Layered, one-sided etched color selection electrode

Claim 1

FOR USE IN A COLOR CATHODE RAY TUBE A CURVED, LAYERED MASK HAVING ELECTRON-TRANSMISSIVE APERTURES ETCHED ONLY FROM ITS CONCAVE SIDE, SAID MASK COMPRISING: A CURVED, RELATIVELY THIN NICKEL APERTURE-DEFINING LAYER SUSCEPTIBLE OF BEING ETCHED BY A FIRST ETCHMENT, AT LEAST ONE INTERMEDIATE LAYER COMPOSED OF AN IRON-NICKEL ALLOY BONDED TO THE CONVEX SURFACE OF THE APERTURE-DEFINING LAYER AND BEING MORE EASLY ETCHED BY THE FIRST ETCHANT THAN THE APERTURE-DEFINING LAYER AND A RELAVATIVELY THICK STEEL SUBSTRATE LAYER BONDED TO THE CONVEX SURFACE OF THE INTERMEDIATE LAYER AND SUSCEPTIBLE OF BEING ETCHED BY A SECOND ETCHANT TO WHICH THE IMTERMEDIATE LAYER AND THE APERTURE-DEFINING LAYER ARE RELATIVELY RESISTANT ALL LAYERS ARE ETCHED THROUGH, AT SELECTED LOCATIONS, WITH A PATTERN OF APERTURES WHOSE WALLS HAVE A ONE-SIDED DOUBLE-ETCHED PROFILE AS WOULD BE FORMED BY ETCHING FROM THE CONCAVE SID OF THE MASK FIRST THROUGH THE APERTURE-DEFINING LAYER AND THE INTERMEDIATE LAYER WITH SAID FIRST ETCHANT AND THEN THROUGH THE SUBSTRATE LAYER WITH SAID SECOND ETCHANT AT THE LOCATIONS PREVIOUSLY ETCHED BY SAID FIRST ETCHANT.