CN1237017C - Pressure forming equipment and method for optical element - Google Patents

Abstract

The present invention provides a kind of pressure molding equipment and molding method for optical elements. When the molding method is implemented by adjusting the molding atmosphere to vacuum only during the pressing process, the molding cycle is shortened, and the impact on the vacuum is greatly reduced. The effect of temperature control. The above-mentioned forming apparatus for forming hot soft glass material by pressure with a pair of upper and lower molds, cooling the glass material and taking out the molded product from the mold includes a first closed chamber that can replace the atmosphere therein; contained in the former and can be independently A second enclosure for replacing the atmosphere therein; a forming unit provided for the second enclosure; glass delivery for feeding glass material contained in the first enclosure to the forming unit and for feeding glass moldings into the first enclosure device.

Description

Pressure molding equipment for optical elements and molding method thereof

technical field

The present invention relates to a pressure molding apparatus for an optical element obtained by pressure molding a hot glass material and a molding method thereof.

Background technique

As a method of manufacturing a glass lens that does not require a polishing process, a method of heating a glass material and press-molding it with a pair of upper and lower molds has been used in the past. Since this method can efficiently produce products like aspheric lenses, it has been developed and applied to lenses with various shapes.

In this method, how to accurately replicate the molding surface of the mold onto the glass article is a focal problem in obtaining very precise optical elements. In order to achieve the above object, during the pressing process, there must not be any air on the molding surface of the mold corresponding to the optically functional surface of the optical element. For this reason, for example, when a convex lens is to be molded, the radius of curvature of the glass material is set to be smaller than the radius of curvature of the molding surface of the mold, so that no air will remain between the mold and the glass.

If a lens with a large curvature (small radius of curvature) or a complex shape is to be produced as in an aspheric lens, it is impossible to mold the desired lens only by changing the shape of the glass material. Even if the lens can be manufactured, it will increase the cost of the glass material. Therefore, in recent years, a method of eliminating molding air in order to form a vacuum state during the pressing work has been studied. According to this method, if the vacuum state is maintained also during the heating and cooling of the molding process, heat exchange (convection) with air does not occur. Then, the heating/cooling time may be extended, or errors may occur in temperature measurement values depending on the difference in contact state (with/without gap) between the mold and a temperature sensor such as a thermocouple. Furthermore, when handling glass materials, glass materials cannot be conveyed by vacuum clamping. Thus, the method of molding products in a constant vacuum state has many inconveniences and is thus unsatisfactory.

Therefore, a forming method in which a vacuum state is formed only during the pressing operation is advantageous. In this case, the number of steps of evacuation and inert gas filling in the molding cycle is increased. Therefore, the time for evacuation and inert gas filling must be shortened as much as possible in order to prevent the production cycle from being unduly extended. In order to shorten the molding cycle, it is best to remove the molded product from the mold at the highest possible temperature in the same way as in the past. Therefore, it is necessary to take out the molded product under an atmosphere of an inert gas to prevent oxidation.

Conventional molding equipment will now be reviewed. The invention described in Japanese Patent Laid-Open No. 3-177318 proposes an apparatus for molding under an inert gas atmosphere. In this device, a mold and a handle for loading and unloading glass material into and out of the mold are arranged in a forming cavity. A load lock cavity is provided behind the forming cavity. The glass material and molded product are sent to and brought from the outside through the load lock chamber, so that continuous molding can be performed without weakening the atmosphere in the molding chamber. As a result, the molded article can be taken out without being oxidized at high temperature, thereby greatly shortening the molding cycle.

When a molding method in which only a vacuum state is formed during pressing is performed by using the conventional molding apparatus described above, the following problems arise. More specifically, in this molding apparatus, since the mold, the handle for loading and unloading the molded product, and the glass material in and out of the mold, etc. are located in one molding cavity, the molding cavity becomes relatively large. Therefore, the evacuation time for removing air is prolonged, which correspondingly prolongs the molding cycle. Additionally, temperature control of the mold and glass material becomes unstable during the molding cycle.

Thus, the forming cavity must be as small as possible. If the above-mentioned handle is only arranged outside the molding cavity, then when the glass material is to be loaded and unloaded, the mold is exposed to the external environment (atmosphere). In order to prevent oxidation of the mold, the mold and the glass molding must be taken out after they have been sufficiently cooled, thus greatly extending the molding cycle.

