PATENT DOCUMENT

Publication Number: US-9208709-B2
Application Number: US-77413910-A
Country: US
Kind Code: B2

Title: Backlight for a display

Abstract:
Systems and devices are provided for using an organic light emitting diode (OLED) as a backlight for a liquid crystal display (LCD) device. In one embodiment, an OLED backlight may include one or more OLED elements disposed between two substrates. The OLED backlight may be optically bonded to the back of an LCD, and may further be electrically connected with the LCD active matrix. In one embodiment, information transmitted to selected pixels of the LCD active matrix may also be used by elements of the OLED backlight which are electrically connected to the selected LCD pixels. For example, the OLED backlight may respond to grayscale information transmitted to selected LCD pixels by emitting a corresponding intensity of light. In some embodiments, the LCD device may include other functions, such as touch sensing capabilities, which may be integrated with the LCD and OLED backlight.

Claims:
What is claimed is: 
     
       1. A liquid crystal display (LCD) device, comprising:
 an organic light emitting diode (OLED) device comprising a plurality of elements disposed between a substrate layer and a cover layer, and a bond disposed about a periphery of the OLED device, wherein the plurality of elements is configured to receive an emission signal generated by a processor and emit light at an intensity based on the emission signal; 
 an optically clear adhesive layer comprising a first face and an opposing second face, wherein the first face is optically bonded to the OLED device; and 
 an active matrix comprising a plurality of active matrix pixels formed in a TFT layer, wherein the plurality of active matrix pixels is configured to receive an image signal generated by the processor and to modulate the transmission of the emitted light based on the image signal, wherein the TFT layer with the active matrix is optically bonded to the second face of the optically clear adhesive layer, the TFT layer is directly bonded to the OLED device via the optically clear adhesive layer, and wherein each of the plurality of active matrix pixels is configured to modulate the transmission of the emitted light from at least one respective element of the plurality of elements. 
 
     
     
       2. The LCD device of  claim 1 , wherein each of the plurality of active matrix pixels is configured to modulate the transmission of the emitted light from a corresponding one of the plurality of elements, and wherein each of the plurality of active matrix pixels comprise a red pixel, a blue pixel, and a green pixel. 
     
     
       3. The LCD device of  claim 1 , wherein the active matrix is configured to modulate the transmission between substantially blocking the emitted light and substantially transmitting the emitted light, and wherein the intensity of the emitted light is low when the active matrix is substantially blocking, relative to the intensity of the emitted light when the active matrix is substantially transmitting. 
     
     
       4. The LCD device of  claim 1 , wherein the intensity of the emitted light is based at least in part on the image signal. 
     
     
       5. The LCD device of  claim 1 , wherein each of the plurality of active matrix pixels is configured to modulate the transmission of the emitted light from a corresponding pair of the plurality of elements, wherein each of the plurality of active matrix pixels comprise a red pixel, a blue pixel, and a green pixel, and wherein each element of the pair of the plurality of elements is differentially driven based on wear considerations. 
     
     
       6. The LCD device of  claim 1 , wherein the LCD device comprises a touchscreen integrally formed with the active matrix, wherein the touchscreen is configured to respond to a user touch, and wherein the OLED device is configured to emit light at an intensity based on the user touch, and wherein the active matrix is configured to modulate the transmission of the emitted light based on the user touch. 
     
     
       7. The LCD device of  claim 1 , wherein the image signal is calibrated based on the intensity of the emitted light. 
     
     
       8. The LCD device of  claim 1 , wherein the processor is configured to generate a data signal comprising the image signal and the emission signal, wherein the image signal is addressed to the plurality of active matrix pixels, and wherein the emission signal is addressed to the plurality of elements. 
     
     
       9. The LCD device of  claim 1 , comprising a black layer disposed behind the LCD device. 
     
     
       10. An electronic device, comprising:
 a touchscreen integrally formed with a light modulating layer, wherein the touchscreen is configured to receive a touch input and is configured to change a displayed screen on the electronic device in response to the touch input; 
 a processor configured to generate an image signal and an emission signal based on the touch input; 
 an organic light emitting diode (OLED) backlight configured to emit light based on the emission signal; 
 the light modulating layer configured to modulate the transmission of the emitted light based on the image signal, wherein the light modulating layer comprises a thin film transistor (TFT) layer; and 
 an optically clear adhesive layer optically bonded to the OLED backlight and to the TFT layer of the light modulating layer, wherein the OLED backlight is directly bonded to the TFT layer via the optically clear adhesive layer. 
 
     
     
       11. The display device of  claim 10 , wherein the light modulating layer comprises a liquid crystal layer, wherein the TFT layer is configured to generate an electric field based on the image signal and the liquid crystal layer is configured to transmit a range of the emitted light based on the electric field. 
     
     
       12. The display device of  claim 10 , wherein the OLED backlight comprises one OLED element. 
     
     
       13. The display device of  claim 10 , wherein the OLED backlight comprises a plurality of OLED elements and the light modulating layer comprises a plurality of pixels, wherein each of the pixels is configured to modulate the transmission of the emitted light from each of the plurality of elements. 
     
     
       14. The display device of  claim 10 , wherein the OLED backlight comprises a plurality of OLED elements and the light modulating layer comprises a plurality of pixels, wherein each of the pixels is configured to modulate the transmission of the emitted light from an element pair of the plurality of OLED elements, and wherein each OLED element of the element pair is alternately activated. 
     
     
       15. The display device of  claim 10 , wherein the processor is configured to generate a data signal comprising the image signal and the emission signal, wherein the image signal is addressed to the light modulating layer, and wherein the emission signal is addressed to the OLED backlight. 
     
     
       16. The display device of  claim 10 , wherein the emission signal results in the OLED backlight emitting light at an intensity corresponding to the transmission of light based on the image signal. 
     
