Fast response colored waveforms for multi-particle electrophoretic displays

Abstract

Fast response colored waveforms for driving multi-particle colored electrophoretic media to improve user experience of displays (e.g., tablets, monitors, or interactive signage) containing multi-particle colored electrophoretic media. In particular, the waveforms produce a crisp and immediate response, which is preferred when writing with a stylus, or typing on a keyboard, or interacting with icons on a sign (e.g., a schedule).

Description

Related applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 610,506, filed December 15, 2024. All patents and publications disclosed herein are incorporated herein by reference in their entirety. Background Technology

[0002] Electrophoretic displays (EPDs) change color by modifying the position of charged colored particles relative to a light-transmitting viewing surface. These electrophoretic displays are often called "electronic paper" or "ePaper" because the resulting display has high contrast and is readable in sunlight, much like ink on paper. In its simplest sense, an electrophoretic display requires only a light-transmitting electrode, a back electrode, and an electrophoretic medium containing one or more types of charged colored particles at the viewing surface. If the back electrode includes controllable regions (pixels)—whether segmented electrodes or an active matrix of pixel electrodes controlled by transistors—a pattern can be electronically displayed at the viewing surface. For example, the pattern could be text in a book.

[0003] Multiple color options are commercially available for electrophoretic displays, including four-color displays (black, white, magenta, yellow; magenta, white, yellow, translucent blue; cyan, yellow, magenta, white). For example, when a single color matching the color of one of the particles is desired at the viewing surface, an electrophoretic display with four types of electrophoretic particles operates in a manner similar to a simple black-and-white display (EPD). However, achieving a wider color gamut (including mixed and printed colors) is more complex and requires finer control over the relative positions of the particles to each other and to the viewing surface. If operated correctly, such a four-particle system allows for the production of hundreds of different colors at each pixel. Further details of such systems are available in the following U.S. patents, all of which are incorporated herein by reference in their entirety: U.S. Patents Nos. 9,361,836, 9,921,451, 10,276,109, 10,353,266, 10,467,984, and 10,593,272.

[0004] In most cases, electrophoretic media, such as those described above, are designed to be driven by low-voltage square waves, such as square waves generated by driver circuitry on a thin-film transistor backplane. Such driver circuitry can be mass-produced inexpensively because it is closely related to the driving circuitry systems and manufacturing methods used to produce liquid crystal display panels, such as those in smartphones, laptop monitors, and televisions. Even when the electrophoretic media is driven directly via isolation electrodes (e.g., segmented electrodes), the driving pulses have historically been delivered as square waves with amplitude and duration. 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, each pixel electrode receives a signal pulse (square wave) for a short time period when the pixel electrode array is addressed row by row. The time period taken to update the entire pixel array, and the time between updates of individual pixel electrodes, is called a frame. The set of voltage impulses required to change the display from a first display state to a second display state is generally referred to as a waveform. The 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.

[0005] When the electrophoretic medium comprises multiple types of particles with the same charge polarity but different charge amplitudes, the final position (and optical state) of a given particle ensemble is typically controlled by a sequence 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 deaggregate the positive particle ensemble and drive unwanted positive particles away from the viewing surface, thus allowing only the desired particle ensemble to be viewed. However, the driving method requiring multiple positive and negative pulses often results in color transitions, which are visually abrupt to the user and are known as “flickering updates.” Flicker can be reduced by making the waveform longer and using smaller voltage steps; however, such waveforms are not suitable for applications such as page turning or stylus writing. In such applications, users expect the display to have a near-instantaneous response and high contrast between a first optical state and a second optical state. (See, for example, U.S. Patent Publication No. 2022 / 0262323, which describes a long gradient waveform.) Historically, achieving short-duration, low-flicker, low-latency colored waveforms has been difficult for such multi-particle systems.

[0006] The term "gray state" is used here in its conventional meaning in the field of imaging, referring to a state intermediate between the two extreme optical states of a pixel, and does not necessarily imply a black-and-white transition between these two extreme states. For example, in the electrophoretic displays described in several IENK patents and publications mentioned below, where the extreme states are white and dark blue, the intermediate gray state is actually light blue. In fact, as already mentioned, a change in optical state may not be a color change at all. The terms "black" and "white" may be used below to refer to the two extreme optical states of a display, and should be understood to generally include extreme optical states that are not strictly black and white, such as the aforementioned white and dark blue states.

[0007] The terms bistable and bistable are used herein in their conventional sense in the art to refer to a display comprising display elements having a first display state and a second display state that are different in at least one optical property, such that after either given element is driven to present its first or second display state by an addressing pulse of finite duration, the state persists for at least several times (e.g., at least four times) the minimum duration of the addressing pulse required to change the state of the display element. As shown in U.S. Patent No. 7,170,670, 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 types of 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.

[0008] When used to refer to driving an electrophoretic display, the term impulse is used here to refer to the integral of the voltage applied over time during the driving period of the display. When used to refer to driving an electrophoretic display, the term waveform is used to describe 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.

[0009] Particles that absorb, scatter, or reflect light over a wide band or at a selected wavelength are referred to herein as colored particles or pigment particles. Various materials other than pigments that absorb or reflect light (meaning insoluble colored materials in the strict sense of the term) may also be used in the electrophoretic media and displays of the present invention, such as dyes or photonic crystals.

[0010] Numerous patents and applications transferred to or in the name of MIT and Einkel describe various techniques for encapsulating electrophoretic and other electro-optic media. Such encapsulated media comprise a plurality of small capsules, each capsule containing an inner phase and a capsule wall surrounding the inner phase, wherein the inner phase contains electrophoretically movable particles in a fluid medium. Typically, the capsules themselves are held in a polymer binder to form a coherent layer located between two electrodes. The techniques described in these patents and applications include:

[0011] (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 7,002,728 and 7,679,814;

[0012] (b) Encapsulation, adhesives, and encapsulation processes; see, for example, U.S. Patent Nos. 6,922,276 and 7,411,719;

[0013] (c) Microunit structures, wall materials, and methods of forming microunits; see, for example, U.S. Patent Nos. 7,072,095 and 9,279,906;

[0014] (d) Methods for filling and sealing microcells; see, for example, U.S. Patent Nos. 7,144,942 and 7,715,088;

[0015] (e) Films and subassemblies containing electro-optic materials; see, for example, U.S. Patent Nos. 6,982,178 and 7,839,564;

[0016] (f) Backplanes, adhesive layers and other auxiliary layers in displays and methods thereof; see, for example, U.S. Patent Nos. 7,116,318 and 7,535,624;

