JP2008050236A - Lead-free glass composition and magnetic head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable low melting point lead-free glass composition, and a magnetic head using this lead-free glass composition. <P>SOLUTION: The lead-free glass composition comprises, in mass% based on oxide, 56-68 Bi<SB>2</SB>O<SB>3</SB>, 4-9 B<SB>2</SB>O<SB>3</SB>, 4-6 ZnO, >13 to ≤21 SiO<SB>2</SB>, 1-7 Na<SB>2</SB>O, 0-2 Sb<SB>2</SB>O<SB>3</SB>, 2-7 Fe<SB>2</SB>O<SB>3</SB>and 0-1 ZrO<SB>2</SB>. The lead-free glass composition preferably comprises, in mass% based on oxide, 60-68 Bi<SB>2</SB>O<SB>3</SB>, 4-8 B<SB>2</SB>O<SB>3</SB>, 5-6 ZnO, >13 to ≤17 SiO<SB>2</SB>, 1-5 Na<SB>2</SB>O, 1-2 Sb<SB>2</SB>O<SB>3</SB>, 2-7 Fe<SB>2</SB>O<SB>3</SB>and 0-1 ZrO<SB>2</SB>. The magnetic head is constituted by using these lead-free glass compositions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a lead-free glass composition. More specifically, the present invention relates to a bonding glass for a magnetic head used for fusing ferrite or metal, for example, a bonding glass suitable for gap formation and bonding of a magnetic head.
Furthermore, the present invention relates to a magnetic head using the above lead-free glass.

  In general, a magnetic head is formed by bonding and integrating magnetic cores made of an oxide magnetic material such as Mn-Zn ferrite or a composite of the oxide magnetic material and a metal magnetic material such as Sendust using bonding glass. Composed. For example, the working gap part of a magnetic head can be obtained by heating and melting a bonding glass drawn in a rod shape to a working high temperature above the melting point, pouring it between magnetic cores, and then cooling the glass between these magnetic cores. It is configured by fusing.

Such bonding glass is required to have severe characteristics in terms of water resistance, corrosion resistance, wear resistance, bonding strength, and the like, and since it can be drawn in a rod shape, a bonding glass mainly composed of PbO, SiO ₂ or the like has been proposed. (For example, refer to Patent Document 1).

By the way, if the thermal expansion coefficient of the magnetic head bonding glass is greatly different from that of an oxide magnetic material or a metal magnetic material, the residual stress is accumulated when the magnetic core is bonded, and thus there is a disadvantage that glass cracks are likely to occur. ing.
Therefore, the bonding glass for bonding an oxide magnetic material such as ferrite or a metal magnetic material has a thermal expansion coefficient of 85 × 10 ^{−7 to} 120 × 10 ⁻⁷ [ It is preferable to use a thing of about [° C. ⁻¹ ] Further, since a high temperature at the time of fusion affects the magnetic properties of the ferrite and metal magnetic thin film, the fusion temperature is preferably 620 ° C. or lower (a glass transition point of 460 ° C. or lower).

However, low-melting glass has a problem that chemical durability such as water resistance and alkali resistance is remarkably inferior to that of high-melting glass, and glass elution with a grinding liquid or a cleaning liquid frequently occurs when processing a magnetic head.
Also, conventional fused glass contains lead oxide PbO in order to lower the melting point, but since lead is an environmental management substance, it has environmental problems and disposal problems, and contains lead-based components. There is a need for low melting glass.

On the other hand, in order to achieve high-density recording, not only magnetic powder coating type but also vapor deposition type has come out and various types of tape sliding lubricants are used accordingly. Of these, lubricants with high abrasiveness are also used. When such a magnetic tape slides on the magnetic head, there is a problem in that the glass exposed on the sliding portion of the magnetic head is unnecessarily polished to cause a step in the sliding portion of the magnetic head. There is a need for glasses with excellent wear properties.
JP 61-101432 A

By the way, the conditions and problems specifically required for the lead-free glass used in the magnetic head are as follows.
(1) It is necessary to make the fusion temperature 620 ° C. or lower (glass transition point 460 ° C. or lower) without containing lead-based components.
(2) The coefficient of thermal expansion is about 85 × 10 ^{−7 to} 120 × 10 ⁻⁷ [° C. ⁻¹ ].
(3) Good chemical durability is required.
(4) Generally, lead-free glass tends to have a higher fusing temperature than lead-based component-containing glass. Therefore, in order to achieve low melting as in (1), B ₂ O ₃ is used as a glass-forming component rather than SiO _2. In many cases, lead-free low-melting glass is significantly inferior in wear resistance as compared with lead-based component-containing low-melting glass.
(5) Accordingly, a lead-free low-melting-point glass having a significantly improved wear resistance while suppressing the fusing temperature to 620 ° C. or lower (glass transition point of 460 ° C. or lower) is required. In a magnetic head using a lead-free glass composition on the sliding surface, it is necessary to make the magnetic head have good electromagnetic conversion characteristics with little uneven wear on the sliding portion of any magnetic tape.

