EP4713743A1

EP4713743A1 - Switchable windows including a bistable liquid crystal cell and a second cell

Info

Publication number: EP4713743A1
Application number: EP24807881.8A
Authority: EP
Inventors: Stephen Joseph Caracci; Celine Claude Guermeur; Mingqian He; Xiang-Dong Mi
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2023-05-17
Filing date: 2024-05-13
Publication date: 2026-03-25
Also published as: WO2024238459A1

Abstract

Switchable windows comprising a first bistable liquid crystal cell and a second bistable cell, selected from a second bistable liquid crystal cell and a bistable electrochromic cell, the first bistable liquid crystal cell and the bistable electrochromic cell bonded together by an interlayer, are provided. Methods of switching a switchable window from a first stable state to a second stable state are further provided.

Description

SWITCHABLE WINDOWS INCLUDING A BISTABLE LIQUID CRYSTAL CELL AND A SECOND CELL

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 63/467,048 filed May 17, 2023, the content of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The present disclosure relates to windows and similar barriers.

BACKGROUND

[0003] Liquid crystal devices are used in various architectural and transportation applications, such as windows, doors, space partitions, and skylights for buildings and automobiles. For many commercial applications, it is desirable for liquid crystal devices to provide high contrast ratio between the on and off states while also providing good energy sufficiency and cost effectiveness. High contrast ratio may be achieved using liquid crystal material and/or light absorbing additives. Achieving a high contrast ratio using a single liquid crystal cell design has been challenging to date.

[0004] Liquid crystal devices including a double cell structure, for example, two back-to-back (or “tandem”) liquid crystal cell units, have conventionally been used to obtain desired high contrast ratios. However, double cell structures may have various drawbacks, such as increased overall weight and thickness of the unit, as well as higher manufacturing cost and complexity due to the additional glass layers and electrode components. Further, the additional glass interfaces may also result in optical losses across the double cell structure.

[0005] Conventional switchable windows may be a polymer stabilized cholesteric texture (“PSCT”) switchable window made from a composite of a cholesteric liquid crystal and a polymer sandwiched between two parallel substrates with transparent electrodes that can be operated in normal mode, reverse mode, and bistable mode. However, the normal mode and the reverse mode require a voltage to be applied to sustain a transparent optical state. Further, the bistable mode requires voltage pulses with different frequencies, which makes the driving circuitry expensive, and the frequencies may change with ambient temperature. Though developments have subsequently resulted in no power being required to maintain the bistable mode, sunlight is not blocked from entering the window in either state of the bistable mode. Other conventional switchable windows may be multi-stable cholesteric liquid crystal switchable windows, but the windows do not block sunlight from entering the window in any of the multi-stable states.

[0006] Bistable electrochromic devices may include electrochromic polymers, which may have improved color change times and coloration efficiencies compared to inorganic electrochromic materials such as metal oxides and their complexes. All-solid-state electrochromic devices usable as rear-view mirrors, sunroof windows for vehicles and vessels, and building glazing units, may include an electrochromic layer, a solid electrolyte layer, and an ion storage layer, and may be safer because nothing may leak when glass of the device is broken. While the electrochromic devices may change transmittance of light, the devices do not provide privacy.

[0007] Conventional liquid crystal devices including bistable liquid crystal and an electrochromic layer have been difficult to fabricate with an interstitial substrate because the liquid crystal and the electrochromic layer require different fabrication process.

[0008] There is a need for the development of switchable windows that increases the number of achievable states. Further, there is a need for the development of switchable windows that require no power to maintain any of the stable states. Further, there is a need for the development of switchable windows that do not include polymer in the liquid crystal mixture.

SUMMARY

[0009] In an example, the present disclosure provides a switchable window. The switchable window includes a first bistable liquid crystal cell, a second liquid crystal cell or a bistable electrochromic cell, and an interlayer disposed between the first bistable liquid crystal cell and the second liquid crystal cell or the bistable electrochromic cell. The first bistable liquid crystal cell includes: a first bistable liquid crystal cell substrate, including a first bistable liquid crystal cell transparent electrode; a second bistable liquid crystal cell substrate, including a second bistable liquid crystal cell transparent electrode; and a liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode. The second liquid crystal cell or the bistable electrochromic cell includes: a first cell substrate, including a first cell transparent electrode; a second cell substrate, including a second cell transparent electrode. The second liquid crystal cell includes a cell layer disposed between the first cell transparent electrode and the second cell transparent electrode. The first bistable liquid crystal cell has a first liquid crystal stable state at zero voltage and a second liquid crystal stable state at zero voltage, the first liquid crystal stable state having a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”) and the second liquid crystal stable state having a second liquid crystal transmittance (“T12”) and a second liquid crystal haze value (“H12”). The second liquid crystal cell or the bistable electrochromic cell has a first stable state at zero voltage, the first stable state having a first transmittance (“T21”) and a first haze value (“H21”). The bistable electrochromic cell has a second stable state at zero voltage, the second stable state having a second transmittance (“T22”) and a second haze value (“H22”). The second bistable liquid crystal cell substrate is bonded to the first cell substrate is bonded to the first cell substrate by the interlayer. In the example of the switchable window, Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and | T21 - T22 | > 5%.

[00010] In another example, the present disclosure provides a switchable window. The switchable window includes a first bistable liquid crystal cell, a second bistable liquid crystal cell, and an interlayer disposed between the first bistable liquid crystal cell and the second bistable liquid crystal cell. The first bistable liquid crystal cell includes: a first bistable liquid crystal cell substrate, including a first bistable liquid crystal cell transparent electrode; a second bistable liquid crystal cell substrate, including a second bistable liquid crystal cell transparent electrode; and a liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode. The second bistable liquid crystal cell includes: a first cell substrate, including a first cell transparent electrode; a second cell substrate, including a second cell transparent electrode; and a cell layer disposed between the first cell transparent electrode and the second cell transparent electrode. The first bistable liquid crystal cell has a first liquid crystal stable state at zero voltage and a second liquid crystal stable state at zero voltage, the first liquid crystal stable state having a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”) and the second liquid crystal stable state having a second liquid crystal transmittance (“T12”) and a second liquid crystal haze value (“H12”). The second bistable liquid crystal cell has a first stable state at zero voltage and a second stable state at zero voltage, the first stable state having a first transmittance (“T21”) and a first haze value (“H21”) and the second stable state having a second transmittance (“T22”) and a second haze value (“H22”). The second bistable liquid crystal cell substrate is bonded to the first cell substrate by the interlayer. In the example of the switchable window, Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and | T21 - T22 | > 5%. [0010] In yet another example, the present disclosure provides a switchable window. The switchable window includes a first bistable liquid crystal cell, a bistable electrochromic cell, and an interlayer disposed between the first bistable liquid crystal cell and the electrochromic cell. The first bistable liquid crystal cell includes: a first bistable liquid crystal cell substrate, including a first bistable liquid crystal cell transparent electrode; a second bistable liquid crystal cell substrate, including a second bistable liquid crystal cell transparent electrode; and a liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode. The bistable electrochromic cell includes: a first cell substrate, including a first cell transparent electrode; and a second cell substrate, including a second cell transparent electrode. The first bistable liquid crystal cell has a first liquid crystal stable state at zero voltage and a second liquid crystal stable state at zero voltage, the first liquid crystal stable state having a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”) and the second liquid crystal stable state having a second liquid crystal transmittance (“T12”) and a second liquid crystal haze value (“H12”). The bistable electrochromic cell has a first stable state at zero voltage and a second stable state at zero voltage, the first stable state having a first transmittance (“T21”) and a first haze value (“H21”) and the second stable state having a second transmittance (“T22”) and a second haze value (“H22”). The second bistable liquid crystal cell substrate is bonded to the first cell substrate by the interlayer. In the example of the switchable window, Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and T21 — T22 > 5%.

[0011] In yet another example, the present disclosure provides a method of switching a bistable switchable window. The method includes applying a voltage to the bistable switchable window such that the switchable window is switched from a first stable state to a second stable state, the bistable switchable window including a first bistable liquid crystal cell and a second cell selected from a liquid crystal cell and a bistable electrochromic cell, the second cell bonded to the first bistable liquid crystal cell by an interlayer. In the first stable state, at zero voltage, the first bistable liquid crystal cell has a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”), and the second cell has a first transmittance (“T21”) and a first haze value (“H21”). In the second stable state, at zero voltage, the first bistable liquid crystal cell has a second liquid crystal transmittance (“T12”) and a second liquid crystal haze value (“H12”), and the second cell has a second transmittance (“T22”) and a second haze value (“H22”). In the example of the method, Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and | T21 - T22 |

5%. [0012] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework for understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated into and constitute a part of this specification. The drawings illustrate various examples of the disclosure, and together with the description, serve to explain the principles and operations of the various examples.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The following detailed description may be further understood when read in conjunction with the following drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. It is to be understood that the figures are not drawn to scale and the size of each depicted component or the relative size of one component to another is not intended to be limiting.

[0014] FIG. 1 illustrates a schematic of a cross-section of an example of a switchable window that includes a bistable liquid crystal cell and a dye-doped liquid crystal cell bonded together by a first interlayer;

[0015] FIG. 2 illustrates a schematic of a cross-section of another example of a switchable window that includes a cholesteric liquid crystal cell and a polarizer-based liquid crystal cell bonded together by a first interlayer;

[0016] FIG. 3 illustrates a schematic of a cross-section of yet another example of a switchable window that includes a bistable liquid crystal cell and a bistable electrochromic cell bonded together by a first interlayer;

[0017] FIG. 4 illustrates a schematic of a cross-section of yet another example of a switchable window that includes a bistable liquid crystal cell and a bistable electrochromic cell, with a first strengthened glass and a second strengthened glass; and

[0018] FIG. 5 illustrates a schematic of a cross-section of yet another example of a switchable window that includes a bistable liquid crystal cell and a bistable electrochromic cell, in which the second interlayer only covers the edges between the first strengthened glass and the first substrate of the bistable liquid crystal cell, and the third interlayer only covers the edges between the second strengthened glass and the second substrate of the bistable electrochromic cell. [0019] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

[0020] For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the present disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles disclosed herein as would normally occur to one skilled in the art to which this disclosure pertains. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0021] As used herein, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0022] In this document, relational terms, such as first and second, top and bottom, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions.

[0023] As used herein, the term “about” means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. Whether or not a numerical value or end-point of a range in the specification recites “about,” the numerical value or endpoint of a range is intended to include two embodiments: one modified by “about,” and one not modified by “about.” It will be further understood that the end-points of each of the ranges are significant both in relation to the other end-point, and independently of the other end-point. [0024] Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range was explicitly recited. As an illustration, a numerical range of “about 1 to about 5” should be interpreted to include not only the explicitly recited values of about 1 to about 5, but also to include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3, and 4, the sub ranges such as from 1-3, from 2-4, from 3-5, etc., as well as 1, 2, 3, 4, and 5 individually. The same principle applies to ranges reciting only one numerical value as a minimum or maximum. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described by the range.

[0025] The terms “substantial,” “substantially,” and variations thereof as used herein, unless defined elsewhere in association with specific terms or phrases, are intended to note that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover, “substantially” is intended to denote that two values are equal or approximately equal. In some embodiments, “substantially” may denote values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other. [0026] Directional terms as used herein — for example up, down, right, left, front, back, top, bottom, above, below, and the like — are made only with reference to the figures as drawn and are not intended to imply absolute orientation.

[0027] As used herein the terms "the," "a," or "an," mean "at least one," and should not be limited to "only one" unless explicitly indicated to the contrary. Thus, for example, reference to "a component" includes embodiments having two or more such components unless the context clearly indicates otherwise.

[0028] Examples of the disclosure will now be discussed with reference to FIGs. 1 - 5, which illustrate various aspects of the present disclosure. The following general description is intended to provide an overview of the claimed devices, and various aspects will be more specifically discussed throughout the disclosure with reference to the non-limiting depicted examples, these examples being interchangeable with one another within the context of the present disclosure. [0029] Referring to FIG. 1, a schematic of a cross-section of an example of a switchable window is illustrated. Switchable window 100 includes bistable liquid crystal cell 132 and liquid crystal cell 134 bonded together by first interlayer 116 is illustrated. In an example, bistable liquid crystal cell 132 is a bistable cholesteric liquid crystal cell. Bistable liquid crystal cell 132 includes first substrate 102 including first transparent electrode 104 and first alignment layer 106. Bistable liquid crystal cell 132 further includes second substrate 114 including second transparent electrode 112 and second alignment layer 110. Bistable liquid crystal cell 132 further includes liquid crystal layer 108 disposed between first alignment layer 106 and second alignment layer 110.

[0030] Bistable liquid crystal cell 132 may have a first stable state at zero voltage and a second stable state at zero voltage, the first stable state having a first transmittance Tn and a first haze value Hu and the second stable state having a second transmittance Tn and a second haze value H , wherein Hu < 5%, H > 80%, Tn > Tn. The first stable state may be transparent to the visible light, with a small haze value. The second stable state may be opaque, scattering visible light, with a high haze value.

[0031] Switchable window 100 further includes liquid crystal cell 134. Liquid crystal cell 134 may be monostable, bistable, or have more than two stable states. Liquid crystal cell 134 may be dye-doped. Liquid crystal cell 134 includes first substrate 118 including first transparent electrode 120 and first alignment layer 122. Liquid crystal cell 134 further includes second substrate 130 including second transparent electrode 128 and second alignment layer 126. Liquid crystal cell 134 further includes liquid crystal layer 124 disposed between first alignment layer 122 and second alignment layer 126. In an example, liquid crystal layer 124 may include a nematic liquid crystal and a dichroic dye.

[0032] In an example, liquid crystal cell 134 may be dye-doped, and may have a first state at zero voltage and a second state at an applied voltage, with the first state having a first transmittance T21 and a first haze value H21 and the second state having a second transmittance T22 and a second haze value T22, wherein H21 < 5%, H22 < 5%, and | T21 - T22 1 > 30%.

[0033] In an example, liquid crystal cell 134 may be dye-doped and include a nematic liquid crystal, a chiral dopant, and a dichroic dye in liquid crystal layer 124. An amount of a chiral dopant may be selected such that a total twist angle of liquid crystal layer 124 may be more than 360 degrees, 540 degrees, 720 degrees, 1880 degrees, or 2880 degrees, but less than 3000 degrees. A switching voltage for liquid crystal layer 124 having a twist angle of more than 3000 degrees may be more than 30 volts. As a twist angle increases, liquid crystal layer 124 may reflect visible light and lower visible light transmittance.

[0034] In an example, liquid crystal cell 134 may be dye-doped and may be either bistable or multi-stable at zero voltage, and first alignment layer 122 and/or second alignment layer 126 may include a grating, which may allow two or more stable states at zero voltage.

[0035] In an example, liquid crystal layer 124 includes normally transparent dye-doped nematic liquid crystal and black dichroic dye. First alignment layer 122 and second alignment layer 126 align the dye-doped liquid crystal nearly vertically in an absence of an applied voltage. An angle between the liquid crystal at first alignment layer 122 and/or second alignment layer 126 may be between 85 and 90 degrees relative to a plane of first substrate 118 or second substrate 130. At zero voltage, the black dichroic dye follows the orientation of the liquid crystal. The nematic liquid crystal has a negative dielectric anisotropy, so the liquid crystal may be switched into a twisted planar state while an external voltage is applied. The black dichroic dye follows the orientation of the liquid crystal, absorbing more light in the twisted planar state than in a vertical state. Liquid crystal cell 134 has a first state with a first transmittance at zero voltage that is higher than a second transmittance at a second state at an applied voltage, or T21 > T22.

[0036] In an example, liquid crystal layer 124 includes normally dark dye-doped nematic liquid crystal and black dichroic dye. First alignment layer 122 and second alignment layer 126 align the dye-doped liquid crystal nearly parallel to the plane of a substrate in an absence of an applied voltage. An angle between the liquid crystal at first alignment layer 122 and/or second alignment layer 126 may be between 0 and 10 degrees relative to a plane of first substrate 118 or second substrate 130. The nematic liquid crystal has a positive dielectric anisotropy, so the liquid crystal may be switched into a vertical (or “homeotropic”) state while an external voltage is applied. The black dichroic dye absorbs less visible light in this state than in the twisted planar state. Liquid crystal 134 has a first state with a first transmittance at zero voltage that is lower than a second transmittance at a second state at an applied voltage, or T21 < T22.

[0037] In an example, liquid crystal cell 134 is dye-doped, and a polarizer may be attached to first substrate 118 and/or second substrate 130 so as to enhance contrast.

[0038] In an example, switchable window 100 may include a first strengthened glass bonded to first substrate 102 of bistable liquid crystal cell 132 by a second interlayer and a second strengthened glass bonded to second substrate 130 of liquid crystal cell 134 by a third interlayer. The second interlayer may hold the first strengthened glass in place in case the first strengthened glass is broken, to provide safety. The third interlayer may add safety to the second strengthened glass. First interlayer 116 and the second interlayer and the third interlayer provide UV protection for bistable liquid crystal cell 132 and liquid crystal cell 134. The UV transmittance of switchable window 100 may be less than 1%, and preferably less than 0.1%. In certain examples, the second interlayer may cover only the outer edges between the first strengthened glass and first substrate 102, and a third interlayer may cover only the outer edges between the second strengthened glass and second substrate 130, and a first insulating gas may be sealed between the first strengthened glass and first substrate 102 and a second insulating gas may be sealed between the second strengthened glass and second substrate 130, providing improved thermal insulation.

