The present invention relates to the field of nanostructured acrylic polymer materials having both very good optical properties and good mechanical and surface properties. The invention relates to an acrylic resin composition containing a PMMA matrix (component 1) having a glass transition temperature of greater than 0° C., dispersed in which is an acrylic block copolymer (component 2). Characteristically, the composition of the invention contains from 60 to 80% by weight of said PMMA matrix, and from 20 to 40% by weight of said block copolymer. According to another aspect, the invention relates to a transparent flat article containing the aforementioned acrylic resin composition, having the following features: a thickness ranging from 300 to 900 microns, preferably from 400 to 700 micrometers; a light transmission at least equal to 91%; a haze of less than or equal to 2%; and no appearance of haze when the temperature rises to 80° C.