GLASS-CERAMIC SUBSTRATE FOR AN INFORMATION STORAGE MEDIUM
First Claim
1. A glass-ceramic substrate for an information storage medium having Young'"'"'s modulus (GPa)/specific gravity of 37 or over and comprising 0 to less than 10 weight percent (expressed on oxide basis) of A2O3.
1 Assignment
0 Petitions
Accused Products
Abstract
There is provided a glass-ceramic substrate for an information storage medium usable in an information storage device of the ramp loading system. The glass-ceramic substrate has Young'"'"'s modulus (GPa)/specific gravity of 37 or over and includes 0 to less than 10 weight percent (expressed on oxide basis) of Al2O3. The glass-ceramic substrate has, as its predominant crystal phases, lithium disilicate (Li2O.2SiO2) and α-quartz (α-SiO2), has a coefficient of thermal expansion within a range from 65×10−7/° C. to 130×10−7/° C. wtihin a temperature range from −50° C. to +70° C. and has a surface roughness (Ra) (arithmetic mean roughness) of 9 Å or below.
-
Citations
13 Claims
- 1. A glass-ceramic substrate for an information storage medium having Young'"'"'s modulus (GPa)/specific gravity of 37 or over and comprising 0 to less than 10 weight percent (expressed on oxide basis) of A2O3.
-
11. A glass-ceramic substrate for an information storage medium having, as its predominant crystal phases, lithium disilicate (Li2O.2SiO2) and α
- -quartz (α
-SiO2) which have fine globular crystal grains and having a surface roughness Ra (arithmetic mean roughness) after polishing of 9 Å
or below.
- -quartz (α
-
12. A method for manufacturing a glass-ceramic substrate for an information storage medium which comprises steps of:
-
melting a base glass having a composition which consists in weight percent expressed on the basis of composition of oxides of;
SiO2 71-81% Li2O 8-11% K2O 0-3% MgO 0.3-2% ZnO 0-1% P2O5 1-3% ZrO2 0.5-5% TiO2 0-3% Al2O3 4-8% Sb2O3 0.1-0.50% SnO2 0-5% MoO3 0-3% NiO 0-2% CoO 0-3% Cr2O3 0-3% forming molten glass, annealing formed glass and then heat treating the formed glass for nucleation under nucleation temperature within a range from 550°
C. to 650°
C. for one to twelve hours and further heat treating the formed glass for crystallization under cyrstallization temperature within a range from 680°
C. to 800°
C. for one to twelve hours and polishing the glass-ceramic to a surface roughness (Ra) of 9 Å
or below.
-
Specification