REFLECTED HIGH GAIN LIQUID CRYSTAL DISPLAY

Related Applications

The disclosure claims priority to U.S. Provisional Application No. 62/569,142 (filed Oct. 6,

2017), the specification of which is incorporated herein in its entirety.

Filed

The disclosed embodiments generally relate to reflective image displays. In one embodiment, the disclosure relates to a total internal reflection-based high gain reflector. In another embodiment, the disclosure relates to combining a reflective liquid crystal display with a total internal reflection-based high gain reflector comprising a polarization retention layer.

BACKGROUND Liquid crystal displays (LCDs) are the most common reflective display on the market.

Conventional LCDs use a thin layer of liquid crystal material to control the reflectance of a surface.

Liquid crystals (LCs) represent an unusual phase of matter since, unlike typical liquids with randomly oriented molecules, LC molecules exhibit some degree of orientational alignment.

Depending on the substance itself and the environmental conditions, a liquid crystal may take one of a number of phases. The phases include nematic, chiral nematic (substances forming this phase are often called cholesteric liquid crystals) and smectic liquid crystals. It is important to note that in all of these phases, an anisotropy results from the preferred orientation of the molecules, particularly in terms of the interaction of light with these materials.

In a conventional LCD display, a thin layer of liquid crystal is typically contained in a gap between two glass plates. An electric field may be applied across the gap to cause the permanent or induced dipoles in the liquid crystal molecules to orient (align) with the dipole axis parallel to the electric field.

Polarization is a characteristic of light that describes the direction of the electric and magnetic fields comprising the wave. For instance, linearly polarized light is a special case in which the electric field points in a single direction. The anisotropy of a liquid crystal resulting from the orientational alignment causes light that is linearly polarized parallel to a specified direction to propagate at a different velocity than light that is linearly polarized perpendicular to that specified direction. In view of this behavior, it is useful to consider that light is a combination of these two linear polarizations. These two polarization components travel through a slab of liquid crystal material at two different velocities, and therefore may emerge from the material with a phase difference that is proportional to the thickness of the material. Thus, the orientational alignment of a liquid crystal affects the change it imparts to the polarization of incident light, which is why they are so useful in image displays.

Linearly polarized light can be produced by passing unpolarized light through a polarizing material that almost completely absorbs one polarization while allowing the other polarization to pass through fairly efficiently. If two such polarizing filters are layered with perpendicular polarization directions (in an arrangement known as crossed polarizers), very little light will pass through since the linearly polarized light emerging from the first polarizer will be absorbed by the second. The insertion of an isotropic material between the two polarizers will have no effect on the transmission of light since the polarization of the light is unchanged as it passes through such a material. A liquid crystal material inserted in this region, however, changes the polarization state such that some of the light will transmit through the stack. The application of an electric field across the liquid crystal can re-orient the liquid crystals to change this anisotropy. In this manner, the amount of light that passes through the stack can be controlled.

Liquid crystals may be used in two primary types of image displays, namely transmissive and reflective. Transmissive displays may be constructed by stacking the appropriate polarizing filters and liquid crystal material to form a LC panel and incorporating a backlight to direct light through the liquid crystal panel toward the viewer. In the bright state, the molecules are oriented such that light passes through the panel. In the dark state, the light is absorbed, and the region looks dark. To generate each of these states, the anisotropy of the liquid crystal material is changed by the application of an electric field.

The reflective configuration is similar, but includes a polarization-preserving rear reflector instead of a backlight. In this case, the bright state again allows polarized incident light to pass fairly efficiently through the layers, where it reflects from the rear reflector, and passes again through the panel to return to the viewer. In the dark state, the light is absorbed, creating a dark appearance. These passive displays rely on the ambient lighting conditions, rather than a backlight, for the image on the display to be visible.

Fig. 1 schematically illustrates a cross-section of a portion of a conventional reflective LC display. Reflective display 100 of Fig. 1 comprises a protective transparent cover sheet 102, such as glass or a polymer, with outward surface 104 facing viewer 106. LC display 100 further comprises a front polarizing film 108 and transparent front electrode layer 1 10. Layer 1 10 typically comprises indium tin oxide (ITO). Display 100 further comprises a liquid crystal layer 1 12, rear common electrode layer 114 and rear glass support sheet 1 16. Layer 112 is typically filled with nematic-type liquid crystals. Electrode layers 110, 114 may be connected by a power source 118 such as a battery. Prior art display 100 may further comprise a second polarizing layer 120 placed at a right angle to front polarizing film 108 and a rear light reflecting sheet 122 such as a mirror. Display 100 may comprise one or more of addressable pixels (not shown) or segments (not shown).

When there is no voltage applied to a pixel or segment of prior art display 100, light may completely pass through the display and be reflected by rear reflective layer 122 back towards viewer 106. The pixel or segment may appear in a light or bright state to viewer 106. When a voltage is applied to a pixel or segment forming an electric field across liquid crystal layer 112 to align the liquid crystals, light may be absorbed. The pixel or segment may appear dark to viewer 106.

A full-color image may also be generated in both the reflective and transmissive display configurations using a color filter overlay. Transmissive liquid crystal displays yield bright, colorful images by illuminating the display with a high intensity backlight. This is a visually effective technique, but because of the substantial power consumption of the backlight, it is inappropriate for low power, battery-operated device applications. Reflective displays, on the other hand, can operate on low power since they reflect the ambient light, but the maximum reflectance of such displays is quite limited. In theory, a monochrome LC display may be at most 50% reflective since at least half of the ambient light must be absorbed by the polarizer. In practice, the maximum reflectance of a typical monochrome reflective display is about 34%, and this value drops to at most about 16% for a full-color reflective liquid crystal display. A powerful front-light is sometimes used to illuminate this display surface for improved legibility. The use of a front light drastically increases the power required to operate the device. Reflective LCDs also typically exhibit an unappealing gray or metallic-like appearance due to the specular-like rear reflector required to maximize the brightness of the display.

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 a cross-section of a portion of a conventional reflective LCD; Fig. 2A schematically illustrates a cross-section of an embodiment of a reflective LCD comprising a TIR-based high gain reflector in a bright state; Fig. 2B schematically illustrates a cross-section of an embodiment of a reflective LCD comprising a TIR-based high gain reflector in a dark state;

Fig. 3 schematically illustrates an experimental apparatus to test for the light polarization retention of reflected light from a hemispherically-shaped convex protrusion;

Fig. 4 schematically illustrates a cross-section of an embodiment of a reflective LCD comprising a TIR-based high gain reflector and a directional front light;

Fig. 5A schematically illustrates a cross-section of an embodiment of a reflective LCD comprising a TIR-based high gain reflector and reflective polarizer in a bright state;

Fig. 5B schematically illustrates a cross-section of an embodiment of a reflective LCD comprising a TIR-based high gain reflector and reflective polarizer in a dark state;

Fig. 6 schematically illustrates an embodiment of a TFT array to drive a display;

Fig. 7 schematically illustrates an exemplary system for implementing an embodiment of the disclosure; and

Fig. 8 is an exemplary method according to one 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.

The disclosure generally relates to liquid crystal-based image displays. The liquid crystal- based image displays may be reflective. According to certain embodiments of the disclosure, a reflective LCD comprises a TIR-based high gain reflector. According to certain embodiments of the disclosure, a reflective LCD comprises a transparent sheet further comprising at least one convex protrusion. In certain embodiments, a reflective LCD comprises a transparent sheet further comprising at least one convex protrusion. In one embodiment, the transparent sheet with convex protrusions substantially retains polarization of incident light upon reflection. In another embodiment, the transparent sheet with convex protrusions does not retain polarization of incident light upon reflection.

In some embodiments, a reflective LCD comprises a transparent sheet further comprises at least one non-depolarizing convex protrusion and a color filter layer. The convex protrusion may be substantially non-depolarizing.

In some embodiments, a reflective LCD comprises a transparent sheet further comprising at least one substantially depolarizing convex protrusion and a directional front light system. In one embodiment, the transparent substrate may be depolarizing; that is, convex protrusion depolarizes the polarized light. In some embodiments, a reflective LCD comprises a transparent sheet further comprising at least one substantially non-depolarizing convex protrusion and a directional front light system; that is, the convex protrusions retains the polarization of the incident light.

In some embodiments, a reflective LCD comprises a transparent sheet further comprising at least one substantially non-depolarizing convex protrusion, a color filter layer and a directional front light system. In some embodiments, a reflective LCD comprises a depolarizing array or a substantially non-depolarizing array of convex protrusions and a reflective polarizer layer. In other embodiments, a reflective LCD comprises a transparent sheet further comprising at least one convex protrusion and a reflective polarizer layer.

The low power reflective display embodiments described herein combine a high gain reflector unit with an LCD layer to increase the overall brightness of reflective LCDs. The high gain reflector unit may comprise a polarization retention, semi-retro-reflective layer. The high gain reflector unit may comprise a de-polarizing, semi-retro-reflective layer. Furthermore, the embodiments described herein may make reflective LC displays more amenable to addition of a color filter layer for full-color reflective LCDs that are brighter than what is currently on the market. In addition, the embodiments described herein may give a reflective LCD a whiter and more visually pleasing paper-like appearance than the conventional displays.

