U.S. patent application number 14/042985 was filed with the patent office on 2014-03-27 for novel systems, methods, and compositions relating to display elements.
This patent application is currently assigned to Zikon Inc.. The applicant listed for this patent is Zikon Inc.. Invention is credited to Mateusz Bryning, Zbigniew Bryning, Remy Cromer.
Application Number | 20140087296 14/042985 |
Document ID | / |
Family ID | 41199428 |
Filed Date | 2014-03-27 |
United States Patent
Application |
20140087296 |
Kind Code |
A1 |
Bryning; Mateusz ; et
al. |
March 27, 2014 |
NOVEL SYSTEMS, METHODS, AND COMPOSITIONS RELATING TO DISPLAY
ELEMENTS
Abstract
A display element is described. The display element includes: a
network; a continuous phase; and a discontinuous mobile phase,
which is capable of responding to an externally applied electric
field such that under influence of the externally applied electric
field, without effecting bulk movement of the continuous phase, the
mobile phase displaces from one location to another location
through or within the network. A process of manufacturing a display
cell is also described. The process includes: obtaining a pair of
electrodes; placing a network between the electrodes; assembling
the electrodes and the network to form a sub-assembly; and
injecting into the subassembly a discontinuous phase.
Inventors: |
Bryning; Mateusz; (Campbell,
CA) ; Bryning; Zbigniew; (Saratoga, CA) ;
Cromer; Remy; (Saratoga, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zikon Inc. |
San Jose |
CA |
US |
|
|
Assignee: |
Zikon Inc.
San Jose
CA
|
Family ID: |
41199428 |
Appl. No.: |
14/042985 |
Filed: |
October 1, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12105927 |
Apr 18, 2008 |
8570636 |
|
|
14042985 |
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Current U.S.
Class: |
430/32 |
Current CPC
Class: |
G02F 1/167 20130101;
G02F 1/0009 20130101; G02F 2001/1678 20130101 |
Class at
Publication: |
430/32 |
International
Class: |
G02F 1/00 20060101
G02F001/00 |
Claims
1. A process of manufacturing an electroresponsive ink, comprising:
obtaining a liquid; obtaining a dye or pigment; and solubilizing in
said liquid said dye or pigment such that in its solubilized state
said dye or pigment is at least one of charged, has a dipole
moment, or is polarizable under the influence of an externally
applied electric field.
2. A composition of material inside a display unit, comprising: a
liquid; and a dye or pigment including at least a portion that is
polarizable or has a dipole moment or is charged when said dye or
pigment is in a solubilized state in said liquid.
3. The composition of claim 2, further comprising a network.
4. The composition of claim 2, wherein said liquid is electrically
insulating.
5. The composition of claim 2, wherein said liquid contains at
least one member selected from a group consisting of: polar
solvent, non-polar solvent, organic solvent, inorganic solvent,
oil, liquid crystal, block copolymers, surfactants, micelles,
emulsions, particles, polymers, dissolved salts, water, dyes, and
ionic liquids.
6. The composition of claim 3, wherein said network includes at
least one material selected from a group consisting of titanium
dioxide, aluminum dioxide, metal oxides, barium sulfate, glass
(silica) particles, and zeolites.
7. The composition of claim 3, wherein said network comprises one
or more fibrous or porous networks, wherein the one or more fibrous
or porous networks comprises at least one material selected from a
group consisting of glass wool, cotton, nanowires and cellulose,
carbon nanotubes, talc or silicates, natural fibers and synthetic
fibers.
8. The composition of claim 3, wherein said network further
comprises a polymer matrix, wherein the polymer matrix comprises at
least one member selected from a group consisting of chemically
crosslinked polymer matrix, physically crosslinked polymer matrix
and uncrosslinked polymer matrix, and wherein said polymer matrix
comprises a polymer including at least one member selected from a
group consisting of polystyrene, silicon dioxide, silicon dioxide
derivatives, polyacrylonitrile, polypropylene, liquid crystal
polymers, conductive polymers, fluorinated polymers, halogenated
polymers, and polymethylsiloxanes.
9. The composition of claim 3, wherein said network contains
chemical or physical sites to which said dye or pigment displaces
when said display element is subjected to an externally applied
electric field.
10. The composition of claim 8, wherein said polymer has at least
one property selected from a group consisting of charged,
uncharged, hydrophobic, hydrophilic, randomly oriented and
aligned.
11. The composition of claim 3, wherein said network is made from
at least one material selected from a group consisting of
micro-fabricated transparent films, micro-fabricated reflective
films, micro-fabricated colored films, nano-fabricated transparent
films and nano-fabricated reflective films and nanofabricated
colored films.
12. The composition of claim 3, wherein said network includes at
least one member selected from a group consisting of porous
filtration media, porous transparent films and porous reflective
films.
13. The composition of claim 2, wherein said dye or pigment
comprises a first dye or pigment and a second dye or pigment.
14. The composition of claim 13, wherein at least one of said first
dye or pigment and said second dye or pigment is solubilized in
said liquid with at least one member selected from a group
consisting of surfactants, block copolymers, amphiphilic molecules
and DNA.
15. The composition of claim 2, wherein said first dye or pigment
and said second dye or pigment are chemically engineered to be
soluble in said liquid by forming conjugates of said first dye or
pigment and said second dye or pigment with small molecules or
polymeric chains.
16. The composition of claim 2, wherein said dye or pigment
includes at least one member selected from a group consisting of
organic dyes, inorganic dyes, ionic dyes, polarizable dyes, quantum
dots, organic pigments, metal ions, fluorescent dyes, carbon black,
carbon nanotubes, colored silica nanoparticles, colored polymeric
nanoparticles, and metallic nanoparticles containing sequestered
dye on the interior or on the surface.
17. The composition of claim 2, wherein said dye or pigment
includes at least one member selected from a group consisting of
surfactant-stabilized dye complex and polymer-stabilized dye
complex.
18. The composition of claim 2, wherein said liquid is an organic,
non-conductive liquid, including a non-polar liquid selected from a
group consisting of alkanes, alkenes, alkynes and aromatic liquids
of any relevant chain length or molecular weight, and wherein said
liquid includes monomeric or polymeric compounds that are linear or
branched and at least one member or derivative thereof selected
from a group consisting of alkanes, alkenes, alkynes and aromatic
liquids of any relevant chain length or molecular weight.
19. The composition of claim 3, further comprising at least one
additional chemical component used within said liquid, said
network, or said dye or pigment, and wherein said additional
chemical components include at least one member selected from a
group consisting of ionic liquids, salts, polymers, surfactants,
aluminum bromide, hexafluorophosphate and tri-n-alkylphosphine.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority under 35 U.S.C.
.sctn.120 to, and is a divisional application of, U.S. patent
application Ser. No. 12/105,927, filed on Apr. 18, 2008. The
referenced previously-filed application is herein incorporated by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to display elements.
