JP2006096604A - Method and apparatus for molding optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the oxidation of a mold by suppressing the flow-in of oxygen into a chamber in the taking in and out glass to a chamber without cooling the mold to a low temperature to keep the whole chamber to the high level low oxygen atmosphere. <P>SOLUTION: In the method of molding the optical device obtained by press-molding a glass base material heated to a temperature equal to or above the softening point using a pair of upper and lower molds arranged in the chamber in an inert gas atmosphere cut off from the outside atmosphere and cooling, the pressure of the inert gas in the chamber when the glass base material is carried into the chamber before the press-molding and the glass based material after cooled is carried out from the chamber is kept to be higher than the outside pressure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical element molding method for molding a heated glass material between a pair of molds and a molding apparatus therefor.

  In a so-called glass mold molding method in which a pair of upper and lower molds and a glass material are heated above the softening transition, the glass material is pressed with the mold, and the molded optical element is taken out after being cooled, the state of the molding surface of the mold is Since it is transferred to glass almost as it is, in order to obtain an optical element having a good optical surface, the surface state of the mold must always be kept good.

  In addition, due to the recent improvement in performance of optical elements, strict demands have been made for surface conditions such as surface roughness.

  However, glass molding is performed at a high temperature of about 400 ° C. even at a low temperature, so it is generally performed in a non-oxidizing atmosphere, and a mold is placed in the chamber to fill the interior with an inert gas. Alternatively, pressing is performed in a vacuum state, and the required value of the oxygen concentration at that time is increasingly required.

  Therefore, when the glass is taken into and out of the chamber, the mold is cooled to a low temperature so that the mold does not oxidize and then the chamber is opened, or a replacement chamber is provided between the chamber body and the outside, Inflow of oxygen into the chamber was prevented by preventing the atmosphere from directly touching the outside (see Patent Document 1 below).

  Here, a brief explanation will be given of the operation in and out of the glass when the exchange chamber is provided. When the glass is put into the chamber, first the door of the exchange chamber leading to the outside is opened and the glass is put into the exchange chamber. After closing the chamber, the replacement chamber is evacuated and then filled with an inert gas. Then, the door leading to the chamber filled with the inert gas is opened to transfer the glass into the chamber. When the glass is taken out, on the contrary, after the glass is transferred from the chamber to the replacement chamber, the door to the chamber is closed, and then the door leading to the outside is opened to take out the glass to the outside.

  In this way, the atmosphere in the chamber was shut off from the outside.

  In addition, regarding the size of the opening of the chamber, consideration is not given to the minimum required size from the standpoint of maintainability such as taking in and out the mold, and also from the workability of taking in and out the glass. It was relatively large.

  Further, when the chamber is opened when the glass is taken in and out, the supply of the inert gas is normally stopped, so that the pressure in the chamber immediately settled down to the same level as the outside air with the opening.

Further, in Patent Document 2 below, a method of supplying an inert gas to the outer periphery of a mold or a barrel mold and forming an inert gas barrier around the mold to suppress the oxygen concentration value near the mold to a low level. Alternatively, a method is also proposed in which these molds are housed in a casing filled with an inert gas, and the molds are moved in the casing, and glass is inserted and removed from shutters provided on the left and right sides of the casing.
JP 2003-342022 A Japanese Patent No. 3103243

  However, in the method of opening the chamber after cooling the mold to a low temperature so that the mold does not oxidize when the glass is put in and out of the chamber, it takes time to cool the mold and raise the temperature, which greatly increases the molding cycle. In addition, the cost was significantly increased, such as increased energy during heating and increased amount of inert gas sprayed during cooling.

  In addition, when an exchange chamber is provided between the chamber body and the outside to place glass in and out of the chamber, an exchange chamber is required, and a relatively expensive door (such as a gate valve) that shuts off the atmosphere from the outside. However, it is not only necessary to install a glass installation table in the replacement chamber, but also increases the handling from the replacement chamber to the chamber. This was a significant cost increase factor.

  Furthermore, in a chamber without a replacement chamber, if the opening of the chamber is relatively large and no inert gas is supplied when the chamber is opened, a large amount of outside air flows into the chamber, increasing the oxygen concentration in the chamber, There was a problem that the mold was oxidized every time molding was repeated.

  In addition, in the method of forming an inert gas barrier around the mold, an atmosphere with a high oxygen concentration exists around the mold and the boundary is not clear. Oxygen began to exist, and it was difficult to reduce the oxygen concentration to a few ppm level.

