WO2019232207A1

WO2019232207A1 - Apparatus for low power reflective image displays

Info

Publication number: WO2019232207A1
Application number: PCT/US2019/034650
Authority: WO
Inventors: Frank W. J. CHRISTIAENS
Original assignee: Clearink Displays, Inc.
Priority date: 2018-05-30
Filing date: 2019-05-30
Publication date: 2019-12-05
Also published as: CN112292636A

Abstract

Electrophoretic displays that are capable of operating at low voltages to move electrophoretically mobile particles may be driven by a low power apparatus. The apparatus may comprise Memory-In-Chip (MIP) technology to enhance or create image stability. MIP may comprise a 1-bit memory SRAM or DRAM circuit located in one or more pixels in a TFT array backplane.

Description

APPARATUS FOR LOW POWER REFLECTIVE IMAGE DISPLAYS

The disclosure claims priority to U.S. Provisional Application Serial No. 62/678,196, filed May 30, 2018 (titled“Apparatus for Low Power Reflective Image Displays”), the specification of which is incorporated herein in its entirety.

Field

The disclosure is directed to an apparatus for reflective image displays. The disclosed embodiments generally relate to the use of Memory -in-Pixel technology in electrophoretic-based displays. In one embodiment, the disclosure relates to an apparatus for low power consumption electrophoretic-based image displays comprising a l-bit SRAM circuit or a l-bit DRAM circuit.

BACKGROUND

Conventional reflective electrophoretic displays (EPDs) comprise, among others, one or more electrophoretically mobile particles suspended in an air or liquid medium located between two or more electrodes. The electrophoretically mobile particles may be moved by application of a voltage bias between opposing electrodes and across the medium to create images or text to convey information to a viewer. Conventional EPD-based reflective image displays may have image stability. Image stability in EPDs is the ability to retain an image when the power is turned off to the display. The level of image stability may be engineered to different degrees ranging from minutes to days to weeks. Increased image stability in EPDs typically leads to decreased power consumption and increased battery life.

BRIEF DESCRIPTION OF DRAWINGS

These and other embodiments of the disclosure will be discussed with reference to the following exemplary and non-limiting illustrations, in which like elements are numbered similarly, and where:

Fig. 1 schematically illustrates one embodiment of an apparatus for low power EPD-based reflective image displays;

Fig. 2 illustrates an embodiment of a microencapsulated reflective image display comprising a memory circuit;

Fig. 3A schematically illustrates an embodiment total internal reflection-based reflective image display comprising a memory circuit; Fig. 3B schematically illustrates a cross-section of a portion of a TIR-based display comprising a memory circuit showing the approximate location of the evanescent wave region;

Fig. 3C schematically illustrates a cross-section of a portion of an overhead view of a TIR- based reflective image display comprising a memory circuit;

Fig. 4 schematically illustrates an embodiment of a microcup-based reflective image display comprising a memory circuit; and

Fig. 5 schematically illustrates an exemplary system for implementing an embodiment of the disclosure.

DETAILED DESCRIPTION

Throughout the following description specific details are set forth in order to provide a more thorough understanding to persons skilled in the art. However, well-known elements may not have been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings are to be regarded in an illustrative, rather than a restrictive or exclusive, sense.

This disclosure generally relates to EPD-based reflective image displays. According to certain embodiments of the disclosure, an EPD-based reflective image may remain substantially stable by using Memory-in-Pixel (MIP) technology. Image stability means that the image continues to be displayed even when the power source (this is typically the case only if there is inherent stability in the electrophoretic ink material itself) is removed from the display module or when the display image does not require constant updating by the surrounding electronic drivers. The MIP technology can store a l-bit value locally at the pixel (on/off state). This can save power since the switching material (such as electrophoretic ink) can be refreshed locally instead of always scanning the display with the image data during every frame of a video. The display may consume nearly zero power in this state.

In an exemplary embodiment, an apparatus to drive static and video images for EPD-based reflective image displays may comprise MIP technology. The apparatus may include a backplane comprising an array of pixels. Each pixel may comprise a thin film transistor (TFT) and further comprise a memory element to drive displays for static images, video data, driving voltages and waveforms. The MIP technology may comprise one or more of a static random access memory (SRAM) circuit or a dynamic random access memory (DRAM) circuit. The rear electrode in an EPD-based reflective image display may comprise a l-bit SRAM circuit or a 1- bit DRAM circuit. The waveforms may comprise one or more of various driving voltages of differing magnitudes, charge polarities or durations of time at which the voltages may be applied.

