Abstract:
A way of driving emissive displays is provided. An apparatus comprises a first panel having one or more contacts in a pre-selected arrangement. The apparatus comprises a display panel having one or more light emitting elements and one or more contacts in the pre-selected arrangement to deliver current to the light emitting elements, wherein the contacts of the display panel are surface mounted to the contacts of the first panel.

Description:
BACKGROUND 
     This invention relates generally to displays, and, more particularly, to driving emissive displays. 
     Emissive displays include light emitting diodes, liquid crystal displays, and organic light emitting displays. These displays generally emit light at the pixel level that can be perceived by viewers. To drive an OLED display, electrical current is typically passed through selected pixels by applying a voltage to the corresponding rows and columns from drivers attached to each row and column. An external controller circuit typically provides the necessary input power, video data signal, and multiplex switches. Data signal is generally supplied to the column lines and synchronized to the scanning of the row lines. When a particular row is selected, the column and row data lines determine which pixels are lit. A video output is thus displayed on the panel by scanning through all the rows successively in a frame time, typically {fraction (1/60)} second. 
     The pixels of an OLED display may be driven by drivers that are typically mounted at the edge of the display panel. In such an edge connection arrangement, it is not uncommon to find a plurality of drivers that may be located on the periphery of the display area. The edge connection arrangement, while effective, may contribute to increased line resistance and capacitance, which may adversely affect the performance of the display, such as reduced brightness. Additionally, the edge connection arrangement may sometimes call for a higher than desired voltage level to drive the pixels. In some cases, the edge connections may require significant area around the periphery of the display, thereby possibly limiting the area available for the display itself. 
     Thus, there is a need for an efficient way of driving emissive displays. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which: 
     FIG. 1 is a stylized block of a module in accordance with one embodiment of the present invention; 
     FIG. 2 illustrates a display panel that may be employed by the module of FIG. 1, in accordance with one embodiment of the present invention; 
     FIG. 3 is a cross-sectional view of the display panel of FIG. 2, in accordance with one embodiment of the present invention; 
     FIG. 4 is an alternative cross-sectional view of the display panel of FIG. 2, in accordance with one embodiment of the present invention; 
     FIG. 5 is a cross-sectional view of the module of FIG. 1, in accordance with one embodiment of the present invention; 
     FIG. 6 is an alternative cross-sectional view of the module of FIG. 1, in accordance with one embodiment of the present invention; 
     FIG. 7 depicts an alternate embodiment of a display panel that may be employed by the module of FIG. 1, in accordance with the present invention; and 
     FIG. 8 is an isometric view of a portable device employing the module of FIG. 1, in accordance with one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1, a module  10  is illustrated in accordance with one embodiment of the present invention. In one embodiment, the module  10  includes a display panel  15  having a first and second surface  16 ,  18  and a back panel  20  having a first and second surface  22 ,  24 . The first surface  16  of the display panel  15  may be a transparent layer, such as glass, for example, or, alternatively, it may be any other useful or desirable substrate. In one embodiment, the second surface  18  of the display panel  15  may include contacts that are surface mounted to contacts on the first surface  22  of the back panel  20 . In one embodiment, the second surface  18  of the display panel  15  may include a two-dimensional array of contact pads that are surface mounted to a matching set of contact pads on the first surface  22  of the back panel  20 . The back panel  20 , in one embodiment, may be flexible. 
     In one embodiment, the two panels  15 ,  20  may be affixed to each other using ball grid array technology, where an array of contacts on the two panels  15 ,  20  may be combined using heat, for example, to form the module  10 . The back panel  20 , in one embodiment, may be constructed using ceramic, conventional circuit board or flex circuit technology. The interconnection medium between the matching contact pads on the two panels may be an appropriate solder, a conductive epoxy, an anisotropic conductive adhesive, or any other appropriate conductive material. 
