Method and system for managing residual voltage during fast update of electrophoretic display

Abstract

A method for actively managing the residual voltage on the backplane electrodes when driving electrophoretic displays, particularly when using short waveforms (e.g. for scrolling, pinch-to-zoom, drop-down menus, even video). The method tracks the change in residual voltage for each backplane electrode during a series of image updates, and uses the same color transition to either raise the optical quality state of the display pixel or lower the residual voltage at the display pixel. Thus, it is not necessary to employ a full reset pulse, which typically drives the backplane electrodes to two extreme voltage states and appears very "flickery" to the user.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 567,299, filed March 19, 2024. All patents and publications disclosed herein are incorporated herein by reference in their entirety. Background Technology

[0003] An electrophoretic display (EPD) changes color by altering the position of charged colored particles relative to a light-transmitting viewing surface. This type of EPD is 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 EPD only requires a light-transmitting electrode, a back electrode, and an electrophoretic medium comprising 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 appear electronically on the viewing surface. This pattern could, for example, be text in 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 particles' colors is desired at the observation surface, the operation of an electrophoretic display with four types of electrophoretic particles is similar to a simple black-and-white display (EPD). However, achieving a wider color gamut (including mixed 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, such a four-particle system allows for the production 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 a color filter array (CFA) 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. Traditionally, CFA displays have red, green, and blue filters; however, other complementary color groups can also be used. Due to 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 certain colors (such as purple) can be approximated by mixing subpixels, a more common approach is to dither colors across pixels in the image to achieve the desired color and chromaticity. However, when dithering is used to increase the available colors in an electrophoretic display, the dithered subpixels involved in the dithering process can suffer from 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 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 low-voltage square waves, such as those generated by driving circuitry from a thin-film transistor backplane. Such driving circuitry can be mass-produced inexpensively because it is closely related to the driving circuitry 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 media was driven directly via isolation electrodes (e.g., segmented electrodes), the driving pulses were delivered 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, each pixel electrode receives a signal pulse (square wave) for a short period when the pixel electrode array is addressed row by row. The time required 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.

[0008] When an electrophoretic medium comprises multiple types of particles with 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 observation 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 observation 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 transitions 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 a near-instantaneous display 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, achieving short, low-flicker, low-latency color waveforms has been difficult for such multi-particle systems.

[0009] Electro-optic displays typically have a backplane with multiple pixel electrodes, each defining a pixel of the display. Each pixel electrode is typically arranged in a rectangular array of pixel electrodes and controlled by a thin-film transistor (TFT), with the TFTs updating line by line. Typically, a single common electrode extending across a large number of pixels (typically the entire display) is positioned on opposite sides of the electro-optic medium. Individual pixel electrodes can be driven directly (i.e., each pixel electrode can be supplied with a separate conductor), 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 inter-pixel gaps of finite width 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 electrodes (in fact, this is often the case for some non-bistable electro-optic media (such as 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] A halo is the tendency for the optical state of an electro-optic medium to change over an area larger than the physical size of the pixel electrode due to the application of a driving voltage to the pixel electrode. The halo region is not a uniform color, but rather a transition zone where the medium's color changes from the desired color to another chromaticity or hue as one moves across the halo region; for example, a desired white pixel may include various shades of gray along its edges, also known as "ghosting." Furthermore, depending on the type of display—black / white, color, or black / white with a color filter—the consequences of ghosting can range from annoying to debilitating. In some cases, asymmetrical halos can also cause ghosting.

[0011] The majority of the discussion below will focus on methods for driving one or more pixels of an electrophoretic display to transition from an initial color state to a final color state (which may differ from or be identical to the initial color state). The term "waveform" will be used to refer to the entire voltage-to-time curve used to achieve a transition from a particular first color state to a particular second color state. Typically, such a waveform will include multiple waveform elements; where these elements are essentially rectangular (V×t) voltage pulses (i.e., where a given element involves applying a constant voltage over a period of time); these elements may be referred to as "pulses" or "driving pulses." The term "driving 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 driving scheme; for example, the aforementioned U.S. Patent No. 7,012,600 teaches that the driving scheme may need to be modified based on parameters such as the display's temperature or the time it has been operating during its lifetime, thus providing the display with multiple different driving schemes for use under conditions such as different temperatures. A set of driving schemes used in this way may be referred to as a "set of related driving schemes." It is also possible to use more than one driving scheme simultaneously in different areas of the same monitor. A group of driving schemes used in this way can be called a "simultaneous driving scheme".

[0012] Regardless of whether the electro-optic medium used is bistable, to achieve a high-resolution display, the individual pixels of the display must be addressable with minimal interference between adjacent pixels. One way to achieve this is to provide an array of nonlinear elements, such as transistors or diodes, with at least one nonlinear element associated with each pixel to 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 a high-resolution array, 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 specified row and a specified 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. Row electrodes are connected to row drivers, which essentially ensure that only one row is selected at any given time. This is achieved by applying a voltage to the selected row electrode to ensure all transistors in that selected row are conductive, while voltages are applied to all other rows to ensure all transistors in those unselected rows remain non-conductive. Column electrodes are connected to column drivers, which apply a voltage to each column electrode selected to drive the pixels in the selected row to their desired optical state. (This voltage is relative to a common front electrode, which is typically located on the side of the electro-optical medium opposite the nonlinear array and extends across the entire display.) After a preselection interval known as the “row addressing time,” the selected row is deselected, the next row is selected, and the voltage on the column drivers is changed, causing the next row of the display to be written. This process is repeated, allowing the entire display to be written row by row.

[0013] At first glance, the ideal method for addressing such impulse-driven electro-optic displays might seem to be the so-called "universal grayscale image stream," where the controller arranges each write of the image so that each pixel directly transitions from its initial grayscale level to its final grayscale level. However, some errors inevitably occur when writing images to impulse-driven displays. Some of these errors encountered in practice include:

[0014] (a) Previous state dependence; for at least some electro-optic media, the impulse required to switch a pixel to a new optical state depends not only on the current and desired optical state, but also on the previous optical state of the pixel.

[0015] (b) Dwell time dependence; for at least some electro-optic media, the impulse required to switch a pixel to a new optical state depends on the time the pixel spends in its various optical states. The exact nature of this dependence is not fully understood, but generally, the longer a pixel remains in its current optical state, the more impulse is required.

[0016] (c) Temperature dependence; the impulse required to switch a pixel to a new optical state depends largely on temperature.

[0017] (d) Humidity dependence; for at least some types of electro-optic media, the impulse required to switch a pixel to a new optical state depends on the ambient humidity.

[0018] (e) Mechanical inconsistencies; the impulse required to switch pixels to a new optical state may be affected by mechanical variations in the display, such as variations in the thickness of the electro-optic medium or associated laminating adhesive. Other types of mechanical inconsistencies may stem from unavoidable differences between media from different manufacturing batches, manufacturing tolerances, and material variations.

[0019] (f) Voltage error; Due to the unavoidable slight error in the voltage delivered by the driver, the impulse actually applied to the pixel will inevitably differ slightly from the impulse theoretically applied.

