PATENT DOCUMENT

Publication Number: US-8508694-B2
Application Number: US-201113324862-A
Country: US
Kind Code: B2

Title: Display with dual-edge light-emitting-diode backlight

Abstract:
An electronic device may have a liquid crystal display with backlight structures. The backlight structures may produce backlight that passes through display layers in the display. The display layers may include color filter elements, a liquid crystal layer, and a thin-film transistor layer. The backlight structures may have a light guide plate with opposing first and second edges. The light guide plate and other display layers may be assembled within support structures such as a metal chassis and a plastic chassis. A first strip of light-emitting diodes may be attached to the first edge of the light guide plate in a position that is floating with respect to the metal chassis. A second strip of light-emitting diodes may be attached to the second edge of the light guide plate in a position that is fixed with respect to the metal chassis.

Claims:
What is claimed is: 
     
       1. A display, comprising:
 at least one display layer having structures configured to display and image; and 
 a backlight unit configured to produce backlight that passes through the at least one display layer, wherein the backlight unit includes a support structure, a light guide plate, first and second strips of light-emitting diodes coupled to the light guide plate at opposing first and second edges of the light guide plate, wherein the first strip of light-emitting diodes at the first edge of the light guide plate has a position that is floating relative to the support structure, and wherein the second strip of light-emitting diodes at the second edge of the light guide plate has a position that is fixed relative to the support structure. 
 
     
     
       2. The display defined in  claim 1  wherein the support structure comprises a rectangular ring-shaped chassis. 
     
     
       3. The display defined in  claim 2  wherein the rectangular ring-shaped chassis comprises a metal chassis. 
     
     
       4. The display defined in  claim 3  further comprising a rectangular ring-shaped plastic chassis. 
     
     
       5. The display defined in  claim 1  wherein the at least one display layer comprises a liquid crystal display thin-film transistor layer. 
     
     
       6. The display defined in  claim 1  further comprising a substrate with which the first strip of light-emitting diodes is attached to the first edge of the light guide plate, wherein the substrate floats with respect to the support structure. 
     
     
       7. The display defined in  claim 6  wherein the substrate comprises a flexible printed circuit. 
     
     
       8. The display defined in  claim 1  further comprising a first substrate with which the first strip of light-emitting diodes is attached to the first edge of the light guide plate and a second substrate to which the second strip of light-emitting diodes is connected. 
     
     
       9. The display defined in  claim 8  wherein the first substrate comprises a first flexible printed circuit and wherein the second substrate comprises a second flexible printed circuit. 
     
     
       10. The display defined in  claim 9  wherein further comprising adhesive with which the second flexible printed circuit is coupled to the light guide plate. 
     
     
       11. The display defined in  claim 10  further comprising a structure that attaches the second flexible printed circuit to the support structure. 
     
     
       12. The display defined in  claim 11  wherein the structure that attaches the second flexible printed circuit to the support structure comprises tape. 
     
     
       13. The display defined in  claim 12  wherein the tape comprises white reflective tape. 
     
     
       14. A display, comprising:
 a chassis; 
 a first strip of light-emitting diodes; 
 a second strip of light-emitting diodes; and 
 a light guide plate having opposing first and second edges that are configured to respectively receive light from the first and second strips of light-emitting diodes, wherein the first strip of light-emitting diodes is attached to the light guide plate at the first edge and has a position that floats relative to the chassis and wherein the second strip of light-emitting diodes has a position that is fixed relative to the chassis and the second edge. 
 
     
     
       15. The display defined in  claim 14  wherein the first strip of light-emitting diodes is separated from the first edge of the light guide plate by a gap of less than 0.2 mm and wherein the second strip of light-emitting diodes is separated from the second edge of the light guide plate by a gap of less than 0.2 mm. 
     
     
       16. The display defined in  claim 15  further comprising adhesive with which the light guide plate is mounted to the chassis at the second edge. 
     
