JPH0547488B2 - - Google Patents

Description

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

BACKGROUND ART In recent years, many attempts have been made to form optical lenses by one-shot molding without a polishing process. The most efficient method is to pour a molten glass material into a mold and press-form it, but it is difficult to control the shrinkage of the glass during cooling, and it is not suitable for precision lens molding. Therefore, a common method is to pre-process a glass material into a certain shape, feed it between molds, heat it, and press-form it. (for example,
JP-A-58-84134, JP-A-60-200833, etc.).

Hereinafter, the above-mentioned conventional molding method will be explained with reference to the drawings.

FIG. 4 is a sectional view showing a state in which a lens is formed by molding a disk-shaped glass material using a single stage, which is one of the conventional methods. 14 is a molded lens, 11 and 12 are a pair of molds, and 13 is a barrel mold. 15 is a heater, and 16 and 17 are parts of a molding device having a pressurizing mechanism. A glass material is supplied into a mold, the mold and the glass material are heated by a heater 15 to a temperature near the softening point of the glass, and then pressure molded by molds 11 and 12. After the deformation is completed, the mold and the molded lens are gradually cooled, and when the temperature reaches a point where the lens can be taken out, the mold is opened and the lens is taken out.

Problems to be Solved by the Invention However, in the above method, since the temperature at which glass used for optical purposes can be formed is as high as 500 to 700°C, heating of the mold and glass material,
Pressure molding and cooling each require a certain amount of time, and it takes a long time from the time the glass material is introduced until the lens is molded. As a result, there is a problem that the efficiency of the molding device is not improved and the cost required for molding is high. Furthermore, in order to shorten the molding cycle, if the glass is deformed and the mold is opened before it has cooled sufficiently, or if it is cooled without applying pressure, there is a problem that the precision required for the lens cannot be achieved.

In view of the above-mentioned problems, the present invention provides a method for molding lenses that improves the efficiency of a molding apparatus, is inexpensive, and has high precision.

Means for Solving the Problems In order to solve the above-mentioned problems, the method for molding a glass lens of the present invention comprises integrally forming a molding block with a pair of press molds, a body mold and a glass material separated from a molding device. The device has a heating stage and two
One or more pressurizing stages are provided, and the first
The first pressure stage is used for pressure deformation, and the second and subsequent pressure stages are used for pressure cooling, and after heating the molding block, which is composed of the glass material and the mold cylinder as one body, to a temperature at which molding is possible on the heating stage, the first This method uses a method in which the cooling lens is deformed on a pressure stage and sequentially transferred to the second and subsequent pressure stages and pressurized while molding the cooling lens. At this time, the temperature of the first pressurizing stage is maintained above the bending point of the glass to easily cause deformation of the glass, and the temperature of the second and subsequent pressurizing stages is sequentially lowered to maintain the temperature of the last stage. This method uses a method of maintaining the temperature below the transition point and sequentially applying pressure while cooling.

Effects The present invention uses the above-described means to separate the heating stage, deforming stage, and cooling stage of the glass and mold, thereby making it possible to keep the temperature of each stage constant, and to control the molding stage itself. No heating and cooling cycles are required, which shortens the molding cycle and increases the efficiency of the molding equipment. In addition, since glass is deformable above the glass transition point, if the pressure applied during cooling is stopped, the shape accuracy of the molded lens may be lost due to residual strain caused by molding. By continuing to apply pressure, lenses with extremely high precision can be molded.

EXAMPLE An example of the glass lens molding method of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the flow of lens molding in one embodiment of the present invention, where K is a molding block constructed as an integral part of a glass material and a mold, S0 is a heating stage, and S1, S2, and S3 are respective stages. These are the first, second, and third pressurization stages. FIG. 2 is a sectional view showing details of the forming block K of FIG. 1. 1 and 2 are press molds, 3 is a body mold, and 4 is a glass material. FIG. 3 shows the temperature over time during the molding process. FIG. 3a shows the temperature course in this embodiment, and FIG. 3b shows the temperature course in the conventional example for comparison. T1
is the temperature at which pressurized deformation occurs, and T3 is the temperature at which pressurized cooling ends. The solid line shows the temperature of the forming block, and the dashed line shows the temperature of each stage.

The temperatures of the heating stage S0 and the first pressurizing stage S1 in FIG. 1 are maintained at a temperature T1 necessary for forming the glass. The temperature of the third pressurization stage S3 is maintained at the pressurization cooling end temperature T3. It is desirable that T3 is below the glass transition point of the glass material. The temperature of the second pressurization stage S2 is an appropriate temperature between T1 and T3.
Set to T2. As shown in FIG. 2, a molded block K made by filling the molds 1 and 2 and the body mold 3 with glass material 4 and forming an integral molding block is placed on a heating stage S0 as shown in FIG. As shown in FIG. 3a, after time _t0 the temperature of the forming block K reaches T1. Therefore, the forming block K is quickly sent to the first pressurizing stage S1 and pressurized for _t1 hour to deform the glass and form it. Immediately after the deformation is completed, the molded block K is sent to the second pressurizing stage S2 and cooled while being pressurized. When the temperature of the molded block K reaches T2 after ₂ hours, it is sent to the third pressurizing stage S3, where it is cooled while being _further pressurized.
Stop pressurizing when it reaches T3.

The above explanation is about one molded block, but the first molded block is stage S1.
When moving to heating stage S, the next molding block is moved to
If the molding blocks are set at 0 and the molding blocks are sent successively in sequence, molding can be performed continuously based on the longest time among t ₀ , t ₁ , t ₂ , and t ₃ .