More particularly, the present invention relates to display
elements that include a network and a mobile phase, which under the
influence of an externally applied electric field, displaces from
one location to another through or within the network to form part
of an image or alternatively, to serve as a light valve for optical
switching applications.
[0003] Electrophoretic displays enjoy significant advantages over
the alternatives of cathode ray tubes (CRTs) and liquid crystal
displays (LCDs) particularly for portable display applications.
Specifically, electrophoretic displays require significantly less
power than the bulky CRTs and provide a wider field of view,
provide significantly less undesirable light absorption, and are
manufactured at a lower cost than the LCDs. Significantly,
electrophoretic displays enable the production of highly
transmissive, highly reflective, or "paperlike," displays, which
are not achievable with current technologies. For more information
on the advantages of electrophoretic displays, reference may be
made to U.S. Pat. No. 5,582,700 issued to Bryning et al., which is
incorporated herein by reference in its entirety for all
purposes.
[0004] FIG. 1 shows a prior art display element 10 generally
described in U.S. Pat. No. 4,419,663 issued to Kohashi. Display
element 10 includes two electrodes 12 and 14, which are shaped like
plates and spaced apart to define a space therebetween. Typically,
at least one of electrode 12 is transparent, allowing a viewer 20
to view display element 10. Disposed in a portion of the space
between electrodes 12 and 14 is ink 16, which is a light
transmissive liquid material and impregnated in numerous distinct
pores or micropores found in a porous material 18. In this
configuration, there exists a gap between electrodes 12 and porous
material 18. Ink 16 can be transparent and porous material 18 can
be white. Furthermore, the index of refraction of ink 16 and porous
material 18 are substantially equal. As a result, when numerous
pores inside porous material 18 are completely or almost completely
impregnated with ink 16, external light entering through the
transparent electrode is not reflected at the contact interface of
ink 16 and porous material 18, but is transmitted therethrough to
provide a display element which appears to be transparent.
[0005] During a typical operation, under the influence of a voltage
potential applied by a voltage source 22 through leads 24 and 26 to
electrodes 12 and 14, ink 16 electroosmotically moves out of the
pores of porous material 18 and moves towards the negatively
charged electrode. During such movement, excess ink 16 occupies the
gap between electrode 12 and porous material 18. Consequently,
voids filled with air exist inside the pores of porous material 18.
The presence of air contributes to a mismatch in the index of
refraction between porous material 18 and voids inside the pores.
As a result, external light, which enters through transparent
electrode 12, is reflected to provide a display element which
appears to be white. When the electric field is reversed, ink 16
returns to porous material 18 by capillary action, impregnating the
porous material.
[0006] If a black background is placed underneath the display
element, when it is in its transparent state, light entering the
display element is absorbed by the black background, and not
reflected. The display element with the black background appears
black when viewed from the direction of the incident light. With
the same black background in place, but when the display element is
in its white state, the light entering the display element is
reflected from the porous material, and the display element will
appear white.
[0007] By way of example, FIG. 2 shows an image of a cross (i.e.,
"+") 50 formed by an electrophoretic display. To form image of a
cross 50, certain display elements 52 appear colored black
(hereinafter "black elements 52") and certain other display
elements 54 contrastingly appear white (hereinafter "white elements
54"). According to the example of FIG. 1 described above, some
display elements under the influence of an electric field will
appear black (when light is absorbed by the black background),
while other display element, at the same time under reversed
electric field will appear white (when the porous material is of
white color). A combination of these numerous black elements 52 and
numerous white display elements 54 together form image of cross 50
shown in FIG. 2.
[0008] Unfortunately the described display element found in the
prior art suffer from several drawbacks. For example, it takes the
ink a relatively long time to return from outside the porous
material back into the pores of a porous material through capillary
action. As a result, the prior art display elements suffer from
poor switching speed. As another example, electroosmotic movement
of the ink requires expending significant amount of energy, raising
the power requirements for this design of display element.
Furthermore, the design is complicated, requiring a gas-containing
gap within the display element.
[0009] What is, therefore, needed is an improved display element
that effectively facilitates the formation of an image, without
suffering from the drawbacks, e.g., poor switching speed and high
power requirements, encountered by the prior art display
elements.
SUMMARY OF THE INVENTION
[0010] In view of the foregoing, this invention provides a display
element. The display element includes: a network; a continuous
phase; and a discontinuous mobile phase, which is capable of
responding to an externally applied electric field such that under
the influence of the externally applied electric field, without
effecting bulk movement of the continuous phase, the mobile phase
displaces from one location to another location through or within
the network.
[0011] The display element may further include a pair of electrodes
having disposed therebetween the network, the continuous phase and
the discontinuous mobile phase. The mobile phase may perform at
least one function selected from a group consisting of absorbing,
scattering and emitting light over a range of wavelengths. The
continuous phase may transmit light over a range of wavelengths.
The network may perform at least one function selected from a group
consisting of absorbing, scattering, emitting and transmitting
light over a range of wavelengths.
[0012] At least one of the pair of electrodes may be transparent
such that when the mobile phase under the externally applied
electric field is displaced, then light that exits the display
element is different from light that enters the display element.
Under the influence of an externally applied electric field, the
mobile phase may be displaced by either flocculating or dispersing
within the network.
[0013] In another embodiment of the present invention, under the
influence of an externally applied electric field, the mobile phase
is displaced at least partially through the network, without
flocculating within the network.
[0014] The network in conjunction with the mobile phase, which when
under the influence of externally applied electric field, may serve
to effect at least one function selected from a group consisting of
obscuring the mobile phase from field of view, nucleating
condensation of the mobile phase, directing motion of the mobile
phase, limiting mobility of the mobile phase, making the display
bistable, and serving as a light-guide within the display
element.
[0015] In one embodiment of the present invention, the display cell
element includes: a pair of substrates having disposed therebetween
the network, the continuous phase and the mobile phase; and a pair
of electrodes applied externally to the pair of substrates, such
that when an external electric field is applied to the pair of
electrodes, the external electric field enables the displacement of
the mobile phase.
[0016] The display element may serve as part of a display. By way
of example, a plurality of display elements may combine to form a
display unit of an image. Alternatively, the display element may be
used as a light valve or optical switch.
[0017] In another aspect, the present invention provides a process
of manufacturing a display element. The process includes: obtaining
a pair of electrodes; placing a network between the electrodes;
assembling the electrodes and the network to form a sub-assembly;
and injecting into the subassembly a discontinuous phase. The step
of assembling may include installing spacers between the pair of
electrodes. The display element manufacturing process may further
include evacuating air from inside the sub-assembly to create
vacuum inside the sub-assembly. The step of injecting may include
injecting a continuous phase into the sub-assembly.
