PATENT DOCUMENT

Publication Number: US-8390759-B2
Application Number: US-201213442712-A
Country: US
Kind Code: B2

Title: Electronic device display structures with controlled chassis reflections

Abstract:
A display may be based on a display unit that is mounted within a chassis. The display unit may be a liquid crystal display unit. A backlight may be used to illuminate the display unit. The backlight may include a light guide plate. Light from a light source may be launched into an edge of the light guide plate. Scattered light from the light guide plate may travel vertically along a vertical axis that is perpendicular to the plane that contains the light guide plate. The scattered light may pass through the display unit and may serve as backlight for the display. The light guide plate may be mounted within a rectangular opening in the chassis. The edges of the rectangular opening and the edges of the light guide plate may be configured to reduce excessive reflections. These edges may have reflection-reducing coatings, non-planar surfaces, and other reflection-reducing configurations.

Claims:
1. A display, comprising: a display unit; a light guide plate having at least one edge; a light source that launches light into the at least one edge of the light guide plate, wherein scattered light from the light guide plate passes through the display unit and serves as backlight for the display; a chassis having a rectangular opening in which the light guide plate is mounted; and a coating on the chassis, wherein the coating is selected from the group consisting of: a light-absorbing coating and a light-reflective coating, and wherein the coating is located along the inner periphery of the chassis. 
     
     
       2. The display defined in  claim 1  wherein the chassis has at least one edge and wherein the coating is formed on the at least one edge. 
     
     
       3. The display defined in  claim 2  wherein the coating is a light-absorbing coating and wherein the light-absorbing coating is an opaque ink layer. 
     
     
       4. The display defined in  claim 3  wherein the edge forms an inner surface for the chassis and wherein the coating is formed on the inner surface. 
     
     
       5. The display defined in  claim 2  wherein the coating is a light-reflecting coating, wherein the edge forms an inner surface for the chassis, and wherein the coating is formed on the inner surface. 
     
     
       6. A display, comprising:
 a display unit; 
 a light guide plate having at least one edge; 
 a light source that launches light into the at least one edge of the light guide plate, wherein scattered light from the light guide plate passes through the display unit and serves as backlight for the display; 
 a chassis having a rectangular opening in which the light guide plate is mounted; and 
 a coating on the chassis, wherein the chassis has at least one beveled edge and wherein the coating is formed on the at least one beveled edge. 
 
     
     
       7. The display defined in  claim 1  wherein the light source comprises light-emitting diodes, wherein the light guide plate comprises a transparent polymer, and wherein the chassis comprises plastic. 
     
     
       8. The display defined in  claim 1  wherein the display unit comprises a liquid crystal display unit. 
     
     
       9. A display, comprising:
 a display unit; 
 a light guide plate having edges; 
 a coating on at least one of the edges; 
 a light source that launches light into an edge surface of the light guide plate, wherein scattered light from the light guide plate passes through the display unit and serves as backlight for the display; and 
 a chassis having a rectangular opening in which the light guide plate is mounted, wherein the chassis comprises at least one beveled edge. 
 
     
     
       10. The display defined in  claim 9  wherein the coating comprises a light-absorbing coating. 
     
     
       11. A display, comprising:
 a display unit; 
 a light guide plate having edges; 
 a coating on at least one of the edges of the light guide plate; 
 a light source that launches light into an edge surface of the light guide plate, wherein scattered light from the light guide plate passes through the display unit and serves as backlight for the display; 
 a chassis having a rectangular opening in which the light guide plate is mounted; and 
 a light-absorbing coating on the chassis. 
 
     
     
       12. A display, comprising:
 a display unit; 
 a light guide plate having edges; 
 a coating on at least one of the edges of the light guide plate; 
 a light source that launches light into an edge surface of the light guide plate, wherein scattered light from the light guide plate passes through the display unit and serves as backlight for the display; 
 a chassis having a rectangular opening in which the light guide plate is mounted; and 
 a reflective coating on the chassis. 
 
