JP2019160384A - Substrate for magnetic disk, method for manufacturing the same, and magnetic disk using substrate for magnetic disk - Google Patents

Abstract

To provide a substrate for a magnetic disk having a stable fluttering characteristic, and a method for manufacturing the substrate.SOLUTION: The substrate for a magnetic disk according to the present invention is characterized in that the flatness is 30 μm or less and the difference in the flatness between before and after heating processing is performed at 190°C for 20 hours is 20 μm or less. The substrate for a magnetic disk can be manufactured by performing heating processing on the substrate for a magnetic disk after polishing at temperatures of 100°C to 250°C within 72 hours after the last polishing step, which is performed at least one time, is performed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic disk substrate having stable fluttering characteristics, a method for manufacturing the same, and a magnetic disk using the magnetic disk substrate.

  Magnetic disks used in computer storage devices are manufactured using magnetic disk substrates that have good plating properties and excellent mechanical properties and workability (hereinafter, the magnetic disk substrates are simply referred to as “substrates”). May be written). This magnetic disk substrate is manufactured from an aluminum alloy substrate based on an aluminum alloy, a glass substrate based on glass, or the like. As an aluminum alloy substrate, for example, JIS5086 aluminum alloy (Mg: 3.5 to 4.5 mass%, Fe: 0.50 mass% or less, Si: 0.40 mass% or less, Mn: 0.20 to 0.70 mass%, Cr: 0.05 to 0.25 mass%, Cu: 0.10 mass% or less, Ti: 0.15 mass% or less, and Zn: 0.25 mass% or less, the balance Al and inevitable impurities) are known. .

  In general manufacturing of a magnetic disk, an annular magnetic disk substrate is first manufactured, and a magnetic material is attached to the surface of the magnetic disk substrate. For example, a magnetic disk using an aluminum alloy magnetic disk substrate made of the JIS 5086 alloy described above is manufactured by the following manufacturing process.

  First, an aluminum alloy material having a predetermined chemical component is cast, the ingot is hot-rolled, and then cold-rolled to produce a rolled material having a necessary thickness as a magnetic disk. This rolled material is preferably annealed during the cold rolling as required. Next, this rolled material is punched into an annular shape to obtain an annular aluminum alloy plate. And in order to remove the distortion etc. which arose by the manufacturing process so far, an annular | circular shaped aluminum alloy board is laminated | stacked, and pressure annealing which performs annealing and pressurizes from both upper surfaces is performed. Thus, an annular aluminum alloy disc blank is produced.

  The aluminum alloy disc blank thus produced is subjected to cutting, grinding, degreasing, etching and zincate treatment (Zn substitution treatment) as pretreatment. Next, Ni—P, which is a hard nonmagnetic metal, is electrolessly plated as a base treatment, and the plated surface is polished (polished), whereby an aluminum alloy substrate for a magnetic disk is manufactured.

  And a magnetic body made from an aluminum alloy is manufactured by sputtering a magnetic material on the manufactured aluminum alloy substrate for a magnetic disk.

  Incidentally, in recent years, due to the need for multimedia and the like, there has been a strong demand for larger capacity and higher density for magnetic disk devices such as HDDs. In order to further increase the capacity, the number of magnetic disks mounted on a storage device tends to increase, and accordingly, the thickness of the magnetic disk is required to be reduced.

  However, there is a problem that disk fluttering is likely to occur due to a decrease in rigidity accompanying the thinning of the magnetic disk and an increase in excitation force with respect to the magnetic disk as the fluid force increases due to high-speed rotation.

  Disk fluttering is a phenomenon caused by vibration (fluttering) of a magnetic disk. Fluttering occurs due to unstable airflow between the disks generated when the magnetic disk is rotated at high speed. When the rigidity of the substrate is low, the amount of displacement due to fluttering becomes large, and it becomes difficult for the head as the reading unit to follow the change. If such disk fluttering continuously occurs, the head positioning error increases.

  For this reason, in recent years, studies have been made to improve fluttering on magnetic disk devices and magnetic disk substrates. For example, as an improvement measure for the structure of the magnetic disk device, it has been proposed to mount an airflow suppression component having a plate facing the disk in the hard disk drive. Patent Document 1 proposes a magnetic disk device in which an air spoiler is installed on the upstream side of an actuator. This air spoiler reduces the turbulent vibration of the magnetic head by weakening the air flow toward the actuator on the magnetic disk. The air spoiler suppresses disk fluttering by weakening the airflow on the magnetic disk.

  In addition, since disk fluttering may occur in association with the rigidity of the magnetic disk substrate, there is an example of study on improving the rigidity of the magnetic disk substrate. As an example, Patent Document 2 proposes a method for improving rigidity by containing a large amount of Si that contributes to improving the rigidity of an aluminum alloy plate.

JP 2002-313061 A International Publication No. 2016/068293

  However, with regard to the problem of disk fluttering, countermeasures from the structural aspect of the magnetic disk device tend to lead to an increase in the cost of the device. In the method disclosed in Patent Document 1 described above, the fluttering suppression effect varies depending on the difference between the installed air spoiler and the magnetic disk substrate. Therefore, in order to obtain a stable fluttering suppression effect, high-precision parts are required in terms of design and processing, and the part cost increases. In the field of storage devices including magnetic disk devices, various storage devices are exposed to intense cost competition. Since magnetic disk devices are also strongly required to reduce costs by improving productivity and the like, it is difficult to select measures that lead to increased costs.

  Therefore, application of a magnetic disk substrate in which the occurrence of disk fluttering is suppressed is expected. However, there are few examples of studying the problem of disk fluttering and dealing with magnetic disk substrates. The method of containing a large amount of Si in the aluminum alloy shown in Patent Document 2 is effective for improving the rigidity of the alloy. However, the fluttering characteristics have not been improved sufficiently. At present, the fluttering characteristic is lowered due to the long-time operation of the magnetic disk device, and the target stable fluttering characteristic is not obtained.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic disk substrate having stable fluttering characteristics and a method for manufacturing the same. A magnetic disk using such a magnetic disk substrate will also be clarified.

  The inventors of the present invention have made extensive investigations and researches on the relationship between the fluttering characteristics of the magnetic disk substrate and the material of the substrate, and have found that changes in the flatness of the substrate surface greatly affect the fluttering characteristics. In particular, the present inventors paid attention to the flatness of the magnetic disk substrate after the surface polishing and before the adhesion of the magnetic material in consideration of the manufacturing process of the magnetic disk substrate. Further, when the flatness of the substrate is a predetermined value or less, and when the predetermined heat treatment is performed on the substrate, fluttering characteristics are reduced in the substrate in which the difference in flatness before and after the treatment is reduced. I found it stable. The present inventors have completed the present invention based on these findings.

