JP2002015418A - Magnetic disk and method of manufacturing magnetic disk - Google Patents

Abstract

[PROBLEMS] To reduce the time of a servo write process by a servo pattern preform process by a magnetic pattern forming process, and as a result, to reduce the manufacturing cost of the entire manufacturing process. . In addition, another object is to enable highly accurate head position detection. The present invention proposes a disk manufacturing method for preforming first and second magnetic patterns (301, 302) constituting a null servo pattern on a disk by a magnetic pattern forming process. The first and second magnetic patterns 301 and 302 have different coercive forces and magnetic characteristics of the same remanent magnetization, and are alternately arranged in the radial direction and the circumferential direction of the disk.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic disk in which a null servo pattern included in a servo data pattern is preformed, particularly to a hard disk drive, and a method of manufacturing the magnetic disk.

[0002]

2. Description of the Related Art In recent years, a hard disk drive (H) using a magnetic disk (hereinafter simply referred to as a disk) as a recording medium has been developed.
DD) has attracted attention not only as a personal computer but also as a storage device for various digital devices because of its characteristics such as large capacity and high-speed access.

As shown in FIG. 8, the HDD is roughly divided into a mechanical system 1 including a head / disk assembly and an electronic circuit system 2 including a servo system and a data recording / reproducing system.
It is composed of The mechanism system 1 includes a disk 10,
A spindle motor 11 for rotating the disk 10, a magnetic head (hereinafter simply referred to as a head) 12 that floats on the disk 10 to record and reproduce data, and a head 12
, And a voice coil motor (VCM) 14. Head arm 13 and VC
M14 constitutes an actuator for moving or positioning the head 12 to a target position on the disk 10 by floating or sliding. Head 12 is MR
A read head composed of elements (including GMR elements and the like) and a write head composed of an inductive thin-film head are composed of a slider separately mounted.

The electronic circuit system 2 has a disk controller (HDC) 20 and is connected to a host system 3 such as a personal computer and various digital devices via the HDC 20 to record and reproduce data (read / write data) and data. Transfers various commands. The above H
In addition to the DC 20, a read / write channel (channel I
C) 21, a CPU 22, a memory 23, and a VCM driver 24. The channel IC 21 is a read / write signal processing circuit, and has a function of modulating (encoding) user data (recording data) transferred from the host system 3 into a magnetic recording signal. In addition, the channel IC 21
Has a function of decoding a magnetic recording signal reproduced by a read head into original user data. Channel I
C21 is a flexible print cable (FP
C) the head 1 via the head amplifier circuit 16
2 are connected. The head amplifier circuit 16 amplifies a read signal (magnetic recording signal) read by the read head and sends the amplified signal to the channel IC 21. The head amplifier circuit 16 converts a recording signal from the channel IC 21 into a write current and writes the write signal. It has a write amplifier (current driver) for sending to the head.

[0005] The CPU 22 controls the operation of the HDD including the data recording / reproducing operation by executing software stored in the memory 23. Also, the CPU 22
It is the main element that constitutes the servo system described later,
The positioning control of the head 12 is executed using the servo data reproduced by the channel IC 21. The VCM driver 24 is an element of the servo system, and supplies a drive current for driving and controlling the VCM 14 based on a control value from the CPU 22.

The aforementioned servo system is a mechanism (CPU 2 is a main element) for controlling the positioning of the head at a target position (a target track or a target cylinder to be accessed) on the disk. The servo system detects the position of the head (track position and position within the track range) using servo data recorded in a predetermined area on the disk, and is a feedback control system that causes the head to follow a target position. is there. A normal servo system employs a sector servo method, and reproduces servo data recorded in a servo area arranged on a data surface (a single magnetic layer provided on a surface layer) of a disk to perform head positioning control. use.

The disk 10 of the sector servo system is shown in FIG.
As shown in (B), a single magnetic layer 91 is provided in each surface layer region on both surfaces of a disk substrate (for example, a glass substrate) 90. The magnetic layer 91 has concentric data tracks 10 as shown in FIG.
0 is formed over the entire movable range of the head 12. Each track 100 is composed of a data area unit called a servo sector 103 for each fan area having a central angle α [deg]. The number of sectors of the servo sector 103 is defined by “360 / α”.

Each servo sector 103 is composed of a servo area 101 on which a servo data pattern is recorded, and a user data area (consisting of a plurality of data sectors) 102 composed of data sectors which are access units of user data. The servo data pattern includes an address code (track number or cylinder code) for identifying each data track 100, a servo sector number, and a burst pattern. The burst pattern is a position error signal pattern for detecting the position (off-track amount or head displacement) of the head 12 within one track as described later.

[0009] The servo data pattern in the servo area 101 is read by a servo track writer (ST) when the HDD is manufactured.
Recorded by a dedicated device called W). The step of recording the servo data pattern is called a servo write step. In this servo write process, the head 12 (or a dedicated magnetic head attached to the STW) of the HDD mechanism already assembled is positioned at a desired position on the surface of the disk 10 by the positioner attached to the STW, and servo for one track is performed. The write is performed. This servo write operation is repeatedly executed by the number of data tracks set according to the storage capacity of the disk 10.

