WO2024118371A1

WO2024118371A1 - Tempering glass for uniform transmission in liquid crystal cells, panels and/or windows

Info

Publication number: WO2024118371A1
Application number: PCT/US2023/080480
Authority: WO
Inventors: James Gregory Couillard
Original assignee: Corning Incorporated
Priority date: 2022-11-29
Filing date: 2023-11-20
Publication date: 2024-06-06

Abstract

Various embodiments for configuring liquid crystal cells, liquid crystal panels, and methods of manufacturing liquid crystal panels are provided, comprising: cooling glass contained in at least one glass layer at a temperature greater than the glass transition temperature of the glass contained therein, assembling a plurality of liquid crystal panel component layers, each liquid crystal component layer comprising: the at least one glass layer; at least one interlayer; and at least one liquid crystal cell; substantially removing entrained air between at least some of the plurality of liquid crystal panel component layers to form a curable stack; and laminating the curable stack to form a liquid crystal panel, the resulting liquid crystal panel is configured with uniform transmission.

Description

TEMPERING GLASS FOR UNIFORM TRANSMISSION IN LIQUID CRYSTAL CELLS, PANELS AND/OR WINDOWS PRIORITY APPLICATIONS [001] This application claims the benefit of priority of U.S. Provisional Application Serial No.63/428581 filed November 29, 2022, the content of which is relied upon and incorporated herein by reference in its entirety. FIELD [002] Broadly, the present disclosure is directed towards configurations and methods for tempering glass in preventing, reducing, and/or mitigating non-uniform transmissions (e.g. dark spots and/or light spots) in liquid crystal cells, panels and/or windows, particularly for use in automotive applications and/or architectural applications. BACKGROUND [003] Smart windows often incorporate a dimmable layer via liquid crystal cells, layers, panels, and/or windows. The dimmable layer is used to control light transmission through the smart window, thereby reducing energy costs and improving occupant comfort. Uniform visual transmission is also desirable, but can pose many challenges in commercialization, especially with respect to the manufacture of large-dimensioned architectural or automotive windows. Liquid crystal cells are made from glass that has a thickness of less than 1 millimeter. Thus liquid crystal cells, in particular, are more subject to deformation. To prevent deformation and improve durability of liquid crystal cells and other liquid crystal components, including layers, panels and windows, soda lime glass (SLG) is typically added. In most instances, however, SLG includes surface irregularities, which may locally distort the liquid crystal cell, resulting in visual non-uniformities. Although various methods have been proposed to improve visual non-uniformity, improved performance and manufacturability of liquid crystal cells, layers, panels, and windows is still desired. 1 ^ SUMMARY [004] In one aspect, a method is provided, comprising: strengthening at least one glass layer, the at least one glass layer comprising a first surface and a second surface; cooling glass contained in the at least one glass layer at a temperature greater than the glass transition temperature of the glass contained therein, positioning the first surface adjacent to a first heat sink surface with a first gap between the first surface and the first heat sink surface such that thermal conduction from the first surface to the first heat sink surface occurs, positioning the second surface adjacent to a second heat sink surface with a second gap between the second surface and the second heat sink surface such that thermal conduction from the second surface to the second heat sink surface occurs, providing a first flow of a first gas to the first gap and a second flow of a second gas to the second gap, whereby the first flow of the first gas and the second flow of the second gas contacts the glass contained in the at least one glass layer such that the glass is cooled by conduction more than convection, cooling the glass contained in the at least one glass layer to a temperature less than the glass transition temperature of glass contained in the at least one glass layer; and assembling a plurality of liquid crystal panel component layers. [005] In preferred embodiments, each liquid crystal component layer comprises: the at least one glass layer; at least one interlayer; and at least one liquid crystal cell. [006] Additional steps of the method include substantially removing entrained air between at least some of the plurality of liquid crystal panel component layers to form a curable stack; and laminating the curable stack to form a liquid crystal panel such that the liquid crystal panel has a substantially uniform transmission. [007] In an additional aspect, the first gap has a length of g₁ and an area of A_g1, the second gap has a length of g₂ and an area of A_g2, the first gas has a heat capacity C_p1 and a thermal conductivity k1, the second gas has a heat capacity Cp2 and a thermal conductivity k2, wherein 2 ^ the first flow of the first gas has at a mass flow rate m1, wherein m1 is greater than zero and less than (2k1Ag1)/(g1Cp1), and wherein the second flow of the second gas has at a mass flow rate m2, wherein m2 is greater than zero and less than (2k2Ag2)/(g2Cp2). [008] In some embodiments, the laminating step further comprises heating the curable stack to a lamination temperature for a duration of time. [009] In some embodiments, the laminating step further comprises applying pressure to the liquid crystal panel component layers during lamination. [0010] In some embodiments, the uniform transmission comprises not greater than 1% disparity in a transmission region, as compared to adjacent transmission regions in the liquid crystal panel. [0011] In some embodiments, the uniform transmission comprises not greater than 2% disparity in a transmission region, as compared to adjacent transmission regions in the liquid crystal panel. [0012] In some embodiments, uniform transmission is detected via visual observation. [0013] In some embodiments, uniform transmission is detected via spectrophotometer. [0014] In some embodiments, the first and second gaps are about 100 μm or less. [0015] In some embodiments, the first or second gas is air. [0016] In some embodiments, the first or second gas is helium. [0017] According to yet another aspect, a method comprises cooling at least two glass layers comprising glass, wherein each glass layer has first and second layer surfaces, the glass contained in each glass layer having a transition temperature, each glass layer being at a temperature greater than the transition temperature at the start of the cooling. [0018] In some embodiments, cooling comprises the steps of: positioning the first layer surface adjacent to