base plate 5 and a transparent film 6 is placed over the negative film 3 as shown in fig3 a generally rectangular frame 7 is placed on the transparent film 6 along its outer periphery a photosensitive liquid resin is poured into the interior of the frame 7 to form a photosensitive liquid resin layer 2 a transparent base film 11 is placed over the liquid resin layer 2 and the masking film 4 is further placed over the film 11 when required a transparent adhesive not shown having good adhesion to the photosensitive resin is applied to the lower surface of the transparent base film 11 in advance as shown in fig4 the resulting assembly is irradiated by light sources 51 from outside the transparent base sheet 5 and the masking sheet 4 to expose the resin to the light for 380 to 400 seconds when exposed the lower portion of the resin layer is cured in corresponding relation to the pattern 31 of the negative film 3 to form relief portions 21 toward the masking sheet 4 on the other hand the liquid resin layer 2 is cured to a large thickness in corresponding relation to the light transmitting patterns 44 46 of the first and second blocking films 43 45 to form mount portions 22 integral with the relief portions 21 where the light through the pattern 46 passes through the first blocking film i e semi light blocking film 43 and is thereby attenuated the upper portion of the resin layer is cured to a small thickness in corresponding relation to the pattern 46 to make a base portion 23 which is.