     
       17. The display defined in  claim 16  wherein the second strip of light-emitting diodes comprises a flexible printed circuit substrate and wherein the adhesive attaches the light guide plate to the flexible printed circuit substrate, the display further comprising tape that attaches the flexible printed circuit to the chassis so that the second edge has the position that is fixed relative to the chassis.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with displays and associated backlight structures. 
     Electronic devices such as computers and cellular telephones have displays. Some displays such as plasma displays and light-emitting diode displays have arrays of display pixels that generate light. In displays of this type, backlighting is not necessary, because the display pixels themselves produce light. Other displays, such as liquid crystal displays, contain passive display pixels. The pixels in a liquid crystal display can alter the amount of light that is transmitted through the display to display information for a user, but do not produce light. As a result, it is often desirable to provide backlight for a liquid crystal display. 
     In a typical backlight structure for a display such as a liquid crystal display, a light guide plate is used to distribute backlight generated by a light source such as a light-emitting diode light source. Optical films such as a diffuser layer and brightness enhancing film may be placed on top of the light guide plate. A reflector may be formed under the light guide plate to improve backlight efficiency. 
     To provide satisfactory backlighting, it may be desirable to locate strips of light-emitting diodes on the top and bottom edges of a light guide plate. The top and bottom strips of light-emitting diodes are typically fixed to a metal chassis. To accommodate thermal expansion of the light guide plate, which is attached along one of its edges to the metal chassis, conventional designs incorporate relatively large air gaps (e.g., a gap of about 0.6 mm) between the light-emitting diodes and the light guide plate. The use of such large gaps can have an adverse impact on backlight efficiency. Poor backlight efficiency, in turn, may decrease power consumption efficiency and can reduce battery life in an electronic device. 
     It would therefore be desirable to be able to provide electronic devices with improved displays and backlights. 
     SUMMARY 
     An electronic device may have a display such as a liquid crystal display with backlight structures. The backlight structures may produce backlight that passes through layers in the display. 
     The backlight structures may produce backlight that passes through the display. The display may have display layers such as a color filter layer, a liquid crystal layer, a thin-film transistor layer, and polarizer layers. The backlight structures may have a light guide plate with opposing first and second edges. The light guide plate and other display structures may be assembled within support structures such as a metal chassis and a plastic chassis to form a display module. 
     In the display module, a first strip of light-emitting diodes may be attached to the first edge of the light guide plate in a position that is floating with respect to the metal chassis. A second strip of light-emitting diodes may be attached to the second edge of the light guide plate in a position that is fixed with respect to the metal chassis. The light-emitting diodes may be separated from the edges of the light guide plate by narrow gaps to enhance backlight efficiency. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an illustrative electronic device with a backlit display in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of an illustrative backlit display in accordance with an embodiment of the present invention. 
         FIG. 3  is a top view of an illustrative display backlight structure showing how two strips of light-emitting diodes may be used in providing backlight for a display in accordance with an embodiment of the present invention. 
         FIG. 4  is a perspective view of illustrative structures in a display module with backlight structures in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional side view of a light-guide plate to which a strip of light-emitting diodes has been attached in accordance with an embodiment of the present invention. 
         FIG. 6  is a perspective view of an upper edge of a light guide plate following attachment of a strip of light-emitting diodes in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional side view of a bottom edge of a metal chassis structure before attachment of a strip of light-emitting diodes in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional side view of the bottom edge of the metal chassis structure of  FIG. 7  in which a strip of light-emitting diodes has been placed to provide backlight illumination for a bottom light guide plate edge in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional side view of the bottom metal chassis structure edge of  FIG. 8  to which the strip of light-emitting diodes has been attached in a fixed position using reflective tape in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional side view of a strip of light-emitting diodes attached to the top edge of a light guide plate in accordance with an embodiment of the present invention. 