[0020] Typically, complex electrophoretic displays suffer from the phenomenon of "error accumulation." For example, suppose that temperature dependence causes 0.2L* in the positive direction for each transition (where L* has the usual CIE definition:

[0021] L*=116(R / R0) 1 / 3 -16,

[0022] Where R is reflectance and R0 is the standard reflectance value, this error accumulates to 10L* after 50 transformations. Perhaps more realistically, let's assume the average error per transformation (expressed as the difference between the display's theoretical and actual reflectance) is ±0.2L*. After 100 consecutive transformations, the pixels will show an average deviation of 2L* from their expected state; for some types of images, this deviation is noticeable to the average observer. The same principle applies to color electrophoretic displays, but the accumulation of error may occur in the a* or b* direction of the CIELAB color space, or some combination of L*, a*, and b*.

[0023] This error accumulation phenomenon applies not only to temperature-induced errors but also to all the types of errors described above. Compensating for this error is possible, but only with limited accuracy, depending on the application, desired performance, and available processing power. For example, temperature errors can be (easily) compensated using a temperature sensor and lookup table, but temperature sensors have limited resolution and may read temperatures slightly different from those of the electro-optic medium. To some extent, prior state dependencies can be compensated for by storing previous states and using multidimensional transition matrices, but controller memory limits the number of states that can be recorded and the size of the transition matrices that can be stored, thus limiting the accuracy of this type of compensation. For advanced applications, computation at the controller level may not be fast enough, thus requiring compensation for error accumulation at the processor level. See, for example, U.S. Patent No. 10,672,350 (incorporated herein by reference in its entirety), in which prior states for optical states, residual voltage, and grayscale drift are considered simultaneously.

[0024] Furthermore, there is a desire to drive electrophoretic displays at even faster speeds, perhaps even fast enough to allow video viewing. Designing waveforms to achieve fast optical response requires using the shortest possible waveform to achieve a given optical state, but this also introduces another pathway for optical state errors and residual voltage accumulation. Designing such short waveforms is challenging, and sometimes it's impossible to go below a certain time threshold due to the limitations of the electrophoretic system itself. As waveforms become shorter, observed optical state errors and history-dependent optical errors increase significantly, making performance unacceptable for normal applications. Most commercially available electrophoretic displays use longer waveforms, resulting in slower refresh rates, making them unsuitable for playing smooth animations or videos. Using short waveforms to increase the refresh rate leads to accumulated optical state errors, causing optical state drift. In particular, repeatedly cycling through state changes using short waveforms results in noticeable color state drift, which causes afterimages or "ghosting." Some manufacturers, such as ONYX BOOX, offer software or hardware buttons that allow users to force a hard refresh of the entire screen to eliminate ghosting.

[0025] Repetitive short drives can also introduce residual voltage accumulation because the short drive waveform may not be DC balanced (waveform impulse = time × voltage; DC balanced = impulse integral is zero), or the DC balanced waveform may be interrupted. Therefore, it is necessary to consider providing a safe boundary for residual voltage accumulation (the voltage generated by the charge stored in the electrophoresis system) after applying a series of waveforms. Unbounded accumulation of residual voltage can permanently damage the display and, in less severe failures, may cause undesirable changes in the display's optical state. Previous attempts to compensate for accumulated residual voltage include the kind of impulse library described in U.S. Patent No. 10,672,350. However, the kind of impulse library described in that '350 patent does not actively compensate for residual voltage for each image update. Therefore, the display may only undergo 6 to 10 image updates before a clear reset pulse or effective residual voltage discharge is required. When updating images at high speeds (such as 10 image frames per second or faster), there is insufficient time for a clear pulse to occur without causing at least some image transitions to "flicker."

[0026] The terms “bistable” and “bistable” are used herein in their conventional sense in the art, referring to a display comprising display elements having a first display state and a second display state that differ in at least one optical characteristic, such that after any given element is driven to present its first or second display state by means of an addressing pulse of finite duration, the state will persist for at least several times, for example, at least four times, the shortest duration of the addressing pulse required to change the state of the display element after the addressing pulse terminates. U.S. Patent No. 7,170,670 shows that some particle-based electrophoretic displays supporting grayscale are stable not only in their extreme black and white states but also in their intermediate gray states, as are some other types of electro-optical displays. This type of display is 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. 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 persistence between updates, also known as “ghosting.”

[0027] As used herein, the term "impulse" refers to the integral of the voltage applied during the driving of an electrophoretic display with respect to time. The term "waveform" as used in the context of driving an electrophoretic display describes a series of voltages or voltage patterns supplied to the electrophoretic medium over a given time period (seconds, frames, etc.) to produce the desired optical effect in the electrophoretic medium.

[0028] 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.

[0029] Numerous patents and applications assigned to or attributed to MIT and Einkel describe various techniques for encapsulating electrophoretic and other electro-optic media. Such encapsulation media comprise multiple small capsules, each capsule itself including 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 techniques described in these patents and applications include:

[0030] (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 7,002,728 and 7,679,814;

[0031] (b) Encapsulation, adhesives, and encapsulation processes; see, for example, U.S. Patent Nos. 6,922,276 and 7,411,719;

[0032] (c) Microunit structures, wall materials, and methods of forming microunits; see, for example, U.S. Patent Nos. 7,072,095 and 9,279,906;

[0033] (d) Methods for filling and sealing microcells; see, for example, U.S. Patent Nos. 7,052,571 and 7,715,088;

[0034] (e) Thin films and subassemblies containing electro-optic materials; see, for example, U.S. Patent Nos. 6,982,178 and 7,839,564;

[0035] (f) Backplanes, adhesive layers and other auxiliary layers used in displays and methods; see, for example, U.S. Patent Nos. 7,116,318 and 7,535,624;

[0036] (g) Color formation and color adjustment; see, for example, U.S. Patent Nos. 7,075,502, 7,839,564, and 9,812,073;

[0037] (h) A method for driving a display; see, for example, U.S. Patent Nos. 7,012,600, 7,453,445, and 9,792,862;

[0038] (i) Applications of displays; see, for example, U.S. Patent Nos. 7,312,784 and 8,009,348; and

[0039] (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.

[0040] 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 electrophoretic fluid droplets and a continuous phase of polymeric material, and the discrete electrophoretic fluid droplets within such a polymer dispersion electrophoretic display can be considered as capsules or microcapsules, even if no discrete capsule membrane is associated with each individual droplet; see, for example, U.S. Patent No. 6,866,760. Therefore, for the purposes of this application, such polymer dispersion electrophoretic media are considered a subclass of encapsulated electrophoretic media.

[0041] One 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 within multiple cavities formed within a carrier medium (typically a polymer membrane). See, for example, U.S. Patents 6,672,921 and 6,788,449.

[0042] Although electrophoretic media are typically 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 the other display state is transparent. See, for example, U.S. Patents 5,872,552; 6,130,774; 6,144,361; 6,172,798; 6,271,823; 6,225,971; and 6,184,856. Dielectric electrophoretic displays are similar to electrophoretic displays but rely on changes in electric field strength and 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.

