Patent Grant
10901287
The present invention is directed to driving methods for color display devices. The methods can greatly reduce complexity of the active matrix backplane used for this type of display devices.
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. The biggest disadvantage of such a technique is that 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.
A first aspect of the invention is directed to a driving method for a display device comprising
In one embodiment, in step (c), no voltage is applied to the pixel electrodes to maintain the pixels in the color state of the third type of particles.
In one embodiment, in step (c), a high voltage is applied to the pixel electrodes wherein the high voltage has the same polarity as the second type of particles to drive the pixels towards the color state of the second type of particles.
In one embodiment, in step (c), a high voltage is applied to the pixel electrodes wherein the high voltage has the same polarity as the first type of particles to drive the pixels towards the color state of the first type of particles.
In one embodiment, the method further comprises a shaking waveform prior to step (a).
In one embodiment, the first type of particles is negatively charged and the second and third types of particles are positively charged.
In one embodiment, the first type of particles is white particles, the second type of particles is black particles and the third type of particles is non-white and non-black particles.
A second aspect of the invention is directed to a driving method for a display device comprising
In one embodiment, in step (c), no voltage is applied to the pixel electrodes to maintain the pixels in the color state of the third type of particles.
In one embodiment, in step (c), a high voltage is applied to the pixel electrodes wherein the high voltage has the same polarity as the first type of particles to drive the pixels towards the color state of the first type of particles.
In one embodiment, in step (c), a high voltage is applied to the pixel electrodes wherein the high voltage has the same polarity as the second type of particles to drive the pixels towards the color state of the second type of particles.
In one embodiment, in step (c), a high voltage is applied to the pixel electrodes wherein the high voltage has the same polarity as the first type of particles, followed by applying a low voltage to the pixel electrodes wherein the low voltage has the same polarity as the fourth type of particles to drive the pixels towards the color state of the fourth type of particles.
In one embodiment, the method further comprises a shaking waveform prior to step (a).
In one embodiment, the first and third types of particles are positively charged and the second and fourth types of particles are negatively charged.
In one embodiment, the first type of particles is black particles, the second type of particles is yellow particles, the third type of particles is red particles and the fourth type of particles is white particles.
In one embodiment, the first type of particles is high positive particles, the second type of particles is high negative particles, the third type of particles is low positive particles and the fourth type of particles is low negative particles.
A third aspect of the invention is directed to a driving method for a color display device comprising a plurality of pixels, wherein each of the pixels is sandwiched between a common electrode and a pixel electrode, the method comprises:
In one embodiment, the method further comprises a shaking waveform.
A fourth aspect of the invention is directed to a backplane system for driving a display device comprising an electrophoretic fluid wherein the fluid comprises a first type of particles, a second type of particles and a third type of particles, all of which are dispersed in a solvent or solvent mixture, wherein the first type of particles carry a charge polarity while the second and third types of particles carry opposite charge polarity, which backplane system has only three levels of voltage, 0V, a high positive voltage and a high negative voltage.
A fifth aspect of the invention is directed to a backplane system for driving a display device comprising an electrophoretic fluid wherein the fluid comprises a first type of particles, a second type of particles, a third type of particles and a fourth type of particles, all of which are dispersed in a solvent or solvent mixture, wherein the first and second types of particles are oppositely charged and the third and fourth types of particles are oppositely charged, which backplane system has only four levels of voltage, 0V, a high positive voltage, a high negative voltage and a low positive voltage or a low negative voltage.
General:
A display fluid of the present invention may comprise three or four types of particles. The multiple types of particles may be of any colors as long as the colors are visually distinguishable. In the fluid, the particles are dispersed in a solvent or solvent mixture.
For white particles, they may be formed from an inorganic pigment, such as TiO2, ZrO2, ZnO, Al2O3, Sb2O3, BaSO4, PbSO4 or the like.
For black particles, they 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.
The colored particles (non-white and non-black) may be of a color such as red, green, blue, magenta, cyan or yellow. The pigments for this type of particles may include, but are not limited to, CI pigment PR254, PR122, PR149, PG36, PG58, PG7, PB28, PB15:3, PY138, PY150, PY155 and PY20. These are commonly used organic pigments described in color index handbooks, “New Pigment Application Technology” (CMC Publishing Co, Ltd, 1986) and “Printing Ink Technology” (CMC Publishing Co, Ltd, 1984). Specific examples include Clariant Hostaperm Red D3G 70-EDS, Hostaperm Pink E-EDS, PV fast red D3G, Hostaperm red D3G 70, Hostaperm Blue B2G-EDS, Hostaperm Yellow H4G-EDS, Hostaperm Green GNX, BASF Irgazine red L 3630, Cinquasia Red L 4100 HD, and Irgazin Red L 3660 HD; Sun Chemical phthalocyanine blue, phthalocyanine green, diarylide yellow or diarylide AAOT yellow.
