Methods for delivering low-ghosting partial updates in color electrophoretic displays

Abstract

Methods for improved local updating in a color electrophoretic display. By identifying the transition boundary between pixels that receive a zero update (no voltage sent to the pixel electrode) and a color update, problem pixels that would otherwise receive a zero update are updated to the same color state, reducing edge ghosting in the updated image and improving color in the updated image.

Description

(19) State Intellectual Property Office (12) Invention Patent Application (10) Application Publication Number (43) Application Publication Date (21) Application Number 202580009573.7 (22) Application Date 2025.01.16 (30) Priority Data 63 / 623229 2024.01.20 US (85) PCT International Application Entering National Phase Date 2026.07.10 (86) PCT International Application Application Data PCT / US2025 / 011835 2025.01.16 (87) PCT International Application Publication Data WO2025 / 155697 EN 2025.07.24 (71) Applicant Einker Company Address Massachusetts, USA (72) Inventors S. Pedafossi K.R. Coraus (74) Patent Agency Beijing Panhua Weiye Intellectual Property Agency Co., Ltd. 11280 Patent Attorney Wang Bo (51) Int.Cl. G09G 3 / 20 (2006.01) G09G 3 / 34 (2006.01) G09G 5 / 06 (2006.01) (54) Invention Title: Method for Achieving Low-Ghosting Local Updates in a Color Electrophoretic Display (57) Abstract: A method for improving local updates in a color electrophoretic display. By identifying the transition boundary between pixels receiving zero updates (no voltage is sent to the pixel electrode) and those receiving color updates, problematic pixels that originally received zero updates are updated to the same color state, thereby reducing edge ghosting in the updated image and improving the colors in the updated image. Claims 2 pages, Description 16 pages, Drawings 7 pages, CN 122535939 A 2026.08.07 CN 1 22 53 59 39 A 1. A method for updating a color electrophoretic display having a controller, the display having a plurality of display pixels in an array and capable of displaying at least black, white, red, and yellow, the method comprising: for each of the plurality of display pixels, determining whether the display pixel has the same color data for a first image and a second image; sending an instruction to the controller to provide a waveform corresponding to the color data of the second image to each display pixel having different color data between the first image and the second image; for each display pixel determined to have the same color data for the first image and the second image, determining whether each of the four closest basic display pixels has a color data change between the first image and the second image; sending an instruction to the controller to provide a waveform corresponding to the color data of the second image to the four closest basic display pixels having the same color data between the first image and the second image.At least one of the display pixels having different color data between the first image and the second image; sending an instruction to the controller to not provide waveforms to each display pixel that has the same color data between the first image and the second image and whose four nearest basic display pixels also have the same color data between the first image and the second image. 2. A method for updating a color electrophoretic display having a controller, the display having a plurality of display pixels and capable of displaying at least black, white, red, and yellow, the method comprising: comparing color data of the plurality of display pixels in a first image with color data of the plurality of display pixels in a second image; determining an m × n array of display pixels, wherein all display pixels have the same color data for both the first and second images; determining an i × j array of display pixels, wherein some display pixels have different color data between the first and second images, wherein a combination of the m × n array of display pixels and the i × j array of display pixels constitutes all display pixels in the plurality of display pixels; sending an instruction to the controller to prevent a pixel region slightly smaller than the m × n array of display pixels from updating during a transition from the first image to the second image; and sending an instruction to the controller to provide a waveform corresponding to the color data of the second image to all remaining display pixels that have not received the non-update instruction, wherein some pixels receiving the waveform corresponding to the color data of the second image are within the m × n array of display pixels. 3. The method of claim 2, wherein the non-updating pixel region is at least two pixel rows smaller than the m × n array of the display pixels, or at least two pixel columns smaller than the m × n array of the display pixels. 4. The method of any one of claims 1-3, wherein the electrophoretic display comprises an electrophoretic medium comprising charged particles dispersed in a fluid and confined within a plurality of capsules or microunits. 5. The method of claim 4, wherein the electrophoretic medium comprises four different types of charged particles, and at least two types of charged particles have opposite polarities. 6. The method of claim 5, wherein six primary colors can be formed at each pixel electrode of the electrophoretic display. 7. The method of any one of claims 1-3, wherein the electrophoretic display comprises a color filter array. 8. The method of claim 7, wherein the color filter array comprises a plurality of filters of different colors, and each filter of different colors is indexed to a pixel electrode of the electrophoretic display.9. The method of claim 8, wherein each of the plurality of display pixels corresponds to a plurality of different color filters indexed to a corresponding plurality of pixel electrodes. 10. The method of any one of claims 1-3, wherein the color data is RGB color data. 11. The method of any one of claims 1-3, wherein the color data has been converted from RGB to color data specific to the electrophoretic display. 12. The method of any one of claims 1-3, wherein the color data represents a color image incorporating dithering. Claims 2 / 2 Page 3 CN 122535939 A Method for Achieving Low Ghosting Local Updates in a Color Electrophoretic Display

[0001] Cross-Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 623,229, filed January 20, 2024. All patents and publications disclosed herein are incorporated herein by reference in their entirety. Background Art

[0003] Electrophoretic displays (EPDs) change color by altering the position of charged colored particles relative to a light-transmitting viewing surface. Such electrophoretic displays are often called "electronic paper" or "ePaper" because the resulting displays have high contrast and are readable in sunlight, much like ink on paper. In its simplest sense, an electrophoretic display only requires a light-transmitting electrode, a back electrode, and an electrophoretic medium comprising one or more types of charged colored particles at the observation 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 appear electronically on the observation surface. This pattern could, for example, be the text of a book.

[0004] Multiple color options are already commercially available for electrophoretic displays, including four-color displays (black, white, red, yellow; red, white, yellow, translucent blue; cyan, yellow, magenta, white). For example, when a single color matching one of the colors of the particles is desired at the observation surface, the operation of an electrophoretic display with four types of electrophoretic particles is similar to that of a simple black-and-white display (EPD). However, obtaining a wider color gamut (including mixed colors and overprinted colors) is more complex and requires finer control over the relative positions of the particles to each other and to the observation surface. If operated correctly, this four-particle system allows for the generation of hundreds of different colors at each pixel. Further details about such systems can be found in the following U.S. patents, all of which are incorporated herein by reference in their entirety: U.S. Patent Nos. 9,361,836, 9,921,451, 10,276,109, 10,353,266, 10,467,984, and 10,593,272.

[0005] Color electrophoretic displays can also be implemented using an array of color filters (CFAs) positioned above or below a layer of electrophoretic display material, such as a layer of microcapsules containing black and white particles with opposite charges, which change position relative to the observer due to the provided electric field. See, for example, U.S. Patents 8,098,418 and 10,444,592. However, electrophoretic displays incorporating CFAs suffer from a loss of color space resolution due to subpixels. See, for example, Figures 1D and 1E of this application, illustrating that a “pixel” (dashed bounding box) of a CFA-supported display typically comprises at least three individually controllable subpixels. Traditionally, CFA displays have red, green, and blue filters; however, other complementary color groups can also be used. Due to the subpixels, if a pixel of the display is to display one of the primary colors, only one-third or less of the display area of ​​that pixel (less because of the fill between subpixels) is used to display that color. The other subpixels are dark to increase the chromaticity of the desired color.

[0006] Of course, most color images require more than just red, green, blue, black, and white pixels. While some colors (e.g., purple) can be approximated by mixing subpixels, a more common approach is to dither colors among pixels in an image to achieve the desired color and chromaticity. However, when dithering is used to increase the colors available in an electrophoretic display, the dithered subpixels involved in the dithering process may be subject to unwanted crosstalk from nearby subpixels, which can cause the dithered colors to appear “incorrect.” See, for example, U.S. Patent No. 11,869,451. Additional problems arise when, for example, only a portion of the image is updated (also known as a partial update), which can also cause colors at unupdated edges on the boundaries of the updated pixels to appear “incorrect.” See, for example, U.S. Patent No. 11,557,260.