     
     
       13. A display, comprising:
 a display unit; 
 a light guide plate having at least one beveled edge; 
 a light source that launches light into an edge surface of the light guide plate, wherein scattered light from the light guide plate passes through the display unit and serves as backlight for the display; 
 a chassis having a rectangular opening in which the light guide plate is mounted; and 
 a coating on the chassis, wherein the coating is selected from the group consisting of: a light-absorbing coating and a light-reflecting coating. 
 
     
     
       14. The display defined in  claim 13  wherein the coating is a light reflecting coating, wherein the chassis has at least one edge, and wherein the light-reflecting coating is formed on the at least one edge. 
     
     
       15. The display defined in  claim 13  wherein the coating is a light absorbing coating, wherein the chassis has at least one edge, and wherein the light-absorbing coating is formed on the at least one edge.

Description:
This application is a continuation of U.S. patent application Ser. No. 12/760,950, filed Apr. 15, 2010, which is hereby incorporated by reference herein in its entirety. This application claims the benefit of and claims priority to U.S. patent application Ser. No. 12/760,950, filed Apr. 15, 2010, now U.S. Pat. No. 8,154,680. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and more particularly, to display structures within electronic devices. 
     Electronic devices such as handheld electronic devices often include displays. For example, a cellular telephone may have a touch screen display that is based on a backlit liquid crystal display unit. This type of display has an array of addressable liquid crystal pixels. A backlight provides light for the display. When the backlight is active, light from the backlight is transmitted through the liquid crystal array for viewing by a user. 
     Backlights for displays are often based on light-emitting diodes (LEDs). An LED-based backlight includes a light guide plate formed from a material such as polycarbonate and an LED light source. The LED light source emits light into one of the edges of the light guide plate. The light guide plate distributes the LED light through the liquid crystal array. 
     The liquid crystal array, the light guide plate, and other display structures are typically mounted within a plastic chassis (“p-chassis”). At the edges of the light guide plate, some of the light escapes and strikes the chassis. The chassis has sidewalls that reflect the escaping light back into the light guide plate. The light reflected from the chassis tends to create an undesirable bright stripe of excessive light intensity along the edge of the light guide plate. A masking structure such as an enlarged bezel could be used to block the light in the bright stripe, but large bezels add bulk and tend not to be aesthetically appealing. 
     It would therefore be desirable to provide improved displays for electronic devices. 
     SUMMARY 
     Displays may be provided with backlights. For example, a liquid crystal display may have a backlit liquid crystal display unit. The liquid crystal display unit may have a liquid crystal layer interposed between respective glass layers. An array of electrodes may be used form an array of controllable pixels for the liquid crystal display unit. 
     Illumination for the liquid crystal display unit may be provided by a backlight. The backlight may be formed from a light guide plate. The light guide plate may be mounted on a reflector. A light source such as a light-emitting diode source may be used to launch light into an edge of the light guide plate. Some of the light that is launched into the light guide plate is confined by total internal reflection. Some of the launched light escapes downwards and is reflected upwards by the reflector. Light that is scattered upwards in the vertical direction passes through the liquid crystal display unit and serves as backlight for the display. 
     The light guide plate may be mounted in a rectangular opening in a chassis. The edges of the chassis and corresponding edges of the light guide plate may be configured to minimize excess light reflection. For example, the edges of the chassis may be oriented at non-zero angles with respect to a vertical axis. Coatings such as opaque ink layers and other layers of reflection-reducing material may be formed on the edges to reduce light reflections. Rectangular and curved undercuts, step shapes, textured surfaces, grooved surfaces, and other surfaces may also be used to minimize unwanted reflections. If desired, reflective coatings may be used to help direct reflected light in desired directions and thereby reduce unwanted excessive light intensity along the edges of the display. 
     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 that includes a display in accordance with an embodiment of the present invention. 
         FIG. 2  is a cross-sectional side view of an illustrative display with a light-emitting diode backlight in accordance with an embodiment of the present invention. 
