Drive sequence for reducing image ghosting in a multi-particle electrophoretic display

Abstract

Multi-particle electrophoretic displays, including three-particle displays and four-particle displays, and methods of driving such displays using waveforms configured to reduce or eliminate image ghosting with dithering pulses.

Description

Cross-reference to related applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 632,717, filed April 11, 2024, entitled “DRIVING SEQUENCES FOR REDUCINGIMAGE GHOSTING IN MULTI-PARTICLE ELECTROPHORETIC DISPLAYS”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention generally relates to a driving method for a color electrophoretic display device that provides high-quality color states and reduces image ghosting. Background Technology

[0003] Electrophoretic displays (electronic paper, ePaper, etc.) (such as commercially available displays from Eink Holdings (Hsinchu, Taiwan)) offer advantages in terms of light weight, durability, and environmental optimization because they consume very little energy. This technology has been integrated into e-readers (e.g., e-books or eBooks) and other display environments (e.g., mobile phones, tablets, electronic shelf labels, hospital signage, road signs, and public transport timetables). The combination of low energy consumption and sunlight readability has enabled the rapid development of so-called "plug-and-play" operation, in which the digital signage system is simply attached to a surface and interfaces with existing communication networks to provide periodic updates of information or images. Because the displays are powered by batteries or solar collectors, there is no need for utility grid infrastructure or even a plug hanging from the display.

[0004] A variety of color options for electrophoretic displays have recently become available, ranging from improved color filter arrays to complex subtractive pigment groups, and high-fidelity color options that rely on multiple sets of reflective color particles. This last type of system has been widely adopted in commercial signage, such as in food stores, clothing stores, and electronics retail stores. In particular, the type of three-color electrophoretic display described in U.S. Patent No. 11,500,261 has been rapidly adopted for outdoor and indoor signage, as well as for room temperature and refrigerated food partitioning. The entire contents of U.S. Patent No. 11,500,261 are incorporated herein by reference.

[0005] U.S. Patent Nos. 11,500,261, 8,717,664, 10,162,242, and 10,339,876 disclose three-particle electrophoresis displays. U.S. Patent Nos. 9,285,649, 9,513,527, and 9,812,073 disclose four-particle electrophoresis displays.

[0006] Multi-particle electrophoretic displays can suffer from image ghosting. Ghosting refers to the phenomenon where a blurred copy or trace of a previous image remains visible on the display after it has been rewritten. Ghosting results in poor display quality and can be distracting to the user. Improved methods are needed to drive multi-particle electrophoretic displays, especially three-particle and four-particle displays, to achieve high-quality color states and reduce image ghosting. Summary of the Invention

[0007] The driving method disclosed in this paper addresses multi-particle electrophoretic displays, particularly three-particle and four-particle electrophoretic displays, to generate high-quality color states and reduce ghosting.

[0008] In a first aspect of the invention, a method for driving an electrophoretic display layer to a desired optical state and reducing image ghosting is disclosed. The electrophoretic display layer is disposed between an observation surface including a light-transmitting electrode layer and a second opposing surface including a driving electrode layer. The display layer includes an electrophoretic medium comprising a nonpolar fluid and at least three types of particles dispersed in the nonpolar fluid. The at least three types of particles have different optical properties from each other. The method includes the following steps for each pixel of an electrophoretic display layer: (a) applying a dithering voltage pulse sequence to the pixel during a first time period to promote mixing of at least three types of particles dispersed in a nonpolar fluid, the dithering voltage pulse sequence comprising a first series of dithering voltage pulses, a second series of dithering voltage pulses, a third series of dithering voltage pulses, and a fourth series of dithering voltage pulses, wherein each series of dithering voltage pulses comprises alternating positive and negative voltage pulses repeated multiple times, and wherein the second series of voltage pulses and the third series of voltage pulses have the same frequency, the first series of voltage pulses has a higher frequency than the second series of voltage pulses and the third series of voltage pulses, and the fourth series of voltage pulses has a lower frequency than the second series of voltage pulses and the third series of voltage pulses; and (b) applying a push-pull voltage pulse sequence to the pixel during a second time period following the first time period to drive the pixel to a target color state on the observation side of the display layer.

[0009] In one or more embodiments, the at least three types of particles include a first type of particle, a second type of particle, a third type of particle, and a fourth type of particle, wherein the first type of particle and the third type of particle have a first polarity of charge, and the second type of particle and the fourth type of particle have a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle, and the second type of particle has a larger charge value than the fourth type of particle.

[0010] In one or more embodiments, the first type of particle, the second type of particle, the third type of particle, and the fourth type of particle are black, yellow, red, and white, respectively.

[0011] In one or more embodiments, the first polarity is positive and the second polarity is negative.

[0012] In one or more embodiments, the at least three types of particles include a first type of particle, a second type of particle, and a third type of particle dispersed in a nonpolar fluid, the first type of particle and the third type of particle having a first polarity of charge, and the second type of particle having a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle.

[0013] In one or more embodiments, the electrophoretic display layer is encapsulated in a microcapsule or a sealed microcell.

[0014] In one or more embodiments, the jitter voltage pulses of the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses, and the fourth series of jitter voltage pulses have the same amplitude.

[0015] In one or more embodiments, the jitter voltage pulses of the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses, and the fourth series of jitter voltage pulses alternate between +15 V and -15 V.

[0016] In one or more embodiments, the jitter voltage pulses of the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses, and the fourth series of jitter voltage pulses have frequencies of approximately 25 Hz, 12.5 Hz, 12.5 Hz, and 3.125 Hz, respectively.

[0017] In one or more embodiments, the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses, and the fourth series of jitter voltage pulses are separated by a zero-voltage pause.

[0018] In one or more embodiments, the first time period is shorter than the second time period.

[0019] In another aspect of the invention, a method for driving an electrophoretic display layer to a desired optical state and reducing image ghosting is disclosed. The electrophoretic display layer is disposed between an observation surface including a light-transmitting electrode layer and a second opposing surface including a driving electrode layer. The display layer includes an electrophoretic medium comprising a nonpolar fluid and at least three types of particles dispersed in the nonpolar fluid. These at least three types of particles have different optical properties from each other. The method includes the following steps for driving each pixel of an electrophoretic display layer to a target color state: (a) selecting a waveform from a set of waveforms stored in a memory for driving the pixel to the target color state, each waveform driving the pixel to a different color state, each waveform in the set of waveforms including a dithering voltage pulse sequence applied in a first time period to promote mixing of at least three types of particles dispersed in a nonpolar fluid, the dithering voltage pulse sequence being followed by a push-pull voltage pulse sequence applied in a second time period to drive the pixel to the target color state, wherein at least two waveforms in the set of waveforms have different dithering voltage pulse sequences, the dithering voltage pulse sequence of each waveform being configured to reduce image ghosting in the target color state caused by the subsequent push-pull voltage pulse sequence in the waveform; and (b) applying the waveform selected in step (a) to drive the pixel to the target color state.

[0020] In one or more embodiments, the at least three types of particles include a first type of particle, a second type of particle, a third type of particle, and a fourth type of particle, wherein the first type of particle and the third type of particle have a first polarity of charge, and the second type of particle and the fourth type of particle have a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle, and the second type of particle has a larger charge value than the fourth type of particle.

[0021] In one or more embodiments, the first type of particle, the second type of particle, the third type of particle, and the fourth type of particle are black, yellow, red, and white, respectively.

[0022] In one or more embodiments, the first polarity is positive and the second polarity is negative.

[0023] In one or more embodiments, the at least three types of particles include a first type of particle, a second type of particle, and a third type of particle dispersed in a nonpolar fluid, the first type of particle and the third type of particle having a first polarity of charge, and the second type of particle having a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle.

[0024] In one or more embodiments, the electrophoretic display layer is encapsulated in a microcapsule or a sealed microcell.

[0025] In one or more embodiments, the jitter voltage pulse sequence of one of the waveforms in the set of waveforms includes multiple series of jitter voltage pulses, wherein each series of jitter voltage pulses includes alternating positive voltage pulses and negative voltage pulses repeated multiple times, and wherein the positive voltage pulses and negative voltage pulses have asymmetrical pulse widths.

