WO2010029878A1 - 磁気ディスク用ガラス基板の製造方法、磁気ディスク用ガラス基板、磁気ディスクの製造方法及び磁気ディスク - Google Patents
磁気ディスク用ガラス基板の製造方法、磁気ディスク用ガラス基板、磁気ディスクの製造方法及び磁気ディスク Download PDFInfo
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- WO2010029878A1 WO2010029878A1 PCT/JP2009/065312 JP2009065312W WO2010029878A1 WO 2010029878 A1 WO2010029878 A1 WO 2010029878A1 JP 2009065312 W JP2009065312 W JP 2009065312W WO 2010029878 A1 WO2010029878 A1 WO 2010029878A1
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- main surface
- glass substrate
- magnetic disk
- magnetic
- substrate
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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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- 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
- G11B2220/23—Disc-shaped record carriers characterised in that the disc has a specific layer structure
Definitions
- the present invention relates to a method for manufacturing a glass substrate for a magnetic disk mounted on a hard disk drive device, a glass substrate for a magnetic disk, a method for manufacturing a magnetic disk, and a magnetic disk.
- a magnetic disk as a magnetic recording medium mounted on a hard disk drive device (HDD device).
- a magnetic disk is manufactured by laminating a magnetic layer or a protective layer on a substrate, a glass substrate, or a ceramic substrate on which a NiP film is deposited on a metal plate made of an aluminum-magnesium alloy or the like.
- an aluminum alloy substrate has been widely used as a substrate for a magnetic disk.
- surface flatness and A glass substrate having excellent strength with a thin plate has been used.
- Such a glass substrate for a magnetic disk includes a material processing step and a first lapping step (first grinding step); an end shape step (a coring step for forming a hole, an end portion (an outer peripheral end portion and an inner peripheral end portion) Chamfering step (chamfered surface forming step)); end surface polishing step (outer peripheral end and inner peripheral end); second lapping step (second grinding step); main surface polishing step (first) And the second polishing step); manufactured through a chemical strengthening step and the like.
- first grinding step an end shape step (a coring step for forming a hole, an end portion (an outer peripheral end portion and an inner peripheral end portion) Chamfering step (chamfered surface forming step)); end surface polishing step (outer peripheral end and inner peripheral end); second lapping step (second grinding step); main surface polishing step (first) And the second polishing step); manufactured through a chemical strengthening step and the like.
- the recording density of magnetic disks is increasing year by year, and magnetic disks of 100 GB or more are being developed on one side.
- the magnetic disk satisfies the recording density required for both sides, but as the recording density increases in this way, an electronic device that does not require much recording density requires only one side.
- the recording density is satisfied. If the recording density required on one side is satisfied in this way, the number of parts can be reduced on the HDD device side, such as one magnetic head for one magnetic disk, and this is advantageous in terms of cost. Thinning can be realized. Therefore, it is expected that the magnetic disk provided with the magnetic layer only on one side will increase in the future (see, for example, JP-A-2001-351229 (Patent Document 1)).
- the main surface polishing step for the main surface without the magnetic layer is omitted, and the cost (polishing cloth, abrasive (slurry), processing Costs, labor costs, etc.).
- the cost polishshing cloth, abrasive (slurry), processing Costs, labor costs, etc.
- an aluminosilicate glass containing an alkali metal such as sodium or lithium may be used as the glass of the magnetic disk glass substrate.
- alkali metals may be eluted on the substrate surface depending on the environment.
- white dirt by visual observation (so-called corrosion).
- Such dirt can be removed in the cleaning process, but it may cause the cleaning apparatus to become dirty, so it should be suppressed as much as possible.
- the present invention has been made in view of the above points, and is a glass substrate for a magnetic disk that can prevent the occurrence of corrosion and obtain a glass substrate for a magnetic disk with a high recording density that uses only one side as a recording surface.
- An object of the present invention is to provide a manufacturing method and a glass substrate for a magnetic disk.
- Another object of the present invention is to provide a magnetic disk having a high recording density that can use only one side as a recording surface in a state in which elution of substrate constituent components is prevented, and a method for manufacturing the magnetic disk. To do.
- the method for producing a glass substrate for a magnetic disk of the present invention is a method for producing a glass substrate for a magnetic disk comprising a main surface polishing step for polishing a glass substrate having a pair of main surfaces, wherein the main surface polishing step includes: A main surface polishing treatment is performed so that one main surface of the glass substrate has a predetermined arithmetic average roughness (Ra), and an arithmetic average roughness of the one main surface with respect to the other main surface of the glass substrate The main surface is polished with respect to the other main surface so as to be rougher than the thickness (Ra), and to be sufficiently rough to prevent elution of components constituting the glass substrate for a magnetic disk from the other main surface. It is characterized by performing processing.
- the main surface polishing process is performed so as to be sufficiently rough to prevent elution of components constituting the magnetic disk glass substrate, so that it is not used as a magnetic recording surface.
- the elution of the substrate constituents from the main surface can be prevented, thereby preventing the occurrence of corrosion on the surface not used as the magnetic recording surface.
- the method for producing a glass substrate for a magnetic disk of the present invention is a method for producing a glass substrate for a magnetic disk comprising a main surface polishing step for polishing a glass substrate having a pair of main surfaces, wherein the main surface polishing step includes: One main surface of the glass substrate is subjected to a main surface polishing treatment so as to have an arithmetic average roughness (Ra) required for magnetic recording, and the one main surface of the glass substrate is subjected to the one main surface.
- the main surface relative to the other main surface is rougher than the arithmetic average roughness (Ra) of the main surface of the magnetic disk, and is sufficiently rough to prevent elution of components constituting the glass substrate for magnetic disks.
- a polishing process is performed.
- the arithmetic average roughness required for performing magnetic recording on the main surface used as the magnetic recording surface is obtained, and the elution of the substrate components from the main surface not used as the magnetic recording surface is prevented.
