JP2004158083A - Magnetic recording medium and magnetic recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reliably prevent alteration of the data on a magnetic recording medium in a magnetic recording device. <P>SOLUTION: At one or more positions on a magnetic recording medium, a write enable flag zone 12 is provided with an asperity pattern to show at least the write enable flag, and a rewrite disable zone (secure zone) 10 which is a normal flat data zone 13 is also provided to write data responding to the flag zone 12. And write enable or disable of the data zone 13 is decided corresponding to the existence of the signal in the flag zone 12. At the initial state, the write enable flag 12 is reproduced and data can be written in the data zone 13.However, when disabling rewriting of this written data, the corresponding write enable flag 12 is dc erased. The flag zone 12 is made into an asperity pattern, and it is hard to recover the flag after erasing. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic recording medium as a magnetic disk having a security function of preventing data tampering due to unauthorized access, and a magnetic recording device such as a hard disk drive using the magnetic recording medium.
In the drawings, the same reference numerals indicate the same or corresponding parts.
[0002]
[Prior art]
In recent years, with the development of computer networks, malicious acts of illegally accessing a recording medium of a magnetic recording device of a server or the like provided through a network and falsifying the contents have been increasing. This is a serious problem in the case of electronic payment and in the field of handling personal information.
Also, in a service in which multimedia contents are digitized and distributed over a network and a license purchaser uses the contents, tampering or copying of the license is a serious problem.
[0003]
However, in the current magnetic recording device, data can be freely rewritten, and it is difficult to completely prevent tampering.
Therefore, as a method of preventing such falsification of the information recording medium, for example, by providing an identifier indicating rewritable / not rewritable to a part of a sector of a disk having a plurality of sectors each having a data part and an ID part, A method of providing a non-rewritable area has been proposed (see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-2000-31450 (pages 1 and 2)
[Patent Document 2]
JP-A-6-68444 [Patent Document 3]
JP-A-7-153047 [Patent Document 4]
Japanese Patent Application Laid-Open No. 2000-306236
[Problems to be solved by the invention]
However, when the method of Patent Document 1 is applied to a magnetic disk, the provided identifier indicating rewritable / non-rewritable may be falsified, and as a result, data that should be in the non-rewritable area is rewritten. Problem can occur. An object of the present invention is to provide a magnetic recording medium and a magnetic recording device that can solve such a problem.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the magnetic recording medium according to claim 1 is
A magnetic recording medium (magnetic disk 1) for recording information by a change in magnetization state along a track on a substrate,
One or more uneven portions (write enable flag area 12) formed with an uneven pattern from which a predetermined information signal (write enable flag 12) can be reproduced;
A data writing area (data zone 13) provided on a normal recording surface of the substrate corresponding to each of the concave and convex portions;
The presence or absence of the information signal indicates permission / prohibition of writing to the data writing area corresponding to the concave / convex portion, respectively.
[0007]
The magnetic recording device of claim 2 is
2. The magnetic recording medium according to claim 1, further comprising means for erasing the information signal reproduced from the concave / convex portion at a desired position by magnetization (DC erase) of the concave / convex portion by a magnetic head (2). .
A magnetic recording device according to a third aspect is the magnetic recording device according to the second aspect,
In the data write area corresponding to the uneven portion from which the information signal has been erased, means for interrupting the write current of the magnetic head (secure area monitor 3, write enable flag checker 4, switch 5, etc.) is provided. .
[0008]
A magnetic recording device according to a fourth aspect is the magnetic recording device according to the second or third aspect,
Means are provided for preventing the peak value of the write current of the magnetic head, which is based on the zero level, from becoming a predetermined value or less.
The operation of the present invention is as follows. At least a write permission flag area 12 consisting of a concavo-convex pattern which cannot be easily recovered and reproduced after being erased by DC erase once on a magnetic disk, and a normal area corresponding to the flag area 12 A data writing area (data zone) 13 comprising a recording surface;
While the write permission flag is reproduced from the flag area 12, writing to the corresponding data zone 13 is permitted. For data to be prevented from being tampered, after the data is written to the data zone 13, The write permission flag 12 corresponding to the zone 13 is erased by DC erase in which a large magnetizing current flows through the magnetic head, and writing to the data zone 13 is prohibited, that is, rewriting of the data zone 13 is prohibited. It is.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the present invention, the surface of a predetermined area of a magnetic recording medium (magnetic disk) is formed in an uneven state and information is engraved therein to generate a signal indicating rewriting permission / non-permission. A method of generating a signal using the unevenness has already been disclosed as a method of engraving servo information on a magnetic recording medium in advance (see Patent Documents 2 and 3).
