Pressure-sensitive writing medium comprising electrophoretic material - Patent Application 20070123633

Abstract

Systems and methods for pressure-sensitive electrophoretic or magnetophoretic displays - Patents.com Systems and methods are disclosed for pressure-sensitive electrophoretic displays, which may optionally include tactile feedback. The display may include a first conductive layer having pressure-sensitive conductivity and an electrophoretic layer positioned adjacent to the first conductive layer, the electrophoretic layer being in electrical communication with the first conductive layer and configured to locally change state based on pressure applied to the first conductive layer. Local and global writing and erasing of the display may also be achieved.

Description

[Background technology]

[0001] (Related Applications) This application claims priority to U.S. Provisional Patent Application No. 62 / 773,891, filed November 30, 2018, which is incorporated by reference in its entirety herein.

[0002] All patents, patent applications, and publications referenced within this document are incorporated by reference in their entirety.

[0003] BACKGROUND OF THEINVENTION The present invention relates to electro-optic displays. More specifically, the present invention relates to systems and methods for pressure-sensitive electrophoretic or magneto-electrophoretic displays. In some embodiments, the displays include tactile feedback. The described displays can be inexpensively manufactured and used for writing and drawing, or they can be integrated into surfaces, touch panels, and the like.

[0004] Tactile feedback is increasingly used in the electronic device industry. Most of these feedback schemes rely on sensing the applied force in some context and then relaying that force to the user via an actuator (piezoelectric, acoustic, etc.). Passive tactile feedback mechanisms are also known in the art. These mechanisms do not require additional control circuitry or additional mechanical relays. Any system with a spring or stiffness is an excellent example of this idea. As the spring is compressed / stretched, the restoring force applied by the spring to the surface to which it is attached becomes larger. As long as the user compressing / stretching the spring is paying attention, the stiffness of the spring provides the tactile feedback.

[0005] Recently, passive tactile feedback has been incorporated into various displays to provide increased feedback and control to users of the display. Such passive tactile feedback is often incorporated into interfaces that allow users to write on the display and effect changes in the state of the display. For example, a touch panel display in an appliance may include both optical and tactile feedback to indicate that a button or function has been activated. Such dual feedback systems are particularly important in household appliances, since there is a large variability in visual and auditory health among users. For example, a visually impaired user needs tactile feedback to know that they have successfully programmed a microwave oven.

[0006] As used herein, "display" includes both visual displays where the output image is rendered using a pixelated backplane (typically addressed as either active or passive matrix), and visual displays where the entire module is a single "pixel." In the former case, writing on the display may involve a stylus interacting with a digitizer combined with active reproduction of the stroke by mapping digitized stylus motion to pixels of the display. Alternatively, particularly in the latter single-pixel displays, the writing implement may interact directly with the medium, causing some physical change that manifests directly as a local change in optical properties. This direct interaction is sometimes described as direct writing.

[0007] Displays in the latter category include the Fisher Price MAGNA DOODLE and Kent Displays BOOGIE BOARD. In the DOODLE case, a magnetic stylus attracts magnetic particles to a viewing surface, which appears as writing. In the BOOGIE BOARD, a localized change in pressure (caused by writing with a hard plastic stylus tip) produces a change in the state of a cholesteric liquid crystal material that leads to scattering of light on a black background. In the BOOGIE BOARD, an imprinted image can be erased by application of an electric field across the display. When this is done, the entire display returns to a dark state; therefore, this type of erasure procedure is referred to as "global" erasure. However, currently available BOOGIE BOARD products do not allow for "local" erasure of writing; that is, a user can erase an entire writing or drawing, but not only parts of it.

[0008] In light of the above, a display capable of both local and global writing and erasing using true changes of state would provide users with an enhanced and natural writing experience. In addition, if this writing functionality was available with tactile feedback, the experience would be further enhanced. Summary of the Invention [Means for solving the problem]

[0009] In light of the above, there exists a need for a display that can provide novel passive tactile feedback configurations and local and global erasure between multiple states. The present disclosure strives to expand on previous electrophoretic display technology by providing systems and methods relating to pressure-sensitive electrophoretic displays with passive tactile feedback. In some aspects, the systems and methods of the present disclosure provide the ability for electrophoretic displays to change state both locally and globally. Unlike the prior art, this change of state can be from a first state to a second state or vice versa. Because writing in either modality is possible, writing and erasure can be accomplished more naturally.

[0010] In one aspect, the present disclosure provides a pressure-sensitive electrophoretic display, which may include a first conductive layer having pressure-sensitive conductivity (e.g., comprising a piezoresistive material) and an electrophoretic layer positioned adjacent to the first conductive layer, the electrophoretic layer being in electrical communication with the first conductive layer and configured to locally change state based on pressure applied to the first conductive layer.

[0011] In another aspect, the present disclosure provides a pressure-sensitive electrophoretic display. The display may include a first electrode layer and a second electrode layer, the first electrode and the second electrode configured to provide a potential difference in response to application of a voltage across the first electrode and the second electrode. The display may also include an electrophoretic layer, the electrophoretic layer positioned between the first electrode and the second electrode. The display may additionally include a dielectric fluid layer, the dielectric fluid layer positioned between the first electrode and the electrophoretic material. Applying pressure to a location on the pressure-sensitive electrophoretic display causes a displacement of at least a portion of the dielectric fluid layer, thereby causing a change in the electric field experienced by the portion of the electrophoretic layer located at that location, thereby causing a local change in the state within the electrophoretic layer.

[0012] In one aspect, the present disclosure provides a pressure-sensitive electrophoretic display. The display may include a magnetic layer configured to generate a magnetic field and an electrophoretic layer comprising an electrically and magnetically addressable ink medium configured to locally change state based on an applied pressure. The display may also include a deformable layer located between the magnetic layer and the electrophoretic layer, where applying pressure to a location on the pressure-sensitive electrophoretic display causes a displacement of at least a portion of the deformable layer, thereby causing a change in the magnetic field experienced by the portion of the electrophoretic layer at that location. The change in the magnetic field causes a local change in state in the electrophoretic layer.