         FIG. 11  is a cross-sectional side view of a top edge of the metal chassis structure during installation of the top edge of the light guide plate with the strip of light-emitting diodes of  FIG. 10  so that the top edge of the light guide plate and light-emitting diodes are in a position that floats with respect to the metal chassis in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of the bottom edge of the metal chassis structure of  FIG. 9  during installation and attachment of the bottom edge of the light guide plate in accordance with an embodiment of the present invention. 
         FIG. 13  is a perspective view of a top edge portion of a metal chassis with a light guide plate and associated light-emitting diodes in accordance with an embodiment of the present invention. 
         FIG. 14  is a perspective view of a bottom edge portion of a metal chassis with a light guide plate and associated light-emitting diodes in accordance with an embodiment of the present invention. 
         FIG. 15  is a cross-sectional side view of a top edge portion of a metal chassis and associated plastic chassis in a display module with a light guide plate and associated light-emitting diodes in accordance with an embodiment of the present invention. 
         FIG. 16  is a cross-sectional side view of a bottom edge portion of a metal chassis and associated plastic chassis in a display module with a light guide plate and associated light-emitting diodes in accordance with an embodiment of the present invention. 
         FIG. 17  is a cross-sectional side view of a bottom edge portion of a metal chassis and light guide plate and associated light-emitting diodes in an arrangement in which a layer of white ink has been formed on a light-emitting diode flex circuit substrate to serve as a reflective layer in accordance with an embodiment of the present invention. 
         FIG. 18  is a flow chart of illustrative steps involved in assembling display structures for a display with a dual-edge light-emitting diode configuration in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A display may be provided with backlight structures. The backlight structures may produce backlight for the display that helps a user of a device view images on the display in a variety of ambient lighting conditions. Displays with backlights may be provided in any suitable type of electronic equipment. 
     An illustrative electronic device of the type that may be provided with a backlit display is shown in  FIG. 1 . Electronic device  10  of  FIG. 1  may be a computer such as a computer that is integrated into a display such as a computer monitor, a laptop computer, a tablet computer, a somewhat smaller portable device such as a wrist-watch device, pendant device, or other wearable or miniature device, a cellular telephone, a media player, a tablet computer, a gaming device, a navigation device, a computer monitor, a television, or other electronic equipment. 
     As shown in  FIG. 1 , device  10  may include a backlit display such as display  14 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or other touch sensor components or may be a display that is not touch sensitive. Display  14  may include image pixels formed from liquid crystal display (LCD) components or other suitable display pixel structures. Arrangements in which display  14  is formed using liquid crystal display pixels are sometimes described herein as an example. This is, however, merely illustrative. Any suitable type of display technology may be used in forming display  14  if desired. 
     Device  10  may have a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a 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.). 
     A cross-sectional side view of display  14  is shown in  FIG. 2 . As shown in  FIG. 2 , display  14  may include backlight structures (backlight unit)  18 . Backlight structures  18  may include a light source such as light-emitting diode light source  24 , a light-guide plate such as light-guide plate  22 , optical films  42 , and a reflector such as reflector  20 . During operation, light-emitting diode light source  24  may emit light  50  into light guide plate  22 . Light guide plate  22  may be formed from a rectangular sheet of clear plastic. Light  50  may travel within light-guide plate  22  due to the principle of total internal reflection. Light that escapes through the upper surface of light-guide plate  22  may pass through overlying display layers in direction Z and may serve as backlight for display  14 . Light that escapes through the lower surface of light-guide plate  22  may be reflected back in the upwards direction by reflector  20 . Reflector  20  may be formed from a reflective material such as white plastic (as an example). Optical films  42  may include brightness enhancing film layers, diffusing film layers, and compensating film layers (as examples). 
