Magnetic recording device and layered structure

Abstract

Provided is a magnetic recording device, said magnetic recording device comprising a plurality of magnetic disks which each include a substrate and a magnetic recording layer formed on the substrate and a spacer which is disposed between the plurality of magnetic disks and which is for stacking the magnetic disks with a prescribed interval therebetween, wherein after a thermal shock test, the change in the flatness of the magnetic disks is not more than 5.0 μm. In the thermal shock test, a temperature raising and lowering program in which, inside a thermal shock device, the magnetic recording device is kept at 70°C for 30 minutes, subsequently cooled to -40°C over two minutes and kept at -40°C for 30 minutes, and then increased in temperature to 70°C over two minutes is repeated for five cycles.

Description

Magnetic recording device and laminated structure

[0001] The present disclosure relates to a magnetic recording device and a laminated structure.

[0002] Recent advances in computer technology have led to a demand for magnetic recording devices with larger storage capacities and smaller footprints. To this end, magnetic recording devices sandwich spacers between multiple magnetic disks, and form a stacked structure of the magnetic disks and spacers by passing a spindle through the inner holes of the magnetic disks and spacers. The magnetic disks and spacers are fixed by pressing them from one side with a clamping member. In such a stack, the magnetic disks do not come into contact with each other, but are spaced apart at predetermined intervals. The magnetic recording device fits into the gaps between the magnetic disks, and performs recording operations and the like on the stacked magnetic disks using a magnetic head (see, for example, Patent Documents 1 to 3).

[0003] Energy-assisted magnetic recording (EAMR), typified by thermally assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR), is a known recording method that increases the recording density of a magnetic layer by increasing the density of magnetic particles. In EAMR, magnetic particles are made smaller to reduce the bit size, and when recording data, energy is applied to the magnetic particles to reduce their coercivity, thereby assisting magnetization reversal and increasing the recording density. Because the magnetic particles are small, EAMR allows for a narrower track width, which also improves the recording density in the track width direction.

[0004] Japanese Patent Laid-Open No. 08-315533 Japanese Patent Laid-Open No. 2000-57727 Japanese Patent Laid-Open No. 2003-272336

[0005] In a magnetic recording device, the high-speed rotation of a magnetic disk causes the ambient temperature to rise, causing the magnetic disk to thermally expand. This expansion causes the track to expand toward the outer periphery. This leads to errors when writing or reading data, which can cause the magnetic head to radially shift beyond the allowable range relative to the track. In energy-assisted magnetic recording (EAMR), the track width is narrow, and the allowable amount of deviation (off-track tolerance) of the magnetic head relative to the track is small, making writing or reading errors (read / write errors) more likely to occur. On the other hand, the positioning accuracy of the magnetic head based on servo information increases in order to increase recording capacity, which can lead to unacceptable changes in the shape of the magnetic disk due to temperature changes. Therefore, it is desirable for the thermal expansion of a magnetic disk with temperature changes to be as small as possible. To ensure the quality of the magnetic disk, a low thermal expansion coefficient is required over a wide temperature range.

[0006] However, it has been found that even if the thermal expansion coefficient of the magnetic disk is within a specified range, when combined with a spacer, the flatness of the magnetic disk when placed in a magnetic recording device may deteriorate and the resulting increase in fluttering may cause read / write errors.

[0007] Therefore, an object of the present disclosure is to provide a magnetic recording device and a laminated structure with high read / write accuracy.

[0008] One embodiment of the present disclosure relates to a magnetic recording device comprising: a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate; and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at predetermined intervals; wherein the change in flatness of the magnetic disks after the following thermal shock test is 5.0 μm or less.

[0009] One embodiment of the present disclosure relates to a magnetic recording device comprising: a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate; and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at a predetermined interval; wherein, after the thermal shock test described below, the change in flatness of the magnetic disks is 8.0 μm or less; and, after the thermal shock test described below, the ratio (value of f / t) of the flatness value f (μm) of the substrate to the thickness t (mm) of the substrate is 20 μm / mm or less.

[0010] One embodiment of the present disclosure relates to a laminated structure comprising: a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate; and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at predetermined intervals, wherein the change in flatness of the magnetic disks after the following thermal shock test is 5.0 μm or less.

[0011] One embodiment of the present disclosure relates to a laminated structure comprising: a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate; and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at a predetermined interval, wherein after the thermal shock test described below, the change in flatness of the magnetic disks is 8.0 μm or less; and after the thermal shock test described below, the ratio (value of f / t) of the flatness value f (μm) of the substrate to the thickness t (mm) of the magnetic disks is 20 μm / mm or less.

[0012] One embodiment of the present disclosure relates to a laminated structure comprising: a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate; and a spacer disposed between the plurality of magnetic disks for stacking the magnetic disks at a predetermined interval, wherein after the thermal shock test described below, the change in flatness of the magnetic disks is 8.0 μm or less; and when an impact of 40 G for 2 ms is applied to the magnetic disks in a state mounted on a magnetic recording device in a normal direction to a main surface of the magnetic disks after the thermal shock test described below, the maximum amplitude due to vibration in the thickness direction of the outer peripheral edge of the magnetic disks is 0.20 mm or less.

[0013] <Thermal Shock Test> In a thermal shock chamber, the magnetic recording device is maintained at 70°C for 30 minutes, then cooled to -40°C in 2 minutes, maintained at this temperature for 30 minutes, and then heated to 70°C in 2 minutes. This temperature increase / decrease cycle is repeated 5 times.

[0014] According to the present invention, it is possible to provide a magnetic recording device and a laminated structure with high read / write accuracy.

[0015] Fig. 1 shows a schematic configuration diagram of a magnetic recording device according to this embodiment. Fig. 2 is a schematic cross-sectional view of a laminated structure. Fig. 3 is a conceptual diagram showing a laminated structure. Fig. 4 is a perspective view of the appearance of a magnetic disk according to this embodiment. Fig. 5 is a cross-sectional view of a magnetic disk according to this embodiment. Fig. 6 is a perspective view of the appearance of a spacer according to this embodiment.