[0039] Referring to FIG. 2, a schematic of a cross-section of another example of a switchable window is illustrated. Switchable window 200 includes bistable liquid crystal cell 132 and polarizer-based liquid crystal cell 202 bonded together by first interlayer 222 is illustrated. Polarizer-based liquid crystal cell 202 includes first substrate 206 including first transparent electrode 208 and first alignment layer 210 and second substrate 218 including second transparent electrode 216 and second alignment layer 214. Liquid crystal layer 212 is disposed between first transparent electrode 208 and second transparent electrode 216. Polarizer-based liquid crystal cell 202 further includes first polarizer 204 attached to first substrate 206 and second polarizer 220 attached to second substrate 218.

[0040] In an example, polarizer-based liquid crystal cell 202 has a first state at zero voltage and a second state at an applied voltage, with the first state having a first transmittance T21 and a first haze value H21 and the second state having a second transmittance T22 and a second haze value H22, wherein H21 < 5%, H22 < 5%, and | T21 - T22 | > 30%.

[0041] In an example, polarizer-based liquid crystal cell 202 is monostable or bistable or multistable at zero voltage. First alignment layer 210 and/or second alignment layer 214 includes a grating, which may allow two or more stable states at zero voltage.

[0042] In an example, polarizer-based liquid crystal cell 202 includes a 90-degree twisted nematic liquid crystal in liquid crystal layer 212. First alignment layer 210 and second alignment layer 214 align the liquid crystal in the plane of first substrate 206 and/or second substrate 218 but are rotated 90 degrees. At zero voltage, the liquid crystal rotates from a first orientation to a second orientation across the cell thickness direction. The absorption axis of an adjacent polarizer is parallel to the adjacent orientation direction. A compensation film is placed between the polarizer and liquid crystal layer 212. When a voltage is applied, the liquid crystal is aligned vertically. When first polarizer 204 and second polarizer 220 are perpendicular to each other, polarizer-based liquid crystal cell 202 is in a normally transparent mode, with T21 > T22. When first polarizer 204 and second polarizer 220 are parallel to each other, polarizer-based liquid crystal cell 202 is in a normally dark mode, with T21 < T22. A small amount of chiral dopant may be added to liquid crystal layer 212. The chiral dopant does not change the total twist angle of the liquid crystal. The chiral dopant may select left-handed or right-handed twist orientation, which may reduce haze caused by the scattering at the boundary of the left-handed and right-handed regions. Table 1 below provides further detail about the relative arrangements of planes and axes of an example of a polarizer-based liquid crystal cell similar to polarizer-based liquid crystal cell 202 illustrated in FIG. 2. The left column of Table 1 lists the elements of a polarizer-based liquid crystal cell in the same order as in polarizer-based liquid crystal cell 202 from first polarizer 204 to second polarizer 220.

TABLE 1

Normally Transparent Single TNLC with > 5 pm Cell Gap

[0043] The polarizer-based liquid crystal cell illustrated in Table 1 has a gap of 6 pm, filled with a nematic liquid crystal having a birefringence of about 0.08 at the wavelength (X) of 550 nm. An*d/X - 0.873 (close to the 1^st minimum 0.866) for X = 0.55 pm. Indium tin oxide (ITO of 30-40 nm thickness was applied to two Corning Eagle XG® glass substrates to form a transparent electrode on one surface of each substrate. The glass substrates were 0.5 mm thick and had width and length dimensions of 370 mm x 470 mm. The active (ITO-coated) area of the cell was about 350 mm x 450 mm (-90% coverage). The ITO coating was continuous, not patterned or pixelated over the active area.

[0044] In the liquid crystal cell, the alignment layers had perpendicular alignment directions of +45° and -45° (315°) relative to the horizontal axis of the liquid crystal window. The polarizer transmission axes and absorption axes were also perpendicular to each other and at +45° and -45° relative to the horizontal axis, respectively. The compensation layers were discotic liquid crystal polymer compensation films (Wide View Film from Fuji Photo co.). The optic axis of each compensation layer films varies in a plane that contains the film thickness direction and an alignment direction. The normal direction of the plane of the compensation layer was parallel to the absorption axis of the corresponding polarizer. The normal directions of the planes for the two compensation films were oriented perpendicularly to each other at +45° and -45° relative to the horizontal axis. Upon an application of voltage, the liquid crystal molecules were oriented to face downward.

[0045] Referring to FIG. 3, a schematic of a cross-section of yet another example of a switchable window is illustrated. Switchable window 300 includes bistable liquid crystal cell 132 and bistable electrochromic cell 302 bonded together by first interlayer 304. Bistable electrochromic cell 302 includes first substrate 306 including first transparent electrode 308 and second substrate 318 including second transparent electrode 316. Bistable electrochromic cell 302 includes electrochromic layer 310, electrolyte layer 312, and ion storage layer 314 disposed between first transparent electrode 308 and second transparent electrode 316. As illustrated in FIG. 3, in some examples, electrochromic layer 310, electrolyte layer 312, and ion storage layer 314 may be disposed sequentially between first transparent electrode 308 and second transparent electrode 316.

[0046] In an example, bistable electrochromic cell 302 has a first stable state at zero voltage and a second stable state at zero voltage, the first stable state having a first transmittance T21 and a first haze value H21 and the second stable state having a second transmittance T22 and a second haze value H22, wherein H21 < 5%, H22 < 5%, and T21 - T22 > 5%. Both of the first and second stable states may have a small haze value less than 5%, or even less than 3%. The second stable state may be a dark or tinted state, having lower transmittance than the first stable state for the visible light. The first stable state may be a transparent state.

[0047] In an example of switchable window 300, first substrate 102 and second substrate 114 are glass substrates, providing desired mechanical strength and maintaining desired cell gap uniformity, while first substrate 306 and second substrate 318 are polymeric substrates, including a polymer such as polyethylene terephthalate (“PET”). Bistable electrochromic cell 302 made from polymeric substrates are cost effective to fabricate and bond to the glass-based bistable liquid crystal cell 132. Such a switchable window has four stable states while being thin and light-weighted.

[0048] Referring to FIG. 4, a schematic of a cross-section of yet another example of a switchable window is illustrated. Switchable window 400 includes bistable liquid crystal cell 132 and bistable electrochromic cell 302, with first strengthened glass 402 and second strengthened glass 408, is illustrated. First strengthened glass 402 is bonded to first substrate 102 of bistable liquid crystal cell 132 by second interlayer 404. Second strengthened glass 408 is bonded to second substrate 318 of bistable electrochromic cell 302 by third interlayer 406. Second interlayer 404 and third interlayer 406 cover the interfaces between first strengthened glass 402 and first substrate 102 of bistable liquid crystal cell 132 and between second strengthened glass 408 and second substrate 318 of bistable electrochromic cell 302, respectively.

[0049] Second interlayer 404 may hold first strengthened glass 402 in place in case first strengthened glass 402 is broken, to provide safety. Third interlayer 406 may add safety to second strengthened glass 408. Each of first interlayer 304, second interlayer 404, and third interlayer 406 may further provide UV protection for bistable liquid crystal cell 132 and bistable electrochromic cell 302. The UV transmittance of switchable window 400 may be less than 1%, and preferably less than 0.1%. First strengthened glass 402 and second strengthened glass 408 may include a coating that minimizes an amount of infrared and ultraviolet light that comes through the glass, without affecting the amount of light that passes through the glass.

[0050] Referring to FIG. 5, a schematic of a cross-section of yet another example of a switchable window is illustrated. Switchable window 500 includes bistable liquid crystal cell 132 and bistable electrochromic cell 302, in which second interlayer 506 only covers the outer edges between first strengthened glass 502 and first substrate 102 of bistable liquid crystal cell 132, and third interlayer 508 only covers the outer edges between second strengthened glass 512 and second substrate 318 of bistable electrochromic cell 302. First insulating gas 504 is sealed between first strengthened glass 502 and first substrate 102. Second insulating gas 510 is sealed between second strengthened glass 512 and second substrate 318. First insulating gas 504 and second insulating gas 510 may provide improved thermal insulation.

[0051] Electrodes

[0052] Each electrode described herein, including, for example, each of first transparent electrode 104, second transparent electrode 112, first transparent electrode 120, second transparent electrode 128, first transparent electrode 208, second transparent electrode 216, first transparent electrode 308, second transparent electrode 316 . . . independently may be any electrode known in the art that is suitable for liquid crystal devices or cells, such as liquid crystal devices or cells used in window applications. In certain examples, the characteristics and properties of each electrode may be independent selected, and may be the same or different from other electrodes in the liquid crystal device, cell, or window. In other examples, each electrode independently may include interdigitated electrodes.

[0053] In certain examples, each electrode independently may include one or more transparent conductive oxides (“TCOs”), such as indium tin oxide (“ITO”), indium zinc oxide (“IZO”), gallium zinc oxide (“GZO”), aluminum zinc oxide (“AZO”), aluminum oxide, gallium oxide, nano-silver paste, or other like materials or suitable transparent conductive material, or any combination thereof. In other examples, each electrode independently may additionally or alternatively include other transparent materials, such as a conductive mesh, for example, including metals such as silver nanowires or other nanomaterials such as graphene or carbon nanotubes, or any combination thereof. In still other examples, each electrode independently may additionally or alternatively include one or more printable conductive ink layers, such as ActiveGrid™ available from C3Nano Inc.

[0054] In certain examples, each electrode may independently have a sheet resistance ranging from (in Q/n) 10 to 1000, 50 to 900, 100 to 800, 200 to 700, 300 to 600, or 400 to 500, or any range that may be made from any two of the foregoing numbers, and all ranges and subranges therebetween.

[0055] In certain examples, each electrode may be fabricated using any technique known in the art, such as vacuum sputtering, film lamination, printing techniques, or any combination thereof.

[0056] In certain examples, each electrode may be deposited on one or more substrate surfaces to form a layer of material that may or may not include a pattern.

[0057] In certain examples, the thickness of each electrode may independently range from 1 nm to 1000 nm, such as from 5 nm to 500 nm, from 10 nm to 300 nm, from 20 nm to 200 nm, from 30 nm to 150 nm, or from 50 nm to 100 nm, or any range that may be made from any two of the foregoing numbers, and all ranges and subranges therebetween.

[0058] Alignment Lavers

[0059] Each alignment layer described herein, including, for example, each of first alignment layer 106, second alignment layer 110, first alignment layer 122, and second alignment layer 126, first alignment layer 210, and second alignment layer 214, independently may include a thin film of material having a surface energy and anisotropy promoting a desired or predetermined orientation for the liquid crystals in direct contact with a surface of the alignment layer. Examples of materials for each alignment layer independently may include a grating; main chain or side chain polyimides, which may be mechanically rubbed to generate layer anisotropy; photosensitive polymers, such as azobenzene-based compounds, which may be exposed to linearly polarized light to generate surface anisotropy; inorganic thin films, such as silica, which may be prepared or deposited using thermal evaporating techniques to form periodic microstructures on the surface; or any combination thereof. In certain examples, organic alignment layers promoting vertical or homeotropic orientation of the liquid crystal molecules may be rubbed to create different pretilt angles other than 90° with respect to the plane of the substrate. In other examples, the pretilt angle of the liquid crystal molecules with respect to the substrate surface may break the symmetry during switching from vertical orientation and may define an azimuthal direction of liquid crystal switching. Alignment layers may also be referred to as “orientation layers” in certain examples.

[0060] Organic alignment layers may be deposited, for example, by spincoating a solution onto a desired surface or by using printing techniques. Inorganic alignment layers may be deposited using thermal evaporation techniques. In certain examples, each alignment layer independently may have a thickness of less than or equal to about 100 nm, for example ranging from about 1 nm to about 100 nm, from about 5 nm to about 90 nm, from about 10 nm to about 80 nm, from about 20 nm to about 70 nm, from about 30 nm to about 60 nm, or from about 40 nm to about 50 nm, or any range that may be made from any two of the foregoing numbers, including all ranges and subranges therebetween.

[0061] In an example, each alignment layer may be or may include a grating. A grating may be any known grating in the art, and may be prepared by known techniques. Such gratings and techniques for making may include those described in (1) Wood et al., Zenithal Bistable Device (ZBD™) Suitable for Portable Applications, 31 SOCIETY FOR INFORMATION DISPLAY (SID) SYMPOSIUM DIGEST OF TECHNICAL PAPERS 124 (2000); (2) Jones, The Zenithal Bistable Display: From concept to consumer, 16 J. SOCIETY FOR INFORMATION DISPLAY (SID) 143 (2008); (3) Jones, et al., Invited Paper: Low Cost Zenithal Bistable Display with Improved White State, 41 SID SYMPOSIUM DIGEST OF TECHNICAL PAPERS (2010); each of which is incorporated herein in its entirety for all purposes.

[0062] In an example, the grating may be produced using standard photolithography techniques, which may include preparing a grating master using hard-contact photolithography, embossing an uncured photopolymer with the grating master, and photocuring the photopolymer to result in the grating. Any suitable photopolymer may be used to form the grating.

[0063] In an example, the grating may have any suitable pitch, such as a pitch of 0.1 microns to 2.0 microns. For example, the pitch (microns) may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or any range formed from any two of the foregoing numbers, such as 0.1 - 2.0, 0.2 - 1.9, 0.3 - 1.8, 0.4 - 1.7, 0.5 - 1.6, 0.6 - 1.5, 0.7 - 1.4, 0.8 - 1.3, 0.9 - 1.2, 1.0 - 1.1, 0.6 - 1.0, 0.7 - 0.9, 0.5 - 0.9, or 0.7 - 1.5. Generally, the pitch is the distance between adjacent peaks. In certain examples, the pitch may be generally uniform throughout the grating. In other examples, the pitch may be not generally uniform throughout the grating because particular areas of the grating have varied pitches or the pitch changes continuously across certain areas. If the pitch is generally uniform throughout the grating, then the pitch is the distance between two adjacent peaks. If the pitch is not generally uniform throughout the grating, then the pitch is an average of a group of 25 adjacent peaks for a particular area, and in such an example, the foregoing numbers in this paragraph are in reference to an average pitch. In still other examples, the grating may have a uniform pitch that is 0.6 - 1 microns or 0.8 microns, or any other number or range disclosed herein. In still other examples, any pitch in this paragraph (or elsewhere herein) may be combined with any depth in the following paragraph (or elsewhere herein) to form a pitch/depth pair to describe a grating.

[0064] In an example, the grating may have any suitable depth, such as a depth of 0.1 microns to 2.0 microns. For example, the depth (microns) may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, or any range formed from any two of the foregoing numbers, such as 0.1 - 2.0, 0.2 - 1.9, 0.3 - 1.8, 0.4 - 1.7, 0.5 - 1.6, 0.6 - 1.5, 0.7 - 1.4, 0.8 - 1.3, 0.9 - 1.2, 1.0 - 1.1, 0.9 - 1.3, 1.0 - 1.2, 0.8 - 1.2, or 1 - 1.8. Generally, the depth is the height of a peak relative to the adjacent valley. In certain examples, the depth may be generally uniform throughout the grating. In other examples, the depth may not be generally uniform throughout the grating because particular areas of the grating have varied depths or the depth changes continuously across certain areas. If the depth is generally uniform throughout the grating, then the depth is the height of a peak relative to the adjacent valley. If the depth is not generally uniform throughout the grating, then the depth is an average of a group of 25 adjacent peak/valley pairs for a particular area, and in such an example, the foregoing numbers in this paragraph are in reference to an average depth. In still other examples, the grating may have a uniform depth that is 0.8 - 1.3 microns or 1.1 microns, or any other number or range disclosed herein. In still other examples, any depth in this paragraph (or elsewhere herein) may be combined with any pitch in the preceding paragraph (or elsewhere herein) to form a pitch/depth pair to describe a grating.

[0065] In an example, a grating may have a sinusoidal shape. In certain examples, a grating may be uniform and have a pitch of 0.6 - 1 microns and a depth of 0.8 - 1.3 microns. In other examples, a grating may be uniform and have a pitch of 0.8 microns and a depth of 1.1 microns. [0066] Improved alignment of liquid crystals may be attained through the use of alignment layers, but alignment layers are not required elements for examples of liquid crystal cells described herein, and it may be possible to remove one or more alignment layer such that no alignment layers are in contact with the liquid crystal layer(s) or only one alignment layer is in contact with the liquid crystal layer. As such, one or more alignment layer may be removed from examples of liquid crystal cells described herein without departing from the scope of the disclosure.