- the occurrence of corrosion on the surface not used as the magnetic recording surface can be suppressed.
- the number of times of main surface polishing treatment performed on one main surface of the glass substrate is set on the other main surface of the glass substrate. It is preferable that the number of main surface polishing treatments to be performed is small. According to this method, cost reduction or the like can be achieved.
- the roughness sufficient to prevent elution of components constituting the magnetic disk glass substrate from the other main surface is 5.0 nm or less. preferable. If the roughness of the other main surface is 5.0 nm or less, at least the final main surface polishing treatment is not performed on the other main surface of the glass substrate in the main surface polishing step. May be.
- an arithmetic average roughness (Ra) is 0.30 nm or less with respect to one main surface of the glass substrate.
- the method for manufacturing a glass substrate for magnetic disk of the present invention it is preferable to further include a step of identifying one main surface of the glass substrate for magnetic disk by optical automatic appearance inspection.
- the glass substrate for a magnetic disk of the present invention is a glass substrate having a pair of main surfaces, one main surface having a predetermined arithmetic average roughness (Ra), and the other main surface being the one main surface. It is rougher than the arithmetic average roughness (Ra), and has a roughness sufficient to prevent elution of components constituting the glass substrate for a magnetic disk from the other main surface. According to this configuration, only one surface can be used as the magnetic recording layer in a state where the occurrence of corrosion on the surface not used as the magnetic recording surface is suppressed.
- the glass substrate for a magnetic disk of the present invention is a glass substrate having a pair of main surfaces, one main surface having an arithmetic average roughness (Ra) required for performing magnetic recording, and the other main surface. Is rougher than the arithmetic average roughness (Ra) of the one main surface, and has a roughness sufficient to prevent elution of components constituting the glass substrate for magnetic disks. According to this configuration, it is possible to realize a single-sided magnetic recording layer that can exhibit required characteristics in a state in which the occurrence of corrosion on a surface that is not used as a magnetic recording surface is suppressed.
- the magnetic disk of the present invention is characterized in that at least a magnetic recording layer is formed on the one main surface of the glass substrate for a magnetic disk.
- At least a magnetic recording layer is formed only on the one main surface of the glass substrate for magnetic disk, and the component constituting the glass substrate for magnetic disk is formed on the other main surface. It is preferable that a substrate constituent component elution preventing layer for preventing elution of is formed.
- the substrate component elution preventing layer for preventing elution of the components constituting the magnetic disk glass substrate is formed on the main surface of the magnetic disk glass substrate, the other glass substrate for the magnetic disk is formed. If the main surface has a sufficient roughness to prevent the components constituting the glass substrate for magnetic disks from being eluted, the elution of the substrate components on the main surface can be further blocked, whereby the magnetic recording surface As a result, it is possible to further suppress the occurrence of corrosion on the surface not used.
- the magnetic disk of the present invention is a magnetic disk in which at least a magnetic recording layer is formed on a glass substrate for a magnetic disk having a pair of main surfaces, and is required for performing magnetic recording on the glass substrate for a magnetic disk. Elution of substrate constituents that prevents at least a magnetic recording layer from being formed on one main surface having arithmetic average roughness (Ra) and prevents the components constituting the glass substrate for magnetic disks from being eluted on the other main surface. A prevention layer is formed.
- the substrate component elution preventing layer for preventing the elution of the components constituting the magnetic disk glass substrate is formed on the main surface of the magnetic disk glass substrate, the elution of the substrate components on the main surface is prevented. It is possible to block, thereby suppressing the occurrence of corrosion on the surface not used as the magnetic recording surface.
- the roughness of the main surface of the magnetic disk glass substrate on the side where the substrate component elution preventing layer is to be formed is preferably 6 nm or less. If the roughness is within this range, the occurrence of corrosion can be effectively suppressed.
- the thickness of the substrate component elution preventing layer is preferably 4 nm or more. By setting the thickness to 4 nm or more, a sufficient effect as a substrate component elution preventing layer can be obtained.
- the substrate component elution preventing layer is made of a titanium alloy containing titanium alone.
- a disk warpage prevention layer is formed on the substrate component elution prevention layer.
- a protective layer formed on the magnetic recording layer is formed on the substrate component elution preventing layer or the disk warp preventing layer.
- the total thickness of the layers formed on the one main surface is the same as the total thickness of the layers formed on the other main surface. According to this configuration, the film stress on both main surfaces can be balanced, and the magnetic disk can be prevented from warping.
- the magnetic disk manufacturing method of the present invention is a method for manufacturing a magnetic disk comprising at least a magnetic recording layer formed on a magnetic disk substrate obtained through a main surface polishing step of polishing a glass substrate having a pair of main surfaces. And at least the magnetic recording layer is formed only on one main surface.
- the magnetic disk manufacturing method of the present invention is a method for manufacturing a magnetic disk comprising at least a magnetic recording layer formed on a magnetic disk substrate obtained through a main surface polishing step of polishing a glass substrate having a pair of main surfaces.
- a substrate structure for forming at least a magnetic recording layer only on one main surface and preventing elution of components constituting the glass substrate for a magnetic disk from the other main surface on the other main surface A component elution prevention layer is formed.
- the substrate component elution preventing layer for preventing the elution of the components constituting the magnetic disk glass substrate is formed on the main surface of the magnetic disk glass substrate, the elution of the substrate components on the main surface is prevented. Thus, the occurrence of corrosion on the surface not used as the magnetic recording surface can be suppressed.
- one main surface of the glass substrate is subjected to main surface polishing so as to have a predetermined arithmetic average roughness, and the other of the glass substrates is processed. It is rougher than the arithmetic mean roughness (Ra) of one main surface with respect to the main surface, and is sufficiently rough to prevent elution of components constituting the glass substrate for magnetic disks from the other main surface. Since the main surface polishing process is performed on the other main surface, the elution of the substrate components from the main surface that is not used as a magnetic recording surface can be prevented, thereby preventing corrosion on the surface that is not used as a magnetic recording surface. Can be suppressed.