     Display  14  may have an upper polarizer layer such as polarizer layer  34  and a lower polarizer layer such as polarizer layer  26 . Polarizer layer  26  may polarize backlight  52 . Thin-film transistor layer  28  may include a layer of thin-film transistor circuitry and an array of associated pixel electrodes. Flex circuit cable  40  may provide image data to display driver integrated circuit  38 . In response, display driver integrated circuit  38  may control the thin-film transistor circuitry in layer  28  so that pixel structures such as thin-film transistor structures and associated pixel electrodes in the array of pixel electrodes on thin-film transistor layer  28  produce electric fields corresponding to image data to be displayed. The electric field produced by each electrode on thin-film transistor layer  20  adjusts the orientation of liquid crystals in an associated portion of liquid crystal layer  30  by a corresponding amount. As light travels through display  14 , the adjustment of the orientation of the liquid crystals adjusts the polarization of the light that has passed through layer  30 . When this light reaches upper polarizer  34 , the polarization state of each pixel of light is attenuated by an amount that is proportional to its polarization, thereby creating visible images for a user. 
     Color filter layer  32  may contain an array of colored pixels (e.g., red, blue, and green color filter elements) for providing display  14  with the ability to form color images. Sealant  36  may be used to seal liquid crystal layer  30  within display  14 . If desired, additional layers may be included in display  14  (e.g., touch sensor layers, etc.). An optional layer of transparent glass or plastic may be used to provide a protective cover for display  14 , as illustrated by cover layer  14 C of  FIG. 2 . 
     To provide backlight illumination of sufficient strength and uniformity, it may be desirable to launch light  50  into light guide plate  22  from more than one edge of plate  22 . As shown in the top view of light guide plate  22  of  FIG. 3 , for example, light  50  may be emitted into light guide plate  22  using a first strip of light-emitting diodes such as light-emitting diodes  24 T along the top edge of light guide plate  22  and using a second strip of light-emitting diodes  24 B along the bottom edge of light guide plate  22 . As backlight travels through the pixel structures of the display layers above backlight unit  18  ( FIG. 2 ), the pixel structures display an image for the user of device  10 . 
       FIG. 4  is an exploded perspective view of display structures that may be used in forming a display module for display  14 . As shown in  FIG. 4 , display  14  may include support structures such as support structures  46  and  48 . A top strip of light-emitting diodes such as top light-emitting diode strip  24 T may be mounted on a flexible printed circuit substrate (“flex circuit”) such as flex circuit  44 T and a bottom strip of light-emitting diodes such as bottom light-emitting diode strip  24 B may be mounted on flex circuit  44 B. Flexible printed circuits such as flex circuits  44 T and  44 B may be formed from sheets of polyimide or other layers of polymer and may include patterned metal traces to which packaged light-emitting diodes are soldered. 
     Display  14  may include optical films  42 , light guide plate  22 , reflector  20 , light-emitting diodes  24 T (and associated flex circuit  44 T), and light-emitting diodes  24 B (and associated flex circuit  44 B) mounted within support structures such as support structures  48  and  46 . Display layers such as polarizer layers  26  and  34 , thin-film transistor layer  28 , and color filter layer  32  of  FIG. 2  may also be mounted in support structures  48  and  46  (e.g., by placing these layers within the interior of support structure  48  on top of layers  42 ). 
     Support structures  48  and  46  may sometimes be referred to as chassis members or chassis structures and may be formed from materials such as plastic, ceramic, fiber composites, metal, or other suitable materials. For example, chassis  46  may be formed from a rectangular ring of metal that is sometimes referred to as a metal chassis or m-chassis, whereas chassis  48  may be formed from a rectangular ring of plastic that is sometimes referred to as a plastic chassis or p-chassis. If desired, display  14  may be formed by mounting light-emitting diodes  24 T and  24 B, optical films  42 , and other display structures directly within housing  12  or by mounting light-emitting diodes  24 T and  24 B, optical films  42 , and other display structures in support structures of other shapes. In the illustrative configuration of  FIG. 4 , rectangular ring-shaped p-chassis  48  and rectangular ring-shaped m-chassis  46  are used in forming a display module for display  14  that may be mounted within housing  12  under a display cover layer such as display cover layer  14 C of  FIG. 2 . Other mounting configurations may be used, if desired. 