[0007] In most cases, electrophoretic media such as those described above are designed to be driven by a low-voltage square wave generated by a driving circuit such as that described on page 1 / 16 of the specification of a thin-film transistor backplane, CN 122535939 A. These driving circuits can be mass-produced inexpensively because they are closely related to the driving circuits and manufacturing methods used to produce liquid crystal display panels, such as those found in smartphones, laptop displays, and televisions. Historically, even when the electrophoretic medium was directly driven via isolation electrodes (e.g., segmented electrodes), the driving pulses were provided in the form of square waves with amplitude and time width. See, for example, U.S. Patent No. 7,012,600, which is incorporated herein by reference in its entirety. Typically, for an active matrix backplane comprising an array of pixel electrodes, when the pixel electrode array is addressed row by row, each pixel electrode receives a signal pulse (square wave) for a short period of time. UpdateThe time required for the entire pixel array to be updated, and the time between updates to individual pixel electrodes, is called a frame. The set of voltage impulses required to change a display from a first display state to a second display state is generally referred to as a waveform. A waveform typically comprises at least three frames, for example, as described in U.S. Patent No. 11,620,959, which is incorporated herein by reference in its entirety.

[0008] When the electrophoretic medium comprises multiple types of particles having the same charge polarity but different charge quantities, the final position (and optical state) of a given set of particles is typically controlled by a series of positive and negative voltage impulses. For example, all positive particles can be driven to the viewing surface, and then a combination of negative and positive voltages is used to disperse the set of positive particles and drive unwanted positive particles away from the viewing surface, so that only the desired set of particles is observed. However, the driving method requiring multiple positive and negative pulses often results in color changes that are noticeably glaring to the user, also known as “flicker updates.” The amount of flicker can be reduced by making the waveform longer and using smaller voltage steps, but such waveforms are not suitable for applications such as page turning or stylus writing. In these applications, users expect the display to have a near-instantaneous response and high contrast between the first and second optical states. (See, for example, U.S. Patent Publication No. 2022 / 0262323 for a description of long gradient waveforms.) Historically, it has been difficult to achieve short, low-flicker, low-latency color waveforms for such multi-particle systems.

[0009] Electro-optic displays typically have a backplane with a plurality of pixel electrodes disposed thereon, each pixel electrode defining a pixel of the display. Each pixel electrode is typically disposed in a rectangular array of pixel electrodes and each pixel electrode is controlled by a thin-film transistor (TFT), and the TFT is updated in a row-by-row manner. Typically, a single common electrode extending across a large number of pixels (typically the entire display) is disposed on opposite sides of the electro-optic medium. Individual pixel electrodes can be driven directly (i.e., a separate conductor can be provided to each pixel electrode) or they can be driven in an active matrix manner, as is well known to those skilled in the art of backplane technology. Since adjacent pixel electrodes are typically at different voltages, they must be separated by a finite-width inter-pixel gap to avoid electrical short circuits between the electrodes. Although at first glance the electro-optic medium covering these gaps may not appear to switch when a driving voltage is applied to the pixel electrode (in fact, this is often the case for some non-bistable electro-optic media (e.g., liquid crystals), where a black mask is typically provided to hide these non-switching gaps), in the case of many bistable electro-optic media, the medium covering the gaps does indeed switch due to a phenomenon known as "blooming."

[0010] Blossoming refers to the tendency of the optical state of the electro-optic medium to change over a region larger than the physical size of the pixel electrode when a driving voltage is applied to the pixel electrode. The blooming region is not a uniform color, but is typically a transition region where...In the transition zone, as the medium moves across the halo region, the color of the medium changes from the desired color to another chromaticity or color. For example, a desired white pixel may include various shades of gray along the edges, also known as "edge ghosting." Furthermore, depending on the type of display—black / white display, color display, black / white display with a color filter—the consequences of edge ghosting can range from annoying to debilitating. In some cases, asymmetrical halos can cause edge ghosting.

[0011] The majority of the following discussion will focus on the method used to drive one or more pixel electrodes of an electro-optic display from a first optical (i.e., color) state to a final optical state (which may differ from or be no different from the initial optical state). The term "waveform" will be used to refer to the entire voltage-to-time curve used to achieve the transition from a particular first color state to a particular second color state. Typically, such a waveform will comprise multiple waveform elements; these elements are essentially rectangular (V×t) voltage pulses (i.e., where a given element comprises applying a constant voltage over a period of time, as described on page 2 / 16 of the specification, CN 122535939 A); these elements may be referred to as “pulses” or “drive pulses.” The term “drive scheme” refers to a set of waveforms sufficient to achieve all possible transitions between gray levels of a particular display. A display may utilize more than one drive scheme; for example, the aforementioned U.S. Patent No. 7,012,600 teaches that the drive scheme may need to be modified based on parameters such as the display’s temperature or the time it has been operating during its lifespan, thus providing the display with multiple different drive schemes for use under conditions such as different temperatures. A set of drive schemes used in this manner may be referred to as a “set of related drive schemes.” As described in the aforementioned MEDEOD applications, more than one driving scheme can also be used simultaneously in different areas of the same display. A set of driving schemes used in this way can be referred to as a "set of simultaneous driving schemes"

[0012] . The terms "bistable" and "bistable" are used herein in their conventional meaning in the art, referring to a display comprising display elements having a first display state and a second display state that are different in at least one optical characteristic, such that after any given element is driven by an addressing pulse of finite duration to present its first or second display state, after the addressing pulse terminates, 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. 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. This type of display is aptly referred to as multistable rather than...It is bistable, but for convenience, the term “bistable” may be used herein to cover both bistable and multistable displays. While the bistable nature of electrophoretic displays allows for significant power savings compared to conventional “always-on” displays such as LCDs and LEDs, bistableness can lead to image retention between updates, also known as “ghosting.”

[0013] The term “impulse” as used herein, when referring to driving an electrophoretic display, refers to the integral of the voltage applied during driving the display with respect to time. The term “waveform” as used herein, when referring to driving an electrophoretic display, describes a series of voltages or voltage patterns supplied to the electrophoretic medium over a given time period (second, frame, etc.) to produce the desired optical effect in the electrophoretic medium.

[0014] 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.

[0015] Numerous patents and applications assigned to or attributed to MIT and Einkel describe various techniques for encapsulating electrophoretic and other electro-optic media. Such encapsulated media comprise multiple small capsules, each capsule itself comprising an inner phase containing electrophoretically moving particles in a fluid medium, and a capsule wall surrounding the inner phase. Typically, the capsules themselves are held within a polymer binder to form a coherent layer located between two electrodes. The technologies 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) capsules, adhesives, and encapsulation processes; see, for example, U.S. Patent Nos. 6,922,276 and 7,411,719;

[0018] (c) microcell structures, wall materials, and methods of forming microcells; 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; Specification 3 / 16 pages 6 CN 122535939 A

[0021] (f) Backplate, adhesive layer and other auxiliary layers and methods used in a display; 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. 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 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;7,312,794;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; 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 / Instruction Manual 4 / 16 Page 7 CN 122535939 A 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;

[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, such as U.S. Patent No. 6,241,921; and U.S. Patent Application Publication No. 2015 / See, for example, U.S. Patent Application Publication Nos. 0277160; and U.S. Patent Application Publications Nos. 2015 / 0005720 and 2016 / 0012710.

