JPS6089806A - Magnetic erasure head - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic erasing head for erasing all AC signals magnetically recorded on a magnetic recording medium, and particularly to a magnetic erasing head with improved erasing efficiency.

[Background technology and its problems]

Conventionally, the rotary magnetic erase head, which has been used as an erase head for video tape recorders (hereinafter referred to as TR), is called a "flying erase head" and is used to record magnetically on magnetic tape, which is a magnetic recording medium. The filtered signals are erased for each recording trunk. In general, such a magnetic erasing head has ferrite core pieces 2 and 3 made of a metal oxide magnetic material joined to a workpiece 9 shown in FIG. 1A through a gap spacer 1 made of a non-magnetic material. It is formed by s9. This gap spacer 1, which is disposed xD on a means such as a spactor, provides a gap distance t of the erase head. Further, the erasing head has a winding hole 4 formed on the escape side in the direction of relative movement of the magnetic tape as indicated by the arrow X with respect to the erasing head that performs all of the tranokinder operations. For example, the coil that is wound in this winding hole is 5MHz.
A signal with a cancellation frequency of about 9 is supplied. Then, a saturation magnetic field is generated in the gearing part, and as the magnetic tape moves relative to each other, the magnetic field applied to the magnetic tape gradually becomes smaller than the saturation magnetic field, so that the residual magnetization on the magnetic tape converges to zero. , alternating current erasure of signals magnetically recorded on magnetic tape is performed. By the way, the metal oxide magnetic material ferrite used as the core pieces 2 and 3 has a high electrical resistance, but the saturation magnetic flux density Bs is about 5000 Gauss, and the magnetic field strength that can be generated in the young part is low. However, it is insufficient to erase signals recorded on a magnetic tape having a high coercive force He' (5) such as a metal tape.

FIG. 1B shows the magnetic field strength distribution around the gear part of the magnetic erasing head of FIG. 1A, plotted on the horizontal axis of distance in the tape relative movement direction.

By the way, as there is a demand for higher density signals recorded on magnetic tapes, magnetic tapes such as metal tapes with high residual magnetic flux density Br are used, as well as magnetic tapes with high cough eradication efficiency. Eraser heads are becoming necessary. Therefore, it is conceivable to use sendust or the like, which is a material with a high saturation magnetic flux density B8, for the pair of core pieces constituting the magnetic erasing head to increase the strength of the magnetic field generated from the gap portion. This Sendust has a saturation magnetic flux density of Bs75
It is high, about Z9000 Gauss. However, Sendust has a low electrical resistance, and even if Sendust is used in the core piece, there is a problem in that the eddy current loss is large (it generates a lot of heat, so the erasing efficiency cannot be improved).

In this way, conventional magnetic erasing heads used, for example, as rotary erasing heads for VTRs, have insufficient erasing efficiency to erase signal sounds recorded on magnetic tapes such as metal tapes having high coercive force Hc. The problem was that it was insufficient.

[Purpose of the invention]

The present invention was proposed in view of the above circumstances, and is a method for erasing nfC signals magnetically recorded on a magnetic recording medium having a high coercive force He, such as a magnetic tape such as a metal tape. The purpose of the present invention is to provide a magnetic erasing head with high erasing efficiency suitable for

[Summary of the invention]

To achieve this objective, the magnetic erase head of the present invention comprises:
Soft magnetic material! A thin film of a soft magnetic material having a higher saturation magnetic flux density than the above-mentioned soft magnetic material is formed on the magnetic gap forming surface side of a pair of core pieces consisting of In the magnetic erasing head that is joined via a gap spacer, the thickness of the magnetic material thin film formed on the core piece on the side where the magnetic recording medium enters is the same as the thickness of the magnetic material thin film formed on the core piece on the side where the magnetic recording medium escapes. It is characterized by a thicker material thin film.

〔Example〕

First, prior to explaining one embodiment of the present invention, the technology on which the present invention is based will be explained.

FIG. 2A shows a magnetic erase head constructed according to tobacco technology. In this magnetic erase head, unlike the erase head formed of the ferrite core pieces 2 and 3, only the both 9111 portions of the gap spacer 1 are made of high saturation magnetic flux density or high magnetic permeability such as sendust. Magnetic films having the same thickness a are bonded or arranged on a substrate or the like.