  In the present invention for solving the above-mentioned problems, the flatness of a magnetic disk substrate is 30 μm or less, and the difference in flatness before and after the magnetic disk substrate is subjected to a heat treatment of 190 ° C. × 20 h is 20 μm or less. This is a magnetic disk substrate.

Further, the present invention is the magnetic disk substrate described above, wherein the product of the plate thickness (mm) and the loss coefficient is 0.10 × 10 ⁻³ or more.

  The present invention also provides a method for manufacturing the magnetic disk substrate. That is, the manufacturing method includes a step of forming a magnetic disk substrate by performing at least one polishing step, and further, for a magnetic disk after polishing within 72 hours after polishing in the final polishing step of the polishing step. It is a method for manufacturing a magnetic disk substrate including a step of heat-treating the substrate at 100 to 250 ° C.

  The magnetic disk substrate according to the present invention can be made of an aluminum alloy. The present invention is the above-described magnetic disk substrate, comprising an aluminum alloy, wherein the aluminum alloy includes at least Fe: 0.10 to 3.00 mass% and Mn: 0.10 to 3.00 mass%. It is a magnetic disk substrate containing any of the remaining Al and inevitable impurities.

  The aluminum alloy of this aluminum alloy substrate has Mg: 0.100-5.000 mass%, Ni: 0.100-5.000 mass%, Cr: 0.010-5.000 mass%, Zr: 0.010-5. One or two selected from the group consisting of 000 mass%, Zn: 0.005 to 5.000 mass%, Cu: 0.005 to 5.000 mass%, and Si: 0.10 to 0.40 mass% The above elements can further be contained.

Furthermore, this aluminum alloy may further contain 0.005 to 5.000 mass% of one or more elements selected from the group consisting of Ti, B, and V in total content.

  The present invention provides a magnetic disk. This magnetic disk is a magnetic disk characterized in that a magnetic layer is provided on the surface of the magnetic disk substrate.

  According to the present invention, it is possible to provide a magnetic disk substrate having stable fluttering characteristics, a method for manufacturing the same, and a magnetic disk using the magnetic disk substrate.

The flowchart which shows the manufacturing method of the aluminum alloy board | substrate for magnetic discs which concerns on this invention. The flowchart which shows the manufacturing method of the glass substrate for magnetic discs which concerns on this invention.

  As described above, according to the present invention, the flatness of the substrate after surface polishing is set to 30 μm or less, and the difference in flatness before and after a predetermined heat treatment of 190 ° C. × 20 h is set to 20 μm or less, so that fluttering characteristics can be obtained. Make a good magnetic disk substrate. The magnetic disk substrate having such flatness characteristics can be made of an aluminum alloy. Moreover, it can also comprise with glass. Hereinafter, the characteristics of the magnetic disk substrate according to the present invention will be described in detail. And regarding the board | substrate which concerns on this invention, the detail about the board | substrate (aluminum alloy board | substrate) comprised with the aluminum alloy and the board | substrate (glass substrate) comprised with glass is demonstrated.

1. Flatness and Damping Characteristics of Magnetic Disk Substrate According to the Present Invention The magnetic disk substrate according to the present invention is characterized by its surface configuration and has characteristics relating to the flatness of the substrate surface. Moreover, it is preferable that the board | substrate which concerns on this invention improves a loss coefficient in addition to control of flatness. Hereinafter, these characteristics will be described.

1-1. Flatness
1-1a. Flatness after substrate surface polishing According to the study by the present inventors, the effect of improving the fluttering characteristics of the substrate is exhibited by reducing the flatness after the substrate surface polishing before adhesion of the magnetic material. Is done. The substrate having a large flatness has a large air resistance when the magnetic disk device is operated, and the fluttering characteristic is deteriorated. On the other hand, a substrate having a small flatness can suppress a decrease in fluttering characteristics. Therefore, the flatness after polishing the substrate surface is set to 30 μm or less. This flatness performed after the substrate surface polishing is preferably 20 μm or less, more preferably 10 μm or less.

1-1b. Difference in flatness before and after heat treatment at 190 ° C. × 20 h According to the present inventors, when a substrate having the above flatness was subjected to heat treatment at 190 ° C. × 20 h, the substrate surface before and after the treatment By reducing the difference in flatness of the substrate, the effect of stabilizing the fluttering characteristics of the substrate is exhibited. A substrate having a large difference in flatness before and after the heat treatment has a lot of internal strain. In such a substrate, when the temperature rises during operation of the magnetic disk device, the internal strain is released and the flatness of the substrate deteriorates. Therefore, air resistance increases and fluttering characteristics deteriorate.

  In contrast, a substrate with a small difference in flatness before and after the heat treatment at 190 ° C. × 20 h has less internal strain, and thus can suppress a decrease in fluttering characteristics. That is, if the difference in flatness before and after this heat treatment is small, the influence of deterioration of flatness due to internal strain is small, so that stable fluttering characteristics can be obtained for a long time even if the magnetic disk device is operated for a long time. .

  For the above reasons, the substrate according to the present invention has a flatness difference of 20 μm or less before and after the heat treatment at 190 ° C. × 20 h. The difference in flatness before and after the heat treatment is preferably 10 μm or less, more preferably 5 μm or less. The heat treatment conditions of 190 ° C. × 20 h as an index of the present invention are determined with reference to the heat treatment conditions of an acceleration test for a long-time operation of a magnetic disk device such as an HDD.

  In the present invention, the flatness is represented by the difference between the maximum peak height and the maximum valley depth of the entire surface of the substrate. Here, the maximum peak height is the difference between the average line of the contour curve in the measurement range and the highest value in the measurement range, and the maximum valley depth is the difference between the average line and the lowest value in the measurement range. .

1-2. Product of thickness and loss factor of substrate The substrate according to the present invention preferably has improved loss factor. Thereby, the effect of improving the impact resistance of the substrate is exhibited. The improvement of the impact resistance of the substrate has an effect of preventing deterioration of the flatness of the substrate when a force is applied to the substrate when the magnetic disk device is dropped and vibration is generated. This is because the higher the loss factor of the substrate, the shorter the time required for the vibration of the substrate to converge, so that contact with other substrates can be avoided and flatness deterioration due to contact between the substrates can be prevented. However, the appropriate value of the loss factor of the substrate greatly varies depending on the thickness of the substrate. This is because the drag is lost against the excitation force by the fluid as the plate thickness decreases.

According to the present inventors, the substrate according to the present invention has excellent impact resistance when the product of the loss factor of the substrate and the plate thickness (unit: mm) is 0.10 × 10 ⁻³ or more. It has been confirmed that a substrate can be obtained. Therefore, the product of the board thickness and the loss factor is preferably 0.10 × 10 ⁻³ or more. The product of the thickness of the substrate and the loss factor is more preferably 0.30 × 10 ⁻³ or more. The upper limit of the product of the thickness of the substrate and the loss factor is not particularly limited, but is naturally determined by the material composition and manufacturing conditions. In the present invention, it is about 10.0 × 10 ⁻³ . Is preferred.

