PATENT DOCUMENT

Publication Number: US-8587758-B2
Application Number: US-37134209-A
Country: US
Kind Code: B2

Title: Electrodes for use in displays

Abstract:
A liquid crystal display (LCD) is provided having a discontinuous electrode. In certain embodiments, finger- or slit-like extensions of the discontinuous electrode may be shaped to reduce or eliminate disclinations of liquid crystals within a pixel aperture used to transmit light, where the liquid crystals are oriented in response to an electric field generated using the discontinuous electrode. Similarly, in other embodiments, the different portions of the discontinuous electrode may be lengthened to extend under an opaque mask or may not be linked at one end to reduce or eliminate the disclinations.

Claims:
What is claimed is: 
     
       1. A liquid crystal display (LCD) comprising a plurality of pixels, each pixel comprising:
 a liquid crystal layer, wherein alignment of a plurality of liquid crystals within the liquid crystal layer is determined by an electric field; 
 an opaque mask defining an aperture over the liquid crystal layer; 
 a circuitry layer beneath the liquid crystal layer, the circuitry layer capable of generating the electric field, the circuit layer comprising:
 an insulating layer; 
 a first electrode formed on a first side of the insulating layer, the electrode comprising two or more finger-like regions that extend away from a thin film transistor in a first direction, wherein respective ends of the two or more finger-like regions extend beneath the opaque mask and have arcuate shapes, and wherein two or more portions of the two or more finger-like regions are substantially straight and parallel, thereby generating substantially zero electric field components operating in the first direction within the aperture; and 
 a second electrode formed on a second side of the insulating layer opposite the first side, wherein the second electrode comprises a common electrode. 
 
 
     
     
       2. The LCD of  claim 1 , wherein the respective ends of the two or more finger-like regions are connected by a crossbar region. 
     
     
       3. The LCD of  claim 1 , wherein the respective ends of the two or more finger-like regions are connected by a region proximate to the thin film transistor. 
     
     
       4. The LCD of  claim 1 , wherein the LCD comprises a fringe field switched (FFS) LCD. 
     
     
       5. The LCD of  claim 1 , wherein the first electrode comprises a pixel electrode. 
     
     
       6. The LCD of  claim 1 , wherein respective ends of the two or more finger-like regions comprise curved edges or curved transition regions. 
     
     
       7. The LCD of  claim 1 , wherein respective ends of the two or more finger-like regions are not connected by a linear segment of the first electrode running perpendicular to the respective ends. 
     
     
       8. An electronic device, comprising:
 one or more input structures; 
 a storage structure encoding one or more executable routines; 
 a processor capable of receiving inputs from the one or more input structures and of executing the one or more executable routines when loaded in a memory; and 
 a liquid crystal display (LCD) capable of displaying an output of the processor, wherein the LCD comprises a plurality of pixels, each pixel comprising:
 a liquid crystal layer comprising a plurality of liquid crystals whose alignment is determined by an electric field, wherein the alignment of the liquid crystals determines the amount of light which passes through the liquid crystal layer at the respective pixel; 
 an opaque mask defining an aperture over the liquid crystal layer; 
 an electrode formed on a first side of an insulating layer, wherein the electrode is used to generate the electric field, the electrode comprising two or more finger-like regions, wherein respective ends of the two or more finger-like regions extend beneath the opaque mask and have arcuate shapes, and wherein the electric field comprises substantially zero electric field components within the aperture that operate in a direction along which the two or more finger-like regions extend away from a thin film transistor; and 
 a common electrode formed along a length of a second side of the insulating layer opposite the first side. 
 
 
     
     
       9. The electronic device of  claim 8 , wherein the electronic device comprises a computer, a cellular telephone, a television, a gaming system, or a media player. 
     
     
       10. The electronic device of  claim 8 , wherein the respective ends of the two or more finger-like regions comprise one or more curved or angled portions. 
     
     
       11. A liquid crystal display (LCD) comprising a plurality of pixels, each pixel comprising:
 a liquid crystal layer, wherein alignment of a plurality of liquid crystals within the liquid crystal layer is determined by an electric field; 
 an opaque mask defining an aperture over the liquid crystal layer; and 
 an electrode capable of generating the electric field, wherein the electrode comprises two or more finger-like regions comprising at least one terminal end having an arcuate shape, and wherein the at least one terminal end is disposed under the opaque mask. 
 
     
     
       12. The LCD of  claim 11 , wherein at least a portion of the two or more finger-like regions are disposed substantially under the opaque mask. 
     
