JPH0519490B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a molding method and molding apparatus for optical elements such as lenses, and the present invention relates to a molding method and a molding apparatus for optical elements such as lenses, and the centering of optical element molded products by using ultrasonic vibrations. This makes it easy to perform this process and improves mold release properties after molding.

[Prior art and its problems]

Conventionally, optical elements, especially glass materials, have been made through a polishing process, but recently, direct press has been developed to manufacture optical elements by softening the element material by heating and press-molding it between molds. (Glass mold method) is beginning to be used.

FIG. 4 is an enlarged view of the molding section showing one example. As shown in the figure, an optical element molded product is produced by sliding the upper die 1 inside the body die 3 and press-molding the heated and softened optical element material 4 between the lower die 2 and the body die 3. It is manufactured.

By the way, it is necessary to align the optical axis of the optical element and the lens center axis within a few microns, and to do this, the inner diameter of the body mold 3 and the outer diameter of the upper and lower molds 1 and 2 must be machined to an accuracy of within a few microns. It won't happen. However, since the temperature of the above-mentioned body mold 3 and molds 1 and 2 rises during molding, lubricating oil or the like cannot be added thereto.
For this reason, if the upper mold 1 is slightly tilted or misaligned, the upper mold 1 will bite the body mold 3, making it impossible to mold, or even if molding is possible, if molded with the misalignment, the molded product There was a problem with the center of both sides being misaligned.

In addition, the thermal expansion coefficient of the upper and lower molds 1 and 2 is the same as that of the body mold 3.
If the coefficient of thermal expansion is larger than that of the upper mold 1, it is necessary to make the gap 5 larger by the expansion in order to prevent the upper and lower molds from interlocking with the body mold during press molding after heating. The problem was that it was more likely to occur.

Furthermore, conventionally, when the upper mold 1 is raised after pressure molding, the molds 1 and 2 and the body mold 3 are stuck together and cannot be easily separated, and the molded optical element is not easily separated from the molds 1 and 2. There was also a problem in that it adhered closely to the body mold 3 and could not be easily released from the mold.

The present invention was proposed as a result of repeated studies to solve these conventional problems.
The object of the present invention is to provide a method and apparatus for molding an optical element, which allows centering of an optical element mold to be performed with high precision, and allows the optical element to be easily released from the mold after pressure molding. .

[Means for solving problems]

For the above purpose, the present invention provides an optical element molding method in which the optical element material is softened by heating and then press-molded.
The feature is that ultrasonic vibration is applied to the molded part of the optical element material before press molding and/or at the time of releasing the optical element from the mold.

The present invention also provides optical element materials that have been softened by heating.
In an optical element molding apparatus configured to perform pressure molding between a body die and a pair of molds, an ultrasonic vibration generator is provided for applying ultrasonic vibration to a molded part of the optical element material. This is its characteristic.

[Effect]

By applying ultrasonic vibration to the molding part consisting of the upper mold 1, lower mold 2, and body mold 3, it is possible to prevent the upper mold 1 from shifting as shown in FIG. 5 during setting, for example.
Even if it is tilted as shown in Fig. 6, the upper die 1 is displaced to the center of the body die 3 by ultrasonic vibration, and the cores of the upper die 1 and the lower die 2 are accurately positioned on the center line of the body die 3. It turns out. Therefore, even if the outer diameters of the upper mold 1 and lower mold 2 and the inner diameter of the body mold 3 are precisely machined to have a difference of about 5 μm during thermal expansion, the upper mold 1 can be smoothly raised and lowered. However, a highly accurate optical element is molded in which the centers of both the upper and lower surfaces coincide without biting into the body mold 3. Moreover, by applying ultrasonic vibration, burning between materials due to heat does not occur.

Such ultrasonic vibrations are applied to the molding part until just before press molding, and during press molding, the vibrations are stopped and the forming circle is performed. In this case, when a spherical preform is used as the optical element material 4 before molding,
The optical element material moves slightly during vibration, but if the lower mold 2 has a concave curved surface, there is no problem because it will be located exactly at the center of the lower mold when the vibration stops.

