JPH04182927A - Magnetic disk - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic disk for a magnetic memory device in which information regarding track positions is embedded in a simple method.

[(Zr Hiroshi P5t7): As the recording density of magnetic disks increases, the track density becomes extremely high. In such cases, servo is applied in a closed loop to accurately position the magnetic head relative to the track.

For this reason, in ancient times, multiple (theoretically, 1
servo information regarding the track position is recorded on the entire surface of one of the magnetic recording surfaces of these disks, and the information is read out with a dedicated read head. Techniques have been used to position a write/read head fixed to the same arm at a desired position. (2) Servo method - In this method, one recording surface and one magnetic disk are occupied by the servo, which is a major drawback in small drives. In a device that uses only one disk, only one of the two magnetic recording surfaces is used for data recording.

In recent years, information regarding track servos is written radially on the recording surface in correspondence with the sectors, and data is written in fan-shaped areas between the areas where information regarding the servos is recorded (hereinafter referred to as servo sections). A recording method (sector servo) is often used, especially in small disk drives.

By the way, like data, this servo information must be magnetically recorded using a magnetic head. However, at the time of writing this servo information, the disk surface is in a "blank state", so it is necessary to provide positional reference information from the outside to position the writing head.

To do this, for example, place the drive (actual machine) with this disk installed on a pedestal, and mechanically move the arm to which the drive head is attached from the outside to finely move the position in accordance with the track. The necessary servo information is written to the disk surface according to the movement.

Currently, most drives write servo information in principle the same way or in a similar way. The device created to write position information onto this blank disk is called a servo track writer. The second operation is performed in a clean room at the factory where the drive is manufactured, with the drive cover not attached.

Servo information regarding this position not only indicates the position in the disk radial direction, but also the position along the circumference must be strictly managed. Otherwise, as the head moves quickly across the track, the position information signal will lose its regularity, causing errors.

For this reason, a rotary encoder is attached to the motor that rotates the disk, and the position in the rotational direction is read and used as a reference.

## is a diagram schematically showing how a magnetic recording pattern is recorded in a conventional sector servo. 21 is a partially enlarged circumferential recording track, n is a format section, and 23 is a user data section. The format section is already written when the drive is shipped from the factory, and the only section that the user can use for recording and playback is the user data section. Servo information regarding the track position is written in the format section. This is recorded by swinging left and right (up and down in the drawing) by a predetermined distance from the regular track center position, and is called a wobble pit. In addition to this, the format section also contains a section indicating the sector number and a synchronization clock pattern for obtaining a reproduction system clock.

When a playback head that is deviated from its normal position reproduces a wobble focus, there will be a difference in the playback of the wobble pit that is wobbling left and right, so you can know the deviation from its normal position from this. Also, it may be known which side the timing of the reproduced signal is shifted to.

FIG. 3 is a diagram schematically showing the arrangement of servo patterns on the disk. 31 is disk, 32 is medium/CAL
, 33 is the M city zone, M is the phrase i-track link, 35 is the format section, and % is the user data section.

[Problems to be Solved by the Invention] In the conventional example, in order to move the head arm from the outside, this work must be performed with the drive cover removed. In other words, unless the work is carried out in a clean room, the disk surface will be contaminated with dust.

Furthermore, since two drives are mounted on the servo track writer to write one track at a time, it takes more than 10 minutes per drive.

For this reason, if mass production is attempted using this method, (1) it is necessary to prepare a large number of complicated and expensive writing devices (servo track writers).

(2) This work requires a large space in the clean room.

Problems such as this arise.

This in turn becomes a major cause of increasing the manufacturing cost of the drive.

An object of the present invention is to solve the above problem by creating servo information on the magnetic disk at the time of manufacturing the disk.

[Efforts to Solve the Problems] The magnetic disk of the present invention uses a resin molded by injection molding as a substrate, and pits are formed on the surface of the substrate to which the magnetic thin film is applied during the injection molding. It is characterized by

[Function] In the present invention, the disk substrate, which was conventionally made of metal or glass, is made of resin, and information regarding the position used for reference when applying the track servo is created as pits during injection molding. (also called emboss), after it is installed in the drive, the presence of the pit is read out from the head as a reproduction electric signal using a normal magnetic head, and the servo is applied by knowing the deviation from the target track position. .

[Example] FIG. 1 is a partially enlarged sectional view of a disk related to the present invention. This is presented to demonstrate the principle by which the presence of pits is read out as a reproduction signal of a magnetic head.

11 is a substrate made by injection molding, and 12 is a pit made at the time of injection molding. The substrate material is suitably polycarbonate or polyetherimide in consideration of moldability, heat resistance, etc., but is not particularly limited to these as long as it satisfies the desired performance.

B is a base film provided on the resin substrate, and has the effect of increasing the strength with which the magnetic film used for recording signals adheres to the resin substrate. Generally, electroless nickel plating is used.

14 is a magnetic recording film, which is a thin film of ferromagnetic alloy.

This thin film is often applied by sputtering or wet plating.

FIG. 1 schematically depicts an enlarged view of the gap portion of the magnetic head. 15 is a magnetic core, and 16 is a magnetic gap. Although the head is not shown in the figure, due to the action of a slider that holds the magnetic head, it is aerodynamically raised about 0.1 μm above the disk surface.

Since the pits 12 are sufficiently thin compared to the thickness of the magnetic thin film 14f, depressions are formed on the disk surface along the pits provided on the substrate.

