JP2009143749A - Method for producing glass gob, method for producing glass molded body, glass gob production device, and glass molded body production device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide production methods where the generation of air pockets can be securely prevented without using a lower die having large ruggedness at the surface, and a glass gob and a glass molded body having reduced surface roughness can be efficiently produced. <P>SOLUTION: When molten glass drops are dropped to a lower die, in such a manner that the collision between the lower die and the molten glass drops is performed in a reduced pressure atmosphere where pressure is made lower than the atmospheric pressure, the region of the circumference of the lower die is depressurized. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a glass gob manufacturing method, a glass molded body manufacturing method, a glass gob manufacturing apparatus, and a glass molded body manufacturing apparatus that are manufactured by dropping molten glass droplets.

  In recent years, glass optical elements are widely used as lenses for digital cameras, optical pickup lenses such as DVDs, camera lenses for mobile phones, coupling lenses for optical communication, and the like. As such a glass optical element, a glass molded body produced by press molding a glass material with a molding die has been used frequently.

  As one of the methods for producing such a glass molded body, a glass preform having a predetermined mass and shape is prepared in advance, and the glass preform is heated together with a molding die to a temperature at which the glass can be deformed and subjected to pressure molding. (Hereinafter also referred to as “reheat press method”) is known.

  Conventionally, glass preforms used in the reheat press method have often been manufactured by machining such as grinding and polishing, but there is a problem that the production of glass preforms by machining requires a lot of labor and time. It was. For this reason, studies are being made on a method for producing a glass preform without machining by dropping a molten glass droplet into a lower mold and cooling and solidifying the dropped molten glass droplet.

  On the other hand, as another method for producing a glass molded body, molten glass droplets are dropped on a lower mold heated to a predetermined temperature, and the dropped molten glass droplets are pressure-molded by an upper mold facing the lower mold and the lower mold. A method for obtaining a glass molded body (hereinafter also referred to as “droplet forming method”) has been proposed. This method is attracting attention because it is possible to produce a glass molded body directly from molten glass droplets without the need to repeat heating and cooling of a molding die or the like, and the time required for one molding can be extremely shortened. .

  However, when a molten glass droplet is dropped on the lower mold for the production of a glass preform or glass molded body, a recess (air pocket) remains on the lower surface of the produced glass preform or glass molded body. There was a problem. This problem will be described with reference to FIG.

  FIG. 11 is a diagram schematically showing a state of the molten glass droplet 50 dropped on the lower mold 11 by a conventional method. FIG. 11A shows a state at the moment when the molten glass droplet 50 collides with the lower mold 11, and FIG. 11B shows a state where the molten glass droplet 50 is deformed round by surface tension thereafter.

  As shown in FIG. 11A, the molten glass droplet 50 at the moment of collision with the lower mold 11 is stretched flat by the impact of the collision. At this time, in the molten glass droplet 50, a minute recess 51 having a diameter of about several tens of μm to several hundreds of μm is formed near the center of the lower surface (contact surface with the lower mold 11). Although the mechanism by which the concave portion 51 is generated is not necessarily clear, according to analysis using simulation or the like, when the molten glass droplet 50 collides with the lower mold 11, the glass of the portion that first collides with the lower mold 11 is rebounded. It may be caused by rebounding upward.

  Thereafter, the molten glass droplet 50 is deformed into a round shape by the action of the surface tension, as shown in FIG. At this time, since the lower surface of the molten glass droplet 50 and the surface of the lower mold 11 are in close contact with each other, there is no escape route for the air accumulated in the recess 51, so that the recess 51 remains as an air reservoir without disappearing.

  In order to address this problem, the surface of the lower mold is roughened (Rmax is 0.05 μm to 0.2 μm), and an air pool remains by securing a flow path of air that has entered the concave portion of the molten glass droplet. A method for preventing this has been proposed (see, for example, Patent Document 1).

In addition, by forming a coating layer including a dissolved layer on the roughened base surface (Ra is 0.005 μm to 0.05 μm), a lower mold that prevents air accumulation and facilitates regeneration is provided. It has been proposed (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 3-137031 JP 2005-272187 A

  As in the methods described in Patent Documents 1 and 2, when a molten glass droplet is dropped on a lower mold having a roughened surface, a minute recess is once formed at the time of collision with the lower mold, Since the air accumulated in the concave portion is pushed out through the gap formed between the lower surface of the molten glass droplet and the surface of the lower mold, it is possible to prevent the air reservoir from remaining in the glass gob after cooling.

