Time shifted waveform providing low flash image update for multi-particle electrophoretic display

Abstract

Electrophoretic displays with multi-particle electrophoretic media and improved methods for driving such multi-particle electrophoretic media, in particular using an active matrix backplane and a controller. A larger lookup table is used that includes a plurality of time shifted waveforms for each color transition. The controller may thus easily cause a phase shift of color flash on the display, which ultimately reduces or eliminates the sense of "flash" of the device during updating from the first image to the second image. The method can be popularized to any electrophoretic display using waveforms, and is particularly suitable for novel multi-particle electrophoretic displays capable of producing four or more colors per pixel.

Description

[0001] Related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 523,484, filed June 27, 2023. All patents and publications disclosed herein are incorporated herein by reference in their entirety. Background Technology

[0003] Electrophoretic displays (EPDs) change color by altering the position of one or more charged colored particles relative to a light-transmitting viewing surface. These EPDs are often called "electronic paper" or "ePaper" because the resulting displays have high contrast and are readable in sunlight, much like ink on paper. EPDs are already widely used in e-readers because they provide a book-like reading experience, consume little power, and allow users to carry hundreds of books in a lightweight handheld device. These devices are increasingly being used to display out-of-home (OOH) digital content, such as shelf labels, outdoor advertising, and traffic signs.

[0004] For many years, electrophoretic displays have only included two types of charged colored particles: black and white. (Of course, "colored" as used here includes both black and white.) White particles are typically light-scattering and include, for example, titanium dioxide, while black particles are absorbent in the visible spectrum and can include carbon black or absorbing metal oxides such as copper chromite. In its simplest sense, a monochrome electrophoretic display only requires a transparent electrode, a back electrode, and an electrophoretic medium containing white and black particles with opposite charges located on the viewing surface. When a voltage of one polarity is applied, the white particles move to the viewing surface, and when a voltage of the opposite polarity is applied, the black particles move to the viewing surface. If the back electrode comprises controllable regions (pixels), whether segmented electrodes or an active matrix of pixel electrodes controlled by transistors, a pattern can be electronically displayed on the viewing surface. This pattern could be, for example, text in a book.

[0005] Recently, a variety of color options have become commercially available for electrophoretic displays, including tri-color displays (black, white, and red; black, white, and yellow) and quad-color displays (black, white, red, and yellow). Similar to the operation of a black-and-white electrophoretic display, electrophoretic displays with three or four reflective pigments operate much like a simple black-and-white display, as the desired colored particles are driven onto the observation surface. The driving scheme is far more complex than that with only black and white, but ultimately, the optical function of the particles remains the same.

[0006] Advanced Color Electronic Paper (ACeP) also includes four types of particles, but the cyan, yellow, and magenta particles are subtractive rather than reflective, thus allowing thousands of colors to be produced at each pixel. Color processing is functionally equivalent to the printing methods long used in offset and inkjet printers. A given color is produced by using the correct proportions of cyan, yellow, and magenta on a bright white paper background. In the case of ACeP, the relative positions of the cyan, yellow, magenta, and white particles relative to the viewing surface determine the color of each pixel. While this type of electrophoretic display allows for thousands of colors per pixel, careful control of the position of each pigment (50 to 500 nanometers in size) within a working space approximately 10 to 20 micrometers thick is crucial. Clearly, variations in pigment position will result in an incorrect color being displayed at a given pixel. Therefore, this system requires precise voltage control. Further details of the system are available in the following U.S. patents, the entire contents of which are incorporated herein by reference: U.S. Patent Nos. 9,361,836, 9,921,451, 10,276,109, 10,353,266, 10,467,984, 10,593,272, and 10,657,869.

[0007] As described in the aforementioned patents, the waveform (i.e., the electric field provided on the electrophoretic medium as a function of time) typically requires the voltage polarity to swing dramatically over a short period of time. Therefore, in some cases, color electrophoretic displays “flicker,” “blink,” or “appear to flicker” when switching between color images. This drawback is particularly noticeable when full-color e-readers switch between full-color images rapidly (i.e., within less than one second). U.S. Patent No. 10,657,869 addresses a similar problem, but '869 does not suggest using a lookup table to store the offset waveform, as described below. Other patents owned by E Ink, such as U.S. Patent No. 8,593,396, also provide solutions for moving the starting point of the waveform or reducing (or increasing) the waveform size to improve grayscale control, but these patents do not recognize that such adjustments, when properly coordinated, reduce flicker.

[0008] In particular, the present invention relates to color electrophoretic displays, and more particularly, but not exclusively, to electrophoretic displays capable of displaying more than two colors using a single-layer electrophoretic material comprising a variety of colored particles (e.g., white, cyan, yellow, and magenta particles). In some cases, two particles are positively charged, and one (or two) 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 types of charges on the particle surface and / or the types of polymers functionalized on the surface may vary. The particles may comprise organic or inorganic pigments or dyes.

[0009] The term "gray state" is used herein in its conventional sense within the field of imaging technology, referring to the state between two extreme optical states of a pixel, and does not necessarily imply a black-and-white transition between these two extreme states. For example, several IENK patents and published applications cited below describe electrophoretic displays where the extreme states are white and dark blue, so the intermediate gray state is actually light blue. In fact, as previously stated, a change in optical state may not be a color change at all. The terms "black" and "white" can be used below to refer to two extreme optical states of a display and should be understood to generally include extreme optical states of black and white in a non-strict sense, such as the aforementioned white and dark blue states.

[0010] The terms bistable and bistable are used herein in their conventional sense in the art, referring to a display comprising display elements having a first display state and a second display state that differ in at least one optical characteristic, such that after any given element is driven to present its first or second display state by means of an addressing pulse of finite duration, the state will persist for at least several times, for example, at least four times, the shortest duration of the addressing pulse required to change the state of the display element after the addressing pulse terminates. U.S. Patent No. 7,170,670 shows that some particle-based electrophoretic displays supporting grayscale are stable not only in their extreme black and white states but also in their intermediate gray states, as are some other types of electro-optical displays. Such displays are aptly referred to as multistable rather than bistable, but for convenience, the term bistable may be used herein to encompass both bistable and multistable displays.

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

[0012] Particles that absorb, scatter, or reflect light over a wide band or at selected wavelengths are referred to herein as colored or pigment particles. Various light-absorbing or light-reflecting materials other than pigments (strictly speaking, the term refers to insoluble colored materials), such as dyes or photonic crystals, may also be used in the electrophoretic media and displays of the present invention.

[0013] For many years, particle-based electrophoretic displays have been a subject of in-depth research and development. In these displays, multiple charged particles (sometimes called pigment particles) pass through a fluid under the influence of an electric field. Compared to liquid crystal displays (LCDs), electrophoretic displays can offer properties such as good brightness and contrast, wide viewing angles, state bistability, and low power consumption. However, long-term image quality issues have hindered their widespread use. For example, the particles constituting an electrophoretic display are prone to settling, leading to a short lifespan for these displays.

[0014] As mentioned above, electrophoretic media require the presence of a fluid. In most prior art electrophoretic media, this fluid is a liquid, but electrophoretic media can also be generated using a gaseous fluid; 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. See also U.S. Patents 7,321,459 and 7,236,291. When such gas-based media are used in a direction that allows particle settling (e.g., in a sign where the media is arranged in a vertical plane), such gas-based electrophoretic media are susceptible to the same type of problems as liquid-based electrophoretic media due to particle settling. In fact, the particle sedimentation problem is more severe in gas-based electrophoresis media than in liquid-based electrophoresis media because the lower viscosity of gaseous suspensions allows electrophoretic particles to settle more quickly than in liquids.