In the servo write process using such an STW, the processing time required for the servo write increases as the storage capacity of the HDD increases (higher track density). Therefore, the increase in the processing time of the servo write process is one of the factors that increase the manufacturing cost as the storage capacity of the HDD increases. Further, the increase in the servo write process time is caused by disturbance during the servo write and the vibration of the spindle motor for rotating the disk 10.
This increases the probability that the track shape on the disk 10 is distorted, and consequently causes the manufacturing yield to deteriorate.

In the sector servo system, the head position relative to the track at the time when the head 12 passes over each servo area 101 is detected. After the head 12 seeks to the target track, the servo system executes a track following control (tracking operation) for causing the head 12 to follow the range of the target track. In this track following control, a position error (off-track amount or head displacement) which is a distance between the current head position and the target track center line.
The CPU 22 calculates the control operation amount of the VCM 14 and adjusts (displaces) the position of the head 12 according to the control operation amount so that is minimized.

Here, the rotational speed of the disk 10 is R [rp
m] and the number of servo sectors is n, the position error is the sampling frequency Fs (Fs = n × (R / 60) [H
z]). Therefore, Nyquist (Nyqui
st) The position of the head 12 can be controlled in a frequency band (Fs / 2) or less. In general, by increasing the sampling frequency (Fs) and increasing the number of outputs of the control operation amount of the VCM 14 per unit time, the servo band, which means a frequency band for suppressing a position error, is broadened, and It is known that positioning accuracy can be improved. Therefore, by increasing the servo bandwidth, it is possible to promote a higher track density of the HDD.

However, to increase the servo bandwidth, it is necessary to increase the number n of servo sectors. In the sector servo method, an increase in the number n of servo sectors results in a decrease in the user data area. Therefore, when the number n of servo sectors is increased for widening the servo bandwidth, the format efficiency, which is the ratio between the servo area 101 and the user data area 102, is reduced, and as a result, an increase in the storage capacity of the HDD is prevented. .

By the way, in a conventional HDD, an amplitude integration type position detection method is generally used as a method of detecting a head position within a track range. In the amplitude integration type position detection method, the servo area formed on the disk is as shown in FIG.
, The preamble 140, the servo mark 14
1, an address code 142, and a burst pattern unit 143 including a plurality of burst blocks (A to D). The preamble 140 is used for automatic gain adjustment (AGC) of a magnetic reproduction signal from a head, phase synchronization (PLL) of an internal clock of the channel IC 21 with respect to a signal frequency, and the like. The servo mark 141 is used as a reference timing signal when generating the address code 142 and the burst blocks (A to D). The address code 142 includes a track number (cylinder code) and a servo sector number, and corresponds to coarse movement information of a head position on the disk 10 and is used for seek control.

Each of the burst blocks (A to D) has a configuration in which positive magnetization dislocation lines and negative magnetization dislocation lines are alternately arranged. The length of each magnetization dislocation line corresponds to a track pitch TP which is a center distance between adjacent tracks. Here, N, N-1, and N + 1 indicate the center lines of the tracks N, N-1, and N + 1, respectively.

Each burst block (A to D) is used for detecting a head position (fine movement information) within one track. The ends of the magnetization dislocation lines of the burst blocks A and B correspond to the track center lines (N, N-1, N + 1). Also,
The ends of the magnetization dislocation lines of the burst blocks C and D are TP / 2 in the disk radial direction (arrow D1) from the track center line.
This corresponds to a position offset by an amount. A portion 144 of each of the burst blocks (A to D) having no magnetization dislocation line is an erased region.

Next, the operation principle of the head position detection by the amplitude integration type position detection method will be described with reference to FIG.

In FIG. 15A, the vertical axis represents a value (burst integrated value) obtained by integrating the amplitude value of the reproduction signal (read signal from the head) from each of the burst blocks (A to D) for a predetermined time, and the horizontal axis represents the value. Indicates the off-track amount (head displacement) TE.
In FIG. 3B, the vertical axis indicates the position error, and the position error signal (PES) 16 due to the burst blocks (A, B).
11 shows a position error signal (PES) 161 due to 0 and burst blocks (C, D).

Assuming that the head is off-track on the burst block in the radial direction (D1) of the disk, the amplitude (integral value) of the reproduction signal from each burst block (A to D) is equal to the off-track amount. It increases and decreases periodically with respect to 2TP. Here, the reason why the amplitude of the reproduction signal is integrated for a certain period of time is to remove medium noise, electromagnetic conversion noise, system noise, and the like by an averaging effect.

