DE4105877A1 - Electromagnetic recording head with improved wear properties - uses glass compsn. with much higher hardness value but low softening point - Google Patents

Abstract

The electromagnetic recording head features 2 half cores with a magnetic gap between them over which the magnetic tape passes. The cores contain a glass material in each half with the compsn.: PbO 72-75 wt.%, B2O2 15-20 wt.%, SiO2 2-3 wt.%, ZnO 5-7 wt.% and Al2O3 0-1 wt.%. The amorphous material is formed as a layer on a surface shaped like a truncated pyramid. The truncation is of such a size that a gap of the correct length (TD) is formed by grinding and lapping. The core halves are connected together by the low melting glass (46). The Vickers hardness of the glass layer (46) is pref. 330-350 HV and the bending strength 40-50 g. The magnetic material (40) used in the head oref. contains Co, especially an alloy of Co-Nb-Zr. The insulating material used (42) is pref. SiO2. A barrier layer (44) is used, pref. of Cr. The core halves are formed by first forming a pyramidal surface in a ferrite substrate material. Then the angular surface is coated in succession with a layer of amorphous magnetic material (40), insulating layer, barrier layer and glass layer. The surface is then truncated by grinding and lapping. USE/ADVANTAGE - The glass shows a much improved wear-out performance. It works satisfactorily even at high temperature and high humidity. The glass softening temp. is the same as for the currently used glasses and the glass does not react with the magnetic material. The low softening point allows the glass to be melted without recrystallising the amorphous magnetic material.

Description

The present invention relates to a magnetic recording and / or Playback head, in particular a magnetic head, which is made with a glass material is provided for use in combination with an amorphous magnetic Material in the form of a magnetic film or layer suitable is.

To meet the requirements for high density magnetic recording, A magnetic head has been developed which is suitable for the magnetic layer amorphous magnetic material used. The magnetic head of this type has one Belt sliding surface, which consists of glass. This glass should necessarily be a low-melting glass, as disclosed in JP-A 29 88 07/1988 is.

The above-mentioned conventional glass material has been found to have problems in actual use and mass production of the magnetic head brings itself. So the glass is subject to e.g. B. irregular wear when the Magnetic head itself with a magnetic tape with high coefficient of friction at high Temperature and high relative humidity (e.g. 40 ° C and 90%) rubs so that the magnetic head output is impaired. An attempt to establish contact between the head and the band by increasing the thickness of the core of the head sliding surface Increasing to a few 10 µm results in an extremely low yield, since that Spalling of glass increases due to its insufficient strength. To the solution This problem requires a new type of glass with higher hardness.  

It is an advantage of the present invention to have a more reliable magnetic head to create which is less during its manufacturing process Flaking or less other damage and less irregular wear that occurs when the head is with rubs the magnetic tape.

According to the invention, a conventional glass material with a Vickers Hardness of around 310 HV replaced by a new glass material with a Vickers hardness from 330 to 350 HV. Vickers hardness is well known Dimensioning for the glass hardness.

Since the magnetic head according to the present invention is an amorphous magnetic one Material used as a magnetic layer, the glass material (for filling and for connection) are processed at a temperature which is less than is the crystallization point of the amorphous magnetic material. This is desirable because once the magnetic material is recrystallized, the magnetic properties of the amorphous magnetic material significantly worsen. There is therefore an upper limit on the filling and connection temperature of the glass material. It is also necessary to change the temperature to be billed in an electric furnace during a Mass production occurs.

Another advantage of the present invention is a glass material for to create the amorphous magnetic head, which has a suitable hardness and Has strength with a low softening point.

To meet this requirement, the optimal composition selected according to the invention as follows:

72 PbO 75; 15 B₂O₃ 20;
2 SiO₂ 3; 5 <Z _n O <7; and
O Al₂O₃ <1; (in% by weight)

Further advantages, features and possible uses of the present Invention emerge from the following description of exemplary embodiments in connection with the drawing. It shows

Fig. 1 is a fragmentary front view of a recording and reproducing system with a rotary head cylinder, which is provided with at least one pair of magnetic heads according to the present invention;

Fig. 2 is an illustration for explaining the basic operation of magnetic heads in general;

Figure 3 is a graphical representation of the hardness and flexural strength of the glass materials shown in Table 1;

Fig. 4 is a plan view of the tape sliding surface of the magnetic head according to an embodiment of the present invention;

Fig. 5 is an enlarged partial plan view of the tape sliding surface of the magnetic head shown in Fig. 4;

Fig. 6 is a plan view of the block from which the core halves are made, and

Fig. 7 is a plan view of the two blocks combined together.

Fig. 1 shows a fragmentary front view of a magnetic recording and reproducing system in which a magnetic recording and reproducing head according to the invention is used. In the center of a guide base 10 is a turret cylinder 12 which is mounted in an inclined position with respect to a base plate 14 by a support which is fixed to the base plate 14 and extends upwards through a central opening formed in the guide base 10 extends so that the turret cylinder 12 is also inclined with respect to the base base 10 . On opposite sides of the turret cylinder 12 are slidable guide support platform components 16 and 16 '. The guide support platform components 16 and 16 'support stems or pillars 18 and 18 ' and columnar guides 20 and 20 ', the pillars 18 , 18 ' are inclined in a parallel relationship to the outer peripheral surface of the rotary head cylinder 12 . When the system is turned on, a magnetic tape 22 is wound around the rotary head cylinder 12 for a circumferential extent of a predetermined angle. The rotary head cylinder 12 includes a plurality of magnetic recording and reproducing heads 24 .

FIG. 2 shows an illustration which will be referred to below with regard to the general functioning of magnetic heads. Although magnetic heads often differ greatly from one another in detail, they basically function in the manner shown in FIG. 2, whether they are recording or reproducing heads or a combination of both.

As shown in Fig. 2, a wire coil 30 is wound on a core 32 made of a material which very easily carries a magnetic flux (ie, the material has a high permeability). A non-magnetic gap 34 is formed in the core 32 at a desired location. These cores often consist of separate core halves which are connected to one another.

When an electric current flows through the coil 30 , the magnetic field lines 33 connected to the current run around the core 32 of high permeability. At the gap 34 , the field lines extend outside the core 32 to form a stray field 36 . The magnetic tape 22 passes through the stray field 36 above the gap 34 and is magnetized in a suitable manner during the recordings.

No current flows through the coil during playback and no stray field 36 is generated at the gap 34 . Rather, the tape previously recorded is moved over the magnetic head. The recorded tape 22 creates its own external magnetic field lines, many of which enter the core of the head. Some of these field lines run directly across the gap 34 into the core and back into the band to complete their loop. These lines are irrelevant to the playback process. Other field lines follow a path around the core 32 and through the coil 30 . These lines passing through the coil 30 are amplified to produce an output signal from the magnetic tape of the recorder.

In many examples, if a core 32 consists of separate core halves, a glass material is used for the two halves. The glass material used in the present invention can be manufactured according to the compositions shown in Table 1. It consists mainly of the oxides of the following five elements - PbO, B₂O₃, SiO₂, ZnO and Al₂O₃. The compositions are designated A to F.

Those prepared according to compositions A to F (shown in Table 1) Glass materials each have the characteristic shown in Table 2 Properties on.

Table 1

Table 2

The glass materials produced in accordance with compositions A to F (shown in Table 1) each have a Vickers hardness and a bending strength, as shown in FIG. 3.

As is apparent from Tables 1, 2 and Fig. 3, the glass materials differ greatly from one another with respect to their Vickers hardness, flexural strength and their reactivity with amorphous magnetic material, although with regard to their softening point temperatures (428-443 ° C) is only slightly different from each other are.

It is also noted that the compositions D, E and F manufactured glass materials in terms of their Vickers hardness and flexural strength are better than compositions A, B and C.

During processing, the glass materials are in relation to the Vickers Hardness less chipped (resulting in higher yields).

It is also noted that the compositions according to compositions C, D, E and F made glass materials only slightly with the amorphous magnetic Material react. This is especially true for those from the compositions  D and E made glass materials that are less than 1/3 as reactive as Composition A.

The above-mentioned effect is assigned to compositions B and C, which differ from the compositions D, E and F in the content of SiO₂ and Differentiate B₂O₃. As can be seen from Table 2 under processability, show compositions A, B and C have poor processing properties if these are used to manufacture the magnetic head. On the other hand found that compositions D, E and F have good processing properties demonstrate.

From the foregoing it is clear that it is possible to use a glass material the desired processability, strength and reactivity with the amorphous magnetic layer without the softening point of the glass material to change significantly. The glass material with a low softening point is for the manufacture of a magnetic head with an amorphous magnetic Layer very beneficial. The manufacture of glass materials with the above Desired properties mentioned is easily feasible if a high Softening point is not up for discussion. According to the present invention the glass material is expected to undergo contacting and heat treatment at a temperature of about 40 ° C above the softening point is subjected, and it is believed that the amorphous magnetic layer has a crystallization temperature Tx of 520 to 550 ° C. With a Crystallization temperature Tx from 520 to 550 ° C, has an amorphous magnetic Co-Nb-Zr layer with a saturated magnetic flux density Bs of 0.9 T to 1.0 T, which is sufficient for the magnetic head to transfer data onto a metal powder bandage with a magnetic field strength Hc of 1400-1500 Oe (where Hc is the magnetic field strength of the magnetic head and Oe the cgs unit from Oersted represents).

