The present disclosure relates to a digital X-ray detector and a thin-film transistor array substrate for the same. Disclosed is a thin-film transistor array substrate for a digital X-ray detector in which deterioration of electrical characteristics of a thin-film transistors made of an oxide semiconductor may be reduced or minimized and aging of a PIN diode caused by external moisture may be reduced or minimized. Further, disclosed is a digital X-ray detector including the array substrate. To this end, the array substrate includes a second protective layer having a variety of patterns so as to cover at least a portion of the PIN diode but not to cover the thin-film transistor. The second protective layer includes SiNx. Thus, a de-hydrogenation path from the thin-film transistor may be secured and an external moisture barrier effect for the PIN diode may be achieved.