As shown in FIG. 15A, reproduced signals 150 and 151 from the burst blocks (A) and (B) are
It changes in proportion to the off-track amount near the center of the track, and changes nonlinearly with the off-track amount near the position offset from the track center by TP / 2. On the other hand, the reproduced signal 1 from the burst blocks (C) and (D)
Numerals 52 and 153 change nonlinearly with the off-track amount near the track center, and change in proportion to the off-track amount near the position offset from the track center by TP / 2. In this case, the reason for the non-linear change is that, unless the track pitch (TP) and the head width (read head width) exactly match, the reproduction near the center of the magnetization dislocation line or the center of the erased region 144 is performed. This is because the output amplitude is saturated.

Using the integrated values (denoted as IA to ID) of the reproduced signals from the burst blocks (A to D), the head is located from the following arithmetic expressions (1) and (2). Position errors PEab (ie, PES160) and PEcd (ie, Pcd) corresponding to the distance from the center line in the track.
PES 161) is required.

PEab = (IA−IB) / (IA + IB) (1) PEcd = (IC−ID) / (IC + ID) (2) Here, the burst in which the integral value changes in proportion to the offset amount. By selecting a block, a position error signal (PES) can be uniquely obtained for the head offset amount. However, when the reproduction signal amplitude fluctuates due to fluctuations in the flying height of the head, there is a problem in that an erroneous PES is obtained. In order to solve such a problem, as shown in the equations (1) and (2), a method of normalizing by a sum of integral values from two adjacent sets of burst blocks is adopted. In addition, the PES 160 and PPES 161 have an off-track amount (T
Since there is a position that is non-linear to E), it is common to select and use one of the PESs that changes in proportion to the offset amount (see FIG. 15B). ). Therefore, in the amplitude integration type position detection method, at least four burst blocks (A to D) are required in order to cope with the saturation problem of the reproduction signal amplitude and the fluctuation of the head flying height.

As a position detection method other than the amplitude integration type position detection method, a null (Nu11) servo method has been proposed (IBM Technical Discl).
osure Bulletin "Nu11 servo
pattern, Vol. 18, No. 8, Janu
ary 1976, pages 2656/7, and
USP 4,412,165 "Sampled Serv
o Position Control System "
Etc.). Servo data pattern used in the null servo method (hereinafter referred to as null servo pattern)
Is different from the amplitude integral type servo pattern in the configuration of the burst block.

The null servo system will be described below with reference to FIGS.
This will be described with reference to FIG.

In the null servo system, the preamble 140, the servo mark 141, and the
The address code 142 is the same as that of the above-described amplitude integration type servo pattern (see FIG. 10). On the other hand, burst block 2 in the burst pattern section
No. 00 is magnetically recorded such that the direction of the leakage magnetic field from the magnetization dislocation lines (200N and 200S) between adjacent regions with respect to the track center line is opposite to the radial direction. In the circumferential direction of the disk, a positive magnetization dislocation line (for example, 200S)
And negative magnetization dislocation lines (for example, 200 N) are alternately arranged.

With such a configuration of the burst pattern portion, as shown in FIG. 10, when the head moving positions 110A to 110C in the circumferential direction are assumed, the amplitude characteristic of each reproduced signal is as shown in FIG. As shown, the signal waveform 111A indicates the maximum amplitude value, the signal waveform 111B indicates almost zero, and the signal waveform 111C indicates the maximum amplitude value. That is, in the case of the head moving positions 110A and 110C,
Each head reproduction output from the burst block 200 has a phase difference of 180 [deg].

Here, as in the case of the amplitude integration type position detection method, the channel IC 21 of the HDD, in accordance with the input of the reproduction signal from the head 12, as shown in FIG. PL
L) is controlled. Further, the reproduction signal output (amplitude) from the head 12 is integrated for a certain period of time (sample hold SH),
The integral value (12
0) is “IR”. Similarly, the burst block 20
0 is integrated for a certain period of time, and an integrated value (121) obtained by adding a positive or negative sign according to the phase to the integrated signal (I)
A ”, the position error signal P is calculated from the following equation (3).
ES is required.

PES = IA / IR (3) Since the position error signal PES is standardized by the integral value IR of the reproduction output from the preamble 140, the head 12
13 (A) is not affected by the flying height fluctuation of
As shown in the figure, the value becomes proportional to the head-off track amount TH. When the head 12 is located at the center of the track, the amplitude value of the position error signal PES is 0 (Nu11). The null servo method has an advantage that even when the track pitch and the read head width do not exactly match, due to the effect of the leakage magnetic field from the adjacent track, the saturation of the read signal amplitude unlike the amplitude integration type does not occur.

[0029]

As described above, in the null servo system, even when the track pitch TP and the read head width do not exactly match, due to the effect of the leakage magnetic field from an adjacent track, the null-integrated type is not used. Since there is an advantage that the saturation of the reproduction signal amplitude does not occur, and there is no influence from the fluctuation of the flying height of the head, the position error signal PES can be obtained ideally in proportion to the head off-track amount TH. . Further, the number of burst blocks included in the null servo pattern can be reduced as compared with the amplitude integration type.