  Moreover, in the method of storing these molds in a casing filled with an inert gas, when the glass is put in and out of the casing, the pressure in the casing immediately settles down to a level equivalent to the outside air. In other words, not a little oxygen is mixed, and a portion having a high oxygen concentration is partially present in the casing, which spreads throughout the casing due to diffusion or the like. In addition to further diffusion, if there are multiple places where glass is taken in and out, the airflow in the casing changes each time the place where the glass is taken out. Occurring and stirring the inside of the casing brings oxygen to the vicinity of the mold, and it has been difficult to maintain a low oxygen atmosphere around the mold at a high level.

  Therefore, the present invention prevents oxygen from flowing into the chamber by keeping the pressure in the chamber higher than the outside when the glass is put in and out of the chamber without cooling the mold to a low temperature. An object of the present invention is to provide a molding method for keeping the whole chamber in a low oxygen atmosphere at a high level while preventing the oxidation of the mold.

  Moreover, an object of this invention is to provide the shaping | molding apparatus for enforcing the said shaping | molding method of an optical element.

  In order to solve the above-mentioned problems, the first invention relating to the method for molding an optical element of the present invention has a softening point or more due to a pair of upper and lower molds arranged in a chamber of an inert gas atmosphere in which the atmosphere from the outside is blocked. In a method of molding an optical element obtained by press-molding and cooling a glass material heated to a temperature of 1, a predetermined portion of the chamber is opened, and the optical element before press-molding is carried into the chamber At this time, the pressure of the inert gas in the chamber when the glass material after cooling is carried out of the chamber is kept higher than the external pressure.

  This makes it possible to optimize the flow of the inert gas in the chamber from the positional relationship between the mold and the place to be taken in and out, and can maintain the flow, even if a certain part of the chamber is opened. Inflow of oxygen from the outside to the mold in the chamber can be suppressed.

  The second invention is characterized in that when a part of the chamber is opened, an inert gas is continuously supplied into the chamber.

  As a result, the pressure inside the chamber is kept higher than the outside, and a flow of inert gas from the inside of the chamber through the open portion is generated due to the pressure difference, thereby further suppressing the inflow of oxygen into the chamber. Can do.

  The third invention is characterized in that the temperature of the pair of upper and lower molds is 250 ° C. or higher when a part of the chamber is opened.

  Thereby, since the inflow of oxygen is suppressed with respect to the mold in a temperature range where oxidation is more likely to proceed, an effect of preventing oxidation can be further obtained.

  According to the fourth aspect of the present invention, when a part of the chamber is opened, the amount of the inert gas sucked from the gas suction port provided in the vicinity of the opening is determined by the supply of the inert gas supplied into the chamber. It is characterized by being below the amount.

  As a result, the outside air in the vicinity of the opening is sucked while the pressure in the chamber is kept higher than the outside, and the flow of outside air into the chamber can be prevented. Can be suppressed.

  5th invention which concerns on the shaping | molding apparatus of the optical element of this invention is an optical element obtained by press-molding the glass raw material heated to the temperature more than a softening point between a pair of upper and lower molds, and taking out from a type | mold after cooling. In an apparatus for molding a glass, a pair of upper and lower molds are enclosed in a fixed position to block the atmosphere from the outside, and an openable / closable opening for inserting and removing the optical element or glass material after molding is provided only at one place. When the chamber is provided, the mold heating / cooling means, the pressing means for pressing the glass material, and the molded optical element and the glass material are taken in and out of the chamber by opening the opening. Supply means for supplying an inert gas into the chamber such that the pressure of the gas is higher than the external pressure.

  As a result, the pressure in the chamber is kept higher than the outside, and a certain inert gas flow is generated from the inside of the chamber through the open portion to the outside due to the pressure difference, thereby further inflowing oxygen into the chamber. It can be set as the shaping | molding apparatus for suppressing.

  The sixth invention is characterized in that the size of the opening is a necessary minimum size in which the opening area is equal to or smaller than the projected area of the entire mold with respect to the opening surface and the glass can be taken in and out. And

  As a result, the outside air inlet is narrowed, and the amount of oxygen inflow can be further suppressed, and the supply amount of the inert gas for keeping the pressure in the chamber higher than the outside can also be suppressed.

  The seventh invention is characterized in that the opening has a cylindrical introduction portion that is connected to the chamber body and protrudes outward.

  As a result, when the inert gas supplied into the chamber flows out to the outside through the opening, the outside air is prevented from being caught in the chamber, and oxygen that has entered due to diffusion from the outside is still not introduced into the chamber. Then, it can be set as the apparatus for making the taking in and out of glass complete before reaching a type | mold.

