PATENT DOCUMENT

Publication Number: US-8552989-B2
Application Number: US-76004907-A
Country: US
Kind Code: B2

Title: Integrated display and touch screen

Abstract:
Disclosed herein are liquid-crystal display (LCD) touch screens that integrate the touch sensing elements with the display circuitry. The integration may take a variety of forms. Touch sensing elements can be completely implemented within the LCD stackup but outside the not between the color filter plate and the array plate. Alternatively, some touch sensing elements can be between the color filter and array plates with other touch sensing elements not between the plates. In another alternative, all touch sensing elements can be between the color filter and array plates. The latter alternative can include both conventional and in-plane-switching (IPS) LCDs. In some forms, one or more display structures can also have a touch sensing function. Techniques for manufacturing and operating such displays, as well as various devices embodying such displays are also disclosed.

Claims:
What is claimed is: 
     
       1. An integrated display touch screen having a plurality of display pixels comprising:
 a first polarizer; 
 a second polarizer; 
 a first substrate having display control circuitry formed thereon, the first substrate being disposed between the first polarizer and the second polarizer and adjacent the first polarizer; 
 a second substrate disposed between the first polarizer and the second polarizer and adjacent the first substrate; 
 a color filter disposed directly or indirectly on the second substrate; 
 a first plurality of touch sensing elements disposed between the first and second substrate; and 
 a second plurality of touch sensing elements disposed between the first and second polarizers but not between the first and second substrates; 
 the first plurality of touch sensing elements comprising a plurality of touch drive electrodes disposed along a first direction and the second plurality of touch sensing elements comprising a plurality of touch sense electrodes disposed along a second direction transverse to the first direction such that capacitive coupling nodes are formed at the crossing of the plurality of touch drive and touch sense electrodes; 
 wherein: 
 a touch stimulation waveform is provided exclusively to the plurality of touch drive electrodes such that the plurality of touch drive electrodes are used exclusively for applying the touch stimulation waveform to the capacitive coupling nodes during a touch sensing mode of operation and, during the touch sensing mode of operation, the plurality of touch sense electrodes exclusively connect the capacitive coupling nodes to capacitive sensing circuitry such that the touch sense electrodes are used exclusively for touch sensing during the touch sensing mode of operation; and 
 the plurality of touch drive electrodes also serving as a display element for the integrated display touch screen during a display mode of operation, the display element operative to provide a voltage waveform different from the touch stimulation waveform during the display mode of operation. 
 
     
     
       2. The touch screen of  claim 1  wherein the plurality of touch drive electrodes are disposed directly or indirectly on the second substrate and the display element comprises a counter electrode such that the plurality of touch drive electrodes also serve as the counter electrode for the integrated display touch screen during the display mode of operation, and the voltage waveform provided by the counter electrode is a common voltage waveform that is different from the touch stimulation waveform. 
     
     
       3. The touch screen of  claim 2  wherein the plurality of touch drive electrodes comprise ITO patterned on top of the color filter. 
     
     
       4. The touch screen of  claim 2  wherein the plurality of touch sense electrodes are disposed directly or indirectly on the second substrate and not between the first and second substrates. 
     
     
       5. The touch screen of  claim 2  wherein the color filter is disposed on the second substrate and the plurality of touch drive electrodes comprise ITO patterned on the color filter. 
     
     
       6. The touch screen of  claim 5  wherein the plurality of touch sense electrodes comprised patterned ITO disposed on the second substrate between the second substrate and the second polarizer. 
     
     
       7. The touch screen of  claim 2 ,
 wherein the capacitive sensing circuitry is operatively coupled to the plurality of touch sense electrodes at least during the touch sensing mode of operation for measuring a change in current and/or voltage resulting from a change in capacitance at the capacitive coupling nodes, the change in capacitance resulting from a perturbation of an electric field at the capacitive coupling nodes as an object is brought in proximity to the touch screen. 
 
     
     
       8. The touch screen of  claim 7 ,
 wherein each of the plurality of touch drive electrodes overlaps plural rows of display pixels to form a single touch drive segment for each overlapped plural rows. 
 
     
     
       9. The touch screen of  claim 8 , wherein each display pixel includes a storage capacitor, and in the display mode of operation, the common voltage waveform is applied to each storage capacitor of the plural rows of display pixels overlapped by each of the touch drive segments. 
     
     
       10. The touch screen as recited in  claim 9 , wherein in the display mode of operation, the common voltage is also applied to the touch drive segments. 
     
     
       11. The touch screen of  claim 10 , wherein in the touch sensing mode of operation, the touch stimulation waveform is applied to the touch drive segments. 
     
     
       12. The touch screen of  claim 11 , wherein in the touch sensing mode of operation, the touch stimulation waveform is also applied to storage capacitors of the display pixels overlapped by a given touch drive segment which receives the touch stimulation signal. 
     
     
       13. The touch screen as recited in  claim 8 , the plurality of display pixels having a plurality of storage capacitors with counter-electrodes, wherein the plurality of touch drive electrodes also serve as the counter-electrodes for the plurality of storage capacitors during a display mode of operation. 
     
     
       14. The touch screen as recited in  claim 8 , wherein the capacitive sensing circuitry includes one or more charge amplifiers, each having an inverting input coupled to receive on output from the plurality of touch sense electrodes, a non-inverting input coupled to a reference potential and an output coupled to the inverting input. 
     
     
       15. The touch screen of  claim 1  wherein the plurality of touch sense electrodes are formed on the second substrate. 
     
     
       16. The touch screen of  claim 1  wherein the display pixels each comprise a storage capacitor having a counter electrode and the display element comprises the counter electrode of the storage capacitors such that the plurality of touch drive electrodes also serve as the counter electrode for the storage capacitors of the integrated display touch screen during a display mode of operation. 
     
     
       17. The touch screen of  claim 16 , wherein the plurality of sense electrodes are disposed on the first polarizer, and wherein a user faces the first substrate such that the first substrate is nearer the user than the second substrate. 
     
     
       18. The touch screen of  claim 17  wherein the plurality of sense electrodes are formed from ITO and the first polarizer is laminated to the first substrate. 
     
     
       19. An integrated display touch screen having a plurality of display pixels comprising:
 a first polarizer; 
 a second polarizer; 
 a first substrate having display control circuitry formed thereon, the first substrate being disposed between the first polarizer and the second polarizer and adjacent the first polarizer; 
 a second substrate disposed between the first polarizer and the second polarizer and adjacent the first substrate; 
 a color filter disposed directly or indirectly on the second substrate; 
 a first plurality of touch sensing elements disposed between the first and second substrate; and 
 a second plurality of touch sensing elements disposed between the first and second polarizers but not between the first and second substrates; 
 the first plurality of touch sensing elements comprising a plurality of touch drive electrodes disposed along a first direction and the second plurality of touch sensing elements comprising a plurality of touch sense electrodes disposed along a second direction transverse to the first direction such that capacitive coupling nodes are formed at the crossing of the plurality of touch drive and touch sense electrodes; 
 wherein: 
 a touch stimulation signal is provided exclusively to the plurality of touch drive electrodes such that the touch drive electrodes are used exclusively for applying the touch stimulation signal to the capacitive coupling nodes during a touch sensing mode of operation and, during the touch sensing mode of operation, the plurality of touch sense electrodes exclusively connect the capacitive coupling nodes to capacitive sensing circuitry such that the touch sense electrodes are used exclusively for touch sensing during the touch sensing mode of operation; and 
 the plurality of touch drive electrodes also serving as black matrix for the integrated display touch screen during a display mode of operation. 
 
     
     
       20. The touch screen of  claim 19  wherein the plurality of touch sense electrodes are disposed directly or indirectly on the second substrate between the second substrate and the second polarizer. 
     
     
       21. The touch screen of  claim 20  wherein the black matrix comprises one of a conductive black matrix or metal drive lines hidden behind a polymer black matrix. 
     
     
       22. The touch screen of  claim 21  wherein the black matrix is a conductive black matrix, and the conductive black matrix is partitioned into separate rectangularly shaped touch drive segments having drive lines with each drive segment comprising a rectangularly shaped two dimensional array of the drive lines interconnected to form plural rows of a mesh pattern and each drive segment is electrically isolated from other drive segments. 
     
     
       23. The touch screen of  claim 21  wherein the black matrix comprises metal drive lines hidden behind a polymer black matrix, and the metal drive lines are partitioned into separate rectangularly shaped touch drive segments with each drive segment comprising a rectangularly shaped two dimensional array of the drive lines interconnected to form plural rows of a mesh pattern and each drive segment is electrically isolated from other drive segments. 
     
     
       24. The touch screen of  claim 21  wherein touch screen comprises a common voltage layer disposed between the first and second substrates and serving as a counter electrode for the display pixels, the common voltage layer being segmented and being separate and distinct from the plurality of touch drive electrodes. 
     
     
       25. An integrated display touch screen having a plurality of display pixels comprising:
 a first polarizer; 
 a second polarizer; 
 a first substrate having display control circuitry formed thereon, the first substrate being disposed between the first polarizer and the second polarizer and adjacent the first polarizer; 
 a second substrate disposed between the first polarizer and the second polarizer and adjacent the first substrate; 
 a color filter disposed directly or indirectly on the second substrate; 
 a first plurality of touch sensing elements disposed between the first and second substrate; and 
 a second plurality of touch sensing elements disposed between the first and second polarizers but not between the first and second substrates; 
 the first plurality of touch sensing elements comprising a plurality of touch drive electrodes disposed along a first direction and the second plurality of touch sensing elements comprising a plurality of touch sense electrodes disposed along a second direction transverse to the first direction such that capacitive coupling nodes are formed at the crossing of the plurality of touch drive and touch sense electrodes; 
 wherein: 
 a touch stimulation signal is provided exclusively to the plurality of touch drive electrodes such that the touch drive electrodes are used exclusively for applying the touch stimulation signal to the capacitive coupling nodes during a touch sensing mode of operation and, during the touch sensing mode of operation, the plurality of touch sense electrodes exclusively connect the capacitive coupling nodes to capacitive sensing circuitry such that the touch sense electrodes are used exclusively for touch sensing during the touch sensing mode of operation; and 
 the plurality of touch drive electrodes also serving as a pixel electrode for each of the display pixels for the integrated display touch screen during a display mode of operation. 
 
     
     
       26. The touch screen of  claim 25  wherein the plurality of sense electrodes are disposed on the first polarizer, and wherein a user faces the first substrate such that the first substrate is nearer the user than the second substrate. 
     
     
       27. The touch screen of  claim 26  wherein the plurality of sense electrodes are formed from ITO and the first polarizer is laminated to the first substrate. 
     
     
       28. The touch screen of  claim 25 , wherein during the display mode of operation, individual rows of the display pixels are selected individually to update the display, and during the touch sensing mode of operation multiple rows of display pixels are selected simultaneously. 
     
     
       29. The touch screen of  claim 28 , wherein a plurality of switches are disposed on the first substrate to control the display pixels, and the plurality of switches are maintained in an off state during the touch sensing mode of operation. 
     
     
       30. The touch screen of  claim 29 , wherein the plurality of switches comprise TFT transistors connected to a data line, a gate line and connected to the pixel electrodes of the display pixels, and wherein a high voltage is applied to the data line during the touch sensing mode of operation to maintain the TFT transistors in an off state. 
     
     
       31. The touch screen as recited in  claim 30 , wherein, during the touch sensing mode of operation, multiple rows of display pixels are selected simultaneously by applying a stimulating voltage to the gate lines of the TFT transistors and wherein the stimulating voltage is at least partially transferred to the pixel electrodes of the display pixels. 
     
     
       32. An electronic device incorporating an integrated display touch screen having a plurality of display pixels, the touch screen comprising:
 a first polarizer; 
 a second polarizer; 
 a first substrate having display control circuitry formed thereon, the first substrate being disposed between the first polarizer and the second polarizer and adjacent the first polarizer; 
 a second substrate disposed between the first polarizer and the second polarizer and adjacent the first substrate; 
 a color filter disposed directly or indirectly on the second substrate; 
 a first plurality of touch sensing elements disposed between the first and second substrate; and 
 a second plurality of touch sensing elements disposed between the first and second polarizers but not between the first and second substrates; 
 the first plurality of touch sensing elements comprising a plurality of touch drive electrodes disposed along a first direction and the second plurality of touch sensing elements comprising a plurality of touch sense electrodes disposed along a second direction transverse to the first direction such that capacitive coupling nodes are formed at the crossing of the plurality of touch drive and touch sense electrodes; 
 wherein: 
 a touch stimulation waveform is provided exclusively to the plurality of touch drive electrodes such that the plurality of touch drive electrodes are used exclusively for applying the touch stimulation waveform to the capacitive coupling nodes during a touch sensing mode of operation and, during the touch sensing mode of operation, the plurality of touch sense electrodes exclusively connect the capacitive coupling nodes to capacitive sensing circuitry such that the touch sense electrodes are used exclusively for touch sensing during the touch sensing mode of operation; and 
 the plurality of touch drive electrodes also serving as a display element for the integrated display touch screen during a display mode of operation, the display element operative to provide a voltage waveform different from the touch stimulation waveform during the display mode of operation. 
 
     
     
       33. The electronic device of  claim 32  wherein the electronic device is selected from the group consisting of a desktop computer, a tablet computer, and a notebook computer. 
     
     
       34. The electronic device of  claim 32  wherein the electronic device comprises at least one of a handheld computer, a personal digital assistant, a media player, and a mobile telephone. 
     
     
       35. The electronic device of  claim 32 , wherein the plurality of touch drive electrodes are disposed directly or indirectly on the second substrate and the display element comprises a counter electrode such that the plurality of touch drive electrodes also serve as the counter electrode for the integrated display touch screen during a display mode of operation, and the voltage waveform provided by the counter electrode is a common voltage waveform that is different from the touch stimulation waveform. 
     
     
       36. The electronic device of  claim 35  wherein the electronic device is selected from the group consisting of a desktop computer, a tablet computer, and a notebook computer. 
     
     
       37. The electronic device of  claim 35  wherein the electronic device comprises at least one of a handheld computer, a personal digital assistant, a media player, and a mobile telephone. 
     
     
       38. The electronic device of  claim 35 , wherein the color filter is disposed on the second substrate and the plurality of touch drive electrodes comprise ITO patterned on the color filter. 
     
     
       39. The electronic device of  claim 38  wherein the electronic device is selected from the group consisting of a desktop computer, a tablet computer, and a notebook computer. 
     
     
       40. The electronic device of  claim 38  wherein the electronic device comprises at least one of a handheld computer, a personal digital assistant, a media player, and a mobile telephone. 
     
     
       41. The electronic device of  claim 32  wherein the plurality of touch drive electrodes comprises a plurality of metal touch drive electrodes disposed behind a black matrix. 
     
     
       42. The electronic device of  claim 41  wherein the electronic device is selected from the group consisting of a desktop computer, a tablet computer, and a notebook computer. 
     
     
       43. The electronic device of  claim 41  wherein the electronic device comprises at least one of a handheld computer, a personal digital assistant, a media player, and a mobile telephone. 
     
     
       44. The electronic device of  claim 32 , wherein the display pixels each comprise a storage capacitor having a counter electrode and the display element comprises the counter electrode of the storage capacitors such that the plurality of touch drive electrodes also serve as the counter electrode for the storage capacitors of the integrated display touch screen during a display mode of operation. 
     
     
       45. The electronic device of  claim 44  wherein the electronic device is selected from the group consisting of a desktop computer, a tablet computer, and a notebook computer. 
     
     
       46. The electronic device of  claim 44  wherein the electronic device comprises at least one of a handheld computer, a personal digital assistant, a media player, and a mobile telephone. 
     
     
       47. The electronic device as recited in  claim 32 ,
 wherein the capacitive sensing circuitry is operatively coupled to the plurality of touch sense electrodes at least during the touch sensing mode of operation for measuring a change in current and/or voltage resulting from a change in capacitance at the capacitive coupling nodes, the change in capacitance resulting from a perturbation of an electric field at the capacitive coupling nodes as an object is brought in proximity to the touch screen; and 
 wherein each of the plurality of touch drive electrodes overlaps plural rows of display pixels to form a single touch drive segment for each overlapped plural rows. 
 
     
     
       48. The electronic device as recited in  claim 47 , wherein the electronic device selected from the group consisting of a desktop computer, a tablet computer, a notebook computer, a handheld computer, a personal digital assistant and a media player. 
     
     
       49. The electronic device as recited in  claim 47 , wherein the capacitive sensing circuitry includes one or more charge amplifiers, each having an inverting input coupled to receive on output from the plurality of touch sense electrodes, a non-inverting input coupled to a reference potential and an output coupled to the inverting input. 
     
     
       50. An electronic device incorporating an integrated display touch screen having a plurality of display pixels comprising:
 a first polarizer; 
 a second polarizer; 
 a first substrate having display control circuitry formed thereon, the first substrate being disposed between the first polarizer and the second polarizer and adjacent the first polarizer; 
 a second substrate disposed between the first polarizer and the second polarizer and adjacent the first substrate; 
 a color filter disposed directly or indirectly on the second substrate; 
 a first plurality of touch sensing elements disposed between the first and second substrate; and 
 a second plurality of touch sensing elements disposed between the first and second polarizers but not between the first and second substrates; 
 the first plurality of touch sensing elements comprising a plurality of touch drive electrodes disposed along a first direction and the second plurality of touch sensing elements comprising a plurality of touch sense electrodes disposed along a second direction transverse to the first direction such that capacitive coupling nodes are formed at the crossing of the plurality of touch drive and touch sense electrodes; 
 wherein: 
 a touch stimulation signal is provided exclusively to the plurality of touch drive electrodes such that the touch drive electrodes are used exclusively for applying the touch stimulation signal to the capacitive coupling nodes during a touch sensing mode of operation and, during the touch sensing mode of operation, the plurality of touch sense electrodes exclusively connect the capacitive coupling nodes to capacitive sensing circuitry such that the touch sense electrodes are used exclusively for touch sensing during the touch sensing mode of operation; and 
 the plurality of touch drive electrodes also serving as black matrix for the integrated display touch screen during a display mode of operation. 
 
