A transparent substrate includes a stack of thin layers successively including, starting from the substrate, an alternation of three metallic functional layers, in particular of functional layers based on silver or on silver-comprising metal alloy, and of four antireflective coatings, each antireflective coating including at least one dielectric layer, so that each metallic functional layer is positioned between two antireflective coatings, wherein: the thicknesses of the metallic functional layers, starting from the substrate, increase as a function of the distance from the substrate, the second metallic functional layer is directly in contact with a blocking layer, referred to as second blocking layer, chosen from a blocking underlayer and a blocking overlayer, respectively referred to as second blocking underlayer and second blocking overlayer, the second blocking underlayer and/or the second blocking overlayer exhibits a thickness of greater than 1 nm.