Contents of the invention

The present invention has been conceived in view of the above circumstances. The object of the present invention is to provide a pressure molding apparatus for an optical element and a molding method thereof, wherein when performing a molding method in which the molding atmosphere is set to vacuum only during pressing, the molding cycle is shortened, thereby greatly reducing the Adverse effects on temperature control in a vacuum atmosphere.

In order to solve the above-mentioned problems and achieve the above-mentioned object, a pressure molding apparatus for an optical element according to the present invention is characterized in that it has the following structure.

More specifically, a pressure molding apparatus for deforming a hot and soft glass material under pressure by using a pair of upper and lower molds, cooling the glass material and taking out an optical element of a glass molded article from said molds includes a a first closed chamber for replacing the atmosphere therein, a second closed chamber housed in said first closed chamber and capable of replacing the atmosphere therein independently of the first closed chamber, provided for the second closed chamber and for Forming device for molding hot glass material by pressurization and for sending glass material contained in a first closed cavity to said forming device in a second closed cavity and glass formed by said forming device The moldings are fed into the glass conveyor of the first closed chamber.

A pressure molding method of an optical element according to the present invention is characterized in that it has the following configuration.

More specifically, a pressure molding method of an optical element by pressure molding a hot soft glass material using a pair of upper and lower molds, cooling the glass material, and taking out a glass molding from said mold, characterized in that the The method employs a molding apparatus comprising a first closed chamber in which the atmosphere can be replaced, a closed chamber housed in said first closed chamber and capable of being replaced independently of said first closed chamber. A second closed chamber with atmosphere and a device for replacing the atmosphere in the first closed chamber and the second closed chamber, the method comprises the following steps: loading glass material into the first closed chamber; Before or after the glass material, replacing the internal atmosphere of the first closed chamber with an inert state; after the above replacement step, introducing the glass material into the forming device in the second closed chamber in an inert state; After introducing the glass material into the second closed cavity, heating the glass material in the second closed cavity; evacuating the inside of the second closed cavity; pressurizing the glass material through the molding device; introducing an inert gas into the second closed cavity after pressure molding the glass material; and cooling the molded article in the second closed cavity; and taking out the molded article through the first closed cavity after the cooling step.

Thus, when a cavity having the minimum required volume is newly provided around the mold, only the atmosphere around the mold can be set to a vacuum state before pressing, and the mold can be loaded and unloaded with glass material under an inert gas atmosphere.

According to an embodiment of the present invention, in a pressure molding apparatus for an optical element, a glass load lock chamber capable of replacing the atmosphere therein independently of the first closed chamber is formed at a position near the first closed chamber, the The load lock chamber can be open and hermetically closed. As a result, only the atmosphere of the load lock chamber, which has a relatively small volume, is replaced without changing the atmosphere of the first closed chamber, whose volume is relatively increased by the glass delivery device, etc., so that glass can always be supplied to the first closed chamber and Remove the glass from it.

Description of drawings

For those skilled in the art, other features and advantages besides the above-mentioned features and advantages can be clearly understood from the following description of a preferred embodiment of the present invention. In the specification, reference is made to the accompanying drawings which form a part hereof, and which illustrate an example of the invention. However, such examples do not exhaustively exemplify the various embodiments of the invention, therefore, in order to define the scope of the invention, reference is also made to the content of the claims following the description.

1 is a longitudinal sectional view of a pressure molding apparatus for an optical element in a pressing operation state according to a first embodiment of the present invention;

Figure 2 is a longitudinal sectional view of a pressure molding apparatus for an optical element in a glass-filled state; and

Fig. 3 is a longitudinal sectional view of a pressure molding apparatus for an optical element according to a second embodiment of the present invention.

Detailed ways

A preferred embodiment of the present invention will be specifically described below with reference to FIGS. 1-3 . 1 and 2 are longitudinal sectional views of a pressure molding apparatus for an optical element according to a first embodiment of the present invention, wherein FIG. 1 shows a state of pressure molding, and FIG. 2 shows a state of glass filling. Fig. 3 is a longitudinal sectional view of a pressure molding apparatus for an optical element according to a second embodiment of the present invention.

