Magnetic recording substrate and magnetic disc

Abstract

The utility model relates to information storage technical field discloses a kind of magnetic recording substrate and magnetic disc, magnetic recording substrate includes: oppositely arranged first main surface and second main surface;Inner circumferential end surface and outer circumferential end surface are composed of first chamfer surface, sidewall surface and second chamfer surface connected in sequence;First chamfer surface is connected with first main surface, and second chamfer surface is connected with second main surface;Sidewall surface is outward convex;First chamfer surface, second chamfer surface are tangent with sidewall surface.This application makes first chamfer surface, second chamfer surface are tangent with sidewall surface by outer circumferential end surface and inner circumferential end surface of magnetic recording substrate, so that outer circumferential end surface and inner circumferential end surface smooth transition, reduce the possibility that tiny crack extends and crack interface produces chip, significantly improve the strength and service life of magnetic recording substrate;Outer circumferential end surface and inner circumferential end surface only have first chamfer surface, second chamfer surface and sidewall surface constitute, shape is simple, easy to process, significantly reduce processing cost and improve processing efficiency.

Description

Technical Field

[0001] This utility model relates to the field of information storage technology, specifically to a magnetic recording substrate and a magnetic disk. Background Technology

[0002] High-density hard disk drive (HDD) devices are frequently used in information storage. These HDD devices include a read / write head and a disk; a special component is located on one side of the disk, and a recording medium layer is formed on the surface of the disk's magnetic recording substrate. When not in operation, the read / write head moves to the special component on the side of the disk; when in operation, the head moves from the special component to above the recording medium layer of the disk to begin reading and writing stored data. During this process, the read / write head is easily affected by airflow turbulence caused by the shape of the disk, making its levitation height unstable. Especially when the head levitation height of the HDD device is less than 5 nanometers, to avoid contact or collision between the head and the recording medium layer, the disk surface must be smooth and flat; furthermore, higher dimensional accuracy and shape quality are required for the inner and outer peripheral end faces of the disk.

[0003] For hard disk drive (HDD) designers and manufacturers, the disk surface is like a "microscopic world." The nanometer-scale undulations on the disk surface cause variations in the distance between the read / write head and the recording medium, ultimately affecting the stability of data retrieval and the limits of storage density. During the manufacturing of the magnetic recording substrate, the main surface of the annular substrate is typically polished, and the outer and inner peripheral end faces are smoothed. Furthermore, the dimensions of the annular substrate, including its outer and inner peripheral end faces, thickness, inner diameter, and outer diameter, are usually machined to a uniform target shape and size. This ensures that the disk can be well assembled into the HDD device and better integrated with components such as the spindle, disk spacers, and spindle cover.

[0004] refer to Figure 1As shown, two main processing methods are used to smooth the outer peripheral end face 2 and inner peripheral end face 3 of the annular magnetic recording substrate. The outer peripheral end face 2 and inner peripheral end face 3 are collectively referred to as the end face. The first method uses laser equipment, utilizing the heat from the focused laser to bring a portion of the end face of the magnetic recording substrate to a specific high temperature, forcing that portion of the end face to soften at high temperature, thus forming a smooth end face. The second method uses mechanical cold processing equipment, specifically, first using a specific grinding wheel to grind the end face of the magnetic recording substrate, and then using a polishing material to polish the end face. For the first method, slight differences in laser energy, laser beam scanning speed, and magnetic recording substrate thickness can lead to varying degrees of softening and deformation of the end face, making it difficult to achieve true shape uniformity in batch processing of magnetic recording substrate end faces. For the second processing method, the end face of the magnetic recording substrate typically consists of sidewalls, a pair of main surfaces, and a pair of chamfered surfaces, where micro-cracks can easily occur at the intersections of different surfaces. Because the magnetic recording substrate is relatively thin, only a few hundred micrometers thick, the aforementioned micro-cracks extend under the action of external mechanical operation and their own stress, and can easily generate debris from the crack interface, which seriously reduces the strength and service life of the magnetic recording substrate. Utility Model Content

[0005] In view of this, the present invention provides a magnetic recording substrate and a magnetic disk that can improve the strength and service life of the magnetic recording substrate, are easy to process and form, and can significantly reduce the processing cost of the magnetic recording substrate and improve the processing efficiency.

