PATENT DOCUMENT

Publication Number: US-9057808-B2
Application Number: US-201313886970-A
Country: US
Kind Code: B2

Title: Textured light guide to reduce friction with film

Abstract:
Systems, devices, and methods are provided for using a textured surface of a light guide plate to reduce friction between the light guide plate and an adjacent film. A textured surface across an interior region of the light guide may guide light towards a top surface of the textured light guide. A film positioned on the bottom surface of the textured light guide may reflect light towards the top surface. The film may be positioned within the interior region as a substantially flat (e.g., planar) layer. The surface features may reduce the friction to enable the textured light guide plate and/or film to expand or contract independently from one another due to varying temperatures without forming wrinkles on the film or changing the planarity of the film.

Claims:
What is claimed is: 
     
       1. A backlight assembly, comprising:
 a textured light guide comprising a first surface, wherein the first surface comprises a surface length, a surface width, and a plurality of surface features across an interior region of the first surface, wherein the plurality of surface features are disposed along and within a perimeter of the interior region, wherein the interior region comprises an interior length and an interior width, wherein the interior length is less than the surface length, and wherein the interior width is less than the surface width; and 
 a film disposed within the perimeter of the interior region and disposed on the plurality of surface features, wherein the film comprises a film length and a film width, wherein the film length is less than the interior length, and wherein the film width is less than the interior width. 
 
     
     
       2. The backlight assembly of  claim 1 , wherein the plurality of surface features is arranged in a pattern across the interior region. 
     
     
       3. The backlight assembly of  claim 1 , wherein the plurality of surface features comprise one or more micro-lenses, micro-prisms, grooves, notches, or printed dots, or any combination thereof. 
     
     
       4. The backlight assembly of  claim 1 , wherein the plurality of surface features comprises perimeter surface features disposed along the perimeter, and the plurality of surface features comprises interior surface features disposed within the perimeter, wherein the perimeter surface features are different from the interior surface features. 
     
     
       5. The backlight assembly of  claim 1 , wherein the a first difference between the interior length and the film length is between approximately 0.1 to 1 mm, and a second difference between the interior width and the film width is between approximately 0.1 to 1 mm. 
     
     
       6. The backlight assembly of  claim 1 , wherein the film is disposed an approximately uniform distance from the first surface at any temperature of the textured light guide, the film, or both between approximately −40° C. to 85° C. 
     
     
       7. The backlight assembly of  claim 6 , wherein each surface feature of the plurality of surface features extends the approximately uniform distance from the first surface, wherein the approximately uniform distance is between 10-40 μm. 
     
     
       8. The backlight assembly of  claim 1 , wherein the film comprises an enhanced specular reflector film. 
     
     
       9. A backlight assembly, comprising:
 a textured light guide comprising a top surface, a bottom surface, and a plurality of edges, wherein the bottom surface comprises an interior region comprising a plurality of surface features within a perimeter, wherein the perimeter is spaced apart from the plurality of edges; 
 a reflector film disposed within the perimeter and disposed adjacent to the plurality of surface features; 
 one or more optical films disposed adjacent to the top surface; and 
 a light source configured to emit light into the textured light guide along a first edge of the plurality of edges toward an opposing second edge of the plurality of edges, wherein at least some of the plurality of surface features are configured to direct the emitted light toward the top surface. 
 
     
     
       10. The backlight assembly of  claim 9 , wherein the perimeter is spaced a first distance from the first edge, the perimeter is spaced a second distance from the second edge, the first distance is greater than the second distance, and the second distance is less than or equal to approximately 1 mm. 
     
     
       11. The backlight assembly of  claim 9 , wherein the plurality of surface features comprises a first group of surface features and a second group of surface features, wherein the first group of surface features comprises surface features of the plurality of surface features proximate to the first edge, and the first group of surface features differ from the second group of surface features in geometry, material, or coefficient of friction, or reflectivity, or any combination thereof. 
     
     
       12. The backlight assembly of  claim 11 , wherein the first group of surface features comprises perimeter surface features of the plurality of surface features disposed along the perimeter, and the second group of surface features comprises interior surface features of the plurality of surface features disposed within the perimeter. 
     
     
       13. The backlight assembly of  claim 9 , wherein the bottom surface is substantially smooth between the plurality of edges and the perimeter. 
     
     
       14. The backlight assembly of  claim 13 , wherein the reflector film is substantially parallel to the bottom surface at temperatures between approximately −40° C. to 85° C., and the bottom surface is substantially planar. 
     