[0018] In yet another aspect, the present invention provides a yet
another process of manufacturing a display cell. This process
includes obtaining a pair of electrodes; assembling the electrodes
to form a sub-assembly; and injecting into the subassembly a
discontinuous phase and network.
[0019] The step of assembling may include installing spacers
between the pair of electrodes. In certain embodiments of the
present invention, the step of assembling further includes
evacuating air from inside the sub-assembly to create vacuum inside
the sub-assembly. The step of injecting may include injecting a
continuous phase into the sub-assembly.
[0020] In yet another aspect, the present invention provides a yet
another process of manufacturing a display cell. The display
element manufacturing process includes: obtaining a pair of
electrodes; applying a continuous phase, a discontinuous phase and
network to at least one of the pair of electrodes; and assembling
the pair of electrodes such that the continuous phase, the
discontinuous phase and the network are disposed between the pair
of electrodes.
[0021] The step of applying may include rolling or brushing the
continuous phase, the discontinuous phase and the network on at
least one of the pair of electrodes. The step of applying may
include applying spacers to the pair of electrodes such that each
of the pair of electrodes is separated from each other by the
spacer. In accordance with one embodiment of the present invention,
the step of obtaining the pair of electrodes includes: depositing a
conductive film on a polymer or glass substrate; and patterning the
film into segments to form an electrode. The pair of electrodes may
include at least one member selected from a group consisting of
indium tin oxide, thin metallic films, thin carbon and thin carbon
nanotubes. In certain embodiments of the present invention, the
display element fabricating process includes treating by
silanization or coating with a hydrophobic monomer, mixture of
monomers, polymer or mixture of polymers at least one electrode to
provide the network with nanostructure features. At least one of
the pair of electrodes may include thin film transistors. The
display element manufacturing process may further include using as
a sealant fluorinated grease or fluorinated glue.
[0022] In yet another aspect, the present invention provides a yet
another process for manufacturing an electroresponsive ink. This
process includes: obtaining a liquid; obtaining a dye or pigment;
and solubilizing in the liquid the dye or the pigment such that in
its solubilized state the dye or the pigment is at least one of
charged, has a dipole moment, or is polarizable under the influence
of an externally applied electric field.
[0023] In yet another aspect, the present invention provides a
composition of material inside a display unit. The composition
includes: a liquid; and a dye or a pigment including at least a
portion that is polarizable or has a dipole moment or is charged
when the dye or the pigment is in a solubilized state in the
liquid.
[0024] The composition may further include a network. In one
embodiment of the present invention, the liquid is non-polar. In an
alternative embodiment of the present invention, the liquid is
polar or polarizable. In another alternative embodiment of the
present invention, the liquid is electrically insulating. In yet
another alternative embodiment of the present invention, the liquid
consists of more than one component. In yet another alternative
embodiment of the present invention, the liquid contains at least
one member selected from a group consisting of: polar solvent,
non-polar solvent, organic solvent, inorganic solvent, oil, liquid
crystal, block copolymers, surfactants, micelles, particles,
polymers, dissolved salts, water, dyes, and ionic liquids.
[0025] The network may include at least one material selected from
a group consisting of titanium dioxide, aluminum dioxide, metal
oxides, barium sulfate, glass (silica) particles, and zeolites.
Alternatively, the network may include fibrous networks or fibrous
minerals. In certain applications, the fibrous networks may include
at least one material selected from a group consisting of glass
wool, cotton, nanowires and cellulose, carbon nanotubes, natural
fibers and synthetic fibers. In other applications, the fibrous
minerals include at least one of talc and silicates. In one
embodiment of the present invention, the network includes at least
one member selected from a group consisting of chemically
crosslinked polymer matrix, physically crosslinked polymer matrix
and uncrosslinked polymer matrix. In another alternative embodiment
of the present invention, the network is made from a polymer, which
includes at least one member selected from a group consisting of
polystyrene, silicon dioxide, silicon dioxide derivatives,
polyacrylonitrile, polypropylene, liquid crystal polymers,
conductive polymers, fluorinated polymers, halogenated polymers,
and polymethylsiloxanes.
[0026] The network may contain chemical or physical sites to which
the dye or the pigment will preferentially move when the display
element is subjected to an externally applied electric field. The
polymer may have at least one property selected from a group
consisting of charged, uncharged, hydrophobic, hydrophilic,
randomly oriented and aligned. The network may contain more than
one type of component. The network may be made from at least one
material selected from a group consisting of micro-fabricated
transparent films, micro-fabricated reflective films,
micro-fabricated colored films, nano-fabricated transparent films
and nano-fabricated reflective films and nanofabricated colored
films. The network may include at least one member selected from a
group consisting of porous filtration media, porous transparent
films and porous reflective films.
[0027] The dye or pigment may be solubilized in the liquid with at
least one member selected from a group consisting of surfactants,
block copolymers, amphiphilic molecules and DNA. In the composition
of the present invention, more than one type of dye or pigment may
be used. The dye or the pigment may be chemically engineered to be
soluble in the liquid by forming conjugates of the dye or the
pigment with small molecules or polymeric chains. The dye or the
pigment may include at least one member selected from a group
consisting of organic dyes, inorganic dyes, ionic dyes, polarizable
dyes, quantum dots, organic pigments, metal ions, fluorescent dyes,
carbon black, carbon nanotubes, colored silica nanoparticles,
colored polymeric nanoparticles, and metallic nanoparticles
containing sequestered dye on the interior or on the surface. The
dye or the pigment may include at least one member selected from a
group consisting of surfactant-stabilized dye complex and
polymer-stabilized dye complex.
[0028] In one embodiment of the present invention, the liquid
includes at least one member selected from a group consisting of
xylene, toluene, diethylbenzene, triethylbenzene, trimethylbenzene,
iso-octane, decane, undecane, tridecane, phenylhexane,
phenylheptane, phenyloctane, phenylnonane, phenyldecane,
phenylundecane, dimethylformamide and water. In an alternative
embodiment of the present invention, the liquid is an organic,
non-conductive liquid, including a non-polar liquid selected from a
group consisting of alkanes, alkenes, alkynes and aromatic liquids
of any relevant chain length or molecular weight. In yet another
embodiment of the present invention, the liquid includes monomeric
or polymeric compounds that are linear or branched and include at
least one member or derivative thereof selected from a group
consisting of alkanes, alkenes, alkynes and aromatic liquids of any
relevant chain length or molecular weight.
[0029] The composition may further include an additional chemical
component used within the liquid, the network, or the dye or
pigment. The additional chemical component may include at least one
member selected from a group consisting of ionic liquids, salts,
polymers, surfactants, aluminum bromide, hexafluorophosphate and
tri-n-octylphosphine.
