Piezoelectric electrophoretic display

Abstract

An electro-optical display is provided herein, which has an electrophoretic material layer, a first conductive layer, and a piezoelectric material located between the electrophoretic material layer and the first conductive layer, the piezoelectric material overlapping a portion of the electrophoretic material layer, and a portion of the first conductive layer overlapping the remaining portion of the electrophoretic material.

Description

[0001] Citation of Related Applications

[0002] This application is related to and claims priority to U.S. Provisional Application No. 62 / 673,092 filed on May 17, 2018. This application is also related to U.S. Provisional Application No. 62 / 727,033 filed on September 5, 2018.

[0003] The entire disclosure of the above application is incorporated herein by reference. Technical Field

[0004] The subject matter disclosed herein relates to piezoelectric electrophoretic displays that can be activated or driven without being connected to a power source and methods of making the same. Background Art

[0005] Non-emissive displays convey information using contrast differences achieved by varying the reflectivity of light of different frequencies; thus, they differ from conventional emissive displays, which emit light to stimulate the eye. One type of non-emissive display is an electrophoretic display, which uses the phenomenon of electrophoresis to achieve contrast. Electrophoresis refers to the movement of charged particles in an applied electric field. When electrophoresis occurs in a liquid, the speed at which the particles move depends primarily on the viscous drag experienced by the particles, their charge, the dielectric properties of the liquid, and the magnitude of the applied electric field.

[0006] Electrophoretic displays utilize charged particles of one color suspended in a dielectric liquid medium of a different color (i.e., light reflected by the particles is absorbed by the liquid). The suspension is contained in a cell located between (or partially defined by) a pair of oppositely disposed electrodes, one of which is transparent. When the electrodes are operated to apply a DC or pulsed field across the medium, the particles migrate toward the electrode of opposite sign. The result is a visually observable color change. In particular, when a sufficient number of particles reach the transparent electrode, their color dominates the display; however, if the particles are attracted to the other electrode, they are obscured by the color of the liquid medium, which instead dominates.

[0007] Many electrophoretic displays are bistable: their state persists even after the activation electric field is removed. This is usually achieved by residual charge on the electrodes and van der Waals interactions between the particles and the walls of the electrophoretic cell. The driving of an electrophoretic display requires a power source, such as a battery, to provide power to the display and / or its drive circuitry. The power source can be a driver IC in order to generate the electric field. The electric field may also need to be enhanced by an electrical circuit. In any case, a physical connection via wires is required to attach the power source to the electrophoretic display and its drive circuitry. Summary of the invention

[0008] According to one aspect of the subject matter disclosed herein, an electro-optic display may include an electrophoretic material layer; a first conductive layer; and a piezoelectric material located between the electrophoretic material layer and the first conductive layer, the piezoelectric material overlapping a portion of the electrophoretic material layer and a portion of the first conductive layer overlapping a remainder of the electrophoretic material. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a cross-sectional view of an exemplary electrophoretic display according to the subject matter disclosed herein;

[0010] Figure 2A yes Figure 1 another cross-sectional view of the display shown;

[0011] Figure 2B yes Figure 1 and Figure 2A Equivalent circuit model of the display shown;

[0012] Figure 3A is a cross-sectional view of another exemplary display according to the subject matter disclosed herein;

[0013] Figure 3B It is along Figure 3A a cross-sectional view of line C1 of the display shown;

[0014] Figure 3C It is along Figure 3A a cross-sectional view of line C2 of the display shown;

[0015] Figure 3D A further embodiment of a display according to the subject matter presented herein is shown;

[0016] Figure 4 is a cross-sectional view of yet another exemplary display according to the subject matter disclosed herein;

[0017] Figure 5 is a cross-sectional view of another exemplary display according to the subject matter disclosed herein;

[0018] Figure 6 One embodiment of a piezoelectric electrophoretic display having a sawtooth pattern according to the subject matter disclosed herein is shown;

[0019] Figure 7 Another embodiment of a piezoelectric electrophoretic display having a pattern according to the subject matter disclosed herein is shown;

[0020] Figure 8 A piezoelectric electrophoretic display according to the subject matter disclosed herein is shown being used as part of a currency note for anti-counterfeiting purposes;

[0021] Fig. 9shows a cross section of yet another embodiment of a piezoelectric display according to the subject matter disclosed herein;

[0022] Fig.10 is a cross-sectional view of a piezoelectric display according to the subject matter disclosed herein having a barrier layer;

[0023] Fig.11A is the top view of the microcell layer;

[0024] Fig. 11B yes Fig.10 A is a cross-sectional view of a micro-unit layer;

[0025] Fig. 12A and Fig. 12B Another embodiment of an electrophoretic display according to the subject matter disclosed herein is shown;

[0026] Fig.13A and Fig. 13B A further embodiment of an electrophoretic display according to the subject matter disclosed herein is shown;

[0027] Fig.14A Another embodiment of an electrophoretic display having a printed image or shape according to the subject matter disclosed herein is shown;

[0028] Figures 14B-14E The present invention shows the subject matter disclosed herein in use. Fig.14A Display;

[0029] Fig.15A Another embodiment of an electrophoretic display having a printed image or shape according to the subject matter disclosed herein is shown; and

[0030] Figures 15B-15C The present invention shows the subject matter disclosed herein in use. Fig.15A display. DETAILED DESCRIPTION

[0031] The term "electro-optical" as applied to a material or display is used herein in its conventional sense in the field of imaging to refer to a material having first and second display states that differ in at least one optical property, the material being caused to change from its first display state to its second display state by application of an electric field to the material. While the optical property is typically color perceptible to the human eye, it may be another optical property, such as light transmission, reflection, luminescence, or, in the case of displays for machine reading, false color in the sense of a change in reflectivity of electromagnetic wavelengths outside the visible range.

