JPH0723225B2 - Glass lens molding method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method for forming a high-precision optical glass element such as a lens or a prism used in optical equipment by an ultra-precision glass molding method that does not require a polishing step. It is a thing.

2. Description of the Related Art In recent years, as a method of manufacturing a high-precision optical lens, in particular, an aspherical glass lens or the like, many attempts have been made and realized by one-shot molding without using an optical polishing method and without a polishing step. As one of the forming methods, there is a method of heating a glass material to a temperature at which it can be deformed, for example, a temperature near the softening point, and forming it by means of press molding or the like. (For example,
Japanese Patent Laid-Open No. 51-60208) An example of the above-mentioned conventional press molding method will be described below with reference to FIG.

FIG. 5 (a) is a state diagram of the molding process, in which 1 is an upper die, 2 is a lower die, 3 is a barrel die, 4 is a glass material, 5 is a moving chuck, 6 is a first press head, and 7 is a die. Two press heads, 8
Is a temperature raising stage, 9 is a pressing stage, 10 is a cooling stage, 11 is a set lane, 12 is a moving lane, and 13 is a take-out lane. FIG. 5 (b) shows a state in which the deposit 15, for example, Pb, glass, etc., has been formed on the surface of the mold after the molding process. FIG. 5 (c) shows the molded lens 16
The state in which the attached matter 15 is attached to the surface of is shown. The deposit is, for example, Pb.

Next, an example of the conventional molding method will be specifically described with reference to FIG.

First, the barrel die 3, the glass material 4, and the upper die 1 are set on the lower die 2 on the set lane 11. After that, it is set on the temperature raising stage 8 through the moving lane 12 by the moving chuck 5. The temperature raising stage 8 and the first press head 6 have already reached the predetermined temperature T +.
It is heated to α ° C. and then heated to a temperature T ° C. at which the upper die, the lower die, the glass material, and the body die can be deformed. Next, it is set on the press stage 9 by a moving chuck. When the upper die, the lower die, the glass material, and the body die are set, the second press head 7 descends in the Z-axis direction until a predetermined deformation amount 1 is deformed. The press stage and the second press head are always heated and stable at a predetermined temperature T ° C. When the second press head deforms by a predetermined deformation amount l, the temperature of the press stage and the second press head is lowered to a predetermined temperature Ts ° C. When the temperature reaches a predetermined temperature Ts ° C., the second press head is opened and set on the cooling stage 10 by the moving chuck. When the upper die, the lower die, the glass material, and the body die reach room temperature, they are moved to the take-out lane by the moving chuck and taken out. This molding process is performed in the same chamber. In this chamber,
N ₂ gas (99.9%) is flowing at 25 l / min, and the oxygen concentration at that time is controlled in the range of 0.01 to 0.006%. That is,
In the above-described conventional molding method, the temperature raising step, the pressing step, and the cooling step are performed within the same oxygen concentration (0.01 to 0.006%). A molding process chart at this time is shown in FIG. The vertical axis shows the mold temperature and oxygen concentration, and the horizontal axis shows the molding process. (The mold temperature is also the temperature of the glass material.) Problems to be Solved by the Invention However, in the molding method described above, FIG.
As shown in (c), the deposit 15 is formed on the surfaces of the upper mold 1, the lower mold 2, and the lens 16. This deposit is a glass material containing lead oxide as one of the compositions (flint glass SF6, composition P
In the case of bO71.3%, SiO ₂ 27.0%, Na ₂ O 0.5%, As ₂ O ₃ 0.2%, K ₂ O 1.0%, Pb is produced. In order to obtain a quality stable lens in such a conventional molding method, it is necessary to remove Pb attached to the mold each time molding is performed, which is a complicated process and an automatic molding device. In consideration of the above, the cost of the lens is increased because the molding apparatus becomes complicated. In addition, Pb attached to the lens surface
Caused a decrease in the transmittance of the lens as shown in FIG. 3 (b). (Theoretical transmittance value is 98.0%.) Means for Solving the Problems In view of the above problems, the present invention controls the oxygen concentration of the atmospheric gas for each molding process to adhere to the mold surface. It focuses on the fact that they are different. The problem of the generation of deposits on the mold surface is that during the temperature raising step, if scattered material Pb from the glass material adheres to the mold surface, even after the molding process is completed,
This means that the deposit Pb remains on the surface of the mold or lens. From this, the oxygen concentration of the atmosphere gas is set to an oxygen concentration at which the components of the glass material do not scatter during the temperature raising step, and the oxygen that does not attach a part of the glass on the surface of the glass material to the upper mold and the lower mold during the pressing process. It uses a technical means of controlling the density and molding.

Action The action of this technical means is based on the discovery of the following phenomenon by experiments. That is, the scattered deposition of Pb occurs when the oxygen concentration of the atmosphere gas is low, but the scattered deposition of Pb does not occur when the oxygen concentration is high. The glass adheres at a high oxygen concentration, and when pressure is applied to the glass material by the press, part of the surface of the glass material adheres to the mold surface.

