JP3228634B2 - Optical element molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding method for molding a glass optical element by pressing a heat-softened glass material with a pair of upper and lower molding dies.

[0002]

2. Description of the Related Art An optical element molding method for molding a glass optical element by press-molding a heat-softened glass material with a pair of molding dies is to provide an aspherical lens that is effective for miniaturization and high precision of an optical system. In recent years, research and development have been actively conducted to enable mass production at low cost.Aspherical lenses mass-produced by this method can be used in cameras and video cameras to reduce the size of optical systems. I have to.

[0003] Briefly, a molding method of this optical element is as follows. A glass material which has been heated and softened to a moldable viscosity is inserted into a molding die maintained at a required molding temperature, and the glass material is removed by the molding die. Press molding, cool as it is,
The process comprises a step of lifting the upper mold and taking out the molded optical element placed on the lower mold.

In order to reduce the molding cost of this molded optical element, shortening of the molding cycle has been studied.
In the final stage of the cooling process, a process is employed in which the upper mold is raised at a relatively high temperature to remove the molded optical element, and molding by this is recently performed.

However, when the upper mold is raised at a high temperature, the upper mold rises while the molding optical element adheres to the upper mold, that is, a so-called upper mold adhesion phenomenon may occur. When this upper mold adhesion phenomenon occurs, it becomes difficult to automatically remove the molding optical element from the molding die, which hinders automation of the molding apparatus.

Heretofore, in order to prevent the upper die from sticking, an external force is applied to the molded optical element that has adhered to the upper die by using an apparatus to apply the molded optical element to the upper die. Peeling from a mold has been performed.

Specifically, for example, Japanese Patent Application Laid-Open No.
In No. 31, when ascending the upper mold, at the interface end between the upper mold forming surface and the molding optical element optical surface, from the direction along the interface,
By pushing the wedge-shaped member, the wedge action at that time,
A method for peeling off a molded optical element attached to an upper mold is shown.

[0008]

However, the above-mentioned prior art has the following drawbacks. 1) The wedge-shaped member is driven by using a cylinder using N2 gas as a working fluid, but it is difficult to adjust the driving force. That is, when the driving force is weak, the force acting on the wedge-shaped member is weak, so that the molded optical element attached to the upper mold cannot be peeled off. Conversely, if the driving force is too strong, the wedge-shaped member will move in an impact manner, and an impact force will be applied to the molded optical element (made of glass) to cause cracks. Therefore, the N2 gas pressure must be set so as to obtain an optimum driving force that does not cause these troubles. 2) The position of the tip of this wedge-shaped member must be accurately aligned with the position of the interface end between the upper mold forming surface and the forming optical element optical surface. That is, if the position of the tip of the wedge-shaped member is too low, the tip will hit the glass and crack the glass. Conversely, if the position of the tip is too high, the tip will hit the molding surface of the mold and normal operation will not be performed. Further, the positioning of the leading end of the wedge-shaped member must be performed every time the shape of the molded product changes, and it takes time to adjust the position. 3) Since the wedge-shaped member, the cylinder serving as the driving device thereof, and the N2 gas pipe for the working fluid must be disposed near the mold, the heat capacity of the mold increases. Therefore, it takes time to raise and cool the mold,
It becomes difficult to shorten the molding cycle. 4) Since a wedge-shaped member, a driving device, and an operation control device for the wedge-shaped member are required, the cost of the molding device is increased.

As described above, there are many problems in the method of applying an external force to the molded optical element to which the upper mold is attached by using an external device and peeling the molded optical element from the molded mold.

[0010]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above circumstances, and by appropriately selecting a combination of an upper mold and a lower mold without using any apparatus, the mold in a state where the upper mold does not adhere is generated. An object of the present invention is to provide an optical element molding method capable of realizing the opening.

[0011]

That is, in the present invention,
In an optical element molding method for molding a glass optical element with a pair of molding dies arranged above and below, in a step of press-molding a heat-softened glass material with a pair of molding dies and cooling, the molding of the molding dies is performed. The distribution of the thermal stress generated inside the glass optical element and the mold that is cooled in a state in which the glass optical element is in close contact with the surface is near the edge of the interface between each optical surface of the glass optical element and the corresponding molding surface of the mold. Σxy = K · rp ^-1 (where σxy: shear stress, r: from the interface end), which indicates the distribution of the shear stress component on the interface (however, the shear stress component in the coordinate system along the interface) The distance of the
K: a parameter of stress distribution, p: a parameter of stress distribution), a mold for forming an optical surface of a glass optical element having a larger value of the parameter K is defined as an upper mold, and the other optical element. By forming a glass optical element using a pair of molds as optical element molding dies and a pair of molding dies as lower molds for forming surfaces, the occurrence of adhesion of the upper mold is prevented.

