JPH07330347A - Method for forming optical element - Google Patents

Abstract

PURPOSE:To mold a high precision optical element free from a crack and a fragment, by preventing formation of a burr at an outer peripheral part of a molded material of glass in the first press molding in molding an optical element by dividedly carrying out the press molding twice. CONSTITUTION:Press molding pressure is controlled in the first press molding and 50-99% of diameters of faces 2a and 2b to be molded of a preform 2 is transferred to a molding face 4a of an upper mold 4 and a molding face 5a of a lower mold 5. Then, in carrying out the second press molding for the preform 2 obtained by the first press molding, since no burr has occurred in the preform 2, the upper mold 4 and the lower mold 5 will not twist the preform 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for press-molding a glass molding material that has been heated and softened to obtain an optical element such as a glass lens. The present invention relates to an optical element molding method for obtaining an optical element.

[0002]

2. Description of the Related Art Heretofore, many proposals have been made as a molding method for finishing a desired surface accuracy by repeating pressing several times. For example, in Japanese Unexamined Patent Publication No. 62-96329, a preforming step of pressing a heat-softened glass material with a molding die to form a shape close to a desired shape, and the preformed glass material are heat-softened A method of manufacturing an optical element comprising a main molding step of press-molding into a desired final shape with the molding die is disclosed, and it is described that a cylindrical glass material is used in the examples as the glass material. There is.

Further, in Japanese Patent Laid-Open No. 3-257030, molten glass is put into a molding die held near the transition temperature of the glass material, and pressing and releasing are performed at least 2 times until the temperature of the molten glass reaches a softening point. A method for molding an optical element is disclosed, in which after initial molding is repeated a number of times, final molding is performed by continuously pressing the glass material that has been initially molded until it reaches a transition point.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention JP-A-62-96
In the manufacturing method of Japanese Patent No. 329, since a cylindrical glass material is used, when the glass material is molded into a shape close to a desired shape in the preforming step, the protruding portion of the glass material surrounds the outer peripheral portion of the molding die. When, in the molding in the main molding step, the protruding portion is bitten on the outer peripheral portion of the molding die due to a slight deviation between the glass material and the molding die or the contraction of the glass material, so that the optical element (molded product) There is a problem in that the outer peripheral portion is cracked or caught and the appearance quality of the molded product is greatly impaired, and desired surface accuracy cannot be obtained. Further, even when the cylindrical glass material is not used, if the press molding is performed to a shape close to the desired shape in the preforming step, a glass material protruding portion is formed in the outer peripheral portion of the forming die, not a little. The problem was unavoidable.

Further, in the molding method disclosed in Japanese Patent Laid-Open No. 3-257030, the viscosity of the glass is sufficiently low because the glass material is made of molten glass. Even if the glass material reaches the outer peripheral portion of the molding die in the initial molding stage even if it does not reach the end of the mold or does not reach the charging step, the same problem as in the manufacturing method of JP-A-62-96329 is encountered. Was occurring.

The present invention has been made in view of the above-mentioned problems of the prior art. The inventions according to claims 1 and 2 cannot obtain a desired quality by a single press molding, and particularly high precision is achieved. It is an object of the present invention to provide an optical element required, an optical element having a large difference in wall thickness, an optical element having a large amount of aspherical deformation during press molding, and an optical element molding method capable of accurately molding an optical element having a large aperture. To do. The invention according to claim 3 is
In addition to the objects of claims 1 and 2, an object of the invention is to provide an optical element molding method capable of molding a glass molding material which is particularly fragile with high accuracy. Further, in addition to the objects of claims 1 and 2, an object of the invention according to claim 4 is to provide an optical element molding method capable of molding medium wall thickness accuracy with high accuracy.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 is to press and mold an optical element by heating and softening a glass molding material and sandwiching it between a pair of molding dies. In addition, a preform that hits the molding surface of the molding die is used as the glass molding material, and press molding is performed.
In a molding method in which the optical element having a desired shape is obtained by repeating
During the first press molding, the surface diameter of the molded surface of the optical element is 50 to
It was configured to transfer 99% to the molding surface. Further, the invention according to claim 2 is configured such that, during the first press molding, the press molding pressure is controlled to transfer 50 to 99% of the surface to be molded of the optical element. further,
The invention according to claim 3 is configured such that, in the first press molding, the heating temperature of the glass molding material is controlled to transfer 50 to 99% of the molding surface of the optical element. The invention according to claim 4 is configured such that, in the first press molding, the interval of the molding die is forcibly controlled by a stopper to transfer 50 to 99% of the molding surface of the optical element.

