PATENT DOCUMENT

Publication Number: US-8941795-B2
Application Number: US-201113332228-A
Country: US
Kind Code: B2

Title: Electronic device with backlit display

Abstract:
An electronic device may have a liquid crystal display with backlight structures. The backlight structures may produce backlight that passes through display layers in the display. The display layers may include color filter elements, a liquid crystal layer, and a thin-film transistor layer. The color filter elements may be interposed between the thin-film transistor layer and the backlight structures or the thin-film transistor layer may be interposed between the color filter elements and the backlight structures. The backlight structures may be formed from optical fiber, a two-dimensional array of light-emitting diodes, a light guide plate that includes a rectangular recess for receiving optical films, or light guide plate structures that include internal light scattering structures. A light guide plate may be provided with alignment features that mate with alignment features on optical films.

Claims:
What is claimed is: 
     
       1. A display, comprising:
 an outer display layer; 
 an inner display layer; 
 a two-dimensional light-emitting diode array that produces display backlight, wherein the light-emitting diode array comprises a first substrate and a plurality of vertical and horizontal control lines on the first substrate that control the operation of each light-emitting diode in the array individually; 
 a layer of liquid crystal material between the outer display layer and the inner display layer, wherein the outer display layer comprises a second substrate and comprises thin-film transistors, wherein the inner display layer comprises a polarizer layer that is interposed between the layer of liquid crystal material and the two-dimensional light-emitting diode array; and 
 a sealant formed on a surface of the polarizer layer, wherein the sealant contains the liquid crystal material on the surface of the polarizer layer and wherein the polarizer layer is mounted directly to the first substrate. 
 
     
     
       2. The display defined in  claim 1  further comprising a layer of color filter elements on the second substrate, wherein the thin-film transistors are interposed between the color filter elements and the second substrate. 
     
     
       3. The display defined in  claim 1  wherein the two-dimensional array of light-emitting diodes comprises an array of vertically mounted light-emitting diodes mounted on the first substrate in rows and columns. 
     
     
       4. The display defined in  claim 1  wherein the array of light-emitting diodes comprises a two-dimensional array of organic light-emitting diodes. 
     
     
       5. The display defined in  claim 1  wherein the light-emitting diode array comprises an array of white-light-emitting diodes configured to emit white light. 
     
     
       6. The display defined in  claim 1  wherein the light-emitting diode array comprises a flexible light-emitting diode array. 
     
     
       7. The display defined in  claim 6  wherein the first substrate comprises a flexible polyimide substrate and wherein the flexible light-emitting diode array comprises an array of light-emitting diodes mounted on the flexible polyimide substrate. 
     
     
       8. The display defined in  claim 1  wherein the polarizer layer comprises a flexible polarizer layer. 
     
     
       9. The display defined in  claim 8  wherein the first substrate comprises a rigid substrate and wherein the light-emitting diode array comprises an array of light-emitting diodes mounted on the rigid substrate, wherein the rigid substrate supports the flexible polarizer layer. 
     
     
       10. The display defined in  claim 1  wherein the control lines are configured to operate the light-emitting diodes in a localized dimming scheme. 
     
     
       11. The display defined in  claim 1  wherein the first substrate comprises a rigid printed circuit board and wherein the light-emitting diode array comprises an array of SMT light-emitting diodes mounted on the rigid printed circuit board. 
     
     
       12. The display defined in  claim 1  wherein the first substrate comprises a glass substrate and wherein the light-emitting diode array comprises a pattern of thin-film light-emitting diode structures on the glass substrate. 
     
     
       13. The display defined in  claim 1  further comprising an additional polarizer layer, wherein the second substrate is interposed between the additional polarizer layer and the thin-film transistors.

