Multi-particle electrophoretic display having low-flash image updates

Abstract

Electrophoretic displays with multi-particle electrophoretic media, and particularly improved methods for driving such multi-particle electrophoretic media using an active matrix backplane and controller. These driving methods use faster gate updates and differential intervals between a series of gate updates for a given pixel. These methods can be extended to any electrophoretic display using push-pull waveforms and are particularly well-suited for novel multi-particle electrophoretic displays capable of generating more than four colors per pixel. Compared to addressing using conventional constant-frame-spacing updates, electrophoretic displays using such methods appear to be less "flickering".

Description

Technical Field

[0001] [Related Applications]

[0002] This application claims the priority of U.S. Provisional Application No. 63 / 523,541, filed on June 27, 2023. All patents and publications disclosed herein are hereby incorporated by reference in their entirety. Prior Art

[0003] An electrophoretic display (EPD) changes color by varying the position of one or more charged colored particles relative to a light-transmissive viewing surface. Such electrophoretic displays are commonly referred to as "electronic paper" or "ePaper" because the resulting displays have high contrast and are visible in sunlight, much like ink on paper. Electrophoretic displays are widely adopted in e-readers because they provide a book-like reading experience, consume very little power, and allow users to carry a library of hundreds of books in a lightweight handheld device. Such devices are increasingly suitable for displaying outdoor (OOH) digital content, such as, for example, shelf labels, outdoor advertising, and traffic signs.

[0004] For many years, electrophoretic displays have included only two types of charged color particles: black and white. (Of course, "color" as used herein includes black and white.) White particles are typically of the light-scattering type and include, for example, titanium dioxide, while black particles are absorptive across the visible spectrum and can include carbon black or absorptive metal oxides, such as, for example, copper chromite. In the simplest sense, a black-and-white electrophoretic display requires only a light-transmissive electrode at the viewing surface, a back electrode, and an electrophoretic medium containing white and black particles of opposite charge. When a voltage of one polarity is provided, the white particles move to the viewing surface, and when a voltage of the opposite polarity is provided, the black particles move to the viewing surface. If the back electrode includes controllable regions (pixels) - an active matrix of segmented electrodes or pixel electrodes controlled by transistors - then patterns can be electronically presented on the viewing surface. The pattern can be, for example, the text of a book.

[0005] Recently, multiple color options have become commercially available for electrophoretic displays, including tri-color displays (black, white, red; black, white, yellow) and quad-color displays (black, white, red, yellow). Similar to the operation of black-and-white electrophoretic displays, the operation of electrophoretic displays with three or four reflective pigments is similar to that of a simple black-and-white display in that the desired color particles are driven to the viewing surface. The driving schemes are much more complex than those with only black and white, but the ultimate optical function of the particles is the same.

[0006] Premium colored e-paper (ACePTM) also contains four types of particles, but the cyan, yellow, and magenta particles are subtractive, not reflective, and thus can produce thousands of colors per pixel. Color processing is functionally equivalent to long-used printing methods in offset printing and inkjet printers. The given color is produced by using the correct ratio of cyan, yellow and magenta on a bright white paper background. In the case of ACeP, the relative position of the cyan, yellow, magenta, and white particles with respect to the viewing surface will determine the color of each pixel. Although this type of electrophoresis display permits thousands of colors per pixel, it is crucial to carefully control the position of each pigment (50 to 500 nm size) in a workspace with a thickness of about 10 to 20 microns. Evidently, a change in the pigment position results in incorrect color display at a given pixel. Therefore, such a system requires precise voltage control. Further details of such a system may be obtained in the following U.S. Patents, wherein the entirety of all these patents is incorporated herein by reference: U.S. Patents Nos. 9,361,836, 9,921,451, 10,276,109, 10,353,266, 10,467,984, 10,593,272, and 186,9.

[0007] As described in the foregoing patents, the waveform (i.e., the electric field provided over the entire electrophoretic medium as a function of time) usually requires a large swing in the voltage polarity over a short period of time. Thus, in some cases, the color electrophoresis display will “flicker,” “blink,” or “look shiny” when switching between color images. This drawback is particularly pronounced when a full-color e-reader switches quickly between full-color images (i.e., in less than 1 second). A solution to reduce flashes in multiparticle electrophoresis displays (e.g., ACEP displays) is introduced below.

[0008] The invention relates to color electrophoretic displays, and in particular, but does not exclusively relate to electrophoresis displays capable of presenting more than two colors using a monolayer electrophoretic material comprising a plurality of colored particles (e.g., white, cyan, yellow, and magenta particles). In some cases, two types of particles are positively charged, and one (or both) particles are negatively charged. In some cases, one particle is positively charged and three particles are negatively charged. In some cases, one particle is negatively charged and three particles are positively charged. Furthermore, the type of charge species on the particle surface of the particle and / or the type of polymer functionally based on the surface can be different. The particles can contain organic or inorganic pigments or dyes.

[0009] The term "gray state" is used herein in its traditional meaning in imaging arts to refer to a state between two extreme optical states of a pixel, and does not necessarily imply a black-white transition between these two extreme states. For example, some of the E Ink patents and published applications mentioned below describe electrophoretic displays where the extreme states are white and dark blue, such that the intermediate gray state is actually light blue. In fact, as already mentioned, the change in optical state may not be a color change at all. The terms black and white may be used hereinafter to refer to the two extreme optical states of a display, and should be understood to generally include extreme optical states that are not exactly black and white, such as, for example, the aforementioned white and dark blue states.

[0010] The terms "bistable" and "bistability" are used herein in their traditional meaning in the art to refer to a display including display elements having first and second display states that are different in at least one optical property, and such that after driving any given element with an addressing pulse of finite duration, it assumes its first or second display state, and after the addressing pulse terminates, that state will persist for at least a number of times, e.g., at least 4 times; the addressing pulse requires a minimum duration to change the state of the display element. U.S. Patent No. 7,170,670 shows some particle-based electrophoretic displays having gray-scale capabilities that are stable not only in their extreme black and white states, but also in their intermediate gray states, and the same is true for some other types of electro-optic displays. Displays of this type may be appropriately referred to as multi-stable rather than bistable, but for convenience, the term "bistable" may be used herein to encompass both bistable and multi-stable displays.

[0011] The term "impulse", when used in reference to driving an electrophoretic display, is used herein to refer to the integral of the voltage applied during driving the display with respect to time.

[0012] Particles that absorb, scatter, or reflect light of a broadband or selected wavelength are referred to herein as colored or pigment particles. Various materials that absorb or reflect light other than pigments (in the strict sense of the term, insoluble colored materials), such as, for example, dyes or photonic crystals, etc., may also be used in the electrophoretic media and displays of the present invention.

[0013] Particle-based electrophoretic displays have been the subject of intensive research for several years. In such displays, plural charged particles (sometimes referred to as pigment particles) move through a fluid under the influence of an electric field. When compared to liquid crystal displays, electrophoretic displays have the characteristics of good brightness and contrast, wide viewing angles, bistable states, and low power consumption. However, long-term image quality problems with these displays have hindered their widespread use. For example, the particles that make up electrophoretic displays tend to settle, resulting in insufficient service life of these displays.

[0014] As described above, an electrophoretic medium requires the presence of a fluid. In most conventional electrophoretic media, this fluid is a liquid, but a gas fluid can be used to produce the electrophoretic medium; see, for example, Kitamura, T., et al., Electrical toner movement for electronic paper-like display, IDW Japan, 2001, Paper HCS1-1 and Yamaguchi, Y., et al., Toner display using insulative particles charged triboelectrically, IDW Japan, 2001, Paper AMD4-4. Also see U.S. Patents Nos. 7,321,459 and 7,236,291. When using such media in an orientation that allows particle settlement (e.g., in the performance of a medium configured in a vertical plane), such gas-based electrophoretic media appear to be susceptible to the same types of problems caused by particle settlement as liquid-based electrophoretic media. More precisely, particle settlement appears to be a more serious problem in gas-based electrophoretic media than in liquid-based electrophoretic media because the lower viscosity of the gas suspension fluid allows for more rapid settlement of the electrophoretic particles compared to a liquid suspension fluid.