  Also, at that time, when the opening and closing of the glass is completed, the opening is closed, and the inactive gas mixed with the remaining oxygen remaining in the introduction portion is sucked to prevent further oxygen from entering. preferable.

  The eighth invention is characterized in that the protruding portion of the cylindrical introduction portion has a length equal to or longer than the square root of the cross-sectional area of the cylinder.

  Thereby, even if the flow rate of the inert gas supplied into the chamber is relatively small, the inert gas in the introduction section 2 is less likely to flow and be disturbed in a laminar flow state. Intrusion can be prevented.

  According to the ninth aspect of the present invention, the supply means for supplying an inert gas to the vicinity of the opening includes a suction means for sucking a gas equal to or less than the supply amount of the inert gas supplied into the chamber. It is characterized by being provided at a position opposite to the opening in the chamber.

  As a result, the flow of the inert gas is generated from the vicinity of the mold toward the opening while keeping the pressure in the chamber higher than the outside, and the outside air near the opening is also sucked. Therefore, it is possible to provide a device for further suppressing the inflow of oxygen into the chamber. Moreover, it can also be used as a means for sucking the inert gas mixed with oxygen remaining in the introduction part, as explained in the seventh invention.

  In the tenth aspect of the present invention, the supply means for supplying the inert gas to the vicinity of the opening is provided with a suction means for sucking a gas equal to or less than the supply amount of the inert gas supplied into the chamber. The opening is provided at a position facing the suction means.

  As a result, nitrogen is supplied and exhausted in the vicinity of the opening, so that the action of blocking the outside air by the flow of nitrogen works, and the outside air that tries to enter the chamber by the entrainment of the flowing out nitrogen is exhausted together with nitrogen. be able to.

  According to the present invention, when the glass is put into and taken out of the chamber, the flow of the inert gas from the inside of the chamber to the outside is kept constant by keeping the pressure inside the chamber higher than the outside pressure. Therefore, even if the chamber is opened in a temperature range where oxidation of the mold tends to proceed, the mold may oxidize without inadvertently entering the chamber and reaching the vicinity of the mold. In addition, the optical element having a high-quality surface shape can be continuously formed.

  Therefore, even if it is a device that does not have a glass replacement chamber or a handling mechanism for moving the glass in the chamber, it is not necessary to cool it down to a low temperature so that the mold does not oxidize and then remove and insert the glass. Not only can the cost of the equipment be greatly reduced, but also the molding cycle can be shortened. At the same time, the energy required for heating and the amount of inert gas blown to the mold during cooling are greatly reduced, reducing the cost of the product. The effect is great.

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

  FIG. 1 is a longitudinal sectional view of a molding apparatus showing a state when a chamber is opened when glass is put in and out in the first embodiment of the present invention. Similarly, FIG. 2 shows the first embodiment of the present invention. It is a longitudinal cross-sectional view of the shaping | molding apparatus which shows the state after pressing in FIG. 3 and 4 are longitudinal sectional views of the molding apparatus showing the state when the chamber is opened in the second and third embodiments of the present invention, respectively.

(First embodiment)
In FIG. 1, the chamber 1 has a sealed structure for shutting off the atmosphere from the outside air, and is provided with an opening 12 for taking in and out the glass, and further connected to a cylindrical introduction part 2. In addition, a door 3 that can also block the atmosphere from the outside air is installed at the terminal portion.

  On the other hand, a body mold 8 is fixed at a specific location inside the chamber 1, and a through hole is formed on the center axis of the body mold 8 so as to penetrate the body mold 8 vertically. Yes. Of these through holes, the upper mold member 6 is inserted into the upper through hole so as to be slidable in the vertical direction in a fitted state.

  A molding surface is formed on the lower surface of the upper mold member 6 to press the glass material 29 and transfer a desired optical function surface to the surface of the upper mold member 6. 1 is connected to an upper shaft 4 for transmitting a press pressure, and a drive source 14 is disposed above the upper shaft 4.

  The upper shaft 4 is provided with a position detection means and a pressure detection means 16 (not shown). Further, a heater 10 for heating the upper mold member 6 and a temperature sensor (not shown) are provided above the body mold 8. Is installed for temperature control.

  On the other hand, the lower mold member 7 is inserted into the lower through hole on the lower side of the trunk mold 8 so as to be slidable in the vertical direction in a fitted state.