The unevenness on the surface of the magnetic recording medium is prepared in advance by preparing a mold in which the unevenness indicating the information is cut, and molding the substrate to be the magnetic recording medium using the mold, so that the uneven pattern of the mold can be formed on the substrate. Transcribed.
[0010]
In addition, the information engraved as irregularities on the surface of the magnetic recording medium can be reproduced and output by using a two-stage magnetization method (see Patent Document 4).
FIG. 8 is an explanatory diagram of the principle of the two-stage magnetization method. In the figure, the upper layer 1a of the magnetic disk 1 having the concave and convex portions including the arrows is a recording layer as a magnetic layer formed on a non-magnetic substrate with diagonal stripes, and the arrows indicate the magnetization direction. .
Referring to FIG. 8, first, a large current (for convenience, referred to as a primary magnetizing current) i1 is passed through the magnetic head 2 and strongly magnetized as shown in FIG. And the recesses) are magnetized in a certain direction.
[0011]
Next, as shown in FIG. 8B, the current of the magnetic head 2 is reduced, and only the protrusions on the surface of the magnetic disk 1 are magnetized with weak magnetization by a small current (for convenience, referred to as a secondary magnetizing current) i2. At this time, the direction of the current (the direction of magnetization) is set to the opposite direction to the first magnetization.
By the above procedure, as shown in FIG. 8C, a read data signal 20 as a reproduction signal of the magnetic disk 1 is obtained from the magnetic head when scanning the uneven portion.
FIG. 1 shows an embodiment of the configuration of a region (also referred to as a secure region) 10 on a track of a magnetic recording medium (magnetic disk) 1 according to the present invention, which is capable of prohibiting rewriting. This figure shows an example in which a plurality of rewritable areas 10 are provided continuously at 10-1, 10-2,....
[0012]
As shown in FIG. 1, each rewritable area (secure area) 10 is composed of 11 to 14 areas arranged in the track direction. Here, 11 is an area in which a concavo-convex pattern defined to indicate the start of the secure area is formed, and 12 is defined to indicate a write permission flag for specifying whether to permit writing to the secure area. An area in which an irregular pattern is formed, 13 is a data zone as a normal data write area having a flat surface without irregularities, and 14 is an irregular pattern defined to indicate the end of the secure area. Area.
By magnetizing the secure area 10, a signal waveform corresponding to a prescribed pattern can be obtained from the areas 11, 12, and 14 of the concavo-convex pattern. Note that the secure area end pattern area 14 can be omitted, and if omitted, for example, the time elapsed from the detection of the signal of the secure area start pattern 11 or the secure area 10 as shown in FIG. For example, in the case of being provided consecutively with -2, the signal of the next secure area start pattern 11 can be used as a mark for delimiting one secure area 10.
[0013]
FIGS. 3, 4 and 5 respectively show the state of the secure area 10 of the magnetic disk 1 according to the present invention at the shipping stage, immediately after data writing to the data zone 13 and after the DC erasure of the write permission flag area 12 for each state. 3 shows an example of the relationship between the cross-sectional pattern of the magnetic disk substrate and the waveform of a read data signal (head reproduction signal) 20 read from each pattern portion.
The write permission flag 12 defines that a write is permitted if a signal is present at that location, and that if the signal is not present, the secure area is write-disabled. At the stage of shipment of the magnetic disk 1, all signals of the "write permission flag" 12 are made to exist by magnetizing the entire surface as shown in FIG.
[0014]
In order to record data to be prohibited from being rewritten, the data is recorded in, for example, the data zone 13 in the secure area 10 (10-1) as shown in FIG. 4, and after the recording is completed, the secure area is recorded as shown in FIG. The portion of the "write permission flag" 12 in 10-1 is erased by DC erase by the magnetic head.
FIG. 7 is an explanatory diagram of this DC erase. FIG. 7 shows the relationship between the magnetization directions (indicated by arrows) of the concave and convex portions of the concavo-convex pattern portion of the magnetic disk 1 and the read data signal 20 as a reproduction signal generated in the magnetic head in the concavo-convex pattern portion. The comparison is made before (FIG. 7A) and after (FIG. 7B) the DC erase. Here, the concavo-convex pattern portion to be DC erased is a portion surrounded by a broken line ellipse in FIG. 7A.
