PATENT DOCUMENT

Publication Number: US-8605232-B2
Application Number: US-201113008300-A
Country: US
Kind Code: B2

Title: Display backlight having light guide plate with light source holes and dual source packages

Abstract:
A display may include a backlight structure. The backlight structure may include a light guide plate. Holes in the light guide plate may be configured to receive corresponding light-emitting diodes. The holes may separate an edge portion of the light guide plate from a main central portion of the light guide plate. Adhesive may be attached to the lower surface of the edge portion. The adhesive may be attached to a device housing or may be attached to a flex circuit that is attached to the housing with additional adhesive. The light-emitting diodes may be mounted within packages in pairs. The packages may be mounted on the flex circuit. Traces on part of the flex circuit may be covered by part of the light guide plate without any intervening adhesive. A reflective structure may be interposed between the traces and parts of the main portion of the light guide plate.

Claims:
What is claimed is: 
     
       1. A display, comprising:
 display structures; 
 a light guide plate having a plurality of holes each of which is surrounded by portions of the light guide plate; 
 light-emitting diodes mounted within the holes, wherein the light-emitting diodes emit backlight for the display structures into the light guide plate; 
 a substrate on which the light-emitting diodes are mounted, wherein the substrate is disposed along a first portion of the light guide plate; 
 a first reflector disposed along a second portion of the light guide plate, wherein an edge of the first reflector is disposed adjacent to an edge of the substrate, and wherein the first reflector does not overlap the substrate; and 
 a second reflector interposed between the light guide plate and at least a portion of the substrate, wherein the second reflector is separate from the first reflector. 
 
     
     
       2. The display defined in  claim 1  wherein the display structures include a thin-film transistor layer and a color filter layer. 
     
     
       3. The display defined in  claim 1  wherein the holes comprise holes arranged in a row parallel to an edge of the light guide plate. 
     
     
       4. The display defined in  claim 1  wherein the light-emitting diodes are mounted in pairs within packages. 
     
     
       5. The display defined in  claim 4  wherein the packages each have a pair of terminals, wherein two light-emitting diodes are connected in series between the pair of terminals in each package, and wherein the terminals are connected to the substrate. 
     
     
       6. The display defined in  claim 1  wherein the substrate comprises a flex circuit. 
     
     
       7. The display defined in  claim 6  further comprising traces on the flex circuit, wherein the second reflector comprises a strip of reflective material that is adjacent to the traces, wherein no adhesive is interposed between the strip of reflective material and the traces. 
     
     
       8. The display defined in  claim 1  wherein the light-emitting diodes in the holes separate an edge portion of the light guide plate on a peripheral side of the holes from a main portion of the light guide plate, the display further comprising a layer of adhesive on a lower surface of the edge portion. 
     
     
       9. The display defined in  claim 8 , wherein the display is mounted within an electronic device housing, wherein the layer of adhesive is attached to the housing, and wherein the display further comprises a reflector under the light guide plate. 
     
     
       10. The display defined in  claim 9  further comprising a flex circuit, wherein the light-emitting diodes are mounted to the flex circuit, wherein the main portion of the light guide plate covers the at least some of the flex circuit, and wherein there is no interposed adhesive between the main portion of the light guide plate and the flex circuit. 
     
     
       11. The display defined in  claim 8 , wherein the adhesive attaches the edge portion of the light guide plate to the substrate. 
     
     
       12. The display defined in  claim 11 , wherein the display is mounted within an electronic device housing, wherein the display further comprises an additional layer of adhesive that attaches a lower surface of the substrate to the housing. 
     
     
       13. The display defined in  claim 12  wherein the substrate comprises a flex circuit and wherein portions of the light guide plate are mounted within a groove in the electronic device housing. 
     
     
       14. Display structures, comprising:
 a light guide plate having holes each of which has edges and each of which is surrounded on all of its edges by portions of the light guide plate, wherein the light guide plate comprises a first portion directly beneath an active area of the display structures and a second portion not directly beneath the active area of the display structures; and 
 a flex circuit on which a row of light-emitting diodes are mounted, wherein each of the light-emitting diodes is received within a respective one of the holes, wherein the row of light-emitting diodes is configured to direct light into the first portion of the light guide plate, wherein the flex circuit comprises one or more conductive traces configured to provide power to the row of light-emitting diodes, and wherein the one or more conductive traces are disposed alongside the row of light-emitting diodes, but not between each light-emitting diode of the row of light-emitting diodes; 
 a first reflector disposed along the first portion of the light guide plate, wherein an edge of the first reflector is disposed adjacent to an edge of the flex circuit, and wherein the first reflector does not overlap the flex circuit; and 
 a second reflector interposed between the light guide plate and at least a portion of the flex circuit, wherein the second reflector is separate from the first reflector. 
 