[0016] Preferred embodiments of the present disclosure will be described with reference to the accompanying drawings (note that in each drawing, components with the same reference numerals have the same or similar configurations). The embodiments described below are intended to facilitate understanding of the present disclosure and are not intended to limit the scope of the present disclosure. The elements of the embodiments, as well as their arrangement, materials, conditions, shape, size, etc., are not limited to those exemplified and can be modified as appropriate. Furthermore, configurations shown in different embodiments can be partially substituted or combined with each other.

[0017] [Magnetic Recording Device] The magnetic recording device according to the first embodiment comprises: a substrate; a plurality of magnetic disks, each including a magnetic recording layer formed on the substrate; and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at a predetermined interval. Furthermore, the magnetic recording device according to the first embodiment exhibits a change in flatness of the magnetic disks of 5.0 μm or less after the thermal shock test described below. <Thermal Shock Test> In a thermal shock chamber, the magnetic recording device is maintained at 70°C for 30 minutes, then cooled to -40°C in 2 minutes, maintained there for 30 minutes, and then heated to 70°C in 2 minutes, a temperature increase / decrease program repeated five times. This configuration allows for a magnetic recording device with high read / write accuracy.

[0018] In the magnetic recording device according to the first embodiment, the change in flatness of the magnetic disk is 5.0 μm or less, preferably 4.0 μm or less, more preferably 3.0 or less, even more preferably 2.5 or less, even more preferably 0 to 1.8, and even more preferably 0.1 to 1.5, from the viewpoint of further improving the accuracy of reading and writing.

[0019] In the magnetic recording device according to the first embodiment, the ratio (value of f / t) of the flatness value f (μm) of the substrate after the thermal shock test to the thickness t (mm) of the substrate is preferably 25 μm / mm or less, more preferably 0 to 20 μm / mm or less, and even more preferably 5 to 18.5 μm / mm or less, from the viewpoint of further improving the accuracy of reading and writing.

[0020] A magnetic recording device according to a second embodiment includes a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate; and a spacer disposed between the plurality of magnetic disks for stacking the magnetic disks at a predetermined interval. Furthermore, in the magnetic recording device according to the second embodiment, the change in flatness of the magnetic disks after the thermal shock test is 8.0 μm or less, and the ratio (f / t value) of the flatness value f (μm) of the substrate to the thickness t (mm) of the substrate after the thermal shock test is 20 μm / mm or less. This configuration allows for a magnetic recording device with high read / write accuracy. Even if the change in flatness is 8.0 μm or less, the read / write accuracy can be improved by keeping the f / t value within the range of 20 μm / mm or less.

[0021] In the magnetic recording device according to the second embodiment, the amount of change in flatness of the magnetic disk is, from the viewpoint of further improving the accuracy of reading and writing, 8.0 μm or less, preferably 7.0 μm or less, more preferably 6.0 or less, even more preferably 5.0 or less, even more preferably 0 to 4.0, and even more preferably 0.1 to 3.0. Even if the amount of change in flatness is within this range, it is possible to further improve the accuracy of reading and writing by keeping the value of f / t, which will be described later, within a predetermined range.

[0022] In the magnetic recording device according to the second embodiment, the ratio (value of f / t) of the flatness value f (μm) of the substrate to the thickness t (mm) of the substrate after the thermal shock test is 20 μm or less, preferably 18.5 μm / mm or less, more preferably 0 to 18.5 μm / mm or less, and even more preferably 5 to 18.5 μm / mm or less, from the viewpoint of further improving the accuracy of reading and writing.

[0023] A laminated structure according to a third embodiment includes: a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate; and a spacer disposed between the plurality of magnetic disks for stacking the magnetic disks at a predetermined interval. Furthermore, in the laminated structure according to the third embodiment, the change in flatness of the magnetic disks after the thermal shock test described below is 8.0 μm or less, and the ratio (f / t value) of the flatness value f (μm) of the substrate to the thickness t (mm) of the magnetic disks after the thermal shock test described below is 20 μm / mm or less. In the magnetic recording device according to the third embodiment, the preferred range of the ratio (f / t value) of the flatness value f (μm) of the substrate to the thickness t (mm) of the substrate after the thermal shock test is the same as the range described in the second embodiment.

[0024] The laminated structure according to the fourth embodiment is a laminated structure comprising: a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate; and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at a predetermined interval, wherein after the thermal shock test described below, the change in flatness of the magnetic disks is 8.0 μm or less; and when an impact of 40 G for 2 ms is applied to the magnetic disks mounted in a magnetic recording device in the normal direction to the main surface of the magnetic disks after the thermal shock test described below, the maximum amplitude due to vibration in the thickness direction of the outer peripheral edge of the magnetic disks is 0.20 mm or less.

[0025] For the laminated structure according to the fourth embodiment, when a magnetic disk mounted on a magnetic recording device is subjected to a 40 G impact for 2 ms in the direction normal to the main surface of the magnetic disk, the maximum amplitude of vibration in the thickness direction of the outer peripheral edge of the magnetic disk is preferably 0.20 mm or less. This maximum amplitude is preferably 0.18 mm or less, and more preferably 0.16 mm or less. By keeping the amplitude within this range, even if the magnetic disk comes into contact with another magnetic disk or other component due to vibration caused by an external impact, chipping of the magnetic disk and generation of particles can be suppressed. The impact test is performed using an AVEX-SM-110-MP testing machine manufactured by Air Brown Co., Ltd.

[0026] The thermal shock test described above is performed according to the following procedure. In a thermal shock apparatus, the magnetic recording device is maintained at 70°C for 30 minutes, then cooled to -40°C in 2 minutes, maintained at this temperature for 30 minutes, and then heated to 70°C in 2 minutes. This temperature increase / decrease program is repeated 5 times. As the thermal shock apparatus, for example, a "TSA-503EL-W" (manufactured by Espec Corporation) can be used. In the thermal shock test, a magnetic recording device incorporating multiple magnetic disks and spacers is used.

