JPS5822810B2 - magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic head in which a track width is regulated by a track width regulating groove provided in a core.

Recently, as the density of magnetic recording increases, the track width of magnetic tape (that is, during recording) tends to become narrower and narrower.

Therefore, the video magnetic head itself used for this purpose has to be of a type compatible with narrow track widths, and in order to maintain the strength of the head core and regulate the predetermined track width, one side is used as shown in Figure 1. A so-called grooving type magnetic head having a track width regulating groove 3 (track width Tw) provided in the magnetic head core 1 has been widely adopted.

Generally, a glass material 4 is widely used as the material filled in the track width regulating groove 3.

As the glass material 4, it is preferable to use 5iO2-PbO glass from the viewpoint of maintaining strength and having almost the same coefficient of thermal expansion and hardness as the head core (e.g. ferrite), and 5i02 and PbO are Each must be contained in an amount of 10% by weight or more.

However, since the coefficient of friction of SiO2 and PbO is large, when the magnetic tape slides in contact with the glass material 4 containing these as main components, excessive stress is applied to the herad core (e.g. ferrite). It has been found through experiments by the present inventor that so-called sliding noise is more likely to occur.

One of the causes of this sliding noise is that irregular vibrations occur due to the large coefficient of friction between the magnetic tape and the surface of the glass material 4, and irregular stress fluctuations are applied to the head core, which causes magnetostrictive phenomena in the head core. This seems to be because it occurs.

Furthermore, as the track width becomes narrower, the contact area between the magnetic tape and the glass material 4 on the tape sliding surface increases, which further increases the sliding noise.

This sliding noise increases particularly in proportion to the running time of the magnetic tape.

Therefore, when this type of magnetic head was conventionally used in, for example, a video tape recorder, there was a problem in that the reproduced image flickered due to the generation of sliding noise, making it impossible to obtain a clear image.

In order to reduce such sliding noise, attempts have been made to reduce the average crystal grain size of the ferrite material, or to mix certain elements or oxides into the ferrite material, but as mentioned above, The reality is that improvements regarding the glass material filled in the track width regulating grooves have not yet been made sufficiently.

The present invention has been made to correct the above-mentioned defects, and provides a magnetic head in which the track 11-1 is regulated by a track width regulating groove provided in the core. Add 0.4 fluorine to
This invention relates to a magnetic head characterized in that it is filled with a 5iO2-pbo glass composition containing ~1.6% by weight.

This makes it possible to significantly reduce sliding noise.

The glass material filled in the track width regulating groove of the magnetic head according to the present invention contains fluorine in an amount of 0.4 to 1.6% by weight.
It is characterized by being an in2-PbO glass composition.

That is, when a 5iO2-PbO glass composition contains fluorine, the radius of pb ions is particularly large among the components of the glass material (the ionic radius of Pb2+ is 1.32λ);
By mixing a predetermined amount of fluorine ions (ion radius of F- ions: 1.33N) that have a large enough negative charge to block this positive charge, the surface energy on the glass surface is reduced and the wetting of the glass surface is reduced. 3 (Furthermore, the fluorine contained in the glass material is SiO2
It seems that the O atom is inserted into the place where the O atom is missing and is bonded.

) This effectively prevents adhesion of fallen magnetic powder and the binder, and prevents irregular vibrations from occurring due to friction between the glass material and the magnetic tape.

Therefore, it is possible to suppress the propagation of irregular stress fluctuations to the head core, thereby suppressing the occurrence of magnetostrictive phenomena in the head core, and it is possible to greatly reduce sliding noise.

In the present invention, it is essential that the content of fluorine contained in the 5in2-PbO glass composition is 0.4 to 1.6% by weight.

That is, if the fluorine content is less than 0.4% by weight, no sliding noise reduction effect can be expected, and if it exceeds 1.6% by weight, the temperature at which the head core is fused through the glass material may be affected. This is because the evaporation of fluorine becomes intense, and as a result, fine defects (ie, pores) are generated in the glass material, which may result in residual strain at room temperature.

The basic composition of the SiO□-PbO glass material filled in the track width regulating groove of the magnetic head according to the present invention is preferably as follows.

5i02 20-60% by weight PbO 15-30 〃 Na2O 10-30% by weight B2O3 10-30 〃 In this basic composition, Al2O3 can be substituted within a range of 10% by weight or less.

However, it is desirable that the total amount of SiO2 and PbO is 45% by weight or more.

