LCD Assembly

Abstract

This application describes dimmable liquid crystal panels and techniques for fabricating them. In some embodiments, the LC panel includes a guest-host liquid crystal layer containing nematic liquid crystals, dye molecules, and a chiral dopant. The GH liquid crystal layer is positioned between a pair of substrates. The LC panel is a film panel, with each substrate including a flexible film and a conductive layer formed on the flexible film. The substrates are separated by a spacer that defines a cell gap. The GH liquid crystal layer is configured to drive the LC panel between dark and bright states in response to a voltage across the conductive layers. The flexible film allows the LC panel to conform to the surface of a window or other rigid surface to which it is attached. The LC panel can be attached via a liquid- or film-based adhesive.

Description

[Technical field]

[0001] This application claims the benefit of and priority to U.S. Provisional Application No. 63 / 116,751, filed November 20, 2020, the contents of which are incorporated herein by reference for all purposes. [Background technology]

[0002] The present disclosure relates generally to liquid crystal panels, and more specifically to various structures incorporating liquid crystal cells and methods of manufacturing such structures. The present disclosure also relates to liquid crystal panels that are dimmable by electrically adjusting the light transmittance of one or more liquid crystal cells within the liquid crystal panel. Summary of the Invention [Means for solving the problem]

[0003] The present disclosure relates to liquid crystal (LC) panels that include one or more liquid crystal cells. The LC cells include liquid crystal molecules contained within a multi-layer stack that may include, among other things, a conductive layer and a protective substrate. LC panels are typically configured as panels with a relatively large surface area (compared to the surface along the thickness dimension) that receives light on one side and transmits light on the opposite side. In some embodiments, the LC panel is electrically controllable to vary the light transmittance of the LC panel. In embodiments featuring LC panels with multiple cells, each cell can correspond to a different segment along the surface of the LC panel, and the cells can be individually controlled to vary the transmittance of each of its segments without affecting the transmittance of the other segments. The dimmable LC panels disclosed herein can be used in a variety of settings, including vehicular settings (e.g., car / automobile windows) and architectural settings (e.g., building windows).

[0004] The construction of an LC panel may depend on the setting and application in which the LC panel will be used. For example, an LC panel used in a vehicular setting may include flexible materials for impact resistance and / or adhesive materials to protect against separation (fragmentation) into many pieces if broken. LC panels used in vehicular environments preferably behave like safety glass, with multiple layers that can be broken into smaller pieces while remaining attached to the LC panel's adhesive layer or substrate. Additionally, LC panels that include one or more flexible layers (e.g., flexible substrates) may be easier to install and more resistant to physical manipulations such as bending. Additionally, because optical clarity is important in vehicular environments, dimmable LC panels can be configured to provide variable transmittance with minimal haze or scattering of light. This allows the occupant to see clearly through the LC panel no matter how the light transmittance changes.

[0005] The present disclosure also relates to techniques for manufacturing liquid crystal panels using a manufacturing process that involves laminating layers of different materials together. In some embodiments, the techniques are applied to incorporate curved layers (e.g., glass panels) into the LC panel. This allows the LC panel to be formed into a shape suitable for use as a vehicle window or other applications that may require a curved LC panel.

[0006] In some embodiments, the dimmable LC panel may be controlled based on one or more sensors, e.g., optical and / or temperature sensors, configured to collect data about the environment surrounding the LC panel. The sensor data may be processed to automatically dim the light in response to changes in the environment, such as changes in location in the environment or brightness of the light source.

[0007] In some embodiments, techniques are applied to laminate LC panels at lower temperatures and / or pressures than are typically used. In particular, LC panels suitable for use in vehicular environments can include one or more polyvinyl butyral (PVB) layers. Lamination of PVB typically requires temperatures and pressures higher than the components of the LC panel can withstand. For example, spacers that separate the opposing substrates that define the walls of the LC cell are prone to deformation and / or dislocation in the presence of heat. High temperatures can also cause defects in the LC cell itself, such as dark spots. Thus, in some embodiments, the temperature and / or pressure are reduced by performing the lamination in a vacuum environment.

[0008] In some embodiments, techniques are applied to laminate LC panels that include one or more ultraviolet (UV) blocking layers. Due to the presence of one or more UV blocking layers, UV curing of an adhesive may not be available as a method to bond two or more components together; for example, bonding a spacer or gasket to a substrate. There are various reasons for including a UV blocking layer. For example, a polarizer is added to the opposite side of the LC cell or is introduced as part of the LC cell itself to form a twisted nematic (TN) liquid crystal display. The polarizer may include a polarizer plate and a protective coating designed to protect the polarizer plate from damage. This protective coating may be formed from a material (e.g., triacetyl cellulose (TAC)) that blocks UV light to the extent that the UV light that can pass through the polarizer is insufficient to fully cure the UV adhesive. Thus, in some embodiments, a non-UV adhesive may be used and may include, for example, an epoxy adhesive or a thermal cure adhesive. Such alternative adhesives may introduce additional problems that are not present when using UV adhesives. For example, epoxy adhesives have a limited working time before the adhesive cures, so the time window in which the parts to be joined can be repositioned (e.g., to correct misalignment) may be short. Furthermore, as shown above, the introduction of heat can damage components that are sensitive to high temperatures, such as spacers in the LC cell or the LC cell itself.

[0009] As indicated above, in some embodiments, the LC panel may include one or more flexible layers. The LC panels described herein may include rigid and / or flexible substrates. In particular, the substrate may be formed as a flexible film (e.g., a layer of flexible material having a thickness of about 200 μm or less) that includes a coating of a conductive material. Flexible substrates include TAC (triacetyl cellulose), polycarbonate (PC), polyethylene terephthalate (PET), or other flexible materials. Flexible substrates may be used in the construction of flexible LC panels. For example, LC panels may be formed that are devoid of glass or other rigid substrates and are thin enough that the entire LC panel functions as a flexible film. LC panels that incorporate one or more flexible films are referred to herein as LC film panels. When LC panels are formed using rigid substrates (e.g., including glass panels or LC cells encased between glass panels), such panels may be used as standalone windows. Alternatively, some embodiments feature flexible substrates that allow the LC panel to be applied as an add-on to a window or other prefabricated rigid surface (e.g., using a transparent, aqueous or solvent-based coating as a thin film). When the surface to which the LC panel is applied is curved, a flexible LC panel is advantageous because the LC panel can conform to the curvature of the surface, thereby eliminating or at least substantially minimizing the presence of air bubbles or gaps between the LC panel and the surface.

[0010] The techniques described herein for manufacturing LC panels can be implemented using a computer system with one or more processing units (e.g., general-purpose processors) that can be configured to perform certain operations or actions (e.g., control of temperature and / or pressure). Access to software, firmware, hardware, or combinations thereof installed on the system. The one or more computer programs can be configured to perform certain operations or actions by including instructions executable by the one or more processing units. The one or more computer programs can be stored on a non-transitory computer-readable medium (e.g., computer storage forming a memory) accessible to the one or more processing units. [Brief description of the drawings]

[0011] [Figure 1] An example of an environment in which an LC panel can be used is shown below. [Figure 2A] 1 shows an example of how a dimmable LC panel can be segmented. [Figure 2B] 1 shows an example of how a dimmable LC panel can be segmented. [Figure 2C] 1 shows an example of how a dimmable LC panel can be segmented. [Figure 3A] 13A-13C show examples of different control schemes for selectively dimming segments according to some embodiments. [Figure 3B] 13A-13C show examples of different control schemes for selectively dimming segments according to some embodiments. [Figure 3C] 13A-13C show examples of different control schemes for selectively dimming segments according to some embodiments. [Figure 4] 1 shows an example of an LC panel that includes asymmetric dimmable segments, according to one embodiment. [Figure 5A] 1 illustrates an example of a dimming system according to one embodiment. [Figure 5B]1 illustrates an example of a dimming system according to one embodiment. [Figure 6A] FIG. 2 is a simplified block diagram of a control unit according to one embodiment. [Figure 6B] 4 shows an example of the arrangement of components of a control unit relative to a window. [Figure 7A] 1 illustrates an example of a liquid crystal cell that can be used to form an LC panel according to some embodiments. [Figure 7B] 1 illustrates an example of a liquid crystal cell that can be used to form an LC panel according to some embodiments. [Figure 7C] 1 illustrates an example of a liquid crystal cell that can be used to form an LC panel according to some embodiments. [Figure 8A] 1 shows voltage-transmittance curves for several examples of dimmable LC panels. [Figure 8B] 1 shows voltage-transmittance curves for several examples of dimmable LC panels. [Figure 8C] 1 shows voltage-transmittance curves for several examples of dimmable LC panels. [Figure 8D] 1 shows voltage-transmittance curves for several examples of dimmable LC panels. [Figure 9A] 1A-1C show examples of LC panels including a PVB layer according to some embodiments. [Figure 9B] 1A-1C show examples of LC panels including a PVB layer according to some embodiments. [Figure 9C] 1A-1C show examples of LC panels including a PVB layer according to some embodiments. [Figure 10] FIG. 1 illustrates an example of a system for laminating LC panels including PVB, according to some embodiments. [Figure 11] 1 shows a UV curing step applied to the LC cell. [Figure 12A] 1 shows an example of an LC panel including indium tin oxide (ITO) electrodes and polarizers with triacetyl cellulose (TAC), according to some embodiments. [Figure 12B]1 shows an example of an LC panel including indium tin oxide (ITO) electrodes and polarizers with triacetyl cellulose (TAC), according to some embodiments. [Figure 13] FIG. 1 shows the expansion of the LC panel during lamination with the PVB and glass panels. [Figure 14] 1 illustrates an LC panel with liquid and film based adhesives according to some embodiments. [Figure 15] 1 shows the shear stress induced in an LC panel when it is held at rest against a surface. [Figure 16] 1 shows an example of an LC panel mounted on a mounting body according to some embodiments. [Figure 17] 1 shows an example of an LC panel mounted on a mounting body according to some embodiments. [Figure 18] 1 shows an example of an LC panel mounted on a mounting body according to some embodiments. [Figure 19] 1 shows an example of an LC panel mounted on a mounting body according to some embodiments. [Figure 20] 1 illustrates an LC panel adapted for mounting on a glass surface, according to some embodiments. [Figure 21] 1 illustrates an LC panel adapted for mounting on a glass surface, according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The drawings depict embodiments of the present disclosure for purposes of illustration only. Those skilled in the art will readily appreciate from the following description that alternative embodiments of the illustrated structures and methods may be employed without departing from the principles or advertised benefits of the present disclosure.

[0013] In the accompanying drawings, similar components and / or features may have the same reference label. Additionally, various components of the same type may be distinguished by following the reference label with a dash and a second label that distinguishes between the similar components. When only the first reference label is used in the specification, the statement applies to any of the similar components having the same first reference label, regardless of the second reference label.

[0014] In the following description, for purposes of explanation, specific details are set forth in order to provide a thorough understanding of particular inventive embodiments. However, it will be apparent that various embodiments may be practiced without these specific details. The drawings and description are not intended to be limiting.

[0015] The present disclosure relates to liquid crystal (LC) panels that include one or more liquid crystal cells. In some embodiments, the LC panels are electrically controllable, i.e., dimmable, to change the light transmittance of the LC panel. In embodiments featuring LC panels with multiple cells, each cell can correspond to a different segment along the surface of the LC panel, and the cells can be individually controlled to change the transmittance of that segment without affecting the transmittance of other segments. The dimmable LC panels disclosed herein can be used in a variety of settings, including vehicular settings (e.g., car / automobile windows) and architectural settings (e.g., building windows).

[0016] The term "dimmable" as used herein refers to the ability to vary light transmission up or down by one or more control signals. For example, an LC cell may include a pair of electrodes on opposite sides of a liquid crystal layer, and by adjusting the voltage applied between the electrodes, the liquid crystal molecules (e.g., individual liquid crystal molecules) are controlled to darken by reducing the amount of light that can pass through the LC cell. Dimmable LC cells come in various types, such as twisted nematic (TN), guest-host (GH), and vertically aligned (VA). Dimmable LC cells can be configured to have maximum light transmission when the value of the control signal is at its minimum (e.g., zero volts). Such cells are sometimes referred to as "normally white" (NW). Alternatively, dimmable LC cells can be configured to have minimum light transmission when the value of the control signal is at its minimum / zero volts. Such cells are sometimes referred to as "normally black" (NB).

[0017] The embodiments of the present disclosure can be used to implement liquid crystal displays (LCDs), including dimmable LCDs. Although LCD structures are not specifically discussed, it will be understood that the LC panels described herein can be adapted to form LCDs, for example, by adding monochromatic or multi-color (e.g., red, green, blue) backlighting.

[0018] Some embodiments of the present disclosure relate to curved windows or LC panels, such that the surface of the window or LC panel is not flat but has a three-dimensional curved surface (eg, convex towards the external environment).

[0019] The present disclosure also relates to techniques for manufacturing LC panels, including LC panels that are dimmable by electrically controlling the light transmittance of one or more LC cells in the LC panel. Some embodiments are directed to dimmable panels that can be used as or incorporated into a window. In general, a window is any substantially rigid structure through which light can pass. In the case of a dimmable window, the degree to which light can pass through the window is controllable within a range of transmittance values. Windows can be curved or flat, can be any number of shapes (e.g., rectangular, triangular, circular), and can be enclosed within a frame or frameless. Additionally, one important aspect of a window for viewing purposes is its optical clarity.

[0020] To make LC panels, particularly dimmable LC panels, suitable for use as or in windows and in safety-critical environments, certain types of materials, and the combination of such materials with other components of the LC panel to form a laminate structure, are described herein. An example of a safety-critical environment is an automobile, as shown in FIG. 1. Other types of environments that can benefit from LC panels according to embodiments described herein include, for example, aircraft (e.g., airplanes), spacecraft, and marine vessels (e.g., ships, boats). LC panels can be used in public or commercial vehicles (e.g., trucks or passenger buses) or other vehicles, and in architectural environments, e.g., building windows, glass walls, or building doors.

[0021] FIG. 1 illustrates an example of an environment in which an LC panel can be used. As shown in FIG. 1, an automobile 120 includes a windshield 122, a rear windshield 124, a sunroof 126, and a side window 128. In the example of FIG. 1, the automobile 120 includes a quarter glass window 129. Quarter glass windows are generally smaller than an automobile's side windows and are typically located above the rear wheels or next to the side mirrors. Due to the shape and location of the automobile body, the quarter glass window is typically substantially triangular. Generally, each window 122, 124, 126, 128, 129 is curved, with different windows having different degrees of curvature. For example, the automobile 120 windows may exhibit a three-dimensional curvature such that one surface (e.g., the surface facing the external environment) is convex and the opposite (e.g., the interior) surface is concave. In the example of Figure 1, LC panels may be formed or retrofitted onto any of the windows 122, 124, 126, 128, 129, and the vehicle 120 may also include one or more sensors 150, which may be used to control the dimming of the vehicle's LC panels, as described below.

[0022] Vehicles move quickly between different lighting situations, for example, when moving from a well-lit general road to a dark tunnel. Since lighting situations can change, it is beneficial to make at least some windows. For example, making the windshield 122 a dimming function can improve driver comfort and improve driving safety. It can be used to prevent the driver from being dazzled or blinded when the intensity of the ambient light exceeds a threshold. For example, when the windshield 122 or a part of the windshield 122 near the driver receives direct sunlight. Conversely, it can also be used when the driver's eyes dark adapt from being in a dark environment for a certain period of time and then transition to a bright environment. That is, it can be controlled to reduce light transmittance when the surrounding environment of 122 is relatively bright, and to increase light transmittance when the surrounding environment is relatively dark.

[0023] Dimming can be controlled in other ways to enhance the safety and comfort of the driver or passengers of the vehicle. For example, prolonged exposure to bright light, especially sunlight, tends to increase the temperature within the cabin of the vehicle. Thus, light transmittance should be reduced based on the cabin temperature exceeding a threshold. Dimming can be provided based on the amount of ambient light, temperature, temperature in combination with the amount of ambient light, and other factors or combinations of factors. Thus, in some embodiments, one or more sensors can include a light sensor 150 and other types of sensors (e.g., temperature sensor or light intensity sensor) installed with the dimmable LC panel and a control unit configured to vary the light transmittance of the dimmable LC panel based thereon. Also, in some cases, the light sensor 150 can be integrated with or attached to the window, e.g., as part of the LC panel.

