JPS60176929A - Mold for press molding glass lens - Google Patents

Abstract

PURPOSE:The titled mold for molding, obtained by working carbon as a base material into a die by vapor deposition of beta-SiC, and coating the surface with A-SiC or alpha-SiC, by vapor deposition, and capable of molding with a high accuracy and direct molding of glass lenses. CONSTITUTION:A mold for direct press molding obtained by manufacturing a nonspherical mold previously from carbon as a base material, applying beta-SiC onto the mole by the chemical or chemical vapor deposition method, reworking the resultant mold into a nonspherical surface to form a dense die of lens shape, coating the resultant film of beta-SiC easily reactive with glass containing much alkali or Ba with A-SiC or alpha-SiC of uniform thickness by the chemical or physical vapor deposition method to form a nonspherical surface slightly reactive with the above-mentioned glass, and capable of direct press molding optical glass lenses capable of focusing good images.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a press-molding mold that does not require a polishing step after press-molding an optical glass lens.

(Conventional Structure and Problems thereof) In recent years, there has been a trend in optical glass lenses to be made into aspherical lenses, which can both simplify the purchase of lens m-imaginary for optical equipment and increase the sharpness of the lens portion. The creation of this aspherical lens requires
The polishing method, which is the conventional method for manufacturing optical lenses, has difficulties in processability and mass production, so direct press molding is seen as promising. In this direct press molding method, a lump of optical glass is heated on an aspherical mold that has been finished to the desired surface quality and surface precision, or the preheated lump of glass is press-molded. This is a method for manufacturing optical lenses that does not require a polishing process.

However, in the method for manufacturing an optical glass lens described above, the image forming quality of the obtained lens must be excellent after press molding. Especially in the case of an aspherical lens, it is required that it can be molded with high precision.

Therefore, the mold material must have minimal chemical action on the glass at high temperatures, be resistant to damage such as scratches on the glass press surface of the mold, and have high resistance to breakage due to thermal shock. These are necessary. For this purpose, silicon carbide (SiC) silicon nitride (813N4) i
It is said that a mold made of any material or a mold made of high-density carbon soil coated with a coating film of silicon carbide or the like is suitable. However, materials such as silicon carbide and silicon nitride have extremely high hardness, so it is extremely difficult to process these materials to produce molds for molding spherical and aspherical lenses with high precision. All of these mold materials conventionally used are sintered types, so h2o3. This method uses a substance that easily reacts with B2O3 glass, which has the disadvantage that lenses cannot be molded with high precision. The mold made by coating silicon carbide etc. on the high-density force ~ cancer molded product also has a coating film of beta silicon carbide (β-5aC).
Although it contains large amounts of sodium and barium, it easily reacts with glass, making it impossible to mold highly precise glass lenses.

(Object of the Invention) An object of the present invention is to provide an optical glass that can easily perform the high-precision mold processing required for a mold for direct press molding of a glass lens, and that can produce a good image by using this mold. For direct press molding of lenses, qJ is capable of providing molds for direct press molding.

(Structure of the Invention) The mold for press-molding a glass lens of the present invention uses carbon as a base material, and deposits β-8iC on the base material by chemical vapor deposition (CVD), evaporation, or physical vapor deposition (PVD). Amorphous silicon carbide (A-8IC), t or alpha silicon carbide (α-8IC) is deposited and processed into a lens-shaped mold with a uniform thickness by CVD or PVD.
) to form a coating film.

The carbon used as the base material here is very easy to process, but has the disadvantage that the base material is porous. However, if β-8IC is attached to this base material soil by CVD or PVD, processing becomes more difficult than using carbon alone, but
8IC is relatively easy to process among SiC types, so by making an aspherical mold in advance with carbon, then attaching β-8iC, and processing it again into an aspherical surface, a dense aspherical mold can be created. can. However, β-8IC easily reacts with glass containing a large amount of alkali or barium. Therefore, amorphous 5IC (A-8iC
) or alpha SiC (α-8IC), an aspherical type that is less likely to react with glass containing a large amount of alkali or barium can be obtained.

(Description of Embodiment) An embodiment of the present invention will be described based on FIG. 1 and FIG. 2.