     In one embodiment, as described in more detail below, the second surface  18  of the display panel  15  includes a plurality of electroluminescent cells, each capable of producing a pixel or subpixel of monochrome or color light. In one embodiment, one or more driver integrated circuits (also referred to as “drivers”)  30 ( 1 - p ) may be affixed to the second surface  24  of the back panel  20  for driving the plurality of cells on the display panel  15 . Interconnection circuitry built on the back panel  20  may provide the desired connection between the one or more drivers  30 ( 1 - p ) and the appropriate interconnection pads on the surface  22  of the back panel  20 . In another embodiment, one or more integrated circuits  35 ( 1 - n ) that may provide system functions (either for the display or the total system) may also be affixed to the second surface  24  of the back panel  20 . The back panel may, in one embodiment, include a connector  40  that provides an electrical interface to the module  10 . In one embodiment, the connector  40  may be an edge connector integrated into the back panel  20  itself. In an alternative embodiment, the connector  40  (shown in dotted lines) may be attached to the back panel  20 . 
     Referring now to FIG. 2, one embodiment of the display panel  15  of the module  10  of FIG. 1 is illustrated, in accordance with the present invention. The first side  16  (i.e., the topside in the illustrated embodiment) of the display panel  15  may be made of transparent material, such as glass. The second surface  18  (i.e., the underside in the illustrated embodiment) of the display panel  15  may include a plurality of electroluminescent pixels (or cells)  210 ( 1 - m ) each including one or more light emitting elements or sub-pixels  215 ( 1 - 3 ). In one embodiment, the light emitting elements  215 ( 1 - 3 ) may be organic light emitting diodes. Although not so limited, in the illustrated embodiment, each cell  210 ( 1 - m ) includes three light emitting elements, red, green, and blue lighting elements  215 ( 1 - 3 ). Because of the transparent nature of the first side  16 , the pixels  210 ( 1 - m ) may be visible when viewing the display panel from the first side  16 . 
     In the illustrated embodiment, pixels  210 ( 1 - m ) are arranged in a two-dimensional array, formed of a plurality of rows  225 ( 1 - t ) and a plurality of columns  230 ( 1 - h ). In one embodiment, adjacent pixels  210 ( 1 - m ) are separated by at least one of a plurality of row sections  232 ( 1 - y ) and column sections  240 ( 1 - k ). In one embodiment, the rows  225 ( 1 - t ) may be made of a film of a high conductivity metal, such as aluminum. In other embodiments a thin film of a low work function metal may also be employed. The columns  230 ( 1 - h ), in one embodiment, may be formed using a transparent conductive film, such as Indium Tin Oxide (ITO). 
     The display panel  15 , in one embodiment, may have a plurality of row contacts  245 ( 1 - w ) formed on one or more of the plurality of rows  225 ( 1 - t ). In one embodiment, the display panel  15  includes a plurality of column contacts  250 ( 1 - r ) formed on one or more of the plurality of columns  230 ( 1 - h ). Although not so limited, in the illustrated embodiment, each of the plurality of rows  225 ( 1 - t ) has a corresponding row contact  245 ( 1 - w ) and each of the plurality of columns  230 ( 1 - h ) has a corresponding column contact  250 ( 1 - r ). In one embodiment, the plurality of column contacts  250 ( 1 - r ) provide a signal to the anode of each corresponding light emitting element  215 ( 1 - 3 ) of each cell  210 ( 1 - m ) and the row contacts  245 ( 1 - w ) provide a signal to the cathode of each corresponding light emitting element  215 ( 1 - 3 ) of each cell  210 ( 1 - m ). 
     The example arrangement of the row contacts  245 ( 1 - w ) and column contacts  250 ( 1 - r ) are provided for illustrative purposes, and it should be appreciated that, in other embodiments, one of a variety of other contact arrangements may be used without deviating from the spirit and scope of the invention. For example, in one embodiment, the column contacts  250 ( 1 - r ) may be arranged in a staggered arrangement (i.e., arranged diagonally, as opposed to a horizontally). Furthermore, in one embodiment, additional or fewer contacts  245 ( 1 - w ),  250 ( 1 - r ) may be utilized, depending on the particular implementation goals. For example, it may be possible to have separate contacts for each of the light emitting elements  215 ( 1 - 3 ) such that the separate contacts may serve as contacts for an active matrix display. In another embodiment, the use of thin film transistors in the display panel  15  may reduce or eliminate the need for redundant contacts, and as few as one contract per row (or column) may be needed. 