Fig. 2A schematically illustrates a cross-section of an embodiment of a reflective LCD comprising a TIR-based high gain reflector in a bright state. Display 200 may be flexible or conformable. Display 200 may comprise an outer transparent sheet 202 with outer surface 204 facing viewer 206. In some embodiments, sheet 202 may be flexible, conformable or configured to conform (flexible may also be referred to as rollable or bendable with the ability to be bent without breaking). Sheet 202 may comprise glass. In some embodiments, sheet 202 may comprise glass of thickness in the range of about 20-2000 Dm. In an exemplary embodiment, sheet 202 may comprise glass of thickness in the range of about 20-250D m. Sheet 202 may comprise a flexible glass such as SCHOTT AF 32® eco or D 263® T eco ultra-thin glass. Sheet 202 may comprise a transparent polymer such as polycarbonate or an acrylic such as poly(methyl methacrylate).

In some embodiments, sheet 202 may also perform as a transparent barrier layer. A barrier layer may be located in various locations within the display embodiments described herein. Sheet 202 may act as one or more of a gas barrier or moisture barrier and may be hydrolytically stable. Sheet 202 may comprise one or more of polyester, polypropylene, polyethylene terephthalate, polyethylene naphthalate or copolymer, or polyethylene. Sheet 202 may comprise one or more of a chemical vapor deposited (CVD) or sputter coated ceramic-based thin film on a polymer substrate. The ceramic may comprise one or more of AI2O3, S1O2 or other metal oxide. Sheet 202 may comprise one or more of a Vitriflex barrier film, Invista OXYCLEAR ^® barrier resin, Toppan GL™ barrier films GL-AEC-F, GX-P-F, GL-AR-DF, GL-ARH, GL-RD, Celplast Ceramis ^® CPT- 036, CPT-001, CPT-022, CPA-001, CPA-002, CPP-004, CPP-005 silicon oxide (SiO _x ) barrier films, Celplast CAMCLEAR ^® aluminum oxide (AlOx) coated clear barrier films, Celplast CAMSHIELD ^® T AlOx-polyester film, Torayfan ^® CBH, Torayfan ^® CBLH biaxially-oriented clear barrier polypropylene films or 3M™ Flexible Transparent Films such as 3M FTB3-50.

Display embodiment 200 in Fig. 2A may comprise an optional color filter array layer 208. Color filter layer 208 may be located anywhere in display embodiment 200. In an exemplary embodiment, color filter array layer 208 may be located on the inner surface of sheet 202. Layer 208 may be removed if a black and white only display is desired. Color filter layer 208 may comprise one or more of red, green, blue, white, clear, cyan, magenta or yellow filters. Color filter layer 208 may be a dye-based color filter. Color filter layer 208 may be pixelated into sub-filters. In an exemplary embodiment, color filter layer 208 may be one or more of flexible or conformable. In an exemplary embodiment, each color filter may be substantially aligned or registered with a pixel. In an exemplary embodiment, each color filter may be substantially aligned or registered with a TFT in layer 212 or 216 or located elsewhere in the display stack.

Display 200 in Fig. 2A may comprise a first light polarizer film 210. Polarizer film 210 may also be referred to as an optical filter. In some embodiments, film 210 may be located adjacent sheet 208 as shown in Fig. 2. In other embodiments, film 210 may be located on the outer surface of sheet 202 facing viewer 206. In an exemplary embodiment, film 210 is an absorptive polarizer. Film 210 may comprise a polymer. Film 210 may comprise a flexible polymer. Film 210 may comprise glass. Film 210 may comprise an aluminum film with fine slits on glass or polymer. Polarizer film 210 may filter or absorb perpendicular or parallel polarized light. Film 210 may comprise one or more of MOXTEK™ (Orem, UT, USA) ProFlux® ABS series of polarizers such as ABB06C, ABB07C, ABB08C, ABG06C, ABG22C, ABG08C, ABR06C, ABR08C, ABR09C, Polaroid™ polarizing films (Minnetonka, MN, USA) or Polarium™ (San Jose, CA, USA) polarizing films.

Display embodiment 200 in Fig. 2A may comprise a top electrode layer 212. In an exemplary embodiment, layer 212 is substantially transparent. In an exemplary embodiment, layer 212 may comprise an active matrix thin film transistor (TFT) array typically used in LCDs. Layer 212 may comprise indium tin oxide (ITO), aluminum, copper, gold, Baytron™, or conductive nanoparticles, silver wires, metal nanowires, graphene, nanotubes, or other conductive carbon allotropes or a combination of these materials dispersed in a polymer. Layer 212 may comprise a segmented or patterned array of electrodes. Layer 212 may comprise a direct drive or passive matrix arrays of electrodes. Layer 212 may comprise of an array of pixels that may be used to drive display embodiment 200. In some embodiments, layer 212 may act as a common electrode. Front electrode layer 212 may comprise a transparent conductive material further comprising silver nano-wires manufactured by C3Nano, Inc. (Hayward, CA, USA). Front electrode layer 212 may comprise C3Nano ActiveGrid™ conductive ink.

Display embodiment 200 in Fig. 2A may comprise a liquid crystal layer 214. In an exemplary embodiment, layer 214 comprises twisted nematic liquid crystals. In other embodiments, layer 214 may comprise nematic, chiral nematic (substances forming this phase are often called cholesteric liquid crystals) or smectic liquid crystals. In some embodiments, the thickness of layer 214 may be in the range about l-50D m. In other embodiments the thickness of layer 214 may be in the range of about 5-25 D m. In an exemplary embodiment, layer 214 may comprise a sealant to prevent loss of the liquid crystals or to prevent moisture or gas ingress.

In an exemplary embodiment, LC layer 214 may comprise beads or fibers to maintain a substantially uniform thickness of layer 214. In other embodiments, layer 214 may comprise spacers to maintain a substantially uniform thickness. The fibers, beads or spacers may be comprised of glass or polymer. In one embodiment, the LC layer comprises separators or walls to form compartment within layer 214. In another embodiment, the LC layer 214 may comprise polymer walls. In an exemplary embodiment, polymer walls in LC layer 214 may be formed by processes and methods described in United States Patent No. 5,668,651 A and PCT applications WO 2016/206771 Al , WO 2016/206772 Al and WO 2016/206774 Al .

Display embodiment 200 in Fig. 2A may comprise a rear electrode layer 216. Rear electrode layer 216 may reside on the opposite side of liquid crystal layer 214 from the front electrode layer 212. In an exemplary embodiment, layer 216 may be substantially transparent. In an exemplary embodiment, layer 216 may comprise an active matrix TFT array typically used in LCDs. Layer 216 may comprise indium tin oxide (ITO), aluminum, copper, gold, Baytron™, or conductive nanoparticles, silver wires, metal nanowires, graphene, nanotubes, or other conductive carbon allotropes or a combination of these materials dispersed in a polymer.

Rear electrode 216 may comprise a segmented or patterned array of electrodes. Layer 216 may comprise a direct drive or passive matrix arrays of electrodes. Layer 216 may comprise an array of pixels that may be used to drive display embodiment 200. In some embodiments, layer 216 may act as a common electrode. Rear electrode layer 216 may comprise a transparent conductive material further comprising silver nano-wires manufactured by C3Nano, Inc. (Hayward, CA, USA). Rear electrode layer 216 may comprise C3Nano ActiveGrid™ conductive ink.

Display embodiment 200 in Fig. 2A may comprise a second light polarizer film 218. Polarizer film 218 may also be referred to as an optical filter. In an exemplary embodiment, film 218 is an absorptive polarizer. Film 218 may comprise a polymer. Film 218 may comprise a flexible polymer. Film 218 may comprise glass. Film 218 may comprise an aluminum film with fine slits on glass or polymer. Polarizer film 218 may filter or absorb perpendicular or parallel polarized light.

Polarizer film 218 may comprise one or more of MOXTEK™ (Orem, UT, USA) ProFlux®

ABS series of polarizers such as ABB06C, ABB07C, ABB08C, ABG06C, ABG22C, ABG08C, ABR06C, ABR08C, ABR09C, Polaroid™ polarizing films (Minnetonka, MN, USA) or Polarium™ (San Jose, CA, USA) polarizing films.

In an exemplary embodiment, film 218 is placed at about a 90° or right angle to first polarizing film 210. In this manner, the first polarizing film 210 removes a first group of incoming rays having a first polarization and the second polarizing film 218 removes a second group of incoming rays having a second polarization; the first and second polarization may be substantially orthogonal to each other (i.e., different by about 90°). In other embodiments, film 218 may be placed at any angle in the range of about 0-90° with respect to film 210. In an exemplary embodiment, films 210 and 218 may be comprised of substantially the same material. In another embodiment, first polarization layer 210 and second polarization layer 218 may have different polarizations. In still another embodiment, first polarization layer 210 and second polarization layer 218 may have substantially similar polarizations.