Now, the magnetic recording film 14 is magnetized in advance using direct current. This may be done by passing a direct current through the magnetic head, but it is more efficient to magnetize it by passing through a magnetic field created by a large magnet.

When the head follows such a magnetized surface, the number of magnetic fluxes flowing through the head core varies greatly depending on the distance between the magnetic film and the head. That is, when there are pits, the number of magnetic fluxes flowing in decreases and then increases, so that positive and negative voltages are induced.

FIG. 4 is a diagram showing the principle by which a magnetic head passing over a pit detects the presence of a pit.

In FIG. 4(a), 41 and 41° each schematically represent a part of the format portion of two adjacent tracks. 46.46" is the part where format information is recorded magnetically. 42.45.48.
Reference numerals 51 and the like are pits made in the substrate during injection molding, and are recessed in the direction of the paper surface.

The head gap flies over the track indicated by 41 and passes through it. At this time, due to the presence of pits, a sudden change occurs in the amount of magnetic flux flowing into the bed gap, so as shown in FIG. , the wave element λ for the pit 45
6 and 47, waveforms 49 and 50 are induced for the pit 48, and waveforms 52 and 53 are induced for the pit 51.

By performing processing such as integration on the reproduced signal waveform, waveform 6
・The ratio of the amplitude of 44 and waveforms 46 and 47 can be calculated. If the center of the head gap deviates from the normal position of the center of the track (indicated by broken !39 in the figure), the amplitude ratio will no longer be l, and by taking it into the servo circuit as a position error signal, Feedback can be applied to correctly center the image.

Note that the reproduced waveform detected by the effect of the pits shown in the drawings is merely an example and may vary depending on the size of the pits, the length of the head gap, the type of head, etc.

For example, if an MR head is used, the reproduction output is not the time differential value of the magnetic flux but the magnitude of the magnetic flux itself.

Even in such a case, it is similarly possible to obtain position error information from pits formed on the wobble by performing appropriate waveform processing. In addition, 40 is 2
This is the boundary between the book tracks and is called the gart band.

In practical use, to ensure safety against noise and defects, it is desirable to repeatedly make several pits and take the average.

In reality, the format part is located at the beginning of the sector, and in addition to the servo information used to know the positional error, it also contains the clock pattern, track number, and sector number used to synchronize the circuit that detects the servo signal. A part where the number is written as code data is required. As shown in FIG. 4, this information can be written magnetically using a magnetic head as in the conventional case, but it can also be created at the time of injection molding, like the wobbled pits.

FIG. 5 is a plan view of another embodiment of the disk according to the present invention, which is manufactured based on this idea.

In the figure, the pits representing wobbled servo information indicated at 42, 45, 48, and 51 are the same as the example in Figure 4, but are followed by a number of pits, indicated as 52. . This expresses predetermined format information by the length and spacing of pits, and in the example shown in FIG. 4, what was recorded magnetically was created by embossing at the time of injection molding. Naturally, these pits designated 52 are located correctly aligned with the center of the track. In this example, the process of writing format information before the drive is shipped from the factory can be eliminated, so the effect is even greater.

[Effects of the Invention] As described above, the present invention provides the following effects.

1. Since the information regarding the track position is embedded at the same time as the substrate is manufactured by injection molding, no special writing equipment or process is required. Creating pits and grooves using injection molding is a technology that has been put to practical use in optical discs, so there is no problem.

2. Since the above operations are performed during the disk manufacturing process, the drive assembly process is completely free from servo signal writing operations.

Therefore, the disk of the present invention makes a significant contribution to reducing drive assembly time and costs associated with assembly.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of a local part of a disk related to the present invention. 11・・・・・・・・・・・・Substrate 1 made by injection molding
2...Pit 14...Magnetic recording film I5...
・・・・・・Magnetic core 16 ・・・・・・・・・Gap Figure 2 schematically shows how magnetic recording patterns are recorded in a conventional sector servo. Figure. 21...... Enlarged part of a circumferential recording track 22... Format section 23...
......User data section 24...
. . . Servo information regarding track position FIG. 3 is a diagram schematically showing the arrangement of servo patterns on the disk. 31・・・・・・・・・Disc, 32・・・・・・
・・・・・・Center hole, 33・・・・・・・・・Recording zone, 34・・・・
・・・・・・Recording track, 35・・・・・・・・・
...Format section, 36...User data section Figures 4 (a) and (b) are diagrams showing the principle by which a magnetic head passing over a pit detects the presence of a pit. . 4I and 41' ・・・・・・・・・Part of the format part of two adjacent tracks 46.46゛ ・・・・・・・・・Format information is transferred by magnetic method Recorded parts 42.45.48.51...Pits drilled in the substrate during injection molding 43.44.46.47.49.50.52.53...
...Head output waveform FIG. 5 is a plan view of a disk according to another embodiment of the present invention. 52・・・・・・・・・・・・ Above the pit Figure 1 Figure 4 (a)

Claims (1)

[Claims] 1. A magnetic disk that magnetically records and reproduces information using a magnetic head, the magnetic disk having a resin molded by injection molding as a substrate, and a magnetic thin film on the substrate. A magnetic disk characterized in that pits are formed on the surface of the disk during the injection molding. 2. Claim 1, wherein the pits are provided in a positional relationship corresponding to a magnetically recorded track.
The magnetic disk described.