By adopting the configuration shown in FIG. 2A, the camping portion can obtain sufficient magnetic field strength, as shown in FIG. 2B. However, as shown in Figure 2B, this erase head has a steep distribution of magnetic field strength, so that the signal at the erase frequency supplied to the coil of the erase head is recorded on the magnetic tape. The disadvantage is that the signal to be erased, which is magnetically recorded on the magnetic tape, is re-recorded as the entire bias of the erased frequency component.

Next, an embodiment of the present invention that solves the above-mentioned technical problems will be described based on the drawings.

FIG. 3 shows a perspective view of the external appearance of the magnetic erasing head according to the present invention, and FIG. 4 shows a perspective view of the main parts thereof. This magnetic erasing head is used, for example, as a rotary erasing head for a VTR, and records signals magnetically recorded on a magnetic recording medium, such as a magnetic tape, for each recording track, at an erasing frequency of, for example, 5 MHz. I am erasing the current. By the way, in the magnetic erase head, the pair of core pieces 10 and 11 are made of a soft magnetic material, for example, manganese zinc ferrite (Mn=Zn ferrite).
Further, a winding hole 12 is formed in the core piece 11 on the escape side in the direction of relative movement of the magnetic tape as indicated by the arrow X with respect to the erasing head that performs the entire tracking operation. In this winding hole 12,
A coil to which a signal for erasing is supplied is wound.

Moreover, on the magnetic gear forming surface 111j of the pair of core pieces 10 and 11, there is a core piece 10. A magnetic thin film 13.14 of a soft magnetic material having a high saturation magnetic flux density Bs or high magnetic permeability, such as Mn-Zn ferrite, for example, so-called SendustF, is formed using a method such as sputtering. . The thin film 1 formed on the core piece 10 side on the entry side in the direction of relative movement of the magnetic tape.
The film thickness e of No. 3 is such that the film thickness f of the thin film 14 formed on the core piece 11 side on the escape side in the direction of relative movement of the magnetic tape is also thicker, that is, e>f. In this example,
For example, the film thickness e is 3 μm, and the film thickness f is 1 μm. By the way, the core pieces 10 and 11 on which the magnetic material thin films 13 and 14 are formed are fused using 16 pieces of glass made of non-magnetic material via 15 gap spacers made of sputtered films of non-magnetic material such as silicon dioxide SiO2. Attachment is completed. This gap spacer 15 ij:,
The gap distance t'(r) of the magnetic gap is given, and an erasing magnetic field is generated from this gigantic portion.

In the above magnetic erasing head having f' configured in this way, the magnetic field strength of the erasing magnetic field generated more often than the gap portion is high, and the intensity distribution of this magnetic field is shown in FIG. 5A. This magnetic field strength distribution with respect to the distance in the tape relative movement direction is asymmetrical with respect to the gap forming position. That is, the intensity distribution in the escape side direction of the relative movement direction of the magnetic tape (the region shown in the figure) has a gentle slope. In FIG. 5A, the vertical axis represents the magnetic field strength, and the horizontal axis represents the distance in the tape relative movement direction.

Further, FIG. 5B, which has a positional relationship corresponding to FIG. 5A, is a sectional view taken along the line II in FIG. 4. Incidentally, the reason why the magnetic field strength has a gentle slope distribution on the escape side is because of the magnetic material thin films 13 and 14 disposed on both sides of the gap spacer 15, the thin film disposed on the escape side is This is due to the fact that the film thickness f of the thin film 14 on the entry side is also thinner than the thin film 14 made of a high saturation magnetic flux density material, causing magnetic saturation to occur first. .

As described above, according to the present invention, the core pieces 10° 110 are also arranged on both sides of the gap spacer 150 in the magnetic material thin films 13 and 14' having a high saturation magnetic flux density i, so that the magnetic field strength generated at the magnetic gap portion is large. In addition, by forming the thin film 14 disposed on the relief side in the direction of relative movement of the magnetic tape to be thinner than the thin film 13, the distribution of magnetic field strength can be made gentler in the relief side direction. 0 For this reason, it has a high coercive force like metal tape ■IC' (l
l - magnetically recorded on a magnetic tape with: f'L fc 4
In addition to being able to obtain a magnetic field strength sufficient to erase the number i, the magnetic field strength distribution extending to the ↓ edge side prevents the signal at the erasing frequency from being recorded on the magnetic tape. A signal that was magnetically recorded on the magnetic tape using the frequency component as a bias will not be re-recorded to be erased. In other words, due to the gently sloped magnetic field strength distribution, the magnetic field applied to the magnetic tape gradually becomes smaller as the tape moves relative to the saturation magnetic field xD, and the residual magnetization on the magnetic tape gradually converges to zero. It starts to cool down.

