Information recording medium tray, tray intermediate, and information recording medium substrate

Abstract

An information recording medium disc according to an embodiment is a disc having a plate thickness of 0.51 mm or less, and is provided with a substrate and a cover layer. The substrate has one main surface and another main surface, and also has a side wall surface connecting the two main surfaces. A cover layer covers both main surfaces and side wall surfaces of the substrate. The disk has a specific elastic modulus E / d [106 m2 / s2] of 40 or more as calculated from a Young's modulus E [GPa] and a density d [g / cm3]. When 30 [G] impact of 2 [m seconds is applied to the disk in the normal direction of the main surface of the disk substrate in a state in which the inner peripheral end of the disk is fixed, the maximum amplitude caused by vibration in the thickness direction of the outer peripheral end of the disk substrate is 0.25 mm or less.

Description

Technical Field

[0001] This invention relates to a disk for an information recording medium with a cover layer covering a substrate, a disk intermediate, and a substrate for an information recording medium. Background Technology

[0002] With the rise of cloud computing in recent years, a large number of hard disk drive (HDD) devices (magnetic recording devices) are used in cloud-oriented data centers to increase storage capacity. In HDD devices, a magnetic recording medium disk with a magnetic layer on a ring-shaped substrate is used as the storage medium. To increase the storage capacity of HDD devices, it is preferable to increase the recording density of the magnetic layer on the magnetic recording medium disk, reduce the thickness of the magnetic recording medium disk, and increase the number of magnetic recording medium disks mounted.

[0003] For disks used as information recording media in HDD devices, stable reading of information recorded on the magnetic layer requires minimizing jitter (surface wobble) during high-speed rotation. However, if the disk is made thinner to increase the number of disks it can hold, the disk becomes too weak, resulting in increased jitter. Therefore, when manufacturing thinner disks, it is preferable to use a substrate made of a harder material with a high Young's modulus. However, hard materials are difficult to cut, and grinding and polishing are required for extended periods to reduce the surface roughness of the substrate, thus hindering efficient substrate production.

[0004] As a conventional substrate used for information recording media discs, it is known to have a laminated structure in which a glass coating is applied to the surface of a ceramic substrate (Patent Document 1). The glass coating is softer and easier to cut than the ceramic material, thus reducing the surface roughness of the laminated substrate in a short time, enabling efficient production of information recording media discs with good surface properties.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 61-48123 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, if the thickness of the conventional laminated substrate is reduced to increase the number of discs for recording information, the ceramic substrate becomes thinner, resulting in insufficient strength and increased disc jitter. Therefore, it is clear that even if the rigidity of the disc is increased to suppress jitter, it is still insufficient to effectively suppress jitter.

[0010] Therefore, the object of the present invention is to provide an information recording medium disk, a disk intermediate, and an information recording medium substrate that can suppress the jitter of the information recording medium disk and improve the problems of the information recording medium disk caused by the thinness of the plate.

[0011] Methods for solving problems

[0012] This disclosure includes the following methods.

[0013] Method 1

[0014] A disk for recording information media, the thickness of which is 0.51 mm or less, the disk for recording information media comprising:

[0015] A substrate having one main surface and another main surface, and a sidewall connecting the two main surfaces; and

[0016] A cover layer that covers the two main surfaces and sidewalls of the substrate.

[0017] The disk is determined based on Young's modulus E [GPa] and density d [g / cm³]. 3 The calculated specific elastic modulus E / d [×10] 6 m 2 / s 2 The value is above 40.

[0018] With the inner peripheral end of the disk fixed, when an impact of 30G for 2 [m sec] is applied to the disk along the normal direction of the main surface of the disk, the maximum amplitude caused by the vibration in the thickness direction of the outer peripheral end of the disk is less than 0.25 mm.

[0019] Method 2

[0020] A disk for recording information media, the thickness of which is 0.51 mm or less, the disk for recording information media comprising:

[0021] A substrate having one main surface and another main surface, and a sidewall connecting the two main surfaces; and

[0022] A cover layer that covers the two main surfaces and sidewalls of the substrate.

[0023] The product of the flutter characteristic F[nm] of the disk, expressed as the sum of the flutter vibrations of the disk at 1000Hz to 4000Hz, and the thickness D[mm] of the disk, F·D, is 47.0 or less.

[0024] With the inner peripheral end of the disk fixed, when an impact of 30G for 2 [m sec] is applied to the disk along the normal direction of the main surface of the disk, the maximum amplitude caused by the vibration in the thickness direction of the outer peripheral end of the disk is less than 0.25 mm.

[0025] Method 3

[0026] A disk for recording information media, the thickness of which is 0.51 mm or less, the disk for recording information media comprising:

[0027] A substrate having one main surface and another main surface, and a sidewall connecting the two main surfaces; and

[0028] A cover layer that covers the two main surfaces and sidewalls of the substrate.

[0029] The product of the flutter characteristic F[nm] of the disk, expressed as the sum of the flutter vibrations of the disk at 1000Hz to 4000Hz, and the thickness D[mm] of the disk, F·D, is 47.0 or less.

[0030] Regarding the thickness in the thickness direction, the ratio T / t of the thickness T [mm] of each of the cover layers covering the two main surfaces to the thickness t [mm] of the substrate is 0.01 to 0.4, the thickness t of the substrate is 0.43 mm or less, and the thickness T of the cover layer is 0.1 mm or less.

[0031] The disk is determined based on Young's modulus E [GPa] and density d [g / cm³]. 3 The calculated specific elastic modulus E / d [×10] 6 m 2 / s 2 The value is 40 or above.

[0032] Method 4

[0033] A disk for recording information media, the thickness of which is 0.51 mm or less, the disk for recording information media comprising:

[0034] A substrate having one main surface and another main surface, and a sidewall connecting the two main surfaces; and

[0035] A cover layer that covers the two main surfaces and sidewalls of the substrate.

[0036] Regarding the thickness in the thickness direction, the ratio T / t of the thickness T [mm] of each of the cover layers covering the two main surfaces to the thickness t [mm] of the substrate is 0.01 to 0.4, the thickness t of the substrate is 0.43 mm or less, and the thickness T of the cover layer is 0.1 mm or less.

[0037] The product of the flutter characteristic F[nm] of the disk, expressed as the sum of the flutter vibrations of the disk at 1000Hz to 4000Hz, and the thickness D[mm] of the disk, F·D, is 47.0 or less.

[0038] Method 5

[0039] Information recording medium disk according to any one of methods 1 to 4,

[0040] The substrate is made of any one of the following materials: ceramic, aluminum alloy, and glass.

[0041] The covering layer is made of glass or nickel alloy.

[0042] Method 6

[0043] Information recording medium disk according to any one of methods 1 to 4,

[0044] The product of the flutter characteristic F[nm] of the disk, expressed as the sum of the flutter vibrations of the disk at 1000Hz to 4000Hz, and the thickness D[mm] of the disk, F·D, is 45.0 or less.

[0045] Method 7

[0046] Information recording medium disk according to any one of methods 1 to 4,

[0047] The plate thickness D [mm] and specific elastic modulus E / d [×10] of the disk 6 m 2 / s 2 The Q value of the disk, Qa, measured at 3000 Hz and 25°C, satisfies the following equation 1.

[0048] 65.0<(Qa×E / d) / 1000×D<270.0.

[0049] Method 8

[0050] Information recording medium disk according to any one of methods 1 to 4,

[0051] The plate thickness D [mm] and specific elastic modulus E / d [×10] of the disk 6 m 2 / s 2 The Q value of the disk, Qa, measured at 3000 Hz and 25°C, satisfies the following equation 2.

[0052] 150 < (Qa × E / d) / 1000 × D < 700.

[0053] Method 9

[0054] Information recording medium disk according to any one of methods 1 to 4,

[0055] The thickness of the plate is less than 0.45 mm.

[0056] Method 10

[0057] The information recording medium disk according to any one of methods 1 to 5

[0058] The cover layer is made of glass and contains a crystalline phase in the interface layer region, which is located at a depth of at least 5% of the thickness T of the cover layer along the thickness direction from the interface with the substrate.

[0059] Method 11

[0060] The information recording medium disk according to method 10

[0061] The cover layer is made of glass and contains a crystalline phase in the interface layer region, which is located at a depth of at least 5% of the thickness T of the cover layer along the thickness direction from the interface with the substrate.

[0062] Method 12

[0063] Information recording medium disk according to any one of methods 1 to 7,

[0064] The cover layer is made of glass and does not contain a crystalline phase in its surface region, which is located at a depth of at least 5% of the thickness T of the cover layer along the thickness direction from the surface of the cover layer opposite to the interface with the substrate.

[0065] Method 13

[0066] Information recording medium disk according to any one of methods 1 to 8,

[0067] The arithmetic mean roughness Ra of the main surface of the substrate is 0.01 μm to 0.75 μm.

[0068] Method 14

[0069] Information recording medium disk according to any one of methods 1 to 9,

[0070] The difference between the maximum and minimum values ​​of the distance in the thickness direction from the surface of the cover layer on the side opposite to the interface of the cover layer to the substrate is 7.5 μm to 12.5 μm.

[0071] Method 15

[0072] Information recording media disc according to any one of methods 1 to 10,

[0073] The main surface of the substrate has portions that repeatedly appear in an alternating concave-convex shape in an undulating curve obtained according to a cross-sectional curve, the cross-sectional curve representing the cross-sectional shape of the substrate in the thickness direction passing through the center of the main surface.

[0074] The length of the repeating units of the concave and convex shapes in the extension direction orthogonal to the thickness direction of the cover layer is 100μm to 150μm.

[0075] Method 16

[0076] Information recording medium disk according to any one of methods 1 to 11,

[0077] The thickness of the cover layer on the sidewall surface is greater than the thickness T of the cover layer on the main surface of the substrate.

[0078] Method 17

[0079] Information recording medium disk according to any one of methods 1 to 12,

[0080] The diameter of the disk is 95mm or more.

[0081] Method 18

[0082] Information recording medium disk according to any one of methods 1 to 13,

[0083] With the inner peripheral end of the disk fixed, when a 50G impact of 2 [m sec] is applied to the disk along the normal direction of the main surface of the disk, the maximum amplitude caused by the vibration in the thickness direction of the outer peripheral end of the disk is less than 0.30 mm.

[0084] Method 19

[0085] Information recording medium disk according to any one of methods 1 to 14,

[0086] The diameter of the disk is 95 mm or more, and the jitter characteristic F, expressed as the sum of the jitter vibrations of the disk from 1000 Hz to 4000 Hz, is 80 nm or less.

[0087] Method 20

[0088] Information recording medium disk according to any one of methods 1 to 15,

[0089] The maximum height Rz of the surface roughness of the main surface at the interface between the substrate and the cover layer is 0.1 μm to 50 μm.

