Piezoelectric electrophoresis film, display and manufacturing method thereof

Abstract

The low-voltage piezoelectric electrophoresis film and the display film comprise a low-profile piezoelectric electrophoresis film and a display. In some embodiments, the piezoelectric material of the piezo-electrophoretic film may be selectively patterned with a high voltage electric field during or after manufacturing of the piezo-electrophoretic film. Such films have high contrast and can be used as security marks, authentication films or sensors. The membrane is typically flexible. Some of the films have a thickness of less than 100 pm. Some of the films have a thickness of less than 50 pm. A display formed from the film does not require an external power source.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 579,375, filed August 29, 2023, and U.S. Provisional Application No. 63 / 579,377, filed August 29, 2023.

[0003] The entire disclosure of the aforementioned application and all other applications or publications mentioned below is incorporated herein by reference in its entirety.

[0004] Field of invention

[0005] The subject matter disclosed herein relates to electrophoretic displays, and more particularly to thin piezoelectric electrophoretic displays with improved contrast and methods for manufacturing the same. The subject matter also relates to low-profile piezoelectric electrophoretic displays that can be activated or driven without connection to a power source and methods for manufacturing the same.

[0006] Background of the invention

[0007] An electrophoretic display (“EPD”) is a non-luminescent device based on the electrophoresis of charged pigment particles dispersed in a solvent or solvent mixture. The display typically includes two electrodes placed opposite each other, which provide an electric field to drive the movement of the charged pigment particles. One of the electrodes is usually transparent. When a voltage difference is applied between the two electrodes, the pigment particles migrate to one side or the other, making the color of the pigment particles or the color of the solvent (if colored) visible from the viewing side.

[0008] Many electrophoretic displays comprise an electrophoretic solution containing a nonpolar solvent and one or more groups of charged pigment particles. These particles may have different optical properties (color), different charges (positive or negative), different charge magnitudes (zeta potential), and / or different absorption properties (broad absorption or broad reflection, or selective absorption or selective reflection). In the presence of multiple groups of particles with opposite charge polarities, the application of an electric field can cause one group of pigment particles to appear on the viewing surface, while other pigment particles are driven away from the viewing surface.

[0009] Many electrophoretic displays are bistable, meaning that the optical state of such displays persists even after the activation electric field is removed. This bistableness is primarily due to the induced dipole charge layer formed around the charged pigment by the complex interactions between the pigment, charge control agent, and free polymer dispersed in the solvent. Bistable displays can persist in their last addressed optical state for years before being switched again by applying a new driving field.

[0010] Driving an electrophoretic display requires a power source such as a battery to power the display and / or its driving circuitry. For example, a battery can be used to power a driver IC, which in turn generates an electric field to power the electrodes of the display. The power source can also be, for example, a photovoltaic cell, a fuel cell, or a source that receives power from a wall outlet. The power source can also be a piezoelectric element that generates charge through physical motion or thermal expansion, as described in U.S. Patent No. 5,930,026, which is incorporated herein by reference in its entirety.

[0011] In all these instances, some type of drive circuit is required to provide an electrical path between the power source and the electrodes. Generally, the circuit also includes control elements (e.g., switches, transistors, etc.) and multiple discrete components (e.g., resistors, capacitors, etc.).

[0012] In most cases, the circuitry used in conventional displays is complex, but well-known to those skilled in the art of display technology. However, including such circuitry limits the display's tolerance to mechanical stresses such as bending and / or torsion. Furthermore, the presence of additional components generally increases the overall physical size of the fully assembled display.

[0013] The physical limitations imposed on displays by increased power supplies and drive circuitry make them unsuitable for a growing number of applications that seek to reduce overall display thickness. Therefore, in efforts to reduce display thickness, some electrophoretic displays utilize low-profile piezoelectric elements that generate charge in response to mechanical strain or thermal cycling. However, the thickness of the piezoelectric material layer is generally directly related to the magnitude of the voltage the piezoelectric material can generate in response to mechanical stress. That is, reducing the thickness of the piezoelectric material also reduces the magnitude of the voltage generated under stress (and vice versa). Therefore, to generate a sufficiently large voltage potential for the amount of charged pigment particle movement to achieve acceptable contrast, conventional piezoelectric electrophoretic displays typically contain excessively thick piezoelectric material layers, making them unsuitable for applications requiring durability and minimal inconspicuousness when incorporated into thin, low-profile end products such as paper or banknotes. Invention Overview

[0015] Therefore, applications such as anti-counterfeiting marks, sensors, and indicators require electrophoretic displays that are simple in structure, flexible, durable, and thin. There is also a need for sufficiently thin and durable piezoelectric electrophoretic displays for applications requiring low profiles in the final product while also providing high contrast.

[0016] 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 the remainder of the electrophoretic material.

[0017] In a first aspect, the present invention includes an electrophoretic display film with a thickness of less than 100 μm (top to bottom), comprising a first adhesive layer, an electrophoretic dielectric layer, a patterned piezoelectric layer containing differentiated polarization regions, and a flexible transparent electrode layer. In some embodiments, the electrophoretic dielectric layer comprises a plurality of microcapsules containing a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer is bent, wherein the microcapsules are bonded to each other with a polymer adhesive. In some embodiments, the electrophoretic dielectric layer comprises a plurality of microunits containing a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer is bent, wherein the nonpolar fluid and charged pigment particles are sealed within the microunits by a sealing layer. In some embodiments, the film thickness is less than 50 μm. In some embodiments, the patterned piezoelectric layer comprises polyvinylidene fluoride (PVDF). In some embodiments, the PVDF is polarized to create differentiated polarization regions. In some embodiments, the flexible transparent electrode layer comprises a metal oxide containing tin or zinc. In some embodiments, the flexible transparent electrode layer comprises poly(3,4-ethylenedioxythiophene) (PEDOT). In some embodiments, the invention includes an electrophoretic display film assembly comprising a release sheet bonded to the electrophoretic display film as described above, wherein the release sheet is bonded to a first adhesive layer. In some embodiments, a second adhesive layer is bonded to the flexible transparent electrode layer, and a second release sheet is bonded to a second adhesive layer.

[0018] In a second aspect, the present invention includes a method for manufacturing an electrophoretic display film. The method includes the following steps: bonding a polyvinylidene fluoride (PVDF) film to a polymer film comprising acrylate, vinyl ether, or epoxide to form a piezoelectric microunit precursor film; bonding the piezoelectric microunit precursor film to a flexible light-transmitting electrode layer; bonding the light-transmitting electrode layer to a first release film with a first adhesive layer; imprinting the piezoelectric microunit precursor film to produce a microunit array, wherein the microunits have a bottom, a wall, and a top opening; filling the microunits with an electrophoretic medium through the top openings; and sealing the top openings of the filled microunits with a water-soluble polymer. In some embodiments, the method further includes applying a primer comprising acrylate, vinyl ether, or epoxide to the polymer film prior to bonding the polymer film to the PVDF film. In some embodiments, the method further includes bonding a water-soluble polymer to a second release film with a second adhesive layer. In some embodiments, the method further includes removing the first release film to produce an electrophoretic display film with a thickness of less than 100 μm. In some embodiments, the electrophoretic dielectric layer comprises a plurality of microunits containing a nonpolar fluid and charged pigment particles, which move toward or away from the piezoelectric layer when the piezoelectric layer bends, wherein the nonpolar fluid and charged pigment particles are sealed within the microunits by a sealing layer. In some embodiments, the PVDF is polarized to form differentiated polarization regions. In some embodiments, the flexible transparent electrode layer comprises a metal oxide containing tin or zinc. In some embodiments, the flexible transparent electrode layer comprises poly(3,4-ethylenedioxythiophene) (PEDOT). In some embodiments, the polyvinylidene fluoride film is patterned with an electric field to form differentiated polarization regions. In some embodiments, the method further includes patterning the completed electrophoretic display film with an electric field to form differentiated polarization regions in the polyvinylidene fluoride film.

[0019] Thirdly, the present invention includes a method for manufacturing an electrophoretic display film. The method includes dispersing a polyvinylidene fluoride (PVDF) solution on a first release film to produce a PVDF film with a thickness of less than 10 μm; bonding the PVDF film to a second release film using a conductive adhesive; removing the first release film; bonding a polymer film comprising acrylate, vinyl ether, or epoxide to form a piezoelectric microunit precursor film; bonding the piezoelectric microunit precursor film to a flexible light-transmitting electrode layer; bonding the light-transmitting electrode layer to the first release film using a first adhesive layer; imprinting the polymer film comprising acrylate, vinyl ether, or epoxide to produce a microunit array, wherein the microunits have a bottom, wall, and top opening; filling the microunits through the top opening with an electrophoretic medium; and sealing the top opening of the filled microunits with a water-soluble polymer. In some embodiments, the method further includes applying a primer to the polymer film comprising acrylate, vinyl ether, or epoxide before bonding the polymer film to the PVDF film. In some embodiments, the method further includes bonding a water-soluble polymer to the second release film using a second adhesive layer. In some embodiments, the method further includes removing a first release film to form an electrophoretic display film with a thickness of less than 100 μm. In some embodiments, the electrophoretic dielectric layer includes a plurality of microunits comprising a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer is bent, wherein the nonpolar fluid and charged pigment particles are sealed within the microunits by a sealing layer. In some embodiments, the PVDF is polarized to form differentiated polarization regions. In some embodiments, the flexible transparent electrode layer comprises a metal oxide containing tin or zinc. In some embodiments, the flexible transparent electrode layer comprises poly(3,4-ethylenedioxythiophene) (PEDOT). In some embodiments, the PVDF film is patterned with an electric field to form differentiated polarization regions. In some embodiments, the method further includes patterning the completed electrophoretic display film with an electric field to form differentiated polarization regions in the PVDF film.

[0020] Fourthly, the electrophoretic display film with a thickness of less than 100 μm (top to bottom) includes a first adhesive layer, a patterned piezoelectric layer containing differentiated polarization regions, an electrophoretic dielectric layer, and a flexible transparent electrode layer. In some embodiments, the electrophoretic dielectric layer includes a plurality of microcapsules containing nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer is bent, wherein the microcapsules are bonded to each other with a polymer adhesive. In some embodiments, the electrophoretic dielectric layer includes a plurality of microunits containing nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer is bent, wherein the nonpolar fluid and charged pigment particles are sealed within the microunits by a sealing layer. In some embodiments, the sealing layer is conductive. In some embodiments, the film thickness is less than 50 μm. In some embodiments, the patterned piezoelectric layer includes polyvinylidene fluoride (PVDF). In some embodiments, the PVDF is polarized to form differentiated polarization regions. In some embodiments, the flexible transparent electrode layer comprises a metal oxide containing tin or zinc. In some embodiments, the flexible transparent electrode layer comprises poly(3,4-ethylenedioxythiophene) (PEDOT). In some embodiments, the invention includes an electrophoretic display film assembly comprising a release sheet bonded to the electrophoretic display film as described above, wherein the release sheet is bonded to a first adhesive layer. In some embodiments, the electrophoretic display film further includes a second adhesive layer bonded to the flexible transparent electrode layer, and a second release sheet bonded to the second adhesive layer.

[0021] Fifthly, the present invention includes a method for patterning a piezoelectric electrophoretic dielectric film. The method includes bonding a polyvinylidene fluoride (PVDF) film to an electrophoretic dielectric layer to form a piezoelectric electrophoretic dielectric film, and patterning the piezoelectric electrophoretic dielectric film using an electric field. In some embodiments, the electric field is provided by corona discharge. In some embodiments, the method further includes providing a conductive mask adjacent to the piezoelectric electrophoretic dielectric film before patterning the piezoelectric electrophoretic dielectric film with corona discharge. In some embodiments, the electric field is provided by a high-voltage write head. In some embodiments, patterning includes forming regions of different polarities in the PVDF. In some embodiments, patterning forms anti-counterfeiting marks. In some embodiments, the electrophoretic dielectric layer includes a plurality of microcapsules containing a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer is bent, wherein the microcapsules are bonded together with a polymer adhesive. In some embodiments, the electrophoretic dielectric layer includes a plurality of micro-units containing nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer bends, wherein the nonpolar fluid and charged pigment particles are sealed in the micro-units by a sealing layer.

[0022] In a sixth aspect, the present invention includes an electrophoretic display film with a thickness of less than 100 μm (top to bottom), comprising an adhesive layer, an electrophoretic dielectric layer, a patterned piezoelectric layer containing differentiated polarization regions, and a conductive adhesive layer. In some embodiments, the electrophoretic dielectric layer comprises a plurality of microcapsules containing a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer is bent, wherein the microcapsules are bonded to each other with a polymeric adhesive. In some embodiments, the electrophoretic dielectric layer comprises a plurality of microunits containing a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer is bent, wherein the nonpolar fluid and charged pigment particles are sealed within the microunits by a sealing layer. In some embodiments, the sealing layer is conductive. In some embodiments, the film thickness is less than 50 μm. In some embodiments, the patterned piezoelectric layer comprises polyvinylidene fluoride (PVDF). In some embodiments, the PVDF is polarized to form differentiated polarization regions. In some embodiments, the present invention includes an electrophoretic display film assembly comprising a release sheet bonded to the electrophoretic display film as described above, wherein the release sheet is bonded to a first adhesive layer. In some embodiments, the present invention includes an electrophoretic display film assembly comprising a release sheet bonded to the electrophoretic display film, the electrophoretic display film including a conductive adhesive layer, wherein the release sheet is bonded to the conductive adhesive layer.

[0023] In a seventh aspect, the present invention includes an electrophoretic display film with a thickness of less than 100 μm (from top to bottom), comprising an adhesive layer, a patterned piezoelectric layer containing differentiated polarization regions, an electrophoretic dielectric layer, and a conductive adhesive layer.

[0024] Eighthly, the present invention includes a method for manufacturing a piezoelectric electrophoretic display. The method includes depositing a first conductive adhesive on a first substrate and depositing a piezoelectric material comprising a polyvinylidene fluoride (PVDF) solution on the first conductive adhesive to produce a piezoelectric layer with a thickness of less than 5 μm. The method further includes applying a mask to the piezoelectric layer, wherein the mask includes a plurality of masked portions that shield a first plurality of regions of the piezoelectric layer and a plurality of unmasked portions that leave a second plurality of regions of the piezoelectric layer unmasked. The method further includes polarizing the piezoelectric layer to produce a plurality of polarized portions of the piezoelectric material corresponding to the second plurality of regions of the piezoelectric layer and a plurality of unpolarized portions of the piezoelectric material corresponding to the first plurality of regions of the piezoelectric layer. The method further includes removing the mask from the piezoelectric layer and bonding the piezoelectric layer to a microcell precursor material. The method further includes imprinting the microcell precursor material to produce a microcell layer, wherein the microcells have a bottom, a wall, and a top opening. The method further includes filling the microcells through the top opening with an electrophoretic medium and sealing the top opening of the filled microcells with a water-soluble polymer to produce a sealing layer. The method further includes depositing a second conductive adhesive on a second substrate and bonding a sealing layer to the second conductive adhesive.

[0025] In some embodiments, the method further includes incorporating a polymer film comprising acrylate, vinyl ether, or epoxide to produce a microunit precursor material. In some embodiments, the method further includes applying a primer to the microunit precursor material prior to incorporating the piezoelectric layer with the microunit precursor material. In some instances, the primer comprises a thermoplastic or thermosetting material or a precursor thereof, such as polyurethane, multifunctional acrylate or methacrylate, vinylbenzene, vinyl ether, epoxide, or oligomers or polymers thereof.

[0026] In some embodiments, the method further includes activating the microcells with vapor plasma treatment before filling them with the electrophoretic medium. In some embodiments, the electrophoretic medium layer comprises a nonpolar fluid and charged pigment particles, which move toward or away from the piezoelectric layer when subjected to mechanical stress, wherein the nonpolar fluid and charged pigment particles are sealed within the microcells by a sealing layer. In some embodiments, the piezoelectric layer is polarized by an electric field. In some embodiments, the electric field is provided by corona discharge.

[0027] In some implementations, the first substrate and the second substrate are release films.

[0028] In some embodiments, the method further includes peeling the second substrate from the second conductive adhesive and bonding the second conductive adhesive to the target object. In some embodiments, bonding the second conductive adhesive to the target object includes heat-pressing the second conductive adhesive onto the target object.

[0029] In some embodiments, the method further includes peeling off the first substrate from the first conductive adhesive and applying a protective coating to the remaining layers of the piezoelectric electrophoretic display and the target object. In some embodiments, the protective coating includes a varnish. In some embodiments, the target object includes paper, banknotes, and banknotes.

[0030] In a ninth aspect, the present invention includes a method for manufacturing a piezoelectric electrophoretic display. The method includes depositing a piezoelectric material comprising a polyvinylidene fluoride (PVDF) solution onto a temporary substrate to produce a piezoelectric layer with a thickness of less than 5 μm. The method further includes bonding the piezoelectric layer onto the first substrate with a first conductive adhesive, wherein the temporary substrate is removed from the piezoelectric layer during the bonding process. The method further includes applying a mask to the piezoelectric layer, wherein the mask includes a plurality of masking portions that shield a first plurality of regions of the piezoelectric layer and a plurality of unmasked portions that leave a second plurality of regions of the piezoelectric layer unmasked. The method further includes polarizing the piezoelectric layer to produce a plurality of polarized portions of the piezoelectric material corresponding to the second plurality of regions of the piezoelectric layer and a plurality of unpolarized portions of the piezoelectric material corresponding to the first plurality of regions of the piezoelectric layer. The method further includes removing the mask from the piezoelectric layer and depositing a second conductive adhesive onto a second substrate. The method further includes bonding the second conductive adhesive to a microcell precursor material and imprinting the microcell precursor material to produce a microcell layer, wherein the microcells have bottom, wall, and top openings. The method further includes filling microcells with an electrophoretic medium through a top opening and sealing the top opening of the filled microcells with a water-soluble polymer to create a sealing layer. The method also includes bonding the sealing layer to a piezoelectric layer.

