PATENT DOCUMENT

Publication Number: US-11693279-B1
Application Number: US-202217683731-A
Country: US
Kind Code: B1

Title: Adjustable windows

Abstract:
A system may have windows. The window may have first and second window layers and a layer of material such as guest-host liquid crystal material between the first and second window layers. Electrodes on the window layers may be used to apply electric fields to the guest-host liquid crystal material to adjust the light transmission properties of the window. To ensure that a desired gap between the first and second window layers is maintained, spacers may be formed between the first and second window layers. The spacers may include key-and-lock spacers that have interlocking portions located, respectively, on the first and second window layers. Spacers such as photoresist posts can be attached using adhesive. Hybrid arrangements may also be used in which key-and-lock spacer structures are attached using adhesive bonds.

Claims:
What is claimed is: 
     
       1. A system, comprising:
 a body; and 
 a window in the body that separates an exterior region from an interior region, wherein the window comprises:
 an outer window layer; 
 an inner window layer separated from the outer window layer by a gap; 
 a guest-host liquid crystal layer in the gap between the outer and inner window layers; and 
 spacers coupled between the inner and outer window layers to maintain the gap, wherein each of the spacers has a first portion on the inner window layer and a second portion on the outer window layer, wherein the second portion of each spacer has slots and a recess, and wherein the recess is configured to receive a mating tip of the first portion. 
 
 
     
     
       2. The system defined in  claim 1  further comprising:
 a first rubbing layer on the inner window layer; and 
 a second rubbing layer on the outer window layer, wherein:
 the first portions comprise photoresist posts having respective tip areas that are not covered by the first rubbing layer; and 
 the second portions comprise photoresist post holders with respective post holder areas that are not covered by the second rubbing layer. 
 
 
     
     
       3. The system defined in  claim 1  wherein the spacers are formed from photoresist. 
     
     
       4. The system defined in  claim 3  wherein the inner window layer is coated with a first transparent electrode layer, wherein the outer window layer is coated with an opposing second transparent electrode layer, and wherein each spacer extends between the first and second transparent electrode layers. 
     
     
       5. The system defined in  claim 4  further comprising adhesive associated with each spacer that attaches the first portion to the second portion in that spacer. 
     
     
       6. The system defined in  claim 5  wherein the first portions comprise rectangular posts. 
     
     
       7. The system defined in  claim 5  wherein the second portions comprise post holders. 
     
     
       8. The system defined in  claim 5  wherein the first portions comprise posts and the second portions comprise post holders that respectively receive the posts. 
     
     
       9. The system defined in  claim 4  further comprising a first rubbing layer on the first transparent electrode layer and a second rubbing layer on the second transparent electrode layer. 
     
     
       10. The system defined in  claim 9  wherein, in each spacer, the first portion has a first convex surface configured to shed at least some of the first rubbing layer and the second portion has a second convex surface configured to shed at least some of the second rubbing layer. 
     
     
       11. The system defined in  claim 9  wherein the first portion of each spacer has a convex surface at the tip. 
     
     
       12. The system defined in  claim 1  wherein the first portion of each spacer comprises a post with a reverse taper. 
     
     
       13. The system defined in  claim 1  wherein the body comprises a vehicle body and wherein the window comprises a vehicle window. 
     
     
       14. A system, comprising:
 a body; and 
 a window in the body that has:
 first and second transparent layers; 
 rubbing layer material on the first transparent layer; 
 spacers between the first and second transparent layers to maintain a gap between the first and second transparent layers, wherein the spacers include passageways for receiving excess portions of the rubbing layer material; and 
 a liquid crystal layer in the gap, wherein the spacers each include a photoresist post attached to the second transparent layer with adhesive. 
 
 
     
     
       15. The system defined in  claim 14  wherein the body comprises a vehicle body and wherein the window comprises a vehicle window. 
     
     
       16. The system defined in  claim 15  wherein the liquid crystal layer comprises a guest-host liquid crystal layer and wherein the first transparent layer comprises a first polymer layer coated with transparent conductive electrode material and wherein the second transparent layer comprises a second polymer layer coated with transparent conductive electrode material. 
     
