Method of processing a cathode-ray tube for eliminating blocked

Abstract

A method is proposed for eliminating so-called halo blocked apertures in color picture cathode-ray tubes. The cathode-ray tube comprises an evacuated envelope having therein a luminescent viewing screen, an electron gun for producing at least one electron beam for exciting the screen to luminescence and an apertured mask closely spaced from the screen for selectively intercepting and transmitting portions of the electron beam. A getter is provided for coating an interior surface of the apertured mask with a gas-sorbing, conductive getter material film. The halo blocked apertures are caused by insulative negatively-charged particles attached to the interior surface of the apertured mask. The conventional tube processing includes the steps of getter flashing, cathode discharge ball gap, cathode conversion, hot shot, first low voltage age, implosion proofing, external coating, frit breakdown check, radio frequency spot knock and final low voltage age. The improved method comprises controlling the getter flashing step so that the getter yields a primary film having about 50 to 75 percent of the available getter material. The getter is reactivated subsequent to the frit breakdown check step and before the final low voltage age step to provide a secondary film of getter material on the interior surface of the mask which will render conductive the insulative particles attached to the interior surface of the apertured mask.