[0026] In one or more embodiments, the positive voltage pulse has a pulse width of approximately 60 ms and the negative voltage pulse has a pulse width of approximately 20 ms, or wherein the positive voltage pulse has a pulse width of approximately 20 ms and the negative voltage pulse has a pulse width of approximately 60 ms.

[0027] In one or more embodiments, the jitter voltage pulses alternate between +15 V and -15 V.

[0028] In one or more embodiments, the jitter voltage pulse sequence of one of the waveforms in the set of waveforms includes at least a first series of jitter voltage pulses, a second series of jitter voltage pulses, a third series of jitter voltage pulses, and a fourth series of jitter voltage pulses in sequence, wherein each series of jitter voltage pulses includes alternating positive voltage pulses and negative voltage pulses repeated multiple times, and wherein the first series of jitter voltage pulses and the third series of jitter voltage pulses have a given frequency, and the second series of jitter voltage pulses and the fourth series of jitter voltage pulses have a frequency greater than the given frequency.

[0029] In one or more embodiments, the jitter voltage pulses alternate between +15 V and -15 V.

[0030] In one or more embodiments, the jitter voltage pulse sequence of one of the waveforms in the group of waveforms includes at least a first series of jitter voltage pulses, a second series of jitter voltage pulses, a third series of jitter voltage pulses, and a fourth series of jitter voltage pulses in sequence, wherein the first series of jitter voltage pulses and the third series of jitter voltage pulses include pulses that alternately repeat multiple times between +15 V and -15 V, and wherein the second series of jitter voltage pulses and the fourth series of jitter voltage pulses include pulses that alternately repeat multiple times between +15 V and 0 V.

[0031] In one or more embodiments, the first series of jitter voltage pulses and the third series of jitter voltage pulses have a frequency of 12 Hz, and the second series of jitter voltage pulses and the fourth series of jitter voltage pulses have a frequency of 20 Hz.

[0032] In one or more embodiments, the jitter voltage pulse sequence of one of the waveforms in the set of waveforms includes at least three series of jitter voltage pulses, each series of jitter voltage pulses including alternating positive and negative voltage pulses having a given pulse width repeated multiple times, wherein each series of jitter voltage pulses is separated by a single pulse with a pulse width greater than the given pulse width.

[0033] In one or more embodiments, the jitter voltage pulses alternate between +15 V and -15 V.

[0034] In one or more embodiments, each individual pulse has an amplitude of +15 V or -15 V. Attached Figure Description

[0035] Figure 1 This is a schematic cross-sectional view of an exemplary electrophoretic display layer containing four different types of particles and capable of displaying four different color states.

[0036] Figures 2A-2F It is similar to Figure 1 The cross-sectional diagram is shown, but it illustrates the changes in particle position caused by the application of a specific charge and polarity driving sequence.

[0037] Figure 3 This is a schematic block diagram showing the driving components of an electrophoresis display device.

[0038] Figure 4 A general "jitter" waveform is shown, which can be used to mix and reset particles in a drive sequence.

[0039] Figure 5 An example of a set of drive waveforms that includes common jitter waveform components is shown.

[0040] Figure 6 The image generated on the monitor is depicted, which includes a set of vertical stripes of different colors (in order: black, white, red, yellow, blue, and green).

[0041] Figure 7 Depicting in Figure 6 The image is then generated on the monitor, which consists of a set of horizontal stripes of different colors (in order: black, white, red, yellow, blue, and green).

[0042] Figure 8 yes Figure 7 A magnified view of the top black horizontal stripe in the image.

[0043] Figure 9 yes Figure 5 An enlarged view of the jitter waveform depicted in the image.

[0044] Figure 10 An exemplary jitter pulse waveform configured to reduce ghosting is shown according to one or more embodiments.

[0045] Figure 11 It shows the use of Figure 10 The jitter waveform generates a black image region with reduced ghosting.

[0046] Figure 12 It is for use Figure 9 and Figure 10 A table comparing the color attributes of images generated from jittery waveforms.

[0047] Figure 13 An example of existing technology jitter waveforms is shown.

[0048] Figure 14 Depicting the use Figure 13 The jitter waveform generates an image on the display, which includes a set of horizontal stripes of different colors (in order: black, white, red, yellow, blue, and green).

[0049] Figure 15-20 Exemplary dithering waveforms according to one or more embodiments are depicted, which are used in conjunction with drive waveforms for generating target color states of black, white, red, yellow, blue, and green, respectively.

[0050] Figure 21 Depicting the use Figure 15-20 The jitter waveform generates an image on the display, which includes a set of horizontal stripes of different colors (in order: black, white, red, yellow, blue, and green).

[0051] Figure 22 It is for use Figure 13 and Figure 15-20 A table comparing the color attributes of images generated from jittery waveforms. Detailed Implementation

[0052] This invention relates to a method for driving an electrophoretic display device. Such a device includes a display layer comprising an electrophoretic medium containing multiple types of particles (e.g., a four-particle system having first-type, second-type, third-type, and fourth-type particles), all of which have different optical properties and are dispersed in a nonpolar fluid. These optical properties are typically colors perceptible to the human eye, but can also be other optical properties such as optical transmission, reflection, and emission, or, in the case of a machine-reading display, pseudo-color in the sense of variations in reflectivity at electromagnetic wavelengths outside the visible light range. The invention broadly covers particles of any color, provided that the multiple types of particles are visually distinguishable. The invention also broadly covers other multi-particle electrophoretic media, including three-particle systems.

[0053] In a four-particle electrophoresis medium, the four types of particles can comprise two pairs of particles with opposite charges. The first pair (type I particles and type II particles) consists of a type I positive particle and a type I negative particle; similarly, the second pair (type III particles and type IV particles) consists of a type II positive particle and a type II negative particle. Of the two pairs of particles with opposite charges, one pair (type I particles and type II particles) carries a stronger charge than the other pair (type III particles and type IV particles). Therefore, these four types of particles can also be referred to as highly positive particles, highly negative particles, lowly positive particles, and lowly negative particles.

[0054] The term “charge potential” may be used interchangeably with “zeta potential” or electrophoretic mobility in the context of this application. The charge polarity and charge potential level of the particles can be altered by methods described in U.S. Patent Application Publication No. 2014 / 0011913, and / or can be measured from the zeta potential. In one embodiment, the zeta potential is determined by a Colloidal Dynamics AcoustoSizer IIM with a CSPU-100 signal processing unit and an ESA EN# Attn flow cell (K:127). Instrument constants, such as the density of the solvent used in the sample, the dielectric constant of the solvent, the velocity of sound in the solvent, and the viscosity of the solvent, are all entered before testing at the test temperature (25°C). The pigment sample is dispersed in a solvent (typically a hydrocarbon fluid having fewer than 12 carbon atoms) and diluted to 5-10 wt%. The sample also contains a charge control agent (Solsperse™ 17000, available from Lubrizol, a Berkshire Hathaway company) at a weight ratio of 1:10 to the particles. The mass of the diluted sample is determined, and then the sample is loaded into a flow cell to determine the zeta potential. The methods and instruments used to measure electrophoretic mobility are well known to those skilled in the art of electrophoretic display technology.

[0055] As Figure 1 In the example shown, the first black particle (K) and the second yellow particle (Y) are the first pair of particles with opposite charges, in which the black particle is a highly positive particle and the yellow particle is a highly negative particle. The third red particle (R) and the fourth white particle (W) are the second pair of particles with opposite charges, in which the red particle is a low-positive particle and the white particle is a low-negative particle.

[0056] In another example not shown, black particles can be highly positive, yellow particles can be low-positive, white particles can be low-negative, and red particles can be highly negative. Of course, any particular color can be replaced with another color depending on the application requirements. For example, if a specific combination of black, white, green, and red particles is needed... Figure 1 The high negative yellow particles shown can be replaced with high negative green particles.

[0057] Furthermore, the color states of the four types of particles can be intentionally mixed. For example, yellow pigment is inherently often tinged with green; if a better yellow state is desired, yellow and red particles can be used, where both types of particles have the same charge polarity, but the yellow particles carry a higher charge than the red particles. As a result, in the yellow state, a small amount of red particles will be mixed with the yellow-green particles to give the yellow state better color purity.