     To help improve backlight efficiency, it may be desirable to minimize gaps between light-emitting diodes and light-guide plate  22 , while ensuring that the resulting structures will be able to accommodate thermal expansion and contraction of light-guide plate  22  during use of device  10  in hot and cold environments. With one suitable arrangement, light-emitting diodes  24 T are attached light guide plate  22  along the top edge of light guide plate without being attached to surrounding support structures. This allows light-emitting diodes  24 T to float with respect to the support structures during thermal expansion and contraction events, while maintaining a small separation between light-emitting diodes  24 T and light-guide plate  22 . At the opposing bottom edge of light guide plate  22 , light guide plate  22  and light-emitting diodes  24 B may be attached to support structures such as m-chassis  46  in a fixed arrangement that does not permit light-emitting diodes  24 B to float with respect to m-chassis  46 . As with the floating top edge of light guide plate  22 , the gap between light emitting diodes and light guide plate  22  may be minimized at the fixed bottom edge of light guide plate  22  and light-emitting diodes  24 B. 
       FIG. 5  is a cross-sectional side view of a portion of display  14  in the vicinity of top light-emitting diodes  24 T. As shown in  FIG. 5 , light-emitting diodes  24 T may be attached to light-guide plate  22  so that light  50  from light-emitting diodes  24 T may be efficiently emitted from edge  58  of light-emitting diodes  24 T into adjacent edge  60  of light guide plate  22  across gap  61 . Gap  61  may be filled with air or an adhesive and may (for at least some of the light-emitting diodes  24 T) be characterized by a gap width G of about 0.2 mm (e.g., less than 0.6 mm, less than 0.5 mm, less than 0.4 mm, less than 0.3 mm, less than 0.2 mm, or less than 0.1 mm). Small gap widths such as these may be achieved because it is not necessary to make gap G large enough to accommodate thermal expansion of plate  22 , due to the floating position of edge  60  and light-emitting diodes  24 T relative to m-chassis  46 . 
     Light-emitting diodes  24 T may extend in a strip along dimension X (into the page in the orientation of  FIG. 5 ) and may be electrically connected to metal traces  63  in flex circuit  44 B. Light-emitting diodes  24 T may be, for example, soldered to metal pads in traces  63  on the upper surface of flex circuit  44 B using solder  65 . During operation of device  10 , electrical power may be supplied to light-emitting diodes  24 T using traces  63 . 
     The relative position between light-emitting diodes  24 T and light guide plate  22  along lateral dimension Y may be fixed by attaching light guide plate to flex circuit  44 B. As shown in  FIG. 5 , light guide plate  22  may be attached to flex circuit  44 B using adhesive such as optically clear adhesive  52 . A reflective layer such as printed white ink or white tape such as white tape reflective layer  54  may be interposed between optically clear adhesive  52  and flex circuit  44 B to help reflect light  50  into light guide plate  22 . White tape reflective layer  54  may be attached to flex circuit  62  by adhesive layer  56  (e.g., adhesive on the underside of white tape reflective layer  54 ). 
     A strip of top light-emitting diodes  24 T may be attached to top edge  60  of light guide plate  22  using flex circuit  44 B, as shown in  FIG. 5  and/or by using adhesive interposed between edges  58  and  60 . A perspective view of light guide plate  22  showing how light-emitting diodes  24 T and flex circuit  44 B may be attached to top edge  60  of light guide plate  22  is shown in  FIG. 6 . 
     An illustrative process for installing light guide plate  22  and light emitting diodes  24  in support structures such as m-chassis  46  is shown in the cross-sectional side views of the display structures of  FIGS. 7 ,  8 ,  9 ,  10 ,  11 , and  12 . 
     A cross-sectional side view of bottom edge  46 B of m-chassis  46  before installing display structures is shown in  FIG. 7 . As shown in  FIG. 7 , bottom edge  46 B may have a channel such as channel  46 B- 1 . During assembly, the edges of display layers such as light guide plate  22  may be received within channel  46 B- 1 . Channel  46 B- 1  may be formed from a recess in m-chassis  46  that is formed between rear wall  46 R, end wall (side wall)  46 B- 3 , and overhanging wall  46 B- 2 . A corresponding channel may be formed along the top edge of m-chassis  46  to receive the top edge of light guide plate  22 . 
     Initially, a strip of bottom light-emitting diodes  24 B may be placed in channel  46 B- 1 , as shown in  FIG. 8 . Light-emitting diodes  24 B may be soldered to flex circuit  44 B. Flex circuit  44 B may be attached to wall  46 -R using a layer of adhesive or, as shown in  FIG. 9 , may be attached to wall  46 -R using white reflective tape  54 . Tape  54  may have adhesive  64  on its underside, so that tape  54  will adhere to the upper surface of flex circuit  44 B and will adhere to the surface of rear wall portion  46 R of m-chassis  46 . After using tape  54  to secure light-emitting diodes  24 B and flex circuit  44 B to bottom edge  46 B of m-chassis  46  so that the position of light-emitting diodes  24 B is fixed with respect to chassis  46 , reflector  20  may be attached to m-chassis  46 . For example, reflector  20  may be attached to tape  54  using adhesive (see, e.g., two-sided tape  62 ). 