Fig. 1 schematically illustrates one embodiment of an apparatus for low power EPD-based reflective image displays. Apparatus may be used to drive an EPD-based reflective image display. Apparatus 100 may comprise a backplane. Backplane 102 may further comprise an array of pixels 104 arranged in columns or rows. For example, pixel Pl, Ll is pixel 1 in line 1. For illustrative purposes, backplane 102 in Fig. 1 comprises 96 columns of pixel and 96 lines of pixels (only a few are shown in embodiment 100 for clarity). Other backplanes of fewer or more pixels and lines may be used. Pixels 104 may be arranged on a support sheet comprising glass, metal or a polymer. Each pixel may comprise at least one TFT. In an exemplary embodiment, one or more pixels may comprise a memory circuit 106. This is illustrated in blow-up view 108 of a single pixel (P96, Ll). Memory circuit 106 may be capable of storing one or more bits of pixel data.

For illustrative purposes, backplane 102 further comprises RAM (random access memory) 106. RAM 106 may be present in at least one pixel as shown in Fig. 1. RAM 106 may comprise a static random access memory (SRAM) circuit. In one embodiment, the SRAM circuit may comprise four transistors where each bit is stored with additional two transistors to control the access to a storage cell forming a six transistor SRAM. In other embodiments, SRAM chips may comprise 8, 10, 12 or more transistors per chip. RAM 106 may comprise at least a l-bit static random access memory (SRAM) circuit. Each bit may be capable of two values of 0 or 1.

RAM 106 may comprise a dynamic random access memory (DRAM) circuit. In one embodiment, a DRAM circuit may comprise at least one capacitor and at least one transistor per bit of data. Memory circuit 106 may comprise at least a l-bit dynamic random access memory (DRAM) circuit. Each bit may be capable of two values of 0 or 1.

SRAM or DRAM memory circuits may be able to store information once it is written.

This may allow designs of products leading to ultra-low power consumption and long battery life. The embedded pixel memory circuit may store graphic data, thus no continuous refresh for SRAM memory circuits may be required for a still image. In some embodiments, DRAM may require a refresh every time the pixel is driven. In other embodiments, the DRAM circuit may further comprise an output buffer to isolate the memory circuit from the pixel electrode. The additional output buffer may further comprise a TFT and a capacitor. Further, in changing images such as in video, each pixel in the display saves the image information so the image only must be rewritten in the pixels where the content has changed. This is commonly referred to as MIP technology. MIP technology typically requires lower operating voltages. Conventional reflective e- paper technology commercialized by E Ink Corporation is unable to utilize MIP technology due to the higher operating voltages required (-15V) to operate the display. Other reflective display technologies are required to use even higher voltages of up to about 80 V to operate the display. These conventional reflective display technologies are thus unable to utilize MIP technology. In some embodiments, MIP technology can be used in combination with reflective image display technologies that may be driven in the 0.1-10V range. In other embodiments, MIP technology may be used in combination with reflective image display technologies that may be driven in the 1-10V range. In still other embodiments, MIP technology may be used in combination with reflective image display technologies that may be driven in the 5-10V range. In still other embodiments, MIP technology may be used in combination with reflective image display technologies that may be driven in the 0.1-5V range. This is an important advantage of low voltage EPD-based displays over other higher operating voltage reflective display technologies as this may allow for low power EPD reflective displays to be used in, for example, electronic shelf labels (ESLs), eReaders, and IoT-based devices.

The addition of MIP technology improves image stability in EPD-based image displays.

As stated, image stability occurs when an image is maintained even after when the power is turned off or set to 0V. Image stability may be created by using chemical or physical phenomena, such as Van der Waals, ionic or other intermolecular forces. MIP technology may be used in combination with the mentioned intermolecular forces to create or improve low power performance in EPD-based reflective image displays.

Apparatus 100 may further comprise one or more memory gate lines 110, one or more signal lines 112 or one or more ink drivers 114. Ink driver 114 may provide isolation between the memory circuit and the pixel electrode. Memory gate lines 110 and signal lines 112 electrically link the pixels within array 104. Apparatus 100 may further comprise a common electrode (VCOM) 116 that provides a polarity inversion signal that drives the common front electrode and pixel cell 118 driven by the rear TFT electrodes in the pixels. In an exemplary embodiment, pixel cell 118 comprises anything between the front electrode and rear electrode in an electrophoretic display. Pixel cell 118 comprises an electrophoretic ink (may also be referred to as a suspension) that modulates the reflected light. The ink may comprise an air or liquid medium and a plurality of electrophoretically mobile particles. In some embodiments, pixel cell 118 may comprise an electro wetting system. The electro wetting system may further comprise an electrophoretically mobile polar fluid and non-polar fluid wherein one of the fluids comprises a color (wherein the color may be formed from a dye or pigment). Pixel cell 118 may also comprise one or more dielectric layers or microcup walls.

