BLACKENING FURNACE AND MANUFACTURE OF SHADOW MASK USING SAID BLACKENING FURNACE

摘要

PURPOSE: To provide a shadow mask with a uniformly thick black oxide film without any film irregularity by dividing furnace body in tunnel shape into two zones, supplying a mixed gas that contains carbon dioxide and carbon monoxide and steam in some cases and does not contain oxygen into a first zone at an entrance side, supplying a mixed gas that contains carbon monoxide and oxygen but does not contain steam into a second zone at an exit side, and performing blackening treatment at a specific temperature. CONSTITUTION: At a heating room 4, when a treatment material is an invar alloy, heating is made for approximately 30 minutes at 500-650 deg.C within an ambient of mixed gas of 5-20 CO2 and 30-50 steam for 1 CO, thus reducing the amount of O2 , suppressing the rapid oxidation of an invar material surface, and forming a uniform black oxide film of Fe3 O4 without any irregularities on the surface. Then, a shutter 7d is opened and closed and is rapidly carried to a cooling room 5, and the treatment material is cooled for approximately 30 minutes under temperature conditions of approximately 200 deg.C in mixed gas atmosphere consisting of air CO2 and CO, thus obtaining an intricate black oxide film of improved adhesion property and sufficient thickness.