In addition to the colors, the multiple types of particles may have other distinct optical characteristics, such as optical transmission, reflectance, or luminescence or, in the case of displays intended for machine reading, pseudo-color in the sense of a change in reflectance of electromagnetic wavelengths outside the visible range.
A display layer utilizing a display fluid of the present invention, as shown in
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.
Each space between two dotted vertical lines in
The multiple types of particles may have different charge levels. In one embodiment, the weaker charged particles have charge intensity being less than about 50%, or about 5% to about 30%, the charge intensity of the stronger charged particles. In another embodiment, the weaker charged particles have charge intensity being less than about 75%, or about 15% to about 55%, the charge intensity of the stronger charged particles. In a further embodiment, the comparison of the charge levels as indicated applies to two types of particles having the same charge polarity.
The charge intensity may be measured in terms of zeta potential. In one embodiment, the zeta potential is determined by Colloidal Dynamics AcoustoSizer IIM with a CSPU-100 signal processing unit, ESA EN #Attn flow through cell (K:127). The instrument constants, such as density of the solvent used in the sample, dielectric constant of the solvent, speed of sound in the solvent, viscosity of the solvent, all of which at the testing temperature (25.degree. C.) are entered before testing. Pigment samples are dispersed in the solvent (which is usually a hydrocarbon fluid having less than 12 carbon atoms), and diluted to between 5-10% by weight. The sample also contains a charge control agent (Solsperse®. 17000, available from Lubrizol Corporation, a Berkshire Hathaway company), with a weight ratio of 1:10 of the charge control agent to the particles. The mass of the diluted sample is determined and the sample is then loaded into the flow through cell for determination of the zeta potential.
If there are two pairs of high-low charge particles in the same fluid, the two pairs may have different levels of charge differentials. For example, in one pair, the low positively charged particles may have a charge intensity which is 30% of the charge intensity of the high positively charged particles. In another pair, the low negatively charged particles may have a charge intensity which is 50% of the charge intensity of the high negatively charged particles.
The solvent in which the multiple types of particles are dispersed is clear and colorless. It preferably has 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. Examples of suitable dielectric solvent 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 or alkylnaphthalene, halogenated solvents such as perfluorodecalin, perfluorotoluene, perfluoroxylene, dichlorobenzotrifluoride, 3,4,5-trichlorobenzotri fluoride, chloropentafluorobenzene, dichlorononane or pentachlorobenzene, and perfluorinated solvents such as FC-43, FC-70 or 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(chlorotrifluoroethylene) 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).
In the present invention, at least one type of particles may demonstrate an electric field threshold. In one embodiment, one type of the higher charged particles has an electric field threshold.
The term “electric field threshold”, in the context of the present invention, is defined as the maximum electric field that may be applied for a period of time (typically not longer than 30 seconds, preferably not longer than 15 seconds), to a group of particles, without causing the particles to appear at the viewing side of a pixel, when the pixel is driven from a color state different from the color state of the group of particles. The term “viewing side”, in the present application, refers to the first surface in a display layer where images are seen by the viewers.
The electric field threshold is either an inherent characteristic of the charged particles or an additive-induced property.
In the former case, the electric field threshold is generated, relying on certain attraction force between oppositely charged particles or between particles and certain substrate surfaces.
In the case of additive-induced electric field threshold, a threshold agent which induces or enhances the threshold characteristics of an electrophoretic fluid may be added. The threshold agent may be any material which is soluble or dispersible in the solvent or solvent mixture of the electrophoretic fluid and carries or induces a charge opposite to that of the charged particles. The threshold agent may be sensitive or insensitive to the change of applied voltage. The term “threshold agent” may broadly include dyes or pigments, electrolytes or polyelectrolytes, polymers, oligomers, surfactants, charge controlling agents and the like.
Three Particle System:
The electrophoretic fluid comprises three types of particles dispersed in a dielectric solvent or solvent mixture. For ease of illustration, the three types of particles may be referred to as a first type of particles, a second type of particles and a third type of particles. As an example shown in
Two of the three types of particles (i.e., the first and second types of particles) have opposite charge polarities and the third type of particles carries the same charge polarity as one of the other two types of particles. For example, if the black particles are positively charged and the white particles are negatively charged, and then the red particles are either positively charged or negatively charged.
