TW201520667A - Multi-color electrophoretic displays - Google Patents

Abstract

An electrophoretic display (100) has stacked first (104) and second (120) electrophoretic layers, each comprising charged particles (W, C, Y, M) in a fluid (106, 122). The first layer contains particles of white (W) and first color (M) particles and has three optical states (a) white particles adjacent a viewing surface; (b) first color particles lie adjacent the viewing surface; and (c) both types of particles shuttered to allow light to pass through the first layer. The second layer contains particles having second (C) and third (Y) colors and has three optical states (d) second particles (C) adjacent the first layer; (e) third particles (Y) adjacent the first layer; and (f) second (C) and third (Y) particles intermixed within the fluid.

Description

Multicolor electrophoretic display

The present invention relates to multicolor electrophoretic media and to displays incorporating such media.

Particle-based electrophoretic displays have been the subject of much research and development over the years in which a plurality of charged particles move through a fluid under the action of an electric field. When compared with liquid crystal displays, electrophoretic displays have good brightness and contrast, wide viewing angle, state bistability and low power consumption. However, the long-term image quality issues with such displays have hampered their widespread use. For example, the particles that make up an electrophoretic display have a tendency to sink, causing a lack of service-life for such displays.

In this context, the term "bistable" ("bistability") is used in the context of the art to refer to displays including display elements having at least one optical characteristic. Distinct first and second display states, and with a limited period of address pulses, such that after any particular component has been driven to assume its first or second display state, the state will continue after the address pulse has terminated The minimum period of the address pulse required to change the state of the display element, for example (at least four times) at least several times. Grayscale is indicated in U.S. Patent No. 7,170,670 Some of the ability of particle-based electrophoretic displays are not only in their extreme black and white states, but also in their gray state, and are also true in some other types of optoelectronic displays. Although for convenience, the term "bistable" is used herein to cover both bistable and multi-stable displays, this type of display is referred to as "multi-stable" rather than dual. Steady state.

As mentioned above, the electrophoretic medium requires the presence of a fluid. In most of the prior art electrophoretic media, the fluid is a liquid, but the electrophoretic medium can be made using a gaseous fluid; see, for example, Kitamura, T. et al., "Moving for Electron Powders for Displays Like Electronic Paper," IDW Japan, 2001, reports HCS1-1, and Yamaguchi, Y. et al., "Toners using triboelectrically charged insulating particles", IDW Japan, 2001, AMD 4-4. See also U.S. Patent Publication Nos. 2005/0259068, 2006/0087479, 2006/0087489, 2006/0087718, 2006/0209008, 2006/0214906, 2006/0231401, 2006/0238488, 2006/0263927, and U.S. Patent Nos. 7,321,459 and 7,236,291. . When the medium is used in an orientation that allows such precipitation, for example, in the marking of the medium in a vertical plane, these gas-based electrophoretic media appear to be due to particle precipitation as a liquid-based electrophoretic medium. Vulnerable to the same type of problem. Indeed, particle precipitation appears to be a more serious problem in gas-based electrophoretic media than in liquid-based electrophoretic media, because lower viscosity gaseous suspension fluids allow electrophoretic particles to be faster than liquids. precipitation.

Many patents and applications that are assigned to or in the name of the Massachusetts Institute of Technology (MIT) and E Ink Corporation describe various techniques used to encapsulate electrophoresis and other optoelectronic media. Such encapsulating media include a plurality of capsules, each of which itself includes an internal phase containing electrophoretic migrating particles in the fluid medium, and a wall surrounding the inner phase. Historically, the capsule itself is contained in a polymeric binder to form an adhesive layer between the two electrodes. The techniques described in these patents and applications include: (a) electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patent Nos. 7,002,728 and 7,679,814; (b) capsules, binders, and packaging processes; see, for example, U.S. Patent No. 6,922,276 and 7,411,719; (c) films and subassemblies comprising photovoltaic materials; see, for example, U.S. Patent Nos. 6,982,178 and 7,839,564; (d) back planes, adhesive layers and other auxiliary layers, and methods for display; See U.S. Patent Nos. 7,116,318 and 7,535,624; (e) color formation and color adjustment; see, for example, U.S. Patent Nos. 6,017,584, 6,664,944, 6,864,875, 7,075, 502, 7, 167, 155, 7, 667, 684 and 7, 791, 789; and U.S. Patent Application Publication No. 2004/0263947 , 2007/0109219, 2007/0223079, 2008/0023332, 2008/0043318, 2008/0048970, 2008/0211764, 2009/0004442, 2009/0225398, 2009/0237776, 2010/0103502, 2010/0156780 and 2010/0225995; (f) A method for driving a display; see, for example, U.S. Patent Nos. 7,012,600 and 7,453,445; and (g) the use of a display; see, for example, U.S. Patent No. 7,312,784; and U.S. Patent Application Publication No. 2006/0279527.

Numerous of the aforementioned patents and applications recognize that the walls surrounding the discrete microcapsules in the encapsulated electrophoretic medium may be replaced by a continuous phase, thereby producing a so-called polymer-dispersed electrophoretic display in which the electrophoretic medium comprises a plurality of discrete electrophoretic fluid droplets. And a continuous phase made of a polymeric material, and even if the discrete capsule film is not associated with each individual droplet, the discrete electrophoretic fluid droplets in the polymer dispersed electrophoretic display can be considered as a capsule or microcapsule; See, for example, U.S. Patent No. 6,866,760. Thus, for the purposes of this application, such polymer-dispersed electrophoretic media are considered to be sub-categories of encapsulated electrophoretic media.

A related type of electrophoretic display is a so-called "microcell electrophoretic display". In a microelectrophoresis display, charged particles and fluid are not encapsulated in the microcapsules, but are retained in a plurality of cavities formed in a carrier medium that is conventionally a polymeric film. See, for example, U.S. Patent Nos. 6,672,921 and 6,788,449 to Sipix Imaging.

Although electrophoretic media are often opaque (eg, due to the fact that in many electrophoretic media, particles substantially block visible light from transmitting through the display) and operate in a reflective mode, many electrophoretic displays can operate in a so-called "brake mode" where one display state is generally not Light and one is light. See, for example, U.S. Patent Nos. 5,872,552, 6,130,774, 6,144,361, 6,172,798, 6,271,823, 6,225,971; and 6,184,856. class A dual electrophoretic display that resembles an electrophoretic display but relies on changes in electric field strength can operate in a similar mode; see U.S. Patent No. 4,418,346. An electrophoretic medium operating in a shutter mode may be useful in a multi-layered structure of a full color display; in such structures, at least one layer adjacent the viewing surface of the display operates in a shutter mode to expose or hide further away from the viewing surface. Second floor.