On the other hand, for comparison, a conventional example without a plurality of pressurizing stages will be explained with reference to FIG. 3b. A molding block is placed in the molding stage in advance, and when the temperature of the molding block reaches T1 after _t10 hours, pressure molding is carried out.After deformation is completed at _t11 hours, the heating of the molding stage is stopped and the molding stage is gradually cooled down. t When the temperature reaches T3 after ₁₂ hours, stop applying pressure and take out the molded lens. With this method, only one lens can be molded in (t ₁₀ +t ₁₁ +t ₁₂ ) time.

In a conventional molding device as shown in Fig. 4, the mold is fixed to the molding device, so heating and
The molding and cooling cycle follows the same sequence as shown in FIG. 3b above.

Since the deformation time t ₁ in the present invention and the deformation time t ₁₁ in the conventional example are essentially the same, t ₁ <(t ₁₀
+t ₁₁ +t ₁₂ ). Generally, the heating time t ₁₀ and the cooling time t ₁₂ are much longer than t ₁₁ , and it can be said that the time required for molding is determined by the heating and cooling times. Heating time can be shortened by increasing the heat capacity of the heating section, but
In this case, it takes time to cool down, and it is difficult to shorten the heating and cooling times at the same time. In the present invention, a pressure stage for cooling is provided, the temperature of which is kept constant lower than that of the pressure stage for molding, and the residence time per stage is set to the molding time t ₁₁
By approaching , one lens can be molded in an extremely short time compared to the conventional example.

The above will be explained using an example of actually molding a lens. SF-6 is used as the glass material, and the outer diameter is 15
A convex lens with a thickness of 3 mm and a thickness of 3 mm was shaped. Temperature of heating stage S0 and first pressurizing stage S1
T1 was set to 500°C. Temperature T3 at which pressurized cooling ends
is 400℃, second pressurization stage S2 is 450℃,
The third pressurization stage S3 was set at 400°C. The time t ₀ for raising the temperature of the shaping block on the heating stage is
1.5 minutes, the time t ₁ to deform the glass is 1 minute, the second
The time to cool down to 450℃ on the pressure stage is 1 minute.
The time required to cool down to 400℃ in the third pressurization stage is
It was hot in 1.5 minutes. The longest residence time of a molded block in an individual stage was 1.5 minutes. That is, 1.5 minutes after the molded block is first transferred from the heating stage to the first pressurizing stage,
The next molded block can be placed into the first molded block without interfering with the subsequent process.
This means that it can be accepted into the pressurized stage of 2000, and it was possible to continuously mold it with a takt time of 1.5 minutes. The optical surface of the molded lens faithfully copied the shape of the mold.

On the other hand, when lenses of the same shape are molded on one molding stage, the time _t10 for heating the stage is 2 minutes,
The time t ₁₁ for deforming the glass was 1 minute, and the time t ₁₂ for cooling to T3 was 10 minutes. This is because it takes a very long time to cool down not only the molding block but also the entire molding stage. In other words, it took 13 minutes to mold one piece. Furthermore, in order to shorten this time, pressurized cooling was stopped after 0.5 minutes and the lens was taken out at 480°C, but the transfer of the optical surface of the lens was insufficient, resulting in variations in performance.

The time required for each stage depends on the size of the lens. In other words, it is determined by the heat capacity of the molding block K that integrates the lens and its corresponding mold, so it is desirable to optimize the heating and pressurizing stages depending on the size of the lens. for example,
Molding time when molding lenses with large heat capacity
Since the cooling time compared to _t1 is very long, the overall molding tact can be shortened by dividing the pressurizing stage into more stages and shortening the residence time in one stage. Furthermore, it is also possible to divide the heating stage into multiple stages to increase efficiency.

The higher the molding temperature, the lower the viscosity of the glass and the shorter the deformation time, so choose the optimal value according to the residence time of each pressure stage, but below the bending point of the glass, the deformation takes a very long time. or very high pressures are required and impractical. In any case, in order to obtain a lens with good shape accuracy, it is important to pressurize the glass until it reaches the glass transition point at which deformation occurs.

Effects of the Invention As described above, the present invention separates the mold from the molding device to form a block integrated with the glass material, and sequentially transfers the molded block in the molding device having multiple stages of heating, molding, and cooling. By continuously molding lenses, the unit time required for molding can be shortened to the residence time of one stage, and the molding efficiency can be increased several times more than in conventional molding methods.

In addition, by molding at a temperature above the bending point of the glass and continuing to apply pressure at a temperature above the glass transition point during cooling, it is possible to accurately transfer the precision of the mold to the glass and obtain highly accurate lenses. Effects can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the flow of a lens molding method in an embodiment of the present invention, FIG. 2 is a sectional view showing a molding block in an embodiment of the present invention, and FIG.
Figures a and b are graphs showing changes in temperature during the molding process, and Figure 4 is a sectional view showing the state of molding a glass lens by a conventional method. 1, 2, 11, 12... Press mold, 3, 13... Body mold, 4... Glass material, 14... Molded lens, 15... Heater, 16, 17... Molding device,
K...molding block, S0, S1, S2, S3,
S4... Stage of the molding device.

Claims (1)

[Claims] 1 A molding device consisting of a heating stage and two or more pressurizing stages each equipped with a heating means independently of the heating stage, in which a molding block consisting of a pair of press molds, a body mold and a glass material is moved to a desired stage. The temperature of the first pressurizing stage is set to be higher than the bending point of the glass material, and the temperature of the second and lower pressurizing stages is successively kept low and constant, and the molded block is After being heated to a moldable temperature in the heating stage, it is supplied to the first pressure stage and pressure-formed, and then sequentially transferred to the second and subsequent pressure stages to reach the glass transition point or below the glass transition point. A method for forming a glass lens characterized by cooling while applying pressure up to the last pressurizing stage set at .