     
     
       15. The display structures defined in  claim 14  wherein the first portion of the light guide plate overlaps a first one or more of the one or more conductive traces underneath the first portion, and the second portion of the light guide plate overlaps a second one or more of the one or more conductive traces underneath the second portion, and wherein no adhesive is interposed between the first one or more of the one or more conductive traces and the first portion of the light guide plate. 
     
     
       16. The display structures defined in  claim 15 , comprising a layer of adhesive interposed between the second portion of the light guide plate and the second one or more of the one or more conductive traces. 
     
     
       17. An electronic device, comprising:
 display structures including a thin-film transistor layer and a color filter array layer; 
 a backlight structure that produces backlight that passes through the display structures, wherein the backlight structure includes a light guide plate with holes and light-emitting diodes that are received within the holes; 
 a substrate on which the light-emitting diodes are mounted, wherein the substrate is disposed along a first portion of the light guide plate; 
 a first reflector disposed along a second portion of the light guide plate, wherein an edge of the first reflector is disposed adjacent to an edge of the substrate, and wherein the first reflector does not overlap the substrate; and 
 a second reflector interposed between the light guide plate and at least a portion of the substrate, wherein the second reflector is separate from the first reflector. 
 
     
     
       18. The electronic device defined in  claim 17  wherein the light guide plate includes an edge portion, wherein at least some of the edge portion is separated from a central portion of the light guide plate by one of the holes and wherein the electronic device further comprises adhesive connected to the edge portion. 
     
     
       19. The electronic device defined in  claim 18  further comprising a housing, wherein the adhesive is connected to the housing. 
     
     
       20. The electronic device defined in  claim 17  wherein the substrate comprises a flex circuit having conductive traces, wherein the light-emitting diodes comprise an array of surface mount technology packages that are mounted in a row along the flex circuit, and wherein the light guide plate overlaps the traces, and wherein there is no adhesive interposed between the flex circuit and the light guide plate where the light guide plate overlaps the traces. 
     
     
       21. The electronic device defined in  claim 20  wherein the second reflector is interposed between the flex circuit and the light guide plate where the light guide plate overlaps the traces. 
     
     
       22. The electronic device defined in  claim 20  wherein each of the surface mount technology packages includes two of the light-emitting diodes.

