WO2011033948A1 - 情報記録媒体用ガラス基板、情報記録媒体及び情報記録媒体用ガラス基板の製造方法 - Google Patents
情報記録媒体用ガラス基板、情報記録媒体及び情報記録媒体用ガラス基板の製造方法 Download PDFInfo
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- WO2011033948A1 WO2011033948A1 PCT/JP2010/065114 JP2010065114W WO2011033948A1 WO 2011033948 A1 WO2011033948 A1 WO 2011033948A1 JP 2010065114 W JP2010065114 W JP 2010065114W WO 2011033948 A1 WO2011033948 A1 WO 2011033948A1
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- glass substrate
- recording medium
- information recording
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- polishing
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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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- 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
- G11B2220/25—Disc-shaped record carriers characterised in that the disc is based on a specific recording technology
- G11B2220/2508—Magnetic discs
- G11B2220/2516—Hard disks
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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.]
- Y10T428/24355—Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
Definitions
- the present invention relates to a glass substrate for information recording medium, an information recording medium, and a method for manufacturing a glass substrate for information recording medium.
- An aluminum substrate has been widely used as a substrate for a magnetic recording medium such as a magnetic disk as an information recording medium.
- a magnetic disk becomes smaller and has a higher recording density, the strength and flatness of the recording surface are improved as compared with an aluminum substrate. It is being replaced by an excellent glass substrate.
- the surface of the magnetic recording medium that is, the surface of the glass substrate for the magnetic recording medium is extremely uniform. It is necessary to finish as a rough surface.
- Patent Document 1 discloses a magnetic disk in which minute waviness has a period of 0.1 mm to 5 mm and an amplitude of 0.1 nm to 1 nm.
- the amplitude Wa of the undulation on the surface when measured at a measurement wavelength of 5.0 mm is in the range of 0.1 nm to 0.5 nm, and the above undulation when measured at a measurement wavelength of 30 ⁇ m to 200 ⁇ m.
- a magnetic disk substrate is disclosed in which the average amplitude Wb of the micro waviness formed in the above is 0.3 nm or less, and the value Wb / Wa obtained by dividing the average amplitude Wb of the micro waviness by the amplitude Wa of the waviness is 0.6 or more. ing.
- the evaluation of the flying height of the magnetic head may be indicated by a glide avalanche value (GA value) (for example, Patent Document 3).
- GA value glide avalanche value
- the magnetic recording medium becomes suitable for high recording density when the GA value becomes smaller.
- the present invention has been made in view of the above-described problems, and the object of the present invention is to provide a glass substrate for an information recording medium capable of obtaining a low GA value, and information recording using the glass substrate for the information recording medium. It is to provide a method for producing a medium and a glass substrate for an information recording medium.
- the surface arithmetic mean waviness Wa is less than 0.6 nm
- a glass substrate for an information recording medium characterized in that a root mean square height Rq of micro-waviness in a radial direction and a measurement wavelength in the range of 80 ⁇ m to 120 ⁇ m is less than 0.01 nm.
- An information recording medium comprising a magnetic film on a surface of the glass substrate for information recording medium according to 1 or 2 above.
- the polishing machine has a polishing step in which the weight of the surface plate is 600 kg / m 2 or less and the rotational speed is 10 rpm or less, The arithmetic average waviness Wa of the surface after the polishing step is less than 0.6 nm,
- a method for producing a glass substrate for an information recording medium characterized in that the root mean square height Rq of the microwaviness in the radial direction in the range of the measurement wavelength of 80 ⁇ m or more and 120 ⁇ m or less is less than 0.01 nm.
- a glass substrate for an information recording medium capable of obtaining a low GA value, an information recording medium using the glass substrate for the information recording medium, and a method for manufacturing the glass substrate for an information recording medium are provided. Can do.
- FIG. 1 It is a figure which shows the whole glass substrate for information recording media. It is a figure which shows the example of the magnetic recording medium provided with the magnetic film on the front main surface of the glass substrate for information recording media. It is an enlarged view of the cross section of a glass substrate, (a) is a figure which shows the wave
- FIG. 1 shows the overall configuration of an information recording medium glass substrate 1 (hereinafter also referred to as a glass substrate 1) which is a substrate of a magnetic disk which is an information recording medium according to the present invention.
