Electro-optical display

Abstract

An electro-optical display includes: an electrophoretic display medium disposed between a first common electrode and a display pixel electrode associated with a display pixel; a storage capacitor, the display pixel electrode being coupled to a first terminal of the storage capacitor; a second common electrode coupled to a second terminal of the storage capacitor; and a driver circuit electrically connected to the first common electrode, the second common electrode, and a transistor associated with the display pixel electrode. The driver circuit applies a waveform drive sequence to the display pixel, which is configured to, after the waveform drive sequence, discharge the storage capacitor via the second common electrode to discharge the display pixel electrode by applying a constant voltage set to zero volts to the second common electrode while the display pixel electrode and the first common electrode are in a floating state.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201980085129.8, entitled "Electro-optical display".

[0002] Citation of Related Applications

[0003] This application relates to U.S. Provisional Application No. 62 / 786,437, filed on December 30, 2018.

[0004] The entire disclosure of the above application is incorporated herein by reference. Technical Field

[0005] The present invention relates to electro-optical display devices, and more particularly, to methods for driving electro-optical displays. Background Art

[0006] Particle-based electrophoretic displays have been the subject of intensive research and development for many years. In such displays, a plurality of charged particles (sometimes referred to as pigment particles) move through a fluid under the influence of an electric field. The electric field is typically provided by a conductive film or a transistor (such as a field effect transistor). Compared with liquid crystal displays, electrophoretic displays have good brightness and contrast, wide viewing angles, bistable states, and low power consumption. However, such electrophoretic displays have a slower switching speed than LCD displays, and electrophoretic displays are generally too slow to display real-time video. Additionally, due to the viscosity of the fluid limiting the movement of the electrophoretic particles, electrophoretic displays may be slow at low temperatures. Despite these drawbacks, electrophoretic displays can be found in everyday products such as e-books (e-readers), mobile phones and phone cases, smart cards, signage, watches, shelf labels, and flash drives.

[0007] Many commercially available electrophoretic media essentially only display two colors, with a gradient between the black and white extremes, called "gray scale". Such electrophoretic media either use a single type of electrophoretic particle having a first color in a colored fluid having a second different color (in which case the first color is displayed when the particles are adjacent to the viewing surface of the display and the second color is displayed when the particles are spaced apart from the viewing surface) or use first and second types of electrophoretic particles having different first and second colors in an uncolored fluid. In the latter case, when the first type of particle is adjacent to the viewing surface of the display, the first color is displayed, while when the second type of particle is adjacent to the viewing surface, the second color is displayed). Typically, these two colors are black and white.

[0008] Although seemingly simple, electrophoretic media and electrophoretic devices exhibit complex behavior. For example, it has been found that simple "on / off" voltage pulses are not sufficient to achieve high-quality text in an electronic reader. Instead, complex "waveforms" are required to drive the particles between states to ensure that the newly displayed text does not retain the memory of the previous text, i.e., "ghosting". In addition, after being driven for some time, charge accumulates in the electrophoretic medium, sometimes referred to as residual voltage. The residual voltage can damage the display over time and cause optical degradation of the electrophoretic medium. Therefore, it is necessary to reduce this residual voltage in electrophoretic displays. Summary of the Invention

[0009] The present invention provides a method for driving an electro-optical display having at least one display pixel coupled to a storage capacitor, the method comprising applying a sequence of waveforms to the at least one display pixel, connecting the storage capacitor to a first bias voltage, and maintaining the last frame voltage level on the display pixel after the applied waveforms are completed.

[0010] The present invention also provides an electro-optical display comprising: an electrophoretic display medium disposed between a first common electrode and a display pixel electrode associated with a display pixel; a storage capacitor, the display pixel electrode being coupled to a first terminal of the storage capacitor; a second common electrode coupled to a second terminal of the storage capacitor; and a driver circuit electrically connected to the first common electrode, the second common electrode, and a transistor associated with the display pixel electrode. The driver circuit is capable of applying a waveform drive sequence to the display pixel by applying one or more time-dependent voltages between the first common electrode and the display pixel electrode via the transistor. The driver circuit is configured to discharge the display pixel electrode via the second common electrode by applying a constant voltage set to zero volts to the second common electrode after the waveform drive sequence while the display pixel electrode and the first common electrode are in a floating state to discharge the storage capacitor. Brief Description of the Drawings