Description:
BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with displays and associated backlight structures. 
     Electronic devices such as computers and cellular telephones may have displays. Some displays such as plasma displays and light-emitting diode displays have arrays of display pixels that generate light. In displays of this type, backlighting is not necessary, because the display pixels themselves are illuminated. Other displays, such as liquid crystal displays, contain passive display pixels. The pixels in a liquid crystal display can alter the amount of light that is transmitted through the display to display information for a user, but do not produce light. As a result, it is often desirable to provide backlight for a liquid crystal display. 
     In a typical backlight structure for a display such as a liquid crystal display, a light guide plate is used to distribute backlight generated by a light source such as a light-emitting diode light source. Optical films such as a diffuser layer and brightness enhancing film may be placed on top of the light guide plate. A reflector may be formed under the light guide plate to improve backlight efficiency. 
     Conventional backlight arrangements are often not as compact as desired. The inclusion of optical films, provisions for registering the positions of the optical films within a device, the size and shape of the conventional light guide plates and light source, and other conventional backlight design features raise challenges when attempting to make backlights less bulky and more efficient. 
     It would therefore be desirable to be able to provide electronic devices with improved displays and backlights. 
     SUMMARY 
     An electronic device may have a display such as a liquid crystal display with backlight structures. The backlight structures may produce backlight that passes through layers in the display. 
     The display may include color filter elements and a thin-film transistor layer. The color filter elements may be interposed between the thin-film transistor layer and the backlight structures or the thin-film transistor layer may be interposed between the color filter elements and the backlight structures. 
     The backlight structures may be formed from optical fiber that is illuminated by a light source such as a light-emitting diode. The surface of the optical fiber may be provided with light leakage promotion features such as a surface texture that facilitates light leakage from within the optical fiber. 
     If desired, the backlight structures may be formed from a two-dimensional light source such as a two-dimensional array of light-emitting diodes. The two-dimensional array of light-emitting diodes may be formed from vertically mounted light-emitting diodes on a substrate or may be formed from a layer of organic light-emitting diodes. 
     Backlight structures may be provided with a light guide plate that includes a rectangular recess for receiving optical films. Backlight may be generated by launching light from a light source into the light guide plate. 
     The light guide plate may include bubbles or other internal light scattering structures to help diffuse the backlight. 
     A light guide plate in a backlight may be provided with alignment features that mate with alignment features on optical films. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an illustrative electronic device with a display such as a portable computer in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram of an illustrative electronic device with a display such as a cellular telephone or other handheld device in accordance with an embodiment of the present invention. 
         FIG. 3  is a diagram of an illustrative electronic device with a display such as a tablet computer in accordance with an embodiment of the present invention. 
         FIG. 4  is a diagram of an illustrative electronic device with a display such as a computer monitor with a built-in computer in accordance with an embodiment of the present invention. 
         FIG. 5  is a circuit diagram showing circuitry that may be used in an array of display pixels in accordance with an embodiment of the present invention. 
         FIG. 6  is a circuit diagram of an illustrative display pixel in accordance with an embodiment of the present invention. 
         FIG. 7  is a diagram of a portion of an illustrative array of color filter elements of the type that may be used for providing a display with the ability to display color images in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of an illustrative liquid crystal display having liquid crystal material interposed between an outer color filter array layer and an inner thin-film transistor layer in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional view of an illustrative liquid crystal display having an outer display layer that includes thin-film transistors and color filter elements in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional view of an illustrative liquid crystal display having a liquid crystal layer interposed between an outer thin-film transistor layer and an inner color filter layer in accordance with an embodiment of the present invention. 
         FIG. 11  is a diagram of illustrative backlight structures that include an array of optical waveguides such as optical fiber waveguides in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of illustrative backlight structures that include an optical fiber in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional end view of illustrative backlight structures that include optical fibers in accordance with an embodiment of the present invention. 
         FIG. 14  is a diagram of illustrative backlight structures that include a structure for dispersing light that is interposed between an array of light-emitting diodes and an array of optical fibers in accordance with an embodiment of the present invention. 
         FIG. 15  is a diagram of an illustrative light source coupled to backlight structures formed from an optical fiber using a tapered waveguide structure in accordance with an embodiment of the present invention. 
         FIG. 16  is a diagram of illustrative backlight structures formed from an optical fiber that has been configured to follow a meandering path across the rear of a display accordance with an embodiment of the present invention. 
         FIG. 17  is a diagram of an illustrative light-emitting diode array of the type that may be used in forming backlight structures for a display in accordance with an embodiment of the present invention. 
         FIG. 18  is a cross-sectional side view of an illustrative light-emitting diode array of the type that may be used in forming backlight structures for a display in accordance with an embodiment of the present invention. 
         FIG. 19  is a cross-sectional side view of a display having an opaque masking layer on the underside of a layer of polarizing material in accordance with an embodiment of the present invention. 
         FIG. 20  is a cross-sectional side view of an illustrative display having a backlight light guide structure with a recessed portion for receiving optical films in accordance with an embodiment of the present invention. 
