Multi-element pixel electrode circuit for electro-optic display and driving method thereof

Abstract

An electro-optic display includes a first sub-pixel electrode and a second sub-pixel electrode associated with a display pixel, and an electrophoretic display medium disposed between a common electrode and the first and second sub-pixel electrodes. The electro-optic display also includes a display controller circuit in electrical communication with the common electrode and a first transistor associated with the display pixel. The display controller circuit is capable of applying a waveform to the display pixel by applying one or more time-dependent voltages between the common electrode and a first sub-pixel electrode to which the one or more time-dependent voltages are applied via a first transistor. The electro-optic display also includes a second transistor in electrical communication with the first sub-pixel electrode and the second sub-pixel electrode. The first enable signal activates the second transistor to cause electrical communication between the first sub-pixel electrode and the second sub-pixel electrode.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 63 / 481,964, filed January 27, 2023, the entire contents of which are incorporated herein by reference. In addition, the entire contents of any patents, published applications, or other published works cited herein are incorporated herein by reference. Technical Field

[0003] The present invention relates to a method for driving a bi-stable electro-optical display according to ambient conditions, and an apparatus for use in such a method. In particular, the present invention relates to a method for driving a bi-stable electro-optical display according to a temperature compensation scheme, and a display pixel circuit for use in such a method. Background Art

[0004] Electrophoretic display media, which are typically characterized by particles that move in an applied electric field, are highly reflective, can be made bistable, are scalable to large areas, and consume very little power. Encapsulated electrophoretic displays also enable printed displays. These properties allow encapsulated electrophoretic display media to be used in many applications where traditional electronic displays are unsuitable, such as flexible displays.

[0005] In many cases, it is desirable to measure and analyze certain environmental factors that may adversely affect display performance so that responses or actions can be taken. For example, the electrical properties of encapsulated electrophoretic display media may change in response to environmental factors such as temperature. It has been observed that temperature-induced display artifacts (such as lateral coupling and blooming) are often most noticeable during high temperatures when the impedance of the front plane laminate, or "FPL," has decreased, and the voltage waveform applied to the electrodes of one display pixel is most likely to adversely affect the optical state of adjacent display pixels.

[0006] In some cases, to achieve repeatable optical states in a display, it may be desirable to alter the drive waveforms applied to the display pixels in response to changes in the electrical properties of the polymer material comprising the encapsulated electrophoretic display medium. Consequently, it may be desirable to measure environmental factors, such as temperature, that may affect the performance of the electrophoretic display and implement a temperature-compensated drive scheme in response. Summary of the Invention

[0007] Traditional solutions, derived from liquid crystal display technology, assume that temperature compensation can be achieved simply by adjusting the voltage applied to the display pixels. However, electrophoretic displays have unique characteristics over different temperature ranges that cannot be addressed by voltage adjustment alone.

[0008] Other conventional solutions attempt to compensate for some of these undesirable display artifacts by dividing display pixel electrodes into multiple sections, each of which can be driven independently of the others. However, doing so can more than double the number of elements in the pixel array that must be individually addressed during a display update. Consequently, such solutions require significant modifications to the display controller circuitry and its corresponding software.

[0009] Thus, the invention described herein overcomes the shortcomings of the prior art by providing innovative multi-element display pixel electrode layouts that do not require a complete redesign of the display controller circuitry and corresponding software. Furthermore, the invention described herein provides display pixel driver circuitry that mitigates performance variations of electrophoretic displays due to changes in ambient temperature. Furthermore, the invention described herein includes temperature compensation methods that utilize all or a portion of the display pixel electrodes to drive each pixel.

[0010] In one aspect, the present invention provides an electro-optical display comprising a first sub-pixel electrode and a second sub-pixel electrode associated with a display pixel, and an electrophoretic display medium disposed between a common electrode and the first sub-pixel electrode and the second sub-pixel electrode. The electro-optical display further comprises a display controller circuit in electrical communication with the common electrode and a first transistor associated with the display pixel. The display controller circuit is capable of applying a waveform to the display pixel by applying one or more time-dependent voltages between the common electrode and the first sub-pixel electrode via the first transistor, wherein the one or more time-dependent voltages are applied to the first sub-pixel electrode. The electro-optical display further comprises a second transistor in electrical communication with the first sub-pixel electrode and the second sub-pixel electrode. A first enable signal activates the second transistor to cause the first sub-pixel electrode and the second sub-pixel electrode to electrically communicate.

[0011] In some embodiments, the electro-optic display includes a temperature sensor disposed proximate the electrophoretic display medium. In some embodiments, the first enable signal activates the second transistor based on a measurement of an ambient temperature from the temperature sensor. In some embodiments, the temperature sensor controls the first enable signal to activate the second transistor based on the measurement of the ambient temperature.

[0012] In some embodiments, the electro-optic display includes a third transistor in electrical communication with the second subpixel electrode and the common electrode. In some embodiments, a second enable signal activates the third transistor to drain residual charge from the second subpixel electrode. In some embodiments, the second enable signal is controlled by a row select signal associated with a row of display pixels, and the display pixel is not a display pixel in the row of display pixels.

[0013] In some embodiments, the electro-optic display includes a physical gap between the first subpixel electrode and the second subpixel electrode. In some embodiments, the electro-optic display includes a physical gap between at least one adjacent edge of the first subpixel electrode and the second subpixel electrode.

[0014] In some embodiments, the electro-optical display includes a third transistor in electrical communication with the common electrode, and a fourth transistor in electrical communication with the second subpixel electrode. In some embodiments, when the second transistor is activated, a first enable signal deactivates the fourth transistor. In some embodiments, a second enable signal activates the third transistor to drain residual charge from the second subpixel electrode. In some embodiments, the second enable signal is controlled by a row select signal associated with a row of display pixels, and the display pixel is not a display pixel in the row of display pixels.

[0015] In another aspect, the present invention provides an electro-optical display comprising a first sub-pixel electrode and a second sub-pixel electrode associated with a display pixel, and an electrophoretic display medium disposed or electrically coupled between a common electrode and the first sub-pixel electrode and the second sub-pixel electrode. The electro-optical display further comprises a display controller circuit in electrical communication with the common electrode and a first transistor associated with the display pixel. The display controller circuit is capable of applying a waveform to the display pixel by applying one or more time-dependent voltages between the common electrode and the first sub-pixel electrode via the first transistor, wherein the one or more time-dependent voltages are applied to the first sub-pixel electrode. The electro-optical display further comprises a second transistor in electrical communication with the first sub-pixel electrode and a third transistor. The third transistor is in electrical communication with the second sub-pixel electrode, and a row select signal associated with the display pixel activates the first transistor and the second transistor to cause the first sub-pixel electrode to communicate electrically with the third transistor.

[0016] In some embodiments, the electro-optical display further comprises a temperature sensor disposed proximate the electrophoretic display medium. In some embodiments, the second enable signal activates the third transistor. In some embodiments, the second enable signal is pulsed at a predetermined rate when the first transistor and the second transistor are activated. In some embodiments, the third transistor is activated at a time that is a subset of the time at which the first transistor and the second transistor are activated.

[0017] In some embodiments, the electro-optic display includes a physical gap between the first subpixel electrode and the second subpixel electrode. In some embodiments, the electro-optic display includes a physical gap between at least one adjacent edge of the first subpixel electrode and the second subpixel electrode.

[0018] These and other aspects of the invention will become apparent from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Further details of one or more embodiments of the subject matter described in this specification are set forth in the following figures and description. Other features, aspects, and advantages of the subject matter will become apparent from the description and drawings contained herein. The figures are not necessarily drawn to scale, and for ease of illustration, elements of similar structure are generally labeled with similar reference numerals throughout the figures. However, the specific properties and functions of elements may vary from embodiment to embodiment. In addition, the figures are intended only to assist in the description of the subject matter. The figures do not illustrate all aspects of the described embodiments and do not limit the scope of the present disclosure or the claims.

[0020] Figure 1 is a circuit diagram illustrating an electrophoretic display according to the subject matter described herein.

[0021] Figure 2 A circuit model of an electro-optical imaging layer according to the subject matter described herein is shown.

[0022] Figure 3 is a graph illustrating impedance versus temperature for an exemplary front plane laminate or "FPL" according to the subject matter described herein.

[0023] Figure 4 is a diagram of an exemplary layout of four display pixel electrodes for a conventional display according to the subject matter described herein, where each display pixel electrode includes a single conductive pad or contact.

[0024] Figure 5 is a diagram of an exemplary layout of four display pixel electrodes, each of which is divided into a plurality of sub-pixel electrodes, according to the subject matter described herein.

[0025] Figure 6 is a diagram of an exemplary layout of four display pixel electrodes, each of which is divided into a plurality of sub-pixel electrodes, according to the subject matter described herein.

[0026] Figure 7 is a schematic diagram of an exemplary pixel including a display pixel driver circuit according to the subject matter described herein.

[0027] Figure 8 is a schematic diagram of an exemplary pixel including a display pixel driver circuit according to the subject matter described herein.

[0028] Figure 9 is a schematic diagram of an exemplary pixel including a display pixel driver circuit according to the subject matter described herein.

[0029] Figure 10 is a schematic diagram of an exemplary pixel including a display pixel driver circuit according to the subject matter described herein.

