JPH09221358A - Production of non-magnetic substrate for magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize yield at the time of compacting and to stabilize production yield when a CaO-TiO2 -NiO non-magnetic substrate for a magnetic head is produced. SOLUTION: Granulated powder having 0.3-4.0wt.% water content is produced using a binder and powder obtd. by weighing powders of CaCO3 , TiO2 and NiO by a prescribed amt. each, wet-mixing them, calcining and pulverizing the resultant mixture. The granulated powder is compacted and fired to produce the objective non-magnetic substrate having a compsn. consisting of 15-45mol% CaO, 40-80mol% TiO2 and 5-30mol% NiO.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video tape recorder (hereinafter referred to as VTR), a digital audio tape recorder (hereinafter referred to as DAT), a digital data recording device, or the like.
The present invention relates to a method for manufacturing a non-magnetic substrate for a magnetic head used in a magnetic head for recording and reading an audio signal, a video signal, an information signal, or the like as a magnetic signal on a recording track of a magnetic recording medium such as a magnetic tape.

[0002]

2. Description of the Related Art In recent years, in order to increase the image quality of recording or reproducing video signals, or to increase the storage capacity, more information signals are recorded or reproduced, so that the wavelength is shorter. A method of recording or reproducing a signal is used. For this reason, as a magnetic recording medium, a ferromagnetic metal powder is used as the magnetic powder in the magnetic layer, and a magnetic tape containing the same is coated on a base film which is a non-magnetic support, or a ferromagnetic metal material. A high coercive force magnetic recording medium such as a vapor deposition tape directly vapor-deposited on a base film has been used.

Further, in order to enable recording or reproducing on these high coercive force magnetic recording media, a metal magnetic material having a high magnetic permeability and a high saturation magnetic flux density, such as iron, is used as a magnetic core material of a magnetic head. Layered magnetic head using a system alloy, iron-nickel system alloy, iron-cobalt system alloy, etc.
Alternatively, a so-called metal-in-gap type magnetic head (hereinafter referred to as MIG head) or the like has been proposed.

In a laminated magnetic head, for example, a magnetic core half body is formed by sandwiching a magnetic core material, which is a film made of the above-mentioned metallic magnetic material, with a guard material made of a nonmagnetic material. The end surfaces of the half magnetic core materials are butted against each other to form a closed magnetic circuit having a magnetic gap. In such a magnetic head, a magnetic core half body is manufactured by a method of forming a metal magnetic film made of a metal magnetic material on a guard material which is a non-magnetic material, and further laminating the guard material. There is.

Therefore, the non-magnetic material used as a guard material for the above-mentioned laminated magnetic head has a thermal expansion coefficient close to that of a metal magnetic material and has excellent wear resistance against various high coercive force magnetic recording media. Is required.

If the thermal expansion coefficient of such a non-magnetic material for a magnetic head is significantly different from the thermal expansion coefficient of a metallic magnetic material,
There is a problem that the metal magnetic film formed on the guard material which is a non-magnetic material is peeled off or the guard material itself is cracked. Further, there arises a problem that the excellent magnetic characteristics of the metal magnetic film cannot be sufficiently obtained. for that reason,
It is desirable that such a non-magnetic material for a magnetic head has a thermal expansion coefficient close to that of a metal magnetic material.

Further, the non-magnetic material for magnetic head has excellent wear resistance to various high coercive force magnetic recording media as described above, and the amount of wear of the metal magnetic film against various high coercive force magnetic recording media. It is desirable that the difference from the above, that is, the uneven wear is small.

Therefore, the present inventors have filed a patent application No. 6-340.
As disclosed in Japanese Patent No. 404, a non-magnetic material for a magnetic head, which has a coefficient of thermal expansion almost equal to that of a metal magnetic film and is excellent in the balance between the amount of wear on a magnetic recording medium such as a magnetic tape and the amount of uneven wear is proposed. did.