     
       13. The LCD of  claim 11 , wherein the at least one terminal end comprises transitions to a crossbar region or thin film transistor (TFT) region linking the two or more finger-like regions. 
     
     
       14. The LCD of  claim 11 , wherein the electrode comprises a body having a substantially rectangular shape. 
     
     
       15. An electronic device, comprising:
 one or more input structures; 
 a storage structure encoding one or more executable routines; 
 a processor capable of receiving inputs from the one or more input structures and of executing the one or more executable routines when loaded in a memory; and 
 a liquid crystal display (LCD) capable of displaying an output of the processor, wherein the LCD comprises a plurality of pixels, each pixel comprising:
 a liquid crystal layer comprising a plurality of liquid crystals whose alignment is determined by an electric field; 
 an electrode used to generate the electric field, the electrode comprising two or more finger-like regions comprising at least one terminal region having an arcuate shape; and 
 an opaque mask substantially overlying the at least one terminal region. 
 
 
     
     
       16. The electronic device of  claim 15 , wherein the one or more input structures comprise a touch sensitive structure disposed with the LCD to form a touch screen. 
     
     
       17. A liquid crystal display (LCD) comprising a plurality of pixels, each pixel comprising:
 an insulating layer; 
 a first electrode formed on a first side of the insulating layer; 
 a second electrode formed across a length of a second side of the insulating layer opposite the first side, the second electrode comprising two or more finger-like extensions, each having an arcuate end region that extends beneath an opaque mask, wherein two or more portions of the finger-like extensions that are not beneath the opaque mask generate an electric field comprising substantially zero electric field components operating in a direction along which the two or more finger-like portions extend away from a thin film transistor, and wherein the two or more portions of the finger-like extensions are substantially parallel with each other; and 
 a plurality of liquid crystals whose alignment is determined by an electric field generated between the first electrode and the second electrode. 
 
     
     
       18. The LCD of  claim 17 , wherein the arcuate end regions are connected by a crossbar or a region proximate to the thin film transistor. 
     
     
       19. The LCD of  claim 17 , comprising an opaque mask defining an aperture over the plurality of liquid crystals, wherein the arcuate end regions are disposed substantially beneath the opaque mask. 
     
     
       20. The LCD of  claim 17 , wherein the arcuate end regions comprise curved edges. 
     
     
       21. The LCD of  claim 17 , wherein the arcuate end regions comprise angled edges. 
     
     
       22. The LCD of  claim 1 , wherein the substantially two or more substantially straight portions of the finger-like regions are substantially perpendicular to at least one side of the aperture.