[0030] Figure 11is a signal timing diagram illustrating drive signals for three pixels having a display pixel drive circuit according to the subject matter described herein.

[0031] Figure 12 is a block diagram of an exemplary electrophoretic display according to the subject matter described herein. DETAILED DESCRIPTION

[0032] The present invention relates to display pixel circuits and methods for driving electro-optic displays, particularly bistable electro-optic displays, and apparatus for use in such methods. More specifically, the present invention relates to a driving method that can reduce "ghosting" and edge effects and flicker in such displays. The present invention is particularly, but not exclusively, intended for use with particle-based electrophoretic displays, in which one or more charged particles are present in a fluid and move through the fluid under the influence of an electric field to alter the appearance of the display.

[0033] The term "electro-optical" as applied to a material or display is used herein in its conventional sense in the field of imaging to refer to a material having first and second display states that differ in at least one optical property, and wherein the material is changed from its first display state to its second display state by applying an electric field to the material. While the optical property is typically color perceptible to the human eye, it may be another optical property, such as light transmission, reflection, luminescence, or, in the case of displays intended for machine reading, false color in the sense of a change in reflectivity of electromagnetic wavelengths outside the visible range.

[0034] The term "gray state" is used herein in its conventional sense in the field of imaging technology to refer to the state between the two extreme optical states of a pixel, and does not necessarily imply a black and white transition between the two extreme states. For example, several of Iinke's patents and published applications cited below describe electrophoretic displays in which the extreme states are white and dark blue, so the intermediate "gray state" is actually light blue. In fact, as mentioned earlier, the change in optical state may not be a color change at all. The terms "black" and "white" may be used hereinafter to refer to the two extreme optical states of a display, and should be understood to generally include extreme optical states that are not strictly black and white, such as the white and dark blue states mentioned above. The term "monochrome" may be used hereinafter to refer to a drive scheme that drives a pixel only to its two extreme optical states without an intermediate gray state.

[0035] Some electro-optic materials are solid in the sense that they have a solid outer surface, but these materials can and often do have interior spaces filled with liquid or gas. For convenience, displays using solid electro-optic materials may be referred to below as "solid-state electro-optic displays." Thus, the term "solid-state electro-optic display" includes rotating two-color component displays, encapsulated electrophoretic displays, microcell electrophoretic displays, and encapsulated liquid crystal displays.

[0036] The terms "bistable" and "bistability" are used herein in their conventional sense in the art to refer to a display comprising display elements having first and second display states that differ in at least one optical property, such that after any given element is driven to assume its first or second display state by means of an addressing pulse of finite duration, that state persists, after termination of the addressing pulse, for at least several times, for example, at least four times, the minimum duration of the addressing pulse required to change the state of the display element. U.S. Patent 7,170,670 shows that some particle-based electrophoretic displays that support grayscale are stable not only in their extreme black and white states but also in their intermediate gray states, as are some other types of electro-optical displays. Such displays are properly referred to as "multistable" rather than bistable, but for convenience, the term "bistable" may be used herein to encompass both bistable and multistable displays.

[0037] The term "impulse" is used herein in its conventional sense, namely, the integral of voltage with respect to time. However, some bistable electro-optical media act as charge transducers, and for such media, an alternative definition of impulse may be used, namely, the integral of current with respect to time (which is equal to the total applied charge). The appropriate definition of impulse should be used depending on whether the medium acts as a voltage-time impulse transducer or a charge-impulse transducer.

[0038] Much of the following discussion will focus on methods for driving one or more pixels of an electro-optical display from an initial grayscale level to a final grayscale level (which may be different from or the same as the initial grayscale level). The term "waveform" will be used to refer to the entire voltage-time curve used to achieve the transition from a particular initial grayscale level to a particular final grayscale level. Typically, such a waveform will include multiple waveform elements; where these elements are substantially rectangular (i.e., where a given element comprises a constant voltage applied over a period of time), these elements may be referred to as "pulses" or "drive pulses." The term "drive scheme" refers to a set of waveforms sufficient to achieve all possible transitions between grayscale levels for a particular display. A display may employ multiple drive schemes; for example, the aforementioned U.S. Patent 7,012,600 notes that the drive scheme may need to be modified based on parameters such as the display's temperature or the amount of time it operates during its lifetime, and thus, multiple different drive schemes may be provided for a display to be used under different temperature conditions. A set of drive schemes used in this manner may be referred to as a "set of correlated drive schemes." As described in several of the aforementioned MEDEOD applications, multiple drive schemes may also be used simultaneously in different areas of the same display; a set of drive schemes used in this manner may be referred to as a "set of simultaneous drive schemes."

[0039] Several types of electro-optic displays are known. One type is the rotating dichroic member type, such as those described in U.S. Patents 5,808,783, 5,777,782, 5,760,761, 6,054,071, 6,055,091, 6,097,531, 6,128,124, 6,137,467, and 6,147,791. (Although this type of display is often referred to as a "rotating dichroic sphere" display, the term "rotating dichroic member" is more accurate because the rotating members in some of these patents are not spherical.) This type of display uses a large number of small bodies (usually spherical or cylindrical) with two or more sections having different optical properties, along with internal dipoles. These bodies are suspended within a matrix of liquid-filled vacuoles, which allow the bodies to rotate freely. Applying an electric field to the display causes the bodies to rotate to different positions, changing which part of the body is visible through a viewing surface, thereby changing the appearance of the display. Electro-optical media of this type are usually bistable.

[0040] Another type of electro-optical display uses an electrochromic medium, such as an electrochromic medium in the form of a nanochromic film, which includes an electrode formed at least in part of a semiconducting metal oxide and a plurality of dye molecules attached to the electrode that are capable of reversibly changing color; see, for example, O'Regan, B. et al., Nature 1991, 353,737; and Wood, D., Information Display, 18(3), 24 (March 2002). See also Bach, U. et al., Adv. Mater., 2002, 14(11), 845. Nanochromic films of this type are also described in U.S. Patents 6,301,038, 6,870,657, and 6,950,220. This type of medium is also generally bistable.

[0041] Another type of electro-optical display is the electrowetting display developed by Philips and described in Hayes, RA et al., “Video-Speed Electronic Paper Based on Electrowetting”, Nature, 425, 383-385 (2003). U.S. Patent 7,420,549 shows that such electrowetting displays can be made bistable.

[0042] One type of electro-optical display that has been the subject of intensive research and development for many years is the particle-based electrophoretic display (EPD), in which multiple charged particles are moved through a fluid under the influence of an electric field. Compared to liquid crystal displays (LCDs), EPDs can offer good brightness and contrast, wide viewing angles, state bistability, and low power consumption. However, long-term image quality issues with these displays have hindered their widespread adoption. For example, the particles that make up EPDs tend to settle, resulting in a short lifespan for these displays.

[0043] As mentioned above, electrophoretic media require the presence of a fluid. In most prior art electrophoretic media, this fluid is a liquid, but electrophoretic media can also be generated using gaseous fluids; see, for example, Kitamura, T. et al., “Electrical toner movement for electronic paper-like display,” IDW Japan, 2001, Paper HCS1-1; and Yamaguchi, Y. et al., “Toner display using insulative particles charged triboelectrically,” IDW Japan, 2001, Paper AMD4-4. See also U.S. Patents 7,321,459 and 7,236,291. When such gas-based media are used in an orientation that allows particle sedimentation (e.g., in a sign where the media is arranged in a vertical plane), such gas-based electrophoretic media are susceptible to the same type of problems as liquid-based electrophoretic media due to particle sedimentation. In fact, the problem of particle sedimentation is more severe in gas-based electrophoretic media than in liquid-based electrophoretic media, because the lower viscosity of the gaseous suspending fluid compared to liquids allows the electrophoretic particles to sediment more quickly.

[0044] Numerous patents and applications assigned to or filed in the names of the Massachusetts Institute of Technology (MIT) and Iink Corporation describe various techniques for encapsulating electrophoretic and other electro-optical media. Such encapsulated media comprise numerous small capsules, each of which itself comprises an inner phase containing electrophoretically mobile 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 positioned between two electrodes. The techniques described in these patents and applications include:

[0045] (a) electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patents 7,002,728 and 7,679,814;

[0046] (b) capsules, adhesives, and encapsulation processes; see, e.g., U.S. Patents 6,922,276 and 7,411,719;

[0047] (c) microcell structures, wall materials, and methods of forming microcells; see, for example, U.S. Patents 7,072,095 and 9,279,906;

[0048] (d) Methods for filling and sealing microlocations; see, e.g., U.S. Patents 7,144,942 and 7,715,088;

[0049] (e) Films and subassemblies containing electro-optical materials; see, for example, U.S. Patents 6,982,178 and 7,839,564;

[0050] (f) Backplanes, adhesive layers, and other auxiliary layers and methods used in displays; see, e.g., U.S. Patents 7,116,318 and 7,535,624;

[0051] (g) Color formation and color adjustment; see, for example, US Patents 7,075,502 and 7,839,564.