[0090] Method 21

[0091] A disk intermediate body, serving as the base plate for a disk used as an information recording medium, has a plate thickness of 0.59 mm or less, and the disk intermediate body comprises:

[0092] A substrate having one main surface and another main surface, and a sidewall connecting the two main surfaces; and

[0093] A cover layer that covers the two main surfaces and sidewalls of the substrate.

[0094] Regarding the thickness in the thickness direction, the ratio of the thickness T [mm] of each of the cover layers to the thickness t [mm] of the substrate, T / t, is 0.1 to 0.75, the thickness t of the substrate is 0.43 mm or less, and the thickness T of the cover layer is 0.15 mm or less.

[0095] The specific elastic modulus E / d[×10] of the intermediate body of the disk, calculated from Young's modulus E [GPa] and density d [g / cm3], is... 6 m 2 / s 2 The value is 40 or above. Attached Figure Description

[0096] Figure 1 This is a diagram showing the external shape of a disk used as an information recording medium in one embodiment.

[0097] Figure 2 It is a diagram showing the layer structure of a disk used for recording information.

[0098] Figure 3 It represents the reflected electron image of the cross section of the covering layer.

[0099] Figure 4 It is a microscope photograph showing a cross-section of a laminated substrate. Detailed Implementation

[0100] The following describes in detail the information recording medium disk and disk intermediate, and the information recording medium substrate of the embodiments.

[0101] The information recording medium disk (hereinafter referred to as disk) in this embodiment includes the disks of the four types described below.

[0102] (First method)

[0103] Figure 1 This is a diagram showing the external shape of disk 1 as the first method. Figure 2 This is a diagram showing the layer structure of disk 1. The thickness of disk 1 is less than 0.51 mm, as shown below. Figure 2 As shown, it includes a substrate 3, a cover layer 5, and a metal film (not shown) (described later).

[0104] By making the thickness of disk 1 0.51 mm or less, the number of disks that can be mounted on the HDD device can be increased, thereby increasing the storage capacity of the HDD device. The thickness of disk 1 is preferably 0.50 mm or less, 0.48 mm or less, 0.46 mm or less, 0.45 mm or less, 0.43 mm or less, 0.42 mm or less, 0.40 mm or less, 0.38 mm or less, 0.35 mm or less, 0.32 mm or less, 0.30 mm or less, 0.28 mm or less, 0.25 mm or less, 0.22 mm or less, 0.20 mm or less, or 0.18 mm or less. There is no particular limitation on the lower limit of the thickness of disk 1; for example, it can be 0.15 mm.

[0105] The substrate 3 is an annular plate with an inner hole. The substrate 3 has one main surface 3a and another main surface 3b, and also has sidewalls (not shown) connecting the two main surfaces 3a and 3b. The main surfaces 3a and 3b are opposite each other and parallel to each other. The sidewalls are located at the outer and inner peripheral ends of the substrate 3, respectively.

[0106] The cover layer 5 is a layer that covers the two main surfaces 3a and 3b and the sidewalls of the substrate 3.

[0107] Disk 1 is preferably selected based on Young's modulus E [GPa] and density d [g / cm³]. 3 ]Calculated specific elastic modulus E / d[10 6 ·m 2 / s 2 The specific elastic modulus E / d is above 40. It is known that the larger the specific elastic modulus E / d, the smaller the jitter (vibration). If the specific elastic modulus E / d of disk 1 is above 40, then the jitter of disk 1 during high-speed rotation is greatly suppressed.

[0108] The Young's modulus E of disk 1 can be measured based on Japanese Industrial Standard JISR 1602-1995. Additionally, a cuboid with a length of 50 mm, a width of 10 mm, and a thickness equal to the thickness of the disk 1 can be cut from disk 1 and measured at room temperature. Furthermore, when the density of substrate 3 is set as d1, the thickness of substrate 3 as t, the density of cover layer 5 as d2, and the thickness of cover layer 5 as T, the density d of disk 1 is calculated using d = {(d1×t)+(d2×2T)} / (t+2T). Furthermore, disk 1 has a metal film including a magnetic layer (magnetic recording layer), but the thickness of the metal film is approximately 100 nm or less. Therefore, the metal film can be ignored in terms of the thickness of disk 1, and its effect on characteristics of disk 1 such as specific elastic modulus E / d, maximum amplitude, and product F·D (described later) can also be ignored.

[0109] The specific elastic modulus E / d of disk 1 [×10] 6 m 2 / s 2The preferred values ​​are 25.0 or higher, 27.0 or higher, 28.0 or higher, 37.5 or higher, 38.2 or higher, 38.5 or higher, and 39.0 or higher; more preferably, 40.0 or higher, 41.0 or higher, 45.0 or higher, and 65.0 or higher. Furthermore, there is no particular limitation on the lower limit of the specific elastic modulus E / d, for example, it is 20.0. From the viewpoint of improving the specific elastic modulus E / d, the Young's modulus E of the disk 1 is preferably 75.0 GPa or higher, more preferably 78.0 GPa or higher, 80 GPa or higher, 86 GPa or higher, 96.0 GPa or higher, 101.0 GPa or higher, 106.0 GPa or higher, 110.0 GPa or higher, 115.0 GPa or higher, and 120.0 GPa or higher. On the other hand, even with a high Young's modulus, if the density is high, there is a possibility that the vibration may increase due to the weight of the disk 1 itself. Therefore, when the substrate 3 is made of ceramic, the density d of the disk 1 is preferably 4.5 g / cm³. 3 Below, 4.0g / cm 3 The above is further optimized to 4.2 g / cm³. 3 Below, 4.0g / cm 3 In the case that the substrate 3 is made of aluminum alloy, the density d of the disk 1 is preferably 2.90 g / cm³. 3 Below, 2.65g / cm 3 The above is further optimized to 2.86 g / cm³. 3 Below, 2.80g / cm 3 In the case that the substrate 3 is made of glass, the density d of the disk 1 is preferably 2.65 g / cm³. 3 Below, 2.45g / cm 3 The above is further preferred to be 2.60 g / cm³. 3 2.50g / cm 3 above.

[0110] When the disk 1 of the first embodiment is subjected to an impact of 30 G for 2 [m s] along the normal direction of the main surface of the disk 1 with the inner peripheral end of the disk 1 fixed, the maximum amplitude caused by the vibration in the thickness direction of the outer peripheral end of the disk 1 is less than 0.25 mm. The vibration generated by the impact from the outside is different from the steady-state jitter vibration generated by the rotating disk and the airflow around it in a steady-state rotation, and decays over time. It is known that the generation of debris in the HDD can be suppressed by reducing the maximum amplitude when a large impact is applied to the disk. Debris is generated by the vibration of the disk displacing in the outward direction of the main surface, which contacts the ramps in the HDD, adjacent disks, and then the top surface of the disk's housing, thereby causing partial damage to the disk. However, it is known that in thin disks with a thickness of 0.51 mm or less, even a small impact can increase the amplitude, causing contact with other components such as the ramps in the HDD, and sometimes it is impossible to suppress the generation of debris. Therefore, in the disk 1 of the first type, the maximum amplitude when subjected to an impact of 30 [G] is limited to 0.25 mm or less. For example, by adjusting the materials and thicknesses of the substrate 3 and the cover layer 5, a disk 1 of the first type with a specific elastic modulus E / d of 40 or more and the aforementioned maximum amplitude of 0.25 mm or less can be obtained. Preferably, when a 50 [G] impact of 2 [m s] is applied to the disk 1 along the normal direction of the main surface of the disk 1 with the inner peripheral end of the disk 1 fixed, the aforementioned maximum amplitude is 0.30 mm or less. In addition to the small amplitude when subjected to small impacts, the amplitude is also small when subjected to larger impacts, thereby effectively suppressing the generation of debris from various external impacts.

[0111] The aforementioned impact test can be performed, for example, using an AVEX-SM-110-MP testing machine from Air-Brown Corporation. The maximum amplitude is preferably measured using a disk 1 with a diameter of 95 mm or 97 mm. The portion of the inner circumference of the disk 1 fixed during the impact test preferably corresponds to the area inside a circle with a diameter of 25 mm (a region with a radius of 12.5 mm from the center of the disk 1). This inner circumference portion is approximately the same size as the portion of the inner circumference fixed when the 95 mm or 97 mm diameter disk 1 is assembled into the HDD device.

[0112] According to the first method, the specific elastic modulus E / d is 40 or more, and the maximum amplitude during the impact test at 30 [G] is within 0.25 mm. As a result, it is possible to suppress vibration and suppress the generation of debris in the HDD.

[0113] (Second method)

[0114] The second type of disk 1 is a disk that replaces the disk of the first type of disk 1 in which the elastic modulus E / d is in the above range and the product F·D described below is in the specified range. Except for this point, it is constructed in the same way as the disk of the first type of disk 1.

[0115] In disk 1 of the second type, the product of the jitter characteristic F [nm], expressed as the sum of the jitter vibrations of disk 1 from 1000 to 4000 Hz (RSS), and the plate thickness D [mm] of disk 1, F·D, is 47.0 or less. Specifically, the jitter characteristic F is the sum of the vibrations when the frequency changes within the range of 1000 Hz to 4000 Hz, and is the square root of the cumulative square of the amplitude of the jitter vibrations. Regarding the RSS in the region of 1000 Hz to 4000 Hz, it is known, for example, that ρ is the density of disk 1 at room temperature [g / cm3], Q is the Q value of disk 1 at room temperature at 3000 Hz, E is the Young's modulus of disk 1 at room temperature [GPa], and ν is the Poisson's ratio of disk 1 at room temperature, by using 2·ρ(1-ν) of disk 1. 2 • Q / E is set to less than 25 [g / cm 3 / GPa], which can reduce it (e.g., set to less than 80nm) (see Re-table 2020 / 032146). The amplitude of the outer periphery of disk 1 is related to ρ·(1-ν). 2 / E / ξ (ξ is the attenuation ratio of disk 1) is proportional to the attenuation ratio ξ, which is expressed as 1 / (2·Q) (Q is the value of Q). Therefore, the above amplitude is proportional to 2·ρ·(1-ν). 2 • Q / E are proportional.

