[0001] The present application claims the priority benefit of U.S. Provisional Serial No. 63/199,122, filed December s, 2020, the contents of which are incorporated by reference herein.

BACKGROUND

[0002] The present disclosure relates to liquid crystal displays. In particular, the displays are configured such that a composite layer thereof is transparent when no voltage is applied and scatters incident light when a voltage is applied.

[0003] State-of-the-art liquid crystal displays for flat panel display applications (e.g., televisions, computer monitors, and smart phones) typically include a light source and a liquid crystal layer. Light is emitted by the light source and the liquid crystal modulates the light intensity. The displays need two polarizers for the liquid crystal to operate properly. The liquid crystal layer is sandwiched between the polarizers. Voltages are applied to the liquid crystal to vary its optical retardation, and thus change the emitted light intensity. The displays also need color filters to display colored images. The polarizers and color filters absorb light, and therefore the displays usually have poor light efficiencies (e.g., less than 10%).

[0004] It would be desirable to develop new liquid crystal displays that do not require polarizers or color filters.

[0005] A liquid crystal display addressing these issues is described in U.S. App. Ser. No. 16/332,102, filed March 11 , 2019, which is incorporated by reference herein in its entirety. The waveguide liquid crystal display may be edgelit and may operate on the light scattering of a polymer-stabilized liquid crystal. When no voltage is applied, the liquid crystal may be uniformly aligned and transparent. The incident light is waveguided by total internal reflection and no light comes out of the viewing side of the display. When a voltage is applied, the liquid crystal may be switched to a micronsized poly-domain structure and become scattering. The incident light may be scattered out of the viewing side of the display.

[0006] It would be desirable to develop new displays with improvements such as at least one of higher brightness, lower driving voltage, sub-millisecond switching time, and higher contrast ratio. The new displays may be suitable for transparent displays, heads-up vehicle displays, augmented displays, and smart window applications.

BRIEF DESCRIPTION

[0007] The present disclosure relates to liquid crystal displays which include patterned electrodes and/or are fabricated using patterned photo-polymerization.

[0008] Disclosed in embodiments is a liquid crystal display comprising in sequence: a first transparent electrode; a first alignment layer; a composite layer comprising a liquid crystal and a polymer; a second alignment layer; and a second transparent electrode; and further comprising at least one light source; wherein when no voltage is applied the composite layer is transparent and the display acts as a waveguide plane through which incident light propagates; wherein when a voltage is applied the composite layer scatters incident light out of the display; and wherein the liquid crystal display does not comprise at least one of polarizers and color filters. In some embodiments, the liquid crystal display includes one or more color filters but no polarizers. In other embodiments, the liquid crystal display includes one or more polarizers but no color filters. In further embodiments, the liquid crystal display is devoid of both polarizers and color filters.

[0009] In some embodiments, the display further includes an absorbing film on a side of the second transparent electrode opposite the second alignment layer.

[0010] The first transparent electrode and the second transparent electrode may comprise indium tin oxide.

[0011] In some embodiments, the liquid crystal has a positive dielectric anisotropy. In other embodiments, the liquid crystal has a negative dielectric anisotropy.

[0012] The liquid crystal may be tilted toward a cell normal direction when the voltage is applied or tilted parallel to the first transparent electrode and the second transparent electrode when the voltage is applied.

[0013] In some embodiments, the at least one light source comprises a lightemitting diode.

[0014] The at least one light source may include a red light-emitting diode, a green light-emitting diode, and a blue light-emitting diode.

[0015] The at least one light source may comprise or consist of a white lightemitting diode. [0016] In some embodiments, the first alignment layer and the second alignment layer comprise a polyimide.

[0017] Disclosed in other embodiments is a liquid crystal display comprising in sequence: a first transparent substrate; a plurality of interdigitated electrodes; a composite layer comprising a liquid crystal and a polymer; and a second transparent substrate; and further comprising at least one light source; wherein when no voltage is applied the composite layer is transparent and the display acts as a waveguide plane through which incident light propagates; wherein when a voltage is applied the composite layer scatters incident light out of the display; and wherein the liquid crystal display does not comprise at least one of polarizers and color filters. In some embodiments, the liquid crystal display includes one or more color filters but no polarizers. In other embodiments, the liquid crystal display includes one or more polarizers but no color filters. In further embodiments, the liquid crystal display is devoid of both polarizers and color filters.

[0018] The interdigitated electrodes may comprise indium tin oxide.