[0015]
As shown in FIG. 7, in the DC erase, a large DC current corresponding to the primary magnetizing current i1 described in FIG. 8 is applied to the magnetic head to make the concave and convex portions of the concave / convex pattern portion of the magnetic disk to be erased the current. This is performed by magnetizing in the same direction as the magnetization direction of the convex portion up to (in other words, inverting the magnetization direction of the concave portion) so that the read data signal 20 is not generated in that portion.
Since the "write permission flag" 12 is made of a concavo-convex pattern, it can be erased as described above after shipment, but it is actually extremely difficult to output a signal again after erasure.
[0016]
The reason for this is as follows. To restore the DC erased portion of the magnetic disk, once the magnetization direction of the erased portion is reversed by another DC erase (in other words, after the magnetization direction of the concave portion is restored), the magnetic head is restored. It is necessary to flow a small DC current corresponding to the secondary magnetizing current i2 described in FIG. 8 to reverse (restore) the magnetization direction of the convex portion of the erase portion.
FIG. 6 shows the magnitude of the secondary magnetizing current, which is the current value of the magnetic head when the convex portion of the DC erased concavo-convex pattern portion of the magnetic disk is magnetized in the direction opposite to the magnetization direction of the concave portion. For example, a characteristic diagram showing a relationship between a peak value (horizontal axis) with the level of the current 0 as a base line and a normalized value (vertical axis) of an output signal (read data signal) of a magnetic head reproduced from the concavo-convex pattern portion. It is.
[0017]
As shown in FIG. 6, the secondary magnetizing current value of the magnetic head that can obtain an effective output from the concavo-convex pattern once DC-erased is 20 mA _0-p or less (where A _0-p is the level of current 0). The peak value is shown based on. On the other hand, the write current value at the time of normal data write depends on the configuration of the recording layer, but can be usually considered to be 35 mA _0-p or more. The magnetic current value will be extremely low.
Therefore, for example, the magnetic recording device is manufactured with a limit in advance so that the peak value based on the 0 level of the write current supplied to the magnetic head of the magnetic recording device cannot be reduced below a certain level. The output of the permission flag 12 can make it impossible to recover once erased.
[0018]
Also, as a matter of course, it is difficult to write a signal indicating the write permission flag 12 with a magnetic head in the same manner as in a general magnetic disk because the relevant portion is on an uneven portion. Therefore, by referring to the presence / absence of the write permission flag 12 and controlling whether the write is permitted or not permitted by hardware, it is possible to protect the data in the secure area 10 from tampering with the data due to hacking or the like. it can.
FIG. 2 is a block diagram showing a configuration of a read (read) and write (write) function part of the magnetic recording apparatus according to the present invention. As shown in the figure, the read / write function unit is composed of 3 to 5 units.
[0019]
Here, reference numeral 3 denotes the arrival of the secure area 10 from the read data signal 20 as a reproduced signal reproduced and output from the magnetic recording medium (magnetic disk) 1 via a magnetic head (not shown). A secure area monitoring unit that monitors the arrival of a signal.
Next, a write permission flag check unit 4 checks the contents of the write permission flag area 12 based on the read data signal 21 in the secure area after the arrival of the secure area 10 is detected.
Reference numeral 5 denotes a switch unit provided in the line of the write data signal 30 toward the magnetic head (not shown) and turned on / off by a switch unit control signal 4a as a check output from the write enable flag check unit 4.
[0020]
Unless the signal indicating the secure area start pattern 11 is detected on the read data signal 20 by the secure area monitoring unit 3, the area is used as a normal data area, and the write permission flag check unit 4 turns on the switch unit 5 The write data signal 30 is written to the magnetic disk 1.
When the secure area monitoring unit 3 detects the secure area start pattern 11, the write permission flag check unit 4 checks the next write permission flag 12 from the read data signal 21 in the secure area.
As a result of this check, if the write permission flag 12 is in the write permission state, that is, if the signal exists in the concave / convex pattern portion of the flag 12, the write permission flag check unit 4 turns on the switch unit 5 by the switch unit control signal 4a. In this state, the write data signal 30 can be freely written in the data zone 13 of the secure area 10.
