JP2934937B2 - Method for molding glass optical element and press device used for this method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a glass optical element such as a glass lens, and more particularly to a method for molding a glass optical element by press molding.

[0002]

2. Description of the Related Art Generally, when a glass optical element is formed by press molding, a glass material to be molded is press-molded using a precision-molded mold. Then, by using a precision-molded mold, a high-precision glass optical element that does not require grinding and polishing after press molding can be obtained.

In such press molding, for example,
Using a mold having an upper mold, a lower mold and a sleeve, disposing the glass material to be molded in this mold at a low temperature, raising the temperature of the glass material to be molded together with the mold, pressing, and thereafter There is also known a method in which a mold is cooled to a predetermined temperature and a molded article (glass optical element) is taken out from the mold. However, in the above-described press molding, since a long time is required for raising and lowering the temperature, the molding cycle time becomes longer.

In order to increase the surface accuracy of a glass optical element in press molding, it is important that the glass is cooled to a temperature near a transition point and solidified after pressing. Once the glass has solidified near the transition point, the glass optical element can be taken out by immediately releasing the mold. Then, the molding die is returned to a predetermined temperature for the next press molding, and the press molding can be sequentially performed. That is, the molding cycle time can be shortened.

In such press molding, in order to shorten the molding cycle time, for example, a glass material to be molded is heated and softened on a ring-shaped member, and then the softened glass material to be molded is transferred to a molding die. After the pressing, the mold is released at a high temperature, that is, before the mold temperature becomes low. As described above, as a method of releasing the mold before the temperature of the mold becomes low (that is, in a high temperature state), for example, a method described in JP-A-61-132525 is known.

In this release method, as shown in FIG. 7, in a molding die having an upper die 11 and a lower die 12,
A releasing member 13 slidable in the vertical direction is provided on the outer periphery of the lower mold 12 and the lower mold 12, and the pressing is performed such that the glass material to be molded 14 protrudes outward from the upper and lower molds at the time of pressing. . After the pressing, the release member 13 is slid to press the protruding portion 14a to release the glass optical element (for example, a lens) from the molding die.

The above-mentioned release method is further disclosed in Japanese Patent Application Laid-Open Nos. Sho 62-153127 and Sho 62-176929.
JP, JP-A-62-196612, and JP-A-4-196612.
629, JP-A-4-44334, and JP-A-4-331725. In any case, according to the methods described in these publications, at the time of pressing, the glass material to be formed is protruded outward from the upper and lower molds to form a protruding excess portion (protruding portion). Release is performed by pressing the excess portion with a release member.

[0008]

As described above, in the conventional mold release method, the glass material to be formed protrudes outward from the upper and lower molds at the time of pressing to form a protruding excess portion. Therefore, the outer shape of the glass molded body becomes larger than the effective diameter of the glass molded body by the protruding excess part, and after the mold release,
For example, it is necessary to sharply remove a protruding excess portion by cold rounding to finish a glass optical element.

In addition, in the conventional mold release method, stress concentration occurs due to the fact that the protruding surplus portion is pressed, that is, a physical force is applied to the protruding surplus portion to perform demolding. The glass optical element is easily broken. Further, when forming the protruding excess portion, it is not always possible to form it uniformly, that is,
Extrusion of the protruding excess portion is different every time pressing is performed. As a result, not only poor surface accuracy occurs, but also chipping and cracking of the glass molded body may occur.

Further, in the conventional release method, it is necessary to provide a release member for pressing the protruding excess portion, so that the structure and operation mechanism of the molding die become complicated.

On the other hand, in the mold release method described in Japanese Patent Application Laid-Open No. 5-70154, a temperature difference is given between the upper mold and the lower mold,
At the time of mold release, the mold is released from the lower temperature mold side, and the glass molded body is attached to the higher temperature mold side. However, also in this method, it is necessary to release the glass molding adhered to one side of the high temperature with the release member as described above. In addition, when a temperature difference is given between the upper mold and the lower mold, warpage occurs in the glass molded body, which is inconvenient especially when high surface accuracy is required.

