JP2014076930A - Manufacturing method of glass preform and manufacturing apparatus of glass preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a glass preform, capable of preventing devitrification during molding.SOLUTION: In a molding process of supplying a glass molten liquid 22 on a molding die 11 from the tip part 14a of a feeding nozzle 14 having the tip part 14a extended in a vertical direction and cooling the molten liquid to form a glass preform 21, gas is sprayed from a spray nozzle 13 extended in a horizontal direction to the glass molten liquid 22 discharged from the feeding nozzle 14 before reaching on the molding die 11.

Description

  The present invention relates to a glass preform manufacturing method and a glass preform manufacturing apparatus.

  Conventionally, as a method for producing a glass optical element such as a glass lens, a method for heat press molding a glass preform is known. For example, Patent Document 1 describes a method for forming a glass preform on a molding die, which is a molten glass lump separated from molten glass that has flowed out from an outflow pipe, as a method for producing a glass preform. In the method for manufacturing a glass preform described in Patent Document 1, gas is blown from a cooling gas blowing port of a cooling gas blowing mechanism that surrounds the entire outflow pipe and has a cooling gas blowing port. Thereby, since cooling of the surface on the side exposed to the atmosphere of the glass lump can be promoted, Patent Document 1 describes that generation of striae can be suppressed.

JP 2009-263228 A

  However, when a glass preform is produced by the production method described in Patent Document 1, there is a problem that devitrification is likely to occur during molding, and crystals are likely to be produced in the glass preform.

  The main object of the present invention is to provide a method for producing a glass preform which is less prone to devitrification during molding.

  In the method for producing a glass preform according to the present invention, the glass preform is molded by supplying the glass melt from the tip of the supply nozzle extending along the vertical direction onto the mold and cooling it. Perform the process. In the molding step, gas is blown from a spray nozzle that extends along the horizontal direction to the glass melt that is discharged from the supply nozzle and reaches the top of the mold.

  The spray nozzle is preferably provided so as to surround the glass melt discharged from the supply nozzle over the entire circumference.

  It is preferable to arrange a shielding member between the tip of the supply nozzle and the spray nozzle to suppress the gas from the spray nozzle from reaching the supply nozzle.

  As the shielding member, a shielding plate reaching the glass melt side from the tip of the spray nozzle may be disposed between the supply nozzle and the spray nozzle in the vertical direction.

  As the shielding member, a cylindrical member surrounding the tip of the supply nozzle may be provided.

  It is preferable to spray a gas of 100 ° C. or less from the spray nozzle.

  The liquid phase viscosity of the glass may be 2.0 dPa · s or less.

  Air, nitrogen or helium may be sprayed from the spray nozzle.

  The glass preform may be molded by causing the glass melt to flow out from the supply nozzle and separating the glass melt supplied onto the mold from the glass melt flowing out from the supply nozzle.

  A glass melt droplet may be discharged from the supply nozzle to form a glass preform from the droplet.

  The apparatus for producing a glass preform according to the present invention includes a supply nozzle, a mold, and a spray nozzle. The tip of the supply nozzle extends along the vertical direction. A supply nozzle supplies glass melt from a front-end | tip part. A glass melt is supplied to the mold from a supply nozzle. The spray nozzle extends along the horizontal direction. The spray nozzle is discharged from the supply nozzle and sprays gas onto the glass melt before reaching the mold.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the glass preform which is hard to produce devitrification at the time of shaping | molding can be provided.

It is a schematic sectional drawing for demonstrating the manufacturing method of the glass preform in 1st Embodiment. It is a schematic sectional drawing for demonstrating the manufacturing method of the glass preform in 1st Embodiment. It is a schematic sectional drawing for demonstrating the manufacturing method of the glass preform in 1st Embodiment. It is a schematic sectional drawing for demonstrating the manufacturing method of the glass preform in 2nd Embodiment. It is schematic-drawing sectional drawing for demonstrating the manufacturing method of the glass preform in 3rd Embodiment.

  Hereinafter, an example of the preferable form which implemented this invention is demonstrated. However, the following embodiment is merely an example. The present invention is not limited to the following embodiments.

  Moreover, in each drawing referred in embodiment etc., the member which has a substantially the same function shall be referred with the same code | symbol. The drawings referred to in the embodiments and the like are schematically described. A ratio of dimensions of an object drawn in a drawing may be different from a ratio of dimensions of an actual object. The dimensional ratio of the object may be different between the drawings. The specific dimensional ratio of the object should be determined in consideration of the following description.