In addition, by applying ultrasonic vibration again during mold release after pressure molding, the upper mold 1, lower mold 2, and body mold 3 that were in close contact with the molded optical element are subjected to impact, so that the optical element can be released from the mold. becomes smooth.

In addition, when the expansion coefficients of the materials of the upper mold 1, the lower mold 2, and the body mold 3 are α1, α2, and α3, respectively, the present invention is particularly effective under the conditions of α1, α2≧α3, and α1,
Under the condition of α2<α3, molds 1 and 2 after heating expansion
Since the gap 5 between the body mold 3 and the body mold 3 opens wider than when set, centering becomes difficult.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3.

〔Example〕

First Embodiment FIG. 1 is a schematic cross-sectional view showing an embodiment of a molding apparatus according to the present invention.

In the figure, 1 is an upper mold, 2 is a lower mold, and the upper mold 1 can be raised and lowered by a cylinder 7. Also 3
is a body mold fixed to a support base 13, and these upper mold 1, lower mold 2, and body mold 3 constitute a molding section for an optical element. Further, 6 is a heater for heating the optical element material, 12 is a seal box for sealing the molding section, 8 is a supply port for supplying atmospheric gas to the shield box, and 9 is a thermoelectric power supply for temperature measurement. It is a pair.

In this embodiment, an ultrasonic vibration generator 10 is installed in the cylinder 7 and the support 13, and applies minute vibrations to the upper mold 1, the lower mold 2, and the body mold 3 through the cylinder 7 and the support 13. are doing.

It goes without saying that the installation position of the ultrasonic vibration generator 10 can be changed arbitrarily as long as the object of the present invention is achieved.

The upper mold 1 described above has a convex curved surface, and SUS420 (thermal expansion coefficient α=120×10 ⁻⁷ ) was used as the base material. In addition, the lower mold 2 has a concave curved surface and is made of cemented carbide tungsten carbide WC as a base material.
(α=47×10 ^-7 ) and use the same method for body type 3.
I used WC.

As the optical element material 4, F2 (manufactured by Ohara Optical Glass Co., Ltd.) polished into a spherical surface was used. For this optical element material, we repeated several press molding experiments and found the optimal molding temperature (480°C when molding F2 glass).
Based on this, the outer diameter dimensions of the upper mold 1 and lower mold 2 were determined.

In this example, the inner diameter of the body mold 3 was set to 20.0 mm, so the dimensions at the time of molding after heating were 20+20×47×10 ^-7 ×480=20.045 mm. In order to match this, the outer diameter of the upper mold 1 is set to 20.040 mm during molding. Therefore, we calculated the upper mold dimension (x) at the time of setting (before temperature rise), and from (x) + (x) × 120 × 10 ^-7 × 480 = 20.040, the outer diameter of upper mold 1 was 19.925 mm. did. Since the lower mold 2 is made of a material with the same coefficient of thermal expansion as the body mold 3, its outer diameter was simply set to 19.995 mm.

After each mold is machined into the desired shape, the surface roughness is set to Rmax = 0.02 μm through a polishing process, the core is cored, the outside diameter is finished to the above dimensions, and finally the surface is coated with platinum gold with a thickness of 2 μm by sputtering. An alloy coating was applied to form a mold.

As for the molding method, first, a spherical optical element material 4 was placed on a lower mold 2 and set as shown in FIG. After setting the optical element material 4, using the ultrasonic vibration generators 10 installed at the upper and lower parts,
Heater 6 was used to heat up to 480°C while applying vibration at about 45KHz. Temperature was measured by thermocouple 9. During heating, non-oxidizing nitrogen gas was flowed through the atmospheric gas supply port 8 to suppress deterioration of the mold due to oxidation.

