic, such as titanized or aluminized Mylar.RTM. polyester,
wherein the metallized surface is in contact with the adhesive
layer or any other layer situated between the supporting substrate
and the adhesive layer. The substrate has any effective thickness,
typically from about 25 microns to about 1000 microns, and
preferably from about 50 microns to about 200 microns, as
previously noted, although the thickness can be outside of this
range.
[0037] The addressing electrode is electrically conductive and can
include any suitable conductive material such as aluminum, copper
etc. It can be a thin semi-transparent conductive coating on the
substrate such as aluminized polyester. It will be appreciated that
in most display applications, the bichromal balls are individually
addressable by the electrodes.
[0038] Indium tin oxide (ITO) is probably the most commonly used
electrode material for display. The conductive electrode can be a
continuous layer or a discontinuous island structure.
[0039] A more complete understanding of the processes and
apparatuses disclosed herein can be obtained by reference to the
accompanying drawings. These figures are merely schematic
representations based on convenience and the ease of demonstrating
one or more exemplary embodiments of the present development, and
are, therefore, not intended to indicate relative size and
dimensions of the devices and/or assemblies or components
thereof.
[0040] Although specific terms are used in the following
description for the sake of clarity, these terms are intended to
refer only to the particular structure of the embodiments selected
for illustration in the drawings, and are not intended to define or
limit the scope of the disclosure. In the drawings and the
following description below, it is to be understood that like
numeric designations refer to component of like function.
[0041] Referring to FIG. 1, an exemplary embodiment array 100
comprises a protective layer 10, a first addressing electrode 20, a
first adhesive layer 30, a layer of bichromal balls 40, a second
adhesive layer 50, a second addressing electrode 60, and a
supporting substrate 70.
[0042] In accordance with another aspect of the present discovery,
another exemplary embodiment array 200 is provided as shown in FIG.
2. The array 200 comprises a protective cover 210, a first
addressing electrode 220, an adhesive layer 230, and at least one
layer of bichromal balls 240. The array 200 further comprises a
second adhesive layer 250, a second addressing electrode 260, and a
supporting substrate 270. Generally, the number of layers of
bichromal balls will be one or two; however, the present discovery
includes a greater number of layers.
[0043] FIG. 3 illustrates another exemplary embodiment array 300
comprising a layer of bichromal balls 310 disposed on an adhesive
layer 320 which is disposed on a layer of paper 330.
[0044] Specifically, the supporting substrate can be constructed by
techniques already known in the art. The charge retaining islands
can be created on or in an encapsulating layer by many means with
any conductive material. One technique, which has been tested,
creates islands of conductive and transparent indium tin oxide
(ITO) on a transparent polyester film. The polyester is coated with
a very thin layer of ITO, and then channels are etched in the ITO
by photolithographic processes well known in the art. The remaining
conductive ITO regions act as charge retaining islands, while
insulating channels are created by the underlying polyester. An
encapsulating layer of polyester patterned with ITO islands of
0.090'' on an edge and 0.010'' channels has been demonstrated.
Extending the process to develop patterns with 0.003'' to 0.005''
channels and island edge dimensions of 0.015'' to 0.025'' is
straight-forward. Still higher resolution can be achieved using
other patterning processes and technologies well known in the art.
Any metal, such as chrome or aluminum, applicable in thin films and
patternable by lithographic processes could be used in place of the
ITO. Many plastic materials, such as PVDC and polyethylene, are
possible candidates for a substrate on which to build the
islands.
[0045] Incorporation of an adhesive layer promotes the formation of
the monolayered embodiments of the encapsulated bichromal balls in
accordance with the present discovery. However, as noted, multiple
adhesive layers can be used. The adhesive layer can include any
suitable adhesive material. Typical adhesive materials include, but
are not limited to, copolymers of styrene and acrylate, polyester
resins, copolymers of acrylonitrile and vinylidene chloride,
polyvinyl acetate, polyvinyl butyral, polyolefin, cyanacrylates,
silicone and/or epoxy etc., and combinations thereof. The adhesive
layer can have any thickness, however is typically in the range of
from about 0.01 to about 20 microns, although the thickness can be
outside of this range.