     
     
       51. The electronic device of  claim 50 , wherein the electronic device is selected from the group consisting of a handheld computer, a personal digital assistant, a media player, and a mobile telephone a desktop computer, a tablet computer, and a notebook computer. 
     
     
       52. The electronic device of  claim 50 , wherein the black matrix is one of a conductive black matrix or metal drive lines hidden behind a polymer black matrix, and the conductive black matrix is partitioned into separate rectangularly shaped touch drive segments having drive lines with each drive segment comprising a rectangularly shaped two dimensional array of the drive lines interconnected to form plural rows of a mesh pattern and each drive segment is electrically isolated from other drive segments. 
     
     
       53. The electronic device incorporating an integrated display touch screen having a plurality of display pixels comprising:
 a first polarizer; 
 a second polarizer; 
 a first substrate having display control circuitry formed thereon, the first substrate being disposed between the first polarizer and the second polarizer and adjacent the first polarizer; 
 a second substrate disposed between the first polarizer and the second polarizer and adjacent the first substrate; 
 a color filter disposed directly or indirectly on the second substrate; 
 a first plurality of touch sensing elements disposed between the first and second substrate; and 
 a second plurality of touch sensing elements disposed between the first and second polarizers but not between the first and second substrates; 
 the first plurality of touch sensing elements comprising a plurality of touch drive electrodes disposed along a first direction and the second plurality of touch sensing elements comprising a plurality of touch sense electrodes disposed along a second direction transverse to the first direction such that capacitive coupling nodes are formed at the crossing of the plurality of touch drive and touch sense electrodes; 
 wherein: 
 a touch stimulation signal is provided exclusively to the plurality of touch drive electrodes such that the touch drive electrodes are used exclusively for applying the touch stimulation signal to the capacitive coupling nodes during a touch sensing mode of operation and, during the touch sensing mode of operation, the plurality of touch sense electrodes exclusively connect the capacitive coupling nodes to capacitive sensing circuitry such that the touch sense electrodes are used exclusively for touch sensing during the touch sensing mode of operation; and 
 the plurality of touch drive electrodes also serving as a pixel electrode for each of the display pixels for the integrated display touch screen during a display mode of operation. 
 
     
     
       54. The electronic device of  claim 53  wherein the electronic device is selected from the group consisting of a desktop computer, a tablet computer, and a notebook computer. 
     
     
       55. The electronic device of  claim 53  wherein the electronic device comprises at least one of a handheld computer, a personal digital assistant, a media player, and a mobile telephone. 
     
     
       56. The electronic device of  claim 53 , wherein the plurality of sense electrodes are formed from ITO and the first polarizer is laminated to the first substrate. 
     
     
       57. The electronic device of  claim 56  wherein the electronic device is selected from the group consisting of a desktop computer, a tablet computer, and a notebook computer. 
     
     
       58. The electronic device of  claim 56  wherein the electronic device comprises at least one of a handheld computer, a personal digital assistant, a media player, and a mobile telephone. 
     
     
       59. A mobile telephone incorporating an integrated display touch screen having a plurality of rows of display pixels, the touch screen comprising:
 a first polarizer; 
 a second polarizer; 
 a first substrate having display control circuitry formed thereon, the first substrate being disposed between the first polarizer and the second polarizer and adjacent the first polarizer; 
 a second substrate disposed between the first polarizer and the second polarizer and adjacent the first substrate; 
 a color filter disposed directly or indirectly on the second substrate; 
 a first plurality of touch sensing elements disposed between the first and second substrate; and 
 a second plurality of touch sensing elements disposed between the first and second polarizers but not between the first and second substrates; 
 the first plurality of touch sensing elements comprising a plurality of touch drive electrodes disposed along a first direction and the second plurality of touch sensing elements comprising a plurality of touch sense electrodes disposed along a second direction transverse to the first direction such that capacitive coupling nodes are formed at the crossing of the plurality of touch drive and touch sense electrodes; 
 wherein: 
 a touch stimulation waveform is provided exclusively to the plurality of touch drive electrodes such that the plurality of touch drive electrodes are used exclusively for applying the touch stimulation waveform to the capacitive coupling nodes during a touch sensing mode of operation and, during the touch sensing mode of operation, the plurality of touch sense electrodes exclusively connect the capacitive coupling nodes to capacitive sensing circuitry such that the touch sense electrodes are used exclusively for touch sensing during the touch sensing mode of operation; and 
 the plurality of touch drive electrodes also serving as a display element for the integrated display touch screen during a display mode of operation, the display element operative to provide a voltage waveform different from the touch stimulation waveform during the display mode of operation. 
 
     
     
       60. The mobile telephone of  claim 59 , wherein the plurality of touch drive electrodes are disposed directly or indirectly on the second substrate and the display element comprises a counter electrode such that the plurality of touch drive electrodes also serve as the counter electrode for the integrated display touch screen during a display mode of operation, and the voltage waveform provided by the counter electrode is a common voltage waveform that is different from the touch stimulation waveform. 
     
     
       61. The mobile telephone of  claim 60 , wherein the color filter is disposed on the second substrate and the plurality of touch drive electrodes comprise ITO patterned on the color filter. 
     
     
       62. The mobile telephone of  claim 59 , wherein the black matrix is one of a conductive black matrix or metal drive lines hidden behind a polymer black matrix, and the conductive black matrix is partitioned into separate rectangularly shaped touch drive segments having drive lines with each drive segment comprising a rectangularly shaped two dimensional array of the drive lines interconnected to form plural rows of a mesh pattern and each drive segment is electrically isolated from other drive segments. 
     
     
       63. The mobile telephone of  claim 59 , wherein the display pixels each comprise a storage capacitor having a counter electrode and the display element comprises the counter electrode of the storage capacitors such that the plurality of touch drive electrodes also serve as the counter electrode for the storage capacitors of the integrated display touch screen during a display mode of operation. 
     
     
       64. The mobile telephone as recited in  claim 59 ,
 wherein the capacitive sensing circuitry is operatively coupled to the plurality of touch sense electrodes at least during the touch sensing mode of operation for measuring a change in current and/or voltage resulting from a change in capacitance at the capacitive coupling nodes, the change in capacitance resulting from a perturbation of an electric field at the capacitive coupling nodes as an object is brought in proximity to the touch screen; and 
 wherein each of the plurality of touch drive electrodes overlaps plural rows of display pixels to form a single touch drive segment for each overlapped plural rows. 
 
     
     
       65. The mobile telephone as recited in  claim 64 , wherein the capacitive sensing circuitry includes one or more charge amplifiers, each having an inverting input coupled to receive on output from the plurality of touch sense electrodes, a non-inverting input coupled to a reference potential and an output coupled to the inverting input. 
     
     
       66. The mobile telephone incorporating an integrated display touch screen having a plurality of display pixels comprising:
 a first polarizer; 
 a second polarizer; 
 a first substrate having display control circuitry formed thereon, the first substrate being disposed between the first polarizer and the second polarizer and adjacent the first polarizer; 
 a second substrate disposed between the first polarizer and the second polarizer and adjacent the first substrate; 
 a color filter disposed directly or indirectly on the second substrate; 
 a first plurality of touch sensing elements disposed between the first and second substrate; and 
 a second plurality of touch sensing elements disposed between the first and second polarizers but not between the first and second substrates; 
 the first plurality of touch sensing elements comprising a plurality of touch drive electrodes disposed along a first direction and the second plurality of touch sensing elements comprising a plurality of touch sense electrodes disposed along a second direction transverse to the first direction such that capacitive coupling nodes are formed at the crossing of the plurality of touch drive and touch sense electrodes; 
 wherein: 
 a touch stimulation signal is provided exclusively to the plurality of touch drive electrodes such that the touch drive electrodes are used exclusively for applying the touch stimulation signal to the capacitive coupling nodes during a touch sensing mode of operation and, during the touch sensing mode of operation, the plurality of touch sense electrodes exclusively connect the capacitive coupling nodes to capacitive sensing circuitry such that the touch sense electrodes are used exclusively for touch sensing during the touch sensing mode of operation; and 
 the plurality of touch drive electrodes also serving as black matrix for the integrated display touch screen during a display mode of operation. 
 
     
     
       67. The mobile telephone incorporating an integrated display touch screen having a plurality of display pixels comprising:
 a first polarizer; 
 a second polarizer; 
 a first substrate having display control circuitry formed thereon, the first substrate being disposed between the first polarizer and the second polarizer and adjacent the first polarizer; 
 a second substrate disposed between the first polarizer and the second polarizer and adjacent the first substrate; 
 a color filter disposed directly or indirectly on the second substrate; 
 a first plurality of touch sensing elements disposed between the first and second substrate; and 
 a second plurality of touch sensing elements disposed between the first and second polarizers but not between the first and second substrates; 
 the first plurality of touch sensing elements comprising a plurality of touch drive electrodes disposed along a first direction and the second plurality of touch sensing elements comprising a plurality of touch sense electrodes disposed along a second direction transverse to the first direction such that capacitive coupling nodes are formed at the crossing of the plurality of touch drive and touch sense electrodes; 
 wherein: 
 a touch stimulation signal is provided exclusively to the plurality of touch drive electrodes such that the touch drive electrodes are used exclusively for applying the touch stimulation signal to the capacitive coupling nodes during a touch sensing mode of operation and, during the touch sensing mode of operation, the plurality of touch sense electrodes exclusively connect the capacitive coupling nodes to capacitive sensing circuitry such that the touch sense electrodes are used exclusively for touch sensing during the touch sensing mode of operation; and 
 the plurality of touch drive electrodes also serving as a pixel electrode for each of the display pixels for the integrated display touch screen during a display mode of operation. 
 
     
     
       68. The mobile telephone of  claim 67 , wherein the plurality of sense electrodes are formed from ITO and the first polarizer is laminated to the first substrate. 
     
     
       69. An integrated display touch screen having a plurality of display pixels comprising:
 a first polarizer; 
 a second polarizer; 
 a first substrate having display control circuitry formed thereon, the first substrate being disposed between the first polarizer and the second polarizer and adjacent the first polarizer; 
 a second substrate disposed between the first polarizer and the second polarizer and adjacent the first substrate; 
 a liquid crystal layer disposed between the first and second substrates; 
 a color filter disposed directly or indirectly on the second substrate; 
 a first plurality of touch sensing elements disposed between the first and second substrate, the first plurality of touch sensing elements disposed between the liquid crystal layer and the second substrate; and 
 a second plurality of touch sensing elements disposed between the first and second polarizers but not between the first and second substrates; 
 a counter electrode disposed between the liquid crystal layer and the second substrate, the counter electrode serving as a common voltage electrode during the display mode of operation; 
 one of the first or second plurality of touch sensing elements comprising a plurality of touch drive electrodes disposed along a first direction and the other of the first or second plurality of touch sensing elements comprising a plurality of touch sense electrodes disposed along a second direction transverse to the first direction such that capacitive coupling nodes are formed at the crossing of the plurality of touch drive and touch sense electrodes; 
 wherein: 
 a touch stimulation signal is provided exclusively to the plurality of touch drive electrodes such that the touch drive electrodes are used exclusively for applying the touch stimulation signal to the capacitive coupling nodes during a touch sensing mode of operation and, during the touch sensing mode of operation, the plurality of touch sense electrodes exclusively connect the capacitive coupling nodes to capacitive sensing circuitry such that the touch sense electrodes are used exclusively for touch sensing during the touch sensing mode of operation. 
 
     
     
       70. The touch screen as recited in  claim 69 , wherein the first plurality of touch sensing elements comprise the plurality of touch drive electrodes and the second plurality of touch sensing elements comprise the plurality of touch sense electrodes. 
     
     
       71. The touch screen as recited in  claim 69  wherein:
 the first plurality of touch sensing elements is disposed directly or indirectly on the second substrate; 
 the counter electrode is disposed directly or indirectly on the second substrate; 
 a dielectric layer disposed between the counter electrode and the first plurality of touch sensing elements; and 
 the first plurality of touch sensing elements is disposed more closely adjacent the second substrate than the counter electrode.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Provisional U.S. Patent Application Ser. No. 60/804,361, filed Jun. 9, 2006, and Provisional U.S. Patent Application Ser. No. 60/883,979, filed Jan. 8, 2007 which are both hereby incorporated by reference in their entirety. 
     This application is related to the following publications, incorporated by reference herein:
     U.S. Patent Publication No. 2006/0197753, titled “Multi-Functional Hand-Held Device,” published Sep. 7, 2006.   U.S. Patent Publication No. 2006/0097991; titled “Multipoint Touch Screen,” published May 11, 2006, and issued as U.S. Pat. No. 7,663,607, issued on Feb. 16, 2010.   U.S. Patent Publication No. 2007/0257890, titled “Multipoint Touch Screen Controller,” published on Nov. 8, 2007.   U.S. Patent Publication No. 2008/0158181, entitled “Double-Sided Touch Sensitive Panel and Flex Circuit Bonding,” published Jul. 3, 2008, and issued as U.S. Pat. No. 8,026,903, issued on Sep. 27, 2011.   U.S. Patent Publication No. 2008/0062147, entitled “Touch Screen Liquid Crystal Display, published Mar. 13, 2008.   U.S. Patent Publication No. 2008/0062148, entitled “Touch Screen Liquid Crystal Display, published Mar. 13, 2008, issued as U.S. Pat. No. 8,243,027, issued on Aug. 14, 2012.   U.S. Patent Publication No. 2008/0062140, entitled “Touch Screen Liquid Crystal Display, published Mar. 13, 2008.   

    
    