[0019] In some embodiments, the liquid crystal has a positive dielectric anisotropy. In other embodiments, the liquid crystal has a negative dielectric anisotropy.

[0020] The liquid crystal may be tilted toward a cell normal direction when the voltage is applied or tilted parallel to the first transparent substrate and the second transparent substrate when the voltage is applied.

[0021] In some embodiments, the at least one light source comprises a lightemitting diode.

[0022] The at least one light source may comprise a red light-emitting diode, a green light-emitting diode, and a blue light-emitting diode.

[0023] In some embodiments, the display further includes an alignment layer between the interdigitated electrodes and the composite layer.

[0024] Disclosed in further embodiments is a method for operating and/or controlling a liquid crystal display. The method includes applying a voltage to change a state of the liquid crystal display from a first state to a second state. In some embodiments, the first state is a light-propagating state, and the second state is a lightscattering state. In other embodiments, the first state is a light-scattering state, and the second state is a light propagating state. [0025] Disclosed in other embodiments is a method for operating and/or controlling a liquid crystal display. The method includes removing an applied voltage to change a state of the liquid crystal display from a first state to a second state. In some embodiments, the first state is a light-propagating state, and the second state is a lightscattering state. In other embodiments, the first state is a light-scattering state, and the second state is a light propagating state.

[0026] The liquid crystal display used in either or both of these methods may include (optionally in sequence): a first transparent substrate; a plurality of interdigitated electrodes; a composite layer comprising a liquid crystal and a polymer; and a second transparent substrate. In other embodiments, the liquid crystal display includes (optionally in sequence) a first transparent electrode, a first alignment layer, a composite layer, a second alignment layer, and a second transparent electrode. The display further includes at least one light source.

[0027] In some embodiments, the display is devoid of at least one of polarizers and color filters.

[0028] In some embodiments, the display is devoid of polarizers but may contain one or more color filters.

[0029] In other embodiments, the display is devoid of color filters but may contain one or more polarizers.

[0030] In further embodiments, the display is devoid of both polarizers and color filters.

[0031] These and other non-limiting aspects and/or objects of the disclosure are more particularly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The following is a brief description of the drawings, which are presented for the purposes of illustrating the exemplary embodiments disclosed herein and not for the purposes of limiting the same.

[0033] FIG. 1 includes schematic diagrams of a waveguide display in (a) a transparent state and (b) a scattering state.

[0034] FIG. 2 includes schematic diagrams of a direct view waveguide display in (a) a dark state and (b) a bright state. [0035] FIG. 3 includes schematic diagrams of a transparent waveguide display in (a) a transparent state and (b) and an opaque state.

[0036] FIG. 4 includes schematic diagrams of a vertical aligned waveguide display in (a) a transparent state and (b) a scattering state.

[0037] FIG. 5 includes schematic diagrams of an in-plane switching waveguide display in (a) a transparent state and (b) a scattering state.

[0038] FIG. 6 includes schematic diagrams of a color sequential waveguide display including: (a) the red-color sub-frame; (b) the green color sub-frame; and (c) the blue color sub-frame.

DETAILED DESCRIPTION

[0039] A more complete understanding of the devices and methods disclosed herein can be obtained by reference to the accompanying drawings. These figures are merely schematic representations based on convenience and the ease of demonstrating the existing art and/or the present development, and are, therefore, not intended to indicate relative size and dimensions of the assemblies or components thereof.

[0040] Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function. In the following specification and the claims which follow, reference will be made to a number of terms, which shall be defined to have the following meanings.

[0041] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0042] As used in the specification and in the claims, the term "comprising" may include the embodiments "consisting of" and "consisting essentially of." The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the named components/steps and permit the presence of other components/steps. However, such description should be construed as also describing devices or methods as "consisting of" and "consisting essentially of" the enumerated components/steps, which allows the presence of only the named components/steps and excludes other components/steps.

[0043] Numerical values in the specification and claims of this application should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

[0044] Numerical values should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

[0045] All ranges disclosed herein are inclusive of the recited endpoint and independently combinable.

[0046] The term “about” can be used to include any numerical value that can vary without changing the basic function of that value. When used with a range, “about” also discloses the range defined by the absolute values of the two endpoints. The term “about” may refer to plus or minus 10% of the indicated number.

[0047] The waveguide displays of the present disclosure do not require polarizers, exhibit ultrafast response time, and allow a color sequential scheme to display colored images. Therefore, the displays have ultrahigh light efficiency.