[0046] The adhesive layer usually is a separate layer of adhesive
coating applied over the electroded substrate. For some
applications such as electrical paper, the adhesive layer can also
include an adhesive coating applied over the paper as exemplified
in FIG. 3.
[0047] The bichromal balls form a closely-packed monolayer adhering
to the adhesive layer. For signage applications, the capsules may
have a diameter of about 120 microns (.mu.m), and the capsules may
be substantially uniform in size in order to optimize performance.
For applications requiring higher resolution, a smaller diameter is
preferred. Bichromal balls having a formulation of
polywax/titania/pigment can be encapsulated within an oil-filled
shell such as a shell formed from gelatin-polyphosphate by chemical
means. The bichromal balls possess electrical dipoles or are
anisotropically charged and they are free to rotate in response to
an imaging electric field. Details of encapsulating bichromal balls
by a gelatin-polyphosphate shell are included in U.S. Pat. Nos.
6,492,025 and 6,488,870, both of which are hereby incorporated by
reference.
[0048] For display applications, the protective cover is
transparent or semi-transparent. It can be either electrically
conductive or insulative. It can comprise an insulative layer with
an electrically conductive coating such as vacuum-deposited
aluminized polyester. Its thickness is typically in the range of
from about 25 to about 2000 microns depending on the particular
application. The protective cover is usually the same as the
supporting substrate, however for display applications, it should
be transparent.
[0049] The monolayer of the various display members in accordance
with the present discovery is generally formed by coating of the
adhesive layer and then coating of the encapsulated bichromal balls
over the adhesive layer.
[0050] The adhesive layer can be coated onto the electroded
substrate or paper as in FIG. 3, by any suitable coating technique.
Typical coating processes include, but are not limited to,
extrusion using slot die, wire-wound rod coating, air-knife
coating, gravure roll coating, dip coating, spray coating, draw-bar
coating and the like.
[0051] Coating of the encapsulated bichromal balls can be
accomplished by cascading them over the adhesive layer. Only the
capsules that are in direct contact with the adhesive layer are
coated, yielding a uniform coating. The capsules not in direct
contact with the adhesive layer remain unattached and can be
removed by a variety of means such as gravity, vacuum suction etc.
Coating uniformity can further be improved by cascading the balls
over the surface several times. Alternatively, uniformity can be
enhanced utilizing vibratory motion, etc., to improve ball
placement into voided areas.
[0052] FIG. 4 illustrates an assembly 400 used in an exemplary
embodiment process system, i.e., cascading application or
fabricating process, according to the present discovery. The
assembly 400 includes a metering hopper 410 positioned above an
inclined surface 440 over which a plurality of bichromal capsules
420 are deposited. Disposed on the upwardly directed face of the
substrate 440 is an adhesive layer 430. The adhesive layer 430
retains a portion of the bichromal capsules 420 deposited thereon.
The excess portion of the bichromal capsules 420 cascade off the
substrate 440 and into a tray or collection container 450.
[0053] Consequently, coating of the encapsulated bichromal balls
can be accomplished by cascading them over the adhesive layer. Only
the capsules that are in direct contact with the adhesive layer are
coated, yielding a uniform coating. The capsules not in direct
contact with the adhesive layer remain unattached and can be
removed by a variety of means such as gravity, vacuum suction, etc.
Coating uniformity can further be improved by cascading the
capsules over the surface several times.
[0054] FIG. 5 illustrates another system 500 for another exemplary
embodiment system and process according to the present discovery.
The system 500 includes a metering hopper 510 which retains a
plurality of bichromal capsules 520. The metering hopper 510
controllably releases the bichromal capsules onto an adhesive layer
of a moving substrate which is guided by rollers 540 and 550 to
provide an appropriate angle of inclination. The adhesive layer
retains a portion of the bichromal capsules 520 such that a single
layer of bichromal capsules is deposited upon the face of an
adhesive layer 530. The excess portion of the bichromal capsules
are collected in a receiving tray or collection container 570.