  However, in order to completely prevent air accumulation, it is necessary to form a sufficiently high unevenness on the surface of the lower mold by roughening so as to ensure a necessary gap. For this reason, the finally obtained glass gob and the lower surface of the glass molded body have a problem that the surface roughness becomes large due to the transfer of irregularities on the surface of the lower mold. In particular, when the manufactured glass molded body or the like is used as an optical element, the optical performance may be greatly affected by surface fogging or scattering due to such surface roughness, and a solution has been desired. Furthermore, even when the obtained glass gob or glass molded body is used as a glass preform for reheat press, in order to eliminate such a large surface roughness, longer molding is required. This was a factor in increasing manufacturing costs.

  In addition, there are various constraints on the material used as a molding die for molding glass, including, for example, cemented carbide materials mainly composed of tungsten carbide, ceramic materials such as silicon carbide and silicon nitride, and carbon. Currently, limited materials such as composite materials must be used.

  However, it is often difficult to uniformly roughen these materials having desirable properties as a molding die so that the surface has a predetermined surface roughness. In addition, although roughening by etching is possible, there are materials in which the roughened surface becomes very brittle and the durability is remarkably deteriorated.

  Therefore, when these materials are used for the lower mold, the method described in Patent Documents 1 and 2 cannot be performed, or even if it can be performed, the durability of the lower mold is inferior, so that glass molding is performed. There was a problem that a body etc. could not be manufactured stably.

  The present invention has been made in view of the technical problems as described above, and the object of the present invention is to reliably prevent the occurrence of air accumulation without using a lower mold having large irregularities on the surface, and to achieve surface roughness. It is providing the manufacturing method which can manufacture efficiently a small glass gob and a glass molded object.

  In order to solve the above problems, the present invention has the following features.

  1. In the method for producing a glass gob having a dropping step of dropping a molten glass droplet onto a lower mold, the lower mold is so formed that a collision between the lower mold and the molten glass droplet is performed in a reduced-pressure atmosphere reduced from atmospheric pressure. A method for producing a glass gob, characterized by decompressing a surrounding region.

  2. The dropping step is a step of dropping the molten glass droplet separated from the tip of the dropping nozzle onto the lower die, and the region to be depressurized collides with the lower die after the molten glass droplet leaves the tip of the dropping nozzle. 2. The method for producing a glass gob as described in 1 above, comprising a path through which the glass gob passes.

  3. The method for producing a glass gob as described in 1 or 2 above, wherein the pressure in the reduced-pressure atmosphere is 1000 Pa to 30000 Pa.

  4). In the manufacturing method of the glass forming body which has the dripping process of dripping a molten glass drop to a lower mold, and the pressurization process of press-molding the molten glass drop with the lower mold and an upper mold, the lower in the dropping process A method for producing a glass molded body, comprising: depressurizing a region around the lower mold so that the mold and the molten glass droplet collide with each other in a reduced-pressure atmosphere reduced from atmospheric pressure.

  5). The dropping step is a step of dropping the molten glass droplet separated from the tip of the dropping nozzle onto the lower die, and the region to be depressurized collides with the lower die after the molten glass droplet leaves the tip of the dropping nozzle. 5. The method for producing a glass molded article as described in 4 above, comprising a path through which the glass molded article passes.

  6). 6. The method for producing a glass molded body according to 4 or 5 above, wherein the pressure in the reduced-pressure atmosphere is 1000 Pa to 30000 Pa.

  7. The said pressurization process is performed in the said pressure-reduced atmosphere, The manufacturing method of the glass molded object of any one of said 4-6 characterized by the above-mentioned.

  8). The said pressurization process is performed outside the said pressure-reduced atmosphere, The manufacturing method of the glass forming body of any one of said 4-6 characterized by the above-mentioned.

  9. In a glass gob manufacturing apparatus, which has a lower mold for receiving molten glass droplets and cools the molten glass droplets dropped on the lower mold to produce a glass gob, a chamber including the lower mold inside, and a large interior of the chamber An apparatus for producing a glass gob, comprising: decompression means for depressurizing from atmospheric pressure.

  10. The lower mold has a dropping nozzle for dropping a molten glass droplet, and the chamber collides with the lower mold after at least the tip portion of the dropping nozzle and the molten glass droplet leaves the tip of the dropping nozzle. 10. The glass gob manufacturing apparatus according to 9, wherein a path through which the glass gob passes is included.

  11. A glass molded body having a lower mold for receiving molten glass droplets and an upper mold for pressing the molten glass droplets together with the lower mold, and producing a glass molded body by pressure molding the molten glass droplets dropped on the lower mold The manufacturing apparatus of the glass molded object characterized by including the chamber which contains the said lower mold | type inside, and the decompression means for decompressing the inside of the said chamber from atmospheric pressure.