This non-magnetic material for magnetic head is made of CaO, T
consisting of iO ₂ and NiO, CaO: 15 mol% to 45
Mol%, TiO ₂ : 40 mol% to 80 mol%, NiO:
It is characterized by having a composition of 5 mol% to 30 mol%.

A non-magnetic substrate for a magnetic head, which is made of a non-magnetic material for a magnetic head having the above composition range, is manufactured, for example, as shown below. That is, first, commercially available CaCO ₃ powder, TiO ₂ powder, and NiO powder are weighed in amounts necessary to form the above composition range, and these are wet-mixed in, for example, a ball mill for 24 hours.
Then, for example, drying, grinding, calcination, grinding, wet mixing,
Dry and pulverize to make powder. Then, a binder such as polyvinyl alcohol (hereinafter referred to as PVA) is added to this powder to produce a granulated powder.

Thereafter, the granulated powder is, for example, 50 times.
Perform press molding at a pressure of about MPa to 200 MPa,
Baking is performed in oxygen at about 1250 ° C to 1400 ° C. Further, a hot isostatic pressing process (hereinafter referred to as HIP process) is performed under a condition of 1150 ° C. to 1350 ° C. while applying a pressure of 100 MPa with Ar to obtain a non-magnetic substrate for a magnetic head.

[0012]

However, when the non-magnetic substrate for a magnetic head is manufactured as described above, the yield at the time of molding such as press molding is not stable and the manufacturing yield is unstable. .

The present invention has been proposed in view of such conventional circumstances. CaO: 15 mol% to 45 mol%,
TiO ₂ : 40 mol% to 80 mol%, NiO: 5 mol%
Provided is a method for producing a non-magnetic substrate for a magnetic head, which stabilizes the production yield during molding when producing a non-magnetic substrate for a magnetic head having a composition of ˜30 mol%. The purpose is to

[0014]

As a result of intensive studies by the present inventors in order to achieve the above object, a CaO—TiO ₂ —NiO based non-magnetic substrate for a magnetic head having a composition range as described above was manufactured. In this case, it was found that the water content in the granulated powder greatly affects the yield during molding.

That is, the method for producing a non-magnetic substrate for a magnetic head according to the present invention is obtained by weighing a predetermined amount of each powder of CaCO ₃ , TiO ₂ and NiO, wet mixing them, and then calcination and pulverization. A granulated powder is produced from the obtained powder and a binder, and the granulated powder is molded and then fired to produce CaO: 15.
In the case of producing a non-magnetic substrate having a composition of mol% to 45 mol%, TiO ₂ : 40 mol% to 80 mol%, NiO: 5 mol% to 30 mol%, the water content in the granulated powder is adjusted to 0. It is characterized by being set to 3% by weight to 4.0% by weight.

In the method for producing a non-magnetic substrate for a magnetic head of the present invention, the amount of water in the granulated powder is 0.3% by weight to.
Since the content is 4.0% by weight, the yield during molding is stable and the manufacturing yield is stable.

[0017]

EXAMPLES Preferred examples of the present invention will be described below based on experimental results, but it goes without saying that the present invention is not limited to these examples.

<Experimental Example 1> First, the effects of the composition of the non-magnetic substrate for the magnetic head on the wear resistance, the uneven wear resistance, the pore state and the coefficient of thermal expansion were investigated.

Experiment 1 First, the effect of the amount of NiO in the non-magnetic substrate for a magnetic head on the amount of wear of the non-magnetic substrate for a magnetic head and the amount of uneven wear of a magnetic head was investigated.

Preparation of Samples Mixing ratio (molar ratio) of CaO and TiO ₂ , CaO / TiO
₂ was kept constant at 45/55 and the amount of NiO was changed from 0 mol% to 80 mol% to manufacture a non-magnetic substrate for a magnetic head.