[0015] Numerous patents and applications, transferred to or registered in the name of MIT and E Ink, describe various techniques for encapsulating electrophoretic and other electro-optic media. Such encapsulation media comprise a plurality of small capsules, each capsule comprising an inner phase and a capsule wall surrounding the inner phase, which contains electrophoretically movable particles in a fluid medium. Typically, the capsules themselves are held within a polymer binder to form a coherent layer located between two electrodes. The techniques described in these patents and applications include:

[0016] (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 7,002,728 and 7,679,814;

[0017] (b) Encapsulation, adhesives, and encapsulation processes; see, for example, U.S. Patent Nos. 6,922,276 and 7,411,719;

[0018] (c) Microunit structures, wall materials, and methods of forming microunits; see, for example, U.S. Patent Nos. 7,072,095 and 9,279,906;

[0019] (d) Methods for filling and sealing microcells; see, for example, U.S. Patent Nos. 7,144,942 and 7,715,088;

[0020] (e) Thin films and subassemblies containing electro-optic materials; see, for example, U.S. Patent Nos. 6,982,178 and 7,839,564;

[0021] (f) Backplanes, adhesive layers and other auxiliary layers and methods for use in displays; see, for example, U.S. Patent Nos. 7,116,318 and 7,535,624;

[0022] (g) Color formation and color adjustment; see, for example, U.S. Patents 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 No. 2008 / 004331 8; 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 2016 / 0140909;

[0023] (h) A 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; 7,3 12,794; 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;9,218,77 3; 9,224,338; 9,224,342; 9,224,344; 9,230,492; 9,251,736; 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 Publications 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 / 032272 1; 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 / 019 4250; 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 Patents and applications numbered / 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 be referred to below as MEDEOD (Method for Driving an Electro-Optical Display) applications);

[0024] (i) Applications of displays; see, for example, U.S. Patent Nos. 7,312,784 and 8,009,348; and

[0025] (j) Non-electrophoretic displays, as described in U.S. Patent No. 6,241,921 and U.S. Patent Application Publication No. 2015 / 0277160; and U.S. Patent Application Publication Nos. 2015 / 0005720 and 2016 / 0012710.

[0026] Many of the aforementioned patents and applications recognize that the walls surrounding discrete microcapsules in an encapsulated electrophoretic medium can be replaced by a continuous phase, thereby producing a so-called polymer dispersion electrophoretic display, wherein the electrophoretic medium comprises a plurality of discrete droplets of electrophoretic fluid and a continuous phase of polymeric material, and the discrete droplets of electrophoretic fluid within such a polymer dispersion electrophoretic display can be considered as capsules or microcapsules, even if no discrete capsule membrane is associated with each individual droplet; see, for example, U.S. Patent No. 6,866,760. Therefore, for the purposes of this application, such polymer dispersion electrophoretic media are considered a subclass of encapsulated electrophoretic media.

[0027] One related type of electrophoretic display is the so-called microcell electrophoretic display. In a microcell electrophoretic display, charged particles and fluid are not encapsulated in microcapsules, but are instead retained in multiple cavities formed within a carrier medium (typically a polymer film). See, for example, U.S. Patents 6,672,921 and 6,788,449.

[0028] Although electrophoretic media are often opaque (because, for example, in many electrophoretic media, particles essentially block visible light transmission through the display) and operate in a reflective mode, many electrophoretic displays can be manufactured to operate in a so-called “shutter mode,” in which one display state is substantially opaque and another display state is transparent. See, for example, U.S. Patents 5,872,552; 6,130,774; 6,144,361; 6,172,798; 6,271,823; 6,225,971; and 6,184,856. Dielectrophoretic displays, similar to electrophoretic displays but dependent on changes in electric field strength, can operate in a similar mode; see U.S. Patent 4,418,346. Other types of electro-optic displays can also be able to operate in a shutter mode. Electro-optic media operating in shutter mode can be used in multilayer structures of full-color displays; in such structures, at least one layer adjacent to the display’s viewing surface operates in shutter mode to expose or conceal a second layer further away from the viewing surface.

[0029] Encapsulated electrophoretic displays generally do not suffer from the aggregation and sedimentation failure modes of conventional electrophoretic equipment and offer further advantages such as the ability to print or coat displays on a variety of flexible and rigid substrates. (The term "print" is intended to include, but is not limited to, all of the following forms of printing and coating: pre-quantity coating such as patch die coating, slot or extrusion coating, slide or cascade coating, curtain coating; roll coating such as roller blade coating, forward and reverse roller coating; gravure coating; dip coating; spray coating; meniscus coating; spin coating; brush coating; air knife coating; screen printing; electrostatic printing; thermal printing; inkjet printing; electrophoretic deposition (see U.S. Patent No. 7,339,715); and other similar techniques.) Therefore, the resulting display can be flexible. Furthermore, because the display medium can be printed (using various methods), the display itself can be manufactured inexpensively.

[0030] As described above, most simple existing electrophoretic media essentially display only two colors. Such electrophoretic media either use a single type of electrophoretic particles with a first color in a colored fluid with a different second color (in this case, the first color is displayed when the particles are near the viewing surface of the display, and the second color is displayed when the particles are spaced apart from the viewing surface), or use a first type and a second type of electrophoretic particles with different first and second colors in an uncolored fluid (in this case, the first color is displayed when the first type of particles are near the viewing surface of the display, and the second color is displayed when the second type of particles are near the viewing surface). Typically, these two colors are black and white. If a full-color display is desired, an array of color filters can be placed on the viewing surface of a monochrome (black and white) display. Displays with color filter arrays rely on area sharing and color mixing to generate color stimuli. Available display areas are 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 one-dimensional (stripes) or two-dimensional (2×2) repeating pattern. Other options of primary colors or more than three primary colors are also known in the art. Three (in the case of an RGB monitor) or four (in the case of an RGBW monitor) subpixels are chosen to be small enough that at the intended viewing distance, they visually blend together to form a single pixel with a uniform color stimulus (“color blending”). An inherent drawback of area sharing is that colorant is always present, and colors can only be modulated by switching the corresponding pixel of the underlying monochrome display to white or black (turning the corresponding primary color on or off). For example, in an ideal RGBW monitor, each of the red, green, blue, and white primary colors occupies one-quarter of the display area (one of the four subpixels), the white subpixel is as bright as the underlying monochrome white, and each colored subpixel is no less than one-third of the monochrome white. The overall white brightness displayed by the monitor cannot exceed half the brightness of the white subpixels (the white area of ​​the monitor is produced by displaying one white subpixel out of every four, plus each colored subpixel in its colored form is equivalent to one-third of the white subpixel, so the combined contribution of three colored subpixels does not exceed that of one white subpixel). The brightness and saturation of colors are reduced by sharing areas with colored pixels that have switched to black. Area sharing is particularly problematic when mixing yellow, as it is lighter than any other color of equal brightness, and saturated yellow is almost as bright as white. Switching the blue pixels (a quarter of the display area) to black makes the yellow too dark.