[0031] In some embodiments, the method further includes combining a polymer film comprising acrylate, vinyl ether, or epoxide to produce a microcell precursor material. In some embodiments, the method further includes applying a primer to the microcell precursor material before bonding a second conductive adhesive to the microcell precursor material. In some embodiments, the method further includes activating the microcells with vapor plasma treatment before filling them with an electrophoretic medium.

[0032] In some embodiments, the electrophoretic dielectric layer comprises a nonpolar fluid and charged pigment particles, which move toward or away from the piezoelectric layer when subjected to mechanical stress, wherein the nonpolar fluid and charged pigment particles are sealed within the microcell by a sealing layer. In some embodiments, the piezoelectric layer is polarized by an electric field. In some embodiments, the electric field is provided by corona discharge.

[0033] In some implementations, the first substrate and the second substrate are release films.

[0034] In some embodiments, the method further includes peeling the second substrate from the second conductive adhesive and bonding the second conductive adhesive to the target object. In some embodiments, bonding the second conductive adhesive to the target object includes heat-pressing the second conductive adhesive onto the target object.

[0035] In some embodiments, the method further includes peeling off the first substrate from the first conductive adhesive and applying a protective coating over the remaining layers of the piezoelectric electrophoretic display and the target object. In some embodiments, the protective coating comprises a varnish. In some embodiments, the target object comprises one of paper, banknotes, and banknotes.

[0036] According to a tenth 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 the remainder of the electrophoretic material.

[0037] Eleventhly, the present invention is characterized by a method for manufacturing a piezoelectric electrophoretic display. The method includes depositing a first conductive material on a first substrate to form a first electrode, and bonding the first electrode to a first surface of an electrophoretic material layer. The method further includes depositing a piezoelectric material on a second surface of the electrophoretic material layer, wherein the piezoelectric material overlaps with a first surface region of the second surface of the electrophoretic material layer. The method further includes depositing a second conductive material to form a second electrode, wherein the second electrode is formed to overlap with a second surface region of all the piezoelectric material and the second surface of the electrophoretic material layer.

[0038] In some embodiments, the electrophoretic material layer includes a first portion of electrophoretic material overlapping a first surface region and a second portion of electrophoretic material overlapping a second surface region. In some embodiments, the first portion of the electrophoretic material has a first resistance, and the second portion of the electrophoretic material has a second resistance.

[0039] In some embodiments, the electrophoretic material layer includes a first portion of electrophoretic material having a first resistance corresponding to a first volumetric electrophoretic material overlapping a first surface region, and a second portion of electrophoretic material having a second resistance corresponding to a second volumetric electrophoretic material overlapping a second surface region. In some embodiments, the values ​​of the first resistance and the second resistance are based on the ratio of the first surface region to the second surface region.

[0040] In some embodiments, applying mechanical stress to the piezoelectric material generates a first voltage across a first portion of the electrophoretic material and a second voltage across a second portion of the electrophoretic material, wherein the first voltage and the second voltage have opposite polarities.

[0041] In some embodiments, the combination includes: coating a first electrode with a microcell precursor material; imprinting the microcell precursor material to create a microcell layer, wherein the microcell has a bottom, multiple walls, and a top opening; filling the microcell through the top opening with an electrophoretic medium; and sealing the top opening of the filled microcell with a water-soluble polymer to create a sealing layer.

[0042] In some embodiments, the method further includes applying a primer to the microcell precursor material before imprinting the microcell precursor material. In some embodiments, the method further includes activating the microcells by vapor plasma treatment before filling them with an electrophoretic medium. In some embodiments, the electrophoretic medium comprises a nonpolar fluid and charged pigment particles, which move toward or away from the piezoelectric material when subjected to mechanical stress, wherein the nonpolar fluid and charged pigment particles are sealed within the microcell by a sealing layer.

[0043] In some embodiments, the method further includes applying an adhesive material layer between a first surface region of the second surface of the piezoelectric material and the electrophoretic material layer, wherein the resistivity of the adhesive material layer is 10. 2 ohm*cm to 10 12 ohm*cm. In some embodiments, the method further includes applying an adhesive material layer between a first surface region of the second surface of the piezoelectric material and the electrophoretic material layer, wherein the adhesive material layer has a resistivity at least one order of magnitude greater than that of the first electrode and the second electrode.

[0044] In some embodiments, the method further includes depositing a dielectric layer prior to depositing a second conductive material, wherein the formed dielectric layer overlaps with a second surface region of the second surface of all piezoelectric and electrophoretic material layers, and wherein the formed second electrode overlaps with all dielectric layers. In some embodiments, the resistivity of the dielectric layer is 10⁻⁶. 2 ohm*cm to 10 12 ohm*cm. In some embodiments, the dielectric layer has a resistivity at least one order of magnitude greater than that of the first and second electrodes.

[0045] In some embodiments, the method further includes printing one or more images onto at least one of a first electrode and a second electrode. In some embodiments, the method further includes attaching the piezoelectric display to a target object selected from paper, banknotes, and banknotes. Brief description of the attached diagram

[0047] Figure 1A This image shows a side view of the piezoelectric electrophoretic display film of the present invention, which includes a star-shaped differential polarization region. Three exemplary locations are shown from the side: a raised area, a neutral area, and a recessed area. The total thickness of the piezoelectric electrophoretic display film can be less than 100 µm, for example, less than 50 µm, or for example, less than 25 µm.

[0048] Figure 1B Showing a top view of the piezoelectric electrophoretic display film of the present invention, which includes star-shaped differential polarization regions. Three exemplary locations are shown from above: convex, neutral, and recessed. When the piezoelectric electrophoretic display film is bent, the differential polarization regions cause particles with opposite charges to appear on the viewing surface.

[0049] Figure 2A This illustrates an exemplary piezoelectric material thin layer on a substrate.

[0050] Figure 2B An example illustrates a method for creating differentiated polarization regions in a thin layer of piezoelectric material using a strong electric field generated by corona discharge. The amount of polarization can be spatially controlled by moving the piezoelectric material closer to or further away from the discharge.

[0051] Figure 2C An example illustrates a method for forming differentiated polarization regions in a thin layer of piezoelectric material using a strong electric field generated by corona discharge. The piezoelectric material is patterned using a conductive mask to form these differentiated polarization regions.

[0052] Figure 2D Illustration Figure 2B and Figure 2C The method can achieve polarization (polarization processing) patterns.

[0053] Figure 3A The illustration shows a side view of a piezoelectric film polarized along direction A.

[0054] Figure 3B The illustration shows a top view of a piezoelectric film polarized along direction A.

[0055] Figure 3C The illustration shows a side view of a piezoelectric film polarized along the G direction using a conductive mask.

[0056] Figure 3D The illustration shows a top view of a piezoelectric film polarized along the G direction using a conductive mask.

[0057] Figure 4A This illustrates an exemplary thin layer of a piezoelectric microcell precursor film on a substrate.

[0058] Figure 4B An example is given of a method for forming differentiated polarization regions in a thin layer of piezoelectric material in a piezoelectric microcell precursor film using a strong electric field generated by corona discharge. The amount of polarization can be spatially controlled by moving the piezoelectric microcell precursor film closer to or further away from the discharge.

[0059] Figure 4C An example is given of a method for forming differentiated polarization regions in a thin layer of piezoelectric material in a piezoelectric microcell precursor film using a strong electric field generated by corona discharge. The piezoelectric material of the piezoelectric microcell precursor film is patterned using a conductive mask to form the differentiated polarization regions.

[0060] Figure 4D Illustration Figure 3B and Figure 3CThe method enables the creation of polarization (poling) patterns in piezoelectric microcell precursor films.

[0061] Figure 5A This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic membrane.

[0062] Figure 5B This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic membrane.

[0063] Figure 5C This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic membrane.

[0064] Figure 5D This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic membrane.

[0065] Figure 6A This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic display.

[0066] Figure 6B This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic display.

[0067] Figure 7 The method for manufacturing piezoelectric electrophoretic membranes or (optionally) displays is described in detail.

[0068] Figure 8A This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic membrane.

[0069] Figure 8B This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic membrane.

[0070] Figure 9A This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic membrane.

[0071] Figure 9B This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic membrane.

[0072] Figure 10A This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic display.

[0073] Figure 10B This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic display.

[0074] Figure 10C This is a schematic cross-section of one embodiment of a piezoelectric electrophoretic display.

[0075] Figure 11 A method for manufacturing low-profile piezoelectric electrophoretic membranes is described in detail.

[0076] Figure 12A It is Figure 11A schematic cross-section of a piezoelectric electrophoretic membrane manufactured by the method shown.

[0077] Figure 12B It is Figure 11 A schematic cross-section of a piezoelectric electrophoretic display fabricated by the method shown.

[0078] Figure 13A It is Figure 11 A schematic cross-section of an alternative piezoelectric electrophoretic membrane manufactured by the method shown.

[0079] Figure 13B It is Figure 11 A schematic cross-section of an alternative piezoelectric electrophoretic display fabricated by the method shown.

[0080] Figure 14 This is a flowchart detailing the steps of a method for manufacturing high-contrast piezoelectric electrophoretic films and displays.

[0081] Figure 15A yes Figure 14 A schematic cross-section of the piezoelectric electrophoretic membrane in step 1440 of the method shown.

[0082] Figure 15B yes Figure 14 A schematic cross-section of the piezoelectric electrophoretic membrane after step 1440 of the method shown.

[0083] Figure 15C yes Figure 14 A schematic cross-section of the piezoelectric electrophoretic membrane after step 1450 of the method shown is completed.

[0084] Figure 15D yes Figure 14 A schematic cross-section of the piezoelectric electrophoretic membrane after step 1470 of the method shown.

[0085] Figure 15E yes Figure 14 After step 1480 of the method shown is completed, the cross-section of the piezoelectric electrophoretic membrane bonded to the target object is shown.

[0086] Figure 15F yes Figure 14 After step 1480 of the method shown is completed, the cross-section of the piezoelectric electrophoretic membrane bonded to the target object and coated with a protective coating is shown.

[0087] Figure 16 A magnified view of a portion of the cross-section of the piezoelectric electrophoresis display.

[0088] Figure 17 Illustration Figure 16 An exemplary equivalent circuit with an enlarged cross-section is shown.

[0089] Figure 18This is a flowchart detailing the steps of a method for manufacturing high-contrast piezoelectric electrophoretic films and displays.

[0090] Figure 19A yes Figure 18 A schematic cross-section of the piezoelectric electrophoretic membrane of step 1810 of the method shown.

[0091] Figure 19B yes Figure 18 A schematic cross-section of the piezoelectric electrophoretic membrane in step 1830 of the method shown.

[0092] Figure 19C yes Figure 18 A schematic cross-section of the piezoelectric electrophoretic membrane after step 1840 of the method shown.

[0093] Figure 19D yes Figure 18 A schematic cross-section of the piezoelectric electrophoretic membrane after steps 1850 and 1860 of the method shown.

[0094] Figure 19E yes Figure 18 A schematic cross-section of the piezoelectric electrophoretic membrane after step 1870 of the method shown is completed.

[0095] Figure 19F It is based on Figure 18 The cross-section of the piezoelectric electrophoretic membrane that is bonded to the target object by the method shown.

[0096] Figure 19G yes Figure 18 After step 1880 of the method shown is completed, the cross-section of the piezoelectric electrophoretic membrane bonded to the target object and coated with a protective coating is shown.

[0097] Figure 20 This is a schematic cross-sectional view of an exemplary piezoelectric electrophoresis display based on the subject matter disclosed herein.

[0098] Figure 21A This is a schematic cross-section illustrating another property of the piezoelectric electrophoretic display according to the subject matter disclosed herein.

[0099] Figure 21B This is a perspective view illustrating further properties of a piezoelectric electrophoretic display based on the subject matter disclosed herein.

[0100] Figure 22 The illustration shows an exemplary equivalent circuit of a piezoelectric electrophoretic display according to the subject matter disclosed herein.

[0101] Figure 23 This is a schematic cross-sectional view of an exemplary piezoelectric electrophoresis display based on the subject matter disclosed herein. Invention Details

[0103] This document discloses low-profile piezoelectric electrophoretic films and displays, as well as methods for manufacturing such films and displays. In some embodiments, the piezoelectric material of the piezoelectric electrophoretic film can be patterned with a high-voltage electric field after the piezoelectric electrophoretic film is manufactured. This feature allows the end user to treat the piezoelectric material during manufacturing with, for example, corona discharge, which may include, for example, a barcode or serial number, visible only when the piezoelectric electrophoretic film is operated on. The low-profile films and displays described below also achieve high contrast. The films and displays described herein are typically flexible and can be used as anti-counterfeiting marks, authentication films, or sensors. Some films have a thickness of less than 100 μm. In some embodiments, the piezoelectric electrophoretic film is less than 50 μm and can be folded without breaking. Displays formed according to the subjects disclosed herein do not require an external power supply.

[0104] When applied to materials or displays, the term "electro-optic" is used herein in its conventional sense in the field of imaging to refer to a material having a first display state and a second display state that differ in at least one optical property, which changes from its first display state to its second display state by applying an electric field to the material. While the optical property is generally color perceptible to the human eye, it can be another optical property, such as transmittance, reflectivity, luminescence, or, in the case of displays intended for machine reading, pseudocolor in the sense of a change in reflectivity at electromagnetic wavelengths outside the visible light range.

[0105] The terms “bistable” and “bistable” are used herein in their conventional sense in the art to refer to a display comprising display elements having a first display state and a second display state that differ in at least one optical property, such that after any given element has been driven to present its first or second display state by means of an addressing pulse of finite duration, the state persists for at least several times, for example, at least four times, the minimum duration of the addressing pulse required to change the state of the display element. U.S. Patent No. 7,170,670 shows that some particle-based electrophoretic displays capable of achieving grayscale are stable not only in their extreme black and white states but also in their intermediate gray states, and similarly, some other types of electro-optical displays. This type of display is appropriately referred to as “multistable” rather than bistable; however, for convenience, the term “bistable” may be used herein to encompass both bistable and multistable displays.

[0106] The term "gray state" is used herein in its conventional meaning in the imaging field to refer to the state between the two extreme optical states of a pixel, and does not necessarily imply a black-and-white transition between those two extreme states. For example, several E Ink patents and published applications mentioned below describe electrophoretic displays where the extreme states are white and dark blue, making the intermediate "gray state" actually a pale blue. In fact, as already mentioned, a change in optical state may not be a color change at all. The terms "black" and "white" can be used below to refer to the two extreme optical states of a display and should be understood to generally include extreme optical states that are not strictly black and white, such as the white and dark blue states mentioned above. The term "monochrome" may be used below to refer to a display or driving scheme that drives pixels only to their two extreme optical states without an intermediate gray state.

[0107] The term "pixel" is used in this article in its conventional sense within the field of displays, referring to the smallest display unit capable of producing all the colors that the display itself can display. In full-color displays, each pixel is typically composed of multiple subpixels, each capable of displaying fewer colors than the display itself can. For example, in most conventional full-color displays, each pixel consists of a red subpixel, a green subpixel, a blue subpixel, and an optional white subpixel, each capable of displaying a range of colors from black to the brightest version of its designated color.

[0108] Several types of electro-optic displays are known. One type of electro-optic display uses an electrochromic medium, such as an electrochromic medium in the form of a nanochromic film, which comprises an electrode at least partially formed of a semiconductor metal oxide and a plurality of dye molecules reversibly capable of changing color attached to the electrode; 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. This type of nanochromic film is also described, for example, in U.S. Patents 6,301,038; 6,870,657 and 6,950,220. This type of medium is generally also bistable.

[0109] Another type of electro-optic 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). U.S. Patent No. 7,420,549 shows that such an electrowetting display can be fabricated to be bistable.

[0110] One type of electro-optic display has been the subject of in-depth research and development for many years: particle-based electrophoretic displays, in which multiple charged particles move through a fluid under the influence of an electric field. Compared to liquid crystal displays, electrophoretic displays can offer advantages such as good brightness and contrast, wide viewing angles, state bistable properties, and low power consumption.

[0111] Electrophoretic displays typically comprise an electrophoretic material layer and at least two other layers disposed on opposite sides of the electrophoretic material, one of which is 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, and the other may be patterned as an elongated column electrode extending perpendicular to the row electrode, with pixels 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 as a matrix of pixel electrodes, where each pixel electrode defines a pixel of the display. In another type of electrophoretic display, intended for use with a stylus, printhead, or similar display-independent movable electrode, only one of the layers adjacent to the electrophoretic layer includes an electrode, and the layers on opposite sides of the electrophoretic layer are generally protective layers intended to prevent damage to the electrophoretic layer by the movable electrode.

[0112] Numerous patents and applications assigned to or registered with MIT and E Ink Corporation describe various techniques for encapsulating electrophoretic media and other electro-optic media. Such encapsulated media comprise a plurality of small capsules, each capsule itself including an inner phase and a capsule wall surrounding the inner phase, the inner phase containing particles that electrophoretically move in a fluid medium. Typically, the capsules themselves are held in a polymer binder to form a coherent layer between two electrodes. The techniques described in these patents and applications include:

[0113] (a) Electrophoretic particles, fluids, and fluid additives; see, for example, U.S. Patents 7,002,728 and 7,679,814;

[0114] (b) Encapsulation, adhesives, and encapsulation methods; see, for example, U.S. Patents 6,922,276 and 7,411,719;

[0115] (c) Films and subassemblies containing electro-optic materials; see, for example, U.S. Patents 6,982,178 and 7,839,564;

[0116] (d) Backplate, adhesive layer and other auxiliary layers and methods for display; see, for example, U.S. Patents 7,116,318 and 7,535,624;

[0117] (e) Color formation and color adjustment; see, for example, U.S. Patents 7,075,502 and 7,839,564;

[0118] (f) A method for driving a display; see, for example, U.S. Patents 7,012,600 and 7,453,445;

[0119] (g) Applications of displays; see, for example, U.S. Patents 7,312,784 and 8,009,348;

[0120] (h) Non-electrophoretic display; as 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;

[0121] (i) Microunit structures, wall materials, and methods of forming microunits; see, for example, U.S. Patents 7,072,095 and 9,279,906; and

[0122] (j) A method for filling and sealing microcells; see, for example, U.S. Patents 7,144,942 and 7,715,088.