Display embodiment 200 in Fig. 2A may comprise a second transparent sheet 220. Sheet 220 may be unnecessary as sheet 218 may be self-supporting. Sheet 220 may be located behind polarizer sheet 218 to provide support to display 200. In some embodiments, sheet 220 may be flexible or conformable. Sheet 220 may comprise glass. In some embodiments, sheet 220 may comprise glass of thickness in the range of about 20-2000□ microns. In an exemplary embodiment, sheet 220 may comprise glass of thickness in the range of about 20-250□ microns. Sheet 220 may comprise a flexible glass such as SCHOTT AF 32 ^® eco or D 263 ^® T eco ultra-thin glass. Sheet 220 may comprise a transparent polymer such as polycarbonate or an acrylic such as poly(methyl methacrylate).

Display embodiment 200 in Fig. 2A may comprise an inward array of at least one convex protrusion 222. The array of at least one protrusion 222 may be located on the surface of sheet 220. In an exemplary embodiment, a color filter layer may be interposed between transparent sheet 220 and protrusions 222. In an exemplary embodiment, protrusions 222 may be located on the inward surface of sheet 220. In some embodiments, sheet 220 and protrusions 222 may be a continuous sheet of the same material; that is, sheet 220 and protrusions 222 may be integrated or formed as one layer. In other embodiments, sheet 220 and protrusions 222 may be separate layers and comprised of different materials. In one embodiment, sheet 220 and protrusions 222 have different refractive indices. In an exemplary embodiment, protrusions 222 may comprise a flexible polymer. In an exemplary embodiment, protrusions 222 may comprise a high refractive index polymer. In some embodiments, convex protrusions 222 may be in the shape of hemispheres. Protrusions 222 may be of any shape or size or a mixture of shapes and sizes. Protrusions 222 may be elongated hemispheres or hexagonally shaped or a combination thereof. In other embodiments the convex protrusions may be glass or polymer microbeads embedded in sheet 220.

Protrusions 222 may have a refractive index of about 1.5 or higher. In an exemplary embodiment, protrusions 222 may have a refractive index of about 1.5-1.9. The protrusions may have a diameter of at least about 0.5 microns. Protrusions 222 may have a diameter of at least about 2 microns. In some embodiments the protrusions may have a diameter in the range of about 0.5-5000 microns. In other embodiments, protrusions 222 may have a diameter in the range of about 0.5-500 microns. In still other embodiments, protrusions 222 may have a diameter in the range of about 0.5-100 microns. The protrusions may have a height of at least about 0.5 microns. In some embodiments, at least one protrusion 222 may have a height in the range of about 0.5- 5000 microns. In other embodiments, at least one protrusion 222 may have a height in the range of about 0.5-500 microns. In still other embodiments, at least one protrusion 222 may have a height in the range of about 0.5-100 microns. In certain embodiments, protrusions 222 may comprise materials having a refractive index in the range of about 1.5 to 2.2. In certain other embodiments, at least one protrusion may be a material having a refractive index of about 1.6 to about 1.9.

Protrusions 224 may comprise substantially rigid, high index material. High refractive index polymers that may be used may comprise high refractive index additives such as metal oxides. The metal oxides may comprise one or more of SiC , ZrCte, ZnC , ZnO or TiC . In some embodiments, convex protrusions 222 may be in the shape of hemispheres as illustrated in Fig. 2A. In some embodiments, the convex protrusions may be randomly sized and shaped. In some embodiments the protrusions may be faceted at the base and morph into a smooth hemispherical or circular shape at the top. In other embodiments, protrusions 222 may be hemispherical or circular in one plane and elongated in another plane. In an exemplary embodiment, the convex protrusions 222 may be manufactured by micro-replication. In an exemplary embodiment, sheet 220 may be a flexible, stretchable or impact resistant material while protrusions 222 may comprise a rigid, high index material. In an exemplary embodiment, the convex protrusions 222 may be arranged in a close-packed array.

Display embodiment 200 in Fig. 2A may further comprise a rear support layer 224 facing the surface of protrusions 222. Rear support layer 224 may be flexible or conformable. Rear support layer 224 may be one or more of a metal, polymer, wood or other material. Sheet 224 may one or more of glass, polycarbonate, polymethylmethacrylate (PMMA), polyurethane, acrylic, polyvinylchloride (PVC), polyimide or polyethylene terephthalate (PET). Rear support layer 224 may form a cavity or gap 226 with protrusions 222. Rear support layer 224 may also act as a barrier layer.

Display embodiment 200 in Fig. 2A may further comprise a low refractive index medium 228 in cavity 226. In an exemplary embodiment, medium 228 is air. Medium 228 may be a gas such as Ar, N2 or CO2. Medium 228 may be a liquid. Medium 228 may be an inert, low refractive index fluid medium. Medium 228 may be a hydrocarbon. Medium 228 may comprise an optically clear adhesive (OCA) with a refractive index in the range of about 1-1.5. In other embodiments, the refractive index of medium 228 may be about 1 to 1.5. In still other embodiments, the refractive index of medium 228 may be about 1.1 to 1.4. In an exemplary embodiment, medium 228 may be a fluorinated hydrocarbon. In another exemplary embodiment, medium 228 may be a perfluorinated hydrocarbon. In an exemplary embodiment, medium 228 has a lower refractive index than the refractive index of convex protrusions 222. In other embodiments, medium 228 may be a mixture of a hydrocarbon and a fluorinated hydrocarbon. In an exemplary embodiment, medium 228 may comprise one or more of Fluorinert™, Novec™ 7000, Novec™ 7100, Novec™ 7300, Novec™ 7500, Novec™ 7700, Novec™ 8200, Teflon™ AF, CYTOP™ or Fluoropel™. In some embodiments, the difference in refractive indices of protrusions 222 and medium 228 may be at least about 0.01. In an exemplary embodiment, the difference in refractive indices of protrusions 222 and medium 228 may be about 0.01 -1.

Display embodiment 200 in Fig. 2A may further comprise a light reflecting layer 230. In an exemplary embodiment, light reflecting layer 230 may be a specular reflector. Light reflecting layer 230 may comprise a metal such as aluminum, chrome, silver or gold. Light reflecting layer 230 may be a mirror. Light reflecting layer 230 may be a metallized film comprising a polymer film with a thin layer of metal. Light reflecting layer 230 may be deposited on rear support layer 224 using a physical vapor deposition process. Light reflecting layer 230 may comprise one or more of polypropylene, polyethylene, polyethylene terephthalate, polytetrafluoroethylene or nylon. In an exemplary embodiment, light reflecting layer 230 may comprise aluminized Mylar™. The combination of protrusion array 222, medium 228 and reflective layer 230 may be referred to as a high gain reflector unit. Light reflecting layer 230 may comprise 3M™ Enhanced Specular Reflector (ESR) film.

Light reflecting layer 230 may be positioned approximately at the focal plane of the surface of the array of convex protrusions 222. In one application, the focal plane is approximately where all light that passes through layer 222 meet. Protrusions 222, which may be in the shape of curved hemispheres as illustrated in Fig. 2A, may act as lenses. The hemisphere-shaped lenses 222 may focus the light that transmits through the region of protrusions 222 where TIR does not occur (this region is conventionally referred to as the "dark pupil" region) toward rear specular reflector 230. The semi-retroreflective gain may be maximized if rear specular reflector 230 is positioned approximately at the focal length of these lens elements (protrusions 222). This may be better explained by examining a single hemisphere in array 222. In this case, the hemisphere acts as focusing lens, and the focal length, of the lens may be approximately determined by the thin- lens equation for a plano-convex lens (Eq. 1) which is:

1/f = (n - 1)/(1/Λ) (1) In Eq. 1 , n is the index of refraction of the hemisphere and R is the radius of the hemisphere.

The optical medium between the lens and the specular reflector is assumed to be air (index of refraction = 1). Using this example, if n = 1.6 and R = 10 microns (hemisphere diameter = 20 microns), the focal length, is approximately 17 microns. Gap distance 226 need not be exactly equivalent to the focal length of the hemispherical lens element. For example, gap distance 226 may be within about 20% of the focal length in order to largely maximize the semi-retroreflective gain. For a TIR reflector with a specific shape and refractive index, the optimal position of the TIR reflector 222 relative to rear specular reflector 230 in order to maximize the semi- retroreflective gain may be determined using standard geometric lens design analysis, including computer ray tracing models.

Display embodiment 200 may further comprise sidewalls 252 located in gap 226. Sidewalls

252 may help to maintain a uniform gap distance such as when the display may be flexed or bent. Sidewalls 252 may be located in gap 226 in a periodic or random array. Sidewalls 252 may comprise polymer, glass or a metal. Sidewalls 252 may be flexible. Sidewalls 252 may be any size or shape. Sidewalls 252 may have a rounded cross-section. The sidewalls or cross-walls may be configured to create wells or compartments in, for example, square-like, triangular, pentagonal or hexagonal shapes or a combination thereof. Sidewalls 252 may comprise a polymeric material and patterned by one or more conventional techniques including photolithography, embossing or molding. In an exemplary embodiment, sidewalls 252 may be comprised of a flexible or conformal polymer. Gap 226 may also comprise spacer units such as beads. Spacer units may comprise a polymer.

