Presensitized diazo lithographic printing plates comprising a hydrophilic phosphate glass and fluoride layer

Claim 1

A STABLE PRE-SENSITIZED PHOTOLITHOGRAPHIC PRINTING PLATE CAPABLE OF BEING STORED IN LIGHT-PROOF PACKAGES SUBSTANTIALLY INDEFINITELY UNDER CONDITIONS OF EXTREME VARIATIONS IN TEMPERTURE AND HUMIDITY WITHOUT AFFECTING THE QUALITY OF SAID PLATES, COMPRISING A BASE METAL SHEET HAVING DEPOSITED ON AT LEAST ONE SURFACE THEREOF AN INITIAL HYDROPHILIC COATING FORMED FROM A SOLUTION COMPRISING AS THE SOLE CONSTITUENTS TO RENDER SAID BASE METAL SHEET SURFACE HYDROPHILIC AN ALKALI METAL PHOSPHATE GLASS AND A FLUORIDE SELECTED FROM THE GROUP CONSISTING OF SODIUM FLUORIDE AND POTASSIUM HEXAFLUOTITANATE AND A COATING OF AN AQUEOUS SOLUBLE LIGHT-SENSITIVE DIAZO RESIN OVERLYING SAID HYDROPHILIC COATING, SAID LIGHT SENSITIVE DIAZO RESIN BEING SUCH THAT, WHEN THE PLATE IS EXPOSED TO A SOURCE OF ULTRAVIOLET LIGHT THROUGH A NEGATIVE OR A STENCIL, THE EXPOSED PORTION OF SAID LIGHT SENSITIVE DIAZO RESIN WILL REACT TO PROVIDE A TANNED, INSOLUBLE IMAGE, THE UNEXPOSED PORTIONS OF THE LIGHT-SENSITIVE DIAZO RESIN BEING CAPABLE OF BEING WASHED AWAY, THEREBY UNCOVERING THE INITIAL COATING UNDER SAID UNEXPOSED PORTIONS.