Here, the loss factor, which those taking the natural logarithm of the ratio of the amplitude adjacent damping free vibration waveform divided by the circular constant [pi, n-th amplitudes a _n at time t _n, similarly n + 1 If the n + m-th amplitude is a _{n + 1} ,... A _{n + m} , the loss coefficient is represented by {(1 / m) × ln (a _n / a _{n + m} )} / π.

2. Manufacturing method of magnetic disk substrate according to the present invention In order to achieve the above-mentioned two standards regarding flatness for a magnetic disk substrate, it is necessary to perform a suitable heat treatment after the polishing step in the manufacturing process. It is.

  In the method of manufacturing a magnetic disk substrate, the formed and processed substrate is polished before the magnetic material is attached. This polishing step includes at least one polishing operation. In addition, both the aluminum alloy substrate and the glass substrate magnetic disk substrate are manufactured through a polishing process. The method for manufacturing a magnetic disk substrate according to the present invention can be manufactured by subjecting the substrate after this polishing step to heat treatment at 100 to 250 ° C. within 72 hours after polishing. The technical significance of this heat treatment will be described in detail later.

3. Aluminum Alloy Substrate for Magnetic Disk According to the Present Invention The magnetic disk substrate according to the present invention can be made of an aluminum alloy. Hereafter, each detail is demonstrated about the alloy composition of the aluminum alloy substrate for magnetic discs concerning this invention, and its manufacturing method.

3-1. Alloy composition of aluminum alloy The aluminum alloy used in the aluminum alloy substrate for a magnetic disk according to the present invention has Fe: 0.10 to 3.00 mass% and Mn: 0.10 to 3. It is preferable to contain at least one of 00 mass% (hereinafter, mass% is simply referred to as “%”). This is for further improving the fluttering resistance, impact resistance, and plating properties of the aluminum alloy substrate.

  Moreover, the aluminum alloy which comprises a board | substrate is Mg: 0.100-5.000%, Ni: 0.100-5.000%, Cr: 0.010-5.000% as a 2nd selective element. Zr: 0.010 to 5.000%, Zn: 0.005 to 5.000%, Cu: 0.005 to 5.000% and Si: 0.10 to 0.40% 1 type (s) or 2 or more types may be further contained.

  Furthermore, the aluminum alloy which comprises a board | substrate is 1 type, or 2 or more types selected from the group which consists of Ti, B, and V whose total content is 0.005-5.000% as a 3rd selective element May further be contained.

  By appropriately adding the above-described various selective elements to the aluminum alloy, an aluminum substrate for a magnetic disk having good fluttering resistance and the like can be obtained. Hereinafter, the action of these selective elements will be described.

Fe:
Fe exists mainly as second-phase particles (Al—Fe-based intermetallic compound or the like), and a part thereof exists as a solid solution in the matrix. Fe exhibits the effect of improving the fluttering characteristics and loss factor of the aluminum alloy substrate due to the generation of the second phase particles and the solid solution in the matrix. This is because the second phase particles quickly absorb vibration energy due to interaction with dislocations and form a material with good fluttering characteristics. Further, the increase of the second phase particles improves the strength (Young's modulus and proof stress) of the alloy by dispersion strengthening. When the Young's modulus and proof stress of the alloy are improved, it is possible to keep the deformation due to the vibration of the substrate within the elastic region when a force is applied to the substrate when the magnetic disk device is dropped or the like and the substrate is vibrated. Thereby, it becomes possible to prevent a change in flatness of the substrate.

  When the Fe content in the aluminum alloy is 0.10% or more, the effects of improving the fluttering characteristics, loss factor, Young's modulus, and strength of the aluminum alloy substrate can be further enhanced. Moreover, when the Fe content in the aluminum alloy is 3.00% or less, the generation of a large number of coarse Al—Fe intermetallic compound particles is suppressed. When coarse Al—Fe-based intermetallic compound particles fall off during etching, zincate treatment, cutting or grinding, a large depression is generated on the substrate surface. By suppressing the generation of coarse Al—Fe-based intermetallic compound particles, generation of dents can be suppressed, and the effect of improving surface smoothness by plating can be further enhanced. Moreover, suppression of a hollow can further suppress that plating peeling arises. Furthermore, the suppression of the depression can further suppress the deterioration of workability in the rolling process. For the reasons described above, the Fe content in the aluminum alloy is preferably in the range of 0.10 to 3.00%. The Fe content is more preferably in the range of 0.60 to 2.40%.

Mn:
Mn exists mainly as second-phase particles (such as Al—Mn intermetallic compounds) and exhibits the effect of improving the fluttering characteristics and loss factor of the aluminum alloy substrate. The second phase particles quickly absorb vibration energy by interaction with dislocations, and form a material with good fluttering characteristics. Further, the increase of the second phase particles improves the strength (Young's modulus and proof stress) of the alloy by dispersion strengthening. This makes it possible to prevent changes in the flatness of the substrate when the substrate is vibrated.

  When the Mn content in the aluminum alloy is 0.10% or more, the effect of improving the fluttering characteristics, loss coefficient, Young's modulus, and strength of the aluminum alloy substrate can be further enhanced. In addition, when the Mn content in the aluminum alloy is 3.00% or less, the generation of a large number of coarse Al—Mn intermetallic compound particles is suppressed. This suppresses the generation of large depressions during etching, zincate processing, cutting, and grinding. And it can suppress further that the fall of the smoothness of a plating surface and plating peeling arise. Moreover, the workability fall in a rolling process can be suppressed further. For the above reasons, the Mn content in the aluminum alloy is preferably in the range of 0.10 to 3.00%. The Mn content is more preferably in the range of 0.10 to 1.50%.

Mg:
Mg is mainly present as a solid solution in the matrix, and part of the Mg is present as second phase particles (Mg—Si intermetallic compound or the like). Thereby, the effect of improving the strength and Young's modulus of the aluminum alloy substrate is exhibited.

  When the Mg content in the aluminum alloy is 0.100% or more, the effect of improving the strength and Young's modulus of the aluminum alloy substrate can be further enhanced. Moreover, when the Mg content in the aluminum alloy is 5.000% or less, the deterioration of fluttering characteristics can be further suppressed. Therefore, the Mg content in the aluminum alloy is preferably in the range of 0.100 to 5.000%. The Mg content is more preferably in the range of 0.100 to 0.800.

Ni:
Ni exists mainly as second-phase particles (such as Al—Ni intermetallic compounds), and exhibits the effect of improving the Young's modulus and strength of the aluminum alloy substrate.