[0123] 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 comprises a plurality of discrete electrophoretic fluid droplets and a continuous phase of polymeric material, and recognize that although no discrete membrane is associated with each individual droplet, the discrete electrophoretic fluid droplets within such a polymer-dispersed electrophoretic display can be considered as capsules or microcapsules; see, for example, the aforementioned U.S. Patent No. 6,866,760. Therefore, for the purposes of this application, such polymer-dispersed electrophoretic media are considered a subclass of encapsulated electrophoretic media.

[0124] One related type of electrophoretic display is the so-called microcell electrophoretic display, also known as MICROCUP®. In a microcell electrophoretic display, charged particles and fluid are not encapsulated in microcapsules, but are held in multiple cavities formed in a carrier medium, typically a polymer film. See, for example, U.S. Patents 6,672,921 and 6,788,449, both of which are incorporated herein by reference in their entirety.

[0125] Although electrophoretic media are often opaque (because, for example, in many electrophoretic media, particles essentially block visible light transmission through the display) and operate in a reflective mode, many electrophoretic displays can be made to operate in a so-called "shutter mode," where one display state is substantially opaque and the other is translucent. See, for example, U.S. Patents 5,872,552; 6,130,774; 6,144,361; 6,172,798; 6,271,823; 6,225,971; and 6,184,856. Dielectric electrophoretic displays, similar to electrophoretic displays but dependent on changes in electric field strength, can operate in a similar mode; see U.S. Patent 4,418,346. Other types of electro-optic displays may also be able to operate in a shutter mode. Electro-optic media operating in shutter mode can be useful in multilayer structures for full-color displays, in which at least one layer adjacent to the viewing surface of the display operates in shutter mode to expose or hide a second layer further away from the viewing surface.

[0126] Encapsulated electrophoretic displays generally do not suffer from the aggregation and sedimentation failure modes of conventional electrophoretic apparatus and offer advantages such as the ability to print or coat the display onto a variety of flexible and rigid substrates (the term "printing" is used to include all forms of printing and coating, including but not limited to: volumetric coating such as patch slot coating, slot or extrusion coating, cascade coating, curtain coating; roll coating such as doctor blade coating, clockwise roll coating, and counterclockwise roll coating; gravure coating; dip coating; spray coating; meniscus coating; spin coating; brush coating; air knife coating; screen printing; electrostatic printing; thermal printing; inkjet printing; electrophoretic deposition (see U.S. Patent No. 7,339,715); and other similar techniques). Therefore, the resulting display can be flexible. Furthermore, because the display medium can be printed using a variety of methods, the display itself can be manufactured inexpensively.

[0127] U.S. Patent No. 6,982,178 describes a method for assembling a solid-state electro-optic display (including an encapsulated electrophoretic display) that is well-suited for mass production. Essentially, the patent describes a so-called “front panel laminate” (“FPL”) comprising, in sequence: a light-transmitting conductive layer; a solid electro-optic dielectric layer electrically in contact with the conductive layer; an adhesive layer; and a release sheet. Generally, the light-transmitting conductive layer is carried on a light-transmitting substrate, which is preferably flexible, meaning that the substrate can be manually wound around a roller with a diameter (e.g.) of 10 inches (254 mm) without permanent deformation. The term “light-transmitting” as used in the patent and herein refers to a layer that transmits sufficient light to allow an observer to see through it and observe changes in the display state of the electro-optic dielectric, typically visible through the conductive layer and adjacent substrates (if present); where the electro-optic dielectric exhibits a change in reflectivity at a non-visible wavelength, the term “light-transmitting” should, of course, be interpreted as referring to the transmission of the relevant non-visible wavelength. The substrate is typically a polymer film and usually has a thickness ranging from about 1 to about 25 mils (25 to 634 μm), preferably from about 2 to about 10 mils (51 to 254 μm). The conductive layer is suitable as a thin metal or metal oxide layer, such as aluminum or ITO, or it may be 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 El duPont de Nemours & Company, Wilmington, Delaware, and such commercial materials can be used with good results in front panel laminates.

[0128] Assembling an electro-optic display using this front-panel laminate can be achieved by removing the release liner from the front-panel laminate and bringing the adhesive layer into contact with the backplate while effectively adhering the adhesive layer to the backplate, thereby securing the adhesive layer, electro-optic dielectric layer, and conductive layer to the backplate. This method is well-suited for mass production because the front-panel laminate can be mass-produced, typically using roll-to-roll coating technology, and then cut into sheets of any size required for use with a specific backplate.

[0129] U.S. Patent No. 7,561,324 describes a so-called "dual release sheet," which is essentially a simplified version of the front panel laminate of the aforementioned U.S. Patent No. 6,982,178. One form of the dual release sheet includes a solid electro-optic dielectric layer sandwiched between two adhesive layers, one or both of which are covered by the release sheet. Another form of the dual release sheet includes a solid electro-optic dielectric layer sandwiched between two release sheets. Both forms of dual release films are intended for use in methods substantially similar to those used for assembling electro-optic displays from the already described front panel laminate, but involve two separate laminations. Generally, in the first lamination, the dual release sheet is laminated to the front electrode to form the front sub-assembly, and then in the second lamination, the front sub-assembly is laminated to the back panel to form the final display; however, the order of these two laminations can be reversed if desired.

[0130] This article presents a structural design and manufacturing method for piezoelectric electrophoretic films and displays that does not require a power source (e.g., battery, wired power, photovoltaic power) to operate the display. This simplifies the assembly process, and such displays are significantly thinner than conventional piezoelectric electrophoretic displays.

[0131] Piezoelectricity is the accumulation of electrical charge in a solid material in response to applied mechanical stress. Materials suitable for the subject matter disclosed herein may include polyvinylidene fluoride (PVDF), quartz (SiO2), berlinite (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 materials.

[0132] The piezoelectric electrophoretic film and piezoelectric electrophoretic display described herein utilize piezoelectricity to drive charged pigment particles in the electrophoretic medium to move toward one of the display electrodes. Therefore, when a piezoelectric material is bonded to the electrophoretic medium layer, manipulating the piezoelectric material or causing physical strain on the piezoelectric material will result in a color change of the electrophoretic material at the viewing surface. For example, by bending a sheet of piezoelectric material or introducing other mechanical stress to it, a voltage can be generated across the electrophoretic medium, and this voltage can be used to induce the movement of colored pigment particles in the electrophoretic medium. Figure 1A and 1B As shown, if only a portion of the electrophoretic dielectric layer is bonded to the piezoelectric material, or if differential polarization regions are created in the piezoelectric material, a pattern with high contrast can be formed using an electrophoretic dielectric with two types of pigments carrying opposite charges. As used herein, the term "contrast ratio" or "CR" for electro-optic displays (e.g., electrophoretic displays) is defined as the ratio of the luminance of the brightest color (white) to the luminance of the darkest color (black) that the display can produce. High contrast ratio is generally an ideal characteristic of electro-optic displays.

[0133] Figure 1A and 1B The illustrations depict side and top views of an exemplary piezoelectric electrophoretic display 100 according to the subject matter disclosed herein. In this embodiment, a piezoelectric material is laminated to an electrophoretic dielectric layer (discussed below) and includes one or more electrodes to provide a suitable electric field that causes electrophoretic particles to travel toward (or away from) the viewing surface. Figure 1A and Figure 1B In the illustrated embodiment, the second region 120 of the piezoelectric material of the piezoelectric electrophoretic display 100 is polarized in the opposite direction to the first region 110. Therefore, when the piezoelectric electrophoretic display 100 is manipulated from a neutral state (position 2) to a first (position 1) optical state or a second (position 3) optical state, the first and second regions (110, 120) will achieve different colors in the two regions. In the case where the electrophoretic medium has black and white groups of particles with opposite charges, a high-contrast image will be formed, for example, as shown in the figure. Figure 1B As shown. Since the first and second regions (110, 120) of the piezoelectric material can be polarized to have good resolution (as discussed below), various images / information can be encoded to be "displayed" when the piezoelectric electrophoretic display 100 is manipulated. For example, a security ribbon can be formed, which exists as a gray strip in a neutral state, but when the security ribbon is bent, the ribbon will display a security stamp, such as... Figure 1B The star shape shown. Of course, security features may optionally include barcodes, numbers, text, telephone numbers and URLs, QR codes, photographs, halftone images or logos.

[0134] In principle, piezoelectric materials (optionally adjacent electrophoretic materials) can be polarized by a localized strong electric field, such as... Figure 2A-3D As shown in the diagram. It is known that piezoelectric materials (especially films) can be stimulated by various external stresses such as mechanical tension, heat, electromagnetic fields, and applied forces to move between polarization states. The piezoelectric effect is closely related to the electric dipole moment that appears in solids. The dipole density, or polarization (P), corresponds to the dipole moment per volumetric crystallographic cell, typically expressed in C / m. 2 Measurement. The resulting dipole density P is a vector field specific to a particular region of the material (i.e., differentiated polarization). Similar to magnets, dipoles that are close to each other tend to align in a specific orientation within a region (Weiss domains). Initially, these regions are typically randomly oriented. However, using various multi-step processes, these regions can be oriented, creating localized differentiated polarization regions. The process of orienting these regions is called polarization treatment.

[0135] Although many piezoelectric materials are crystalline, many flexible piezoelectric active polymers are known, such as polyvinylidene fluoride (PVDF) and its copolymers, polyamides, and parylene-C. Amorphous polymers, such as polyimide and polyvinylidene chloride (PVDC), belong to amorphous bulk polymers. The standard process for manufacturing piezoelectric active films such as PVDF is to manufacture a polymer film and stretch it to generate stress and orient the dipoles. Stretching transforms the unpolarized α-phase region of PVDF into a polarized β-phase. For example, a strong electric field is used to apply subsequent stimulation to the polarized region of the β-phase. Other methods for orienting the β-phase, such as laser irradiation and strong magnetic fields, have been described in the literature. See, for example, U.S. Patent No. 9,831,417. If stimulation can be performed at a sufficiently high resolution, the polarized region can be used to create visible patterns, such as... Figure 1A and 1B As illustrated in the figure. In some embodiments, an electric field is applied at an elevated temperature; however, this is not always necessary. In particular, for very thin piezoelectric films, such as less than 20 μm, less than 10 μm, or less than 5 μm, polarization of the film without raising the temperature is feasible, provided the electric field is strong enough. In the case of PVDF, an additional advantage is that such films are also optically transparent, so either they can be bonded to the electrophoretic medium between the viewing surface and the electrophoretic medium, or the electrophoretic medium layer can be located between the piezoelectric film and the viewing surface.

[0136] Figure 2A-2DThe illustration depicts an exemplary method for polarizing a thin film of a piezoelectric material. A piezoelectric material film 210, such as PVDF, can be melted and spin-coated onto a substrate 220 to form a film. The film can optionally be thermally tempered or stretched prior to polarization. Suitable bulk PVDF is available from, for example, Sigma-Aldrich in packaged powder or film form. Pre-stretched piezoelectric active PVDF films are also available from, for example, PolyK Technologies (State College, PA). Such procured films may also have a metallized electrode coating on one side, which can also be used for piezoelectric electrophoretic films and displays; however, it is difficult to polarize piezoelectric electrophoretic materials with a backing metal layer using an electric field. Copolymers of PVDF, such as polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), are also available from Sigma-Aldrich and PolyK. In some embodiments, films of PVDF and PVDF copolymers can be manufactured by preparing a concentrated solution of bulk PVDF in a compatible volatile solvent such as dimethylformamide (DMF), and slit-coating the concentrated solution onto a suitable transfer substrate or release film, for example using a roll-to-roll process. The PVDF-coated substrate is then heated to remove the DMF, yielding a PVDF film (e.g., less than 20 μm, less than 10 μm, less than 5 μm). By carefully controlling the thermal cycling, the resulting film can be pre-conditioned to have a greater number of β-phase domains suitable for polarization treatment.

[0137] like Figure 2B and 2C As shown, the thin film of piezoelectric material 210 can be polarized using a high-voltage corona discharge 230 with spatial focusing. Suitable corona discharge equipment can be obtained from, for example, Simco-Ion (Alameda, CA). Such a device can generate a localized electric field of 10-50 kV, such as 30 kV or 20 kV, which can be introduced into the piezoelectric material to be polarized within a few micrometers. Spatial focusing can be achieved by guiding the electric field and / or gas flow, which focuses / guides the ion flow generated by the corona discharge. Figure 2B As shown, the high-voltage corona discharge 230 can be moved three-dimensionally to form differentiated polarization regions, i.e., patterning the piezoelectric material 210. Alternatively, the piezoelectric material 210 can be mounted on an XYZ platform, allowing the film workpiece to approach the high-voltage corona discharge 230 in a controlled manner. In alternative embodiments, such as Figure 2CAs shown, a conductive mask 240 can be used to protect areas of the piezoelectric material 210 from the high-voltage corona discharge 230. The conductive mask can be made of, for example, conductive stainless steel or another conductive material capable of withstanding near-corona discharge. Alternative masks made of charge-absorbing or charge-blocking materials such as glass, plastic, or rubber can also be used. As the high-voltage corona discharge 230 moves across the thin film of the piezoelectric material 210, the film of the piezoelectric material 210 is polarized only in areas of the film of the piezoelectric material 210 not covered by the conductive mask 240. Alternatively, the polarity of the high-voltage corona discharge 230 can be reversed, such that some areas are polarized in a first direction, some areas are polarized in a second direction, and some areas are randomly polarized or unpolarized. See also Figures 3A-3D .

[0138] use Figure 2B and 2C The technique shown directly manufactures thin films of piezoelectric material 210 with differentiated polarization regions P1 and P2, such as Figure 2D As shown in Figure 2D, regions 260 and 270 are polarized differently. These polarized regions 260 and 270 do not necessarily have equal sizes and opposite polarities; however, such a configuration is common when a two-particle electrophoretic medium is used in conjunction with a thin film of piezoelectric material 210 to provide better contrast. For example, as shown in 2D, the first region 260 may be polarized toward the viewer, while the second region 270 may be polarized away from the viewer. Figures 3A-3D The diagram further illustrates the technology. Figures 3A-3D This illustrates how a single region 360 of a thin film of piezoelectric material deposited on substrate 320 can be polarized to have a polarization vector emanating from the page, such as... Figure 3B As shown in the diagram. Therefore, when manipulating (bending) a thin film of piezoelectric material, it will preferentially drive a polar electrophoretic particle toward the viewing surface. Figure 3C As shown, the second region 370 of the piezoelectric material film can be polarized in different directions, with or without a conductive mask 340, forming a variety of patterned combinations of polarity and size required for the application. Figure 3D As shown, some portions of 370 are polarized to the viewing surface, but have shadows produced by the conductive mask 340. Therefore, when the piezoelectric material is manipulated (bent), it will preferentially drive a polar electrophoretic particle toward the viewing surface, while the polarized masked area will remain in a neutral gradation, thus producing a pattern, such as a security stamp.

[0139] Figure 2A-3D The illustrations depict various techniques that can be used to form differentiated polarization regions in thin films of piezoelectric material 210. For example... Figures 4A-4D As illustrated in the diagram, these same techniques can also be used to form differentiated polarization regions in a thin piezoelectric electrophoretic dielectric film 405. Figure 4AAs shown, the thin film of piezoelectric material 410 can be bonded to the layer of electrophoretic microunit 420 to form a piezoelectric electrophoretic dielectric film 405. The thin film of piezoelectric material 410 can be bonded to the layer of electrophoretic microunit 420 using an adhesive layer (not shown), or the thin film of piezoelectric material 410 can be directly spin-coated to the layer of electrophoretic microunit 420, as described above. Figure 2A The electrophoretic microunit 420 is generally formed of polymers such as acrylates, vinyl ethers, or epoxides, as detailed in U.S. Patents 6,930,818, 7,052,571, 7,616,374, 8,361,356, and 8,830,561, all of which are incorporated herein by reference in their entirety. In some embodiments, the layer of electrophoretic microunit 420 may be filled with an electrophoretic medium 425 comprising two or more types of electrophoretic particles 423 and 427, which generally have different electrophoretic mobilities and optical properties. The electrophoretic medium 425 may be sealed with a sealing layer 430, preferably a water-soluble sealing layer as described in U.S. Patents 7,560,004, 7,572,491, 9,759,978, or 10,087,344, all of which are incorporated herein by reference in their entirety. In some embodiments, the layer of electrophoretic microunit 420 is formed on a release film, filled with an electrophoretic medium 425 and sealed with a sealing layer 430, and then the filled and sealed electrophoretic microunit 420 is used as a substrate for fabricating a thin film of piezoelectric material 410. The resulting structure is a thin piezoelectric electrophoretic medium film 405. In other embodiments, the thin film of piezoelectric material 410 is laminated to an acrylate, vinyl ether, or epoxide film, which is a precursor to the layer of electrophoretic microunit 420. The combined thin film of piezoelectric material 410 and precursor material are then imprinted on the precursor side (discussed below), subsequently filled with an electrophoretic medium 425 and sealed with a sealing layer 430 to produce a thin piezoelectric electrophoretic medium film 405. In yet another embodiment ( Figures 4A-4D (Not shown in the text) A complete microcell front-plate laminate of the type described in U.S. Patent No. 7,158,282 and commercially available from E Ink can be used as a substrate for the thin film of the piezoelectric material 410, which can be polarized as described below. Notably, when using a front-plate laminate material, the final structure additionally includes a conductive layer, which is generally transparent. The front-plate laminate can be oriented such that the transparent electrode layer contacts the thin film of the piezoelectric material 410, or the front-plate laminate can be flipped so that the sealing layer contacts the thin film of the piezoelectric material 410.