[0024] Another example of a sensor that the sensor 150 can use to control dimming is an occupant sensor configured to detect the presence of a person in a vehicle, for example based on the wearing of a seat belt, the pressure of the occupant's weight against the seat, or the capture of an image of the occupant by an onboard camera. The light transmittance of a window near or facing the occupant can be controlled to enhance the comfort of the occupant. Also, occupant sensing can be incorporated into the control unit as to whether and to what extent the transmittance should be adjusted. For example, if there is no occupant facing the window, the window glass does not need to adjust its transmittance. This is also the case for a car windshield, where an autonomous or remotely operated car does not need to adjust its transmittance when there is no occupant sitting in the driver's seat of the car.

[0025] Although dimmable LC panels may have potential use in other types of applications, incorporating dimmable LC panels into windows in safety-critical environments is challenging. For example, automotive window glass is commonly curved, as noted above. Thus, dimmable LC panels must also be curved or be able to conform to the curvature of the window to which the dimmable LC panel is applied. Additionally, automotive windows are often subject to strict regulations designed to ensure safety. For example, the United Nations Economic Commission for Europe's Regulation No. 43 sets out various performance requirements for different types of vehicle windows. Window types governed by Regulation No. 43 include "tempered glass" (single layer glass specially treated to increase mechanical strength and regulate fragmentation after shattering), "laminated glass" (two or more layers), and "tempered glass" (two or more layers). glass bonded by one or more interlayers of plastic material), "treated laminated glass" (where at least one of the several glass layers has been specially treated to increase its mechanical strength and adjust for fragmentation after shattering), and "ordinary laminated glass" (where none of the glass layers have been treated).

[0026] The performance requirements specified in Regulation 43 relate to crush resistance, mechanical strength (e.g., ball drop test), abrasion resistance, temperature resistance, radiation resistance, moisture resistance, light transmission, optical distortion, color, fire resistance, and other properties. When modifying automotive windows to incorporate dimmable LC panels, complying with regulations such as Regulation 43 can be difficult and there may also be limitations on how the dimmable LC panels can be manufactured.

[0027] FIG. 2A illustrates a windshield at 210. The windshield 210 can be designed to form a dimmable LC panel or attached to the windshield to provide a dimmable windshield. The windshield 210 is divided into multiple segments 202-1, 202-2, and 202-3. Each of these segments can be individually dimmed. For example, each segment 202-1 through 202-3 can be an LC cell that can be partially dimmed by individually applying a voltage between the electrodes. In the example of FIG. 2A, the segments can be individually or simultaneously controlled to selectively darken different areas of the windshield 202.

[0028] FIG. 2B shows a windshield 220 with segments 204-1 to 204-5 arranged horizontally. The dimmable segments can also be arranged up, down, left and right as shown in FIG. 2C. In FIG. 2C, a sunroof 230 is divided into four segments 206-1 to 206-4. For example, one segment can be arranged above each seat in a car.

[0029] The segmentation shown in Figures 2A through 2C can be achieved by forming each segment as a stand-alone LC panel. For example, each segment 206 can be formed as a separate LC panel. When placed together next to each other, the LC panels may be separated by small gaps that are nevertheless imperceptible to the naked eye or may correspond to different cells within a single LC panel. The thickness of the material (e.g., a rubber gasket or other type of sealant) that separates adjacent cells of such an LC panel may also define gaps that are not noticeable, or at least difficult to detect, at first glance from a normal viewing distance. For example, a gap in a windshield may be difficult to see when sitting in the driver's seat and looking through the windshield. Segmentation can also be applied to a single LC cell by patterning a conductive layer to form an LC panel with less visible gaps. As shown in the examples of Figures 2A through 2C and Figure 4 (discussed below), the LC panel can be segmented in any number of ways, including different division schemes or different shaped segments.

[0030] Figures 3A through 3C show examples of different control schemes for selectively dimming segments, according to some embodiments. In Figure 3A, the transmittance on the left (e.g., driver) side of the windshield 122 is reduced 140 to cause a corresponding reduction in the amount of sunlight that passes through the windshield 122 and reaches the eyes 300 of the vehicle occupants 120. Dimming can be done manually or automatically based on sensor data as described above. In Figure 3B, the entire windshield 122 is darkened. The darkening in Figure 3B can be achieved by jointly controlling all segments of the windshield 122. In Figure 3C, the left side of the windshield 122 is made darker than the right side 140 to reduce sunlight glare.

[0031] The dimmable LC panels described herein can be configured such that the light transmittance can be varied within a predetermined range so that even at the lowest levels of transmittance, at least some light can pass through the LC panel. For example, as shown in FIG. 3B, visibility is maintained even when the entire windshield 120 of a tree 130 outside a car is darkened. The ability to see through the windshield is essential to driving a car, highlighting an important difference between dimmable LC technologies designed for safety and comfort, and dimmable LC technologies designed for other types of applications, such as privacy. In the former, the light transmittance can be finely controlled by many gradations of transmittance levels, and it is usually desirable to maintain a high level of optical clarity. In contrast, dimmable LC panels designed to operate as privacy screens (such as to protect a conference room from the outside) typically have two modes of operation, where the liquid crystals are either transparent or opaque. Furthermore, privacy screens are not necessarily opaque in that opacity does not necessarily mean zero or near-zero light transmittance. Instead, the opaque mode is one where some light gets through, but the image seen through the privacy screen is blurred or fuzzy.

[0032] FIG. 4 shows an example of an LC panel. The LC panel 400, which includes dimmable segments 402, is asymmetric. The segments 402 are polygonal in shape. However, the segments can be formed in any shape based on the shape of the LC cells to which they correspond. An LC panel that includes dimmable segments can also include one or more non-dimmable segments. For example, the entire area outside the segment 402 can be made non-dimmable by excluding from this area one or more components that contribute to the dimming function of the segment 402. For example, the area outside the segment 402 may be devoid of electrodes or polarizers.

[0033] 5A and 5B show an example of a dimming system. 500 includes an LC panel 510 attached to a window 520, according to one embodiment. The LC panel 510 can correspond to any of the dimmable LC panels described herein. For example, the LC panel 510 can include a twisted nematic (TN) liquid crystal cell that includes polarizers on either side of the liquid crystal layer, as described below. As shown in FIG. 5A, the LC panel is substantially the same size and shape as the window 520, except that the LC panel includes a small cutout. The cutout provides space for mounting a control unit. The control unit 530 is placed in one corner 512 of the window 520. Thus, the dimming system 500 corresponds to the entire LC panel 510 combined with the window 520, the window 520, and the control unit 530. FIGS. 5A and 5B are merely examples. In other implementations, the control unit 530 may be located elsewhere, such as in the center of the window 520 or mounted on the surface of the LC panel 510 rather than directly on the window 520. In practice, the LC panel 510 and window 520 may not overlap completely. For example, the LC panel 510 may be smaller than the window 520 by more than 1 mm on one side. However, the LC panel 510 can be manufactured in a variety of size configurations to fit a variety of window sizes.

[0034] The LC panel 510 and control unit 530 may be provided in a kit that may further include a flexible cable for electrically coupling the LC panel 510 and control unit 530, adhesive for attaching the LC panel 510 and / or the control unit 530 to a window 520, a tool (such as a squeegee) for squeezing out any air bubbles between the LC panel 510 and the window 520, and / or other accessories to facilitate installation of the various components of the dimming system 500.

[0035] As shown in FIG. 5B, a side view of the dimming system is shown with the LC panel 510 having a surface 522 and a window 520 attached to it. The window 520 can include rigid glass and can be, for example, an architectural window or an automotive window (e.g., a sunroof). While not strictly necessary, it is generally a good idea to have the surface 522 facing the inside surface of the window 520, for example, facing the cabin of an automobile or the interior of a building or room. Such an arrangement protects the LC panel 510 against damage and contaminants from the outside environment. The LC panel 510 can be affixed to the surface 522 in a variety of ways. One option for attaching the LC panel 510 is to use a transparent adhesive that can be sprayed or otherwise applied to the surface 522 and / or to the surface of the LC panel 510. The adhesive can be water-based or solvent-based. For example, the adhesive could be a solution of soap in water. After wetting the LC Panel 510 or Surface 522 with a soap, the LC Panel 510 can be brought into contact with the Surface 522. The soap will cause the LC Panel 510 to cling to the Surface 522 as a thin film. When the solution dries, the soap will form a bond that holds the LC Panel 510 to the Surface 522. The bond may be strong enough to hold the LC Panel 510 without falling off, but strong enough to manually remove the LC Panel 520. The Control Unit 530 can be attached to the Window 520 in a similar manner, using the same or a different adhesive. Alternatively, the Control Unit 530 can be attached to the LC Panel 510 via a socket or connector on the Control Unit 530 that is held in place against the Window 520, but is not attached directly to the Window.

[0036] In some embodiments, the LC panel 510 may include a ready-to-apply adhesive on its window-facing surface. Such an adhesive may be applied during manufacture of the LC panel. 510 This may be, for example, a liquid adhesive that is sprayed onto the window-facing surface and allowed to harden. Alternatively, the ready-to-apply adhesive may be a film-based adhesive. The film-based adhesive may be carried on a transparent, flexible film, for example similar to single-sided or double-sided tape. Additionally, the film-based adhesive may cover a cutout. 512 allowing attachment of the control unit 530 without a separate adhesive. The ready-to-apply adhesive may be covered with a temporary protective film, so that the LC panel 510 can be attached to the window 520 in a peel-and-stick manner.

[0037] As shown in FIG. 5B, the LC panel 510 can be significantly thinner than the window 520. Additionally, the LC panel 510 can be formed using flexible substrates and can include additional flexible layers if desired. A conventional liquid crystal cell is formed of a liquid crystal material sandwiched between a pair of rigid substrates (e.g., glass). According to some embodiments, at least one of these rigid substrates can be replaced with a flexible substrate. Additionally, a flexible substrate can be used as the layer facing the window of the LC panel 510. The inclusion of a flexible substrate is advantageous because it allows the LC panel 510 to align with the surface 522 of the window, although 522 is shown as a flat surface, there may be slight differences in height along the surface 522. These differences may not be noticeable to the naked eye, but may result in gaps or air bubbles between the LC panel 510 and the surface 522. Gaps or air bubbles may be noticeable to a user and may also increase the likelihood of the LC panel being exposed. 510 peeling off the window520. A flexible substrate reduces the occurrence of such gaps and bubbles, and any remaining gaps and bubbles can be pushed out by hand or with a tool such as a squeegee or rolling pin. This can be done before the adhesive dries. Additionally, as mentioned above, some windows are curved. The inclusion of a flexible substrate helps the LC panel510 conform to the curvature of such windows. For example, one of the windows122, 124, 126, 128, and 129see Figure 1.

[0038] The control unit 530 is configured to vary the light transmittance of the LC panel 510 by outputting one or more control signals to the LC panel cutout 512, allowing the control unit 530 to be mounted separately from the LC panel. Thus, the control unit 530 may include an electrical interface to the LC panel 510. The electrical interface may include a physical connector for establishing a wired connection to the electrodes of the LC panel 510. For example, the LC panel 510 control device may include a connector that may be coupled to a connector of the control unit via a flexible cable or via direct coupling of the connector. The control unit 530 may be mounted to the window 520 of the LC panel 510 in a similar manner, e.g., using the same adhesive. A more detailed example of the control unit is described below with reference to FIG. 6A.

[0039] In another embodiment, the LC panel 510 may not include a cutout to accommodate the control unit 530. Instead, the control unit 530 may be outside the area of ​​the window 520 (e.g., mounted on a wall next to the window 520) or on the LC panel 510 itself. In general, there are no limitations on the location of the control unit 530. All that is needed is for the control unit 530 to be able to provide a control signal to vary the transmittance of the LC panel 510. For example, in an automobile, the control unit 530 may be co-located or integrated with the automobile's electronic control unit (ECU) and may be connected to multiple LC panels via cables running within the automobile's body. As another example, if the window 520 frame has a control unit 530, it may be located along an edge or corner of the frame. Alternatively, in some embodiments, the control unit 530 may be integrally molded with the LC panel 510 or may be pre-attached to the LC panel 520 (e.g., via a film-based adhesive that is also used to attach the LC panel) such that the LC panel 510 and the control unit 530 attached to the window 520 become a single unit.

[0040] The control unit 530 can be powered by an internal battery or an external power source. In some embodiments, such as the embodiment shown in FIG. 6A, the power source is a rechargeable battery. Various charging methods can be used to replenish the energy stored in the battery. For example, as shown in FIG. 6A, a solar cell can be used to recharge the battery using ambient light.

[0041] 5A and 5B show examples of dimming systems in which an LC panel is applied to a window as an "aftermarket" product. That is, the LC panel is manufactured separately from the window and can be installed, for example, by the window manufacturer or user. However, in some embodiments, the dimmable LC panel can be integrally formed with the window.

[0042] 6 is a simplified block diagram of a control unit 600 according to one embodiment. The control unit 600 may correspond to a control unit 610 including a photovoltaic cell 610, a battery 620, and a control module 630. For example, the control unit 600 may include a printed circuit board (PCB) on which the photovoltaic cell 610, the battery 620, and the control module 630 are mounted. The control unit 600 may further include a housing with an opening or window that allows light to enter the photovoltaic cell 610.

[0043] The solar cell 610 is configured to convert light into an electrical signal to charge the battery 620. If the control unit 600 is placed in an area not covered by the LC panel (e.g., cutout 512 in Figure 5A), the solar cell 610 can receive the light unaltered by passing through the LC panel. Alternatively, if the control unit 600 has a cutout 512 in Figure 5A, the light received by the solar cell 610 is the light that has passed through the LC panel, the solar cell. Setting the light transmittance of the LC panel 610 lower will result in less energy being generated. However, even at the lowest transmittance level, some light is expected to pass through the LC panel. Thus, the solar cell 610 may be able to charge the battery 620 even though the LC panel also receives light, but the charging efficiency may be reduced if there is no cutout.

[0044] The battery 620 may be any type of rechargeable battery, preferably with a small form factor to minimize the footprint of the control unit 600. For example, the battery 620 could be a lithium-ion coin cell. The battery 620 provides power to the control module 630 and enables the control module 630 to perform its operations.

[0045] The control module 630 can be implemented in hardware and / or software. For example, the control module 630 can be implemented using circuitry such as an integrated circuit (IC), a field programmable gate array (FPGA), a microcontroller, etc. The control module 630 is configured to set a transmittance level of the LC panel via one or more control signals 602. The control module 630 can output an electrical interface 612 of the control unit 600. For example, the electrical interface 612 can include a connector or socket adapted to receive a cable, the cable including a first wire leading to a first electrode of the LC panel and a second wire leading to a second electrode of the LC panel.

[0046] The control module 630 can set the transmittance level based on manual input or automatically. The manual input can be provided, for example, via a touch sensor or physical button on the control unit 600. In some embodiments, the control module 630 can set the transmittance level based on a wireless command from a user device. For example, a command sent from a mobile phone via a Bluetooth or Wi-Fi connection. Additionally, instead of manual input, the control module 630 may use sensor data to determine the transmittance level to set. As discussed above, such sensors may include light sensors, temperature sensors, or other types of sensors. Thus, as shown in FIG. 6A, the control unit 600 may include an additional electrical interface 614 through which sensor data is received from one or more external sensors from 604. In some implementations, the electrical interface 614 may be a wireless interface. Additionally, in some implementations, the electrical interface 612 and the electrical interface 614 are combined into a single interface, such as a communication bus.

