# US 10,319,403 B2 · Magnetic-disk substrate, magnetic disk, and method for manufacturing magnetic-disk substrate > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,319,403 B2 - Document ID: US10319403B2 - Status: Granted - Kind: B2 - Application number: 15/545,969 - Filed: 2016-03-31 - Published: 2018-01-04 - Granted: 2019-06-11 - Earliest claimed: 2015-03-31 - Assignees: Hoya Corporation - Applicants: Hoya Corporation - Inventors: Masanobu Itaya; Kinobu Osakabe - Web page: https://patentgrep.com/patent/US10319403B2 ## CPC - G11B 5/82: Disk carriers - G11B 5/73913: {Composites or coated substrates} - G11B 5/73919: {Aluminium or titanium elemental or alloy substrates} - G11B 5/73921: {Glass or ceramic substrates} - G11B 5/84: Processes or apparatus specially adapted for manufacturing record carriers - G11B 5/8404: {manufacturing base layers} - B82Y 10/00: Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic - B82Y 40/00: Manufacture or treatment of nanostructures - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) - B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES ## Abstract A magnetic-disk substrate has a pair of main surfaces and arithmetic average roughnesses Ra of the main surfaces are each 0.11 nm or less. Also, in surface unevenness of the main surfaces, an average area of regions occupied by a plurality of protrusions having a height of 0.1 nm or more from an average plane of the surface unevenness is 25 nm2/protrusion or less. The arithmetic average roughness Ra and the surface unevenness are measured using an atomic force microscope with a probe having a probe tip provided with a carbon nanofiber rod-shaped member. ## Claims ### Claim 1 A magnetic-disk substrate, comprising: a pair of main surfaces, an arithmetic average roughness Ra of each of the main surfaces being 0.11 nm or less, and the arithmetic average roughness Ra being a value obtained through measurement using an atomic force microscope provided with a probe having a probe tip provided with a carbon nanofiber rod-shaped member. ### Claim 2 (depends on 1) The magnetic-disk substrate according to claim 1, wherein an average area of regions occupied by a plurality of protrusions having a height of 0.1 nm or more from an average plane of surface unevenness is 20 nm2/protrusion or less. ### Claim 3 (depends on 1) The magnetic-disk substrate according to claim 1, wherein a difference between an average area of regions occupied by a plurality of protrusions having a height of 0.1 nm or more from an average plane of surface unevenness and an average area of regions occupied by a plurality of protrusions having a height of 0.2 nm or more from the average plane of the surface unevenness is 13 nm2/protrusion or less. ### Claim 4 (depends on 1) The magnetic-disk substrate according to claim 1, wherein the carbon nanofiber rod-shaped member provided at the probe tip has a Young's modulus or 100 GPa or less. ### Claim 5 (depends on 1) The magnetic-disk substrate according to claim 1, wherein the carbon nanofiber rod-shaped member is electrically conductive, and one end of the carbon nanofiber rod-shaped member is connected to earth. ### Claim 6 (depends on 1) The magnetic-disk substrate according to claim 1, wherein the arithmetic average roughness Ra or surface unevenness of the main surfaces is obtained based on information on a position of the probe that is obtained by changing the position of the probe in accordance with the surface unevenness of the main surfaces such that the probe oscillates at a constant amplitude. ### Claim 7 (depends on 6) The magnetic-disk substrate according to claim 6, wherein in the measurement performed using the atomic force microscope, the probe is oscillated at a spring constant of 0.1 to 80 N/m and a frequency of 30 to 400 KHz. ### Claim 8 (depends on 1) The magnetic-disk substrate according to claim 1, wherein the substrate is a magnetic-disk substrate for energy-assisted magnetic recording. ### Claim 9 (depends on 1) A magnetic disk, wherein at least a magnetic film is formed on a surface of the magnetic-disk substrate according to claim 1. ### Claim 10 A magnetic-disk substrate, comprising: a pair of main surfaces, in surface unevenness of the main surfaces, an average area of regions occupied by a plurality of protrusions having a height of 0.1 or more from an average plane of the surface unevenness being 25 nm2/protrusion or less, and the surface unevenness of the main surfaces being a value obtained through measurement using an atomic force microscope provided with a probe having a probe tip provided with a carbon nanofiber rod-shaped member. ### Claim 11 (depends on 10) The magnetic-disk substrate according to claim 10, wherein the average area of the regions occupied by the plurality of protrusions having a height of 0.1 nm or more from the average plane of the surface unevenness is 20 nm2/protrusion or less. ### Claim 12 (depends on 10) The magnetic-disk substrate according to claim 10, wherein a difference between the average area of the regions occupied by the plurality of protrusions having a height of 0.1 nm or more from the average plane of the surface unevenness and an average area of regions occupied by a plurality of protrusions having a height of 0.2 nm or more from the average plane of the surface unevenness is 13 nm2/protrusion or less. ### Claim 13 (depends on 10) The magnetic-disk substrate according to claim 10, wherein the carbon nanofiber rod-shaped member provided at the probe tip has a Young's modulus of 100 GPa or less. ### Claim 14 (depends on 10) The magnetic-disk substrate according to claim 10, wherein the carbon nanofiber rod-shaped member is electrically conductive, and one end of the carbon nanofiber rod-shaped member is connected to earth. ### Claim 15 (depends on 10) The magnetic-disk substrate according to claim 10, wherein an arithmetic average roughness Ra of each of the main surfaces or the surface unevenness is obtained based on information on a position of the probe that is obtained by changing the position of the probe in accordance with the surface unevenness of the main surfaces such that the probe oscillates at a constant amplitude. ### Claim 16 (depends on 15) The magnetic-disk substrate according to claim 15, wherein in the measurement performed using the atomic force microscope, the probe is oscillated at a spring constant of 0.1 to 80 N/m and a frequency of 30 to 400 KHz.