[0026] Many of the foregoing 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 electrophoretic fluid droplets and a continuous phase of polymer material, and the discrete electrophoretic fluid droplets within such a polymer dispersion electrophoretic display can be regarded 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 regarded as a subclass of encapsulated electrophoretic media.

[0027] A related type of electrophoretic display is the so-called “micro-unit electrophoretic display”. In a micro-unit electrophoretic display, charged particles and fluids are not encapsulated in microcapsules, but are retained in a plurality of cavities formed within a carrier medium (typically a polymer membrane). See, for example, U.S. Patent Nos. 6,672,921 and 6,788,449.

[0028] Although electrophoretic media are generally opaque (because, for example, in many electrophoretic media, particles essentially block visible light from passing through the display) and operate in reflective mode, some electrophoretic displays can be made to operate in a so-called “shutter mode,” in which one display state is essentially opaque and one display state is transparent. See, for example, U.S. Patent Nos. 5,872,552; 6,130,774; 6,144,361; 6,172,798; 6,271,823; 6,225,971; and 6,184,856. Dielectric electrophoretic displays are similar to electrophoretic displays but depend on changes in electric field strength and can operate in a similar mode; see U.S. Patent No. 4,418,346. Other types of electro-optic displays may also be able to operate in 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 viewing surface of the display 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 aggregation and settling 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 “printing” is intended to include all forms of printing and coating, including but not limited to: pre-load coating such as patch die coating, slot or extrusion coating, slide or cascade coating, curtain coating; roll coating such as doctor blade coating, forward and reverse roll coating; gravure coating; dip coating; spray coating; meniscus coating; spin coating; brush coating; air knife coating; screen printing process; static coating ...Electroprinting processes; thermal printing processes; inkjet printing processes; 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. Additionally, as described in U.S. Patent Application Publication No. 2021 / 0132459, the encapsulated electrophoretic medium can be incorporated into non-planar surfaces, which in turn are incorporated into everyday objects. Therefore, the surfaces of products, building materials, etc., can be designed to change color when a suitable electric field is provided. Summary of the Invention

[0030] This document discloses a method for improving local updates in a color electrophoretic display. A color electrophoretic display presents the user with more colors than black and white and grayscale, i.e., showing at least red, yellow, black, and white. In a first aspect, a method for updating a color electrophoretic display having a controller and a plurality of display pixels in an array. The method includes: for each of a plurality of display pixels in the specification (page 5 / 16, CN 122535939 A), determining whether the display pixel has the same color data for a first image and a second image; sending an instruction to a controller to provide a waveform corresponding to the color data of the second image to each display pixel that has different color data between the first image and the second image; for each display pixel determined to have the same color data for the first image and the second image, determining whether there is a color data change between the first image and the second image for each of its four nearest basic display pixels; sending an instruction to the controller to provide a waveform corresponding to the color data of the second image to each display pixel that has the same color data between the first image and the second image and at least one of its four nearest basic display pixels that has different color data between the first image and the second image; and sending an instruction to the controller not to provide a waveform to each display pixel that has the same color data between the first image and the second image and whose four nearest basic display pixels also have the same color data between the first image and the second image. In some embodiments, the electrophoretic display includes an electrophoretic medium comprising charged particles dispersed in a fluid and confined within a plurality of capsules or microunits. In some embodiments, the electrophoretic medium comprises four different types of charged particles, and at least two types of charged particles have opposite polarities. In some embodiments, six primary colors may be formed at each pixel electrode of the electrophoretic display. In some embodiments, the electrophoretic display comprises a color filter array. In some embodiments, the color filter array comprises multiple filters of different colors, and each filter of a different color is indexed to a pixel electrode of the electrophoretic display. In some embodiments, multiple displaysEach display pixel in the pixel array corresponds to a filter of multiple different colors indexed to a corresponding plurality of pixel electrodes. In some embodiments, the color data is RGB color data. In some embodiments, the color data has been converted from RGB to color data specific to the electrophoretic display. In some embodiments, the color data represents a color image incorporating dithering.

[0031] In another aspect, a method for updating a color electrophoretic display having a controller and a plurality of display pixels. The method includes: comparing color data of a plurality of display pixels in a first image with color data of a plurality of display pixels in a second image; determining an m × n array of display pixels, wherein all display pixels have the same color data for both the first and second images; determining an i × j array of display pixels, wherein some display pixels have different color data between the first and second images, wherein a combination of the m × n array and the i × j array constitutes all display pixels in the plurality of display pixels; sending an instruction to a controller to prevent a pixel region slightly smaller than the m × n array of display pixels from updating during a transition from the first image to the second image; and sending an instruction to the controller to provide a waveform corresponding to the color data of the second image to all remaining display pixels that have not received the non-update instruction, wherein some pixels receiving the waveform corresponding to the color data of the second image are within the m × n array of display pixels. In some embodiments, the non-update pixel region is at least two pixel row heights smaller than the m × n array of display pixels, or at least two pixel column widths smaller than the m × n array of display pixels. In some embodiments, the electrophoretic display includes an electrophoretic medium comprising charged particles dispersed in a fluid and confined within a plurality of capsules or microunits. In some embodiments, the electrophoretic medium comprises four different types of charged particles, and at least two types of charged particles have opposite polarities. In some embodiments, six primary colors may be formed at each pixel electrode of the electrophoretic display. In some embodiments, the electrophoretic display comprises a color filter array. In some embodiments, the color filter array comprises a plurality of filters of different colors, and each filter of different colors is indexed to a pixel electrode of the electrophoretic display. In some embodiments, each of a plurality of display pixels corresponds to a plurality of filters of different colors indexed to a corresponding plurality of pixel electrodes. In some embodiments, the color data is RGB color data. In some embodiments, the color data has been converted from RGB to color data specific to the electrophoretic display. In some embodiments, the color data represents a color image incorporating dithering. Specification 6 / 16 pages 9 CN 122535939 A Brief Description of the Drawings

[0032] This patent or application document contains at least one color drawing. The patent or application disclosed in this patent or application document contains a color drawing.A copy of the figures will be provided by the Patent Office upon request and payment of the necessary fees.

[0033] Figure 1A is a representative cross-sectional view of a four-particle electrophoretic display in which the electrophoretic medium is encapsulated in microcapsules.

[0034] Figure 1B is a representative cross-sectional view of a four-particle electrophoretic display in which the electrophoretic medium is encapsulated in microcells.

[0035] Figure 1C is a representative cross-sectional view of an electrophoretic display, which includes, for example, an electrophoretic layer of black and white particles with opposite charges coupled to a color filter array (CFA) disposed between the electrophoretic layer and the observer.

[0036] Figure 1D is an exemplary RBGW color filter array pattern that can be used with a CFA-enabled color electrophoretic display. The dashed line defines a “pixel” for the purpose of defining a pixel in an image. Each pixel of an RGBW CFA includes independently controllable red, green, and blue portion transmission filter portions, referred to as “subpixels”; transparent (also known as white) subpixels help improve white and light colors in the image. Below each subpixel is an independently controllable pixel electrode of the type shown in FIG2B.

[0037] FIG1E is an exemplary RGB color filter array pattern that can be used with a CFA-enabled color electrophoretic display. The dashed line defines a “pixel” for the purpose of defining a pixel in an image. Each pixel of the RGB CFA includes independently controllable red, green, and blue partial transmission filter portions, referred to as subpixels; the portion around each subpixel is transparent (also known as partially filled CFA) to improve whites and light colors in the image, but with a higher overall resolution compared to FIG1D. Below each subpixel is an independently controllable pixel electrode of the type shown in FIG2B.

[0038] FIG2A shows an exemplary equivalent circuit of a single pixel of an electrophoretic display using an active matrix backplane with storage capacitors.