Because of the attraction force between the black and white particles, the black particles (K) are assumed to have an electric field threshold of λV. Therefore, the black particles would not move to the viewing side if an applied voltage potential difference is W or lower.
The red particles carry a charge weaker than that of the black and white particles. As a result, the black particles move faster than the red particles (R), when an applied voltage potential is higher than λV because of the stronger charge carried by the black particles.
In
In
In
It is noted that the lower voltage (+λV or −λV) applied usually has a magnitude of about 5% to about 50% of the magnitude of the full driving voltage required to drive the pixel from the black state to the white state (−hV) or from the white state to the black state (+hV). In one embodiment, +hV and −hV may be +15V and −15V, respectively and +λV and −λV may be +3V and −3V, respectively. In addition, it is noted that the magnitudes of +hV and −hV may be the same or different. Likewise, the magnitude of +λV and −λV may be the same or different.
The term “driving voltage potential difference” refers to the voltage difference between the common electrode and a pixel electrode. In the previous driving method, the common electrode shared by all pixels remains grounded and each pixel is driven by the voltage applied to the corresponding pixel electrode. If such an approach is used to drive the fluid system as described in
The present inventors now propose a new driving method where the backplane system is simplified while color states of high quality can still be displayed.
The shaking waveform applied before phase I consists of a pair of opposite driving pulses for many cycles. For example, the shaking waveform may consist of a +15V pulse for 20 msec and a −15V pulse for 20 msec and such a pair of pulses is repeated for 50 times. The total time of such a shaking waveform would be 2000 msec.
With this added shaking waveform, the color state (i.e., red) can be significantly better than that without the shaking waveform, on both color brightness and color purity. This is an indication of better separation of the white particles from the red particles as well as the black particles from the red particles.
Each of the driving pulses in the shaking waveform is applied for not exceeding half of the driving time from the full black state to the full white state or vice versa. For example, if it takes 300 msec to drive a display device from a full black state to a full white state or vice versa, the shaking waveform may consist of positive and negative pulses, each applied for not more than 150 msec. In practice, it is preferred that the pulses are shorter.
With this driving method in which the common electrode is modulated in the initial step, the backplane system would only need to have each pixel electrode at three different levels of voltage, 0V, +hV and −hV, which is much simplified than the backplane system used in the previous method.
Four Types of Particles:
In this example, the black and yellow particles carry opposite charge polarities. For example, if the black particles are positively charged, the yellow particles are negatively charged. The red and white particles are also oppositely charged. However the charges carried by the black and yellow particles are stronger than the charges carried by the red and white particles.
For example, the black particles (K) carry a high positive charge; the yellow particles (Y) carry a high negative charge; the red (R) particles carry a low positive charge; and the white particles (W) carry a low negative charge. The driving sequence of this type of color display device is shown in
In
Also in
In
In
It is also noted that in
It is noted that the lower voltage (+λV or −λV) applied usually has a magnitude of about 5% to about 50% of the magnitude of the full driving voltage required to drive the pixel from the black state to the yellow state (−hV) or from the yellow state to the black state (+hV). In one embodiment, +hV and −hV may be +15V and −15V, respectively and +λV and −λV may be +3V and −3V, respectively. In addition, it is noted that the magnitudes of +hV and −hV may be the same or different. Likewise, the magnitude of +λV and −λV may be the same or different.
The shaking waveforms as described for
With this driving method in which the common electrode is modulated in the initial step, the backplane system would only need to have each pixel electrode at four different levels of voltage, 0V, +hV, −hV and −λV which is much simplified than the backplane system used in the previous method in which the system would be required to have each pixel at five different levels of voltage, 0V, +hV, −hV, +λV and −λV.
In the illustration above, in the initial step, all pixels are driven to the red state. However it is also possible to drive all pixels to the white state in the initial step (by keeping the pixel electrodes grounds and applying a −hV followed by +λV to the common electrode), followed by driving pixels to be black from white to black (+hV), driving pixels to be yellow from white to yellow (−hV), and applying no driving voltage potential difference to white pixels to remain white. The pixels to be red are driven from white to yellow (−hV) and then from yellow to red (+λV). In this scenario, the backplane system would only need to have each pixel electrode at four different levels of voltage, 0V, +hV, −hV and +λV.
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 true spirit and 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.