  12 The lower mold has a dropping nozzle for dropping a molten glass droplet, and the chamber collides with the lower mold after at least the tip portion of the dropping nozzle and the molten glass droplet leaves the tip of the dropping nozzle. 12. The apparatus for producing a glass molded body as described in 11 above, wherein a path through which the glass molded body passes is contained inside.

  13. 13. The apparatus for producing a glass molded body according to 11 or 12, wherein the upper mold is disposed inside the chamber.

  14 13. The apparatus for producing a glass molded body according to 11 or 12, wherein the upper mold is disposed outside the chamber.

  In the present invention, since the collision between the molten glass droplet and the lower mold is performed in a reduced pressure atmosphere reduced from the atmospheric pressure, it is possible to reliably prevent the occurrence of air accumulation without using a lower mold having large irregularities on the surface. be able to. Therefore, it is possible to efficiently produce a glass gob or a glass molded body having no air accumulation and a small surface roughness.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS.

(Glass Gob Manufacturing Equipment and Manufacturing Method)
First, the manufacturing apparatus and manufacturing method of the glass gob of this invention are demonstrated, referring FIGS. 1-4. FIG. 1 is a flowchart showing an example of a glass gob manufacturing method. 2 and 3 are schematic views of the glass gob manufacturing apparatus 10 according to this embodiment. FIG. 2 shows the state in the step (S13) of dropping the molten glass droplet on the lower mold, and FIG. 3 shows the state in the step (S14) of cooling and solidifying the dropped molten glass droplet on the lower mold. Yes. FIG. 4 is a schematic view of a glass gob manufacturing apparatus 10a according to another embodiment of the present invention.

  The glass gob manufacturing apparatus 10 shown in FIGS. 2 and 3 has a melting tank 15 for storing molten glass 52, a dropping nozzle 16 connected to the lower part of the melting tank 15, and a lower mold 11 for receiving the molten glass droplet 50. is doing. The chamber 12 is configured so that the inside of the chamber 12 can be depressurized by a depressurizing means including a valve 13 and a pump 14. The interior of the chamber 12 includes a path through which the dropping nozzle 16, the lower mold 11, and the molten glass droplet 50 pass after leaving the tip 16 s of the dropping nozzle 16 and colliding with the lower mold 11.

  If the molten glass droplet 50 is affected by the wind while it is falling, the position of the glass droplet 50 that collides with the lower mold 11 varies, which causes variations in the quality of the obtained glass gob and the like. By including a path through which the dropping nozzle 16, the lower mold 11, and the molten glass droplet 50 pass from the tip 16 s of the dropping nozzle 16 until they collide with the lower mold 11 inside the chamber 12, The influence by such wind can be suppressed to the minimum, and a more stable quality glass gob can be manufactured.

  The glass gob manufacturing apparatus 10 shown in FIGS. 2 and 3 has an advantage that the entire apparatus can be downsized because the melting tank 15 is not included in the chamber 12. However, since the upper surface 53 of the molten glass 52 stored in the melting tank 15 is under atmospheric pressure, the molten glass inside the dropping nozzle 16 is sucked into the decompressed chamber 12 and the molten glass droplet 50 The dropping interval may be too short. From the viewpoint of avoiding such a problem, it is also preferable that the entire melting tank 15 is included in the chamber 12.

  Furthermore, as shown in FIG. 10, it is also preferable to have another chamber 12b including the melting tank 15 inside. The glass gob manufacturing apparatus 10b of FIG. 10 has two chambers 12 and 12b, and the internal pressure can be independently adjusted by the valves 13 and 13b and the pumps 14 and 14b provided respectively. It has become. In this way, by adjusting the difference between the pressure in the chamber 12 and the pressure in the chamber 12b, the dropping interval of the molten glass droplet 50 can be adjusted to a desired interval. When it is desired to shorten the dropping interval, the pressure in the chamber 12 is adjusted to be low, and when it is desired to increase the dropping interval, the pressure in the chamber 12b is adjusted to be low.

  Here, in order to prevent the air gob from being generated in the glass gob 54, it is only necessary that the collision between the molten glass droplet and the lower mold is performed in a reduced pressure atmosphere reduced from the atmospheric pressure. Therefore, it is sufficient that at least the lower mold 11 is included in the chamber 12 as in the glass gob manufacturing apparatus 10a shown in FIG. The chamber 12 of the glass gob manufacturing apparatus 10a is provided with a shutter 17 that can be opened and closed. The inside of the chamber 12 is depressurized with the shutter 17 closed, and the molten glass droplet 50 is introduced into the chamber 12 by opening the shutter 17 in accordance with the dropping timing of the molten glass droplet 50. The collision between the droplet 50 and the lower mold 11 can be performed in a reduced pressure atmosphere. As described above, the configuration in which only the lower mold 11 is included in the chamber 12 has an advantage that the chamber 12 can be very miniaturized and a large-scale decompression unit is not required.