         FIG. 3  is a perspective view of a light guide plate and corresponding chassis in accordance with an embodiment of the present invention. 
         FIG. 4  is a top view of a portion of a display showing how a display chassis may be provided with recesses that receive mating tabs on a light guide plate in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional side view of a conventional liquid crystal display taken through a light guide plate tab and corresponding chassis recess showing how light that is reflected from the edge of a chassis member may be blocked by an overhanging portion of a chassis. 
         FIG. 6  is a cross-sectional side view of a conventional liquid crystal display taken through a portion of the light guide plate other than the tab showing how light that is reflected from the edge of a chassis member creates a bright stripe of excessive light intensity when viewed from the front of the display. 
         FIG. 7  is a cross-sectional side view of a display taken through a tab on a light guide plate and an adjoining beveled chassis member in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional side view of a display taken through a light guide plate and an adjoining beveled chassis member in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional side view of a beveled chassis member in a display in accordance with an embodiment of the present invention. 
         FIG. 10  is a graph showing how the use of chassis members with non-vertical edges may help reduce excessive light intensity in a light guide plate in accordance with an embodiment of the present invention. 
         FIG. 11  is a cross-sectional side view of a light guide plate with a vertical edge and a corresponding chassis with a vertical edge that has been covered with a coating layer in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of a light guide plate with a vertical edge and a corresponding chassis with a non-planar edge surface in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional side view of a light guide plate with a vertical edge and a corresponding chassis with an undercut region having a curved edge surface in accordance with an embodiment of the present invention. 
         FIG. 14  is a cross-sectional side view of a light guide plate with a vertical edge and a corresponding chassis with an edge that has a rectangular undercut region in accordance with an embodiment of the present invention. 
         FIG. 15  is a cross-sectional side view of a light guide plate with a vertical edge and a corresponding chassis with a non-planar stepped edge surface in accordance with an embodiment of the present invention. 
         FIG. 16  is a cross-sectional side view of a light guide plate with a beveled edge and a corresponding chassis with a beveled edge in accordance with an embodiment of the present invention. 
         FIG. 17  is a cross-sectional side view of a light guide plate with a vertical edge that has been covered with a coating layer and a corresponding chassis with a beveled edge in accordance with an embodiment of the present invention. 
         FIG. 18  is a cross-sectional side view of a light guide plate with a vertical edge and a corresponding chassis with a beveled edge that has been covered with a coating layer in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Displays such as liquid crystal displays have backlights. A display backlight includes a light guide plate mounted in a chassis. 
     A display may be provided with reflection control features that control the intensity of reflected light at the edges of the light guide plate. The reflection control features may be implemented using non-planar and angled chassis edges, non-planar and angled light guide plate edges, and coatings. 
     The displays in which the reflection control features are provided may be mounted in electronic devices in which it is desired to display visual information to a user. The electronic devices may, for example, be desktop computers, televisions, or other consumer electronics equipment. The electronic devices may also be portable electronic devices such as laptop computers and tablet computers. If desired, portable electronic devices may be somewhat smaller devices. Examples of smaller portable electronic devices include wrist-watch devices, pendant devices, headphone and earpiece devices, and other wearable and miniature devices. With one suitable arrangement, the portable electronic devices may be handheld electronic devices such as cellular telephones and media players. 
     Handheld electronic devices and other electronic devices may include displays to display text, graphics, video, interactive options, and other visual information to users. An illustrative electronic device of the type that may have a display is shown in  FIG. 1 . Device  10  of  FIG. 1  may be, for example, a handheld electronic device such as a cellular telephone with circuitry that runs email and other communications applications, web browsing applications, media playback applications, games, etc. 