  When the Ni content in the aluminum alloy is 0.100% or more, the effect of improving the Young's modulus and strength of the aluminum alloy substrate can be further enhanced. In addition, when the Ni content in the aluminum alloy is 5.000% or less, the generation of a large number of coarse Al—Ni intermetallic compound particles is suppressed. This suppresses the generation of large depressions during etching, zincate processing, cutting, and grinding. And it can suppress further that the fall of the smoothness of a plating surface and plating peeling arise. Moreover, the workability fall in a rolling process can be suppressed further. For the above reasons, the Ni content in the aluminum alloy is preferably in the range of 0.100 to 5.000%. The Ni content is more preferably in the range of 0.100 to 1.000%.

Cr:
Cr exists mainly as second-phase particles (such as Al—Cr-based intermetallic compounds), and exhibits the effect of improving the Young's modulus and strength of the aluminum alloy substrate. When the Cr content in the aluminum alloy is 0.010% or more, the effect of improving the Young's modulus and strength of the aluminum alloy substrate can be further enhanced. In addition, when the Cr content in the aluminum alloy is 5.000% or less, the generation of a large number of coarse Al—Cr intermetallic compound particles is suppressed. This suppresses the generation of large depressions during etching, zincate processing, cutting, and grinding. And it can suppress further that the fall of the smoothness of a plating surface and plating peeling arise. Moreover, the workability fall in a rolling process can be suppressed further. For the above reasons, the Cr content in the aluminum alloy is preferably in the range of 0.010 to 5.000%. The Cr content is more preferably in the range of 0.100 to 1.000%.

Zr:
Zr exists mainly as second-phase particles (Al—Zr-based intermetallic compound or the like), and exhibits the effect of improving the Young's modulus and strength of the aluminum alloy substrate.

  When the Zr content in the aluminum alloy is 0.010% or more, the effect of improving the Young's modulus and strength of the aluminum alloy substrate can be further enhanced. In addition, when the Zr content in the aluminum alloy is 5.000% or less, the generation of a large number of coarse Al—Zr intermetallic compound particles is suppressed. This suppresses the generation of large depressions during etching, zincate processing, cutting, and grinding. And it can suppress further that the fall of the smoothness of a plating surface and plating peeling arise. Moreover, the workability fall in a rolling process can be suppressed further. For the above reasons, the Zr content in the aluminum alloy is preferably in the range of 0.010 to 5.000%. The Zr content is more preferably in the range of 0.100 to 1.000%.

Zn:
Zn reduces the amount of Al dissolved during the zincate treatment, adheres the zincate film uniformly, thinly and densely, and exhibits the effect of improving the smoothness and adhesion in the subsequent plating step. In addition, the second phase particles are formed with other additive elements, and the effect of improving the Young's modulus and strength is exhibited.

  When the Zn content in the aluminum alloy is 0.005% or more, the amount of dissolved Al during the zincate treatment is reduced, and the zincate film is uniformly, thinly and densely adhered to improve the smoothness of the plating. The effect can be further enhanced. In addition, when the Zn content in the aluminum alloy is 5.000% or less, it is possible to further suppress that the zincate film is uniform and the smoothness of the plating surface is lowered, and that plating peeling occurs. Further suppression can be achieved. Moreover, the workability fall in a rolling process can be suppressed further. For the above reasons, the Zn content in the aluminum alloy is preferably in the range of 0.005 to 5.000%. The Zn content is more preferably in the range of 0.100 to 0.700%.

Cu:
Cu exists mainly as second-phase particles (Al—Cu intermetallic compound or the like), and exhibits the effect of improving the strength and Young's modulus of the aluminum alloy substrate. Moreover, the amount of Al dissolution at the time of a zincate process is reduced. Further, the zincate film is uniformly, thinly and densely adhered, and the effect of improving the smoothness in the next plating step is exhibited.

  When the Cu content in the aluminum alloy is 0.005% or more, the effect of improving the Young's modulus and strength of the aluminum alloy substrate and the effect of improving smoothness can be further enhanced. Moreover, when the Cu content in the aluminum alloy is 5.000% or less, the generation of a large number of coarse Al—Cu intermetallic compound particles is suppressed. This suppresses the generation of large depressions during etching, zincate processing, cutting, and grinding. And it can suppress further that the fall of the smoothness of a plating surface and plating peeling arise. Moreover, the workability fall in a rolling process can be suppressed further. For the above reasons, the Cu content in the aluminum alloy is preferably in the range of 0.005 to 5.000%. The Cu content is more preferably in the range of 0.005 to 1.000%.

Si:
Si exists mainly as second-phase particles (Si particles, Al—Fe—Si intermetallic compounds, etc.) and exhibits the effect of improving fluttering characteristics, loss coefficient, Young's modulus and strength of the aluminum alloy substrate. . When vibration is applied to such a material, vibration energy is quickly absorbed by the interaction between the second phase particles and dislocations, and good fluttering characteristics and a loss factor are obtained. Further, the Young's modulus is improved by increasing the number of second phase particles having a Young's modulus higher than that of aluminum. Further, the increase in the second phase particles improves the strength due to dispersion strengthening.

  When the Si content in the aluminum alloy is 0.100% or more, the effects of improving the fluttering characteristics, loss coefficient, Young's modulus, and strength of the aluminum alloy substrate can be further enhanced. In addition, when the Si content in the aluminum alloy is 0.400% or less, the generation of a large number of coarse Si particles is suppressed. This suppresses the generation of large depressions during etching, zincate processing, cutting, and grinding. And it can suppress further that the fall of the smoothness of a plating surface and plating peeling arise. Moreover, the workability fall in a rolling process can be suppressed further. For the above reasons, the Si content in the aluminum alloy is preferably in the range of 0.100 to 0.400%, more preferably in the range of 0.100 to 0.350%.

Ti, B, V:
Ti, B, and V form second phase particles (boride such as TiB ₂ or Al ₃ Ti or Ti—V—B particles) during the solidification process at the time of casting. Therefore, the crystal grains can be miniaturized. As a result, the plating property is improved. In addition, by making the crystal grains finer, the non-uniformity of the size of the second phase particles is reduced, and the effect of reducing the fluttering characteristics, loss coefficient, Young's modulus, and strength variations in the aluminum alloy substrate is exhibited. .

  If the total content of Ti, B and V is less than 0.005%, the above effect cannot be obtained. On the other hand, even if the total content of Ti, B and V exceeds 5.000%, the effect is saturated, and no further significant improvement effect is obtained. Therefore, the total content of Ti, B and V when adding Ti, B and V is preferably in the range of 0.005 to 5.000%. The total content of Ti, B and V is more preferably in the range of 0.005 to 0.500%. The total amount is the amount of this one type when only one of Ti, B and V is contained, and the total amount of these two types when any two are contained. When all three types are contained, the total amount of these three types.

Other elements:
The balance of the aluminum alloy used in the present invention consists of Al and inevitable impurities. Here, Ga, Sn, etc. are mentioned as an unavoidable impurity. If the elements that are inevitable impurities are each less than 0.10% and less than 0.20% in total, the characteristics of the aluminum alloy substrate obtained in the present invention are not impaired.

