New interesting Blackberry patent

SYSTEM AND METHOD OF INTEGRATING A TOUCHSCREEN WITHIN AN LCD

Abstract
A touchscreen liquid crystal display, method for using a liquid crystal display as a user input, and a mobile electronic device are provided. The touchscreen liquid crystal display comprises: a liquid crystal display having a viewing surface and including a plurality of parallel first electrodes located on one side of a liquid crystal containing area and overlapping with a plurality of parallel second electrodes located on an opposite side of the liquid crystal containing area, the first and second electrodes overlapping to form an array of liquid crystal pixel elements, at least some of the first electrodes being displaceable towards the second electrodes in response to external pressure applied to the viewing surface; a driver circuit coupled to the first and second electrodes for driving the electrodes for selectively controlling a display state of the display pixel elements; and a measurement circuit coupled to the electrodes for measuring display pixel element voltages for at least some of the display pixel elements formed by the first electrode, and for each display pixel element for which a display pixel element voltage is measured, comparing the measured voltages to reference voltages and determining a relative force of the external pressure on the viewing surface based on the measured voltages.

Description
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RELATED APPLICATION DATA

[0001] The present application is a continuation of non-provisional U.S. patent application Ser. No. 10/717,877, filed Nov. 20, 2003, which claims priority to provisional U.S. patent application Ser. No. 60/427,963, filed Nov. 21, 2002. The entire contents of non-provisional application Ser. No. 10/717,877 and of provisional application 60/427,963 are hereby incorporated by reference.

TECHNICAL FIELD

[0002] The present disclosure relates to the field of liquid crystal displays (LCDs), and more specifically to touchscreen LCDs.

BACKGROUND

[0003] Although there are several types of touchscreens possible, the two most commonly used touchscreens in handheld electronic devices are resistive and capacitive touchscreens.

[0004] Resistive touchscreens use a thin, flexible membrane over a glass substrate. The substrate surface and the facing membrane surface have a transparent metallic coating and are separated by spacers. When a user presses on the outer surface of the membrane, the inner surface of the membrane meets the substrate causing a change in resistance at the point of contact. A touchscreen controller measures this resistance using the membrane and the substrate as a probe. The two resistance measurements provide the x and y coordinates of the point of contact. Resistive touchscreens reduce the reflection and clarity of the LCD because of the added membrane layer and air gap in front of the surface of the LCD. A solution is required that does not require added layers that reduces the LCD visibility.

[0005] Capacitive touchscreens use a metallic coating on a glass sensor. Typically, voltage is applied to the four corners of the sensor. When the screen is not in use, the voltage spreads across the sensor in a uniform field. When the user touches the sensor, the touchscreen controller recognizes a disturbance of the field and sends the x-y coordinate of the point of contact to the CPU of the device. Capacitive touchscreens can only be used with a bare finger or conductive stylus. A touchscreen solution is required that can convert any touch into touchscreen data.

[0006] Resistive and capacitive touchscreens add thickness to the LCD module because of the added layers to provide touchscreen capabilities. With the demand for streamlining and minimizing the size of handheld devices, LCD modules need to be as thin as possible. A touchscreen solution is required to maximize the reflective characteristics of an LCD and to minimize the thickness of an LCD module.