(first embodiment)

Referring to Figures 1 and 2, the outer cavity 1 has a closed structure for isolating its internal atmosphere from the outside air. A gate valve 13 is fixed on the inlet and outlet of the outer cavity 1 and can be opened and closed by a driving device 21 . A load lock chamber 3 is formed in such a way that it can be brought into close contact with the gate valve 13 and released from said gate valve by a different drive 17 . A carriage 12 which is movable vertically by a different drive 20 is arranged in the load lock chamber 3 .

A barrel mold 8 is fixed in the outer cavity 1 and it has a through hole perpendicular to its central axis. A patrix 6 is vertically slidably fitted in the upper through hole.

The lower surface of the upper mold 6 has a molding surface that presses the glass material 9 to transfer a desired optically functional surface onto the surface of the glass material. Above the upper mold 6 and outside the outer chamber 1 , a driving device 14 is arranged to generate the pressure to be applied to the glass material 9 , through which an upper rod 4 for transmitting the pressure passes. A heater 10 for heating the upper mold 6 is provided in the upper portion of the cylindrical mold 8 .

A lower die 7 is vertically slidably fitted in the lower through hole of the cylindrical die 8 .

The upper surface of the lower mold 7 has a molding surface for transferring a desired optically functional surface onto the lower surface of the glass material 9 . Below the lower mold 7 and outside the outer chamber 1 , a driving device 15 is arranged, and a lower rod 5 connected to the driving device 15 passes through the outer chamber 1 . Another heater 10 for heating the lower mold 7 is provided in the lower part of the barrel mold 8 .

In the outer cavity 1 , an inner cavity 2 is provided around the cylindrical mold 8 so as to cover the entire cylindrical mold so as to isolate the atmosphere therein from the atmosphere of the outer cavity 1 . The inner chamber 2 can be moved independently of the upper rod 4 by a drive 16 mounted outside the outer chamber 1 . When the lower opening of the inner cavity 2 is in close contact with the bottom of the outer cavity 1, a closed space can be formed.

A handle 11 is provided in the outer chamber 1 in order to feed the glass material 9 and the molding 29 into the inner chamber 2 or out of it. The handle 11 can be rotated by a drive 18 mounted outside the outer chamber 1 and moved vertically by a different drive 19 so that the glass material 9 and the molding 29 can be transferred between the lower mold 7 and the support 12 .

The outer chamber 1, the inner chamber 2 and the load lock chamber 3 are all connected to a nitrogen gas input pipe and a vacuum exhaust pipe respectively. These nitrogen inlet pipes and vacuum exhaust pipes are equipped with opening and closing valves N1-N3 and V1-V3 and leakage valves R1-R3.

The opening and closing valves N0 and V0 are equipped for the nitrogen supply source and the vacuum exhaust source respectively. For example, when the nitrogen valve N0 of the nitrogen supply source is closed and the nitrogen valves N1 and N3 of the outer chamber 1 and the load lock chamber 3 are opened, the outer chamber 1 and the load lock chamber 3 can communicate with each other, so that the outer chamber and the load lock chamber can be connected to each other. Adjust to an atmosphere with the same pressure.

A process of molding a lens using the apparatus having the above structure will be described below. First, as shown in FIG. 1 , the gate valve 13 at the inlet and outlet of the outer chamber 1 is closed to move the inner chamber 2 to an upper position and open the inner chamber. Also open the nitrogen valve N0 of the nitrogen supply source and the vacuum valve V0 of the vacuum exhaust source.

In this state, the vacuum valve V1 of the outer chamber 1 is opened to vacuum the outer chamber. When the inside of the outer chamber 1 reaches a predetermined vacuum degree, the vacuum valve V1 is closed. Subsequently, the nitrogen valve N1 of the outer chamber 1 is opened to supply nitrogen gas thereto. When the inside of the outer chamber 1 reaches a predetermined pressure, the nitrogen valve N1 is closed, thus completing the replacement of the atmosphere in the outer chamber 1 .

The glass material 9 located outside the outer cavity 1 is fed into the mould. First, as shown in FIG. 1, the glass material 9 is delivered to the support 12 waiting outside the outer chamber 1 through an outer handle (not shown). The load lock chamber 3 moves upward to come into close contact with the closed gate valve 13, thereby forming a closed space. Open the vacuum valve V3 of the load lock chamber 3 and evacuate it. When the inside of the load lock chamber 3 reaches a predetermined vacuum degree, the vacuum valve V3 is closed. Subsequently, the nitrogen valve N3 of the load lock chamber 3 is opened to deliver nitrogen gas to the load lock chamber. When the inside of the load lock chamber 3 reaches a predetermined pressure, the nitrogen valve N3 is closed, thereby completing the atmosphere replacement in the load lock chamber 3 . Next, the gate valve 13 is opened and the holder 12 is moved up as shown in FIG. 2 , so that the glass material 9 stops in the outer chamber 1 .