- Ra arithmetic mean roughness
- one main surface has a predetermined arithmetic average roughness (Ra), and the other main surface is rougher than the arithmetic average roughness (Ra) of the one main surface, Preventing elution of substrate constituent components from a main surface not used as a magnetic recording surface because it has sufficient roughness to prevent elution of components constituting the magnetic disk glass substrate from the other main surface. Thus, the occurrence of corrosion on the surface not used as the magnetic recording surface can be suppressed.
- At least a magnetic recording layer is formed only on one main surface having an arithmetic average roughness (Ra) required for magnetic recording of a glass substrate for a magnetic disk having a pair of main surfaces.
- Ra arithmetic average roughness
- the method for manufacturing a magnetic disk of the present invention comprises forming at least a magnetic recording layer only on one main surface of a glass substrate for a magnetic disk obtained through a main surface polishing step for polishing a glass substrate having a pair of main surfaces.
- the main component surface not used as a magnetic recording surface is formed on the other main surface so as to form a substrate component elution preventing layer for preventing elution of components constituting the glass substrate for magnetic disk from the other main surface.
- the elution of the substrate constituents can be blocked, thereby preventing the occurrence of corrosion on the surface not used as the magnetic recording surface.
- aluminosilicate glass soda lime glass, borosilicate glass, or the like can be used as the material for the magnetic disk glass substrate.
- aluminosilicate glass can be preferably used in that it can be chemically strengthened and can provide a glass substrate for a magnetic disk excellent in flatness of the main surface and substrate strength.
- the manufacturing process of the glass substrate for a magnetic disk includes a material processing process and a first lapping process; an edge shape process (a coring process for forming a hole, a chamfered surface at an outer edge and / or an inner edge) Chamfering step (chamfered surface forming step)); second lapping step; end surface polishing step (outer peripheral end and inner peripheral end); main surface polishing step (first and second polishing step); chemical strengthening step Including such processes.
- a molten glass is used as a material, and a known manufacturing method such as a press method, a float method, a down draw method, a redraw method, or a fusion method is used. Can be manufactured. Of these methods, if a press method is used, a sheet glass can be produced at a low cost.
- both main surfaces of the sheet glass are lapped to form a disk-shaped glass substrate.
- This lapping process can be performed using alumina free abrasive grains by a double-sided lapping apparatus using a planetary gear mechanism. Specifically, the lapping platen is pressed on both sides of the plate glass from above and below, the grinding liquid containing free abrasive grains is supplied onto the main surface of the plate glass, and these are moved relative to each other for lapping. Do. By this lapping process, a glass substrate having a flat main surface can be obtained.
- Second Lapping Step the second lapping process is performed on both main surfaces of the obtained glass substrate in the same manner as in the first lapping step.
- the fine irregularities / surface damages / scratches formed on the main surface in the previous process are removed, and the surface roughness is further reduced as compared with the first lapping. It becomes possible to complete the polishing process for the main surface in a short time.
- the end surface polishing step the outer peripheral end surface and the inner peripheral end surface of the glass substrate are mirror-polished by a brush polishing method.
- abrasive grains for example, a slurry containing cerium oxide abrasive grains (free abrasive grains) can be used.
- Main surface polishing step As the main surface polishing step, first, a first polishing step is performed.
- the first polishing process is a process whose main purpose is to remove the scratches and distortions remaining on the main surface in the above-described two-stage lapping process and to adjust the roughness of the previous stage for creating the surface roughness in the final polishing process. is there.
- the main surface is polished using a hard resin polisher by a double-side polishing apparatus having a planetary gear mechanism.
- the abrasive cerium oxide abrasive grains can be used.
- this first polishing step it is sufficient to prevent elution of components (for example, alkali metal) constituting the glass substrate from the surface opposite to the magnetic recording surface of the glass substrate (surface not provided with the magnetic recording layer). Polishing is performed so that the surface becomes rough.
- components for example, alkali metal
- FIG. 1 is a characteristic diagram showing the relationship between the arithmetic average roughness (Ra) of a glass substrate made of aluminosilicate glass and the elution amount of an alkali metal that is a component constituting the glass substrate.
- the arithmetic average roughness can be obtained, for example, by measuring a measurement area of 2 ⁇ m ⁇ 2 ⁇ m square with a resolution of 256 ⁇ 256 pixels using an atomic force microscope.
- the alkali metal elution amount indicates the elution amount when a corrosion test is performed in which the glass substrate is exposed to an environment of 80 ° C. and 80% RH for 7 days.
- the count is the number of bright spots per unit area (approximately 200 ⁇ m ⁇ 300 ⁇ m region) of the glass substrate after the corrosion test with an optical microscope ( ⁇ 200 magnification).
- This “bright spot” is caused by an alkali component that is diffused on the surface of the glass substrate due to accelerated alkali diffusion under a high temperature and high humidity environment. Therefore, the greater the number of bright spots, the worse the corrosion resistance.
- the main surface of the present invention is subjected to main surface polishing treatment so that one main surface of the glass substrate has a predetermined arithmetic average roughness, and to the other main surface of the glass substrate.
- the other main surface is rougher than the arithmetic mean roughness (Ra) of one main surface, and is sufficiently rough to prevent elution of components constituting the glass substrate for magnetic disks from the other main surface.
- the main surface polishing process is performed to suppress the occurrence of corrosion on the surface that is not used as the recording surface of the glass substrate for a magnetic disk that uses only one surface as the magnetic recording surface.
- the first polishing step at least the arithmetic average roughness of the surface opposite to the magnetic recording surface is rough enough to prevent the components constituting the magnetic disk glass substrate from eluting.