This application is a division of copending application Ser. No. 15/294,983, filed Oct. 17, 2016 (Publication No. 2017/0031229), which itself is a division of application Ser. No. 14/279,125, filed May 15, 2014 (Publication No. 2014/0340734, now U.S. Pat. No. 9,501,981, issued Nov. 22, 2016), which claims the priority of U.S. Provisional Application No. 61/824,928, filed May 17, 2013; the contents of all the aforementioned applications are incorporated herein by reference in their entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 6017584 | Albert | Jan 2000 | A |
| 6545797 | Chen | Apr 2003 | B2 |
| 6664944 | Albert | Dec 2003 | B1 |
| 6751007 | Liang | Jun 2004 | B2 |
| 6788452 | Liang | Sep 2004 | B2 |
| 6864875 | Drzaic | Mar 2005 | B2 |
| 6914714 | Chen | Jul 2005 | B2 |
| 6972893 | Chen | Dec 2005 | B2 |
| 7038655 | Herb | May 2006 | B2 |
| 7038656 | Liang | May 2006 | B2 |
| 7038670 | Liang | May 2006 | B2 |
| 7046228 | Liang | May 2006 | B2 |
| 7052571 | Wang | May 2006 | B2 |
| 7075502 | Drzaic | Jul 2006 | B1 |
| 7167155 | Albert | Jan 2007 | B1 |
| 7342556 | Oue | Mar 2008 | B2 |
| 7385751 | Chen | Jun 2008 | B2 |
| 7492505 | Liang | Feb 2009 | B2 |
| 7652656 | Chopra | Jan 2010 | B2 |
| 7667684 | Jacobson | Feb 2010 | B2 |
| 7684108 | Wang | Mar 2010 | B2 |
| 7791789 | Albert | Sep 2010 | B2 |
| 7800813 | Wu | Sep 2010 | B2 |
| 7821702 | Liang | Oct 2010 | B2 |
| 7834844 | Kim | Nov 2010 | B2 |
| 7839564 | Whitesides et al. | Nov 2010 | B2 |
| 7848009 | Machida | Dec 2010 | B2 |
| 7859741 | Chikazawa | Dec 2010 | B2 |
| 7872633 | Zhou | Jan 2011 | B2 |
| 7910175 | Webber | Mar 2011 | B2 |
| 7952790 | Honeyman | May 2011 | B2 |
| 7956841 | Albert | Jun 2011 | B2 |
| 7982941 | Lin | Jul 2011 | B2 |
| 8040594 | Paolini, Jr. | Oct 2011 | B2 |
| 8054526 | Bouchard | Nov 2011 | B2 |
| 8098418 | Paolini, Jr. | Jan 2012 | B2 |
| 8159636 | Sun | Apr 2012 | B2 |
| 8213076 | Albert | Jul 2012 | B2 |
| 8363299 | Paolini, Jr. | Jan 2013 | B2 |
| 8422116 | Sprague | Apr 2013 | B2 |
| 8441714 | Paolini, Jr. | May 2013 | B2 |
| 8441716 | Paolini, Jr. | May 2013 | B2 |
| 8462102 | Wong | Jun 2013 | B2 |
| 8466852 | Drzaic | Jun 2013 | B2 |
| 8503063 | Sprague | Aug 2013 | B2 |
| 8576470 | Paolini, Jr. | Nov 2013 | B2 |
| 8576475 | Huang | Nov 2013 | B2 |
| 8593721 | Albert | Nov 2013 | B2 |
| 8605354 | Zhang | Dec 2013 | B2 |
| 8649084 | Wang | Feb 2014 | B2 |
| 8670174 | Sprague | Mar 2014 | B2 |
| 8704753 | Miyazaki | Apr 2014 | B2 |
| 8704756 | Lin | Apr 2014 | B2 |
| 8717664 | Wang | May 2014 | B2 |
| 8786935 | Sprague | Jul 2014 | B2 |
| 8797634 | Paolini, Jr. | Aug 2014 | B2 |
| 8810899 | Sprague | Aug 2014 | B2 |
| 8830559 | Honeyman | Sep 2014 | B2 |
| 8873129 | Paolini, Jr. | Oct 2014 | B2 |
| 8902153 | Bouchard | Dec 2014 | B2 |
| 8902491 | Wang | Dec 2014 | B2 |
| 8917439 | Wang | Dec 2014 | B2 |
| 8964282 | Wang | Feb 2015 | B2 |
| 9013783 | Sprague | Apr 2015 | B2 |
| 9116412 | Lin | Aug 2015 | B2 |
| 9146439 | Zhang | Sep 2015 | B2 |
