Multi-curved optical device and method for making same - Patents.com

Abstract

The optical device includes a low flexibility carrier having a multi-curved surface, a flexible liquid crystal film structure conformally provided on the multi-curved surface, and an adhesive interposed between the multi-curved surface and the liquid crystal film structure. The flexible liquid crystal film structure is laminated to the shape of the multi-curved surface. The carrier can be a window, a windshield, a cockpit, a display, a head-up display, a sunroof, a mirror, an augmented or virtual reality headset, goggles, a visor, a lens, a pair of glasses, or sunglasses.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority and any other benefit of U.S. Provisional Patent Application No. 63 / 262,277, entitled MULTICURVED OPTICAL DEVICES, AND METHODS FOR MAKING SAME, filed on October 8, 2021, the entire disclosure of which is hereby incorporated by reference in its entirety.

[0002] The present disclosure relates to optical devices, and in particular to optical devices that include multi-curved liquid crystal film structures. [Background technology]

[0003] Liquid crystal ("LC") devices offer a low-cost, low-power approach to active light management. Traditionally, they have been employed in display applications using glass substrates. Recently, curved displays have entered the market. There is a growing need for conformal devices, but products to date have been limited to cylindrical geometries (curved in one dimension). However, there is a large market for optical devices with curvature in two or more dimensions. Unfortunately, among other reasons, it is difficult to adapt flat devices to multi-surface configurations due to the need to modify area to meet topographical conditions.

[0004] Several solutions have been proposed to this problem. One solution is to create curved LC devices. This is possible by starting with multi-curved substrates. These substrates can be thermoformed to the desired curvature beforehand and then assembled (i.e. filled with the LC mixture) with traditional LC device manufacturing methods. However, there are two fundamental difficulties with this approach that have hindered growth. First, in order to keep the gap between the LC substrates constant, the curvature of the two substrates must be maintained within the tolerance of the LC device construction. This tolerance is only a few microns, making the fabrication of these substrates very difficult and costly. Furthermore, this tolerance must be the same regardless of size. This means that the curvature of the substrates needs to match over, for example, a meter for some applications. Holding a tolerance of a few microns over a meter is very difficult and expensive. Secondly, the difficulties associated with handling two multi-curved substrates significantly hinder large-scale production. Current production systems are designed to handle large areas of flat glass.

[0005] Another approach is to fabricate a flat LC device (i.e., a device with two substrates already assembled to maintain the desired gap, with or without the LC mixture), and then thermoform the device into the final curved configuration, as described in patents US 7,811,482, US 7,705,959, and US 7,102,602. While the thermoforming method has offered some success in limited applications, the temperature of the LC device must be above the glass transition temperature of the substrates, which creates a new set of challenges associated with maintaining the structural integrity of the LC device during such heating. Solutions to this new problem generally require modifying key features of the device itself, for example, using gel-type materials as used in suspended particle devices (SPDs), or adding polymers to avoid gap changes, such as in polymer dispersed liquid crystal (PDLC) devices, but such changes in device architecture may sacrifice important performance attributes. Furthermore, it should be noted that the glass transition temperature of many plastic substrates is higher than the nematic to isotropic transition temperature of the liquid crystal. Thus, thermoforming is performed while the liquid crystal is in a different (e.g., isotropic) phase. This can lead to non-uniformity in the final device after it is returned to operating temperature due to changes in the physical properties of the liquid crystal in the isotropic phase.

[0006] There is a need for multi-curved small and large area LC devices that do not have the drawbacks associated with thermoformed LC devices. To this end, therefore, new approaches are needed to realize multi-curved devices with high optical clarity / low haze and low driving voltages. Summary of the Invention [Means for solving the problem]

[0007] According to some embodiments of the present disclosure, an optical device includes a low flexibility carrier having a multi-curved surface, a flexible liquid crystal film structure conformally provided on the multi-curved surface, and an adhesive interposed between the multi-curved surface and the liquid crystal film structure. The flexible liquid crystal film structure is laminated to the shape of the multi-curved surface. The carrier can be a window, a windshield, a cockpit, a display, a head-up display, a sunroof, a mirror, an augmented or virtual reality headset, a goggle, a visor, a lens, a pair of glasses, or a pair of sunglasses.

[0008] According to some embodiments of the present disclosure, there is provided a method of making an optical device, the method comprising: providing a low-flex carrier having a multi-curved surface; and providing a flexible liquid crystal film structure. The flexible liquid crystal film structure may comprise a first flexible substrate and a second flexible substrate spaced apart from the first flexible substrate to form a gap designed to contain the electro-optical material, an outer surface of the first flexible substrate corresponding to the first surface of the flexible liquid crystal film structure, and an outer surface of the second flexible substrate corresponding to the second surface of the flexible liquid crystal film structure. The method further comprises applying an adhesive to i) the multi-curved surface, ii) the first surface of the flexible liquid crystal film structure, or iii) both (i) and (ii). The carrier is aligned to the flexible liquid crystal film structure, and pressure is applied between the multi-curved surface and the first surface of the flexible liquid crystal film structure to mold the flexible liquid crystal film structure according to the multi-curved surface of the carrier. The method further comprises conformally adhering the molded flexible liquid crystal film structure to the multi-curved surface. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective schematic diagram of an optical device according to some embodiments of the present disclosure. [Diagram 2] 1A-1C are cross-sectional views illustrating flexible liquid crystal film structures according to some embodiments of the present disclosure. [Diagram 3] 1 is a perspective schematic diagram of a multi-curved surface according to some embodiments of the present disclosure. [Figure 4]1 is a perspective schematic diagram of a multi-surface and a projected virtual area according to some embodiments of the present disclosure. [Diagram 5] 1 is a cross-sectional view of an optical device according to some embodiments of the present disclosure. [Figure 6] 1 is a cross-sectional view of an optical device according to some embodiments of the present disclosure. [Figure 7] FIG. 1 is a block diagram illustrating steps for creating an optical device according to some embodiments of the present disclosure. [Figure 8A] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 8B] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 8C] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 8D] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 8E] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 8F] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 8G] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 9A] 2 is a cross-sectional view of a roller according to some embodiments of the present disclosure. [Figure 9B] 2 is a cross-sectional view of a roller according to some embodiments of the present disclosure. [Figure 10A] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 10B] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 10C] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 10D] 1A-1C are a series of cross-sectional views illustrating configurations of optical devices according to some embodiments of the present disclosure. [Figure 11] 1 is a cross-sectional view of an optical device according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Various techniques relating to multi-curved optical devices and methods for making them will now be described with reference to the drawings, it being understood that the drawings are for purposes of illustrating the concepts of the disclosure and may not be to scale.

[0011] 1 is a perspective schematic diagram of an optical device according to some embodiments of the present disclosure. The optical device 80 includes a carrier 60 having a multi-curved surface 62 including at least a first curvature 62-1 along a first axis and a second curvature 62-2 along a second axis. The optical device 80 further includes a flexible liquid crystal film structure 10 conformally provided on the multi-curved surface 62. An intervening adhesive 40 bonds the flexible liquid crystal film structure 10 to the multi-curved surface 62. The flexible liquid crystal film structure is laminated to the shape of the multi-curved surface. Additional details about each of these elements are provided below.

