JP6818915B2 - A driver that provides a DC balanced refresh sequence for a color electrophoresis display - Google Patents

Description

(Related application)
The present application claims priority to US Provisional Application Nos. 15 / 454,276 filed on March 9, 2017 and US Provisional Application Nos. 62 / 509,512 filed on May 22, 2017. It is a thing. The contents of the above application are incorporated herein by reference.

The present invention uses an electro-optical display, particularly a single layer of electrophoretic material, comprising a plurality of colored particles, such as white, cyan, yellow, and magenta particles, although not exclusively. A method for driving an electrophoretic display capable of rendering more colors than two particles are positively charged, two particles are negatively charged, one positively charged particle and one. One negatively charged particle relates to a method having a thick polymer shell.

The term "color" includes black and white as used herein. White particles are often of the light scattering type.

The term "gray state", as used herein in its conventional sense in imaging techniques, refers to a state intermediate between the extreme optical states of two pixels, not necessarily black-white between these two extreme states. It does not imply a transition. For example, several E Ink patents and published applications referenced below describe electrophoretic displays in which the extreme states are white and dark blue, so that the intermediate gray state would actually be light blue. doing. In fact, as already mentioned, the change in optical state may not be a change in color at all. The terms "black and white" can be used herein to refer to the two extreme optical states of a display and are usually not strictly black and white, such as the aforementioned white and white. It should be understood as including a dark blue state.

The terms "bi-stability" and "bi-stability", in their conventional sense in the art, include at least one display element having different first and second display states with different optical properties, the first or of which. A finite duration addressing pulse is used to drive any given element to exhibit any of the second display states, and then change the state of the display element after the addressing pulse ends. As used herein to refer to a display that will last at least several times, for example, at least four times, the minimum duration of the addressing pulse required to cause it. Some grayscale-enabled particle-based electrophoretic displays are 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 optics. It is shown in US Pat. No. 7,170,670 that this applies to optical displays. This type of display is appropriately referred to as "multi-stability" rather than "bi-stability", but for convenience the term "bi-stability" is used herein as a bis-stable and multi-stable display. Can be used to cover both.

The term "impulse", when used to refer to the drive of an electrophoretic display, is used herein to refer to the integral of the applied voltage with respect to the time between periods during which the display is driven. ..

Particles that absorb, scatter, or reflect light at either the wide band or at selected wavelengths are referred to herein as colored or pigmented particles. Various materials other than pigments (in the strict sense of the term as to mean insoluble colored materials) that absorb or reflect light, such as dyes or photonic crystals, are also used in the electrophoresis media and displays of the invention. May be used.

Particle-based electrophoretic displays have been the subject of intense research and development for many years. In such displays, multiple charged particles (sometimes also referred to as pigment particles) move through the fluid under the influence of an electric field. Electrophoretic displays can have the attributes of good brightness and contrast, wide viewing angle, state bistability, and low power consumption when compared to liquid crystal displays. Nonetheless, the long-term image quality problems of these displays hinder their widespread use. For example, the particles that make up an electrophoretic display tend to settle, resulting in an inadequate useful life for these displays.

As mentioned above, the electrophoretic medium requires the presence of fluid. In most prior art electrophoresis media, the fluid is a liquid, but the electrophoresis medium can also be produced using gaseous fluids. For example, Kitamura, T.M. , Et al. , Electrical toner movement for electronics paper-like display, IDW Japan, 2001, Paper HCS1-1, and Yamaguchi, Y. et al. , Et al. , Toner display using particles charged triboelectrically, IDW Japan, 2001, Paper AMD4-4. See also U.S. Pat. Nos. 7,321,459 and 7,236,291. Such gas-based electrophoresis media are liquid-based due to particle settling when the medium is used in an orientation that allows such settling, for example, signs in which the medium is placed in a vertical plane. It is considered to be susceptible to the same type of problems as the electrophoresis medium. In fact, particle settling is liquid-based in gas-based electrophoresis media because the lower viscosity of the gaseous suspended fluid allows faster settling of electrophoretic particles compared to that of liquid. It is considered to be a more serious problem.

Numerous patents and applications, transferred to or in the name of Massachusetts Institute of Technology (MIT) and E Ink Corporation, are various techniques used within encapsulated electrophoresis and other electro-optical media. Is explained. Such an encapsulated medium comprises a large number of small capsules, each of which comprises an internal phase containing electrophoretic movable particles in the fluid medium and a capsule wall surrounding the internal phase. Typically, the capsule itself forms a coherent layer that is retained within the polymer binder and is located between the two electrodes. Techniques described in these patents and applications include:
(A) Electrophoretic particles, fluids, and fluid additives (see, eg, US Pat. Nos. 7,002,728 and 7,679,814).
(B) Capsules, binders, and encapsulation processes (see, eg, US Pat. Nos. 6,922,276 and 7,411,719).
(C) Microcell structures, wall materials, and methods of forming microcells (see, eg, US Pat. Nos. 7,072,095 and 9,279,906).
(D) Methods for filling and sealing microcells (see, eg, US Pat. Nos. 7,144,942 and 7,715,088).
(E) Films and subassemblies containing electro-optic materials (see, eg, US Pat. Nos. 6,982,178 and 7,839,564).
(F) Methods used in backplanes, adhesive layers, and other auxiliary layers, and displays (see, eg, US Pat. Nos. 7,116,318 and 7,535,624).
(G) Color formation and color adjustment (eg,
reference)
(H) Method for driving the display (eg,
(See No.) (These patents and applications may now be referred to as MEDEOD (methods for driving electro-optic displays) applications).
(I) Display applications (see, eg, US Pat. Nos. 7,312,784 and 8,009,348).
(J) Non-electrophoretic displays (see, eg, US Pat. No. 6,241,921 and US Patent Application Publication No. 2015/0277160 and US Patent Application Publication Nos. 2015/0005720 and 2016/0012710).

In many of the aforementioned patents and applications, the wall surrounding the discrete microcapsules within the encapsulated electrophoresis medium is replaced with a continuous phase, thus the electrophoresis medium with multiple discrete droplets of the electrophoresis fluid. So-called polymer-dispersed electrophoretic displays can be produced that include a continuous phase of polymer material, and discrete droplets of electrophoretic fluid within such a polymer-dispersed electrophoretic display can be individually individual in any discrete capsule membrane. Recognize that it can be considered a capsule or microcapsule, even though it is not associated with a droplet. See, for example, US Pat. No. 6,866,760. Therefore, for the purposes of the present application, such polymer-dispersed electrophoresis media are considered variants of the encapsulated electrophoresis medium.

A related type of electrophoresis display is the so-called "microcell electrophoresis display". In microcell electrophoretic displays, charged particles and fluids are not encapsulated within microcapsules, but instead are kept within a propagation medium, typically multiple cavities formed within a polymer film. For example, both are Shipix Imaging, Inc. See U.S. Pat. Nos. 6,672,921 and 6,788,449, assigned to.

Electrophoretic media are often opaque (eg, in many electrophoretic media, because the particles substantially block the transmission of visible light through the display), but many can operate in reflective mode. An electrophoretic display can be made to operate in a so-called "shutter mode" in which one display state is substantially opaque and one is light transmissive. For example, U.S. Pat. Nos. 5,872,552, 6,130,774, 6,144,361, 6,172,798, 6,271,823, 6,225,971. See No. 6,184,856. Dielectrophoretic displays are similar to electrophoretic displays, but rely on fluctuations in electric field strength and can operate in similar modes. See U.S. Pat. No. 4,418,346. Other types of electro-optical displays may also be able to operate in shutter mode. Electro-optic media operating in shutter mode can be used in a multi-layer structure for full color displays. In such a structure, at least one layer adjacent to the visible surface of the display operates in shutter mode to expose or conceal a second layer further away from the visible surface.

Encapsulated electrophoresis displays typically print or coat the display on a variety of flexible and rigid substrates without suffering from the clustering and sedimentation failure modes of conventional electrophoresis devices. Provides additional benefits such as capabilities. (The use of the term "printing" is not limited, but pre-weighing coatings such as patch die coatings, slot or extrusion coatings, slide or cascade coatings, curtain coatings, etc., roll coatings such as knife overroll coatings, forwards.・ Reverse roll coating, gravure coating, immersion coating, spray coating, meniscus coating, spin coating, brush coating, air knife coating, silk screen printing process, electrostatic printing process, thermal printing process, inkjet printing process, electrophoresis precipitation (US Patent No. 1) It is intended to include all forms of printing and coating, including 7,339,715), and other similar techniques.) Therefore, the resulting display can be flexible. Moreover, since the display medium can be printed (using various methods), the display itself can be inexpensively made.

As mentioned above, the simplest prior art electrophoresis media essentially display only two colors. Such an electrophoresis medium is a single type of electrophoresis particle having a first color in a colored fluid having a second different color, in which case the first color is that the particles are adjacent to the visible surface of the display. The first and second types have different first and second colors in the uncolored fluid), or the second color is displayed when the particles are separated from the visible surface). (In which case, the first color is displayed when the first type of particles are adjacent to the visible surface of the display, and the second color is the second type of particles on the visible surface. (Displayed when adjacent to) is used. Typically, the two colors are black and white. If a full color display is desired, a color filter array may be deposited over the visible surface of the monochrome (black and white) display. Displays with color filter arrays rely on area sharing and color hybrids to create color stimuli. The available display area is shared among 3 or 4 primary colors such as red / green / blue (RGB) or red / green / blue / white (RGBW), and the filter is one-dimensional (striped) or two-dimensional (2). × 2) Can be arranged in a repeating pattern. Other selections of primary colors or more than three primary colors are also known in the art. Three (for RGB displays) or four (for RGBW displays) subpixels become a single pixel, both visually with uniform color stimuli (“color mixing”) at the intended viewing distance. Selected to be small enough to be mixed. The inherent disadvantage of area sharing is that colorants are always present and the colors are only modulated by switching the corresponding pixels of the underlying monochrome display to white or black (turning the corresponding primary colors on or off). Is what you can do. For example, in an ideal RGBW display, the red, green, blue, and white primary colors each occupy a quarter of the display area (one of the four subpixels), with the white subpixels of the underlying monochrome display. As bright as white, but each tinted subpixel is less bright than one-third of the white of a monochrome display. The overall white brightness indicated by the display cannot exceed half the brightness of the white subpixels (the white area of the display is the white subpixel in addition to the white subpixel of each of the four). It is produced by displaying each colored subpixel in its colored form, which is comparable to one-third of a pixel, and therefore the three colored subpixels combined do not contribute more than one white subpixel). Color brightness and saturation are reduced by area sharing with color pixels that can be switched to black. Area sharing is especially problematic when mixing yellows, as brighter than any other color of equal brightness, saturated yellows are about as bright as whites. Switching from blue pixels (a quarter of the display area) to black makes yellow significantly darker.

