Nozzle tip for producing glass fibers and method for producing glass fibers

1. A nozzle tip for producing a glass fiber that is flat in cross-sectional shape, the nozzle tip being used by downwardly projecting from a bottom surface portion of a storage tank that stores a glass melt,

the nozzle tip comprising a pair of long-side walls and a pair of short-side walls, each of the long-side walls and the short-side walls comprising platinum or a platinum alloy, and a nozzle orifice for discharging the glass melt,

wherein the nozzle orifice has a flat hole shape in horizontal cross-section,

wherein each of the long-side walls has a cut-out on a discharge side of the glass melt, a width of the cut-out being 10-55% of a length of a longitudinal center axis of the flat hole shape of the nozzle orifice, the width of the cut-out being defined along the longitudinal center axis of the flat hole shape of the nozzle orifice, and

wherein the pair of long-side walls has a symmetrical shape about the center axis of the nozzle orifice,

wherein an end surface on a side of the cut-out of the long-side wall has an inclined surface resulting from a gradual decrease of a thickness of the long-side wall toward the side of the cut-out, and

wherein the inclined surface faces an inner side of the nozzle tip.

2. The nozzle tip as claimed in claim 1 , wherein the cut-out is formed at a center on a discharge side of the long-side wall.

3. The nozzle tip as claimed in claim 1 , wherein an opening portion by the cut-outs has an area (a total of an area of the two cut-outs) that is 1% to 45% of a total area (the total area containing the area of the opening portion by the cut-outs) of an inner periphery of the pair of long-side walls and the pair of short-side walls.

4. The nozzle tip as claimed in claim 3 , wherein the opening portion by the cut-outs has an area (a total of an area of the two cut-outs) that is 3% to 40% of the total area (the total area containing the area of the opening portion by the cut-outs) of the inner periphery of the pair of long-side walls and the pair of short-side walls.

5. The nozzle tip as claimed in claim 1 , wherein a ratio of a length of the longitudinal center axis to a length of a longest portion in a short-length direction of the nozzle orifice is from 2 to 8.

6. The nozzle tip as claimed in claim 5 , wherein the ratio of the length of the longitudinal center axis to the length of the longest portion in the short-length direction of the nozzle orifice is from 3 to 8.

7. The nozzle tip as claimed in claim 5 , wherein the ratio of the length of the longitudinal center axis to the length of the longest portion in the short-length direction of the nozzle orifice is from 3 to 6.

8. A method for producing a glass fiber with a flat cross-section that is symmetrical about a longitudinal center axis of a flat cross-sectional shape, the glass fiber producing method comprising the steps of:

passing a glass melt through the nozzle orifice of the nozzle tip of claim 1 , which is fixed to a bottom surface of a storage tank that stores the glass melt; and

drawing and discharging the glass melt out of the nozzle orifice, thereby quenching and fiberizing the glass melt.

9. The nozzle tip as claimed in claim 1 , wherein the flat hole shape of the nozzle orifice is an oblong shape.

10. The nozzle tip as claimed in claim 1 , wherein the flat hole shape of the nozzle orifice is one selected from the group consisting of a rectangular shape, an oval shape, a trapezoidal shape, a gourd shape, a dumb-bell shape, and a triangular shape.

11. The nozzle tip as claimed in claim 1 , wherein the platinum alloy is a first alloy comprising platinum and a noble metal that is at least one selected from the group consisting of rhodium, gold, palladium and silver, or a reinforced metal in which fine particles of zirconia are dispersed in the noble metal or the first alloy.

12. The nozzle tip as claimed in claim 11 , wherein the first alloy is a platinum rhodium alloy containing 5-30 weight % of rhodium in platinum, and the reinforced metal is a strengthened platinum rhodium alloy in which zirconia fine particles are dispersed in the platinum rhodium alloy.

13. The nozzle tip as claimed in claim 1 , wherein the width of the cut-out is 15-55% of the length of the longitudinal center axis of the flat hole shape of the nozzle orifice.

14. The nozzle tip as claimed in claim 1 , wherein the width of the cut-out is 20-55% of the length of the longitudinal center axis of the flat hole shape of the nozzle orifice.

15. The nozzle tip as claimed in claim 1 , wherein a length of the longitudinal center axis of the nozzle orifice is 2-10 mm, and a length of a longest portion in a short-length direction of the nozzle orifice is 0.3-2 mm.

16. The nozzle tip as claimed in claim 15 , wherein the length of the longitudinal center axis of the nozzle orifice is 2-8 mm, and the length of the longest portion in the short-length direction of the nozzle orifice is 0.5-2 mm.

17. The nozzle tip as claimed in claim 1 , wherein the nozzle tip has a vertical length of 0.5-7 mm, and a capacity of 0.3-140 mm 3 .

18. The nozzle tip as claimed in claim 1 , wherein the cut-out has a height that is 2-80% of the vertical length of the nozzle tip.

19. The nozzle tip as claimed in claim 1 , wherein the cut-out is rectangular in shape.