[0039] FIG2B shows an exemplary equivalent circuit of a simplified electrophoretic display of the present invention, allowing for row-column driving.

[0040] FIG3 shows an exemplary electrophoretic display including a display module. The electrophoretic display also includes a processor, 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 based on the surrounding environment, such as temperature and lighting.

[0041] Figure 4A shows preferred positions for each of the four groups of particles that produce eight standard colors in a white-cyan-magenta-yellow (WCMY) four-particle electrophoretic display, where white particles are reflective and cyan, magenta, and yellow particles are absorptive.

[0042] Figure 4B shows preferred positions for each of the four groups of particles that produce seven standard colors in a white-red-yellow-blue semi-absorbent (WRYB*) four-particle electrophoretic display, where white, red, and yellow particles are reflective and blue particles are semi-absorbent (B*).

[0043] Figure 5 illustrates the common problem of edge ghosting in electrophoretic displays.

[0044] Figure 6 illustrates a simple local update in a color electrophoretic display, where the first part of the display, i.e., m × n pixels, does not receive an update because the content between the first and second images remains unchanged, while the second part of the display, i.e., i × j pixels, receives a complete update because the content between the first and second images has been updated.

[0045] Figure 7 illustrates the fundamental neighboring pixel electrodes of the target pixel electrode (x, y).

[0046] Figure 8 illustrates an improved local update in a color electrophoretic display, where a given pixel electrode that has not been updated can be updated based on the update state of the fundamental neighboring pixels of the given pixel. The overall result is fewer “flickering” transitions, thereby achieving better color performance with less energy consumption.

[0047] Figure 9 is a flowchart describing the method of the present invention. Specification 7 / 16 pages 10 CN 122535939 A Detailed Description

[0048] The present invention details a method for improving local updates in a color electrophoretic display. Partial updates are typically used when only a portion of the display needs updating between the first and second images. This is because 1) only a portion of the display is being updated, i.e., due to drop-down menus, updated text boxes, pop-ups, etc., while the remaining image is static, or 2) some pixels have the same color state between the first and second images. Partial updates are energy-efficient because fewer pixel electrodes need to be switched between the first and second images. Furthermore, since fewer pixels are being updated, the transition is perceived as less "flickering," meaning the transition is less glaring to the observer. However, due to inter-pixel coupling, i.e., as discussed in the background art (also known as "halo"), the boundary between updated and unupdated pixel electrodes during a partial update can experience unexpected color state drift. This can lead to incorrect chromaticity of a given subpixel, incorrect color of a given image pixel, or incorrect color in jittery areas of the image. Inter-pixel coupling can also cause ghosting (also known as "ghosting") in the updated image. Ghosting can be particularly noticeable when an area of ​​the display is repeatedly driven, i.e., when the video rate countdown clock is running. Using the method of the present invention, many color and ghosting problems in color electrophoretic displays can be minimized, regardless of the nature of the color electrophoretic display, whether it is a display with multiple different colored particles at each pixel electrode or a color filter array display including black and white particles below the subpixels of each display pixel.

[0049] Methods for manufacturing electrophoretic displays comprising two, three, four (or more) types of particles have been discussed in the prior art. The electrophoretic fluid can be encapsulated in microcapsules or incorporated into a microcell structure subsequently sealed with a polymer layer.The microcapsules or micro-unit layers can be coated or laminated onto a plastic substrate or film with a coating of transparent conductive material. Alternatively, microcapsules can be coated onto a light-transmitting substrate or other electrode material using a spraying technique. (See U.S. Patent No. 9,835,925, which is incorporated herein by reference.) The resulting assembly can be laminated to a backplane including pixel electrodes using a conductive adhesive. The assembly can also be attached to one or more segmented electrodes on the backplane, wherein the segmented electrodes are directly driven. In another embodiment, the assembly (which may include a non-planar light-transmitting electrode material) is sprayed with capsules and then coated with a back electrode material. (See U.S. Patent Publication No. 2021 / 0132459, which is incorporated herein by reference.) Alternatively, electrophoretic fluid can be directly dispensed onto a thin open-cell mesh already arranged on a backplane including an active matrix of pixel electrodes. The filled mesh can then be top-sealed with an integrated protective sheet / light-transmitting electrode.

[0050] Electrophoretic displays typically include an electrophoretic material layer and at least two other layers disposed on opposite sides of the electrophoretic material, one of which is an electrode layer. In most such displays, both layers are electrode layers, and one or both electrode layers are patterned to define pixels of the display. For example, one electrode layer may be patterned as an elongated row electrode, and the other as an elongated column electrode extending perpendicularly to the row electrode, with pixels defined by the intersection of the row and column electrodes. Alternatively, more commonly, one electrode layer has the form of a single continuous electrode, and the other electrode layer is patterned as a matrix of pixel electrodes, each pixel electrode defining one pixel of the display. In another type of electrophoretic display designed for use with a stylus, printhead, or similar movable electrodes separate from the display, only one layer of the adjacent electrophoretic layer includes electrodes, and the layers on opposite sides of the electrophoretic layer are typically protective layers designed to prevent damage to the electrophoretic layer by the movable electrodes.

[0051] The electrophoretic medium used herein includes charged particles that vary in color, reflective or absorptive properties, charge density, and mobility in an electric field (measured in zeta potential). 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 reflecting materials other than pigments (strictly speaking, this term refers to insoluble colored materials), such as dyes or photonic crystals, can also be used in the electrophoretic medium and display of the present invention. For example, the electrophoretic medium may include: a fluid; a plurality of first particles and a plurality of second particles dispersed in the fluid, the first and second particles carrying 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 and fourth ... having a certain polarity of charge, the first particles being light-scattering particles and the second particles having a certain polarity 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 being light-scattering particles and the fourth particles having a certain polarity 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 particlesWith opposite polarities of charge, the third and fourth particles each have a subtractive primary color that is different from each other and different from that of the second particle, 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.

[0052] The electrophoretic medium of the present invention may contain any additives used in prior art electrophoretic media, such as those described in the aforementioned Einkel 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 the various particles, and polymers with a number average molecular weight greater than about 20,000 and substantially non-adsorbed onto the particles may be dissolved or dispersed in the fluid to improve the bistability of the display, as described in the aforementioned U.S. Patent No. 7,170,670.

[0053] In one embodiment, the present invention uses light-scattering particles that are generally white and three substantially non-light-scattering particles. Of course, there are no particles that are completely light-scattering or completely non-light-scattering, and the minimum light scattering of light-scattering particles and the maximum tolerable light scattering of substantially non-light-scattering particles used in the electrophoresis of this invention may vary depending on factors such as the specific pigments used, their colors, and the user's or application's tolerance for some deviation from the desired color. The light scattering and absorption characteristics of pigments can be evaluated by measuring the diffuse reflectance of a pigment sample dispersed in a suitable matrix or liquid on white and black backgrounds. The results of such measurements can be interpreted according to various models known in the art, such as one-dimensional Kubelka-Munk processing. In this invention, it is preferred that the white pigment, when approximately isotropically distributed by volume at 15% in a 1 μm thick layer comprising the pigment and a liquid with a refractive index less than 1.55, exhibits a diffuse reflectance of at least 5% measured at 550 nm on a black background. Yellow, magenta, and cyan pigments preferably exhibit diffuse reflectances of less than 2.5% measured at 650 nm, 650 nm, and 450 nm on a black background, respectively, under the same conditions. (The wavelengths selected above for measuring yellow, magenta, and cyan pigments correspond to the spectral regions where these pigments absorb the least.) Colored pigments that meet these criteria are referred to below 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.