[0140] Once the thin piezoelectric electrophoretic dielectric film 405 has been formed, it can be processed as described above. Figure 2A-3D The thin film of the piezoelectric material 410 is processed. In other words, the thin film of the piezoelectric material 410 can be polarized using a high-voltage corona discharge 230 with spatial focusing, such as... Figure 4B As shown, for example, by mounting a thin piezoelectric electrophoretic dielectric film 405 on an XYZ platform, the film workpiece is brought into controlled proximity to the high-voltage corona discharge 230. In an alternative embodiment, a conductive mask 240 may be used to protect areas of the thin piezoelectric electrophoretic dielectric film 405 from the high-voltage corona discharge 230, such as... Figure 4C As shown. (Regarding...) Figure 2A-3D The polarity of the high-voltage corona discharge 230 discussed can be reversed, allowing some regions to be polarized in a first direction, some in a second direction, and some randomly polarized or unpolarized. (This is consistent with the above.) Figure 2D Similarly, the thin-film polarization treatment of the piezoelectric material 410 in the thin piezoelectric electrophoretic dielectric film 405 produces differentiated polarization regions P1 and P2, such as... Figure 4D As shown in 460 and 470, since the thin piezoelectric electrophoretic dielectric film 405 can be manufactured prior to polarization treatment, the final step of forming the desired polarization treatment design in the thin piezoelectric electrophoretic dielectric film 405 can be controlled by the end customer. Therefore, if the final product will include a security stamp or serial number, the security stamp or serial number can be placed after the final product is completed and verified. For example, the U.S. Treasury could print a serial number with metallic ink on a $100 banknote, while simultaneously, a security strip containing the thin piezoelectric electrophoretic dielectric film 405 is polarized to generate a verification code corresponding to the serial number. This feature eliminates many logistical problems and associated costs because, for example, it is not necessary to match pre-made security markings with specific products further downstream in the supply chain.

[0141] The above technology can be used to realize a variety of thin piezoelectric films, as described in the figure below.

[0142] like Figures 5A-6BAs shown in 8A-10C and 12A-13B, a piezoelectric electrophoretic membrane or piezoelectric electrophoretic display comprises a layered stack of a number of components, including a thin piezoelectric membrane and an electrophoretic dielectric layer. The piezoelectric material can be any of the materials listed above; however, polymers such as PVDF and its copolymers are preferred because they can be made into very thin membranes. The electrophoretic dielectric generally contains one or more groups of charged particles that move through a nonpolar solvent in the presence of an electric field. The electrophoretic dielectric is generally contained, i.e., in microcapsules, microunits, or dispersed droplets. The electrophoretic dielectric can also be contained in an open slot or pore sealed within a larger flexible container. The piezoelectric electrophoretic membranes and piezoelectric electrophoretic displays illustrated herein can be made very thin, for example, with a thickness of 100 μm or less, for example, 70 μm or less, for example, 50 μm or less, for example, 35 μm or less, for example, 20 μm or less, for example, 10 μm or less. Such thin materials can be bent without breaking or leaking, and remain unnoticeable when incorporated into final products such as paper or banknotes. Furthermore, many piezoelectric electrophoretic films or displays comprise layers that are both light-transmitting and / or thin enough to be light-transmitting, thus enabling a piezoelectric electrophoretic response when viewed from both above and below. In such piezoelectric electrophoretic films or displays, when viewed from the upper surface, for example… Figure 1B When the first image can be observed at position 1, the lower surface will generally display a negative image, such as... Figure 1B Position 3. However, when more than two types of particles are added to the electrophoresis medium, the top and bottom may not display reversed images due to the mixed particle states at one of the two surfaces.

[0143] Piezoelectric electrophoretic films or displays often include at least one electrode layer, which can be transparent and flexible. Suitable materials include commercially available ITO-coated PET, which can be used as a substrate for fabrication. In some other embodiments, flexible and transparent conductive coatings can be used, including other transparent conductive oxides (TCOs) such as zinc oxide, zinc tin oxide, indium zinc oxide, aluminum zinc oxide, indium tin zirconium oxide, indium gallium oxide, indium gallium zinc oxide, or fluorinated derivatives of these oxides, such as fluorine-doped tin oxide. In many embodiments described herein, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is used because of its excellent flexibility and optical transparency. Although its overall conductivity is not as high as, for example, PET / ITO, PEDOT:PSS is sufficient to provide the necessary electric field to drive the electrophoretic particles in the electrophoretic medium. Other materials include polymers doped with conductive materials such as carbon black, metal flakes, metal whiskers, carbon nanotubes, silicon nitride nanotubes, or graphene, and generally transparent polymers. In some cases, the electrode layer is a metal film such as copper, silver, gold, or aluminum film or foil. Metal-coated polymer films are also suitable as electrode layers. The resistance of the electrode layer can be 500 ohm-m or lower, for example, 100 ohm-m or lower, for example, 1 ohm-m or lower, for example, 0.1 ohm-m or lower, for example, 0.01 ohm-m or lower (for comparison, electrophoretic dielectric layers typically have a resistance of about 10 ohms-m). 7 Up to 10 8 The resistance is ohm-m, and the piezoelectric material has 10 ohm-m. 11 Up to 10 14 (ohm-m resistance).

[0144] Piezoelectric electrophoretic membranes or displays often include at least one adhesive layer formed from a polymer, such as acrylic acid or polyurethane. Polyurethane, polyurea, polycarbonate, polyamide, polyester, polycaprolactone, polyvinyl alcohol, polyether, polyvinyl acetate derivatives such as poly(ethylene-co-vinyl acetate), polyvinyl fluoride, polyvinylidene fluoride, polyvinyl butyral, polyvinylpyrrolidone, poly(2-ethyl-2-oxazoline), acrylic acid or methacrylic acid copolymers, maleic anhydride copolymers, vinyl ether copolymers, styrene copolymers, diene copolymers, siloxane copolymers, cellulose derivatives, gum arabic, alginate, lecithin, and polymers derived from amino acids, etc. Additionally, the adhesive may contain one or more low-dielectric polymers or oligomers, ionic liquids, or conductive fillers such as carbon black, metal sheets, metal whiskers, carbon nanotubes, silicon nitride nanotubes, or graphene. Adhesives containing such charged and / or conductive materials are called conductive adhesives. The polymers and oligomers used in the adhesive layer may have multiple functional groups for chain extension or crosslinking during or after lamination. 6 ohm*cm to 10 8 ohm*cm, preferably less than 10 12 The resistivity value in ohm*cm.

[0145] Among the polymers and oligomers mentioned above, polyurethanes, polyureas, polycarbonates, polyesters, and polyamides, especially those containing functional groups, are particularly preferred because they exhibit excellent adhesive and optical properties as well as high environmental resistance. Examples of functional groups include, but are not limited to, -OH, -SH, -NCO, -NCS, -NHR, -NRCONHR, -NRCSNHR, vinyl or epoxides and their derivatives, including cyclic derivatives. The "R" in the aforementioned functional groups can be hydrogen or an alkyl, aryl, alkylaryl, or aralkyl group with up to 20 carbon atoms, which may optionally be substituted or spaced by N, S, O, or a halogen. "R" is preferably hydrogen, methyl, ethyl, phenyl, hydroxymethyl, hydroxyethyl, hydroxybutyl, etc. Functionalized polyurethanes such as hydroxyl-terminated polyester polyurethanes or polyether polyurethanes, isocyanate-terminated polyester polyurethanes or polyether polyurethanes, or acrylate-terminated polyester polyurethanes or polyether polyurethanes are particularly preferred.

[0146] In many embodiments, the piezoelectric electrophoretic film or display often includes a release sheet. The release sheet can be used temporarily to facilitate the processing of the piezoelectric electrophoretic film or display, for example, during imprinting, filling, cutting, etc. In other embodiments, the release sheet can be used to deliver the final piezoelectric electrophoretic film or display, which will adhere to the final product. In some cases, the release sheet will protect a functional adhesive layer that will be used to manipulate the piezoelectric electrophoretic film or display before it is placed in the final product. The release sheet can be formed from a material selected from polyethylene terephthalate (PET), polycarbonate, polyethylene (PE), polypropylene (PP), paper, and their laminates or overlays. The release sheet may also be metallized to facilitate quality control measurements and / or control static electricity during handling, transportation, and downstream product addition. In some implementations, a silicone release coating may be applied to the release sheet to improve release performance.

[0147] although Figures 5A-6B , Figure 8A-10C Not shown in 12A-13B, but which may be omitted, piezoelectric electrophoretic films or displays may also include additional edge seals and / or barrier materials to enable the piezoelectric electrophoretic film or display to maintain a desired humidity level and to prevent leakage of, for example, nonpolar solvents or adhesives, as well as to prevent the ingress of water, dust, or gases. The barrier material can be any flexible material, generally a polymer with a WVTR (water vapor transmission rate) that is low to negligible. Suitable materials include polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyimide, cycloolefins, and combinations thereof. If the piezoelectric electrophoretic film or display will be exposed to particularly harsh conditions, flexible glass such as WILLOW® glass (Corning, Inc.) may be used for the barrier layer. The edge seal may be a metallized foil or other barrier foil adhered to the edge of the piezoelectric electrophoretic film or display. Edge seals can also be formed from dispensed sealants (thermally, chemically, and / or radiation-cured), polyisobutylene, or acrylate-based sealants, which may be cross-linked. In some embodiments, the edge seal may be sputtered ceramics such as alumina or indium tin oxide, or advanced ceramics such as those available from Vitex Systems, Inc. (San Jose, California).

[0148] Generally, the layers of piezoelectric electrophoretic films 501-504 can be arranged / laminated in order to produce the best performance for the final application. For example, as Figure 5AAs shown, the piezoelectric electrophoretic membrane 501 can be prepared by placing a micro-unit precursor material onto a release membrane 510 containing a release adhesive 520. The micro-unit precursor can then be imprinted or photolithographically etched to produce an array of micro-units 530. The micro-units 530 can be thermosetting or cured using electromagnetic radiation such as ultraviolet light. The micro-units 530 can then be filled with an electrophoretic medium and sealed with a sealing layer 540, as described above for... Figure 4A The micro-units 530 adjacent to the sealing layer 540 are filled with an electrophoretic medium containing charged particles in a nonpolar solvent, although the electrophoretic medium is not shown in subsequent figures. The piezoelectric layer 560 can be laminated to the sealing layer 540 using an adhesive 550, which is generally an optically transparent adhesive formed from one of the materials listed above. Finally, the flexible electrode 580 is bonded to the piezoelectric electrophoretic membrane using a conductive adhesive 570. Such a piezoelectric electrophoretic membrane 501 can then be manipulated by processing a release film 510 until the stack with the release film 510 removed is fixed to the final product. In the piezoelectric electrophoretic membrane 501, the piezoelectric layer 560 is generally polarized to form differentiated polarization regions before the flexible electrode 580 is bonded to the piezoelectric electrophoretic membrane. In some embodiments, the flexible electrode 580 and the conductive adhesive 570 can be replaced with a thin layer of a transparent conductive oxide such as ITO. ITO can be directly sputtered onto the piezoelectric layer 560.

[0149] Figures 5B-5D The text displays closely related but optional stacks. Figure 5BIn this process, a piezoelectric electrophoretic membrane 502 is fabricated, wherein a piezoelectric layer 560 is prepared prior to fabrication on a separate release membrane 510. For example, the piezoelectric layer 560 may be a pre-stretched PVDF film that has been polarized to form an anti-counterfeiting pattern. The piezoelectric layer 560 is then bonded to a sealed micro-unit layer 530, which has been bonded to a flexible electrode 580. Notably, in the piezoelectric electrophoretic membrane 502, the openings of the micro-unit layer 530 face away from the piezoelectric layer 560, which promotes good adhesion between the micro-unit layer 530 and the piezoelectric layer 560. This adhesion can be improved by introducing a primer 535 to improve the adhesion of the piezoelectric layer 560 to the micro-unit material, which is generally a polymer containing acrylates, vinyl ethers, or epoxides. Primer 535 can be a polar oligomer or polymeric material such as a polyhydroxy-functionalized polyester acrylate (e.g., BOMAR® BDE 1025 from Dymax) or an alkoxylated acrylate such as ethoxylated nonylphenol acrylate (e.g., SR504 from Sartomer), ethoxylated trimethylolpropane triacrylate (e.g., SR9035 from Sartomer), or ethoxylated pentaerythritol tetraacrylate (e.g., SR494 from Sartomer). Examples of polar polymers suitable for use as primer 535 include solvent-based urethane polymers, such as Irostic® polymers.

[0150] Of course, a stack can also be constructed such that the opening of the microcell layer 530 faces the piezoelectric layer 560, such as... Figure 5D The piezoelectric electrophoretic membrane 504 is illustrated in the diagram. Alternatively, as... Figure 5C As shown, the piezoelectric electrophoresis membrane 503 is arranged such that the opening of the micro-unit layer 530 faces away from the piezoelectric layer 560, while the piezoelectric layer 560 is directly bonded to the flexible electrode 580.

[0151] Figures 5A-5D The piezoelectric electrophoretic membranes (501, 502, 503, 504) shown can be replaced by adding a second flexible electrode 680. Figures 5A-5D The release layer in the middle is transformed into a piezoelectric electrophoretic display (601, 602). The piezoelectric electrophoretic display (601, 602) generally also includes a second conductive adhesive 670; however, it should be noted that in some cases, the conductive adhesive 670 alone is sufficient to provide the necessary electric field to switch the electrophoretic material. Additionally, a micro-unit layer 530 ( Figure 6A ) or sealing layer 540 ( Figure 6B A thin layer of transparent conductive oxide is directly coated on the bottom of the piezoelectric electrophoresis display (601, 602) to form the second electrode. Alternatively, if viewing through the top and bottom of the display is not necessary, a conductive metal foil can be used as the second flexible electrode 680. Figure 6A and 6BAs shown, a release film 510 is typically added to the completed piezoelectric electrophoretic displays (601, 602) to improve operation, and a ready-to-use adhesive is provided to fix the piezoelectric electrophoretic displays (601, 602). In some embodiments, the piezoelectric electrophoretic display 601 can be formed by simply bonding a piezoelectric layer 560 to a commercial front-panel laminate including a second flexible electrode 680 and a sealed micro-unit layer 530 containing an electrophoretic medium. In such cases, the piezoelectric layer 560 is typically polarized to form differentiated polarization regions before the front-panel laminate is bonded to the piezoelectric layer 560. Although Figure 6A and 6B The piezoelectric electrophoresis displays (601, 602) show a piezoelectric layer 560 above the hermetically sealed microcell layer 530, but it should be understood that the piezoelectric layer 560 can also be placed below the hermetically sealed microcell layer 530 to create a similar effect. Figure 5B and 5D Piezoelectric electrophoresis display.

[0152] Prototype performance

[0153] A series of flexible electrodes 580 were fabricated using PEDOT:PSS film as the flexible electrode. Figure 5A The examples illustrate the type of piezoelectric electrophoretic film. The piezoelectric layer 560 is modified (composition and thickness) as shown in Table 1. The piezoelectric film is derived from TE Connectivity (Norwood, MA), Fishman (Andover, MA), or internally cast and cured using PVDF powder from Sigma-Aldrich. The polarization direction is changed using the described polarization treatment technique to create the pattern. The electrophoretic medium comprises a low-pressure formulation of black and white particles, or black and red particles, or red and black particles, designed to switch color states at + / -3V. As shown in Table 1, all variations provide suitable switching.

[0154] Table 1: Prototype piezoelectric electrophoretic membrane

[0155]

[0156] Table 1 shows that various types of electrophoretic media will respond appropriately to the small electric field generated by the bent thin piezoelectric film. In particular, spin-coated polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) films smaller than 3 μm were found to have sufficient charge injection to induce DV electrophoretic media switching. See Experiment No. 7. Such a piezoelectric electrophoretic film 801 (see...) Figure 8A ) can be used Figure 7 The method described in the text is formed. First, as... Figure 7As shown in step 710, a thin film of piezoelectric material 940 is fabricated by casting a concentrated PVDF / DMF solution onto a suitable substrate (slit coating) and heating to remove the solvent. In step 720, the piezoelectric film 960 is removed from the substrate. The cast piezoelectric film 960 may be 10 μm or thinner, for example, 5 μm or thinner, such as 3 μm or thinner. The piezoelectric film 960 may also be stretched to increase the number of β-phase domains and / or treated with a suitable electric field polarization as discussed above. In step 730, a release film 910 and an adhesive 920 are provided, and then in step 740, the release film 910 and the adhesive 920 are laminated onto the cast piezoelectric film 960. Then, in step 750, an electrophoretic layer is coated onto / bonded to the piezoelectric film 960. The electrophoretic layer may be a sealed micro-unit layer, including filled micro-units 930 and a sealing layer 940, or alternatively, the electrophoretic layer may include an encapsulated electrophoretic medium 990 in a polymer adhesive 995, such as... Figure 9A and 9B As shown in the diagram. The bonding of the piezoelectric film 960 to the electrophoretic layer can be facilitated using an intermediate primer layer 935, for example, one of the primer materials discussed above. If the electrophoretic layer is a hermetically sealed micro-unit layer, it can be as follows... Figure 8A The micro-unit 930 can be configured such that the sealing layer 940 is adjacent to the piezoelectric film 960, or the micro-unit 930 can be configured such that the sealing layer 940 is located on the side opposite to the piezoelectric film 960, i.e. Figure 8B As shown in the diagram. As a final step 760, an electrode layer 980 is fabricated and bonded / deposited onto the microcell 930, as illustrated. Figure 8A As in the middle, or combined / deposited on the sealing layer 940, such as Figure 8B As described above, electrode layer 980 may comprise a flexible conductive material such as PEDOT:PSS, or it may comprise a directly deposited (e.g., sputtered or vapor-deposited) transparent conductive oxide (TCO). In some embodiments, electrode 980 may comprise an ITO film pre-formed on a polymer substrate such as PET. The piezoelectric electrophoretic membrane 801, comprising a directly deposited TCO electrode layer 980, a thin piezoelectric layer 960, and microunits 930 (approximately 10 μm thick), is very thin (i.e., less than 25 μm thick, excluding release film 910), which allows the piezoelectric electrophoretic membrane 801 to bend without failure and is imperceptible when attached to an object such as a banknote. The corresponding piezoelectric electrophoretic membrane 901, including microcapsules, may also be made with a total thickness of less than 25 µm. Of course, alternative constructions using a thin piezoelectric membrane 960 are also possible, such as positioning the piezoelectric membrane 960 between electrode 980 and the electrophoretic layer, i.e., microcapsule layer 990, as... Figure 9B As shown in the diagram. As an alternative option, Figures 8A-9BElectrode 980 can be replaced with a conductive adhesive (not shown) or a conductive adhesive bonded to an additional release layer (not shown).