[0031] U.S. Patents 8,576,476 and 8,797,634 describe a multicolor electrophoretic display having a single backplate including independently addressable pixel electrodes and a common transparent front electrode. Multiple electrophoretic layers are disposed between the backplate and the front electrode. The displays described in these applications are capable of displaying any primary color (red, green, blue, cyan, magenta, yellow, white, and black) at any pixel location. However, the use of multiple electrophoretic layers between a single set of addressable electrodes has disadvantages. The electric field experienced by particles in a particular layer is lower than that of a single electrophoretic layer addressed at the same voltage. Furthermore, optical losses in the electrophoretic layer closest to the observation surface (e.g., due to light scattering or unwanted light absorption) can affect the appearance of the image formed in the underlying electrophoretic layer.

[0032] 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 comprising an electrophoretic fluid comprising one or two types of pigment particles dispersed in a transparent and colorless or colored solvent, the electrophoretic fluid being disposed between a common electrode and a plurality of pixels 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 comprising two types of charged particles with opposite charge polarities and two contrasting colors. The two types of pigment particles are dispersed in a colored solvent, or a solvent of uncharged or slightly charged colored particles. This method involves driving the display unit by applying a driving voltage of 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. Patent Nos. 8,717,664 and 8,964,282 describe an electrophoretic fluid and a method for driving an electrophoretic display. The fluid comprises pigment particles of types one, two, and three, all dispersed in a solvent or solvent mixture. The first and second types of pigment particles carry opposite charge polarities, and the third type of pigment particles has a charge level approximately 50% lower than that of the first or second types. These three types of pigment particles have different threshold voltage levels or different mobility levels, or both.

[0033] U.S. Patent Nos. 10,475,399 and 10,678,111 describe electrophoretic displays capable of displaying any color at any pixel location. In '399, a display is described in which a white (light-scattering) pigment moves in a first direction when addressed with a low applied voltage and in the opposite direction when addressed with a higher voltage. In '111, a full-color electrophoretic display is described with four pigments: white, cyan, magenta, and yellow, two of which are positively charged and two are negatively charged. U.S. Patent Publication 2022 / 0082896 describes a full-color electrophoretic display with four pigments: white, cyan, magenta, and yellow, three of which are positively charged and the white pigment is negatively charged. Embodiments of this type of invention are referred to as CMYW embodiments.

[0034] In addition, there are multi-particle display designs in which colored pigments scatter light (i.e., reflective colored particles). U.S. Patent No. 10,339,876 describes this type of display, which has black, white, and red particles capable of displaying three states. Similar display designs incorporating four pigments can display four different colors, see, for example, U.S. Patent No. 9,922,603, or, by using translucent colored particles, such displays can display six colors, see, for example, U.S. Patent No. 11,640,803. Many multi-particle display designs using light-scattering particles combine with lengthy and “flickering” updates, which are unattractive to some observers. The solutions described below can be used to reduce the “flickering” of updates in such displays and typically require very little additional cost in terms of new controllers or drivers. Summary of the Invention

[0035] This document discloses an improved method for driving a full-color electrophoretic display and a full-color electrophoretic display using these driving methods. In one aspect, the invention includes an electrophoretic display comprising a light-transmitting electrode, an active matrix backplane including multiple rows of pixel electrodes, each pixel electrode being coupled to a thin-film transistor including gate lines and source lines, and an electrophoretic medium disposed between the light-transmitting electrode and the active matrix backplane, wherein the electrophoretic medium comprises at least three different types of charged pigment particles. The electrophoretic display also includes a controller coupled to multiple gate lines and a non-transitory memory coupled to the controller and including a lookup table. Each gate line is coupled to a thin-film transistor in one row of multiple rows of pixel electrodes, and the controller is coupled to multiple source lines. The controller is also configured to address the pixel electrodes in a row-by-row manner by providing a gate voltage and a source voltage to each thin-film transistor. For a transition between a first color and a second color, the lookup table includes a first waveform for transitioning the electrophoretic medium between the first color and the second color, and a second waveform for transitioning the electrophoretic medium between the first color and the second color. The first and second waveforms are identical in the number of voltage pulses and the polarity and amplitude of each voltage pulse, but the time shift of the first and second waveforms is at least 1 millisecond, such as 5 milliseconds, 8 milliseconds, or 12 milliseconds. Additionally, when updating the electrophoretic display between a first image and a second image, the controller performs the following steps: receiving the first waveform from the lookup table; providing the first waveform to the first row of pixel electrodes; receiving the second waveform from the lookup table; and providing the second waveform to the second row of pixel electrodes adjacent to the first row of pixel electrodes.

[0036] In one embodiment, the lookup table further includes a third waveform for transitioning the electrophoretic medium between a first color and a second color, wherein the first, second, and third waveforms are identical in the number of voltage pulses and the polarity and amplitude of each voltage pulse, but wherein the first, second, and third waveforms are time-shifted relative to each other by at least 5 milliseconds, and the controller further performs the steps of receiving the third waveform from the lookup table and providing the third waveform to a third row of pixel electrodes adjacent to the second row electrodes, wherein the second row electrodes are located between the first row electrodes and the third row electrodes. In one embodiment, the lookup table further includes a fourth waveform for transitioning the electrophoretic medium between a first color and a third color, wherein the third waveform is different from the first and second waveforms in the number of voltage pulses and the polarity and amplitude of each voltage pulse, but wherein the first, second, and third waveforms are time-shifted relative to each other by at least 1 millisecond. In one embodiment, the time shift of the first and second waveforms is at least 5 milliseconds, optionally at least 10 milliseconds, and optionally between 12 and 20 milliseconds. In one embodiment, the time shift of the first and second waveforms is one frame, where one frame is the time required to address each pixel in the active matrix backplane once when addressing the active matrix backplane in a line-by-line manner. In one embodiment, the amplitude of the voltage pulse is between -15V and +15V, or between -24V and +24V. In one embodiment, the electrophoretic medium comprises reflective white particles and at least one subtractive particle, or reflective white particles and at least one reflective colored particle. In one embodiment, the electrophoretic medium comprises a fourth type of electrophoretic particles. In one embodiment, two types of particles are negatively charged and two types of particles are positively charged, or one type of particles is negatively charged and three types of particles are positively charged, or three types of particles are negatively charged and one type of particle is positively charged. In one embodiment, the electrophoretic medium is encapsulated in microcapsules or microcells. Attached Figure Description

[0037] Figure 1A This is a representative cross-sectional view of a four-particle electrophoresis display, in which the electrophoretic medium is encapsulated in a capsule. Figure 1A The structure can be used in multi-particle electrophoretic media that have both reflective and subtractive pigment particles.

[0038] Figure 1B This is a representative cross-sectional view of a four-particle electrophoretic display, in which the electrophoretic medium is encapsulated in microcells. Figure 1B The structure can be used in multi-particle electrophoretic media that have both reflective and subtractive pigment particles.

[0039] Figure 2 An exemplary equivalent circuit for a single pixel of an electrophoretic display is shown, which uses an active matrix backplane of pixel electrodes coupled to storage capacitors.

[0040] Figure 3 This is a schematic diagram of an exemplary driving system for controlling the voltage supplied to the pixel electrodes in an active matrix device. The resulting driving voltage can be used to set the optical state of a multi-particle electrophoretic medium.

[0041] Figure 4 An exemplary electrophoretic display including a display module is shown. The electrophoretic display also includes a processor, non-transitory memory, one or more power supplies, and a controller. The electrophoretic display may also include sensors to allow it to adjust operating parameters based on ambient conditions, such as temperature and light intensity.

[0042] Figure 5 The preferred positions of each of the four groups of particles that produce eight standard colors in a white-cyan-magenta-yellow (WCMY) four-particle electrophoretic display are shown, where the white particles are reflective and the cyan, magenta, and yellow particles are absorptive.

