Method of depositing particulate solid material on selected portions of a substrate

Claim 1

IN THE METHOD OF DEPOSITING PARTICULATE SOLID MATERIAL ON SELECTED PORTIONS OF A SUBSTRATE, COMPRISING THE STEPS OF: FORMING ON SAID SUBSTRATE A LAYER MADE OF A COMPOSITION CONTAINING A PHOTOSENSITIZING SUBSTANCE, SAID PHOTOSENSITIZING SUBSTANCE IMPEDING THE TRANSMISSION OF RADIANT ENERGY OF A GIVEN FORM THROUGH SAID COMPOSITION AND SAID COMPOSITION HAVING A HARDNESS WHICH INCREASES AND A SOLUBILITY IN A GIVEN SOLVENT WHICH DECREASES, IN RESPONSE TO EXPOSURE OF SAID COMPOSITION TO RADIANT ENERGY OF SAID GIVEN FORM, BY RESPECTIVE AMOUNTS DIRECTLY DEPENDENT ON BOTH THE CONCENTRATION OF SAID PHOTOSENSITIZING SUBSTANCE AND THE QUANTITY OF RADIANT ENERGY OF SAID GIVEN FORM TO WHICH SAID COMPOSITION IS EXPOSED; EXPOSING THOSE REGIONS OF SAID LAYER OVERLYING SAID SELECTED PORTIONS OF SAID SUBSTRATE TO RADIANT ENERGY OF SAID FORM THROUGHOUT THE THICKNESS AND SAID LAYER, SAID EXPOSURE BEING SUFFICIENT TO RENDER SAID REGIONS SUBSTANTIALLY LESS SOLUBLE IN SAID GIVEN SOLVENT THAN THE UNEXPOSED REGIONS OF SAID LAYER; DEPOSITING SAID PARTICULATE MATERIAL ON AT LEAST THE EXPOSED PORTIONS OF THE SURFACE OF SAID LAYER OPPOSING AND REMOTE FROM SAID SUBSTRATE, AND WASHING SAID LAYER WITH SAID GIVEN SOLVENT SUFFICIENTLY TO REMOVE SELECTIVELY BOTH SAID UNEXPOSED REGIONS OF SAID LAYER AND PARTICLES OF SAID MATERIAL DEPOSITED ON SAID UNEXPOSED REGIONS, THE IMPROVEMENT WHICH COMPRISES FORMING SAID LAYER SO THAT THE THE CONCENTRATION OF SAID PHOTOSENSITIZING SUBSTANCE THEREIN DECREASES ALONG AT LEAST PART OF ITS THICKNESS FROM A GIVEN VALUE ADJACENT SAID SUBSTRATE TO A LESSER VALUE ADJACENT SAID OPPOSING SURFACE, WHEREBY ALL PARTS OF SAID LAYER CAN BE HARDENED APPROXIMATELY UNIFORMLY EVEN THOUGH THE PART THEREOF ADJACENT SAID OPPOSING SURFACE IS EXPOSED TO MORE RADIANT ENERGY OF SAID GIVEN FROM THAN OTHER PARTS THEREOF.