JP2000000828A - Manufacturing method of glass mold for glasses - Google Patents

Abstract

(57) [Summary] [Purpose] A master mold having a molding surface having a male-female relationship with a molding surface of an eyeglass glass mold, and a pressing mold paired with the master mold are used. Between the mold and the pressing mold, a glass preform to be a glass mold is inserted, and heated and softened to form the glass mold for press molding. A glass mold manufacturing method capable of reducing the variation in the outer diameter of the glass mold to be performed. [Constitution] When the molding surface of a glass mold to be molded is concave, the radius of curvature of the pressing surface of the pressing mold is set to be larger than the radius of curvature of the molding surface of the master mold to form the glass mold to be molded. A method for manufacturing a glass mold for glasses, wherein when the surface is convex, the radius of curvature of the pressing surface of the pressing mold is set smaller than the radius of curvature of the molding surface of the master mold.

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 mold used for molding a plastic lens for spectacles.

[0002]

2. Description of the Related Art Molding of plastic lenses for eyeglasses involves setting a glass mold above and below an annular gasket to form a molding space, and injecting a plastic monomer into the molding space and polymerizing and curing. It is done in. Therefore, it is necessary to prepare an extremely large number of glass molds according to the eyeglass lens shape. In particular, recent plastic lenses for spectacles tend to widely use an axisymmetric aspherical surface, a progressive multifocal aspherical surface, a bonded lens, and the like, and the molding surface shapes thereof are more diverse.

Conventionally, this glass mold is directly machined, or a heat-resistant mother mold is machined, a glass material is placed on the machine, and the material is softened by heating so as to form the mother mold by its own weight. Has been formed by However, since the hot drooping method requires a long time for processing, a glass molding method that can be molded in a short time has recently been used. The glass mold method uses a master mold having a molding surface and a molding surface in a male-female relationship with a molding surface of a glass mold, and a pressing mold paired with the master mold. In this method, a glass preform to be used as a glass mold is inserted and heated and softened for molding.

In this glass molding method, since pressure is applied to both surfaces of the glass preform, there is a property that the amount of change in the outer diameter with respect to the molding amount is large. For this reason, there is a problem that the outer diameter of the glass mold after the molding is largely varied due to a slight difference in the molding amount, a slight change in the molding factor such as a variation in the outer diameter or the center thickness of the preform, or the like. If the diameter of the molded glass mold is smaller than the predetermined diameter, a gap is formed between the glass mold and the gasket, and liquid leakage occurs during polymerization.

[0005] In order to prevent such a problem, conventionally,
Means have been taken to set the processing tolerance of the glass preform strictly, measure the outer diameter and center thickness of each preform, and determine the molding amount according to the outer diameter and center thickness. However, if the tolerance is reduced, the number of defects increases, and changing the molding conditions by measuring the outer diameter and the center thickness of each glass preform causes an increase in man-hours and an increase in cost.

[0006]

SUMMARY OF THE INVENTION The present invention has been made based on the above-mentioned problem of the conventional method for manufacturing a glass mold for eyeglasses, and has a constant diameter of a glass mold to be formed without making the tolerance of a glass preform so tight. It is an object of the present invention to provide a method for manufacturing a glass mold for glasses that can be kept within a narrow tolerance.

[0007]

SUMMARY OF THE INVENTION In the present invention, only the molding surface onto which the molding surface shape of the master mold is transferred is important in the glass mold for eyeglasses, and the surface pressed by the pressing mold paired with the master mold. Has succeeded in suppressing the dimensional variation of the glass mold to be formed by using the surface that does not require the accuracy, based on the fact that the accuracy is not required.

That is, the present invention provides a master mold having a molding surface in a male-female relationship with a molding surface of a glass mold used for molding a plastic lens for spectacles, and a pressing mold paired with the master mold. In the method of manufacturing a glass mold for glasses, which has a mold and inserts a glass preform to be a glass mold between the master mold and the pressing mold, and heat-softens and press-molds the glass, When the molding surface of the mold is concave, the radius of curvature of the pressing surface of the pressing mold is set to be larger than the radius of curvature of the molding surface of the master mold, and when the molding surface of the glass mold to be molded is convex, It is characterized in that the radius of curvature of the pressing surface of the pressing die is set smaller than the radius of curvature of the molding surface of the master die.

According to another expression, the present invention relates to a method for controlling the center of a glass mold during and after molding between a radius of curvature of a pressing surface of a pressing mold and a radius of curvature of a molding surface of a master mold. The difference is that the molding pressure is made larger than the molding pressure of the peripheral portion.

