JPH09167339A - Magnetic disk and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively provide a magnetic disk having a recording density exceedingly higher than the recording density of a magnetic disk having the highest recording density currently used. SOLUTION: This magnetic disk is constituted by perforating recording tracks 21 on a nonmagnetic substrate with a density of >=8.35KTpi to obtain the surface recording density of >=0.9Gbit/inch<2> . This process for production is executed by forming a plastic substrate having rugged preformat patterns formed by an equipment and method similar to these of the prior art, then baking the plastic substrate to cause thermal shrinkage, thereby producing a high-purity amorphous carbon substrate. The preformat patterns formed on the amorphous carbon substrate by the ratio corresponding to the shrinkage rate of the plastic substrate are made finer and the recording density thereof is made higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk and a method for manufacturing the same, and more particularly, to a magnetic disk having a non-magnetic substrate having a concavo-convex preformat pattern formed on the surface thereof, and manufacturing of such a magnetic disk. With respect to the method.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Laid-Open No. 3-86912.
As described in Japanese Unexamined Patent Publication (Kokai), a magnetic layer is formed on a pre-format pattern forming surface of a non-magnetic substrate on which pits for recording information and guard band grooves for magnetically separating adjacent tracks are pre-formatted. A magnetic disk formed by forming a magnetic disk has been proposed. The non-magnetic substrate is
A master disc called a stamper on which a reverse pattern of the pre-format pattern is formed is produced from a disc master on which a desired pre-format pattern is accurately formed, and then a molding die in which this master disc is mounted is manufactured. It is reproduced by filling molten plastic by injection molding or the like.

The disc master is formed by forming a photoresist layer having a constant thickness on a smooth glass disc, and the disc master with the pre-format pattern is a photoresist while rotating the disc master. A laser beam intensity-modulated by a required preformat signal is focused on the photoresist layer through an objective lens arranged opposite to the layer, and a latent image corresponding to the preformat signal is recorded, and then this exposed master disc is recorded. Is developed and the latent image portion is selectively removed.

As the pits, servo pits for guiding the magnetic head device along recording tracks formed on the magnetic disk, header pits for recording header information of each recording track, or read-only user information is recorded. ROM pits and the like are formed as necessary. The servo signal, the header signal, and the ROM signal are forcibly magnetized in one direction on the magnetic layer formed on the substrate as described in Japanese Patent Laid-Open No. 3-228219, or the entire magnetic layer is exposed to a strong magnetic field. Is forcibly magnetized in one direction, then only the magnetic layer formed on the pit surface is magnetized in the opposite direction with a weak magnetic field, and the leak magnetic field generated from the uneven portion of the magnetic layer can be read by the magnetic head device. .

As described above, the magnetic disk having the pits and the guard band grooves formed on the surface of the substrate can finish the physical format at the time of molding the substrate. Therefore, after forming the magnetic disk, the format signal is recorded one by one. It is more convenient to use than other types of magnetic disks, and it is possible to produce a large number of magnetic disks of the same format.
There is an advantage that it can be provided at a low cost. Further, in the magnetic disk having the guard band groove formed on the surface of the substrate, since adjacent tracks are magnetically separated, there is no signal crosstalk and signal recording with a high C / N ratio (carrier to noise ratio) is performed. There is an advantage that it can be realized.

[0006]

By the way, in this type of magnetic disk, improvement of recording density, that is, increase of recording capacity is one of the most important technical problems. In order to improve the recording density and the recording capacity, the width of the recording track is narrowed, the track pitch is reduced, and in a magnetic disk having information pits such as servo pits, header pits or ROM pits, It is necessary to downsize the pit.

As described above, the non-magnetic substrate is duplicated from the disc master on which the desired preformat pattern is accurately formed, and the disc master with the preformat pattern is strengthened by the required preformat signal in the photoresist layer. It is made by focusing a modulated laser beam. Therefore, the width and track pitch of the recording track, and the size of servo pits and information pits are determined by the wavelength of the recording laser and the numerical aperture of the objective lens used, and the shorter the wavelength of the recording laser and the smaller the objective lens used. The larger the numerical aperture, the finer the preformat pattern can be formed.