[0011] Figure 1 An electrophoretic display in accordance with the subject matter disclosed herein is shown;

[0012] Figure 2 An illustration of an Figure 1 equivalent circuit of the proposed electrophoretic display in accordance with the subject matter disclosed herein;

[0013] Figure 3 An active matrix circuit in accordance with the subject matter disclosed herein is shown;

[0014] Figure 4 A schematic diagram of a display pixel in accordance with the subject matter proposed herein is shown;

[0015] Figure 5 illustrates one method of driving an electrophoretic display in accordance with the subject matter presented herein;

[0016] Figure 6 illustrates an example setup for driving an electrophoretic display in accordance with the subject matter presented herein;

[0017] Figure 7 is a schematic diagram showing the change of the white state of a display in accordance with the subject matter presented herein;

[0018] Figure 8 illustrates another method of driving an electrophoretic display in accordance with the subject matter presented herein;

[0019] Figure 9 illustrates another setup for driving an electrophoretic display in accordance with the subject matter presented herein; and

[0020] Figure 10 is another schematic diagram showing the change of the white state of a display in accordance with the subject matter presented herein. DETAILED DESCRIPTION

[0021] As described above, the subject matter presented herein provides methods and apparatus for reducing charge accumulation in an electrophoretic display medium and improving electro-optic display performance.

[0022] As a term "electro-optic" applied to a material or a display, as used herein, it has its conventional meaning in the imaging field, referring to a material having a first and a second display state, at least one optical property of which is different between the first and the second display states, and the material is changed from its first display state to the second display state by applying an electric field to the material. Although the optical property is usually the color perceptible to the human eye, it can be another optical property, such as light transmission, reflection, luminescence, or in the case of a display for machine reading, a pseudo-color in the sense of a change in reflectance of an electromagnetic wavelength outside the visible light range.

[0023] The term "gray state" is used herein in its conventional meaning in the imaging field, referring to a state intermediate between two extreme optical states of a pixel, but not necessarily implying a black-and-white transition between these two extreme states. For example, several E Ink patents and published applications referred to below describe electrophoretic displays in which the extreme states are white and dark blue, such that the intermediate "gray state" is actually light blue. In fact, as already mentioned, the change in optical state may not be a color change at all. The terms "black" and "white" may be used below to refer to the two extreme optical states of a display, and should be understood to generally include extreme optical states that are not strictly black and white, such as the white and dark blue states mentioned above. The term "monochromatic" may be used below to denote a driving scheme that drives a pixel only to its two extreme optical states without an intermediate gray state.

[0024] The terms "bistable" and "bistability" are used herein in their conventional meaning in the art, referring to a display including a display element having first and second display states, at least one of the optical properties of the first and second display states being different, such that after driving any given element with an addressing pulse of a finite duration to present its first or second display state, after termination of the addressing pulse, the state will persist for a time that is at least several times (e.g., at least 4 times) the minimum duration of the addressing pulse required to change the state of the display element. As shown in published U.S. Patent Application No. 2002 / 0180687 (see also corresponding International Application Publication No. WO 02 / 079869), some particle-based electrophoretic displays that support grayscale can be stable not only in their extreme black and white states, but also in their intermediate gray states, and the same is true for some other types of electro-optic displays. Displays of this type are properly referred to as "multistable" rather than bistable, but for convenience, the term "bistable" may be used herein to cover both bistable and multistable displays.

[0025] The term "impulse" is used herein in its conventional meaning, i.e., the integral of voltage with respect to time. However, some bistable electro-optic media are used as charge converters, and for such media, an alternative definition of impulse can be used, i.e., the integral of current with respect to time (which is equal to the total charge applied). Depending on whether the medium is used as a voltage-time impulse converter or as a charge impulse converter, the appropriate definition of impulse should be used.