In an exemplary embodiment, electronic paper technology utilizing one or more pluralities of electrophoretically mobile particles in microcapsules in a liquid or air medium may be driven by MIP-based technology at operating voltages in the range of about 0.1-10V. The one or more electrophoretically mobile particles may comprise a first plurality of particles with a positive charge polarity of a first color and a second plurality of particles comprising negative charge polarity of a second color that differs from the color of the first plurality of particles. In other embodiments, the pluralities of particles in EPDs comprising MIP technology may comprise different charge magnitudes, electrophoretic mobilities and colors.

Fig. 2 illustrates an embodiment of a microencapsulated reflective image display comprising a memory circuit. Microencapsulated reflective image display embodiment 200 comprises a transparent front sheet 202 with outer surface 204 facing viewer 206. Front sheet 202 may be comprised of glass or polymer. Display 200 may further comprise rear support sheet 208. Sheet 208 may comprise one or more of a polymer, glass or metal. Front sheet 202 and rear sheet 208 may form a gap therebetween 210.

Fig. 2 may represent an exemplary embodiment of a pixel. That is, a pixel may be considered to include front sheet 202 to rear sheet 208 an everything in between (e.g., front electrode 222, adhesive 220, microcapsule 212, particles 214, 216, medium 218, rear electrode 224 and optionally rear electrode 208).

A layer of a plurality of microcapsules 212 are located within gap 210. Microcapsules 212 may comprise a polymer-based shell. In one embodiment, microcapsules 212 may comprise a first plurality 214 of charged, electrophoretically mobile particles of a first color (represented as black particles in Fig. 2) and a second plurality 216 of oppositely charged electrophoretically mobile particles of a second color (represented as white particles in Fig. 2) in a liquid or air medium 218. In some embodiments, additional pluralities of particles of different colors may be present comprising different electrophoretic mobilities. In some embodiments, particles 214,

216 may comprise an inorganic material, such as a metal oxide, or an organic material. In other embodiments, particles 214, 216 may comprise a combination of organic and inorganic material. In an exemplary embodiment, one of the pluralities of particles 214, 216 may comprise TiCh. In an exemplary embodiment, one of the pluralities of particles 214, 216 may comprise copper chromate (CuCrCri), carbon black, or FeiC

In an exemplary embodiment, medium 218 may be a substantially transparent liquid. Medium 218 may further comprise one or more of charge control agents, surfactants or viscosity modifiers. Medium 218 may comprise a hydrocarbon-based liquid. In some embodiments, medium 218 may comprise a dye. In an exemplary embodiment, medium 218 may comprise a dye and a plurality of electrophoretically mobile particles of one charge polarity and color. In an exemplary embodiment, polyisobutylene may be used as a viscosity modifier. In an exemplary embodiment, microcapsules 212 may be adhered together in a layer using an adhesive 220.

Display 200 in Fig. 2 comprises a transparent front electrode layer 222. In an exemplary embodiment, front electrode 222 is located on the inner surface of front sheet 202. Front electrode may be comprised of one or more of indium tin oxide (ITO), metal nanowires in a polymeric matrix or a conducting polymer such as BAYTRON™.

Display 200 further comprises a rear electrode layer 224. Rear electrode 224 may comprise an active matrix array of thin film transistors (TFTs), a passive matrix array of electrodes or a direct drive array of pixelated electrodes. Display 200 may further comprise a voltage bias source 226. Bias source 226 may provide a bias between front electrode 222 and rear electrode 224 across gap 210. A bias across gap 226 may move the charged

electrophoretically mobile particles 214, 216 to the front or rear electrodes. Movement of the particles 214, 216 in various combinations to the front electrode 222 in display 200 may be used to form images or text observed by viewer 206. In an exemplary embodiment, display 200 may be driven in the range of about 0.1-10V.

In an exemplary embodiment, rear electrode 224 in display 200 comprises backplane electronics embodiment 100 described in Fig. 1. Layer 224 may comprise a SRAM or DRAM circuit as previously described herein. In an exemplary embodiment, layer 224 may comprise a l-bit SRAM circuit or a l-bit DRAM circuit as previously described herein.