However, as the miniaturization of the preformat pattern progresses, the precision of the preformat pattern deteriorates,
Since the error rate of the reproduction signal becomes high, it is meaningless to miniaturize the preformat pattern ignoring the performance of the recording / reproducing apparatus used. From this point of view, the inventors of the present application previously considered the performance of the recording / reproducing apparatus currently used, and then used a recording laser beam with a wavelength of 351 nm and an objective lens with a lens numerical aperture of 0.9, Track density is 7.1 KTpi (pitch width is 3.6 μm), linear recording density is 100 Kbpi, areal recording density is 710 Mbit / in.
It was clarified that the information recording of ch ² can be achieved (40
th Annual Conference Magnetism and Magnetic Materia
ls Nov.6-9, 1995, BQ-06). At the current technical level of the relevant technical field, it is considered that obtaining such a recording density is the limit.

Further, if a laser having a shorter wavelength and more excellent stability is developed, or an objective lens having a larger lens numerical aperture is developed, a higher density can be realized. However, we cannot expect that these developments will be made in a short period of time. Further, it is possible to adopt a technical method of compensating for an increase in error rate due to miniaturization of the preformat pattern by improving the signal processing circuit of the recording / reproducing apparatus. Since the recording / reproducing apparatus becomes very expensive, it is not feasible at present.

The present invention has been invented in view of such circumstances, and an object of the invention is to provide a magnetic disk at a low cost, which has a remarkably high recording density as compared with a current product.

[0011]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a magnetic disk device in which a magnetic layer is laminated on a pre-format pattern forming surface of a non-magnetic substrate to provide a magnetic head device. In a magnetic disk in which information is recorded or reproduced by magnetic means by running along recording tracks provided on the non-magnetic substrate, the recording tracks are arranged in a radial direction of the non-magnetic substrate at a density of 8.35 KTpi or more. Arranged and 0.9 Gbit /
The structure has an areal recording density of inch ² or more.

As the pre-format pattern formed on the surface of the non-magnetic substrate, there are guard band grooves for partitioning adjacent recording tracks, servo pits for guiding the magnetic head device along the recording tracks, or read-only information. At least one of the information pits to be recorded can be formed. Further, as the information pit, a header pit for recording header information of each recording track or a ROM pit for recording read-only user information can be formed. Further, as the servo pits or the information pits, it is possible to form circular ones or elliptical ones in plan view, but in order to obtain a higher C / N ratio, the projections or depressions in square plan view are used. It is preferably formed. In addition,
Texture grooves may be formed on the surfaces of the recording tracks and the pits to reduce frictional forces acting between the recording tracks and the pits. Further, instead of such a configuration, it is possible to provide a head sliding portion composed of a group of fine irregularities for sliding the floating magnetic head device, outside the area where the recording track is formed.

On the other hand, regarding a method of manufacturing a magnetic disk, a step of manufacturing a plastic substrate is a step of exposing a photoresist layer of a disk master to a desired preformat pattern by an optical means, and developing the exposed disk master. The step of processing to form an uneven pre-format pattern on the surface of the master disc, and metal plating is applied to the pre-format pattern forming surface of the developed master disc, and the directions of the pre-format pattern and the irregularities are reversed. A step of forming a metal stamper having a reverse pattern, and a step of molding a plastic substrate having the same concavo-convex pattern as the preformat pattern by filling molten plastic in a mold provided with the stamper, Baking the molded plastic substrate and heat shrinking High purity amorphous carbon substrates were composed of a process of manufacturing.

In order to make the preformat pattern formed on the amorphous carbon substrate much finer than that of the conventional product, it is necessary to form the finest preformat pattern on the plastic substrate, that is, the disk master. Most preferably, when the desired preformat pattern is exposed on the photoresist layer of the disk master, the exposure is performed under the condition that the finest preformat pattern currently considered can be exposed. As an example, while rotating the disk master, a recording laser beam having a wavelength of 351 nm is focused on the photoresist layer by an objective lens having a numerical aperture of 0.9 arranged opposite to the photoresist layer. A method of forming recording tracks with a pitch of 0.6 μm in a spiral shape or a concentric shape concentric with the rotation center of the disk master can be mentioned.