[0027] The amount of change in flatness of the magnetic disk can be adjusted by the combination of the material and thickness of the magnetic disk substrate and the spacer material. More specifically, a predetermined amount of change in flatness can be obtained by adjusting the thermal expansion coefficient and Young's modulus of the magnetic disk substrate material and the spacer material, and adjusting their combination. In addition to adjusting the materials of the magnetic disk and spacer, the value of this parameter can also be adjusted by the shape of the spindle and the clamping force.

[0028] The value of f / t can be set within the above range by adjusting the amount of change in flatness and the thickness t of the substrate.

[0029] Hereinafter, a configuration common to the first and second embodiments will be referred to as the present embodiment. ４It is preferable to satisfy the formula: CTE(spa)·E(spa)≦1.0×10 ４ By satisfying the above condition, the magnetic recording device has further improved shock resistance and fluttering characteristics. ４ is preferably 0.1 × 10 or less. ４ ~0.7 × 10 ４ More preferably, it is within the range of 0.2 × 10 ４ ~0.4 × 10 ４ is within the range.

[0030] The substrate has a CTE (sub)·E (sub)≦0.5×10 ４ It is preferable to satisfy the formula: CTE(sub)·E(sub)≦0.5×10 ４ By satisfying this condition, the magnetic recording device has further improved shock resistance and fluttering characteristics. ４ or less, more preferably 0.10 × 10 ４ ~0.40 x 10 ４ More preferably, it is within the range of 0.20 × 10 ４ ~0.35 x 10 ４ is within the range.

[0031] The substrate preferably satisfies the formula: CTE(sub) / E(sub)≦1.5. By satisfying the formula: CTE(sub) / E(sub)≦1.5, the magnetic recording device can suppress fluttering characteristics in the environment in which the magnetic recording device is used, even if the substrate thickness is 0.51 mm or less. The value of CTE(sub) / E(sub) is 1.5 or less, preferably 0.8 or less, and more preferably in the range of 0.35 to 0.5.

[0032] CTE(sub) is the thermal expansion coefficient of the substrate at 100 to 300°C (×10 －７ / K). A sample cut to a length of 50 mm and a width of 10 mm is used to determine the change in length over a predetermined temperature range using a thermal dilatometer based on laser interferometry, and this is taken as the average linear expansion coefficient at 100 to 300°C. Note that, because the influence of the magnetic film contained in the magnetic disk on the thermal expansion coefficient is negligible, the thermal expansion coefficient of the magnetic disk may be taken as the thermal expansion coefficient of the substrate. Note that a more detailed measurement method is as described in the Examples.

[0033] CTE(spa) is the thermal expansion coefficient of the spacer at 100 to 300°C (×10 －７ In measuring the thermal expansion coefficient of a spacer, if it is not possible to cut out a sample of the same dimensions as the substrate, the conductive film on the outer surface is removed, the crushed sample is washed and dried, and then remelted at a specified temperature to obtain a sample of the same dimensions as the substrate, and measurement is performed using this sample.

[0034] E(sub) is the Young's modulus (GPa) of the substrate. Young's modulus can be measured based on JIS R1602:1995. A test specimen for measurement is cut out from the magnetic disk as a rectangular parallelepiped having a length of 50 mm, a width of 10 mm, and a thickness the same as the plate thickness of the magnetic disk, and measurement can be performed at room temperature. Note that, since the influence of the magnetic film contained in the magnetic disk on the thermal expansion coefficient is negligible, the thermal expansion coefficient of the magnetic disk may be used as the thermal expansion coefficient of the substrate.

[0035] E (spa) is the Young's modulus (GPa) of the spacer. Young's modulus can be measured based on JIS R1602:1995. To prepare a test piece for measuring the spacer, the conductive film on the outer surface of the spacer is removed, the pulverized sample is washed and dried, and then remelted at a predetermined temperature. The sample is cut into a rectangular parallelepiped with the same thickness as the magnetic disk, and the measurement is performed at room temperature.

[0036] The magnetic recording device according to this embodiment will be described in detail below. FIG. 1 shows a schematic configuration diagram of the magnetic recording device according to this embodiment. The magnetic recording device 1 has a stacked structure 2 of a plurality of magnetic disks 21. In the magnetic recording device 1 according to this embodiment, the stacked structure 2 is mounted on a spindle motor (not shown). The magnetic disks 21 of the stacked structure 2 are rotated by the spindle motor.

[0037] The head assembly 3 includes a head slider 31. The head assembly 3 includes multiple stages of head sliders 31. The head slider 31 includes a magnetic head near the tip. The head slider 31 records and reproduces information from the rotating magnetic disk 21. By forming multiple stages of head sliders 31, it is possible to read information from the magnetic disks 21 stacked at a predetermined interval. In this case, the magnetic disk 21 is less likely to deform due to temperature changes in the usage environment, and has improved shock resistance, so that the head slider or magnetic head is less likely to interfere with the magnetic disk when recording or reading information.

[0038] Fig. 2 is a schematic cross-sectional view of a laminated structure. The laminated structure 2 includes a plurality of magnetic disks 21 and spacers 22 arranged between the plurality of magnetic disks 21 for stacking the magnetic disks 21 at predetermined intervals. Fig. 2 shows an example in which the laminated structure 2 includes three magnetic disks 21, but the number of magnetic disks 21 is not particularly limited.

[0039] 2, multiple magnetic disks 21 are inserted onto a rotating spindle 23 with spacers 22 sandwiched between them, and are fixed to the spindle 23 by clamping members 24, fixed with screws or the like, from above the stacked structure 2 of the magnetic disks 21 and spacers 22, thereby mounting the magnetic disks 21 at predetermined intervals. The clamping members 24 press against the uppermost magnetic disk 21. This pressing force also presses and fixes the entire stack. The clamping members 24 have circular projections 241 formed around the central axis of the spindle 23 for pressing against the magnetic disks 21.

[0040] As shown in FIG. 3, magnetic disks 21 and spacers 22 are alternately stacked to form a laminated structure, which is then incorporated into a magnetic storage device.

[0041] 4 is a perspective view of the appearance of the magnetic disk 21 according to this embodiment. The magnetic disk 21 is annular and has a spindle hole 215. The magnetic disk 21 has two opposing main surfaces 216. The pair of main surfaces are substantially parallel. Here, "substantially parallel" means that the parallelism is, for example, 5 μm or less.