[0006] In a first aspect, this utility model provides a magnetic recording substrate, comprising: The main surface includes a first main surface and a second main surface that are disposed opposite to each other. Outer peripheral end face; inner peripheral end face; Both the inner and outer peripheral end faces are composed of a first chamfered surface, a sidewall surface, and a second chamfered surface connected in sequence; the first chamfered surface is connected to the first main surface, and the second chamfered surface is connected to the second main surface; and the sidewall surface protrudes outward; the first chamfered surface and the second chamfered surface are both tangent to the sidewall surface.

[0007] Optionally, the sidewall is an arc, and the radius of curvature of the sidewall along the thickness direction of the magnetic recording substrate is less than 1000 micrometers.

[0008] Optionally, the length of the first chamfered surface and the second chamfered surface in the direction of the main surface of the magnetic recording substrate is L1, the thickness of the magnetic recording substrate is T, and L1 / T is 0.05~0.2.

[0009] Optionally, the length of the first chamfered surface and the second chamfered surface in the thickness direction of the magnetic recording substrate is L2, and L2 / T is 0.05~0.2.

[0010] Optionally, both the first chamfered surface and the second chamfered surface are planar.

[0011] Optionally, in a cross section along the thickness direction of the magnetic recording substrate, the intersection point of the first chamfered surface and the first main surface is A, and the intersection point of the second chamfered surface and the second main surface is B. The length between A and B and the outermost protruding position of the sidewall surface along the direction parallel to the main surface is L3, where L3 is less than 300 micrometers.

[0012] Optionally, the angle between the first main surface and the plane extending outward from the first chamfered surface is in the range of 25° to 65°; the angle between the second main surface and the plane extending outward from the second chamfered surface is in the range of 25° to 65°.

[0013] Optionally, the thickness of the magnetic recording substrate ranges from 0.4 mm to 0.8 mm.

[0014] Optionally, the point of tangency between the first chamfered surface and the sidewall surface is the intersection of the first chamfered surface and the sidewall surface, and the point of tangency between the second chamfered surface and the sidewall surface is the intersection of the second chamfered surface and the sidewall surface.

[0015] Secondly, the present invention also provides a magnetic disk, including any of the magnetic recording substrates described above, wherein the surface of the magnetic recording substrate has at least a recording medium layer.

[0016] Compared to existing technologies, this application adopts the above-mentioned technical solution, by setting the first chamfer surface and the second chamfer surface tangentially to the sidewall surface at the outer and inner peripheral end faces of the magnetic recording substrate, so that the outer and inner peripheral end faces are smoothly transitioned, reducing the possibility of micro-crack propagation and debris generation at the crack interface at the outer and inner peripheral end faces of the magnetic recording substrate, and significantly improving the strength and service life of the magnetic recording substrate; in addition, the outer and inner peripheral end faces are only composed of the first chamfer surface, the second chamfer surface, and the sidewall surface, which has a simple shape, is easy to process and form, and has low requirements for forming grinding wheels, significantly reducing the processing cost of the magnetic recording substrate and improving the processing efficiency of the magnetic recording substrate. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the three-dimensional structure of a magnetic recording substrate in the prior art; Figure 2 This is a cross-sectional view of the end face of the magnetic recording substrate provided in this embodiment of the present invention. Figure 3 This is a schematic diagram showing the parameter markings at the end face of the magnetic recording substrate provided in this embodiment of the present invention; Figure 4 This is a cross-sectional structural diagram of the magnetic recording substrate provided in the embodiment of this utility model.

[0019] Explanation of reference numerals in the attached figures: 1. Main surface; 11. First main surface; 12. Second main surface; 2. Outer peripheral end face; 21. First chamfered surface; 211. First outer peripheral chamfered surface; 22. Side wall surface; 221. Outer peripheral side wall surface; 23. Second chamfered surface; 231. Second outer peripheral chamfered surface; 3. Inner peripheral end face; 311. First inner peripheral chamfered surface; 322. Inner peripheral side wall surface; 332. Second inner peripheral chamfered surface. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0021] refer to Figure 1 And combined with, for example Figures 2 to 4 One specific embodiment of the magnetic recording substrate shown includes: a main surface 1, an outer peripheral end face 2, and an inner peripheral end face 3. The magnetic recording substrate has a circular hole at its center, and the inner peripheral end face 3 is disposed along the circular hole. The magnetic recording substrate is annular in shape.