- a polishing process is performed.
- the roughness sufficient to prevent elution of the components constituting the magnetic disk glass substrate is, for example, 5.0 nm or less.
- the surface opposite to the magnetic recording surface is subjected to a polishing process so that the arithmetic average roughness thereof is sufficiently rough to prevent elution of components constituting the magnetic disk glass substrate. Accordingly, it is possible to suppress the occurrence of corrosion on the surface not used as the magnetic recording surface of the glass substrate for a high recording density, which uses only one surface as the magnetic recording surface.
- polishing process is a process aiming at finishing only the surface used as a recording surface among both main surfaces in a mirror surface shape.
- mirror polishing of the main surface is performed using a soft foamed resin polisher by a double-side polishing apparatus having a planetary gear mechanism.
- the slurry cerium oxide abrasive grains or colloidal silica finer than the cerium oxide abrasive grains used in the first polishing step can be used.
- the main surface (A surface) used as the magnetic recording surface is subjected to final polishing treatment
- the main surface (B surface) not used as the magnetic recording surface is subjected to final polishing treatment. Absent.
- the A surface has a predetermined arithmetic average roughness (Ra)
- the B surface is rougher than the arithmetic average roughness of the A surface
- the glass from the B surface is glass. It has sufficient roughness to prevent elution of the components constituting the substrate.
- the predetermined roughness is, for example, an arithmetic average roughness required for performing magnetic recording.
- the arithmetic average roughness required for performing magnetic recording can be determined according to the recording density of the magnetic recording layer.
- the final polishing process is performed in a state where the main surface that is not used as the magnetic recording surface is masked.
- costly final polishing treatment can be performed only on one main surface, preventing the elution of components on the surface not used as a magnetic recording surface, and suppressing the occurrence of corrosion, Cost reduction can be achieved.
- the main surface polishing performed on the main surface not used as the magnetic recording layer of the magnetic disk glass substrate than the number of main surface polishing processes performed on the main surface used as the magnetic recording layer of the magnetic disk glass substrate.
- the number of processes will be small.
- the arithmetic average roughness of the main surface not used as the magnetic recording layer of the glass substrate for magnetic disks is rougher than the arithmetic average roughness (Ra) of the main surface used as the magnetic recording layer.
- the B surface is sufficient to prevent elution of components constituting the glass substrate. If not rough, the final polishing process may be performed on the B surface. Further, in the above description, the case where only the final polishing process is not performed on the B surface is described, but the present invention is not limited to this, and the B surface prevents elution of components constituting the glass substrate. If the roughness is sufficient to achieve this, neither the first polishing process nor the final polishing process may be performed on the B surface.
- Chemical strengthening step the glass substrate that has been subjected to the lapping step and the polishing step described above is chemically strengthened.
- a chemical strengthening solution used for chemical strengthening for example, a mixed solution of potassium nitrate (60%) and sodium nitrate (40%) can be used.
- the chemical strengthening solution is heated to 300 ° C. to 400 ° C., the cleaned glass substrate is preheated to 200 ° C. to 300 ° C., and immersed in the chemical strengthening solution for 3 hours to 4 hours.
- the immersion is preferably performed in a state of being accommodated in a holder so that the plurality of glass substrates are held at the end surfaces.
- the lithium ions and sodium ions in the surface layer of the glass substrate are respectively replaced with sodium ions and potassium ions having a relatively large ion radius in the chemical strengthening solution. Will be strengthened.
- the main surface polishing process is performed so that one main surface of the glass substrate for magnetic disk has a predetermined arithmetic average roughness, and glass for magnetic disk is obtained. Roughness sufficient to prevent elution of components constituting the glass substrate for magnetic disk from the other main surface, which is rougher than the arithmetic mean roughness (Ra) of one main surface relative to the other main surface of the substrate.
- the main surface polishing process is performed on the other main surface so that the elution of the substrate components from the main surface that is not used as a magnetic recording surface can be prevented, and thus the surface that is not used as a magnetic recording surface It is possible to suppress the occurrence of corrosion on the surface.
- the adhesion layer 12, the soft magnetic layer 13, the nonmagnetic underlayer 14, the perpendicular magnetic recording layer 15, and the protection are formed on the surface A of the glass substrate 11 on the surface A of the glass substrate obtained through the above-described steps.
- the perpendicular magnetic recording disk is manufactured by sequentially forming the layer 16 and the lubricating layer 17.
- the material constituting the adhesion layer 12 include a Cr alloy.
- the material constituting the soft magnetic layer 13 include a CoTaZr-based alloy.
- the nonmagnetic underlayer 14 include a granular nonmagnetic layer.
- the perpendicular magnetic recording layer 15 include a granular nonmagnetic layer.
- Examples of the material constituting the protective layer 16 include hydrogenated carbon.
- Examples of the material constituting the lubricating layer 17 include a fluororesin.
- these recording layers and the like are more specifically formed by using an in-line sputtering apparatus on a glass substrate, a CrTi adhesion layer, a CoTaZr / Ru / CoTaZr soft magnetic layer, and a CoCrSiO 2 nonmagnetic granular material.
- An underlayer, a CoCrPt—SiO 2 ⁇ TiO 2 granular magnetic layer, and a hydrogenated carbon protective film are sequentially formed, and a perfluoropolyether lubricating layer is formed by dipping.
- this recording layer forming step at least a magnetic recording layer is formed on the main surface used as the magnetic recording layer, and a magnetic disk substrate is formed from the main surface on the main surface not used as the magnetic recording layer. It is preferable to form a substrate component elution prevention layer (buffer layer) that prevents elution of components.
- buffer layer a substrate component elution prevention layer that prevents elution of components.