Description:
BACKGROUND 
     1. Technical Field 
     Embodiments of the present disclosure relate generally to electrodes used in displays, such as liquid crystal displays. 
     2. Description of the Related Art 
     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, audio and video 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. 
     The performance of an LCD may be measured with respect to a variety of factors. For example, the brightness of the display, the visibility of the display when viewed at an angle, the refresh rate of the display, and various other factors may all describe an LCD and/or determine whether a display will be useful in the context of a given device. For example, with respect to brightness, factors which may affect the brightness of a display include the area available to transmit light at each picture element (i.e., pixel) of the display. Likewise, another factor that may influence the brightness of an LCD may be the manner in which the liquid crystals forming the display are modulated. In particular, such modulation of the liquid crystals determines the amount of light transmitted by a pixel at a given time and artifacts, discontinuities, or irregularities in the fields affecting the liquid crystals may affect the perceived brightness of a pixel. 
     SUMMARY 
     Certain aspects commensurate in scope with the originally claimed invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below. 
     The present disclosure relates to increasing the light transmission of LCD pixels. In accordance with the present disclosure, an electrode of a pixel may be shaped or positioned to modify or reduce certain characteristics of an electric field generated using the electrode. For example, a field characteristic to be reduced may be associated with the improper alignment or orientation of liquid crystals at specific locations in the pixel, potentially reducing light transmittance at these locations. The occurrence or observed effect of such characteristics may be reduced by shaping and/or sizing an electrode used to generate the electric field. 
     For example, slat- or finger-like extensions of a pixel electrode may be provided without a cross-bar at one end of the electrode and/or may be extended further under a mask region of the pixel. Such implementations may result in an electric field having improved characteristics with respect to the manner in which liquid crystals align in the light modulating portion of a liquid crystal layer, e.g., the liquid crystals may align more uniformly. Similarly, in certain embodiments, the extensions of the pixel electrode may be rounded, curved, and/or angled to affect the characteristics of an electric field generated using the electrode such that liquid crystals oriented in the field are aligned more uniformly in the light modulating portion of a liquid crystal layer. In this manner, by shaping and/or positioning portions of an electrode to account for undesired field effects, more uniform liquid crystal alignment in the light modulating portion of a pixel may be achieved, and light transmittance through the pixel thereby increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Advantages of the present disclosure may become apparent 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, in accordance with aspects of the present disclosure; 
         FIG. 2  is a front view of a handheld electronic device in accordance with aspects of the present disclosure; 
         FIG. 3  is a view of a computer in accordance with aspects of the present disclosure; 
         FIG. 4  is an exploded view of exemplary layers of a pixel of an LCD panel, in accordance with aspects of the present disclosure; 
         FIG. 5  is a circuit diagram of switching and display circuitry of LCD pixels, in accordance with aspects of the present disclosure; 
         FIG. 6  is a plan view of an LCD pixel in accordance with the prior art; 
         FIG. 7  is a partial cross section of the LCD pixel of  FIG. 6 , in accordance with aspects of the prior art; 
         FIG. 8  is a plan view of an embodiment of an LCD pixel in accordance with aspects of the present disclosure; 
         FIG. 9  is a plan view of another embodiment of an LCD pixel in accordance with aspects of the present disclosure; 
         FIG. 10  is a plan view of an additional embodiment of an LCD pixel in accordance with aspects of the present disclosure; 
         FIG. 11  is a plan view of a further embodiment of an LCD pixel in accordance with aspects of the present disclosure; 
         FIG. 12  is a plan view of another embodiment of an LCD pixel in accordance with aspects of the present disclosure; and 
         FIG. 13  is a plan view of an additional embodiment of an LCD pixel in accordance with aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments will be described below. These described embodiments are provided only by way of example, and do not limit the scope of the present disclosure. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be 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 increasing light transmittance in LCD pixels. In certain embodiments, the increase in light transmittance may be accomplished by providing an electrode of a pixel that is shaped and/or positioned so as to reduce certain characteristics of a field generated using the pixel. For example, a characteristic of the field that may be reduced may be the magnitude of the field in a given dimension at certain locations. In particular, it may be useful to reduce field components in a given dimension within the portion of a liquid crystal layer used to modulate light transmitted through a pixel. 
     Example of electrodes that may provide such useful field characteristics may include electrodes which do not include a cross-bar to connect slat- or finger-like extensions of the electrode. Likewise, extensions of the pixel may be extended further beneath an opaque mask layer such that the field characteristics of interest are localized above the opaque mask and not in the portion of the pixel used to modulate light. Similarly, portions of the pixel may be shaped to as to reduce the undesired field components or to localize such components away from the region of the pixel used to modulate light. 
