U.S. patent application number 14/242793 was filed with the patent office on 2015-09-24 for color display device.
This patent application is currently assigned to SiPix Imaging, Inc.. The applicant listed for this patent is SiPix Imaging, Inc.. Invention is credited to Peter LAXTON, Yu LI, Ming WANG.
Application Number | 20150268531 14/242793 |
Document ID | / |
Family ID | 54141984 |
Filed Date | 2015-09-24 |
United States Patent
Application |
20150268531 |
Kind Code |
A1 |
WANG; Ming ; et al. |
September 24, 2015 |
COLOR DISPLAY DEVICE
Abstract
The present invention provides a reflective color display device
which can display multiple color states, without the disadvantages
associated with previously known color display devices. The display
fluid of the present invention comprises (a) black and white
electrophoretic particles which are oppositely charged and (b)
charged color-generating particles having photonic crystal
characteristics, all of which are dispersed in a solvent or solvent
mixture.
Inventors: |
WANG; Ming; (Fremont,
CA) ; LAXTON; Peter; (Alameda, CA) ; LI;
Yu; (Fremont, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SiPix Imaging, Inc. |
Fremont |
CA |
US |
|
|
Assignee: |
SiPix Imaging, Inc.
Fremont
CA
|
Family ID: |
54141984 |
Appl. No.: |
14/242793 |
Filed: |
April 1, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61955129 |
Mar 18, 2014 |
|
|
|
Current U.S.
Class: |
359/296 ;
252/583 |
Current CPC
Class: |
G02F 2202/32 20130101;
G02F 1/1685 20190101; G02F 2203/34 20130101; G02F 1/167 20130101;
G02F 2001/1678 20130101 |
International
Class: |
G02F 1/167 20060101
G02F001/167; G02F 1/00 20060101 G02F001/00 |
Claims
1. A display fluid comprising: (a) black and white electrophoretic
particles which are oppositely charged, and (b) charged
color-generating particles having photonic crystal characteristics;
all of which are dispersed in a solvent or solvent mixture.
2. The fluid of claim 1, wherein all of the color-generating
particles are either positively or negatively charged.
3. The fluid of claim 1, wherein the charged color-generating
particles have electrical polarization characteristics.
4. The fluid of claim 1, wherein the solvent or solvent mixture has
electrical polarization characteristics.
5. The fluid of claim 1, wherein both the color-generating
particles and the solvent or solvent mixture have electrical
polarization characteristics.
6. The fluid of claim 1, wherein the color-generating particles are
formed of silicon (Si), titanium (Ti), barium (Ba), strontium (Sr),
iron (Fe), nickel (Ni), cobalt (Co), lead (Pb), aluminum (Al),
copper (Cu), silver (Ag), gold (Au), tungsten (W), molybdenum (Mo),
or a compound thereof.
7. The fluid of claim 1, wherein the color-generating particles are
formed of polymer materials such as PS (polystyrene), PE
(polyethylene), PP (polypropylene), PVC (polyvinyl chloride), or
PET (polyethylene terephthalate).
8. The fluid of claim 1, wherein the color-generating particles are
formed by coating particles or a cluster having no electric charge
with a material having electric charges.
9. The fluid of claim 3, the color-generating particles include a
material which is electrically polarized with any one of electronic
polarization, ionic polarization, interfacial polarization or
rotational polarization due to asymmetrical charge distribution of
atoms or molecules as an external electric field is applied.
10. The fluid of claim 1, wherein the color-generating particles
include a ferroelectric material.
11. The fluid of claim 1, wherein the color-generating particles
include a superparaelectric material.
12. The fluid of claim 1, wherein the color-generating particles
include a material having a perovskite structure.
13. The fluid of claim 4, wherein the solvent is water,
trichloroethylene, carbon tetrachloride, di-iso-propyl ether,
toluene, methyl-t-bytyl ether, xylene, benzene, diethyl ether,
dichloromethane, 1,2-dichloroethane, butyl acetate, iso-propanol,
n-butanol, tetrahydrofuran, n-propanol, chloroform, ethyl acetate,
2-butanone, dioxane, acetone, methanol, ethanol, acetonitrile,
acetic acid, dimethylformamide, dimethyl sulfoxide or propylene
carbonate.