[0013] In another aspect, the present disclosure provides a method of using any of the pressure-sensitive electrophoretic displays described herein. The method may include creating an area of ​​increased pressure by contacting the display, the area of ​​increased pressure producing a local change in the state of the display, and producing a global change in the state of the display. One of the steps may include varying an electric or magnetic field applied to the electrophoretic layer. The local change in the state of the display may be a local erasure of a previous change in the state of the display. The present invention provides, for example, the following items. (Item 1) 1. A pressure-sensitive electrophoretic display, the display comprising: a first conductive layer having a first pressure sensitive conductivity; an electrophoretic layer positioned adjacent to the first conductive layer, the electrophoretic layer in electrical communication with the first conductive layer and configured to locally change state based on pressure applied to the first conductive layer; A display comprising: (Item 2) 2. The display of claim 1, wherein the first conductive layer is configured to provide a restoring force, the restoring force acting to return the first conductive layer to an initial state. (Item 3) Item 13. The display of item 1, wherein the first conductive layer comprises a piezo-resistive material. (Item 4) 2. The display of claim 1, wherein the first conductive layer is electrically connected in parallel or series to the electrophoretic layer. (Item 5) 2. The display of claim 1, further comprising an electrode layer, the electrode layer contacting both the first conductive layer and the electrophoretic layer. (Item 6) 2. The display of claim 1, further comprising a second conductive layer having a second pressure-sensitive conductivity and electrically connected in parallel to the electrophoretic layer. (Item 7) 7. The display of claim 6, wherein the mechanical properties of the first conductive layer are different from the mechanical properties of the second conductive layer. (Item 8) 2. The display of claim 1, wherein at least one of the magnitude or duration of the pressure applied to the first conductive layer affects the change in state of the electrophoretic layer. (Item 9) 2. The display of item 1, wherein application of reduced pressure returns the electrophoretic layer to its initial state. (Item 10) 2. The display of claim 1, further comprising a fixed current-limiting resistor in electrical communication with at least one of the first conductive layer or the electrophoretic layer. (Item 11) 1. A pressure-sensitive electrophoretic display, the display comprising: A first electrode layer; a second electrode layer, the first electrode and the second electrode configured to provide a potential difference in response to application of a voltage across the first electrode and the second electrode; an electrophoretic layer positioned between the first electrode and the second electrode; a dielectric fluid layer comprising a dielectric fluid, the dielectric fluid layer being positioned between the first electrode and the electrophoretic layer; and wherein applying pressure to a location on the pressure-sensitive electrophoretic display causes a displacement of at least a portion of the dielectric fluid layer, thereby causing a change in the electric field experienced by a portion of the electrophoretic layer located at that location, thereby causing a local change of state within the electrophoretic layer. (Item 12) Item 12. The display of item 11, wherein the electrophoretic layer is further configured to locally change state back to an initial state. (Item 13) Item 13. The display of item 12, wherein the electrophoretic layer is configured to locally change state from a first state to a second state or from the second state to the first state based on the applied pressure and a change in an applied potential difference. (Item 14) Item 12. The display of item 11, further comprising one or more structural members positioned between the first electrode layer and the electrophoretic layer. (Item 15) Item 12. The display of item 11, wherein the electrophoretic layer comprises a first group of particles having electrophoretic mobility and a second group of particles having electrophoretic mobility, the first group of particles having a different color than the second group of particles. (Item 16) 1. A pressure-sensitive electrophoretic display, the display comprising: a magnetic layer configured to generate a magnetic field; an electrophoretic layer comprising an electrically and magnetically addressable ink medium, the electrophoretic layer configured to locally change state based on an applied pressure; a deformable layer positioned between the magnetic layer and the electrophoretic layer; wherein applying a pressure to a location on the pressure-sensitive electrophoretic display causes a displacement of at least a portion of the deformable layer, thereby causing a change in the magnetic field experienced by a portion of the electrophoretic layer located at that location, thereby causing a local change of state within the electrophoretic layer. (Item 17) Item 17. The display of item 16, wherein the electrophoretic layer is configured to locally change from a first state to a second state or from the second state to the first state based on the applied pressure and the magnitude or direction of the magnetic field. (Item 18) Item 17. The display of item 16, wherein the deformable layer comprises a material selected from the group consisting of a gel, a foam, or a viscous liquid. (Item 19) Item 17. The display of item 16, wherein the electrophoretic layer comprises a first group of particles having electrophoretic mobility and a second group of particles having electrophoretic mobility, the first group of particles having a different color and the second group of particles. (Item 20) A method for using the pressure-sensitive electrophoretic display according to item 1, the method comprising: A) creating an area of ​​increased pressure by contacting the display, the area of ​​increased pressure producing a localized change in a state of the display; B) producing a global change in state of the display; and A method comprising: (Item 21) A method for using the pressure-sensitive electrophoretic display according to item 11, comprising: A) creating an area of ​​increased pressure by contacting the display, the area of ​​increased pressure producing a localized change in a state of the display; B) producing a global change in state of the display; and A method comprising: [Brief description of the drawings]

[0014] [Figure 1A] FIG. 1A is an exemplary illustration of a pressure-sensitive electrophoretic display construction having a conductive layer in a non-compressed state.

[0015] [Figure 1B] FIG. 1B is an exemplary illustration of a pressure-sensitive electrophoretic display construction having a conductive layer in compression.

[0016] [Figure 2A] FIG. 2A is another exemplary illustration of a pressure-sensitive electrophoretic display construction having a conductive layer in an uncompressed state.

[0017] [Figure 2B] FIG. 2B is another exemplary illustration of a pressure-sensitive electrophoretic display construction having a conductive layer in compression.

[0018] [Figure 3A] FIG. 3A is an exemplary illustration of a pressure-sensitive electrophoretic display construction having two conductive layers both in an uncompressed state.

[0019] [Figure 3B] FIG. 3B is an exemplary illustration of a pressure-sensitive electrophoretic display construction having two conductive layers, where a first conductive layer is in a compressed state while a second conductive layer is in a non-compressed state.

[0020] [Figure 3C] FIG. 3C is an exemplary illustration of a pressure-sensitive electrophoretic display construction having two conductive layers, where a first conductive layer is in an uncompressed state while a second conductive layer is in a compressed state.

[0021] [Figure 4A] FIG. 4A is another exemplary illustration of a pressure-sensitive electrophoretic display in an initial state.

[0022] [Figure 4B] FIG. 4B illustrates the pressure-sensitive electrophoretic display of FIG. 4A after a compressive force is applied to the display, causing the upper and lower electrodes of the electrophoretic layer to move closer together, thereby producing a change in the display state.