[0058] The particles are preferably opaque; in a sense, they should be reflective rather than translucent. It will be apparent to those skilled in color science that if the particles were translucent, some color states appearing in the following specific embodiments would be severely distorted or unattainable. White particles, of course, scatter light rather than reflect it, but care must be taken to ensure that not too much light passes through the white particle layer. For example, as described below, if in Figure 2F In the white state shown, the white particle layer allows a large amount of light to pass through and be reflected by the black and yellow particles behind it, which greatly reduces the brightness of the white state.

[0059] In some embodiments, the particles are primary particles without a polymer shell. Alternatively, each particle may contain an insoluble core with a polymer shell. The core may be an organic or inorganic pigment, and it may be a single core particle or an aggregate of multiple core particles. The particles may also be hollow particles.

[0060] White particles can be formed from inorganic pigments such as TiO2, ZrO2, ZnO, Al2O3, Sb2O3, BaSO4, PbSO4, or the like. Black particles can be formed from Cl pigments Black 26 or 28 or the like (e.g., manganese ferrite black spinel or copper chromite black spinel) or carbon black. Other colored particles (neither white nor black) can be red, green, blue, magenta, cyan, yellow, or any other desired colored particles, and can be formed from, for example, CI pigments PR254, PR122, PR149, PG36, PG58, PG7, PB28, PB15:3, PY83, PY138, PY150, PY155, or PY20. These are common organic pigments described in the Color Index Manual, "New Pigment Application Technology" (CMC Publishing, 1986), and "Printing Ink Technology" (CMC Publishing, 1984). Specific examples include Clariant Hostaperm Red D3G 70-EDS, Hostaperm Powder E-EDS, PV Fast Red D3G, Hostaperm Red D3G 70, Hostaperm Blue B2G-EDS, Hostaperm Yellow H4G-EDS, Novoperm Yellow HR-70-EDS, Hostaperm Green GNX, BASF Irgazine Red L 3630, Cinquasia Red L 4100 HD, and Irgazin Red L 3660HD; and SunChem Phthalocyanine Blue, Phthalocyanine Green, Benzidine Yellow, or Benzidine AAOT Yellow. The colored particles can also be inorganic pigments, such as red, green, blue, and yellow. Examples may include, but are not limited to, CI Pigment Blue 28, CI Pigment Green 50, and CI Pigment Yellow 227.

[0061] The nonpolar fluid in which the four types of particles are dispersed can be transparent and colorless. It preferably has a low viscosity and a dielectric constant in the range of about 2 to about 30, and preferably about 2 to about 15 for high particle mobility. Examples of suitable dielectric solvents include hydrocarbons (such as isoparaffins, decahydronaphthalene (naphthalene), 5-ethylidene-2-norbornene, fatty oils, paraffin oils, and silicone fluids), aromatic hydrocarbons (such as toluene, xylene, phenylxylene ethane, dodecylbenzene, or alkylnaphthalene), halogenated solvents (such as perfluorodecahydronaphthalene, perfluorotoluene, perfluoroxylene, dichlorotrifluorotoluene, 3,4,5-trichlorotrifluorotoluene, chloropentafluorobenzene, dichlorononane, or pentachlorobenzene), and perfluorinated solvents (such as FC-43, FC-70, or FC-5060 from 3M Inc. in St. Paul, Minnesota, USA), low molecular weight halogenated polymers (such as poly(perfluoropropylene oxide) and poly(trifluorochloroethylene) from TCIAmerica in Portland, Oregon, USA), and Halocarbon from River Edge, New Jersey, USA). Halocarbon oil from Product Company, perfluoropolyethers (such as Galden from Ausimont or Krytox oil and grease K-Fluid series from DuPont Delaware), and polydimethylsiloxane silicone oil (DC-200) from Dow Corning.

[0062] The percentage of different types of particles in the fluid can vary. For example, one type of particle may account for 0.1% to 10% of the volume of the electrophoretic fluid, preferably 0.5% to 5%; another type of particle may account for 1% to 50% of the volume of the fluid, preferably 5% to 20%; and each of the remaining types of particles may account for 2% to 20% of the volume of the fluid, preferably 4% to 10%.

[0063] Various types of particles can have different particle sizes. For example, smaller particles can have sizes ranging from about 50 nm to about 800 nm. Larger particles can have sizes from about 2 to about 50 times that of smaller particles, more preferably from about 2 to about 10 times that of smaller particles.

[0064] Electrophoretic displays typically comprise 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 on opposite sides of the electrophoretic material are electrode layers, and one or both electrode layers are patterned to define pixels of the display. For example, in a passive matrix system, one electrode layer may be patterned as elongated row electrodes, while the other electrode layer is patterned as elongated column electrodes extending perpendicularly to the row electrodes, with pixels defined by the intersections of the row and column electrodes. Alternatively, more commonly, one electrode layer may have the form of a single continuous electrode, while the other electrode layer is patterned as a matrix of pixel electrodes, each pixel electrode defining a display pixel of the display. In another type of electrophoretic display, intended for use with a stylus, printhead, or similar movable electrodes separate from the display, only one layer adjacent to the electrophoretic layer includes electrodes, and the layers on opposite sides of the electrophoretic layer are typically protective layers to prevent damage to the electrophoretic layer by the movable electrodes.

[0065] Numerous patents and applications, assigned to or in the name of MIT, Einkel Corporation, Einkel California LLC, Einkel Holdings, Prime View International, and related companies, describe various techniques for encapsulation and micro-unit electrophoresis and other electro-optic media. Encapsulated electrophoretic media comprise numerous small capsules, each capsule itself comprising an inner phase of electrophoretically movable particles contained 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. In micro-unit electrophoretic displays, charged particles and fluid are not encapsulated in microcapsules but are retained in multiple cavities formed within a carrier medium, typically a polymer film. The techniques described in these patents and applications include:

[0066] (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 7,002,728 and 7,679,814;

[0067] (b) Encapsulation, adhesives, and encapsulation processes; see, for example, U.S. Patent Nos. 6,922,276 and 7,411,719;

[0068] (c) Microunit structures, wall materials, and methods of forming microunits; see, for example, U.S. Patent Nos. 7,072,095 and 9,279,906;

[0069] (d) Methods for filling and sealing microcells; see, for example, U.S. Patent Nos. 7,144,942 and 7,715,088;

[0070] (e) Thin films and subassemblies containing electro-optic materials; see, for example, U.S. Patent Nos. 6,982,178 and 7,839,564;

[0071] (f) Methods used in backsheets, adhesive layers and other auxiliary layers, and displays; see, for example, U.S. Patent Nos. 7,116,318 and 7,535,624;

[0072] (g) Color formation and color adjustment; see, for example, U.S. Patent Nos. 7,075,502 and 7,839,564;

[0073] (h) A method of driving a display; see, for example, U.S. Patent Nos. 7,012,600 and 7,453,445;

[0074] (i) Applications of displays; see, for example, U.S. Patent Nos. 7,312,784 and 8,009,348; and

[0075] (j) Non-electrophoretic displays, as described in U.S. Patent No. 6,241,921 and U.S. Patent Application Publication No. 2015 / 0277160; and applications of packaging and microcell technologies other than displays; see, for example, U.S. Patent Application Publication Nos. 2015 / 0005720 and 2016 / 0012710.

[0076] 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 in 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, the aforementioned U.S. Patent Application Publication No. 2002 / 0131147. Therefore, for the purposes of this application, such polymer dispersion electrophoretic media are considered a subclass of encapsulated electrophoretic media.

[0077] One related type of electrophoretic display is the so-called "micro-unit electrophoretic display." In a micro-unit electrophoretic display, charged particles and suspended fluid are not encapsulated in microcapsules, but rather retained in multiple cavities formed within a carrier medium (typically a polymer film). See, for example, International Application Publication No. WO 02 / 01281 and U.S. Patent No. 6,788,449.

[0078] Preferred embodiments of the invention will now be described in detail with reference to the accompanying drawings, though only as illustrations.