a first heat sink surface with a first gap between the first layer surface and the first heat sink surface such that thermal conduction from the first layer surface to the first 3 ^ heat sink surface occurs, the first gap having a length across the first gap of g1 and an area of the first gap of Ag1, positioning the second layer surface adjacent to a second heat sink surface with a second gap between the second sheet surface and the second heat sink surface such that thermal conduction from the second layer surface to the second heat sink surface occurs, the second gap having a length across the second gap of g2 and an area of the second gap of Ag2, providing a first flow of a first gas to the first gap and providing a second flow of a second gas to the second gap, the first gas having a heat capacity Cp1 and a thermal conductivity k1, the second gas having a heat capacity Cp2 and a thermal conductivity k2, the flow provided at a mass flow rate ী1 of the first gas, wherein ী1 is greater than zero and less than (2k1Ag1)/(g1Cp), to the first gap, and at a mass flow rate ী2 of the second gas, wherein ী2 is greater than zero and less than (2k2Ag2)/(g2Cp2), to the second gap, whereby the first and second flows contact the at least one glass layer, and the at least one glass layer is cooled, by conduction more than by convection, and sufficiently creating a surface compressive stress and a central tension of the sheet; forming at least two liquid crystal panel component layers. [0019] In some embodiments, each liquid crystal panel component layer comprises: a first glass layer of the at least two glass layers; a first interlayer; a liquid crystal cell; a second interlayer; a second glass layer of the at least two glass layers; substantially removing entrained air between the at least two liquid crystal panel component layers to form a curable stack; and laminating the curable stack to form a liquid crystal panel such that the liquid crystal panel has a substantially uniform transmission. [0020] In some embodiments, the first heat sink surface has multiple first apertures and the second heat sink surface has multiple second apertures, and wherein providing a first flow of a first gas to the first gap comprises flowing the first gas to the first gap only through the multiple first apertures and wherein providing a second flow of a second gas to the second gap consists of flowing the second gas to the second gap only through the multiple second apertures. 4 ^ [0021] In some embodiments, each aperture has a cross-sectional dimension of less than 0.5 mm. [0022] In some embodiments, each aperture has a cross-sectional dimension of less than 0.01 mm. [0023] In some embodiments, at least some of the multiple apertures in the first and second heat sink surfaces are within 20 degrees of perpendicular to the respective first and second heat sink surfaces. [0024] In some embodiments, the first and second gaps are about 100 μm or less. [0025] In some embodiments, the first or second gas is air. [0026] In some embodiments, the first or second gas is helium. [0027] In some embodiments, the method further comprises the step of heating each glass layer principally by conduction through a gas from a heat source, the step of heating each glass layer principally by conduction being performed prior to the step of cooling. [0028] Additional features and advantages will be set forth in the detailed description which follows and will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings. [0029] It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework to understanding the nature and character of the disclosure as it is claimed. [0030] The accompanying drawings are included to provide a further understanding of principles of the disclosure, and are incorporated in, and constitute a part of, this specification. The drawings illustrate one or more embodiment(s) and, together with the description, serve to explain, by way of example, principles and operation of the disclosure. It is to be understood that various features of the disclosure disclosed in this specification and in the drawings can be 5 ^ used in any and all combinations. By way of non-limiting examples, the various features of the disclosure may be combined with one another according to the following aspects. BRIEF DESCRIPTION OF THE DRAWINGS [0031] These and other features, aspects and advantages of the present disclosure are better understood when the following detailed description of the disclosure is read with reference to the accompanying drawings, in which: [0032] Figure 1A depicts a schematic cut-away side view of an embodiment of a liquid crystal (alternatively “LC”) panel in accordance with various embodiments of the present disclosure. [0033] Figure 1B depicts a close-up cut away side schematic view of a region of Figure 1A, showing a close-up of a portion of the panel, depicting the second glass layer, the interlayer, the conductive layer, and the liquid crystal region, which includes a liquid crystal mixture and a plurality of spacers, in accordance with one or more embodiments of the present disclosure. [0034] Figure 2 is a false color contour map of surface topography measurements on a glass layer utilized in the panel (e.g. float glass), which is believed to be a representative sample of tempered soda lime glass (SLG), showing wavy surface discontinuity (i.e. out-of-plane discontinuity), with peaks and troughs averaging ~50 μm high/deep, in accordance with one or more aspects of the present disclosure. [0035] Figure 3A depicts a schematic view of an embodiment of a liquid crystal panel, showing a liquid crystal cell laminated via first and second interlayers, to corresponding first and second glass layers, in accordance with one or more aspects of the present disclosure. [0036] Figure 3B depicts a schematic view of an embodiment of a liquid crystal window, showing a liquid crystal panel configured with a frame, seal between frame and panel, and with 6 ^ a coating on a surface of the panel, in accordance with one or more aspects of the present disclosure. [0037] Figure 4 depicts a method of making a liquid crystal panel, , in accordance with one or more aspects of the present disclosure. [0038] Figure 5 is a photograph of a laminated liquid crystal window showing dark spots which correspond to out-of-plane features in tempered SLG. [0039] Figure 6 schematically illustrates a conventional thermally strengthening/tempering process for SLG. [0040] Figure 7 schematically illustrates a tempering process of SLG in accordance with embodiments of the present disclosure. [0041] Figure 8 is a flow chart illustrating embodiments of methods of tempering glass layers in the liquid crystal panel during manufacture to prevent, reduce, and/or eliminate mura in accordance with embodiments of the present disclosure. [0042] Figure 9 is a flow chart illustrating embodiments of methods of tempering glass layers in the liquid crystal panel during manufacture to prevent, reduce, and/or eliminate mura in accordance with embodiments of the present disclosure. [0043] Figure 10 is a contour map of a glass layer tempered in accordance with embodiments of the present disclosure. DETAILED DESCRIPTION OF THE DRAWINGS [0044] In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of various principles of the present disclosure. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present disclosure may be practiced in other embodiments that depart from the specific details 7 ^ disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of various principles of the present disclosure. Finally, wherever applicable, like reference numerals refer to like elements. [0045] Referring to Figure 1A, a schematic cut-away side view of an embodiment of a liquid crystal panel 10 is depicted. FIG. 1A further illustrates how the liquid crystal cell 20 is configured (sandwiched) between two glass layers (e.g. a first glass layer 12 and a second glass layer 14), with corresponding interlayers (e.g. first interlayer 26 and second interlayer 28) positioned between each of the first glass layer 12 and the first side of the liquid crystal cell 20, and the second glass layer 14 and the second side of the liquid crystal cell 20. [0046] The liquid crystal cell 20 is configured with two glass layers, a first glass sheet 30 and a second glass sheet 40, set apart in spaced relation from each other with a liquid crystal region 48 defined therebetween. Each of the first glass sheet 30 and the second glass sheet 40 is configured with a conductive layer (e.g. first conductive layer 34 and second conductive layer 44) where each conductive layer (34, 44) is configured between the liquid crystal region 48 and the first or second glass sheets 30, 40, such that the conductive layers 34, 44 are configured in electrical communication with the liquid crystal region 48. [0047] The liquid crystal region 48 includes a plurality of spacers 38 and a liquid crystal mixture 36. The spacers 38 are provided in spaced relation throughout the liquid crystal mixture 36, such that the spacers 38 are configured to promote a cell gap that is substantially uniform (e.g. not exceeding a predefined threshold) from one position within the liquid crystal cell 20 to another position in the liquid crystal cell 20. The liquid crystal mixture 36 can include: at least one liquid crystal material, at least one dye, at least one host material, and/or at least one additive. The liquid crystal mixture 36 is configured to electrically switch/actuate, thereby providing the actuation element in a corresponding liquid crystal cell 20, liquid crystal panel 10, and liquid crystal window to provide a contrast (e.g. dark) and a non-contrast (e.g. clear) 8 ^ state when actuated. Actuation of the liquid crystal mixture 36 is completed by the electrical connections via first electrode 32 (adjacent to the first major surface 22 of the liquid crystal cell 20) and the second electrode 42 (adjacent to the second major surface 24 of the liquid crystal cell 20). The electrode (one of 32 and 42) is configured to direct an electrical current or potential from a power source through the corresponding electrode acting as anode, through the corresponding conductive layer (one of 34 or 44), through the liquid crystal region 48 to actuate the liquid crystal mixture 36, through the corresponding conductive layer (the other of 34 or 44) and exiting the system through the electrode (the other of 32 and 42). By turning on and off the power source, and thereby, the current or potential through the liquid crystal mixture, the liquid crystal mixture is actuated from a first transmission state to a second transmission state (where the first transmission state is different from the second transmission state). [0048] As shown, the liquid crystal panel 10 includes a first glass layer 12, a second glass layer 14, a liquid crystal cell 20, a first interlayer 26, and a second interlayer 28. The liquid crystal cell 20 includes a liquid crystal material 36 (e.g. molecules, dyes, and/or additives), spacers 38 (configured to cooperate with the glass layers to maintain the cell gap in the liquid crystal cell), a first conductive layer 34, a second conductive layer 44, a first electrode 32, a second electrode 42, a first glass sheet 30, and a second glass sheet 40. [0049] In some embodiments, the first glass layer 12 and second glass layer 14 are thick. In some embodiments, the first glass layer and the second glass layer each have a thickness of at least 3 mm thick. In some embodiments, the first glass layer and the second glass layer each have a thickness of at least 3 mm thick to not greater than 7 mm thick. [0050] In some embodiments, the first sheet of glass 30 and second sheet of glass 40 are thin. In some embodiments, the first glass sheet and the second glass sheet each have a 9 ^ thickness of at not greater than 1 mm. In some embodiments, the first glass layer and the second glass layer each have a thickness of at least 0.3 mm thick to not greater than 1 mm. [0051] In some embodiments, the first sheet of glass 30 and second sheet of glass 40 are thinner than the first glass layer 12 and the second glass layer 14. [0052] In some embodiments, the glass sheets (30, 40) are configured in the liquid crystal cell 20, adjacent to major surfaces 22, 24 of the liquid crystal cell and adjacent to the liquid crystal material 36 to retain liquid crystal components (e.g. conductive layers (34, 44), liquid crystal material 36, spacers 38) in place. In some embodiments, first interlayer 26 is configured between first glass layer 12 and first sheet of glass 30 (first surface 22 of liquid crystal cell 20). In some embodiments, second interlayer 28 is configured between second glass layer 14 and second sheet of glass 40 (second surface 24 of liquid crystal cell 20). [0053] In some embodiments, the glass sheet (e.g. first sheet of glass 30 or second sheet of glass 40) is configured with a thickness of less than 1 mm; less than 0.8 mm, less than 0.7 mm, less than 0.5 mm, or less than 0.3 mm. In some embodiments, the first sheet of glass 30 has the same thickness as the second sheet of glass 40. In some embodiments, the first sheet of glass 30 has a different thickness than the second sheet of glass 40. [0054] For example, conductive layer (34 or 44) is configured in the liquid crystal cell 20 between the sheet of glass (30 or 40) and the liquid crystal region 48. The conductive layer (34 or 44) is attached to one or more electrodes (32 or 34) (e.g. configured to communicate with the conductive layers and a power source (not shown) to direct an electric field across the liquid crystal cell 20, actuating the liquid crystal panel/smart window to an on position (having a first contrast) and off position (having a second contrast)), based on whether the electric field is