As already indicated, encapsulated or microelectrophoretic displays have not encountered the problems of conventional electrophoresis device clustering and precipitation failure modes and provide further advantages such as the ability to print or coat displays on a wide variety of flexible and rigid substrates. (The use of the word "printing" is intended to encompass all forms of printing and coating, including but not limited to: pre-metered coating, such as patch die coating, slit type Or slot or extrusion coating, slate or cascade coating, curtain coating; roller coating, such as on-roller coating, smooth reverse coating; gravure ( Gravure) coating; dip coating; spray coating; meniscus coating; rotary coating; brush coating; air knife coating; silk screen printing process; Thermal printing process; inkjet printing process; electrophoretic deposition (see U.S. Patent No. 7,339,715); and other similar techniques). Thus, the resulting display can be flexible. Furthermore, the display itself can be inexpensive due to the printable display medium (using various methods).

Most of the conventional electrophoretic media exhibit essentially only two colors. These electrophoretic media use a single type of electrophoretic particles or first and second types of electrophoretic particles, the single type of electrophoretic particles in the first Second, the color of the color of the dissimilar color has a first color (in this case, the first color is displayed when the particles are located adjacent to the viewing surface of the display, and the second color is displayed when the particles are separated from the viewing surface), The first and second types of electrophoretic particles have different first and second colors in the uncolored fluid (in this case, the first color is displayed when the first type of particles are located adjacent to the viewing surface of the display, and The second type of particles, when placed adjacent to the viewing surface, displays a second color). In the past, the two colors are black and white. For a full color display, a color filter array can be placed on the viewing surface of a monochrome (black and white) display. These color filter arrays have traditionally been of the red/green/blue ("RGB") or red/green/blue/white ("RGBW") type. A display with color filters relies on a region sharing method that acts as a single full color pixel with three (in the case of an RGB display) or four (in the case of an RGBW display) sub-pixels. Unfortunately, each color can only be displayed in a partial display area. For example, in an RGBW display, each of red, green, and blue can only be displayed in a partial display area (one of the four sub-pixels) and white can effectively display the area in part (four of them) One complete sub-pixel, plus each colored sub-pixel is used as 1/3 white, such that the three colored sub-pixels together provide another fully white sub-pixel) display. This area sharing method causes the color to be slightly darker than expected.

Alternatively, a full color display can be constructed using multiple color changing layers operating in a shutter mode. See, for example, U.S. Patent No. 6,727,873, which is incorporated herein by reference in its entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire entire portion In addition to being complex and potentially expensive, such multi-layer displays require precise alignment of various layers and highly transparent electrodes (and transistors, if active matrix displays), Because of the absorption and reflection of the electrodes, the layers cause some loss of light, and in particular the transistors in active matrix displays. Multi-layer displays also suffer from parallax problems due to the thickness of the display stack approaching or exceeding the size of the pixels.

However, electrophoretic media are still required to display more colors in each pixel, so that, for example, such media can reproduce the appearance of high quality color printing. It has always been effective to use at least four inks, cyan/magenta/yellow/black ("CMYK"). Often the undetected person is the so-called "four-color" CMYK printing system which is actually a five-color system, and the fifth color is the white background provided by the paper (or similar) surface when no ink is applied. Because in an electrophoretic medium that is substantially opaque, there is no comparable background color unless it is used in the shutter mode, so the electrophoretic medium in the non-glide mode should be able to display five colors (black, white, and three). The main color, the three main colors are always cyan, magenta and yellow, or red, green and blue).

The present invention provides a full color display capable of displaying all colors in each portion of the active area of a display using only two electrophoretic layers. The present invention also provides an electrode structure and a method of driving an electrophoretic display that simplifies the bottom plate of such a full color display. The electrode structure and driving method of the present invention are also useful in other types of displays.

In one aspect, the invention provides an electrophoretic display having a viewing surface and including a first electrophoretic layer adjacent the viewing surface and a side of the first electrophoretic layer opposite the viewing surface a second electrophoretic layer, the first electrophoretic layer comprising a first fluid, a plurality of charged white particles and a plurality of light-transmitting charged particles of a first color different from white, the white and first color particles being dispersed In the first fluid, the first electrophoretic layer is provided with a driving means capable of driving the white and first color particles into three distinct optical states, that is, (a) a first optical state, wherein the white particles Located adjacent to the viewing surface and the first color particles are separated from the viewing surface; (b) a second optical state, wherein the first color particles are located adjacent to the viewing surface and the white particles are separated from the viewing surface And (c) a third optical state, wherein the white and first color particles occupy only a small portion of the first electrophoretic layer, thereby allowing light to enter the first electrophoretic layer via the viewing surface, through the first An electrophoretic layer to the second electrophoretic layer; and the second electrophoretic layer includes a second fluid, a plurality of charged particles different from white and a second color of the first color, and a plurality of different colors and first and second a charged particle of a third color of color, wherein the second and third color particles are dispersed in the second fluid, and the second electrophoretic layer is configured to drive the second and third color particles into three different colors a driving means of an optical state, that is, (d) a fourth optical state, wherein the second particles are located adjacent to the first electrophoretic layer and the third color particle system is spaced apart from the layer; (e) a fifth optical state, Wherein the third particles are located adjacent to the first electrophoretic layer and the second color particle system is spaced apart from the layer; and (f) a sixth optical state, wherein the second and third color particles are in the second The fluids are mixed with each other.

In one form of the "double layer" electrophoretic display of the present invention, the second and third color particles are reflective. First second And the third color (in either order) may be cyan, magenta, and yellow. Because the reflective cyan and yellow pigments with superior color saturation are readily available, the second and third colors can be cyan and yellow, and the first color is magenta.

In principle, the first and second electrophoretic layers of the display of the invention may be unpackaged. However, for the above reasons, and because "dielectrophoresis drive" (see below if used) and shutter mode drive are effective for packaged displays, it is generally preferred to be the first of the two-layer electrophoretic displays of the present invention. And encapsulating the second electrophoretic layer, that is, confining the particles and fluids to a plurality of capsules or micelles, or presenting a plurality of discrete droplets, the droplets being from a continuous phase containing a polymeric material Surrounding, the display is an electrophoretic display of polymer dispersion as previously discussed.