As described above, the conventional glass optical element molding method has various problems at the time of mold release, and in any case, it is difficult to mold a glass optical element with high surface accuracy.

An object of the present invention is to provide a molding method capable of reliably and easily releasing a press-molded glass molded body from a molding die to obtain a glass optical element with high surface accuracy.

[0014]

According to the present invention, there is provided a glass for press-molding a glass material to be molded, which has been softened by heating to a predetermined temperature, using a mold having first and second molds. In the method for molding an optical element, a method for molding a glass optical element is provided, comprising a pressure reducing step of reducing the pressure around the glass molded body after the press molding.

The above-mentioned press molding is performed, for example, in a molding chamber, and in the depressurizing step, the pressure in the molding chamber is reduced before or after the mold is released, so that the periphery of the glass molded body is reduced.

In the depressurizing step, the inside of the mold may be depressurized before or after the mold is released, so that the periphery of the glass molded body is depressurized.

The temperature of the mold and the glass molded body at the time of release is preferably a temperature corresponding to a glass viscosity of 10 ¹² poise or more, but it is not necessary to lower the temperature to a low temperature below the strain point. In the depressurizing step, the pressure in the molding chamber may be reduced to 10 Torr or less, and preferably 1 Torr.
Reduce the pressure to r or less.

Further, in the present invention, the glass optical element is obtained by press-molding a glass material to be molded which has been heated and softened to a predetermined temperature using a molding die having first and second dies. Used for molding, the first mold is disposed in a molding chamber, the second mold receives the glass material to be molded at a predetermined transfer position, and moves the second mold from the transfer position. First moving means for moving into the forming chamber; press means for moving the first mold to press-mold the glass material to be formed with the first and second molds;
Mold releasing means for releasing the first and second molds, pressure reducing means for reducing the pressure of the molding chamber to a predetermined pressure before or after the mold releasing, and forming the second mold into the mold And a second moving means for moving from the chamber to the transfer position.

[0019]

In general, press molding is performed in a non-oxidizing gas atmosphere at 1 atm or slightly higher than atmospheric pressure. The press molding causes the glass molded body to adhere to the molding die, and as a result, a slight vacuum is created between the molding die and the glass molded body. The shrinkage coefficient of glass is generally larger than that of a mold, and, for example, in a lens having a concave surface, a more remarkable vacuum occurs. In the present invention, since the periphery of the glass molded body is kept in a reduced pressure state after the press molding, the close contact due to the vacuum state is released, and the glass molded body can be reliably and easily released.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Referring to FIG. 1, first, the configuration of the press apparatus used in the present invention will be described. The illustrated press device includes an upper die 21 and a lower die 22.
A molding die is constituted by 1 and the lower die 22. Upper die 21
Are supported by an upper mold support rod 23, while the lower mold 22
Are supported by a lower mold support rod 24, and the upper mold 21 and the lower mold 22 face each other. A disk-shaped flange portion 24a protruding outward at a predetermined position of the lower die support rod 24.
Are formed. Further, the outer peripheral surfaces of the upper die 21 and the lower die 22 are respectively provided with an upper heater 21a and a lower heater 22a.
Is attached.

The upper die supporting rod 23 penetrates the first plate 25, and an O-ring 25a is fitted in the first plate 25 as a sealing member as shown in the drawing. Airtightness is maintained. The upper die supporting rod 23 is connected to, for example, a cylinder (not shown), and the upper die supporting rod 23 is driven vertically by the cylinder in the drawing. The first plate 25 has an exhaust port 25b and a gas inlet 25c.

A second plate 26 is disposed below the first plate 25 at a predetermined interval, and the first and second plates 25 and 26 are formed by a tube member as shown in the drawing. (For example, a silica tube) 27. That is,
One end (upper end) of the tube member 27 is inserted and fixed to the first plate via an O-ring 27a, and the other end (lower end) of the tube member 27 is inserted into the second plate via an O-ring 27b. Fixed. The first and second plates 25 and 26 and the tube member 27 form the molding chamber A.
Is defined. A hole 26a for inserting the lower die 22 into the molding chamber is formed in the second plate 26 as described later, and an O-ring 26b is arranged on the lower surface of the second plate 26. Has been established.

