JPH0881229A - Molding of glass optical element and pressing device used for the same method - Google Patents

Abstract

PURPOSE: To obtain a glass optical element having high face accuracy by surely and readily releasing a molded article of press molded glass from a mold. CONSTITUTION: In press molding a glass material to be molded which is heated to a fixed temperature and softened by using a mold having a top mold 21 and a bottom mold 22 to a molded article of glass, the material is press molded and the circumference of the molded article is made into a reduced pressure state. In the press molding, the molded article of glass is stuck fast to a mold and the gap between the mold and the molded article of glass is made in a vacuum state. Consequently, as mentioned above, when the circumference of the molded article of glass is made in a reduced pressure state, the close adhesion by this vacuum state is released and the molded article of glass can be surely and readily released. In making the circumference of the molded article of glass in a reduced pressure state, for example, the pressure of a molding chamber A is objected to a reduced state before or after releasing the mold.

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 forming a glass optical element by press molding, a glass material to be molded is press-molded by using a precision-processed molding die. Then, by using a precision-processed mold, it is possible to obtain a highly accurate glass optical element that does not require grinding and polishing after press molding.

In such press molding, for example,
Using a mold having an upper mold, a lower mold and a sleeve, arranging a glass material to be molded in this mold in a low temperature state, heating the glass material to be molded together with the mold, and then pressing, A method is known in which the molding die is cooled to a predetermined temperature and a molded product (glass optical element) is taken out from the molding die. However, in the above press molding, since it takes a long time to raise and lower the temperature, the molding cycle time becomes long.

By the way, in press molding, in order to make the surface accuracy of the glass optical element highly accurate, the process until the glass is cooled near the transition point and solidified after pressing is important. When the glass is solidified near the transition point, the glass optical element can be taken out immediately after releasing the mold. Then, the molding die can be 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, the glass material to be molded is heated and softened on the ring-shaped member, and then the softened glass material to be molded is transferred to a molding die. After 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 molding die becomes low (that is, in a high temperature state), for example, a method described in JP-A-61-232525 is known.

In this mold releasing method, as shown in FIG. 7, in a molding die having an upper die 11 and a lower die 12, the upper die 11
Further, a releasing member 13 which is slidable in the vertical direction is arranged on the outer circumference of each of the lower mold 12 and the lower mold 12, and at the time of pressing, the glass material 14 to be molded is pressed so as to protrude outward from the upper and lower molds. . After the pressing is completed, the release member 13 is slid to press the protruding portion 14a to release the glass optical element (for example, lens) from the mold.

The releasing method as described above is further described in JP-A-62-153127 and JP-A-62-176929.
JP-A-62-196612, JP-A-4-
629, JP-A-4-44334, JP-A-4-331725, and the like. In any case, in the methods described in these publications, the glass material to be formed is extruded outward from the upper and lower molds at the time of pressing to form a protruding extra thickness part (extrusion part), Mold release is performed by pressing the excess thickness portion with a mold release member.

[0008]

As described above, in the conventional mold releasing method, the glass material to be formed is extruded outward from the upper and lower molds at the time of pressing to form the protruding extra thickness portion. Therefore, the outer shape of the glass molded body becomes larger than the effective diameter of the glass molded body by the protruding extra thickness portion, and after the mold release,
For example, it is necessary to finish the glass optical element by sharply scraping off the protruding surplus portion by cold rolling.

In addition, in the conventional mold releasing method, stress concentration occurs due to the fact that the protruding margin part is pressed, that is, the mold releasing is performed by applying a physical force to the protruding margin part. The part that becomes the glass optical element is easily broken. Furthermore, when forming the protruding extra thickness portion, it is not always possible to form uniformly, that is,
The protrusion of the protruding extra thickness portion differs from one press to another, resulting in not only poor surface accuracy but also chipping and cracking in the glass molded body.

Further, in the conventional mold releasing method, since it is necessary to dispose the mold releasing member for pressing the protruding extra thickness portion, the structure and operating mechanism of the molding die become complicated.

