JPS61291424A - Forming mold of glass lens and forming method - Google Patents

Abstract

PURPOSE:To form an optically good convex surface readily, by preforming a glass material using a forming mold having air vent holes in the central contact surface part and forming the optical surface of the lens. CONSTITUTION:A glass material 1 is prepared by cutting out a planar flat glass having both ground surfaces with a cutter and placed between molds 2 and 3, which are heated to a temperature required for forming and moved in the direction for compressing the glass material 1. Thus, the glass material 1 is deformed and formed by pressurization. The formed glass material 1 is then pressed to a state in which the central parts of both surfaces thereof enter air vent holes a little to complete the preforming in the shape of the glass material 1 having slight protruding parts 8. The resultant preformed glass material 1' is then fed between mold 4 and 5, which are heated to a temperature near the softening point of the glass to pressurize and form the glass material 1' and give the aimed lens having the desired shape.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a mold and a molding method used for molding glass lenses used in optical equipment.

2. Description of the Related Art In recent years, many attempts have been made to form optical lenses by one-shot molding without a polishing process, and to manufacture not only spherical lenses but also aspherical lenses at low cost.

For this purpose, the most efficient method is to pour the glass material from a molten state into a mold and press-form it, but it is difficult to control the shrinkage of the glass during cooling, so it is not suitable for molding precision optical lenses. do not have. Therefore, a common method is to preprocess a glass material into a certain shape, supply it between molds, heat it, and press-form it (for example,
84134). When molding a lens with a convex surface by such a method, as described in Japanese Patent Application Laid-Open No. 59-116137, a glass material is formed into a spherical shape in advance, and defects on the surface are removed by polishing, polishing, etc. It is necessary to remove it.

The conventional molding method mentioned above will be explained below with reference to the drawings. FIG. 4 is a sectional view showing the convex lens immediately before molding, in which 6 is a glass material and 4 and 5 are a pair of molds.

The glass material 6 is heated to a temperature near the softening point of glass by an appropriate method, and then pressure-molded using the molds 4 and 5. As shown in the figure, the radius of curvature of the surface forming the optical surface of the glass material 6 in contact with the mold 4.5 needs to be smaller than the radius of curvature of the mold 4.5. This is because if the radius of curvature of this surface is large, or if the surface of the glass material 7 is flat or concave as shown in Figure 5, air will remain between the mold and the glass when pressing. This is because bubbles are generated on the surface of the molded lens. Also, JP-A-59-1
As stated in Publication No. 16137, if defects on the surface of the glass material are not removed, there will be no place for the air to escape from the minute irregularities remaining on the surface, and the formed surface will become unsuitable as an optical surface. It will be sufficient. That is, conventional forming methods typically require heat forming using a spherical glass material with a relatively smooth surface.

Problems to be Solved by the Invention However, with the above method, it takes time and effort to process the glass material. That is, processing glass into a spherical or convex shape requires special equipment and takes time.

Furthermore, polishing to remove defects on the surface of the spherical glass also requires special equipment and requires a lot of processing time.

In view of the above-mentioned problems, the present invention provides a mold and a molding method that can easily pre-process a glass material and easily mold a lens having an optically good convex surface.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention uses a mold having an air vent hole in the center of the concave surface of the mold to preform a flat glass material into a desired lens. A lens having a convex surface is obtained by processing the glass material into a shape similar to the shape of the lens, holding the glass material in a mold having a desired lens shape, heating it, and press-molding it.

Function The present invention significantly simplifies the processing of glass materials by using the above manufacturing method. In other words, cutting a glass material into a flat plate is an extremely simple process, and
It is also very easy to polish these to remove surface defects since each surface is flat. As a result, it is possible to shorten the time and cost of glass material processing. Furthermore, a preforming mold equipped with an air vent makes it possible to easily obtain a glass material free of air bubbles.

Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sketch showing a state in which a glass material is to be preformed using the mold of the present invention. In FIG. 1, 1 is a glass material to be preformed, 2 and 3 are molds, and the cross section thereof is shown. The inner surface forming the optical surface of the mold 2.3 is processed into a concave surface according to the shape of the lens in order to obtain a lens having the desired convex surface, and an air vent hole (for example, a round hole) is provided in the center thereof.

The glass material 1 is a flat glass plate with both sides polished and cut into a disk shape using a cutting machine.

This glass material is placed between mold 2 and mold 3, mold 2゜3 is heated to the temperature required for molding, mold 2 or mold 3 is moved in a direction to compress the glass material, and glass material 1 is pressurized. By doing so, the glass material 1 is deformed and molded. At this time, the air between the glass material 1 and mold 2 or mold 3 is
and escapes from the air vent hole in the center of mold 3. Second
The figure shows the completed state of this preforming. The preforming is completed by pressing the formed glass material until the center of both sides slightly enters the air vent hole, leaving a slight protrusion 8.

The glass material preformed in this manner is then subjected to final molding as shown in FIG. In FIG. 3, 4 and 5 are molds for forming a desired optical surface on the lens.

The preformed glass material 1' is supplied between the molds 4 and 5, and the mold 4.5 is heated to a temperature near the softening point of the glass, applying pressure to the glass material 1' and molding it into the desired shape. obtain a lens having

In this example, the following precautions must be taken to prevent bubbles from forming on the optical surface of the lens. In Figure 3, type 4
．． In order for all the air between the glass material 1' and the glass material 1' to escape, the curvature of the surface of the glass material 1' in contact with the mold 4.5 must be smaller than the curvature of the optical surface of the molds 4 and 5. Therefore, the curvatures of the optical surfaces of molds 2 and 3 in FIG. 1 are machined to be smaller than the curvatures of the optical surfaces of the corresponding molds 4 and 5 in FIG. 3, respectively. Furthermore, it is necessary that the protrusion 8 is smoothly connected to the surroundings.

Therefore, it is preferable to chamfer the ends of the air handling holes in molds 2 and 3.

In this embodiment, a case where both surfaces of the lens are convex has been described, but a lens having only one side convex or a meniscus lens can also exhibit the same effect.

Effects of the Invention As described above, the present invention uses a preforming mold having air vent holes when molding glass to manufacture a lens having a convex surface, so that the shape of the glass material supplied to the molding operation can be made into a simple circle. This makes it possible to use a plate, extremely simplifies the preliminary processing of the glass material, and has a great effect on shortening the process time and ultimately reducing costs.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views showing the mold and preforming state in an embodiment of the present invention, FIG. 3 is a cross-sectional view showing a molding state in an embodiment of the present invention, and FIG.
FIG. 5 is a cross-sectional view showing a molding state in a conventional example, and FIG. 5 is a cross-sectional view showing a molding state in another example for comparison. 1.1', 6.7...Glass material 2, 3.4°5
...Molding mold patent applicant Matsushita Electric Industrial Co., Ltd. 6 - Glass material Figure 4

Claims (2)

[Claims] (1) A mold for a glass lens, characterized by having a smooth concave surface and an air vent hole in the center of the concave surface. (2) When heating a glass material and press-molding it with a pair of molds to form a lens with at least one convex surface, the glass material is preformed using a mold that has an air vent hole in the center of the glass contact surface. , followed by press molding using a mold that forms the optical surface of the lens.