     
       17. An electronic system, comprising:
 a processor configured to generate a data signal comprising an image signal and an emission signal; and 
 a display comprising:
 a backlight assembly comprising a plurality of organic light emitting diode (OLED) elements configured to emit light at an intensity according to the emission signal; and 
 a light modulating layer optically bonded to the backlight assembly, wherein the light modulating layer comprises a thin film transistor (TFT) layer directly bonded with the backlight assembly, the light modulating layer comprises a plurality of light modulating pixels configured to transmit the emitted light at a transmission percentage according to the image signal, and each of the plurality of OLED elements is electrically connected to a respective one of the plurality of light modulating pixels. 
 
 
     
     
       18. The electronic system of  claim 17 , comprising a bus configured to transmit the data signal to the connection between each of the plurality of OLED elements and the respective one of the plurality of light modulating pixels, wherein the emission signal is addressed to each of the plurality of OLED elements and the image signal is addressed to the respective one of the plurality of light modulating pixels. 
     
     
       19. The electronic system of  claim 17 , comprising a sensor configured to measure an intensity of light emitted by the plurality of OLED elements, wherein the processor is configured to determine an intensity ratio of the measured light intensity relative to the emission signal and configured to calibrate the image signal based on the emission signal and the intensity ratio. 
     
     
       20. The electronic system of  claim 19 , wherein the processor is configured to generate an image signal such that the light modulating layer transmits the emitted light at an increased transmission percentage, wherein the increased transmission percentage is inversely related to a decrease between the determined intensity ratio and a threshold intensity ratio. 
     
     
       21. The electronic system of  claim 17 , comprising a touchscreen configured to respond to a user touch, and wherein the backlight assembly is configured to emit light at an intensity based on the user touch, and wherein the light modulating layer is configured to modulate the transmission of the emitted light based on the user touch. 
     
     
       22. The electronic system of  claim 17 , comprising a light sensor configured to generate a sensor signal in response to sensed ambient light, wherein the OLED elements are configured to emit light at an intensity according to the sensor signal. 
     
     
       23. The electronic system of  claim 22 , wherein the light sensor is a photovoltaic sensor coupled in series with a diode gate of the OLED element.

Description:
BACKGROUND 
     The present disclosure relates generally to displays for use in electronic devices and, more particularly, to liquid crystal display devices using organic light emitting diodes as a backlight. 
     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. 
     Liquid crystal displays (LCDs) are commonly used as screens or displays for a wide variety of electronic devices, including such consumer electronics as televisions, computers, and handheld devices (e.g., cellular telephones, portable media players, gaming systems, and so forth). Such LCD devices typically provide a flat display in a relatively thin package that is suitable for use in a variety of electronic goods. In addition, such LCD devices typically use less power than comparable display technologies, making them suitable for use in battery powered devices or in other contexts where it is desirable to minimize power usage. 
     LCD devices generally include a light source, as liquid crystal materials themselves do not emit light. A typical light source, also referred to as a backlight, may include light sources along one or more edges which emit light into light guide panels (LGPs) which guide the light across the display area. To increase the uniformity and brightness over the display area, a typical LCD device may also include brightness enhancement film (BEF) layers which reflect and enhance the light. However, such efforts to increase uniformity and/or brightness may also increase the thickness and complexity of the backlight and the LCD device. Furthermore, the different films and parts of an LCD having a LED backlight may be susceptible to contamination. 
     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. 
     The present disclosure generally relates to a liquid crystal display (LCD) device having an organic light emitting diode (OLED) backlight. In one embodiment, an OLED backlight may include one or more OLED pixels disposed between two glass substrates. The OLED backlight may be optically bonded to the back of an LCD, which may prevent contamination between the LCD and the OLED backlight and increase the mechanical rigidity of the display device. Further, the OLED backlight may also be electrically connected with light modulating portions of the LCD, such that information transmitted to selected pixels of the LCD active matrix may also be transmitted to areas of the OLED backlight electrically connected to the selected LCD pixels. For example, grayscale information transmitted to selected LCD pixels may also be received by corresponding areas of the OLED backlight. 
    
    
     
       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 block diagram of exemplary components of an electronic device that includes a display device, in accordance with aspects of the present disclosure; 
         FIG. 2  is a perspective view of an electronic device in the form of a computer, in accordance with aspects of the present disclosure; 
         FIG. 3  is a front-view of a portable handheld electronic device, in accordance with aspects of the present disclosure; 
         FIG. 4  is a perspective view of a tablet-style electronic device that may be used in conjunction with aspects of the present disclosure; 
         FIG. 5  is an exploded view of layers of a pixel of a liquid crystal display (LCD) panel, in accordance with aspects of the present disclosure; 
         FIG. 6  is another exploded view of layers of a pixel of a liquid crystal display (LCD) panel, in accordance with aspects of the present disclosure; 
         FIG. 7  is a circuit diagram of switching and display circuitry of LCD pixels, in accordance with aspects of the present disclosure; 
         FIG. 8  is a cross-sectional side view of an organic light emitting diode (OLED) backlight of the LCD panel having multiple OLED elements, in accordance with aspects of the present disclosure; 
         FIG. 9  is a cross-sectional side view of an OLED display of the LCD panel having one OLED element, in accordance with aspects of the present disclosure; and 
         FIG. 10  is a top view of an OLED backlight, in accordance with aspects of the present disclosure. 
     
