JPH0629151B2 - Sealing glass - Google Patents

Description

TECHNICAL FIELD The present invention relates to a glass for sealing a ferrite magnetic head.

2. Description of the Related Art Ferrite is widely used as a core material for magnetic heads because it has excellent magnetic properties, wear resistance, and machinability. FIG. 1 shows a typical structure of a video head using ferrite as a core material. This head is configured by facing ferrite core materials 1 with a gap equal to the gap width, the gap being formed by a gap glass 2, joined by a reinforcing glass 3, and finally winding a coil 4. As the gap glass, a material such as SiO ₂ or Pyrex glass which hardly reacts with ferrite even at a high temperature is generally used, and as a result, a head having a narrow gap width is stably obtained.

On the other hand, the reinforcing glass has to be softened and flown when heated in order to bond the core, but at this time, if the temperature is too high, mutual diffusion of the reinforcing glass and ferrite occurs,
Track width (TW) 5 is reduced. Fig. 2 shows a top view of the head, where the TW should originally be formed as shown in (a) by the mutual diffusion of the reinforcing glass and ferrite.
It is shown in (b) that the value has decreased. The length of the mutually diffused region is shown as an erosion amount 6.

The heating temperature is usually 750 ° C. or lower. If it is higher than that, the Pyrex glass used for the gap glass is softened or promotes erosion. Therefore, the reinforcing glass needs to be a glass that easily flows at 750 ° C or lower.
The coefficient of thermal expansion of the reinforced glass must be close to that of ferrite. Generally, the value is (90 ~ 115)
× 10 ^-7 / ° C, but in recent years, ferrite with a high saturation magnetic flux density, which is compatible with high resolution tapes, has a density of about 130 × 1.
It even reaches 0 ⁻⁷ / ° C. (for example, Horikawa et al., Proceedings of the Japan Society of Applied Physics 4a-ZE-8 (October 1985)).

Further, the head undergoes a polishing process during processing. Since water is used in this step, it is necessary that the reinforced glass has excellent water resistance.

Summarizing the above, the conditions required for the reinforcing glass for a ferrite head are shown as follows: softening at a working temperature of 750 ° C. or lower,
They are to flow and not to erode the ferrite, to have a coefficient of thermal expansion of (90 to 130) × 10 ⁻⁷ / ° C., and to be excellent in water resistance.

Conventionally, as a reinforced glass that takes such points into consideration, (1) Japanese Patent Publication No. Sho 49-8011 discloses a glass having a working temperature of 700 ° C. or less and a coefficient of thermal expansion (90 to 110) × 10 ⁻⁷ / ° C. Kaisho 50-
32210,32211,32212,32213 No. working temperature 700-75
Glass having a coefficient of thermal expansion (90 to 110) × 10 ⁻⁷ / ° C. at 0 ° C. (3) Working temperature 690 to 770 in JP-A-56-37246
Glass having a coefficient of thermal expansion (85 to 110) × 10 ⁻⁷ / ° C., (4) Working temperature of 350 to 380 in JP-A-57-55528.
Glass having a thermal expansion coefficient of (110 to 120) × 10 ⁻⁷ / ° C., (5) Working temperature of 730 ° C. in JP-A-59-223248,
A glass having a coefficient of thermal expansion (92 to 95) × 10 ⁻⁷ / ° C. is disclosed. (6) JP-A-53-145825 discloses a glass containing a ferrite component and having a ZnO content of 3% by weight or less.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, conventional glasses have not always been satisfactory in the following points. That is, the inventors have found Pb, Ba, Na and the like as glass components that erode ferrite, but the glasses (1) and (2) contain a large amount of PbO and Na ₂ O, and (3), (5) Since the glass of () contains a large amount of Na ₂ O and BaO, and the glass of (4) contains a large amount of PbO, it was easy to erode ferrite. Also, (3) and (5) are B
Since it contained a large amount of aO, B ₂ O ₃ and Na ₂ O, it had poor water resistance and was easily devitrified during work. Also (4) is PbF ₂
Since it contains a lot of water, the water resistance was poor. Furthermore, none of the above glasses had a coefficient of thermal expansion of 120 × 10 ⁻⁷ / ° C. or more. On the other hand, in (6), a glass containing about 7.7% or more of a ferrite component is disclosed as an example, but since the glass is deeply colored, the gap depth 7 shown in FIG. 3 is specified. There was a problem that the Apex 8 could not be seen when adjusting to the depth of.

In view of the above problems, an object of the present invention is to provide a glass for sealing having a novel composition.

Means for Solving the Problems SiO ₂ = 30 to 36% by weight%, B ₂ O ₃ = 0 to 5
%, PbO = 29 to 51%, ZnO + CdO = 4 to 20
%, Na ₂ O = 0 to 5%, K ₂ O = 9 to 16%, RO
(R is an alkaline earth metal) = 0 to 5%, Al ₂ O ₃ = 0
5%, a sealing glass consisting of _As 2 _{O 3} or _Sb 2 _O 3 = _0~0.5%. Preferably Is more effective in suppressing erosion. Further, if at least one of Fe ₂ O ₃ , MnO ₂ , and NiO, which are ferrite components, is contained up to 2%, erosion is further reduced.

Action The sealing glass of the present invention has excellent water resistance and has a coefficient of thermal expansion of (90 to 130) × 10 ⁻⁷ / ° C. By using this, corrosion of ferrite is suppressed and the track width is reduced. It is possible to easily obtain a head having a small number of heads.