In order to incorporate fluorine into the 5iO2-PbO glass material, fluoride may be mixed into the above-mentioned glass components, but the fluoride used is zinc fluoride (Z n F
2), aluminum fluoride (AlF3), cadmium fluoride (CdF2), potassium fluoride (KF), calcium fluoride (CaF2), silver fluoride (AgF), chromium fluoride ([
) (Cr F 2 ), chromium fluoride l1Il) (Cr
F3), strontium fluoride (SrF2), cesium fluoride (CsF), silver fluoride (FeF3), sodium fluoride (NaF), lead(II) fluoride (PbF2), barium fluoride (BaF2), fluoride conversion, ;<-qs(13iF
3), magnesium fluoride (Mg F 2 ), mangaf fluoride QI) (Mn F 2 ), lithium fluoride (L
iF), etc.

Next, an example will be described to explain the present invention in more detail.

Example PbF2 was mixed as a fluoride into the following glass components.

(However, the proportion of fluorine in the mixture is 0.14% by weight, 0.
．． 45% by weight, 0.74% by weight, 1.02% by weight, 1.
41% by weight respectively) Using a glass material made of the above mixture, as shown in FIG. The groove 3 was filled and the head core 1 was fused to produce a magnetic head for a video tape recorder.

At this time, the head gap 11 may be filled with the glass material 4, or if it is not filled, 5iO1SiO2 or the like may be sputtered or vapor-deposited on the core surface of the gap 11.

Then, this magnetic head is attached to a helical scan type video tape recorder together with a head drum, and the magnetic head is made of Co-γ system (γ-Fe2O3 containing Co).
When the sliding noise (5 MHz) after running a video tape having a magnetic layer for a predetermined period of time was measured, the results shown in FIG. 3 were obtained.

In Fig. 3, the sliding noise ratio on the vertical axis is the first time the tape is run (that is, the first time the tape is run).
It shows the amount normalized by the sliding noise at .

That is, the above-mentioned sliding noise represents the ratio of the noise when the demagnetized tape is running to the amplifier noise at 5 MHz when the demagnetized tape is running, and when this sliding noise is expressed in decibels, it is as follows. In FIG. 3, the sliding noise expressed by the above equation during the first tape run is set to 0 (db).

Note that when the tape is run for a certain amount of time, the unevenness on the tape surface becomes less and the tape surface becomes clearer, so the sliding noise becomes smaller, and as a result, the sliding noise ratio [db ] becomes 0 (db) or less once.

However, as the number of runs increases further, the sliding noise starts to rise again.

□As is clear from Figure 3, when PbF2 is not added, the sliding noise increases rapidly with the passage of travel time, and when PbF2 is added to 1 part by weight (fluorine content: 0)
．． 14% by weight), the amount is too small and a sudden increase in sliding noise is observed.

However, it can be seen that when the amount of PbF2 added is increased, the sliding noise is significantly reduced.

That is, the amount of PbF2 added was 3 parts by weight (fluorine content: 0
．． 45% by weight), a significant reduction in sliding noise was observed, and the amount added was 5 parts by weight (fluorine content: 0.74% by weight) and 7 parts by weight (fluorine content: 1.02% by weight). ,1
It can be seen that as the content of fluorine increases to 0 parts by weight (fluorine content: 1.41% by weight), the sliding noise is further reduced.

Therefore, the addition range of fluorine according to the present invention is 0.4 to 1.
At 6% by weight, the sliding noise can be most effectively reduced by using a glass material having a fluorine content near the upper limit of 1.6% by weight.

Note that, other than ferrite, for example, sendust can also be used as the core material.

The shape and structure of the magnetic head may be as shown in FIG. 1 or as shown in FIG. 4 (track width regulating grooves are formed in both cores, respectively).

Further, the present invention can be applied to erasing heads, and can also be applied to magnetic heads for audio.

As described above, the present invention provides at least the track width regulating groove,
5iO2-PbO containing 0.4-1.6% by weight of fluorine
Since the system is filled with a glass composition, the presence of a predetermined amount of fluorine reduces the surface energy of the sliding surface of the glass material, which allows smooth sliding between the glass material and the magnetic tape, resulting in a large amount of sliding noise. can be reduced in width.

[Brief explanation of the drawing]

FIG. 1 is a front view of a conventional magnetic head. 2 and 3 show an embodiment of the present invention. FIG. 2 is a front view when the present invention is applied to a video magnetic head, and FIG. 3 is a front view of the above-mentioned video magnetic head. FIG. 2 is a graph showing the relationship between running time and sliding noise when using. FIG. 4 is a front view showing a modification of the above-described embodiment. In addition, in the symbols used in the drawings, 1...
・Head core, 3...Track width regulation groove, 4.
. . . Glass material, 11 . . . Head gap.

Claims (1)

[Claims] 1. In a magnetic head in which the track width is regulated by a track width regulating groove provided in the core, at least the track width regulating groove is coated with 0.4 to 1.6 fluorine.
A magnetic head characterized in that it is filled with a 5in2-PbO-based glass composition containing 5in2-PbO in an amount by weight.