     In the configuration shown in  FIG. 9 , the lower strip of light-emitting diodes (i.e., bottom light-emitting diodes  24 B) and bottom flex circuit  44 B are attached to m-chassis  46  and do not move relative to m-chassis  46 . In subsequent assembly operations, light guide plate  22  may be mounted in a fixed relation to bottom light-emitting diodes  24 B and bottom flex circuit  44 B, so that the position of light guide plate  22  is fixed relative to chassis  46 . 
     To accommodate thermal contraction and expansion in light guide plate  22 , the upper edge of light guide plate may be attached to top light-emitting diodes  24 T in a fixed relationship, without attaching light-emitting diodes  24 T, flex circuit  44 T, or the upper edge of light guide plate  22  to m-chassis  46 . The bottom edge of display  14  may therefore have a light guide plate and light-emitting diode backlight source that are in a fixed position relative to chassis  46 , whereas the top edge of display  14  may have a light guide plate and light-emitting diode backlight source that are in a floating position relative to chassis  46 . 
       FIG. 10  is a cross-sectional side view the upper end of light guide plate  22 , showing how top light-emitting diodes  24 T and top flex circuit  44 B may be attached to the top edge of light guide plate  22  in preparation for installation of the top edge of light guide plate  22  in m-chassis  46 . As described in connection with  FIG. 5 , light-emitting diodes  24 T and flex circuit  44 B may, for example, be attached to light guide plate  22  using adhesive  52  (e.g., optically clear adhesive that thermally cures at room temperature). 
     After attaching the top strip of light-emitting diodes to light guide plate  22  as shown in  FIG. 10 , the top edge of light guide plate  22  and the attached light-emitting diodes may be inserted into top channel  46 T- 1  of m-chassis  46  in direction  66 , as shown in  FIG. 11 . Flex circuit  44 T may be left unattached to m-chassis  46 , so that flex circuit  44 T may slide freely within m-chassis  46  to accommodate thermal expansion and contraction of light guide plate  22  (i.e., the top edge of light guide plate  22  and attached light-emitting diodes  24 T and flex circuit  44 T may float with respect to m-chassis  46  in channel  46 T- 1 ). 
     After sliding top edge  22 T of light guide plate  22  into top m-chassis channel  46 T- 1 , opposing bottom edge  22 B of light guide plate  22  may be inserted into bottom m-chassis channel  46 B- 1  in direction  68 , as shown in  FIG. 12 . During insertion of bottom edge  22 B into channel  46 B- 1 , light guide plate  22  may move relative to m-chassis  46 , while the structures that were previously attached to m-chassis  46  such as bottom light-emitting diodes  24 B, bottom flex circuit  44 B, and bottom reflective tape  54  remain fixed relative to m-chassis  46 . Once lower edge portion  22 B of light guide plate  22  has come to rest against bottom light-emitting diodes  24 B, light guide plate  22  may be pressed downwards in direction  72 . 
     When pressed in direction  72 , adhesive  70  may attach light guide plate  22  to chassis  46  (via interposed structures such as reflective tape  54  and flex circuit  44 B). Adhesive  70  may be, for example, optically clear adhesive. When attached in this way, light guide plate  22  will float relative to m-chassis  46  at top edge  22 T of light guide plate  22  of  FIG. 11  and will be fixed relative to m-chassis  46  at bottom edge  22 B of light guide plate  22  of  FIG. 12 . By allowing edge  22 B to contact at least some of the exposed surfaces of light-emitting diodes  24 B before pressing downward in direction  72  to attach light guide plate  22  to m-chassis  46 , the size of gap G between the lower edge of light guide plate  22  and the edge of at least some of light-emitting diodes  24 B may be minimized. For example, the magnitude of G may, for most or all of light-emitting diodes  24 B, be less than 0.6 mm, less than 0.5 mm, less than 0.4 mm, less than 0.3 mm, less than 0.2 mm, less than 0.1 mm, or other suitable size. 
       FIG. 13  is a perspective view of top portion  46 T of m-chassis  46  following insertion of top edge portion  22 T of light guide plate  22  and top light-emitting diode strip  24 T.  FIG. 14  is a perspective view of bottom portion  46 B of m-chassis  46  following insertion and attachment of bottom edge portion  22 B of light guide plate  22  and bottom light-emitting diode strip  24 B. 
     After mounting light guide plate  22  and light-emitting diodes  24  in m-chassis  46 , p-chassis  48  may be attached to m-chassis  46 , as shown in  FIGS. 15 and 16 . Display layers  72  of  FIGS. 15 and 16  (e.g., polarizer layers, thin-film transistor layers, color filter layers, and other display layers of the type shown in  FIG. 2 ) may then be mounted in the rectangular inner opening of p-chassis  48  to form a display module for display  14 . 
