WO2005093720A1 - 磁気ディスク用ガラス基板 - Google Patents
磁気ディスク用ガラス基板 Download PDFInfo
- Publication number
- WO2005093720A1 WO2005093720A1 PCT/JP2005/005362 JP2005005362W WO2005093720A1 WO 2005093720 A1 WO2005093720 A1 WO 2005093720A1 JP 2005005362 W JP2005005362 W JP 2005005362W WO 2005093720 A1 WO2005093720 A1 WO 2005093720A1
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- WIPO (PCT)
- Prior art keywords
- magnetic disk
- glass substrate
- glass
- tensile stress
- polishing
- Prior art date
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Classifications
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- 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
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- 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
- G11B5/73921—Glass or ceramic substrates
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- 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
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
- Y10T428/24479—Structurally defined web or sheet [e.g., overall dimension, etc.] including variation in thickness
- Y10T428/24612—Composite web or sheet
Definitions
- the present invention relates to a magnetic disk glass substrate and a magnetic disk used for a hard disk drive (HDD) as a magnetic disk device, and a method for manufacturing the magnetic disk glass substrate and the magnetic disk.
- HDD hard disk drive
- HDD hard disk drive
- a magnetic layer or the like is formed on a substrate such as an aluminum-based alloy substrate or a glass substrate.
- a magnetic head flies above a magnetic disk that rotates at a high speed, information signals are recorded on the magnetic layer as a magnetization pattern by the magnetic head, and reproduction is performed.
- the glass substrate is made of a brittle material.
- various methods for strengthening glass substrates have been conventionally proposed.
- Japanese Patent No. 2657967 (Cited Example 1) Is to immerse a glass substrate in a mixed solution of KNO and NaNO for a predetermined time.
- a glass substrate chemically strengthened by the same method as described in Reference 1 has a thickness of 0.5 mm to 1. Omm. Te you, if the thickness of the compressive stress layer and 30 mu m to 100 mu m, the compressive stress in the compressive stress layer and 2KgZmm 2 to 15KgZmm 2, the tensile stress in the tensile stress layer 1. 5 kgZmm 2 or less and It is described that it is desirable to do it!
- a magnetic disk has a very high information recording speed and information reproducing speed (response speed) as compared with other information recording media, and can write and read information as needed.
- a small hard disk drive equipped with a magnetic disk using a substrate with an outer diameter of 50 mm or less, or 30 mm or less, and a board thickness of less than 0.5 mm or 0.4 mm or less.
- Such a small hard disk drive used in a portable so-called mopile device is always exposed to impact such as impact due to dropping or vibration. Therefore, in such applications, in order to improve the reliability, each of the components inside the hard disk drive, including the magnetic disk, is required to have higher impact resistance than ever.
- a magnetic disk using a glass substrate also has utility as a magnetic disk used in a hard disk drive used in such a portable device.
- the glass substrate made of a hard material, glass glass has a higher rigidity than the substrate made of a metal material, which is a soft material. As described above, a desired strength is obtained by means such as chemical strengthening. Because it can do it.
- an object of the present invention is to provide a portable information device such as a mobile phone, a digital camera, a portable MP3 player, or a PDA, or an in-vehicle device such as a car navigation system.
- a portable information device such as a mobile phone, a digital camera, a portable MP3 player, or a PDA
- an in-vehicle device such as a car navigation system.
- Another object of the present invention is to provide a small hard disk drive that does not break even when subjected to a shock of, for example, 2000G or more, and that the magnetic head can fly low, for example, head flying.
- An object of the present invention is to provide a glass substrate for a magnetic disk having an amount of lOnm or less.
- Still another object of the present invention is to provide a magnetic disk using such a glass substrate for a magnetic disk.
- the present inventor has studied a causal relationship between a failure of a magnetic disk in a drop test of a hard disk drive or the like and a manufacturing process of a glass substrate for a magnetic disk, particularly, a chemical strengthening process.
- the present inventor has conducted research to solve the above-mentioned problems, and as a result, in the manufacturing process of a glass substrate for a magnetic disk, by appropriately setting and controlling the conditions of chemical strengthening, the problems have been solved. We found that we could solve it.
- the strength of the glass substrate can be improved under the conditions of chemical strengthening, the waviness existing on the substrate surface (Waviness, abbreviated as “Wa”) can be improved. ) was worsened, and as a result, it was found that the height of the magnetic disk using the glass substrate could be deteriorated, and the flying height of the magnetic head could be hindered.
- the present inventor conducted further research to simultaneously solve the two problems of the impact resistance of the glass substrate and the undulation (Wa) existing on the substrate surface. It has been found that the above two problems can be solved at the same time by appropriately setting and controlling.
- the present invention has the following aspects.
- the glass substrate for a magnetic disk according to the present invention has a disk thickness of less than 0.5 mm to be mounted on a 1-inch hard disk drive or a hard disk drive using a magnetic disk smaller in diameter than the 1-inch hard disk drive.
- a glass substrate for a magnetic disk which has a predetermined disk thickness by lapping both main surfaces and a mirror surface from which cracks are removed by polishing both main surfaces.
- a compressive stress layer with a thickness of dl and d2 is formed on the surface layer on both main surface sides, and a tensile stress layer with a thickness of L is formed between these compressive stress layers.