That is, first, commercially available CaCO ₃ powder, TiO ₂ powder, and NiO powder were weighed in appropriate amounts so as to obtain the respective compositions, pure water was added to the mixed powders constituting the respective compositions, and the mixture was mixed in a ball mill for 24 hours. Wet mixed for hours.
Then, each of these mixed powders is dried at 100 ° C. for 20 hours or more, coarsely crushed with an Ishikawa type Laikai machine, and then at 5 ° C. at 1100 ° C.
It was calcined for hours. Thereafter, each calcined mixed powder was pulverized with an Ishikawa-type raikai machine.

Then, pure water was added again to each of the pulverized mixed powders, and they were wet-mixed in a ball mill for 24 hours. further,
Each of these mixed powders is dried at 100 ° C. for 20 hours or more,
Pulverize each of these mixed powders after crushing with an Ishikawa type raikai machine.
10% by weight aqueous solution of 10% by weight was added so as to be 10% by weight of each mixed powder, and granulated to obtain a granulated powder.

Then, each of these granulated powders was adjusted to 80M.
Press molded at Pa and in oxygen from 1250 ° C to 1400
Fired at ℃. Further, HIP treatment was performed at 1150 ° C. to 1350 ° C. while pressurizing with Ar at 100 MPa to manufacture non-magnetic substrates for magnetic heads having different compositions of NiO.

Fabrication of Magnetic Head Then, magnetic heads were fabricated using the non-magnetic substrates for magnetic heads having different NiO contents produced as described above. In this experimental example, a laminated magnetic head was manufactured as the magnetic head.

In the magnetic head, as shown in FIG. 1, a pair of magnetic core halves 1 and 2 forming a closed magnetic path are butted and joined together, and a magnetic recording medium sliding surface 3 is formed. The magnetic gap G faces.

The magnetic core halves 1 and 2 are the guard material 11 and the laminated magnetic material films 4 and 5 which are non-magnetic substrates for magnetic heads.
Consists of The end faces of the laminated magnetic films 4, 5 are abutted on the abutting faces of the magnetic core halves 1, 2, and a magnetic gap G facing the magnetic recording medium sliding face 3 is formed between them. . The track width Tw of the magnetic gap G is regulated by the film thickness of the laminated magnetic films 4, 5 since the guard material 11 is a non-magnetic material. Further, a winding window 6 is formed on the abutting surface of the magnetic core half body 1 for regulating the depth Dp of the magnetic gap G and for winding a coil. It may also be formed on the abutting surface of the body 2.

Here, for the purpose of improving the head efficiency, the laminated magnetic films 4 and 5 are magnetic film 2 as shown in FIG.
It is preferable that the unit laminated magnetic film 23 in which 1 and the non-magnetic film 22 are alternately deposited is a laminated magnetic film deposited via an insulator film 24. In this magnetic head,
CoZrNbTa with a film thickness of 241 nm is used as the magnetic film 21.
The amorphous film is used as the non-magnetic film 22 and the film thickness is 10 nm.
Of the SiO ₂ film of 200 nm as the insulator film 24
Using the SiO ₂ film. Further, the unit laminated body film 23 was formed by laminating eight layers of the magnetic body film 21 with the non-magnetic body film 22 interposed therebetween, and the total film thickness was 2 μm. Further, the laminated magnetic films 4 and 5 are separated from each other by the unit laminated film 23 with the insulating film 24 interposed therebetween.
The layers were laminated, and the total film thickness was 19.6 μm.
In addition, the magnetic head is 2 mm (width) x 2 mm (height)
X 0.2 mm (thickness) with a track width of 1
The contact width was 9.6 μm and the radius of curvature was 8 mm.

Measurement of Wear Amount and Uneven Wear Amount of each magnetic head having the above-described structure is set so that the protrusion of the magnetic head from the drum is 30 μm.
It was mounted on a Sony VTR (BVW-50, trade name).
And two types of Sony video tapes (brand name BC
T-90ML and BCT-90MLA, hereinafter referred to as tapes A and B, respectively. Was slid for 100 hours under the conditions of 30 ° C. and 80% RH.