     
       15. The backlight assembly of  claim 9 , wherein the reflector film comprises a specular reflector or a diffuse reflector. 
     
     
       16. The backlight assembly of  claim 9 , wherein the light source comprises one or more light emitting diodes (LEDs). 
     
     
       17. An electronic display, comprising:
 a liquid crystal display panel comprising a display region; and 
 a backlight assembly configured to supply light to illuminate the liquid crystal display panel, wherein the backlight assembly comprises:
 a textured light guide comprising a top surface and bottom surface, wherein the bottom surface comprises a plurality of surface features across an interior region of the bottom surface, an interior area of the interior region is greater than or equal to a display area of the display region, the interior region is disposed beneath the display region, and the interior region comprises an interior length and an interior width; 
 a reflector film disposed adjacent to the plurality of surface features and disposed within the interior region of the textured light guide, wherein the film comprises a film length and a film width, the film length is less than the interior length, and the film width is less than the interior width; 
 one or more optical films disposed adjacent to the top surface of the textured light guide; and 
 a light source configured to emit light into the textured light guide along a first edge of the textured light guide between the top surface and the bottom surface of the textured light guide, wherein at least some of the plurality of surface features are configured to direct the emitted light through the optical films and the display area. 
 
 
     
     
       18. The electronic display of  claim 17 , wherein the reflector film is configured to slide without wrinkling within the interior region along the plurality of surface features relative to the textured light guide when the textured light guide expands or contracts relative to the reflector film. 
     
     
       19. The electronic display of  claim 17 , wherein the reflector film comprises a plurality of reflector layers and a laminate layer. 
     
     
       20. The electronic display of  claim 19 , wherein a thickness of the reflector film is less than approximately 0.165 mm. 
     
     
       21. The electronic display of  claim 17 , wherein the optical films comprise a brightness enhancement film, a diffuser film, or both. 
     
     
       22. An electronic device, comprising:
 one or more input structures; 
 a storage structure encoding one or more executable routines; 
 a processor capable of receiving inputs from the one or more input structures and of executing the one or more executable routines when loaded in the storage structure; and 
 a display device configured to display an output of the processor, wherein the display device comprises:
 a liquid crystal display panel; and 
 a backlight assembly configured to supply light to illuminate the liquid crystal display panel, wherein the backlight assembly comprises:
 a textured light guide comprising a top surface, a bottom surface, and a plurality of edges, wherein the bottom surface comprises an interior region comprising a plurality of surface features within a perimeter, wherein the perimeter is spaced at least a second distance from the plurality of edges of the textured light guide; and 
 a reflector film disposed adjacent to the bottom surface of the textured light guide, wherein the reflector film is spaced between approximately 0.1 to 1 mm from the perimeter. 
 
 
 
     
     
       23. The electronic device of  claim 22 , wherein the electronic device comprises a desktop computer, a laptop computer, a tablet computer, a media player, a portable phone, a personal data organizer, or a handheld game platform. 
     
     
       24. A method for manufacturing an electronic display, comprising:
 forming surface features across an interior region of a bottom surface of a textured light guide, wherein the surface features are molded, etched, or printed, or any combination thereof; 
 positioning a reflector film adjacent to the interior region, wherein the reflector film is vertically spaced a first distance from the bottom surface, and wherein the reflector film is positioned within the interior region and spaced between approximately 0.1 to 1 mm from a perimeter; 
 forming a backlight assembly about the textured light guide and reflector film; and 
 joining the backlight assembly with a liquid crystal display panel and a frame. 
 
     
     