Description:
BACKGROUND 
     This relates to electronic devices with displays, and more particularly, to backlight structures for displays. 
     Electronic devices such as computers and other electronic equipment often use backlit displays. A typical backlight structure may include light-emitting diodes that launch light into the edge of a plastic light guide plate. As light travels within the light guide plate, some of the light is scattered through the surface of the plate and serves as backlight for overlapping display structures. 
     In some displays, the edge of the light guide plate is serrated to accommodate a row of light-emitting diodes. A bezel structure may be used to help hold the components in a display of this type such as the light guide plate and other backlight structures in position within an electronic device. 
     It may be desirable to form a groove in a housing to help retain the backlight and other display structures within the housing without using bezel structures. With this type of arrangement, one edge of the light guide plate may be retained within the groove and another edge of the light guide plate may be held in place using adhesive. The use of this type of arrangement may help minimize the size of the device, but the presence of the adhesive under the light guide plate may affect the quality of the backlight that is produced. 
     It would therefore be desirable to be able to provide improved arrangements for backlighting displays for electronic devices. 
     SUMMARY 
     An electronic device may include a display such as a liquid crystal display. The display may include display structures such as a thin-film transistor layer and a color filter layer. Liquid crystal material may be interposed between the thin-film transistor layer and the color filter layer. Polarizer layers and other optical films may be included in the display structures. An array of electrodes associated with the thin-film transistor layer may be used to produce an image in the display structures. 
     The display may include a backlight structure. The backlight structure may include a light guide plate. Holes in the light guide plate may be configured to receive corresponding light-emitting diodes. The holes may be rectangular and may have four edges or may have other suitable shapes to receive light-emitting diodes packaged within non-rectangular packages. Portions of the light guide plate may surround the edges of each hole. The holes may separate an edge portion of the light guide plate that is located along a peripheral region of the light guide plate from a main central portion of the light guide plate. 
     Adhesive may be attached to the lower surface of the edge portion of the light guide plate. The adhesive may be attached to a device housing or may be attached to a flex circuit that is attached to the housing with additional adhesive. 
     The light-emitting diodes may be mounted within packages in pairs. The packages may be mounted in a row on the flex circuit. Traces on part of the flex circuit may be covered by part of the central portion of the light guide plate without any intervening adhesive. A reflective structure may be interposed between the traces and overlapping parts of the main central portion of the light guide plate. 
     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 perspective view of an illustrative electronic device having display backlight structures in accordance with an embodiment of the present invention. 
         FIG. 2  is a top view of a conventional light guide plate and associated light-emitting diodes. 
         FIG. 3  is a side view of a conventional display having a light guide plate and light-emitting diodes of the type shown in  FIG. 2 . 
         FIG. 4  is a perspective view of a package of the type that may be used in housing light source structures such as light-emitting diodes in accordance with an embodiment of the present invention. 
         FIG. 5  is a top view of a conventional printed circuit on which conventional light-emitting diodes for illuminating a light guide plate in a backlight structure have been mounted. 
         FIG. 6  is a side view of a conventional display that has been mounted within an electronic device using display bezel structures. 
         FIG. 7  is a side view of a conventional display that has been mounted within an electronic device using a housing groove and adhesive. 
         FIG. 8  is a perspective view of a light guide plate with holes to accommodate light-emitting diodes in accordance with an embodiment of the present invention. 
         FIG. 9  is a side view of an illustrative electronic device in which a display having a light guide plate of the type shown in  FIG. 8  has been mounted in accordance with an embodiment of the present invention. 
         FIG. 10  is a side view of an illustrative display in an electronic device in which a strip of ancillary reflective material has been mounted under a portion of a light guide plate to prevent underlying substrate material from adversely affecting backlight quality in accordance with an embodiment of the present invention. 
         FIG. 11  is a side view of an illustrative display that has been mounted in a housing of an electronic device in a configuration in which flex circuit substrate material for a light-emitting diode array does not extend under the outermost edge portion of a light guide plate in accordance with an embodiment of the present invention. 