In the above description, the intermetallic compound means a precipitate or a crystallized substance. Specifically, an Al—Fe-based intermetallic compound (Al ₃ Fe, Al ₆ Fe, Al ₆ (Fe, Mn ), Al—Fe—Si, Al—Fe—Mn—Si, Al—Fe—Ni, Al—Cu—Fe, etc.), Mg—Si based intermetallic compounds (Mg ₂ Si, etc.) and the like. Other intermetallic compounds include Al—Mn intermetallic compounds (Al ₆ Mn, Al—Mn—Si), Al—Ni intermetallic compounds (Al ₃ Ni, etc.), Al—Cu intermetallic compounds (Al ₂ Cu), Al—Cr intermetallic compounds (Al ₇ Cr, etc.), Al—Zr intermetallic compounds (Al ₃ Zr, etc.), and the like. The second phase particles include Si particles and the like in addition to the intermetallic compound.

3-2. Method for Manufacturing Magnetic Disk Aluminum Substrate According to the Present Invention Hereinafter, each process and process conditions of the manufacturing process of the magnetic disk aluminum alloy substrate according to the present embodiment will be described in detail. FIG. 1 is a flow for explaining an aluminum alloy substrate for a magnetic disk according to the present embodiment and a method for manufacturing a magnetic disk using the same. In FIG. 1, the adjustment process (step S101) to cold rolling (step S105) of the aluminum alloy component is a process of manufacturing an aluminum alloy material by melt casting and using this as an aluminum alloy plate. Next, an aluminum alloy disk blank is manufactured by a pressure flattening step (step S106). Then, a pretreatment such as a cutting / grinding process (step S107) is performed on the manufactured disc blank, a zincate process (step S109) and a Ni-P plating process (step S110) are performed, and then surface polishing and Through the heat treatment (step S111), an aluminum alloy substrate for a magnetic disk is manufactured. The manufactured aluminum alloy substrate for a magnetic disk becomes a magnetic disk by the magnetic material attaching step (step S111). Hereinafter, the contents of each step will be described in detail while following the flow of FIG.

  First, a molten aluminum alloy material having the above component composition is prepared by heating and melting in accordance with a conventional method (step S101). Next, the prepared molten aluminum alloy material is cast by a semi-continuous casting (DC casting) method, a continuous casting (CC casting) method, or the like to cast an aluminum alloy material (step S102). The production conditions of the aluminum alloy material in the DC casting method and the CC casting method are as follows.

  In the DC casting method, the molten metal poured through the spout is deprived of heat by the cooling water discharged directly to the outer periphery of the bottom block, the water-cooled mold wall, and the ingot (ingot) and solidifies. Then, it is drawn downward as an aluminum alloy ingot.

  On the other hand, in the CC casting method, molten metal is supplied through a casting nozzle between a pair of rolls (or belt casters and block casters), and a thin aluminum alloy sheet is directly cast by heat removal from the rolls.

  A major difference between the DC casting method and the CC casting method is the cooling rate during casting. The CC casting method having a large cooling rate is characterized in that the size of the second phase particles is smaller than that of the DC casting. In both casting methods, the cooling rate during casting is preferably in the range of 0.1 to 1000 ° C./s. By setting the cooling rate during casting to 0.1 to 1000 ° C./s, a large number of second phase particles are generated, and the loss factor and Young's modulus are improved. Moreover, the amount of Fe solid solution increases and the effect which improves an intensity | strength can be acquired. When the cooling rate at the time of casting is less than 0.1 ° C./s, the Fe solid solution amount decreases, and the strength may be lowered. On the other hand, if the cooling rate at the time of casting exceeds 1000 ° C./s, the number of second phase particles may decrease, and sufficient fluttering characteristics, loss coefficient, and Young's modulus may not be obtained.

  The aluminum alloy ingot that has been DC-cast is subjected to a homogenization process as necessary (step S103). When performing a homogenization process, it is preferable to perform the heat processing for 0.5 to 30 hours at 280-620 degreeC, and it is more preferable to perform the heat processing for 1 to 24 hours at 300-620 degreeC. When the heating temperature during the homogenization treatment is less than 280 ° C. or the heating time is less than 0.5 hours, the homogenization treatment is insufficient and there is a possibility that the variation of the loss factor for each aluminum alloy substrate becomes large. If the heating temperature during the homogenization treatment exceeds 620 ° C., melting may occur in the aluminum alloy ingot. Even if the heating time during the homogenization treatment exceeds 30 hours, the effect is saturated, and no further remarkable improvement effect can be obtained.

  Next, the aluminum alloy ingot (DC casting) that has been subjected to homogenization treatment or not subjected to homogenization treatment as necessary is hot-rolled to obtain a plate material (step S104). In the hot rolling, the conditions are not particularly limited, but the hot rolling start temperature is preferably 250 to 600 ° C, and the hot rolling end temperature is preferably 230 to 450 ° C.

  Next, the hot-rolled rolled plate or the cast plate cast by the CC casting method is cold-rolled to obtain an aluminum alloy plate of about 1.3 mm to 0.45 mm (step S105). Finish to the required product thickness by cold rolling. The conditions for cold rolling are not particularly limited, and may be determined according to the required product plate strength and plate thickness, and the rolling rate is preferably 10 to 95%. An annealing treatment may be performed before cold rolling or during cold rolling to ensure cold rolling processability. In the case of carrying out the annealing treatment, for example, batch heating is preferably performed at 300 to 450 ° C. for 0.1 to 10 hours, and continuous heating is preferably performed at 400 to 500 ° C. It is preferably performed under the condition of holding for 60 seconds. Here, the holding time of 0 seconds means cooling immediately after reaching the desired holding temperature.

  Then, an aluminum alloy plate obtained by cold rolling is punched into an annular shape to obtain an annular aluminum alloy plate. The annular aluminum alloy plate becomes a disk blank by the pressure flattening process (step S106). In the pressure flattening treatment, pressure annealing is performed in the air at, for example, 150 to 270 ° C. for 0.5 to 10 hours, and a flattened blank is produced.

  The disc blank is held for 0.5 to 10.0 hours in the range of 130 to 280 ° C., for example, in the cutting / grinding process (step S107) and the heating process (step S109) before the zincate process or the like. . By this heat treatment, it is possible to suppress a decrease in dislocation, and fluttering characteristics and impact resistance can be improved. When the heat treatment temperature exceeds 280 ° C. or when the heat treatment time exceeds 10.0 hours, dislocations are reduced, and as a result, fluttering characteristics and impact resistance may be reduced. On the other hand, when the heat treatment temperature is less than 130 ° C., or when the heat treatment time is less than 0.5 hour, the distortion introduced by the processing is insufficiently removed, and as a result, the flatness of the substrate due to the change over time. As a result, the use as an aluminum alloy substrate for a magnetic disk may be difficult. For the above reasons, it is preferable that the heat treatment of the blank after cutting and grinding is held for 0.5 to 10.0 hours in the range of 130 to 280 ° C.