By applying an alternating electric field ("AC drive"), the white and first color particles can be driven to their third (shutter mode) optical state, and the first electrophoretic layer is provided with appropriate electrodes and drivers to enable application of this An alternating electric field. For example, as described in U.S. Patent No. 7,999,787, particle migration due to AC drive has heretofore been considered to be due to dielectrophoresis. However, it is practically difficult to determine whether the AC-driven particle migration is due to dielectrophoresis or electroosmotic force (see, for example, U.S. Patent Nos. 6,120,839 and 7,746,544), and therefore AC drive will be discussed below without attempting to describe the relevant particle migration. The exact physical phenomenon. The AC drive has the advantage of requiring only two electrodes to be provided normally, one on each side of the electrophoretic medium, and thus can be achieved with conventional substrates. However, AC drives may require the use of high frequency waveforms typically up to about 1 kHz, and such high Frequency waveforms can be difficult to perform in active matrix displays. Therefore, it is generally preferred to provide the optical state of the shutter mode by limiting the white and first color particles to electrodes occupying only a small portion of each of the pixels of the first electrophoretic layer, thereby allowing light to enter the viewing surface. The first electrophoretic layer freely passes through a major portion of the pixel and reaches the second electrophoretic layer; an electrode that occupies only a small portion of the pixel is conventionally referred to as a "side" or "auxiliary" electrode. Except for the term "side electrode", these electrodes are not necessarily located at the periphery of each pixel; for example, each auxiliary electrode may be annular or partially annular around the periphery of the pixel, or one or more small electrodes in the pixel.

In another aspect, the invention provides a novel way of interconnecting the sides or auxiliary electrodes of an electrophoretic display, wherein each sub-pixel has a primary and at least one auxiliary electrode on one side of the electrophoretic medium and on the opposite side of the electrophoretic medium There is a third electrode. (The term "pixel" as used herein refers to the smallest unit of a display that can display all colors that can be displayed on the display. The term "sub-pixel" as used herein refers to the smallest unit of a display that can change color. It should be understood that In a display such as a two-layer display of the present invention in which all colors of the display are capable of displaying all colors, the sub-pixels are equal to the pixels.) The electrophoretic display includes a fluid and at least one type of charged particles dispersed in the fluid. (The electrophoretic display may or may not be a two-layer electrophoretic display of the present invention.) In this electrophoretic display, the auxiliary electrodes of a plurality of sub-pixels are connected to a common driving line. Such a display can be driven by first driving all of the charged particles in a plurality of pixels adjacent to the auxiliary electrode, and then driving at least one of the plurality of sub-pixels to an optical state in which at least some of the charged particles are not located adjacent to the auxiliary electrode.

In such an "interconnected auxiliary electrode or IAE" display, it is convenient for the auxiliary electrode of all sub-pixels in the display to be connected to a common drive line. The third electrode of each sub-pixel can be a conventional form of a single common front electrode that extends across the entire display. There are two main variants of IAE. If all charged particles carry a charge of the same polarity (since the display uses only a single type of charged particle, has been in a colored fluid, or because the display uses more than two types of charged particles, the charged particles carry a charge of the same polarity, but with a phase Different electrophoretic mobility), each sub-pixel requires only a single auxiliary electrode, and such a display may hereinafter be referred to as a "single interconnected auxiliary electrode or SIAE" display. However, if any sub-pixel includes particles carrying two polar charges, the sub-pixel requires two auxiliary electrodes such that a potential of opposite polarity (potential with respect to the third electrode) can be applied to the two auxiliary electrodes to Particles carrying two polar charges are pulled to the two auxiliary electrodes, thus making the main portion of the sub-pixel region clear. Such a display can be conveniently determined to be a "dual interconnected auxiliary electrode" display of the present invention.

100‧‧ ‧ pixels

102‧‧‧ front electrode

102A‧‧‧Upper surface

104‧‧‧First Electrophoresis Layer

106‧‧‧First fluid

108‧‧‧ wall

110‧‧‧Main back electrode

112‧‧‧Auxiliary back electrode

114‧‧‧Auxiliary back electrode

118‧‧‧ front electrode

120‧‧‧Second Electrophoresis Layer

122‧‧‧Second fluid

124‧‧‧ wall

126‧‧‧ back electrode

102A‧‧‧View surface

100‧‧‧ display

300‧‧ ‧ pixels

302‧‧‧ front electrode

302A‧‧‧ upper surface

306‧‧‧First fluid

304‧‧‧First Electrophoresis Layer

308‧‧‧ wall

312‧‧‧Auxiliary back electrode

314‧‧‧Auxiliary back electrode

318‧‧‧ front electrode

320‧‧‧Second Electrophoresis Layer

322‧‧‧Second fluid

324‧‧‧ wall

326‧‧‧Back electrode

200R‧‧‧ subpixel

200G‧‧‧ subpixel

200B‧‧‧ subpixel

202R‧‧‧Coloring fluid

202G‧‧‧Coloring fluid

202B‧‧‧Coloring fluid

204‧‧‧ front electrode

210R‧‧‧main back electrode

210G‧‧‧main back electrode

210B‧‧‧Main back electrode

212R‧‧‧Auxiliary back electrode

212G‧‧‧Auxiliary back electrode

212B‧‧‧Auxiliary back electrode

220‧‧‧Black back substrate

202B‧‧‧Blue fluid

202R‧‧‧Red Fluid

230‧‧‧ Grid

230A‧‧‧Gate

230B‧‧‧Gate

Figure 1A of the accompanying drawings is a schematic cross section through a pixel of a first two-layer electrophoretic display of the present invention, wherein the present invention uses white, cyan, magenta, and yellow particles. Figure 1A shows the pixel in its white optical state.

The 1B-1H diagram is similar to the schematic section of Figure 1A, but the display is represented by its magenta, cyan, yellow, red, blue, green, and black optical states, respectively.

2A-2E is a schematic cross-section through a pixel of a second two-layer electrophoretic display of the present invention, similar to the schematic cross-section of Figures 1A-1H, wherein the present invention uses white, red, green, and blue particles.

Figure 3A is a schematic cross section through three sub-pixels of a single interconnected auxiliary electrode display of the present invention.

Figure 3B is a schematic top plan view of a modification of the single interconnected auxiliary electrode display shown in Figure 3A.

Figure 4 is a schematic top plan view of a dual interconnected auxiliary electrode display of the present invention, similar to the schematic top plan view of Figure 3B.

Obviously from the foregoing summary of the invention, the invention has two main points of view, namely a two-layer electrophoretic display and an interconnected auxiliary electrode display. These two points of view will be discussed primarily individually below, but it should be understood that the two points of the present invention can be incorporated into a single physical display.