[0032] The terms "bistable" and "bistable" are used herein in their conventional sense in the art to refer to a display including a display element having first and second display states, the first and second display states differing in at least one optical property such that after any given element is driven to assume its first or second display state with an addressing pulse of finite duration, that state will persist after termination of the addressing pulse for a time at least several times (e.g., at least 4 times) the minimum duration of the addressing pulse required to change the state of the display element. It is shown in U.S. Pat. No. 7,170,670 that some particle-based electrophoretic displays supporting gray scales can be stable not only in their extreme black and white states, but also in intermediate gray states, as well as some other types of electro-optical displays. This type of display is properly referred to as "multistable" rather than bistable, but for convenience, the term "bistable" will be used herein to cover both bistable and multistable displays.

[0033] The term "gray state" is used herein in its conventional sense in the field of imaging, referring to a state between the two extreme optical states of a pixel, but does not necessarily mean a black-white transition between the two extreme states. For example, several patents and published applications of Iink Corporation referred to below describe electrophoretic displays in which the extreme states are white and dark blue, so that the intermediate "gray state" is actually light blue. In fact, as already mentioned, the change in optical state may not be a color change at all. The terms "black" and "white" may be used below to refer to the two extreme optical states of the display, and should be understood to generally include extreme optical states that are not strictly black and white, such as the white and dark blue states mentioned above. The term "monochromatic" may be used below to refer to a display or drive scheme in which pixels are driven only to their two extreme optical states, without an intermediate gray state.

[0034] The term "pixel" is used herein in its conventional meaning in the display field, referring to the smallest unit of a display capable of generating all the colors that the display itself can display. In a full-color display, each pixel is typically composed of multiple sub-pixels, each of which can display fewer colors than the display itself can display. For example, in most conventional full-color displays, each pixel is composed of a red sub-pixel, a green sub-pixel, a blue sub-pixel, and an optional white sub-pixel, each of which can display a range of colors from black to the brightest version of the specified color.

[0035] Several types of electro-optical displays are known. One type of electro-optical display is a rotating two-color component type, such as described in, for example, U.S. Patent Nos. 5,808,783, 5,777,782, 5,760,761, 6,054,071, 6,055,091, 6,097,531, 6,128,124, 6,137,467, and 6,147,791 (although this type of display is generally referred to as a "rotating two-color ball" display, the term "rotating two-color component" is preferably more accurate because in some of the above-mentioned patents, the rotating component is not spherical). This display uses many small bodies (usually spherical or cylindrical) and internal dipoles, and the body includes two or more parts with different optical properties. These bodies are suspended in a liquid-filled vacuole in a matrix, and the vacuole is filled with liquid so that the body can rotate freely. The appearance of the display is changed by applying an electric field to the display, thereby rotating the body to various positions and changing which part of the body is seen through the viewing surface. This type of electro-optic medium is usually bistable.

[0036] Another type of electro-optical display uses an electrochromic medium, for example in the form of a nanochromic film that includes an electrode formed at least in part from a semiconducting metal oxide and a plurality of dye molecules attached to the electrode that are capable of reversible color change; see, for example, O'Regan, B. et al., Nature 1991, 353, 737; and Wood, D., Information Display, 18(3), 24 (March 2002). See also Bach, U. et al., Adv. Mater., 2002, 14(11), 845. Nanochromic films of this type are also described, for example, in U.S. Patent Nos. 6,301,038; 6,870,657; and 6,950,220. This type of medium is also typically bistable.

[0037] Another type of electro-optical display is the electrowetting display developed by Philips and described in Hayes, RA et al., "Video-Speed ​​Electronic Paper Based on Electrowetting", Nature, 425, 383-385 (2003). It is shown in US Pat. No. 7,420,549 that such an electrowetting display can be made bistable.

[0038] One type of electro-optical display that has been the subject of intensive research and development for many years is a particle-based electrophoretic display, in which a plurality of charged particles move through a fluid under the influence of an electric field. Compared to liquid crystal displays, electrophoretic displays can have the attributes of good brightness and contrast, wide viewing angles, state bistability, and low power consumption.

[0039] As mentioned above, the electrophoretic medium requires the presence of a fluid. In most prior art electrophoretic media, the fluid is a liquid, but the electrophoretic medium can be produced using a gaseous fluid; see, for example, Kitamura, T. et al., "Electronic toner movement for electronic paper-like display", IDW Japan, 2001, Paper HCS 1-1, and Yamaguchi, Y. et al., "Toner display using insulative particles charged triboelectrically", IDW Japan, 2001, Paper AMD4-4). See also U.S. Patent Nos. 7,321,459 and 7,236,291. When such a gas-based electrophoretic medium is used in a direction that allows particle sedimentation, such as when used in a signboard where the medium is arranged in a vertical plane, such a gas-based electrophoretic medium is susceptible to the same type of problems due to the same particle sedimentation as a liquid-based electrophoretic medium. In fact, the particle sedimentation problem is more severe in gas-based electrophoretic media than in liquid-based electrophoretic media because the lower viscosity of the gaseous suspending fluid compared to liquids allows for faster sedimentation of the electrophoretic particles.