[0054] Alternative groups of particles may also be used, including four groups of reflective particles, or one absorbing 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 made from inorganic pigments such as TiO2, ZrO2, ZnO, Al2O3, Sb2O3, BaSO4, and PbSO4.The black particles can be formed from CI pigments such as Black 26 or 28 (e.g., manganese iron black spinel or chromium copper black spinel) or carbon black. The third / fourth / fifth types of particles can be 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 Sunlight-resistant Red D3G, Hostaperm Red D3G 70, Hostaperm Blue B2G-EDS, Hostaperm Yellow H4G-EDS, Hostaperm Green GNX; BASF's Irgazine Red L 3630, Cinquasia Red L 4100 HD, and Irgazin Red L 3660 HD; and Solar Chemicals' Phthalocyanine Blue, Phthalocyanine Green, Diaryl Yellow, or DiarylAAOT Yellow.

[0055] As shown in Figures 1A, 1B, and 1C, the electrophoretic display (101, 102, 103) typically includes a top transparent electrode 110, an electrophoretic medium 120, and a bottom electrode 130, the bottom electrode 130 being typically a pixel electrode of an active matrix of pixels controlled by thin-film transistors (TFTs). However, the bottom electrode 130 can be a single, larger electrode, such as a graphite backing, a PET / ITO film, a metallized film, or a conductive coating. In the electrophoretic medium 120 described in Figures 1A and 1B, there are four different types of particles 121, 122, 123, and 124; however, more particle groups can be used with the methods and displays described herein. In the CFA display 103, the electrophoretic medium 120 can include an encapsulated electrophoretic medium having only black and white particles with opposite charges. Figure 1D is an exemplary RBGW color filter array pattern that can be incorporated into the CFA display 103, as described on page 9 / 16 of CN 122535939 A. Colored elements can be directly disposed on the top transparent electrode 110, which can be, for example, indium tin oxide (ITO). Such CFA films are available from Toppan Printing Co., Ltd. (Japan). Alternatively, color filter elements can be applied to the electrophoretic medium 120 using inkjet or other precision printing processes. See U.S. Patent No. 10,209,556. As shown in Figures 1D and 1E, the dashed line defines a "pixel" for the purpose of defining pixels in an image. In Figure 1D, each pixel of the RGBW CFA includes independently controllable red, green, and blue subpixels, as well as an equal-sized transparent (also known as white) subpixel, to improve whites and lighter colors in the image. In Figure 1E, RGB...CFA pixels comprise independently controllable red, green, and blue subpixels, with the area surrounding each subpixel being transparent (also known as partially filled CFA) to improve whites and light colors in the image. In practice, the CFA pattern of Figure 1E is superior to that of Figure 1D because each image pixel is slightly smaller, thus allowing for higher resolution for the same number of pixel electrodes per inch (PPI) (typically between 100 and 400 PPI, more commonly between 150 and 300 PPI).

[0056] In Figures 1A and 1B and similar embodiments, two of the four different types of particle groups 121, 122, 123, and 124 have a first polarity, while the other two have a second (opposite) polarity. In some embodiments, one of the four different types of particle groups 121, 122, 123, and 124 has a first polarity, while the other three have a second (opposite) polarity. In some embodiments, two of the four different types of particle groups have a first polarity, while the other two have opposite polarities. Electrophoretic media 120 is typically separated by the walls of microcapsules 126 or microunits 127. An optional adhesive layer 140 may be disposed adjacent to either 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 protect only the top electrode 110 from damage, or it may surround the entire display (101, 102) to prevent the ingress of water, etc. The electrophoretic displays (101, 102) may also include a sealing layer 180, if desired. In some embodiments, adhesive layer 140 may include a primer component to improve adhesion to electrode layer 110, or a separate primer layer (not shown in FIG. 1B) may be used. The structure and components of the electrophoretic display, pigments, binders, electrode materials, etc., are described in numerous patents and patent applications published by Einkel, such as U.S. Patent Nos. 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.

[0057] In some embodiments, such as as shown in FIG1A, the electrophoretic display may include only a first transparent electrode, an electrophoretic medium, and a second (back) electrode, which may also be transparent. However, in order to produce a high-resolution display, such as as shown in FIG1B, each pixel must, of course, be addressable without interference from adjacent pixels so that the image file is faithfully reproduced in the display. One way to achieve this is to provide an array of nonlinear elements such as transistors or diodes.Columns, in which at least one nonlinear element is associated with each pixel, produce an "active matrix" display. The addressing or pixel electrode of a pixel is connected to an appropriate voltage source via the associated nonlinear element. Typically, when the nonlinear element is a transistor, the pixel electrode is connected to the drain of the transistor; this arrangement will be assumed in the following description, although it is essentially arbitrary and the pixel electrode can be connected to the source of the transistor. Typically, 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 electrode, while the gates of all transistors in each row are connected to a single row electrode; similarly, assigning sources to rows and gates to columns is conventional but essentially arbitrary and can be reversed if desired. The row electrodes are connected to a row driver, which essentially ensures that only one row is selected at any given time, i.e., a selection voltage is applied to the selected row electrode to ensure that all transistors in the selected row are conductive, while a non-selection voltage is applied to all other rows to ensure that all transistors in these non-selected rows remain non-conductive. Column electrodes are connected to column drivers, which apply voltages to each column electrode selected to drive the pixels in the selected row to their desired optical state. (The voltage specification mentioned above, page 10 / 16, CN 122535939 A, is 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.)

[0058] After a preselection interval called the “row addressing time,” the selected row is deselected, the next row is selected, and the voltage on the column driver is changed so that the next row of the display is written. This process is repeated so that the entire display is written row by row. The entire process is coordinated by a clock circuit. The time between the nth addressing of a pixel and the next (n+1) addressing is called a “frame.” Thus, a display updated at 60Hz has a frame of 16 milliseconds. However, the term “frame” is not limited to use with active matrix backplanes. The driving frame described herein can also be used to refer to, for example, the time unit between updates of a single backplane. While the electrophoretic medium can be driven using analog voltage signals (e.g., generated by a power supply and potentiometer), the use of a digital controller discretizes the waveform into blocks typically on the order of 10 ms; however, shorter or longer frame widths are possible. For example, frames can be 0.5 ms or longer, such as 1 ms, 5 ms, 10 ms, 15 ms, 20 ms, 30 ms, or 50 ms. In most cases, frames are less than 100 ms, such as 250 ms, 200 ms, 150 ms, or 100 ms. In most applications described herein, frame widths are between 5 ms and 30 ms, for example, 8 ms.ms. Dedicated drive controllers for electrophoretic displays are available from, for example, Ultrachip and Rockchip; however, programmable voltage drivers, such as those available from Digi-Key and other electronics suppliers, can also be used.

[0059] In conventional electrophoretic displays 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 Publication WO 01 / 07961. In some embodiments, an N-type semiconductor (e.g., amorphous silicon) may be used to form the transistor, and the “select” and “non-select” voltages applied to the gate electrode may be positive and negative, respectively.

[0060] FIG. 2A of the figures depicts an exemplary equivalent circuit of a single pixel of an electrophoretic display. As shown, the circuit includes a capacitor 10 formed between the pixel electrode and the capacitor electrode. The electrophoretic medium 20 is represented as a capacitor and a resistor connected in parallel. In some cases, the direct or indirect coupling capacitance 30 between the gate electrode of the transistor associated with the pixel and the pixel electrode (often referred to as “parasitic capacitance”) may introduce undesirable noise into the display. Typically, the parasitic capacitance 30 is much smaller than the capacitance of the storage capacitor 10, and the parasitic capacitance 30 may cause a small negative offset voltage, also known as a "recoil voltage," to the pixel electrode when a pixel row of the display is selected or deselected, which is typically less than 2 volts. [In some embodiments, to compensate for the unwanted "recoil voltage," a common potential Vcom can be provided to the top plane electrode and the capacitor electrode associated with each pixel, such that when Vcom is set to a value equal to the recoil voltage (VKB), each voltage supplied to the display can be offset by the same amount and does not experience a net DC imbalance.]