[0012]

[Function] Since the molding surface of the molding die is mirror-polished and the surface roughness is smooth, the molding surface of the molding die and the optical surface of the molded glass in the state where the molding die is press-molded, Microscopically, they are very close to each other, and an intermolecular attractive force acts between them, so that the mold and the glass are in close contact with each other.

Further, in a temperature range where the glass formed under pressure is cooled, the coefficient of thermal expansion of the glass is larger than the coefficient of thermal expansion of the mold, so that the glass is cooled in a close contact state. Thermal stress occurs. Then, it is considered that when the thermal stress increases with cooling and the adhesive force (intermolecular attractive force) between the mold and the glass is overcome, the molded optical element is separated from the molding surface of the mold (releases).

The inventor obtained experimentally and numerically calculated the cross-sectional shape of the molded optical element, the distribution of thermal stress generated in the mold and the inside of the glass, and the temperature relationship at which the molded optical element was released from the mold. After examining the stress distribution,
The following findings were obtained. 1) The distribution of the thermal stress is that the stress is concentrated at the end of the interface between each optical surface of the molding optical element and the molding surface of the corresponding mold. 2) When examining the distribution of stress on the interface at the stress concentration portion at the interface end, the distribution of shear stress in the coordinate system along the interface is expressed by a stress distribution equation σxy = K · rp ^-1 (where σxy: Shear stress, r: distance from interface edge,
K: parameter of stress distribution, p: parameter of stress distribution). 3) The thermal stress increases with cooling, and the numerical value of the parameter K of the stress distribution increases accordingly. 4) The release temperature at the time when the molded optical element is peeled from the mold greatly changes depending on the shape of the molded optical element. 5) The value of the parameter K obtained from the stress distribution of the shear stress component at the stress concentrated portion at the interface end of the thermal stress generated in the molding optical element and the inside of the molding die immediately before the molding optical element is separated from the mold. Is almost constant regardless of the shape of the molded optical element.

From these results, the inventor has found that the stress state when the molded optical element is separated from the mold can be expressed as follows. That is, when the value of the parameter K, which increases with cooling, reaches a certain value, the molded optical element is separated from the mold, while the mold optical element is first released from the two optical surfaces. If the upper mold is formed after forming the other optical surface as the upper mold, and the lower mold as the other optical surface, the upper mold is lifted after at least the upper surface of the molding optical element is released from the mold. No mold sticking occurs. Here, the surface to be released first can be considered to be the surface on which the value of the parameter K obtained from the stress concentration of the thermal stress generated by cooling becomes larger.

Therefore, in the present invention, as described above,
The mold that forms the optical surface with the larger value of the parameter K is the upper mold, and the mold that forms the other optical surface is the lower mold. Then, the glass optical element is molded with such a pair of molding dies, and at least after the molded optical element is peeled off from the upper mold, by raising the upper mold, it is possible to prevent the upper mold from being attached to the molded optical element. .

The value of the parameter K is generally obtained as follows. The stress in the above-mentioned stress distribution formula is stress σ _{x ′} , σ _{y ′} , σ _{x′y ′} expressed in a coordinate system. Then, the stress on the interface near the end of the interface between the mold and the glass is converted into stress in a coordinate system along the interface by the following stress conversion formula.

Σ _x = σ _{x '} cos ² θ + σ _y' sin ² θ + σ
_{x'y '} sin2θ σ _y = σ _x' sin ² θ + σ _{y '} cos ² θ-σ _x'y' sin2
θ σ _xy = {(σ _{y ′} −σ _{x ′} ) sin2θ} / 2 + σ _{x′y ′} co
s2θ Next, the distribution of the distance r from the end of the interface and the shear stress σ _xy at the stress calculation point on the interface is determined, and the relationship between the two is calculated by log σ _xy
Is plotted on a graph of
K and (p-1) are obtained by the least squares method, and the parameter K
And p are obtained.