on or off. 10 ^ [0055] Each conductive layer includes a conductive film, for example, a transparent conductive oxide. Some non-limiting examples of thin conductive film is ITO (indium tin oxide), FTO (fluorine-doped tin oxide), or metals. [0056] In some embodiments, an alignment layer such as polyimide may be disposed between the thin conductive film and the liquid crystal material to promote orientation of the liquid crystal molecules (within the liquid crystal material 36) with a desired angle. [0057] Figure 1B depicts a close-up cut away side view of a region of Figure 1A, showing a close-up of the second glass layer 14 (e.g. tempered SLG), second interlayer 28, and second glass sheet 40 of the liquid crystal cell 20, further depicting the liquid crystal region’s 48 liquid crystal mixture 36 and a spacer 38 retained in the liquid crystal cell 20. As shown in Figure 1B, the surface discontinuity of the first glass layer and second glass layer 14 (here, only second glass layer shown) as compared to the second layer of glass 40 is apparent. In this illustrated example, the surface discontinuity attributed to the area 50 of the liquid crystal panel 10 is an area of a non-uniformity/discontinuity in the liquid crystal cell 20. This example may be viewed by an observer as a dark spot in the liquid crystal panel 10. The spacers 38 are configured to extend across the cell gap of the liquid crystal cell 20. [0058] Figure 2 depicts a contour map of a representative sample of a first glass layer 12 or second glass layer 14 utilized in the liquid crystal panel 10 as described herein. The float glass has a surface waviness/contoured topography at production, which can be exacerbated with tempering to provide a surface topography similar to that of the representative example in Figure 2. This tempered soda lime glass exhibits a surface discontinuity (out-of-plane discontinuity), with peaks and troughs averaging ~50 μm high/deep, which provides challenges in laminating to manufacture a liquid crystal panel 10. [0059] In one non-limiting example, the waviness can be analytically determined through mechanical or optical measurement devices and in accordance with standard methods. In one 11 ^ non-limiting example, the waviness can be determined by measurement in accordance with ASTM C1651: Standard Test Method for Measurement of Roll Wave Optical Distortion in Heat-Treated Flat Glass. Other standard methods may also be utilized to understand the surface-waviness of the flat glass layers in accordance with one or more embodiments disclosed herein. [0060] Figure 3A depicts a schematic cut away side view of an embodiment of a single cell liquid crystal panel 10, which illustrates a liquid crystal cell laminated onto two glass layers (12, 14) via two interlayers (26, 28) to form a liquid crystal panel 10. The liquid crystal panel depicts a symmetrical component configuration, with an axis drawn through the liquid crystal material 48, from one portion of the depicted liquid crystal cell seal 52 towards the other depicted liquid crystal cell seal 52. [0061] Figure 3B depicts a schematic cut-away side view of an embodiment of a single cell liquid crystal window 1000. The liquid crystal window 1000 includes a liquid crystal cell 20 embodied within a liquid crystal panel 10, the panel also having first interlayer 26, second interlayer 28, first glass layer 12, and second glass layer 14. The liquid crystal window 1000 is configured with a frame 16 configured on an edge of the liquid crystal panel 10, with a seal 18 configured between at least a portion of the frame 16 and at least a portion of an edge of the liquid crystal panel 10 to provide compressive engagement of the liquid crystal panel 10 within the frame 16 without damaging the edge of the liquid crystal panel 10. Also, Figure 3B depicts an optional coating 46 on a surface of the liquid crystal panel 10. Here, the coating is configured on the outer surface of the second glass layer 14 on the liquid crystal panel 10. [0062] Figure 4 depicts a method of making a liquid crystal panel. As shown, the lamination process includes assembling the liquid crystal panel component layers into a stack. The various component layers, including a first glass layer, a first interlayer, a liquid crystal cell, a second interlayer, and a second glass layer are placed into contact with one another to form the stack. 12 ^ The interlayer is selected from the group of polymers and ionomers. As a non-limiting example, the interlayer comprises PVB (polyvinyl butyral) at a thickness of 0.76 mm. [0063] Next, the lamination process includes substantially removing entrapped or entrained air between the various layers of the stack to form a curable stack. Non-limiting examples of air removal include nip rolling, using an evacuation pouch, vacuuming via at least one vacuum ring, or a laminating via a flatbed laminator. [0064] Laminating is completed on the curable stack in order to bond the first glass layer and the second glass layer to major surfaces of the liquid crystal cell (e.g. as shown in Figure 1A, generally opposing major surfaces of the liquid crystal cell via the corresponding first and second interlayers, which attach (e.g. bond) the first glass layer onto the first surface of the liquid crystal cell and the second glass layer on the second side of the liquid crystal cell. Non- limiting examples of laminating include utilizing a flatbed laminator or an autoclave. After laminating for a duration of time, at a temperature, and under a target pressure, the curable stack is formed into a LC panel. [0065] In a non-limiting example, the liquid crystal panel is made into a liquid crystal window by configuring a seal and a frame around an outer edge of the liquid crystal panel, to retain the liquid crystal panel within the frame. Additionally, electrical communication is configured from a power supply to the electrodes so that the liquid crystal window can be actuated via an electrical field directed across the liquid crystal window via the electrodes, conductive layers, and liquid crystal material. [0066] Figure 5 is a photograph of a laminated liquid crystal window showing dark spots which correspond to out-of-plane features in tempered SLG. [0067] Figure 6 schematically illustrates a conventional thermally strengthening/tempering process for SLG, including the steps of heating in an oven. Typically, in conventional tempering processes SLG is heated to above 600 °C. The SLG then undergoes a high-pressure 13 ^ cooling procedure called "quenching” in the quenching apparatus. During this process, which lasts a few seconds, high-pressure air blasts the surface of the SLG from an array of cooling nozzles in varying positions. Quenching cools the outer surfaces of the glass more quickly than the center. As the center of the SLG cools, it tries to pull back from the outer surfaces. As a result, the center remains in tension, and