    
    
     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. 
     The application is generally directed to implementing one or more organic light emitting diode (OLED) elements as a backlight in a liquid crystal display (LCD) device. In some embodiments, an OLED backlight may include one or more OLED elements bonded between two glass pieces. The OLED backlight may be optically bonded to the back of light modulating layers of the LCD, which may prevent and/or reduce possible contamination between layers of the LCD and the OLED backlight. The bonding of the OLED backlight in the LCD may also increase the mechanical rigidity of the LCD, which may enable the use of thinner glass substrates and possibly reduce the thickness of the overall device. Further, an OLED backlight may generally be thinner than a typical LED backlight, and may also provide improved light uniformity without the use of light guides or additional brightness enhancing films. 
     In one embodiment, OLED elements of the OLED backlight may be electrically connected within the LCD, such that a signal may be selectively transmitted to pixels of the LCD and corresponding OLED elements of the backlight. For example, grayscale information transmitted to selected pixels of the LCD active matrix may also be received by individual OLED elements, such that the OLED elements may emit light at an intensity complementing or corresponding to the desired light transmission characteristics of the selected LCD pixels. In some embodiments, the LCD device with OLED backlight may also have other integrated features, such as wear balancing schemes for OLED elements, image calibration for the LCD active matrix, and/or touch sensing capabilities, as will be discussed. 
     With these foregoing features in mind, a general description of suitable electronic devices for performing these functions is provided below with respect to  FIGS. 1-4 . Specifically,  FIG. 1  is a block diagram depicting various components that may be present in electronic devices suitable for use with the present techniques.  FIG. 2  depicts an example of a suitable electronic device in the form of a computer.  FIG. 3  depicts another example of a suitable electronic device in the form of a handheld portable electronic device. Additionally,  FIG. 4  depicts yet another example of a suitable electronic device in the form of a computing device having a tablet-style form factor. These types of electronic devices, and other electronic devices providing comparable display capabilities, may be used in conjunction with the present techniques. 
     Keeping the above points in mind,  FIG. 1  is a block diagram illustrating components that may be present in one such electronic device  10 , and which may allow the device  10  to function in accordance with the techniques discussed herein. 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, such as a hard drive or system memory), 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 merely intended to illustrate the types of components that may be present in the electronic device  10 . For example, in the illustrated embodiment, these components may include a display  12 , input/output (I/O) ports  14 , input structures  16 , one or more processors  18 , memory device(s)  20 , non-volatile storage  22 , expansion card(s)  24 , RF circuitry  26 , and power source  28 . 
     The display  12  may be used to display various screens generated by the electronic device  10 . The display may be any suitable display such as a liquid crystal display (LCD), for example. In one embodiment, the display  12  may be an LCD employing fringe field switching (FFS), in-plane switching (IPS), or other techniques useful in operating such LCD devices. The display  12  may be a color display utilizing a plurality of color channels for generating color images. By way of example, the display  12  may utilize a red, green, blue, or white color channel. The display  12  may include a backlight such an organic light emitting diode (OLED). In one embodiment, the OLED backlight may be optically bonded to the LCD of the display  12 . 
     In certain embodiments, the display  12  may include an arrangement of unit pixels defining rows and columns that form a viewable region of the display  12 . A source driver circuit may output voltage signals to the display  12  by way of source lines defining each column of the display  12 . Each unit pixel may include a thin film transistor (TFT) configured to switch a pixel electrode. When activated, the TFT may store image signals received via a respective data or source line as a charge in the pixel electrode. The image signals stored by the pixel electrode may be used to generate an electrical field between the respective pixel electrode and a common electrode. Such an electrical field may align liquid crystals molecules within an adjacent liquid crystal layer to modulate light transmission through the liquid crystal layer. The light to be transmitted through the liquid crystal layer may be emitted by a backlight device, such as an OLED backlight. As will be discussed further below, in some embodiments, the image signals driven by the source driver circuit may be used by both modulating elements of the LCD, as well as light emitting elements of the backlight, such as an OLED backlight. Furthermore, the control of image signals or other signals driven to the display may be performed by any suitable processor  18  of the system  10 , including processors or controllers in the display  12 . 
     In some embodiments, the present techniques may also be applied to displays that utilize multiple common voltage lines. For instance, in one implementation, two or more common voltages may be supplied to respective common voltage lines coupled to respective sets of pixels to define discrete regions within an integrally-formed touch sensing system. For example, a display device may utilize two or more common voltages to provide touch sensing functions, and the LCD and the OLED backlight may change a displayed screen in response to such touch sensing functions. 
     Such a touch sensing system may be provided in conjunction with the display  12  and may be commonly referred to as a touchscreen. The touchscreen may be used as part of a control interface for the device  10 . In such embodiments, the touchscreen may be formed integrally with the display  12  as one of the input structures  16 . For instance, certain capacitive elements forming the pixels of the display  12  may dually function as pixel storage capacitors or as capacitive elements of a touch sensing system for detecting touch inputs. In this manner, a user may interact with the device by touching the display  12 , such as with the user&#39;s finger or a stylus. In response to the touchscreen interaction, a suitable processor (e.g., processor(s)  18 ) or display controller may control the image signals driven to the LCD active matrix and/or the OLED elements to control the displayed image. 