[0052] (h) Display applications; see, for example, U.S. Patents 7,312,784; 8,009,348;

[0053] (i) non-electrophoretic displays, such as those described in U.S. Patent No. 6,241,921 and U.S. Patent Application Publication No. 2015 / 0277160; and applications of packaging and microcell technology other than displays; see, for example, U.S. Patent Application Publications Nos. 2015 / 0005720 and 2016 / 0012710; and

[0054] (j) Methods for driving displays; see, e.g., U.S. Patents 5,930,026; 6,445,489; 6,504,524; 6,512,354; 6,531,997; 6,753,999; 6,825,970; 6,900,851; 6,995,550; 7,012,600; 7,023,420; 7,034,783; 7,061,166; 7,061,662; 7,116,466; 7,119,772; 7,177,066; 7,193,625; 7,202,847; 7,242,514; 7,259,744; 7,304,787; 7,312,794; 7,327,511; 7,408,699; 7,453,445; 7,492,339; 7,528,822; 7,545,358; 7,583,251; 7,602,374; 7,612,760; 7,679,599; 7,679,813; 7,683,606; 7,688,297; 7,729,039; 7,733,311; 7,733,335; 7,787,169; 7,859,742; 7,952,557; 7,956,841; 7,982,479; 7,999,787; 8,077,141; 8,125,501; 8,139,050; 8,174,490; 8,243,013; 8,274,472; 8,289,250; 8,300,006; 8,305,341; 8,314,784; 8,373,649; 8,384,658; 8,456,414; 8,462,102; 8,537,105; 8,558,783; 8,558,785; 8,558,786; 8,558,855; 8,576,164; 8,576,259; 8,593,396; 8,605,032; 8,643,595; 8,665,206; 8,681,191; 8,730,153; 8,810,525; 8,928,562; 8,928,641; 8,976,444; 9,013,394; 9,019,197; 9,019,198; 9,019,318; 9,082,352; 9,171,508; 9,218,773; 9,224,338; 9,224,342; 9,224,344; 9,230,492; 9,251,736; 9,262,973;and U.S. Patent Application Publication Nos. 2003 / 0102858; 2004 / 0246562; 2005 / 0253777; 2007 / 0070032; 2007 / 0076289; 2007 / 0091418; 2007 / 0103427; 2007 / 0176912; 2007 / 0296452; 2008 / 0024429; 2008 / 0024482; 2008 / 0136774; 2008 / 0169821; 2008 / 0218471; 2008 / 0291129; 2008 / 0303780; 2009 / 0174651; 2009 / 0195568; 2009 / 0322721; 2010 / 0194733; 2010 / 0194789; 2010 / 0220121; 2010 / 0265561; 2010 / 0283804; 2011 / 0063314; 2011 / 0175875; 2011 / 0193840; 2011 / 0193841; 2011 / 0199671; 2011 / 0221740; 2012 / 0001957; 2012 / 0098740; 2013 / 0063333; 2013 / 0194250; 2013 / 0249782; 2013 / 0321278; 2014 / 0009817; 2014 / 0085355; 2014 / 0204012; 2014 / 0218277; 2014 / 0240210; 2014 / 0240373; 2014 / 0253425; 2014 / 0292830; 2014 / 0293398; 2014 / 0333685; 2014 / 0340734; 2015 / 0070744; 2015 / 0097877; 2015 / 0109283; 2015 / 0213749; 2015 / 0213765; 2015 / 0221257; 2015 / 0262255; 2016 / 0071465; 2016 / 0078820; 2016 / 0093253; 2016 / 0140910 and 2016 / 0180777.

[0055] Many of the aforementioned patents and applications recognize that the walls surrounding discrete microcapsules in encapsulated electrophoretic media can be replaced by a continuous phase, thereby producing so-called polymer-dispersed electrophoretic displays, wherein the electrophoretic medium comprises a plurality of discrete droplets of electrophoretic fluid and a continuous phase of polymer material, and that the discrete droplets of electrophoretic fluid within such polymer-dispersed electrophoretic displays can be considered capsules or microcapsules, even though no discrete capsule membrane is associated with each individual droplet; see, for example, the aforementioned 2002 / 0131147. Therefore, for purposes of this application, such polymer-dispersed electrophoretic media are considered a subclass of encapsulated electrophoretic media.

[0056] A related type of electrophoretic display is the so-called "microcell electrophoretic display." In a microcell electrophoretic display, the charged particles and suspended fluid are not encapsulated within microcapsules, but rather are retained within a plurality of cavities formed within a carrier medium (e.g., a polymer film). See, for example, International Application Publication No. WO 02 / 01281 and published U.S. Application No. 2002 / 0075556, both assigned to Sipix Imaging.

[0057] Many of the aforementioned patents and applications by Iink and MIT also consider microcell electrophoretic displays and polymer dispersed electrophoretic displays. The term "encapsulated electrophoretic display" may refer to all such display types, which may also be collectively referred to as "microcavity electrophoretic displays" to summarize the morphology of the walls.

[0058] Another type of electro-optical display is the electrowetting display developed by Philips and described in Hayes, RA et al., "Video-Speed Electronic Paper Based on Electrowetting," Nature, 425, 383-385 (2003). Co-pending application Ser. No. 10 / 711,802, filed Oct. 6, 2004, shows that this type of electrowetting display can be made bi-stable.

[0059] Other types of electro-optical materials may also be used. Of particular note, bistable ferroelectric liquid crystal displays (FLCs) are known in the art and exhibit residual voltage behavior.

[0060] While electrophoretic media can be opaque (because, for example, in many electrophoretic media, the particles substantially block visible light from passing through the display) and operate in a reflective mode, some electrophoretic displays can be made to operate in a so-called "shutter mode," in which one display state is substantially opaque and the other is light-transmissive. See, for example, U.S. Patents 6,130,774 and 6,172,798, and U.S. Patents 5,872,552, 6,144,361, 6,271,823, 6,225,971, and 6,184,856. Dielectrophoretic displays, which are similar to electrophoretic displays but rely on variations in electric field strength, can operate in a similar mode; see U.S. Patent 4,418,346. Other types of electro-optical displays may also be capable of operating in a shutter mode.

[0061] High-resolution displays can include individual pixels that are addressable without interference from adjacent pixels. One way to achieve such pixels is to provide an array of nonlinear elements, such as transistors or diodes, with each pixel associated with at least one nonlinear element, to produce an "active matrix" display. The addressing or display pixel electrode that addresses a display pixel is connected to an appropriate voltage source through the associated nonlinear element. When the nonlinear element is a transistor, the display pixel electrode can be connected to the drain of the transistor, an arrangement that will be assumed in the following description, but which is essentially arbitrary, and the display pixel electrode can be connected to the source of the transistor. In a high-resolution array, the pixels can be arranged in a two-dimensional array of rows and columns, such that any particular pixel is uniquely defined by the intersection of a designated row and a designated column. The sources of all transistors in each column can be connected to a single column electrode, while the gates of all transistors in each row can be connected to a single row electrode; the assignment of sources to rows and gates to columns can also be reversed if desired.

[0062] The display can be written to row by row. The row electrodes are connected to a row driver, which applies a voltage to a selected row electrode to ensure that all transistors in the selected row are turned on, while applying a voltage to all other rows to ensure that all transistors in these unselected rows remain non-conducting. The column electrodes are connected to a column driver, which applies a selected voltage to each column electrode to drive the pixels in the selected row to their desired optical state. (The above voltages are relative to a common front electrode, which can be located on the side of the electro-optic medium opposite the nonlinear array and extends across the entire display. As is known in the art, voltage is relative and is a measure of the difference in charge between two points. The value of one voltage is relative to another voltage value. For example, zero voltage ("0V") means there is no voltage difference relative to another voltage.) After a preselected interval called the "line addressing time", the selected row is deselected, another row is selected, and the voltage on the column driver is changed to allow the next line of the display to be written.

[0063] However, in use, certain waveforms may generate a residual voltage across the pixels of an electro-optic display. The term "residual voltage" is sometimes used as a convenient term to refer to the overall phenomenon. However, the switching behavior of impulse-driven electro-optic displays is based on the application of a voltage impulse (the time integral of the voltage) across the electro-optic medium. The residual voltage may reach a peak immediately after the application of the drive pulse and may decay exponentially thereafter. A residual voltage that persists for a considerable period of time may impose a "residual impulse" on the electro-optic medium. Strictly speaking, this residual impulse, rather than the residual voltage, may be the cause of the effects on the optical state of the electro-optic display (usually attributed to the residual voltage). This residual voltage produces some unwanted optical effects and is generally undesirable.

[0064] As used herein, a "shift" in the optical state associated with an addressing pulse refers to a situation where the initial application of a particular addressing pulse to an electro-optic display results in a first optical state (e.g., a first gray tone) and the subsequent application of the same addressing pulse to the electro-optic display results in a second optical state (e.g., a second gray tone). A residual voltage may cause this shift in the optical state because the voltage applied to a pixel of the electro-optic display during the application of the addressing pulse includes the sum of the residual voltage and the voltage of the addressing pulse.

[0065] "Drift" of the display's optical state over time refers to changes in the optical state of an electro-optic display when the display is in a quiescent state (e.g., during periods when no addressing pulses are applied to the display). Residual voltage can cause this drift in the optical state because the optical state of a pixel can depend on the pixel's residual voltage, which can decay over time.

[0066] As mentioned above, "ghosting" refers to the condition where traces of a previous image remain visible after an electro-optical display has been rewritten.