An object of the present invention is to provide a lead-free glass composition that satisfies the characteristics required for a glass for a magnetic head and has no problems in the working environment and disposal.
Another object of the present invention is to provide a magnetic head using such lead-free glass.

In order to achieve the above-mentioned problems, the inventors increase the amount of SiO ₂ that is a glass-forming component and is thought to improve wear resistance, and the amount of other elements such as B ₂ O ₃ and Bi ₂ O _3. By adjusting the above, a glass composition having wear resistance equal to or higher than that of leaded glass was found without significantly increasing the fusing temperature.

That is, the lead-free glass composition according to the present invention is expressed in terms of mass% based on oxide, Bi ₂ O ₃ : 56 to 68%, B ₂ O ₃ : 4 to 9%, ZnO: 4 to 6%, SiO ₂ : More than 13% and 21% or less, Na ₂ O: 1 to 7%, Sb ₂ O ₃ : 0 to 2%, Fe ₂ O ₃ : 2 to 7%, ZrO ₂ : 0 to 1%, such as PbO It is characterized by not containing leaded components.

Moreover, the lead-free glass composition according to the present invention is expressed in terms of mass% based on oxide, Bi ₂ O ₃ : 60 to 68%, B ₂ O ₃ : 4 to 8%, ZnO: 5 to 6%, SiO ₂ : 13 % And 17% or less, Na ₂ O: 1 to 5%, Sb ₂ O ₃ : 1 to 2%, Fe ₂ O ₃ : 2 to 7%, ZrO ₂ : 0 to 1%. It is characterized by not containing lead components.

The lead-free glass composition according to the present invention is any one of the lead-free glasses described above, and is expressed in terms of mass% on the basis of oxide, and B ₂ O ₃ is 1 and the ratio of SiO ₂ is 1.8 or more. It is characterized by that.

  A magnetic head according to the present invention is characterized by using the above lead-free glass composition.

Bi ₂ O ₃ is a main component of the lead-free glass composition and has an effect of lowering the softening point and viscosity. This content is 56 to 68% (hereinafter, “%” means “% by mass” unless otherwise specified). If the content of Bi ₂ O ₃ exceeds 68%, the wear resistance of the glass is significantly worse than that of leaded glass, so this glass cannot be used for the sliding surface of the magnetic head. Since the glass contains a large amount of SiO ₂ that raises the fusing temperature, if the content of Bi ₂ O _{3 that has} the effect of lowering the fusing temperature is less than 56%, the fusing temperature becomes higher than the applicable range and the wettability deteriorates. From the viewpoint of the fusing temperature, a more preferable content of Bi ₂ O ₃ is in the range of 60 to 68%.

B ₂ O ₃ has an effect as a glass forming component together with SiO ₂ described later, and its content is 4 to 9%. When the content of B ₂ O ₃ exceeds 9%, the wear resistance of the glass is remarkably worse than that of leaded glass, and this glass contains a large amount of glass forming component SiO ₂ that raises the fusing temperature. Therefore, if the content of B ₂ O ₃ is less than 4%, the fusing temperature becomes higher than the applicable range. From the viewpoint of wear resistance and alkali resistance, a more preferable content of B ₂ O ₃ is in the range of 4 to 8%.

ZnO is effective in stabilizing the glass. This content is 4-6%. If the ZnO content exceeds 6%, the wear resistance of the glass is significantly deteriorated as compared with leaded glass, and it is difficult to use this glass for the sliding surface of the magnetic head. When the amounts of B ₂ O ₃ and SiO ₂ that are vitrification elements are insufficient, ZnO has an effect of assisting in vitrification, so if it is less than 4%, the glass becomes unstable and tends to devitrify. The more preferable content of ZnO from the viewpoint of glass formation is in the range of 5 to 6%.