[0021]
On the other hand, if the write permission flag 12 is in the write-disabled state, that is, if the concave / convex pattern portion of the write permission flag 12 is DC-erased by the magnetic head and no signal is present, the write permission flag check unit 4 switches the switch unit. The switch unit 4 is turned off by the control signal 4a, and writing of the write data signal 30 to the data zone 13 of the secure area 10 is disabled. Therefore, if there is data already written in the data zone 13 of the secure area 10, rewriting of this data is prohibited.
By doing as described above, it is possible to provide a rewrite-protected area at an arbitrary position on the magnetic disk 1.
[0022]
The secure area 10 may be provided on the entire surface of the magnetic disk, but this will reduce the actual data area. Therefore, depending on the application, a method of setting a part of the magnetic disk, for example, the inner part of the magnetic disk as a secure area and the other part as a normal data part, or providing a secure area on one side and a normal data side on the opposite side It is also possible to do.
[0023]
【The invention's effect】
According to the present invention, at least a write permission flag area 12 made of a concavo-convex pattern and a data write area (data zone) 13 made of a recording surface similar to the normal one corresponding to the flag area 12 are provided on the magnetic disk.
While the write permission flag is reproduced from the flag area 12, the writing to the corresponding data zone 13 is permitted. For the data to be prevented from being falsified, the data is written to the data zone 13, and then the data zone 13 is written. Is erased by DC erase in which a large magnetizing current flows through the magnetic head, and writing to the data zone 13 is disabled.
Since the write permission flag area 12 erased by the DC erase cannot be easily restored, it is possible to reliably prevent the data written in the data zone 13 from being falsified.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a rewritable area (secure area) on a magnetic recording medium according to an embodiment of the present invention. FIG. 2 is a configuration of a main part of a magnetic recording apparatus as an embodiment of the present invention. FIG. 3 is a waveform diagram showing a relationship between a substrate pattern and a read data signal before data recording in a secure area as one embodiment of the present invention. FIG. 4 is a secure diagram as one embodiment of the present invention. FIG. 5 is a waveform diagram showing the relationship between a substrate pattern and a read data signal immediately after data is recorded in an area. FIG. 5 is a diagram showing an embodiment of the present invention. FIG. 6 is a waveform diagram showing a relationship with a data signal. FIG. 6 is a characteristic diagram showing an example of a relationship between a secondary magnetizing current and a normalized reproduced signal in a concavo-convex pattern portion. FIG. Illustration of a two-step deposition magnetizing method of illustration of chromatography's 8 irregularity pattern section [Description of symbols]
1 Magnetic recording media (magnetic disks)
1a Recording layer 2 Magnetic head 3 Secure area monitoring section 4 Write permission flag check section 4a Switch section control signal 5 Switch section 10 (10-1, 10-2) Rewriting prohibited area (secure area)
11 Secure area start pattern 12 Write permission flag 13 Data zone 14 Secure area end pattern 20 Read data signal (head reproduction signal)
21 Read data signal in secure area 30 Write data signal

Claims (4)

A magnetic recording medium that records information by changing a magnetization state along a track on a substrate,
One or more uneven portions formed with an uneven pattern from which a predetermined information signal can be reproduced;
A data write area provided on a normal recording surface of the substrate corresponding to each of the concave and convex portions,
A magnetic recording medium, wherein the presence or absence of the information signal indicates permission or prohibition of writing to the data writing area corresponding to the uneven portion. A magnetic recording medium for recording information by a change in magnetization state along a track on a substrate, wherein one or a plurality of concave and convex portions formed with a concave and convex pattern capable of reproducing a predetermined information signal, and each of the concave and convex portions And a data write area provided on a normal recording surface of the substrate, and the presence or absence of the information signal indicates permission / inhibition of writing to / from the data write area corresponding to the concave / convex portion, respectively. Magnetic recording medium,
A magnetic recording apparatus, comprising: means for erasing the information signal reproduced from the concave / convex portion at a desired location by magnetization of the concave / convex portion by a magnetic head. The magnetic recording device according to claim 2,
A magnetic recording apparatus, comprising: means for interrupting a write current of a magnetic head in a data write area corresponding to an uneven portion from which the information signal has been erased. The magnetic recording device according to claim 2, wherein
A magnetic recording apparatus comprising: means for preventing a peak value of a write current of a magnetic head from a zero level as a base line from becoming a predetermined value or less.

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