  The lower mold | type 11 is comprised so that it can heat to predetermined temperature with the heating means which is not shown in figure. As the heating means, known heating means can be appropriately selected and used. For example, a cartridge heater that is used by being embedded inside the lower mold 11, a sheet heater that is used while being in contact with the outside of the lower mold 11, an infrared heating device, a high-frequency induction heating device, or the like can be used.

  As described above, in the present invention, since the collision between the molten glass droplet 50 and the lower mold 11 is performed in a reduced-pressure atmosphere reduced from the atmospheric pressure, it is necessary to roughen the surface of the lower mold 11 by etching or the like. Absent. Therefore, the material of the lower mold 11 can be selected without considering the ease of roughening and the durability when roughened.

  Therefore, the material of the lower mold 11 can be appropriately selected from materials known as molding mold materials according to conditions. Examples of materials that can be preferably used include, for example, various heat-resistant alloys (such as stainless steel), super hard materials mainly composed of tungsten carbide, various ceramics (such as silicon carbide, silicon nitride, and aluminum nitride), and composite materials containing carbon. Is mentioned.

  It is also preferable to provide a coating layer on the surface in order to improve the durability of the lower mold 11 and prevent fusion with the molten glass droplet 50. There are no particular restrictions on the material of the coating layer. For example, various metals (chromium, aluminum, titanium, etc.), nitrides (chromium nitride, aluminum nitride, titanium nitride, boron nitride, etc.), oxides (chromium oxide, aluminum oxide, etc.) , Titanium oxide, etc.) can be used.

  Among these, it is particularly preferable that at least one element of chromium, aluminum, and titanium is included. A film containing these elements is characterized in that the surface is oxidized by heating in the atmosphere and a stable oxide layer is formed. Chromium, aluminum, and titanium oxides all have low standard generation free energy (standard generation Gibbs energy) and are very stable, so they do not react easily even when they come into contact with hot molten glass droplets. Has great advantages.

  The method for forming the coating layer is not limited and may be appropriately selected from known film forming methods. For example, vacuum deposition, sputtering, CVD, etc. are mentioned.

  Next, an example of the glass gob manufacturing method of the present invention will be described with reference to the flowchart shown in FIG. 1, taking as an example the case of using the glass gob manufacturing apparatus 10 shown in FIGS.

  First, the lower mold 11 is heated in advance to a predetermined temperature (step S11). If the temperature of the lower mold 11 is too low, large wrinkles may occur on the lower surface of the glass gob (contact surface with the lower mold 11), and cracks and cans may occur due to rapid cooling. On the other hand, if the temperature is set higher than necessary, fusion may occur between the glass and the lower mold 11 or the life of the lower mold 11 may be shortened. Actually, the appropriate temperature differs depending on various conditions such as the glass type, shape, size, material and size of the lower mold 11, the position of the heater and the temperature sensor, etc. It is preferable to keep it. Usually, it is preferable to set the glass to a temperature of about Tg (glass transition temperature) -100 ° C. to Tg + 100 ° C.

  Next, the pressure inside the chamber 12 is reduced (step S12). The pressure is reduced by opening the valve 13 and exhausting the air inside the chamber 12 by the pump 14. What is necessary is just to set suitably the pressure inside the chamber 12 after pressure reduction according to the generation | occurrence | production condition of an air pocket, etc. The lower the pressure inside the chamber 12, the higher the effect of suppressing the occurrence of air pockets. Therefore, the occurrence of air pockets can be prevented even if the surface of the lower mold 11 is small. If the pressure in the reduced-pressure atmosphere is too high, the effect of suppressing the occurrence of air accumulation may not be sufficient. Conversely, if the pressure in the reduced-pressure atmosphere is too low, it will take a long time to reduce the pressure, and the production efficiency It may get worse. From such a viewpoint, it is usually preferable that the pressure inside the vacuum chamber 12 (depressurized atmosphere) is set to 1000 Pa to 30000 Pa.

  In addition, the order of process S11 and process S12 is not limited to this, Process S11 may be performed after process S12, and process S11 and process S12 may be performed simultaneously.

