JP3884139B2 - Magnetic disk manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic disk used as a recording medium for storing, for example, data in a computer, a manufacturing method thereof, and a magnetic recording / reproducing apparatus.
[0002]
[Prior art]
This type of magnetic disk includes a disk-shaped nonmagnetic substrate and magnetic layers formed on both sides of the substrate. Conventionally, as disclosed in, for example, Japanese Patent Laid-Open No. 63-255816, a method is known in which a plastic similar to a known optical disk is used as a substrate material, and this is injection molded to mold the substrate.
[0003]
Further, when the physical format of the magnetic disk is formed, it takes a lot of time to record the format signal in the entire area of the magnetic layer by the magnetic head. As a new type of magnetic disk for avoiding this, Japanese Patent Laid-Open No. 3-86912 discloses that a servo signal is uniformly determined in advance in a substrate uneven state, and a substrate having the same unevenness by injection molding or the like is used. Mass production, magnetic layer is uniformly formed on the uneven side of each substrate, this magnetic layer is forcibly magnetized in one direction, and the leakage magnetic field resulting from the unevenness of this magnetic layer is detected by the magnetic head, A device that attempts to read a servo signal is known. This is promising as a means for providing a magnetic disk on which a physical format is formed in large quantities and at low cost.
[0004]
Such a magnetic disk is widely used as a recording medium for storing data and the like in a computer. A magnetic recording / reproducing apparatus using this magnetic disk is called a so-called winch-esta type as a system for floating the magnetic head with respect to the magnetic disk. In other words, in this magnetic recording / reproducing apparatus, the magnetic head and the magnetic head are placed in a state where the magnetic head is levitated by an air flow generated by the relative motion with the magnetic disk so as to maintain a minute interval of 50 nm or less from the surface of the magnetic disk. Data is recorded or reproduced by transferring magnetic fields between the disks.
[0005]
Here, in order to float the magnetic head to an appropriate state, it is necessary to keep the surface deflection of the magnetic disk small. This surface deflection amount can be reduced by increasing the flatness of the entire substrate.
[0006]
[Problems to be solved by the invention]
However, in the conventional magnetic disk, the same surface roughness Ra is set so that both surfaces of the disk-shaped non-magnetic substrate made of plastics are sufficiently smooth, and when the surface roughness Ra is 2 nm or less, When the amount of runout increased, there was a problem.
[0007]
Therefore, it is conceivable to increase the surface roughness Ra as much as possible to suppress the surface shake amount. However, in this case, it is difficult to obtain good magnetic characteristics for recording and reproduction. It is desirable that the substrate be as smooth as possible. However, when both surfaces of the substrate are smooth surfaces such as mirror surfaces, a large frictional force acts between the mold and both surfaces of the substrate when the substrate is released from the mold after molding. Therefore, the substrate was deformed, and the flatness of the entire substrate could not be secured.
[0008]
In light of such circumstances, the present invention reduces the deformation of a disk-shaped nonmagnetic substrate when released from a mold, improves the flatness of the entire substrate, and reduces the amount of surface deflection. The purpose is to provide. The present invention also provides a method of manufacturing a magnetic disk capable of obtaining the above-mentioned magnetic disk in a large quantity and at a low cost, and further, magnetic recording / reproducing with the above-mentioned magnetic disk and capable of appropriately transferring data. The object is to provide a device.
[0009]
[Means for Solving the Problems]
As a result of intensive investigations to achieve the above object, the present inventors set the surface roughness of one surface of a disk-like nonmagnetic substrate formed by plastic injection molding or injection compression molding to be small. In addition, if the surface roughness of the other surface is set large, the deformation of the substrate is reduced when releasing from the molding die, the flatness of the entire substrate is ensured, and the surface deflection of the magnetic disk is reduced. Knowing that it can be suppressed, the present invention has been completed.
[0011]
Ie The present invention , Corresponds to the surface roughness of one surface of a disk-shaped nonmagnetic substrate Surface roughness is 2nm or less Corresponds to the surface roughness of the first stamper having the transfer surface and the other surface of the substrate. Surface roughness is 4nm or more A second stamper having a transfer surface is disposed in a mold for injection molding or injection compression molding with the respective transfer surfaces facing each other. In this mold A plastic non-magnetic substrate is formed by injection molding or injection compression molding, and at the same time, the surface roughness of each transfer surface is transferred to the substrate. Then, the deformation of the substrate when the substrate is released from the mold is reduced so that the surface roughness of one surface of the substrate is 2 nm or less and the surface roughness of the other surface is 4 nm or more. A disk-shaped non-magnetic substrate in which the flatness of the entire substrate is ensured is manufactured, and a magnetic disk is manufactured by providing a magnetic layer on both sides of the substrate. Magnetic disk manufacturing method characterized in that In It is related.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of the magnetic disk of the present invention, and FIG. 2 is an enlarged cross-sectional view showing a part of FIG.