[0015] Many patents and applications assigned to or in the name of the Massachusetts Institute of Technology (MIT) and E Ink Corporation describe various technologies used in electrophoretic and other electro-optic media. Such capsule-based media include many small capsules, each capsule itself including an internal phase of electrophoretic moving particles contained within a fluid medium and a capsule wall surrounding the internal phase. Typically, the capsules themselves are held within a polymeric binder to form a coherent layer between two electrodes. The technologies described in these patents and applications include: (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Pat. Nos. 7,002,728 and 7,679,814; (b) Capsules, binders, and encapsulation processes; see, for example, U.S. Pat. Nos. 6,922,276 and 7,411,719; (c) Micellar structures, wall materials, and methods of forming micelles; see, for example, U.S. Pat. Nos. 7,072,095 and 9,279,906; (d) Methods for filling and sealing micelles; see, for example, U.S. Pat. Nos. 7,144,942 and 7,715,088; (e) Thin films and sub-assemblies containing electro-optic materials; see, for example, U.S. Pat. Nos. 6,982,178 and 7,839,564; (f) Backplanes, adhesive layers, and other auxiliary layers and methods used in displays; see, for example, U.S. Pat. Nos. 7,116,318 and 7,535,624; (g) Color formation and color adjustment; see, for example, U.S. Patent Nos. 6,017,584; 6,545,797; 6,664,944; 6,788,452; 6,864,875; 6,914,714; 6,972,893; 7,038,656; 7,038,670; 7,046,228; 7,052,571; 7,075,502; 7,167,155; 7,385,751; 7,492,505; 7,667,684; 7,684,108; 7,791,789; 7,800,813; 7,821,702; 7,839,564; 7,910,175; 7,952,790; 7,956,841; 7,982,941; 8,040,594; 8,054,526; 8,098,418; 8,159,636; 8,213,076; 8,363,299; 8,422,116; 8,441,714; 8,441,716; 8,466,852; 8,503,063; 8,576,470; 8,576,475; 8,593,721; 8,605,354; 8,649,084; 8,670,174; 8,704,756; 8,717,664; 8,786,935; 8,797,634; 8,810,899; 8,830,559; 8,873,129; 8,902,153; 8,902,491; 8,917,439; 8,964,282; 9,013,783; 9,116,412; 9,146,439; 9,164,207; 9,170,467; 9,170,468; 9,182,646; 9,195,111; 9,199,441; 9,268,191; 9,285,649; 9,293,511; 9,341,916; 9,360,733; 9,361,836; 9,383,623; and 9,423,666; and U.S. Patent Application Publication Nos. 2008 / 0043318; 2008 / 0048970; 2009 / 0225398; 2010 / 0156780; 2011 / 0043543; 2012 / 0326957; 2013 / 0242378; 2013 / 0278995; 2014 / 0055840; 2014 / 0078576; 2014 / 0340430; 2014 / 0340736; 2014 / 0362213; 2015 / 0103394;2015 / 0118390; 2015 / 0124345; 2015 / 0198858; 2015 / 0234250; 2015 / 0268531; 2015 / 0301246; 2016 / 0011484; 2016 / 0026062; 2016 / 0048054; 2016 / 0116816; 2016 / 0116818; and Patent Nos. 2016 / 0140909; ; (h) Method for driving a display; see, for example, U.S. Patent Nos. 5,930,026; 6,445,489; 6,504,524; 6,512,354; 6,531,997; 6,753,999; 6,825,970; 6,900,851; 6,995,550; 7,012,600; 7,023,420; 7,034,783; 7,061,166; 7,061,662; 7,116,466; 7,119,772; 7,177,066; 7,193,625; 7,202,847; 7,242,514; 7,259,744; 7,304,787; 7,312,794; 7,327,511; 7,408,699; 7,453,445; 7,492,339; 7,528,822; 7,545,358; 7,583,251; 7,602,374; 7,612,760; 7,679,599; 7,679,813; 7,683,606; 7,688,297; 7,729,039; 7,733,311; 7,733,335; 7,787,169; 7,859,742; 7,952,557; 7,956,841; 7,982,479; 7,999,787; 8,077,141; 8,125,501; 8,139,050; 8,174,490; 8,243,013; 8,274,472; 8,289,250; 8,300,006; 8,305,341; 8,314,784; 8,373,649; 8,384,658; 8,456,414; 8,462,102; 8,514,168; 8,537,105; 8,558,783; 8,558,785; 8,558,786; 8,558,855; 8,576,164; 8,576,259; 8,593,396; 8,605,032; 8,643,595; 8,665,206; 8,681,191; 8,730,153; 8,810,525; 8,928,562; 8,928,641; 8,976,444; 9,013,394; 9,019,197; 9,019,198; 9,019,318; 9,082,352; 9,171,508; 9,218,773; 9,224,338; 9,224,342; 9,224,344; 9,230,492; 9,251,736;U.S. Pat. Nos. 9,262,973; 9,269,311; 9,299,294; 9,373,289; 9,390,066; 9,390,661; and 9,412,314; and U.S. Patent Application Publication Nos. 2003 / 0102858; 2004 / 0246562; 2005 / 0253777; 2007 / 0091418; 2007 / 0103427; 2007 / 0176912; 2008 / 0024429; 2008 / 0024482; 2008 / 0136774; 2008 / 0291129; 2008 / 0303780; 2009 / 0174651; 2009 / 0195568; 2009 / 0322721; 2010 / 0194733; 2010 / 0194789; 2010 / 0220121; 2010 / 0265561; 2010 / 0283804; 2011 / 0063314; 2011 / 0175875; 2011 / 0193840; 2011 / 0193841; 2011 / 0199671; 2011 / 0221740; 2012 / 0001957; 2012 / 0098740; 2013 / 0063333; 2013 / 0194250; 2013 / 0249782; 2013 / 0321278; 2014 / 0009817; 2014 / 0085355; 2014 / 0204012; 2014 / 0218277; 2014 / 0240210; 2014 / 0240373; 2014 / 0253425; 2014 / 0292830; 2014 / 0293398; 2014 / 0333685; 2014 / 0340734; 2015 / 0070744; 2015 / 0097877; 2015 / 0109283; 2015 / 0213749; 2015 / 0213765; 2015 / 0221257; 2015 / 0262255; 2015 / 0262551; 2016 / 0071465; 2016 / 0078820; 2016 / 0093253; 2016 / 0140910; and 2016 / 0180777 (these patents and applications may hereinafter be referred to as the MEDEOD (Methods for Driving Electro-Optical Displays) applications); (i) Applications of the display; see, for example, U.S. Pat. Nos. 7,312,784 and 8,009,348; and (j) Non-electrophoretic displays, such as U.S. Patent No. 6,241,921; U.S. Patent Application Publication No. 2015 / 0277160; and U.S. Patent Application Publication Nos. 2015 / 0005720 and 2016 / 0012710.

[0016] Many of the above patents and applications recognize that the walls surrounding discrete microcapsules in a capsule-based electrophoretic medium can be replaced by a continuous phase, resulting in so-called polymer-dispersed electrophoretic displays, where the electrophoretic medium comprises a plurality of discrete droplets of electrophoretic fluid and a continuous phase of polymeric material, and the electrophoretic fluid of the discrete droplets within such polymer-dispersed electrophoretic displays can be considered capsules or microcapsules even without discrete capsule membranes associated with each individual droplet; see, e.g., U.S. Patent No. 6,866,760. Thus, for the purposes of this application, such polymer-dispersed electrophoretic media are considered a sub-species of capsule-based electrophoretic media.

[0017] A related type of electrophoretic display is the so-called "microcell electrophoretic display". In a microcell electrophoretic display, instead of loading charged particles and fluid into microcapsules, they are held within a plurality of cavities formed within a carrier medium (e.g., a polymeric film). See, e.g., U.S. Patents Nos. 6,672,921 and 6,788,449.

[0018] Although electrophoretic media are typically light-opaque (because, for example, in many electrophoretic media, the particles substantially block the transmission of visible light through the display) and operate in a reflective mode, some electrophoretic displays can be made to operate in a so-called "shutter mode", in which one display state is substantially light-opaque and one display state is light-transmissive. See, e.g., U.S. Patents Nos. 5,872,552; 6,130,774; 6,144,361; 6,172,798; 6,271,823; 6,225,971; and 6,184,856. Dielectrophoretic displays (which are similar to electrophoretic displays but rely on changes in electric field strength) can operate in a similar mode; see U.S. Patent No. 4,418,346. Other types of electro-optic displays are also capable of operating in a shutter mode. Electro-optic media operating in a shutter mode can be used in multi-layer structures for full-color displays; in such structures, at least one layer adjacent to the viewing surface of the display operates in a shutter mode to expose or hide a second layer further from the viewing surface.

[0019] An encapsulated electrophoretic display generally does not suffer from the clustering and settling failure modes of conventional electrophoretic devices and offers additional advantages such as the ability to print or coat the display on a variety of flexible and rigid substrates. (The use of the word "print" is intended to include all forms of printing and coating, including but not limited to: pre-metered coatings (e.g., patch die coating, slot or extrusion coating, slide or cascade coating, and curtain coating); roll coating (e.g., knife over roll coating and forward and reverse roll coating); gravure coating; dip coating; spray coating; meniscus coating; spin coating; brush coating; air-knife coating; silk screen printing processes; electrostatic printing processes; thermal printing processes; ink jet printing processes; electrophoretic deposition (see U.S. Patent No. 7,339,715); and other similar techniques). Thus, the resulting display can be flexible. Moreover, because the display medium can be printed (using a variety of methods), the display itself can be manufactured inexpensively.

[0020] As described above, the simplest known electrophoretic media essentially exhibit only two colors. Such electrophoretic media use a single type of electrophoretic particle having a first color in a colored fluid having a second different color (in which case, when the particles are adjacent to the viewing surface of the display, the first color is displayed, and when the particles are spaced apart from the viewing surface, the second color is displayed) or use first and second types of electrophoretic particles having different first and second colors in a colorless fluid (in which case, when the first type of particles are adjacent to the viewing surface of the display, the first color is displayed, and when the second type of particles are adjacent to the viewing surface, the second color is displayed). Typically, the two colors are black and white. If full-color display is desired, a color filter array can be deposited on the viewing surface of a monochromatic (black and white) display. Displays with color filter arrays rely on area sharing and color blending to produce color stimuli. The available display area is shared among three or four primary colors such as red / green / blue (RGB) or red / green / blue / white (RGBW), and the filters can be arranged in a 1-dimensional (line) or 2-dimensional (2×2) repeating pattern. The selection of other primary colors or more than three primary colors is also known in the art. Three (in the case of an RGB display) or four (in the case of an RGBW display) subpixels are selected to be small enough so that at a predetermined viewing distance they visually blend together into a single pixel with a uniform color stimulus ("color blending"). An inherent disadvantage of area sharing is that the colorants are always present, and the color can only be modulated by switching the corresponding pixels of the underlying monochromatic display to black or white (turning on or off the corresponding primary colors). For example, in an ideal RGBW display, each of the red, green, blue, and white primary colors occupies 1 / 4 of the display area (one of four subpixels), and the white subpixel is as bright as the underlying white monochromatic display, and each of the colored subpixels is no brighter than 1 / 3 of the white monochromatic display. The brightness of the white shown by the display is generally no greater than half the brightness of the white subpixel (by displaying one white subpixel out of every four subpixels, and each colored subpixel in the form of an equivalent of 1 / 3 of a white subpixel, the white area of the display is produced, so the combination of three colored subpixels contributes no more than one white subpixel). The brightness and saturation of the color are reduced by area sharing and switching the colored pixels to black. Area sharing can be particularly problematic when mixing yellow because it is lighter than any other color of the same brightness, and saturated yellow is almost as bright as white. Switching the blue pixel (1 / 4 of the display area) to black makes the yellow too dark.

