LCD with self regulating PTC thermistor heating element

Claim 1

In a heated liquid crystal display the combination comprising: a liquid crystal cell containing a liquid crystal material and said liquid crystal cell having a back; a support member placed in physical contact with said back of said liquid crystal cell; said support member having substantially planar and substantially parallel opposite surfaces and an outer periphery; said support member being of a material that is pervious to light such that a source of illumination positioned adjacent one of said surfaces will illuminate objects positioned adjacent the other of said surfaces; heater means mounted on said support member in a heat transfer relationship therewith for heating said support member; said heater means including positive temperature coefficient thermistor means switchable between high and low resistance states in a predetermined ambient temperature range; said thermistor means performing the dual functions of heating and determining when heating occurs; said heater means occupying not more than 20% of the areas of one of said opposite surfaces; and a light source for illuminating said display; said light source positioned on the opposite side of said support member from said liquid crystal cell.