Similarly, the lower die supporting rod 24 is connected to a cylinder (not shown), and the lower die supporting rod 24 is driven vertically by the cylinder.
When the lower die support rod 24 is driven upward, the lower die 2
2 is inserted into the molding chamber from the transfer chamber B through the hole 26a, and is pressed by the upper mold 21 and the lower mold 22 as described later. At this time, the flange portion 24a comes into close contact with the lower surface of the second plate body 26 via the O-ring 26b, and the molding chamber A becomes a closed chamber.

Further, referring to FIG. 1, in the above press apparatus, the pressure is slightly higher than the atmospheric pressure in an atmosphere of 2% of H _{2 and} 98% of N ₂ , and the upper die 21 and the lower die 22 was used in which a hard carbon film was formed on a dense SiC type surface.

First, as a first embodiment, a barium borosilicate optical glass (transition point 534) was used as a glass material to be molded.
An example in which a meniscus lens (an outer diameter of 15 mm), which is a kind of glass optical element, is formed by using (° C., yield point: 576 ° C.).

In FIG. 1, a preform preheating chamber (not shown) is provided on the left side of the transfer chamber B, and a glass material to be formed (hereinafter simply referred to as a preform. In this case, a marble-like material having no surface defects is used. After heating (using a hot-formed preform) 28 to 514 ° C., which is slightly lower than the transition point, on the ring-shaped member in the preform preheating chamber, the preform 28 is transferred onto the lower mold 22 using a pad. did. At this time, the upper mold 21 and the lower mold 22 are maintained at a temperature of 514 ° C. by the upper heater 21a and the lower mold heater 22a.

Referring to FIG. 2, as described above, the lower die support rod 24 is driven upward by the cylinder, and as a result, the flange portion 24a is connected to the second plate 26 via the O-ring 26b. The molding chamber A adheres to the lower surface and becomes a closed chamber. At this time, the lower mold 22 is located in the molding chamber, and there is a gap of about 5 mm between the preform 28 and the upper mold 21.

Thereafter, the upper mold 21 and the lower mold 22 are immediately heated to a temperature of 63 by the upper heater 21a and the lower heater 22a.
Raise the temperature to 0 ° C. As a result, the temperature of the preform 28 becomes 630 ° C. Then, as shown in FIG. 3, the upper die support rod 23 is driven by a cylinder to lower the upper die 21, and press is performed at a pressure of 100 kg / cm ² for 30 seconds.

With the pressure maintained, the upper heater 21a
Then, the upper mold 21 and the lower mold 22 are cooled down to a temperature of 524 ° C. by the lower mold heater 22a.
The mold was released by elevating mm. At this time, the glass molded body 29 is released from the lower mold 22, but is stuck to the upper mold 21. Immediately after the mold release, air is exhausted from the exhaust port 25b by a vacuum pump (not shown), and the molding chamber A is set to 0.1 Ton.
When the pressure was reduced to rr, the glass molded body 29 became
And fell on the lower mold 22 naturally.

Thereafter, a mixed gas (2% H ₂ + 98% N ₂ ) was immediately introduced into the molding chamber A from the gas inlet 25c.
As shown in FIG. 4, the lower mold support rod 24 was driven downward to lower the lower mold 22 to the transfer position. Then, the glass molded body 29 was transferred by a pad to a slow cooling chamber (not shown) on the right side of the transfer chamber B.

In the same manner, as a result of continuously and repeatedly performing press molding, a lens (glass molded body) with high surface accuracy could be obtained in a short cycle time.

In the above embodiment, the upper die 21 is 5 m
After elevating the upper mold 21, the evacuation was performed. However, the evacuation may be performed without elevating the upper mold 21, and then the demolding may be performed. In this case, the lower mold 22 is released by the demolding.
The glass molding will be on top. On the other hand, when vacuum evacuation was not performed, the glass molded body remained stuck to the upper mold 21 even when the upper mold temperature was greatly reduced.

Next, as a second embodiment, the formation of a biconvex lens having an outer diameter of 15 mm, a curvature radius of an upper surface R of 80 mm, and a lower surface R of 30 mm will be described.