[0116] The Q value (Quality Factor) is obtained by dividing the vibrational energy accumulated by the disk 1 vibrating over one cycle by the energy dissipated from the vibrating disk 1. The smaller the value, the greater the vibration attenuation. For example, the Q value at 3000 Hz is obtained as follows. First, the disk 1, which is rotated on a rotary table, is vibrated using a laser Doppler oscillometer (LDV). The vibration is measured by irradiating the approximately outer periphery of the disk 1 with a laser. The obtained data is then subjected to an appropriate Fourier transform to obtain the 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)) is obtained using the half-width method (a method that calculates using frequencies f1, f2 (>f1) corresponding to values ​​3 dB lower than the peak of NRRO, and the frequency f0 (resonance frequency) corresponding to that peak). The measured results were plotted on an XY plane with frequency on the horizontal axis and Q value on the vertical axis. A linear approximation based on the least squares method was performed to obtain an approximate straight line. The Q value at 3000 Hz could be obtained by extrapolating the approximate straight line, either directly or as needed. Furthermore, the disk 1 used for evaluating the laser Doppler vibrometer was set to have an outer diameter of 95 mm to 97 mm, an inner diameter of 25 mm, and a plate thickness of 0.51 mm or less. The disk rotation speed was 6900 rpm, and the measurement was performed at room temperature at a radius of 46.5 mm to 47.5 mm from the center of the disk (1 mm inside the outer perimeter).

[0117] Furthermore, the impact of jitter vibration in the frequency band below 1000Hz has decreased due to recent advancements in magnetic head servo technology. On the other hand, jitter vibration in the frequency band above 4000Hz was already minimal. Therefore, reducing jitter vibration in the 1000Hz–4000Hz frequency band becomes important.

[0118] When the disk plate thickness is relatively large, the magnitude of vibration is significantly affected by the plate thickness, and the vibration caused by jitter is suppressed. However, when the disk plate thickness is relatively thin, the vibration caused by jitter becomes larger. Even when the disk plate thickness is thin, by controlling the product of the jitter characteristic F[nm] and the plate thickness D[mm], F·D[nm·mm], to 47.0 or less, damage or debris caused by contact between the disk and other components can be prevented, thereby preventing read / write errors on the disk. According to the inventors' research, when the disk plate thickness is set to D, the product of the jitter characteristic F[nm] and the plate thickness D[mm], F·D[nm·mm], can be used as an indicator to evaluate the magnitude of jitter in a thin disk during rotation. When the product F·D is 47.0 or less, the jitter of the disk 1 during high-speed rotation can be significantly suppressed. Therefore, in the disk 1 of the second embodiment, the product F·D is limited to 47.0 or less. That is, by making the product F·D 47.0 or less, the jitter of the disk 1 during high-speed rotation can be significantly suppressed. The jitter characteristic F is a property dependent on the material and thickness of the substrate 3 and the cover layer 5. Therefore, a disk 1 with a product F·D of 47.0 or less can be obtained by adjusting the material and thickness of the substrate 3 and the cover layer 5 respectively. When the diameter of the disk 1 is 95 mm, the jitter characteristic F of the disk 1 is preferably 80 nm or less. For disks 1 with a diameter of 95 mm or more, since jitter tends to increase, a small jitter characteristic F like this is effective in suppressing jitter. From the viewpoint of further improving the effect of suppressing the jitter of disks 1 with a board thickness of 0.5-1.0 mm or less, the product F·D is more preferably 45.0 or less, 43.0 or less, 40.0 or less, more preferably 35.0 or less, 32.0 or less, and more preferably 30.0 or less, 24.0 or less, 20.0 or less.

[0119] According to the disk 1 of the second method, the product F·D is 47.0 or less, and the maximum amplitude mentioned above during the impact test at 30 [G] is within 0.25 mm. As a result, it is possible to suppress jitter and suppress the generation of debris in the HDD.

[0120] (Third method)

[0121] The third type of disk 1 is a disk that replaces the disk of the first type in which the maximum amplitude in the impact test is within the range mentioned above, so that the product F·D is 47.0 or less, and the thickness T of the cover layer 5, the thickness t of the substrate 3, and the thickness ratio T / t are within the specified range. Except for this point, it is constructed in the same way as the disk of the first type.

[0122] In the third embodiment, regarding the thickness of the disk 1 in the thickness direction, the ratio T / t of the thickness T [mm] of each of the cover layers 5 on both sides of the substrate 3 to the thickness t [mm] of the substrate 3 is 0.01 to 0.4, the thickness t of the substrate 3 is 0.49 mm or less, and the thickness T of the cover layer 5 is 0.15 mm or less. By making the ratio T / t less than 0.4, even if the thickness of the disk 1 is limited, the thickness T of the cover layer 5 will not become too thick, thus ensuring the thickness t of the substrate 3. As a result, the rigidity of the disk 1 is ensured, which helps to suppress jitter. On the other hand, by making the ratio T / t greater than 0.01, the thickness T of the cover layer 5 will not become too thin, thereby suppressing the deterioration of the flatness of the disk 1. According to the inventors' research, when manufacturing the disk 1, if the thickness T of the cover layer 5 is too thin during the heat treatment of the metal film provided on the surface of the cover layer 5, the cover layer 5 will partially peel off from the substrate 3, resulting in sometimes deterioration of the flatness of the disk 1. By making the thickness t of the substrate 3 0.49 mm or less, it is easy to make the thickness of the disk 1 0.51 mm or less, and to ensure the thickness T of the cover layer 5. If the thickness T of the cover layer 5 is too thin, the flatness of the disk 1 may sometimes deteriorate as described above. Furthermore, by making the thickness T of the cover layer 5 0.15 mm or less, it is easy to make the thickness of the disk 1 0.51 mm or less, and to ensure the thickness t of the substrate 3. If the thickness t of the substrate 3 is too thin, it is difficult to ensure the rigidity of the disk 1 as described above, and it is difficult to suppress jitter. That is, by making the ratio T / t, thickness t, and thickness T of the disk 1 within the above ranges, it is possible to suppress the jitter of the disk 1 and suppress the deterioration of the surface properties of the disk 1. Furthermore, from the viewpoint of effectively achieving the above effects, it is preferable that the Young's modulus of the substrate 3 is higher than that of the cover layer 5.

[0123] The ratio T / t is preferably 0.01 to 0.4, 0.01 to 0.3, and more preferably 0.085 to 0.3. The thickness t of the substrate 3 is preferably 0.49 mm or less, more preferably 0.43 mm or less, and even more preferably 0.38 mm or less. The thickness T of the cover layer 5 is preferably 0.025 mm or less, and more preferably 0.01 mm or less or 0.006 mm or less.

[0124] Furthermore, the flatness of disk 1 (the flatness specified in JIS B0621-1984) is 15 μm or less, preferably 10 μm or less. Disk 1 with such flatness can further reduce jitter during high-speed rotation. Flatness can be measured, for example, using an interferometric flatness measuring machine, by phase measurement interferometry (phase shift method) at a specified measurement wavelength (e.g., 680 nm). The thickness deviation of disk 1 (the difference between the maximum and minimum thickness) is 15 μm or less, preferably 10 μm or less.

[0125] According to the third-party disk 1, the above-mentioned ratio T / t is 0.01 to 0.4, the thickness t is 0.43 mm or less, the thickness T is 0.1 mm or less, the product F·D is 47.0 or less, and the specific elastic modulus E / d is 40 or more. As a result, it is possible to suppress jitter and take into account both the suppression of jitter of disk 1 and good surface properties.

[0126] (Fourth method)

[0127] The disk 1 of the fourth type does not require the specific elastic modulus E / d to be within the above-mentioned range as a necessary condition. Apart from this, it is otherwise constructed in the same way as the disk 1 of the third type.

[0128] According to the disk 1 of the fourth method, the above-mentioned ratio T / t is 0.01 to 0.4, the thickness t is 0.43 mm or less, the thickness T is 0.1 mm or less, and the product F·D is 47.0 or less. Thus, it is possible to suppress jitter and take into account both the suppression of jitter of disk 1 and good surface properties.

[0129] The disk 1 of the first to fourth methods described above is preferably equipped with an additional structure as follows.

[0130] The disk 1 of the first and second embodiments, like the disk 1 of the third and fourth embodiments, preferably has a ratio T / t, a thickness t of substrate 3, and a thickness T of cover layer 5. This allows for a balance between suppressing disk 1's jitter and achieving good surface properties.

[0131] The disk 1 of the first method preferably has the same product F·D as the disks 1 of the second, third, and fourth methods. As a result, the effect of suppressing jitter is increased.

[0132] The disk 1 of the second and fourth types preferably has the same specific elastic modulus E / d as the disk 1 of the first and third types. As a result, the effect of suppressing jitter is increased.

[0133] The disk 1 of the third and fourth types preferably has the same maximum amplitude when impacted as the disk 1 of the first and second types. As a result, the generation of debris within the HDD can be suppressed.

[0134] As described above, disk 1 includes a metal film. The metal film, for example, includes at least an adhesion layer, a base layer, a magnetic layer (magnetic recording layer), a protective layer, and a lubricating layer, sequentially stacked on the main surface of the cover layer 5, starting from the surface closest to the main surface. The adhesion layer, base layer, and magnetic layer are formed, for example, by introducing a laminated substrate with the main surface of the cover layer 5 as the main surface into a vacuum-sealed film-forming apparatus, and then sequentially forming the film on the main surface of the cover layer 5 in an Ar atmosphere using DC (Direct Current) magnetron sputtering. For example, CrTi can be used as the adhesion layer, and for example, a material containing Ru or MgO can be used as the base layer. Furthermore, a soft magnetic layer and a heat dissipation layer may be appropriately added. After the above film formation, for example, a protective layer is formed using C2H4 via CVD (Chemical Vapor Deposition), and a nitriding treatment is performed in the same chamber to introduce nitrogen into the surface. Then, for example, PFPE (fluoropolymer polyether) is coated onto the protective layer by dip-coating, thereby forming the lubricating layer. This allows disk 1 to be manufactured.

[0135] To achieve further high-density recording on disk 1, the magnetic recording layer preferably comprises 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. Furthermore, "based" here refers to materials containing. That is, disk 1 preferably has a magnetic recording layer comprising Fe and Pt, or Co and Pt. For information on magnetic recording layers containing such magnetic materials and methods for forming such layers, please refer to paragraph 0074 of WO2011 / 019010A1 and the embodiments described in that publication. Furthermore, disk 1 having such a magnetic recording layer is preferably applied to a magnetic recording apparatus based on a recording method called Energy-Assisted Magnetic Recording (EAMR). In Energy-Assisted Recording, the recording method assisted by near-field light or the like to reverse magnetization is called Heat-Assisted Magnetic Recording (HAMR), and the recording method assisted by microwaves is called Microwave-Assisted Magnetic Recording (MAMR). For details on these methods, please refer to paragraph 0075 of WO2011 / 019010A1. In addition, conventional CoPtCr-based materials can also be used as magnetic materials for forming magnetic recording layers.