[0030] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following descriptions of specific
embodiments when read in connection with the accompanying
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 shows a general representation of a side-sectional
view of a display element of an electroosmotic display found in the
prior art.
[0032] FIG. 2 shows an image of a cross "+" formed by a multitude
of display elements.
[0033] FIG. 3A shows a side-sectional view of a display element,
according to one embodiment of the present invention, including a
network of spherical particles and a charged mobile phase, which
under an electrically applied electric field, displaces through the
network to concentrate on an electrode that carries a charge
opposite to the charge of the mobile phase.
[0034] FIG. 3B shows the display element of FIG. 3A under
conditions when the applied electric field is reversed and the
charged mobile phase displaces to the opposite electrode, which is
charged opposite to the charge of the mobile phase.
[0035] FIG. 4A shows a side-sectional view of a display element,
according to an alternative embodiment of the present invention,
including a porous membrane as a network within the display element
and through which a charged mobile phase, under an externally
applied electric field, is displaced to concentrate near an
electrode that carries a charge opposite to that of the mobile
phase.
[0036] FIG. 4B shows the display element of FIG. 4A under
conditions when the applied electric field is reversed and the
charged mobile phase displaces to the opposite electrode, which is
charged opposite to the charge of the mobile phase.
[0037] FIG. 5A shows a side-sectional view of a display element,
according to another alternative embodiment of the present
invention, including a network of conical wells and a charged
mobile phase, which under an externally applied electric field, is
displaced through the network to concentrate on and spread out
along a length of an electrode that carries a charge opposite to
the charge of the mobile phase.
[0038] FIG. 5B shows the display element of FIG. 5A under
conditions when the applied electric field is reversed and the
mobile phase displaces to the opposite electrode, which is charged
opposite to the charge of the mobile phase.
[0039] FIG. 6A shows a side-sectional view of a display element,
according to a yet another alternative embodiment of the present
invention, including a polymer network disposed within the display
element and a polarizable mobile phase that is dispersed through
the network in the absence of an electric field.
[0040] FIG. 6B shows the display element of FIG. 6A when the
polarizable mobile phase, under an externally applied electric
field, displaces to an area of the locally strongest electric field
and agglomerates to form structures resulting from dipole-dipole
interactions between components of the polarized mobile phase.
[0041] FIG. 7A shows a side-sectional view of a display element
that is substantially shown in FIG. 3A, except that the network and
mobile phase are contained inside two sheets of substrate, all of
which assemble to form a "pouch" that is permanently or, in the
alternative, removably attached to the two electrodes.
[0042] FIG. 7B shows a side-sectional view of the display element
shown in FIG. 7A under conditions when the applied electric field
is reversed and the charged mobile phase displaces to the opposite
electrode, which is charged opposite to the charge of the mobile
phase.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0043] In the following description numerous specific details are
set forth in order to provide a thorough understanding of the
present invention. It will be apparent, however, to one skilled in
the art that the present invention may be practiced without
limitation to some or all of these specific details. In other
instances, well known process steps have not been described in
detail in order to not unnecessarily obscure the invention.
[0044] FIG. 3A shows a display element 100, according to one
embodiment of the present invention. Element 100 includes two
substrates 102 and 104 having disposed therebetween two electrodes
106 and 108. Electrode 106 is transparent, and therefore, allows
natural light inside element 100. A network 110, a continuous phase
(not shown to simplify illustration) and a mobile phase 112 are
provided between electrodes 106 and 108. As shown in FIG. 3A,
network 110 includes reflective spherical particles. In other
words, network 110 reflects the natural light entering element 100
through electrode 106. A voltage source 114 is connected through
leads 116 and 118 to electrodes 106 and 108, respectively.
[0045] FIG. 3B shows a display element 100', which is substantially
similar in components and their assembly to element 100 of FIG. 3A,
except the polarity of voltage source 114' is reversed. In the
configuration of FIG. 3B, substrates 102 and 104, electrodes 106
and 108, network 110, continuous phase, and leads 116 and 118
appear in substantially the same configuration as shown in FIG. 3A.
The mobile phase 112 in FIG. 3B is displaced from its position in
FIG. 3A due to the reversed polarity of the voltage source.
[0046] Display element 100 is shown to include two substrates 102
and 104, which are optional. In those embodiments where such
substrates are employed, they are made from a rigid or flexible
material which provides mechanical support to the display element.
By way of example, such substrates are made of glass or polymer. In
those embodiments, where one electrode is transparent, such as
transparent electrode 106 of FIG. 3A, the substrate adjacent to the
transparent electrode is also preferably transparent to allow the
natural light into the display element.
[0047] Electrodes 106 and 108 can be made from any conductive
material that is capable of conducting the charge provided by
voltage source 114 during operation. Preferably, however,
electrodes 106 and 108 are made from at least one member selected
from a group consisting of indium tin oxide (ITO), thin metallic
films, conductive polymers, carbon, and carbon nanotubes. Of these
materials, indium tin oxide is most commonly used and represents a
more preferred embodiment.
[0048] In certain embodiments of the present invention, spacing
between the electrodes can be controlled by using spacers (not
shown to simplify illustration). Appropriately sized particles,
when sandwiched between the electrodes, effectively serve as
spacers. Typically, such particles are directly deposited on the
electrode surface and provide the desired uniform space between the
electrodes. Spacing between electrodes can vary depending on the
application or design of the display element. Electrode spacing can
be, for example, between about 3 microns and about 5 microns. In
other instances, spacing between electrodes can be between about 5
microns and about 10 microns. In still other instances, spacing can
be between about 10 microns and about 50 microns or more.
[0049] Network 110 in FIG. 1 is shown as spherical particles.
However, such particles need not be spherical and can be any shape
that serves as a matrix which occupies the space between the
electrodes. It is, however, preferable to have network 110 that is
packed in such a way as to provide pores of a suitable amount of
space for the mobile phase to move through or within the network.
In one embodiment of the present invention, such particles are
white or some other color. In other embodiments of the present
invention, such particles are transparent. Regardless of whether
these particles are colored or are transparent, it is not necessary
for network 110 to be charged or to be responsive to electric
fields to any appreciable extent. According to one embodiment of
the present invention, representative materials that are suitable
for manufacturing network 110 include at least one material
selected from a group consisting of titanium dioxide (i.e.,
titanium IV oxide), barium sulfate, and zeolites. Furthermore, such
particles may be chemically treated, e.g., by silanization or other
surface modification well known to those skilled in the art, to
provide the desired properties. In certain embodiments, particles
that serve as network 110 may also contain nanostructured features.
Such nanostructured features may provide at least one of the
following: porosity, nucleation sites, surface reactivity, and
surface neutrality.
[0050] In those embodiments of the present invention where network
110 is designed to be transparent, silicon dioxide or polymers may
be used to manufacture the particles which form network 110.