[0017] (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; No. 7,821,702; No. 7,839,564; No. 7,910,175; No. 7,952,790; No. 7,956,841; No. 7,982,941; No. 8,040,594; No. 8,054,526; No. 8,098,418; No. 8,159,636; No. 8,2 No. 13,076; No. 8,363,299; No. 8,422,116; No. 8,441,714; No. 8,441,716; No. 8,466,852; No. 8,503,063; No. 8,576,470; No. 8,576,475; No. 8,593,721; No. 8,605,3 No. 54; No. 8,649,084; No. 8,670,174; No. 8,704,756; No. 8,717,664; No. 8,786,935; No. 8,797,634; No. 8,810,899; No. 8,830,559; No. 8,873,129; No. 8,902,153 No. 8,902,491; No. 8,917,439; No. 8,964,282; No. 9,013,783; No. 9,116,412; No. 9,146,439; No. 9,164,207; No. 9,170,467; No. 9,170,468; No. 9,182,646; No. 9, U.S. Patent Application Publication Nos. 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, and 2013 / 0278995.No. 2014 / 0055840; No. 2014 / 0078576; No. 2014 / 0340430; No. 2014 / 0340736; No. 2014 / 0362213; No. 2015 / 0103394; No. 2015 / 0118390; No. 2015 / 0124345; No. 2015 / 0198858; Nos. 2015 / 0234250, 2015 / 0268531, 2015 / 0301246, 2016 / 0011484, 2016 / 0026062, 2016 / 0048054, 2016 / 0116816, 2016 / 0116818, and 2016 / 0140909;

[0018] (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; and 7,202,847. No. 7,242,514; No. 7,259,744; No. 7,304,787; No. 7,312,794; No. 7,327,511; No. 7,408,699; No. 7,453,445; No. 7,492,339; No. 7,528,822; No. 7,545,358; No. 7,5 No. 83,251; No. 7,602,374; No. 7,612,760; No. 7,679,599; No. 7,679,813; No. 7,683,606; No. 7,688,297; No. 7,729,039; No. 7,733,311; No. 7,733,335; No. 7,787,1 No. 69; No. 7,859,742; No. 7,952,557; No. 7,956,841; No. 7,982,479; No. 7,999,787; No. 8,077,141; No. 8,125,501; No. 8,139,050; No. 8,174,490; No. 8,243,013; No. 8,274,472; No. 8,289,250; No. 8,300,006; No. 8,305,341; No. 8,314,784; No. 8,373,649; No. 8,384,658; No. 8,456,414; No. 8,462,102; No. 8,514,168; No. 8,5 No. 37,105; No. 8,558,783; No. 8,558,785; No. 8,558,786; No. 8,558,855; No. 8,576,164; No. 8,576,259; No. 8,593,396; No. 8,605,032; No. 8,643,595; No. 8,665,2 No. 06; No. 8,681,191; No. 8,730,153; No. 8,810,525; No. 8,928,562; No. 8,928,641; No. 8,976,444; No. 9,013,394; No. 9,019,197; No. 9,019,198; No. 9,019,318;Patent Application Publication Nos. 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; and 2007 / 0091418. No. 2007 / 0103427; No. 2007 / 0176912; No. 2008 / 0024429; No. 2008 / 0024482; No. 2008 / 0136774; No. 2008 / 0291129; No. 2008 / 0303780; No. 2009 / 0174651; No. 200 No. 9 / 0195568; No. 2009 / 0322721; No. 2010 / 0194733; No. 2010 / 0194789; No. 2010 / 0220121; No. 2010 / 0265561; No. 2010 / 0283804; No. 2011 / 0063314; No. 2011 / 017 No. 5875; No. 2011 / 0193840; No. 2011 / 0193841; No. 2011 / 0199671; No. 2011 / 0221740; No. 2012 / 0001957; No. 2012 / 0098740; No. 2013 / 0063333; No. 2013 / 0194250 No. 2013 / 0249782; No. 2013 / 0321278; No. 2014 / 0009817; No. 2014 / 0085355; No. 2014 / 0204012; No. 2014 / 0218277; No. 2014 / 0240210; No. 2014 / 0240373; No. 201 No. 4 / 0253425; No. 2014 / 0292830; No. 2014 / 0293398; No. 2014 / 0333685; No. 2014 / 0340734; No. 2015 / 0070744; No. 2015 / 0097877; No. 2015 / 0109283; No. 2015 / 021 No. 3749; No. 2015 / 0213765; No. 2015 / 0221257; No. 2015 / 0262255; No. 2015 / 0262551; No. 2016 / 0071465; No. 2016 / 0078820; No. 2016 / 0093253; No. 2016 / 0140910;and No. 2016 / 0180777;

[0019] (i) Applications of displays; see, for example, U.S. Patent Nos. 7,312,784 and 8,009,348; and

[0020] (j) Non-electrophoretic displays, such as those described in U.S. Patent No. 6,241,921; U.S. Patent Application Publication No. 2015 / 0277160; and U.S. Patent Application Publication Nos. 2015 / 0005720 and 2016 / 0012710.

[0021] 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 without a discrete capsule membrane 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.

[0022] 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 held in multiple cavities formed within a carrier medium (typically a polymer membrane). See, for example, U.S. Patents 6,672,921 and 6,788,449.

[0023] Although electrophoretic media are typically 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 made to operate in a so-called shutter mode, in which one display state is substantially opaque and the other display state is transmissive. 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. Dielectric electrophoretic 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 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.

[0024] Encapsulated electrophoretic displays typically do not suffer from the aggregation and sedimentation failure modes of conventional electrophoretic equipment and offer several advantages, such as the ability to print or coat displays on a variety of flexible and rigid substrates. (The term "printing" is used to include all forms of printing and coating, including but not limited to: pre-metering coatings such as patch die coating, slot or extrusion coating, slide or stack coating, curtain coating; roller coatings such as roller blade coating, forward and reverse roller coating; concave 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. Furthermore, as described in U.S. Patent Application Serial 17 / 088,762, the encapsulated electrophoretic medium can be incorporated into non-planar surfaces, which in turn can be incorporated into everyday objects. Therefore, the surfaces of products, building materials, etc., can be designed to change color when a suitable electric field is applied. Summary of the Invention