  Next, the molten glass droplet 50 is dropped on the lower mold 11 (step S13). The melting tank 15 provided above the lower mold 11 is heated by a heater (not shown), and a molten glass 52 is stored therein. A dropping nozzle 16 is provided in the lower part of the melting tank 15, and the molten glass 52 passes through a flow path provided inside the dropping nozzle 16 by its own weight and accumulates at the tip 16s by surface tension. When a certain amount of molten glass accumulates, it is naturally separated from the tip 16s of the dropping nozzle 16, and a certain amount of molten glass droplet 50 is dropped downward (see FIG. 2).

  Since the inside of the chamber 12 is decompressed by the previous step S12, the lower mold 11 and the molten glass droplet 50 collide with each other in a decompressed atmosphere. Accordingly, the concave portion generated on the lower surface of the molten glass droplet 50 at the time of collision disappears due to the surface tension in the subsequent cooling process, so that it can be prevented from remaining as an air pocket in the glass gob 54.

  The mass of the molten glass droplet 50 to be dropped can be adjusted by the outer diameter of the tip 16s of the dropping nozzle 16, and depending on the type of glass, about 0.1 to 2 g of molten glass droplet can be dropped. The dropping interval of the glass droplets can be adjusted by the inner diameter, length, heating temperature, etc. of the dropping nozzle 16. Therefore, by appropriately setting these conditions, it is possible to drop molten glass droplets having a desired mass at desired intervals.

  There is no restriction | limiting in particular in the kind of glass which can be used, A well-known glass can be selected and used according to a use. Examples thereof include optical glasses such as borosilicate glass, silicate glass, phosphate glass, and lanthanum glass.

  Further, the molten glass droplet 50 is not directly dropped onto the lower mold 11 from the dropping nozzle 16, but the molten glass droplet 50 dropped from the dropping nozzle 16 is collided with a member provided with a through-hole, and the molten glass droplet collided A part of the fine particles may be dropped on the lower mold 11 through the through pores as fine droplets. Thereby, it becomes possible to manufacture a finer glass gob. This method is described in detail in JP-A No. 2002-154834. In this case, from the viewpoint of stabilizing the dropping position, it is preferable that the tip 16 s of the dropping nozzle 16, the member provided with the through-holes, and the lower mold 11 are all provided inside the chamber 12.

  Next, the dropped molten glass droplet 50 is cooled and solidified on the lower mold 11 (step S14) (see FIG. 3). By leaving on the lower mold 11 for a predetermined time, the molten glass droplet 50 is cooled by heat radiation to the lower mold 11 and solidified.

  Thereafter, the solidified glass gob 54 is collected (step S15), and the production of the glass gob is completed. Furthermore, when manufacturing the glass gob 54 subsequently, the process after process S13 should just be repeated.

  In addition, the glass gob manufactured by the manufacturing method of this embodiment can be used as a glass preform used for manufacturing various precision optical elements by a reheat press method.

(Glass compact manufacturing apparatus and manufacturing method)
1st Embodiment of the manufacturing apparatus and manufacturing method of the glass forming body of this invention is described, referring FIGS. FIG. 5 is a flowchart showing an example of a method for producing a glass molded body. 6 and 7 are schematic views of the glass molded body manufacturing apparatus 20 in the present embodiment. 6 shows the state in the step (S24) of dropping the molten glass droplet 50 onto the lower mold 11, and FIG. 7 shows the state in the step (S26) of pressurizing the dropped molten glass droplet 50 with the lower mold 11 and the upper mold 21. Respectively. Moreover, FIG. 8, FIG. 9 is a schematic diagram of the manufacturing apparatus 20a of the glass molded object in another embodiment. FIG. 8 shows the state in step S24, and FIG. 9 shows the state in step S26.

  The glass molded body manufacturing apparatus 20 includes a melting tank 15 for storing molten glass 52, a dropping nozzle 16 connected to a lower portion of the melting tank 15, a lower mold 11 for receiving a molten glass drop 50, and a molten glass together with the lower mold 11. An upper mold 21 for pressurizing the droplet 50 is provided. The chamber 12 is configured so that the inside of the chamber 12 can be depressurized by a depressurizing means including a valve 13 and a pump 14. The inside of the chamber 12 includes a path through which the dripping nozzle 16, the lower mold 11, the upper mold 21, and the molten glass droplet 50 pass after leaving the tip 16 s of the dripping nozzle 16 and colliding with the lower mold 11. ing.

  The lower mold 11 has a position (dropping position P1) for receiving the molten glass droplet 50 below the dropping nozzle 16 and a position for pressurizing the molten glass droplet 50 facing the upper mold 21 by driving means (not shown). It is configured to be movable between (pressurizing position P2). Further, the upper mold 21 is configured to be movable in a direction (a vertical direction in the figure) in which a molten glass droplet is pressurized with a lower mold 11 by a driving unit (not shown).