- the glass substrate 1 has a donut-shaped disk shape with a hole 5 formed in the center.
- 10t is an outer peripheral end surface
- 20t is an inner peripheral end surface
- 7a is a front main surface
- 7b is a back main surface.
- FIG. 2 is a diagram showing an example of a magnetic recording medium (also referred to as a magnetic disk D) having the magnetic film 2 on the front main surface 7a of the glass substrate 1 shown in FIG.
- the magnetic film 2 can also be provided on the back main surface 7b.
- FIG. 3A and 3B are enlarged views of the cross section of the glass substrate.
- a solid line in FIG. 3A is a measurement cross-sectional curve 11 indicating the surface shape of the glass substrate.
- a broken line is the waviness curve 12 showing the waviness of the surface of a glass substrate.
- FIG. 3B is an enlarged view of a part of FIG. 3A, showing a fine waviness curve 13 that is a roughness curve generated on the waviness curve 12, and L represents a measurement wavelength. Show.
- HDD Hard Disk Drive
- information is read and written by magnetism when the head moves over the magnetic disk.
- the magnetic disk In order for the magnetic disk to be able to cope with a high recording density, it is necessary that the head can perform recording and reproduction with a low flying height.
- a magnetic disk inspection as a method for evaluating the flying height of the head, there is a measurement of a glide avalanche value (GA value).
- GA value glide avalanche value
- the GA value of the present embodiment is the flying height when the head flying height is gradually lowered and the head flying becomes unstable in the inspection magnetic disk.
- the smaller the GA value the smaller the flying height of the head with respect to the magnetic disk, and it is possible to cope with a high recording density.
- the GA value was affected by the micro-waviness of the entire magnetic disk.
- the inventors have intensively studied how the GA value can be reduced.
- radial waviness greatly affects the GA value.
- the inventors presumed that micro waviness seen from the radial direction closer to the movement of the head might have an effect on the GA value, and focused on the micro waviness in the radial direction of the magnetic disk, thereby reaching the present invention.
- a value Rq (hereinafter referred to as root mean square height Rq) obtained by calculating a root mean square root height in the radial direction in the measurement wavelength L range of 80 ⁇ m to 120 ⁇ m is preferably less than 0.01 nm. It was found that a GA value sufficiently low in practical use can be obtained by setting the thickness to less than 0.007 nm.
- the micro swell exceeding 120 ⁇ m of the measurement wavelength L can be followed by the head, and the micro swell of less than 80 ⁇ m is not an individual micro swell, but the head follows a virtual surface where these are smoothed.
- 4A and 4B, 8 schematically shows the surface shape of the magnetic disk, and H schematically shows the trajectory of the head.
- the measurement wavelength L1 of the fine undulation in FIG. 4A is a value exceeding 120 ⁇ m
- the measurement wavelength L2 of the fine undulation in FIG. 4B is a value less than 80 ⁇ m.
- the range where the measurement wavelength L of the microwaviness is 80 ⁇ m or more and 120 ⁇ m or less is considered to be a range close to the lower limit value at which the head can follow each microwaviness.
- Rq is expressed by the root mean square, which means that it will be averaged, and if the measurement range covers the waviness of the entire disk surface, Rq will be averaged, thus realizing a low GA. It is considered that the difference between the substrate that can be made and the substrate that is not so does not appear significantly.
- the microwaviness has been described.
- the small waviness on which the microwaviness is superimposed is also necessary for obtaining a low GA value, and the arithmetic average waviness Wa is less than 0.6 nm, preferably 0.8. It must be less than 55 nm.
- the undulation of the undulation curve 12 in FIG. 3A is measured over the entire surface of the glass substrate using a multi-function disk interferometer (Optiflat: manufactured by Phase Shift Technology Inc.).
- the measurement principle is a method of measuring a subtle shape change of the surface by irradiating the surface of the glass substrate with white light and measuring an intensity change of interference between the reference light and the measurement light having different phases.
- the obtained measurement data is measured at a measurement wavelength of 0.1 mm to 5 mm, and the swell is measured, and the arithmetic average swell Wa is obtained according to JIS B0601: 2001.
- the microwaviness of the microwaviness curve 13 generated on the radial waviness curve 12 of FIG. 3B is measured by an optical surface analyzer OSA (CANDELA, RMS application).