[0012] FIG. 2 is a cross-sectional view illustrating a flexible liquid crystal film structure 10 according to some embodiments of the present disclosure. In some embodiments, the flexible liquid crystal film structure can be a variable transmission device that can be used to darken windows, visors, AR / VR goggles, glasses, or the like, as described elsewhere herein. The flexible liquid crystal film structure 10 includes a first substrate 12 and a second substrate 14. The outer surface of the first substrate 12 corresponds to a first surface 13 of the flexible liquid crystal film structure 10. The outer surface of the second substrate 14 corresponds to a second surface 15 of the flexible liquid crystal film structure 10. Depending on the application, the substrates can be optionally coated with a conductive layer 16. Optically transparent conductive layers include indium tin oxide (ITO), conductive polymers, conductive nanowires, and the like. Alternatively or additionally, the substrates can also be coated with an alignment layer 18, such as polyimide or the like.

[0013] Substrates 12 and 14 are made of transparent flexible materials such as transparent plastics or flexible glass suitable for constructing flexible liquid crystal film structural units, sometimes referred to as "cells". Substrate 12 may be the same as or different from substrate 14 in terms of chemical composition, thickness, optical clarity or other characteristics. Suitable plastics include, for example, polycarbonate (PC), polycarbonate and copolymer blends, polyethersulfone (PES), polyethylene terephthalate (PET), cellulose triacetate (TAC), polyamide, p-nitrophenyl butyrate (PNB), polyetheretherketone (PEEK), polyethylene aphthalate (PEN), polyetherimide (PEI), polyarylate (PAR), polyvinyl acetate, cyclic olefin polymer (COP) or other similar plastics known in the art. Flexible glass includes materials such as Corning® Willow® Glass and the like. When flexible liquid crystal film structures are laminated to multiple curved surfaces, plastic substrates are generally preferred herein. Many of these substrates are commercially available, for example from Mitsubishi Plastics or Teijin DuPont Films, and may come standard with various optional coatings, such as hard coats. As used herein, "transparent" means a material that has greater than 45% transmittance for visible radiation having wavelengths between 450 nm and 700 nm. In some examples, a transparent substrate may have a transmittance of 50%, 60%, 70%, or 80%. In some embodiments, substrate 14 may have a higher light transmittance or lower haze than substrate 12. In some embodiments, one or both substrates comprise a flexible polymeric material that has an ultimate tensile strength of less than 300 MPa, alternatively less than 200 MPa, or even less than 100 MPa. In some embodiments, one or both substrates comprise a plastic polymeric material having an ultimate tensile strength in the range of 20-50 MPa, 50-100 MPa, 100-150 MPa, 150-200 MPa, 200-300 MPa, 300-500 MPa, or any combination of ranges therein.In some embodiments, one or both substrates comprise a flexible polymeric material having a Young's modulus of less than 10 GPa, alternatively less than 5 GPa.

[0014] In some embodiments, the thickness of substrate 12 or 14 can be in the range of 10-20 μm, 20-30 μm, 30-40 μm, 40-50 μm, 50-75 μm, 75-100 μm, 100-150 μm, 150-200 μm, 200-250 μm, 250-300 μm, 300-350 μm, 350-400 μm, 400-450 μm, 450-500 μm, 500-600 μm, 600-800 μm, 800-1000 μm, or any combination of adjacent ranges thereof.

[0015] The substrates 12, 14 are generally separated by a controlled gap 25 or distance, which in some embodiments may be maintained by a spacer 24. The volume between the substrates is filled with an electro-optic material ("EOM") 26.

[0016] Spacers 24 may be used to maintain a controlled distance or gap between the substrates. In some embodiments, the controlled gap 25 is within the range of 3-4 μm, alternatively 4-5 μm, 5-6 μm, 6-7 μm, 7-8 μm, 8-9 μm, 9-10 μm, 10-12 μm, 12-14 μm, 14-16 μm, 16-18 μm, 18-20 μm, 20-25 μm, 25-30 μm, 30-40 μm, 40-50 μm, 50-60 μm, 60-80 μm, 80-100 μm, or any combination of adjacent ranges thereof. A "controlled" gap or distance means that the variation in the distance between the substrates should remain less than an average of 30% of the spacer diameter (which determines a controlled gap). In some embodiments, the variation is less than 25%, 20%, 15%, 10%, or 5% of the spacer diameter. In some embodiments, the gap across the active area of ​​the liquid crystal film structure is maintained at 30% of the average gap measured across the active area.

[0017] Generally, according to various embodiments of the present disclosure, two types of spacers can be used to maintain a controlled distance between the substrates. One category includes "patterned spacers" which are spacers that are intentionally placed or created on the substrate to form a predetermined pattern, or they are created using photolithography or similar methods known in the art to generate a desired pattern. Examples include polymer walls. In some cases, the patterned spacers can have a length and width larger than the flexible liquid crystal film structure gap, i.e., they have an aspect ratio of the long side to the flexible liquid crystal film structure gap that is >20 in a pattern that can generate a visible pattern in the device, which may be undesirable.

[0018] Another category includes "unpatterned spacers," defined herein as spacers that are randomly (e.g., sprayed) or printed so as not to produce optical aberrations such as diffraction patterns or the like. Unpatterned spacers of the present disclosure can be spherical, or they can be rectangular with an aspect ratio (length / width) of less than 30 / 1, 20 / 1, 10 / 1, 5 / 1, 4 / 1, or 3 / 1. Spacers are used to maintain a distance between the substrates of 3-100 μm, preferably 4-20 μm, or 5-10 μm.

[0019] As used herein, a "diffraction pattern" refers to a periodic light pattern that results from the propagation of light through a periodic structure whose spacing is less than 100 times the wavelength of the incident light, i.e., when the periodicity of the repeating pattern (e.g., spacers or AGCs) is less than 100 times the wavelength of the light.

[0020] In some embodiments, device performance is better when the substrate is covered with a greater density of smaller spacers than when long patterned spacers are placed at selected locations. In some embodiments, the spacer count is measured in square millimeters (mm 2) is at least 80 per

[0021] In some embodiments, the spacers 24 may be pre-applied to the substrate (e.g., a sheet is pre-coated with spacers) or may be applied to the substrate during the EOM filling process, e.g., during a roll-filling process. For example, the spacers 24 may be sprayed or coated onto a layer in which the spacers are randomly arranged or arranged in a diffraction-generating pattern. They may be dispersed using wet or dry methods as known in the art. The spacers may be placed on top of or sprayed onto the alignment layer (18 in FIG. 2) or may be placed within the alignment layer. In some embodiments, the spacers may include adhesive elements, e.g., they may be coated with an adhesive layer (not shown).

[0022] The spherical spacers differ from spherically encapsulated liquid crystals as described in patent application PCT / US1982 / 001240 (WO / 1983 / 001016), entitled "Encapsulated Liquid Crystal and Method," by FERGASON, because they do not encapsulate any volume of the EOM.

[0023] In certain embodiments, the spacers 24 may be deposited within or as part of the alignment layer 18, such that they are applied when the alignment layer is applied to one or both substrates. In other embodiments, the spherical spacers 24 may be incorporated within the electro-optic material that is deposited on the substrate.

[0024] In some embodiments, the flexible liquid crystal film structure 10 further includes a boundary seal (edge ​​seal) 27 / 28, which contains the EOM 26 within the flexible liquid crystal film structure and forms a barrier between the external environment and the EOM, preventing the EOM 26 from flowing out of the flexible liquid crystal film structure and preventing environmental factors (air, moisture, debris) from entering the flexible liquid crystal film structure. In some examples, the boundary seal 27 / 28 is formed by applying a boundary sealant to one or both of the substrates 12, 14, which when cured together, forms a boundary seal around the EOM contained within the flexible liquid crystal film structure. In some embodiments, the active area or portion of the flexible liquid crystal film structure corresponds to the area where the EOM is confined by the boundary seal.