[0067] Liquid Crystal Lavers

[0068] Each liquid crystal cell described herein includes at least one liquid crystal layer. Each liquid crystal layer described herein, including, for example, each of liquid crystal layer 108, liquid crystal layer 124, and liquid crystal layer 212 independently may be disposed between two alignment layers, or at least between an alignment layer and another element, such as an electrode, as described elsewhere herein, or may be disposed between two alignment layers, or at least between an alignment layer and another element, such as an electrode, as described elsewhere herein. In certain examples, each liquid crystal layer independently may be in direct contact with an alignment layer that facilitates the alignment layer imparting alignment to the liquid crystal molecules in the liquid crystal layer. In other examples, each liquid crystal layer independently may be in direct contact with an alignment layer that facilitates the alignment layer imparting alignment to the liquid crystal molecules in the liquid crystal layer.

[0069] In an example, the orientation of a liquid crystal layer may be described by a unit vector, referred to herein as a “director,” which may represent the average local orientation of the long molecular axes of the liquid crystal molecules. A vertical alignment or homeotropic state may be achieved when a liquid crystal director may have a perpendicular or substantially perpendicular orientation with respect to the plane of a liquid crystal cell (for example, the plane of any of the alignment layer, electrode, and/or substrate). A planar alignment (homogeneous state or low pre-tilt) may be achieved when the liquid crystal director has a parallel or substantially parallel orientation with respect to the plane of the liquid crystal cell. An oblique alignment or grayscale state may be achieved when the liquid crystal director has a large angle with respect to the plane of a liquid crystal cell, which is substantially different from planar or homeotropic, in other words, ranging from 20° to 70°, such as from 30° to 60°, or from 40° to 50°, including all ranges and subranges therebetween. In certain examples, a liquid crystal layer may include multiple stable states (for example, first and second stable states). At least one of the stable states may include liquid crystals aligned substantially perpendicular (for example, within 10°) to at least one of the first alignment layer, the second alignment layer (if present), the first electrode, and the second electrode. Another of the stable states may include liquid crystals aligned substantially parallel (for example, within 10°) to at least one of the first alignment layer, the second alignment layer (if present), the first electrode, and the second electrode. In other examples, the alignment layers and electrodes may be in planes that are parallel to each other, such that the liquid crystals are perpendicular or parallel to all of the alignment layers and electrodes.

[0070] In an example, each liquid crystal layer described herein independently may include a cell gap or a cavity filled with liquid crystals. A thickness of a liquid crystal layer, or a cell gap distance, may be maintained by particle spacers and/or columnar spacers dispersed in the liquid crystal layer. Each liquid crystal layer independently may have a thickness of less than or equal to 0.2 millimeters, including, for example, ranging from 0.001 millimeters to 0.1 millimeters, from 0.002 millimeters to 0.05 millimeters, from 0.003 millimeters to 0.04 millimeters, from 0.004 millimeters to 0.03 millimeters, from 0.005 millimeters to 0.02 millimeters, or from 0.01 millimeters to 0.015 millimeters, or any range formed from any two of the foregoing numbers, including any ranges and subranges therebetween.

[0071] In an example, each liquid crystal layer independently may include liquid crystals (in other words, liquid crystal molecules), and one or more additional components, such as dichroic dyes or other coloring agents (for example, to absorb light transmitted through the liquid crystal layer), chiral dopants, polymerizable reactive monomers, photoinitiators, polymerized structures, or any combination thereof. Liquid crystals may have any liquid crystal phase, such as achiral nematic liquid crystal (“NLC”), chiral NLC, cholesteric liquid crystal (“CLC”), polymer stabilized cholesteric texture (“PCST”), or smectic liquid crystal, which may be operable over a broad range of temperatures, such as from -20° C to 100° C.

[0072] In an example, each liquid crystal layer independently may be any suitable liquid crystal known in the art. In certain examples, each liquid crystal layer independently may include a cyano-biphenyl, a cyano-terphenyl, 7V-(4-methoxybenzylidene)-4-butylaniline (“MBBA”), or any combination thereof. In certain examples, each liquid crystal layer independently may include only one type of liquid crystal material. In other examples, each liquid crystal layer may include a plurality of liquid crystal materials, such as two, three, four, five, or more liquid crystal materials. In still other examples, each liquid crystal layer independently may include a first liquid crystal material and a second liquid crystal material. In still other examples, a ratio (by weight) of a first liquid crystal material to a second liquid crystal material may be in a range of from 1 :99 to 99: 1, including from 10:90 to 90: 10, 20:80 to 80:20, 70:30 to 30:70, 60:40 to 40:60, 55:45 to 45:55, or 50:50, including all ranges and subranges therebetween.

[0073] In an example, each liquid crystal cell described herein includes first and second electrodes and at least a first alignment layer, and at zero applied voltage to the first and second electrodes, at least a portion of the liquid crystal may be present in at least one of a first stable state and a second stable state by way of alignment imparted by at least the first alignment layer. In such an example, at least a portion of the liquid crystals may be aligned in either a first stable state or a second stable state at zero applied voltage, which generally means that a liquid crystal cell including such liquid crystals is consuming no power or substantially no power in either the “dark” or “light” states. In other words, in such an example, at least a portion of the liquid crystals may be aligned in a first stable state, and upon an appropriate stimulus, at least a portion of the liquid crystals may become aligned in a second stable state, and both the first and the second stable states may have different transmittances to visible light, such as a difference of at least 20% as described elsewhere herein. In a multi-stable-state system, two or more stable states of the liquid crystal may be possible, such as two, three, four, five, or six stable states. Generally, however, two stable states corresponding to “light” and “dark” states may be desirable so as to provide a liquid crystal cell that may either allow or prevent transmittance through the liquid crystal cell. In certain examples, a liquid crystal may be aligned in at least one of a continuous texture or a defect texture, and such continuous or defect textures may correspond to at least one of the first and second stable states of the liquid crystal.

[0074] In certain examples, one stable state (for example, a first stable state) of the liquid crystal may be switchable to another stable state (for example, a second stable state) by application of a first stimulus. The switching process may be reversible, such that application of a second stimulus may switch the liquid crystal back to the one stable state. In this regard, the first stable state may be switchable to the second stable state by application of a first stimulus, and the second stable state may be switchable to the first stable state by application of a second stimulus, in which the first and second stimuli are different. In other examples, a first and second stimuli are the same in magnitude but opposite in sign, as described elsewhere herein. The methods disclosed elsewhere herein may be applicable to the stimuli referenced herein with respect to switching between stable states.

[0075] A. Nematic Liquid Crystals

[0076] In an example, a liquid crystal layer may include a nematic liquid crystal.

[0077] In certain examples, the nematic liquid crystal may be a nematic bistable liquid crystal, in which a first alignment layer aligns at least a portion of the nematic liquid crystal in a first orientation or in a second orientation near the first alignment layer, such that at least a portion of the liquid crystal layer remains in a first stable state at zero voltage when the nematic liquid crystal is aligned in the first orientation and in a second stable state at zero voltage when the nematic liquid crystal is aligned in the second orientation.

[0078] In other examples, the liquid crystal layer may further include a dichroic dye. In still other examples, the liquid crystal layer may further include a chiral dopant. For example, liquid crystal layer 124 may include a nematic liquid crystal and a dichroic dye. In another example, liquid crystal layer 212 may include a nematic liquid crystal. [0079] In an example, a nematic liquid crystal may be a twisted nematic liquid crystal (“TNLC”). In certain examples, a TNLC may have positive dielectric anisotropy. Examples of TNLCs may be HTG-135200-100 from Jiangsu Hecheng Display Technology (“HCCH”) (As = +57.2 @ IKHz, An = 0.204 @ 589 nm, clearing temperature Tc = 97° C). In other examples, the dielectric anisotropy (As) may range from about +2 to about +100 @ 1 KHz and 20° C and/or Tc can range from 60° C to 120° C. In still other examples, the birefringence (An) of the TNLC may range from about 0.02 to about 0.3 at 589 nm. In still other examples, the extraordinary refractive index n_e may range from about 1.5 to about 1.7 and/or the ordinary refractive index n₀ may range from about 1.4 to about 1.6. The TNLC may be operable over a broad range of temperatures, such as from about -40° C to about 100° C.

[0080] B. Cholesteric Liquid Crystals (CLCs)

[0081] Cholesteric liquid crystals (CLCs) may be formed from mixing a nematic liquid crystal and a chiral dopant, or from chiral nematic liquid crystal. CLCs possess a helical structure in which elongated liquid crystal molecules twist spatially around an orthogonal axis referred to as the “helical axis.” The distance over which the molecules twist 360° around the helical axis is referred to as the “helical pitch” and is denoted by “P.” The optical property of a CLC sandwiched between two parallel substrates may depend on the direction of the helical axis with respect to the substrates, and a CLC sandwiched between two parallel substrates may exhibit three “states” (also referred to as “textures”) with different optical properties due to different orientations of the helical axis.

[0082] A first texture is a planar state in which the helical axis may be perpendicular to the substrates, and the CLC reflects at the wavelength X according to formula (I) with the bandwidth AX according to formula (II):

X = [(n_e + n_o)/2]P (I)

AX = (n_e - n_o)P (II) where n_e and n_o are the extraordinary and ordinary refractive indices of the CLC, respectively. If the reflection peak is out of the visible light region and there are no defects, the planar state may be transparent for visible light. A second state is a focal conical state in which the CLC may form a poly-domain structure with the helical axis varying randomly from domain to domain, and the CLC may be optically scattering, or opaque. A third state is a homeotropic state in which the helical structure is unwound by externally applied voltages, with the CLC molecules aligned perpendicularly to the substrates, and the CLC may become transparent. [0083] CLCs may be switched between the states. The switching may depend on the dielectric anisotropy and elastic constants of the CLCs. For a CLC with a positive dielectric anisotropy, the CLC may be switched from the transparent planar state to the opaque focal conical state by a low voltage. When the low voltage is removed, the CLC will remain in the opaque focal conical state if there is no strong homogenous alignment layer on the inner surface of the substrates. If a high voltage is applied, the CLC may be switched to the homeotropic state. When the high voltage is removed, the CLC may relax back to an intermediate state, called transient planar state, and then to the planar state. The transient planar state is not stable and has a pitch around P’ = (K33/K22)P, where K22 and K33 are the twist elastic constant and bend elastic constant of the CLC, respectively. In certain examples of CLCs, K33 > K22, and there are many defects in the planar state. Defects in the planar state scatter light and may make the material hazy. In other examples of CLCs, a twist elastic constant K22 and a bend elastic constant K33 are close to each other, which may be referred to as an elastic-constant matched cholesteric liquid crystal (“EMCLC”). EMCLCs may have a positive dielectric anisotropy.

[0084] In an example, EMCLCs may be sandwiched between two parallel substrates with transparent electrode(s). EMCLCs may have two stable states (or textures) in the absence of applied voltage. One of the bistable states may be a transparent planar state. The other of the bistable states may be the opaque focal conical state. An EMCLC may be switched from the transparent planar state to the opaque focal conical state by applying a low voltage or a series of low voltage pulses. The EMCLC will remain in the opaque focal conical state when the applied voltage is removed. The EMCLC may be switched from the opaque focal conical state back to the transparent planar state by applying a high voltage or a series of high voltage pulses. When a high voltage is initially applied, the EMCLC may be switched to the homeotropic state, and once the high voltage is removed, the EMCLC may relax directly to the transparent planar state. The transparent planar state may have no defect and ultrahigh transmittance.

[0085] Examples of CLCs may include E-series and BL-series liquid crystals (commercially available from Merck). Examples of E-series liquid crystals may include E7, E44, E48, or mixtures thereof. Examples of BL-series liquid crystals may include BL003, BL006, BL038, or mixtures thereof.

[0086] In certain examples, a CLC may include a cyano-biphenyl material. In other examples, a CLC may include a cyano-terphenyl material. In still other examples, a CLC may include a mixture of at least one cyano-biphenyl material and at least one cyano-terphenyl material. In still other examples, a CLC may include only one type of liquid crystal material. In still other examples, a CLC may include a plurality of distinct liquid crystal materials. The plurality may include two, three, four, five, six, seven, eight, nine, ten, or more liquid crystal materials.

[0087] In still other examples, a CLC may include at least two different liquid crystal materials. A ratio by weight of a first liquid crystal material to a 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.

[0088] In an example, a CLC may include an elastic constant adjuster. In certain examples, the elastic constant adjuster is a dimer. The dimer may be l”-7”-bis(4-cyanobiphenyl-4’- yl (heptane, which has the following structural formula: l"-7"-bis(4-cyanobiphenyl-4'-yl)heptane.

In other examples, the elastic constant adjuster may have a small bend elastic constant of less than 130% of the twist elastic constant. In still other examples, the elastic constant adjuster may be a liquid crystal with a bent molecular shape.

[0089] In an example, the elastic constant adjuster and the chiral dopant control the transmittance of the scattering focal conical state.

[0090] In an example, no polymer is mixed with the CLC. In another example, no dichroic dye is mixed with the CLC. In yet another example, a small amount of dichroic dye in the range of from 0.1% by weight to 5.0% by weight is mixed with the CLC.

[0091] In an example, liquid crystal layer 108 may be a cholesteric liquid crystal (CLC).

Liquid crystal layer 108 may include a chiral dopant.

[0092] C. Polymer Stabilized Cholesteric Texture (“PCST”)

[0093] A polymer stabilized cholesteric texture (PSCT) may have two stable states at zero voltage: a homeotropic state in which the liquid crystal molecules may be aligned vertically, perpendicularly to the substrates; and a focal conical state in which the liquid crystal molecules may be aligned randomly. The PCST may include a CLC material including a polymer matrix including nematic liquid crystals stabilized or supported therein. A nematic liquid crystal is a dual frequency material, which has a positive dielectric anisotropy at a low frequency of between 20 Hz and 100 Hz, and a negative dielectric anisotropy at a high frequency of more than 10000 Hz. The polymer matrix may be generally formed by polymerization or crosslinking of at least one polymerizable monomer or crosslinkable polymer with non-reactive nematic liquid crystals, and a chiral additive. The chiral additive may be a chiral dopant. Polymerization or crosslinking may be initiated in any suitable manner, such as by ultraviolet (“UV”) radiation, or thermally, depending upon the polymer used.

[0094] In certain examples, the CLC material may include at least about 90.0% by weight nematic liquid crystal material, at least about 3.0% by weight of chiral dopant material, and at least about 0.5% by weight of photo-initiator. In other examples, the CLC material may include at least about 90% by weight of a nematic liquid crystal material, at least about 3.0% by weight of a chiral dopant, and at least about 3.0% by weight of a monofunctional monomer and at least about 3.0% by weight of a bi-functional monomer. The amount of the chiral dopant may be selected such that the bistable liquid crystal may be transparent for visible light when the CLC is in a planar state.

[0095] In other examples, the polymer matrix may be formed from crosslinking a mixture of crosslinkable monomer(s), non-crosslinkable liquid crystal(s), and chiral dopant(s). A liquid crystal PCST may be formed when a small amount of a UV-crosslinkable polymer in its liquid crystal phase and a photoinitiator are mixed with a CLC, the pitch of which is tuned to the infrared region. The crosslinkable monomer concentration may be greater than about 5.0% by weight of the total CLC mixture. The mixture may then be cured by exposure to UV radiation while a voltage or a magnetic field is applied to align the liquid crystal as well as the polymer molecules in the direction across the device thickness, forming the poly-domain structure of microdomains of liquid crystal molecules.

[0096] With a field applied during curing, the CLC molecules may be aligned in a homeotropic, transparent planar state after the curing. After polymerization, when the applied voltage is turned off, the liquid crystal may remain in a homeotropic state, because of the aligning and confining effects of the polymer network. In the homeotropic state, the liquid crystal is parallel to the polymer network, and the PSCT material is transparent. When a sufficiently high voltage of high frequency is applied, the liquid crystal may have a negative dielectric anisotropy and may be titled away from the substrate normal direction. The material is switched to the poly-domain state in which the PSCT material becomes scattering. When the applied high frequency voltage is turned off, the material may remain in the scattering state due to intermolecular interaction between the liquid crystal molecules, which favor the twist state. In the scattering state, the orientation of the liquid crystal may be random with respect to the polymer network and the polymer network may not unwind the twist structure of the liquid crystal, and therefore may not align the liquid crystal parallel to the substrate normal direction. When a sufficiently high voltage of low frequency is applied, the liquid crystal may have a positive dielectric anisotropy and the twist structure of the liquid crystal may be unwound, with the liquid crystal aligned parallel to the substrate normal direction. The material may be switched to the homeotropic state and the PSCT material becomes transparent. When the applied low frequency voltage is turned off from the homeotropic state, the material may remain in the transparent state in a stable condition.