[0019]

1 and 2 show a first embodiment of the present invention. FIG. 1 shows a pair of upper and lower molds (lower mold) used in a molding optical element molding method according to the present invention. 2
The upper mold 3) and the molded optical element 1 (made of glass) cooled in a state in which it is in close contact with the molding surface of the mold are shown. FIG. 2 is a diagram for explaining the configuration of the molding die.

The lower mold 2 and the upper mold 3 for molding the molding optical element 1 are arranged so as to be able to move up and down with respect to the barrel mold 4 so as to slide on the same axis. The upper die 3 is fastened to a press rod 5, and an ultrasonic flaw detector 6 is arranged inside the press rod 5. The temperature of the mold is a thermocouple 7
By adjusting the output of the heater 8 disposed inside the body mold 4 based on the result, the temperature of the mold can be controlled.

In this embodiment, the shape of the molded optical element is, for example, a biconvex lens, and the diameter φ =
14 mm, center thickness t = 5.1 mm, upper surface R = 10.9 m
m, lower surface R = 20.5 mm. The material of the molded optical element is an optical glass SK12, and the glass material for molding the optical element has a shape similar to the molded optical element. The material of the molding die is a cemented carbide, the molding surface of which is polished, and a diamond-like carbon film having a releasing effect is formed on the molding surface.

Next, a molding process of a molding optical element using the molding die and the glass material will be described. First, 530
Insert the glass material into the mold at 620 ℃
After the glass is softened, the press rod 5 is lowered to press the glass material. After pressing for 1 minute to change the shape of the glass material to the shape of the molded optical element 1, the mold is cooled at a cooling rate of 10 ° C. per minute. Under these molding conditions,
When the molded optical element 1 having this shape was molded, it was observed by the ultrasonic flaw detector 6 that the molded optical element 1 peeled (released) from the molding surface of the upper mold 3 at 540 ° C.
Thereafter, after the molding optical element was cooled to 535 ° C., the upper mold 1 was raised. As a result, no adhesion of the upper mold occurred, and the molding optical element 1 was placed on the lower mold 2. Using the adsorption device, it was possible to take out automatically.
That is, when forming a biconvex lens of this shape,
It can be seen that the upper mold does not adhere by arranging the molding dies so that the optical surface of R = 10.9 in the upper mold and the optical surface of R = 20.5 in the lower mold.

Here, the value of the parameter K when the molding optical element 1 is cooled down at a constant temperature in a state in which the molding optical element 1 is in close contact with the lower mold 2 and the upper mold 3 is set at the end of the interface between the molding optical element 1 and the lower mold 2. Each part and the end of the interface between the molding optical element 1 and the upper mold 3 were determined, and the magnitudes were compared. Specifically, the value of the parameter K was determined by the following method. 1) An optical element is actually molded, the molded optical element is cut into a cross section, and the cross-sectional shape is measured. (The edge portion of this molded optical element has a cross-sectional shape that bulges outward due to the flow of the glass when the glass material is pressed and molded.) 2) The mold and the glass during cooling A mesh of the shape of the mold and the shape of the optical element required for calculating the thermal stress generated inside and by the finite element method is created based on the measurement result of the above item 1). Subsequently, assuming that thermal stress occurs when the temperature of the optical element reaches 570 ° C., the thermal stress when cooling to 520 ° C. is obtained by numerical calculation by the finite element method (for a temperature higher than 570 ° C., glass It is considered that thermal stress does not occur due to the stress relaxation phenomenon caused by the viscoelastic properties of the varnish). In this numerical calculation, the measured values were used as the physical properties of the mold and the glass (Young's modulus, Poisson's ratio, thermal expansion coefficient, thermal conductivity), and the elastic thermal stress analysis was performed on the assumption that the physical properties of the glass were elastic. . 3) From the thermal stress distribution numerically calculated in 2), the shear stress component on the interface near the edge of the interface between each optical surface of the optical element and the corresponding molding surface of the mold (however, The distribution of the shear stress component in a coordinate system along the axis is expressed by the following stress distribution equation: σxy = K · rp ⁻¹ (where σxy: shear stress, r: distance from the interface end,
K: stress distribution parameter, p: stress distribution parameter), and the values of the parameter K and the parameter p are obtained by the least square method. The evaluation of the stress distribution was performed within a range of 0.025 mm from the edge of the interface.