- the material of the buffer layer is not particularly limited as long as it can prevent elution of components constituting the glass substrate for magnetic disks, but the layer thickness can be reduced, and the adhesion to the glass substrate is good.
- a titanium alloy film containing a simple titanium and a chromium alloy film containing a simple chromium are preferable, and a CrTi film is particularly preferable.
- the structure which is sufficient roughness in order to prevent the elution of the component which comprises the glass substrate for magnetic discs was shown, specifically 5 nm or less was shown
- the buffer layer is provided on the B surface.
- the elution of the component can be suppressed by forming a buffer layer on the B surface.
- the glass substrate for magnetic disk is incorporated by forming a buffer layer on the B surface. The elution of the component can be suppressed to the extent that there is no problem in using the HDD device.
- FIG. 4 is a characteristic showing the relationship between the thickness of a buffer layer formed on a glass substrate composed of a multicomponent glass containing an aluminosilicate glass and the amount of alkali metal that is a component constituting the glass substrate.
- FIG. 4 As for the elution amount of the alkali metal, the magnetic disk was exposed to an environment of 65 ° C. and 90% RH for 5 days, this magnetic disk was installed in an HDD device, and a seek test was conducted (40 million seeks, The number of read / write errors (R / W errors) was counted), and the count number was defined as the alkali metal elution amount.
- the roughness of the B surface is 6 nm. That is, in a high-temperature and high-humidity environment, corrosion is promoted, and the corrosion product that has come out of the surface not used as the magnetic recording layer (B-side) is scattered by the disk rotation and used as the magnetic recording layer (A-side). In the seek test, the scattered matter adheres to the magnetic head and induces an R / W error. Therefore, the greater the count number, the greater the alkali metal elution amount (poor corrosion resistance).
- Multicomponent glass is glass that has other components added to improve glass melting and other properties in addition to Si, which forms the main skeleton of the glass, and many other than the above aluminosilicate glass. There is no glass. Of these, aluminosilicate glass, aluminoborosilicate glass and soda lime glass are particularly preferable as the glass substrate for magnetic disks.
- the present inventors need to form a buffer layer having a certain thickness on a surface that is not used as a magnetic recording surface of a glass substrate for a magnetic disk in order to block elution of the substrate constituent components. As a result, the present invention has been completed.
- the essence of the present invention is a substrate which forms at least a magnetic recording layer on one main surface and prevents elution of components constituting the glass substrate for a magnetic disk from the other main surface on the other main surface.
- the component elution preventing layer it is possible to block the elution of the substrate component on the main surface that is not used as the magnetic recording surface, and to suppress the occurrence of corrosion on the surface that is not used as the magnetic recording surface.
- a buffer layer 18 that is at least a substrate component elution preventing layer is formed on a surface (lower surface in FIG. 3) that is not used as a magnetic recording layer of a glass substrate for a magnetic disk.
- the thickness of the buffer layer 18 is preferably 4 nm or more based on the findings shown in FIG. Further, examples of the material constituting the buffer layer 18 include Ti, Cr, and carbon.
- a magnetic recording layer or the like is formed on the main surface (A surface) used as the magnetic recording layer and a layer is not formed on the main surface (B surface) not used as the magnetic recording layer, the space between the A surface and the B surface It is conceivable that the balance of film stress in the magnetic field is lost and the magnetic disk is warped. Considering this, it is preferable to form a disk warp preventing layer 19 on the buffer layer 18 as shown in FIG.
- the material constituting the disc warpage preventing layer 19 include a material constituting the layer formed on the A surface, such as a Cr alloy. In this case, it is preferable that the total thickness of the layers formed on the A surface is the same as the total thickness of the layers formed on the B surface.
- the thickness of the disc warpage preventing layer 19 is appropriately determined in consideration of the configuration and thickness of the layers formed on the A surface so that the total thickness of the layers on both main surfaces is the same. It is desirable.
- a protective layer or a lubricating layer formed on the A surface may be formed on the buffer layer 18 or the disk warpage preventing layer 19 as necessary.
- a main surface (A surface) used as a magnetic recording surface is identified, and a magnetic recording layer or the like is formed on the main surface to manufacture a magnetic disk. explain.
- the manufactured magnetic disk glass substrate has a main surface (A surface) used as a magnetic recording surface and a main surface (B surface) not used as a magnetic recording surface. Therefore, in consideration of the magnetic disk manufacturing process, it is necessary to identify the A surface of the manufactured magnetic disk glass substrate so that a magnetic recording layer or the like is definitely formed on the A surface. Since the glass substrate is a transparent body and also has a predetermined level of arithmetic average roughness for the B surface, it is very difficult to accurately identify the A surface by visual inspection. For this reason, for example, the surface A is accurately identified using an appearance inspection apparatus 2 using an optical automatic appearance inspection (AOI) as shown in FIG.
- AOI optical automatic appearance inspection
- the visual inspection apparatus 2 shown in FIG. 5 includes two defect detection probe lasers 21a and 21b, and four detectors 22a to 22d that each detect scattered light in almost all directions of the laser light. .
- the two defect detection probe lasers 21a and 21b are spaced apart with the same laser output direction.
- the defect detection probe laser 21a emits measurement laser light
- the defect detection probe laser 21b emits reference laser light.
- the detectors 22a, 22b, and 22c are arranged at positions where the diffracted / scattered light at the laser irradiation position of the defect detection probe laser 21a can be detected, and detect the diffracted / scattered light from the magnetic disk glass substrate 10 respectively. Obtain scattered light intensity information.
- the detector 22b is arranged so as to detect one of the lights divided by the beam splitter 23 arranged in front of the detector 22c.
- the detector 22d is disposed at a position where it can detect the diffracted / scattered light at the laser irradiation position of the laser 21b for defect detection probe, detects the diffracted / scattered light serving as a reference for the glass substrate 10 for magnetic disk, Obtain reference scattered light intensity information.