[0047] The one or more sensors 604 providing sensor data can be located in various locations, such as the LC panel, a window, the control unit 600, or other locations in the environment (such as the cabin of an automobile). Additionally, the sensor 604 providing sensor data can be part of the control unit 600 itself. For example, the solar cell 610 can be used as a light sensor. The amount of energy a solar cell produces is proportional to the amount of light incident on the solar cell 610. The output of the solar cell 610 (e.g., an electrical signal 620 that recharges the battery) can be measured to determine the intensity of the ambient light. This determination can be performed by the control module 630, perhaps with the solar cell 610 receiving light unaltered, or light that has been modified by passing through the LC panel. Alternatively, a separate light sensor, such as a photodiode, can be provided. For example, a photodiode can be incorporated into the side of the LC panel facing the window, such that the photodiode receives light that has not been modified by passing through the LC panel.

[0048] FIG. 6B shows one example of how the components of the control unit function. 600 can be positioned with respect to a window 520. The window is shown in FIG. 6B as being covered by an LC panel 510, similar to FIG. 5A. In FIG. 6B, the control unit is in the lower right corner of the window 520, similar to the configuration shown in FIG. 5A. As shown in FIG. 6B, the control unit can include a solar panel 600 650 and circuitry 660. The solar panel 650 is positioned alongside circuitry 610 corresponding to one or more instances of solar cells 660. The circuitry 660 includes a control module 630 and, in some implementations, a battery 620 (e.g., the control module 630 and the battery 620 are implemented on the same PCB). Alternatively, the solar panel 650 and circuitry 660 can be stacked. For example, the circuitry 660 can be placed on top of the solar panel 650 so that the circuitry 660 is farther from the window 520 than the solar panel 650.

[0049] Although the control unit 600 is shown with a solar cell connected to a battery, the power source for the dimmable LC panel can have other forms. For example, the power source may be a disposable battery, a battery that is recharged by plugging into an external power source, or an external power source wired directly to the control unit 600. In embodiments featuring a solar cell, the LC panel is typically in a normally white configuration to reduce power consumption. A normally white configuration can also be used in situations where a lighted state must be the default or fail-safe operating mode, such as when the LC panel is part of a motorcycle helmet visor. A normally black configuration for the dimmable LC panel can be used in applications where a dark state is the normal operating mode, or where the normal operating mode is a bright state, but where the cost of maintaining an electric field across the LC conductors is not critical. Assembly is not critical.

[0050] 7A to 7C show examples of liquid crystal cells that can be used to form an LC panel according to some embodiments. In FIG. 7A, a liquid crystal cell 700 includes a first substrate 702, a first electrode 704, a sealant 706, a spacer 708, a second electrode 710, a second substrate 712, and liquid crystal 714.

[0051] The first substrate 702 and the second substrate 712 can be made of a transparent material to pass the incoming light 730 through the liquid crystals 714 which become the outgoing light 732. The first substrate 702 and the second substrate 712 can be made of glass or other rigid materials. Alternatively, at least one of the substrates 702, 712 can be formed of a flexible material such as polycarbonate (PC), polyethylene terephthalate (PET), cellulose triacetate (TAC), etc., allowing the liquid crystal cell 700 to conform to curved surfaces such as windshields, curved architectural glass panels, etc.

[0052] The sealant 706 defines the sidewalls of the LC cell 700, with the cell space between the first substrate 702 and the second substrate 712 being filled with liquid crystal 714. The sealant 706 acts as a gasket that isolates the liquid crystal 714, making it resistant to environmental influences and tightly confines the liquid crystal 714, sandwiched between the substrates 702 and 712. The sealant 706 may be formed of plastic, elastomeric materials, or other relatively soft materials, for example, using plastic injection molding. Additionally, in some embodiments, an additional seal (not shown in FIG. 7A) may be provided, such as a circumferential seal between the LC cell 700 and other layers (e.g., glass panel) 700 of the LC panel incorporating the LC cell. Such a circumferential seal, if provided, may seal the sandwich structure in a "floating" manner by acting as a cushion between the sandwich structure and other layers of the LC panel. An example of such an additional seal is shown in FIG. 14 (discussed below) as an edge seal.

[0053] The spacers 708 can provide structural support between the first substrate 702 and the second substrate 712 and maintain a uniform cell gap distance d between the substrates. For example, they can include silica gel balls, plastic balls, etc., and can be coated with a black coating to reduce light transmission. Although FIG. 7A shows only two spacers 708, LC panels according to embodiments described herein can include any number of spacers between a pair of substrates on opposite sides of the liquid crystal. The spacers 708 can firmly bond the substrates 702 and 712 together. For example, by the addition of an adhesive that bonds to the electrodes 704 and 710. In some embodiments, the bond between the spacers 708 and the electrodes 704 and 710 can occur as a result of a baking process. The temperature and pressure at which baking is performed are typically significantly lower than the temperature and pressure used for automotive window laminates that incorporate polyvinyl butyral (PVB) as a constituent layer. Alternatively, the spacers 708 can be fixed by friction or compression. Additionally, in some embodiments, the spacers 708 can be movable. For example, ball-shaped spacers are free to roll within the liquid crystal material. Rigidly bonded spacers can be advantageous in scenarios where the LC panel is mounted vertically, such as in the case of LC panels mounted in architectural windows. When the LC panel is mounted vertically, gravity tends to cause the liquid crystal to pool around the sidewall closest to the ground, which can lead to the bottom of the LC panel having a wider cell gap than the top of the LC panel. Rigidly bonded spacers are fixed in place, allowing them to maintain a uniform cell gap regardless of the orientation of the LC panel.

[0054] PVB is often used in automotive windows to improve impact resistance and reduce fragmentation. Accordingly, one aspect of the present disclosure relates to techniques for forming LC panels that include one or more PVB layers. This allows LC panels to be incorporated into automotive windows without the need to use another material in place of PVB. Automotive manufacturers are familiar with PVB and the process of using PVB to create windows, and switching to another material may not be possible without a new manufacturing process. Automotive manufacturers may not want to invest time and other resources in developing such a new manufacturing process, so a PVB-compatible LC panel would help them bring to market LC panels for use in automotive applications.

[0055] The first electrode 704 and second electrode 710 may correspond to a coating of conductive material on the substrates 702 and 712. For example, the first electrode 704 and second electrode 710 may comprise indium tin oxide (ITO). Conducting a voltage across the electrodes 704 and 710 that establishes an electric field 714 changes the orientation of the liquid crystal molecules. As described below, the orientation of the liquid crystal molecules in the liquid crystal material allows the light transmittance across the liquid crystal cell to be tuned, resulting in an intensity of the emitted light 732.

[0056] The first electrode 704 and the second electrode 710 can optionally include rubbing patterns to align the liquid crystal molecules 714 in a default orientation 700 that can set the initial / default state of the light transmission of the liquid crystal cell. Alternatively, in some embodiments, the rubbing pattern can be located on an additional layer located between the electrodes 704, 710 and the liquid crystal 714. Such an additional layer can be formed using, for example, polyamide (PI). Depending on the configuration of the liquid crystal, the rubbing pattern may be omitted. As described below in connection with Figures 20 and 21, a normally black LC panel incorporating guest-host (GH) liquid crystals can be realized without a rubbing pattern on the PI layer, while a normally white LC panel incorporating GH liquid crystals can include a rubbing pattern.

[0057] FIG. 7A is a simplified example intended to show components that are typical of the LC panels described herein with respect to other embodiments. As will be apparent from the discussion of such other embodiments (e.g., the embodiments shown in FIGS. 9A through 9C), the LC panel may include more or fewer components, or different arrangements of components. For example, in some embodiments, the LC panel includes an infrared (IR) filter to block IR light and / or an ultraviolet (UV) filter to block UV light. The UV or IR filter not only helps protect against glare, but also against overheating due to electromagnetic radiation of wavelengths related to IR or UV. Similarly, in some embodiments, the LC panel may include an anti-reflective coating as one or more layers.

[0058] A diagram 714 illustrates an example of a liquid crystal configuration that provides tunable light transmission. As shown in FIG. 7B, the liquid crystal 714 can be configured as a twisted nematic (TN) liquid crystal. The liquid crystal molecules can be aligned by the rubbing pattern described above to form a twisted helical structure in the absence of an applied electric field (e.g., at zero volts). The helical structure can rotate the polarization axis of the polarized light as it traverses the liquid crystal layer, and the angle of rotation is adjustable by an electric field applied across the liquid crystal layer, e.g., an electric field generated by the control unit 600. As the polarized light passes through the liquid crystal layer, the polarization axis of the polarized light is rotated by the helical structure by a certain angle (e.g., 90°) determined by the rubbing pattern. When an electric field is applied, the liquid crystal molecules can be aligned parallel to the electric field. When light traverses the aligned liquid crystal molecules, the polarization axis of the polarized light is maintained and does not rotate. The embodiments featuring TN liquid crystals are not limited to configurations that rotate the helical structure by a 90° twist angle. For example, in some implementations, the LC panel can be configured to rotate the helical structure in the range of 180° to 270° (characteristic of supertwisted nematic (STN) displays). In some implementations, the rotation may be less than 90° (sometimes used to form mixed-mode TN (MTN) displays). Additionally, TN liquid crystals can include nematic liquid crystals with chiral dopants that impart chirality to the nematic liquid crystal. Thus, TN liquid crystals can be any liquid crystal that has a twisted structure in the default or voltage-off state, i.e., before applying an electric field to "untwist" the liquid crystal molecules. Additionally, although FIG. 7B shows a single rotation direction, the LC panel can have liquid crystals with two or more rotation directions in some implementations, for example, to allow alignment of the liquid crystal molecules in the first segment differently from the liquid crystal molecules.

[0059] In certain embodiments, the conductive layer corresponding to the electrodes may be divided into different regions. For example, the layer corresponding to the electrodes 704 and the layer corresponding to the electrodes 710 may each be divided into different regions corresponding to segments of different shapes and / or sizes. The different regions may be formed by chemically or mechanically etching the conductive layer to form an etched pattern. The etched pattern, unlike the rubbing pattern described above (which sets a general initial orientation of the liquid crystals), may be used to form separate segments, or in the case of an LCD, separate pixels (e.g., red, green, or blue subpixels). Such segments may be individually dimmable by controlling the liquid crystal arrangement within the segments to display stripes, logos, text, or other graphics, with or without the aid of an electrically controllable illumination source such as a backlight. For example, an LC panel may be configured as a seven-segment display, in which case dimming different combinations of the seven segments will display different numbers. Thus, the conductive layer may include multiple electrodes that, in combination with corresponding electrodes on the opposing conductive layer, form different electrode pairs. Each pair of electrodes may establish a voltage across the pair of electrodes, corresponding to a different region that is individually controllable by application of a corresponding electrical signal.

[0060] As shown in Figure 7B, the liquid crystal 714, and the first substrate 702 and the second substrate 712 can be sandwiched between the first polarizer layer 726 and the second polarizer layer 728. Alternatively, the polarizer layers 726, 728 can be interposed between the substrates 702, 712 and the liquid crystal 714. In a normally white configuration, the first polarizer layer 226 can have a polarization axis A, while the second polarizer layer 228 can have a polarization axis B. The two polarization axes can form a 90 degree angle with respect to each other. The incident light 730 can be linearly polarized by the first polarizer layer 726. The linearly polarized light can be rotated by the liquid crystal 714. The angle changes depending on the angle that the TN structure forms as described above. The transmission is maximum when no electric field is applied. When no electric field is applied, the polarization axis of the polarized light that has passed through the liquid crystal 714 is rotated to align with the second polarization axis by the time it reaches the second polarizer layer. When an electric field is applied, the polarization axis of the light does not rotate and the polarization axis of the polarized light is perpendicular to the polarization axis B, resulting in minimum transmission. In this case, the polarization coincides with the absorption axis of the second polarizer layer. The magnitude of the electric field determines the angle of rotation of the polarization, which can change the fraction of the incident light. The output light 732 passing through the liquid crystal cell 714 can be seen from the liquid crystal cell 714. A typical range of light transmission achievable by TN liquid crystals can be between 0.5% and 36%.

[0061] TN liquid crystals offer various advantages over other liquid crystal technologies. For example, TN liquid crystals generally have a very fast response time, allowing light transmittance to be adjusted in a short time (e.g., less than 100 milliseconds). TN liquid crystals also have excellent light blocking properties. For example, the minimum light transmittance of TN liquid crystals can reach 0.1%. In addition, TN liquid crystals generally do not have suspended particles or polymers that scatter light, so TN liquid crystal cells can have less haze and improve visibility over a range of light transmittance levels.

[0062] Additionally, as discussed above, it may be advantageous to include a flexible substrate in the LC panel. For example, the substrate 702 and / or the substrate 712 may include a transparent, flexible material (e.g., PET or PC). Thus, in some embodiments, a dimmable LC panel includes a flexible substrate, a liquid crystal layer including TN liquid crystal, and a polarizer layer. Additionally, such an LC panel may include a rigid transparent layer (e.g., glass or PC) configured to act as a structural support for the LC panel and to act as a window. This rigid transparent layer may be formed integrally with the LC panel using a flexible substrate (e.g., substrate 702 or substrate 712), possibly with one or more intervening layers (e.g., connecting layers that hold the rigid transparent layer and the flexible substrate together) between the rigid transparent layer and the flexible substrate. Thus, the rigid transparent layer may be formed integrally with the LC panel. However, as discussed above with reference to FIG. 5A, it is also possible to manufacture the LC panel separately so that the LC panel can later be attached to the window as a thin film.

[0063] FIG. 7C shows another example of the configuration of the liquid crystal. 714 to provide tunable light transmittance. In FIG. 7C, the liquid crystal cell 700 shows an example that does not include the polarizing layers 726 and 728. In the example of FIG. 7C, the use of polarizers is not required. 714 can be configured as a GH liquid crystal with liquid crystal molecules, molecules 740 acting as hosts, and dye molecules 750 acting as guests. The liquid crystal molecules 740 and dye molecules 750 can vary in size and include liquid crystal molecules and dye molecules. The liquid crystal molecules 740 and dye molecules 750 can modulate light transmittance based on the guest-host effect. Specifically, they can be configured to absorb light with an electric field perpendicular to the molecular long axis direction of the dye molecules 750. The liquid crystal molecules in the GH liquid crystal can be nematic and, in some embodiments, can include a chiral dopant in addition to the dye molecules. The chiral dopant acts to twist the nematic liquid crystal molecules (which act as achiral hosts) into a helical structure in a manner similar to conventional TN liquid crystals.

[0064] In FIG. 7C, the rubbing patterns described above with reference to FIG. 7A can have anti-parallel rubbing directions to set the initial orientation of the liquid crystal molecules and dye particles depending on the operation mode of the liquid crystal cell. In a normally white mode, where the liquid crystal cell is in a transparent state when no electric field is applied, the rubbing direction can be configured such that the long axis of the dye particles is parallel to the electric field of the incident light. 730 (shown on the right side of FIG. 7C), which can be set to minimize the absorption of light by the dye particles. When an electric field is applied to the liquid crystal molecules, the orientation of the liquid crystal molecules 740, and the dye molecules 750, can be changed accordingly. As a result, a portion of the incident light 730 is absorbed by the dye molecules 750, and the light transmittance 700 of the liquid crystal cell, which is adjustable by the electric field applied to the liquid crystal. On the other hand, in a normally black mode, the rubbing direction can be configured such that the long axis of the dye molecules is perpendicular to the electric field of the incident light. 730 (shown on the left side of FIG. 7C), which maximizes the absorption of light. The absorption of light can be reduced by changing the orientation of the dye particles when an electric field is applied to the liquid crystal.

[0065] The exemplary configurations shown in Figures 7B and 7C are not mutually exclusive. In some implementations, the liquid crystal can be both a TN liquid crystal (with a twisted structure) and a GH liquid crystal (with dye molecules). For example, as described above, some embodiments can feature a GH liquid crystal that includes a chiral dopant that imparts a twist to the nematic liquid crystal molecules.

[0066] By omitting the polarizer, GH-based LC panels can increase the achievable overall light transmittance while providing reasonable light blocking properties. For example, using the guest-host effect, the light transmittance can range from 10% to 80%. GH liquid crystals also have fast response properties, allowing them to adjust the light transmittance in a very short time. In addition, similar to TN liquid crystals, GH liquid crystals may not have suspended particles (e.g., colloidal spheres) or polymeric medium to scatter light. Furthermore, the color of the dye molecules in GH liquid crystals can be selected to selectively transmit certain colors of light and block other colors.