[0048] The displays include two parallel substrates with at least one transparent electrode and a composite layer containing a liquid crystal and a polymer. The liquid crystal/polymer composite layer is sandwiched between the two substrates. A light source, such as a light-emitting diode (LED), is installed on the edge of the display. The (unpolarized) light produced by the edge light source is provided into the display. When no voltage is applied, the liquid crystal/polymer composite is transparent and the display acts as a waveguide plate through which the incident light propagates. No light comes out of the display. When a voltage is applied across the composite layer, the material becomes scattering, and the incident light is scattered out of the display. This display does not need polarizers and has ultrahigh energy efficiency. It also has ultrafast response time. When three colored light (e.g., red, green, and blue) sources are installed on the edge, it can be operated as a color sequential display. With a black absorbing film placed beneath it, the display can be used as a regular flat panel display. Without the absorbing film, it can be used as a transparent display. When no voltage is applied, the display is transparent to ambient light and the scene behind the display can be seen.

[0049] The structure of a display in accordance with some embodiments of the present disclosure is schematically shown in FIG. 1 , wherein 110 denotes an edgelight, 120 denotes transparent electrodes, 130 denotes polymer networks, 140 denotes liquid crystals, 150 denotes the rubbing direction, and 160 denotes voltage applied pixels. The display includes two substrates, a layer of liquid crystal/polymer composite, and an edge light source. The substrates have a transparent electrode (e.g., and indium-tin-oxide or ITO electrode) on a surface thereof. On top of the ITO, an alignment layer is coated and/or rubbed for homogeneous alignment of the liquid crystal/polymer composite. The liquid crystal/polymer layer is sandwiched between the two substrates. An edge light, such as a LED, is installed on the edge of the display perpendicular (or parallel) to the alignment rubbing direction. The edge light produces light which is provided into the substrates and liquid crystal/polymer layer. When the incident light hits the substrate-air interface with a large incident angle (defined with respect to the normal of the substrate), it will be total internally reflected because the refractive index of the substrate is larger than that of air. When no voltage is applied, the liquid crystal/polymer composite is transparent. The incident light is waveguided through the display and no light comes out as shown in (a). When a voltage is applied to the composite in some pixel (region), the material is switched into a poly-domain structure and becomes light scattering, due to the aligning effects of the electric field and the polymer network. The incident light is scattered away from its original propagation direction. It hits the substrate-air interface with a small incident angle and comes out of the display as shown in (b). This display does not need polarizers, and therefore its light efficiency is at least two times higher than regular polarizer-based liquid crystal displays.

[0050] The waveguide displays of the present disclosure can be used as direct view displays. A non-limiting example of a design is schematically shown in FIG. 2, wherein 210 denotes an edgelight, 230 denotes polymer networks, 240 denotes liquid crystals, 260 denotes voltage applied pixels, 270 denotes an absorbing film, and 280 denotes ambient light. An absorbing film is placed beneath the bottom substrate, which absorbs ambient light. When no voltage is applied, the liquid crystal/polymer composite is transparent, and no light comes out as shown in (a). The display appears dark. When a voltage is applied across a pixel, the material in the pixel becomes scattering, and light comes out as shown in (b). The pixel appears bright.

[0051] The waveguide displays of the present disclosure can also be used as transparent displays. A non-limiting example of a design is schematically shown in FIG. 3, wherein 310 denotes an edgelight, 330 denotes polymer networks, 340 denotes liquid crystals, and 360 denotes voltage applied pixels. When no voltage is applied, the liquid crystal/polymer composite is transparent, and the scene behind the display can be seen as shown in (a). When a voltage is applied across a pixel, the material in the pixel becomes scattering, and the scene behind the display is blocked as shown in (b).

[0052] In the waveguide displays discussed in some of the preceding paragraphs, the liquid crystal and polymer network are generally initially aligned parallel to the display substrate. The liquid crystal has a positive dielectric anisotropy. When no voltage is applied, the material is transparent. When a voltage is applied in the vertical direction, the liquid crystal is tilted toward the cell normal direction and becomes scattering. Another geometry of alignment, the vertical alignment, can also be used for the waveguide display, as shown in FIG. 4, wherein 410 denotes an edgelight, 430 denotes polymer networks, 440 denotes liquid crystals, and 460 denotes voltage applied pixels. Initially, the liquid crystal and polymer network are aligned perpendicular to the display substrate. The liquid crystal has a negative dielectric anisotropy. When no voltage is applied, the material is transparent as shown in (a). When a voltage is applied in the vertical direction, the liquid crystal is tilted toward parallel to the display substrate and becomes scattering as shown in (b).