     
       17. The system defined in  claim 16  wherein the photoresist posts comprise posts with reverse tapers. 
     
     
       18. The system defined in  claim 16  wherein the photoresist posts have convex tips that are not covered with the rubbing layer material. 
     
     
       19. The system defined in  claim 18  wherein the adhesive attaches the convex tips to the second polymer layer coated with the transparent conductive electrode material. 
     
     
       20. A vehicle window, comprising:
 first and second window layers separated by key-and-lock spacers, wherein each key-and-lock spacer has a first spacer portion on the first window layer and a second spacer portion on the second window layer that mates with the first spacer portion, and wherein the second spacer portion has slots extending radially outward from the second spacer portion; and 
 a guest-host liquid crystal layer between the first and second window layers. 
 
     
     
       21. The vehicle window defined in  claim 20  wherein the first spacer portions comprise bars of photoresist with additional slots and wherein the second spacer portions comprise bars of photoresist that are received within the additional slots. 
     
     
       22. The vehicle window defined in  claim 20  wherein the first and second spacer portions have tapered sidewalls.

Description:
This application claims the benefit of provisional patent application No. 63/162,767, filed Mar. 18, 2021, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to structures that pass light, and, more particularly, to windows. 
     BACKGROUND 
     Windows are used in buildings and vehicles. Windows may be formed from glass or other transparent material. 
     SUMMARY 
     A system may have windows. The system may be a building, vehicle, or other system with an interior region that is separated from a surrounding exterior region by the windows. The windows may be electrically adjustable. In an illustrative arrangement, control circuitry in the system may be used to adjust an adjustable light modulator or other optical component in a window. 
     A window with an adjustable light modulator may have first and second window layers. The window layers may include first and second respective structural glass layers and/or other transparent layers such as polymer films. Glass and/or polymer in the transparent layers may serve as substrates for electrodes in the adjustable light modulator. The adjustable light modulator may have a layer of material such as a layer of guest-host liquid crystal material sandwiched between the first and second window layers and the electrodes on the window layers. 
     To ensure that a desired gap is maintained between the first and second window layers even in the presence of mechanical and thermal stress, spacers may be formed between the first and second window layers. The spacers may include key-and-lock spacers that have interlocking portions located, respectively on the first and second window layers. Spacers such as photoresist posts can also be attached to a window layer surface using adhesive to enhance the ability of the spacers to resist separation between the window layers. Spacer structures may have convex surfaces to help shed polyimide rubbing layer that is deposited on the inner surfaces of the window layers facing the liquid crystal layer. The absence of rubbing layer material on the exposed surfaces of the spacer structures helps the adhesive satisfactorily adhere to the spacer structures (e.g., to help attach spacer structures to window layers). If desired, hybrid arrangements may be used in which adhesive helps to secure structures in key-and-lock spacers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an illustrative system with a window in accordance with an embodiment. 
         FIG.  2    is a cross-sectional side view of an illustrative window in accordance with an embodiment. 
         FIG.  3    is a diagram showing illustrative operations involved in forming a window with spacers in accordance with an embodiment. 
         FIGS.  4  and  5    are cross-sectional side views of an illustrative window with interlocking key-and-lock spacers in accordance with embodiments. 
         FIG.  6    is a top view of the illustrative spacers of  FIGS.  4  and  5    in accordance with an embodiment. 
         FIG.  7    is a diagram showing additional illustrative operations involved in forming a window with spacers in accordance with an embodiment. 
         FIGS.  8 ,  9 , and  10    show illustrative spacer structures that may be used in a window in accordance with an embodiment. 
         FIG.  11    is a diagram showing top and side views of illustrative window structures with spacers before assembly in accordance with an embodiment. 