[0097] Particularly useful polymerizable materials may include acrylate and methacrylate monomers. Examples of suitable photopolymerizable monomers may include acrylic acid and methacrylic acid, esters thereof, each of which may include an alkyl group, an aryl group, or a cycloalkyl group including three or more carbons, and halides thereof. Examples of photocurable monomers may include isobutyl acrylate, stearyl acrylate, lauryl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, //-butyl methacrylate, w-lauryl methacrylate, tridecyl methacrylate, w-stearyl methacrylate, w-cyclohexyl methacrylate, benzyl methacrylate, isobornyl methacrylate, 2-phenoxyethyl methacrylate, 2-phenoxyethyl methacrylate,

2.2.3.4.4.4-hexafluorobutyl methacrylate, 2,2,3,4,4,4-hexachlorobutyl methacrylate, 2, 2,3,3- tetrachloropropyl methacrylate, 2,2,3,3-tetrachloropropyl acrylate, perfluorooctylethyl methacrylate, perfluorooctylethyl acrylate, and perchlorooctylethyl methacrylate. Polyfunctional compounds may also be used. Examples of polyfunctional compounds may include ethylene glycol dimethacrylate, bisphenol-A diacrylate, bisphenol-A dimethacrylate,

1.4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane triacrylate, and tetramethylolmethane tetraacrylate. Other examples of monomers may include monofunctional monomer SK (Liquid Crystal Institute and Kent State University) and bi-functional monomer SK (Liquid Crystal Institute and Kent State University). Monomers and polyfunctional compounds may be used independently or in a combination of two or more.

[0098] In an example, liquid crystal layer 108 may be a polymer stabilized cholesteric texture (PCST).

[0099] D. Smectic Phase Liquid Crystal

[00100] Examples of smectic phase liquid crystals may include a silicon-based compound, 4-cyano-4-octyl-biphenyl, and 4-acetate decalactone-4-cyano-biphenyl. Liquid crystal layers including smectic phase liquid crystals may also include an additive. Examples of additives may include conductive additives such as hexadecyl triethyl ammonium bromide. [00101] In an example, a liquid crystal layer may include a smectic phase liquid crystal in an amount of from about 90% to about 99.999% by weight, and an additive in an amount of from about 0.001 % to about 10% by weight, including all ranges and subranges therebetween. In certain examples, a liquid crystal layer may further include a dichroic dye.

[00102] In an example, a liquid crystal layer including a smectic phase liquid crystal may have a stable transparent state and a stable opaque state at zero voltage. In certain examples, the stable opaque state may be achieved by an application of a low frequency of from 50 Hz to 200 Hz with a second long pulse of from 30 to 200 volts, including all ranges and subranges therebetween. In other examples, the stable transparent state may be achieved by an application of a high frequency of 1000 Hz or greater and a second long pulse of from 30 to 200 volts.

[00103] In an example, a cell that includes a liquid crystal layer including a smectic phase liquid crystal may include a first alignment layer. In other examples, a cell may further include a second alignment layer. In still other examples, a cell may not include a first alignment layer or a second alignment layer.

[00104] E. Dyes

[00105] In an example, each liquid crystal layer independently may include a dye or other coloring agent. In certain examples, a dye may be dichroic. In other examples, a dye that is not dichroic may be included in a liquid crystal layer or in another layer of a liquid crystal cell, for example, to provide color to the liquid crystal cell. When a dichroic dye is included in a liquid crystal layer, at least a portion of the dichroic dye may align with the liquid crystals in the stable states of the liquid crystal, such as the first and second stable states. In still other examples, a dichroic dye may absorb more visible light when aligned with one stable state (for example, a first or second stable state) compared to another stable state (for example, the other of the first or second stable states).

[00106] In an example, any suitable amount of dichroic dye may be included. The amount of dichroic dye is not particularly limited and may be selected so as to achieve a desired visible light transmittance of a liquid crystal cell. In certain examples, the amount (% by weight) of dichroic dye and cell gap may be tuned to control a visible light transmittance when the liquid crystal is aligned vertically or horizontally through a cell thickness, according to the relationship represented by the following formula (III): h_ght ~ To x e ~^{(c x wt}'°^{/o x gap)} (III) In the relationship in formula (III), Tn_ght is the visible light transmittance of a liquid crystal cell in a “light” stable state, To is the visible light transmittance without any dichroic dye present, c is a coefficient related to a dichroic dye’ s absorption properties, wt.% is an amount of dichroic dye present relative to a total mass of a liquid crystal layer, and “gap” is a thickness of the liquid crystal layer. Generally, To may be about 90%, but may be larger or smaller depending on materials employed in a liquid crystal cell. By controlling a product of wt.% x gap, the visible light transmittance ( u_ght) may be adjusted to any value described elsewhere herein, such as at least 45% or at least 85%. However, smaller visible light transmittance values may be attained as desired, such as less than 45% or less than 20%.

[0100] Generally, dichroic dyes may have light absorption properties that may depend on the orientation of a dichroic dye relative to propagation and/or polarization directions of incident light. For example, and without wishing to be bound by theory, dichroic dyes may typically absorb light more strongly along a direction parallel to a direction of a transition dipole moment in a dye molecule, which typically may be the longer molecular axis of the dye molecule. Dye molecules oriented with a long axis perpendicular to a direction of light polarization generally may provide low light attenuation, whereas dye molecules oriented with a long axis parallel to the direction of light polarization generally may provide strong light attenuation. In certain aspects, a dichroic dye may have any suitable absorption properties to impart a color to a liquid crystal layer when aligned in a desired direction. In other examples, a color may be black, which may maximize contrast between “light” and “dark states. However, a color may be any other color, such as red, orange, yellow, green, blue, indigo, violet, pink, purple, or any combination thereof. In still other examples, a dichroic dye may be a black dichroic dye. In still other examples, a dye may facilitate achieving a higher contrast ratio between “light” and “dark” states.

[0101] F. Chiral Dopant

[0102] In an example, each liquid crystal layer independently may include at least one chiral dopant. Examples of chiral dopants may include R811, S811, R1011, S1011, R5011, S5011, and CB15 (available from Merck). In certain examples, a chiral dopant may include pairs of enantiomers.

[0103] In an example, a chiral dopant may impart a rotation to a liquid crystal about an axis when in at least one of the first stable state and the second stable state. In certain examples, a chiral dopant may impart a rotation to a liquid crystal about an axis when in a stable state corresponding to a “dark” state or a “light” state, or both the “dark” and “light” states. In other examples, an axis is parallel or perpendicular to a plane of the liquid crystal cell (for example, a plane of any of an alignment layer, an electrode, and/or a substrate). In still other examples, a total rotation angle of a liquid crystal from a first alignment layer to a second alignment layer (or relative to a thickness of a liquid crystal layer perpendicular to the liquid crystal cell plane) (degrees) is 45, 90, 180, 270, 360, 450, 540, 630, 720, 810, 900, 990, 1080, 1170, 1260, 1350, 1440, 1530, 1620, 1710, 1800, 1890, 1980, 2070, 2160, 2250, 2340, 2430, 2430, 2520, 2610, 2700, 2790, 2880, 2970, 3060, 3150, 3240, 3330, 3420, 3330, 3420, 3510, 3600, or any range that can be made from any two of the foregoing numbers, such as 45 - 3600, 180 - 3510, 360 - 3060, 45 - 1260, 720 - 1710, 1080 - 2250, 1980 - 2970, or 2610 - 3510, including any ranges and subranges therebetween.

[0104] In an example, a rotation of a liquid crystal layer including at least one chiral dopant may be quantified by a ratio (d/p) of cell gap thickness (d) to helical pitch (p). For liquid crystal applications, an amount of chiral dopant dissolved in a liquid crystal mixture may be controlled to achieve a desired amount of rotation across a given cell gap distance. It is within the ability of one skilled in the art to select an appropriate chiral dopant and its amount so as to achieve a desired rotation effect. A pitch of a liquid crystal determines a wavelength of light that may be reflected by the liquid crystal. A range of reflected wavelengths (R) may be defined by p*no < R <p*n_e, where n_e > no, n_e is the extraordinary refractive index, and no is the ordinary refractive index of the liquid crystal. In certain examples, a d/p range may be from 0 to 10, from 2 to 10, from 3 to 8, from 0.1 to 2, from 0.1 to 1, from 0.2 to 0.8, from 0.4 to 0.6, from 0.5 to 5, from 0.5 to 1, from 0.25 to 2, from 0.125 to 3, or from 0.8 to 1.7.

[0105] In an example, inclusion of a chiral dopant may not substantially change a visible light transmittance in one stable state (for example, the “light” stable state), but the chiral dopant may change a visible light transmittance of another stable state (for example, the “dark” stable state).

[0106] In an example, a liquid crystal layer may include a chiral liquid crystal.

[0107] Substrates

[0108] Each cell described herein independently may include one or more substrates. Each substrate described herein, including, for example, each of first substrate 102, second substrate 114, first substrate 118, second substrate 130, first substrate 206, second substrate 218, first substrate 306, and second substrate 318 independently may be optically transparent.

[0109] In an example, a cell may include first and second substrates, for example, glass substrates. In certain examples, first and second substrates may be disposed between first and second electrodes. In other examples, an alignment layer (for example, a grating) may be formed into at least one of the first and second electrodes. In still other examples, an alignment layer (for example, a grating) may be formed into at least one of the first and second substrates. In still other examples, a cell may include first and second electrodes and first and second glass substrates, the first and second electrodes disposed between the first and second glass substrates, and optionally, at least one of the first and second alignment layers includes a grating formed into at least one of the first and second electrodes.

[0110] In an example, each substrate independently may have a UV transmittance of less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, less than 0.5%, or less than 1%. In certain examples, a substrate may provide UV protection for first and second polarizing layers and a liquid crystal layer. In other examples, only one substrate may have UV protection, the substrate with UV protecting being toward an exterior of a cell so as to provide UV protection for all components toward the interior of the cell.

[OHl] In an example, a substrate may include a low-emissivity (Low-E) material, such as a Low-E glass. In certain examples, a substrate may include a coating that minimizes an amount of infrared and/or ultraviolet light transmittance through a cell while minimizing or not affecting an amount of visible light transmittance through the cell. Any suitable coating for such purpose known in the art may be used, such as Thinsulate™ available from 3M, and other similar coatings.

[0112] In an example, a substrate in a cell described herein may include a glass sheet. In certain examples, each substrate independently may have any shape and/or size, such as a rectangle, square, or any other suitable shape, including regular and irregular shapes and shapes with one or more curvilinear edges, or any combination of such shapes and/or sizes. In other examples, each substrate independently may have a thickness (millimeters) of 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.5, 2.6, 2.8, 3.0, 3.2, 3.4, 3.5, 3.8, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, or 10.0 millimeters, or any range that may be formed from any two of the foregoing numbers, such as 0.01 - 4.0, 0.1 - 4.0, 0.2 - 3.0, 0.3 - 2.0, 0.5 - 1.5, 0.6 - 1.0, 0.8 - 1.0, 1.0 - 3.0, 1.5 - 2.0, 1.0 - 3.0, 1.0 - 4.0, 1.0 - 5.0, 1.0 - 6.0, 1.0 - 7.0, 1.0 - 8.0, 1.0 - 9.0, 1.0 - 10.0, 2.0 - 3.0, 2.0 - 4.0, 2.0 - 5.0, 2.0 - 6.0, 2.0 - 7.0, 2.0 - 8.0, 2.0 - 9.0, 2.0 - 10.0, 3.0 - 4.0, 3.0 - 5.0, 3.0 - 6.0, 3.0 - 7.0, 3.0 - 8.0, 3.0 - 9.0, 3.0 - 10.0, 4.0 - 5.0, 4.0 - 6.0, 4.0 - 7.0, 4.0 - 8.0, 4.0 - 9.0, 4.0 - 10.0, 5.0 - 6.0, 5.0 - 7.0, 5.0 - 8.0, 5.0 - 9.0, 5.0 - 10.0, 6.0 - 7.0, 6.0 - 8.0, 6.0 - 9.0, 6.0 - 10.0, 7.0 - 8.0, 7.0 - 9.0, 7.0 - 10.0, 8.0 - 9.0, 8.0 - 10.0, or 9.0 - 10.0, and so forth. In still other examples, a first and a second substrate may generally be thinner (for example 0.01 - 2 millimeters) than a third and a fourth substrate (for example, 2.0 - 10.0 millimeters), because the third and the fourth substrates may be present to provide structural integrity.

[0113] In certain examples, each substrate independently may include any glass known in the art, such as soda-lime silicate, aluminosilicate, alkali-aluminosilicate, borosilicate, alkaliborosilicate, aluminoborosilicate, alkali-aluminoborosilicate, or other suitable displayquality glasses. In other examples, each substrate and each strengthened glass, including, for example, each of first strengthened glass 402, second strengthened glass 408, first strengthened glass 502, and second strengthened glass 512, independently may include thermally strengthened glass, chemically strengthened glass, tempered glass, or any combination thereof, bonded to a substrate by an interlayer. Examples of suitable commercially available glasses may include EAGLE XG®, Lotus™, Willow®, and Gorilla® glasses from Corning Incorporated. Chemically strengthened glass may be provided in accordance with U.S. Patent Nos. 7,666,511, 4,483,700, and 5,674,790, each of which is incorporated herein by reference in its entirety for all purposes. Each of third and fourth substrates, when present, may provide mechanical strength against damage from external forces, such as consumers, pets, storms and other weather conditions, and so forth. Each strengthened glass may have a coating that minimizes an amount of infrared and ultraviolet light that comes through the glass, without affecting an amount of light that passes through the glass.

[0114] In an example, a substrate may be chosen from glass sheets produced by a fusion draw process. Without wishing to be bound by theory, the fusion draw process may provide glass sheets with a relatively low degree of waviness (in other words, a high degree of flatness), which m ay be beneficial for various liquid crystal applications. An exemplary glass substrate may thus, in certain aspects, include a surface waviness of less than about 100 nanometers as measured with a contact profilometer, such as about 80 nm or less, about 50 nm or less, about 40 nm or less, or about 30 nm or less, including all ranges and subranges therebetween. An exemplary standard technique for measuring waviness (0.8 - 8 millimeters) with a contact profilometer is outlined in SEMI D15-1296 “FPD Glass Substrate Surface Waviness Measurement Method,” incorporated by reference herein in its entirety for all purposes.

[0115] In an example, a substrate may be made from a polymer, such as PET.

[0116] Interlayers

[0117] Each switchable window described herein may include at least one interlayer. Each interlayer, including, for example, first interlayer 116, first interlayer 222, first interlayer 304, second interlayer 404, third interlayer 406, second interlayer 506, and third interlayer 508 independently may improve the safety of the switchable window, for example, by holding one or more substrates in place in case of breakage, and/or preventing shattering of one or more substrates, which may present a safety hazard.

[0118] In an example, an interlayer may be present between at least one substrate/substrate interface within a switchable window. In certain examples, an interlayer may include one or more materials including polyvinyl butyral (“PVB”), ethylene-vinyl acetate (“EVA”), polylactic acid, polyurethanes, ionoplast polymer such as SentryGlas® and SentryGlas® from DuPont, other suitable materials, or any combination thereof.

[0119] In an example, an interlay may provide UV and/or IR protection for components of a switchable window or a cell thereof, such as an alignment layer, a liquid crystal layer, an electrode, a substrate, and so forth. In certain examples, a UV and/or IR transmittance of an interlayer, or a combination of interlayers, may be less than 5%, such as less than 2%, less than 1%, less than 0.5%, or less than 0.1%, including all ranges or subranges therebetween. In other examples, if more than one interlayer is present, each interlayer may have the same UV and/or IR transmittance, or different transmittances. In still other examples, an interlayer toward an exterior of a switchable window may have UV and/or IR protection, and an interlayer toward an interior of a switchable window may not have UV and/or IR protection because an exteriorfacing interlayer may provide sufficient UV and/or IR protection.

[0120] Polarizers

[0121] In an example, a switchable window described herein may include a cell including one or more polarizers. Each polarizer described herein, including, for example, first polarizer 204 and second polarizer 220 independently may have an absorption axis or a transmission axis. Each polarizer may be attached to a substrate. In certain examples, a cell including one or more polarizers may also include one or more compensation layers between a polarizer and a substrate. In other examples, a cell may include a first compensation layer having a first optical axis varying in a first optical plane between a first polarizer and a first substrate, and a second compensation layer having a second optical axis varying in a second optical plane between a second polarizer and a second substrate. In still other examples, a cell including one or more polarizers may also include a twisted nematic liquid crystal (TNLC).

[0122] Examples of polarizers may include iodine-based polarizers and dye-based polarizers. In certain examples, a polarizer may include a polyvinyl alcohol (“PVA”) film that is doped with iodine, referred to as an “H type” polarizer. In other examples, a polarizer may include a PVA film that is doped with iodine and subsequently dehydrated, referred to as “K type,” which may be more resistant to humidity and heat. In still other examples, a polarizer may be a 3M Vikuiti™ KE type polarizer, which includes iodine-doped PVA with unoriented chromophores destroyed by UV bleaching. A KE polarizer may have a higher transmittance. In still other examples, a polarizer may be a dye-based polarizer. Examples of dye-based polarizers may include the Polatchno GHC, VHC, and VHC-type polarizers available from Nippon Kayaku (Japan) or the High-Temperature Linear Polarizing Film (XP40HT) available from Edmund Optics.