         FIG. 21  is a diagram of a portion of a conventional display in a housing with registration pins that mate with holes in backlight optical films. 
         FIG. 22  is a diagram of a display having backlight structures with alignment features such as holes that mate with corresponding alignment features such as protrusions on a backlight light guide structure in accordance with an embodiment of the present invention. 
         FIG. 23  is a cross-sectional side view of an illustrative display in which optical films have been aligned with a light guide structure using protrusions on the light guide structure in accordance with an embodiment of the present invention. 
         FIG. 24  is a cross-sectional side view of a conventional backlight for a display. 
         FIG. 25  is a cross-sectional side view of a display backlight light guide structure having embedded scattering structures in accordance with an embodiment of the present invention. 
         FIG. 26  is a cross-sectional side view of a display backlight light guide structure having multiple layers of embedded light scattering structures in accordance with an embodiment of the present invention. 
         FIG. 27  is a cross-sectional side view of a display backlight light guide structure having embedded scattering structures distributed unevenly throughout the light guide structure in accordance with an embodiment of the present invention. 
         FIG. 28  is a cross-sectional side view of a display backlight light guide structure having a textured surface light-leakage promotion structure in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     A display may be provided with backlight structures. The backlight structures may produce backlight for the display that helps a user of a device view images on the display in a variety of ambient lighting conditions. Displays with backlights may be provided in any suitable type of electronic equipment. 
     An illustrative electronic device of the type that may be provided with a backlit display is shown in  FIG. 1 . Electronic device  10  may be a computer such as a computer that is integrated into a display such as a computer monitor, a laptop computer, a tablet computer, a somewhat smaller portable device such as a wrist-watch device, pendant device, or other wearable or miniature device, a cellular telephone, a media player, a tablet computer, a gaming device, a navigation device, a computer monitor, a television, or other electronic equipment. 
     As shown in  FIG. 1 , device  10  may include a backlit display such as display  14 . Display  14  may be a touch screen that incorporates capacitive touch electrodes or other touch sensor components or may be a display that is not touch sensitive. Display  14  may include image pixels formed from liquid crystal display (LCD) components or other suitable display pixel structures. Arrangements in which display  14  is formed using liquid crystal display pixels are sometimes described herein as an example. This is, however, merely illustrative. Any suitable type of display technology may be used in forming display  14  if desired. 
     Device  10  may have a housing such as housing  12 . Housing  12 , which may sometimes be referred to as a case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. 
     Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     As shown in  FIG. 1 , housing  12  may have multiple parts. For example, housing  12  may have upper portion  12 A and lower portion  12 B. Upper portion  12 A may be coupled to lower portion  12 B using a hinge that allows portion  12 A to rotate about rotational axis  16  relative to portion  12 B. A keyboard such as keyboard  18  and a touch pad such as touch pad  20  may be mounted in housing portion  12 B. 
     In the example of  FIG. 2 , device  10  has been implemented using a housing that is sufficiently small to fit within a user&#39;s hand (i.e., device  10  of  FIG. 2  may be a handheld electronic device such as a cellular telephone). As show in  FIG. 2 , device  10  may include a backlit display such as display  14  mounted on the front of housing  12 . Display  14  may be substantially filled with active display pixels or may have an inactive portion and an inactive portion. Display  14  may have openings (e.g., openings in the inactive or active portions of display  14 ) such as an opening to accommodate button  22  and an opening to accommodate speaker port  24 . 
       FIG. 3  is a perspective view of electronic device  10  in a configuration in which electronic device  10  has been implemented in the form of a tablet computer. As shown in  FIG. 3 , backlit display  14  may be mounted on the upper (front) surface of housing  12 . An opening may be formed in display  14  to accommodate button  22 . 
       FIG. 4  is a perspective view of electronic device  10  in a configuration in which electronic device  10  has been implemented in the form of a computer integrated into a computer monitor. As shown in  FIG. 4 , backlit display  14  may be mounted on the front surface of housing  12 . Stand  26  may be used to support housing  12 . 
     Display  14  may include an array of display pixels. Each display pixel may be used to control the light intensity associated with a portion of the display. An illustrative array of display pixels is shown in  FIG. 5 . As shown in  FIG. 5 , display  14  may have a pixel array with rows and columns of pixels  40 . There may be tens, hundreds, or thousands of rows and columns of display pixels  40 . Display driver circuitry such as a display driver integrated circuit and, if desired, associated thin-film transistor circuitry formed on a display substrate layer may be used to produce data signals D on data lines in display  14  and may produce gate line signals G on gate lines in display  14 . During operation, the display driver circuitry may control the values of D and G to control the light intensity associated with each of the display pixels and thereby display images on display  14 . 
       FIG. 6  is a circuit diagram of an illustrative display pixel in the pixel array of display  14 . Pixels such as pixel  40  of  FIG. 6  may be located at the intersection of each gate line and data line in display  14 . 
     A data signal D may be supplied to terminal  50  from one of the data lines in display  14 . Thin-film transistor  52  (e.g., a thin-film polysilicon transistor or an amorphous silicon transistor) may have a gate terminal such as gate  54  that receives gate line signal G from display driver circuitry (e.g., gate driver circuitry). When signal G is asserted, transistor  52  will be turned on and signal D will be passed to node  56  as voltage Vp. Data for display  14  may be displayed in frames. Following assertion of signal G in one frame, signal G may be deasserted. Signal G may then be asserted to turn on transistor  52  and capture a new value of Vp in a subsequent display frame. 
     Pixel  40  may have a signal storage element such as capacitor Cst or other charge storage element. Storage capacitor Cst may be used to store signal Vp between frames (i.e., in the period of time between the assertion of successive signals G). 