In some embodiments, display 200 may further comprise a directional front light system 228. Front light system may further comprise light source 230 and waveguide 232. Light source 230 injects light into waveguide 232. Waveguide 232 may further comprise light extractor units (not shown) to extract light from the waveguide and direct the light towards the layer of microcapsules 212.

In some embodiments, display 200 may comprise an ambient light sensor (ALS) or front light controller 236. In dim lighting conditions, ALS 234 may detect low light and send a signal to front light controller 236 to increase power to light source 230 to increase emitted light from waveguide 232. In bright lighting conditions, ALS 234 may detect a high level of light and send a signal to front light controller 236 to decrease power to light source 230 to decrease emitted light from waveguide 232. In some embodiments, display 200 may comprise at least one dielectric layer on one or both of the front electrode 222 or rear electrode 224. In some embodiments, the dielectric layer may be a polymer such as parylene, halogenated parylene or polyimide. In other embodiments, the dielectric layer may be a nitride such as SiN_x or a metal oxide such as one or both of AI2O3 or SiC .

Fig. 3A illustrates an embodiment of a total internal reflection-based reflective image display comprising a memory circuit. Total internal reflection (TIR) based reflective display 300 comprises a transparent front sheet 302 with outer surface 304 facing viewer 306. Display 300 further comprises a layer of a plurality 308 of individual convex protrusions 310, rear support sheet 312, a transparent front electrode 314 on the surface of the plurality of convex protrusions 308 and a rear electrode 316. In some embodiments, protrusions 310 may be hemispherical or semi-hemispherical shaped. Protrusions may be arranged in a close-packed array. In an exemplary embodiment, protrusions 310 may have a refractive index in the range of about 1.5- 2 2

Rear electrode 316 may comprise a passive matrix array of electrodes, a thin film transistor (TFT) array or a direct drive array of electrodes. The rear array of electrodes may be formed in an array of pixels. Fig. 3 A also shows low refractive index medium 318 which is disposed within cavity or gap 320 formed between the surface of protrusions 308 and rear support sheet 312. Medium 318 may be an air or a liquid. In some embodiments, medium 318 may comprise a fluorinated liquid. In an exemplary embodiment, medium 318 may have a refractive index in the range of about 1-1.5. In an exemplary embodiment, the refractive index of protrusions 310 is greater than the refractive index of medium 318. Medium 318 contains a plurality of light absorbing electrophoretically mobile particles 322 as previously described herein. In some embodiments, medium 318 contains a first plurality of electrophoretically mobile particles of a first charge and color and a second plurality of electrophoretically mobile particles of an opposite charge and second color. In other embodiments, a second plurality of particles may be contained in the medium hat are not electrophoretically mobile.

Display 300 may further include a voltage source 324 capable of creating a bias across cavity 320. Display 300 may further comprise one or more dielectric layers 326, 328 on front electrode 314 or rear electrode 316 or on both the front and rear electrodes, and a color filter layer 330. In some embodiments, dielectric layer 326, 328 may be a polymer such as parylene, halogenated parylene or polyimide. In other embodiments, the dielectric layer may be a nitride such as SiNx or a metal oxide such as one or both of AI2O3 or SiCh. In Fig. 3A, color filter layer 330 is located between sheet 302 and convex protrusion layer 308. Color filter layer 330 may also be located on the outer surface 304 of sheet 302 facing viewer 306. Adding a color filter array (CFA) layer over the front surface of the display is a conventional method to transform a black and white reflective display into a full color display.

A color filter layer typically comprises one or more sub-pixel color filters. Sub-pixel color filters may comprise one or more colors of red, green, blue, white, black, clear, cyan, magenta or yellow. The sub-pixel color filters are typically grouped into two or more colors and arrayed in a repeatable pattern. The repeatable pattern makes up a pixel such as, for example, RGB (red- green-blue) sub-pixels or RGBW (red-green-blue-white) sub-pixels. For illustrative purposes, a portion of TIR-based display 300 in Fig. 3A comprises color filter layer 330, further comprising a red sub-pixel color filter 332, a green sub-pixel color filter 334 and a blue sub-pixel color filter 336. Other sub-pixel color filter combinations may be used. In an exemplary embodiment, a sub-pixel color filter may be aligned with a pixel cell which may further be aligned with a single TFT wherein the pixel cell further comprises a memory circuit.