Next, the disk blank surface is degreased and etched, and a zincate process (Zn substitution process) is performed (step S109). In the zincate treatment, a zincate film is formed on the disk blank surface. For the zincate treatment, a commercially available zincate treatment solution can be used, and it is preferably performed under conditions of a temperature of 10 to 35 ° C., a treatment time of 0.1 to 5 minutes, and a concentration of 100 to 500 mL / L. The zincate treatment is performed at least once and may be performed twice or more. By performing the zincate treatment a plurality of times, fine Zn can be deposited and a uniform zincate film can be formed. In the case where the zincate treatment is performed twice or more, a Zn peeling treatment may be performed between the two times. The Zn stripping treatment is preferably performed using an HNO ₃ solution under conditions of a temperature of 15 to 40 ° C., a treatment time of 10 to 120 seconds, and a concentration of 10 to 60%. The second and subsequent zincate treatments are preferably carried out under the same conditions as the first zincate treatment.

  Furthermore, an electroless Ni-P plating process (step S110) is performed on the surface of the disk blank subjected to the zincate process as a base process for adhering the magnetic material. In the electroless Ni-P plating treatment step, it is preferable to use a commercially available plating solution or the like and perform the plating treatment under conditions of a temperature of 80 to 95 ° C., a treatment time of 30 to 180 minutes, and a Ni concentration of 3 to 10 g / L.

  Polishing for smoothing is performed on the plated surface after the electroless Ni-P plating treatment (step S111). In this polishing step, it is preferable to perform polishing in a plurality of stages in which the diameter of the abrasive grains is adjusted. For example, the main surface is polished using a polishing liquid containing large-diameter abrasive grains having a particle diameter of 0.1 to 1.0 μm and a hard or soft polishing pad. Next, the surface is polished using a polishing liquid containing a small-diameter abrasive grain having a particle size of about 0.01 to 0.1 μm and a soft polishing pad.

  And in the manufacturing method of the aluminum alloy substrate for magnetic disks which concerns on this invention, with respect to the aluminum alloy substrate after grinding | polishing before making a magnetic body adhere, it heat-processes at 100-250 degreeC within 72 hours after grinding | polishing, (Step S112).

  As described above, by performing the heat treatment at 100 to 250 ° C. within 72 hours after the surface polishing of the substrate, it becomes possible to suppress the change in flatness when the magnetic disk device is operated, and to stabilize the fluttering characteristics. . If the substrate is left for a long time after polishing, the strain introduced by the polishing tends to be stabilized. According to the study by the present inventors, if heat treatment is performed for a time exceeding 72 h after polishing, the stabilized strain is not sufficiently released. The distortion remaining on the substrate without being released is released when the magnetic disk device is operated for a long time, and the flatness deteriorates. Therefore, in the present invention, the heat treatment is performed within 72 hours after the surface polishing. The time from polishing to heat treatment is preferably within 48 hours, more preferably within 24 hours.

  The reason why the heat treatment temperature is set to 100 to 250 ° C. is that it is an optimum condition for releasing strain while taking into consideration the time interval (72 h) from surface polishing to heat treatment. That is, when the heat treatment temperature is less than 100 ° C., the distortion introduced by polishing becomes insufficient, and as a result, the flatness of the substrate deteriorates due to the change over time when the magnetic disk device is operated for a long time, resulting in flutter. Ring characteristics deteriorate. On the other hand, when the heating temperature exceeds 250 ° C., the flatness deteriorates, and as a result, the fluttering characteristics deteriorate. Further, if the heating temperature exceeds 250 ° C., the impact resistance of the substrate may be lowered. Therefore, heat treatment is performed at 100 to 250 ° C. within 72 hours after polishing. The temperature of the heat treatment is preferably in the range of 120 to 230 ° C.

  In performing this heat treatment, the treatment time is not limited. However, if the treatment time is too long, it leads to an increase in cost. Here, the holding time of 0 minutes means that the cooling is performed immediately after reaching the desired holding temperature.

  The aluminum substrate for a magnetic disk according to the present invention is manufactured by the heat treatment after the surface polishing described above. Finally, a magnetic material is attached to the electroless Ni—P plating surface of the aluminum substrate by sputtering (step S113). Thereby, a magnetic disk made of an aluminum alloy is manufactured.

4). Magnetic Disk Glass Substrate According to the Present Invention The magnetic disk substrate according to the present invention can also be made of a glass material. Hereinafter, with respect to the glass substrate for a magnetic disk according to the present invention, the glass material to be applied and the manufacturing method of the substrate will be described in detail.

4-1. As a glass material , glass ceramics such as amorphous glass and crystallized glass can be used. In addition, it is preferable to use amorphous glass from a viewpoint of moldability and workability. For example, it is preferable to use aluminosilicate glass, soda lime glass, soda aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, or the like.

4-2. Method for Manufacturing Magnetic Disk Glass Substrate According to the Present Invention Next, an example of a method for manufacturing a magnetic disk glass substrate according to the present embodiment will be described. FIG. 2 is a flowchart showing an example of the magnetic disk glass substrate and the magnetic disk manufacturing method according to the present embodiment. Hereinafter, the contents of each step will be described while following the flow of FIG.

First, the glass plate used as a raw material is manufactured (step S201). Next, the glass plate manufactured in step S201 is cored and a donut-shaped glass substrate is formed from the glass plate (step S202).

  Next, a chamfer surface is formed on the inner and outer peripheral end surfaces of the molded glass substrate (step S203). Then, after polishing the inner and outer peripheral end surfaces of the glass substrate on which the chamfer surface is formed, surface polishing is performed. This polishing process includes rough polishing (step S204) and precision polishing (step S205). In the step of rough polishing (step S204), a rough polishing step of polishing the main surface using a polishing liquid containing large abrasive grains having a particle size of 0.1 to 1.0 μm and a hard or soft polishing pad. I do. In the subsequent precision polishing (step S205), the main surface of the glass substrate roughly polished using a polishing liquid containing a small diameter abrasive grain having a particle size of about 0.01 to 0.1 μm and a soft polishing pad. Polish more precisely.

  The glass substrate for a magnetic disk according to the present invention is subjected to heat treatment at 100 to 250 ° C. within 72 hours after polishing by the above precision polishing (step S206).

  As described above, by performing the heat treatment at 100 to 250 ° C. within 72 hours after the surface polishing of the substrate, it becomes possible to suppress the change in flatness when the magnetic disk device is operated, and to stabilize the fluttering characteristics. . If the substrate is left for a long time after polishing, the strain introduced by the polishing tends to be stabilized. According to the study by the present inventors, if heat treatment is performed for a time exceeding 72 h after polishing, the stabilized strain is not sufficiently released. The distortion remaining on the substrate without being released is released when the magnetic disk device is operated for a long time, and the flatness deteriorates. Therefore, in the present invention, the heat treatment is performed within 72 hours after the surface polishing. The time from polishing to heat treatment is preferably within 48 hours, more preferably within 24 hours.