Display embodiment 200 may further comprise a voltage bias source 232. Bias source 232 may create an electric field or electromagnetic flux across liquid crystal layer 214 situated between front electrode 212 and rear electrode 216. The flux may rearrange the orientation of the liquid crystals in layer 214. In an exemplary embodiment, twisted nematic liquid crystals located in layer 214 may re-orient by application of a bias. Twisted nematic liquid crystals in layer 214 may return to their previous state upon removal of an applied voltage bias.

Bias source 232 may be coupled to one or more processor circuitry and memory circuitry configured to change or switch the applied bias in a predefined manner and/or for predetermined durations. For example, the processing circuity may switch the applied bias to display characters on display 200.

Display embodiment 200 of Fig. 2A may be operated as follows. Embodiment 200 in Fig. 2A exhibits a pixel in a bright state. Multiple modes of reflection to create an enhanced bright state relative to conventional LCD displays will be illustrated. It should be noted that these modes are representative only. Many other modes of reflection may be possible.

In a first illustrative mode of reflection illustrated in Fig. 2A, light ray 234 enters display embodiment 200 and passes through first front polarizing layer 210. Light ray 234 may be an incoming ray of light. As is known in the industry, light is an electromagnetic wave, and the electric field of this wave oscillates perpendicularly to the direction of propagation. Light is unpolarized if the direction of this electric field fluctuates randomly in time. In the disclosed embodiments, incoming light may be polarized or unpolarized.

Referring to Fig. 2A, incoming ray of light 234 crosses polarizing layer 210 which absorbs a portion of the incident light 234. It is assumed, for illustrative purposes only, that polarizer layer 210 absorbs perpendicular polarized light only and allows all parallel polarized light waves to be transmitted and approach layer 214. Layer 214 is the liquid crystal layer. It is further assumed that layer 214 comprises twisted nematic liquid crystals. The twisted nematic liquid crystals are in their natural twisted state as it is assumed that no voltage is being applied to the front 212 and rear electrodes 216. As the transmitted parallel polarized light enters layer 214, the twisted nematic liquid crystals interact with and convert the light from parallel to perpendicular polarized light. The perpendicular polarized light is allowed to pass through rear absorptive polarizing layer 218 that lies at about a 90° angle to polarizing layer 210. This allows light to continue to pass through rear polarizing layer 218 towards array of convex protrusions 222. Some light is allowed to directly pass through array 222 as light enters at an angle such that it does not undergo total internal reflection (TIR) at the interface of high refractive index layer 222 and low refractive index medium 228. In one embodiment, the interface between protrusions 222 and medium 228 is called the evanescent wave region where TIR may occur. Light rays incident upon the interface at angles less than critical angle, Q _c , may be transmitted through the interface (Commonly known as the "dark pupil" region). This is represented by incident light 234. Light rays incident upon the interface at angles greater than Q _c may undergo TIR at the interface as represented by rays 238 and 240. 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 medium 228 with preferably as small a refractive index Ο73) as possible and to have a transparent front sheet composed of a material having a refractive index (ηι) preferably as large as possible. The critical angle, Q _c , is calculated by the following equation (Eq. 2):

6 _C = sin- (g (2)

In this example, light passes through the "dark pupil" region at an angle less than Q _c . The light may then be reflected by rear light reflecting layer 230 back towards viewer 206. This is represented by reflected light ray 236. Reflected light 236 represents a fraction of the incoming light 234.

Another example mode of reflection is illustrated in Fig. 2A. Representative incident light

238, 240 may enter a pixel in display 200 and first polarizer layer 210 where perpendicular polarized light may be absorbed, and parallel polarized light may continue to enter the display. Parallel polarized light 238, 240 may then enter layer 214 where the twisted nematic liquid crystals reside. Parallel polarized light 238, 240 may interact with the nematic liquid crystals (if engaged by an appropriate bias) in such a manner as to convert the parallel polarized light to perpendicular polarized light. Perpendicular polarized light 238, 240 may then pass through rear absorptive polarizer layer 218 that is at an approximately 90° angle to front polarizer layer 210. Light 238, 240 may then proceed to pass through transparent sheet 220 towards the interface of the array of high refractive index protrusions 222 and low refractive index medium 228. It should be known that a semi-retro-reflective array of convex protrusions, such as hemispherical array of protrusions, typically behaves as a light depolarizer. Other related retro-reflectors, such as 3M™ Diamond Grade film comprised of corner cubes, also behave as depolarizers.

Polarized light that is reflected by a semi-retro-reflective array of high refractive index convex protrusions 222 may return as substantially polarized light if the design and materials of construction are carefully controlled. In other words, the high gain reflector unit comprises an array of high refractive index convex protrusions that semi-retro-reflects light in a manner that substantially retains the polarization of the incident light. This prevents the reflected light from being absorbed by rear polarizer layer 218 which is the same layer the light initially passed through. This is illustrated in Fig. 2A where incident light rays 238, 240 are semi-retro-reflected as light rays, 242, 244, respectively, at the interface of the inward surface of high refractive index protrusions 222 and low index of refractive medium 228.

The optical design is selected so as to ensure that a substantial portion of the individual ray paths have the characteristic that the cumulative effective phase shift difference between orthogonal polarization states is an integer multiple of 2π, so as to substantially recover full polarization of the reflected light. The cumulative effective phase shift difference arises from both changes in direction of the light ray path and differences of the phase shifts of each of the two polarizations upon total internal reflection. This is achieved by ensuring that rays with several (N) reflections undergo individual phase shift differences where the magnitude of the difference is approximately inversely proportional to N. The refractive index of the material comprising the array of high index convex protrusions is selected to optimize the desired effect.

As a first example, to achieve the goal of a cumulative phase shift difference of 2π, for a ray that undergoes four reflections by TIR after which it is substantially retro-reflected, there may be π/4 radians of phase shift upon each total internal reflection and a further π radians of phase shift associated with the overall directional change of the light rays. This achieves a net change of about 2π. The π/4 radians of phase shift upon each total internal reflection is approximately achieved by selecting a sufficiently high refractive index value n (as typical, it is the difference between the index of the structures 222 and the surrounding medium 228 that matters).

As a second example, if there were six TIR reflections, the desirable phase shift arising from

TIR in each of those reflections would be π/6. Fortunately as the number of reflections N, increases, so does the incident angle, which means that the difference of 90° (or π/2 radians) minus the incident angle becomes smaller. In turn, this may cause the TIR based phase shift to decrease such that the cumulative phase shift remains approximately the same. This implies that the same refractive index, n, achieves the desired cumulative phase shift for most reflective paths, independent of N. Not all structures that exhibit TIR exhibit this characteristic as described, but hemispheres or hemisphere-like shapes do exhibit this behavior, especially at higher refractive index values.

The reflection modes described herein illustrate how the display embodiments may lead to a brighter reflective LCD than what is currently on the market. This allows for a color filter array layer to be added to the display to enable color-based applications. Additionally, due to the nature of the TIR semi-retro-reflective interface of array 222 and medium 228, the bright state of the display may appear whiter to the viewer. This is much more visually pleasing appearance as opposed to the metallic gray appearance of conventional LC displays.

Fig. 2B schematically illustrates a cross-section of an embodiment of a reflective LCD comprising a TIR-based high gain reflector in a dark state. Display 200 in Fig. 2B is the same as shown in Fig. 2 A but in a dark state. Display 200 in the dark state may operate as follows. As a light enters display 200, the light enters front polarizer layer 210. This is represented by incident light 246, 248, 250. The incoming light ray may be unpolarized. Front polarizer 210 absorbs one polarization (about 50% of the light) and allows the other polarization (first polarized ray) to pass through. It is assumed, for illustrative purposes, that perpendicular polarized light is absorbed by layer 210 and parallel light is allowed to pass through layer 210 toward liquid crystal layer 214. A voltage may be applied across LC layer 214 by voltage source 232 to re-orient the LCs to interact with the first polarized ray. Depending on the applied voltage, the re-orientation of the liquid crystals may occur to varying degrees to control the amount of light that passes through. For conceptual purposes illustrated in Fig. 2B, it is assumed that a sufficient voltage may be applied to cause substantially all of the first polarized light to be absorbed by layer 214. After passing through layer 214, parallel polarized light 246, 248, 250 may then be absorbed by rear absorptive polarizing layer 218 that is placed at about a 90° angle to front absorptive polarizer layer 210. This creates a dark state as viewed by viewer 206.

As mentioned previously, voltages of various levels may be applied across layer 214 in order to re-orient the twisted nematic liquid crystals to varying degrees. This varies the amount of light that may be absorbed by or pass through layer 218. Gray states may be formed by partial reorientation of the twisted nematic liquid crystals in layer 214. Some light may thus be absorbed by lay er 218 while some light may be reflected by the high gain reflective unit described previously herein to form a desired gray state.

Table 1 displays ray tracing data showing advantages of refractive index of convex protrusions on light polarization retention. A convex protrusion was tested using ray tracing software Zemax OpticStudio 16.5 SP5 (version June 19, 2017). The convex protrusion tested had a hemispherical-like structure of the same radius and height (1 : 1 ratio). The convex protrusion was also tested with a range of refractive indices from about 1.5 to about 1.74 against air (for reference, air has a refractive index of 1).

