JPH053646B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a magnetic head suitable for recording and reproducing high frequency signals such as video signals on and from high coercive force media such as metal tapes.

(b) Prior art In general VTRs (β and VHS), oxide magnetic material (ferrite) is often used as the core material of the magnetic head. This is because it has excellent wear resistance and is easy to manufacture. For high coercive force media such as metal tapes used for dense recording, this magnetic head does not have a large saturation magnetic flux density (about 5500 Gauss at most), so it is not possible to perform recording that takes advantage of the performance of the medium. difficult. Therefore, a magnetic head has been proposed in which a metallic magnetic material (such as sendust) exhibiting a high saturation magnetic flux density is attached to the periphery of the front gear where magnetic saturation is most likely to occur (Japanese Patent Application Laid-Open No. 103116/1982). This known magnetic head proposes configuring the interface between the oxide magnetic material and the metal magnetic material so that the area of the interface is larger than that of the front gap constituting surface so that magnetic saturation does not occur at the interface. This is achieved by forming a thin film made of a metallic magnetic material with an inclined surface on the opposite side from the tape contact surface.In order to reduce the track width and make the boundary surface sufficiently large, it is necessary to The disadvantage is that the thickness must be increased and it takes time to form the film.

(c) Object of the Invention The present invention aims to provide a magnetic head in which the track width can be reduced and the boundary surface can be made sufficiently large without increasing the thickness of the thin film.

A further object of the present invention is to provide a magnetic head with good yield, which can prevent peeling of the thin film and keep the track width within a predetermined dimension.

(d) Structure of the Invention The present invention has a structure in which a thin film made of an alloy magnetic material exhibiting a high saturation magnetic flux density is attached to the front gear side surface of the main part of the magnetic core made of a high resistivity material, and the thin films are opposed to each other. In order to define the track width of the front gap to be smaller than the total width of the tape contact surface when viewed from the tape contact surface side, from each edge of the thin film facing the front gap, the tape contact surface is The main part of the magnetic core is provided with a notch having a ridgeline extending to the side surface of the main part of the magnetic core, and the notch forms the shape of the thin film on the tape contacting surface into a substantially isosceles trapezoid, and the main part of the magnetic core The width of the lower base of the isosceles trapezoid, which is the interface between the isosceles trapezoid and the thin film, is larger than the track width.

Further, the present invention provides an arrangement in which the angle of intersection between the leg sides of the isosceles trapezoid and the imaginary line perpendicular to the front gear is 20° or more.
It is characterized by having an angle of 50° or less, which improves the manufacturing yield and makes it less susceptible to crosstalk.

(e) Embodiment FIG. 1 is a perspective view showing one embodiment of the magnetic head of the present invention. In the figure, for convenience of explanation, the total thickness W is shown larger than the aspect ratio of the magnetic head.
Furthermore, the gap length L of the front gear F is also shown to be significantly extended. Furthermore, the illustration of the coil to be attached is also omitted. This magnetic head has an extremely small overall shape, for example, about 3 mm in both length and width, so when it is mounted on a rotating body of a VTR, for example, the side surface S ₁ should be placed so that the tape contact surface S ₂ protrudes outward. Head space (not shown)
Consideration is given to ease of handling.

This magnetic head is made of oxide magnetic material (ferrite).
The main part of the magnetic core exhibiting a high specific resistance consisting of 1,
2, thin films 3 and 4 with a thickness of about 5 μm and exhibiting a high saturation magnetic flux density made of an alloy magnetic material (for example, Sendust) attached on the surfaces 1a and 2a of the main part of the magnetic core on the side of the front gap F; A spacer 5 made of a non-magnetic material such as SiO ₂ is provided between the two. Further, this magnetic head has a coil window 6 extending through it in its thickness direction, and the upper edge of this coil window is configured to coincide with the lower edge (fat end) of the front gap F.

