A substrate for a display device comprises a first pattern and a second pattern disposed within an active region of the substrate; a first overlay pattern disposed at corner regions of the active region and made of the same material as that of the first pattern; and a second overlay pattern disposed at corner regions of the active region and made of the same material as that of the second pattern, wherein the first overlay pattern includes gradations, and the second overlay pattern includes gradations to face the gradations of the first overlay pattern.