# US 7,407,902 B2 · Bismuth glass composition, and magnetic head and plasma display panel including the same as sealing member

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- Number: US 7,407,902 B2
- Document ID: US7407902B2
- Status: Granted
- Kind: B2
- Application number: 10/509,491
- Filed: 2003-03-28
- Published: 2005-08-18
- Granted: 2008-08-05
- Earliest claimed: 2002-03-29
- Assignees: Matsushita Electric Industrial Co., Ltd.
- Inventors: Shinya Hasegawa; Hiroshi Onishi; Mikie Kanai; Tetsuya Kamimoto
- Web page: https://patentgrep.com/patent/US7407902B2

## CPC

- C03C 8/24: Fusion seal compositions being frit compositions having non-frit additions, i.e. for use as seals between dissimilar materials, e.g. glass and metal; Glass solders
- C03C 3/068: containing rare earths
- Y10T 428/11: Magnetic recording head
- Y10T 428/1121: Multilayer
- C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A Bismuth glass composition including 0.5 to 14 wt % of SiO2, 3 to 15 wt % of B2O3, 4 to 22 wt % of ZnO, 55 to 90 wt % of Bi2O3 and 4 wt % or less of Al2O3, and further including 5 wt % or less of an oxide of Group A, 12 wt % or less of an oxide of Group B and 0.1 to 10 wt % of an oxide of Group C, wherein the oxide of Group A is at least one selected from the group consisting of Li2O, Na2O and K2O, the oxide of Group B is at least one selected from the group consisting of MgO, CaO, SrO and BaO, and the oxide of Group C is at least one selected from the group consisting of Sc2O3, Y2O3, La2O3, CeO2, Pr2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3 and Lu2O3.

## Claims

### Claim 1

A Bismuth glass composition comprising 1.7 to 12 wt % of SiO2, 3 to 9 wt % of B2O3, 9.5 to 19 wt % of ZnO, 62 to 80 wt % of Bi2O3 and 0.1 to 4 wt % of Al2O3, and
further comprising 5 wt % or less of an oxide of Group A, 12 wt % or less of an oxide of Group B and 0.1 to 10 wt % of an oxide of Group C, wherein
the oxide of Group A is at least one selected from the group consisting of Li2O, Na2O and K2O,
the oxide of Group B is at least one selected from the group consisting of MgO, CaO, SrO and BaO, and
the oxide of Group C is at least one selected from the group consisting of Sc2O3, Y2O3, La2O3, CeO2, Pr2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3 and Lu2O3, and
the weight ratio of Al2O3 to SiO2 is 0.5 or less.

### Claim 2

The bismuth glass composition comprising 1.1 to 4.5 wt % of SiO2, 4 to 9 wt % of B2O3, 9.5 to 18 wt % of ZnO and 72 to 85 wt % of Bi2O3 and 4 wt % or less of Al2O3, and
further comprising 5 wt % or less of an oxide of Group A, 12 wt % or less of an oxide of Group B and 0.1 to 10 wt % of an oxide of Group C, wherein
the oxide of group A is at least one selected from the group consisting of Li2O, Na2O and K2O,
the oxide of Group B is at least one selected from the group consisting of MgO, CaO, SrO and BaO,
the oxide of Group C is at least one selected from the group consisting of Sc2O3, Y2O3, La2O3, CeO2, Pr2O3, Nd2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3 and Lu2O3, and
the weight ratio of Al2O3 to SiO2 is 0.5 or less.

### Claim 3 (depends on 1)

The bismuth glass composition in accordance with any one of claim 1 comprising 4 wt % or less of the oxide of Group A.

### Claim 4 (depends on 3)

The bismuth glass composition in accordance with claim 3, wherein the oxide of Group A comprises 2 wt % or less of Li2O, 3 wt % or less of Na2O and 4 wt % or less of K2O.

### Claim 5 (depends on 1)

The bismuth glass composition in accordance with any one of claim 1 comprising 10 wt % or less of the oxide of Group B.