[0067] In some embodiments, the LC cell may include vertically aligned (VA) liquid crystals. In VA liquid crystals, the liquid crystal molecules are homeotropic. That is, in the absence of an applied electric field, the liquid crystal molecules align perpendicular to the substrate surface. The homeotropic liquid crystal molecules can be realigned to be parallel to the substrate surface by applying an electric field. VA liquid crystals generally have negative dielectric anisotropy. In some embodiments, the VA liquid crystal in the LC cell is a dual frequency liquid crystal (DFLC) with positive dielectric anisotropy at low frequency and negative dielectric anisotropy at high frequency, called dual VA. The VA liquid crystal may also be a GH liquid crystal with pigment particles introduced.

[0068] Figures 8A-8D show voltage-transmittance (VT) curves for several examples of dimmable LC panels. In Figure 8A, the LC panel includes TN liquid crystals configured in a normally white mode and has the following characteristics: voltage at 90% transmittance (V90) = 1.82 V, voltage at 10% transmittance (V10) = 2.95 V, cell gap = 6 micrometers (μm), twist angle = 60°, wavelength = 550 nanometers (nm), and frequency = 64 hertz (Hz). The frequency is the frequency of the electrical signal used to drive the LC panel (e.g., the conditions for establishing a voltage between the electrodes). The wavelength is the wavelength of the incident light, in this example, green light. For a given voltage, the transmittance is generally stable with only minor variations across the wavelengths of interest (e.g., the visible spectrum). For example, the transmittance may vary from about 20% to about 30% from 400 to 700 nm. As shown in FIG. 8A, the V T curve is relatively flat between 0 and 1.5 V (maximum transmittance of about 30%) and then slopes downward to a minimum transmittance of about 0.1% at about 4 V.

[0069] In FIG. 8B, the LC panel includes GH liquid crystals configured in a normally white mode, and the measurement conditions were wavelength=550 nm, V90=1.8 V, V10=3.7 V, and frequency=64 Hz, with cell conditions of cell gap=9 μm and twist angle=360°. As shown in FIG. 8B, the VT curve is significantly steeper compared to FIG. 8A. Because the VT curve is steeper, the LC panel of FIG. 8B may require more precise control of the applied electric field, especially the voltage across the slope portion of the curve. However, it is possible to configure a control module (e.g., control module 630 of FIG. 6A). For example, control module 630 can look up a table stored in the memory of control unit 600. Here, the table maps different voltage points to corresponding transmittance levels. The lookup table for the configuration of FIG. 8B can include finer voltage gradations compared to the lookup table for the configuration of FIG. 8A. Alternatively, in some embodiments, the control module may be programmed or configured with a non-linear function that approximates the actual VT curve of the LC panel. Another performance difference between the configurations of Figure 8A and 8B is that the minimum transmittance level is higher in Figure 8B.

[0070] In Figure 8C, the LC panel includes GH liquid crystal (dual VA) configured in normally white mode and has the following characteristics: V90=2.24V, V10=5.5V, cell gap=9μm, twist angle=0°, wavelength=550nm, frequency=64Hz. Compared to the configurations of Figures 8A and 8B, the dual VA configuration of Figure 8C provides a higher maximum transmittance than Figures 8A and 8B, and approximately the same minimum transmittance as Figure 8B.

[0071] Figure 8D shows the VT curves of another GH-based configuration. In Figure 8D, the LC panel contains GH liquid crystals configured in a normally white mode and has the following characteristics: V90 = 1.72 V, V10 = 3.1 V, cell gap = 9 μm, twist angle = 360°, wavelength = 550 nm, and frequency = 64 Hz. The VT curve in Figure 8D is similar to that in Figure 8B, but is characterized by a slightly higher maximum transmittance level.

[0072] 9A-9C are diagrams illustrating examples of LC panels including a PVB layer, according to some embodiments. These LC panels can be formed as a laminated structure using appropriate levels of heat and pressure. In FIG. 9A, the LC panel 900 includes, from top to bottom, a first glass layer 902, a first PVB layer 904, a PET layer 906, a second PVB layer 908, a first TAC protective polarizer 910, a first optically clear adhesive (OCA) layer 912, a first PC layer 914, a first ITO layer 916, a sealant 918, a second ITO layer 920, a second PC layer 922, a second OCA layer 924, a second TAC protective polarizer 926, a third PVB layer 928, and a second glass layer 930.

[0073] An example of the thickness of some of the above components when the LC Panel 900 configuration for use as an automobile sunroof (total thickness approximately 6,100 µm) is as follows:

[0074] Glass layers 902 and 930: 2 millimeters (mm) each,

[0075] PVB layers 904, 908, and 928: 380 μm each,

[0076] PET layer 906: 105μm,

[0077] TAC Protective Polarizers 910 and 926: 170μm each,

[0078] OCA layers 912 and 924: 50 μm each;

[0079] PC layers 914 and 922: 105 μm each,

[0080] Sealant 918 (same as liquid crystal) 940): 9~15μm, and

[0081] ITO layers 916 and 920: 100-1000 Å each

[0082] Each of the TAC protected polarizers 910, 926 may include a polarizer protected by one or more TAC layers. Thus, although shown as a single layer, each of the TAC protected polarizers 910, 926 may correspond to a layered structure including a polarizer and a TAC layer on at least one surface of the polarizer. Polarizers are susceptible to damage from handling. Applying TAC to the polarizer helps prevent such damage and isolate the polarizer from environmental effects. Additionally, in some embodiments, the polarizer may include a UV blocking material. For example, a TAC protected polarizer may include the following layers in order: a first TAC layer, a polarizer, a second TAC layer, and a UV protective coating that filters out UV light. Alternatively, the UV blocking material may be incorporated into the material of the TAC layer.

[0083] The LC panel 900 further includes a spacer 938, a liquid crystal 940, and an electrical connector 950. The spacer 938 corresponds to the spacer 708 in FIG. 7A. The liquid crystal 940 corresponds to 714 in FIG. 7A (e.g., TN or GH liquid crystal). In FIG. 9A, the electrical connector 950 is configured to transmit a signal to a pair of electrodes corresponding to the ITO layers 916 and 920. An electric field can be established by a signal transmitted by the electrical connector 950, which can be connected to a control unit (e.g., a control unit) via a cable, such as 600 in FIG. 6A. Additionally, the LC panel 900 can include a circumferential seal or edge seal (not shown) that cushions against the glass layers 902 and 930, as described above with reference to FIG. 7A. The circumferential seal 952 can be positioned to wrap around the periphery of the LC panel.

[0084] The PET layer 906 corresponds to a flexible substrate and may include an IR protection layer. For example, the PET layer 906 may be formed with an IR blocking additive or coated with a layer of IR blocking material. IR blocking may be useful in automotive applications, especially sunroofs, as blocking IR radiation can prevent overheating. In some embodiments, the PET layer 906 may be replaced with another flexible material (such as PC or TAC) that also provides an IR protection layer. For applications where IR protection is not required, the IR protection may be omitted to avoid loss of light transmission.

[0085] The OCA layers 912 and 924 can be formed with a clear adhesive. In some embodiments, they are formed using liquid OCA (LOCA) that is sprayed directly onto the PC layers 914 and 922, or in preparation for lamination of the TAC protective polarizers 910, 926.

[0086] The PC layer 914 or the PC layer 922 may be formed of flexible polycarbonate and may correspond to the substrate. Thus, the PC layers 914, 922 and the PET layer 906 may be formed as a flexible film. The ITO layers 916 and 920 PC layers correspond to the conductive layers on the substrate of the PC layers 914 and 922. The ITO layers 916 and 920 of the PC layers 914 and 922 define the top and bottom walls of the LC cell. The LC cell is laminated or bonded to the glass layers 902 and 930. The glass layers 902, 930, although in reality they appear flat on the glass layers, may not be perfectly equidistant at all points along the glass 930 surface (this is because the glass layers 902 and glass layers 930 are designed to have the same curvature). To compensate for such defects, the PVB layers 904, 908 and 928 can be heated until they melt, thereby covering the defects (gap filling). Upon cooling, the PVB layers 904, 908 and 928 solidify and hold adjacent layers together, which helps the constituent layers of the LC panel avoid uneven distribution of pressure during the lamination process of 900. In some embodiments, the PVB layers 904, 908 and 928 can be replaced with a different adhesive or plastic, such as ethyl vinyl acetate (EVA), PET, acrylic, epoxy, silicone-based adhesives, or other optically clear adhesives (e.g., the same material as the OCA layer). Additionally, in some embodiments, one or more TAC layers 910 and 926, such as the TAC portion of a TAC-protected polarizer, can be formed as a flexible substrate. Thus, a flexible LC panel can include one or more flexible layers, where the one or more flexible layers are the same material or different materials.

[0087] FIG. 9B illustrates an LC panel 980 according to one embodiment. Similar elements are labeled with the same reference numbers as in FIG. 9A. In the embodiment of FIG. 9B, the PVB layer 904 and the PET layer 906 are replaced with an IR coating layer 960. The IR coating layer 960 acts as an IR filter. The IR coating layer 960 can be formed by sputtering an IR blocking material onto a glass layer.

[0088] Figure 9C is a structure according to one embodiment using an LC panel 990. Similar elements are numbered the same as in Figure 9A. The LC panel 990 does not include the PET layer 906 and the IR coating 960 of Figure 9B. Thus, the LC panel 990 may not provide infrared protection.

[0089] An example of the thickness of some of the above components when an LC panel is constructed for use as a 990mm automobile side window (total thickness approximately 5,600 µm) is as follows:

[0090] Glass layers 902 and 930: 2 mm each,

[0091] PVB layer 908:380μm,

[0092] TAC Protective Polarizers 910 and 926: 170μm each,

[0093] OCA layers 912 and 924: 50 μm each;

[0094] PC layers 914 and 922: 105 μm each,

[0095] Sealant 918 (same as LCD) 940): 9~15 μm

[0096] ITO layers 916 and 920: 4 μm each.

[0097] As mentioned previously, flexible LC panels are advantageous, especially when used in conjunction with curved rigid substrates (e.g., curved automobile windows). However, flexible LC panels are sensitive to non-uniform pressure distribution and stress. Therefore, techniques that distribute pressure or stress evenly during lamination can help avoid damage to flexible LC panels. As mentioned previously, melting PVB or other adhesives to fill gaps between surfaces is one way to ensure uniform pressure distribution.

[0098] Another challenge for flexible LC panels is the temperature dependence of the flexible substrate (e.g. PC / PET / TAC substrate), the liquid crystal and the rigid substrate (e.g. glass). All three may have different thermal expansion coefficients. For example, the expansion coefficient of the flexible substrate may be higher than that of the glass panels (e.g. two glass panels forming the outer layers of the LC panel where the LC cell with the flexible substrate is laminated between the glass). Furthermore, the liquid crystal may have a higher expansion coefficient than the flexible substrate. Thus, when exposed to temperature changes such as warming the LC panel in an oven as part of the lamination process, the liquid crystal has a higher expansion coefficient and therefore undergoes greater expansion compared to the flexible substrate, which may lead to damage.

[0099] Temperature changes can also occur outside of manufacturing. For example, certification testing for car windows involves temperature shock testing, in which the temperature changes from, for example, 70°C or higher to -20°C or lower within a very short time frame. This rapid temperature change can generate high stresses in any number of components within or associated with the LC panel. To address the issue of differential thermal expansion between the different layers, a lamination setup is provided in some embodiments. The lamination setup includes one or more adhesives that form a strong bond while at the same time being flexible enough to tolerate thermal expansion without breaking over many thermal expansion cycles (e.g., hundreds of thousands of cycles). Additionally, as described below in connection with FIG. 19, some embodiments may feature expansion joints that provide room for expansion and contraction after the LC panel is installed, for example, in a vehicle body. The expansion joint feature can be used in combination with flexible adhesives to prevent breakage due to differences in thermal expansion coefficients.

[0100] Furthermore, as mentioned above, PVB-based processes applied to safety glass in the automotive industry traditionally require high temperatures (140°C) and high pressures (12-15 bar). Such temperatures and pressures usually damage the LC panel (such as the spacer and polarizing layer). To prevent damage to the LC panel, the maximum temperature and maximum pressure to which the LC panel is subjected during production can be limited. The maximum temperature to which the LC panel is exposed can be limited to about 100 to 160°C (preferably between 110 and 120°C). The maximum pressure can be set to about 1-4 bar. Also, if pressure is applied mechanically, it can be set in the range of 10-15 bar.

[0101] In certain embodiments, techniques are provided that allow for successful lamination of LC panels containing PVB, such as the LC panels shown in Figures 9A to 9C, including environmental side solutions implemented by controlling the environment in which the lamination / bonding is performed, and LC side solutions implemented by proper design of the LC panel and its components.

[0102] In some embodiments, the spacers (e.g., spacer 938) are formed of a high temperature resistant material. Additionally or alternatively, the spacers can be formed in a shape that can withstand high pressures. For example, instead of forming spacer 938 as a sphere, spacer 938 can be formed as a rectangular block, a cylinder, or other geometric shape that is less likely to deform. As an example, in FIG. 9A, spacer 938 can be replaced with a plastic cylinder (such as a circular or elliptical cylinder) that contacts ITO layers 916 and 920. In addition to the spacers, other components of the LC panel, such as polarizers, can be formed of high temperature resistant materials to enable the LC panel to withstand the lamination process.

[0103] In some embodiments, the spacer or layers in contact with the spacer are coated to make the substrate more resistant to damage caused by the application of high pressure, such as penetration of the substrate by the spacer. For example, the spacer 938 or the ITO layers 916 and 920, PC layers 914 and 922 can be coated with a transparent substance that has a higher hardness. Alternatively, the material of the spacer or layers in contact with the spacer can undergo a tempering process to strengthen the material.

[0104] FIG. 10 illustrates an example of a system 1000 for laminating LC panels, including a PVB according to some embodiments. In FIG. 10, heat and pressure must be applied during lamination of the LC panel in the system 1000. 1020 is in a vacuum bag or chamber. LC Panel 1000 Shown in FIG. 10 is a simplified representation of an LC panel, shown as including a first substrate 1002, a first PVB layer 1004 between the first substrate 1002 and an LC cell 1006, a second substrate 1010, and a second PVB layer 1008 between the LC cell 1006 and the second substrate 1010. However, the LC panel can represent any LC panel including a PVB. The liquid crystal cell 1006 includes any liquid crystal described herein, such as a TN liquid crystal, a GH liquid crystal, or a VA liquid crystal, with or without a chiral dopant.

[0105] The objective of the lamination process is to form a stacked multi-layer structure in which the layers of the stack are held tightly together with minimal air bubbles or gaps between the layers. FIG. 10 shows air bubbles 1012 between the substrates 1002 and PVB layer 1004 and between the substrates 1010 and PVB layer 1008. As mentioned above, such air bubbles are formed due to variations in the height of the surfaces of the substrates. The application of pressure will push the air bubbles out, and such pressure is traditionally applied mechanically. For example, by clamping the layers together using a relatively high pressure. Thus, in some embodiments, mechanical pressure is applied to push the air out of the multi-layer structure (e.g., from the center of the multi-layer structure towards the outer edges). However, as shown in FIG. 10, a vacuum chamber or bag allows for the removal of air bubbles using a lower pressure. Thus, the mechanical pressure can be replaced by atmospheric pressure generated using a vacuum environment.

[0106] PVB layer 1004 and PVB layer 1008 are adhesive layers that bond substrate 1002 and 1010, which represent LC cell 1006. They can be configured to allow air to escape when pressure is applied to substrate 1010. For example, the surface of PVB layer 1008 in contact with substrate 1002 can include channels that allow air movement (e.g., microgrooves 1012 having a width narrower than the diameter of an air bubble), and the channels are removed by melting the PVB layer. Similarly, substrate 1002 and PVB layer 1004 can include channels that are filled with molten material. Figure 10 is merely an example intended to illustrate a lamination process for forming an LC panel using a stack of layers. 912 and 924 in Figure 9A. In some implementations, PVB layers 1004 and 1008 can be replaced with another material that melts and bonds the two layers together, such as the same OCA material as the OCA layer.