[0025] Methods for including an EOM in a flexible liquid crystal film structure 10 are well known in the art. For example, in some embodiments, the EOM 26 can be injected into the gaps of the flexible liquid crystal film structure 10 using a vacuum filling process or a single drop filling process. For a vacuum filling process, the edge seal around the flexible liquid crystal film structure 10 is not yet continuous and has an opening called a "fill hole". The flexible liquid crystal film structure 10 is then placed in a vacuum chamber to evacuate the air in the flexible liquid crystal film structure 10. After this step, while still under vacuum, the EOM 26 is introduced into the fill hole. The EOM then fills the gaps in the flexible liquid crystal film structure 10 due to capillary forces. This can be accelerated by bringing the flexible liquid crystal film structure 10 to atmospheric pressure after the EOM is introduced into the fill hole. Once the EOM fills the gaps in the flexible liquid crystal film structure, the process is complete. In some cases, the amount of EOM in the flexible liquid crystal film structure 10 may be larger than the expected volume to avoid future problems (e.g., shrinkage, bubble formation, etc.). In such cases, the flexible liquid crystal film structure 10 is then pressed to remove the excess EOM by a process called "cold pressing". The fill holes are then sealed, for example, by using epoxy to prevent air from entering the flexible liquid crystal film structure.

[0026] The EOM filling process, called single drop filling or ODF, is well known in the art and can be used to fill flexible liquid crystal film structures.

[0027] In some embodiments, the EOM 26 may be introduced using a roll-filling method, such as that disclosed in U.S. Pat. No. 11,435,610 (Miller et al.), the entire contents of which are incorporated herein by reference for all purposes.

[0028] 2 illustrates the variation of the border seal 27 / 28 in response to various coatings on the substrates 12, 14 when the border seal is applied. In FIG. 2, on one side, the border seal 27 seals the flexible substrates 12, 14 together. Alternatively, the border seal configuration can be as depicted on the other side of the flexible liquid crystal film structure 10, with the border seal 28 sealing the gap between the alignment 18 and / or conductive layer 16. The particular arrangement will depend on the timing and method of application of the border seal and filling of the EOM 26.

[0029] The border seal 27 / 28 can be applied using any technique known in the art, including but not limited to using a brush, roller, film or pellet, spray gun, applicator gun, screen printing, inkjet printing, flexographic printing, flat coating, roller pressing, or heat pressing, or any combination thereof. All of these can be done manually or automated into a machine, or combinations thereof. The border seal can be a suitable adhesive (UV, heat, chemical, pressure, multi-component epoxy, and / or radiation cured), polyisobutylene or acrylate based sealant, etc., or a pressure sensitive adhesive, two-component adhesive, moisture curing adhesive, etc. Other types of border (edge) seals can consist of metalized foils or other barrier foils bonded to the edges of the flexible liquid crystal film structure. It has been found that hybrid radiation and heat cured sealants (i.e. UV curable with thermal post bake) can offer certain advantages. In some embodiments, Threebond 30Y-491 material (from Threebond Corporation, Cincinnati, Ohio) may be particularly useful due to its favorable water vapor barrier properties, low viscosity at high temperatures for easy deposition of edge seal materials, good wetting characteristics, and manageable cure characteristics. Those skilled in the art and familiar with advanced sealants will be able to identify other sealants that provide comparable performance.

[0030] The flexible liquid crystal film structure 10 is filled with an electro-optic material (EOM) 26. The electro-optic material may be any material that responds to an electric field applied across the flexible liquid crystal film structure to have the desired operating characteristics intended for the device, including any material that can be altered by the application of a current or voltage. For example, the EOM may be one or a combination of liquid crystal materials, electrochromic materials, suspended particle devices (SPDs), other additives such as dyes (dichroic dyes, pleochroic dyes, etc.), etc., where the electro-optic material can be altered by the application of a current or voltage. In a preferred embodiment, the EOM is a guest-host liquid crystal dichroic dye mixture.

[0031] In some embodiments, the electro-optic material is generally non-polymeric, non-encapsulated, and non-individualized, and thus in these embodiments, EOM excludes polymeric or encapsulated liquid crystal compositions such as PDLC, PELC, PSCT, PNLC, NCAP, or the like.

[0032] As used herein, "non-polymerizable" means an EOM composition that does not contain the amount of chemical components (e.g., polymer precursors) necessary to dimensionally stabilize the EOM layer by changing the phase of the material to a solid, semi-solid, gel, etc. A non-polymerizable EOM contains less than 10% polymerizable material.

[0033] By "non-individualized" it is meant an EOM that is not divided into separate, distinct compartments, such as by encapsulation, polymer walls, polymer networks, patterned spacers, or the like.

[0034] "Non-encapsulated" means an EOM that is not contained within the interior or volume of a capsule. A capsule refers to a containment device or medium that confines a quantity of an EOM, such as a liquid crystal, such that an "encapsulated EOM" is a quantity of EOM that is confined or contained within an encapsulation medium, e.g., a polymer capsule. A capsule may have a spherical shape or any other suitable shape. Encapsulated EOMs (e.g., encapsulated liquid crystals) are created to prevent them from flowing. Some non-limiting examples of encapsulated EOMs include polymer dispersed liquid crystals (PDLCs), which consist of droplets of liquid crystal within a polymer network.

[0035] For example, a method of microencapsulation has been described by FERGASON in Patent No. 4,435,047, entitled "Encapsulated liquid crystal and method" (1984), and in Patent Application PCT / US1982 / 001240 (WO / 1983 / 001016), entitled "Encapsulated Liquid Crystal and Method". In this method, a resin material is used to encapsulate liquid crystal (LC) material, forming curved, spherical capsules that contain discrete amounts of the LC material. These are created by mixing together the LC material and an encapsulation medium (e.g., a resin) in which the LC material is insoluble, allowing the formation of individual capsules that contain the LC material. In microencapsulation, the liquid crystal is mixed with a polymer dissolved in water. When the water evaporates, the liquid crystal is enveloped in the polymer. Many small "capsules" are produced and dispersed throughout the bulk polymer. The material produced by encapsulation is called NCAP, or nematic curvilinearly aligned phase.

[0036] In alternative embodiments, the EOM may include mesogenic polymerizable components such as those found in PNLC or PSCT and the like.

[0037] In yet other embodiments, the EOM may include polymeric materials, such as those found in PDLC or NCAP, created using commonly known processes such as PIPS (polymerization induced phase separation), SIPS (solvent induced phase separation), TIPS (temperature induced phase separation), or the like.

[0038] In some embodiments, for example when the flexible liquid crystal film structure size is large, in addition to the unpatterned spacers, the flexible liquid crystal film structure may include one or more adhesive gap control elements or AGCs. The AGCs are adhesive elements placed randomly or in a non-diffractive pattern to assist in bonding the two flexible liquid crystal film structure substrates 12, 14. In some embodiments, the AGC elements are walls that form a matrix within the flexible liquid crystal film structure unit but do not divide the flexible liquid crystal film structure in terms of its electrical connectivity, i.e., the flexible liquid crystal film structure and its EOM are activated by a single electrical connection, and the flexible liquid crystal film structure or the entire device is not pixelated or segmented.

[0039] In other embodiments, if the conductive layer 16 (e.g., ITO) contains segmented regions, the AGC may be used to separate the segments (i.e., the AGC coincides with the segment boundaries). In yet other embodiments, if the conductive layer contains segmented regions, the AGC may not coincide with the ITO segment boundaries.