  On the upper surface of the lower mold member 7, a molding surface for transferring a desired optical functional surface to the lower surface of the glass material is formed. Further, below the lower mold member 7, outside the outer chamber 1, A lower shaft 5 connected to the drive source 15 is installed in a configuration in which the drive source 15 is disposed and penetrates the outer chamber 1, and the upper end of the lower shaft 5 is detachable from the lower surface portion of the lower mold member 7. It is in a state.

  The lower shaft 5 is provided with position detection means and pressure detection means 17 (not shown). Further, a heater 10 for heating the lower mold member 7 and a temperature sensor (not shown) are provided below the body mold 8. Is installed for temperature control.

A nitrogen gas introduction pipe connected to an N ₂ gas supply source 21 is provided on the surface opposite to the introduction portion 2 of the chamber 1, and a vacuum exhaust source 22 such as a vacuum pump is provided near the door of the introduction portion 2. Are connected to vacuum exhaust pipes connected to each other, and open / close valves U ₁ and V ₁ and regulating valves U ₂ and V ₂ are prepared, respectively, and an exhaust pipe is connected to the introduction section 2 and a leak valve R ₁ is also prepared. Has been.

  Further, the number of vacuum exhaust pipes near the door of the introduction part 2 is not limited to one, and for example, a plurality of vacuum exhaust pipes may be provided so as to surround the introduction part 2.

  Next, a procedure for molding a lens by the apparatus configured as described above will be described.

First, set the upper mold member 6, the lower mold member 7, and a body mold 8 in the chamber 1 as shown in FIG. 2, after closing the door 3, vacuum by opening the on-off valve V ₁ of the evacuation pipe I do. Regulating valve V ₂ at this time is in the open state, so as to reach a predetermined vacuum state in the shortest time. Then by closing the on-off valve V _1, it is filled with nitrogen gas into the chamber 1 by opening the closing valve U ₁ nitrogen inlet tube, nitrogen fills the adjustment valve U ₂ also opening amount at this time in a short period of time in the large To do. Then the chamber 1 is to stop the supply of nitrogen by closing the on-off valve U ₁ at the time of reaching the predetermined pressure P _1.

Note that to suppress oxygen penetration even reached the pressure in the chamber 1 is than the pressure P ₂ of at least the chamber of the external (atmospheric) may be set to be high, there is a very slight leak in the chamber 1 even Thus, it is possible to maintain an extremely low oxygen concentration immediately after the nitrogen supply is stopped.

Next, in a state where the upper mold member 6 is slid upward with respect to the body mold 8 and escaped from the lower mold member 7, the heater 10 is turned on to start heating the mold, and the upper mold member 6 and the lower mold member 7 when it is (slightly lower temperature than the temperature corresponding to the glass transition point Tg of e.g. glass to be molded) a predetermined temperature, the door from the supplying nitrogen into the chamber 1 by opening the closing valve U ₁ nitrogen inlet tube In this state, the flow rate of the regulating valve U ₂ is adjusted so that the pressure in the chamber 1 does not temporarily become lower than the pressure P ₂ outside the chamber 1 at least in this state.

  As a result, as shown in FIG. 1, nitrogen is introduced from the nitrogen gas introduction pipe on the surface opposite to the introduction part 2 of the chamber 1, flows around the mold in the chamber, and enters the introduction part 2 from the opening 12. A constant flow of nitrogen is generated that flows out through the chamber, and oxygen can be prevented from entering the chamber 1 from the outside.

  In addition, the area of the opening 12 is reduced to a level at which the glass can be taken in and out of the chamber, and in this case, the opening 12 is almost the same size as the opening for taking in and out the glass vacated in the body mold 8. At the same time, the length of the introduction part 2 is set to be relatively long compared to the area of the opening 12 (for example, a length equal to or larger than the square root of the area of the opening 12). Even if the flow rate is relatively small, the nitrogen in the introduction section 2 is less likely to flow and be disturbed in a laminar flow state, so that it becomes difficult to involve outside air and oxygen can be prevented from entering.

  In this state, the glass material 29 is placed on the molding surface of the lower die 7 from the outside of the chamber 1 through the opening of the body mold 8 by a supply means (not shown). In this case as well, the glass material 29 and the supply means (not shown) are used. Since it proceeds against the flow of nitrogen, oxygen attached to the glass material 29 and the supply means (not shown) is removed and discharged to the outside.

  When the glass material 29 is supplied and a supply means (not shown) is taken out of the chamber 1, the door 3 is immediately closed.

  At this time, since the introduction portion 2 is relatively long, the oxygen concentration around the mold is suppressed to a very low level. In some cases, the oxygen concentration in the introduction portion 2 is somewhat increased, and if left as it is, oxygen diffuses throughout the chamber 1.