- the measurement wavelength L is performed in a band of 80 ⁇ m or more and 120 ⁇ m or less, and the root mean square height Rq is obtained according to JIS B0601: 2001.
- the measurement of the radial direction of the microwaviness using the optical surface analyzer OSA is performed by dividing the glass substrate into 125 parts at an angle of 2.88 ° in the circumferential direction and 0.89 ⁇ m steps in the radial direction from each of the divided inner diameters to outer diameters. Every time, the root mean square height Rq is calculated.
- the glass substrate according to the present invention has a root-mean-square height Rq of less than 0.01 nm in all 125 radial directions.
- the size of the glass substrate there is no limitation on the size of the glass substrate.
- glass substrates of various sizes such as an outer diameter of 2.5 inches, 1.8 inches, 1 inch, and 0.8 inches.
- the thickness of the glass substrate is not limited, and there are glass substrates having various thicknesses such as 2 mm, 1 mm, and 0.64 mm.
- a glass material is melted (glass melting process), molten glass is poured into a lower mold, and press molding is performed with an upper mold to obtain a disk-shaped glass substrate precursor (press molding process).
- the disk-shaped glass substrate precursor may be produced by cutting a sheet glass formed by, for example, a downdraw method or a float method with a grinding stone, without using press molding.
- aluminosilicate glass and borosilicate glass are particularly preferable because they are excellent in impact resistance and vibration resistance.
- the press-molded glass substrate precursor is drilled in the center with a core drill or the like equipped with a diamond grindstone or the like in the cutter (coring process).
- both surfaces of the glass substrate are polished to preliminarily adjust the overall shape of the glass substrate, that is, the parallelism, flatness and thickness of the glass substrate (first lapping step).
- inner and outer diameter processing is performed by grinding the outer peripheral end surface and the inner peripheral end surface of the glass substrate with, for example, a grinding wheel such as a drum-shaped diamond (inner / outer diameter processing step).
- the corners of the chamfered portions are curved by brush polishing using a polishing liquid, and fine scratches are removed (inner peripheral end face processing step).
- both surfaces of the glass substrate are polished again to finely adjust the parallelism, flatness and thickness of the glass substrate (second lapping step).
- the outer peripheral end surface of the glass substrate is made to have a curved corner at the chamfered portion by brush polishing using a polishing liquid, and fine scratches are removed (outer peripheral end surface processing step).
- the order from the first lapping step after the coring processing to the outer peripheral end surface processing step is not limited to that shown in FIG. 5 and can be changed as appropriate according to the situation.
- the lapping process may be performed first, and then the inner / outer diameter machining process, the inner circumference, and the outer circumference end face machining process may be performed.
- a second lapping step, an inner circumference and an outer circumference end face machining step may be performed.
- a polishing machine for polishing a glass substrate in the first and second lapping steps will be described.
- a known polishing machine called a double-side polishing machine can be used.
- the double-side polishing machine includes a disk-shaped upper surface plate and a lower surface plate that are arranged vertically in parallel with each other, and rotate in opposite directions.
- a plurality of diamond pellets for polishing the main surface of the glass substrate are attached to the opposing surfaces of the upper and lower surface plates.
- the diamond pellet can be substituted by a resin sheet in which diamond abrasive grains are embedded.
- the carrier is provided with a plurality of holes, and a glass substrate is fitted into the holes.
- the upper and lower surface plates, the internal gear, and the sun gear can be operated by separate driving.
- the polishing operation of the polishing machine is such that the upper and lower surface plates rotate in opposite directions, and the carrier sandwiched between the surface plates via the diamond pellets rotates with the surface plate holding a plurality of glass substrates. Revolves in the same direction as the lower surface plate with respect to the center of rotation.
- the glass substrate can be polished by supplying a grinding liquid between the upper surface plate and the glass substrate, and the lower surface plate and the glass substrate.
- the weight of the surface plate applied to the glass substrate and the number of rotations of the surface plate are adjusted as appropriate according to the desired polishing state.
- the weight in the first and second lapping steps is preferably 600 kg / m 2 to 1200 kg / m 2 .