14. A method for generating a full spectrum of colors, comprising
applying an electric field to the display fluid of claim 1 to
control the inter-particle distances of the color-generating
particles.
15. The method of claim 14, wherein the intensity of the colors
displayed is controlled by adjusting locations of the black and
white electrophoretic particles or mixing levels of the black and
white particles.
Description
[0001] This application claims the benefit of U.S. Provisional
Application 61/955,129, filed Mar. 18, 2014, which is incorporated
herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention is directed to a color display device
which can display high quality color states, and a display fluid
for such a color display device.
BACKGROUND OF THE INVENTION
[0003] In order to achieve a color display, color filters are often
used. The most common approach is to add color filters on top of
black/white sub-pixels of a pixellated display to display the red,
green and blue colors. When a red color is desired, the green and
blue sub-pixels are turned to the black state so that the only
color displayed is red. When the black state is desired, all
three-sub-pixels are turned to the black state. When the white
state is desired, the three sub-pixels are turned to red, green and
blue, respectively, and as a result, a white state is seen by the
viewer.
[0004] The biggest disadvantage of such a technique is that since
each of the sub-pixels has a reflectance of about one third (1/3)
of the desired white state, the white state is fairly dim. To
compensate this, a fourth sub-pixel may be added which can display
only the black and white states, so that the white level is doubled
at the expense of the red, green or blue color level (where each
sub-pixel is only one fourth [1/4] of the area of the pixel).
Brighter colors can be achieved by adding light from the white
pixel, but this is achieved at the expense of color gamut to cause
the colors to be very light and unsaturated. A similar result can
be achieved by reducing the color saturation of the three
sub-pixels. Even with this approach, the white level is normally
substantially less than half of that of a black and white display,
rendering it an unacceptable choice for display devices, such as
e-readers or displays that need well readable black-white
brightness and contrast.
[0005] An alternative of color display device employs colored
pigment particles, in addition to the black and white particles.
This type of color display can display multiple color states by
moving the black, white and colored particles to the viewing side.
However, the number of the color states displayed is limited by how
many types of different colored particles are in the display fluid
and how well their movement can be controlled.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 illustrates a display fluid of the present
invention.
[0007] FIGS. 2-1 to 2-5 illustrate how different color states may
be displayed by the color display device of the present
invention.
[0008] FIG. 3 demonstrates how locations of the black and white
particles influence the intensity/brightness of the color displayed
by the color-generating particles.
[0009] FIG. 4 demonstrates how mixing levels of the black and white
particles influence the intensity/brightness of the color displayed
by the color-generating particles.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to a display fluid
comprising
[0011] (a) black and white electrophoretic particles which are
oppositely charged, and
[0012] (b) charged color-generating particles having photonic
crystal characteristics, all of which are dispersed in a solvent or
solvent mixture.
[0013] In one embodiment, all of the color-generating particles are
either positively or negatively charged.
[0014] In one embodiment, the charged color-generating particles
have electrical polarization characteristics. In one embodiment,
the solvent or solvent mixture has electrical polarization
characteristics. In one embodiment, both the color-generating
particles and the solvent or solvent mixture have electrical
polarization characteristics.
[0015] In one embodiment, the color-generating particles are formed
of silicon (Si), titanium (Ti), barium (Ba), strontium (Sr), iron
(Fe), nickel (Ni), cobalt (Co), lead (Pb), aluminum (Al), copper
(Cu), silver (Ag), gold (Au), tungsten (W), molybdenum (Mo), or a
compound thereof.
[0016] In one embodiment, the color-generating particles are formed
of polymer materials such as PS (polystyrene), PE (polyethylene),
PP (polypropylene), PVC (polyvinyl chloride), or PET (polyethylene
terephthalate).
[0017] In one embodiment, the color-generating particles are formed
by coating particles or a cluster having no electric charge with a
material having electric charges.