     Device  10  may have housing  12 . Housing  12  may be formed of materials such as plastic, glass, ceramics, metal, carbon fiber composites and other composite materials, other suitable materials, or a combination of these materials. Housing  12  may be formed using a unibody construction in which most or all of the exterior of housing  12  and at least some of its interior structures are formed from a single piece of material (e.g., molded plastic, machined metal, cast or stamped metal with machined surfaces, etc.). Housing  12  may also be formed using a multi-piece construction in which portions of the housing are formed from separate parts (e.g., housing side walls, a rear housing surface, internal supports and frame structures, etc.). 
     Display  16  may be mounted on the front surface of device  10  and may, if desired, be surrounded by peripheral structures such as bezel  14 . Bezel  14  may be formed from plastic, metal, portions of housing  12 , or other cosmetic and structural elements. Bezel  14  may serve to hold display  16  on device  10 . Bezel  14  may also form an aesthetically pleasing trim around the edge of device  10 . If desired, displays such as display  16  may be mounted in housing  12  without using bezel  14 . 
     Display  16  may be a liquid crystal display (LCD) or other display that includes a backlit array of active pixels. In a liquid crystal display, individual pixels in the array are addressed using driver circuits that control voltages on pixel electrodes in the array. 
     A protective outer layer of plastic or glass may be provided over the outermost surface of display  16  to protect display  16  from damage. This layer is sometimes referred to as a cover glass layer. If desired, touch screen functionality may be integrated into display  16  or may be provided using a separate touch pad device. An advantage of integrating a touch screen into display  16  to make display  16  touch sensitive is that this type of arrangement can save space and reduce visual clutter. 
     If desired, electronic device  10  may include input-output devices such as button  20  and other buttons, input-output connectors for signal ports, a speaker port such as speaker port  18 , microphone and camera ports, and other input-output devices. 
     In the example of  FIG. 1 , display  16  is shown as being mounted on the front face of handheld electronic device  10 , but display  16  may, if desired, be mounted on the rear face of handheld electronic device  10 , on a side of device  10 , on a flip-up portion of device  10  that is attached to a main body portion of device  10  by a hinge (for example), or using any other suitable mounting arrangement. 
     Display  16  may have an active central portion that contains image pixels and an inactive peripheral portion. No image is created in the inactive portion of the display. In the active central portion of the display, image pixels can be controlled to display a desired image. In the example of  FIG. 1 , active central rectangular portion  28  of display  16  lies within dashed rectangle  24 . Inactive peripheral portion  26  of display  16  lies outside of rectangle  24 . Peripheral portion  26  forms an inactive boundary that surrounds the rectangular active region. Components such as button  20  and speaker port  18  may be formed in this inactive boundary. 
     To block internal structures in the inactive regions of display  16  from view by a user of device  10 , the cover glass of display  16  may be provided with an opaque mask. The opaque mask may be formed from a black ink or other substance that blocks visible light. The opaque mask may be formed over the inactive portions of display  16 . For example, the periphery of the cover glass of display  16  may be provided with an interior coating of black ink. The portion of the cover glass that overlaps active region  28  may be uncovered with ink so that this region remains transparent. To ensure that device  10  has a compact and aesthetically pleasing design, it may be desirable to minimize the width of inactive border region  26  and the ring of associated black ink that is formed on the underside of the display cover glass. 
     A cross-sectional side view of portions of an illustrative display is shown in  FIG. 2 . As shown in  FIG. 2 , display  16  may include a liquid crystal layer such as layer  32 . Liquid crystal layer  32  may be formed between upper glass layer  30  and lower glass layer  34 . A backlight provides rear illumination for the liquid crystal layer. The backlight may include a light source such as light-emitting diode source  42 , light guide plate  38 , reflector  40 , and optical films  36 . Light source  42  produces visible light  44  (e.g., white light). Light  44  is launched into the interior of light guide plate  38  through a textured edge region of light guide plate  38 . 