The upper die 6 is slid upward relative to the barrel die 8 in advance, whereby it is separated from the lower die 7 . In this state, the handle 11 supports the glass material 9 and delivers the glass material to the molding surface of the lower mold 7 through the opening of the cylindrical mold 8 . The process works like this. First, the handle 11 is moved downwards so that its gripping portion for the glass material 9 approaches the glass material 9 resting on the holder 12 . After clamping the glass material 9 , for example by vacuum clamping, the handle 11 is moved up and its distal end passed through the opening of the barrel mold 8 by turning. When the glass material 9 came above the lower mold 7, the handle 11 was stopped and moved down. When the glass material 9 approaches the lower mold 7 , the glass material leaves the handle 11 and is placed on the lower mold 7 .

In this process, the upper mold 6 and the lower mold 7 are adjusted to temperatures corresponding to predetermined molding conditions by the heater 10 .

When the glass material 9 is fed to the molding surface of the lower mold 7, a heater (not shown) is inserted into the barrel mold 8 through the opening of the barrel mold 8 to heat the glass material 9. Alternatively, the glass material 9 can be heated outside the mold beforehand and the hot glass material can be fed into the mold. When the upper mold 6 and the lower mold 7 and the glass material 9 reach a predetermined temperature required before the pressing operation, the heater (not shown) is withdrawn to the outside of the barrel mold 8 . The inner cavity 2 immediately moves down so as to closely contact the bottom surface of the outer cavity 1, thereby forming a closed space. Next, open the vacuum valve V2 of the inner chamber 2 to evacuate the inner chamber into a vacuum. When the atmosphere around the mold reaches a predetermined degree of vacuum and the upper and lower molds 6 and 7 reach a predetermined pressurization temperature, the driving device 14 of the upper mold 6 is activated to form the glass material 9 by pressurization. When the lower surface of the flange of the upper mold 6 abuts on the upper surface of the barrel mold 8, the molding operation of the glass material 9 ends.

Subsequently, a cooling process is performed. At this time, the vacuum valve V2 of the inner chamber 2 is closed, and the nitrogen valve N2 of the inner chamber 2 is opened so as to deliver nitrogen gas to the inner chamber. When the inside of the inner chamber 2 reaches a predetermined pressure, the nitrogen valve N2 is closed. The leak valve R2 of the inner chamber 2 is opened in order to set the interior of the inner chamber 2 to the same pressure as in the outer chamber 1 . Subsequently, the leakage valve R2 is closed. Alternatively, after closing the vacuum valve V2 of the inner chamber 2, immediately open the leakage valve R2 to introduce nitrogen from the outer chamber 1, thereby adjusting the interior of the inner chamber 2 to the same nitrogen pressure as the outer chamber 1.

The inner cavity 2 is moved to an upper position and opened, thereby releasing the heat accumulated in the inner cavity to improve cooling efficiency. Nitrogen or similar gas is sprayed onto the mold through a nitrogen inlet tube (not shown) to facilitate cooling. When the mold is cooled to a desired temperature, the molded product 29 is pressed from below by the lower mold 7 so that the surface shape of the molded product 29 will not be deformed. In this state, continue to cool. When the mold reaches a predetermined temperature, the pressure applied by the lower mold 7 is released.

Subsequently, cooling is continued. When the mold reaches a predetermined temperature, the upper mold 6 is moved up, and the molded product 29 on the lower mold 7 is taken out through the opening of the cylindrical mold 8 through the handle 11 according to the reverse procedure of the operation when the glass material is injected into the mould. onto bracket 12. The holder 12 has two positions, namely a position for placing the glass material 9 and a position for placing the molding 29 . When the handle 11 sends the glass material 9 into the mold for molding, the bracket 12 receives a new piece of glass material 9 from outside the outer cavity 1 and returns it to the outer cavity 1 . Thus, the handle 11 pulls out the molding 29 and feeds new glass material 9 into the mould. Next, the molding process starts again.

