Patent ID: 8951652
Filing Date: 2015-02-10
Classification: G01B,G06F,G11B,Y10T

Abstract:
1. A substrate for a magnetic recording medium having a disc shape with a central hole and having at least a magnetic layer on the surface of the substrate, wherein the substrate has a principal surface and a surface roughness of the principal surface of the substrate is 1 angstrom or less in terms of root mean square roughness (Rq) when a space period (L) of an undulation in a circumferential direction is in the range 10 to 1,000 μm, and wherein when a component in a vertical axis direction of a line segment Z connecting a point A with the space period (L) of 10 μm and a point B with the space period (L) of 1,000 μm in a curve S marked on a double logarithmic graph which is obtained by analyzing the surface roughness using a spectrum and in which a horizontal axis is set to the space period (L) (μm) and the vertical axis is set to a power spectrum density (PSD) (k·angstrom