[0079] Figure 1 This is a cross-sectional schematic diagram of an example of a display layer that can be driven by the method of the present invention. The display layer has two main surfaces, a first viewing surface 13 (e.g., Figure 1The display layer includes an upper surface (shown above), through which the user observes the display, and a second surface 14, located on the side of the display layer opposite to the first surface 13. The display layer comprises an electrophoretic medium comprising a fluid and first black particles (K) with a high positive charge, second yellow particles (Y) with a high negative charge, third red particles (R) with a low positive charge, and fourth white particles (W) with a low negative charge. It should be understood that assigning a specific color to a specific charged particle is somewhat arbitrary, and other color combinations can be substituted. Therefore, the color displayed at the first surface 13 will depend on the color assigned to each charge / magnitude particle (e.g., high positive charge particles). The display layer is provided with electrodes known in the art for applying an electric field across the display layer, i.e., comprising two electrode layers, the first of which is a light-transmitting or transparent common electrode layer 11 extending across the entire viewing surface 13 of the display layer. This electrode layer 11 may be formed of indium tin oxide (ITO) or a similar light-transmitting conductor. The other electrode layer 12 is a layer of discrete pixel electrodes 12a on the second surface 14, which define individual pixels of the display. Figure 1 The vertical dashed line indicates this. Alternatively, the other electrode layer 12 can be a solid electrode, such as a metal foil, graphite plate, or conductive polymer. Alternatively, electrode layer 12 can also be a light-transmitting or transparent electrode layer, similar to the transparent common electrode layer 11. (An electric field is created for the pixel by the potential difference between the voltage applied to the common electrode and the voltage applied to the respective pixel electrode.) Pixel electrodes 12a can form part of an active matrix driving system having, for example, a thin-film transistor (TFT) backplane, but other types of electrode addressing can be used, provided that the electrodes provide the necessary electric field across the display layer.

[0080] The pixel electrode may be as described in U.S. Patent No. 7,046,228. The pixel electrode 12a may form part of the backplane of an active matrix thin-film transistor (TFT), but other types of electrodes (e.g., segmented electrodes) may also be used for addressing, provided that these electrodes provide the necessary electric field across the display layer.

[0081] In one embodiment, the charge carried by a "low-charge" particle may be less than about 50% of the charge carried by a "high-charge" particle, preferably about 5% to about 30%. In another embodiment, the charge carried by a "low-charge" particle may be less than about 75% of the charge carried by a "high-charge" particle, or about 15% to about 55%. In yet another embodiment, the listed comparison of charge levels applies to two types of particles having the same charge polarity. The charges on "highly positive" particles and "highly negative" particles may be the same or different. Similarly, the magnitudes of the charges on "lowly positive" particles and "lowly negative" particles may be the same or different. In any given electrophoretic fluid, two pairs of high- and low-charge particles may have different levels of charge difference. For example, in one pair, the low-positive charged particles may have a charge intensity of 30% of the charge intensity of the high-positive charged particles, while in another pair, the low-negative charged particles may have a charge intensity of 50% of the charge intensity of the high-negative charged particles.

[0082] Figures 2A-2F It shows that it can be used Figure 1 The diagram shows the four color states displayed at the view surface of each pixel in the display layer, and the transitions between them. As previously stated, high positive particles are black (K); high negative particles are yellow (Y); low positive particles are red (R); and low negative particles are white (W).

[0083] exist Figure 2A and 2B In the middle, when the high negative drive voltage (hereinafter referred to as V) H2 When an electric field is generated by applying a voltage (e.g., -15 V, e.g., -30 V) to pixel electrode 22a (in the following, it will be assumed that common electrode 21 will be kept at 0 V, so in this case the common electrode is strongly positive relative to pixel electrode) for a sufficient period of time, highly negative yellow particles are driven to neighboring common electrode 21, and highly positive black particles are driven to neighboring pixel electrode 22a, to produce… Figure 2A The state.

[0084] Low-positive red (R) particles and low-negative white (W) particles move more slowly than the higher-charged black and yellow particles because they carry a weaker charge. As a result, they remain in the center of the pixel, with white particles above red particles, and both are obscured by yellow particles, making them invisible at the viewing surface. Therefore, yellow appears at the viewing surface.

[0085] Conversely, when the high positive drive voltage (hereinafter referred to as V) H1 When an electric field is generated when a voltage (e.g., +15 V, e.g., +30 V) is applied to the pixel electrode 22a for a sufficient period of time (making the common electrode 21 strongly negative relative to the pixel electrode), highly positive black particles are driven to the neighboring common electrode 21, and highly negative yellow particles are driven to the neighboring pixel electrode 22a. Figure 2BThe obtained state and Figure 2A It is the complete opposite of the others, and appears black on the observed surface.

[0086] Figure 2C and 2D Low positive (red) particles are shown. Figure 1 The method shown illustrates how the view surface of the display layer is displayed. This process begins from... Figure 2A The (yellow) state shown indicates the start, and as... Figure 2C The following is repeated. A low positive voltage (V) will be applied. L1 For example, +3 V, +5 V, or +10 V are applied to the pixel electrode 22a (i.e., making the common electrode 21 slightly negative relative to the pixel electrode) for a sufficient period of time, causing highly negative yellow particles to move towards the pixel electrode 22a, and highly positive black particles to move towards the common electrode 21. However, when the yellow and black particles meet in the middle between the pixel electrode and the common electrode, as... Figure 2D As shown, they remain in the middle position because the electric field generated by the low driving voltage is not strong enough to overcome the attraction between them. As illustrated, the yellow and black particles remain in a mixed state between the pixel electrode and the common electrode.

[0087] The term “attraction” as used in this article encompasses electrostatic interactions that are linearly dependent on the particle charge potential and can be further enhanced by other forces, such as van der Waals forces, hydrophobic interactions, or the like.

[0088] Clearly, attractive forces also exist between low-positive red particles and high-negative yellow particles, and between low-negative white particles and high-positive black particles. However, these forces are not as strong as those between black and yellow particles, so the weak attractive forces on red and white particles can be overcome by the electric field generated by the low driving voltage, thus separating low-charged and high-charged particles of opposite polarities. The electric field generated by the low driving voltage is also sufficient to separate low-negative white particles from low-positive red particles, causing red particles to move to the vicinity of the common electrode 21, and white particles to move to the vicinity of the pixel electrode 22a. As a result, the pixel displays red, while the white particles are closest to the pixel electrode, such as... Figure 2D As shown.

[0089] Figure 2E and 2F Low negative (white) particles were shown. Figure 1 The method shown is how the observation surface is displayed. This process starts from... Figure 2B The (black) state begins, and as Figure 2E Repeat as shown. Apply a low negative voltage (V) L2A voltage (e.g., -3 V, -5 V, -10 V) is applied to the pixel electrode (i.e., making the common electrode slightly positive relative to the pixel electrode) for a sufficient period of time, causing highly positive black particles to move towards the pixel electrode 22a, and highly negative yellow particles to move towards the common electrode 21. However, when yellow and black particles meet in the middle between the pixel electrode and the common electrode, as... Figure 2F As shown, they remain in the middle position because the electric field generated by the low driving voltage is not strong enough to overcome the attraction between them. Therefore, as previously referenced... Figure 2D The yellow and black particles discussed are in a mixed state and remain between the pixel electrode and the common electrode.

[0090] As referenced above Figure 2C and 2D The attractive forces discussed also exist between low-positive red particles and high-negative yellow particles, and between low-negative white particles and high-positive black particles. However, these attractive forces are not as strong as those between black and yellow particles, so the weak attractive forces on red and white particles can be overcome by the electric field generated by the low driving voltage, thus separating low-charged and high-charged particles of opposite polarities. The electric field generated by the low driving voltage is sufficient to separate low-negative white particles and low-positive red particles, causing white particles to move to the vicinity of the common electrode 21, and red particles to move to the vicinity of the pixel electrode 22a. As a result, the pixel displays white, while the red particles are closest to the pixel electrode, such as... Figure 2F As shown.