[0053] In the waveguide displays discussed in some of the preceding paragraphs, the transparent electrodes are on the inner surface of the top and bottom substrates. When a voltage is applied, the generated electric field is perpendicular to the substrates. Another geometry of electrode, the in-place switching (IPS)Zfringe-field switching (FFS) electrode, can also be used for the waveguide display, as shown in FIG. 5, wherein 510 denotes an edgelight, 520 denotes electrodes, 530 denotes polymer networks, 540 denotes liquid crystals, and 560 denotes voltage applied pixels. The interdigitated electrodes are only on the inner surface of one substrate. When a voltage is applied, the generated electric field is approximately parallel to the substrates. Initially the liquid crystal and polymer network are aligned perpendicular to the display substrate. The liquid crystal has a positive dielectric anisotropy. When no voltage is applied, the material is transparent as shown in (a). When a voltage is applied, the liquid crystal is tilted toward parallel to the display substrate and becomes scattering as shown in (b).

[0054] The waveguide display has very fast response time. Both turn-on and turnoff times can be less than 1 ms. Therefore, it can be operated in a color sequential mode (also called field sequential color mode) to display full color images. A nonlimiting example of a design is schematically shown in FIG. 6, wherein 610 denotes an edgelight and 660 denotes voltage applied pixels. Three LEDs with the primary colors red (R), green (G), and blue (B), respectively, are installed on the edge of the display. The addressing frame is divided into three sub-frames: R, G, and B. During the R sub-frame, a voltage is applied to the red LED to turn it on. During the G subframe, a voltage is applied to the green LED to turn it on. During the B sub-frame, a voltage is applied to the blue LED to turn it on. The voltage applied to the liquid crystal/polymer composite is synchronized with the voltages applied to the LEDs. A red color image is displayed when the voltage is only applied to liquid crystal/polymer material during the R sub-frame. A green color image is displayed when the voltage is only applied to liquid crystal/polymer material during the G sub-frame. A blue color image is displayed when the voltage is only applied to liquid crystal/polymer material during the B sub-frame. A yellow color image is displayed when the voltage is applied to liquid crystal/polymer material during the R and G sub-frames. A magenta color image is displayed when the voltage is applied to liquid crystal/polymer material during the R and B sub-frames. A cyan color image is displayed when the voltage is applied to liquid crystal/polymer material during the G and B sub-frames. A white color image is displayed when the voltage is applied to liquid crystal/polymer material during the R, G, and B sub-frames. Regular liquid crystal displays need color filters, which absorb more than two-thirds of the incident light, in order to show colored images. This waveguide display can show colored images without color filters. Therefore, it can further greatly increase light efficiency.

[0055] Non-limiting examples of liquid crystals include the E-series and BL-series liquid crystals (commercially available from Merck). [0056] In some embodiments, the E-series liquid crystal includes one or more of E7, E44, and E48.

[0057] In some embodiments, the BL-series liquid crystal includes one or more of BL003, BL006, and BL038.

[0058] In some embodiments, the liquid crystal component includes a cyanobiphenyl material.

[0059] In some embodiments, the liquid crystal component includes a cyanoterphenyl material.

[0060] In some embodiments, the liquid crystal component includes at least one cyano-biphenyl material, at least one cyano-terphenyl material, or a mixture thereof.

[0061] In some embodiments, the liquid crystal component includes only one type of liquid crystal material.

[0062] In other embodiments, the liquid crystal component includes a plurality of distinct liquid crystal materials.

[0063] The plurality may include two, three, four, five, six, seven, eight, nine, ten, or more liquid crystal materials.

[0064] In more particular embodiments, the liquid crystal component includes at least two different liquid crystal materials. The ratio (by weight) of the first liquid crystal material to the second liquid crystal material may be in the range of about 1 :99 to about 99:1 , including from about 10:90 to about 90:10, about 20:80 to about 80:20, about 70:30 to about 30:70, about 40:60 to about 60:40, about 45:55 to about 55:45, and about 50:50.

[0065] The electrodes may be made from any film that is electrically conducting and optically transparent. Non-limiting examples include indium tin oxide electrodes and conducting polymer electrodes.