[0157] and Figure 6A and 6B similar, Figures 8A-9B The piezoelectric electrophoretic film may include a second electrode layer to form a corresponding display (1001, 1002, 1003), such as Figures 10A-10C As shown in the diagram. Both electrode layer 980 and second electrode layer 1080 may comprise a flexible conductive material such as PEDOT:PSS, or both electrode layer 980 and second electrode layer 1080 may comprise a directly deposited (e.g., sputtered or vapor-deposited) transparent conductive oxide (TCO), or some combination thereof. Furthermore, when both electrode layer 980 and second electrode layer 1080 use thin TCO films, the resulting piezoelectric electrophoretic displays (1001, 1002, 1003) can be fabricated to be very thin, i.e., less than 25 µm thick, excluding the release film 910. In some embodiments, electrode layer 980 is fabricated in combination with / deposited on microcell 930, such as Figure 10A As in the example. In other embodiments, the electrode layer 980 is bonded to / deposited on the sealing layer 940, such as... Figure 10B As in the example. The components of piezoelectric electrophoretic displays 1001 and 1002 can also be used with microcapsules 990, which contain an electrophoretic medium held together with an adhesive 995, thereby forming a piezoelectric electrophoretic display 1003, as shown. Figure 10C As shown in the diagram. As an alternative option, Figures 10A-10C Electrodes 980 / 1080 can be replaced with a conductive adhesive (not shown) or a conductive adhesive bonded to an additional release film (not shown).

[0158] Reference Figure 11The flowchart describes alternative methods for constructing piezoelectric electrophoretic membranes and piezoelectric electrophoretic displays. A piezoelectric membrane 1260 is obtained, which can be a commercially available membrane or a cast membrane as described above. In step 1110, the piezoelectric membrane 1260 is laminated onto a microcell precursor material. The piezoelectric membrane 1260 may be stretched and / or polarized prior to lamination. The precursor material is generally an acrylate polymer; however, any suitable imprintable material can be used, such as a vinyl ether polymer or an epoxide polymer membrane. Generally, the precursor membrane thickness is 30 μm or less, for example, 20 μm or less. The precursor membrane may be treated with a primer 1235 prior to lamination step 1110. Once the piezoelectric film 1260 and the microcell precursor material have been connected, the side of the piezoelectric film 1260 opposite to the microcell precursor material is coated with a transparent conductive material, such as those selected above, typically indium tin oxide (optionally, depending on the application, a conductive adhesive may be applied to the side of the piezoelectric film 1260 opposite to the microcell precursor material, said adhesive being carried by a release layer). This coating step generates electrodes 1280, respectively on... Figure 12A and 12B The piezoelectric electrophoresis membrane 1201 and piezoelectric electrophoresis display 1202 shown in the figure (although in Figure 11Not shown, but an alternative construction is used to obtain a piezoelectric film 1260 pre-coated with a transparent conductive material, followed by laminating the pre-coated piezoelectric film 1260 and the microcell precursor material together, including optionally using a primer 1235. After the stack of electrodes 1280, piezoelectric film 1260, and microcell precursor is formed, the stack is laminated to a carrier substrate 1255 using an adhesive layer 1250, as shown in step 1130. The carrier substrate 1255 can be any of the materials described above for use as a release film, and the adhesive 1250 can be any of the adhesives described above. In practice, the carrier substrate 1255 is generally PET, because PET sheets are easy to handle during imprinting step 1140. In step 1140, the stack comprising a carrier substrate 1255, an adhesive 1250, a piezoelectric film 1260, and a microcell precursor is microimprinted using the techniques described above in conjunction with U.S. Patents 6,930,818, 7,052,571, 7,616,374, 8,361,356, and 8,830,561. When this process is performed with a thin piezoelectric film and a thin microcell precursor, the final stack thickness (excluding the carrier substrate) can be 30 μm or less, for example, 20 μm or less. This creates an open microcell structure, which is then filled with a desired electrophoretic medium and sealed with a water-soluble sealing layer 1240 in step 1150. The sealing layer 1240 can be made conductive by containing a conductive material. The sealing layer 1240 is generally translucent or transparent. Before filling the microcells with the desired electrophoretic medium, the microcells with openings can be cleaned / activated using vapor plasma treatment 1145. Finally, in step 1160, release sheet 1210 is bonded to sealing layer 1240 with adhesive 1220 to facilitate the transfer of piezoelectric electrophoretic membrane 1201 and promote placement of electrophoretic membrane 1201 onto the final product. Adhesive 1220 may also be conductive. The resulting structure is as follows. Figure 12A As shown in the diagram. Importantly, this can be accomplished without polarizing the piezoelectric film 1260. Figure 11 The steps thus enable the end user to pattern the piezoelectric electrophoretic membrane 1201 at the final assembly location, for example, by generating differentiated polarity regions using corona discharge as described above.

[0159] like Figure 12B As shown, Figure 11The method can be extended to fabricate the piezoelectric electrophoretic display 1202 by adding a second electrode 1285. The second electrode 1285 may also comprise a transparent conductive material, which is added directly to the sealing layer 1240, replacing the release film 1210 and adhesive 1220. However, in other embodiments, the release film 1210 is removed, and the second electrode 1285 is laminated to the sealing layer 1240 with adhesive 1220. If the piezoelectric electrophoretic display 1202 does not require the electrophoretic medium to be visible from both sides, the second electrode 1285 may be a metal film. Alternatively, the second electrode 1285 may be a conductive polymer, such as PEDOT:PSS. In some other embodiments, the adhesive 1220 may be a conductive adhesive that provides sufficient conductivity to function as the second electrode 1285.

[0160] Finally, it should be recognized that the electrodes do not need to be bonded to the piezoelectric film 1260 before imprinting the stack comprising the piezoelectric film 1260 and the microcell precursor material. Instead, a stack comprising the release film 1210, adhesive 1220, piezoelectric film 1260, and microcell precursor can be prepared, followed by imprinting, filling, and sealing of the microcell precursor as described above. Alternatively, as Figure 13B As shown, a stack comprising a release film 1210, an adhesive 1220, an electrode 1285, a piezoelectric film 1260, and a microcell precursor can also be prepared, followed by imprinting, filling, and sealing of the microcell precursor as described above. The resulting piezoelectric electrophoretic film 1301 and piezoelectric electrophoretic display 1302 are respectively... Figure 13A and 13B As shown in the figure. The piezoelectric electrophoretic membrane 1301 and the piezoelectric electrophoretic display 1302 can be advantageous for applications where it is desirable for the piezoelectric membrane 1260 to be as close as possible to the attachment surface on the final product, i.e., if the piezoelectric electrophoretic membrane 1301 is used as a strain sensor, and it is important that the intermediate electrophoretic dielectric layer does not dissipate the force from the surface.

[0161] Figure 14 This is a flowchart detailing the steps of method 1400 for producing a high-contrast piezoelectric electrophoretic film and a piezoelectric electrophoretic display. Method 1400 has been optimized for producing a piezoelectric electrophoretic film using a roll-to-roll manufacturing method.

[0162] refer to Figure 15A-15FMethod 1400 is described. Method 1400 begins at step 1410, in which a first electrode—electrode 1550—is formed on a first substrate—substrate 1555—by depositing a conductive material, such as those selected above, onto a substrate. For example, a thin layer of conductive material can be directly deposited (e.g., sputtering, vapor deposition) onto a suitable substrate such as a polymer substrate (e.g., PET). In some embodiments, substrate 1555 can be any of the materials described above used as a release liner, which is temporarily used to facilitate the fabrication of a piezoelectric electrophoretic membrane. In some embodiments, the conductive material used to form electrode 1550 is an adhesive or bonding layer comprising a transparent conductive material (e.g., a first conductive adhesive), the transparent conductive material comprising a conductive metal oxide, a conductive polymer, and / or other suitable conductive agents coated on substrate 1555. In some embodiments, to form electrode 1550, an adhesive or bonding layer is deposited on substrate 1555, and a conductive polymer such as PEDOT is deposited on the bonding layer. In some cases, electrode 1550 is a metal film, such as a copper, silver, gold, or aluminum film or foil, bonded to a flexible, transparent substrate, such as a polymer film. In some embodiments, the thickness of electrode 1550 is less than 5 μm. In some embodiments, the thickness of electrode 1550 is between 1 and 3 μm.

[0163] Next, in step 1420, a piezoelectric layer 1560 is formed on electrode 1550 by depositing a piezoelectric material onto a conductive material (e.g., electrode 1550). For example, electrode 1550 can be coated with a piezoelectric material using spin coating or casting (e.g., slot coating) methods as described above, such as thin film coatings of piezoelectric materials selected from those described above, such as PVDF. In some embodiments, film deposition methods such as printing, spraying, or gravure coating are used to form the piezoelectric layer 1560 on electrode 1550. In some embodiments, the thickness of the resulting piezoelectric layer 1560 is less than 10 μm. In some embodiments, the thickness of the resulting piezoelectric layer 1560 is about 3 μm.

[0164] After the piezoelectric layer 1560 is formed on the electrode 1550, as shown in step 1430, a mask 1540 is applied to the piezoelectric material of the piezoelectric layer 1560. As in the above embodiment, the mask 1540 can be used to shield or insulate first plurality of regions of the piezoelectric layer 1560 from a high-voltage corona discharge 1533 used to polarize the piezoelectric layer 1560. This allows the piezoelectric layer 1560 to be patterned with images, text, and other information (e.g., machine-readable code). The mask 1540 may be made of a material with sufficient dielectric strength to withstand at least a localized 5 kV electric field. In some embodiments, the mask 1540 is formed of a disposable material that can be applied in a roll-to-roll method. For example, the mask 1540 may be formed of paper, such as electrically insulating paper, having a pressure-sensitive adhesive for bonding to the piezoelectric layer 1560 and applied to a surface. Alternatively, the mask 1540 can be a reusable fixture made of charge-absorbing or charge-blocking material, which is integrated into a roll-to-roll translation stage, similar to screen printing methods or rotary rollers.

[0165] Figure 15A Is Figure 14 A schematic cross-section 1501 of the piezoelectric electrophoretic membrane in step 1440 of the method shown. Figure 15A As shown, mask 1540 includes a masking portion 1542 and an unmasked portion 1544. The masking portion 1542 shields or insulates a corresponding region of piezoelectric layer 1560 from the high-voltage corona discharge 1533, and the unmasked portion 1544 polarizes the corresponding region of piezoelectric layer 1560 in areas not covered by mask 1540. Then, in step 1440, the piezoelectric material is polarized. For example, the high-voltage corona discharge discussed above (e.g., high-voltage corona discharge 1533) or other suitable electric field can be used to polarize the unmasked portion of piezoelectric layer 1560 in a first direction, while leaving the masked portion unpolarized. If a disposable material such as paper is used for the mask, then the mask is then removed from piezoelectric layer 1560.

[0166] In some implementations, the patterning process of the piezoelectric material can begin with a single sheet or roll of polarized PVDF film. The film can be patterned by laser cutting, laser ablation (e.g., laser photoablation), die-cutting, or other cutting methods, and then laminated to an electrode layer, or laminated to a microcapsule or microcell-based front plate laminate or FPL as described above.

[0167] Figure 15B yes Figure 14 A schematic cross-section 1502 of the piezoelectric electrophoretic membrane after step 1440 of the method shown is obtained. Figure 15BAs shown, the piezoelectric layer 1560 now includes an unpolarized portion 1562 corresponding to the location of the masked portion 1542 of the mask 1540, and a polarized portion 1564 corresponding to the location of the unmasked portion 1544 of the mask 1540.

[0168] Then, in step 1450, the piezoelectric material is bonded to the electrophoretic material. For example, the piezoelectric layer 1560 can be coated with an electrophoretic dielectric layer comprising a plurality of microcapsules containing nonpolar fluid and charged pigment particles. Figure 15B (Not shown in the image). Alternatively, the electrophoretic dielectric layer including the microunit 1530 can be used with... Figure 11 The method shown in the flowchart is similar to that used to form on the piezoelectric layer 1560. For example, an imprintable microcell precursor material can be laminated onto the piezoelectric layer 1560. Prior to lamination, the precursor material can be treated or coated with a microcell primer, for example, using one of the primer materials discussed above. In some instances, the microcell primer includes thermoplastic or thermosetting materials or precursors thereof, such as polyurethanes, multifunctional acrylates or methacrylates such as lauryl methacrylate, vinylbenzene, vinyl ethers, epoxides or oligomers or polymers thereof.

[0169] The micro-unit precursor is microimprinted using the above technique to obtain an open micro-unit structure. The micro-unit structure is then filled with a desired electrophoretic medium and sealed with sealing layer 1535. Figure 15C As shown, Figure 15C yes Figure 14 A schematic cross-section 1503 of the piezoelectric electrophoretic membrane after step 1450 of the method shown. The microcells with the openings can optionally be treated with steam plasma to clean / activate them before filling the microcells 1530 with the desired electrophoretic medium.

[0170] In some embodiments, the thickness of the micro-unit layer 1530 is 8 to 20 μm, and the thickness of the sealing layer 1535 is 3 to 10 μm. In some embodiments, the thickness of the micro-unit layer 1530 is about 10 μm, and the thickness of the sealing layer 1535 is about 5 μm.

[0171] In an alternative implementation, instead of forming micro-units on piezoelectric layer 1560, piezoelectric layer 1560, such as Figure 15B The piezoelectric layer 1560 shown is bonded or laminated to the microcapsule or microcell-based front plate laminate or FPL as described above.

[0172] In step 1460, a second electrode—electrode 1585—is formed on the second substrate—substrate 1586. Electrode 1585 can be formed on substrate 1586 using one of the methods described above for electrode 1550 and substrate 1555. As an example, substrate 1586 may be a release sheet temporarily used to facilitate the fabrication of a piezoelectric electrophoretic membrane, and electrode 1585 may be formed from an adhesive or bonding layer comprising a transparent conductive material deposited on substrate 1586. In some embodiments, the thickness of electrode 1585 is less than 5 μm. In some embodiments, the thickness of electrode 1585 is between 1 and 3 μm.

[0173] Then, in step 1470, the conductive material deposited on the second substrate is bonded with the electrophoretic material. For example, the substrate 1586 and the electrode 1585 can be laminated to the sealing layer 1535 of the microcell 1530 to form Figure 15D The structure shown is Figure 14 A schematic cross-section 1504 of the piezoelectric electrophoretic membrane after step 1470 of the method shown. Electrodes 1585 (and a substrate 1586) are added to the piezoelectric electrophoretic membrane to form a piezoelectric electrophoretic display that can be bonded to a target object. For example, Figure 15D The structure shown can be a piezoelectric electrophoretic display sandwiched between two release sheets (e.g., substrate 1550 and substrate 1586).

[0174] exist Figure 14 In an alternative embodiment not shown, steps 1460-1470 are replaced by the following process: The sealing layer 1535 of the microcell 1530 may be coated with a conductive material, such as PEDOT or one of the aforementioned materials, to form an electrode 1585. Subsequently, in step 1480 described below, the electrode 1585 may be coated with an adhesive material (e.g., a heat-sealing adhesive (“HSA”), or one of the aforementioned materials) for bonding the piezoelectric electrophoretic display to the target object.

[0175] Return to Figure 14 In step 1480, the piezoelectric electrophoretic display can be attached to the target object. For example, a piezoelectric electrophoretic display, such as... Figure 15D The piezoelectric electrophoretic display shown can be processed and attached to a target object 1588, such as paper or banknotes. Figure 15E As shown, Figure 15E yes Figure 14 After step 1480 of the method shown is completed, the cross section 1505 of the piezoelectric electrophoretic membrane bonded to the target object.

[0176] In some embodiments, substrate 1586 is a release sheet peeled or removed from electrode 1585, and electrode 1585 is bonded to the surface of target object 1588 using a hot stamping process. For example, during a roll-to-roll hot stamping process that presses a piezoelectric electrophoretic display onto target object 1588, heat and pressure can be applied to the piezoelectric electrophoretic display and / or target object 1588. The adhesive (not shown) remaining on electrode 1585 after substrate 1586 is peeled off is activated by heat and pressure, bonding the piezoelectric electrophoretic display to target object 1588.