     BACKGROUND 
     There exist today many types of hand-held electronic devices, each of which utilizes some sort of user interface. The user interface can include an output device in the form of a display, such as a Liquid Crystal Display (LCD), and one or more input devices, which can be mechanically actuated (e.g., switches, buttons, keys, dials, joysticks, joy pads) or electrically activated (e.g., touch pads or touch screens). The display can be configured to present visual information such as text, multi-media data, and graphics, and the input devices can be configured to perform operations such as issuing commands, making selections, or moving a cursor or selector in the electronic device. 
     Recently work has been progressing on integrating various devices into a single hand-held device. This has further led to attempts to integrate many user interface models and devices into a single unit. A touch screen can be used in such systems for both practical and aesthetic reasons. Additionally, multi-touch capable touch screens can provide a variety of advantages for such a device. 
     Heretofore, it has been assumed that touch screens, whether single touch or multi-touch, could be produced by fabricating a traditional LCD screen, and disposing a substantially transparent touch sensing device in front of this screen. However, this presents a number of disadvantages, including substantial manufacturing costs. 
     SUMMARY 
     According to one embodiment of the invention, an integrated liquid crystal display touch screen is provided. The touch screen can include a plurality of layers including a first polarizer, a first substrate having display control circuitry formed thereon (e.g., a TFT plate or array plate), a second substrate (e.g., a color filter plate) adjacent the first substrate, and a second polarizer. The touch screen can further include one or more touch sensing elements, wherein at least one of the touch sensing elements can be located between the substrates. Additional touch sensing elements may also be between the polarizers but not between the substrates. 
     The touch sensing elements between the substrates can include a plurality of touch drive electrodes, which can, for example, be formed on the second substrate. These electrodes can be indium-tin oxide (ITO) patterned on top of a color filter. Alternatively, a color filter can be formed on top of the touch drive electrodes. These electrodes can also be configured so serve as V COM  for the display. A plurality of touch sense electrodes can also be provided that are not between the substrates, for example, either on the second substrate or on the second polarizer. The touch sensing elements between the substrates can also include a conductive black matrix segmented into a plurality of touch drive electrodes or a plurality of metal touch drive electrodes disposed behind a black matrix, which can be a polymer black matrix. The touch sensing elements between the substrates can also include a plurality of drive electrodes deposited on the first substrate, which can, in some embodiments, also be used for display pixel drivers or electrodes for display pixel storage capacitors. 
     In another embodiment, an electronic device incorporating an integrated LCD touch screen is provided. The electronic device can take the form of a desktop computer, a tablet computer, and a notebook computer. The electronic device can also take the form of a handheld computer, a personal digital assistant, a media player, and a mobile telephone. In some embodiments, a device may include one or more of the foregoing, e.g., a mobile telephone and media player. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  illustrates a multipoint sensing arrangement. 
         FIG. 2  illustrates a number of contact patches on a multipoint sensing system. 
         FIG. 3  illustrates a simplified schematic diagram of a mutual capacitance circuit. 
         FIG. 4  illustrates a process for operating a multipoint sensing arrangement. 
         FIG. 5  illustrates a representative layout for an LTPS transflective subpixel. 
         FIG. 6  illustrates a simplified model of an LTPS as viewed from the top and side. 
         FIG. 7  illustrates a circuit diagram for a subpixel and shows on which glass substrate the components are fabricated. 
         FIG. 8  illustrates a basic process flow for manufacturing LCDs. 
         FIG. 9  illustrates a finished small size LCD module. 
         FIG. 10  illustrates a block diagram of a touch screen LCD with separate touch driver and LCD driver chips. 
         FIG. 11  illustrates a block diagram of a touch screen LCD with an integrated LCD and touch driver chip. 
         FIG. 12  illustrates a basic stackup of a touch screen LCD. 
         FIG. 13  illustrates an alternative embodiment of a touch screen LCD. 
         FIG. 14  illustrates an electrode pattern. 
         FIG. 15  illustrates a stackup diagram embodiment of a touch-screen LCD. 
         FIG. 16  illustrates a touch pixel circuit for the touch-screen LCD illustrated in  FIG. 15 . 
         FIG. 17  illustrates a touch-sensing layer protected by a plastic cover. 
         FIG. 18  illustrates an output column and a linked set of output gates for a region of a touch-screen. 
         FIG. 19  illustrates a layout of a touch pixel for a touch-screen LCD. 
         FIG. 20  illustrates a stackup diagram for one embodiment of a touch screen LCD. 
         FIG. 21  illustrates a touch sensor array. 
         FIG. 22  illustrates a physical implementation for Concepts A and B, with top and side views of cabling and subsystem placement. 
         FIG. 23  illustrates a high-level block diagram showing one possible architecture of bottom glass components. 
         FIG. 24  illustrates elongated conductive dots. 
         FIG. 25  illustrates a high-level block diagram for a Touch/LCD Driver integrated circuit. 
         FIG. 26  illustrates a flexible printed circuit for use with various LCD embodiments described herein 
         FIG. 27  illustrates a process for simultaneous display updating and touch scanning. 
         FIG. 28  illustrates a Open Circuit V CST  touch drive option. 
         FIG. 29  illustrates a Drive-V CST  touch drive option. 
         FIG. 30  illustrates an electrical model for the situation where touch drive is used for both touch sensing and LCD V COM  modulation. 
         FIG. 31  illustrates connecting V STM  to Cst lines on both sides through conductive dots. 
         FIG. 32  illustrates a manufacturing process flow for a touch screen LCD. 
         FIG. 33  illustrates using one-line inversion of V COM  as a touch stimulus signal. 
         FIG. 34  illustrates a stackup diagram for an alternative embodiment of a touch screen LCD. 
         FIG. 35  illustrates a manufacturing process flow for a touch screen LCD. 
         FIG. 36  illustrates an embodiment substituting a conductive black matrix for a touch drive layer. 
         FIG. 37  illustrates a circuit diagram for an embodiment of a touch screen LCD. 
         FIG. 38  illustrates a stackup diagram for a touch screen LCD. 
         FIG. 39  illustrates a row-by-row update of display pixels for a touch screen LCD. 
         FIG. 40  illustrates a touch sensing process for a set of touch-sensitive display rows in a touch screen LCD. 
         FIG. 41  illustrates a process of detecting touches for three pixels located in different regions of a touch screen LCD. 
         FIG. 42  illustrates a circuit diagram of another embodiment of a touch screen LCD. 
         FIG. 43  illustrates a stack up diagram of the embodiment illustrated in  FIG. 42 . 
         FIG. 44  illustrates an embodiment substituting a conductive black matrix for a touch sense layer. 
         FIG. 45  illustrates a stackup diagram of another embodiment of a touch screen LCD. 
         FIG. 46  illustrates a top view of the embodiment illustrated in  FIG. 55 . 
         FIG. 47  illustrates another embodiment of a touch screen LCD. 
         FIG. 48  illustrates an equivalent circuit of the embodiment of  FIG. 47 . 
         FIG. 49  illustrates the waveforms that can be used for touch sensing in the embodiment of  FIGS. 47-48 . 
         FIG. 50  illustrates further aspects of touch screen integration for the embodiment of  FIG. 47 . 
         FIG. 51  illustrates another embodiment of a touch screen LCD. 
         FIG. 52  illustrates the waveforms that can be used for touch sensing in the embodiment of  FIGS. 51 and 53 . 
         FIG. 53  illustrates an equivalent circuit of the embodiment of  FIG. 51 . 
         FIG. 54  illustrates further aspects of touch screen integration for the embodiment of  FIG. 51 . 
         FIG. 55  illustrates a stackup diagram for a touch-screen LCD. 
         FIG. 56  illustrates a process of updating a touch-screen LCD. 
         FIG. 57  illustrates a stackup diagram for an embodiment of a touch-screen LCD. 
         FIG. 58  illustrates a stackup diagram for an embodiment of a touch-screen LCD. 
         FIG. 59  illustrates an exemplary LCD display divided into three regions that can be updated or touch-scanned independently. 
         FIG. 60  illustrates update and touch-scanning of a touch-screen LCD with three regions. 
         FIG. 61  illustrates an electrode layout for a touch-screen LCD. 
         FIG. 62  illustrates circuit components for a touch-screen LCD. 
         FIG. 63  illustrates a snapshot of an update arrangement for a touch-screen LCD. 
         FIG. 64  illustrates how metal lines and gaps in ITO that can be fully or partially hidden behind a black matrix. 
         FIG. 65  illustrates a stackup diagram for a touch-screen LCD. 
         FIG. 66  illustrates a touch-screen LCD segmented into three regions. 
         FIG. 67  illustrates a process of performing display updates and touch-scanning in a touch-screen LCD. 
         FIG. 68  illustrates wiring and ITO layout to segment a touch screen LCD into three regions. 
         FIG. 69  illustrates a top view and cross-section of a region of a touch-screen LCD that includes guard traces. 
         FIG. 70  illustrates a top view and cross-section of a region of a touch-screen LCD that does not include guard traces. 
         FIG. 71  illustrates a region of an exemplary display that contains six touch pixels and their signal wiring. 
         FIG. 72  illustrates a stackup diagram for another embodiment of a touch-screen LCD. 
         FIG. 73  illustrates a stackup diagram for another embodiment of a touch-screen LCD. 
         FIG. 74  illustrates a circuit diagram highlighting V COM  signal coupling for a touch screen LCD. 
         FIG. 75  illustrates an exemplary display. 
         FIG. 76  illustrates a possible scan pattern for a touch-screen LCD. 
         FIG. 77  illustrates a circuit diagram for the embodiment of  FIG. 79 . 
         FIG. 78  illustrates segment ITO layers. 
         FIG. 79  illustrates a stackup diagram for another embodiment of a touch-screen LCD. 
         FIG. 80  illustrates a combined wiring and stackup diagram for the embodiment of  FIG. 79 . 
         FIG. 81  illustrates a physical realization of the embodiment of  FIG. 79 . 
         FIG. 82  illustrates in-plane switching LCD cells. 
         FIG. 83  illustrates an organization of electrodes for in-plane switching LCD cells. 
         FIG. 84  illustrates a circuit diagram for an embodiment of an IPS-based touch-screen LCD. 
         FIG. 85  illustrates a stackup diagram corresponding to  FIG. 84 . 
         FIG. 86  illustrates a stackup diagram for another embodiment of an IPS-based touch-screen LCD. 
         FIG. 87  illustrates a physical model for Concept F, an embodiment of an IPS-based touch-screen LCD. 
         FIG. 88  illustrates a stackup diagram corresponding to the embodiment of  FIG. 87 . 
         FIG. 89  illustrates a side view of an all glass touch screen LCD. 
         FIG. 90  illustrates a side view of a touch screen LCD including a plastic layer. 
         FIG. 91  illustrates a touch screen having multiple plastic layers. 
         FIG. 92  illustrates a touch screen having a PET layer patterned on two sides with a connection through the PET layer. 
         FIG. 93  illustrates a combination PET/glass touch screen. 
         FIG. 94  illustrates a touch screen LCD device assembly. 
         FIG. 95  illustrates a touch screen LCD having a touch layer patterned on the inside of a transparent plastic housing. 
         FIG. 96  illustrates a patterned PET substrate that may be used with a touch screen LCD. 
         FIG. 97  illustrates flexible printed circuits bonded to the PET substrate of  FIG. 96 . 
         FIG. 98  illustrates a cover affixed to the assembly of  FIG. 97 . 
         FIG. 99  illustrates a simplified diagram of a level shifter/decoder chip on glass. 
         FIG. 100  illustrates a modified Touch/LCD Driver and peripheral transistor circuit. 
         FIG. 101  illustrates a simplified block diagram of a fully-integrated Touch/LCD Driver. 
         FIG. 102  illustrates an application of a touch screen LCD. 
         FIG. 103  illustrates a block diagram of a computer system incorporating a touch screen. 
         FIG. 104  illustrates a variety of electronic device and computer system form factors that may be used with a touch-screen LCD according to the present invention. 
         FIG. 105  illustrates a plurality of IPS LCD sub-pixels connected to form a plurality of touch sense columns. 
         FIG. 106  illustrates a plurality of IPS LCD sub-pixels connected to form a plurality of touch sense rows. 
         FIG. 107  illustrates an IPS LCD with integrated touch sensing. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the claims. 
     1. LCD and Touch Sensing Background 
     Disclosed herein are techniques to integrate touch sensing technology into liquid crystal displays. 
     As known to those skilled in the art, an LCD includes a plurality of layers, most basically, a top glass, a liquid crystal, and a bottom glass. The top and bottom glass can be patterned to provide the boundaries of the cells that contain the liquid crystal for a particular display pixel. The top and bottom glass can also be patterned with various layers of conducting materials and thin film transistors that allow the voltage across the liquid crystal cells to be varied to manipulate the orientation of the liquid crystal, thereby controlling the color and brightness of the pixel. 
     As described in the applications incorporated by reference, a touch surface, and specifically, a multi-touch capable transparent touch surface can be formed from a series of layers. The series of layers can include at least one substrate, e.g., glass, which can have disposed thereon a plurality of touch sensitive electrodes. For example, a mutual capacitance arrangement can include a plurality of drive electrodes and a plurality of sense electrodes separated by a non-conducting layer, i.e., the glass. Capacitive coupling between the drive and sense electrodes can be affected by proximity of a conductive object (e.g., a user&#39;s finger). This change in capacitive coupling can be used to determine the location, shape, size, motion, identity, etc. of a particular touch. These parameters can then be interpreted to control operation of a computer or other electronic device. Self-capacitance arrangements, as described below, are also known to those skilled in the art. 
     By integrating the layered structure of an LCD and a touch sensor, a variety of benefits can be achieved. This integration can include combining or interleaving the layered structures described above. Integration can further include eliminating redundant structures and/or finding dual purposes (e.g., one purpose for the touch function and another for the display function) for particular layers or structures. This can permit some layers to be eliminated, which can reduce cost and thickness of the touch screen LCD, as well as simplify manufacturing. A variety of different arrangements are possible, some of which are discussed in greater detail herein. 
     Specifically, various embodiments of an integrated touch screen LCD are discussed below. However, those skilled in the art will appreciate that the detailed description given herein with respect to these figures is exemplary and not exhaustive and that many variations on these embodiments are possible. Additionally, although many of the disclosed embodiments relate to multi-touch capable arrangements, many of the teachings can be applied to single-touch displays as well. 
     1.1. Multi-Touch Sensing 
     Recognizing multiple simultaneous or near-simultaneous touch events may be accomplished with a multi-touch sensing arrangement as illustrated in  FIG. 1 . Multi-touch sensing arrangement  100  can detect and monitor multiple touch attributes (including, for example, identification, position, velocity, size, shape, and magnitude) across touch sensitive surface  101 , at the same time, nearly the same time, at different times, or over a period of time. Touch-sensitive surface  101  can provide a plurality of sensor points, coordinates, or nodes  102  that function substantially independently of one another and that represent different points on a touch sensitive surface. Sensing points  102  may be positioned in a grid or a pixel array, with each sensing point capable of generating a signal at the same time. Sensing points  102  may be considered as mapping touch sensitive surface  101  into a coordinate system, for example, a Cartesian or polar coordinate system. 
     A touch-sensitive surface may, for example, be in the form of a tablet or a touch screen. To produce a touch screen, the capacitance sensing points and other associated electrical structures can be formed with a substantially transparent conductive medium, such as indium tin oxide (ITO). The number and configuration of sensing points  102  may be varied. The number of sensing points  102  generally depends on the desired resolution and sensitivity. In touch-screen applications, the number of sensing points  102  may also depend on the desired transparency of the touch screen. 
     Using a multi-touch sensing arrangement, like that described in greater detail below, signals generated at nodes  102  of multi-touch sensor  101  may be used to produce an image of the touches at a particular point in time. For example, each object (e.g., finger, stylus, etc.) in contact with or in proximity to touch-sensitive surface  101  can produce contact patch area  201 , as illustrated in  FIG. 2 . Each contact patch area  201  may cover several nodes  102 . Covered nodes  202  may detect the object, while remaining nodes  102  do not. As a result, a pixilated image of the touch surface plane (which may be referred to as a touch image, a multi-touch image, or a proximity image) can be formed. The signals for each contact patch area  201  may be grouped together. Each contact patch area  201  may include high and low points based on the amount of touch at each point. The shape of contact patch area  201 , as well as the high and low points within the image, may be used to differentiate contact patch areas  201  that are in close proximity to one another. Furthermore, the current image can be compared to previous images to determine how the objects may be moving over time, and what corresponding action should be performed in a host device as a result thereof. 
     Many different sensing technologies can be used in conjunction with these sensing arrangements, including resistive, capacitive, optical, etc. In capacitance-based sensing arrangements, as an object approaches touch-sensitive surface  101 , a small capacitance forms between the object and sensing points  102  in proximity to the object. By detecting changes in capacitance at each of the sensing points  102  caused by this small capacitance, and by noting the position of the sensing points, a sensing circuit  103  can detect and monitor multiple touches. The capacitive sensing nodes may be based on self-capacitance or mutual-capacitance. 
     In self-capacitance systems, the “self” capacitance of a sensing point is measured relative to some reference, e.g., ground. Sensing points  102  may be spatially separated electrodes. These electrodes can be coupled to driving circuitry  104  and sensing circuitry  103  by conductive traces  105   a  (drive lines) and  105   b  (sense lines). In some self-capacitance embodiments, a single conductive trace to each electrode may be used as both a drive and sense line. 
     In mutual capacitance systems, the “mutual” capacitance between a first electrode and a second electrode can be measured. In mutual capacitance sensing arrangements, the sensing points may be formed by the crossings of patterned conductors forming spatially separated lines. For example, driving lines  105   a  may be formed on a first layer and sensing lines  105   b  may be formed on a second layer  105   b  such that the drive and sense lines cross or “intersect” one another at sensing points  102 . The different layers may be different substrates, different sides of the same substrate, or the same side of a substrate with some dielectric separation. Because of separation between the drive and sense lines, there can be a capacitive coupling node at each “intersection.” 
     The arrangement of drive and sense lines can vary. For example, in a Cartesian coordinate system (as illustrated), the drive lines may be formed as horizontal rows, while the sense lines may be formed as vertical columns (or vice versa), thus forming a plurality of nodes that may be considered as having distinct x and y coordinates. Alternatively, in a polar coordinate system, the sense lines may be a plurality of concentric circles with the drive lines being radially extending lines (or vice versa), thus forming a plurality of nodes that may be considered as having distinct radius and angle coordinates. In either case, drive lines  105   a  may be connected to drive circuit  104 , and sensing lines  105   b  may be connected to sensing circuit  103 . 
     During operation, a drive signal (e.g., a periodic voltage) can be applied to each drive line  105   a . When driven, the charge impressed on drive line  105   a  can capacitively couple to the intersecting sense lines  105   b  through nodes  102 . This can cause a detectable, measurable current and/or voltage in sense lines  105   b . The relationship between the drive signal and the signal appearing on sense lines  105   b  can be a function of the capacitance coupling the drive and sense lines, which, as noted above, may be affected by an object in proximity to node  102 . Capacitance sensing circuit (or circuits)  103  may sense sensing lines  105   b  and may determine the capacitance at each node as described in greater detail below. 