(First embodiment)
1 to 3 are schematic cross-sectional views for explaining a method for producing a glass preform in the present embodiment.

  In this embodiment, a glass preform is manufactured using the manufacturing apparatus 1 shown in FIGS. The manufacturing apparatus 1 has a molding die 11 for molding a glass preform. Although the shaping | molding die 11 is not specifically limited, In this embodiment, you may be comprised with the porous body. The constituent material of the mold 11 is not particularly limited, and examples thereof include silicon carbide, a carbon material, and a metal.

  Above the molding die 11, a supply nozzle 14 for supplying a glass melt is provided on the molding surface 11 a of the molding die 11. The front end portion 14a of the supply nozzle 14 extends along the vertical direction. A glass melt is supplied onto the molding surface 11a from the tip 14a of the supply nozzle 14.

  The mold 11 is supported by the support tube 10. A through hole 10 a that faces the mold 11 is formed in the support tube 10. A gas supply mechanism (not shown) is connected to the through hole 10a. The gas supply mechanism supplies an inert gas such as air or nitrogen to the through hole 10a. As described above, since the mold 11 is composed of a porous body, the gas supplied to the through hole 10 a passes through the mold 11 and is ejected from the molding surface 11 a of the mold 11. Therefore, on the molding surface 11a, the glass melt is held in a state of floating from the molding surface 11a.

  A spray nozzle 13 is provided below the tip (lower end) of the supply nozzle 14 in the vertical direction v. The spray nozzle 13 is provided so as to surround the vicinity of the tip portion 14a of the supply nozzle 14 over the entire circumference in a plan view (when viewed from the v direction). Therefore, the spray nozzle 13 is provided so as to surround the glass melt 22 discharged from the supply nozzle 14 over the entire circumference. The spray nozzle 13 extends along the horizontal direction.

  Next, a method for manufacturing the glass preform 21 (see FIG. 3) using the manufacturing apparatus 1 will be described in detail.

  First, as shown in FIG. 1 and FIG. 2, a glass melt 22 having a weight corresponding to the weight of the glass preform 21 to be manufactured is supplied from the supply nozzle 14 in a state where gas is jetted from the molding surface 11 a. It is supplied on the molding surface 11a. Specifically, as shown in FIGS. 1 and 2, the glass melt 22 is accumulated on the mold 11 while the mold 11 is slowly lowered. When the glass melt 22 accumulated on the molding surface 11a reaches a predetermined weight, the molding die 11 is rapidly lowered. Thereby, a predetermined amount of the glass melt 22 is separated, and a glass lump made of the glass melt is disposed on the molding surface 11 a of the mold 11. In addition, you may produce a glass lump by cut | disconnecting the glass melt which flows out out of the supply nozzle 14. FIG. Then, the glass preform 21 shown by FIG. 3 can be obtained by cooling a glass lump.

  In this embodiment, a gas such as air, nitrogen, or helium is discharged from the spray nozzle 13 that extends along the horizontal direction in the molding process to the glass melt 22 that is discharged from the supply nozzle 14 and reaches the mold 11. Spray. For this reason, the gas is sprayed from all directions perpendicular to the vertical direction v onto the glass melt 22 before being discharged from the supply nozzle 14 and reaching the mold 11.

  By the way, as described in Patent Document 1, when the cooling gas reaches the supply nozzle, the temperature of the supply nozzle is undesirably lowered. Therefore, the cooling gas spray nozzle is usually directed toward the center of the supply nozzle. It is provided so as to extend obliquely downward.

  However, as a result of diligent research by the present inventors, it has been found that when the spray nozzle is provided so as to extend obliquely downward toward the center of the supply nozzle, devitrified matter may be mixed into the glass preform. . As a result of further diligent research, the inventor has a glass lump (hereinafter referred to as “main glass lump”) for forming a glass preform because the glass lump is easily cut by the cooling gas blown obliquely downward from the blowing nozzle. .) Was formed, and it was found that minute additional glass lumps were formed, and the devitrified matter was mixed by mixing the small glass lumps into the main glass lumps.

