Abstract: A light transmitting plate member for illuminated signals, illuminated tas or similar illuminated flat items and intended for uniform diffusion of light from a light source positioned at a side edge of the light transmitter which has a flat side and an opposing side which has a gradual slope. The plate member has a reduced thickness in the direction away from said side edge, with the opposite sides being produced with optically smooth surfaces as the light transmitting plate member includes transparent and light transparent material with specific optical properties. The side with the gradual slope is provided with a number of angled divisions which are defined by transverse divisional lines which run parallel to the side edge and which are positioned with either uniform intervals or with graded intervals which are reduced in the direction receeding from the side edge.