[0061] In many embodiments, the TFT array forms an active matrix 260 for image driving, as shown in FIG2B. For example, each pixel electrode 253 (corresponding to 130 in FIG1A and 1B) is coupled to a thin-film transistor 262 patterned as an array and connected to a gate (column) driver line 264 and a source (row) driver line 206, the source driver line 206 extending perpendicularly to the gate driver line 264. Furthermore, typically, the common (top) transparent electrode 257 (corresponding to 110 in Figures 1A and 1B) has the form of a single continuous electrode, while another electrode or electrode layer is patterned as a matrix of pixel electrodes 253, each pixel electrode defining one pixel of the display. An electrophoretic medium 200 can be disposed between the pixel electrodes 253 and the common electrode 257. Any of the electrophoretic media described above can be used, and although Figure 2B depicts the electrophoretic medium as being contained within microcapsules, microcells as shown in Figure 1B are also suitable. A source driver (not shown) is connected to the source driver line 206 and directs the input to all TFTs to be addressed in the column.262 provides the source voltage. A gate driver (not shown) is connected to gate driver line 264 to provide a bias voltage that will turn on (or off) the gate of each TFT 262 in that row. The gate scan rate is typically about 60-150 Hz. When the TFT 262 is n-type, making the gate-source voltage positive allows the source voltage to be short-circuited to the drain. Making the gate negative relative to the source causes the drain-source current to drop and the drain to effectively float. Because the scan drivers operate sequentially, there is typically a measurable delay in the update time between the top and bottom row electrodes. It should be understood that the allocation of the "row" and "column" electrodes is, to some extent, arbitrary, and TFT arrays with the roles of row and column electrodes can be fabricated. Each pixel of the active matrix 260 also includes a storage capacitor 274 as discussed above with respect to FIG. 2A. The storage capacitor 274 is typically coupled to Vcom line 276. In some embodiments, a common transmittance electrode 257 is coupled to ground, as shown in FIG. 2B. In other embodiments, the common light-transmitting electrode 257 is also coupled to the Vcom line 276 (not shown in FIG. 2B).

[0062] The active matrix 260 described with respect to FIG. 2B (i.e., including the electrophoretic medium 200 and the common light-transmitting electrode 257) is typically covered and sealed by a protective sheet (e.g., an integrated barrier layer) to form a display module 55 as shown in FIG. 3. Such a display module 55 becomes the core of the electrophoretic display 40. The electrophoretic display 40 will typically include a processor 50, which is configured to coordinate a number of functions related to displaying content on the display module 55 and to convert a “standard” image (e.g., an sRGB image) into a color mode that best reproduces the image on the display module 55. In some embodiments, the processor 50 performs the method of the invention by determining which pixel electrodes should be updated during local updates. In particular, when using dithering for color generation, the processor 50 can determine which areas of the dithered color are most likely to be at risk of haloing due to updates of nearby pixel electrodes. In other embodiments, some or all of the steps of the invention may be performed by a controller 60. With advancements in the controller 60 architecture, more image processing can be embedded within the controller 60, allowing advanced controllers to be integrated into the same package as the display module 55 and pre-programmed with the tools needed to identify pixel electrodes at risk of haloing during local updates. Advanced controllers for electrophoretic displays are available from ULTRACHIP and NEXTRONIX.

[0063] The processor 50 is typically a mobile processor chip manufactured, for example, by Freescale or Qualcomm, but other manufacturers are also known. The processor 50 communicates frequently with the non-transitory memory 70, retrieving images from the non-transitory memory 70.Like files and / or lookup tables, the non-transitory memory 70 can perform the color image conversion described below. Where a particular color conversion may require different gate drive modes, the non-transitory memory 70 may also include gate drive instructions. 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 the controller 60, which causes a voltage sequence to be sent to the corresponding thin-film transistors (as described above). These voltages are typically derived from one or more power supplies 80, which may include, for example, a power management integrated chip (PMIC). The electrophoretic display 40 may also include a communication interface 85, which may be, for example, a Wi-Fi protocol or Bluetooth, and allows the electrophoretic display 40 to receive images and instructions, which may also be stored in the memory 70. The electrophoretic display 40 may also include one or more sensors 90, which may include temperature sensors and / or photoelectric sensors, and this information may be fed to the processor 50 to allow the processor to select the optimal lookup table when the lookup table is indexed for ambient temperature or incident illumination intensity or spectrum. In some cases, multiple components of the electrophoretic display 40 can be embedded in a single integrated circuit. For example, an application-specific integrated circuit can implement the functions of the processor 50 and the controller 60.

[0064] As described above, a color electrophoretic display can include an array of color filters or an extended particle system capable of generating all colors above each pixel electrode. As shown in FIG4A, in the case of a four-particle system comprising subtractive cyan, yellow, and magenta particles paired with reflective white particles, each of the eight primary colors (red, green, blue, cyan, magenta, yellow, black, and white) corresponds to a different arrangement of the four pigments. For example, for an advanced color electronic paper (ACeP) display, the three particles providing the three subtractive primary colors can be substantially non-light-scattering (“SNLS”). Using SNLS particles allows color mixing and provides more color results than the same number of scattering particles could achieve. These thresholds must be sufficiently separated relative to the voltage drive level to avoid crosstalk between particles, and this separation necessitates the use of high addressing voltages for some colors. Furthermore, addressing the colored particle with the highest threshold also causes all other colored particles to move, and these other particles must then be switched to their desired positions at a lower voltage.

[0065] The system in Figure 4A works similarly to printing on bright white paper, where the observer only sees the colored pigments on the viewing side of the white pigment (i.e., the pigment that only scatters light). In Figure 4A, the viewing surface of the display is assumed to be...At the top (as shown in the figure), which is the direction from which the user observes the display, and from which light enters. As already noted, in the preferred embodiment, only one of the four particles in the electrophoretic medium used in this invention substantially scatters light, and in Figure 4A, this particle is assumed to be white pigment. This light-scattering white particle forms a white reflector, thereby allowing any particle above the white particle (as shown in Figure 4A) to be observed. Light entering the viewing surface of the display passes through these particles, is reflected by the white particles, passes through these particles again, and exits from the display. Therefore, the particles above the white particles can absorb a variety of colors, and the color presented to the user is the color produced by the combination of particles above the white particles. Any particles positioned below the white particles (behind the white particles 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 substantially non-light-scattering, their order or arrangement relative to each other is not important, but for the reasons mentioned above, their order or arrangement relative to the white (light-scattering) particles is crucial.

[0066] More specifically, when cyan, magenta, and yellow particles are below white particles (case [A] in FIG4A), there are no particles above the white particles, and the pixel displays only white. When a single particle is above a white particle, the color of that single particle is displayed, which is yellow, magenta, and cyan in cases [B], [D], and [F] of FIG4A, respectively. When two particles are above white particles, the displayed color is a combination of the colors of the two particles; in FIG4A, in case [C], magenta and yellow particles display red, in case [E], cyan and magenta particles display blue, and in case [G], yellow and cyan particles display green. Finally, when all three colored particles are above white particles (case [H] in FIG4A), all incident light is absorbed by the three subtractive primary color particles, and the pixel displays black. Since the order of particles between the pixel electrode and the observer is crucial, a pixel electrode that is not updated during a local update may be disturbed by a neighboring pixel that is being updated. Furthermore, since the particles with the highest charge (typically cyan) move the most due to inter-pixel coupling, the resulting color shift may be unpredictable.