[0022] like Figure 2As shown, the main surface 1 includes a first main surface 11 and a second main surface 12 disposed opposite to each other. Both the inner peripheral end face 3 and the outer peripheral end face 2 are composed of a first chamfered surface 21, a sidewall surface 22, and a second chamfered surface 23 connected in sequence; the first chamfered surface 21 and the second chamfered surface 23 are collectively referred to as chamfered surfaces. The outer peripheral end face 2 and the inner peripheral end face 3 are collectively referred to as end faces. The first chamfered surface 21 is connected to the first main surface 11, and the second chamfered surface 23 is connected to the second main surface 12; the sidewall surface 22 protrudes outwards; both the first chamfered surface 21 and the second chamfered surface 23 are tangent to the sidewall surface 22. By employing the above-described embodiment, by tangenting the first chamfered surface 21 and the second chamfered surface 23 to the sidewall surface 22 at both the outer peripheral end face 2 and the inner peripheral end face 3 of the magnetic recording substrate, a smooth transition is achieved between the outer peripheral end face 2 and the inner peripheral end face 3. This reduces the possibility of micro-crack propagation and debris generation at the crack interface at the outer peripheral end face 2 and the inner peripheral end face 3 of the magnetic recording substrate, significantly improving the strength and service life of the magnetic recording substrate. Furthermore, since the outer peripheral end face 2 and the inner peripheral end face 3 are composed only of the first chamfered surface 21, the second chamfered surface 23, and the sidewall surface 22, their shapes are simple, easy to process and shape, and have low requirements for the forming grinding wheel, significantly reducing the processing cost of the magnetic recording substrate and improving the processing efficiency of the magnetic recording substrate.

[0023] Specifically, such as Figure 4 As shown, the inner peripheral end face 3 is composed of a first inner peripheral chamfered surface 311, an inner peripheral sidewall surface 322, and a second inner peripheral chamfered surface 332 connected in sequence; the outer peripheral end face 2 is composed of a first outer peripheral chamfered surface 211, an outer peripheral sidewall surface 221, and a second outer peripheral chamfered surface 231 connected in sequence.

[0024] Specifically, such as Figure 2 and Figure 3 As shown, the sidewall 22 is an arc, and the radius of curvature R of the sidewall 22 along the thickness direction of the magnetic recording substrate is less than 1000 micrometers. Preferably, the radius of curvature R of the sidewall 22 along the thickness direction of the magnetic recording substrate is in the range of 300 micrometers to 700 micrometers.

[0025] Furthermore, such as Figure 3 As shown, the length of the first chamfered surface 21 and the second chamfered surface 23 along the direction of the main surface 1 of the magnetic recording substrate is L1, the thickness of the magnetic recording substrate is T, and L1 / T is 0.05~0.2. In this way, the boundary between the main surface 1 and the chamfered surface will not appear sharp, and it is not easy to generate debris, which can effectively ensure the strength and service life of the magnetic recording substrate, while ensuring the effective area of ​​the disk substrate.

[0026] Furthermore, such as Figure 3As shown, the length of the first chamfered surface 21 and the second chamfered surface 23 in the thickness direction of the magnetic recording substrate is L2, and L2 / T is 0.05~0.2. Similarly, when the value of L2 / T is within this range, the boundary between the main surface 1 and the chamfered surface will not appear sharp, and it is not easy to generate debris, which can effectively ensure the strength and service life of the magnetic recording substrate, while ensuring the effective area of ​​the disk substrate.

[0027] Specifically, such as Figure 2 As shown, both the first chamfered surface 21 and the second chamfered surface 23 are flat, which makes them easier to process.

[0028] Specifically, such as Figure 3 As shown, in a cross-section along the thickness direction of the magnetic recording substrate, the intersection point A of the first chamfered surface 21 and the first main surface 11, and the intersection point B of the second chamfered surface 23 and the second main surface 12, are such that the length L3 between A and B and the outermost protruding position of the sidewall surface 22 along the direction parallel to the main surface 1 is less than 300 micrometers. Preferably, the length L3 is within 200 micrometers.