Double layer electrophoretic display

As already indicated, in one aspect of the invention, a two-layer electrophoretic display is provided. The display has a viewing surface and individual first and second electrophoretic layers, the first electrophoretic layer being located adjacent the viewing surface and the second electrophoretic layer being located on a side of the first electrophoretic layer opposite the viewing surface. The first electrophoretic layer includes a (first) fluid, and charged white particles dispersed in the fluid and light-transmitting charged particles of a first color other than white. The first electrophoretic layer can be driven into three distinct optical states, namely (a) a first optical state, wherein the white particles are located adjacent to the viewing surface and the first color particle system is separated from the viewing surface, so The surface appears white; (b) a second optical state in which the first color particles are located Adjacent to the viewing surface and the white particles are spaced apart from the viewing surface, the viewing surface displays a first color (as discussed below, unless modified by the action of the second electrophoretic layer); and (c) a third optical state, The white and first color particles occupy only a small portion of the first electrophoretic layer, thereby allowing light to enter the first electrophoretic layer through the viewing surface, through the first electrophoretic layer to the second electrophoretic layer. The second electrophoretic layer includes a second fluid (which may be the same as or different from the first fluid), and charged particles dispersed in the second fluid different from white and the second color of the first color, and different from white and Charged particles of a third color of the first and second colors. The second electrophoretic layer can be driven into three distinct optical states, that is, (d) a fourth optical state, wherein the second particles are located adjacent to the first electrophoretic layer and the third color particle systems are separated from the layer; (e) a fifth optical state, wherein the third color particles are located adjacent to the first electrophoretic layer and the second color particle system is spaced apart from the layer; and (f) a sixth optical state, wherein the second optical state The third color particles are mixed with each other in the second fluid.

Purely based on practical reasons for the availability of suitable materials, although red, green and blue particles can also be used, it is generally preferred that the first color is magenta, the second color is cyan and the third color is yellow. Referring to Figures 1A-1H, the manner in which the two-layer electrophoretic display of the present invention using these color choices displays white, black, magenta, cyan, yellow, red, green, and blue will now be explained. For the sake of illustration, although it is apparent that either or both of these charge distributions may be reversed, or one or both of the electrophoretic layers may use the same charge but differ in the two types of particles of electrophoretic mobility, it is assumed White and cyan particles carry a positive charge while magenta and yellow particles carry a negative charge.

Figure 1A shows a single pixel (generally designated 100) of the first two-layer electrophoretic display of the present invention. The pixel 100 includes a light transmissive front electrode 102 that forms a viewing surface of the display (actually, the front electrode 102 has historically included a thin layer of indium tin oxide, a carbon nanotube conductor or a surface disposed beneath the transparent polymeric film The conductive polymer (as shown), but the internal structure of the front electrode 102 is not critical to the purpose of the present invention. The pixel 100 further includes a first electrophoretic layer (generally indicated by 104), the first electrophoretic layer including positively scattering (ie, reflecting) white particles W and negatively transmissive magenta particles in the first fluid 106 M. The first electrophoretic layer 104 is shown encapsulating particles W and M and a first fluid 106 that are contained within a single-capsule bound by the balloon wall 108; the single-capsule is shown for purposes of illustration only and There will always be more than one capsule in each pixel.

On the side of the capsule opposite the front electrode 102, the pixel 100 further includes a main back electrode 110 and two auxiliary back electrodes 112 and 114. The electrodes 110, 112, and 114 are connected to voltage supply lines (not shown) that enable the potentials of the three electrodes to be controlled independently of each other.

Immediately following the electrodes 110, 112 and 114 (i.e., on the side of the electrodes opposite the front electrode 102) but insulated from here as a further electrode 118, which acts as a second electrode (generally indicated at 120) before the electrode The second electrophoretic layer includes cyan particles C with positive electric reflection and yellow particles Y with negative electric reflection in the second fluid 122. The second electrophoretic layer 120 is shown encapsulated with particles C and Y and a second fluid 122 that are contained in a single-capsule bound by the balloon wall 124; further, the single-capsule is only One or more capsules are present in each pixel as shown for the purpose of the illustration. A single further electrode 126 as a back electrode of the second electrophoretic layer 120 is disposed on a side of the second electrophoretic layer opposite to the electrode 118.

Figure 1A shows the display in its white state. In order to drive the display to this state, the front electrode 102 is negative with respect to the back electrodes 110, 112 and 114 such that the white particles W are located adjacent to the front electrode and the magenta particles M are adjacent to the back electrodes 110, 112 and 114, resulting in a display The viewing surface 102A displays white. Since the positions of the cyan particles C and the yellow particles Y in the second electrophoretic layer 120 are irrelevant (the magenta particles M, the cyan particles C, and the yellow particles Y are all hidden by the white particles W), the potentials of the electrodes 118 and 126 are not These electrodes are allowed to float in a relevant and convenient manner.

Figure 1B shows the display in its magenta state. In order to drive the display to this state, the front electrode 102 is positive with respect to the back electrodes 110, 112 and 114 such that magenta particles M are located adjacent to the front electrode 102 and the white particles W are adjacent to the back electrodes 110, 112 and 114, such that viewing is via The light entering the display of surface 102A passes through the transmissive magenta particles M and the first fluid 106, is reflected from the white particles W, and returns through the first fluid 106 and the transmissive magenta particles M, and thus on the viewing surface 102A of the display Show magenta. Furthermore, the positions of the cyan particles C and the yellow particles Y in the second electrophoretic layer 120 are irrelevant (both the cyan particles C and the yellow particles Y are shielded by the white particles W), so the potentials of the electrodes 118 and 126 are irrelevant. These electrodes are conveniently allowed to float.

As illustrated in FIG. 1C, in order to generate cyan, one of the auxiliary back electrodes (illustrated as electrode 112 for convenience) is negative with respect to the front electrode 102 and the main back electrode 110, and another An auxiliary electrode 114 is positive. The white particles W migrate adjacent to the negative auxiliary electrode 112, and the magenta particles migrate adjacent to the positive auxiliary electrode 114, thereby effectively shielding both the white and magenta particles and opening the main portion of the first electrophoretic layer 104 for light from the viewing surface 102A. Passing to the second electrophoretic layer 120 (the portion of the cross-sectional area of the capsule occupied by the magenta and white particles in the figure 1C and the like is greatly exaggerated for ease of illustration. In fact, it is easy to make more than 80% The capsule is transparent.). At the same time, with respect to its back electrode 126, the front electrode 118 of the second electrophoretic layer 120 is made negative such that the reflective cyan particles C are located adjacent to the front electrode 118 and the yellow particles Y are located adjacent to the back electrode 126. Thus, the light entering the display 100 via the viewing surface 102A passes through the first (transmissive) first electrophoretic layer 104, and from the cyan particles C of the adjacent electrode 118 (the cyan particles C are used to occlude the yellow particles Y of the adjacent electrode 126) Reflected, and pixel 100 displays cyan.

As shown in FIG. 1D, in order to generate yellow, the potentials of the electrodes 102, 110, 112, and 114, and therefore, the positions of the white particles W and the magenta particles M are the same as those in the first FIG. However, with respect to its back electrode 126, the front electrode 118 of the second electrophoretic layer 120 is now made positive such that the reflective yellow particles Y are located adjacent to the front electrode 118 and the cyan particles C are located adjacent to the back electrode 126. Therefore, the light entering the display 100 via the viewing surface 102A passes through the first first electrophoretic layer 104 that is turned on, and the yellow particles Y from the adjacent electrode 118 (the yellow particles Y) The cyan particles C) for occluding the adjacent electrode 126 are reflected, and the pixel 100 displays yellow.