| 9164207 | Honeyman | Oct 2015 | B2 |
| 9170467 | Whitesides | Oct 2015 | B2 |
| 9170468 | Lin | Oct 2015 | B2 |
| 9182646 | Paolini, Jr. | Nov 2015 | B2 |
| 9195111 | Anseth | Nov 2015 | B2 |
| 9199441 | Danner | Dec 2015 | B2 |
| 9268191 | Paolini, Jr. | Feb 2016 | B2 |
| 9285649 | Du | Mar 2016 | B2 |
| 9293511 | Jacobson | Mar 2016 | B2 |
| 9341916 | Telfer et al. | May 2016 | B2 |
| 9360733 | Wang | Jun 2016 | B2 |
| 9361836 | Telfer | Jun 2016 | B1 |
| 9383623 | Lin | Jul 2016 | B2 |
| 9423666 | Wang | Aug 2016 | B2 |
| 9459510 | Lin | Oct 2016 | B2 |
| 9513527 | Chan | Dec 2016 | B2 |
| 9541814 | Lin | Jan 2017 | B2 |
| 9671668 | Chan | Jun 2017 | B2 |
| 9697778 | Telfer | Jul 2017 | B2 |
| 9740076 | Paolini | Aug 2017 | B2 |
| 9759980 | Du | Sep 2017 | B2 |
| 9812073 | Lin et al. | Nov 2017 | B2 |
| 10037735 | Amundson | Jul 2018 | B2 |
| 10162242 | Wang | Dec 2018 | B2 |
| 10209556 | Rosenfeld | Feb 2019 | B2 |
| 20070268244 | Chopra | Nov 2007 | A1 |
| 20080043318 | Whitesides | Feb 2008 | A1 |
| 20080048970 | Drzaic | Feb 2008 | A1 |
| 20090225398 | Duthaler | Sep 2009 | A1 |
| 20100156780 | Jacobson | Jun 2010 | A1 |
| 20100194733 | Lin | Aug 2010 | A1 |
| 20110043543 | Chen | Feb 2011 | A1 |
| 20110175939 | Moriyama | Jul 2011 | A1 |
| 20120326957 | Drzaic | Dec 2012 | A1 |
| 20130242378 | Paolini, Jr. | Sep 2013 | A1 |
| 20130278995 | Drzaic | Oct 2013 | A1 |
| 20140009818 | Brochon | Jan 2014 | A1 |
| 20140055840 | Zang | Feb 2014 | A1 |
| 20140078576 | Sprague | Mar 2014 | A1 |
| 20140362213 | Tseng | Dec 2014 | A1 |
| 20150097877 | Lin | Apr 2015 | A1 |
| 20150118390 | Rosenfeld | Apr 2015 | A1 |
| 20150268531 | Wang | Sep 2015 | A1 |
| 20150301246 | Zang | Oct 2015 | A1 |
| 20160026062 | Zhang | Jan 2016 | A1 |
| 20160048054 | Danner | Feb 2016 | A1 |
| Number | Date | Country |
|---|---|---|
| 2981084 | Apr 2013 | FR |
| 2009251032 | Oct 2009 | JP |
| Entry |
|---|
| Kao, W.C., Ye, J.A. and Lin, C. (Jan. 2009) Image Quality Improvement for Electrophoretic Displays by Combining Contrast Enhancement and Halftoning Techniques. ICCE 2009 Digest of Technical Papers, 11.2-2. Jan. 14, 2009. |
| Kao, W.C., Ye, J.A., Chu, M.I and Su, C.Y. (Feb. 2009) Image Quality Improvement for Electrophoretic Displays by Combining Contrast Enhancement and Halftoning Techniques. IEEE Transactions on Consumer Electronics, 2009, vol. 55, Issue 1, pp. 15-19. Feb. 1, 2009. |
| European Patent Office, EP Appl. No. 14797909.0, Extended European Search Report, dated Sep. 16, 2016. Sep. 16, 2016. |
| Korean Intellectual Property Office, PCT/US2014/038234, International Search Report and Written Opinion, dated Sep. 25, 2014. |
| Number | Date | Country | |
|---|---|---|---|
| 20190179209 A1 | Jun 2019 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61824928 | May 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15294983 | Oct 2016 | US |
| Child | 16280517 | US | |
| Parent | 14279125 | May 2014 | US |
| Child | 15294983 | US |