For this reason, a null servo type position detection method,
By combining with the sector servo method, there is an advantage that the problem of format efficiency deterioration due to the servo broadband can be reduced as compared with the case where the amplitude integration type position detection method is used.

However, when the servo write operation of the null servo pattern is performed by the normal STW, a fringe occurs near the track center line due to the influence of the leakage magnetic field from the recording head for recording the burst block 200. Probability is high. Due to this effect, in the null servo method, as shown in FIG. 13B, a portion 130 that changes nonlinearly with respect to the off-track amount TE occurs near zero (0) of the position error signal PES. Also, in the servo write process by the STW, the servo write is performed for each track, so if a slight rotation fluctuation of the spindle motor for rotating the disk occurs during the servo write, the magnetization dislocation line between the adjacent tracks causes the head to move around. Direction (circumferential direction). The fluctuation of the magnetization dislocation line in the circumferential direction causes a decrease in the amplitude of the reproduction signal. Thereby, S
The servo write operation of the null servo pattern using the TW results in erroneous detection of a position error, which leads to a decrease in head positioning accuracy. Further, in the servo write process using not only the null servo method but also a normal STW, the time required for the servo write operation increases with an increase in the capacity of the HDD.
D is becoming a factor that causes an increase in the manufacturing cost.

Accordingly, an object of the present invention is to preform a burst block composed of magnetization dislocation lines on a disk by a servo write step of a servo pattern which is essentially different from a servo write step by an STW, and to form a track center on a track. It is an object of the present invention to provide a magnetic disk having a null servo pattern capable of detecting a position with high accuracy without generating a fringe near a line. It is another object of the present invention to reduce the time required for the servo write process as compared with the conventional servo write process using the STW, and as a result, to reduce the manufacturing cost of the entire manufacturing process.

[0033]

SUMMARY OF THE INVENTION A first aspect of the present invention is as follows.
The present invention relates to a magnetic disk in which a null servo pattern is recorded in a servo area by a pattern forming process such as a semiconductor manufacturing process, not a servo write process using a normal servo track writer.

That is, in the magnetic disk of the present invention, a null servo pattern is provided at a predetermined position on the disk substrate by using a magnetic pattern forming process using a pattern forming mask. The burst pattern included in the null servo pattern is composed of a plurality of positive and negative magnetization dislocation lines in the circumferential direction of the track, and the joining position of the magnetic material corresponding to the magnetization dislocation line and the track boundary adjacent in the radial direction. At the position, it is made of a magnetic material having mutually different coercive forces and magnetic properties of the same remanence.

With a magnetic disk having such a configuration,
When applied to a disk drive, it is possible to realize a null servo method capable of performing high-precision head positioning control without generating a position error signal that becomes non-linear near the track center line. Further, according to the present invention, a null servo pattern having a relatively small number of burst blocks can be preformed on a disk with high precision, and as a result, servo bandwidth can be widened without deteriorating the format efficiency. .

A second aspect of the present invention is a step of forming a null servo pattern, wherein a predetermined pattern is formed in a circumferential direction of a track and a radial direction of a disk by forming a pattern of a magnetic film having a first coercive force. Forming a plurality of positive and negative magnetization dislocation lines in the circumferential direction by forming a first magnetic pattern at intervals of and by embedding a magnetic film having a second coercive force between the first magnetic patterns. Forming a second magnetic material pattern alternately arranged with the first magnetic material pattern at a joining position of the magnetic material to be formed and alternately arranged with the first magnetic material pattern at a track boundary position adjacent in the radial direction. And a method for manufacturing a magnetic disk.

In short, the manufacturing method of the present invention utilizes a pattern forming process such as a semiconductor manufacturing process,
Coercive forces different from each other (Hc1, Hc2: Hc1 <Hc
This is a method of forming the respective magnetic material patterns having substantially the same residual magnetization (Mr), and preforming a null servo pattern on a disk.

With such a manufacturing method, the conventional ST
In a servo write process using W, it is possible to prevent a situation in which fringes are generated near the track center line due to the influence of a leakage magnetic field from a recording head when recording a burst block. Further, it is possible to prevent a situation in which a minute rotation fluctuation of the spindle motor for rotating the disk influences and causes a decrease in the amplitude of the reproduction signal.

Further, in a specific manufacturing process to which the method of the present invention is applied, the surface of each magnetic material pattern having a different coercive force is polished, and each magnetic material pattern is subjected to a magnetizing process (for example, using a dedicated recording head). Are magnetized in mutually opposite directions. In this case, although the magnetic properties are different, each magnetic body pattern made of the same magnetic material is polished, so that a higher flatness (good surface property) is obtained as compared with a case where a magnetic body and a non-magnetic body are polished. It is possible to obtain Thereby, the flying or contact sliding characteristics of the slider on which the head is mounted are improved, and stable reproduction output characteristics are obtained.

In the magnetizing step, the conventional independent erasing step can be reduced by performing the erasing process on the magnetic layer of the user data area other than the servo area on the disk simultaneously with the magnetization of the servo pattern. Can be.