[0067] Figure 4B shows an alternative particle group using reflective colored particles. In the embodiment of Figure 4B, the reflective particles are white, red, and yellow, and they are combined with translucent blue; however, alternative color groups can be used, provided the color combination adequately covers the useful color spectrum. In the system of Figure 4B, for white, red, and yellow, the colors observed at the surface are due to direct reflection from the colored particles, and for orange, it is a mixture of red and yellow reflective pigments. For green, blue, and black observed at the surface, the colors observed at the surface are due to translucent blue particles, respectively.The light is produced by mixing reflective yellow, white, and red particles. Since the light seen by the observer interacts primarily with only one pigment surface, the image produced using the system of Figure 4B appears more saturated than the colors in Figure 4A. However, the overall color gamut of the system using Figure 4B is reduced compared to Figure 4A because it is difficult to achieve fine control over the amount of specific particles that are mixed together to form secondary colors (e.g., orange, green, purple). In applications such as digital signage, saturation is often more important than color gamut, and many users are satisfied with combinations of seven or eight "standard" colors. It should also be appreciated that, with respect to Figure 4B, reflective red and translucent blue particles can be interchanged to create an electrophoretic display medium comprising reflective white, yellow, and blue particles as well as translucent red particles. Such a system produces a set of primary colors similar to that of Figure 4B, but the red at the viewing surface is produced by a combination of translucent red and white. Since the system of Figure 4B primarily comprises reflective particles, electrophoretic displays comprising this medium are less affected by inter-pixel coupling. However, the method of the present invention can still be used with these systems.

[0068] Different combinations of light-scattering and light-absorbing particle groups are also possible. For example, a subtractive primary color can be represented by particles that scatter light, such that the display will include two types of light-scattering particles, one white and the other 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 presenting black (when all three types of 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 presented would be the color of the scattering colored particles, not black). Of course, in the absence of absorbing black particles, it is not easy to present black if more than one type of colored particles scatters light.

[0069] Figures 4A and 4B show an idealized case where the color is not contaminated (i.e., the light-scattering white particles completely cover any particles located behind the white particles in Figure 4A, or the selected reflective particles cover all other particles that should not be visible in Figure 4B). In practice, the masking of white particles may be imperfect, so particles that would ideally be completely masked may still have some light absorption. This contamination typically reduces both the brightness and chromaticity of the presented color. In the case of Figure 4B, the presence of light-absorbing particles usually makes the overall image appear darker due to the imperfect scattering of reflective particles. This is particularly problematic for green hues, as the human eye is very sensitive to different shades of green, while different shades of red are less so. In some embodiments, this can be achieved by including particles with different spatial steric hindrance or charge properties.Additional particles, such as green scattering particles, are used for correction; however, adding additional particles complicates the driving scheme and may require a wider driving voltage range. Clearly, in the electrophoretic medium described herein, this color contamination should be minimized so that the resulting color conforms to industry standards for color representation. A particularly preferred standard is SNAP (Newspaper Advertising Production Standard), which specifies the L*, a*, and b* values ​​for each of the eight primary colors mentioned above.

[0070] The waveforms used to drive the four-particle electrophoretic medium have been described previously. Waveforms used to drive a color electrophoretic display with four particles are described in U.S. Patents 9,921,451, 9,812,073, and 11,640,803, all of which are incorporated herein by reference. Due to the widespread availability of manufacturing facilities and the cost of various raw materials, most commercial electrophoretic displays use amorphous silicon-based thin-film transistors (TFTs) in the construction of the active matrix backplane (260). Amorphous silicon TFTs may become unstable when the provided gate voltage allows switching voltages above approximately + / - 15V. Therefore, as described in the previous patents / applications concerning such systems, improved performance is achieved by altering the bias voltage of the top transparent electrode relative to the bias voltage on the backplane pixel electrodes (a technique known as top-plane switching). Thus, if a voltage of +30V (relative to the backplane) is required, the top plane can be switched to -15V while the appropriate backplane pixel is switched to +15V. The method of driving a four-particle electrophoresis system with top-plane switching is described in more detail, for example, in U.S. Patent No. 9,921,451. In an alternative embodiment, a metal-oxide-semiconductor can be incorporated into the thin-film transistor for the active matrix backplane (260), including IGZO, as described in U.S. Patent No. 11,776,496, which is incorporated herein by reference in its entirety.

[0071] As discussed above, local updates of image transitions help reduce transition flicker, especially when the second image is largely the same as the first image. This includes cases where only a portion of the screen is changing, such as a drop-down menu, in which case it is preferable not to update the unaffected portion of the screen to avoid distracting flicker. However, as shown in Figure 5, inter-pixel coupling can cause the portion of the electrophoretic medium above the non-switching pixel electrode to experience an electric field, causing some particles to shift from their desired locations. For example, in Figure 5, pixels 1, 3, 5, 6, 7, and 9 are intended to remain white in the first and second images, while pixels 2 and 8 will transition from white to a (non-black) grayscale tone, and pixel 4 will transition from white to black. Due to inter-pixel coupling, for pixels 1, 3, 5, 6, 7, and 9, the portion of the electrophoretic medium adjacent to the pixel electrode being updated is unintentionally recolored. This phenomenon is called edge ghosting or differential halo ghosting, andAnd overall, it may result in a "residual" image after the image is updated. In addition to display shape, edge ghosting may also affect the perceived color when one of the unupdated pixel electrodes is a subpixel of a CFA image pixel or when the electrophoretic medium is sensitive to ghosting colors (as described above regarding subtractive particle systems). Edge ghosting may also cause color shifts when dithering is used to form colors that are not present in the primary color palette produced by the electrophoretic particle system.

[0072] A simple solution for local updates in a color electrophoretic display is to create a bounding box slightly smaller than the area of ​​the display that is undergoing transformation, and then send zero updates to all pixels within that bounding box, as shown in Figure 6. Using this method, the edges of the unupdated areas of the display are forced to update to the same image, thereby eliminating most of the edge ghosting caused by the actual updated content changing the color state. As shown in Figure 6, a text box is being removed between the first and second images to give the full library menu. The unupdated area (m × n) of the display is typically not updated, but a bounding box (green box) is created that is slightly smaller than the (m × n) area that should not be updated using a local update method. This smaller-than-desirable bounding box creates a transition region (red box) where the bottom of the transition region (corresponding to the upper edge of the updated portion (i × j)) will have the same color in both the first and second images because all pixels in the lower part of the transition region actively update to the same state. Meanwhile, the top of the transition region (red box) will receive zero updates, but most of the adjacent pixels along the horizontal boundary between the top and bottom rows of the transition region have roughly the same color, so inter-pixel coupling will result in a less noticeable color shift in the unupdated area. In some embodiments, the transition region (red box) is only two rows of pixel electrodes high or only two columns of pixel electrodes wide. More typically, particularly for CFA devices, the transition region (red box) is four rows of pixel electrodes high or four columns of pixel electrodes wide to constitute a subpixel of the pixel image. Therefore, the bounding box will be at least two rows of pixel electrodes or at least two columns of pixel electrodes (or both) smaller than it should be.