Relative to mobile phase 112, these particles may or may not have a
significantly different dielectric constant and thus may or may not
significantly affect the electric field or index of refraction
within the medium. As mentioned above with respect to colored
particles, such transparent particles may also undergo chemical
treatment e.g., by silanization or other surface modification well
known to those skilled in the art, and may also contain
nanostructure features.
[0051] In an alternative embodiment of the present invention,
fibrous networks or matrices (e.g., glass wool, cotton wool,
nanowires and cellulose) or fibrous minerals (e.g., talc and
silicates) may be used as network 110 in FIG. 3A.
[0052] In another alternative embodiment of the present invention,
network 110 can be made from at least one member selected from a
group consisting of chemically crosslinked polymer matrix,
physically crosslinked polymer matrix and uncrosslinked polymer
matrix. The polymers used in this embodiment may be charged,
uncharged, aligned or randomly oriented. Representative examples of
polymers used to make network 110 include at least one member
selected from a group consisting of polystyrene, silicon dioxide
derivatives (i.e., silica gels), polyacrylonitrile, Teflon,
fluorinated polymers, liquid crystal polymers, conductive polymers
and polymethylsiloxanes.
[0053] In yet another alternative embodiment of the present
invention, network 110 is made from at least one member selected
from a group consisting of micro-fabricated transparent films,
micro-fabricated reflective films, nano-fabricated transparent
films and nano-fabricated reflective films. Each of the films may
include pores that are any one of conical, tubular or spherical
shaped. In this embodiment, other examples of suitable material for
making network 110 include porous filtration media (e.g.,
poly(tetrafluoroethylene) (also known as "PTFE") and cellulose),
porous transparent films and porous reflective films. Porous
transparent films and porous reflective films may be made through
or mediated by the self-assembly of colloidal particles,
surfactants, polymers or microparticles.
[0054] In one embodiment of the present invention, the combination
of mobile phase 112 and continuous phase used in display element
100 of FIG. 3A forms electroresponsive ink. In this embodiment, the
continuous phase is a clear or colored liquid and the
discontinuous, mobile phase contains a dye or a pigment. In certain
embodiments of the present invention, the dye or pigment is
stabilized within the continuous phase by surfactants. Those
skilled in the art may characterize this ink as an emulsion. When a
non-polar liquid is used as the continuous phase in conjunction
with a polar mobile phase, then those skilled in the art may
characterize the ink as a reverse emulsion. In certain other
embodiments of the present invention, the mobile phase is made from
molecular or supramolecular complexes which include charged dye or
charged pigment. By way of example, these complexes include at
least one member selected from a group consisting of chemically
bonded polymer-dye conjugate, or a stabilized polymer-dye complex
(stabilized via charge-charge interaction or salt bridges),
chemically engineered dye or pigment that contains a polar or
charged component and a non-polar component, complexes of dye or
pigment with non-chemically bonded stabilizing agents such as
polymers or, for example, salts. In other embodiments of the
present invention, the mobile phase includes colored, or
fluorescent or luminescent particles or color-producing
nanoparticles. Representative color-producing nanoparticles include
quantum dots, dyes embedded in latex, dyes sequestered in glass
particles. Alternatively the dyes can associated with the surface
of these particles especially when metallic nanoparticles such as
gold or silver are used.
[0055] The continuous phase and mobile phase 112 together
constitute the ink. In those embodiments of the present invention
where a non-polar or weakly polar solvent is used as the continuous
phase, the discontinuous, mobile phase 112 preferably includes
charged, polar, or polarizable dye molecules suspended in a solvent
or charged, polar, or polarizable pigment particles suspended in a
solvent. The continuous phase may include any number of organic
solvents. More specifically, the continuous phase in this
embodiment may preferably be an organic non-conductive liquid,
comprised of non-polar liquids selected from alkanes, alkenes,
alkynes or aromatic liquids (of any relevant chain length or
molecular weight). The compounds could be monomeric or polymeric,
linear or branched. Each of these classes of molecules could be
derivatized with any or all of the others. By way of example,
aromatic compounds could be derivatized with alkanes, alkenes,
alkynes or aromatic.
[0056] In another embodiment of the present invention, continuous
phase includes at least one member selected from a group consisting
of xylene, toluene, phenols, iso-octane, benzene, decane, undecane,
tridecane, phenylhexane, phenylheptane, phenyloctane, phenylnonane,
phenyldecane, phenylundecane, phenyldodecane, and related aromatic
or aliphatic compounds, or their corresponding halogenated
solvents. In alternative embodiments of the present invention,
these solvents may further be derivatized with a variety of
chemical groups as would be familiar to those skilled in the art.
In accordance with one preferred embodiment of the present
invention, the continuous phase is oil, such as silicone oil. It is
not necessary that the continuous phase be an organic liquid,
rather the continuous phase can be any liquid, especially with
working voltages inside the liquid's electrochemical window, i.e.,
a voltage range in which the substance is neither oxidized nor
reduced. The continuous phase may be transparent, or may have a
color different from the mobile phase. Note that the continuous
phase could be saturated with dispersed, monomeric components or
fractions of the dispersed phase. Surfactants, polymers, ionic
liquids, salts, or other chemical compounds could for example
therefore represent a large part of the continuous phase.
[0057] In an alternative embodiment, the continuous phase may be
polar or polarizable. Examples of such a continuous phase include
the aforementioned classes of liquids that are fully or partially
derivatized with halogens and or heteroatoms such as O, N, S. P,
Si, or other atoms selected from groups V, VI from the periodic
table. Each of these atoms may also be at a higher oxidation state,
as for example: alcohols, carbonyls, carboxyls, nitriles, nitro,
nitroso, n-oxide, oximes, sulfoxide, sulfones, sulfates, phosphine
oxides, phosphonates and phosphates. The continuous phase could
also be partially charged by ionization of the functional groups
such as ammonium, iminiums, sulfonates, sulfates, phosphates,
phosphonates or carboxylates. In general, the continuous phase
preferably has a high boiling point and preferably has a very low
freezing point, and preferably has low volatility.
[0058] The mobile phase 112 is preferably a colored droplet or a
particle smaller than one micron. In alternative embodiments of the
present invention, the particle is smaller than 500 nm or even
smaller, i.e., smaller than 50 nm. Such small particles used in the
display elements of the present invention easily move through or
within network 110 and do not readily sediment under gravity as
encountered with heavier particles used in the prior art display
elements.