Protrusions 310 and medium 318 may have different refractive indices that may be characterized by a critical angle 9_C. The critical angle characterizes the interface between the surface of the protrusions 310 (with refractive index hί) and the low refractive index medium 318 (with refractive index ). Light rays incident upon the interface at angles less than 0_C may be transmitted through the interface. Light rays incident upon the interface at angles greater than 0c may undergo TIR at the interface. A small critical angle (e.g, less than about 50°) is preferred at the TIR interface since this affords a large range of angles over which TIR may occur. It may be prudent to have a fluid medium 318 with preferably as small a refractive index (1/3) as possible and to have protrusions composed of a material having a refractive index (1/1) preferably as large as possible. The critical angle, 6_C, is calculated by the following equation (Eq. 1):

When particles 322 are electrophoretically moved towards front electrode 314 near the interface of high refractive index protrusions 310 and low refractive index medium 318, they enter into a location so called the“evanescent wave region”. In this location, particles 322 may frustrate TIR. The depth of the evanescent wave region can be typically about 0.25 Dm, though this can vary with wavelength of incident light and the refractive indices of the front sheet and medium. This is shown to the right of dotted line 338 and is illustrated by incident light rays 340 and 342 being absorbed by particles 322. This area of the display, such as at a pixel, may appear as a dark, colored or grey state to viewer 306.

When particles are moved away from front sheet 302 and out of the evanescent wave region towards rear electrode 316 (as shown to the left of dotted line 338) incident light rays may be totally internally reflected at the interface of the surface of dielectric layer 326 on convex protrusion array 308 and medium 318. This is represented by incident light ray 344, which is totally internally reflected and exits the display towards viewer 306 as reflected light ray 346.

The display pixel may appear white, bright, colored or grey to the viewer.

TIR-based display 300 may further comprise sidewalls 348 that bridge front sheet 302 to rear sheet 312. Sidewalls may comprise at least one dielectric layer 350. In some embodiments, dielectric layer 350 may be a polymer such as parylene, halogenated parylene or polyimide. In other embodiments, the dielectric layer may be a nitride such as SiN_x or a metal oxide such as one or both of AI2O3 or SiC . Display 300 may further comprise a directional front light system 352. Front light system 352 may comprise light source 354 and waveguide 356. In some embodiments, front light system 352 may further comprise an ALS 360 and front light controller 362.

Fig. 3B schematically illustrates a cross-section of a portion of a TIR-based display comprising a memory circuit showing the approximate location of the evanescent wave region. Drawing 380 in Fig. 3B is a close-up view of a portion of drawing 300 in Fig. 3A. The evanescent wave region 382 is located at the interface of dielectric layer 326 and medium 318. This location is illustrated in drawing 380, wherein the evanescent wave region 382 is located approximately between dotted line 384 and dielectric layer 326. It should be noted that the evanescent wave region 382 is an illustration and its depth or reach may vary according to the design of the display and the materials of construction used. The evanescent wave is typically conformal to the surface of layer of protrusions 308. The depth of the evanescent wave region is about one micrometer, as previously mentioned.

Fig. 3C schematically illustrates a cross-section of a portion of an overhead view of a TIR- based reflective image display comprising a memory circuit. The view in Fig. 3C looks down on surface 304 of sheet 302. This is the view of viewer 306 in Figs. 3A-B. Convex protrusions 310 are arranged in a layer 308 on the opposite side of sheet 302 and are depicted as dotted line circles representing hemispheres arranged into a close packed array. Other arrangements of convex protrusions 310 may be possible. Protrusions 310 may be arranged in non-close packed rows.

In an exemplary embodiment, TIR-based displays 300 comprising electrophoretically mobile particles in a liquid or air medium may be driven by MIP-based technology at operating voltages in the range of about 0.1-10V. Images may be formed in TIR-based display 300 by moving electrophoretically mobile particles into and out of the evanescent wave region at pixels to frustrate TIR. In an exemplary embodiment, rear electrode 316 in display 300 comprises backplane electronics embodiment 100 described in Fig. 1. In an exemplary embodiment, rear electrode layer 316 in display 300 may comprise at least one TFT. In an exemplary

embodiment, rear electrode layer 316 in display 300 may comprise at least one SRAM or DRAM memory circuit. In an exemplary embodiment, display 300 may comprise a l-bit SRAM circuit or a l-bit DRAM circuit.