Multilayer stacking electrophoresis displays are known in the art. For example, J. Heikenfeld, P.M. Drzaic, JS Yeo and T.M. Koch, Journal of the SID, 19 (2), 2011, pp. See 129-156. In such displays, ambient light passes through the images in each of the three subtractive primary colors, just as in traditional color printing. U.S. Pat. No. 6,727,873 describes a stack-type electrophoresis display in which three layers of switchable cells are placed over a reflective background. Similar displays are also known in which the colored particles are moved laterally (see International Application WO2008 / 065605) or sequestered into microcells using a combination of vertical and lateral motion. .. In both cases, each layer requires a thin film transistor (TFT) layer (two of the three layers of the TFT must be substantially transparent) and a light transmissive counter electrode, each of which is a thin film transistor (TFT). As such, electrodes are provided that serve to concentrate or disperse the colored particles pixel by pixel. Electrodes with such a complex array are costly to manufacture and are sufficiently transparent for pixel electrodes, as currently state-of-the-art technology requires that the white state of the display be visible through several layers of the electrode, in particular. It is difficult to provide a plane. Multilayer displays also suffer from parallax problems as the thickness of the display stack approaches or exceeds the pixel size.

US Application Publication Nos. 2012/0008188 and 2012/0134009 provide a multicolor electrophoretic display with a single backplane with independently addressable pixel electrodes and a common light transmissive front electrode. Explaining. A plurality of electrophoresis layers are arranged between the backplane and the front electrode. The displays described in these applications are capable of rendering any of the primary colors (red, green, blue, cyan, magenta, yellow, white, and black) at any pixel location. However, there is the disadvantage of using multiple electrophoresis layers located between a single set of addressing electrodes. The electric field exerted by the particles in a particular layer is lower than that would be the case for a single electrophoretic layer addressed at the same voltage. In addition, optical loss in the electrophoresis layer closest to the visible surface (eg, caused by light scattering or undesired absorption) can affect the appearance of the image formed within the underlying electrophoresis layer.

Attempts have been made to provide a full-color electrophoretic display using a single electrophoretic layer. For example, US Patent Application Publication No. 2013/0208338 comprises an electrophoretic fluid comprising one or two types of pigment particles dispersed in a clear, colorless or colored solvent, wherein the electrophoretic fluid is a plurality of common electrodes. Describes a color display that is placed between the pixels or the drive electrodes. The drive electrodes are arranged to expose the background layer. U.S. Patent Application Publication No. 2014/0177031 describes a method for driving a display cell, which is filled with an electrophoretic fluid containing two types of charged particles that have opposite charge polarities and are two contrast colors. doing. The two types of pigment particles are dispersed in a coloring solvent or a solvent with uncharged or weakly charged colored particles dispersed therein. The method comprises the step of driving the display cell by applying a drive voltage which is about 1 to about 20% of the total drive voltage to display the color of the solvent or the color of the uncharged or weakly charged colored particles. U.S. Patent Application Publication Nos. 2014/0092465 and 2014/0092466 describe electrophoretic fluids and methods for driving electrophoretic displays. The fluid comprises first, second, and third types of pigment particles, all of which are dispersed in a solvent or solvent mixture. The first and second types of pigment particles have opposite charge polarities, and the third type of pigment particles have a charge level that is less than about 50% of the charge level of the first or second type. The three types of pigment particles have different levels of threshold voltage, or different levels of mobility, or both. Neither of these patent applications discloses a full-color display in the sense that the term is used below.

US Patent Application Publication No. 2007/0031031 is an image for processing image data to display an image on a display medium, where each pixel can display white, black, and one other color. Describes the processing device. U.S. Patent Application Publication Nos. 2008/0151355, 2010/0188732, and 2011/0279885 describe color displays in which moving particles move through a porous structure. U.S. Patent Application Publication Nos. 2008/0303779 and 2010/0020384 describe display media comprising first, second, and third particles of different colors. The first and second particles can form aggregates, and the smaller third particles can move through the openings left between the agglomerated first and second particles. U.S. Patent Application Publication No. 2011/0134506 describes a display device, which is an electrophoretic display element comprising a plurality of types of particles encapsulated between a pair of substrates. At least one of them is translucent, each of the individual types of particles is charged with the same polarity, has different optical properties, differs in either the transition rate and / or the electric field threshold for movement, and is semi-transparent. The transparent display side electrode is provided on the substrate side on which the translucent substrate is arranged, the first back side electrode is provided on the side of the other substrate, faces the display side electrode, and the second back side electrode is the other. An electrophoresis display element and a voltage control section provided on the side of the substrate and facing the display side electrode, wherein the voltage control section is a type of particle having the fastest transition rate from a plurality of types of particles. Alternatively, the type of particle having the lowest threshold from multiple types of particles is moved in the sequence by each of the different types of particles to the first backside electrode or the second backside electrode, and then the first backside. It includes a voltage control section that controls the voltage applied to the display side electrode, the first back side electrode, and the second back side electrode so that the particles moved to the electrode are moved to the display side electrode. U.S. Patent Application Publication Nos. 2011/0175939, 2011/0298835, 2012/0327504, and 2012/0139966 describe color displays that rely on the aggregation and threshold voltage of multiple particles. US Patent Application Publication No. 2013/0222884 describes colored particles containing a charged group-containing polymer and a colorant, and at least selected from a group of reactive monomers and specific monomers as copolymerization components attached to the colored particles. Described are electrophoretic particles containing a branched silicone-based polymer containing one monomer. US Patent Application Publication No. 2013/0222885 has a dispersion medium, a group of colored electrophoretic particles dispersed in the dispersion medium and migrated under an electric field, and a group of colored electrophoresis particles that do not migrate and have a different color from that of the group of electrophoresis particles. , A group of non-electrophoretic particles and a compound having a neutral polar group and a hydrophobic group contained in the dispersion medium at a ratio of about 0.01 to about 1% by mass based on the entire dispersed liquid. Describes dispersion liquids for electrophoretic displays. U.S. Patent Application Publication No. ^{2013/0222886, 7.95 (J / cm 3} ) involves the difference in ^half or more soluble parameter, coloring agent and a hydrophilic resin, and the core particles, the core particles of each Describes a dispersion liquid for a display that covers a surface, contains a hydrophobic resin, contains a shell, contains floating particles. U.S. Patent Application Publication Nos. 2013/0222887 and 2013/0222888 describe electrophoretic particles having a defined chemical composition. Finally, US Patent Application Publication No. 2014/010467 includes first and second colored particles that move in response to an electric field and a dispersion medium, where the second colored particles are the first colored particles. It has a larger diameter and the same charge characteristics as the charge characteristics of the first colored particles, and the ratio of the charge amount Cs of the first colored particles to the charge amount Cl of the second colored particles per unit area of the display (Cs / Describes particle dispersion where Cl) is less than or equal to 5. Some of the aforementioned displays offer full color, but at the expense of requiring a time-consuming and cumbersome addressing method.

U.S. Patent Application Publication Nos. 2012/0314273 and 2014/0002888 contain a plurality of first and second electrophoretic particles contained within an insulating liquid, wherein the first and second particles are different from each other. Described an electrophoretic device having different charge properties, the device further comprises a porous layer contained in an insulating liquid and formed from a fibrous structure. These patent applications are not full-color displays in the sense that the term is used below.

See also U.S. Patent Application Publication No. 2011/0134506 and the aforementioned Application Nos. 14 / 277,107. The latter describes a full-color display that uses three different types of particles in the colored fluid, but the presence of the colored fluid limits the quality of the white state that can be achieved by the display.

To obtain a high resolution display, the individual pixels of the display must be addressable without interference from adjacent pixels. One way to achieve this goal is to provide an array of non-linear elements, such as transistors or diodes, with at least one non-linear element associated with each pixel to produce an "active matrix" display. Is. Addressing or pixel electrodes, which address one pixel, are connected to the appropriate voltage source through the associated non-linear elements. Typically, when the non-linear element is a transistor, the pixel electrode is connected to the drain of the transistor, and this arrangement is, as will be assumed in the description below, being arbitrary in nature. Pixel electrodes can also be connected to the source of the transistor. Traditionally, in high resolution arrays, pixels are arranged in a two-dimensional array of rows and columns such that any concrete pixel is uniquely defined by the intersection of one defined row and one defined column. Will be done. The source of all transistors in each column is connected to a single row electrode, while the gates of all transistors in each row are connected to a single row electrode. Again, the allocation of sources to rows and gates to columns is conventional, but is inherently arbitrary and can be reversed if desired. The row electrode is connected to the row driver, which essentially means that only one row is selected at any given moment, i.e. all transistors in the selected row are conductive. While a selective voltage is applied to the selected row electrodes to ensure that all transistors in these non-selected rows remain non-conducting, the non-selective voltage is applied. Ensure that it is applied to all other rows. A column electrode is connected to a column driver, which applies a voltage selected on the various column electrodes to drive the pixels in the selected row to their desired optical state. (The voltage described above is for a common front electrode that is traditionally provided on the opposite side of the non-linear array of electro-optic media and extends across the entire display.) Preliminary known as "line address time". After the interval selected to, the selected row is deselected, the next row is selected, and the voltage on the column driver is changed so that the next line of the display is written. The process is repeated so that the entire display is written in a line-by-line format.

Traditionally, each pixel electrode has a capacitor electrode associated with it so that the pixel electrode and the capacitor electrode form a capacitor. See, for example, International Patent Application No. WO 01/07961. In some embodiments, an N-type semiconductor (eg, amorphous silicon) may be used to form the transistor, with the "selective" and "non-selective" voltages applied to the gate electrodes, respectively. Can be positive and negative.

