A thin film transistor substrate for a display device having a plurality of thin film transistors and pixel electrodes connected to the thin film transistors, said thin film transistor substrate includes: a plurality of pad electrodes in a non-display area of the display device for applying signals to the plurality of thin film transistors in a non-display area of the display device; a protective film covering the pad electrodes in the non-display area; and a slit in the protective film adjacent to at least one of the plurality of pad electrodes.