[0021] U.S. Patents Nos. 8,576,476 and 8,797,634 describe multicolor electrophoretic displays having a single backplane with individually addressable pixel electrodes and a common transparent front electrode. A plurality of electrophoretic layers are disposed between the backplane and the front electrode. The displays described in these applications are capable of presenting any primary color (red, green, blue, cyan, magenta, yellow, white, and black) at any pixel location. However, there are disadvantages to using multiple electrophoretic layers between a single set of addressing electrodes. The electric field experienced by the particles in a particular layer is lower than in the case of a single electrophoretic layer addressed with the same voltage. In addition, optical losses (e.g., caused by light scattering or unwanted absorption) in the electrophoretic layer closest to the viewing surface may affect the appearance of the image formed in the underlying electrophoretic layer.

[0022] Attempts have been made to provide full-color electrophoretic displays using a single electrophoretic layer. For example, U.S. Patent No. 8,917,439 describes a color display that includes an electrophoretic fluid containing one or two types of pigment particles dispersed in a transparent and colorless or colored solvent. The electrophoretic fluid is disposed between a common electrode and a plurality of pixel or driving electrodes. The driving electrodes are configured to expose a background layer. U.S. Patent No. 9,116,412 describes a method for driving a display unit filled with an electrophoretic fluid containing two types of charged particles having opposite charge polarities and two contrasting colors. The two types of pigment particles are dispersed in a colored solvent or in a solvent containing uncharged or slightly charged colored particles. The method includes driving the display unit by applying a driving voltage that is about 1% to about 20% of the full driving voltage to display the color of the solvent or the color of the uncharged or slightly charged colored particles. U.S. Patents Nos. 8,717,664 and 8,964,282 describe an electrophoretic fluid and a method for driving an electrophoretic display. The fluid contains first, second, and third types of pigment particles, all of which are dispersed in a solvent or solvent mixture. The first and second types of pigment particles have opposite charge polarities, and the charge level of the third type of pigment particle is less than the charge level of the first or second type of pigment particle by about 50%. The three types of pigment particles have different levels of critical voltage or different levels of mobility, or both.

[0023] Electrophoretic displays capable of presenting any color at any pixel position have been described in U.S. Patent Nos. 10,475,399 and 10,678,111. In the '399 patent, a display is described in which white (light-scattering) pigments move in one direction when addressed with a low applied voltage and in the opposite direction when addressed with a higher voltage. In the '111 patent, a full-color electrophoretic display is described in which there are four pigments: white, cyan, magenta, and yellow, with two pigments being positively charged and two pigments being negatively charged. U.S. Patent Publication No. 2022 / 0082896 describes a full-color electrophoretic display in which there are four pigments: white, cyan, magenta, and yellow, with three of the colored pigments being positively charged and the white pigment being negatively charged. Embodiments of this type of invention are referred to as CMYW embodiments.

[0024] In addition, there are multi-particle display designs in which colored pigments scatter light (i.e., reflect colored particles). U.S. Patent No. 10,339,876 describes a display of this type that has black, white, and red particles capable of presenting three states. A similar display design with four pigments can present four different colors, see, for example, U.S. Patent No. 9,922,603, or by using translucent colored particles, such a display can present six colors, see, for example, U.S. Patent No. 11,640,803. Many multi-particle display designs using light-scattering particles involve long and "flashing" updates, which some viewers find unappealing. The solutions described below can be used to reduce the "flashing" of updates in such displays and, in some cases, reduce the update time. SUMMARY OF THE INVENTION

[0025] This disclosure relates to improved methods for driving a full-color electrophoretic display and full-color electrophoretic displays using these driving methods. In one aspect, the present invention relates to an electrophoretic display that includes: a light-transmissive electrode; an active matrix backplane that includes a plurality of pixel electrodes, each pixel electrode being coupled to a thin-film transistor that includes a gate line and a source line, and each pixel electrode being coupled to a storage capacitor; and an electrophoretic medium disposed between the light-transmissive electrode and the active matrix backplane, wherein the electrophoretic medium includes at least three different types of charged pigment particles. The electrophoretic display also includes a controller that is coupled to a plurality of gate lines of the plurality of pixel electrodes and a plurality of source lines of the plurality of pixel electrodes, the controller being configured to address the pixel electrodes in a column-by-column manner. The controller is configured to update an image on the electrophoretic display by performing the following steps: addressing a first column of pixel electrodes by providing a first gate voltage at a first time; addressing a second column of pixel electrodes by providing a second gate voltage at a second time; addressing the first column of pixel electrodes by providing a third gate voltage at a third time; addressing the second column of pixel electrodes by providing a fourth gate voltage at a fourth time; and addressing the first column of pixel electrodes by providing a fifth gate voltage at a fifth time, wherein the first time, the second time, the third time, the fourth time, and the fifth time are different, and the time elapsed between the first time and the third time is shorter than the time elapsed between the third time and the fifth time.

[0026] In one embodiment, the time elapsed between the third time and the fifth time is at least twice the time elapsed between the first time and the third time. In one embodiment, the time elapsed between the first time and the third time is less than 20 milliseconds, optionally less than 10 milliseconds, and optionally about 8 milliseconds. In one embodiment, the controller simultaneously provides a first source voltage to a pixel of the first column of pixel electrodes at the first time and a second source voltage to the pixel of the first column of pixel electrodes at the third time, and the polarities of the first source voltage and the second source voltage are opposite. In one embodiment, the amplitudes of the first source voltage and the second source voltage are different. In one embodiment, the amplitudes of the first source voltage and the second source voltage are between -15V and +15V or between -24V and +24V. In one embodiment, the controller simultaneously provides a third source voltage to the pixel of the first column of pixel electrodes at the fifth time. In one embodiment, the first source voltage and the third source voltage have the same polarity and amplitude. In one embodiment, when the controller updates the image, a portion of the electrophoretic medium above a pixel electrode in the first column of pixel electrodes and a portion of the electrophoretic medium above a pixel electrode in the second column of pixel electrodes undergo the same color transition. In one embodiment, the controller performs the following additional steps: addressing a third column of pixel electrodes by providing a sixth gate voltage at a sixth time; and addressing the third column of pixel electrodes by providing a seventh gate voltage at a seventh time, wherein the first time, the second time, the third time, the fourth time, the fifth time, the sixth time, and the seventh time are different, and the time elapsed between the first time and the third time is the same as the time elapsed between the sixth time and the seventh time. In one embodiment, there are n columns of pixel electrodes in the active matrix backplane, and the first column of pixel electrodes and the second column of pixel electrodes are separated by n / 2 columns of pixel electrodes. In one embodiment, the controller provides at least two individual gate voltages to each thin film transistor of the active matrix backplane between the first time and the fifth time. In one embodiment, the electrophoretic medium includes a reflective white particle and at least one color-reducing particle or a reflective white particle and at least one reflective color particle. In one embodiment, the electrophoretic medium includes a fourth type of electrophoretic particle. In one embodiment, two of the types of particles are negatively charged, and two of the types of particles are positively charged, or one of the types of particles is negatively charged, and three of the types of particles are positively charged, or three of the types of particles are negatively charged, and one of the types of particles is positively charged. In one embodiment, the electrophoretic medium is encapsulated in microcapsules or microcells. Brief Description of the Drawings

[0027] FIG. 1A is a representative cross-section of a four-particle electrophoretic display, where the electrophoretic medium is encapsulated in capsules. The structure of FIG. 1A can be used for a multi-particle electrophoretic medium having reflective pigment particles and subtractive pigment particles;

[0028] FIG. 1B is a representative cross-section of a four-particle electrophoretic display, where the electrophoretic medium is encapsulated in microcells. The structure of FIG. 1B can be used for a multi-particle electrophoretic medium having reflective pigment particles and subtractive pigment particles;

[0029] FIG. 2 illustrates an exemplary equivalent circuit of a single pixel of an electrophoretic display with an active matrix backplane using a pixel electrode coupled to a storage capacitor;

[0030] FIG. 3 is a schematic diagram of an exemplary driving system for controlling the voltage supplied to a pixel electrode in an active matrix device. The resulting driving voltage can be used to set the optical state of a multi-particle electrophoretic medium.

[0031] FIG. 4 illustrates an exemplary electrophoretic display including a display module. The electrophoretic display also includes a processor, a memory, one or more power supplies, and a controller. The electrophoretic display may also include sensors to allow the electrophoretic display to adjust operating parameters according to the surrounding environment (e.g., temperature and lighting);

[0032] FIG. 5 illustrates the preferred positions of each of four sets of particles for generating eight standard colors in a white - cyan - magenta - yellow (WCMY) four-particle electrophoretic display, where the white particles are reflective and the cyan, magenta, and yellow particles are absorptive;

[0033] FIG. 6A shows an exemplary push-pull driving scheme for addressing an electrophoretic medium containing three subtractive (cyan, yellow, magenta) particles and one scattering (white) particle;

[0034] FIG. 6B shows an exemplary push-pull driving scheme for addressing an electrophoretic medium containing one absorptive (black) particle, two reflective (red, yellow) particles, and one scattering (white) particle;

[0035] FIG. 7 depicts a "typical" driving waveform transmitted to a pixel electrode during a single update from a first color to a second color. In particular, the waveform includes repeated push-pull voltages;

[0036] Figure 8A illustrates the color transients that occur when addressing an electrophoretic display having a repeating dipole pair of a first 5 ms pulse of +24 V and a second 10 ms pulse of -12 V and containing white reflective particles and subtractive particles of cyan, yellow, and magenta (measured by filter color optical density = analytical density);

[0037] Figure 8B illustrates the color transients that occur when addressing an electrophoretic display having a repeating dipole pair of a first 5 ms pulse of -24 V and a second 10 ms pulse of +12 V and containing white reflective particles and subtractive particles of cyan, yellow, and magenta (measured by filter color optical density = analytical density);