On the other hand, in the mold releasing method described in Japanese Patent Laid-Open No. 5-70154, a temperature difference is applied between the upper mold and the lower mold,
At the time of releasing the mold, the mold side having a lower temperature is released so that the glass molded body is attached to the mold side having a higher temperature. However, also in this method, it is necessary to release the glass molding adhered to one side at high temperature from the mold releasing member as described above. In addition, when a temperature difference is applied 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, in the conventional glass optical element molding method, there are various problems when releasing the mold, and in any case, it is difficult to mold a glass optical element having 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, a glass for press-molding a molded glass material, which has been softened by heating to a predetermined temperature, into a glass molded body by using a molding die having a first mold and a second mold. In the method for molding an optical element, there is provided a method for molding a glass optical element, which comprises a depressurizing step of reducing the pressure around the glass molded body after the press molding.

The above-mentioned press molding is carried out, for example, in a molding chamber, and in the depressurizing step, the pressure in the molding chamber is depressurized before or after the mold is released from the mold to depressurize the periphery of the glass molding.

In the depressurizing step, the interior of the glass molding may be depressurized by depressurizing the inside of the molding die before or after releasing the molding die.

The temperature of the molding die and the glass molded body at the time of releasing 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 temperature below the strain point. In the pressure reducing step, the pressure in the molding chamber may be reduced to 10 Torr or less, preferably 1 Torr.
Reduce the pressure to r or less.

Furthermore, in the present invention, a glass optical element is obtained by press-molding a glass material to be molded which has been softened by heating to a predetermined temperature by using a molding die having first and second molds. Used during molding, the first mold is placed in a molding chamber, the second mold receives the glass material to be molded at a predetermined transfer position, and the second mold is moved from the transfer position. First moving means for moving the glass into the forming chamber; pressing means for moving the first mold to press-mold the glass material to be molded 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 the second mold for molding And a second moving means for moving from the chamber to the transfer position.

[0019]

In general, press molding is carried out in a non-oxidizing gas atmosphere at a pressure of 1 atmosphere or slightly above atmospheric pressure. The glass molded body is brought into close contact with the molding die by press molding, and as a result, a slight vacuum state is maintained between the molding die and the glass molded body. The shrinkage coefficient of glass is generally larger than that of the mold, and for example, in a lens having a concave surface, a vacuum state is more significantly generated. In the present invention, after the press molding, the pressure around the glass molded body is kept in a reduced pressure state, so that the adhesion in the above vacuum state is released, and the glass molded body can be released from the glass mold reliably and easily.

[0020]

EXAMPLES The present invention will be described below with reference to examples.

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

The upper die support rod body 23 penetrates the first plate body 25, and an O-ring 25a is fitted into the first plate body 25 as a seal member as shown in the figure, whereby the O-ring 25a is fitted. Airtightness is maintained. The upper die support rod 23 is connected to, for example, a cylinder (not shown), and the cylinder drives the upper die support rod 23 in the vertical direction in the drawing. Further, an exhaust port 25b and a gas introduction port 25c are formed in the first plate body 25.

A second plate body 26 is arranged below the first plate body 25 at a predetermined interval, and the first and second plate bodies 25 and 26 are tube members as shown in the drawing. It is connected to (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 through the O-ring 27a, and the other end (lower end) of the tube member 27 is inserted into the second plate through the O-ring 27b. It is fixed. Then, the molding chamber A is formed by the first and second plate members 25 and 26 and the tube member 27.
Is prescribed. A hole 26a for inserting the lower mold 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. It is set up.

Similarly, the lower die support rod 24 is connected to a cylinder (not shown), and the lower die support 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-mentioned pressing apparatus, the pressure is slightly raised from the atmospheric pressure in an atmosphere of H ₂ of 2% and N ₂ of 98%. As 22, a dense SiC type having a hard carbon film formed on its surface was used.