[0025] This document discloses an improved method for driving an electrophoretic medium with fast, high contrast, the electrophoretic medium comprising at least four types of particles, each of which has different optical properties relative to each other, and each type of particle having a different combination of charge polarity and charge amplitude relative to each other. In one aspect, the invention includes a method for inducing color state transitions in a four-particle electrophoretic display. The electrophoretic medium of the display typically comprises a negative particle set and three distinct positive particle sets, each particle set being a different color, and one of the particle sets being white. Typically, the display is configured to provide at least five voltages to the pixel electrodes of the display: V++, V+, 0, V-, and V--, and the method comprises: providing a first sequence comprising at least three sequential frames of the same polarity (+ or -), wherein the first frame of the first sequence is at the corresponding highest voltage (V++, V--); providing a second sequence comprising at least three sequential frames of opposite polarities (- or +); and providing a third sequence comprising at least one frame of the same polarity (+ or -) or zero volt. In some embodiments, the first sequence comprises frames at V++ and V+ or at V-- and V-. In some embodiments, the second sequence includes frames at V-- and V- or at V++ and V+. In some embodiments, the display is further configured to provide an additional positive voltage between V++ and 0 and an additional negative voltage between V-- and 0, and the first sequence includes frames at an additional positive voltage between V++ and 0 or at an additional negative voltage between V-- and 0. In some embodiments, the display is further configured to provide an additional positive voltage between V++ and 0 and an additional negative voltage between V-- and 0, and the second sequence includes frames at an additional negative voltage between V-- and 0 or at an additional positive voltage between V-- and 0. In some embodiments, the voltages are V++=24V, V+=6V, 0V, V-=-6V, and V--=-24V, and the additional positive voltage between V++ and 0 is +12V, and the additional negative voltage between V-- and 0 is -12V. In some embodiments, the voltages are V++=24V, V+=6V, 0V, V-=-6V, and V--=-24V, with an additional positive voltage between V++ and 0 of +12V and an additional negative voltage between V-- and 0 of -12V. In some embodiments, the third sequence terminates with a 0V frame. In some embodiments, the display starts from an initial white state condition, under which white particles are present at the viewing surface of the display. In some embodiments, the transition from the white state to the final color at the viewing surface takes less than 300ms or less than 250ms. In some embodiments, the duration of each frame is less than 20ms, or less than 15ms, or less than 10ms.

[0026] In another aspect, the present invention includes a method for inducing color state transitions in a four-particle electrophoretic display. The electrophoretic medium of the display typically comprises two sets of negative particles and two distinct sets of positive particles, each set being a different color, and one of the particle sets being white. Typically, the display is configured to provide at least five voltages to the pixel electrodes of the display: V++, V+, 0, V-, and V--. The method includes: providing a first sequence comprising at least three sequential frames of the same polarity (+ or -), wherein the first frame of the first sequence is at the corresponding highest voltage (V++, V--); providing a second sequence comprising at least three sequential frames of opposite polarities (- or +); and providing a third sequence comprising at least one frame of the same polarity (+ or -) or zero volt. In some embodiments, the first sequence comprises frames at V++ and V+ or at V-- and V-. In some embodiments, the second sequence comprises frames at V-- and V- or at V++ and V+. In some embodiments, the display is further configured to provide an additional positive voltage between V++ and 0 and an additional negative voltage between V-- and 0, and a first sequence includes frames with an additional positive voltage between V++ and 0 or an additional negative voltage between V-- and 0. In some embodiments, the display is further configured to provide an additional positive voltage between V++ and 0 and an additional negative voltage between V-- and 0, and a second sequence includes frames with an additional negative voltage between V-- and 0 or an additional positive voltage between V-- and 0. In some embodiments, the voltages are V++=24V, V+=6V, 0V, V-=-6V, and V--=-24V, and the additional positive voltage between V++ and 0 is +12V, and the additional negative voltage between V-- and 0 is -12V. In some embodiments, the voltages are V++=24V, V+=6V, 0V, V-=-6V, and V--=-24V, with an additional positive voltage between V++ and 0 of +12V and an additional negative voltage between V-- and 0 of -12V. In some embodiments, the third sequence terminates with a 0V frame. In some embodiments, the display starts from an initial white state condition, under which white particles are present at the viewing surface of the display. In some embodiments, the transition from the white state to the final color at the viewing surface takes less than 300ms or less than 250ms. In some embodiments, the duration of each frame is less than 20ms, or less than 15ms, or less than 10ms.

[0027] In another aspect, the present invention includes a method for inducing color state transitions in a four-particle electrophoretic display. The electrophoretic medium of the display typically comprises a set of positive particles and three distinct sets of negative particles, each set being a different color, and one of the sets being white. Typically, the display is configured to provide at least five voltages to the pixel electrodes of the display: V++, V+, 0, V-, and V--. The method includes: providing a first sequence comprising at least three sequential frames of the same polarity (+ or -), wherein the first frame of the first sequence is at the corresponding highest voltage (V++, V--); providing a second sequence comprising at least three sequential frames of opposite polarities (- or +); and providing a third sequence comprising at least one frame of the same polarity (+ or -) or zero volt. In some embodiments, the first sequence comprises frames at V++ and V+ or at V-- and V-. In some embodiments, the second sequence comprises frames at V-- and V- or at V++ and V+. In some embodiments, the display is further configured to provide an additional positive voltage between V++ and 0 and an additional negative voltage between V-- and 0, and a first sequence includes frames with an additional positive voltage between V++ and 0 or an additional negative voltage between V-- and 0. In some embodiments, the display is further configured to provide an additional positive voltage between V++ and 0 and an additional negative voltage between V-- and 0, and a second sequence includes frames with an additional negative voltage between V-- and 0 or an additional positive voltage between V-- and 0. In some embodiments, the voltages are V++=24V, V+=6V, 0V, V-=-6V, and V--=-24V, and the additional positive voltage between V++ and 0 is +12V, and the additional negative voltage between V-- and 0 is -12V. In some embodiments, the voltages are V++=24V, V+=6V, 0V, V-=-6V, and V--=-24V, with an additional positive voltage between V++ and 0 of +12V and an additional negative voltage between V-- and 0 of -12V. In some embodiments, the third sequence terminates with a 0V frame. In some embodiments, the display starts from an initial white state condition, under which white particles are present at the viewing surface of the display. In some embodiments, the transition from the white state to the final color at the viewing surface takes less than 300ms or less than 250ms. In some embodiments, the duration of each frame is less than 20ms, or less than 15ms, or less than 10ms. Attached Figure Description

[0028] Figure 1A This is a representative cross-section of a four-particle electrophoretic display, in which the electrophoretic medium is encapsulated in microcapsules.

[0029] Figure 1BThis is a representative cross-section of a four-particle electrophoretic display, in which the electrophoretic medium is encapsulated in microcells.

[0030] Figure 2A An exemplary equivalent circuit for a single pixel of an electrophoretic display using an active matrix backplane with storage capacitors is shown.

[0031] Figure 2B An exemplary equivalent circuit of the simplified electrophoresis display of the present invention is shown, which allows for row-column driving.

[0032] Figure 3 An exemplary electrophoretic display including a display module is shown. 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 it to adjust operating parameters based on the surrounding environment, such as temperature and lighting.

[0033] Figure 4A The preferred positions of each of the four particle sets 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.

[0034] Figure 4B Preferred positions of each of the four particle sets that produce seven standard colors are shown in a white-red-yellow-blue semi-absorbent (WRYB*) four-particle electrophoretic display, wherein the white, red, and yellow particles are reflective, and the blue particles are semi-absorbent (B*).

[0035] Figure 5A A push-pull waveform (existing technology) is shown, which can be used to achieve specific colors in an EPD system comprising one reflective (white) particle and three subtractive (cyan, yellow, magenta) particles.

[0036] Figure 5B A push-pull waveform (of the prior art) is shown, which can be used to achieve specific colors in an EPD system that includes reflective white, red and yellow particles as well as semi-absorbent blue particles.

