# US 5,707,706 A · Magnetic recording disk medium having a magnetic layer with uniform properties over the disk surface > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,707,706 A - Document ID: US5707706A - Status: Granted - Kind: A - Application number: 08/483,981 - Filed: 1995-06-07 - Granted: 1998-01-13 - Earliest claimed: 1994-07-20 - Assignees: Hitachi, Ltd. - Inventors: Shinji Fukaya; Yoshinori Honda; Akira Kato; Shuichi Kojima - Web page: https://patentgrep.com/patent/US5707706A ## CPC - G11B 5/8404: {manufacturing base layers} - G11B 5/7368: {Non-polymeric layer under the lowermost magnetic recording layer (base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739)} - 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 5/82: Disk carriers - G11B 5/84: Processes or apparatus specially adapted for manufacturing record carriers - G11B 5/851: Coating a support with a magnetic layer by sputtering - Y10S 428/90: Magnetic feature - Y10T 428/26: Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension - Y10T 428/266: of base or substrate - 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) - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract A magnetic recording has very low warp characteristics but excellent film characteristics. Particularly, the recording medium has a high coercivity with a small range of coercivity distribution, with a warp characteristic below 3 .mu.m per radial inch. The medium is formed by heating a substrate at a high temperature with a temperature distribution on the substrate that is improved by the use of a heat distribution mask, which reduces the temperature distribution of the substrate to below .+-.3%. ## Claims ### Claim 1 A magnetic disk recording medium, comprising: a substrate; a base layer on the substrate; a magnetic layer on the base layer; a protective layer on the magnetic layer; and a lubricating layer on the protective layer; wherein the magnetic disk recording medium is fabricated by heating the substrate through a heat radiation distribution mask to produce a substrate of elevated temperature, and then forming the magnetic layer on the substrate of elevated temperature; and wherein the magnetic disk recording medium has a radial warp due to said substrate heating that does not exceed 3 .mu.m/inch from a center thereof. ### Claim 2 (depends on 1) A magnetic disk recording medium as claimed in claim 1, wherein the heat radiation distribution mask has a heat-blocking region and a heat-transmitting region. ### Claim 3 (depends on 1) A magnetic disk recording medium as claimed in claim 1, wherein the heat radiation distribution mask has a heat-absorbing region and a heat-transmitting region. ### Claim 4 (depends on 1) A magnetic disk recording medium as claimed in claim 1, wherein the heat radiation distribution mask has a heat-reflecting region and a heat-transmitting region. ### Claim 5 (depends on 3) A magnetic disk recording medium as claimed in claim 3, wherein the heat-absorbing region absorbs a primary portion of the heat that is directed toward the center of the substrate surface facing the heat source. ### Claim 6 (depends on 4) A magnetic disk recording medium as claimed in claim 4, wherein the heat-reflecting region reflects a primary portion of the heat that is directed toward the center of the substrate surface facing the heat source. ### Claim 7 (depends on 3) A magnetic disk recording medium as claimed in claim 3, wherein the heat radiation distribution mask has a heat-absorbing region and a plurality of heat-transmitting portions arranged around, but not to include, a portion of the heat-absorbing region that is centrally disposed on the mask. ### Claim 8 (depends on 4) A magnetic disk recording medium as claimed in claim 4, wherein the heat radiation distribution mask has a heat-reflecting region and a plurality of heat-transmitting portions arranged around, but not to include, a portion of the heat-reflecting region that is centrally disposed on the mask. ### Claim 9 (depends on 1) A magnetic disk recording medium as claimed in claim 1, wherein the substrate is heated to elevate the temperature of the substrate to a target temperature distribution of .