[0040] In some embodiments, the EOM comprises a "guest-host" liquid crystal dye mixture, the mixture comprising an amount of one or more dichroic dyes "guest" mixed in a liquid crystal "host" solution. The liquid crystal "host" molecules have an orientation axis that can be altered by adjusting the voltage applied across the substrate. The "guest" dye mixture comprises one or more dichroic dyes that dissolve in the liquid crystal host, align with the orientation of the liquid crystal molecules, and whose absorption of polarized light is strongly dependent on the polarization direction relative to the absorption dipole of the dye molecules. The applied voltage results in switching between a first state in which the guest-host orientation allows maximum light transmission, referred to herein as the "clear state," a second state in which the guest-host orientation allows minimum light transmission, referred to herein as the "dark state," and a combination of intermediate states between the completely clear and completely dark states. Depending on the composition of the guest-host mixture, the clear state can occur at zero voltage (off state). Alternatively, the mixture can be formulated such that zero voltage (off state) corresponds to the dark (minimum transmission) state. In some embodiments, the EOM may further optionally include a photochromic (PC) dye or a photochromic dichroic (PCDC) dye whose light absorbance can be activated by exposure to UV light, such as sunlight. In some embodiments, the EOM may further include a small amount of a conventional absorbing dye, for example, to provide the device with a desired overall hue in the clear state.

[0041] Flexible liquid crystal film structures incorporating guest-host liquid crystal dye mixtures are particularly suitable for manufacturing according to the methods described herein due to their greater tolerance to variations in the flexible liquid crystal film structure gap, i.e., they are more tolerant and can perform well even with slight variations in the flexible liquid crystal film structure gap (within a tolerance such as ±5%, 10%, 15%, 20%, 25%, or even 30% of the spacer diameter) compared to flexible liquid crystal film structures that rely on phase retardation, such as polarizer-based LC devices, where the tolerance or variation in the flexible liquid crystal film structure gap must be kept to less than 1%.

[0042] In some embodiments, the guest-host liquid crystal dye mixtures described above are used to attenuate light in an optical device (e.g., where the carrier is a pair of glasses, AR or VR goggles, a visor, a window, a windshield, a cockpit, or the like).

[0043] In operation, for example, a flexible liquid crystal film structure can be achieved that has a clear state (maximum transmittance) at zero voltage (OFF state) where the guest-host liquid crystal dye mixture has homeotropic alignment (i.e., perpendicular to the substrate). When no voltage is applied, the liquid crystal host has negative dielectric anisotropy and the dichroic dye has positive dichroism, i.e., maximum absorption when polarized light is parallel to the long molecular axis of the dye molecules and minimum absorption when polarized light is perpendicular to the long axis. In such a device, upon application of voltage (ON state), the guest-host mixture adopts a planar or homogeneous alignment, i.e., a configuration parallel to the substrate, resulting in a state of maximum light absorption (dark). Such configurations can be used, for example, in goggles, eyewear, visors, etc., where it may be desirable to "darken" the device in response to an applied voltage when bright light is present. Other applications include windows (vehicles, buildings, aircraft, etc.), sun / moon roofs, display devices, and the like.

[0044] In another embodiment, reverse alignment can be implemented such that a guest-host liquid crystal dye mixture can have planar alignment (homogeneous) in the dark state when the applied voltage is off, and homeotropic alignment in the clear state when a voltage is applied. This can be achieved by using a planar surface treatment of the alignment layer in conjunction with a dye with positive dichroism and a liquid crystal material with positive dielectric anisotropy. Such an arrangement may be used, for example, in windows or sunroofs where it is desirable for the device to be normally in a "dark" state, but be able to be switched to a clear state by application of a voltage.

[0045] 2, the flexible liquid crystal film structure 10 may be connected to a control circuit 30 for applying an electric field or voltage across the flexible liquid crystal film structure. The voltage source may be either AC or DC.

[0046] In some embodiments, the flexible liquid crystal film structure 10 has a thickness 29 in the range of 100-150 μm, 150-200 μm, 200-250 μm, 250-300 μm, 300-350 μm, 350-400 μm, 400-450 μm, 450-500 μm, 500-600 μm, 600-700 μm, 700-800 μm, 800-900 μm, 900-1000 μm, or any combination of adjacent ranges thereof.

[0047] glue Pressure Activated Adhesive In some cases, the adhesive may be a pressure activated adhesive ("PAA"), which is a material that increases its tack or adhesiveness when pressure is applied. In some embodiments, the PAA includes a viscoelastic polymer and optionally a tackifier. The PAA may include an acrylate polymer, a silicone polymer, a natural rubber, or a thermoplastic elastomer. The PAA may further include a resin (e.g., rosin and its derivatives, terpenes and modified terpenes, aliphatic, cycloaliphatic, and aromatic resins (C5 aliphatic resins, C9 aromatic resins, and C5 / C9 aliphatic / aromatic resins), hydrogenated hydrocarbon resins, and mixtures thereof, terpene phenolic resins (TPR, frequently used in ethylene vinyl acetate adhesives), or Novolacs). The PAA may be moisture resistant.

[0048] In some embodiments, PAA is supplied as a roll and provided between a backing and a release layer, both of which are removed when used as described below. When using PAA, the application of heat or UV radiation is generally not required. However, in some embodiments, heat or UV or some other treatment process may be used in a post-lamination step to further stabilize the system.

[0049] Curable adhesive In some embodiments, the adhesive may be formed from a curable material or precursor that contains chemically reactive functional groups or components that cause a change in the adhesive during the curing step. The curing step may include heat treatment, UV irradiation, mixing of components, exposure to air, or some other curing process. Curing by heat treatment should be done at a temperature that is compatible with the flexible liquid crystal structure. In some cases, curing causes polymerization or other reactions that form an adhesive that can bond the liquid crystal film structure to the carrier. For example, the curable material may include epoxies, cyanoacrylates, acrylic esters, alkylene vinyl acetates, or other curable reactive materials. The curable material itself may be in the form of a liquid, gel, or preformed film. In some embodiments, the curable adhesive may be used in conjunction with PAA.

[0050] Hot Melt Adhesives In some embodiments, the adhesive may be a hot melt adhesive that does not require curing, but is activated by exposure to high temperatures to cause softening and / or melting. Some non-limiting examples of hot melt materials include polyolefins and thermoplastic polyurethanes. For example, a hot melt film may be provided between the liquid crystal film structure and the carrier. Upon application of heat and pressure, the hot melt film softens to form an adhesive film (adhesive). Some typical heating temperatures are 50°C, 60°C, 80°C, or even 100°C or higher. Generally, the heating temperature or time is selected to be effective and compatible with the EOM and flexible liquid crystal film structure. For example, the liquid crystal EOM and / or substrate may be selected to accommodate such high temperatures. However, such selection may limit the design freedom for creating the flexible liquid crystal film structure, so in some cases, hot melt adhesives may be less preferred. Hot melt adhesives may be used in combination with PAA.

[0051] The adhesive may have a thickness of 10-15 μm, 15-20 μm, 20-25 μm, 25-30 μm, 30-40 μm, 40-50 μm, 50-60 μm, 60-70 μm, 70-80 μm, 80-90 μm, 90-100 μm, 100-125 μm, 125-150 μm, 150-175 μm, 175-200 μm, 200-250 μm, 250-500 μm, or any combination of adjacent ranges thereof.

[0052] In some embodiments, rather than using a single layer of adhesive material, multiple sub-layers of adhesive may be stacked to form adhesive 40. Such sub-layers may have the same or different chemical compositions or thicknesses. For example, a first PAA may adhere better to a flexible liquid crystal film structure, a second PAA may adhere better to a carrier, and the first and second PAA sub-layers adhere well to each other.