[0091] exist Figure 1 and Figures 2A-2F In the display layer shown, black particles (K) carry a high positive charge, yellow particles (Y) carry a high negative charge, red particles (R) carry a low positive charge, and white particles (W) carry a low negative charge. However, in principle, particles carrying a high positive charge, a high negative charge, a low positive charge, or a low negative charge can be of any color. All these variations are within the scope of this application.

[0092] It should also be noted that, in order to achieve Figure 2D and 2F The low potential difference applied can drive a pixel from a high positive particle color state to a high negative particle color state (i.e., as shown in the image) to the color state. Figure 2A and 2B (As shown) The required high potential difference is approximately 5% to approximately 50%, and vice versa.

[0093] Although for the sake of explanation, Figure 1 and Figures 2A-2FThe display layer shown is unencapsulated, but electrophoretic fluid can be filled into the display unit, which can be a cup-shaped microunit as described in U.S. Patent No. 6,930,818. The display unit can also be other types of microcontainers, such as microcapsules, microchannels, or equivalents, regardless of their shape or size. All of these are within the scope of this application.

[0094] For those skilled in imaging science, it is obvious that if one wants to... Figures 2A-2F To achieve a "clean," well-saturated color in the various color states shown, all non-black and non-white particles used in the electrophoretic medium should be reflective rather than translucent. (White particles inherently scatter light, while black particles inherently absorb light.) For example, in... Figure 2D In the red state, if the red particles are essentially translucent, then a significant proportion of the light entering the electrophoretic layer through the observation surface will pass through the red particles, and a portion of this transmitted light will pass "behind" the red particles (i.e., as shown in the image). Figure 2D The yellow particles (shown below) are reflected back. The overall effect would be the desired red being heavily "contaminated" by yellow, which is a very undesirable result.

[0095] Figure 3 This is a schematic block diagram illustrating an exemplary electrophoretic display device 100, which includes a central processing unit (CPU) 102, a CPU memory 104, an electrophoretic display 106, and a display controller 108. The display controller 108 includes a display controller CPU 112, a lookup table 114, and an image memory 110. The CPU 102 can read from or write to the CPU memory 104 via a computer bus. The CPU memory 104 is sometimes referred to as the "main memory" in a system. In display applications, images are stored in the CPU memory 104. When an image is to be displayed, the CPU 102 transfers image data from the CPU memory 104 to the display controller 108 via the computer bus. The display controller CPU 112 stores the image data in the image memory 110 and consults the lookup table 114 to find the appropriate waveform to be applied to each pixel of the display based on the image data. The selected driving waveform is then sent to the display 106 to drive the display to the desired image.

[0096] To ensure both color brightness and color purity, a dithering waveform can be applied before the display layer is driven from one color state to another. Figure 4This is an example of a voltage versus time plot of a prior art jitter waveform. A jitter waveform can comprise pairs of opposite drive pulses repeating multiple cycles. When used with an active matrix display, each positive or negative pulse is at least the width of an updated frame. For example, when the display updates at 60 Hz, each pulse width can be on the order of 16 milliseconds. However, in reality, the frame time is typically slightly longer due to the various charging and decay times of the backplane capacitor elements. For example, as... Figure 4 As shown, the jitter waveform can consist of a +15 V pulse of 20 milliseconds and a -15 V pulse of 20 milliseconds, repeated 50 times. The total duration of this jitter waveform will be 2000 milliseconds. For ease of illustration, Figure 4 Only seven pairs of pulses are shown.

[0097] The pulse width is not limited to the frame time, and each pulse may include multiple frames, such as a 40-millisecond pulse width, a 60-millisecond pulse width, an 80-millisecond pulse width, or a 100-millisecond pulse width. In some embodiments, the pulse width of each unit of the dithering pulse may be 80 milliseconds or less, such as 60 milliseconds or less, 40 milliseconds or less, or 20 milliseconds or less. In practice, there may be at least four repetitions (i.e., four pairs of positive and negative pulses), for example, at least six repetitions, for example, at least eight repetitions, for example, at least ten repetitions, for example, at least twelve repetitions, for example, at least fifteen repetitions. The dithering waveform may be applied without regard to the optical state before the driving voltage is applied. After the dithering waveform is applied, the optical state (at the observation surface, or, if visible, at a second surface) will not be a solid color, but a mixture of colors from various types of pigment particles. In some cases, multiple dithering pulses will be delivered with a 0 V pause between the dithering pulses to allow the electrophoretic medium to balance and / or allow the charge accumulated on the electrodes to dissipate.

[0098] Figure 4 In the dithering waveform example, each voltage pulse is applied for no more than 50% (or no more than 30%, 10%, or 5%) of the drive time required to drive from a high-positive-particle color state to a high-negative-particle color state, and vice versa. For example, if the display device is from... Figure 2B Color state drive to Figure 2A If the color state requires 300 milliseconds, or vice versa, then the jitter waveform can consist of positive and negative pulses, with each pulse applied for no more than 150 milliseconds. In practice, shorter pulses are preferred.

[0099] For the current purpose, high drive voltage (V) H1 or V H2 The driving voltage is defined as sufficient to drive a pixel from a color state with high positive particles to a color state with high negative particles, and vice versa (see [reference]). Figure 2A and 2B Low drive voltage (V) L1 or V L2 The driving voltage is defined as sufficient to drive a pixel from a color state with high charged particles to a color state with low charged particles (see [reference]). Figure 2D and 2F Typically, V L (For example, V) L1 or V L2 The value of ) is less than V H (For example, V) H1 or V H2 The range is 50%, or preferably less than 40%.

[0100] A waveform with jitter pulses configured to reduce image ghosting

[0101] One aspect of the invention relates to a method for driving a multi-particle electrophoresis display (including a three-particle display and a four-particle display), wherein the waveform has jitter pulses configured to significantly reduce image ghosting.

[0102] Figure 5 An example of a set of waveforms 50 for driving a four-particle electrophoretic medium to black, white, red, yellow, blue, and green optical states is shown. Each waveform 50 includes a common set of dithering pulses 52, followed by a specific set of push-pull pulses 54 for driving the medium to the desired color optical state. The dithering pulses 52 are used to separate the particles from each other and promote uniform mixing of the particles, such that the push-pull pulses 54 are applied to the mixed color state, in which the particles are generally randomly distributed to more effectively drive the medium to the target color optical state. As shown, the dithering pulses 52 are the same for all waveforms. The push-pull pulses 54 that follow the dithering pulses 52 vary and are displayed in different colors corresponding to their respective target optical states. Figure 9 This is an enlarged view of the dithering pulse 52. As shown, the dithering pulse 52 includes four pulse segments 60, 62, 64, and 66, each pulse segment being separated by a zero-voltage interval to allow for the balancing of the electrophoretic medium and / or to allow the dissipation of charge accumulated on the electrodes.

[0103] Because the dithering pulse 52 has a limited available time in waveform 50, electrophoretic particles may not be fully mixed by the dithering pulse 52. Therefore, when the display switches from one color to another (e.g., as shown in the image), the electrophoretic particles may not be fully mixed. Figure 6-8 When (as shown), ghosting may occur. Figure 6 An example of an initial image showing vertical stripes of a set of different colors (black, white, red, yellow, blue, and green) on a display is shown. This image is the result of the display being driven to this optical state multiple times. Then, using... Figure 5The waveform 50 shown is generated on the display. Figure 7 The image consists of a set of horizontal stripes in different colors (black, white, red, yellow, blue, and green). Figure 7 The image has black horizontal stripes at the top. Figure 8 Zoom in. The black area covers... Figure 6 The portion of the previously generated black, white, red, yellow, blue, and green areas. Therefore, Figure 7 and Figure 8 The particles in the black region rearrange from multiple different initial color states into a single black optical state. Unless Figure 5 The dithering pulses of the waveform thoroughly and uniformly mix the particles of each initial color state; otherwise, traces of these colors (i.e., ghosting) might appear after the push-pull drive pulse, such as... Figure 8 As shown.