[0023] [Figure 5A] FIG. 5A is an exemplary illustration of a pressure-sensitive electro-magnetic phoretic display including a magnetic substrate and a compressible medium.

[0024] [Figure 5B] FIG. 5B shows the resulting state changes when a compressive force is applied to the electro-magnetophoretic display of FIG. 5A.

[0025] [Figure 6] FIG. 6 is a method flow chart for using a pressure-sensitive electrophoretic display.

[0026] [Figure 7] FIG. 7 is a photograph of the experimental pressure-sensitive electrophoretic display after it has been addressed with a finger. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The term "electro-optical," as applied to a material or display, is used herein in its conventional sense in the imaging arts to refer to a material having first and second display states that differ in at least one optical property, which is changed from its first display state to its second display state by application of an electric field to the material. The optical property is typically color perceptible to the human eye, but may be another optical property, such as optical transmittance, reflectance, luminescence, or, in the case of displays intended for machine reading, pseudocolor in the sense of a change in reflection of electromagnetic wavelengths outside the visible range.

[0028] Some electro-optic materials are solid in the sense that the material has a solid exterior surface, but the material can, and often does, have internal liquid- or gas-filled spaces. Such displays using solid electro-optic materials may hereinafter be referred to for convenience as "solid electro-optic displays." Thus, the term "solid electro-optic displays" includes rotating bichromal member displays, encapsulated electrophoretic displays, microcell electrophoretic displays, and encapsulated liquid crystal displays.

[0029] The terms "bistable" and "bistable" are used herein in their conventional sense in the art to refer to a display with display elements having first and second display states differing in at least one optical property, such that any given element is driven with an addressing pulse of finite duration to assume either its first or second display state, and remains in that state after the addressing pulse is terminated for at least several times (e.g., at least four times) the minimum duration of the addressing pulse required to change the state of the display element. In U.S. Pat. No. 7,170,670, it is shown that some particle-based electrophoretic displays capable of gray scale 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 electro-optic displays. This type of display is properly referred to as "multistable" rather than bistable, but for convenience the term "bistable" may be used herein to cover both bistable and multistable displays.

[0030] One type of electro-optic display that has been the subject of intense research and development for many years is the particle-based electrophoretic display, in which a plurality of charged particles move through a fluid under the influence of an electric field. Electrophoretic displays (also called electrophoretic displays) can have attributes of good brightness and contrast, wide viewing angles, state bistability, and low power consumption when compared to liquid crystal displays. Nevertheless, problems with the long-term image quality of these displays have prevented their widespread use. For example, the particles that make up electrophoretic displays tend to settle, which results in a poor usable lifespan for these displays.

[0031] Numerous patents and applications assigned to or in the name of Massachusetts Institute of Technology (MIT) and E Ink Corporation describe various techniques used in encapsulated electrophoretic and other electro-optical media. Encapsulated electrophoretic media comprises a number of small capsules, each of which itself comprises an internal phase containing electrophoretically mobile particles in a fluid medium, and a capsule wall surrounding the internal phase. Typically, the capsules themselves are held in a polymer binder to form a coherent layer positioned between two electrodes. Alternatively, in microcell electrophoretic displays, the charged particles and fluid are not encapsulated in microcapsules, but instead are held in a number of cavities formed in a carrier medium, typically a polymer film. The term "microcavity electrophoretic display" may be used to encompass both encapsulated and microcell electrophoretic displays. Technologies described in these patents and applications include:

[0032] (a) Electrophoretic particles, fluids, and fluid additives (see, e.g., U.S. Pat. Nos. 7,002,728 and 7,679,814)

[0033] (b) Capsules, binders, and encapsulation processes (see, e.g., U.S. Pat. Nos. 6,922,276 and 7,411,719)

[0034] (c) Microcell structures, wall materials, and methods of forming the microcells (see, e.g., U.S. Pat. Nos. 7,072,095 and 9,279,906).

[0035] (d) Methods for filling and sealing microcells (see, e.g., U.S. Pat. Nos. 7,144,942 and 7,715,088)

[0036] (e) Films and subassemblies containing electro-optical materials (see, e.g., U.S. Pat. Nos. 6,982,178 and 7,839,564)

[0037] (f) Backplanes, adhesive layers, and other auxiliary layers and methods used in displays (see, e.g., U.S. Pat. Nos. 7,116,318 and 7,535,624)

[0038] (g) Color formation and color control (see, e.g., U.S. Pat. Nos. 7,075,502 and 7,839,564)

[0039] (h) Methods for driving displays (see, e.g., U.S. Pat. Nos. 7,012,600 and 7,453,445)

[0040] (i) Display applications (see, e.g., U.S. Pat. Nos. 7,312,784 and 8,009,348)

[0041] (j) Non-electrophoretic displays (as described in U.S. Pat. No. 6,241,921, as well as U.S. Patent Application Publication Nos. 2015 / 0277160, 2015 / 0005720, and 2016 / 0012710)

[0042] Many of the aforementioned patents and applications recognize that the walls surrounding individual microcapsules in an encapsulated electrophoretic medium may be replaced with a continuous phase, thus producing so-called polymer-dispersed electrophoretic displays, in which the electrophoretic medium comprises a plurality of individual droplets of electrophoretic fluid and a continuous phase of polymer material, and in which the individual droplets of electrophoretic fluid in such polymer-dispersed electrophoretic displays may be considered capsules or microcapsules even though individual capsule membranes are not associated with each individual droplet. Thus, for purposes of this application, such polymer-dispersed electrophoretic media are considered a subspecies of encapsulated electrophoretic media.

[0043] The term "impulse" is used herein in its conventional sense of the integral of voltage with respect to time. However, some bistable electro-optic media act as charge converters. In such media, an alternative definition of impulse may be used, namely, the integral of current over time (equal to the total charge applied). The appropriate definition of impulse should be used depending on whether the medium acts as a voltage-to-time impulse converter or a charge impulse converter.

[0044] Many of the aforementioned patents and applications recognize that the walls surrounding individual microcapsules in an encapsulated electrophoretic medium may be replaced with a continuous phase, thus producing so-called polymer-dispersed electrophoretic displays, in which the electrophoretic medium comprises a plurality of individual droplets of electrophoretic fluid and a continuous phase of polymer material, and in which the individual droplets of electrophoretic fluid in such polymer-dispersed electrophoretic displays may be considered capsules or microcapsules even though individual capsule membranes are not associated with each individual droplet; see, for example, the aforementioned U.S. Patent No. 6,866,760. Thus, for purposes of this application, such polymer-dispersed electrophoretic media are considered a subspecies of encapsulated electrophoretic media.