In order to generate red color in the pixel 100, it is necessary to generate light absorption by both the magenta particle M and the yellow particle Y. Therefore, as shown in FIG. 1E, the front electrode 102 is made positive with respect to the main back electrode 110, and both or one of the auxiliary electrodes 112 and 114 is negative (for ease of illustration, the auxiliary electrode 112 is made Both and 114 are expressed as negative). Therefore, the light-transmissive magenta particles M are located adjacent to the front electrode 102, and the white particles W are located adjacent to the negative auxiliary electrodes 112 and 114, thereby shielding the white particles W. Meanwhile, as shown in FIG. 1B, the front electrode 118 of the second electrophoretic layer 120 is made positive with respect to the back electrode 126 such that the reflective yellow particles Y are located adjacent to the front electrode 118 and the cyan particles C are located adjacent to the back electrode. 126. Therefore, the light entering the display 100 via the viewing surface 102A passes through the magenta particles M (absorbs the green wavelength), and the yellow particles Y from the adjacent electrode 118 (the yellow particles Y are used to occlude the cyan particles C of the adjacent electrode 126) are reflected. The blue wavelength is absorbed and returned through the magenta particle M such that the pixel 100 displays red.

As shown in Fig. 1F, in order to generate blue, the relative potentials of the electrodes 102, 110, 112, and 114, and therefore, the positions of the white particles W and the magenta particles M are the same as those in Fig. 1E. However, with respect to its back electrode 126, the front electrode 118 of the second electrophoretic layer 120 is now made negative such that the reflective cyan particles C are located adjacent to the front electrode 118 and the yellow particles Y are located adjacent to the back electrode 126. Thus, light entering display 100 via viewing surface 102A passes magenta particles M (absorbs green wavelengths) and cyan particles C from adjacent electrodes 118 (such cyan Particle C is used to smear the yellow particles Y) of the adjacent electrode 126, absorb the red wavelength, and return through the magenta particle M such that the pixel 100 displays blue.

As shown in FIG. 1G, in order to generate green, the relative potentials of the electrodes 102, 110, 112, and 114, and therefore, the positions of the white particles W and the magenta particles M are the same as those in the first and second graphs, that is, , masking white particles W and magenta particles M. However, in the case where the cyan particles C and the yellow particles Y are mixed with each other in the second fluid 122, such mutual mixing can be accomplished by first transferring the cyan particles C and the yellow particles Y to the first and first F1. The position shown in one of them, and then the relative potential of the electrode is inverted, so that the cyan particles C and the yellow particles Y are mixed with each other in the second fluid 122. Thus, light entering the display 100 via the viewing surface 102A passes through the first first electrophoretic layer 104 that is turned on, and is reflected from both the yellow particles Y and the cyan particles C in the fluid 122, and the pixel 100 displays green.

Finally, as shown in FIG. 1H, in order to generate black pixels, the relative potentials of the electrodes 102, 110, 112, and 114, and therefore, the positions of the white particles W and the magenta particles M are the same as those in the first FIG. Meanwhile, as illustrated in FIG. 1G, the cyan particles C and the yellow particles Y are mixed with each other in the second fluid 122. Thus, light entering display 100 via viewing surface 102A passes magenta particles M (absorbs green wavelengths), and yellow particles Y (which absorb blue wavelengths) and cyan particles C (which absorb red wavelengths) from fluid 122 are both The reflection is such that substantially no light is returned via the first electrophoretic layer 104 and the pixel 100 displays black.

From the foregoing, it will be seen that the display illustrated in Figures 1A-1H can display white, black, cyan, magenta, yellow, red, green, and blue through its entire display area. As mentioned previously, displays using RGB color filter arrays can only display red, green, and blue through one-third of their display area, black through the entire display area, and through one-third of the display area. Displays white for processing equal to white. Similarly, a display using an RGBW color filter array can only display red, green, and blue through a quarter of its display area, black through the entire display area, and display a pair of white through the display area equal to white. The processing of white. Therefore, if the design is well designed with highly saturated pigments, the two-layer electrophoretic display of the present invention illustrated in Figures 1A-1H should produce a larger display color than the color display based on the prior art color filter array. Domain (gamut) and comparison.

It will be seen from the description of Figures 1C-1H above that the ability of display 100 to display various colors depends on the front electrophoretic layer 104 by limiting one or both of the electrophoretic particles to a small portion of the active region of pixel 100. The ability to mask one or both of the electrophoretic particles. As already mentioned, the necessary shielding of the first electrophoretic layer can be achieved using an auxiliary electrode or by AC driving; in the case of a display using a microcell instead of a capsule, the auxiliary electrode can be placed in the side wall of the microcell. Regardless of the method used to mask the particles in the first electrophoretic layer, the method should limit the particles to as small as possible in one of the pixel regions, thus providing a portion of the transparent region as much as possible through which the light can pass. Arrived at the second electrophoretic layer. The particle masking and particle loading efficiency in the first electrophoretic layer will determine the optical transmittance of this layer in its masked state, which will necessarily be less than 100%. First electrophoresis The unavoidable absorption of light in the layer will result in a reduction in the color saturation of the color displayed by the second electrophoretic layer. For most users, since the reflectivity of the white state of the display is an important criterion for the display, it is advantageous to retain the white particles in the first electrophoretic layer because of the incomplete masking of the first electrophoretic layer. The light loss and the absorption of the electrodes and the thin film transistors disposed between the first and second electrophoretic layers will inevitably reduce the reflectance of the white particles in the second electrophoretic layer. For similar reasons, the particles in the second electrophoretic layer should have a highly saturated color to deplete the light due to incomplete masking of the first electrophoretic layer and the electrodes and films disposed between the first and second electrophoretic layers. The color saturation caused by the absorption of the transistor is minimized. Cyan and yellow pigments having superior color saturation are widely available and are therefore preferably used in the second electrophoretic layer of the dual layer display of the present invention.