[0123] Polarizers may also be lyotropic polymer polarizers or metal wire grid polarizers. Dyebased polarizers and metal wire grid polarizers made of aluminum or silver may be particularly suitable because of the improved thermal and UV stability over iodine-based polarizers.

[0124] Compensation Lavers

[0125] In an example, a switchable window described herein may include one or more compensation layers to improve a viewing angle of a normally dark (“ND”) TNLC and/or a viewing angle of a “dark” state of a normally transparent (“NT”) TNLC. “Viewing angle” is defined by a “polar viewing angle” and an “azimuthal viewing angle.” A polarizing viewing angle is measured from a normal direction of a liquid crystal layer, and an azimuthal viewing angle is measured in a plane of a liquid crystal layer relative to a chosen direction such as rubbing or alignment direction. Typically a good viewing angle is defined by a contrast of 10 or higher. In both the transparent state of a ND TNLC and the “dark” state of a NT TNLC, a liquid crystal is oriented vertically in the center of the cell gap, while the liquid crystal is tilted near the alignment layers.

[0126] Examples of a compensation layer may include a Wide View Film from Fuji Photo Co., which is a discotic liquid crystal polymer film. An optical axis of the compensation layer may vary along a thickness of the compensation layer, as discussed in Hiroyuki Mori, et al., Performance of a novel optical compensation film based on negative birefringence of discotic compound for wide-viewing-angle twisted nematic liquid-crystal displays, 36 JAPANESE J. APPLIED PHYSICS 143 (1997), which is incorporated by reference herein in its entirety for all purposes.

[0127] In an example, a compensation layer may include a biaxial plate, an A-plate, a C-plate, or a combination of A-plate and C-plate. A biaxial plate may have a thickness d and three different refractive indices: Nx, Ny, and Nz in the x, y, and z directions, respectively. An inplane retardation (Nx - Ny)*d and an out-of-plane retardation [Nz - (Nx + Ny)/2]*d of a compensation layer may be tuned to compensate a viewing angle dependence of a transmittance for the “dark” state of a ND TNLC. An A-plate or C-plate each may have a thickness d and two different refractive indices such as extraordinary index Ne and ordinary index No. The A- plate may have its optic axis oriented in the plane of a compensation layer, while the C-plate may have its optic axis oriented orthogonally to the plane of the compensation layer. The retardation of the A-plate and the C-plate, defined by (Ne - No)*d may be independently tuned to compensate the viewing angle dependence of a transmittance for the “dark” state of a ND TNLC.

[0128] Electrochromic Cells

[0129] In an example, an electrochromic cell described herein may include a first electrode that is coated with a polymer. In certain examples, the first electrode may be spin-coated with a polymer. In other examples, the polymer may be a black-to-transmissive electrochromic polymer. In still other examples, the first electrode may be an indium tin oxide (ITO) electrode. In still other examples, the first electrode may be octadecyltrichlorosilane-modified (“OTS- modified”). In still other examples, the electrochromic cell may include a second electrode. In still other examples, the second electrode may be a colorless ITO.

[0130] In an example, an electrochromic cell may display a contrast of about 40% or more. In certain examples, an electrochromic cell may display a contrast of 43.6%, switching from a saturated black state (L* = 37.8, a* = 2.5, b* = -6.4) to a transmissive state (L* = 72.6, a* = - 8.0, b* = -6.5).

[0131] In an example, an electrochromic cell may switch color from black (a* is -5 to 0, b* is -10 to 0), when a potential of -1 V is applied, to transmissive (a* is -8 to 0, *b is -5 to 0), when a potential of 1.8 V is applied, and a* and b* are hue and chroma values, respectively. During the transition of such color change, a* and b* are consistently in a range of -13 to 0.

[0132] In an example, an electrochromic cell may switch color from black (as described herein, for example, L* = 37.8, a* = 2.5, b* = -6.4), when a potential of -1 V is applied, to transmissive (as described herein, for example, L* = 72.6, a* = -8.0, b* = -6.5), when a potential of 1.8 V is applied. Here, L* represents lightness (ranging from 0 to 100).

[0133] In an example, a black polymer is a black-to-transmissive electrochromic conjugated copolymer, which may absorb across the entire visible spectrum and may realize an obvious color change from black (as described herein, for example, L* = 49.2, a* = 3.6, b* = -7.7), to transmissive (as described herein, for example, L* = 85, a* = -4.6, b* = -5.8), with an applied voltage of 0 - 1.2 V. An optical contrast as high as nearly 70% may be reached within 10 seconds in electrochromic thin films made of the black polymer. Moreover, long-term “redox” (oxidation-reduction) stability has been demonstrated with an optical loss as low as 2.1% after 1400 switching cycles.

[0134] In an example, a polymer may be a black-to-transmissive polymer of Formula (IV): each of R¹, R², R³, R⁴, R⁵, R⁶, R⁷, R⁸, R⁹, and R¹⁰ is independently hydrogen, optionally substituted C1-C30 alkyl, optionally substituted C2-C30 alkenyl, optionally substituted C2-C30 alkynyl, optionally substituted C2-C30 alkylcarbonyl, optionally substituted C1-C30 alkoxy, optionally substituted C3-C30 alkoxyalkyl, optionally substituted C2-C30 alkoxycarbonyl, optionally substituted C4-C30 alkoxycarbonylalkyl, optionally substituted C1-C30 aminylcarbonyl, optionally substituted C4-C30 aminylalkyl, optionally substituted C1-C30 alkylaminyl, optionally substituted C1-C30 alkyl sulfonyl, optionally substituted C3-C30 alkylsulfonylalkyl, optionally substituted Ce-Cis aryl, optionally substituted C3-C15 cycloalkyl, optionally substituted C3-C30 cycloalkylaminyl, optionally substituted C5-C30 cycloalkylalkylaminyl, optionally substituted C5-C30 cycloalkylalkyl, optionally substituted C5-C30 cycloalkylalkyloxy, optionally substituted C1-C20 heterocyclyl, optionally substituted C1-C12 heterocyclyloxy, optionally substituted C1-C30 heterocyclylalkyloxy, optionally substituted C1-C30 heterocyclylaminyl, optionally substituted C5-C30 heterocyclylalkylaminyl, optionally substituted C2-C12 heterocyclylcarbonyl, optionally substituted C3-C30 heterocyclylalkyl, optionally substituted C1-C13 heteroaryl, or optionally substituted C3-C30 heteroarylalkyl; each r, s, and t is independently an integer equal to or greater than 1; n is an integer equal to or greater than 1; and the average ratio of , and in the polymer is x:y:z, wherein x ranges from about 0.2 to about 0.6, y ranges from about 1.2 to about 1.45, and z ranges from about 0.2 to about 0.45, and x+y+z is about 2. “Substituted” means that one or more hydrogen atoms are replaced by a bond to an amino, alkylaminyl, cyano, hydroxyl, imino, nitro, oxo, thioxo, halo, alkyl, alkoxy, alkylminyl, thioalkyl, aryl, aralkyl, cycloalkyl, cycloalkylalyl, haloalkyl, heterocyclyl, 7V-heterocyclyl, heterocyclylalkyl, heteroaryl, 7V-heteroaryl, and/or heteroarylalkyl group.

[0135] In certain examples, x ranges from about 0.2 to about 0.6, y ranges from about 1.2 to about 1.45, and z ranges from about 0.2 to about 0.35. In other examples, x ranges from about 0.2 to about 0.4, y ranges from about 1.3 to about 1.45, and z ranges from about 0.2 to about 0.35. In still other examples, x is about 0.2, y is about 1.2, and z is about 0.35. In still other examples, x is about 0.3, y is about 1.45, and z is about 0.25. In still other examples, x is about 0.4, y is about 1.35, and z is about 0.25. In still other examples, x is about 0.4, y is about 1.4, and z is about 0.2. In still other examples, x is about 0.6 y is about 1.2, and z is about 0.2.

[0136] In an example, an electrochromic cell described herein may include an electrochromic layer, an electrolyte layer, and an ion storage layer disposed between the first electrode and the second electrode. In certain examples, the electrochromic layer, the electrolyte layer, and the ion storage layer are disposed sequentially between the first electrode and the second electrode. In other examples, the electrolyte layer may be solid. It may be advantageous to use such a solid-state electrochromic cell due to safety concerns because nothing may leak when the glass is broken.

[0137] In certain examples, the ion storage layer may include one or more oxides of metal elements in Groups 4-12 of the periodic table that are capable of storing cations during a reduction reaction. Examples of oxides of metal elements may include oxides of Ti, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ir, Ni, Cu, Zn, or any mixture of these oxides or any one of these metal oxides doped by any other metal oxides, for example, Nb2Os doped with 5 % by weight of TiO₂, among others now known or later developed. In other examples, the ion storage layer may include a transition-metal complex. Examples of transition-metal complexes may include one of Prussian green, Prussian white, Prussian brown, or Tenshi blue, Fe4[Fe(CN)e]3, ferrous oxide, ferric oxide, ferroferric oxide, KFeFe(CN)e, FeNiHCF, FeHCF, NiHCF, Prussian blue nanoparticles, or N_xMy{Fe(CN)e}, where M is a metal element such as Fe, Co, Ni, Ni, Mn, Zn, or Cu, and N is an alkali metal ion. In still other examples, the ion storage layer may include one or more of redox-active polymers such as redox active nitroxyl or galvinoxyl radical polymers, or conjugated polymers. In still other examples, the ion storage layer may include composites of transition-metal complexes and metal oxides, transition-metal complexes and redox active polymers, or metal oxides and redox active polymers.

[0138] In certain examples, the electrochromic layer may include one or more of WO3, poly(decylviologen) and its derivatives, polyaniline and its derivatives, electrochromic conjugated polymers such as polypyrrole and its derivatives, polythiophene and its derivatives, poly(3,4-ethylenedi oxythiophene) and its derivatives, poly(propylenedi oxythiophene) and its derivatives, polyfurane and its derivatives, polyfluorene and its derivatives, polycarbazole and its derivatives, and copolymers thereof, and copolymers thereof further including a certain ratio of acceptor units, such as benzothiadiazole, benzoselenadiazole, benzoxazole, benzotri azole, benzoimidazole, quinoxalines, and diketopyrrolopyrroles.

[0139] In certain examples, the solid electrolyte layer may include ion conducting polymers copolymerized with monomers or oligomers, wherein the monomers or oligomers have plasticizing moieties as side chains. In other examples, the solid electrolyte layer may include ion conducting polymers chemically linked with plasticizing linear polymers that have a glass transition temperature less than -20° C. In still other examples, the solid electrolyte layer may include ion conducting polymers chemically linked with plasticizing polymer blocks that have plasticizing groups as side chains. In still other examples, the solid electrolyte layer may include brush copolymers having a main chain of soft polymers and side chains of ionconducting species and one or more non-miscible groups. In still other examples, additives with cross-linking functional groups may be added to enhance the mechanical modulus of the solid electrolyte layer.

[0140] Insulating Gases

[0141] Each switchable window described herein may include at least one gap including an insulating gas. Each insulating gas, including, for example, each of first insulating gas 504 and second insulating gas 510 independently may provide thermal insulation to the switchable window, including the components that are more interior to the switchable window than the gap including an insulating gas. In certain examples, at least one gap is located between two substrates. In other examples, at least one gap is located between an electrode and a substrate. In still other examples, at least one gap is located between a substrate and a strengthened glass. In still other examples, there are multiple gaps filled with one or more insulating gases. When multiple gaps including insulating gases are present, each gap may contain the same insulating gas or different insulating gases. In still other examples, an insulating gas may be any suitable insulating gas, such as nitrogen, argon, helium, ambient air, or any combination thereof. In still other examples, the gaps may include one or more spacers, for example, to maintain structural integrity of a gap.

[0142] Applications

[0143] In an example, the switchable windows described herein may be used in various architectural and transportation applications. For example, the switchable windows may be included in doors, space partitions, skylights, and windows for buildings, automobiles, and other transportation vehicles such as trains, planes, motorhomes, boats, and the like. In certain examples, a switchable window for use in architectural applications may have any desired dimension including 2 feet wide by 4 feet long, 3 feet wide by 5 feet long, 5 feet wide by 8 feet long, 6 feet wide by 8 feet long, 7 feet wide by 10 feet long, and 7 feet wide by 12 feet long. Larger and smaller switchable windows are also envisioned and are intended to fall within the scope of this disclosure. In other examples, any switchable window described herein may include one or more additional components such as a frame or other structural component, a power source, and/or a control device or system. In still other examples, any switchable window described herein may be a component of a window or a display. In still other examples, a frame is made of any suitable material, such as wood, vinyl, aluminum, or any combination thereof. In still other examples, any switchable window described herein may include a seal to maintain spacer integrity, prevent moisture from infiltrating into insulating gas cavities, and/or prevent leakage of the insulating gas from cavities. In still other examples, a seal is made of a polymer, such as those in the art for such sealing purposes.

[0144] Transmittance and Haze

[0145] In an example, any liquid crystal cell or electrochromic cell described herein may have any suitable visible light transmittance. In an example, a visible light transmittance in one stable state (for example, a first stable state) may be different from a visible light transmittance in any other stable state (for example, a second stable state) by at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, or at least 70%. Alternatively, or additionally, the visible light transmittance in one stable state (for example, the first stable state) may be different from the visible light transmittance in any other stable state (for example, the second stable state) by less than 70%, less than 65%, less than 60%, less than 55%, less than 50%, less than 45%, less than 40%, less than 35%, less than 30%, or less than 25%. Any of the two foregoing open-ended ranges may be combined in any manner to describe a closed range for visible light transmittance, such as 20 - 70%, 20 - 65%, 20 - 55%, 20 - 50%, 20 - 45%, 20 - 40%, 20 - 35%, 20 - 30%, 20 - 25%, 25 - 70%, 25 - 65%, 25 - 60%, 25 - 55%, 25 - 50%, 25 - 45%, 25 - 40%, 25 - 35%, 25

- 30%, 30 - 70%, 30 - 65%, 30 - 60%, 30 - 55%, 30 - 50%, 30 - 45%, 30 - 40%, 30 - 35%, 35 - 70%, 35 - 65%, 35 - 60%, 35 - 50%, 35 - 45%, 35 - 40%, 40 - 70%, 40 - 65%, 40 - 60%, 40 - 55%, 40 - 50%, 40 - 45%, 45 - 70%, 45 - 65%, 45 - 60%, 45 - 55%, 45 - 50%, 50 - 70%, 50 - 65%, 50 - 60%, 50 - 55%, 55 - 70%, 55 - 65%, 55 - 60%, 60 - 70%, 60 - 65%, or 65 - 70%. Differences in visible light transmittance between various stable states may be calculated by measuring the visible light transmittance (for example, X%) in one stable state, measuring the visible light transmittance in another stable state (for example, Y%), and taking the absolute value of the result of X% - Y%, or “| X% - Y% |.”

[0146] In an example, visible light transmittance may be at least 45% in one stable state (for example, first or second stable state), and visible light transmittance may be less than 45% in another stable state (for example, the other of the first or second stable states). In certain examples, one stable state (for example, first or second stable state) may have a visible light transmittance of at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, or at least 85%, or alternatively, or additionally, less than 85%, less than 80%, less than 75%, less than 70%, less than 65%, less than 60%, less than 55%, or less than 50%. Any of the foregoing open-ended ranges may be combined in any manner to describe a closed range for visible light transmittance in one stable state (for example, a first or second stable state), such as 45 - 85%, 45 - 80%, 45 - 75%, 45 - 70%, 45 - 65%, 45 - 60%, 45 - 55%, 45 - 50%, 50 - 85%, 50 - 80%, 50 - 75%, 50 - 70%, 50 - 65%, 50 - 60%, 50 - 55%, 55 - 85%, 55 - 80%, 55 - 75%, 55 - 70%, 55 - 65%, 55 - 60%, 60 - 85%, 60 - 80%, 60

- 75%, 60 - 70%, 60 - 65%, 65 - 85%, 65 - 80%, 65 - 75%, 65 - 70%, 70 - 85%, 70 - 80%, 70 - 75%, 75 - 85%, 75 - 80%, or 80 - 85%. In other examples, the other stable state may have a visible light transmittance of less than 45%, less than 40%, less than 35%, less than 30%, less than 25%, less than 20%, less than 15%, less than 10%, less than 5%, or less than 1%, or alternatively, or additionally, at least 1%, at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, or at least 40%. Any of the two foregoing open- ended ranges may be combined in any manner to describe a closed range for visible light transmittance in the other stable state (for example, a first or second stable state), such as 1 - 45%, 1 - 40%, 1 - 35%, 1 - 30%, 1 - 25%, 1 - 20%, 1 - 15%, 1 - 10%, 1- 5%, 5 - 45%, 5 - 40%, 5 - 35%, 5 - 30%, 5 - 25%, 5 - 20%, 5 - 15%, 5 - 10%, 10 - 45%, 10 - 40%, 10 - 35%, 10 - 30%, 10 - 25%, 10 - 20%, 10 - 15%, 15 - 45%, 15 - 40%, 15 - 35%, 15 - 30%, 15 - 25%, 15 - 20%, 20 - 45%, 20 - 40%, 20 - 35%, 20 - 30%, 20 - 25%, 25 - 45%, 25 - 40%, 25

- 35%, 25 - 30%, 30 - 45%, 30 - 40%, 30 - 35%, 35 - 45%, 35 - 40%, or 40 - 45%. In still other examples, visible light transmittance may be at least 45% in the first stable state or the second stable state; and visible light transmittance may be less than 45% in the other of the first stable state or the second stable state.