With a disk drive using a magnetic disk manufactured by such a manufacturing method, high-precision head positioning control using a null servo method can be realized. As a result, an increase in storage capacity due to a high track density is achieved. Can be achieved. In addition, since the servo write process can be particularly improved, it is possible to realize an efficient and cost-effective manufacturing process of the entire drive.

[0042]

Embodiments of the present invention will be described below with reference to the drawings.

(Disk Manufacturing Process) A process for preforming a null servo pattern in a servo area on the disk in the disk manufacturing process of the embodiment will be described below with reference to FIG. The disk of the embodiment has the same configuration as the disk of the conventional amplitude integration type position detection method except that the burst block recorded in the burst pattern portion as servo data is a null servo pattern (see FIG. 9). reference). A disk drive using the disk of the embodiment is almost the same as a drive employing a conventional amplitude integration type position detection method (see FIG. 8).

The preform step of the null servo pattern according to the embodiment has a pattern formation process using, for example, a part of a semiconductor manufacturing process, and is completely different from a servo write step by a conventional STW (servo track writer). It is. Hereinafter, the process will be specifically described.

First, as shown in FIG. 1A, a thin film magnetic material 301 having magnetic properties of coercive force (Hc1) and residual magnetization (Mr) is formed on a disk substrate 300 by using a sputtering apparatus. . A resist 400 is applied on the surface of the magnetic body 301.

Next, a mask 401 for forming a desired servo pattern is provided on the resist 400 and exposed by a light source 500 (see FIG. 1B). When this is developed, the unmasked portion of the resist 400
Is removed (see FIG. 1C). In this state, the resist 400 is developed by, for example, ion milling.
The magnetic film 301 immediately below the portion from which is removed is removed (see FIG. 1D).

Here, when the resist 400 is removed, a magnetic film (that is, a first magnetic pattern) 301 having the same shape as the mask shape remains on the disk substrate 300 (FIG. 1E). reference). A magnetic body 302 having a coercive force (Hc2) greater than the coercive force (Hc1) and substantially the same magnetic properties of remanent magnetization (Mr) is formed on the disk substrate 300 in this state by using the above-described sputtering apparatus. Film (see FIG. 1 (F)). That is, the disk substrate 3
00, a magnetic pattern 301 having a coercive force (Hc1)
A magnetic film 302 having a coercive force (Hc2) is formed on the surface of the substrate and in an adjacent section formed by pattern formation.

The surface layer of such a disk substrate 300 is
For example, polishing treatment is performed by a chemical polishing method. By this polishing process, the coercive force (Hc
A magnetic body having a configuration in which the magnetic body patterns 301 of 1) and the magnetic body patterns 302 of the coercive force (Hc2) are alternately formed (see FIG. 1G). Here, in the polishing method of the embodiment, the magnetic properties (coercive force) are different, but the magnetic films 301 and 302 made of the same magnetic material are used.
Therefore, higher flatness (good surface properties) can be obtained as compared with the case where different materials such as a magnetic material and a non-magnetic material are polished. Then, by applying a protective film 303 on the disk substrate 300, the servo pattern preform process is completed (FIG. 1).
(H)).

The above-described servo pattern preform process relates to a burst pattern portion (burst block) which is a null servo pattern. In the actual disk manufacturing process, not only the preform step but also a preamble step of a preamble and an address code and a preform step of a magnetic film in a user data area are required. In this case, if the magnetic characteristic of the magnetic film in the user data area is the same as one of the two magnetic material patterns constituting the servo pattern, the procedure shown in FIG. It can be implemented by almost the same procedure. If the magnetic characteristics of the magnetic film in the user data area are different from those of the two magnetic patterns forming the servo pattern, the user data area is masked during the servo pattern preform process, and the user data area is masked after the preform. Conversely, during the step of sputtering the magnetic film, it is necessary to mask the servo pattern.

(Method of Magnetizing Servo Pattern) Hereinafter, a method of magnetizing the disk 300 on which the first and second magnetic material patterns 301 and 302 are preformed will be described with reference to FIG.
This will be described with reference to FIG.

The magnetizing step is a step of magnetizing the first and second magnetic patterns 301 and 302 so that the magnetization directions thereof are opposite to each other. Specifically, by using a dedicated magnetizing head (recording head) 600 and changing the strength and direction of the recording magnetic field, that is, the value and direction of the current applied to the magnetizing head 600, 2 Generate a magnetization state in the direction.

In the magnetizing step, the disk substrate 300 on which the null servo pattern is preformed is mounted on a spindle motor and rotated to move the magnetizing head 600 as shown in FIGS. 3A and 3B. (Circumferential direction 701, 70
0 indicates the radial direction of the disk) while the null servo pattern is magnetized. The magnetizing head 600 is an inductive type head or a MIG head having a width larger than the head width of the head 12 used in the drive.