[0013]
1 and 2, reference numeral 1 denotes a disk-like non-magnetic substrate, which is formed by injection molding or injection compression molding of a plastic. At least a magnetic layer 2 is formed on both surfaces 1 a and 1 b of the substrate 1. Reference numeral 3 denotes a driven central hole formed in the substrate 1. The surface roughness Ra of one surface 1a of the substrate 1 is set to 2 nm or less with high smoothness, and the surface roughness Ra of the other surface 1b is 4 nm or more, preferably 5 nm or more (usually 10 nm) with low smoothness. Up to).
[0014]
For the production of the magnetic disk M substrate, a mold for injection molding (or injection compression molding) is used. The structure of this mold will be schematically described with reference to FIG.
In FIG. 3, the mold 24 includes a fixed mold 24A connected to the nozzle side of the injection molding machine, and a movable mold 24B set to be movable relative to the fixed mold 24A in the direction of the white arrow. The fixed mold 24A has a runner 241 that guides the molten plastic from the nozzle to the chamber S between the fixed mold 24A and the movable mold 24B. The movable mold 24B has a cylinder function for releasing the substrate. An ejector 242 and a gate cutter 243 for forming a central hole are formed.
[0015]
A fixed core 246A having inner and outer holders 244A and 245A is installed in the fixed mold 24A, while a movable side having inner and outer holders 244B and 245B is installed in the movable mold 24B. A core 246B is installed. The fixed side core 246A holds the first stamper 23A for forming one surface 1a of the substrate 1 via the holders 244A and 245A, while the movable side core 246B holds the first stamper 23A via the holders 244B and 245B. Thus, the second stamper 23B for forming the other surface 1b of the substrate 1 is held. Plastic from the runner 241 is injected into the space S between the stampers 23A and 23B. Reference numerals 247A and 247B denote cooling medium flow paths formed in the fixed side and movable side cores 246A and 246B, respectively.
[0016]
Next, a method for manufacturing the magnetic disk M will be described with reference to FIG.
The processes until the disk-shaped nonmagnetic substrate 1 is manufactured are the same as the well-known optical disk substrate manufacturing process. That is, first, as shown in FIG. 4A, a photoresist layer 22 is formed on the surface of a glass master 21 by spin coating. At that time, in order to obtain the surface roughness Ra of the one surface 1a of the substrate 1, the surface roughness Ra of the master disk 21 is controlled to 2 nm or less in the polishing process of the master disk 21.
[0017]
Next, as shown in FIG. 4B, the first stamper 23A is manufactured by sticking to the surface of the master 21. A transfer surface 23a having a surface roughness Ra of 2 nm or less is formed on the first stamper 23A. Similarly, a second stamper 23B having a transfer surface 23b having a surface roughness Ra of 4 nm or more is manufactured.
[0018]
As shown in FIG. 4C, the stampers 23A and 23B produced in this way are opposed to the transfer surfaces 23a and 23b in the mold 24 (24A and 24B) for injection molding (or injection compression molding). Arrange in a state to do. When a disk-shaped nonmagnetic substrate 1 is produced by injection molding (or injection compression molding) of a plastic material, which is a substrate material, on this substrate 1, the transfer surfaces 23a, 23b of the stampers 23A, 23B are formed. Is transcribed. That is, as a result, the surface roughness Ra of one surface 1a of the substrate 1 is 2 nm or less, and the surface roughness Ra of the other surface 1b is 4 nm or more.
[0019]
Plastics that are materials of the substrate 1 include polyetherimide, polyethersulfone, polyphenylenesulfide, polyacrylate, polyetherketone, polymethylpentene, polymethylmethacrylate, polycarbonate, Resins with excellent heat resistance and transferability such as norbornene resins are used. In order to avoid contamination (contamination by harmful substances) contained in the plastic material, polycarbonate and norbornene resin are particularly preferable.
