The drive frequency of the high-frequency electric-field-coupled lamp was raised from 5 MHz of the previous report to 13.56 MHz, which resulted in reduced drive voltage, lower electrode temperature, and weaker Ne visible emission. These evidences show decrease in energy loss at the cathode fall region and also increase in efficacy. By optimizing electrode configuration, luminance uniformity in the axial direction of 74.8 % was attained. Average luminance of a 390 mm-long lamp was 2750 cd/m^2 with a diffuser plate. Since the lamp uses external electrodes, the lamp is expected to have a long life. Also the lamp length can be extended arbitrary to cope with large LCD areas by attaching multiple number of electrodes.