Table 1.

Fig. 3 schematically illustrates an experimental apparatus to test for the light polarization retention of reflected light from a hemispherically-shaped convex protrusion. Apparatus 300 comprises light source 302 which is capable of emitting polarized and non-polarized light. The light emitted from light source 302 may be emitted in a perpendicular direction towards hemispherical-like structure 304. Structure 304 comprises a radius, R, and height, H, shown in Fig. 3 and listed in Table 1. This is equivalent to light being directed in a substantially perpendicular direction from the direction of viewer 206 in display embodiment 200, towards structures 222 in Fig. 2A. Polarized light 306 passes through an incident light meter 308 then towards structure 304. Light 306 may undergo TIR at the interface of structure 304 and air. Some of the locations where TIR may occur are denoted at 310, 312. These are just representative conceptual examples as many other modes and locations of reflections may occur. Light 306 may be retro-reflected back towards a wide angle reflected light analyzer 314 and viewer 316. The exiting light is represented by ray 318. Wide angle reflected light analyzer 314 may be aligned with the polarization of the light used in the experiment. Any light that passes through the structures, such as through the "dark pupil" region previously mentioned (at angles less than 0 _C ), may be detected by light transmission meter 320.

When incident polarized light aligned with the y direction, and the analyzer is also aligned with the y direction, the polarization of the light is retained for the hemispherical structure at about 83% when the refractive index of the structure is 1.5 as shown in Table 1. This value of polarization retention of y polarized light increases, using the same experimental set-up, to a substantial amount of about 90% when the refractive index of the structure is increased to 1.74. When incident source light emits polarized light aligned with the x direction, and the analyzer is cross polarized in the y direction, the y polarized light detected for the hemispherical structure is about 17% when the refractive index of the structure is 1.5 as shown in Table 1. This value of polarization retention oiy polarized light decreases, using the same experimental set-up, to an amount of about 10% when the refractive index of the structures is increased to 1.74. The data shows from the tests that polarization retention of the incident polarized light increases as the refractive index increases for a hemispherical structure (while keeping the refractive index of the adjacent medium, such as air, at 1).

Table 2 lists measured data on a sheet of hemispherical-shaped convex protrusions on glass at two different refractive indices. The protrusions for first sample, Hemisphere 1, had a refractive index of about 1.64, an average radius of about 11.2□ microns and an average height of about 9.4 microns. The second sample, Hemisphere 2, had a refractive index of about 1.73, an average radius of about 11.3 D microns and an average height of about 9.7□ microns. It is assumed that the hemispheres are adjacent a medium with a refractive index of 1 (such as air). The radius and height of the samples were measured with a Park Systems NX- 10 atomic force microscope and the data was analyzed used software package XEI 4.2.0.Build 3. Collimated white LED light was used as the incident light source. A linear polarizer was used as the analyzer.

Table 2.

When incident polarized light aligned with the y direction, and the analyzer is also aligned with the y direction, the polarization of the light is substantially retained for shape Hemisphere 1 at about 85% when the refractive index of the hemispheres is about 1.64 as shown in Table 2. This is similar to what was observed in the modeling data for samples at 1.62 (87%) and 1.66 (88%) listed in Table 1. This value of polarization retention ofy polarized light increases, using the same experimental set-up, to a substantial amount of about 91% when the refractive index of the hemispheres is increased to 1.73 as shown in the data for sample Hemisphere 2. This is similar to the 1.72 and 1.74 refractive index data in Table 1 (90%).

When incident source light emits polarized light aligned with the x direction, and the analyzer is cross polarized in the direction, the polarized light detected for structure Hemisphere 1 is about 15% when the refractive index of the hemispherical structures is 1.64 as shown in Table 2. This value of polarization retention of y polarized light decreases, using the same experimental set-up, to an amount of about 9% when the refractive index of the hemispherical structures is increased to 1.73 as seen for Hemisphere 2. In summary, the data in Table 2 shows that polarization retention of the incident polarized light increases as the refractive index increases for both Hemisphere 1 and Hemisphere 2 structures. This supports the modeled data shown in Table 1.

Fig. 4 schematically illustrates a cross-section of an embodiment of a reflective LCD comprising a TIR-based high gain reflector and a directional front light. Display embodiment 400 in Fig. 4 is similar to embodiment 200 but further comprises a directional front light system. Display embodiment 400 may comprise transparent front sheet 402 with front surface 404 facing viewer 406. Display embodiment 400 may further comprise one or more of a color filter array layer 408, front light polarizer layer 410, front electrode layer 412, liquid crystal layer 414, rear electrode layer 416, rear light polarizer layer 418, transparent support sheet 420, array of at least one high index of refraction convex protrusion 422 and rear support layer 424. Color filter layer 408 may be located anywhere within display embodiment 400 such as on the inner or outer surface of sheet 420. Rear support layer 424 may form a gap 426 with surface of array 422. Within gap or cavity 426 may reside air, an optically clear adhesive or liquid medium 428. On the inward surface of rear support layer 424 may reside light reflection layer 430. Display embodiment 400 may further comprise a voltage source 432. One or more of layers 402, 424 may also act as a barrier layer. Display embodiment 400 may also comprise one or more sidewalls 442 located within gap 426.

Display embodiment 400 in Fig. 4 may further include a directional front light system 434. Directional front light system 434 may comprise an outer surface 436 facing viewer 406. Front light system 434 may comprise a light source 438 to emit light to and through an edge of a light guide 440. Light source 438 may comprise one or more of a light emitting diode (LED), cold cathode fluorescent lamp (CCFL) or a surface mounted technology (SMT) incandescent lamp. In an exemplary embodiment, light source 438 may define an LED whose output light emanates from a refractive or reflective optical element that concentrates said diode's output emission in a condensed angular range to an edge of light guide 440. In some embodiments, light source 438 may be optically coupled to light guide 440. In an exemplary embodiment, directional front light system 434 may be flexible or conformable.

Light guide 440 may comprise one or more of a glass or polymer. Light guide 440 may comprise one or more of a flexible or conformable polymer. Light guide 440 may comprise more than one layer. Light guide 440 may comprise one or more contiguous light guiding layers parallel to each other. Light guide 440 may comprise at least a first light guiding layer that forms a transparent bottom surface. Light guide 440 may comprise a second layer that forms a transparent top or outer surface. Light guide 440 may comprise a third layer that forms a central transparent core. The refractive indices of the layers of light guide 440 may differ by at least 0.05. The multiple layers may be optically coupled. In an exemplary embodiment, light guide 440 may comprise an array of light extractor elements (not shown). The light extractor elements may comprise one or more of light scattering particles, dispersed polymer particles, air pockets, tilted prismatic facets, parallel prism grooves, curvilinear prism grooves, curved cylindrical surfaces, conical indentations, spherical indentations or aspherical indentations. The light extractor elements may be arranged such that they redirect light towards semi-retro-reflective interface of convex protrusions 422 and medium 428 in a substantially perpendicular direction with a non- Lambertian narrow-angle distribution. Light guide 440 may comprise diffusive optical haze. Light guide system 434 in display embodiment 400 may comprise a light guide system used with conventional LCD displays or a FLEx Front Light Panel made from FLEx Lighting (Chicago, IL). Light guide 440 may comprise an ultra-thin, flexible light guide film manufactured by Nanocomp Oy, Ltd. (Lehmo, Finland).

Display embodiment 400 may further comprise spacer beads (not shown) or spacer units (not shown) to maintain a substantially consistent and uniform spacing in gap 426. Spacer beads and spacer units may perform in a similar manner as sidewalls 442.

Fig. 5A schematically illustrates a cross-section of an embodiment of a reflective LCD comprising a TIR-based high gain reflector and reflective polarizer in a bright state. Display embodiment 500 in Fig. 5 is similar to display embodiments 200, 400 in Figs. 2A-B and 4, respectively, but further comprises a reflective polarizer layer 534. Display embodiment 500 may comprise transparent front sheet 502 with front surface 504 facing viewer 506. Display embodiment 500 may further comprise one or more of a color filter array layer 508, front light polarizing layer 510, front electrode layer 512, liquid crystal layer 514, rear electrode layer 516, rear light polarizer layer 518, transparent support sheet 520, array of at least one high index of refraction convex protrusion 522 and rear support layer 524. Layer 522 may reflect light in a semi- retro-reflective manner. Color filter layer 508 may be located anywhere within display embodiment 500 such as on the inner or outer surface of sheet 520. Rear support layer 524 may form a gap 526 with surface of array 522. Within gap 526 may reside low refractive index ambient air, gas, an optically clear adhesive or liquid medium 528 as described previously herein. On the inward surface of rear support layer 524 may reside light reflection layer 530. Display embodiment 500 may further comprise a voltage source 532. One or more of layers 502, 524 may also act as a barrier layer. Display embodiment 500 may further comprise sidewalls 556 located in gap 526. Sidewalls 556 may help to maintain a uniform gap distance if the display is flexed or bent. Sidewalls 556 may be located in gap 526 in a periodic or random array. Sidewalls 556 may comprise polymer, glass or a metal. Sidewalls 556 may be flexible. Gap 526 may also comprise spacer units such as beads. The spacer units may comprise a polymer, glass or metal.