     With these foregoing features in mind, a general description of suitable electronic devices using LCD displays having such increased light transmittance is provided below. In  FIG. 1 , a block diagram depicting various components that may be present in electronic devices suitable for use with the present techniques is provided. In  FIG. 2 , one example of a suitable electronic device, here provided as a handheld electronic device, is depicted. In  FIG. 3 , another example of a suitable electronic device, here provided as a computer system, is depicted. These types of electronic devices, and other electronic devices providing comparable display capabilities, may be used in conjunction with the present techniques. 
     An example of a suitable electronic device may include various internal and/or external components which contribute to the function of the device.  FIG. 1  is a block diagram illustrating the components that may be present in such an electronic device  8  and which may allow the device  8  to function in accordance with the techniques discussed herein. Those of ordinary skill in the art will appreciate that the various functional blocks shown in  FIG. 1  may comprise hardware elements (including circuitry), software elements (including computer code stored on a computer-readable medium) or a combination of both hardware and software elements. It should further 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 a device  8 . For example, in the presently illustrated embodiment, these components may include a display  10 , I/O ports  12 , input structures  14 , one or more processors  16 , a memory device  18 , a non-volatile storage  20 , expansion card(s)  22 , a networking device  24 , and a power source  26 . 
     With regard to each of these components, the display  10  may be used to display various images generated by the device  8 . In one embodiment, the display  10  may be a liquid crystal display (LCD). For example, the display  10  may be an LCD employing fringe field switching (FFS), in-plane switching (IPS), or other techniques useful in operating such LCD devices. Additionally, in certain embodiments of the electronic device  8 , the display  10  may be provided in conjunction with touch-sensitive element, such as a touch screen, that may be used as part of the control interface for the device  8 . 
     The I/O ports  12  may include ports configured to connect to a variety of external devices, such as a power source, headset or headphones, or other electronic devices (such as handheld devices and/or computers, printers, projectors, external displays, modems, docking stations, and so forth). The I/O ports  12  may support any interface type, such as a universal serial bus (USB) port, a video port, a serial connection port, a IEEE-1394 port, an Ethernet or modem port, and/or an AC/DC power connection port. 
     The input structures  14  may include the various devices, circuitry, and pathways by which user input or feedback is provided to the processor  16 . Such input structures  14  may be configured to control a function of the device  8 , applications running on the device  8 , and/or any interfaces or devices connected to or used by the electronic device  8 . For example, the input structures  14  may allow a user to navigate a displayed user interface or application interface. Examples of the input structures  14  may include buttons, sliders, switches, control pads, keys, knobs, scroll wheels, keyboards, mice, touchpads, and so forth. 
     In certain embodiments, an input structure  14  and display  10  may be provided together, such an in the case of a touchscreen where a touch sensitive mechanism is provided in conjunction with the display  10 . In such embodiments, the user may select or interact with displayed interface elements via the touch sensitive mechanism. In this way, the displayed interface may provide interactive functionality, allowing a user to navigate the displayed interface by touching the display  10 . 
     User interaction with the input structures  14 , such as to interact with a user or application interface displayed on the display  10 , may generate electrical signals indicative of the user input. These input signals may be routed via suitable pathways, such as an input hub or bus, to the processor(s)  16  for further processing. 
     The processor(s)  16  may provide the processing capability to execute the operating system, programs, user and application interfaces, and any other functions of the electronic device  8 . The processor(s)  16  may include one or more microprocessors, such as one or more “general-purpose” microprocessors, one or more special-purpose microprocessors and/or ASICS, or some combination of such processing components. For example, the processor  16  may include one or more reduced instruction set (RISC) processors, as well as graphics processors, video processors, audio processors and/or related chip sets. 
     The instructions or data to be processed by the processor(s)  16  may be stored in a computer-readable medium, such as a memory  18 . Such a memory  18  may be provided as a volatile memory, such as random access memory (RAM), and/or as a non-volatile memory, such as read-only memory (ROM). The memory  18  may store a variety of information and may be used for various purposes. For example, the memory  18  may store firmware for the electronic device  8  (such as a basic input/output instruction or operating system instructions), various programs, applications, or routines executed on the electronic device  8 , user interface functions, processor functions, and so forth. In addition, the memory  18  may be used for buffering or caching during operation of the electronic device  8 . 
     The components may further include other forms of computer-readable media, such as a non-volatile storage  20 , for persistent storage of data and/or instructions. The non-volatile storage  20  may include flash memory, a hard drive, or any other optical, magnetic, and/or solid-state storage media. The non-volatile storage  20  may be used to store firmware, data files, software, wireless connection information, and any other suitable data. 