A potential problem with the first embodiment of the invention shown in Figures 1A-1H is that the electrodes 112 and 114 will be held in the electrode 110 in order to shield the magenta and white particles while maintaining the electrodes 112 and 114 at different potentials. The substantial dipole is induced, thus causing the magenta and white particles to occupy part of the electrode 110 and thus increase the portion of the pixel area that is obscured by the magenta and white particles. If this problem is found to be severe in any particular display, there are two ways to reduce the problem. As already discussed, the first one is driven by AC to achieve both shades of magenta and white particles (note that this AC drive will cause white and magenta particles to mix with each other when they are obscured, to the display The operation is the same. In the display states shown in the 1C, 1D, 1G, and 1H diagrams, whether white or magenta particles are mixed or masked at individual positions is no different from the appearance of the display. In the display state in which only the white particles are shielded as shown in Fig. 1H, of course, such shielding is normally achieved by the auxiliary electrode, although in the two cases where the electrodes 112 and 114 are at the same potential, there is no dipole in the electrode 110. Therefore, the above problems have not occurred. ). The second method eliminates electrode 110, thus avoiding any possibility of inducing a dipole in this electrode. Fig. 1B shows a display state which is only significantly affected by the erasing electrode 110 (the position of the magenta particles is changed in the state shown in Fig. 1A, but this is not relevant because the magenta particles are covered by white particles and thus Not seen by the viewer of the display). In the display state shown in FIG. 1B, the erasing electrode 110 concentrates on the white particles adjacent to the electrodes 112 and 114 so that the white particles cannot pass over the entire area of the pixel 100 to reflect back the magenta light passing through the magenta particle layer. Therefore, if the electrode 110 is to be eliminated, it is sensible to provide a white reflector adjacent or as part of the frontmost electrode 126, acting as a reflector in the display state shown in Fig. 1B, and shielding the cyan and yellow particles to allow passage. The light of the magenta particles is reflected from this reflector.

The 2A-2E diagram is a schematic cross section similar to the 1A-1H diagram, through a schematic cross section of a pixel (generally indicated at 300) of the second electrophoretic display of the present invention. The second electrophoretic display uses white, red, green, and blue particles in place of the white, magenta, cyan, and yellow particles used in the first display described above, and all of the particles are reflective. Moreover, in the second display, the main back electrode of the first electrophoretic layer (110 in Fig. 1A) is omitted.

More specifically, pixel 300 includes a light transmissive front electrode 302, the upper surface 302A of which forms the viewing surface of the display. Pixel 300 Further included is a first electrophoretic layer (generally designated 304) that includes positively charged white particles W and negatively charged red particles R in the first fluid 306. The first electrophoretic layer 304 is encapsulated with particles W and R and a first fluid 306 that are contained in a single-capsule bound by the balloon wall 308; the single-capsule is shown for purposes of illustration only and There will always be more than one pocket in the pixel.

On the side of the capsule opposite the front electrode 302, the pixel 300 further includes two auxiliary back electrodes 312 and 314. The electrodes 312 and 314 are connected to voltage supply lines (not shown) that enable the potentials of the electrodes to be controlled independently of each other.

Immediately following the electrodes 112 and 114 (i.e., on the side of the electrodes opposite the front electrode 302) but insulated therefrom as a further electrode 318, which acts as the second electrode of the second electrophoretic layer (labeled 320). The second electrophoretic layer includes positively charged blue particles B and negatively reflected green particles G in the second fluid 322. The second electrophoretic layer 320 is encapsulated with particles B and G and a second fluid 322 that are contained in a single-capsule bound by the balloon wall 324; further, the single-capsule is shown for illustrative purposes only. And there will always be more than one capsule in each pixel. A single further electrode 326 as a back electrode of the second electrophoretic layer 320 is disposed on a side of the second electrophoretic layer opposite to the electrode 318.

Fig. 2A shows that the pixel 300 is in its white state. In order to drive the pixel to this state, the front electrode 302 is made negative with respect to the back electrodes 312 and 314 such that the white particles W are located adjacent to the front electrode 302 and the red particles R are located adjacent to the back electrodes 312 and 314, resulting in the viewing surface 302A of the pixel. Show white. Blue B in the second electrophoretic layer 320 The position of the green G particles is irrelevant (the red particles R, the blue particles B, and the green particles G are all hidden by the white particles W), and for ease of illustration, the green particles G are represented as adjacent electrodes 318 and blue. The color particle B is adjacent to the electrode 326.

Figure 2B shows pixel 300 in its red optical state. In order to drive the pixel to this state, the front electrode 302 is positive with respect to the back electrodes 312 and 314 such that the red particles R are located adjacent to the front electrode 302 and the white particles W are located adjacent to the back electrodes 312 and 314, resulting in the viewing surface 302A of the pixel. Show red. It is noted that the position of the blue B and the green G particles in the second electrophoretic layer 320 is irrelevant because the red particles R are reflective rather than transmissive (the white particles W, the blue particles B, and the green particles G are all The red particles R are hidden, and further, for ease of illustration, the green particles G are shown as being adjacent to the electrode 318 and the blue particles B are adjacent to the electrode 326.

Figure 2C shows pixel 300 in its blue optical state. As in the cyan optical state shown in FIG. 1C, with respect to the front electrode 302, one of the back electrodes (illustrated as electrodes 312 for convenience) is negative, and the other electrode 314 is made positive. of. The white particles W migrate adjacent to the negative electrode 312, and the red particles R migrate adjacent to the positive electrode 314, thereby effectively shielding both the white and red particles and opening the main portion of the first electrophoretic layer 304 for light to pass through the viewing surface 302A. Up to the second electrophoretic layer 320 (as in the first C-figure, the cross-sectional area portion of the pixel occupied by the red and white particles in the second C-2E diagram is greatly exaggerated for ease of illustration. In fact, it is easy to make more than 80 % of the pixels are transparent.). At the same time, the second electrophoretic layer 320 is made opposite to the back electrode 326 thereof. The front electrode 318 is negative such that the blue particles B are located adjacent to the front electrode 318 and the green particles G are located adjacent to the back electrode 326. Thus, the light entering the pixel 300 via the viewing surface 302A passes through the first (transmissive) first electrophoretic layer 304, and the blue particles B from the adjacent electrode 318 (the blue particles B are used to occlude the green of the adjacent electrode 326) Particle G) reflects and pixel 300 displays blue.

As shown in FIG. 2D, in order to generate green, the potentials of the electrodes 302, 312, and 314, and therefore, the positions of the white particles W and the red particles R are the same as those in the second FIG. However, with respect to its back electrode 326, the front electrode 318 of the second electrophoretic layer 320 is now made positive such that the green particles G are located adjacent to the front electrode 318 and the blue particles B are located adjacent to the back electrode 326. Therefore, the light entering the pixel 300 via the viewing surface 302A passes through the first first electrophoretic layer 304 that is turned on, and is reflected from the green particles G of the adjacent electrode 318 (the green particles G are used to trap the blue particles B of the adjacent electrode 326). And pixel 300 displays green.

Finally, as shown in FIG. 2E, in order to generate black pixels, the relative potentials of the electrodes 302, 312, and 314, and therefore, the positions of the white particles W and the red particles R are the same as those in the 2C and 2D drawings. At the same time, the blue particles B and the green particles G are mixed with each other in the second fluid 322. Therefore, light entering the pixel 300 via the viewing surface 302A passes through the first electrophoretic layer 304, and blue particles B (which absorb red and green wavelengths) and green particles G (which absorb red and blue wavelengths) from the fluid 322 The reflection is such that substantially no light is returned via the first electrophoretic layer 304 and the pixel 300 displays black.