  In the glass molded body manufacturing apparatus 20 according to the present embodiment, the upper mold 21 is disposed inside the chamber 12 and the molten glass droplet 50 is dropped on the lower mold 11 (S24), and the dropped molten glass droplet 50 is dropped below. The step of pressurizing the mold 11 and the upper mold 21 (S26) is configured to be performed inside the same chamber 12. By adopting such a configuration, when repeatedly producing a large number of glass molded articles, it is possible to carry out while maintaining a constant depressurized state without always depressurizing the inside of the chamber 12, A glass molded object can be manufactured efficiently.

  However, including the upper mold 21 inside the chamber 12 and pressurizing the molten glass droplet 50 inside the chamber 12 is not necessarily an essential requirement in the present invention. As in the case of the glass gob manufacturing apparatus described above, if at least the lower mold 11 is inside the chamber 12, and the collision between the lower mold 11 and the molten glass droplet 50 is performed in a reduced pressure atmosphere, An effect of suppressing the occurrence of air pockets can be obtained.

  For example, the upper mold | type 21 can also be arrange | positioned outside the chamber 12 like the manufacturing apparatus 20a of the glass molded object shown to FIG. 8, FIG. The glass molded body manufacturing apparatus 20 a has a shutter 22 for moving the lower mold 11 in the chamber 12, and the lower mold 11 that has received the molten glass droplet 50 moves to the outside of the chamber 12 to move the upper mold 21. At the same time, the molten glass droplet 50 is pressurized. With such a configuration, there is an advantage that the chamber 12 can be miniaturized and the manufactured glass molded body can be collected and sent to the next step immediately after each production.

  Next, an example of the method for producing a glass molded body of the present invention will be described according to the flowchart shown in FIG. 5, taking as an example the case of using the glass molded body production apparatus 20 shown in FIGS.

  First, the lower mold 11 and the upper mold 21 are heated in advance to a predetermined temperature (step S21). The lower mold 11 and the upper mold 21 are configured to be heated to a predetermined temperature by a heating means (not shown). It is preferable that the lower mold 11 and the upper mold 21 be configured to be capable of independently controlling the temperature. The predetermined temperature is the same as that in step S11 in the above-described glass gob manufacturing method, and a temperature at which a good transfer surface can be formed on the glass molded body by pressure molding may be appropriately selected. The heating temperature of the lower mold 11 and the upper mold 21 may be the same or different.

  Next, the pressure inside the chamber 12 is reduced (Step S22). About the method and conditions of pressure reduction, it is the same as that of the case of process S12 in the manufacturing method of the above-mentioned glass gob.

  Next, the lower mold | type 11 is moved to the dripping position P1 (process S23), and the molten glass droplet 50 is dripped from the dripping nozzle 16 (process S24) (refer FIG. 6). About the conditions at the time of dripping the molten glass droplet 50, it is the same as that of the case of process S13 in the manufacturing method of the above-mentioned glass gob. Since the inside of the chamber 12 is decompressed by the previous step S22, the lower mold 11 and the molten glass droplet 50 collide with each other in a decompressed atmosphere. Accordingly, the concave portion generated on the lower surface of the molten glass droplet 50 at the time of collision disappears due to the surface tension in the subsequent cooling process, so that it can be prevented from remaining as an air pocket in the glass molded body 55.

  Next, the lower mold 11 is moved to the pressing position P2 (step S25), the upper mold 21 is moved downward, and the molten glass droplet 50 is pressurized with the lower mold 11 and the upper mold 21 (process S26) ( (See FIG. 7).

  The molten glass droplet 50 is cooled and solidified by heat radiation from the contact surface with the lower mold 11 and the upper mold 21 while being pressurized. After cooling to a temperature at which the shape of the transfer surface formed on the glass molded body does not collapse even if the pressure is released, the pressure is released. Although it depends on the type of glass, the size and shape of the glass molded body, the required accuracy, etc., it is usually sufficient that the glass is cooled to a temperature in the vicinity of Tg of the glass.

  The load applied to press the molten glass droplet 50 may be always constant or may be changed with time. What is necessary is just to set the magnitude | size of the load to load suitably according to the size etc. of the glass forming body to manufacture. The driving means for moving the upper die 21 up and down is not particularly limited, and known driving means such as an air cylinder, a hydraulic cylinder, and an electric cylinder using a servo motor can be appropriately selected and used.