[0107] The vacuum environment provided by the vacuum bag / chamber 1020 removes the air bubbles 1012. The vacuum bag / chamber 1020 also allows for low-pressure lamination. For example, the LC panel 1000 can be placed in a vacuum chamber, the pressure set to about 1-2 bar (1 bar equals 100,000 Pascals) and the temperature set to about 110°C (the vacuum chamber also functions as a convection oven or autoclave). The PVB layers 1004, 1008 are melted. Depending on how much melting of the PVB layers is desired (e.g., completely melted or melted to a certain depth), a temperature of about 110°C can be maintained for a certain period of time. Upon cooling, the PVB layers 1004, 1008 resolidify, after which the entire LC panel 1000 can be removed from the vacuum chamber. The pressure and temperature inside the vacuum bag / chamber 1020 can be monitored using a pressure and temperature sensor 1030. A pressure gauge 1032 is installed, and the temperature and pressure are connected to a controller 1040 and can be set.

[0108] Compared to vacuum chambers, vacuum bags are less expensive to set up and operate, but generally require higher temperatures and pressures compared to vacuum chambers. For example, to laminate an LC panel, a vacuum bag 1000 can be used to evacuate the air from the vacuum bag through a tube 1022, which can reach a pressure of about 3-4 bar. At a pressure of 3-4 bar, the LC panel 1000 can be heated (e.g., by placing the vacuum bag in an oven) to about 120°C to melt the PVB layers 1004, 1008. The vacuum bag itself can be formed of a heat-resistant material so that the vacuum bag can be reused. Thus, the pressure can be set to 1-4 bar, and typically, when using a vacuum bag, a higher pressure is set than when using a vacuum chamber.

[0109] While the lamination techniques discussed above in relation to Figure 10 can be applied to reduce temperatures and pressures, there may be advantages to avoiding the PVB entirely. Figure 13 shows the unfolding of an LC panel 1300 during lamination with a PVB panel 1310 and a glass panel 1320. As shown in Figure 13, the LC panel 1300 expands when heated (represented by solid arrows) and contracts when cooled (represented by dashed arrows), resulting in wrinkles 1350. Also, since the LC panel becomes bonded through the PVB panel during the cooling process, the contraction of the LC panel 1300 is constrained, generating stresses that can cause damage such as severing of bonds around the edge seal (not shown). Also, because the liquid crystal is not uniformly distributed throughout the LC panel, this can result in uneven pressure distribution, which can result in visual artifacts and patterns. Such artifacts are especially noticeable in the minimally transparent (dark) state.

[0110] Thus, a process such as the technique of FIG. 10 may be applied to form a laminated LC panel including glass and PVB layers. However, because of the complexity of implementing such a process, it may be advantageous to use a material other than PVB to bond the LC panel to the substrate, such as replacing the PVB layer with OCA, as discussed above. Instead of the PVB layer, an adhesive including OCA, silicone, resin, etc. may be used to bond the LC panel. The adhesive may be film-based or liquid. For example, adhesives exist that have a very low viscosity (e.g., lower than water), are suitable for filling bubble-sized gaps, and can cure relatively quickly, within a few minutes at ambient temperatures, e.g., between 20 and 30 degrees Celsius. Additionally, as described below, some embodiments may feature a combination of a film-based adhesive and a liquid adhesive. In some cases, the cure of the PVB substitute can be done without the application of heat or pressure, and in embodiments without a UV blocking layer, can be rapidly cured using UV light. Alternative bonding materials such as OCA, silicone, or resin may have advantages beyond the manufacturing process. For example, PVB alternatives maintain their functionality over a wider temperature range (e.g., at higher temperatures than PVB can sustain) and have a higher transmittance than PVB, minimizing their impact on the overall transmittance of the LC panel.

[0111] The optical performance of an LC panel can be improved by selecting an adhesive with at least 99% transmittance and a refractive index that at least somewhat matches that of the substrates to which the LC cell is bonded, thus minimizing transmission losses. The desired refractive index of the adhesive can be calculated based on the Fresnel model. For p-polarized light (electric field parallel to the plane of incidence), the Fresnel equation for the transmission coefficient τ across a boundary between two media k and k-1, where k-1 is the incident medium and k is the transmission medium, is given by:

[0112] Similarly, the transmission coefficient τ for ns polarization (electric field perpendicular to the plane of incidence) is given by:

[0113] As an example, applying the Fresnel equation for s-polarized light to each of the six boundaries of the example LC panel described in the table below gives an overall transmittance of 79% (τn=0.79) after accounting for transmission losses through the PC substrate and GH liquid crystals, when the refractive index of the ITO layer is matched (substantially equal) to that of the PC substrate. In this example, the refractive index of the PC substrate is 1.586, and the refractive index of the ITO layer is 1.54 for the matched case and 1.9 for the mismatched case. When the refractive index of the ITO is mismatched, the overall transmittance is 78%. Depending on the degree of matching, the overall transmittance can range from 80% to 76%.

[0114] [Table 1]

[0115] In automotive applications, a minimum of 70% transmittance is required by law for windshields and front side windows in most countries, so to avoid the overall transmittance dropping below 70% after the addition of one or more adhesive layers, the adhesive materials as well as the materials of at least some layers in the LC panel (e.g., ITO layer and substrate) are chosen to have matching or close refractive index matches.

[0116] In some embodiments, such as the examples in the table above, glass can be replaced with PC. Other materials that are more flexible or lighter than glass, such as PET, can also be used. Returning to Figures 9A-9C, the PC layer (914, 922) can form the substrate of the LC cell. A traditional LC cell is a sandwich structure containing liquid crystal between two glass substrates. Replacing the glass with PC improves the impact resistance of the LC panel and provides some flexibility compared to rigid glass without sacrificing transparency or optical clarity. In general, any glass layer in an LC panel can be replaced with a PC layer. For example, PC can replace a glass layer. The PC layer is not limited to LC panels that are integrally formed with a window, but can also be included in LC panels designed to be attached to a window.

[0117] When used as an outer layer (e.g., in place of a glass layer 902 or glass layer 930), PC is softer than glass, so the surface of the PC layer can be coated with a scratch-resistant material to protect it from abrasion. Due to its impact resistance and ability to be formed into many different shapes, PC can be incorporated into one or more layers to form LC panels suitable for use in automotive windows, such as side windows. PC is also lighter than glass, allowing the weight of the LC panels to be reduced, thus reducing the weight of the vehicle. For example, switching from glass to PC windows could reduce the weight of a vehicle by approximately 50 pounds, resulting in fuel / battery savings.1

[0118] FIG. 11 illustrates the steps where light is incident on the LC cell. In FIG. 7A through FIG. 11, light 1130 is applied to both sides of the LC cell. In some implementations, only one side of the LC cell is illuminated, which may be sufficient for the light to pass through the other side of the LC cell. When UV light 1130 is incident on the LC cell, it cures the adhesive 1102 and contacts the substrate-facing surface of the sealant 706. Once bonded 1102, it cures and bonds 706 to the substrate 702, 712 and the sealant.

[0119] If the substrate 702, 712 has been replaced with a material that blocks UV light 1130, or if some of the UV light 1102 does not reach the adhesive, it may be insufficient to fully cure the adhesive 1130. Similarly, if one or more UV blocking layers are introduced between the substrate and the UV adhesive, the UV adhesive cannot be cured using UV light.

[0120] UV-curing based adhesives are often used in the automotive industry. One advantage of UV adhesives is that parts to be bonded with UV adhesives can be repositioned at any time before exposure to UV light. If a part is misaligned or not positioned correctly, it can be easily moved before curing. However, as explained above, UV adhesives are not compatible with UV blocking materials. In addition, some types of LC panels rely on the use of one or more UV blocking materials. For example, in TN LC cells, such as those shown in Figure 7B, polarizers are used to control the direction of light entering and exiting the liquid crystals. As discussed above in connection with Figure 9A, the polarizers can be protected using TAC and may also include a UV protective coating. Thus, UV curing may not be possible with TN LC cells or other LC cells that contain polarizers.

[0121] Due to the UV blocking properties of the UV protective coating typically found in TAC protected polarizers, such polarizers are not traditionally used in combination with LC components that are bonded using UV adhesives. For example, the three layers of electrodes 704, 710 in Figure 11 can be formed using ITO or other materials that are easy to bond with UV adhesives. Thus, traditional LC panels do not feature TAC protected polarizers combined with ITO-based electrodes. In contrast, Figures 12A and 12B show an example featuring a TAC protected polarizer combined with an ITO-based electrode.

[0122] 12A shows an LC panel 1200 according to one embodiment. From top to bottom, the LC panel 1200 includes a first glass layer 1202, a first OCA layer 1204, a first TAC protective polarizer 1206, a second OCA layer 1208, a first PC layer 1210, a first ITO layer 1212, a sealant 1214, a second ITO layer 1216, a second PC layer 1218, a third OCA layer 1220, a second TAC protective polarizer 1222, a fourth OCA layer 1224, and a glass layer 1226.

[0123] In Figure 12A, TAC protected polarizer 1206 is bonded to a glass layer 1202 with OCA layer 1204, which is further bonded to a PC layer with OCA layer 1208. Similarly, TAC protected polarizer 1222 is bonded to a glass layer with OCA layer 1224, which is further bonded to a PC layer with OCA layer 1220. Each of the OCA layers shown in Figure 12A can be liquid OCA. Additionally, each of the TAC protected polarizers 1206 and 1222 can include a UV protective coating.

[0124] The ITO layers 1212, 1216 represent electrodes. However, the electrodes of the LC panels according to the embodiments described herein can be made of another conductive material, for example graphene.

[0125] FIG. 12B illustrates an embodiment of an LC panel 1290. LC panel 1290 includes similar elements to LC panel 1200, except that PC layers 1210 and 1218 are omitted. In the absence of these PC layers, the TAC protected polarizers 1206 and 1222 are attached directly to the ITO layers 1212 and 1216. Thus, in some embodiments, the ITO layer can be formed directly on the TAC protected polarizer or any other layer that includes TAC. For example, the ITO layer 1212 can be sputtered directly onto the TAC 1206 portion of the TAC protected polarizer.

[0126] To allow the LC panel to include UV blocking components such as TAC protective polarizers, the present disclosure is directed to alternatives to UV adhesives. In particular, embodiments relate to the use of non-UV curing adhesives such as epoxies and heat activated adhesives. For example, adhesive 1102 in FIG. 11 can be replaced with a two-part epoxy that has a relatively long working time. The working time of an epoxy resin can be, for example, a few minutes, as this is generally sufficient to prepare the LC panel for lamination and allows a short time frame to reposition parts if necessary. Alternatively, a heat activated adhesive can be used that cures at or below the temperature of the lamination process.

[0127] FIG. 14 illustrates an LC panel 1400 according to some embodiments. As discussed above, for example with respect to the OCA layer of FIGS. 12A and 12B, a liquid adhesive can be incorporated into the LC panel to bond the LC cell to a glass panel or other substrate, perhaps as an alternative to bonding via PVB. In the example of FIG. 14, the LC panel 1400 includes an LC cell 1410 bonded to an outer substrate 1420. It is also constructed of a combination of an inner substrate 1430, a liquid adhesive 1440, and a film-based adhesive 1450.

[0128] As used herein in connection with FIG. 14 and other figures below, an outer substrate refers to the substrate closest to the exterior environment when the LC panel is installed as a window. Similarly, an inner substrate refers to the substrate closest to the interior environment. In an automotive setting, such a substrate is typically glass. For simplicity, FIG. 14 and the various figures that follow show the LC cell as a single layer. However, as noted above, an LC cell can include other layers besides the liquid crystal layer. Thus, the LC cell 1410 can include a stack of layers that form a panel, including, for example, polarizers, intermediate substrates, moisture barrier layers, or IR or UV blocking layers.

[0129] The liquid adhesive 1440 is applied to the surface of the LC cell 1410 facing the outer substrate 1420, and after curing, it solidifies to bond the LC cell. The liquid adhesive 1440 can be extended on the outer substrate 1420 to contact the inner substrate 1430 as shown in Figure 14. The liquid adhesive 1440 helps to fill the gap between the LC cell and the glass or other (such as PC) substrate. Although 1420 in Figure 14 shows the outer substrate, and the inner substrate 1430 are flat, in reality, the height may vary slightly across the surface of the substrate. The distance 1405 between the outer substrate 1420 and the inner substrate 1430 is not uniform. The height difference is especially prevalent when the substrate is curved, such as an automobile window. A melt adhesive such as PVB can be used to bond the LC cell to the substrate, but the melt adhesive, when in a solid state, tends to exert pressure against the LC cell after it is melted. Height variations can cause uneven pressure on the molten adhesive, especially if the molten adhesive is not completely melted before cooling, which can distort the LC cell and result in visual artifacts or other undesirable optical properties. For example, in a dark state, the LC cell may have some areas that are darker than others. Additionally, the liquid adhesive remains flexible after curing, allowing for thermal expansion and contraction, thus avoiding pressure spots.

[0130] The film-based adhesive 1450 is a solid adhesive that bonds the LC cell 1410. It can be applied to fix the LC cell 1410 onto the inner substrate 1430. Like the liquid adhesive 1440, the film-based adhesive 1450 is flexible enough to allow for thermal expansion and contraction prior to application (e.g., by injection) of the liquid adhesive 1440 to the inner substrate 1430. The film-based adhesive 1450 can be applied on a transparent, flexible film. For example, the film-based adhesive 1450 can be coated on both sides of a plastic film such that one side of the plastic film can be attached to the LC cell 1410. The other side of the plastic film can be applied to the inner substrate 1430, a plastic film that forms part of the LC panel, or the film-based adhesive 1450 can be provided on a temporary film that can be peeled off leaving no film between the LC cell and the film-based adhesive 1450.

[0131] The LC panel 1400 includes one or more edge seals 1460. In some embodiments, a single edge seal extends around the perimeter of the LC panel to protect against the ingress of moisture and contaminants. For example, the edge seal 1460 can be a gasket ring formed using a synthetic rubber, such as butyl rubber. However, the edge seal need not cover the entire perimeter. For example, the LC panel can include four edge seal strips, one on each side of the LC panel, so that the perimeter is collectively covered by the edge seals. Additionally, as shown in FIG. 15 (discussed below), the edge seal may be adhered to the substrate of the LC panel, for example, using an adhesive. Other materials may be used for the edge sealing. In some embodiments, the edge seal 1460 can be formed of a material similar to the sealant 706 of FIGS. 7A to 7C. For example, a plastic, an elastomeric material, or another relatively soft material, such as PET.

[0132] 15 shows the shear stresses 1505 that occur in the LC panel 1500, the LC cells 1510 bonded to the external substrate 1520, the internal substrate 1530, the liquid adhesive 1540, and the film-based adhesive 1550 when the LC panel 1500 is placed on a surface (e.g., the ground), during storage or transportation before installation of the LC panel 1500. The configuration of the panel is shown in FIG. 14 for the LC panel 1400.

[0133] The LC panel 1500 further includes an edge seal 1560, which extends around the perimeter of the LC panel to prevent the ingress of moisture and contaminants. The edge seal 1560 is similar to the edge seal 1460; therefore, it may be formed of a plastic, elastomeric material, or other relatively soft material such as PET or butyl rubber. 1508 are located at the ends of the LC panel's outer substrate 1520, inner substrate 1530, and LC cell 1510 that extend beyond the edge seal 1560.

[0134] Liquid Adhesive 1540 and Film-Based Adhesive 1550 can have a wide operating temperature range, e.g., maintaining a stable but flexible bond between -40 degrees Celsius and +115 degrees Celsius, and maintaining a relatively short cure time (e.g., 1 to 5 minutes for both adhesives). In some implementations, at least one of Adhesives 1540 and 1550 is acrylic-based. Acrylic is a suitable adhesive for LC panels because it is color stable and does not yellow over time. Acrylic-based adhesives are sensitive to moisture, so portions of LC panels bonded using acrylic-based adhesives may be protected from moisture by a sealant at the edges, such as Edge Seal 1560.