[0066] In some embodiments, the alignment layer(s) include a polyimide, poly(vinyl alcohol), and/or poly(methyl methacrylate).

[0067] Non-limiting examples of photoinitiators which may be used in the systems and methods of the present disclosure include benzoin methyl ether and the Irgacure series of photoinitiators (e.g., Irgacure 184 and Irgacure 651).

[0068] In some embodiments, the photoinitiator includes one or more of azobisisobutyronitrile (Al BN), a benzoyl peroxide, and camphorquinone. [0069] The polymer networks may be formed from one or more reactive monomers/reactive mesogens. Non-limiting examples of reactive monomers/reactive mesogens include Merck’s RM series and HCCH’s HCM series. In some embodiments, the reactive monomer(s) is/are selected from RM257, RM82, HCM- 024, and HCM-028.

[0070] In some embodiments, the polymer networks are formed via reactions involving one or more of 2-Methylbenzene-1 ,4-diyl bis{4-[3- (acryloyloxy)propoxy]benzoate} (CAS No. 174063-87-7), 1 ,4-Bis-[4-(6- acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene (CAS No. 125248-71-7), 2- methyl-1 ,4-phenylene bis(4-(3-(acryloyloxy)propoxy)benzoate) (CAS No. 174063-87- 7), 2-methyl-1 ,4-phenylene bis(4-((6-(acryloyloxy)hexyl)oxy)benzoate) (CAS No. 125248-71-7), 4-methoxyphenyl 4-((6-(acryloyloxy)hexyl)oxy)benzoate (CAS No. 82200-53-1), 4-cyanophenyl 4-((6-(acryloyloxy)hexyl)oxy)benzoate (CAS No. 83847- 14-7), 6-(4-hydroxyphenoxy)hexyl acrylate, 4-(3-(acryloyloxy)propoxy)benzoic acid (CAS No. 245349-46-6), 4-((6-(acryloyl oxy)hexyl)oxy)benzoic acid (CAS No. 83883- 26-5), 6-((4'-cyano-[1 ,1 '-biphenyl]-4-yl)oxy)hexyl acrylate, 4-((11 -(acryloyl oxy)undecyl)oxy)benzoic acid, and 4-((6-(acryloyl oxy)hexyl)oxy)phenyl 4-methoxy benzoate.

[0071] Methods for operating and/or controlling a liquid crystal display are also disclosed. The methods may include either (a) applying a new voltage and/or (b) removing an applied voltage to change a state of the liquid crystal display from a first state to a second state.

[0072] In some embodiments, the first state is a light-propagating state, and the second state is a light-scattering state. In other embodiments, the first state is a lightscattering state, and the second state is a light propagating state. The liquid crystal display used in these methods may include (optionally in sequence): a first transparent substrate; a plurality of interdigitated electrodes; a composite layer comprising a liquid crystal and a polymer; and a second transparent substrate. The display further includes at least one light source. In some embodiments, the display does not contain polarizers. In other embodiments, the display does not contain color filters. In further embodiments, the display does not contain polarizers or color filters.

[0073] In some embodiments, the voltage is in the range of from about 1 to about 100 V, including from about 2 to about 80 V, from about 5 to about 70 V, from about 10 to about 50 V, from about 20 to about 40 V, from about 25 to about 35 V, and about 30 V.

[0074] In some embodiments, the pulse width of the applied voltage is in the range of from about 1 to about 1000 ms, from about 50 to about 700 ms, from about 75 to about 400 ms, from about 100 to about 300 ms, from about 150 to about 250 ms, and about 200 ms.

[0075] The displays of the present disclosure find use in many industries and applications. Non-limiting examples include mobile devices, televisions, and transparent displays for advertisements.

[0076] Thanks to their merits of high resolution, high brightness, flat paneled, and low manufacturing cost, liquid crystal displays (LCDs) are the leading technology for information displays and are widely used in many applications from small-size devices, such as smartphones, to large screen devices such as TVs. LCDs include twisted nematic (TN) LCDs, in-plane-switching (IPS) LCDs, vertical alignment (VA) LCDs, and fringe field switch (FFS) LCDs. In embodiments, the liquid crystal does not emit light; instead, it modulates the intensity of the light produced by backlight or edgelight through the help of polarizers; and display colored images through the help of color filters. Thus, the energy efficiency of LCDs is low due to the employment of the polarizers and color filters which absorb more than 90% of the light produced by the backlight or edgelight. Furthermore, they are not suitable for new applications such transparent displays, heads-up vehicle displays, augmented displays, and smart windows.