[0020]
After this molding, the substrate 1 is taken out from the mold 24, and as shown in FIG. 4D, the magnetic layer 2 and the protective layer (not shown) are sequentially formed on both surfaces 1a and 1b of the substrate 1 by a sputtering method. , Form each. Examples of the constituent material of the magnetic layer 2 include cobalt / platinum alloy, cobalt / chromium / platinum alloy, and cobalt / palladium alloy. Examples of the constituent material of the protective layer include carbon and silicon oxide.
[0021]
The magnetic layer 2 is preferably formed with an underlayer such as chromium or molybdenum so that a high coercive force can be obtained even at low temperature. Prior to the formation of the underlayer for the purpose of preventing cracks in the magnetic layer 2 due to the difference in thermal expansion between the substrate 1 and the magnetic layer 2 and improving the magnetic properties, aluminum, titanium, Amorphous and ceramic materials such as aluminum / titanium alloy, silicon, silicon nitride, and silicon oxide may be formed on the substrate 1.
[0022]
After the magnetic layer 2 is formed, burnishing is performed using a brush 25 as shown in FIG. 4E in order to remove fine protrusions on the surface of the protective layer. Finally, in order to improve the running performance of the magnetic head 12 (see FIG. 13), as shown in FIG. 4 (f), when the lubricant 26 is applied by the spin coat method, the magnetism using the plastic substrate 1 is improved. A disk M is produced. As the lubricant 26, for example, “Fomblin Z-DOL” (trade name) is preferably used.
[0023]
Thus, since the plastic is injection molded or injection compression molded to form the disk-shaped non-magnetic substrate 1, the substrate 1 can be manufactured in a large amount and at a low cost. In addition, a transfer surface having a surface roughness corresponding to both surfaces 1a and 1b of the substrate 1 may be directly formed on the inner wall of the mold 24 in advance, but in this case, it is unavoidable that the mold cost increases. Absent. On the other hand, by using the first and second stampers 23A and 23B as described above, a desired surface roughness is imparted to the both surfaces 1a and 1b simultaneously with the formation of the substrate without incurring high costs. be able to.
[0024]
Here, when both surfaces of the substrate 1 are highly smooth (mirror-like), a large frictional force acts between the mold 24 and the substrate 1 when the substrate 1 is released from the mold 24. The substrate 1 tries to deform. However, as described above, if the surface roughness Ra of one surface 1a of the substrate 1 is set to 2 nm or less and the surface roughness Ra of the other surface 1b is set to 4 nm or more, the substrate 1 is released at the time of mold release. The frictional force between the other surface 1b of the metal plate 24 and the mold 24 is reduced, and it is possible to prevent the substrate 1 from being deformed due to an excessive force applied thereto, and as a result, the entire flatness of the substrate 1 to be manufactured is ensured well. Is done.
[0025]
Next, a second embodiment of the present invention will be described with reference to the drawings.
FIG. 5 is a sectional view showing the magnetic disk of the present invention, and FIG. 6 is an enlarged sectional view showing a part of FIG. This shows a pre-embossed magnetic disk M having a structure in which a concave and convex portion (prepit) is physically provided on the other surface of the substrate.
[0026]
In both figures, reference numeral 11 denotes a disk-like non-magnetic substrate, which is formed by injection or injection compression molding of a plastic. At least the magnetic layer 2 is formed on both surfaces 11 a and 11 b of the substrate 1. Reference numeral 3 denotes a driven central hole formed in the substrate 11. The surface roughness Ra of one surface 11a of the substrate 11 is set to 2 nm or less with high smoothness, and the surface roughness Ra of the other surface 11b is set to 4 nm or more with low smoothness. The other surface 11b is constituted by a concavo-convex portion (pre-embossed pattern) 10 such as a guard band groove or a recording track.
[0027]
FIG. 7 shows the appearance of the pre-embossed pattern 10.
In the figure, reference numeral 12 denotes a magnetic head, which performs a recording or reproducing operation by making a relative motion along a track in the circumferential direction (arrow a direction) of the magnetic disk M. As the pattern 10, the other surface 11b of the substrate 11 is concentric with the substrate 11, that is, parallel to the circumferential movement locus of the magnetic head 12, and continuously or intermittently in the circumferential direction. The guard band grooves 13 are provided at substantially equal intervals in the radial direction (arrow b direction), and the recording track 14 is intermittently provided in the circumferential direction between the adjacent guard band grooves 13 in the radial direction. Is provided.