The value of K obtained from this result is K = 25 on the upper surface (R = 10.9 mm) side of the molded optical element,
It can be seen that K = 14 on the lower surface (R = 20.5 mm) side, and that the value of K is higher on the upper surface. That is, the parameter K
A pair of molding dies, in which the molding die forming the optical surface of R = 10.9 mm where the value becomes large is an upper die, and the molding die forming the optical surface of R = 20.5 mm is a lower die, are arranged vertically. By using the optical element molding die having the structure, the diameter φ is 14m.
m, center thickness t = 5.1 mm, R = 10.9 mm and R
It was found that by forming a biconvex lens of 20.5 mm, it is possible to prevent the upper mold from adhering. (Comparative Example) In order to confirm that the molding using the combination of the upper and lower dies described above is effective in preventing the occurrence of the adhesion of the upper mold, the upper mold when the molding was performed using the combination of the upper and lower dies was reversed. The incidence of mold adhesion is compared with the case of this example.

The molding conditions are the same as in the embodiment,
After the molded optical element was cooled to 535 ° C., the upper mold was raised. Table 1 shows the results.

[0026]

[Table 1] It should be noted that, in the combination of the dies in the embodiment of the present invention, 10
When molding was performed 0 times, no upper mold adhesion occurred. On the other hand, when molding was performed 100 times with the combination of the dies of the comparative example in which the combination of the dies was turned upside down, only 9 times did not cause the upper die to adhere, and the remaining 91 times were the upper die. Adhesion occurred. Forty-eight times, the molding optical element could not be taken out and the automatic operation of the molding apparatus stopped because the vacuum suction device entered the molding die with the molding optical element adhered to the upper mold. . For the remaining 43 times, before the vacuum suction device enters the molding die, the molding optical element that had adhered to the upper mold dropped from the upper mold, and the molding optical element that had fallen 12 times was used by the vacuum suction device for 12 times. I was able to take it out. In the remaining 31 times, the molding optical element could not be taken out by the vacuum suction device due to the position error of the molding optical element that fell and the molding optical element was damaged, and the automatic operation of the molding apparatus was stopped urgently.

As described above, it can be seen that molding the optical element with the combination of the upper and lower molds according to the present invention has a great effect in preventing the upper mold from adhering.

FIG. 3 shows a second embodiment of the present invention, in which a pair of upper and lower molding dies (lower mold 2 and upper mold 3) used in the molding optical element molding method according to the present invention. In addition, the molded optical element 1 is cooled while being in close contact with the molding surface of the mold. The configuration of the molding apparatus is the same as that of the previous embodiment shown in FIG.

The molded optical element 1 molded in this embodiment
Is a convex meniscus lens with a diameter φ =
24 mm, center thickness t = 3.3 mm, convex surface R = 23 mm,
The concave surface R is 41 mm. In this example, the convex optical surface of the molded optical element 1 was formed by the upper mold 3 and the concave optical surface was formed by the lower mold 2. The material of the molding optical element 1 is optical glass SF8, and the glass material for molding the optical element has a shape similar to the molding optical element 1, and the surface of the glass material A glass thin film is coated to prevent the volatilization of the lead component from the glass at the time. Furthermore, a molding die (lower die 2 and upper die 3)
Is a cemented carbide, and its molding surface is polished.

Next, a description will be given of a molding process of a molding optical element using the molding die and the glass material. First, 410
Insert the glass material into the mold at 520 ℃
After the glass is softened, the press rod 5 is lowered to press the glass material. After pressing for 2 minutes to change the shape of the glass material into the shape of the molding optical element 1, the mold is cooled at a cooling rate of 10 ° C. per minute. Under these molding conditions,
When the molded optical element 1 having this shape was molded, it was observed by the ultrasonic flaw detector 6 that the molded optical element 1 peeled (released) from the molding surface of the upper mold 3 at 420 ° C. Then, after cooling the molded optical element to 415 ° C., the upper mold 1
Is raised, the upper mold does not adhere, the molding optical element 1 is placed on the lower mold 2, and the molding optical element 1 can be automatically taken out using a vacuum suction device.

That is, when molding the convex meniscus lens 1 having this shape, the upper mold 3 forms a convex optical surface of R = 23 mm and the lower mold 2 forms a concave optical surface of R = 41 mm. It was found that the placement of the molding die did not cause the upper die to adhere.