- the thickness L of the tensile stress layer measured by observing the longitudinal section of the glass substrate for magnetic disk using the Babinet compensator method. , Pull in the tensile stress layer
- the product L'Pt with the maximum value Pt of the tensile stress to a desired value, it has a predetermined impact resistance and a predetermined undulation (Wa) existing on the main surface
- the impact resistance is an impact of 3000 G or more
- the undulation (Wa) is 1. Onm or less.
- the product L′ Pt of the thickness L of the tensile stress layer and the maximum value Pt of the tensile stress in the tensile stress layer is 0.4 kg. Not less than Zmm, 2. Not more than OkgZmm.
- the thickness L of the tensile stress layer is 0.4 mm or less, and the maximum value Pt of the tensile stress in the tensile stress layer is: and it has a 10kg / mm 2 or less.
- the thickness dl of the compressive stress layer generated on one main surface side and the thickness dl of the compressive stress layer generated on the other main surface side The sum D of the thickness d2 is at least 40% of the disc thickness T.
- the maximum value Pt of the tensile stress in the tensile stress layer is 10 kgZmm 2 or less. That is, the following relationship is established in the glass substrate for a magnetic disk.
- the maximum value Pc of the compressive stress in the compressive stress layer is 4 kgZmm 2 or more.
- the glass substrate for a magnetic disk of the first aspect is used for a magnetic disk mounted on a hard disk drive that performs a start / stop operation by a load / unload method.
- a magnetic disk according to the present invention includes the magnetic disk glass substrate of the first aspect, and at least a magnetic layer is formed on the magnetic disk glass substrate.
- a method for manufacturing a glass substrate for a magnetic disk according to the present invention is a method for manufacturing a glass substrate for a magnetic disk for manufacturing the glass substrate for a magnetic disk according to the first aspect, and includes a chemical strengthening process.
- this chemical strengthening treatment step the glass substrate is brought into contact with a molten nitrate containing at least three kinds of alkali metal elements, and the surface portions on both main surface sides of the glass substrate are subjected to low-temperature ion exchange. Then, a compressive stress layer is formed, and a tensile stress layer is formed between these compressive stress layers.
- the present invention provides the method for manufacturing a glass substrate for a magnetic disk according to the ninth aspect, further comprising a polishing treatment step, wherein the polishing treatment step comprises using colloidal silicon abrasive grains or diamond abrasive grains. While supplying, the polishing cloth and the glass substrate are relatively moved to remove cracks on both main surfaces of the glass substrate to make a mirror surface.
- the present invention provides the method for manufacturing a glass substrate for a magnetic disk according to the tenth aspect.
- the arithmetic mean roughness (Ra) of the main surface is set to a mirror surface of 0.4 nm or less.
- the method of manufacturing a magnetic disk according to the present invention uses the glass substrate for a magnetic disk manufactured by the method of manufacturing a glass substrate for a magnetic disk according to the ninth aspect described above. Next, at least a magnetic layer is formed.
- the thickness of the compressive stress layer formed on the surface layer on both main surfaces by chemical strengthening treatment is dl, d2, and the thickness of the tensile stress layer is L.
- the maximum value of the tensile stress Pt in the tensile stress layer is Pt
- the product L'Pt of the thickness of the tensile stress layer and the maximum value of the tensile stress is set to a desired value to obtain a predetermined impact resistance and , A swell (Wa) existing on a predetermined main surface.
- the predetermined impact resistance and the predetermined waviness (Wa) existing on the main surface are defined as a magnetic disk glass substrate having a disk thickness of less than 0.5 mm, and a 1-inch glass substrate.
- the glass substrate has a low level of shock resistance (for example, 3000 G or less) that does not pose a practical problem.
- the above impact) and the undulation (Wa) for example, Wa is 1. Onm or less) existing on the main surface of the glass substrate are shown.
- the thickness of the tensile stress layer is L and the maximum value of the tensile stress in the tensile stress layer is Pt
- the thickness of the tensile stress layer and the maximum value of the tensile stress Since the product L'Pt is 0.4 kgZmm or more and 2. OkgZmm or less, good impact resistance can be realized and undulation (Wa) existing on the substrate surface can be improved.
- the thickness L of the tensile stress layer is set to 0.4 mm or less, or the thickness dl of the compressive stress layer generated on one main surface side and the other, By setting the total D of the thickness d2 of the compressive stress layer generated on the main surface side to 40% or more of the disk thickness T, good impact resistance can be realized.
- the tensile stress in the tensile stress layer By setting the maximum value Pt of the above to 10 kg / mm 2 or less, good impact resistance and durability can be achieved, and the undulation (Wa) existing on the substrate surface can be improved.
- good impact resistance can be achieved by setting the maximum value Pc of the compressive stress in the compressive stress layer to 4 kgZmm 2 or more.
- the magnetic disk according to the present invention has good impact resistance and durability since at least a magnetic layer is formed on the above-mentioned glass substrate for a magnetic disk.
- a magnetic disk can be provided. This magnetic disk can be used well as a magnetic disk mounted on a hard disk drive that performs a start / stop operation by a load / unload method.
- the present invention provides a highly portable device such as a portable information device such as a mobile phone, a digital camera, a portable MP3 player, or a PDA, or a vehicle-mounted device such as a car navigation system. It is suitable for a small hard disk drive that can be mounted on equipment. For example, it is possible to provide a glass substrate for a magnetic disk that is not broken even when an impact of, for example, 2000 G or more is applied to the hard disk drive. Also, it is possible to provide a magnetic disk using such a magnetic disk glass substrate.