First, as a first example, barium borosilicate optical glass (transition point 534
An example of molding a meniscus lens (outer diameter of 15 mm), which is a type of glass optical element, using a temperature of ℃ and a deformation point of 576 ° C. will be described.

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

With reference 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 of the second plate 26 is inserted through the O-ring 26b. The molding chamber A becomes a hermetically sealed chamber by closely contacting the lower surface. 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.

Immediately thereafter, the upper die 21 and the lower die 22 are heated to a temperature of 63 by the upper die heater 21a and the lower die heater 22a.
Raise the temperature to 0 ° C. As a result, the temperature of the preform 28 also 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 pressing is performed at a pressure of 100 kg / cm ² for 30 seconds.

While maintaining the pressure, the upper die heater 21a
The upper die 21 and the lower die 22 are cooled to a temperature of 524 ° C. by the lower die heater 22a, and then the upper die 21 is heated to 5
The mold was lifted up by mm. At this time, the glass molding 29 is released from the lower mold 22, but is stuck to the upper mold 21. Immediately after releasing the mold, the vacuum pump (not shown) evacuates the gas through the exhaust port 25b to set the molding chamber A to 0.1 To.
When the pressure was reduced to rr, the glass molding 29 showed the upper mold 21.
It fell naturally from and got on the lower mold 22.

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

In the same manner, as a result of performing press molding continuously and repeatedly, it was possible to obtain a lens (glass molding) with high surface accuracy in a short cycle time.

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

Next, as a second embodiment, molding of a biconvex lens having an outer diameter of 15 mm and a radius of curvature of R80 mm on the upper surface and R30 mm on the lower surface 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 It was softened to a poise viscosity by heating, the floating tray 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 die 22 is maintained at a temperature of 576 ° C. by the lower die heater 22a.

Immediately thereafter, as described in the first embodiment, the lower mold 22 is 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 die 21 is maintained at a temperature of 576 ° C. by the upper die heater 21a. Then, the upper mold 21 and the lower mold 22 were cooled to a temperature of 534 ° C. by the upper mold heater 21a and the lower mold heater 22a while maintaining the pressure, and then the upper mold 21 was lifted by 5 mm and released. On this occasion,
Although the glass molded body was released from the lower mold 22, the upper mold 21
I became clinging to.

Immediately thereafter, when the gas was exhausted from the exhaust port 25b using a vacuum pump, the pressure in the molding chamber A was 1
When it reached about Torr, the glass molding was the upper mold 2.
It fell from 2 and got 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 the slow cooling chamber using the pad.

In this way, as a result of performing press molding continuously and repeatedly, it was possible to obtain a lens (glass molding) with high surface accuracy in a short cycle time.

When the vacuum evacuation was not carried out, the glass molded body naturally dropped on the lower mold when the temperature of the mold decreased by about 100 ° C. from the transition point.

Next, a third embodiment will be described. In this example, a biconvex lens was formed in which the radius of curvature of the upper surface and the lower surface was set to be opposite to that of the second example. That is,
Outer diameter is 15 mm, radius of curvature is upper surface R30 mm, lower surface R80
A biconvex lens of mm was molded (note that the other configurations are the same as those in the second embodiment).

With reference to FIG. 1, in the third embodiment, after pressing, after cooling to a transition point temperature of 534 ° C., the upper mold 2
When 1 was raised by 5 mm and released from the mold, the glass molded body was on the lower mold 22.

Here, since the lower mold 22 is immediately lowered to the transfer position and transferred to the slow cooling chamber without evacuation, the glass molded body cannot be adsorbed when attempted to be adsorbed by the pad. Adsorption error occurred.

On the other hand, after releasing from the mold, it was evacuated and then the mixed gas was introduced to lower the lower mold 21 to the transfer position and suck it by the pad, and it was able to be well adsorbed.

Thus, in the present invention, the glass viscosity is 10
^{In the range of 12 to} 10 ^14.5 poises, the glass molding adhered to the molding die can be easily and surely released without causing cracks or cracks.