       25. The method of  claim 24 , wherein the reflector film is substantially planar and is positioned to be substantially parallel to the textured light guide.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Non-Provisional Application of U.S. Provisional Patent Application No. 61/699,759, entitled “Textured Light Guide to Reduce Friction with Film”, filed Sep. 11, 2012, which is herein incorporated by reference. 
     BACKGROUND 
     The present disclosure relates generally to a backlight assembly for an electronic display and, more particularly, to a backlight assembly having a patterned light guide. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Electronic displays, such as liquid crystal displays (LCDs), commonly appear in many different electronic devices, such as televisions, computers, and phones. LCDs portray images by modulating the amount of light that passes through a liquid crystal layer within pixels of varying color. A display driver for the LCD produces images on the display by adjusting the image signal supplied to each pixel across the display. The brightness of an LCD depends on the amount of light provided by a backlight assembly. As the backlight assembly provides more light, the brightness of the LCD increases. 
     Backlight assemblies may be arranged in a direct-lit backlight configuration in which a light source (e.g., a lamp or light emitting diodes) is provided behind, and directs light through a light guide plate, or light guide, to an LCD panel. To reduce the thickness of the LCD, an edge-lit backlight configuration may instead be used, in which the light source is oriented to illuminate an edge of the light guide, which in turn distributes such light to the LCD panel. Various films may be used with the light guide to affect the light directed to the LCD panel. Unfortunately, non-uniformities in a film may affect the appearance of the display. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     Embodiments of the present disclosure relate to systems, devices, and methods for using a textured surface of a light guide plate to reduce friction between the light guide plate and an adjacent film. By reducing the friction between the light guide plate and the film, non-uniformities of the film may be avoided when temperature changes cause the light guide plate and the film to expand and/or contract at different rates. In one example, a light source (e.g., light emitting diodes (LEDs), cold cathode fluorescent lamps (CCFLs)) may emit light along a first edge of the light guide. The first edge is between a top face and an opposing bottom face of the light guide. The bottom face may include a textured surface across an interior region of the light guide. The textured surface may include a pattern of dots, bumps, notches, grooves, or other surface features spaced a distance from the perimeter of the light guide. In some embodiments, at least part of the textured surface may direct the light towards the top face of the textured light guide. A film (e.g., reflector) positioned on the bottom face of the textured light guide may reflect light from the light source towards the top face. The film may be positioned on the textured light guide within the interior region as a substantially flat (e.g., planar) layer to enable the display to have a uniform appearance, such as by uniformly reflecting light toward the top face. The surface features may reduce the friction to enable the textured light guide plate and/or film to expand or contract independently from one another without forming wrinkles on the film or changing the planarity of the film. 
     Various refinements of the features noted above may be made in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a schematic block diagram of an electronic device that incorporates a display with a textured light guide plate, in accordance with an embodiment; 
         FIG. 2  is a perspective view of an example of the electronic device of  FIG. 1  in the form of a notebook computer, in accordance with an embodiment; 
         FIG. 3  is a front view of an example of the electronic device of  FIG. 1  in the form of a handheld electronic device, in accordance with an embodiment; 
         FIG. 4  is an exploded-view of the electronic display of the electronic device with a backlight assembly, in accordance with an embodiment; 
         FIG. 5  is a schematic view of an embodiment of the backlight assembly of  FIG. 4 , taken along line  5 - 5 , illustrating a light guide and a reflector film; 
         FIG. 6  is a top view of a light guide and a reflector film positioned within an interior region of the light guide, in accordance an embodiment; and 
         FIG. 7  is a flow chart of a method for manufacturing the electronic display of  FIG. 4 , in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an example,” or the like, are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     As mentioned above, embodiments of the present disclosure relate to a textured light guide plate that reduces friction between the textured light guide plate and a film. Surface features may be spread across an interior region of a surface of the textured light guide. The film may be a reflector film positioned along a plane beneath the textured light guide. The film may be positioned within the interior region and spaced a distance from an interior region perimeter so that the film remains within the interior region regardless of temperature. The surface features may reduce the friction between the textured light guide and film so that differences in magnitudes and/or rates of thermal expansion and contraction of the textured light guide and film do not cause the film to wrinkle or form non-uniformities along its plane. The surface features may enable the film to slide relative to the textured light guide. 