     Display  14  may have a common electrode coupled to node  58 . The common electrode (which is sometimes referred to as the Vcom electrode) may be used to distribute a common electrode voltage such as common electrode voltage Vcom to nodes such as node  58  in each pixel  40  of array  24 . Capacitor Cst may be coupled between nodes  56  and  58 . A parallel capacitance Clc arises across nodes  56  and  58  due to electrode structures in pixel  40  that are used in controlling the electric field through the liquid crystal material of the pixel (liquid crystal material  60 ). As shown in  FIG. 6 , electrode structures  62  may be coupled to node  56 . Capacitance Clc is associated with the capacitance between electrode structures  62  and common electrode Vcom at node  58 . During operation, electrode structures  62  may be used to apply a controlled electric field (i.e., a field having a magnitude proportional to Vp-Vcom) across a pixel-sized portion of liquid crystal material  60  in pixel  40 . Due to the presence of storage capacitor Cst, the value of Vp (and therefore the associated electric field across liquid crystal material  60 ) may be maintained across nodes  56  and  58  for the duration of the frame. Electrode structures  62  may have any suitable shape. For example, each display pixel may have an electrode that is formed from multiple electrode fingers. 
     The electric field that is produced across liquid crystal material  60  causes a change in the orientations of the liquid crystals in liquid crystal material  60 . This changes the polarization of light passing through liquid crystal material  60 . The change in polarization may be used in controlling the amount of light that is transmitted through each pixel  40  in display  14 . 
     To provide display  14  with the ability to display color images, display  14  may be provided with color filter elements. For example, display  14  may be provided with color filter elements such as red, green, and blue elements. Each color filter element may be used to impart color to the light associated with a respective display pixel in display  14 . 
     As shown in  FIG. 7 , color filter elements  80  may be formed in an array (e.g., an array of alternating red, green, and blue color filter elements) and may therefore sometimes be referred to as a color filter array  80  or color filter array structures  80 . The illustrative color filter array of  FIG. 7  shows how color filter elements may be arranged in rows and columns (e.g., rows and columns corresponding to respective rows and columns of display pixels  40  of  FIG. 6 ). 
     The color filter array for display  14  may be formed using structures that are located above or that are located below thin-film transistor structures in display  14 . An illustrative configuration for display  14  in which liquid crystal layer  60  is interposed between an upper (outer) color filter layer and a lower (inner) thin-film transistor layer is shown in  FIG. 8 . 
     With an arrangement of the type shown in  FIG. 8 , display  14  may receive backlight  82  from backlight structures  84 . Backlight structures  84  (which may sometimes be referred to as a backlight or backlight unit) may be located on the inner (lower) surface of display  14 . Backlight  82  from backlight structures  84  passes through layers  81  of display  14  and exits upper (outer) display surface  90 . A user of electronic device  10  such as viewer  86  may observe images on display  14  by looking in direction  88 . 
     Display layers  81  may include an upper polarizer layer such as layer  68  and a lower polarizer layer such as layer  74 . In a configuration of the type shown in  FIG. 8 , upper polarizer layer  68  may be attached to color filter array layer  70 . Color filter array layer  80  may be formed from a sheet of glass or plastic or other material that includes an array of color filter elements. Display  14  may be covered with a layer of glass or plastic (i.e., a display cover layer) or a layer such as color filter layer  80  may be provided with sufficient thickness (and therefore strength) to serve as the outermost structural layer of display  14 . 
     Lower polarizer layer  74  may be located between backlight  84  and thin-film transistor layer  92 . Thin-film transistor layer  92  may include a substrate such as substrate  94 . Substrate  94  may be formed from a layer of transparent material such as a sheet of clear glass or plastic. Thin-film transistor structures  96  may be formed on the surface of substrate  94  facing liquid crystal layer  60 . Thin-film transistor structures  96  may include thin-film circuitry such as thin-film transistors in gate driver circuitry and thin-film display pixel transistors such as transistor  52  of  FIG. 6 , electrode structures such as electrode  62  of  FIG. 6 , gate line conductors, data line conductors, and other thin-film circuitry for controlling display pixels  40 . 
     Display layers  81  may, if desired, include additional layers of material such as patterned opaque masking layers, smudge-resistance layers, anti-scratch layers, antireflection coatings, etc. 
     Liquid crystal layer  60  may be interposed between color filter layer  80  and thin-film transistor layer  92 . Sealant  99  (e.g., epoxy) may be provided around the periphery of display  14  to help contain liquid crystal layer  60 . As backlight  82  from backlight structures  84  passes through lower polarizer  74 , lower polarizer  74  polarizes light  82 . As polarized light  82  passes through liquid crystal material  60 , liquid crystal material  60  may rotate the polarization of light  82  by an amount that is proportional to the electric field through liquid crystal material  60 . If the polarization of light  82  is aligned in parallel with the polarization of polarizer  68 , the transmission of light  82  through layer  68  will be maximized. If the polarization of light  82  is aligned so as to run perpendicular to the polarization of polarizer  68 , the transmission of light  82  through layer  68  will be minimized (i.e., light  82  will be blocked). Display control circuitry may be used in adjusting the voltages Vp across the electrodes  62  of display pixels  40  in display  14 , thereby selectively lightening and darkening pixels  40  and presenting an image to a user of device  10  such as viewer  86 , viewing display  14  in direction  88 . 
     Displays such as display  14  may be mounted on one or more surfaces of device  10 . For example, displays such as display  14  may be mounted on a front face of housing  12 , on a rear face of housing  12 , or on other portions of device  10 . 
     If desired, the color filter array in display  14  may be located between the thin-film transistor layer and backlight structures  84 . Displays with layers that are stacked in this way may sometimes be referred to as having an inverted or flipped configuration, because the thin-film transistor layer is located above the color filter layer. 