When the glass viscosity exceeds 10 ¹² poise, viscous flow does not occur in a short time, and it can be considered that the glass is almost solidified. As a result, good surface accuracy can be obtained without causing deformation or the like of the glass molded body after releasing from the mold.

In the above-mentioned embodiments, the example in which the pressure in the molding chamber is reduced before or after the mold release is described, but before or after the mold release, only the inside of the mold may be depressurized. . At this time, for example, the molding die 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 the body die 31.
Will be guided to. Specifically, at the time of press molding, the upper mold 21
The lower mold 22 is guided by the body mold 31 to press-mold the glass material to be molded.

As shown in the figure, the exhaust port 3 is provided on the side surface of the body mold 31.
1a is formed, and the inside of the molding die is, for example, evacuated to a depressurized state via the exhaust port 31a after press molding. This evacuation may be performed before or after releasing the mold (note that the upper heater and the lower heater are not shown in FIG. 6).

As can be easily understood from the above-described embodiments, the inside of the molding chamber or the molding die may be evacuated to reduce the pressure to reduce the pressure around the glass molded body, whereby a good glass molded body can be obtained. 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 examples, but the type and the material are selected so that the glass material to be molded and the molding die do not react with each other. . Further, the structure of the molding die, the heating method, and the structure of the pressing device are appropriately designed as necessary. Furthermore, in the above-mentioned examples, a silica tube was used to observe the state of mold 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 (glass viscosity of 10 ^{12 to} 10 ^14.5 poise) without forming an extra protruding portion. Can be released. As a result, there is an effect that it is possible to obtain a glass optical element having a high surface accuracy with a minimum required amount of glass and a short cycle time without causing chipping and cracking.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a main part of a pressing device according to the present invention in a state where a glass material to be molded (preform) is placed on a lower mold.

FIG. 2 is a cross-sectional view showing a state immediately before pressing with the lower die raised in the pressing apparatus shown in FIG.

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

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

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

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

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

[Explanation of symbols]

 21 Upper Mold 22 Lower Mold 23 Upper Mold Support Rod 24 Lower Mold Support Rod 25 First Plate 26 Second Plate 27 Tube Member (Silica Tube) 28 Molded Glass Material (Preform) 29 Glass Molded Body 31 body type

Claims (6)

[Claims] 1. A method for molding a glass optical element, comprising press-molding a glass material to be molded, which has been softened by heating to a predetermined temperature, into a glass molded body by using a molding die having first and second molds, wherein the press molding is performed. After that, there is provided a depressurizing step of bringing a pressure-reduced state around the glass molded body to a molding method of a glass optical element. 2. The method for molding a glass optical element according to claim 1, wherein the press molding is performed in a molding chamber,
The depressurizing step depressurizes the molding chamber before or after releasing the molding die so that the circumference of the glass compact is depressurized. 3. The method for molding a glass optical element according to claim 1, wherein the depressurizing step depressurizes the inside of the molding die before or after releasing the molding die to surround the glass molded body. The method for molding a glass optical element is characterized in that the pressure is reduced. 4. The glass optical element molding method according to claim 2, wherein the mold and the glass molded body have a glass viscosity of 10 ¹² poise or more during the mold release. A method for molding a glass optical element, wherein the temperature is a temperature corresponding to. 5. The method for molding a glass optical element according to claim 1, wherein in the depressurizing step, the circumference of the glass compact is depressurized to a pressure of 1 Torr or less. A method for molding a glass optical element having a feature. 6. When molding a glass optical element by press-molding a glass material to be molded, which has been softened by heating to a predetermined temperature, using a molding die having first and second molds, to obtain a glass optical element. The first mold is used in the molding chamber, the second mold receives the glass material to be molded at a predetermined transfer position, and the second mold is moved from the transfer position into the molding chamber. First moving means for moving, and 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 the second mold for molding A second moving means for moving the chamber from the chamber to the transfer position.