A method of manufacturing a thin film transistor array substrate that includes photolithographically forming an active layer on a substrate. , whereby a homogeneous mixture in the molten state is formed, in which the sodium initially introduced is in the sodium oxide state; and recovering the molten mixture thus obtained and cooling it, whereby a vitrified matrix of homogeneous composition is obtained that incorporates the initially introduced sodium as constituent oxide of the said vitrified matrix. A negative pressure region that can be generated at a back surface side of the vehicle is reduced and, therefore, air resistance of the vehicle is reduced and fuel economy is enhanced.