Two cylindrical carbon rods with a diameter of 30 mm and a length of 50 mm were prepared, and an upper mold 1 having a concave shape with a radius of curvature of 46.1 mm and a notch on the periphery as shown in Fig. 1 was prepared. radius of curvature is 2
A pair of press molding molds consisting of a lower mold 2 having a concave shape of 001 is processed. Next, this mold was placed in a furnace heated to 1400°C and silicon tetrachloride (SiCl2) ethylene (C2I (
2) A mixed gas of hydrogen (H2) is flowed to deposit 171 β-8 ICs in 0.2 mm depths using the CVD method. Next, the press forming surface 3 of the upper die 1 has a curvature radius of 46.0.
The press forming surface 4 of the lower die 2 has a radius of curvature of 200. Orn
The upper die 1 and the lower die 2 are machined for 4 hours using ultra-fine diamond abrasive grains until the maximum sphericity of the surface reaches an accuracy of 0.02 μm. Finally, an amorphous SIC film with a thickness of 2 μm is formed on this mirror stop using the Snow E-Tuttering method to produce a mold for glassless molding.

The mold made in this way was set in the press machine shown in Figure 2, and the sto was 68% and the B2O3 was 11%.

Borosilicate alkali optical glass containing 10% Na2O, 8% K2O, and trace amounts of the rest, and 510
Two types of barium borosilicate optical glass consisting of 31% B2O3, 17% B2O3, 50% BaO, and the remainder fine components were pressed into a spherical raw material glass lump 5 with a radius of 20m1. Molded into a convex lens shape. On this occasion,
For press forming, a heater 6 is wound around the upper mold 1 and a heater 7 is wound around the lower mold 2. The raw material lath lump 5 is held by a raw material glass supply jig 8 and molded using a glass preheating tunnel furnace 9. The temperature was 800°C and the press pressure was 40ky//C1n, and the molded product was cooled to 400°C together with the mold, and the molded product was taken out. This removal is performed through the molded product and the exit port 10. Note that 11 is a piston cylinder for the upper mold, and 12 is a piston cylinder for the lower mold.

The results for the above-mentioned borosilicate alkali glass are shown in Table 1, Sample A1, and the results for borosilicate-glyum glass are shown in Table 2, Sample A2. For comparison, conventional molds made of silicon carbide and silicon nitride were manufactured and attached to the press machine shown in FIG. 2 in place of the mold of the present invention, and press molding was performed in the same manner as described above. Note that the silicon carbide and silicon nitride molds were manufactured by performing electrical discharge machining, finishing by grinding, and mirror-polishing the surfaces using diamond abrasive grains.

This mirror polishing process alone reduces the maximum surface roughness to 0.
β-8IC on the carbon mentioned above to finish with 02μmi
It took 10 to 15 times as long to finish a flat surface with 0.02 μml, that is, 40 to 50 hours. The results of press molding using this silicon carbide mold are also shown in Table 1 (Sample, %]], 12) and Table 2 (Sample All, 1) as comparative examples.
2) is shown.

From Tables 1 and 2, it is clear that the press molds of Samples 1 to 8 of the present invention, with different experimental conditions, are superior to the conventional molds.

Note that Samples /I67 and Ya8 in Tables 1 and 2 are described as comparative examples and outside the scope of the claims of the present application.

(Effect of the invention) The mold for direct press molding of a glass lens according to the invention has the following features:
Compared to molds mainly made of silicon carbide or silicon nitride, which have been used in the past, it has less reactivity when molding glass, and also has the effect of allowing mold grinding to be performed more easily and with higher accuracy in a shorter time than conventional molds.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a mold for press molding a glass lens according to an embodiment of the present invention, and FIG. 2 is a perspective view of a press machine. 1. Upper mold, 2. Lower mold, 3. Pressing surface of upper mold, 4 Pressing surface of lower mold, 5. Glass block material, 6. Heater for upper mold, 7. Lower mold. heater, 8. Raw glass supply jig, 9. Glass preheating tunnel furnace, 10. Molded product outlet, 11. Piston cylinder for upper mold, 1
2... Vineton cylinder for lower mold. Figure 1

Claims (1)

[Claims] Using carbon as a base material, beta silicon carbide (β-5tC) is attached by chemical vapor deposition or physical vapor deposition, processed into a lens-shaped mold, and then further coated with chemical vapor deposition or physical vapor deposition. Amorphous silicon carbide (A-SIC) or alpha silicon carbide (α-5aC) with uniform thickness
) A glass lens press molding mold characterized by being coated with.