The moldings 29 are discharged outside the outer chamber 1 . This is done in the following way. First, the bracket 12 moves down to enter the load lock chamber 3 , and then the gate valve 13 is closed to seal the outer chamber 1 . Open the leak valve R3 of the load lock chamber 3. When the nitrogen pressure in the load lock chamber 3 is reduced to atmospheric pressure, the leak valve R3 is closed. The load lock chamber 3 is moved down and its interior is communicated with the atmosphere.

In this state, the molding 29 on the holder 12 is withdrawn with an outer handle (not shown). The new glass material 9 is placed on the support 12 and sent into the outer chamber 1 through the load lock chamber 3 again, and then the handle is in the state of waiting for the next molding to start. Press forming is repeated in the above-mentioned manner.

The molding conditions will be specifically described below taking a lens in a camera as an example. In this case, disc-shaped crown glass (refractive index: 1.58, Abbe number: 59.4, transition point: 506°C) with a diameter of 10 mm and a thickness of 3.5 mm was used as the glass material 9 so that a diameter of A biconvex lens with a diameter of 12 mm and a central thickness of 2.5 mm, such that it has a lower convex surface with a radius of curvature of 40 mm and an upper convex spherical surface (with a radius of curvature of about 29 mm).

First, glass material 9 is injected onto the molding surface of lower mold 7 . When the temperature of the upper mold 6 and the lower mold 7 reaches 570°C (corresponding to ^109.5 poise) and the temperature of the glass material 9 also reaches 570°C (corresponding to ^109.5 poise), the inner cavity 2 is closed and vacuumized, thereby The degree of vacuum in the inner chamber 2 becomes 2.7 Pa or less. Continue heating. When the temperature of the upper mold 6 and the lower mold 7 reached 580° C. (corresponding to 10 ^9.0 Poise), the driving means 14 of the upper mold 6 was actuated with a force of 2900 Newtons for 40 seconds. Next, the pushing operation of the upper mold 6 is ended. Even after this, the pressure of the upper mold 6 against the barrel mold 8 is maintained. Then, cooling is started and nitrogen gas is immediately introduced into the inner chamber 2 to adjust the pressure in the inner chamber 2 to a pressure equal to the pressure in the outer chamber 1 . Subsequently, the lumen 2 is moved up and opened.

When the temperature reached 560° C. (corresponding to 10 ^9.8 poise), a force of 2000 N was applied to the molded article 29 with the lower mold 7 and cooling was continued. When the temperature reached 490° C. (corresponding to 10 ^13.5 poise), the pressure on the lower mold 7 was released. Cooling was continued until 470°C was reached (corresponding to 10 ^15.2 poise). Next, the upper mold 6 is moved up to open the mold, and the molded product 29 is ejected.

A lens is molded through the series of operations described above. Even when a disk-shaped lens material is used, no air is left and a molded product with high surface accuracy can be obtained.

The time required to evacuate the inner cavity 2 is 20 seconds or less, and the molding cycle required for one charge can also be adjusted to 5 minutes or less. Since the outer chamber 1 has a large volume, it takes 5 minutes or more to be evacuated.

(second embodiment)

Fig. 3 is a longitudinal sectional view of a pressure molding apparatus for an optical element according to a second embodiment of the present invention. This molding apparatus is basically the same as that of the first embodiment, and it differs from the apparatus of the first embodiment in the following respects. First, the molding equipment does not have a load lock cavity. A bracket 42 is fixed in the outer cavity 31 . On the support 42 side, an inlet and outlet are formed on the side of the outer chamber 31 to load and unload the outer chamber 31 with glass materials. The outer cavity 31 is isolated from the outside atmosphere through a gate valve 43 .

In addition to the heater 10 built in the barrel mold 8, a heater 40 for heating the mold and glass is formed on the inner side of the cavity 32. As shown in FIG. A water cooling jacket or jet cooling mechanism 22 is formed on the outer side of the inner cavity 32 . The lumen 32 can be moved vertically in the same manner as in the first embodiment. Other than that, the second embodiment is the same as the first embodiment, and thus a detailed description thereof is omitted.

The process of molding a lens with the apparatus having the above structure will be described below. First, as shown in FIG. 3 , the gate valve 43 at the inlet and outlet of the outer chamber 31 is closed to move the inner chamber 32 to an upper position and open the inner chamber. Also open the nitrogen valve N0 of the nitrogen supply source and the vacuum valve V0 of the vacuum exhaust source.