     As discussed above, drive lines  105   a  can be driven one at a time, while the other drive lines are grounded. This process can be repeated for each drive line  105   a  until all the drive lines have been driven, and a touch image (based on capacitance) can be built from the sensed results. Once all the lines  105   a  have been driven, the sequence can repeat to build a series of touch images. However, in some embodiments of the present invention, multiple drive lines may be driven substantially simultaneously or nearly simultaneously, as described in U.S. patent application Ser. No. 11/619,466, titled “Simultaneous Sensing Arrangement,” filed Jan. 3, 2007. 
       FIG. 3  illustrates a simplified schematic diagram of mutual capacitance circuit  300  corresponding to the arrangement described above. Mutual capacitance circuit  300  may include drive line  105   a  and sense line  105   b , which can be spatially separated thereby forming capacitive coupling node  102 . Drive line  105   a  may be electrically (i.e., conductively) coupled to drive circuit  104  represented by voltage source  301 . Sense line  105   b  may be electrically coupled to capacitive sensing circuit  103 . Both drive line  105   a  and sense line  105   b  may, in some cases, include some parasitic capacitance  302 . 
     As noted above, in the absence of a conductive object proximate the intersection of drive line  105   a  and sense line  105   b , the capacitive coupling at node  102  can stay fairly constant. However, if an electrically conductive object (e.g., a user&#39;s finger, stylus, etc.) comes in proximity to node  102 , the capacitive coupling (i.e., the capacitance of the local system) changes. The change in capacitive coupling changes the current (and/or voltage) carried by sense line  105   b . Capacitance sensing circuit  103  may note the capacitance change and the position of node  102  and report this information in some form to processor  106  ( FIG. 1 ). 
     With reference to  FIG. 1 , sensing circuit  103  may acquire data from touch surface  101  and supply the acquired data to processor  106 . In some embodiments, sensing circuit  103  may be configured to send raw data (e.g., an array of capacitance values corresponding to each sense point  102 ) to processor  106 . In other embodiments, sensing circuit  103  may be configured to process the raw data itself and deliver processed touch data to processor  106 . In either case, the processor may then use the data it receives to control operation of computer system  107  and/or one or more applications running thereon. Various implementations along these lines are described in the applications referenced above, and include a variety of computer systems having touch pads and touch screens. 
     In some embodiments, sensing circuit  103  may include one or more microcontrollers, each of which may monitor one or more sensing points  102 . The microcontrollers may be application specific integrated circuits (ASICs) that work with firmware to monitor the signals from touch sensitive surface  101 , process the monitored signals, and report this information to processor  106 . The microcontrollers may also be digital signal processors (DSPs). In some embodiments, sensing circuit  103  may include one or more sensor ICs that measure the capacitance in each sensing line  105   b  and report measured values to processor  106  or to a host controller (not shown) in computer system  107 . Any number of sensor ICs may be used. For example, a sensor IC may be used for all lines, or multiple sensor ICs may be used for a single line or group of lines. 
       FIG. 4  illustrates at a high level process  400  for operating a multi-touch sensing arrangement, like that described above. The process may begin at block  401  where plurality of sensing points  102  can be driven. Following block  401 , the process flow can proceed to block  402 , where the outputs from sensing points  102  can be read. For example, a capacitance value for each sensing point  102  can be obtained. Following block  402 , the process can proceed to block  403  where an image or other form of data (signal or signals) of the touch at one moment in time can be produced and thereafter analyzed to determine where objects touching or in proximity to the touch sensor may be located. Following block  403 , the process can proceed to block  404 , where the current image or signal may be compared to one or more past images or signals to determine a change in one or more of the shape, size, location, direction, speed, acceleration, pressure, etc. for each object. This information can be subsequently used (in step  405 ) to perform an action in computer system  107 , ranging from moving a pointer or cursor to complex gesture-based interactions. 
     1.2. Transflective LCDs 
     To better understand integration of touch-sensing technology with transflective LCDs, a brief introduction to transflective LCDs may be helpful. The following is an overview of a typical subpixel cell found in low temperature poly silicon (LTPS) transflective LCDs. 
     1.2.1. Circuit Basics 
       FIG. 5  shows a representative layout for an LTPS transflective subpixel  500 . Display information can be transferred to the subpixel&#39;s capacitors C ST  and C LC  (not shown) when a voltage representing the desired grey level is applied to the data bus  501  and the select line  502  is asserted. The select line  502  assertion level can be near the gate drive positive supply voltage. During the time when select line  502  is asserted, the voltage on V CST  (and V COM , which is not shown) can be constant. All the circuit elements shown in  FIG. 5 , which includes metal, poly, active, oxide, and ITO, can be fabricated on the LCD&#39;s bottom glass. 
       FIG. 6  shows a simplified model of a low temperature poly-silicon (LTPS) LCD  600 , including a top view  601  and a side view  602 . Top view  601  shows a see-through view of the V CST  routing  603  on the bottom glass  608  in both the display area  604  and the non-display area  605 . Side view  602  shows a cross section of the display. 
     Each display row can include horizontal traces for V CST    606  and select (not shown). The select traces connect to gate drive circuitry made up of poly-silicon thin film transistors (p-Si TFTs), also not shown. The V CST  traces  606  can run from display edge to display edge and can connect together, e.g., as shown on the left. The V CST  traces can also connect, through a conductive dot  607 , to an ITO plane  609  on the top glass  610 . Typically, four conductive dots, one in each corner, can be used to connect the V COM  plane to V COM Drive  611 .  FIG. 6  shows only one dot  607  for simplicity. The voltage of V CST  and top glass ITO  609  can be set by V COM Drive, which can be provided by the LCD driver IC (not shown). V CST  can also be connected to another drive source other than V COM Drive  611 . 
       FIG. 7  illustrates a circuit diagram  700  for a subpixel and shows on which glass substrate various components can be fabricated. The bottom glass  701  can be the substrate for the integration of all the TFT pixel circuitry  703 . This can include the select line drivers and control logic. The bottom glass can also serve as the substrate for chip on glass (COG) components, such as the LCD driver (not shown). The upper electrode  704  of capacitor C LC  can be on the top glass  702 . Electrode  704  can be an ITO plane that covers the entire display area and forms the counter electrode to the bottom electrode  705  making C LC . Upper electrode  704  can also connect, e.g., through four corner-located conductive dots  706  (only one shown), to V COM Drive  707  on bottom glass  701 . 
     1.2.2. V COM    
     Minimizing or eliminating the DC component of the voltage across the liquid crystal (LC) can reduce or eliminate some undesirable image artifacts. Therefore, the electric field across the LC can be periodically flipped while maintaining overall balance between the two field directions. Obtaining perfect electric field balance can be difficult, which can lead to small DC offsets that can produce unwanted image artifacts. To mask flicker due to DC offsets one of several inversion schemes known to those skilled in the art, such as dot inversion, can be employed. 
     1.2.3. Modulating V COM    
     In some embodiments, it may be desirable to reduce the voltage range of data drivers. Therefore, the V COM  ITO plane and the V CST  traces can be modulated from ground to the supply rail to produce an AC voltage across the LC. However, this can restrict the available inversion methods to only the frame and line types. 
     V COM Drive requirements can be fairly simple: its voltage can remain constant until the charge transfer has completed for a row of pixels, thus setting their grey levels. Once the display pixels are set, V COM Drive can change without significantly affecting the LC state provided that parasitic pathways into and out of the subpixel remain small. 
     1.2.4. Constant V COM    
     V COM  modulation can complicate the integration of touch sensing with LCDs. Various techniques for overcoming these complications are discussed below. An alternative method of minimizing the DC component of the voltage across the liquid crystal can be employed. One such alternative method is disclosed in J. Hector and P. Buchschacher, “Low Power Driving Options for an AMLCD Mobile Display Chipset”, SID 02 Digest, pp. 695-697, which is incorporated by reference herein. This alternative method can allow V COM  to remain at a constant voltage, does not require large-voltage range data drivers, and can consume low power. Various advantages of using a constant V COM  are described below. 
     1.3. LCD Manufacturing 
     The manufacturing of LCD panels can be done using a batch process on large pieces of glass called mother-glass. Two pieces of mother-glass can be used: a top mother-glass, which can provide the substrate for the color filter, black matrix, and the upper electrode for C LC ; and a bottom mother-glass, which can provide the substrate for the active matrix TFT array and drive circuitry. 
     A basic process flow  800  for manufacturing LCDs is shown in  FIG. 8 . Two large sheets of mother-glass, one for the top portion of the LCD and one for the bottom portion, can go through separate processing steps  801  and  802  before being aligned (block  803 ), pressed together, and heated (block  804 ) to cure seals between the top and bottom glass thereby producing a stable panel structure. The large panel can then be scribed and broken into smaller modules of the desired dimensions (block  805 ). The individual modules can have their edges ground (block  806 ) before being filled with liquid crystals (block  807 ). After filling, the modules can be sealed (block  808 ). Polarizers and electrical components can be attached (block  809 ). Flexible printed circuits (FPCs) can be attached to their substrates at or near the end of the process (block  810 ). 
     A finished LCD module  900  is shown in  FIG. 9 . The illustrated LCD module includes a chip on glass (COG) LCD driver  901  attached to the bottom glass  902  and also includes a flex on glass (FOG) flexible printed circuit (FPC)  903  attached to the bottom glass  902 . Both components can be electrically connected to bottom glass pads and held in place using an anisotropic conductive adhesive (ACA). Bottom glass  902  can extend beyond top glass  904  to provide a shelf  905  to mount the COG LCD driver  901 , the FPC  903 , and other supporting components. For handheld devices, the system processor board that manages the data and controls for the LCD can be placed under the backlight  906 . 
     Additional components used to support touch sensing (e.g., FPCs) can also attach to shelf  905 . Other attachment points are also possible. Details are discussed in conjunction with relevant embodiments described below. 
     1.4. Combining LCDs and Touch Sensing 
     The stack up diagrams discussed herein may be better understood in conjunction with the block diagrams of  FIGS. 10 and 11 . Starting at the top, touch sense electrodes  1001 ,  1101  can be deposited on the top (user side) of LCD top glass  1002 ,  1102 . Touch drive electrodes  1003 ,  1103  can be patterned on the bottom side of top glass  1002 ,  1102 . Conductive dots  1004 ,  1104  can connect drive electrodes  1003 ,  1103  to driver  1005 ,  1105 , which can also be located on bottom glass  1006 ,  1106 . A shelf  1007 ,  1107  on bottom glass  1006 ,  1106  can house LCD driver chip  1008 ,  1108  and the touch sensor driver chip  1009 , which can interface with each other ( FIG. 10 ) or be integrated into a single component ( FIG. 11 ). Finally, a FPC  1010 ,  1110 , also bonded to the shelf can connect host device  1011 ,  1111 . 
     2. Integration Options 
     Some embodiments of an LCD with integral touch sensing can include a top glass and a bottom glass. Display control circuitry can be formed on one and/or both of these glass layers to affect the amount of light that passes through a layer of liquid crystal between the two glass layers. The space between the external edges of the top and bottom glass is referred to herein as the liquid crystal module (LCM). 
     A typical LCD stackup  1200  typically includes additional layers, as illustrated in  FIG. 12 . In  FIG. 12 , a hard-coated PMMA layer  1201  can protect a LCD polarizer  1202  and the top glass  1203 , and a second polarizer  1205  can be included between bottom glass  1204  and a backlight  1206 . 
     Integrating touch-sensing technology into an LCD can be achieved using a variety of techniques. For instance, different touch-sensing elements and/or layers may be incorporated in a LCD display, with different embodiments varying in factors such as display and/or manufacturing cost, display size, display complexity, display durability, display functionality, and image display quality. In some embodiments, touch-sensing capability can be included into an LCD by integrating touch-sensing elements on the LCD display outside of the LCM. In other embodiments, touch-sensing elements can be added both inside the LCM (e.g., between the two glass layers) as well as outside of the LCM. In still other embodiments, a set of touch-sensing elements can be added only inside the LCM (e.g., between the two glass layers). The following sections describe a number of concepts for each of the above-mentioned embodiments. 
     2.1. Touch-Sensing Outside of the Liquid Crystal Module 
     Adding touch-sensing elements outside of the LCM allows touch sensing capabilities to be added to an LCD display with little to no impact on typical LCD manufacturing practices. For instance, a touch sensing system and LCD display system might be fabricated separately and integrated in a final step to form an LCD with touch sensing capabilities. Including the touch-sensing elements outside of the LCM can also allow the touch-sensing elements to be placed close to the area touched by the user, potentially reducing electrical interference between the display and touch components. 
     The following two embodiments, identified as Concept C and Concept N, can incorporate such external touch-sensing elements. 
     2.1.1. Concept C 
     One embodiment of the present invention, Concept C, uses the stackup illustrated in  FIG. 13 , which allows the touch function to be separate from the LCD. In Concept C, two additional indium-tin oxide (ITO) layers (ITO 1   1301  and ITO 2   302 ) can be patterned on top of the color filter (CF) plate (e.g., the top glass layer) These layers can be used for touch sense and touch drive elements of a touch sensor, e.g., a mutual-capacitance touch sensor. These ITO layers can be patterned into columns and/or rows (as shown in  FIGS. 1 and 2 , and described in the preceding multi-touch sensing description), and can be separated by a dielectric  1305 , such as a glass substrate or a thin (e.g., 5-12 mm) SiO 2  layer. 
     In some embodiments, the electrode pattern used in the touch elements may be optimized to reduce visual artifacts. For instance,  FIG. 14  illustrates a diamond electrode pattern, which can reduce visual artifacts. 
     In Concept C, the FPCs that carry touch sensing data can attach to the top surface of the top glass  1303 . 
     2.1.2. Concept N 
     One embodiment of the present invention, Concept N, can implement capacitive sensing on the outside surface of the color filter (CF) plate using self-capacitance sensing. Concept N can use the stackup illustrated in  FIG. 15 , in which the touch sensing components can be located on top of CF plate  1501  (top glass). LCDs based on Concept N can be built without altering standard LCD processing by forming TFTs  1503  with two metal layers and patterned ITO  1500  on CF plate  1501  using, for example, the same LTPS process used for conventional TFT plate  1504 . Touch ITO layer  1500  can be patterned into a plurality of touch pixels  1612  ( FIG. 16 ). Touch ITO layer  1500  can be protected by a plastic cover  1702  (shown in  FIG. 17 ) that can also serve as the surface touched by a user. 
       FIG. 16  illustrates a self-capacitance touch pixel circuit for Concept N. Each ITO touch pixel  1612  can be connected to two TFTs, e.g., an input TFT  1604  and an output TFT  1608 . The input TFT  1604  can charge ITO touch pixel  1612 , while output TFT  1608  can discharge ITO touch pixel  1612 . The amount of charge moved can depend on the ITO touch pixel&#39;s  1612  capacitance, which can be altered by the proximity of a finger. Further details of self-capacitance touch-sensing are described above and in U.S. Pat. No. 6,323,846, titled “Method and Apparatus for Integrating Manual Input,” issued Nov. 27, 2001, which is hereby incorporated by reference in its entirety. 
     In one embodiment, an output column  1610  can be shared by touch pixels vertically, and output gates  1606  can be shared by touch pixels horizontally, as shown in  FIGS. 16 and 18  for output column  1610  ‘C 0 ’ and output gates  1606  ‘R 3 ’.  FIG. 19  shows a detailed layout of a touch pixel. 
     2.2. Partially-Integrated Touch-Sensing 
     Integrating touch-sensing elements inside the LCM can provide a variety of advantages. For example, touch-sensing elements added inside the LCM could “reuse” ITO layers or other structures that would otherwise be used only for display functions to also provide touch-sensing functionality. Incorporating touch-sensing features into existing display layers can also reduce the total number of layers, which can reduce the thickness of the display and simplify the manufacturing process. 
     The following embodiments can include touch-sensing elements inside and outside the LCM. Because integrating touch-sensing elements within the LCM may result in noise and interference between the two functions, the following designs can also include techniques that allow elements to be shared while reducing or eliminating any negative effects on the display and/or touch-sensing outputs caused by electrical interference between the two. 
     2.2.1. Concept A 
     Concept A can use the basic stackup  2000  illustrated in  FIG. 20 , with a multi-touch capable (“MT”) ITO sense layer (ITO 1 )  2001  positioned on the user side of top glass  2002 , between top glass and polarizer  2003 . Starting from the top, the touch sensing layers can include: ITO 1   2001  (an ITO layer that can be patterned into N sense (or drive) lines) and ITO 2   2004  (an ITO layer that can be patterned into M drive (or sense) lines). ITO 2  layer  2004  can also serve as the V COM  electrode for the LCD. 
     2.2.1.1. Concept A: Touch Sensor Electrodes 
     The touch sensor electrode array can include two layers of patterned ITO as illustrated in  FIG. 21  (left side).  FIG. 21  is a simplified view of one possible implementation of touch sensor electrodes. The layer closer to the viewer, ITO 1   2101 , can be the touch output layer also called the sense layer or the sense lines. The touch drive layer  2102  can be located on layer ITO 2 . ITO 2  can also form the upper electrode of the capacitor C LC  (see  FIG. 7 ).  FIG. 21  (right side) also shows a detail of three sense pixels  2103   a ,  2103   b , and  2103   c  along with associated capacitors. Both the sense and drive lines can have a 5 mm pitch with a 10 to 30 micron gap. The gap can be just small enough to be invisible to the naked eye, but still large enough to be easy to etch with a simple proximity mask. (Gaps in the figure are greatly exaggerated.) 
       FIG. 22  shows one possible physical implementation for Concept A, with top view  2201  and side view  2202  of cabling and subsystem placement. Top view  2201  shows the approximate positions of FPC  2203  (discussed in greater detail below) in an unfolded state.  FIG. 22  represents just one physical implementation where a discrete touch level shifter/decoder COG can be used. Alternative architectures that minimize the number of discrete touch components are discussed below. For mechanical stability, the FPC can be bent, as shown in side view  2201 , so that stress on the T-tab  2204  and B-tab  2205  bonds are minimized.  FIG. 23  is a high-level block diagram showing one possible architecture  2300  of the main bottom glass components, and the segmented ITO 2  layer  2301  on the top glass used for touch sensing. The segments  2302  of ITO 2  on the top glass each connect through a conductive dot  2303  to a corresponding pad on the bottom glass. The pads on the bottom glass can each connect to the touch driver, discussed below. 
     2.2.1.2. Concept A: Conductive Dots 
     Conductive dots located in the corners of the LCD can be used to connect the V COM  electrode to drive circuits. Additional conductive dots can be used to connect the touch drive lines to touch-drive circuitry. The dots can have sufficiently low resistance so as to not add significantly to the phase delay of the touch drive signals (discussed in greater detail below). This can include limiting the resistance of a conductive dot to 10 ohms or less. The size of the conductive dot can also be limited to reduce the real estate needed. 
     As shown in  FIG. 24 , elongated conductive dots  2401  can be used to reduce both dot resistance and real estate requirements. Touch drive segments  2402  can be about 5 mm wide, which can provide a large area to reduce dot resistance. 
     2.2.1.3. Concept A: Flex Circuit and Touch/LCD Driver IC 
     A conventional display (e.g.,  FIG. 9 ) can have an LCD Driver integrated circuit (IC)  901 , that can control low-level operation of the display. A system host processor can exercise high-level control over the display by sending commands and display data to LCD Driver  901 . Multi-touch systems can also have one or more driver ICs. One exemplary multi-touch capable system, described in the incorporated references includes three ICs: a multi-touch controller, an external level-shifter/decoder, and controller, such as an ARM processor. The ARM processor can exercise low-level control over the multi-touch controller, which can subsequently control the level-shifter/decoder. A system host processor can exercise high-level control over and receive touch data from the ARM processor. In some embodiments, these drivers can be integrated into a single IC. 