         FIG.  12    is a diagram showing top and side views of the illustrative window structures with spacers of  FIG.  11    following assembly in accordance with an embodiment. 
         FIG.  13    is a cross-sectional side view of illustrative spacer structures in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A system may have a transparent structure such as a window that includes one or more adjustable layers. The adjustable layers may include an adjustable light modulator layer and/or other adjustable components such as adjustable layers that provide desired amounts of opacity, haze, and/or color cast. A light modulator layer for a window may be based on a guest-host liquid crystal light modulator, a cholesteric liquid crystal light modulator, or other layer with an adjustable opacity. The use of guest-host liquid crystal light modulators may sometimes be described herein as an example. When it is desired to block light transmission through the window, the opacity of the light modulator may be increased. When it is desired to allow light to pass through the window, the opacity of the light modulator may be decreased. 
     The system in which the window is used may be a building, a vehicle, or other suitable system. Illustrative configurations in which the system is a vehicle may sometimes be described herein as an example. This is merely illustrative. Window structures may be formed in any suitable systems. 
     When an adjustable light modulator is provided in a vehicle window, the light modulator may be controlled to adjust the vehicle window between transparent and opaque states. The window may be opaque, may be completely transparent, or may be characterized by an intermediate level of light transmission. In a transparent state, a vehicle occupant in the interior of a vehicle can view the environment surrounding the vehicle through the window. In an opaque state, privacy is enhanced because people surrounding the vehicle will not be able to view occupants in the vehicle interior through the window. Ambient light such as sunlight may also be blocked and prevented from reaching the vehicle interior when the window is opaque. 
     An illustrative system of the type that may include windows is shown in  FIG.  1   . System  10  may be a vehicle, building, or other type of system. In an illustrative configuration, system  10  is a vehicle. As shown in  FIG.  1   , system  10  may have support structures such as body  12 . Body  12  may be a vehicle body that includes doors, trunk structures, a hood, side body panels, a roof, and/or other body structures. System  10  may include a chassis to which wheels are mounted, may include propulsion and steering systems, and may include other vehicle systems. Seats may be formed in the interior of body  12 . Window  14 , which may be a vehicle window, and portions of body  12  may be used to separate interior  18  of system  10  from the exterior environment (exterior  16 ) that is surrounding system  10 . 
     Windows such as window  14  may be coupled to body  12 . The windows in system  10  such as window  14  may include a front window on the front of a vehicle, a moon roof (sun roof) window or other window extending over some or all of the top of a vehicle, a rear window at the rear of a vehicle, and/or side windows on the sides of a vehicle. Window  14  may be flat (e.g., window  14  may lie in the X-Y plane of  FIG.  1   ) or window  14  may have one or more curved portions (e.g., window  14  may have a curved cross-sectional profile and may be oriented to lie generally parallel to the X-Y plane so that a convex surface of window  14  faces outwardly in direction -Z of  FIG.  1   ). 
     System  10  may include control circuitry and input-output devices. Control circuitry in system  10  may include one or more processors (e.g., microprocessors, microcontrollers, application-specific integrated circuits, etc.) and storage (e.g., volatile and/or non-volatile memory). Input-output devices in system  10  may include displays, sensors, buttons, light-emitting diodes and other light-emitting devices, haptic devices, speakers, and/or other devices for providing output and/or for gathering environmental measurements and/or user input. The sensors may include ambient light sensors, touch sensors, force sensors, proximity sensors, optical sensors, capacitive sensors, resistive sensors, ultrasonic sensors, microphones, three-dimensional and/or two-dimensional images sensors, radio-frequency sensors, and/or other sensors. Output devices may be used to provide a user with haptic output, audio output, visual output (e.g., displayed content, light, etc.), and/or other suitable output. 
