PATENT DOCUMENT

Publication Number: US-10969628-B1
Application Number: US-201815988978-A
Country: US
Kind Code: B1

Title: Backlight units with support posts and cavity height monitoring

Abstract:
An electronic device may have a display with a backlight. The backlight provides backlight illumination for an array of pixels that is displaying images. The backlight may include an array of cells. Each cell may contain a light source with one or more light-emitting diodes and a cavity reflector that reflects light from the light source outwardly through a diffuser for use in forming the backlight illumination. The light sources may be mounted to a printed circuit. Support posts on the printed circuit may be used to maintain the diffuser at a fixed distance from the printed circuit. The support posts may have opposing first and second ends. The first ends may be attached to the diffuser with fixed connections such as adhesive connections. The second ends may be attached to the printed circuit using floating connections.

Claims:
What is claimed is: 
     
       1. A display, comprising:
 an array of pixels configured to display images; and 
 a backlight configured to produce backlight illumination for the array of pixels, wherein the backlight has a two-dimensional array of cells that each includes a light source and a reflector, a printed circuit on which the light sources are mounted, a diffuser, and support posts that extend between the printed circuit and the diffuser to support the diffuser, and floating coupling structures, wherein the two-dimensional array of cells extends in first and second directions, wherein the support posts each has a first portion that is coupled to the diffuser and a second portion that is coupled to the printed circuit, and wherein the floating coupling structures couple the second portion of each support post to the printed circuit while allowing the second portion to shift relative to the printed circuit in at least one direction selected from the group of the first direction and the second direction to accommodate a thermal coefficient of expansion mismatch between the diffuser and the printed circuit. 
 
     
     
       2. The display defined in  claim 1  further comprising a layer of adhesive that attaches the first portion of each support post to the diffuser. 
     
     
       3. The display defined in  claim 2  wherein the coupling structures include a first member and a second member and wherein the second portion is captured between the first member and the second member. 
     
     
       4. The display defined in  claim 3  wherein the first and second members are metal plates. 
     
     
       5. The display defined in  claim 4  wherein the printed circuit has solder pads and wherein the second member is attached to the solder pads with solder. 
     
     
       6. The display defined in  claim 5  wherein the second portion is wider than the first portion. 
     
     
       7. The display defined in  claim 5  wherein the second portion comprises a sacrificial alignment structure configured to mate with an opening in the second member. 
     
     
       8. The display defined in  claim 7  wherein the support posts comprise polymer. 
     
     
       9. The display defined in  claim 3  wherein the floating coupling structures include a plate with openings. 
     
     
       10. The display defined in  claim 9  wherein the support posts each has a sacrificial alignment structure configured to be received within a respective one of the openings. 
     
     
       11. The display defined in  claim 10  wherein the floating coupling structures comprise a member that is attached to the plate, wherein the plate and the member are configured to capture a portion of each support post while allowing that support post to move relative to the printed circuit. 
     
     
       12. A display, comprising:
 an array of pixels configured to display images; and 
 a backlight configured to produce backlight illumination for the array of pixels, wherein the backlight has a two-dimensional array of cells that each includes a light source and a reflector, a printed circuit on which the light sources are mounted, a diffuser, and an array of support posts that are configured to separate the diffuser from the printed circuit, wherein the support posts are interposed between and separate the reflectors of adjacent cells in the two-dimensional array of cells, wherein the support posts have opposing first and second ends, and wherein the first ends are coupled to the diffuser with adhesive. 
 
     
     
       13. The display defined in  claim 12  further comprising coupling structures that are configured to couple the second ends of the support posts to the printed circuit while allowing the second ends of the support posts to shift position relative to the printed circuit. 
     
     
       14. The display defined in  claim 13  wherein the coupling structures include first and second members with portions that are separated from each other by a gap, wherein the second ends of the support posts are received within the gaps. 
     