  Since the volume of the small glass lump is small, it is easily cooled. For this reason, before the main glass lump is absorbed, the temperature of the minute glass lump is easily cooled down to a temperature range where crystal nuclei are generated. Therefore, the fine glass lump including the crystal nucleus is absorbed by the main glass lump. On the other hand, the main glass block has a larger volume than the fine glass block. For this reason, the temperature of the main glass lump is less likely to decrease than that of the fine glass lump, and the temperature of the main glass lump when the fine glass lump is absorbed by the main glass lump is usually higher than the temperature range where the crystal grows. . Therefore, the fine glass lump taken into the main glass lump rises in temperature again by the main glass lump and passes through the temperature range where the crystal grows more slowly than when cooling. At that time, crystal growth is promoted. As a result, it is considered that devitrified materials are mixed into the glass preform.

  On the other hand, in the present embodiment, air, nitrogen or helium is applied to the glass melt 22 before being discharged from the supply nozzle 14 and reaching the mold 11 from the spray nozzle 13 extending in the horizontal direction in the molding step. Spray gas.

  In this embodiment, the spray nozzle 13 is provided so as to extend horizontally. Therefore, the gas from the spray nozzle 13 is sprayed perpendicularly to the glass melt 22. Therefore, the glass lump is difficult to be cut and a small glass lump is hardly formed. Therefore, in this embodiment, devitrified substances are not easily mixed into the glass preform 21.

  Moreover, since the glass melt 22 is cooled by gas being sprayed from the spray nozzle 13, the occurrence of striae can be suppressed.

  Note that devitrification is more likely to occur when glass having a low liquidus viscosity is used for molding. Therefore, the technology capable of suppressing the mixing of devitrified substances into the glass preform 21 of the present embodiment is that the liquid phase viscosity of the glass is 2.0 dPa · s or less, 1.5 dPa · s or less, 1.0 dPa · s or less, Furthermore, it is more suitable when it is 0.8 dPa · s or less. The “liquid phase viscosity” is the viscosity at the liquid phase temperature of the glass.

  From the viewpoint of suppressing the occurrence of striae in the glass preform 21, it is preferable to blow a gas of 100 ° C. or less from the spray nozzle 13.

  In this embodiment, the glass preform 21 is caused to flow out from the supply nozzle 14 and the glass melt supplied onto the mold 11 is separated from the glass melt flowing out from the supply nozzle 14. The example which forms the glass lump for comprising was demonstrated. However, the present invention is not limited to this configuration. For example, a glass melt droplet may be discharged from the supply nozzle 14 and the glass preform 21 may be formed from the droplet.

  Other examples of preferred embodiments of the present invention will be described below. In the following description, members having substantially the same functions as those of the first embodiment are referred to by the same reference numerals, and description thereof is omitted.

(Second and third embodiments)
FIG. 4 is a schematic cross-sectional view for explaining the glass preform manufacturing method according to the second embodiment. FIG. 5 is a schematic cross-sectional view for explaining the glass preform manufacturing method according to the third embodiment.

  As shown in FIGS. 4 and 5, in the second and third embodiments, the gas from the spray nozzle 13 reaches the supply nozzle 14 between the tip portion 14 a of the supply nozzle 14 and the spray nozzle 13. The shielding member 15 which suppresses is provided. For this reason, it can suppress that the temperature of the supply nozzle 14 falls undesirably by the gas from the spray nozzle 13.

  Specifically, in the second embodiment, as shown in FIG. 4, the shielding member 15 is constituted by a shielding plate 15a. The shielding plate 15 a is provided between the supply nozzle 14 and the spray nozzle 13 in the vertical direction v so as to reach the glass melt 22 side (center side of the tip portion 14 a of the supply nozzle 14) from the tip of the spray nozzle 13. It has been. The shielding plate 15a is provided in a disc shape having a circular opening at the center.

  In 3rd Embodiment, as FIG. 5 shows, the shielding member 15 is comprised by the cylindrical member 15b. The cylindrical member 15 b is provided so as to surround the tip end portion 14 a of the supply nozzle 14. It is preferable that the lower end of the cylindrical member 15b is flush with the lower end of the distal end portion 14a or reaches below the lower end of the distal end portion 14a. Moreover, it is preferable that the lower end part of the cylindrical member 15b is provided in the taper shape so that it may taper down. In this case, the temperature drop of the supply nozzle 14 due to the gas from the spray nozzle 13 can be more effectively suppressed.