       FIG. 25  shows an example high-level block diagram for a Touch/LCD Driver integrated circuit  2501 . The IC has two main functions: 1) LCD control and update, and 2) touch scanning and data processing. These two functions can be integrated by an LCD driver portion  2502  for LCD control and an ARM processor  2503  and multi-touch controller  2504  for touch scanning and processing. The touch circuits can be synchronized with LCD scanning to prevent one from interfering with the other. Communication between the host and either the LCD Driver or the ARM processor can be through the host data and control bus  2505 . A more fully integrated Touch/LCD Driver is discussed below. 
     As shown in  FIG. 26 , an FPC  2601  that brings together the signals for the various touch and display layers can have three connector tabs, a T-tab  2602 , a B-tab  2603 , and a host tab  2604 . The T-tab can connect to sense line pads on the top glass. The T-tab traces  2605  can connect to corresponding pads on B-tab  2603 , which can also attach to the bottom glass. B-tab  2603  can also provide pass-through routes  2606  from Host tab  2604  that can enable the host to connect to the Touch/LCD Driver IC. FPC  2601  can also provide the substrate for various components  2607  supporting touch and LCD operation, and can also connect to the backlight FPC through two pads  2608 . 
     The FPC  2601  can be TAB bonded to both the top and bottom glass. Alternatively, other bonding methods can be employed. 
     2.2.1.4. Concept A: Touch Drive Integrated on Bottom Glass 
     A level shifter/decoder chip, along with a separate voltage booster (e.g., a 3V to 18V booster), can provide high voltage drive circuitry for touch sensing. In one embodiment, the Touch/LCD Driver IC can control the level shifter/decoder chip. Alternatively, the voltage booster and/or the level shifter/decoder can be integrated into the Touch/LCD Driver IC. For example, such integration can be realized using a high voltage (18V) LTPS process. This can allow integrating the level shifter/decoder chip and the voltage booster into the periphery of the bottom glass. The level shifter/decoder can also provide the voltages for V COM  modulation and touch drive as discussed below. 
     2.2.1.5. Concept A: Sharing Touch Drive with LCD V COM    
     As discussed above, Concept A can add one layer of ITO to a standard LCD stackup, which can function as the touch sense lines. The touch drive layer can be shared with the LCD&#39;s V COM  plane, also denoted ITO 2 . For display operation, a standard video refresh rate (e.g., 60 fps) can be used. For touch sensing, a rate of at least 120 times per second can be used. However, the touch scanning rate can also be reduced to a slower rate, such as 60 scans per second, which can match the display refresh rate. In some embodiments, it may be desirable to not interrupt either display refresh or touch scanning. Therefore, a scheme that can allow the sharing of the ITO 2  layer without slowing down or interrupting display refresh or touch scanning (which can be taking place at the same or different rates) will now be described. 
     Simultaneous display update and touch scanning is illustrated in  FIG. 27 . In this example, five multi-touch drive segments  2700 ,  2701 ,  2702 ,  2703 ,  2704  are shown. Each touch drive segment can overlap M display rows. The display can be scanned at 60 frames per second while the multi-touch sensor array can be scanned at 120 times per second. The illustration shows the time evolution of one display frame lasting 16.67 msec. The area of the display currently being updated preferably should not overlap an active touch drive segment. 
     Patch  2705  indicates where the display rows are being updated. Patch  2706  indicates an active touch drive segment. In the upper left corner of  FIG. 27 , at the start of the display frame the first M/2 display lines can be refreshed. At the same time, touch drive segment  1   2701  can be driven for the purpose of touch sensing. Moving to the right in the figure, at time t=1.67 ms, the next picture shows the next M/2 display rows being refreshed, while simultaneously touch drive segment  2   2702  can be driven. After about 8.3 msec of this pattern, (start of second row) each touch drive segment can have been driven once, and half the display will have been refreshed. In the next 8.3 msec, the entire touch array can be scanned again, thus providing a scanning rate of 120 fps, while the other half of the display is updated. 
     Because display scanning typically proceeds in line order, touch drive segments can be driven out of sequential order to prevent an overlap of display and touch activity. In the example shown in  FIG. 27 , the touch drive order was 1, 2, 3, 4, 0 during the first 8.3 msec and 1, 2, 4, 3, 0 in the second 8.3 msec period. The actual ordering can vary depending on the number of touch drive segments and the number of display rows. Therefore, in general, the ability to program the order of touch drive usage may be desirable. However, for certain special cases, a fixed sequence ordering may be sufficient. 
     It may also be desirable (for image quality reasons) to separate the active touch drive segment farther away from the area of the display being updated. This is not illustrated in  FIG. 27 , but can easily be done given a sufficient number of touch drive segments (e.g., 6 or more segments). 
     Such techniques can effectively allow different refresh rates for the display and touch-sense elements without requiring multiplex circuitry to support a high-frequency display drive element. 
     2.2.1.6. Concept A: V CST  Drive Options 
     As illustrated in  FIG. 7 , V CST  and V COM  can be connected together and can thus be modulated together to achieve the desired AC waveform across the LC. This can help achieve proper display refresh when using V COM  modulation. When V COM  is used for touch drive, it is not necessary to also modulate V CST . This can be considered as the Open Circuit V CST  Option, described below. However, if V CST  is modulated with V STM , the capacitive load on the touch drive signal, V STM , can be reduced, which can lead to a smaller phase delay in the touch signal. This can be considered as the Drive V CST  Option, described below. 
       FIG. 28  illustrates the Open Circuit V CST  Option. Bottom drawing  2802  illustrates how one touch drive segment  2803  can overlap M display rows  2804 . Touch drive segments  2803  located on the top glass can connect electrically to circuits on the bottom glass through a conductive dot  2805 . The M V CST  lines of the M rows under the touch drive segment can connect together on the edge of the display  2806 . Top drawing  2801  shows the basic circuit for a subpixel with its separate storage capacitor CST. Area  2807  in the upper drawing can represent M contiguous rows of subpixels covered by a single touch drive segment. Display operation and touch sensing for a particular touch drive/display group can occur at different times, as discussed above. When the display driver is ready to set the state of the subpixels in the M rows, switches  2808 ,  2809  can connect V COM  Drive  2810  to the M V CST  lines  2804  and to the touch drive segment (V COM ). The V COM  Drive voltage can be set by the LCD driver to either ground or the supply rail, depending on the phase of the inversion. Later, when this touch drive/display group is available for touch usage, switches  2808 ,  2809  can connect the touch drive segment to V STM    2811  and disconnect V CST  from V COM  Drive  2810 , thus leaving it in the open state  2812 . 
       FIG. 29  illustrates the Drive-V CST  option. Bottom drawing  2902  illustrates how one touch drive segment  2903  can overlap M display rows  2904 . The touch drive segments  2903  located on the top glass can connect electrically to circuits on the bottom glass through conductive dot  2905 . The M V CST  lines of the rows under a particular touch drive segment can connect together on the edge of the display  2906 . Top drawing  2901  shows the basic circuit for a subpixel having a separate storage capacitor C ST . Area  2907  in the upper drawing can represent M contiguous rows of subpixels covered by a single touch drive segment. Display operation and touch sensing can occur at different times. When the display driver is ready to set the state of the subpixels in the M rows, switch  2908  can connect V COM  Drive  2910  to the M V CST  lines  2904  and to the touch drive segment (V COM ). The V COM  Drive  2910  voltage can be set by the LCD driver to typically either ground or a supply rail depending on the phase of the inversion. Later, when this touch drive/display group is available for touch usage, switch  2908  can connect the V CST  and the touch drive segment (V COM ) to V STM    2911 . 
     2.2.1.7. Concept A: MT-Drive Capacitive Loading 
     The capacitive load on Concept A&#39;s touch drive line can be high, for example, because of the thin (e.g., ˜4 μm) gap between the touch drive layer and the bottom glass, which can be covered by a mesh of metal routes and pixel ITO. The liquid crystals can have a rather high maximum dielectric constant (e.g., around 10). 
     The capacitance of the touch drive segment can affect the phase delay of the stimulating touch pulse, V STM . If the capacitance is too high, and thus there is too much phase delay, the resulting touch signal can be negatively impacted. Analysis performed by the inventors indicates that keeping ITO 2  sheet resistance to about 30 ohms/sq or less can keep phase delay within optimal limits. 
     2.2.1.8. Concept A: Electrical Model and V COM -Induced Noise 
     Because ITO 2  can be used simultaneously for both touch drive and LCD V COM , modulating V COM  can add noise to the touch signal. 
     For example, a noise component may be added to the touch signal when one touch drive segment is being modulated with V COM  at the same time another touch drive segment is being used for touch sensing. The amount of added noise depends on the phase, amplitude, and frequency of the V COM  modulation with respect to V STM . The amplitude and frequency of V COM  depend on the inversion method used for the LCD. 
       FIG. 30  shows an electrical model for the situation where touch drive  3001  is used for both touch sensing and LCD V COM  modulation. The model shows the input path through which V COM  modulation can add noise to the input of charge amplifier  3002 . 
     In some embodiments, charge amplifier  3002  may need additional headroom to accommodate noise induced by V COM    3003 . Additionally, subsequent filtering circuits (e.g., synchronous demodulators, not shown) may need to remove the noise signal due to the V COM  modulation. 
     2.2.1.9. Concept A: V STM  Effects 
     V STM  modulation, under certain conditions, can have a negative impact on the voltages of the subpixels underneath the touch drive segment being modulated. If the subpixel RMS voltage changes appreciably, display artifacts may be produced. One or more of the following techniques may be employed to minimize display distortion that may result. 
     Touch drive from two sides can reduce the distortion of the LC pixel voltage. As shown in  FIG. 31 , touch drive from both sides can be achieved by employing the existing low resistance C ST  routes  3101  on the bottom glass by connecting V STM  to C ST  lines on both sides through conductive dots  3102 . Alternatively, single-ended touch drive can produce a pixel offset voltage that is uniform for all pixels, which can be reduced or eliminated by adjusting the data drive levels. Also, reducing the ITO sheet resistance can help reduce display artifacts. Finally, the phase and frequency of V STM  can also be tied to the phase and frequency of V COM  to reduce the amount of noise in the touch signal. 
     2.2.1.10. Concept A: Impact on Manufacturing 
     The manufacturing process for Concept A can include additional steps relative to a typical LCD manufacturing process. Some may be new steps entirely and some may be modifications to existing steps.  FIG. 32  shows a manufacturing process flow for Concept A. Blocks  3201 ,  3202 , and  3204  represent new steps, and blocks  3205 ,  3206 , and  3207  represent a modified step, both relative to a conventional LCD manufacturing processes (e.g., that of  FIG. 8 ). 
     Applying and patterning ITO 1  (blocks  3201 ,  3202 ) can be done using known methods. The ITO can be protected during the remainder of the LCD processing. Photoresist can be used to provide a removable protective coating. Alternatively, silicon dioxide can provide a permanent protective covering. ITO 2  can be applied and patterned (block  3204 ) to form the touch drive segments in similar fashion. 
     An analysis of phase delay indicates that the sheet resistance of ITO 1  and ITO 2  can be as high as 400 ohms/square for small displays (&lt;=4″ diagonal), provided that the capacitive loading on either plane is small. As discussed above, the capacitive loading with Concept A can be of such magnitude that it may be desired to limit the maximum sheet resistance for ITO 2  to around 30 ohms/square or less. 
     2.2.2. Concept A 60   
     Concept A 60  can be physically similar to Concept A and can provide a different approach to the problem of synchronizing display updates and touch scanning. This can be accomplished by using the 1-line inversion of V COM  as the stimulus for the touch signal (i.e., V STM ). This is illustrated in  FIG. 33 , which shows how a single touch drive segment  3301  can be modulated while other touch drive segments can be held at a constant voltage. With this approach, the problem of removing the unwanted V COM -induced noise from the touch signal can be eliminated. Furthermore, it is not necessary to spatially separate display updating and touch sensor scanning. However, using this approach, demodulation can be done at a single frequency (i.e., the V COM  modulation frequency, e.g., ˜14.4 kHz) as opposed to the multi-frequency demodulation described in U.S. patent application Ser. No. 11/381,313, titled “Multipoint Touch Screen Controller,” filed May 2, 2006, incorporated by reference herein. Furthermore, using this approach, the touch sensor scan rate can be fixed at the video refresh rate (e.g., 60 per second). 
     2.2.3. Concept B 
     Concept B, illustrated in  FIG. 34 , can be similar to Concept A, sharing many of the same electrical, cabling, and structural aspects. However, Concept B can integrate the touch drive layer into the V COM  layer. Concept B can therefore differ in the number and stack position of ITO layers used for LCD and touch sensing. Because of the similarities, Concept B will now be described by highlighting differences between Concepts A and B. 
     Concept B can split the shared ITO 2  layer of Concept A into two ITO layers, using one layer for touch sensing (ITO 2 )  3402  and one layer for the LCD V COM  (ITO 3 )  3403 . Starting from the top, layers used for touch sensing can include: ITO 1   3401 , an ITO layer that can be patterned into N touch sense lines; ITO 2   3402 , an ITO layer that can be patterned into M touch drive lines; and ITO 3   3403 , an ITO layer that can serve as the V COM  electrode for the LCD. Touch drive layer (ITO 2 )  3402  can be deposited on the lower surface of top glass  3404 , above the color filter  3405 . 
     Separating V COM  from touch drive elements can reduce interference. 
     2.2.3.1. Concept B: Touch Sensor Electrodes 
     Concept B can include touch sensor electrodes substantially similar to those described above for Concept A. 
     2.2.3.2. Concept B: Conductive Dots 
     As in Concept A, Concept B can use additional conductive dots  3406 , which can be located in the corners of the LCD, to connect the touch drive segments to dedicated circuitry. Because V COM  need not be shared with touch sensing, Concept B can retain the corner dots that connect V COM  to its drive circuitry. Additionally (as discussed below), Concept B may add even more conductive dots for V COM . 
     2.2.3.3. Concept B: Flex Circuit and Touch/LCD Driver IC 
     Concept B can use a FPC and Touch/LCD Driver IC substantially similar to those described for Concept A. 
     2.2.3.4. Concept B: Synchronization with LCD Scanning 
     For Concept B, although the V COM  layer can be separate from the touch drive layer, it still may be desired to synchronize touch scanning with LCD updating to physically separate the active touch drive from the display area being updated. The synchronization schemes previously described for Concept A can also be used for Concept B. 
     2.2.3.5. Concept B: MT-Drive Capacitive Loading 
     As with Concept A, the capacitive load on Concept B&#39;s touch drive line can be high. The large capacitance can be due to the thin (e.g., ˜5 μm) dielectric between touch drive (ITO 2 )  3402  and V COM  plane (ITO 3 )  3403 . One way to reduce undesirable phase delay in the touch stimulus signal can be to lower the ITO drive line resistance through the addition of parallel metal traces. Phase delay can also be reduced by decreasing the output resistance of the level shifter/decoder. 
     2.2.3.6. Concept B: Electrical Model and V COM -Induced Noise 
     Because the entire V COM  plane can be coupled to the touch drive layer, multi-touch charge amplifier operation may be disrupted by noise induced by V COM  modulation. To mitigate these effects Concept B can have a constant V COM  voltage. 
     Conversely, the coupling between ITO 2   3402  and ITO 3   3403  (V COM  and touch drive) can cause interference with the V COM  voltage that can cause the wrong data voltage can be stored on the LC pixel. To reduce the modulation of V COM  by V STM , the number of conductive dots connecting V COM  to the bottom glass can be increased. For example, in addition to V COM  dots at each corner of the viewing area, conductive dots can be placed at the middle of each edge. 
     Distortion resulting from V COM -V STM  coupling can be further reduced by synchronizing V STM  with V COM  and turning off the pixel TFT at just the right time. For example, if the line frequency is 28.8 kHz, and the touch drive frequency is a multiple of this (e.g., 172.8, 230.4 and 288 kHz) then the V COM  distortion can have the same phase relationship for all pixels, which can reduce or eliminate visibility of the V COM  distortion. Additionally, if the gates of the pixel TFTs are turned off when the distortion has mostly decayed, the LC pixel voltage error can be reduced. As with Concept A, the phase and frequency of V STM  can be tied to the phase and frequency of V COM  to reduce the amount of noise in the touch signal. 
     2.2.3.7. Concept B: Impact on Manufacturing 
     As with Concept A, Concept B can also add steps to the LCD manufacturing process.  FIG. 35  shows a manufacturing process flow for Concept B, in which blocks  3501 ,  3502 ,  3503 , and  3504  represent new steps relative to a conventional LCD manufacturing process (e.g., that depicted in  FIG. 8 ), and blocks  3506 ,  3507 ,  3508 , and  3509  represent a modification to an existing step (e.g., also relative to  FIG. 8 ). 
     ITO 1  can be applied (block  3501 ) and patterned (block  3502 ) using known methods, as with Concept A. The sheet resistance of ITO 1  and ITO 2  can also be substantially similar to that described for Concept A. For Concept B, the ITO 2  layer deposition (block  3503 ) can be routine because it can be directly applied to glass. Electrical access between the ITO 2  layer and the bottom glass for the conductive dots that connect to the touch drive segments can be easily accomplished by etching using a shadow mask (block  3504 ). 
     ITO 3  (e.g., the LCD&#39;s V COM  layer), which can have a sheet resistance between 30 and 100 ohms/square, can also be applied (block  3505 ) using conventional methods. However, as discussed above, V COM  voltage distortion can be reduced by reducing the resistance of the ITO 3  layer. If necessary, lower effective resistance for ITO 3  can be achieved by adding metal traces that run parallel to the touch drive segments. The metal traces can be aligned with the black matrix so as to not interfere with the pixel openings. The density of metal traces can be adjusted (between one per display row to about every 32 display rows) to provide the desired resistance of the V COM  layer. 
     2.2.4. Concept B′ 
     Concept B′ can be understood as a variation of Concept B that eliminates the ITO 2  drive layer and instead uses a conductive black matrix (e.g., a layer of CrO 2  below the top glass) as the touch drive layer. Alternatively, metal drive lines can be hidden behind a black matrix, which can be a polymer black matrix. This can provide several benefits, including: (1) eliminating an ITO layer; (2) reducing the effect of V STM  on the V COM  layer; and (3) simplifying the manufacturing process. The manufacturing process can be simplified because using the black matrix for touch drive can eliminate the need to pattern an ITO layer above the color filter. 
       FIG. 36  shows a side view  3601  and top view  3602  of Concept B′. As can be seen, side view  3601  looks very much like a standard LCD stack-up, except for the top layer of ITO  3603  used for touch sensing. The bottom diagram of  FIG. 36  shows how the black matrix  3604  can be partitioned into separate touch drive segments. The mesh pattern can follow the pattern of a conventional black matrix, except that each drive segment can be electrically isolated from the other segments. To compensate for reduced touch signal strength that can be caused by using the black matrix mesh for touch drive, the charge amp gain can be increased (e.g., about 4×). 
     Because the touch sensing layer may not be shielded from the V COM  layer, V COM  modulation may interfere with the touch signal. Furthermore, touch drive may still interfere with the V COM  voltage. Both of these issues can be addressed by segmenting the V COM  layer as described with Concept A and/or spatially separating display updating and touch sensing as described above. A constant V COM  voltage can also be used to address these issues. 
     2.2.5. Concept K 
     Concept K is illustrated in  FIGS. 37  (circuit diagram) and  38  (stackup diagram). Concept K utilizes the fact that select pulses in the TFT LCD can be partially transferred to the pixel ITO when the CST-on-gate configuration is used. 