By the way, as the magnetic material of the core pieces 10 and 11, Mn-
In addition to Zn ferrite, nickel zinc ferrite (
Ni--Zn ferrite) or the like may also be used. In addition to the above-mentioned so-called sendust of the iron-aluminum-silicon system (Fe-AJ-8t system), examples of the high saturation magnetic flux density material for the magnetic material thin film 13.14 include the amorphous material shown by M-X. Materials may also be used. Here, M is Fet-C
o (cobalt), Ni, X is for example Si, B
(It boron) P [phosphorus], C (carbon), etc. Specifically, as the above amorphous material, Fe-Co-8i-B
Since the magnetic material of the system is increased, the thickness of the magnetic material thin films 13 and 14 is preferably set to 1 to 5 μm for the thin film 13 disposed on the entrance side.

It is preferable that the thin film 14 disposed on the relief side be less than one part of the thin film 13 and 0°1 μm or more. This is thin film 13
If the film thickness is 5 μm or more, cracks may occur during bonding or peeling of the film may occur due to the difference in thermal expansion coefficient between the ferrite core piece 10.11 and the glass 16 for fusion bonding. However, if the thickness is less than 1 μm, the effect of placing the high saturation magnetic flux density material in the gap forming portion will be lost. Moreover, the reason why the thickness of the thin film 14 is set to be less than 100 of the total thickness of the thin film 13 is to avoid asymmetry in the above-mentioned magnetic field strength distribution.
, i .mu.m or more is necessary in order to make the magnetic field strength distribution on the escape side in the direction of relative movement of the magnetic tape full-length or in the form of a vertical slope. Note that the magnetic erasing head of the present invention may be used not only as a rotary erasing head for a VTR, but also as a fixed erasing head.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, thin films of magnetic material having a saturation magnetic flux density higher than that of the magnetic material constituting the pair of core pieces are disposed on both sides of the gap spacer. However, the thickness of the thin film on the escape side of the magnetic recording medium, for example, the magnetic tape in the direction of relative movement, is also made thinner. In addition, for example, high coercive force Hck such as metal tape
It is possible to obtain a magnetic field strength 2 sufficient to erase the signals stored on the magnetic tape, and the signal at the erasing frequency is recorded on the magnetic tape due to the magnetic field strength distribution having a slope on the side of the escape. There is no need to worry,
If this erasing frequency component is used as a bias, the signal to be erased will not be recorded again on the magnetic tape, thereby preventing re-recording.

According to the present invention, a magnetic erasing head with high erasing efficiency can be realized.

[Brief explanation of the drawing]

FIG. 1A is a schematic cross-sectional view of a conventional magnetic erasing head, FIG. 1B is a characteristic diagram showing the magnetic field strength distribution of the magnetic erasing head of FIG. 1A, and FIG. FIG. 2B is a characteristic diagram showing the magnetic field strength distribution of the magnetic erase head of FIG. 2A, and FIG. 3 is an external perspective view of the magnetic erase head according to the present invention. 4 is a perspective view of the main parts of the magnetic erasing head in FIG. 3, FIG. 5A is a characteristic diagram showing the magnetic field strength distribution 7 of the magnetic erasing head in FIG. 3, and FIG. 5 13 is a line I-I in FIG. 4. FIG. to, ii-- Core piece 12... Winding holes 13, 14,..., Magnetic material thin film 15-- Gap spacer 16, Ai, Glass X... Direction of relative movement of magnetic tape Patent applicant N2 1 Co., Ltd. Agent Patent Attorney Koike Mima 1) Sakae Mura - Figure 1 (A) -4゜Figure 1 (B) Tape engraving e-Dyokuryokuenmura High School 1 - Figure 2 (A) 2 Figure (B) Thea's objective: power force # - Figure 3 Figure 4 Figure 6 Figure 5 (A) Figure 5 (B)

Claims (1)

[Claims] A thin film of a soft magnetic material having a higher saturation magnetic flux density than the above-mentioned soft magnetic material is formed on the magnetic gap forming surface side of a pair of core pieces made of a soft magnetic material, and the pair of core pieces are In a magnetic erasing head that is joined via a gap spacer made of non-magnetic material, the thickness of the thin film of magnetic material formed on the core piece on the side where the magnetic recording medium enters is the same as that formed on the core piece on the side where the magnetic recording medium escapes. A magnetic erasing head characterized in that the film thickness is greater than that of the above-mentioned thin film of magnetic material.