[0045] A related type of electrophoretic display is the so-called "microcell electrophoretic display." In a microcell electrophoretic display, the charged particles and fluid are not encapsulated in microcapsules, but instead are held within a plurality of cavities formed in a carrier medium, typically a polymer film. See, for example, U.S. Patent Nos. 6,672,921 and 6,788,449 (both assigned to Sipix Imaging, Inc.).

[0046] Although in many cases the electrophoretic medium is opaque and operates in a reflective mode (e.g., because in many electrophoretic media the particles substantially block the transmission of visible light through the display), many electrophoretic displays can be made to operate in a so-called "shutter mode," in which one display state is substantially opaque and one is light transmissive. See, for example, U.S. Pat. Nos. 5,872,552, 6,130,774, 6,144,361, 6,172,798, 6,271,823, 6,225,971, and 6,184,856. Dielectrophoretic displays, which are similar to electrophoretic displays but rely on variations in electric field strength, can operate in a similar mode; see U.S. Pat. No. 4,418,346. Other types of electro-optic displays may also be capable of operating in a shutter mode. Electro-optic media operating in shutter mode may be used in multi-layer structures for full color displays; in such structures, at least one layer adjacent the viewing surface of the display operates in shutter mode to reveal or conceal a second layer that is further from the viewing surface. Other types of electro-optic media may also be used in displays of the invention.

[0047] Encapsulated electrophoretic displays typically do not suffer from the clustering and settling failure modes of conventional electrophoretic devices, and offer additional advantages such as the ability to print or coat the display on a variety of flexible and rigid substrates. (The use of the word "printing" is intended to include all forms of printing and coating, including, but not limited to, pre-metered coating (patch die coating, slot or extrusion coating, slide or cascade coating, curtain coating, etc.), roll coating (knife-over-roll coating, forward and reverse roll coating, etc.), gravure coating, dip coating, spray coating, meniscus coating, spin coating, brush coating, air knife coating, silk screen printing processes, electrostatic printing processes, thermal printing processes, inkjet printing processes, electrophoretic deposition (see U.S. Pat. No. 7,339,715), and other similar techniques.) Thus, the resulting display can be flexible. Furthermore, because the display medium can be printed using a variety of methods, the display itself can be inexpensively made.

[0048] Other types of electro-optic materials may also be used in the present invention.

[0049] An electrophoretic display typically comprises a layer of electrophoretic material and at least two other layers disposed on either side of the electrophoretic material, one of these two layers being an electrode layer. In most such displays, both layers are electrode layers, and one or both of the electrode layers are patterned to define the pixels of the display. For example, one electrode layer may be patterned into elongated row electrodes and the other into elongated column electrodes extending at right angles to the row electrodes, the pixels being defined by the intersections of the row and column electrodes. Alternatively, and more commonly, one electrode layer has the form of a single continuous electrode and the other electrode layer is patterned into a matrix of pixel electrodes, each of which defines one pixel of the display. In another type of electrophoretic display, where the display is intended for use with a separate stylus, printhead, or similar movable electrode, only one of the layers adjacent to the electrophoretic layer comprises an electrode; the layer on the opposite side to the electrophoretic layer is typically a protective layer intended to prevent the movable electrode from damaging the electrophoretic layer.

[0050] In yet another embodiment as described in US Pat. No. 6,704,133, an electrophoretic display may be constructed from two continuous electrodes, an electrophoretic layer between the electrodes, and a photoconductive layer between the electrodes. Because the photoconductive material changes resistivity with absorption of photons, incident light may be used to modify the state of the electrophoretic medium. Such a device is illustrated in FIG. 1. As described in US Pat. No. 6,704,133, the device of FIG. 1 works best when driven by an emission source (such as an LCD display) located on the opposite side of the display from the viewing surface. In some embodiments, the device of US Pat. No. 6,704,133 incorporated a special barrier layer between the front electrode and the photoconductive material to reduce the "dark current" caused by incident light from the front of the display leaking past the reflective electro-optic medium.

[0051] The aforementioned U.S. Patent No. 6,982,178 describes a method for assembling solid electro-optic displays (including encapsulated electrophoretic displays) that is highly suitable for mass production. Essentially, this patent describes a so-called "front plane laminate" ("FPL"), which comprises, in order, a light-transmitting conductive layer, a layer of solid electro-optic medium in electrical contact with the conductive layer, an adhesive layer, and a release sheet. Typically, the light-transmitting conductive layer is carried on a light-transmitting substrate, which is preferably flexible in the sense that the substrate can be wrapped by hand around a 10 inch (254 mm) diameter drum (for example) without permanent deformation. The term "light-transmitting" is used herein to mean that the layer so designated transmits sufficient light to enable an observer looking through the layer to observe a change in the display state of the electro-optic medium, which change in display state can usually be seen through the conductive layer and the adjacent substrate (if present). When the electro-optic medium displays changes in reflection at non-visible wavelengths, the term "optically transparent" should be interpreted to refer to the transmission of the relevant non-visible wavelengths. The substrate is typically a polymer film, usually having a thickness within the range of about 1 to about 25 mils (25 to 634 μm), preferably about 2 to about 10 mils (51 to 254 μm). The conductive layer can conveniently be a thin metal or metal oxide layer, for example, aluminum or ITO, or a conductive polymer. Poly(ethylene terephthalate) (PET) films coated with aluminum or ITO are commercially available, for example, as "aluminized Mylar" ("Mylar" is a registered trademark) from EI du Pont de Nemours & Company, Wilmington DE, and such commercial materials can be used with good results in front plane laminates.

[0052] Many types of electro-optic media are essentially monochromatic in the sense that any given medium has two extreme optical states and a range of gray levels between the two extreme optical states. However, today, there is an increasing demand for full-color displays, even for small portable displays; for example, most displays in mobile phones are full-color today. In order to provide a full-color display using a monochromatic medium, it is necessary to either place a color filter array (the display can be viewed through the color filter array) or place areas of different electro-optic media capable of displaying different colors adjacent to each other.