Here, the value of the parameter K when the molding optical element 1 is cooled down at a constant temperature in a state in which the molding optical element 1 is in close contact with the lower mold 2 and the upper mold 3 is set at the end of the interface between the molding optical element 1 and the lower mold 2. And the end of the interface between the molded optical element 1 and the upper mold 3 were determined, and the magnitudes of the respective parts were compared. The specific method is the same as in the previous embodiment, the shape of the molded product is measured, the thermal stress generated between the molded product and the inside of the mold is determined by the finite element method, The parameter K was determined from the distribution of the thermal stress. Note that here, 460
Assuming that thermal stress is generated from the temperature, the thermal stress at the time of cooling to 410 ° C. was calculated. The value of the parameter K obtained from this result is K = 19 on the upper surface (convex surface R = 23 mm) side of the molded optical element, and K = 19 on the lower surface (concave surface R = 41 mm) side.
7, which indicates that the value of K is larger on the upper surface. That is, the upper mold was a mold that formed a convex optical surface of R = 23 mm where the value of the parameter K was larger, and the lower mold was a mold that formed a concave optical surface of R = 41 mm. Then, in an optical element molding die having a structure in which the pair of molding dies are arranged vertically, a diameter φ = 24 mm, a center thickness t = 3.3 mm,
It can be seen that by forming a convex meniscus lens having a convex surface R = 23 mm and a concave surface R = 41 mm, the upper mold can be prevented from adhering. (Comparative Example) In order to confirm that the molding by the combination of the upper and lower molds described above is effective in preventing the occurrence of the adhesion of the upper mold, a molding mold having a combination of the upper and lower molds was used.
The rate of occurrence of upper die adhesion in the case of molding is compared with the case of the present example. The molding conditions were the same as in the case of the second example. After the molded optical element was cooled to 415 ° C., the upper mold was raised. Table 2 shows the results.

[0033]

[Table 2] In addition, when molding was performed 100 times with the combination of the dies of the second example, no upper mold adhesion occurred. On the contrary,
When molding was performed 100 times with the combination of the molds of the comparative example in which the combination of the molds was turned upside down, the upper mold did not adhere only 5 times, and the upper mold adhered 95 times. In 81 of these cases, the vacuum suction device came into the molding die with the molding optical element adhered to the upper mold, so that the molding optical element could not be taken out and the automatic operation of the molding device was stopped immediately. Was. For the remaining 14 times, before the vacuum suction device enters the molding die, the molding optical element that had adhered to the upper mold dropped from the upper mold, and seven times of that, the dropped molding optical element was removed by the vacuum suction device. I was able to take it out. For the remaining seven times, the molding optical element could not be taken out by the vacuum suction device due to the position error of the molding optical element that fell and the molding optical element was damaged, and the automatic operation of the molding apparatus stopped. As described above, it was found that molding the optical element by combining the upper and lower molds according to the present invention has a great effect in preventing the upper mold from adhering.

FIG. 4 shows a third embodiment of the present invention, in which a pair of upper and lower molding dies (lower mold 2 and upper mold 3) used in the molding optical element molding method according to the present invention, and Shown is a molded optical element 1 that is cooled in close contact with the molding surface of the mold. The configuration of the molding apparatus is the same as that of the first embodiment shown in FIG.

Molded optical element 1 molded in this embodiment
Is a biconvex lens with a diameter φ = 10 m
m, center thickness t = 3.7 mm, convex surface R = 7.8 mm, and R = 16.5 mm. The material of the molded optical element is an optical glass SK12, and the glass material for molding the optical element has a shape similar to the molded optical element. Furthermore, the material of the mold is a cemented carbide,
The molding surface is polished, and a diamond-like carbon film is formed on the molding surface to improve releasability.

In this embodiment, before actually molding the molding optical element using the mold, the value of the parameter K is predicted, the optical surface to be formed by the upper mold is determined, and the molding die is actually molded. An embodiment in which the above is performed will be described. That is, at the stage before the molded optical element is actually molded, it is naturally impossible to know the bulged shape of the edge portion of the molded optical element. Therefore, in order to predict the value of the parameter K before molding, as shown in FIG. 5, the thermal stress generated in the optical element having a straight edge portion is obtained by the finite element method, The value of the parameter K was determined for each optical surface from the thermal stress distribution of Here, it is assumed that thermal stress occurs from 570 ° C.
The thermal stress when cooled down was calculated. The value of the parameter K obtained as a result is K = 24 on the plane with R = 7.8 mm, K = 3 on the plane with R = 16.5 mm, and R = 7.
It can be seen that the value of K is larger for the 8 mm surface. That is, it can be predicted that by forming the optical surface of R = 7.8 mm with the upper mold, the upper mold can be prevented from adhering.