     As shown in the display stackup of  FIG. 38 , the viewer can face active array plate  3801  rather than CF plate  3802 . ITO pixels  3803  on the active array can provide the V STM  pulses for the touch sensor, with the display rows alternatively being used for V STM  pulses and for display addressing. ITO sense layer  3804  on plastic polarizer  3805  can be laminated to the back of array plate  3801  to provide the touch-sensing layer. A thin glass layer (e.g., 0.2 mm) can help improve the signal-to-noise ratio. 
     During display updates, rows can be selected individually to update the pixel data (as shown in  FIG. 39 ). To generate V STM  for touch sensing, multiple rows  4001  can be selected simultaneously, while high data voltage  4003  can be applied to the column lines  4002  to keep the TFTs off (as shown in  FIG. 40 ). The column driver can adjust the timing of data signals from a display memory to accommodate the touch drive intervals. 
     In one embodiment, a touch pulse sequence can simultaneously pulse about 30 rows  4001  during a touch scan interval.  FIG. 41  shows the effect of a touch drive pulse (V STM ) on the subpixel voltages of the LCD. The added voltage from the V STM  pulses can be compensated by a DC offset of V COM  and/or gamma correction of the display data grey levels. 
     Concept K can allow a number of advantages. Because the display pixels and touch sensors share drive circuitry, the level shifter/decoder may be eliminated. Additionally, a conventional CF plate can be used. Furthermore, no extra conductive dots between the top and bottom glass are needed. Busline reflections may increase the reflectance (R) for portions of the display, and hence call for the use of an extra film under the buslines (such as CrO under Cr) that can reduce R. 
     2.2.6. Concept X′ 
     Concept X′ is illustrated in  FIG. 42  (circuit diagram) and  FIG. 43  (stackup diagram). Concept X′ utilizes the fact that V STM  pulses can be similar to gate pulses for the TFT pixel switches (e.g., a 15 to 18 V swing). In Concept X′, the touch drive segments  4301  can be part of the LTPS active array and can form the counter electrode for the pixel storage capacitors C ST . C ST  can be formed between two ITO layers  4301 ,  4302 . In this embodiment, the active array plate  4303 , rather than the color filter plate  4304  can be on the user side of the display. 
     As shown in  FIG. 42 , a pulse sequence with three different frequencies  4201  for V STM  can be shared by three rows of pixels  4202  to select those rows. The ITO touch drive segments  4203  can be patterned under a set of rows adjacent to addressed rows. Touch drive segments  4203  can be connected to GND by TFTs  4204  when not connected to V STM . 
     Changes that can be made to the processing steps to construct Concept X′ can include the following. First, a patterned sense ITO can be added on the outside of the array substrate. Second, SiO 2  protection can be added on the sense ITO during LTPS processing. Protective resist could also be used. Third, touch drive ITO can be deposited and patterned under the SiO 2  barrier layer (which can be found in typical LTPS processes) for the LTPS array. Finally, vias can be patterned in the barrier SiO 2  to contact the touch drive ITO layer. This step can be combined with a subsequent process step. 
     Concept X′ can allow a number of advantages. For example, because the display and touch sensors share drive circuitry, the level shifter/decoder chip can be eliminated. Additionally, no change to the CF plate is required, so conventional color filter processing can be used. Further, because the storage capacitor C ST  can be located between two ITO layers, high transmittance can be achieved. Another advantage can be that extra conductive dots between the array plate  4303  and CF plate  4304  may be eliminated. 
     2.3. Fully-Integrated Touch-Sensing 
     A third set of embodiments of the present invention fully integrate the touch-sensing elements inside the LCM. As with partially-integrated touch-sensing, existing layers in the LCM can serve double duty to also provide touch-sensing functionality, thereby reducing display thickness and simplifying manufacturing. The fully-integrated touch-sensing layers can also be protected between the glass layers. 
     In some embodiments, the fully-integrated LCD can include a V COM  layer similar to those described in previous embodiments. In other embodiments, the fully-integrated touch-sensing LCD can include in-plane-switching (IPS) LCD constructions, which are described in further detail in the following sections. 
     2.3.1. Fully-Integrated V COM -Based LCDs 
     2.3.1.1. Concept A′ 
     Concept A′ can be considered as a variation of Concept A that eliminates the ITO sense layer (ITO 1   2001  in  FIG. 20 ) in favor of a conductive black matrix layer (below the top glass) used as the touch sense layer. Alternatively, metal sense lines can be hidden behind a black matrix, which can be a polymer black matrix. As a result, Concept A′ can also eliminate the T-tab on the FPC and the corresponding bonding to the top glass. Touch sense lines can be routed through conductive dots to the bottom glass and can directly connect to the Touch/LCD Driver chip. Furthermore, the FPC can be a standard LCD FPC. Elimination of manufacturing steps and components can lead to a reduction in cost compared to Concepts A and B. 
       FIG. 44  shows one way substitution of a conductive black matrix for the touch sense layer can be accomplished.  FIG. 44  includes a side view  4401  of the upper portion of a single pixel with its black matrix  4403  running between primary color sections  4404 . Touch drive segment  4405  can be separated from black matrix lines  4403  by planarizing dielectric layer  4406 .  FIG. 44  also shows top view  4402  of the display with black matrix lines  4403  running vertically. Approximately 96 black matrix lines (e.g., 32 pixels worth) can connect together into the negative terminal of charge amplifier  4907 . Touch drive segments  4405  can be driven as described above. A finger approaching top glass  4408  can perturb the electric field between vertical black matrix lines  4403  and touch drive segment  4405 . The perturbation can be amplified by charge amplifier  4407  and further processed as described elsewhere herein. 
     Because of the depth of touch sense lines  4403  in the display, the minimum distance between a finger or touch object and sense lines  4403  may be limited. This can decrease the strength of the touch signal. This can be addressed by reducing the thickness of layers above the touch sense layer, thereby allowing a closer approach of the finger or other touch object to the sense lines. 
     2.3.1.2. Concept X 
     Concept X is illustrated in  FIGS. 45 and 46 . The stack-up for Concept X, shown in  FIG. 45 , can be basically identical to that of a standard LCD. Touch sense layer  4501  can be embedded within the V COM  layer (ITO 2 ), which can serve the dual purpose of providing the V COM  voltage plane and acting as the output of the touch sensor. The touch drive layer can also be embedded within an existing LCD layer. For example, touch drive can be located on bottom glass  4503  and can be part of the LCD select line circuitry (see  FIG. 5 ). The select circuit can thus serve a dual purpose of providing gate signals for the subpixel TFTs and the touch drive signal V STM .  FIG. 46  is a top view of Concept X showing one possible arrangement of the touch sense layer with its floating pixels  4601  embedded in the V COM  layer. 
     2.3.1.3. Concept H 
     Concept H is illustrated in  FIGS. 47-50 . Concept H need not include any ITO outside the top glass or plastic layer of the display. As a result, the manufacturing processes can be very similar to existing display manufacturing processes. 
     As shown in  FIG. 47 , the touch-sensing part of the screen can be a transparent resistive sheet  4701 , for example, a glass or plastic substrate having an unpatterned layer of ITO deposited thereon. The V COM  layer of the display may be used for this touch-sensing part. Because this layer need not be patterned, a photolithography step can be eliminated from the manufacturing process as compared to some embodiments discussed above. For purposes of reference herein, the sides will be referred to as north, south, east, and west as indicated in the drawing. 
     A plurality of switches  4702  can be arranged about the perimeter of the resistive sheet. These switches can be implemented as TFTs on glass. Also shown are a plurality of conductive dots  4703 , at each switch location, that can connect V COM  (on the top glass) to the TFT layer on the bottom glass, in the border region of the display. Switches  4702  can be connected together into two busses, for example, with the north and east switches connected to one bus  4704  and the south and west switches connected to a second bus  4705 . 
     For touch sensing, switches  4702  can be operated as follows. The north and south switches can be used to measure the Y-direction capacitance. The left and right side switches can be used to measure the X-direction capacitance. The switches at the northeast and southwest corners can be used for both X and Y measurement. Capacitance can be measured by stimulating resistive sheet  4701  with a modulation waveform V MOD , illustrated in  FIG. 49 . The current (i.e., charge) required to drive the sheet to the desired voltage can be measured and used to determine the location of the touch. 
     Specifically, as illustrated in the waveforms for  FIG. 49 , in the absence of touch, the baseline capacitances  4902  can indicate the current (charge) required to stimulate the sheet  4701  to the V MOD  voltage. In the presence of touch, greater current  4903  (charge) may be required because of the capacitance of the finger. This greater current is illustrated in the lower group of waveforms. The position of the touch can then be determined by simple mathematical combination of the baseline and signal waveforms as illustrated in  FIG. 49 . 
     An equivalent circuit for the touch screen during the X-direction (i.e., east-west) measurement is illustrated in  FIG. 48 . C_PARA  4801  can be the distributed parasitic resistance of the sheet, and C_FINGER  4802  can be the capacitance of a touch, e.g., located approximately 75% of the way to the east side. The block diagrams indicate how the plate can be driven to V MOD  and how the charge can be measured, combined, processed, and sent to the host. 
       FIG. 50  illustrates how Concept H can be integrated with an LCD. Specifically, conductive dots  5001  can connect to the TFT layer, which can allow resistive sheet  5002  (V COM ) to be modulated for display operation. Touch sensing operation and display operation can be time multiplexed. For example, assuming a 60 Hz screen refresh rate, corresponding to a 16 ms LCD update period, part of this time can be used for writing information to the LCD, and another part can be used for touch sensing. During LCD updating, V MOD  can be V COM  from the LCD driver circuit. During touch sensing, waveforms having different frequencies and amplitudes may be used depending on the exact details of the touch system, such as desired SNR, parasitic capacitances, etc. It should also be noted that the touch-sensing circuitry in this embodiment, illustrated in block diagram form, can either be integrated into the LCD driver or can be a separate circuit. 
     2.3.1.4. Concept J 
     Concept J, like Concept H, need not include any ITO outside the top glass or plastic layer of the display. Physical construction of Concept J is illustrated in  FIG. 51 . The touch-sensing surface can be a resistive sheet  5101  like Concept H, but patterned into a number of row strips  5102 . Patterning may be accomplished by photolithography, laser deletion, or other known patterning techniques. By patterning resistive sheet  5101  into a plurality of strips  5102 , the switches along the top and bottom (north and south) can be eliminated, leaving east and west switches  5103  connected to the row strips. Each row  5102  can be stimulated in sequence, using, for example, the V MOD  waveform  5201  illustrated in  FIG. 52 . The current (charge) required to drive each row  5102  to the modulation voltage can be a function of the capacitance of the row, which can be a combination of the parasitic capacitance (C_PARA  5301 ,  FIG. 53 ) for a given row and the capacitance of the finger or other touch object (C_FINGER  5302 ,  FIG. 53 ). 
     As shown in  FIG. 52 , the signal in the presence of touch  5202  can be mathematically combined with the baseline signal  5203  to compute the coordinates of the touch. The Y outputs can be determined by the centroids of Z outputs for each row. The X outputs can be determined by a weighted average of the X outputs for each row. 
       FIG. 54  shows how the Concept J touch sensor can be integrated with an LCD. Conductive dots  5401  can connect V COM  on the top glass to the TFT layer on the bottom glass. Touch and display operations need not be time division multiplexed. Rather, while a portion of the display is being updated, another portion may be scanned for touch. Various techniques for so doing are discussed above with respect to other embodiments. The touch sensing may use different frequencies and amplitudes, but may be phase synchronized with the LCD row inversion. Switches  5402  can be implemented as TFTs on glass. The measurement circuitry can either be integrated with the LCD controller or a separate component. 
     2.3.1.5. Concept L 
     In Concept L, active TFT layers can be added to the color filter glass to allow a segmented ITO layer to provide multiple functions simultaneously across different regions of an LCD display. A stackup diagram for Concept L is illustrated in  FIG. 55 . Concept L can contain the same number of ITO layers as a standard LCD display. However, while ITO 1   5509  and other structures  5507 ,  5508  on bottom glass  5511  can remain standard, an active TFT layer  5501  on the color filter glass  5505  can allow a region (e.g., a horizontal row) of ITO 2   5504  to be switched between the role of V COM , touch drive, or touch sense. 
       FIG. 56  illustrates a Concept L display with a horizontally-segmented ITO 2  layer  5504 . Different regions of the display are concurrently: undergoing V COM  modulation (region  5601 ) and/or being written (region  5602 ); providing touch stimulus (region  5603 ); being measured to provide touch sense (region  5604 ); and maintaining a hold state (region  5605 ). The transistors in the active TFT layer  5501  can switch the signals for each horizontal row to the desired function for a specified time interval. Each region can have equal exposure to each state, in the same sequence, to substantially eliminate non-uniformity. Because providing touch stimulus may disturb the voltage across the LC, LCD pixel writing can take place just after the touch stimulus phase to reduce the time duration of any disturbance. LCD pixel writing for a region can occur during V COM  modulation, while adjacent segments can be undergoing V COM  modulation to maintain uniform boundary conditions during pixel writing. 
     The color filter plate can be formed using a process similar to the process used for the active array. Forming the additional TFT layers may involve additional steps, but the back-end processing of the two substrates can remain substantially similar to that of a standard LCD. These techniques can allow such displays to scale to larger-sized panels without using low-resistivity ITO. 
     2.3.1.6. Concepts M 1  and M 2   
       FIGS. 57 and 58  show stackup diagrams for Concepts M 1  and M 2 , respectively. Concepts M 1  and M 2  can add layers of patterned ITO and metal to the color filter glass for touch sensing. While concepts M 1  and M 2  are similar, one difference relates to different uses of the ITO 1  and ITO 2  layers. Concept M 1  can use ITO 1   5701  for touch sense and can use ITO 2   5702  for both V COM  (when setting/holding LCD pixel voltages) and touch drive (when not writing pixel voltages). Concept M 2  can use ITO 1   5801  for touch drive, and can use ITO 2   5802  for V COM  and touch sense. For both Concepts M 1  and M 2 , top glass  5703 ,  5803  need not include any transistors or other active components. 
     In either concept M 1  or M 2 , V COM  can be segmented to allow one region of the display to keep a constant V COM  during display updating while another region can be independently scanned for touches. This can reduce interference between the touch-sensing and display functions. 
       FIGS. 59 ,  60 , and  61  show an exemplary display (corresponding to Concept M 2 ) that has been segmented into three regions ( 5901 ,  5902 ,  5903 ;  FIG. 59 ), and wherein two regions can be simultaneously touch-scanned (e.g., regions  5901 ,  5902 ) while a third region&#39;s display pixels can be updated (e.g., region  5903 ). On the left side of  FIG. 61 , twenty seven vertical drive lines  6101  in the ITO 1  and M 1  (metal  1 ) layers can provide three different regions with nine touch columns each. Each drive line (3 per touch column) can have a conductive dot (not shown) down to the array glass, and can be routed to a driver ASIC. 
     The right side of  FIG. 61  shows the possible modes for the segmented horizontal rows of the ITO 2  layer, which include V COM  and V HOLD  for a first set of alternating rows  6102  and V COM , V HOLD , and V SENSE  for a second set of alternating rows  6103 . Each ITO 2  row can connect via a conductive dot (not shown) down to the array glass, from which the mode of the row can be switched using LTPS TFT switches. The right side of  FIG. 61  shows twenty-one sense rows, of which fourteen can be sensed at any time (although other numbers of rows could also be more). 
       FIG. 62  shows the circuit diagram for touch sensing in the exemplary display illustrated in  FIGS. 59 ,  60 , and  61 . V STM  driver  6200  sends a signal through metal drive column  6202 , which can have a resistance of R metcol  and a parasitic capacitance of C drv . Touch capacitance C sig  can be measured across the ITO row, which can have a resistance of R ito2row  and a parasitic capacitance of C ito2row . The touch-sensing charge can also be affected by two additional resistances, R sw1  and R border , before reaching charge amplifier  6204 . 
     A display frame update rate of 60 fps can correspond to a touch scan rate of 120 fps. If desired (e.g., in small multi-touch displays) designers may choose to reduce the touch scan rate (e.g., to 60 fps), thereby saving power and possibly reducing complexity. As a result, some regions of the display can be left in a “hold state” when neither display updating nor touch scanning is occurring in that region. 
       FIG. 63  shows a display in which the display regions can be scanned and updated horizontally instead of vertically (as in  FIG. 60 ). The touch drive and touch sense regions can be interleaved so that a stimulus applied to touch drive row  6301  can be simultaneously sensed from two sense rows  6302  and  6303 , as indicated by sense field lines  6305 . 
     The black mask layer can be used to hide metal wires and/or gaps in ITO layers. For example, the metal drive lines, etched gaps in ITO 2 , and etched gaps in ITO 1  can be fully or partially hidden behind the black mask (as shown in  FIG. 64 ). This can reduce or eliminate the visual impact these items may have on the display&#39;s user. 
     2.3.1.7. Concept M 3   
     As shown in  FIG. 65 , Concept M 3  can be similar to Concepts M 1  and M 2 , but with touch drive and touch sense integrated into a single, segmented ITO layer  6501 . While various embodiments described above included drive and sense electrodes on separate layers, Concept M 3  can include drive and sense electrodes in the same plane. A dielectric layer  6502  can be added to shield the touch-sensing elements from other electrical fields and/or effects. 
       FIGS. 66 and 67  illustrate a Concept M 3  display segmented into three regions  6601 ,  6602 ,  6603 , each of which can alternate through a touch stim/sense phase, a LCD pixel writing phase, and a hold phase during every cycle update of the display frame.  FIG. 68  illustrates a wiring detail and layout arrangement that enables partitioning the display. ITO 1  rows  6801  can connect via conductive dots  6802  to LTPS switches on the TFT glass that switch the voltage for the row between V COM  and V HOLD . Three sense lines  6803  can be used for each column (one sense line for each region), with the lines multiplexed so that the signal for the active region can be measured in the corresponding timeframe. During touch scanning for a region, the touch drive elements corresponding to a row in the region can be activated, and all of the columns for that row can be simultaneously sensed. During the time that one region of the display is scanned for touches, another region can be modulating V COM  and/or updating the display pixels. 
     Metal segments ( 6805  in  FIG. 68 ) can be added to regions of the ITO to reduce the resistance of the ITO. For example, short metal segments can be added to the ITO 1  drive electrodes  6804  to reduce phase delay of the touch signal. These metal lines may be hidden behind a black mask layer. 
     As illustrated in  FIG. 69 , guard traces  6903  can be used to block field lines between the touch and sense electrodes that do not pass up through the glass where they would be affected by a finger or other touch object. This can reduce noise and enhance the measured effect of touches to the display.  FIG. 70  shows a top-view  7001  and a cross-section  7002  of a display without guard traces, in which a narrow gap separates the rows of touch-sensing elements, e.g., drive electrodes  7003  and sense electrodes  7004 . Grounding the ITO 2  layer  7005  (V COM ) when touch sensing is active can shield touch sensing and display functions from one another.  FIG. 69  shows a top-view  11101  and a cross-section  6902  of a display that includes grounded guard traces  6903  between rows of touch-sensing elements on ITO 1 , e.g., drive electrodes  6904  and sense electrodes  6905 . 
     2.3.1.8. Concepts P 1  and P 2   
     Concepts P 1  and P 2 , like Concept M 3 , can provide touch drive and touch sense electrodes in the same plane. However, Concepts P 1  and P 2  can provide an additional benefit of individually-addressable touch-pixels, as shown in  FIG. 71 . Each touch pixel can include a drive electrode  7102 , a sense electrode  7103 , and corresponding drive lines  7104  and sense lines  7105  that can be individually routed and connected to a bus on the border of the display. These lines may be formed using conductive black mask, thereby allowing black mask areas already present in the display to provide additional service for touch sensing. Alternatively, the lines may be metal lines disposed behind a black matrix, which can be a polymer black matrix. 
