JPH05213622A - Production of preform for biconcave face pressed glass lens - Google Patents

Abstract

PURPOSE:To provide the process for production of the preform for a biconcave face glass pressed lens which enables the easy execution of press forming of a biconcave face lens. CONSTITUTION:This process for production of the preform for the biconcave face glass pressed lens comprises placing a disk-shaped glass member 1 in the prescribed position on a horizontal supporting member 3 having a circular aperture 2 slightly smaller than the external size of this member, heating this glass member 1 up to the prescribed temp. above the yield point and below the softening point of the glass member 1 and holding the member for a prescribed period of time, thereby forming the perpendicular section of the glass member 1 to a shape approximated to a catenary curve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a preliminarily molded material for a biconcave glass press lens, which is suitable for manufacturing an optical lens, for example.

[0002]

2. Description of the Related Art Conventionally, a method of grinding and polishing has been the mainstream for manufacturing an optical lens, but in recent years, development of a lens manufacturing technology by press molding has attracted attention as a highly efficient lens manufacturing method. ing.

Here, the principle of press molding is to heat and soften a glass preliminary material to plastically deform it by an opposing metal mold to obtain a desired lens shape.

Various shapes such as discs, spheres, lenses, cylinders, and spheroids are available as the shape of the glass preliminary material. Which shape of the glass preliminary material is selected from these is selected. Is generally performed according to the desired lens shape. On the other hand, from the molding principle,
It is desirable to place the glass spare material near the center of the mold.

[0005]

However, in the case where one of the molds has a concave surface, if the concave surface is the lower mold at the time of molding,
Although the above requirements are satisfied by using the spherical preliminary material,
In order to mold a biconcave lens composed of a convex surface in any of the molds, it is difficult to satisfy the above requirements with any spare material, which is an obstacle to the application of the press molding method to the biconcave lens. There was a problem that was.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing a pre-forming material for a biconcave glass press lens, which can easily press-form a biconcave lens.

[0007]

As shown in FIG. 1, a disk-shaped glass member 1 is provided with a circular opening slightly smaller than its outer shape, for example, as shown in FIG. By placing the glass member 1 at a predetermined position on a horizontal support member 3 and heating the glass member 1 to a predetermined temperature not lower than the sag point and not higher than the softening point and holding the glass member 1 for a predetermined time, the vertical direction of the glass member 1 is increased. This is a method in which the cross section is shaped to approximate a catenary curve.

[0008]

According to the method of manufacturing the pre-forming material for a biconcave glass press lens of the present invention, the disk-shaped glass member 1 is provided on the horizontal support member 3 having the circular opening 2 which is slightly smaller than its outer shape. By placing the glass member 1 at a position, heating the glass member 1 to a predetermined temperature not lower than the softening point and not higher than the softening point, and maintaining the glass member 1 for a predetermined time, the vertical cross section of the glass member 1 is approximated to a catenary curve. It becomes possible to easily press-form a biconcave lens, which has been difficult in the past.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for producing a pre-forming material for a biconcave glass press lens of the present invention will be described below with reference to FIGS.

First, as shown in FIG. 1A, a disk-shaped glass member 1 prepared in advance by a processing method such as grinding and polishing to a predetermined shape dimension has an opening 2 slightly smaller than the outer shape of the disk 1. It is placed at a predetermined position on the support material 3.

In order to prevent fusion with the glass which may occur during heating, the support material 3 is the same as that used in the molding die, and therefore, a material that does not wet the glass is used, or aluminum hydroxide, magnesium carbonate, carbon, etc. The mold release material is applied.

Next, the heating operation is started, and the temperature-time schedule at this time is set in the range from the yield point to the softening point of this glass material, that is, in the range of 10 ¹¹ poise to 10 ^7.6 poise in terms of viscosity. desirable. If the temperature is lower than this temperature range, the deformation takes a long time and is not practical. On the contrary, if the temperature is higher than this temperature range, the deformation will occur rapidly,
It becomes difficult to control.

The softened and deformed shape can be approximated by a free suspension curve due to the weight of the glass member, that is, a catenary curve (see FIG. 1B).

Therefore, a preforming material was manufactured under various conditions, and it was evaluated whether or not the preforming material was suitable for glass pressing. The results are shown in Table 1.

[0015]

[Table 1]

Here, six cases of Sample 1 to Sample 6 were examined. As can be seen from the results in Table 1, it is most desirable that the end point of the deformation be slightly larger than the radius of curvature near the center of the convex surface of the die corresponding to the lower die (see FIGS. 2 and 3). Samples 1, 3,
And 5 satisfy this condition.

Further, regarding the finishing accuracy of the upper and lower surfaces of the glass member, Ra <0.01 μm, which is usually equivalent to the polished surface, is preferable, but even when the temperature-time schedule is adjusted so as to be equivalent to the ground surface, the so-called fire polishing effect is obtained. Can also make the surface smooth. Comparing the groups of Samples 1 and 2 with the groups of Samples 3 and 4, the surface roughness before heating was Ra = 1 μm, respectively.
However, the viscosities of the glass when heated are 10 ¹¹ poises and 10 ^7.6 poises, respectively, and it can be seen that the fire polishing effect appears by heating since the groups 3 and 4 have lower viscosities.

The molding evaluation is represented by ◯, Δ, and x. Here, ○ represents the case where there is no defect in the lens, and △
Indicates that a part of the lens has a defect, and x indicates that the lens has an external defect such as an air pocket. From this evaluation, samples 3 and 5 show good results.

From the above, according to this example, the disk-shaped glass member 1 is provided with a circular opening 2 slightly smaller than its outer shape.
The glass member 1 is placed at a predetermined position on a horizontal support member 3 and is heated to a predetermined temperature not lower than the yield point and not higher than the softening point of the glass member 1 and held for a predetermined time, whereby the vertical cross section of the glass member 1 is changed. By making the shape close to the catenary curve, the glass preliminary material can be placed in the vicinity of the center of the mold, so that press molding of a biconcave lens, which has been difficult in the past, can be easily performed. Further, even when the surface was limited to the ground surface, by adjusting the temperature-time schedule, the surface could be smoothed by utilizing the so-called fire polishing effect. Also,
The line has enabled mass production of lenses.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

[0021]

As described above, according to the present invention,
It becomes possible to easily press-form a biconcave lens, which has been difficult in the past. Further, even when the surface is limited to the ground surface, the surface can be smoothed by adjusting the temperature-time schedule and utilizing the so-called fire polishing effect.

[Brief description of drawings]

FIG. 1 is a constitutional view showing an embodiment of a method for producing a pre-forming material for a biconcave glass press lens of the present invention.

FIG. 2 is a configuration diagram showing installation of a molding preliminary material in a mold according to this example.

FIG. 3 is a configuration diagram showing press forming of a preliminary forming material according to this example.

[Explanation of symbols]

 1 glass member 2 opening 3 support material

Claims (1)

[Claims] 1. A disk-shaped glass member is placed at a predetermined position on a horizontal support member having a circular opening slightly smaller than its outer shape, and heated to a predetermined temperature not lower than the yield point and not higher than the softening point of the glass member. By holding for a predetermined time,
A method for producing a preliminarily molded material for a biconcave glass press lens, characterized in that a vertical cross section of the glass member is shaped to approximate a catenary curve.