  Thereafter, the upper mold 21 is moved upward and retracted, and the solidified glass molded body 55 is recovered (step S27), whereby the manufacture of the glass molded body is completed. Thereafter, when the glass molded body is subsequently manufactured, the lower mold 11 is moved again to the dropping position P1 (step S23), and the subsequent steps may be repeated.

  In addition, the manufacturing method of the glass forming body of this invention may include another process other than having demonstrated here. For example, a step of inspecting the shape of the glass molded body before collecting the glass molded body, a step of cleaning the lower mold 11 and the upper mold 21 after collecting the glass molded body, and the like may be provided.

  The glass molded body manufactured by the manufacturing method of the present invention can be used as various optical elements such as an imaging lens such as a digital camera, an optical pickup lens such as a DVD, and a coupling lens for optical communication. Moreover, various optical elements can also be manufactured by heating a glass molded object again and pressure-molding by a reheat press method.

(Example 1)
The glass gob 54 was manufactured according to the flowchart shown in FIG. 1 using the glass gob manufacturing apparatus 10 shown in FIGS.

  As the glass material, phosphoric acid glass having a Tg of 530 ° C. was dropped from the platinum dropping nozzle 16 having an outer diameter of φ6 mm onto the lower mold 11. As the material of the lower mold 11, a super hard material mainly composed of tungsten carbide was used. The lower mold 11 was prepared with five types of lower molds having different arithmetic average roughnesses (Ra) by changing the polishing conditions with a flat surface shape for receiving molten glass droplets. The arithmetic average roughness (Ra) was 0.005 μm, 0.01 μm, 0.02 μm, 0.1 μm, and 0.3 μm, respectively. The arithmetic average roughness (Ra) is a roughness parameter defined in JIS B 0601: 2001, and was measured by AFM (D3100 manufactured by Digital Instruments).

  The heating temperature of the lower mold 11 in the step S11 was 570 ° C. The pressure inside the chamber 12 in step S12 was 1000 Pa.

  A glass gob was produced using the above five types of lower molds, and the presence or absence of air accumulation and the arithmetic average roughness (Ra) of the surface in contact with the lower molds were evaluated. The presence or absence of air pockets was determined with a 50 × optical microscope. Arithmetic average roughness (Ra) was measured using the said measuring machine. Among the glass gobs in which no air retention occurred, the one having the smallest arithmetic average roughness (Ra) of the surface in contact with the lower mold was extracted. Table 1 shows the arithmetic average roughness (Ra) of the extracted sample and the arithmetic average roughness (Ra) of the lower mold used.

  As shown in Table 1, according to the conditions of Example 1 (pressure: 1000 Pa), even if the arithmetic average roughness (Ra) is a lower mold of 0.005 μm, no air pocket is generated, The arithmetic average roughness (Ra) of the glass gob was very good at 0.003 μm.

(Examples 2 and 3)
A glass gob was produced and evaluated under the same conditions as in Example 1 except that the pressure inside the chamber 12 in Step S12 was set to 10,000 Pa (Example 2) and 30000 Pa (Example 3). Under each condition, out of the glass gob where no air accumulation occurred, a glass gob having the smallest arithmetic average roughness (Ra) of the surface in contact with the lower mold was extracted. Table 1 shows the arithmetic average roughness (Ra) of the extracted sample and the arithmetic average roughness (Ra) of the lower mold used.

  As shown in Table 1, according to the conditions of Example 2 (pressure: 10000 Pa), even if the arithmetic average roughness (Ra) is a lower mold of 0.005 μm, no air pockets are generated, The arithmetic average roughness (Ra) of the glass gob was very good at 0.003 μm. Further, in the case of the conditions of Example 3 (pressure: 30000 Pa), even when the lower mold having an arithmetic average roughness (Ra) of 0.01 μm is used, no air retention occurs, and the arithmetic average roughness of the glass gob (Ra) was as good as 0.007 μm.

(Comparative example)
Unlike Examples 1 to 3, the glass gob was manufactured and evaluated while the inside of the chamber was not depressurized and remained at atmospheric pressure (about 0.1 MPa). The results are also shown in Table 1.

  In the case of the conditions of the comparative example, in order to prevent air accumulation, the arithmetic average roughness (Ra) of the surface of the lower mold must be increased to 0.3 μm, and the arithmetic average roughness ( Ra) was confirmed to be very large at 0.18 μm.