- FIG. 1 is a cross-sectional view showing a stress layer profile of a cross section of a glass substrate for a magnetic disk according to the present invention.
- FIG. 2 shows the maximum value Pt of the bow I tension stress in the bow I tension stress layer and the thickness of the tensile stress layer in the glass substrate for a magnetic disk manufactured under various chemical strengthening conditions.
- 13 is a graph in which the results of L are plotted.
- FIG. 3 shows the waviness (Wa) present on the surface of the glass substrate for the magnetic disk glass substrate manufactured under various chemical strengthening conditions and the glide of the magnetic disk manufactured using the glass substrate. It is the graph which plotted the result of height.
- the main surface of the sheet glass is lapped (ground) to form a glass base material, and the glass base material is cut to cut out a glass disk.
- various shapes of plate glass can be used as the plate glass to be subjected to the lapping treatment.
- the shape of the sheet glass may be a rectangular shape or a disk shape (disk shape).
- the disk-shaped glass sheet is used in the production of a conventional glass substrate for a magnetic disk, and can be subjected to a lapping process using a wrapping apparatus, and performs highly reliable processing at a low cost. be able to.
- the size of the sheet glass needs to be larger than the glass substrate for a magnetic disk to be manufactured.
- the diameter of the glass substrate for a magnetic disk is approximately 10 mm. It is about 30 mm to 30 mm. Therefore, the diameter of the disk-shaped sheet glass is preferably 30 mm or more, and more preferably 48 mm or more.
- a glass substrate for a magnetic disk used for a magnetic disk mounted on a plurality of 1-inch hard disk drives can be obtained from a single glass plate. It is suitable for mass production.
- the upper limit of the size of the sheet glass is not particularly limited, but in the case of a disk-shaped sheet glass, it is preferable to use one having a diameter of 100 mm or less.
- the sheet glass can be manufactured using a known manufacturing method such as a pressing method, a float method, or a fusion method using molten glass as a material. Among them, if the pressing method is used, sheet glass can be manufactured at low cost.
- the material of the plate glass used in the present invention is not particularly limited as long as it is chemically strengthened glass, and aluminosilicate glass can be preferably mentioned. Particularly, aluminosilicate glass containing lithium is preferable. Such an aluminosilicate glass can be subjected to an ion-exchange type chemical strengthening treatment, in particular, a low-temperature ion-exchange type chemical strengthening treatment, to form a compressive stress layer having a preferable compressive stress and a tensile stress layer having a tensile stress. Is particularly preferred as a material for a chemically strengthened glass substrate for a magnetic disk.
- ZrO is 0.5 to 2.0, and the weight ratio of Al O to ZrO (Al O / ZrO) is 0.4 to 2.5
- the lapping process is performed to improve the shape accuracy (for example, flatness) and dimensional accuracy (for example, plate thickness accuracy) of the main surface of the work, that is, the sheet glass.
- the main surface of the sheet glass is pressed by pressing a grindstone or a platen on the main surface of the sheet glass and the plate glass and the grindstone or the platen are relatively moved. This is done by grinding.
- Such a lapping process can be performed using a double-sided lapping device using a planetary gear mechanism.
- a grinding liquid is supplied to the main surface of the sheet glass to wash away the sludge (grinding debris) as well as to cool the ground surface.
- a slurry in which free grinding particles are contained in the grinding fluid may be supplied to the main surface of the workpiece to perform grinding.
- a diamond grindstone can be used as a grindstone used for the lapping treatment.
- alumina abrasive ⁇ zirconia abrasive or silicon carbide abrasive it is preferable to use hard cannonballs.
- the main surface of the glass base material is made flat by lapping, and the plate thickness is reduced.
- the glass base material can be cut, and a glass disk can be cut out from the glass base material. That is, in the present invention, it is possible to prevent the occurrence of defects such as chipping, cracking and cracking when cutting a glass disk from a glass base material.
- the flatness of the glass base material is, for example, preferably 30 m or less, more preferably 10 m or less, in 7088 mm 2 (area of a circle having a diameter of 95 mm).
- the flatness is measured by using OPTIFLAT (trade name) manufactured by PHASE SHIFT TECHNOLOGY or a device equivalent thereto.
- the glass base material is a circular substrate having a diameter of 95 mm
- the flatness is 200 nm to the entire circle.
- the maximum value is calculated from the pellicle with a wavelength of 95 mm.
- the thickness of the glass base material is preferably 2 mm or less, more preferably 0.8 mm or less.
- the thickness of the glass base material is less than 0.2 mm, the glass base material itself may not be able to withstand the load in the process of cutting the glass disk. Therefore, the thickness of the glass base material is preferably 0.2 mm or more. On the other hand, if the thickness of the glass base material exceeds 2 mm, accurate cutting cannot be performed because the thickness is too large! / There is a risk of chipping, cracking, and cracking when cutting the glass disc. Defects may occur.
- the size of the glass base material must be larger than the glass substrate for the magnetic disk to be manufactured.
- the diameter of the glass substrate for a magnetic disk is approximately 10 mm to 30 mm. It is. Therefore, the diameter of the glass base material is preferably 30 mm or more, and more preferably 48 mm or more.
