Method of forming a reflection reducing coating

Claim 1

THE METHOD OF FORMING ON THE NORMALLY LIGHT REFLECTING SURFACE OF AN ARTICLE A SURFACE RAFLECTION REDUCING COATING HAVING AN INDEX OF REFRACTION PROGRESSIVELY INCREASING IN VALUE FROM APPROXIMATELY UNITY AT ITS AIR-INTERFACE TO A VALUE APPROACHING THAT OF THE ARTICLE AT ITS ARTICLE-INTERFACE, SAID METHOD COMPRISING THE STEPS OF APPLYING ONTO THE SURFACE OF SAID ARTICLE A SUBSTANTIALLY UNIFORM THIN LAYER OF A VOLATILE LIQUID CONTAINING SUBSTANTIALLY UNIFORMLY DISPERSED THEREIN A PLURALITY OF DISCRETE, SUB-MICROSCOPIC, MICROGRANULAR, APPROXIMATELY ISOMETRIC, TRANSPARENT PARTICLES OF SOLID, SUBSTANTIALLY ANHYDROUS, INORGANIC MATERIAL HAVING AN INDEX OF REFRACTION GREATER THAN UNITY, SAID PARTICLES BEING OF A DIAMETER LESS THAN 625 ANGSTROMS AND SUBSTANTIALLY INSOLUBLE IN THE LIQUID, SAID LIQUID FURTHER CONTAINING MINOR AMOUNTS OF A DECOMPOSABLE SILICON COMPOUND SOLUBLE IN THE LIQUID, THE LIQUID BEING SUBSTANTIALLY INERT IN ITS EFFECT ON SAID DECOMPOSABLE SILICON COMPOUND, THE PARTICLES AND SAID SURFACE OF THE ARTICLE, AND ALLOWING SAID LIQUID TO EVAPORATE TO DEPOSIT THE PARTICLES ON SAID SURFACE OF SAID ARTICLE AND TO SIMULTANEOUSLY CAUSE THE SILICON COMPOUND TO DECOMPOSE AND PRODUCE A THIN FILM OF SILICA ON THE PARTICLES, WHILE RETAINING THE PARTICLES SUBSTANTIALLY UNCHANGED IN THEIR PHYSICAL CHARACTER THROUGHOUT THE PROCESS, THE THICKNESS OF THE LIQUID LAYER APPLIED BEING CONTROLLED ACCORDING TO THE CONCENTRATION OF THE PARTICLES IN SAID LAYER TO PRODUCE A RESULTANT DRY LAYER OF SAID PARTICLES PILED IN A PLURALITY OF MOUND-LIKE PROJECTIONS TO APPROXIMATELY A QUARTER WAVE-LENGTH IN THICKNESS AND THE PROPORTION OF DECOMPOSABLE SILICON COMPOUND BEING CONTROLLED TO PERMIT THE FILM OF SILICA PRODUCED ON THE PARTICLES TO BE SUFFICIENT TO BOND THE PARTICLES TO EACH OTHER AND TO THE SURFACE OF THE ARTICLE WHILE MAINTAINING INTERCONNECTING INTERSTICES THEREBETWEEN, WHEREBY A SURFACE REFLECTION REDUCING COATING OF THE DESIRED CHARACTER RESULTS.