[0053] In some cases, the adhesive should be able to form a relatively uniform film between the multi-curved surface 62 and the first surface 13 of the flexible liquid crystal film structure 10. In some embodiments, "relatively uniform" means having a thickness that has a variation within 30% of the average thickness, or within 20%, 15%, or 10%. In some embodiments, the PAA is optically clear.

[0054] In some embodiments, the adhesive and liquid crystal film structure collectively transmit at least 40% of visible light in the wavelength range of 450 nm to 700 nm, or transmit at least 50%, 60%, 70%, 80%, 85%, or 90%. In some embodiments, the adhesive and liquid crystal film structure collectively provide a haze value of less than 15%, 10%, 7%, 5%, 3%, 2%, or 1% in the off or maximum transmission state. In some embodiments, the ratio of the average thickness of the adhesive to the average thickness of the liquid crystal film structure is less than 10, 8, or 5.

[0055] Multi-surface and carrier As mentioned, the carrier includes a polycurved surface. The polycurved surface of FIG. 1 is only one of many possible examples. As used herein, "polycurved surface" refers to a non-planar shape having a compound curve, also referred to as a non-developed shape, including but not limited to spherical, aspherical, toroidal, etc., having different curvatures along two orthogonal axes (horizontal and vertical axes), such as toroidal, spheroidal, oblong, oblong, or saddle shapes or surfaces in which the principal curvatures of the surface along two orthogonal planes are opposite, such as a horse or monkey saddle. Other examples of polycurved surfaces include but are not limited to elliptical hyperboloids, hyperbolic paraboloids, and spherocylindrical surfaces, and polycurved surfaces may have constant or varying radii of curvature. Polycurved surfaces may also include segments or portions of such surfaces, or may be composed of combinations of such curves and surfaces. In some embodiments, polycurved surfaces may have radii of curvature along two orthogonal axes. In various embodiments, polycurved surfaces may be asymmetric.

[0056] 3, the multi-curved surface 62 may be characterized as having a first curvature 62-1, possibly having a first height H1 and a first length L1 measured along a first direction, with a first curvature ratio C1=H1 / L1. The multi-curved surface may be further characterized as having a second curvature 62-2, possibly having a second height H2 and a second length L2 measured along a second direction different from the first direction, with a second curvature ratio C2=H2 / L2. In some embodiments, the second direction may be orthogonal to the first direction. Although the curvature height is shown as a positive value measured above an imaginary plane formed by L1 and L2, in some embodiments, one or both of C1 and C2 may be negative where the height is a distance below the plane. In some embodiments as shown in FIG. 3, L1 and L2 may correspond to the entire point-to-point length corresponding to the portion intended for lamination with a flexible liquid crystal film structure. In some embodiments, L1 and L2 may instead correspond to a portion of a polysurface that defines a length between inflection points in the curve. In some embodiments, both C1 and C2 are non-zero, and the absolute value of at least one or optionally both of C1 and C2 is less than 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4. 0.3, 0.2, 0.1, 0.05, 0.02, 0.01, 0.005, 0.002, or 0.001. Alternatively, the curvature at any point may be described in terms of a local "diopter", defined as D=0.5 / R, where R is the radius of curvature in any one direction at the point measured in meters. In some cases, D in any one direction may be less than 8, 7, 6, 5, 4, 3, 2, 1, 0.5, or 0.2.

[0057] In some embodiments, the multi-curved surface 62 may be characterized by a first curvature 62-1 curved to a first value greater than 0 diopters and a second curvature 62-2 curved along a different axis than the first curvature to a second value greater than 0 diopters. In some embodiments, the second curvature may be orthogonal to the first curvature. One or both of the first and second values ​​are less than 10, 8, 6, 5, 4, 3, 2, or 1.

[0058] 4, the surface area 62A of the multi-curved surface 62 is larger than the imaginary area 62V defined by the projection of the multi-curved surface onto a flat surface. Relative to the imaginary area 62V, the surface area 62A is 0.1-0.2%, 0.2-0.3%, 0.3-0.4%, 0.4-0.5%, 0.5-0.6%, 0.6-0.7%, 0.7-0.8%, 0.8-1.0%, 1.0-1.2%, 1.2-1.4%, 1.4-1.6%, 1.6-1.8%, 1.8-2.0%, 2.0-2.2%, 2.2-2.4%, 2.4-2.8%, 2.8-2.9%, 2.9-3.0%, 3.0-3.1%, 3.0-3.2%, 3.0-3.3%, 3.0-3.4%, 3.0-3.5%, 3.0-3.6%, 3.0-3.7%, 3.0-3.8%, 3.0-3.9%, 3.0-3.8%, 3.0-3.9%, 3.0-3.1%, 3.0-3.2%, 3.0-3.3%, 3.0-3.4%, 3.0-3.5%, 3.0-3.6%, 3.0-3.7%, 3.0-3.8%, 3.0-3.9%, 3.0-3.9%, 3.0-3.1%, 3.0-3.2%, 3.0-3.2%, 3.0-3.2%, 3.0-3.3%, 3.0-3.4%, 3.0-3.5%, 3.0-3.5%, 3.0-3.6%, 3.0-3.7%, The range may be greater than 0.5%, 2.5-3.0%, 3.0-3.5%, 3.5-4.0%, 4.0-4.5%, 4.5-5%, 5-6%, 6-7%, 7-8%, 8-9%, 9-10%, 10-11%, 11-12%, 12-13%, 13-14%, 14-15%, 15-20%, or any combination of adjacent ranges thereof.

[0059] The flexible liquid crystal film structure is laminated into the shape of a multi-curved surface by a lamination process described below. The flexible liquid crystal film structure subjected to lamination may be referred to as a laminated liquid crystal film structure herein. The laminated liquid crystal film structure may have a changed surface area relative to the original flexible liquid crystal film structure. In some cases, the active portion of the laminated liquid crystal film structure may cover the entire carrier. In some embodiments, the active portion of the laminated liquid crystal film structure may cover only a portion of the carrier.

[0060] In some non-limiting examples, the carrier may function as a window, a windshield, a cockpit, a display, a head-up display, a sunroof, a mirror, a headset (e.g., an augmented reality or virtual reality headset), goggles, a visor, a lens, glasses (e.g., including sunglasses or AR / CR glasses), or some other eyewear. While there are no particular limitations on the carrier, in most embodiments, the carrier transmits (or reflects, if a mirror) at least 10% of visible light in the wavelength range of 450 nm to 700 nm. In some embodiments, the carrier transmits at least 40%, 50%, 60%, 70%, 80%, 90%, or 95% of visible light in the wavelength range of 450 nm to 700 nm. In some embodiments, the carrier may transmit light or may reflect light with low light scattering. In some cases, the carrier may have an intentionally cloudy appearance or scattered light, for example, similar to a privacy window. In some cases, the carrier may appear clear or colorless, but in some embodiments, the carrier may have a hue or color. Generally, at least a portion of the carrier to which the liquid crystal film structure is attached has less flexibility than the liquid crystal film structure, i.e., a "low-flexibility carrier." A low-flexibility carrier may include a carrier material (e.g., glass, metal, certain plastics, or composite materials) having a Young's modulus of at least 10 GPa, or alternatively at least 20 GPa, 30 GPa, 40 GPa, 50 GPa, 60 GPa, 70 Gpa, 80 GPa, or 90 Gpa. In some embodiments, a low-flexibility carrier may be characterized as having a shear modulus of at least 10 GPa, or alternatively at least 20 GPa. In some embodiments, the thickness of the adhesive and the liquid crystal film structure combined is less than 2%, 1%, 0.5%, or 0.2% of the maximum length of the carrier in any dimension on which the liquid crystal film structure is provided.

