JPS6220607B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic head made of two metal oxide magnetic cores bonded together and intended for high coercive force magnetic tapes such as metal tapes.

When recording signals on high coercive force tape, it is necessary to increase the saturation magnetic flux density of the head core material.
Instead of conventional metal oxide magnetic materials such as ferrite, metal-based magnetic materials such as sendust are commonly used. However, since metallic magnetic materials such as sendust have low electrical resistivity, they suffer from large eddy current losses at high frequencies, and in order to prevent this, conventionally it has been necessary to use a stack of thin plates. in this case,
Reliable magnetic gap formation techniques such as sputtering or metal fusion cannot be used due to misalignment between the laminates or the heat resistance or gas generation of the adhesive used to bond the laminates; It had become a drawback.

As a means to solve this problem, it is possible to form a film of a metallic magnetic material such as sendust having a high saturation magnetic flux density on at least the front gap portion of the ferrite core by sputtering or vapor deposition. In terms of recording, this method has the ability to record on high coercive force metal tapes, similar to conventional laminated heads, and in terms of playback, by selecting an appropriate film thickness, playback efficiency is improved. It has the advantage of being possible.

As a related technology, in order to prevent the influence of the roughness of the gap abutting surface of the ferrite core, a permalloy or sendust film is formed on the gap abutting surface of the ferrite core to improve the magnetic gap formation. Patent No.
It is known from No. 3079470 and Japanese Patent Publication No. 53-47811.

In these known examples, when forming the sendust film on the gap portion of the magnetic head, as shown in FIG. As shown in FIG. 2, a method has been adopted in which a sendust film 3 is formed over the entire winding window 4 and rear gap 5. In these known examples, the purpose of providing the sendust film was to improve the roughness of the gap abutting surfaces, and there was no need to increase the thickness of the film formed. On the other hand, when the purpose is to record and reproduce high coercive force metal tapes, the magnetic properties of the sendust film itself become an issue, and the sendust film must have a certain thickness, at least 3 μm. is necessary.

Through experiments conducted by the present inventors, it has been found that manufacturing a magnetic head having such a thick sendust film on the gap abutting surfaces causes the following problems.

(1) As shown in Fig. 1, in the magnetic head in which the sendust film 3 is formed only on the front gap 2, the abutting surfaces of the ferrite cores 1a and 1b are not parallel, as shown in Fig. 3, and the head is stable. I can't get the desired magnetic gap.

(2) In the case of a magnetic head as shown in Figure 2, the fourth
As shown in the figure, a phenomenon occurs in which the center of the sendust film 3 swells due to the influence of the edge portion of the winding window 4, and the film formation is extremely disturbed, making the magnetic gap extremely unstable and not suitable for practical use. It is difficult to

Therefore, it is an object of the present invention to combine a ferrite core and a sendust film in a form that is highly reliable and suitable for mass production without the drawbacks of the prior art described above, and enables efficient recording and reproduction of high coercive force tapes. The object of the present invention is to provide a magnetic head that can perform the following steps.

In order to achieve the above object, the magnetic head according to the present invention includes a metal-based magnetic material film at least in the front gap portion of at least one metal oxide magnetic core, and the metal-based magnetic material film has a thickness of 3 μm.
The thickness is between 100 μm, and in at least one metal oxide magnetic core, the contact surface between the metal oxide magnetic material in the front gap portion and the metal-based magnetic material film is the same as the metal oxide magnetic material surface in the rear gap portion. Alternatively, the gist is that it is not on the same plane as the contact surface between the metal oxide magnetic material and the metal-based magnetic material film in the rear gap portion.

In an advantageous embodiment of the invention, the two cut surfaces of the winding window are inclined at an obtuse angle with respect to the abutting surface of the gap, thereby forming the sendust film more stably. be done.

The advantageous sendust film thickness is determined by the following considerations.