So open the on-off valve V ₁ of the vacuum exhaust pipe after the door 3 is closed, and the mold together with the nitrogen to which oxygen is flowing in the vicinity inlet portion 2 by left open even off valve U ₁ nitrogen supply pipe Is sucked in the opposite direction, and oxygen can be discharged without increasing the oxygen concentration around the mold.

At this time, by adjusting the nitrogen and vacuum control valves U ₂ and V ₂ , the vacuum exhaust amount is made smaller than the supply amount of nitrogen, so that the pressure P ₁ inside the chamber ₁ is higher than the external pressure P ₂ . I try not to lower it.

Further, the supply amount of nitrogen and the evacuation amount at this time are arbitrarily determined, but when the supply of nitrogen is excessive and the pressure P ₁ inside the chamber 1 becomes a predetermined pressure or more, it is provided in the introduction unit 2. was Yes as the leak valve R ₁ in the exhaust pipe relieve pressure open, oxygen does not flow through the mold in a direction in the vicinity the introduction part 2 at this time, it is discharged to the outside.

Then, closing the on-off valve V ₁ of the vacuum exhaust pipe after a predetermined time has elapsed, the pressure P ₁ inside the chamber 1 is opened and closed valve U ₁ is closed at the time of reaching a predetermined pressure stops the supply of the nitrogen To do.

  Thus, the operation of supplying the glass material 29 into the chamber 1 is completed, but at this time, the oxygen concentration is kept at a high level throughout the entire chamber.

  On the other hand, when the glass material 29 is supplied, the temperature of the mold is further increased, and the glass material 29 is also heated at the same time. At this time, a heating member (not shown) is inserted through the opening of the body mold 8, The glass material 29 may be heated.

  When the upper mold member 6, the lower mold member 7 and the glass material 29 reach a predetermined pressing temperature, the driving source 14 on the upper mold member 6 side is immediately pushed out to perform the press molding of the glass material. Then, when the lower surface of the flange portion of the upper mold member 6 comes into contact with the upper surface of the body mold 8, the deformation operation of the glass material in the upper mold member 6 is completed.

  Thereafter, the process proceeds to a cooling step, where cooling is promoted by blowing nitrogen gas to the mold by means of a nitrogen introduction pipe (not shown), but when the mold is cooled to a desired temperature, the surface shape of the molded product 29 is not collapsed. Then, the drive source 15 on the lower mold member 7 side is pushed out, and pressure is applied from below the molded product 29 by the lower mold member 7. Then, cooling is continued in this state, and when the temperature reaches a predetermined temperature, the driving source 15 on the lower mold member 7 side is pulled to release the pressure from the lower mold member 7.

  After cooling, when the temperature reaches below a predetermined temperature, that is, a temperature at which the glass surface is not easily deformed even if the glass is peeled off or conveyed, the nitrogen gas to the mold The cooling by spraying is stopped, the driving source 14 on the upper mold member 6 side is pulled in, the upper mold member 6 is moved upward, and the mold is opened.

  The temperature of the glass transition point varies depending on the glass material, and in the current glass mold, there is a temperature range from below 300 ° C. to above 700 ° C. The mold opening temperature is appropriately determined for each, but the highest possible temperature is the molding. Since the cycle can be shortened, in this embodiment, the mold is opened with the glass transition point or less as a target.

When the mold opening is completed, the door 3 of the chamber 1 is opened. At this time, the pressure in the chamber 1 is lower than the pressure P ₂ outside the chamber 1 as in the supply of the glass material 29 into the chamber 1. In order to prevent this, the opening / closing valve U ₁ of the nitrogen introduction pipe is opened to supply nitrogen into the chamber 1.

  Then, a discharge means (not shown) is introduced into the chamber 1 from the door 3 through the introduction portion 2, and the molded product 29 on the lower mold member 7 is taken out from the opening of the barrel mold 8 and is moved out of the chamber 1. And discharged.

  Thereafter, a new glass material 29 is supplied into the chamber 1 and thereafter molding is repeated.

  Here, detailed molding conditions will be described by taking a lens used for a camera as an example.

  The glass is heavy crown glass (refractive index 1.58, Abbe number 59.4, transition point 506 ° C.), and a biconvex lens having an outer diameter of φ12 mm is formed.

  The mold material used was cemented carbide or ceramics as a base material, and the molding surface was provided with a carbon-based film such as diamond-like carbon or a noble metal-based film such as platinum.