[0042] 5 is a cross-sectional view of the magnetic disk 21 according to this embodiment. The magnetic disk 21 includes a substrate 211 having a thickness of 0.51 mm or less and a magnetic recording layer 213.

[0043] The substrate preferably has a thickness of 0.51 mm or less, preferably 0.50 mm or less, more preferably 0.30 to 0.50 mm, and even more preferably 0.32 to 0.45 mm.

[0044] Examples of materials for the substrate include metal materials such as stainless steel, titanium, aluminum, and aluminum alloys, ceramics, and glass. Among these, the substrate is preferably a glass substrate.

[0045] The glass composition of the glass substrate is preferably SiO ２ 55 to 80 mol%, Al ２ O ３ 5 to 25 mol%, B ２ O ３ 0 to 8 mol%, P ２ O ５ 0 to 5 mol % of MO, 5 to 25 mol % of MO (MO is at least one selected from MgO, CaO, SrO and BaO, and the content thereof is the total value of the contents of MgO, CaO, SrO and BaO), and 0 to 15 mol % of M ２ O (M ２ O is Li ２ O, Na ２ O and K ２ At least one selected from Li, O, ２ O, Na ２ O and K ２The glass composition of the glass substrate may consist of these components.

[0046] The preferred contents of each component in the glass composition of the glass substrate are as follows:

[0047] SiO ２ is a glass network forming component. SiO ２ From the viewpoint of increasing the stability of the glass and improving the meltability during production, the content of is preferably 55 to 80 mol %, more preferably 57 to 75 mol %, and even more preferably 60 to 70 mol %.

[0048] Al ２ O ３ From the viewpoint of improving the heat resistance of the glass and enhancing the stability of the glass, the content of is preferably 5 to 25 mol %, more preferably 10 to 20 mol %, and even more preferably 12 to 18 mol %.

[0049] B ２ O ３ is a glass network forming component. ２ O ３ The content is preferably 0 to 8 mol %, more preferably 0.1 to 5 mol %, and even more preferably 0.1 to 3 mol %.

[0050] P ２ O ５ The content is preferably 0 to 5 mol %, more preferably 0 to 3 mol %, and even more preferably 0 to 2 mol %.

[0051] MO is at least one selected from MgO, CaO, SrO, and BaO, and its content is the total content of MgO, CaO, SrO, and BaO. From the viewpoint of adjusting the Young's modulus, the content of MO is preferably 5 to 25 mol%, more preferably 6 to 20 mol%, and even more preferably 14 to 18 mol%. From the viewpoint of adjusting the Young's modulus, the content of MgO is preferably 3 to 20 mol%, more preferably 4 to 19 mol%, and even more preferably 8 to 18 mol%.

[0052] From the viewpoint of improving productivity, the CaO content is preferably 0 to 10 mol %, more preferably 0 to 8 mol %, and even more preferably 0 to 6 mol %.

[0053] From the viewpoint of reducing the specific gravity of the glass, the content of SrO is preferably 0 to 5 mol %, more preferably 0 to 3 mol %, and even more preferably 0 to 1.5 mol %.

[0054] From the viewpoint of reducing the specific gravity of the glass, the content of BaO is preferably 0 to 5 mol %, more preferably 0 to 4 mol %, and even more preferably 0 to 1.5 mol %.

[0055] M ２ O is Li ２ O, Na ２ O and K ２ At least one selected from Li, O, ２ O, Na ２ O and K ２ The total value of O. ２ The O content is preferably 0 to 15 mol %, more preferably 0 to 10 mol %, and even more preferably 0.5 to 9 mol %.

[0056] Li ２ From the viewpoint of improving heat resistance, the O content is preferably 0 to 5 mol %, more preferably 0 to 7 mol %, and even more preferably 0.5 to 6 mol %.

[0057] Na ２ The O content is preferably 0 to 10 mol %, more preferably 0 to 7 mol %, and even more preferably 0.5 to 5 mol %.

[0058] K ２ The O content is preferably 0 to 3 mol %, more preferably 0 to 1 mol %, and even more preferably 0 to 0.3 mol %.

[0059] The substrate is a glass substrate, and the glass substrate satisfies the formula (5): CTE(sub) / E(sub)≦1.5 (5), and the glass composition of the glass substrate is SiO ２ 55 to 80 mol%, Al２ O ３ 5 to 25 mol%, B ２ O ３ 0 to 8 mol % of MO, 5 to 25 mol % of MO (MO is at least one selected from MgO, CaO, SrO and BaO, and the content thereof is the total value of the contents of MgO, CaO, SrO and BaO), and 0 to 15 mol % of M ２ O (M ２ O is Li ２ O, Na ２ O and K ２ At least one selected from Li, O, ２ O, Na ２ O and K ２ It is preferable that the polymer contains 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,

[0060] Examples of the glass composition of the glass substrate include the following SU1, SU2, and SU3.

[0061] SU1: SiO ２ 60 to 70 mol%, Al ２ O ３ 8 to 15 mol%, B ２ O ３ 1 to 5 mol % of MO, 10 to 20 mol % of MO (MO is at least one selected from MgO, CaO, SrO and BaO, and the content is the total value of the contents of MgO, CaO, SrO and BaO), 0 to 1 mol % of M ２ O (M ２ O is Li ２ O, Na ２ O and K ２ At least one selected from Li, O, ２ O, Na ２ O and K ２ The alkali-free glass containing

[0062] SU2: SiO ２ 60 to 70 mol%, Al ２ O ３ 8 to 15 mol%, B ２ O ３1 to 5 mol % of MO, 10 to 20 mol % of MO (MO is at least one selected from MgO, CaO, SrO and BaO, and the content is the total value of the contents of MgO, CaO, SrO and BaO), 0 to 1 mol % of M ２ O (M ２ O is Li ２ O, Na ２ O and K ２ At least one selected from Li, O, ２ O, Na ２ O and K ２ The alkali-free glass containing