       FIG. 2  illustrates an embodiment of the electronic device  10  in the form of a computer  30 . The computer  30  may include computers that are generally portable (such as laptop, notebook, tablet, and handheld 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. of Cupertino, Calif. The depicted computer  30  includes a housing or enclosure  33 , the display  12 , I/O ports  14 , and input structures  16 . 
     The display  12  may be integrated with the computer  30  (e.g., such as the display of a laptop computer) or may be a standalone display that interfaces with the computer  30  using one of the I/O ports  14 , such as via a DisplayPort, DVI, High-Definition Multimedia Interface (HDMI), or analog (D-sub) interface. For instance, in certain embodiments, such a standalone display  12  may be a model of an Apple Cinema Display®, available from Apple Inc. As will be discussed below, the display  12  may be an LCD  34  that is backlit by one or more OLED elements. 
     The electronic device  10  may also take the form of other types of devices, such as mobile telephones, media players, personal data organizers, handheld game platforms, cameras, and/or combinations of such devices. For instance, as generally depicted in  FIG. 3 , the device  10  may be provided in the form of a handheld electronic device  32  that includes various functionalities (such as the ability to take pictures, make telephone calls, access the Internet, communicate via email, record audio and/or video, listen to music, play games, connect to wireless networks, and so forth). By way of example, the handheld device  32  may be a model of an iPod®, iPod® Touch, or iPhone® available from Apple Inc. 
     In the depicted embodiment, the handheld device  32  includes the display  12 , which may be in the form of an LCD  34 . The LCD  34  may display various images generated by the handheld device  32 , such as a graphical user interface (GUI)  38  having one or more icons  40 . As will be discussed below, backlighting for the LCD  34  may be provided by one or more OLED elements which may each emit light at varying intensities according to the image(s) to be displayed by the LCD  34 . 
     In another embodiment, the electronic device  10  may also be provided in the form of a portable multi-function tablet computing device  50 , as depicted in  FIG. 4 . In certain embodiments, the tablet computing device  50  may provide the functionality of one or more of a media player, a web browser, a cellular phone, a gaming platform, a personal data organizer, and so forth. By way of example only, the tablet computing device  50  may be a model of an iPad® tablet computer, available from Apple Inc. 
     The tablet device  50  includes the display  12  in the form of an LCD  34  that may be used to display GUI  38 . The LCD  34  may include an OLED backlight, and in one embodiment, the OLED backlight may be optically bonded to the active matrix of the LCD  34 . The GUI  38  may include graphical elements that represent applications and functions of the tablet device  50 . For instance, the GUI  38  may include various layers, windows  58 , screens, templates, or other graphical elements that may be displayed in all, or a portion, of the display  12 . As shown in  FIG. 4 , the LCD  34  may include a touch-sensing system  56  (e.g., a touchscreen) that allows a user to interact with the tablet device  50  and the GUI  38 . By way of example only, the operating system GUI  38  displayed in  FIG. 4  may be from a version of the Mac OS® (e.g., OS X) operating system, available from Apple Inc. 
     With the foregoing discussion in mind, it may be appreciated that an electronic device  10  in the form of a computer  30 , a handheld device  32 , or a tablet device  50 , may be provided with an LCD  34  as the display  12 . Such an LCD  34  may be utilized to display the respective operating system and application interfaces running on the electronic device  10  and/or to display data, images, or other visual outputs associated with an operation of the electronic device  10 . 
     In embodiments in which the electronic device  10  includes an LCD  34 , the LCD  34  may include an array or matrix of picture elements (i.e., pixels). In operation, the LCD  34  generally operates to modulate the transmission of light through the pixels by controlling the orientation of liquid crystal disposed at each pixel. In general, the orientation of the liquid crystals is controlled by a varying an electric field associated with each respective pixel, with the liquid crystals being oriented at any given instant by the properties (strength, shape, and so forth) of the electric field. The light to be modulated by and/or transmitted through each pixel may be emitted by an OLED element, as will be discussed. 
     Different types of LCDs may employ different techniques in manipulating these electrical fields and/or the liquid crystals. For example, certain LCDs employ transverse electric field modes in which the liquid crystals are oriented by applying an in-plane electrical field to a layer of the liquid crystals. Example of such techniques include in-plane switching (IPS) and fringe field switching (FFS) techniques, which differ in the electrode arrangement employed to generate the respective electrical fields. 
     While control of the orientation of the liquid crystals in such displays may be sufficient to modulate the amount of light emitted by a pixel, color filters may also be associated with the pixels to allow specific colors of light to be emitted by each pixel. For example, in embodiments where the LCD  34  is a color display, each pixel of a group of pixels may correspond to a different primary color. For example, in one embodiment, a group of pixels may include a red pixel, a green pixel, and a blue pixel, each associated with an appropriately colored filter. The intensity of light allowed to pass through each pixel (by modulation of the corresponding liquid crystals), and its combination with the light emitted from other adjacent pixels, determines what color(s) are perceived by a user viewing the display. As the viewable colors are formed from individual color components (e.g., red, green, and blue) provided by the colored pixels, the colored pixels may also be referred to as unit pixels. 
     With the foregoing in mind, and turning once again to the figures,  FIG. 5  depicts an exploded view of different layers of a pixel of a display  12 . The pixel  60  includes an upper polarizing layer  62  and a lower polarizing layer  64  that polarize light emitted by a backlight assembly  70 . An upper substrate  66  is disposed below the polarizing layer  64 , and a color filter layer  68 , a liquid crystal layer  70  and a thin film transistor (TFT) layer  72  may be disposed between the upper substrate  66  and a lower substrate  74 . The upper and lower substrates  66  and  74  may be formed from a light-transparent material, such as glass, quartz, and/or plastic. The back side of the lower substrate  74  may be bonded to a backlight assembly  78  using an optically clear adhesive layer  76 , in one embodiment. The TFT layer  72  and the backlight assembly  78  may be simplified in  FIG. 5  as single layers. However, each of the TFT layer  72  and the backlight assembly  78  may include a number of structures and layers, which are discussed in detail with respect to  FIGS. 7 and 8 . As such,  FIGS. 5-7  may be discussed concurrently. 