Example 1
As a glass composition, SiO ₂ 3.2 mass%, B ₂ O ₃ 17 mass%, ZnO 13.4 mass%, WO ₃ 1.2 mass%, TiO ₂ 1.5 mass%, La ₂ O ₃ 33.3 wt%, the _Gd 2 _{O 3} 11.5 mass%, _Ta 2 _{O 5} to 14 mass%, _Nb 2 _{O 5} 0.6 wt%, a ZrO ₂ 4 wt%, the Li ₂ O 0.3 mass%, the _Sb 2 _{O 3} to prepare a raw material such that the 0.05 wt% was melted for 4 hours at 1200 ° C..

  Using the production apparatus 1 depicted in FIG. 1, molten glass was supplied as a glass lump (mass 4 g) onto a mold, and a glass preform was molded. At this time, nitrogen gas at 20 ° C. was blown onto the glass melt at a flow rate of 10 liters / minute from the spray nozzle for 10 seconds from immediately after the glass melt started to flow out from the supply nozzle until the glass lump was formed.

  When observed at any 10 locations on the surface of the glass preform, devitrification and striae were not confirmed at any location.

The physical properties of the obtained glass preform were as follows: glass transition point 590 ° C., softening point 691 ° C., liquidus temperature 1020 ° C., thermal expansion coefficient 75 × 10 ⁻⁷ / ° C., refractive index nd 1.852, Abbe number νd 40. 1

(Comparative Example 1)
A glass preform was molded and observed in the same manner as in Example 1 except that nitrogen gas was blown obliquely downward as described in Patent Document 1. As a result, devitrification was confirmed in all 10 locations. No striae was observed.

(Comparative Example 2)
A glass preform was molded and observed in the same manner as in Example 1 except that nitrogen gas was not blown. As a result, striae were confirmed in all 10 locations. Devitrification was not observed.

DESCRIPTION OF SYMBOLS 1 ... Manufacturing apparatus 10 ... Support pipe 10a ... Through-hole 11 ... Mold 11a ... Molding surface 11b ... Through-hole 13 ... Spray nozzle 14 ... Supply nozzle 14a ... Tip part 21 of supply nozzle ... Glass preform 22 ... Glass melt

Claims (11)

A glass melt is supplied onto the mold from the tip of the supply nozzle extending along the vertical direction of the tip, and a glass preform is formed by cooling, and a molding process is provided.
A method for producing a glass preform, wherein, in the molding step, gas is blown from a spray nozzle that extends along a horizontal direction to a glass melt discharged from the supply nozzle and before reaching the mold.   The manufacturing method of the glass preform of Claim 1 which provides the said spray nozzle so that the glass melt discharged from the said supply nozzle may be surrounded over the perimeter.   The manufacturing method of the glass preform of Claim 1 or 2 which arrange | positions the shielding member which suppresses the gas from the said spray nozzle reaching the said supply nozzle between the front-end | tip part of the said supply nozzle, and the said spray nozzle. Method.   4. The glass preform according to claim 3, wherein as the shielding member, a shielding plate is disposed between the supply nozzle and the spray nozzle in the vertical direction so as to reach the glass melt side from the tip of the spray nozzle. Production method.   The manufacturing method of the glass preform of Claim 3 or 4 which arrange | positions the cylindrical member which surrounds the front-end | tip part of the said supply nozzle as said shielding member.   The manufacturing method of the glass preform as described in any one of Claims 1-5 which sprays the gas of 100 degrees C or less from the said spray nozzle.   The manufacturing method of the glass preform as described in any one of Claims 1-6 whose liquid phase viscosity of the said glass is 2.0 dPa * s or less.   The manufacturing method of the glass preform as described in any one of Claims 1-7 which sprays air, nitrogen, or helium from the said spray nozzle.   The glass melt is caused to flow out from the supply nozzle, the glass melt supplied onto the mold is separated from the glass melt flowing out from the supply nozzle, and the glass preform is formed. The manufacturing method of the glass preform as described in any one of these.   The method for producing a glass preform according to claim 1, wherein droplets of glass melt are discharged from the supply nozzle, and the glass preform is formed from the droplets. A supply nozzle for supplying a glass melt from the tip, the tip extending along the vertical direction;
A mold for supplying the glass melt from the supply nozzle;
A spray nozzle that extends along a horizontal direction, is discharged from the supply nozzle, and blows a gas to the glass melt before reaching the mold;
An apparatus for manufacturing a glass preform.

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