[0008]

In the first aspect of the present invention, in the first press molding, the press condition is controlled so that 50 to 99% of the surface diameter of the optical element to be molded is transferred to form the glass. Prevents the material from protruding to the outer periphery of the mold. Next, a glass molding material in which 50 to 99% of the surface to be molded has been molded is press-molded into a desired final shape to obtain a highly accurate optical element. That is, a heating furnace that heats and softens the glass molding material, and conveys the heat-softened glass molding material between a pair of molding dies having a molding surface that is disposed opposite to and has a desired optical element shape inverted, Using a molding machine that press-molds the glass molding material by bringing the molding dies relatively close to each other, first use a preform that hits the molding surface of the molding die as the glass molding material and heat it in the heating furnace. The softened glass forming material is conveyed between the forming dies and press-formed for the first time. At this time, the press molding conditions are controlled so that the pressed state is maintained when 50 to 99% of the surface diameter of the optical element to be molded is transferred to the molding surface, and the glass molding material is cooled and solidified.
After that, the mold is relatively separated to release the glass molding material, and the glass molding material is heated and softened again in the heating furnace and conveyed between the molding dies to be press-molded. By controlling the second press-molding condition, the entire surface to be molded of the optical element is transferred to the molding surface of the molding die, and when the glass is solidified, the molding die is relatively separated to form a glass molded article (optical element). Release and store.

In the second aspect of the present invention, in the first press molding, the press pressure is controlled so that 50 to 99% of the surface diameter of the optical element to be molded is transferred to form the glass. Prevents the material from protruding to the outer periphery of the mold. Next, a glass molding material in which 50 to 99% of the surface to be molded has been molded is press-molded into a desired final shape to obtain a highly accurate optical element. That is, a heating furnace that heats and softens the glass molding material, and conveys the heat-softened glass molding material between a pair of molding dies having a molding surface that is disposed opposite to and has a desired optical element shape inverted, Using a molding machine that press-molds the glass molding material by bringing the molding dies relatively close to each other, first use a preform that hits the molding surface of the molding die as the glass molding material and heat it in the heating furnace. The softened glass forming material is conveyed between the forming dies and press-formed for the first time.
At this time, by setting the pressing pressure to a desired value, the pressed state is maintained when 50 to 99% of the diameter of the surface to be molded of the optical element is transferred to the molding surface, and the glass molding material is cooled and solidified. After that, the mold is relatively separated to release the glass molding material, and the glass molding material is heated and softened again in the heating furnace and conveyed between the molding dies to be press-molded. By setting the second pressing pressure to a desired value, the entire surface to be molded of the optical element is transferred to the molding surface of the molding die, and when the glass is solidified, the molding die is relatively separated to form a glass molded article (optical element). ) Is released and stored.

According to the structure of claim 3, in the first press molding, the heating temperature of the glass molding material is controlled to mold 50 to 99% of the molding surface diameter of the optical element in a transferred state. This prevents the glass molding material from protruding to the outer peripheral portion of the mold. Next, 50 of the molding surface
A highly accurate optical element can be obtained by press-molding a glass molding material having a molding of ˜99% into a desired final shape. That is, a heating furnace that heats and softens the glass molding material, and conveys the heat-softened glass molding material between a pair of molding dies having a molding surface that is disposed opposite to and has a desired optical element shape inverted, Using a molding machine that press-molds the glass molding material by bringing the molding dies relatively close to each other, first use a preform that hits the molding surface of the molding die as the glass molding material and heat it in the heating furnace. The softened glass forming material is conveyed between the forming dies and press-formed for the first time. At this time, the heating temperature of the glass molding material is controlled by setting the heating furnace to a desired temperature, and 50 to 99% of the molding surface diameter of the optical element is transferred to the molding surface, and the pressed state is changed. Hold and allow the glass molding material to cool and solidify. After that, the mold is relatively separated to release the glass molding material, and the glass molding material is heated and softened again in the heating furnace and conveyed between the molding dies to be press-molded. By setting the second pressing pressure to a desired value, the entire surface to be molded of the optical element is transferred to the molding surface of the molding die, and when the glass is solidified, the molding die is relatively separated to form a glass molded article (optical element). ) Is released and stored.

