EP0756743A1 - Substrat de disque ameliore - Google Patents

Substrat de disque ameliore

Info

Publication number
EP0756743A1
EP0756743A1 EP95916245A EP95916245A EP0756743A1 EP 0756743 A1 EP0756743 A1 EP 0756743A1 EP 95916245 A EP95916245 A EP 95916245A EP 95916245 A EP95916245 A EP 95916245A EP 0756743 A1 EP0756743 A1 EP 0756743A1
Authority
EP
European Patent Office
Prior art keywords
disk
disk substrate
substrate
angstroms
surface roughness
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95916245A
Other languages
German (de)
English (en)
Inventor
Oh-Hun Kwon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Saint Gobain Ceramics and Plastics Inc
Original Assignee
Saint Gobain Norton Industrial Ceramics Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Saint Gobain Norton Industrial Ceramics Corp filed Critical Saint Gobain Norton Industrial Ceramics Corp
Publication of EP0756743A1 publication Critical patent/EP0756743A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
    • G11B5/8404—Processes or apparatus specially adapted for manufacturing record carriers manufacturing base layers
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/64—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
    • G11B5/739—Magnetic recording media substrates
    • G11B5/73911—Inorganic substrates
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B2220/00—Record carriers by type
    • G11B2220/20—Disc-shaped record carriers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/90—Magnetic feature