     
       15. The display defined in  claim 12  wherein the support posts include inner and outer support post portions. 
     
     
       16. The display defined in  claim 12  wherein the second ends of the support posts are coupled to the printed circuit with respective screws. 
     
     
       17. The display defined in  claim 16  wherein the screws are configured to allow the second ends of the support posts to shift position relative to the printed circuit. 
     
     
       18. A display, comprising:
 an array of pixels configured to display images; and 
 a backlight configured to produce backlight illumination for the array of pixels, wherein the backlight has a two-dimensional array of cells that each includes a light source and a reflector, a printed circuit on which the light sources are mounted, and a diffuser and wherein the backlight has support posts that are configured to separate the diffuser from the printed circuit, wherein the support posts each has a first portion and a second portion, wherein the first portion is attached to the diffuser with a fixed connection and wherein the second portion is attached to the printed circuit with a floating connection that couples the support post to the printed circuit while allowing the second portion to shift in a direction planar to the two-dimensional array of cells. 
 
     
     
       19. The display defined in  claim 18  wherein the floating connection has first and second members with portions that are spaced apart from each other to capture the second portions while accommodating movement of the second portions relative to the printed circuit.

Description:
This application is continuation of U.S. patent application Ser. No. 15/719,412, filed Sep. 28, 2017, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to displays, and, more particularly, to backlit displays. 
     Electronic devices often include displays. For example, computers and cellular telephones are sometimes provided with backlit liquid crystal displays. Edge-lit backlight units have light-emitting diodes that emit light into an edge surface of a light guide plate. The light guide plate then distributes the emitted light laterally across the display to serve as backlight illumination. Direct-lit backlight units have arrays of light-emitting diodes that emit light vertically through the display. 
     Direct-lit backlights may have locally dimmable light-emitting diodes that allow dynamic range to be enhanced. If care is not taken, however, the light produced by a direct-lit backlight may not be sufficiently uniform. For example, variations in the distance between the light-emitting diodes and an overlapping diffuser layer may lead to undesired uniformity variations in a backlight. 
     SUMMARY 
     An electronic device may have a display with a backlight. The backlight provides backlight illumination for an array of pixels that is displaying images. The backlight may include an array of backlight cells. Each cell may contain a light source with one or more light-emitting diodes and a cavity reflector that reflects light from the light source outwardly through a diffuser for use in forming the backlight illumination. 
     The light sources may be mounted to a printed circuit. Support posts may be used to maintain the diffuser at a fixed distance from the printed circuit. The support posts may have opposing first and second ends. The first ends may be attached to the diffuser with fixed connections such as adhesive connections. The second ends may be attached to the printed circuit using floating connections. The floating connections may allow the second ends to shift laterally relative to the printed circuit to accommodate mismatch in the coefficients of thermal expansion between the diffuser and the printed circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an illustrative electronic device having a display in accordance with an embodiment. 
         FIG. 2  is a cross-sectional side view of an illustrative display in accordance with an embodiment. 
         FIG. 3  is a top view of an illustrative backlight cell array having rows and columns of light source cells for a direct-lit backlight unit in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of an illustrative light source such as a light-emitting diode in a cavity reflector of a backlight cell in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative transparent support post for a backlight in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative support post having a white shot of plastic that is at least partly covered by a clear shot of plastic in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of a portion of an illustrative support post having a white shot of plastic with a rounded tip that is at least partly covered by a clear shot of plastic in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of a portion of an illustrative diffuser layer with a support post of the type that may be formed form an integral portion of the diffuser layer in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of an illustrative support post for a backlight having an inverted cone shape in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of an illustrative support post for a backlight having a floating connection to a substrate in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of an illustrative support post for a backlight having a floating connection in accordance with an embodiment. 