[0037] Figure 6A An exemplary fast response waveform is shown for the transition of a four-particle WCMY electrophoretic medium above the display electrode from white to the corresponding color.

[0038] Figure 6B This illustrates the transformation of the four-particle WCMY electrophoretic medium above the display electrodes from white to... Figure 6A The color transformation obtained by modeling the corresponding colors shown (as experienced by the user).

[0039] Figure 7A An exemplary electrophoretic display is shown, which includes an electrophoretic medium layer encapsulated in microcapsules, the display being configured to receive input from a stylus.

[0040] Figure 7B An exemplary electrophoretic display is shown, which includes an electrophoretic medium layer encapsulated in microcapsules, the display being configured to receive input from a stylus. Detailed Implementation

[0041] This invention details a fast-response colored waveform for driving a multi-particle colored electrophoretic medium to improve the user experience of displays (e.g., tablets, monitors, or interactive signage) incorporating such media. Specifically, the waveform produces a crisp and immediate response, which is preferred when writing with a stylus, typing on a keyboard, or interacting with icons on interactive signage (e.g., timetables). Typically, the multi-particle colored electrophoretic medium has at least four distinct sets of electrophoretic particles, for example, where at least three sets are colored and subtractive, and at least one set is scattering / reflecting; or where at least three sets are colored and reflective, and at least one set is subtractive or translucent. Typically, such a system includes a reflective white particle set and subtractive primary color particles of cyan, yellow, and magenta; or a reflective red, yellow, and blue particle set and an absorbing black particle set; or a reflective white, red, and yellow particle set and a translucent blue particle set (alternatively, a reflective white, blue, and yellow particle set and a translucent red particle set). Of course, alternative color choices can be used as long as the appropriate primary color is selected. Furthermore, the fast-response colored waveforms used to drive such multi-particle systems are suitable for electrophoretic display systems that include more and different types of particles, such as five-particle, six-particle, seven-particle, and eight-particle systems.

[0042] Methods for fabricating electrophoretic displays comprising four (or more) particles have been discussed in the prior art. Electrophoretic fluids can be encapsulated in microcapsules or contained within microcell structures, subsequently sealed with a polymer layer. The microcapsule or microcell layer can be coated or laminated onto a plastic substrate or a film with a transparent coating of 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 assembly can be laminated to a backplane with pixel electrodes using a conductive adhesive. Alternatively, the assembly can be attached to one or more segmented electrodes on the backplane, wherein the segmented electrodes are directly actuated. In another embodiment, the assembly (which may include a non-planar transparent electrode material) is sprayed as a capsule and then externally coated with a back electrode material (see U.S. Patent Publication No. 2021 / 0132459, incorporated herein by reference). Alternatively, the electrophoretic fluid can be directly dispensed onto a thin, open-cell grid arranged on a backplane of an active matrix including pixel electrodes. The filled grid can then be top-sealed with an integrated protective sheet / transparent electrode.

[0043] Electrophoretic displays typically comprise a layer of electrophoretic material 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 of the electrode layers are patterned to define pixels of the display. For example, one electrode layer may be patterned as elongated row electrodes, and the other electrode layer may be patterned as elongated column electrodes extending perpendicularly to the row electrodes, with pixels defined by the intersections of the row and column electrodes. Alternatively, and more commonly, one electrode layer may have the form of a single continuous electrode, while 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, intended for use with a stylus, printhead, or similar movable electrodes detached from the display, only one layer adjacent to the 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.

[0044] The electrophoretic medium used herein includes charged particles that differ 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 broad wavelength or at a selected wavelength are referred to herein as colored or pigment particles. Various light-absorbing or reflecting materials other than pigments (meaning insoluble colored materials in the strict sense of the term), such as dyes or photonic crystals, may 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 charges, 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 particles carrying opposite charges, each having a subtractive primary color different from each other and different from the second particles, 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.

[0045] The electrophoretic medium of the present invention may contain any additives used in prior art electrophoretic media, such as those described in the aforementioned patents and applications of Einkel and MIT. Thus, for example, the electrophoretic medium of the present invention will typically contain at least one charge control agent to control the charge on different particles, and the fluid may have polymers dissolved or dispersed therein having a number average molecular weight of more than about 20,000 and substantially non-adsorbed onto the particles to improve the bistability of the display, as described in the aforementioned U.S. Patent No. 7,170,670.

[0046] In one embodiment, the invention uses light-scattering particles (typically white) and three substantially non-light-scattering particles. Of course, there are no completely light-scattering particles or completely non-light-scattering particles, and the minimum degree of light scattering in the light-scattering particles used in the electrophoretic medium of the invention, and the maximum tolerable degree of light scattering in the substantially non-light-scattering particles, can vary depending on factors such as the exact pigments used, their colors, and the user's or application's ability to tolerate some deviation from the desired color. The scattering and absorption properties of a 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 various models known in the art (e.g., one-dimensional Kubelka-Munk processing). In the invention, it is preferred that the white pigment exhibits a diffuse reflectance of at least 5% at 550 nm measured against a black background when the white pigment is approximately isotropically distributed at 15% by volume in a 1 µm thick layer comprising the pigment and a liquid with a refractive index less than 1.55. Yellow, magenta, and cyan pigments preferably exhibit diffuse reflectance of less than 2.5% at 650 nm, 650 nm, and 450 nm, respectively, measured against a black background under the same conditions. (The wavelengths selected above for measuring yellow, magenta, and cyan pigments correspond to the minimum absorption spectral regions of these pigments.) Colored pigments meeting these criteria are referred to hereinafter 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.

[0047] Alternative particle sets may also be used, including four sets of reflective particles, or one set of absorbing particles with three or four different sets of reflective particles, i.e., as described, for example, 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, or the like, while black particles may be formed from CI Pigment Black 26 or 28 or the like (e.g., manganese iron oxide black spinel or copper chromium black spinel) or carbon black. The third / fourth / fifth type particles may be colors such as red, green, blue, magenta, cyan, or yellow. Pigments used for this type of particle may 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 Hostaperm Red D3G 70-EDS, Hostaperm Powder E-EDS, PV Solid Red D3G, Hostaperm Red D3G 70, Hostaperm Blue B2G-EDS, Hostaperm Yellow H4G-EDS, Hostaperm Green GNX, BASF Irgazine Red L 3630, Cinquasia Red L 4100 HD, and Irgazin Red L 3660 HD; Sun Chemical Phthalocyanine Blue, Phthalocyanine Green, Benzidine Yellow, or Benzidine AAOT Yellow.