the outer surfaces go into compression, which results in tempering of the SLG. However, in conventional tempering the glass is heated and cooled primarily by radiative and convective heat transfer (via heater bars and air movement). These methods can result in local nonuniformity of the heating/cooling rates, which in turn lead to surface irregularities such as those shown in FIG.2. [0068] Figure 7 schematically illustrates a tempering process of SLG in accordance with embodiments disclosed herein that provide for tempering of SLG with minimal surface waviness/topography. In contrast to conventional tempering methods, the glass is transported by air bearing, which eliminates differences in heat conduction caused by roller bearings. The glass is heated and cooled by close proximity to a substantially uniform flat plate at a fixed temperature. [0069] An apparatus for the tempering process may generally include three zones – a hot zone, a transition zone, and a quench zone. The gaps between the top and bottom thermal bearings (heat sinks) in the hot zone and the quench zone are preferably set to desired spacings. Gas flow rates in the hot zone, transition zone, and quench zone are set to ensure centering of the part on the air-bearing. The hot zone is pre-heated to the desired T₀, the temperature from which the glass article will be subsequently quenched. To ensure uniform heating, glass articles may be pre-heated in a separate pre-heating apparatus, such as a batch or continuous furnace. Generally, glass sheets are pre-heated for greater than 5 minutes prior to loading in the hot zone. For soda lime glasses, pre-heating is done around 450 °C. After the pre-heat phase, the glass article is loaded into the hot zone and allowed to equilibrate, where equilibration is where 14 ^ the glass is uniformly at T0. T0 can be determined by the tempering desired, but is generally kept in the range between the softening point and the glass transition temperature. The time to equilibration is dependent at least on the thickness of the glass. For example, for glass sheets of approximately 1.1 mm or less, equilibration occurs in approximately 10 seconds. For 3 mm glass sheets, equilibration occurs in approximately 30 seconds. For thicker sheets, up to approximately 6 mm, the equilibration time may be on the order of 60 seconds (for articles approximately 6 mm thick). Once the glass has equilibrated to T0, it is rapidly transferred through the transition zone on air bearings and into the quench zone. The glass article rapidly quenches in the quench zone to a temperature below the glass transition temperature, Tg. The glass sheet can be maintained in the quench zone for any period of time from 1 second, 10 seconds, or to several minutes or more, depending on the degree of quench desired and/or the desired temperature of the glass at removal. Upon removal, the glass is optionally allowed to cool before handling. [0070] The method further includes cooling or heating at least a portion of the surface of the glass surface by conduction more than by convection, the conduction mediated through a gas to or from a heat sink or a heat source and not through direct contact between the surface and the heat sink or heat source, and sufficiently to thermally strengthen the article or at least a portion of the surface of the article. The conduction is performed, during at least some time of the heating or cooling, at a rate of at least 450 kW per square meter. [0071] Figures 8 and 9 are generally directed towards embodiments of methods of tempering the SLG layer or layers in the liquid crystal panel during manufacture to prevent, reduce, and/or eliminate mura (e.g. dark spots), such as those shown in Figure 5. [0072] In one aspect, an overall process for strengthening a glass sheet comprises supporting or guiding at least a portion of a glass sheet having a transition temperature, on a first surface, at least in part by a flow or a pressure of a gas delivered to a gap between the first surface and 15 ^ a first heat sink, the sheet temperature being above the transition temperature of the glass, and then cooling the glass sheet by thermal conduction more than by convection. Conduction is a process of heat transfer where energy is transmitted through interactions between adjacent molecules, while convection is a process of heat transfer where energy is communicated via motion of a fluid (e.g., air, helium, etc.), such as where heated fluid moves away from a heat source and is replaced by cooler fluid. In at least some embodiments, the terms “glass ceramic” or “ceramic” can be substituted and/or equally applied where the term “glass” is used. [0073] In some embodiments, an overall process for strengthening a glass sheet comprises heating a glass sheet in a hot zone and then cooling the glass sheet. The glass sheet has a transition temperature, which occurs is where the viscosity of the glass has a value of ^ = 10¹²- 10^13.3 Poise. The glass is heated sufficiently to bring the glass sheet above the transition temperature. Optionally, the glass can be transitioned from the hot zone to a cool zone through a transition zone. The surfaces of the glass sheet are positioned adjacent to heat sinks, one on either glass surface with a gap in between the glass surface and the heat sink. Gas is delivered into the gaps through multiple apertures in the heat sinks. The glass sheet is cooled by conduction more than by convection and sufficiently to fix or create a thermally induced surface compression and a thermally induced central tension of the sheet. [0074] An apparatus for enabling the processes described can include a heating zone for heating a glass sheet to a temperature above the transition temperature and a cooling zone for cooling the heated glass sheet from to provide a strengthened glass sheet. The apparatus can include an optional transition zone between the heating zone and the cooling zone. The cooling zone can comprise a pair of gas bearings disposed on opposite sides of a gap, which can be configured to deliver a gas to the gap to cool the heated glass sheet by conduction more than by convection. In some embodiments, the gas bearings can include a plurality of apertures for 16 ^ delivering the gas to the gap, and gas bearing surfaces that provide heat sinks capable of conducting heat away from the heated glass sheet by conduction more than by convection. [0075] One embodiment of a method according to this disclosure is illustrated in the flow chart of Figure 8. The method 100 includes the step 160 of supporting a glass sheet at least in part by a gas (through gas flow and pressure as in some convective gas strengthening processes). The sheet can be heated to above its glass transition temperature while at the same time cooling the sheet: 1) by conduction more than by convection through the gas to a heat sink, and 2) sufficiently to create or fix a thermally-induced