[0104] One aspect of the invention relates to a specific configuration of dithering pulses designed to reduce image ghosting. The applicant has discovered that altering the pulse frequency in a dithering pulse sequence can result in more efficient mixing of particles in an electrophoretic medium, regardless of their initial color optical state. This more uniform mixing removes image artifacts and allows subsequent push-pull drive pulses to produce an optical state with reduced ghosting. Figure 10 An exemplary jitter pulse sequence 70 configured to reduce ghosting according to one or more embodiments is illustrated. The jitter pulse sequence 70 includes a first segment 72, a second segment 74, a third segment 76, and a fourth segment 78, each segment separated by a zero-voltage pause. The voltage pulses of the second segment 74 and the third segment 76 have the same frequency. The voltage pulse of the first segment 72 has a higher frequency than the voltage pulses of the second segment 74 and the third segment 76. The voltage pulse of the fourth segment 78 has a lower frequency than the voltage pulses of the second segment 74 and the third segment 76. In one exemplary embodiment, the jitter voltage pulses of the first segment 72, the second segment 74, the third segment 76, and the fourth segment 78 have frequencies of approximately 25 Hz, 12.5 Hz, 12.5 Hz, and 3.125 Hz, respectively.

[0105] In one or more embodiments, the jittered voltage pulses of the first segment 72, the second segment 74, the third segment 76, and the fourth segment 78 have the same amplitude. For example, the jittered voltage pulses may alternate between approximately +15 V and -15 V.

[0106] In one or more embodiments, the jitter voltage pulse 70 is applied for a shorter period of time compared to the push-pull drive voltage pulse 54. For example, the jitter voltage pulse 70 is applied for approximately 3400 ms, while the push-pull drive voltage pulse 54 is applied for approximately 6000 ms.

[0107] It has been discovered that Figure 10 The dithered voltage pulse 70 better resets the particle distribution in the electrophoretic medium, thereby leading to improved optical conditions via the subsequent push-pull drive voltage pulse 54. Figure 9 Compared to the pulse, Figure 10 The frequency variation of the jitter pulse significantly reduces ghosting, for example, as Figure 11 As shown, Figure 11 It shows something similar to Figure 8 The image contains black areas, but with significantly reduced or invisible color variations. Figure 12 The table provides test data, which shows the results compared to... Figure 9 Compared to pulses, using Figure 10 The dithering pulses reduce color variations, especially in the final black optical state.

[0108] Another aspect of the invention relates to reducing image ghosting in multi-particle electrophoresis displays by using waveforms with different dithering voltage pulse sequences for different target color states. The dithering voltage pulse sequences can differ from one another based on, for example, vibration mode, number of dithering pulse segments, dithering pulse frequency, dithering pulse amplitude, and dithering pulse width.

[0109] Figure 13 A prior art example of a single dithering waveform 80 for multiple drive waveforms used for different target color states is shown. It has been found that image ghosting can occur when areas with different colors on a display are updated to a single color using the same dithering waveform 80, especially at extreme operating temperatures, such as 50°C. For example, Figure 14 The image shown is a result of a display screen that generates horizontal stripes of different colors (black, white, red, yellow, blue, and green). This image updates an initial image on the display screen, which includes elements similar to... Figure 6 A set of vertical stripes in different colors (black, white, red, yellow, blue, and green). Unless Figure 13 The dithering pulses of the waveform thoroughly and uniformly mix the particles in each initial color state; otherwise, after applying the push-pull drive pulse, traces of these colors (i.e., ghosting) may remain, such as... Figure 14 As shown.

[0110] As described below, by using multiple dithering waveforms, image ghosting can be significantly reduced. Each dithering waveform is specifically adapted to a particular push-pull waveform to produce a specific target color state. The dithering waveform adaptation ensures that particles of each color vibrate in a way that optimally resets the particle distribution to produce the desired color state.

[0111] Figure 15-20Exemplary dithering waveforms 82, 84, 86, 88, 90, and 92 are depicted for driving waveforms to produce target color states of black, white, red, yellow, blue, and green, respectively. At least some parts of the dithering waveforms 82, 84, 86, 88, 90, and 92 are different from each other. In this example, only the white dithering waveform 84 and the blue dithering waveform 90 are identical.

[0112] Figure 15 An exemplary dithering waveform 82 for generating a black optical state is depicted. Waveform 82 includes four series of positive and negative voltage pulses alternating between +15 V and -15 V. The voltage pulses have asymmetrical pulse widths. In some embodiments, at least some of the positive voltage pulses have a pulse width of approximately 60 ms, and the negative voltage pulses have a pulse width of approximately 20 ms. In other embodiments, at least some of the positive voltage pulses have a pulse width of approximately 20 ms, and the negative voltage pulses have a pulse width of approximately 60 ms.

[0113] Figure 17 An exemplary jitter waveform 86 for generating a red optical state is depicted. Waveform 86 includes, in sequence, a first series of jitter voltage pulses, a second series of jitter voltage pulses, a third series of jitter voltage pulses, and a fourth series of jitter voltage pulses. Each series includes positive and negative voltage pulses alternating between +15 V and -15 V. The first and third series of jitter voltage pulses have frequencies lower than the frequencies of the second and fourth series of jitter voltage pulses. In some embodiments, the first and third series of jitter voltage pulses have frequencies of approximately 12.5 Hz, and the second and fourth series of jitter voltage pulses have frequencies of approximately 20 Hz.

[0114] Figure 20 An exemplary jitter waveform 92 for generating a green optical state is depicted. Waveform 92 includes, at least sequentially, a first series of jitter voltage pulses, a second series of jitter voltage pulses, a third series of jitter voltage pulses, and a fourth series of jitter voltage pulses. The first and third series of jitter voltage pulses consist of pulses alternating between +15 V and -15 V. The second and fourth series of jitter voltage pulses consist of pulses alternating between +15 V and 0 V. The first and third series of jitter voltage pulses have a frequency of approximately 12.5 Hz, and the second and fourth series of jitter voltage pulses have a frequency of approximately 20 Hz.

[0115] Figure 16 , 18Figures 19 and 19 depict exemplary dithering waveforms 84, 88, and 90, respectively, used to generate white, yellow, and blue optical states. Each of waveforms 84, 88, and 90 comprises at least three series of alternating positive and negative voltage pulses with a given pulse width. Each series of dithering voltage pulses is separated by a single pulse with a pulse width greater than the given pulse width. The positive and negative voltage pulses alternate between +15 V and -15 V. A single pulse has an amplitude of +15 V (for blue waveform 90 and white waveform 84) or -15 V (for yellow waveform 88).

[0116] and Figure 13 Compared to a single jitter waveform, Figure 15-20 The jitter waveform significantly reduces ghosting, for example, as Figure 21 As shown in the displayed image, these ghosting effects have been reduced or the color changes are no longer visible. Figure 22 The table provides test data, which shows the results compared to... Figure 13 Compared to a single jitter waveform, using Figure 15-20 The jitter waveform reduces color variation.

[0117] While the invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes and equivalent substitutions can be made without departing from the scope of the invention. Furthermore, many modifications can be made to adapt specific circumstances, materials, compositions, processes, and process steps to the purpose and scope of the invention. All such modifications are within the scope of the appended claims.

Claims

1. A method for driving an electrophoretic display layer to a desired optical state and reducing image ghosting, the electrophoretic display layer being disposed between an observation surface including a light-transmitting electrode layer and a second opposing surface including a driving electrode layer, the display layer comprising an electrophoretic medium containing a nonpolar fluid and at least three types of particles dispersed in the nonpolar fluid, the at least three types of particles having different optical properties from each other, the method comprising the following steps for each pixel of the electrophoretic display layer: (a) Applying a dithered voltage pulse sequence to a pixel during a first time period to promote mixing of the at least three types of particles dispersed in the nonpolar fluid, the dithered voltage pulse sequence sequentially comprising a first series of dithered voltage pulses, a second series of dithered voltage pulses, a third series of dithered voltage pulses, and a fourth series of dithered voltage pulses, wherein each series of dithered voltage pulses comprises alternating positive and negative voltage pulses repeated multiple times, and wherein the second series of voltage pulses and the third series of voltage pulses have the same frequency, the first series of voltage pulses has a higher frequency than the second series of voltage pulses and the third series of voltage pulses, and the fourth series of voltage pulses has a lower frequency than the second series of voltage pulses and the third series of voltage pulses; and (b) Apply a push-pull voltage pulse sequence to the pixel in a second time period following the first time period to drive the pixel to the target color state on the viewing side of the display layer.