Fig. 4 schematically illustrates an embodiment of a microcup-based reflective image display comprising a memory circuit. Microcup-based reflective display 400 comprises a transparent front sheet 402 with outer surface 404 facing viewer 406. Display 400 comprises a rear support sheet 408 which further forms a gap 410. Within gap 410 comprises walls 412 that completely or partially bridge rear sheet 408 to front sheet 402. Walls 412 may form microcups 414. Microcups 414 may also be referred to as microwells. Microcups 414 may be in the form of square-like, rectangular-like, hexagonal-like, circular-like or any other shapes. Microcups 414 comprise an air or liquid medium 416. Within medium 416 may be suspended one or more pluralities of charged electrophoretically mobile particles. In some embodiments, medium 416 may comprise a first color with a plurality of electrophoretically mobile particles of a second color. In an exemplary embodiment, medium 416 may comprise a first plurality of positively charged particles of a first color 418 (represented as white particles in Fig. 4), and a second plurality of particles 420 (represented by black particles in Fig. 4) of an opposite charge and a second color.

Display 400 in Fig. 4 further comprises a transparent front electrode 422 on the inner side of sheet 402 and a rear electrode layer 424 on the inner surface of rear sheet 408. In an exemplary embodiment, electrode layer 424 may be pixelated. Each pixel may comprise at least one TFT. Display 400 comprises a voltage bias source 426. Bias source 426 may be used to form a bis across gap 410 in order to electrophoretically move particles 418, 420 to the front electrode 422 or rear electrode 424.

In some embodiments, front electrode layer 422 or rear electrode layer 424 may comprise at least one dielectric layer (not shown). In some embodiments, the dielectric layer may be a polymer such as parylene, halogenated parylene or polyimide. In other embodiments, the dielectric layer may be a nitride such as SiN_x or a metal oxide such as one or both of AhCh or SiC .

Display 400 may further comprise a directional front light system 428. Front light system 428 may further comprise a light source 430 and light guide 432. In an exemplary embodiment, light guide 432 may comprise light extraction units (not shown). Front light system 428 may further comprise an ALS 434 or front light controller 436. Display 400 may operate as follows. When dark colored particles 420 are brought near the front electrode surface, incident light rays may be absorbed. This is represented by light rays 438, 440. This portion of display 400 where light is absorbed may appear dark to viewer 406. When light or white colored particles 418 are brought to the front electrode surface 422 by application of a bias of the correct polarity, light may be reflected off the particles appearing bright or white to viewer 406. This is represented by incident light ray 442 that is reflected off particles 418 as reflected light ray 444. By bringing particles of various colors in different combinations to the front of the microcups 414 near front electrode 422 facing viewer 406, images or text may be formed to convey information to viewer 406. In some embodiments, display 400 may further comprise a color filter layer similar to layer 330 in display 300 to form color images. In an exemplary embodiment, at least one color filter sub-pixel may be substantially aligned with a microcup 414.

In an exemplary embodiment, microcup-based display 400 comprising electrophoretically mobile particles in a liquid or air medium may be driven by MIP-based technology at operating voltages in the range of about 0.1-10V. Images may be formed in microcup-based display 400 by moving electrophoretically mobile particles to the front electrode 422 or rear electrode 424.

In an exemplary embodiment, rear electrode 424 in display 400 comprises backplane electronics embodiment 100 described in Fig. 1. In an exemplary embodiment, rear electrode layer 424 in display 400 may comprise at least one TFT. In an exemplary embodiment, rear electrode layer 424 in display 400 may comprise at least one SRAM or DRAM memory circuit. In an exemplary embodiment, display 400 may comprise a l-bit SRAM circuit or a l-bit DRAM circuit.

Pulse and DC (direct current) driving schemes may be utilized to derive and maintain desired optical state (i.e. gray state) levels within the pixels of the EPD-based display embodiments described herein. The driving schemes may comprise one or more of variable applied positive or negative voltages, variable voltage ON times (i.e. ON state pulse widths) and variable voltage OFF times (i.e. OFF state pulse widths).

Fig. 5 schematically illustrates an exemplary system for implementing an embodiment of the disclosure. In Fig. 5, display 200, 300, 400 is controlled by controller 540 having processor 530 and memory 520. Other control mechanisms and/or devices may be included in controller 540 without departing from the disclosed principles. Controller 540 may define hardware, software or a combination of hardware and software. For example, controller 540 may define a processor programmed with instructions (e.g., firmware). Processor 530 may be an actual processor or a virtual processor. Similarly, memory 520 may be an actual memory (i.e., hardware) or virtual memory (i.e.. software).

Memory 520 may store instructions to be executed by processor 530 for driving display 200, 300, 400. The instructions may be configured to operate display 200, 300, 400. In one embodiment, the instructions may include biasing electrodes associated with display 200, 300, 400 through power supply 550. When biased, the electrodes may cause movement of electrophoretic particles towards or away from a region proximal to a surface to thereby absorb or reflect light received at the front transparent sheet. By appropriately biasing the electrodes, electrophoretically mobile particles (e.g., particles 214, 216 in Fig. 2; particles 322 in Fig. 3A; particles 418, 420 in Fig. 4) may be controlled.