         FIG. 12  is a cross-sectional side view of an illustrative support post for a backlight unit coupled to a substrate with a floating connection in accordance with an embodiment. 
         FIG. 13  is a cross-sectional side view of an illustrative support post for a backlight unit coupled to a substrate with a floating connection in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with backlit displays. The backlit displays may include liquid crystal pixel arrays or other display structures that are backlit by light from a direct-lit backlight unit. A perspective view of an illustrative electronic device of the type that may be provided with a display having a direct-lit backlight unit is shown in  FIG. 1 . Electronic device  10  of  FIG. 1  may be a computing device such as a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     As shown in  FIG. 1 , device  10  may have a display such as display  14 . Display  14  may be mounted in housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Housing  12  may have a stand such as optional stand  18 , may have multiple parts (e.g., housing portions that move relative to each other to form a laptop computer or other device with movable parts), may have the shape of a cellular telephone or tablet computer (e.g., in arrangements in which stand  18  is omitted), and/or may have other suitable configurations. The arrangement for housing  12  that is shown in  FIG. 1  is illustrative. 
     Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. 
     Display  14  may include an array of pixels  16  formed from liquid crystal display (LCD) components or may have an array of pixels based on other display technologies. A cross-sectional side view of display  14  is shown in  FIG. 2 . 
     As shown in  FIG. 2 , display  14  may include a pixel array such as pixel array  24 . Pixel array  24  may include an array of pixels such as pixels  16  of  FIG. 1  (e.g., an array of pixels having rows and columns of pixels  26 ). Pixel array  24  may be formed from a liquid crystal display module (sometimes referred to as a liquid crystal display or liquid crystal layers) or other suitable pixel array structures. A liquid crystal display for forming pixel array  24  may, as an example, include upper and lower polarizers, a color filter layer and a thin-film transistor layer interposed between the upper and lower polarizers, and a layer of liquid crystal material interposed between the color filter layer and the thin-film transistor layer. Liquid crystal display structures of other types may be used in forming pixel array  24 , if desired. 
     During operation of  14 , images may be displayed on pixel array  24 . Backlight unit  42  (which may sometimes be referred to as a backlight, backlight layers, backlight structures, a backlight module, a backlight system, etc.) may be used in producing backlight illumination  44  that passes through pixel array  24 . This illuminates any images on pixel array  24  for viewing by a viewer such as viewer  20  who is viewing display  14  in direction  22 . 
     Backlight unit  42  may have optical films  26 , a light diffuser such as light diffuser (light diffuser layer)  34 , and light source array  36 . Light source array  36  may contain a two-dimensional array of light sources  38 . Each light source  38  may contain one or more light-emitting diodes and may be associated with a respective one of backlight cells  38 C. Cells  38 C may contain reflectors for reflecting light through pixel array  24 . Cells  38 C may be arranged in an array with rows and columns in the X-Y plane of  FIG. 2 . 
     Light sources  38  in cells  38 C may be controlled in unison by control circuitry in device  10  or may be individually controlled (e.g., to implement a local dimming scheme that helps improve the dynamic range of images displayed on pixel array  24 ). The light produced by each cell  38 C may travel upwardly along dimension Z through light diffuser  34  and optical films  26  before passing through pixel array  24 . Light diffuser  34  may contain light-scattering structures that diffuse the light from light-emitting diode array  36  and thereby help provide uniform backlight illumination  44 . Optical films  26  may, as an example, include films such as dichroic filter  32 , phosphor layer  30 , and films  28 . Films  28  may include brightness enhancement films that help to collimate light  44  and thereby enhance the brightness of display  14  for user  20  and/or other optical films (e.g., compensation films, etc.). 