     With the foregoing in mind, a general description of suitable electronic devices that may employ electronic displays with a textured light guide will be provided below. In particular,  FIG. 1  is a block diagram depicting various components that may be present in an electronic device suitable for use with such a display.  FIGS. 2 and 3  illustrate various examples of suitable electronic devices in the form of a notebook computer and a handheld electronic device, respectively. 
     Turning first to  FIG. 1 , an electronic device  10  according to an embodiment of the present disclosure may include, among other things, one or more processor(s)  12 , memory  14 , nonvolatile storage  16 , a display  18  having a textured light guide plate  20 , input structures  22 , an input/output (I/O) interface  24 , network interfaces  26 , and a power source  28 . The various functional blocks shown in  FIG. 1  may include hardware elements (including circuitry), software elements (including computer code stored on a computer-readable medium) or a combination of both hardware and software elements. It should be noted that  FIG. 1  is merely one example of a particular implementation and is intended to illustrate the types of components that may be present in electronic device  10 . 
     By way of example, the electronic device  10  may represent a block diagram of the notebook computer depicted in  FIG. 2 , the handheld device depicted in  FIG. 3 , or similar devices. It should be noted that the processor(s)  12  and/or other data processing circuitry may be generally referred to herein as “data processing circuitry.” Such data processing circuitry may be embodied wholly or in part as software, firmware, hardware, or any combination thereof. Furthermore, the data processing circuitry may be a single contained processing module or may be incorporated wholly or partially within any of the other elements within the electronic device  10 . 
     In the electronic device  10  of  FIG. 1 , the processor(s)  12  and/or other data processing circuitry may be operably coupled with the memory  14  and the nonvolatile storage  16  to execute instructions to carry out various functions of the electronic device  10 . Among other things, these functions may include generating image data to be displayed on the display  18 . The programs or instructions executed by the processor(s)  12  may be stored in any suitable article of manufacture that includes one or more tangible, computer-readable media at least collectively storing the instructions or routines, such as the memory  14  and/or the nonvolatile storage  16 . The memory  14  and the nonvolatile storage  16  may represent, for example, random-access memory, read-only memory, rewritable flash memory, hard drives, and optical discs. Also, programs (e.g., an operating system) encoded on such a computer program product may also include instructions that may be executed by the processor(s)  12  to enable other functions of the electronic device  10 . 
     The display  18  may be a touch-screen liquid crystal display (LCD), for example, which may enable users to interact with a user interface of the electronic device  10 . By way of example, the display  18  may be a MultiTouch™ display that can detect multiple touches at once. The display  18  may include a textured light guide plate  20  to guide (e.g., reflect and/or refract) light from light sources to illuminate substantially the entire display  18 . Illuminating the display  18  may increase the visibility of the image data shown on the display  18 . As discussed in detail below, textured light guide  20  may include light-extracting elements, such as printed dots, micro-lenses, and/or micro-prisms, or any other type of optical feature suitable for disrupting total internal reflection within the textured light guide  20 . The light-extracting elements or other surface features may reduce the friction between the light guide and an adjacent film. Reducing the friction between the textured light guide  20  and an adjacent film may enable the textured light guide  20  to expand and contract relative to the film without sticking to the film and forming wrinkles, folds, ridges, or other planar irregularities. Sticking may be defined herein as exerting a friction force sufficient to compress or fold the film. The textured light guide  20  may enable the electronic device  10  to be exposed to large temperature shifts (e.g., approximately 50° C. or more) without forming non-uniformities of the film adjacent to the textured light guide  20  that may affect the appearance of the display  18 . 
     The input structures  22  of the electronic device  10  may enable a user to interact with the electronic device  10  (e.g., pressing a button to increase or decrease a volume level). The I/O interface  24  may enable electronic device  10  to interface with various other electronic devices, as may the network interfaces  26 . The network interfaces  26  may include, for example, interfaces for a personal area network (PAN), such as a Bluetooth network, for a local area network (LAN), such as an 802.11x Wi-Fi network, and/or for a wide area network (WAN), such as a 3G or 4G cellular network. The power source  28  of the electronic device  10  may be any suitable source of power, such as a rechargeable lithium polymer (Li-poly) battery and/or an alternating current (AC) power converter. 
     The electronic device  10  may take the form of a computer or other type of electronic device. Such computers may include computers that are generally portable (such as laptop, notebook, and tablet computers) as well as computers that are generally used in one place (such as conventional desktop computers, workstations and/or servers). In certain embodiments, the electronic device  10  in the form of a computer may be a model of a MacBook®, MacBook® Pro, MacBook Air®, iMac®, Mac® mini, or Mac Pro® available from Apple Inc. By way of example, the electronic device  10 , taking the form of a notebook computer  30 , is illustrated in  FIG. 2  in accordance with one embodiment of the present disclosure. The depicted computer  30  may include a housing  32 , a display  18 , input structures  22 , and ports of an I/O interface  24 . The input structures  22 , such as a keyboard and/or touchpad, may be used to interact with the computer  30 . Via the input structures  22 , a user may start, control, or operate a GUI or applications running on computer  30 . 