[0018] In one embodiment, the color-generating particles include a
material which is electrically polarized with any one of electronic
polarization, ionic polarization, interfacial polarization or
rotational polarization due to asymmetrical charge distribution of
atoms or molecules as an external electric field is applied.
[0019] In one embodiment, the color-generating particles include a
ferroelectric material.
[0020] In one embodiment, the color-generating particles include a
superparaelectric material.
[0021] In one embodiment, the color-generating particles include a
material having a perovskite structure.
[0022] In one embodiment, the solvent is water, trichloroethylene,
carbon tetrachloride, di-iso-propyl ether, toluene, methyl-t-bytyl
ether, xylene, benzene, diethyl ether, dichloromethane,
1,2-dichloroethane, butyl acetate, iso-propanol, n-butanol,
tetrahydrofuran, n-propanol, chloroform, ethyl acetate, 2-butanone,
dioxane, acetone, methanol, ethanol, acetonitrile, acetic acid,
dimethylformamide, dimethyl sulfoxide or propylene carbonate.
[0023] In one embodiment, the present invention is directed to a
method for generating a full spectrum of colors, which method
comprises applying an electric field to the display fluid of the
present invention to control the inter-particle distances of the
color-generating particles.
[0024] In one embodiment, the intensity of the colors displayed is
controlled by adjusting locations of the black and white
electrophoretic particles or mixing levels of the black and white
particles.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention provides a reflective color display
device which can display multiple color states, without the
disadvantages associated with previously known color display
devices.
[0026] The display fluid of the present invention, as shown in FIG.
1, comprises (a) black (11) and white (12) electrophoretic
particles which are oppositely charged and (b) charged
color-generating particles (13) having photonic crystal
characteristics, all of which are dispersed in a solvent or solvent
mixture. All the color-generating particles carry the same charge
polarity, positive or negative.
[0027] The display fluid is sandwiched between two electrode
layers. One of the electrode layers is a common electrode (14)
which is a transparent electrode layer (e.g., ITO), spreading over
the entire top of the display device. The other electrode layer
(15) is a layer of pixel electrodes (15a).
[0028] The pixel electrodes are described in U.S. Pat. No.
7,046,228, the content of which is incorporated herein by reference
in its entirety. It is noted that while active matrix driving with
a thin film transistor (TFT) backplane is mentioned for the layer
of pixel electrodes, the scope of the present invention encompasses
other types of electrode addressing as long as the electrodes serve
the desired functions.
[0029] The black electrophoretic particles (11) may be formed from
CI pigment black 26 or 28 or the like (e.g., manganese ferrite
black spinel or copper chromite black spinel) or carbon black.
[0030] The white electrophoretic particles (12) may be formed from
an inorganic pigment, such as TiO.sub.2, ZrO.sub.2, ZnO,
Al.sub.2O.sub.3, Sb.sub.2O.sub.3, BaSO.sub.4, PbSO.sub.4 or the
like.
[0031] As stated, the black and white particles are oppositely
charged. If the black particles are positively charged, then the
white particles are negatively charged, or vice versa.
[0032] The percentages of the black and white particles in the
fluid may vary. For example, the black electrophoretic particle may
take up 0.1% to 10%, preferably 0.5% to 5%, by volume of the
electrophoretic fluid; the white electrophoretic particle may take
up 1% to 50%, preferably 5% to 20%, by volume of the fluid.
[0033] The size of the black and white particles in the fluid may
vary. For example, both the black and white particle may have a
size between 100 nm to 10 um, preferably between 200 nm to 1
um.
[0034] The charged color generating particles having photonic
crystal characteristics are described in U.S. Pat. No. 8,238,022.
Some of the description in U.S. Pat. No. 8,238,022 is quoted below.
However, it is noted that the content of the entire patent is
incorporated herein by reference.
[0035] The color generating particles are charged. They may have
electrical polarization characteristics or the solvent may have
electrical polarization characteristics or both may have electrical
polarization characteristics. In any case, the inter-particle
distances may be controlled by applying an electric field to the
display fluid, thereby implementing a full spectrum of colors using
the photonic crystal characteristics of the color-generating
particles.