FIG. 1 of the accompanying drawing depicts an exemplary equivalent circuit of a single pixel in an electrophoretic display. As shown, the circuit includes a capacitor 10 formed between a pixel electrode and a capacitor electrode. The electrophoresis medium 20 is represented as a parallel capacitor and resistor. In some instances, the direct or indirect coupling capacitance 30 (usually referred to as "parasitic capacitance") between the gate electrode and the pixel electrode of the transistor associated with the pixel causes unwanted noise. Can bring to the display. Generally, the parasitic capacitance 30 is much smaller than that of the storage capacitor 10, and when the pixel row of the display is selected or deselected, the parasitic capacitance 30 is also known as the "kickback voltage". A slight negative offset voltage can be brought to the pixel electrode, which is usually less than 2 volts. In some embodiments, when V _com is set to a value equal to the kickback voltage ( _VKB ) to compensate for the undesired "kickback voltage", all voltages supplied to the display are identical. the amount by an offset, as a net DC nonequilibrium can not incurred, the common potential V _com may be supplied to the top plane electrode and the capacitor electrode associated with each pixel.

However, problems can arise when V _com is set to a voltage that is not compensated for the kickback voltage. This can occur when it is desired to apply a higher voltage to the display than is available from the backplane alone. For example, the maximum voltage applied to the display can be doubled if the backplane is supplied with a selection of, for example, nominal + V, 0, or -V, while the V _com is supplied with -V. Good things are well known in the art. The maximum voltage applied in this case is + 2V (ie, in the backplane relative to the top plane), while the minimum voltage is zero. If a negative voltage is required, the V _com potential must be raised to at least zero. The waveform used to address the display with positive and negative voltages using topplane switching must therefore have a specific frame allocated to each of the more than one V _com voltage setting. Must be.

A set of waveforms for driving a color electrophoresis display with four particles is described in US Application No. 14 / 849,658 (incorporated herein by reference). In US Application No. 14 / 849,658, seven different voltages are applied to the pixel electrodes, i.e. three positives, three negatives, and zero. However, in some embodiments, the maximum voltage used in these waveforms is higher than that can be handled by an amorphous silicon thin film transistor. In such cases, a suitable high voltage can be obtained by using top plane switching. A separate power source may be used when the V _com is systematically set to the V _KB (as described above). However, when topplane switching is used, it is costly and inconvenient to use as many separate power sources as the _Vcom settings. In addition, top plane switching is known to increase kickback, thereby degrading color state stability. Therefore, there is a need for a method of compensating for the DC offset caused by the kickback voltage using the same power source for the backplane and _Vcom . Of course, a full DC offset results in a longer impulse sequence and therefore a longer image refresh.

The present invention involves a driver configured to deliver a two-part reset pulse to a pixel in a color electrophoresis display. The two-part reset pulse is effective in removing the last state information, but does not require more energy or time than required. As a result, the controller described allows 3 (or more) particle electrophoretic displays to be updated faster while using less energy. Surprisingly, the controller also provides a larger color gamut when the reset pulse is tuned to the individual colors. The present invention also provides a method of driving an electro-optical display that is DC balanced regardless of the presence of a kickback voltage and changes in the voltage applied to the front electrodes.

In one aspect, the present invention is a display medium located between a front electrode, a backplane, and a front electrode and a backplane, comprising a set of three differently colored particles. Accompanied by a method for driving an electrophoretic display having and. The method includes applying a reset phase and a color transition phase to the display. The reset phase has a first polarity, a first amplitude as a function of time, and a first duration, the step of applying a first signal to the front electrode and a first opposite to the first polarity. A step of applying a second signal on the backplane for a first duration, with a second polarity, a second amplitude as a function of time, and a second polarity opposite to the first polarity. A fourth signal, which has a third amplitude as a function of time, is equal to the sum of the first and second amplitudes of the step of applying a third signal on the front electrode for a second duration. Includes a step of applying the signal onto the backplane for a second duration. The color transition phase applies a fifth signal onto the front electrodes, which has a second polarity, a fourth amplitude as a function of time, and a third duration following the first and second durations. A sixth signal is applied onto the backplane, having a first polarity, a fifth amplitude as a function of time, and a fourth duration following the first and second durations. The sum of the first and second amplitudes as a function of time integrated over the first duration, including steps, and the first, second, as a function of time integrated over the second duration. And the sum of the third amplitude, and the fourth amplitude as a function of time integrated over the third duration, and the fifth amplitude as a function of time integrated over the fourth duration are reset. It produces an amplitude offset designed to maintain DC equilibrium on the display medium across the phase and color transition phases. In some embodiments, the reset phase erases the optical properties before being rendered on the display. In some embodiments, the color transition phase substantially alters the optical properties displayed by the display. In some embodiments, the first polarity is a negative voltage. In some embodiments, the first polarity is a positive voltage. In some embodiments, the impulse offset is proportional to the kickback voltage applied by the display medium. In some embodiments, the fourth duration occurs during the third duration. In some embodiments, the third duration and the fourth duration start at the same time.

In another aspect, the present invention is a display medium located between a front electrode, a backplane, and a front electrode and a backplane, comprising a set of three differently colored particles. Includes a method for driving an electrophoretic display with a medium, the method comprising applying a reset phase and a color transition phase to the display. The reset phase has a first polarity, a first amplitude as a function of time, and a first duration, a step of applying a first signal onto the front electrode, and a first duration of the signal. A second signal with a step not applied on the backplane for time and a second polarity opposite to the first polarity, a second amplitude as a function of time, for a second duration. A step of applying a third signal on the backplane for a second duration, with a step of applying on the front electrode and a step of applying a third signal having a third amplitude as a function of the first polarity and time. Including. The color transition phase applies a fourth signal onto the front electrodes, which has a first polarity, a fourth amplitude as a function of time, and a third duration following the first and second durations. A fifth signal is applied onto the backplane, having a second polarity, a fifth amplitude as a function of time, and a fourth duration following the first and second durations. The sum of the first amplitudes as a function of time integrated over the first duration, and the sum of the second and third amplitudes as a function of time integrated over the second duration, including the step. , And a fourth amplitude as a function of time integrated over a third duration, and a fifth amplitude as a function of time integrated over a fourth duration are displayed across the reset phase and the color transition phase. Produces an amplitude offset designed to maintain DC equilibrium on the medium. In some embodiments, the reset phase erases the optical properties before being rendered on the display. In some embodiments, the color transition phase substantially alters the optical properties displayed by the display. In some embodiments, the first polarity is a negative voltage. In some embodiments, the first polarity is a positive voltage. In some embodiments, the impulse offset is proportional to the kickback voltage applied by the display medium. In some embodiments, the fourth duration occurs during the third duration. In some embodiments, the third duration and the fourth duration start at the same time.

In another aspect, the present invention is a display medium located between a front electrode, a back plane, and a front electrode and a back plane, comprising a set of three differently colored particles. Includes a controller for an electrophoretic display with a medium, the controller is operably coupled to the front electrodes and back plane and configured to apply a reset phase and a color transition phase to the display. The reset phase has a first polarity, a first amplitude as a function of time, and a first duration, the step of applying a first signal onto the front electrode and the opposite of the first polarity. A step of applying a second signal on the backplane for a first duration, with a second polarity, a second amplitude as a function of time, and a second opposite to the first polarity. A fourth, equal to the sum of the first and second amplitudes, with the step of applying a third signal on the front electrode for a second duration, having a third amplitude as a function of polarity, time. Includes a step of applying the signal of the above on the backplane for a second duration. The color transition phase applies a fifth signal onto the front electrodes, which has a second polarity, a fourth amplitude as a function of time, and a third duration following the first and second durations. A sixth signal is applied onto the backplane, having a first polarity, a fifth amplitude as a function of time, and a fourth duration following the first and second durations. The sum of the first and second amplitudes as a function of time integrated over the first duration, including steps, and the first, second, as a function of time integrated over the second duration. And the sum of the third amplitude, and the fourth amplitude as a function of time integrated over the third duration, and the fifth amplitude as a function of time integrated over the fourth duration are reset. It produces an amplitude offset designed to maintain DC equilibrium on the display medium across the phase and color transition phases. In some embodiments, the controller applies different reset phases, depending on the color to be displayed by the electrophoretic display. In some embodiments, the display medium comprises white, cyan, yellow, and magenta particles. In some embodiments, the display medium comprises white, red, blue, and green particles.

In another aspect, the present invention is a display medium located between a front electrode, a back plane, and a front electrode and a back plane, comprising a set of three differently colored particles. Includes a controller for an electrophoretic display with a medium, the controller is operably coupled to the front electrodes and back plane and configured to apply a reset phase and a color transition phase to the display. The reset phase has a first polarity, a first amplitude as a function of time, and a first duration, a step of applying a first signal onto the front electrode, and a first duration of the signal. A second signal with a step not applied on the backplane for time and a second polarity opposite to the first polarity, a second amplitude as a function of time, for a second duration. A step of applying a third signal on the backplane for a second duration, with a step of applying on the front electrode and a step of applying a third signal having a third amplitude as a function of the first polarity and time. Including. The color transition phase applies a fourth signal onto the front electrodes, which has a first polarity, a fourth amplitude as a function of time, and a third duration following the first and second durations. A fifth signal is applied onto the backplane, having a second polarity, a fifth amplitude as a function of time, and a fourth duration following the first and second durations. The sum of the first amplitudes as a function of time integrated over the first duration, and the sum of the second and third amplitudes as a function of time integrated over the second duration, including the step. , And a fourth amplitude as a function of time integrated over a third duration, and a fifth amplitude as a function of time integrated over a fourth duration are displayed across the reset phase and the color transition phase. Produces an amplitude offset designed to maintain DC equilibrium on the medium. In some embodiments, the controller applies different reset phases, depending on the color to be displayed by the electrophoretic display. In some embodiments, the display medium comprises white, cyan, yellow, and magenta particles. In some embodiments, the display medium comprises white, red, blue, and green particles.