[0040] Numerous patents and applications assigned to or in the name of the Massachusetts Institute of Technology (MIT) and Ink Corp. describe various techniques for encapsulated electrophoretic and other electro-optical media. Such encapsulated media include a plurality of small capsules, each of which itself includes an inner phase containing electrophoretically mobile particles in a fluid medium and a capsule wall surrounding the inner phase. Typically, the capsules themselves are held in a polymer binder to form a coherent layer located between two electrodes. The techniques described in these patents and applications include:

[0041] (a) electrophoretic particles, fluids, and fluid additives; see, e.g., U.S. Pat. Nos. 7,002,728 and 7,679,814;

[0042] (b) capsules, binders and encapsulation processes; see, e.g., U.S. Pat. Nos. 6,922,276 and 7,411,719;

[0043] (c) Films and subassemblies containing electro-optical materials; see, e.g., U.S. Pat. Nos. 6,982,178 and 7,839,564;

[0044] (d) Backplanes, adhesive layers and other auxiliary layers and methods for use in displays; see, e.g., U.S. Pat. Nos. 7,116,318 and 7,535,624;

[0045] (e) color formation and color adjustment; see, e.g., U.S. Pat. Nos. 7,075,502 and 7,839,564;

[0046] (f) Methods for driving displays; see, e.g., U.S. Patent Nos. 7,012,600 and 7,453,445;

[0047] (g) Display applications; see, e.g., U.S. Patent Nos. 7,312,784 and 8,009,348;

[0048] (h) non-electrophoretic displays, such as those described in U.S. Patent Nos. 6,241,921; 6,950,220; 7,420,549 and 8,319,759 and U.S. Patent Application Publication No. 2012 / 0293858;

[0049] (i) microcell structures, wall materials, and methods of forming microcells; see, e.g., U.S. Pat. Nos. 7,072,095 and 9,279,906; and

[0050] (j) Methods for filling and sealing microlocations; see, e.g., U.S. Patent Nos. 7,144,942 and 7,715,088.

[0051] Many of the aforementioned patents and applications recognize that the walls surrounding discrete microcapsules in an encapsulated electrophoretic medium can be replaced by a continuous phase, thereby producing a so-called polymer-dispersed electrophoretic display, wherein the electrophoretic medium includes a plurality of discrete droplets of electrophoretic fluid and a continuous phase of polymer material, and the discrete droplets of electrophoretic fluid within such a polymer-dispersed electrophoretic display can be considered to be capsules or microcapsules, even though there is no discrete capsule membrane associated with each individual droplet; see, e.g., aforementioned U.S. Patent No. 6,866,760. Therefore, for the purposes of this application, such polymer-dispersed electrophoretic media are considered to be a subclass of encapsulated electrophoretic media.

[0052] 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 are held in a plurality of cavities formed in a carrier medium (usually a polymer film). See, for example, U.S. Patent Nos. 6,672,921 and 6,788,449, both assigned to Sipix Imaging.

[0053] Although electrophoretic media are typically opaque (because, for example, in many electrophoretic media, the particles substantially block visible light from being transmitted through the display) and operate in a reflective mode, many electrophoretic displays can be made to operate in a so-called "shutter mode," in which one display state is substantially opaque and one display state is light transmissive. See, for example, U.S. Patents 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 changes in electric field strength, can operate in a similar mode; see U.S. Patent No. 4,418,346. Other types of electro-optical displays can also operate in a shutter mode. Electro-optical media operating in shutter mode may be used in a multilayer structure for a full color display in which at least one layer adjacent to a viewing surface of the display is operated in shutter mode to expose or hide a second layer further from the viewing surface.

[0054] Packaged electrophoretic displays are generally not plagued by the aggregation and sedimentation failure modes of conventional electrophoretic devices and offer additional benefits, 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 such as patch die coating, slot or extrusion coating, slide or laminate coating, curtain coating; roll coating such as roller blade coating, forward and reverse roll coating; gravure coating; dip coating; spray coating; meniscus coating; spin coating; brush coating; air knife coating; screen printing process; electrostatic printing process; thermal printing process; inkjet printing process; electrophoretic deposition (see U.S. Patent No. 7,339,715); and other similar technologies.) Therefore, the resulting display can be flexible. In addition, because the display medium can be printed using a variety of methods, the display itself can be manufactured inexpensively.

[0055] Other types of electro-optical materials may also be used in the present invention.

[0056] Electrophoretic displays typically include a layer of electrophoretic material and at least two other layers disposed on opposite sides of the electrophoretic material, one of the two layers being an electrode layer. In most such displays, both layers are electrode layers, and one or both electrode layers are patterned to define pixels of the display. For example, one electrode layer may be patterned as an elongated row electrode, while the other electrode layer may be patterned as an elongated column electrode extending at right angles to the row electrode, with the pixel being defined by the intersection of the row electrode and the column electrode. Alternatively, and more typically, one electrode layer has the form of a single continuous electrode, while the other electrode layer is patterned as a matrix of pixel electrodes, each pixel electrode defining a pixel of the display. In another type of electrophoretic display intended for use with a stylus, a print head, or a similar movable electrode separate from the display, only one of the layers adjacent to the electrophoretic layer includes an electrode, and 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.

[0057] In yet another embodiment, such as described in U.S. Patent No. 6,704,133, an electrophoretic display can be constructed with two continuous electrodes and an electrophoretic layer and a photophoretic layer between the electrodes. Since the photophoretic material changes resistivity with the absorption of photons, incident light can be used to change the state of the electrophoretic medium. Such a device is Figure 1 As described in U.S. Patent No. 6,704,133, Figure 1 The device works best when driven by an emissive source located on the opposite side of the display from the viewing surface (e.g., an LCD display). In some embodiments, the device of U.S. Patent No. 6,704,133 includes a specific barrier layer between the front electrode and the electro-optical material to reduce "dark current" caused by incident light from the front of the display leaking through the reflective electro-optic medium.