[0067] "Edge ghosting" is another type of ghosting in which the outline (edge) of a portion of the previous image remains visible. This type of artifact is caused by inter-pixel effects, also known as "blooming." For example, in both monochrome and color systems, the electric field generated by a display pixel electrode tends to affect a wider area of the electro-optic medium than the display pixel electrode itself, so that, in effect, the optical state of one pixel spreads into parts of adjacent pixels. Furthermore, in some instances, driving adjacent pixels can result in a final optical state in the area between the pixels that differs from the optical state achieved by either adjacent pixel itself. This final optical state in the area between adjacent pixels is caused by the electric field experienced in the inter-pixel area, which is the average of the electric fields applied to the adjacent pixels. It has been found that edge ghosting can be mitigated by driving the electro-optic display with a DC unbalanced waveform. However, as mentioned above, a DC unbalanced waveform can generate residual voltages.

[0068] In summary, residual voltage, as a phenomenon, can manifest in a variety of ways as image ghosting or visual artifacts, the severity of which can vary with the time between image updates. Residual voltage can also cause DC imbalance and ultimately shorten the display's lifespan. Therefore, the effects of residual voltage can impair the quality of electrophoretic or other electro-optical devices, and minimizing the sensitivity of the residual voltage itself and the device's optical state to its effects is desirable. Therefore, relieving residual voltage in electro-optical displays can improve displayed image quality, even when the residual voltage is already low.

[0069] Figure 1 A schematic diagram of a pixel 100 of an electrophoretic display or EPD according to the subject matter submitted herein is shown. Pixel 100 may include an imaging film 110. In some embodiments, imaging film 110 may be bi-stable. In some embodiments, imaging film 110 may include, but is not limited to, an encapsulated electrophoretic imaging film that may include, for example, charged pigment particles.

[0070] The imaging film 110 may be disposed between the front electrode 102 and the back electrode 104. The front electrode 102 may be formed between the imaging film and the front portion of the display. In some embodiments, the front electrode 102 may be transparent. In some embodiments, the front electrode 102 may be formed from any suitable transparent material, including but not limited to indium tin oxide (ITO). The back electrode 104 may be formed opposite the front electrode 102. In some embodiments, parasitic capacitance (not shown) may be formed between the front electrode 102 and the back electrode 104.

[0071] Pixel 100 can be one of a plurality of pixels. The plurality of pixels can be arranged in a two-dimensional array of rows and columns to form a matrix, such that any particular pixel is uniquely defined by the intersection of a designated row and a designated column. In some embodiments, the matrix of pixels can be an "active matrix," wherein each pixel is associated with at least one nonlinear circuit element 120. Nonlinear circuit element 120 can be coupled between backplate electrode 104 and addressing electrode 108. In some embodiments, nonlinear element 120 can include a diode and / or a transistor, including but not limited to a MOSFET. The drain (or source) of the MOSFET can be coupled to backplate electrode 104, the source (or drain) of the MOSFET can be coupled to addressing electrode 108, and the gate of the MOSFET can be coupled to a drive electrode 106 configured to control activation and deactivation of the MOSFET. (For simplicity, the terminal of the MOSFET coupled to backplate electrode 104 will be referred to as the drain of the MOSFET, and the terminal of the MOSFET coupled to addressing electrode 108 will be referred to as the source of the MOSFET. However, those skilled in the art will recognize that in some embodiments, the source and drain of the MOSFET can be interchanged.)

[0072] In some embodiments of an active matrix, the addressing electrodes 108 of all pixels in each column can be connected to the same column electrode, and the drive electrodes 106 of all pixels in each row can be connected to the same row electrode. The row electrodes can be connected to a row driver that can select one or more rows of pixels by applying a voltage to the selected row electrode sufficient to activate the nonlinear elements 120 of all pixels 100 in the selected row. The column electrodes can be connected to a column driver that can apply a voltage to the addressing electrodes 106 of the selected (activated) pixels that is suitable for driving the pixels to a desired optical state. The voltage applied to the addressing electrodes 108 can be relative to the voltage applied to the frontplate electrodes 102 of the pixels (e.g., a voltage of approximately zero volts). In some embodiments, the frontplate electrodes 102 of all pixels in the active matrix can be coupled to a common electrode.

[0073] In some embodiments, the pixels 100 of the active matrix can be written to row by row. For example, a row driver can select a row of pixels, and a column driver can apply a voltage to the pixels corresponding to the desired optical state of the row of pixels. After a preselected interval, known as the "line addressing time," the selected row can be deselected, another row can be selected, and the voltage on the column driver can be changed to write to another line of the display.

[0074] Figure 2A circuit model of an electro-optical imaging layer 110 disposed between the front electrode 102 and the back electrode 104, according to the subject matter described herein, is shown. Resistor 202 and capacitor 204 may represent the resistance and capacitance of the electro-optical imaging layer 110, the front electrode 102, and the back electrode 104 (including any adhesive layers). Resistor 212 and capacitor 214 may represent the resistance and capacitance of the laminating adhesive layer. Capacitor 216 may represent the capacitance that may form between the front electrode 102 and the back electrode 104 (e.g., at the interfacial contact area between the layers, such as between the imaging layer and the laminating adhesive layer and / or between the laminating adhesive layer and the backplane electrode). The voltage Vi across the imaging film 110 of a pixel may include the residual voltage of the pixel.

[0075] It has been observed that the performance of electrophoretic displays may vary with environmental conditions. For example, changes in the impedance of the FPL may be related to temperature fluctuations. Figure 3 3 is a graph 300 showing the impedance of an exemplary front plane laminate versus temperature. Specifically, graph 300 shows the FPL impedance Z at 10 Hz on the Y-axis. real Graph 305 shows the relationship between the impedance of the FPL (unit: MΩcm²) and the temperature (unit: degrees Celsius) on the x-axis. As shown in graph 300, the FPL impedance decreases as the temperature increases. It should be understood that the FPL referred to herein may include, but is not limited to, the light-transmitting conductive layer, electro-optical dielectric layer, and adhesive layer of an electrophoretic display.

[0076] Conventionally, for an electrophoretic display including a plurality of display pixels or a matrix of display pixels, each display pixel is associated with only one display pixel electrode. For example, as described above, each display pixel of an active matrix is typically associated with a discrete transistor configured to drive the display pixel by applying one or more voltages to a display pixel electrode including a single conductive pad or contact. Figure 4 Diagram 400 is an exemplary layout of four display pixel electrodes (display pixel electrode 401 , display pixel electrode 402 , display pixel electrode 403 , and display pixel electrode 404 ) of a conventional display, where each display pixel electrode includes a single conductive pad or contact.

[0077] like Figure 4 As shown, the display pixel electrode 401 is spaced apart from the laterally adjacent display pixel electrode 402 by a distance 430. Figure 4 Although not explicitly marked, the display pixel electrode 403 is also separated from the laterally adjacent display pixel electrode 404 by a distance 430. In addition, the display pixel electrode 401 is separated from the vertically adjacent display pixel electrode 403 by a distance 431. Figure 4Although not explicitly marked, the display pixel electrode 402 is also separated from the vertically adjacent display pixel electrode 404 by a distance 431. In some embodiments, the distance 430 and the distance 431 are substantially equal.

[0078] Electrophoretic displays can include circuitry for estimating the impedance of the FPL based on one or more ambient temperature measurements. Conventional solutions attempt to mitigate undesirable optical artifacts by simply adjusting the voltage applied to the display pixels in response to the temperature measurements. This conventional solution is not suitable for electrophoretic displays because electrophoretic displays have unique characteristics over different temperature ranges that cannot be compensated for through voltage adjustments alone. Other conventional solutions utilize display pixel electrodes that are segmented into multiple sections that can be individually addressed by a display controller. However, such solutions more than double the number of elements in the pixel array that must be managed and controlled during a display update, thereby increasing complexity and requiring significant modifications to the conventional display controller circuitry (integrated circuits and printed circuit board wiring) and its corresponding software. Furthermore, applying such solutions to electrophoretic displays can lead to panel degradation due to mismatches in the kickback voltages associated with each driver element.

[0079] Therefore, as referenced below Figure 5-12 As described in detail, the invention described herein overcomes the shortcomings of the prior art by providing innovative multi-element display pixel electrode layouts and associated drive circuits that do not require a complete redesign of the display controller circuitry and corresponding software.

[0080] Figure 5 FIG5 is a diagram of an exemplary layout of four display pixel electrodes (display pixel electrode 501, display pixel electrode 502, display pixel electrode 503, and display pixel electrode 504), each of which is divided into a plurality of sub-pixel electrodes. Figure 5As shown, the center of pixel electrode 501 is a solid rectangular sub-pixel electrode 501a (e.g., the first sub-pixel electrode), and sub-pixel electrode 501a is surrounded by a hollow rectangular sub-pixel electrode 501b (e.g., the second sub-pixel electrode). A gap 532 (e.g., a physical gap) exists between the edge of sub-pixel electrode 501a and the inner edge of sub-pixel electrode 501b (e.g., a physical gap between adjacent edges). For example, sub-pixel electrode 501a and sub-pixel electrode 501b can both be conductive pads or contacts formed on a substrate or backplane such that their edges are separated by a certain distance (e.g., between 0.5 mil and 1 mil, between 1 mil and 2 mils, between 2 mils and 5 mils, between 5 mils and 50 mils, or between 1 mm and 5 mm). In some embodiments, gap 532 is a uniform distance around the perimeter of sub-pixel electrode 501a. In some embodiments, the length of gap 532 varies between a horizontal direction (e.g., a physical gap in the horizontal direction) and a vertical direction (e.g., a physical gap in the vertical direction).

