JP2650975B2 - Glass optical element molding method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for molding a glass optical element by heating and softening a glass material and press-molding a desired optical element with a molding die. The present invention also relates to a method for forming a glass optical element that does not require deburring.

[Conventional technology]

In general, when forming an optical element that does not require centering by heating and softening the glass material and applying pressure with a mold, the thickness of the lens or the shape accuracy of the lens surface after molding can be accurately obtained unless the weight variation of the glass material is reduced. However, there is a disadvantage that the cost of the glass material is high, for example, it is necessary to process the glass material to reduce the variation in weight.

Conventionally, in order to solve the above-mentioned drawbacks, a method has been devised in which a surplus glass material due to weight variation is pressure-formed while being housed in a space portion, and for example, a molded glass lens disclosed in Japanese Patent Application Laid-Open No. 60-171231 is disclosed. Methods for molding are known.

FIG. 4 is a cross-sectional view of a main part of a glass lens manufacturing apparatus disclosed in Japanese Patent Application Laid-Open No. Sho 60-171231.
An annular space having a predetermined depth dimension and the same outer diameter as the desired lens 1 is provided on the outer edge portion located outside the effective diameter of the desired lens 1 and on the lens surface side on which the mold surface 3 of the upper mold 2 is formed. A portion 4 is formed, and a surplus glass material due to weight variation of the glass material is stored (absorbed) in the annular space portion 4.
It is configured so that the lens shape accuracy and the lens outer diameter dimensional accuracy can be formed to be constant.

[Problems to be solved by the invention]

In the conventional method of manufacturing the glass lens 1, the surplus glass that has flowed into the annular space 4 is formed upright on the surface of the glass lens 1, so that the surplus glass is incorporated in the frame of the optical system of the glass lens 1. In such a case, there is a case where the surplus glass portion needs to be removed, and there is a problem that a processing cost is required for that.

The present invention has been made in view of the above problems, and provides a method of forming a glass optical element that does not require centering, which does not require removal processing of a surplus glass material portion that has flowed out into a surplus space accommodating the surplus glass material. The purpose is to provide.

[Means for solving the problem]

In order to achieve the above object, a method for molding a glass optical element of the present invention comprises heating and softening a glass material disposed between a pair of molding dies arranged opposite to each other in a body mold, and then press-molding the glass material with a molding die. In the method of molding a glass optical element to obtain a molded product by cooling while molding, the inner diameter portion of the body mold for regulating the outer peripheral portion of the molding die and the outer peripheral portion of the molded product made of a material having a linear expansion coefficient smaller than the linear expansion coefficient of the glass material. Forming a glass optical element having an annular molding portion at the outer edge by performing pressure molding with the molding die while flowing excess glass of the glass material into an annular space having a width of 0.5 mm or less formed by and During cooling of the glass optical element, the annular molded portion is prevented from being radially contracted by the outer peripheral portion of the molding die, thereby causing a crack in the annular molded portion, and detaching the annular molded portion from the glass optical element. And butterflies.

[Action]

According to the above molding method, when cooled, the glass material shrinks more greatly than the molding die, so that the annular molded portion formed by the glass material flowing out into the annular space receives stress and cracks, and the molded lens Be removed from.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a sectional view showing a molding apparatus 10 for carrying out a method for molding a glass optical element of the present invention.

The molding device 10 has an upper die 12 and a lower die 13 having molding surfaces 12a and 13a, which are molding dies, facing each other at the inner diameter of a cylindrical body die 11, and is inserted between the upper die 12 and the lower die 13. A heater 14 for heating and softening the placed glass material (not shown) is provided on the outer peripheral portion of the body mold 11.

The upper mold 12 is provided with a stepped portion 12b on the outer periphery of the tip having a molding surface 12a, the tip 12c is formed to have a smaller diameter than the upper mold body 12d, and the distance between the tip 12c and the inner diameter of the body mold 11 is 0.5 mm or less. Annular space 15
Is formed, and is formed of a material smaller than the linear expansion coefficient of the glass material.

The body mold 11 is provided with an appropriate number of air vent holes 16 corresponding to the position of the stepped portion 12b of the upper mold 12 to allow the gas between the upper mold 12 and the lower mold 13 to pass from inside the body mold 11 to the outside. It can be exhausted.

Next, a method of forming a glass optical element by the forming apparatus 10 having the above configuration will be described.

First, a glass material is placed between the upper mold 12 and the lower mold 13, and a predetermined pressure P is applied to the glass material by the heater 14 so that the upper mold 1 is pressed.
2, The glass material is formed under pressure by the inner diameter of the lower mold 13 and the body mold 11. In such a case, the softened glass material is
2, while being molded by the molding surfaces 12a, 13a of the lower mold 13,
Excess glass material is placed in the annular space 15 in the step 12b of the upper die 12.
Flows into an annular shape in contact with the lens, and is formed on a molded lens 17 having an annular molded portion 17b on the outer edge of the lens surface 17a.