At this time, the amount of wear of the magnetic head (amount of change in protrusion) and the amount of uneven wear between the guard material and the laminated magnetic substance film at the gap were examined and evaluated. The relationship between the NiO content and the amount of uneven wear after sliding the tapes A and B is shown in FIG. 3 shows the result when the tape A was slid, and □ in the figure shows the result when the tape B was slid.
In a laminated magnetic head, uneven wear is generally a separation loss, and the separation loss is roughly represented by the following formula.

Separation loss = 54.6 d / λ (dB) (1) At this time, the d is the amount of uneven wear, and λ is the recording wavelength. As can be seen from this equation, when the uneven wear amount d becomes large, the output decreases particularly in the short wavelength region (high frequency region), so the uneven wear amount is preferably 15 μm or less.

FIG. 4 shows the relationship between the NiO content and the amount of wear after sliding the tapes A and B. Also in FIG. 4, ◯ indicates the result when the tape A was slid, and □ in the figure indicates the result when the tape B was slid.
If the amount of wear is large, the life of the head is shortened, so naturally the higher the wear resistance, the better.

Therefore, based on these results, when the balance of the amount of wear and the amount of uneven wear is comprehensively evaluated, the non-magnetic substrate for the magnetic head having the NiO content of 5 mol% to 30 mol% is suitable as the guard material. I knew it was.

Experiment 2 Next, the relationship between the content of CaO and TiO ₂ in the non-magnetic substrate for the magnetic head, the pore state and the coefficient of thermal expansion was investigated.

Preparation of Samples Sample Nos. For which CaO, TiO ₂ and NiO are shown in Tables 1 and 2. Commercially available CaCO so as to have a composition of 1 to 32
₃ powder, TiO ₂ powder and NiO powder are weighed in appropriate amounts, and 3
Two kinds of mixed powders were prepared, pure water was added to each of them, and they were wet-mixed in a ball mill for 24 hours.

[0035]

[Table 1]

[0036]

[Table 2]

Next, these mixed powders are heated at 100 ° C. for 2 hours.
After drying for 0 hours or more and coarsely pulverizing with an Ishikawa-type Raikai machine,
Calcination was performed at 00 ° C. for 5 hours. Thereafter, each calcined mixed powder was pulverized with an Ishikawa-type raikai machine.

Then, pure water was added again to each of the pulverized mixed powders, and they were wet-mixed in a ball mill for 24 hours. further,
Each mixed powder is dried at 100 ° C. for 20 hours or more, crushed with an Ishikawa type Laikia machine, and each mixed powder is mixed with 10 parts of PVA.
A weight% aqueous solution was added so as to be 10% by weight of each mixed powder, and granulated to obtain a granulated powder.

Then, each granulated powder was press-molded at 80 MPa and fired at 1250 ° C. to 1400 ° C. in oxygen. Further, while pressurizing with Ar at 100 MPa,
The sample N was subjected to HIP treatment at 150 ° C. to 1350 ° C.
o. 1-32 non-magnetic substrates for magnetic heads were obtained.

Measurement of Pore State and Coefficient of Thermal Expansion Next, sample No. of each molar ratio obtained as described above was used.
Regarding the non-magnetic substrates for magnetic heads 1 to 32, the state of pores and the coefficient of thermal expansion were evaluated. The results are shown in Table 1 and Table 2.
Are shown together.

In Table 1 and Table 2, in the evaluation result of the pore state, the mark ◯ indicates the state where the porosity is 0.1% or less,
The mark x indicates a state in which there are many pores that cannot be densified by HIP treatment.

From the results of Table 1 and Table 2, sample No. 7,
8, 15, 16, 22, 23, 24, 29, 30, 3
When the content of CaO exceeds 45 mol% and the content of TiO ₂ is less than 40 mol% as in Nos. 1 and 32,
It was found that these non-magnetic substrates for magnetic heads were unsuitable as a guard material because they did not densify even after HIP treatment and had a large number of pores, because the results in the pore state were poor.