[0177] In some embodiments, electrode 1585 is formed of an adhesive or bonding layer, which is activated during the bonding process to bond the piezoelectric electrophoretic display to the target object 1588. In some embodiments, a roll-to-roll lamination method is used to bond the piezoelectric electrophoretic display to the target object 1588.

[0178] In some embodiments, substrates 1555 and 1586 are release liner pieces, and the force required to remove each release liner piece is individually adjusted to ensure that substrate 1586 is removed before substrate 1555 during the bonding process. For example, adhesives for temporarily adhering substrates 1555 and 1586 to electrodes 1555 and 1585, respectively, can be formulated or selected such that the force required to peel substrate 1586 from the piezoelectric electrophoretic display is less than the force required to peel substrate 1555 from the piezoelectric electrophoretic display.

[0179] Figure 15F yes Figure 14 After step 1480 of the method shown is completed, the cross-section 1506 of the piezoelectric electrophoretic membrane, which is bonded to the target object and coated with a protective coating, is shown. Figure 15F As illustrated in the example, after the piezoelectric electrophoretic display is bonded to the target object 1588, the substrate 1555 can be peeled off from the electrode 1550, and a protective coating 1589 can be applied to the surfaces of the piezoelectric electrophoretic display and the target object 1588 bonded to it. In some embodiments, the protective coating 1589 is a paint layer applied to the surfaces of the piezoelectric electrophoretic display and the target object 1588 using a printing method. Suitable materials for the protective coating 1589 may include UV-curable polyester acrylates, polyurethane acrylates, UV-curable epoxides, and thermosetting epoxides, or any material sufficient to seal the piezoelectric electrophoretic display and the target object 1588 to prevent dust and excessive moisture absorption.

[0180] Therefore, combining Figure 14The described method can be used to produce piezoelectric electrophoretic displays with a thickness much smaller than that of conventional displays, thus allowing them to be incorporated into target objects such as banknotes or denominations without substantially increasing the overall thickness or becoming substantially inconspicuous. In some embodiments, the total thickness of the piezoelectric electrophoretic display can be from 50 μm to 100 μm. In some embodiments, the total thickness of the piezoelectric electrophoretic display can be from 25 μm to 50 μm. In some embodiments, the total thickness of the piezoelectric electrophoretic display can be less than 25 μm.

[0181] Figure 16 An enlarged cross-sectional view 1600 of a piezoelectric electrophoretic display 1601 manufactured according to the subject matter disclosed herein is shown. For the purpose of describing the operation of the display, only a subset of the layers of the piezoelectric electrophoretic display 1601 is shown: electrode 1550, piezoelectric layer 1560 including unpolarized portion 1562 and polarized portion 1564, microcell 1530, sealing layer 1535, and second electrode 1585. In the enlarged view 1600, microcell 1530 and sealing layer 1535 are represented by electrophoretic layer 1631.

[0182] The enlarged view 1600 includes an unpolarized portion 1562 and a polarized portion 1564. A first portion 1632 of the electrophoretic layer 1631 lies over the unpolarized portion 1562, and a second portion 1634 lies over the polarized portion 1564, as shown by dashed line 1602. Each of the first portion 1632 and the second portion 1634 has a resistance based on the volume of the electrophoretic layer 1631 it contains. Furthermore, the unpolarized portion 1562 also has a resistance based on the volume of the piezoelectric layer 1560 it contains. As indicated by the "+" and "-" symbols, for example, a voltage is generated in the polarized portion 1564 of the piezoelectric layer 1560 in response to bending of the piezoelectric material or mechanical stress thereto.

[0183] Figure 17 Illustration Figure 16 The exemplary equivalent circuit 1700 with an enlarged cross-section is shown. Figure 16 The three nodes or points shown, 'A' at polarization portion 1564, 'B' at electrode 1585, and 'C' at electrode 1550, correspond to... Figure 17 The equivalent circuit 1700 shows the same points. Resistor R1 corresponds to the sum of the resistances of the first portion 1632 of the electrophoretic layer 1631 and the unpolarized portion 1562 of the piezoelectric layer 1560. Resistor R2 corresponds to the resistance of the second portion 1634 of the electrophoretic layer 1631.

[0184] The polarization portion 1564 of the piezoelectric layer 1560 is represented as a cell, and the voltage V PZThis is the voltage generated by the polarization section 1564 across points A and C. Resistors R1 and R2 are shown in series because a voltage source present beneath a portion of the electrophoretic layer 1631 effectively divides the layer into separate portions with different electrical properties (as shown by dashed line 1602). For example, when a voltage V has been generated... PZ At this point, the voltage potential at point A is higher than the voltage potential at points B or C. Using the conventional current flow paradigm, current 1701 flows from point A through resistor R1 to point B, and from point B through resistor R2 to point C. Therefore, the voltage across resistor R1 and the voltage across resistor R2 have opposite polarities. In fact, the separate parts across the electrophoretic layer connected in series produce two opposite voltages.

[0185] Therefore, manufacturing a piezoelectric electrophoretic display according to method 1400 offers advantages over conventional piezoelectric electrophoretic displays. For example, in the absence of a matrix of individually addressable pixel electrodes, selectively polarizing the piezoelectric layer advantageously provides an improved means of driving pigment particles with opposite charges in the electrophoretic medium in opposite directions. Thus, piezoelectric electrophoretic displays produced according to method 1400 can be made thin enough for applications requiring durability and to be substantially inconspicuous when added to thin, low-profile end products such as paper or banknotes, while still providing high contrast between polarized and unpolarized regions due to the aforementioned effects. Furthermore, in this embodiment, the piezoelectric layer requires only a single polarization operation.

[0186] Figure 18 This is a flowchart detailing the steps of method 1800 for producing high-contrast piezoelectric electrophoretic films and piezoelectric electrophoretic displays. Method 1800 has been optimized for producing piezoelectric electrophoretic films using a roll-to-roll manufacturing method.

[0187] refer to Figure 19A-19G Description method 1800. For ease of understanding, where possible, in... Figure 19A-19G The same or similar figure labels and names were used to refer to the same Figure 15A-15F The elements shown correspond to or are functionally similar to those shown herein. However, based on the description herein, those skilled in the art will understand that the elements of each embodiment need not be identical in composition and structure, and that elements disclosed in one embodiment may be beneficially used in other embodiments without specific description.

[0188] Method 1800 begins at step 1810, in which a piezoelectric layer 1960 is formed on the temporary substrate 1965 by depositing a piezoelectric material onto the temporary substrate 1965. For example, the temporary substrate 1965 can be coated with a thin film of a piezoelectric material, such as PVDF, selected from those described above, using spin coating methods or casting techniques (e.g., slot coating) as described above. The temporary substrate 1965 may be a release sheet temporarily used to assist in the fabrication of the piezoelectric electrophoretic film. In some embodiments, the temporary substrate 1965 is a release sheet, which may be formed from a material selected from polyethylene terephthalate (PET), polycarbonate, polyethylene (PE), polypropylene (PP), paper, and their laminates or overlays. A silicone release coating may also be applied to the temporary substrate 1965 to improve release properties. Figure 19A This is a schematic cross-section 1901 of the piezoelectric electrophoretic membrane in step 1810 of method 1800.

[0189] In some embodiments, film deposition methods such as printing, spraying, or gravure coating are used to form the piezoelectric layer 1960 on the temporary substrate 1965. In some embodiments, the thickness of the resulting piezoelectric layer 1960 is less than 10 μm. In some embodiments, the thickness of the resulting piezoelectric layer 1960 is about 3 μm.

[0190] In step 1820, the piezoelectric material is bonded to a conductive material coated on the first substrate. For example, a temporary substrate 1965 can be peeled off from the piezoelectric layer 1960, and the piezoelectric layer 1960 can be laminated onto a first electrode—electrode 1950, which is formed on the first substrate—substrate 1955. Electrode 1950 can be formed on substrate 1955 using one of the methods described above for electrode 1550 and substrate 1555. As an example, substrate 1955 can be a release sheet temporarily used to assist in the fabrication of a piezoelectric electrophoretic membrane, and electrode 1950 can be formed from an adhesive or bonding layer comprising a transparent conductive material deposited on substrate 1955. In some embodiments, the thickness of electrode 1950 is less than 5 μm. In some embodiments, the thickness of electrode 1950 is between 1 and 3 μm.

[0191] exist Figure 18In an alternative embodiment not shown, steps 1810 and 1820 are replaced by the following process. Instead of using a temporary substrate 1965, substrate 1955 may be coated with a conductive material (e.g., one of the materials described above) to form electrode 1950. In some embodiments, to form electrode 1950, an adhesive or bonding layer is deposited on substrate 1955, and a conductive polymer such as PEDOT is deposited on the bonding layer. After forming electrode 1950, a piezoelectric material is bonded to electrode 1950 to form piezoelectric layer 1960. For example, piezoelectric material may be coated onto electrode 1950 as described above.

[0192] Return to Figure 18 After the piezoelectric layer 1960 is bonded to the electrode 1950, a mask 1940 is applied to the piezoelectric layer 1960, as shown in step 1830. As in the above embodiment, the mask 1940 can be used to shield or insulate areas of the piezoelectric layer 1960 from the high-voltage corona discharge 1933 used to polarize the piezoelectric layer 1960. This allows the piezoelectric layer 1960 to be patterned with images, text, and other information (e.g., machine-readable code). The mask 1940 may be made of a material with sufficient dielectric strength to withstand at least a localized 5 kV electric field. In some embodiments, the mask 1940 is formed of a disposable material that can be applied in a roll-to-roll method. For example, the mask 1940 may be formed of paper, such as electrically insulating paper, having a pressure-sensitive adhesive applied to a surface for bonding to the piezoelectric layer 1960. Alternatively, the mask 1940 can be a reusable fixture made of charge-absorbing or charge-blocking material, which is integrated into a roll-to-roll translation stage, similar to screen printing methods or rotary rollers.

[0193] Figure 19B Is Figure 18 A schematic cross-section 1902 of the piezoelectric electrophoretic membrane in step 1830 of the method shown. (See figure) Figure 19B As shown, the mask 1940 includes a masked portion 1942 and an unmasked portion 1944. The masked portion 1942 shields or insulates a corresponding area of ​​the piezoelectric layer 1960 from the high-voltage corona discharge 1933, while the unmasked portion 1944 allows the corresponding area of ​​the piezoelectric layer 1960 to be polarized in areas of the piezoelectric layer 1960 not covered by the mask 1940.

[0194] Then, in step 1840, the piezoelectric material is polarized or polarized. For example, the high-voltage corona discharge discussed above (e.g., high-voltage corona discharge 1933) or other suitable electric field can be used to polarize the unmasked portion of the piezoelectric layer 1960 in the first direction, while leaving the masked portion unpolarized. If a disposable material such as paper is used as the mask, then the mask is removed from the piezoelectric layer 1960.

[0195] Figure 19Cyes Figure 18 A schematic cross-section 1903 of the piezoelectric electrophoretic membrane after step 1840 of the method shown is obtained. Figure 19C As shown, the piezoelectric layer 1960 now includes an unpolarized portion 1962 corresponding to the location of the masked portion 1942 of the mask 1940, and a polarized portion 1964 corresponding to the location of the unmasked portion 1944 of the mask 1940.

[0196] In step 1850, a second electrode—electrode 1985—is formed on the second substrate—substrate 1986—by depositing a conductive material, such as those selected from those described above, onto the substrate. Electrode 1985 can be formed on substrate 1986 using one of the methods described above for electrode 1550 and substrate 1555. In one example, to form electrode 1985, an adhesive or bonding layer is deposited on substrate 1986, and a conductive polymer such as PEDOT is deposited on the bonding layer. In some embodiments, the thickness of electrode 1986 is less than 5 μm. In some embodiments, the thickness of electrode 1985 is between 1 and 3 μm.

[0197] Then, in step 1860, the electrophoretic material is bonded to the conductive material. For example, electrode 1985 can be coated with an electrophoretic dielectric layer comprising multiple microcapsules containing nonpolar fluid and charged pigment particles. Figure 19D (Not shown in the image). Alternatively, the electrophoretic dielectric layer including the microunit 1930 can be used with... Figure 11 The method shown in the flowchart is similar to that used to form on electrode 1985. For example, an imprintable microcell precursor material can be laminated onto electrode 1985. Before lamination, the precursor material can be treated with a primer, for example, one of the primer materials discussed above. Microimprinting of the microcell precursor using the above technique yields an open microcell structure, which is then filled with a desired electrophoretic medium and sealed with a sealing layer 1935, such as... Figure 19D As shown, Figure 19D yes Figure 18 A schematic cross-section 1904 of the piezoelectric electrophoretic membrane after steps 1850 and 1860 of the method shown. The microcells with the openings can optionally be treated with steam plasma to clean / activate them before filling the microcells 1930 with the desired electrophoretic medium.

[0198] In some embodiments, the thickness of the micro-unit layer 1930 is between 8 and 20 μm, and the thickness of the sealing layer 1935 is between 3 and 10 μm. In some embodiments, the thickness of the micro-unit layer 1930 is about 10 μm, and the thickness of the sealing layer 1935 is about 5 μm.

[0199] In an alternative embodiment, instead of forming microcells on electrode 1985, electrode 1985 is such as Figure 19D The electrode 1985 shown is bonded or laminated to the front plate laminate or "FPL" based on microcapsules or microcells as described above.

[0200] Then, in step 1870, the piezoelectric material deposited on the first electrode is bonded to the electrophoretic material. For example, the piezoelectric layer 1960 can be laminated onto the sealing layer 1935 of the microcell 1930 to form Figure 19E The structure shown, Figure 19E yes Figure 18 A schematic cross-section 1905 of the piezoelectric electrophoretic membrane after step 1870 of the method shown is presented. In some embodiments, the piezoelectric layer 1960 may be made of an adhesive layer ( Figure 19E (Not shown in the image) is incorporated into the sealing layer 1935.

[0201] A piezoelectric layer 1960 having electrodes 1550 (and a substrate 1555) is added to the piezoelectric electrophoretic film to form a piezoelectric electrophoretic display that can be bonded to a target object. For example, Figure 19E The structure shown can be a piezoelectric electrophoretic display sandwiched between two release sheets (e.g., substrate 1950 and substrate 1986).

[0202] In step 1880, the piezoelectric electrophoretic display can be attached to the target object. For example, a piezoelectric electrophoretic display, such as... Figure 19E The piezoelectric electrophoretic display shown can be processed and attached to a target object such as paper or banknotes 1988, as Figure 19F As shown, Figure 19F It is based on Figure 18 The cross-section 1906 of the piezoelectric electrophoretic membrane combined with the target object by the method shown.

[0203] In some embodiments, substrate 1986 is a release sheet peeled or removed from electrode 1985, and electrode 1985 is bonded to the surface of target object 1988 using the hot stamping method described above.

[0204] In some embodiments, electrode 1985 is formed of an adhesive or bonding layer, which is activated during the bonding process to bond the piezoelectric electrophoretic display to the target object 1988. In some embodiments, a roll-to-roll lamination method is used to bond the piezoelectric electrophoretic display to the target object 1988.

[0205] In some embodiments, substrates 1955 and 1986 are release liner pieces, and the force required to remove each release liner piece is individually adjusted to ensure that substrate 1986 is removed before substrate 1955 during the bonding process. For example, adhesives for temporarily adhering substrates 1955 and 1986 to electrodes 1955 and 1985, respectively, can be formulated or selected such that the force required to peel substrate 1986 from the piezoelectric electrophoretic display is less than the force required to peel substrate 1955 from the piezoelectric electrophoretic display.

[0206] Figure 19G yes Figure 18 After step 1880 of the method shown is completed, the cross-section 1907 of the piezoelectric electrophoretic membrane, which is bonded to the target object and coated with a protective coating, is shown. Figure 19G As illustrated in the example, after the piezoelectric electrophoretic display is bonded to the target object 1988, the substrate 1955 can be peeled off from the electrode 1950, and a protective coating 1989 can be applied to the surface of the piezoelectric electrophoretic display and the target object 1988 to which the piezoelectric electrophoretic display is bonded, as described above.

[0207] Therefore, combining Figure 18 The described process can be used to produce piezoelectric electrophoretic displays with a thickness much smaller than conventional displays, and thus can be incorporated into target objects such as banknotes or denominations without substantially increasing the overall thickness or being substantially inconspicuous. In some embodiments, the total thickness of the piezoelectric electrophoretic display can be between 50 μm and 100 μm. In some embodiments, the total thickness of the piezoelectric electrophoretic display can be between 25 μm and 50 μm. In some embodiments, the total thickness of the piezoelectric electrophoretic display can be less than 25 μm. Therefore, the piezoelectric electrophoretic display produced using method 1800 provides substantially similar benefits and advantages to the piezoelectric electrophoretic display produced using method 1400 described above.

[0208] Those skilled in the art will understand that the steps of methods 1400 and 1800 do not need to be performed in the exact order presented herein. As an example, steps 1810-1840 of method 1800 do not necessarily have to occur before steps 1850 and 1860.

[0209] It should be understood that the piezoelectric electrophoretic film and piezoelectric electrophoretic display described herein can be combined with other known technologies for the manufacture of anti-counterfeiting marks or labels. For example, the piezoelectric electrophoretic film or piezoelectric electrophoretic display may additionally include a translucent overlay that does not change its optical properties when the piezoelectric film is manipulated. For example, a smiley face overlay may include eyes made of a piezoelectric electrophoretic display such that the eyes appear to blink when the layered material is bent. In some embodiments, an image or shape may be printed or laminated on a solid color (such as white) background and the pre-arranged pattern must be viewed through the piezoelectric electrophoretic film to be seen. Thus, when not in use, the viewer sees only the solid color, i.e., the printed image or shape is hidden. However, when the device is manipulated, the printed image or shape is displayed. It is also feasible to adhere the piezoelectric electrophoretic film or piezoelectric electrophoretic display to a separate translucent polymer film included in a target product (such as a banknote), such that the pattern in the piezoelectric layer is only visible when the target product is held up to a light source and manipulated.