     In accordance with at least one embodiment of the present invention, one or more redundant contacts may be used to provide electrical signals to the pixels  210 ( 1 - m ). That is, in one embodiment, additional contacts may be provided in row sections  240 ( 3 - k ) and/or in column sections  232 ( 3 - y ), for example, where these (redundant) contacts may also be able to deliver electrical signals to the desired light emitting elements  215 ( 1 - 3 ) of the pixels  210 ( 1 - m ). Redundant contacts may provide one of several desirable advantages. For example, redundant contacts may improve the yield of the manufacturing process, as the problems caused by faulty or otherwise inoperable contacts may be cured by using redundant contacts to provide the electrical signals to the light emitting elements  215 ( 1 - 3 ) of the pixels  210 ( 1 - m ). Additionally, using redundant contacts may assist in reducing the capacitance and/or resistance commonly associated in edge connection arrangements, particularly since the length of the lines from the drivers  30 ( 1 - p ) (see FIG. 1) to the light emitting elements  215 ( 1 - 3 ) maybe shorter. 
     Referring now to FIG. 3, a cross-sectional view of the display panel  15  along the line  260 — 260  of FIG. 2 is illustrated. A cross-sectional view of the first surface  16 , which may include glass, is provided. The light emitting elements  215 ( 1 - 3 ) shown in FIG. 3, in one embodiment, lie between the column  230 ( 1 - 6 ), which may be an ITO anode rail, for example, and row  225 ( 1 ), which may be a cathode rail, for example. The cross-sectional view includes the row contact  245 ( 1 ), which, as described in more detail below, may be a contact pad that is adapted to be coupled to a corresponding contact pad on the back panel  200  (see FIG.  1 ). In one embodiment, the electrical signals received through the row contact  245 ( 1 ) are applied to the cathode of each light emitting elements  215 ( 1 - 3 ) in the first row  225 ( 1 ) of the display panel  15 . As shown in the cross-sectional view of FIG. 3, the light emitting elements  215 ( 1 - 3 ) in the first row  225 ( 1 ) are isolated from each other by isolation, non-conductive, material  320 , such as polyamides or other insulating material. 
     Referring now to FIG. 4, a cross-sectional view of the front panel  15  along the line  270 — 270  of FIG. 2 is illustrated. A cross-sectional view of the front panel  15  shows the insulation material  420  that isolates each of the column contacts  250 ( 1 - 6 ) from each other, in one embodiment. Each of the column contacts  250 ( 1 - 6 ) in the illustrated embodiment is respectively coupled to each of the columns  230 ( 1 - 6 ) (i.e., anode rails). The contacts  250 ( 1 - 6 ) are adapted to be coupled to corresponding contacts on the first surface  22  of the back panel  20  (see FIG.  1 ). 
     While FIGS. 3 and 4 illustrate cross-sectional perspectives of two portions of the display panel  15 , it should be appreciated that, in one embodiment, the remaining portions of the display panel  15  may be constructed in a similar fashion as shown in FIGS. 3 and 4. Furthermore, it should be appreciated that the example arrangement of contacts in FIGS. 3 and 4 are for illustrative purposes, and that in alternative embodiments, other arrangements may be employed. 
     Referring now to FIG. 5, a cross-sectional view of the display panel  15  and the back panel  20  along the line  260 — 260  (see FIG. 2) is illustrated, in accordance with one embodiment of the present invention. For illustrative purposes, as is evident from the like reference numerals, the cross-sectional view of the display panel  15  shown in FIG. 6 is substantially the same view as that of FIG.  3 . In one embodiment, one or more of the drivers  30 ( 1 - p ) and integrated circuits  35 ( 1 - n ) may be attached to the second surface  24  of the back panel  20  (see also FIG.  1 ). 
     In one embodiment, the back panel  20  includes a contact  502  that is adapted to be coupled to the contact  245 ( 1 ) of the display panel  15 . The contacts  245 ( 1 ) and  502  may be coupled in one of a variety of ways, including by a solder joint  505 . For clarity and ease of illustration, only one contact (e.g., contacts  245  and  502 ) connection between the display panel  15  and the back panel  20  is shown, although those skilled in the art will appreciate that one or more contacts of the display panel  15  may be similarly coupled to one or more corresponding contacts of the back panel  20 . In one embodiment, once all of the desired contacts  245 ( 1 - p ) of the display panel  15  are coupled to the corresponding contacts (e.g.,  502 ) of the back panel  20 , one of a variety of filling material  507 , such as insulating epoxy, may be applied at the juncture of the two panels  15  and  20 . 