[0053] An electrophoretic display typically comprises a layer of electrophoretic material and at least two other layers disposed on either side of the electrophoretic material, one of these two layers being an electrode layer. In most such displays, both layers are electrode layers, and one or both of the electrode layers are patterned to define the pixels of the display. For example, one electrode layer may be patterned into elongated row electrodes and the other electrode layer into elongated column electrodes extending at right angles to the row electrodes, the pixels being defined by the intersections of the row and column electrodes. Alternatively, and more commonly, one electrode layer has the form of a single continuous electrode and the other electrode layer is patterned into a matrix of pixel electrodes, each of which defines one pixel of the display. In another type of electrophoretic display, intended for use with a display and a separate stylus, printhead, or similar movable electrode, only one of the layers adjacent to the electrophoretic layer comprises an electrode; the layer on the opposite side of the electrophoretic layer is typically a protective layer intended to prevent the movable electrode from damaging the electrophoretic layer.

[0054] Encapsulated electrophoretic media typically comprise electrophoretic capsules disposed within a polymer binder, which serves to form the individual capsules into a coherent layer. The continuous phase in polymer-dispersed electrophoretic media and the cell walls of microcellular media perform similar functions. It has been found by E INK researchers that the particular material used as the binder in an electrophoretic medium can affect the electro-optical properties of the medium. Among these, the electro-optical properties of electrophoretic media that are affected by the choice of binder are so-called "dwell time dependent". It has been found that, at least in some cases, the impulse required for a transition between two particular optical states of a bistable electrophoretic display varies with the dwell time of a pixel in its initial optical state, a phenomenon referred to as "dwell time dependent" or "DTD". Clearly, it is desirable to keep the DTD as small as possible, since it can affect the difficulty of driving the display and the quality of the images produced; for example, the DTD can cause pixels that are intended to form uniform gray areas to differ slightly from each other in gray level; this can be problematic because the human eye is very sensitive to such variations. Although it is known that the choice of binder affects the DTD, selecting an appropriate binder for any particular electrophoretic medium has thus far been based on trial and error, and essentially the relationship between the DTD and the binder chemistry is not understood.

[0055] As used herein, "passive tactile feedback" may be considered feedback that replicates the sensation of touch by applying a force to the user, and accomplishes this without the use of additional control circuitry or additional mechanical relays. This tactile feedback may provide variable levels of force experienced by the user.

[0056] As used herein, the terms "localized writing" and "localized erasing" refer to a change of state that occurs only within a particular region of a pressure-sensitive display. Often this region overlaps with and may result from the region to which pressure has been applied. Whether or not a localized change of state is considered, writing or erasing often depends on the user's intent and situational context.

[0057] As used herein, the terms "global writing" and "global erasing" refer to a change of state that occurs over a large area of ​​a pressure-sensitive display or over all areas of the pressure-sensitive display. In many cases, global erasing can result from a change in electric or magnetic field experienced by the entire electrophoretic layer. Whether a global change of state is considered, writing or erasing often depends on the user's intent and situational context.

[0058] Although the pressure-sensitive display systems and methods of the present disclosure are primarily intended for use in electronic writers, those skilled in the art will recognize that the teachings disclosed herein may be applied to numerous situations calling for both optical and tactile feedback.

[0059] Unless otherwise indicated by the context, the electrophoretic layer of the pressure-sensitive display described herein may comprise any of the structures described above. The electrophoretic layer may comprise a microcell electrophoretic display structure. The electrophoretic layer may comprise an encapsulated electrophoretic display structure. The electrophoretic layer may comprise a first group of particles having electrophoretic mobility and a second group of particles having electrophoretic mobility, the first group of particles having a different color than the second group of particles. The electrophoretic layer may also comprise a third group of particles having electrophoretic mobility that has a different color than the first and second groups.

[0060] The particles of the electrophoretic medium typically include one or more pigment types. The pigments may be both electrically and magnetically controllable (i.e., electro-magnetic). In a multi-pigment display, only one pigment type may be both electrically and magnetically controllable. An example of a multi-pigment display is a display that includes white and black pigment particles. The black pigment particles may be both electrically and magnetically controllable, as an example. Commercially available magnetic particles such as Bayferrox 8600, 8610; Northern Pigments 604, 608; Magnox 104, TMB-100; Columbian Mapico Black; Pfizer CX6368 and CB5600, and equivalents, may be used alone or in combination with other pigments to produce pigments that are both electrically and magnetically controllable. The white pigment may be, for example, titanium dioxide.

[0061] Pigments can be surface functionalized with polymers to control the charge and steric properties of the pigment. In addition, charge control agents are typically included in the electrophoretic medium to achieve the desired zeta potential for the pigment type. Thus, for example, the electrophoretic medium of the present invention typically comprises at least one charge control agent to control the charge on the various particles. The electrophoretic fluid can dissolve or disperse the polymer within the fluid, the polymer having an average molecular weight number greater than about 20,000 and essentially non-absorbing in the particles to improve the bistability of the display, as described, for example, in U.S. Pat. No. 7,170,670.

[0062] In one aspect, the present disclosure provides a pressure-sensitive electrophoretic display that may include a first conductive layer having pressure-sensitive conductivity and an electrophoretic layer positioned adjacent to the first conductive layer, the electrophoretic layer being in electrical communication with the first conductive layer and configured to locally change state based on pressure applied to the first conductive layer.

[0063] The conductivity of the first conductive layer may change when subjected to an applied pressure and the resulting volume change. For example, the first conductive layer may become more conductive during compression. The first conductive layer may be configured to provide a restoring force that acts to return the first conductive layer to an initial state. This restoring force may provide passive tactile feedback to any user of the display as a result of the mechanical properties of the first conductive layer. In this manner, any user of the display may experience both optical and tactile feedback.

[0064] As described below, it is understood that a "conductive layer" in a pressure-sensitive display has a conductivity that changes, for example, with deformation or compression. For example, a piezoresistive material such as doped germanium may be used as a pressure-sensitive conductor. Alternatively, a polymer with oriented conductive particles may be used. When the shape or density of the polymer is changed (e.g., due to deformation or pressure), the conductivity of the material changes. The polymer may be polyethylene or polyester, and the oriented conductive particles may be carbon nanotubes or metal whiskers. Alternatively, specially machined materials such as vertically oriented conductive block copolymer films may be used. See, for example, Singh et al., "Large-Scale Roll-to-Roll Fabrication of Vertically Oriented Block Copolymer Films," in Thin Films,” ACS Nano, 2013,7(6), pp5291-5299.