         FIG. 12  is a side view of an illustrative surface mount technology package in which a pair of light-emitting diodes has been mounted for launching backlight into a light guide plate in a backlight structure in accordance with an embodiment of the present invention. 
         FIG. 13  is a top view of a packaged pair of light-emitting diodes mounted to pad-shaped traces on a flexible printed circuit substrate for a backlight structure in a display in accordance with an embodiment of the present invention. 
         FIG. 14  is a diagram comparing layouts of two different light-emitting diode arrays for backlight structures in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Displays with backlight structures may be incorporated into electronic devices. Backlight structures allow displays to be used in a variety of lighting conditions. 
     An illustrative electronic device that may be provided with a backlit display is shown in  FIG. 1 . Electronic devices such as illustrative electronic device  10  of  FIG. 1  may be laptop computers, tablet computers, cellular telephones, media players, other handheld and portable electronic devices, smaller devices such as wrist-watch devices, pendant devices, headphone and earpiece devices, other wearable and miniature devices, or other electronic equipment. 
     As shown in  FIG. 1 , device  10  may have a housing such as housing  12 . Housing  12 , which is sometimes referred to as a case, may be formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other composites, metal, other materials, or a combination of these materials. Device  10  may be formed using a unibody construction in which most or all of housing  12  is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures). In the illustrative configuration of  FIG. 1 , device housing  12  has an upper portion (display housing  12 A) and a lower portion (base housing  12 B) that are coupled using hinge structures. The hinge structures allow rotational movement of housing structures  12 A and  12 B relative to each other about rotational axis  20 . If desired, device housing  12  may omit the hinge structures (e.g., when forming a handheld device or tablet device). The hinged housing arrangement of  FIG. 1  is merely an example. 
     Device  10  may have one or more displays such as display  14 . Display  14  may, for example, be a touch screen that incorporates capacitive touch electrodes. Display  14  may include image pixels formed from liquid crystal display (LCD) components or other suitable image pixel structures. A cover glass member may cover the surface of display  14 . The cover glass member may be formed from clear plastic, glass, or other transparent materials. If desired, the cover glass may be omitted and other structures in display  14  such as a polarizer layer or a color filter array layer may serve as the outermost layer of display  14 . 
     Openings in housing  12  may be used to form input-output ports, microphone ports, speaker ports, button openings, media ports, etc. Input-output components such as touch pad  16  and keyboard  18  may, if desired, be mounted within housing  12 . 
     To provide a display with backlight, conventional backlight structures are provided with light-emitting diodes that emit light into the edge of a light guide plate. A conventional backlight arrangement of this type is shown in  FIG. 2 . As shown in  FIG. 2 , light guide plate  22  may have a series of notches such as notches  28  along one of its edges that receive light-emitting diodes  24 . Light guide plate  22  may be formed from clear plastic. Light-emitting diodes  24  may be mounted on a strip of flexible printed circuit (“flex circuit”) material. 
     During operation, light-emitting diodes  24  each emit light  26  into light guide plate  22 , as shown in  FIG. 2 . As shown in the cross-sectional side view of conventional display  38   FIG. 3 , light  26  tends to travel within the light guide plate due to total internal reflection. Some of light  26  escapes through the lower surface of light guide plate  22  and is redirected upwards by reflector  32 . Other light  26  escapes directly through upper surface  36  of light guide plate  22 . The light that has escaped from light guide plate  22  travels outwardly through display structures  34  as shown by light rays  30  in  FIG. 3 . Display structures  34  may be liquid crystal display structures that create an array of colored image pixels for display  38 . 
     In creating backlight for display  14  of device  10 , it may be desirable to mount multiple light emitting diodes within a single package. An illustrative light-emitting diode package is shown in  FIG. 4 . As shown in  FIG. 4 , light-emitting diode package  40  may have conductive terminals  52 . Terminals  52  may include a positive terminal and a negative terminal at opposing ends of package structure  48 . When power is applied to terminals  52 , current flows through the light-emitting diode structures within package  40  and light is emitted. 
     As shown in  FIG. 4 , central portion  50  of package structure  48  may be free of terminal structures. Structure  48  may be formed from a non-conducting material (e.g., polymeric material) so that current does not flow between terminals  52  along the surface of package  48 , but rather flows through the light-emitting diode structures that are packaged within package structure  48 . 