[0058] The aforementioned U.S. Patent No. 6,982,178 describes a method of assembling a solid electro-optic display (including encapsulated electrophoretic displays) that is well suited for mass production. In essence, the patent describes a so-called "front plane laminate" ("FPL") that includes, in sequence, a light-transmitting conductive layer, a solid electro-optic medium layer in electrical contact with the conductive layer, an adhesive layer, and a release sheet. Typically, the light-transmitting conductive layer will be carried on a light-transmitting substrate, which is preferably flexible in the sense that the substrate can be manually wound onto a drum of (for example) 10 inches (254 mm) in diameter without permanent deformation. The term "light-transmitting" is used in the patent and refers herein to a layer so designated that transmits sufficient light to enable an observer to observe through the layer a change in the display state of the electro-optic medium, which will typically be observed through the conductive layer and the adjacent substrate (if present); in the case where the electro-optic medium displays a change in reflectivity of non-visible wavelengths, the term "light-transmitting" should of course be interpreted as referring to the transmission of the relevant non-visible wavelengths. The substrate is typically a polymer film and will typically have a thickness ranging from about 1 to about 25 mils (25 to 634 microns), preferably from about 2 to about 10 mils (51 to 254 microns). The conductive layer is conveniently a thin metal or metal oxide layer such as aluminum or ITO, or may be a conductive polymer. Polyethylene terephthalate (PET) films coated with aluminum or ITO are commercially available, such as "aluminized Mylar" ("Mylar" is a registered trademark) from DuPont of Wilmington, Delaware, and such commercial materials can have good results in front plane laminates.

[0059] Assembly of an electro-optical display using such a front plane laminate can be accomplished by removing a release sheet from the front plane laminate and contacting the adhesive layer with the backplane under conditions that effectively adhere the adhesive layer to the backplane, thereby securing the adhesive layer, electro-optical medium layer, and conductive layer to the backplane. This process is well suited for mass production because the front plane laminate can typically be mass produced using roll-to-roll coating techniques and then cut into pieces of any size for a particular backplane.

[0060] U.S. Patent No. 7,561,324 describes a so-called "double release sheet" which is essentially a simplified version of the front plane laminate of the aforementioned U.S. Patent No. 6,982,178. One form of the double release sheet comprises a solid electro-optic medium layer sandwiched between two adhesive layers, one or both of which are covered by a release sheet. Another form of the double release sheet comprises a solid electro-optic medium layer sandwiched between two release sheets. Both forms of double release sheet films are intended to be used in a process generally similar to that already described for assembling an electro-optic display from a front plane laminate, but involving two separate laminations; typically, in a first lamination, the double release sheet is laminated to the front electrode to form a front subassembly, and then in a second lamination, the front subassembly is laminated to the backplane to form the final display, but the order of the two laminations can be reversed if desired.

[0061] U.S. Patent No. 7,839,564 describes a so-called "inverted front plane laminate" which is a variation of the front plane laminate described in the aforementioned U.S. Patent No. 6,982,178. The inverted front plane laminate comprises, in sequence, at least one of a light-transmissive protective layer and a light-transmissive conductive layer, an adhesive layer, a solid electro-optic medium layer, and a release sheet. The inverted front plane laminate is used to form an electro-optic display having a laminated adhesive layer between the electro-optic layer and the front electrode or front substrate; a second adhesive layer, which is typically thinner, may or may not be present between the electro-optic layer and the backplane. Such an electro-optic display can combine good resolution with good low temperature performance.

[0062] The photoelectrophoretic properties of certain pigments were recognized some time ago. For example, U.S. Patent No. 3,383,993 discloses a photoelectrophoretic imaging device that can be used to reproduce a projected image on a medium (such as ITO) that is typically a transparent electrode. However, the photoelectrophoretic process described in the '993 patent and other related patents of Xerox Corporation is irreversible because the photoelectrophoretic process involves the migration of the photoelectrophoretic particles to an "injection electrode" where they will then attach to the electrode. Due to the lack of reversibility, as well as the cost and complexity of installation, this phenomenon has not been widely commercialized.

[0063] The subject matter presented herein relates to several piezoelectric electrophoretic display structural designs that do not require a power source (eg, battery or wired power, etc.) to operate the electrophoretic display, thereby simplifying the assembly of such an electrophoretic display.

[0064] Piezoelectricity is the accumulation of electrical charge in a solid material in response to an applied mechanical stress. Suitable materials for the disclosed subject matter herein may include polyvinylidene fluoride (PVDF), quartz (SiO2), monolithic aluminum phosphate (AlPO4), gallium orthophosphate (GaPO4), tourmaline, barium titanate (BaTiO3), lead zirconate titanate (PZT), zinc oxide (ZnO), aluminum nitride (AlN), lithium tantalate, lanthanum gallium silicate, potassium sodium tartrate, and any other known piezoelectric material.

[0065] Some aspects of the subject matter presented herein utilize piezoelectricity to drive the pigments of an electrophoretic material to change the color of the electrophoretic material when viewed from a viewing surface. For example, by bending or applying stress to a piece of piezoelectric material, a voltage can be generated, and the voltage can be used to cause movement of the color pigments of the electrophoretic material. As used herein, the term "contrast ratio" (CR) for an electro-optical display (e.g., an electrophoretic display) is defined as the ratio of the brightness of the brightest color (white) to the darkest color (black) that the display is capable of producing. Typically, a high contrast ratio or CR is a desirable aspect of a display.

[0066] Figure 1 A cross-sectional view of an exemplary electro-optic display 100 according to the subject matter disclosed herein is shown, which uses a piezoelectric material 102 to drive an electrophoretic material (EPD) film 104. In this embodiment, the piezoelectric film 102 can be laminated to a portion of the EPD film 104, and a conductive adhesive material (e.g., copper tape) can be used to cover the remainder of the piezoelectric film 102 and the EPD film 104, as in Figure 1 and Figure 2A . In some embodiments, a conductive adhesive material may be used as electrode 2108 and fixed to a substrate (not shown). In some other embodiments, electrode 2108 may be used as a pixel electrode for modulating a voltage potential across the EPD film 104 to display a color or image (e.g., by changing the grayscale of the EPD film 104). In addition, opposite to electrode 2108, electrode 1106 may overlap the EPD film layer 104. In yet another embodiment, the EPD film 104 may be initially fabricated onto electrode 1106. For example, electrode 1106 may first be patterned to include a micro-unit structure, wherein an electrophoretic fluid having electrophoretic particles may be imprinted into the micro-unit structure to form an EPD film layer. The details will be described below. Fig. 9 and 11A -B. In this configuration, the EPD film 104 and the electrode 1 106 can be an integral structure. In some other embodiments, both the electrode 1 106 and the electrode 2 108 can be transparent, or either the electrode 1 106 or the electrode 2 108 can be transparent so that the display 100 can be observed from any direction.

[0067] In practice, the CR of the electro-optic display 100 may vary depending on the ratio of the surface area A1 110 of the EPD film 104 (i.e., the portion of the EPD film 104 that overlaps with, is covered by, or is in direct contact with the piezoelectric material 102) compared to the area of ​​area A2 112 (i.e., the portion of the EPD film 104 that overlaps with, is covered by, or is in direct contact with the piezoelectric material 102), as shown in FIG. Figure 1 The experimental results of CR are shown in Table 1 below.

[0068]

[0069] Table 1. Display CR and piezoelectric film surface area

[0070] like Figure 1 As shown, such as Figure 1 The display shown can improve its CR by reducing the total surface area (e.g., A2) of the EPD film 104 overlapping or on the electrode 2 108 (i.e., the conductive adhesive material). When the ratio of the EPD film 104 on the piezoelectric film 102 (e.g., A1) to the EPD film 104 on the electrode 2 108 (e.g., A2) is 1:2, the CR is 2, and when the ratio becomes 2:1, the CR is improved to 7. In some embodiments, to further improve the CR, any applied physical stress can be applied to the longer side of the electrode 2 108 in the vertical direction to reduce the width of the electrode 1 106 or the electrode 2 108.

[0071] Figure 2B The subject matter disclosed herein is shown Figure 1 104. The portion of the EPD film 104 in contact with the piezoelectric film 102 may have a resistance value R1, and the portion covered by the electrode 2 108 may have a resistance value R2. In practice, the voltage generated by the piezoelectric film 104 may be distributed between R1 and R2 in a series configuration. In some embodiments, an adhesive layer may be present between the piezoelectric film 102 and the EPD film layer 104, wherein the resistivity value of the adhesive layer may be approximately 10 8 Ohm*cm, and preferably less than 10 12 Ohm*cm.

[0072] In another embodiment according to the subject matter disclosed herein, as Figure 1 and Figure 2A Instead of laminating the piezoelectric film directly onto or overlapping the EPD film as shown, the piezoelectric film 302 can be laminated onto the semiconductive or high resistance layer 304, which is then laminated onto the electrode 1 layer 306, as shown in FIG. Figure 3AAs shown in Table 2 below, the resistivity level of the semiconductive layer 304 is compared with the resulting CR. As shown in the figure, when the semiconductive layer 304 has a 10 8 The best CR ratio that can be achieved is 12 when the resistivity is 1 Ohm*cm.

[0073]

[0074] Table 2. Display CR and resistance

[0075] In addition, the display CR can be optimized by adjusting the resistance value of the semiconductive layer 304. For example, at about 10 8 In another embodiment, the resistance of the electrode 1 layer 306 may be about 450 ohm / sq, the resistance of the electrode 2 layer 310 may be 0.003 ohm / sq, and the EPD film 308 may have a resistance of about 10 7 Up to 10 8 Ohms, and the piezoelectric material 302 may have a resistance of 10 13 Up to 10 14 Ohms of resistance.

[0076] Figure 3B and 3C yes Figure 3A A cross-sectional view of the display shown. Figure 3B shows a cross section of the display along line C1, and Figure 3C A cross section of the display along line C2 is shown. In practice, it is possible that only the EPD portion 308 of the display is made visible to the user, while the piezoelectric film portion may be covered. Figure 3B and 3C As shown, the electrode 2 layer 310 can be segmented. As a result, the grayscale changes in the EPD film layer 308 will also appear segmented. Alternatively, if the electrode 2 310 is a single continuous piece, the grayscale changes in the EPD film layer 308 will also be continuous. It should be understood that both the electrode 1 306 and the electrode 2 310 can be transparent, and all layers (e.g., layers 302, 304, 310, etc.) can be transparent so that the display can be viewed from an orientation or direction.

[0077] In another embodiment, Figure 3DA cross-sectional view of another display 312 according to the subject matter presented herein is shown. The display 312 is Figure 3A The display shown is different in that only a portion of the piezoelectric film layer 318 overlaps the electrode 1 316 layer. In this configuration, the piezoelectric film layer 318 can be avoided from being placed in a neutral plane position so that a better image can be generated from the piezoelectric film 318. In addition, the piezoelectric film layer 318 can be a metallized piezoelectric film and can be covered by a metal layer 320. In some embodiments, a first semiconductive layer 314 can be located between the metal layer 320 and the electrode 1 layer 316. Another second semiconductive layer 322 can be located between the piezoelectric film layer 318 and the electrode 2 layer 324. It should be understood that all layers presented herein, including the electrode 1 316 and electrode 2 324 layers, can be transparent so that the display can be observed from a direction or orientation.

[0078] In yet another embodiment, similar to Figure 1 and 2A The configuration shown in FIG. 1 is different from that shown in FIG. 1 , but a semiconductive layer 402 may be placed between the electrode 2 layer 404 and the piezoelectric film layer 406 and the EPD film layer 408, as shown in FIG. Figure 4 The semiconducting layer 402 can insulate the piezoelectric film layer 406 and the EPD film layer 408 from the electrode 2 404. Similarly, Figure 3A The display shown is modified to include an additional semiconducting layer to insulate the piezoelectric film and the EPD film from the electrode 2. In various configurations, Figure 4 The display shown exhibits the best CR performance at 18. Regardless, the display configuration herein enables one to construct a piezoelectric actuator with a thickness less than 50 um, and also greatly simplifies the device structure and makes the display more sensitive to smaller applied physical stresses.

[0079] Figure 5 Another design 500 of a display is shown. The display 500 is similar to Figure 3A The display shown in , except that an additional semiconducting layer 502 is placed between the piezoelectric layer 504 and the electrode 2 layer 506. A comparison of the CR ratios between the various designs is shown in Table 3 below.

[0080] Display response to strain changes The piezoelectric film is in direct contact with the two electrodes Contrast ratio: 1.7 Figure 1 Contrast ratio: 7 Figure 3A Contrast ratio: 12 Figure 4 Contrast ratio: 18 Figure 5 Contrast ratio: 14

[0081] Table 3. Comparison of CR

[0082] It should be understood that Figure 4 and Figure 5 All layers shown in, including those of Electrode 1 and Electrode 2, may be transparent so that the displays may be viewed from any direction or orientation.

[0083] It should also be noted that reference Figure 1-5In the display configuration shown in , the conductive path between electrode 1 and electrode 2 and the piezoelectric material layer and the EPD film layer is complete, and no other conductor or electrode is required between electrode 1 and electrode 2. This effectively reduces the overall thickness of the device and improves the CR ratio of the display.

[0084] Figure 6 and 7 An embodiment of a piezoelectric electrophoretic display is shown that can be configured to display various patterns, such as Figure 6 The sawtooth pattern and Figure 7 The star pattern in Figure 6 In FIG. 6 , display 600 may include a plurality of electrodes 602 designed to transfer charge to electrophoretic display media 604s and 606s. Figure 6 In the embodiment shown, display medium 604 is red and display medium 606 is black. It should be understood that other colors can be easily used. In this configuration, the electrode 602 on the top of the display can be connected to the black display medium 606, and the electrode 602 on the bottom can be connected to the red display medium 604. In use, when a force is applied to the display 600, the display media 606 and 604 can display black and red. Conductive material printing can be used Figure 6 The particular configuration shown greatly simplifies the manufacturing process.

[0085] In some other embodiments, a piezoelectric electrophoretic display according to the subject matter disclosed herein may be combined with another device, e.g. Figure 8 . In this embodiment, a display may be affixed to one end of the note, and when physical stress is applied, the display may switch between one or more grayscales. In this way, a user may easily distinguish a genuine note from a counterfeit note. As described above, the electrodes for the display may be segmented, and the grayscale tones of the resulting EPD material layer may be presented segmentally. Alternatively, the electrodes for the display may be a continuous sheet, and the grayscale tones of the resulting EPD material may be varied in a continuous manner.

[0086] Manufacturing method

[0087] Fig. 9 9 shows a cross-sectional view of yet another embodiment of a piezoelectric display 910 according to the subject matter presented herein. Fig. 9As shown, the EPD layer 900 may extend partially under the piezoelectric material 902 to substantially overlap the piezoelectric material 902 and ensure a strong connection with the piezoelectric material 902. In this embodiment, the EPD layer 900 may have a portion 906 having microcells and another portion 904 that is substantially flat, which is configured to establish a connection with the piezoelectric material 902. In this configuration, the piezoelectric material 902 is positioned to overlap on the substantially flat portion 904, ensuring a good connection with the EPD layer 900. This configuration may advantageously establish a strong connection between the piezoelectric material 902 and the EPD layer 900. For example, this configuration provides a robust connection between the piezoelectric material 902 and the EPD layer 900 that can withstand repeated bending or stress applied to the display device 910. In addition, an adhesive layer 908 may be placed between the piezoelectric material layer 902 and the conductor 912. In another embodiment, the piezoelectric material 902 may be annular and surround the EPD material 900. In addition, as Fig. 9 As shown, the piezoelectric material 902 and the EPD layer 900 can be sandwiched between two layers of conductors or conductive materials, and all of the above layers and materials can be placed on a flexible substrate. Preferably, the thickness of the substrate is less than 10 microns to make the entire device thin. In some embodiments, ITO / PET can be used as a substrate in this article. In some other embodiments, a flexible and transparent conductive coating such as PEDOT:PSS, graphene, carbon nanotubes, or silver nanowires can be used. In some other embodiments, such as Fig.10 As shown, a barrier layer can be sputtered onto a substrate layer (e.g., PET) before applying a conductive layer to provide a barrier to ink solvents. In some cases, the barrier layer can be SiOx. Since the substrate is thin in this case, the barrier layer can also be applied to the other side of the substrate. In addition, other optical layers can be printed onto the substrate for decorative purposes. In some embodiments, the carrier film can be discarded after the display is assembled. And the rest of the display without the carrier film can be integrated with other structures. It should be understood that all layers presented herein, including the layers of electrode 1 and electrode 2, can be transparent so that the display can be observed from a direction or orientation.