The electrophoresis medium used in the display of the present invention may be any of those described in the above-mentioned application No. 14 / 849,658. Such media typically comprises white, light-scattering particles and three substantially non-light-scattering particles. The electrophoresis medium of the present invention may be in any of the above-mentioned forms. Thus, the electrophoresis medium may be in the form of unencapsulated, discrete capsules enclosed by a capsule wall, or polymer-dispersed or microcell medium.
The present specification also provides, for example, the following items.
(Item 1)
A method for driving an electrophoretic display having a front electrode, a backplane, and a display medium located between the front electrode and the backplane, wherein the display medium is colored in three different ways. The method comprises a set of particles.
Applying a reset phase and a color transition phase to the display.
The reset phase is
Applying a first signal with a first polarity, a first amplitude as a function of time, and a first duration onto the front electrode,
Applying a second signal having a second polarity opposite to the first polarity, a second amplitude as a function of time, onto the backplane during the first duration.
Applying a third signal having a second polarity opposite to the first polarity, a third amplitude as a function of time, over the front electrode for a second duration,
Applying a fourth signal equal to the sum of the first and second amplitudes onto the backplane for the second duration.
Including
The color transition phase is
Applying a fifth signal having the second polarity, the fourth amplitude as a function of time, and the third duration following the first and second durations is applied onto the front electrode. ,
Applying a sixth signal on the backplane with the first polarity, the fifth amplitude as a function of time, and the fourth duration following the first and second durations. ,
Including
Including
The sum of the first and second amplitudes as a function of time integrated over the first duration, and the first, second, and as a function of time integrated over the second duration. The sum of the third amplitudes, the fourth amplitude as a function of time integrated over the third duration, and the fifth amplitude as a function of time integrated over the fourth duration. To produce an amplitude offset designed to maintain DC equilibrium on the display medium over the reset phase and the color transition phase.
(Item 2)
The method of item 1, wherein the reset phase erases optical properties before being rendered on the display.
(Item 3)
The method of item 1, wherein the color transition phase substantially alters the optical properties displayed by the display.
(Item 4)
The method according to item 1, wherein the first polarity is a negative voltage.
(Item 5)
The method according to item 1, wherein the first polarity is a positive voltage.
(Item 6)
The method of item 1, wherein the impulse offset is proportional to the kickback voltage applied by the display medium.
(Item 7)
The method of item 1, wherein the fourth duration occurs during the third duration.
(Item 8)
7. The method of item 7, wherein the third duration and the fourth duration start simultaneously.
(Item 9)
A method for driving an electrophoretic display having a front electrode, a backplane, and a display medium located between the front electrode and the backplane, wherein the display medium is colored in three different ways. The method comprises a set of particles.
Applying a reset phase and a color transition phase to the display.
The reset phase is
Applying a first signal with a first polarity, a first amplitude as a function of time, and a first duration onto the front electrode,
No signal is applied onto the backplane during the first duration and
Applying a second signal having a second polarity opposite to the first polarity, a second amplitude as a function of time, over the front electrode for a second duration,
Applying a third signal with a third amplitude as a function of the first polarity and time onto the backplane during the second duration.
Including
The color transition phase is
Applying a fourth signal having the first polarity, the fourth amplitude as a function of time, and the third duration following the first and second durations is applied onto the front electrode. ,
Applying a fifth signal on the backplane with the second polarity, the fifth amplitude as a function of time, and the fourth duration following the first and second durations.
Including
Including
The sum of the first amplitudes as a function of time integrated over the first duration, and the sum of the second and third amplitudes as a function of time integrated over the second duration, And the fourth amplitude as a function of time integrated over the third duration, and the fifth amplitude as a function of time integrated over the fourth duration are the reset phase and said. A method of producing an amplitude offset designed to maintain DC equilibrium on the display medium over the color transition phase.
(Item 10)
9. The method of item 9, wherein the fourth duration occurs during the third duration.
(Item 11)
10. The method of item 10, wherein the third duration and the fourth duration start simultaneously.
(Item 12)
A controller for an electrophoretic display comprising a front electrode, a backplane, and a display medium located between the front electrode and the backplane, the display medium being colored in three different ways. The controller is operably coupled to the front electrode and the backplane and is configured to apply a reset phase and a color transition phase to the display.
The reset phase is
Applying a first signal with a first polarity, a first amplitude as a function of time, and a first duration onto the front electrode,
Applying a second signal with a second polarity opposite to the first polarity, a second amplitude as a function of time, onto the backplane during the first duration.
Applying a third signal having a second polarity opposite to the first polarity, a third amplitude as a function of time, over the front electrode for a second duration,
Applying a fourth signal equal to the sum of the first and second amplitudes onto the backplane for the second duration.
Including
The color transition phase is
Applying a fifth signal having the second polarity, the fourth amplitude as a function of time, and the third duration following the first and second durations is applied onto the front electrode. ,
Applying a sixth signal on the backplane with the first polarity, the fifth amplitude as a function of time, and the fourth duration following the first and second durations.
Including
The sum of the first and second amplitudes as a function of time integrated over the first duration, and the first, second, and as a function of time integrated over the second duration. The sum of the third amplitudes, the fourth amplitude as a function of time integrated over the third duration, and the fifth amplitude as a function of time integrated over the fourth duration. Is a controller that produces an amplitude offset designed to maintain DC equilibrium on the display medium over the reset phase and the color transition phase.
(Item 13)
The controller according to item 12, wherein the controller applies different reset phases depending on the color to be displayed by the electrophoresis display.
(Item 14)
12. The controller of item 12, wherein the display medium comprises white, cyan, yellow, and magenta particles.
(Item 15)
12. The controller of item 12, wherein the display medium comprises white, red, blue, and green particles.
(Item 16)
A controller for an electrophoretic display comprising a front electrode, a backplane, and a display medium located between the front electrode and the backplane, the display medium being colored in three different ways. With a set of particles, the controller is operably coupled to the front electrode and the backplane and configured to apply a reset phase and a color transition phase to the display.
The reset phase is
The reset phase and the color transition phase are applied to the display, and the reset phase is
Applying a first signal with a first polarity, a first amplitude as a function of time, and a first duration onto the front electrode,
No signal is applied onto the backplane during the first duration and
Applying a second signal having a second polarity opposite to the first polarity, a second amplitude as a function of time, over the front electrode for a second duration,
Applying a third signal with a third amplitude as a function of the first polarity and time onto the backplane during the second duration.
Including
The color transition phase is
Applying a fourth signal having the first polarity, the fourth amplitude as a function of time, and the third duration following the first and second durations is applied onto the front electrode. ,
Applying a fifth signal on the backplane with the second polarity, the fifth amplitude as a function of time, and the fourth duration following the first and second durations.
Including
The sum of the first amplitudes as a function of time integrated over the first duration, and the sum of the second and third amplitudes as a function of time integrated over the second duration, And the fourth amplitude as a function of time integrated over the third duration, and the fifth amplitude as a function of time integrated over the fourth duration are the reset phase and said. A controller that produces an amplitude offset designed to maintain DC equilibrium on the display medium over the color transition phase.
(Item 17)
16. The controller of item 16, wherein the controller applies different reset phases depending on the color to be displayed by the electrophoresis display.
(Item 18)
16. The controller of item 16, wherein the display medium comprises white, cyan, yellow, and magenta particles.
(Item 19)
16. The controller of item 16, wherein the display medium comprises white, red, blue, and green particles.

FIG. 1 illustrates a single pixel exemplary equivalent circuit of an electrophoretic display.

FIG. 2 is a schematic cross-sectional view showing the positions of various colored particles in the electrophoresis medium of the present invention when displaying black, white, subtractive three primary colors, and additive three primary colors.

FIG. 3 shows, in schematic form, four types of different pigment particles used in a multi-particle electrophoresis medium.

FIG. 4 shows, in schematic form, the relative intensity of the interaction between particle pairs in a multi-particle electrophoresis medium.

FIG. 5 shows the behavior of a plurality of different particles in an electrophoresis medium when subjected to a variable intensity and duration electric field.

FIG. 6 is an exemplary waveform including a two-part reset phase (A) and a color transition phase (B).

FIG. 7 shows a schematic voltage pair showing the time-dependent variation of the waveform used to generate one color in the drive scheme of the present invention and the voltage obtained across the electrophoresis medium. It is a time diagram.

FIG. 8A shows experimental data of the color gamut produced using various voltage combinations of the two-part reset phase.

FIG. 8B shows the total experimental color gamut available by implementing a controller that changes the two-part reset phase according to the desired color.

FIG. 9 shows an embodiment of a DC balanced reset pulse.

FIG. 10 shows the DC equilibrium reset pulse of FIG. 9 as covered by the electrophoretic particles.

As mentioned above, the present invention may be used in combination with an electrophoresis medium comprising one light scattering particle (typically white) and three other particles providing the subtractive three primary colors. Such a system is graphically shown in FIG. 2 and can provide white, yellow, red, magenta, blue, cyan, green, and black for all pixels.

The three particles that provide the subtractive three primary colors may be substantially non-light scattering (“SNLS”). The use of SNLS particles allows color mixing and provides more color results than can be achieved with the same number of scattered particles. The aforementioned US8,587,859 uses particles with subtractive primary colors, but requires two different voltage thresholds for independent addressing of non-white particles (ie, the display has three positives and three. Addressed using two negative voltages). These thresholds must be well separated to avoid crosstalk, and this separation forces the use of high addressing voltages for some colors. In addition, addressing the colored particles at the highest threshold also moves all other colored particles.

These other particles must then be switched to their desired position at a lower voltage. Such a stepwise color addressing scheme results in unwanted color blinking and long transition times. The present invention does not require the use of such stepwise waveforms, and addressing for all colors can only be achieved with two positive and two negative voltages, as described below. Five different voltages (ie, two positives, two negatives, and only zeros are required in the display, but in some embodiments, more different voltages are used, as described below. , It may be preferable to address the display).

As already mentioned, FIG. 2 of the accompanying drawings is a schematic cross-section showing the positions of the various particles in the electrophoresis medium of the invention when displaying black, white, subtractive primaries, and additive primaries. .. In FIG. 2, the visible surface of the display is assumed to be at the top (as shown), i.e., the user views the display from this direction and the light is incident from this direction. As already mentioned, in a preferred embodiment, only one of the four particles used in the electrophoresis medium of the invention substantially scatters light, and in FIG. 2, the particles are white. It is assumed to be a pigment. Basically, the light-scattering white particles form a white reflector, on which any particles above the white particles (as shown in FIG. 2) are visible. Light passing through these particles and entering the visible surface of the display is reflected by the white particles, returned through these particles, and emerges from the display. Thus, the particles above the white particles can absorb a variety of colors, and the colors that appear to the user result from a combination of particles above the white particles. Any particles placed below the white particles (behind the user's point of view) are masked by the white particles and do not affect the displayed color. The order or arrangement of the second, third, and fourth particles with respect to each other is not important because they are substantially non-light scattering, but for the reasons already mentioned, white (light scattering) particles. Its order or sequence with respect to is important.

More specifically, when the cyan, magenta, and yellow particles are below the white particles (situation [A] in FIG. 2), there are no particles above the white particles, and the pixels are simply: Display white. When the single particle is above the white particle, the color of the single particle is displayed in yellow, magenta, and cyan in situations [B], [D], and [F] in FIG. 2, respectively. Will be done. When the two particles are above the white particles, the color displayed is a combination of those two particles. That is, in the situation [C] in FIG. 2, the magenta and yellow particles display red, in the situation [E] the cyan and magenta particles display blue, and in the situation [G] yellow and Cyan-colored particles display green. Finally, when all three colored particles are above the white particles (situation [H] in FIG. 2), all incident light is absorbed by the subtractive three primary color colored particles and the pixels display black.