     During operation, control circuitry in system  10  may gather information from sensors and/or other input-output devices such as ambient light measurements and/or other sensor data, user input such as voice commands provided to a microphone, a touch command supplied to a touch sensor, button input supplied to one or more buttons, etc.). Control circuitry in system  10  may use this input in controlling the operation of one or more electrically adjustable components in window  14 . For example, control circuitry in system  10  may adjust the amount of opacity (and therefore the amount of light transmission) through window  14  (e.g., for light passing from interior  18  to exterior  16  and for light passing from exterior  16  to interior  18 ) and/or may make other adjustments to window  14  based on user input, ambient light measurements, other sensor data, and/or other information gathered using input-output devices in system  10 . 
     Window  14  may be formed from one or more layers of transparent glass, clear polymer (e.g., polycarbonate), polymer adhesive layers, and/or other layers. As shown in  FIG.  1   , a light modulator active layer such guest-host liquid crystal layer  22  may be sandwiched between outer window layer  20  and inner window layer  24 . Outer window layer  20  may include multiple sublayer such as outer glass layer  26 , optically clear adhesive layer  28 , a polymer film such as polymer layer  30 , and electrode layer  32 . Inner window layer  24  may include sublayers such as inner glass layer  40 , optically clear adhesive layer  38 , a polymer film such as polymer layer  36 , and electrode layer  34 . Electrode layers for forming electrodes  32  and  34  may be formed from a transparent conductive material such as indium tin oxide. Electrodes  32  and  34  and guest-host liquid crystal layer  22  form a guest-host liquid crystal light modulator for window  14 . Guest-host liquid crystal layer  22  includes dichroic dye guest material in liquid crystal host material. Control signals may be applied to electrodes  32  and  34  during operation to control the electric field across layer  22  and thereby adjust the opacity of the light modulator. 
     As illustrated by this example, one or more layers of material (e.g., sublayers such as polymer layer  30  and/or glass layer  26 ) may serve as structural layers that form a supporting substrate for electrode  32  and one or more layers of layers of material (e.g., sublayers such as polymer layer  36  and glass layer  40 ) may serve as structural layers that form a supporting substrate for opposing electrode  34 . This is illustrative. Any suitable set of one or more layers of glass, polymer, transparent ceramic, other materials, and/or combinations of these materials may be used as electrode substrates for electrodes  34  and  36  and window  14  may include one or more structural window layers. In the example of  FIG.  1   , glass layers  26  and  40  may have sufficient thickness and rigidity to serve as structural layers that provide strength for window  14  and thereby support window  14  within system support structures such as body  12 . If desired, one or more polymer layers and/or other structures may be used in providing window  14  with structural support. 
     The thickness of layer  22  is preferably constant throughout window  14  to ensure that the transmission of window  14  is uniform. As shown in  FIG.  2   , support structures such as spacers  42  may be formed between layers  20  and  24  to help maintain a uniform cell gap for liquid crystal layer  22  in light modulator  44 . Spacers  42  may be formed from patterned photosensitive materials extending between the opposing inner surfaces of layers  20  and  24  (e.g., between electrodes  32  and  34  on respective layers  30  and  36 , etc.) and may therefore sometimes be referred to as photospacers. 
     Variations in the size of the liquid-crystal-filled gap between electrodes  32  and  34  will tend to affect the amount of light modulation produced by the guess-host material in the gap. As a result, there is a risk that undesired gap thickness variations can create areas with uneven transmission and other undesirable visual features. For example, large dark spots may appear on an otherwise uniformly transparent window if the cell thickness varies too much. 
     During use of system  10 , window  14  may be subject to stress from vibrations, thermal expansion and contraction, gravity, and/or other forces. As one example, gravity may tend to make the liquid of guest-host liquid crystal layer  22  pool near the bottom of window  14  (e.g., when window  14  is mounted vertically in the side of a vehicle). Shear forces (forces tangential to the surfaces of the layers of window  14 ) and tensile forces (forces that are parallel to surface normals n of the window layers and that are therefore perpendicular to the shear forces) may be produced by these stresses. To ensure that the separation between layers  20  and  24  (and therefore the gaps between electrodes  32  and  34  and the corresponding thickness of layer  22 ) is constant across window  14 , window  14  may be provided with robust spacers. Spaces  42  may, for example, be configured to resist the forces of gravity and stress from vibrations and temperature changes, thereby helping to prevent liquid crystal thickness variations arising from shear and tensile stresses applied to layers  20  and  24 . 