The thickness of the sendust film on the front gear surface is t.
μm, the resistivity is ρμΩcm, the magnetic flux density at a point sufficiently far from the gap is B ₀ , and the magnetic flux density at the front gap is B ₁ , then B ₁ /B ₀ and t(μ
There is a relationship between m)/ρ(μΩcm) as shown in FIG. B ₁ /B ₀ varies with the values of t and ρ because the eddy current effects depend on them, and therefore B ₁ /B ₀ also depends on frequency, as shown in Figure 5. The curve is the value measured at a frequency of 4MHz. The point where B ₁ becomes larger than B ₀ by 2 dB, that is, the point where B ₁ /B ₀ becomes 1.25, is t/ρ=0.03.
Since the average resistivity of sendust is 100 μΩ·cm, t=3 μm. If the film thickness is less than this, the eddy current effect will be small and the concentration of magnetic flux will be less than 2 dB, making it ineffective for writing on high coercive force tapes such as metal tapes. The saturation magnetic flux density of Sendust is
10000 Gauss, the saturation magnetic flux density of ferrite is approximately
Since it is 4000 Gauss, at the point where B ₁ /B ₀ =2.5, that is, at a thickness of t/ρ1 or more, sendust is saturated, and B ₁ remains unchanged even if the film is made thicker. That is, the thickness of the sendust film in the magnetic head of the present invention is preferably between 3 μm and 100 μm.

According to the present invention, the step between the front gear face and the rear gear face provided on the ferrite core can eliminate the sendust film on the rear gear part, or make the film thickness at the rear gear part smaller than the film thickness at the front gear part by the difference in level. bring benefits. In order to make it as easy as possible for the magnetic flux to pass through the rear gap, it is advantageous not to have a sendust film that inherently causes eddy current loss and makes it difficult for the magnetic flux to pass through. The sendust film must be sufficiently thin.

The present invention will be explained in more detail below using examples with reference to the accompanying drawings, but these are merely illustrative, and it goes without saying that various modifications and improvements may be made without going beyond the scope of the present invention. be.

FIG. 6 is a perspective view of the magnetic head in the first embodiment of the present invention, in which both ferrite cores 1
A sendust film 3 is formed on the front gap 2 and winding window 4 of a and 1b. FIG. 7 is a plan view of the magnetic head shown in FIG. 6, viewed from the magnetic path plane.
The major difference between this magnetic head and conventional magnetic heads is that the sendust film 3 in the front gap
The contact surface 7a of the ferrite core 1a is not on the same plane as the rear gap surface 5 of the ferrite core 1a, and with the sendust film 3 formed, the sendust film surface and the surface of the rear gap 5 of the ferrite core 1a are almost on the same plane. It is a certain thing. The same is true for the ferrite core 1b; the contact surface 7b and the surface of the rear gap 5 of the ferrite core 1b are not on the same plane, and with the sendust film 3 formed, the gap forming surface becomes almost flat, and the ferrite cores 1a, 1b A very stable gap is formed by abutting the two through a non-magnetic layer. In FIGS. 6, 7, and the following figures, the nonmagnetic layer is not drawn for clarity.

8 to 11 show the manufacturing process of the magnetic head shown in FIG. 6. FIG. 8 shows a state where a front gap surface 9 and a winding window surface 10 have been processed on a ferrite substrate 8. At this time, the winding window surface 1
The cut surfaces 10a and 10b of 0 form an obtuse angle with respect to the mirror-finished surface 11 which becomes the gap abutting surface. The reason for this is that if the cut surfaces 10a, 10b form sharp angles with the mirror-finished surface, the formation of the sendust film will be greatly disturbed. Front gear surface 9
In this case, it is better to make the cut surface 9a slope with respect to the mirror-finished surface 11 so as not to form sharp edges. As will be explained later, the influence of the edges can be removed by polishing the tape sliding surface, so this is not much of a problem. The width W of the front gap surface 9 is selected to be slightly larger than the magnetic gap depth required for the magnetic head.

