Optical layered body, polarizer, and image display device

The present invention provides an optical layered body having excellent hardness, abrasion resistance, and flexibility. The present invention provides an optical layered body having a hard coat layer on one side of a triacetylcellulose substrate, wherein a Martens hardness (N1) of a surface of the hard coat layer, a Martens hardness (N2) of the center of the cross-section of the hard coat layer, and a Martens hardness (N3) of the center of the cross-section of the triacetylcellulose substrate have a relationship of N2>N1>N3 as determined by nanoindentation, and the hard coat layer has a pencil hardness of 4H or more as measured by a test in accordance with a pencil hardness test defined in JIS K5600-5-4 (1999) at a load of 4.9 N.