Example The contents of components Pb, Na, alkaline earth metals, etc. that attack ferrite are reduced, and instead of these, K, Zn, C are used.
It was found that by increasing d, glass that is less likely to erode ferrite was obtained, and various experiments were conducted.

Sample Nos. 1 to 72 in the table are 30 to 30 of the glass for sealing of the present invention.
The thermal expansion coefficient, softening point, lead elution amount and erosion amount at 300 ° C are shown (Fig. 2b). Samples Nos. 73-90 show those of glasses outside the composition range of the present invention. The lead elution amount is the elution amount of Pb ions in the supernatant water when 200 to 350 mesh glass powder was boiled in 100 ml of pure water for 1 hour, and was used as a measure of water resistance. That is, with respect to the glass having a lead elution amount of 2 ppm or less, even if the head shown in FIG. 1 was immersed in pure water at 60 ° C. for 1 hour, there was almost no clouding or roughening on the surface of the reinforcing glass, and there was no practical problem. . As the ferrite material, Fe ₂ O ₃ = 64 mol% of Mn-
Zn ferrite (coefficient of thermal expansion = 130 × 10 ⁻⁷ / ° C.),
SiO ₂ was used as the gap glass, and a head having a gap width of 0.3 μm and a track width of 30 μm was prototyped.

As is clear from the table, the glass of NO.
To 130) × 10 ^-7 / ° C, the softening point is 640 ° C or less, so the fluidity at 750 ° C is also good, and the lead elution amount is 2.0 ppm or less, which is water resistant. The property was good, and the erosion amount when formed into a head was as small as 2.0 μm or less.

On the other hand, in the glass of Nos. 73 to 90, the erosion amount was about twice, and the ferrite was easily eroded, and the accurate track width could not be obtained.

Here, if SiO ₂ exceeds 36%, the softening point of the glass becomes too high, which is not preferable, and if it is less than 30%, devitrification tends to occur.

If B ₂ O ₃ exceeds 5%, the water resistance of the glass is lowered and the erosion is increased.

When PbO exceeds 51%, erosion becomes large, and when it is less than 29%, the working temperature becomes 750 ° C. or higher, which is not preferable.

When ZnO and CdO exceed 20%, the softening point becomes high, and when it is less than 4%, there is no effect of suppressing erosion. Also C
The more dO, the lower the softening point of the glass, and the lower the working temperature.

Na ₂ O increases erosion when it exceeds 5%.

If K ₂ O exceeds 16%, the water resistance of the glass decreases, and
If it is less than 5%, the softening point becomes high and there is no effect of suppressing erosion. If RO and Al ₂ O ₃ are not less than 5% including the amount that is inevitably mixed from the raw materials, the erosion will be increased or the softening will occur. The points are set too high.

As ₂ O ₃ or Sb ₂ O ₃ is suitable as a fining agent at 0.5% or less.

At least one of Fe ₂ O ₃ , MnO ₂ , and NiO has a function of further reducing the corrosion of ferrite. However, all of them also serve as coloring materials, so 0.5 to 2% is preferable. This is because if it exceeds 2%, it will be deeply colored and the apex in FIG. 3 will not be visible.

For the above glass, silica sand, boric acid, lead oxide, zinc oxide, cadmium oxide, soda ash, potassium carbonate, arsenous acid are used as raw materials, and other oxides or carbonates are used as the crucible for alumina or platinum crucible. Using 130
It was melted at 0 ° C. to 1400 ° C. for 30 minutes to 1 hour, and collected by water quenching or twin roller quenching. After that, it was processed into a wire with a diameter of 1 mm so that it could be easily worked, and used as a prototype of the head.

In the above description, application to a magnetic head has been described, but metal (for example, platinum, titanium, chromium-iron alloy, etc.) or glass (soda-lime glass, lead-potassium glass, etc.) having a similar coefficient of thermal expansion is bonded, or CRT is used. It goes without saying that it can also be applied to tube adhesion, hermetic sealing, etc.

EFFECTS OF THE INVENTION As described above, the glass for sealing of the present invention is excellent in water resistance, fluidity, and compatibility with the coefficient of thermal expansion of ferrite, and in particular, does not corrode ferrite and reduces track width. It is possible to easily obtain a magnetic head having a small amount.

[Brief description of drawings]

FIG. 1 is a structural diagram of a video head using the sealing glass of one embodiment of the present invention as a reinforcing glass, and FIG. 2 is a top view of the same head. (A) shows a case where the track width is obtained correctly. (B) is a state diagram when the track width is reduced by erosion, and FIG. 3 is an enlarged view of the abex portion of the head. 1 ... Core, 2 ... Gap glass, 3 ... Reinforcing glass, 4 ... Coil.

Claims (3)

[Claims] 1. SiO ₂ = 30-36% by weight, B ₂ O
₃ = 0 to 5%, PbO = 29 to 51%, MO (M is Z
n, at least one of Cd) = 4 to 20%, Na
₂ O = 0 to 5%, K ₂ O = 9 to 16%, RO (R is an alkaline earth metal) = 0 to 5%, Al ₂ O ₃ = 0 to 5%, A
Glass for sealing, comprising s ₂ O ₃ or Sb ₂ O ₃ = 0 to 0.5%. 2. The glass for sealing according to claim 1, wherein: 3. The glass for sealing according to claim 1 or 2, which contains 0.5 to 2% by weight of at least one of Fe ₂ O ₃ , MnO ₂ and NiO.