     The display  18  of the computer  30  may be a backlit liquid crystal display (LCD). A textured light guide  20  may guide light from light sources to illuminate an LCD panel to display images on the display  18 . Substantially planar films (e.g., reflective films) may be positioned adjacent to the textured light guide  20  to affect the appearance (e.g., brightness, viewing angle, polarization) of the display  18 . As discussed in detail below, surface features of the textured light guide  20  may enable the textured light guide  20  to expand and contract differently than any film positioned adjacent to the textured light guide  20  without affecting the planarity of the film. 
       FIG. 3  depicts a front view of a handheld device  34 , which represents one embodiment of the electronic device  10 . The handheld device  34  may represent, for example, a portable phone, a media player, a personal data organizer, a handheld game platform, or any combination of such devices. By way of example, the handheld device  34  may be a model of an iPod® or iPhone® available from Apple Inc. of Cupertino, Calif. In other embodiments, the handheld device  34  may be a tablet-sized embodiment of the electronic device  10 , which may be, for example, a model of an iPad® available from Apple Inc. 
     The handheld device  34  may include an enclosure  36  to protect interior components from physical damage and to shield them from electromagnetic interference. The enclosure  36  may surround the display  18 , which may display indicator icons  38 . The indicator icons  38  may indicate, among other things, a cellular signal strength, Bluetooth connection, and/or battery life. The I/O interfaces  24  may open through the enclosure  36  and may include, for example, a proprietary I/O port from Apple Inc. to connect to external devices. 
     User input structures  40 ,  42 ,  44 , and  46 , in combination with the display  18 , may allow a user to control the handheld device  34 . For example, the input structure  40  may activate or deactivate the handheld device  34 , the input structure  42  may turn the display  18  on or off, the input structure  42  may navigate a user interface to a home screen, a user-configurable application screen, and/or activate a voice-recognition feature of the handheld device  34 , the input structures  44  may provide volume control, and the input structure  46  may toggle between vibrate and ring modes. A microphone  48  may obtain a user&#39;s voice for various voice-related features, and a speaker  50  may enable audio playback and/or certain phone capabilities. A headphone input  52  may provide a connection to external speakers and/or headphones. 
     Like the display  18  of the computer  30 , the display  18  of the handheld device  34  may be a backlit liquid crystal display (LCD). The textured light guide  20  may enable the display  18  to maintain a substantially uniform display appearance after exposure to varying temperatures. For example, surface features of the textured light guide  20  may reduce friction between the textured light guide  20  and any adjacent films (e.g., specular reflector film). The textured light guide  20  may reduce wrinkling, gathering, or unevenness of the films as the textured light guide  20  expands and contracts in varying amounts relative to adjacent films. 
     One example of the display  18  appears in exploded-view in  FIG. 4 . The display  18  generally includes an LCD panel  60  and a backlight assembly  62 , which may be assembled within frame  64 . The backlight assembly  62  supplies the light that illuminates the LCD panel  60 . This light derives from a light source  66 , which is routed through portions of the backlight assembly  62  before being emitted toward the LCD panel  60 . The light source  66  may include a cold-cathode fluorescent lamp (CCFL), one or more light emitting diodes (LEDs), or any other suitable source of light. As may be appreciated, the LCD panel  60  may include numerous pixels that selectively modulate the amount and color of light passing from the backlight assembly  62  through a display region  68  of the LCD panel  60  viewable by a user. The LCD panel  60  may employ any suitable liquid crystal display architecture, such as twisted nematic (TN), in-plane switching (IPS), fringe-field switching (FFS), and/or vertical alignment (e.g., multi-domain vertical alignment (MVA) or patterned vertical alignment (PVA)). 
     The backlight assembly  62  may include a variety of individual layers and components. Some of these layers and components appear in a schematic view of the backlight assembly  62  that appears in  FIG. 5 . The backlight assembly  62  illustrates the interface between a textured light guide  20  that receives light from the light source  66  (e.g., via light-emitting diodes (LEDs)  70 ) and a film  72  (e.g., specular reflector film). As such, it should be appreciated that the backlight assembly  62  may include other layers and components disposed above and below those shown in  FIG. 5 . Moreover, the textured light guide  20  and the film  72  are shown in separated from one another for clarity. When the backlight assembly  62  is manufactured, however, the textured light guide  20  and the film  72  are adjacent one another. 