The invention is further described with reference to FIG. 4. This figure shows a top view of the tape sliding surface of the magnetic head of the present invention. A layer 40 of an amorphous magnetic material (hereinafter referred to as an amorphous magnetic layer 40 ), an insulating layer 42 made of SiO₂, a protective layer 44 made of Cr, and a layer 46 Filled and contacted glass material (hereinafter referred to as glass layer 46 ), a gap material 48 made of SiO₂, a ferrite substrate 50 , an angled surface 52 , a tip 52 'of the angled surface and a core half 54 are shown.

The magnetic head shown in Fig. 4 consists of two core halves 54 , 54 'between which the gap material 48 is inserted. Each core half 54 , 54 'consists of a ferrite substrate 50 with the angled surface 52 , the amorphous magnetic layer 40 , the insulating layer 42 and the protective layer 44 , which are successively formed on the angled surface 52 , and the filled glass layer 46th The two core halves 54 , 54 'are butted, such that the ground and lapped surfaces face each other. The grinding and lapping are performed on the amorphous magnetic layer 40 to achieve a desired track width.

At the time of merging, the gap material 48 (SiO₂) and the glass layer 46 react with one another to form an integral glass body.

FIG. 5 shows an enlarged view of the belt sliding surface shown in FIG. 4. In Fig. 5, the same reference numerals designate the same parts as in Fig. 4. In Fig. 5, a uniformly integrated glass layer 46 is shown, which is formed when the two core halves 54 , 54 'are butted, as mentioned above. The formation of the integrated glass layer 46 by the sintering or glazing of the glass material and the gap material is desirable for the firm butt joint of the two core halves. Unfortunately, the glazing expands on the split part. This shortens the desired track width (indicated by T _D in Fig. 4). This happens more often when glass composition A (shown in Table 1) is used. In addition, the filled glass material also reacts with the amorphous magnetic layer 40 to deteriorate the magnetic properties (increase in H _c ) of the amorphous magnetic layer. This also reduces the effective gap width and adversely affects the function of the magnetic head. The above-mentioned incident is conceptually indicated by the encircled area A in FIG. 5.

The above-mentioned undesirable event can be caused by using glass material to be avoided, the composition of which is described in the following the present invention specifies:

72 PbO 75; 15 B₂O₃ 20; 2 SiO₂ 3; 5 ZnO <7; and O Al₂O₃ 1; (in% by weight)

This effect is evident when the glass material e.g. B. is prepared from the composition D shown in Table 1. In this case, the part indicated by the encircled area A (shown in FIG. 5) is 1/3 smaller than the area in the case where the glass material is made from the composition A. In addition, the reduction in the track width T _{D is} less than 0.2 µm. In practice, this value is negligibly small. Using the glass material specified above increases the yields of the magnetic heads by more than 20%.

The glass material of composition D does not require any for its processing special conditions. In other words, it can be filled and contacted using the same temperature profile as for the glass material of the Composition A is used.

In another embodiment, a magnetic head was made from the glass material of composition E made using the same procedure and temperature profile as in the case of the glass material of composition D. It was found that the glass material was only slightly amorphous magnetic material responds and reducing the track width through its Glazing reaction with the fissile material was small. This made it possible manufacture very accurate, reliable magnetic heads with high yield.

The magnetic heads, each of the glass material of the composition D and composition E contained irregular wear and changing the output signal by running the magnetic tape for tested for an extended period of time. By the compositions mentioned above the magnetic heads worked without problems, even in one High temperature and high humidity environment.  

The previous explanations show that the contacting of the core halves is achieved more effectively by using any of the glass materials of the Compositions C to F, in particular compositions D to F, shown in Table 1.

The compositions shown in Table 1 are approximately whole numbers expressed, but they can also have decimals within the example weight percentages mentioned.

In the following, the method for manufacturing the magnetic heads of the present invention is explained. In Fig. 6 a plan view is shown of a block from which the core halves are produced. Shown are the amorphous magnetic layer 40 , the insulating layer 42 (SiO₂ layer), the protective layer 44 (Cr layer), the glass layer 46 , the gap material 48 (SiO₂ layer), the ferrite substrate 50 , the angled surface 52 and a Block 56 for the core halves 54 , 54 '.

The process begins with the angled serrated surface 52 in the ferrite substrate using a cutting saw or the like.

On the angled serrated surface 52 , the amorphous magnetic layer 40 (20 to 30 µm thick) made of an amorphous magnetic material (such as Co-Nc-Zr) is formed by a well-known sputtering method. On the amorphous magnetic layer 40 , the insulating layer 42 made of SiO₂ (0.3 µm thick) and the protective film 44 made of Cr (0.5 µm thick) are formed one above the other by sputtering. The insulating layer 42 and the protective layer 44 prevent the amorphous magnetic layer 40 from reacting with the glass material (mentioned later).