     The embodiment illustrated in  FIG. 1  may also include one or more card or expansion slots. The card slots may be configured to receive an expansion card  22  that may be used to add functionality, such as additional memory, I/O functionality, or networking capability, to the electronic device  8 . Such an expansion card  22  may connect to the device through any type of suitable connector, and may be accessed internally or external to the housing of the electronic device  8 . For example, in one embodiment, the expansion card  22  may be flash memory card, such as a SecureDigital (SD) card, mini- or microSD, CompactFlash card, Multimedia card (MMC), or the like. 
     The components depicted in  FIG. 1  also include a network device  24 , such as a network controller or a network interface card (NIC). In one embodiment, the network device  24  may be a wireless NIC providing wireless connectivity over any 802.11 standard or any other suitable wireless networking standard. The network device  24  may allow the electronic device  8  to communicate over a network, such as a Local Area Network (LAN), Wide Area Network (WAN), or the Internet. Further, the electronic device  8  may connect to and send or receive data with any device on the network, such as portable electronic devices, personal computers, printers, and so forth. Alternatively, in some embodiments, the electronic device  8  may not include a network device  24 . In such an embodiment, a NIC may be added as an expansion card  22  to provide similar networking capability as described above. 
     Further, the components may also include a power source  26 . In one embodiment, the power source  26  may be one or more batteries, such as a lithium-ion polymer battery or other type of suitable battery. The battery may be user-removable or may be secured within the housing of the electronic device  8 , and may be rechargeable. Additionally, the power source  26  may include AC power, such as provided by an electrical outlet, and the electronic device  8  may be connected to the power source  26  via a power adapter. This power adapter may also be used to recharge one or more batteries if present. 
     With the foregoing in mind,  FIG. 2  illustrates an electronic device  8  in the form of a handheld device  30 , here a cellular telephone. It should be noted that while the depicted handheld device  30  is provided in the context of a cellular telephone, other types of handheld devices (such as media players for playing music and/or video, personal data organizers, handheld game platforms, and/or combinations of such devices) may also be suitably provided as the electronic device  8 . Further, a suitable handheld device  30  may incorporate the functionality of one or more types of devices, such as a media player, a cellular phone, a gaming platform, a personal data organizer, and so forth. 
     For example, in the depicted embodiment, the handheld device  30  is in the form of a cellular telephone that may provide various additional functionalities (such as the ability to take pictures, record audio and/or video, listen to music, play games, and so forth). As discussed with respect to the general electronic device of  FIG. 1 , the handheld device  30  may allow a user to connect to and communicate through the Internet or through other networks, such as local or wide area networks. The handheld electronic device  30 , may also communicate with other devices using short-range connections, such as Bluetooth and near field communication. By way of example, the handheld device  30  may be a model of an iPod® or iPhone® available from Apple Inc. of Cupertino, Calif. 
     In the depicted embodiment, the handheld device  30  includes an enclosure or body that protects the interior components from physical damage and shields them from electromagnetic interference. The enclosure may be formed from any suitable material such as plastic, metal or a composite material and may allow certain frequencies of electromagnetic radiation to pass through to wireless communication circuitry within the handheld device  30  to facilitate wireless communication. 
     In the depicted embodiment, the enclosure includes user input structures  14  through which a user may interface with the device. Each user input structure  14  may be configured to help control a device function when actuated. For example, in a cellular telephone implementation, one or more of the input structures  14  may be configured to invoke a “home” screen or menu to be displayed, to toggle between a sleep and a wake mode, to silence a ringer for a cell phone application, to increase or decrease a volume output, and so forth. 
     In the depicted embodiment, the handheld device  30  includes a display  10  in the form of an LCD  32 . The LCD  32  may be used to display a graphical user interface (GUI)  34  that allows a user to interact with the handheld device  30 . The GUI  34  may include various layers, windows, screens, templates, or other graphical elements that may be displayed in all, or a portion, of the LCD  32 . Generally, the GUI  34  may include graphical elements that represent applications and functions of the electronic device. The graphical elements may include icons  36  and other images representing buttons, sliders, menu bars, and the like. The icons  36  may correspond to various applications of the electronic device that may open upon selection of a respective icon  36 . Furthermore, selection of an icon  36  may lead to a hierarchical navigation process, such that selection of an icon  36  leads to a screen that includes one or more additional icons or other GUI elements. The icons  36  may be selected via a touch screen included in the display  10 , or may be selected by a user input structure  14 , such as a wheel or button. 
     The handheld electronic device  30  also may include various input and output (I/O) ports  12  that allow connection of the handheld device  30  to external devices. For example, one I/O port  12  may be a port that allows the transmission and reception of data or commands between the handheld electronic device  30  and another electronic device, such as a computer. Such an I/O port  12  may be a proprietary port from Apple Inc. or may be an open standard I/O port. 