- a glass base material with a diameter of 65 mm or more is used, a plurality of glass disks to be used as a magnetic disk glass substrate for a magnetic disk mounted on a 1-inch hard disk drive are cut out from one glass base material. Can be mass Suitable for production.
- the upper limit of the size of the glass base material is not particularly limited, but in the case of a disk-shaped glass base material, the diameter is preferably 100 mm or less.
- Cutting of the glass base material can be performed using a cutting blade or a ganite containing a substance harder than glass, such as a diamond cutter or a diamond drill.
- the cutting of the glass base material may be performed using a laser cutter.
- a particularly preferable size of the glass disk on which the glass base material strength is also produced is a diameter of 30 mm or less.
- the lapping-processed glass disk is subjected to at least polishing processing to make the main surface of the glass disk mirror-finished.
- a platen on which a polishing cloth (for example, a polishing node) is adhered is pressed against the main surface of a glass disk, and a polishing liquid is supplied to the main surface of the glass disk. This is performed by relatively moving the glass disk and the surface plate and polishing the main surface of the glass disk.
- the polishing liquid preferably contains abrasive grains. Colloidal silica polishing can be used as the polishing cannon. Laboratory It is desirable to use a bomb with an average bomb size of lOnm to 200 nm.
- a tape-shaped polishing cloth for example, a polishing tape
- a polishing liquid is supplied to the main surface of the glass disk.
- a tape polishing method of relatively moving the polishing cloth and polishing the main surface of the glass disk may be used.
- the polishing liquid preferably contains abrasive grains.
- Diamond polishing can be used as the polishing cannon. It is preferable to use an abrasive having an average particle diameter of lOnm to 200 nm as the abrasive cannon.
- the polishing pad or the polishing surface of the polishing tape used in the present invention is preferably formed of a resin material such as polyurethane or polyester.
- the polishing surface is preferably made of foamed resin (for example, polyurethane foam), and for a polishing tape, the polishing surface is preferably made of resin fiber (for example, polyester resin fiber).
- a lapping process is performed before polishing the glass disk.
- the lapping process at this time can be performed by the same method as the rubbing process for the sheet glass described above.
- the end face of the glass disk is mirror-polished. Since the end surface of the glass disk is cut or in the shape of a pear ground, this end surface is polished to a mirror surface. As a result, generation of particles can be suppressed, and a thermal asperity disorder can be satisfactorily prevented in a magnetic disk manufactured using the magnetic disk glass substrate. Further, if the end face is a mirror surface, it is possible to prevent a delay due to a minute crack; As the mirror surface state of the end face, a mirror surface having an arithmetic average roughness (Ra) of 100 nm or less when measured by AFM is preferable.
- Ra arithmetic average roughness
- a chemical strengthening treatment is performed before and / or after the polishing step of the glass disk.
- a chemical strengthening treatment By performing the chemical strengthening treatment, a high compressive stress can be generated on the surface of the glass substrate for a magnetic disk, and the impact resistance can be improved.
- aluminosilicate glass is used as the material of the glass disk, Can be subjected to a chemical strengthening treatment.
- the chemical strengthening treatment in the present invention is not particularly limited as long as it uses a known chemical strengthening treatment method.
- the chemical strengthening treatment of the glass disk is performed, for example, by bringing the glass disk into contact with a heated molten salt for strengthening the glass and ion-exchanging ions of the surface layer of the glass disk with ions of the chemical strengthening salt.
- the ion exchange method a low-temperature type ion exchange method, a high-temperature type ion exchange method, a surface crystallization method, a method for removing alkali from a glass surface, and the like are known.
- the alkali ions in the glass are replaced with alkali ions having a larger ion radius than the alkali ions in a temperature range below the annealing point of the glass.
- a compressive stress is generated on the glass surface by increasing the volume of the ion exchange section, and the glass surface is strengthened.
- the heating temperature of the molten salt during the chemical strengthening treatment is 280 ° C to 660 ° C, particularly 300 ° C to 400 ° C in order to perform ion exchange well. Better!/,.
- the time for bringing the glass disk into contact with the molten salt is preferably several hours to several tens of hours.
- the glass disk it is preferable to heat the glass disk to 100 ° C. to 300 ° C. as preheating before bringing the glass disk into contact with the molten salt.
- the glass disk after the chemical strengthening treatment becomes a product (a glass substrate for a magnetic disk) through a cooling step, a cleaning step, and the like.
- the material of the treatment tank for performing the chemical strengthening treatment is not particularly limited as long as it is a material having excellent corrosion resistance and low dust generation.
- Chemically strengthened salts and chemically strengthened molten salts are oxidizing and have a high processing temperature, so by selecting a material with excellent corrosion resistance, damage and dust generation can be suppressed, and thermal asperity failure and head Need to suppress crashes.
- a quartz material is particularly preferable as the material of the treatment tank, but a stainless steel material, in particular, a martensitic or austenitic stainless steel having excellent corrosion resistance can also be used.
- the quartz material is excellent in corrosion resistance, but is expensive, and can be appropriately selected in consideration of profitability.
- a nitrate containing an alkali metal element for example, a nitrate containing potassium nitrate, sodium nitrate, lithium nitrate and the like.