[0026] Many recently published patents and applications assigned to or in the name of the Massachusetts Institute of Technology (MIT) and E Ink Corporation describe encapsulated electrophoretic media. Such encapsulated media include a number of small vesicles, each of which itself includes an internal phase and a vesicle wall surrounding the internal phase, where the internal phase contains electrophoretically mobile particles suspended in a liquid suspension medium. Typically, the vesicles themselves are held in a polymeric binder to form a coherent layer located between two electrodes. The techniques described in these patents and applications include:

[0027] (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 7,002,728 and 7,679,814;

[0028] (b) Vesicles, binders, and encapsulation processes; see, for example, U.S. Patent Nos. 6,922,276 and 7,411,719;

[0029] (c) Microcell structures, wall materials, and methods of forming microcells; see, for example, U.S. Patent Nos. 7,072,095 and 9,279,906;

[0030] (d) Methods for filling and sealing microcells; see, for example, U.S. Patent Nos. 7,144,942 and 7,715,088;

[0031] (e) Thin films and subassemblies containing electro-optic materials; see, for example, U.S. Patent Nos. 6,982,178 and 7,839,564;

[0032] (f) Backplanes, adhesive layers, and other auxiliary layers used in displays, and methods; see, for example, U.S. Patent Nos. D485,294; 6,124,851; 6,130,773; 6,177,921; 6,232,950; 6,252,564; 6,312,304; 6,312,971; 6,376,828; 6,392,786; 6,413,790; 6,422,687; 6,445,374; 6,480,182; 6,498,114; 6,506,438; 6,518,949; 6,521,489; 6,535,197; 6,545,291; 6,639,578; 6,657,772; 6,664,944; 6,680,725; 6,683,333; 6,724,519; 6,750,473; 6,816,147; 6,819,471; 6,825,068; 6,831,769; 6,842,167; 6,842,279; 6,842,657; 6,865,010; 6,873,452; 6,909,532; 6,967,640; 6,980,196; 7,012,735; 7,030,412; 7,075,703; 7,106,296; 7,110,163; 7,116,318; 7,148,128; 7,167,155; 7,173,752; 7,176,880; 7,190,008; 7,206,119; 7,223,672; 7,230,751; 7,256,766; 7,259,744; 7,280,094; 7,301,693; 7,304,780; 7,327,511; 7,347,957; 7,349,148; 7,352,353; 7,365,394; 7,365,733; 7,382,363; 7,388,572; 7,401,758; 7,442,587; 7,492,497; 7,535,624; 7,551,346; 7,554,712; 7,583,427; 7,598,173; 7,605,799; 7,636,191; 7,649,674; 7,667,886; 7,672,040; 7,688,497; 7,733,335; 7,785,988; 7,830,592; 7,843,626; 7,859,637; 7,880,958; 7,893,435; 7,898,717; 7,905,977; 7,957,053; 7,986,450; 8,009,344; 8,027,081; 8,049,947; 8,072,675; 8,077,141;8,089,453; 8,120,836; 8,159,636; 8,208,193; 8,237,892; 8,238,021; 8,362,488; 8,373,211; 8,389,381; 8,395,836; 8,437,069; 8,441,414; 8,456,589; 8,498,042; 8,514,168; 8,547,628; 8,576,162; 8,610,988; 8,714,780; 8,728,266; 8,743,077; 8,754,859; 8,797,258; 8,797,633; 8,797,636; 8,830,560; 8,891,155; 8,969,886; 9,147,364; 9,025,234; 9,025,238; 9,030,374; 9,140,952; 9,152,003; 9,152,004; 9,201,279; 9,223,164; 9,285,648; and 9,310,661; as well as U.S. Patent Application Publication Nos. 2002 / 0060321; 2004 / 0008179; 2004 / 0085619; 2004 / 0105036; 2004 / 0112525; 2005 / 0122306; 2005 / 0122563; 2006 / 0215106; 2006 / 0255322; 2007 / 0052757; 2007 / 0097489; 2007 / 0109219; 2008 / 0061300; 2008 / 0149271; 2009 / 0122389; 2009 / 0315044; 2010 / 0177396; 2011 / 0140744; 2011 / 0187683; 2011 / 0187689; 2011 / 0292319; 2013 / 0250397; 2013 / 0278900; 2014 / 0078024; 2014 / 0139501; 2014 / 0192000; 2014 / 0210701; 2014 / 0300837; 2014 / 0368753; 2014 / 0376164; 2015 / 0171112; 2015 / 0205178; 2015 / 0226986; 2015 / 0227018; 2015 / 02228666; 2015 / 0261057; 2015 / 0356927; 2015 / 0378235; 2016 / 077375; 2016 / 0103380; and 2016 / 0187759; as well as International Application Publication No. WO 00 / 38000; European Patent Nos. 1,099,207B1 and 1,145,072B1;