[0063] SU3: SiO ２ 55 to 75 mol%, Al ２ O ３ 5 to 20 mol%, B ２ O ３ 0 to 3 mol % of MO, 12 to 25 mol % of MO (MO is at least one selected from MgO, CaO, SrO and BaO, and the content is the total value of the contents of MgO, CaO, SrO and BaO), 0.1 to 10 mol % of M ２ O (M ２ O is Li ２ O, Na ２ O and K ２ At least one selected from Li, O, ２ O, Na ２ O and K ２ O)

[0064] In the present disclosure, the glass composition is expressed as a glass composition based on oxides. Here, "glass composition based on oxides" refers to a glass composition obtained by converting the glass raw materials into oxides present in the glass after they are all decomposed during melting. The glass composition in the present disclosure can be determined by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Quantitative analysis is performed for each element using ICP-AES. The analytical values ​​are then converted into oxide notation. The analytical values ​​obtained by ICP-AES may contain, for example, a measurement error of about ±5% of the analytical value. Therefore, the oxide notation values ​​converted from the analytical values ​​may also contain an error of about ±5%. Furthermore, in the present disclosure, a content of 0 mol% of a constituent component means that the constituent component is substantially absent, and indicates that the content of the constituent component is at or below the impurity level. The level of impurities or less means, for example, less than 0.01 mol %.

[0065] Coefficient of thermal expansion of the substrate at 100 to 300°C (CTE (sub)) (unit: × 10 －７ / K) is preferably 10 to 110, more preferably 25 to 98, and even more preferably 30 to 55.

[0066] The Young's modulus E(sub) (unit: GPa) of the substrate is preferably 75 to 120, more preferably 80 to 110, and even more preferably 85 to 105.

[0067] The value of the specific elastic modulus E / d of the substrate is preferably 32.0×10 ６ m ２ / s ２ More preferably, it is 33.5×10 ６ m ２ / s ２ or more, preferably 35.0×10 ６ m ２ / s ２That's all. When the substrate has a specific elastic modulus E / d within this range, impact resistance is further improved. Note that when the substrate has a thickness of 0.51 mm or less, the above-mentioned effect is more pronounced when the specific elastic modulus E / d is within the above-mentioned range. The specific elastic modulus E / d means the value obtained by dividing Young's modulus by specific gravity.

[0068] The magnetic disk 21 includes a magnetic recording layer 213. The magnetic disk 21 may have, for example, an adhesive layer, an underlayer, a magnetic recording layer (magnetic layer), a protective layer, and a lubricating layer stacked in this order from the side closest to the main surface on the main surface of a smoothly polished glass substrate. Of these, the adhesive layer, underlayer, and magnetic recording layer are sequentially deposited on the main surface of the glass substrate in an Ar atmosphere by DC (Direct Current) magnetron sputtering, for example, by introducing the glass substrate into a vacuum-drawn film-forming apparatus. For example, CrTi can be used as the adhesive layer, and a material containing Ru or MgO can be used as the underlayer. A soft magnetic layer and a heat sink layer may be added as appropriate. After the above-mentioned films are deposited, a C layer is formed on the main surface of the glass substrate by, for example, a CVD (Chemical Vapor Deposition) method. ２ H ４ The protective layer is formed using a nitriding agent, and then a nitriding process is performed in the same chamber to introduce nitrogen into the surface. After that, for example, PFPE (polyfluoropolyether) is applied to the protective layer by a dip coating method, thereby forming a lubricating layer. In this manner, the magnetic disk 21 can be manufactured.

[0069] To achieve even higher density recording on the magnetic disk 21, it is preferable that the magnetic recording layer contain a magnetic material with high magnetic anisotropy energy. From this perspective, preferred magnetic materials include Fe—Pt-based magnetic materials and Co—Pt-based magnetic materials. Here, "based" means containing.

[0070] That is, the magnetic disk 21 preferably has a magnetic recording layer containing Fe and Pt, or Co and Pt. WO2011 / 019010 can be referred to for magnetic recording layers containing such magnetic materials and methods for forming such layers. Furthermore, the magnetic disk 21 having such a magnetic recording layer is preferably applied to a magnetic recording device using a recording method called energy-assisted magnetic recording (EAMR). Among energy-assisted recording methods, a recording method that assisted magnetization reversal by irradiation with near-field light or the like is called thermally-assisted magnetic recording (HAMR), and a recording method that assisted magnetization reversal by microwaves is called microwave-assisted magnetic recording (MAMR). For details of these methods, WO2011 / 019010 can be referred to. Note that a CoPtCr-based material may also be used as the magnetic material for forming the magnetic recording layer.

[0071] 6 is a perspective view of the appearance of the spacer 22 according to this embodiment. The spacer 22 is annular in shape and has a spindle hole 225. The spacer 22 has main surfaces 226 that face each other. The pair of main surfaces are substantially parallel. Here, "substantially parallel" means that the parallelism is, for example, 5 μm or less.

[0072] Examples of the spacer material include metal materials such as stainless steel, titanium, aluminum, and aluminum alloys, ceramics, and glass. Among these, glass spacers are preferred.

[0073] The glass composition of the spacer is preferably SiO ２ 55 to 88 mol%, Al ２ O ３ 0 to 20 mol%, B ２ O ３ 1 to 30 mol%, P ２ O ５ 0 to 5 mol % of MO, 0 to 20 mol % of MO (MO is at least one selected from MgO, CaO, SrO and BaO, and the content thereof is the total value of the contents of MgO, CaO, SrO and BaO), and 0 to 15 mol % of M ２ O (M ２ O is Li ２ O, Na ２ O and K２ At least one selected from Li, O, ２ O, Na ２ O and K ２ The glass composition of the glass substrate may be composed of these components. It is preferable that the glass composition of the spacer is different from that of the substrate.

[0074] The preferred contents of each component in the glass composition of the spacer are as follows:

[0075] SiO ２ is a glass network forming component. SiO ２ From the viewpoint of increasing the stability of the glass and improving the meltability during production, the content of is preferably 55 to 88 mol %, more preferably 65 to 85 mol %, and even more preferably 75 to 85 mol %.

[0076] Al ２ O ３ From the viewpoint of improving the heat resistance of the glass and enhancing the stability of the glass, the content of is preferably 0 to 20 mol %, more preferably 1 to 17 mol %, and even more preferably 1 to 5 mol %.