One subtractive primary color can be rendered by the light-scattering particles so that the display comprises two types of light-scattering particles, one of which is white and the other will be colored. It can be considered as a possibility. However, in this case, the position of the light-scattering colored particles with respect to the other colored particles covering the white particles will be important. For example, when rendering black (when all three colored particles are above the white particles), the scattered colored particles cannot be above the non-scattered colored particles (otherwise they are scattered particles). The color that is partially or completely concealed behind and rendered is that of scattered colored particles, not black).

Rendering black may not be easy if more than one type of colored particles scatters light.

FIG. 2 shows an ideal situation where the color is not contaminated (ie, the light-scattering white particles completely mask any particles behind the white particles). In practice, a mask with white particles can be imperfect so that there may be slight absorption of light by the particles that would ideally be completely masked. Such contamination typically reduces both the lightness and saturation of the rendered color. In the electrophoresis medium of the present invention, such color contamination should be minimized to the point where the colors formed are comparable to industrial standards for color rendering. A particularly preferred standard is SNAP (Standard for Newspaper Advertising Production), which defines L ^* , a ^* , and b ^* values for each of the eight primary colors referenced above. (Hereinafter, "primary colors" will be used to refer to the eight colors, namely black, white, subtractive three primary colors, and additive three primary colors, as shown in FIG. 2.)

As shown in FIG. 2, a method for electrophoretically arranging a plurality of different colored particles in a "layer" is described in the prior art. The simplest such method involves "competitive" pigments with different electrophoretic mobilities. See, for example, US Pat. No. 8,040,594. Such competition is more complex than seemingly understandable because the motion of the charged pigment itself changes the electric field locally applied in the electrophoretic fluid. For example, as a positively charged particle moves towards the cathode and a loaded electric particle towards the anode, its charge shields the electric field borne by the intermediate charged particle between the two electrodes. Pigment competition is involved in the electrophoresis of the present invention, but it is considered that this is not a single phenomenon related to the arrangement of particles shown in FIG.

A second phenomenon that can be employed to control the movement of multiple particles is heterologous aggregation between different pigment types. See, for example, US 2014/0092465 described above. Such agglutination can be charge mediated (Coulomb force) or can occur, for example, as a result of hydrogen bonds or van der Waals interactions. The intensity of the interaction can be influenced by the choice of surface treatment of the pigment particles. For example, Coulomb interactions are weakened when a steric barrier (typically a polymer grafted or adsorbed to the surface of one or both particles) maximizes the closest proximity of countercharged particles. obtain. In the present invention, as mentioned above, such polymer barriers are used on first and second types of particles, and with and without third and fourth types of particles. In some cases.

A third phenomenon that can be used to control the motion of multiple particles is voltage or current dependent mobility, as described in detail in Japanese Patent Application No. 14 / 277,107 above.

FIG. 3 shows a schematic cross-sectional representation of the four pigment types (1-4) used in preferred embodiments of the present invention. The polymer shell adsorbed on the core pigment is indicated by dark shading, while the core pigment itself is shown as unshaded. As is well known in the art, aggregates of smaller particles (ie, "bundles of grapes"), spherical, needle-shaped, or otherwise equiangular, small pigment particles or dyes dispersed in the binder. Various forms, such as composite particles, may be used for the core pigment. The polymer shell may be a covalently bonded polymer produced by a graft binding process or chemisorption, or may be physically adsorbed on the particle surface, as is well known in the art. For example, the polymer may be a block copolymer with insoluble and soluble compartments. Several methods for adhering the polymer shell to the core pigment are described in the examples below.

The first and second particle types in one embodiment of the invention preferably have a more substantial polymer shell than the third and fourth particle types. Light-scattering white particles are of the first or second type (charged either negatively or positively). In subsequent discussions, white particles are assumed to carry a negative charge (ie, type 1), but the general principles explained will also apply to a set of particles in which white particles are positively charged. Will be apparent to those skilled in the art.

In the present invention, the electric field required to separate aggregates formed from a mixture of type 3 and 4 particles in a suspension solvent containing a charge control agent is any other of the two types of particles. It exceeds what is required to separate the aggregates formed from the combination. On the other hand, the electric field required to separate the aggregates formed between the first and second types of particles is formed between the first and fourth particles or between the second and third particles. Less than what is required to separate the agglomerates (of course, less than what is required to separate the third and fourth particles).

In FIG. 3, the core pigments constituting the particles are shown to have substantially the same size, and the zeta potentials of the particles are also assumed to be approximately the same, although not shown. What varies is the thickness of the polymer shell that surrounds each core pigment. As shown in FIG. 3, the polymer shell is thicker than Type 3 and 4 particles with respect to Type 1 and 2 particles, which is, in fact, a preferred situation for certain embodiments of the present invention.

It may be useful to consider force equilibrium between particle pairs to understand how the thickness of the polymer shell affects the electric field required to separate aggregates of oppositely charged particles. .. In reality, an agglomerate can consist of a large number of particles, and the situation will be much more complicated than in the case of simple pairwise interactions. Nonetheless, particle pair analysis provides some guidance for understanding the present invention.

The force acting on one of the particle pairs in the electric field is given by:
Wherein, F _App is a force applied on the particles by the applied electric field, F _C is a Coulomb force applied to the particles by the second particles opposite _{charge, F VW} is , an attractive van der Waals forces applied on one of the particles by the second particles, F _D is the depletion of the particles to a (optional) result of containing stabilizing polymer into the suspending medium It is an attractive force given by aggregation.

The force _FApp applied on the particles by the applied electric field is given by:
In the equation, q is the charge of the particle, which is related to the zeta potential (ζ), as shown in equation (2) (approximately Huckel limit), where a is the core pigment radius. S is the thickness of the solvent-expanded polymer shell, and other symbols have its conventional meaning known in the art.

For particles 1 and 2, the magnitude of the force exerted by another particle on one particle as a result of Coulomb interaction is approximately given by:

F _App force applied to each particle, while acting to separate particles, the other three forces, it is noted that attraction between particles. If the _FApp force acting on one particle is higher than that acting on the other (because the charge on one particle is higher than that on the other), the pair is separated according to Newton's third law. The force acting for is given by the weaker of the two _{FA pp} forces.

From (2) and (3), the magnitude of the difference between the attracting and separating Coulomb terms is given by the following if the particles are of equal radius and zeta potential:
Therefore, it can be seen that making (a + s) smaller or making ζ larger would make it more difficult for the particles to separate. Therefore, in one embodiment of the invention, it is preferred that the Type 1 and 2 particles are large and have a relatively low zeta potential, while the particles 3 and 4 are small and have a relatively large zeta potential.

However, the van der Waals force between the particles can also change substantially as the thickness of the polymer shell increases. The polymer shell on the particles is expanded by the solvent and moves further away from the surface of the interacting core pigment through van der Waals forces. For spherical core pigments with radii (a ₁ , a ₂ ) much larger than the distance between them (s ₁ + s ₂ ),
In the formula, A is a Hamaker constant. As the distance between the core pigments increases, the formula becomes more complex, but the effects remain the same. That is, an increase in s ₁ or s ₂ has a significant effect on reducing attracted van der Waals interactions between particles.

Based on this background, it is possible to understand the rationale behind the particle types illustrated in FIG. Type 1 and 2 particles are expanded by the solvent and move the core pigment further away, and they have or do not have a smaller polymer shell than possible for Type 3 and 4 particles. It has a substantial polymer shell that reduces van der Waals interactions between. According to the present invention, it is possible to arrange the intensity of the interaction between pairwise aggregates to comply with the above requirements, even if the particles have zeta potentials of approximately the same size and size.

For more complete details of the preferred particles for use in the display of FIG. 3, the reader should refer to application 14/849,658, supra.

FIG. 4 shows, in schematic form, the strength of the electric field required to separate the particle-type pairwise aggregates of the present invention. The interaction between type 3 and 4 particles is stronger than that between type 2 and 3 particles. The interaction between Type 2 and 3 particles is about the same as that between Type 1 and 4 particles and is stronger than that between Type 1 and 2 particles. All interactions between pairs of identically charged particles are as weak or weaker as interactions between Type 1 and Type 2 particles.

FIG. 5 generally shows how these interactions can be utilized to produce all primary colors (subtractive, additive, black, and white), as discussed with reference to FIG. ..

When addressed using a low electric field (FIG. 5 (A)), particles 3 and 4 are aggregated and not separated. Particles 1 and 2 move freely in the electric field. When the particle 1 is a white particle, the color visible when viewed from the left is white, and the color visible when viewed from the right is black. The reversal of the polarity of the electric field switches between the black state and the white state. However, the transition color between the black and white states is colored. The agglomerates of particles 3 and 4 will move very slowly in the electric field with respect to particles 1 and 2. It can be found that the particle 2 moves beyond the particle 1 (to the left), while the aggregates of the particles 3 and 4 do not move significantly. In this case, the particles 2 will be visible from the left, while the aggregates of particles 3 and 4 will be visible from the right. In certain embodiments of the invention, the agglomerates of particles 3 and 4 are weakly positively charged and are therefore located in the vicinity of particle 2 at the onset of such a transition.

When addressed in a high electric field (FIG. 5B), particles 3 and 4 are separated. Which of the particles 1 and 3 (each having a negative charge) becomes visible when viewed from the left will depend on the waveform (see below). As shown, particle 3 is visible from the left and the combination of particles 2 and 4 is visible from the right.

Starting from the state shown in FIG. 5 (B), a low voltage of opposite polarity will move the positively charged particles to the left and the loaded electric particles to the right. However, the positively charged particle 4 will encounter the loaded electric particle 1, and the loaded electric particle 3 will encounter the positively charged particle 2. The resulting combination of particles 2 and 3 is visible from the left and particle 4 is visible from the right.

As described above, preferably, the particles 1 are white, the particles 2 are cyan, the particles 3 are yellow, and the particles 4 are magenta.

The core pigment used within the white particles is typically a high refractive index metal oxide, as is well known in the art of electrophoretic displays. Examples of white pigments are described in the following examples.

The core pigments used to make Type 2-4 particles as described above provide the three subtractive primary colors, namely cyan, magenta, and yellow.