[0033] (g) Color formation and color adjustment; see, for example, U.S. Patent Nos. 7,075,502 and 7,839,564;

[0034] (h) Methods for driving a display; see, for example, U.S. Patent Nos. 7,012,600 and 7,453,445;

[0035] (i) Applications of a display; see, for example, U.S. Patent Nos. 7,312,784 and 8,009,348;

[0036] (j) Non-electrophoretic displays, as described in U.S. Patent No. 6,241,921; and U.S. Patent Application Publication No. 2015 / 0277160; and U.S. Patent Application Publication Nos. 2015 / 0005720 and 2016 / 0012710.

[0037] All of the above patents and patent applications are incorporated herein by reference in their entirety.

[0038] Many of the foregoing patents and applications recognize that the walls surrounding discrete microcapsules in an encapsulated electrophoretic medium can be replaced by a continuous phase, thereby resulting in so-called polymer dispersed electrophoretic displays, where the electrophoretic medium includes a plurality of discrete droplets of electrophoretic fluid and a continuous phase of polymeric material, and the discrete droplets of electrophoretic fluid within such polymer dispersed electrophoretic displays can be considered capsules or microcapsules even if there is no discrete capsule film associated with each individual droplet; see, for example, the aforementioned 2002 / 0131147. Thus, for the purposes of this application, such polymer dispersed electrophoretic media are considered a subclass of encapsulated electrophoretic media.

[0039] Encapsulated electrophoretic displays are generally not plagued by the aggregation and sedimentation failure modes of conventional electrophoretic devices and offer additional advantages such as the ability to print or coat the display on a variety of flexible and rigid substrates. (The use of the word "print" is intended to include all forms of printing and coating, including but not limited to: pre-metered coating such as patch die coating, slot or extrusion coating, slide or laminate coating, curtain coating; roll coating such as roll knife coating, forward and reverse roll coating; concave coating; dip coating; spraying; meniscus coating; spin coating; brush coating; air knife coating; screen printing processes; electrophotographic printing processes; thermal printing processes; inkjet printing processes; and other similar techniques.) Thus, the resulting display can be flexible. Additionally, because the display medium can be (using a variety of methods) printed, the display itself can be manufactured inexpensively.

[0040] One related type of electrophoretic display is the so-called "microcell electrophoretic display". In a microcell electrophoretic display, charged particles and a suspending fluid are not encapsulated within microcapsules, but rather are held within a plurality of cavities formed within a carrier medium (typically a polymeric film). See, for example, International Application Publication No. WO 02 / 01281, and Published U.S. Application No. 2002 / 0075556, both of which are assigned to Sipix Imaging, Inc.

[0041] Electro-optic displays of the above type are bistable and are typically used in a reflective mode, but as described in some of the above patents and applications, such displays can be operated in a "shutter mode", in which the electro-optic medium is used to modulate the transmission of light such that the display operates in a transmissive mode. Of course, liquid crystals, including polymer-dispersed liquid crystals, are also electro-optic media, but are typically not bistable and operate in a transmissive mode. Some embodiments of the invention described below are limited to reflective displays, while other embodiments can be used for both reflective and transmissive displays, including conventional liquid crystal displays.

[0042] Regardless of whether the display is reflective or transmissive, and regardless of whether the electro-optic medium used is bistable or not, in order to obtain a high-resolution display, each pixel of the display must be addressable without interference from adjacent pixels. One way to achieve this is to provide an array of non-linear elements (such as transistors or diodes), and at least one non-linear element is associated with each pixel to produce an "active matrix" display. The addressing or pixel electrode used to address a pixel is connected to an appropriate voltage source through the associated non-linear element. Typically, when the non-linear element is a transistor, the pixel electrode is connected to the drain of the transistor, and this arrangement will be assumed in the following description, although it is essentially arbitrary and the pixel electrode could be connected to the source of the transistor. Conventionally, 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 particular row and a particular column. The sources of all the transistors in each column are connected to a single column electrode, and the gates of all the transistors in each row are connected to a single row electrode; furthermore, the source-to-row and gate-to-column arrangements are conventional but essentially arbitrary and can be reversed as desired. The row electrodes are connected to a row driver, which essentially ensures that at any given moment, only one row is selected, i.e., a voltage is applied to the selected row electrode, for example to ensure that all the transistors in the selected row are conducting, while a voltage is applied to all the other rows, for example to ensure that all the 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 aforementioned voltages are with respect to a common front electrode, which is conventionally provided on the opposite side of the electro-optic medium from the non-linear array and extends across the entire display.) After a preselected interval called the "row address time", the selected row is deselected, the next row is selected, and the voltages on the column driver are changed so that the next row of the display is written. This process is repeated, thereby writing the entire display row by row.

