JPH04367529A - Production of jig for forming glass - Google Patents

Abstract

PURPOSE:To obtain a jig for glass forming excellent in mold release property, lubricating property and mechanical strength by etching a molding containing >=5% boron nitride and having prescribed shape and selectively exposing boron nitride. CONSTITUTION:A mixture consisting of >=5wt.% BN and the balance Si3N4 is pressed and fired to afford a molding having prescribed shape, to which is then subjected to etching with fluorine to dissolve Si3N4 and selectively expose BN. Thereby the objective jig for glass forming excellent in mold release property, lubricating property and mechanical strength is obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a glass forming jig containing boron nitride.

0002

[Prior Art] As described in Japanese Patent Publication No. 61-317, a molded body of BN (boron nitride) is an excellent heat-resistant material that can withstand temperatures of 2000°C or more in an inert atmosphere. In order to exhibit excellent lubricity and mold release properties, molds for molding glass optical elements or parts thereof, crucibles for storing molten glass, cutlery for cutting molten glass,
It has excellent properties as a glass molding tool such as a transportation jig.

However, the BN molded body has extremely low mechanical strength as it is, so it has the problem that it cannot be used in areas where a relatively large load is applied or where it slides or comes into contact with other members. For example, when a BN molded body is used as a material for an optical element mold, cracks and chips may occur due to the pressure applied during molding. Furthermore, when used for a member that slides or contacts another member, such as a mounting plate that holds an optical element, powder may be generated by the sliding or contact and may adhere to the surface of the optical element. On the other hand, in order to increase the strength of the glass forming jig and prevent glass from fusing,
The BN film is coated with Al2O3 or Z by sputtering etc.
A method of coating the surface of a base material such as rO2 is also considered, but there are problems in practicality because BN has poor wettability with the base material, is difficult to sputter, and is easy to peel off even after forming the BN film. . Therefore, it is necessary to increase the mechanical strength while maintaining the excellent lubricity and mold release properties of BN for glass molding jigs and tools.
Molded bodies mixed with O3, ZrO2, etc. have been developed.

0004

[Problem to be solved by the invention] However, in glass forming jigs and tools, when the BN content decreases, B
It became impossible to maintain the excellent lubricity and mold releasability of N, and the glass fused together, while when the BN content increased, there was a problem that it became impossible to maintain the mechanical strength as a tool. .

The present invention has been made in consideration of the above circumstances, and an object thereof is to provide a method for manufacturing a glass forming jig that prevents glass from fusing and can maintain sufficient mechanical strength. do.

[0006]

[Means for Solving the Problems] The method for manufacturing a glass forming jig of the present invention is to form a glass molding tool into a predetermined shape in a state containing 5% by weight or more of boron nitride, and then to selectively expose the boron nitride. The method is characterized in that the molded body is etched.

[0007]

[Operation] In the etching in the above structure, components other than BN in the molded body are removed, and BN is selectively exposed on the surface of the molded body. Therefore, a jig and tool having the excellent lubricity and mold releasability of BN can be obtained. Also, this characteristic is BN
It is sufficient to contain 5% by weight or more of the other components, and since the composition of the other components is relatively large, the high mechanical strength of the other components can be imparted to the tool.

[0008]

[Example 1] Si3 N4 and BN were mixed at six weight percentages shown in Table 1.

[0009]

[Table 1]

[0010] This mixture was pre-pressed at 1 ton, pre-sintered at a temperature of 900°C for 10 hours, and then ground to obtain a molded product having a shape and dimensions similar to the desired base material. This molded body was fired for 80 hours at a temperature of 1400°C, and then ground and
Polishing was performed to form a desired shape as a mold for molding an optical element. Then, these six types of molds were classified into those that were immersed in a 1% concentration hydrofluoric acid solution for 10 minutes and those that were not immersed, and were designated as Samples 1 to 12.

Using the molds of Samples 1 to 12, LaK glass was melted at 1450°C and molded at a mold temperature of 690°C, and the results shown in Table 1 were obtained. That is, samples 1, 3, 5, 7, 9, and 11, which were immersed in a hydrofluoric acid solution to combine fluorine and Si and volatilize to dissolve Si3N4 and expose BN, had a glass mold. The incidence of defects due to fusion bonding was relatively low. Moreover, among these samples, samples 1, 3, 7, and 9 containing 5% by weight or more of BN had almost no defects and had extremely good results. In addition, sample 11 contained BN at 25% by weight (
(i.e., 5% by weight or more), and by treatment with hydrofluoric acid, B
Even though N is exposed on the molding surface, the evaluation is "
△", but this is because the BN content is too high.
This is because "chips" occurred on the molding surface after 200 shots. Therefore, it was only found that Sample 11 is not suitable for use as a glass molding mold which is subjected to a considerable load if the BN content is 25% by weight or more. That is, B
Even if the N content is 25% by weight or more, it can be used, for example, in a mounting plate 6 for an optical element 5 to which hardly any load is applied, as shown in FIG. In the case of FIG. 1, by applying hydrofluoric acid treatment only to the inner circumferential surface 7 of the mounting plate 6 that is in contact with the heated and molded optical element 5, and exposing the BN to this inner circumferential surface 7, It can fully function as a mounting plate. In addition, (Note 1) for sample 6 in Table 1 is
Further molding was discontinued because the glass was firmly fused to the mold and could not be removed.

0012

[Example 2] Partial stability ratio is ZrO2 95% by weight, BN
Mixed at 5% by weight and processed in the same manner as in Example 1,
It was molded into the shape of the sleeve 2 of the mold shown in FIG. Figure 2
1 is an upper mold, and 3 is a lower mold. A sleeve 2 is provided so as to surround the molding surfaces of the upper mold 1 and the lower mold 3, and constitutes a mold for pressing a glass gob 4. In this case, the upper die 1 or the lower die 3 slides on the inner surface of the sleeve 2 when the glass gob 4 is press-molded. Before using this sleeve 2, boil it in distilled water for 10 minutes and
The rO2 was dissolved. Further, ultrasonic cleaning was performed for 1 hour. Through this operation, ZrO2 was dissolved and BN was exposed on the inner surface of the sleeve, and BN powder with insufficient bonding strength was also removed.

Next, using this sleeve 2, a glass gob 4 was press-molded as shown in FIG. In this molding, B
There were no surface defects caused by the N powder separating and adhering to the glass molded product. In addition, since this sleeve 2 has BN exposed on its inner surface, the glass does not fuse and has good sliding properties even under high temperatures.Moreover, it has high mechanical strength and does not crack, and has an extremely long life and excellent properties. It was able to demonstrate this and no problems occurred even after using it 2000 times.

On the other hand, as a comparative example, partially stabilized ZrO2
As a result of glass molding using a sleeve made in the same way with a mixing ratio of 70% by weight of BN and 30% by weight of BN,
The sleeve of this comparative example broke after being used about 100 times, and could no longer be used.

[0015]

[Effects of the Invention] The present invention selectively exposes BN by etching a molded product containing 5% by weight or more of BN. Molding jigs and tools can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a mounting plate using Example 1 of the present invention.

FIG. 2 is a sectional view of a mold using Example 2 of the present invention.

[Explanation of symbols]

1 Upper mold 2 Sleeve 3 Lower mold 4 Glass lump 5 Optical element 6 Placement plate

Claims (1)

[Claims] 1. A jig for glass forming, characterized in that the formed body is formed into a predetermined shape in a state containing 5% by weight or more of boron nitride, and then the formed body is etched so that boron nitride is selectively exposed. Production method.