Definitions

  • Figure 1 discloses a conventional disk drive 1 in which the actuator arm 2 moves the head 3 over disk 4 so that the circuitry on the head can magnetically transmit bits of information between leads (not shown) and the disk 4.
  • Figure 2 discloses a conventional disk wherein a substrate 5 (typically an Al/Mg alloy) has deposited thereon, consecutively, an electroless or anodized coating (Ni/P) 6, a magnetic coating 7, a protective overcoat 8, and a liquid lubricant 9.
  • a substrate 5 typically an Al/Mg alloy
  • Ni/P electroless or anodized coating
  • the head Due to the high density of information typically stored on a disk, the head must come very close to the disk during data transmission in order to insure accurate transfer. Accordingly, the space between the head and the disk (called a "flying height" or “air gap”) is often between about 4-6 microinches. At such extremely small distances, both the head and the disk must be very flat. Thus, the material used for the disk should be very stiff and amenable to a fine finish.
  • the disk and actuator arm move relative to each other, an air flow develops and allows the head to "float" above the disk.
  • the head's ability to float prevents wear-inducing contact between the head and disk which degrades the accuracy of data transfer.
  • the starting and stopping of the disk or arm often produces physical contact between the head and disk. Therefore, it is also desirable to make the disk substrate from a material which is wear resistant.
  • most conventional disks are made from a Mg/Al alloy overcoated with Ni/P and a magnetic film. This alloy has been selected as the material of choice for the disk due to its superior wear resistance, stiffness and polishablity, and performs well in the current relatively large disk drives.
  • the current hard disk is about 65-275 mm in diameter and 0.64 mm to 1.5 mm in thickness, and is expected to be less than about 38 mm in diameter and less than about 0.4 mm in thickness in the future.
  • the air gap will be reduced to no more than 2 microinches.
  • use of Al/Mg alloys as disk substrates will be problematic in that the elastic modulus of Al/Mg alloys (only about 80 GPa) will not provide the stiffness required in the thin disks of the future (wherein the required stiffness will likely be at least about 200 GPa) .
  • JP 62078716 discloses a zirconia based magnetic disk substrate for use in disk drives. However, the surface roughness (Ra) of this material is reported to be only 0.01 um. (100 angstroms). JP 62078715 discloses a zirconia based magnetic disk substrate for use in disk drives. However, the low density of this material would likely yield an even lower surface roughness (Ra) .
  • EPO Patent Application 0 131 895 reports a zirconia based magnetic disk substrate for use in disk drives. However, the best surface roughness (Ra) of any disclosed material is reported to be only 0.003 um (30 angstroms). JP 01112518 discloses a zirconia based magnetic disk substrate for use in disk drives. However, the surface roughness (Ra) of this material is reported to be only 5- 8 nm (50-80 angstroms) .
  • a partially stabilized zirconia substrate (preferably in the form of a disk substrate for use in a disk drive) , the substrate consisting essentially of partially stabilized zirconia and having a surface roughness (Ra) of no more than 10 angstroms.
  • a disk substrate for use in a disk drive, the disk substrate consisting essentially of partially stabilized zirconia and having a textured surface.
  • a disk drive comprising: a) a head, and b) an underlying disk as disclosed above, wherein the in- use airgap between the head and the disk is no more than 2 microinches.
  • a process comprising: a) polishing a partially stabilized zirconia substrate with a diamond or alumina paste to a finish of no more than 10 angstroms.
  • Figure 1 presents a conventional disk drive system.
  • Figure 2 presents a conventional disk.
  • the most of the promising disk substrate candidate materials possess inadequate toughness or a too high surface roughness (Ra) .
  • the toughness required for the thin disks of the future will be at least about 4 MPa m 1/2 and the surface roughness (Ra) requirement will be no more than 10 angstroms.
  • Ra surface roughness
  • high toughness is required in these future disk substrates because it affords superior machinability and damage tolerance, and the fine finish (low surface roughness) is required for increased recording density.
  • partially-stabilized zirconia typically has a toughness of at least about 7 MPa m 12 and can now be made to have a surface roughness of no more than 10 angstroms, it is believed that these materials will be required in the disks of the future.
  • fracture toughness is measured by the Chantikul indentation strength method as disclosed in the Journal of the American Ceramics Society, 64(9), 1981, pp. 539-44. (CITE) ; surface roughness Ra" is the universally recognized as the arithmetic mean of the departures of the profile from the mean surface; and grit sizes used in finishing refer to the average diameter of the grit. Any conventional partially-stabilized zirconia
  • PSZ ceramic such as yttria-partially stabilized tetragonal zirconia polycrystal ceramic (“YTZP”)
  • YTZP yttria-partially stabilized tetragonal zirconia polycrystal ceramic
  • commercial partially-stabilized zirconias have at least about 30% (and often more than about 70%) tetragonal zirconia and a toughness of at least about 4.5 MPa m 1/2 , preferably at least about 6 MPa m 12 .
  • the zirconia is partially stabilized by a rare earth, and more preferably at a concentration of between about 2.5 mol% and about 6 mol%, as rare earth oxide, most preferably at a concentration of between about 2.5 mol% and about 4 mol%, as rare earth oxide.
  • the zirconia is YZ110, an yttrium-stabilized zirconia available from the Norton Company of Worcester, MA.
  • any conventional method of making the zirconia disk substrate may be used.
  • rare earth oxide powder and zirconia powder are mixed, the mixture is cipped (uniaxially or isostatically) at between 50 and 500 MPa to form a green piece; the green piece is sintered at between 1300°C and 1500°C for 0.5-4 hours to achieve a density of at least 95%; and the sintered piece is hipped in inert gas at between 1200°C and 1500°C for between 0.5 and 4 hours to achieve a density of at least 99.9%.
  • yttria powder and zirconia powder are mixed, cold-pressed, sintered to at least 96% density and hipped to at least 99.9% density.
  • a highly pure disk substrate that is, a substrate having less than 0.3% of impurity or sintering aid, especially if the impurity or sintering aid tends to form a second phase.
  • impurity or sintering aids include silica, iron and manganese. It has been found that using YTZP powders, available from Daiichi Kigenso (DKK) of Osaka, Japan, without sintering aid produces a partially stabilized disk substrate having the desired levels of purity which can be finished to the desired levels of surface roughness (Ra) . Accordingly, there is provided a partially stabilized zirconia disk substrate having no more than 0.3% impurity or sintering aid and a surface roughness of no more than 10 angstroms.
  • Disk preparation generally involves only two steps: making a thin ceramic body and then finishing the body.
  • Any conventional method of making thin ceramic bodies may be used in accordance with the invention, including diamond saw slicing of ceramic rods, tape casting, extrusion, and die pressing.
  • the thin disk substrates are made by slicing a ceramic rod with a diamond saw.
  • the slicing should produce a disk having an Ra of between about 2-7 um and a thickness of less than about 1 mm, preferably less than about 0.5 mm.
  • Any conventional lapping method may be used to help attain the required finish on the disk substrate of the present invention, including lapping with a diamond paste or alumina.
  • the lapping should produce a finish of less than about 125 angstroms.
  • the polishing entails selecting either a diamond paste or alumina grain having an average size of between about 3 and 15 um, preferably less than 10 um.
  • polishing the lapped disk substrate with a fine diamond paste or alumina produces a finish of less than about 10 angstroms.
  • the polishing step uses diamond, alumina or a mixture thereof, having an average size of about 0.01 and 0.2 um, preferably less than 0.1 um.
  • disks which are too smooth stick to the head. Accordingly, disks often require a surface texture. Any conventional method of texturing may be used, including thermal etching, laser etching, chemical etching and plasma etching, and combinations thereof. If thermal etching is selected to texture zirconia, the temperature of the etch is typically between about 800 and 1400°C, preferably about 1000°C at about 30 minutes.
  • zirconia toughened alumina may be used, preferably AZ67, available from the Norton
  • boron carbide may be selected. If boron carbide is selected as the disk substrate, any conventional boron carbide ceramic may be used. It is believed that when boron carbide is either hot pressed or sinter-hipped, and then lapped and polished as above yields the desired finish. It typically has a modulus of elasticity of at least about 435 GPa.
  • the boron carbide also has a porosity of less than about 0.1% and a surface roughness (Ra) of no more than 10 angstroms.
  • the boron carbide is Norbide, a hot-pressed boron carbide available from the Norton Company of Worcester, MA.
  • COMPARATIVE EXAMPLE A YZ110-H blank rod having a 1.5" diameter and a 3" length, available from the Norton Company of Worcester, MA, was sliced with a diamond saw. The surface of this slice was subjected to a number of finishing steps including grinding, lapping and polishing steps.
  • the slice was first ground with a 320 grit diamond blank to produce a surface roughness (Ra) of about 0.110 um.
  • the lapped slice was serially lapped and polished with diamond on a 12 inch lapping machine according to the specifications set out in Table I below:
  • This test slice did not achieve the desired 0.001 um (10 angstrom) surface roughness (Ra) .
  • EXAMPLE I A YZ110-H blank rod having a 1.5" diameter and a 3" length, available from the Norton Company of Worcester, MA, was sliced with a diamond saw into six slices A to F. Slices E and F were sliced at a higher feed rate. The thickest and thinnest cross sections, as well as the surface roughness Ra of these six slices are presented in Table II. The surface roughness (Ra) was measured by
  • EXAMPLE II Two Daiichi powders (3mol%Y-TZP and 4mol%Y-TZP) were cipped at 200 MPa to form green rods, sintered in air at 1350° for 60 minutes to achieve at least 98% density, and hipped in argon at 1350°C and 200 MPa for about 45 minutes to produce rods having a density of at least 99.9%.
  • ground disk blanks were lapped using 9 um alumina grit on a cast-iron lapping wheel having slurry continuously dripping from the wheel. Lapping took about 30 minutes and produced a surface roughness of about 125 angstroms.
  • the lapped slices were then final-polished with a 0.05 um alumina/diamond paste to a surface roughness (Ra) of 10 angstroms, as measured by TENCOR methodology.
  • EXAMPLE III This example proceed substantially similarly to Example II, except that the lapping step used 9 um alumina only and the final-polish step used 50 nm alumina only.
  • the resulting disk substrate had a surface roughness of about 10 angstroms, as measured by AFM.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Magnetic Record Carriers (AREA)
  • Compositions Of Oxide Ceramics (AREA)