     With one suitable inverted display arrangement, which is shown in  FIG. 9 , color filter elements  80  may be formed in a layer on the same substrate (substrate  94 ) as thin-film transistor structures  96 . Substrate  94  may be formed from a clear sheet of plastic or glass or other suitable transparent substrate materials. Thin-film transistor structures  96  may be formed on the inner (lower) surface of substrate  94  (e.g., using semiconductor processing techniques such as photolithography). Color filter elements  80  (e.g., a color filter array layer) may be formed on the deposited layer of thin-film transistor structures (e.g., on the inner surface of substrate  96 ). Color filter elements  80  include colored materials such as colored pigments or dyes and may be deposited using physical vapor deposition, chemical vapor deposition, ink-jet printing, spraying, pad printing, screen printing, spin-on coating, or other deposition techniques. The outer surface of the resulting thin-film transistor and color filter layer (i.e., display layer  100  of  FIG. 9 ) may be covered with additional layers such as polarizer  68 . 
     Liquid crystal layer  60  may be interposed between layer  100  and lower polarizer  74 . Lower polarizer  74  may be formed from a polymer sheet. To provide a rigid support for lower polarizer layer  74 , lower polarizer layer  74  may, if desired, be mounted to a clear glass substrate and/or other support structures such as a supporting layer of material associated with backlight structures  84 . 
     Another suitable inverted display arrangement that may be used for display  14  is shown in  FIG. 10 . As in the configuration of  FIG. 9 , the color filter elements of  FIG. 10  are located between the thin-film transistor layer and the backlight. In the configuration of  FIG. 10 , however, color filter layer  80  of  FIG. 10  has been implemented using a substrate layer (e.g., a glass or plastic layer or other substrate) that is separate from thin-film transistor substrate layer  96 . In this configuration, liquid crystal material  60  may be interposed between thin-film transistor layer  92  (e.g., thin-film transistor substrate layer  94  and thin-film transistor structures  96 ) and color filter array layer  80 . As with display  14  of  FIG. 9 , display  14  of  FIG. 10  may be provided with backlight  82  using backlight structures  84 . 
     In configurations of the types shown in  FIGS. 9 and 10 , the outermost substrate layer in display  14  may be formed from the thin-film transistor layer (i.e., thin-film transistor substrate  94 ). Layer  94  may be implemented using a material that is thick enough (and therefore sufficiently strong) to allow layer  94  to be used in place of a separate cover glass layer. This may help reduce the size and weight of display  14 . If desired, a cover layer of glass or plastic may be used to cover the outer layer of display  14 . 
     As shown in  FIGS. 8 ,  9 , and  10 , backlight  82  may travel vertically upwards (outwards) in through display layers  81  of display  14  to be viewed by a user such as viewer  86  looking at display  14  in direction  88 . Backlight  82  may be generated using any suitable type of backlight structure. For example, a clear sheet of glass or a clear sheet of plastic such as acrylic or other transparent member may be used to form a substantially planar light guide structure. This type of planar light guide structure may sometimes be referred to as a light guide plate. 
     A light-emitting diode array or other light source may be used to emit light into an edge of the light guide plate. The light guide plate in this type of backlight unit may guide light internally in accordance with the principle of total internal reflection. Light that leaks outwards from the light guide plate towards viewer  86  may serve as backlight  82 . A reflector in the backlight such as a sheet of white plastic or a layer of metal may be used to reflect light that leaks inwards from the light guide plate back in the outwards direction to serve as additional backlight  82 . 
     If desired, other types of backlight structures may be used in implementing backlight structures  84  for displays such as displays  14  of  FIGS. 8 ,  9 , and  10 . 
       FIG. 11  is a bottom view of illustrative backlight structures  84  showing how backlight structures  84  may be formed from optical waveguide structures such as optical fibers  154 . Optical fibers  154  may be formed from material such as plastic or glass (as examples). Fibers  154  may be formed from a single material (e.g., a single glass or plastic material) or may have an inner portion (e.g., a higher index of refraction portion) that is coated with an outer portion (e.g., a lower index of refraction portion). 
     Fibers  154  may have a circular cross-sectional shape (as an example). If desired, waveguide structures with other cross-sectional shapes may be used in forming backlight structures  84 . For example, optical waveguide structures for backlight structures  84  may have a square cross-sectional shape, a rectangular cross-sectional shape, an oval cross-sectional shape, a shape with curved edges, a shape with straight edges, a shape with a combination of curved and straight edges, or other suitable cross-sectional shapes. Optical fibers or other waveguides such as fibers  154  may be mounted to a support structure (e.g., a rigid or flexible glass or plastic substrate or a layer of resin) or may be mounted directly within housing structures  12  or other support structures. 
     Light sources such as one or more light-emitting diodes  150  may be used in providing backlight for display  14 . As shown in  FIG. 11 , for example, an array of light-emitting diodes  150  may be used to launch light into each of multiple optical fibers  154 . 
     Fibers  154  may be provided with light leakage promotion structures along their lengths to help scatter light out of fibers  154  through display  14 . As an example, the outermost (uppermost) surface of fibers  154  may be roughened. The roughened texture on fibers  154  may promote light leakage from fibers  154  through display layers  181 . If desired, a reflector may be provided under fibers  154  to help reflect stray light through display layers  81 . 
     As shown in  FIG. 11 , backlight structures  84  may be provided with one or more optical films  152 . Optical films  152  may be interposed between fibers  154  and display layers  81 . Examples of layers that may be included in optical films  81  include brightness enhancing film layers, diffusing film layers, and compensating film layers (as examples). 
       FIG. 12  is a cross-sectional view of backlight structures such as backlight structures  84  of  FIG. 11 . As shown in  FIG. 12 , light source  150  (e.g., a light-emitting diode) may emit light  158  into an adjacent end of optical fiber  154  (or other suitable optical waveguide structure). Optical fiber  154  may have light leakage promotion features such as features  154 F (e.g., surface roughness on the upper surface of fiber  154 ). As light  158  propagates within fiber  154 , some of light  158  leaks out of fiber  154  upwards and forms backlight  82 A. Any light that escapes in the downwards direction (away from viewer  86 ) may be reflected back in the upwards direction by reflector  156  (e.g., a sheet of white plastic, metal, or other reflective substance). Optical films  152  (e.g., a diffuser, a brightness enhancement film, etc.) may be interposed between optical fiber  154  and display layers  81  in display  14 . 