[0036] All of the color-generating particles carry the same charge
polarity, either positive or negative. They may be arranged at
predetermined spaces from each other by the repulsive force between
them caused by electric charges of the same polarity.
[0037] The diameter of the color-generating particles may range
from several nm to several hundred microns; but the particle
diameter is not necessarily limited thereto.
[0038] As indicated in U.S. Pat. No. 8,238,022, the
color-generating particles may be formed of elements, such as
silicon (Si), titanium (Ti), barium (Ba), strontium (Sr), iron
(Fe), nickel (Ni), cobalt (Co), lead (Pb), aluminum (Al), copper
(Cu), silver (Ag), gold (Au), tungsten (W), molybdenum (Mo), or a
compound thereof. In addition, the color-generating particles may
be formed of polymer materials such as PS (polystyrene), PE
(polyethylene), PP (polypropylene), PVC (polyvinyl chloride), or
PET (polyethylene terephthalate).
[0039] Furthermore, the color-generating particles may be formed by
coating particles or a cluster having no electric charge with a
material having electric charges. Examples of these particles may
include particles whose surfaces are processed (or coated) with an
organic compound having a hydrocarbon group; particles whose
surfaces are processed (or coated) with an organic compound having
a carboxylic acid group, an ester group or an acyl group; particles
whose surfaces are processed (or coated) with a complex compound
containing halogen (F, CI, Br or I) elements; particles whose
surfaces are processed (or coated) with a coordination compound
containing amine, thiol or phosphine; and particles having electric
charges generated by forming radicals on the surfaces.
[0040] Meanwhile, in order for the color-generating particles to
effectively exhibit photonic crystal characteristics by maintaining
a stable colloidal state without precipitation in a solvent, the
value of the electrokinetic potential (i.e., zeta potential) of the
colloidal solution (comprising the particles and a solvent) may be
greater than or equal to a preset value. For example, the absolute
value of the electrokinetic potential of the colloidal solution may
be more than or equal to 10 mV. In addition, the difference in
specific gravity between the particles and the solvent may be less
than or equal to a preset value, for example, less than or equal to
5. Furthermore, the difference in refractive index between the
solvent and the particles may be greater than or equal to a preset
value, for example, more than or equal to 0.3.
[0041] Further, if the color-generating particles have electrical
polarization characteristics, the particles may include a material
which is electrically polarized with any one of electronic
polarization, ionic polarization, interfacial polarization or
rotational polarization due to asymmetrical charge distribution of
atoms or molecules as an external electric field is applied.
[0042] Moreover, the color-generating particles may include a
ferroelectric material, which shows an increase in polarization
upon application of an external electric field and shows a large
remnant polarization and remnant hysteresis even without the
application of an external electric field. Alternatively, the
color-generating particles may include a superparaelectric
material, which shows an increase in polarization upon application
of an external electric field and shows no remnant polarization and
no remnant hysteresis when no external electric field is
applied.
[0043] Further, the color-generating particles may include a
material having a perovskite structure. Examples of materials
having a perovskite structure, such as ABO.sub.3, may include
materials such as PbZrO.sub.3, PbTiO.sub.3, Pb(Zr,Ti)O.sub.3,
SrTiO.sub.3 BaTiO.sub.3, (Ba, Sr)TiO.sub.3, CaTiO.sub.3,
LiNbO.sub.3 or the like.