From the results of Tables 1 and 2, sample N
o. The content of CaO is 1 like 1, 9, 17, and 25.
When it is less than 5 mol% and the content of TiO ₂ is 80 mol%
When it exceeds 1.0, the coefficient of thermal expansion is less than 100 × 10 ⁻⁷ / ° C., which is much smaller than the coefficient of thermal expansion of the metal magnetic film. Therefore, it was found that these non-magnetic substrates for magnetic heads are not suitable as a guard material.

That is, from these results, when the compounding ratios of CaO and TiO ₂ are in the ranges of 15 mol% to 45 mol% and 40 mol% to 80 mol%, the state of pores and the thermal expansion coefficient are good. Was confirmed.

Therefore, from the results of Experimental Example 1 and Experimental Example 2, CaO, TiO ₂ and NiO were contained, and CaO: 1
The non-magnetic substrate for a magnetic head having a composition of 5 mol% to 45 mol%, TiO ₂ : 40 mol% to 80 mol%, and NiO: 5 mol% to 30 mol% has a small porosity and is almost equal to a metal magnetic film. It was confirmed that it has a coefficient of thermal expansion of, and is excellent in the balance between the amount of wear on the magnetic tape and the amount of uneven wear.

<Experimental Example 2> Next, in manufacturing a non-magnetic substrate for a magnetic head, the influence of the water content in the granulated powder on the yield during molding was investigated.

First, suitable amounts of commercially available CaCO ₃ powder, TiO ₂ powder and NiO powder were weighed so that CaO, TiO ₂ and NiO were 32 mol%, 48 mol% and 20 mol%, respectively. Pure water was added and wet-mixed in a ball mill for 24 hours. Next, this mixed powder was dried at 100 ° C. for 20 hours or more, coarsely pulverized by an Ishikawa type Laikia machine, and then calcined at 1100 ° C. for 5 hours. Then, the calcined mixed powder was pulverized again by an Ishikawa type raikai machine.

Then, pure water was added again to the pulverized mixed powder, and the mixture was wet-mixed in a ball mill for 24 hours. Next, this mixed powder is dried at 100 ° C. for 20 hours or more, pulverized with an Ishikawa type Laikai machine, and then a 10 wt% aqueous solution of PVA is added to this mixed powder so as to be 10 wt% of the total powder weight, and granulated. , And granulated powder.

After that, the drying conditions of the dryer were adjusted to produce granulated powders in which the water content of the granulated powder was adjusted in the range of 0% by weight to 8% by weight.

Then, the influence of the amount of water in the granulated powder on the moldability was investigated. That is, each granulated powder having a water content of 0 wt% to 8 wt% was filled into a mold having an inner diameter of φ120 mm so that the height was 20 mm, and the pressure was 100 MPa.
The presence or absence of cracks and cracks in the molded product and the releasability of the molded product from the mold when press-molded under pressure were investigated. The results are shown in Table 3 together with the water content in the granulated powder. The results of mold releasability with the mold are those that can be easily removed from the mold and have good mold releasability, and those that are difficult or impossible to remove from the mold by clinging to the mold. It shows with x.

[0051]

[Table 3]

From the results shown in Table 3, it was found that when the water content in the granulated powder was less than 0.3% by weight, the end of the molded body was chipped or cracks were generated. It was also found that when the water content in the granulated powder exceeds 4.0% by weight, the granulated powder sticks to the mold and cannot be released from the mold.
That is, CaO: 15 mol% to 45 mol%, Ti
O ₂ : 40 mol% to 80 mol%, NiO: 5 mol% to 3
When manufacturing a non-magnetic substrate having a composition of 0 mol%,
When the amount of water in the granulated powder is 0.3% to 4% by weight, the molded body is free from chipping and cracks at the time of molding, the mold releasability from the mold is good, and the yield is stable. It was confirmed to do.