[0043] Encapsulated electrophoretic displays generally do not suffer from the aggregation and sedimentation failure modes of conventional electrophoretic equipment and offer further advantages such as the ability to print or coat displays on a variety of flexible and rigid substrates. (The term "printing" is intended to include all forms of printing and coating, including but not limited to: pre-load coating such as 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; 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 Publication No. 2021 / 0132459, the encapsulated electrophoretic medium can be bonded to non-planar surfaces, which in turn are bonded to everyday consumer goods. 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

[0044] This document discloses a method for improving residual voltage management during rapid updates of an electrophoretic display. The method of the present invention results in less color drift during rapid updates (i.e., A2), allows for interruptible updates, and reduces the risk of damage to the display when driven at high speeds (i.e., watching video). In a first aspect, a method for regulating residual voltage in an electrophoretic display, the electrophoretic display including an electrophoretic dielectric layer disposed between a light-transmitting electrode and a plurality of driving electrodes, and a controller coupled to the plurality of driving electrodes. The method includes: for each display pixel in an electrophoretic display, determining whether the display pixel has the same color state for a first image and a second image; sending an instruction to a controller to provide a waveform corresponding to a transition from the color state of the first image to the color state of the second image to each display pixel that does not have the same color state for the first image and the second image; determining a calculated residual voltage for each display pixel that has the same color state for the first image and the second image; determining a predicted residual voltage for each display pixel that has the same color state for the first image and the second image when the display pixel receives an instruction to improve its optical quality state; comparing the predicted residual voltage of each display pixel that has the same color state for the first image and the second image with a residual voltage threshold; sending an instruction to the controller to provide a waveform that leads to an improvement in the optical quality state to each display pixel that has the same color state for the first image and the second image and whose predicted residual voltage is less than the residual voltage threshold; and sending an instruction to the controller to provide a waveform that leads to a decrease in the residual voltage to each display pixel that has the same color state for the first image and the second image and whose predicted residual voltage is greater than or equal to the residual voltage threshold. In one embodiment, the method further includes comparing a calculated residual voltage with a residual voltage threshold and sending an instruction to a controller to provide a waveform causing a clear transition to each display pixel for which the calculated residual voltage is greater than or equal to the residual voltage threshold. In one embodiment, the determination and comparison steps are performed by a processor coupled to a memory and a controller. In one embodiment, the memory includes a lookup table of waveforms indexed by color state transitions and residual voltages. In one embodiment, each display pixel corresponds to one of a plurality of driving electrodes. In one embodiment, the electrophoretic display includes an electrophoretic medium comprising electrically charged particles dispersed in a fluid and confined within a plurality of vesicles or microcells. In one embodiment, the electrophoretic medium comprises four different types of electrically charged particles, and at least two types of electrically charged particles have opposite polarities. In one embodiment, six primary colors may be formed at each pixel electrode of the electrophoretic display. In one embodiment, the electrophoretic display includes a color filter array, and each display pixel includes a plurality of driving electrodes. In one embodiment, the color filter array includes a plurality of different colored filters, and each different colored filter is indexed to a respective driving electrode.In one embodiment, the waveform that leads to an improved optical quality state is tuned to reduce the increase in residual voltage while improving the optical quality state. In another embodiment, the waveform that leads to a decrease in residual voltage is tuned to maintain the optical quality state. In one embodiment, the first and second images are displayed on the electrophoretic display within 100 ms (preferably within 50 ms). In one embodiment, a plurality of driving electrodes are arranged in a pixel electrode array, and each pixel electrode is coupled to a thin-film transistor (TFT), which preferably comprises a metal-oxide-semiconductor, most preferably IGZO.

[0045] On the other hand, there is an electrophoretic display configured to actively manage residual voltage during updates. The electrophoretic display includes a transparent electrode, a plurality of driving electrodes, an electrophoretic dielectric layer disposed between the transparent electrode and the plurality of driving electrodes, a controller coupled to the plurality of driving electrodes, and a processor. The processor is configured to: for each display pixel in the electrophoretic display, determine whether the display pixel has the same color state for a first image and a second image; send an instruction to a controller to provide a waveform corresponding to the transition from the color state of the first image to the color state of the second image to each display pixel that does not have the same color state for the first image and the second image; determine a calculated residual voltage for each display pixel that has the same color state for the first image and the second image; determine a predicted residual voltage for each display pixel that has the same color state for the first image and the second image when the display pixel receives an instruction to improve its optical quality state; compare the predicted residual voltage of each display pixel that has the same color state for the first image and the second image with a residual voltage threshold; send an instruction to the controller to provide a waveform that leads to an improvement in the optical quality state to each display pixel that has the same color state for the first image and the second image and whose predicted residual voltage is less than the residual voltage threshold; and send an instruction to the controller to provide a waveform that leads to a decrease in the residual voltage to each display pixel that has the same color state for the first image and the second image and whose predicted residual voltage is greater than or equal to the residual voltage threshold. In one embodiment, the processor is further configured to compare the calculated residual voltage with a residual voltage threshold and send instructions to the controller to provide a waveform resulting in a clear transition to each display pixel whose calculated residual voltage is greater than or equal to the residual voltage threshold. In one embodiment, the electrophoretic display further includes a memory comprising a lookup table of waveforms indexed by color state transitions and residual voltage. In one embodiment, each display pixel corresponds to one of a plurality of driving electrodes. In one embodiment, the electrophoretic medium comprises electrically charged particles dispersed in a fluid and confined within a plurality of vesicles or microunits. In one embodiment, the electrophoretic medium comprises four different types of electrically charged particles, and at least two types of electrically charged particles have opposite polarities. In one embodiment, six primary colors can be formed at each pixel electrode of the electrophoretic display. In one embodiment, the electrophoretic display includes a color filter array, and each display pixel includes a plurality of driving electrodes. In one embodiment, the color filter array includes a plurality of different colored filters, and each different colored filter is indexed to a respective driving electrode. In one embodiment, the waveform resulting in an improved optical quality state is tuned to reduce the increase in residual voltage while improving the optical quality state. In one embodiment, the waveform that causes a decrease in residual voltage is tuned to maintain optical quality. In one embodiment, the first and second images are displayed on the electrophoresis display within 100 ms (preferably within 50 ms).In one embodiment, a plurality of driving electrodes are arranged in a pixel electrode array, and each pixel electrode is coupled to a thin-film transistor (TFT), which preferably comprises a metal oxide semiconductor, and most preferably IGZO. Attached Figure Description

[0046] This patent or application document contains at least one color drawing. A copy of this patent or patent application disclosed with the color drawing will be provided by the Patent Office upon request and payment of the necessary fees.

[0047] Figure 1A This is a representative cross-sectional view of a four-particle electrophoresis display, in which the electrophoretic medium is encapsulated in microcapsules.

[0048] Figure 1B This is a representative cross-sectional view of a four-particle electrophoretic display, in which the electrophoretic medium is encapsulated in microcells.

[0049] Figure 1C This is a representative cross-sectional view of an electrophoretic display, which for example includes 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.

[0050] Figure 2A An exemplary equivalent circuit for a single pixel of an electrophoretic display using an active matrix backplane with storage capacitors is shown.