SiO ₂ forms a network structure of glass, and is effective in stabilizing the glass, expanding the vitrification range, increasing the melting point, and improving the chemical durability and wear resistance. This content exceeds 13% and is 21% or less. When the content of SiO ₂ exceeds 21%, the fusing temperature becomes higher than the application range, and the thermal expansion coefficient becomes smaller than the application range. On the other hand, if the SiO ₂ content is 13% or less, the wear resistance of the glass is significantly deteriorated as compared with leaded glass, and it becomes difficult to use this glass for the sliding surface of the magnetic head. From the viewpoint of the fusing temperature, the more preferable content of SiO ₂ is in the range of more than 13% and 17% or less.

Na ₂ O has an effect of promoting the melting of the glass and lowers the fusing temperature. However, when contained in a large amount, the reliability of the glass is lowered and the thermal expansion becomes larger than the applicable range. Therefore, this content was 1-7%. If the Na ₂ O content exceeds 7%, the wear resistance of the glass will be significantly reduced, making it difficult to use it on the sliding surface of the magnetic head. It deteriorates and the thermal expansion coefficient becomes smaller than 85 × 10 ⁻⁷ [° C. ⁻¹ ]. From the viewpoint of wear resistance, water resistance, alkali resistance and thermal expansion, a more preferable content of Na ₂ O is in the range of 1 to 5%.

By substituting Sb ₂ O _{3 with} a part of Bi ₂ O ₃ , there is an effect of improving water resistance and alkali resistance without relatively increasing the glass fusing temperature. This content is 0 to 2%. If the content of Sb ₂ O ₃ exceeds 2%, the glass becomes unstable, and precipitates are likely to be generated in the glass at the time of fusing, resulting in poor wetting of the glass or cracks in the precipitation part. Or From the viewpoint of water resistance and alkali resistance, the more preferable content of Sb ₂ O ₃ is in the range of 1 to 2%.

Fe ₂ O ₃ has the effect of improving chemical durability such as water resistance and alkali resistance without relatively increasing the glass fusing temperature, and has the effect of slightly improving the wear resistance. The content of Fe ₂ O ₃ is 2 to 7%. Since Fe ₂ O ₃ is not a vitrifying element, if the content of Fe ₂ O ₃ exceeds 7%, the glass becomes unstable and cannot be drawn. Further, if the content of Fe2O3 is less than 2%, the wear resistance of the glass is remarkably deteriorated as compared with leaded glass, and it becomes difficult to use this glass for the sliding surface of the magnetic head.

ZrO ₂ has an effect of improving chemical durability such as water resistance and alkali resistance, and also has an effect of greatly improving the wear resistance. This content is 0 to 1%. Since the amount of SiO ₂ is large, if the content of ZrO ₂ exceeds 1%, the glass fusing temperature rises and wettability deteriorates.

  Since the lead-free glass composition according to the present invention does not contain a lead-based component, the lead-free glass composition has an effect of improving the working environment and not causing any trouble with disposal.

In addition, the conventional lead-free glass is significantly inferior in wear resistance compared to the leaded glass, but the glass composition according to the present invention contains SiO ₂ in a certain ratio or more with respect to B ₂ O ₃ . Thus, the fusion temperature can be suppressed to 620 ° C. or lower while having wear resistance equivalent to or higher than that of leaded glass and ensuring chemical durability. Therefore, the magnetic head using the lead-free glass composition of the present invention on the sliding surface is a magnetic head that has a good electromagnetic conversion characteristic, and is less likely to cause a glass dent in the sliding portion with respect to any magnetic tape. It is also a magnetic head that is easy to manufacture.

  Embodiments of the present invention will be described below.

  First, the lead-free glass composition according to the present embodiment will be described. Each component which comprises lead-free glass was mixed in the ratio shown in the Example of Table 1, and lead-free glass was created. The unit is mass%. In addition, what was put on the comparative example is the lead-free glass of the lead-free glass of the composition outside the claim, and the present use.

  About each glass obtained by the composition of Table 1, a thermal expansion coefficient (100-350 degreeC), a glass transition point, and a glass yield point were measured. The results are shown in Table 2.

Of the glasses obtained from the compositions shown in Table 1, all of Example Samples 1 to 13 and Comparative Samples 14 to 15 were vitrified, and no crystallization or devitrification was observed. Moreover, as shown in Table 2, the thermal expansion coefficients (at 100 to 350 ° C.) of Example Samples 1 to 13 are 87 × 10 ^{−7 to} 105 × 10 ⁻⁷ [/ ° C.], and the glass transition point is 434 to 454 ° C. It became.