As the raw material of the plastic substrate, it is preferable that the shrinkage rate at the time of firing is small, and especially 15%.
It is preferable to use a plastic material having the above linear shrinkage. Further, as the raw material of the plastic substrate, the transfer property of the preformat pattern is good, and in order to prevent the molten plastic from entering the die mating surface and prevent the formation of burrs, the heat measured by the disc cure method is used. It is particularly preferable to use a granular plastic having a fluidity of 60 to 100 mm. Furthermore, a phenolic resin can be used as a raw material plastic for the plastic substrate, and the molding method for the plastic substrate includes injection molding, injection compression molding, transfer molding,
Alternatively, any molding method selected from extrusion molding can be used. After firing the amorphous carbon substrate, if necessary, a desired surface of the substrate may be subjected to polishing processing so that the surface is mirror-finished.

[0016]

[Function] When a high-purity amorphous carbon substrate is manufactured by baking a plastic substrate, the preformat pattern formed on the plastic substrate has a value corresponding to the contraction rate due to heat contraction of the resin generated in the baking step. Miniaturize. Since a linear shrinkage of about 15% can be obtained with a certain kind of known phenol resin, a preformat pattern equivalent to that of the current highest recording density magnetic disk, that is, a track density of 7.1 KTpi is obtained on the plastic substrate. And the linear recording density is 100 Kbp
By forming the pre-format pattern of i, the track density is 1.18 times 8.35 KTpi,
A 118 Kbpi preformat pattern having a linear recording density of 1.18 can be formed on an amorphous carbon substrate, and an areal recording density of 0.985 Gbit / inch ² can be realized. In this case, the formation of the pre-format pattern on the plastic substrate can be performed by directly applying the conventional technique, and it is not necessary to develop a short wavelength laser light source or an objective lens with a large numerical aperture. It is possible to easily manufacture a magnetic disk having a remarkably large areal recording density as compared with the highest recording density magnetic disk.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the structure of a magnetic disk according to the present invention will be described with reference to FIGS. FIG. 1 is an enlarged perspective view of an essential part showing an example of a preformat pattern formed on a non-magnetic substrate, and FIG. 2 is a perspective view of a magnetic disk.

As is apparent from FIG. 2, the magnetic disk 1 of this example has a circular non-magnetic substrate 2 having a center hole 2a.
And a magnetic layer 3 formed on the surface (preformat pattern forming surface) of the non-magnetic substrate 2. A metal or non-metal center hub may be attached to the center of the magnetic disk 1 as needed.

The non-magnetic substrate 2 is made of high-purity amorphous carbon produced by baking a phenolic resin, and has an uneven preformat pattern as shown in FIG. 1 on its surface. Has been done. As is apparent from FIG. 1, the magnetic disk 1 of the present example is provided with the guard band grooves 13 at equal intervals in the circumferential direction, that is, in parallel with the locus of the magnetic head device 20 indicated by the arrow in the drawing. Adjacent guard band groove 13,
Recording tracks 21 having a constant width and a constant pitch are formed between the tracks 13.

Each recording track 21 is divided into a recording area 18 in which user data is recorded and a servo area 19 in which a control signal is recorded. In the servo area 19, the magnetic head device 20 is formed as a required recording track. 21, a servo pit train 15 for guiding along the track 21, and a phase pit 16 for controlling the recording / reproducing timing of information on each recording track 21.
And a clock pit 17 for drawing in a clock required for recording / reproducing information on / from the recording track 21. As apparent from FIG. 1, the servo pit rows 15 are arranged in a zigzag pattern to the left and right with respect to the track center 14, and the magnetic head device 20 is controlled by controlling the outputs from the left and right servo pits to be equal. Follow the track center 14. In the present embodiment, one of the two servo pits arranged in a staggered pattern is shared with one of the two servo pits arranged in the adjacent tracks, but one of the two servo pits is provided for each recording track. It is of course possible to form the servo pit row 15 as a set. These servo pit rows 15 are arranged at regular intervals of several hundreds, for example, about 800, per recording track circumference.

