Bismuth glass composition, and magnetic head and plasma display panel including the same as sealing member

1. A Bismuth glass composition comprising 1.7 to 12 wt % of SiO 2 , 3 to 9 wt % of B 2 O 3 , 9.5 to 19 wt % of ZnO, 62 to 80 wt % of Bi 2 O 3 and 0.1 to 4 wt % of Al 2 O 3 , 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 Li 2 O, Na 2 O and K 2 O,

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 Sc 2 O 3 , Y 2 O 3 , La 2 O 3 , CeO 2 , Pr 2 O 3 , Nd 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , Tb 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Yb 2 O 3 and Lu 2 O 3 , and

the weight ratio of Al 2 O 3 to SiO 2 is 0.5 or less.

2. The bismuth glass composition comprising 1.1 to 4.5 wt % of SiO 2 , 4 to 9 wt % of B 2 O 3 , 9.5 to 18 wt % of ZnO and 72 to 85 wt % of Bi 2 O 3 and 4 wt % or less of Al 2 O 3 , 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 Li 2 O, Na 2 O and K 2 O,

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 Sc 2 O 3 , Y 2 O 3 , La 2 O 3 , CeO 2 , Pr 2 O 3, Nd 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , Tb 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Yb 2 O 3 and Lu 2 O 3 , and

the weight ratio of Al 2 O 3 to SiO 2 is 0.5 or less.

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

4. The bismuth glass composition in accordance with claim 3 , wherein the oxide of Group A comprises 2 wt % or less of Li 2 O, 3 wt % or less of Na 2 O and 4 wt % or less of K 2 O.

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

6. 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.

7. 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.

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

9. 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.

10. 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.

11. The bismuth glass composition in accordance with any one of claims 1 and 2 to 6 , wherein the weight ratio of ZnO to B 2 O 3 is 0.8 to 2.8.

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

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

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

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

21. 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.

22. 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.

23. 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.