In Table 3, the result of having evaluated the abrasion resistance of the glass of each material 1-15 in an Example and a comparative example is shown.

  As shown in FIG. 1, the abrasion resistance test method uses an open reel long-distance friction measuring device, and is perpendicular to the tape running direction at the position where the magnetic tape 2 slides on the side surface of the fixed drum 1. A rod-shaped glass 3 is attached with resin in the direction, and a magnetic tape brought into contact with the glass with a constant tension is slid by a predetermined distance. A side surface of the glass 3 at that time is shown in FIG. 2, and a part of the glass is shaved with a tape, and the shaved portion is defined as a dense hatched area A. The scraped width 2Y was measured, and the scraped volume was calculated from the wire diameter 2R of the glass 3, the scraped width 2Y and the scraped length (depth). However, since the length (depth) of the cut glass 3 is the tape width, it is constant and there is no problem even if it is not included in the calculation for the comparison of the cut dimensions. And compared. Therefore, it can be said that the smaller the area, the better the wear resistance. Measure the outer diameter of each sample with glass drawn to an outer diameter of 0.5 ± 0.02 mm, and use epoxy resin to adhere the glass 3 to the sliding surface of the glass 3 with the magnetic tape 2. The resin was not attached. The environment (temperature and humidity) is set to 40 ° C and 30% in a thermostatic chamber, and Tape 2 uses a 1/4 inch wide vapor deposition tape (using solid lubricant) for digital video. A new tape is used each time the glass is changed. It was used and reciprocated 10m one way 140m. The tape speed at this time is 5 m / sec, and the drum 1 does not rotate.

  The shaved area was determined as follows. As shown in FIG. 2 (cross section of the rod-shaped glass 3), the cut width is 2Y, the cut cross-sectional area is the dense hatched area A, and the fan-shaped area including the dense hatched area A and the coarse hatched area B From this, the area of the triangle (coarse shaded area B) was determined and used as the scraped area A.

FIG. 3 shows the relationship between the glass transition point (horizontal axis) described in Table 2 and the wear resistance (vertical axis) described in Table 3. The smaller the scraped area, the better the wear resistance. Sample 14 of the comparative example because a small amount of SiO ₂ to _B 2 _{O 3,} poor abrasion resistance. As in the examples, by increasing the ratio of SiO ₂ to B ₂ O ₃ to 1.8 or more, the current lead glass is maintained with the glass transition point kept at 460 ° C. or less (at a fusion temperature of 620 ° C. or less). Abrasion resistance equal to or higher than that of the sample 15 is obtained.

  Next, a magnetic head as shown in FIG. 4 is prepared using the glass of Sample 1, Sample 8, Comparative Sample 14 and Sample 15 of the examples, and the tape is slid to slide the ferrite on the sliding surface. The level difference with the glass was measured. The magnetic head 11 according to this embodiment is a so-called metal-in-gap (MIG) type magnetic head, and a high magnetic permeability metal magnetic thin film 13 is formed on the abutting surfaces of the ferrite core halves 12L and 12R. The two ferrite core halves 12L and 12R are joined with the glass composition 14 so that a magnetic gap g is formed between the metal magnetic thin films 13 via a gap film. Reference numeral 16 denotes a coil wound around the ferrite core half.

  The step between the ferrite and glass on the sliding surface when the tape is slid shows the wear resistance of the head, not the wear resistance of the glass alone. The lower the step, the better the wear resistance. The result is shown in FIG. Sample 1 and sample 8 in the example have a step difference between ferrite and glass 75 hours later compared to sample 14 in the comparative example, and the same level as sample 15 that is lead-based glass is maintained.