In the present specification, the phase pit 1
The 6 and the clock pit 17 may be collectively referred to as a header pit. In addition to the phase pits 16 and the clock pits 17, address pits for displaying the address of each recording track 21 may be formed in the recording portion of the header pit. In addition, the recording area 18
Can be formed in a continuous flat band, or ROM pits in which read-only user information such as an operating system, application programs, and dictionary contents of a word processor are recorded can be arranged. These pits can be formed as protrusions or depressions on the substrate surface.

The recording area 18 and the pits 15 to
As shown in FIG. 3, a shallow groove called a textured groove 22 for reducing the frictional force acting between the magnetic head device 20 and the magnetic layer 3 and preventing the magnetic layer 3 from being damaged is formed on the surface of the magnetic recording medium 17 and the like. It can also be formed (see JP-A-63-255816).

The recording area 18 and the pits 15 are also provided.
In the case where the textured groove 22 is not formed on the surface such as 17 to 17, as shown in FIG. 4, a collection of fine irregularities for sliding the floating magnetic head device outside the area where the recording track 21 is formed. It is also possible to provide the head sliding portion 23 consisting of. The width a of the head sliding portion 23 is formed to be at least wider than the sliding width of the magnetic head device (including the slider). Further, the ratio of the protrusion 23a and the recess 23b that form the head sliding portion 23 is appropriately determined by measuring the amount of frictional resistance and the amount of wear. That is, if the ratio of the protrusion 23a to the entire area of the head sliding portion 23 is reduced, the frictional resistance acting between the head sliding portion 23 and the magnetic head device can be reduced, but on the other hand, the amount of wear of the magnetic layer 3 increases, In order to improve the balance between them, the protrusion 2 with respect to the entire area of the head sliding portion 23 is tested.
Determine the proportion of 3a. Specifically, the value of (w ² / p ² ) is preferably about 1 to 10%. The head sliding portion 23 can also be formed by a set of ROM pits.

The card band groove 13 and the texture groove 22 formed on the non-magnetic substrate 2 do not necessarily have to be continuously formed from one end to the other end of the pit or recording area 18, and are formed in the circumferential direction of the substrate. It may be discontinuous as long as it is formed along the locus of the magnetic head device.

If necessary, another film may be laminated on the surface or the base of the magnetic layer 3. For example, a lubricating layer may be provided on the surface of the magnetic layer 3 to reduce the frictional resistance acting on the magnetic head device.

Each pit formed on the non-magnetic substrate 2 is
The plane shape can be formed into a circle or an ellipse, but in order to realize signal reproduction with a high C / N ratio, it is particularly preferable to form the plane shape into a square or a rectangle as shown in FIG. The recording track 21 is 8.35K
The linear recording density of each recording track 21 is 118 Kbpi arranged in the radial direction of the non-magnetic substrate 2 at a density of Tpi or more.
It is manufactured so that In this case, the areal recording density of the magnetic disk 1 is 0.985 Gbit / inch ² .

Since these pieces of information are formed in advance on the non-magnetic substrate 2 by means of unevenness, the initialization at the time of use may be achieved by only magnetizing the magnetic layer 3 in one direction with a strong magnetic field. Information can be read by detecting the leakage magnetic field generated by the unevenness of the magnetic head device 20. Further, in order to increase the output from the leakage magnetic field, the magnetic layer 3 is magnetized in one direction with a strong magnetic field, and then only the magnetic layer on the pit is magnetized in the opposite direction with a weak magnetic field so that the magnetic force in the concave portion and the convex portion is increased. The layer 3 is initialized by magnetizing it in the opposite direction. Further, the magnetic head device for performing the initialization may be a magnetic head device which is sufficiently wider than the track width, which also makes it possible to shorten the initialization time.

The magnetic head device 20 runs relative to the magnetic disk along a recording track 21 provided in the circumferential direction of the non-magnetic substrate and generates a magnetic field between the magnetic layer formed on the recording track 21 and the magnetic layer. Information is recorded or reproduced by magnetic means by exchanging information.

When the servo signal and the header information are recorded in the form of pits on the surface of the substrate as described above, the conventional magnetic disk in which the servo signal and the header information are written one by one by magnetic means after the magnetic disk is manufactured is initialized. Compared to this, it can be initialized in a short time, which makes it convenient to use. Moreover, since the initialization can be performed by a low-priced servo writer that does not require highly accurate positioning, the equipment cost can be reduced.

Further, the recording track 21 is set to 8.35 KTp.
are arranged in the radial direction of the non-magnetic substrate 2 at a density of i or more,
Since the areal recording density of 9 Gbit / inch ² or more is obtained, the magnetic recording medium has the highest recording density as compared with the conventionally known magnetic disk (track density of 7.1 KTpi, areal recording density of 710 Mbit / inch ² ). Also 26
It is possible to realize a large increase in recording density of at least%.

Next, an example of a method of manufacturing a magnetic disk according to the present invention will be described with reference to FIG. As shown in FIG. 5, the magnetic disk manufacturing method of this example includes a disk master cutting step, a stamper manufacturing step, a plastic substrate molding step, a non-magnetic substrate forming step, and a magnetic layer forming step. Consists of. Hereinafter, each of these steps will be described separately for each item.

<Disc Master Cutting Step> First, a disc master is prepared in which a positive photoresist layer having unexposed portions as a pattern is uniformly formed on a smooth and clean glass plate (step S1). The spin coating method can be used for coating the photoresist on the glass plate, and the thickness of the photoresist layer after drying is 0.2 μm.
m. This disc master is attached to a rotating device, and while being driven to rotate at a required speed, an optical cutting device arranged opposite to the photoresist layer is moved in the radial direction of the disc master, and an objective lens provided in the optical cutting device is used. A laser beam whose intensity is modulated by a desired preformat signal is focused on the photoresist layer, and a latent image corresponding to the preformat pattern is recorded on the photoresist layer (step S2). At this time, as the objective lens, one having a lens aperture number of 0.9 can be used. Further, as the laser beam,
A laser beam with a wavelength of 351 nm can be used. When such an objective lens and a laser beam are used, the spot diameter of the laser beam irradiated on the photoresist layer is about 0.4 μm. Further, the rotation of the disc master can be adjusted to a constant number of rotations of 600 rpm, and the feeding speed of the objective lens (laser beam) is 2
It can be adjusted to a constant speed of μm / sec. In this case, the moving amount of the laser beam is 0.2 μm per one rotation of the glass substrate. By using the optical cutting device under these conditions, the track density is 7.1 Ktpi.
(Pitch width is 3.6 μm), linear recording density is 100 Kbp
i, a pre-format pattern having an areal recording density of 710 Mbit / inch ² can be cut on the photoresist layer. In the case where the texture groove is exposed on the surface of the recording area 18 and the pit, the laser light intensity for exposing the pit and the guard band groove and the laser light intensity for exposing the texture groove are appropriately switched, These exposures are continuously performed. That is, when exposing the pits and guard band grooves, the photoresist layer is exposed with a large power capable of exposing to the bottom (film thickness of 0.2 μm), and when exposing the texture grooves, the laser light intensity is adjusted. So-called halftone cutting is performed so that the photoresist layer is exposed to a depth of 0.05 μm. Also, the exposure of the rectangular pit is described in JP-A-2-
It can be carried out by the means shown in 267730. In addition, the formation of the irregular and discontinuous texture grooves described above,
This can be done by inputting random noise to the laser beam modulator that modulates the intensity of the laser beam. The disk master (exposed master) on which the latent image has been exposed as described above is developed, the exposed portion is removed, and an uneven preformat pattern is exposed on the photoresist layer (step S3). The development processing of the exposed master can be performed by a so-called spin development method. After development processing, by performing fixing processing and water washing processing,
It is possible to obtain a cut master (master disc) having a desired preformat pattern.

<Stamper Manufacturing Step> A conductive film is attached to the preformat pattern forming surface of the master disk manufactured as described above by, for example, a vacuum evaporation method,
Then, electroplating (electroforming) is performed using the conductive film as one electrode to form a metal film of nickel or the like (step S4). After that, the interface between the preformatted pattern forming surface of the master disk and the conductive film is peeled off to obtain a metal stamper having a so-called inverted pattern in which the direction of the unevenness is opposite to that of the preformatted pattern (step S
5).

<Plastic Substrate Molding Step> The stamper manufactured as described above is attached to the cavity of the plastic substrate molding die (step S6). Next, the required molten plastic is filled in the cavity, solidified, and then taken out from the mold to obtain a plastic substrate to which the shape of the cavity portion including the inversion pattern is transferred (step S7). A preformat pattern similar to that formed on the master disk is duplicated on this plastic substrate. As a molding method of the plastic substrate, an injection molding method, a compression molding method, an injection compression molding method, a transfer molding method, or the like can be applied. As the molding apparatus and molding method for the plastic substrate having the textured groove 22, the apparatus and method of Japanese Patent Application No. 7-93941 previously proposed by the inventors of the present application are preferably used. As the plastic substrate material suitable for the present invention, those described in JP-A-6-206234 are preferably used. That is, when the light transmittance of 1 mm of the optical path of visible light having a wavelength of 800 nm is 80% or more,
cm ³ per pore diameter 100μm or more, preferably less than one or more pores 20 [mu] m, moreover the metal content 200
A phenol resin high-fluidity molded product having a weight ppm or less is used as a raw material resin and is granulated by, for example, a self-curing modified novolac resin method or a solid resol resin method, and the melting point of the granular phenol resin is 30 to 160 ° C.
The low surface tension substance of the above is a composition ratio of phenol resin to phenol of 0.2 to 5
A phenol resin molding material coated with a weight% amount is used. The granular phenol resin has a water content of 1% by weight or less and a particle size of 50 μm or more,
Thermal fluidity measured by disc cure method is 60-160
mm, more preferably 60 to 100 mm is used. When molding a plastic substrate, the phenol resin molding material is once completely melted and homogenized by high-speed flow (in the case of transfer molding) or kneading (in the case of injection molding or extrusion molding), and then the mold. Fill the inside to mold the desired plastic substrate.

<Nonmagnetic Substrate Forming Step> The plastic substrate produced as described above is subjected to 10 times in an inert gas.
Baking is performed at 00 ° C to 1800 ° C to produce a high-purity amorphous carbon substrate (step S8). In the firing step of step S8, the plastic substrate is three-dimensionally stably shrunk to be miniaturized and thinned. As a result, the preformat pattern transferred to the surface of the plastic substrate is miniaturized. For example, with the phenol resin molding material, a linear shrinkage of 15% or more can be obtained by firing.
Therefore, the preformat pattern formed on the plastic substrate with a track density of 7.1 Ktpi, a linear recording density of 100 Kbpi, and an areal recording density of 710 Mbit / inch ² has a track density of 1.18 times 8.35.
Ktpi, linear recording density of 1.18 times 118 Kb
since the pi, 0.985Gbit / inch ^2, and the areal recording density of about 1 Gbit / inch ² can be achieved. After firing the amorphous carbon substrate, the surface of the substrate is polished with a wrapping tape or the like to finish the substrate surface into a mirror surface (step S9). This step is selectively performed on a necessary surface as needed.

<Magnetic Layer Forming Step> The magnetic layer 3 is formed on the pre-format pattern forming surface of the non-magnetic substrate 2 after firing by a vacuum film forming method such as a sputtering method, as shown in FIG.
The magnetic disk shown in is manufactured (step S10). As the magnetic layer material, it is possible to use a material containing cobalt and chromium as main components, to which nickel, tantalum, platinum or the like is added. The thickness of the magnetic layer 3 is usually 20 nm
It is adjusted to about 60 nm. Incidentally, another film can be laminated on the surface and / or the base of the magnetic film 3 as required. For example, on the surface of the magnetic film 3, the magnetic film 3
Can be laminated with a carbon film for protection, and a burnishing treatment or a lubricant coating is applied on the carbon film to eliminate foreign substances on the substrate so as not to damage the magnetic head device. It can be performed. Further, a chucking hub made of metal or non-metal can be attached to the opening of the center hole 2a of the magnetic disk 1 produced in this way. Further, the magnetic disk 1 manufactured in this way can be housed in a portable cartridge case to be a removable medium.

The results of the scratch test and the wear resistance test of the magnetic disk according to the present invention will be described below with reference to FIGS. 6 and 7. FIG. 6 is a graph showing the results of the scratch test of the product of the present invention in comparison with the conventional product.
FIG. 4 is a graph showing the results of the abrasion resistance test of the product of the present invention in comparison with the conventional product.

In the scratch test, the sliding pin is brought into contact with the surface of the sample substrate, and the load applied to the sliding pin (load output).
While varying variously, the substrate surface was vibrated and the force (cartridge output) acting on the sliding pin was measured. According to this test, the magnitude of the frictional resistance on the substrate surface and the dent of the substrate can be observed. As is apparent from FIG. 6, in the conventional product (APO substrate), the cartridge output suddenly increases when the load output exceeds about 10 g, and the substrate is easily deformed. On the other hand, in the product of the present invention, even if the load output is 50 g, the cartridge output only linearly increases, and it is understood that the substrate is not easily deformed.

The abrasion resistance test was carried out by repeating contact start / stop (CSS) of the magnetic head device on the substrate surface and measuring the increase in the friction coefficient. As is clear from FIG. 7, the conventional product (APO substrate) has a sharp increase in the friction coefficient when CSS is repeated about 100 times and wear resistance is poor. On the other hand, it can be seen that the product of the present invention does not increase the friction coefficient even after CSS is repeated 10,000 times and has excellent wear resistance.

[0040]

As described above, according to the magnetic disk of the present invention, the recording track is 8.35 on the non-magnetic substrate.
Pre-formatted at a density of KTpi or higher and 1
Since the linear recording density of 18 Kbpi or more is obtained, it is possible to realize a surface recording density of about 1 Gbit / inch ² , which is significantly higher than that of the current highest recording density magnetic disk.

Further, according to the magnetic disk manufacturing method of the present invention, the preformat pattern is miniaturized by utilizing the heat shrinkage of the resin generated when the plastic substrate is baked to produce the high-purity amorphous carbon substrate.
As the equipment and method for cutting the preformat pattern on the master disc, the conventional technique can be applied as it is. Therefore, without needing to develop a short wavelength laser light source or an objective lens with a large number of apertures, it is possible to achieve a significantly higher areal recording density than the current highest recording density magnetic disk. A magnetic disk having a high recording density can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is an enlarged perspective view of a main part of a magnetic disk according to an embodiment.

FIG. 2 is a perspective view of a magnetic disk according to an embodiment.

FIG. 3 is an explanatory diagram of texture grooves.

FIG. 4 is an explanatory diagram of a head sliding portion.

FIG. 5 is a flowchart showing a manufacturing process of the magnetic disk according to the example.

FIG. 6 is a graph showing a scratch test result of the product of the present invention in comparison with a conventional product.

FIG. 7 is a graph showing the results of the abrasion resistance test of the product of the present invention in comparison with the conventional product.

[Explanation of symbols]

 1 magnetic disk 2 non-magnetic substrate 2a center hole 3 magnetic layer 15 servo pit row 16 phase pit 17 clock pit 18 recording area 19 servo area 20 magnetic head device 21 recording track 22 texture groove 23 head sliding portion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyoshi Adachi 1-88, Tora, Ibaraki City, Osaka Prefecture Hitachi Maxell Co., Ltd. Within Hitachi Maxell, Ltd.