- the magnitude of the arithmetic average roughness is determined from the scattered light intensity information and the reference scattered light intensity information thus obtained.
- the main surface (B surface) with a large arithmetic average roughness has a relatively large scattered light intensity
- the main surface (A surface) with a small arithmetic average roughness has a relatively small scattered light intensity.
- the difference between the scattered light intensity and the reference scattered light intensity is relatively large
- the difference between the scattered light intensity and the reference scattered light intensity is relatively small.
- the laser diameter is small, for example, about 5 ⁇ m, the laser wavelength is short, and the power is high, so that the identification accuracy is high.
- laser light is emitted from the two defect detection probe lasers 21 a and 21 b to the surface of the magnetic disk glass substrate 10 while moving the magnetic disk glass substrate 10. Irradiation is performed, and the diffracted / scattered light at that time is detected by the detectors 22a to 22d. Thereafter, output signals from the detectors 22a to 22d are taken in by a determination circuit (not shown), and the A surface / B surface of the magnetic disk glass substrate 10 is identified based on the output signals.
- the outer peripheral edge of the glass substrate was mirror polished by a brush polishing method.
- a slurry (free abrasive grains) containing cerium oxide abrasive grains was used as the abrasive grains.
- the glass substrate after the mirror polishing process was washed with water.
- the diameter of the glass substrate was 65 mm, and the substrate used for the 2.5-inch magnetic disk could be obtained.
- a first polishing step was performed on both main surfaces of the glass substrate.
- a double-side polishing machine was used as the polishing apparatus.
- a polishing pad in this polishing apparatus a soft suede pad was used.
- a cerium abrasive was used as the abrasive.
- the polishing conditions were a processing surface pressure of 130 g / cm 2 and a processing rotation speed of 22 rpm. Thereby, the arithmetic mean roughness (Ra) of the glass substrate became about 1.5 nm.
- a second polishing process was performed only on the main surface used as the magnetic recording surface in a state where the main surface not used as the magnetic recording surface of the glass substrate was masked.
- a double-side polishing machine was used as the polishing apparatus.
- a polishing pad in this polishing apparatus a soft suede pad (Asker C hardness: 54, compression deformation amount: 476 ⁇ m or more, density: 0.53 g / cm 3 or less) was used.
- the abrasive a cerium abrasive having an average particle diameter of 100 nm was used.
- the polishing conditions were a processing surface pressure of 60 g / cm 2 and a processing rotation speed of 20 rpm.
- the arithmetic average roughness (Ra) of the main surface used as the magnetic recording surface of the glass substrate was about 0.30 nm.
- the glass substrate after the second polishing step is immersed in a KOH solution, cleaned by applying ultrasonic waves for 120 seconds, scrubbed using an alkali cleaning solution for 4 seconds, diluted with a dilute sulfuric acid diluted in a trace amount, and After washing with the alkaline washing solution, IPA (isopropyl alcohol) was vapor-dried.
- chemical strengthening was performed on the glass substrate after the second polishing step described above.
- a chemical strengthening solution in which potassium nitrate (60%) and sodium nitrate (40%) are mixed is prepared, this chemical strengthening solution is heated to 380 ° C., and the cleaned glass substrate is placed therein for about 4 hours. This was done by dipping. Then, acid cleaning, alkali cleaning, and pure water cleaning were sequentially performed on the glass substrate after the chemical strengthening. Thus, a glass substrate for a magnetic disk was produced.
- a corrosion test was performed on 100 glass substrates of each experimental example obtained in this way, and exposed for 7 days in an environment of 80 ° C. and 80% RH.
- the glass substrate after the corrosion test was observed with an optical microscope ( ⁇ 200 magnification), and the number of bright spots per unit area (region of about 200 ⁇ m ⁇ 300 ⁇ m) was measured.
- the results are shown in Table 2.
- ⁇ Formation of layer> An adhesion layer, a soft magnetic layer, a nonmagnetic underlayer, a perpendicular magnetic recording layer, a protective layer, and a lubricating layer were sequentially laminated on the A surface of the produced magnetic disk glass substrate. Further, as shown in Table 2, a magnetic disk was manufactured by forming a titanium layer as a buffer layer on the B surface of some samples. The 100 magnetic disks thus obtained were exposed to an environment of 65 ° C. and 90% RH for 5 days, this magnetic disk was incorporated into an HDD device, and a seek test was performed (40 million seeks, reading / reading during that time). Count the number of write errors (R / W errors)). The results are shown in Table 2.
- the occurrence of corrosion could be suppressed by setting the surface roughness of the B surface to 5 nm or less.
- the number of read / write errors can be reduced by forming a buffer layer on the B surface.