It is a flowchart which shows one example of the manufacturing method of a glass gob. It is a schematic diagram of the glass gob manufacturing apparatus 10 (step S13). It is a schematic diagram of the glass gob manufacturing apparatus 10 (step S14). It is a schematic diagram of the manufacturing apparatus 10a of the glass gob which is another embodiment. It is a flowchart which shows one example of the manufacturing method of a glass forming body. It is a schematic diagram of the manufacturing apparatus 20 of a glass molded object (process S24). It is a schematic diagram of the manufacturing apparatus 20 of a glass molded object (process S26). It is a schematic diagram of the manufacturing apparatus 20a of the glass molded body which is another embodiment (process S24). It is a schematic diagram of the manufacturing apparatus 20a of the glass molded body which is another embodiment (process S26). It is a schematic diagram of the glass gob manufacturing apparatus 10b which is another embodiment. It is a figure which shows typically the state of the molten glass droplet 50 dripped at the lower mold | type 11 by the conventional method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10a, 10b Glass gob manufacturing apparatus 11 Lower mold 12 Chamber 13 Valve 14 Pump 15 Melting tank 16 Dropping nozzle 16s Tip of dropping nozzle 16 17 Shutter 20, 20a Glass molding body manufacturing apparatus 21 Upper mold 22 Shutter 50 Molten glass droplet 51 Concavity 52 Molten Glass 54 Glass Gob 55 Glass Molded Body

Claims (14)

In the method for producing a glass gob having a dropping step of dropping a molten glass droplet on the lower mold,
A method for producing a glass gob, characterized in that the area around the lower mold is decompressed so that the collision between the lower mold and the molten glass droplet is performed in a reduced-pressure atmosphere reduced from atmospheric pressure. The dropping step is a step of dropping a molten glass droplet separated from the tip of a dropping nozzle onto the lower mold,
2. The glass gob manufacturing method according to claim 1, wherein the region to be depressurized includes a path through which a molten glass droplet passes from the tip of the dropping nozzle until it collides with the lower mold.   The method for producing a glass gob according to claim 1 or 2, wherein the pressure in the reduced-pressure atmosphere is 1000 Pa to 30000 Pa. In a method for producing a glass molded body, comprising: a dropping step of dropping a molten glass droplet onto a lower mold; and a pressing step of pressure-molding the molten glass droplet with the lower mold and the upper mold.
An area around the lower mold is decompressed so that the collision between the lower mold and the molten glass droplet in the dropping step is performed in a reduced-pressure atmosphere reduced from atmospheric pressure. Production method. The dropping step is a step of dropping a molten glass droplet separated from the tip of a dropping nozzle onto the lower mold,
The method for producing a glass molded body according to claim 4, wherein the region to be depressurized includes a path through which a molten glass droplet passes from the tip of the dropping nozzle until it collides with the lower mold.   The method for producing a glass molded body according to claim 4 or 5, wherein the pressure in the reduced-pressure atmosphere is 1000 Pa to 30000 Pa.   The said pressurization process is performed in the said pressure-reduced atmosphere, The manufacturing method of the glass molded object of any one of Claims 4-6 characterized by the above-mentioned.   The said pressurization process is performed outside the said pressure-reduced atmosphere, The manufacturing method of the glass molded object of any one of Claims 4-6 characterized by the above-mentioned. In a glass gob manufacturing apparatus that has a lower mold for receiving molten glass droplets and that cools the molten glass droplets dropped on the lower mold to manufacture a glass gob,
A chamber containing the lower mold inside;
An apparatus for producing a glass gob, comprising: decompression means for decompressing the interior of the chamber from atmospheric pressure. Having a dropping nozzle for dropping molten glass droplets in the lower mold,
10. The chamber includes at least a tip portion of the dropping nozzle and a path through which a molten glass droplet passes from the tip of the dropping nozzle until it collides with the lower mold. An apparatus for producing a glass gob as described in 1. A glass molded body having a lower mold for receiving molten glass droplets and an upper mold for pressing the molten glass droplets together with the lower mold, and producing a glass molded body by pressure molding the molten glass droplets dropped on the lower mold In the manufacturing equipment of
A chamber containing the lower mold inside;
And a decompression means for decompressing the interior of the chamber from atmospheric pressure. Having a dropping nozzle for dropping molten glass droplets in the lower mold,
12. The chamber includes at least a tip portion of the dropping nozzle and a path through which a molten glass droplet passes from the tip of the dropping nozzle until it collides with the lower mold. The manufacturing apparatus of the glass molded object of description.   The said upper type | mold is arrange | positioned inside the said chamber, The manufacturing apparatus of the glass molded object of Claim 11 or 12 characterized by the above-mentioned.   The apparatus for producing a glass molded body according to claim 11 or 12, wherein the upper mold is disposed outside the chamber.

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