[0029] Specifically, such as Figure 3 As shown, the angle θ between the first main surface 11 and the outwardly extending plane of the first chamfered surface 21 ranges from 25° to 65°; the angle θ between the second main surface 12 and the outwardly extending plane of the second chamfered surface 23 also ranges from 25° to 65°. Tests have shown that when θ is in the range of 25° to 65°, the strength and service life requirements of the magnetic recording substrate are met. Preferably, the angle θ between the first main surface 11 and the outwardly extending plane of the first chamfered surface 21 ranges from 30° to 60°; the angle θ between the second main surface 12 and the outwardly extending plane of the second chamfered surface 23 also ranges from 30° to 60°. Tests have shown that when θ is in the range of 30° to 60°, debris is less likely to be generated at the boundary between the main surface 1 and the chamfered surface, ensuring the strength and service life of the magnetic recording substrate. Simultaneously, the length L1 of the chamfered surface in the direction of the main surface 1 is appropriate, ensuring the effective area of ​​the magnetic recording substrate while reducing residual micro-cracks on the chamfered surface, resulting in better performance.

[0030] It should be noted that if the radius of curvature R of the sidewall 22 is less than the above range, the outward protrusion of the outer peripheral end face 2 and the inner peripheral end face 3 of the annular magnetic recording substrate will be sharper, increasing the length L1 of the chamfer surface in the direction of the main surface 1 of the magnetic recording substrate and the length L2 of the chamfer surface in the thickness direction of the magnetic recording substrate. If the length L2 of the chamfer surface in the thickness direction of the magnetic recording substrate is increased, the magnetic recording substrate is prone to relative sliding with the grinding and polishing carrier during the subsequent grinding and polishing process of the main surface 1 of the magnetic recording substrate. In severe cases, it may even slide out of the grinding and polishing carrier, resulting in cracks or breakage damage to the magnetic recording substrate. If the radius of curvature R of the sidewall 22 of the magnetic recording substrate is greater than the above range, the angle θ between the first main surface 11 and the plane extending outward from the first chamfer surface 21 and the angle θ between the second main surface 12 and the plane extending outward from the second chamfer surface 23 will be too large. The boundary between the main surface 1 and the chamfer surface will be sharper, easily generating debris and reducing the strength and service life of the magnetic recording substrate.

[0031] Specifically, when the thickness of the magnetic recording substrate is between 0.4 mm and 0.8 mm, the range of thickness T is 0.4 mm to 0.8 mm. Tests have shown that a thickness T of 0.4 mm ensures the rigidity of the magnetic recording substrate, preventing the risk of vibration during high-speed rotation; simultaneously, the magnetic recording substrate occupies a moderate amount of space within the hard disk drive, avoiding the increased demands on the motor driving the disk at high speeds due to the increased weight of the disk.

[0032] Furthermore, such as Figure 2 As shown, the tangent point C between the first chamfered surface 21 and the sidewall surface 22 is the intersection point of the first chamfered surface 21 and the sidewall surface 22, and the tangent point D between the second chamfered surface 23 and the sidewall surface 22 is the intersection point of the second chamfered surface 23 and the sidewall surface 22. This arrangement further ensures a smooth transition between the outer peripheral end face 2 and the inner peripheral end face 3, reducing the possibility of micro-crack propagation and debris generation at the crack interface on the outer peripheral end face 2 and the inner peripheral end face 3 of the magnetic recording substrate, thereby further improving the strength and service life of the magnetic recording substrate.

[0033] Specifically, there are no particular limitations on the diameter of the magnetic recording substrate provided in this application. It can be a magnetic recording substrate with a nominal diameter of 2.5 inches or a magnetic recording substrate with a nominal diameter of 3.5 inches.

[0034] Specifically, there are no particular requirements for the material of the magnetic recording substrate provided in this application. It can be a magnetic recording substrate made of soda-lime-silicon glass, a magnetic recording substrate made of high-alumina glass, a magnetic recording substrate made of microcrystalline glass, or a magnetic recording substrate made of sapphire. Sapphire, which has high strength and rigidity, and chemically strengthenable glass are preferred as the materials for the annular magnetic recording substrate.

[0035] The inner peripheral end face 3 and outer peripheral end face 2 of the annular magnetic recording substrate provided in this application have simple shapes, are easy to process and form, have low requirements for forming grinding wheels, and cause less damage to the jigs used for grinding and polishing the inner peripheral end face 3 and outer peripheral end face 2. Figure 2 and Figure 3 As shown in the cross-sectional structural diagram along the thickness direction of the magnetic recording substrate, the chamfered surface is tangent to the sidewall surface 22, and the point of tangency between the chamfered surface and the sidewall surface 22 is the intersection point. The connection between the chamfered surface and the sidewall surface 22 is smooth, which can reduce the extension of microcracks in the magnetic recording substrate and the possibility of debris generation at the interface, thereby increasing the strength and service life of the magnetic recording substrate.