In this state, the vacuum valve V1 of the outer chamber 31 is opened to evacuate the outer chamber. When the inside of the outer chamber 31 reaches a predetermined vacuum degree, the vacuum valve V1 is closed. Subsequently, the nitrogen valve N1 of the outer chamber 31 is opened to supply nitrogen thereto. When the inside of the outer chamber 1 reaches a predetermined pressure, the nitrogen valve N1 is closed, thus completing the replacement of the atmosphere in the outer chamber 1 .

The inner cavity 32 is moved downward so as to cover the mold, so that it forms a closed space together with the bottom surface of the outer cavity 31 . The mold is heated by the heater 10 to a predetermined temperature required to inject the glass material and maintained at the temperature. The glass material outside the outer cavity 31 is fed into the mould. When the inner chamber 32 is at a lower position, the leakage valve R1 of the outer chamber 31 is opened to reduce the nitrogen pressure in the outer chamber 31 to atmospheric pressure. Open gate valve 43. The glass material is brought directly from the outside of the outer chamber 31 to the holder 42 in the outer chamber 31 by an outer handle (not shown) and placed on the holder 42 .

Subsequently, the replacement of the atmosphere in the outer chamber 31 is carried out again. After the atmosphere in the outer chamber 31 returns to the nitrogen atmosphere, move up and open the inner chamber 32 . The glass material on the support 42 is delivered to the molding surface of the lower mold 37 by the handle 11 in the same manner as in the first embodiment. In this operation, the upper mold 36 and the lower mold 37 are adjusted to temperatures equal to predetermined molding conditions by the heater 10 as described above.

The cavity 32 is moved down and closed again, while the heaters 10, 40 heat the upper and lower molds 36, 37 and the glass material. When the upper mold 36 and the lower mold 37 and the glass material reach the desired predetermined temperature before the pressing operation, the vacuum valve V2 of the inner cavity 2 is opened at once to vacuum the inner cavity. Subsequently, when the atmosphere around the mold reaches a predetermined vacuum degree and the upper mold 36 and the lower mold 37 reach a predetermined pressurization temperature, the driving device 14 of the upper mold 36 is activated to shape the glass material by pressurization.

Thereafter, a cooling process is performed. At this time, close the vacuum valve V2 of the inner chamber 32 and open the nitrogen valve N2 of the inner chamber 32 to deliver nitrogen gas. When the inside of the inner chamber 32 reaches a predetermined pressure, the nitrogen valve N2 is closed. In the second embodiment, cooling continues while the inner chamber 32 is in the lower position and closed. In this state, nitrogen gas or the like is sprayed onto the mold through a nitrogen gas inlet pipe (not shown) to promote cooling. The heater 40 in the interior 32 is switched off and the interior 32 itself is also cooled by the cooling mechanism 22 . Thus, cooling is promoted despite the cavity 32 remaining closed.

When the mold is cooled to a desired temperature, pressure is applied to the molded product 39 with the lower mold 37, whereby the surface shape of the molded product 39 will not be deformed. When the mold reaches a predetermined temperature, the pressure applied by the lower mold 37 is released.

Subsequently, cooling is continued. When the mold reaches a predetermined temperature, the leak valve R2 of the inner cavity 32 is opened to adjust the inside of the inner cavity 32 to have the same nitrogen pressure as that of the outer cavity 31 . Leakage valve R2 is closed and cavity 32 is moved to the upper position and then opened. In addition, the upper mold 36 is moved upward, and the molded product 39 on the lower mold 37 is pulled toward the holder 42 through the opening of the barrel mold 8 using the handle 11 .

The holder 42 has two positions, one for the glass material and one for the molding 39 . While the handle 11 feeds the glass material into the mold and performs the molding operation, the support 42 receives a new piece of glass material from outside the outer cavity 31 and waits aside. The handle 11 then pulls out the molding 39 and feeds new glass material into the mould. Next, the cavity 32 is closed and the molding process restarts.

The moldings 29 are discharged outside the outer chamber 1 . This is done in the following way. After the inner chamber 32 is closed, the leakage valve R1 of the outer chamber 31 is opened. Reduce the nitrogen pressure in the outer chamber 31 to atmospheric pressure, and close the leak valve R1. After opening the gate valve 43, the molded product 39 is withdrawn by an external handle (not shown). Place new glass material on support 42. The gate valve 43 is closed and the replacement of the atmosphere in the outer chamber 31 takes place again. Put the handle in the state of waiting for the start of the next molding. The press forming operation was repeatedly performed in the above-mentioned manner.