  The chamber 1 has a rectangular shape with a main body diameter of 250 mm, a height of 250 mm, a width of the opening 12 of 30 mm, and a height of 20 mm (the opening of the body for taking in and out the glass has the same dimensions). There was a 40 mm long introduction part.

First, after evacuating the chamber 1 by the above-described process, nitrogen is introduced, and the gauge pressure is set to an internal pressure of 0.02 MPa (megapascal) and an oxygen concentration of 1 ppm or less. After that, heating of the mold is started by the heater 10, but since nitrogen is also heated at this time, the pressure in the chamber 1 is increased, but the state of about 0.02 MPa (megapascal) is caused by the action of the leak valve R _1. Kept.

When the temperature of the upper mold member 6 and the lower mold member 7 reaches 480 ° C. (equivalent to ^101.43 poise), the opening / closing valve U ₁ of the nitrogen introduction pipe is opened and 10 liters of nitrogen is supplied into the chamber 1 per minute. When the supply is started, the door 3 is opened, and the glass material 29 is supplied into the mold by a supply means (not shown). Thereafter, when the supply means (not shown) is taken out of the chamber 1, the door 3 is immediately closed.

Then, after several seconds the exhaust in the exhaust amount of the opening and closing valve V ₁ is opened every content of 5 liters of a vacuum exhaust pipe, closes the on-off valve V _1, shutoff valve U ₁ nitrogen inlet tube also closed supply nitrogen Is stopped. The pressure also in the chamber 1 at this time is increased, it is kept approximately 0.02 MPa (megapascals) also by the action of the leak valve R _1.

  The supply amount of nitrogen at this time is not constant, and may be changed according to the situation, for example, a large amount immediately after opening the door 3 and a decrease thereafter.

  Thus, the operation of supplying the glass material 29 into the chamber 1 is completed. The oxygen concentration in the chamber 1 was about 10 seconds from opening the door 3 to closing it. There was almost no change in concentration, and although an oxygen concentration increase of several ppm was observed in the introduction part, after the door 3 was closed and exhausted, the state returned to 1 ppm or less.

Thereafter, the mold and the glass material 29 are heated, and the temperature of the upper mold member 6 and the lower mold member 7 becomes 580 ° C. (equivalent to 10 ^9.0 poise), and the temperature of the glass material is also 580 ° C. (equivalent to 10 ^9.0 poise). Then, the drive source 14 on the upper mold member 6 side is operated for 40 sec with a force of 2900 N (Newton), and the pushing operation of the upper mold member 6 is completed. After that, the pressure of the upper mold member 6 in contact with the body mold 8 is maintained as it is.

Thereafter, cooling was started, and when the temperature reached 560 ° C. (equivalent to 10 ^9.8 poise), a force of 2000 N (Newton) was applied to the molded product 29 by the lower mold member 7, and the cooling was continued as it was, and 490 ° C. (10 ^13.5 The pressure of the lower mold member 7 was released at the point of time corresponding to Poise. Then, after further cooling to 480 ° C. (equivalent to ^101.43 poise), the cooling was finished, the upper mold member 6 was raised, and the mold was opened.

  Then, in the same manner as when the glass material 29 is supplied into the chamber 1, the supply of nitrogen into the chamber 1 is started and the door 3 is opened. First, the molded product 29 on the molding surface of the lower mold 7 is not shown. Then, a new glass material 29 was supplied into the chamber 1 and then repeatedly formed in the same manner.

  At this time, 1000 shots were molded, but the mold was not oxidized and the surface state of the molding surface was not deteriorated (while maintaining a few nanometers in RMS surface roughness), and a good molded product was obtained. I was able to.

(Second Embodiment)
Although the second embodiment will be described with reference to FIG. 3, the configuration of the molding apparatus is the same as that of the first embodiment, and thus the description thereof is omitted. Further, the process from heating the glass to pressing it to cooling it is the same, and only the process of putting the glass in and out of the chamber 1 will be described here.

First, although from where to retrieve the molded glass, nitrogen upper mold member 6 performs mold opening is moved upward to open the closing valve U ₁ nitrogen inlet tube into the chamber 1 when the cooling process is completed supplies, further opening the door 3 to open the closing valve V ₁ of the evacuation pipe, but the evacuation amount than the supply amount of nitrogen by adjusting the regulating valve U _2, V ₂ of nitrogen and vacuum this time By making it small, the pressure P ₁ inside the chamber 1 is prevented from becoming lower than the external pressure P ₂ .