     In addition to handheld devices  30 , such as the depicted cellular telephone of  FIG. 2 , an electronic device  8  may also take the form of a computer or other type of electronic device. Such computers may include computers that are generally portable (such as laptop, notebook, and tablet computers) as well as computers that are generally used in one place (such as conventional desktop computers, workstations and/or servers). In certain embodiments, the electronic device  8  in the form of a computer may be a model of a MacBook®, MacBook® Pro, MacBook Air®, iMac®, Mac® mini, or Mac Pro® available from Apple Inc. By way of example, an electronic device  8  in the form of a laptop computer  50  is illustrated in  FIG. 3  in accordance with one embodiment. The depicted computer  50  includes a housing  52 , a display  10  (such as the depicted LCD  32 ), input structures  14 , and input/output ports  12 . 
     In one embodiment, the input structures  14  (such as a keyboard and/or touchpad) may be used to interact with the computer  50 , such as to start, control, or operate a GUI or applications running on the computer  50 . For example, a keyboard and/or touchpad may allow a user to navigate a user interface or application interface displayed on the LCD  32 . 
     As depicted, the electronic device  8  in the form of computer  50  may also include various input and output ports  12  to allow connection of additional devices. For example, the computer  50  may include an I/O port  12 , such as a USB port or other port, suitable for connecting to another electronic device, a projector, a supplemental display, and so forth. In addition, the computer  50  may include network connectivity, memory, and storage capabilities, as described with respect to  FIG. 1 . As a result, the computer  50  may store and execute a GUI and other applications. 
     With the foregoing discussion in mind, it may be appreciated that an electronic device  8  in the form of either a handheld device  30  or a computer  50  may be provided with an LCD  32  as the display  10 . Such an LCD  32  may be utilized to display the respective operating system and application interfaces running on the electronic device  8  and/or to display data, images, or other visual outputs associated with an operation of the electronic device  8 . 
     In embodiments in which the electronic device  8  includes an LCD  32 , the LCD  32  may include an array or matrix of picture elements (i.e., pixels). In operation, the LCD  32  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. 
     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 electrical field that is generally in-plane 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  32  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. 4  depicts an exploded view of different layers of a pixel of an LCD  32 . The pixel  60  includes an upper polarizing layer  64  and a lower polarizing layer  66  that polarize light emitted by a backlight assembly  68  or light-reflective surface. A lower substrate  70  is disposed above the polarizing layer  66  and is generally formed from a light-transparent material, such as glass, quartz, and/or plastic. 
     A thin film transistor (TFT) layer  72  is depicted as being disposed above the lower substrate  70 . For simplicity, the TFT layer  72  is depicted as a generalized structure in  FIG. 4 . In practice, the TFT layer may itself 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 or silicon nitride) 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 , as described in further detail with regard to  FIG. 5 . An alignment layer  74  (formed from polyimide or other suitable materials) may be provided between the TFT layer  72  and an overlying liquid crystal layer  78 . 
     The liquid crystal layer  78  includes liquid crystal molecules in a fluid shape or suspended in a polymer matrix. The liquid crystal molecules may be oriented or aligned with respect to an electrical field generated by the TFT layer  72 . The orientation of the liquid crystal particles in the liquid crystal layer  78  determines the amount of light transmission through the pixel  60 . Thus, by modulation of the electrical field applied to the liquid crystal layer  78 , the amount of light transmitted though the pixel  60  may be correspondingly modulated. 
     Disposed on the other side of the liquid crystal layer  78  from the TFT layer  72  may be one or more alignment and/or overcoating layers  82  interfacing between the liquid crystal layer  78  and an overlying color filter  86 . The color filter  86 , in certain embodiments, may be a red, green, or blue filter, such that each pixel  60  corresponds to a primary color when light is transmitted from the backlight assembly  68  through the liquid crystal layer  78  and the color filter  86 . 
     The color filter  86  may be surrounded by a light-opaque mask or matrix, e.g., a black mask  88  which circumscribes the light-transmissive portion of the pixel  60 . For example, in certain embodiments, the black mask  88  may be sized and shaped to define a light-transmissive aperture over the liquid crystal layer  78  and around the color filter  86  and to cover or mask portions of the pixel  60  that do not transmit light, such as the scanning line and data line driving circuitry, the TFT, and the periphery of the pixel  60 . In the depicted embodiment, an upper substrate  92  may be disposed between the black mask  88  and color filter  86  and the polarizing layer  64 . In such an embodiment, the upper substrate may be formed from light-transmissive glass, quartz, and/or plastic. 
     Referring now to  FIG. 5 , an example of a circuit view of pixel driving circuitry found in an LCD  32  is provided. For example, such circuitry as depicted in  FIG. 5  may be embodied in the TFT layer  72  described with respect to  FIG. 4 . As depicted, the pixels  60  may be disposed in a matrix that forms an image display region of an LCD  32 . In such a matrix, each pixel  60  may be defined by the intersection of data lines  100  and scanning or gate lines  102 . 