[0036] The annular magnetic recording substrate provided in this application may have the same sidewall 22 and chamfered surface on its inner peripheral end face 3 and outer peripheral end face 2, or may have different sidewall 22 and chamfered surface.

[0037] In a specific embodiment, the thickness T of the magnetic recording substrate is 0.6 mm, the radius of curvature R of the sidewall surface 22 along the thickness direction of the magnetic recording substrate is 0.52 mm, the length L1 of the first chamfered surface 21 and the second chamfered surface 23 in the direction of the main surface 1 of the magnetic recording substrate is 0.023 mm, the length L2 of the first chamfered surface 21 and the second chamfered surface 23 in the thickness direction of the magnetic recording substrate is 0.04 mm, and the angle θ between the first main surface 11 and the plane extending outward from the first chamfered surface 21 is 60°. The angle θ between the second main surface 12 and the outwardly extending plane of the second chamfered surface 23 is 60°. The length L3 between the intersection point A of the first chamfered surface 21 and the first main surface 11, and the intersection point B of the second chamfered surface 23 and the second main surface 12, and the outermost protruding position of the sidewall 22, along the direction parallel to the main surface 1, is 0.093 mm. There is no limitation on the diameter of the annular magnetic recording substrate. The inner peripheral end face 3 and the outer peripheral end face 2 can form the same sidewall 22 and chamfered surface, or they can form different sidewall 22 and chamfered surfaces. Experimental verification shows that the magnetic recording substrate of the above embodiment has good implementation effect, is easy to process and form, and has a high yield.

[0038] In a specific embodiment two, the thickness T of the magnetic recording substrate is 0.6 mm, the radius of curvature R of the sidewall surface 22 along the thickness direction of the magnetic recording substrate is 0.368 mm, the length L1 of the first chamfered surface 21 and the second chamfered surface 23 in the direction of the main surface 1 of the magnetic recording substrate is 0.04 mm, the length L2 of the first chamfered surface 21 and the second chamfered surface 23 in the thickness direction of the magnetic recording substrate is 0.04 mm, and the angle θ between the first main surface 11 and the plane extending outward from the first chamfered surface 21 is 45°. The angle θ between the second main surface 12 and the outwardly extending plane of the second chamfered surface 23 is 45°. The length L3 between the intersection point A of the first chamfered surface 21 and the first main surface 11, and the intersection point B of the second chamfered surface 23 and the second main surface 12, and the outermost protruding position of the sidewall surface 22, along the direction parallel to the main surface 1, is 0.148 mm. There is no limitation on the diameter of the annular magnetic recording substrate. The inner peripheral end face 3 and the outer peripheral end face 2 can form the same sidewall surface 22 and chamfered surface, or they can form different sidewall surfaces 22 and chamfered surfaces. Experimental verification shows that the magnetic recording substrate of the above embodiment two has the best implementation effect, is the easiest to process and form in the embodiment, and has the highest yield.

[0039] In a specific embodiment three, the thickness T of the magnetic recording substrate is 0.6 mm, the radius of curvature R of the sidewall surface 22 along the thickness direction of the magnetic recording substrate is 0.208 mm, the length L1 of the first chamfered surface 21 and the second chamfered surface 23 in the direction of the main surface 1 of the magnetic recording substrate is 0.208 mm, the length L2 of the first chamfered surface 21 and the second chamfered surface 23 in the thickness direction of the magnetic recording substrate is 0.12 mm, and the angle θ between the first main surface 11 and the plane extending outward from the first chamfered surface 21 is 30°. The angle θ between the second main surface 12 and the outwardly extending plane of the second chamfered surface 23 is 30°. The length L3 between the intersection point A of the first chamfered surface 21 and the first main surface 11, and the intersection point B of the second chamfered surface 23 and the second main surface 12, and the outermost protruding position of the sidewall 22, along the direction parallel to the main surface 1, is 0.312 mm. There is no limitation on the diameter of the annular magnetic recording substrate. The inner peripheral end face 3 and the outer peripheral end face 2 can form the same sidewall 22 and chamfered surface, or they can form different sidewall 22 and chamfered surfaces. Experimental verification shows that the magnetic recording substrate of the above embodiment 3 has a good implementation effect, but L2 is relatively large, which affects the processing difficulty to a certain extent.

