ACTIVE MATRIX LIQUID CRYSTAL DEVICE

摘要

An active matrix liquid crystal device (AMLCD) comprises an active matrix substrate (1) having an active matrix area (2) and a counter electrode substrate carrying a common electrode whose voltage may vary so as to reduce liquid crystal degradation. A layer of liquid crystal material is disposed between the substrates and a temperature measuring arrangement (10) is provided on the active matrix substrate (1). This arrangement (10) comprises a temperature sensing liquid crystal capacitor (11) which in turn comprises a first electrode formed on the active matrix substrate (1) outside the image generating region of the active matrix area (2) and separated from the common electrode, which forms the second electrode of the capacitor, by the liquid crystal layer, which forms the capacitor dielectric. During operation of the active matrix, a measuring circuit (12, 13, 15) repeatedly performs a precharging step, in which the capacitor (11) is precharged to a fixed stable known voltage magnitude, and a step in which a signal representing the capacitance is formed. For example, the charge stored in the capacitor (11)may be charge-shared with a transfer capacitor to form thereacross a voltage representing the capacitance of the liquid crystal capacitor (11) and hence representing the liquid crystal temperature. The sampling is performed repeatedly, preferably in synchronism with addressing performed by the active matrix of the device. The resulting temperature measurement may be used, for example, to compensate the AMLCD for the effects of temperature variation in the liquid crystal properties.