     The one or more drivers  30 ( 1 - p ) for the display panel  15  may provide an electrical signal to a rail  510  of the back panel  20 . The rail  510  may be coupled to another rail  520  of the back panel  20  through an electrically conductive via  530 . The electrical signal from the rail  530  may be provided to the row  225 ( 1 ) (e.g., cathode rail) through the contacts  245 ( 1 ) and  502 . In one embodiment, additional vias may be utilized for providing electrical signals to other row contacts  245 ( 2 - p ). In another embodiment, the same via may be used to provide electrical signals to other redundant contacts of the same row. In one embodiment, the back panel  20  may include at least one via for each row contact  245 ( 2 - p ). 
     It should be appreciated that a wide range of “circuit board” technologies may be used to fabricate interconnection structures such as those illustrated here for the back panel. One or more embodiments of the present invention described herein are not limited to the description provided herein, and may include other well-known approaches. For example, the via  530  may be filled or open. It may be desirable to avoid the vias in some embodiments, and, instead, make the interconnections between the two surfaces at the edges of the back panel  20 . 
     Referring now to FIG. 6, a cross-sectional view of the display panel  15  and the back panel  20  along the line  270 — 270  (see FIG. 2) is illustrated, in accordance with one embodiment of the present invention. For illustrative purposes, as is evident from the like reference numerals, the cross-sectional view of the display panel  15  of FIG. 4 is substantially the same as that of FIG.  4 . In the illustrated embodiment of FIG. 6, one or more of the drivers  30 ( 1 - p ) and integrated circuits  35 ( 1 - n ) are attached to the second surface  24  (see also FIG. 1) of the back panel  20  (see also FIG.  1 ). 
     In one embodiment, the back panel  20  includes a plurality of contacts  602 ( 1 - 6 ) that are adapted to be coupled to each of contacts  250 ( 1 - 6 ) of the display panel  15 . In one embodiment, the contacts  250 ( 1 - 6 ) and  602 ( 1 - 6 ) may be coupled to each other in one of a variety of ways, including by solder joints  640 . For clarity and ease of illustration, the connection between the display panel  15  and the back panel  20  is shown through only six contacts  250 ( 1 - 6 ) and  602 ( 1 - 6 ), although those skilled in the art will appreciate that other contacts  250 ( 7 - r ) (see FIG. 2) of the display panel  15  may be similarly coupled to one or more corresponding contacts of the back panel  20 . In one embodiment, once the desired contacts  250 ( 1 - r ) of the display panel  15  are coupled to the corresponding contacts (e.g.,  602 ( 1 - 6 )) of the back panel  20 , one of a variety of filling material  507 , such as insulating epoxy, may be applied at the juncture of the two panels  15  and  20 . 
     The one or more drivers  30 ( 1 - p ) for the display panel  15  may provide an electrical signal to any one of a plurality of rails  610 ( 1 - 6 ) of the back panel  20 , in one embodiment. Each rail  610 ( 1 - 6 ) may be coupled to a corresponding rail  630 ( 1 - 6 ) of the back panel  20  through a corresponding via  632 ( 1 - 6 ). For ease of illustration, not all of the portions of the interconnection between the rails  610 ( 1 - 6 ) and the one or more drivers  30 ( 1 - p ) may be shown, as such interconnections may be made by one skilled in the art. The electrical signal from each rail  630 ( 1 - 6 ) may be provided to each corresponding column  230 ( 1 - 6 ) through the respective contacts  602 ( 1 - 6 ) and  250 ( 1 - 6 ). In one embodiment, additional vias may be utilized for providing electrical signals to other contacts  250 ( 7 - r ) (see FIG.  2 ). In one embodiment, the back panel  20  may include at least one via for each contact  250 ( 7 - r ). In another embodiment, one via may provide electrical signals to other redundant contacts of the same column. 
     The cross-sectional views provided in FIGS. 3-6 are illustrative only and may not necessarily be drawn to scale. Those skilled in the art may appreciate that the desired size of selected elements shown in the cross-sectional views of FIGS. 3-6 may vary from one implementation to another. 