[0051] Figure 2B An exemplary equivalent circuit of the simplified electrophoresis display of the present invention is shown, allowing it to be driven in a row-column manner.

[0052] Figure 3 An exemplary electrophoresis display including a display module is shown. The electrophoresis display also includes a processor, memory, one or more power supplies, and a controller. The electrophoresis display may also include sensors to allow the electrophoresis display to adjust operating parameters based on the surrounding environment, such as temperature and lighting.

[0053] Figure 4A The preferred positions of each of the four groups of particles that produce eight standard colors in a white-cyan-magenta-yellow (WCMY) four-particle electrophoretic display are shown, where the white particles are reflective and the cyan, magenta, and yellow particles are absorptive.

[0054] Figure 4B Preferred positions of each of the four groups of particles that produce seven standard colors are shown in a white-red-yellow-blue semi-absorbent (WRYB*) four-particle electrophoretic display, where the white, red, and yellow particles are reflective and the blue particles are semi-absorbent (B*).

[0055] Figure 5A flowchart illustrating an embodiment of the present invention is shown, showing the active control of residual voltage during rapid updates of an electrophoretic display.

[0056] Figure 6 An exemplary residual voltage-dependent renderer suitable for calculating the residual voltage penalty for accessing the next improved optical state is shown. The next improved optical state and the resulting residual voltage (current residual voltage + penalty) are used to look up the desired waveform from a lookup table, and the identified waveform is passed to the controller.

[0057] Figure 7 An exemplary color quality and residual voltage plot for a fast drive scheme of A2 (pseudo-two-bit) from black (K) to white (W) is shown. Similar color quality and residual voltage plots can be created for other fast color transitions, and the same technique can be extended to create multidimensional plots of color quality and residual voltage transitions.

[0058] Figure 8 This demonstrates the consistency of color states resulting from alternating black-to-white transitions at an A2 velocity in a white-cyan-magenta-yellow (WCMY) four-particle system when the method of the present invention is used.

[0059] Figure 9 The image shows the color states and residual voltage accumulation resulting from alternating black-to-white transitions at A2 velocities in a white-cyan-magenta-yellow (WCMY) four-particle system using the conventional A2-driven method. Notably, the conventional method leads to higher and more inconsistent b* values ​​with repeated driving. This change in b* is perceived as a yellowish tinge. See also... Figure 12 .

[0060] Figure 10A The tuning waveforms for the white-to-black (top right) transition and the black-to-white (bottom left) transition used in this invention are shown. Figure 10B The waveform is tuned to be shorter (5 frames versus 6 frames) and has a smaller overall impulse, resulting in a reduction in the penalty for residual voltage while improving the optical quality of the color state of a given pixel.

[0061] Figure 10B The optical quality improvement (“stomp”) waveforms used to drive the transition to an improved black state (top right) and an improved white state (bottom left) are shown.

[0062] Figure 11 The diagram illustrates the alternating black-to-white transitions at an A2 velocity in a white-cyan-magenta-yellow (WCMY) four-particle system when the method of the present invention is used and includes a tuned waveform.

[0063] Figure 12The image shows a still video image of a pinch-scale test in A2 mode using conventional (top) residual voltage management and driven by the method of the present invention (bottom) on a white-cyan-magenta-yellow (WCMY) four-particle system. It is clear that using the method of the present invention, the final white state after two pinch-scale cycles exhibits less yellowing. The increased yellowing is caused by residual voltage accumulation and typically requires a full page refresh to clear. Detailed Implementation

[0064] This invention details methods for actively managing residual voltage on backplane electrodes when driving an electrophoretic display. These methods are particularly useful for rapid updates such as scrolling, pinch-to-zoom, drop-down menus, and even video. These methods involve tracking the residual voltage changes of each backplane electrode during a series of image updates and using so-called same-color transitions to enhance the optical state of the transition or reduce the residual voltage. Using these methods, it is not necessary to employ a full reset pulse (which typically drives the backplane electrodes to two extreme voltage states and appears very “flickering” to the user). Such methods are readily adaptable to electrophoretic displays by incorporating the methods of this invention into a processor coupled to the electrophoretic display. Using the methods of this invention, many color drift and ghosting problems in color electrophoretic displays can be reduced, 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.

[0065] Methods for manufacturing electrophoretic displays comprising two, three, four (or more) particles have been discussed in the prior art. Electrophoretic fluids can be encapsulated in microcapsules or incorporated into microcell structures subsequently sealed with polymer layers. Microcapsules or microcell layers can be coated or laminated onto a plastic substrate or film with a transparent conductive material coating. 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, 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 alternatively 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 with a capsule and then coated with a back electrode material. (See U.S. Patent Publication No. 2021 / 0132459, which is incorporated herein by reference.) Alternatively, the electrophoretic fluid can be directly dispensed onto a thin, open-cell mesh already arranged on a backplane of an active matrix including pixel electrodes. The filled mesh can then be top-sealed with an integrated protective sheet / transmitting electrode.

[0066] 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 the pixel defined by the intersection of the row and column electrodes. Alternatively, and more commonly, one electrode layer may have the form of a single continuous electrode, typically a light-transmitting electrode, while the other electrode layer includes multiple driving electrodes, i.e., a matrix patterned as pixel electrodes, each driving electrode defining a pixel of the display. In some embodiments, more than one driving electrode may be associated with a pixel of the display, particularly in a color filter array (CFA) arrangement, in which case each driving electrode is associated with a sub-pixel of a 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 contains the electrodes, and the layers on the opposite side of the electrophoretic layer are typically protective layers designed to prevent the movable electrodes from damaging the electrophoretic layer.

[0067] The electrophoretic medium used herein includes charged particles that vary in color, reflectance or absorption properties, charge density, and mobility in an electric field (measured by 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 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.

[0068] 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 typically include at least one charge control agent to control the charge on 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.

[0069] In one embodiment, the present invention uses light-scattering particles, typically white, and three types of substantially non-light-scattering particles. Of course, there are no completely light-scattering particles or completely non-light-scattering particles, and the minimum light scattering of the light-scattering particles and the maximum tolerable light scattering of the substantially non-light-scattering particles used in the electrophoresis of the present 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 properties of the 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 the present invention, it is preferred that the diffuse reflectance of the white pigment measured at 550 nm on a black background is at least 5%, 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% measured, respectively, at 650 nm, 650 nm, and 450 nm against a black background, under the same conditions. (The wavelengths selected above for measuring yellow, magenta, and cyan pigments correspond to the spectral regions where these pigments have minimal absorption.) Colored pigments that meet these criteria are referred to below as “non-scattering” or “substantially non-scattering.” Specific examples of suitable particles are disclosed in U.S. Patent No. 9,921,451, which is incorporated herein by reference.

