Magnetic recording device and laminated structure

Abstract

This magnetic recording device includes: a plurality of magnetic disks including a substrate having a thickness of 0.51 mm or less and a magnetic recording layer formed on the substrate; and a spacer disposed between the plurality of magnetic disks and serving for stacking the magnetic disks at predetermined intervals. The substrate and the spacer satisfy: [CTE(sub)∙E(spa)] / [CTE(spa)∙E(sub)] < 1.0 … (1) (In the formula, CTE(sub) is the coefficient of thermal expansion (×10-7 / K) of the substrate at 100°C to 300°C, CTE(spa) is the coefficient of thermal expansion (×10-7 / K) of the spacer at 100°C to 300°C, E(sub) is the Young's modulus (GPa) of the substrate, and E(spa) is the Young's modulus (GPa) of the spacer.

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

[0004] However, if the difference in thermal expansion coefficient between the magnetic disk substrate and the spacer is large, the substrate may expand due to temperature changes during operation of the magnetic recording device, resulting in damage to the substrate. By using the same material for the spacer as the substrate, the thermal expansion coefficients can be matched, preventing damage due to temperature changes. However, it has become clear that using a thin substrate causes deformation of the substrate due to temperature changes in the operating environment, which in turn reduces impact resistance and fluttering characteristics.

[0005] Therefore, an object of the present disclosure is to provide a magnetic recording device, a laminated structure, and a spacer with improved impact resistance and fluttering characteristics.

[0006] The inventors have discovered that by combining a substrate and a spacer that satisfy a predetermined relationship, deformation of the substrate that may occur due to temperature changes in the usage environment can be suppressed, and impact resistance and fluttering characteristics can be improved, even when a thin substrate is used.

[0007] One embodiment of the present disclosure is a magnetic recording device comprising: a plurality of magnetic disks, each including a substrate having a thickness of 0.51 mm or less 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 substrate and the spacers satisfy the formula (1): [CTE(sub)·E(spa)] / [CTE(spa)·E(sub)]<1.0 (1) (wherein, CTE(sub) is the thermal expansion coefficient (×10) of the substrate at 100 to 300° C. －７ / K), and CTE(spa) is the thermal expansion coefficient of the spacer at 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.

[0008] One embodiment of the present disclosure is a laminated structure including: a plurality of magnetic disks, each including a substrate having a thickness of 0.51 mm or less 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 glass substrate and the spacers satisfy the formula (1): [CTE(sub)·E(spa)] / [CTE(spa)·E(sub)]<1.0 (1) (wherein, CTE(sub) is the coefficient of thermal expansion of the substrate at 100 to 300° C. (×10 －７ / K), and CTE(spa) is the thermal expansion coefficient of the spacer at 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.

[0009] According to this embodiment, it is possible to provide a magnetic recording device, a laminated structure, and a spacer in which the substrate is less likely to deform due to temperature changes in the usage environment.

[0010] 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.

[0011] 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.

[0012] [Magnetic Recording Device] The magnetic recording device according to this embodiment comprises: a substrate having a thickness of 0.51 mm or less; 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. The magnetic recording device according to this embodiment further comprises a substrate and a spacer each satisfying the formula (1): [CTE(sub)·E(spa)] / [CTE(spa)·E(sub)]<1.0 (1) (wherein, CTE(sub) is the coefficient of thermal expansion (×10) of the substrate at 100 to 300°C). －７ / K), and CTE(spa) is the thermal expansion coefficient of the spacer at 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 above configuration provides a magnetic recording device with improved impact resistance and fluttering characteristics.

[0013] The magnetic recording device according to this embodiment uses a combination of a substrate and a spacer that satisfy the formula (1): [CTE(sub)·E(spa)] / [CTE(spa)·E(sub)]<1.0, so that when a plurality of magnetic disks and spacers are stacked and used, the substrate is less likely to deform, even when the magnetic recording device is used in a high-temperature environment. Conventionally, it has been believed that using the same material for the spacer as the glass substrate can match the thermal expansion coefficient and prevent damage due to temperature changes, but it has been revealed that the substrate is less likely to deform when the value of [CTE(sub)·E(spa)] / [CTE(spa)·E(sub)] is less than 1.0, rather than when the value is 1.0.