[0136] The substrate 3 and the cover layer 5 of the disk 1 in the first embodiment are preferably made of materials that give the disk 1 a specific elastic modulus E / d of 40 or more and a maximum amplitude of 0.25 mm or less when the disk 1 is subjected to an impact test at 30 [G].

[0137] In the second embodiment, the substrate 3 and the cover layer 5 of the disk 1 are preferably made of materials that make the area F·D of the disk 1 less than 47.0 and the maximum amplitude of the disk 1 when subjected to an impact test at 30 [G] less than 0.25 mm.

[0138] In the third embodiment, the substrate 3 and the cover layer 5 of the disk 1 are preferably made of materials that give the disk 1 a specific elastic modulus E / d of 40 or more and a product F·D of 47.0 or less.

[0139] In the fourth embodiment, the substrate 3 and the cover layer 5 of the disk 1 are preferably made of materials that make the area F·D of the disk 1 less than 47.0.

[0140] From the perspective of easily achieving a specific elastic modulus E / d of 40 or higher for disk 1, the material of substrate 3 is preferably any one of ceramic, aluminum alloy, and glass.

[0141] The ceramic material is preferably any one of silicon carbide (SiC), sapphire (Al2O3), aluminum oxide (Al2O3), aluminum nitride (AlN), silicon nitride (Si3N4), titanium carbide (TiC), and titanium nitride (TiN). Among these, silicon carbide (SiC), sapphire (Al2O3), and aluminum oxide (Al2O3) are preferred from the viewpoint that it is easy to make the product F·D of disk 1 less than 47.0.

[0142] The preferred aluminum alloy material is an aluminum alloy containing Si in the range of 3.0 to 40.0% by mass or an aluminum alloy containing Fe in the range of 0.1 to 5.0% by mass, which are materials with high rigidity and a Young's modulus E [GPa] of 75 or higher.

[0143] The preferred glass materials are silica-based glasses with high purity (e.g., 90% or more by mass) containing silica (SiO2), aluminosilicate glasses containing 20% ​​or more alumina (Al2O3), crystallized glasses, and other materials with high rigidity and a Young's modulus E [GPa] of 80 or more.

[0144] The cover layer 5 is preferably glass or a nickel alloy.

[0145] Glass materials are preferred because their surface properties can be easily adjusted through grinding and polishing. Aluminosilicate glass, soda-lime glass, sodium-aluminosilicate glass, aluminoborosilicate glass, borosilicate glass, and polysilazane SiO2 are preferred glass materials. Furthermore, from the viewpoint of ensuring heat resistance during heat treatment of the magnetic layer, the glass transition temperature (Tg) of the glass material is preferably 750°C or higher, more preferably 770°C or higher.

[0146] Nickel alloys are preferred materials for improving the rigidity of disk 1 by compensating for the rigidity of substrate 3. Nickel-phosphorus (NiP) alloys are preferred. Furthermore, to prevent magnetization caused by heating during disk manufacturing, NiWP-based coatings containing tungsten W in the range of 10 to 30% by mass or NiPMo-based coatings containing molybdenum Mo in the range of 0.1 to 10% by mass are preferred.

[0147] Preferred combinations of materials for the substrate 3 and the cover layer 5 include, for example:

[0148] • Alumina and other ceramics (substrate) and glass or nickel alloys (coating),

[0149] • High-rigidity aluminum alloy (substrate) and glass or nickel alloy (coating),

[0150] • High-rigidity glass (substrate) and glass or nickel alloy (coating). Here, high-rigidity aluminum alloy and high-rigidity glass refer to aluminum alloys or glass that give the disk 1 a specific elastic modulus E / d of 40 or more, or a maximum amplitude of the disk 1 when subjected to an impact test at 30 [G] with a thickness of 0.51 mm or less, preferably a maximum amplitude of the disk 1 when subjected to an impact test at 50 [G] of 0.30 mm or less. As described above, the high-rigidity aluminum alloy material is preferably an aluminum alloy containing Si in the range of 3.0 to 40.0% by mass or an aluminum alloy containing Fe in the range of 0.1 to 5.0% by mass, etc., which are materials with high rigidity such as Young's modulus E [GPa] of 75 or more. In addition, high-rigidity glass materials are preferably silica-based glasses with high purity (e.g., more than 90% by mass) of silica (SiO2), aluminosilicate glasses with more than 20% by mass of alumina (Al2O3), crystallized glass, single crystal glass, and other materials with high rigidity such as Young's modulus E [GPa] of 80 or more.

[0151] On the other hand, when using aluminum alloys other than high-rigidity aluminum alloys or glass other than high-rigidity glass as the substrate material, even when combined with a cover layer, the desired impact resistance and vibration characteristics cannot be obtained when the thickness of disk 1 is less than 0.51 mm.

[0152] The disk 1 of the first to fourth methods preferably also has the structure described below.

[0153] The thickness D [mm] and specific elastic modulus E / d [×10] of disk 1 6 m 2 / s 2 The Q value, Qa, of disk 1 measured at 3000 Hz and at 25°C preferably satisfies the following equation 1:

[0154] 65.0 < (Qa × E / d) / 1000 × D < 270.0 (Equation 1)

[0155] According to the inventors' research, especially when the specific elastic modulus E / d of disk 1 is small, if Equation 1 is satisfied, the product F·D tends to decrease. For example, when the specific elastic modulus E / d is less than 75 [×10], 6 m 2 / s 2 In disk 1, it is preferable that the product F·D is easily reduced to 40.0 or less by satisfying Equation 1. It is also preferable that the disk 1 with a small product F·D further improves the effect of suppressing jitter in disk 1 with a plate thickness of 0.51 mm or less. By satisfying Equation 1, even disk 1 with relatively low rigidity and large maximum amplitude can be obtained with a thin plate thickness that suppresses jitter.

[0156] On the other hand, the thickness D [mm] and specific elastic modulus E / d [×10] of disk 1 6 m 2 / s 2 The Q value of disk 1, i.e., Qa, measured at 3000 Hz and 25°C, preferably satisfies the following equation 2:

[0157] 150 < (Qa × E / d) / 1000 × D < 700 (Equation 2)

[0158] According to the inventors' research, especially when the specific elastic modulus E / d of disk 1 is large, if Equation 2 is satisfied, the product F·D tends to decrease. For example, when the specific elastic modulus E / d is 75 [×10], 6 m 2 / s 2 In the disk 1 described above, it is preferable that the product F·D is easily reduced to 40.0 or less by satisfying Equation 2. It is also preferable that the disk 1 with a small product F·D further improves the effect of suppressing jitter in disks 1 with a plate thickness of 0.51 mm or less.

[0159] Figure 3 This is a BSE (Browsing Electron) image representing a cross-section of the cladding layer 5. For example... Figure 3 As shown, the cover layer 5 is preferably made of glass, and further extends along the thickness direction from the interface 5a with the substrate 3 (the surface in contact with the main surface 3a of the substrate 3). Figure 3 The interface layer region Ta located at a depth of at least 5% of the thickness T of the capping layer 5 (in the vertical direction) contains crystalline phase 5c. Crystalline phase 5c in... Figure 3 The middle part is the whitish area near the interface 5a of overlay layer 5 (see reference). Figure 3(The portion surrounded by a rectangle). According to the inventors' research, by containing a crystalline phase 5c in the interface layer region Ta, the cover layer 5 is firmly bonded to the substrate 3 and is difficult to peel off from the substrate 3. By having such a cover layer 5 on the disk 1, local peeling of the cover layer 5 during heat treatment of the magnetic layer can be suppressed, and deterioration of the flatness of the disk 1 can be suppressed.

[0160] In this case, such as Figure 3 As shown, in the cross-section along the thickness direction of the interface layer region Ta, it is preferably along the extension direction of the cover layer 5, which is orthogonal to the thickness direction. Figure 3 The crystalline phase 5c exists in a region that comprises at least 50% of the total length per unit length (in the left and right directions). By having the crystalline phase 5c present at a high density near the interface 5a, the effect of suppressing the peeling of the capping layer 5 from the substrate 3 is greatly enhanced. The total area where the crystalline phase 5c is present is preferably at least 70% per unit length, and more preferably at least 90%. In order to obtain an interface layer region Ta containing such a crystalline phase at a high density, for example, it is preferable to coat the glass that will become the capping layer 5 onto the surface of the substrate 3 and then hold it at a specified temperature (e.g., 700°C to 1200°C) for a specified time (e.g., 30 minutes to 120 minutes).

[0161] The cover layer 5 is made of glass, and preferably, it extends along the thickness direction from the surface (main surface of the cover layer 5) 5b on the side opposite to the interface 5a of the cover layer 5 and the substrate 3. Figure 3 The surface region Tb, representing at least 5% of the depth of the capping layer 5 in the vertical direction, does not contain the crystalline phase 5c. The glass ratio that forms the crystalline phase 5c is less than that that that forms the amorphous phase (…). Figure 3 The glass surrounding the dark-looking portion of the capping layer 5 (the part of the crystalline phase 5c) is hard and difficult to cut. Therefore, when the capping layer 5 formed on the main surface of the substrate 3 is ground or polished, it results in an uneven surface texture, potentially deteriorating the surface properties of the disk 1. To obtain a surface region Tb that does not contain such a crystalline phase or has a low concentration of crystalline phase, it is preferable, for example, to accelerate the cooling rate (e.g., 10°C / min to 30°C / min) after the glass that will become the capping layer 5 is coated onto the surface of the substrate 3 and held at a specified temperature for a specified time. Furthermore, "low concentration of crystalline phase" refers to a region where the crystalline phase exists that is, for example, less than 10% of the total length per unit length in the extension direction of the capping layer 5.

[0162] The arithmetic mean roughness Ra (JIS B0601:2001) of the main surfaces 3a and 3b of the substrate 3 is preferably 0.01 μm to 0.75 μm, more preferably 0.05 μm to 0.5 μm. With such an arithmetic mean roughness Ra, the main surfaces 3a and 3b of the substrate 3 have relatively large unevenness, and the portion of the cover layer 5 in contact with the substrate 3 enters the recesses therein, thereby achieving an anchoring effect that firmly bonds the cover layer 5 to the substrate 3. Therefore, the effect of suppressing the peeling of the cover layer 5 from the substrate 3 is improved. In particular, the inventors have confirmed that crystal growth readily occurs in the interface layer region Ta of the glass-made cover layer 5, starting from the portion in contact with the unevenness of the main surfaces 3a and 3b of the substrate 3. Therefore, if the arithmetic mean roughness Ra of the main surfaces 3a and 3b of the substrate 3 is within the above range, a large amount of crystalline phase 5c can be formed in the interface layer region Ta of the cover layer 5, enabling the cover layer 5 to adhere more firmly to the substrate 3.