[0040] In a specific embodiment four, the thickness T of the magnetic recording substrate is 0.6 mm, the radius of curvature R of the sidewall surface 22 along the thickness direction of the magnetic recording substrate is 0.254 mm, the length L1 of the first chamfered surface 21 and the second chamfered surface 23 in the direction of the main surface 1 of the magnetic recording substrate is 0.139 mm, the length L2 of the first chamfered surface 21 and the second chamfered surface 23 in the thickness direction of the magnetic recording substrate is 0.08 mm, and the angle θ between the first main surface 11 and the plane extending outward from the first chamfered surface 21 is 30°. The angle θ between the second main surface 12 and the outwardly extending plane of the second chamfered surface 23 is 30°. The length L3 between the intersection point A of the first chamfered surface 21 and the first main surface 11, and the intersection point B of the second chamfered surface 23 and the second main surface 12, and the outermost protruding position of the sidewall 22, along the direction parallel to the main surface 1, is 0.266 mm. There is no limitation on the diameter of the annular magnetic recording substrate. The inner peripheral end face 3 and the outer peripheral end face 2 can form the same sidewall 22 and chamfered surface, or they can form different sidewall 22 and chamfered surfaces. Experimental verification shows that the magnetic recording substrate of the above embodiment four has good implementation effect, is easy to process and form, and has a high yield.

[0041] This application also proposes a magnetic disk, comprising: the aforementioned magnetic recording substrate, wherein at least one recording medium layer is present on the surface of the magnetic recording substrate. The magnetic disk of this invention has good strength and a long service life.

[0042] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by this application.

Claims

1. A magnetic recording substrate, characterized in that, include: The main surface (1) includes a first main surface (11) and a second main surface (12) that are disposed opposite to each other. Outer peripheral end face (2); Inner peripheral end surface (3); The inner peripheral end face (3) and the outer peripheral end face (2) are both composed of a first chamfered surface (21), a side wall surface (22) and a second chamfered surface (23) connected in sequence; the first chamfered surface (21) is connected to the first main surface (11) and the second chamfered surface (23) is connected to the second main surface (12); and the side wall surface (22) is convex outward; the first chamfered surface (21) and the second chamfered surface (23) are both tangent to the side wall surface (22).

2. The magnetic recording substrate according to claim 1, characterized in that, The sidewall (22) is an arc, and the radius of curvature of the sidewall (22) along the thickness direction of the magnetic recording substrate is less than 1000 micrometers.

3. The magnetic recording substrate according to claim 1, characterized in that, The length of the first chamfered surface (21) and the second chamfered surface (23) in the direction of the main surface (1) of the magnetic recording substrate is L1, the thickness of the magnetic recording substrate is T, and L1 / T is 0.05~0.

2.

4. The magnetic recording substrate according to claim 3, characterized in that, The length of the first chamfered surface (21) and the second chamfered surface (23) in the thickness direction of the magnetic recording substrate is L2, and L2 / T is 0.05~0.

2.

5. The magnetic recording substrate according to any one of claims 1-4, characterized in that, Both the first chamfered surface (21) and the second chamfered surface (23) are planes.

6. The magnetic recording substrate according to any one of claims 1-4, characterized in that, In a cross section along the thickness direction of the magnetic recording substrate, the intersection of the first chamfered surface (21) and the first main surface (11) is A, and the intersection of the second chamfered surface (23) and the second main surface (12) is B. The length between A and B and the outermost protruding position of the sidewall surface (22) along the parallel direction of the main surface (1) is L3, and L3 is less than 300 micrometers.

7. The magnetic recording substrate according to any one of claims 1-4, characterized in that, The angle between the first main surface (11) and the plane extending outward from the first chamfered surface (21) is in the range of 25° to 65°; the angle between the second main surface (12) and the plane extending outward from the second chamfered surface (23) is in the range of 25° to 65°.

8. The magnetic recording substrate according to any one of claims 1-4, characterized in that, The thickness of the magnetic recording substrate ranges from 0.4 mm to 0.8 mm.

9. The magnetic recording substrate according to claim 1, characterized in that, The point of tangency between the first chamfered surface (21) and the side wall surface (22) is the intersection of the first chamfered surface (21) and the side wall surface (22), and the point of tangency between the second chamfered surface (23) and the side wall surface (22) is the intersection of the second chamfered surface (23) and the side wall surface (22).

10. A hard disk, characterized in that, The magnetic recording substrate includes any one of claims 1-9, wherein the surface of the magnetic recording substrate has at least a recording medium layer.

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