     Furthermore, the described layers of the pixel  60  are only examples of materials which may construct an LCD display device using an OLED backlight. In some embodiments, not all illustrated layers may be present, and/or additional layers may be utilized. For example, in one embodiment of a pixel as illustrated in  FIG. 6 , a layer of glass between the LCD portion of the pixel  60  and the backlight portion of the pixel  60  may be eliminated. As illustrated in  FIG. 6 , the lower substrate  74  may be eliminated such that the backlight assembly  78  may be directly bonded by the optically clear adhesive layer  76  to the TFT layer  72 . Alternatively, a top layer of glass of the backlight assembly  78  may be eliminated, and the backlight assembly may be directly bonded to the lower substrate  74  of the LCD portion of the pixel. 
     Referring to either  FIG. 5  or  6 , the TFT layer  72  may comprise various conductive, non-conductive, and semiconductive layers and structures which generally form the electrical devices and pathways which drive operation of the pixel  60 . For example, in an embodiment in which the pixel  60  is part of an FFS LCD panel, the TFT layer  72  may include the respective data lines, scanning or gate lines, pixel electrodes, and common electrodes (as well as other conductive traces and structures) of the pixel  60 . Such conductive structures may, in light-transmissive portions of the pixel, be formed using transparent conductive materials, such as indium tin oxide (ITO). In addition, the TFT layer  72  may include insulating layers (such as a gate insulating film) formed from suitable transparent materials (such as silicon oxide) and semiconductive layers formed from suitable semiconductor materials (such as amorphous silicon). In general, the respective conductive structures and traces, insulating structures, and semiconductor structures may be suitably disposed to form the respective pixel and common electrodes, a TFT, and the respective data and scanning lines used to operate the pixel  60 . The TFT layer  72  may also include an alignment layer (not illustrated) formed from polyimide or other suitable materials at the interface with the liquid crystal layer  70 . 
       FIG. 7  provides an example of a circuit view of pixel driving circuitry found in an LCD  34 . For example, such circuitry as depicted in  FIG. 7  may be embodied in the TFT layer  72  described with respect to  FIG. 5  or  6 . As depicted, the pixels  60  may be disposed in a matrix that forms an image display region of an LCD  34 . In such a matrix, each pixel  60  may be defined by the intersection of data lines  100  and scanning or gate lines  102 . The matrix of pixels  60  in the TFT layer  72  may also be referred to as the active matrix of the LCD  34 , and the portion of the pixels  60  defined by the TFT layer  72  may also be referred to as active matrix pixels  60 . 
     Although only seven unit pixels, referred to individually by the reference numbers  60   a - 60   g , respectively, are shown in the present example for purposes of simplicity, it should be understood that in an actual LCD implementation, each data line  100  and scanning line  102  may include hundreds or even thousands of unit pixels to form LCD  34  devices having any combination of display resolutions (e.g., 1024×768, 960×640, etc.) and screen sizes. By way of example, in a color LCD panel  34  having a display resolution of 960×640, each data line  100 , which may define a column of the pixel array, may include 640 unit pixels, while each scanning line  102 , which may define a row of the pixel array, may include 960 groups of pixels, wherein each group has a red, blue, and green pixel, thus totaling 2886 unit pixels per scanning line  102 . 
     In the present illustration, the group of unit pixels  60   a - 60   c  may represent a group of pixels having a red pixel ( 60   a ), a blue pixel ( 60   b ), and a green pixel ( 60   c ). A group of pixels (e.g., a red pixel  60   a , a blue pixel  60   b , and a green pixel ( 60   c ) may generally be referred to as a pixel  60  or an RGB pixel  60 . In some embodiments, the color of each pixel  60  may be determined by the alignment of the light modulating portion of the pixel  60  with the color filter layer  68  ( FIG. 5  or  6 ). The intensity of light allowed to transmit through each of the red pixel  60   a , the blue pixel  60   b , and the green pixel  60   c  and the corresponding color of the color filter layer  68 , and its combination with the light emitted from other adjacent pixels, determines what color(s) are perceived by a user viewing the display. 
     Furthermore, in some embodiments, a white pixel may also be used. For example, the group of unit pixels  60   d - 60   g  may represent a group of pixels having a red pixel ( 60   d ), a blue pixel ( 60   e ), a green pixel ( 60   f ), and a white pixel ( 60   g ), and may generally be referred to as a pixel  60  or an RGBW pixel  60 . In some embodiments, the white unit pixel  60   g  may be individually activated to display white (e.g., unfiltered) light. Though the RGB and RGBW pixels  60  are illustrated as having a strip configuration, the configuration of unit pixels  60  forming a pixel  60  may have different configurations. For example, an RGBW pixel  60  may have quadrants of each a red, blue, green, and white pixel. In embodiments, the display  12  may include a matrix of RGB pixels  60  or RGBW pixels  60 , or combinations of RGB and RGBW pixels. 
     The color filter layer  68  may be in a strip arrangement, for example, having adjacent filters which are red, green, and blue in color. In embodiments using an RGBW pixel configuration, the color filter layer  68  arrangement may also include an unfiltered or clear region to transmit light modulated by the white pixel  60   g . For example, the white unit pixel  60   g  may be activated to transmit light white (e.g., unfiltered by the color filter layer  68 ) emitted by the OLED backlight  78 . In one embodiment, the color filter  68  may be surrounded by a light-opaque mask or matrix, e.g., a black mask which circumscribes the light-transmissive portion of the pixel  60 . In other embodiments, the black mask may be eliminated from the configuration of the pixel  60  entirely (e.g., eliminated from the color filter and from a typical placement in the backlight). Rather, in such embodiments where no black masks are used in the pixel, a black layer may be implemented behind the entire LCD panel  34 . 