[0043] Figure 6A illustrates an exemplary push-pull drive scheme for addressing an electrophoretic medium comprising three subtractive (cyan, yellow, and magenta) particles and one scattering (white) particle.

[0044] Figure 6B illustrates an exemplary push-pull drive scheme for addressing an electrophoretic medium comprising an absorbing (black) particle, two reflective (red and yellow) particles, and a scattering (white) particle.

[0045] Figure 7 The “typical” drive waveform transmitted to the pixel electrode during a single update from the first color to the second color is depicted. Notably, the waveform includes repeating push-pull voltages.

[0046] Figure 8 Three identical push-pull waveforms are shown, time-shifted by one frame (approximately 12 milliseconds) to reduce the flash of the update from the first color to the second color.

[0047] Figure 9 The present invention illustrates a display in which offset identical waveforms are transmitted to pixel electrodes in three adjacent rows that undergo the same color transition.

[0048] Figure 10 The illustration shows an update mode for the display of the present invention, in which three different offset waveforms are transmitted to various rows in a portion of the display undergoing the same transition from a first color to a second color. The same technique can also be used when more than one color transition is required in a portion of the display undergoing the update.

[0049] Figure 11AThis demonstrates an electrophoretic display comprising white reflective particles and subtractive particles of cyan, yellow, and magenta applied across the entire display. Figure 7 The color transients generated when addressing with a repetitive dipole waveform and without using a time-shifted (interlaced) waveform (measured by reflectance in L*, a*, b* space).

[0050] Figure 11B This demonstrates an electrophoretic display comprising white reflective particles and subtractive particles of cyan, yellow, and magenta applied across the entire display. Figure 7 The color transients (measured by reflectivity in L*, a*, b* space) are generated when the repeating dipole waveform is addressed and the odd and even pixel electrode rows receive time-shifted (interleaved) waveforms. Each even row receives the same waveform and each odd row receives the same waveform, but the odd rows are time-shifted by approximately 12 milliseconds.

[0051] Figure 11C This demonstrates an electrophoretic display comprising white reflective particles and subtractive particles of cyan, yellow, and magenta applied across the entire display. Figure 7 The color transients (measured by reflectivity in L*, a*, b* spaces) are generated when the repeating dipole waveform is addressed and three different time-shifted waveforms are used, with each time-shifted waveform being transmitted to one-third of the line. Each subsequent line is offset by one frame (approximately 12 milliseconds) until the time-shifted waveform is in phase with the preceding waveform. Detailed Implementation

[0052] This invention includes an electrophoretic display with a multi-particle electrophoretic medium, and an improved method for driving such a multi-particle electrophoretic medium. The display of this invention typically includes an active matrix backplane of pixel electrodes controlled by thin-film transistors. Typically, each pixel electrode is also coupled to a storage capacitor. While the driving method of the display can be generalized to all different types of electrophoretic displays (segmented, direct-driven, indirect-driven, active matrix) and can be used with a wide variety of waveforms, the display of this invention is typically used to drive more complex electrophoretic media, for example, where precise simultaneous control of three, four, or more particles is required. In a preferred embodiment, the display of this invention uses an active matrix backplane controlled by a thin-film transistor array, and the driving waveform is a repeating "push-pull" type. Using the techniques described herein, electrophoretic displays incorporating the disclosed driving scheme are generally less "flickering" compared to those using a single "best" waveform for a specific color transition for addressing in a conventional line-by-line update manner, which has been the state-of-the-art for some time. Such displays may include multiple subtractive colored electrophoretic particles and / or multiple reflective colored electrophoretic particles. In a preferred embodiment, the electrophoretic medium includes white particles and subtractive primary color particles of cyan, yellow and magenta, i.e., the WCMY system.

[0053] Methods for fabricating electrophoretic displays comprising four (or more) particles have been discussed in the prior art. The electrophoretic fluid can be encapsulated in microcapsules or incorporated into microcell structures, then sealed with a polymer layer. The microcapsules or microcell layers can be coated or laminated onto a plastic substrate or film with a transparent coating of a conductive material. Alternatively, microcapsules can be coated onto a transparent substrate or other electrode material using a spraying technique. (See U.S. Patent No. 9,835,925, incorporated herein by reference). The resulting component can be laminated to a backplane with pixel electrodes using a conductive adhesive. Alternatively, the component can be attached to one or more segmented electrodes on the backplane, wherein the segmented electrodes are directly actuated.

[0054] This invention particularly provides an architecture and method for addressing an electrophoretic display with dipoles using a thin-film transistor array. A larger lookup table is used, comprising multiple time-shifted waveforms for each color transition. The controller can thus easily induce a phase shift in the color flash on the display, which ultimately reduces or eliminates the perceived "flicker" of the device during updates from a first image to a second image. Therefore, a wide variety of multi-particle (color) electrophoretic displays can be addressed without visible flicker or flash.

[0055] The electrophoretic medium used herein comprises charged particles with varying colors, reflective or absorptive properties, charge densities, and mobility in an electric field (measured in zeta potential). Particles that absorb, scatter, or reflect light over a broad wavelength or at selected wavelengths are referred to herein as colored or pigment particles. Various materials that absorb or reflect light, other than pigments (strictly speaking, this term refers to insoluble colored materials), such as dyes, photonic crystals, quantum dots, etc., can also be used in the electrophoretic medium and displays of this invention. For example, the electrophoretic medium may comprise a fluid, a plurality of first particles and a plurality of second particles dispersed in the fluid, and a plurality of third particles and a plurality of fourth particles dispersed in the fluid, wherein the first and second particles carry charges of opposite polarities, the first particle is a light-scattering particle, the second particle has one of the subtractive primary colors, the third and fourth particles carry charges of opposite polarities, and each of the third and fourth particles has a subtractive primary color different from each other and different from that of the second particle, wherein the electric field required to separate aggregates formed by the third and fourth particles is greater than the electric field required to separate aggregates formed by any other two types of particles.

[0056] The electrophoretic medium of the present invention may contain any additives used, for example, in prior art electrophoretic media described in the aforementioned E Ink and MIT patents and applications. Thus, for example, the electrophoretic medium of the present invention will generally include at least one charge control agent to control the charge on various particles, and a fluid may dissolve or disperse polymers with a number-average molecular weight greater than about 20,000 and substantially non-absorbable on the particles therein to improve the bistability of the display, as described in the aforementioned U.S. Patent No. 7,170,670.

[0057] In one embodiment, the present invention uses light-scattering particles, typically white, and three basic non-light-scattering particles. Of course, there are no completely light-scattering particles or completely non-light-scattering particles, and the minimum light scattering of the light-scattering particles and the maximum tolerable light scattering of the basic non-light-scattering particles used in the electrophoresis of the present invention can vary depending on factors such as the exact pigments used, their colors, and the user's or application's tolerance for some deviation from the desired color. The scattering and absorption characteristics of the pigment can be evaluated by measuring the diffuse reflectance of a pigment sample dispersed in a suitable matrix or liquid against white and black backgrounds. The results of such measurements can be interpreted according to many models known in the art, such as one-dimensional Kubelka-Munk processing. In the present invention, preferably, when the pigment is approximately isotropically distributed at 15% by volume in a 1-micron-thick layer comprising the pigment and a liquid with a refractive index less than 1.55, the white pigment exhibits at least 5% diffuse reflectance at 550 nm when measured against a black background. Under the same conditions, measured against a black background, yellow, magenta, and cyan pigments preferably exhibit diffuse reflectance of less than 2.5% at 650, 650, and 450 nm, respectively. (The wavelengths selected above for measuring yellow, magenta, and cyan pigments correspond to the spectral regions of minimum absorption for these pigments.) Colored pigments that meet these criteria are referred to below as “non-scattering” or “fundamentally non-scattering.” Specific examples of suitable particles are disclosed in U.S. Patent No. 9,921,451, which is incorporated herein by reference.