It will be observed that the display using red, green and blue particles shown in Figure 2A-2E cannot display yellow, cyan and magenta in a single pixel, and in order to produce yellow, cyan and magenta, it is necessary to The form of regional modulation. For example, in order to produce a yellow color, it is necessary to display red pixels adjacent to the green pixels. Similarly, to produce cyan, green pixels adjacent to the blue pixels are displayed; and to produce magenta, red pixels adjacent to the blue pixels are displayed. However, the resulting color will still be superior to that of prior art displays using color filters, for example, in fact, the RGBW display based on color filters can still be used throughout the display. The area shows yellow.

It will be seen from the foregoing that the dual layer display of the present invention can display a wide range of colors per pixel, has a superior white state, and does not require an electrophoretic layer having more than two layers of particles in each layer. Thus, a two-layer display can have a larger color gamut than a color electrophoretic display that is shared based on the area of the color filter array above the monochromatic electrophoretic layer.

Interconnected auxiliary electrode display

In the display as illustrated in the above 1A-1E and 2A-2E, wherein each pixel requires more than one auxiliary electrode, the potential must not change due to the potential of the main electrode of the same pixel, and the auxiliary is established. The necessary connections of the electrodes, especially in high resolution active matrix displays, cause substantial problems. Heretofore, in an active matrix display, the auxiliary electrode has been normally driven in a manner exactly parallel to the main electrode; each row of the auxiliary electrode is connected to a data line parallel to the data line for driving the row of the associated main electrode, And by taking the initiative The column driver of the matrix display scans the columns of the active matrix display and applies a potential to the auxiliary electrodes of the pixels in the selected column while applying a potential to the main electrode of the same pixel. This configuration at least doubles the number of data lines required, and in the case of the display as shown in Figures 1A-1H and 2A-2E, each pixel requires two auxiliary electrodes to make the required information The number of lines is tripled. The increase in the number of data lines substantially increases the complexity and cost of the backplane, and in high resolution displays, very narrow data lines are required, which may result in increased data line failure rates and thus reduced backplane yield. Moreover, the increase in the number of data lines doubles or triples the amount of data that must be transmitted when each display is updated, thereby increasing the complexity and cost of the display.

It is now known that by arranging the auxiliary electrodes of a plurality of pixel rows (and preferably all of the pixels of the display), the configuration of the substrate used for the display having the auxiliary electrodes can be greatly simplified. A two-step driving method can be used to drive a display having interconnected auxiliary electrodes to display any desired image. In the two-step driving method, the main electrode and the front electrode are used, and all pixels are first driven to the shadow thereof. The state and then the pixels that do not need to be in the shadow state are driven to their final state.

Figure 3A is a schematic cross section through three sub-pixels (indicated by 200R, 200G, and 200B, respectively) of the interconnected auxiliary electrodes of the present invention produced by modifying a known type of color-packaged electrophoretic display. Each of the sub-pixels includes white charged particles W (which are assumed to be positively charged for the sake of illustration) of the colored fluids 202R, 202G, and 202B, which are colored red, green, and blue, respectively. The display The device transmits a continuous common front electrode 204 that forms the viewing surface of the display, and each of the sub-pixels has a primary back electrode 210R, 210G or 210B and a single auxiliary back electrode 212R, 212G or 212B. The primary and secondary back electrodes are translucent and disposed on the black backing substrate 220; alternatively, the primary and secondary back electrodes themselves may be colored black.

As illustrated in Figure 3A, each sub-pixel has three distinct optical states. In the first optical state illustrated for the sub-pixel 200G, the primary back electrode 210G is made positive with respect to the front electrode 204 such that the white particles W are located adjacent to the front electrode 204, and the sub-pixels exhibit a white appearance. In the second optical state illustrated for the sub-pixel 200B, the primary back electrode 210B is made negative with respect to the front electrode 204 such that the white particles W are located adjacent to the main back electrode 210B. Light entering the sub-pixel 200B via the front electrode 204 passes through the blue fluid 202B, is reflected from the white particle W, and returns through the blue fluid 202B. Thus, the sub-pixels present the color of the fluid, in this case blue. In the third optical state illustrated for the sub-pixel 200R, the back auxiliary electrode 212R is made negative with respect to both the main back electrode 210R and the front electrode 204, so that the white particles W are attracted to the auxiliary electrode 212R, and thus are Shaded. Light entering the sub-pixel 200R via the front electrode 204 is absorbed by the red fluid 202R and is absorbed by the black substrate 220 such that the sub-pixels exhibit a black appearance.

As already mentioned, in prior art displays, the primary and secondary back electrodes are driven by parallel data lines, resulting in increased cost and complexity of the backplane. Figure 3B is a top plan view showing how the backplane of the display shown in Figure 3A can be modified in accordance with the present invention to allow for simplification Base plate. As shown in FIG. 3B, the back auxiliary electrodes of all of the pixels are replaced by a continuous grid 230 extending around all of the main back electrodes; this continuous gate only needs to be connected to the voltage supply line at a single point. As described above for the sub-pixel 200R in FIG. 3A, in order to drive the display, the voltage of the gate 230 is first set to be lower than the voltages of both the main back electrode and the front electrode, so that all the white particles W are attracted to the gate 230. And all subpixels have a black appearance. Thereafter, the gate 230 is set to the same voltage as the front electrode 204 and the voltages of the main back electrodes of the various sub-pixels are adjusted to drive those sub-pixels that are not intended to display a black appearance in the final image to a desired color state. For example, to display the green area of the image, the red and blue sub-pixels are left in their black state, and the green sub-pixels are switched to their green state.

Figure 4 of the accompanying drawings is similar to the top plan view of Figure 3B, but the illustration is applicable to an electrophoretic medium (e.g., the previous electrophoretic layer shown in Figures 1A-1H or the previous electrophoretic layer shown in Figure 2A-2E). In the form of interconnected auxiliary electrodes, which use two types of electrophoretic particles having opposite polarity charges. The gates 230A, 230B shown in FIG. 4 can be considered to be derived from the gate 230 by driving the gate 230 along the center line of each row of sub-pixels, thus creating two connections to individual voltage supply lines (not The individual sub-gates 230A, 230B are shown to enable independent control of the potential of the two sub-gates. The bottom plate shown in FIG. 4 is driven in a manner very similar to that shown in FIG. 3B; first, the two sub-gates 230A, 230B are positive and negative with respect to the front and main back electrodes, respectively, and thus attract Two types of electrophoretic particles are applied to the two sub-gates. Sub-pixels that are in other optical states are then driven to those states of the conventional mode.