     Terminals  52  may be formed from metal or other suitable conductive materials. Package structure  48  and terminals  52  may, if desired, be configured to allow light-emitting diode package  40  to be mounted to a printed circuit board using solder (e.g., solder that electrically and mechanically connects each of terminals  52  to a corresponding conductive trace such as a pad-shaped portion of a trace on a printed circuit). A tool such as a surface mount technology (SMT) mounting tool may be used in attaching package  40  to the printed circuit substrate or other suitable substrate (i.e., package  40  may be an SMT package). 
     In conventional SMT light-emitting diode structures, light is emitted from a single embedded light-emitting diode, as illustrated by dashed line  26  of  FIG. 4 . In embodiments of the backlight used in display  14  of  FIG. 1 , one or more, two or more, or three or more light-emitting diodes may be mounted within a package such as SMT light-emitting diode package  40 . In a configuration in which there are two light-emitting diodes contained within package structure  48 , light may be emitted from package  40  at two locations along edge  42  of package  40 , as illustrated by lines  46  in  FIG. 4 . 
     In a typical arrangement, terminals  52  are mounted face down on a printed circuit or other substrate. In the perspective view of  FIG. 4 , package  40  is shown from the bottom to avoid obscuring terminals  52 . 
     A conventional printed circuit on which conventional light-emitting diodes  24  have been mounted is shown in  FIG. 5 . Printed circuit structures  62  include flexible printed circuit substrate  54 . Conductive traces are formed on substrate  54  such as traces  60  and traces  56 . These traces and extensions to traces  60  that run along the length of substrate  54  are used to distribute power to the conductive terminals of light-emitting diodes  24 . The terminals of diodes  24  are located at the left and right ends of each diode  24  under regions  58 . Solder is used to connect the diode terminals to pad-shaped trace portions  56 . In one configuration, the length D 1  of each diode  24  is about 2.8 mm and the length D 2  of the gap between each adjacent pair of diodes  24  is about 2.6 mm. 
     A side view of a conventional liquid crystal display that is illuminated using light-emitting diode structures of the type shown in  FIG. 5  is shown in  FIG. 6 . With the conventional display arrangement of  FIG. 6 , display  64  has edge mounted light-emitting diodes  24  that emit light  26  into the edge of light guide plate  22  as described in connection with  FIG. 2 . Light-emitting diodes  24  are mounted to a printed circuit substrate of the type shown in  FIG. 5 . During operation of display  64 , backlight from light guide plate  22  may be scattered upwards through liquid crystal display (LCD) structures  34 , as shown by light rays  30 . Adhesive  66  may help attach the display structures of  FIG. 6  to a device housing. Bezel structures  68  may surround the periphery of display  64  and may press display structures  34  and  22  downwards in direction  70 , thereby securing display  64  within the electronic device in which display  64  is used. 
     Conventional arrangements of the type shown in  FIG. 6  require the use of display bezel  68 . In compact devices and devices were a display bezel is not desired for aesthetic reasons, it may be preferable to mount display  64  without using a display bezel. A conventional configuration in which display  64  has been mounted without using a display bezel is shown in  FIG. 7 . As shown in  FIG. 7 , display  64  has been mounted within device housing  84 . Housing  84  has an end portion  78  that is separated from end  80  of light guide plate  22  by gap  76  to accommodate flexing of light guide plate  22  during use of display  64 . Lip portion  72  overhangs end  80  and forms a groove (groove  74 ) in housing  84  that helps retain the right-hand edge portion of display (e.g., light guide plate  22 , display structures  34 , and reflector  32 ) within housing  84 . The left-hand portion of display  64  is attached to housing  84  using adhesive  82 . In particular, adhesive  82  holds the left-hand edge of light guide plate  22  to flex circuit  54  (on which light-emitting diodes  24  are mounted). Flex circuit  54  is attached to housing  84 , so attachment of light guide plate  22  to flex circuit  54  holds light guide plate  22  to housing  84 . 
     By using adhesive  82  and housing groove  74 , the use of display bezel  68  ( FIG. 6 ) can be avoided when mounting display  64  within a device. However, the presence of adhesive  82  can cause visible artifacts in the backlight  30  that is being emitted through the surface of display  64 . This is because adhesive  82  typically includes bubbles and other imperfections that can affect light  26  as light  26  reflects from the lower surface of light guide plate in the vicinity of adhesive  82 . 
