In this paper, we describe the characteristics of Low‐pressure Cold Cathode Fluorescent Lamp for the uniformity of brightness. Cold Cathode Fluorescent Lamps are key parts of the TFT‐LCD display devices. The most commonly used lamps for the backlight units have a brightness overshoot phenomenon for the beginning of turn‐on time. Main reason for this artifact is widely known that plasma ions conflict strongly in the lamp having high gas pressure. In this paper, we have studied how much pressure is good for the brightness uniformity and how much gas pressure doesn't effect the life time and brightness of the lamps. There are three factors for the best brightness uniformity — Lamp, diffuser plate and BLU design of having heat‐Sink function. We show the experimental results of the relations of lamp pressure and brightness. And we suggest how we can find out the best method for the brightness uniformity of BLU.