Here, the magnetizing head 600 moves in the direction (counterclockwise rightward CCW) shown in FIG.
A magnetic field Ha (Ha> Hc2) is generated. This allows
The entire magnetic layer in the burst block 200 is magnetized rightward (magnetization direction 800A). Next, FIG.
As shown in FIG. 7, the magnetic field Hb (Hc1 <Hb <Hc) is generated by the magnetization head 600 in the CW direction (clockwise or leftward).
2) is generated. As a result, the magnetization direction of the second magnetic pattern 302 having the coercive force (Hc2) is changed in the CCW direction 8.
00A, and the magnetization direction of the first magnetic pattern 301 having the coercive force (Hc1) is 800B in the CW direction. At this moment, an opposing magnetic field is formed in the thin-film magnetic layer, so that a magnetic field is generated outside the disk surface from the joining position of the two magnetic bodies 301 and 302. This junction position becomes the magnetization dislocation line (200N, 200S in FIG. 10). When the servo pattern is magnetized, it is efficient to perform an erase process on the magnetic film in the user data area on the disk.

(Configuration of Null Servo Pattern) By the preform process and the magnetizing process, as shown in FIG. 2A, the servo areas on the disk substrate 300 have different magnetization directions and coercive forces. A null servo pattern (burst block 200) composed of different magnetic material patterns 301 and 302 is formed. In addition, FIG.
(C) shows aA and bB shown in FIG.
FIG. 4 is a diagram showing a radial cross section in FIG.

By the way, as shown in FIG. 4, the servo data pattern in the null servo system of the embodiment is specifically a preamble 140, a servo mark 141, an address code 142, a burst block (denoted as a burst pattern A) 200. And burst block (block B)
201. Burst block (burst pattern B
Will be described later.

Preamble 140 and servo mark 14
Numeral 1 is composed of a plurality of positive and negative magnetization dislocation lines continuous from the inner circumference to the outer circumference of the disk (that is, coercive force (Hc1),
(The joining position of each magnetic body of (Hc2) is located on the disk radiation). The address code 142 has a magnetization dislocation line configured to reproduce a magnetic signal corresponding to a track number (cylinder code) or a servo sector number.

In the burst pattern A and the burst pattern B, both ends of the magnetization dislocation line having the length TP (track pitch) are located on the track center line, and the direction of the leakage magnetic field from the magnetization dislocation line is opposite in the adjacent track. It is configured as follows. The burst pattern B is formed at a position where the burst pattern A is offset by TP / 2 in the radial direction of the disk. Address code 1
42 may be located after the burst blocks 200 and 201. Here, FIG. 2A shows a trajectory 11 when the head moves on the burst pattern A in FIG.
It shows the disk cross section at 0A.

(Disk Drive) A description will now be given, with reference to FIGS. 5 to 7, of head positioning control of a disk drive (HDD) using a disk on which a null servo type servo pattern is formed according to the embodiment.

When the head 12 moves on the servo pattern as shown in FIG. 6A, a reproduced signal waveform shown in FIG. 6B is obtained. In the channel IC 21 of the drive,
The output of the read signal from the preamble 140 automatically adjusts the gain of the read amplifier, and the PLL synchronizes the channel IC internal clock with the read signal frequency (or n times the read signal frequency). After that, the channel IC
At 21, the amplitude of the magnetic reproduction output from the latter half of the preamble, the burst pattern A, and the burst pattern B is integrated for a certain period of time (that is, equivalent to the total amplitude of the reproduction output sampled and held in synchronization with the internal clock). Further, an integral value IR (output 120) to which a positive or negative sign is added according to the phase of the reproduction output (output 120), and a burst integral value IA
(Output 121) and burst integration value IB (output 122)
Is calculated. The above equation (3) is replaced by the burst integrated value IA.
And the position error signal 900 (PES-A) and the position error signal 9 shown in FIG.
01 (PES-B) is required. In this embodiment, since the two magnetic materials forming the magnetization dislocation line are preformed, the position error signal 900 (PES-A) and the position error signal 901 (PES-B) are respectively the head off-track amount TH. It has linearity in relation to That is,
PES-A and PES-B change at a period of 2TP while being out of phase with each other by TP / 2. Drive C
PU22 is a position error signal (PES-A, PES-B)
, The track following control and the seek control of the head 12 are executed.

When the preformed disc is incorporated into the spindle motor 11, the disc (track) is eccentric with respect to the spindle motor rotation center due to the gap between the inner diameter of the disc and the hub supporting the disc. There is. Therefore, at least in the track following control, as shown in FIG. 7, a feedforward control system that learns and estimates the amount of eccentricity of the disk and generates an operation amount C that suppresses the eccentricity is replaced with a normal track following control system. Must be used together. The feedforward control system detects an eccentricity EC included in the position error PE between the target position PR and the displacement Y of the head, and includes an element 71 for calculating an eccentricity suppression operation amount ECS for suppressing the eccentricity EC. Have. The feedforward control system controls the operation amount calculated by the control element 70 (control value based on the position error PE).
The plant (actually, the VCM 14 for driving the head) is obtained from the operation amount C obtained by adding the eccentricity suppression operation amount ECS to the plant (actually, the VCM 14 for driving the head).
72 is driven and controlled.

