Since launching the world's first LCD for automotive, we have devoted to improve LCD reliability and supplied LCD to various automotive interior parts. In recent HUD, luminance and temperature have been increasing, and light leakage may occur as a specific problem. As a result of investigation, it was found that the uneven distribution of the temperature on the polarizer could be the root cause of the shrinkage. Proper introduction of wire-grid substrate can be an effective countermeasure to improve the light leakage.