[0077] B ２ O ３ is a glass network forming component. ２ O ３ The content is preferably 1 to 30 mol %, more preferably 5 to 28 mol %, even more preferably 8 to 28 mol %, and still more preferably 10 to 20 mol %.

[0078] P ２ O ５ The content is preferably 0 to 5 mol %, more preferably 0 to 3 mol %, and even more preferably 0 to 2 mol %.

[0079] MO is at least one selected from MgO, CaO, SrO, and BaO, and its content is the total content of MgO, CaO, SrO, and BaO. From the viewpoint of adjusting the Young's modulus, the content of MO is preferably 0 to 20 mol%, more preferably 0 to 5 mol%, and even more preferably 0 mol%. From the viewpoint of adjusting the Young's modulus, the content of MgO is preferably 0 to 10 mol%, more preferably 0 to 5 mol%, and even more preferably 0 mol%.

[0080] From the viewpoint of improving productivity, the CaO content is preferably 0 to 10 mol %, more preferably 0 to 5 mol %, and even more preferably 0 mol %.

[0081] From the viewpoint of reducing the specific gravity of the glass, the content of SrO is preferably 0 to 4 mol %, more preferably 0 to 3 mol %, and even more preferably 0 mol %.

[0082] From the viewpoint of reducing the specific gravity of the glass, the content of BaO is preferably 0 to 5 mol %, more preferably 0 to 3 mol %, and even more preferably 0 mol %.

[0083] M ２ O is Li ２ O, Na ２ O and K ２ At least one selected from Li, O, ２ O, Na ２ O and K ２ The total value of O. ２ The O content is preferably 0 to 15 mol %, more preferably 0 to 10 mol %, and even more preferably 0.1 to 8 mol %.

[0084] Li ２ From the viewpoint of improving heat resistance, the O content is preferably 0 to 4 mol %, more preferably 0 to 3 mol %, and even more preferably 0 to 2 mol %.

[0085] Na ２ The O content is preferably 0 to 15 mol %, more preferably 0.1 to 10 mol %, and even more preferably 1 to 5 mol %.

[0086] K ２ The O content is preferably 0 to 3 mol %, more preferably 0 to 2 mol %, and even more preferably 0.1 to 0.5 mol %.

[0087] The spacer is a glass substrate, and the glass substrate satisfies the formula (5): CTE(sub) / E(sub)≦1.5 (5), and the glass composition of the spacer is SiO ２ 55 to 88 mol%, Al ２ O ３ 0 to 20 mol%, B ２ O ３ 1 to 30 mol % of MO, 0 to 20 mol % of MO (MO is at least one selected from MgO, CaO, SrO and BaO, and the content thereof is the total value of the contents of MgO, CaO, SrO and BaO), and 0 to 15 mol % of M ２ O (M ２ O is Li ２ O, Na ２ O and K ２ At least one selected from Li, O, ２ O, Na ２ O and K ２ It is preferable that the spacer contains SiO 2 and O 2 , and that the glass composition of the spacer is different from the glass composition of the substrate of the magnetic disk.

[0088] The glass composition of the spacer is, for example, SP-1 below.

[0089] SP-1: SiO ２ 78 to 88 mol%, Al ２ O ３ 1 to 5 mol%, B ２ O ３ 10 to 28 mol % of MO, 3 to 8 mol % of MO (MO is at least one selected from MgO, CaO, SrO and BaO, and the content is the total value of the contents of MgO, CaO, SrO and BaO), and 0 to 5 mol % of M ２ O (M ２ O is Li ２ O, Na ２ O and K ２At least one selected from Li, O, ２ O, Na ２ O and K ２ The total value of O is the borosilicate glass containing

[0090] The spacer preferably comprises a glass spacer substrate and a conductive film on the outer surface of the spacer substrate. ２ (tin oxide), ZnO, In ２ The conductive film may be a conductive oxide such as O3 or ITO (indium tin oxide). The conductive film may be a fluorine-doped conductive oxide. The conductive film may also be a metal film. Examples of components of the metal film include chromium, titanium, tantalum, tungsten, alloys containing these metals, and nickel alloys such as NiP (nickel phosphorus) and NiW (nickel tungsten). It is preferable that the nickel alloy is non-magnetic. The conductive film is formed by a dipping method, vapor deposition method, sputtering method, or the like used in plating processes such as electroless plating.

[0091] Coefficient of thermal expansion of spacer CTE (spa) at 100 to 300°C (unit: x 10 －７ / K) is preferably 10 to 105, more preferably 25 to 95, and even more preferably 30 to 45.

[0092] The Young's modulus E (spa) (unit: GPa) of the spacer is preferably 30 to 120, more preferably 50 to 80, and even more preferably 50 to 75.

[0093] Preferred examples of the combination of glass substrate and spacer include SU1 and SP1, SU2 and SP1, and SU3 and SP1. These combinations make it difficult for the substrate to deform due to temperature changes in the usage environment.

[0094] Examples of materials for the spindle include aluminum and stainless steel. Of these, aluminum is preferred from the perspective of lightweight design. The magnetic disk 21 and spacer 22 are preferably fixed to a spindle made of aluminum or stainless steel. As mentioned above, aluminum spindles are lightweight, but tend to have a high thermal expansion coefficient and a low Young's modulus. However, the combination of the magnetic disk and spacer according to this embodiment makes it less likely for the substrate to deform due to temperature changes in the usage environment.

[0095] When a magnetic disk mounted on a magnetic recording device is subjected to a 40 G impact for 2 ms in the direction normal to the main surface of the magnetic disk, the maximum amplitude of vibration in the thickness direction of the outer peripheral edge of the magnetic disk is preferably 0.25 mm or less. This maximum amplitude is preferably 0.23 mm or less, and more preferably 0.18 mm or less. By keeping the amplitude within this range, even if the magnetic disk comes into contact with another magnetic disk or other component due to vibration caused by an external impact, chipping of the magnetic disk and generation of particles can be suppressed. The impact test is performed using an AVEX-SM-110-MP testing machine manufactured by Air Brown Co., Ltd.