[0038] Figure 9 illustrates the smooth variation of the optical density of the displays of Figures 8A and 8B for a generalized push-pull waveform. Figure 9 illustrates that the total length of time to transition to one of the limit cycle colors in the system (i.e., magenta, green, yellow, or blue) is approximately the same regardless of the duration of the individual pulses that make up the dipole;

[0039] Figure 10 illustrates the gate voltage (VG) and source voltage (VS) applied to a thin film transistor coupled to a pixel electrode using the method of the present invention. In addition, the voltage (VP) across the electrophoretic medium is also shown. The voltage across the electrophoretic medium is maintained by a storage capacitor associated with each pixel electrode (see Figure 2);

[0040] Figure 11 is a general description of the driving method of the present invention, where subsequent electrode columns are not driven in a typical column-by-column manner. This driving method results in non-uniform intervals between three consecutive gate pulses for a single image update. In many cases, each pixel of the backplane receives two gate pulses before any pixel receives a third gate pulse;

[0041] Figure 12 depicts an embodiment of the low-flash memory update scheme of the present invention;

[0042] Figure 13 depicts an embodiment of the low-flash memory update scheme of the present invention;

[0043] Figure 14 depicts an embodiment of the low-flash memory update scheme of the present invention;

[0044] Figure 15 provides more details of the driving scheme depicted in Figure 14;

[0045] FIG. 16A depicts column-by-column driving of the prior art for comparison with an embodiment of the present invention shown in FIG. 16B;

[0046] FIG. 16B provides more details of the driving scheme depicted in FIG. 14. Embodiments

[0047] The present invention includes an electrophoretic display having a multi-particle electrophoretic medium and an improved method for driving such a multi-particle electrophoretic medium. The display of the present invention generally includes an active matrix backplane of pixel electrodes controlled by thin film transistors, wherein each pixel electrode is also coupled to a storage capacitor. Although the driving method of the display can be generalized to any electrophoretic display using push-pull waveforms, the display of the present invention is preferably used to drive more complex electrophoretic media, for example, which require precise control of three, four, or more types of particles simultaneously. The advantage is that the display incorporating the disclosed driving scheme generally appears to be less "flickery" compared to addressing using traditional column-by-column fixed frame rate updates that have been the state of the art for decades. Such a display can include multiple subtractive color electrophoretic particles and / or multiple reflective color electrophoretic particles. In a preferred embodiment, the electrophoretic medium includes white particles and cyan, yellow, and magenta subtractive primary color particles, i.e., the WCMY system.

[0048] Methods for manufacturing electrophoretic displays containing four (or more) types of particles have been described in the prior art. The electrophoretic fluid can be encapsulated in microcapsules or contained in microcell structures, which are then sealed with a polymer layer. The microcapsules or microcell layers can be coated or laminated onto a plastic substrate or film with a coating of transparent conductive material. Alternatively, the microcapsules can be coated onto a light-transmissive substrate or other electrode material using spraying techniques. (See U.S. Patent No. 9,835,925, which is incorporated herein by reference). The resulting assembly can be laminated to a backplane with pixel electrodes using a conductive adhesive. Alternatively, the assembly can be attached to one or more segmented electrodes on the backplane, where the segmented electrodes are directly driven.

[0049] The present invention provides an architecture and method for addressing a dipole electrophoresis display using a thin film transistor array. In a first embodiment, both pulses of the dipole are provided at the (conventional) frame rate of the display, which is different from the prior art method that requires each pulse in the dipole to have a duration of at least one frame. In an embodiment of the present invention, the total time length of the dipole is equal to the duration of a conventional frame. In a second embodiment, the columns of the display are divided into two groups, each group being scanned twice to complete a full update frame. The first embodiment of the display allows a flexible selection of the ratio between the time lengths of the "push" and "pull" pulses in the dipole, while in the second embodiment, the ratio of the "push" to "pull" durations is 3:1. An electrophoretic composition is provided that allows the display to be addressed to produce a color image without visible flicker or flashing.

[0050] The electrophoretic medium used herein comprises charged particles having different colors, reflection or absorption characteristics, charge densities, and mobilities in an electric field (measured as zeta potential). Particles that absorb, scatter, or reflect broadband or selected wavelength light are referred to herein as colored or pigment particles. Various light-absorbing or light-reflecting materials other than pigments (which in the strict sense of the term are insoluble colored materials), such as dyes, photonic crystals, quantum dots, etc., can also be used in the electrophoretic medium and display of the present invention. For example, the electrophoretic medium can comprise a fluid; a plurality of first particles and a plurality of second particles dispersed in the fluid, the first particles and the second particles having opposite polarities of charge, the first particles being light-scattering particles, and the second particles having one of the subtractive primary colors; and a plurality of third particles and a plurality of fourth particles dispersed in the fluid, the third particles and the fourth particles having opposite polarities of charge, the third and fourth particles each having a subtractive primary color different from each other and different from the second particles, wherein the electric field required to separate the aggregates formed by the third and fourth particles is greater than the electric field required to separate the aggregates formed by any other two types of particles.

[0051] The electrophoretic medium of the present invention can comprise any additives used in conventional electrophoretic media described, for example, in the above-mentioned E Ink and MIT patents and applications. Thus, for example, the electrophoretic medium of the present invention typically comprises at least one charge control agent to control the charge on the various particles, and the fluid can have a polymer dissolved or dispersed therein, wherein the polymer has a number average molecular weight of more than about 20,000 and is substantially non-absorbent on the particles to improve the bistability of the display, as described in the aforementioned U.S. Patent No. 7,170,670.

[0052] In one embodiment, the present invention uses a light-scattering particle (usually white) and three substantially non-light-scattering particles. Of course, there are no completely light-scattering particles or completely non-light-scattering particles, and the minimum light-scattering degree of the light-scattering particles used in the electrophoresis of the present invention and the maximum light-scattering degree tolerable in the substantially non-light-scattering particles may vary somewhat, depending on factors such as the exact pigments used, their colors, and the ability of the user or application to tolerate some deviation from the desired ideal color. The scattering and absorption characteristics of the pigments can be evaluated by measuring the diffuse reflectance of a pigment sample dispersed in a suitable matrix or liquid against white and dark backgrounds. The results from such measurements can be interpreted according to some models well known in the art (e.g., one-dimensional Kubelka-Munk treatment). In the present invention, preferably, when the white pigment is distributed nearly isotropically at 15 vol% in a 1-μm-thick layer containing the white pigment and a liquid with a refractive index less than 1.55, the white pigment exhibits at least 5% diffuse reflectance measured against a black background at 550 nm. The yellow, magenta, and cyan pigments preferably exhibit less than 2.5% diffuse reflectance measured against a black background at 650, 650, and 450 nm, respectively, under the same conditions. (The wavelengths selected above for measuring the yellow, magenta, and cyan pigments correspond to the spectral regions of minimum absorption of these pigments.) Colored pigments that meet these criteria are hereinafter referred to as "non-scattering" or "substantially non-light-scattering". Specific examples of suitable particles are disclosed in U.S. Patent No. 9,921,451, which is incorporated herein by reference.

[0053] Alternative particle sets can also be used, including four sets of reflective particles, or one set of absorbing particles and three or four sets of different reflective particles, i.e., as described in U.S. Patent Nos. 9,922,603 and 10,032,419, which are hereby incorporated by reference. For example, the white particles can be formed from inorganic pigments such as TiO 2, ZrO 2, ZnO, Al 2O 3, Sb 2O 3, BaSO 4, PbSO 4, etc., while the black particles can be formed from CI pigment black 26 or 28, etc. (e.g., manganese ferrite black spinel or copper chromite black spinel) or carbon black. The third / fourth / fifth type of particles can have colors such as red, green, blue, magenta, cyan, or yellow. Pigments for this type of particles can include, but are not limited to, CI pigment PR 254, PR 122, PR 149, PG 36, PG 58, PG 7, PB 28, PB 15:3, PY 138, PY 150, PY 155, or PY 20. 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.

[0054] As shown in FIGS. 1A and 1B, electrophoretic displays (101, 102) typically include a top transparent electrode 110, an electrophoretic medium 120, and a bottom electrode 130, where the bottom electrode 130 is typically a pixel electrode of a pixel active matrix controlled by thin film transistors (TFTs). In the electrophoretic medium 120 described herein, there are four different types of particles 121, 122, 123, and 124, although more (or fewer) particle sets can be used in the methods and displays described herein. For example, the techniques of the present invention can be used with three types of particles, e.g., white, black, and red, where one of the three different types of particles has a charge value lower than the other two types of particles. In some cases, two particles will be positively charged and one (or two) particles will be negatively charged. In some cases, one particle will be positively charged and three particles will be negatively charged. In some cases, one particle will be negatively charged and three particles will be positively charged. The electrophoretic medium 120 is typically divided by microcapsules 126 or the walls 127 of microcells. An optional adhesive layer 140 can be provided adjacent to any layer, however, it is typically adjacent to an electrode layer (110 or 130). More than one adhesive layer 140 can be present in a given electrophoretic display (105, 106), however, it is more common to have only one layer. The entire display stack is typically disposed on a substrate 150, which can be rigid or flexible. The displays (101, 102) typically also include a protective layer 160, which can simply protect the top electrode 110 from damage, or it can enclose the entire display (101, 102) to prevent water ingress, etc. As needed, the electrophoretic displays (101, 102) can also include a sealing layer 180. In some embodiments, the adhesive layer 140 can include a primer component to improve adhesion to the electrode layer 110, or a separate primer layer (not shown in FIG. 1B) can be used. The structure and component parts, pigments, adhesives, electrode materials, etc. of electrophoretic displays are described in many patents and patent applications published by E Ink Corporation, e.g., U.S. Pat. Nos. 6,922,276; 7,002,728; 7,072,095; 7,116,318; 7,715,088; and 7,839,564, which are hereby incorporated by reference in their entirety.