Moreover, in the measurement of FIG. 5, the result of having observed the interference fringe of the sliding surface after running a tape for 50 hours is described in FIG. FIG. 6A shows a schematic diagram of a magnetic head sliding surface (however, FIG. A shows one of two heads having different azimuth directions). FIG. 6B is a photomicrograph of the sliding surface of the magnetic head, in which the metal magnetic film 13, the ferrite core halves 12L and 12R, and the glass portion 14 of the head are shown. In FIG. 6B, some ring-shaped stripes over the head are interference fringes, and the same height portions are connected by the same line. The deviation of the interference fringes represents a step. That is, the greater the deviation of the interference fringes, the greater the step between the ferrite 12L, 12R and the glass 14 on the sliding surface, and the lower the wear resistance. The interference fringes before sliding are in a state of no deviation and no step (not shown).
Each photograph in FIG. 6B is a copy of the state of interference fringes on the sliding surface after 50 hours of tape running, that is, after sliding for 50 hours. The left and right photographs are the sliding surfaces of a pair of magnetic heads with different azimuth orientations. In sample 14, the interference fringes are greatly displaced after running the tape for 50 hours, whereas in samples 1 and 8, no step is seen even if the tape is run for 50 hours. It can be seen that the same level can be maintained. As described above, it can be said that Sample 1 and Sample 8 are superior in wear resistance as a head as compared with Sample 14.

Since the sample 14 has SiO ₂ of 13% or less and the ratio of SiO ₂ to B ₂ O ₃ is also less than 1.8, a step occurs when this glass is used for the sliding surface. Therefore, this glass cannot be used for the sliding surface of the magnetic head.
On the other hand, it has been found that glass satisfying the conditions of claims 1, 2, 3, or 4 has the same characteristics as lead glass in terms of thermal expansion, chemical durability, wear resistance, and level difference. Therefore, even if the glass is exposed on the sliding surface of the magnetic head, it is possible to produce a magnetic head having chemical durability, wear resistance, and level difference equivalent to those of conventional lead glass.

  Although the embodiments of the present invention have been described above, the lead-free glass composition and the magnetic head according to the present invention are not limited to the above-described embodiments. For example, as a magnetic head constituted by using the lead-free glass composition according to the present invention, a MIG type magnetic head has been described as an example. However, it can be applied to other types of magnetic heads such as a metal thin film laminated type head. it can.

  Also, for example, in the MIG type magnetic head configured using the lead-free glass composition according to the present invention, the lead-free glass composition according to the present invention is used as a fused glass provided on the so-called front gap side exposed on the sliding surface, The lead-free glass composition and the magnetic head according to the present invention can be variously modified and modified, such as a configuration using a glass composition having another composition on the so-called back gap side separated from the sliding surface. .

It is a block diagram which shows the measuring method of abrasion resistance. It is explanatory drawing with which it uses for calculation of the area of the cut glass. It is the graph which showed the evaluation result of the Example of Table 2 and Table 3, and the comparative example as a graph, and shows the relationship between a glass transition point and the scraped area. 1 is a configuration diagram showing an embodiment of a magnetic head according to the present invention. It is the graph which showed the relationship between sliding time and a level | step difference by making the evaluation result of the level | step difference of a part of Example and a comparative example into a graph. Fig. A is a schematic diagram of the sliding surface of the magnetic head, and Fig. B is 50 hours of a magnetic head (one pair with different azimuth orientations on the left and right) using part of the example and comparative glass as sliding surfaces. It is a microscope picture of the sliding surface after sliding.

Explanation of symbols

  11 .. Magnetic head, 12L, 12R ... Ferrite core half, 13. Metallic magnetic thin film, 14 ... Glass, g ... Magnetic gap

Claims (6)

Bi ₂ O ₃ : 56 to 68%, B ₂ O ₃ : 4 to 9%, ZnO: 4 to 6%, SiO ₂ : more than 13% and 21% or less, Na ₂ O: 1 to 7%, Sb ₂ O ₃ : 0 to 2%, Fe ₂ O ₃ : 2 to 7%, ZrO ₂ : 0 to 1%. _{2. The} lead-free glass composition according to claim 1, wherein B ₂ O ₃ is 1 in terms of mass% on an oxide basis and SiO ₂ is 1.8 or more. Bi ₂ O ₃ : 60 to 68%, B ₂ O ₃ : 4 to 8%, ZnO: 5 to 6%, SiO ₂ : more than 13% and 17% or less, Na ₂ O: 1 to 5%, Sb ₂ O ₃ : 1 to 2%, Fe ₂ O ₃ : 2 to 7%, ZrO ₂ : 0 to 1%. The lead-free glass composition according to claim ₃ , wherein B ₂ O ₃ is 1 and SiO ₂ is in a ratio of 1.8 or more in terms of mass% on an oxide basis. A magnetic head comprising the lead-free glass composition according to claim 1, 2, 3, or 4. The magnetic head according to claim 5, wherein at least a part of the lead-free glass composition is exposed on a sliding surface facing the recording medium.