[0058] Alternative particle groups may also be used, including four groups of reflective particles, or one absorptive particle with three or four different groups of reflective particles, as described in U.S. Patent Nos. 9,922,603 ​​and 10,032,419, which are incorporated herein by reference. For example, white particles may be formed from inorganic pigments such as TiO2, ZrO2, ZnO, Al2O3, Sb2O3, BaSO4, PbSO4, etc., while black particles may be formed from CI pigment black 26 or 28, etc. (e.g., manganese ferrite black spinel or copper chromate black spinel) or carbon black. Third / fourth / fifth class particles may have colors such as red, green, blue, magenta, cyan, or yellow. Pigments used for this type of particle can include, but are not limited to, CI pigments PR 254, PR122, PR149, PG36, PG58, PG7, PB28, PB15:3, PY138, PY150, PY155, or PY20. Specific examples include Clariant's 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, and Hostaperm Green GNX; BASF's Irgazine Red L 3630, Cinquasia Red L 4100 HD, and Irgazin Red L 3660 HD; and SunChemical's Phthalocyanine Blue, Phthalocyanine Green, Diaryl Yellow, or Diaryl AAOT Yellow.

[0059] like Figure 1A and 1BAs shown, electrophoretic displays (101, 102) typically include a top transparent electrode 110, an electrophoretic medium 120, and a bottom electrode 130, the bottom electrode 130 typically being a pixel electrode of an active matrix of pixels 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; however, more (or fewer) groups of particles can be used with the methods and displays described herein. For example, the technique of the present invention can be used with groups of three types of particles, such as white, black, and red, wherein one of the three different types of particles has a lower charge than the other two types. In some cases, two particles are positively charged and one (or two) 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. The electrophoretic medium 120 is typically separated by walls or microcapsules 126 of microcells 127. The optional adhesive layer 140 can be disposed adjacent to any layer; however, it is typically adjacent to the electrode layers (110 or 130). More than one adhesive layer 140 may be present in a given electrophoretic display (105, 106); however, a single layer is more common. The entire display stack is typically disposed on a substrate 150, which may be rigid or flexible. The displays (101, 102) typically also include a protective layer 160, which may simply protect the top electrode 110 from damage, or it may enclose the entire display (101, 102) to prevent water ingress, etc. The electrophoretic displays (101, 102) may also include a sealing layer 180 if desired. In some embodiments, the adhesive layer 140 may include a primer component to improve adhesion to the electrode layer 110, or a separate primer layer may be used ( Figure 1B (Not shown in the image). The structure and components of the electrophoretic display, pigments, binders, electrode materials, etc., are described in many patents and patent applications published by E Ink, such as US 6,922,276; 7,002,728; 7,072,095; 7,116,318; 7,715,088; and 7,839,564, all of which are incorporated herein by reference in their entirety.

[0060] In some embodiments, such as Figure 1A As shown, an electrophoretic display may include a transparent electrode, an electrophoretic medium, and multiple back pixel electrodes. To produce a high-resolution display, for example, for displaying images, each pixel electrode 130 is individually addressable without interference from neighboring pixels, allowing the image file to be faithfully reproduced on the display. One way to achieve this is to provide an array of nonlinear elements, such as transistors or diodes, where at least one nonlinear element is associated with each pixel to produce an "active matrix" display. (See also...) Figure 2Addressing a pixel, or pixel electrode 130, is connected to an appropriate voltage source via an associated nonlinear element. Typically, when the nonlinear element is a transistor, the pixel electrode is connected to the drain of the transistor, and this arrangement will be assumed in the following description, although it is inherently arbitrary and the pixel electrode may be connected to the source of the transistor.

[0061] Traditionally, in high-resolution arrays, pixels are arranged in a two-dimensional array of rows and columns, such that any particular pixel is uniquely identified by the intersection of a specified row and a specified column. (See also...) Figure 3 In each column, the sources of all transistors are connected to a single column electrode, while the gates of all transistors in each row are connected to a single row electrode. Similarly, the source-to-row and gate-to-column assignments are conventional but essentially arbitrary and can be interchanged if needed. Row electrodes are typically connected to row drivers (gate drivers, gate controllers), which essentially ensure that only one row is selected at any given time; that is, a selected voltage is applied to the selected row electrode to ensure that all transistors in the selected row are turned on, while non-selected voltages are applied to all other rows to ensure that all transistors in those non-selected rows remain off. Column electrodes are typically connected to column drivers (source drivers, source controllers), which apply selected voltages to each column electrode to drive the pixels in the selected row to their desired optical state. (These voltages are relative to a common front electrode, which is typically located on the side of the electro-optic medium opposite to the nonlinear array and extends across the entire display.) After a preselection interval known as the “line addressing time,” the selected row is deselected, the next row is selected, and the voltage on the column driver is changed to write the next line of the display. This process is repeated to write the data line by line across the entire display. The time between addresses on the display is called a "frame". Therefore, a display updating at 60Hz has a 16-millisecond frame. A display updating at 85Hz has a 12-millisecond frame. A display updating at 120Hz has an 8-millisecond frame.

[0062] It should be noted that the magnitude of the voltage that can be provided in such row-column drive is limited by the material used to fabricate the nonlinear element, such as a thin-film transistor. In many embodiments, the semiconductor material is silicon, particularly amorphous silicon, which can control drive voltages on the order of ±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 for a wider range of drive voltages, such as up to ±30V, as described in U.S. Patent Publication No. US2022 / 0084473. This design feature is particularly critical when the drive waveform is used to sort pigments in a multi-particle system. In such systems, it is beneficial to provide at least five voltage levels (high positive, low positive, zero, low negative, high negative), and the higher the total voltage, the easier it is to separate particles. For further details, see U.S. Patent Publication No. 2021-0132459.

[0063] The attached image Figure 2 An exemplary equivalent circuit for a single pixel of an electrophoretic display is depicted. As shown, the circuit includes a pixel electrode ( Figure 1A and 1B The storage capacitor 10 is formed between the element 130 and the capacitor electrode. The electrophoretic dielectric 20 is represented as a capacitor and resistor connected in parallel. In some cases, the direct or indirect coupling capacitance 30 (often referred to as "parasitic capacitance") between the gate electrode of the transistor associated with the pixel and the pixel electrode can introduce unwanted noise into the display. Typically, the parasitic capacitance 30 is much smaller than the capacitance of the storage capacitor 10, and when a pixel row of the display is selected or deselected, the parasitic capacitance 30 can cause a small negative offset voltage, also known as "recoil voltage," at the pixel electrode, which is typically less than 2 volts. [In some embodiments, to compensate for the unwanted "recoil voltage," a common potential V com It can be provided to the top planar electrode and capacitor electrode associated with each pixel, such that when V com Set to equal to the recoil voltage (V) KB When the value of is reached, each voltage supplied to the display can be offset by the same amount, and no net DC imbalance will be experienced.

[0064] In conventional electrophoretic displays using active matrix backplanes, each pixel electrode is associated with a capacitor electrode (storage capacitor), 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 a transistor, and the “selected” and “unselected” voltages applied to the gate electrode can be positive and negative, respectively.