### Claim 6 (depends on 5)

The bismuth glass composition in accordance with claim 5, wherein the oxide of Group B comprises 5 wt % or less of MgO, 6 wt % or less of CaO, 8 wt % or less of SrO and 10 wt % or less of BaO.

### Claim 7 (depends on 1, 2, 6)

The bismuth glass composition in accordance with any one of claims 1 to 2 to 6 comprising 0.1 to 5 wt % of the oxide of Group C.

### Claim 8 (depends on 2, 3)

The bismuth glass composition in accordance with claim 2 or 3 comprising 0.1 to 2 wt % of Al2O3.

### Claim 9 (depends on 2, 3)

The bismuth glass composition in accordance with any one of claims 2 or 3 comprising 8 wt % or less of the oxide of Group B.

### Claim 10 (depends on 9)

The bismuth glass composition in accordance with claim 9, wherein the oxide of Group B comprises 2 wt % or less of MgO, 0.1 to 4.5 wt % of CaO, 0.1 to 4.5 wt % of SrO and 4 wt % or less of BaO.

### Claim 11 (depends on 1, 2, 3, 4, 5, 6)

The bismuth glass composition in accordance with any one of claims 1 and 2 to 6, wherein the weight ratio of ZnO to B2O3 is 0.8 to 2.8.

### Claim 12 (depends on 2, 3)

The bismuth glass composition in accordance with any one of claims 2 or 3, wherein the weight ratio of ZnO to B2O3 is 1.1 to 2.5.

### Claim 13 (depends on 1, 2, 3, 4, 5, 6)

A sealing member for a magnetic head comprising the bismuth glass composition in accordance with any one of claims 1 and 2 to 6.

### Claim 14 (depends on 2, 3)

A sealing member for a plasma display panel comprising the bismuth glass composition in accordance with any one of claims 2 or 3.

### Claim 15 (depends on 14)

The sealing member for a plasma display panel in accordance with claim 14 further comprising a low-expansion ceramic filler in a weight ratio of 0.01 to 4 with respect to the bismuth glass composition.

### Claim 16 (depends on 15)

The sealing member for a plasma display panel in accordance with claim 15, wherein the low-expansion ceramic filler is at least one selected from the group consisting of cordierite, willemite, forsterite, anorthite, zircon, mullite, β-eucryptite, β-spodumene, cristobalite, barium titanate, titanium oxide, tin oxide, aluminum oxide, zirconium oxide and quartz glass.

### Claim 17 (depends on 13)

A magnetic head comprising a pair of magnetic core halves, at least one of which being provided with a coil groove, a magnetic gap member interposed between surfaces of the magnetic core halves facing to a magnetic gap, and the sealing member in accordance with claim 13 for bonding the pair of magnetic core halves.

### Claim 18 (depends on 17)

The magnetic head in accordance with claim 17 further comprising a magnetic metal film on at least one of the surfaces facing to the magnetic gap.

### Claim 19 (depends on 17)

The magnetic head in accordance with claim 17, wherein each of the paired magnetic core halves comprises a pair of nonmagnetic substrates and a magnetic metal film sandwiched between the nonmagnetic substrates.

### Claim 20 (depends on 17)

A magnetic recording/reproducing device comprising the magnetic head in accordance with claim 17 to perform recording and reproducing information to and from a magnetic information recording medium.

### Claim 21 (depends on 14)

A plasma display panel comprising a front plate and a rear plate facing to each other, display electrodes and address electrodes arranged between the front plate and the rear plate, barrier ribs for isolating the address electrodes, dielectric layers covering the surfaces of the display electrodes and the address electrodes, respectively, and the sealing a member in accordance with of claim 14 for bonding the peripheries of the front plate and the rear plate.

### Claim 22 (depends on 21)

The plasma display panel in accordance with claim 21 provided with an air hole formed in the front plate or the rear plate, further comprising a glass tube communicating with the air hole, wherein an opening end of the air hole and an end of the glass tube are bonded with the sealing member.

### Claim 23 (depends on 2)

The bismuth glass composition in accordance with claim 2, wherein said bismuth glass composition has a thermal expansion coefficient of 60×10−7/° C. to 80×10−7/° C.