JP2007220179A - Dc demagnetization head, dc demagnetizer, and dc demagnetization method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC demagnetization head capable of DC-demagnetizing the recording layer of a magnetic tape suitably in a perpendicular direction to secure magnetic field intensity contributing to DC magnetization suitably, and suppressing the recording surface of the magnetic tape from occurring an error cause. <P>SOLUTION: A DC magnetizer, which is an apparatus for DC-demagnetizing the recording layer MT2 of the magnetic tape MT, is provided with: a running system to which the magnetic tape MT is set; a DC magnetization head 21 provided with a first magnetic pole 21a<SB>1</SB>and a second magnetic pole 21a<SB>2</SB>which are arranged so as to respectively oppose one and the other surfaces of the magnetic tape MT while inserting the set magnetic tape MT; and a control part which makes the magnetic tape MT run by controlling the running system. The DC magnetization head 21 generates a magnetic field from one of the first magnetic pole 21a<SB>1</SB>and the second magnetic pole 21a<SB>2</SB>to the other to perform DC-demagnetization of the recording layer MT2 in a vertical direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a DC demagnetizing head, a DC demagnetizing device, and a DC demagnetizing method that demagnetize a recording layer of a magnetic tape.

  In recent years, high-density recording of magnetic tapes has progressed, and those having a storage capacity of about 100 gigabytes have come out for computer backup. For this purpose, several hundred data tracks are formed in the recording layer of the magnetic tape in the width direction. Therefore, the width of the data track is very narrow, and the space between adjacent data tracks is also very narrow. Therefore, in order to trace the recording / reproducing element of the magnetic head to the data track, a servo signal is written in advance on the magnetic tape, and this servo signal is read by the magnetic head to thereby determine the position of the magnetic head (in the width direction of the magnetic tape). Servo position).

  Here, in the magnetic tape recording / reproducing apparatus, the change point of magnetization in the servo signal is detected by the change of electric resistance by the servo signal reading element (MR element), and the change point of magnetization as the read signal is differentiated waveform (voltage value). ). Therefore, as the change in the electrical resistance of the MR element increases, the peak voltage value of the read signal of the servo signal increases and the SN ratio of the read signal improves.

  However, in the future, when the recording density of magnetic tape is increased to about several tens of terabytes, the number of data tracks on magnetic tape will increase, the width of data tracks and the distance between adjacent data tracks will become narrower, and the magnetic The tape itself is also thinned. As a result, the amount of magnetism that can be detected when reading the servo signal decreases, the peak voltage value of the read signal of the servo signal decreases, and the SN ratio of the read signal deteriorates. As a result, in the magnetic tape recording / reproducing apparatus, the servo signal cannot be read accurately, and the position control of the magnetic head with high accuracy cannot be performed.

Therefore, as a method for improving the S / N ratio of the read signal of the servo signal, the servo band of the magnetic tape is magnetized in one direction (hereinafter, referred to as the traveling direction of the magnetic tape) in one direction (e.g., the traveling direction of the magnetic tape). There is a method of writing a servo signal by magnetizing this servo band in a direction opposite to one direction after “DC demagnetization”. In this method, when the servo signal is read by the servo signal reading element of the magnetic head, the change rate and change of the magnetic field at the switching portion between the ground portion in one direction and the servo pattern magnetized in the reverse direction. Since the amount increases, the output of the servo signal increases, and the SN ratio of the read signal of the servo signal can be improved. In order to DC demagnetize the recording layer of the magnetic tape, a DC demagnetizing head arranged on the recording surface (recording layer side surface) side of the magnetic tape has been used (Patent Document 1, Patent Document 2, Patent Document 3). , Patent Document 4, Patent Document 5, and Patent Document 6).
JP 2004-318977 A US Pat. No. 6,970,312 US Patent Application Publication No. 2005/0099718 US Patent Application Republished No. 2005/0105967 US Patent Application Publication No. 2005/0168869 US Patent Application Publication No. 2005/0219734

  As described above, the conventional technique in which the DC degaussing head is arranged on the recording surface side of the magnetic tape can cope with the horizontal magnetic recording, but the recording layer is arranged in the vertical direction corresponding to the perpendicular magnetic recording. It was difficult to degauss. Further, in the conventional technique, since the DC demagnetization is performed using the leakage magnetic field, the magnetic field strength contributing to the DC demagnetization is less than half of the magnetic field strength of the magnet (DC demagnetization head). In the prior art, friction between the DC degaussing head and the magnetic tape causes various problems such as scratches on the recording surface, pseudo signals, and dust adhesion, which are the causes of errors.