Viewing the tape contact surface _S2 from the front, each edge 3a, 3b, 4 of the thin film facing the front gap F
A notch 8 having ridgelines 7a, 7b, 7c, 7d extending from a, 4b to side surfaces 1b, 1c, 2b, 2c on the magnetic core main parts 1, 2 constituting the tape contact surface.
a, 8b, 8c, 8d, and notches 8a,
8c, 8b, and 8d are filled with glass 9a, 9b that acts as a bonding material. Therefore, the thin films 3 and 4 are both shaped to have a substantially isosceles trapezoid shape. The upper bases 3c, 4c are equal to the track width T,
The lower bases 3d and 4d, which are the interfaces between the magnetic core main parts 1 and 2 and the thin films 3 and 4, are larger than the track width T and smaller than the total thickness W.

The extending direction of the front gap F is deviated from a right angle by 10° with respect to the traveling direction P of the magnetic head, and is configured to have a so-called azimuth angle α. Then, each leg side of the isosceles trapezoid, that is, the ridge lines 7a, 7b, 7c, 7d, and the front gap F.
The intersecting angles θ ₁ , θ ₂ , θ ₃ , and θ ₄ with the virtual line 10 orthogonal to the imaginary line 10 are all defined to be 20° or more and 50° or less (see FIG. 9).

2 to 4 briefly show examples of manufacturing a magnetic head according to the present invention. A thin film 21 of sendust is attached to the entire surface of a wafer 20 made of magnetic ferrite material using a sputtering method, and a spacer film (not shown) of SiO ₂ is further applied to the surface of this thin film where the front gap is to be formed to the required gap length L. Attach only half of the Next, a plurality of (three in the illustrated example) grooves 22 are formed so as to form a land portion 21a having a width X that matches the track width T. FIG. 2 shows a perspective view of the block half _B1 which has undergone the above processing. The other block half B ₂ facing this block half in FIG.
A groove 23 for the coil window 6 is added to the block half shown in the figure.
The track width defining groove 22 is opened in a direction perpendicular to the track width defining groove 22 as shown in FIG. As shown in FIG. 4, these two block halves B ₁ and B ₂ are butted against each other so that the respective thin films 21 and 21 face each other, and the track width defining groove 22 is filled with glass 22 to be integrated. Integrated block B
Surface Ba is rounded to obtain tape contact surface _S2 ,
Thereafter, this block is sliced along the broken line 25 so as to have an azimuth angle of 10°, and the thickness is processed as necessary to manufacture the magnetic head shown in FIG.

Here, a supplementary explanation will be given of the method of machining the track width defining groove 22. Figure 5 is a plan view showing the state in which the cutter 30 is cutting the workpiece block half _B1 (however, the cutter is shown with imaginary lines to make the figure easier to see), and Figure FIG. 3 is a cross-sectional view showing a cut surface taken along line 31 in the figure.

The cutter 30 is a disc-shaped diamond cutter having an angle θ, and rotates in the direction of the arrow 32.
The workpiece moving downward in the area above the center line 30
It cuts B ₁ and acts to move away from the workpiece in the lower region. According to experiments, it has been found that the tendency of the thin film 21 to peel off during the process of cutting the groove 22 differs significantly depending on the angle θ. Figure 7 A and B are characteristic diagrams showing the probability of peeling.
sec and (b) 0.1mm/sec. In both cases, the probability of occurrence becomes extremely large when the angle θ becomes smaller than 20°. This phenomenon can be understood as follows.

If this angle θ exists even slightly, under ideal conditions there would be no chance of contact between the cutter blade surface and the machined surface of the workpiece in the region below the center line 31, so the above-mentioned peeling should not occur. In reality, in a range where the angle θ is small due to cutter deflection or expansion of the blade that is elastically deformed during the cutting operation, the cutter 30 comes into contact with the workpiece B ₁ even below the center line 31 and peels off the thin film due to frictional force. It acts to cause Since the above-mentioned intersecting angles θ ₁ to _{θ 4} correspond to this angle θ, they are selected to be 20° or more in order to prevent thin film peeling and improve manufacturing yield.