[0088] Fig.11A Shows Fig. 9 900. As shown, the EPD layer 900 can be made by patterning the microcell structure onto only a portion of the layer 900 while leaving the rest of the layer substantially flat. In this way, the substantially flat portion 1102 without microcells (i.e., the only portion 1102 designated as having a microcell structure) can be used to establish a connection with the piezoelectric layer, such as Fig. 9As shown. This method of manufacturing provides several advantages. First, it is easier to manufacture the EPD layer in this manner, in which the contact portion and the microcell portion 1102 are manufactured simultaneously, than in an alternative method of manufacturing the contact portion (i.e., the substantially flat portion) and the microcell portion 1102 separately. Second, because the substantially flat contact portion 1100 and the microcell portion 1102 are manufactured together, they are more robust in structure, which results in a better connection between the EPD layer and the piezoelectric layer, and a more durable display device. Fig. 11B It shows that Fig.11A 100. The cross-sectional view of the EPD layer shown. The EPD layer may include a first portion 1104 with patterned microcells and a flat portion 1106 without microcells. In fact, the substantially flat portion 1106 and the microcell portion 1104 may be patterned in the same photolithography step. In some embodiments, once the pattern has been defined and after the embossing step, a strip of a release liner may be laminated to the substantially flat portion, wherein the thickness of the release liner may be the same as the microcell height. Preferably, the surface energy of the release liner is high enough so that the sealing layer will not dewet on the top of the release liner, and in some embodiments, the surface energy may be adjusted to a specific level according to the application. In this case, the release liner may include polyvinyl alcohol or other water-soluble polymers. In addition, after the filling and sealing steps, the release liner may be removed together with the ink and sealing layer on its top to expose the flat area below. In practice, removing the release liner will remove the sealing layer / material and ink from the substantially flat portion of the EPD layer. This process can ensure that the ink and sealing material are substantially cleanly separated from the microcell portion 1104. A non-metallized piezoelectric film can be laminated to the flat surface. The combined thickness of the piezoelectric film and adhesive layer can be similar to the combined thickness of the seal layer and microcells. Additionally, an adhesive layer can be laminated to the release liner and the entire display panel. In-line humidification or an off-line chamber humidification step can be used to ensure good optical performance of the display. In practice, Fig.11A and 11B Once the pattern is defined in , the structure can be cut along the A'A' line to create a display.

[0089] In some embodiments, a method for manufacturing a display as described above may include manufacturing an electrophoretic display material layer having a first portion 1102 and a second portion 1100, the first portion 1102 having a plurality of microcells, and the second portion 1100 being substantially flat. The method may further include providing a piezoelectric material, and aligning the piezoelectric material with the second portion of the electrophoretic display material so that the piezoelectric material substantially overlaps the second portion. In some embodiments, a single photolithography step is used to manufacture the first portion 1102 and the second portion 1100 of the electrophoretic material. The method may further include placing the electrophoretic display material and the piezoelectric material on a substrate, wherein the substrate may be flexible. In some embodiments, the method may further include providing a conductive electrode on the substrate, and providing a barrier layer between the conductive electrode and the substrate. In some embodiments, after the step of manufacturing the electrophoretic display layer, the method may further include providing a layer of release liner. Wherein, the height of the release liner is substantially similar to the height of the plurality of microcells.

[0090] In addition, if Figure 6 As shown, another second electrode can be printed on top of the substrate. In order to connect the second electrode to the EPD material, a conductive trace or line can be patterned using conductive ink. In some embodiments, the pattern can contain two parts. The first part can be printed as a small strip, and the second part can be a two-pixel pattern. Wherein, each pixel can be connected to one or two small strips using conductive ink. These patterns can then be aligned and laminated on the above-mentioned FPL, where the piezoelectric film is located on top of the small strip.

[0091] Fig. 12A and 12B Another embodiment of an electrophoretic display 1200 utilizing piezoelectric materials is shown. As shown, a piezoelectric material layer 1202 may be stacked with a display medium layer 1204 (eg, an electrophoretic medium layer) to form a display. Fig. 12A and 12B As shown, two electrodes, electrode 1 1206 and electrode 2 1208, can be located on both sides to sandwich the EPD layer 1204 and the piezoelectric material layer 1202 in the middle to complete the conductive path of the charge. In some embodiments, electrode 2 1208 can be a metal on the piezoelectric film or a laminated conductive adhesive on the piezoelectric film. In this configuration, no other connection is required to drive the electrophoretic display material 1204.

[0092] In use, when a force is applied to the piezoelectric material layer 1202, charge separation occurs within the piezoelectric material 1202. Charges on the interface of the electrophoretic display medium layer 1204 and the piezoelectric material layer 1202 can induce charges on the EPD film and the electric field passes through the EPD to cause the particles to move. Fig. 12B A view of the charge distribution is shown.

[0093] In yet another embodiment, in order to obtain a better contrast ratio, piezoelectric films with opposite polarization directions may be arranged in parallel, such as Fig.13A and 13B In use, PZ1 and PZ2 can generate opposite voltages under applied force, Fig. 13B An example of charge distribution when a force is applied is shown. It should be understood that the present invention Figures 12A-13B All layers present in, including the layers of electrode 1 and electrode 2. may be transparent so that the display can be observed from a direction or orientation.

[0094] Figures 12A-13B The illustrated embodiment not only reduces the thickness of the entire device to less than 50 microns, but also greatly improves the CR. In addition, it simplifies the device structure and makes the display device more sensitive to smaller strain changes.