[0043] Processes for fabricating active matrix displays have been well established. For example, various deposition and lithography techniques can be used to fabricate thin film transistors. The transistor includes a gate, an insulating dielectric layer, a semiconductor layer, and source and drain electrodes. Applying a voltage to the gate provides an electric field across the dielectric layer, thereby greatly increasing the source-drain conductivity of the semiconductor layer. This change allows conduction between the source and the drain. Typically, the gate, source, and drain are patterned. Typically, the semiconductor layer is also patterned to minimize stray conduction (i.e., crosstalk) between adjacent circuit elements.

[0044] Liquid crystal displays typically use amorphous silicon ("a-Si") and thin film transistors ("TFTs") as switching devices for display pixels. Such TFTs typically have a bottom gate configuration. Within a pixel, a thin film capacitor typically stores the charge transferred by the switching TFT. Electrophoretic displays can use similar TFTs with capacitors, although the function of the capacitor is slightly different from that in liquid crystal displays; see the above co-pending application Serial No. 09 / 565,413 and publications 2002 / 0106847 and 2002 / 0060321. Thin film transistors can be fabricated to provide high performance. However, the manufacturing process can result in substantial costs.

[0045] In a TFT addressing array, the pixel electrode is charged via the TFT during the row address time. During the row address time, the TFT is switched to the on state by changing the applied gate voltage. For example, for an n-type TFT, the gate voltage is switched to the "high" state to switch the TFT into the on state.

[0046] In addition, crosstalk occurring between the data line supplying the drive waveform and the pixel electrode of the display pixel can cause unwanted effects such as voltage offsets. Similar to the above voltage offsets, crosstalk between the data line and the pixel electrode can be caused by capacitive coupling between the two, even when the display pixel is not being addressed (e.g., the associated pixel TFT is depleted). Such crosstalk can lead to an undesired voltage offset as it can cause optical artifacts such as image streaks.

[0047] In some cases, an electrophoretic display or EPD can include two substrates (e.g., plastic or glass), with a front plane laminate or FPL located between the two substrates. In some embodiments, the bottom of the top substrate can be coated with a transparent conductive material to serve as a conductive electrode (i.e., V com plane). The top of the bottom substrate can include an array of electrode elements (e.g., conductive electrodes for each display pixel). A semiconductor switch such as a thin film transistor or TFT can be associated with each of these pixel electrodes. Applying a bias voltage to the pixel electrode and the V com plane can cause an electro-optical conversion of the FPL. This optical conversion can be used as a basis for displaying text or graphic information on the EPD. To display the desired image, an appropriate voltage needs to be applied to each pixel electrode.

[0048] Figure 1A schematic model of a display pixel 100 of an electro-optical display in accordance with the subject matter presented herein is shown. Pixel 100 may include an imaging film 110. In some embodiments, imaging film 110 may be an electrophoretic material layer and is bistable in nature. The electrophoretic material may include a plurality of charged color pigment particles (e.g., black, white, yellow, or red) that are disposed in a fluid and are capable of moving through the fluid under the influence of an electric field. In some embodiments, imaging film 110 may be an electrophoretic film having micro-cells that have charged pigment particles. In some other embodiments, imaging film 110 may include, but is not limited to, an encapsulated electrophoretic imaging film that may include, for example, charged pigment particles. It should be understood that the driving methods presented below can be readily used with any type of electrophoretic material (e.g., encapsulated or film having micro-cells).

[0049] In some embodiments, imaging film 110 may be disposed between a front electrode 102 and a rear electrode or pixel electrode 104. Front electrode 102 may be formed between the imaging film and the front of the display. In some embodiments, front electrode 102 may be transparent and light transmissive. In some embodiments, front electrode 102 may be formed of any suitable transparent material, including but not limited to indium tin oxide (ITO). Rear electrode 104 may be formed on the side of imaging film 110 opposite to front electrode 102. In some embodiments, a parasitic capacitance (not shown) may be formed between front electrode 102 and rear electrode 104.