In the conventional technology, since the temperature raising step and pressing step were performed in a low oxygen concentration, Pb was scattered and adhered as described above, and adhered to the mold surface and lens surface, which adversely affects lens performance. Was there.

In the present invention, by using the above-mentioned phenomenon, the temperature is raised in a high oxygen concentration, and a low oxygen concentration is used during the pressing process to form a glass lens without causing scattering of Pb or adhesion of glass. I found a way to do it.

Example Hereinafter, the above-mentioned operation will be described in detail by experimental results.

FIG. 4 shows a state diagram of adhesion to the mold surface, which is the basis of the present invention, obtained from the experiment. The vertical axis shows the adhesion amount on the vertical axis,
The horizontal axis represents oxygen concentration. (The absolute amount is not specified.) As can be seen from Fig. 4, a glass material containing lead oxide as one of its compositions (flint glass SF6, composition PbO7 1.3%, Si
O ₂ 27.0%, Na ₂ O 0.5%, As ₂ O ₃ 0.2%, K ₂ O 1.0%)
When both the pressing step and the cooling step are molded under the same oxygen concentration, the oxygen concentration is roughly classified into two areas, that is, a Pb-attached area and a glass-attached area, and the boundary is about 0.04%.
However, there is another region where both Pb and glass adhere by controlling the trace oxygen concentration. (It goes without saying that products such as Pb
The area of the oxygen concentration to be attached becomes different. ) Therefore
There is no area where both Pb and glass do not adhere. for that reason,
This deposit causes a bad influence on the performance of the molded lens. For example, in a lens molded under a region where glass adheres, since a part of the glass on the surface adheres to the mold, a concave portion appears in the lens and a good shape cannot be obtained. Performance cannot be obtained. In addition, under the area where Pb adheres, lens performance is not adversely affected by molding several times, but as the number of moldings increases, Pb adheres and accumulates on the mold surface, degrading the accuracy of the mold surface. However, the desired lens shape cannot be obtained. Further, a part of the accumulated Pb is transferred to the surface of the lens, and the transmittance of the lens is lowered (shown in FIG. 3 (b)).

Next, Table 1 shows the experimental results for determining in which step of the molding process the adhesion of Pb or glass described in FIG. 4 occurs.

The results of Table 1 will be described with reference to FIG. 5. In a low oxygen concentration region, for example, 0.01%, Pb is scattered on the temperature raising stage, that is, during the temperature raising process, and adheres to the mold surface. After that, even if the pressing process and the cooling process are completed, the Pb that has been scattered and adhered remains on the mold surface or the lens surface during the temperature raising step. In addition, at a high oxygen concentration, for example, 0.1%, the pressure of the press head was not applied during the temperature raising step, so that not only Pb but also glass did not adhere. But,
In the pressing step, the pressure required for the deformation of the glass material is applied, so that a part of the glass of the glass material adheres to the mold surface, and the glass remains attached even after the cooling step. That is,
The adhesion of Pb occurs in the low oxygen concentration atmosphere during the temperature raising process. In a high oxygen concentration atmosphere, Pb
Does not scatter and adhere. However, it was confirmed by experiments that glass adhered during the pressing process.

An embodiment of the present invention based on the phenomenon of the above-described experimental result will be described in detail with reference to the drawings.

FIG. 1 shows a process chart when the oxygen concentration of the atmosphere gas is controlled in the molding process utilizing the above phenomenon. The vertical axis shows the mold temperature and oxygen concentration, and the horizontal axis shows the molding process.

The glass used was flint glass SF6 (composition PbO71.3
_{%, SiO 2 27.0%, Na} 2 O0.5%, As 2 O 3 0.2%, a K ₂ O1.0%),
It is processed in advance into a shape close to a desired lens shape and having a large amount of deformation. As a mold for molding,
A cemented carbide (WC) coated with titanium nitride (TiN) was used. As the molding apparatus, it is necessary to control the atmosphere for each molding process, so that a chamber 14 is provided as shown in FIG. The atmosphere was controlled by mixing and adjusting N ₂ gas (99.9%) and O ₂ gas (O ₂ 21.0%).