Next, the heater 14 is turned off to cool the molded lens 17. Upon cooling of the molded lens 17, since the upper mold 12 is formed of a material smaller than the linear expansion coefficient of the glass of the molded lens 17, the molded lens 17 contracts more than the upper mold 12, but the annular molded portion 17b The contraction in the radial direction (radial direction) of the molded lens 17 is prevented by the stepped portion 12b of the upper mold 12, and stress acts on the annular molded portion 17b. Since the annular molded portion 17b is formed as thin as 0.5 mm or less, the annular molded portion 17b is cracked by the stress and detaches from the molded lens 17. Then, after cooling the molded lens 17, the lens from which the annular molded portion 17b has been removed is taken out of the body mold 11, and the lens shown in FIG.
You can get 18.

In the present embodiment, BaLF3 (linear expansion coefficient α = 10 × 10 ⁻⁷ ) as a glass material and cemented carbide (α = 6.5 × 10
^-7 ), at a heating temperature of 550 ° C and a pressing pressure of 30 kg / cm ² ,
Press molding was performed for 10 minutes, and then cooled at a cooling rate of 10 ° C./minute to form a lens 18 of φ22. Then, according to the method of the present embodiment, the width of the annular space portion 15 is 0.2 mm, 0.5 mm, 0.7 mm, 1.0 m
The lens 18 was molded by setting to m, and the results shown in Table 1 were obtained. That is, if the width of the annular space 15 is 0.5 mm or less, after cooling,
The annular molded portion 17b was separated from the molded lens 17, and did not need to be post-processed. On the other hand, when the width is 0.7 mm or 1.0 mm, the annular molded portion 17b fits into the mold and is difficult to remove, and
Did not leave 7

(Second Embodiment) The molding method of the optical element of the present embodiment uses the molding apparatus shown in FIG.
According to 10, SF7 (α = 8.8 × 10 ^-7 ) was used as the glass material,
Press molding was performed at a heating temperature of 520 ° C. under a press pressure of 10 kg / cm ² for 10 minutes, and then cooled at a cooling rate of 10 ° C./min to form a φ16 lens. Then, the lens was formed by setting the width of the annular space 15 to 0.2 mm, 0.5 mm, 0.7 mm, and 1.0 mm by the method of the present embodiment, and the results shown in Table 1 were obtained. That is, according to the present embodiment, the difference between the linear expansion coefficient of the glass and the molding die was smaller and the lens diameter was smaller than that of the first embodiment.
The same effect as that of the embodiment was obtained.

As a comparative example, the coefficient of linear expansion is SF7 which is a glass material.
Table 1 shows examples in which a lens was molded using a molding die made of a larger Ni-Cr alloy (α = 13 × 10 ⁻⁷ ). According to this example, the annular molded portion did not come off during cooling, and post-processing for removing the annular molded portion was necessary.

Third Embodiment FIG. 3 is a cross-sectional view showing a molding apparatus 20 for performing the method for molding a glass optical element of the present invention.

In the figure, reference numeral 21 denotes an upper mold, and the upper mold 21 is the upper mold 12.
A stepped portion 21b is formed on the outer periphery of the tip in the same manner as described above, and a protrusion 21c is provided in the outer peripheral direction (radial direction) on the entire periphery of the corner on the molding surface 21a side of the stepped portion 21b. The width between the surface and the outer diameter of the projection 21c is configured to be 0.5 mm or less. The other configuration of the molding apparatus 20 is the same as that of the molding apparatus 10, and therefore, the same portions are denoted by the same reference numerals and description thereof will be omitted.

The method of molding an optical element using the molding apparatus 20 is the same as in the first and second embodiments, and a description thereof will be omitted.

According to the present embodiment, the annular molded portion 17b generated by molding
Since the notch 17c is formed by the protrusion 21c on the inner side, a crack is generated from the notch 17c due to the stress due to the amount of thermal contraction between the molded lens 17 and the upper mold 21 during cooling, so that the annular molded portion 17b Has the effect of making it possible to determine the disengagement position and to facilitate disengagement.

〔The invention's effect〕

As described above, according to the present invention, it is possible to remove a ring-shaped formed portion formed by a surplus glass material flowing out into a ring-shaped space portion without performing excess processing, and to mold a glass optical element that does not require centering. . Therefore, the processing cost of the glass optical element can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a molding apparatus for carrying out a first embodiment and a second embodiment of the method for molding a glass optical element of the present invention, and FIG. 2 is a glass optical element molded by the molding apparatus of FIG. FIG. 3 is a sectional view showing a molding apparatus for carrying out a third embodiment of the method for molding a glass optical element of the present invention, and FIG. 4 is a sectional view showing a conventional molding apparatus. 10: molding apparatus, 11: trunk mold 12, 13: molding mold, 15: annular space part 17b: annular molding part

Claims (1)

(57) [Claims] A glass optical element is obtained by heating and softening a glass material disposed between a pair of molding dies opposed to each other in a body die, and then cooling the glass material while pressing and molding with a molding die to obtain a molded product. In the method, an annular space portion having a width of 0.5 mm or less formed by an outer peripheral portion of a molding die made of a material having a linear expansion coefficient smaller than a linear expansion coefficient of the glass material and the inner diameter portion of the body mold that regulates an outer peripheral portion of a molded product. A glass optical element having an annular molded portion on the outer edge is formed by performing pressure molding with the molding die while allowing excess glass of the glass material to flow out, and upon cooling the glass optical element, the diameter of the annular molded portion is reduced. A method for molding a glass optical element, comprising: causing a crack in an annular molded part by preventing shrinkage in a direction by an outer peripheral portion of a molding die, and separating the annular molded part from the glass optical element.