[0095] Latent Image

[0096] In some embodiments, having a configuration similar to or based on Fig. 12A or Figure 1 The display of the configuration shown may be modified to display a latent image. Fig.14A 1 is a display device 1400 similar to Fig. 12A , but with an image or shape laminated or printed on electrode 1 1406 or electrode 2 1408. It should be understood that Fig.14A The configuration shown in is used to illustrate the concept, because other configurations can be easily adopted to achieve the same effect. In practice, each layer of display 1400 can be transparent (e.g., layers 1402, 1404, 1406, 1408, etc.), even the adhesive layer and the electrodes 1 and 2 layers, so that the display can be observed from a direction or orientation.

[0097] In some embodiments, an image or shape can be printed or laminated onto a white background and onto electrode 1 1406 or electrode 2 1408 and viewed from the opposite side. In use, when the EPD layer 1404 appears white, the printed image or shape will be hidden (i.e., see Fig. 14B ), and when the EPD 1404 switches to another color when force is applied, a printed image or shape can be displayed (i.e., see Fig. 14C ).

[0098] In yet another embodiment, a dark image or shape can be produced on electrode 1 1406 or electrode 2 1408 without a background and can be viewed from the opposite side. In this configuration, when the display 1400 is placed on a black background, as shown in FIG. Fig.14DAs shown, no matter how the EPD 1404 is bent, the printed image or shape will remain hidden. Alternatively, when the display 1400 is placed on a white or light background, the printed image or shape will be displayed and will be more obvious when the EPD 1404 is switched to a darker color, such as Fig.14E shown.

[0099] In yet another embodiment, Fig.15A As shown, an image or shape can be produced on the outside of electrodes 1 1502, 1504 or EPD display 1 1506 and EPD display 2 1508. The two EPD displays 1506, 1508 can be integrated together using a transparent adhesive material. When a force is applied (e.g., bending), both EPD display 1 1506 and EPD display 2 1508 can change color. When EPD display 2 1508 becomes darker and EPD display 1 1506 becomes white, the printed image or shape will not appear, as shown in FIG. Fig. 15C Alternatively, when EPD display 2 1508 turns white and EPD display 1 1506 turns dark, the printed image or shape will emerge, as shown. Fig. 15B shown.

[0100] It should also be noted that reference Figure 9-14A In the display configuration shown, the conductive path between electrode 1 and electrode 2 and the piezoelectric material layer and the EPD film layer is complete, and no other conductor or electrode is required between electrode 1 and electrode 2. In the case of the display shown in Figure 15, no additional conductor or electrode is required for each stacked display 1506 and 1508. This effectively reduces the overall thickness of the device and improves the CR ratio of the display.

[0101] It will be apparent to those skilled in the art that many changes and modifications may be made to the specific embodiments of the invention described above without departing from the scope of the invention.Therefore, the entire foregoing description is to be interpreted in an illustrative rather than a limiting sense.

Claims

1. An electro-optical display comprising: electrophoretic material layer; a first conductive layer; a piezoelectric material between the electrophoretic material layer and the first conductive layer, wherein the piezoelectric material overlaps only a first portion of the electrophoretic material layer, and the first conductive layer overlaps all of the piezoelectric material and a second portion of the electrophoretic material layer that does not overlap with the piezoelectric material, and wherein the first portion of the electrophoretic material layer includes a first plurality of microcells and has a first resistance, and the second portion of the electrophoretic material layer includes a second plurality of microcells and has a second resistance; and An adhesive layer located between the piezoelectric material and the electrophoretic material layer, wherein the resistivity of the adhesive layer is greater than or equal to 10 8 Ohm*cm and less than 10 12 Ohm*cm.

2. An electro-optic display as claimed in claim 1, further comprising a second conductive material positioned proximate to the layer of electrophoretic material and opposite the piezoelectric material.

3. An electro-optical display comprising: electrophoretic material layer; Semiconducting material, with about 10 8 Resistivity in Ohm*cm; as well as A piezoelectric material is stacked with the semiconductive material, wherein the piezoelectric material and the semiconductive material are positioned side by side with the layer of electrophoretic material.

4. The electro-optic display of claim 3, further comprising a first conductive layer overlapping the piezoelectric material and the electrophoretic material.

5. An electro-optic display as claimed in claim 4, further comprising a layer of a second semi-conductive material between the first conductive layer and the piezoelectric material and the electrophoretic material.

6. The electro-optic display of claim 3 further comprising a second conductive layer overlapping the semiconductive material and the electrophoretic material.

7. An electro-optical display comprising: electrophoretic material layer; a first piezoelectric material layer; as well as A second piezoelectric material layer, wherein the first piezoelectric material layer and the second piezoelectric material layer are placed side by side and overlap the electrophoretic material layer, wherein the first piezoelectric material layer and the second piezoelectric material layer have opposite polarization directions.

8. A method of manufacturing a display, comprising: manufacturing an electrophoretic display material layer having a first portion and a second portion, the first portion having a plurality of microcells, and the second portion being substantially flat; Providing piezoelectric materials; as well as The piezoelectric material is aligned with a second portion of the electrophoretic display material such that the piezoelectric material substantially overlaps the second portion.

9. The method according to claim 8, wherein: The first and second parts of the electrophoretic display material are manufactured using a single photolithographic step.

10. The method of claim 8, further comprising placing the electrophoretic display material and the piezoelectric material on a substrate.

11. The method according to claim 10, wherein: The substrate is flexible.

12. The method of claim 10, further comprising providing a conductive electrode on the substrate.

13. The method of claim 12, further comprising providing a barrier layer between the conductive electrode and the substrate.

14. The method according to claim 8, further comprising providing a release liner after the step of manufacturing the electrophoretic display layer.

15. The method according to claim 14, wherein: The release liner has a height substantially similar to a height of the plurality of microlocations.

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