     Illustrative operations for forming spacers  42  are shown in  FIG.  3   . Initially, a layer of photoresist (e.g., a negative acrylate photoresist or other suitable photoresist) may be deposited onto a substrate and patterned using photolithography to form spacers. As shown in  FIG.  3   , for example, photoresist may be patterned to form spacers  42  on bottom substrate  50 . Substrate  50  may be formed from a polymer layer or other dielectric layer coated with an electrode (e.g., layer  30  with electrode  32 ) and may optionally include additional window sublayers (e.g., layers  26  and  28 ). A liquid crystal alignment layer such as polyimide rubbing layer  52  may then be deposited on substrate  50  over spacers  42 . 
     In preparation for application of adhesive to the tops of spacers  42 , a non-sticky layer of material such as release liner  54  may be formed on carrier  56 . Carrier  56  may be a glass or polymer layer (as examples). Adhesive  58  may be deposited on top of release liner  54 . 
     To apply adhesive  58  to the upper surfaces of spacers  42 , carrier  56  is pressed face down on top of spacers  42 . This causes adhesive  58  to stick to the tops of spacers  42 . Carrier  56  is then removed, which causes release liner  54  to peel away from the portions of adhesive  58  that are stuck to the tops of spacers  42 . In this way, patches of adhesive  58  are attached to the exposed outer surface of each spacer  42 . Spacers  42  may be columns (posts) with square footprints or may have other suitable spacer shapes. 
     In preparation for final assembly, a liquid crystal alignment layer such as polyimide rubbing layer  60  may be deposited on the inner surface of substrate  62 . Substrate  62  may be formed from a polymer layer or other dielectric layer coated with an electrode (e.g., layer  36  with electrode  34 ) and may optionally include additional window sublayers (e.g., layers  38  and  40 ). 
     Following application of rubbing layer  60  to substrate  62 , substrate  62  may be placed face down over substrate  50  and guest-host liquid crystal layer  22  may be dispensed between substrates  62  and  50 . Substrate  62  may then be pressed inwardly so that the patches of adhesive  58  on spacers  42  attach substrate  62  to substrate  50 , thereby enclosing liquid crystal material  22 . After substrate  62  is attached to substrate  50  in this way, adhesive  58  may be cured (e.g., by application of heat, etc.). The presence of cured adhesive  58  attaches spacers  42  to layer  60  and layer  62  (and the electrode in layer  62 ) and thereby helps prevent lateral and normal movements of these layers relative to substrate  50  that could affect the thickness of liquid crystal layer  22 . Glass layers  26  and  40  may be attached to layers  30  and  36  before or after using adhesive  58  to attach spacers  42 . 
     Another illustrative spacer arrangement for modulator  44  is shown in  FIGS.  4 ,  5 , and  6   . In this example, spacers  42  are formed from interlocking “key-and-lock” spacer structures.  FIG.  4    is a cross-sectional side view of key-and-lock spacers  42  prior to assembly. Each spacer  42  has a first portion such as a rectangular post  42 - 1  and a second portion such as a cup-shaped post holder  42 - 2  that is configured to mate with the first portion. Posts  42 - 1  may be formed by patterning photoresist on substrate  50 . Post holders  42 - 2  may be formed by patterning photoresist on substrate  62  (e.g., using a halftone mask). Each post holder  42 - 2  may have sidewall portions that surround a recess. The recess of each post holder  42 - 2  may be configured to receive a corresponding tip portion of a respective post  42 - 1 . 
     After aligning posts  42 - 1  with post holders  42 - 2 , the tips of posts  42 - 1  may be inserted into the mating recesses of post holders  42 - 2  as shown in the cross-sectional side view of modulator layer  44  of  FIG.  5   . The shapes of the posts and post holders help lock these portions of the spacers together to form a robust spacer structure that secures substrates  50  and  62  together. 