Abstract

L'invention concerne un substrat de disque s'utilisant dans une unité de disque, constitué essentiellement de zircone partiellement stabilisée et possédant une rugosité de surface (RA) non supérieure à 10 angstroms.
EP95916245A 1994-04-19 1995-04-18 Substrat de disque ameliore Withdrawn EP0756743A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US23004494A 1994-04-19 1994-04-19
US230044 1994-04-19
PCT/US1995/004325 WO1995028703A1 (fr) 1994-04-19 1995-04-18 Substrat de disque ameliore

Publications (1)

Publication Number Publication Date
EP0756743A1 true EP0756743A1 (fr) 1997-02-05

Family

ID=22863733

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95916245A Withdrawn EP0756743A1 (fr) 1994-04-19 1995-04-18 Substrat de disque ameliore

Country Status (6)

Country Link
EP (1) EP0756743A1 (fr)
JP (1) JPH09512127A (fr)
KR (1) KR970702550A (fr)
CN (1) CN1147312A (fr)
CA (1) CA2188150A1 (fr)
WO (1) WO1995028703A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3311308B2 (ja) * 1998-03-03 2002-08-05 株式会社オハラ 垂直磁気記録媒体用ガラスセラミックス基板
US6383645B1 (en) * 1998-03-23 2002-05-07 Kabushiki Kaisha Ohara Glass-ceramic substrate for an information storage medium
CN1151622C (zh) * 2000-12-18 2004-05-26 信息产业部电信传输研究所 基于多径信道能量窗重心跟踪环路的导频信道跟踪方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6022733A (ja) * 1983-07-19 1985-02-05 Hitachi Metals Ltd 磁気デイスク基板
JPH0715753B2 (ja) * 1985-08-22 1995-02-22 株式会社日立製作所 磁気記録媒体
JPH0740350B2 (ja) * 1985-09-30 1995-05-01 京セラ株式会社 磁気デイスク基板
US4738885A (en) * 1986-02-24 1988-04-19 Kyocera Corporation Magnetic disk, substrate therefor and process for preparation thereof

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9528703A1 *

Also Published As

Publication number Publication date
CN1147312A (zh) 1997-04-09
KR970702550A (ko) 1997-05-13
CA2188150A1 (fr) 1995-10-26
JPH09512127A (ja) 1997-12-02
WO1995028703A1 (fr) 1995-10-26

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