surface compression stress and a thermally-induced central tension stress, of the sheet when at ambient temperature. [0076] According to a variation on the embodiment of Figure 8, depicted as method 100' in the flow chart of Figure 9, the method can include the step 110 of heating a glass sheet sufficiently such that the sheet is above a transition temperature of the glass. In step 130A the method further includes positioning a first sheet surface facing a first heat sink surface across a first gap and, in step 130B, positioning the second sheet surface facing a second heat sink surface across a second gap, the second heat sink surface. The heat sink surfaces can include apertures and/or can be porous. The method 100 can further include, in step 160, cooling the sheet, by conduction more than by convection through a gas to the respective heat sink surfaces, sufficiently to strengthen the glass, that is, sufficiently to create or fix in the sheet a thermally- induced surface compression stress and a thermally-induced central tension stress. The step 160 of cooling the sheet also can include delivering the gas to the first and second gaps through the apertures or porous heat sink. In some embodiments, the gas is delivered only through the apertures of the heat sink or only through the pores or pores and apertures of the porous heat sink. [0077] Figure 10 is a contour map of an example of a glass layer tempered using the methods disclosed herein. The map represents a glass layer of about 12 inches by 16 inches, showing a 17 ^ color representation of substantially uniform flatness across the center of the part. The vertical deviation is less than about 10 μm across the glass layer, except for the corners. [0078] In some embodiments, liquid crystal (LC) material is sandwiched between two pieces of commercially available fusion formed borosilicate glass, such as Corning^® EAGLE XG^® to form the liquid crystal cell. However, such glass has thickness < 1 mm, and so is not rigid enough to withstand exposure to the wind and snow loads commonly experienced by large-dimensioned windows in architectural applications. As such, liquid crystal windows of the present disclosure include a liquid crystal cell having thin glass (e.g. less than 1 mm), which are laminated to thick (^3 mm) pieces of soda lime glass (SLG) for additional strength and/or support. The SLG is tempered (per ASTM C1048) for additional strength and breakage protection, however, the tempering process is known to induce out-of-plane distortion in the SLG, which can be significant, impacting the liquid crystal panel. [0079] After lamination, if the thin glass(es) from the liquid crystal cell is well-adhered to the SLG, the out-of-plane distortion from the SLG can pull on the thin glass, which may drive stresses acting on the liquid crystal cell, including locally increasing the liquid crystal cell gap and/or producing undesirable local changes in visual appearance. The liquid crystal panel or resulting liquid crystal window can have spots of non-uniform transmission, or regions having 1-2% or greater variation in visible light transmission relative to the average visible light transmission across the visible area of the panel (e.g. dark spots or light spots). Without being bound by any particular mechanism or theory, non-uniform transmission areas or regions are believed to be attributed to a thicker cell gap in the liquid crystal cell, which is generated during manufacturing of the liquid crystal window. [0080] One or more advantages of using thin glass to fabricate the liquid crystal cell include: (a) compatibility with existing LCD fabrication equipment; lower window weight, making it easier to transport and install and lowering overall carbon footprint; higher visible light 18 ^ transmission in the clear state; thinner overall window structures, and/or additional room for gas in an IGU, thereby improving the insulation efficiency. [0081] One or more embodiments of the present disclosure are directed towards configurations and methods for reducing, preventing, and/or eliminating areas or regions of non-uniform transmission (e.g. dark spots or light spots) in a liquid crystal panel. Thus, one or more liquid crystal panels of the present disclosure are configured with uniform transmission (e.g. regions at no greater than 1-2% variation in visible light transmission relative to the average visible light transmission across an adjacent area (visible area) of the window). [0082] In some embodiments, dark spots or light spots (‘spots’) are detectable by visual observation (in a static mode of the liquid crystal window, spots, if any are detectable in at least one of the first contrast state and the second contrast state, where the contrast states are an on position and an off position. [0083] In some embodiments, a spot means that transmission of the window in a region is greater than 1-2% lower transmission in the dark spot region, as compared to the surrounding, non-dark spot region. As a non-limiting example, transmission is measurable with a spectrometer (e.g. percent transmission or visible light transmission). [0084] In one aspect, a method is provided, comprising: assembling a plurality of liquid crystal window component layers to form a stack; removing any entrained air between the component layers of the stack to form a curable stack; laminating the curable stack for a duration of time, at a lamination temperature, and at a pressure to form a liquid crystal window; wherein the liquid crystal window is configured with a uniform transmission. [0085] In some embodiments, a uniform transmission comprises not greater than 2% disparity in a transmission region (e.g. visible light transmission), as compared to adjacent transmission regions. [0086] In some embodiments, uniform transmission is detected via visual observation. 19 ^ [0087] In some embodiments, uniform transmission is detected via spectrophotometer. [0088] The providing step further comprises assembling further comprises positioning a first glass layer, a first interlayer, a liquid crystal cell, a second interlayer, and a second glass layer into a stacked configuration. [0089] In one aspect, an apparatus is provided, comprising: a liquid crystal cell, wherein the liquid crystal cell comprises: a first glass layer, a second glass layer, configured in spaced relation from the first glass layer, and a liquid crystal material comprising an electrically switchable material (e.g. including a first contrast state and a second contrast state) positioned (retained) between the first glass layer and the second glass layer, a plurality of spacers, wherein the spacers are configured to sit between the first glass layer and the second glass layer and among the liquid crystal material, wherein the spacers are configured to maintain a liquid crystal gap (e.g. distance from the first glass sheet to the second glass sheet) of the liquid