       FIG. 72  shows a stackup diagram for Concept P 1 . Concept P 1  can differ from a standard LCD process in various respects. For example, a portion of the standard polymer black mask can be changed to black chrome with low-resistance metal backing. These conductive lines can then be used to route signals to and from the touch pixels. A layer of patterned ITO  7202  can be added behind the black mask in an additional mask step. STN-style conductive dots  7203  can be added to route the drive and sense signals for each touch pixel to the LTPS TFT plate (e.g., using 2 dots per touch pixel). The color filter layer and the bordering planarization layer  7204  can also be thickened to decrease the capacitance between the touch drive and V COM . 
       FIG. 73  shows a stackup diagram for Concept P 2 . In addition to incorporating the four changes described above with respect to Concept P 1 , Concept P 2  can also include a patterned ITO layer  7301  that can be used to create a segmented V COM . Segmenting V COM  can isolate touch drive and display operation, thereby potentially improving the signal-to-noise ratio.  FIG. 74  shows a circuit diagram highlighting the V COM  signal coupling for Concept P 2 . Keeping independent buses (Vholdbus 1  and Vholdbus 2 ) for return current can reduce the coupling charge. Also, using complementary drive for half of the touch pixels can reduce the return current in Vholdbus 1 . 
       FIGS. 71 and 75  illustrate an exemplary routing of touch sense and touch drive lines to and from the sense and drive pixels. A set of drive and sense lines can be routed horizontally from bus lines  7501 ,  7502  at the sides of the display to each individual touch pixel  7101 . These lines can be hidden behind a black mask layer, or can be incorporated into a conductive black mask layer. This routing can also be on a single layer. Signals for individual touch pixels can be addressed and multiplexed through the bus lines using LTPS TFTs. 
     The ability to drive individual pixels, rather than whole rows, can be used to reduce parasitic capacitance. Individually-addressable touch pixels can also allow the touch array to be scanned in “random access” mode, rather than just row-by-row. This can increase flexibility in interlacing touch sensing and display updating. For example  FIG. 76  illustrates a possible scan pattern. Because the system can scan the touch pixels in any desired pattern, a scan pattern can be designed that ensures that adjacent rows and adjacent pixels are never driven at the same time, thereby avoiding fringe field interaction that can result in signal loss or a lower signal-to-noise ratio. In  FIG. 76 , the squares  7601  and  7602  each comprise one drive electrode and one sense electrode. Squares  7601  correspond to in phase drive while squares  7602  correspond to 180 degree out-of-phase drive signal. In the figure, two rows (totaling twenty pixels) can be covered in five sequences, with four pixels scanned at a time. 
     2.3.1.9. Concept D 
     Another embodiment, Concept D, can support multi-touch sensing using two segmented ITO layers and an additional transistor for each touch pixel.  FIG. 77  shows a circuit diagram for Concept D. During display updates, the circuit can function as in a standard LCD display. Gate drive  7700  can drive two transistors (Q 1   7702  and Q 2   7704 ), thereby allowing signals from V COM  bus  7706  and data lines  7708  to transfer charge to a set of capacitors controlling the LC (C ST    7710 , C LC1    7712 , and C LC2    7714 ). When transistor Q 2   7704  is turned off V COM    7706  is disconnected from C ST    7710 , allowing V COM  line  7706  to be used for touch sensing. Specifically, V COM  line  7706  can be used to send charge through C IN    7716  and C OUT    7718 , through the data line  7708  (which acts as a touch sense line) into charge amplifier  7720 . A conductive object (such as a user&#39;s finger, stylus, etc.) approaching the display can perturb the capacitances of the system in a manner that can be measured by the charge amplifier  7720 . 
       FIGS. 78 and 79  show stackup diagrams for a sub-pixel in a Concept D-based display. In  FIG. 78 , the ITO 1  layer can be segmented into two plates, A  7722  and C  7726 . The ITO 2  layer can be segmented into islands (e.g., B  7724 ) that can be located over sub-pixels and serve as the counter-electrodes to the plates in the ITO 1  layer. During display update, voltage differences between island  7724  and the plates (A  7722 , C  7726 ) can be used to control liquid crystal  7804 . During touch sensing, perturbations to the capacitances throughout the subpixel (e.g., C LC1 , C LC2 , Cin, Cout, and Cst in  FIG. 77 ) can be measured to determine the proximity of a conductive object. 
       FIG. 80  shows a combined wiring and stackup diagram for Concept D.  FIG. 81  shows a physical realization for one embodiment of Concept D. 
     2.3.2. Fully-Integrated IPS-Based LCDs 
     In-plane switching (IPS), as illustrated schematically in  FIG. 82 , can be used to create LCD displays with wider viewing angles. While some LCDs (such as twisted nematic LCDs) use vertically-arranged electrode pairs (e.g., as shown in  FIG. 20 ), in IPS LCDs both electrodes  8201 ,  8202  used to control orientation of the liquid crystals  8203  can be parallel to one another in the same layer (e.g., in a single plane). Orienting the electrodes in this way can generate a horizontal electric field  8200  through the liquid crystal, which can keep the liquid crystals parallel to the front of the panel, thereby increasing the viewing angle. Liquid crystal molecules in an IPS display are not anchored to layers above or below (as shown in  FIG. 82 , for example), but instead can rotate freely to align themselves with electric field  8200  while remaining parallel to one another and the plane of the display electrodes.  FIG. 83  shows a more realistic arrangement of an interdigitated pair of electrodes  8301 ,  8302  in a display that can use in-plane switching. 
     Because IPS displays lack a V COM  layer that can also be used for touch drive or touch sense, some embodiments of the present invention can provide touch-sensing capabilities by allowing the same electrodes used for display updating to also be used for touch sensing. These electrodes can be complimented by additional circuitry. In some embodiments discussed above, touch pixels can overlap a large number of display pixels. In contrast, because the IPS embodiments discussed below can use the same electrodes used for display control and touch sensing, higher touch resolution can be obtained with little to no additional cost. Alternatively, a number of touch pixels can be grouped to produce a combined touch signal with a lower resolution. 
     2.3.2.1. Concept E 
     One IPS embodiment, Concept E, is illustrated in  FIG. 84 . As mentioned above, the electrodes in IPS-based touch sensing displays can be in the same plane and can have an interdigitated structure (as shown in  FIG. 84 ). While electrode A  8400  and electrode B  8402  can be used to orient the liquid crystal layer during display updating, these same electrodes can also be used (in combination with additional elements) to achieve touch sensing. For example, Concept E can use additional switches  8404  to change the drives for a set of signal lines based on whether the pixel is undergoing display updating or touch-sensing. Concept E can also include capacitances (CIN_A  8406 , COUT_A  8408 , CIN_B  8410 , and COUT_B  8412 ) and two transistors (transistor Q 1   8414  and transistor Q 2   8416 ) to control when the electrodes will be used for display updating or touch sensing. 
     During touch sensing, transistors Q 1   8414  and Q 2   8418  are turned off, disconnecting the electrodes from display signals and allowing the electrodes to be used to measure capacitance. The V COM  metal line  8416  can then be connected to touch stimulation signal  8418 . This stimulation signal can be sent through CIN_A  8406  and CIN_B  8410  to COUT_A  8408  and COUT_B  8412 , which can connect to charge amplifier  8422 . A capacitance C SIG  (not shown) between CIN and COUT can be used to detect touch. When the sense pixel is not being touched, charge delivered to the charge amplifier  8422  can depend mainly on the capacitance between the two pairs of CIN and COUT capacitors. When an object (such as a finger) approaches the electrodes, the C SIG  capacitance can be perturbed (e.g., lowered) and can be measured by charge amplifier  8422  as a change in the amount of charge transferred. The values for CIN and COUT can be selected to fit a desired input range for charge amplifier  8422  to optimize touch signal strength. 
     The electrodes can be used to perform touch sensing without negatively affecting the display state by using a high-frequency signal during touch sensing. Because LC molecules are large and non-polar, touches can be detected without changing the display state by using a high-frequency field that does not change or impose a DC component on the RMS voltage across the LC. 
       FIG. 85  shows a stackup diagram for Concept E. As described, all touch elements can be formed on TFT plate  8501 . 
     2.3.2.2. Concept Q 
     Another embodiment of an IPS-based touch-sensing display, Concept Q, also permits the TFT glass elements of an LCD (such as metal routing lines, electrodes, etc.) to be used for both display and touch sensing functions. A potential advantage of such an embodiment is that no changes to display factory equipment are required. The only addition to conventional LCD fabrication includes adding the touch-sensing electronics. 
     Concept Q includes two types of pixels, illustrated in  FIGS. 105 and 106 . Pixel type A is illustrated in  FIG. 105 . Each pixel  10501  includes three terminals, a select terminal  10502 , a data terminal  10503 , and a common terminal  10504 . Each of the A type pixels have their common terminal connected along columns  10505  to form touch-sensing columns. Pixel type B is illustrated in  FIG. 106 . Each pixel  10601  also includes three terminals, select  10602 , data  10603 , and common  10604 . Each of the B type pixels have their common terminal connected along rows  10605  to form touch sensing rows. The pixels can be arranged as shown in  FIG. 107  with a plurality of touch sense rows  10702  and a plurality of touch sense columns  10703 . A touch sensing chip  10701 , which can include the drive stimulation and sensing circuitry can be connected to the rows and columns. 
     The touch sensing chip can operate as follows. During a first time period, all of the rows and columns can be held at ground while the LCD is updated. In some embodiments, this may be a period of about 12 ms. During a next time period the A type pixels, i.e., touch columns, can be driven with a stimulus waveform while the capacitance at each of the B type pixels, i.e., touch rows, can be sensed. During a next time period, the B type pixels, i.e., touch rows, can be driven with a stimulus waveform while the capacitance at each of the A type pixels, i.e., touch columns, can be sensed. This process can then repeat. The two touch-sense periods can be about 2 ms. The stimulus waveform can take a variety of forms. In some embodiments it may be a sine wave of about 5V peak-to-peak with zero DC offset. Other time periods and waveforms may also be used. 
     2.3.2.3. Concept G 
     One issue that can arise in an IPS-based touch-sensing display is that a lack of shielding between the touch and the LC means a finger (or other touch object) can affect the display output. For instance, a finger touching the screen can affect the fields used to control the LC, causing the display to distort. One solution to this issue can be to put a shield (e.g., a transparent ITO layer) between the user and the display sub-pixels. However, such a shield can also block the electric fields used for touch sensing, thereby hindering touch sensing. 
     One embodiment, Concept G, overcomes this issue by flipping the layers of the display as shown in the stackup diagram in  FIG. 86 . This can place LC  8600  on the opposite side of the TFT plate  8602  from the user. As a result, the field lines used to control the LC  8600  can be generally oriented away from the touch side of the LCD. This can allow metal areas, such as the data lines, gate lines, and electrodes, that are now between the touching object and the LC  8600  to provide partial or full shielding for the LC. 
     2.3.2.4. Concept F 
     Another embodiment, Concept F (illustrated in  FIG. 87 ), can reduce display perturbation while leaving the LCD data bus unchanged (in relation to non-touch IPS displays) and without requiring additional ITO layers or making the alignment of layers more difficult. Instead of using a shared data line (as in Concepts E and G), Concept F can reduce potential display perturbation by adding a set of routed metal lines in a metal layer (M 1 ) that can serve as output sense lines  8700 . These output sense lines  8700  can run vertically underneath the display circuitry across the full area of the display, as shown in  FIG. 87  and in the stackup diagram for a Concept F sub-pixel shown in  FIG. 88 . By using a separate metal layer for output sense, Concept F can allow one of the transistors shown for Concept E ( FIG. 84 ) to be removed. Note also that Concept F flips the layers of the display to further reduce potential display perturbation, as described above with respect to Concept G. 
     3. Enabling Technologies 
     A variety of aspects can apply to many of the embodiments described above. Examples of these are described below. 
     3.1. DITO 
     In many embodiments, ITO may be deposited and patterned on two sides of a substrate. Various techniques and processes for doing so are described in U.S. patent application Ser. No. 11/650,049, titled “Double-Sided Touch Sensitive Panel With ITO Metal Electrodes,” filed Jan. 3, 2007, which is hereby incorporated by reference in its entirety. 
     3.2. Replacing Patterned ITO with Metal 
     Various embodiments can eliminate the patterned ITO layer that forms touch sense electrodes and replace this layer with very then metal lines deposited on one of the layers, for example, on the top glass. This can have a number of advantages, including eliminating an ITO processing step. Additionally, the sense line electrodes may be made quite thin (e.g., on the order of 10 microns), so that they do not interfere with visual perception of the display. This reduction in line thickness can also reduce the parasitic capacitance which can enhance various aspects of touch screen operation, as described above. Finally, because the light from the display does not pass through a layer substantially covered with ITO, color and transmissivity can be improved. 
     3.3. Use of Plastic for Touch Sense Substrate 
     Various embodiments described above have been described in the context of glass substrates. However, in some embodiments, cost savings and reduced thickness can be achieved by replacing one or more of these substrates with plastic.  FIGS. 89 and 90  illustrate some differences between glass-based systems, illustrated in  FIG. 89 , and plastic-based systems, illustrated in  FIG. 90 . Although illustrated in the context of one particular embodiment, the principle of substituting a plastic substrate may be applied to any of the concepts. 
       FIG. 89  illustrates a stack up of a glass based system. Dimensions illustrated are exemplary using current technology, but those skilled in the art will understand that other thickness may be used, particularly as the various fabrication technologies advance. Starting from the top, a cover  8901 , having an exemplary thickness of about 0.8 mm, can be above an index matching layer  8902  (e.g., approximately 0.18 mm thick). Below the index matching layer can be top polarizer  8903 . The top polarizer  8903  can have a thickness of approximately 0.2 mm. The next layer can be glass layer  8904  (e.g., about 0.5 mm thick) having ITO patterned on each side. Sense electrodes can be patterned on the top side, for example, which can also be bonded to FPC  8905 . The drive electrodes and V COM  layer for the LCD can be patterned on the bottom of glass layer  8905 . Below this can be another glass layer  8906 , having an exemplary thickness of about 0.3 mm, on which the TFT layers for the display can be formed. The top of this glass layer can also be bonded to FPC  8907  connecting to both the display and touch sensing circuitry  8908 . Below this can be the bottom polarizer, below which can be the display backlight  8910 . 
     The overall thickness from top to bottom can be approximately 2.0 mm. Various ASICs and discrete circuit components may be located on the glass or connected via the FPCs. Patterned ITO can be placed on another plastic layer, for example, the bottom side of the top cover, etc. 
       FIG. 90  illustrates a similar arrangement in which middle glass layer  9001  can be reduced in thickness by moving touch sense layer  9002  to plastic polarizer  9003 . Patterning touch sense layer  9002  on plastic polarizer  9003  can be accomplished by various known methods. Reduction in thickness can be accomplished because the glass need not be patterned on both sides. Because of handling issues, glass used in LCD processes may be processed at a thickness of about 0.5 mm, for example, and then ground down to about, 0.3 mm, for example, after processing. Having circuit elements on both sides precludes grinding down the glass. However, because in the embodiment of  FIG. 90  middle glass  9001  has electrodes patterned on only one side, it may be ground down, giving an overall thickness reduction of about 0.2 mm. This arrangement may include additional FPC connection  9004  to the polarizer, which can be bonded using a low temperature bonding process. An additional advantage of using a plastic substrate can arise in that materials with different dielectric constants can be used, which can provide flexibility and enhance operation of capacitive sensing circuits. 
     A variation on the plastic substrate embodiment is illustrated in  FIG. 91 . Electrodes  9101  (e.g., drive or sense lines) can be patterned on multiple plastic substrates  9102 ,  9103  that can then be adhered together. Because the plastic substrates can be thinner (e.g., approximately half the thickness of a glass substrate) such techniques can allow even thinner touch screens. 
     In another variation, illustrated in  FIG. 92 , polyester substrate  9201  can have electrodes  9202  patterned on either side. This embodiment can include an access hole  9203  through substrate  9201  for connection between the two sides. Polyester substrate  9201  can be disposed in cover  9204  of a device, such as a handheld computer. Still another variation is illustrated in  FIG. 93 , which illustrates a polyester layer  9301  having ITO electrodes  9302  patterned on a top surface, with access hole  9303  through substrate  9301  to a second glass substrate  9304 , also with ITO electrode  9305  patterned on the top surface. 
       FIG. 94  illustrates an upside down view of a device, for example a handheld computer  9401 . By upside down, it is meant that the user surface of the device is the bottom surface (not shown). ITO touch sensing electrodes  9402  can be patterned on the back of the user surface, with a stack up  9403  having ITO disposed on the facing surface being disposed therein during device assembly. A further variation of this concept is illustrated in  FIG. 95 , which shows ITO electrodes  9501  patterned on the inside of molded plastic cover  6702  and on the top of a stack up of layers  9503  according to one of the various embodiments discussed herein. In the diagram of  FIG. 95 , the user face of the device can be top surface  9504 . 
       FIGS. 96 ,  97 , and  98  illustrate a sequence of steps in manufacturing a polyester substrate having a pattern of ITO electrodes disposed thereon that may be suitable for touch sensing as described herein.  FIG. 96  illustrates a patterned polyester sheet  9601  patterned into a grid of isolated squares of ITO  9602 . The ITO resistivity can be about 200 ohms or less. The individual electrodes can be approximately 1 mm by 1 mm, with 30 micron gaps between. In the illustrated embodiment, sheet  9601  can be approximately 50 mm by 80 mm, which can be a suitable size for a handheld computer, multimedia player, mobile telephone, or similar device, although a variety of other sizes and/or applications will occur to those skilled in the art. As illustrated in the sectional view, the sheet may be as little as 25 microns thick, although dimensions of 25 to 200 microns may also be used. Obviously, this can provide significant advantages in terms of device thickness. 
     In  FIG. 97 , FPCs  9701  can be bonded to the patterned substrate  9702 . In  FIG. 98  cover  9801 , which can be, for example, an approximately 0.8 mm thick layer of PMMA, can be adhered to the PET substrate  9802  using an optically clear adhesive. 
     3.4. Level Shifter/Decoder Integration with LCD Controller 
     In some embodiments, additional circuitry (active, passive, or both) can be placed in the peripheral area of the LCD (see  FIG. 6 ) to support delivery of V STM  signals to the touch drive segments. Details of the peripheral area circuitry and its design rules can depend on the particular manufacturing process details and on which TFT technology (i.e., PMOS, NMOS or CMOS) is used. The following four sub-sections discuss approaches for realizing peripheral touch drive circuits in view of different drive circuit integration arrangements. 
     3.4.1. Discrete Level Shifter/Decoder Chip 
     In one approach, a discrete level shifter/decoder COG can be attached to the bottom glass (see  FIG. 22 ). In this arrangement metal traces may be needed in the peripheral area. The number of traces can depend on the number of touch drive segments, which may be less than twenty for small displays. Design objectives of this approach can include reducing capacitive coupling, which can be affected by the spacing between touch drive traces, and the space between the touch drive traces and other LCD circuits in the peripheral area. Low trace impedance can also help reduce capacitive coupling between adjacent touch drive traces. 
     For example, the combined resistance of the longest trace, the level shifter/decoder output resistance, the conductive dot, and the ITO drive segment may be limited to about 450 ohms. The resistance of the touch drive ITO may be around 330 ohms (assuming ITO sheet resistance of 30 ohms/sq and 11 squares), which can leave 120 ohms for other components. The following table shows one allocation of this resistance for each component in the touch drive circuit. 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                 Level shifter/ 
                   