The display device may be constructed using the electrophoretic fluid of the present invention in some methods known in the prior art. The electrophoretic fluid may be encapsulated in microcapsules or incorporated into a microcell structure and then sealed with a polymer layer. The microcapsules or microcell layers may be coated or embossed on a plastic substrate or film carrying a transparent coating of conductive material. The assembly may be laminated to a backplane carrying pixel electrodes using a conductive adhesive.

A first embodiment of the waveform used to achieve each of the particle arrangements shown in FIG. 2 will be described herein. In this discussion, the first particle is white and loaded, the second particle is cyan and positively charged, and the third particle is yellow and loaded. It is assumed that the fourth particle is magenta and is positively charged. Those skilled in the art can assume that one of the first and second particles is white, so how would the color transition change if these assignments of particle color were changed? Will understand. Similarly, the polarity of the charge on all particles can be reversed, and the electrophoretic medium still reverses the polarity of the waveform (see next paragraph) used to drive the medium. Assuming that, it will work in the same fashion.

In the discussion that follows, the waveform (voltage vs. time curve) applied to the pixel electrodes of the backplane of the display of the present invention is described and plotted, but the front electrodes are assumed to be grounded (ie, zero potential). ). The electric field applied by the electrophoretic medium is, of course, determined by the potential difference between the backplane and the front electrodes and the distance that separates them. The display is typically visible through its front electrode, and thus this is a particle adjacent to the front electrode that controls the color displayed by the pixels, and sometimes the potential of the front electrode relative to the backplane. Is taken into account, it is easier to understand the accompanying optical transitions. This can be done simply by inverting the waveforms discussed below.

These waveforms are five, where each pixel of the display is designated as + V _high , + V _low , 0, -V _low , and -V _high and is illustrated as 30V, 15V, 0, -15V, and -30V. It requires that it can be driven at different addressing voltages. In practice, it may be preferable to use a larger number of addressing voltages. If only three voltages (ie, + V _high , 0, and -V _high ) are available, the lower voltage by addressing is accompanied by a pulse of voltage V _high , but with a duty cycle of 1 / n. It may be possible to achieve the same result as addressing at (eg, V _high / n, where n is a positive integer> 1).

The waveform used in the present invention is corrected for three phases, that is, the DC imbalance caused by the waveform before it is applied to the pixel, or the DC imbalance suffered in the subsequent color rendering transition (the present). A DC equilibrium phase (as is known in the art), a "reset" phase in which pixels are returned to a starting configuration that is at least nearly identical regardless of the optical state prior to the pixel, and "color rendering" as described below. It may have a phase. The DC equilibrium and reset phases are optional and may be omitted depending on the demands of the particular application. The "reset" phase, if adopted, may be identical to the magenta color rendering waveform described below, or may be accompanied by continuous drive of the maximum possible positive and negative voltages, or display there. It may be some other pulse pattern on the premise that the subsequent color can be reproducibly acquired from.

Production of eight primary colors (white, black, cyan, magenta, yellow, red, green, and blue) using the second drive scheme applied to the display of the invention (such as that shown in FIG. 2). The general principles used in will be explained here. It is assumed that the first pigment is white, the second pigment is cyan, the third pigment is yellow, and the fourth pigment is magenta. Let's go. It will be apparent to those skilled in the art that the colors presented by the display will change as the pigment color assignments change.

The maximum positive and negative voltages applied to the pixel electrodes (designated as ± V _{max in} FIG. 6) are the mixture of the second and fourth particles (cyan and magenta to produce blue-), respectively. (See FIG. 2E) or the third particle alone (yellow-see FIG. 2B-white pigments scatter light and are between the colored pigments) to produce the color formed. These blues and yellows are not necessarily the best blues and yellows achievable by the display. Intermediate levels of positive and negative voltages applied to the pixel electrodes (designated as ± V _{mid in} FIG. 6) produce colors, which are black and white, respectively (not necessarily, but achievable by the display). Best black and white-see Figure 5A).

From these blue, yellow, black, or white optical states, the other four primary colors move only the second particle (in this case, the cyan particle) relative to the first particle (in this case, the white particle). It can be obtained by allowing it to be achieved using the lowest applied voltage (designated as ± V _{min in} FIG. 6). Therefore, moving cyan from blue (by applying −V _min to the pixel electrodes) produces magenta (see FIGS. 2 [E] and 2 [D] for blue and magenta, respectively). Moving cyan into yellow (by applying + V _min to the pixel electrodes) provides green (see Figures 2 [B] and 2 [G] for yellow and green, respectively). Moving cyan from black (by applying −V _min to the pixel electrodes) provides red (see Figures 2 [H] and 2 [C] for black and red, respectively) and cyan. Moving into white (by applying + V _min to the pixel electrodes) provides cyan (see FIGS. 2 [A] and 2 [F] for white and cyan, respectively).

While these general principles are useful for the structure of waveforms to produce a particular color in the displays of the present invention, in practice the ideal behavior described above may not be observed and is a modification of the basic scheme. However, preferably, it is adopted.

A general purpose waveform for addressing the color electrophoresis display of the present invention is shown in FIG. 6, where the abscissa represents time (arbitrary unit) and the ordinate is the voltage between the pixel electrode and the common front electrode. Represents the difference. The magnitudes of the three positive voltages used in the drive scheme illustrated in FIG. 6 may be from about + 3V to + 30V, and the three negative voltages may be from about -3V to -30V. In one preferred embodiment, the maximum positive voltage + V _max is + 30V, the intermediate positive voltage + V _mid is 15V, and the minimum positive voltage + V _min is 9V. In a similar fashion, the negative voltages −V _max , −V _mid , and −V _min are −30V, −15V, and −9V in preferred embodiments. For any of the three voltage levels, the magnitude of the voltage does not have to be | + V | = | −V |, but in some cases it may be.

There are two distinctly different phases in the general purpose waveform illustrated in FIG. In the first phase, a pulse (“pulse” refers to a unipolar square wave, ie, the application of a constant voltage over a given time) is supplied at + V _max and −V _max before being rendered on the display. It serves to erase the image (ie, "reset" the display). The lengths of these pulses (t ₁ and t ₃ ) and the rest (ie, the period of zero voltage between them (t ₂ and t ₄ ) are the entire waveform (ie, the overall waveform as illustrated in FIG. 6). The voltage integration over time may be chosen to be DC balanced (ie, the voltage integration over time is virtually zero). The DC equilibrium is the net impulse delivered within this phase. However, the length of the pulse in phase A is equal in magnitude and opposite in sign to the net impulse delivered in phase B (during which the display is switched to a particular desired color). It can be achieved by adjusting the voltage and the rest.

As used herein, the term "frame" refers to a single update of every row in the display. For displays of the invention driven using thin film transistor (TFT) arrays, the available time increments on the abscissa of FIG. 6 will typically be quantized by the frame rate of the display. However, it will be obvious to those skilled in the art. Similarly, the display is addressed by varying the potential of the pixel electrode with respect to the front electrode, which may be accomplished by varying the potential of either or both of the pixel electrode and the front electrode. Will also be obvious. In this state-of-the-art technology, a matrix of pixel electrodes typically resides on the backplane, while the front electrodes are common to all pixels. Therefore, when the potential of the front electrode is changed, the addressing of all pixels is affected. The basic structure of the waveform described above with reference to FIG. 6 is the same regardless of whether a variable voltage is applied to the front electrodes.

The general purpose waveform illustrated in FIG. 6 requires the drive electronics to provide as many as seven different voltages to the data line during the update of selected rows of the display. While multi-level source drivers capable of delivering seven different voltages are available, many commercially available source drivers for electrophoretic displays have only three different voltages during a single frame. Allows delivery (typically positive, zero, and negative voltage). Adapted to the 3-level source driver architecture, assuming that the three voltages supplied to the panel (typically + V, 0, and -V) can be varied from one frame to the next. It is considered possible to modify the general-purpose waveform of FIG. (That is, for example, in frame n, voltage (+ V _max , 0, −V _min ) can be supplied, while in frame n + 1, voltage (+ V _mid , 0, −V _max ) can be supplied).

Occasionally, it may be desirable to control the electrophoretic display using a so-called "top plane switching" drive scheme. In the topplane switching drive scheme, the topplane common electrode can be switched between -V, 0, and + V, while the voltage applied to the pixel electrodes can also vary from -V, 0 to + V. Yes, pixel transitions in one direction are handled when the common electrode is at 0, and transitions in the other direction are handled when the common electrode is at + V.

When topplane switching is used in combination with a three-level source driver, the same general principles as described above with reference to FIG. 6 apply. Top plane switching may be preferred when the source driver is unable to supply a voltage comparable to the preferred V _max . Methods for driving electrophoretic displays using topplane switching are well known in the art.

The typical waveform of the (E Ink) prior art is shown in Table 1 below, and the numbers in parentheses are driven by the indicated backplane voltage (relative to the top plane, which is assumed to be at zero potential). Corresponds to the number of frames.

In the reset phase of this waveform, the maximum negative and positive voltage pulses are provided, erasing the previous state of the display. The number of frames in each voltage, the color is rendered, (shown as a color x about delta _x) high / medium voltage and low / amount to compensate for the net impulse of the intermediate voltage in phase are offset. To achieve DC equilibrium, Δ _x is chosen to be half its net impulse. The reset phase need not be precisely implemented in the manner shown in the table. For example, when topplane switching is used, it is necessary to allocate a certain number of frames to negative and positive drives. In such cases, it is preferable to provide a maximum number of high voltage pulses coincident with attainment of DC balanced (i.e., if necessary, to subtract 2.DELTA. _X negative or positive frame).

In the high / intermediate voltage phase, an N-repetitive sequence of pulse sequences appropriate for each color is provided, where N can be 1-20, as described above. As shown, the sequence comprises 14 frames to which positive or negative voltages or zeros of magnitude V _max or V _mid or 0 are distributed. The pulse sequence shown is consistent with the argument given above. In this phase of the waveform, it can be seen that the pulse sequences for rendering white, blue, and cyan are the same. Similarly, in this phase, the pulse sequences for rendering yellow and green are the same (because green is achieved starting from the yellow state).

In the low / intermediate voltage phase, blue and cyan are obtained from white and green is obtained from yellow.