In this state, the molded product 29 is taken out by a discharge means (not shown), and when a new glass material 29 is supplied into the chamber 1 by a supply means (not shown), the door 3 is closed and a predetermined time has elapsed. later, it closed off valve V ₁ of the evacuation pipe on-off valve U ₁ nitrogen inlet tube also closed, the supply of nitrogen was stopped to end the process of loading and unloading of the chamber 1 of the glass.

  That is, in this case, the point that the exhaust from the vacuum exhaust pipe is performed while the door 3 is opened is different from the first embodiment. As a result, the outside air near the opened door 3 is sucked into the exhaust pipe together with nitrogen from the chamber 1 before entering the chamber 1 due to the entrainment of flowing nitrogen or the like, and the oxygen concentration in the chamber 1 is reduced. The rise can be suppressed. Moreover, since the amount of vacuum exhaust is made smaller than the supply amount of nitrogen, the pressure in the chamber 1 does not decrease from the outside, and this also prevents the entry of outside air.

(Third embodiment)
Although the second embodiment will be described with reference to FIG. 4, the nitrogen introduction pipe is provided in the vicinity of the door 3 of the introduction section 2 and at a position facing the vacuum exhaust pipe, and when the molded glass is taken out, before opening the door 3, also opens the closing valve U ₁ nitrogen inlet tube of nitrogen is supplied to the chamber 1 performs suction further open the opening and closing valve V ₁ of the evacuation pipe, and out of the glass in this state Is done.

At this time, the pressure P ₁ inside the chamber 1 is lower than the external pressure P ₂ by adjusting the nitrogen and vacuum regulating valves U ₂ and V ₂ to make the vacuum exhaust amount smaller than the nitrogen supply amount. I try not to be.

  The operation of supplying and exhausting nitrogen is omitted because it is the same as that described in FIG. 3, but in this case, nitrogen is supplied and exhausted in the vicinity of the door 3, so that the action of blocking outside air by the flow of nitrogen works. In addition, by sucking in the vicinity of the door, the outside air trying to enter the chamber 1 due to the entrainment of nitrogen flowing out can be exhausted together with the nitrogen, and the vacuum exhaust amount is made smaller than the supply amount of nitrogen. Therefore, it is possible to prevent the pressure in the chamber 1 from being lowered compared to the outside, and as a result, it is possible to suppress an increase in the oxygen concentration in the chamber 1.

(Other embodiments)
Although the first to third embodiments have been described above, the following embodiments are also possible.

In each of the above embodiments, the glass is put in and out, and the supply of nitrogen is continued after the door 3 is closed. At the same time, the vacuum is exhausted. However, the present invention is not limited to this, and the vacuum exhaust is performed even when the door 3 is closed. Instead, only the supply of nitrogen may be continued for a predetermined time. When the pressure in this case the chamber 1 becomes equal to or higher than a predetermined pressure, since the leak valve R ₁ in the exhaust pipe provided in the inlet portion 2 are so as to release the pressure by opening and enters the inlet section 2 oxygen Is discharged with nitrogen. At this time, oxygen can be discharged in a short time by temporarily increasing the supply amount of nitrogen. Of course, if the oxygen that has entered the introduction section 2 is less than the allowable amount, the door 3 may be closed and the supply of nitrogen may be stopped.

  In addition, the shape of the introduction part 2 is cylindrical and the cross section is rectangular in the specific example, but considering the flow of nitrogen when the door is opened, the cross section is more preferably circular, but a glass supply jig, etc. Therefore, it is desirable to have a minimum cross-sectional area. Of course, since the flow of nitrogen is not determined only by the shape of the cross section, it is desirable to have a shape that reduces the protrusion shape and the depression, etc., without causing stagnation or entrainment of the flow as much as possible.

  Furthermore, the supply amount of nitrogen and the exhaust amount of suction are also set as appropriate depending on the size of the chamber and the size of the opening. However, the smaller the opening is, the more nitrogen is reduced compared to the size of the chamber. The supply amount can be reduced, which is advantageous. Therefore, it is desirable to provide a relatively small door dedicated to taking in and out of glass as in this embodiment, assuming that a relatively large door for taking out the mold is provided separately.

  Conversely, when the chamber is sufficiently large or when nitrogen can be sufficiently supplied, the door 2 may be installed directly on the opening 12 of the chamber 1 without the introduction portion 2.

  Moreover, in each embodiment, although the example of nitrogen is given as an inert gas, of course, it is not limited to this.

  Furthermore, the mold is opened and removed at 480 ° C, and as described above, the extraction temperature differs depending on the glass material, but the material constituting the mold is usually oxidized from around 200 ° C. Therefore, if the temperature is 250 ° C. or higher, the effect of the present case can be sufficiently obtained.