[0044] If the color-generating particles have electrical
polarization characteristics, the solvent does not have to have
electrical polarization characteristics. In this case, the solvent
may be a dielectric solvent, examples of which include, but are not
limited to, solvents having a low viscosity and a dielectric
constant in the range of about 2 to about 30, preferably about 2 to
about 15 for high particle mobility. Specific examples of suitable
dielectric solvent may include hydrocarbons such as isopar,
decahydronaphthalene (DECALIN), 5-ethylidene-2-norbornene, fatty
oils, paraffin oil; silicon fluids; aromatic hydrocarbons such as
toluene, xylene, phenylxylylethane, dodecylbenzene and
alkylnaphthalene; halogenated solvents such as perfluorodecalin,
perfluorotoluene, perfluoroxylene, dichlorobenzotrifluoride,
3,4,5-trichlorobenzotrifluoride, chloropentafluoro-benzene,
dichlorononane, pentachlorobenzene; and perfluorinated solvents
such as FC-43, FC-70 and FC-5060 from 3M Company, St. Paul Minn.,
low molecular weight halogen containing polymers such as
poly(perfluoropropylene oxide) from TCI America, Portland, Oreg.,
poly(chlorotrifluoro-ethylene) such as Halocarbon Oils from
Halocarbon Product Corp., River Edge, N.J., perfluoropolyalkylether
such as Galden from Ausimont or Krytox Oils and Greases K-Fluid
Series from DuPont, Del., polydimethylsiloxane based silicone oil
from Dow-corning (DC-200).
[0045] If the color-generating particles do not have electrical
polarization characteristics, the solvent has to have electrical
polarization characteristics, which may be created by
methods/materials as described above for the color-generating
particles. For example, the solvent may include a material which is
electrically polarized with any one of electronic polarization,
ionic polarization, interfacial polarization, or rotational
polarization due to asymmetrical charge distribution of atoms or
molecules as an external electric field is applied; or the solvent
may include a ferroelectric material; or the solvent may include a
superparaelectric material; or the solvent may include a material
having a perovskite structure as described above; or the solvent
may include a material having a polarity index of 1 or greater.
[0046] Examples of solvent having electrical polarization
characteristics may include, but are not limited to, water,
trichloroethylene, carbon tetrachloride, di-iso-propyl ether,
toluene, methyl-t-bytyl ether, xylene, benzene, diethyl ether,
dichloromethane, 1,2-dichloroethane, butyl acetate, iso-propanol,
n-butanol, tetrahydrofuran, n-propanol, chloroform, ethyl acetate,
2-butanone, dioxane, acetone, methanol, ethanol, acetonitrile,
acetic acid, dimethylformamide, dimethyl sulfoxide and propylene
carbonate.
[0047] The color-generating particles carrying the same charge
polarity are dispersed in a solvent which has electrical
polarization characteristics. When an electric field is applied to
the dispersion, electrical attraction proportional to the intensity
of the electric field and the charge amount of the particles, act
on the particles due to the electric charges of the particles. As a
result, the particles move in a predetermined direction by
electrophoresis, thus narrowing the inter-particle distances. In
contrast, electrical repulsion generated between the particles
having the electric charges of the same polarity increases as the
inter-particle distances become smaller resulting in a
predetermined equilibrium state while preventing the inter-particle
distances from continuing to decrease.
[0048] Further, the solvent is electrically polarized in a
predetermined direction due to the electrical polarization
characteristics of the solvent. Thus, electrical attraction is
locally generated and exerts a predetermined effect upon the
inter-particle distances between the particles electrically
interacting with the polarized solvent. That is, the
color-generating particles can be regularly arranged at distances
where electrical attraction induced by an external electric field,
electrical repulsion between the particles having electric charges
of the same polarity and electrical attraction induced by
polarization, are in equilibrium. As a result, the inter-particle
distances can be controlled at predetermined levels, and the
particles arranged at predetermined distances can function as
photonic crystals. Since the wavelength of light reflected from the
regularly spaced particles is determined by the inter-particle
distance, the wavelength of the light reflected from the particles
can be arbitrarily controlled by controlling the inter-particle
distances. Therefore, a pattern of the wavelength of reflected
light may be diversely represented by the factors, such as the
intensity and direction of the applied electric field, the size and
mass of the particles, the refractive indices of the particles and
the solvent, the charge amount of the particles, the electrical
polarization characteristics of the solvent or the concentration of
the particles dispersed in the solvent.