     The light-emitting diodes of light sources  38  may emit light of any suitable color. With one illustrative configuration, the light-emitting diodes emit blue light. Dichroic filter layer  32  may be configured to pass blue light from light-emitting diodes  38  while reflecting light at other colors. Blue light from light-emitting diodes  38  may be converted into white light by a photoluminescent material such as phosphor layer  30  (e.g., a layer of white phosphor material or other photoluminescent material that converts blue light into white light). If desired, other photoluminescent materials may be used to convert blue light to light of different colors (e.g., red light, green light, white light, etc.). For example, layer  30  (which may sometimes be referred to as a photoluminescent layer or color conversion layer) may include quantum dots that convert blue light into red and green light (e.g., to produce white backlight illumination that includes, red, green, and blue components, etc.). Configurations in which light-emitting diodes  38  emit white light (e.g., so that layer  30  may be omitted, if desired) and/or in which light-emitting diodes  38  emit blue or ultraviolet pump light for pixels containing quantum dots may also be used. 
     In configurations in which layer  30  emits white light such as white light produced by phosphorescent material in layer  30 , white light that is emitted from layer  30  in the downwards (−Z) direction may be reflected back up through pixel array  24  as backlight illumination by dichroic filter layer  32  (i.e., layer  32  may help reflect backlight outwardly away from array  36 ). In configurations in which layer  30  includes, for example, red and green quantum dots, dichroic filter  32  may be configured to reflect red and green light from the red and green quantum dots, respectively to help reflect backlight outwardly away from array  36 . By placing the photoluminescent material of backlight  42  (e.g., the material of layer  30 ) above diffuser layer  34 , light-emitting diodes  38  may be configured to emit more light towards the edges of the light-emitting diode cells (tiles) of array  36  than at the centers of these cells, thereby helping enhance backlight illumination uniformity. 
       FIG. 3  is a top view of an illustrative light source array for backlight  42 . As shown in  FIG. 3 , array  36  may contain row and columns of light-sources  38 . Each light source  38  may be associated with a respective cell  38 C. The length D of the edges of cells  38 C may be 2 mm, 18 mm, 1-10 mm, 1-4 mm, 10-30 mm, more than 5 mm, more than 10 mm, more than 15 mm, more than 20 mm, less than 25 mm, less than 20 mm, less than 15 mm, less than 10 mm, or other suitable size. If desired, hexagonally tiled arrays and arrays with light sources  38  that are organized in other suitable array patterns may be used. In arrays with rectangular cells, each cell may have sides of equal length (e.g., each cell may have a square outline in which four equal-length cell edges surround a respective light-emitting diode) or each cell may have sides of different lengths (e.g., a non-square rectangular shape). The configuration of  FIG. 3  in which array  36  has rows and columns of square light-emitting regions such as cells  38 C is merely illustrative. 
     If desired, each cell  38 C may have a light source that is formed from an array of light-emitting diode dies (e.g., multiple individual light-emitting diodes  38 D arranged in an array such as a 2×2 cluster of light-emitting diodes forming a four-die light source  38  at the center of each cell  38 C). This type of configuration is illustrated by light source  38  in the leftmost and lowermost cell  38 C of  FIG. 3 , which has been formed from a 2×2 array of light-emitting diodes  38 D (e.g., four separate light-emitting diode dies). The diodes  38 D in light source  38  in the lower left corner of array  36  of  FIG. 3  may be mounted on a common package substrate, may be mounted on a printed circuit board substrate that extends across array  36 , or may be mounted in array  36  using other suitable arrangements. In general, each cell  38 C may include a light source  38  with a single light-emitting diode  38 D, a pair of light-emitting diodes  38 D, 2-10 light-emitting diodes  38 D, at least two light-emitting diodes  38 D, at least 4 light-emitting diodes  38 D, at least eight light-emitting diodes  38 D, fewer than five light-emitting diodes  38 D, or other suitable number of light-emitting diodes. 
