Planographic printing plate

Claim 1

A METHOD OF MAKING A DIRECT IMAGE PAPER BASE PLANOGRAPHIC PRINTING PLATE COMPRISING COATING THE ENTIRE SURFACE OF A HIGH WET-STRENGTH HARD SYNTHETIC THERMOPLASTIC RESIN-PRINTED PAPER BASE SUPPORT WITH A FIRST COATING COMPOSITION TO PROVIDE AN INTERMEDIATE MICROPOROUS LAYER, SAID COATING COMPOSITON CONSISTING OF 10 TO 50 PARTS OF ADHESIVE BINDER PER 100 PARTS OF MINERAL PIGMENT, SAID MINERAL PIGMENT CONSISTING OF FROM ABOUT 20 TO ABOUT 40 PARTS OF ZINC OXIDE AND FROM ABOUT 80 TO ABOUT 60 PARTS OF HYDROUS CLAY, SAID ADHESIVE BINDER BEING A ZINC AMMONIA CASEIN COMPLEX CONTAINING FROM ABOUT 1 TO ABOUT 6% OF ZINC METAL BY WEIGHT OF THE CASEIN, THEREAFTER APPLYING A SECOND COATING OVER THE INTERMEDIATE MICROPOROUS COATING TO GIVE A HARD TOP COATING, SAID SECOND COATING CONSISTING OF ALKALI-STABILIZED COLLOIDAL SILICA WITH UP TO 35 PARTS OF SYNTHETIC RESIN PER 100 PARTS OF SILICA, SAID SYNTHETIC RESIN BEING SELECTED FROM THE GROUP CONSISTING OF UREA-FORMALDEHYDE, MELAMINE FORMALDEHYDE, AND MIXTURES OF UREA-FORMALDEHYDE, MELAMINE FORMALDEHYDE AND MIXTURES OF UREA-FORMALDEHYDE AND MELAMINE FORMALDEHYDE, SAID SILICA HVING A PARTICLE SIZE OF 1 TO 100 MILLIMICRONS, A MOLECULAR WEIGHT AS DETERMINED BY LIGHT SCATTERING OF MORE THAN ONE-HALF MILLION, THE ALKALI FOR STABILIZING SAID COLLOIDAL SILICA BEING ALL OUTSIDE THE SILICA PARTICLES AND HAVING A SILICA TO ALKALI RATIO OF FROM ABOUT 60:1 TO ABOUT 130:1, THE SILICA BEING DEPOSITED FROM AQUEOUS COLLOIDAL DISPERSION AT ALKALINE PH BY TREATING WITH VOLATILE ACID, EVAPORATING SAID TOP COATING AND CALENDERING THE COATED SHEET UNDER HIGH PRESSURE.