[0077] Some light wave guide liquid crystal displays are based on light scattering which is caused by random variation of refractive index of a polymer stabilized liquid crystal. The material may be a mixture of a liquid crystal with a concentration more than 90% and a photo-polymerizable monomer with a concentration less than 10%. The material is filled into a display cell made from two parallel substrates with transparent (e.g., Indium-Tin-Oxide or ITO) electrode(s) on the inner surface of the substrates. On top of ITO an alignment layer is coated, which generates a uniform alignment of the liquid crystal and monomer. Then the cell is irradiated by UV light to polymerize the monomer. When the monomer molecules are polymerized, they phase separate from the liquid crystal and form a polymer network consisting of fibrils. The polymer fibrils are long, anisotropic and in the same direction as the liquid crystal. The fibrils have an aligning effect on the liquid crystal, which try to remain the liquid crystal in the initial direction. The locations of the fibrils are random throughout the cell. The refractive indices of the liquid crystal and the fibrils are close to each other.

[0078] In the waveguide display, LEDs are installed on the edge of the display. The produced light is coupled into the display. When no voltage is applied, the material is a uniform optical medium and does not scatter light. The incident light is waveguided through the cell by total internal reflection at the substrate-air interface. No light comes out of the viewing side of the display. When a voltage is applied across the cell in the vertical direction, the electric field tries to align the liquid crystal (with a positive dielectric anisotropy) in the vertical direction, while the polymer fibrils try to retain the liquid crystal in the initial direction. The liquid crystal is switched into a random polydomain structure with a length scale comparable to the wavelength of light. The incident light encounters different refractive indices in different liquid crystal domains. Therefore, it is scattered by the liquid crystal. Some of the scattered light incident on the substrate-air interface with a small incident angle (with respect to the substrate normal), and therefore comes out of the viewing side of the display.

[0079] The outgoing light intensity of the waveguide display depends on the light scattering of the polymer stabilized liquid crystal, which in term depends on the randomness of the liquid crystal domain. In the voltage-off state (dark state) the orientation of the liquid crystal should be as uniform as possible to minimize the scattering. In the voltage-on state (bright state), the orientation of the liquid crystal should be as random as possible to maximize the scattering. In non-limiting embodiments, this is achieved using one or both of the techniques discussed below. The first technique to enhance the scattering in the voltage-on state is to use patterned ITO electrode. The electrode is patterned into stripes or other patterns. In the voltage- off state, there is no electric field anywhere inside the cell. Therefore, the patterning does change the orientation of the liquid crystal, and thus the optical property remains the same. In the voltage-on state, in the region, where there is ITO electrode and thus there is an electric field, the liquid crystal will reorient under the electric field in the same way as before, while in the region, where there is no ITO electrode and thus there is no electric field, the liquid crystal does not reorient. This will increase the randomness of the liquid crystal and thus enhance of the scattering. The second technique to enhance scattering in the voltage-on state is to use patterned photo- polymerization. The photomask includes alternating black and transparent stripes or other patterns. When the cell is placed under UV light to photo-polymerize the monomer molecules, the photomask is put on top of the display facing the UV light. In the region of the cell under the back stripe, the UV light is blocked, and thus sparse polymer network forms, while in the region of the cell under the transparent stripe, dense polymer network forms. After the polymerization, in the voltage-off state, the liquid crystal is uniformly aligned in the aligning direction of the alignment, and thus the optical property remains the same. In the voltage-on state, in the region where the polymer network is sparse, the liquid crystal will reorient more under the electric field, while in the region where polymer network is dense, the liquid crystal tilts less under the electric field. Therefore, the patterned photo-polymerization will increase the randomness of the liquid crystal and thus enhance of the scattering.

[0080] As discussed above, the patterning may be stripes in the photomask and/or configuring the transparent electrodes in stripes. One or both sides of the cell may include the striped electrode configuration. The electrode width may be equal to or approximately equal to the distance between adjacent electrodes. In other embodiments, these may be dissimilar. The widths of the electrodes may be the same or different. The distances may be the same or different. The (at least partially) transmitting and (at least partially) blocking stripes in the photomask may have the same or different widths. The stripes may have widths in the range of about 1 pm to about 25 pm, including from about 2 pm to about 20 pm, about 5 pm to about 15 pm, about 7 pm to about 13 pm, about 8 pm to about 12 pm, about 9 pm to about 11 pm, and about 10 pm.