       FIG. 4  is a cross-sectional side view of an illustrative backlight cell  38 C in backlight  42 . As shown in  FIG. 4 , each cell  38 C in array  36  may have a reflector such as cavity reflector  68 . Reflector  68  may have a square outline (i.e., a square footprint when viewed from above) or may have other suitable shapes and may be formed from sheet metal (e.g., stamped sheet metal), metallized polymer film, a thin-film metal on a plastic carrier, a dielectric thin-film stack that forms a dielectric mirror (a thin-film interference mirror) on a polymer film or molded plastic carrier, a white reflective film (e.g., a glossy white polymer sheet formed from a white ink layer or other white layer on a polymer carrier covered with a glossy coating such as a glossy polymer coating), or other suitable reflector structure. 
     An opening may be formed in reflector  68  in each cell  38 C to accommodate a respective light source  38 . The light source  38  in each cell may have an upper portion that protrudes through the opening in reflector  68  and a lower portion with contacts that are soldered or otherwise mounted to metal traces in printed circuit  60 . 
     The reflectors in cells  38 C may have cross-sectional profiles with curved portions to help reflect light from light sources  38  upwards as backlight illumination  44 . With one illustrative configuration, a polymer film (e.g., a film coated with a dielectric thin-film interference mirror surface or a glossy white reflective surface) may be embossed using a roller (e.g., the film may be thermoformed using patterned structures on a heated roller). Following thermoforming operations to form the curved walls of reflector  68  in each cell  38 C, a die cutting tool or other cutting apparatus may cut openings for each of light sources  38 . 
     As shown in  FIG. 4 , a transparent structure such as transparent dome structure  70  may be formed over each light source  38  to help laterally distribute light  80  that has been emitted by that light source. Dome structure  70  may be formed from a bead of clear silicone or other transparent polymer (as an example). During operation, light source  38  emits light  80  that is refracted away from the Z axis by dome structure  70 . 
     Some rays of light  80  are oriented at relatively large angles with respect to the Z axis of  FIG. 4 . These off-axis rays of light  80  are reflected upwardly in direction Z from reflector  68 . Other rays of light  80  are oriented at smaller angles with respect to the Z axis (surface normal of display  14 ). If desired, backlight  42  may include an optional filter layer with an angularly dependent light transmission characteristic such as filter layer  97 . Diffuser layer  34  may include light-diffusing layer  34 ′. Layer  34 ′ may include light-scattering particles such as particles  72  in a polymer binder and/or may have other light-scattering structures for diffusing light  80  from light sources  38 . Filter layer  97  may be a thin-film interference filter formed from multiple dielectric layers  97 ′ or other suitable filter with an angularly dependent light transmission characteristic. Filter layer  97  may be formed on a substrate that is separate from layer  34 ′ or may be formed on layer  34 ′ in diffuser  34  as shown in the illustrative configuration of  FIG. 4 . 
     The layers of display  14  may not be perfectly flat due to external pressure, due to expansion and/or contraction caused by thermal fluctuations, and/or due to manufacturing variations. This may create undesired fluctuations in the separation distance H (sometimes referred to as optical distance H) between printed circuit  60  and diffuser  34 . With one illustrative configuration, display  14  may include an array of supporting posts in backlight  42  that help maintain a desired fixed value for height H across display  14 . 
       FIG. 5  is a cross-sectional side view of an illustrative portion of backlight  42  showing how backlight  42  may include a support post. As shown in  FIG. 5 , support post  90  may extend between the upper surface  60 U of printed circuit  60  and the opposing lower surface (surface  34 L) of diffuser  34  (as an example). Posts  90  may be cylindrical (radially symmetric) or may have other shapes (e.g., shapes in which one or more sides of posts  90  have flat portions). Radially symmetric arrangements for posts  90  may help to reduce shadows. 
     The presence of support posts such as support post  90  of  FIG. 5  may help maintain a fixed separation height H between diffuser  34  and printed circuit  60  and may therefore help to stabilize the vertical separation between light sources  38  in array  36  and diffuser  34 . This stabilization will help reduce fluctuations in light intensity that might otherwise result in hotpots and dark zones in areas of display  14 . 