[0028]
A plurality of radial tracks 14 form a data recording area 18, and a servo area 19 is provided between each data recording area 18 adjacent in the circumferential direction. In the servo area 19, a row of servo pits 15, a row of phase pits 16, and a row of clock pits 17 are formed. The rows of servo pits 15 are arranged so as to be shifted in the radial direction and the circumferential direction with respect to the recording track center 14a, and the magnetic pits 15 adjacent to each other in the radial direction detected by the magnetic head 12 are magnetically connected. The position of the magnetic head 12 is controlled so that the outputs are equal. Thereby, the magnetic head 12 is always positioned at the recording track center 14a.
[0029]
FIG. 8 shows an example of the track format of the magnetic disk M.
In FIG. 8A, the track 14 is composed of a plurality of sectors (1 to M), and the sector is divided into a plurality of segments (1 to N). (SM) is formed. The servo mark (SM) is composed of an access code, a crotch mark, and a fire pattern. The header includes a sector mark, a track number, a sector number, a redundancy check (CRC), and an automatic gain control (AGC).
[0030]
FIG. 8B shows the planar shape of the servo mark. The access code is used to check the moving speed of the magnetic head 12 at the time of access, and the clock mark is used to record the timing of the synchronous clock or servo mark position when recording or playback is performed by the magnetic head 12. Used to get. That is, the clock mark is set to appear continuously every N clocks and processed by the servo circuit. Further, the pattern is a pattern for indicating a relative position (phase) from the recording track center 14a, and a tracking operation is performed by obtaining position information from the magnetic head 12.
[0031]
Next, a method for manufacturing the magnetic disk M will be described with reference to FIG.
The process until the disk-shaped nonmagnetic substrate 1 is manufactured is the same as the well-known optical disk substrate manufacturing process. First, as shown in FIG. 9A, a photoresist layer 22 is applied to the surface of a glass master 21 by a spin coating method. At this time, in order to adjust the surface roughness Ra of the one surface 11 a of the substrate 11, the surface roughness Ra of the master disk 21 is controlled to 2 nm or less in the polishing process of the master disk 21. Further, after the photoresist layer 22 is formed in the same manner as described above, the pattern is cut on the layer 22 by an optical beam L having a pattern short wavelength (λ = 351 nm). By developing, a desired uneven pattern is formed as shown in FIG.
[0032]
The subsequent steps are the same as those in the first embodiment. That is, the first stamper 23A having a transfer surface 23a having a surface roughness of 2 nm or less is manufactured by sticking to the surface of the master 21, and as shown in FIG. 2 stamper 23B is produced. An uneven transfer surface 23b is formed on the surface of the stamper 23B corresponding to the surface roughness of the other surface 11b of the substrate 11.
[0033]
As shown in FIG. 9D, the stampers 23A and 23B are arranged in the mold 24 (24A and 24B) for injection molding (or injection compression molding) with the transfer surfaces 23a and 23b facing each other. To do. A plastic material, which is a substrate material, is injection molded (or injection compression molded) to produce a disk-shaped nonmagnetic substrate 11. The form of the transfer surfaces 23a and 23b of the stampers 23A and 23B is transferred to the substrate 11. Thereby, the surface roughness Ra of the one surface 11a of the substrate 11 is 2 nm or less, and the other surface 11b is constituted by the guard band groove 13 or the like. The depth of the guard band groove 13 and the like can be controlled by the coating thickness of the photoresist layer 22 and is usually set to 50 to 200 nm.
[0034]
After the molding, the substrate 11 is taken out of the mold 24, and as shown in FIG. 9E, the magnetic layer 2 and the protective layer (not shown) are sequentially formed on both surfaces 11a and 11b by the sputtering method. . Thereafter, in order to remove fine protrusions on the protective layer, burnishing is performed with a brush 25 as shown in FIG. 9 (f), and finally, lubrication is performed on the protective layer as shown in FIG. 9 (g). Agent 26 is applied.
[0035]
Also in the magnetic disk M of this form, the non-magnetic substrate 11 having a disk shape is formed by injection molding (or injection compression molding) of the plastic, so that the substrate 11 can be manufactured in large quantities and at low cost. Further, the surface roughness Ra of one surface 11a of the substrate 11 is set to 2 nm or less, and the other surface 11b is constituted by the concavo-convex portion 10 including the guard band groove 13, whereby the substrate 11 is molded with a mold 24. When the mold is released, the frictional force with the other surface 11b of the substrate 11 is small, and the substrate 11 is hardly deformed as described above, and the flatness of the entire substrate 11 is improved.