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Abstract
Description
本実施の形態において、磁気ディスク用ガラス基板の材料としては、アルミノシリケートガラス、ソーダライムガラス、ボロシリケートガラスなどを用いることができる。特に、化学強化を施すことができ、また主表面の平坦性及び基板強度において優れた磁気ディスク用ガラス基板を提供することができるという点で、アルミノシリケートガラスを好ましく用いることができる。
まず、素材加工工程においては、例えば溶融ガラスを材料として、プレス法やフロート法、ダウンドロー法、リドロー法、フュージョン法など、公知の製造方法を用いて製造することができる。これらの方法うち、プレス法を用いれば、板状ガラスを廉価に製造することができる。
コアリング工程においては、例えば、円筒状のダイヤモンドドリルを用いて、このガラス基板の中心部に内孔を形成し、円環状のガラス基板とする。チャンファリング工程においては、内周端面及び外周端面をダイヤモンド砥石によって研削し、所定の面取り加工を施す。
第2ラッピング工程においては、得られたガラス基板の両主表面について、第1ラッピング工程と同様に、第2ラッピング加工を行う。この第2ラッピング工程を行うことにより、前工程において主表面に形成された微細な凹凸形状/表面ダメージ・傷などを除去し、かつ第1ラッピングよりもさらに表面粗さを低減することで、後続の主表面に対する研磨工程を短時間で完了させることができるようになる。
端面研磨工程においては、ガラス基板の外周端面及び内周端面について、ブラシ研磨方法により、鏡面研磨を行う。このとき、研磨砥粒としては、例えば、酸化セリウム砥粒を含むスラリー(遊離砥粒)を用いることができる。この端面研磨工程により、ガラス基板の端面での汚染・ダメージ・傷の除去を行うことで、ナトリウムやカリウムのようなコロージョンの原因となるイオン析出の発生を防止できる状態になる。
主表面研磨工程として、まず第1研磨工程を施す。第1研磨工程は、前述の2段のラッピング工程で主表面に残留したキズや歪みの除去及び最終研磨工程における表面粗さ創生のための前段階の粗さ調整を主たる目的とする工程である。この第1研磨工程においては、遊星歯車機構を有する両面研磨装置により、硬質樹脂ポリッシャを用いて、主表面の研磨を行う。研磨剤としては、酸化セリウム砥粒を用いることができる。
次に、最終研磨工程として、第2研磨工程を施す。第2研磨工程は、両主表面のうち記録面となる面のみを鏡面状に仕上げることを目的とする工程である。この第2研磨工程においては、遊星歯車機構を有する両面研磨装置により、軟質発泡樹脂ポリッシャを用いて、主表面の鏡面研磨を行う。スラリーとしては、第1研磨工程で用いた酸化セリウム砥粒よりも微細な酸化セリウム砥粒やコロイダルシリカなどを用いることがきる。
化学強化工程においては、前述のラッピング工程及び研磨工程を終えたガラス基板に化学強化を施す。化学強化に用いる化学強化液としては、例えば、硝酸カリウム(60%)と硝酸ナトリウム(40%)の混合溶液などを用いることができる。化学強化においては、化学強化液を300℃~400℃に加熱し、洗浄済みのガラス基板を200℃~300℃に予熱し、化学強化溶液中に3時間~4時間浸漬することによって行う。この浸漬の際には、ガラス基板の表面全体が化学強化されるようにするため、複数のガラス基板が端面で保持されるように、ホルダに収納した状態で行うことが好ましい。
上述した工程を経て得られたガラス基板のA面に、図3に示すように、ガラス基板11の表面に付着層12、軟磁性層13、非磁性下地層14、垂直磁気記録層15、保護層16、及び潤滑層17を順次成膜することにより、垂直磁気記録ディスクを製造する。付着層12を構成する材料としては、Cr合金などを挙げることができる。軟磁性層13を構成する材料としては、CoTaZr基合金などを挙げることができる。非磁性下地層14としては、グラニュラー非磁性層などを挙げることができる。垂直磁気記録層15としては、グラニュラー非磁性層などを挙げることができる。保護層16を構成する材料としては、水素化カーボンなどを挙げることができる。潤滑層17を構成する材料としては、フッ素樹脂などを挙げることができる。例えば、これらの記録層等は、より具体的には、インライン型スパッタリング装置を用いて、ガラス基板の上に、CrTiの付着層、CoTaZr/Ru/CoTaZrの軟磁性層、CoCrSiO2の非磁性グラニュラー下地層、CoCrPt-SiO2・TiO2のグラニュラー磁性層、水素化カーボン保護膜を順次成膜し、さらに、ディップ法によりパーフルオロポリエーテル潤滑層を成膜する。
(実験例1~4)
まず、溶融させたアルミノシリケートガラスを上型、下型、胴型を用いたダイレクトプレスによりディスク形状に成型し、アモルファスの板状ガラス素材(ブランクス)を得た。この時点でブランクスの直径は66mmである。次に、このブランクスの両主表面を第1ラッピング加工して後、円筒状のコアドリルを用いて、このガラス基板の中心部に穴部を形成し円環状のガラス基板に加工(コアリング)を実施、そして端部(外周端部及び内周端部)に面取り面を形成するチャンファリング工程(面取り面形成工程))を施し、その後第2ラッピング加工を行った。
研磨条件を調整したり、ガラス基板の磁気記録面として使用しない主表面をマスクした状態で第1研磨処理を施したりすること以外は、実験例1~4と同様にして、表2に示す算術表面粗さを有する磁気ディスク用ガラス基板を作製した。
作製した磁気ディスク用ガラス基板のA面上に、付着層、軟磁性層、非磁性下地層、垂直磁気記録層、保護層及び潤滑層を順次積層した。また、表2のように、一部のサンプルに対し、B面上に、バッファ層としてチタン層を形成して磁気ディスクを作製した。このようにして得られた磁気ディスク100枚を65℃、90%RH環境下に5日間暴露し、この磁気ディスクをHDD装置に組み込み、シークテストを実施した(4000万回シーク、その間の読み出し/書き込みエラー(R/Wエラー)数をカウント)。この結果を表2に示す。
Claims (20)
- 一対の主表面を有するガラス基板を研磨する主表面研磨工程を含む磁気ディスク用ガラス基板の製造方法であって、前記主表面研磨工程において、前記ガラス基板の一方の主表面に対して所定の算術平均粗さ(Ra)になるように主表面研磨処理を行い、前記ガラス基板の他方の主表面に対して前記一方の主表面の算術平均粗さ(Ra)よりも粗く、前記他方の主表面から前記磁気ディスク用ガラス基板を構成する成分の溶出を防止するために十分な粗さになるように前記他方の主表面に対して主表面研磨処理を行うことを特徴とする磁気ディスク用ガラス基板の製造方法。