- the lithium element contained in the nitrate is lOppm-3000ppm (When mixing three types of nitrates, potassium nitrate, sodium nitrate, and lithium nitrate, they should be mixed in the range of 0.0001 vol%-0.3 vol% as lithium nitrate. Is preferable. If there are too many lithium ions in the chemically strengthened molten salt, ion exchange will be inhibited.
- Such a chemically strengthened salt has a desired rigidity, impact resistance, and surface presence on a glass surface for a magnetic disk when a glass, particularly an aluminosilicate glass containing a lithium element is subjected to a strengthening treatment.
- Undulation (Wa) can be realized.
- the glass substrate for a magnetic disk according to the present invention manufactured as described above has a disk thickness of less than 0.5 mm, particularly, a thin magnetic disk having a disk thickness of 0.1 mm to 0.4 mm. Glass substrates are particularly preferred. Further, as the glass substrate for a magnetic disk, a glass substrate for a small magnetic disk having a disk diameter (outer diameter) of 30 mm or less is particularly preferable.
- the magnetic disk glass substrate is suitable as a magnetic disk glass substrate mounted on a 1-inch hard disk drive or a hard disk drive smaller than the 1-inch hard disk drive.
- the diameter of a glass substrate for a magnetic disk for manufacturing a magnetic disk to be mounted on a 1-inch type hard disk drive is about 27.4 mm, and the disk thickness is 0.38 lmm.
- the diameter of the magnetic disk glass substrate for manufacturing a magnetic disk to be mounted on a 0.85-inch hard disk drive is about 21.6 mm, and the disk thickness is 0.381 mm.
- the magnetic layer formed on the glass substrate for a magnetic disk for example, a magnetic layer that also has a cobalt (Co) -based ferromagnetic material force may be used. it can.
- cobalt platinum (Co—Pt) -based ferromagnetic materials which provide high coercive force
- the magnetic layer also has a cobalt-chromium (Co-Cr) ferromagnetic material.
- a DC magnetron sputtering method can be used as a method for forming the magnetic layer.
- an underlayer or the like is appropriately inserted between the glass substrate and the magnetic layer.
- an Al-Ru alloy, a Cr alloy, or the like can be used as a material of these underlayers.
- a protective layer for protecting the magnetic disk from the impact of the magnetic head can be provided.
- a hard hydrogenated carbon protective layer is preferably used.
- a lubricating layer having a PFPE (perfluoropolyether) bonding property on this protective layer, interference between the magnetic head and the magnetic disk can be reduced.
- This lubricating layer can be formed, for example, by applying a film by dipping.
- the method of manufacturing a glass substrate for a magnetic disk in the present embodiment described below includes the following process powers (1) to (7).
- a disk-shaped glass base material made of amorphous aluminosilicate glass was prepared.
- This aluminosilicate glass contains lithium.
- the composition of this aluminosilicate glass is 63.6% by weight of SiO, 14.2% by weight of Al 2 O, 10.4% by weight of Na 2 O
- a down-draw method or a float method is generally used.
- a disk-shaped glass base material may be obtained by direct pressing.
- the aluminosilicate glass which is the material of this sheet glass, contains 58 to 75 weight percent SiO.
- the glass disk was subjected to a lapping process in order to improve dimensional accuracy and shape accuracy.
- This lapping step was carried out using a double-sided lapping apparatus and a cannonball having a particle size of # 400.
- both sides of the glass disk housed in the carrier were Was wrapped to a flatness of 0 to 2 ⁇ m and a surface roughness (Rmax) of about 6 ⁇ m.
- the flatness is a value obtained by calculating the maximum value among the pellicles having a wavelength of 28.7 mm at a power of 200 nm using OPTIFLAT (trade name) manufactured by PHASE SHIFT TECHNOLOGY.
- the surface roughness (Rmax) was obtained by measurement using a stylus type roughness meter.
- a hole was formed in the center portion of the glass disk using a cylindrical gantry, and after grinding the outer peripheral end surface, a predetermined chamfering process was performed on the outer peripheral end surface and the inner peripheral end surface.
- the surface roughness of the end surface of the glass disk was about 4 / zm in Rmax as measured by a stylus type roughness meter.
- the disk thickness was 0.427 mm
- the flatness was 0 to 2 / ⁇
- the surface roughness of the main surface was Rmax Was about 2 ⁇ m
- Ra was about 0.2 ⁇ m.
- OPTIFLAT (trade name) manufactured by TECHNOLOGY Co., Ltd.
- the maximum value is calculated from the spikes.
- the surface roughness (Rmax, Ra) was obtained by measurement with a stylus-type roughness meter.
- the glass disk having been subjected to such a fine lapping step was sequentially immersed in each of cleaning tanks of a neutral detergent and water to which ultrasonic waves had been applied, and subjected to ultrasonic cleaning.
- a force for polishing the end surface by overlapping the glass disks is used in order to avoid scratches and the like on the main surface of the glass disk. It is preferably performed before a first polishing (polishing) step described later or before and after a second polishing (polishing) step.
- the end surface of the glass disk was processed into a mirror surface state capable of preventing dust generation of particles and the like.
- the diameter of the glass disk was measured after the end mirror polishing (polishing) process, and was 27.4 mm.
- a first polishing (polishing) step was performed using a double-side polishing apparatus in order to remove scratches and distortion remaining in the fine lapping step described above.