     Light guide plate  38  may be formed from a transparent dielectric such as transparent (translucent) plastic (e.g., polycarbonate, acrylic, cyclic olefin copolymer materials, etc.). The thickness of the light guide plate may be 0.2 to 0.5 mm or 0.1 to 1.0 mm (as examples). At least some of light  44  is confined within light guide plate  38  by total internal reflection. A pattern of light scattering structures may be formed on the light guide plate. The light scattering structures scatter the light that is traveling horizontally within light guide plate  38 . Some of the scattered light exits light guide plate  38  and display  16  in vertical direction  46 . Scattered light that exits the rear surface of light guide plate  38  is reflected in direction  46  by reflector  40 . Reflector  40  may be formed from a metalized polymer sheet (e.g., a silvered sheet of acrylic or other polymer materials, a layer of metal, or a reflector sheet that is formed by alternating high index of refraction and low index of refraction layers). Optical films  36  may include a diffuser sheet that smoothes the light exiting the surface of display  16 . 
     Display structures such as light guide plate  38  may be mounted in a chassis such as chassis  52  of  FIG. 3 . Chassis  52  may be formed from a ring of plastic or other suitable material that serves as an interface between the structures of display  16  and surrounding portions of housing (e.g., a plastic ring with a thickness of about 0.2 to 1.5 mm). If desired, chassis  52  may be formed from a plate of material that includes a rectangular recess to accommodate display structure such as light guide plate  38 . Chassis  52  may be formed from housing structures (e.g., as part of a housing frame, part of a unibody housing such as a metal housing, etc.). 
     As shown in  FIG. 3 , light guide plate  38  may have protruding alignment structures such as alignment tabs  48 . Chassis  52  may have corresponding recesses  50  or other alignment features that receive alignment tabs  48 . Alignment tabs  48  and recesses  50  serve to align light guide plate  38  in chassis  52  and prevent light guide plate  38  from sliding within chassis  52 . 
     A top view of a portion of light guide plate  38  and chassis  52  in the vicinity of one of tabs  48  is shown in  FIG. 4 . As shown in  FIG. 4 , tab  48  may protrude into recess  50  in chassis  52 . Inner peripheral edge  62  of chassis  52  runs parallel to outer peripheral edge  64  of light guide plate  38 . An air gap of about 10-60 microns may separate edges  62  and  64  (as an example). 
     A cross-sectional side view of a conventional display in the vicinity of a light guide tab (i.e., a sectional view taken along a line such as line  54  of  FIG. 4  and viewed in direction  56 ) is shown in  FIG. 5 . As shown in  FIG. 5 , light  274  travels through the interior of light guide  238 . Some of light  274  is scattered and reflected upwards in direction  275  and serves as backlight for a display. Some of light  274  escapes from vertical planar edge  264  of light guide plate  238  and is reflected from vertical planar edge  262  of chassis  252  (forming reflected light  276 ). Tab  278  is received in a recess formed under overhanging portion  268  of chassis  252 . Overhanging portion  268  and black ink masking border  272  block at least some of light  276 , creating a locally darkened appearance to the display when viewed in direction  270 . 
     A cross-sectional side view of the conventional display of  FIG. 5  in a portion of the display that does not include tab  278  of  FIG. 5  (i.e., a sectional view taken along a line such as line  58  of  FIG. 4  and viewed in direction  60 ) is shown in  FIG. 6 . As shown in  FIG. 6 , in portions of the display without tabs, light  274  that escapes from light guide plate edge  262  and that is reflected from chassis edge  262  as reflected light  276  is not blocked by overhanging portions of chassis  252  or black ink  272 . As a result, reflected light  276  is visible in direction  270 . Portions of the display that are not adjacent to edge  262  are not affected by the presence of edge  262  and do not receive reflected light such as reflected light  276 . Reflected light  276  therefore creates a bright stripe of excessive light around the periphery of a conventional display. 
     A cross-sectional side view of portions of display  16  taken through line  54  of  FIG. 4  and viewed in direction  56  is shown in  FIG. 7 . As shown in  FIG. 7 , tab  48  of light guide plate  38  may be received within recess  50  of chassis  52 . Edge  62  of chassis  52  may, if desired, be angled (beveled) in the vicinity of edge  64  of light guide plate  48 . In the arrangement of  FIG. 7 , edge  62  is angled downwards at a non-zero angle with respect to vertical axis  66 , so that the intensity of reflected light in direction  76  is reduced. Vertical axis  66  is perpendicular to the plane in which light guide plate  38  lies and is perpendicular to the surface of display  16 . With the structures of  FIG. 7 , reflected light in direction  76  may also be blocked by overhanging portion  72  of chassis  52  and by opaque masking layer  70  on display cover glass  68  (i.e., a border of black ink). 