       FIG. 8  is an exploded perspective view of backlight structures that may be used in a display such as display  14  of electronic device  10  of  FIG. 1 . The backlight structures of  FIG. 8  include a light guide plate such as light guide plate  90  and light sources such as packaged light-emitting diodes  40 . Light guide plate  90  may have a row of holes  92  that extends parallel to one of the edges of light guide plate  90 . Each hole  92  may separate an edge portion of light guide plate  90  such as edge portion  96  on the outer side of holes  92  near the periphery of light guide plate from main portion  94  of light guide plate  90  on the inner side of holes  92  near the center of light guide plate  90 . In this configuration, holes  92  are surrounded on all four sides by portions of light guide plate  90  so that each hole  92  is enclosed and surrounded by light guide plate material. Light guide plate  90  may be formed from a sheet of clear acrylic or other transparent polymer and may have a thickness of about 0.1 to 1 mm (as an example). The outline of light guide plate  90  may match that of display  14 . 
     Holes  92  may have any suitable shape that accommodates light-emitting diode packages  40  when light-emitting diode packages  40  are mounted to light guide plate  90 . In the example of  FIG. 8 , light-emitting diode packages  40  have elongated rectangular shapes (e.g., using SMT package structures of the type shown in  FIG. 4 ). In this type of configuration, holes  92  may be rectangular and may be sized to mate with the outlines of diode packages  40 . In general, light-emitting diodes  40  may be packaged within any suitable packages (e.g., packages with circular outlines, cylindrical packages, packages with combinations of planar portions and curved portions, packages with outlines having both curved and straight edges, etc.). The example of  FIG. 8  in which rectangular hole shapes are used to receive rectangular light-emitting diode packages is merely illustrative. Different hole (opening) shapes that allow light-emitting diodes  40  in non-rectangular packages to be received within the plane of light guide plate  40  may be used if desired. 
     As shown in  FIG. 8 , light-emitting diode packages  40  may be mounted in a row along a substrate such as substrate  86 . In this type of configuration, light-emitting diode packages  40  may sometimes be referred to as forming a light-emitting diode array. One or more edges of display  14  may be provided with such light-emitting diode arrays to provide backlight for the display. Illustrative configurations in which the left-hand edge of display  14  (in the orientation showing in the drawings) has been provided with an array of light-emitting diode packages  40  are sometimes described as an example. 
     Light-emitting diode array substrate  86  may be a rigid printed circuit board formed from material such as fiberglass-filled epoxy (e.g., FR4), may be flexible printed circuit (“flex circuit”) formed from a flexible sheet of polymer such as a layer of polyimide, may be a ceramic substrate, a plastic substrate, a glass substrate, etc. Conductive traces may be formed on and/or within substrate  86  (e.g., using copper or other metals). These conductive traces, which are shown schematically as traces  88  in  FIG. 8 ) may have the shape of pads (see, e.g. pads  56  of  FIG. 5 ) and may help dissipate heat from packaged light-emitting diodes  40 . Each light-emitting diode package  40  on substrate  86  may have a pair of terminals  52  as shown in  FIG. 4 . These terminals may be soldered to traces  88 . During operation, power may be provided to the light emitting diodes via traces  88 . Tail portion  91  of substrate  86  may be used to interconnect traces  88  to a source of power in electronic device  10 . 
     The presence of edge portion  96  of light guide plate  90  (which is attached to main portion  94  by the material that is interposed between adjacent holes  92 ) may facilitate attachment of the left-hand edge of light guide plate  90  to the housing of device  10  without the need to use adhesive  82  of  FIG. 7  or bezel structures  68  of  FIG. 6 . As shown in  FIG. 9 , portion  96  of light guide plate  90  may be attached to flex circuit substrate  86  using adhesive  104 . 
     Light-emitting diode packages  40  may be soldered or otherwise mounted to flex circuit substrate  86 , so that light  46  can be emitted into portion  94  of light guide plate  90 . Flex circuit substrate  86  may be mounted to housing  12  using adhesive  108 . Because flex circuit substrate  86  is attached to housing  12  (e.g., a planar rear housing wall portion of housing  12 ), light guide plate portion  96  can be securely mounted to housing  12  by attaching portion  96  to flex circuit substrate  86  with the adhesive (adhesive  104 ) that is interposed between portion  96  and flex circuit substrate  86 . Portion  106  of flex circuit substrate  86  need not be covered with adhesive. As a result, the likelihood that light  46  from packaged light-emitting diode  40  will be adversely affected by adhesive and other structures in the vicinity of portion  106  will be reduced and the quality of backlight  112  that is emitted from light guide plate  90  in region  94  can be enhanced. 
     Reflector  100  may help increase the amount of light  112  that is emitted from light guide plate  90 . Reflector  100  may be formed from a reflective material such as white polyester (as an example). Reflector  100  may, as an example, have a thickness of about 0.1 mm to about 0.2 mm. Backlight  112  may pass through display structures  98 . Display structures  98  may include an array of image pixel structures such as liquid crystal display (LCD) image pixels. In an LCD display, display structures  98  may include layers such as thin-film transistor layer  98 B that includes an array of thin-film transistors for controlling LCD image pixels, a corresponding color filter array layer such as layer  98 A that includes an array of colored filter element for providing display  14  with color imaging capabilities, a layer of interposed liquid crystal material between layers  98 A and  98 B, and other optical films (e.g., diffusers, polarizers, etc.). Display structures  98  may use LCD technology or may use alternative display technologies. Touch screen functions may be included in display structures  98  of display  14  (e.g., by including a layer of transparent capacitor electrodes to form a capacitive touch sensor array). 
