PURPOSE: To prevent the deterioration of the printing quality of patterns due to abrasion and at the same time to reduce the influence of dust and scratches upon the reading of patterns.

CONSTITUTION: An optically almost-transparent protective film 14 provided on the surface of an information recording medium 10 on which dot patterns 12 are printed prevents the deterioration of the printing quality of the dot patterns 12 due to abrasion. Further, the protective film 14 is formed so as to have such an optical thickness that the contrast of the dot patterns 12 is lowered by a predetermined quantity. Thereby, dust 30 which adheres onto the protective film 14 and scratches make an out-of-focus image on the surface 22 of an image pick-up element, so that the influence of dust and scratches upon the reading of the dot patterns 12 my be reduced.