[0070] Alternative particle groups may also be used, including four groups of reflective particles, or one absorbent particle with three or four different groups of reflective particles, as described in U.S. Patent Nos. 9,922,603 ​​and 10,032,419, which are incorporated herein by reference. For example, white particles may be formed from inorganic pigments such as TiO2, ZrO2, ZnO, Al2O3, Sb2O3, BaSO4, PbSO4, etc., while black particles may be formed from CI 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 type of 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 PR254, PR122, PR149, PG36, PG58, PG7, PB28, PB15:3, PY138, PY150, PY155, or PY20. Specific examples include Clariant's Hostaperm Red D3G70-EDS, Hostaperm Pink E-EDS, PV Sunlight-resistant Red D3G, Hostaperm Red D3G70, Hostaperm Blue B2G-EDS, Hostaperm Yellow H4G-EDS, Hostaperm Green GNX; BASF's Irgazine Red L3630, Cinquasia Red L4100HD, and Irgazin Red L3660HD; and Solar Chemicals' Phthalocyanine Blue, Phthalocyanine Green, Diaryl Yellow, or Diaryl AAOT Yellow.

[0071] like Figure 1A , 1B As shown in 1C, electrophoretic displays (101, 102, 103) typically include a top transparent electrode 110, an electrophoretic medium 120, and a bottom electrode 130, whereby the bottom electrode 130 is 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. Figure 1A and 1BThe electrophoretic medium 120 contains 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 may include an encapsulated electrophoretic medium having only black and white particles with opposite charges. The CFA display 103 typically includes red, green, and blue color elements, such as an RBGW color filter array pattern. The colored elements may be directly disposed on a top transparent electrode 110, which may be, for example, indium tin oxide (ITO). Such CFA films are available from Toppan Printing Co., Ltd. (Japan). Alternatively, the color filter elements may be applied to the electrophoretic medium 120 using inkjet printing or other precision printing processes. See U.S. Patent No. 10,209,556. In a common configuration, each subpixel of an RGB CFA includes an independently controllable red, green, or blue subpixel, with a portion surrounding each subpixel being transparent (also known as a partially filled CFA) to improve whites and light colors in the image. It is worth noting that the introduction of color filters reduces display resolution because the number of image pixels depends on the color filter pattern, which is a certain ratio of pixel electrodes on the backplane. For example, for an RGB CFA, a backplane with 300 pixel electrodes per inch (PPI) has a color pixel resolution of approximately 100 PPI.

[0072] exist Figure 1A and 1B In similar embodiments, two of the four different types of particle groups 121, 122, 123, and 124 have a first polarity, while the other two groups 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 groups 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 groups have opposite polarities. The electrophoretic medium 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). There may be more than one adhesive layer 140 in a given electrophoretic display (105, 106), however, it is more common to have only one layer. The entire display stack is typically disposed on a substrate 150, which 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. Depending on the requirements, the electrophoretic displays (101, 102) may also include a sealing layer 180. 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 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.

[0073] 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 (back) electrode of which may also be transparent. However, to produce a high-resolution display, for example... Figure 1B As shown. Of course, each pixel must be addressable without interference from neighboring pixels so that the image file is faithfully reproduced on the display. One way to achieve this is to provide an array of nonlinear elements, such as transistors or diodes, with at least one nonlinear element associated with each pixel to 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 specified row and a specified 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. Row electrodes are connected to row drivers, which essentially ensure that only one row is selected at any given time. This means a selection voltage is applied to the selected row electrode to ensure all transistors in that selected row are conductive, while a non-selection voltage is applied to all other rows to ensure all transistors in those 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. (These voltages are relative to a common front electrode, which is typically located on the side of the electro-optical medium opposite the nonlinear array and extends across the entire display.)

[0074] After a preselection interval known as the “row addressing time,” the selected row is deselected, the next row is selected, and the voltage on the column driver is changed, causing the next row of the display to be 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 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, for example, the time unit between updates of a single backplane. While the electrophoretic medium can be driven with analog voltage signals (e.g., generated by power supplies and potentiometers), the use of digital controllers discretizes the waveform into blocks typically on the order of 10ms; however, shorter or longer frame widths are possible. For example, frames can be 0.5ms or longer, such as 1ms, 5ms, 10ms, 15ms, 20ms, 30ms, or 50ms. In most cases, the frame rate is less than 100ms, such as 250ms, 200ms, 150ms, or 100ms. In most applications described herein, the frame rate is between 5ms and 30ms, for example, 8ms. Dedicated drive controllers for electrophoretic displays are available from companies such as Ultrachip and Rockchip; however, programmable voltage drivers can also be used, for example, from Digi-Key and other electronics suppliers.

[0075] 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.

[0076] The attached diagram 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 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") can introduce undesirable noise into the display. Typically, the parasitic capacitance 30 is much smaller than the capacitance of the storage capacitor 10, and when a pixel row of the display is selected or deselected, the parasitic capacitance 30 can cause a small negative offset voltage, also known as a "recoil voltage," at the pixel electrode, which is typically less than 2 volts. [In some embodiments, to compensate for the undesirable "recoil voltage," a common potential V can be provided to the top plane electrode and the capacitor electrode associated with each pixel.] com , so that when Vcom Set to equal to the recoil voltage (V) KB When the value of is given, each voltage supplied to the display can be offset by the same amount, and no net DC imbalance is experienced.

[0077] 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 1B 130) 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. Additionally, typically, a common (top) transparent electrode 257 (corresponding to...) Figure 1A and 1B 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 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 The electrophoretic medium is depicted as being contained within microcapsules, but as Figure 1B The microcells shown are also suitable. A source driver (not shown) is connected to source driver line 206 and provides a source voltage to all TFTs 262 to be addressed in the column. 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 "row" and "column" electrodes is somewhat arbitrary, and TFT arrays with interchangeable row and column electrode roles can be fabricated. Each pixel of the active matrix 260 also includes, as described 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).

[0078] about Figure 2BThe described active matrix 260 (i.e., including the electrophoretic medium 200 and the common transparent electrode 257) is typically covered and sealed by a protective sheet (e.g., an integrated barrier layer) to form a shape such as Figure 3 The display module 55 is shown. This display module 55 forms the core of the electrophoretic display 40. The electrophoretic display 40 typically includes a processor 50 configured to coordinate numerous functions related to displaying content on the display module 55. These functions may include the methods of the present invention, namely coordinating residual voltage management, waveform selection, and providing waveform instructions to the controller. The processor 50 (and associated memory) may also be used to convert “standard” images (e.g., sRGB images) into a color mode that optimally reproduces the image on the display module 55. Depending on the complexity of the controller 60, some steps of the present invention may be performed by the controller 60. With advancements in controller 60 architecture, more residual voltage management can be incorporated into 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 manage residual voltage. Advanced controllers for electrophoretic displays are available from ULTRACHIP and NEXTRONIX.

[0079] Processor 50 is typically a mobile processor chip manufactured by, for example, Freescale or Qualcomm, but other manufacturers are also known. Processor 50 communicates frequently with non-transitory memory 70, retrieving image files and lookup tables (LUTs) from it to perform residual voltage management during the fast drive described below. Non-transitory memory 70 may also include gate drive instructions where different gate drive modes may be required for specific color transitions. Electrophoretic display 40 may have more than one non-transitory memory chip. Non-transitory memory 70 may be flash memory. Once the desired image has been converted for display on display module 55, specific image instructions are sent to 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). Electrophoretic display 40 may also include a communication interface 85, which may be, for example, a Wi-Fi protocol or Bluetooth, and allows electrophoretic display 40 to receive images and instructions, which may also be stored in memory 70. 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 may be embedded in a single integrated circuit. For example, an application-specific integrated circuit (ASIC) may implement the functions of the processor 50 and the controller 60.