2. The method of claim 1, wherein the at least three types of particles include a first type of particle, a second type of particle, a third type of particle, and a fourth type of particle, the first type of particle and the third type of particle having a first polarity of charge, and the second type of particle and the fourth type of particle having a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle, and the second type of particle has a larger charge value than the fourth type of particle.

3. The method according to claim 2, wherein the first type of particle, the second type of particle, the third type of particle and the fourth type of particle are black, yellow, red and white, respectively.

4. The method of claim 2, wherein the first polarity is positive and the second polarity is negative.

5. The method of claim 1, wherein the at least three types of particles include a first type of particle, a second type of particle, and a third type of particle dispersed in the nonpolar fluid, the first type of particle and the third type of particle having a first polarity of charge, and the second type of particle having a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle.

6. The method according to claim 5, wherein the first type of particle, the second type of particle, and the third type of particle are black, red, and white, respectively.

7. The method of claim 5, wherein the first polarity is positive and the second polarity is negative.

8. The method according to any one of the preceding claims, wherein the electrophoretic display layer is encapsulated in a microcapsule or a sealed microcell.

9. The method according to any one of the preceding claims, wherein the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses, and the fourth series of jitter voltage pulses have the same amplitude.

10. The method according to any one of the preceding claims, wherein the jitter voltage pulses of the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses and the fourth series of jitter voltage pulses alternate between +15 V and -15 V.

11. The method according to any one of the preceding claims, wherein the jitter voltage pulses of the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses and the fourth series of jitter voltage pulses have frequencies of approximately 25 Hz, 12.5 Hz, 12.5 Hz and 3.125 Hz, respectively.

12. The method according to any one of the preceding claims, wherein the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses, and the fourth series of jitter voltage pulses are separated by a zero-voltage pause.

13. The method according to any one of the preceding claims, wherein the first time period is shorter than the second time period.

14. An electrophoresis display device, comprising: An electrophoretic display layer is disposed between an observation surface including a light-transmitting electrode layer and a second opposing surface including a driving electrode layer. The display layer includes an electrophoretic medium comprising a nonpolar fluid and at least three types of particles dispersed in the nonpolar fluid, the at least three types of particles having different optical properties from each other. A memory stores a set of waveforms for driving each pixel of the electrophoretic display layer to a target color state. Each waveform in the set includes a dithering voltage pulse sequence applied in a first time period to promote mixing of the at least three types of particles dispersed in the nonpolar fluid. The dithering voltage pulse sequence is followed by a push-pull voltage pulse sequence applied in a second time period to drive the pixel to the target color state. Each dithering voltage pulse sequence sequentially includes a first series of dithering voltage pulses, a second series of dithering voltage pulses, a third series of dithering voltage pulses, and a fourth series of dithering voltage pulses. Each series of dithering voltage pulses includes alternating positive and negative voltage pulses repeated multiple times. The second series of voltage pulses and the third series of voltage pulses have the same frequency. The first series of voltage pulses has a higher frequency than the second series of voltage pulses and the third series of voltage pulses. The fourth series of voltage pulses has a lower frequency than the second series of voltage pulses and the third series of voltage pulses. as well as A processor is configured to select from the set of waveforms a waveform suitable for driving each pixel to a desired color state and to apply the waveform to the pixel.

15. The display device of claim 14, wherein the at least three types of particles include a first type of particle, a second type of particle, a third type of particle, and a fourth type of particle, the first type of particle and the third type of particle having a first polarity of charge, and the second type of particle and the fourth type of particle having a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle, and the second type of particle has a larger charge value than the fourth type of particle.

16. The display device according to claim 15, wherein the first type of particle, the second type of particle, the third type of particle and the fourth type of particle are black, yellow, red and white, respectively.

17. The display device of claim 15, wherein the first polarity is positive and the second polarity is negative.

18. The display device of claim 14, wherein the at least three types of particles include a first type of particle, a second type of particle, and a third type of particle dispersed in the nonpolar fluid, the first type of particle and the third type of particle having a first polarity of charge, the second type of particle having a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle.

19. The display device according to claim 18, wherein the first type of particle, the second type of particle, and the third type of particle are black, red, and white, respectively.

20. The display device of claim 18, wherein the first polarity is positive and the second polarity is negative.

21. The display device according to any one of the preceding claims, wherein the electrophoretic display layer is encapsulated in a microcapsule or a sealed microcell.

22. The display device according to any one of the preceding claims, wherein the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses and the fourth series of jitter voltage pulses have the same amplitude.

23. The display device according to any one of the preceding claims, wherein the jitter voltage pulses of the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses and the fourth series of jitter voltage pulses alternate between +15 V and -15 V.

24. The display device according to any one of the preceding claims, wherein the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses and the fourth series of jitter voltage pulses have frequencies of approximately 25 Hz, 12.5 Hz, 12.5 Hz and 3.125 Hz, respectively.

25. The display device according to any one of the preceding claims, wherein the first series of jitter voltage pulses, the second series of jitter voltage pulses, the third series of jitter voltage pulses and the fourth series of jitter voltage pulses are separated by a zero-voltage pause.

26. The display device according to any one of the preceding claims, wherein the first time period is shorter than the second time period.

27. The display device according to any one of the preceding claims, wherein the processor includes a display controller and the memory includes a lookup table.

28. A method for driving an electrophoretic display layer to a desired optical state and reducing image ghosting, the electrophoretic display layer being disposed between an observation surface including a light-transmitting electrode layer and a second opposing surface including a driving electrode layer, the display layer comprising an electrophoretic medium containing a nonpolar fluid and at least three types of particles dispersed in the nonpolar fluid, the at least three types of particles having different optical properties from each other, the method comprising the steps of driving each pixel of the electrophoretic display layer to a target color state: (a) Selecting a waveform from a set of waveforms stored in memory for driving a pixel to a target color state, each waveform driving a pixel to a different color state, each waveform in the set including a dithering voltage pulse sequence applied in a first time period to promote mixing of the at least three types of particles dispersed in the nonpolar fluid, the dithering voltage pulse sequence being followed by a push-pull voltage pulse sequence applied in a second time period to drive the pixel to the target color state, wherein at least two waveforms in the set have different dithering voltage pulse sequences, the dithering voltage pulse sequence of each waveform being configured to reduce image ghosting in the target color state caused by the subsequent push-pull voltage pulse sequence in the waveform; and (b) Apply the waveform selected in step (a) to drive the pixel to the target color state.

29. The method of claim 28, wherein the at least three types of particles include a first type of particle, a second type of particle, a third type of particle, and a fourth type of particle, the first type of particle and the third type of particle having a first polarity of charge, and the second type of particle and the fourth type of particle having a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle, and the second type of particle has a larger charge value than the fourth type of particle.

30. The method of claim 29, wherein the first type of particle, the second type of particle, the third type of particle, and the fourth type of particle are black, yellow, red, and white, respectively.

31. The method of claim 29, wherein the first polarity is positive and the second polarity is negative.

32. The method of claim 28, wherein the at least three types of particles include a first type of particle, a second type of particle, and a third type of particle dispersed in the nonpolar fluid, the first type of particle and the third type of particle having a first polarity of charge, and the second type of particle having a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle.

33. The method of claim 32, wherein the first type of particle, the second type of particle, and the third type of particle are black, red, and white, respectively.

34. The method of claim 32, wherein the first polarity is positive and the second polarity is negative.

35. The method according to any one of the preceding claims, wherein the electrophoretic display layer is encapsulated in a microcapsule or a sealed microcell.

36. The method according to any one of the preceding claims, wherein the jittered voltage pulse sequence of one of the waveforms in the set of waveforms comprises a plurality of series of jittered voltage pulses, wherein each series of jittered voltage pulses comprises alternating positive voltage pulses and negative voltage pulses repeated multiple times, and wherein the positive voltage pulses and the negative voltage pulses have asymmetrical pulse widths.