     As shown in  FIG. 5 , support post  90  may have a lower portion such as lower portion  90 B and an upper portion such as upper portion  90 F. Portion  90 B may have straight sides (e.g., portion  90 B may be a cylinder) and portion  90 F may be tapered outwardly (e.g., portion  90 F may have an inverted cone shape). Reflector  68  may have an array of openings with each opening receiving a respective support post  90 . There may be a support post at each corner of each cell  38 C or support posts  90  may be more sparsely arrayed in backlight  42  (e.g., to accommodate separation height measurement sensors, etc.). 
     Support post  90  of  FIG. 5  may be attached to layer  60  using adhesive  94  and/or using a screw such as screw  96 . Screw  96  may have a shaft that passes through an opening in printed circuit substrate  60  and engages threads in a threaded opening in portion  90 B of post  90 . Upper portion  90 F of post  90  may be attached to diffuser  34  using adhesive  92 . To prevent dark spots from forming on backlight  42  due to the presence of posts  90 , post  90  may be formed from a transparent material such a clear polymer. Adhesive  92  may also be formed from a clear material (e.g., a clear polymer). During operation, light  80  from light source  38  may strike portion  90 F of post  90  and may be redirected within post  90  as illustrated by light ray  80 - 1  (e.g., by refraction). Refraction at the interface between post  90  and diffuser  34  may cause light ray  80 - 2  to be angled at a non-zero angle with respect to light ray  80 - 1  and refraction at the interface between diffuser  34  and air (or other materials) above diffuser  34  may cause light ray  44  (e.g. the backlight illumination exiting diffuser  34 ) to be angled at a non-zero angle with respect to light ray  80 - 2 . Light  80 - 2  may also be scattered by scattering features in diffuser  34 . The flared shape of portion  90 F and the transparency of portion  90 F may help guide off-axis light rays such as illustrative ray  80  over post  90 , so that illumination  44  is present over post  90 . As a result, local dark spots in backlight illumination  44  due to the presence of posts  90  may be reduced or eliminated. 
     Other configurations for supporting diffuser  34  in backlight  42  may be used, if desired. In the illustrative configuration of  FIG. 6 , post  90  includes multiple shots of plastic. A first shot of plastic such as a white polymer is used in forming lower post portion  90 W. A second shot of plastic, which is formed at least partly on top of portion  90 W is used in forming upper post portion  90 C. Portion  90 C may be transparent (e.g., portion  90 C may be formed from clear polymer). With this type of configuration, a light ray such as illustrative off-axis light ray  80  may enter clear portion  90 C and refract to form light ray  80 A. Light ray  80 A may reflect off of reflective white surface  92  of portion  90 W to form reflected ray  80 B. Ray  80 B may reflect from the inner surface of portion  90 C (e.g., the interface between portion  90 C and surrounding air in the space between diffuser  34  and printed circuit  60 ) in accordance with the principal of total internal reflection, thereby forming reflected ray  80 C. Ray  80 C may enter diffuser  34  and, following passage through diffuser  34  and possible scattering by diffuser  34 , can exit diffuser  34  as backlight illumination  44 . Different rays may take different paths through post  90  and layer  34 . Nevertheless, as the illustrative path of ray  80  of  FIG. 6  demonstrates, the presence of white portion  90 W of post  90  may help to reflect light so that light is not absorbed and lost at post  90  and the presence of clear portion  90 C may help redirect light above post  90  to serve as illumination  44 . As a result, post structures of the type shown in  FIG. 6  may help reduce dark spots that might otherwise arise from incorporating supports into backlight  42 . 
     In the illustrative configuration of  FIG. 7 , post  90  includes portion  90 WR (e.g., a white polymer portion) and portion  90 C (e.g., a clear polymer portion). Surface  92  of post portion  90 WR is rounded. This shape may help redirect light upwards through diffuser  34  (e.g., less light may be reflected laterally and more light may be reflected upwards). Portion  90 C can be flared (tapered) outwardly (e.g., so that the top of portion  90 C adjacent to diffuser  34  is wider than the bottom of portion  90 C adjacent to post portion  90 WR) so as to facilitate the redirection of light that passes through portion  90 C upwards through diffuser  34 . Other shapes may be used for post portions  90 WR and  90 C if desired. The configuration of  FIG. 7  is merely illustrative. 