The water content is 0.3% by weight to 4%.
A molded body made of a granulated powder in a weight percentage of 135 is put in oxygen.
A non-magnetic substrate for a magnetic head was prepared by firing at 0 ° C. and then HIPing at 1200 ° C. while applying 100 MPa of Ar, and all these substrates were free from cracks and had a porosity of 0.1% or less. And was good.

In this experimental example, CaO and TiO
₂ and NiO are 32 mol%, 48 mol% and 2 respectively
Although the case of the composition of 0 mol% was described, CaO: 15
Mol% to 45 mol%, TiO _2: 40 mol% to 80 mol%, NiO: if the composition range of 5 mol% to 30 mol%, is similar.

As described above, when a nonmagnetic substrate having a composition of CaO: 15 mol% to 45 mol%, TiO ₂ : 40 mol% to 80 mol%, and NiO: 5 mol% to 30 mol% is manufactured, It was confirmed that if the amount of water in the granular powder is set to 0.3% by weight to 4.0% by weight, the yield during molding is stabilized and the production yield is stabilized.

That is, from the results of Experimental Example 1 and Experimental Example 2, the non-magnetic substrate for the magnetic head was set to CaO, TiO ₂ and N.
If it is composed of iO and has a composition of CaO: 15 mol% to 45 mol%, TiO ₂ : 40 mol% to 80 mol%, and NiO: 5 mol% to 30 mol%, the porosity is small and the metal is small. In addition to having a coefficient of thermal expansion almost equal to that of the magnetic film, it can be made to have an excellent balance between the amount of wear on the magnetic tape and the amount of uneven wear. When manufacturing this non-magnetic substrate for a magnetic head, CaCO ₃ , TiO ₂ , N
A predetermined amount of each powder of iO was weighed, wet-mixed, calcined, and pulverized to obtain a powder and a binder, and the water content was 0.3% to 4.0% by weight. It has been confirmed that if the powder is manufactured, and the powder is molded and then fired, the yield during molding is stabilized and the manufacturing yield is stabilized.

[0057]

As is apparent from the above description, in the method of manufacturing a non-magnetic substrate for a magnetic head of the present invention, the amount of water in the granulated powder is set to 0.3% by weight to 4.0% by weight. Therefore, the yield during molding is stable, the production yield is stable, and CaO: 15 mol% to 45 mol%, Ti
O ₂ : 40 mol% to 80 mol%, NiO: 5 mol% to 3
It is possible to stably manufacture a non-magnetic substrate for a magnetic head having a composition of 0 mol%.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing the configuration of a magnetic head.

FIG. 2 is a schematic view showing a laminated magnetic film.

FIG. 3 is a characteristic diagram showing the relationship between the NiO content and the uneven wear amount.

FIG. 4 is a characteristic diagram showing the relationship between the NiO content and the wear amount.

[Explanation of symbols]

 1, 2 Magnetic core half body 3 Magnetic recording medium sliding surface 4, 5 Metal magnetic film 6 Winding window 11 Guard material 21 Magnetic material film 22 Non-magnetic material film 23 Unit laminated film 24 Insulator film

Claims (1)

[Claims] 1. A granulated powder is produced from a powder obtained by weighing a predetermined amount of each of CaCO ₃ , TiO ₂ and NiO powder, wet-mixing the powder, and calcining and pulverizing the powder and a binder. , CaO: 15 after molding and firing
Mol% to 45 mol%, TiO _2: 40 mol% to 80 mol%, NiO: The method of manufacturing a non-magnetic substrate for a magnetic head for producing a non-magnetic substrate having a 5 mol% to 30 mol% having a composition, granulating A method for producing a non-magnetic substrate for a magnetic head, characterized in that the amount of water in the powder is 0.3% by weight to 4.0% by weight.