[0081] like Figure 5 As shown, the sub-pixel electrode 501b is separated from the laterally adjacent sub-pixel electrode 502b by a distance 530. Figure 5 Although not explicitly marked, the sub-pixel electrode 503b is also separated from the laterally adjacent sub-pixel electrode 504b by a distance 530. In addition, the sub-pixel electrode 501b is separated from the vertically adjacent sub-pixel electrode 503b by a distance 531. Figure 5 Although not explicitly marked, the sub-pixel electrode 502b is also separated from the vertically adjacent sub-pixel electrode 504b by a distance 531. In some embodiments, the distance 530 and the distance 531 are substantially equal.

[0082] When used in conjunction with one of the display pixel drive circuits described in detail below, Figure 5 The multi-element display pixel electrode layout shown enables each hollow rectangular sub-pixel electrode to be selectively driven or disconnected independently of its associated solid rectangular sub-pixel electrode. For example, the hollow sub-pixel electrode can be selectively disconnected (e.g., left floating, grounded, or connected to V COM ), so that the drive waveform applied to the pixel electrode is applied only to the rectangular sub-pixel electrode at its center. This effectively increases the distance between the electrodes that apply voltage to the electro-optical imaging layer. Specifically, when sub-pixel electrodes 501b and 502b are disconnected, the lateral distance between pixel electrodes 501 and 502 effectively increases to distance 534, i.e., the distance between sub-pixel electrodes 501a and 502a. Similarly, when sub-pixel electrodes 501b and 503b are disconnected, the vertical distance between display pixel electrodes 501 and 503 effectively increases to distance 535, i.e., the distance between sub-pixel electrodes 501a and 503a.

[0083] It has been observed that temperature-induced display artifacts (such as lateral coupling and blooming) are typically most pronounced during high temperatures, when the impedance of the FPL has decreased, and the voltage waveform applied to the electrodes of one display pixel is most likely to adversely affect the optical state of adjacent display pixels. The multi-element display pixel electrode layout of diagram 500 and the pixel driver circuit described below enable a drive scheme that effectively compensates for fluctuations in FPL temperature. For example, selectively disconnecting some or all of the hollow sub-pixel electrodes during high temperatures, thereby increasing the distance between the driven portions of the display pixel electrodes, can reduce or eliminate temperature-induced display artifacts.

[0084] Figure 6 FIG600 is a diagram of an exemplary layout of four display pixel electrodes (display pixel electrode 601, display pixel electrode 602, display pixel electrode 603, and display pixel electrode 604), each of which is divided into a plurality of sub-pixel electrodes. Figure 6 As shown, the display pixel electrode 601 includes a rectangular sub-pixel electrode 601a (e.g., a first sub-pixel electrode) and an L-shaped sub-pixel electrode 601b (e.g., a second sub-pixel electrode) located near its left edge and bottom edge. A gap 632 exists between the edge of the sub-pixel electrode 601a and the inner edge of the sub-pixel electrode 601b. In some embodiments, the gap 632 has a uniform distance along the entire inner edge of the L-shaped sub-pixel electrode 601b. In some embodiments, the length of the gap 632 is different in the horizontal direction and the vertical direction. In some embodiments, the L-shaped sub-pixel electrode 601b is rotated 180 degrees clockwise and located near the right edge and bottom edge of the sub-pixel electrode 601a. Those skilled in the art will appreciate that other sub-pixel electrode configurations are also within the scope of the present disclosure.

[0085] like Figure 6 As shown, the sub-pixel electrode 601a is separated from the laterally adjacent sub-pixel electrode 602b by a distance 630. Figure 6 Not shown, the sub-pixel electrode 603a is also separated from the laterally adjacent sub-pixel electrode 604b by a distance 630. In addition, the sub-pixel electrode 601b is separated from the vertically adjacent sub-pixel electrode 603a by a distance 631. Figure 6 Not shown, the sub-pixel electrode 602b is also separated from the vertically adjacent sub-pixel electrode 604a by a distance 631. In some embodiments, the distance 630 and the distance 631 are substantially equal.

[0086] The multi-element display pixel electrode layout of diagram 600 can also be used with the pixel driver circuit described below to implement a temperature compensated drive scheme, thereby reducing or eliminating temperature-induced display artifacts. In addition, the L-shaped sub-pixel electrode configuration simplifies the layout and manufacture of multiple display pixel electrodes and their associated driver circuitry. For example, because the L-shaped sub-pixel electrode does not completely surround the corresponding rectangular sub-pixel electrode, conductive traces can be routed to the rectangular sub-pixel electrode without having to drill holes and perform conductive plating to connect to traces on different layers of the substrate or backplane. For similar reasons, this configuration simplifies the placement and routing of additional display pixel driver circuit components.

[0087] As described above, the present disclosure includes a number of innovative display pixel driver circuits that can be used in conjunction with the multi-element display pixel electrode layouts described herein to implement a temperature-compensated drive scheme for an electro-optical display. The configuration of each driver circuit varies depending on the preferred voltage and drive characteristics of the subpixel electrode.

[0088] Figure 7 is a schematic diagram of an exemplary pixel 700 including display pixel drive circuitry according to the subject matter described herein. As with conventional displays, display pixel 700 includes a transistor 720 (e.g., a first transistor) that applies a voltage (e.g., a time-dependent voltage) on an addressing electrode 708 to a display pixel electrode (in this example, subpixel electrode 701a) when a gate voltage sufficient to activate transistor 720 is applied to a drive electrode 706. For example, drive electrode 706 can be connected to row select circuitry of a display controller or driver. The voltage applied to addressing electrode 708 can be a voltage relative to that applied to V COM The voltage applied to the front plate electrode 702 (e.g., the common electrode) is typically approximately zero volts, but is not limited thereto and can be positive or negative. The storage capacitor 750 (e.g., the first storage capacitor) maintains the voltage across the electro-optical medium 710 (e.g., the electrophoretic display medium) between updates.

[0089] like Figure 7As shown, unlike conventional pixel designs, display pixel 700 includes a transistor 740 (e.g., a second transistor) between subpixel electrode 701a (e.g., a first subpixel electrode) and subpixel electrode 701b (e.g., a second subpixel electrode) to enable operation in both high and low temperature modes. For example, when the temperature is low, a voltage sufficient to activate transistor 720 is applied to enable signal 746 (e.g., a first enable signal), which drives the gate signal of transistor 740. Transistor 740 conducts in the activated state, thereby electrically connecting subpixel electrode 701a and subpixel electrode 701b. Consequently, the voltage applied to addressing electrode 708 is simultaneously applied to subpixel electrode 701a and subpixel electrode 701b. When transistor 740 is activated, an additional storage capacitor 752 (e.g., a second storage capacitor) also maintains the voltage across electro-optical medium 710 between updates.

[0090] Conversely, when the temperature is high and the FPL impedance decreases, the enable signal 746 can be set to a low state to disable the transistor 740, thereby placing the sub-pixel electrode 701b in a high impedance (e.g., floating, non-conductive) state and preventing the voltage applied to the sub-pixel electrode 701a from also being applied to the sub-pixel electrode 701b. As described above, when using Figure 5 and Figure 6 When multiple elements are shown for display pixel electrodes, selectively disconnecting the sub-pixel electrode 701b during high temperatures increases the distance between the driving portions of the display pixel electrodes and can reduce or eliminate temperature-induced display artifacts.

[0091] Figure 12 is a block diagram of an exemplary electrophoretic display 1200 according to the subject matter described herein. Electrophoretic display 1200 includes display controller circuitry 1280, display stack 1290, and temperature sensor 1285.

[0092] The display stack 1290 includes a front plate or common electrode 1222, an imaging film 1210, and an array of four display pixel electrodes, each display pixel electrode being divided into a plurality of sub-pixel electrodes: display pixel electrode 1201 includes sub-pixel electrode 1201a and sub-pixel electrode 1201b; display pixel electrode 1202 includes sub-pixel electrode 1202a and sub-pixel electrode 1202b; display pixel electrode 1203 includes sub-pixel electrode 1203a and sub-pixel electrode 1203b; and display pixel electrode 1204 includes sub-pixel electrode 1204a and sub-pixel electrode 1204b. Figure 12 The sub-pixel electrodes of each display pixel electrode shown in FIG. Figure 6, wherein one sub-pixel electrode is rectangular and the other sub-pixel electrode is L-shaped. It will be appreciated by those skilled in the art that other sub-pixel electrode configurations are also within the scope of the present disclosure. Furthermore, it will be appreciated by those skilled in the art that the present invention is not limited to electro-optical displays having four display pixel electrodes.

[0093] Common electrode 1222 can be formed from any suitable conductive transparent material, including but not limited to aluminum indium tin oxide (ITO). Imaging film 1210 can include but is not limited to an encapsulated electrophoretic imaging film, which can include, for example, charged pigment particles. Electrophoretic display 1200 is typically viewed from the common electrode 1222 side, rather than from the display pixel electrodes 1201-1204 side. However, components of electrophoretic display 1200 can be selected so that electrophoretic display 1200 can be viewed from the display pixel electrodes 1201-1204 side, or even from either side.