     As shown in  FIG. 8 , support posts for backlight  42  may be formed from integral portions of diffuser  34 . In the example of  FIG. 8 , portion  34 P of diffuser  34  is serving as a support post and extends between the lower surface of diffuser  34  and the opposing upper surface of printed circuit  60 . Portion  34 P may be formed from the same material(s) as diffuser  34  and may, for example, be formed by molding a diffuser  34  with integral support posts  34 P so that these integral support posts are protrusions from the planar portion of diffuser  34 . Configurations in which posts such as post  34 P of  FIG. 8  are formed separately from diffuser  34  and attached to diffuser  34  (e.g., using adhesive or other attachment mechanisms) may also be used. Support post  34 P may be formed from clear or translucent plastic (e.g., transparent polymer, transparent polymer with light-scattering particles or other light-scattering features, etc.). The lower portion of support post  34 P may be cylindrical and the upper portion of support post  34 P may have a curved outwardly flared profile. Other shapes may be used for integral support posts such as support post  34 P, if desired. 
     Support post  34 P may be attached to printed circuit  60  using adhesive, a screw, or other attachment mechanisms. Printed circuit  60  may overlap a metal backlight chassis layer such as metal chassis  61  or other suitable support structure. This type of arrangement may be used in backlight  42  whenever it is desired to provide additional support for the layers of backlight  42 . 
     In the example of  FIG. 8 , support post  34 P is configured to receive a screw such as screw  96  (e.g., support post  34 P may have a threaded opening that receives a threaded shaft portion of screw  96 ). Elastomeric gasket  100  (e.g., a ring-shaped washer) may be received in opening  102  of metal chassis  61 . The shaft of screw  96  may pass through an opening in gasket  100  and an opening in layer  60  (e.g., an opening that is wider than the shaft of screw  96 ). The presence of gasket  100  between a head portion of screw  96  and metal chassis  61  may help accommodate lateral mismatch between the locations of posts  34 P and the locations of openings  102  in printed circuit  60  (e.g., to satisfy alignment tolerances, to accommodate lateral shifts due to thermal expansion and contraction, etc.). 
     As shown in  FIG. 9 , support post  90  (e.g., a clear polymer support post, a white polymer support post, etc.) may have an inverted cone shape or other configuration that minimizes the size (diameter W) of the upper portion of post  90  where post  90  contacts diffuser  34 . In configurations in which the ratio of diffuser thickness T to post top diameter W is sufficient (e.g., at least 1, at least 2, at least 3, less than 100, etc.), shadowing of light from light sources  38  will be minimized and the presence of posts  90  will not significantly disrupt the uniformity of emitted backlight illumination  44 . 
     In configurations in which one end of support post  90  has a fixed connection (e.g., a fixed connection to diffuser  34 ) whereas another end of support post  90  has a floating connection (e.g., to printed circuit  60 ), mismatch in the coefficients of thermal expansion for diffuser  34  and printed circuit  60  may be accommodated. 
     In the example of  FIG. 10 , support post  90  has a widened lower portion  90 ′. Portion  90 ′ is captured in a floating connection structure. As shown in  FIG. 10 , portion  90 ′ is captured in a gap between a portion of upper member  150  (e.g., a top metal plate) and a corresponding portion of lower member  152 . Upper member  150  and lower member  152  may be attached to each other using welds, solder, adhesive, fasteners, or other coupling mechanisms (see, e.g., welds  154  of  FIG. 10 ). Upper portion  90 ″ of support post  90  is connected to the lower surface of light diffuser  34  (sometimes referred to as a light diffuser panel, light diffuser sheet, or light diffuser layer) using adhesive  160  (e.g., pressure sensitive adhesive). Lower member  152 , which is connected to upper member  150  may be attached to a substrate such as printed circuit  60  using solder  162  and solder pads  60 P on printed circuit  60  or other suitable attachment mechanisms. Light diffuser  34  and printed circuit  60  may be formed from materials that have different coefficients of thermal expansion. To accommodate relative lateral movement between light diffuser  34  and printed circuit  60 , the connection formed between post  90  and printed circuit  60  may have a floating configuration. 
     With the illustrative floating configuration of  FIG. 10 , lateral space DE is provided between inner surface  156  of member  150  and outer surface  158  of widened portion  90 ′ of post  90 . This allows post  90  to move laterally in dimensions X and Y to accommodate differences in the coefficient of thermal expansion between diffuser  34  and printed circuit  60 . 