[0096] As described above, according to this embodiment, it is possible to provide a magnetic recording device and a laminated structure with high read / write accuracy.

[0097] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[0098] <Thermal Expansion Coefficient> The thermal expansion coefficient of the substrate was measured by measuring a sample cut from the magnetic disk to a length of 50 mm and a width of 10 mm, and measuring the change in length over a specified temperature range using a thermal dilatometer based on laser interferometry. This was taken as the average linear expansion coefficient at 100 to 300°C. Since the magnetic film contained in the magnetic disk has a negligible effect on the thermal expansion coefficient, the thermal expansion coefficient of the magnetic disk was used as the thermal expansion coefficient of the substrate. When measuring the thermal expansion coefficient of the spacer, since it is not possible to cut out a sample with the same dimensions as the magnetic disk, the spacer was heated and melted, then poured into a flat mold and slowly cooled to room temperature at a rate of 50°C / 10 min or less to obtain a 0.5 mm thick glass plate. Measurements were then performed using a sample cut to a length of 50 mm and a width of 10 mm. Note that multiple spacers with the same composition can be used to create a sample.

[0099] <Young's Modulus> The Young's modulus E of the substrate was measured in accordance with JIS R1602:1995. A test specimen for measurement was cut from the magnetic disk as a rectangular parallelepiped with a length of 50 mm, a width of 10 mm, and a thickness equal to the thickness of the magnetic disk, and the measurement was performed at room temperature. Since the influence of the magnetic film contained in the magnetic disk on the thermal expansion coefficient is negligible, the thermal expansion coefficient of the magnetic disk was used as the thermal expansion coefficient of the substrate. In measuring the Young's modulus of the spacer, since it is not possible to cut out a sample with the same dimensions as the magnetic disk, the spacer was heated and melted, then poured into a flat mold and slowly cooled to room temperature at a rate of 50°C / 10 min or less to obtain a glass plate with a thickness of 0.5 mm. Measurements were then performed using a sample cut to a length of 50 mm and a width of 10 mm. Note that multiple spacers with the same composition can be used to create a sample.

[0100] <Specific Gravity> The specific gravity was measured by the Archimedes method.

[0101] Since the effect of the magnetic film on the thermal expansion coefficient, Young's modulus, and density (specific gravity) of the magnetic disk is negligible, the thermal expansion coefficient, Young's modulus, and density (specific gravity) of the magnetic disk can be set to the thermal expansion coefficient, Young's modulus E, and density (specific gravity) of the substrate.

[0102] <Specific Elastic Modulus E / d> Calculated by dividing Young's modulus by specific gravity.

[0103] <Flatness> The flatness of the magnetic disk was measured as the maximum height difference (PV value) on the surface of the magnetic disk using an OptiFlat manufactured by Phase Shift Technology, Inc., using interference fringes from a semiconductor laser. The flatness of the magnetic disk was measured for the magnetic disk located on the top surface of the magnetic recording device, with multiple magnetic disks stacked and fixed with spacers between them. Any items that might interfere with the measurement (such as the cover or ramp of the magnetic recording device) were removed from the magnetic recording device in advance.

[0104] <Thermal Shock Test and Amount of Change in Flatness> The thermal shock test was performed using a thermal shock device "TSA-503EL-W" (product name, manufactured by Espec Corporation). The magnetic recording device was placed in the device, and after maintaining the temperature at 70°C for 30 minutes, the device was cooled to -40°C in 2 minutes, maintained for 30 minutes, and then heated to 70°C in 2 minutes. This temperature increase / decrease program was repeated 5 times. After the test, the flatness of the magnetic disk in the magnetic recording device was measured using the measurement method described above. The amount of change in flatness of the magnetic disk before and after the thermal shock test was expressed as an absolute value.

[0105] <Maximum Amplitude> <Impact Test: Maximum Amplitude> The impact test was carried out using an AVEX-SM-110-MP model testing machine manufactured by Air Brown Co., Ltd. An impact of 40 G was applied for 2 ms to the magnetic disk mounted in a magnetic recording device in the normal direction to the main surface of the magnetic disk. The maximum amplitude due to vibration in the thickness direction of the outer peripheral edge of the magnetic disk was recorded to evaluate the impact resistance.

[0106] (Examples and Comparative Examples) In Example 1, a thermal shock test, measurement of the change in flatness, maximum amplitude, and maximum displacement were performed using a magnetic recording device equipped with a stack of nine magnetic disks as described below sandwiched between the following spacers. In other Examples and Comparative Examples, a thermal shock test, measurement of the change in flatness, and measurement of the maximum amplitude were performed using a magnetic recording device in which the substrates and spacers used for the magnetic disks were changed as shown in Table 1. The results are shown in Table 1. Spacer: Outer diameter 32 mm, inner diameter 25 mm, thickness 1.8 mm, chamfered surface: radial length 250 μm on both the inner and outer periphery, angled 45 degrees relative to the inner and outer periphery. Width L of the main surface was 3.0 mm. Magnetic disk: A magnetic film and the like were formed on a substrate with a diameter of 97 mm, an inner diameter of 25 mm, and a thickness of 0.5 mm. For the other Examples and Comparative Examples, evaluations were performed in the same manner as in Example 1 using the spacers and substrates shown in Table 1. The results are shown in Table 1.

