TH24237B - Glass substrate for recording media - Google Patents

Abstract

In the DC60 magnetic recording medium, the surface roughness of the glass substrate and the variation of the inhibited surface roughness, i.e., surface roughness (Rmax, Ra, Rq) and the relationship (Rmax/Ra) between Rmax and Ra, restricted by Ra, show the centerline average roughness. Rmax is defined by the maximum height, showing the difference between the peak and the trough, and Rq shows the root mean square roughness. Therefore, the fine grain of the crystalline layer below and the magnetic layer built on it are equal. The surface roughness is defined specifically by Rmax ≤ 15 nm, Ra ≤ 1 nm, and Rq ≤ 1.5 nm, and the ratio between the surface roughness Rmax and the surface roughness Ra is in the range of 10⁻³⁰. In the magnetic recording medium, the surface roughness of the glass substrate and the variation of... Inhibited surface roughness, i.e., surface roughness (Rmax Ra, Rq) and the relationship (Rmax/Ra) between Rmax and Ra, restricted by Ra, shows the centerline average roughness. Rmax is defined by the maximum height, showing the difference between the peak and the trough, and Rq shows the root mean square roughness. Therefore, the fine grain of the crystalline layer below and the magnetic layer built on it are equal. Surface roughness is defined specifically by Rmax ≤ 15 nm, Ra ≤ 1 nm, and Rq ≤ 1.5 nm, and the ratio between surface roughness Rmax and surface roughness Ra is in the range of 10⁻³⁰.

Claims (3)

1. A glass substrate for use as a data recording medium has surface roughness values Ra, Rmax, and Rq, where Ra is represented as linear mean roughness, Rmax is defined as the maximum height representing the difference between the highest and lowest points, and Rq is represented as the root mean square roughness. Surface roughness is defined as Rmax ≤ 15 nm, Ra ≤ 1 mm, and Rq ≤ 1.5 nm. The Rmax/Ra ratio falls within the range of 10⁻⁶ and 30, and surface roughness is measured using an interatomic force microscope. 2. Glass substrates as claimed in Reputation 1, where the surface roughness is defined by Rmax less than or equal to 10 nm, Ra less than or equal to 0.5 nm, and Rq less than or equal to 0.7 nm. 3. Glass substrates as claimed in Reputation 1, where the surface roughness is defined by Rmax less than or equal to 5 nm, Ra less than or equal to 0.3 nm, and Rq less than or equal to 0.4 nm.