  In the first and second embodiments, when opening the door, nitrogen is supplied from the opposite side of the door in the chamber in order to keep the pressure in the chamber higher than the outside, but the outside air enters. If the shape of the chamber and the direction of supplying nitrogen are devised to make it difficult, this is not the case. Furthermore, as a method of keeping the pressure in the chamber high compared to the outside, in addition to supplying nitrogen, the pressure in the chamber is sufficiently raised in advance, and an introduction portion that is sufficiently small compared to the volume of the chamber is provided, A method in which loading and unloading is completed within a certain period of time, a partition or the like may be moved temporarily to reduce the volume in the chamber, or the atmospheric temperature in the chamber may be increased.

The longitudinal cross-sectional view of the shaping | molding apparatus which shows the state at the time of the chamber opening at the time of putting in / out glass in the 1st Embodiment of this invention. The longitudinal cross-sectional view of the shaping | molding apparatus which shows the state after the press in the 1st Embodiment of this invention The longitudinal cross-sectional view of the shaping | molding apparatus which shows the state at the time of the chamber opening at the time of putting in / out glass in the 2nd Embodiment of this invention. The longitudinal cross-sectional view of the shaping | molding apparatus which shows the state at the time of the chamber opening at the time of putting in / out glass in the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Chamber 2 ... Introduction part 3 ... Door 4 ... Upper shaft 5 ... Lower shaft 6 ... Upper mold member 7 ... Lower mold member 8 ... Body mold 10 ... Heater 12 ... Opening part 14, 15 ... Driving means 16, 17 ... Pressure Detection means 29 ... Molded product (glass material)
U ₁ , V ₁ ... open / close valve R ₁ ... leak valve U ₂ , V ₂ ... regulating valve P ₁ , P ₂ ... pressure 21 ... N ₂ gas supply source 22 ... vacuum exhaust source

Claims (10)

  An optical element obtained by pressing and cooling a glass material heated to a temperature equal to or higher than a softening point by a pair of upper and lower molds arranged in an inert gas atmosphere chamber that blocks the atmosphere from the outside. In the molding method, when certain portions of the chamber are opened and the optical element before press molding is carried into the chamber, and the glass material after cooling is carried out of the chamber, the inert gas in the chamber A method for molding an optical element, characterized in that the pressure is kept higher than the external pressure.   The method for molding an optical element according to claim 1, wherein when the chamber is partially opened, an inert gas is continuously supplied into the chamber.   3. The method for molding an optical element according to claim 1, wherein when opening a part of the chamber, the temperature of the pair of upper and lower molds is 250 ° C. or more.   When opening a part of the chamber, the suction amount of the inert gas sucked from the gas suction port provided in the vicinity of the opening portion is less than the supply amount of the inert gas supplied into the chamber. The method for molding an optical element according to claim 2, wherein:   In an apparatus for molding an optical element obtained by pressing a glass material heated to a temperature equal to or higher than the softening point between a pair of upper and lower molds, and cooling and removing the mold from the mold, the pair of upper and lower molds are positioned at a certain position. A chamber provided with an opening that can be opened and closed for taking in and out the molded optical element or glass material, a heating / cooling means for the mold, and a glass material. Press means for pressing, and when the optical element and the glass material after molding are opened and removed from the chamber by opening the opening, the pressure in the chamber is made higher than the external pressure. An optical element molding apparatus comprising: a supply means for supplying an inert gas.   6. The size of the opening is the minimum necessary size that allows the opening area to be equal to or less than the projected area of the entire mold with respect to the opening surface and allows the glass to be taken in and out. Optical element molding apparatus.   The optical element molding apparatus according to claim 5, wherein the opening includes a cylindrical introduction portion that is connected to the chamber body and protrudes outward.   The optical element molding apparatus according to claim 7, wherein the projecting portion of the introduction portion has a length equal to or greater than a square root of a cross-sectional area of the cylinder.   A suction means for sucking a gas equal to or less than a supply amount of an inert gas supplied into the chamber is provided in the vicinity of the opening, and the supply means for supplying the inert gas includes the opening in the chamber. The optical element molding apparatus according to claim 5, wherein is provided at a position on the opposite side.   The suction means for sucking the gas below the supply amount of the inert gas supplied into the chamber is in the vicinity of the opening, and the supply means for supplying the inert gas is the suction means at the opening. The optical element molding apparatus according to claim 5, wherein the optical element molding apparatus is provided at a position opposite to the optical element.

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