According to the structure of claim 4, in the first press molding, the interval between the molding dies is controlled by the stopper to mold 50 to 99% of the surface diameter of the optical element to be molded. By doing so, the glass molding material is prevented from protruding to the outer peripheral portion of the molding die. Next, a glass molding material in which 50 to 99% of the surface to be molded has been molded is press-molded into a desired final shape to obtain a highly accurate optical element. That is, a heating furnace that heats and softens the glass molding material, and conveys the heat-softened glass molding material between a pair of molding dies having a molding surface that is disposed opposite to and has a desired optical element shape inverted, Using a molding machine that press-molds the glass molding material with the molding dies relatively close to each other,
First, a preform that hits the molding surface of the molding die is used as the glass molding material, and the glass molding material that has been softened by heating in the heating furnace is conveyed between the molding dies to perform the first press molding. At this time, by setting a desired gap between the molding dies with a stopper, the pressed state is maintained when 50 to 99% of the surface diameter of the optical element to be molded is transferred to the molding surface, and the glass molding material is cooled. Let it solidify. After that, the mold is relatively separated to release the glass molding material, and the glass molding material is heated and softened again in the heating furnace and conveyed between the molding dies to be press-molded.
By setting the second pressing pressure to a desired value, the entire surface to be molded of the optical element is transferred to the molding surface of the molding die, and when the glass is solidified, the molding die is relatively separated from each other to form a glass molded article (optical element). ) Is released and stored.

[0012]

Embodiment 1 FIGS. 1 and 2 show Embodiment 1 of the present invention, and FIG. 1 is a sectional view showing a first press-molding state, FIG.
Is a sectional view showing a second press-molding state, and FIG. 3 is a sectional view schematically showing a main part of a molding apparatus used in Example 1 of the present invention.

First, the molding apparatus 1 used in this embodiment will be described with reference to FIG. The molding apparatus 1 includes a heating furnace 3 for heating and softening a preform (glass molding material) 2, an upper mold 4 and a lower mold 5 adjacent to the heating furnace 3, and a transfer arm 6 for transferring the preform 2. It is equipped. Upper mold 4
Molding surfaces 4a and 5a are formed on the lower mold 5 by reversing the shapes of the molding surfaces 2a and 2b of the desired optical element.
The upper die 4 and the lower die 5 are arranged coaxially with the molding surfaces 4a, 5a facing each other. The lower die 5 is provided to be movable up and down by a drive device (not shown) so that it can be moved toward and away from the upper die 4, and the preform 2 conveyed between the upper die 4 and the lower die 5 is also provided. A desired press pressure can be applied to the. The transfer arm 6 is provided movably in the heating furnace 3 and between the upper and lower molds 4 and 5 from the outside by driving means (not shown), and the preform 2 is mounted on the tip thereof. The support portion 6a of the transport tray 7 is formed in a U shape. The transfer tray 7 is formed in a ring shape, and a step portion 7a on which the preform 2 is placed is provided substantially in the center of the inner diameter portion thereof, and the inner diameter portion has a function of restricting the outer circumferences of the preform 2 and the optical element. Have The upper inner diameter portion of the step portion 7a is formed to have a larger diameter than the lower inner diameter portion of the step portion 7a, and the lower inner diameter portion is formed to have a larger diameter than the lower die 5 so that the lower die 5 can be inserted. ing. Further, the collar portion 7 is provided on the outer periphery of the upper end of the transport tray 7.
b is formed, a part of the outer periphery of the transfer tray 7 is surrounded by the supporting portion 6a of the transfer arm 6, and the transfer tray 7 is mounted on the transfer arm 6 in a state in which the flange 7b is locked on the upper surface of the transfer arm 6. It can be placed. Also, preform 2
The molded surfaces 2a, 2b are formed to be convex so as to hit the molding surfaces 4a, 5a of the upper and lower dies 4, 5 with each other.

