# US 8,785,011 B2 · Glass for use as substrate for information recording medium, substrate for information recording medium and information recording medium, and their production methods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,785,011 B2 - Document ID: US8785011B2 - Status: Granted - Kind: B2 - Application number: 13/605,006 - Filed: 2012-09-06 - Published: 2012-12-27 - Granted: 2014-07-22 - Earliest claimed: 2006-06-08 - Assignees: Hoya Corporation - Applicants: Kazuo Tachiwana; Yoichi Hachitani; Xuelu Zou; Mikio Ikenishi; Kinobu Osakabe - Inventors: Kazuo Tachiwana; Yoichi Hachitani; Xuelu Zou; Mikio Ikenishi; Kinobu Osakabe - Web page: https://patentgrep.com/patent/US8785011B2 ## CPC - G11B 5/739: {Magnetic recording media substrates} - C03C 3/083: containing aluminium oxide or an iron compound - C03C 3/087: containing calcium oxide, e.g. common sheet or container glass - C03C 3/095: containing rare earths - C03C 3/097: containing phosphorus, niobium or tantalum - C03C 15/00: Surface treatment of glass, not in the form of fibres or filaments, by etching (etching or surface-brightening compositions, in general C09K13/00) - C03C 19/00: Surface treatment of glass, not in the form of fibres or filaments, by mechanical means (sand-blasting, grinding, or polishing glass B24) - C03C 21/002: {to perform ion-exchange between alkali ions (C03C21/005 takes precedence)} - C03C 23/0075: {Cleaning of glass (specially adapted to plate glass B08B11/00)} - G11B 5/7315 - G11B 5/82: Disk carriers - G11B 5/8404: {manufacturing base layers} - Y10T 428/24273: including aperture - Y10T 428/315: Surface modified glass [e.g., tempered, strengthened, etc.] - 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) - C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract According to one aspect of the present invention, provided is glass for use in substrate for information recording medium, which comprises, denoted as molar percentages, a total of 70 to 85 percent of SiO2 and Al2O3, where SiO2 content is equal to or greater than 50 percent and Al2O3 content is equal to or greater than 3 percent; a total of equal to or greater than 10 percent of Li2O, Na2O and K2O; a total of 1 to 6 percent of CaO and MgO, where CaO content is greater than MgO content; a total of greater than 0 percent but equal to or lower than 4 percent of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3 Y2O3 and TiO2; with the molar ratio of the total content of Li2O, Na2O and K2O to the total content of SiO2, Al2O3, ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2 ((Li2O+Na2O+K2O)/(SiO2+Al2O3+ZrO2+HfO2+Nb2O5+Ta2O5+La2O3+Y2O3+TiO2)) being equal to or less than 0.28. Further provided are the substrate for information recording medium, information recording medium and their manufacturing methods according to the present invention. ## Claims ### Claim 1 A glass substrate for information recording medium, which is comprised of glass comprising, denoted as molar percentages, a total of 70 to 85 percent of SiO2 and Al2O3, where SiO2 content is equal to or greater than 50 percent and Al2O3 content is equal to or greater than 3 percent; a total of equal to or greater than 10 percent of Li2O, Na2O and K2O; equal to or greater than 5 percent of Li2O, a total of 1 to 6 percent of CaO and MgO, where CaO content is greater than MgO content; a total of greater than 0 percent but equal to or lower than 3 percent of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2; with a molar ratio of MgO content to CaO content (MgO/CaO) being equal to or greater than 0.14; with the molar ratio of a total content of Li2O, Na2O and K2O to a total content of SiO2, Al2O3, ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2 ((Li2O+Na2O+K2O)/(SiO2+Al2O3+ZrO2+HfO2+Nb2O5+Ta2O5+La2O3+Y2O3+TiO2)) being equal to or less than 0.28 and a molar ratio of Li2O content to Na2O content (Li2O/Na2O) being equal to or less than 0.7904, and, which has been subjected to chemical strengthening treatment, and has a hole in the center. ### Claim 2 (depends on 1) The glass substrate for information recording medium according to claim 1, wherein BaO is not incorporated as a glass component. ### Claim 3 (depends on 1) The glass substrate for information recording medium according to claim 1, wherein SiO2 content is equal to or greater than 60 molar percent, and a total content of SiO2 and Al2O3 is equal to or greater than 75 molar percent. ### Claim 4 (depends on 1) The glass substrate for information recording medium according to claim 1, wherein, denoted as molar percentages, a total content of CaO and MgO is greater than a total content of SrO and BaO, and a molar ratio of a total content of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O2 and TiO2 to a total content of Li2O, Na2O, K2O, MgO, CaO, SrO and BaO ((ZrO2+HfO2+Nb2O5+Ta2O5+La2O3+Y2O3+TiO2)/(Li2O+Na2O+K2O+MgO+CaO+SrO+BaO)) is equal to or greater than 0.035. ### Claim 5 (depends on 1) The glass substrate for information recording medium according to claim 1, which comprises, denoted as molar percentages, 50 to 75 percent of SiO2; 3 to 15 percent of Al2O3; 5 to 15 percent of Li2O; 5 to 15 percent of Na2O; 0 to 3 percent of K2O; greater than 0.5 percent but equal to or less than 5 percent of CaO; equal to or greater than 0 percent but less than 3 percent of MgO; 0.3 to 4 percent of ZrO2. ### Claim 6 (depends on 1) The glass substrate for information recording