     To provide light to the LCD panel  60 , the light source  66  supplies light  74  to the textured light guide  20 . The light  74  may pass through the textured light guide  20  via total internal reflection until exiting the textured light guide  20 . Light rays  76   a ,  76   b , and  76   c  illustrate light  74  passing into the textured light guide  20 . Surface features  78  may be molded, etched, or otherwise positioned on the textured light guide  20 . The surface features  78  disrupt the total internal reflection of the light rays through the textured light guide  20  and direct the light toward the LCD panel  60 . For ease of explanation, the backlight assembly  62  may be described in relation to a coordinate system along a vertical Y-axis  80 , a horizontal X-axis  82 , and a horizontal Z-axis  84 . Points higher along the Y-axis  80  may be referred to as “above,” “higher,” “on top of,” and so forth. Points lower along the Y-axis  80  may be referred to as “beneath,” “lower,” “below,” and so forth. The light source  66  emits light  74  into a first edge  86  of the textured light guide  20  primarily along the X-axis  82  toward an opposing second edge  88 . The surface features  78  on a bottom surface  90  may reflect the light rays  76   a ,  76   b ,  76   c  upward along the Y-axis  80  towards the LCD panel  60  through an opposing top surface  92 . The textured light guide  20  extends a plate length  94  along the X-axis  82 . The textured light guide  20  may be set a distance  96  (e.g., approximately 5 mm, 3 mm, or 1 mm, or less) from the light source  66 . The textured light guide  20  is shown in  FIG. 5  as taking a generally planar shape horizontally along the X-axis  82  and Z-axis  84 . In other embodiments, however, the textured light guide  20  may have a generally wedge shape, in which the thickness (e.g., vertically along the Y-axis  80 ) may decrease from the first edge  86  to the opposing second edge  88  (e.g., vertically along the X-axis  82 ). 
     The bottom surface  90  of the textured light guide  20  may be substantially planar (e.g., flat) except for an interior length  98  of an interior region  100  having the surface features  78 . A perimeter  102  of the interior region  100  may be spaced a first distance  104  from the first edge  86  and a second distance  106  from the second edge  88 . In some embodiments, the first distance  104  may be between approximately 1-5 mm, approximately 2-4 mm, or approximately 3 mm. In some embodiments, the bottom surface  90  is substantially smooth and planar (e.g., flat) except for the interior length  98  of the interior region  100  having the surface features  78 . The surface features  78  may extend a distance D 1  from the bottom surface  90 . The surface features  78  may be integrally molded with the light guide  20 . In some embodiments, the distance D 1  the surface features  78  extend may be a relatively constant value between 1-50 μm, 10-40 μm, 30-40 μm, or approximately 35 μm. The surface features  78  may include light-extracting elements, such as printed dots, micro-lenses, and/or micro-prisms. Light-extracting elements enable the textured light guide  20  to guide light  74  through the first top surface  92  of the textured light guide  20 . The light-extracting elements may distribute the light  74  evenly across the display region  68  of the LCD panel  60 . In some embodiments, the interior region  100  and respective the surface features  78  (e.g., light-extracting elements) may be approximately greater than or equal to the area of the display region  68 . In some embodiments, light-extracting elements positioned proximate to the first end  86  may attenuate the light  74  more than light-extracting elements positioned proximate to the second end  88 . 
     A second top surface  108  of the film  72  may be positioned adjacent to the surface features  78  of the bottom surface  90 . The film  72  may be substantially planar (e.g., flat) along the X-axis  82  and Z-axis  84 . The film  72  may lie flat adjacent to the surface features  78  and spaced a substantially uniform distance D 1  from the bottom surface  90 . The film  72  may have a thickness  109  with a uniform vertical profile along the Y-axis  80 . When the electronic device  10  is assembled, the frame  64  and/or LCD panel  66  may provide a normal force to position the film  72  adjacent to the textured light guide  20 . The film  72  may be positioned within the interior region  100  of the textured light guide  20 . For example, the film  72  may have a film length  110  less than the interior length  98  such that the film  72  is spaced a distance D 2  from the perimeter  102  of the interior region  100 . In some embodiments, the film  72  is spaced the distance D 2  from the perimeter  102  on each edge of the film  72 . For example, D 2  may be between approximately 0.1-1 mm, approximately 0.3-0.7 mm, or approximately 0.5 mm. In other embodiments, the film  72  is spaced a distance D 3  from the perimeter  102  proximate to the light source  66 , and the distance D 3  may be greater than D 2 . For example, D 3  may be between approximately 0.3 to 2 mm, approximately 0.5 to 1.5 mm, or approximately 0.7 to 1 mm. 
     In some embodiments, the surface features  78  of the interior region  100  may include friction reducing features that do not extract light from the textured light guide  20 . Perimeter surface features  112  along the perimeter  102  and/or proximate to the light source  66  may have different geometries than interior surface features  114  within the perimeter  102 . For example, the perimeter surface features  112  may be printed dots of the same or different material as the textured light guide  20  to reduce friction with the film  72 , and the interior surface features  114  may be microlenses and/or microprisms to guide light through the first top surface  92 . Different perimeter surface features  112  may enable the light  74  to be primarily distributed across the display region  68  of the LCD panel  60  by the interior surface features  114 . 