[0080] like Figure 4A As shown, in a four-particle system consisting of 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, in 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 for 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 subsequently be switched to their desired positions at lower voltages.

[0081] Figure 4AThe system works similarly to printing on bright white paper, where the observer only sees the colored pigments on the observation 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), i.e., the user views the display from that direction, and light is incident from that direction. 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... Figure 4A In this context, the particle is assumed to be a white pigment. This light-scattering white particle forms a white reflector, thereby reflecting any particle above the white particle (such as...). Figure 4A All of the above (as shown) were 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 various colors, and the color presented to the user is the color produced by the combination of the particles above the white particles. Any particles 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 essentially non-light-scattering, their order or arrangement relative to each other is not important; however, for the reasons mentioned above, their order or arrangement relative to the white (light-scattering) particles is crucial.

[0082] 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 4A In scenarios [B], [D], and [F], the colors are yellow, magenta, and cyan, respectively. When two particles are positioned above a white particle, the displayed color is a combination of the colors of those two particles; 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. Since the order of the particles between the pixel electrode and the observer is crucial, a pixel electrode that is not being updated during a local update may be disturbed by a neighboring pixel that is being updated. Furthermore, because the particles with the highest charge (typically cyan) move the most due to inter-pixel coupling, the resulting color shift may be unpredictable.

[0083] Figure 4B An alternative particle group using reflective colored particles is shown. Figure 4BIn the embodiments, the reflective particles are white, red, and yellow, and they are combined with translucent blue; however, alternative color combinations can be used, provided that the color combination appropriately covers the useful color spectrum. Figure 4B In this system, for white, red, and yellow, the colors observed 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 observed at the surface, the colors are due to the mixing of translucent blue particles with reflective yellow, white, and red particles, respectively. Since the light seen by the observer primarily interacts with only one type of pigment surface, using... Figure 4B The images produced by the system look better than Figure 4A The colors are more saturated. However, compared to Figure 4A Compared to using Figure 4B The overall color gamut of the system is reduced because it is difficult to achieve fine control over the amount of specific particles that mix together to form secondary colors (such as orange, green, and 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 recognized that regarding... Figure 4B Reflective red and translucent blue particles can switch roles, creating an electrophoretic display medium that includes reflective white, yellow, and blue particles as well as translucent red particles. Such a system produces something similar to... Figure 4B A set of primary colors, but the red at the observation surface is produced by a combination of translucent red and white. Because... Figure 4B The systems primarily involve reflective particles, and electrophoretic displays using this medium are less affected by inter-pixel coupling. However, the method of the present invention can still be used with these systems.

[0084] 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, resulting in a display that includes 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 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 displayed 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 display black if more than one type of colored particle scatters light.

[0085] Figure 4A and 4B The color was not contaminated (i.e., the light-scattering white particles were completely covered). Figure 4AAny particle located behind the white particle, or the selected reflective particle, is obscured. Figure 4B This is an idealized scenario (where all other particles should not be visible). In practice, the masking of white particles may be imperfect, so particles that would ideally be completely masked may still have some slight absorption of light. This contamination typically reduces both the brightness and chromaticity of the presented color. Figure 4B In certain situations, the presence of light-absorbing particles typically 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, such as green scattering particles, with different spatial steric hindrance or charge properties; however, adding additional particles complicates the driving scheme and may require a wider driving voltage range. Clearly, in the electrophoretic media described herein, this color contamination should be minimized to ensure that the resulting color conforms to industry standards for color representation.

[0086] 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 can become unstable when the provided gate voltage allows switching voltages higher than 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 using 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 (MODS) may be incorporated into a 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.

[0087] In the multi-particle system described above, rapid updates are preferred for displaying moving text, such as scrolling, page turning, pinch-to-zoom, and even short videos. Consumers expect to be able to navigate black-and-white text at speeds similar to LCD displays, i.e., at least 20 image updates per second. In existing devices, this high speed is typically achieved by changing the driving mode from a first mode with a large number of color states (e.g., grayscale) to a driving mode with only two color states (typically black and white). This driving mode is often referred to as A2 and can operate as a true 1-bit system when only black and white particles are used. In systems involving more than two particles, the A2 state is approximate because driving all particles of one charge to the viewing surface will result in mixed colors. However, since the time a pixel spends in each color state is limited in A2 mode, changes in color level (also known as optical quality) are generally not noticeable.

[0088] To correct color variations, a display driven in A2 mode (a portion of the display) undergoes a transition update upon completion of the A2 drive, restoring most of the original grayscale hue or color. See, for example, U.S. Patent Publication No. 2024 / 0078981. However, during A2 driving, the updates are so rapid that there is insufficient time for each update to utilize a sufficiently long waveform to achieve DC balancing. Consequently, in A2 mode, residual voltage at a given pixel electrode can accumulate rapidly, leading to image errors such as color drift and ghosting. In some cases, when the transistor gate is not energized, the accumulated residual voltage can become large enough to damage the module by causing current to flow through the thin-film transistor. This discharge condition typically results in the pixel electrode becoming uncontrollable by the controller. To avoid such damage, prior art devices wisely use a combination of "top-off" pulses and refresh pulses to jointly improve color state and remove excess charge accumulation. See, for example, U.S. Patent No. 11,145,261.

[0089] Compared to existing technologies, the method of this invention actively manages residual voltage and utilizes each "same color" transition (i.e., black to black or white to white) to both improve the optical quality of the color state and reduce residual voltage accumulation. Furthermore, the method of this invention limits the magnitude of residual voltage jumps by transitioning only one optical quality state at a time. Figure 5As shown, starting with the identified current (510) state and target (505) state, the values ​​of the current (510) state and the target (505) state are compared, and it is determined whether they are the same or different (515). If the current (510) color and the target (505) color are different (i.e., due to the color transition of image pixels between the first and second images), a waveform instruction (520) is sent to the controller, as occurs in a typical image update. Optionally, if the current (510) state and the target (505) state are the same color state, a calculated residual voltage (530) is determined for the current (510) state, and the calculated residual voltage is compared with a residual voltage threshold (525). For this option, if it is determined that the calculated residual voltage exceeds the residual voltage threshold, the controller is instructed to implement a clear transition (535), which may be, for example, a drive waveform sufficient to drive the electrophoretic medium to each electrode and then return to the current (510) state.