37. The method of claim 36, wherein the positive voltage pulse has a pulse width of approximately 60 ms and the negative voltage pulse has a pulse width of approximately 20 ms, or wherein the positive voltage pulse has a pulse width of approximately 20 ms and the negative voltage pulse has a pulse width of approximately 60 ms.

38. The method of claim 36, wherein the jittering voltage pulse alternates between +15 V and -15 V.

39. The method according to any one of the preceding claims, wherein the jitter voltage pulse sequence of one of the waveforms in the group of waveforms comprises at least a first series of jitter voltage pulses, a second series of jitter voltage pulses, a third series of jitter voltage pulses, and a fourth series of jitter voltage pulses in sequence, wherein each series of jitter voltage pulses comprises alternating positive voltage pulses and negative voltage pulses repeated multiple times, and wherein the first series of jitter voltage pulses and the third series of jitter voltage pulses have a given frequency, and the second series of jitter voltage pulses and the fourth series of jitter voltage pulses have a frequency greater than the given frequency.

40. The method of claim 39, wherein the first series of jitter voltage pulses and the third series of jitter voltage pulses have a frequency of 12 Hz, and the second series of jitter voltage pulses and the fourth series of jitter voltage pulses have a frequency of 20 Hz.

41. The method of claim 39, wherein the jittering voltage pulse alternates between +15 V and -15 V.

42. The method according to any one of the preceding claims, wherein the jittered voltage pulse sequence of one of the waveforms in the group of waveforms comprises at least a first series of jittered voltage pulses, a second series of jittered voltage pulses, a third series of jittered voltage pulses, and a fourth series of jittered voltage pulses in sequence, wherein the first series of jittered voltage pulses and the third series of jittered voltage pulses comprise pulses that alternately repeat multiple times between +15 V and -15 V, and wherein the second series of jittered voltage pulses and the fourth series of jittered voltage pulses comprise pulses that alternately repeat multiple times between +15 V and 0 V.

43. The method of claim 42, wherein the first series of jitter voltage pulses and the third series of jitter voltage pulses have a frequency of 12 Hz, and the second series of jitter voltage pulses and the fourth series of jitter voltage pulses have a frequency of 20 Hz.

44. The method according to any one of the preceding claims, wherein the jitter voltage pulse sequence of one of the waveforms in the set of waveforms comprises at least three series of jitter voltage pulses, each series of jitter voltage pulses comprising alternating positive and negative voltage pulses having a given pulse width repeated multiple times, wherein each series of jitter voltage pulses is separated by a single pulse having a pulse width greater than the given pulse width.

45. The method of claim 44, wherein the jittering voltage pulse alternates between +15 V and -15 V.

46. ​​The method of claim 45, wherein each individual pulse has an amplitude of +15 V or -15 V.

47. An electrophoresis display device, comprising: An electrophoretic display layer is disposed between an observation surface including a light-transmitting electrode layer and a second opposing surface including a driving electrode layer. The display layer includes an electrophoretic medium comprising a nonpolar fluid and at least three types of particles dispersed in the nonpolar fluid, the at least three types of particles having different optical properties from each other. A memory storing a set of waveforms for driving each pixel of the electrophoretic display layer to a target color state, each waveform comprising a dithering voltage pulse sequence applied in a first time period to promote mixing of the at least three types of particles dispersed in the nonpolar fluid, the dithering voltage pulse sequence being followed by a push-pull voltage pulse sequence applied in a second subsequent time period to drive the pixel to the target color state, wherein at least two waveforms in the set of waveforms have different dithering voltage pulse sequences, and the dithering voltage pulse sequence of each waveform is configured to reduce image ghosting in the target color state caused by the subsequent push-pull voltage pulse sequence in the waveform; as well as A processor is configured to select from the set of waveforms a waveform suitable for driving each pixel to a desired color state and to apply the waveform to the pixel.

48. The display device of claim 47, wherein the at least three types of particles include a first type of particle, a second type of particle, a third type of particle, and a fourth type of particle, the first type of particle and the third type of particle having a first polarity of charge, and the second type of particle and the fourth type of particle having a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle, and the second type of particle has a larger charge value than the fourth type of particle.

49. The display device according to claim 48, wherein the first type of particle, the second type of particle, the third type of particle and the fourth type of particle are black, yellow, red and white, respectively.

50. The display device of claim 48, wherein the first polarity is positive and the second polarity is negative.

51. The display device of claim 47, wherein the at least three types of particles include a first type of particle, a second type of particle, and a third type of particle dispersed in the nonpolar fluid, the first type of particle and the third type of particle having a first polarity of charge, and the second type of particle having a second polarity of charge opposite to the first polarity, wherein the first type of particle has a larger charge value than the third type of particle.

52. The display device according to claim 51, wherein the first type of particle, the second type of particle, and the third type of particle are black, red, and white, respectively.

53. The display device according to claim 51, wherein the first polarity is positive and the second polarity is negative.

54. The display device according to any one of the preceding claims, wherein the electrophoretic display layer is encapsulated in a microcapsule or a sealed microcell.

55. The display device according to any one of the preceding claims, wherein the jitter voltage pulse sequence of one of the waveforms in the group of waveforms comprises a plurality of series of jitter voltage pulses, wherein each series of jitter voltage pulses comprises alternating positive voltage pulses and negative voltage pulses repeated multiple times, and wherein the positive voltage pulses and the negative voltage pulses have asymmetrical pulse widths.

56. The display device of claim 55, wherein the positive voltage pulse has a pulse width of approximately 60 ms and the negative voltage pulse has a pulse width of approximately 20 ms, or wherein the positive voltage pulse has a pulse width of approximately 20 ms and the negative voltage pulse has a pulse width of approximately 60 ms.

57. The display device of claim 55, wherein the jitter voltage pulse alternates between +15 V and -15 V.

58. The display device according to any one of the preceding claims, wherein the jitter voltage pulse sequence of one of the waveforms in the group of waveforms comprises at least a first series of jitter voltage pulses, a second series of jitter voltage pulses, a third series of jitter voltage pulses, and a fourth series of jitter voltage pulses in sequence, wherein each series of jitter voltage pulses comprises alternating positive voltage pulses and negative voltage pulses repeated multiple times, and wherein the first series of jitter voltage pulses and the third series of jitter voltage pulses have a given frequency, and the second series of jitter voltage pulses and the fourth series of jitter voltage pulses have a frequency greater than the given frequency.

59. The display device according to claim 58, wherein the first series of jitter voltage pulses and the third series of jitter voltage pulses have a frequency of 12 Hz, and the second series of jitter voltage pulses and the fourth series of jitter voltage pulses have a frequency of 20 Hz.

60. The display device of claim 58, wherein the jitter voltage pulse alternates between +15 V and -15 V.

61. The display device according to any one of the preceding claims, wherein the jitter voltage pulse sequence of one of the waveforms in the group of waveforms comprises at least a first series of jitter voltage pulses, a second series of jitter voltage pulses, a third series of jitter voltage pulses, and a fourth series of jitter voltage pulses in sequence, wherein the first series of jitter voltage pulses and the third series of jitter voltage pulses comprise pulses that alternately repeat multiple times between +15 V and -15 V, and wherein the second series of jitter voltage pulses and the fourth series of jitter voltage pulses comprise pulses that alternately repeat multiple times between +15 V and 0 V.

62. The display device according to claim 61, wherein the first series of jitter voltage pulses and the third series of jitter voltage pulses have a frequency of 12 Hz, and the second series of jitter voltage pulses and the fourth series of jitter voltage pulses have a frequency of 20 Hz.

63. The display device according to any one of the preceding claims, wherein the jitter voltage pulse sequence of one of the waveforms in the group of waveforms comprises at least three series of jitter voltage pulses, each series of jitter voltage pulses comprising alternating positive and negative voltage pulses having a given pulse width repeated multiple times, wherein each series of jitter voltage pulses is separated by a single pulse with a pulse width greater than the given pulse width.

64. The display device of claim 64, wherein the jitter voltage pulse alternates between +15 V and -15 V.

65. The display device of claim 64, wherein each individual pulse has an amplitude of +15 V or -15 V.

66. The display device according to any one of the preceding claims, wherein the processor includes a display controller and the memory includes a lookup table.

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