[0135] The edge seal 1560 is bonded to the substrates 1520 and 1530 via an adhesive 1562, which may be a resin-based adhesive or other adhesive with relatively high adhesive strength compared to the liquid adhesive 1540, and the film-based adhesive 1550 may have a wide operating temperature range similar to the liquid adhesive 1540, for example, between -40 degrees Celsius and +115 degrees Celsius. Additionally, the adhesive 1562 may be moisture resistant and stable for many years of operation (e.g., at least 15 years). For automotive applications, the adhesive 1562 may be a non-silicone-based adhesive. To prevent damage during handling or installation of the LC panel 1500, the material of the edge seal 1560 may be selected to have a coefficient of friction equal to or less than that of the substrates 1520 and 1530 (e.g., the same coefficient of friction as glass). A high coefficient of friction may result in a concentration of forces on the edge seal 1560. Without uniform distribution of force across the edge seal 1560 , damage could result to the substrates 1520 and 1530 and the LC cell 1510 .

[0136] As shown in Figure 15, the LC panel rests on one corner 1505 of the edge. From the edge 1508 it is not fully supported by the surface of the LC panel 1500. In this position, the weight of the substrate not in contact with the surface (in this example, the inner substrate 1530) is pulling in the direction of gravity. Pushing in the opposite direction to the effect of this gravity force combined with the surface force creates shear stresses that can lead to damage or delamination of the LC cell 1510. For example, the shear stresses can overcome the strength of the adhesive 1562 around the edge seal 1560, which can cause the liquid adhesive 1540 to leak past the edge seal 1560 and create voids that look like cracks as they are located along the perimeter of the LC panel. Glass substrates in particular are heavy. To reduce the weight of the substrates and therefore the amount of shear stress, at least one of the substrates can be made thinner, as shown in Figure 16.

[0137] FIG. 16 shows an LC panel 1600, according to some embodiments, mounted on a mounting body 1612, which is generally a rigid structure that supports the LC panel. For example, it may be the roof of an automobile. The LC panel 1600 includes similar components to those shown in FIG. 15, such as an LC cell 1610; an outer substrate 1620, an inner substrate 1630, a liquid adhesive 1640, a film-based adhesive 1650, and an edge seal 1660. In the example of FIG. 16, the inner substrate 1630 is significantly thinner than the outer substrate 1620 to reduce the shear stresses discussed above in connection with FIG. 15. The outer substrate 1620 can also be thin. However, for safety reasons, there is generally a limit to how thin the outer substrate can be. For automotive applications, the thickness of the outer substrate 1620 ranges from about 2 mm to 3.5 mm, while the thickness of the inner substrate 1630 ranges from about 0.7 mm to 2 mm, for a total thickness of the entire LC panel of about 5 mm or less. As shown in Figure 16, the outer substrate 1620 is designed to extend beyond the edge seal 1660 and is hooked onto the mounting body 1612. Here, the thickness of the outer substrate 1620 facilitates a robust and secure mounting of the LC panel 1600. The weight of the LC panel 1600 is carried by the outer substrate 1620, protecting the more fragile inner substrate 1630 from damage. Additionally, since both substrates 1620 and 1630 are supported against the mounting body 1612, shear stresses do not typically occur once the LC panel is installed.

[0138] FIG. 17 shows an LC panel 1700 mounted to a mounting body 1712. According to some embodiments, the LC panel 1700 is the same as the LC panel 1600, except for the addition of padding 1705. In combination with the exterior substrate 1620, the padding 1705 provides a flat surface for flush mounting the LC panel 1700 to the mounting body 1712. In the example of FIG. 17, the weight of the LC panel 1700 is supported by both the outer substrate 1620 and the padding 1705, which can be formed of the same or similar material as the edge seal 1660, and can have a coefficient of friction equal to or less than the coefficient of friction of the substrates 1620 and 1630, as discussed above in connection with the example of FIG. 15.

[0139] FIG. 18 shows an LC panel 1800 mounted on a mounting body 1812. According to some embodiments, the LC panel 1800 is similar to the LC panel 1500. The outer substrate 1820, inner substrate 1830, and edge seal 1860, which correspond to the outer substrate of FIG. 15, each extend to the edge of the LC panel. Thus, the weight of the LC panel 1800 is carried by the outer substrate 1820. Like the LC panel 1600, the inner substrate 1830 is thinner than the outer substrate 1820. Even though the inner substrate 1830 is thinner than the outer substrate, it may be robust enough to support the LC panel 1800, depending on the weight of the LC panel 1800. In the configuration shown in FIG. 18, the thinning of the inner substrate may be applicable to other mounting configurations, including configurations where the LC panel is placed with its edge facing the ground, such as a side window of an automobile.

[0140] FIG. 19 illustrates an LC panel 1900, according to some embodiments, configured to accommodate thermal expansion and contraction. It is similar to the LC panel 1600. It includes an LC cell 1910, and is comprised of an outer substrate 1920, an inner substrate 1930, and an edge seal 1960. However, the LC cell 1910 is separated from the edge seal 1960 by a first gap 1902. Additionally, the edge seal 1960 and the inner substrate 1930 are also separated from the mounting body 1912. A second gap 1904 is attached to the LC cell 1910. The gaps 1902 and 1904 are approximately 1 mm wide in some implementations. Both gaps 1902 and 1904 are filled with a flexible sealant that acts as an expansion joint to accommodate the thermal expansion and contraction of the LC cell 1910. The LC cell 1910 and the substrates may have different thermal expansion coefficients. For example, the outer layer of the LC cell may be plastic, while the substrate may be plastic. The gaps 1920 and 1930 may be glass so that the LC cell expands more than the substrate in response to heat. Thus, a change in temperature can cause the LC cell 1910 to expand or contract relative to the substrate.

[0141] Similar to the example of FIG. 14, the LC panel 1900 includes a liquid adhesive 1940 and a film-based adhesive 1950. In some embodiments, the flexible sealant in at least one of the gaps 1902 and 1904 is a non-adhesive sealant. For example, the gap sealant 1902 can be a liquid adhesive similar to the liquid adhesive 1940; or a film-based adhesive 1950 similar to the film-based adhesive, and the gap sealant 1904 can be a non-adhesive sealant that prevents the edge seal 1960 from sticking to the mounting body 1912. The liquid adhesive 1940, the film-based adhesive 1950, and the gap sealants 1902 and 1904 can compensate for differences in thermal expansion coefficients by remaining flexible over a wide temperature range (e.g., -40 to 115 degrees Celsius) to allow the LC panel to expand and contract. Without such flexible components, stress buildup can cause the LC cell to tear or delaminate. The sealant-filled gap 1902 acts as a buffer between the LC cell 1910 and the edge seal 1960. Similarly, the sealant-filled gap 1904 acts as a buffer between the edge seal 1960. The thermal expansion coefficients of the LC cell 1910 and the mounting body 1912, the substrates 1920 and 1930 are compensated primarily by the combination of the liquid adhesive 1940. With the LC cell 1910 firmly attached to the substrates 1920 and 1930, the film-based adhesive 1950, and the gap sealant 1902 can contribute to allowing lateral movement of the LC cell 1910 for each of these three components. Additionally, the gap sealant 1904 provides additional cushioning in the event that the edge seal 1960 moves relative to the mounting body 1912, e.g., by pushing or pulling the gap sealant 1902 by the LC cell 1910. In some embodiments, the gap 1404 can expand to cover the mounting surface of the external substrate 1920. This cushions the outer substrate 1920 and the inner substrate 1930 in addition to the edge seal 1960.

[0158] As discussed above in connection with FIG. 7A, some embodiments may feature UV or IR blocking layers for glare reduction and overheating prevention. For example, a UV / IR blocking layer may be disposed between the LC cell and the outer substrate to reduce heating of the interior environment. Similarly, a UV / IR blocking layer may be disposed between the LC cell and the inner substrate to reduce the amount of heat transferred from the interior environment to the exterior environment. Such blocking layers are particularly beneficial in architectural environments where long-term climate control and seasonal temperature changes are desirable. Blocking UV and IR radiation may also prevent damage to the liquid crystal (e.g., fading of dopant or dye particles in GH-based liquid crystals). The example of FIG. 9A through 9C features UV blocking in the TAC portion of the polarizer. However, the UV or IR blocking layer may be incorporated in other layers or as a separate layer. For example, an LC panel may feature a first IR blocking layer applied (e.g., sputtered) to the inner surface of the outer substrate and a second IR blocking layer applied to the inner surface of the inner substrate. If it is difficult to apply a blocking layer to the inner or outer substrate (e.g., if the substrate is 3-dimensional curved glass) or if the LC panel is formed separately from the outer substrate (as in the case of an add-on window), the blocking layer may be applied to the surface of the LC panel. For example, a blocking layer may be applied to the surface of a flexible film. 2016 In some embodiments, UV or IR blocking may be provided by an adhesive with blocking properties or by including blocking particles, e.g., UV blocking particles in a flexible film.

[0142] FIG. 20 shows an LC panel 2000 adapted for attachment to glass 2020. The LC panel 2000 may correspond to an LC panel 510. In this case, the glass 2020 corresponds to a window 520. The LC panel 2000 may include, from top to bottom: a first flexible film 2004, a first SiO2 layer 2006, a first ITO layer 2008, an LC layer 2010, a second ITO layer 2012, a second SiO2 layer 2014, and a second flexible film 2016. The LC panel 2000 is attached to the glass 2020 2018 via an adhesive.

[0143] The adhesive 2018 can be applied to the flexible film 2016 during manufacture or application (to the flexible film 2016) or installation to the glass 2020. The adhesive 2018 can be a liquid adhesive or film based. The adhesive 2018 can be a UV or IR blocking adhesive. Alternatively, a UV or IR blocking layer can be applied between the LC layer 2010 and the glass 2020. For example, the adhesive 2018 can be a film based adhesive that includes a first adhesive layer attached to the flexible film 2016. If a UV and IR blocking film is applied, the UV and IR blocking film will be sandwiched between the first adhesive layer and the glass 2020. In this case, a second adhesive layer can also be applied between the UV and IR blocking film and the glass 2020. a) Another example is a flexible film 2016 that contains UV blocking ingredients.

[0144] The flexible films 2004 and 2016 can be formed of PET or a similar flexible, transparent material. The flexible films 2004 and 2016 enable the LC panel 2000 to bend and conform to the mounting surface of the glass 2020. The adhesive 2018 is flexible and may correspond to, for example, a liquid adhesive 1540, or a film-based adhesive 1550. The flexible film 2004 can include a self-healing material (e.g., a self-healing polymer or elastomer) that can be incorporated into the material of the flexible film 2004 or as an additional coating to protect the LC panel 2000 against impact and abrasion in some embodiments.

[0145] The SiO2 layers 2006 and 2014 act as a moisture barrier to prevent moisture from penetrating into the interior of the LC panel 2000. Together with the edge seal (not shown), the SiO2 layers 2006 and 2014 provide protection against moisture from all directions.

[0146] In a normally black configuration, the LC layer 2010 may include GH liquid crystals, which include a mixture of nematic liquid crystal molecules and dye molecules, as described above in connection with FIG. 7C. GH liquid crystals may further include a chiral dopant that twists the liquid crystal molecules into a helical structure, similar to TN liquid crystals. However, the LC layer 2010 may be formed of other types of liquid crystal materials. Although not strictly necessary, the chiral dopant creates a helical structure that allows the LC layer 2010 to absorb light from all polarization angles, since natural light is 360° polarized. In some embodiments, the percentage of chiral dopant in the GH liquid crystal is at least 0.5% by weight. When no electric field is applied across the ITO layers 2008 and 2012, the long axes of the liquid crystals and dye particles can align perpendicular to the incident light. When an electric field is applied across the ITO layers, the liquid crystals and dye particles align parallel to the incident light, allowing light to be transmitted through the LC panel 2000. This GH-based normally black configuration can be achieved without a rubbing pattern.

[0147] Figure 21 shows the LC panel 2100 adapted for attachment to glass 2020. As mentioned above, it may correspond to the window 520. The LC panel 2100 is similar to the LC panel 2000. It is separated from the LC layer 2010 except for the ITO layers 2008 and 2012 by polyamide (PI) layers 2120 and 2122, respectively. Like the LC panel 2000, the liquid crystals in the LC layer 2010 may be GH liquid crystals containing nematic liquid crystal molecules, dye particles, and chiral dopants. To generate a normally white configuration, a rubbing pattern 2105 can be formed on each of the PI layers facing the LC layer 2010. The rubbing pattern 2105 is formed by rubbing the PI along a predetermined direction, inducing a vertical alignment of the liquid crystals and dye particles at the top and bottom of the helical structure to set the initial alignment of the liquid crystals and therefore the dye particles in the LC layer 2010. This causes the liquid crystals and dye particles to align along the rubbing direction. When no electric field is applied, the liquid crystals and dye particles located near the rubbed surface align substantially vertically, allowing the passage of light. The amount of twist in the helical structure is determined by the chiral dopant. Application of an electric field across the ITO layer untwists the helical structure in a manner similar to that described for the TN liquid crystal in Figure 7B. In the untwisted state, the liquid crystals and dye particles 2010 of the LC layer are oriented substantially horizontally to block light.

[0148] Depending on the orientation of the rubbing pattern, the LC panel 2100 can be set to normally black instead of normally white. The LC panel 2100 of FIG. 21 may have less haze in the dark state than the LC panel 2000 of FIG. 20 due to the alignment provided by the rubbing pattern 2105. The optical performance of an LC panel, such as the LC panels of FIGS. 20 and 21, can be configured by setting the values ​​of one or more parameters of Beer's Law. For example, the transmittance can be varied by setting the cell gap distance (labeled in FIG. 7A). Thus, a first cell gap of the LC panel 2100 can provide a transmittance of 13% to 63% in the dark and light states, respectively, and a second cell gap of the LC panel 2100 can provide a transmittance of 19% to 68%. In general, the transmittance of any embodiment incorporating GH liquid crystals is less than 25% (e.g., 1% to 20%) in the dark state and greater than 20% (e.g., 20% to 70%) in the light state. Typical cell gaps for GH-based embodiments such as those of Figures 20 and 21 range from 2.5 to 30 micrometers, and in some cases from 4.5 micrometers to 20 micrometers.

[0149] The features described with respect to the above embodiments and in connection with the accompanying drawings (FIGS. 1-21) can be combined in various ways. Below are specific examples that incorporate aspects of the above-described embodiments. Additional combinations of features and further modifications will be apparent to those of skill in the art in light of this disclosure.

[0150] Example 1 In a particular embodiment, a liquid crystal (LC) film panel includes a liquid crystal layer, a first substrate and a second substrate disposed on either side of the liquid crystal layer, and a first outer layer. The liquid crystal layer includes TN liquid crystal. For example, in FIG. 9A, liquid crystal 940 can include liquid crystal having a twist angle in a default (voltage off) state. The first substrate has a first conductive layer, e.g., ITO layer 916. Similarly, the second substrate has a second conductive layer, e.g., ITO layer 920. Each of the first substrate and the second substrate includes a flexible film. For example, as shown in FIG. 9A, layers 914 and 922 correspond to PC layers. The first outer layer includes a rigid transparent material. For example, the first outer layer can correspond to glass layer 902.

[0151] Optionally, the TN liquid crystal has a twist angle less than or greater than 90 degrees. As mentioned above, the TN liquid crystal is not limited to a twist angle of 90 degrees and can include, for example, STN, MTN, and liquid crystals with chiral dopants.

[0152] Optionally, the first outer layer has a three-dimensional curvature. For example, the glass layer 902 can be curved to match the shape of a vehicle window. Thus, the first outer layer can be a vehicle window, such as a car, airplane, or boat window.

[0153] Optionally, the first exterior layer may be an architectural window, such as a glass door or a window in a building.

[0154] Optionally, the LC film panel can include a second outer layer comprising a rigid transparent material, the second outer layer having a three-dimensional curvature (e.g., a curvature that matches the curvature of the first outer layer), the first substrate being in contact with the second substrate, and the liquid crystal layer being between the first outer layer and the second outer layer. For example, the second outer layer can correspond to glass layer 930.