By using only one or two voltage supply lines to shield the entire display, the backplane and drive electronics can be fabricated at very low cost, especially for shielding waveforms requiring high frequency or high voltage. Executing one or two high current drivers for the entire display is possible, but performing a large number of such drivers, one for each pixel, can be costly and prone to failure.

As already mentioned, the interconnected auxiliary electrode structures of the present invention have significant benefits when used to control the first electrophoretic layer of the two-layer electrophoretic display of the present invention. If the back electrode structure of the first electrophoretic layer comprises two consecutive sub-gates instead of individual auxiliary back electrodes, thousands of data lines can be eliminated, the exact number depending on the resolution and area of the display, thus reducing the cost of the display . Furthermore, as already explained, the drive of the display is simplified.

In summary, the display of the interconnected auxiliary electrodes of the present invention provides a means to shield the display without adding significant complexity or cost to the display backplane or controller. Only one or two drivers are required to shield the gate. Such a driver can be expensive relative to a pixel electrode driver, but using only one or two higher cost drivers can significantly reduce overall display cost. Such drivers may even be designed to produce the higher voltages and frequencies required for electrophoretic masking, which is very difficult to achieve with individual auxiliary electrodes at each pixel or sub-pixel.

100‧‧ ‧ pixels

102‧‧‧ front electrode

102A‧‧‧Upper surface

104‧‧‧First Electrophoresis Layer

106‧‧‧First fluid

108‧‧‧ wall

110‧‧‧Main back electrode

112‧‧‧Auxiliary back electrode

114‧‧‧Auxiliary back electrode

118‧‧‧ front electrode

120‧‧‧Second Electrophoresis Layer

122‧‧‧Second fluid

124‧‧‧ wall

126‧‧‧ back electrode

Claims (16)

An electrophoretic display (300) having a viewing surface (302A) and including a first electrophoretic layer (304) adjacent to the viewing surface (302A) and a viewing surface (302A) of the first electrophoretic layer (304) a second electrophoretic layer (320) on the opposite side, the electrophoretic display characterized in that the first electrophoretic layer (304) comprises a first fluid (306), a plurality of charged white particles (W), and a plurality of a white-reflectively charged first color particle (R), the white particle (W) and the first color particle (R) being dispersed in the first fluid, the first electrophoretic layer (304) being provided a driving means capable of driving the white particles (W) and the first color particles (R) into three distinct optical states, that is, (a) a first optical state, wherein the white particles (W) are located adjacent to the viewing a surface (302A) and the first color particles (R) are spaced apart from the viewing surface (302A); (b) a second optical state, wherein the first color particles (R) are located adjacent to the viewing surface (302A) And the white particles (W) are spaced apart from the viewing surface (302A); and (c) the third optical state, wherein the white particles (W) and the first color The particle (R) occupies only a small portion of the first electrophoretic layer (304), thereby allowing light to enter the first electrophoretic layer (304) via the viewing surface (302A), through the first electrophoretic layer (304) to The second electrophoretic layer (320); and the second electrophoretic layer (320) includes a second fluid (322), a plurality of charged second color particles different from white (W) and the first color (R) (G) ), and a plurality of bands different from white and the first color (R) and the second color (G) Electrical third color particles (B), the second color particles (G) and third color particles (B) are dispersed in the second fluid (322), and the second electrophoretic layer (320) is provided with energy Driving the second color particles (G) and the third color particles (B) into driving means of three different optical states, that is, (d) a fourth optical state, wherein the second color particles (G) are located Adjacent to the first electrophoretic layer (304) and the third color particles (B) are separated from the layer; (e) a fifth optical state, wherein the third color particles (B) are located adjacent to the first electrophoresis a layer (304) and the second color particles (G) are spaced apart from the layer; and (f) a sixth optical state, wherein the second color particles (G) and the third color particles (B) are The second fluid (322) is mixed with each other. The electrophoretic display of claim 1, wherein the second color particles (G) and the third color particles (B) are reflective. The electrophoretic display of claim 1, wherein the first, second and third colors are in any order of red, green and blue. The electrophoretic display of claim 3, wherein the first color is red and the second and third colors are green and blue. The electrophoretic display of claim 1, wherein in the first electrophoretic layer (304) and the second electrophoretic layer (320), the particles (W, R, G, B) and the fluid (306, 322) is confined to a plurality of capsules or microcells, or appears as a plurality of discrete droplets surrounded by a continuous phase of polymeric material. The electrophoretic display of claim 1, wherein the first electrophoretic layer is provided with a plurality of electrodes and a plurality of drivers capable of applying an alternating electric field to the first electrophoretic layer. The electrophoretic display of claim 1, wherein at least one pixel of the first electrophoretic layer (304) is provided with at least one electrode (213, 314) that occupies only a small portion of the pixel. The electrophoretic display of claim 7, wherein the at least one pixel of the first electrophoretic layer (304) is provided with two electrodes (213, 314), each of which occupies only a small portion of the pixel. The potentials of the two electrodes (213, 314) are independently controllable. An electrophoretic display comprising an electrophoretic layer comprising a fluid (202R, 202G, 202B) and a plurality of charged particles (W) dispersed in the fluid (202R, 202G, 202B), the display having a plurality of pixels, each The pixel includes at least one sub-pixel (200R, 200G, 200B), and each sub-pixel (200R, 200G, 200B) has one main (210R, 210G, 210B) and at least one auxiliary electrode (212R) on one side of the electrophoretic layer. And 212G, 212B; 230) and having a third electrode (204) on an opposite side of the electrophoretic layer, the auxiliary electrodes (212R, 212G, 212B; 230) of the plurality of sub-pixels being connected to a common driving line. An electrophoretic display according to claim 9 wherein the auxiliary electrodes (212R, 212G, 212B; 230) of all sub-pixels of the display are connected to a common drive line. An electrophoretic display according to claim 9 wherein all of said charged particles (W) carry charges of the same polarity and each sub-pixel comprises only one auxiliary electrode (212R, 212G, 212B). An electrophoretic display according to claim 11, wherein all of the auxiliary electrodes of the display are connected to a single drive line. The electrophoretic display of claim 9, wherein the electrophoretic layer comprises two different types of charged particles carrying opposite polarity charges, and each sub-pixel comprises two auxiliary electrodes (230A, 230B), each of the sub-pixels The two auxiliary electrodes (230A, 230B) are connected to individual drive lines. An electrophoretic display according to claim 9, wherein the charged particles (W) and the fluid (202R, 202G, 202B) are localized in a plurality of capsules or micelles. An electrophoretic display according to claim 9 wherein said charged particles and said fluid are present as a plurality of discrete droplets surrounded by a continuous phase comprised of polymeric material. An electrophoretic display according to claim 9 wherein the flow system is in a gaseous state.