- the rotation speed of the surface plate is preferably about 10 to 30 rpm, and the rotation speed of the upper surface plate is preferably about 30% to 40% slower than the rotation speed of the lower surface plate. Increasing the load on the surface plate and increasing the rotation speed of the surface plate increases the amount of polishing, but if the load is increased too much, the surface roughness will not be good, and if the rotation speed is too high, the flatness will be good. Not. Further, when the load is small and the rotation speed of the surface plate is slow, the polishing amount is small and the production efficiency is lowered.
- the surface roughness of the main surface of the glass substrate is Rz (maximum height) of 2 ⁇ m to 4 ⁇ m, Ra (arithmetic mean roughness) Is preferably about 0.1 ⁇ m to 0.4 ⁇ m.
- the surface roughness at the time when the first lapping step is completed is preferably such that Rz is 4 ⁇ m to 8 ⁇ m and Ra is about 0.3 ⁇ m to 0.8 ⁇ m.
- the inner and outer end faces of the glass substrate are polished by brushing in the inner and outer end face processing steps.
- the brush is preferably made of nylon, polypropylene or the like having a diameter of about 0.2 to 0.3 mm.
- the polishing liquid is preferably cerium oxide having a particle size of about several ⁇ m.
- the surface roughness of the inner and outer end faces is preferably such that Rz is 0.2 ⁇ m to 0.4 ⁇ m and Ra is about 0.02 ⁇ m to 0.04 ⁇ m.
- the shape of the end surface of the glass substrate that has undergone the inner and outer diameter processing steps and the inner and outer peripheral end surface processing steps is such that the corner formed by the main surface and the end surface is removed, and the position is about 0.2 mm to 0.5 mm from the outer peripheral end surface. From the main surface.
- Ra absolute mean roughness
- Rz maximum height
- the diamond pellet and the grinding liquid are used when polishing the glass substrate.
- a polishing method by attaching a pad to the polishing surface of the upper and lower surface plates and supplying the polishing liquid.
- the abrasive include cerium oxide, zirconium oxide, aluminum oxide, manganese oxide, colloidal silica, and diamond. These are dispersed in water and used as a slurry.
- the pad is divided into a hard pad and a soft pad, but can be appropriately selected and used as necessary.
- the hard pad include pads made of hard velor, urethane foam, pitch-containing suede, etc.
- examples of the soft pad include pads made of suede, velor, etc.
- the polishing method using a pad and an abrasive can correspond to rough polishing to precision polishing by changing the particle size of the abrasive and the type of pad. Therefore, in the first lapping step and the second lapping step, the abrasive, the particle size of the abrasive, and the pad are appropriately combined so that the above-mentioned surface roughness can be obtained by efficiently removing large undulations, chips, cracks, etc. Can respond.
- polishing machines used in the first lapping process and the second lapping process have the same configuration, but it is preferable to perform polishing using different polishing machines prepared for each process. This is because the dedicated diamond pellets are pasted, so that the replacement is a large-scale operation, and complicated operations such as resetting the polishing conditions are required, resulting in a reduction in manufacturing efficiency.
- an annealing step is performed.
- the glass substrate is placed in an electric heating furnace and held at a temperature of 200 ° C. or higher and 400 ° C. or lower for 10 to 120 minutes.
- the rate of temperature increase and the rate of temperature decrease are not particularly specified, but it is preferable that the temperature is raised to a predetermined temperature in about 10 to 30 minutes and the cooling is performed over a period of about 10 to 60 minutes.
- the annealing step is preferably performed in an oil such as silicone oil that hardly deteriorates at an annealing temperature, in an inert gas such as argon gas or helium gas, or in nitrogen gas.
- an oil such as silicone oil that hardly deteriorates at an annealing temperature
- an inert gas such as argon gas or helium gas, or in nitrogen gas.
- the next polishing process may be one process, but two processes are preferable, and in this embodiment, two processes are used.
- the surface roughness is improved and the glass according to the present invention is improved in the second polishing step so that the surface roughness finally required in the second polishing step can be efficiently obtained. Polishing is performed so that the surface shape of the substrate can be obtained efficiently.
- the polishing method uses a polishing machine having the same configuration as the polishing machine used in the first and second lapping processes except that a suede pad and a polishing liquid are used instead of the diamond pellets and the grinding liquid used in the lapping process. .
