US 12,266,389 B2
Magnetic disk substrate, magnetic disk, annular-shaped substrate, and method for manufacturing magnetic disk substrate
Shuhei Azuma, Hung Yen Province (VN); and Toshio Takizawa, Akishima (JP)
Assigned to HOYA CORPORATION, Tokyo (JP)
Appl. No. 18/547,572
Filed by HOYA CORPORATION, Tokyo (JP)
PCT Filed Feb. 24, 2022, PCT No. PCT/JP2022/007710
§ 371(c)(1), (2) Date Aug. 23, 2023,
PCT Pub. No. WO2022/181715, PCT Pub. Date Sep. 1, 2022.
Claims priority of application No. 2021-027888 (JP), filed on Feb. 24, 2021.
Prior Publication US 2024/0135970 A1, Apr. 25, 2024
Prior Publication US 2024/0233764 A9, Jul. 11, 2024
Int. Cl. G11B 5/73 (2006.01); G11B 5/82 (2006.01); G11B 5/84 (2006.01)
CPC G11B 5/73921 (2019.05) [G11B 5/82 (2013.01); G11B 5/84 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A magnetic-disk substrate comprising:
two main surfaces; and
an outer circumferential edge surface,
wherein the outer circumferential edge surface includes two chamfered surfaces that are respectively connected to the main surfaces, and a side wall surface that extends between the two chamfered surfaces,
the side wall surface is a curved surface that protrudes outward,
the side wall surface has a radius of curvature of 1100 μm or more on a cross-section of the magnetic-disk substrate extending along a plate thickness direction of the magnetic-disk substrate, and
the magnetic-disk substrate has a plate thickness of less than 0.6 mm.