[0036]
Next, a method for magnetizing the magnetic disk M will be described with reference to FIG.
First, as shown in FIG. 10A, the magnetic layer 2 formed on the surface of the substrate 11 is saturated and magnetized in one direction (black arrow direction) with a strong magnetic field 32A by the magnetizing magnetic head 31. Thereafter, as shown in FIG. 10B, a weak magnetic field 32B in the reverse direction is applied to the magnetic layer 2 by the magnetic head 31, and the magnetic layer corresponding to the convex portion 33 on the surface of the substrate 11 is applied. Only 2 is magnetized. As a result, as shown in FIG. 10C, a leakage magnetic flux 35 is generated from the concave portion 34 on the surface of the substrate 11. Therefore, by detecting the leakage magnetic flux 35 with the magnetic head 12, a signal corresponding to the pitch can be detected as shown in the lower part of FIG.
[0037]
FIG. 11 and FIG. 12 show a magnetic recording / reproducing apparatus N provided with the magnetic disk M. In both figures, a spindle motor 44 is installed in a case 43 consisting of a base 41 and a cover 42 fitted to the base 41. One or a plurality of magnetic disks M can be mounted so as to be substantially coaxial with the rotation center of the motor 44.
[0038]
Reference numeral 45 denotes an actuator for shifting the magnetic head arranged in the case 43, and is composed of, for example, a voice coil motor. The actuator 45 is configured to position the magnetic head 12 in the radial direction with respect to the magnetic disk M via a support spring 46. Each operation of the spindle motor 44 and the actuator 45 and the recording / reproducing operation of the magnetic head 12 are controlled by a controller (not shown) provided in the case 43. In the magnetic recording / reproducing apparatus N in this example, the magnetic heads 12 are arranged corresponding to both surfaces of each magnetic disk M described above.
[0039]
As shown in FIG. 13, the magnetic head 12 is supported on the distal end side of the support spring 46 via a slider 51. Such a magnetic head 12 and the slider 51 have a magnetic disk which is generated by the buoyancy generated by the relative movement with the magnetic disk M, the weight of the magnetic head 12 and the slider 51, and the support force of the support spring 46. It is set so as to float at a minute interval of 20 to 200 nm, preferably 50 nm or less with respect to M.
[0040]
When the magnetic disk M of each of the above-described embodiments is magnetically recorded / reproduced by the magnetic recording / reproducing apparatus N, the entire flatness of each magnetic disk M is maintained. The vibration can be suppressed, and the minute distance between the magnetic head 12 and the magnetic disk M can be properly maintained. For this reason, the recording / reproducing operation of the magnetic disk M can be appropriately performed.
[0041]
【Example】
Hereinafter, the embodiment of the magnetic disk of the present invention will be described in more detail.
[0042]
Example 1
As the first embodiment, the surface roughness Ra of one surface 1a of the substrate 1 is fixed to 1 nm, and the surface roughness Ra of the other surface 1b is changed to 1 to 6 nm. The magnetic disk shown in FIG. The magnetic disk was rotated at 3,600 rpm, and the surface deflection of the magnetic disk was measured with a displacement meter using a laser. The surface run-out amount is expressed by the amplitude of one rotation displacement at the outer peripheral portion of the magnetic disk. The result was as shown in FIG. As is apparent from the figure, it has been found that when the surface roughness Ra of the other surface 1b of the substrate 1 is increased to 4 nm or more, preferably 5 nm or more, the surface fluctuation can be largely suppressed. In the present embodiment, a magnetic disk having a magnetic layer formed on both sides of the substrate is shown. However, the same effect as described above can be expected even in a magnetic disk having a magnetic layer provided on only one side of the substrate.
[0043]
In addition, the surface roughness of the substrate surface is “TOPO-2D, 3D” manufactured by WYKO using a phase difference measurement method, “Sutcom 920A” manufactured by Tokyo Seimitsu Co., Ltd. using an astigmatism method, Digital Instruments It can be measured by “Nano Scope II” (manufactured by atomic force microscope). Here, the surface roughness Ra was measured using “TOPO-2D, 3D” manufactured by WYKO. The definition of the surface roughness Ra is based on JIS-B0601. The surface roughness Ra was adjusted by adjusting the polishing of the glass master.
[0044]
Example 2
As the second embodiment, the magnetic disk shown in FIGS. 5 and 6 was produced. With respect to this magnetic disk, the surface runout amount was measured in the same manner as in Example 1. The result was as shown in FIG. From the figure, it was found that even if the surface roughness Ra of one surface of the substrate was 2 nm or less, the surface run-out amount hardly increased.