+-.3%. ### Claim 10 (depends on 9) A magnetic disk recording medium as claimed in claim 9, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 11 (depends on 9) A magnetic disk recording medium as claimed in claim 9, wherein the magnetic disk recording medium has a diameter of 2.5 inches. ### Claim 12 (depends on 1) A magnetic disk recording medium as claimed in claim 1, wherein the mask is cooled while the substrate is heated. ### Claim 13 (depends on 1) A magnetic disk recording medium as claimed in claim 1, wherein the substrate is heated to a temperature of at least 250.degree. C. ### Claim 14 (depends on 13) A magnetic disk recording medium as claimed in claim 13, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 15 (depends on 13) A magnetic disk recording medium as claimed in claim 13, wherein the magnetic disk recording medium has a diameter of 2.5 inches. ### Claim 16 (depends on 1) A magnetic disk recording medium as claimed in claim 1, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 17 (depends on 1) A magnetic disk recording medium as claimed in claim 1, wherein the magnetic disk recording medium has a diameter of 2.5 inches. ### Claim 18 A magnetic disk recording medium, comprising: a substrate; a base layer on the substrate; a magnetic layer on the base layer: protective layer on the magnetic layer; and a lubricating layer on the protective layer; wherein the magnetic disk recording medium is fabricated by heating the substrate through a heat radiation distribution mask to introduce a substrate of elevated temperature, and then forming the magnetic layer on the substrate of elevated temperature; and wherein no part of the magnetic disk recording medium periphery has a warp due to said heating that exceeds 10 .mu.m relative to the magnetic disk recording medium center. ### Claim 19 (depends on 18) A magnetic disk recording medium as claimed in claim 18, wherein the heat radiation distribution mask has a heat-blocking region and a heat-transmitting region. ### Claim 20 (depends on 18) A magnetic disk recording medium as claimed in claim 18, wherein the heat radiation distribution mask has a heat-absorbing region and a heat-transmitting region. ### Claim 21 (depends on 18) A magnetic disk recording medium as claimed in claim 18, wherein the heat radiation distribution mask has a heat-reflecting region and a heat-transmitting region. ### Claim 22 (depends on 20) A magnetic disk recording medium as claimed in claim 20, wherein the heat-absorbing region absorbs a primary portion of the heat that is directed toward the center of the substrate surface facing the heat source. ### Claim 23 (depends on 21) A magnetic disk recording medium as claimed in claim 21, wherein the heat-reflecting region reflects a primary portion of the heat that is directed toward the center of the substrate surface facing the heat source. ### Claim 24 (depends on 20) A magnetic disk recording medium as claimed in claim 20, wherein the heat radiation distribution mask has a heat-absorbing region and a plurality of heat-transmitting portions arranged around, but not to include, a portion of the heat-absorbing region that is centrally disposed on the mask. ### Claim 25 (depends on 21) A magnetic disk recording medium as claimed in claim 21, wherein the heat radiation distribution mask has a heat-reflecting region and a plurality of heat-transmitting portions arranged around, but not to include, a portion of the heat-reflecting region that is centrally disposed on the mask. ### Claim 26 (depends on 18) A magnetic disk recording medium as claimed in claim 18, wherein the substrate is heated to elevate the temperature of the substrate to a target temperature distribution of .+-.3%. ### Claim 27 (depends on 26) A magnetic disk recording medium as claimed in claim 26, wherein the magnetic disk recording medium has a radial warp due to said heating that does not exceed 3 .mu.m/inch from a center thereof. ### Claim 28 (depends on 27) A magnetic disk recording medium as claimed in claim 27, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 29 (depends on 27) A magnetic disk recording medium as claimed in claim 27, wherein the magnetic disk recording medium has a diameter of 2.5 inches. ### Claim 30 (depends on 26) A magnetic disk recording medium as claimed in claim 26, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 31 (depends on 26) A magnetic disk recording medium as claimed in claim 26, wherein the magnetic disk recording medium has a diameter of 2.5 inches. ### Claim 32 (depends on 18) A magnetic disk recording medium as claimed in claim 18, wherein the mask is cooled while the substrate is heated. ### Claim 33 (depends on 18) A magnetic disk recording medium as claimed in claim 18, wherein the substrate is heated to a temperature of at least 250.degree. C. ### Claim 34 (depends on 33) A magnetic disk recording medium as claimed in claim 33, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 35 (depends on 33) A magnetic disk recording medium as