[0061] In some embodiments, the optical device may include more than one liquid crystal film structure. For example, FIG. 5 is a cross-sectional view of an optical device 180 similar to that shown in FIG. 1, having a carrier 160 with a multi-curved surface 162, an adhesive layer 140 on the multi-curved surface 162, and a first flexible liquid crystal film structure 110-1 with a first surface 113 provided on the adhesive. This cross-section shows only the first curvature 162-1. The first flexible liquid crystal film structure 110-1 may be as described above, including first and second substrates, EOMs, spacers, alignment layers, conductive layers, and other features, which are omitted for clarity. In FIG. 5, the optical device further includes an adhesive layer 145 on the multi-curved second surface 115 of the first flexible liquid crystal film structure 110-1. The adhesive layer 145 may be the same as or different from the adhesive layer 140. A second flexible liquid crystal film structure 110-2 may be provided on the adhesive layer 145. The second flexible liquid crystal film structure may be the same or different from the first flexible liquid crystal film structure in terms of materials, physical properties and / or functions. The second flexible liquid crystal film structure may be laminated to the shape of the multi-curved second surface 115 of the first flexible liquid crystal film structure.

[0062] In some embodiments, the optical device may have a flexible liquid crystal film structure on the opposite side of the carrier. For example, FIG. 6 is a cross-sectional view of an optical device 280 similar to that shown in FIG. 1 with a carrier 260 having a multi-curved surface 262, an adhesive layer 240 on the multi-curved surface 262, and a first flexible liquid crystal film structure 210-1 having a first surface 213 provided on the adhesive. This cross-section shows only the first curvature 162-1. The first flexible liquid crystal film structure may be as described above, including first and second substrates, EOMs, spacers, alignment layers, conductive layers, and other features, which are omitted for clarity. In FIG. 6, the optical device further includes an adhesive layer 245 in contact with an opposite surface 264 of the carrier. The opposite surface 264 may be flat, curved, or multi-curved. The adhesive layer 245 may be the same as or different from the adhesive layer 240. A second flexible liquid crystal film structure 210-2 may be provided in contact with the adhesive layer 245. The second flexible liquid crystal film structure may be the same as or different from the first flexible liquid crystal film structure in terms of materials, physical properties or functions.

[0063] Lamination formation The various steps result in a laminated liquid crystal film structure and may be collectively referred to herein as lamination. As described herein, lamination generally involves the use of adhesives and the application of pressure to change the shape of the flexible liquid crystal film structure, but does not involve temperatures approaching the transition temperatures of the flexible liquid crystal film structure, such as the substrate glass transition temperature or Tg or the EOM nematic isotropic transition temperature (TNI) or both. In some embodiments, the steps used to laminate with the flexible liquid crystal film structure may be performed at a temperature at least 10° C. lower than the substrate Tg or EOM (TNI). In some cases, the steps used to laminate with the flexible liquid crystal film structure may be performed at a temperature less than 70° C., or even less than 60° C., 50° C., 40° C., 30° C., or 20° C. Such steps may be optionally performed at room temperature (e.g., within the range of 15-25° C.). These temperature ranges may correspond to temperatures measured at the flexible liquid crystal film structure itself. In some cases, the lamination components or tools may have higher temperatures than those listed above, but the temperature of the flexible liquid crystal structure may remain within the aforementioned ranges, for example, by limiting the time of exposure to the heated lamination components or tools. Lamination may in some cases cause some stretching or compression of one or both substrates of the flexible liquid crystal film structure.

[0064] In some preferred embodiments, the term "lamination" refers to the fact that the curvature of the laminated flexible liquid crystal structure has undergone a permanent change (i.e., at least some change in curvature from its pre-lamination state) while still maintaining its electro-optical properties. For example, when a laminated flexible liquid crystal structure is peeled off its carrier, it will have a different curvature than it had before lamination.

[0065] 7 is a block diagram illustrating steps for making an optical device by lamination according to some embodiments of the present disclosure. In step 301, a carrier having a multi-curved surface is provided together with a flexible liquid crystal film structure having a first surface and a second surface. The carrier and the flexible liquid crystal film structure are described above.

[0066] In step 303, adhesive is applied to the multi-curved surface of the carrier or the first surface of the flexible liquid crystal film structure. Alternatively, the adhesive material may be applied to both the multi-curved surface of the carrier and the first surface of the flexible liquid crystal film structure. FIGS. 8A-8G are a series of cross-sectional views illustrating the configuration of an optical device using PAA, according to some embodiments of the present disclosure. As described and shown in the cross-sectional view of FIG. 8A, PAA 440 may be provided between a backing layer 441 and a release liner 442 (collectively, PAA precursor sheet 444) in some embodiments. In some embodiments, as shown in FIG. 8B, the PAA precursor sheet may be pre-cut to a desired size, the backing layer 441 may be removed, and the exposed PAA surface may be applied to a target surface, such as the multi-curved surface 462 of the carrier 460 and / or the first surface of the flexible liquid crystal film structure. Application of PAA to the target surface may include the use of one or more rollers or dies to ensure uniform application. 8C, a portion of the release layer 442 can be removed to form an exposed portion 446 of the PAA 440. The PAA 440 can include any of the materials or properties previously described.

[0067] In some embodiments, liquid glue (not illustrated) may also be used in conjunction with the PAA. Such liquid glue may be applied to the PAA or to a surface intended to receive and adhere to the PAA. In some cases, the liquid glue may help eliminate air bubbles when laminating structures together. In some embodiments, a liquid other than glue may be applied to the PAA or to a surface intended to receive and adhere to the PAA, such as wet lamination to eliminate trapped air. The liquid may be a solvent-based material.

[0068] In step 305, the carrier is aligned to the flexible liquid crystal film structure. This may be done using a jig, a die, or some other tool. In some embodiments, such as shown in FIG. 8D, part of the alignment may include contacting one edge of the flexible liquid crystal film structure 410 with the PAA, e.g., exposed portion 446 of the PAA with first surface 413 of the liquid crystal film structure. The contact may be initially soft to effect alignment. Once alignment is achieved, harder contact may be made to secure the structure to the carrier. The flexible liquid crystal film structure 410 may be as described above, including first and second substrates, EOMs, spacers, alignment layers, conductive layers, and other features, which are omitted for clarity.

[0069] In step 307, pressure is applied between the multi-curved surface and the first surface of the flexible liquid crystal film structure to conformally adhere the flexible liquid crystal film structure to the multi-curved surface. In some embodiments, as shown in FIG. 8E, the aligned structure from FIG. 8D is provided in a roller assembly including at least a top roller 471 and, optionally, a bottom roller 472 designed to provide pressure 473 between the multi-curved surface and the first surface of the flexible liquid crystal film structure. The rollers may optionally include internal stems 474 and 475 about which the rollers rotate. The remaining portion of the release layer 442 is removed. In FIG. 8F, the roller assembly applies pressure and moves over the carrier and the flexible liquid crystal film structure, laminating the carrier and the flexible liquid crystal film structure together, thereby forming the optical device 480 shown in FIG. 8G. The roller assembly itself may move, or alternatively, the carrier and the flexible liquid crystal film structure may move through the roller assembly, or both. Although not shown, in some embodiments, a curable liquid or gel adhesive material can be applied to the PAA after the release layer 442 is removed (FIG. 8E) and then cured, for example by UV exposure, as the leading edge exits the roller.

[0070] In some embodiments, the pressure 473 applied along at least the length of the top roller between the curved surface of the flexible liquid crystal structure and the first surface is within 50%, or alternatively within 40%, 30%, 20%, or 10% of the average pressure applied.