     Referring back to  FIG. 7 , each pixel  60  includes a pixel electrode  110  and thin film transistor (TFT)  112  for switching the pixel electrode  110 . In the depicted embodiment, the source  114  of each TFT  112  is electrically connected to a data line  100 , extending from respective data line driving circuitry  120 . Similarly, in the depicted embodiment, the gate  122  of each TFT  112  is electrically connected to a scanning or gate line  102 , extending from respective scanning line driving circuitry  124 . In the depicted embodiment, the pixel electrode  110  is electrically connected to a drain  128  of the respective TFT  112 . 
     In one embodiment, the data line driving circuitry  120  sends image signals to the pixels via the respective data lines  100 . Such image signals may be applied by line-sequence, i.e., the data lines  100  may be sequentially activated during operation. The scanning lines  102  may apply scanning signals from the scanning line driving circuitry  124  to the gate  122  of each TFT  112  to which the respective scanning lines  102  connect. Such scanning signals may be applied by line-sequence with a predetermined timing and/or in a pulsed manner. The data line driving circuitry  120  and/or the scanning line driving circuitry  124  may be controlled by a display controller  132 . For example, the display controller  132  may transmit data and/or clock signals via a synchronous bus to the data line driving circuitry  120 , and the data line driving circuitry  120  may latch data and drive the resulting image signals through the data lines  100  to the TFTs  112  of the pixels  60 . 
     Each TFT  112  serves as a switching element which may be activated and deactivated (i.e., turned on and off) for a predetermined period based on the respective presence or absence of a scanning signal at the gate  122  of the TFT  112 . When activated, a TFT  112  may store the image signals received via a respective data line  100  as a charge in the pixel electrode  110  with a predetermined timing. 
     The image signals stored at the pixel electrode  110  may be used to generate an electrical field between the respective pixel electrode  110  and a common electrode. In some embodiments, a storage capacitor may also be provided in parallel to the liquid crystal capacitor formed between the pixel electrode  110  and the common electrode to prevent leakage of the stored image signal at the pixel electrode  110 . For example, such a storage capacitor may be provided between the drain  128  of the respective TFT  112  and a separate capacitor line. 
     The electric field generated between the pixel electrode  110  and the common electrode of a pixel may be applied to the liquid crystal layer  70  ( FIG. 5  or  6 ) of the respective pixel  60 . The liquid crystal layer  70  may include liquid crystal particles or molecules suspended in a fluid or gel matrix. The liquid crystal particles or molecules may be oriented or aligned with respect to generated electrical field (e.g., based on the shape, strength, etc. of the electrical field). The orientation or alignment of the liquid crystal particles in the liquid crystal layer  70  determines the amount of light which may be transmitted through the pixel  60 . For example, the liquid crystal particles may be oriented (e.g., parallel to the layer  70 ) to substantially block light or oriented (e.g., perpendicular to the layer  70 ) to substantially transmit light, or oriented to transmit any percentage of light between fully blocking and fully transmitting. As will be further discussed with respect to  FIG. 8 , the light which may be transmitted through the pixel  60  may be emitted by a backlight  78  ( FIG. 5 ) associated with the LCD panel  34 . Thus, by modulation of the electrical field applied to the liquid crystal layer  70 , the amount of light emitted by the backlight  78  and transmitted though the pixel  60  may be correspondingly modulated. As the liquid crystal layer  70  and the TFT layer  72  of the pixel  60  may generally modulate light transmission, the layers  70  and  72  may be referred to as the light modulating portion of a pixel  60 . 
     Turning now to  FIG. 8  a cross-sectional view of the layers which may be present in a backlight of a particular embodiment are depicted. For example, the layers as depicted in  FIG. 8  may be embodied in the backlight assembly  78  described with respect to  FIG. 5  or  6 . In one embodiment, the backlight assembly  78 , such as an OLED backlight, may include a substrate layer  88  (e.g., a glass substrate layer) on which a layer of OLED elements  80  may be formed. Each element  80  may be printed, deposited, or otherwise formed on the substrate layer  88 , and may include two electrodes with organic electroluminescent materials between the two electrodes. For example, each OLED element  80  may be an optoelectronic device typically including an anode, a hole-transporting layer made of an organic compound, an organic electroluminescent layer with suitable dopants, an electron transport layer, and a cathode. 
     The OLED backlight  78  may also include a cover or external layer  82  (e.g., a cover glass) that forms the external viewing surface facing a viewer. In certain embodiments the cover layer  82  may perform various color filtration and/or polarization functions with respect to the light emitted by the OLED elements  80 . In one embodiment, the cover layer  82  and the substrate layer  88  may be bonded together, such as by a glass frit bond  84 , along all or part of the periphery of the surface and/or substrate layers. Further, in some embodiments, the OLED backlight  78  may include a light sensor  90  (e.g., a photodetector, a photodiode, a photovoltaic sensor, and so forth) which may operate as a pixel-level ambient light sensor. For example, the light sensor may be in the form of a photovoltaic sensor  90  which may generate an electric signal in response to an intensity of light emitted by one or more elements  80 . As will be discussed, the light intensity sensed by the light sensor  90  may be used to determine whether and/or when an image signal may be recalibrated. In one implementation, the OLED backlight  78  is between approximately 1.5 mm and 1.9 mm in thickness. In some embodiments, the backlight assembly  78  may be optically bonded with the light modulating components (e.g., the liquid crystal layer  70  and the TFT layer  72 ) within the LCD  34  by an optically clear adhesive (OCA). For example, the backlight assembly  78  may be bonded to the lower substrate  74 . Additionally, in some embodiments, the lower substrate  74  may be eliminated (as illustrated in  FIG. 6 ) or a top glass substrate of the backlight assembly  78  may be eliminated such that the LCD portion of the pixel  60  is directly bonded to the backlight assembly  78 . 