       FIG. 13  is a cross-sectional end view of backlight structures  84  that have been formed from a series of optical fibers  154 . In the illustrative configuration of  FIG. 13 , each optical fiber  154  has been located immediately adjacent to another of optical fibers  154 . If desired, optical fibers  154  may be spread out so that fewer fibers are needed in backlight structures  84 . In configurations in which fibers  154  are spread out (and in configurations of the type shown in  FIG. 13 ), diffuser layers may be used to ensure that backlight  82  is uniformly distributed over display  14 . 
     If desired, a diffusing and guiding structure such as optical diffusing and guiding structure  160  of  FIG. 14  may be used to diffuse and guide light  158  that has been emitted from light-emitting diodes  150 . Structure  160  may be formed from plastic, glass, or other transparent materials and may help distribute light  158  uniformly among multiple optical fibers  154  in backlight structures  84 . With this type of arrangement, fewer light-emitting diodes  150  may be used in providing illumination for fibers  154  (i.e., a larger number of fibers  154  may be used than light-emitting diodes  150 ). 
     If desired, optical diffusing and guiding structures in backlight structures  84  such as structure  160  of  FIG. 14  or other structures may be provided with tapered portions to help concentrate light into fibers  154 . This type of arrangement is shown in  FIG. 15 . As shown in  FIG. 15 , light-emitting diode  150  may emit light  158  into structure  160 ′. Structures such as structure  160 ′ of FIG.  15  may be provided between each of a plurality of light-emitting diodes and each respective one of a plurality of optical fibers  154 , if desired. 
     As shown in  FIG. 16 , optical fiber  154  may be configured to have a meandering path in backlight structures  84 . This type of arrangement may help distribute backlight over a relatively large area of display  14  without requiring the use of an overly large number of light-emitting diodes. 
     If desired, a two-dimensional array of light-emitting diodes may be used in providing display  14  with backlight. An illustrative two-dimensional light-emitting diode array is shown in  FIG. 17 . As shown in  FIG. 17 , light-emitting diode array  162  may include signal lines such as control lines  164  that control an array of light-emitting diodes  166 . Light emitting diodes  166  may be organized in an array having multiple rows and multiple columns. There may be any suitable number or rows and columns of light-emitting diodes  166  in array  162  (e.g., ten or more rows and ten or more columns, 100 or more rows and 100 or more columns, 1000 or more rows and/or columns, etc.). Control lines  164  may run vertically and horizontally across array  162 . To conserve control circuit resources, it may be desirable to electrically short some of lines  164  together (e.g., so that multiple columns and/or rows of light-emitting diodes  166  may be controlled together). If desired, all of light-emitting diodes  166  may be controlled together (e.g., by configuring control lines  164  to power all of light-emitting diodes  166  at the same time using a common direct current or alternating current power signal). Light-emitting diodes  166  or relatively small sections of light-emitting diodes  166  may also be individually controlled (e.g., in configurations in which it is desirable to implement a localized dimming scheme for increasing the contrast ratio for display  14 ). 
     Light-emitting diodes  166  may be white-light diodes or other monochromatic diodes (as an example). Each light-emitting diode  166  may be implemented using a separate surface-mount technology (SMT) packaged light-emitting diode component (e.g., a component that has solderable leads) or may be implemented using thin-film structures. For example, array  162  may be implemented by mounting rows and columns of SMT light-emitting diodes to a substrate such as a rigid or flexible printed circuit board, a layer of glass, or other suitable substrate. Light-emitting diode array  162  may also be implemented by depositing and patterning thin-film (e.g., polysilicon and/or amorphous silicon) light-emitting diode structures on a glass substrate, a rigid or flexible polymer substrate, or other suitable substrate. Light-emitting diode array  162  may, if desired, be formed from rows and columns of organic light-emitting diodes. Each organic light-emitting diode may include an organic emissive layer. An array of organic light-emitting diodes may be formed on a polymer substrate such as a polyimide substrate or a substrate formed from glass or other materials. The substrate on which the organic light-emitting diodes are formed may be flexible or may be rigid. Multiple layers of material may also be used in forming a substrate for light-emitting diodes  166 , if desired. 
       FIG. 18  is a side view of an illustrative array of light-emitting diodes  116 . As shown in  FIG. 18 , light-emitting diodes  166  may be formed on substrate  168 . Substrate  168  may be formed from a layer of polyimide or other polymer (plastic), from a layer of glass, from a layer of ceramic, from other suitable substrate materials, or from a combination of two or more of these materials. One or more layers of patterned interconnects may be formed in substrate  168 , as illustrated by conductive lines  164  of  FIG. 18 . Lines  164  may be used for controlling light-emitting diodes  166 , as described in connection with  FIG. 17 . 
     As shown in  FIG. 18 , light-emitting diodes  166  may be configured to emit backlight such as backlight  82 D that travels in off-axis directions (i.e., directions that are angled with respect to surface normal  170 , which is perpendicular to the surface of substrate  168  and display  14 ). If desired, light-emitting diodes  166  may be vertically mounted light-emitting diodes that are configured to emit backlight such as backlight  82 U in a direction that is parallel to surface normal  170  (i.e., in a vertical direction that is parallel to an axis such as axis  170  that is perpendicular to the surface of substrate  168 ). Vertically mounted light-emitting diodes or other light-emitting diodes  166  that are configured to emit backlight vertically may help enhance backlight brightness. 
     An array of light-emitting diodes  166  such as array  162  of  FIGS. 17 and 18  (e.g., an organic light-emitting diode array) may be used as to form backlight structures  84  in displays such as displays  14  of  FIGS. 8 ,  9 , and  10  (as examples). 
     In a display configuration of the type shown in  FIG. 8 , light-emitting diode array  162  may be mounted under polarizer  74  to serve as backlight structures  84  of  FIG. 8 . Optical films (e.g., diffuser films, brightness enhancement films, etc.) may be interposed between light-emitting diode array  162  and polarizer  74  or may be omitted. Polarizer  74  and, if desired, light-emitting diode array  162  may be formed from flexible materials. Substrate  94  of thin-film transistor layer  92  may be used to provide structural support for light-emitting diode array  162 , if desired. 