[0045]
Comparative example
In the same manner as in Example 1, a magnetic disk having the same surface roughness Ra on both surfaces of the substrate was produced. With respect to this magnetic disk, the surface runout amount was measured in the same manner as in Example 1. The result was as shown in FIG. As is apparent from this figure, it has been found that when the surface roughness Ra is 2 nm or less, the amount of surface deflection increases rapidly.
[0046]
【The invention's effect】
As described above, according to the present invention, the surface roughness of one surface of a disk-like nonmagnetic substrate injection-molded or injection-compressed using a plastic is 2 nm or less, and the surface roughness of the other surface is reduced. By setting it to 4 nm or more, there is little deformation of the substrate when releasing from the molding die, and the flatness of the entire substrate can be kept good, thereby effectively reducing the surface deflection of the magnetic disk. Can be reduced.
[0047]
In manufacturing the magnetic disk having the above-described configuration, the first and second stampers having transfer surfaces corresponding to the surface roughness of both surfaces of a disk-shaped nonmagnetic substrate are formed by injection molding or injection compression molding. And forming the substrate by molding the plastic, and simultaneously transferring the transfer surfaces of the two stampers to both sides of the substrate, so that the desired substrate can be obtained without causing a significant increase in manufacturing cost. It can be easily obtained in large quantities. Furthermore, by using the magnetic disk having the above-described configuration, it is possible to easily obtain a magnetic recording / reproducing apparatus capable of appropriately performing a recording / reproducing operation while maintaining a fine interval between the magnetic head and the magnetic disk.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a magnetic disk according to a first embodiment of the present invention.
2 is an enlarged cross-sectional view of a portion A in FIG.
FIG. 3 is a cross-sectional view showing an example of a substrate molding die for the magnetic disk.
FIG. 4 is a cross-sectional view showing the method of manufacturing the magnetic disk in the order of steps.
FIG. 5 is a cross-sectional view showing a magnetic disk according to a second embodiment of the present invention.
6 is an enlarged cross-sectional view of a portion A in FIG.
FIG. 7 is a perspective view showing a surface structure of the magnetic disk.
FIG. 8 is an explanatory diagram of the track format of the magnetic disk.
FIG. 9 is a cross-sectional view showing the method of manufacturing the magnetic disk in the order of steps.
FIG. 10 is an explanatory diagram of a method of magnetizing the magnetic layer of the magnetic disk.
FIG. 11 is a plan view showing a magnetic recording / reproducing apparatus equipped with the magnetic disk of the present invention with a cover removed.
FIG. 12 is a sectional view of the magnetic recording / reproducing apparatus.
FIG. 13 is an explanatory diagram of a floating state of the magnetic head.
FIG. 14 is a characteristic diagram showing the measurement results of the surface runout amount of the magnetic disk of Example 1.
15 is a characteristic diagram showing the measurement results of the surface runout amount of the magnetic disk of Example 2. FIG.
FIG. 16 is a characteristic diagram showing the measurement result of the surface runout amount of the magnetic disk of the comparative example.
[Explanation of symbols]
1,11 Disc-shaped non-magnetic substrate
1a, 11a One side of the substrate
1b, 11b The other side of the substrate
2 Magnetic layer
10 Concavity and convexity
13 Guard band groove
23A First stamper
23a First stamper transfer surface
23B Second stamper
23b Transfer surface of second stamper
24 mold
a Circumferential direction

Claims (1)

Surface roughness of a surface roughness corresponding to the surface roughness of the one surface of the disc-shaped non-magnetic substrate and a first stamper having the transfer surface 2 nm, corresponding to the surface roughness of the other surface of the substrate A second stamper having a transfer surface of 4 nm or more is placed in a mold for injection molding or injection compression molding with the respective transfer surfaces facing each other, and the plastic is injection molded or injected in this mold. At the same time as forming a disk-shaped non-magnetic substrate by compression molding, the surface roughness of each transfer surface is transferred to the substrate, and then the substrate is released from the mold. A disk-shaped non-magnetic substrate is produced in which the surface roughness of one surface of the substrate is 2 nm or less and the surface roughness of the other surface is 4 nm or more and the flatness of the entire substrate is ensured with less deformation. characterized by producing a magnetic disk by providing a magnetic layer on both surfaces of the substrate Manufacturing method of the gas disk.

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