Here, a burst block (burst pattern B) 201 as well as a burst block (burst pattern A) 200 are provided in the servo data pattern of the null servo system of the embodiment. Now, temporarily,
When the head 12 is positioned at the track boundary (± T from the track center line)
When moving on the position (P / 2 offset position), the address code (track number) 142 is obtained from reproduction signals from two adjacent tracks. In this case, the track number to be reproduced corresponds to one of the two tracks. Also, due to the influence of the vibration of the spindle motor in the radial direction of the disk, the track at which the center of the read head is located may be different between when moving on the address code 142 and when moving on the burst pattern A. Therefore, the track number and the position error signal (PES
With only -A), the position where the read head exists when the burst pattern A is obtained cannot be determined exactly.
Here, when the head moves on the track boundary,
The position error signal (PES-B) takes a value near 0. By checking the sign of the position error signal (PES-B), it is possible to determine whether the track is an even track or an odd track. Even if an adjacent track number is reproduced, the track number where the read head exists when the burst pattern A is obtained can be accurately estimated. Therefore, no matter how the head moves with respect to the track position, the position on the track is uniquely determined by the track number and the position error signal (PES-A) by using the burst pattern B. It is possible to do.

As described above, according to the embodiment, the first
In addition, a null servo pattern can be preformed in a servo area of a disk by a magnetic pattern forming process instead of a servo write process using a conventional STW. Therefore, in the conventional servo write process, a fringe is generated on the track center line due to the influence of the leakage magnetic field from the recording head at the time of burst block recording, and changes nonlinearly with respect to the off-track amount near 0 of the position error signal. Can be prevented. Further, it is possible to solve a problem that a minute rotation fluctuation of a spindle motor for rotating a disk influences and causes a decrease in amplitude of a reproduction signal from a head. Therefore, since a highly accurate null servo pattern can be used, the accuracy of head positioning control can be improved.

Second, as compared with the conventional servo write process using the STW, the process of preforming the servo pattern by the pattern forming process has a relatively short processing time and is lower than the equipment cost such as the STW. It can be realized with cost equipment. Therefore, it is possible to reduce the processing time of the entire disk manufacturing process including the servo pattern writing process and the manufacturing cost. As a result, it is possible to improve the efficiency and cost of the manufacturing process of the disk drive incorporating the disk.

Further, by forming the servo pattern by the preform process, a large number of track shapes formed by the servo pattern become perfect concentric circles, and the track pitch margin required when the track shape fluctuates can be reduced. The effect that can be obtained is also obtained. Further, according to the disk manufacturing method of the embodiment, a null servo method having an advantage compared with the conventional amplitude integration type can be realized, such as reducing the number of burst blocks included in the servo pattern. It is possible to maintain and widen the servo bandwidth.

In this embodiment, the case of the longitudinal magnetic recording system in which the circumferential direction of the head and the magnetization direction of the magnetic layer are parallel has been described. The present invention can also be applied to a perpendicular magnetic recording system in which the circumferential direction is perpendicular to the magnetization direction of the magnetic layer. The method of pre-patterning and magnetizing the servo pattern itself can be applied to, for example, an amplitude integration type other than the null servo method.

[0066]

As described above in detail, according to the present invention, a burst block composed of magnetization dislocation lines is formed on a disk by a servo write process of a servo pattern substantially different from a servo write process by an STW. It is possible to provide a magnetic disk capable of performing high-precision position detection without forming a fringe near a track center line after preforming. Further, as compared with the conventional servo write process using the STW, the time of the servo write process can be reduced, and as a result, the manufacturing cost of the entire manufacturing process can be reduced. As a result, the disk drive using the disk of the present invention can improve the manufacturing efficiency and, in particular, can improve the disk formatting efficiency using the null servo method, and as a result, a large capacity disk drive can be realized.

[Brief description of the drawings]

FIG. 1 is a view for explaining a disk manufacturing process related to an embodiment of the present invention.

FIG. 2 is an exemplary view for explaining a configuration of a null servo pattern on a disk according to the embodiment;

FIG. 3 is an exemplary view for explaining a magnetizing method related to the embodiment;

FIG. 4 is an exemplary view for explaining a configuration of a servo data pattern of a null servo system related to the embodiment;

FIG. 5 is an exemplary view for explaining the principle of a null servo system related to the embodiment;

FIG. 6 is an exemplary view for explaining the principle of a null servo system related to the embodiment;

FIG. 7 is an exemplary block diagram showing a track following control system related to the embodiment;

FIG. 8 is a block diagram showing a main part of a conventional disk drive.

FIG. 9 is an exemplary view for explaining the configuration of a disk used in the disk drive.

FIG. 10 is a view for explaining a conventional null servo pattern.

FIG. 11 is a diagram showing a reproduced signal waveform of the null servo pattern.

