Sumita Optical Glass Inc. has developed a long-lasing luminescent glass that can be produced in the same manner as conventional glass. Appli-cations for the glass include high-density recording in the x-ray imaging and data processing fields. One type the company has developed is an oxide glass that contains a small amount of terbium, a rare-earth ion. The accumulation of light in the glass is possible with UV to visible light, and the afterglow, which is green, lasts more than 10 hours. The company also has developed a red glass.