[0107]

[0108] The meanings of the various symbols in the table are as follows: (Substrate) SU-1: Glass substrate (Young's modulus 83 GPa, thermal expansion coefficient 37×10 －７ / K alkali-free glass) SU-2: Glass substrate (Young's modulus 79 GPa, thermal expansion coefficient 95 × 10 －７ / K alkali-containing glass) SU-3: Glass substrate (Young's modulus 90 GPa, thermal expansion coefficient 45 × 10 －７ / K alkali-containing glass) (Spacer) SP-1: Glass spacer (Young's modulus 71 GPa, thermal expansion coefficient 94 × 10 －７ / K glass) SP-2: Glass spacer (Young's modulus 65 GPa, thermal expansion coefficient 33 × 10 －７ / K glass) SP-3: Metal spacer (Young's modulus 69 GPa, thermal expansion coefficient 225 × 10 －７ / K Al metal) SP-4: Metal spacer (Young's modulus 116 GPa, thermal expansion coefficient 93 × 10 －７ / K Ti metal)

[0109] REFERENCE SIGNS LIST 1...magnetic recording device, 2...laminated structure, 21...magnetic disk, 22...spacer, 23...spindle, 24...clamp member, 211...substrate, 213...magnetic recording layer, 215...spindle hole, 216...main surface, 225...spindle hole, 226...main surface, 241...protrusion, 3...head assembly, 31...head slider

Claims

1. A magnetic recording device comprising: a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate; and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at predetermined intervals, wherein the change in flatness of the magnetic disks after the following thermal shock test is 5.0 μm or less: <Thermal shock test> In a thermal shock chamber, the magnetic recording device is maintained at 70°C for 30 minutes, then cooled to -40°C in 2 minutes, maintained at this temperature for 30 minutes, and then heated to 70°C in 2 minutes, with five cycles of this temperature increase / decrease program.

2. A magnetic recording device comprising: a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate; and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at a predetermined interval, wherein, after the thermal shock test described below, the change in flatness of the magnetic disks is 8.0 μm or less, and the ratio (f / t value) of the flatness value f (μm) of the substrate to the thickness t (mm) of the substrate after the thermal shock test described below is 20 μm / mm or less. <Thermal shock test> In a thermal shock chamber, the magnetic recording device is maintained at 70°C for 30 minutes, then cooled to -40°C in 2 minutes, maintained at this temperature for 30 minutes, and then heated to 70°C in 2 minutes, a temperature increase / decrease program is repeated 5 times.

3. The substrate has a thickness of 0.51 mm or less and a specific elastic modulus E / d of 32.0 (×10 ６ m ２ / s ２ 3. The magnetic recording device according to claim 1, wherein the number of magnetic recording layers is equal to or greater than 1.

4. The magnetic recording device according to claim 1 or 2, wherein the spacer comprises a spacer substrate made of glass and a conductive film on the outer surface of the spacer substrate.

5. The magnetic recording device according to claim 1 or 2, wherein the magnetic disk and the spacer are fixed to an aluminum spindle.

6. CTE(sub) is the coefficient of thermal expansion of the substrate in the temperature range of 100 to 300°C (×10 －７ / K), and CTE(spa) is the thermal expansion coefficient of the spacer in the temperature range of 100 to 300°C (×10 －７ / K), E(sub) is the Young's modulus (GPa) of the substrate, and E(spa) is the Young's modulus (GPa) of the spacer, the spacer having a Young's modulus (GPa) of the substrate satisfies the formula: CTE(spa)·E(spa)≦1.0×10 ４ and the substrate satisfies the formula: CTE(sub)·E(sub)≦0.5×10 ４ 3. The magnetic recording device according to claim 1, wherein the following is satisfied:

7. The substrate is a glass substrate, and the glass substrate satisfies the formula (5): CTE(sub) / E(sub)≦1.5 (5) (wherein, CTE(sub) is the thermal expansion coefficient (×10 －７ / K), and E(sub) is the Young's modulus (GPa) of the substrate. ２ 55 to 80 mol%, Al ２ O ３ 5 to 25 mol%, B ２ O ３ 0 to 8 mol % of MO, 5 to 25 mol % of MO (MO is at least one selected from MgO, CaO, SrO and BaO, and the content thereof is the total value of the contents of MgO, CaO, SrO and BaO), and 0 to 15 mol % of M ２ O (M ２ O is Li ２ O, Na ２ O and K ２ At least one selected from Li, O, ２ O, Na ２ O and K ２ 3. The magnetic recording device according to claim 1, wherein the total value of the total of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 8. A magnetic recording device according to claim 1 or 2, wherein when a 40 G impact is applied for 2 ms in the normal direction to the main surface of the magnetic disk mounted on the magnetic recording device, the maximum amplitude of vibration in the thickness direction of the outer edge of the magnetic disk is 0.25 mm or less.

9. A laminated structure comprising: a substrate, a plurality of magnetic disks each including a magnetic recording layer formed on the substrate; and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at predetermined intervals, wherein the change in flatness of the magnetic disks after the following thermal shock test is 5.0 μm or less: <Thermal shock test> In a thermal shock chamber, the magnetic recording device is maintained at 70°C for 30 minutes, then cooled to -40°C in 2 minutes, maintained at this temperature for 30 minutes, and then heated to 70°C in 2 minutes, with five cycles of this temperature increase / decrease program.

10. A laminated structure comprising a substrate and a plurality of magnetic disks, each including a magnetic recording layer formed on the substrate, and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at predetermined intervals, wherein after the thermal shock test described below, the change in flatness of the magnetic disks is 8.0 μm or less, and after the thermal shock test described below, the ratio (f / t value) of the flatness value f (μm) of the substrate to the thickness t (mm) of the magnetic disks is 20 μm / mm or less. <Thermal shock test> In a thermal shock chamber, the magnetic recording device is maintained at 70°C for 30 minutes, then cooled to -40°C in 2 minutes, maintained at this temperature for 30 minutes, and then heated to 70°C in 2 minutes, a heating and cooling program is repeated 5 times.

11. A laminated structure comprising a plurality of magnetic disks, each including a substrate and a magnetic recording layer formed on the substrate, and spacers disposed between the plurality of magnetic disks for stacking the magnetic disks at predetermined intervals, wherein after the thermal shock test described below, the change in flatness of the magnetic disks is 8.0 μm or less, and when a 40 G shock for 2 ms is applied to the magnetic disks mounted in a magnetic recording device in the normal direction to the main surface of the magnetic disks after the thermal shock test described below, the maximum amplitude of vibration in the thickness direction of the outer edge of the magnetic disks is 0.20 mm or less. <Thermal shock test> In a thermal shock chamber, the magnetic recording device is maintained at 70°C for 30 minutes, then cooled to -40°C in 2 minutes, maintained at this temperature for 30 minutes, and then heated to 70°C in 2 minutes, a heating and cooling program is repeated 5 times.

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