[0065] Figure 3Further details of row-column addressing used in an "active matrix" display are shown. Addressing or pixel electrodes, which address a pixel, are fabricated on substrate 402 and connected to appropriate voltage sources 404 and 406 via associated nonlinear elements. It should be understood that voltage sources 404 and 406 may originate from individual circuit elements or may deliver voltage with the aid of a single power supply and power management integrated circuit (PMIC). In some cases, an intermediate source controller 420 is used to control the supplied voltage; however, in other embodiments, controller 460 is configured to control the entire addressing process, including coordinating the gate and source lines. It should also be understood that... Figure 3 This is a diagram of the layout of an active matrix backplane 400, but in reality, the active matrix has depth, and some elements, such as TFTs, can actually be below the pixel electrodes, with vias to provide electrical connections from the drain to the pixel electrodes above.

[0066] Traditionally, in high-resolution arrays, pixels are arranged in a two-dimensional array of rows and columns, such that any particular pixel is uniquely defined by the intersection of a designated row and a designated column. The sources of all transistors in each column are connected to a single column (scan) line 406, while the gates of all transistors in each row are connected to a single row (gate) line 408; similarly, the source-to-row and gate-to-column assignments are conventional but essentially arbitrary and can be interchanged if necessary. Gate lines 408 are optionally connected to gate line drivers 412, which essentially ensures that only one row is selected at any given time—that is, a selected voltage is applied to the selected row electrode to ensure that all transistors in the selected row are turned on, while non-selected voltages are applied to all other rows to ensure that all transistors in these non-selected rows remain off. Column scan lines 406 are optionally connected to scan line drivers 410, which apply selected voltages to the respective scan lines 406 to drive the pixels in the selected row to their desired optical state. (The voltages mentioned above are relative to a common top electrode and are not included in the standard optical state.) Figure 3 (As shown in the diagram.) Using a conventional driver, after a preselection interval known as "line addressing time," the selected row is deselected, the next row is selected, and the voltage on the column driver is changed to write the next line of the display. This process is repeated linearly, thus writing to the entire display line by line. Figure 3 As shown, the time interval between gate voltage pulses in each frame is typically constant and reflects the rhythm of line-by-line addressing. It is noteworthy that, for a given address row of a pixel electrode, this invention does not achieve a uniform interval between gate voltage pulses.

[0067] refer to Figure 3 The described active matrix backplane is coupled to an electro-optic medium, for example, such as Figure 1A and 1BAs shown, and is typically sealed to create display module 55, such as Figure 4 As shown. This display module 55 becomes the focus of the electrophoretic display 40. The electrophoretic display 40 typically includes a processor 50 configured to coordinate a number of functions related to displaying content on the display module 55 and to transform “standard” images (e.g., sRGB images) into a color system that best reproduces the image on the display module 55. Of course, if the electrophoretic display is used as a sensor or counter, the content may be related to other inputs. The processor is typically a mobile processor chip, such as those manufactured by Freescale or Qualcomm, but other manufacturers are also known. The processor communicates frequently with a non-transitory memory 70, retrieving image files and / or lookup tables from the non-transitory memory 70 to perform the color image transformations described below. The non-transitory memory 70 may also include gate drive instructions such that a particular color transition may require a different gate drive mode. The electrophoretic display 40 may have more than one non-transitory memory chip. The non-transitory memory 70 may be flash memory. In many embodiments, by... Figure 4 All components are integrated into a circuit board or package, and the non-transitory memory 70 is directly integrated into the end consumer device. However, in some cases, the drive circuitry is not directly integrated into the display, such as when the display is external to an object such as a car.

[0068] Waveforms (discussed below) are typically stored in non-transitory memory 70; however, they may also be incorporated into controller 60 or processor 50, or they may be stored in the cloud and downloaded via communication unit 85. Multiple lookup tables can be used to aid the method of the invention, particularly to appropriately provide time-shifted waveforms to controller 60. Specifically, for a given transition from a first color to a second color in an electrophoretic medium with eight primary colors, the lookup table may include: instructions for updating from color 1 to a subsequent color (without time shift) in lookup slots 1 to 8, instructions for updating from color 1 to a subsequent color (with a first time shift) in lookup slots 9 to 16, and instructions for updating from color 1 to a subsequent color (with a second time shift) in lookup slots 17 to 24, and so on. Of course, such lookup tables can also be indexed for operating conditions such as device temperature, battery health, front light color, and front light intensity to improve performance.

[0069] Once the desired image has been converted for display on display module 55, specific image instructions are sent to controller 60, which facilitates the transmission of voltage sequences to the corresponding thin-film transistors (as described above). These voltages typically originate from one or more power supplies 80, which may include, for example, a power management integrated circuit (PMIC). Electrophoretic display 40 may additionally include a communication unit 85, which may be, for example, a Wi-Fi protocol or Bluetooth, and allows electrophoretic display 40 to receive images and instructions, which may also be stored in memory 70. Electrophoretic display 40 may additionally include one or more sensors 90, which may include temperature sensors and / or light sensors, and this information can be fed to processor 50 to allow the processor to select the optimal lookup table when such a lookup table is indexed for ambient temperature or incident light intensity or spectrum. In some cases, multiple components of electrophoretic display 40 may be embedded in a single integrated circuit. For example, an application-specific integrated circuit (ASIC) may implement the functions of processor 50 and controller 60.

[0070] like Figure 5 As shown, the ACEP (e.g., WCMY) system works similarly to printing on bright white paper, because the observer only sees the colored pigments on the observation side—the white pigment (i.e., the only pigment that scatters light). Figure 5 In this scenario, we assume the viewing surface of the monitor is at the top (as shown in the figure), meaning the user views the monitor from this direction, and the illumination light also enters from this direction. Figure 5 In this context, light-scattering particles are assumed to be white pigment. These light-scattering white particles form a white reflector, and any particles above the white particles (such as...) Figure 5 (As shown) are all observed relative to the reflector. A portion of the incident light passes through the subtractive particles, is reflected from the white particles below them, returns through these particles, and exits the display. Different portions of the incident light are absorbed by the subtractive particles. Therefore, the particles above the white particles can absorb a variety of colors, and the color presented to the user is produced by the combination of the particles above the white particles. Any particles located below the white particles (behind them from the user's perspective) are obscured by the white particles and do not affect the displayed color. Because the second, third, and fourth particles are essentially non-light-scattering, their order or arrangement relative to each other is not important; however, for the reasons already stated, their order or arrangement relative to the white (light-scattering) particles is crucial.

[0071] More specifically, when cyan, magenta, and yellow particles are located below white particles ( Figure 5 In case [A]), there are no particles above the white particle and the pixel simply displays white. When a single particle is above a white particle, the color of that single particle is displayed. Figure 5In cases [B], [D], and [F], the colors are yellow, magenta, and cyan, respectively. When two particles are positioned above a white particle, the displayed color is a combination of the colors of those two particles; in... Figure 5 In case [C], magenta and yellow particles appear red; in case [E], cyan and magenta particles appear blue; and in case [G], yellow and cyan particles appear green. Finally, when all three colored particles are above the white particle ( Figure 5 In the case of [H], all incident light is absorbed by the three subtractive primary color particles and the pixel displays black.