medium according to claim 1, wherein TiO2 content is within a range of 0 to 1 molar percent. ### Claim 7 A glass substrate for information recording medium, which is comprised of glass comprising, denoted as mass percentages, 57 to 75 percent of SiO2; 5 to 20 percent of Al2O3, with a total content of SiO2 and Al2O3 being equal to or greater than 74 percent; a total of greater than 0 percent but equal to or less than 6 percent of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2; greater than 1 percent but equal to or less than 9 percent of Li2O; 5 to 18 percent of Na2O, with a mass ratio, Li2O/Na2O, being equal to or less than 0.5; 0 to 6 percent of K2O; 0 to 4 percent of MgO; greater than 0 percent but equal to or less than 5 percent of CaO, with a total content of MgO and CaO being equal to or less than 5 percent and CaO content being greater than MgO content, with a mass ratio, MgO/CaO, being equal to or greater than 0.1; a total of 0 to 3 percent of SrO and BaO; the mass ratio of the content of ZrO2 to the total content of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3, and TiO2 (ZrO2/(ZrO2 +HfO2+Nb2O5+Ta2O5+La2O3+Y2O3+TiO2)) falls within a range of 0.8 to 1; and which has been subjected to chemical strengthening treatment, and has a hole in the center. ### Claim 8 (depends on 7) The glass substrate for information recording medium according to claim 7, wherein a total content of SiO2 and Al2O3 is greater than 79 percent. ### Claim 9 (depends on 7) The glass substrate for information recording medium according to claim 7, which comprises equal to or greater than 11 percent of Al2O3. ### Claim 10 (depends on 7) The glass substrate for information recording medium according to claim 7, which comprises 0.1 to 4 percent of MgO. ### Claim 11 (depends on 7) The glass substrate for information recording medium according to claim 7, wherein a total content of SiO2, Al2O3, ZrO2, Li2O, Na2O, K2O, MgO and CaO is equal to or greater than 99 percent. ### Claim 12 (depends on 1) The glass substrate for information recording medium according to claim 1, which further comprises Fe. ### Claim 13 (depends on 7) The glass substrate for information recording medium according to claim 7, which further comprises Fe. ### Claim 14 (depends on 1) The glass substrate for information recording medium according to claim 1, which has a main surface with a roughness Ra of less than 0.25 nm. ### Claim 15 (depends on 7) The glass substrate for information recording medium according to claim 7, which has a main surface with a roughness Ra of less than 0.25 nm. ### Claim 16 (depends on 1) The glass substrate for information recording medium according to claim 1, which has a deflecting strength of equal to or greater than 10 kg. ### Claim 17 (depends on 7) The glass substrate for information recording medium according to claim 7, which has a deflecting strength of equal to or greater than 10 kg. ### Claim 18 (depends on 1) The glass substrate for information recording medium according to claim 1, which has a thickness of equal to or less than 1 mm. ### Claim 19 (depends on 7) The glass substrate for information recording medium according to claim 7, which has a thickness of equal to or less than 1 mm. ### Claim 20 (depends on 1) The glass substrate for information recording medium according to claim 1, which has a thickness of equal to or greater than 0.3 mm. ### Claim 21 (depends on 7) The glass substrate for information recording medium according to claim 7, which has a thickness of equal to or greater than 0.3 mm. ### Claim 22 (depends on 1) An information recording medium comprising an information recording layer on the glass substrate for information recording medium according to claim 1. ### Claim 23 (depends on 22) The information recording medium according to claim 22, which is a perpendicular magnetic recording-mode magnetic recording medium. ### Claim 24 (depends on 23) The information recording medium according to claim 23, which has a soft magnetic underlayer, an amorphous underlayer, a crystalline underlayer, a perpendicular magnetic recording layer, a protective layer and a lubricating layer in this order on the substrate. ### Claim 25 (depends on 22) The information recording medium according to claim 22, which has a recording density of equal to or greater than 130 Gbit/inch2. ### Claim 26 (depends on 7) A method of manufacturing a glass substrate for information recording medium, which comprises a step of mirror polishing processing the glass according claim 7, and a cleaning step in which acid cleaning and alkali cleaning are conducted following mirror polishing. ### Claim 27 (depends on 7) An information recording medium comprising an information recording layer on the glass substrate for information recording medium according to claim 7. ### Claim 28 (depends on 27) The information recording medium according to claim 27, which is a perpendicular magnetic recording-mode magnetic recording medium. ### Claim 29 (depends on 28) The information recording medium according to claim 28, which has a soft magnetic underlayer, an amorphous underlayer, a crystalline underlayer, a perpendicular magnetic recording layer, a protective layer and a lubricating layer in this order on the substrate. ### Claim 30 (depends on 27) The information recording medium according to claim 27, which has a recording density of equal to or greater than 130 Gbit/inch2.