[0048] like Figure 1A and Figure 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). 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 herein, four different types of particles 121, 122, 123, and 124 are present; however, more particle sets can be used in the methods and displays described herein. In some embodiments, two of the four different types of particle sets 121, 122, 123, and 124 are of a first polarity, while the other two sets are of a second (opposite) polarity. In some embodiments, one of the four different types of particle sets 121, 122, 123, and 124 is of a first polarity, while the other three sets are of a second (opposite) polarity. The electrophoretic medium 120 is typically separated by microcapsules 126 or walls 127 of microcells. An optional adhesive layer 140 can be disposed near any layer; however, it is typically near the electrode layers (110 or 130). More than one adhesive layer 140 may be present in a given electrophoretic display (105, 106); however, it is more common to have only one adhesive layer. 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 encapsulate 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, 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 of the patents and patent applications published by Einkel, such as U.S. Patents 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.

[0049] In some embodiments, such as Figure 1A As shown, an electrophoretic display may consist only of a first transparent electrode, an electrophoretic medium, and a second (back) electrode; the second electrode may also be transparent. However, to produce a high-resolution display, for example... Figure 1BAs shown. Of course, each pixel must be addressable without interference from neighboring pixels so that the image file can be faithfully reproduced on the display. One way to achieve this is to provide an array of nonlinear elements, such as transistors or diodes, with each pixel associated with at least one nonlinear element to create an "active matrix" display. The addressing electrode, or pixel electrode, that addresses a pixel is connected to a suitable 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, and this arrangement will be assumed in the following description, although it is essentially arbitrary, and the pixel electrode can also be connected to the source of the transistor. Conventionally, 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, and the gates of all transistors in each row are connected to a single row electrode; again, it is conventional to assign sources to rows and gates to columns, but is essentially arbitrary, and can be reversed if necessary. Row electrodes are connected to row drivers, which essentially ensure that only one row is selected at any given time. That is, a selection voltage is applied to the selected row electrode to ensure all transistors in the selected row are turned on, while a non-selection voltage is applied to all other rows to ensure all transistors in these unselected rows remain off. Column electrodes are connected to column drivers, which apply selected voltages to different column electrodes to drive the pixels in the selected row to their desired optical state. (The aforementioned voltages are relative to a common front electrode, which is conventionally positioned on the side of the electro-optic medium opposite to the nonlinear array and extends across the entire display.)

[0050] 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 to write the next row of the display. This process is repeated, thus writing to the entire display 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 updating at 60Hz has a 16-millisecond frame. 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 the time unit between updates (e.g., updates of a single backplane). While the electrophoretic medium can be driven with analog voltage signals (e.g., signals generated by power supplies and potentiometers), and the waveform can be discretized into blocks typically on the order of 10ms using a digital controller, it can also be shorter or longer frame widths. For example, a frame can be 0.5ms, or longer, such as 1ms, 5ms, 10ms, 15ms, 20ms, 30ms, or 50ms. In most instances, the frame length is less than 100ms, such as 250ms, 200ms, 150ms, or 100ms. In most applications described herein, the frame width is between 5ms and 30ms, such as 8ms. Dedicated drive controllers for electrophoretic displays are available from companies such as Ultrachip and Rockchip; however, programmable voltage drivers, such as those available from Digi-Key and other electronics component suppliers, can also be used.

[0051] In conventional electrophoretic displays using an active matrix backplane, each pixel electrode has an associated capacitor electrode (storage capacitor), such that the pixel electrode and the capacitor electrode form a capacitor; see, for example, International Patent Publication WO01 / 07961. In some embodiments, an N-type semiconductor (e.g., amorphous silicon) may be used to form a transistor, and the “select” and “non-select” voltages applied to the gate electrode may be positive and negative, respectively.

[0052] The attached image Figure 2A An exemplary equivalent circuit for a single pixel of an electrophoretic display is depicted. As shown, the circuit includes a capacitor 10 formed between a pixel electrode and a capacitor electrode. The electrophoretic dielectric 20 is represented as a capacitor and a resistor connected in parallel. In some instances, 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") can cause unwanted noise to 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 may cause a small negative offset voltage, also known as a "recoil voltage," to appear on the pixel electrode, which is typically less than 2 volts. [In some embodiments, to compensate for the unwanted "recoil voltage," a common potential V can be provided to the top planar electrode and the capacitor electrode associated with each pixel.]com , so that when V com Set to be equal to the recoil voltage (V) KB When the value of is 0, each voltage supplied to the display may deviate by the same amount and will not experience a net DC imbalance.

[0053] In many embodiments, the TFT array forms an active matrix 260 for image driving, such as Figure 2B As shown. For example, each pixel electrode 253 (corresponding to Figure 1A and Figure 1B 130) is coupled to a patterned array of thin-film transistors 262 and connected to a gate (row) driver line 264 and a source (column) driver line 206, the source driver line 206 extending at right angles to the gate driver line 264. Additionally, typically, a common (top) transparent electrode 257 (corresponding to...) Figure 1A and Figure 1B TFT 252 (110) 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 may be disposed between the pixel electrodes 253 and the common electrode 257. Any of the electrophoretic media described above may be used. A source driver (not shown) is connected to source driver line 206 and provides a source voltage to all TFTs 262 in the column to be addressed. 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 along 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 decrease, and the drain is effectively floated. Because the scan drivers operate sequentially, there is typically some measurable delay in the update time between the top and bottom row electrodes. It should be understood that the allocation of "row" and "column" electrodes is somewhat arbitrary, and TFT arrays can be fabricated by interchangeably changing the roles of row and column electrodes. Each pixel of the active matrix 260 also includes, as mentioned above... Figure 2A The storage capacitor 274 is discussed. The storage capacitor 274 is typically coupled to V. com Line 276. In some embodiments, the common transparent electrode 257 is coupled to ground, such as... Figure 2B As shown. In other embodiments, the common transparent electrode 257 is also coupled to V. com Line 276 ( Figure 2B (Not shown in the image).

[0054] about Figure 2B The described active matrix 260 is typically covered and sealed by a protective sheet (e.g., an integrated barrier layer) to create the display module 55, such as... Figure 3 As shown. Such a display module 55 becomes the focus of the electrophoretic display 40. The electrophoretic display 40 will typically include a processor 50, which is configured to coordinate many 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 involve other inputs. The processor 50 is typically a mobile processor chip, such as those manufactured by Freescale or Qualcomm, although other manufacturers are also known. The processor 50 communicates frequently with a non-transitory memory 70 from which it retrieves image files and / or lookup tables to perform the color image transformations described below. The non-transitory memory 70 may also include gate drive instructions in the sense that a particular color transformation 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. Once the desired image is transformed for display on the display module 55, specific image instructions are sent to a controller 60, which facilitates the transmission of voltage sequences to the corresponding thin-film transistors (as described above). Such voltages typically originate from one or more power supplies 80, which may include, for example, a power management integrated circuit (PMIC). The electrophoretic display 40 may additionally include communication 85, which may be, for example, a Wi-Fi protocol or Bluetooth, and allow the electrophoretic display 40 to receive images and instructions, which may also be stored in memory 70. The electrophoretic display 40 may additionally include one or more sensors 90, which may include temperature sensors and / or light sensors, and such information may be fed to processor 50 to allow the processor to select the optimal lookup table when indexing such lookup tables for ambient temperature or incident illumination intensity or spectrum. In some instances, multiple components of the 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.