Display embodiment 500 may further include a reflective light polarizer layer 534. Reflective polarizer layer 534 may be interposed between layer 518 and sheet 520. Layer 534 may be located elsewhere in the display in other embodiments. As shown in the data in Tables 1-2, although most of the polarized incident light retains its polarization after reflection at the interface of high refractive index protrusions 522 and medium 528, some of the light may be depolarized. This may be attributed to defects in the shape of convex protrusions 522. It may also be attributed to a non-uniform refractive index throughout the convex protrusions. This may be due to nonuniform distribution of high index particles within protrusions 522. In order to attain high brightness in the display embodiments described herein, it may be important to recycle the depolarized light until it achieves the correct polarization so that it can be reflected back towards the viewer. Adding a reflective polarizer layer to the display may aid in achieving this objective.

Layer 534 may transmit perpendicular or parallel polarized light while reflecting and/or recycling the non-transmitted polarized light. Layer 534 may comprise one or more of a polymer or glass. Layer 534 may be flexible or conformable. Layer 534 may be placed in the range of about 0-90° with respect to layers 510, 518. Layer 534 may comprise one or more of 3M™ (Maplewood, MN, USA) DBEF, 3M™ BEFRP, 3M™ BEF, 3M™ APF, Vikuiti™ DRPF, DuPont Teijin™ (Chester, VA, USA) ST504, ST506, ST510, STCH 11, STCH12, TCH 11, TCH 12, MELINEX® STCH22UV, STCH24UV, TCH22UV, TCH24UV, 3T Frontiers model 3105, 3205, 3205-H12, 3205-AL, 3205-N, 3205-Y or 3205-M reflective polarizer film.

In one embodiment, display 500 of Fig. 5A may operate as follows. Light that enters the display and is polarized by layer 510, may continue to pass through the display as previously described towards array of convex protrusions 522. Some light that is incident at the interface of layer 522 and medium 528 may do so at an angle less than Q _c may not undergo TIR and pass through sheet 522 towards rear reflector 524. This light may then be reflected back towards viewer 506. This is represented by incident light 536 and reflected light 538. A portion of reflected light 538 may be depolarized. Normally this light would be absorbed by rear polarizer layer 518 and be lost. Reflective polarizer layer 534 may instead reflect the depolarized light back towards layer 522 before it reaches rear polarizer layer 518. Reflected polarized light 540 is represented by a dotted line in Fig. 5A. Light 540 may be recycled until it achieves the correct polarization and be allowed to pass through reflective polarizer layer 534 and rear polarizer layer 518 and exit the display towards viewer 506. This is represented by reflected light 542 (dotted line).

Another mode of reflection is represented by incident light 544. The majority of the light may undergo TIR at the interface of array 522 and medium 528 and be retro-reflected back towards viewer 506. This is represented by reflected light 546. A small portion of the light may be depolarized. This is represented by light 548 (dot-dash line) that is reflected by reflective polarizer 534 back towards layer 522. Light 548 may be retro-reflected two or more times until the light attains the correct polarization to be able to pass through layers 534 and 518 back towards viewer 506. This light that attains the correct polarization is represented by reflected light 550 (dot-dash line).

It should be noted that many reflection modes are possible. The reflection modes described herein are for illustrative purposes only. The arrangement of Fig. 5A, leads to a brighter reflective LCD than conventional LCD devices as less light is absorbed by absorptive polarizers 510, 516 and more light is allowed to exit the display. This allows for a color filter array to be added to the display to enable color-based applications that reflective LC displays currently on the market are not able to be used in. Additionally, due to the nature of the totally internally reflective semi-retro- reflective interface of array 522 and medium 528, the bright state of the display may appear whiter to the viewer. This is a much more visually pleasing appearance as opposed to the metallic gray appearance of conventional reflective LC displays on the market. This whiter appearance further allows more products for the invention described herein to be used in.

Fig. 5B schematically illustrates a cross-section of an embodiment of a reflective LCD comprising a TIR-based high gain reflector and reflective polarizer in a dark state. Display 500 in Fig. 5B is the same as shown in Fig. 5A but in a dark state as substantially all incoming light is absorbed by optical filter layers 510 and 516.

In one embodiment, display 500 in the dark state may operate as follows. As a light enters display 500, the light enters front polarizer layer 510. This is represented by incident light 552, 554. Front polarizer absorbs one polarization (about 50% of the light) and allows the other polarization to pass through. It is assumed, for illustrative purposes, that perpendicular polarized light is absorbed by layer 510 and parallel light is allowed to pass through layer 510 toward liquid crystal layer 514. A voltage may be applied across layer 514 by voltage source 532 to re-orient the liquid crystals. Depending on the applied voltage, the re-orientation of the liquid crystals may occur to varying degrees to control the amount of light that passes through. For conceptual purposes illustrated in Fig. 5B, it is assumed that a sufficient voltage may be applied to substantially cause all light to be passed through layer 514. After passing through layer 514, parallel polarized light 552, 554 may then be absorbed by rear absorptive polarizing layer 518 that is placed at about a 90° angle to front absorptive polarizer layer 510. This creates a dark state as viewed by viewer 506.

As mentioned previously, voltages of various levels may be applied across layer 514 in order to re-orient the twisted nematic liquid crystals to varying degrees. This varies the amount of light that may be absorbed by or pass through layer 518. Gray states may be formed by partial reorientation of the twisted nematic liquid crystals in layer 514. Some light may thus be absorbed by layer 518 while some light may be reflected by the high gain reflective unit described previously herein to form a desired gray state.

In an exemplary embodiment, display 500 may further comprise a directional front-light system. The front-light system may be similar to the front light system illustrated in Fig. 4 and described herein.

It should be noted that in some embodiments, display 500 may be designed with no regard to a specific design and refractive index, as illustrated in Tables 1 and 2, for convex protrusions in layer 522 to maximize the maintaining of polarization of the light. For example, layer 522 may be designed such that the majority of the light loses polarization by reflection at the interface of layer 522 and medium 528 or by reflective layer 530. Reflective polarizer layer 534 may be employed to allow the light with the correct polarization to pass and reflect the depolarized light until the depolarized light attains the correct polarization and is allowed to pass through layer 534. Reflective polarizer layer 534 is a key component of an exemplary embodiment. The reflective polarizer layer 534 is configured to maximize brightness by preventing . If light of the incorrect polarization is allowed to pas back towards the viewer, it will be absorbed by the first or second polarizer layers thus causing the display to be dimmer; the reflective polarizer layer 534 prevents this occurrence.

Fig. 6 schematically illustrates an embodiment of a TFT array to drive a display. The TFT array is similar to the arrays used to drive conventional LCDs. The orientation of liquid crystals in layer 214 in Figs. 2A-B, layer 414 in Fig. 4 and layer 514 in Figs. 5A-B may be controlled by TFT array embodiment 600 in Fig. 6. In an exemplary embodiment, TFT array 600 may be used as the top electrode layer 212 in Figs. 2A-B, layer 412 in Fig. 4 and layer 512 in Figs. 5A-B. In other embodiments, TFT array 600 may be used as the bottom electrode layer 216 in Figs. 2A-B, layer 416 in Fig. 4 and layer 516 in Figs. 5 A-B. TFT array 600 may be located anywhere in display embodiments 200, 400, 500. TFT array 600 may comprise an array of pixels 602 to drive the display embodiments described herein. A single pixel 602 is highlighted by a dotted line box in Fig. 6. Pixels 602 may be arranged in rows 604 and columns 606 as illustrated in Fig. 6 but other arrangements may be possible. In an exemplary embodiment, each pixel 602 may comprise a single TFT 608. In array embodiment 600, each TFT 608 may be located in the upper left of each pixel 602. In other embodiments, the TFT 608 may be placed in other locations within each pixel 602. Each pixel 602 may further comprise a conductive layer 610 to address each pixel of the display. Layer 610 may comprise ITO, aluminum, copper, gold, Baytron™, or conductive nanoparticles, silver wires, metal nanowires, graphene, nanotubes, or other conductive carbon allotropes or a combination of these materials dispersed in a polymer. TFT array embodiment 600 may further comprise column 612 and row 614 wires. Column wires 612 and row wires 614 may comprise a metal such as aluminum, copper, gold or other electrically conductive metal. Column 612 and row 614 wires may comprise ITO. The column 612 and row 614 wires may be attached to the TFTs 608. Pixels 602 may be addressed in rows and columns. TFTs 608 may be formed using amorphous silicon or poly crystalline silicon. The silicon layer for TFTs 608 may be deposited using plasma-enhanced chemical vapor deposition (PECVD). In an exemplary embodiment, each pixel may be substantially aligned with a single color filter in layers 208, 408 or 508. Column 612 and row 614 wires may be further connected to integrated circuits and drive electronics to drive the display.