As shown in FIG. 2, an upper mold 1, a lower mold 2, a barrel mold 3, and a glass material 4 are set on a set lane 11 and sent to a temperature raising stage 8 which has been adjusted and heated to a predetermined temperature of about 500 ° C. . Hold on this for 3 minutes. As shown in FIG. 4, the inside of this chamber is controlled at 0.1% below the region where glass adheres when the oxygen concentration is the same in the conventional temperature raising step, pressing step and cooling step. Next, the upper die, the lower die, the barrel die, and the glass material are moved onto the press stage 9 which is adjusted and heated to a predetermined temperature of about 500 ° C. Immediately after being set on the stage, the second press head 7 descends in the Z-axis direction and applies pressure to deform it by a predetermined deformation amount l. Press pressure at this time is about 10
It is 0 kg. The pressing time is 120 seconds. As a result, the desired lens shape is transferred. At this time, the oxygen concentration in the chamber was 0.01% below the area where Pb adheres when the same oxygen concentration is used in the conventional temperature raising step, pressing step, and cooling step.
Is controlled by. The internal pressure in this chamber is set slightly high so that oxygen does not enter from other chambers. When the press is completed, the press stage, the second press head, the upper die, the lower die, the barrel die and the glass material are simultaneously pressed in that state.
The temperature is lowered to around 400 ° C, and then it is moved and set on the cooling stage. The inside of this chamber is controlled to 0.1% below the area where glass adheres when the same oxygen concentration is used in the conventional temperature raising process, pressing process, and cooling process, and the upper mold and lower mold are placed on the water-cooled stage. The barrel and glass material are cooled to room temperature. Then, it is moved onto the take-out stage and taken out.

The molding process chart at this time is shown in FIG. The vertical axis shows the mold temperature and oxygen concentration, and the horizontal axis shows the molding process.

The lens obtained by the method as described above, that is, the oxygen concentration of the atmosphere gas in each step is controlled to be the oxygen concentration at which neither Pb nor glass adheres in each step shown in Table 1, is glass, Pb was not attached and the shape and transmittance were good. The transmittance of the lens obtained by the above method is shown in FIG.

In this example, the oxygen concentration during the temperature raising step was set to 0.1%, but as can be seen from FIG. 4, only glass adheres when the same oxygen concentration is used in the conventional temperature raising step, pressing step, and cooling step. There is no problem as long as it is the oxygen concentration below the region to be processed. Similarly, the oxygen concentration in the pressing process was set to 0.01%, but there is no problem if the oxygen concentration is below the region where only Pb adheres when the same oxygen concentration is used in the conventional temperature raising process, pressing process, and cooling process. . The oxygen concentration in the cooling process was 0.1% below the area that adheres when the same oxygen concentration was used in the conventional temperature raising process, pressing process, and cooling process, but as can be seen from Table 1, it affects the adhesion during the cooling process. Since there is no oxygen, there is no problem with the oxygen concentration under the region where glass or Pb is attached.

Effect of the Invention As described above, by using the present invention, adhesion of glass and Pb to the mold surface does not occur. As a result, it has become possible to obtain a high-precision lens with no variation in quality. In other words, the molding method is capable of omitting complicated steps such as work for removing adhered substances and realizing continuous molding suitable for an automatic molding apparatus such as the apparatus used in the examples.

The desired high-precision shape (wavefront aberration 0.02 to 0.03λ, surface roughness) because glass on the lens surface does not adhere to the mold
0.03 μm or less) is obtained.

Further, since Pb does not adhere and accumulate on the mold surface, the same high precision lens as described above can be continuously obtained. As a matter of course, since there is no transfer adhesion of Pb to the lens surface, the transmittance can be stably obtained at a high level (theoretical value of 98%).

[Brief description of drawings]

FIG. 1 is a molding process chart when the oxygen concentration of an atmospheric gas is controlled for each molding step in one embodiment of the present invention, FIG. 2 is a side view of a molding apparatus used in one embodiment, and FIG.
FIG. 6A is a graph showing the transmittance of the lens obtained in the example of the present invention, and FIG. 9B is a graph showing the transmittance of the lens obtained by molding in the same conventional oxygen concentration. FIG. 4 is a deposition state diagram showing the relationship between oxygen concentration and the deposition amount of Pb and glass, which is the basis of the present invention, and FIG. 5 (a) is a side view showing the state at each step of a conventional molding apparatus, (B) is a state diagram of deposits on the mold surface, (c) is a state diagram of deposits transferred and adhered to the lens, and FIG. 6 is a molding process chart diagram in conventional oxygen concentration control. 1 ... upper mold, 2 ... lower mold, 3 ... body mold, 4 ... glass material, 5
…… Movement chuck, 6 …… First press head, 7 ……
Second press head, 8 ... Temperature raising stage, 9 ... Press stage, 10 ... Cooling stage, 11 ... Set lane,
12 ... moving lane, 13 ... take-out lane, 14 ... chamber, 15 ... adhesion.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Daijiro Yoneya 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Takahisa Kondo, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A press molding method in which a glass material is supplied to a space formed by an upper mold, a lower mold and a body mold, and then heated and pressed,
The oxygen concentration of the atmosphere gas is controlled to an oxygen concentration at which the components of the glass material do not disperse during the temperature raising step and to an oxygen concentration at which some glass on the surface of the glass material does not adhere to the upper mold and the lower mold during the pressing process. A method of molding a glass lens, which is characterized by the above. 2. The oxygen concentration of the atmosphere gas during the ascending process
The glass lens molding method according to claim 1, wherein the oxygen concentration of the atmosphere gas in the pressing step is 0.1% or more and the oxygen concentration is 0.01% or less. 3. A method of molding a glass lens according to claim 1, wherein a flint glass material is used.