[0055] like Figure 4AAs shown, in an example 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. The three particles providing the three subtractive primary colors, for example, in advanced colored electronic paper (ACeP) displays, can be substantially non-light-scattering (“SNLS”). Using SNLS particles allows for color mixing and provides more color results than could be achieved using the same number of scattering particles. 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 certain colors. Furthermore, addressing the colored particle with the highest threshold also moves all other colored particles, and these other particles must subsequently be switched to their desired positions at lower voltages.

[0056] Figure 4A The system, in principle, works similarly to printing on bright white paper, because the viewer only sees the colored pigments on the viewing side of the white pigment (i.e., the only pigment that scatters light). Figure 4A In this embodiment, it is assumed that the viewing surface of the display is at the top (as shown in the figure), that is, the user views the display from this direction, and light is incident from this direction. As mentioned earlier, in the preferred embodiment, only one of the four particles used in the electrophoretic medium of the present invention substantially scatters light, and... Figure 4A The particle is assumed to be white pigment. This light-scattering white particle forms a white reflector, and against this white reflector as a background, any particle above the white particle (such as...) Figure 4A All of these particles (as shown) are visible. Light entering the viewing surface of the display passes through these particles, is reflected by the white particles, returns through these particles, and exits the display. Therefore, the particles above the white particles can absorb various colors, and the colors displayed to the user are obtained by the combination of the particles above the white particles. Any particles positioned below the white particles (behind them from the user's perspective) are obscured by the white particles and do not affect the displayed colors. Because the second, third, and fourth particles are essentially non-light-scattering, their order or arrangement relative to each other is not important, but for the reasons already stated, their order or arrangement relative to the white (light-scattering) particles is crucial.

[0057] More specifically, when cyan, magenta, and yellow particles are located below white particles ( Figure 4A In scenario [A], there are no particles above the white particle, and the pixel displays only white. When a single particle is above a white particle, the color of that single particle is displayed. Figure 4AIn cases [B], [D], and [F], yellow, magenta, and cyan are displayed, respectively. When two particles are positioned above a white particle, the displayed color is a combination of the colors of those two particles; Figure 4A 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 4A In the case of [H], all incident light is absorbed by the three subtractive primary color particles, and the pixel displays black.

[0058] Using alternative particle sets of reflective colored particles, such as Figure 4B As shown. In Figure 4B In one embodiment, the reflective particles are white, red, and yellow, and they are combined with translucent blue particles; however, alternative color sets can be used as long as the color combination appropriately spans the useful color spectrum. Figure 4B In this system, for white, red, and yellow, the colors seen at the surface are due to the direct reflection of colored particles; for orange, it is a mixture of red and yellow reflective pigments. For green, blue, and black at the viewing surface, the colors are due to the mixing of translucent blue particles with reflective yellow, white, and red particles, respectively. Because the light seen by the viewer primarily interacts with only one type of pigment surface, using... Figure 4B The images generated by the system appear better than Figure 4A The colors are more saturated. However, compared to Figure 4A Compared to the system, using Figure 4B The overall color gamut of such systems is reduced because it becomes difficult to achieve fine control over the amount of specific particles mixed together to produce 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 a set of seven or eight "standard" colors. Regarding... Figure 4B It should also be recognized that reflective red and translucent blue particles can switch roles, i.e., to create electrophoretic display media comprising reflective white, yellow, and blue particles as well as translucent red particles. Such a system provides a set of... Figure 4B The primary color, but the red on the viewing surface is produced by a combination of translucent red and white.

[0059] Different combinations of light-scattering and light-absorbing particle sets are also possible. For example, a subtractive primary color can be represented by particles that scatter light, such that 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 displaying 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 displayed would be the color of the scattering colored particles, not black). Of course, displaying black would be difficult if more than one type of colored particle scatters light without the presence of absorbing black particles.

[0060] Figure 4A and 4B The diagram illustrates an idealized scenario where the color is uncontaminated (i.e., light-scattering white particles completely obscure the image). Figure 4A Any particle located behind the white particle, or a selected reflective particle, is obscured. Figure 4B (All other particles that shouldn't be visible). In reality, the masking of white particles may not be perfect, so particles that would ideally be completely masked may exhibit some small absorption of light. This contamination typically reduces the brightness and chromaticity of the presented color. Figure 4B In some cases, the presence of light-absorbing particles often makes the overall image appear darker due to imperfect scattering by reflective particles. This is particularly problematic for green hues, as the human eye is highly sensitive to different shades of green, while different shades of red are less so. In some embodiments, this can be corrected by including additional particles with different spatial steric hindrance or charge properties (e.g., green scattering particles); however, adding additional particles complicates the driving scheme and may require a wider range of driving voltages. Clearly, in the electrophoretic media described herein, this color contamination should be minimized to the extent that the resulting color is comparable to industry standards for color reproduction. 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.

[0061] Waveforms for driving a four-particle electrophoretic medium have been previously described. Waveforms for driving a colored 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. Most commercial electrophoretic displays use amorphous silicon-based thin-film transistors (TFTs) in the construction of the active matrix backplane (260) due to the wider availability of manufacturing facilities and the cost of various starting materials. Amorphous silicon TFTs can become unstable when the provided gate voltage allows switching above approximately + / -15V. Therefore, as described in previous patents / applications concerning such systems, improved performance is achieved by additionally changing the bias of the top transparent electrode relative to the bias of the backplane pixel electrode (a technique known as top-plane switching). Thus, if a voltage of +30V (relative to the backplane) is required, the topplane can be switched to -15V while the appropriate backplane pixel is switched to +15V. The method of using a top-plate switching-driven four-particle electrophoresis system is described in more detail, for example, in U.S. Patent No. 9,921,451. In an alternative embodiment, a metal-oxide-semiconductor (MODS) may be incorporated into a thin-film transistor for the active matrix backplane (260), including IGZO, i.e., as described in U.S. Patent No. 11,776,496, which is incorporated herein by reference in its entirety.

[0062] In previous embodiments of advanced colored electronic paper (ACeP), the waveforms (voltage versus time curves) of the pixel electrodes applied to the backplane of the display of the present invention were described and plotted, while the front electrode was assumed to be grounded (i.e., zero potential). The electric field experienced by the electrophoretic medium is, of course, determined by the potential difference between the backplane and the front electrode and the distance between them. The display is typically viewed through its front electrode, and thus it is the particles adjacent to the front electrode that control the color displayed by the pixels, and the optical transitions involved are sometimes easier to understand if the potential of the front electrode relative to the backplane is taken into account; this can be easily achieved by reversing the waveforms discussed below.