[0059] In accordance with one embodiment of the present invention,
operation of display cell 100 of FIG. 3A begins when voltage source
114 is powered up and an electric field is applied to electrodes
106 and 108. Under the influence of this electric field, charged
mobile phase 112 physically moves within network 110 and through
the continuous phase. Such movement by charged mobile phase 112 is
attributed to electrophoretic forces. The mobile phase migrates
towards the electrode, which is charged oppositely to the ink, and
concentrates there. In the example of FIG. 3A, electrode 106 is
transparent and carries a charge opposite to that of the mobile
phase under the influence of an electric field. As a result,
electrode 106 is rich with mobile phase 112 while electrode 108 is
depleted of the mobile phase. In this embodiment, transparent
electrode 106 of display element 100 provides the color of mobile
phase 112. Under the influence of the same electric field, if
electrode 108 is also transparent, if network 110 is made from
reflective spherical particles (e.g., made from titanium dioxide),
if the continuous phase is transparent, if the mobile phase is
colored, and display element 100 is viewed from the opposite side
(i.e., through electrode 108 of FIG. 3A), then the display element
will appear to have the color of network 110 (e.g., a white color
of the titanium dioxide). Those skilled in the art will recognize
that in the embodiment of FIG. 3A and under the influence of an
electric field, electrode 106 contributes the color of the mobile
phase to form a portion of the image. Similarly, a display element
can be designed to use electrode 108 as the transparent electrode
so that it under similar circumstances can contribute the color of
the network to form a portion of another image. Furthermore, by
selecting the appropriate color for the mobile phase and the
network, numerous display elements can be selectively used as
described above to form the desired image (e.g., the image of a
cross, "+," shown in FIG. 2).
[0060] Under conditions of reversed electric field, as shown in
FIG. 3B, charged mobile phase 112 migrates to the opposite
electrode, e.g., electrode 108 in FIG. 3B that is charged opposite
to the mobile phase. In this configuration, the display element,
when viewed from the side of electrode 106 will appear to take on
the color of the network, and when viewed from the side of
electrode 108, will appear to have the color of the mobile
phase.
[0061] FIG. 4A shows a display element 200, which has components
(i.e., substrates 202 and 204, electrodes 206 and 208, mobile phase
212, continuous phase, voltage source 214, leads 216 and 218)
corresponding to those found in FIG. 3A (i.e., substrates 102 and
104, electrodes 106 and 108, mobile phase 112, continuous phase,
voltage source 114, leads 116 and 118). Instead of using particles
to serve as network 110 as shown in FIG. 3A, the embodiment of FIG.
4A shows that at least one porous, reflective or colored membrane
serves as the network 210.
[0062] FIG. 4B shows a display element 200', which is substantially
similar in components and their assembly to element 200 of FIG. 4A,
except the electric field generated by voltage source 214' is
reversed. Substrates 202 and 204, electrodes 206 and 208, network
210, continuous phase, and leads 216 and 218 shown in FIG. 4A
appear in substantially the same configuration as they do in FIG.
4B. The mobile phase 212 in FIG. 4B is displaced from its position
in FIG. 4A due to the reversed polarity of the voltage source.
[0063] In the embodiment shown in FIG. 4A, under the influence of
an electric field, charged mobile phase 212 physically moves
through network 210, i.e., shown as porous membrane in FIG. 4A, by
electrophoretic forces towards electrode 206, which is charged
opposite to the mobile phase. As a result, the region of the
display element between electrode 206 and network 210 is rich with
the mobile phase while the region of the display element between
electrode 208 and network 210 is depleted of the mobile phase. At
electrode 206, charged mobile phase may further concentrate and
spread out along the length and width of the electrode. When
display element is viewed through transparent electrode 206, it
displays the color of the mobile phase. If electrode 208 is
transparent, if the continuous phase is also transparent, and
display element 200 is viewed from the opposite side (i.e., through
electrode 208 of FIG. 4A), then the electrode 208 displays the
color of the porous membrane.
[0064] Under conditions of reversed electric field as shown in FIG.
4B, mobile phase 212 migrates to the opposite region of the display
element, i.e., the region between network 210 and electrode 208. In
this configuration, if the continuous phase is transparent,
electrode 206 will display the color of network while electrode
208, if transparent, will display the color of the mobile
phase.
[0065] Similar to FIG. 4A, FIG. 5A also has some of the same
components as found in FIG. 3A. In FIG. 5A, display element 300
includes substrates 302 and 304, electrodes 306 and 308, mobile
phase 312, continuous phase, voltage source 314, leads 316 and 318
similar to their corresponding components found in FIG. 3A (i.e.,
substrates 102 and 104, electrodes 106 and 108, mobile phase 112,
continuous phase, voltage source 114, leads 116 and 118). Instead
of using particles to serve as network 110 as shown in FIG. 3A, the
embodiment of FIG. 5A shows that an array of patterned wells serves
as the network 310.
[0066] FIG. 5B shows a display element 300', which has
substantially similar components as element 300 shown in FIG. 5A,
except the electric field of voltage source 314' in FIG. 3B is
reversed relative to that of voltage source 314 of FIG. 3A.
Substrates 302 and 304, electrodes 306 and 308, network 310,
continuous phase, leads 316 and 318 shown in FIG. 5A appear in
substantially the same configuration in FIG. 5B. The mobile phase
312 in FIG. 5B is displaced from its position in FIG. 3A due to the
reversed polarity of the voltage source.
[0067] Although patterned wells 310 shown in FIGS. 5A and 5B can be
reflective like network 110 and 210 as shown in FIGS. 3A and 4A,
respectively, it is preferable that wells 310 are transparent. In
such preferred embodiments of the present invention, mobile phase
312, under the influence of an electric field, electrophoretically
moves towards electrode 306, which is charged opposite to mobile
phase 312. Furthermore, charged mobile phase 312 spreads out, along
the length and width of electrode 306 and concentrates there as
shown in FIG. 5A. As a result, electrode 306 displays the color of
the mobile phase.
[0068] Under conditions of reversed electric field as shown in FIG.
5B, mobile phase 312 migrates to electrode 308, which has disposed
thereon patterned wells 310. In this configuration, mobile phase
312 concentrates inside the conical cavity of patterned wells 310,
as opposed to being spread out as shown in FIG. 5A. As a result,
color contribution by mobile phase 312 is limited, and the color of
patterned wells 310 is expressed as the color of display element
300'. In those preferred embodiments where patterned wells 310 are
transparent and the continuous phase is also transparent, display
element 300' appears transparent as well.
[0069] While wishing to not be bound by theory, FIGS. 3A, 3B, 4A,
4B, 5A and 5B show that the charged mobile phase, under the
influence of an electric field, undergoes electrophoretic movement.
It is, however, not necessary that the mobile phase be charged
under the influence of an electric field for it to move from one
location to another as described in the present invention. FIG. 6A
shows dielectrophoretic addressing, where under the influence of an
electric field, at least a component of the mobile phase is
polarizable and capable of movement from one location to another.
Importantly, however, in the present invention, the mobile phase,
as a whole, need not be charged to effect movement under the
influence of an electric field.