[0049] Alternatively, when the color-generating particles having
both electric charges of the same polarity and electrical
polarization characteristics are dispersed in a solvent and if an
electric field is applied to the particles and the solvent,
electrical attraction proportional to the intensity of the electric
field and the charge amount of the particles act on the particles
due to the electric charges of the particles. Therefore, the
particles move in a predetermined direction by electrophoresis,
thus narrowing the inter-particle distance. In contrast, electrical
repulsion generated between the particles having the electric
charges of the same polarity increases as the inter-particle
distances decreases, thus reaching a predetermined equilibrium
state while preventing the inter-particle distances from continuing
to decrease. The particles are electrically polarized in a
predetermined direction due to the electrical polarization
characteristics of the particles. Thus, electrical attraction is
locally generated between the polarized particles and exerts a
predetermined effect upon the inter-particle distances.
[0050] As a result, the color-generating particles can be regularly
arranged at a distance where electrical attraction induced by an
external electric field, electrical repulsion between the particles
having electric charges of the same polarity and electrical
attraction induced by polarization, are in equilibrium.
Accordingly, the inter-particle distances can be controlled at
predetermined intervals, and the particles arranged at
predetermined intervals can function as photonic crystals. Since
the wavelength of light reflected from the regularly arranged
color-generating particles is determined by the inter-particle
distances, the wavelength of the light reflected from the particles
can be accurately controlled by controlling the inter-particle
distances. Therefore, a pattern of the wavelength of reflected
light may be diversely represented by the factors, such as the
intensity and direction of an electric field, the size and mass of
the particles, the refractive indices of the particles and the
solvent, the charge amount of the particles, the electrical
polarization characteristics of the particles or the concentration
of the particles dispersed in the solvent.
[0051] It is possible for both the color-generating particles and
the solvent to have electrical polarization characteristics.
[0052] FIGS. 2-1 to 2-5 illustrate how different color states may
be displayed by a display device of the present invention.
[0053] As shown, a display fluid comprises two types of
electrophoretic particles, black (21) and white (22), and one type
of color-generating particles (23). It is assumed that the black
electrophoretic particles are positively charged and the white
electrophoretic particles are negatively charged. The
color-generating particles carry a positive charge and the charge
level of the color-generating particles is lower than that of the
charges carried by the black and white particles.
[0054] When a high positive driving voltage V2 is applied for a
short period of time t2, the positively charged black particles are
driven to the viewing side (i.e., the side of the common
electrode). As a result, a black color is seen (FIG. 2a). The high
driving voltage, in this case, is referred to as a driving voltage
which is sufficiently high to drive the black particles to the
viewing side during a short driving time (i.e., t2). Such a driving
voltage may be +15V, as an example. The short driving time t2 is
usually less than 500 msec.
[0055] When a high negative driving voltage V1 is applied for a
short period of time t1, the negatively charged white particles are
driven to the viewing side. As a result, a white color is seen
(FIG. 2b). The high driving voltage, in this case, is referred to
as a driving voltage which is sufficiently high to drive the white
particles to the viewing side during a short driving time, t1. Such
a driving voltage may be -15V, as an example. The short driving
time is usually also less than 500 msec.
[0056] In FIGS. 2a and 2b, because the color-generating particles
are lesser charged and the driving times are short, the
color-generating particles remain scattered in the display
fluid.
[0057] If a negative driving voltage V3 is applied to the fluid in
FIG. 2a for a period of time, t3, which driving voltage and the
driving time are not sufficient to drive a pixel to the white color
state of FIG. 2b, and instead, the white and black particles are
driven to the middle of the pixel as shown in FIG. 2c, the color
seen would be the color (i.e., a first color state) of the
color-generating particles.
[0058] Similarly, if a positive driving voltage V4 is applied to
the fluid in FIG. 2b for a period of time, t4, which driving
voltage and the driving time are not sufficient to drive a pixel to
the black color state of FIG. 2a, and instead, the white and black
particles are driven to gather in the middle of the pixel as shown
in FIG. 2d, the color seen would also be the color of the
color-generating particles.