     Any suitable material may form the textured light guide  20 . In one example, the textured light guide  20  may be formed from polymethyl-methacrylate, an acrylic glass commonly referred to as “PMMA.” The film  72  may be a reflector film to increase the amount of light reflected from the bottom surface  90  through the textured light guide  20  towards the LCD panel  60 . In some embodiments, the film  72  may include multiple layers, such as one or more reflector layers and a substrate or laminate layer, such as polyethylene terephthalate (PET). By way of example, the film  72  may be a diffuse reflector or a specular reflector. Some examples of specular reflectors include a silver reflector film or an enhanced spectral reflector (ESR) film, including a model of Vikuiti® ESR film, available from 3M Company. In some embodiments, the film  72  may be between approximately 0.05-0.25 mm, approximately 0.065-0.2 mm, or approximately 0.1-0.165 mm. While the embodiments discussed above include surface features  78  on the bottom surface  90  of the textured light guide  20  and a film  72  positioned adjacent to the bottom surface  90 , presently contemplated embodiments also include surface features  78  on the first top surface  92  and optical films such as brightness enhancement films and/or diffuser films positioned above the first top surface  92 . 
     During operation and/or storage of the electronic device  10 , the textured light guide  20  and film  72  may be exposed to varying temperatures and accompanying thermal stresses. For example, thermal stresses from high temperatures (e.g., approximately 50° C. to 85° C.) may cause components of the backlight assembly  62  to expand relative to components at room temperature (e.g., approximately 23° C.), and low temperatures (e.g., approximately 0° C. to −40° C.) may cause components of the backlight assembly  62  to contract relative to room temperature components. The textured light guide  20  and film  72  may expand and contract horizontally along the X-axis  82  and the Z-axis  84 . The surface features  78  may reduce the friction between the textured light guide  20  and the film  72  and enable the film  72  to slide relative to the textured light guide  20 . By reducing the friction, the surface features  78  enable the textured light guide  20  and the film  72  to expand and contract independently from one another without affecting the planarity of the film  72 , that is without folding or compressing the film  72  to form vertical non-uniformities along the Y-axis  80 . 
     In some embodiments, the textured light guide  20  may expand and contract along the X-axis  82  more or at a greater rate than the film  72  may expand and contract when exposed to varying temperatures. For example, the coefficient of thermal expansion for the textured light guide  20  may be greater than the coefficient of thermal expansion for the film  72 .  FIG. 5  illustrates the plate length  94  and film length  110  at a room temperature (e.g., 23° C.). The plate length  94  may increase to an expanded plate length  116  and the film length  110  may increase to an expanded film length  118  at a first high temperature (e.g., 65° C.). The plate length  94  may decrease to a contracted plate length  120  and the film length  110  may decrease to a contracted film length  122  at a first low temperature (e.g., −20° C.). The interior length  98  may expand and contract similar to the plate length  94 . In some embodiments, the film  72  remains positioned within the interior region  100  regardless of the temperature because the textured light guide  20  has a greater coefficient of thermal expansion than the film  72  and/or because the interior region  100  is sized to be larger along the X-axis  82  and Z-axis  84  than the film  72 . The surface features  78  may reduce the friction between the textured light guide  20  and the film  72  so that the friction is insufficient to compress the film  72  and form wrinkles or cause vertical unevenness along the Y-axis  80  when the textured light guide  20  contracts relative to the film  72  (e.g., the plate length  94  contracts from the expanded plate length  116  to the contracted plate length  122 ). Moreover, the surface features  78  may reduce the friction so that the friction is insufficient restrict the film  72  to form wrinkles or otherwise affect the planarity of the film  72  when the film  72  relative to the textured light guide  20  (e.g., the film  72  expands from the contracted film length  122  to the expanded film length  118 ). The surface features  78  may enable the film  72  to slide relative to the textured light guide  20  without affecting the uniformity of the distance D 1  between the bottom surface  90  of the textured light guide  20  and the second top surface  108  of the film  72 . The planarity of the film  72  relative to the textured light guide  20  affects the appearance of the display  18 . Thus, the surface features  78  may aid the maintenance of a uniform display appearance by enabling the film  72  to move relative to the textured light guide  20  in varying temperature environments. While the above discussion addresses the expansion and contraction of the textured light guide  20  and film  72  horizontally along the X-axis  82 , the surface features  78  may have a similar affect during expansion and contraction of the textured light guide  20  and film  72  horizontally along the Z-axis  84 . 
       FIG. 6  illustrates a top-view of an embodiment of the backlight assembly  62  with the film  72  shown within the interior region  100  beneath the textured light guide  20 . In some embodiments, the surface features  78  may be distributed across the interior region  100  of the textured light guide  20  with non-uniform and/or unpatterned spacing between the surface features  78 , as shown in  FIG. 6 . Alternatively, the surface features  78  may be distributed across the interior region  100  with regular spacing between surface features  78 , or the spacing may be based on a pattern (e.g., decreasing along the X-axis  82  towards the second edge  88 ). 