     Conductive traces  88  may be used to route power signals to the light-emitting diodes in packages  40 . Traces  88  may be uncovered with adhesive in region  106  of flex circuit substrate  86 , which may help prevent light scattering due to the presence of traces  88  in region  106 . In region  96  of flex circuit substrate  86 , adhesive  104  may be interposed between flex circuit substrate  86  (and its associated traces  88 ) and the lower surface of portion  96  of light guide panel. Light  46  is not emitted into this region, so the presence of adhesive  104  and traces  88  under region  96  will not affect the quality of backlight  112 . 
     If desired, housing  12  may have a groove such as groove  12 - 1  that is formed by housing structures such as sidewall structure  12 - 3  and housing lip structure  12 - 2 . Groove  12 - 1  may be use to hold light guide plate  90  in place within housing  12  along the right-hand edge of light guide plate  90  (in the orientation of  FIG. 9 ). Adhesive  104  (and optionally additional adhesive such as adhesive  110  on the upper surface of region  96  of light guide plate  90 ) may also be used in mounting display  14  within housing  12  if desired. 
     Another illustrative arrangement that may be used for display  14  of  FIG. 1  is shown in  FIG. 10 . In the arrangement of  FIG. 10 , portion  106  of flex circuit substrate  86  has been covered with reflective structure  114 . Structure  114  may be, for example, a strip of reflective material (e.g., a sheet of white polyester having a thickness of about 0.03 to 0.07 mm). If desired, a layer of white ink may be deposited on flex circuit substrate  86  to serve as structure  114 . Structure  114  may reflect light  46  that has been emitted from packaged light-emitting diode  40  and therefore serves as an extension to reflector  100 . Because reflective structure  114  helps prevent light from reaching traces  88  in portion  106  of flex circuit substrate  86 , reflective structure  114  can reduce light scattering from traces  88  and can enhance the quality of backlight  112 .  FIG. 11  is a side view of display  14  showing how a single layer of adhesive (portion  116  of adhesive layer  108 ) may be interposed between edge portion  96  of light guide plate  90  and housing  12 . In this type of arrangement, flex circuit substrate  86  does not extend under edge portion  96  (or at least not all of edge portion  96 ), so portion  96  can be attached directly to housing  12  by adhesive portion  116 . To accommodate the thickness of flex circuit substrate  86  and reflector  100 , housing  12  may be provided with a protrusion such as protrusion  12 - 4 . Due to the presence of protrusion  12 - 4  or other structures that raise the height of housing  12  in the vicinity of light guide plate portion  96 , housing  12  may, as an example, have a thickness T 1  that is larger under light guide plate region  96  than housing thickness T 2  under light-emitting diode package  40 . If desired, housing  12  may have a curved shape (e.g., for providing housing  12  with an eased edge), as illustrated by dashed line  118  in  FIG. 11 . The presence of portion  12 - 4  of housing  12  may facilitate the formation of thickened dimension T 1  and/or curved housing edge  118  in device  10 . 
     To ensure that light guide panel  90  is sufficiently strong in the vicinity of holes  92 , it may be desirable to ensure that the regions of light guide panel  90  between adjacent holes  92  are sufficiently large. If holes  92  are too numerous and are too close to each other, the amount of material that remains in the regions interposed between adjoining holes  92  will be relatively small, which might make light guide plate  90  too flexile and therefore too weak along its edge. One way to reduce the size of holes  92  involves minimizing the number and size of the light-emitting diodes that are used to form the backlight illumination. When fewer light-emitting diodes are included in display  14 , there is a reduced need for holes  92 . When weaker light-emitting diodes are used, the size of the required packaging for each diodes may be reduced and the size for holes  92  can be corresponding reduced. In general, either or both of these approaches may be used to ensure that light guide plate  90  is not excessively weakened in the vicinity of holes  92 . 
     Another way in which to ensure that light guide plate  90  is not overly weakened due to the presence of holes  92  involves packaging multiple light-emitting diodes into each SMT package without proportionally increasing the package size. For example, a pair of light-emitting diodes may be incorporated into a package such as package  48  of  FIG. 4  in which the length of the package is less than twice the length of a comparable package for a single light-emitting diode. 