Next, an optical element molding method of this embodiment using the molding apparatus 1 having the above structure will be described with reference to FIGS. First, as shown in FIG. 3, the transfer tray 7 on which the preform 2 is placed is placed on the transfer arm 6 and transferred from the outside into the heating furnace 3 by the transfer arm 6 to heat and soften the preform 2. After that, while the heat-softened preform 2 is placed on the transfer tray 7, the upper and lower molds 4 are moved by the transfer arm 6.
Transport between 5. Then, the lower die 5 is lifted by a driving device (not shown) to form the molding surfaces 4a of the upper and lower dies 4, 5,
The preform 2 placed on the transport tray 7 by 5a is subjected to the first press molding at a predetermined pressure. As shown in FIG. 1, this press molding is performed on the surface 2 to be molded of the preform 2.
When 50 to 99% of the diameters a and 2b are transferred to both molding surfaces 4a and 5a of the upper and lower molds 4 and 5, the press molding state is maintained as it is, and the press molding is performed when the preform 2 is cooled and solidified. To finish.

After the first press-molding is completed, the lower mold 5 is lowered by a driving device (not shown) to release the preform 2, and the transfer arm 6 moves the preform 2 into the heating furnace 3. It is transported together with the transport tray 7 and heated and softened again. After that, the preform 2 is again conveyed between the upper and lower molds 4 and 5 by the conveying arm 6, and this time, the surface to be molded 2 is formed.
The preform 2 is press-molded with a pressure capable of transferring all the diameters a and 2b to the molding surfaces 4a and 4b, and the surfaces 2a and 2b to be molded are completely transferred as shown in FIG. Then, while maintaining the pressed state, the glass is cooled and solidified, and the optical element 8
After the press molding is completed, the lower die 5 is lowered by a driving device (not shown) to release the optical element 8, and the optical element 8 is collected to the outside by the transfer arm 6.

Next, applying this embodiment, using glass material SF11, φ20 mm, medium thickness 4 mm, one molded surface is a spherical surface with a radius of curvature of 88 mm, and the other molded surface is an aspheric surface amount 7
A case where a biconvex lens having an aspherical surface of 00 μm and a paraxial curvature radius of 35 mm is molded will be described with reference to FIGS. 1 to 3. The preform 2 has a radius of curvature of the aspherical surface-side molded surface 2a of 30 mm and a radius of curvature of the spherical surface-side molded surface 2b of 70 mm.
mm, medium thickness 4.5 mm biconvex shape, and the shape of the preform 2 that has been softened by heating immediately before the first press molding has a spherical surface side molded surface 2b with a radius of curvature of 50 mm and an aspherical surface molded surface. The radius of curvature of the surface 2a was set to about 35 mm. Further, the upper mold 4 is provided with the aspherical molding surface 4a and the lower mold 5 is provided with the spherical molding surface 5a.
It was set to 0 Kgf.

After heating and softening the preform 2 by setting the heating temperature of the heating furnace 3 to 700 ° C. and the heating time to 30 seconds, the first press molding was performed, the inner wall thickness was 4.1 mm, and the transfer diameter was aspherical. When the preform 2 was press molded under the same pressurizing condition and heating condition for the second time, the side molded surface 2a was transferred by about 70% and the spherical side molded surface 2b was transferred by about 90%. Both 2b could be molded so that the entire surface was transferred, the inner wall thickness was 4 mm, and the surface accuracy was a very good value of 0.5 μm PV. Further, as a result, defects such as burrs and chips did not occur on the outer circumference of the biconvex lens.
Further, in the molding of the biconvex lens, the pressure applied in the first press molding is set to 250 Kgf to reduce the transfer diameter of the aspherical surface-side molded surface 2a to about 50% (at this time, the spherical surface-shaped molded surface 2b). The transfer diameter is about 70%). When the second press molding was performed so that the applied pressure was 300 Kgf and the entire surfaces 2a and 2b to be molded were transferred, the inner wall thickness was 4 m.
m, the surface accuracy was 0.7 μm PV, and the results within the tolerance were obtained. Similarly, when the transfer diameter of the aspherical surface-side molded surface 2a in the first press molding was changed and the transfer accuracy of the second press-molded biconvex lens was examined using the preform 2 having the transfer diameter. , As shown in Figure 4,
Transfer diameter in the first press molding is about 50% or more 99
% Or less, good surface accuracy was obtained, and at 100%, burrs were generated on the outer periphery. Note that FIG. 4 also shows the relationship between the set pressure and the transfer diameter during the first press molding.