  The reason why the heat treatment temperature is set to 100 to 250 ° C. is that it is an optimum condition for releasing strain while taking into consideration the time interval (72 h) from surface polishing to heat treatment. That is, when the heat treatment temperature is less than 100 ° C., the distortion introduced by polishing becomes insufficient, and as a result, the flatness of the substrate deteriorates due to the change over time when the magnetic disk device is operated for a long time, resulting in flutter. Ring characteristics deteriorate. On the other hand, when the heating temperature exceeds 250 ° C., the flatness deteriorates, and as a result, the fluttering characteristics deteriorate. Further, if the heating temperature exceeds 250 ° C., the impact resistance of the substrate may be lowered. Therefore, heat treatment is performed at 100 to 250 ° C. within 72 hours after polishing. The temperature of the heat treatment is preferably in the range of 120 to 230 ° C.

  In performing this heat treatment, the treatment time is not limited. However, if the treatment time is too long, it leads to an increase in cost. Here, the holding time of 0 minutes means that the cooling is performed immediately after reaching the desired holding temperature.

  The glass substrate for a magnetic disk according to the present invention is manufactured by the heat treatment after the surface polishing described above. Finally, a magnetic material is attached to the polished surface of the glass substrate by sputtering (step S207). Thereby, a glass magnetic disk is manufactured.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto. In this example, a plurality of aluminum alloy substrates and glass substrates were manufactured as magnetic disk substrates, and their characteristics were evaluated.

A. Production of Aluminum Alloy Substrate for Magnetic Disk First, each alloy material having the component composition shown in Tables 1 to 3 was melted in accordance with a conventional method to produce a molten aluminum alloy (step S101). In Tables 1 to 3, “-” indicates less than the measurement limit value.

  Next, the molten aluminum alloy was cast by a DC casting method to produce an ingot having a thickness of 200 mm (step S102). Prior to homogenization, both sides of the ingot were chamfered by 15 mm.

  Next, no. Except for A2, homogenization treatment was performed at 380 ° C. for 10 hours (step S103). Next, hot rolling was performed under conditions of a hot rolling start temperature of 370 ° C. and a hot rolling end temperature of 230 ° C. to obtain a hot rolled plate having a plate thickness of 3.0 mm (step S104).

  After hot rolling, no. A3, A5 and AC1 alloy hot-rolled sheets were annealed (batch type) at 300 ° C. for 2 hours. All the hot rolled sheets thus produced were rolled to a final thickness of 0.8 mm by cold rolling (rolling rate: 73.3%) to obtain aluminum alloy sheets (step S105). This aluminum alloy plate was punched out into an annular shape having an outer diameter of 96 mm and an inner diameter of 24 mm to produce an annular aluminum alloy plate.

The annular aluminum alloy plate thus produced was subjected to pressure annealing (pressure flattening treatment) at 230 ° C. for 3 hours to obtain a disk blank (step S106). The disk blank was subjected to end face processing (cutting) to obtain an outer diameter of 95 mm and an inner diameter of 25 mm, and grinding (surface 25 μm grinding) was performed (step S107). Further, heat treatment was performed at 250 ° C. for 1 hour (step S108). Then, after degreasing for 5 minutes at 60 ° C. with AD-68F (trade name, manufactured by Uemura Kogyo), acid etching is performed for 1 minute at 65 ° C. with AD-107F (trade name, manufactured by Uemura Kogyo). Desmutted with 30% aqueous HNO ₃ (room temperature) for 20 seconds.

After the surface condition was adjusted in this manner, the disk blank was immersed in a 20 ° C. zincate treatment solution of AD-301F-3X (trade name, manufactured by Uemura Kogyo Co., Ltd.) for 0.5 minutes to give a zincate treatment to the surface ( Step S109). The zincate treatment was performed twice in total, and the surface was peeled off by dipping in a 30% aqueous HNO ₃ solution at room temperature for 20 seconds during the zincate treatment. The surface subjected to zincate treatment was subjected to electroless plating with a thickness of 13 μm using Ni-P plating solution (Nimden HDX (trade name, manufactured by Uemura Kogyo)) (step S110).

The obtained plated surface was roughly polished using an alumina slurry having an average particle diameter of 800 nm and a urethane foam polishing pad. The amount of rough polishing was 2 μm. Subsequently, finish precision polishing (polishing) was performed using a colloidal silica and urethane foam polishing pad (step S111). In the finish polishing process, the thickness per side is determined by using a urethane foam polishing pad and a polishing liquid in which water is added to colloidal silica having a particle diameter of 70 to 90 nm and an average particle diameter of 80 nm to form free abrasive grains. Polished by 1 μm. As other polishing conditions in the precision polishing step, the polishing time was 8.5 minutes, and the processing pressure was 50 to 120 g / cm ² . Next, each test material was subjected to heat treatment under the conditions shown in Tables 4 to 6 to obtain a magnetic disk substrate (step S112).

B. Manufacture of glass substrate for magnetic disk As Examples 57-63 and Comparative Examples 7-13 shown in Table 7, the glass plate which consists of aluminosilicate glass was manufactured using the redraw method, and the glass substrate for magnetic disks was manufactured.

  The glass plate produced above is cored to form a donut-shaped glass substrate, and a chamfer surface is formed on the inner and outer periphery. The glass has a thickness of 0.8 mm, an outer diameter of 95 mm, and a circular hole with an inner diameter of 25 mm. A substrate was manufactured (steps S201 to S203).

  Next, a rough polishing process (step S204) and a precision polishing process (step S205) according to the above-described manufacturing method were performed on these glass substrates using a double-side simultaneous polishing machine.

  Here, in the rough polishing process (step S204), water is added to the urethane polishing pad and the cerium oxide polishing abrasive grains having a particle diameter of 0.1 to 0.4 μm and an average particle diameter of 0.19 μm to form free abrasive grains. A glass substrate having the above-described characteristics was polished with a polishing liquid as described above so that the rough polishing amount per side was 14 μm.

  Further, in the precision polishing step (step S205), using a foamed urethane polishing pad and a polishing liquid in which water is added to colloidal silica having a particle diameter of 70 to 90 nm and an average particle diameter of 80 nm to form free abrasive grains, The roughly polished glass substrate was polished by a thickness of 1 μm per side. As other polishing conditions in the precision polishing step, the polishing time was 8.5 minutes and the processing pressure was 50 to 120 g / cm 2.

  After the above polishing process, heat treatment was performed under the conditions shown in Table 7 to obtain a magnetic disk substrate (step S206).