[0147] Any visible light transmittance difference described herein (relative to different stable states) may be paired with any actual visible light transmittance described herein. For example, one stable state may have a visible light transmittance of less than 15% and the visible light transmittance difference form another stable state may be at least 35% (making the visible light transmittance of the other stable state at least 50%). Any other combination of such features may be made and a similar calculation performed.

[0148] In an example, any liquid crystal cell and electrochromic cell described herein may have any suitable haze. In certain examples, a haze may be less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4.5%, less than 4%, less than 3.5%, less than 3%, less than 2.5%, less than 2%, less than 2%, less than 1.5%, less than 1%, less than 0.5%, or less than 0.1%, or alternatively, or additionally, at least 0.1%, at least 0.5%, at least 1%, at least 1.5%, at least 2%, at least 2.5%, at least 3%, at least 3.5%, at least 4%, at least 4.5%, at least 5%, at least 6%, at least 7%, at least 8%, or at least 9%. Any of the two foregoing open-ended ranges may be combined in any manner to describe a closed range for haze, such as 0.1 - 10%, 0.1 - 9%, 0.1 - 8%, 0.1 - 7%, 0.1 - 6%, 0.1 - 5.0%, 0.1 - 4.5%, 0.1 - 4.0%, 0.1

- 3.5%, 0.1 - 3.0%, 0.1 - 2.5%, 0.1 - 2.0%, 0.1 - 1.5%, 0.1 - 1.0%, 0.1 - 0.5%, 0.5 - 10%, 0.5 - 9%, 0.5 - 8%, 0.5 - 7%, 0.5 - 6%, 0.5 - 5.0%, 0.5 - 4.5%, 0.5 - 4.0%, 0.5 - 3.5%, 0.5 - 3.0%, 0.5 - 2.5%, 0.5 - 2.0%, 0.5 - 1.5%, 0.5 - 1.0%, 1.0 - 10%, 1.0 - 9%, 1.0 - 8%, 1.0 - 7%, 1.0 - 6%, 1.0 - 5.0%, 1.0 - 4.5%, 1.0 - 4.0%, 1.0 - 3.5%, 1.0 - 3.0%, 1.0 - 2.5%, 1.0 - 2.0%, 1.0 - 1.5%, 1.5 - 10%, 1.5 - 9%, 1.5 - 8%, 1.5 - 7%, 1.5 - 6%, 1.5 - 5.0%, 1.5 - 4.5%, 1.5 - 4.0%, 1.5 - 3.5%, 1.5 - 3.0%, 1.5 - 2.5%, 1.5 - 2.0%, 2.0 - 10%, 2.0 - 9%, 2.0 - 8%, 2.0 - 7%, 2.0 - 6%, 2.0 - 5.0%, 2.0 - 4.5%, 2.0 - 4.0%, 2.0 - 3.5%, 2.0 - 3.0%, 2.0 - 2.5%,

2.5 - 10%, 2.5 - 9%, 2.5 - 8%, 2.5 - 7%, 2.5 - 6%, 2.5 - 5.0%, 2.5 - 4.5%, 2.5 - 4.0%, 2.5 - 3.5%, 2.5 - 3.0%, 3.0 - 10%, 3.0 - 9%, 3.0 - 8%, 3.0 - 7%, 3.0 - 6%, 3.0 - 5.0%, 3.0 - 4.5%, 3.0 - 4.0%, 3.0 - 3.5%, 3.5 - 10%, 3.5 - 9%, 3.5 - 8%, 3.5 - 7%, 3.5 - 6%, 3.5 - 5.0%, 3.5 - 4.5%, 3.5 - 4.0%, 4.0 - 10%, 4.0 - 9%, 4.0 - 8%, 4.0 - 7%, 4.0 - 6%, 4.0 - 5.0%, 4.0 - 4.5%,

4.5 - 10%, 4.5 - 9%, 4.5 - 8%, 4.5 - 7%, 4.5 - 6%, 4.5 - 5.0%, 5.0 - 10%, 5.0 - 9%, 5.0 - 8%, 5.0 - 7%, 5.0 - 6%, 6 - 10%, 6 - 9%, 6 - 8%, 6 - 7%, 7 - 10%, 7 - 9%, 7 - 8%, 8 - 10%, 8 - 9%, or 9 - 10%. Generally, the haze is in reference to a liquid crystal cell or electrochromic cell in all possible stable states, such as first and second stable states. However, in certain aspects, the haze may be in reference to a specific stable state, and any haze value described herein may be applied to that specific stable state (such as a first stable state, or a second stable state, or both the first and second stable states).

[0149] The uses of the terms “a” and “an” and “the” and similar referents in the context of describing the present disclosure (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term “plurality of’ is defined by the Applicant in the broadest sense, superseding any other implied definitions or limitations hereinbefore or hereinafter unless expressly asserted by Applicant to the contrary, to mean a quantity of more than one. All methods described herein may be performed in any suitable order unless otherwise indicated herein by context.

[0150] As will be understood by one skilled in the art, for any and all purposes, all ranges recited herein also encompass any and all possible sub-ranges and combinations of sub-ranges thereof, as well as the individual values making up the range, particularly integer values. It is therefore understood that each unit between two particular units is also disclosed. For example, if “10 to 15” is disclosed, then 11, 12, 13, and 14 are also disclosed, individually, and as part of a range. A recited range (for example, weight percentages or carbon groups) includes each specific value, integer, decimal, or identity within the range. Any listed range may be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, or tenths. As will also be understood by one skilled in the art, all language such as “up to,” “at least,” “greater than,” “less than,” “more than,” “or more,” and the like, include the number recited and such terms refer to ranges that can be subsequently broken down into sub-ranges. In the same manner, all ratios recited herein also include all sub-ratios falling within the broader ratio. Accordingly, specific values recited for radicals, substituents, and ranges are for illustration only; they do not exclude other defined values or other values within defined ranges for radicals and substituents. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0151] One skilled in the art will also readily recognize that where members are grouped together in a common manner, such as in a Markush group, the invention encompasses not only the entire group listed as a whole, but each member of the group individually and all possible subgroups of the main group. Additionally, for all purposes, the invention encompasses not only the main group, but also the main group absent one or more of the group members. The invention therefore envisages the explicit exclusion of any one or more of members of a recited group. Accordingly, provisos may apply to any of the disclosed categories or examples whereby any one or more of the recited elements, species, or examples may be excluded from such categories or examples, for example, for use in an explicit negative limitation.

[0152] As used herein, the terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The present description also contemplates other examples “comprising,” “consisting of,” and “consisting essentially of,” the examples or elements presented herein, whether explicitly set forth or not. [0153] In describing elements of the present disclosure, the terms “1^st,” “2^nd,” “first,” “second,” “A,” “B,” “(a),” “(b),” and the like may be used herein. These terms are only used to distinguish one element from another element, but do not limit the corresponding elements irrespective of the nature or order of the corresponding elements.

[0154] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meanings as those generally understood by those skilled in the art to which the present disclosure pertains. Such terms as those defined in a generally used dictionary are to be interpreted as having meanings equal to the contextual meanings in the relevant field of art. [0155] As used herein, the term “about,” when used in the context of a numerical value or range set forth means a variation of ±15% or less, of the numerical value. For example, a value differing by ±15%, ±14%, ±10%, or ±5%, among others, would satisfy the definition of “about,” unless more narrowly defined in particular instances.

[0156] As used herein, the term “stable state” refers to an ability of a liquid crystal to maintain a state without continuous application of voltage for a certain time period, typically at least 1 hour. However, other time periods are also possible, including at least 2 hours, at least 3 hours, at least 4 hours, at least 6 hours, at least 8 hours, at least 10 hours, at least 12 hours, at least 16 hours, at least 20 hours, or at least 24 hours, or more, including all ranges and sub-ranges that can be made from any two of the foregoing numbers. Stability is in reference to a liquid crystal layer as a whole, including any other materials that may be present in addition to the liquid crystals, such as chiral dopants, polymers, and so forth, and other layers such as one or more alignment layers. Liquid crystals having multiple stable states may be used as smart windows or displays to provide at least two stable states in the absence of applied voltage. In certain examples, a first stable state is more transparent to visible light (a “light” state) than a second stable state (a “dark” state). In other examples, the liquid crystal may be switched from the first stable state to the second stable state and vice versa via a stimulus, such as one or more voltage pulses. In still other examples, additional stable states may be possible with the same or different transparency to light as the first and/or second stable states, allowing for the possibility of different visible light transparencies.

[0157] As used herein, “bistable” refers to a liquid crystal having two “stable” states.

[0158] As used herein, “ultraviolet light” or “UV light” refers to electromagnetic radiation having a wavelength in a range of from 10 nm to <380 nm.

[0159] As used herein, “visible light” refers to electromagnetic radiation having a wavelength in a range of from 380 to <750 nm.

[0160] As used herein, “infrared light” or “IR light” refers to electromagnetic radiation having a wavelength in a range of from 750 nm to 1 mm.

[0161] As used herein, “haze” refers to the percent of transmitted light that is scattered so that its direction deviates more than 2.5 degrees from the direction of the incident beam, and “luminous transmittance” is defined as the percent of transmitted light, per American Society for Testing and Materials (“ASTM”) D1003 “Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics.” The terms “transmittance,” “luminous transmittance,” “visible light transmittance,” and similar terms are used interchangeably herein and are intended to have the same meaning, unless clearly contradicted by context (for example, transmittance relating specifically to UV and/or IR). Haze and transmittance can be measured by various haze meters such as BYK-Gardner’s Haze-Gard. As used herein, the haze and transmittance of a liquid crystal cell refers to the haze and transmittance as measured through the first and second electrodes, first and second alignment layers (if both are present), a liquid crystal layer, first and second substrates (if one or both are present), and one or more polarizers (if present). Generally, transmittance as disclosed herein does not include transmittance through interlayers, insulating gases, third and fourth substrates, UV/IR layers, and so forth.

[0162] As used herein, “switchable” refers to an ability of a liquid crystal to move between stable states of a liquid crystal such that the liquid crystal in a given system (in other words, considering all other materials and structures present) is capable of being changed from one stable state to another stable state by application of an appropriate stimulus, such as one or more voltage pulses.

[0163] As used herein, the terms “light” and “dark” states are generally used in reference to light transmittance, in which light transmittance in the “dark” state is less than light transmittance in the “light” state as viewed perpendicular to the plane of the liquid crystal cell. In a multi-stable state liquid crystal cell, such as a bistable liquid crystal cell, or a bistable electrochromic cell, the “dark” state corresponds to one stable state of the liquid crystals and the “light” state corresponds to another stable state of the liquid crystals (for example, stable states at zero applied voltage).

[0164] As used herein, the term “optically transparent” and similar terms refer to a transmission of greater than 80% of electromagnetic radiation in the visible region of the electromagnetic spectrum (-400 - 700 nm). However, a heightened level of optical transparency may also be employed herein, such a transmission of at least 85%, at least 90%, at least 95%, at least 99%, or 100% of light in the visible region of the electromagnetic spectrum (-400 - 700 nm). Any such optical transparency values generally apply to a liquid crystal cell or an electrochromic cell, but may also be applied to any individual or combination structure disclosed herein, such as a substrate, electrode, liquid crystal layer, and so forth.

[0165] Although the present disclosure has been described with reference to examples and the accompanying drawings, the present disclosure is not limited thereto, but may be variously modified and altered by those skilled in the art to which the present disclosure pertains without departing from the spirit and scope of the present disclosure.

[0166] The subject-matter of the disclosure may also relate, among others, to the following aspects:

[0167] A first aspect relates to a switchable window, comprising: a first bistable liquid crystal cell; a second liquid crystal cell or a bistable electrochromic cell; and an interlayer disposed between the first bistable liquid crystal cell and the second liquid crystal cell or the bistable electrochromic cell; wherein the first bistable liquid crystal cell comprises: a first bistable liquid crystal cell substrate, comprising a first bistable liquid crystal cell transparent electrode; a second bistable liquid crystal cell substrate comprising a second bistable liquid crystal cell transparent electrode; and a liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode; wherein the second liquid crystal cell or the bistable electrochromic cell comprises: a first cell substrate, comprising a first cell transparent electrode; and a second cell substrate, comprising a second cell transparent electrode; wherein the second liquid crystal cell comprises a cell layer disposed between the first cell transparent electrode and the second cell transparent electrode; wherein the first bistable liquid crystal cell has a first liquid crystal stable state at zero voltage and a second liquid crystal stable state at zero voltage, the first liquid crystal stable state having a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”) and the second liquid crystal stable state having a second liquid crystal transmittance (“T12”) and a second liquid crystal haze value (“H12”); wherein the second liquid crystal cell or the bistable electrochromic cell has a first stable state at zero voltage, the first stable state having a first transmittance (“T21”) and a first haze vale (“H21”); wherein the bistable electrochromic cell has a second stable state at zero voltage, the second stable state having a second transmittance (“T22”) and a second haze value (“H22”); wherein the second bistable liquid crystal cell substrate is bonded to the first cell substrate by the interlayer; and wherein Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and | T21 - T22 | > 5%.

[0168] A second aspect relates to the switchable window of aspect 1, wherein the liquid crystal layer is a cholesteric liquid crystal layer.

[0169] A third aspect relates to the switchable window of aspect 2, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the cholesteric liquid crystal layer is disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

[0170] A fourth aspect relates to the switchable window of aspect 1, wherein the liquid crystal layer comprises a nematic liquid crystal and a chiral dopant.

[0171] A fifth aspect relates to the switchable window of aspect 4, wherein the first bistable liquid crystal cell substrate comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the nematic liquid crystal and the chiral dopant are disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

[0172] A sixth aspect relates to the switchable window of aspect 1, wherein the liquid crystal layer is a smectic phase liquid crystal layer.

[0173] A seventh aspect relates to the switchable window of aspect 6, wherein the first bistable liquid crystal cell substrate further comprises a first liquid crystal cell alignment layer; and wherein the smectic phase liquid crystal layer is disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode.

[0174] An eighth aspect relates to the switchable window of any of aspects 1 to 7, comprising a second liquid crystal cell.

[0175] A ninth aspect relates to the switchable window of any of aspects 1 to 8, wherein the second liquid crystal cell has a second stable state at zero voltage, the second stable state having the second transmittance (T22) and the second haze value (H22).

[0176] A tenth aspect relates to the switchable window of aspect 9, wherein | T21 - T22 1 > 30%. [0177] An eleventh aspect relates to the switchable window of any of aspects 1 to 10, wherein the first cell substrate further comprises a first cell alignment layer and the second cell substrate further comprises a second cell alignment layer.

[0178] A twelfth aspect relates to the switchable window of aspect 11, wherein the cell layer is a liquid crystal layer disposed between the first cell alignment layer and the second cell alignment layer.

[0179] A thirteenth aspect relates to the switchable window of aspect 11 or 12, wherein one or both of the first cell alignment layer and the second cell alignment layer comprise a grating such that the second stable state is achieved at an applied voltage of zero.

[0180] A fourteenth aspect relates to the switchable window of any one of aspects 1 to 13, wherein the cell layer comprises a chiral dopant.

[0181] A fifteenth aspect relates to the switchable window of any one of aspects 1 to 14, wherein the second liquid crystal cell further comprises a first polarizer attached to the first cell substrate and a second polarizer attached to the second cell substrate.

[0182] A sixteenth aspect relates to the switchable window of any of aspects 1 to 8, wherein the cell layer comprises a nematic liquid crystal.

[0183] A seventeenth aspect relates to the switchable window of any of aspects 1 to 8 or 16, wherein the cell layer comprises a chiral dopant. [0184] An eighteenth aspect relates to the switchable window of any of aspects 1 to 8, 16, or 17, wherein the second liquid crystal cell further comprises a dichroic dye.

[0185] A nineteenth aspect relates to the switchable window of any of aspects 1 to 8, wherein the second liquid crystal cell is dye-doped.

[0186] A twentieth aspect relates to the switchable window of any of aspects 1 to 8 or 19, wherein the second liquid crystal cell has a second stable state at zero voltage, the second stable having the second transmittance (T22) and the second haze value (H22).

[0187] A twenty-first aspect relates to the switchable window of any of aspects 1 to 8, 19, or 20, wherein the cell layer is a liquid crystal layer comprising a nematic liquid crystal and a dichroic dye.

[0188] A twenty-second aspect relates to the switchable window of any of aspects 1 to 8 or 19 to 21, wherein the cell layer comprises a chiral dopant.

[0189] A twenty -third aspect relates to the switchable window of any of aspects 1 to 8 or 19 to 22, wherein the first cell substrate further comprises a first cell alignment layer and the second cell substrate further comprises a second cell alignment layer.