Hereinafter, molding conditions will be described in detail in the same manner as in the first embodiment, taking a lens used for a camera as an example.

Shaped similar to the final product, made of phosphate glass (refractive index: 1.56, Abbe number: 60.8, transition point: 345°C) and having two surfaces polished to have the same radius of curvature as the final shape The blank was used as a glass material to form a diffractive optical element in the shape of a biconvex lens with a diameter of 34 mm and a central thickness of 5.4 mm, so that it has a lower convex surface with a radius of curvature of 62 mm and a radius of curvature of 96 mm. mm, and as a result it has a microstructure consisting of a large number of concentric circular grooves 10 μm deep with a pitch of 100 μm-1 mm.

First, a glass material is injected onto the molding surface of the lower mold 37 . The lumen 32 is closed and heated. When the temperature of the upper mold 36 and the lower mold 37 reaches 390° C. (corresponding to 10 ^9.0 poise of the glass viscosity) and the temperature of the glass material also reaches 390° C. (corresponding to 10 ^9.0 poise of the glass viscosity), start vacuuming in this way operation so that the degree of vacuum in the inner cavity 32 becomes 2.7 Pa or less. Continue heating. When the temperature of the upper mold 36 and the lower mold 37 reached 395° C. (corresponding to 10 ^8.7 poise of glass viscosity), the driving device 14 of the upper mold 36 was actuated with a force of 5900 Newtons for 60 seconds. Next, the pushing operation of the upper die 36 is ended. Even after this, the pressure of the upper mold 36 against the barrel mold 8 is maintained.

Subsequently, cooling is started and nitrogen gas is immediately injected into the inner cavity 32 to continue cooling in the inner cavity 32 . When the temperature reached 380° C. (corresponding to 10 ^9.7 Poise of glass viscosity), a force of 4900 Newtons was applied to the molding 39 from the lower mold 37 and cooling was continued. When the temperature reached 325° C. (corresponding to 10 ^14.5 poise of glass viscosity), the pressure on the lower mold 37 was released.

Cooling is continued until 320° C. (corresponding to 10 ^15.3 Poise of glass viscosity) is reached, and the pressure in inner chamber 32 is adjusted to be equal to the nitrogen pressure in outer chamber 31 . Next, the lumen 32 is moved upward and opened. The upper mold 36 is further moved up and the mold is opened, whereby the molded product 39 is taken out.

The diffractive optical element is molded using the series of operations described above. The grooved microstructure is precisely transferred without leaving any gas, whereby molded articles with excellent surface transfer properties can be obtained. The time required to evacuate the inner cavity 32 is 20 seconds or less, and the molding cycle required for one charge is also adjusted to 8 minutes or less. Since the outer chamber 31 has a large volume, it takes 5 minutes or more to be evacuated.

Since the second embodiment has no load lock chamber, the outer chamber can be loaded and unloaded with glass material only when the inner chamber is closed. In addition, since the atmosphere replacement of the outer chamber is performed at each delivery, the consumption of nitrogen gas increases. In addition, the overall equipment is simplified. Either device (first embodiment or second embodiment) can be selected according to the molding form of the whole system.

Since the device has a heater and a cooling mechanism inside and outside the inner cavity, the heating efficiency can be improved without greatly reducing the cooling efficiency. Since the cavity is not affected by cooling and heating, the atmosphere around the mold can be isolated from the outside world, although the cooling efficiency is slightly lower than when the cavity is kept open. Therefore, the temperature distribution of the mold and the glass becomes smaller, and more precise moldings can be obtained. This method can also be chosen according to the required precision and cost of the glass moldings.

(other embodiments)

The above-mentioned embodiments have been described by citing examples of molding ordinary lenses and diffractive optical elements. However, the present invention is not limited thereto, and the present invention can be applied to various products such as lenses having free-form surfaces or rectangular lenses for which the shape of the glass material is difficult to adjust and thus may leave gas. In the above embodiments, an example in which one product is formed from one blank has been described. However, the invention can of course also be used in the case of forming a number of products from one blank or from many blanks.