[0081] The following examples are provided to illustrate the devices and methods of the present disclosure. The examples are merely illustrative and are not intended to limit the disclosure to the materials, conditions, or process parameters set forth therein.

EXAMPLES

[0082] Example 1

[0083] The polymer stabilized liquid crystal was made from 94.5 wt.% of nematic liquid crystal BOE-5 (from BOE), which has a positive dielectric anisotropy (As > 0), 5 wt.% of bifunctional reactive mesogenic monomer RM-257 (from Merck), and 0.5 wt.% photo-initiator BME (from PolyScience). The display cell was made from two parallel glass plates with ITO coating. A homogeneous alignment layer polyimide SE 2170 (from Nissan Chemical Industries, Ltd.) was spin coated on top of the ITO, pre-baked at 80°C, hard backed at 200°C, and then mechanically rubbed. The cell gap was controlled by 2 pm polymer sphere spacers. The liquid crystal/mixture was filled into the cell by capillary action on a hot plate.

[0084] The cell was placed under an LED UV light (365 nm) to photo-polymerize the monomer. The UV light intensity was 7 mW/cm ² .

[0085] Photomasks were used for the patterned photo-polymerization, The photomasks had patterned stripes consisting of alternating transparent and black stripes. Five photomasks with different transparent and black stripe widths were used to make five displays, respectively. In the fabrication of display P1 , the widths of the black stripe and transparent stripe of the used mask were all 5 pm, denoted as 5pm x 5 pm. In the fabrication of display P2, the widths of the black stripe and transparent stripe of the used mask were all 10 pm, denoted as 10 pm x 10 pm. In the fabrication of display P3, the widths of the black stripe and transparent stripe of the used mask were all 20 pm, denoted as 20 pm x 20 pm. In the fabrication of display P4, the widths of the black stripe and transparent stripe of the used mask were 25 pm and 250 pm, respectively, denoted as 25 pm x 250 pm. In the fabrication of display P5 (the reference display), no mask was used.

[0086] A white LED was installed on the edge of the display parallel to the stripe. The produced light was coupled into the display cell.

[0087] The intensities of the light coming out of the displays are measured. The displays made under patterned photo-polymerization are all better than the one made under no mask. The patterned photo-polymerization increases the outgoing light intensity but does not change the driving voltage. Display P2, made under the 10 pm x 10 pm mask, has the best performance. The driving voltages, maximum light intensities and contrast ratios of the displays are listed in T able 1 . The patterned photopolymerization does not affect the orientation of the liquid crystal in the voltage-off state. Therefore, the outgoing light intensity of the voltage-off state remains unchanged. The randomness of the liquid crystal of the voltage-on state is enhanced and the outgoing light intensity is increased. The turn-on and turn-off times of the displays remain unchanged. As an example, the dynamic response of display P2 to a voltage pulse is discussed. The amplitude of the pulse is 15 V. The turn-on time is 0.23 ms and the turn-off time is 1 .2 ms.

Table 1 Performance of the waveguide displays with patterned photo-polymerization

[0088] Example 2

[0089] The polymer stabilized liquid crystal was made from 94.5 wt.% of nematic liquid crystal BOE-5 (from BOE), which has a positive dielectric anisotropy (As > 0), 5 wt.% of bifunctional reactive mesogenic monomer RM-257 (from Merck), and 0.5 wt.% photo-initiator BME (from PolyScience). The display cell was made from two parallel glass plates with ITO coating. A homogeneous alignment layer polyimide SE 2170 (from Nissan Chemical Industries, Ltd.) was spin coated on top of the ITO, pre-baked at 80°C, hard backed at 200°C, and then mechanically rubbed. The cell gap was controlled by 2 pm polymer sphere spacers. The liquid crystal/mixture was filled into the display cell by capillary action on a hot plate.

[0090] The cell was placed under an LED UV light (365 nm) to photo-polymerize the monomer. The UV light intensity was 7 mW/cm ² . The UV irradiation time was 30 m.

[0091] A photomask was used for the patterned photo-polymerization. The photomask had a 10 pm x 10 pm square pattern consisting of alternating transparent and black squares. The display is called display P6.

[0092] A white LED was installed on one edge of the display. The produced light was coupled into the display cell.

[0093] The intensity of the light coming out of the display was measured. For comparison, the light intensity as a function of applied voltage of display P2 was evaluated. The performance of display P6 is close to that of display P2 but is much better than display P5 (without patterned polymerization).