[0190] A twenty-fourth aspect relates to the switchable window of aspect 23, wherein one or both of the first cell alignment layer and the second cell alignment layer comprise a grating such that the second stable state is achieved at an applied voltage of zero.

[0191] A twenty-fifth aspect relates to the switchable window of any of aspects 1 to 8 or 19 to

24, wherein the liquid crystal layer further comprises a chiral dopant.

[0192] A twenty-sixth aspect relates to the switchable window of any one of aspects 23 to 25, wherein the first cell alignment layer and the second cell alignment layer align the second liquid crystal cell substantially parallel to a plane of the first cell substrate and the second cell substrate in the absence of an applied voltage, such that T21 > T22.

[0193] A twenty-seventh aspect relates to the switchable window of any one of aspects 23 to

25, wherein the first cell alignment layer and the second cell alignment layer align the second liquid crystal cell substantially perpendicularly to a plane of the first cell substrate and the second cell substrate in the absence of an applied voltage, such that T21 < T22.

[0194] A twenty-eighth aspect relates to the switchable window of any of aspects 1 to 8 or 19 to 27, wherein the second liquid crystal cell further comprises a first polarizer attached to the first cell substrate or the second cell substrate.

[0195] A twenty-ninth aspect relates to the switchable window of any of aspects 1 to 8, comprising a bistable electrochromic cell. [0196] A thirtieth aspect relates to the switchable window of any of aspects 1 to 8 or 29, wherein the bistable electrochromic cell comprises an electrochromic layer, an electrolyte layer, and an ion storage layer disposed between the first cell transparent electrode and the second cell transparent electrode.

[0197] A thirty-first aspect relates to the switchable window of aspect 30, wherein the electrochromic layer, the electrolyte layer, and the ion storage layer are disposed sequentially. [0198] A thirty-second aspect relates to the switchable window of any of aspects 1 to 8 or 29 to 31, further comprising a conductive additive.

[0199] A thirty-third aspect relates to the switchable window of any of aspects 1 to 8 or 29 to

32, further comprising a dichroic dye.

[0200] A thirty-fourth aspect relates to the switchable window of any of aspects 1 to 8 or 29 to

33, wherein the bistable electrochromic cell has more than two stable states at zero voltage.

[0201] A thirty-fifth aspect relates to the switchable window of any of aspects 1 to 8 or 29 to

34, wherein the first cell transparent electrode or the second cell transparent electrode is coated with a polymer.

[0202] A thirty-sixth aspect relates to the switchable window of aspect 35, wherein the polymer is an electrochromic polymer.

[0203] A thirty-seventh aspect relates to the switchable window of any one of aspects 1 to 36, further comprising a first strengthened glass bonded to the first bistable liquid crystal cell substrate by a second interlayer.

[0204] A thirty-eighth aspect relates to the switchable window of any one of aspects 1 to 37, further comprising a second strengthened glass bonded to the second cell substrate of the second liquid crystal cell or the bistable electrochromic cell by a third interlayer.

[0205] A thirty-ninth aspect relates to the switchable window of aspect 37 or 38, wherein a first insulating gas is sealed between the first strengthened glass and the first bistable liquid crystal cell substrate.

[0206] A fortieth aspect relates to the switchable window of aspect 38 or 39, wherein a second insulating gas is sealed between the second strengthened glass and the second cell substrate.

[0207] A forty-first aspect relates to the switchable window of any of aspects 1 to 40, wherein Hu < 3%, H21 < 3%, and/or H22 < 3%.

[0208] A forty-second aspect relates to the switchable window of any of aspects 1 to 41, wherein | T21 - T22 | > 40%. [0209] A forty -third aspect relates to the switchable window of any of aspects 1 to 42, wherein the window is a vehicle or a building.

[0210] A forty-fourth aspect relates to a switchable window, comprising: a first bistable liquid crystal cell; a second bistable liquid crystal cell; and an interlayer disposed between the first bistable liquid crystal cell and the second bistable liquid crystal cell; wherein the first bistable liquid crystal cell comprises: a first bistable liquid crystal cell substrate, comprising a first bistable liquid crystal cell transparent electrode; a second bistable liquid crystal cell substrate, comprising a second bistable liquid crystal cell transparent electrode; and a liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode; wherein the second bistable liquid crystal cell comprises: a first cell substrate, comprising a first cell transparent electrode; a second cell substrate, comprising a second cell transparent electrode; and a cell layer disposed between the first cell transparent electrode and the second cell transparent electrode; wherein the first bistable liquid crystal cell has a first liquid crystal stable state at zero voltage and a second liquid crystal stable state at zero voltage, the first liquid crystal stable state having a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”) and the second liquid crystal stable state having a second liquid crystal transmittance (“Tn”) and a second liquid crystal haze value (“Hu”); wherein the second bistable liquid crystal cell has a first stable state at zero voltage and a second stable state at zero voltage, the first stable state having a first transmittance (“T21”) and a first haze value (“H21”) and the second stable state having a second transmittance (“T22”) and a second haze value (“H22”); wherein the second bistable liquid crystal cell substrate is bonded to the first cell substrate by the interlayer; and wherein Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and | T21 - T22 | > 5%.

[0211] A forty-fifth aspect relates to the switchable window of aspect 44, wherein the liquid crystal layer is a cholesteric liquid crystal layer.

[0212] A forty-sixth aspect relates to the switchable window of aspect 45, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the cholesteric liquid crystal layer is disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

[0213] A forty-seventh aspect relates to the switchable window of aspect 44, wherein the liquid crystal layer comprises a nematic liquid crystal and a chiral dopant. [0214] A forty-eighth aspect relates to the switchable window of aspect 47, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the nematic liquid crystal and the chiral dopant are disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

[0215] A forty-ninth aspect relates to the switchable window of aspect 44, wherein the liquid crystal layer is a smectic phase liquid crystal layer.

[0216] A fiftieth aspect relates to the switchable window of aspect 49, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer; and wherein the smectic phase liquid crystal layer is disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode.

[0217] A fifty-first aspect relates to the switchable window of any one of aspects 44 to 50, wherein the first cell substrate comprises a first cell alignment layer and the second cell substrate further comprises a second cell alignment layer.

[0218] A fifty-second aspect relates to the switchable window of aspect 51, wherein the cell layer is a liquid crystal layer disposed between the first cell alignment layer and the second cell alignment layer.

[0219] A fifty-third aspect relates to the switchable window of aspect 51 or 52, whereon one or both of the first cell alignment layer and the second cell alignment layer comprise a grating such that the second stable state is achieved at an applied voltage of zero.

[0220] A fifty-fourth aspect relates to the switchable window of any one of aspects 44 to 53, wherein the cell layer comprises a chiral dopant.

[0221] A fifty-fifth aspect relates to the switchable window of any one of aspects 44 to 54, wherein the second bistable liquid crystal cell further comprises a first polarizer attached to the first cell substrate or the second cell substrate.

[0222] A fifth-sixth substrate relates to the switchable window of aspect 55, wherein the second bistable liquid crystal cell further comprises a second polarizer attached to the second cell substrate, and wherein the first polarizer is attached to the first cell substrate.

[0223] A fifty-seventh aspect relates to the switchable window of any one of aspects 44 to 56, wherein the cell layer comprises a nematic liquid crystal. [0224] A fifty-eighth aspect relates to the switchable window of any one of aspects 44 to 57, wherein the second bistable liquid crystal cell further comprises a dichroic dye.

[0225] A fifty-ninth aspect relates to the switchable window of any one of aspects 44 to 58, wherein the second bistable liquid crystal cell is dye-doped.

[0226] A sixtieth aspect relates to the switchable window of any one of aspects 57 to 59, wherein the cell layer is a liquid crystal layer comprising the nematic liquid crystal and the dichroic dye.

[0227] A sixty-first aspect relates to the switchable window of any one of aspects 44 to 60, wherein the liquid crystal layer further comprises a chiral dopant.

[0228] A sixty-second aspect relates to the switchable window of any one of aspects 51 to 61, wherein the first cell alignment layer and the second cell alignment layer align the second bistable liquid crystal cell substantially parallel to a plane of the first cell substrate and the second cell substrate in the absence of an applied voltage, such that T21 > T22.

[0229] A sixty-third aspect relates to the switchable window of any one of aspects 51 to 61, wherein the first cell alignment layer and the second cell alignment layer align the second bistable liquid crystal cell substantially perpendicularly to a plane of the first cell substrate and the second cell substrate in the absence of an applied voltage, such that T21 < T22.

[0230] A sixty -fourth aspect relates to the switchable window of any one of aspects 44 to 63, further comprising a first strengthened glass bonded to the first bistable liquid crystal cell substrate by a second interlayer.

[0231] A sixty-fifth aspect relates to the switchable window of any one of aspects 44 to 64, further comprising a second strengthened glass bonded to the second bitable liquid crystal cell substrate by a third interlayer.

[0232] A sixty-sixth aspect relates to the switchable window of aspect 64 or 65, wherein a first insulating gas is sealed between the first strengthened glass and the first bistable liquid crystal cell substrate.

[0233] A sixty-seventh aspect relates to the switchable window of aspect 65 or 66, wherein a second insulating gas is sealed between the second strengthened glass and the second bistable liquid crystal cell substrate.

[0234] A sixty-eighth aspect relates to the switchable window of any one of aspects 44 to 67, wherein Hu < 3%, H21 < 3%, and/or H22 < 3%.

[0235] A sixty-ninth aspect relates to the switchable window of any one of aspects 44 to 68, wherein | T21 - T22 | > 40%. [0236] A seventieth aspect relates to the switchable window of any one of aspects 44 to 69, wherein the window is in a vehicle or a building.

[0237] A seventy-first aspect relates to the switchable window of any one of aspects 44 to 70, wherein the first bistable liquid crystal cell has more than two stable states at zero voltage.

[0238] A seventy-second aspect relates to the switchable window of any one of aspects 44 to 71, wherein at least one of the first bistable liquid crystal cell substrate and the second bistable liquid crystal cell substrate are made of a glass; and wherein at least one of the first cell substrate and the second cell substrate are made of a polymer.

[0239] A seventy-third aspect relates to a switchable window, comprising: a first bistable liquid crystal cell; a bistable electrochromic cell; and an interlayer disposed between the first bistable liquid crystal cell and the electrochromic cell; wherein the first bistable liquid crystal cell comprises: a first bistable liquid crystal cell substrate, comprising a first bistable liquid crystal cell transparent electrode; a second bistable liquid crystal cell substrate, comprising a second bistable liquid crystal cell transparent electrode; and a liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode; wherein the bistable electrochromic cell comprises: a first cell substrate, comprising a first cell transparent electrode; and a second cell substrate, comprising a second cell transparent electrode; wherein the first bistable liquid crystal cell has a first liquid crystal stable state at zero voltage and a second liquid crystal stable state at zero voltage, the first liquid crystal stable state having a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”) and the second liquid crystal stable state having a second liquid crystal transmittance (“Tn”) and a second liquid crystal haze value (“Hu”); wherein the bistable electrochromic cell has a first stable state at zero voltage and a second stable state at zero voltage, the first stable state having a first transmittance (“T21”) and a first haze value (“H21”) and the second stable state having a second transmittance (“T22”) and a second haze value (“H22”); wherein the second bistable liquid crystal cell substrate is bonded to the first cell substrate by the interlayer; and wherein Hu < 5%, Hn > 80%, Tn > Tn, H21 < 5%, H22 < 5%, and T21 - T22 > 5%.

[0240] A seventy-fourth aspect relates to the switchable window of aspect 73, wherein the liquid crystal layer is a cholesteric liquid crystal layer.

[0241] A seventy-fifth aspect relates to the switchable window of aspect 74, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the cholesteric liquid crystal layer is disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

[0242] A seventy-sixth aspect relates to the switchable window of aspect 73, wherein the liquid crystal layer comprises a nematic liquid crystal and a chiral dopant.

[0243] A seventy-seventh aspect relates to the switchable window of aspect 76, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the nematic liquid crystal and the chiral dopant are disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

[0244] A seventy-eighth aspect relates to the switchable window of aspect 73, wherein the liquid crystal layer is a smectic phase liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode.

[0245] A seventy-ninth aspect relates to the switchable window of aspect 78, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer; and wherein the smectic phase liquid crystal layer is disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode.

[0246] An eightieth aspect relates to the switchable window of any one of aspects 73 to 79, wherein the bistable electrochromic cell comprises an electrochromic layer, an electrolyte layer, and an ion storage layer disposed between the first cell transparent electrode and the second cell transparent electrode.

[0247] An eighty-first aspect relates to the switchable window of aspect 80, wherein the electrochromic layer, the electrolyte layer, and the ion storage layer are disposed sequentially. [0248] An eighty-second aspect relates to the switchable window of any one of aspects 78 to 81, wherein the smectic phase liquid crystal layer comprises a conductive additive.

[0249] An eighty -third aspect relates to the switchable window of any one of aspects 73 to 82, wherein the liquid crystal layer comprises a dichroic dye.

[0250] An eighty-fourth aspect relates to the switchable window of any one of aspects 73 to 83, wherein the bistable electrochromic cell has more than two stable states at zero voltage. [0251] An eighty-fifth aspect relates to the switchable window of any one of aspects 73 to 84, wherein the first cell transparent electrode or the second cell transparent electrode is coated with a polymer.

[0252] An eighty-sixth aspect relates to the switchable window of aspect 85, wherein the polymer is an electrochromic polymer.

[0253] An eighty-seventh aspect relates to the switchable window of any one of aspects 73 to

86, further comprising a first strengthened glass bonded to the first bistable liquid crystal cell substrate by a second interlayer.

[0254] An eighty-eighth aspect relates to the switchable window of any one of aspects 73 to

87, further comprising a second strengthened glass bonded to the second cell substrate of the bistable electrochromic cell by a third interlayer.

[0255] An eighty-ninth aspect relates to the switchable window of aspect 87 or 88, wherein a first insulating gas is sealed between the first strengthened glass and the first bistable liquid crystal cell substrate.

[0256] A ninetieth aspect relates to the switchable window of aspect 88 or 89, wherein a second insulating gas is sealed between the second strengthened glass and the second cell substrate.

[0257] A ninety-first aspect relates to the switchable window of any one of aspects 73 to 90, wherein Hu < 3%, H21 < 3%, and/or H22 < 3%.

[0258] A ninety-second aspect relates to the switchable window of any one of aspects 73 to 91, wherein | T21 - T22 | > 40%.

[0259] A ninety-third aspect relates to the switchable window of any one of aspects 73 to 92, wherein the window is in a vehicle or a building.

[0260] A ninety-fourth aspect relates to the switchable window of any one of aspects 73 to 93, wherein the first bistable liquid crystal cell has more than two stable states at zero voltage.

[0261] A ninety-fifth aspect relates to the switchable window of any one of aspects 73 to 94, wherein at least one of the first bistable liquid crystal cell substrate and the second bistable liquid crystal cell substrate are made of a glass; and wherein at least one of the first cell substrate and the second cell substrate are made of a polymer.

[0262] A ninety-sixth aspect relates to a method of switching a bistable switchable window, comprising: applying a voltage to the bistable switchable window such that the switchable window is switched from a first stable state to a second stable state, the bistable switchable window comprising a first bistable liquid crystal cell and a second cell selected from a liquid crystal cell and a bistable electrochromic cell, the second cell bonded to the first bistable liquid crystal cell by an interlayer; wherein in the first stable state, at zero voltage, the first bistable liquid crystal cell has a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”), and the second cell has a first transmittance (“T21”) and a first haze value (“H21”); wherein the second stable state, at zero voltage, the first bistable liquid crystal cell has a second liquid crystal transmittance (“T12”) and a second liquid crystal haze value (“H12”), and the second cell has a second transmittance (“T22”) and a second haze value (“H22”); and wherein Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and | T21 - T22 | > 5%.

[0263] A ninety-seventh aspect relates to the method of aspect 96, further comprising: applying a second voltage different from the first voltage such that the switchable window is switched from the second stable state to the first stable state.

[0264] In addition to the features mentioned in each of the independent aspects enumerated above, some examples may show, alone or in combination, the optional features mentioned in the dependent aspects and/or as disclosed in the description above and shown in the figures.