[0055] FIG. 6 shows a further system 600 for an additional
exemplary embodiment system and process according to the
disclosure. The system 600 includes a metering hopper 610 which
delivers bichromal capsules 605 to an application container 620.
The bichromal capsules are applied onto an adhesive layer 625 of a
moving substrate 630 which is guided by rollers 640, 650 and 660
into the application container 620. The adhesive layer 625 retains
a portion of the bichromal capsules 605 such that a single layer of
closely-packed bichromal capsules 605 are deposited upon the face
of the adhesive layer 625. The excess portion of the bichromal
capsules 605 are dropped off into application container 620. This
results in the production of a monolayer of closely-packed
bichromal capsules.
[0056] Various trials were conducted in which various layered
arrays were formed in accordance with the present discovery.
[0057] An adhesive coating was applied to 100 .mu.m thick
aluminized polyester by spraying. Encapsulated bichromal Gyricon
balls having two hemispheres, one red and one white, approximately
125 to 150 .mu.m in diameter, were cascaded over the adhesive
surface several times to yield a very uniform coating. Microscopic
examination showed that the balls were closely-packed with respect
to each other in a monolayer. A protective cover including a 100
.mu.m thick layer of aluminized polyester was placed on top of the
coated bichromal balls to form a sandwiched structure or layered
array as shown schematically in FIG. 1.
[0058] Application of an electric field of one polarity caused the
bichromal balls to orient preferentially in one direction (red).
Reversing the polarity of the electric field caused the bichromal
balls to orient in the opposite direction (white). The switching
voltage threshold was observed to be about 80 volts.
[0059] In another trial, an adhesive coating was applied to 100
.mu.m thick aluminized polyester by spraying. Encapsulated
bichromal Gyricon balls having two hemispheres, one black and one
white, approximately 125 to 150 .mu.m in diameter, were cascaded
over the adhesive surface several times to yield a very uniform
coating. Microscopic examination showed that the balls were
closely-packed with respect to each other in a monolayer. The
produced sheet was cut in half. The sheets were then placed
face-to-face with each other to form a dual-layered structure as
shown schematically in FIG. 2.
[0060] Application of an electrical voltage, approximately 200
volts, of one polarity caused the bichromal balls to orient
preferentially in one direction (black). Reversing the polarity of
the electric field caused the bichromal balls to orient in the
opposite direction (white). The produced display member showed
excellent contrast of the image.
[0061] In an additional example, the release liner of an adhesive
label, such as one produced commercially by Xerox was removed. The
resulting sheet included an adhesive layer coated on white paper.
Encapsulated bichromal Gyricon balls having two hemispheres, one
red and one white, approximately 125 to 150 .mu.m in diameter, were
cascaded over the adhesive surface several times to yield a very
uniform coating. A Gyricon display was made by sandwiching the
coated paper between two pieces of conducting glass having indium
tin oxide conductive coating as electrodes.
[0062] Application of an electrical voltage of about 200 volts of
one polarity caused the bichromal balls to orient preferentially in
one direction (red). Reversing the polarity of the electric field
caused the bichromal balls to orient in the opposite direction
(white).
[0063] The present discovery enables the production of a display
having a monolayer of bichromal balls.
[0064] The monolayer structure of the display members in accordance
with one of the exemplary embodiments provides the advantages of
smaller thickness which reduces the switching voltage and improves
resolution, increases contrast, enables a simplified manufacturing
process and lower cost. The invention also enables the display to
exhibit improved flexibility and have many of the characteristics
associated with paper.
[0065] While the discovery has been described specifically using
encapsulated (shelled) bichromal balls, other encapsulated
materials such as encapsulated electrophoretic particles have been
used to form displays including those described in U.S. Pat. No.
6,492,025, and those described in U.S. Pat. No. 5,961,804, both of
which are hereby incorporated by reference.
[0066] While particular embodiments have been described,
alternatives, modifications, variations, improvements, and
substantial equivalents that are or may be presently unforeseen may
arise to applicants or others skilled in the art. Accordingly, the
appended claims as filed and as they may be amended are intended to
embrace all such alternatives, modifications variations,
improvements, and substantial equivalents.
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