LIQUID CRYSTAL DISPLAY DEVICE

PURPOSE:To prevent the characteristics of a thin film transistor and a liquid crystal from being deteriorated by using a glass substrate having the composition constituted of an alkali ion of 10 - 15wt.% and forming the surface layer of a potassium ion having high density on the surface where the thin film transistor is formed. CONSTITUTION:In a liquid crystal display device where the plural thin film transistors are arranged on the glass substrate 31 in a matrix state, the glass substrate 31 has the composition constituted of the alkali ion of 10 - 15wt.% and the surface layer of the potassium ion 23 having the high density is formed on the surface where the thin film transistors are formed. That means, when a sodium ion 12 exists on the surface of the glass, the concentration of the sodium ion 12 is reduced, first. Next, the surface layer is formed by using potassium salt. Since the radius of the potassium ion 23 is larger than the sodium ion 12, the sodium ion 12 is restrained from being scattered to the surface by the existence of the potassium ion 23 on the surface even when the sodium ion 12 in the mesh structures 11 and 21 of the glass constituted by the bond Si - O is scattered. Thus, the characteristics of the thin film transistor and the liquid crystal are prevented from being deteriorated.