[0071] In some embodiments, at least one roller 471, 472 is a deformable roller that can substantially conform to the multi-curved surface 462 as the lamination process progresses. The deformable roller may include a compressible material. In some cases, the deformable roller may have a durometer in the range of less than 90, 80, 70, or 60. The deformable roller may include multiple segments along its length, e.g., internal wheels, to independently adjust the applied force at each segment to improve the overall uniformity of the applied pressure along the roller. In other embodiments, the deformable roller may include a flexible roller, where the internal stem 474 of the roller flexes in response to pressure applied to the multi-curved surface.

[0072] When applying pressure to a convex, multi-curved surface, roller 471 may have a concave transverse shape where the roller radius at the center of the length of the roller is smaller than the radius at the ends of the roller. This is shown in the cross section of FIG. 9A along the length of roller 571 including internal stem 574. In addition to the shape, roller 571 may also be a deformable roller. When applying pressure to a concave, multi-curved surface, roller 471 may have a convex transverse shape where the roller radius at the center of the length is larger than the radius at the ends of the roller. This is shown in the cross section of FIG. 9B along the length of roller 671 including internal stem 674. In addition to the shape, roller 671 may also be a deformable roller.

[0073] In some embodiments, the roller may be heated to improve adhesion, but such heating should be maintained below the Tg of the first or second substrate of the flexible liquid crystal film structure. For example, the roller may be heated to a temperature at least 30° C., at least 10° C., below the Tg of either substrate. In some embodiments, the roller surface may have a coating or treatment that inhibits undesirable adhesion between the second surface of the flexible liquid crystal film structure and the roller. For example, such a coating or treatment may include the application of a fluorinated polymer or surface group.

[0074] In some embodiments, rather than rolling, the elements described above as "rollers" may simply slide across the surface, as long as the friction between the element and the liquid crystal film structure is low. Alternatively, elements of other shapes may be used to apply uniform pressure.

[0075] Rather than using rollers to apply pressure, a mold may be used that has a shape (the "mold face") that corresponds to the multi-curved surface. The mold face need not be identical to the multi-curved surface shape, but in some embodiments, the mold face is sufficiently similar to the multi-curved surface that the pressure applied across the multi-curved surface is within 50%, or even within 40%, 30%, 20%, or 10% of the average pressure.

[0076] 10A-10D are a series of cross-sectional views illustrating a non-limiting embodiment of applying pressure using a mold, as in step 307. In FIG. 10A, a carrier 760 with adhesive 740 is aligned to a flexible liquid crystal film structure 710 having a first surface 713. The flexible liquid crystal film structure 710 may be as described above, including first and second substrates, EOMs, spacers, alignment layers, conductive layers, and other features, which are omitted for clarity. The flexible liquid crystal film structure 710 is positioned within a mold 775 having a mold face 776 of similar shape to the multi-curved surface 762. The flexible liquid crystal film structure 710 is generally flat in this view, but may alternatively be partially curved. In FIG. 10B, the carrier, adhesive, and flexible film structure are moved together to make initial contact. Such contact (as shown here) may be at or near the center of the multi-curved surface, but need not be. In Figure 10C, a force 773 is applied between the mold and the opposing surface 764 of the carrier (opposite the multi-curved surface 762) to conformally adhere the flexible liquid crystal film structure and create optical device 780 (Figure 10D). In some embodiments, the force applied to the opposing surface of the carrier may include the use of a second mold having a second surface similar in shape to the opposing surface.

[0077] In some embodiments, the mold(s) may be heated to improve adhesion, but such heating should be kept below the Tg of the first or second substrate of the flexible liquid crystal film structure. For example, the mold(s) may be heated to a temperature at least 30° C., and at least 10° C., below the Tg of either substrate. If the adhesive is not PAA, a curing step may be included while the parts are in place as in FIG. 10C.

[0078] In some embodiments, the mold may have some flexibility to allow for improved contact and uniform application of pressure, especially when the mold surface is not uniform with the multi-curved surface. In some cases, the mold may be more flexible than the carrier, but less flexible than the flexible liquid crystal film structure. In some embodiments, the mold surface may have a coating or treatment that inhibits undesirable adhesion between the second surface of the flexible liquid crystal film structure and the mold surface. For example, such a coating or treatment may include the application of a fluorinated polymer or surface group.

[0079] In some embodiments, more pressure may be applied to the outer areas of the flexible liquid crystal film structure than the central area. In some embodiments, applying pressure as in step 307 may be performed in an environment or chamber where the flexible liquid crystal film structure, adhesive, and carrier are all under reduced pressure, i.e., pressure less than atmospheric pressure. For example, applying pressure may be performed in an environment having a gas pressure of less than 100, 50, 10, 5, or 1 Torr. The gas may be a mixture of nitrogen, argon, or air, etc. Lamination under reduced pressure may reduce the generation of trapped air that may cause bubbles. In some embodiments, post-processing through an autoclave may also reduce or eliminate trapped air. In some embodiments, lamination may be performed using a vacuum bag process.

[0080] In some embodiments, the optical device may include two carriers. FIG. 11 is a cross-sectional view of an optical device, according to some embodiments. The optical device 880 includes a first carrier 860-a having a multi-curved surface 862-a. The optical device 880 further includes a flexible liquid crystal film structure 810 conformally provided on the multi-curved surface 862-a of the first carrier 860-a. An intervening first adhesive 840-a bonds the flexible liquid crystal film structure 810 to the multi-curved surface 862-a. A second carrier 860-b having a multi-curved surface 862-b may be provided on top of the flexible liquid crystal film structure 810. An intervening second adhesive 840-b bonds the multi-curved surface 862-b to the flexible liquid crystal film structure 810. The flexible liquid crystal film structure 810 may be as described above, including the first and second substrates, EOMs, spacers, alignment layers, conductive layers, and other features, which are omitted for clarity. Similarly, the first and second adhesives, first and second carriers, and certain lamination methods may include any of those described above.

[0081] In some embodiments, a two-step lamination process may be used to create the optical device 880. For example, as a first step, the flexible liquid crystal structure 810 may be laminated onto the multi-curved surface 862-a of a first carrier. As a second step, a second carrier may be laminated or otherwise bonded to the top surface of the laminated liquid crystal structure. In some cases, the second step does not involve lamination because the flexible liquid crystal structure may already have its desired shape. Alternatively, as a first step, the flexible liquid crystal structure 810 may be laminated onto the multi-curved surface 862-b of a second carrier, and in a second step, the first carrier may be laminated or otherwise bonded to the bottom surface of the laminated liquid crystal structure.

[0082] In some embodiments, the optical device may have only a single carrier and one or more laminated liquid crystal film structures. Such a structure may be simpler to manufacture in some cases. For example, an augmented reality headset as a carrier may include one or more laminated liquid crystal film structures, but may not include a second carrier to be superimposed, such as a glass plate or the like.

[0083] In the previous figures and descriptions, the flexible liquid crystal film structure has been generally described as flat before lamination. However, in some embodiments, the flexible liquid crystal film structure may have some partial curvature before lamination. That is, the flexible liquid crystal film structure to undergo lamination may be non-flat, but may not yet have the full curvature of the multi-curved surface of the carrier.