[0094] Display stack 1290 also includes an adhesive layer 1240 between common electrode 1222 and imaging film 1210, and an adhesive layer 1241 between imaging film 1210 and display pixel electrodes 1201-1204. In some embodiments, the adhesive layer may include an integrated primer component to enhance adhesion, or a separate primer layer ( Figure 12 (The structure of electrophoretic displays and their components, pigments, adhesives, electrode materials, etc., are described in numerous patents and patent applications published by Iink, Inc., such as U.S. Patents 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.)

[0095] although Figure 12 Although not shown, the display stack 1290 may include one or more additional layers as desired. As an example, the display pixel electrodes 1201-1204 may be components of a backplane that includes a substrate layer on which the display pixel electrodes 1201-1204 are disposed. Furthermore, the common electrode 1222 may be disposed on a substrate layer, such as a polyethylene terephthalate (PET) film, which is commercially available as "aluminized Mylar" ("Mylar" is a registered trademark of DuPont de Nemours and Company, Wilmington, Delaware).

[0096] Display controller circuitry 1280 represents the circuitry and components that provide the supply voltages and control signals 1295 required to operate electrophoretic display 1200. For example, display controller circuitry 1280 may include power management circuitry for generating and providing multiple voltages to display stack 1290, as well as row and column drivers for addressing the array of display pixel electrodes and drive waveforms sufficient to change the optical state of imaging film 1210. In some embodiments, transistors for addressing and driving the display pixel electrodes are located near the array of display pixel electrodes.

[0097] Display controller circuit 1280 also controls the state of enable signal 1246, which corresponds to the state of the enable signal 1246 described above in conjunction with Figure 7 The enable signal 746 is described. Although Figure 12 Not shown, but the display controller circuit 1280 may also be configured to control the following in combination Figure 8-10 The states of the additional enable signals used in the described embodiments.

[0098] Those skilled in the art will appreciate that the display controller circuit 1280 of the present invention can be implemented in a variety of different physical forms and can utilize a variety of analog and digital components. For example, the display controller circuit 1280 can include a multi-purpose microprocessor and appropriate peripheral components (e.g., one or more digital-to-analog converters, "DACs") for converting the microprocessor's digital output into appropriate voltages for application to the pixels. Alternatively, the display controller circuit 1280 can be implemented using an application-specific integrated circuit ("ASIC") or a field-programmable gate array ("FPGA"). Those skilled in the art will appreciate that the display controller circuit 1280 can include both processing components and power management circuitry.

[0099] In some embodiments, the display controller circuit 1280 includes a timing controller integrated circuit ("IC") that receives input image data and outputs control signals to a set of data and select driver ICs (e.g., a row driver IC and a column driver IC) to generate appropriate voltages on the display pixel electrodes to display the desired image. In some embodiments, a host controller in communication with the display controller circuit requests an update of the electrophoretic display 1200 and provides image data for the update to the display controller circuit. In some embodiments, the display controller circuit 1280 receives image data by accessing a storage buffer containing the image data, or receives a signal to extract the image data therefrom. In some embodiments, the storage buffer has a structure similar to that described in U.S. Patent No. 9,721,495. In some embodiments, the display controller circuit 1280 receives a serial signal containing the information required to perform the necessary calculations to generate the drive impulses (e.g., drive waveforms) applied to the electrophoretic medium during scanning of the pixel array.

[0100] Temperature sensor 1285 measures the temperature of the electrophoretic medium or its immediate surroundings and provides temperature information to display controller circuitry 1280 via interface 1286. In some embodiments, temperature sensor 1285 is located within the encapsulated electrophoretic medium of imaging film 1210. In some embodiments, temperature sensor 1285 includes multiple temperature sensors located at different physical locations around or within imaging film 1210.

[0101] Temperature sensor 1285 may be a sensor whose electrical characteristics (e.g., resistance or capacitance) change in response to temperature fluctuations. In some embodiments, temperature sensor 1285 includes a thermocouple, a resistance temperature detector (RTD), and / or a thermistor (e.g., a negative temperature coefficient (NTC) thermistor). In some embodiments, temperature sensor 1285 includes a semiconductor-based integrated circuit for sensing temperature.

[0102] In some embodiments, interface 1286 is an integrated bus interface or similar bus interface that temperature sensor 1285 uses to communicate temperature information to display controller circuit 1280. In some embodiments, interface 1286 is a signal output by temperature sensor 1285 to convey the measured temperature. For example, interface 1286 may be a signal that temperature sensor 1285 is configured to drive high when the measured temperature exceeds a threshold. In some embodiments, electrophoretic display 1200 is configured such that temperature sensor 1285 controls the state of an enable signal without intervention by display controller circuit 1280.

[0103] exist Figure 7 The circuit shown is referenced in the context of Figure 12 When the temperature near the electrophoretic medium of the imaging film 1210 is low and the appearance and influence of temperature-induced display artifacts are reduced, the enable signal 1246 is driven to activate the transistor (e.g., Figure 7 1201a is also applied to subpixel electrode 1201b. Similarly, enable signal 1246 activates the transistor located between subpixel electrodes 1202a and 1202b, the transistor located between subpixel electrodes 1203a and 1203b, and the transistor located between subpixel electrodes 1204a and 1204b, thereby electrically connecting each pair of subpixel electrodes. This configuration effectively increases the total area of each display pixel electrode and reduces the distance between adjacent display pixel electrodes.

[0104] In contrast, when the temperature near the electrophoretic medium is high and the appearance and influence of the display artifact caused by the temperature are most obvious, the enable signal 1246 is driven to enable the transistor (e.g., Figure 7 1201a is not applied to subpixel electrode 1201b. Similarly, enable signal 1246 disables the transistor located between subpixel electrodes 1202a and 1202b, the transistor located between subpixel electrodes 1203a and 1203b, and the transistor located between subpixel electrodes 1204a and 1204b, thereby electrically isolating each pair of subpixel electrodes. By effectively reducing the total area of each display pixel electrode and increasing the distance between adjacent display pixel electrodes, this configuration can reduce or eliminate temperature-induced display artifacts that may occur at high temperatures. In addition, a single enable signal can be used to select a high-temperature or low-temperature drive scheme, thereby reducing the complexity of the drive scheme using subpixels.

[0105] In some embodiments, the array of display pixel electrodes is divided into multiple subgroups (e.g., halves, quarters, etc.), each subgroup including multiple display pixel electrodes, and each subgroup is associated with an enable signal and temperature sensor. This enables each subgroup of display pixels to operate in either a low-temperature or high-temperature mode independently of the other subgroups. For example, a display used for applications such as outdoor signage may have a portion of its surface exposed to direct sunlight, while another portion of the surface is largely shaded. In this case, if the temperature of the electrophoretic medium in the portion of the display exposed to direct sunlight exceeds a threshold, the display pixels corresponding to that portion may operate in the high-temperature mode, while the display pixels corresponding to the shaded portion may operate in the low-temperature mode.

[0106] therefore, Figure 7 An aspect of the present invention is shown, featuring an electro-optic display comprising a first subpixel electrode and a second subpixel electrode associated with a display pixel, and an electrophoretic display medium disposed between a common electrode and the first subpixel electrode and the second subpixel electrode. In some embodiments, the electro-optic display comprises a physical gap between the first subpixel electrode and the second subpixel electrode. In some embodiments, the electro-optic display comprises a physical gap between at least one adjacent edge of the first subpixel electrode and the second subpixel electrode.

[0107] The electro-optical display further includes a display controller circuit in electrical communication with the common electrode and a first transistor associated with the display pixel. The display controller circuit is capable of applying a waveform to the display pixel by applying one or more time-dependent voltages between the common electrode and a first sub-pixel electrode via the first transistor, wherein the one or more time-dependent voltages are applied to the first sub-pixel electrode. The electro-optical display further includes a second transistor in electrical communication with the first sub-pixel electrode and a second sub-pixel electrode. A first enable signal activates the second transistor to cause the first sub-pixel electrode to electrically communicate with the second sub-pixel electrode.

[0108] If combined Figure 12 The electro-optical display may include a temperature sensor disposed near a display pixel for measuring a temperature of the electrophoretic display medium or a temperature near the electrophoretic display medium. In some embodiments, the first enable signal activates the second transistor based on a measurement of an ambient temperature from the temperature sensor. In some embodiments, the temperature sensor controls the first enable signal to activate the second transistor based on the measurement of the ambient temperature.

[0109] Figure 8 is a schematic diagram of another exemplary pixel 800 including display pixel driving circuitry according to the subject matter described herein. Pixel 800 is similar to pixel 700 but further includes a transistor 860 (eg, a third transistor) between subpixel electrode 801b and frontplate electrode 802.

[0110] This embodiment is configured such that the row select signal for the previous row of display pixels within the array controls the state of an enable signal 866 (e.g., a second enable signal) that activates or deactivates transistor 860 by controlling the state of a gate signal of transistor 860. Thus, in the high temperature mode, when transistor 840 is deactivated, subpixel electrode 801 b is not merely in a floating state, but is refreshed to the voltage applied to frontplate electrode 802 during each frame immediately prior to updating the state of pixel 800.