On the other hand, increasing the angle .theta. has the disadvantage that it becomes difficult to define the track width T. This will be explained with reference to FIG. Even if the thickness D of the workpiece _B1 is set to a predetermined value and the workpiece is set at the reference position Q, the workpiece of the cutter 30
When the access to _B1 changes from the predetermined solid line state to the adjacent broken line state, the track width T
changes from T ₁ to T ₂ , and the tendency of this change depends on the magnitude of the angle θ. That is, if the angle .theta. is large, a small error will cause a large variation in the track width T. By finishing the thickness variation of workpiece B ₁ within 1 μm and taking measures to eliminate unevenness in the thickness of the adhesive layer when fixing the workpiece to the adhesive table, the track width T can be reduced when the angle θ is up to about 50°. It is relatively easy to suppress the variation within an allowable range of ±2 μm. Therefore, the intersecting angle θ ₁ ~
θ ₄ is suitably 50° or less.

Increasing this angle of intersection also has the disadvantage of increasing noise components in the low frequency range. This point will be explained with reference to FIG. The figure shows truck B.
The recording state of track A adjacent to is shown.
During recording, the original signal is recorded on track A at an azimuth angle α (=10°) by the front gap F, and since the ridge line 7d acts as a gap on the already recorded adjacent track B, the signal is parallel to the ridge line. A record of any omissions will be made. In order to prevent this leakage recorded component from being reproduced at the front gap F' of the magnetic head having an azimuth angle -α during reproduction of the B track, the angle β in the figure needs to be at least 20°, which causes azimuth loss. Since β=90−θ−2α (here α=10°), β=70−θ(20), so θ50°. Follow,
In order not to reproduce the leaked recorded components, the intersection angle θ ₁
It is appropriate that ~θ ₄ is 50° or less.

(E) Effects of the Invention In the magnetic head of the present invention, the peripheral part of the front gap is made of an alloy magnetic material with a high saturation magnetic flux density (for example, sendust), so even if the recording current is increased for recording on a metal tape, magnetic saturation will not occur. There is no risk of causing In addition, since the main part of the magnetic core is made of a high resistivity oxide magnetic material (e.g. ferrite), it is less susceptible to deterioration of reproduction output characteristics due to eddy current loss, and already established manufacturing methods can be used. Therefore, manufacturing is easy. Furthermore, the interface between the alloy magnetic material and the oxide magnetic material can be increased by increasing the above-mentioned intersection angle, and there is no need to increase the film thickness as in the conventional example, making manufacturing easier in this respect as well. It is. Furthermore, since the above-mentioned intersection angle is selected to be between 20° and 50°, peeling of the thin film on the main part of the magnetic core can be prevented and the accuracy of the track width can be improved. At the same time, since the leaked recorded components are not reproduced, the S/N characteristics can be improved.

[Brief explanation of the drawing]

The drawings all relate to the present invention; Fig. 1 is a perspective view of the structure of one embodiment, Figs. 2, 3, and 4 are explanatory views of the manufacturing process of this magnetic head, and Figs. 5 and 6. The figures are a plan view and a sectional view for explaining the cutting operation, FIGS. 7A and 7B are characteristic diagrams of the probability of occurrence of thin film peeling, and FIGS. 8 and 9 are diagrams for explaining the upper limit of the intersection angle. Explanation of the main drawing numbers, 1, 2...Main parts of the magnetic core,
3, 4...Thin film, F...Front gap, 7a
~7d...Ridge line, _θ1 ~ _θ4 ...Intersection angle.

Claims (1)

[Claims] 1 A magnetic core made of a magnetic core made of a high resistivity magnetic material, with thin films made of an alloy magnetic material attached on both sides of the front gap when viewed from the tape contacting surface side, and the thin films facing each other. a notch having a ridge line extending from each edge of the thin film facing the front gap to a side surface on the main portion of the magnetic core defining the overall width of the tape contact surface to define the track width of the front gap in the head; The shape of the thin film on the tape contacting surface is formed into a substantially isosceles trapezoid, and the angle of intersection between the legs of the isosceles trapezoid and an imaginary line perpendicular to the front gap is 20° or more and 50° or less. A magnetic head characterized by: