JPH0542372B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a manufacturing method for forming glass lenses used in optical instruments by precision glass molding.

BACKGROUND ART In recent years, many attempts have been made to form optical lenses by one-shot molding without a polishing process. One of the forming methods is to heat the material to a temperature near its softening point,
There is a method of pressure molding. (For example, JP-A-51-
60208 Publication) The above-mentioned conventional molding method will be described below with reference to the drawings.

FIG. 3a shows the state immediately before molding. 1 is an upper mold, 2 is a lower mold, 3 is a body mold, 4 is a mold holding fitting, 5
6 is a press head, and 6 is a glass material. b is a diagram showing a completed molding state. c shows a state in which deposits are formed on the surfaces of the upper and lower molds after molding. 7 is a deposit.

First, the body mold 3 and the glass material 6 are set in the lower mold 2 as shown in FIG. 3a, and heated to a temperature near the softening point.
The atmosphere at this time is controlled to an oxygen concentration of 0.01% or less. Thereafter, by applying pressure, it is molded into a predetermined shape as shown in Figure b.

Problems to be Solved by the Invention In the above-described molding method, deposits 7 are generated on the surfaces of the molds 1 and 2 as shown in FIG. This had the problem of having an adverse effect.

Means for Solving the Problems In view of the above problems, the present invention focuses on the fact that the state of adhesion changes by changing the oxygen concentration, and uses a method of molding by changing the oxygen concentration every fixed number of molding cycles. It is.

Function The present invention uses the above-mentioned means to naturally remove deposits on the mold surface and enable continuous molding without affecting lens performance.

EXAMPLE A method for molding a glass lens according to an example of the present invention will be described below with reference to the drawings.

FIG. 2 forms the basis of the present invention. Shows the adhesion state on the mold surface during molding. The horizontal axis shows the oxygen concentration, and the vertical axis shows the amount of adhesion. (The absolute amount of deposits is not specified.) As can be seen from Figure 2, when lead-based glass material is molded, depending on the oxygen concentration, areas where Pb adheres, areas where glass adheres, and areas where both Pb and glass adhere. There are three regions where both Pb and glass do not adhere together. Therefore, this deposit is a cause of adverse effects on the performance of the molded lens. For example, in a lens molded in a region where glass adheres, a portion of the glass on the molded lens surface adheres to the mold and is peeled off, so naturally good lens performance cannot be obtained. In addition, in the area where Pb adheres, there is no particular problem until about a few dozen times, but if the molding continues further, the transmittance will decrease. This is because the mold surface becomes uneven when Pb adheres to it, and the unevenness is transferred to the molded lens surface. Therefore, as the number of molding increases and the amount of Pb deposited increases, the unevenness of the mold surface also increases, and as a result, the molded lens surface also becomes uneven, and the transmittance of the lens decreases. There were such negative effects.

On the other hand, experiments have shown that the amount of Pb attached to the mold surface gradually decreases when molding is performed in the area where glass adheres, and eventually it is completely removed. They also confirmed that glass began to adhere to the glass as molding continued, and established a molding method that takes advantage of this phenomenon to automatically remove Pb. The molding method will be described below.

FIG. 1 shows the state of adhesion when molding is performed by changing the oxygen concentration with a constant number of moldings, utilizing the above-mentioned phenomenon. The horizontal axis shows the number of moldings, and the vertical axis shows the amount of adhesion (absolute amount is not specified).

First, the oxygen concentration was set to 10 in the Pb adhesion region below 0.01%.
Rotate. During this time, Pb gradually adheres to the mold surface. (Figure 1: The number of molding cycles is between 1 and 10.) However, if this is the case, the lens performance will not be affected at all.

Next, the oxygen concentration was set to 0.1% and molding was performed twice under the area where the glass would be attached. (Figure 1, between 10 and 12 times of molding) Most of the Pb is removed during this molding. Of course, there is no problem in terms of performance with lenses molded under these conditions. The reason why the number of moldings under the glass area was set twice is because if molding is repeated more than this, there is a risk that all of the Pb will be removed and the glass will adhere.

By repeating the above molding process, the Pb adhesion is naturally removed, and continuous molding is possible while maintaining lens performance without glass adhesion.

The above explanation is just one example, and the oxygen concentration is 0.01
One cycle was defined as 10 times at 0.1% oxygen concentration and 2 times at 0.1% concentration, but it is also possible to perform molding more than 10 times at 0.01% oxygen concentration (it even determines how to determine the transmittance level).
Moreover, it is highly probable that the number of times of molding changes depending on the set level of oxygen concentration.
Furthermore, it is quite conceivable to reduce the amount of deposits by changing the oxygen concentration not only at two levels but also more minutely and continuously.

Effects of the Invention As described above, by using the present invention, it is possible to realize continuous molding while maintaining lens performance. Furthermore, for example, in the case of this embodiment, it is sufficient to control the oxygen concentration to two levels, 0.01% and 0.1%, which can be easily realized in terms of equipment.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the state of adhesion when the glass lens molding method of the present invention is used and the oxygen concentration is changed every fixed number of molding cycles. Characteristic diagram showing the relationship between concentration and amount of adhesion; Figures 3a and b are cross-sectional views of the conventional example showing the state of the glass material and mold during molding; and Figure 3c is the same diagram showing the state of adhesion on the mold surface. FIG.

Claims (1)

[Claims] 1. A method for forming a glass lens, which is characterized by changing the oxygen concentration of an atmospheric gas when forming a lens by heating a glass material containing lead oxide as one component and press-molding it with a mold.