[0163] Although the surface of substrate 3 is covered by capping layer 5, cross-sectional images of the main surfaces 3a and 3b of substrate 3 can be obtained, and the arithmetic mean roughness Ra can be calculated. Specifically, firstly, using ion polishing, the main surface of disk 1 is cut through the center of disk 1 and perpendicular to the main surface to create a sample exposing the main surfaces 3a and 3b of substrate 3. For this cross-section, a cross-sectional image at, for example, 5000x magnification is obtained using a scanning electron microscope (SEM). Based on this image, for example, binarization processing of the cross-sectional image or visual tracking processing is performed to obtain the unevenness curve of the main surfaces 3a and 3b of substrate 3 that form the interface with capping layer 5. The arithmetic mean roughness Ra is calculated by extracting a 20μm wide region located at any part of the unevenness curve.

[0164] The difference between the maximum and minimum distances from the surface 5b of the cover layer 5 opposite to the interface 5a of the substrate 3 (the main surface of the cover layer 5) to the thickness direction of the substrate 3 is preferably 7.5 μm to 12.5 μm, more preferably 8.5 μm to 11.5 μm. Such a disk 1 has large irregularities on the main surfaces 3a and 3b of the substrate 3, thus increasing the anchoring effect of the cover layer 5 on the substrate 3 and increasing the effect of preventing the cover layer 5 from peeling off from the substrate 3. The distance between the main surface of the cover layer 5 and the substrate 3 can be obtained by obtaining the irregularity curve of the main surfaces of the substrate 3 and the cover layer 5 using the method described above for calculating the arithmetic mean roughness Ra of the main surfaces 3a and 3b of the substrate 3, for example, by extracting a 20 μm wide region located at any point on this irregularity curve.

[0165] Figure 4 It is a cross-section of a laminated substrate. For example... Figure 4As shown, in a cross-sectional image of a stacked substrate taken using a scanning electron microscope (SEM) at, for example, a magnification of 200x to 500x, the main surfaces 3a and 3b of the substrate 3 preferably have portions that repeatedly appear in an alternating concave-convex curve obtained from a cross-sectional curve, which represents the thickness direction of the substrate 3 passing through the center of the main surfaces 3a and 3b. Figure 4 The cross-sectional shape (vertical direction). In this case, the extension direction of the covering layer 5, which is orthogonal to the plate thickness direction (vertical direction). Figure 4 The length P of the repeating unit of the concavity and convexity in the left and right directions (in) Figure 4 In this context, P represents the length of the main surface 3a of the corresponding substrate 3, which is preferably 100 μm to 150 μm. According to the inventors' research, it has been confirmed that if the length P of the repeating unit with uneven surfaces is 100 μm to 150 μm, the effect of the cover layer 5 in firmly bonding to the substrate 3 is increased. (Additionally...) Figure 4 The scale bar at the bottom of the microscope image represents a length of 100 μm. The undulation curve can be calculated from the cross-sectional curve obtained by measuring the surface properties of the main surfaces 3a and 3b of the substrate 3. Specifically, the cross-sectional curve is obtained by measuring using a stylus-type measuring device (JIS B0651:2001). Then, according to JIS B0632:2001, the specified cutoff values ​​(λc and λf) are set, and a phase compensation filter (bandpass filter) that allows only the wavelength components between λc and λf to pass is applied to the cross-sectional curve, thereby calculating the undulation curve composed of the wavelength components between λc and λf. The length of the repeating unit of the undulation is, for example, the average length of the undulation (wavelength of the undulation curve) P that appears within the measured length range.

[0166] The thickness T2 of the cover layer 5 at the sidewall surface of the substrate 3 is preferably thicker than the thickness T1 of the cover layer 5 at the main surfaces 3a and 3b of the substrate 3. By making the thickness T2 of the cover layer 5 at the sidewall surface of the substrate 3 thicker, the cover layer 5 can reliably cover the substrate 3 at the sidewall surface of the disk 1, preventing the substrate 3 from being exposed. If a chamfered surface is formed at the outer peripheral end of the disk 1, the effect of suppressing the generation of debris in the HDD is improved by ensuring that the maximum amplitude during the impact test at 30[G] is 0.25 mm or less. The chamfered surface refers to a surface that is connected to the two main surfaces of the disk 1, formed at both ends of the sidewall surface of the disk 1, and extends in a direction inclined relative to the thickness direction. In addition, when the thickness T2 of the cover layer 5 at the sidewall surface of the substrate 3 has a thickness distribution in the thickness direction, it refers to the maximum thickness. From the viewpoint of ensuring the chamfered surface and the length of the main surface direction of the substrate 3 to maintain the rigidity of the disk 1, the ratio of the thickness T2 of the cover layer 5 to the thickness T1, T2 / T1, is preferably 1.01 to 1.5, more preferably 1.05 to 1.15.

[0167] The diameter of disk 1 is preferably 95 mm or more (nominal 3.5 inches or more). This larger diameter disk 1, due to the larger area of ​​the magnetic layer, helps increase the storage capacity of the HDD device. On the other hand, it also increases the likelihood of jitter, leading to read / write errors. Furthermore, the larger the outer diameter of disk 1, the greater the amplitude of vibrations caused by external impacts, and the more difficult it is to attenuate. As described above, the disk 1 of this embodiment suppresses jitter, thus suppressing read / write errors in the HDD device and increasing storage capacity. Additionally, when the maximum amplitude of disk 1 during a 30[G] impact test is 0.25 mm or less, even with a large diameter disk 1, as described above, the generation of debris within the HDD can be suppressed. There is no particular upper limit to the diameter of disk 1; for example, it can be 98 mm.

[0168] The diameter of the inner hole of disk 1 is, for example, 25mm or 20mm. When the diameter of disk 1 is 95mm or more, the diameter of the inner hole is preferably 25mm.

[0169] The maximum surface roughness height Rz (JIS B0601:2001) of the main surfaces 3a and 3b of the substrate 3 is preferably 0.1 μm to 50 μm, more preferably 5 μm to 50 μm. On the main surfaces 3a and 3b of the substrate 3 where the maximum height Rz is within the above range, there are locally large unevennesses, and the portion of the cover layer 5 in contact with the substrate 3 penetrates deeper into the recesses therein, thereby increasing the anchoring effect of the cover layer 5 firmly adhering to the substrate 3. Furthermore, in the interface layer region Ta of the glass-made cover layer 5, crystal growth can be easily generated starting from the portion that contacts the large unevenness of the substrate 3. Regarding the maximum height Rz of the surface roughness of the main surfaces 3a and 3b of the substrate 3, it can be obtained by using a scanning electron microscope (SEM) to obtain a cross-sectional image at 5000x magnification, following the method described above for calculating the arithmetic mean roughness Ra of the main surfaces 3a and 3b of the substrate 3. Specifically, an average line is drawn from the image at the interface between the substrate 3 and the capping layer 5, and the distance between the line parallel to the average line passing through the highest point in the interface within a 20μm range relative to the length direction of the interface and the line parallel to the average line passing through the lowest point in the interface is taken as the maximum height Rz.

[0170] (Intermediate part of the disk)

[0171] Next, the disk intermediate body of one embodiment will be described.

[0172] In this embodiment, the disk intermediate body is a sheet material with a thickness of 0.59 mm or less, which serves as the base plate for forming the disk 1 described above, which has a thickness of 0.51 mm or less. The disk 1 is manufactured, for example, by grinding the main surface of the disk intermediate body to form a metal film containing a magnetic layer.

[0173] The disk's intermediate body comprises a substrate and a cover layer.

[0174] The substrate is a plate having one main surface and another main surface, and also having sidewalls connecting the two main surfaces. The substrate is constructed in the same way as the substrate 3 of disk 1.

[0175] The cover layer is a layer that covers the two main surfaces and sidewalls of the substrate. Except for its thickness and surface properties, the cover layer is constructed in the same way as the cover layer 5 of the disk 1.

[0176] As the intermediate body of the disk, regarding the thickness in the thickness direction, the ratio T / t of the thickness T [mm] of each cover layer to the thickness t [mm] of the substrate is 0.1 to 0.75, the thickness t of the substrate is 0.43 mm or less, and the thickness T of the cover layer is 0.15 mm or less. By keeping the ratio T / t, thickness t, and thickness T of the intermediate body of the disk within the above range, it is possible to suppress the jitter of the disk 1 made from the intermediate body and suppress the deterioration of the surface properties of the disk 1.

[0177] The specific elastic modulus E / d of the disk intermediate, calculated based on Young's modulus E [GPa] and density d [g / cm3], is [×10]. 6 m 2 / s 2 The specific elastic modulus E / d is 40 or higher. By making the specific elastic modulus E / d 40 or higher, the jitter during high-speed rotation is greatly suppressed in the disk 1 made of the disk intermediate.

[0178] (Information recording medium substrate)

[0179] Next, a substrate for an information recording medium according to one embodiment will be described.

[0180] The information recording medium substrate (hereinafter referred to as the disk substrate or substrate) of this embodiment is the substrate 3 described above for the disk 1 described above, and is a substrate made of any one of ceramic, aluminum alloy, and glass. The ceramic, aluminum alloy, and glass are the same as those described above. The disk 1 made using such a substrate 3 can achieve the effects of the disk 1 described above.

[0181] (Manufacturing method of disk, disk intermediate, and substrate)

[0182] The disk 1, disk intermediate, and substrate 3 described above can be manufactured by, for example, the following processes. First, a substrate of substrate 3 is made into a base plate that serves as the original substrate of substrate 3. Then, the substrate of substrate 3 is shaped. Next, a cover layer 5 is formed on the surface of the substrate of substrate 3, resulting in a laminated substrate with the cover layer 5 stacked on substrate 3. Then, the laminated substrate undergoes end face grinding, main surface grinding, first grinding of the main surface, and second grinding of the main surface. The disk intermediate described above can be an intermediate (laminated substrate) after the cover layer has been formed, or it can be an intermediate that has undergone end face grinding, main surface grinding, or polishing. Furthermore, it is not necessary to always perform the above processes; the order of the processes can be appropriately changed, or they can be omitted. For example, in the above example, end face grinding and second grinding of the main surface can be omitted. After the final processing, a metal film containing a magnetic layer is formed on the main surface of the laminated substrate. Each process will be described below.