- the double-side polishing apparatus a glass disk held by a carrier is brought into close contact between an upper and lower platen to which a polishing pad is attached, and this carrier is combined with a sun gear and an internal gear, and the glass disk is attached. It is clamped by the upper and lower platens. Then, while supplying the polishing liquid between the polishing surface of the polishing pad and the main surface of the glass disk, the sun gear is rotated so that the glass disk revolves around the internal gear while rotating on the surface plate. Then, both main surfaces are simultaneously polished.
- the same apparatus is used as a double-side polishing apparatus used in the following examples. Specifically, the first polishing (polishing) step was performed using foamed polyurethane as the polishing pad.
- the polishing conditions used were a cerium oxide and a polishing liquid of RO hydraulic power.
- the glass discs are sequentially placed in cleaning tanks of a neutral detergent, pure water (1), pure water (2), IPA (isopropyl alcohol), and IPA (steam drying). They were immersed, ultrasonically cleaned and dried.
- the polish was changed to a soft polishing pad (polyurethane foam), and the second polishing (polishing) was performed as a mirror polishing step for the main surface. ) Step was performed.
- the second polishing (polishing) step cracks are surely removed while maintaining the flat main surface obtained in the first polishing (polishing) step, and the surface roughness of the main surface is reduced. This is performed in order to obtain a mirror surface in which Ra is reduced to, for example, about 0.4 to 0.1 nm.
- the surface roughness Ra is obtained by measurement by AFM.
- the polishing liquid used was a colloidal silica polishing cannon (average particle size of 80 nm) and a polishing liquid having RO hydraulic power, the load was 100 g / cm 2 , and the polishing time was 5 minutes.
- the glass disk after the second polishing step is placed in each cleaning tank of a neutral detergent, pure water (1), pure water (2), IPA (isopropyl alcohol), and IPA (steam drying). They were sequentially immersed, ultrasonically washed, and dried.
- the chemical strengthening treatment is performed by mixing the molten salt of 59.9995 vol% of potassium citrate, 39.9995 vol% of sodium citrate and 0.001 vol% of lithium citrate. It was carried out using. Then, when the lithium content was measured using an ICP emission spectrometer, it was 10 ppm.
- the chemically strengthened solution was heated to 340 ° C, and the glass disk that had been washed and dried was immersed for 2 hours to perform a chemical strengthening treatment.
- the magnetic disk glass substrate was housed in a holder so that a plurality of magnetic disk glass substrates were held at the end faces.
- the glass substrate for a magnetic disk after the chemical strengthening treatment was immersed in a water bath at 20 ° C, rapidly cooled, and maintained for about 10 minutes.
- the glass substrate for a magnetic disk that had been quenched was immersed in concentrated sulfuric acid heated to about 40 ° C for cleaning.
- the glass substrate for magnetic disks after washing with sulfuric acid and sulfuric acid is sequentially immersed in each of pure water (1), pure water (2), IPA (isopropyl alcohol), and IPA (steam drying) cleaning tanks, Sonic clean and dry.
- the surface roughness of the main surface of the magnetic disk glass substrate obtained through the above-described process was measured by AFM, and was found to be 2.5 nm for Rmax and 0.30 nm for Ra. It was confirmed that the mirror surface was perfect.
- the numerical value of the surface roughness was calculated based on the surface shape measured by AFM according to Japanese Industrial Standards (JIS) B0601.
- the obtained magnetic disk glass substrate had an inner diameter of 7 mm, an outer diameter of 27.4 mm, and a thickness of 0.381 mm.
- the predetermined size of the magnetic disk glass substrate used for a 1-inch type magnetic disk was Was confirmed.
- the surface roughness of the inner peripheral end face of the circular hole of the glass substrate for a magnetic disk was 40 nm for Ra and 50 nm for Ra on the side wall as measured by AFM.
- the surface roughness Ra on the outer peripheral end face was 40 nm at the chamfered portion and 70 nm at the side wall portion.
- the inner peripheral end face was mirror-finished similarly to the outer peripheral end face.
- the main surface of the obtained magnetic disk glass substrate was precisely analyzed using an electron microscope, and it was confirmed that the surface was a mirror surface with no force cracks or the like.
- Mirror polishing of the main surface using colloidal silica abrasive grains enabled a smooth mirror surface of 0.30 nm with Ra.
- the obtained glass substrate for a magnetic disk was cut into strips having a width of about 3 mm so that a cut surface perpendicular to the main surface appeared. Further, the cut surface was ground and polished using an abrasive and a polishing pad so that the distance between the cut surfaces (substrate cross sections) on both sides of the section was about 0.5 mm.
- FIG. 1 is a cross-sectional view showing a stress layer profile of a cross section of the glass substrate for a magnetic disk.
- the cross section of the glass substrate for a magnetic disk revealed in this way was measured using the Babinet compensator method, and as shown in FIG. 1, the stress layer profile of the cross section of the glass substrate for a magnetic disk was measured. Is obtained.
- a Babinet compensator is an instrument that includes two opposite quartz wedges (wedges) that are equal and angled. It moves in the length direction. The optical axes of these two wedges are perpendicular to each other, and the axial direction of the moving prism is along the moving direction. This instrument is widely used for inspection of glass with retardation of retardation (retardation) ⁇ degree of birefringence or glass with internal stress.