[0210] Figure 20 The illustration shows a cross-section of another exemplary piezoelectric electrophoretic display 2000 according to the subject matter disclosed herein. The display 2000 uses a piezoelectric material 2002 to generate a voltage potential sufficient to drive charged pigment particles within an electrophoretic material layer 2004. The display 2000 includes a first electrode—electrode 2006—that overlaps or covers a first surface of the electrophoretic material layer 2004. The display 2000 also includes a first portion of the piezoelectric material 2002 that overlaps or covers a second surface of the electrophoretic material layer 2004, such as… Figure 20 The surface region 2020 is shown in the diagram. The second electrode—electrode 2008—overlaps with a second portion of the second surface of all piezoelectric materials 2002 and the electrophoretic material layer 2004, as shown in the diagram. Figure 20 The surface region 2021 is shown in the figure.

[0211] The piezoelectric material 2002 can be a piezoelectric film bonded to the surface region 2020 of the electrophoretic material layer 2004 using a lamination method. In some embodiments, the piezoelectric material 2002 is formed by depositing a piezoelectric material onto the electrophoretic material layer 2004. For example, the surface region 2020 of the electrophoretic material layer 2004 can be coated with a piezoelectric material, such as a PVDF film, using a spin coating method or a casting process (e.g., slot coating). In some embodiments, film deposition methods such as printing, spraying, or gravure coating are used to form the piezoelectric material 2002 on the electrophoretic material layer 2004. In some embodiments, the thickness of the resulting piezoelectric material 2002 is less than 10 μm. In some embodiments, the thickness of the resulting piezoelectric material 2002 is about 3 μm.

[0212] Electrode 2008 overlaps with or covers the surface region 2021 of piezoelectric material 2002 and electrophoretic material layer 2004. Electrode 2008 may be a conductive adhesive material (e.g., copper strip) applied to the surface region 2021 of piezoelectric material 2002 and electrophoretic material layer 2004. In some embodiments, electrode 2008 is a metal film, such as a copper, silver, gold, or aluminum film or foil, bonded to a flexible, transparent substrate (not shown), such as a polymer film. In some embodiments, electrode 2008 is an adhesive or bonding layer comprising a transparent conductive material (e.g., a first conductive adhesive), said transparent conductive material comprising conductive metal oxides, conductive polymers, and / or other suitable conductive agents coated on a substrate (not shown). For example, a thin layer of conductive material may be directly deposited (e.g., sputtering, vapor deposition) onto a suitable substrate, such as a polymer substrate (e.g., PET). In some embodiments, the thickness of electrode 2008 is less than 5 μm. In some embodiments, the thickness of electrode 2008 is between 1 and 3 μm. In some implementations, the thickness of electrode 2008 is less than 1 μm.

[0213] The first electrode—electrode 2006—is bonded to an electrophoretic material layer 2004 on the surface opposite the piezoelectric material 2002 and the electrode 2008. For example, electrode 2006 may be laminated to electrophoretic material layer 2004 to form a front plate laminate or FPL based on microcapsules or microcells, as described above in conjunction with U.S. Patent No. 6,982,178.

[0214] Electrode 2006 can be pre-formed on a substrate (not shown) using one of the methods described above for electrode 2008. In some embodiments, electrode 2006 can be formed from an adhesive or bonding layer comprising a transparent conductive material deposited on the substrate. The substrate can be a release sheet temporarily used to assist in the fabrication of the piezoelectric electrophoretic membrane. In some embodiments, the thickness of electrode 2006 is less than 5 μm. In some embodiments, the thickness of electrode 2006 is between 1 and 3 μm.

[0215] In some embodiments, the electrophoretic material layer 2004 is fabricated on the electrode 2006 prior to bonding with the piezoelectric material 2002 and the electrode 2008. For example, the electrode 2006 may be coated with an electrophoretic dielectric layer comprising a plurality of microcapsules containing nonpolar fluid and charged pigment particles. Figure 20(Not shown in the image). Alternatively, an electrophoretic dielectric layer comprising multiple microcell structures can be formed on electrode 2006. For example, an imprintable microcell precursor material can be laminated to electrode 2006. Prior to lamination, the precursor material can be treated or coated with a microcell primer comprising, for example, acrylates, vinyl ethers, or epoxides, as detailed in U.S. Patents Nos. 6,930,818, 7,052,571, 7,616,374, 8,361,356, and 8,830,561, all of which are incorporated herein by reference in their entirety. The microcell precursor is microimprinted or photolithographically formed to create an open microcell structure, which is then filled with the desired electrophoretic dielectric and sealed with a sealing layer. Optionally, the open microcells can be cleaned / activated by steam plasma treatment before being filled with the desired electrophoretic dielectric.

[0216] In some embodiments, the thickness of the electrophoretic material layer 2004 is between 10 and 30 μm. In some embodiments, the thickness of the electrophoretic material layer 2004 is approximately 15 μm.

[0217] In some embodiments, electrode 2006 may be segmented (not shown). As a result, the change in gray tone caused by the movement of charged pigment particles in electrophoretic material layer 2004 will also appear segmented. Alternatively, electrode 2006 may comprise a single continuous sheet or film of conductive material, and the change in gray tone will appear continuous. It should be understood that all layers of display 2000 (e.g., layer 2002, layer 2004, layer 2006, layer 2008) may be made transparent, allowing display 2000 to be viewed in any orientation or from any direction.

[0218] In fact, the CR of the piezoelectric electrophoretic display 2000 can vary depending on the ratio of surface region 2020 (i.e., the surface region of the electrophoretic material layer 2004 that is overlapped or covered by the piezoelectric material 2002) to surface region 2021 (i.e., the surface region of the electrophoretic material layer 2004 that is overlapped or covered by the electrode 2008). The experimental results of CR are shown in Table 2 below.

[0219] Table 2. Ratio of CR to surface area of ​​the display

[0220]

[0221] As shown in Table 2, increasing the ratio of surface area 2020 to surface area 2021 can improve the display's CR. For example, the display CR increases from a value of 2 when the ratio of surface area 2020 to surface area 2021 is 1:2 to a value of 7 when the ratio is 2:1.

[0222] In some embodiments, an adhesive layer (not shown) is present between the piezoelectric material 2002 and the electrophoretic material layer 2004. In some embodiments, the resistivity of the adhesive layer is 10 Ω·cm. 2 ohm*cm to 10 8 ohm*cm, preferably less than 10 12 ohm*cm. In some embodiments, the resistivity of the adhesive layer is at least an order of magnitude greater than that of the electrodes. Therefore, the adhesive layer can have the resistivity properties of a semiconductor material or a high-resistance insulating material. In this configuration, the adhesive layer can act as a dielectric to prevent the piezoelectric material 2002 from rapidly dissipating locally generated charges, thereby improving the display's CR. Furthermore, it has been determined that reducing the width of electrode 2006 or electrode 2008 and applying physical stress perpendicularly to the longer side of electrode 2008 can further improve the display's CR.

[0223] Figure 21A This is an illustration based on the subject matter disclosed in this article. Figure 20 A schematic cross-section illustrating another property of the piezoelectric electrophoretic display 2000 shown. A first portion 2132 of the electrophoretic material layer 2004 overlaps with or is adjacent to the piezoelectric material 2002, and a second portion 2134 of the electrophoretic material layer 2004 overlaps with or is adjacent to the electrode 2008, as shown by dashed line 2122. Each of the first portion 2132 and the second portion 2134 has a resistance based on the volume of the electrophoretic material they contain. As indicated by the "+" and "-" symbols, a voltage has been generated by charge separation occurring within the piezoelectric material 2002, for example, in response to bending of the piezoelectric material 2002 or mechanical stress thereto.

[0224] Figure 21B This is an illustration based on the subject matter disclosed in this article. Figure 20 A perspective view of another property of the piezoelectric electrophoresis display 2000 shown. For ease of viewing, electrode 2006 is not shown. Figure 21B As shown in the image. From Figure 21B As can be seen, the first portion 2132 of the electrophoretic material layer 2004 overlaps with the piezoelectric material 2002 at or near the first surface region 2020 (depicted by dashed lines), and the second portion 2134 of the electrophoretic material layer 2004 overlaps with the second electrode 2008 at or near the second surface region 2021 (depicted by dashed lines).

[0225] Figure 22 The illustration illustrates the subject matter disclosed in this article. Figure 21A and 21B An exemplary equivalent circuit 2200 of the piezoelectric electrophoresis display 2000 shown is illustrated. Figure 21AThe three nodes or points shown, point 'A' near piezoelectric material 2002 and part 2132, point 'B' at electrode 1 2106, and point 'C' at electrode 2 2108, correspond to Figure 22 The same three points A, B, and C are shown in the equivalent circuit 2200. Resistor R1 corresponds to the resistance of the first portion 2132 of the electrophoretic material layer 2004, and resistor R2 corresponds to the resistance of the second portion 2134 of the electrophoretic material layer 2004.

[0226] piezoelectric material layer 2002 in Figure 22 The middle is represented as a battery, and the voltage V PZ This is the voltage generated by the piezoelectric material across points A and C. Resistors R1 and R2 are shown in series because the voltage source, existing only beneath a portion of the electrophoretic material layer 2004, effectively divides the layer into separate sections with different electrical properties (as shown by dashed line 2122). For example, when a voltage V has been generated... PZ At this point, the voltage potential at point A is higher than the voltage potential at points B or C. Using a conventional current flow paradigm, current 2201 flows from point A through resistor R1 to point B, and from point B through resistor R2 to point C. Therefore, the voltage generated across resistor R1 is opposite in polarity to the voltage generated across resistor R2. In fact, the series connection of the separated portions of the electrophoretic material layer 2004 generates two opposite voltages.

[0227] Figure 23 This is a schematic cross-sectional view of an exemplary piezoelectric electrophoretic display 2300 according to the subject matter disclosed herein. The configuration of the display 2300 is similar to... Figure 20 , 21A The configuration of the display 2000 shown in 21B. For example, the display 2300 includes a piezoelectric material 2302 that overlaps with or covers a first portion of the surface region of the electrophoretic material layer 2304, such as... Figure 23 The surface region 2320 is shown in the diagram. However, the display 2300 includes a dielectric layer 2330 overlapping all the piezoelectric materials 2302, and a second portion of the surface region of the electrophoretic material layer 2304, as shown in the diagram. Figure 23 The surface region 2321 is shown in the diagram. The electrodes 2308 of the display 2300 overlap with all dielectric layers 2330.

[0228] Dielectric layer 2330 can be similar to bonding Figure 20 The adhesive layer described in the display 2000. For example, the dielectric layer 2330 may be formed of a material having the resistivity properties of a semiconductor material or a high-resistivity insulating material. In some embodiments, the resistivity of the dielectric layer 2330 is 10. 2 ohm*cm to 10 8 ohm*cm, preferably less than 10 12ohm*cm.

[0229] The dielectric layer 2330 serves to prevent the rapid dissipation of charges generated by the piezoelectric material 2320, which would otherwise dissipate quickly if the piezoelectric material 2320 were in direct contact with the electrode 2308. This allows these charges to be applied more effectively and efficiently throughout the electrophoretic material layer 2304, thereby maximizing the movement of charged pigment particles, which in turn improves the display's CR (chromatic amplification).

[0230] Table 3 below illustrates a comparison of the resistivity (CR) achieved between various display designs. The first display, manufactured with the piezoelectric material at least partially overlapping or in contact with the two electrodes, achieved a CR of 1.7. As mentioned above, when the ratio of surface region 2020 to surface region 2021 is 2:1, the display 2000 achieves a CR of 7. In various configurations, when the resistivity of dielectric layer 2330 is approximately 10... 8 When ohm*cm, Figure 23 The monitor 2300 shown in the illustration exhibits a best contrast ratio of 18.

[0231] Table 3. Comparison of CR between monitor configurations

[0232]

[0233] It should be understood that all layers of the display 2300 can be made transparent, allowing the display 2300 to be viewed in any orientation or from any direction. It should also be noted that, according to... Figure 20-23 The display configuration illustrated in the figure establishes a conductive path between the electrodes, piezoelectric material, and electrophoretic material layers, eliminating the need for any additional conductors or contacts to operate the display. This advantageously reduces the overall thickness of the final piezoelectric electrophoretic display device while also increasing the display's CR ratio.

[0234] latent image

[0235] Displays manufactured according to the subject matter of this article can be used to display hidden images, or so-called "latent" images. In particular, images (e.g., shapes, text, barcodes, etc.) can be laminated or printed onto any of the electrodes of the display, such that the image is only visible when charged pigment particles move in response to voltage movement generated by bending the piezoelectric material or introducing other mechanical stresses into the piezoelectric material.

[0236] In some implementations, an image is printed or laminated onto one of the electrodes on a white background, and the display is viewed from the electrodes on the opposite side. When the display shows white (e.g., white pigment particles are located closest to the electrode on which no image is printed), the printed image is blurred or hidden. However, when the position of the pigment particles moves in response to mechanical stress on the piezoelectric material, the white pigment particles move away from the viewing surface, while pigment particles of another color (generally a darker color) move towards the viewing surface, thus displaying the image.

[0237] In another embodiment, the dark image is printed or laminated onto one of the electrodes without a background color, and the display is viewed again from the electrodes on the opposite side. In this embodiment, when the display is held in front of a dark or black background, the image remains essentially blurred or hidden regardless of whether the display is showing white or another color. However, when the display is held in front of a bright or white background, the image becomes visible. In this embodiment, the image becomes visible when the display shows white, but is more clearly visible when the display shows a darker color.

[0238] The piezoelectric electrophoretic display produced as described above can be fixed to low-profile objects, such as banknotes or banknotes. Therefore, the image can be integrated into the banknote, allowing users to easily distinguish genuine from counterfeit banknotes based on how the optical state of the display changes (or remains unchanged) when the banknote is bent or folded.

[0239] The display configuration described in this paper enables the manufacture of fully functional piezoelectric driven display devices with a thickness of less than 50 μm. Furthermore, the structure of the display described in this paper is greatly simplified, and the resulting display is more sensitive to smaller applied physical stresses.

[0240] Therefore, fabricating piezoelectric electrophoretic displays with the structure described herein offers advantages over conventional piezoelectric electrophoretic displays. For example, the piezoelectric electrophoretic display described herein provides an improved device for driving pigment particles with opposite charges in different directions within the electrophoretic medium without requiring individually addressable pixel electrode matrices. Thus, piezoelectric electrophoretic displays manufactured as described herein can be made thin enough for applications requiring durability and to be substantially inconspicuous when incorporated into thin, low-profile end products such as paper or banknotes, while still providing high contrast between different portions of the electrophoretic material layer due to the aforementioned effects.

[0241] It will be apparent to those skilled in the art that numerous changes and modifications can be made to the specific embodiments of the present invention described above without departing from the scope of the invention. Therefore, the entire description above should be interpreted in an illustrative rather than restrictive sense.

[0242] This disclosure provides the aspects and implementation methods set forth in the following terms:

[0243] Clause 1: An electrophoretic display film having a thickness of less than 100 μm (from top to bottom) comprises, in sequence: a first adhesive layer; an electrophoretic dielectric layer; a patterned piezoelectric layer including differentiated polarization regions; and a flexible transparent electrode layer.

[0244] Clause 2: The electrophoretic display film of Clause 1, wherein the electrophoretic dielectric layer comprises a plurality of microcapsules containing a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the patterned piezoelectric layer when the patterned piezoelectric layer is bent, wherein the microcapsules are bonded together with a polymer adhesive.

[0245] Clause 3: The electrophoretic display film of Clause 1, wherein the electrophoretic dielectric layer comprises a plurality of micro-units, the micro-units containing a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the patterned piezoelectric layer when the patterned piezoelectric layer is bent, wherein the nonpolar fluid and charged pigment particles are sealed in the micro-units by a sealing layer.

[0246] Clause 4: The electrophoretic display membrane of any one of Clauses 1-3, wherein the thickness of the electrophoretic display membrane is less than 50 μm.

[0247] Clause 5: The electrophoretic display film of any one of Clauses 1-4, wherein the patterned piezoelectric layer comprises polyvinylidene fluoride (PVDF).

[0248] Clause 6: The electrophoretic display film described in Clause 5, wherein the PVDF is polarized to produce differentially polarized regions.

[0249] Clause 7: The electrophoretic display film of any one of Clauses 1-6, wherein the flexible transparent electrode layer comprises a metal oxide containing tin or zinc.

[0250] Clause 8: The electrophoretic display membrane of any one of Clauses 1-6, wherein the flexible transparent electrode layer comprises poly(3,4-ethylenedioxythiophene) (PEDOT).

[0251] Clause 9: An electrophoretic display film assembly comprising a release sheet bonded to an electrophoretic display film as described in any one of Clauses 1-8, wherein the release sheet is bonded to a first adhesive layer.

[0252] Clause 10: The electrophoretic display film assembly of Clause 9 further includes a second adhesive layer bonded to the flexible transparent electrode layer, and a second release sheet bonded to the second adhesive layer.

[0253] Clause 11: A method of manufacturing an electrophoretic display film, comprising: bonding a polyvinylidene fluoride (PVDF) film to a polymer film comprising an acrylate, a vinyl ether, or an epoxide to produce a piezoelectric microcell precursor film; bonding the piezoelectric microcell precursor film to a flexible light-transmitting electrode layer; bonding the light-transmitting electrode layer to a first release film using a first adhesive layer; imprinting the piezoelectric microcell precursor film to produce an array of microcells, wherein the microcells have a bottom, a wall, and a top opening; filling the microcells through the top opening with an electrophoretic medium; and sealing the top opening of the filled microcells with a water-soluble polymer to produce an electrophoretic medium layer.