[0183] (a) Fabrication of the substrate material of the substrate

[0184] The substrate of substrate 3 is preferably prepared by slicing a cylindrical block of ceramic, aluminum alloy, or glass. By slicing the substrate material block, multiple substrates 3 with relatively thin thickness can be efficiently produced. Furthermore, by adjusting the cutting blade and cutting time for slicing the workpiece, the main surface of the sliced ​​substrate 3 can be adjusted to the desired surface characteristics, and the range of the arithmetic mean roughness Ra and maximum height Rz described above can be obtained for the substrate 3 of disk 1. Additionally, the length range of the repeating units of the unevenness described above can be obtained from the undulation curve obtained for substrate 3. In disk 1, the surface of substrate 3 is covered by a cover layer 5, and the surface characteristics of disk 1 can be adjusted by grinding or polishing the cover layer 5. Therefore, grinding or polishing the main surface of substrate 3 can be omitted, improving the productivity of disk 1. The substrate of substrate 3 can also be manufactured by other methods such as stamping instead of the slicing method described above.

[0185] (b) Shape processing

[0186] Next, shape processing is performed. In shape processing, firstly, after fabricating the substrate of substrate 3, a circular hole and outer periphery are formed using a known processing method, thereby obtaining a disk-shaped substrate 3 with a circular hole. Then, chamfering is performed on the end faces of substrate 3. This forms a sidewall surface on the end face of substrate 3 that connects to the main surfaces 3a and 3b and includes a chamfered surface inclined in the thickness direction. In the chamfering process, a forming grinding wheel can also be used to grind the end faces of substrate 3, thereby forming a sidewall surface including the chamfered surface. Alternatively, shape processing can be performed on a block of substrate material before the aforementioned slicing. That is, the substrate of substrate 3 can also be fabricated using a block of substrate material after shape processing. In this case, shape processing after fabricating the substrate of substrate 3 is omitted.

[0187] (c) Formation of the covering layer

[0188] Next, a capping layer 5 is formed. The glass capping layer 5 is formed, for example, by spraying a glass slurry onto the surface of the substrate 3 and then firing it. Specifically, a glass slurry with a thickness ranging from 10 to 300 μm is coated onto the substrate 3 by spraying the glass slurry onto the surface of the substrate 3 from the nozzle opening while moving the nozzle relative to the substrate 3. After coating, the slurry is heated to a temperature above its glass transition temperature, depending on the material used, and then cooled at a predetermined rate, thereby forming the capping layer 5 in a state where there is no residual strain in the glass. Specifically, the cooling time is set to be longer than the heating time. The capping layer 5 is thus formed, and a laminated substrate is fabricated. Furthermore, the thickness of the coated glass is determined considering the machining allowance for grinding or polishing, and is, for example, 10 μm to 300 μm, preferably 40 μm to 150 μm.

[0189] (d) End face grinding

[0190] Next, the end faces of the laminated substrate are polished. End face polishing is performed, for example, by supplying polishing slurry containing free abrasive particles between the polishing brush and the outer and inner peripheral end faces of the laminated substrate, thereby causing the polishing brush and the laminated substrate to move relative to each other. In end face polishing, the inner and outer peripheral end faces of the laminated substrate are the polishing targets, and the inner and outer peripheral end faces are made to a mirror finish.

[0191] (e) Grinding (rough grinding, fine grinding)

[0192] In rough grinding, the main surfaces on both sides of the laminated substrate are ground. Free abrasive grains are used as the grinding material. In rough grinding, the laminated substrate is ground to approximately the target thickness and the flatness of the main surfaces. Furthermore, rough grinding is performed based on the dimensional accuracy or surface roughness of the formed laminated substrate, and may be omitted depending on the circumstances.

[0193] Next, the main surface of the laminated substrate is precision ground. For example, a double-sided grinding apparatus with a planetary gear mechanism is used to grind the main surface of the laminated substrate. In this case, for example, grinding is performed with fixed abrasive grains set on a platform. Alternatively, grinding with free abrasive grains can also be performed. In addition, precision grinding may be omitted depending on the circumstances.

[0194] (f) First grinding (coarse grinding)

[0195] Next, a first grinding process is performed on the main surface of the laminated substrate. This first grinding utilizes free abrasive grains and a grinding pad attached to the platform. For example, this first grinding removes residual cracks and strain from the main surface during fine grinding using fixed abrasive grains. In this first grinding, excessive concavity or convexity at the ends of the main surface can be prevented, and the surface roughness of the main surface, such as the arithmetic mean roughness Ra, can be reduced.

[0196] There are no particular restrictions on the free abrasive grains used in the first grinding stage; for example, cerium oxide abrasive grains or zirconium oxide abrasive grains can be used. Alternatively, the first grinding stage may be omitted depending on the circumstances.

[0197] (g) Second grinding (mirror polishing)

[0198] Next, a second polishing process is performed on the laminated substrate. The purpose of the second polishing is to achieve a mirror finish on the main surface. In the second polishing, a polishing apparatus with the same structure as the first polishing is used. In the second polishing, the type and size of the free abrasive particles are changed compared to the first polishing, and a polishing pad with a softer resin polishing head is used for mirror polishing. This prevents excessive concavity or protrusion of the edges of the main surface and reduces the surface roughness. Regarding the surface roughness, the arithmetic mean roughness Ra (JIS B0601 2001) is preferably 0.2 nm or less. Afterwards, the laminated substrate is cleaned.

[0199] Next, an adhesion layer, a base layer, a magnetic layer (magnetic recording layer), a protective layer, and a lubricating layer are sequentially stacked on the main surface of the laminated substrate to form a metal film, thereby manufacturing disk 1. Then, an HDD containing disk 1 and a magnetic head is manufactured.

[0200] Here, a method for manufacturing the disk 1 using the aforementioned high-rigidity aluminum alloy material as the substrate 3 will be described. The high-rigidity aluminum alloy can be, for example, an aluminum alloy containing 3.0 to 40.0% by mass of Si or an aluminum alloy containing 0.1 to 5.0% by mass of Fe. The nickel alloy film can be, for example, a Ni-P (nickel-phosphorus) alloy coating containing at least phosphorus.

[0201] First, a disc-shaped substrate is cut from a high-rigidity aluminum alloy sheet, heated and annealed at a specified temperature and time, and then the main surface is machined and the end faces are shaped. In the end face shaping, a forming tool or a single-point turning tool is used to grind or cut the end face into a specified shape. Annealing can be performed after the end face and surface machining. Then, a nickel alloy coating with a thickness of, for example, 3μm to 70μm is formed on the surface to fabricate a laminated substrate. Here, the coating thickness is sufficiently small relative to the overall thickness of the laminated substrate, so the shape of the end faces formed by grinding or cutting remains approximately the same after the coating is formed. Then, the surface of the laminated substrate is ground. From the viewpoint of balancing improved surface quality and increased productivity, the grinding process preferably employs two or more grinding stages, similar to the grinding of the laminated substrate described above. Regarding the specific grinding method, except that a grinding fluid containing alumina abrasive grains is preferably used in the first grinding (coarse grinding), it can be approximately the same as the grinding of the laminated substrate described above.

[0202] (Experiment 1)

[0203] To investigate the effect of disk 1 in the first method, disks of various specifications were made.

[0204] (Disk Creation)

[0205] A cylindrical substrate material block with a diameter of 100 mm and a length of 30 mm was sliced ​​using a cutting blade to create a substrate material. A circular hole with a diameter of 25 mm and an outer perimeter with a diameter of 95 mm were formed on the substrate material to create a substrate (Examples 11-14, 17, 18; Comparative Examples 11, 12, 15). Except for Example 17, a glass paste was sprayed onto the surface of the substrate and fired to form a cover layer on the surface of the substrate, resulting in a laminated substrate. In Example 17, a NiP film was formed by electroless plating to cover the entire surface of the substrate.

[0206] In addition, following the above-mentioned principles, a substrate is made by annealing, machining the main surface, and shaping the end face of a disc-shaped substrate cut from an aluminum alloy sheet. A NiP film is formed by electroless plating to cover the entire surface of the substrate (Example 16, Comparative Example 13, Comparative Example 14).

[0207] The laminated substrates of each embodiment and comparative example are subjected to end face grinding, polishing, first grinding, and second grinding.

[0208] On the multilayer substrates of the obtained embodiments and comparative examples, a metal film (thickness less than 30 nm) containing a magnetic layer is further formed on the main surface to fabricate a disk.

[0209] The composition or type of materials of the substrate and cover layer shown in the table are as follows.

[0210] (Substrate)

[0211] • "High-rigidity aluminum alloy 1": An aluminum alloy containing 3.0 to 40.0% by mass of Si.

[0212] • "High-rigidity glass 1": A silica-based glass containing more than 90% by mass of SiO2.

[0213] • "High-rigidity glass 2": Crystallized glass

[0214] • "Glass": Aluminosilicate glass

[0215] • "Aluminum alloy": An aluminum alloy containing more than 3.5% by mass of magnesium.

[0216] (Overlay)

[0217] • "Glass": All-hydrogen polysilazane

[0218] • "NiP": A nickel alloy containing at least 3 to 10% by mass of P, with the remainder being Ni.

[0219] (Specific elastic modulus E / d)

[0220] Calculate the specific elastic modulus E / d of the disk according to the above principles. A specific elastic modulus E / d of 40 or above is considered to have sufficient rigidity and can suppress jitter, while a specific elastic modulus E / d of less than 40 is considered to have a small effect in suppressing jitter.

[0221] (maximum amplitude)

[0222] The maximum amplitude of the disk is determined by mounting it on an evaluation device equipped with a high-speed camera. This evaluation device can apply an external impact (acceleration) of any magnitude, and capture a dynamic image of the resulting motion (vibration) at the outer periphery of the disk. Furthermore, by analyzing this dynamic image, the displacement of the outer periphery in the normal direction of the main surface can be measured.

[0223] Using this evaluation device, an impact test was performed on the disk, applying a 30G impact for 2 seconds along the normal direction of the disk's main surface. The vibration in the normal direction of the main surface towards the outer periphery was measured. Based on the waveform data obtained from the measurement, the maximum displacement of the center of displacement 0 relative to the outer periphery of the disk in any direction along the normal direction was determined as the maximum amplitude. Using the same method, an impact test was performed with an impact magnitude of 50G, and the maximum amplitude was determined.

[0224] Furthermore, in actual HDDs, the ramps equipped with ramp loading mechanisms for the read / write heads leave a 0.25mm gap between the two main surfaces when installing each disk. That is, the gap between the ramps for the disk to enter is the disk thickness + 0.5mm. In actual HDDs, this gap is designed to remain constant even if the disk thickness changes. On the other hand, this ramp is not provided in the evaluation device. Therefore, the maximum amplitude of disk vibration is used to determine whether the disk vibration causes contact with other components (adjacent disks, ramps, or the HDD's housing) in the actual HDD. If the maximum amplitude is less than 0.25mm, it can be determined that no contact with the ramp occurs. If the maximum amplitude exceeds 0.25mm, the possibility of contact with other components is extremely high. The maximum amplitude of three disks was investigated, and the average of the maximum amplitudes was used. In the evaluation of this invention, the disks are evaluated in a stationary state without rotation.