[0073] Figures 7 and 8 illustrate a superior solution that achieves a more aesthetically pleasing transition and better overall color quality. As shown in Figure 7, each pixel (x, y) of a candidate pixel that does not undergo a color change and is a zero transition between the first and second images is also evaluated against its fundamental neighbor pixels. Similar to the basic axes (north, south, east, west) of a compass, an unupdated pixel has neighboring pixels directly above, below, to the left, and to the right, and if these pixels are undergoing a transition between the first and second images, the transition of fundamental neighboring pixels is more likely to cause edge ghosting.(See Figure 5). When one or more of the fundamental neighboring pixels are undergoing a transition, the controller receives an instruction to update pixel (x, y) to ensure there is no color drift due to edge ghosting. How many fundamental neighboring pixels need to change their color state between the first and second images to send the same update instruction to pixel (x, y) is somewhat arbitrary. In some cases, such as video rate transitions, additional self-updating of pixel (x, y) may not be worthwhile because the difference will not be noticeable to the observer. On the other hand, for high-resolution images or images where color matching is crucial, the color changes of the secondary fundamental pixels of pixel (x, y) (i.e., northeast, southeast, southwest, and northwest) and their potential impact on the color state of pixel (x, y) in the second image can be evaluated. The pseudocode for implementing this update is as follows:

[0074] If PU_enable is true

[0075] If currState(i, j) == nextState(i, j), and for all 8 adjacent pixels (*) currState=nextState, then apply E_Transition(empty, local update)

[0076] where an empty transition means sending a no-update instruction to pixel (i, j), and it retains its previous color state.

[0077] As shown in Figure 8, the above method can also be used to avoid color shifts when transitioning between two images with similar pixel color compositions but different presentations. In Figure 8, the e-reader has a small drop-down menu that obscures a portion of an image of a lake and sky. The color content of the updated areas between images 1 and 3 and image 2 is actually very similar. A large number of white pixels are needed to produce the light blue of the sky. The drop-down menu has a white background, so for a true local update that only updates pixels that are undergoing color changes, many white pixels will receive zero transitions between images 1, 2, and 3. However, the scattered blue pixels and the white-to-black-to-white transition of the dropdown menu text often cause ghosting in the dropdown text in Image 3. Furthermore, due to slight jitter in the sky in the presented images, the sky color is actually slightly different between Images 1 and 3. Using the method of this invention, only the same pixel color transitions between Images 2 and 3 that do not have fundamentally adjacent pixels undergoing color transitions receive a zero (empty) update instruction. All other pixels with the same pixel color transition but adjacent pixels undergoing the transition (see page 15 / 16 of the specification, CN 122535939 A) will receive an instruction to update to the same color by driving the pixel back to the desired color state. While this method results in more pixels being updated compared to when no analysis is performed, the end result is less ghosting and more...Optimal color rendering. Nevertheless, this method consumes less energy than the method shown in Figure 6 because many pixels that present the same color in images 2 and 3 are not updated.

[0078] A flowchart describing the method is shown in Figure 9. In step 302, pixels that have the same color state in the first and second images are identified. Those pixels that are not the same between the first and second images are updated normally (step 304). Next, in step 306, for the nearest neighbor pixels that have different colors between the first and second images, pixels that do not change color between images are evaluated. If a pixel that does not change color has a fundamental neighbor pixel that changes color, then in step 310 the pixel receives an active same-state transition waveform. The same-state transition waveform can be a complete transition to a neutral state and back to the image color, or a series of smaller pulses designed to simply “complement” the color. (Complementary pulses are typically used for same-state transitions from white to white or black to black). In step 308, pixels that also maintain the same color between the first and second images and all fundamental neighbor pixels receive a zero transition instruction, i.e., no energy is supplied to the pixel electrode corresponding to that image pixel.

[0079] Having described several aspects and embodiments of the technology of this application, it should be understood that various changes, modifications, and improvements will readily occur to those skilled in the art. These changes, modifications, and improvements are intended to fall within the spirit and scope of the technology described herein. For example, various other means and / or structures for performing functions and / or obtaining the 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 equivalent layouts of the specific embodiments described herein using only conventional experimentation. Therefore, it should be understood that the foregoing embodiments are presented as examples 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 equivalent layouts. Furthermore, any combination of two or more features, systems, articles of manufacture, materials, kits, and / or methods described herein that do not contradict each other is included within the scope of this disclosure. Instruction manual, 16 / 16 pages, 19 CN 122535939 A, Figure 1A, Figure 1B, Figure 1C; Instruction manual drawings, 1 / 7 pages, 20 CN 122535939 A, Figure 1D, Figure 1E; Instruction manual drawings, 2 / 7 pages, 21 CN 122535939 A, Figure 2A, Figure 2B; Instruction manual drawings, 3 / 7 pages, 22 CN 122535939 A, Figure 3, Figure 4A; Instruction manual drawings, 4 / 7 pages, 23 CN 122535939 AFigure 4B (H-1648PR) Figure 5 Appendix 5 / 7, Page 24, CN 122535939 A Figure 6 Figure 7 Figure 8 Appendix 6 / 7, Page 25, CN 122535939 A Figure 9 Appendix 7 / 7, Page 26, CN 122535939 A

Claims

1. A method for updating a color electrophoretic display with a controller, the display having a plurality of display pixels in an array and capable of displaying at least black, white, red, and yellow, the method comprising: For each of the plurality of display pixels, determine whether the display pixel has the same color data for the first image and the second image; Send instructions to the controller to provide a waveform corresponding to the color data of the second image to each display pixel that has different color data between the first image and the second image; For each display pixel determined to have the same color data for the first image and the second image, determine whether there is a color data change between the first image and the second image for each of the four closest basic display pixels; Send instructions to the controller to provide a waveform corresponding to the color data of the second image to each display pixel that has different color data between the first image and the second image, and that has the same color data between the first image and the second image, and that has the same color data between the first image and the second image; The controller is instructed not to provide waveforms to each display pixel that has the same color data between the first image and the second image, and whose four nearest basic display pixels also have the same color data between the first image and the second image.

2. A method for updating a color electrophoresis display having a controller, the display having a plurality of display pixels and capable of displaying at least black, white, red, and yellow, the method comprising: The color data of the plurality of display pixels in the first image are compared with the color data of the plurality of display pixels in the second image; Determine an m × n array of display pixels, wherein all display pixels have the same color data for both the first image and the second image; An i × j array of display pixels is determined, wherein some of the display pixels have different color data between the first image and the second image, and wherein the combination of the m × n array of display pixels and the i × j array of display pixels constitutes all of the plurality of display pixels; Send an instruction to the controller to prevent a pixel region of an m × n array slightly smaller than the display pixels from being updated when transitioning from the first image to the second image; as well as An instruction is sent to the controller to provide a waveform corresponding to the color data of the second image to all remaining display pixels that have not received an update instruction, wherein some pixels that receive the waveform corresponding to the color data of the second image are in the m × n array of display pixels.

3. The method of claim 2, wherein the non-updated pixel region is at least two pixel rows smaller than the m × n array of the display pixels, or at least two pixel columns smaller than the m × n array of the display pixels.

4. The method according to any one of claims 1-3, wherein the electrophoretic display comprises an electrophoretic medium comprising charged particles dispersed in a fluid and confined within a plurality of capsules or microunits.

5. The method of claim 4, wherein the electrophoretic medium comprises four different types of charged particles, and at least two types of charged particles have opposite polarities.

6. The method of claim 5, wherein six primary colors can be formed at each pixel electrode of the electrophoretic display.

7. The method according to any one of claims 1-3, wherein the electrophoretic display comprises a color filter array.

8. The method of claim 7, wherein the color filter array comprises a plurality of filters of different colors, and each filter of different colors is indexed to a pixel electrode of the electrophoretic display.

9. The method of claim 8, wherein each of the plurality of display pixels corresponds to a plurality of different color filters indexed to corresponding plurality of pixel electrodes.

10. The method according to any one of claims 1-3, wherein the color data is RGB color data.

11. The method according to any one of claims 1-3, wherein the color data has been converted from RGB to color data specific to the electrophoretic display.

12. The method according to any one of claims 1-3, wherein the color data represents a color image incorporating dithering.

Images