[0059] The brightness of the color of the color-generating
particles can be adjusted by controlling locations of the black and
white particles and mixing levels through magnitude of driving
voltages V3 and V4 and/or driving times, t3 and t4. The magnitude
of driving voltages V3 and V4, in this case, may be higher than, or
equal to, 10V. The driving times, t3 and t4, may be the same as t1
and t2, but in this case, they are preferably shorter than t1 and
t2.
[0060] When a low positive driving voltage V5 is applied to the
fluid in FIG. 2c and the voltage is applied for a relatively long
period of time, t5, an external electric field created between the
common electrode and the pixel electrode would alter the spatial
distances between the color-generating particles. As a result, the
color-generating particles would reflect light of a different
wavelength (i.e., a second color state of FIG. 2e), according to
the applied voltage. The color or the reflective light spectrum
from color-generating particles is adjustable by driving voltage V5
and it continuously changes with the change of the driving voltage.
Usually with higher driving voltage, the spectrum of reflective
light shifts from low frequency to high frequency range. The
reflective light band may cover not only the range of visible light
but also the infrared and ultraviolet light ranges. The low driving
voltage V5, in this case, is usually lower than V1 and V2, because
of which the black and white particles in this scenario remain
substantially unmoved. V5 may be less than, or equal to, +5V, as an
example. The time period, t5, is usually longer than t1 and t2.
[0061] The same phenomenon may also be achieved with V6 applied to
the fluid of FIG. 2c for a relatively long period of time, t6, to
generate a third color state of a different wavelength (see FIG.
2f).
[0062] When a voltage of V7 is applied to the fluid of FIG. 2e for
a period of time, t7, a third color state may be displayed (see
FIG. 2f).
[0063] The driving voltages V6 and V7 are lower than V1 and V2 and
the time periods t6 and t7 are longer than t1 and t2.
[0064] The phenomenon illustrated in FIG. 2 for the fluid of (c),
(e) and (f) can be similarly applied to the fluid of (d), (e) and
(f), with driving voltages, V8, V9 and V10 and driving times, t8,
t9 and t10, respectively. For example, V8, V9 and V10 are usually
lower than V1 and V2 and the time periods t8, t9 and t10 are longer
than t1 and t2. The driving voltages and driving times, V5-V7 and
t5-t7, may be the same or different from the driving voltages and
driving times, V8-V10 and t8-t10.
[0065] The colors referred to in the drawings, a first color, a
second color and a third color, may be red, green and blue,
respectively. However, this is in no way limiting the scope of the
present invention. It is noted that each of the pixels in the
present color display device may display an unlimited number of
color states, because when different external electric fields are
applied, they would cause the color-generating particles to reflect
light of different wavelengths.
[0066] As stated above, the brightness of the color of the
color-generating particles can be adjusted by controlling the
locations and mixing levels of the black and white particles. This
is shown in FIGS. 3 and 4, respectively.
[0067] In FIG. 3, pixel (a) has the highest brightness of the color
generated by the color-generating particles as the white particles
are on top of the black particles and are the closest to the
viewing side. Pixels (b) and (c) have brightness lower than pixel
(a). Pixel (d) is darker than pixel (c) as in pixel (d), the black
particles are on top of the white particles. Pixel (f) has the
lowest brightness because the black particles are closest to the
viewing side.
[0068] FIG. 4 shows how different mixing levels of the black and
white particles influence the brightness of the color generated by
the color-generating particles. In pixel (a), there are more black
particles than the white particles facing the viewing side and
therefore that pixel is darker than the other pixels. In pixel (c),
there are more white particles than the black particles facing the
viewing side and therefore that pixel is brighter. In pixel (b),
the black and white particles are more evenly distributed which
causes the color intensity between pixel (a) and pixel (c).
[0069] While the present invention has been described with
reference to the specific embodiments thereof, it should be
understood by those skilled in the art that various changes may be
made and equivalents may be substituted without departing from the
scope of the invention. In addition, many modifications may be made
to adapt a particular situation, materials, compositions,
processes, process step or steps, to the objective and scope of the
present invention. All such modifications are intended to be within
the scope of the claims appended hereto.
* * * * *