  The present invention was devised in view of such a background. The recording layer of the magnetic tape is preferably DC-demagnetized in the vertical direction, the magnetic field strength contributing to DC demagnetization is preferably ensured, and the recording of the magnetic tape is performed. It is an object of the present invention to provide a DC demagnetizing head, a DC demagnetizing device, and a DC demagnetizing method that can suppress the occurrence of an error on the surface.

  As means for solving the above-mentioned problems, the present invention is a DC degaussing head for DC demagnetizing a recording layer of a magnetic tape, and faces one side and the other side of the magnetic tape with the magnetic tape interposed therebetween. And demagnetizing the recording layer in the vertical direction by generating a magnetic field from one of the first magnetic pole and the second magnetic pole to the other of the first magnetic pole and the second magnetic pole. It is possible.

  According to such a DC demagnetizing head, magnetization can be performed in a direction perpendicular to the surface of the recording layer, so that the recording layer can be suitably DC demagnetized in the perpendicular direction. Further, since the magnetic field of the DC degaussing head contributes to DC demagnetization, the magnetic field strength contributing to DC demagnetization can be suitably ensured. Further, since friction between the DC demagnetizing head and one surface of the magnetic tape, that is, the recording surface can be avoided, it is possible to suppress the occurrence of an error on the recording surface of the magnetic tape due to DC demagnetization.

  Further, as means for solving the above-mentioned problems, the present invention provides a DC demagnetizing device for DC demagnetizing a recording layer of a magnetic tape, comprising: a traveling system on which the magnetic tape is set; and the set magnetic tape. A DC degaussing head having a first magnetic pole and a second magnetic pole disposed so as to face one surface and the other surface of the magnetic tape, respectively, and the magnetic tape is controlled by controlling the traveling system. And a DC degaussing head that demagnetizes the recording layer in the vertical direction by generating a magnetic field from one of the first magnetic pole and the second magnetic pole to the other. It is characterized by.

  According to such a DC demagnetizer, since magnetization can be performed in a direction perpendicular to the surface of the recording layer, the recording layer can be suitably DC demagnetized in the perpendicular direction. Further, since the magnetic field of the DC degaussing head contributes to the DC demagnetization, the magnetic field strength contributing to the DC demagnetization can be suitably ensured. Further, since friction between the DC demagnetizing head and one surface of the magnetic tape, that is, the recording surface can be avoided, it is possible to suppress the occurrence of an error on the recording surface of the magnetic tape due to DC demagnetization.

  In the DC demagnetizing device described above, the DC demagnetizing head may be composed of a permanent magnet.

  In the DC demagnetizing device described above, the DC demagnetizing head may be composed of an electromagnet, and the control unit may generate a magnetic field in the electromagnet by energizing a coil of the electromagnet.

  Further, as a means for solving the above-mentioned problems, the present invention provides a DC demagnetization method for DC demagnetizing a recording layer of a magnetic tape, wherein the magnetic tape travels and the traveling magnetic tape is sandwiched. A DC degaussing head having a first magnetic pole and a second magnetic pole disposed so as to face one surface and the other surface of the magnetic tape is respectively connected from one of the first magnetic pole and the second magnetic pole to the other. The recording layer is DC demagnetized in the vertical direction by generating a magnetic field toward

  According to such a DC demagnetization method, magnetization can be performed in a direction perpendicular to the surface of the recording layer, so that the recording layer can be suitably DC demagnetized in the perpendicular direction. Further, since the magnetic field of the DC degaussing head contributes to the DC demagnetization, the magnetic field strength contributing to the DC demagnetization can be suitably ensured. Further, since friction between the DC demagnetizing head and one surface of the magnetic tape, that is, the recording surface can be avoided, it is possible to suppress the occurrence of an error on the recording surface of the magnetic tape due to DC demagnetization.

  According to the present invention, it is possible to suitably demagnetize the recording layer of the magnetic tape in the vertical direction. Moreover, the magnetic field intensity contributing to DC demagnetization can be suitably secured. Further, since friction between the DC demagnetizing head and one surface of the magnetic tape, that is, the recording surface can be avoided, it is possible to suppress the occurrence of an error on the recording surface of the magnetic tape due to DC demagnetization.

Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. Similar parts are denoted by the same reference numerals, and redundant description is omitted. In the following embodiments, a case where the DC demagnetizer of the present invention is applied to a servo writer that records a servo signal in a servo band of a recording layer of a magnetic tape will be described as an example.
In the drawings to be referred to, FIG. 1 is a system configuration diagram showing a servo writer according to an embodiment of the present invention. 2A and 2B are schematic views showing the relationship between the DC degaussing head and the magnetic tape, where FIG. 2A is a view seen from the upstream side in the magnetic tape traveling direction, and FIG. In FIG. 2, the magnetic field is schematically shown using arrows. Each figure is exaggerated and omitted for the sake of clarity, and does not represent an accurate dimension.