- This stress layer profile was defined as follows.
- T thickness of glass substrate for magnetic disk (total thickness) [mm]
- the obtained glass substrate for magnetic disk was manufactured by Air Brown.
- a Dana impact test was performed using AVEX-SM-110-MP.
- the magnetic disk glass substrate was assembled into a dedicated jig for impact test, and a half-sine wave pulse impact was applied sequentially from 1000 G to 5000 G in the vertical direction to the main surface to damage the magnetic disk glass substrate. I went by looking at the situation.
- the glass substrate for a magnetic disk manufactured in this example was able to withstand an impact of 3000 G in the impact test.
- the substrate undulation (Wa) is a kind of substrate surface shape having a waveform having a period of millimeter order and an amplitude of nanometer order. Smaller periods are called “roughness”, while larger periods are called “flatness”.
- the terms “roughness”, “undulation”, and “flatness” are concepts that represent the shape of the substrate surface, and the light that defines them There are no hard standards.
- irregularities hereinafter referred to as “minimal irregularities” whose period and amplitude are both in the order of Angstroms are randomly present.
- “Roughness” is the appearance of “minimal irregularities” captured in a span of micrometer order. In the “roughness”, the appearance of the “minimal irregularities” is a random force. A constant periodicity is confirmed when captured with a relatively long span. The periodicity of the appearance mode of the “minimal irregularities” is “undulation”. Therefore, it can be said that “undulation” is a tendency of the appearance of “minimal irregularities”.
- the undulation (Wa) was measured with an optical measuring device OPTIFLAT (trade name) manufactured by PHASE SHIFT TECHNOLOGY.
- OPTIFLAT trade name
- the radial position (r) from the disk center should be in the range of 3.5 to 13.7 mm.
- the average value of the undulation at a wavelength of 200 nm to 5 mm over the entire circumference of the substrate was calculated.
- the glass substrate for a magnetic disk manufactured in this example was measured.
- Wa 0.54 nm.
- a seed layer of A1—Ru alloy, an underlayer of Cr—W alloy, Co—Cr A Pt—Ta alloy magnetic layer and a hydrogenated carbon protective layer were sequentially formed.
- the seed layer has the function of reducing the magnetic grains of the magnetic layer
- the underlayer has the function of orienting the axis of easy magnetization of the magnetic layer in the in-plane direction.
- the magnetic disk includes a glass substrate for a magnetic disk, which is a non-magnetic substrate, a magnetic layer formed on the glass substrate for a magnetic disk, a protective layer formed on the magnetic layer, And a lubricating layer formed on the protective layer.
- a nonmagnetic metal layer composed of a seed layer and an underlayer is formed between the magnetic disk glass substrate and the magnetic layer.
- all layers other than the magnetic layer are made of non-magnetic material.
- the magnetic layer and the protective layer, the protective layer and the lubricating layer are formed in contact with each other.
- an A1-Ru (aluminum ruthenium) alloy Al: 50at%, Ru: 50at%) is used as a sputtering target, and a 30-nm-thick A1-Ru film is formed on a glass substrate for a magnetic disk.
- a seed layer made of an alloy was formed by sputtering.
- a Cr-W (chromium-tungsten) alloy (Cr: 80 at%, W: 20 at%) is used as a sputtering target, and a 20 nm-thick Cr—W alloy copper underlayer is formed on the seed layer 5.
- a sputtering target composed of a Co—Cr Pt—Ta (cobalt—chromium platinum tantalum) alloy (Cr: 20 at%, Pt: 12 at%, Ta: 5 at%, balance Co) is used as the sputtering target.
- a magnetic layer having a Co—Cr—Pt—Ta alloy strength of 15 nm in thickness was formed by sputtering.
- a protective layer having a hydrogenated carbon power was formed on the magnetic layer, and a lubricating layer made of PFPE (perfluoropolyether) was formed by a dipping method.
- the protective layer also functions to protect the magnetic layer from the impact force of the magnetic head. Thus, a magnetic disk was obtained.
- the glide height (Glide Height) of this magnetic disk was 4.3 nm.
- the glide head having a head flying height of 10 nm no colliding foreign matter was detected, and a stable flying state could be maintained.
- Example 2 the stress layer profile of the cross-section of the glass substrate for the magnetic disk and the undulation (Wa) existing on the main surface are arbitrarily controlled to produce multiple samples did.
- Example 2 the stress layer profile of the cross-section of the glass substrate for the magnetic disk and the undulation (Wa) existing on the main surface are arbitrarily controlled to produce multiple samples did.
- Example 2 the stress layer profile of the cross-section of the glass substrate for the magnetic disk and the undulation (Wa) existing on the main surface are arbitrarily controlled to produce multiple samples did.
- Example 2 the stress layer profile of the cross-section of the glass substrate for the magnetic disk and the undulation (Wa) existing on the main surface are arbitrarily controlled to produce multiple samples did.
- Example 2 the production conditions (chemical strengthening conditions) of these samples are shown in Table 1 including Example 1.
- Example 2-Example 12 and Comparative Example 1-Comparative Example 10 A glass magnetic disk substrate and a magnetic disk were manufactured under the same conditions as in Example 1 except that the chemical strengthening conditions were changed.