     If desired, the reflective properties of white reflective tape  54  may be provided using white ink such as white ink  86  of  FIG. 17 . White ink  86  may be deposited on a flex circuit such as flex circuit  44 B on which light-emitting diodes  24  are mounted using screen printing or other suitable deposition technique. White ink  86  may be printed on upper flex circuit  44 T (e.g., for use in place of white reflective tape  54  of  FIG. 5 ). As shown in  FIG. 17 , flex circuit  44 B may be attached to m-chassis  46  using adhesive such as two-sided tape  84 . 
     Illustrative steps involved in assembling display  14  (e.g., assembly operations for forming a display module or other display structures formed using support structures such as m-chassis  46  and p-chassis  48  or other suitable support structures) are shown in  FIG. 18 . 
     At step  90 , bottom flexible substrate  44 B and the strip of light-emitting diodes  24 B that are mounted on substrate  44 B may be attached to m-chassis  46 . Bottom flexible substrate  44 B may, for example, be attached to m-chassis  46  using reflective tape  54  ( FIG. 9 ), using two-sided tape, or using other suitable attachment mechanisms (e.g., adhesive, fasteners, etc.). 
     Following attachment of flexible substrate  44 B and light-emitting diodes  24 B to m-chassis  46  in the bottom channel of m-chassis  46 , reflector  20  may, as step  92 , be attached to m-chassis  46  (e.g., using adhesive such as two-sided tape  62  of  FIG. 9  or other attachment mechanisms). 
     At step  94 , the upper end of light guide plate  22  may be prepared for mounting to m-chassis  46 . In particular, light-emitting diodes  24 T and flexible substrate  44 T may be attached to top edge portion  22 T of light guide plate  22 , as shown in  FIG. 10 . 
     At step  96 , the top of light guide plate  22  (e.g., top portion  22 T and attached flexible substrate  44 T and top light-emitting diode strip  24 T) may be slid into U-shaped channel  46 T- 1  of m-chassis  46  ( FIG. 11 ). 
     At step  98 , the bottom of light guide plate  22  (e.g., bottom portion  22 B) may be slid in direction  68  of  FIG. 12  until portion  22 B of light guide plate  22  touches bottom light-emitting diodes  24 B (e.g., so that there is a gap G of less than 0.6 mm, less than 0.5 mm, less than 0.4 mm, less than 0.3 mm, less than 0.2 mm, or less than 0.1 mm between the edge of light guide plate  22  and some or all of light-emitting diodes  24 B). Once light guide plate  22  has come to rest against the lower strip of light emitting diodes, light guide plate portion  22 B may be pressed downwards in direction  72  ( FIG. 12 ) to attach light guide plate  22  to m-chassis  46  with optically clear adhesive  70  ( FIG. 12 ). Adhesive  70  may cure thermally (e.g., at room temperature), thereby fixing the position of light guide plate  22  relative to the bottom strip of light-emitting diodes and m-chassis  46 . The top edge of light guide plate  22  is not attached to m-chassis  46  (i.e., the top edge of light guide plate  22  is floating), so thermal expansion and contraction events can be accommodated. The process of attaching top light-emitting diodes  24 T to light guide plate edge  22 T (step  94 ) and the process of attaching light guide plate  22  to flex  44 B (and thereby m-chassis  46 ) after placing light guide plate  22  against light-emitting diodes  24 B may help minimize the size G of the gaps that are created between light emitting diodes  24  and the upper and lower edges of light guide plate  22 . Particularly in configurations with small G (e.g., when G is less than 0.2 mm or is less than 0.1 mm), coupling efficiency between light-emitting diodes  24  and light guide plate  22  may be enhanced. 
     During the operations of step  100 , display module assembly operations may be completed by attaching p-chassis  48  and m-chassis  46  as shown in  FIGS. 15 and 16  and by including optical films  42  and other display layers (see, e.g., the layers of  FIG. 2 ) into the display module (e.g., as layers  72  of  FIGS. 15 and 16 ). The assembled display module may then be installed in device  10  to serve as display  14  (e.g., by installing the display structures under a display cover layer such as cover layer  14 C of  FIG. 2 ). 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20111213
Publication Date: 20130813
Grant Date: 20130813
Priority Date: 20111213
Inventors: ZHU WENYONG
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B6/0091", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133611", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T29/49117", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0011", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0091", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133603", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T29/49117", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0091", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 47116329