     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. 
     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. Such an electrical field may align liquid crystals within the liquid crystal layer  78  ( FIG. 4 ) to modulate light transmission through the liquid crystal layer  78 . 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. 
     Turning now to  FIGS. 6-13 , plan and cross-sectional views of pixels for use in a fringe field switched (FFS) LCD are provided. In  FIGS. 6 and 7 , a plan view and a partial cross-sectional view of a prior art pixel are provided depicting a transparent pixel electrode  110  and TFT  112  used as a switch for the pixel. A black mask  88  defines an aperture  150  through which light may be transmitted by the pixel  60 . The black mask  88  may be formed from any suitable opaque material, such as opaque polymeric compositions (e.g., plastics), metals, and so forth. In the depicted example, the pixel electrode  110  is formed over a passivation layer  160  (such as a silicon nitride layer) which insulates the pixel electrode  110  from an underlying common electrode  168  ( FIG. 7 ). The common electrode may be continuous across the pixel or across multiple pixels and may be transparent to light. During operation, the common electrode  166  may function to provide a common voltage, V com , across one or more pixels. In certain embodiments, both the pixel electrode  110  and the common electrode  166  are formed from indium tin oxide (ITO). 
     In the depicted example, the pixel electrode  110  is formed so as to have two or more spaced apart extensions  162  or projections, e.g., fingers or slits, that span the aperture  150  in the y-direction. In certain embodiments, the pixel electrode extensions  162  may be between about 500 Å to about 600 Å in thickness. In the depicted example, the extensions  162  are connected at one end of the pixel electrode  110  by a crossbar region  164  and at the other end of the pixel electrode  110  by a TFT region  166  proximate to and in contact with the TFT  112 . 
     In the depicted example, the regions linking the extensions  162 , i.e., the crossbar region  164  and the TFT region  166 , are adjacent to or extend into the aperture  150  through which light passes through the pixel. Because the pixel electrode is typically formed from a transparent conductive material, e.g., ITO, these portions of the pixel electrode  110  do not themselves substantially reduce the amount of light passing through the aperture  150 . However, the electric field generated near the crossbar region  164  and the TFT region  166  may have characteristics that result in disclinations where the liquid crystals in these regions are not fully or properly aligned. Thus, in portions of liquid crystal layer  78  ( FIG. 4 ) near the crossbar region  164  and the TFT region  166 , the liquid crystals may not align to allow unimpeded transmission of light through the corresponding portion of the aperture  150  when such transmission is specified. 
     In particular, in the example of an IPS or FFS LCD pixel, an transverse electric field is generated between adjacent pixel electrode extensions  162  to orient liquid crystals by application of an in-plane electric field. That is, electric field components operating in the x-direction are used to orient the liquid crystals. However, areas near the crossbar region  164  and the TFT region  166  may generate electric field components in the y-direction, causing the affected liquid crystals to be misaligned or poorly aligned with respect to other liquid crystal in the pixel. As a result, light transmission may be reduced near the crossbar region  164  and the TFT region  166  of the pixel electrode  110 . 
     Turning now to  FIG. 8 , an embodiment of a pixel  60  is depicted in which the pixel electrode extensions  162  are not linked by a crossbar region  164 . In addition, in the depicted embodiment, the extensions  162  may extend further under the black mask  88  than in embodiments where the extensions are linked by a crossbar region  162 . In such an embodiment, where the extensions  162  extend further under the black mask  88  and/or where a crossbar region is not present, portions of the electric field running in the y-direction may be present, but may be localized to a region over the black mask  88 . In this manner, undesired disclinations of the liquid crystals may be localized over the black mask  88  where they will not interfere with the transmission of light through the pixel  60 . 
     Further,  FIG. 8  also depicts an example of an embodiment in which the TFT region  166  linking the extensions at the TFT  112  end of the pixel  60  is under the black mask  88 . That is, the extensions  162  extend under the black mask  88  at the TFT end of the pixel as well. In this manner, disclinations may be reduced or eliminated at the TFT end of the pixel  60  because portions of the electric field having y-direction components may be localized over the black mask  88  in this region as well. Thus, in this embodiment, it may be possible to improve the transverse directionality (here in the x-direction) of the electric field over the aperture  150  by moving those portions of the pixel electrode  110  that contribute y-direction components of the electric field under the opaque black mask  88 . 
     In addition, turning to  FIG. 9 , in some embodiments the shape of the pixel  110  may be adapted to reduce the generation of field components in the y-direction and/or to localize such components over the black mask  88 . For example, in the depicted embodiment, a curved transition  170  may be employed to shape the electric field generated by the pixel electrode  110 . In this example, the curved transition  170  (as opposed to a perpendicular, linear transition as depicted in  FIG. 6 ) is employed where the crossbar region  164  and the TFT region  166  link the extensions  162 . Such a curved transition  170  may change the shape of the extensions  162  and/or the corresponding linking region at the location where y-direction field components are generated. Such a curvature may alter the shape of the associated electric field to reduce the strength of the y-direction field components, to reduce in size the region of the electric field exhibiting such y-direction characteristics, and/or to localize such y-direction field characteristics over the opaque black mask  88 . 