  As shown in FIG. 1, the servo writer 1 according to the embodiment of the present invention includes a traveling system 10, a head unit 20, a DC demagnetizing circuit 31, a pulse generating circuit 32, and a control device 40. Yes.

[Running system 10]
The traveling system 10 is for traveling the magnetic tape MT so that DC demagnetization, recording of servo signals and detection of recorded servo signals can be performed on the magnetic tape MT, and the magnetic tape MT is wound around the traveling system 10. A pair of reels 11, 11, a plurality of guides 12, 12,... For guiding the traveling magnetic tape MT, and a drive device 13 that rotationally drives the pair of reels 11, 11 are provided. The reel 11 and the guide 12 are rotatable, and the magnetic tape MT travels when the pair of reels 11 and 11 are rotationally driven.

[Head unit 20]
The head unit 20 performs DC demagnetization, recording of servo signals, and detection of recorded servo signals on the traveling magnetic tape MT. As shown in FIG. 1, the head unit 20 includes a DC demagnetizing head 21, a servo signal writing head 22, and a verify head 23 in order from the upstream side in the magnetic tape traveling direction.
The DC degaussing head 21 demagnetizes (DC demagnetization) the recording layer MT2 (see FIG. 2) of the magnetic tape MT. DC demagnetization by the DC demagnetization head 21 is performed by magnetizing the magnetic material in the recording layer MT2 in the vertical direction, that is, in the direction perpendicular to the surface of the magnetic tape MT. In this embodiment, an electromagnet is used as the DC degaussing head 21 as described later, but a permanent magnet may be used.
The servo signal write head 22 records (writes) a servo signal in the servo band of the recording layer MT2 de-energized. Servo signal recording by the servo signal writing head 22 is performed by magnetizing a DC-demagnetized magnetic material in the servo band of the recording layer MT2 in a direction opposite to the direction of DC demagnetization.
The verify head 23 detects a servo signal recorded in the servo band. The detected servo signal is output to the control device 40.

[DC demagnetization circuit 31]
The DC demagnetization circuit 31 is a circuit that supplies a predetermined DC current to the coil 21b (see FIG. 2A) of the DC demagnetization head 21, and includes various electronic components.

[Pulse generation circuit 32]
The pulse generation circuit 32 is a circuit that supplies a recording pulse current to the servo signal write head 22 and includes various electronic components. In the pulse generation circuit 32, a positive polarity positive pulse current → zero current → plus pulse current → zero current is successively generated based on a pulse control signal from the control device 40, and then no current is generated for a predetermined time (zero). Current) pattern is repeated to generate a recording pulse current. The pulse generation circuit 32 supplies this recording pulse current to a coil (not shown) of the servo signal write head 22. The current value of the plus pulse current is a current value sufficient to magnetize the recording layer (magnetic layer) MT2 (see FIG. 2) of the magnetic tape MT by the leakage magnetic flux from the head gap of the servo signal write head 22. Yes, set in consideration of the characteristics of the coil of the servo signal write head 22. Further, the pulse width (time) of the plus pulse current can define a predetermined width in the longitudinal direction of the servo pattern, and is set in consideration of the traveling speed of the magnetic tape MT, the shape of the head gap of the servo signal writing head 22, and the like. Is done. Further, the predetermined time of zero current can be defined by a predetermined interval for forming the servo pattern, and is set in consideration of the traveling speed of the magnetic tape MT and the like.

[Control device 40]
The control device 40 is a device that controls the operation of each part of the servo writer 1, and includes a CPU (Central Processing Unit), various storage devices, and the like.
The control device 40 generates a motor current signal for controlling the motor current of the driving device 13 and transmits the motor current signal to the driving device 13 in order to keep the traveling speed of the magnetic tape MT when writing the servo signal constant. .
Further, the control device 40 generates a predetermined DC current by controlling the DC demagnetization circuit 31.
Further, the control device 40 sets the servo signal that defines the width in the longitudinal direction of the servo pattern and the predetermined interval for forming the servo pattern, the current value of the plus pulse current of the recording pulse current, the pulse width, A pulse control signal for controlling the generation timing is generated and transmitted to the pulse generation circuit 32. That is, the control device 40 generates the above-described pulse pattern of plus pulse current → zero current → plus pulse current → zero current.
Further, the control device 40 controls the verify head 23 to acquire the detection result of the verify head 23 and determine whether the servo signal writing head 22 has succeeded in writing the servo signal.