[0014] It has also been discovered that a magnetic recording device's impact resistance is improved by satisfying formula (1). In order to increase the storage capacity of a magnetic recording device or reduce the size of the device, it is conceivable to make the substrate thinner so that a greater number of magnetic disks can be stacked, or to make the same number of magnetic disks stacked but smaller in size. However, when the substrate is made thin, there is a problem that it is more susceptible to damage due to a drop impact. This problem is also solved by satisfying the above formula (1).

[0015] The substrate and spacers in the magnetic recording device according to this embodiment preferably satisfy the following formula (2): 0.30≦[CTE(sub)·E(spa)] / [CTE(spa)·E(sub)] (2).

[0016] The value of [CTE(sub)·E(spa)] / [CTE(spa)·E(sub)] is less than 1.0, preferably in the range of 0.30 to 0.98, more preferably in the range of 0.35 to 0.95, even more preferably in the range of 0.56 to 0.95, still more preferably in the range of 0.80 to 0.95, and even more preferably in the range of 0.82 to 0.92. By being in this range, deformation of the substrate due to temperature changes in the usage environment becomes less likely to occur, and furthermore, impact resistance is further improved and the occurrence of fluttering is suppressed.

[0017] The spacer satisfies the formula (3): CTE(spa)·E(spa)≦1.0×10 ４ It is preferable that the formula (3) is satisfied. By satisfying the formula (3), the impact resistance of the magnetic recording device is further improved, and the fluttering characteristics are further improved. CTE(spa)·E(spa) is preferably 0.8×10 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.

[0018] The substrate satisfies the formula (4): CTE(sub)·E(sub)≦0.5×10 ４ It is preferable that the formula (4) is satisfied. By satisfying the formula (4), the impact resistance of the magnetic recording device is further improved, and the fluttering characteristics are further improved. CTE(sub)·E(sub) is preferably 0.45×10 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.

[0019] The substrate preferably satisfies formula (5): CTE(sub) / E(sub)≦1.5 (5). By satisfying formula (4), 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.

[0020] The substrate and spacer preferably satisfy formula (6): [CTE(spa)·E(spa)] / [CTE(sub)·E(sub)]<1 (6). By satisfying formula (6), the magnetic recording device satisfies formula (1), and by further satisfying formula (6), the impact resistance and fluttering characteristics are further improved. The value of [CTE(spa)·E(spa)] / [CTE(sub)·E(sub)] is less than 1, preferably 0.98 or less, preferably 0.95 or less, and more preferably in the range of 0.30 to 0.90.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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 ３0 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 ２ The glass composition of the glass substrate may consist of these components.

[0035] The preferred contents of each component in the glass composition of the glass substrate are as follows:

[0036] 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 %.

[0037] 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 %.

[0038] 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 %.

[0039] P ２ O ５The content is preferably 0 to 5 mol %, more preferably 0 to 3 mol %, and even more preferably 0 to 2 mol %.

[0040] 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%.

[0041] 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 %.

[0042] 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 %.

[0043] 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 %.

[0044] 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 %.

[0045] 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 %.

[0046] 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 %.

[0047] 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 %.

[0048] 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%, 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 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,

[0049] Examples of the glass composition of the glass substrate include the following SU-1, SU-2, and SU-3.

[0050] SU-1: 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 M２ 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

[0051] SU-2: 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

[0052] SU-3: 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)

[0053] 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 %.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] Examples of the spacer material include metal materials such as stainless steel, titanium, aluminum, and aluminum alloys, ceramics, and glass. Among these, the spacer is preferably made of at least one material selected from the group consisting of glass, stainless steel, and titanium, and more preferably a glass spacer.

[0062] 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 (M２ 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 glass composition of the glass substrate may consist of these components. The glass composition of the spacer is preferably different from the glass composition of the substrate.

[0063] The preferred contents of each component in the glass composition of the spacer are as follows:

[0064] 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 %.

[0065] 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 %.

[0066] 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 %.

[0067] 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 %.

[0068] 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%.

[0069] 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 %.

[0070] 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 %.

[0071] 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 %.

[0072] 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 %.

[0073] 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 %.

[0074] 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 %.