[0155] The flexible film of the LC film panel can be made of various flexible materials. For example, the flexible film of the first substrate or the second substrate can include PC, PET, or TAC.

[0156] Optionally, the LC film panel can include an infrared blocking layer between the first substrate and the first outer layer, the infrared blocking layer including polyethylene terephthalate (PET) or another material that functions as an infrared filter. For example, the infrared blocking layer can correspond to PET layer 906.

[0157] If desired, the first substrate and the first outer layer can be bonded with an adhesive. For example, PVB can be used as an adhesive to bond the glass layer to the surface of the LC cell, with or without an intervening layer, as shown in the lamination process shown in Figures 9A-9C and 10.

[0158] Optionally, the first substrate and first outer layer are laminated with one or more intervening layers between them, for example, in FIG. 9A, a glass layer 902 is separated by a PC layer 914, a PET layer 906, and a polarizer 910.

[0159] Optionally, the LC film panel may be configured to generate one or more control signals that establish a voltage between the first conductive layer and the second conductive layer through a control unit (e.g., control unit 530 or 600), the magnitude of the voltage determining the orientation of the TN liquid crystals in the liquid crystal layer. Additionally, the first outer layer may be a window 520 (e.g., a window). The control unit may be attached to the window as shown in Figures 5A and 5B. Additionally, as shown in Figures 5A and 5B, the LC film panel may include a cutout (e.g., cutout 512) that is shaped to accommodate the control unit such that the control unit may be attached to the window without the LC film panel being interposed. Additionally, the LC film panel may include an optional battery (e.g., battery 620) configured to power an optional solar cell (e.g., solar cell 610). The solar cell is configured to recharge the battery using light from a light source that illuminates the LC film panel, the battery and solar cell being housed within the control unit.

[0160] If desired, the first and second conductive layers can be etched to form a pattern on the surface of the first and second conductive layers. As described above in connection with FIG. 7B, the pattern can correspond to a plurality of regions that can be individually dimmed to display graphics or text. For example, each region of the plurality of regions can include a first electrode corresponding to the first conductive layer and a second electrode corresponding to the second conductive layer, and the region can be individually dimmed by establishing a voltage between the first electrode and the second electrode.

[0161] Example 2 In certain embodiments, a window (e.g., window 520 in FIG. 5A) includes attaching an LC film panel to a window, where the window is a window of an automobile or building (architecture), and the LC film panel includes a liquid crystal layer, a first substrate, and a second substrate disposed on an opposite side. The liquid crystal layer includes TN liquid crystal. The first substrate has a first conductive layer. Similarly, the second substrate has a second conductive layer. Each of the first substrate and the second substrate includes a flexible film. Attaching the LC film panel to the window can include positioning the LC film panel relative to the window such that a surface of the first substrate substantially matches a surface of the window. For example, in FIG. 5B, the window 520 has a three-dimensional curvature (as in the case of a sunroof of an automobile), and positions the LC panel 510. In FIG. 9A, for the LC panel 510 to match the curvature of the window 520, it can cause the LC panel 914, which includes a flexible film such as a PC layer, toward the window 520. Additionally, flexible films can allow LC film panels to conform to surfaces that are substantially, but not perfectly, flat. For example, an architectural window may appear flat to the naked eye, but may have slight height variations of 1 mm or more across its surface.

[0162] As an alternative to TN liquid crystals, the LC film panel attached to the window can include GH liquid crystals, for example, structured according to the examples of Figure 20 or Figure 21. Thus, the LC film panel can be replaced with a GH liquid crystal layer that includes a mixture of nematic liquid crystals acting as a host, dye molecules acting as a guest, and optionally a chiral dopant. The LC film panel can further include a first substrate having a first conductive layer and a second substrate having a second conductive layer (similar to the first and second substrates in the TN embodiment described earlier in this example). For example, both conductive layers can be formed as ITO coatings. The first and second substrates are disposed on opposite sides of the GH liquid crystal layer. The first and second substrates 2004 and 2016 each include a flexible film (e.g., a flexible film). Although Figures 20 and 21 do not show spacers, spacers 708 can be incorporated into the layers of Figure 7A to define a cell gap between, for example, 2.5 μm and 30 μm. The amount of chiral dopant in the GH liquid crystal layer can be at least 0.5% by weight of the GH liquid crystal layer. Similar to the TN-based example described above, the GH liquid crystal can be configured to transition the LC film panel between a dark state (a state of minimum light transmission) and a bright state (a state of maximum light transmission) in response to a change in voltage between the first conductive layer and the second conductive layer. In the dark state, the LC film panel can have an overall light transmission (total transmission across all layers of the LC film panel) of between 1% and 20%. In the brightened state, the overall light transmission of the LC film panel is between 20% and 70%. The LC film panel can be attached in a similar manner to that described above by positioning the LC film panel against a window such that the first substrate conforms to the surface of the window.

[0163] Optionally, the flexible film of the first substrate or the flexible film of the second substrate may include PC, PET, or TAC.

[0164] Optionally, attaching the LC film panel to the window can further include applying an adhesive to at least one of the surfaces of the first substrate or the surface of the window before placing the LC film panel against the window. The adhesive can be a liquid adhesive, e.g., a clear water-based or solvent-based adhesive that forms a bond between the LC film panel and the window upon evaporation. Alternatively, the adhesive can be film-based. In some implementations, the film-based adhesive can be covered with a protective film on at least the side facing the window, and the protective film can be peeled off to expose the film-based adhesive. The film-based adhesive can be pre-applied to the LC film panel (e.g., on the first substrate during manufacturing) or applied to the LC film panel when the LC film panel is attached to the window.

[0165] Optionally, attaching the LC film panel to the window can further include applying pressure to the LC film panel after placing the LC film panel against the window, such that the pressure removes any air bubbles trapped between the first substrate and the window. The pressure can be applied manually, possibly with a tool such as a squeegee, to direct the air bubbles toward the edges of the LC film panel.

[0166] Optionally, the method may include attaching a control unit to the window, the control unit configured to apply a voltage to the first conductive layer and the second conductive layer by generating one or more control signals. The method may further include connecting the control unit to an electrical interface of the LC film panel using a cable configured to carry the one or more control signals, for example, as described above in connection with FIG. 6A. The control unit may be attached anywhere on the window. For example, the method may include placing the control unit at a corner of the window or in the center of the window.

[0167] Typically, the LC film panel is approximately the same size as a window, in which case the control unit can be placed along an edge of the LC film panel. For example, the control unit can be attached by placing the control unit within a cutout 512 (e.g., a cutout) provided in the LC film panel. The cutout is configured to allow ambient light (e.g., sunlight) to reach the photovoltaic cell of the control unit without passing through the various layers (e.g., the first substrate and the second substrate) of the LC cell. As described above in connection with FIG. 6A, the photovoltaic cell can be used to charge the battery of the control unit.

[0168] Example 3 In certain aspects, an LC film panel suitable for installation in an architectural window comprises a GH liquid crystal layer including a nematic liquid crystal acting as a host, a dye molecule acting as a guest, and optionally a chiral dopant. Such an LC film panel can be structured, for example, according to the examples of FIG. 20 or FIG. 21, and can incorporate aspects of additional embodiments described herein. The LC film panel includes a first substrate having a first conductive layer and a second substrate having a second conductive layer. The first substrate and the second substrate are disposed on opposite sides of the GH liquid crystal layer. The first substrate and the second substrate each include a flexible film. The LC film panel further includes a plurality of spacers between the first substrate and the second substrate. The spacers can be configured to define and maintain a cell gap between 2.5 μm and 30 μm. The chiral dopant is at least 0.5% by weight of the GH liquid crystal layer. The GH liquid crystal layer is configured to transition the LC film panel between a dark state and a light state in response to application of a voltage between the first conductive layer and the second conductive layer. In the dark state, the LC film panel has an overall light transmittance of 1%-20%. In the brightened state, the LC film panel has an overall light transmittance of 20%-70%. The LC film panel is attached to the glass surface of the architectural window, e.g., with the first substrate being the outermost layer of the LC film panel closest to the architectural window. The LC film panel can be switched directly or gradually (e.g., in step increments) between the darkened and brightened states under the direction of a control unit, such as the control unit of FIG. 6A.

[0169] Optionally, the LC film panel is normally black, and the GH liquid crystal layer is configured to establish a dark state in the absence of a voltage between the first conductive layer and the second conductive layer.

[0170] Optionally, the LC film panel is normally white, and the GH liquid crystal layer is configured to establish a lighted state with no voltage applied to the first conductive layer and the second conductive layer.

[0171] If desired, the LC film panel can be formed separately from the architectural window and attached via an adhesive placed between the first substrate and the architectural window. Thus, the LC film panel can be installed as an aftermarket product. The adhesive can be liquid adhesive or film-based.

[0172] When the outermost layer facing the architectural window is the first substrate, the flexible film of the first substrate can be configured to conform to the height variations along the glass surface of the architectural window. The LC film panel as a whole can also conform to the glass surface of the architectural window.

[0173] Optionally, the flexible film of the first substrate or the flexible film of the second substrate may include PC, PET, or TAC.

[0174] If necessary, the LC film panel may further include a first PI coating between the first conductive layer and the GH liquid crystal layer, and similarly, a second PI coating between the second conductive layer and the GH liquid crystal layer. The first PI coating and the second PI coating may correspond to the PI layers 2120 and 2122, respectively. Thus, they may each include a rubbing pattern that determines the initial orientation of the nematic liquid crystals (and therefore also the initial orientation of the dye molecules).

[0175] Optionally, the LC film panel may further include a control unit configured to vary the voltage across the first conductive layer and the second conductive layer in response to the level of ambient light. An example of such a control unit is described in connection with FIG. 6A, where the control unit includes a battery and a solar cell configured to charge the battery using the ambient light.

[0176] If desired, the LC film panel may further include a cutout 512 (e.g., a cutout) shaped to accommodate a control unit. The cutout can be located along an edge or corner of the LC film panel (as shown in FIG. 5A), allowing the control unit to be mounted directly to the architectural window.

[0177] Optionally, the LC film panel may further include one or more of the following additional layers: (2) a blocking layer configured to reduce the amount of infrared light transmitted to the GH liquid crystal layer, or (3) a moisture-proof layer configured to prevent moisture from reaching the GH liquid crystal layer. For example, the LC film panel may include a combined UV and IR blocking film, separate UV and IR blocking films, UV and / or IR blocking particles on the first substrate or second substrate, one or more SiO2 coatings (e.g., SiO2 layers 2006 and 2014), or any combination thereof.

[0178] If desired, the first and second conductive layers may be divided into multiple regions that are individually controllable to adjust the light transmittance of each region. The regions may be formed, for example, by etching a pattern into the first conductive layer and a corresponding pattern into the second conductive layer to define multiple pairs of electrodes. Such regions may allow selective dimming of individual regions, as described above in connection with Figures 3A-3C and 4.

[0179] Example 4 In certain aspects, an LC film panel adapted for mounting on an automobile window (e.g., sunroof) includes a GH liquid crystal layer including a nematic liquid crystal acting as a host, a dye molecule acting as a guest, and optionally a chiral dopant. Such an LC film panel can be structured, for example, according to the examples of FIG. 20 or FIG. 21, and can incorporate aspects of additional embodiments described herein. The LC film panel includes a first substrate having a first conductive layer and a second substrate having a second conductive layer. The first substrate and the second substrate are disposed on opposite sides of the GH liquid crystal layer. The first substrate and the second substrate each include a flexible film. The LC film panel further includes a plurality of spacers between the first substrate and the second substrate. The spacers can be configured to define and maintain a cell gap between 2.5 μm and 30 μm. The chiral dopant is at least 0.5% by weight of the GH liquid crystal layer. The GH liquid crystal layer is configured to transition the LC film panel between a dark state and a bright state in response to application of a voltage between the first conductive layer and the second conductive layer. In the dark state, the overall light transmittance of the LC film panel is between 1% and 20%. In the brightened state, the overall light transmittance of the LC film panel is between 20% and 70%. The LC film panel is attached to a three-dimensionally curved surface of an automobile window, e.g., the first substrate is the outermost layer of the LC film panel closest to the automobile window. The LC film panel can be switched directly or gradually (e.g., in stepwise increments) between the darkened and brightened states under the direction of a control unit, such as the control unit of FIG. 6A.

[0180] Optionally, the LC film panel is normally black, and the GH liquid crystal layer is configured to establish a dark state in the absence of a voltage between the first conductive layer and the second conductive layer.

[0181] Optionally, the LC film panel is normally white, and the GH liquid crystal layer is configured to establish a lighted state with no voltage applied to the first conductive layer and the second conductive layer.

[0182] Optionally, the LC film panel is formed separately from the vehicle window and attached via an adhesive disposed between the first substrate and the vehicle window. Thus, the LC film panel can be installed as an aftermarket product. The adhesive can be liquid adhesive or film-based.

[0183] When the outermost layer facing the car window is the first substrate, the flexible film of the first substrate can be configured to conform to the curvature of the three-dimensional curved surface. The LC film panel as a whole can also conform to the curvature of the three-dimensional curved surface.

[0184] Optionally, the flexible film of the first substrate or the flexible film of the second substrate may include PC, PET, or TAC.

[0185] If necessary, the LC film panel may further include a first PI coating between the first conductive layer and the GH liquid crystal layer, and similarly, a second PI coating between the second conductive layer and the GH liquid crystal layer. The first PI coating and the second PI coating may correspond to the PI layers 2120 and 2122, respectively. Thus, they may each include a rubbing pattern that determines the initial orientation of the nematic liquid crystals (and therefore also the initial orientation of the dye molecules).

[0186] Optionally, the LC film panel may further include a control unit configured to vary the voltage across the first conductive layer and the second conductive layer in response to the level of ambient light. An example of such a control unit is described in connection with FIG. 6A, where the control unit includes a battery and a solar cell configured to charge the battery using the ambient light.

[0187] If desired, the LC film panel may further include a cutout shaped to accommodate a control unit, such as cutout 512. The cutout can be located along an edge or corner of the LC film panel (as shown in FIG. 5A), allowing the control unit to be mounted directly to the automobile window.

[0188] Optionally, the LC film panel may further include one or more of the following additional layers: (2) a blocking layer configured to reduce the amount of infrared light transmitted to the GH liquid crystal layer, or (3) a moisture barrier layer configured to prevent moisture from reaching the GH liquid crystal layer. For example, the LC film panel can include a combined UV and IR blocking film, separate UV and IR blocking films, UV and / or IR blocking particles on the first substrate or second substrate, one or more SiO2 coatings (e.g., SiO2 layers 2006 and 2014), or any combination thereof.

[0189] If desired, the first and second conductive layers may be divided into multiple regions that are individually controllable to adjust the light transmittance of each region. The regions may be formed, for example, by etching a pattern into the first conductive layer and a corresponding pattern into the second conductive layer to define multiple pairs of electrodes. Such regions may allow selective dimming of individual regions, as described above in connection with Figures 3A-3C and 4.

[0190] Example 5 In certain embodiments, a method of laminating an LC panel includes stacking a first rigid outer layer, a PVB layer, a first substrate having a first conductive layer, a liquid crystal layer, a second conductive layer, and a second rigid outer layer. For example, the stack may correspond to LC panel 1000. The method further includes, after forming the stack, heating the PVB layer until the PVB layer at least partially melts, and then cooling the PVB layer until the PVB layer re-solidifies.

[0191] Optionally, the liquid crystal layer comprises twisted nematic liquid crystal, guest-host liquid crystal, or vertically aligned liquid crystal.

[0192] Optionally, at least one of the first substrate, the second substrate, or the outer layer comprises polycarbonate.

[0193] Optionally, the stack further includes a polarizer including a polarizer, a TAC coating, and a UV blocking coating. As previously described, LC panel 1000 FIG. 10 is a simplified diagram of an LC panel. Thus, the stack to be laminated may correspond to one of the previously described LC panels, such as LC panel 900 of FIG. 9A. Additionally, the method may include forming a liquid crystal cell to include liquid crystal in the liquid crystal layer, the forming of the liquid crystal cell including applying a sealant between the first substrate and the second substrate using a non-UV curable adhesive, where the first substrate, the second substrate, and the sealant each define a boundary of the liquid crystal cell. For example, as previously described, adhesive 1102 in FIG. 11 is a UV adhesive, but may be replaced with a two-part epoxy or other non-UV curable adhesive.