- the pad is a hard pad having a hardness A of about 70 to 90, and it is preferable to use urethane foam, for example.
- the abrasive is preferably used in the form of a slurry by dispersing cerium oxide or the like having a particle size of 0.2 to 1.5 ⁇ m in water.
- the mixing ratio of water and abrasive is preferably about 1: 9 to 3: 7.
- Weighted on the glass substrate by platen it can be adjusted arbitrarily, preferably the 1100 kg / m 2 from 900 kg / m 2 in terms of productivity.
- the load applied to the glass substrate by the surface plate greatly affects the shape of the outer peripheral edge.
- the inner side of the outer peripheral end portion tends to fall and rise toward the outside.
- the outer peripheral end portion tends to be close to a flat surface and the surface sagging increases. The weight can be determined while observing these trends.
- the rotation speed of the surface plate can be arbitrarily adjusted.
- the rotation speed of the upper surface plate is set to 30 rpm from the rotation speed of the lower surface plate. % To 40% is preferred.
- the polishing amount is preferably 30 ⁇ m to 40 ⁇ m according to the above polishing conditions. If it is less than 30 ⁇ m, scratches and defects cannot be removed sufficiently. On the other hand, when the thickness exceeds 40 ⁇ m, the polishing is performed more than necessary, and the production efficiency is lowered.
- the second polishing step is a step of polishing the surface of the glass substrate after the first polishing step more precisely.
- the pad used in the second polishing step is a soft pad having a hardness of about 65 to 80 (Asker-C) softer than the pad used in the first polishing step.
- urethane foam or suede is preferably used.
- the abrasive the same cerium oxide or colloidal silica as in the first polishing step can be used, but in order to make the surface of the glass substrate smoother, it is preferable to use an abrasive having a finer particle size and less variation. preferable.
- the mixing ratio of water and abrasive is preferably about 1: 9 to 3: 7, and further, sulfuric acid or hydrogen peroxide is added to make the pH lower than 7, more preferably pH 2 or lower. And By making the polishing liquid acidic, agglomeration of the abrasive can be suppressed, polishing with the original particle size of the abrasive can be performed, and more precise polishing can be performed.
- the glass substrate is loaded and processed as in the lapping process.
- the waviness of the substrate is forcibly relaxed and polished in a flattened state.
- the polishing process causes the glass substrate to have less undulation, but if the weight is removed from the glass substrate, the undulation that was forcibly suppressed is restored, and the undulation is greater than before the weight removal.
- the weight is 600 kg / m 2 or less, which is less than the conventional weight, and the lower limit is not particularly defined, but the range of 550 kg / m 2 to 600 kg / m 2 is preferable from the viewpoint of productivity.
- the weight is gradually reduced below 550 kg / m 2 , the weight becomes insufficient for polishing the glass substrate, and more time is required for polishing, and finally it becomes impractical. End up.
- the rotation speed of the surface plate shall be 10 rpm or less.
- the rotational speed exceeds 10 rpm, vibration occurs in the rotating surface plate, and as a result, undulation occurs in the glass substrate.
- the number of rotations of the surface plate is set to 10 rpm or less, vibration generated on the surface plate can be suppressed, and undulation and minute undulation generated on the glass substrate can be reduced.
- the lower limit is not particularly defined, if the rotational speed is gradually reduced, more time is required to perform polishing, and eventually it becomes impractical.
- the arithmetic mean waviness Wa is less than 0.6 nm
- the square mean of the microwaviness in the radial measurement wavelength L is in the range of 80 ⁇ m to 120 ⁇ m.
- the square root height Rq can be less than 0.01 nm.
- the polishing amount is preferably 2 ⁇ m to 5 ⁇ m. When the polishing amount is within this range, minute defects such as minute roughness and undulation generated on the surface and minute scratches generated in the process so far can be efficiently removed.
- the polishing process is a single process, the first polishing process of the present embodiment may be omitted.
- FIG. 2 shows a perspective view of a magnetic disk D that is a magnetic recording medium in which a magnetic film is provided on the glass substrate described so far.
- a magnetic film 2 is directly formed on the surface of a circular glass substrate 1 for an information recording medium.