[0050] Pixel 100 may be one of a plurality of pixels. The plurality of pixels may 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 particular row and a particular column. In some embodiments, the matrix of pixels may be an "active matrix" in which each pixel is associated with at least one non-linear circuit element 120. The non-linear circuit element 120 may be coupled between the backplane electrode 104 and the addressing electrode 108. In some embodiments, the non-linear element 120 may be a diode and / or a transistor, including but not limited to a metal oxide semiconductor field effect transistor (MOSFET) or a thin film transistor (TFT). The drain (or source) of the MOSFET or TFT may be coupled to the backplane or pixel electrode 104, the source (or drain) of the MOSFET or TFT may be coupled to the addressing electrode 108, and the gate of the MOSFET or TFT may be coupled to the driver electrode 106, which is configured to control the activation and deactivation of the MOSFET or TFT. (For simplicity, the terminal of the MOSFET or TFT coupled to the backplane electrode 104 will be referred to as the drain of the MOSFET or TFT, and the terminal of the MOSFET or TFT coupled to the addressing electrode 108 will be referred to as the source of the MOSFET or TFT. However, one of ordinary skill in the art will recognize that in some embodiments, the source and drain of the MOSFET or TFT may be interchanged.)

[0051] In some embodiments of the active matrix, the addressing electrodes 108 of all pixels in each column may be connected to the same column electrode, and the driver electrodes 106 of all pixels in each row may be connected to the same row electrode. The row electrodes may be connected to a row driver, which may select one or more rows of pixels by applying a voltage to the selected row electrodes, the voltage being sufficient to activate the non-linear elements 120 of all pixels 100 in the selected row. The column electrodes may be connected to a column driver, which may apply a voltage suitable for driving the pixels to a desired optical state to the addressing electrodes 106 of the selected (activated) pixels. The voltage applied to the addressing electrode 108 may be relative to the voltage applied to the front plate electrode 102 of the pixel (e.g., a voltage of approximately zero volts). In some embodiments, the front plate electrodes 102 of all pixels in the active matrix may be coupled to a common electrode.

[0052] In use, the pixels 100 of the active matrix may be written in a row-by-row manner. For example, the row driver may select a row of pixels, and the column driver may apply a voltage corresponding to the desired optical state of the pixel row to the pixels. After a preselected interval referred to as the "row address time", the selected row may be deselected, another row may be selected, and the voltage on the column driver may be changed such that another row of the display is written.

[0053] Figure 2 A circuit model of an electro-optic imaging layer 110 according to the subject matter presented herein is shown. The electro-optic imaging layer 100 is disposed between a front electrode 102 and a rear electrode 104. Resistors 202 and capacitors 204 may represent the resistance and capacitance of the electro-optic imaging layer 110, the front electrode 102, and the rear electrode 104 (including any adhesive layers). Resistors 212 and capacitors 214 may represent the resistance and capacitance of the laminated adhesive layer. Capacitor 216 may represent a capacitance that may be formed between the front electrode 102 and the rear electrode 104, e.g., an interfacial contact region between layers such as the interface between the imaging layer and the laminated adhesive layer and / or the interface between the laminated adhesive layer and the backplane electrode. The voltage Vi on the imaging film 110 of the pixel may include the residual voltage of the pixel.

[0054] Figure 3 An exemplary active matrix for driving an electrophoretic display is shown. In some embodiments, each display pixel of the electrophoretic display may be controlled by a thin film transistor (TFT). The TFT may be turned on and off to receive a driving voltage to modulate the optical state of the associated display pixel. To effectively control the driving of the associated display pixel, a gate line signal, a data line signal, a V Figure 3 line signal, and a storage capacitor may be provided to each TFT 102 as shown. In one embodiment, as shown, the gate of each TFT 102 may be electrically coupled to a scan line, and the source or drain of the transistor may be connected to a data line, and the two terminals of the storage capacitor may be connected to the V com line and the pixel electrode, respectively. In some embodiments, the V Figure 1 line grid on the bottom of the top substrate and the V com line grid on the top of the bottom substrate may be connected to the same DC source. com and the V com line grid on the top of the bottom substrate may be connected to the same DC source.