[0075] 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 %.

[0076] 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.

[0077] The glass composition of the spacer is, for example, SP-1 below.

[0078] 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

[0079] 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.

[0080] Coefficient of thermal expansion of spacer at 100 to 300°C CTE (spa) (unit: x 10 －７ / K) is preferably 10 to 105, more preferably 25 to 95, and even more preferably 30 to 45.

[0081] 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.

[0082] Preferred examples of combinations of glass substrate and spacer include SU-1 and SP-1, SU-2 and SP-1, and SU-3 and SP-1. These combinations improve impact resistance and fluttering properties.

[0083] 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.

[0084] 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.

[0085] As described above, according to this embodiment, it is possible to provide a magnetic recording device, a laminated structure, and a spacer with improved impact resistance and fluttering characteristics.

[0086] 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.

[0087] <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 predetermined temperature range using a thermal dilatometer based on laser interferometry. This was taken as the average linear expansion coefficient at 100 to 300°C. Note that, since it is not possible to cut out a sample of 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 samples can be prepared using multiple spacers as long as they have the same composition.

[0088] <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. Note that, since it is not possible to cut out a sample with the same dimensions as the magnetic disk when measuring the Young's modulus of the spacer, the spacer is 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. Then, a sample cut to a length of 50 mm and a width of 10 mm can be used for measurement. Note that, as long as the spacers have the same composition, a sample can be prepared using multiple spacers.

[0089] <Density> The density was measured by the Archimedes method.

[0090] Since the influence of the magnetic film on the thermal expansion coefficient, Young's modulus and density of the magnetic disk is negligible, the values ​​of the magnetic disk can be taken as the thermal expansion coefficient, Young's modulus and density of the substrate.

[0091] <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.

[0092] <Fluttering Characteristics> A laser Doppler vibrometer (OFV-512 manufactured by Polytec Corporation) was used to generate vibrations on a magnetic disk rotated by a spin stand, and the vibrations were measured by irradiating a laser onto approximately the outer peripheral edge of the magnetic disk. The obtained data was then appropriately Fourier transformed to obtain a frequency response function (horizontal axis: frequency (unit: Hz), vertical axis: NRRO (Non Repeatable Runout) Amplitude (unit: nm)). Next, for each peak observed in the frequency response function, the Q value (= f0 / (f2-f1)) was determined using the half-width method (a calculation method using frequencies f1, f2 (> f1) corresponding to a value 3 dB lower than the NRRO peak value and the frequency f0 (resonance frequency) corresponding to the peak value). The obtained measurement results were plotted on an XY plane with frequency on the horizontal axis and Q value on the vertical axis, and a linear approximation was performed using the least squares method to obtain an approximate straight line. The Q value at 3000 Hz was obtained on the obtained approximation line or by extrapolating the approximation line as necessary. The total RSS of the NRRO Amplitude (nm), which is the flutter vibration amount of the disk measured by the laser Doppler vibrometer, from 1000 to 4000 Hz was calculated, and the fluttering value F [nm] was obtained. In the evaluation using the laser Doppler vibrometer, the magnetic disk rotation speed was 6900 rpm, the measurement position was a radial position of 46.5 mm from the center of the magnetic disk (1 mm inside from the outer edge), and the measurement was performed at room temperature (25°C). The fluttering characteristics were evaluated using the value of F·D, where D is the thickness (mm) of the magnetic disk.

[0093] (Examples and Comparative Examples) In Example 1, the maximum amplitude and fluttering characteristics were measured using a magnetic recording device equipped with a stack of 10 magnetic disks as described below sandwiched between the following spacers. In other examples and comparative examples, the maximum amplitude and fluttering characteristics were measured 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 surfaces. Width L of the main surface was 3.0 mm. Magnetic disk: A magnetic film, etc. was formed on a substrate with a diameter of 97 mm, an inner diameter of 25 mm, and a thickness of 0.5 mm or 0.45 mm.