     The interior length  98  of the interior region  100  extends along the plate length  94 . An interior width  124  of the interior region  100  extends along a plate width  126 . The film  72  may be positioned within the interior region  100  and spaced a distance D 2  from the perimeter  102  of the interior region  100 . The film length  110  may be less than the interior length  98 , and a film width  128  may be less than the interior width  124 . In some embodiments, the film length  110  and film width  128  may be substantially equal to the respective dimensions of the display region  68  of the LCD panel  60  of  FIG. 4 , while the interior length  98  and interior width  124  may be greater than the respective dimensions of the display region  68 . The surface features  78  of the interior region  100  may direct light towards the LCD panel  60  and reduce friction between the textured light guide  20  and the film  72 . 
     As discussed above, the textured light guide  20  and film  72  may expand and contract horizontally along the X-axis  82  and Z-axis  84  based at least in part on the temperature. The surface features  78  of the interior region  100  may extend a sufficient distance D 2  beyond the film  72  so that the film  72  is within the interior region  100  at high temperatures (e.g., 85° C.) and low temperatures (e.g., −40° C.). Moreover, the surface features  78  reduce the friction between the film  72  and the textured light guide  20  to enable the film  72  to slide relative to the textured light guide  20  during thermal expansion and contraction without wrinkling the film  72 . For example, the surface features  78  may reduce friction to enable the backlight assembly  62  to cycle between low temperatures (e.g., −40° C.) and high temperatures (e.g., 85° C.) without wrinkling the film  72 ). The surface features  78  may substantially prevent the bottom surface  90  from sticking to the second top surface  108  during thermal expansion and thermal contraction of the textured light guide  20 . In some embodiments, the film  72  may be constrained proximate to the second end  88  so that the film  72  expands under thermal stress towards the light source  66 , such that the distance D 3  is greater than D 2 , and the interior region  100  extends further horizontally along the X-axis  82  and Z-axis  84  than the expanded film  72 . As discussed above with  FIG. 5 , the film  72  may be spaced the distance D 3  from the perimeter  102  proximate to the light source  66 . The film  72  is positioned the distance D 3  from the perimeter  102  so that the film  72  is in contact with multiple surface features  78  regardless of the thermal expansion and thermal contraction of the textured light guide  20  and/or film  72 . 
     The electronic display  18  shown in  FIG. 4  may be manufactured according to a flowchart  150  of  FIG. 7 . Specifically, the textured light guide plate  20  may be manufactured (block  152 ) with surface features  78  across the interior region  100 . The surface features  78  may be molded, etched, or otherwise formed on the first top surface  92  and/or the bottom surface  90 . In some embodiments, the surface features  78  may be formed when the material to form the textured light guide  20  is injected into a steel mold. Initially creating, in the steel mold, the pattern that will produce the surface features  78  may involve a laser process. Namely, a laser may cut into the steel mold a very small pattern inverse to the resulting surface features  78  in the interior region  100 . Additionally or alternatively, the surface features  78  may be formed on the textured light guide plate  20  using photolithography to etch the textured light guide plate  20 . 
     The film  72  may be positioned (block  154 ) within the interior region  100  and horizontally spaced a distance within a perimeter  102 . The film  72  may be a specular reflector, a diffuse reflector, or an optical enhancing film. The film  72  may be substantially flat (e.g., planar) and positioned (block  154 ) so that all edges are within the interior region  100 . The surface features  78  within the interior region  100  may enable the film  72  to slide relative to the textured light guide  20  to reduce non-uniformities of the film  72  when temperature changes cause the film  72  and textured light guide  20  to expand and/or contract at different rates. Thereafter, the backlight assembly  62  may be formed (block  156 ). The light source  66  and/or additional films  72  may be positioned adjacent the textured light guide  20  to form the backlight assembly  62 . The backlight assembly  62 , LCD panel  60 , and frame  64  may be joined (block  158 ) together to form the electronic display  18 . 
     The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.

Metadata:
Filing Date: 20130503
Publication Date: 20150616
Grant Date: 20150616
Priority Date: 20120911
Inventors: SCARDATO STEVEN M.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B6/0036", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133606", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0035", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F2203/60", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0068", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133608", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133615", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133608", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F2203/60", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2203/60", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133606", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0036", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0036", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133608", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0068", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133606", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B6/0035", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133615", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 50232960