[0035] Referring to FIG. 1, in this embodiment, by using a floating pan split type for heating and softening while by ejecting a gas to float the preform from inside pan, about 10 ^6.5 while floating the preform After heating and softening to a poise viscosity, the floating pan was opened left and right on the lower mold 22 and the preform was dropped onto the lower mold 22. At this time, the lower mold 22 is maintained at a temperature of 576 ° C. by the lower heater 22a.

Thereafter, as described in the first embodiment, the lower mold 22 is immediately raised to make the molding chamber A a closed chamber, and the upper mold 21 is lowered for 10 seconds at a pressure of 100 kg / cm ^2. Pressing was performed (this state is shown in FIG. 5). At this time, the upper mold 21 is maintained at a temperature of 576 ° C. by the upper heater 21a. Then, while maintaining the pressure, the upper mold 21 and the lower mold 22 were cooled to a temperature of 534 ° C. by the upper heater 21a and the lower heater 22a, respectively, and then the upper mold 21 was lifted by 5 mm and released from the mold. On this occasion,
Although the glass molding was released from the lower mold 22, the upper mold 21
It was stuck to the state.

After that, immediately after the air was exhausted from the exhaust port 25b using a vacuum pump, the pressure in the molding chamber A became 1
When the pressure reaches about Torr, the glass molded body is
2 and fell naturally on the lower mold 22. Immediately thereafter, the mixed gas (2% H ₂ +98
% N ₂ ) was introduced into the molding chamber A, and the lower mold 22 was lowered to the transfer position as in the first embodiment. Then, the glass molded body was transferred to an annealing room using a pad.

As described above, as a result of continuously and repeatedly performing press molding, a lens (glass molded body) with high surface accuracy was obtained in a short cycle time.

In the case where the vacuum evacuation was not performed, the glass compact naturally dropped onto the lower mold when the temperature of the mold dropped about 100 ° C. from the transition point.

Next, a third embodiment will be described. In this embodiment, a biconvex lens was formed in which the radii of curvature of the upper surface and the lower surface were set to be opposite to those of the second embodiment. That is,
Outer diameter 15mm, radius of curvature is upper surface R30mm, lower surface R80
A bi-convex lens having a thickness of 2 mm was formed (the other components are the same as those of the second embodiment).

Referring to FIG. 1, in the third embodiment, after pressing, after cooling to a transition point temperature of 534 ° C.,
1 was lifted by 5 mm and released from the mold. As a result, the glass molded body was on the lower mold 22.

Here, since the lower mold 22 is immediately lowered to the transfer position without being evacuated and transferred to the cooling chamber, the glass molded body is not adsorbed when the pad is tried to be adsorbed by the pad. An adsorption error has occurred.

On the other hand, after releasing from the mold, the vacuum was evacuated and then the mixed gas was introduced. The lower mold 21 was lowered to the transfer position and was adsorbed by the pad.

As described above, in the present invention, the glass viscosity is 10
^In the region of ^{12 to} 10 ^14.5 poise, the glass molded body in close contact with the mold can be easily and reliably released without causing chipping or cracking.

When the glass viscosity exceeds 10 ¹² poise, viscous flow does not occur in a short time, and it may be considered that the glass is almost solidified. As a result, the glass molded body is not deformed after the mold release, and a good surface accuracy is obtained.

In the above-described embodiment, an example has been described in which the pressure in the molding chamber is reduced before or after the mold release. However, before or after the release, only the inside of the mold may be in a reduced pressure state. . In this case, for example, a mold shown in FIG. 6 is used. As shown in FIG. 6, the molding die includes an upper die 21 and a lower die 22, and the upper die 21 and the lower die 22 are
Will be guided to. Specifically, at the time of press molding, the upper mold 21
The lower mold 22 is guided by the barrel mold 31 to press-mold the glass material to be molded.

As shown in FIG.
1a is formed, and the inside of the mold is evacuated to a reduced pressure state through the exhaust port 31a after press molding. This vacuum evacuation may be performed before or after the mold release (in FIG. 6, the illustration of the upper heater and the lower heater is omitted).