Claims

CLAIMS What is claimed is:

1. A switchable window, comprising: a first bistable liquid crystal cell; a second liquid crystal cell or a bistable electrochromic cell; and an interlayer disposed between the first bistable liquid crystal cell and the second liquid crystal cell or the bistable electrochromic cell; wherein the first bistable liquid crystal cell comprises: a first bistable liquid crystal cell substrate, comprising a first bistable liquid crystal cell transparent electrode; a second bistable liquid crystal cell substrate, comprising a second bistable liquid crystal cell transparent electrode; and a liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode; wherein the second liquid crystal cell or the bistable electrochromic cell comprises: a first cell substrate, comprising a first cell transparent electrode; and a second cell substrate, comprising a second cell transparent electrode; wherein the second liquid crystal cell comprises a cell layer disposed between the first cell transparent electrode and the second cell transparent electrode; wherein the first bistable liquid crystal cell has a first liquid crystal stable state at zero voltage and a second liquid crystal stable state at zero voltage, the first liquid crystal stable state having a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”) and the second liquid crystal stable state having a second liquid crystal transmittance (“T12”) and a second liquid crystal haze value (“H12”); wherein the second liquid crystal cell or the bistable electrochromic cell has a first stable state at zero voltage, the first stable state having a first transmittance (“T21”) and a first haze value (“H21”); wherein the bistable electrochromic cell has a second stable state at zero voltage, the second stable state having a second transmittance (“T22”) and a second haze value (“H22”); wherein the second bistable liquid crystal cell substrate is bonded to the first cell substrate by the interlayer; and wherein Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and | T21 - T22 | > 5%.

2. The switchable window of claim 1, wherein the liquid crystal layer is a cholesteric liquid crystal layer.

3. The switchable window of claim 2, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the cholesteric liquid crystal layer is disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

4. The switchable window of claim 1, wherein the liquid crystal layer comprises a nematic liquid crystal and a chiral dopant.

5. The switchable window of claim 4, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the nematic liquid crystal and the chiral dopant are disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

6. The switchable window of claim 1, wherein the liquid crystal layer is a smectic phase liquid crystal layer.

7. The switchable window of claim 6, wherein the first bistable liquid crystal cell substrate further comprises a first liquid crystal cell alignment layer; and wherein the smectic phase liquid crystal layer is disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode.

8. The switchable window of claim 1, comprising a second liquid crystal cell.

9. The switchable window of claim 8, wherein the second liquid crystal cell has a second stable state at zero voltage, the second stable state having the second transmittance (T22) and the second haze value (H22).

10. The switchable window of claim 9, wherein | T21 - T22 | > 30%.

11. The switchable window of claim 10, wherein the first cell substrate further comprises a first cell alignment layer and the second cell substrate further comprises a second cell alignment layer.

12. The switchable window of claim 11, wherein the cell layer is a liquid crystal layer disposed between the first cell alignment layer and the second cell alignment layer.

13. The switchable window of claim 11, wherein one or both of the first cell alignment layer and the second cell alignment layer comprise a grating such that the second stable state is achieved at an applied voltage of zero.

14. The switchable window of claim 13, wherein the cell layer comprises a chiral dopant.

15. The switchable window of claim 8, wherein the second liquid crystal cell further comprises a first polarizer attached to the first cell substrate and a second polarizer attached to the second cell substrate.

16. The switchable window of claim 8, wherein the cell layer comprises a nematic liquid crystal.

17. The switchable window of claim 8, wherein the cell layer comprises a chiral dopant.

18. The switchable window of claim 8, wherein the second liquid crystal cell further comprises a dichroic dye.

19. The switchable window of claim 8, wherein the second liquid crystal cell is dye- doped.

20. The switchable window of claim 19, wherein the second liquid crystal cell has a second stable state at zero voltage, the second stable state having the second transmittance (T22) and the second haze value (H22).

21. The switchable window of claim 20, wherein the cell layer is a liquid crystal layer comprising a nematic liquid crystal and a dichroic dye.

22. The switchable window of claim 21, wherein the cell layer further comprises a chiral dopant.

23. The switchable window of claim 20, wherein the first cell substrate further comprises a first cell alignment layer and the second cell substrate further comprises a second cell alignment layer.

24. The switchable window of claim 23, wherein one or both of the first cell alignment layer and the second cell alignment layer comprise a grating such that the second stable state is achieved at an applied voltage of zero.

25. The switchable window of claim 24, wherein the liquid crystal layer further comprises a chiral dopant.

26. The switchable window of claim 23, wherein the first cell alignment layer and the second cell alignment layer align the second liquid crystal cell substantially parallel to a plane of the first cell substrate and the second cell substrate in the absence of an applied voltage, such that T21 > T22.

27. The switchable window of claim 23, wherein the first cell alignment layer and the second cell alignment layer align the second liquid crystal cell substantially perpendicularly to a plane of the first cell substrate and the second cell substrate in the absence of an applied voltage, such that T21 < T22.

28. The switchable window of claim 19, wherein the second liquid crystal cell further comprises a first polarizer attached to the first cell substrate or the second cell substrate.

29. The switchable window of claim 1, comprising a bistable electrochromic cell.

30. The switchable window of claim 29, wherein the bistable electrochromic cell comprises an electrochromic layer, an electrolyte layer, and an ion storage layer disposed between the first cell transparent electrode and the second cell transparent electrode.

31. The switchable window of claim 30, wherein the electrochromic layer, the electrolyte layer, and the ion storage layer are disposed sequentially.

32. The switchable window of claim 30, wherein the liquid crystal layer is a cholesteric liquid crystal layer.

33. The switchable window of claim 32, wherein the first bistable liquid crystal cell substrate comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate comprises a second bistable liquid crystal cell alignment layer; and wherein the cholesteric liquid crystal layer is disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

34. The switchable window of claim 30, wherein the liquid crystal layer is a smectic phase liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode.

35. The switchable window of claim 34, wherein the first bistable liquid crystal cell substrate comprises a first bistable liquid crystal cell alignment layer.

36. The switchable window of claim 34, further comprising a conductive additive.

37. The switchable window of claim 34, further comprising a dichroic dye.

38. The switchable window of claim 29, wherein the bistable electrochromic cell has more than two stable states at zero voltage.

39. The switchable window of claim 29, wherein the first cell transparent electrode or the second cell transparent electrode is coated with a polymer.

40. The switchable window of claim 39, wherein the polymer is an electrochromic polymer.

41. The switchable window of claim 1, further comprising a first strengthened glass bonded to the first bistable liquid crystal cell substrate by a second interlayer.

42. The switchable window of claim 41, further comprising a second strengthened glass bonded to the second cell substrate of the second liquid crystal cell or the bistable electrochromic cell by a third interlayer.

43. The switchable window of claim 41, wherein a first insulating gas is sealed between the first strengthened glass and the first bistable liquid crystal cell substrate.

44. The switchable window of claim 42, wherein a second insulating gas is sealed between the second strengthened glass and the second cell substrate.

45. The switchable window of claim 1, wherein Hu < 3%, H21 < 3%, and/or H22 < O / /O.

46. The switchable window of claim 1, wherein | T21 - T22 | > 40%.

47. The switchable window of claim 1, wherein the window is in a vehicle or a building.

48. A switchable window, comprising: a first bistable liquid crystal cell; a second bistable liquid crystal cell; and an interlayer disposed between the first bistable liquid crystal cell and the second bistable liquid crystal cell; wherein the first bistable liquid crystal cell comprises: a first bistable liquid crystal cell substrate, comprising a first bistable liquid crystal cell transparent electrode; a second bistable liquid crystal cell substrate, comprising a second bistable liquid crystal cell transparent electrode; and a liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode; wherein the second bistable liquid crystal cell comprises: a first cell substrate, comprising a first cell transparent electrode; a second cell substrate, comprising a second cell transparent electrode; and a cell layer disposed between the first cell transparent electrode and the second cell transparent electrode; wherein the first bistable liquid crystal cell has a first liquid crystal stable state at zero voltage and a second liquid crystal stable state at zero voltage, the first liquid crystal stable state having a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”) and the second liquid crystal stable state having a second liquid crystal transmittance (“T12”) and a second liquid crystal haze value (“H12”); wherein the second bistable liquid crystal cell has a first stable state at zero voltage and a second stable state at zero voltage, the first stable state having a first transmittance (“T21”) and a first haze value (“H21”) and the second stable state having a second transmittance (“T22”) and a second haze value (“H22”); wherein the second bistable liquid crystal cell substrate is bonded to the first cell substrate by the interlayer; and wherein Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and | T21 - T22 | > 5%.

49. The switchable window of claim 48, wherein the liquid crystal layer is a cholesteric liquid crystal layer.

50. The switchable window of claim 49, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the cholesteric liquid crystal layer is disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

51. The switchable window of claim 48, wherein the liquid crystal layer comprises a nematic liquid crystal and a chiral dopant.

52. The switchable window of claim 51, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the nematic liquid crystal and the chiral dopant are disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

53. The switchable window of claim 48, wherein the liquid crystal layer is a smectic phase liquid crystal layer.

54. The switchable window of claim 53, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer; and wherein the smectic phase liquid crystal layer is disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode.

55. The switchable window of claim 48, wherein the first cell substrate further comprises a first cell alignment layer and the second cell substrate further comprises a second cell alignment layer.

56. The switchable window of claim 55, wherein the cell layer is a liquid crystal layer disposed between the first cell alignment layer and the second cell alignment layer.

57. The switchable window of claim 55, wherein one or both of the first cell alignment layer and the second cell alignment layer comprise a grating such that the second stable state is achieved at an applied voltage of zero.

58. The switchable window of claim 57, wherein the cell layer comprises a chiral dopant.

59. The switchable window of claim 48, wherein the second bistable liquid crystal cell further comprises a first polarizer attached to the first cell substrate and a second polarizer attached to the second cell substrate.

60. The switchable window of claim 48, wherein the cell layer comprises a nematic liquid crystal.

61. The switchable window of claim 48, wherein the cell layer comprises a chiral dopant.

62. The switchable window of claim 48, wherein the second bistable liquid crystal cell further comprises a dichroic dye.

63. The switchable window of claim 48, wherein the second bistable liquid crystal cell is dye-doped.

64. The switchable window of claim 63, wherein the cell layer is a liquid crystal layer comprising a nematic liquid crystal and a dichroic dye.

65. The switchable window of claim 64, wherein the cell layer further comprises a chiral dopant.

66. The switchable window of claim 63, wherein the first cell substrate further comprises a first cell alignment layer and the second cell substrate further comprises a second cell alignment layer.

67. The switchable window of claim 66, wherein one or both of the first cell alignment layer and the second cell alignment layer comprise a grating such that the second stable state is achieved at an applied voltage of zero.

68. The switchable window of claim 67, wherein the liquid crystal layer further comprises a chiral dopant.

69. The switchable window of claim 66, wherein the first cell alignment layer and the second cell alignment layer align the second bistable liquid crystal cell substantially parallel to a plane of the first cell substrate and the second cell substrate in the absence of an applied voltage, such that T21 > T22.

70. The switchable window of claim 66, wherein the first cell alignment layer and the second cell alignment layer align the second bistable liquid crystal cell substantially perpendicularly to a plane of the first cell substrate and the second cell substrate in the absence of an applied voltage, such that T21 < T22.

71. The switchable window of claim 63, wherein the second bistable liquid crystal cell further comprises a first polarizer attached to the first cell substrate or the second cell substrate.

72. The switchable window of claim 48, further comprising a first strengthened glass bonded to the first bistable liquid crystal cell substrate by a second interlayer.

73. The switchable window of claim 72, further comprising a second strengthened glass bonded to the second bistable liquid crystal cell substrate of the second bistable liquid crystal cell by a third interlayer.

74. The switchable window of claim 72, wherein a first insulating gas is sealed between the first strengthened glass and the first bistable liquid crystal cell substrate.

75. The switchable window of claim 73, wherein a second insulating gas is sealed between the second strengthened glass and the second cell substrate.

76. The switchable window of claim 48, wherein Hu < 3%, H21 < 3%, and/or H22 O /Zo.

77. The switchable window of claim 48, wherein | T21 - T22 | > 40%.

78. The switchable window of claim 48, wherein the window is in a vehicle or a building.

79. The switchable window of claim 48, wherein the first bistable liquid crystal cell has more than two stable states at zero voltage.

80. The switchable window of claim 48, wherein at least one of the first bistable liquid crystal cell substrate and the second bistable liquid crystal cell substrate are made of a glass; and wherein at least one of the first cell substrate and the second cell substrate are made of a polymer.

81. A switchable window, comprising: a first bistable liquid crystal cell; a bistable electrochromic cell; and an interlayer disposed between the first bistable liquid crystal cell and the electrochromic cell; wherein the first bistable liquid crystal cell comprises: a first bistable liquid crystal cell substrate, comprising a first bistable liquid crystal cell transparent electrode; a second bistable liquid crystal cell substrate, comprising a second bistable liquid crystal cell transparent electrode; and a liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode; wherein the bistable electrochromic cell comprises: a first cell substrate, comprising a first cell transparent electrode; and a second cell substrate, comprising a second cell transparent electrode; wherein the first bistable liquid crystal cell has a first liquid crystal stable state at zero voltage and a second liquid crystal stable state at zero voltage, the first liquid crystal stable state having a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”) and the second liquid crystal stable state having a second liquid crystal transmittance (“T12”) and a second liquid crystal haze value (“H12”); wherein the bistable electrochromic cell has a first stable state at zero voltage and a second stable state at zero voltage, the first stable state having a first transmittance (“T21”) and a first haze value (“H21”) and the second stable state having a second transmittance (“T22”) and a second haze value (“H22”); wherein the second bistable liquid crystal cell substrate is bonded to the first cell substrate by the interlayer; and wherein Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and T21 - T22 > 5%.

82. The switchable window of claim 81, wherein the liquid crystal layer is a cholesteric liquid crystal layer.

83. The switchable window of claim 82, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the cholesteric liquid crystal layer is disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

84. The switchable window of claim 81, wherein the liquid crystal layer comprises a nematic liquid crystal and a chiral dopant.

85. The switchable window of claim 84, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell substrate further comprises a second bistable liquid crystal cell alignment layer; and wherein the nematic liquid crystal and the chiral dopant are disposed between the first bistable liquid crystal cell alignment layer and the second bistable liquid crystal cell alignment layer.

86. The switchable window of claim 81, wherein the liquid crystal layer is a smectic phase liquid crystal layer disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode.

87. The switchable window of claim 86, wherein the first bistable liquid crystal cell substrate further comprises a first bistable liquid crystal cell alignment layer; and wherein the smectic phase liquid crystal layer is disposed between the first bistable liquid crystal cell transparent electrode and the second bistable liquid crystal cell transparent electrode.

88. The switchable window of claim 81, wherein the bistable electrochromic cell comprises an electrochromic layer, an electrolyte layer, and an ion storage layer disposed between the first cell transparent electrode and the second cell transparent electrode.

89. The switchable window of claim 88, wherein the electrochromic layer, the electrolyte layer, and the ion storage layer are disposed sequentially.

90. The switchable window of claim 86, wherein the smectic phase liquid crystal layer comprises a conductive additive.

91. The switchable window of claim 81, wherein the liquid crystal layer comprises a dichroic dye.

92. The switchable window of claim 81, wherein the bistable electrochromic cell has more than two stable states at zero voltage.

93. The switchable window of claim 81, wherein the first cell transparent electrode or the second cell transparent electrode is coated with a polymer.

94. The switchable window of claim 93, wherein the polymer is an electrochromic polymer.

95. The switchable window of claim 81, further comprising a first strengthened glass bonded to the first bistable liquid crystal cell substrate by a second interlayer.

96. The switchable window of claim 95, further comprising a second strengthened glass bonded to the second cell substrate of the bistable electrochromic cell by a third interlayer.

97. The switchable window of claim 95, wherein a first insulating gas is sealed between the first strengthened glass and the first bistable liquid crystal cell substrate.

98. The switchable window of claim 96, wherein a second insulating gas is sealed between the second strengthened glass and the second cell substrate.

99. The switchable window of claim 81, wherein Hu < 3%, H21 < 3%, and/or H22 < 3%.

100. The switchable window of claim 81, wherein | T21 - T22 | > 40%.

101. The switchable window of claim 81, wherein the window is in a vehicle or a building.

102. The switchable window of claim 81, wherein the first bistable liquid crystal cell has more than two stable states at zero voltage.

103. The switchable window of claim 81, wherein at least one of the first bistable liquid crystal cell substrate and the second bistable liquid crystal cell substrate are made of a glass; and wherein at least one of the first cell substrate and the second cell substrate are made of a polymer.

104. A method of switching a bistable switchable window, comprising: applying a voltage to the bistable switchable window such that the switchable window is switched from a first stable state to a second stable state, the bistable switchable window comprising a first bistable liquid crystal cell and a second cell selected from a liquid crystal cell and a bistable electrochromic cell, the second cell bonded to the first bistable liquid crystal cell by an interlayer; wherein in the first stable state, at zero voltage, the first bistable liquid crystal cell has a first liquid crystal transmittance (“Tn”) and a first liquid crystal haze value (“Hu”), and the second cell has a first transmittance (“T21”) and a first haze value (“H21”); wherein in the second stable state, at zero voltage, the first bistable liquid crystal cell has a second liquid crystal transmittance (“T12”) and a second liquid crystal haze value (“H12”), and the second cell has a second transmittance (“T22”) and a second haze value (“H22”); and wherein Hu < 5%, H12 > 80%, Tn > T12, H21 < 5%, H22 < 5%, and | T21 - T22 | > 5%.

105. The method of claim 104, further comprising: applying a second voltage different from the first voltage such that the switchable window is switched from the second stable state to the first stable state.