According to the present embodiment, since the entire surfaces 2a, 2b to be molded are not transferred in the first press molding, the outer periphery of the preform 2 does not have a double thickness. It is possible to obtain a highly accurate optical element without causing a problem that the upper and lower molds 4 and 5 bite the resulting double-thickness to cause cracks or chips in the optical element during the second press molding.

[0019]

Second Embodiment A second embodiment of the present invention is characterized in that the heating temperature of the preform is controlled during the first press molding to obtain a desired transfer diameter. That is, in this embodiment, the transfer diameter at the time of the first press molding is controlled by the heating temperature of the preform instead of the molding method of controlling the press pressure in the first embodiment. The molding method is the same as in Example 1. The molding apparatus used in this example is the molding apparatus 1 (see FIG. 3) used in Example 1.
See).

Next, applying the molding method of this embodiment, using glass material SF11, φ20 mm, medium thickness 4 mm, one molded surface is a spherical surface having a curvature radius of 88 mm, and the other molded surface is an aspheric surface amount of 700 μm. A case where a biconvex lens having an aspherical surface with a paraxial curvature radius of 35 mm is molded will be described with reference to FIGS. 1 to 3. As the preform 2, the aspherical surface-side molded surface 2a has a radius of curvature of 30 mm, the spherical surface-side molded surface 2b has a radius of curvature of 70 mm, and a medium thickness of 4.5 mm is used. The biconvex lens was molded by changing the heating temperature of the preform 2 during molding. Further, the upper mold 4 was provided with the aspherical molding surface 4a and the lower mold 5 was provided with the spherical molding surface 5a, and the pressing force of the lower mold 5 was fixed to 300 Kgf.

First, the heating temperature of the heating furnace 3 is set to 600.degree.
To 800 ° C., the transfer diameter at the time of the first press molding is 30%, 65%,
It was changed by 99% and 100%. Next, using the preform 2 having each of the transfer diameters, the pressing force 3 was applied in the same manner as in Example 1.
When press molding was performed a second time under the conditions of 00 Kgf and a heating temperature of 700 ° C., the biconvex lens obtained transfer accuracy almost similar to that of Example 1, as shown in FIG. That is, as shown in FIG. 8, when the transfer diameter is set to 99% or less during the first press molding, the biconvex lens 8 having no burr on the outer periphery is formed.
was gotten. Note that FIG. 5 also shows the relationship between the set heating temperature and the transfer diameter during the first press molding. Then, as shown in FIG. 9, when the transfer diameter in the first press molding was 100%, burrs were generated on the outer periphery of the biconvex lens 8a. In this example, the case where the heating set temperature was changed during the first press molding was described, but the same was true when the heating set temperature was kept constant and the heating time was changed.

According to the present embodiment, in addition to the effect of the first embodiment, the viscosity of the preform 2 is changed depending on the heating temperature, so that the preform 2 is subjected to an excessive press molding pressure.
Surface cracks and distortions are less likely to occur.