- a method for forming the magnetic film 2 a conventionally known method can be used. For example, a method in which a thermosetting resin in which magnetic particles are dispersed is spin-coated on a substrate, or a method by sputtering or electroless plating is used. A method is mentioned.
- the film thickness by spin coating is about 0.3 ⁇ m to 1.2 ⁇ m
- the film thickness by sputtering is about 0.04 ⁇ m to 0.08 ⁇ m
- the film thickness by electroless plating is 0.05 ⁇ m to 0.1 ⁇ m. From the viewpoint of thinning and densification, film formation by sputtering and electroless plating is preferable.
- the magnetic material used for the magnetic film is not particularly limited, and a conventionally known material can be used. However, in order to obtain a high coercive force, Ni having a high crystal anisotropy is basically used, and Ni or A Co-based alloy to which Cr is added is suitable. Specific examples include CoPt, CoCr, CoNi, CoNiCr, CoCrTa, CoPtCr, and CoNiPt containing Co as a main component, CoNiCrPt, CoNiCrTa, CoCrPtTa, CoCrPtB, and CoCrPtSiO.
- the magnetic film may have a multilayer structure (for example, CoPtCr / CrMo / CoPtCr, CoCrPtTa / CrMo / CoCrPtTa) that is divided by a nonmagnetic film (for example, Cr, CrMo, CrV, etc.) to reduce noise.
- a nonmagnetic film for example, Cr, CrMo, CrV, etc.
- granular materials such as ferrite, iron-rare earth, and non-magnetic films made of SiO 2 , BN, etc. are dispersed with magnetic particles such as Fe, Co, FeCo, CoNiPt, etc. Also good.
- the magnetic film may be either an inner surface type or a vertical type recording format.
- a lubricant may be thinly coated on the surface of the magnetic film in order to improve the sliding of the magnetic head.
- the lubricant include those obtained by diluting perfluoropolyether (PFPE), which is a liquid lubricant, with a freon-based solvent.
- an underlayer or a protective layer may be provided.
- the underlayer in the magnetic disk is selected according to the magnetic film.
- the material for the underlayer include at least one material selected from nonmagnetic metals such as Cr, Mo, Ta, Ti, W, V, B, Al, and Ni.
- Cr alone or a Cr alloy is preferable from the viewpoint of improving magnetic characteristics.
- the underlayer is not limited to a single layer, and may have a multi-layer structure in which the same or different layers are stacked.
- a multilayer underlayer such as Cr / Cr, Cr / CrMo, Cr / CrV, NiAl / Cr, NiAl / CrMo, or NiAl / CrV may be used.
- Examples of the protective layer that prevents wear and corrosion of the magnetic film include a Cr layer, a Cr alloy layer, a carbon layer, a hydrogenated carbon layer, a zirconia layer, and a silica layer.
- These protective layers can be formed continuously with an in-line type sputtering apparatus, such as an underlayer and a magnetic film.
- these protective layers may be a single layer, or may have a multilayer structure including the same or different layers. Note that another protective layer may be formed on the protective layer or instead of the protective layer.
- tetraalkoxysilane is diluted with an alcohol-based solvent on the Cr layer, colloidal silica fine particles are dispersed and applied, and then baked to form a silicon dioxide (SiO 2 ) layer. It may be formed.
- the glass substrate for an information recording medium is not limited to a magnetic recording medium (magnetic disk) but can also be used for a magneto-optical disk, an optical disk, and the like.
- the glass substrates and magnetic disks of Examples 1 to 4 and Comparative Examples 1 to 4 were produced as follows.
- Aluminosilicate glass (Tg: 500 ° C.) was used as a glass material, and a molten glass was press-molded to produce a blank material.
- a glass substrate having an outer diameter of 65 mm and an inner diameter of 20 mm was obtained through an inner and outer peripheral processing step and a lapping step.
- the thickness of the glass substrate was 0.64 mm.
- An annealing process As an annealing process, an electric heating furnace was used in an air atmosphere, and 100 glass substrates were respectively produced at an annealing temperature of 350 ° C. and an annealing time of 10 minutes.
- the temperature rising time from room temperature was 30 minutes, and the temperature lowering time to room temperature was 1 hour. (Polishing process)
- a urethane pad manufactured by Nitta Haas was used, and cerium oxide was used as the abrasive.
