A thin film transistor array panel for a flat panel display includes a substrate, a first signal line formed on the substrate, a second signal line intersecting and insulated from the first signal line, a switching element having a first terminal connected to the first signal line, a second terminal connected to the second signal line, and a third terminal, a pixel electrode connected to the third terminal of the switching element, and first and second light blocking members extending parallel to the second signal line, each being disposed on an opposite side of and partially overlapping an respective edge of the second signal line, an interval between the first and second light blocking members being in a range of from more than 1.5 μm to less than 4 μm. The array panel prevents light leakage from the display and improves its transmittance, aperture ratio and color reproducibility.