     As shown in the top view of  FIG.  6   , post holders  42 - 2  may have radially extending slots  64 . In each post holder  42 - 2 , slots  64  may extend from the central recessed portion of the post holder to the periphery of the post holder. Slots  64  form passageways that allow excess rubbing layer material to exit from the recessed portions of post holders  42 - 2  (e.g., when posts  42 - 1  are inserted into the recesses). Because each post holder  42 - 2  surrounds the tip of the post that has been mated with the post holder, the key-and-lock spacer design of  FIGS.  4 ,  5   , ad  6  may help prevent lateral motion (shifting) of substrates  62  and  50  with respect to each other. Friction between the ends of posts  42 - 1  and the mating surfaces of post holders  42 - 2  may also help prevent substrates  50  and  62  from separating (e.g., movement in both the normal and lateral directions may be resisted). 
     To help strengthen the key-and-lock spacer arrangement of  FIGS.  4 ,  5 , and  6   , key-and- lock spacers may be provided with adhesive such as adhesive  58  of  FIGS.  3   , thereby forming hybrid adhesive-attached-key-and-lock spacers. Consider, as an example, the optional assembly operations shown in  FIG.  7   . As shown in  FIG.  7   , posts  42 - 1  may be formed on substrate  50  then covered with rubbing layer  52 . In preparation for adhesive attachment, release liner  54  may be formed on carrier  56 . A layer of adhesive  58  may then be deposited on liner  54 . 
     Carrier  56  may be inverted and pressed against posts  42 - 1  to deposit patches of adhesive  58  on the top of each post  42 - 1 . Carrier  56  may then be removed. 
     Post holders  42 - 2  may be formed on substrate  62  by patterning a layer of photoresist using photolithography (e.g., using a halftone mask). Rubbing layer  60  may then be deposited on substrate  62  over post holders  42 - 2 . 
     To form modulator layer  44 , liquid crystal layer  22  may be placed between substrates  62  and  50  while top substrate  62  is inverted and positioned to align post holders  42 - 2  with respective posts  42 - 1  on bottom substrate  50 . Post holders  42 - 2  and posts  42 - 1  may be mated with each other by pressing substrates  50  and  62  together. Following the formation of spacers  42  by mating posts  42 - 1  with post holders  42 - 2 , adhesive  58  may be cured (e.g., by application of heat). Adhesive  58  is present at the top of each post  42 - 1  and the mating surface of the recess in each corresponding post holder  42 - 2 , so adhesive  58  helps secure posts  42 - 1  to post holders  42 - 2 . As this example demonstrates, the use of a hybrid arrangement in which adhesive  58  is used in attaching mating key-and-lock spacer structures together may enhance the strength of the connection between substrates  50  and  62 . For example, the presence of the sidewalls in post holders  42 - 2  may help the spacers resist shearing forces (by maintaining the tips of the posts in place) and the presence of adhesive  58  in the recesses of the post holders may help resist forces normal to the surfaces of substrates  50  and  62  (by preventing the tips of posts  42 - 1  from pulling away from the post holder recesses). 
     If desired, the amount of polyimide rubbing layer material between posts  42 - 1  and post holders  42 - 2  may be reduced to help strengthen spacers  42 . Consider, as an example, the arrangement of  FIG.  8   . As shown in  FIG.  8   , tip  74  of post  42 - 1  and bottom  72  of recess  70  in post holder  42 - 2  may be provided with convex surfaces. These convex surface shapes (in which the cross-sectional side view of posts  42 - 1  and the recessed portions of post holders  42 - 2  are characterized by curved profiles that bow outwardly) may help polyimide rubbing layer material associated with rubbing layers  52  and  60  to be shed from the spacer structures and thereby flow away from the mating surfaces of key-and-lock spacers  42  of  FIG.  8    before the spacers are assembled. 
       FIG.  9    shows how post holders  42 - 2  may have slots  64  that allow rubbing layer material that is deposited on bottom  72  in the center of post holder  42 - 2  to flow outwardly through slots  64  so that this rubbing layer material is not present between tip  74  and bottom  72  when post  42 - 1  is attached to post holder  42 - 2  (with or without adhesive  58 ). 