[0065] In the case of a pressure-sensitive electrophoretic display, when the first conductive layer undergoes compression, the compressed layer may better conduct the applied charge, which may produce a resultant change in state of the electrophoretic layer. The electrically connected source of the applied charge may be any commonly known in the art, such as a battery or a voltage supply source. The change in state of the electrophoretic layer may be a distinct change from a first state to one or more further states, such as from white to black. Alternatively, the change may occur gradually between two or more states. For example, the change in state may be from a first state to a gradual change in color, reflectance, brightness, or other optical property based on the amount of pressure applied and the subsequent compression of the conductive layer.

[0066] FIG. 1A depicts a pressure-sensitive electrophoretic display 100 having a first conductive layer 102 and an electrophoretic layer 104. The first conductive layer is depicted in an uncompressed state. In this depiction, the first conductive layer and the electrophoretic layer may be considered to be, in effect, electrically connected in series. FIG. 1B depicts the same display 100 at a time after the first conductive layer 102 has undergone compression. Such compression allows sufficient current to flow through the first conductive layer 102 to produce a change in state of the electrophoretic imaging device 104. This change in state of the display and various other components of the electrophoretic display are not depicted for reasons of clarity. The charge present is not depicted, but rather is represented by the symbol "V". The transition from the uncompressed (FIG. 1A) state to the compressed (FIG. 1B) state results in a reduction in resistance between the source of the applied charge "V" and the electrophoretic layer. Due to the reduced resistance, electrophoretic layer 104 experiences a stronger electric field, which is sufficient to cause electrophoretic layer 104 to change a display state. In cases where the first conductive layer has resistance to compression (which is common), display 100 may be incorporated into a button, for example, to provide both visual and tactile feedback to a user.

[0067] FIG. 2A depicts a second embodiment of a pressure-sensitive electrophoretic display 200 having a first conductive layer 202 and an electrophoretic layer 204. Interposed between and electrically connected to these two layers is a first electrode layer 206. This first electrode layer is electrically connected to a fixed current-limiting resistor 210. In this depiction, the first conductive layer and the electrophoretic layer may be considered to be, in effect, electrically connected in parallel. FIG. 2B depicts the same display 200 at a time after the first conductive layer 202 has been subjected to compression. Such compression allows sufficient current to flow through the first conductive layer 202 to produce a change in state of the electrophoretic display 204. In this configuration, the amount of pressure applied may increase or decrease the charge potential experienced by the electrophoretic layer 204. The change in state of the display and various other components of the electrophoretic display 200 are not depicted for reasons of clarity. The charge present is not depicted, but rather is represented by a "V" and an additional lower "-V."

[0068] 3A depicts a third embodiment of a pressure-sensitive electrophoretic display 300 having a first conductive layer 302, a second conductive layer 303, and an electrophoretic layer 304. Interposed between the first conductive layer 302 and the second conductive layer 303 is a first electrode layer 306 in contact with and electrical communication with the first layer 302. A second electrode layer 308 is also interposed between the first conductive layer 302 and the second conductive layer 303 and in contact with and electrical communication with the second conductive layer 303. An insulating layer 307 is positioned between the first electrode layer 306 and the second electrode layer 308. A third electrode 309 is interposed between the second conductive layer 303 and the electrophoretic layer 304 and in contact with and electrical communication with both. A first fixed current-limiting resistor 310 is electrically connected to the second electrode layer 308. A second fixed current-limiting resistor 311 is electrically connected to both the first electrode layer 306 and the third electrode layer 309. In this depiction, the first conductive layer 302 and the electrophoretic layer 304 may be considered to be, in effect, electrically connected in series. The second conductive layer 303 and the electrophoretic layer 304 may be considered to be, in effect, electrically connected in parallel. The charge present is not depicted, but rather is represented by a "V" and an additional lower "-V".

[0069] FIG. 3B depicts the same display 300 at a time after the first conductive layer 302 has been subjected to compression. Because the deformation in the first conductive layer 302 dominates the deformation of the second conductive layer 303, the charge potential experienced by the electrophoretic layer 304 is pulled toward "-V". To create such an isolated compression in only one of the layers, the first conductive layer 302 may have a lower yield strength and / or stiffness than the second conductive layer 303. This difference in mechanical properties allows an applied pressure of small magnitude and / or short duration to compress only the first conductive layer 302. A reduction in the applied pressure may allow the display 300 to return to the initial state depicted in FIG. 3A.

[0070] FIG. 3C again depicts the same display 300 at a time after the second conductive layer 303 has been subjected to compression. Because the deformation in the second conductive layer 303 dominates the deformation of the first conductive layer 302, the charge potential experienced by the electrophoretic layer 304 is pulled toward "V". To create such isolated compression, the first conductive layer 302 may also have a higher yield strength and / or stiffness than the second conductive layer 303. This difference in mechanical properties allows an applied pressure of large magnitude and / or long duration to compress the second conductive layer 303. A reduction in the applied pressure may allow the display 300 to return to the initial state depicted in FIG. 3A.

[0071] The material properties of the conductive layer(s) may be specifically tailored to the application for which the display is intended to be used. Different applications may require varying sensitivity requirements resulting from the magnitude, duration, and frequency of the applied pressure. The conductive layer(s) may be required to have specific compressive strength, elasticity, stiffness, tensile strength, toughness, or yield strength properties. The conductive layer(s) may comprise a piezo-resistive material.

[0072] 1A-3C depict the elements of the display as contacting each other, often in a linear arrangement, but one skilled in the art can apply these teachings to a variety of configurations, including arrangements in which one or more conductive layers are spatially separated from the electrophoretic imaging display. In addition, the electrophoretic layers can be designed to have low image stability, thereby allowing for fast state changes.

[0073] In another aspect, the present disclosure provides a pressure-sensitive electrophoretic display. The display may include a first electrode layer and a second electrode layer, the first electrode and the second electrode configured to provide a potential difference. The display may also include an electrophoretic layer, the electrophoretic layer positioned between the first electrode and the second electrode and configured to locally change state based on pressure applied to the first electrode layer. In this embodiment, the compressible layer (not piezoresistive) separates the electrodes when the compressible layer is in a non-compressed state. The compressible layer may be a dielectric fluid layer, the dielectric fluid layer comprising a dielectric fluid and positioned between the first electrode and the electrophoretic material.