[0055] In some embodiments, for example, as shown in FIG. 1A, an electrophoretic display may include a light-transmissive electrode, an electrophoretic medium, and a plurality of rear pixel electrodes. To produce, for example, a high-resolution display for displaying images, each pixel electrode 130 is individually addressable without interference from adjacent pixels, such that an image file is faithfully reproduced on the display. One way to achieve this goal is to provide an array of non-linear elements (e.g., transistors or diodes), where at least one non-linear element is associated with each pixel to produce an “active matrix” display (see FIG. 2). The addressing or pixel electrode 130 for a pixel is connected to an appropriate voltage source through an associated non-linear element. Typically, when the non-linear element is a transistor, the pixel electrode is connected to the drain of the transistor, and this configuration will be adopted in the following description, but it is substantially arbitrary, so the pixel electrode can be connected to the source of the transistor.

[0056] Traditionally, in a high-resolution array, pixels are arranged in a two-dimensional array of columns and rows such that any particular pixel is uniquely defined by the intersection of a designated column and a designated row (see FIG. 3). The sources of all the transistors in each row are connected to a single row electrode, and the gates of all the transistors in each column are connected to a single column electrode; similarly, the source-to-column and gate-to-row assignments are conventional but substantially arbitrary, and thus can be reversed if desired. The column electrodes are typically connected to a column driver (gate driver, gate controller), which substantially ensures that only one column is selected at any given time, i.e., a selection voltage is applied to the selected column electrode to ensure that all the transistors in the selected column are turned on, while a non-selection voltage is applied to all the other columns to ensure that all the transistors in these non-selected columns remain off. The row electrodes are typically connected to a row driver (source driver, source controller), which applies a selected voltage to each of the row electrodes to drive the pixels in the selected column to their desired optical state. (The above voltages are relative to a common front electrode, which is typically disposed on the side of the electro-optic medium opposite the non-linear array and extends across the entire display.) After a preselected interval called the “line address time,” the selection of the deselected column is canceled, the next column is selected, and the voltage on the row driver is changed to write the next row of the display. This process is repeated to write the entire display column by column. The time between successive updates of a particular column in the display is called a “frame.” Thus, a display updated at 60 Hz has a frame with a time length of 16 milliseconds. Multiple frame times can be used for electrophoretic displays, for example, 8 millisecond frames, 12 millisecond frames, 5 millisecond frames, etc. In some cases, the frame is greater than 1 millisecond and less than 30 milliseconds.

[0057] It should be noted that the magnitude of the voltage that can be provided in such a row drive may be limited by the materials used to fabricate non-linear elements (e.g., thin-film transistors). In many embodiments, the semiconductor material is silicon, particularly amorphous silicon, which can control the drive voltage to approximately ±15V. In other embodiments, the semiconductor of the thin-film transistor can be a metal oxide, such as indium gallium zinc oxide (IGZO), which allows a wider range of drive voltages, e.g., up to ±30V, as described in U.S. Patent Publication No. 2022 / 0084473. This design feature is particularly appropriate when the drive waveform is used to classify pigments in a multi-particle system. In such a system, it is advantageous to provide at least five voltage levels (high positive voltage, low positive voltage, zero voltage, low negative voltage, high negative voltage), and the higher the total voltage, the easier it is to separate the particles. For more details, see U.S. Patent Publication No. 2021-0132459.

[0058] FIG. 2 in the accompanying drawings depicts an exemplary equivalent circuit of a single pixel of an electrophoretic display. As shown, the circuit includes a storage capacitor 10 formed between the pixel electrode (element 130 in FIGS. 1A and 1B) and the capacitor electrode. The electrophoretic medium 20 is represented as a capacitor and a resistor in parallel. In some cases, the direct or indirect coupling capacitance 30 (commonly referred to as "parasitic capacitance") between the gate electrode of the transistor associated with the pixel and the pixel electrode may generate unwanted noise in the display. Generally, the parasitic capacitance 30 is much smaller than the capacitance of the storage capacitor 10, and when the pixel columns of the display are selected or deselected, the parasitic capacitance 30 may generate a small negative bias on the pixel electrode, which is also referred to as the kickback voltage, and is typically less than 2 volts. [In some embodiments, to compensate for the unwanted "kickback voltage", a common potential Vcom can be provided to the top plate electrode and the capacitor electrode associated with each pixel, such that when Vcom is set to a value equal to the kickback voltage (VKB), each voltage applied to the display may be offset by the same amount and will not experience a net DC imbalance.]

[0059] In a conventional electrophoretic display using an active matrix backplane, each pixel electrode has a capacitor electrode (storage capacitor) associated with it, such that the pixel electrode and the capacitor electrode form a capacitor. See, for example, International Patent Application WO 01 / 07961. In some embodiments, an N-type semiconductor (e.g., amorphous silicon) can be used to form the transistor, and the "select" and "deselect" voltages applied to the gate electrode can be positive and negative, respectively.

[0060] Additional details of row and column addressing used in an "active matrix" display are shown in FIG. 3. The addressing electrodes or pixel electrodes for addressing a pixel are fabricated on substrate 402 and are connected to appropriate voltage sources 404 and 406 through associated nonlinear elements. It should be understood that voltage sources 404 and 406 may originate from different circuit elements or may convey voltages with the help of a single power supply and a power management integrated circuit (PMIC). In some cases, an intervening source controller 420 is used to control the voltages provided, whereas in other embodiments, controller 460 is configured to control the entire addressing process, which includes coordinating the gate lines and source lines. It should also be understood that FIG. 3 is an illustration of the layout of active matrix backplane 400, but in reality, the active matrix has depth and some elements (e.g., TFTs) may actually be located under the pixel electrodes, with vias providing electrical connection from the drain to the pixel electrode above.

[0061] Traditionally, in a high-resolution array, pixels are arranged in a two-dimensional array of columns and rows such that any particular pixel is uniquely defined by the intersection of a designated column and a designated row. The sources of all the transistors in each row are connected to a single row (scan) line 406, while the gates of all the transistors in each column are connected to a single column (gate) line 408; likewise, the source-to-column and gate-to-row assignments are conventional but are substantially arbitrary and can be reversed if desired. The gate line 408 is optionally connected to a gate controller 430, which substantially ensures that only one column is selected at any given moment, i.e., a select voltage is applied to the selected column electrodes to ensure that all the transistors in the selected column are conducting, while a non-select voltage is applied to all the other columns to ensure that all the transistors in these non-selected columns remain non-conducting. The row scan line 406 is optionally connected to a source controller 420, which applies the selected voltages on the respective scan lines 406 to drive the pixels in the selected column to their desired optical states. (The above voltages are relative to a common top electrode and are not shown in FIG. 3.) For conventional driving, after a preselected interval called the "row address time", the selection of the deselected column is cancelled, the next column is selected, and the voltage on the row driver is changed in order to write the next row of the display. In a "typical" backplane drive, this process is repeated linearly in order to write the entire display column by column. As shown in FIG. 3, the time interval between the gate voltage pulses for each frame is typically fixed and represents the rhythm of row-by-row addressing. It should be noted that the present invention does not enforce a uniform interval between the individual gate voltage pulses for the pixel electrodes of a given addressed column.

[0062] The active matrix backplane described with respect to FIG. 3 is coupled to an electro-optic medium such as shown in FIGS. 1A and 1B and is typically sealed to form a display module 55 as shown in FIG. 4. Such a display module 55 is the focus of the electrophoretic display 40. The electrophoretic display 40 will typically include a processor 50 configured to coordinate a number of functions related to displaying content on the display module 55 and to convert a “standard” image such as an sRGB image into a color regime that can best reproduce the image on the display module 55. Of course, if the electrophoretic display is used as a sensor or a counter, the content can be related to other inputs. The processor is typically a mobile processor chip such as made by Freescale or Qualcomm, but other manufacturers are also known. The processor frequently communicates with a non-transitory memory 70 from which the processor fetches image files and / or lookup tables to perform the color image conversion described below. The non-transitory memory 70 may also contain gate drive instructions such that different gate drive patterns may be required for specific color transitions. The electrophoretic display 40 may have more than one non-transitory memory chip. The non-transitory memory 70 may be flash memory. Once the desired image has been converted for display on the display module 55, specific image instructions are sent to a controller 60 which facilitates sending a voltage sequence to the respective thin film transistors (as described above). Such voltages typically originate from more than one power source 80 which may include, for example, a power management integrated circuit (PMIC). The electrophoretic display 40 may additionally include a communication facility 85 which may be, for example, a WIFI protocol or Bluetooth and which allows the electrophoretic display 40 to receive images and instructions which may also be stored in the memory 70. The electrophoretic display 40 may additionally include more than one sensor 90 which may include a temperature sensor and / or a light sensor and such information may be fed to the processor 50 to allow the processor to select an optimal lookup table in cases where the lookup table is indexed against the ambient temperature or the incident illumination intensity or spectrum. In some cases, multiple components of the electrophoretic display 40 may be embedded in a single integrated circuit. For example, an application specific integrated circuit may implement the functions of the processor 50 and the controller 60.

[0063] As shown in FIG. 5, the advanced color electrophoretic composition ACEP (e.g., comprising a WCMY particle system) works in principle similarly to printing on bright white paper, because the viewer only sees those colored pigments on the viewing side of the white pigment (i.e., the only pigment that scatters light). In FIG. 5, it is assumed that the viewing surface of the display is at the top (as shown), i.e., the user views the display from this direction, and the illumination light also enters from this direction. In FIG. 5, it is assumed that the light-scattering particles are white pigments. These light-scattering white particles form a white reflector, against which any particles above the white particles can be viewed (as shown in FIG. 5). A portion of the incident light passes through the subtractive particles, reflects from the white particles below the subtractive particles, passes back through these particles, and exits from the display. Different portions of the incident light are absorbed by the subtractive particles. Thus, the particles above the white particles can absorb various colors, and the color presented to the user is the color produced by the combination of the particles above the white particles. Any particles arranged below the white particles (behind from the user's perspective) are shielded by the white particles and do not affect the displayed color. Since the second, third, and fourth particles are substantially non-light-scattering, their order or arrangement relative to each other is not important, but due to the reasons already stated, their order or arrangement relative to the white (light-scattering) particles is crucial.

