High-and Uniform-Luminance Flat Discharge Lamp with Insulated Electrodes for LCD Backlighting

Abstract

An LCD backlight with an extremely simple structure has been developed utilizing a flat discharge volume with insulated electrodes, A 5.6-in. diagonal discharge volume is a mere open space. The thickness of the volume can be varied from device to device between 1 and 3 mm. Hg is admitted into the volume together with Ar. A pair of electrodes is provided at the top and bottom portions of the front glass plate, with a 70 μm-thick dielectric layer covering the electrodes. Phosphor is deposited on the rear glass plate so that visible emission can be extracted from the discharge volume efficiently. Each of the electrodes is driven by trains of negative pulses, 180° out of phase to each other. Luminance uniformity was measured to be within ±7% when a diffuser sheet is not used. Luminance can be dimmed down to 2% of the peak value by extending the pulse period. Since the conductive electrodes are insulated from the discharge, and since the phosphor is not attacked by ion bombardments, long lifetime can be expected.