[0063] Figure 5A It shows the drive Figure 4A The waveforms depicted are typical (in simplified form) of a four-particle colored electrophoretic display system of this type. These waveforms have a simple "push-pull" structure: that is, they consist of dipoles comprising two pulses of opposite polarities. The amplitude and length of these pulses determine the color obtained. At least five such voltage levels should exist. Figure 5AHigh and low positive and negative voltages, as well as zero volts, are shown. Generally, "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. 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 electrophoretic medium. In some embodiments, the high negative voltage is between -30V and -20V, the medium negative voltage is between -20V and -2V, the medium positive voltage is between 2V and 20V, and the high positive voltage is between 20V and 30V. For example, the high negative voltage is -27V, the medium negative voltage is -15V, the medium positive voltage is 15V, and the high positive voltage is 27V. If only three voltages are available (i.e., +V...),... 高 0 and -V 高 ), then by using a voltage of V 高 However, addressing is achieved using pulses with a duty cycle of 1 / n at lower voltages (e.g., V). 高 The same result is addressed under / n, where n is a positive integer greater than 1. Push-pull (PP) waveforms can be implemented with more drive levels. For example, a seven-level driver can provide seven different voltages (e.g., V) to the data lines during the update of a selected pixel of the display. H V H '、V H ''、0、V L ''、V L '、V L For example, +V H +V M +V L , 0, -V L -V M -V H The intervals between drive levels can be the same or different, depending on the composition of the electrophoretic medium. For example, +V H =27V、+V M =15V, +V L =5V, 0, -V L =-5V、-V M =-15V, -V H =-27V. For example, +V H =30V、+V M =20V、+V L =10V, 0, -V L =-10V, -V M =-20V、-V H=-30V. However, when using a seven-level driver to drive an active matrix backplane with a single controller, the controller can only update a given pixel one frame at a time. Therefore, any enhanced push-pull waveform consists of some combination of pulses, each lasting one frame's time period. See, for example... Figure 6A The waveform obtained to achieve the desired optical state in the medium is... Figure 6A It is constructed from a certain combination of pulses, assuming that such a waveform may have no or a certain number (n) of pulses. Figure 6A Each pulse in the sequence.

[0064] As a response Figure 5A The supplement is used to achieve Figure 4B The set of waveforms depicting the color states of the system is shown in Figure 5B The set of waveforms is described more comprehensively in U.S. Patent No. 11,640,803. Although in principle... Figure 4B The system's various colors can be achieved through Figure 5A The push-pull waveform of the type shown is generated, but Figure 4B The system has been used in larger devices, typically constructed with amorphous silicon backplanes, which can only deliver voltages from +15V to -15V. The intermediate voltage level between +15V and -15V is usually achieved by including one or more power management chips (PMICs), which can also be integrated into the controller 60, for example... Figure 3 As shown. When limited by this voltage range, a more complex waveform is preferred, as shown in the reference below. Figure 5B As stated, it provides better color separation over a longer period of time. However, there is no reason why it cannot be... Figure 4B The system is used with more exotic thin-film transistor materials, such as metal oxides and hybrid metal oxides, such as IGZO.

[0065] Unfortunately, Figure 5A and 5B The push-pull waveform described is "flickering," meaning the user sees dramatic color fluctuations over a short period. Flickering is necessary to separate different sets of particles and redistribute them in the correct order to achieve the desired color. See, for example... Figure 4A and 4B Furthermore, to achieve good color saturation, the push-pull waveform is repeated, for example, as shown below. Figure 5B As shown, this makes the update both "flickering" and long. Alternatively, as... Figure 6AAs shown, each color state can be reconstructed as a so-called "shaping pulse" transition structure, which consists of only a finite set of positive or negative shaping pulses, with as few overlaps between positive and negative as possible. Furthermore, for the specific applications described below, an initial frame can be selected to create a user experience in which the user perceives the color change as almost instantaneous.

[0066] A “shaping pulse” is defined as a series of frames with the same sign voltage, excluding 0V frames:

[0067]

[0068] as well as:

[0069]

[0070] By modifying the number of pulses in each waveform and exploring different combinations of voltage levels within the pulses, the shaping pulse transitions are optimized to achieve specific optical states. Optimization can be simplified by limiting or presetting the number of pulses per transition, limiting the number of voltage levels per pulse, and so on. The resulting structure remains flexible enough to allow waveforms to achieve a variety of optical states and sufficiently constrained to be supported by lookup tables indexed by color, display use case (e.g., stylus input), and environmental conditions (such as temperature, ambient light level, or spectrum). Typically, the waveforms are implemented using a minimum five-level drive scheme, including V++, V+, 0, V-, and V--, where the amplitudes of V++ and V-- are at least 24V. Additional voltage levels can be added, for example, a seven-level drive scheme including V+++, V++, V+, 0, V-, V--, and V---, where the amplitudes of V+++ and V--- are at least 24V. In some embodiments, the amplitude of the highest amplitude voltage level can be 27V or higher, or 30V or higher.

[0071] like Figure 6A As shown, the transition appearance is managed by the number and length of the shaping pulses. The number of pulses per waveform sets the number of color changes during the transition. Setting the number of shaping pulses to m ensures that the brightness oscillates at most m times throughout the transition, as the overall waveform is limited to m drives with consecutive positive and negative pulses. Furthermore, by forcing the shaping pulses to be longer than a certain length, the color oscillations will form more slowly and over a longer period, resulting in a smoother transition appearance with less flicker.

[0072] The responsiveness of the transition is managed by shifting the waveform to the left and forcing a positive or negative pulse at the beginning of the waveform (depending on the initial optical state). For example, driving with a high-voltage pulse when transitioning from a white optical state will generate a rapid response to black or gray, such as... Figure 6AThe waveforms are shown in the image. Because these colors have high contrast with the initial white state, the response will be immediately apparent to the observer. In applications using so-called "night mode" (i.e., white writing / text on a dark background), the initial frame can use a high negative voltage pulse to provide a rapid contrast with the dark background, then gradually transition to the desired color.

[0073] For ACEP type systems (i.e., such as Figure 4A (As depicted), it can be predicted that at 25°C, it will start from an initial white state. Figure 6A The color change alters the appearance. From Figure 6B It can be seen that the high responsiveness is achieved by generating a clear grayscale in the first 24ms—providing high contrast relative to a white background. The smooth transition appearance is evident from the absence of significant brightness oscillations from the start to the end of the transition. The optical response is either white → black → color, or white → black → white → color. Therefore, the shaping pulse transition structure is simple and allows electrophoretic display devices to achieve the desired optical state on multi-pigment electrophoretic displays while keeping flicker and the delay required to reach the initial response low. The number and length of the shaping pulses cause the waveform to transition slowly between colors. Forcing a positive pulse at the beginning of the waveform causes an instantaneous change in contrast as the transition from white begins, making it appear responsive.