       FIG. 12  is a side view of a light-emitting diode package arrangement that is being used to accommodate multiple light-emitting diodes. In the example of  FIG. 12 , light-emitting diode package  40  contains a pair of diodes  120  connected in series between terminals  52 . A parallel configuration may be used for diodes  120  if desired. 
       FIG. 13  is a top view of this type of light-emitting diode package  40  mounted onto pads (traces  88 ) on flex circuit substrate  86 . The length D 3  of package  40  of  FIG. 13  (i.e., the longer dimension of package structure  48  of  FIG. 4 ) may be less than twice the dimension D 1  of conventional diode  24  of  FIG. 2  in a configuration where each light-emitting diode  120  has a strength equal to the strength of the single conventional light-emitting diode packaged within conventional package  24  of  FIG. 2 . 
       FIG. 14  is a diagram showing how linear packaging space may be conserved by packaging a given type of light-emitting diode into packages in pairs rather than individually. Light-emitting diode array PU of  FIG. 14  is formed from a row of conventional packaged light-emitting diodes  24 . Diode packages  24  each contain one light-emitting diode of a given strength. Light-emitting diode array PL of  FIG. 14  contains is formed from a row of double-diode packages  40 . Each light-emitting diode package  40  in diode array PL of  FIG. 14  contains two light-emitting diodes  120  each of which as the same given strength as the conventional diode packaged into each of packages  24  in array PU. 
     Each of packages  24  has a length D 1  of 2.8 mm and is separated by a distance D 2  of 2.6 mm to ensure that an adequate amount of heat can be dissipated from pads  56 . 
     Each of packages  40  includes two diodes  120 . For example, instead of packaging diodes A and B in respective individual packages  24 , diodes A and B can be packaged within a shared package  40 . Diodes C and D can likewise be packaged in a common SMT package  40  rather than being packaged in respective individual packages  24  as in diode array PU. Due to packaging efficiencies, the length D 3  of each package  40  can be less than twice the length of each package  24 . In particular, D 3  may be about 4.2 mm (as an example), which is less than 5.6 mm (2×2.8 mm). Distance D 4  may be selected so that the linear density of light-emitting diodes  120  is the same in the array of portion PL as in the array of portion PU (i.e., distance D 4  may be 6.6 mm in this example). 
     The example of  FIG. 14  shows that efficiencies may be created by packaging multiple light-emitting diodes in each package that allow for expanded gaps between adjacent holes  92 . In diode array PU, there are gaps of 2.6 mm between each pair of adjacent diode packages, whereas the arrangement of array PL allows gap size to be increased to 6.6 mm without changing the amount of light emitted per unit length. Although there are more gaps of length D 2  per unit length in the arrangement of portion PU than there are gaps of length D 4  per unit length in the arrangement of portion PU, there is more light guide plate material per unit length with the arrangement of portion PL (6.6 compared to 5.2), enhancing the strength of light guide plate  90  in the vicinity of holes  92 . 
     It is not necessary to configure dimensions D 3  and D 4  and the sizes and strengths of the light emitting diodes so that display  14  uses an array PL that has the same backlight intensity per unit length as array PU. The comparison of  FIG. 14  is presented to demonstrate the efficiencies that are produced when packaging multiple light-emitting diodes in a shared package. Smaller or larger packages, more or fewer light-emitting diodes, stronger or weaker light-emitting diodes, and different magnitudes for dimensions D 3  and D 4  may be used if desired. 
     To accommodate a layout of the type described in connection with diode array PL of  FIG. 14 , holes  92  may each have a length of 4.2 mm or more (to accommodate the length D 3  of packages  40 ) and may be separated by a distance D 4  of about 6.6 mm or less. The width W of each package  40  and therefore the width of each hole  92  may be about 2.5 mm (as an example). Other hole configurations may be used in light guide plate  90  if desired. For example, holes  92  may each be about 12 mm in length and 2.5 mm in width and may be separated by gaps of 2.5 mm (as an example). Light-emitting diode packages  40  may be arranged on substrate  86  so as to accommodate this layout of holes  92  in light guide plate  90 . Other configurations for holes  92  and packaged light-emitting diodes  40  may be used if desired. These are merely illustrative configurations. 
     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: 20110118
Publication Date: 20131210
Grant Date: 20131210
Priority Date: 20110118
Inventors: QI JUN
POSNER BRYAN W.
MATHEW DINESH C.
GARELLI ADAM T.
YIN VICTOR H.
HENDREN KEITH J.
DEFOREST LAURA M.
AUGENBERGS PETERIS K.
WILSON, JR. THOMAS W.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B6/0068", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0021", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0068", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0021", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0091", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0073", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0073", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0091", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 46490530