     A cross-sectional side view of portions of display  16  taken through line  58  of  FIG. 4  and viewed in direction  60  is shown in  FIG. 8 . As shown in  FIG. 8 , edge  62  of chassis  52  may be angled downwards so that its planar surface forms a non-zero angle with respect to vertical axis  66  (and the vertical plane that is parallel to axis  66  and that contains vertical planar edge  64  of light guide plate  38 ). 
     The angle of beveled chassis edge  62  reduces the intensity of the light that is reflected from edge  62  in direction  76  after escaping from edge  64  of light guide plate  38 , thereby reducing or eliminating the stripe of excess light intensity that is present along the edges of conventional displays. 
     The way in which peripheral light intensity is reduced by the presence of the beveled shape of edge  62  of chassis  52  is illustrated in  FIG. 9 . Light that escapes from edge  64  of light guide plate  38  is illustrated by light ray  44 . In the diagram of  FIG. 9 , light ray  44  is shown as traveling horizontally (i.e., parallel to the upper and lower planar surfaces of light guide  38 ). In practice, light travels at a range of angles about horizontal ray  44 . 
     When light  44  strikes chassis edge  62 , at least some of the light is reflected. The angle of the bevel of edge  62  affects the direction in which light is reflected from chassis  52 . In the illustrative configuration of FIG.  9 , most or all of light  44  is reflected downwards as shown by reflected light ray  74 . Light reflections in direction  76  are eliminated or at least minimized. This eliminates or at least minimizes the bright stripe of excess light intensity that would otherwise be presence along the edge of the display (i.e., near dashed line  24  in  FIG. 1 ). 
       FIG. 10  is a graph that compares the amount of reflected light in conventional displays versus displays with reflected edge light control features of the type shown in  FIGS. 7 and 8 . In the graph of  FIG. 10 , curve  78  corresponds to the intensity I of reflected light from a conventional vertical planar chassis edge such as chassis edge  262  of  FIG. 6  as a function of reflection angle θ ( FIG. 8 ). Curve  80  corresponds to the intensity I of reflected light from a chassis edge such as beveled chassis edge  62  of  FIGS. 7 and 8 . Because chassis edge  62  of  FIGS. 7 and 8  has a shape that reduces the amount of light that is reflected in direction  76 , the maximum light intensity I is reduced (i.e., from a maximum of IH for conventional displays at reflection angle LM to a reduced value of IL at reflection angle LM). Reflection angle LM may be about 10-40° and may correspond to direction  76  in  FIGS. 7 ,  8 , and  9  and direction  276  in  FIGS. 5 and 6 . 
     In the example of  FIGS. 7 ,  8 , and  9 , unwanted reflections from edge  62  of chassis  52  in direction  76  were minimized by providing edge  62  with a bevel (i.e., an angle tilting the surface of edge  62  away from vertical axis  66  of  FIG. 7 ). If desired, other configurations may be used to minimize reflections in direction  76 . In particular, edges  62  and  64  may be provided with textured or non-planar surfaces, edges  62  and  64  may be provided with coatings, or combinations of these types of arrangements may be used. 
     As shown in  FIG. 11 , for example, edge  62  of chassis  52  may be provided with coating layer  82 . Coating  82  may be formed from plastic, metal, ink, paint, or any other suitable material. The presence of coating  82  may reduce reflections. For example, coating  82  may be based on a light-absorbing material such as matte black ink. When light strikes a coating of this type, the coating absorbs a portion of the light and thereby minimizes the intensity of light reflected in direction  76 . Coatings that absorb more light than an uncoated planar plastic surface are sometimes referred to herein a reflection-reducing coatings. 
     If desired, coating  82  may be formed from a reflective material such as metal. Coating  82  may, for example, be formed from a layer of silver paint or a coating of aluminum or other reflective materials (e.g., high-low dielectric stacks). With this type of coating, light reflections from the surface of edge  62  tend to exhibit increased directionality (i.e., the reflections are specular). The increased reflectivity that is provided to edge  62  when this type of reflective coating is applied to edge  62  may help enhance the ability of the bevel to direct reflected light downwards away from direction  76 . Reflective coatings may be used on beveled edges, on textured edges, on non-planar edges, or on other types of surfaces. 
       FIG. 12  shows how edge  62  on chassis  52  may be provided with multiple triangular grooves (i.e., a pattern of repeating small parallel bevels that provide edge  62  with a sawtooth profile). The grooves may run parallel to one another along edge  62  and may have any suitable cross-sectional shape (i.e., triangular as shown in  FIG. 12 , semicircular, curved, straight, rectangular, etc.). The grooves may all be the same size or may have different sizes. If desired, edge  62  may be provided with other types of textures to reduce reflections in direction  76  (e.g., random bumps, cross-hatched grooves, etc.). 