[0055] Figure 4 A top view of a display pixel 400 according to the subject matter disclosed herein is shown. The display pixel 400 includes a pixel electrode 404 configured to drive the display pixel. In use, the display pixel 400 will be driven by a series of voltage pulses induced on the pixel electrode 404. The series of voltage pulses may be applied to the pixel electrode 404 through a transistor 408. The transistor 408 may be used as a switch to turn on and off the signal path to the pixel electrode 404. For example, the gate 416 of the transistor 408 may be connected to a signal selection gate line 402. In use, the gate 402 may be used to selectively turn on and off the transistor 408 by applying or not applying a voltage to the gate 416 of the transistor 408. Additionally, a series of voltage pulses may be provided through a data line 406. The data line 406 is also electrically coupled to the transistor 408, as Figure 4As shown. In operation, a signal (e.g., an electrical pulse) can be transmitted through the gate line 402 to activate or turn on the transistor 408, and once the transistor 408 is turned on, the electrical signal applied through the data line 406 can be transmitted through the transistor 408 to the pixel electrode 404. In Figure 4 V is also shown com line 410. In some embodiments, this V com line 410 can be electrically coupled to the top electrode of the display ( Figure 4 not shown in com ) to hold the top electrode at a constant voltage level (e.g., V com ). Generally, this V com line 410 is located at the device level below the pixel electrode 404. The electrode 414 of the storage capacitor is also connected to this V com line 40, where the electrode 414 can be located on the same device layer as the V Figure 6 shown storage capacitor Cst 602 or Figure 9 shown Cst 902.

[0056] Figure 5 shows a way to drive the EPD. In this configuration, the storage capacitor or Cst and the EPD electrophoretic material layer (represented by its resistance Repd) are connected together to a constant voltage V com , as Figure 6 shown. In operation, the waveform for driving the display pixels of the EPD can end with a driving portion of 0V to discharge all the residual voltage in the storage capacitor (i.e., Cst).

[0057] However, in some cases, the EPD module may suffer from a jump voltage, which may cause an unwanted change or shift in the optical quality of the EPD. Figure 7 shows a graph depicting the shift of the white state of the EPD due to the jump effect, where the jump effect can be the effect experienced by the inner phase of the display due to an electric field equal and opposite to the initially applied field, which may cause any image on the medium to be erased if both electrodes are grounded (or placed at a common potential) after full polarization.

[0058] Now referring to Figure 7 , the end of the drive waveform or waveform sequence is approximately at time scale 27.7, where the L* of the white state immediately decays by approximately 8L*. Figure 7 Exactly what is shown in Figure 5 is the time when the waveform in

[0059] Alternatively, as Figure 8 and 9As shown, the storage capacitor (i.e., Cst 902) and the EPD display medium layer (i.e., Repd 904) can be biased separately. For example, the storage capacitor Cst 902 can be biased by a V Figure 4 line similar to com the V com line 410 shown (e.g., TFT V com 906). And the display medium Repd 904 can be biased and controlled separately by a V com plane such as the above-mentioned FPL V com 908. In addition, at the end of the waveform driving sequence, the source and gate of the associated TFT can be turned off instead of driving with a period of zero volts. In other words, the display pixel can hold the voltage of the last frame of the waveform or remain in a substantially floating state (i.e., the pixel is substantially isolated or in a state as if it is not connected to any conductive path). And the storage capacitor can discharge gradually. In some embodiments, FPL V com 908 can be configured to be in a floating state in the next frame. In some embodiments, to ensure a small timing difference between the pixel and V com control, the FPL V com 908 voltage can be set to float one frame before the waveform ends on the pixel. In some embodiments, the voltage of TFT V com 906 is controlled differently and can be set to zero volts or a DC voltage to ensure that the storage capacitor is charged correctly. In some other embodiments, TFT V com 906 can be configured to float, while FPL V com 908 can be configured to float or be in a zero-volt bias.

[0060] Alternatively, in the embodiment shown as Figure 5 shown, the voltages of TFT V com 906 and FPL V com 908 can be electrically coupled and programmed to float.

[0061] In some embodiments, an electro-optical display as described herein can be driven by first applying a waveform sequence to the display pixels of the display, connecting the storage capacitor associated with the display pixels to a first bias voltage such as the TFT V com voltage, and maintaining the voltage level of the last frame on the display pixels when the driving sequence is completed. In addition, at the end of the driving sequence, the storage capacitor can remain floating, and the display medium of the display can remain floating or be in a zero-volt bias.