[0225] (Quality Evaluation)

[0226] The quality evaluation of the manufactured disks involved disassembling commercially available HDDs, mounting the disks and spacers of each embodiment and comparative example onto a spindle, and then mounting a simulated ramp component made of engineering plastic protruding from the disk surface. A gap of 0.25 mm was left between the ramp component and the disk. Then, with the disk fixed in place, an impact test was conducted, applying a 30G impact for 2 [m s] along the normal direction of the main surface of disk 1. This test was an accelerated test that deliberately caused the outer periphery of disk 1 to collide with the ramp component several times or more. The debris distribution around the disk surface in contact with the ramp component was then observed. Furthermore, due to difficulties in quantification, a relative evaluation was used.

[0227] Level 1: Almost no debris

[0228] Level 2: The number of debris is moderate.

[0229] Level 3: High quantity of debris

[0230] The evaluation results are shown in Table 1 below.

[0231] The smaller the grade value, the better the quality evaluation, with grade 1 representing the highest evaluation.

[0232] [Table 1]

[0233]

[0234] [Table 2]

[0235]

[0236]

[0237] According to the comparison between Examples 11 to 14, Examples 16 to 18 and Comparative Examples 11 to 15, even for disks with thin plates (less than 0.43 mm in this case) designed to accommodate a large number of disks in an HDD, it is possible to suppress vibration and reduce the amount of debris by making the specific elastic modulus E / d 40 or more and the maximum amplitude during the impact test at 30 [G] 0.25 mm or less.

[0238] In Comparative Example 14, because the board thickness exceeds 0.51 mm, it is difficult to increase the number of sheets mounted on the HDD device to increase the storage capacity.

[0239] Comparative Example 15 has a maximum amplitude exceeding 0.25 mm, resulting in a small effect in reducing the number of debris.

[0240] In addition, the impact magnitude was changed from 30G to 50G for the above impact test and the quality was evaluated. The results showed that Examples 11-13 and 16-18 were grade 1, but Example 14 was grade 2 and Comparative Example 15 was grade 3.

[0241] (Experiment 2)

[0242] To investigate the effect of disk 2 in the first method, disks of various specifications were made.

[0243] (Disk Creation)

[0244] A cylindrical substrate material block with a diameter of 100 mm and a length of 30 mm was sliced ​​using a cutting blade to create a substrate material. A circular hole with a diameter of 25 mm and an outer perimeter with a diameter of 95 mm were formed on the substrate material to create a substrate (Examples 21-24, Examples 27-30, Comparative Example 25). Except for Examples 25 and 27, a glass paste was sprayed onto the surface of the substrate and fired to form a cover layer on the substrate surface, resulting in a laminated substrate. In Examples 25 and 27, a NiP film was formed by electroless plating to cover the entire surface of the substrate. The laminated substrates of each example and comparative example underwent end-face grinding, main surface grinding, first grinding, and second grinding.

[0245] Furthermore, following the above-described principles, a disc-shaped substrate cut from an aluminum alloy sheet was annealed, its main surface was machined, and its end faces were shaped to produce a substrate (Examples 20, 25, 26, and Comparative Example 23). In Examples 25 and 23, a NiP film was formed by electroless plating to cover the entire surface of the substrate. In Examples 20 and 26, a glass paste was sprayed onto the surface of the substrate and then fired to form a cover layer on the surface of the substrate, resulting in a laminated substrate. The laminated substrates of each example and comparative example were subjected to end face grinding, main surface grinding, first grinding, and second grinding.

[0246] On the laminated substrates of the various embodiments and comparative examples obtained as described above, a metal film (thickness less than 30 nm) containing a magnetic layer is further formed on the main surface to fabricate a disk.

[0247] Received

[0248] The composition or type of the substrate and cover layer materials shown in the table are the same as those shown in Tables 1 and 2. Among the substrate materials shown in Tables 3 and 4, "high-rigidity aluminum alloy 2" refers to an aluminum alloy containing at least one of Fe, Mn, and Ni, and the total content of Fe, Mn, and Ni is in the range of 3.5% to 8.0% by mass.

[0249] (Calculation of the flutter characteristic F)

[0250] Using a laser Doppler vibrometer, the Q value from 0 Hz to 4000 Hz was calculated according to the above-described procedure, and the Q value at 3000 Hz was designated as Qa. In addition to the obtained Q value, the sum of the jitter vibrations RSS was calculated using the pre-calculated density, Young's modulus, and Poisson's ratio of disk 1, and was taken as the jitter characteristic F [nm]. In the evaluation using the laser Doppler vibrometer, the rotational speed of disk 1 was 6900 rpm, the measurement position was 46.5 mm from the center of disk 1 (1 mm inside the outer perimeter), and the measurement was performed at room temperature (25°C).

[0251] In order to evaluate disks with different board thicknesses, the product F·D is calculated based on the obtained jitter characteristic F and the board thickness D of disk 1. Cases with a product F·D of less than 47.0 are evaluated as being able to suppress jitter, while cases with a product F·D of more than 47.0 are evaluated as having a small effect in suppressing jitter.

[0252] [Table 3]

[0253]

[0254]

[0255] [Table 4]

[0256]

[0257] According to the comparison between Examples 20 to 30 and Comparative Examples 23 and 25, even for disks with thin boards (less than 0.51 mm in this case) designed to accommodate a large number of disks in an HDD, it is possible to suppress jitter and reduce the amount of debris by making the area F·D less than 47.0 and the maximum amplitude during the impact test at 30 [G] less than 0.25 mm.

[0258] In Comparative Example 23, the effect of suppressing jitter is small because the product F·D exceeds 47.0. In addition, if the plate thickness exceeds 0.51 mm, it is difficult to increase the number of sheets mounted on the HDD device to increase the storage capacity.

[0259] Comparative Example 25 has a maximum amplitude exceeding 0.25 mm, resulting in a small effect in reducing the number of debris.

[0260] In addition, the impact magnitude was changed from 30G to 50G for the above impact test and the quality was evaluated. The results showed that Example 24 and Comparative Example 23 were grade 2, and Comparative Example 25 was grade 3.

[0261] The specific elastic modulus E / d of Examples 21-24 and Comparative Example 25 was calculated, and the result was 75 [×10]. 6 m 2 / s 2 [The above.] Based on the comparison between Examples 21 to 24 and Comparative Example 25, when the specific elastic modulus E / d of the disk is large and (Qa·E / d) / (1000D) is 150 to 700, the product F·D is small, which is 40.0 or less.

[0262] Furthermore, the specific elastic modulus E / d of Examples 20, 25-30, and Comparative Example 23 were all calculated to be less than 75 [×10]. 6 m 2 / s 2 Based on the comparison of Examples 20, 25-28 with Examples 29, 30 and Comparative Example 23, when the specific elastic modulus E / d of the disk is small and (Qa·E / d) / (1000D) is 65.0-270.0, the product F·D is small, which is 40.0 or less.

[0263] (Experiment 3)

[0264] To investigate the effects of disk 1 in the third and fourth methods, disks of various specifications were made.

[0265] (Disk Creation)

[0266] A cylindrical substrate material block with a diameter of 100 mm and a length of 30 mm was sliced ​​using a cutting blade to prepare the substrate material. A circular hole with a diameter of 25 mm and an outer perimeter with a diameter of 95 mm were formed on the prepared substrate material to prepare the substrate. Glass slurry was sprayed onto the surface of the substrate and fired to form a cover layer on the surface of the substrate, thereby obtaining a laminated substrate (Examples 31, 33, 34, 38, 40, Comparative Examples 32, 37 to 39).

[0267] In addition, following the above-mentioned principles, a substrate is made by annealing, machining the main surface, and shaping the end face of a disc-shaped substrate cut from an aluminum alloy sheet. A NiP film is formed by electroless plating to cover the entire surface of the substrate (Examples 35, 36, Comparative Examples 33, 34).

[0268] The laminated substrates or glass substrates of each embodiment and comparative example are subjected to end face grinding, polishing, first grinding, and second grinding.

[0269] On the laminated substrate or glass substrate of the above-described embodiments and comparative examples, a metal film (thickness less than 30 nm) containing a magnetic layer is further formed on the main surface to fabricate a disk.

[0270] Received

[0271] The composition or type of the substrate and cover layer shown in the table is the same as that of the materials shown in Tables 1 to 4.

[0272] (Thickness of the cover layer and substrate)

[0273] The thickness T of the capping layer and the thickness t of the substrate are the average of the thicknesses measured at multiple locations within the measured length using SEM images representing cross-sections.

[0274] (Evaluation of flatness and area F·D)

[0275] The flatness of the fabricated disk was measured using a flatness meter. The results were categorized as follows: flatness below 15 μm was rated A; flatness between 15 μm and 20 μm was rated B; and flatness above 20 μm was rated C.

[0276] In addition, for the disk product F·D calculated according to the above method, the case below 40.0 is evaluated as A, the case above 40.0 but below 45.0 is evaluated as B, and the case above 45.0 is evaluated as C.

[0277] To perform the above evaluation based on the magnitude of the specific elastic modulus E / d, for a specific elastic modulus E / d greater than 75 [×10], 6 m 2 / s2 For the disks shown in Table 5 above, those with an evaluation of A or B for the product F·D and an evaluation of A for flatness are considered to have suppressed jitter and achieved good flatness. Additionally, for disks with a modulus smaller than the elastic modulus E / d (less than 75 × 10⁻⁶), the evaluation is considered to be good flatness. 6 m 2 / s 2 The disks shown in Table 6 are evaluated as having suppressed jitter and achieved good flatness when both the F·D and flatness ratings are A.

[0278] [Table 5]

[0279]

[0280]

[0281] [Table 6]

[0282]

[0283]

[0284] A comparison of Examples 31, 33, 34, and 40 with Comparative Examples 37 to 39 shows that even for disks with thin boards (0.43 mm or less in this case) designed to accommodate a large number of disks in an HDD, for disks with a larger elastic modulus E / d, when the product F·D is 47.0 or less, the ratio T / t is 0.01 to 0.4, the substrate thickness t is 0.43 mm or less, and the cover layer thickness T is 0.1 mm or less, the product F·D is rated as A or B, the flatness is rated as A, and the jitter can be suppressed, and good surface properties can be obtained.

[0285] On the other hand, Comparative Examples 37 to 39 did not meet the requirements of a product F·D of 47.0 or less, a ratio T / t of 0.01 to 0.4, a substrate thickness t of 0.43 mm or less, and a capping layer thickness T of 0.1 mm or less. Therefore, a product F·D rating of A or B and a flatness rating of A were not obtained. Consequently, in Comparative Examples 37 to 39, it was impossible to suppress vibration and obtain good surface properties.