[0023]

[Embodiment 3] FIG. 6 is a cross-sectional view showing a main part of a molding apparatus used in Embodiment 3 of the present invention. Other configurations are the same as those of the molding apparatus 1 used in Embodiment 1 (see FIG. 3). Therefore, illustration and description thereof are omitted. A dial gauge 12 is fixed to the upper surface 11 of the molding chamber for fixing the upper mold 4 via the heat insulating member 10 from outside the molding chamber in the vicinity of the upper mold 4.
An upper stopper 13 extending in the molding chamber is attached to the dial gauge 12, and the tip 13a thereof has a molding surface 4a.
It is located in the vicinity of. This top stopper 13
The dial gauge 12 allows the position of its tip 13a to be adjusted (moved) in the vertical direction, and the adjustment amount can be measured by the scale of the dial gauge 12. On the other hand, a lower stopper mounting member 15 is fixed to the outer peripheral surface near the tip of the movable shaft 14 for fixing the lower die 4, and a lower stopper 16 is mounted to the tip of the lower stopper mounting member 15. The lower stopper 16
The lower stopper mounting member 15 is provided so as to be rotatable about its mounting portion, and the tip 16a of the lower stopper 16 when the lower stopper 16 is started up is the tip 13a of the upper stopper 13.
The upper mold 4 and the lower mold 5 are stopped by the contact between the tips 13a and 16a when the lower mold 5 is lifted. It is configured to be able to forcibly control the interval. Also,
The lower stopper 16 can be rotated to retract from the position where it abuts against the upper stopper 13.

In the molding method of this embodiment, when the first press molding is carried out, the tip 13a of the upper stopper 13 and the tip 16a of the lower stopper 16 are brought into contact with each other to form the upper and lower molds 4, 5, 5.
The distance between both molding surfaces 4a, 5a of the preform 2 is regulated.
The transfer diameter is controlled and the contact between the lower stopper 16 and the upper stopper 13 is avoided during the second press molding, and the entire surface of the preform 2 is transferred to mold a desired optical element. Other molding methods are the same as in the first embodiment.

Next, applying this embodiment, using the glass material SF11, φ 20 mm, medium thickness 4 mm, one molded surface is a spherical surface having a curvature radius of 88 mm, and the other molded surface is an aspherical surface amount 7
A case where a biconvex lens having an aspherical surface of 00 μm and a paraxial radius of curvature of 35 mm is molded will be described with reference to FIGS. 1 to 3 and 6. The preform 2 is formed in a biconvex shape having a radius of curvature of the aspherical surface-side molded surface 2a of 30 mm, a radius of curvature of the spherical surface-side molded surface 2b of 70 mm, and a medium thickness of 4.5 mm.
The upper mold 4 was provided with an aspherical molding surface 4a and the lower mold 5 was provided with a spherical molding surface 5a.

First, before the first press-molding, since the inner diameter of the biconvex lens is 4 mm, the thickness of the preform 2 after the first press-molding is 4.1 mm when the transfer diameter is 100%. Therefore, the distance between the tip 13a of the upper stopper 13 and the tip 16a of the lower stopper 16 is adjusted with the dial gauge 12 in advance, and the relationship between the ratio of the transfer diameter and the scale of the dial gauge 12 is obtained. Then, the pressing force of the lower mold 5 is set to 600 Kgf, the heating temperature of the heating furnace 3 is set to 700 ° C., and the heating time is set to 30 seconds to heat and soften the preform 2 and the tip 13 of the upper stopper 13.
The first position was adjusted by adjusting the position a with the dial gauge 12 and changing the transfer diameter by 30%, 60%, 99%, and 100%. Next, the lower stopper 16 is rotated to avoid contact with the upper and lower stoppers 13 and 16,
Example 1 using the preform 2 having the respective transfer diameters
When the second press molding was performed under the conditions of a pressing force of 300 Kgf and a heating temperature of 700 ° C in the same manner as above, the biconvex lens was
As shown in FIG. 7, almost the same transfer accuracy as in Example 1 was obtained. That is, as shown in FIG. 8, when the transfer diameter was set to 99% or less during the first press molding, the biconvex lens 8 having no burr on the outer periphery was obtained. Note that FIG. 7 also shows the relationship between the scale of the dial gauge 12 and the transfer diameter during the first press molding. Then, as shown in FIG.
When the transfer diameter during the first press molding was 100%, burrs were generated on the outer circumference of the biconvex lens 8a.

According to this embodiment, in addition to the effects of the first embodiment, the upper and lower stoppers 13, 1 are formed by the first press molding.
Since the inner wall of the preform 2 is controlled by 6, the variation in the inner wall of the preform 2 can be reduced by half as compared with the first and second embodiments.