The aforementioned discussion of waveforms, specifically the discussion of DC equilibrium, ignores the problem of kickback voltage. In practice, as mentioned above, all backplane voltages are offset from the voltage supplied by the power source by an amount equal to the kickback voltage _VKB . Therefore, if the power source used provides three voltages + V, 0, and -V, the backplane will actually receive the voltages V + V _KB , V _KB , and -V + V _KB . _{(V KB,} in the case of amorphous silicon TFT, it is noted normally be a negative number). However, the same power source will supply + V, 0, and −V to the front electrodes without any kickback voltage offset. Thus, for example, when the front electrode is supplied with −V, the display will suffer a maximum voltage of 2V + V _KB and a minimum voltage of V _KB . Instead of feeding the _VKB to the front electrodes using a separate power source, which can be costly and inconvenient, the waveform is that the front electrodes are fed positive, negative, and _VKB. , May be divided into sections.

As mentioned above, in some of the waveforms described in Application 14 / 849,658 above, seven different voltages, namely three positives, three negatives, and zeros, are applied to the pixel electrodes. Can be done. Preferably, the maximum voltage used in these waveforms is higher than that handled by the amorphous silicon thin film transistors in current state-of-the-art technology. In such cases, a high voltage can be obtained by using top plane switching and the drive waveform can be configured to compensate for the kickback voltage, essentially by the methods of the invention. Can be DC balanced. FIG. 7 graphically depicts one such waveform used to display a single color. As shown in FIG. 7, the waveforms for all colors have the same basic morphology. That is, the waveform is essentially DC balanced and two compartments or phases, i.e. (1) a "reset" of the display, from which any color can be reproducibly obtained, with the rest of the waveform in between. A series of preliminary frames used to provide a state that provides DC non-equilibrium equal to and opposite to DC non-equilibrium, and (2) a series of frames specific to the color to be rendered. Can be provided. See waveform categories A and B shown in FIG.

During the first "reset" phase, a display reset ideally erases any memory in the previous state, including the residual voltage and pigment composition specific to the previously displayed color. Such erasure is most effective when the display is addressed to the maximum possible voltage in the "reset / DC balanced" phase. In addition, sufficient frames may be allocated in this phase to allow for the most non-equilibrium color transition equilibrium. Since some colors require positive DC equilibrium in the second section of the waveform and negative equilibrium in others, the front electrode voltage _Vcom is about half of the frame in the "reset / DC balanced" phase. It is set to V _pH (allowing the maximum possible negative voltage between the back plane and the front electrode), and for the rest, V _com is set to V _nH (between the back plane and the front electrode). Allows maximum possible positive voltage). Experimentally, it has been found that it is preferable that the V _com = V _nH frame precedes the V _com = V _pH frame.

A "desired" waveform (ie, the actual voltage vs. time curve, preferably applied across the electrophoresis medium) is illustrated below FIG. 7, and its implementation with topplane switching is shown above. The potential applied to the front electrode (V _com ) and backplane (BP) is shown. The column driver has the following voltages: V _pH , V _nH (typically in the range of ± 10 to 15 V, maximum positive and negative voltages), V _pL , V _nL (typically ± Lower positive and negative voltages in the range of 1-10V), and zero are assumed to be used connected to a available power source. In addition to these voltages, kickback voltage V _{KB (e.g.,} as measured as described in U.S. Patent No. 7,034,783, small values specific to a particular backplane to be used), additional It can be supplied to the front electrodes by a power source.

As shown in FIG. 7, all backplane voltages are offset from the voltage supplied by the power source by _VKB (shown as a negative number), while the front electrode voltage is the front electrode with the above. as explained, except when it is explicitly set to V _KB, so no offset.

The display of the present invention has been described as producing eight primary colors, but in practice it is preferred that as many colors as possible be produced at the pixel level. A full-color grayscale image may then be rendered by dithering between these colors using techniques well known to those of skill in the art in imaging techniques. For example, in addition to the eight primary colors produced as described above, the display may be configured to render eight additional colors. In one embodiment, these additional colors are light red, light green, light blue, dark cyan, dark magenta, dark yellow, and two levels of gray between black and white. The terms "light" and "dark" as used in this context have substantially the same hue angle as a reference color in a color space such as CIE L ^* a ^* b ^* , but are higher or higher, respectively. Refers to a color with a low L ^* .

In general, light colors are obtained using waveforms that are in the same fashion as dark colors but have slightly different net impulses in phases B and C. Thus, for example, the pale red, pale green, and pale blue waveforms have more negative net impulses than the corresponding red, green, and blue waveforms in phases B and C, while dark cyan, dark magenta, and dark. Yellow has a net impulse that is more positive than the corresponding cyan, magenta, and yellow waveforms in phases B and C. Changes in net impulses may be achieved by modifying the length of the pulses, the number of pulses, or the magnitude of the pulses in phases B and C.

The gray color is typically achieved by a sequence of pulses that oscillate between low or medium voltages.

In a display of the invention, driven using a thin film transistor (TFT) array, the available time increments on the abscissa of FIG. 7 will typically be quantized by the frame rate of the display. That will be clear to those skilled in the art. Similarly, it is also clear that the display is addressed by varying the potential of the pixel electrode with respect to the front electrode, which can be accomplished by varying the potential of either or both of the pixel electrode and the front electrode. Will be. In the latest technology, the matrix of pixel electrodes typically resides on the backplane, while the front electrodes are common to all pixels. Therefore, when the potential of the front electrode is changed, the addressing of all pixels is affected. The basic structure of the waveform described above with reference to FIG. 7 is the same regardless of whether a variable voltage is applied to the front electrodes.

The general purpose waveform illustrated in FIG. 7 requires the drive electronics to provide as many as seven different voltages to the data line during the update of selected rows of the display. While multi-level source drivers capable of delivering seven different voltages are available, many commercially available source drivers for electrophoretic displays have only three different voltages during a single frame. Allows delivery (typically positive, zero, and negative voltage). As used herein, the term "frame" refers to a single update of every row in the display. Figured to adapt to a three-level source driver architecture, assuming that the three voltages supplied to the panel (typically + V, 0 and -V) can be varied from one frame to the next. It is considered possible to modify the general-purpose waveform of 7. (That is, for example, in frame n, voltage (+ V _max , 0, −V _min ) can be supplied, while in frame n + 1, voltage (+ V _mid , 0, −V _max ) can be supplied).

Here, referring to FIG. 6, it can be seen that in phase A (reset phase), this phase is divided into two sections of equal duration (shown by dotted lines). When topplane switching is used, the topplane will be held at a potential in the first of these sections and at a potential of opposite polarity in the second section. In the specific case of FIG. 6, the first between such division, the top plane is held in _{V p} H, backplane, _{V n} H is held _{in, V n H-V p H} ( This representation will achieve a potential drop across the electrophoretic fluid) (used for reference to the backplane potential relative to that of the topplane). During the second segment, the top plane will be held at V _n H and the backplane will be held at V _p H. As shown, during the second segment, the electrophoretic fluid will be subject to a potential of _Vp H-V _n H, which is the highest potential available. However, for rendering a color, exposure to this high voltage can result in an initial pigment arrangement that would be difficult to achieve in the ideal final configuration. For example, as described in the prior art, magenta pigments (having the same charge polarity as cyan pigments) need to be associated in aggregates with yellow pigments in order to render cyan. Such aggregates will be split by the high applied potential and therefore the magenta color will be uncontrolled and contaminate the cyan color.

However, it is not necessary to use the maximum possible voltage in both sections of waveform phase A. What is required in phase A is that the newly rendered color is the same regardless of which color precedes it, and that the net impulse provided in phase A is balanced with the net impulse in phase B. It only erases the previous color state.

Therefore, the experiment was conducted so that the voltage applied in each of the two sections of phase A was fluctuated while the phase B of the type of waveform shown in Table 1 was kept constant (however, the same). A number of frames were allocated to phase A in each example, ie 60 frames for the first division and 60 frames for the second division, for a total of 120 frames). After addressing the display, the CIELabL ^* , a ^* and b ^* values of each primary color were measured.

Table 2 shows a default example in which the maximum possible negative and positive voltages are applied in the first and second compartments of phase A. This is done using topplane switching, where the first enumerated voltage is applied to the backplane while the second enumerated voltage is applied to the topplane. The color gamut measured as the volume of the convex hull containing the eight points listed in Table 2 is 21,336 ΔE ³ .

Table 3 shows an example in which the backplane is held at zero during the first section of phase A. The applied voltage is less than the example in Table 2 in this example. The voltage applied in the second section of phase A is the same as the example in Table 2. In order to maintain DC equilibrium, the time of application of the lower voltage must, of course, be correspondingly longer. The color gamut measured as the volume of the convex hull containing the eight points listed in Table 2 is 20,987 ΔE ³ .

Table 4 shows an example in which the backplane is held at zero during the second section of phase A. The voltage applied in the first section of phase A is the same as the example in Table 2. The color gamut measured as the volume of the convex hull containing the eight points listed in Table 2 is 20,339ΔE ³ .

FIG. 8A shows the results of these experiments as a projection onto an a ^* / b ^* plane. The abscissa represents a ^* and the ordinate represents b ^* . Some colors (eg, red, magenta, and blue) are better rendered with the Phase A settings corresponding to Tables 2 or 3, while others (cyan, green, and yellow) are in Table 4. It can be seen that the phase A setting corresponding to is better rendered.

Interestingly, an alternative experiment in which the order of the first and second divisions of Phase A was reversed gave very poor results and all colors were contaminated with yellow.

Table 5 shows the best color combinations from this experiment. The color gamut measured as the volume of the convex hull containing the eight points listed in Table 2 is 28,092ΔE ³ . Therefore, with proper selection of the voltage applied in the reset phase (phase A) of the waveform, the color gamut was increased by about 50%. The results in Table 5 are depicted in FIG. 8B.

The method of the present invention is especially important when it is desired to make the waveform as short as possible. When a fixed voltage is used in phase A, phase B needs to be lengthened for a color to compensate for the bias introduced in phase A.

Although the present invention has been described with only two compartments associated with phase A, one of ordinary skill in the art will appreciate that any reasonable number of compartments may be used. However, when topplane switching is adopted, the topplane potential of the same structure is fixed regardless of the color to be rendered. According to the present invention, the backplane settings for each topplane potential follow the rendered color, but without violating the condition that the overall waveform with phases A and B is DC balanced. It fluctuates in phase A.

DC equilibrium of the reset pulse can be achieved in the following ways.