     As depicted in  FIG. 10 , in another embodiment, the extensions  162  may not be connected by a crossbar region  164  at the end of the pixel  60  away from the TFT  112  and may still use curved edges  172  to change the shape of the electrode extensions  162 . In this example, the extensions  162  each have a curved edge  172  (as opposed to straight edges) at the tip portion of the extension  162  away from the TFT  112 . In one embodiment, the curved edge  172  is generally under the black mask  88 . In other embodiments, some or all of the curved edge  172  may not be covered by the black mask  88 . Such curved edges  172  may change the shape of the extensions  162  at the location where y-direction field components are generated. As previously discussed, such curvature may alter the shape of a generated electric field to reduce the strength of the y-direction field components, to reduce the size of the region of the electric field exhibiting such y-direction characteristics, and/or to localize such y-direction field characteristics over the opaque black mask  88 . 
     In another embodiment, such curved regions of the extension  102  may be asymmetric with respect to the primary axis of the respective extension  162 . For example, turning now to  FIG. 11 , curved edges  172  may be used to provide a curved tip that is angled or slanted for some or all of the extensions  162 . All or only a portion of the curved edges  172  may be covered by the black mask  88 . As noted above, such curved edges  172  may change the shape of the extensions  162  at the locations where y-direction field components are generated, resulting in a reduction in the strength of the y-direction field components of an electric field, a reduction of the region of the electric field exhibiting such y-direction characteristics, and/or a localization of such y-direction field characteristics over the opaque black mask  88 . 
     Turning now to  FIGS. 12 and 13 , in further embodiments, the linearity of each extension  162  may be broken not by the use of curved edges or tips, but by the use of angled regions  178 , such as angled tips, of the extensions  162 . Such angled regions  178  may be formed using linear segments angled relative to the primary axis of the extensions  162  and may be wholly or partly covered by the black mask  88 . Though the depicted examples do not include a crossbar member  164 , in other embodiments such a linking crossbar  164  may be provided, with the angled regions  178  of the extensions  162  defined by the shape of the transition region between extensions  162  provided by the crossbar  164 . Such angled regions, as with the curved regions discussed above, may shape an electric field generated by the electrode  110  to reduce or eliminate disclinations in the liquid crystals within the aperture  150 . 
     In addition, the transition between extensions  162 , such as at TFT region  166  of the electrode  110 , may formed as something other than a perpendicular transition (as depicted in  FIG. 6 ). Instead, other angled or non-perpendicular transitions  180  may be employed in connecting the extensions  162  such that adjacent extensions  162  are not connected by a single linear segment. The angled or non-perpendicular transitions  180  may be wholly or partly covered by the black mask  88 . Such angled or non-perpendicular transitions  180  may shape an electric field generated by the electrode  110  to reduce disclinations in the liquid crystals within the aperture  150 , as discussed above. 
     While the preceding examples describe configurations of pixels for use in a FFS LCD device, it should be understood that these examples are not intended to be limiting in scope and, indeed, the present teachings may also be applicable to other types of LCDs, such as in-plane switched (IPS) LCDs or others. Further, for simplicity the present examples describe circuitry in which the pixel electrode  110  is discontinuous (i.e., includes separated fingers or extensions  162 ) and the common electrode  166  is continuous. As will be appreciated, this arrangement may be reversed or otherwise varied. For example, in certain embodiments, the common electrode  166  may be discontinuous and the pixel electrode  110  may be continuous. In such embodiments, the extensions (strips, fingers, and so forth) of the common electrode may vary in shape, size, length, and/or transition to achieve the benefits discussed herein. Likewise, in certain embodiments, the relative position of the pixel electrode  110  and the common electrode  166  may be reversed, i.e., the common electrode  166  may be proximate to the liquid crystal layer  78  while the pixel electrode  110  may be further away. In such embodiments, varying the shape, size, length, and/or transitions of the discontinuous electrode (whether pixel or common) may be performed as described herein to achieve the results described. 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.

Metadata:
Filing Date: 20090213
Publication Date: 20131119
Grant Date: 20131119
Priority Date: 20090213
Inventors: CHEN CHENG
XU MING
CHANG SHIH CHANG
GU MINGXIA
GETTEMY SHAWN ROBERT
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/1393", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2201/122", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/134372", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/134363", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133512", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/134372", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/134381", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/134363", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/1393", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/134381", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2201/122", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133512", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 42559431