[0062] Figure 8The driving method shown can be applied to some or all of the waveforms in a look-up table (LUT). For example, if the LUT has black, white, red, and yellow states and thus has four waveforms, the designer can select which waveforms can run Figure 8 the sequences described in. And they can end at the last frame of the LUT. In this case, other waveforms that do not run the sequence need to end at least one frame earlier to be driven to zero volts. The driving sequence can eliminate or at least reduce the jump effect. Among them, the light trace of the new sequence is as Figure 10 shown.

Claims

1. An electro-optical display, comprising: an electrophoretic display medium disposed between a first common electrode and a display pixel electrode associated with a display pixel; a storage capacitor, the display pixel electrode being coupled to a first terminal of the storage capacitor; a second common electrode coupled to a second terminal of the storage capacitor; and a driver circuit electrically connected to the first common electrode, the second common electrode, and a transistor associated with the display pixel electrode, wherein the driver circuit is capable of applying one or more time-dependent voltages between the first common electrode and the display pixel electrode via the transistor to apply a waveform drive sequence to the display pixel, and wherein the driver circuit is configured to, after the waveform drive sequence, discharge the storage capacitor via the second common electrode to discharge the display pixel electrode by applying a constant voltage set to zero volts to the second common electrode while the display pixel electrode and the first common electrode are in a floating state.

2. The electro-optical display according to claim 1, wherein the driver circuit is configured to separately control the first common electrode and the second common electrode to a zero-volt bias voltage or a floating state.

3. The electro-optical display according to claim 1, wherein the driver circuit is configured to connect the storage capacitor and the layer of the electrophoretic display medium together to a constant voltage during the waveform drive sequence.

4. The electro-optical display according to claim 1, wherein the driver circuit is configured to place the first common electrode in a floating state after the waveform drive sequence.

5. The electro-optical display according to claim 1, wherein the driver circuit is configured to set the second common electrode to zero volts after the waveform drive sequence.

6. The electro-optical display according to claim 1, wherein the second common electrode includes a V COM line signal.

7. The electro-optical display according to claim 1, wherein the driver circuit is configured to place the first common electrode in a floating state one frame after the display pixel electrode after the waveform drive sequence.

8. The electro-optical display according to claim 1, wherein the driver circuit is further configured to place the first common electrode in a floating state one frame before the display pixel electrode after the waveform drive sequence.

9. An electro-optical display, comprising: an electrophoretic display medium disposed between a first common electrode and a display pixel electrode associated with a display pixel; a storage capacitor, the display pixel electrode being coupled to a first terminal of the storage capacitor; a second common electrode coupled to a second terminal of the storage capacitor; and a driver circuit electrically connected to the first common electrode, the second common electrode, and a transistor associated with the display pixel electrode, the driver circuit being capable of applying a waveform sequence to the display pixel by applying one or more time-dependent voltages between the first common electrode and the display pixel electrode via the transistor, the driver circuit being configured to: Apply a waveform sequence to the display pixel electrode to provide a driving voltage to the electrophoretic display medium between the display pixel electrode and the first common electrode. Apply a first bias voltage to the second common electrode during the waveform sequence. After completing the applied waveform sequence, maintain the last frame voltage level on the display pixel electrode by placing the display pixel electrode and the first common electrode in a floating state, and Discharge the last frame voltage level on the display pixel electrode by discharging the storage capacitor through the second common electrode, wherein during the discharge, the first bias voltage applied to the second common electrode is a constant voltage set to zero volts.

10. The electro-optic display according to claim 9, wherein the driver circuit is further configured to connect the storage capacitor and the layer of the electrophoretic display medium together to a constant voltage during the waveform sequence.

11. The electro-optical display according to claim 9, wherein the second common electrode includes a V COM line signal.

12. The electro-optic display according to claim 9, wherein the driver circuit is further configured to place the first common electrode in a floating state one frame after the display pixel electrode when maintaining the last frame voltage level on the display pixel electrode.

13. The electro-optic display according to claim 9, wherein the driver circuit is further configured to place the first common electrode in a floating state one frame before the display pixel electrode when maintaining the last frame voltage level on the display pixel electrode.

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