Patent ID: 9012047
Filing Date: 2015-04-21
Classification: C03C,G11B,Y10T

Abstract:
1. A magnetic disk glass substrate having a main surface, the magnetic disk glass substrate being used as a magnetic disk substrate adapted for a DFH (dynamic fly height) head, wherein a surface roughness Ra is 0.15 nm or less when a 2 μm×2 μm square measurement area of the main surface of the substrate is measured using an atomic force microscope with a resolution of 256×256 pixels, and wherein when laser light with a wavelength of 405 nm and a power of 25 mW is irradiated with a spot size of 5 μm onto the main surface of the substrate and scattered light from the main surface of the substrate is detected, a number of defects detected to have a size of 0.1 μm or more and 0.3 μm or less is less than 50 (0 exclusive) per 24 cm