C. Characteristic evaluation of the manufactured magnetic disk substrate After the heat treatment (steps S112 and S206), the flatness (after the heat treatment and after the heat treatment at 190 ° C. × 20 h), disk fluttering is performed by the following method. Characteristics and loss factor characteristics were evaluated.

[Flatness]
First, the flatness of the magnetic disk substrate subjected to the heat treatment after polishing as described above was measured. Thereafter, the substrate was subjected to a heat treatment of 190 ° C. × 20 h, the flatness after the heat treatment was measured, and the difference from the flatness before the heat treatment was calculated. The significance of flatness is as described above. The flatness was measured with a ZyGO non-contact flatness measuring machine.

[Measurement of disk fluttering characteristics]
The magnetic disk substrate after the heat treatment after the polishing (steps S112 and S206) was subjected to a heat treatment of 190 ° C. × 20 h, and then the disk fluttering was measured. The disk fluttering characteristics were measured by installing an aluminum alloy substrate and a glass substrate in the presence of air in the hard disk drive. The hard disk drive was a commercially available 3.5-inch hard disk drive, and the motor was driven by directly connecting a brushless motor driver (trade name: SLD102 manufactured by Techno Hands Co., Ltd.) to the motor.

  The number of rotations during the measurement was 7200 rpm, and a plurality of disks were always installed, and surface vibration was observed on the surface of the magnetic disk on the upper surface by a laser Doppler meter (trade name: LDV1800, manufactured by Ono Sokki Co., Ltd.). The observed vibration was subjected to spectrum analysis using an FFT analyzer (trade name: DS3200, manufactured by Ono Sokki Co., Ltd.). The observation was performed by opening a hole in the lid of the hard disk drive and observing the disk surface from the hole. In addition, the evaluation was performed by removing the squeeze plate installed on the commercially available hard disk.

  The fluttering characteristics were evaluated by the maximum displacement (disc fluttering (nm)) of a broad peak in the vicinity of 300 to 1500 Hz at which fluttering appears. This broad peak is called NRRO (Non-Repeatable Run Out) and is known to have a great influence on head positioning error. Evaluation of fluttering characteristics is “A (excellent)” in the case of 30 nm or less in air, “B (good)” exceeding 30 nm to 40 nm, and “C (possible)” exceeding 40 nm to 50 nm or less. ", When it was larger than 50 nm, it was determined as" D (poor) ".

[Loss coefficient x thickness]
A sample of 60 mm × 8 mm was taken from the magnetic disk substrate after the heat treatment after polishing (steps S112 and S206), and the loss coefficient was measured by the attenuation method. Then, loss coefficient × plate thickness was calculated based on the thickness (mm) of the substrate. The loss factor was measured at room temperature using a JE-RT type measuring device manufactured by Nippon Techno Plus Co., Ltd.

  Tables 8 to 11 show the evaluation results of the characteristics of the magnetic disk substrate manufactured in this example.

  As shown in Tables 8, 9, and 11, in Examples 1 to 63, stable fluttering characteristics could be obtained.

  On the other hand, as shown in Tables 10 and 11, in Comparative Examples 1 to 12, since any flatness was inferior, stable fluttering characteristics could not be obtained.

  Specifically, in Comparative Examples 1, 2, 7, and 8, the time from the polishing to the heat treatment was too long. Therefore, the difference in flatness before and after the treatment when the substrate was subjected to a heat treatment of 190 ° C. × 20 h exceeded 20 μm, and the fluttering characteristics were inferior. It is considered that the internal strain was stabilized because the time from polishing to heat treatment exceeded 72 h, and the internal strain was not sufficiently released even after heat treatment.

  In Comparative Examples 5, 6, 9, and 10, the temperature of the heat treatment after polishing was too high. As a result, the flatness after the heat treatment after polishing increased beyond 30 μm, and the fluttering characteristics were inferior.

  In Comparative Examples 3, 4, 11, and 12, the temperature of the heat treatment after polishing was too low. Therefore, the difference in flatness before and after the treatment when the substrate was subjected to a heat treatment of 190 ° C. × 20 h exceeded 20 μm, and the fluttering characteristics were inferior. The difference in flatness before and after the heat treatment at 190 ° C. × 20 h was large and inferior. It is presumed that the heat treatment temperature after polishing was low and internal strain was not sufficiently released.

  In the present invention, the flatness of the magnetic disk substrate surface is defined in two directions. That is, the difference between the flatness after the heat treatment after polishing (30 μm or less) and the flatness before and after the treatment when the substrate is heated at 190 ° C. × 20 h (20 μm or less). From the above examples, it was confirmed that both flatness is required to be stable in order to stabilize the disk fluttering. This criterion for flatness has been found to apply to both aluminum alloy substrates and glass substrates. And in order to make these flatness favorable, implementation of an appropriate heat processing is preferable within 72h after grinding | polishing of a board | substrate. This tendency also applies to both aluminum alloy substrates and glass substrates.

  According to the present invention, a magnetic disk substrate having stable fluttering characteristics, a manufacturing method thereof, and a magnetic disk using the magnetic disk substrate can be obtained.

Claims (7)

In magnetic disk substrates,
The flatness is 30 μm or less,
A magnetic disk substrate, wherein the difference in flatness before and after the heat treatment at 190 ° C. × 20 h is 20 μm or less. The magnetic disk substrate according to claim 1, wherein a product of a plate thickness (mm) and a loss factor is 0.10 × 10 ⁻³ or more. A method for manufacturing a magnetic disk substrate according to claim 1 or 2, wherein
Including at least one polishing step to form a magnetic disk substrate;
Furthermore, the manufacturing method of the magnetic disk board | substrate which includes the process of heat-processing the magnetic disk board | substrate after grinding | polishing at 100-250 degreeC within 72h after grinding | polishing in the last grinding | polishing process of the said grinding | polishing process. The magnetic disk substrate according to claim 1 or 2, wherein
Made of aluminum alloy,
The said aluminum alloy contains at least any one of Fe: 0.10-3.00mass% and Mn: 0.10-3.00mass%, The board | substrate for magnetic discs which consists of remainder Al and an unavoidable impurity.   Aluminum alloy is Mg: 0.100-5.000 mass%, Ni: 0.100-5.000 mass%, Cr: 0.010-5.000 mass%, Zr: 0.010-5.000 mass%, Zn: One or more elements selected from the group consisting of 0.005 to 5.000 mass%, Cu: 0.005 to 5.000 mass%, and Si: 0.10 to 0.40 mass% The magnetic disk substrate according to claim 4, which is contained.   The aluminum alloy further contains one or more elements selected from the group consisting of Ti, B, and V, and further contains 0.005 to 5.000 mass% in total content. 5. The magnetic disk substrate according to 5. For magnetic disks,
7. A magnetic disk, wherein a magnetic layer is provided on the surface of the magnetic disk substrate according to claim 1.

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