     Each OLED element  80  in the OLED backlight  78  may be activated to emit light by applying a current through the layers of the OLED element  80 . The current applied to the OLED element  80 , referred to as the emission signal, may flow from one electrode to another (e.g., from the cathode to the anode), and through the organic materials between the two electrodes. The organic electroluminescent materials may emit photons (perceived as light) in response to the emission signal. The light may be emitted through a substantially transparent electrode (e.g., the cathode) to be modulated and/or transmitted through the light modulating portion of the pixel  60 . In one embodiment, one or more driver chips  86  (such as a chip-on-glass (COG)) may drive the emission signal (received from a suitable controller or processor(s)  18 ) to one or more OLED elements  80 . In another embodiment, as will be discussed, the emission signal may also be driven by a common driver of the TFT layer  72 , such as the data line driving circuitry  120 , for example. 
     While multiple OLED elements  80  are illustrated in  FIG. 8 , an LCD panel  34  may use one or a plurality of OLED elements  80  in accordance with the present techniques. For example, as illustrated in  FIG. 9 , an OLED backlight  78  may have a single OLED element  80  emitting light to be transmitted through the light modulating portion of all the pixels  60  in the LCD  34 . The intensity of light emitted by the single OLED element  80  may be controllable based on the operation of the light modulating portion of the pixels  60 . For example, an image signal may be driven to the TFTs  112  ( FIG. 5  or  6 ) of the TFTs layer  72  of the pixels  60  to reduce light transmission through the liquid crystal layer  70  of the pixels  60 . The grayscale information of the same image signal may be used by the OLED backlight  78  to determine the intensity of light emitted, thus reducing power consumption when a mostly black or a relatively dark image is to be displayed on a corresponding portion of the LCD  34 . 
     In some embodiments, an OLED backlight  78  may have multiple OLED elements  80 , and each element  80  may be individually coordinated and/or controlled. For example, the magnitude of the emission signal transmitted to each OLED element  80  may be controllable, and the intensity of light emitted by each element  80  may depend on the magnitude of the emission signal. Further, each element  80  in an array of OLED elements  80  may be activated according to the operation of the active matrix pixel(s)  60  in the TFT layer  72  ( FIGS. 5-7 ) for which the element  80  is providing backlight. In one embodiment, the emission signal transmitted to an element  80  may cause the element  80  to emit light at an intensity which is related to the amount of light to be transmitted by the pixel  60  for which the element is backlighting. For example, an image signal sent to a pixel may result in substantially no light transmission through the liquid crystal layer  70 , and a corresponding emission signal may result in substantially no light emission from the OLED element  80 . Similarly, an image signal sent to a pixel may result in transmitting only a certain percentage (e.g., 50%) of light through the liquid crystal layer  70 , and the emission signal may result in the corresponding element  80  emitting light at a certain intensity (e.g., approximately 50% of a maximum intensity or some other reduced intensity level). Such operations of the OLED element  80  based on the light transmission of the pixel  60  may result in power savings, as no power is used to emit a higher intensity of light from the element  80  which will only be blocked by the light modulating portion of the pixel  60 . 
       FIG. 10  depicts an arrangement of OLED elements  80  in an LCD  34  in one embodiment. Each of the elements  80  may emit light to be transmitted through and/or modulated by the light modulating portion of a pixel  60 . For example, the element  80   m  may emit light for a pixel  60  (e.g., including the red pixel  60   a , the blue pixel  60   b , and the green pixel  60   c  in  FIG. 7 ). For embodiments including a white LCD pixel  60 , each element  80  may emit light for the red, blue, green, and white unit pixels  60 . For example, the element  80   n  may emit light for the red pixel  60   d , the blue pixel  60   e , the green pixel  60   f , and the white pixel  60   g . The elements  80   p  and  80   q  may be a backlight for similarly structured pixels (e.g., RGB and/or RGBW pixels  60 ). Further, in some embodiments, each element  80  may emit light for multiple groups of pixels  60  (e.g., multiple groups of pixels  60   a - c  and/or pixels  60   d - g ). 
     In one embodiment, emission of light (e.g., the intensity of light to be emitted) from the OLED element  80   n  ( FIG. 10 ) and the amount of light to be transmitted through the light modulating portions of the pixel  60  including unit pixels  60   d - g  ( FIG. 7 , referred to as pixel  60   d - g ), may be based on a data signal transmitted to the TFTs  112  of pixel  60   d - g  and/or the corresponding element  80 . The data signal may be generated by any suitable processor(s)  18  of the system  10 , or any controller (e.g., the display controller  132 ) of the display  12  and may include the image signal directed to the TFTs  112  and the emission signal directed to the elements  80 . The image signal may be transmitted to pixel  60   d - g  via data lines  100  from the data line driving circuitry  120 , and the emission signal may be transmitted to the OLED element  80   n  via a line  130 . 
     In some embodiments, each element  80  of the OLED backlight  78  may be electrically connected to a respective active matrix pixel  60  in the TFT layer  72 . For example, the driver chip  86  may be electrically connected to the display controller  132 , or any other suitable controller in the display  12 . The display controller  132  may control the transmission of image signals from the data line driving circuitry  120 , as well as the transmission of emission signals from one or more drivers  86  of the OLED backlight  78 . In some embodiments, a processor(s)  18  of the electronic system  10  ( FIG. 1 ) may communicate with the display controller  132  to determine corresponding emission signals sent to the OLED backlight  34  based on the image signals sent to the active matrix of the LCD  34 . 
     In other embodiments, the driver  86  of the OLED backlight  78  may also be connected to the data line driving circuitry  120 . For example, the data line driving circuitry  120  may direct emission signals to be driven by the driver  86  to the elements  80  via the lines  130 . Alternatively, the data lines  100  themselves may be connected to the OLED backlight  78 . For example, the data line driving circuitry  120  may drive an image signal having information to the red pixel  60   d , the blue pixel  60   e , the green pixel  60   f , and the white pixel  60   g  via data lines  100  in the active matrix and also drive an emission signal via line  130  to the OLED element  80   n . In such configurations, the lines  130  delivering current to the elements  80  may extend from the data line driving circuitry  120  or from the data lines  100 . Further, in some embodiments, a separate driver chip  86  in the OLED backlight  78  may not be necessary, as the data line driving circuitry  120  may drive the emission signal for activating the OLED elements  80 . 