- a suede pad manufactured by FILWEL was used, and cerium oxide and colloidal silica were used as the abrasive.
- the polishing conditions of the second polishing step are as follows: pad hardness 80 (Asker-C), abrasive particle size 20 nm to 30 nm, polishing solution with hydrogen peroxide to about pH 2 and upper and lower platen rotation speed (rpm)
- the weighting (kg / m 2 ) conditions are shown in Table 1.
- Wash process As a cleaning process, brush scrubbing with a roll scrubbing machine and cup scrubbing machine was performed, followed by cleaning with an ultrasonic cleaner.
- the height of the microwaviness in the measurement wavelength L range of 80 ⁇ m or more and 120 ⁇ m or less was measured using an optical surface analyzer OSA (CANDELA, RMS application), and the root mean square height Rq was obtained.
- OSA optical surface analyzer
- the results are shown in Table 1.
- (Production of magnetic disk) On the surface of the obtained glass substrate, magnetic particles CoPt were sputtered to form a 0.05 ⁇ m magnetic film, thereby producing a magnetic disk.
- GA value measurement A magnetic disk is attached as an inspection disk to a dedicated device for GA value measurement, rotated at a constant speed, and the head is floated on the disk. In this state, while observing the signal from the head, depressurize the space where the head is floating on the inspection disk, and obtain the air pressure at which the signal from the head becomes unstable. The GA value was determined.
- the GA value needs to be practically less than 3 nm, and as a determination in Table 1, it is indicated by symbols ( ⁇ , ⁇ , ⁇ ) according to the following criteria.
- the magnetic average waving Wa is less than 0.6 nm and the root mean square height Rq of the microscopic waviness in the radial direction is less than 0.01 nm. Results were obtained.
- Glass substrate for information recording media (glass substrate) 2 magnetic film 5 hole 7a front main surface 7b back main surface 10t outer peripheral end surface 11 measurement cross-section curve 12 waviness curve 13 micro waviness curve 20t inner peripheral end surface D magnetic disk
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Abstract
Description
且つ、径方向であって、測定波長が80μm以上120μm以下の範囲における微小うねりの二乗平均平方根高さRqが0.01nm未満であることを特徴とする情報記録媒体用ガラス基板。
前記研磨工程後の表面の算術平均うねりWaが0.6nm未満であり、
且つ、径方向であって、測定波長が80μm以上120μm以下の範囲における微小うねりの二乗平均平方根高さRqが0.01nm未満であることを特徴とする情報記録媒体用ガラス基板の製造方法。
(情報記録媒体用ガラス基板の製造工程)
情報記録媒体用ガラス基板の製造工程に関して図5の製造工程図を用いて説明する。
(磁性体成膜)
これまで説明したガラス基板に磁性膜を設けた磁気記録媒体である磁気ディスクDの斜視図を図2に示す。この磁気ディスクDは、円形の情報記録媒体用ガラス基板1の表面に磁性膜2を直接形成されている。磁性膜2の形成方法としては従来公知の方法を用いることができ、例えば磁性粒子を分散させた熱硬化性樹脂を基板上にスピンコートして形成する方法や、スパッタリング、無電解めっきにより形成する方法が挙げられる。スピンコート法での膜厚は約0.3μm~1.2μm程度、スパッタリング法での膜厚は0.04μm~0.08μm程度、無電解めっき法での膜厚は0.05μm~0.1μm程度であり、薄膜化及び高密度化の観点からはスパッタリング法及び無電解めっき法による膜形成が好ましい。