[0070] FIG. 6A shows display element 400, which has components
assembled in substantially the same configuration as display
element 200 of FIG. 3A. Display element 400 includes substrates 402
and 404, electrodes 406 and 408, network 410, continuous phase,
mobile phase 412, leads 416 and 418 as their counterparts are shown
in FIG. 3A. Instead of a voltage source in the dispersed (off)
state, leads 416 and 418 in FIG. 6A are shown connected to ground
414. Similarly, FIG. 6B also contains components described above in
the same configuration as shown in FIG. 6A, except display element
400' includes a voltage source 414' performing under conditions of
an applied external electric field. In FIGS. 6A and 6B, network 410
is preferably a polymer network.
[0071] Under the influence of an electric field, at least a part of
mobile phase 412' is polarized, causing the mobile phase to migrate
to an area of the strongest electric field. In such areas of the
strongest electric field, the mobile phase aligns to form a
columnar structure due to dipole-dipole interactions. In this
columnar arrangement, the mobile phase is invisible or nearly
invisible to the human eye and the color of the polymer network
410' or the continuous phase is displayed as the color of display
element 400'.
[0072] When the electric field is removed as shown in FIG. 6A,
mobile phase is spread out through and within the polymer network
and the color of mobile phase 412 is displayed as the color of
display element 400.
[0073] Regardless of whether the mobility of the charged
discontinuous, mobile phase is attributed to electrophoretic or
dielectrophoretic addressing, those skilled in the art will
recognize that by applying and reversing, or, in the alternative,
not applying an electric field to the assemblies described in FIGS.
3A, 3B, 4A, 4B, 5A, 5B, 6A and 6B, the color of the display
elements can be selectively changed to form a desired image.
Significantly, in the present invention, when an external electric
field is applied, the discontinuous, mobile phase moves from one
location to another, without effecting bulk movement of the
continuous phase. The electrophoretic or dielectrophoretic
addressing described in the present invention, as a result, does
not suffer from the drawbacks encountered by electroosmotic
addressing as disclosed in U.S. Pat. No. 4,419,663 to Kohashi.
Specifically, under the influence of an electric field, a display
element modulates the entering natural light (e.g., impacts the
intensity, reflectivity or transmissivity of natural light) by
movement of the mobile phase, without effecting bulk movement of
the continuous phase. Consequently, the poor switching speeds and
high power requirements encountered to carry out electroosmotic
movement of the continuous phase along with the discontinuous,
mobile phase are minimized.
[0074] For dielectrophoretic addressing as shown in FIG. 6A, a
polymer network is employed. The polymer network contains sites
that the mobile phase preferentially moves toward under an
externally applied electric field, and aggregated structures then
form upon these sites. These sites consist of features on the
polymer network that are similar in polarity, charge, or geometry
to the mobile phase. When the porosity of the polymer network is
not much larger than the size of the mobile phase, the presence of
the network also prevents or reduces long range drift of the mobile
phase by diffusion or any unwanted electrophoretic motion due to,
for example, unwanted field non-uniformity.
[0075] In the present invention, electrophoretic addressing, i.e.,
movement of charged mobile phase under the influence of an electric
field, allows a display element to effectively function in at least
two different states of stability. By way of example, in FIG. 4A
where a porous membrane 210 serves as the network disposed between
two electrodes, a first state includes the condition when
application or removal of the external electric field changes the
color of the pixel. When an external electric field is applied, the
charged mobile phase moves through the porous membrane to collect
and concentrate on the side of the membrane that is charged
opposite to the mobile phase. If the mobile phase concentrates on
the side of the transparent electrode (e.g., electrode 206 of FIG.
4A), then display element 200 will display the color of the mobile
phase. If the external electric field is removed, the mobile phase
disperses throughout the continuous phase and a portion of the
mobile phase moves to the other side of the porous membrane. Since
the concentration of the mobile phase is reduced near the electrode
206 the color intensity of the display element 200 will change.
[0076] In a second state, when the electric field is turned off,
the charged mobile phase does not have sufficient energy to move
through to the other side of the membrane, i.e., to the side of the
opposite electrode 208. Instead, the charged mobile phase is
scattered between the membrane and transparent electrode 206. As a
result, the display element continues to display the color of the
mobile phase even though the voltage source has been turned off and
there is an absence of an electric field. If an electric field is
then applied in the opposite direction, the mobile phase will then
have sufficient energy to move through to the other side of the
membrane, i.e., to the side of the opposite electrode 208, and the
color of the display element will then be the color of the
membrane. To those skilled in the art, this second state is
frequently referred to as "bistability," and a display operating in
this state is called a "bistable" display.
[0077] In another example, the two different states of the electric
field in the embodiment FIG. 4B are considered. In this embodiment,
in a new first state when the electric field is reversed, the
charged mobile phase moves through the porous membrane towards the
opposite electrode, e.g., electrode 108, and concentrates on the
opposite side of the membrane near the opposite electrode. In this
configuration, the display element 200' will appear to have the
color of the porous membrane. In a second state, when the electric
field is turned off, the mobile phase, however, does not have
sufficient energy to go back through to the other side of the
membrane, i.e., on the side of the electrode 206. Instead, the
mobile phase is scattered between the membrane and the electrode
208. As a result, the display element continues to display the
color of the porous membrane in the absence of an electric
field.
[0078] In both examples of FIGS. 4A and 4B mentioned above, there
are two different states of stability. In these examples, certain
properties of the membrane (e.g., pore size, thickness, surface
chemistry) and of the mobile phase (e.g., size, charge, surface
chemistry) will determine whether the display element will function
in the first state (when an image is retained only under a
continuously applied external electric field) or in the second
state (i.e., bistable state; when an image is retained with or
without a continuously applied external electric field.) Regardless
of whether the display functions the first state or the second
state, in FIG. 4A, the color of the mobile phase is expressed as
the color of the display element. Similarly, in FIG. 4B, the color
of the porous membrane is expressed as the color of the display
element in both the first state and in the second state.
Embodiments of the present invention, which rely upon
electrophoretic addressing, are ideally suited for low-power
applications, such as e-paper, e-book, and signage.
[0079] Display elements of FIGS. 6A and 6B where image formation
relies upon dielectrophoretic addressing, i.e., movement of mobile
phase having a polarizable component under the influence of an
electric field, are ideally suited for fast response applications,
e.g., laptops and television. However, either electrophoretic or
dielectrophoretic addressing, or a combination of both, may be used
for either fast response or for low-power applications.