After reaching the predetermined temperature, the ultrasonic vibration is stopped and the second
As shown in the figure, the cylinder 7 was lowered and the optical element material 4 was press-molded at a pressure of about 100 kg/cm ² .

After that, it is cooled, and when the temperature of the molded part falls below the transition point of the optical glass material (430℃), ultrasonic vibration is applied again, and then the pressure is released and the cylinder 7
was raised to take out the molded optical element 11 (FIG. 3).

By repeating molding under the above conditions, it was possible to mold a high-precision optical element with good reproducibility, without interlocking of the molds, and with a surface eccentricity of 5 μm or less.

Second example: The lower mold 2 and body mold 3 are made of the same material WC as in the first example.
(α=47×10 ^-7 ), and the upper mold 1 was made of nickel.
Ni material (α=140×10 ^-7 ), as optical element material 4
SFS01 (manufactured by Ohara Optical Glass) was used.

As in the first example, the optimum molding temperature was found to be 420°C through previous experiments, and the dimensions of the mold were designed.

In this embodiment, the inner diameter of the body mold 3 is 10 mm, so the inner diameter after heating and forming is 10+10×47×10 ^-7 ×420=10.020 mm. At this time, the outer diameter of upper mold 1 is 10.015mm.
Therefore, the outer diameter dimension (y) of the upper mold when set was 9.956 mm from the following formula (y) + (y) x 140 x 10 ^-7 x 420 = 10.015. In addition, the lower mold 13
The outer diameter dimension is 9.995mm.

Regarding the mold making method and molding method, as in the first embodiment, constant vibration was applied during heating, and then,
By performing pressure molding with vibrations stopped and then applying vibrations to release the mold immediately before releasing the mold, it was possible to mold a high-precision optical element with an eccentricity of 5 μm or less with good reproducibility.

Note that the present invention can be applied not only to glass lenses but also to molding plastic lenses and the like. Furthermore, it is effective to apply ultrasonic vibration not only to the entire molding part but also to a portion of the mold, such as the upper mold or the body mold.

〔Effect of the invention〕

According to the molding method and molding apparatus of the present invention described above, since ultrasonic vibration is applied to the molding portion until immediately before press molding, the centering of the mold and the body mold can be performed accurately. Therefore, even if the mold and body mold are made with high precision so that the core can be pulled out within a few microns, the mold and body mold will slide smoothly and the mold will not bite. Therefore, the core of the optical element can be accurately drawn out.

Moreover, since ultrasonic vibrations are applied to the molding part even after molding, the mold slides smoothly with the body mold even when the mold is raised. Furthermore, the molded optical element can be easily released from the mold and the body mold.

[Brief explanation of the drawing]

1 is a schematic cross-sectional view showing an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view showing the state during press molding, FIG. 3 is a schematic view of a molded optical element, and FIG.
The figure is an enlarged cross-sectional schematic diagram of the molding part in a general optical element molding device, Figure 5 is an enlarged cross-sectional schematic diagram showing a state in which the upper mold is misaligned, and Figure 6 is a similar state in which the upper mold is tilted. It is an enlarged cross-sectional schematic diagram showing. 1... Upper die, 2... Lower die, 3... Body die, 4... Optical element material, 5... Gap between mold and body die, 6... Heater,
7... Cylinder, 8... Atmospheric gas supply port, 9... Thermocouple, 10... Ultrasonic vibration generator, 11... Molded optical element.

Claims (1)

[Scope of Claims] 1. An optical element molding method in which the optical element material is softened by heating and then press-molded, wherein the molded portion of the optical element material is provided with A method for molding an optical element, characterized by applying ultrasonic vibration when releasing the element. 2. In an optical element molding apparatus configured to press-mold a heat-softened optical element material between a body mold and a pair of molds, for applying ultrasonic vibration to the molded part of the optical element material. 1. An optical element molding apparatus, characterized in that it is equipped with an ultrasonic vibration generator.