Abstract: Disclosed herein is a base material having dyed membrane(s) on the surface thereof, the dyed membrane(s) being obtained by a process comprising the steps of applying a photoreactive resin composition (D), which comprises (i) a copolymer (A) of a vinyl monomer having photosensitive group(s) and another vinyl monomer which is copolymerizable with the vinyl monomer having photosensitive group(s) and has group(s) having an affinity for an anionic dyestuff, (ii) an initiator (B) of photo-reaction as an optional component of the photoreactive resin composition (D) and (iii) a solvent (C), onto the surface of the base plate, thereby forming a membrane from the thus applied resin composition (D) on the surface of the base material, irradiating the thus formed membrane(s) with activating light, thereby initiating a reaction in the membrane, and thereafter dyeing the thus treated membrane with the anionic dye.