[0084] In some embodiments, the flexible liquid crystal film structure includes an EOM during lamination, i.e., applying pressure. Filling the gap with an EOM can help distribute the pressure between the two substrates of the flexible liquid crystal film structure. However, in some embodiments, the EOM can be added after applying pressure using the filling methods discussed above (e.g., vacuum filling). In some cases, it may be preferable to add the EOM later, since it may be sensitive to the pressure or optional heating or additional curing steps that may be used during bonding with the PAA. Alternatively, the gap can be temporarily filled with a material that helps distribute the pressure between the substrates during the application of pressure, such as a harmless low vapor pressure solvent, and then removed after the step of applying pressure and refilled with the desired EOM. Non-limiting examples of such low vapor pressure solvents can include certain hydrofluoroethers.

[0085] The methods and materials of the present disclosure allow for the manufacture of optical devices that do not have the drawbacks associated with the aforementioned thermoformed LC devices. Such optical devices can be made with high yields and, surprisingly, do not suffer from defects such as wrinkling of the flexible liquid crystal film structure that would be expected when laminated onto a multi-curved surface without thermoforming. The optical devices of the present disclosure can have high optical clarity / low haze and low driving voltage.

[0086] Additional layers or materials may optionally be applied to protect the surface or edges of the optical device from damage from scratches, UV radiation, moisture, or the like. Such additional layers or materials may also, or instead, enhance some performance characteristic, such as anti-reflection, polarization, tint, or the like.

[0087] The specific details of the particular embodiments may be combined in any suitable manner without departing from the spirit and scope of the embodiments of the invention, however, other embodiments of the invention may be directed to certain particular embodiments in relation to each individual aspect, or particular combinations of these individual aspects.

[0088] The above description of exemplary embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to be limited to the precise form described, and many modifications and variations are possible in light of the above teaching.

[0089] In the preceding description, for purposes of explanation, numerous details are set forth in order to provide an understanding of various embodiments of the present technology. However, it will be apparent to one skilled in the art that certain embodiments may be practiced without some of these details or with additional details.

[0090] Although several embodiments have been described, it will be recognized by those skilled in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, some well-known processes and elements have not been described in order to avoid unnecessarily obscuring the invention. Additionally, the details of any particular embodiment may not always be present in variations of that embodiment or may be added to other embodiments.

[0091] Where a range of values ​​is provided, unless the context dictates otherwise, it is understood that each intervening value between the upper and lower limits of that range is also specifically disclosed to the tenth of the unit of the lower limit. Each subrange between any stated or intervening value in a stated range and any other stated or intervening value in that stated range is included. The upper and lower limits of these smaller ranges may be independently included or excluded in the range, and each range in which either, neither, or both limits are included in the smaller range is also included within the invention, subject to any specifically excluded limits in the stated range. Where a stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

[0092] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to a "method" includes a plurality of such methods, a reference to a "layer" includes one or more layers and equivalents thereof known to those skilled in the art, and so forth. The invention has been described in detail herein for purposes of clarity and understanding. It will be understood, however, that certain changes and modifications can be practiced within the scope of the appended claims.

[0093] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes. [Explanation of symbols]

[0094] 10 Flexible Liquid Crystal Film Structure 12 First substrate 13 First Surface 14 Second board 15 Second Surface 16 Conductive layer 18 Alignment layer 24 Spacer 25 Gap 26 Electro-Optical Materials (EOM) 27 Boundary seal (edge ​​seal) 28 Boundary seal (edge ​​seal) 29 Thickness 30 Control circuit 40 Adhesive 60 Career 62 Multi-curved surface 62A Surface Area 62V Virtual Area 62-1 First Curvature 62-2 Second Curvature 80, 180, 280 Optical Devices

Claims

1. 1. An optical device comprising: a low-flexibility carrier having a multi-curved surface; a flexible liquid crystal film structure conformally provided on the multi-curved surface; an adhesive interposed between the multi-curved surface and the liquid crystal film structure, wherein the flexible liquid crystal film structure is laminated to the shape of the multi-curved surface.

2. The optical device of claim 1 , wherein the adhesive comprises a pressure-activated adhesive.

3. The optical device of claim 1 , wherein the adhesive comprises a curable adhesive.

4. 10. The optical device of claim 1, wherein the liquid crystal film structure comprises a first flexible substrate in contact with the adhesive, a second flexible substrate spaced apart from the first flexible substrate to form a gap, and an electro-optical material provided in the gap and surrounded by a boundary seal.

5. The optical device of claim 4 , wherein the electro-optic material comprises a guest-host dichroic dye liquid crystal mixture.

6. The optical device of claim 4 , wherein the electro-optic material contains less than 10% by weight of a polymeric material.

7. The optical device of claim 4 , wherein the liquid crystal film structure further comprises an unpatterned spacer provided between the first flexible substrate and the second flexible substrate.

8. 5. The optical device of claim 4, wherein the gap across the active area of ​​the liquid crystal film structure is maintained within 20% of an average gap measured across the active area.

9. 5. The optical device of claim 4, wherein over at least 95% of the liquid crystal film structure area, the gap is maintained within 20% of an average gap measured over the entire liquid crystal film structure area.

10. The optical device of claim 4, wherein the average gap is in the range of 5 μm to 10 μm.

11. The optical device of claim 4 , wherein the first substrate, the second substrate, or both, comprise a flexible polymeric material.

12. The optical device of claim 4 , wherein at least one substrate comprises polyethylene terephthalate, polycarbonate, polyvinyl acetate, or a cyclic olefin polymer.

13. The optical device of claim 4 , wherein the first substrate differs from the second substrate in terms of chemical composition or thickness.

14. 5. The optical device of claim 4, wherein at least the first substrate has an average thickness in the range of 75 μm to 300 μm.

15. 10. The optical device of claim 1, wherein the liquid crystal film structure has an average thickness in the range of 150 μm to 750 μm.

16. The optical device of claim 1 , wherein the adhesive comprises a viscoelastic polymer and a tackifier.

17. The optical device of claim 1 , wherein the adhesive has an average thickness in the range of 25 μm to 100 μm.

18. The optical device of claim 1 , wherein the ratio of the average thickness of the liquid crystal film structure to the average thickness of the adhesive is less than 10.

19. The polysurface is i) a first curvature having a first height H1 and a first length L1 measured along a first direction, the first curvature having a first curvature ratio C1=H1 / L1; ii) a second curvature having a second height H2 and a second length L2 measured along a second direction orthogonal to the first direction, the second curvature having a second curvature ratio C2=H2 / L2; The optical device of claim 1 , wherein both C1 and C2 are greater than zero and at least one of C1 and C2 is less than 0.

5.

20. Multi-surfaces, i) a first curvature curved to a first value greater than 0 diopters; ii) a second curvature orthogonal to the first curvature and curved to a second value greater than 0 diopters; The optical device of claim 1 , wherein at least one of the first value and the second value is less than 8 diopters.

21. 21. The optical device of claim 20, wherein at least one of the first value and the second value is less than four.

22. The optical device of claim 1 , wherein the area of ​​the polycurved surface is between 0 and 15% larger than the imaginary area defined by the projection of the polycurved surface onto a plane.

23. The optical device of claim 1 , wherein the adhesive and the liquid crystal film structure collectively transmit at least 40% of visible light.

24. The optical device of claim 1 , wherein the adhesive and the liquid crystal film structure collectively provide a haze value of less than 10% in the off state.

25. 10. The optical device of claim 1, wherein the carrier comprises a window, a windshield, a cockpit, a display, a head-up display, a sunroof, a mirror, an augmented reality or virtual reality headset, goggles, a visor, a lens, eyeglasses, or sunglasses.

26. 2. The optical device of claim 1, wherein the combined thickness of the adhesive and the liquid crystal film structure is less than 1% of the maximum length of the carrier on which the liquid crystal film structure is provided.

27. The optical device of claim 1 , wherein the active portion of the liquid crystal film structure covers only a portion of the carrier.

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