Patent ID: 6495480
Filing Date: 2002-12-17
Classification: C03C,G11B

Abstract:
A glass-ceramic substrate for an information storage medium made of a glass-ceramic having a crystal phase dispersed in a glass matrix wherein a ratio of the crystal phase (the amount of crystal) in the glass-ceramic is within a range from 50 wt % to 70 wt % and said glass-ceramic substrate has a microstructure in the surface portion thereof exhibiting excellent adhesion Niâ€”P plating, said microstructure being comprised of crystal grains having an average crystal grain diameter within a range from 0.10 &mgr;m to 0.50 &mgr;m and being exposed above the glass matrix on the surface of the substrate, said glass-ceramic containing less than 20% by weight of aluminum oxide, wherein said glass-ceramic contains, as its predominant crystal phase or phases at least one crystal selected from the group consisting of cordierite (Mg2Al4Si5O18), cordierite solid solution (Mg2Al4Si5O18) solid solution), Spinel ((Mg or Zn) (Al or Ti)2O4, Spinel solid solution ((Mg or Zn) (Al or Ti)2O4), enstatite (MgSiO3), enstatite solid solution (MgSiO3 solid solution), quartz (SiO2) and quartz solid solution (SiO2), and wherein the glass ceramic has a composition which comprises, in weight percent:SiO2â€‰40-60%MgOâ€‰10-18%MgO + ZnOâ€‰10-18%Al2O3â€‰10-less than 20%CaO0.5-4%TiO22.5-8%.