[0194] In addition to applying a sealant between the first substrate and the second substrate, the method can further include disposing a spacer between the first substrate and the second substrate, the spacer being rectangular or cylindrical and defining a cell gap between the first substrate and the second substrate.

[0195] When the sealant is applied between the first and second substrates, the first conductive layer or the second conductive layer can include ITO. For example, the first conductive layer and the second conductive layer can correspond to ITO layers 916 and 920, respectively. Thus, in some cases, the sealant can be applied to the surface of the ITO layer.

[0196] Optionally, the heating of the PVB layers can be done by applying pressure to the stack, either mechanically or through a vacuum environment, at a temperature between 100 and 160 °C. For example, the temperature can be set to 110-120 °C to heat the PVB layers. The pressure applied to the stack can be generated using a vacuum chamber or a vacuum bag. In this case, this method requires the pressure to be set to 1-4 bar. Alternatively, the pressure can be 10-15 bar of mechanically applied pressure.

[0197] Example 6 In certain embodiments, the LC panel includes a stack including, in order: a first rigid outer layer, a PVB layer, a first substrate including a first flexible film and having a first conductive layer, a liquid crystal layer including a nematic liquid crystal and a chiral dopant, a second substrate including a second flexible film and having a second conductive layer, and a second rigid outer layer. The stack is a laminated stack formed as a result of heating the PVB layer until it is at least partially melted, followed by cooling the PVB layer until it resolidifies (FIG. 10).

[0198] Optionally, the liquid crystal layer comprises a guest-host liquid crystal.

[0199] Optionally, at least one of the first rigid outer layer or the second rigid outer layer comprises polycarbonate.

[0200] Optionally, the stack further includes a polarizer including a polarizer plate, a TAC coating, and a UV blocking coating. Additionally, the LC panel can further include a liquid crystal cell including nematic liquid crystals in the liquid crystal layer, the liquid crystal cell including a sealant applied between the first substrate and the second substrate using a non-UV curable adhesive, the first substrate, the second substrate, and the sealant each defining a boundary of the liquid crystal cell. Additionally, the LC panel can include a spacer between the first substrate and the second substrate, the spacer being rectangular or cylindrical and defining a cell gap between the first substrate and the second substrate. Optionally, the first conductive layer or the second conductive layer can include ITO and can be disposed between the polarizer and the liquid crystal layer.

[0201] Example 7 In certain aspects, the LC panel includes a first substrate and a second substrate. The first substrate and the second substrate may be rigid or flexible. In some embodiments, the first substrate and the second substrate include glass. The LC panel further includes an LC panel between the first substrate and the second substrate. The LC panel further includes an edge seal that extends at least partially around the periphery of the LC panel. As with the LC panel, the edge seal is disposed between the first substrate and the second substrate. The overall thickness of the LC panel, including the first substrate, the second substrate, and the LC panel, can be configured to allow the LC panel to function as a window (e.g., a sunroof or a side window) of an automobile.

[0202] The LC panel is a multi-layer stack that includes an LC layer between a first conductive layer and a second conductive layer. The LC panel further includes one or more additional layers between the first conductive layer and the first substrate and / or between the second conductive layer and the second substrate. The one or more additional layers include a material (e.g., PVB) different from the first substrate and the second substrate. Thus, the LC panel has a different thermal expansion coefficient than the first substrate and the second substrate.

[0203] The LC panel is bonded to the first and second substrates by a combination of a liquid adhesive and a film-based adhesive, for example as described above in connection with FIG. 14, which maintains a flexible bond over a temperature range of at least −40 to +115° C. Optionally, the edge seal may be bonded to the first and second substrates using an adhesive that has a higher bond strength compared to the liquid adhesive and the film-based adhesive. In some embodiments, the liquid adhesive and the film-based adhesive include acrylic, and the edge seal adhesive includes a resin.

[0204] Optionally, the edge seal has a coefficient of friction less than or equal to that of the first and second substrates, For example, when the first and second substrates comprise glass, the edge seal may comprise PET.

[0205] Optionally, the thickness of the second substrate is less than the thickness of the first substrate. For example, as described above in connection with FIG. 16, the outer substrate (e.g., the first substrate) may be in the range of about 2 mm to 3.5 mm, and the inner substrate (e.g., the second substrate) may be in the range of about 0.7 mm to 3.5 mm. The total thickness of the entire LC panel is about 5 mm or less.

[0206] Optionally, the first substrate extends beyond the edge seal and the second substrate to provide a mounting surface for mounting the LC panel to the mounting body, for example, as shown in FIG. 16. The LC panel is secured to a padding block (e.g., padding 1705), which is flush with the first substrate. Alternatively, the first substrate, second substrate, and edge seal are adjacent to define a flush mounting surface, as shown in FIG. 18.

[0207] Optionally, the edge seal is separated from the LC panel by a first gap filled with a flexible sealant. The first gap may be completely filled with the liquid adhesive or may be filled with a different material (e.g., another adhesive) in the areas not occupied by the liquid adhesive, as shown in FIG. 19. In addition to the first gap, the edge seal may optionally be separated from the mounting body by a second gap when the LC panel is in an attached configuration relative to the mounting body. Similar to the first gap, the second gap is filled with a flexible sealant. The sealant in the second gap may be applied to the edge seal during manufacture of the LC panel or applied when the LC panel is attached to the mounting body. The sealant in the first gap and / or the second gap may be a non-adhesive sealant.

[0208] The foregoing description of embodiments of the present disclosure has been presented for purposes of illustration and is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. Those skilled in the art will recognize that numerous modifications and variations are possible in light of the above disclosure.

[0209] Some portions of this description may describe the disclosed embodiments in terms of algorithms and symbolic representations of operations on information. These algorithmic descriptions and representations are commonly used by those skilled in the data processing arts to effectively convey the substance of their work to others skilled in the art. While these operations are described functionally, computationally, or logically, it will be understood that they are implemented by computer programs or equivalent electrical circuits, microcode, or the like. Further, without loss of generality, it is sometimes convenient to refer to arrangements of these operations as modules. The described operations and their associated modules may be embodied in software, firmware, and / or hardware.

[0210] The described steps, operations, or processes may be performed or implemented in one or more hardware or software modules, alone or in combination with other devices. In some embodiments, the software modules are implemented in a computer program product that includes a computer-readable medium containing computer program code and may be executed by a computer processor to perform any or all of the described steps, operations, or processes.

[0211] The embodiments of the present disclosure may also relate to an apparatus for performing the described operations. The apparatus may be specially constructed for the required purposes or may comprise a general-purpose computing device selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a non-transitory tangible computer-readable storage medium, or any type of medium suitable for storing electronic instructions, that may be coupled to a computer system bus. Additionally, any computing system referred to herein may include a single processor or may be an architecture employing a multiple processor design to increase computing power.

[0212] Embodiments of the present disclosure may also relate to products produced by the computing processes described herein. Such products may include information resulting from the computing processes, the information being stored on a non-transitory, tangible, computer-readable storage medium and may include any of the embodiments of the computer program products or combinations of other data described herein.

[0213] The language used in the specification has been selected primarily for ease of reading and explanation, and may not have been selected to delineate or limit the subject matter of the invention. Accordingly, the scope of the disclosure is intended to be limited not by this detailed description, but by any claims that issue on an application based on this specification. Accordingly, the disclosure of the embodiments is intended to be illustrative, but not limiting, of the scope of the disclosure, which is set forth in the appended claims.

[0214] Although several embodiments have been described, various modifications, alternative constructions, and equivalents can be used without departing from the spirit of the present disclosure. For example, the above elements may only be components of a larger system, and other rules may take precedence or modify the application of the various embodiments. Also, some steps may be performed before, during, or after the above elements are considered. Therefore, the above description does not limit the scope of the present disclosure.

Claims

1. a liquid crystal (LC) film panel, comprising a guest-host (GH) liquid crystal layer comprising nematic liquid crystals, dye molecules and chiral dopants; a first substrate having a first conductive layer and a second substrate having a second conductive layer, the first substrate and the second substrate being disposed on opposite sides of the GH liquid crystal layer, the first substrate and the second substrate each comprising a flexible film; a plurality of spacers between the first substrate and the second substrate, the plurality of spacers maintaining a cell gap between 2.5 μm and 30 μm; the chiral dopant is added at least 0.5% by weight of the GH liquid crystal layer, the GH liquid crystal layer is configured to drive an LC film panel between a dark state and a light state in response to application of a voltage between the first conductive layer and the second conductive layer, in the dark state, an overall light transmittance of the LC film panel is between 1% and 20%, and in the light state, an overall light transmittance of the LC film panel is between 20% and 70%, and attached to a glass surface of an architectural window; The LC film panel comprises: a control unit configured to vary a voltage across the first conductive layer and the second conductive layer in response to an ambient light level; and a cutout shaped to accommodate a control unit, the cutout being located along an edge or corner of the LC film panel, allowing the control unit to be directly attached to the architectural window.

2. 2. The LC film panel of claim 1, wherein the GH liquid crystal layer is configured to establish the dark state when no voltage is applied to the first conductive layer and the second conductive layer.

3. 10. The LC film panel of claim 1, wherein the GH liquid crystal layer is configured to establish a bright state with no voltage applied to the first conductive layer and the second conductive layer.

4. 10. The LC film panel of claim 1, wherein the LC film panel is formed separately from the architectural window and attached via an adhesive disposed between a first substrate and the architectural window.

5. The LC film panel of claim 4 , wherein the adhesive is a liquid adhesive.

6. The LC film panel of claim 4 , wherein the adhesive is a film-based adhesive.

7. 10. The LC film panel of claim 1, wherein the flexible film of the first substrate is configured to conform to height variations along a glass surface of an architectural window.

8. 2. The LC film panel of claim 1, wherein the first substrate flexible film or the second substrate flexible film comprises polycarbonate (PC), polyethylene terephthalate (PET), or triacetyl cellulose (TAC).

9. 2. The LC film panel of claim 1, further comprising: a first polyamide (PI) coating between the first conductive layer and the GH liquid crystal layer and a second PI coating between the second conductive layer and the GH liquid crystal layer, the first PI coating and the second PI coating respectively including a rubbing pattern that determines an initial orientation of the nematic liquid crystal.

10. 10. The LC film panel of claim 1, wherein the control unit includes a battery and a solar cell, the solar cell being configured to use ambient light to charge the battery.

11. 13. The LC film panel of claim 1, further comprising one or more of a blocking layer configured to reduce an amount of ultraviolet light transmitted through the GH liquid crystal layer, a blocking layer configured to reduce an amount of infrared light transmitted through the GH liquid crystal layer, and a moisture barrier configured to prevent moisture from reaching the GH liquid crystal layer.

12. 10. The LC film panel of claim 1, wherein the first conductive layer and the second conductive layer are divided into a plurality of regions that are individually controllable to adjust the light transmittance of each region.

13. a liquid crystal (LC) film panel comprising: a guest-host (GH) liquid crystal layer comprising nematic liquid crystals, dye molecules and a chiral dopant; a first substrate having a first conductive layer and a second substrate having a second conductive layer, the first substrate and the second substrate being disposed on opposite sides of the GH liquid crystal layer, the first substrate and the second substrate each comprising a flexible film; a plurality of spacers between the first substrate and the second substrate, the plurality of spacers maintaining a cell gap between 2.5 μm and 30 μm; a control unit configured to vary a voltage across the first conductive layer and the second conductive layer in response to an ambient light level; and a cutout shaped to accommodate the control unit, the cutout being disposed along an edge or corner of the LC film panel, allowing the control unit to be directly attached to a window; 1. An LC film panel, wherein a chiral dopant is at least 0.5% by weight of a GH liquid crystal layer, the GH liquid crystal layer is configured to transition the LC film panel between a dark state and a light state in response to application of a voltage between a first conductive layer and a second conductive layer, wherein in a dark state, an overall light transmittance of the LC film panel is between 1% and 20%, and in a light state, an overall light transmittance of the LC film panel is between 20% and 70%, and the LC film panel is attached to a three-dimensional curved surface of an automobile window.

14. 14. The LC film panel of claim 13, wherein the automobile window is a sunroof.

15. 14. The LC film panel of claim 13, wherein the LC film panel is formed separately from the automobile window and attached via an adhesive between the first substrate and the automobile window.

16. 16. The LC film panel of claim 15, wherein the adhesive is a liquid adhesive or a film-based adhesive.

17. 14. The LC film panel of claim 13, wherein the flexible film of the first substrate is configured to conform to the curvature of a three-dimensional curved surface.

18. 14. The LC film panel of claim 13, wherein the first substrate flexible film or the second substrate flexible film comprises polycarbonate (PC), polyethylene terephthalate (PET), or cellulose triacetate (TAC).

19. 14. The LC film panel of claim 13, wherein the first conductive layer and the second conductive layer are divided into a plurality of regions that are individually controllable to adjust the light transmittance of each region.

20. 1. A method of strengthening a window, the method comprising: attaching a liquid crystal (LC) film panel to a surface of the window using an adhesive; The LC film panel includes a guest-host (GH) liquid crystal layer including a nematic liquid crystal, a dye molecule, and a chiral dopant; a first substrate having a first conductive layer and a second substrate having a second conductive layer, the first substrate and the second substrate being disposed on opposite sides of the GH liquid crystal layer, the first substrate and the second substrate each comprising a flexible film; a plurality of spacers between the first substrate and the second substrate, the plurality of spacers maintaining a cell gap between 2.5 μm and 30 μm; a control unit configured to vary a voltage across the first conductive layer and the second conductive layer in response to an ambient light level; a cutout shaped to receive a control unit, the cutout being located along an edge or corner of the LC film panel and allowing the control unit to be directly attached to the window; a chiral dopant is added at least 0.5% by weight of the GH liquid crystal layer, the GH liquid crystal layer being configured to drive an LC film panel between a dark state and a light state in response to application of a voltage between a first conductive layer and a second conductive layer, wherein in a dark state, the LC film panel has an overall light transmittance of between 1% and 20%, and in a light state, the LC film panel has an overall light transmittance of between 20% and 70%, and attaching the LC film panel to the window includes positioning the LC film panel relative to the window such that the first substrate conforms to a surface of the window.

21. The method of claim 20 , wherein the window surface has three-dimensional curvature.

22. 21. The method of claim 20, wherein the first substrate flexible film or the second substrate flexible film comprises polycarbonate (PC), polyethylene terephthalate (PET), or cellulose triacetate (TAC).

23. 21. The method of claim 20, wherein the adhesive is a liquid adhesive, and attaching the LC film panel to the window further comprises applying the liquid adhesive to at least one of a surface of the first substrate or the window prior to placing the LC film panel against the window.

24. 24. The method of claim 23, wherein the liquid adhesive is a clear water-based or solvent-based adhesive that upon evaporation forms a bond between the LC film panel and the window.

25. 21. The method of claim 20, wherein the adhesive is a film-based adhesive covered with a protective film, and the protective film is removed to expose the film-based adhesive immediately prior to mounting and attaching the LC film panel to the window.

26. 21. The method of claim 20, further comprising applying pressure to the LC film panel after placing the LC film panel against the window, the pressure removing any air bubbles trapped between the first substrate and the window.

27. 21. The method of claim 20, further comprising: attaching a control portion of the LC film panel to the window, the control unit configured to apply a voltage between the first conductive layer and the second conductive layer, and connecting the control unit to an electrical interface of the LC film panel, the electrical interface configured to transmit an electrical signal from the control unit to establish the voltage.

28. 28. The method of claim 27, wherein the control unit includes a battery and a solar cell, the solar cell configured to charge the battery using ambient light, and mounting the control unit to the window includes placing the control unit within the cutout in the LC film panel, the cutout configured to allow ambient light to reach the solar cell without passing through the first substrate and the second substrate.

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