Next, the DC demagnetization by the DC demagnetization head 21 will be described in more detail.
As shown in FIGS. 2A and 2B, the magnetic tape MT includes a base film MT1 and a recording layer (magnetic layer) MT2 laminated on the base film MT1. The recording layer MT2 is a perpendicularly recordable layer and is provided on one surface side (recording surface side) of the magnetic tape MT.
The DC degaussing head 21 includes a C-shaped head core 21a and a coil 21b wound around the head core 21a. At both ends of the head core 21a, the first pole 21a ₁ and the second magnetic pole 21a ₂ is formed.
The first pole 21a ₁ and the second magnetic pole 21a ₂ are arranged so as to sandwich the magnetic tape MT, the first pole 21a ₁ is one face of the magnetic tape MT (recording surface), i.e. the recording layer MT2 side opposed, second magnetic pole 21a ₂ is other face, that face the base film MT1 side of the magnetic tape MT. Further, the first pole 21a ₁ and the second magnetic pole 21a _2, are arranged so as to overlap when viewed from the direction perpendicular to the plane of the magnetic tape MT.
The control device 40 controls the drive device 13 to run the magnetic tape MT and magnetizes the recording layer MT2 with a saturation magnetization amount or more.

Thus, one side of the first pole 21a ₁ magnetic tape MT (recording surface), that is, the recording layer MT2 from the side facing the second magnetic pole 21a ₂ and the other surface, i.e. the base film MT1 side of the magnetic tape MT Since they are opposed to each other, magnetization can be performed in a direction perpendicular to the surface of the recording layer MT2, so that the recording layer MT2 can be suitably DC demagnetized in the perpendicular direction.

Further, the first pole 21a ₁ and the second magnetic pole 21a ₂ is because it is arranged so as to sandwich the magnetic tape MT, so that the magnetic field of the DC demagnetizing head 21 contributes to DC demagnetization. Therefore, the magnetic field strength contributing to DC demagnetization can be suitably ensured as compared with the prior art using a leakage magnetic field.

Further, it is possible to suitably secure the contributing field strength in DC demagnetization, it is possible to separate the magnetic tape MT with the first magnetic pole 21a ₁ and the second magnetic pole 21a _2, to prevent these contact Can do. Therefore, it is possible to suppress the occurrence of an error cause on the recording surface of the magnetic tape MT.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A design change is possible suitably in the range which does not deviate from the summary of this invention.
For example, the structure of the magnetic tape MT is not limited to that described above, and may include other functional layers.
Further, the DC degaussing head may be constituted by a single magnetic pole head arranged on one side of the magnetic tape and an auxiliary magnetic pole arranged on the other side instead of the above-mentioned C-shape.

1 is a system configuration diagram illustrating a servo writer according to an embodiment of the present invention. It is a schematic diagram which shows the relationship between DC demagnetizing head and a magnetic tape, (a) is the figure seen from the magnetic tape advancing direction upstream, (b) is a X arrow directional view of (a).

Explanation of symbols

1 Servo writer (DC demagnetizer)
DESCRIPTION OF SYMBOLS 10 Traveling system 20 Head part 21 DC demagnetizing head 21a ₁ 1st magnetic pole 21a ₂ 2nd magnetic pole 22 Servo signal write head 23 Verify head 31 Degaussing circuit 32 Pulse generation circuit 40 Controller MT Magnetic tape MT2 Recording layer

Claims (5)

A DC degaussing head for DC demagnetizing a recording layer of a magnetic tape,
Comprising a first magnetic pole and a second magnetic pole disposed so as to face one surface and the other surface of the magnetic tape, respectively, across the magnetic tape;
A DC demagnetizing head, wherein the recording layer can be DC demagnetized in a vertical direction by generating a magnetic field from one of the first magnetic pole and the second magnetic pole to the other. A DC degaussing device for DC demagnetizing a recording layer of a magnetic tape,
A traveling system in which the magnetic tape is set;
A DC demagnetizing head comprising a first magnetic pole and a second magnetic pole disposed so as to face one surface and the other surface of the magnetic tape across the set magnetic tape;
A control unit for running the magnetic tape by controlling the running system;
With
The DC demagnetizing head is configured to demagnetize the recording layer in a vertical direction by generating a magnetic field from one of the first magnetic pole and the second magnetic pole to the other.   The DC degaussing device according to claim 2, wherein the DC degaussing head is composed of a permanent magnet. The DC degaussing head is composed of an electromagnet,
The DC demagnetizer according to claim 2, wherein the controller generates a magnetic field in the electromagnet by energizing a coil of the electromagnet. A DC demagnetization method for demagnetizing a recording layer of a magnetic tape,
A DC demagnetizing head having a first magnetic pole and a second magnetic pole disposed to face the one surface and the other surface of the magnetic tape with the magnetic tape traveling and sandwiching the traveling magnetic tape However, a DC demagnetization method comprising: demagnetizing the recording layer in the vertical direction by generating a magnetic field from one of the first magnetic pole and the second magnetic pole to the other.

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