The space above the protective layer 44 is filled with a glass material of composition D shown in Table 1. One way in which this is accomplished is to place the sheet glass material on the angled serrated surface and heat it in a nitrogen atmosphere at 470 ° C for 20 minutes using an electric oven.

The top surface of the glass layer 46 is ground and lapped as much as is necessary to cut or blunt the tip of the angle of the magnetic layer to achieve the desired track width. The grinding and lapping ensure that the surface of the magnetic layer becomes a mirror surface with a surface roughness of approximately 0.05 S (tip-tip 0.05 µm). The mirror-like surface is provided by atomizing with the gap material 48 made of SiO₂. This achieves block 56 for core halves.

The block 56 is connected to another similarly shaped block 56 with the same parts as shown in Fig. 7 facing each other. In Figs. 6 and 7, the same reference numerals denote the same parts. One way of connecting the blocks 56 is accomplished by heating the two core halves in a nitrogen atmosphere at 473 ° C for 20 minutes using an electric furnace. This creates an integrated block. This block is cut along the cutting dimensions 58 into a plurality of head chips using a dicing saw or wire saw. One of the head chips thus obtained is shown in FIG. 4.

As mentioned above, the present invention provides a magnetic head with good Resistance to wear and high reliability, which is effective with a Minimum reaction of the glass material with the amorphous magnetic layer can be manufactured. These advantages are based on the selection of a glass material the optimal composition, which has a low softening point. This glass material can undergo a heat treatment for filling and contacting experienced a temperature of about 40 ° C above its softening point. This temperature for the heat treatment is lower than the crystallization point of the amorphous magnetic material.

Claims (9)

1. Electromagnetic recording / playback head with a coil connected to a power source associated with a pair of core halves with a magnetic gap inserted between the core halves such that the introduction of a magnetic tape on the surface of the electromagnetic head lines of force flow caused at the magnetic gap, which each allow the recording and reproduction of electrical signals, the electromagnetic head having the following:
an angled surface on a ferrite substrate,
an amorphous layer on the angular surface of the ferrite substrate,
a space of the angled surface which is filled with a glass material, the glass material
between about 72 and about 75% by weight of PbO,
between about 15 and about 20% by weight B₂O₃,
between about 2 and about 3% by weight SiO₂,
between about 5 and about 7 wt% ZnO, and
between approximately 0 and approximately 1% by weight Al₂O₃,
has, and
a blunt tip of the amorphous layer, the blunt tip connected to another, similarly blunt tip, with a gap material interposed therebetween. 2. A magnetic head having a pair of core halves connected by a glass material with an insulating layer interposed between them as a magnetic gap and each core half being formed by coating a substrate with an amorphous magnetic layer, the glass material
between about 72 and about 75% by weight of PbO,
between about 15 and about 20% by weight B₂O₃,
between about 2 and about 3% by weight SiO₂,
between about 5 and about 7 wt% ZnO, and
between approximately 0 and approximately 1% by weight Al₂O₃,
such that the glass material has a Vickers hardness between about 330 and about 350 HV and a flexural strength between about 40 and about 50 g. 3. A magnetic head according to claim 2, wherein at least part of the amorphous magnetic layer consists of an amorphous magnetic material, which has Co. 4. A magnetic head according to claim 3, wherein the amorphous magnetic material, which contains Co, is Co-Nb-Zr. 5. Magnetic head according to claim 2, wherein the insulating layer SiO₂ contains. 6. A magnetic head according to claim 2, wherein the substrate is an angled Surface which is coated with the amorphous magnetic layer, the tip of the angled surface being blunted to a to form the desired track width by grinding and lapping, and at which the pair of core halves are joined together, the insulating Layer between them is inserted through the glass material, which is the angled Surface only contacts the truncated surface. 7. Magnetic head according to claim 6, wherein the angled surface further with the insulating layer and the protective layer is coated, 8. Magnetic head according to claim 7, wherein the insulating layer SiO₂ and contains the protective layer Cr.   9. A method of manufacturing a magnetic head, comprising the following steps:
Forming an angled surface in a ferrite substrate,
Forming an amorphous layer on the angular surface of the ferrite substrate,
Filling a space of the angled surface with a glass material, the glass material
between about 72 and about 75% by weight of PbO,
between about 15 and about 20% by weight B₂O₃,
between about 2 and about 3% by weight SiO₂,
between about 5 and about 7 wt% ZnO, and
between approximately 0 and approximately 1% by weight Al₂O₃,
having,
Blunt a tip of the amorphous layer, and
Connect the blunted tip to another, similarly shaped tip, with a gap material inserted between them.