FIG. 12 is a view for explaining the principle of the null servo system.

FIG. 13 is a view for explaining the principle of the null servo system.

FIG. 14 is a diagram showing a servo pattern for explaining a conventional amplitude integration type position detection method.

FIG. 15 is a reproduction signal waveform diagram for explaining the amplitude integration type position detection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Disc 11 ... Spindle motor 12 ... Head 13 ... Head arm 21 ... Read / write channel (channel IC) 22 ... CPU 140 ... Preamble 141 ... Servo mark 142 ... Address code 200 ... Burst block (null servo pattern A) 201 ... Burst block (null servo pattern B) 300: disk substrate 301: first magnetic pattern 302: second magnetic pattern 600: magnetizing head

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 21/10 G11B 21/10 B F term (Reference) 5D006 BB07 DA03 5D044 AB01 BC01 CC05 DE02 EF05 GK12 5D096 AA02 BB01 CC01 DD08 EE03 GG01 HH14 WW02 5D112 AA05 AA24 DD05 FA04 GA19 GA26

Claims (9)

[Claims] 1. A magnetic disk on which a servo data pattern necessary for head positioning control is recorded as a recording medium of a magnetic disk device, using a magnetic pattern forming process using a pattern forming mask. A magnetic disk, wherein the servo data pattern is provided at a predetermined position on a disk substrate. 2. The servo data pattern includes a burst pattern for generating a position error signal within a range of each track, and the burst pattern includes a plurality of positive and negative magnetization dislocation lines in a circumferential direction of the track. The magnetic servo pattern is formed of a magnetic material having mutually different coercive forces and the same remanent magnetization magnetic characteristics at the joint position of the magnetic material corresponding to the magnetization dislocation line and the track boundary position adjacent in the radial direction. The magnetic disk according to claim 1, wherein 3. The null servo pattern includes a first burst pattern and a second burst pattern for each track, and each position obtained from each of the first burst pattern and the second burst pattern. When calculating the off-track value of the head in accordance with the error signal, the first burst pattern and the second burst pattern are so set that each off-track value is offset by approximately 1/2 track in the radial direction. 3. The magnetic disk according to claim 2, wherein. 4. The magnetic disk according to claim 1, wherein the servo data pattern includes an address code for identifying each track. 5. A method of manufacturing a magnetic disk used as a recording medium of a magnetic disk device, comprising: forming a magnetic film having a first coercive force on a disk substrate; A step of forming a null servo pattern for generation, wherein the pattern forming process of the magnetic film having the first coercive force causes the first magnetic layer to be formed at predetermined intervals in a circumferential direction of the track and a radial direction of the disk. Forming a body pattern, and embedding a magnetic film having a second coercive force larger than the first coercive force between the first magnetic body patterns and magnetizing the plurality of magnetic films in the circumferential direction. The first magnetic material is alternately arranged with the first magnetic material pattern at the joining position of the magnetic material forming the positive and negative magnetization dislocation lines and at the track boundary position adjacent in the radial direction. Forming a second magnetic pattern alternately arranged with the pattern. 6. In the step of forming the second magnetic pattern, after embedding the second magnetic film, the first and second magnetic patterns are made to have the same thickness by polishing. 6. A method for manufacturing a magnetic disk according to claim 5, further comprising a step of configuring said null servo pattern. 7. When the magnetic disk is being rotated,
Using a dedicated recording head, a recording magnetic field greater than or equal to the second coercive force is generated to magnetize the first and second magnetic material patterns in one direction. 7. The method for manufacturing a magnetic disk according to claim 5, further comprising a step of generating a recording magnetic field less than the second coercive force to invert a magnetization direction of the first magnetic material pattern. . 8. A method of manufacturing a magnetic disk used as a recording medium of a magnetic disk device, comprising: a null servo pattern for generating a position error signal within a range of each track on the disk substrate; A first magnetic material pattern having a first coercive force and a second magnetic material pattern having a second coercive force are alternately arranged in the circumferential direction of the track and the radial direction of the disk. Forming a null servo pattern; and, after the step is completed, using a dedicated recording head to generate a recording magnetic field that is equal to or greater than the second coercive force to cause the first and second magnetic material patterns to move in one direction. And a magnetizing step of generating a recording magnetic field that is greater than or equal to the first coercive force and less than the second coercive force to reverse the magnetization direction of the first magnetic material pattern. Method of manufacturing a magnetic disk according to claim. 9. A magnetic disk drive for magnetically recording and reproducing data on a magnetic disk by a head, wherein the magnetic disk is located at a predetermined position by using a magnetic pattern forming process using a pattern forming mask. A position error signal within a range of each track is generated, and a null servo pattern including a plurality of magnetic material patterns having magnetic characteristics of mutually different coercive forces and an address code for identifying each track are generated. And a head positioning control means for controlling the positioning of the head at a target position on the magnetic disk based on servo data obtained by reading the servo data pattern by the head. A magnetic disk drive characterized by the above-mentioned.