A sendust film 3 is formed on the ferrite substrate 8 processed as described above by a vacuum technique such as sputtering or vapor deposition. FIG. 9 then shows a sectional view taken perpendicular to the groove for the winding window.
The thickness of the sendust film 3 is made equal to or greater than the thickness of the sendust film required for the front gap portion of the magnetic head. FIG. 10 shows such a ferrite substrate 8 polished until a mirror-finished surface 11 appears. In this state, the ferrite substrate 8 is cut along the dotted lines. Two ferrite blocks 12a obtained by cutting,
12b are bonded via a nonmagnetic layer as shown in FIG. By cutting this as shown by the dotted line and polishing the tape sliding surface 13, the magnetic head shown in FIG. 6 is obtained. In a head having such a structure, the surface of the sendust film 3 formed on the ferrite substrate 8 by sputtering or the like is removed by the surface of the sendust film 3 formed on the substrate by the processing of the front gap surface 9 and the winding window surface 10. Even if the surface is disturbed by edges, these effects are removed in the subsequent polishing process.
The gap butting surface can be made sufficiently flat,
It has excellent mass productivity and enables highly reliable gap formation.

FIG. 12 is a perspective view of a magnetic head according to a second embodiment of the present invention. The difference from the first embodiment is that in this embodiment, a sendust film 3 is also present on the rear gap surface 5. It is to be.
Ferrite core 1a in front gap part
and the contact surface 7a of the sendust film 3, and the ferrite core 1a and the sendust film 3 at the rear gap part.
The contact surface 14a, the contact surface 7b between the ferrite core 1b and the sendust film 3 in the front gap section, and the contact surface 14b between the ferrite core 1b and the sendust film 3 in the rear gap section are not on the same plane, and there is a step between them. There is. 1st
FIG. 3 is a plan view of the magnetic head shown in FIG. 12, viewed from the magnetic path plane.

FIGS. 14 and 15 show the manufacturing process of a magnetic head in a second embodiment of the present invention. Unlike FIG. 10, when the sendust film surface is polished, the sendust film 3 is left on the mirror-finished surface 11 as well. The advantage of this method is that the polishing surface is always only the sendust film 3, and the polishing process is stable. The ferrite substrate is cut along the dotted line in FIG. 14, and the resulting two ferrite blocks 15a and 15b are joined via a nonmagnetic layer as shown in FIG. 15, and then cut along the dotted line. death,
The tape sliding surface 13 is polished and
The magnetic head shown in Figure 3 is obtained. Similarly to the magnetic head of the first embodiment, the magnetic head having such a structure also has the advantage that the magnetic gap can be formed extremely stably.

In the two manufacturing processes described above, two grooves for winding windows were formed on the ferrite substrate 8, but many grooves were formed on a larger substrate, as shown in FIGS. 10 to 14. You can cut out a ferrite block similar to the one shown in
A magnetic head with such a structure is suitable for mass production.

FIGS. 16 and 17 are plan views of magnetic heads in third and fourth embodiments of the present invention, respectively. In both embodiments, the sendust film 3 is formed on the entire surface of the gap abutting surface of the ferrite core 1a, and the ferrite core 1b in FIG. 16 is different from that in FIG. 6, and the ferrite core 1b in FIG. It is the same as that in Figure 13. These also have the same effect as the magnetic head shown earlier.

18 and 19 show a fifth embodiment of the present invention and correspond to FIGS. 6 and 7, respectively, but the basic difference is that in this embodiment, the volume The sendust film 3 is not present in the line window 4.

20 and 21 show a sixth embodiment of the present invention and correspond to FIGS. 12 and 13, respectively, but with the same differences as in the fifth embodiment. be.

FIGS. 22 and 23 are plan views of magnetic heads in seventh and eighth embodiments of the present invention, respectively. In both embodiments, the sendust film 3 is formed on the entire surface of the gap abutting surface of the ferrite core 1a, and the ferrite core 1b in FIG. 22 is different from that in FIG. 18, and the ferrite core 1b in FIG. It is the same as that in Figure 20.