Claims (15)

[Claims] 1. A magnetic layer is laminated on a preformat pattern forming surface of a non-magnetic substrate, and information is magnetically transferred by running a magnetic head device along a recording track provided on the non-magnetic substrate. In a magnetic disk for recording or reproducing, the recording track has 8.35 KTp
arranged in the radial direction of the non-magnetic substrate at a density of i or more,
A magnetic disk having an areal recording density of 0.9 Gbit / inch ² or more. 2. The magnetic disk according to claim 1, wherein the non-magnetic substrate is formed of high-purity amorphous carbon obtained by baking resin. 3. The magnetic disk according to claim 1, wherein a guard band groove for partitioning adjacent recording tracks is provided on the surface of the non-magnetic substrate as the preformat pattern, and the magnetic head device is provided on the recording track. A magnetic disk, wherein at least one of a servo pit for guiding along or an information pit for recording read-only information is formed. 4. The magnetic disk according to claim 3, wherein the information pit is a header pit for recording header information of each recording track. 5. The magnetic disk according to claim 3, wherein the information pits are ROM pits for recording read-only user information. 6. The magnetic disk according to claim 3, wherein the servo pits or information pits are formed by protrusions or depressions having a square or rectangular planar shape. 7. The magnetic disk according to claim 3, wherein texture grooves are formed on the surfaces of the recording tracks and the pits to reduce a frictional force acting between the recording head and the magnetic head device. Characteristic magnetic disk. 8. The magnetic disk according to claim 1, further comprising a head sliding portion formed outside the recording track forming area, the head sliding portion including a set of fine irregularities for sliding the floating magnetic head device. A magnetic disk characterized by. 9. A method for manufacturing a magnetic disk, comprising forming a plastic substrate having a predetermined shape and then forming a magnetic layer on the surface of the plastic substrate, wherein the step of producing the plastic substrate is desired for a photoresist layer of a disk master. Of exposing the pre-formatted pattern of the disc master by optical means, developing the exposed disc master to form an uneven pre-format pattern on the surface of the disc master, and pre-processing the developed disc master. Metal plating is applied to the format pattern formation surface,
The step of forming a metal stamper having an inversion pattern in which the direction of concavities and convexities is opposite to that of the preformat pattern, and filling the molten plastic in a mold provided with the stamper to make it the same as the preformat pattern A method of manufacturing a magnetic disk, comprising: a step of molding a plastic substrate having a concavo-convex pattern; and a step of firing the molded plastic substrate to produce a heat-shrinkable high-purity amorphous carbon substrate. 10. The method of manufacturing a magnetic disk according to claim 9, wherein when the desired preformat pattern is exposed on the photoresist layer of the disk master, the disk master is rotated while being opposed to the photoresist layer. From the objective lens with a numerical aperture of 0.9
A recording laser beam having a wavelength of 351 nm is focused on the photoresist layer, and recording tracks having a pitch of 3.6 μm are formed in a spiral or concentric shape concentric with the rotation center of the disk master. Production method. 11. The method of manufacturing a magnetic disk according to claim 9, wherein a plastic material having a linear shrinkage rate of 15% or more during firing is used as a raw material of the plastic substrate. Method. 12. The method of manufacturing a magnetic disk according to claim 9, wherein the raw material of the plastic substrate has a thermal fluidity of 60 to 100 m measured by a disk cure method.
A method of manufacturing a magnetic disk, wherein m of granular plastic is used. 13. The method of manufacturing a magnetic disk according to claim 9, wherein a phenol resin is used as a raw material plastic for the plastic substrate. 14. The method of manufacturing a magnetic disk according to claim 9, wherein the molding method of the plastic substrate is any molding method selected from injection molding, injection compression molding, transfer molding, and extrusion molding. A method for manufacturing a magnetic disk characterized by the above. 15. The method for manufacturing a magnetic disk according to claim 9, wherein after the amorphous carbon substrate is fired, a required surface of the substrate is subjected to polishing processing so that the surface is mirror-finished. Method for manufacturing magnetic disk.