[0064] More specifically, when the cyan, magenta, and yellow particles are located below the white particles (Case [A] in FIG. 5), there are no particles above the white particles, and the pixel simply shows white. When a single type of particle is located above the white particles, the color of this single type of particle is shown, which are yellow, magenta, and cyan in Cases [B], [D], and [F] of FIG. 5, respectively. When two types of particles are located above the white particles, the color shown is the combination of the colors of these two types of particles; in FIG. 5, in Case [C], the magenta and yellow particles show red, in Case [E], the cyan and magenta particles show blue, and in Case [G], the yellow and cyan particles show green. Finally, when all three colored particles are located above the white particles (Case [H] in FIG. 5), all the incident light is absorbed by these three subtractive primary colored particles, and the pixel shows black.

[0065] A subtractive primary color can be presented by particles that scatter light, such that the display will include two types of light-scattering particles, one of which is white and the other is colored. However, in this case, the position of the light-scattering colored particles relative to other colored particles that cover the white particles will be important. For example, when presenting black (when all three colored particles are located above the white particles), the scattering colored particles cannot be located above the non-scattering colored particles (otherwise they will be partially or completely hidden behind the scattering particles, and the color presented will be the color of the scattering colored particles, rather than black).

[0066] Figure 5 shows an ideal situation where the colors are not contaminated (i.e., the light-scattering white particles completely obscure any particles located behind the white particles). In practice, the masking by the white particles may be imperfect, such that particles that would be completely masked in the ideal situation may absorb some small amount of light. This contamination generally reduces the brightness and chromaticity of the colors presented. In the electrophoretic medium of the present invention, such color contamination should be minimized to the extent that the colors formed are commensurate with the industry standards for color rendition. A particularly favored standard is SNAP (Newspaper Advertising Production Standard), which specifically specifies the L*, a*, and b* values for each of the above eight primary colors. (Hereinafter, "primary color" will be used to mean the eight colors of black, white, the three subtractive primary colors, and the three additive primary colors as shown in Figure 5.)

[0067] Figure 6A (in simplified form) shows a typical waveform for driving the above-described four-particle WCMY electrophoretic display system. Such waveforms have a "push-pull" structure: that is, they consist of dipoles that include pulses of two opposite polarities. Generally, each dipole has a pulse of voltage V1 with an application time t1, followed by a pulse of voltage V2 with an application time t2. When V1t1 + V2t2 = 0, the dipole reaches pulse balance. The amplitudes and lengths of these pulses determine the colors obtained. There should be at least five such voltage levels. Figure 6A shows high and low positive and negative voltages, as well as zero volts. Generally, "low" (L) means a range of about 5 - 15 V, and "high" (H) means a range of about 15 - 30 V. Generally speaking, the higher the amplitude of the "high" voltage, the better the color gamut achieved by the display. In some cases, particularly when more colors are needed, medium voltages are also included. The "medium" (M) level is typically about 15 V; however, the value of M depends to some extent on the composition of the particles and the environment of the electrophoretic medium.

[0068] Note that for the dipole waveforms of FIG. 6A, the dipoles used to provide magenta, yellow, green, and blue are at least approximately pulse balanced. On the other hand, it is not necessary to use dipole addressing to produce black and white. A simple monopole pulse in either direction will move the colored and white pigments with opposite charges towards and away from the viewing surface, so the display behaves like a traditional display containing black and white pigments in these cases. Additionally, since these monopole pulses are not DC balanced, an additional charge clearing pulse must be incorporated into the device drive protocol at the start or end of image updates that may occur, for example, when scrolling text, or at the end of an extended unbalanced drive sequence. However, even when the waveforms are overall pulse balanced, dipole addressing will disrupt symmetry. For example, there will be , and . See, for example, Dukhin AS, Dukhin SS, “Aperiodic capillary electrophoresis method using an alternating current electric field for separation of macromolecules.” Electrophoresis, 2005 Jun;26(11):2149-53. Then, as long as the pigment mobility depends on the applied electric field, this waveform will cause overall pigment drift.

[0069] FIG. 6B shows two typical push-pull waveforms for causing the colors of smaller charged particles to appear on the viewing surface of a four-particle system that includes a scattering white particle, an absorbing black particle, and two colored scattering particles (yellow and red). See, for example, U.S. Patent No. 10,339,876. In the example shown in FIG. 6B, the yellow particles have a higher negative charge, while the white particles have a lower negative charge. The black particles have a higher positive charge, while the red particles have a lower positive charge.

[0070] As shown in FIGS. 6A-6B, the duration of one of the pulses of a dipole that is typically used to generate a specific color is shorter than the duration of the other pulse. Furthermore, although FIGS. 6A and 6B show the simplest push-pull waveforms (dipoles) required to form colors, it can be understood that actual waveforms typically require multiple repetitions of these patterns, as shown in FIG. 7. The repeated dipoles are the main source of flicker in the display because the pigments are first driven in one direction and then in the other direction. If the frequency of this flicker is too low, the appearance of the transition from one color to another will be glaring. Therefore, preferably, the length of any one of the pulses of the dipole used to address the display of the present invention is less than about 17 milliseconds, which corresponds to the critical value of human perception of flash (about 60 Hz). Unfortunately, for typical column-by-column driving, where each frame is approximately 10-20 milliseconds, the pulses spanning two frames are usually visible and the overall update experience is considered to be "flickery".

[0071] Nevertheless, when different pigment migration rates are caused by the field effect, it is not necessary to drive the pigments across the width of the cavity that houses the pigments. This provides an option to switch (at least partially) colors without generating (human-perceivable) flicker. For example, this occurs when the field-dependent migration rate is the polarization effect. In this case, since the pigments are much smaller than the cavities that house them, the polarization of the pigments is faster than the polarization of the entire cell. In this case, a frequency higher than the frequency required to switch the pigments from one extreme state to another can be selected for pigment sorting, thereby eliminating human-visible flicker.

[0072] In traditional active matrix addressing, the duration of a pulse of a dipole cannot be shorter than the duration of a frame (a frame = the time to address each pixel from one corner to the diagonal of the active matrix, where each column is addressed sequentially, the time to address each column is the same, and no column is re-addressed until each column in the display has been addressed once). Thus, the longer pulse of the dipole must be an integer multiple of the frame duration length (assuming the display is typically addressed at a fixed frame rate). If the ratio between the longer pulse and the shorter pulse in the dipole is r, and the dipole time is required to be shorter than about 17 ms (approximately the limit of perceptible flicker), then the scan frequency of the display must be higher than 1000 / 17 multiplied by r + 1. For example, if the longer pulse is twice the shorter pulse, then the scan rate of the display must be at least 3000 / 17 = approximately 177 Hz. Higher pulse length ratios would require higher frame rates. Unfortunately, at the current state of the art, providing such high frame rates results in high costs and high power consumption for electronic products. Such advanced electronic products are generally not favored in consumer electronics because the sales of consumer electronics are largely influenced by price.

[0073] Referring again to FIG. 6A, three different types of color transitions can be identified in the push-pull waveforms of the WCMY system. These are referred to herein as "rail states", "rail bounce states", and "limit cycle states". The term "rail" as used in the art of electrophoretic displays refers to the fact that an electric field between two walls of a cavity is used to move the pigments. When the movement of a pigment is restricted by one of these walls, we say it is on a rail, and the process of moving it to that position is called "railing". The two rail states of the WCMY system correspond to black (where all three subtractive pigments are on the viewing surface and the white pigment is on the opposite rail) and white (where the positions of the pigments are reversed).

[0074] In the "rail bounce state", the pigments need to be arranged in one of two rail states, and then the direction of the electric field is reversed in a relatively short time. The colored pigment with the highest mobility will be the pigment that moves fastest through the white pigment and is thus the pigment adjusted during the second pulse period. In the present invention, the rail bounce states are red and cyan. Red is achieved by first switching the display to the black rail state (using a positive pulse) and then pulling back the cyan pigment using a negative pulse, where the length of the negative pulse is not sufficient to significantly transfer the magenta or yellow pigments. Cyan is achieved by reversing this waveform, first providing the white rail state (where the three colored pigments are in the rear rail), and then using a short positive pulse to bring the cyan pigment to the viewing surface. Since the rail bounce state requires all three colored pigments to be guided in the first pulse, this pulse cannot be shorter than the time required for the slowest moving pigment to cross the width of the cavity containing the electrophoretic fluid. Therefore, to avoid visible flicker when creating the rail bounce colors, the time required for the slowest pigment to cross the cavity must be less than 17 ms. In some embodiments of the present invention (where the cavity is very narrow), this is possible, but in other embodiments, it is not. In these cases, flicker occurs when entering the rail bounce state, which can be addressed, for example, by interleaving the update of the pixels in the display.

[0075] The "limit cycle" colors of the present invention are magenta and yellow and their opposite states (green and blue). These colors are obtained using dipole addressing, but compared to the rail bounce state, the length of the pulses in the dipoles does not need to be long enough for any pigment to cross the cavity containing the electrophoretic fluid. In fact, the longest pulse in the dipole sequence used to provide the limit cycle colors can be as short as about 2 milliseconds (or possibly shorter - the equipment used by the inventors to address the experimental display does not allow shorter pulses). Note that the yellow pigment can carry a relatively weak positive or negative charge and still behave in the manner shown in FIGS. 8A - 9.