     If desired, post  42 - 1  may have a tapered shape that helps secure post  42 - 1  to post holder  42 - 2 . As shown in  FIG.  8   , for example, the tip portion of post  42 - 1  (near the surface of tip  74 ) may have a width W1 that is wider than the width W2 of post  42 - 1  near its base. This tapered shape may sometimes be referred to as a “reverse taper” because in cross-section the protruding tip of post  42 - 1  tends to be wider than the base of post  42 - 1 . When a post with a reverse taper is pressed into a mating recess in a post holder, the sidewalls of the post holder tend to press radially inwardly towards the tip of the post. As shown in  FIG.  10   , this results in portions  76  of post holder  42 - 2  surrounding the tip of post  42 - 1 . The presence of surrounding portions  76  and the reverse taper of post  42 - 1  help lock post  42 - 1  within post holder  42 - 2  and thereby help prevent post  42 - 1  and post holder  42 - 2  from pulling apart when stressed. 
     The mating first and second portions of key-and-lock spacers may be formed using spacer structures with any suitable shapes.  FIG.  11    shows a top view and side view of substrates  50  and  62  prior to assembly. In the example of  FIG.  11   , key-and-lock spacers  42  are formed by first strip-shaped portions (bars)  42 A that have slots  80  and second strip-shaped portions (unslotted bars)  42 B that are configured to be received within slots  80  when mated.  FIG.  12    shows a corresponding top view and side view for substrates  50  and  62  and their associated spacers  42  following assembly. As shown in  FIG.  12   , each of portions  42 A has a slot  80  that has received a mating second portion  42 B. Portions  42 A and/or  42 B may be provided with tapered profiles (e.g., reverse tapers) to help resist separation of substrates  50  and  62 . 
     The presence of rubbing layer material (e.g., polyimide) between spacer structures (e.g., between first and second mating spacer portions) or between spacer structures and the electrodes of modulator  44  may degrade adhesion at adhesive interfaces. For example, in arrangements in which a post and post holder are being joined by a layer of adhesive, the presence of residual rubbing layer material between the post and post holder may reduce adhesion of the adhesive layer being used to attach the surfaces of the post and post holder together. As another example, a spacer may be attached to the surface of an electrode using adhesive. In the presence of rubbing layer material on the top of the spacer, the adhesive that is placed on the top of the spacer to attach the spacer to the electrode may exhibit reduced adhesion to the spacer. 
     To help avoid the lowering of adhesive bond strength due to the presence of rubbing layer material at adhesive joint interfaces, spacers and other structures in modulator  44  may be provided with concave surfaces. In the example of  FIG.  8   , tip  74  of post  42 - 1  and corresponding bottom  72  of recess  70  in post holder  42 - 2  in a key-and-lock spacer have convex surfaces that help shed rubbing layer polymer. In the illustrative example of  FIG.  13   , post-shaped spacer  86  has a convex tip surface. Spacer  86  of  FIG.  13    may form a spacer such as spacer  42  of  FIG.  2    (as an example). In some configurations convex surfaces may be provided to other types of spacers such as portions of key-and-lock spacers on which adhesive joints are formed. Rubbing layer  84  of  FIG.  13    may be formed from polyimide or other rubbing layer polymer. Due to the convex shape of the tip of spacer  86 , rubbing layer  84  is shed from the tip of spacer  86  (e.g., after liquid polyimide is dispensed, the liquid will flow down the sides of spacer  86  away from the convex tip). This leaves the convex tip of spacer  86  uncovered with rubbing layer material, so that adhesive bonds can be securely formed at the convex tip. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20220301
Publication Date: 20230704
Grant Date: 20230704
Priority Date: 20210318
Inventors: LEE, YUNSEOK
XIANYU, HAIQING
LIM, Junhwan
MASSCHELEIN, PETER F
CHOI, SANG UN
LI, XIAOKAI
CHEN, YUAN
GE, ZHIBING
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/1339", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/134309", "inventive": true, "first": false, "tree": "[]"}, {"code": "B60J3/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13725", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1339", "inventive": true, "first": true, "tree": "[]"}, {"code": "B60J3/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13725", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/134309", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13725", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13394", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60J1/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "B60J3/04", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B17/10036", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B17/10467", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B17/10504", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B17/10174", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 86993286