As can be easily understood from the above-described embodiment, the inside of the molding chamber or the mold may be evacuated and depressurized to reduce the pressure around the glass molded body. Obtainable.

The type of the glass material to be molded and the material of the molding die can be appropriately selected without being limited to the embodiment. However, the type and the material are selected so that the glass material to be molded does not react with the molding die. . Further, the structure of the mold, the heating method, and the structure of the press device are appropriately designed as needed. Further, in the above-described embodiment, a silica tube was used to observe the state of the release.

[0050]

As described above, according to the present invention, a glass molded body can be reliably and easily formed in a relatively high temperature region (a region having a glass viscosity of 10 ^{12 to} 10 ^14.5 poise) without forming an extra protrusion. Can be released. As a result, there is an effect that a glass optical element having high surface accuracy can be obtained without causing chipping and cracking, and with a short cycle time with a minimum amount of glass.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a main part of a press device according to the present invention in a state where a glass material to be molded (preform) is placed on a lower die.

FIG. 2 is a cross-sectional view showing a state immediately before pressing by lowering a lower die in the press device shown in FIG.

FIG. 3 is a cross-sectional view showing a press forming state in the press device shown in FIG.

FIG. 4 is a cross-sectional view showing a state in which the lower mold is lowered to a predetermined transfer position after press molding is completed in the press device shown in FIG.

FIG. 5 is a sectional view showing another embodiment of the press molding according to the present invention.

FIG. 6 is a sectional view showing another example of a molding die used in the present invention.

FIG. 7 is a cross-sectional view for explaining conventional press forming.

[Explanation of symbols]

 Reference Signs List 21 upper die 22 lower die 23 upper die support rod 24 lower die support rod 25 first plate 26 second plate 27 tube member (silica tube) 28 glass material to be molded (preform) 29 glass molded body 31 torso

Continuation of front page (56) References JP-A-5-97457 (JP, A) JP-A-2-184533 (JP, A) JP-A-5-70154 (JP, A) JP-A-4-331725 (JP) JP-A-4-44334 (JP, A) JP-A-4-629 (JP, A) JP-A-62-196612 (JP, A) JP-A-62-176929 (JP, A) 62-153127 (JP, A) JP-A-61-132525 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C03B 11/00

Claims (6)

(57) [Claims] 1. A method for forming a glass optical element, wherein a glass material to be formed heat-softened to a predetermined temperature is press-formed into a glass formed body using a forming die having first and second dies. A method for forming a glass optical element, further comprising a pressure reducing step of reducing the pressure around the glass molded body. 2. The method for molding a glass optical element according to claim 1, wherein the press molding is performed in a molding chamber.
The method of molding a glass optical element, wherein, in the decompression step, the pressure in the molding chamber is reduced before or after the mold is released, so that the periphery of the glass molded body is reduced. 3. The method of molding a glass optical element according to claim 1, wherein the depressurizing step comprises reducing the pressure inside the molding die before or after releasing the molding die, and surrounding the glass molded body. Wherein the pressure is reduced. 4. The method for molding a glass optical element according to claim 2, wherein a temperature of the molding die and the temperature of the glass molded body at the time of releasing the mold is equal to or higher than 10 ¹² poise. A method for molding a glass optical element, wherein the temperature is a temperature corresponding to the temperature. 5. The method for molding a glass optical element according to claim 1, wherein in the depressurizing step, the pressure around the glass molded body is reduced to a pressure of 1 Torr or less. A method for forming a glass optical element. 6. A method of molding a glass optical element by press-molding a glass material to be molded which has been heated and softened to a predetermined temperature by using a molding die having first and second dies. Used, the first mold is disposed in a molding chamber, the second mold receives the glass material to be molded at a predetermined transfer position, and moves the second mold into the molding chamber from the transfer position. First moving means for moving; pressing means for moving the first mold to press-mold the glass material to be molded into the glass molded body with the first and second molds;
Mold releasing means for releasing the first and second molds, pressure reducing means for reducing the pressure of the molding chamber to a predetermined pressure before or after the mold releasing, and forming the second mold into the mold A second moving means for moving the chamber from the chamber to the transfer position.