[0074] Figure 6A One application of the waveform is in colored electrophoretic displays that can interact with the Stylus 580 or other input devices. For example, such as... Figure 7A The electrophoretic display module 500, as depicted, may include a four-particle electrophoretic display medium 530 packaged as discussed above. The tablet 500 includes a top transparent electrode layer 510 and an active matrix backplane including thin-film transistors 550 and pixel electrodes 560 disposed on a substrate 570. During module assembly, an adhesive layer 540 is disposed between the packaged four-particle electrophoretic display medium 530 and the active matrix backplane. The electrophoretic display module 500 will be incorporated into a base 610 to produce an electrophoretic display tablet 600, similar to tablets currently offered by companies such as Amazon (Kindle Scribe), ReMarkable, and OnyxBOOX (Note Air 3). Such an electrophoretic display tablet 600 may also include physical control buttons 640, or control devices that can be integrated into the system. Furthermore, such an electrophoretic display tablet 600 may also have Bluetooth or other wireless connectivity, allowing for the use of, for example, a mouse or keyboard with the electrophoretic display tablet 600.

[0075] like Figure 7AAs shown, the electrophoretic display module 500 includes a digitization layer 575 that tracks the position of the stylus 580. Because the stylus 580 includes an induction coil, the movement of the stylus interacts with the electromagnetic field generated by the digitization layer 575, allowing the digitization layer to determine its position in the XY plane defined by the digitization layer 575. The digitization layer 575 is typically coupled to a memory, allowing the movement of the stylus 580 to be recorded in an electronic file, which can then be printed, converted into a .pdf document, sent via email, etc. Furthermore, after a certain amount of writing is completed, the electronic file can serve as the basis for a global update of the image (e.g., via a display driver). When a user “writes” on the electrophoretic display tablet 600 with the stylus 580, the user expects the resulting graphic 690 to appear almost instantaneously and with good color depth. For example, if the user selects to underline black text in red on a white .pdf document, the user expects the red line to appear instantaneously as the stylus 580 is dragged across the display screen. Figure 6A The waveform will show instantaneous changes (i.e., within less than 50ms, less than 30ms, and ideally less than 20ms), especially starting from the white state when the stylus 580 is placed. Furthermore, Figure 6A The waveform allows a given pixel to fill with the correct color within 250ms (typically within 200ms), accompanied by very slight flicker. Most users won't actually notice that the initial color change isn't a true color, only that it's darker against a white background and correctly positioned relative to the stylus 580 tip. Furthermore, when using... Figure 4A In the electrophoretic display tablet 600 of the ACEP system described, drawing black lines on white or displaying black text on white only requires 5-10 frames of maxV, which is similar to... Figure 6A The initial frame of the red waveform. The black waveform can also be modified into a push-pull waveform for DC balanced drive, or a series of maxV frames can be offset at a later time through active residual voltage management.

[0076] Having described several aspects and embodiments of the technology described herein, 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 fall within the spirit and scope of the technology described herein. For example, those skilled in the art will readily conceive of various other means and / or structures for performing the functions described herein and / or obtaining the results and / or one or more advantages described herein, and each such variation and / or modification 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 schemes of the specific embodiments described herein using no more than conventional experimentation. Therefore, it should be understood that the foregoing embodiments are presented as examples, and that inventive embodiments may be practiced in ways different from 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 that are not inconsistent with each other is included within the scope of this disclosure.

Claims

1. A method for inducing a color state transition in a four-particle electrophoretic display, the four-particle electrophoretic display comprising a negative particle set and three distinct positive particle sets, wherein each particle set is a different color, and one of the particle sets is white, and wherein the display is configured to provide at least five voltages to pixel electrodes of the display: V++, V+, 0, V-, and V--, the method comprising: A first sequence is provided, comprising at least three sequential frames of the same polarity (+ or -), wherein the first frame of the first sequence is at the corresponding highest voltage (V++, V--). Provide a second sequence comprising at least three sequential frames of opposite polarity (- or +); and A third sequence is provided, the third sequence comprising at least one frame of the same polarity (+ or -) or zero volts.

2. A method for inducing a color state transition in a four-particle electrophoretic display, the four-particle electrophoretic display comprising two sets of negative particles and two distinct sets of positive particles, wherein each set of particles is a different color, and one of the sets of particles is white, and wherein the display is configured to provide at least five voltages to pixel electrodes of the display: V++, V+, 0, V-, and V--, the method comprising: A first sequence is provided, comprising at least three sequential frames of the same polarity (+ or -), wherein the first frame of the first sequence is at the corresponding highest voltage (V++, V--). Provide a second sequence comprising at least three sequential frames of opposite polarity (- or +); and A third sequence is provided, the third sequence comprising at least one frame of the same polarity (+ or -) or zero volts.

3. A method for inducing a color state transition in a four-particle electrophoretic display, the four-particle electrophoretic display comprising a set of positive particles and three distinct sets of negative particles, wherein each set of particles is a different color, and one of the sets of particles is white, and wherein the display is configured to provide at least five voltages to pixel electrodes of the display: V++, V+, 0, V-, and V--, the method comprising: A first sequence is provided, comprising at least three sequential frames of the same polarity (+ or -), wherein the first frame of the first sequence is at the corresponding highest voltage (V++, V--). Provide a second sequence comprising at least three sequential frames of opposite polarity (- or +); and A third sequence is provided, the third sequence comprising at least one frame of the same polarity (+ or -) or zero volts.

4. The method of any one of claims 1, 2 or 3, wherein the first sequence comprises frames in V++ and V+ or in V-- and V-.

5. The method of any one of claims 1, 2 or 3, wherein the second sequence comprises frames in V-- and V- or in V++ and V+.

6. The method of any one of claims 1, 2 or 3, wherein the display is further configured to provide an additional positive voltage between V++ and 0 and an additional negative voltage between V-- and 0, and the first sequence includes frames with the additional positive voltage between V++ and 0 or the additional negative voltage between V-- and 0.

7. The method of any one of claims 1, 2 or 3, wherein the display is further configured to provide an additional positive voltage between V++ and 0 and an additional negative voltage between V-- and 0, and the second sequence includes frames with the additional negative voltage between V-- and 0 or with the additional positive voltage between V-- and 0.

8. The method of claim 6, wherein the voltages are V++=24V, V+=6V, 0V, V-=-6V and V--=-24V, and the additional positive voltage between V++ and 0 is +12V, and the additional negative voltage between V-- and 0 is -12V.

9. The method of claim 7, wherein the voltages are V++=24V, V+=6V, 0V, V-=-6V and V--=-24V, and the additional positive voltage between V++ and 0 is +12V, and the additional negative voltage between V-- and 0 is -12V.

10. The method of any one of claims 1, 2 or 3, wherein the third sequence terminates with a 0V frame.

11. The method of any one of claims 1, 2 or 3, wherein the display begins from an initial white state condition, under which white particles are present on the viewing surface of the display.

12. The method of claim 11, wherein the transition from the white state to the final color at the viewing surface takes less than 300 ms or less than 250 ms.

13. The method of any one of claims 1, 2 or 3, wherein the duration of each frame is less than 20 ms, or less than 15 ms, or less than 10 ms.

Images