                   
                   
               
               
                 decoder Output 
                 Metal Trace 
                 Conductive Dot 
                 ITO Segment 
               
               
                   
               
             
            
               
                 10 ohms 
                 100 ohms 
                 10 ohms 
                 330 ohms 
               
               
                   
               
            
           
         
       
     
     Wider traces and/or lower sheet resistances may be used to obtain the desired trace resistance. For example, for a trace resistance of 100 ohms, a trace width of 0.18 mm or more may be desirable if the sheet resistance is 200 mohms/sq. 
     Of course, only the longest touch drive traces need the greatest width. Other touch drive traces, being correspondingly shorter, may have correspondingly smaller widths. For example, if the shortest trace is 5 mm, then its width could be around 0.01 mm. 
       FIG. 99  shows a simplified diagram of the level shifter/decoder COG  9901  for Concept A. (For Concept B, transistor Q 1  and ENB_LCD[x] decoder can be eliminated.) Registered decoder block  9902  can be comprised of three separate registered decoders, which can be loaded one at a time. One of the three decoders can be selected by two signals from the Touch/LCD Driver and can be programmed using 5-bit data. The decoder outputs can control the three transistors Q 1 , Q 2 , Q 3  associated with each output section of the level shifter/decoder. Each output section can be in one of three states: 1) LCD (Q 1  on, Q 2  and Q 3  off), 2) touch (Q 2  on, Q 1  and Q 3  off), or 3) GND (Q 3  on, Q 1  and Q 2  off). As mentioned above, Q 2 &#39;s output resistance can be approximately 10 ohms or less to reduce V STM  phase delay. For Concept B, the LCD decoder and Q 1  can be eliminated. 
     3.4.2. Level Shifter/Decoder Fully-Integrated in Peripheral Area 
     The level shifter/decoder function ( FIG. 99 ) can also be fully integrated in the peripheral area of the bottom glass. With this approach, the type of TFT technology becomes relevant to power consumption. While CMOS TFT technology may give lower power consumption, it may be more expensive than NMOS or PMOS. However, any technology may be used depending on particular design constants. 
     To further reduce touch drive resistance, the transistor width may be enlarged to compensate for relatively low LTPS TFT mobility (e.g., ˜50 cm 2 /V*sec). 
     3.4.3. Level Shifter/Decoder Partially Integrated in Touch/LCD Driver 
     In some embodiments, the level shifter/decoder function can be partially integrated in the Touch/LCD Driver and partially integrated in the peripheral area. This approach can have several benefits including, for example, eliminating CMOS in the peripheral area, which can reduce cost, and eliminating logic in the peripheral area, which can reduce power consumption.  FIG. 100  shows a modified Touch/LCD Driver  10001  and peripheral transistor circuit  10002  that can be used in this approach. The level shifter and boost circuit  10003  can be integrated on the bottom glass and positioned between the segment drivers and the Touch/LCD chip. There can be one segment driver for each touch drive segment. Each touch drive segment can be in one of three states: GND, modulated by V STM , or modulated by V COM . In this arrangement level shifter circuits may be needed on the bottom glass to enable the low voltage Touch/LCD chip to control the transistor switches. 
     3.4.4. Level Shifter/Decoder Fully Integrated in Touch/LCD Driver 
     In some embodiments, the level shifter/decoder function can be completely integrated in the Touch/LCD Driver. By moving the Level shifter/decoder function to the Touch/LCD Driver, the separate level shifter/decoder COG can be eliminated. Furthermore, eliminating CMOS and logic from the peripheral area can be achieved. 
       FIG. 101  shows a simplified block diagram of the fully integrated Touch/LCD driver  10101 , which can include the boost circuitry  10102  to generate V STM . Passive components (such as capacitors, diodes, and inductors) may also needed, but, as with all the other approaches, have not been shown for simplicity. 
     4. Uses, Form Factors, etc. 
     Exemplary applications of the integral touch screen LCD described herein will now be described. Handheld computers can be one advantageous application, including devices such as PDAs, multimedia players, mobile telephones, GPS devices, etc. Additionally, the touch screen may find application in tablet computers, notebook computers, desktop computers, information kiosks, and the like. 
       FIG. 102  is a perspective view of an application of a touch screen  10201 , in accordance with one embodiment of the present invention. Touch screen  10201  can be configured to display a graphical user interface (GUI) including perhaps a pointer or cursor as well as other information to the user. By way of example, the touch screen may allow a user to move an input pointer or make selections on the graphical user interface by simply pointing at the GUI on the display  10202 . 
     In general, touch screens can recognize a touch event on the surface  10204  of the touch screen and thereafter output this information to a host device. The host device may, for example, correspond to a computer such as a desktop, laptop, handheld or tablet computer. The host device can interpret the touch event and can perform an action based on the touch event. The touch screen shown in  FIG. 102  can be configured to recognize multiple touch events that occur at different locations on the touch sensitive surface  10204  of the touch screen at the same time. As shown, the touch screen can, for example, generate separate tracking signals S 1 -S 4  for each touch point T 1 -T 4  that occurs on the surface of the touch screen at a given time. 
     The multiple touch events can be used separately or together to perform singular or multiple actions in the host device. When used separately, a first touch event may be used to perform a first action while a second touch event may be used to perform a second action that can be different than the first action. The actions may, for example, include moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device connected to the host device etc. When used together, first and second touch events may be used for performing one particular action. The particular action may for example include logging onto a computer or a computer network, permitting authorized individuals access to restricted areas of the computer or computer network, loading a user profile associated with a user&#39;s preferred arrangement of the computer desktop, permitting access to web content, launching a particular program, encrypting or decoding a message, and/or the like. 
     Referring back to  FIG. 102 , touch screen  10201  may be a stand alone unit or may integrate with other devices. When stand alone, touch screen  10201  can act like a peripheral device (e.g., a monitor) that can include its own housing. A stand alone display arrangement can be coupled to a host device through wired or wireless connections. When integrated, touch screen  10201  can share a housing and can be hard wired into the host device, thereby forming a single unit. By way of example, the touch screen  10201  may be disposed inside a variety of host devices including but not limited to general purpose computers such as a desktop, laptop or tablet computers, handhelds such as PDAs and media players such as music players, or peripheral devices such as cameras, printers, mobile telephones, and/or the like. 
       FIG. 103  is a block diagram of a computer system  10301 , in accordance with one embodiment of the present invention. Computer system  10301  may correspond to personal computer systems such as desktops, laptops, tablets or handhelds. By way of example, the computer system may correspond to any Apple or PC-based computer system. The computer system may also correspond to public computer systems such as information kiosks, automated teller machines (ATM), point of sale machines (POS), industrial machines, gaming machines, arcade machines, vending machines, airline e-ticket terminals, restaurant reservation terminals, customer service stations, library terminals, learning devices, and the like. 
     As shown, computer system  10301  can include processor  56  configured to execute instructions and to carry out operations associated  10302  computer system  10301 . For example, using instructions retrieved for example from memory, processor  10302  may control the reception and manipulation of input and output data between components of computing system  10301 . Processor  10302  can be a single-chip processor or can be implemented with multiple components. 
     In most cases, processor  10302  together with an operating system operates to execute computer code and produce and use data. The computer code and data may reside within program storage block  10303  that can be operatively coupled to processor  10302 . Program storage block  10303  can provide a place to hold data being used by computer system  10301 . By way of example, the program storage block may include read-only memory (ROM)  10304 , random-access memory (RAM)  10305 , hard disk drive  10306 , and/or the like. The computer code and data could also reside on a removable storage medium and loaded or installed onto the computer system when needed. Removable storage media can include, for example, CD-ROM, PC-CARD, floppy disk, magnetic tape, and a network component. 
     Computer system  10301  can also include an input/output (I/O) controller  10307  that can be operatively coupled to processor  10302 . I/O controller  10307  may be integrated with processor  56  or it may be a separate component as shown. I/O controller  10307  can be configured to control interactions with one or more I/O devices. I/O controller  66  can operate by exchanging data between the processor and the I/O devices that desire to communicate with the processor. The I/O devices and the I/O controller can communicate through data link  10312 . Data link  10312  may be a one way link or two way link. In some cases, I/O devices may be connected to I/O controller  10307  through wired connections. In other cases, I/O devices may be connected to I/O controller  10307  through wireless connections. By way of example, data link  10312  may correspond to PS/2, USB, Firewire, IR, RF, Bluetooth, or the like. 
     Computer system  10301  can also include display device  10308 , e.g., an integral touch screen LCD as described herein, that can be operatively coupled to processor  10302 . Display device  10308  may be a separate component (peripheral device) or may be integrated with the processor and program storage to form a desktop computer (all in one machine), a laptop, handheld or tablet or the like. Display device  10308  can be configured to display a graphical user interface (GUI) including, for example, a pointer or cursor as well as other information displayed to the user. 
     Display device  10308  can also include an integral touch screen  10309  (shown separately for clarity, but actually integral with the display) that can be operatively coupled to the processor  10302 . Touch screen  10309  can be configured to receive input from a user&#39;s touch and to send this information to processor  10302 . Touch screen  10309  can recognize touches and the position, shape, size, etc. of touches on its surface. Touch screen  10309  can report the touches to processor  10302 , and processor  10302  can interpret the touches in accordance with its programming. For example, processor  10302  may initiate a task in accordance with a particular touch. 
     The touch screen LCDs described herein may find particularly advantageous application in multi-functional handheld devices such as those disclosed in U.S. patent application Ser. No. 11/367,749, entitled “Multi-functional Hand-held Device”, filed Mar. 3, 2006, which is hereby incorporated by reference. 
     For example, principles described herein may be used to devise input devices for a variety of electronic devices and computer systems. These electronic devices and computer system may be any of a variety of types illustrated in  FIG. 104 , including desktop computers  10401 , notebook computers  10402 , tablet computers  10403 , handheld computers  10404 , personal digital assistants  10405 , media players  10406 , mobile telephones  10407 , and the like. Additionally, the electronic devices and computer systems may be combinations of these types, for example, a device that is a combination of personal digital assistant, media player and mobile telephone. Other alternations, permutations, and combinations of the aforementioned embodiments are also possible. 
     Moreover, the principles herein, though described with reference to capacitive multi-touch systems, may also apply to systems in which touch or proximity sensing depends on other technologies. It is therefore intended that the following claims be interpreted as including all alterations, permutations, combinations and equivalents of the foregoing.

Metadata:
Filing Date: 20070608
Publication Date: 20131008
Grant Date: 20131008
Priority Date: 20060609
Inventors: HOTELLING STEVE PORTER
CHEN WEI
KRAH CHRISTOPH HORST
ELIAS JOHN GREER
YAO WEI HSIN
ZHONG JOHN Z.
HODGE ANDREW BERT
LAND BRIAN RICHARDS
DEN BOER WILLEM
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/04184", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04112", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04164", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0444", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13338", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0443", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0444", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04164", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13338", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04112", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 39169105