[0076] Figures 8A and 8B show the optical transients that occur when using an appropriate dipole sequence to generate limit cycle colors. Figures 8A and 8B additionally provide insights into the movement of multiple subtractive particles with different charges relative to each other. The optical transients shown in Figures 8A and 8B are described using "analysis density", which is a metric where the optical density measured by reflection when addressing the display is decomposed into the respective contributions of cyan, magenta, and yellow pigments. In Figure 8A, an experimental display starting in the white state is addressed by a dipole sequence that includes a first pulse of +24V and a duration of 5 ms, followed by a second pulse of -12V and a duration of 10 ms. Between the pulses is a "rest period", i.e., a period during which the display is addressed at 0V for 10 milliseconds. These rest periods are not required to form colors, but due to the limitations of the spectrometer integration used, it is necessary to measure the optical density as the waveform progresses. It can be seen that using this pulse-balanced pulse sequence, all three color pigments move in phase, but the magenta pigment moves further backward in the high-voltage pulse of the dipole than it does in the low-voltage phase. The movement of the cyan pigment is similar to that of the magenta pigment, but with a much larger amplitude, while the yellow pigment never becomes visibly distinct. Thus, at the end of this dipole sequence, the display oscillates between a magenta state (when the cyan pigment retreats) and a blue state (when the cyan pigment advances).

[0077] Figure 8B shows the results when the polarity of the waveform is inverted, i.e., the display is addressed by a dipole sequence that starts from the end point of the waveform shown in Figure 8A and includes a first pulse of -24V and a duration of 5 ms, followed by a second pulse of +12V and a duration of 10 ms. All three colored pigments move in phase again. The magenta pigment retreats further in the high-voltage pulse than it advances during the low-voltage pulse and thus evolves to a position away from the viewing surface. Conversely, the yellow pigment advances further during the low-voltage pulse than it retreats during the high-voltage pulse and thus ultimately reaches the viewing surface. The oscillation amplitude of the cyan pigment is larger than that of the other colored pigments. At the end of this dipole sequence, the display oscillates between a yellow state (when the cyan pigment retreats) and a green state (when the cyan pigment advances).

[0078] In the related representation, FIG. 9 schematically shows how the analytical density due to each of the three color pigments changes during a substantially pulse-balanced dipole sequence at low and high voltages. Importantly, as shown in FIG. 9, regardless of the duration of the pulse constituting the dipole (e.g., in the range of about 1 - 200 ms for each pulse), the total length of the transition to one of the limit cycle colors (magenta, yellow, green, blue) is substantially the same. Thus, considering the limitations of electronic products, it is possible and preferable to make the pulses for the limit cycle colors as short as possible (i.e., shorter than about 17 ms) in order to avoid visible flicker during the transition. The preferred ratio of the lengths of the two pulses in the dipole is in the range of 1:1 - 1:10, with the shorter pulse having the higher voltage.

[0079] If the higher voltage pulse is positive, the display oscillates between magenta and cyan. If the higher voltage pulse is negative, the display oscillates between yellow and green. Optionally, if the pulse is too short for the cyan pigment to reach its preferred position, a "top-up" pulse can be provided at the end of the waveform, adjusting its amplitude and duration to move the cyan pigment with minimal detrimental effect on the yellow and magenta pigments. Note that the same pulse duration ratio can be used to generate any limit cycle color. The analytical representations of FIGS. 8A - 9 are widely applicable to the push - pull waveforms of FIG. 6B, and the following techniques can be used equally successfully to reduce the flash in a multi - particle electrophoretic display having more than one reflective particle. [Offset Gate Pulse Drive]

[0080] Due to the constancy of the pulse ratios for the extreme cycle colors and their insensitivity to pulse width, an alternative addressing scheme can be used that provides a full dipole for every two conventional frames of the backplane (conventional frame = the time to update each pixel of the active matrix backplane only once in a column-by-column manner). This driving is not possible for the conventional column-by-column driving of an active matrix backplane using the push-pull waveforms of FIGS. 6A or 6B, which requires at least three (usually more) frames. Using this alternative drive, shorter individual voltage pulses can be used, and these shorter pulses result in less physical movement of the pigments, so the update appears to be without flicker. Thus, the display can switch between color images with less flicker, which is more satisfactory to the viewer. In principle, one of the dipole pulses is shorter than the time required to scan each column in the display using conventional column-by-column addressing (i.e., one frame). Further selection of the ratio of the two pulse lengths is also possible. In some cases, the entire push-pull pulse can be transmitted during the conventional frame time (i.e., the time required to address each pixel from one corner to the diagonal corner in a column-by-column manner). Importantly, using the method of the present invention, at least one column of pixel electrodes is updated two (or more) times before each pixel electrode in the active matrix is updated once.

[0081] An exemplary green push-pull waveform (see FIG. 6A) using the drive scheme of the present invention is shown in FIG. 10 (which is not drawn to scale). It is understood that FIG. 10 is merely exemplary, and the driving method can be used for other colors and for subtractive and reflective particle systems. In addition, the three voltage plots of FIG. 10 all represent the voltage provided as a function of time. The space between each hash along the x-axis represents a conventional frame time, i.e., the time required for conventional column-by-column driving. The present invention is not limited to each dipole spanning only two conventional frames, but such dipoles are favored by conventional drive electronics (e.g., controllers). Furthermore, all the pulses of a dipole waveform can be transmitted during a single conventional frame period using the method of the present invention.

[0082] In FIG. 10, VG shows the voltage provided to a specific gate line of the TFT associated with the pixel electrode. The voltage is ultimately measured and supplied by the controller, although an intermediate gate driver and / or gate controller can be used (see FIGS. 2 and 3). In the active matrix driving of the prior art, the consecutive gate voltages during the image update process have the same decay time between each gate pulse (see FIG. 3), while in the new driving scheme, the gate voltages are staggered and have different decay times (ΔtG) between, for example, the first and second gate pulses and the second and third gate pulses. Due to the repetitive nature of the actual driving signal (see FIG. 7), there is a repetition of the three-pulse structure. However, these three pulses are not evenly spaced in time as typical in the current state-of-the-art driving.

[0083] Due to the (relatively) fast gate driving time and due to the storage capacitor associated with the pixel electrode, when the controller provides an appropriate scan voltage (VS) to the source line associated with the same TFT, a voltage (VP) is provided across the pixel coupled to the TFT. As shown in the following figure, the result of coordinating the gate lines and the scan lines is to provide a push-pull waveform across the pixel in a repetitive manner. In some cases, if the push pulse and the pull pulse have equal areas (as shown in the V / t graph), the resulting waveform will be DC balanced, but the waveform does not need to be DC balanced and in many cases, they will not be DC balanced. Due to this driving scheme, the duration ratio of the push pulse and the pull pulse is 1:3. Both the push pulse and the pull pulse are transmitted to a specific column within the time required to update all columns twice. This cannot be achieved using the conventional column-row driving with a consistent gate pulse interval. Since this new push-pull waveform is shorter, it will not be "flashing".

[0084] Using conventional column-by-row driving, the first gate line (i.e., the one at the top of the matrix) is addressed, then the next column, then the next column after that, all the way to the nth column, and then the process starts over with the first column. As a result, each column of pixels is addressed by gate pulses at uniform intervals. However, in the method of the present invention, it is not possible to address each column between the first and second gate pulses of the first column. Thus, (depending on the shape of the push-pull waveform) only some columns are updated during the time elapsed between the first and second gate pulses of the first column. For example, as shown in FIG. 11, line 2 does receive a gate pulse between the first and second gate pulses of the first gate line, but subsequent gate lines do not receive the first gate pulse until the first gate line has received both the first and second gate pulses. Thus, in at least some embodiments, the columns are divided into two groups (which need not be contiguous). The first group of columns is updated twice within the first conventional frame time, while the second group of columns is updated twice within the second conventional frame time. The controller updates the display by providing a first gate voltage (to the first column) at a first time and a second gate voltage (to the second column) at a second time, then providing a third gate voltage (to the first column) at a third time and a fourth gate voltage (to the second column) at a fourth time, and finally providing a fifth gate voltage (to the first column) at a fifth time and so on. The first and second columns need not be adjacent, and in fact, in many cases, they will not be adjacent. The first, second, third, fourth, and fifth times are not the same (i.e., not addressed simultaneously), and the time elapsed between the first time and the third time is shorter than the time elapsed between the third time and the fifth time. In many cases, the time elapsed between the third time and the fifth time will be less than 17 ms.

[0085] This driving method is illustrated in FIG. 11, where the time elapsed between the first time and the third time is Δt G1, and the time elapsed between the third time and the fifth time is Δt G1'. When the columns are divided into two groups, Δt G1' is three times as long as Δt G1. It should be understood that FIG. 11 is an example of a single push-pull waveform that is sent to multiple columns of pixels for updating. In other embodiments, Δt G1' can be more than three times as long as Δt G1. The second column (including the second and fourth times) does not have to be directly adjacent to the first column. Additionally, for the entire display (or at least the part of the display represented in FIG. 11), all columns receive the same type of continuously repeating waveform or push-pull waveform with opposite polarities that are required to update that part of the display to the color requested by the image update. However, the technique shown in FIG. 11 can be used for all other limit cycle colors, but the voltages applied to the source lines can be different to achieve different colors. For example, the push voltage can be positive or negative and have a high or low amplitude, while the pull voltage usually has the opposite polarity, but not necessarily the same amplitude. Of course, the two voltages can also have the same polarity in order to produce a longer pulse (the duration is twice the frame time). The techniques of the present invention can be used to achieve the colors of the guide bounce state (i.e., red and cyan) by using a longer pulse in this way. However, if the driving pulse is too short for the cyan pigment to reach its optimal position, a "supplemental" pulse can be provided at the end of the waveform to move the cyan pigment to the correct position while having a minimal detrimental effect on the yellow and magenta pigments. Additionally, when updating an electrophoretic medium that contains reflective particles (i.e., as shown in FIG. 6B), the same driving technique can be used to reduce flicker. In principle, if the longer of the two dipole pulses used to address the guide bounce colors is shorter than about 17 ms, then all 8 primary colors of the WCMY system can be presented without flicker. Additionally, other colors can be provided through dithering. For example, if animation, scrolling, etc. are required, dithering may be preferred.