[0010] The molding surface of the glass mold and the molding surface of the master mold may be either spherical or aspherical.
The radius of curvature of the molding surface of the master mold is the radius of curvature of the approximate spherical surface of the aspheric surface.

The glass preform is processed to have an outer diameter smaller than the final formed outer diameter. There is no particular limitation on the material of both the master mold and the pressing mold.

[0012]

1 and 2 are schematic sectional views of an embodiment in which a method for manufacturing a glass mold for glasses according to the present invention is applied to a case where a molding surface of a glass mold to be molded is concave. 1 shows a state before molding, and FIG. 2 shows a state after molding. The upper die is the master die 10 and the lower die is the pressing die 20. The convex molding surface (spherical surface or aspherical surface) 11 of the master mold 10 is a surface that forms a male and female relationship with the molding surface of the glass mold to be manufactured. It is determined in consideration of shrinkage at the time and shrinkage of the glass.

On the other hand, the pressing surface 21 of the pressing die 20 is formed of a convex spherical surface, and its curvature radius r is the radius of curvature of the convex forming surface 11 of the master die (in the case of an aspherical surface, the radius of curvature of the approximate spherical surface). ) Is R, R <r. 1 and 2, the difference between R and r is determined by the difference between the pressing surface 21 of the pressing die 20 and the glass preform 30 before the start of molding.
Are set to such an extent that the glass preform softened during molding can escape into the gap by closely adhering at the central portion and forming a gap at the peripheral portion. Alternatively, before the start of molding, the pressing surface 21 of the pressing mold 20 and the glass preform 30 are closely attached to each other at the central portion to form a gap at the peripheral portion. The molding pressure is set so as to be larger than the molding pressure in the peripheral portion.

The master mold 10 is made of, for example, a cemented carbide (tungsten carbide), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), a titanium alloy, or the like. These materials have relatively excellent workability and are easy to obtain a mirror surface.
The molding surface 11 is precisely machined into a molding surface shape, and then, on the surface thereof, platinum-based, diamond-like carbon (DIAMOND LIKE CARBON),
It is preferable to form a protective film such as Cr ₂ O ₃ alone or in combination.

The pressing mold 20 can be made of the same material as that of the master mold 10, but other materials which cannot be mirror-finished may be used. For example, glass mold ceramics and free-cutting ceramics used in the heat sag method can be used. When using these glass mold ceramics or free-cutting ceramics, a protective film is not required.

Such a master mold 10 and a pressing mold 2
When the glass preform 30 is molded according to 0, the glass preform 30 is pressed against the pressing surface 2 of the pressing mold 20 at the time of molding.
Since the glass preform 30 escapes to the peripheral portion, variations in molding factors such as the outer diameter, center thickness, and molding amount of the glass preform 30 can be absorbed by changes in the amount of escape of the glass preform to the escape portion. In other words, it is possible to suppress the variation of the forming factor from appearing in the outer diameter of the glass mold after forming. For this reason, the variation in the outer diameter of the formed glass mold can be kept within a narrow range.

[Embodiment] Next, a specific embodiment will be described. This embodiment uses a number of glass preforms 30.
And the variation of the outer diameter was examined. The shaping surface 11 of the master mold 10 was shaved to a desired shape by an ultraprecision lathe, and then polished to a surface roughness Rmax = 0.02 μm or less using a diamond paste abrasive.
The outer diameter of the master mold 10 was 86 mmφ, and the radius of curvature R of the molding surface 11 was 900 mm.

Ultra-hard diamond-like carbon (DLC) was formed on the molding surface 11 by a CVD method to form a 0.8 μm-thick DLC thin film. The pressing mold 20 was manufactured by the same manufacturing method. The outer diameter of the pressing mold 20 is 86 mmφ, and the radius of curvature r of the pressing surface 21 is 1200 m.
m.

On the other hand, S3 (trade name, Tg =
570 ° C.) and the radius of curvature on the molding surface 11 side is 900 m
m, radius of curvature on the pressing surface 21 side is 1000 mm, outer diameter φI
Formed a large number of glass preforms 30 having a diameter of 80.8 ± 0.2 mmφ and a thickness of 6 mm. The final target shape is
The radius of curvature on the molding surface 11 side is 900 mm, the radius of curvature on the pressing surface 21 side is 1200 mm, and the outer diameter is 81.0 ± 0.2 mm.
φ, thickness is 5.6 mm.

Using the above master mold 10, pressing mold 20, and glass preform 30, 100 glass molds for glasses were molded under molding conditions at a molding temperature of 675 ° C., and the outer diameter φI ′ was measured. Are shown in Table 1.