[0090] If the calculated residual voltage is less than the residual voltage threshold that requires instructing the controller to implement a clear transition (535), or if the feature of (535) is not used, a lookup table is accessed to determine the residual voltage penalty for improving the optical quality state (545) of the current (510) state. The sum of the residual voltage penalty (545) and the current residual voltage (530) becomes the expected residual voltage, which is compared with the residual voltage threshold at (540) to determine whether improving the optical quality of the current (510) state would result in the residual voltage still being less than the residual voltage threshold. If so, an instruction is sent to the controller to improve the optical quality state by sending an appropriate waveform accessed from the lookup table indexed by color state and residual voltage. If not, i.e., the sum of the residual voltage penalty (545) and the current residual voltage (530) exceeds the residual voltage threshold, an instruction is sent to the controller to reduce the residual voltage (555) without changing the optical state by sending an appropriate waveform accessed from the lookup table indexed by color state and residual voltage. Figure 5 The output of the flowchart is a new color state, which may differ from the target (505) state but becomes the new current (510) state. This process is repeated until the color state is stable, there is no calculated residual voltage, and the highest possible optical state is reached, or until the display leaves A2 mode, at which point a transition mode (not shown) can be used to correct the color state of the individual display pixels.

[0091] Importantly, this invention utilizes a residual voltage-dependent renderer (600) and a residual voltage-dependent waveform lookup table (LUT) (665) to achieve fast and interruptible waveform updates for the electrophoretic display while maintaining bounded residual voltages. Figure 6As shown, the residual voltage dependent renderer (600) achieves this by using a specially designed state transition graph (650) that contains intermediate optical quality states for each color, tuned interruptible waveforms from one quality state to another, and tuned discharge waveforms for reducing accumulated residual voltage without changing the quality state. This process is typically implemented per display pixel, but larger areas (patches) of the display (e.g., background or margins) can be addressed simultaneously. The residual voltage dependent renderer (600) calculates the next achievable optical state (closest to the next desired optical state) and the next generated residual voltage state; these are then used as inputs to look up the appropriate waveform to be applied from the residual voltage dependent waveform lookup table (LUT) (665).

[0092] The state transition graph (650) performs residual voltage-dependent rendering to calculate the next achievable optical quality state that is closest to the next desired optical state (target state) based on the display's current optical state and the residual voltage state (current state). One implementation of the state transition graph may include instructions such as the pseudocode below executed by the processor:

[0093] State transition diagram ( Represented as function f )

[0094] enter:

[0095] 1. Next desired color state: represented by the symbol T

[0096] 2. Current color status: indicated by the symbol C n express

[0097] 3. Current (optical) quality status: indicated by the symbol X n express

[0098] 4. Current (residual) voltage state: indicated by the symbol R n express

[0099] Output:

[0100] 1. Next color state: C n+1

[0101] 2. Next quality state: X n+1

[0102] 3. Next voltage state: R n+1

[0103] External parameters:

[0104] 1. Voltage state boundary: B

[0105] 2. Lookup table for residual voltage changes caused by waveforms: using the function S(X) n+1 -X n C n C n+1 )express

[0106] Algorithm for defining a state transition diagram:

[0107] function f(C) n , X n , R n , T){

[0108] C n+1 =T / / The next color state is always guaranteed to be the desired color state.

[0109] If T==C n {

[0110] / / If the desired color is the same as the current color

[0111] / / Improve the quality state if possible; otherwise, improve the voltage state.

[0112] If S(1, C) n , T)-B <R n <B-S(1, C n , T){

[0113] X n+1 =X n +1; R n+1 =R n +S(1, C n , T)}

[0114] Otherwise { X n+1 =X n ; R n+1 =min(R n +S(0, C n , T), 0);}

[0115] }

[0116] otherwise{

[0117] / / Reset the quality status to its lowest level

[0118] X n+1 =0; R n+1 =R n +S(0, C n , T)

[0119] }

[0120] Return to C n+1, X n+1 , R n+1

[0121] }

[0122] Use in residual voltage-dependent renderers:

[0123] C n , X n , R n Initialize it to its initial value

[0124] When a new T is added to the processing queue: {

[0125] Get a new T from the queue.

[0126] / / Calculate the state transitions to be applied

[0127] C n+1 , X n+1 , R n+1 =f(C n , X n , R n , T)

[0128] / / Find the waveform W to be applied to the display from the R2 set LUT. n

[0129] W n =Waveform_LUT([C n , X n , R n ], [T, X n+1 , R n+1 ])

[0130] / / Update the current state value in memory

[0131] C n =C n+1 X n =X n+1 ; R n =R n+1

[0132] }

[0133] Figure 7 A state transition diagram is shown, illustrating the operation of the state transition diagram algorithm (described above) in A2 mode for black-to-white and white-to-black transitions in a four-particle WCMY system. This state transition diagram shows the available optical quality and residual voltage state transitions of the display pixel within a bounded residual voltage state space. The state space representation can be generalized as follows:

[0134]

[0135] in Indicates color status , Indicates quality status ,as well as Indicates residual voltage state The state space representation does not require only two color states, and Figure 7 State transition diagrams can be generalized to more dimensions by using more color states. Figure 7 In the diagram, the A2 mode represents a color state containing black (K) and white (W), each color having... A quality state, and The residual voltage state tracking is limited to a number of residual voltage states. arrive Between volts, this boundary can be any number or determined by physical parameters, such as the breakdown voltage of transistors in an active matrix backplane.

[0136] Figure 8 and Figure 9 The use of () is shown respectively Figure 8 ) and not using ( Figure 9 )like Figure 5-7 The diagram shows an exemplary test waveform of the active residual voltage management method of the present invention. For Figure 8 and Figure 9 The WCMY four-particle system (also known as ACeP®, or Gallery™3) is repeatedly driven between black and white optical states with a repetition period of approximately 0.5 seconds. Using the method of this invention, namely... Figure 8 The transitions involve two white optical quality states and two black optical quality states, namely W0, W1, K0, and K1, with transitions from W1 to K0 and from K1 to W0. This represents a smaller cumulative residual voltage (the area under the curve in the bottom row approaches zero, denoted as "rV"). Figure 9 As shown, in the prior art, black-to-white driving can lead to a larger residual voltage accumulation, which manifests as color drift in b* measurements in the WCMY four-particle system. Figure 8 The Δb* drift is only about 2, while Figure 9 The Δb* drift is close to 8. Furthermore, in Figure 9 There are some a* drifts, while Figure 8 In reality, this shift is almost nonexistent. When these features appear on a monitor displaying an image, this drift manifests as artifacts or ghosting. Color shift can be particularly noticeable when image pixels are part of a jittery object, so the overall effect may be a genuine offset of the large object rather than an image pixel that appears misplaced. Due to human perception, jitter errors in food and skin tones are especially offensive.

[0137] Additional benefits are gained by tuning the color transition waveform to achieve faster implementation and reduced residual voltage. These modifications also allow for interruption of image updates (waveform truncation) without causing significant fluctuations in residual voltage. As a general form, we divide each color state (N) into Q quality states. (In...) Figure 7 In the example, N=2 and Q=3. Then, Q×N scan frame waveforms are created to sequentially drive the display state from one quality state to another (improving quality using each N-frame portion). (A scan frame is the time required to update each pixel electrode in the active matrix line-by-line.) Figure 10A An exemplary tuning waveform for improving optical quality towards black and towards white is shown, but tuning waveforms of other shapes are also possible. (White to black is the upper right panel, and black to white is the lower left panel.) The first portion of the waveform is tuned to change the color state from another color and achieve the lowest possible optical quality state for the target color (allowing for fast display update / refresh rates). Subsequent Q-1 N-frame portions of the tuning waveform are each selected to improve the quality state when the opportunity arises in the rendering sequence.