     Referring now to FIG. 7, a plane view of the display module  15  of the module  10  of FIG. 1 is illustrated, in accordance with one embodiment of the present invention. FIG. 7 shows one example of a redundant contact arrangement that may be employed to attach the display panel  15  to the back panel  20  of the module  10  of FIG. 1, although in other embodiments, any variety of arrangements may be employed, depending on, for example, the technology design rules that may be available to lay out the contacts, the design rules and number of layers available on the back panel  20  (see FIG.  1 ), and/or electrical performance details associated with the front panel  15  (see FIG.  1 ), details such as circuit resistances, capacitances, operating frequency, current requirement, and the like. 
     The display panel  15  in the illustrated embodiment includes a two-dimensional array of a plurality of pixels  210 ( 1 - m ), where each pixel  210 ( 1 - m ) is formed of three sub-pixels  215 ( 1 - 3 ). In the example arrangement of FIG. 7, the contacts  702  are repeated every seven pixels  210 ( 1 - m ). In one embodiment, electrical signal may be provided to the anode of selected sub-pixels  215 ( 1 - 3 )) by a contact  702  that may be coupled to a corresponding contact pad  704  on the back panel  20  (see FIG.  1 ). In one embodiment, at least one via  706  is provided for delivering an electrical signal to the anode of the selected sub-pixel  215 ( 1 - 3 ) in the manner shown in FIG.  7 . The redundant arrangement shown in FIG. 7 may provide one or more of the advantages described above. The degree of redundancy (shown here to be repeated every seven pixels) is not limited to this example, and could be greater or lesser, depending on one or more of the conditions described above. 
     In accordance with one or more embodiments of the present invention, an array contacting architecture may provide certain desired advantages over the conventional edge connection configurations. For example, in one embodiment, an array contact configuration may provide reduced line resistances and capacitances for improved performances. In another instance, array contact arrangements may be more conducive for constructing larger, more efficient display arrays. Additionally, an array contact configuration may reduce the need for a “window” frame around the periphery of the display that is otherwise common in edge connection configurations. 
     Integrating the drivers  30 ( 1 - p ) and/or integrated circuits in accordance with one or more embodiments of the present invention may reduce the footprint on the back panel  20  and may prove to be advantageous when the module  10  is utilized in portable devices, such as mobile phones, personal digital assistants, music players, laptops, and the like. In some cases, integrating the drivers  30 ( 1 - p ) and other integrated circuits  35 ( 1 - n ) on the back panel  20  of the module  10  may also reduce manufacturing costs. 
     Referring now to FIG. 8, an isometric view of a portable device  710  employing the module  10  of FIG. 1 is illustrated, in accordance with one embodiment of the present invention. Although not so limited, in the illustrated embodiment, the portable device  710  is a cellular telephone. A “portable device” in one embodiment may be any device that is battery-powered, for example, and may include music players, cameras, portable movie players, laptop computers, personal digital assistants, paging devices, and the like. The display panel  15  of the module  10  in the illustrated embodiment serves as the display for the portable device  710 . In one embodiment, the size of the display panel  15  of the module  10  may be increased to any desirable size, based on the available area. 
     In one embodiment, the desired integrated circuits  35 ( 1 - n ) for the portable device  710  may be coupled to the second surface  24  (see FIG. 1) of the back panel  20  of the module  10 . Additionally, in one embodiment, one or more drivers  30 ( 1 - p ) for driving the display panel  15  may be attached to the second surface  24  of the back panel  20  of the module  10 . As mentioned above, allowing integrated circuits  35 ( 1 - n ) and/or  30 ( 1 - p ) to be attached to the second surface  24  of the pack panel  20  may result in cost savings, as well as improved performance because of reduced line capacitance and resistance. 
     The portable device  710 , in one embodiment, includes a power supply interface  712  for interfacing with the module  10  through the connector  40 . The power supply interface  710  in one embodiment may include a battery. The portable device  710  may include an antenna  715  for transmitting and receiving signals using radio frequency. In one embodiment, the portable device  710  may include an input keypad  717  for allowing a user to input telephone numbers or to select one or more features supported by the portable device  710 . The portable device  710  may include a speaker  720  and a microphone  730  for respectively outputting and receiving audio signals to and from the user. In one embodiment, the portable device  710  may include a recharging port  740  for recharging the power supply source of the portable device  710 , such as a rechargeable battery. 
     The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.