     In a configuration of the type shown in  FIG. 9 , light-emitting diode array  162  may also be mounted under polarizer  74  to serve as backlight structures  84 . As in the arrangement of  FIG. 8 , optical films (e.g., diffuser films, brightness enhancement films, etc.) may be interposed between light-emitting diode array  162  and polarizer  74  of  FIG. 9  or may be omitted. Polarizer  74  may be formed from a flexible material (e.g., a sheet of polymer). Accordingly, it may be desirable to support polarizer  74  with a rigid structure. The rigid structure may be formed by a rigid planar member that is mounted under light-emitting diode array  162  and/or that forms part of light-emitting diode array  162 . For example, light-emitting diode array  162  for backlight structures  84  of  FIG. 9  may be formed from a layer of glass (i.e., a glass substrate) or a rigid layer of plastic or other materials (i.e., a rigid plastic substrate or a rigid substrate of other materials). A flexible light-emitting diode array may be used, if desired. The flexible light-emitting diode may be supported by an underlying rigid planar support structure (e.g., a rigid layer of glass, plastic, ceramic, or metal, part of housing  12 , or other suitable support structures). 
     In a configuration of the type shown in  FIG. 9 , color filter layer  80  may, if desired, be formed from a rigid layer of glass, plastic, or other material. In this type of arrangement, color filter layer  80  may be used to provide rigidity for polarizer layer  74  and a flexible organic light-emitting diode array or other light-emitting diode array  162 . If desired, light-emitting diode array  162  may be formed from a rigid material such as glass, plastic, or ceramic or may be formed from a flexible substrate that is attached to a planar rigid support structure formed from glass, plastic, ceramic, or other suitable support structure materials, a portion of housing  12 , etc. 
       FIG. 19  is a cross-sectional side view of an illustrative arrangement that may be used for display  14  in which an opaque masking layer such as opaque masking layer  170  has been formed on the underside of the periphery of lower polarizer layer  74 . As shown in  FIG. 19 , display  14  may include liquid crystal layer  60 . Liquid crystal layer  60  may be sandwiched between thin-film transistor layer  92  and color filter layer  80 . Driver integrated circuit  176  may be mounted on a ledge portion of thin-film transistor layer  92 . A layer of plastic, black ink, or other opaque masking material  174  may be formed between color filter layer  80  and thin-film transistor layer  92  in peripheral border regions of display  14  (i.e., in an inactive border region that does not contain any active display pixels  40 ). Color filter layer  80 , liquid crystal layer  60 , and thin-film transistor layer  92  may be interposed between upper polarizer  68  and lower polarizer  74 . Backlight structures  84  may include a light guide plate such as light guide plate  180  and a light-emitting diode array or other light source  178 . Light source  178  (e.g., a light-emitting diode light source) may emit light into light guide plate  180  to serve as backlight  82 . Reflector  182  in backlight structures  84  may serve to reflect light through display layers  81  to viewer  86 . 
     With this type of arrangement, the edges of light guide plate  180  such as illustrative right-hand edge in  FIG. 19  may be bright due to reflected light from light-source  178 . To prevent bright edges  172  from being visible from the exterior of device  10 , opaque masking layer  170  may be provided on the lower surface of polarizer  74  in a shape that overlaps edges  172 . Opaque masking layer  170  may be formed in a peripheral region (e.g., an inactive border region) surrounding the edges of display  14  (e.g., layer  170  may be patterned to cover a rectangular ring-shaped area on the lower surface of polarizer  74 ). Opaque masking layer  170  and layer  174  may be formed from black ink, opaque plastic, or other opaque materials. Due to the presence of masking layer  170 , edge  172  may be located in a region of device  10  that is relatively far from the edge of layer  92  and the edge of polarizer layer  74 , thereby creating additional room within device  10  for mounting other components. 
     As shown in  FIG. 20 , light-guide structures  180  may be configured to form a recess such as rectangular pocket  184  under display layers  181 . Light guide structures  180  may be formed from a plastic such as acrylic, glass, or other transparent material. Recess  184  may have a depth that is sufficient to receive optical films  186 . Optical films  186  may have a rectangular outline. Recess  184  may have a rectangular outline that is sufficiently large to receive optical films  186 . Optical films  186  may include films such as a diffusing layer, a brightness enhancing film, and other optical material layers. Light guide structures  180  (sometimes referred to as a planar light guide member or light guide plate) may have protruding sidewalls such as sidewall portions  180 ′ that protrude upwards around the four edges at the periphery of display  14  and thereby define four sides for recess  184 . If desired, recess  184  may be sufficiently large to accommodate some of display layers  181  such as polarizer layer  74 . 
     Light  158  may be emitted from light source  150  into an edge or other surface of backlight light guide structures  180 . Light  158  may leak upwards out of upper surface of structure  180  to serve as backlight  82 . Reflector  182  may help reflect light  158  that has leaked downwards back in an upwards direction to serve as additional backlight  82 . Light guide plate  180  may serve as the main or exclusive structural element in backlight structures  84 . For example, light guide plate  180  may provide support for optical films  186  and/or reflector  182 . Reflector  182  may, as an example, be formed from a layer of metal that is deposited as a coating on light guide plate  180  or may be formed from a material that is attached to light guide plate  180 . 
     Adhesive such as adhesive  188  (e.g., epoxy) may be used to attach light-guide structure  180  of backlight structures  84  to display layers  81  (e.g., by attaching light-guide structure sidewall portions  180 ′ to the lower surface of thin-film transistor layer  92 ). If desired, light guide structures with a rectangular-pocket-shaped recess such as recess  184  of  FIG. 20  may be used in backlight structures such as backlight structures  84  of  FIGS. 9 and 10  (e.g., to provide backlight to a inverted-type display in which the color filter layer is interposed between the thin-film transistor structures and the backlight). 
     Backlight light guide structures such as structures  180  of  FIG. 20  may be provided with alignment features to help laterally align optical films  186 . The alignment features may be implemented in the form of protrusions on structures  180  or other suitable alignment features that are configured to mate with mating alignment features on optical films  186 . 