[0094]

[0095] 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 83 GPa, thermal expansion coefficient 35 × 10 －７ / K alkali-free glass) SU-3: Glass substrate (Young's modulus 98 GPa, thermal expansion coefficient 45 × 10 －７ / K alkali-containing glass) SU-4: Glass substrate (Young's modulus 79 GPa, thermal expansion coefficient 95×10 －７ / K alkali-containing glass) SU-5: Glass substrate (Young's modulus 83 GPa, thermal expansion coefficient 80×10 －７ / K alkali-containing glass) SU-6: Glass substrate (Young's modulus 83 GPa, thermal expansion coefficient 70 × 10 －７ / K alkali-containing glass) SU-7: Glass substrate (Young's modulus 83 GPa, thermal expansion coefficient 30 × 10 －７ / K non-alkali glass) (Spacer) SP-1: Glass spacer (Young's modulus 65 GPa, thermal expansion coefficient 33 × 10 －７ / K glass) SP-2: Ti spacer (Young's modulus 116 GPa, thermal expansion coefficient 93 × 10 －７ / K Ti metal) SP-3: Glass spacer (Young's modulus 71 GPa, thermal expansion coefficient 94 × 10 －７ / K glass) SP-4: Glass spacer (Young's modulus 83 GPa, thermal expansion coefficient 80 × 10 －７ / K alkali-containing glass (same glass as glass substrate SU-5)) SP-5: Glass spacer (Young's modulus 83 GPa, thermal expansion coefficient 70 × 10 －７ / K alkali-containing glass (same glass as glass substrate SU-6)) SP-6: Glass spacer (Young's modulus 83 GPa, thermal expansion coefficient 30 × 10 －７ / K alkali-free glass (same glass as SU-7 glass substrate)) SP-7: Stainless steel spacer (Young's modulus 206 GPa, thermal expansion coefficient 108 × 10 －７ / K 19Cr ferritic stainless steel)

[0096] 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 of which includes a substrate having a thickness of 0.51 mm or less 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 substrate and the spacers satisfy the formula (1): [CTE(sub)·E(spa)] / [CTE(spa)·E(sub)]<1.0... (1) (wherein, CTE(sub) is the thermal expansion coefficient (×10) of the substrate at 100 to 300°C －７ / K), and CTE(spa) is the thermal expansion coefficient of the spacer at 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.

2. The magnetic recording device according to claim 1, wherein the substrate and the spacer satisfy the following formula (2): 0.30≦[CTE(sub)·E(spa)] / [CTE(spa)·E(sub)] (2).

3. The spacer satisfies the formula (3): CTE(spa)·E(spa)≦1.0×10 ４ 2. The magnetic recording device according to claim 1, wherein the following expression (3) is satisfied.

4. The substrate satisfies the formula (4): CTE(sub)·E(sub)≦0.5×10 ４ 2. The magnetic recording device according to claim 1, wherein the following expression (4) is satisfied.

5. 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%, Al ２ O ３ 5 to 25 mol%, B ２ O ３ 0 to 8 mol %, MO is 5 to 25 mol % (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), M ２ O from 0 to 15 mol% (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 2. The magnetic recording device according to claim 1, wherein the total value of the magnetic recording medium is 0.

6. A magnetic recording device as described in claim 1, wherein when a 40 G impact is applied for 2 ms in the normal direction to the main surface of the magnetic disk while the magnetic disk is 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.

7. A laminated structure comprising: a substrate having a thickness of 0.51 mm or less; 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 substrate and the spacers satisfy the formula (1): [CTE(sub)·E(spa)] / [CTE(spa)·E(sub)]<1.0... (1) (wherein, CTE(sub) is the thermal expansion coefficient (×10) of the substrate at 100 to 300°C). －７ / K), and CTE(spa) is the thermal expansion coefficient of the spacer at 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.

8. The laminate structure according to claim 7, wherein the substrate and the spacer satisfy the following formula (2): 0.30≦[CTE(sub)·E(spa)] / [CTE(spa)·E(sub)] (2).

9. The spacer satisfies the formula (3): CTE(spa)·E(spa)≦1.0×10 ４ The laminated structure according to claim 7, which satisfies the following expression (3):

10. The substrate satisfies the formula (4): CTE(sub)·E(sub)≦0.5×10 ４ The laminated structure according to claim 7, which satisfies the following expression (4):

11. 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%, 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 The laminate structure according to claim 7 , wherein the total value of the total of (I) and (II) is O.

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