The magnetic head having the structure shown in FIGS. 18 to 23 is one in which a sendust film is formed on a ferrite substrate by sputtering or the like, and then a winding window is formed. Since these magnetic heads are processed after the film is formed, the cut surface of the winding window may be perpendicular to the gap abutting surface, or at an angle close to a perpendicular angle. Regarding gap formation, these embodiments are also equivalent to the first and second embodiments, and a magnetic head with excellent mass productivity and high reliability can be easily obtained.

FIG. 24 shows a modification of the present invention, in which a metal-based magnetic material film 3 is formed only on one of two opposing metal oxide magnetic cores 1a and 1b, and the other 1a is made of metal oxide. It is conceivable to form a magnetic head using a non-magnetic layer while maintaining the magnetic material. In this case, since the saturation magnetic flux density is different at both ends of the magnetic gap, the magnetic field exiting from the front gap 2 to the outside will be asymmetrical, but this is not a major problem in practice, and the same effects as the other embodiments described so far are expected. can.

In the above description, the case where sendust was used as the metallic magnetic material was described, but other materials such as permalloy and amorphous materials can be used similarly.

In addition, in order to apply narrow track processing as seen in conventional video tape recorder heads, it is necessary to form a sendust film after the narrow track processing has been performed, or to form a sendust film, perform narrow track processing, and then The same head processing process as the conventional one can be used and can be easily carried out.

As explained above, according to the present invention, at least one of the two ferrite cores constituting the magnetic head is provided with a step between the front gear face and the rear gear face, and sendust is sputtered onto these. Afterwards, the entire gap forming surface is polished to improve the surface quality, and the two ferrite cores are bonded together via a nonmagnetic layer. This creates an extremely reliable magnetic gap, as well as a highly saturated magnetic gap. It is possible to obtain a magnetic head which has the great feature of being able to record on a high coercive force metal tape by using a sendust film having a high magnetic flux density.

[Brief explanation of the drawing]

Figures 1 and 2 are perspective views of a conventional magnetic head, Figures 3 and 4 are plan views of a conventional magnetic head, and Figure 5 shows the magnetic flux density in the front gap and the thickness of the metallic magnetic material film. 6, 12, 18, and 20.
The figures are perspective views of various magnetic heads according to the invention, FIGS. 7, 13, 19, and 21.
The figures are plan views of the magnetic head shown in Fig. 6, Fig. 12, Fig. 18, and Fig. 20, respectively, and Figs. 8 to 11 are perspective views or cross-sectional views showing the manufacturing process of the magnetic head shown in Fig. 6. 14 and 15 are cross-sectional views and perspective views showing the manufacturing process of the magnetic head in FIG. 12, FIG. 16, FIG. 17, FIG. 22,
FIGS. 23 and 24 are plan views of various magnetic heads in other embodiments of the invention. 1a, 1b... Ferrite core, 2... Front gap, 3... Sendust film, 4... Winding window, 5... Rear gap, 6... Winding, 7a, 7
b... Contact surface between the ferrite core and sendust film in the front gap part, 8... Ferrite substrate, 9... Front gap surface, 9a... Cutting surface of the front gap surface, 10... Winding window surface, 1
0a, 10b... cut surface of winding window surface, 11...
Mirror-finished surfaces, 12a, 12b, 15a, 15b...
...Ferrite block, 13...Tape sliding surface,
14a, 14b...Contact surface between the ferrite core and the sendust film in the rear gap portion.

Claims (1)

[Claims] 1. In a magnetic head formed by joining two metal oxide magnetic cores, a metal-based magnetic material film is present at least in the front gap portion of at least one of the metal oxide magnetic cores, and the metal-based magnetic material film is 3
In at least one metal oxide magnetic core, the contact surface between the metal oxide magnetic material in the front gap portion and the metal-based magnetic material film has a thickness between 100 μm and 100 μm. A magnetic head characterized in that it is not on the same plane as the magnetic surface or the contact surface between the metal oxide magnetic material and the metal magnetic material film in the rear gap part.