[0138] For example, Figure 10A The waveform for N=6 frames tuned to A2 mode, which includes black and white color states, is shown. The designed waveform uses Q=4, with the remaining Q-1 portions using... Figure 10B The waveform shown. Figure 10B In the diagram on the right, the upper right and lower left quadrants show the quality improvement waveforms from black to black and from white to white, respectively. The upper left and lower right quadrants show the all-zero waveforms, which are used as discharge waveforms to maintain the same quality state for a given color but drive the residual voltage state toward 0 (see [link to diagram]). Figure 11 Typically, a non-zero waveform can also be tuned to a discharge waveform to maintain the optical (quality and color state) but drive the residual voltage state to 0 at a faster rate; however, this architecture requires currently quite expensive advanced power management (PMIC) chips. Figure 11 It shows something similar to Figure 8 and Figure 9 The simulation of a black and white repeating cycle, but implemented Figure 10A The tuned waveform.

[0139] At fast update rates, the optical state of a pixel or pixel block may degrade due to the use of short waveforms. Optical states that appear only as rapid transients and then change to other optical states do not need to be implemented at the highest quality due to the low perceptibility of such rapid changes. However, optical states with degraded quality that remain unchanged across multiple frames are more perceptible to the observer if left unprocessed. Using interruptible waveforms, intermediate optical states can be implemented with a quality trade-off within a short update time, and then the quality of the optical states can be continuously improved over multiple update frames, thus allowing the use of fast update rates without affecting the overall perceptible quality.

[0140] Example

[0141] The method of this invention has been implemented in a 10-inch diagonal Gallery™ 3 electrophoresis display incorporating an IGZO active matrix backplane. The same pinch-scale image sequence was used in normal A2 mode ( Figure 12 (Top row) and the active residual voltage management method of the present invention ( Figure 12 Execute at the bottom row. Figure 12 (Top row) shows the evolution (degradation) of the optical state over two cycles of the pinch-to-scale animation loop (simply using short waveforms to achieve an update rate of 12 frames per second (12fps)). Figure 12 (Bottom line) shows the evolution (improvement) of the optical state in the same pinch-scale animation loop (at 12fps) using the interruptible, residual voltage-dependent waveform design and rendering of this invention. It is clear that even after this short sequence, Figure 12 The significantly less yellowing in the bottom sequence indicates less residual voltage accumulation and less color drift.

[0142] 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. These 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 functions and / or obtaining the results and / or one or more advantages described herein, 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.

Claims

1. A method for adjusting residual voltage in an electrophoretic display, the electrophoretic display comprising an electrophoretic dielectric layer disposed between a transparent electrode and a plurality of driving electrodes and a controller coupled to the plurality of driving electrodes, the method comprising: For each display pixel in the electrophoretic display, determine whether the display pixel has the same color state for the first image and the second image; Send instructions to the controller to provide a waveform corresponding to the transition from the color state of the first image to the color state of the second image to each display pixel that does not have the same color state for the first image and the second image; Determine the calculated residual voltage for each display pixel that has the same color state for the first image and the second image; For each display pixel that has the same color state for the first image and the second image, when the display pixel receives an instruction to improve the optical quality state, the expected residual voltage is determined; The expected residual voltage of each display pixel having the same color state for the first image and the second image is compared with a residual voltage threshold. Send instructions to the controller to provide a waveform that improves the optical quality state for each display pixel that has the same color state for the first image and the second image and whose expected residual voltage is less than the residual voltage threshold; as well as The controller is instructed to provide a waveform that causes a reduction in residual voltage to each display pixel that has the same color state for the first image and the second image and whose expected residual voltage is greater than or equal to the residual voltage threshold.

2. The method of claim 1, further comprising comparing the calculated residual voltage with the residual voltage threshold and sending an instruction to the controller to provide a waveform causing a clear transition to each display pixel for which the calculated residual voltage is greater than or equal to the residual voltage threshold.

3. The method of claim 1, wherein the determining step and the comparing step are performed by a processor coupled to the memory and the controller.

4. The method of claim 3, wherein the memory comprises a lookup table of waveforms indexed by color state transitions and residual voltage.

5. The method of claim 1, wherein each display pixel corresponds to one of the plurality of driving electrodes.

6. The method of claim 1, wherein the electrophoretic display comprises an electrophoretic medium comprising electrically charged particles dispersed in a fluid and confined within a plurality of capsules or microunits.

7. The method of claim 6, wherein the electrophoretic medium comprises four different types of electrically charged particles, and at least two types of electrically charged particles have opposite polarities.

8. The method of claim 7, wherein six primary colors can be formed at each pixel electrode of the electrophoretic display.

9. The method of claim 1, wherein the electrophoretic display comprises a color filter array, and each display pixel comprises a plurality of driving electrodes.

10. The method of claim 9, wherein the color filter array comprises a plurality of different colored filters, and each different colored filter is indexed to a driving electrode.

11. The method of claim 1, wherein the waveform that leads to an improvement in optical quality is tuned to reduce the increase in residual voltage while improving the optical quality.

12. The method of claim 1, wherein the waveform causing a decrease in residual voltage is tuned to maintain the optical quality state.

13. The method according to claim 1, wherein the first image and the second image are displayed on the electrophoresis display within 100 ms, preferably within 50 ms.

14. An electrophoretic display configured to actively manage residual voltage during an update, comprising: Transparent electrode; Multiple driving electrodes; An electrophoretic dielectric layer disposed between the light-transmitting electrode and the plurality of driving electrodes; A controller coupled to the plurality of driving electrodes; as well as Processor, the processor being configured to: For each display pixel in the electrophoretic display, determine whether the display pixel has the same color state for the first image and the second image; Send instructions to the controller to provide a waveform corresponding to the transition from the color state of the first image to the color state of the second image to each display pixel that does not have the same color state for the first image and the second image; Determine the calculated residual voltage for each display pixel that has the same color state for the first image and the second image; For each display pixel that has the same color state for the first image and the second image, when the display pixel receives an instruction to improve the optical quality state, the expected residual voltage is determined; The expected residual voltage of each display pixel having the same color state for the first image and the second image is compared with a residual voltage threshold. Send instructions to the controller to provide a waveform that improves the optical quality state for each display pixel that has the same color state for the first image and the second image and whose expected residual voltage is less than the residual voltage threshold; as well as The controller is instructed to provide a waveform that causes a reduction in residual voltage to each display pixel that has the same color state for the first image and the second image and whose expected residual voltage is greater than or equal to the residual voltage threshold.

15. The electrophoretic display of claim 14, wherein the processor is further configured to compare the calculated residual voltage with the residual voltage threshold and send instructions to the controller to provide a waveform causing a clear transition to each display pixel for which its calculated residual voltage is greater than or equal to the residual voltage threshold.

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