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1. (WO2017061501) GLASS FOR DATA STORAGE MEDIUM SUBSTRATE, GLASS SUBSTRATE FOR DATA STORAGE MEDIUM, AND MAGNETIC DISK

Pub. No.:    WO/2017/061501    International Application No.:    PCT/JP2016/079688
Publication Date: Fri Apr 14 01:59:59 CEST 2017 International Filing Date: Thu Oct 06 01:59:59 CEST 2016
IPC: C03C 3/087
C03C 21/00
G11B 5/73
Applicants: ASAHI GLASS COMPANY, LIMITED
旭硝子株式会社
Inventors: MAEDA Eriko
前田 枝里子
HIJIYA Hiroyuki
土屋 博之
NAGAI Kensuke
永井 研輔
NAKASHIMA Tetsuya
中島 哲也
KUROIWA Yutaka
黒岩 裕
Title: GLASS FOR DATA STORAGE MEDIUM SUBSTRATE, GLASS SUBSTRATE FOR DATA STORAGE MEDIUM, AND MAGNETIC DISK
Abstract:
The present invention pertains to a glass for a data storage medium substrate which contains a specific amount of each of SiO2, Al2O3, MgO, CaO, SrO, BaO, Li2O, Na2O, and K2O, in molar percentage based on the oxides, and does not substantially contain B2O3 or ZrO2, wherein the sum of the Li2O, Na2O, and K2O contents (R2O), the molar ratio of the SiO2 content to the Al2O3 content (SiO2/Al2O3), and the molar ratio of the sum of the SiO2 and Al2O3 contents (SiO2+Al2O3) to R2O [(SiO2+Al2O3)/R2O] fall within their specific ranges, formula (1): 90 < [SiO2] + 2 × [Al2O3] + 0.8 × [RO] - 0.5 × [R2O] [in formula (1), RO represents the sum of the MgO, CaO, SrO, and BaO contents] is satisfied, and the glass transition point Tg, the alkali resistance, and the acid resistance fall within their specific ranges.