(ガラス基板の作製)
ガラス材料としてアルミノシリケートガラス(Tg:500℃)を用い、溶融ガラスをプレス成形してブランク材を作製した。内外周加工工程、ラッピング工程を経て、外径65mm、内径20mmのガラス基板とした。ガラス基板の厚みは0.64mmとした。
(アニール工程)
アニール工程として、空気雰囲気で電気加熱炉を用い、アニール温度350℃、アニール時間10分でそれぞれガラス基板を100枚ずつ作製した。常温からの昇温時間は、30分とし、常温への降温時間は1時間とした。
(ポリッシング工程)
第1ポリッシング工程として、ニッタ・ハース社製のウレタンパッドを用い、研磨剤としては、酸化セリウムを用いた。
(洗浄工程)
洗浄工程として、ロールスクラブ機、カップスクラブ機でのブラシ洗浄を行い、その後超音波洗浄機で洗浄を行った。
(うねりの高さ、微小うねりの測定)
Opti Flat(Phase Shift Technology 社製、測定波長0.1~5mm)を用いて、作製したガラス基板表面のうねりを測定し、その算術平均うねりWaを求めた。
(磁気ディスクの作製)
得られたガラス基板の表面に、磁性粒子CoPtをスパッタリングして、0.05μmの磁性膜を形成し、磁気ディスクを作製した。
(GA値測定)
磁気ディスクを検査用ディスクとしてGA値測定用の専用装置に取り付け一定のスピードで回転させ、ヘッドをディスク上に浮上させる。この状態で、ヘッドからの信号を観測しながら検査用ディスク上でヘッドが浮上している空間内を減圧してゆき、ヘッドからの信号が不安定になる時点での空気圧を求め、この空気圧からGA値を求めた。
◎:2nm未満
○:2nm以上3nm未満
×:3nm以上
2 磁性膜
5 孔
7a 表主表面
7b 裏主表面
10t 外周端面
11 測定断面曲線
12 うねり曲線
13 微小うねり曲線
20t 内周端面
D 磁気ディスク
Claims (5)
- 表面の算術平均うねりWaが0.6nm未満であり、
且つ、径方向であって、測定波長が80μm以上120μm以下の範囲における微小うねりの二乗平均平方根高さRqが0.01nm未満であることを特徴とする情報記録媒体用ガラス基板。 - 前記算術平均うねりWaが0.55nm未満であり、且つ、前記微小うねりの二乗平均平方根高さRqが0.007nm未満であることを特徴とする請求項1に記載の情報記録媒体用ガラス基板。
- 請求項1又は2に記載の情報記録媒体用ガラス基板の表面に磁性膜を有することを特徴とする情報記録媒体。
- 研磨機の定盤の加重が600kg/m2以下であり、且つ、回転数が10rpm以下である研磨工程を有し、
前記研磨工程後の表面の算術平均うねりWaが0.6nm未満であり、
且つ、径方向であって、測定波長が80μm以上120μm以下の範囲における微小うねりの二乗平均平方根高さRqが0.01nm未満であることを特徴とする情報記録媒体用ガラス基板の製造方法。 - 前記算術平均うねりWaが0.55nm未満であり、且つ、前記微小うねりの二乗平均平方根高さRqが0.007nm未満であることを特徴とする請求項4に記載の情報記録媒体用ガラス基板の製造方法。
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SG2012018008A SG179136A1 (en) | 2009-09-18 | 2010-09-03 | Glass substrate for information recording medium, information recording medium and method of manufacturing glass substrate for information recording medium |
JP2011531885A JPWO2011033948A1 (ja) | 2009-09-18 | 2010-09-03 | 情報記録媒体用ガラス基板、情報記録媒体及び情報記録媒体用ガラス基板の製造方法 |
US13/496,425 US9135939B2 (en) | 2009-09-18 | 2010-09-03 | Glass substrate for information recording medium, information recording medium and method of manufacturing glass substrate for information recording medium |
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JP2012216278A (ja) * | 2011-03-31 | 2012-11-08 | Hoya Corp | 磁気ディスク用ガラス基板の製造方法及び磁気ディスクの製造方法 |
JP2013114730A (ja) * | 2011-11-30 | 2013-06-10 | Showa Denko Kk | 磁気記録媒体用基板、磁気記録媒体、磁気記録媒体用基板の製造方法及び表面検査方法 |
JP2013211069A (ja) * | 2012-03-30 | 2013-10-10 | Konica Minolta Inc | 情報記録媒体用ガラス基板の製造方法 |
JP2016110689A (ja) * | 2013-12-26 | 2016-06-20 | Hoya株式会社 | 磁気ディスク用基板、磁気ディスク、及び磁気ディスクドライブ装置 |
CN110958800A (zh) * | 2018-09-27 | 2020-04-03 | 苹果公司 | 用于钛部件的纹理化表面 |
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US10210895B2 (en) * | 2015-03-19 | 2019-02-19 | Western Digital Technologies, Inc. | Anti-corrosion insulation layer for magnetic recording medium |
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