     A conventional arrangement for aligning optical films in a computer with a backlit display is shown in  FIG. 21 . As shown in  FIG. 21 , optical films  202  are provided with tabs  208  that are received within corresponding notches in aluminum computer housing  200 . Aluminum pins  206  are formed as part of aluminum computer housing  200  and are received within openings  204  in optical films  202 . Under the influence of gravity, optical films  202  are pulled downwards in direction  212  and are held in place by the interaction between pins  206  and holes  204 . Optical films  202  are formed from plastic, whereas housing  200  is formed from aluminum. There is therefore a non-negligible mismatch in the coefficients of thermal expansion between housing  200  and optical films  202 . As a result, the gaps that are formed between tabs  208  and notches  210  tend to be large to accommodate thermal expansion mismatch. 
     Light guide structures such as light guide plate  180  of  FIG. 20  may be formed from a material such as plastic and may therefore be characterized by a coefficient of thermal expansion that is comparable to that of plastic (polymer) optical films  186 . By providing alignment features on light guide plate  180  and using light guide plate  180  as a structural element into which optical films  186  are assembled to form backlight structures  84  as described in connection with  FIG. 20 , gap sizes can be reduced and alignment tolerances can be enhanced. 
     An illustrative arrangement that may be used for backlight structures  84  in a configuration in which alignment features for backlight structure optical films are formed on light guide plate  180  is shown in  FIG. 22 . As shown in  FIG. 22 , backlight structures  84  may include a light guide plate or other light guide structures  180 . Light guide structures  180  may be formed from a rectangular plate without sidewalls (i.e., without a recessed portion) or may be formed from a rectangular plate with protruding sidewall portions such as sidewall portions  180 ′ of  FIG. 20 . 
     Light guide structures  180  may be provided with alignment features that mate with corresponding alignment features on optical films  186 . For example, light guide structures  180  may be provided with protrusions  180 P. Protrusions  180 P may be formed from rectangular pins or other protruding structures. Optical films  186  may be provided with mating openings such as holes  220 . When display  14  is held in a particular orientation in a laptop computer or compute monitor or in other suitable device arrangements, optical films  186  will be pulled in direction  222  under the influence of gravity. As a result, the edges of holes  220  will bear against corresponding edges of protruding portions  180 P of light guide structures  180 , aligning optical films  186  within backlight structures  84 . 
       FIG. 23  is a cross-sectional view of backlight structures such as backlight structures  84  of  FIG. 22  that have been mounted within electronic device housing  12 . In the illustrative configuration of  FIG. 23 , gravity is causing optical films  186  to move in direction  222 . This causes upper edge  240  of opening  220  in optical films  186  to register against the adjacent edge of protruding portion  180 P of light guide plate  180 . 
     A conventional light guide plate is shown in  FIG. 24 . Light  300  from a light-emitting diode array enters the edge of light guide plate  302 . Textured lower surface  304  helps scatter light  300  so that some of light  300  leaks vertically upward from light guide plate  302  and, after passing through optical films  310  such as diffuser and brightness enhancing films, serves as backlight  306 . Reflector  308  reflects light that has leaked downwards back upwards to serve as additional backlight  306 . 
     If desired, light scattering features may be implemented within light guide structures such as a glass or plastic light guide plate. If light is sufficiently well dispersed (diffused) by the light scattering structures within the light guide plate, diffuser layers and other optical films may be omitted from backlight structures  84 . This type of arrangement is shown in  FIG. 25 . As shown in  FIG. 25 , backlight structures  84  include a light guide structure such as light guide plate  180  that includes internal structures  320 . Internal structures  320  may be formed from bubbles filled with air, particles formed from materials with an index of refraction that is greater than or less than the index of refraction of light guide plate  180 , or particles or voids with other properties that scatter light  158  from a light source such as a light-emitting diode light source. The inclusion of bubbles, particles, or other structures within the interior of light guide plate  180  may reduce or eliminate the need for diffusing films (as an example). Reflector  182  may be used to improve backlight efficiency. 
     In the illustrative configuration of  FIG. 26 , light guide structures  84  have been formed from a multilayer light guide plate that includes lower light guide plate layer  180 B (having a first type of bubbles or other internal structures  320 ) and an upper light guide plate layer  108 A (having a second type of bubbles or other internal structures  320 ). There may be three or more layers in light guide plate  180  if desired. Each layer may have a different type of internal structures (e.g., a different density of internal structures, internal structures of different sizes, shapes, internal structures formed from different materials, etc.). Reflector  182  may be used to improve backlight efficiency. 
     In the illustrative configuration of  FIG. 27 , light guide plate  180  of backlight structures  84  has been provided with bubbles or other internal structures  320  with sizes, shapes, and/or materials properties that change smoothly (e.g., structure types that vary following a linear or curved gradient). As an example, the properties of internal structures  320  may vary as a function of vertical distance within light guide plate  180 . Backlight efficiency may be enhanced using reflector  182 , if desired. 
     Another illustrative arrangement for backlight structures  84  is shown in  FIG. 28 . In the configuration of  FIG. 28 , light guide plate  180  has been provided with a textured surface or other surface treatment on the upper surface of light guide plate  180  that promotes light leakage. The inclusion of textured surface  322  causes light  158  to exit light guide plate  180  to serve as backlight  82 . Reflector  182  may be used to enhance backlight efficiency for backlight structures  84 . 
     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: 20111220
Publication Date: 20150127
Grant Date: 20150127
Priority Date: 20111220
Inventors: GARELLI ADAM T.
QI JUN
YIN VICTOR H.
WILSON, JR. THOMAS W.
MATHEW DINESH C.
POSNER BRYAN W.
HENDREN KEITH J.
AUGENBERGS PETERIS K.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B6/001", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/001", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B6/0006", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0068", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0073", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0088", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0068", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0073", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0088", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B6/0006", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 48609800