claimed in claim 33, wherein the magnetic disk recording medium has a diameter of 2.5 inches. ### Claim 36 (depends on 18) A magnetic disk recording medium as claimed in claim 18, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 37 (depends on 18) A magnetic disk recording medium as claimed in claim 18, wherein the magnetic disk recording medium has a diameter of 2.5 inches. ### Claim 38 A magnetic disk recording medium, comprising: a substrate; a base layer on the substrate; a magnetic layer on the base layer; a protective layer on the magnetic layer; and a lubricating layer on the protective layer; wherein the magnetic layer has a coercive force of at least 2000 Oe and a range of in-plane coercive force distribution of .+-.5%; and wherein the magnetic disk recording medium is fabricated by heating the substrate through a heat radiation distribution mask to produce a substrate of elevated temperature, and then forming the magnetic layer on the substrate of elevated temperature. ### Claim 39 (depends on 38) A magnetic disk recording medium as claimed in claim 38, wherein the heat radiation distribution mask has a heat-blocking region and a heat-transmitting region. ### Claim 40 (depends on 38) A magnetic disk recording medium as claimed in claim 38, wherein the heat radiation distribution mask has a heat-absorbing region and a heat-transmitting region. ### Claim 41 (depends on 38) A magnetic disk recording medium as claimed in claim 38, wherein the heat radiation distribution mask has a heat-reflecting region and a heat-transmitting region. ### Claim 42 (depends on 40) A magnetic disk recording medium as claimed in claim 40, wherein the heat-absorbing region absorbs a primary portion of the heat that is directed toward the center of the substrate surface facing the heat source. ### Claim 43 (depends on 41) A magnetic disk recording medium as claimed in claim 41, wherein the heat-reflecting region reflects a primary portion of the heat that is directed toward the center of the substrate surface facing the heat source. ### Claim 44 (depends on 40) A magnetic disk recording medium as claimed in claim 40, wherein the heat radiation distribution mask has a heat-absorbing region and a plurality of heat-transmitting portions arranged around, but not to include, a portion of the heat-absorbing region that is centrally disposed on the mask. ### Claim 45 (depends on 41) A magnetic disk recording medium as claimed in claim 41, wherein the heat radiation distribution mask has a heat-reflecting region and a plurality of heat-transmitting portions arranged around, but not to include, a portion of the heat-reflecting region that is centrally disposed on the mask. ### Claim 46 (depends on 38) A magnetic disk recording medium as claimed in claim 38, wherein the substrate is heated to elevate the temperature of the substrate to a target temperature distribution of .+-.3%. ### Claim 47 (depends on 46) A magnetic disk recording medium as claimed in claim 46, wherein the magnetic disk recording medium has a radial warp due to said heating that does not exceed 3 .mu.m/inch from a center thereof. ### Claim 48 (depends on 47) A magnetic disk recording medium as claimed in claim 47, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 49 (depends on 47) A magnetic disk recording medium as claimed in claim 47, wherein the magnetic disk recording medium has a diameter of 2.5 inches. ### Claim 50 (depends on 46) A magnetic disk recording medium as claimed in claim 46, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 51 (depends on 46) A magnetic disk recording medium as claimed in claim 46, wherein the magnetic disk recording medium has a diameter of 2.5 inches. ### Claim 52 (depends on 38) A magnetic disk recording medium as claimed in claim 38, wherein the mask is cooled while the substrate is heated. ### Claim 53 (depends on 38) A magnetic disk recording medium as claimed in claim 38, wherein the substrate is heated to a temperature of at least 250.degree. C. ### Claim 54 (depends on 53) A magnetic disk recording medium as claimed in claim 53, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 55 (depends on 53) A magnetic disk recording medium as claimed in claim 53, wherein the magnetic disk recording medium has a diameter of 2.5 inches. ### Claim 56 (depends on 38) A magnetic disk recording medium as claimed in claim 38, wherein the magnetic disk recording medium has a diameter of 3.5 inches. ### Claim 57 (depends on 38) A magnetic disk recording medium as claimed in claim 38, wherein the magnetic disk recording medium has a diameter of 2.5 inches.