JPS60195026A - Material for direct press molding of optical glass part - Google Patents

Abstract

PURPOSE:To carry out direct press molding of optical glass lens having improved image forming quality, by using silicon carbide shown by alpha type SiC as a molding material. CONSTITUTION:A sintered rod of silicon carbide shown by alpha type SiC is processed to prepare a pair of molds for press molding, consisting of the upper mold 1 having the concave face 3 and the lower mold 2 having the concave face 4, which are set in a press machine. The massive glass 11 of optical glass is placed on the lower mold 2, heated, by the heater 6, a pair of the molds 1 and 2 are transferred by the piston cylinders 7 and 8 and the massive glass 11 is press molded. Since the molds 1 and 2 are molds made of silicon carbide shown by alpha type SiC as a material, no chemical reaction occurs at the contact face between the molds and glass, and glass after molding will not cause devitrification.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing optical glass parts, such as prisms and lenses, and in particular to a method for manufacturing optical glass parts by direct press molding, which does not require a polishing process after press molding. The present invention relates to a press molding mold material that can be used for manufacturing.

Conventional configurations and their problems In recent years, optical glass components, especially optical glass lenses, have been trending towards aspheric surfaces, which can simultaneously simplify the configuration of the lens system of optical equipment and reduce the weight of the lens part. . For manufacturing this aspherical lens, the polishing method, which is a conventional optical lens manufacturing method, is difficult to process and mass-produce, so direct press molding is seen as promising.

This direct press molding method uses an aspherical mold that has been finished to the desired surface quality and precision in advance.
A method of manufacturing optical lenses by heating a lump of optical glass or press-molding a pre-heated lump of optical glass, without requiring post-processes such as further polishing or polishing after press-molding. be.

However, the method for manufacturing the optical glass lens described above,
After press molding, the image forming quality of the obtained lens is required to be excellent to the extent that it is not impaired.

Therefore, as a mold material, it must have minimal chemical action on glass at high temperatures, be resistant to damage such as scratches on the glass pressing surface of the mold, and have high resistance to destruction due to thermal shock. etc. are necessary.

Conventionally, materials such as silicon carbide and silicon nitride have been considered suitable for this purpose, and various studies have been conducted.

However, silicon carbide, which is considered the most promising material for use in the above-mentioned purpose, has many polymorphic crystal structures, each with very different chemical and physical properties. However, there is a problem in that some materials react significantly with the glass composition, and it cannot be said that silicon carbide, which is a compound of St and C that can be confirmed by compositional analysis, is suitable as a mold material. .

OBJECTS OF THE INVENTION In view of the above drawbacks, the present invention provides a mold material for press molding which allows direct press molding of optical glass parts, especially optical glass lenses having good image forming quality.

Structure of the Invention In order to achieve the above object, the mold material for direct press molding of the present invention is characterized in that it is silicon carbide designated as α-type SiC. By performing direct press molding of ordinary optical glass using this, it becomes easy to manufacture optical glass parts, especially optical glass lenses.

Description of examples Examples of the present invention will be described below.

Prepare two cylindrical sintered α-shaped silicon carbide rods each having a diameter of 30 mm and a length of 50 mm as shown in Table 1, and have notches around them as shown in Figure 1. A pair of press molding molds were formed, including an upper mold 1 having a concave surface 3 with a radius of curvature of 46 mm and a lower mold 2 having a four-sided surface 4 with a radius of curvature of 200 mm.

The press-molded surfaces of each pair of blocks were polished to a mirror finish using ultra-fine diamond abrasive grains to an accuracy of 0.02 μm or less in maximum surface roughness. Set in the press machine shown in Fig. 2, in an argon gas atmosphere containing 2% hydrogen, spherical lumps 11 with a radius of 20 mm of optical glass having the following two types of compositions are placed in a pair of molds in a container. The structure has a piston cylinder 7.8 in which heaters 5 and 6 are arranged so that heaters 5 and 6 can be attached and heated. Raw glass lumps 1
1 is held between the raw material glass supply jig 10, passed through the glass preheating tunnel furnace 9, and put into the press machine. 7. Press a glass lump by moving a pair of molds 1°2 according to 8.

The glass molded product after pressing is taken out from the atomizer outlet 12. The two types of optical glass examined in the press were one containing 68 wt% SiO2 and 11w B2O3.
t%.

The other is a borosilicate optical glass consisting of 10 wt% NaO, 8 wt% 2O, and trace components, and the other is 31 wt% 8102 and 17 wt% B2O3.

This is a barium borosilicate optical glass consisting of 50 wt% BaO and the remainder as trace components.

Press molding of the glass lump was performed at a mold temperature of 800°C. The press molding results for the above borosilicate glass are shown in Table 2, and the results for the above barium borosilicate glass are shown in Table 3.

For comparison purposes, a mold of β-type SiC, which is another type of silicon carbide, was prepared and set in the press machine shown in FIG. Press molding was carried out under the following conditions. The results are also shown in Tables 2 and 3.

Although this β-type silicon carbide mold was finished in the press mold shape of A-type silicon carbide (Table 1 - Sample 1), CV
A film of 30 crystal structures, i.e., β-type silicon carbide, with a thickness of 200 μm is formed using the D method, and this surface is further mirror-polished using ultrafine diamond abrasive grains to a maximum surface roughness of 0.02 μm. It has been completed.

It was discovered that β-type silicon carbide molds reacted with glass during press molding, making them unsuitable as mold materials.

As can be seen from Tables 2 and 3, the press mold of this example can significantly press mold optical glass compared to the β-type silicon carbide mold, which has the same chemical composition and has a significantly different crystal structure. It turns out that he has excellent sex.

Table 1 Margin Table 2 Press moldability of borosilicate glass However, ◯ indicates good.

Margin Table 3: Press moldability of barium borosilicate glass However, ◯ indicates good.

Effects of the Invention As described above, the mold for direct press molding of optical glass parts of the present invention is a mold made of silicon carbide indicated as a-type SiC, so that it is possible to press a glass lump for optical glass parts. When molded, no chemical reaction occurs at the contact surface between the mold and the glass, and the glass surface does not devitrify after molding.
In addition, it has excellent properties such as good peelability between the glass and the mold during molding, and by using this material in the mold, direct press molding is significantly easier to mass produce than conventional methods for manufacturing optical glass parts. law becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a press molding die according to an embodiment of the present invention, and FIG. 2 is a cutaway perspective view of a main part of the press machine. 1...Top mold, 2...Bottom mold, 3...
...Press surface of upper die, 4...Press surface of lower die,
5... Heater for upper mold, 6... Heater for lower mold, 7... Piston cylinder for upper mold, 8
・・・・・・Piston cylinder for lower mold, 9・・・・・・
・Glass preheating tunnel furnace, 10...Raw material glass supply jig, 11...Raw material glass lumps, 1
2...Molded product outlet. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 2

Claims (1)

[Claims] A mold material for direct press molding of optical glass parts, characterized in that the mold for press molding is silicon carbide designated as α-type SiC.