The invention relates generally to displays having pixels that include capacitive elements, and more particularly to displays in which capacitive elements of the pixels that form part of the display system that generates an image on the display also form part of a touch sensing system that senses touch events on or near the display. A touch screen including display pixels with capacitive elements is provided.
The touch screen includes first common voltage lines connecting capacitive elements in adjacent display pixels, and a second common voltage line connecting first common voltage lines. The pixels can be formed as electrically separated regions by including breaks in the common voltage lines. The regions can include a drive region that is stimulated by stimulation signals, a sense region that receives sense signals corresponding to the stimulation signals. A grounded region can also be included, for example, between a sense region and a drive region. A shield layer can be formed of a substantially high resistance material and disposed to shield a sense region. A black mask line and conductive line under the black mask line can be included, for example, to provide low-resistance paths between a region of pixels and touch circuitry outside the touch screen borders.
Here's Apple's background and summary of the invention: "Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location dictated by a user interface (UI) being displayed by the display device. In general, touch screens can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.
"Mutual capacitance touch sensor panels can be formed from a matrix of drive and sense lines of a substantially transparent conductive material, such as Indium Tin Oxide (ITO), often arranged in rows and columns in horizontal and vertical directions on a substantially transparent substrate. It is due in part to their substantial transparency that capacitive touch sensor panels can be overlaid on a display to form a touch screen, as described above. However, overlaying a display with a touch sensor panel can have drawbacks, such as added weight and thickness, and decreased brightness of the display.
"This relates to displays including pixels with dual-function capacitive elements. Specifically, these dual-function capacitive elements form part of the display system that generates an image on the display, and also form part of a touch sensing system that senses touch events on or near the display. The capacitive elements can be, for example, capacitors in pixels of an LCD display that are configured to operate individually, each as a pixel storage capacitor, or electrode, of a pixel in the display system, and are also configured to operate collectively as elements of the touch sensing system. In this way, for example, a display with integrated touch sensing capability may be manufactured using fewer parts and/or processing steps, and the display itself may be thinner and brighter."
The inventors are Steve Porter Hotelling, Shih Chang Chang, Lili Huang and John Z. Zhong. The graphic below illustrates a partial circuit diagram of an example LCD display including a plurality of LCD pixels according to embodiments of the present invention.
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