In a first embodiment of the invention, the mold is heated by heaters inside the barrel mold. How to heat or cool the mold should not be particularly limited. As in the second embodiment, a heater or cooling mechanism provided in the inner cavity may be employed. As for the timing of the opening and closing of the inner cavity, it is sufficient as long as the inner cavity is closed and evacuated at least during the pressing operation. The lumen can be kept closed from heating to cooling. The technical combination of these alternatives can be determined in advance according to the precision and cost of the required product (molding cycle, equipment cost).

Similarly, in the second embodiment of the present invention, a heater may be provided inside the barrel mold to heat the mold. In the description of the second embodiment, one glass blank is loaded and unloaded for the outer chamber for each feeding. Alternatively, the size of the support can be enlarged so that the outer cavity can be loaded and unloaded with a number of glass blanks equal to several feeds at one time. Therefore, although the movement of the handle becomes somewhat complicated, it is not necessary to replace the atmosphere inside the outer chamber every time, thereby reducing the consumption of nitrogen gas.

As described above, according to the above-mentioned embodiments, in the pressure molding apparatus and the molding method thereof that adjust the vacuum atmosphere before the pressing operation at least once and then start the pressing operation, a minimum of the surrounding mold is provided in the first closed cavity. A second closed chamber of required volume. Therefore, many effects can be obtained. For example, the time required for evacuation before the pressing operation can be greatly shortened, and the amount of inert gas to be added later can be reduced.

Since the handle is arranged outside the second closed cavity and inside the first closed cavity to load and unload the glass material for the mould, the glass can be loaded and unloaded under an inert gas atmosphere. Therefore, when the mold is heated to a high temperature, glass can be attached and detached without oxidizing the mold. As a result, the molding cycle can be greatly shortened.

Due to the provision of the load lock chamber, glass material can be transported between the first closed chamber and its environment, regardless of whether the second closed chamber is open or closed. Therefore, the timing of opening or closing the second closed cavity can be freely set according to molding conditions. In addition, the volume of the load lock chamber is much smaller than that of the first closed chamber. Thus, the amount of inert gas required when transporting the glass material between the first closed chamber and its surroundings can be substantially reduced.

When the molding operation is performed with the above equipment under inert gas atmosphere during heating and cooling and under vacuum atmosphere during pressing operation, good transfer performance can be obtained with short molding cycle without causing residual gas problems moldings, regardless of the shape of the product or the shape of the glass material.

The present invention is not limited to the above-described embodiments, and various changes and modifications can be conceived within the spirit and scope of the present invention. Therefore, to inform the public of the scope of protection of the present invention, the following claims are drawn up.

Claims (3)

1. A pressure molding apparatus for an optical element that press-forms a hot soft glass material by using a pair of upper and lower molds, cools the glass material and takes out a glass molding from said mold, characterized in that it comprises The following components: a first closed chamber in which the atmosphere can be replaced; a second enclosed chamber housed within said first enclosed chamber and capable of replacing the atmosphere therein independently of said first enclosed chamber; forming means provided for the second closed cavity and for forming hot glass material by pressurization; and for sending the glass material contained in the first closed chamber to the molding device in the second closed chamber and sending the glass moldings molded by the molding device into the first closed chamber. Glass delivery device with closed cavity. 2. The apparatus according to claim 1, wherein a glass load-lock cavity capable of replacing the atmosphere therein independently of the first closed cavity is formed in the vicinity of the first closed cavity, the load-locked cavity The cavity can be opened and closed gas-tight. 3. A pressure molding method of an optical element by pressure molding a hot soft glass material by using a pair of upper and lower molds, cooling the glass material and taking out the glass molded product from said mold, characterized in that the method adopts Such a molding device, that is, the molding device includes a first closed chamber in which the atmosphere can be replaced; A second closed chamber and a device for replacing the atmosphere in the first closed chamber and the second closed chamber, the method comprising the following steps: loading glass material into the first closed cavity; replacing the internal atmosphere of said first closed chamber with an inert state before or after loading glass material; introducing glass material in an inert state into said forming device in said second closed chamber after the above replacement step; heating the glass material within the second enclosed chamber after introducing the glass material into the second enclosed chamber; evacuating the interior of the second closed cavity into a vacuum; pressure-molding the glass material by the molding device; introducing an inert gas into said second closed cavity after pressure molding the glass material; and cooling the molded article within said second closed cavity; and After the cooling step, the moldings are removed through said first closed cavity.

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