     As shown in  FIG. 13 , chassis  52  may be provided with a curved undercut. Edge  62  may, for example, have curved section  86 . When light exiting light guide plate  38  strikes curved edge portion  86 , the light will be directed downwards away from direction  76 . 
     Another possible arrangement for reducing undesired edge reflections from chassis  52  is shown in  FIG. 14 . In the example of  FIG. 14 , chassis  52  is provided with a rectangular undercut so that edge  62  has upper planar surface  62 A and recessed lower planar surface  62 B. The presence of upper surface  62 A helps hold light guide plate  38  in place. The presence of overhang  88  on chassis  52  helps block reflections of light from surface  62 B in direction  76 . 
     As shown in  FIG. 15 , edge  62  may be provided with multiple rectangular steps. This type of pattern may spread out the location of light reflecting from edge  62  and thereby may reduce the maximum local intensity of reflected light in direction  76 . The arrangement of  FIG. 15  has three rectangular steps, but edge profiles with more than three rectangular steps or fewer than three rectangular steps may be used. If desired, steps of other shapes may be formed (e.g., curved steps, triangular steps, combinations of curved, triangular, and rectangular steps, etc.). 
     In the illustrative arrangement of  FIG. 16 , both edge  62  of chassis  52  and edge  64  of light guide plate  38  are beveled. The angle of edge  62  and edge  64  in this type of configuration may be matched or each edge may have a bevel of a different angle. Bevel angles that may be used for edges  62  and  64  may range from 10-30° relative to vertical, 5-45°, 4-60°, may be less than 50°, less than 40°, may be less than 20°, etc. 
       FIG. 17  shows how edge  64  of light guide plate  38  may be provided with a coating such as coating  90 . Coating  90  may be a light-absorbing coating (i.e., a reflection-reducing coating of matte black ink or other suitable material), etc. The presence of a light-absorbing coating such as coating  90  on end  64  of light guide plate  38  may help reduce the amount of light that exits end  64  and may thereby help reduce the amount of light that reflects from edge  62  of chassis  52 . As the  FIG. 17  example demonstrates, different types of reflection-reducing structures may be used simultaneously. For example, coating  90  may be provided on light guide plate  38  while chassis  52  is provided with a beveled edge. 
     As shown in  FIG. 18 , coatings may be provided on edges that have other reflection-reducing structures (e.g., sawtooth grooves or grooves of other shapes, other types of textures such as textures formed from bumps, step-shaped structures, curved structures, overhangs, etc.). In the  FIG. 18  example, coating  92  has been provided on angled edge  62 . Coating  92  may be a light-absorbing coating that helps reduce the amount of light that is reflected from edge  62  or may be a reflective coating that helps direct light downwards away from direction  76 . 
     Reflection-reducing structures may be used in the vicinity of tabs  48  (i.e., on the protruding edges along the outer portions of tabs  48  and the corresponding edges within the mating portions of recesses  50 ). Preferably, reflection-reducing structures are used on the other portions of chassis  52  and light guide plate  38  (i.e., on the portions of chassis  52  and light guide plate  38  that are located away from tabs  48 ). Different portions of the edges of light guide plate  38  and chassis  52  may be provided with different edge treatments if desired. For example, a chassis with a rectangular opening that has four edges may have different types of reflection-reducing structures on each of its four edges. A chassis may also be provided with different reflection-reducing structures along different portions of an edge. 
     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: 20120409
Publication Date: 20130305
Grant Date: 20130305
Priority Date: 20100415
Inventors: DOYLE DAVID A.
WURZEL JOSHUA G.
GETTEMY SHAWN R.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/133615", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133317", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0055", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0088", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2201/38", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2201/38", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133615", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0088", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133317", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0055", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 44787955