According to the present invention, an optical element which cannot obtain a desired quality by a single press molding, and which requires particularly high precision,
Optical element molding capable of highly accurately molding an optical element having a large difference in wall thickness, an optical element having an aspherical surface with a large amount of deformation during press molding, and an optical element having a large aperture, and also capable of accurately molding a medium thickness For the purpose of providing the method, it can be configured as follows. When a glass molding material is heated and softened, and is sandwiched between a pair of molding dies to press-mold an optical element, a preform that hits the molding surface of the molding die is used as the glass molding material. In the molding method in which the optical element having the desired shape is obtained by carrying out two times, the gap between the molding dies during the first press molding is adjusted by a dial gauge provided on the stopper to forcibly control the diameter of the molded surface of the optical element. 50-99% of the above is transferred to the molding surface. According to the above configuration, in the first press molding, the glass molding material is molded by controlling the interval between the molding dies by the stopper to mold 50 to 99% of the molding surface diameter of the optical element to be transferred. Prevent it from protruding to the outer periphery of the mold. Next, a glass molding material in which 50 to 99% of the surface to be molded has been molded is press-molded into a desired final shape to obtain a highly accurate optical element. Then, by previously examining the correlation between the adjustment amount by the dial gauge and the transfer diameter, the transfer diameter of the molding surface diameter of the optical element can be easily controlled.

[0029]

As described above, according to the inventions according to claims 1 to 4 of the present application, glass molding is performed by transferring 50 to 99% of the glass molding material during the first press molding. Because there is no meat on the outer periphery of the material,
It is possible to obtain a highly accurate optical element without the problem that the optical element is cracked, chipped or the like due to the molding die biting the outer peripheral portion of the glass molding material during the second press molding.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first press molding in each example of the present invention.

FIG. 2 is a cross-sectional view showing a second press molding in each example of the present invention.

FIG. 3 is a sectional view schematically showing a main part of a molding apparatus used in Examples 1 and 2 of the present invention.

FIG. 4 is a diagram showing a relationship between a press set pressure for obtaining a transfer diameter at the first press molding and a transfer accuracy at the second press molding at the transfer diameter in Example 1 of the present invention.

FIG. 5 is a diagram showing a relationship between a heating set temperature for obtaining a transfer diameter at the first press molding and a transfer accuracy at the second press molding at the transfer diameter in Example 2 of the present invention.

FIG. 6 is a sectional view schematically showing a main part of a molding apparatus used in Example 3 of the present invention.

FIG. 7 is a diagram showing a relationship between stopper positions for obtaining a transfer diameter at the first press molding and a transfer accuracy at the second press molding at the transfer diameter in the embodiment of the present invention.

FIG. 8: Transfer diameter of 50 to 99% during the first press molding
FIG. 6 is an explanatory view showing a biconvex lens which is a final molded product when the above is set.

FIG. 9 is an explanatory diagram showing a biconvex lens that is a final molded product when the transfer diameter is 100% during the first press molding.

[Explanation of symbols]

 2 Preforms 2a, 2b Molded surface 3 Heating furnace 4 Upper mold 4a 5a Molding surface 5 Lower mold 13 16 Stopper

Claims (4)

[Claims] 1. When a glass molding material is heated and softened and sandwiched between a pair of molding dies to press-mold an optical element,
In a molding method for obtaining an optical element having a desired shape by performing press molding twice using a preform that hits the molding surface of the molding die as the glass molding material, the molding of the optical element is performed during the first press molding. An optical element molding method, wherein 50 to 99% of the surface diameter is transferred to the molding surface. 2. The optical element molding method according to claim 1, wherein in the first press molding, a press molding pressure is controlled to form the transfer diameter. 3. The optical element molding method according to claim 1, wherein in the first press molding, the heating temperature of the glass molding material is controlled to mold the glass molding material to the transfer diameter. 4. The method of molding an optical element according to claim 1, wherein in the first press molding, the interval between the molds is forcibly controlled by a stopper to mold to the transfer diameter.