crystal cell; a first conductive layer and a second conductive layer, wherein the first conductive layer is configured between the first glass layer and a first side of the liquid crystal cell such that the first conductive layer is in electrical communication with the first side of the liquid crystal cell, wherein the second conductive layer is configured between the second glass layer and the second liquid crystal sidewall such that the second conductive layer is in electrical communication with the second side of the liquid crystal cell, a first electrode configured adjacent to a cell perimeter and in electrical communication with the first conductive layer; and a second electrode configured adjacent to the second conductive layer; wherein, the electrodes are configurable to a power source, such that the liquid crystal cell is electrically configured to electrically actuate the electrically switchable material in the liquid crystal mixture. [0090] In some embodiments, the spacers are configured from a polymer material. [0091] In some embodiments, the first glass layer is a thin glass. [0092] In some embodiments, the first glass layer has a thickness of less than 1 mm. 20 ^ [0093] In some embodiments, the first glass layer has a thickness of not greater than 0.5 mm. In some embodiments, the second glass layer is a thin glass. [0094] In some embodiments, the second glass layer has a thickness of less than 1 mm. In some embodiments, the second glass layer has a thickness of not greater than 0.5 mm. [0095] In some embodiments, the liquid crystal gap is not greater than 10 microns. [0096] In some embodiments, the conductive layer comprises ITO and polyimide. [0097] In another aspect, an apparatus is provided, comprising: a liquid crystal cell (liquid crystal cell), configured to retain an electrically switchable liquid crystal material; a first glass sheet configured along a first side of the liquid crystal cell; a second glass sheet configured along a second side of the liquid crystal cell; a first interlayer positioned between the first glass sheet and the first side of the liquid crystal cell, wherein the first interlayer adheres the first glass layer to the first side of the liquid crystal cell; and a second interlayer positioned between the second glass sheet and the second side of the liquid crystal cell, wherein the second interlayer is configured to adhere the second glass layer to the second side of the liquid crystal cell. [0098] In some embodiments, the apparatus is a laminate. [0099] In some embodiments, the apparatus is a liquid crystal window. [00100] In some embodiments, the liquid crystal window has a surface area of at least 1 foot by at least 2 feet. [00101] In some embodiments, the liquid crystal window has a surface area of at least 2 feet by at least 4 feet. [00102] In some embodiments, the liquid crystal window has a surface area of at least 3 feet by at least 5 feet. [00103] In some embodiments, the liquid crystal window has a surface area of at least 5 feet by at least 7 feet. 21 ^ [00104] In some embodiments, the liquid crystal window has a surface area of at least 7 feet by at least 10 feet. [00105] In some embodiments, the liquid crystal window has a surface area of at least 10 feet by at least 12 feet. [00106] In some embodiments, the apparatus is an architectural liquid crystal window. [00107] In some embodiments, the apparatus is an automotive liquid crystal window. [00108] In some embodiments, the first glass layer comprises a soda lime glass. [00109] In some embodiments, the first glass layer comprises a tempered soda lime glass. [00110] In some embodiments, the first glass layer comprises a thickness of at least 2 mm. [00111] In some embodiments, the first glass layer comprises a thickness of at least 2 mm to not greater than 6 mm. [00112] In some embodiments, the first glass layer comprises a thickness of 3 mm. [00113] In some embodiments, the first glass layer comprises a thickness of 4 mm. [00114] In some embodiments, the second glass layer comprises a soda lime glass. [00115] In some embodiments, the second glass layer comprises a tempered soda lime glass. [00116] In some embodiments, the second glass layer comprises a thickness of at least 2 mm. [00117] In some embodiments, the second glass layer comprises a thickness of at least 2 mm to not greater than 6 mm. [00118] In some embodiments, the second glass layer comprises a thickness of 3 mm. [00119] In some embodiments, the second glass layer comprises a thickness of 4 mm. [00120] In some embodiments, the first interlayer comprises a thickness of not greater than 2 mm. [00121] In some embodiments, the first interlayer comprises a thickness of 0.76 mm. [00122] In some embodiments, the first interlayer comprises a polymer. [00123] In some embodiments, the first interlayer comprises PVB. 22 ^ [00124] In some embodiments, the second interlayer comprises a thickness of not greater than 2 mm. [00125] In some embodiments, the second interlayer comprises a thickness of 0.76 mm. [00126] In some embodiments, the second interlayer comprises a polymer. [00127] In some embodiments, the second interlayer comprises PVB. [00128] In some embodiments, at least one surface of the liquid crystal panel comprises a coating. [00129] In some embodiments, at least one surface of the liquid crystal panel comprises a low emissivity coating. [00130] In some embodiments, the outer surface of the second glass layer of the liquid crystal panel comprises a low emissivity coating. For example, the low emissivity coating can be comprised of a combination of metals and oxides, including non-limiting examples of silicon nitride, metallic silver, silicon dioxide, tin oxide, zirconium oxide, and/or combinations thereof, to name a few. [00131] As some non-limiting examples, the coating includes: a low emissivity coating, an anti-reflective coating; a tint coating; an easy clean coating; or an anti-bird strike coating. In some embodiments, the coating is a partial coating. In some embodiments, the coating is a full coating. In some embodiments (e.g. anti-bird strike coating), the coating is patterned along discrete portions of the surface. [00132] In some embodiments, the laminate comprises a coating on at least one of: a first major surface of the liquid crystal panel, a second major surface of the liquid crystal panel, and both the first major surface of the liquid crystal panel and the second major surface of the liquid crystal panel. [00133] In some embodiments, the apparatus is an architectural product. [00134] In some embodiments, the apparatus is an architectural window. 23 ^ [00135] In some embodiments, the apparatus is an automotive window. [00136] Many variations and modifications may be made to the above-described embodiments of the disclosure without departing substantially from the spirit and various principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims. 24 ^