Any of the display embodiments described herein may comprise a diffuser layer. A diffuser layer may be used to soften the incoming light or reflected light or to reduce glare. Diffuser layer may comprise a flexible polymer. Diffuser layer may comprise ground glass in a flexible polymer matrix. Diffuser may comprise a micro-structured or textured polymer. Diffuser layer may comprise 3M™ anti-sparkle or anti-glare film. Diffuser layer may comprise 3M™ GLR320 film (Maplewood, MN) or AGF6200 film. A diffuser layer may be located at one or more various locations within the display embodiments 200, 400, 500 described herein.

Any of the display embodiments described herein may further comprise at least one optically clear adhesive (OCA) layer. OCA layer may be flexible or conformable. The OCA layer may have a refractive index in the range of about 1 -1.5. OCA's may be used to adhere display layers together within the display stack and to optically couple the layers. Any of display embodiments 200, 400, 500 described herein may comprise one or more optically clear adhesive layers in any location within the displays further comprised of one or more of 3M™ optically clear adhesives 3M™ 8211 , 3M™ 8212, 3M™ 8213, 3M™ 8214, 3M™ 8215, 3M™ OCA 8146-X, 3M™ OCA 817X, 3M™ OCA 821X, 3M™ OCA 9483, 3M™ OCA 826XN or 3M™ OCA 8148-X, 3M™ CEF05XX, 3M™ CEF06XXN, 3M™ CEF19XX, 3M™ CEF28XX, 3M™ CEF29XX, 3M™ CEF30XX, 3M™ CEF31 , 3M™ CEF71XX, Lintec MO-T020RW, Lintec MO-3015UV series, Lintec MO-T015, Lintec MO-3014UV2+, Lintec MO-3015UV.

Any of the display embodiments described herein may further include at least one optional dielectric layer. The one or more optional dielectric layers may be used to protect one or both of the layers in any of the display embodiments described herein. In some embodiments, the dielectric layers may comprise different compositions. The dielectric layers may be substantially uniform, continuous and substantially free of surface defects. The dielectric layers may be at least about 5 nanometers in thickness or more. In some embodiments, the dielectric layer thickness may be about 5 to 300 nanometers. In other embodiments, the dielectric layer thickness may be about 5 to 200 nanometers. In still other embodiments, the dielectric layer thickness may be about 5 to 100 nanometers. The dielectric layers may each have a thickness of at least about 30 nanometers. In an exemplary embodiment, the thickness may be about 30-200 nanometers. In other embodiments, parylene may have a thickness of about 20 nanometers. The dielectric layers may comprise at least one pin hole. The dielectric layer may define a conformal coating and may be free of pin holes or may have minimal pin holes. The dielectric layer may also be a structured layer. The dielectric layer may also act as a barrier layer to prevent moisture or gas ingress. The dielectric layers may have a high or low dielectric constant. The dielectric layers may have a dielectric constant in the range of about 1 -15. Dielectric compounds may be organic or inorganic in type. The most common inorganic dielectric material is SiC commonly used in integrated chips. The dielectric layer may be SiN. The dielectric layer may be AI2O3. The dielectric layer may be a ceramic. Organic dielectric materials are typically polymers such as polyimides, fluoropolymers, polynorbomenes and hydrocarbon-based polymers lacking polar groups. The dielectric layers may be a polymer or a combination of polymers. The dielectric layers may be combinations of polymers, metal oxides and ceramics. In an exemplary embodiment, the dielectric layers comprise parylene. In other embodiments the dielectric layers may comprise a halogenated parylene. Other inorganic or organic dielectric materials or combinations thereof may also be used for the dielectric layers. One or more of the dielectric layers may be CVD or sputter coated. One or more of dielectric layers may be a solution coated polymer, vapor deposited dielectric or sputter deposited dielectric. In an exemplary embodiment, at least one dielectric layer may be located on at least one of the front or rear electrodes.

Any of the display embodiments described herein may further comprise a conductive crossover. A conductive cross-over may bond to the front electrode layer and to a trace on the rear electrode layer such as a TFT. This may allow a driver integrated circuit (IC) to control the voltage at the front electrode. In an exemplary embodiment, the conductive cross-over may comprise an electrically conductive adhesive that is flexible or conformable.

In order to bend or flex any of the display embodiments described herein comprising convex protrusions, the protrusions may be spaced far enough apart such that they do not impinge on neighboring protrusions. As the amount of flex is desired in the display increases, the spacing may need to be increased to prevent impinging of adjacent protrusions. The smaller the spacing, the less the display may be allowed to flex or bend. In some embodiments the spacing between the protrusions may be about 0.01 Dm or larger. In other embodiments, the spacing between the protrusions may be about 0.01-lODm. In still other embodiments, the spacing between the protrusions may be about 1-5 Dm. In some embodiments, the ratio of the height of a protrusion to the spacing of adjacent protrusions is in the range of about 100: 1 to about 5: 1.

At least one edge seal may be employed with the disclosed display embodiments. The edge seal may prevent ingress of moisture or other environmental contaminants from entering the display. The edge seal may be a thermally, chemically or a radiation cured material or a combination thereof. The edge seal may comprise one or more of an epoxy, silicone, polyisobutylene, acrylate or other polymer based material. In some embodiments the edge seal may comprise a metallized foil. In some embodiments the edge sealant may comprise a filler such as SiC or AI2O3. In other embodiments, the edge seal may be flexible or conformable after curing. In still other embodiments, the edge seal may also act as a barrier to moisture, oxygen and other gasses.

Various control mechanisms for the invention may be implemented fully or partially in software and/or firmware. This software and/or firmware may take the form of instructions contained in or on a non-transitory computer-readable storage medium. Those instructions may then be read and executed by one or more processors to enable performance of the operations described herein. The instructions may be in any suitable form, such as but not limited to source code, compiled code, interpreted code, executable code, static code, dynamic code, and the like. Such a computer-readable medium may include any tangible non-transitory medium for storing information in a form readable by one or more computers, such as but not limited to read only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; a flash memory, etc.

In some embodiments, a tangible machine-readable non-transitory storage medium that contains instructions may be used in combination with the disclosed display embodiments. In other embodiments the tangible machine-readable non-transitory storage medium may be further used in combination with one or more processors.

Fig. 7 shows an exemplary system for controlling a display according to one embodiment of the disclosure. In Fig. 7, display embodiments 200, 400 or 500 may be controlled by controller 740 having processor 730 and memory 720. Other control mechanisms and/or devices may be included in controller 740 without departing from the disclosed principles. Controller 740 may define hardware, software or a combination of hardware and software. For example, controller 740 may define a processor programmed with instructions (e.g., firmware). Processor 730 may be an actual processor or a virtual processor. Similarly, memory 720 may be an actual memory (i.e., hardware) or virtual memory (i.e., software). Memory 720 may store instructions to be executed by processor 730 for driving any of the display embodiments described herein such as 200, 400 or 500. The instructions may be configured to operate display 200, 400 or 500. In one embodiment, the instructions may include biasing electrodes associated with display 200, 400 or 500 through power supply 750. By appropriately biasing the electrodes, liquid crystals (e.g. , liquid crystals 214 in Figs. 2A-B; liquid crystals 414 in Fig. 4; liquid crystals 514 in Figs. 5A-B) may be controlled such as the orienting or re-orienting of twisted nematic liquid crystals. Absorbing the incoming light creates a dark or colored state. By appropriately biasing the electrodes, liquid crystals (e.g. , liquid crystals 214 in Figs. 2A-B; liquid crystals 414 in Fig. 4; liquid crystals 514 in Figs. 5A-B) may be controlled such as the orienting or re-orienting of twisted nematic liquid crystals in order to reflect or absorb the incoming light. Reflecting the incoming light creates a light state.

In an exemplary embodiment, controller 740 controls power (bias) 750 to the display. That is, controller 740 may increase or decrease power supplied to the display in order to appropriately activate liquid crystals in the display. Activation of the liquid crystals, as discussed above, modulates the incoming light to create light and dark states as desired. In one embodiment, the controller causes the liquid crystal layer to convert the first polarized light ray to one of: (1) pass through the second optical polarization layer, or (2) to be absorbed by the second optical polarization layer. 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. The IoT devices may comprise a touch screen. The IoT devices may further comprise a voice recognition system.

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, smart watches, fitness tracker (i.e. , Fitbit™), wearables, military display applications, automotive displays, automotive license plates, shelf labels, flash drives and outdoor billboards or outdoor signs comprising a display. The automotive displays may include a dashboard, an odometer, speedometer, gas gauge, audio system or rear back up camera. The displays may be powered by one or more of a battery, solar cell, wind power, electrical generator, electrical outlet, AC power, DC power or other means.

Fig. 8 is an exemplary method according to one embodiment of the disclosure. The method of Fig. 8 may be stored at a memory circuitry (e.g., memory 720 of Fig. 7) and may be implemented by a processor circuitry executing a controller (e.g., processor 730, controller 740, Fig. 7). The method of Fig. 8 may be implemented as a process flow.