[0074] The electrophoretic layer may further be configured to locally change state back to an initial state. For example, if the initial change of state is from white to black in a localized region of the display, this same localized region may be changed from black to white by reversing the polarity of the electrodes. This local erasure may also result from a change in the magnitude and / or duration of the applied pressure. Such a change in the magnitude and / or duration of the applied pressure may also involve a change in the potential difference from the first and second electrode layers. In addition, the electrophoretic layer may be globally changed to a uniform state by changing the potential difference or by applying a clearing waveform (applied pulse). This global erasure may be used to, in effect, reset the display to a desired state. For example, the display may be globally changed from a state in which both local white and local black states are present on the display to a fully white state.

[0075] FIG. 4A depicts a pressure-sensitive electrophoretic display 400 having a first electrode layer 401, a second electrode layer 402, and an electrophoretic layer 404 positioned between the first and second electrode layers. The electrophoretic layer 404 is typically encapsulated in, for example, gelatin. Alternatively, the electrophoretic layer 404 may include a plurality of prefabricated microcells filled with an electrophoretic material. The electrophoretic layer may also include a polymer-dispersed electrophoretic medium (i.e., as described in the patents listed above). The electrode layer may be electrically connected to one or more charge sources and electronic components (not depicted). The electrode layer may comprise indium tin oxide, PEDOT (poly(3,4-ethylenedioxythiophene)), or other polymers (e.g., polyethylene further comprising a conductive matrix material (e.g., metal flakes, whiskers, or fibrils), or a fullerene-type compound (e.g., carbon nanotubes or graphene)). Although only two electrodes are depicted, additional electrodes may be present in the display 400 and used to generate distinct potential differences.

[0076] A compressible layer, the dielectric fluid layer 403, is located between the first electrode layer 401 and the electrophoretic layer 404. The dielectric fluid layer 403, the first electrode layer 401, and the second electrode layer 402 may be transparent or nearly transparent. The dielectric fluid may comprise a dielectric solvent having a low relative dielectric constant, such as hydrocarbons, chlorinated hydrocarbons, and fluorocarbons. The dielectric fluid may be naphtha, C8-C 11 The dielectric fluid may be selected from the group consisting of isoalkanes, perfluorocarbons, paraffins, PTFE, polyethylene, silicone oils, or combinations thereof. The dielectric fluid may be doped with ionic charge carriers, such as salts or conductive monomers or polymers, to change the relative dielectric constant to an optimal value. The dielectric fluid layer may have a relative dielectric constant between 2 and 6, for example, the dielectric fluid layer may have a relative dielectric constant between 2 and 4.

[0077] The display 400 of FIG. 4A also depicts a flexible cover 406 in contact with the first (transparent) electrode 401. The flexible cover 406 may be transparent or nearly transparent in addition to having other display cover optical properties commonly known in the art. The display 400 may also include sidewalls 412 that may contact the dielectric fluid layer 403 and the electrophoretic layer 404. A substrate layer 408 may contact the second electrode layer 402 and a back plate 410. The substrate 408 may be flexible, and the back plate 410 may be configured to provide structural support to the substrate 408 and other components of the display 400. For example, the back plate 410 may increase the overall rigidity of the display 400. An adhesive layer (not depicted) may be present between any of the component layers to help maintain contact between the layers. For example, a conductive adhesive layer may be positioned between the second electrode 402 and the electrophoretic imaging material 404.

[0078] One or more structural members 414 may be located within the dielectric fluid layer 403. The structural members 414 may be configured to maintain a uniform height of the dielectric fluid layer 403 by providing a restoring force or resistance to any applied pressure. The structural members 414 may be selected from the group consisting of beads, threads, mesh, and combinations thereof. The structural members 404 may comprise a polymeric material.

[0079] FIG. 4B again depicts the same display 400 at a later time when pressure is applied by an object 416. The object 416 may be a finger, stylus, or other item capable of generating sufficient pressure to generate a deformed area in the dielectric fluid layer 403. The flexible cover 406 and the first (transparent) electrode 401 flex as a result of the pressure applied from the object 416, generating a deformed area in the dielectric fluid layer 403. This movement within the display 400 allows the first electrode layer 401 to move closer to the electrophoretic layer 404. Based on the charge supplied to the first 401 electrode layer and / or the second 402 electrode layer, the electrophoretic layer 404 may locally change state. This change of state may be from an initial state to a second state or from the second state back to the initial state. For example, the display 400 may be locally changed from white to black, which may be considered local writing. By using a change in the charge supplied to the first 401 and / or second 402 electrode layers, the display 400 can then be changed locally from black to white, which can be considered a local erase. In addition, the electrophoretic layer 404 can be changed globally to a uniform state by changing the magnitude of the charge supplied to the first 401 and / or second 402 electrode layers. This change can be in the form of a pulse. For a global change, an applied pressure may not be necessary.

[0080] In one aspect, the present disclosure provides a pressure-sensitive electrophoretic display. The display may include a magnetic layer configured to generate a magnetic field and an electrophoretic layer comprising an addressable ink medium that is responsive to both electric and magnetic fields and configured to locally change state based on an applied pressure. The display may also include a deformable layer located between the magnetic layer and the electrophoretic layer, such that applying pressure to a location on the pressure-sensitive electrophoretic display causes a displacement of at least a portion of the deformable layer, thereby causing a change in the magnetic field experienced by the portion of the electrophoretic layer located at that location, thereby causing a local change of state in the electrophoretic layer.

[0081] The electrophoretic layer may further be configured to locally change state back to an initial state. For example, if the initial change of state is from white to black in a localized region of the display, this same localized region may be changed from black to white. This local erasure may result from a change in the magnitude and / or duration of the applied pressure. Such a change in the magnitude and / or duration of the applied pressure may also involve a change in the magnetism and / or direction of the magnetic field produced by the magnetic layer. In addition, the display may be globally changed to a uniform state by applying a voltage pulse to the electrophoretic layer. This global erasure may be used to, in effect, reset the display to a desired state. For example, the display may be globally changed from a state in which both local white and local black states are present on the display to a fully white state.