     In some embodiments, more than one OLED element  80  (e.g., two elements  80 ) may be positioned to backlight each pixel  60  (e.g., pixel  60   a - c  and/or pixel  60   d - g ), such that each of the two elements  80 , both smaller than a pixel  60 , may be activated differentially over the life of the LCD  34 , thus providing wear balancing for the backlight assembly  78 . Alternatively, wear balancing may also be implemented by differentially driving two elements  80  which are each larger than the light modulating area of the pixel  60 . In another embodiment, wear balancing may be implemented by differentially driving two different layers of OLED elements  80 . For example, as depicted by the dotted line outlining element  80   r , two elements  80  (e.g., element  80   q  and element  80   r ) may be substantially overlapping, and may be on different OLED layers in an OLED backlight  78 . The substantially overlapping OLED elements  80  may be driven differentially to provide wear balancing of the backlight  78 . Further, in some embodiments, a first element  80  may be activated for a period of time and faded out while another element (e.g., an adjacent element or an element substantially overlapping with the out-fading element  80 ) may be faded in until it is fully activated. Such wear balancing operations may not be substantially noticeable in a user&#39;s experience of a displayed image on the LCD  34 . 
     In some embodiments, the image signals driven to the light modulating portion of the pixel  60  may also change over the life of the LCD  34 . For example, characteristics of the OLED backlight  78  may change over time (e.g., emit a lower intensity light in response to the same amplitude current of an emission signal). The image signal transmitted to the active matrix pixels  60  may be calibrated to accommodate for predicted light emission changes of the OLED backlight  78 . For example, if elements  80  in the OLED backlight  78  are expected to emit light with degraded intensity, an image signal sent to the active matrix pixels  60  may be adjusted such that more of the (possibly weakened) light emitted from the OLED backlight  78  may be transmitted. For example, a calibrated image signal may generate an electric field at the pixel electrode  110  ( FIG. 7 ) which aligns the crystals in the liquid crystal layer  70  to transmit light at an increased percentage to compensate for a decreased intensity of light emitted by the backlight  78 . 
     In one embodiment, such a calibration may be made by a processor  18  ( FIG. 1 ), by the display controller  132  ( FIG. 7 ) of the display  12  ( FIG. 1 ), or by any other suitable processor in the system  10 . Furthermore, such calibrations may be pre-programmed to occur after one or more time intervals of the LCD  34  lifespan, based on predicted degradation or changes in the OLED backlight  78 . Calibrations may also be made according to light sensors  90  ( FIGS. 8 and 9 ) which may generate a signal in response to an intensity of light emitted by the OLED backlight  78 . In some embodiments, a signal generated by the light sensor  90  may be transmitted to a suitable processor or controller (e.g., processor  18  or controller  132 , for example) to determine when to recalibrate the image signals sent to the LCD active matrix pixels  60 . For example, the light sensor  90  may measure the intensity of light emitted by an element  80  and the controller  132  may recalibrate the image signals based on the measured light intensity. 
     In some embodiments, the generated signal may be directly utilized by the elements  80  of the backlight  78  to affect an intensity of light emitted by the elements  80 . For example, a photovoltaic sensor  90  may be connected in series to a diode gate of one or more elements  80  such that an element  80  may transmit light at an increased (or reduced) intensity in response to the ambient light sensed by the sensor  90 . Thus, the intensity of light emitted by the elements  80  may also be adjustable. Further, the closed-loop system between the light sensors  90  and the elements  80  may result in power reduction. 
     Recalibration of image signals and/or readjusting the intensity of light emitted by the elements  80  based on a light sensed by the light sensor  90  may also be used to decrease the negative affects of glare or uneven lighting on the surface of the LCD  34 . For example, a photovoltaic sensor  90  may sense ambient light which may obstruct the viewing of the displayed image. The photovoltaic sensor  90  may generate a signal in response to detected light to recalibrate image signals and/or readjust the intensity of light emitted by the elements  80 . Furthermore, as the photovoltaic sensor  90  may control an individual unit pixel  60  (or groups of pixels  60 ), uneven lighting may be addressed by recalibrating and/or readjusting light transmission and/or emission for only the affected pixels  60 . 
     Furthermore, embodiments of an LCD  34  having an OLED backlight  78  also include touch sensing mechanisms (e.g., touchscreen). The touchscreen may be formed integrally with the LCD  34  having an OLED backlight  78 . For example, a user may interact with interface elements of the LCD  34  by touching the display, which may generate electrical signals indicative of the user&#39;s touch input. Such touch input signals may be stored in the LCD  34 , in capacitive elements of the pixel  60 , for example. Touch input signals may be routed via suitable pathways (e.g., an input bus) to be processed by a processor(s)  18 . The images displayed by the LCD  34  may then change based on the touch input signals. For example, the user may interact with the touchscreen to display a different image on the LCD  34 . Based on the user&#39;s touch input and the processing of the touch input signal, the processor(s)  18  may direct the display controller  132  to transmit data signals to display the desired screen. For example, an emission signal may be sent to activate OLED elements  80  of the OLED backlight  78 , and an image signal may be sent to the active matrix pixels  60 . Each OLED element  80  may emit an intensity of light corresponding to the image signals sent to the active matrix pixels  60 . 
     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: 20100505
Publication Date: 20151208
Grant Date: 20151208
Priority Date: 20100505
Inventors: MERZ NICHOLAS GEORGE
Assignee: APPLE INC
CPC Classifications: [{"code": "G09G5/003", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G3/3648", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/2092", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/3648", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09G3/20", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09G5/003", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09G3/2092", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 44901613