[0111] The addition of transistor 860 is beneficial because it allows residual charge to be drained from subpixel electrode 801b, which could otherwise remain and cause undesirable image artifacts such as haloing and shifts in the optical state of the displayed pixel. For example, when the display is in a low-temperature mode with transistor 840 activated, subpixel electrode 801b can be driven to a particular voltage. Without transistor 860, if the display enters a high-temperature mode before its next update, transistor 840 would be deactivated, and any charge remaining on subpixel electrode 801b would be stored by storage capacitor 852 (e.g., a second storage capacitor), resulting in the aforementioned image artifacts. Because transistor 860 is activated by enable signal 866 during each frame, residual charge is beneficially drained from subpixel electrode 801b, and this configuration advantageously allows for the removal of residual voltage regardless of the temperature mode in which the display is in.

[0112] therefore, Figure 8 An aspect of the present invention is shown, featuring an electro-optic display comprising a first subpixel electrode and a second subpixel electrode associated with a display pixel, and an electrophoretic display medium disposed between a common electrode and the first subpixel electrode and the second subpixel electrode. In some embodiments, the electro-optic display comprises a physical gap between the first subpixel electrode and the second subpixel electrode. In some embodiments, the electro-optic display comprises a physical gap between at least one adjacent edge of the first subpixel electrode and the second subpixel electrode.

[0113] The electro-optic display also includes a display controller circuit in electrical communication with the common electrode and a first transistor associated with the display pixel. The display controller circuit is capable of applying a waveform to the display pixel by applying one or more time-dependent voltages between the common electrode and a first subpixel electrode via the first transistor, wherein the one or more time-dependent voltages are applied to the first subpixel electrode.

[0114] The electro-optical display further includes a second transistor in electrical communication with the first subpixel electrode and the second subpixel electrode. A first enable signal activates the second transistor to electrically communicate with the first subpixel electrode and the second subpixel electrode. The electro-optical display further includes a third transistor in electrical communication with the second subpixel electrode and the common electrode. In some embodiments, a second enable signal activates the third transistor to drain residual charge from the second subpixel electrode. In some embodiments, the second enable signal is controlled by a row select signal associated with a row of display pixels, and the display pixel is not a display pixel in the row of display pixels.

[0115] Combined with Figure 7 Similar to the electro-optical display described, Figure 8The electro-optical display exemplified in the embodiment of the present invention may include a temperature sensor disposed near a display pixel for measuring a temperature of the electrophoretic display medium or a temperature near the electrophoretic display medium. In some embodiments, the first enable signal activates the second transistor based on a measurement of an ambient temperature from the temperature sensor. In some embodiments, the temperature sensor controls the first enable signal to activate the second transistor based on the measurement of the ambient temperature.

[0116] Figure 9 FIG2 is a schematic diagram of another exemplary pixel 900 including display pixel driver circuitry according to the subject matter described herein. Pixel 900 is similar to pixel 800 but further includes a transistor 941 (e.g., a fourth transistor) between subpixel electrode 901 b and transistor 960 (e.g., a third transistor). In this embodiment, an enable signal 946 (e.g., a first enable signal) drives the gate signals of transistors 940 (e.g., a second transistor) and 941, but the enable signal 946 is inverted at the gate signal of transistor 941, such that the state of transistor 941 is always opposite to the state of transistor 940. Those skilled in the art will appreciate that a logic inverter circuit need not necessarily be present between the enable signal 946 and the gate signal of transistor 941. For example, in some embodiments, transistor 940 is an n-type transistor, while transistor 941 is a p-type transistor.

[0117] During operation, when the display is in a low temperature mode, transistor 940 is activated and transistor 941 is deactivated. When the display enters a high temperature mode, the state of enable signal 946 switches, and transistor 940 is deactivated, while transistor 941 is subsequently activated. Thus, subpixel electrode 901b is refreshed to the voltage applied to front plate electrode 902 only when the display is in the high temperature mode. Similar to display pixel 800, the row select signal for the previous row of display pixels in the array controls the state of enable signal 966 that activates or deactivates transistor 960, so that refreshing occurs during each frame immediately prior to updating the state of display pixel 900 when the previous row of display pixels is selected and enable signal 966 activates transistor 960. This solution is useful during high temperature operation when the display controller's back-drive discharge routine is unable to drain residual charge from subpixel electrode 901b.

[0118] therefore, Figure 9An aspect of the present invention is shown, featuring an electro-optic display comprising a first subpixel electrode and a second subpixel electrode associated with a display pixel, and an electrophoretic display medium disposed between a common electrode and the first subpixel electrode and the second subpixel electrode. In some embodiments, the electro-optic display comprises a physical gap between the first subpixel electrode and the second subpixel electrode. In some embodiments, the electro-optic display comprises a physical gap between at least one adjacent edge of the first subpixel electrode and the second subpixel electrode.

[0119] The electro-optic display also includes a display controller circuit in electrical communication with the common electrode and a first transistor associated with the display pixel. The display controller circuit is capable of applying a waveform to the display pixel by applying one or more time-dependent voltages between the common electrode and a first subpixel electrode via the first transistor, wherein the one or more time-dependent voltages are applied to the first subpixel electrode.

[0120] The electro-optical display also includes a second transistor that is in electrical communication with the first sub-pixel electrode and the second sub-pixel electrode. The first enable signal activates the second transistor to electrically communicate with the first sub-pixel electrode and the second sub-pixel electrode. The electro-optical display also includes a third transistor that is in electrical communication with the common electrode, and a fourth transistor, wherein the fourth transistor is in electrical communication with the second sub-pixel electrode. In some embodiments, the second enable signal activates the third transistor to discharge residual charge from the second sub-pixel electrode. In some embodiments, when the second transistor is activated, the first enable signal deactivates the fourth transistor. In some embodiments, the second enable signal activates the third transistor to discharge residual charge from the second sub-pixel electrode. In some embodiments, the second enable signal is controlled by a row select signal associated with a row of display pixels, wherein the display pixel is not a display pixel of the row of display pixels.

[0121] Combined with Figure 7 and Figure 8 Similar to the electro-optical display described, Figure 9 The electro-optical display exemplified in the embodiment of the present invention may include a temperature sensor disposed near a display pixel for measuring a temperature of the electrophoretic display medium or a temperature near the electrophoretic display medium. In some embodiments, a first enable signal activates the second transistor and deactivates the fourth transistor based on a measurement of an ambient temperature from the temperature sensor. In some embodiments, the temperature sensor controls the first enable signal to activate the second transistor and deactivate the fourth transistor based on the measurement of the ambient temperature.

[0122] Figure 10FIG2 is a schematic diagram of another exemplary display pixel 1000 including display pixel driver circuitry according to the subject matter described herein. Display pixel 1000 includes many similar elements to other display pixels described herein (e.g., display pixel 800), but is configured to control the voltage of subpixel electrode 1001 b within a specific range when the display is in a high temperature mode.

[0123] exist Figure 10 In the illustrated configuration, the upper terminals of subpixel electrode 1001b (e.g., the second subpixel electrode) and storage capacitor 1052 (e.g., the second storage capacitor) are not located between transistor 1040 (e.g., the second transistor) and transistor 1060 (e.g., the third transistor) as in the configuration of display pixel 800. Instead, they are connected on the far side of transistor 1060 such that they are not directly connected to transistor 1040. Furthermore, in the display pixel circuit of display pixel 1000, the row select logic of the display controller connected to drive electrode 1006 controls the gate signals of transistor 1020 (e.g., the first transistor) and transistor 1040. Thus, the row select logic of the display controller connected to drive electrode 1006 functions similarly to an enable signal for transistor 1040 (e.g., similar to an enable signal for transistor 1040). Figure 7 746 in Figure 8 846 and Figure 9 Thus, whenever transistor 1020 is activated, transistor 1040 is also activated, and the state of transistor 1060 controls whether the voltage applied to subpixel electrode 1001a (eg, the first subpixel electrode) is also applied to subpixel electrode 1001b.

[0124] The configuration of display pixel 1000 enables the voltage applied to subpixel electrode 1001b to be controlled within a specific range by modulating the duty cycle and / or amplitude of enable signal 1066 (e.g., a second enable signal). In some embodiments, enable signal 1066 can operate similarly to a pulse-width modulation ("PWM") circuit. For example, enable signal 1066 can be pulsed between a gate-on threshold and a gate-off threshold of transistor 1060, and the frequency and / or duration of the on and off periods can be controlled, thereby regulating the voltage applied to subpixel electrode 1001b.

[0125] therefore, Figure 10An aspect of the present invention is shown, featuring an electro-optic display comprising a first subpixel electrode and a second subpixel electrode associated with a display pixel, and an electrophoretic display medium disposed or electrically coupled between a common electrode and the first subpixel electrode and the second subpixel electrode. In some embodiments, the electro-optic display comprises a physical gap between the first subpixel electrode and the second subpixel electrode. In some embodiments, the electro-optic display comprises a physical gap between at least one adjacent edge of the first subpixel electrode and the second subpixel electrode.

[0126] The electro-optic display also includes a display controller circuit in electrical communication with the common electrode and a first transistor associated with the display pixel. The display controller circuit is capable of applying a waveform to the display pixel by applying one or more time-dependent voltages between the common electrode and a first subpixel electrode via the first transistor, wherein the one or more time-dependent voltages are applied to the first subpixel electrode.

[0127] The electro-optic display further includes a second transistor in electrical communication with the first subpixel electrode, and a third transistor in electrical communication with the second subpixel electrode, wherein a row select signal associated with the display pixel activates the first and second transistors to place the first subpixel electrode in electrical communication with the third transistor.