[0082] FIG. 5A depicts a pressure-sensitive electromagnetophoretic display 500 having a magnetic layer 501, an electromagnetophoretic layer 504, and a deformable layer 503 located therebetween. The depicted electromagnetophoretic layer 504 is consistent with an encapsulated electrophoretic display configuration, but other electrophoretic display configurations may be readily substituted. The magnetic layer 501 may comprise a permanent magnet or a system for generating a magnetic field. For example, the magnetic layer 501 may comprise a polymer composite of a permanent magnet, or a sheet of magnetizable material around which a coil of current carrying wire is wrapped. The deformable layer 503 may comprise a polymer, a fluid, or some other material that may be easily compressed. The deformable layer 503 may comprise a material selected from the group consisting of a gel, a foam, or a viscous liquid. For example, the deformable layer may comprise a dielectric fluid, such as silicone oil, silicone gel, polyurethane foam, polyethylene foam, polyester foam, non-conductive grease, or heavy oil. Additional components may also be present in the display, such as a flexible cover, a back plate, an electrode layer, one or more charge sources, and electronic components.

[0083] FIG. 5B again depicts the same display 500 at a later time when pressure is applied by an object 516. The object 516 may be a finger, stylus, or other item capable of generating sufficient pressure to generate a deformed region in the deformable layer 503. The electro-magnetic layer 504 may bend as a result of the applied pressure from the object 516, generating a deformed region in the deformable layer 503. This movement within the display allows the electro-magnetic layer 504 to move closer to the magnetic layer 501. The localized region with closer proximity to the magnetic layer 501 may experience an increased magnetic force and locally change state. In addition, an electric pulse may be applied to the electro-magnetic layer 504. The change of state may be from an initial state to a second state or from the second state back to the initial state. For example, the display 500 may be locally changed from white to black, which may be considered local writing. By using a change in the magnetic field produced by the magnetic layer 501 and / or the application of an electric pulse to the magnetophoretic layer 504, an applied pressure can locally change the display 500 from black to white, which can be considered a local erasure. In addition, the magnetophoretic layer 504 can be globally changed to a uniform state by changing the magnitude of the magnetic field or the magnitude of the charge applied to the magnetophoretic layer 504. For a global change, an applied pressure may not be necessary.

[0084] In another aspect, the disclosure provides a method for using any of the pressure-sensitive displays described herein. The method may include a first step of creating an area of ​​increased pressure by contacting the display, the area of ​​increased pressure producing a localized change in a state of the display.

[0085] 6 depicts a method flow chart 700 for using a pressure-sensitive electrophoretic display. The method includes a first step 601 of creating an area of ​​increased pressure by touching the display.

[0086] In the method, generating the area of ​​increased pressure may include contacting the display with a finger, stylus, or other item capable of generating sufficient pressure. The local change in the state of the display may be a local erasure of a previous change in the state of the display. The method may further include a second step of producing a global change in the state of the display. Producing the global or local change may also include varying an electric or magnetic field applied to the electrophoretic layer. EXAMPLES

[0087] The following examples are provided to demonstrate and further illustrate certain embodiments and aspects of the present disclosure and should not be construed as limiting the scope of the disclosure.

[0088] Example 1 FIG. 7 is an image of an experimental pressure-sensitive electrophoretic display constructed according to the teachings of the present disclosure. The overall structure of the device in FIG. 7 is similar to FIG. 4A and FIG. 4B. This experimental display uses transparent and graphite electrodes and a dielectric fluid layer to provide passive tactile feedback and local and global writing and erasing. The message "Hello, world!" was successfully written on the display with a finger. The area with the dielectric fluid (silicone oil, Dow-Corning) is the smaller, more lightly colored rectangle that bounds the message. The larger rectangular substrate is actually a "standard" E INK front plane laminate as used to build various electronic readers. The flexible cover is polyethylene and the transparent electrode layer is PET-ITO. The electrophoretic medium includes white and black charged particles dispersed in naphtha, and the electrophoretic medium is encapsulated in a gelatin-acacia capsule.

[0089] Thus, the present disclosure provides systems and methods for pressure-sensitive electrophoretic displays with passive tactile feedback.

[0090] Although the present invention has been described in some detail with reference to certain embodiments, those skilled in the art will recognize that the present invention may be practiced by other than the described embodiments, and that the described embodiments are presented for purposes of illustration and not limitation. Accordingly, the scope of the appended claims should not be limited to the description of the embodiments contained herein.

Claims

1. 1. A pressure-sensitive electrophoretic display, the display comprising: A first electrode layer; a second electrode layer, the first electrode layer and the second electrode layer configured to provide a potential difference in response to application of a voltage across the first electrode layer and the second electrode layer; an electrophoretic layer positioned between the first electrode layer and the second electrode layer, the electrophoretic layer comprising a first group of particles having electrophoretic mobility and a second group of particles having electrophoretic mobility, the first group of particles having a color different from a color of the second group of particles, the electrophoretic layer further comprising at least one charge control agent for controlling charge on the first group of particles and the second group of particles, the first group of particles comprising a first group of pigments that are surface functionalized with a polymer, and the second group of particles comprising a second group of pigments that are surface functionalized with a polymer; a dielectric fluid layer comprising a dielectric fluid, the dielectric fluid layer being positioned between the first electrode layer and the electrophoretic layer; wherein applying pressure to a location on the pressure-sensitive electrophoretic display causes a displacement of at least a portion of the dielectric fluid layer, thereby causing the first electrode layer to move closer to the electrophoretic layer, thereby causing a change in the electric field experienced by the portion of the electrophoretic layer located at that location, thereby causing a local change of state within the electrophoretic layer.

2. The display of claim 1 , wherein the electrophoretic layer is further configured to locally change state back to an initial state.

3. 3. The display of claim 2, wherein the electrophoretic layer is configured to locally change state from a first state to a second state, or from the second state to the first state, based on the applied pressure and a change in an applied potential difference.

4. The display of claim 1 , further comprising one or more structural members positioned between the first electrode layer and the electrophoretic layer.

5. The display of claim 1 , wherein the dielectric fluid comprises a hydrocarbon, a chlorinated hydrocarbon, or a fluorocarbon.

6. The dielectric fluid is naphtha, C ８ -C １１ 10. The display of claim 1, wherein the organic solvent is selected from the group consisting of isoalkanes, perfluorocarbons, paraffins, PTFE, polyethylene, silicone oils, and combinations thereof.

7. The display of claim 1 , wherein the dielectric fluid layer has a relative dielectric constant of 2-6.

8. The display of claim 1 , wherein the dielectric fluid layer has a relative dielectric constant of 2-4.

9. 13. A method of using the pressure-sensitive electrophoretic display of claim 1, comprising: A) creating an area of ​​increased pressure by contacting the display, the area of ​​increased pressure producing a localized change in a state of the display; B) producing a global change in state of the display; and A method comprising:

Images