BOROSILICATE GLASS COMPOUND FOR PRODUCING GLASS TUBE, AND USE OF THE SAME FOR PRODUCTION OF GLASS TUBE AND AS SLEEVE FOR LAMP

PROBLEM TO BE SOLVED: To provide a glass compound capable of forming a glass tube by a conventional tube-drawing process such as a Velo process or Danner process and giving glass tubes ideally having very little tendencies to cause deformation (shrinkage and bending) and to stick with each other at a processing temperature up to 700°C in a subsequent process.SOLUTION: The borosilicate glass includes, in terms of mol% of oxide, SiO74-81, BO8.5-14.5, AlO0.5-3.5, NaO 1.5-3.5, KO 1.0-2.0, LiO 0-1.0, MgO 0.5-1.5, CaO 0.5-1.5, BaO 0-0.6, TiO2.0-3.5 and ZrO0-1.0 and, as a clarifier, SbO0-0.15, CeO0-0.5 and SnO0-0.5 and has the molar ratio satisfying 0.4