[Table 1]

Reference Example (Conventional Example) As a reference example, a pressing die 2 having a pressing surface 21 having a curvature radius of 600 mm instead of the pressing die 20 and the glass preform 30 of the above embodiment.
Using a glass preform 30 having 0 and an outer diameter φP of 78.0 ± 0.1 mmφ, 100 glass molds for glasses were molded in the same manner as in the example, and the outer diameter φP ′ was measured. Table 2 shows the results. In this reference example, contrary to the embodiment, the curvature radius r of the pressing surface 21 of the pressing die 20 and the master die 10
Is set to satisfy r <R. 3 and 4 are cross-sectional views showing a conventional molding method and corresponding to FIGS.

[Table 2]

FIG. 5 is a graph in which the results of Tables 1 and 2 are plotted. From this result, in the example, the outer diameter of the glass preform 30 was 80.8 ± 0.2 mmφ, and the outer diameter of the glass preform 30 of the comparative example was 78.0 ± 0.1 mm.
The outer diameter of the molded glass mold for spectacles is 80.66 to 81.37 m in the comparative example, though the tolerance is loosened from φ.
While the variation is as large as mφ, in the example of the present invention, the variation is as small as 80.90 to 81.09 mmφ.

In the above embodiment, the present invention is applied when the molding surface of the glass mold for glasses to be molded is concave, but when the molding surface is convex, the pressing mold is used. If the radius of curvature of the pressing surface is set smaller than the radius of curvature of the molding surface of the master mold, the same operation and effect can be obtained.

[0024]

According to the present invention, variations in the outer diameter of the glass mold for spectacles to be molded can be suppressed without making the tolerance of the glass preform strict.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view before molding showing an embodiment in which the method for manufacturing a glass mold for glasses according to the present invention is applied to a case where the molding surface of the glass mold is concave.

FIG. 2 is a cross-sectional view after the molding.

FIG. 3 is a cross-sectional view before molding showing a conventional method for manufacturing a glass mold for glasses.

FIG. 4 is a sectional view after the molding.

FIG. 5 is a graph showing a number of glass molds formed by the method of the present invention and a conventional method, and variations in outer diameters thereof were examined.

[Explanation of symbols]

 Reference Signs List 10 master mold 11 molding surface 20 pressing mold 21 pressing surface 30 glass preform

Claims (5)

[Claims] 1. A master mold having a molding surface in a male-female relationship with a molding surface of a glass mold used for molding a plastic lens for spectacles, and a pressing mold paired with the master mold. In a method for manufacturing a glass mold for eyeglasses, wherein a glass preform serving as the glass mold is inserted between the master mold and the pressing mold, and heated and softened to form the glass mold, the glass mold to be molded is provided. A method of manufacturing a glass mold for eyeglasses, characterized in that when the molding surface is concave, the radius of curvature of the pressing surface of the pressing mold is set to be larger than the radius of curvature of the molding surface of the master mold. 2. A master mold having a molding surface having a male-female relationship with a molding surface of a glass mold used for molding a plastic lens for spectacles, and a pressing mold paired with the master mold. In a method for manufacturing a glass mold for eyeglasses, wherein a glass preform serving as the glass mold is inserted between the master mold and the pressing mold, and heated and softened to form the glass mold, the glass mold to be molded is provided. Wherein the radius of curvature of the pressing surface of the pressing die is set to be smaller than the radius of curvature of the pressing surface of the master die when the molding surface is convex. 3. A master mold having a molding surface in a male-female relationship with a molding surface of a glass mold used for molding a plastic lens for spectacles, and a pressing mold forming a pair with the master mold. A method for manufacturing a glass mold for glasses, in which a glass preform serving as the above-mentioned glass mold is inserted between the master mold and the pressing mold, and is softened by heating and pressed, the pressing of the pressing mold is performed. The difference between the radius of curvature of the surface and the radius of curvature of the molding surface of the master mold is such that the molding pressure at the center of the glass mold during molding and at the end of molding is greater than the molding pressure at the periphery. A method for producing a glass mold for eyeglasses. 4. The manufacturing method according to claim 1, wherein the molding surface of the glass mold and the molding surface of the master mold are aspherical, and the radius of curvature of the molding surface of the master mold is And a method of manufacturing a glass mold for eyeglasses having a radius of curvature of an approximate spherical surface of the aspheric surface. 5. The method according to claim 1, wherein the glass preform is processed to have an outer diameter smaller than a final molding outer diameter.