[0072] It is possible to render a subtractive primary color using particles that scatter light, so the display would include two types of light-scattering particles: one white and one colored. However, in this case, the position of the light-scattering colored particles relative to other colored particles covering the white particles will be important. For example, when rendering the color as black (when all three colored particles are above the white particles), the scattering colored particles cannot be above the non-scattering colored particles (otherwise they would be partially or completely hidden behind the scattering particles, and the color rendered would be the color of the scattering colored particles, not black).

[0073] Figure 5 This illustrates an idealized scenario where color is uncontaminated (i.e., light-scattering white particles completely block any particles located behind them). In practice, the blocking of white particles may be imperfect, resulting in a small amount of light being absorbed by particles that would ideally be completely blocked. This contamination typically reduces both the brightness and chromaticity of the resulting color. In the electrophoretic medium of this invention, this color contamination should be minimized to the extent that the resulting color is comparable to industry standards for color reproduction. A particularly popular standard is SNAP (the standard for newspaper advertising production), which specifies the L*, a*, and b* values ​​for each of the eight primary colors mentioned above. (In the following text, "primary color" will be used to refer to...) Figure 5 The eight colors shown are black, white, three subtractive primary colors, and three additive primary colors.

[0074] Figure 6A shows the push-pull waveform (in simplified form) used to drive the aforementioned four-particle WCMY electrophoresis display system. This waveform consists of dipoles comprising two pulses of opposite polarity. Typically, each dipole has a pulse of voltage V1 applied at time t1 followed by voltage V2 applied at time t2. The dipoles are impulse-balanced when V1t1 + V2t2 = 0. The amplitude and length of these pulses determine the resulting color. There should be at least five such voltage levels. Figure 6A shows high and low positive and negative voltages, as well as zero voltage. Typically, "low" (L) refers to a range of approximately 5–15V, while "high" (H) refers to a range of approximately 15–30V. Generally, the higher the amplitude of the "high" voltage, the better the color gamut achieved by the display. In some cases, especially where more colors are required, medium voltages are also included. The "medium" (M) level is typically around 15V; however, the value of M will depend to some extent on the composition of the particles and the environment of the electrophoresis medium.

[0075] It is worth noting that for the dipole waveform in Figure 6A, the dipoles used to provide magenta, yellow, green, and blue are at least approximately impulse balanced. On the other hand, dipole addressing is not necessary to generate black and white. A simple monopole pulse in either direction would cause the colored and white pigments with opposite charges to move toward and away from the viewing surface, so the display behaves in these cases like a conventional display containing black and white pigments. Furthermore, because these monopole pulses are not DC balanced, additional charge-clearing pulses must be incorporated into the device drive protocol, whether at the beginning or end of an image update, or at the end of an extended unbalanced drive sequence, such as when scrolling text. However, even if the waveform is impulse balanced overall, dipole addressing breaks symmetry. For example, it can have… ,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. Thus, as long as the pigment mobility depends on the applied electric field, this waveform could lead to overall pigment drift.

[0076] Figure 6B illustrates two typical push-pull waveforms used in a four-particle system comprising scattering white particles, absorbing black particles, and two colored scattering particles (yellow and red). These waveforms are used to make the color of the less charged particles appear on the observed surface. See, for example, U.S. Patent No. 10,339,876. In the example shown in Figure 6B, the yellow particles carry a high negative charge, while the white particles carry a low negative charge. The black particles carry a high positive charge, while the red particles carry a low charge and are both positive.

[0077] As can be seen from Figures 6A-6B, one pulse in a dipole typically used to generate a specific color has a shorter duration than the other pulse. Furthermore, although Figures 6A and 6B show the simplest push-pull waveform (dipole) required to form a color, it should be understood that actual waveforms often require multiple repetitions of these patterns, such as... Figure 7 As shown. Repeating dipoles are the primary source of flicker in displays because the pigment is first driven in one direction and then in another. If the frequency of this flicker is too low, the transition from one color to another will appear discordant.

[0078] For a given transition from a first color to a second color, one way to reduce flicker is to provide a waveform that is (slightly) offset in time for the same transition. Similar to noise-canceling headphones, by providing coordinated peaks where the main waveform has troughs, the observer does not perceive large swaying between colors, i.e., the image is optically quieter. Figure 8-10 A method for this improvement is illustrated in more detail. In one embodiment, the first line of the display receives a "normal" waveform, and subsequent lines receive time-shifted waveforms until the pattern begins to repeat again. For example, the waveform sent to the second line of the display is shifted by one frame, the waveform sent to the third line is shifted by another frame relative to the waveform sent to the second line, and so on. Regarding Figure 8 The first row can receive phase 2 (bottom), the second row can receive phase 1 (middle), the third row can receive phase 0 (top), or other orders. It should also be understood that different rows can use waveforms with offsets less than (or greater than) one frame, for example, an offset of approximately 10 milliseconds, or an offset of approximately 5 milliseconds.

[0079] Figure 9The interaction of the same waveform is illustrated, which is time-shifted in two forms and stored in a lookup table in non-transitory memory. For the first row of the active matrix backplane, pixels undergoing a transition from color 1 to color 2 receive the first waveform to induce a desired change in the electrophoretic medium. Subsequent rows receive the same waveform in terms of pulse number, pulse amplitude, and pulse polarity, but in which the waveform is time-shifted, for example, by one frame, such as 5 milliseconds, 8 milliseconds, or 12 milliseconds. This second waveform is stored in a different group of waveforms from the lookup table. The second waveform may belong to a group of time-shifted waveforms, which are assigned every other row, every three rows, every four rows, etc. Subsequent rows receive a third waveform that is the same in terms of pulse number, pulse amplitude, and pulse polarity, but in which the waveform is further time-shifted. Figure 10 It shows the use of Figure 9 The technology utilizes a wider raster pattern. Using this technique, the overall color update from color 1 to color 2 is only extended by tens of milliseconds, which is imperceptible to a human observer compared to conventional driving methods where each row of the color update receives the same waveform during a single frame. Furthermore, because non-transitory memory is relatively inexpensive, providing a time-shifted waveform set for each possible color transition incurs almost no additional cost, such as that stored in one or more lookup tables. Figure 9 and Figure 10 Another benefit of the interleaved time-shift mode is that it makes the current consumption of the gate drivers more uniform, especially when most of the display is driven between the same colors during image updates. Under normal drive, all gate lines in the update region consume current approximately simultaneously, as defined by the push-pull waveform. Interleaved time-shift drive results in fewer gate lines consuming all current simultaneously. In some cases, this reduced current sway will allow for the use of cheaper electronics in the device. In other cases, this current equalization will result in less power consumption, thus extending battery life for the same number of updates. In other embodiments, interleaved gate line orientation scanning allows current to be consumed in almost the same way as in non-interleaved mode. If interleaving is used with source drivers (i.e., through source lines), misalignment of the interleaved waveform can lead to greater current consumption overhead than normal, as more frequent voltage switching is required even for uniform color patches.