[0128] In some embodiments, the electro-optic display further comprises a temperature sensor disposed near the electrophoretic display medium and / or the display pixel. In some embodiments, the second enable signal activates the third transistor. In some embodiments, the second enable signal is pulsed at a predetermined rate when the first transistor and the second transistor are activated. In some embodiments, the third transistor is activated at a time that is a subset of the time at which the first transistor and the second transistor are activated.

[0129] Figure 11 It shows that Figure 10 Figure 1100 shows a signal timing diagram of one possible implementation of drive signals for three display pixels in the configuration of display pixel 1000. In this example, the three display pixels are from adjacent rows of the active matrix, where 10061 represents the state of the drive electrode of display pixel 10001, which is located in the first row and is activated during an update; 10062 represents the state of the drive electrode of display pixel 10002, which is located in the second row and is activated during an update; and 10063 represents the state of the drive electrode of display pixel 10003, which is located in the third row and is activated during an update. Enable signal 1066 is a global signal that controls the activation and deactivation of transistor 10601 of display pixel 10001, transistor 10602 of display pixel 10002, and transistor 10603 of display pixel 10003.

[0130] When the measured ambient temperature is low enough to be below the threshold at which temperature-induced display artifacts (such as lateral coupling and blooming) are typically most noticeable, enable signal 1066 is maintained in a high state during display updates to activate transistor 10602 and allow the voltage applied to subpixel electrode 1001a2 to also be applied to subpixel electrode 1001b2. Figure 11 , the state of the enable signal 1066 in this low temperature mode is represented by “ 1066 (low temperature)”.

[0131] exist Figure 11 In the following description, the enable signal 1066 is controlled in high temperature mode, which means that the measured ambient temperature is high enough that if the display is driven so that the entire voltage or charge applied to the sub-pixel electrode 1001a2 is also applied to the sub-pixel electrode 1001b2, temperature-induced display artifacts are likely to occur. Figure 11 , the state of the enable signal 1066 in this high temperature mode is represented by “ 1066 (high temperature)”.

[0132] like Figure 11 As shown, at time t1, the driving electrode 10061 is driven to a high level to select a row of display pixels including the display pixel 10001 for updating.

[0133] At time t2, the enable signal 1066 is switched to a high level to activate the transistor 10601 and allow the voltage applied to the subpixel electrode 1001a1 to be applied to the subpixel electrode 1001b1 for a portion of the time applied to the subpixel electrode 1001a1.

[0134] At time t3, drive electrode 10061 is driven low to deselect a row of display pixels including display pixel 10001, and drive electrode 10062 is driven high to select a row of display pixels for updating including display pixel 10002. Enable signal 1066 is also switched low at time t3 to deactivate transistor 10601 and interrupt the connection between sub-pixel electrode 1001a1 and sub-pixel electrode 1001b1.

[0135] At time t4, the enable signal 1066 is switched to a high level to activate the transistor 10602 and allow the voltage applied to the sub-pixel electrode 1001a2 to be applied to the sub-pixel electrode 1001b2 for a portion of the time it is applied to the sub-pixel electrode 1001a2.

[0136] At time t5, drive electrode 10062 is driven low to deselect a row of display pixels including display pixel 10002, and drive electrode 10063 is driven high to select a row of display pixels for updating including display pixel 10003. Enable signal 1066 is also switched low at time t5 to deactivate transistor 10602 and interrupt the connection between sub-pixel electrode 1001a2 and sub-pixel electrode 1001b2.

[0137] At time t6, the enable signal 1066 is switched to a high level to activate the transistor 10603 and allow the voltage applied to the sub-pixel electrode 1001a3 to be applied to the sub-pixel electrode 1001b3 for a portion of the time it is applied to the sub-pixel electrode 1001a3.

[0138] Finally, at time t7, drive electrode 10063 is driven low to deselect a row of display pixels including display pixel 10003. Enable signal 1066 is also switched low at time t7 to deactivate transistor 10603 and interrupt the connection between subpixel electrode 1001a3 and subpixel electrode 1001b3.

[0139] Therefore, it can be seen that the configuration of display pixel 1000 enables the impedance between sub-pixel electrode 1001a and sub-pixel electrode 1001b to be controlled by the duty cycle and / or voltage level of enable signal 1066, so that the voltage difference between sub-pixel electrode 1001a and sub-pixel electrode 1001b can be fine-tuned and optimized.

[0140] This configuration provides additional options for implementing temperature-compensated drive schemes for electro-optical displays. For example, in low-temperature mode, enable signal 1066 can be configured to provide a constant connection between each subpixel electrode 1001a and its corresponding subpixel electrode 1001b, maximizing the area of each display pixel electrode that is energized and drives the charged particles in the electrophoretic medium. When the display enters high-temperature mode, the voltage supplied to subpixel electrode 1001b can be precisely adjusted to maintain the display's contrast and update speed without introducing the aforementioned image artifacts.

[0141] Therefore, as described herein, the innovative multi-element display pixel electrode layout and display pixel driver circuit can mitigate performance variations of electrophoretic displays due to changes in ambient temperature. Those skilled in the art will appreciate that various changes and modifications may be made to the specific embodiments of the present invention without departing from the scope of the present invention. Therefore, the above description should be interpreted as illustrative only and not restrictive.

[0142] The contents of all of the above patents and applications are incorporated herein by reference in their entirety.

Claims

1. An electro-optical display comprising: a first subpixel electrode and a second subpixel electrode associated with a display pixel; an electrophoretic display medium disposed between the common electrode and the first sub-pixel electrode and the second sub-pixel electrode; a display controller circuit in electrical communication with the common electrode and a first transistor associated with the display pixel, the display controller circuit being capable of applying a waveform to the display pixel by applying one or more time-dependent voltages between the common electrode and the first subpixel electrode via the first transistor, wherein the one or more time-dependent voltages are applied to the first subpixel electrode; as well as A second transistor is in electrical communication with the first subpixel electrode and the second subpixel electrode, wherein a first enable signal activates the second transistor to place the first subpixel electrode in electrical communication with the second subpixel electrode.

2. The electro-optic display of claim 1 further comprising a temperature sensor disposed proximate the display pixel.

3. The electro-optic display of claim 2, wherein the first enable signal activates the second transistor based on a measurement of ambient temperature from the temperature sensor.

4. The electro-optic display of claim 2, wherein the temperature sensor controls the first enable signal to activate the second transistor based on a measurement of an ambient temperature.

5. The electro-optic display of claim 1, further comprising a third transistor in electrical communication with the second subpixel electrode and the common electrode.

6. The electro-optic display of claim 5, wherein a second enable signal activates the third transistor to drain residual charge from the second sub-pixel electrode.

7. An electro-optic display according to claim 6, wherein the second enable signal is controlled by a row select signal associated with a row of display pixels, wherein the display pixel is not a display pixel of the row of display pixels.

8. The electro-optic display of claim 2, further comprising a third transistor in electrical communication with the common electrode, and a fourth transistor, wherein the fourth transistor is in electrical communication with the second subpixel electrode.

9. The electro-optic display of claim 8, wherein the first enable signal disables the fourth transistor when the second transistor is activated.

10. The electro-optic display of claim 9, wherein a second enable signal activates the third transistor to drain residual charge from the second sub-pixel electrode.

11. The electro-optic display of claim 10, wherein the second enable signal is controlled by a row select signal associated with a row of display pixels, wherein the display pixel is not a display pixel of the row of display pixels.

12. The electro-optic display of claim 1, further comprising a physical gap between the first subpixel electrode and the second subpixel electrode.

13. The electro-optic display of claim 1, further comprising a physical gap between at least one adjacent edge of the first subpixel electrode and the second subpixel electrode.

14. An electro-optical display comprising: a first subpixel electrode and a second subpixel electrode associated with a display pixel; an electrophoretic display medium disposed between the common electrode and the first sub-pixel electrode and the second sub-pixel electrode; a display controller circuit in electrical communication with the common electrode and a first transistor associated with the display pixel, the display controller circuit being capable of applying a waveform to the display pixel by applying one or more time-dependent voltages between the common electrode and the first subpixel electrode via the first transistor, wherein the one or more time-dependent voltages are applied to the first subpixel electrode; as well as a second transistor in electrical communication with the first subpixel electrode and the third transistor, wherein the third transistor is in electrical communication with the second subpixel electrode, and Wherein a row select signal associated with the display pixel activates the first transistor and the second transistor to electrically communicate the first sub-pixel electrode with the third transistor.

15. The electro-optic display of claim 14, further comprising a temperature sensor disposed adjacent the electrophoretic display medium.

16. The electro-optic display of claim 14, wherein a second enable signal activates the third transistor.

17. The electro-optic display of claim 16, wherein the second enable signal is pulsed at a predetermined rate when the first transistor and the second transistor are activated.

18. The electro-optic display of claim 16, wherein a time at which the third transistor is activated is a subset of a time at which the first transistor and the second transistor are activated.

19. The electro-optic display of claim 14, further comprising a physical gap between the first subpixel electrode and the second subpixel electrode.

20. The electro-optic display of claim 14, further comprising a physical gap between at least one adjacent edge of the first subpixel electrode and the second subpixel electrode.

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