[0086] FIG. 12 shows a first column scanning scheme using the method of the present invention. Each dot in the figure represents the activation of a particular column. In this embodiment, instead of scanning each column of the display before starting a new backplane scan, the columns are divided into two groups. The first group of columns is scanned twice, and then the second group of columns is scanned twice. In each double scan, first a dipole "push" voltage is provided by the source driver applicable to each row, and then a "pull" voltage is provided.

[0087] The ratio of the "push" length to the "pull" length is determined by the number of columns in the first and second groups to be scanned. If the ratio of the columns scanned in the first scan is f, then the ratio of the "push" length to the "pull" length is f:(2 - f). Thus, if f = 1 / 2, the ratio of the pulse lengths is 0.5:1.5 = 1:3. If there is a fixed time delay between the end of one scan and the start of the next scan, then only a small constant needs to be added to each number in this ratio.

[0088] One possible difficulty with the scheme depicted in Figure 12 is that there is a "seam" between the top and bottom of the display where the phase of the push-pull part of the waveform changes. This seam is visible in the final image but is not usually seen during updates because its frequency is too high. Figure 13 shows an alternative scheme that can achieve a push-pull ratio of 1:3 without a seam. In this scheme, the addressing of each odd line is repeated twice, followed by the addressing of each even line being repeated twice. This provides the same push-pull timing effect as continuous columns dividing the panel into two equal blocks.

[0089] Figure 14 shows another embodiment of the driving scheme where column addressing is done in an interleaved manner, but in this case, a wide range of different push-pull ratios can be freely chosen. In Figures 13 and 14, there is also no "seam" between different parts of the display during scanning. The driving method of Figure 14 is also suitable for updating an active matrix display field where some nearby pixels change to different colors during the image update process.

[0090] The driving scheme of Figure 14 is shown in more detail in Figures 15 and 16B. Figure 15 shows a schematic plan view of the active matrix array of the present invention including thin film transistors, and the transconductance of the thin film transistors is adjusted by the gate voltage provided by the gate lines spanning the backplane in the column direction. Figure 16B shows addressing the (n + m)-th column by using a gate driver to provide a select electrode to the gate line of the (n + m)-th column and providing a non-select voltage to all other columns. The source driver supplies the appropriate voltage for the first pulse for the dipole (i.e., the "push" in "push-pull") applied to the (n + m)-th column to the source line. For simple comparison, the conventional column-by-column addressing (which is the current state of the art) is shown in Figure 16A.

[0091] Returning to FIG. 16B, after the n+m-th column is addressed, the n-th column is addressed by using the gate driver to provide a select voltage to the gate lines of the n-th column and a non-select voltage to all other columns. The source driver provides the appropriate voltage for the second pulse for the dipoles in the n-th column (i.e., the "pull" in "push-pull") to the source lines. The addressing now proceeds to the n+m+1-th column, and so on. No more than one column is selected at any time. If the total number of columns in the display is r, the ratio of the dipole duration is m / (r-(m+a)), where a is a constant that depends on the delay between frames and is typically much smaller than r or m.

[0092] All of the above driving embodiments can be implemented using a single gate driver suitable for providing such capabilities or a combination of more conventional synchronized gate drivers. It can be seen that with this design, each column is addressed twice during the elapsed time of a conventional frame, so the column addressing time is half that of a conventional display, where each line is addressed only once during a single frame. In some prior art TFT designs, a single gate line is connected to two columns of pixels, and twice the number of source lines are provided so that the pixels in the two columns are addressed simultaneously. Such a design (or other similar designs) can be used to increase the column addressing time. There are also some less attractive alternatives to the above TFT addressing method. For example, an array with two TFTs per pixel can be provided, but this would require doubling the number of gate lines and source lines, increasing the cost, and possibly imposing more severe resolution limitations due to the need to accommodate the additional lines. Conventional TFT addressing can also be used, but with alternating frame times of different durations. However, in this case, the shorter frame time must be equal to the shorter pulse of the dipole in terms of duration; this is not necessary in the present invention, where the entire dipole has the same duration as the frame time. It can be seen that with this design, each column is addressed twice in a frame, so the column addressing time is half that of a conventional display, where each line is addressed only once during a single frame. In some prior art TFT designs, a single gate line is connected to two columns of pixels, and twice the number of source lines are provided so that the pixels in the two columns are addressed simultaneously. Such a design (or other similar designs) can be used to increase the column addressing time.

[0093] The present invention allows for non - flickering updates of multi - pigment color displays without requiring very short frame times to address the display in a traditional column - by - column manner. Several aspects and embodiments of the technology of this application have been described. It should be understood that those of ordinary skill in the art will readily envision various changes, modifications, and improvements. Such changes, modifications, and improvements are intended to be within the spirit and scope of the technology described in this application. For example, those of ordinary skill in the art will readily conceive of various other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such changes and / or modifications is considered to be within the scope of the embodiments described herein. Those familiar with the art will recognize or be able to determine many equivalents of the specific embodiments described herein using only routine experimentation. Therefore, it should be understood that the foregoing embodiments are presented by way of example only, and that within the scope of the appended claims and their equivalents, embodiments of the present invention may be practiced in a manner different from that specifically described. Additionally, any combination of two or more of the features, systems, articles, materials, kits, and / or methods described herein is included within the scope of the present invention without mutual contradiction.

[0094] 10: Storage capacitor 20: Electrophoretic medium 30: Coupling capacitor 40: Electrophoretic display 50: Processor 55: Display module 60: Controller 70: Non - transitory memory 80: Power supply 85: Communication facility 90: Sensor 101: Electrophoretic display 102: Electrophoretic display 110: Top transparent electrode 120: Electrophoretic medium 121: Particle 122: Particle 123: Particle 124: Particle 126: Microcapsule 127: Wall of the microcell 130: Bottom electrode 140: Adhesive layer 150: Substrate 160: Protective layer 180: Sealing layer 400: Active matrix backplane 402: Substrate 404: Voltage source 406: Voltage source 406: Single row (scan) line 408: Single column (gate) line 420: Intermediate source controller 460: Controller

Claims

1. An electrophoresis display, comprising: One transparent electrode; An active matrix backplane includes a plurality of pixel electrodes, each pixel electrode coupled to a thin-film transistor including a gate line and a source line, and each pixel electrode coupled to a storage capacitor; an electrophoretic medium disposed between the light-transmitting electrode and the active matrix backplane, wherein the electrophoretic medium contains at least three different types of charged pigment particles; a controller coupled to a plurality of gate lines and a plurality of source lines of the plurality of pixel electrodes, the controller being configured to address the pixel electrodes in a column-by-column manner, the controller being further configured to update an image on the electrophoretic display by performing the following steps: addressing a first column of pixel electrodes by providing a first gate voltage at a first time; addressing a second column of pixel electrodes by providing a second gate voltage at a second time; and addressing the first column of pixel electrodes by providing a third gate voltage at a third time. The second column of pixel electrodes is addressed by providing a fourth gate voltage at a fourth time; and the first column of pixel electrodes is addressed by providing a fifth gate voltage at a fifth time, wherein the first time, the second time, the third time, the fourth time, and the fifth time are different, and the elapsed time between the first time and the third time is shorter than the elapsed time between the third time and the fifth time, wherein there are n columns of pixel electrodes in the active matrix backplane, and the first column of pixel electrodes and the second column of pixel electrodes are separated by n / 2 columns of pixel electrodes.

2. The electrophoretic display as claimed in claim 1, wherein the time elapsed between the third time and the fifth time is at least twice the time elapsed between the first time and the third time.

3. The electrophoretic display as requested in claim 1, wherein the time elapsed between the first time and the third time is less than 20 milliseconds, optionally less than 10 milliseconds, optionally about 6 milliseconds or less.

4. The electrophoretic display of claim 1, wherein the controller simultaneously provides a first source voltage to a pixel of the first column of pixel electrodes at a first time and provides a second source voltage to the pixel of the first column of pixel electrodes at a third time, and the polarity of the first source voltage is opposite to the polarity of the second source voltage.

5. The electrophoretic display as claimed in claim 4, wherein the amplitude of the first source voltage is different from the amplitude of the second source voltage.

6. The electrophoretic display as claimed in claim 4, wherein the amplitude of the first source voltage and the amplitude of the second source voltage are between -15V and +15V or between -24V and +24V.

7. The electrophoretic display as claimed in claim 4, wherein the controller simultaneously provides a third source voltage to the pixel of the first column pixel electrode at the fifth time.

8. The electrophoretic display as claimed in claim 7, wherein the first source voltage and the third source voltage have the same polarity and amplitude.

9. The electrophoretic display of claim 1, wherein the controller performs the following additional steps: addressing a third column of pixel electrodes by providing a sixth gate voltage at a sixth time; and addressing the third column of pixel electrodes by providing a seventh gate voltage at a seventh time, wherein the first time, the second time, the third time, the fourth time, the fifth time, the sixth time, and the seventh time are different, and the elapsed time between the first time and the third time is the same as the elapsed time between the sixth time and the seventh time.

10. The electrophoretic display of claim 1, wherein the controller provides at least two individual gate voltages to each thin-film transistor of the active matrix backplane between the first time and the fifth time.

11. The electrophoretic display of claim 1, wherein the electrophoretic medium comprises a reflective white particle and at least one subtractive color particle or a reflective white particle and at least one reflective color particle.

12. The electrophoretic display of claim 1, wherein the electrophoretic medium comprises a fourth type of electrophoretic particles.

13. An electrophoretic display as claimed in claim 12, wherein two types of particles of such types are negatively charged and two types of particles of such types are positively charged, or wherein one type of particles of such types is negatively charged and three types of particles of such types are positively charged, or wherein three types of particles of such types are negatively charged and one type of particles of such types is positively charged.

14. An electrophoretic display as claimed in any of claims 1 to 13, wherein the electrophoretic medium is encapsulated in microcapsules or microcells.

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