[0254] Clause 12: The method described in Clause 11 further includes applying a primer to the polymer film comprising an acrylate, a vinyl ether, or an epoxide prior to bonding the polymer film to the polyvinylidene fluoride (PVDF) film.

[0255] Clause 13: The method described in Clause 11 or 12 further includes bonding a water-soluble polymer to a second release film using a second adhesive layer.

[0256] Clause 14: The method of any one of Clauses 11-13 further includes removing the first release film to produce an electrophoretic display film with a thickness of less than 100 μm.

[0257] Clause 15: The method of any one of Clauses 11-14, wherein the electrophoretic dielectric layer comprises a plurality of microunits containing nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer of the piezoelectric microunit precursor film when the piezoelectric layer is bent.

[0258] Clause 16: The method of any one of Clauses 11-15, wherein the PVDF is polarized to produce a differential polarization region.

[0259] Clause 17: The method of any one of Clauses 11-16, wherein the flexible transparent electrode layer comprises a metal oxide containing tin or zinc.

[0260] Clause 18: The method of any one of Clauses 11-16, wherein the flexible transparent electrode layer comprises poly(3,4-ethylenedioxythiophene) (PEDOT).

[0261] Clause 19: The method of any one of Clauses 11-18, wherein the polyvinylidene fluoride membrane is patterned with an electric field to produce differentially polarized regions.

[0262] Clause 20: The method of any one of Clauses 11-18 further includes patterning the completed electrophoretic display film with an electric field to create differentiated polarization regions in the polyvinylidene fluoride film.

[0263] Clause 21: A method for manufacturing a piezoelectric electrophoretic display, the method comprising: depositing a first conductive adhesive on a first substrate; and depositing a piezoelectric material comprising a polyvinylidene fluoride (PVDF) solution on the first conductive adhesive to produce a thickness of less than 5 mm. A piezoelectric layer of μm thickness is formed; a mask is applied to the piezoelectric layer, the mask comprising a plurality of masking portions shielding a first plurality of regions of the piezoelectric layer and a plurality of unmasked portions leaving a second plurality of regions of the piezoelectric layer unshielded; the piezoelectric layer is polarized to generate a plurality of polarized portions of piezoelectric material corresponding to the second plurality of regions of the piezoelectric layer and a plurality of unpolarized portions of piezoelectric material corresponding to the first plurality of regions of the piezoelectric layer; the mask is removed from the piezoelectric layer; the piezoelectric layer is bonded to a microcell precursor material; the microcell precursor material is imprinted to generate a microcell layer, wherein the microcell has a bottom, a wall, and a top opening; the microcell is filled with an electrophoretic medium through the top opening; the top opening of the filled microcell is sealed with a water-soluble polymer to generate a sealing layer; a second conductive adhesive is deposited on a second substrate; and the sealing layer is bonded to the second conductive adhesive.

[0264] Clause 22: The method described in Clause 21 further includes combining a polymer film comprising an acrylate, a vinyl ether, or an epoxide to produce a micro-unit precursor material.

[0265] Clause 23: The method described in Clause 21 or 22 further includes applying a primer to the microcell precursor material prior to bonding the piezoelectric layer to the microcell precursor material.

[0266] Clause 24: The method of any one of Clauses 21-23 further comprises activating the microcells by steam plasma treatment prior to filling the microcells with the electrophoretic medium.

[0267] Clause 25: The method of any one of Clauses 21-24, wherein the electrophoretic dielectric layer comprises a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer is subjected to mechanical stress, wherein the nonpolar fluid and charged pigment particles are sealed in the microcell by a sealing layer.

[0268] Clause 26: The method of any one of Clauses 21-25, wherein the piezoelectric layer is polarized by an electric field.

[0269] Clause 27: The method described in Clause 26, wherein the electric field is provided by corona discharge.

[0270] Clause 28: The method of any one of Clauses 21-27, wherein the first substrate and the second substrate are release films.

[0271] Clause 29: The method described in Clause 28 further includes: peeling the second substrate from the second conductive adhesive; and bonding the second conductive adhesive to the target object.

[0272] Clause 30: The method described in Clause 29, wherein bonding the second conductive adhesive to the target object includes heat-pressing the second conductive adhesive onto the target object.

[0273] Clause 31: The method described in Clause 29 further includes: peeling the first substrate from the first conductive adhesive; and applying a protective coating to the remaining layers of the piezoelectric electrophoretic display and the target object.

[0274] Clause 32: The method described in Clause 31, wherein the protective coating includes paint.

[0275] Clause 33: The method of any one of Clauses 29-32, wherein the target object includes one of paper, banknotes, and banknotes.

[0276] Clause 34: A method for manufacturing a piezoelectric electrophoretic display, the method comprising: depositing a piezoelectric material comprising a polyvinylidene fluoride (PVDF) solution onto a temporary substrate to produce a thickness less than 5 mm. A piezoelectric layer of μm thickness is formed; the piezoelectric layer is bonded to a first substrate using a first conductive adhesive, wherein a temporary substrate is removed from the piezoelectric layer during the bonding process; a mask is applied to the piezoelectric layer, the mask comprising a plurality of masking portions shielding a first plurality of regions of the piezoelectric layer and a plurality of unmasked portions leaving a second plurality of regions of the piezoelectric layer unmasked; the piezoelectric layer is polarized to generate a plurality of polarized portions of piezoelectric material corresponding to the second plurality of regions of the piezoelectric layer and a plurality of unpolarized portions of piezoelectric material corresponding to the first plurality of regions of the piezoelectric layer; the mask is removed from the piezoelectric layer; a second conductive adhesive is deposited onto a second substrate; the second conductive adhesive is bonded to a microcell precursor material; the microcell precursor material is imprinted to generate a microcell layer, wherein the microcell has a bottom, a wall, and a top opening; the microcell is filled with an electrophoretic medium through the top opening; the top opening of the filled microcell is sealed with a water-soluble polymer to generate a sealing layer; and the sealing layer is bonded to the piezoelectric layer.

[0277] Clause 35: The method described in Clause 34 further includes combining a polymer film comprising acrylate, vinyl ether, or epoxide to produce the microunit precursor material.

[0278] Clause 36: The method described in Clause 35 further includes applying a primer to the microcell precursor material before bonding the second conductive adhesive to the microcell precursor material.

[0279] Clause 37: The method of any one of Clauses 34-36 further comprises activating the microcells by steam plasma treatment prior to filling the microcells with an electrophoretic medium.

[0280] Clause 38: The method of any one of Clauses 34-37, wherein the electrophoretic dielectric layer comprises a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric layer when the piezoelectric layer is subjected to mechanical stress, wherein the nonpolar fluid and charged pigment particles are sealed in the microcell by a sealing layer.

[0281] Clause 39: The method of any one of Clauses 34-38, wherein the piezoelectric layer is polarized by an electric field.

[0282] Clause 40: The method described in Clause 39, wherein the electric field is provided by corona discharge.

[0283] Clause 41: The method of any one of Clauses 34-40, wherein the first substrate and the second substrate are release films.

[0284] Clause 42: The method described in Clause 41 further includes: peeling the second substrate from the second conductive adhesive; and bonding the second conductive adhesive to the target object.

[0285] Clause 43: The method of Clause 42, wherein bonding the second conductive adhesive to the target object includes heat-pressing the second conductive adhesive onto the target object.

[0286] Clause 44: The method described in Clause 42 further includes: peeling the first substrate from the first conductive adhesive; and applying a protective coating to the remaining layers of the piezoelectric electrophoretic display and the target object.

[0287] Clause 45: The method described in Clause 44, wherein the protective coating includes paint.

[0288] Clause 46: The method of any one of Clauses 42-45, wherein the target object includes one of paper, banknotes, and banknotes.

[0289] Clause 47: A method for manufacturing a piezoelectric electrophoretic display, the method comprising: depositing a first conductive material on a first substrate to form a first electrode; bonding the first electrode to a first surface of an electrophoretic material layer; depositing a piezoelectric material on a second surface of the electrophoretic material layer, wherein the piezoelectric material overlaps with a first surface region of the second surface of the electrophoretic material layer; and depositing a second conductive material to form a second electrode, wherein the second electrode is formed to overlap with all piezoelectric materials and a second surface region of the second surface of the electrophoretic material layer.

[0290] Clause 48: The method of Clause 47, wherein the electrophoretic material layer comprises: a first portion of electrophoretic material overlapping a first surface region; and a second portion of electrophoretic material overlapping a second surface region.

[0291] Clause 49: The method of Clause 48, wherein the first portion of the electrophoretic material includes a first resistor, and the second portion of the electrophoretic material includes a second resistor.

[0292] Clause 50: The method described in Clause 49, wherein the values ​​of the first resistor and the second resistor are based on the ratio of the first surface region to the second surface region.

[0293] Clause 51: The method described in Clause 49 or 50, wherein applying mechanical stress to the piezoelectric material generates a first voltage across a first portion of the electrophoretic material and a second voltage across a second portion of the electrophoretic material, wherein the first voltage and the second voltage have opposite polarities.

[0294] Clause 52: The method of Clause 47, wherein the electrophoretic material layer comprises: a first portion of electrophoretic material having a first resistance corresponding to a first volume of electrophoretic material overlapping a first surface region; and a second portion of electrophoretic material having a second resistance corresponding to a second volume of electrophoretic material overlapping a second surface region.

[0295] Clause 53: The method described in Clause 52, wherein the values ​​of the first resistor and the second resistor are based on the ratio of the first surface region to the second surface region.

[0296] Clause 54: The method described in Clause 52 or 53, wherein applying mechanical stress to the piezoelectric material generates a first voltage across a first portion of the electrophoretic material and a second voltage across a second portion of the electrophoretic material, wherein the first voltage and the second voltage have opposite polarities.

[0297] Clause 55: The method of any one of Clauses 52-54, wherein the combination comprises: coating a first electrode with a microcell precursor material; imprinting the microcell precursor material to produce a microcell layer, wherein the microcell has a bottom, a plurality of walls and a top opening; filling the microcell through the top opening with an electrophoretic medium; and sealing the top opening of the filled microcell with a water-soluble polymer to produce a sealing layer.

[0298] Clause 56: The method described in Clause 55 further includes applying a primer to the microcell precursor material before imprinting the microcell precursor material.

[0299] Clause 57: The method described in Clause 56 further includes activating the microcells by steam plasma treatment prior to filling the microcells with the electrophoretic medium.

[0300] Clause 58: The method of any one of Clauses 55-57, wherein the electrophoretic medium comprises a nonpolar fluid and charged pigment particles, wherein the charged pigment particles move toward or away from the piezoelectric material when the piezoelectric material is subjected to mechanical stress, wherein the nonpolar fluid and charged pigment particles are sealed in a microcell by a sealing layer.

[0301] Clause 59: The method of any one of Clauses 55-58, further comprising applying an adhesive material layer between a first surface region of the second surface of the piezoelectric material and the electrophoretic material layer, wherein the adhesive material layer has 10 2 ohm*cm to 10 12 Resistivity in ohm*cm.

[0302] Clause 60: The method of any one of Clauses 55-59 further comprises applying an adhesive material layer between a first surface region of the second surface of the piezoelectric material and the electrophoretic material layer, wherein the adhesive material layer has a resistivity at least one order of magnitude greater than that of the first and second electrodes.

[0303] Clause 61: The method of any one of Clauses 55-60 further includes depositing a dielectric layer prior to depositing the second conductive material, wherein the dielectric layer is formed to overlap a second surface region of the second surface of all piezoelectric and electrophoretic material layers, and wherein the second electrode is formed to overlap all dielectric layers.

[0304] Clause 62: The method of Clause 61, wherein the dielectric layer has 10 2 ohm*cm to 10 12 Resistivity in ohm*cm.

[0305] Clause 63: The method of Clause 61, wherein the dielectric layer has a resistivity at least one order of magnitude greater than that of the first electrode and the second electrode.

[0306] Clause 64: The method of any one of Clauses 55-63 further includes printing one or more images onto at least one of the first electrode and the second electrode.

[0307] Clause 65: The method of any one of Clauses 55-64 further includes attaching the piezoelectric display to a target object selected from paper, banknotes, and banknotes.

Claims

1. A method for manufacturing a piezoelectric electrophoretic display, the method comprising: depositing a first conductive adhesive on a first substrate; depositing a piezoelectric material comprising a polyvinylidene fluoride (PVDF) solution on the first conductive adhesive to produce a piezoelectric layer having a thickness of less than 5 μιη; applying a mask to the piezoelectric layer, the mask comprising a plurality of masked portions that shield a first plurality of regions of the piezoelectric layer and a plurality of unmasked portions that leave a second plurality of regions of the piezoelectric layer unshielded; polarizing the piezoelectric layer to produce a plurality of polarized portions of the piezoelectric material corresponding to the second plurality of regions of the piezoelectric layer and a plurality of unpolarized portions of the piezoelectric material corresponding to the first plurality of regions of the piezoelectric layer; removing the mask from the piezoelectric layer; bonding the piezoelectric layer to a microcell precursor material; imprinting the microcell precursor material to produce a microcell layer, wherein the microcells have a bottom, a wall, and a top opening; filling the microcells through the top openings with an electrophoretic medium; capping the top openings of the filled microcells with a water-soluble polymer to produce a sealing layer; depositing a second conductive adhesive on a second substrate; and bonding the sealing layer to the second conductive adhesive.

2. The method of claim 1, further comprising bonding a polymer film comprising an acrylate, a vinyl ether, or an epoxide to produce the microcell precursor material.

3. The method of claim 2, further comprising applying a primer to the microcell precursor material prior to bonding the piezoelectric layer to the microcell precursor material.

4. The method of claim 1, further comprising activating the microcells with a vapor plasma treatment prior to filling the microcells with the electrophoretic medium.

5. The method of claim 1, wherein the electrophoretic medium layer comprises a nonpolar fluid and charged pigment particles that move toward or away from the piezoelectric layer when the piezoelectric layer is subjected to mechanical stress, wherein the nonpolar fluid and charged pigment particles are sealed in the microcells with the sealing layer.

6. The method of claim 1, wherein the piezoelectric layer is polarized with an electric field.

7. The method of claim 6, wherein the electric field is provided by a corona discharge.

8. The method of claim 1, wherein the first and second substrates are release films.

9. The method of claim 8, further comprising: peeling the second substrate from the second conductive adhesive; and bonding the second conductive adhesive to a target object.

10. The method of claim 9, wherein bonding the second conductive adhesive to a target object comprises hot stamping the second conductive adhesive to a target object.

11. The method of claim 9, further comprising: peeling the first substrate from the first conductive adhesive; and applying a protective coating over the remaining layers of the piezoelectric electrophoretic display and the target object.

12. The method of claim 11, wherein the protective coating comprises a lacquer.

13. The method of claim 9, wherein the target object comprises one of a paper, a banknote, and a currency note.

14. A method for manufacturing a piezoelectric electrophoretic display, the method comprising: depositing a piezoelectric material comprising a solution of polyvinylidene fluoride (PVDF) onto a temporary substrate to produce a piezoelectric layer having a thickness of less than 5 μm; bonding the piezoelectric layer to a first substrate with a first conductive adhesive, wherein the temporary substrate is removed from the piezoelectric layer during bonding; applying a mask to the piezoelectric layer, the mask comprising a plurality of masked portions that shield a first plurality of regions of the piezoelectric layer and a plurality of unmasked portions that leave a second plurality of regions of the piezoelectric layer unshielded; polarizing the piezoelectric layer to produce a plurality of polarized portions of piezoelectric material corresponding to the second plurality of regions of the piezoelectric layer and a plurality of unpolarized portions of piezoelectric material corresponding to the first plurality of regions of the piezoelectric layer; removing the mask from the piezoelectric layer; depositing a second conductive adhesive onto a second substrate; bonding the second conductive adhesive to a microcell precursor material; imprinting the microcell precursor material to produce a microcell layer, wherein the microcells have a bottom, a wall, and a top opening; filling the microcells through the top opening with an electrophoretic medium; capping the top opening of the filled microcells with a water-soluble polymer to produce a sealing layer; and bonding the sealing layer to the piezoelectric layer.

15. The method of claim 14, further comprising bonding a polymer film comprising an acrylate, a vinyl ether, or an epoxide to produce the microcell precursor material.

16. The method of claim 15, further comprising applying a priming agent to the microcell precursor material prior to bonding the second conductive adhesive to the microcell precursor material.

17. The method of claim 14, further comprising activating the microcells with a vapor plasma treatment prior to filling the microcells with the electrophoretic medium.

18. The method of claim 14, wherein the electrophoretic medium layer comprises a non-polar fluid and charged pigment particles that move toward or away from the piezoelectric layer when the piezoelectric layer is subjected to mechanical stress, wherein the non-polar fluid and charged pigment particles are sealed in the microcells with the sealing layer.

19. The method of claim 14, wherein the piezoelectric layer is polarized with an electric field.

20. The method of claim 19, wherein the electric field is provided by a corona discharge.

21. The method of claim 14, wherein the first substrate and the second substrate are release films.

22. The method of claim 21, further comprising: peeling the second substrate from the second conductive adhesive; and bonding the second conductive adhesive to a target object.

23. The method of claim 22, wherein bonding the second conductive adhesive to a target object comprises hot stamping the second conductive adhesive to the target object.

24. The method of claim 22, further comprising: peeling the first substrate from the first conductive adhesive; and applying a protective coating over the remaining layers of the piezoelectric electrophoretic display and the target object.

25. The method of claim 24, wherein the protective coating comprises a lacquer.

26. The method of claim 22, wherein the target object comprises one of a paper, a banknote, and a currency bill. ​ ​ ​

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