[0094] Example 3 [0095] The polymer stabilized liquid crystal was made from 94.5 wt.% of nematic liquid crystal BOE-5 (from BOE), which has a positive dielectric anisotropy (As > 0), 5 wt.% of bifunctional reactive mesogenic monomer RM-257 (from Merck), and 0.5 wt.% photo-initiator BME (from PolyScience). The display cell was made from two parallel glass plates with ITO coating. A homogeneous alignment layer polyimide SE 2170 (from Nissan Chemical Industries, Ltd.) was spin coated on top of the ITO, pre-baked at 80°C, hard backed at 200°C, and then mechanically rubbed. The cell gap is controlled by 2 pm polymer sphere spacers. The liquid crystal/mixture was filled into the display cell by capillary action on a hot plate.

[0096] Cells with patterned electrodes were used to make waveguide displays. The cell consisted of two parallel glass plates with ITO electrode on the inner surface. One of the electrodes of the cell was not patterned and the other electrode was patterned into stripes. In display S1 , the width of the ITO electrode was 5 pm and the gap between two adjacent electrodes was 5 pm, denoted as 5 pm x 5 pm. In display S2, the width of the ITO electrode was 20 pm and the gap between electrodes was 20 pm, denoted as 20 pm x 20 pm. In display S3, the width of the ITO electrode was 250 pm and the gap between electrodes was 25 pm, denoted as 250 pm x 25 pm. In display S4 (the reference display), the electrode was not patterned.

[0097] The cell was placed under an LED UV light (365 nm) to photo-polymerize the monomer. No photomask was used. The UV light intensity was 7 mW/cm ² .

[0098] A white LED was installed on one edge of the display. The produced light was coupled into the display cell.

[0099] The intensity of the light coming out of the display was measured. The light intensity as a function of applied voltage of the display was evaluated. The driving voltages, maximum light intensities and contrast ratios of the displays are listed in Table 2. Compared with display S4 (with non-patterned electrode), Display S3 has a better performance: the maximum outgoing light intensity is higher, and the driving voltage is the same; Displays S1 and S2 have higher maximum outgoing light intensities, but their driving voltages are higher. As example, the dynamic response of display S3 to a voltage pulse was measured. In the measurement, a voltage pulse with 15 V amplitude and 500 ms width was applied, and the outgoing light intensity as a function of time was evaluated. The turn-on time and turn-off time are 0.22 ms and 1.1 ms, respectively, which are superfast and adequate for color sequence operation. Table 2: Performance of the waveguide displays with single side patterned electrodes

[00100] Example 4

[00101] The polymer stabilized liquid crystal was made from 94.5 wt.% of nematic liquid crystal BOE-5 (from BOE), which has a positive dielectric anisotropy (As > 0), 5 wt.% of bifunctional reactive mesogenic monomer RM-257 (from Merck), and 0.5 wt.% photo-initiator BME (from PolyScience). The display cell was made from two parallel glass plates with ITO coating. A homogeneous alignment layer polyimide SE 2170 (from Nissan Chemical Industries, Ltd.) was spin coated on top of the ITO, pre-baked at 80°C, hard backed at 200°C, and then mechanically rubbed. The cell gap was controlled by 2 pm polymer sphere spacers. The liquid crystal/mixture was filled into the cell by capillary action on a hot plate.

[00102] The cell was placed under an LED UV light (365 nm) to photo-polymerize the monomer. The UV light intensity was 7 mW/cm ² .

[00103] A display with patterned ITO with "LCI" characters was fabricated. It was polymerized under the mask with the 10 pm x 10 pm stripe pattern.

[00104] The display can be operated in either transparent display mode, or direct view display mode. To demonstrate the displays in transparent display mode, a picture of Kent State University was placed behind them. When no voltage was applied, the display was very transparent with a transmittance about 90%, and the picture behind them could be seen clearly. When 15 V was applied, the ITO region with "LCI" characters became bright, while the region without ITO remained transparent. To demonstrate the display in direct view display mode, a black absorbing layer was placed behind them. When no voltage was applied, the displays appeared black. When 15 V was applied, the ITO region with "LCI" characters became bright, while the region without ITO remained dark. The contrast ratio of the display was about 50:1 . [00105] The present disclosure has been described with reference to exemplary embodiments. Obviously, modifications and alternations will occur to others upon reading and understanding the preceding detailed description. It is intended that the present disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.