[0080] Regardless of whether electrophoretic or dielectrophoretic
addressing is effected, it is not necessary that substrate 202 and
204 be disposed outside and connected to leads 216 and 218 as shown
in FIG. 3A. In fact, FIG. 7A shows a design of display element 500
where electrodes 506 and 508 are disposed outside a "pouch," which
includes substrates 502 and 504 having disposed therebetween a
network, e.g., network 510 of particles as shown in FIG. 3A, a
continuous phase (not shown to simplify illustration), a mobile
phase 512. A voltage source 514 through leads 516 and 518 connected
to electrodes 506 and 508, engages externally with the pouch. It is
possible that to manufacture display element 500, the "pouch"
sub-assembly and the electrodes, leads and voltage source
sub-assembly can be manufactured separately, but in parallel. Once
the sub-assemblies are complete, they can be easily assembled
together as mentioned above to form display element 500.
[0081] Those skilled in the art will recognize that FIG. 7B
includes components in the same configuration as FIG. 7A, except
display element 500' includes voltage source 514' operating under
conditions of a reversed electric field relative to voltage source
514 of FIG. 7A. The operation of display elements 500 and 500' are
substantially similar to the described operation of display
elements 100 and 100', respectively.
[0082] In display elements of the present invention, the presence
of a network between the electrodes provides a significant
advantage over the display elements of the prior art. Specifically,
a network in conjunction with the mobile phase, which under the
influence of an externally applied electric field, serves to effect
at least one function selected from a group consisting of obscuring
the mobile phase from field of view (e.g., porous membrane 210
obscures mobile phase 212 in FIG. 3B,), nucleating condensation of
the mobile phase (e.g., polymer network in FIGS. 6A and 6B contains
sites that the mobile phase preferentially moves toward under an
externally applied electric field, and forms agglomerated
structures upon these sites.); directing motion of the mobile phase
(e.g., conical cavities of patterned wells 310 direct the motion of
mobile phase 312 to concentrate into small regions at the bottom of
the wells in FIG. 5B); limiting mobility of the mobile phase (e.g.,
the polymer network in FIGS. 6A and 6B prevents the mobile phase
from diffusing distances much greater than the pore size of the
network), making the display bistable (e.g., porous membrane 210
shown in FIGS. 4A and 4B and particle network 110 in FIGS. 3A and
3B provide bistable addressing); and provides a flexible film that
simplifies manufacturing of flexible display. This film or pouch
that packages the network and ink can easily be integrated with
roll-to-roll manufacturing processes of flexible displays.
[0083] Display elements of the present invention can be
manufactured according to numerous methods. In one embodiment of
the present invention, the process begins when a pair of electrodes
is obtained. In an alternative embodiment of the present invention,
electrodes 106 and 108 are manufactured by first depositing a film
on a polymer or glass substrate, and then patterning the film into
pixels or segments depending on the type of display element that is
ultimately desired. In another alternative embodiment of the
present invention, electrodes 106 and 108 are designed to include
thin film transistors (TFTs) which provide the electrodes with
active addressing capability. Active addressing provides an x-y
addressing scheme such that a charge is stored within each display
element to provide a more constant external electric field while
other display elements are being addressed.
[0084] A network is then placed between the electrodes. Next, the
electrodes and network are assembled to form a subassembly. By way
of example, two electrodes containing the network may be assembled
by applying adhesives to the electrode edges to bind them together.
Into this subassembly, a continuous phase and a mobile,
discontinuous phase are injected. In those embodiments where
spacers are desired, the spacers are provided between the
electrodes before forming the subassembly.
[0085] In an alternative embodiment of the present invention, the
process of forming a display element begins with obtaining a pair
of electrodes. Next the mobile phase and network are applied to the
at least one of the electrodes. If a continuous phase and spacers
are deemed necessary, then they are also applied in this step. In a
next step, the electrodes with the above-described materials
disposed therebetween are assembled to form a sub-assembly.
[0086] The step of applying the network, the mobile phase and the
optional continuous phase and spacers is preferably carried out by
first forming a paste and then applying that paste using rollers or
brushes to at least one of the electrodes. This method of applying
the network is preferred for the production of flexible display
elements. Those skilled in the art may recognize this process as
applicable for roll-to-roll processing.
[0087] The present invention envisions using electroresponsive ink
that is disposed between the electrodes for electrophoretic and
dielectrophoretic addressing. The electroresponsive ink includes a
continuous phase and a discontinuous, mobile phase. Under the
influence of an electric field, the mobile phase moves from one
location to another as described above in the description of
various embodiments. Electroresponsive ink is formed by obtaining a
liquid and a dye or pigment. In a next step, the dye or pigment is
solubilized in the liquid such that in its solubilized state, the
dye or pigment is capable of being at least one of charged, having
a dipole moment or being polarizable. The mobile phase can move
separately from the continuous phase when under the influence of an
externally applied electric field. This can be achieved by making
the continuous and mobile phases immiscible by using a combination
of polar and non-polar liquids, or liquids that are polar to a
different degree, or liquids that become immiscible when under an
external electric field, or by applying certain processes (e.g.,
high-shear emulsification) or chemical agents (e.g., encapsulating
shells or surfactants) that would prevent the mobile and continuous
phases from being miscible with each other. Alternately, the mobile
phase can be a particle, or a stable molecular or super-molecular
complex that is insoluble within the continuous phase, at least
when under the influence of an external electric field. It is
preferred that the continuous phase is electrically insulating or
weakly conductive. The dye or pigment includes a portion that is
polarizable or has a dipole moment or is charged in its solubilized
state in the presence of an externally applied electric field.
[0088] The methods and processes of the present invention represent
a marked improvement over the prior art. By way of example, prior
art display elements enjoy a reflectivity of about 6 to about 10%.
Display elements according to the present invention enjoy
reflectivities ranging from about 70%. As another example, the
prior art display elements require numerous films and filters,
e.g., color filter protective film, color filter, orientation film,
liquid crystals, light diffusion, light guide for backlighting, all
of which are not necessary to make display elements of the present
invention. As a result, the display elements of the present
invention represent a simpler design in which materials costs are
reduced by 60%.
[0089] It should be noted that a display element need not equal one
pixel, which is well known to those skilled in the art as an image
unit. Rather, more than one display unit could combine to form a
pixel and therefore a pixel could span more than one boundary of a
display element. It is also not necessary that a pixel include a
whole number of display elements. Rather it is plausible that a
pixel include both whole number and a fraction of display
elements.
[0090] Although illustrative embodiments of this invention have
been shown and described, other modifications, changes, and
substitutions are intended. By way of example, display elements of
the present invention can be used as a light valve, and not be used
to form an image. In such embodiments, the display element serves
as an optical switch to route light (e.g., between fiberoptic
cables in telecommunications applications or within light guides),
or to change the transmissivity of surfaces (e.g., in self-dimming
windows or sunglasses). The advantages of electrophoretic display
elements in these applications include lower cost to manufacture,
higher switching efficiency, and low power consumption.
Accordingly, it is appropriate that the appended claims be
construed broadly and in a manner consistent with the scope of the
disclosure, as set forth in the following claims.
* * * * *