- Example 2 Example 12 and Comparative Example 1 From the stress layer profile of the cross section of the glass substrate for magnetic disk obtained in Comparative Example 10, Pt, Pc, DZ2, DZT, L and L'Pt were calculated. The glass substrate impact test (3000 G) and the measurement of the undulation (Wa) existing on the main surface of the glass substrate were also performed in the same manner as in Example 1. Table 2 shows the results, including Example 1.
- FIG. 2 is a graph in which the measurement results of Pt and L are plotted for each magnetic disk glass substrate shown in Table 2.
- the black circles in the drawing are the glass substrates for magnetic disks obtained in Example 1 to Example 12.
- a black triangle indicates a glass substrate for a magnetic disk which cannot withstand a shock of 3000 G in the comparative example.
- a black square indicates a glass substrate for a magnetic disk in which the waviness (Wa) existing on the main surface in the comparative example exceeds 1.
- Wa waviness
- Example 2 Example 12 and Comparative Example 1
- the glide height test using the AE sensor was performed on the magnetic disks obtained in the same manner as in Example 1.
- a glide inspection was performed using a glide head having a head flying height of 10 nm.
- Table 3 shows the measured values of waviness (Wa) present on the main surface of the glass substrate for a magnetic disk obtained in Example 2—Example 12 and Comparative Example 1—Comparative Example 10, and Example 2—Example 12 Comparative Example 1
- the glide height of the magnetic disk obtained in Comparative Example 10 and the results of the glide inspection are also shown, including Example 1.
- Example 2 to Example 12 were the same as in Example 1. As described above, when the recording / reproducing test was performed at 700 kFCI, a sufficient signal intensity ratio (SZN ratio) was obtained, and no signal error was confirmed. Furthermore, as in Example 1, when mounted and driven on a 1-inch type hard disk drive that required an information recording density of 60 gigabits per square inch or more, recording and reproduction could be performed without any particular problem. . That is, the crash failure ⁇ the thermal asperity failure did not occur.
- Comparative Example 1 Comparative Example 10 was subjected to a recording / reproducing test at 700 kFCI in the same manner as in Example 1.
- Comparative Example 1 Comparative Example 3, Comparative Example 4, The magnetic disk obtained in Comparative Example 10 was able to obtain a sufficient signal intensity ratio (SZN ratio), and a signal error was not confirmed. Because of the poor head flying characteristics, a sufficient signal intensity ratio (SZN ratio) could not be obtained, and a signal error was confirmed.
- SZN ratio sufficient signal intensity ratio
- Example 1 the disk drive was mounted on a 1-inch type hard disk drive that required an information recording density of 60 gigabits per square inch or more, and was driven.
- the magnetic disks obtained in Comparative Examples 4 and 10 could be recorded and reproduced without any particular problems, but the magnetic disks obtained in other comparative examples could be recorded and reproduced well. Failed, crash failure ⁇ thermal asperity failure occurred.
- the diameter (size) of the glass substrate for a magnetic disk is not particularly limited.
- the present invention exhibits excellent usefulness particularly when producing a glass substrate for a magnetic disk having a small diameter.
- the small diameter is, for example, a glass substrate for a magnetic disk having a diameter of 30 mm or less.
- a small-diameter magnetic disk having a diameter of 30 mm or less is used in a storage device in an in-vehicle device such as a car navigation system or a portable device such as a PDA or a mobile phone terminal device.
- an in-vehicle device such as a car navigation system or a portable device such as a PDA or a mobile phone terminal device.
- the glass substrate for a magnetic disk according to the present invention is mounted on a hard disk drive, and is used as a storage device in a vehicle-mounted device such as a force navigation system or a portable device such as a PDA or a mobile phone terminal device.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Manufacturing Of Magnetic Record Carriers (AREA)
- Magnetic Record Carriers (AREA)
- Surface Treatment Of Glass (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/594,248 US7891212B2 (en) | 2004-03-25 | 2005-03-24 | Magnetic disk glass substrate |
JP2006511492A JPWO2005093720A1 (ja) | 2004-03-25 | 2005-03-24 | 磁気ディスク用ガラス基板 |
US13/004,716 US20110129693A1 (en) | 2004-03-25 | 2011-01-11 | Magnetic disk glass substrate |
Applications Claiming Priority (2)
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US55602104P | 2004-03-25 | 2004-03-25 | |
US60/556,021 | 2004-03-25 |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US13/004,716 Division US20110129693A1 (en) | 2004-03-25 | 2011-01-11 | Magnetic disk glass substrate |
Publications (1)
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WO2005093720A1 true WO2005093720A1 (ja) | 2005-10-06 |
Family
ID=35056417
Family Applications (1)
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PCT/JP2005/005362 WO2005093720A1 (ja) | 2004-03-25 | 2005-03-24 | 磁気ディスク用ガラス基板 |
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US (2) | US7891212B2 (ja) |
JP (1) | JPWO2005093720A1 (ja) |
CN (1) | CN100538827C (ja) |
WO (1) | WO2005093720A1 (ja) |
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CN100538827C (zh) | 2009-09-09 |
US20080241603A1 (en) | 2008-10-02 |
JPWO2005093720A1 (ja) | 2008-02-14 |
US7891212B2 (en) | 2011-02-22 |
CN1934620A (zh) | 2007-03-21 |
US20110129693A1 (en) | 2011-06-02 |
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