The method of Fig. 8 starts at step 800 where the incoming light is received at the display device. The display device may comprise a liquid crystal display configured to provide TIR. The incoming light may have at least one of a first polarization state and a second polarization state. At step 810, a first optical filter is used to filter the incoming light ray to absorb the first polarization state of the incoming light ray thereby forming a first polarized light ray.

At step 820, the first polarized light ray is converted to a second polarized light ray by modulating the orientation of a plurality of liquid crystals processing the first polarized light ray. As discussed, a controller may receive input (e.g., from an external sensor (not shown)) to modulate the liquid crystals to produce the desired effect on the first polarized light ray.

At step 830, the second polarized light ray may be filtered at a second filter to one of: (1) absorb the second polarized light ray at the second optical filter, or (2) to allow the second polarized light ray to pass through the second optical filter. If the light is entirely absorbed by the second filter a dark state may be created.

At step 840, the light that has passed through the second filter (the second polarized light ray) is directed to a high gain reflection layer. If the light (second polarized light) enters the high gain reflection layer at an angle less than the critical angle (0 _C ), then the incoming light is passed through the high gain reflection layer to a reflector and reflected back through the display to the viewer. On the other hand, if light enters the high gain reflection layer at an angle substantially equal or greater than the critical angel (0 _C ), then the incoming light is totally -internally reflected at the high gain reflection layer. The following non-limiting examples are provided to further illustrate some of the disclosed embodiments.

Example 1 is directed to a liquid crystal display, comprising: a first transparent sheet to receive an incoming light ray, the incoming light ray having at least one of a first polarization state and a second polarization state; a first optical polarization layer to receive the incoming light ray, absorb the first polarization state of the incoming light ray and allow a first polarized light ray to pass therethrough; a tunable liquid crystal layer to receive the first polarized light ray and to convert the first polarized light ray to a second polarized light ray; a second optical polarization layer to receive the second polarized light ray from the tunable liquid crystal layer and to one of absorb the second polarized light ray or to and allow the second polarized light ray to pass therethrough; a high gain reflector layer in optical communication with the second optical polarization layer, the high gain reflector layer having a first and a second medium arranged to form an interface therebetween, the interface configured to allow the second polarized light ray to pass therethrough when the second polarized light ray enters the interface at an angle less than a critical angle (0 _C ) or to totally internally reflect the second polarized light ray when the second polarized light ray enters the interface at an angle that is greater than the critical angle (0 _C ); and a reflection layer positioned to optically communicate with the second medium.

Example 2 is directed to the display of example 1, further comprising a reflective polarizer layer configured to receive the second polarized light ray from the second optical polarization layer and allow the received second polarized light ray to one of pass therethrough or to be reflected as a function of the polarization of the second polarized light ray.

Example 3 is directed to the display of example 1, wherein the first optical polarization layer is configured to remove a polarization state that is substantially orthogonal to the polarization state removed by the second optical polarization layer.

Example 4 is directed to the display of example 1, wherein the high gain reflector is configured to semi-retro-reflect the first perpendicular polarized light ray, the first perpendicular polarized light ray substantially retaining its polarization through the high gain reflector.

Example 5 is directed to the display of example 1, wherein the ratio of the refractive index of the first medium to the second medium is in the range of about 1.5 to 1.8.

Example 6 is directed to the display of example 1, further comprising a first and a second electrode in communication with the liquid crystal layer.

Example 7 is directed to the display of example 1, further comprising a light reflection layer in optical communication with the plurality of protrusions, wherein the plurality of protrusions are separated from the light reflection layer by a cavity. Example 8 is directed to the display of example 1 , further comprising a light source to communicate light into an edge of a light guide formed over the first transparent sheet.

Example 9 is directed to the display of example 1 , further comprising a controller and a bias source, the controller to control a bias input to the liquid crystal layer.

Example 10 is directed to the display of example 1, wherein the controller causes the liquid crystal layer to convert the first polarized light ray to one of: pass through the second optical polarization layer or to be absorbed by the second optical polarization layer.

Example 1 1 is directed to the display of example 1 , further comprising a color filter.

Example 12 is directed to the display of example 1, wherein the critical angle is about 30° or larger.

Example 13 is directed to a liquid crystal display, comprising: a first transparent sheet to receive an incoming light ray, the incoming light ray having at least one of a first polarization state and a second polarization state; a first optical polarization layer to receive the incoming light ray, absorb the first polarization state of the incoming light ray and allow a first polarized light ray to pass therethrough; a tunable liquid crystal layer to receive the first polarized light ray and to convert the first polarized light ray to a second polarized light ray; a second optical polarization layer to receive the second polarized light ray from the tunable liquid crystal layer and to one of absorb the second polarized light ray or to and allow the second polarized light ray to pass therethrough; a high gain reflector layer in optical communication with the second optical polarization layer, the high gain reflector layer having an array of convex protrusions that semi- retro-reflect light while substantially retaining the polarization state of the second polarized light ray; and a reflection layer positioned to optically communicate with the high gain reflector layer.

Example 14 is directed to the display of example 13, further comprising a reflective polarizer layer configured to receive the second polarized light ray from the second optical polarization layer and allow the received second polarized light ray to one of pass therethrough or to be reflected as a function of the polarization of the second polarized light ray.

Example 15 is directed to the display of example 13, wherein the high gain reflector unit further comprises a first medium arranged to form an interface with the array of convex protrusions, the interface configured to allow the second polarized light ray to pass therethrough when the second polarized light ray enters the interface at an angle less than a critical angle (6c) or to totally internally reflect the second polarized light ray when the second polarized light ray enters the interface at an angle that is greater than the critical angle (6c).

Example 16 is directed to the display of example 13, wherein the ratio of the refractive index of the convex protrusions to the first medium is in the range of about 1.5 to 1.8. Example 17 is directed to the display of example 13, wherein the critical angle is about 30° or larger.

Example 18 is directed to the display of example 13, wherein the array of convex protrusions has a substantially higher refractive index than the first medium.

Example 19 is directed to the display of example 13, wherein the first optical polarization layer is configured to remove a polarization state that is substantially orthogonal to the polarization state removed by the second optical polarization layer.

Example 20 is directed to the display of example 13, further comprising a first and a second electrodes in communication with the liquid crystal layer.

Example 21 is directed to the display of example 13, further comprising a light reflection layer in optical communication with the plurality of protrusions, wherein the plurality of protrusions are separated from the light reflection layer by a cavity.

Example 22 is directed to the display of example 13, further comprising a light source to communicate light into the edge of a light guide formed over the first transparent sheet.

Example 23 is directed to the display of example 13, further comprising a controller and a bias source, the controller to control a bias input to the liquid crystal layer.

Example 24 is directed to the display of example 13, wherein the controller causes the liquid crystal layer to convert the first polarized light ray to one of: pass through the second optical polarization layer or to be absorbed by the second optical polarization layer.

Example 25 is directed to the display of example 13, further comprising a color filter.

Example 26 is directed to a method to provide a display with a liquid crystal device, comprising: receiving an incoming light ray, the incoming light ray having at least one of a first polarization state and a second polarization state; filtering, at a first optical filter, the incoming light ray to absorb the first polarization state of the incoming light ray thereby forming a first polarized light ray; converting the first polarized light ray to a second polarized light ray by modulating orientation of a plurality of liquid crystals processing the first polarized light ray; filtering, at a second optical filter, the second polarized light ray to one of absorb the second polarized light ray at the second optical filter or to allow the second polarized light ray to pass through the second optical filter; directing the second polarized light ray to a reflection layer when the second polarized light ray enters a high gain reflector interface at an angle less than a critical angle (6c); and totally-internally reflecting the second polarized light ray when the second polarized light ray enters the interface at an angle that is greater than the critical angle (6c).

Example 27 is directed to the method of example 26, further comprising receiving the second polarized light ray from the second optical polarization layer and allowing the received second polarized light ray to one of pass through a reflective polarizer layer or to be reflected by the reflective polarizer layer as a function of a polarization state of the second polarized light ray.

Example 28 is directed to the method of example 26, wherein the step of totally -internally reflecting the second polarized light ray further comprises totally-internally reflecting the second polarized light ray through a convex protrusion that semi-retro-reflects the second polarized light ray while substantially retaining the polarization state of the second polarized light ray.

Example 29 is directed to the method of example 26, wherein the high gain reflector layer further comprises a first medium wherein the ratio of the refractive index of the array of convex protrusions to the first medium is in the range of about 1.5 to 1.8.

Example 30 is directed to the method of example 26, wherein the critical angle is greater than about 30°.

Example 31 is directed to the method of example 26, wherein the first optical filter has a polarization state that is substantially orthogonal to the polarization state of the second optical filter.

Example 32 is directed to the method of example 26, further comprising biasing the plurality of liquid crystals to convert the first polarized light ray to a second polarized light ray.

Example 33 is directed to the method of example 26, wherein receiving an incoming light ray further comprises injecting the incoming light ray into a light guide layer.

Example 34 is directed to the method of example 26, further comprising controlling a bias input to the liquid crystals to orient the plurality of liquid crystals from a first orientation to a second orientation.

Example 35 is directed to the method of example 26, further comprising displaying an output light from the device through a light filter.

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.