Treatment of metal surfaces for the manufacture of lithographic plates

Claim 1

A LITHOGRAPHIC PLATE COMPRISING A METAL BASE A SURFACE OF WHICH BEARS A CONTINOUS, TRANSPARENT, WATER-IN SOLUBLE HYDROPHILLIC LAYER RESISTANT TO DILUTE ACIDS, TO ABRASION AND TO AIR OXIDATION AND WHICH IS FORMED BY COATING THE METAL BASE WITH A HOT AQUEOUS SOLUTION CONSISTING OF A PHOSPHATE GLASS SELECTED FROM THE CLASS CONSISTING OF ALKALI METAL AND ALKALINE EARTH PHOSPHATE GLASSES IN AN AMOUNT OF ABOUT 2 TO 1K% BY WEIGHT, AN ALKALI METAL SILICATE IN AN AMOUNT OF FROM ANOUT .5% TO 3% BY WEIGHT AND A COMPOUND SELECTED FROM THE CLASS CONSISTING OF ALKALI METAL AND ALKALINE EARTH METAL BORATES, -PHOSPHOMOLYBDATES AND -SILICOMOLYBDATES INAN AMOUNT OF ABOUT .5 TO 3% BY WEIGHT AND DRIED, SAID HYDROPHILIC LAYER ADHERING TENACIOUSLY TO THE SURFACE OF THE METAL BASE, SAID HYDROPHILIC BEING OVERCOATED WITH A WATER-SOLUBLE, HIGH MOLECULAR WEIGHT, LIGHT-SENSITIVE DIAZO COMPOUND CAPABLE OF BEING TANNED BY U.V. LIGHT, ASID SENSITIZER ADHERING TENACIOUSLY TO THE HYDROPHILIC SURFACE.