- 一対の主表面を有するガラス基板を研磨する主表面研磨工程を含む磁気ディスク用ガラス基板の製造方法であって、前記主表面研磨工程において、前記ガラス基板の一方の主表面に対して、磁気記録を行うために求められる算術平均粗さ(Ra)になるように主表面研磨処理を行い、前記ガラス基板の他方の主表面に対して前記一方の主表面の算術平均粗さ(Ra)よりも粗く、前記磁気ディスク用ガラス基板を構成する成分の溶出を防止するために十分な粗さになるように前記他方の主表面に対して主表面研磨処理を行うことを特徴とする磁気ディスク用ガラス基板の製造方法。
- 前記主表面研磨工程において、前記ガラス基板の一方の主表面に対して行う主表面研磨処理の回数よりも前記ガラス基板の他方の主表面に対して行う主表面研磨処理の回数が少ないことを特徴とする請求項1又は2に記載の磁気ディスク用ガラス基板の製造方法。
- 前記他方の主表面から前記磁気ディスク用ガラス基板を構成する成分の溶出を防止するために十分な粗さが5.0nm以下であることを特徴とする請求項1又は2に記載の磁気ディスク用ガラス基板の製造方法。
- 前記ガラス基板の一方の主表面に対して算術平均粗さ(Ra)が0.30nm以下になるように主表面研磨処理を行うことを特徴とする請求項1又は2に記載の磁気ディスク用ガラス基板の製造方法。
- 光学式自動外観検査により、前記ガラス基板の一方の主表面を識別する工程をさらに具備することを特徴とする請求項1又2に記載の磁気ディスク用ガラス基板の製造方法。
- 一対の主表面を有する磁気ディスク用ガラス基板であって、一方の主表面が所定の算術平均粗さ(Ra)を有し、他方の主表面が前記一方の主表面の算術平均粗さ(Ra)よりも粗く、前記他方の主表面から前記磁気ディスク用ガラス基板を構成する成分の溶出を防止するために十分な粗さを有することを特徴とする磁気ディスク用ガラス基板。
- 一対の主表面を有する磁気ディスク用ガラス基板であって、一方の主表面が磁気記録を行うために求められる算術平均粗さ(Ra)を有し、他方の主表面が前記一方の主表面の算術平均粗さ(Ra)よりも粗く、前記磁気ディスク用ガラス基板を構成する成分の溶出を防止するために十分な粗さを有することを特徴とする磁気ディスク用ガラス基板。
- 請求項7又は8に記載の磁気ディスク用ガラス基板の前記一方の主表面上に少なくとも磁気記録層が形成されてなることを特徴とする磁気ディスク。
- 請求項7又は8に記載の磁気ディスク用ガラス基板の前記他方の主表面上に、前記磁気ディスク用ガラス基板を構成する成分の溶出を防止する基板構成成分溶出防止層が形成されていることを特徴とする磁気ディスク。
- 一対の主表面を有する磁気ディスク用ガラス基板上に少なくとも磁気記録層が形成されてなる磁気ディスクであって、
前記磁気ディスク用ガラス基板の磁気記録を行うために求められる算術平均粗さ(Ra)を有する一方の主表面上のみに、少なくとも前記磁気記録層が形成され、他方の主表面上に前記磁気ディスク用ガラス基板を構成する成分の溶出を防止する基板構成成分溶出防止層が形成されていることを特徴とする磁気ディスク。 - 前記基板構成成分溶出防止層の厚さが4nm以上であることを特徴とする請求項11に記載の磁気ディスク。
- 前記基板構成成分溶出防止層がチタン単体を含むチタン合金で構成されていることを特徴とする請求項11に記載の磁気ディスク。
- 前記基板構成成分溶出防止層上にディスク反り防止層が形成されていることを特徴とする請求項11に記載の磁気ディスク。
- 前記基板構成成分溶出防止層上に、前記磁気記録層上に形成される保護層が形成されていることを特徴とする請求項11に記載の磁気ディスク。
- 前記ディスク反り防止層上に、前記磁気記録層上に形成される保護層が形成されていることを特徴とする請求項14に記載の磁気ディスク。
- 前記一方の主表面上に形成されている層の合計厚さと、前記他方の主表面上に形成されている層の合計厚さとが同じであることを特徴とする請求項11に記載の磁気ディスク。
- 請求項7又は8に記載の磁気ディスク用ガラス基板上に少なくとも磁気記録層を形成してなる磁気ディスクの製造方法であって、一方の主表面上のみに少なくとも磁気記録層を形成することを特徴とする磁気ディスクの製造方法。
- 一対の主表面を有するガラス基板を研磨する主表面研磨工程を経て得られた磁気ディスク用ガラス基板上に少なくとも磁気記録層を形成してなる磁気ディスクの製造方法であって、前記磁気ディスク用ガラス基板の一方の主表面上のみに少なくとも磁気記録層を形成し、他方の主表面上に、前記他方の主表面からの前記磁気ディスク用ガラス基板を構成する成分の溶出を防止する基板構成成分溶出防止層を形成することを特徴とする磁気ディスクの製造方法。
- 前記磁気ディスク用ガラス基板の他方の主表面に対して少なくとも最終の主表面研磨処理を行わないことを特徴とする請求項19に記載の磁気ディスクの製造方法。
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- 2009-09-02 US US13/063,106 patent/US8895165B2/en not_active Expired - Fee Related
- 2009-09-02 WO PCT/JP2009/065312 patent/WO2010029878A1/ja active Application Filing
- 2009-09-02 MY MYPI2011001012A patent/MY159838A/en unknown
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Also Published As
Publication number | Publication date |
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MY159838A (en) | 2017-02-15 |
JP5373511B2 (ja) | 2013-12-18 |
US8895165B2 (en) | 2014-11-25 |
CN102150209A (zh) | 2011-08-10 |
JP2010257560A (ja) | 2010-11-11 |
US20110165439A1 (en) | 2011-07-07 |
CN102150209B (zh) | 2013-03-27 |
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