In an exemplary embodiment, at least one pixel in a backplane comprising TFT arrays with MIP technology may be substantially aligned with a color sub-pixel in a color filter array in an EPD. In an exemplary embodiment, at least one SRAM or DRAM circuit may be aligned with one pixel in any of displays 200, 300 or 400. In an exemplary embodiment, at least one l-bit SRAM or l-bit DRAM circuit may be aligned with one pixel in any of displays 200, 300 or 400. Each pixel aligned with a SRAM or DRAM circuit may further be aligned with a color sub-pixel filter such as red, green, blue or white.

In the exemplary display embodiments described herein, they may be used in Internet of Things (IoT) devices. The IoT devices may comprise a local wireless or wired communication interface to establish a local wireless or wired communication link with one or more IoT hubs or client devices. The IoT devices may further comprise a secure communication channel with an IoT service over the internet using a local wireless or wired communication link. The IoT devices comprising one or more of the display devices described herein may further comprise a sensor. Sensors may include one or more of a temperature, humidity, light, sound, motion, vibration, proximity, gas or heat sensor. The IoT devices comprising one or more of the display devices described herein may be interfaced with home appliances such as a refrigerator, freezer, television (TV), close captioned TV (CCTV), stereo system, heating, ventilation, air conditioning (HVAC) system, robotic vacuum, air purifiers, lighting system, washing machine, drying machine, oven, fire alarms, home security system, pool equipment, dehumidifier or dishwashing machine. The IoT devices comprising one or more of the display devices described herein may be interfaced with health monitoring systems such as heart monitoring, diabetic monitoring, temperature monitoring, biochip transponders or pedometer. The IoT devices comprising one or more of the display devices described herein may be interfaced with transportation monitoring systems such as those in an automobile, motorcycle, bicycle, scooter, marine vehicle, bus or airplane.

In the exemplary display embodiments described herein, they may be used in IoT and non- IoT applications such as in, but not limited to, electronic book readers, portable computers, tablet computers, cellular telephones, smart cards, signs, watches, wearables, military display applications, automotive displays, automotive license plates, shelf labels, flash drives and outdoor billboards or outdoor signs comprising a display. The displays may be powered by one or more of a battery, solar cell, wind, electrical generator, electrical outlet, AC power, DC power or other means.

The following are exemplary and non-limiting embodiment of the disclosure. The following exemplary embodiments are presented to further illustrate the principles disclosed herein and do not limit the disclosed principles.

Example 1 is directed to a reflective image display, comprising: a front plane having a front sheet; a front electrode formed over the plurality front sheet; a backplane positioned to form a gap with the front electrode, the backplane having a rear electrode with a plurality of pixels, each pixel further comprising: a memory circuitry to store a bit value, and an ink driver circuitry configured to operate at about 0.1-10V.

Example 2 is directed to the reflective image display of example 1, wherein the reflective image display is a totally internally reflective (TIR) display.

Example 3 is directed to the reflective image display of example 1, wherein the ink driver circuitry is configured to operate at about 1-10V.

Example 4 is directed to the reflective image display of example 1, wherein the ink driver circuitry is configured to operate at about 0.1-5V.

Example 5 is directed to the reflective image display of example 1, further comprising a medium and a plurality of microcapsules positioned in the gap.

Example 6 is directed to the reflective image display of example 5, wherein each microcapsule further comprises a plurality of electrophoretically mobile particles.

Example 7 is directed to the reflective image display of example 5, wherein each microcapsule further comprises a first group of electrophoretically mobile particles and a second group of electrophoretically mobile particles.

Example 8 is directed to the reflective image display of example 1, further comprising a medium and a plurality of microcups positioned in the gap wherein each microcup further comprises a plurality of electrophoretically mobile particles. Example 9 is directed to the reflective image display of example 8, wherein each microcup further comprises a first group of electrophoretically mobile particles and a second group of electrophoretically mobile particles.

Example 10 is directed to the reflective image display of example 1, wherein the memory circuitry further comprises one or more of a random access memory (RAM).

Example 11 is directed to a totally internally reflective (TIR) image display device, comprising: a front plane having a front sheet further comprising a plurality of hemispherical protrusions; a front electrode formed over the plurality of hemispherical protrusions; a backplane positioned to form a gap with the front electrode, the backplane having a rear electrode with a plurality of pixels, each pixel further comprising: a memory circuitry to store a bit value, and an ink driver circuitry configured to operate at about 0.1-10V.

