Gas-filled display devices have come into wide use, and these devices are generally of three types, D.C. devices, A.C. devices, and quasi A.C. devices. In D.C. devices, the panel electrodes are disposed within the gas filling of the panel; in A.C. devices, all of the electrodes are insulated from the gas filling by a glass coating; and, in quasi A.C. devices, there is a combination of electrodes, both in contact with and insulated from the gas filling by means of a glass coating formed thereon. When devices of the A.C. and quasi A.C. types are engineered, various factors including the various thermal coefficients of expansion must be taken into account, and, in selecting glasses for coatings, factors to consider are the thermal coefficient of expansion, light transmissivity, and softening temperature.
Up to the present time, glasses suitable for use in various types of display panels have all included lead. As is well known, lead is an undesirable element to have present in the manufacturing process. These lead glasses are readily degraded by thermal processing during fabrication operations and by high electric fields such as those encountered during device operation. In addition, the use of lead-bearing glasses presents a potential environmental and personnel health problem, and this requires complex and expensive protective measures to alleviate.
The present invention provides a new lead-free glass composition which is usable in display panels and the like devices.