Accordingly, a pair of upper and lower molding dies, each having an upper surface for forming the optical surface of R = 7.8 mm and a lower surface for forming the optical surface of R = 16.5 mm. Form a convex lens. The molding conditions are the same as in the first embodiment. Molded optical element 1 of this shape
Peel from mold surface of upper mold 3 at 35 ° C (release)
This was observed by the ultrasonic flaw detector 6. Then 5
After being cooled to 30 ° C., the upper mold 1 was raised,
The upper mold does not adhere, the molding optical element 1 is placed on the lower mold 2, and the molding optical element 1 can be automatically removed using a vacuum suction device.

That is, when the biconvex lens 1 having this shape is molded, the upper mold 3 forms an optical surface of R = 7.8 mm and the lower mold 2 forms an optical surface of R = 16.5 mm. It was found that the placement of the molding die did not cause the upper die to adhere. Here, the value of the parameter K is determined using the actual shape of the molded optical element, and the value is compared with the predicted value. Specifically, as in the first embodiment,
The sectional shape of the molded optical element is measured, the thermal stress is calculated by the finite element method, and the value of the parameter K is obtained.

The value of the parameter K obtained from this result is K = 2 on the upper surface (R = 7.8 mm) side of the molding optical element.
3, K = 5 on the lower surface (R = 16.5 mm) side, the value of K is larger on the upper surface, and the value of this parameter K is almost equal to the predicted value of the parameter K. Understand. That is, R where the value of the parameter K increases
= 7.8 mm optical surface
An optical element molding die having a structure in which a pair of molding dies are arranged vertically above and below a molding surface forming an optical surface of 16.5 mm. The diameter φ is 10 mm and the center thickness is 3.7 m.
It can be seen that by forming a biconvex lens having m, R = 7.8 mm and R = 16.5 mm, the occurrence of the upper mold adhesion can be prevented.

[0040]

As described above, by forming a molding optical element with a pair of upper and lower molding dies of the combination according to the present invention, the upper surface of the molding optical element when the upper mold is lifted to take out the molding optical element is removed. Mold adhesion can be prevented,
The equipment operation rate and the non-defective rate are improved, and the production cost can be reduced.

In particular, a conventional method of applying an external force to a molded optical element with an upper mold attached thereto by using some type of upper mold adhesion preventing device to separate the molded optical element with the upper mold adhered from the upper mold. In comparison, the present invention can prevent the upper mold adhesion without using any apparatus, so that the cost of the upper mold adhesion prevention device can be reduced, and since there is no upper mold adhesion prevention device, the heat capacity of the mold can be reduced, and the molding can be performed. The cycle can be shortened, the molding cost is reduced, the adjustment of the position and operating force of the upper die adhesion preventing device is not required, and the setup time is shortened, so that the operation efficiency of the device is improved. Further, according to the present invention, since no external force is applied to the molded optical element, the molded optical element is not damaged, and the yield rate is improved. As described above, the method of molding an optical element according to the present invention can prevent the upper mold from adhering, automatically operate the apparatus, and reduce the production cost.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment.

FIG. 2 is a diagram illustrating a first embodiment.

FIG. 3 is a diagram illustrating a second embodiment.

FIG. 4 is a diagram illustrating a second embodiment.

FIG. 5 is a diagram illustrating a second embodiment. .

[Explanation of symbols]

 1 Molded optical element 2 Lower mold 3 Upper mold

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kiyoshi Yamamoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-6-16436 (JP, A) JP-A-2 -184531 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C03B 11/00-11/16

Claims (1)

(57) [Claims] 1. A pair of molding dies arranged vertically,
In an optical element molding method for molding a glass optical element, in a step of press-molding a heat-softened glass material with a pair of molds and cooling, the glass optical element is cooled in a state in which it is in close contact with a molding surface of the mold. And the distribution of the thermal stress generated inside the mold, the shear stress component on the interface near the edge of the interface between each optical surface of the glass optical element and the corresponding mold surface of the mold (however, Σxy = K · rp ⁻¹ (where σxy: shear stress, r: distance from the interface end,
K: stress distribution parameter, p: stress distribution parameter), the upper mold is the mold that forms the optical surface of the glass optical element in which the value of the parameter K is larger, and the other is the optical mold. An optical element molding method, comprising: molding a glass optical element by using a pair of molding dies as optical element molding dies, wherein a molding die for forming a surface is a lower mold.