Example 12 is directed to the TIR image display device of example 11, wherein the ink driver circuitry is configured to operate at about 1-10V.

Example 13 is directed to the TIR image display device of example 11, wherein the ink driver circuitry is configured to operate at about 0.1-5V.

Example 14 is directed to the TIR image display device of example 11, further comprising a medium and a plurality of electrophoretically mobile particles positioned in the gap.

Example 15 is directed to the TIR image display device of example 11, further comprising one of a microcapsule or one of a microcup positioned in the gap wherein each microcapsule or microcup further comprises a plurality of electrophoretically mobile particles.

Example 16 is directed to the TIR image display device of example 11, wherein the memory circuitry further comprises one or more of a random access memory (RAM).

Example 17 is directed to the TIR image display device of example 11, wherein the pixel cell comprises a red subpixel, a green subpixel green and a blue subpixel.

Example 18 is directed to the TIR image display device of example 11, further comprising an ambient light sensor in communication with a front light controller, the ambient light sensor configured to detect ambient light and the front light sensor configured to direct an auxiliary light source to direct light rays to the front plane.

Example 19 is directed to the TIR image display device of example 11, further comprising a wave guide formed over the front sheet, the wave guide configured to receive a light ray from an auxiliary light source in response to a change in ambient light condition.

While the principles of the disclosure have been illustrated in relation to the exemplary embodiments shown herein, the principles of the disclosure are not limited thereto and include any modification, variation or permutation thereof.

Claims

What is claimed is:

1. A reflective image display, comprising: a front plane having a front sheet; a front electrode formed over the plurality front sheet; a backplane positioned to form a gap with the front electrode, the backplane having a rear electrode with a plurality of pixels, each pixel further comprising: a memory circuitry to store a bit value, and an ink driver circuitry configured to operate at about 0.1 -10V.

2. The reflective image display of claim 1, wherein the reflective image display is a totally internally reflective (TIR) display.

3. The reflective image display of claim 1, wherein the ink driver circuitry is configured to operate at about 1-10V.

4. The reflective image display of claim 1, wherein the ink driver circuitry is configured to operate at about 0.1-5V.

5. The reflective image display of claim 1, further comprising a medium and a plurality of microcapsules positioned in the gap.

6. The reflective image display of claim 5, wherein each microcapsule further comprises a plurality of electrophoretically mobile particles.

7. The reflective image display of claim 5, wherein each microcapsule further comprises a first group of electrophoretically mobile particles and a second group of electrophoretically mobile particles.

8. The reflective image display of claim 1, further comprising a medium and a plurality of microcups positioned in the gap wherein each microcup further comprises a plurality of electrophoretically mobile particles.

9. The reflective image display of claim 8, wherein each microcup further comprises a first group of electrophoretically mobile particles and a second group of electrophoretically mobile particles.

10. The reflective image display of claim 1, wherein the memory circuitry further comprises one or more of a random access memory (RAM).

11. A totally internally reflective (TIR) image display device, comprising: a front plane having a front sheet further comprising a plurality of hemispherical protrusions; a front electrode formed over the plurality of hemispherical protrusions; a backplane positioned to form a gap with the front electrode, the backplane having a rear electrode with a plurality of pixels, each pixel further comprising: a memory circuitry to store a bit value, and an ink driver circuitry configured to operate at about 0.1-10V.

12. The TIR image display device of claim 11, wherein the ink driver circuitry is configured to operate at about 1-10V.

13. The TIR image display device of claim 11, wherein the ink driver circuitry is configured to operate at about 0.1-5V.

14. The TIR image display device of claim 11, further comprising a medium and a plurality of electrophoretically mobile particles positioned in the gap.

15. The TIR image display device of claim 11, further comprising one of a microcapsule or one of a microcup positioned in the gap wherein each microcapsule or microcup further comprises a plurality of electrophoretically mobile particles.

16. The TIR image display device of claim 11, wherein the memory circuitry further comprises one or more of a random access memory (RAM).

17. The TIR image display device of claim 11, wherein the pixel cell comprises a red subpixel, a green subpixel green and a blue subpixel.

18. The TIR image display device of claim 11, further comprising an ambient light sensor in communication with a front light controller, the ambient light sensor configured to detect ambient light and the front light sensor configured to direct an auxiliary light source to direct light rays to the front plane.

19. The TIR image display device of claim 11, further comprising a wave guide formed over the front sheet, the wave guide configured to receive a light ray from an auxiliary light source in response to a change in ambient light condition.