GLASS SUBSTRATE FOR MAGNETIC DISK AND MAGNETIC DISK

• Main Authors: SHIDA NORIHITO, ITO MASABUMI, TAKANO SHIGEKI, OTSUKA HARUHIKO
• Format: Patent
• Language: English; Japanese
• Published: 23.05.2016
• Subjects: INFORMATION STORAGE; INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORDCARRIER AND TRANSDUCER; PHYSICS

PROBLEM TO BE SOLVED: To provide a glass substrate for a magnetic disk that is compatible with high recording density.SOLUTION: A glass substrate for a magnetic disk is characterized as follows: the glass substrate for the magnetic disk is provided with a main surface; an arithmetic average roughness Ra measured by an atomic force microscope in the main surface is 0.15 nm or less; an angular direction arithmetic average roughness Ra_deg in each angular direction of a predetermined area is calculated, based on results measured by the atomic force microscope, while changing an angular direction from 0° to 180° every 1°; and the value of (Ra_deg_max)/(Ra_deg_min) is 2.6 or less when the highest value among the calculated angular direction arithmetic average roughness Ra_deg is assumed as a maximum angular direction arithmetic average roughness Ra_deg_max, and the lowest value is assumed as a minimum angular direction arithmetic average roughness Ra_deg_min. Thereby, the problem is solved by providing the glass substrate for the magnetic disk.SELECTED DRAWING: Figure 3 【課題】高記録密度化に対応した磁気ディスク用ガラス基板を提供する。【解決手段】主表面を有する磁気ディスク用ガラス基板であって、前記主表面において原子間力顕微鏡により測定した算術平均粗さＲａが０．１５ｎｍ以下であって、原子間力顕微鏡により測定した結果に基づき、所定の領域を、角度方向を０°から１８０°まで１°ごとに変化させながら各々の角度方向における角度方向算術平均粗さＲａ＿ｄｅｇを算出し、前記算出された角度方向算術平均粗さＲａ＿ｄｅｇのうち、最も大きい値を角度方向算術平均粗さ最大値Ｒａ＿ｄｅｇ＿ｍａｘとし、最も小さい値を角度方向算術平均粗さ最小値Ｒａ＿ｄｅｇ＿ｍｉｎとした場合に、（Ｒａ＿ｄｅｇ＿ｍａｘ）／（Ｒａ＿ｄｅｇ＿ｍｉｎ）の値が、２．６以下であることを特徴とする磁気ディスク用ガラス基板を提供することにより上記課題を解決する。【選択図】 図３