Claims

CLAIMS What is claimed is: 1. A method, comprising: strengthening at least one glass layer, the at least one glass layer comprising a first surface and a second surface; cooling glass contained in the at least one glass layer at a temperature greater than the glass transition temperature of the glass contained therein, positioning the first surface adjacent to a first heat sink surface with a first gap between the first surface and the first heat sink surface such that thermal conduction from the first surface to the first heat sink surface occurs, positioning the second surface adjacent to a second heat sink surface with a second gap between the second surface and the second heat sink surface such that thermal conduction from the second surface to the second heat sink surface occurs, providing a first flow of a first gas to the first gap and a second flow of a second gas to the second gap, whereby the first flow of the first gas and the second flow of the second gas contacts the glass contained in the at least one glass layer such that the glass is cooled by conduction more than convection, 25 ^ cooling the glass contained in the at least one glass layer to a temperature less than the glass transition temperature of glass contained in the at least one glass layer; assembling a plurality of liquid crystal panel component layers, each liquid crystal component layer comprising: the at least one glass layer; at least one interlayer; and at least one liquid crystal cell; substantially removing entrained air between at least some of the plurality of liquid crystal panel component layers to form a curable stack; and laminating the curable stack to form a liquid crystal panel such that the liquid crystal panel has a substantially uniform transmission.

2. The method of claim 1, wherein the first gap has a length of g1 and an area of Ag1, the second gap has a length of g₂ and an area of A_g2, the first gas has a heat capacity C_p1 and a thermal conductivity k₁, the second gas has a heat capacity C_p2 and a thermal conductivity k₂, wherein the first flow of the first gas has at a mass flow rate m₁, wherein m₁ is greater than zero and less than (2k₁A_g1)/(g₁C_p1), and wherein the second flow of the second gas has at a mass flow rate m₂, wherein m₂ is greater than zero and less than (2k₂A_g2)/(g₂C_p2).

3. The method of claim 1 or claim 2, wherein the laminating step further comprises heating the curable stack to a lamination temperature for a duration of time. 26 ^

4. The method of any one of claims 1 to 3, wherein the laminating step further comprises applying pressure to the liquid crystal panel component layers during lamination.

5. The method of any one of claims 1 to 4, wherein the uniform transmission comprises not greater than 1% disparity in a transmission region, as compared to adjacent transmission regions in the liquid crystal panel.

6. The method of any one of claims 1 to 4, wherein the uniform transmission comprises not greater than 2% disparity in a transmission region, as compared to adjacent transmission regions in the liquid crystal panel.

7. The method of any one of claims 1 to 6, wherein uniform transmission is detectable via visual observation.

8. The method of any one of claims 1 to 6, wherein uniform transmission is detectable via a spectrophotometer.

9. The method according to any one of claims 1-8, wherein the first gap and the second gap are about 100 μm or less.

10. The method according to any one of claims 1-9, wherein the first gas is air.

11. The method according to any one of claims 1-9, wherein the first gas is helium.

12. An article, comprising: at least two glass layers comprising glass, wherein each glass layer has a first layer surface and a second layer surface, the glass contained in each glass layer having a transition temperature, each glass layer is configured to be cooled at a temperature greater than the transition temperature at the start of the cooling, wherein cooling comprises: positioning the first layer surface adjacent to a first heat sink surface with a first gap between the first layer surface and the first heat sink surface such that thermal conduction from the first layer surface to the first heat sink 27 ^ surface occurs, the first gap having a length across the first gap of g1 and an area of the first gap of Ag1, positioning the second layer surface adjacent to a second heat sink surface with a second gap between the second sheet surface and the second heat sink surface such that thermal conduction from the second layer surface to the second heat sink surface occurs, the second gap having a length across the second gap of g2 and an area of the second gap of Ag2, providing a first flow of a first gas to the first gap and providing a second flow of a second gas to the second gap, the first gas having a heat capacity C_p1 and a thermal conductivity k₁, the second gas having a heat capacity C_p2 and a thermal conductivity k₂, the first flow provided at a mass flow rate ۦ₁ of the first gas, wherein ۦ₁ is greater than zero and less than (2k1Ag1)/(g1Cp), to the first gap, and at a mass flow rate ۦ2 of the second gas, wherein ۦ2 is greater than zero and less than (2k2Ag2)/(g2Cp2), to the second gap, whereby the first flow and the second flow contact each of the at least two glass layers, and each of the at least two glass layers is cooled, by conduction more than by convection, and sufficiently creating a surface compressive stress and a central tension of each of the at least two glass layers; at least two liquid crystal panel component layers, wherein each liquid crystal panel component layer is formed and comprises: a first glass layer of the at least two glass layers; a first interlayer; 28 ^ a liquid crystal cell; a second interlayer; a second glass layer of the at least two glass layers; wherein substantially removing entrained air between the at least two liquid crystal panel component layers forms a curable stack; and wherein laminating the curable stack forms a liquid crystal panel such that the liquid crystal panel has a substantially uniform transmission.

13. The article according to claim 12, wherein the first heat sink surface has multiple first apertures and the second heat sink surface has multiple second apertures, and wherein providing the first flow of a first gas to the first gap comprises flowing the first gas to the first gap only through the multiple first apertures and wherein providing a second flow of a second gas to the second gap consists of flowing the second gas to the second gap only through the multiple second apertures.

14. The article according to claim 13, wherein each aperture has a cross-sectional dimension of less than 0.5 mm.

15. The article according to claim 13, wherein each aperture has a cross-sectional dimension of less than 0.01 mm.

16. The article according to any one of claims 13-15, wherein at least some of the multiple apertures in the first and second heat sink surfaces are within 20 degrees of perpendicular to the respective first and second heat sink surfaces. 29 ^

17. The article according to any one of claims 12-16, wherein the first and second gaps are about 100 μm or less.

18. The article according to any one of claims 12-17, wherein the first gas is air.

19. The article according to any one of claims 12-17, wherein the first gas is helium.

20. The method according to any one of claims 1-8, further comprising the step of heating each glass layer principally by conduction through a gas from a heat source, wherein the step of heating each glass layer principally by conduction is being performed prior to the step of cooling. 30 ^