[0080] It should be noted that Figure 8-10The technique is not limited to active matrix backplanes, as adjacent segmented displays can also utilize time-shifted waveforms to reduce flicker, especially when using repetitive push-pull waveforms to drive color transitions. Furthermore, the technique is not limited to repetitive push-pull waveforms, as more complex waveforms that are not simple push-pull can be time-shifted to provide less flickering transitions. Additionally, for drive systems combining push-pull waveforms and more complex waveforms, it is possible to "hide" the more complex waveforms within the time-shifted interlaced push-pull waveforms using the described method. For example, in an ACEP system with eight color waveforms as shown in Figure 6A, when one waveform is not push-pull (and is more complex) while the others are, the multi-line interlacing of the push-pull waveforms hides the more complex transitions, making the overall transition less "dissonant" to the observer. While extended lookup tables can be used to apply all the previous techniques, the controller can also be programmed (communicating with both gate and source lines) to provide a brief pause before continuing the next line update, resulting in less flickering updates. Furthermore, the technique is not limited to interlacing every other line or every three lines. Interleaving does not have to be line-by-line and can include blocks of lines. For example, a 4-frame periodic push-pull waveform can be interleaved with 4 single-pixel lines, or a 3-frame periodic push-pull waveform can be interleaved with 3 double-pixel lines, or a 3-frame periodic push-pull waveform can be interleaved with 6 single-line lines. Half-frame offset can be achieved by changing the source / gate drive, etc.

[0081] example

[0082] Figures 11A to 11C Various interleaving schemes facilitated by extended lookup tables are shown, illustrating the optical transients that occur when a display is updated from color 1 to color 2 using a repeated push-pull waveform. Figures 11A to 11C The optical transients show the measured reflectances of L*, a*, and b* for each color in cyan, magenta, and yellow media. Figure 11A In the experiment, the display was driven by a three-frame repeating push-pull waveform, similar to... Figure 7 However, there are interpolated intervals. The display starts in a white state, and all pixels of the display are addressed by a dipole sequence consisting of a first pulse of -24V and a duration of 12 milliseconds, followed by a second pulse of +12V and a duration of 16 milliseconds. A 12-millisecond 0V interval is interpolated between the first and second pulses. (These intervals are not necessary for color formation, but are necessary for measuring optical density during waveform travel due to the integration limitations of the spectrometer used.) Figure 11A In this example, all rows are addressed using typical line-by-line addressing, and there is no time-shift waveform. It can be seen that in... Figure 11A In this process, all three colors of pigment move in phase, causing the measured reflectance of the color to swing back and forth dramatically, resulting in a “very flashy” update.

[0083] Figure 11B The diagram illustrates reflectance measurements of the same display driven from a white state to a second color using the same waveforms, but with the waveforms provided for every other row time-shifted by one frame (approximately 12 milliseconds), i.e., interlaced. Due to the interaction of peaks and troughs in reflectance caused by the time-shifted waveforms, the overall effect is a smaller oscillation in overall reflectance, and as a result, the display updates appear less flickering. This technique can be further extended to include three distinct time-shifted waveforms, each delivered interlaced to one-third of the display. Figure 11C As can be seen, in this case, the fluctuation of reflectivity almost disappears, and the resulting transition from white to the first color is gradual and more subtle than... Figure 11A The example took a little longer. Figure 11A and Figure 11C In comparison, the advantages of this invention are very obvious.

[0084] This invention allows for flicker-free updates of multi-pixel color displays without requiring substantial modifications to the driving electronics. Several aspects and embodiments of the technology described herein have been so described, and it should be understood that various changes, modifications, and improvements will readily occur to those skilled in the art. Such changes, modifications, and improvements are intended to remain within the spirit and scope of the technology described herein. For example, various other means and / or structures for performing the described functions and / or obtaining the described results and / or one or more advantages described herein will readily occur to those skilled in the art, and each of these changes and / or modifications is considered to be within the scope of the embodiments described herein. Those skilled in the art will recognize, or be able to determine, many equivalents to the specific embodiments described herein using experiments not exceeding conventional experimentation. Therefore, it should be understood that the foregoing embodiments are given by way of example only, and embodiments of the invention may be practiced in ways other than those specifically described within the scope of the appended claims and their equivalents. Furthermore, any combination of two or more features, systems, articles, materials, kits, and / or methods described herein, provided that such features, systems, articles, materials, kits, and / or methods are not contradictory, is included within the scope of this disclosure.

Claims

1. An electrophoresis display, comprising: Transparent electrode; An active matrix backplane including multiple rows of pixel electrodes, each pixel electrode being coupled to a thin-film transistor including a gate line and a source line; An electrophoretic medium disposed between the light-transmitting electrode and the active matrix backplate, wherein the electrophoretic medium comprises at least three different types of charged pigment particles; A controller coupled to multiple gate lines, each gate line coupled to a thin-film transistor in one of the multiple rows of pixel electrodes, and the controller coupled to multiple source lines, the controller being further configured to address the pixel electrodes in a row-by-row manner by providing a gate voltage and a source voltage to each thin-film transistor; and A non-transitory memory coupled to the controller and including a lookup table, wherein for a transition between a first color and a second color, the lookup table includes a first waveform for transitioning the electrophoretic medium between the first color and the second color, and a second waveform for transitioning the electrophoretic medium between the first color and the second color, wherein the first waveform and the second waveform are identical in terms of the number of voltage pulses and the polarity and amplitude of each voltage waveform in the voltage pulses, but wherein the time shift of the first waveform and the second waveform is at least 1 millisecond. When the electrophoresis display is updated between the first and second images, the controller performs the following steps: Receive the first waveform from the lookup table; The first waveform is provided to the first row of pixel electrodes; Receive the second waveform from the lookup table; as well as The second waveform is provided to the second row of pixel electrodes adjacent to the first row of pixel electrodes.

2. The electrophoretic display of claim 1, wherein the lookup table further includes a third waveform for transitioning the electrophoretic medium between the first color and the second color, wherein the first waveform, the second waveform, and the third waveform are identical in the number of voltage pulses and in the polarity and amplitude of each of the voltage pulses, but wherein the first waveform, the second waveform, and the third waveform are time-shifted relative to each other by at least 5 milliseconds, and the controller further performs the steps of receiving the third waveform from the lookup table and providing the third waveform to a third row of pixel electrodes adjacent to the second row electrodes, wherein the second row electrodes are located between the first row electrodes and the third row electrodes.

3. The electrophoretic display according to claim 1 or 2, wherein the lookup table further comprises a fourth waveform for switching the electrophoretic medium between the first color and the third color, wherein the third waveform is different from the first waveform and the second waveform in terms of the number of voltage pulses and the polarity and amplitude of each of the voltage pulses, but wherein the first waveform, the second waveform and the third waveform are time-shifted relative to each other by at least 1 millisecond.

4. The electrophoretic display according to any one of claims 1 to 3, wherein, The time shift of the first waveform and the second waveform is at least 5 milliseconds, optionally at least 10 milliseconds, and optionally between 12 milliseconds and 20 milliseconds.

5. The electrophoretic display according to any one of claims 1 to 3, wherein, The time shift of the first waveform and the second waveform is one frame, where one frame is the time required to address each pixel in the active matrix backplane once when addressing the active matrix backplane in a row-by-row manner.

6. The electrophoretic display according to any one of the preceding claims, wherein, The amplitude of the voltage pulse is between -15V and +15V, or between -24V and +24V.

7. The electrophoretic display according to any one of the preceding claims, wherein, The electrophoretic medium comprises reflective white particles and at least one subtractive particle, or comprises reflective white particles and at least one reflective colored particle.

8. The electrophoretic display according to any one of the preceding claims, wherein the electrophoretic medium comprises a fourth type of electrophoretic particles.

9. The electrophoretic display of claim 8, wherein two types of particles are negatively charged and two types of particles are positively charged, or one type of particles is negatively charged and three types of particles are positively charged, or three types of particles are negatively charged and one type of particles is positively charged.

10. The electrophoretic display according to any one of the preceding claims, wherein the electrophoretic medium is encapsulated in a microcapsule or microcell.

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