     During manufacturing, a sacrificial alignment structure  162  may be attached to the lower surface of post  90  within corresponding opening  152 ′ of lower member  152 . Alignment structure  162  may help post  90  to center itself within opening  102  during assembly and gluing operations as post  90  is mounted into the cavity formed between upper member  150  and lower member  152  and breaks off during subsequent use. 
     In the illustrative floating connection configuration of  FIG. 11 , support post  90  is formed from an outer member  90 - 1  that receives and surrounds inner member  90 - 2 . Members  90 - 1  and  90 - 2  have corresponding surfaces  166  and  168  that capture member  150 M. Member  150 M may be coupled to a substrate such as printed circuit  60  or other support structures (e.g., using adhesive, solder, welds, etc.). Adhesive  160  may be used to couple support post  90  to light diffuser  34 . Inner surface  170  of member  150 M and outer surface  172  of member  90 - 2  may be separated by lateral space DE to accommodate coefficient of thermal expansion mismatch, as described in connection with space DE of  FIG. 10 . 
       FIG. 12  shows how a floating coupling structure may be formed using screw  96 . Screw  96  may be provided with a head portion  96 H that is sufficiently wide to capture portions of printed circuit  60  and optional metal chassis  61 . As shown in  FIG. 12 , screw  96  may be separated by lateral space DE from printed circuit  60  and chassis  61  to accommodate coefficient of thermal expansion mismatch, as described in connection with space DE of  FIG. 10 . A portion of opening  102  in chassis  61  may, if desired, be recessed to accommodate portion  96 H of screw  96 . 
     Another illustrative support post configuration with opposing ends having fixed and floating connections is shown in  FIG. 13 . In the configuration of  FIG. 13 , the outer portion of support post portion  96 H of screw  96  captures printed circuit  60  and an unrecessed portion of optional chassis  61  and also has been arranged to accommodate lateral motion (see, e.g., space DE). 
     When using an adhesive layer (e.g., adhesive layer  160 ) to attach post  90  to light diffuser  34  and floating coupling structures with lateral spaces DE to accommodate relative lateral movement of substrate layer(s) such as printed circuit  60 , post  90  has a fixed upper connection and a floating lower connection. This configuration helps maintain the flatness of diffuser  34 , so that height H may be minimized (e.g., to a value of 2-4 mm, at least 2 mm, at least 2.5 mm, less than 5 mm, less than 4 mm, less than 3.5 mm, or other suitable value) and so that the spacing between light sources  38  (e.g., the lateral dimensions of cells  38 C) may be about 15-25 mm, at least 12 mm, or less than 30 mm (as examples). 
     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: 20180524
Publication Date: 20210406
Grant Date: 20210406
Priority Date: 20170928
Inventors: ZWEIGLE, ERIK A.
SUN, YU P.
HONG, ZIRUO
YIN, VICTOR H.
BENSON, ERIC L.
LIU, RONG
GU, MINGXIA
Durand, Robert J.
Wr Ramli, Wr Jamarulan
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F2203/60", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133608", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133605", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133603", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2202/28", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133606", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2203/21", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133603", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133612", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133608", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13338", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133528", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133514", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133605", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133614", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133621", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133603", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133528", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133514", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133606", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133614", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133608", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133612", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13338", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2203/21", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2202/28", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133621", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133605", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 75275685