For the DC balanced reset process, a set of voltages must be selected for all transitions in the waveform. Choosing a set of voltages can be problematic because some palette colors require high voltage while others require low voltage. For devices where large amounts of simultaneous backplane voltage are available, this is not a problem as each transition is individually balanced, but in the case of topplane switching, each transition is coupled together by the topplane, which is , Force the transitions to align with each other. Additional constraints are also imposed by the source driver standard, which currently limits the number of simultaneous backplane voltages to three.

The transition is a sequence of voltages applied to the backplane and topplane.
And in the ceremony,
Is the backplane voltage with respect to the transition j in frame i.
Is the top plane voltage in frame i.
Is the total impulse of T _j prior to the application of the DC equilibrium reset (in the equation, n _j is the update length of T _j (in frame units) and V _KB is the kickback voltage of the display).

sigma _j was the desired DC balancing pulses offset (time × V), the d _r a desired total duration of DC balancing reset. The DC balanced reset has two pulses in it, so the top plane voltage needs to be elected for each pulse and the backplane voltage is elected for each pulse and each transition. Will need.
Is the voltage of the kth pulse of the transition _Tj (in the equation,
Is the backplane voltage for the kth reset pulse of transition _Tj .
Is the top plane voltage for the kth reset pulse). The voltage for the two pulses is
It is important that is chosen to have the opposite sign for each transition.

A "zero" voltage, which would ideally be 0V, needs to be selected, but this is not always possible.
Will be.

Next, the maximum duration is calculated for each of the two pulses.

Then
Calculate the "ideal" duration of each pulse for each transition, which is the duration in the case of. Notation
To define. Therefore, it becomes as follows.

Each pulse is then split into an "active" part and a "zero" part to balance the transition.

Now you are ready to configure the DC balanced reset phase of the waveform. Top plane is duration
Over
Duration after being driven by
Over
Driven by. For each transition _Tj , the duration, as shown in FIG.
Over
Duration after being driven by
Over
Driven by, then duration
Over
Driven by, then duration
Over
Driven by. The resulting waveform covered by the ink is shown in FIG.

At first glance, sequential scans of the various rows of the active matrix display show that when the voltage on the front electrode changes (typically during continuous scans of the active matrix), the scan reaches the associated pixel and that pixel electrode. The upper voltage is adjusted to compensate for changes in the front electrode voltage, and the period between the change in front plane voltage and the time it takes for the scan to reach the associated pixel varies depending on the row in which the associated pixel is located. Until then, it can be considered that each pixel of the display would be subject to "incorrect" voltage, thus overturning the aforementioned calculations designed to ensure accurate DC equilibrium of waveforms and drive schemes. However, further investigation shows that the actual "error" in the impulse applied to a pixel is proportional to the period between the change in front plane voltage x the change in front plane voltage and the time it takes for the scan to reach the associated pixel. Will show. The latter period leaves the final front plane voltage equal to the initial one, for any sequence of changes in the front plane voltage, the sum of the impulse "errors" is zero and the overall DC equilibrium of the drive scheme is , Fixed assuming no change in scan rate so that it will not be affected.

Therefore, the present invention provides DC equilibrium waveforms for multi-particle electrophoresis displays. Although some aspects and embodiments of the technique of the present application have been described so far, it should be understood that various modifications, modifications and improvements will be readily recalled to those skilled in the art. Such modifications, modifications, and improvements are intended to be within the spirit and scope of the techniques described herein. For example, one of ordinary skill in the art facilitates various other means and / or structures for performing the functions described herein and / or obtaining one or more of the results and / or advantages. Assuming, each such variant and / or modification is considered to be within the scope of the embodiments described herein. One of ordinary skill in the art will be able to recognize or confirm many equivalents of the specific embodiments described herein using mere routine experimentation. Therefore, the aforementioned embodiments are presented only as an example, and within the scope of the appended claims and their equivalents, the embodiments of the present invention may be practiced differently from those specifically described. Please understand that. In addition, any combination of two or more features, systems, articles, materials, kits, and / or methods described herein can also be such features, systems, articles, materials, kits, and / or. If the methods are consistent with each other, they are included within the scope of this disclosure.

Claims (19)

A method for driving an electrophoretic display having a front electrode, a backplane, and a display medium located between the front electrode and the backplane, wherein the display medium is colored in three different ways. The method comprises a set of particles.
Applying a reset phase and a color transition phase to the electrophoresis display
The reset phase is
Applying a first signal with a first polarity, a first amplitude as a function of time, and a first duration onto the front electrode,
Applying a second signal having a second polarity opposite to the first polarity, a second amplitude as a function of time, onto the backplane during the first duration.
Applying a third signal having a second polarity opposite to the first polarity, a third amplitude as a function of time, over the front electrode for a second duration,
Including applying a fourth signal equal to the sum of the first and second amplitudes onto the backplane for the second duration.
The color transition phase is
Applying a fifth signal having the second polarity, the fourth amplitude as a function of time, and the third duration following the first and second durations is applied onto the front electrode. ,
And applying the first polarity, the fifth amplitude as a function of time, and a sixth signal having the first and second fourth following the duration of the duration, the backplane Including, including
The sum of the first and second amplitudes as a function of time integrated over the first duration, and the first, second, and as a function of time integrated over the second duration. The sum of the third amplitudes, the fourth amplitude as a function of time integrated over the third duration, and the fifth amplitude as a function of time integrated over the fourth duration. To produce an amplitude offset designed to maintain DC equilibrium on the display medium over the reset phase and the color transition phase. The method of claim 1, wherein the reset phase erases optical properties before being rendered on the electrophoretic display. The method of claim 1, wherein the color transition phase substantially alters the optical properties displayed by the electrophoresis display. The method of claim 1, wherein the first polarity is a negative voltage. The method of claim 1, wherein the first polarity is a positive voltage. The method of claim 1, wherein the impulse offset is proportional to the kickback voltage applied by the display medium. The method of claim 1, wherein the fourth duration occurs during the third duration. The method of claim 7, wherein the third duration and the fourth duration start at the same time. A method for driving an electrophoretic display having a front electrode, a backplane, and a display medium located between the front electrode and the backplane, wherein the display medium is colored in three different ways. The method comprises a set of particles.
Applying a reset phase and a color transition phase to the electrophoresis display
The reset phase is
Applying a first signal with a first polarity, a first amplitude as a function of time, and a first duration onto the front electrode,
No signal is applied onto the backplane during the first duration and
A second signal having a second polarity opposite to the first polarity, a second amplitude as a function of time, is applied onto the front electrode for a second duration.
Including applying a third signal having a third amplitude as a function of the first polarity and time onto the backplane for the second duration.
The color transition phase is
Applying a fourth signal having the first polarity, the fourth amplitude as a function of time, and the third duration following the first and second durations is applied onto the front electrode. ,
Applying a fifth signal on the backplane with the second polarity, the fifth amplitude as a function of time, and the fourth duration following the first and second durations. Including, including
The sum of the first amplitudes as a function of time integrated over the first duration, and the sum of the second and third amplitudes as a function of time integrated over the second duration, And the fourth amplitude as a function of time integrated over the third duration, and the fifth amplitude as a function of time integrated over the fourth duration are the reset phase and said. A method of producing an amplitude offset designed to maintain DC equilibrium on the display medium over the color transition phase. The method of claim 9, wherein the fourth duration occurs during the third duration. The method of claim 10, wherein the third duration and the fourth duration start at the same time. A front electrode, a back plane, a controller for a display medium and Ru electrophoresis display includes a positioned between the front electrode and the back plane, wherein the display medium comprises at least three differently With a set of colored particles, the controller is operably coupled to the front electrode and the back plane and is configured to apply a reset phase and a color transition phase to the electrophoresis display.
The reset phase is
Applying a first signal with a first polarity, a first amplitude as a function of time, and a first duration onto the front electrode,
And applying the first polarity opposite to the second polarity, the second signal having a second amplitude as a function of time during said first time duration, the backplane,
Applying a third signal having a second polarity opposite to the first polarity, a third amplitude as a function of time, over the front electrode for a second duration,
Including applying a fourth signal equal to the sum of the first and second amplitudes onto the backplane for the second duration.
The color transition phase is
Applying a fifth signal having the second polarity, the fourth amplitude as a function of time, and the third duration following the first and second durations is applied onto the front electrode. ,
Applying a sixth signal on the backplane with the first polarity, the fifth amplitude as a function of time, and the fourth duration following the first and second durations. Including
The sum of the first and second amplitudes as a function of time integrated over the first duration, and the first, second, and as a function of time integrated over the second duration. The sum of the third amplitudes, the fourth amplitude as a function of time integrated over the third duration, and the fifth amplitude as a function of time integrated over the fourth duration. Is a controller that produces an amplitude offset designed to maintain DC equilibrium on the display medium over the reset phase and the color transition phase. The controller according to claim 12, wherein the controller applies different reset phases depending on the color to be displayed by the electrophoresis display. 12. The controller of claim 12, wherein the display medium comprises white, cyan, yellow, and magenta particles. 12. The controller of claim 12, wherein the display medium comprises white, red, blue, and green particles. A controller for an electrophoretic display comprising a front electrode, a back plane, and a display medium located between the front electrode and the back plane, the display medium being colored in at least three different ways. The controller is operably coupled to the front electrode and the back plane and is configured to apply a reset phase and a color transition phase to the electrophoretic display.
The reset phase,
Applying a first signal with a first polarity, a first amplitude as a function of time, and a first duration onto the front electrode ,
And the signal during said first duration, not applied to the backplane,
A second signal having a second polarity opposite to the first polarity, a second amplitude as a function of time, is applied onto the front electrode for a second duration .
The first third of the signal between the second duration having a third amplitude as a function of the polarity and time, and a applying to the backplane,
The color transition phase is
Applying a fourth signal having the first polarity, the fourth amplitude as a function of time, and the third duration following the first and second durations is applied onto the front electrode. ,
Applying a fifth signal on the backplane with the second polarity, the fifth amplitude as a function of time, and the fourth duration following the first and second durations. Including
The sum of the first amplitudes as a function of time integrated over the first duration, and the sum of the second and third amplitudes as a function of time integrated over the second duration, And the fourth amplitude as a function of time integrated over the third duration, and the fifth amplitude as a function of time integrated over the fourth duration are the reset phase and said. A controller that produces an amplitude offset designed to maintain DC equilibrium on the display medium over the color transition phase. 16. The controller of claim 16, wherein the controller applies different reset phases depending on the color to be displayed by the electrophoresis display. 16. The controller of claim 16, wherein the display medium comprises white, cyan, yellow, and magenta particles. 16. The controller of claim 16, wherein the display medium comprises white, red, blue, and green particles.