[0286] In particular, the ratio T / t of Comparative Example 39 is less than 0.01, and the flatness evaluation is B, so the effect of making the disk flat is small.

[0287] Furthermore, in Comparative Example 38, the thickness T of the covering layer exceeded 0.1 mm, and the product F·D was rated as C, thus the effect of suppressing vibration was small.

[0288] According to the comparison between Examples 35, 36, and 38 and Comparative Examples 32 to 34, even for disks with thin boards (0.43 mm or less in this case) in order to accommodate a large number of disks in an HDD, for disks with a smaller elastic modulus E / d, when the product F·D is 47.0 or less, the ratio T / t is 0.01 to 0.4, the substrate thickness t is 0.43 mm or less, and the cover layer thickness T is 0.1 mm or less, the product F·D and flatness evaluation are both A, which can suppress jitter and obtain good surface properties.

[0289] On the other hand, Comparative Examples 32 to 34 did not meet the requirements of a product F·D of 47.0 or less, a ratio T / t of 0.01 to 0.4, a substrate thickness t of 0.43 mm or less, and a capping layer thickness T of 0.1 mm or less. The product F·D and flatness evaluations both failed to obtain an A result. Therefore, in Comparative Examples 32 to 34, it was impossible to suppress vibration and obtain good surface properties.

[0290] In particular, Comparative Example 33 had a small effect on suppressing tremor because its product F·D exceeded 47.0.

[0291] Comparative Example 34 has a plate thickness exceeding 0.51 mm, making it difficult to increase the number of sheets mounted on the HDD device to increase storage capacity.

[0292] Comparative Example 34 has a ratio T / t of less than 0.01 and a flatness rating of B, thus its effect on achieving good disk flatness is small.

[0293] Furthermore, based on the comparison between Examples 35, 36, and 38 and Comparative Examples 32 to 34, the specific elastic modulus E / d of the disk is smaller (less than 75 × 10⁻⁶). 6 m 2 / s 2 When (Qa·E / d) / (1000D) is 65.0 to 270.0, the product F·D is small, below 40.0.

[0294] The above provides a detailed description of the information recording medium disk, disk intermediate, and information recording medium substrate of the present invention. However, the present invention is not limited to the above embodiments and examples. Various improvements or modifications can be made without departing from the spirit of the present invention.

[0295] Explanation of reference numerals in the attached figures

[0296] 1. Information recording medium disk

[0297] 3. Substrate for information recording media

[0298] 5. Covering layer

[0299] 5a Main surface of the cover layer

[0300] 5b Interface between the capping layer and the substrate

[0301] 5c crystalline phase

Claims

1. A disk for recording information, wherein the thickness of the disk is 0.51 mm or less, wherein, The information recording medium disk has the following features: A substrate having one main surface and another main surface, and a sidewall connecting the two main surfaces; and A cover layer that covers the two main surfaces and sidewalls of the substrate. The disk is determined based on Young's modulus E [GPa] and density d [g / cm³]. 3 The calculated specific elastic modulus E / d is 40 [×10] 6 m 2 / s 2 ]above, With the inner peripheral end of the disk fixed, when an impact of 30G for 2 [m sec] is applied to the disk along the normal direction of the main surface of the disk, the maximum amplitude caused by the vibration in the thickness direction of the outer peripheral end of the disk is less than 0.25 mm.

2. A disk for recording information, wherein the thickness of the disk is 0.51 mm or less, wherein, The information recording medium disk has the following features: A substrate having one main surface and another main surface, and a sidewall connecting the two main surfaces; and A cover layer that covers the two main surfaces and sidewalls of the substrate. The product of the flutter characteristic F[nm] of the disk, expressed as the sum of the flutter vibrations of the disk at 1000Hz to 4000Hz, and the thickness D[mm] of the disk, F·D, is 47.0 or less. With the inner peripheral end of the disk fixed, when an impact of 30G for 2 [m sec] is applied to the disk along the normal direction of the main surface of the disk, the maximum amplitude caused by the vibration in the thickness direction of the outer peripheral end of the disk is less than 0.25 mm.

3. A disk for recording information, wherein the thickness of the disk is 0.51 mm or less, wherein, The information recording medium disk has the following features: A substrate having one main surface and another main surface, and a sidewall connecting the two main surfaces; and A cover layer that covers the two main surfaces and sidewalls of the substrate. The product of the flutter characteristic F[nm] of the disk, expressed as the sum of the flutter vibrations of the disk at 1000Hz to 4000Hz, and the thickness D[mm] of the disk, F·D, is 47.0 or less. Regarding the thickness in the thickness direction, the ratio T / t of the thickness T [mm] of each of the cover layers covering the two main surfaces to the thickness t [mm] of the substrate is 0.01 to 0.4, the thickness t of the substrate is 0.43 mm or less, and the thickness T of the cover layer is 0.1 mm or less. The disk is determined based on Young's modulus E [GPa] and density d [g / cm³]. 3 The calculated specific elastic modulus E / d is 40 [×10] 6 m 2 / s 2 ]above.

4. A disk for recording information, wherein the thickness of the disk is 0.51 mm or less, wherein, The information recording medium disk has the following features: A substrate having one main surface and another main surface, and a sidewall connecting the two main surfaces; and A cover layer that covers the two main surfaces and sidewalls of the substrate. Regarding the thickness in the thickness direction, the ratio T / t of the thickness T [mm] of each of the cover layers covering the two main surfaces to the thickness t [mm] of the substrate is 0.01 to 0.4, the thickness t of the substrate is 0.43 mm or less, and the thickness T of the cover layer is 0.1 mm or less. The product of the flutter characteristic F[nm] of the disk, expressed as the sum of the flutter vibrations of the disk at 1000Hz to 4000Hz, and the thickness D[mm] of the disk, F·D, is 47.0 or less.

5. The information recording medium disk according to any one of claims 1 to 4, wherein, The product of the flutter characteristic F[nm] of the disk, expressed as the sum of the flutter vibrations of the disk at 1000Hz to 4000Hz, and the thickness D[mm] of the disk, F·D, is 45.0 or less.

6. The information recording medium disk according to any one of claims 1 to 4, wherein, The plate thickness D [mm] and specific elastic modulus E / d [×10] of the disk 6 m 2 / s 2 The Q value of the disk, Qa, measured at 3000 Hz and 25°C, satisfies the following equation 1. 65.0<(Qa×E / d) / 1000×D<270.

0.

7. The information recording medium disk according to any one of claims 1 to 4, wherein, The plate thickness D [mm] and specific elastic modulus E / d [×10] of the disk 6 m 2 / s 2 The Q value of the disk, Qa, measured at 3000 Hz and 25°C, satisfies the following equation 2. 150 < (Qa × E / d) / 1000 × D < 700.

8. The information recording medium disk according to any one of claims 1 to 4, wherein, The substrate is made of any one of the following materials: ceramic, aluminum alloy, and glass. The covering layer is made of glass or nickel alloy.

9. The information recording medium disk according to any one of claims 1 to 4, wherein, The thickness of the plate is less than 0.45 mm.

10. The information recording medium disk according to any one of claims 1 to 4, wherein, The cover layer is made of glass and contains a crystalline phase in the interface layer region, which is located at a depth of at least 5% of the thickness T of the cover layer along the thickness direction from the interface with the substrate.

11. The disk for information recording medium according to claim 10, wherein, In the cross-section of the interface layer region along the thickness direction, the crystalline phase exists in a region of more than 50% of the length per unit length in the extension direction of the capping layer orthogonal to the thickness direction.

12. The information recording medium disk according to any one of claims 1 to 4, wherein, The cover layer is made of glass and does not contain a crystalline phase in the following surface region, which is located at a depth of at least 5% of the thickness T of the cover layer along the thickness direction from the surface of the cover layer opposite to the interface with the substrate.

13. The information recording medium disk according to any one of claims 1 to 4, wherein, The arithmetic mean roughness Ra of the main surface of the substrate is 0.01 μm to 0.75 μm.

14. The information recording medium disk according to any one of claims 1 to 4, wherein, The difference between the maximum and minimum values ​​of the distance in the thickness direction from the surface of the cover layer on the side opposite to the interface of the cover layer to the substrate is 7.5 μm to 12.5 μm.

15. The disk for an information recording medium according to any one of claims 1 to 4, wherein, The main surface of the substrate has portions that repeatedly appear in an alternating concave-convex shape in an undulating curve obtained according to a cross-sectional curve, the cross-sectional curve representing the cross-sectional shape of the substrate in the thickness direction passing through the center of the main surface. The length of the repeating units of the concave and convex shapes in the extension direction orthogonal to the thickness direction of the cover layer is 100μm to 150μm.

16. The information recording medium disk according to any one of claims 1 to 4, wherein, The thickness of the cover layer on the sidewall surface is greater than the thickness T of the cover layer on the main surface of the substrate.

17. The information recording medium disk according to any one of claims 1 to 4, wherein, The diameter of the disk used for recording information is 95mm or more.

18. The information recording medium disk according to any one of claims 1 to 4, wherein, With the inner peripheral end of the disk fixed, when a 50G impact of 2 [m sec] is applied to the disk along the normal direction of the main surface of the disk, the maximum amplitude caused by the vibration in the thickness direction of the outer peripheral end of the disk is less than 0.30 mm.

19. The information recording medium disk according to any one of claims 1 to 4, wherein, The diameter of the disk is 95 mm or more, and the jitter characteristic F, expressed as the sum of the jitter vibrations of the disk from 1000 Hz to 4000 Hz, is 80 nm or less.

20. The disk for an information recording medium according to any one of claims 1 to 4, wherein, The maximum height Rz of the surface roughness of the main surface at the interface between the substrate and the cover layer is 0.1 μm to 50 μm.

21. A disk intermediate, which serves as the base plate for a disk used as an information recording medium, has a plate thickness of 0.59 mm or less, wherein, The disk intermediate body comprises: A substrate having one main surface and another main surface, and a sidewall connecting the two main surfaces; and A cover layer that covers the two main surfaces and sidewalls of the substrate. Regarding the thickness in the thickness direction, the ratio of the thickness T [mm] of each of the cover layers to the thickness t [mm] of the substrate, T / t, is 0.1 to 0.75, the thickness t of the substrate is 0.43 mm or less, and the thickness T of the cover layer is 0.15 mm or less. The intermediate of the disk is based on Young's modulus E [GPa] and density d [g / cm³]. 3 The calculated specific elastic modulus E / d is 40 [×10] 6 m 2 / s 2 ]above.

22. A substrate for an information recording medium, used in any one of claims 1 to 4, wherein, The substrate for the information recording medium is made of any one of the following materials: ceramic, aluminum alloy, and glass.

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