JP2009120457A - Lower mold, production method for glass gob, and production method for glass molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lower mold which can suitably prevent generation of an air pool without narrowing a selection range of a material for the lower mold, and excels in durability. <P>SOLUTION: The lower mold has a receiving face to receive molten glass droplets dropped from an upper part. Wherein a buffer space is provided so as to make air entering a concave portion of the molten glass droplet, formed by colliding with the receiving face, to escape from the concave portion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a lower mold having a receiving surface for receiving molten glass droplets dripped from above, a method for producing a glass gob using the lower mold, and a method for producing a glass molded body.

  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, investigations have been made on a method for producing a glass preform without machining by dropping molten glass droplets on the receiving surface of the lower die and cooling and solidifying the dropped molten glass droplets on the lower die. .

  On the other hand, as another method for producing a glass molded body, molten glass droplets are dropped on a receiving surface of a lower mold heated to a predetermined temperature, and the dropped molten glass droplets are pressed by an upper mold facing the lower mold and the lower mold. A method of forming a glass molded body by molding (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 receiving surface of the lower mold for manufacturing a glass preform or a glass molded body, a recess (air pocket) remains on the lower surface of the manufactured glass preform or glass molded body. There was a problem of doing. This problem will be described with reference to FIG.

  FIG. 12 is a diagram schematically showing a state of the molten glass droplet 50 dropped on the conventional lower mold 70. FIG. 12A shows a state at the moment when the molten glass droplet 50 collides with the lower mold 70, and FIG. 12B shows a state where the molten glass droplet 50 is deformed round by surface tension thereafter.

  As shown in FIG. 12A, the molten glass droplet 50 at the moment of collision with the lower mold 70 is stretched flat by the impact of the collision. At this time, in the molten glass droplet 50, a minute concave portion 51 having a diameter of about several tens of μm to several hundreds of μm is generated near the center of the lower surface (contact surface with the receiving surface 71). Although the mechanism by which the concave portion 51 is generated is not necessarily clear, according to the analysis using simulation or the like, when the molten glass droplet 50 collides with the lower mold 70, the glass of the portion that first collides with the lower mold 70 is rebounded. It may be caused by rebounding upward.

  Thereafter, as shown in FIG. 12B, the molten glass droplet 50 is deformed into a round shape by the action of the surface tension. At this time, the lower surface of the molten glass droplet 50 and the receiving surface 71 are in close contact with each other, and there is no escape path 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 receiving surface is roughened (Rmax is 0.05 μm to 0.2 μm) to prevent air from remaining by securing the air flow path that has entered the recess. A method 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

  In order to prevent the occurrence of air accumulation by the methods described in Patent Documents 1 and 2, it is necessary to roughen the surface by etching or the like so that the surface of the lower mold has a predetermined surface roughness.

  In general, there are various constraints on the material used as a molding die for molding glass, it is difficult to react with glass at high temperatures, a mirror surface is obtained, workability is good, it is hard, and it is not brittle. It is necessary to satisfy many conditions. Materials satisfying these conditions are very limited. For example, super hard materials mainly composed of tungsten carbide, ceramic materials such as silicon carbide and silicon nitride, and composite materials containing carbon are preferably used. ing.

  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, it is possible to roughen the surface by etching, such as a cemented carbide material mainly composed of tungsten carbide, but the roughened surface becomes very brittle and the durability is significantly deteriorated. Some materials will end up.

  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 an object of the present invention is to prevent the occurrence of air accumulation without narrowing the choice of the lower mold material and is excellent in durability. It is to provide a lower mold. Another object of the present invention is to provide a glass gob production method capable of stably producing a glass gob free of air accumulation, and to stably produce a glass molded body free of air accumulation. It is providing the manufacturing method of the glass forming body which can be performed.

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

  1. A lower mold having a receiving surface for receiving molten glass droplets dripping from above, and having a buffer space for letting air that has entered the concave portion of the molten glass droplet formed by collision with the receiving surface escape from the concave portion. A lower mold characterized by

  2. 2. The lower mold according to 1 above, wherein the buffer space is a hole formed in the receiving surface.

  3. 2. The lower mold as described in 1 above, wherein the buffer space is a concave groove formed in the receiving surface.

  4). The buffer space is a porous film formed on the receiving surface, and the porous film has a surface arithmetic average roughness (Ra) of 1 nm to 100 nm and a porosity of 20% to 50%. 2. The lower mold according to the above 1, characterized by.

  5). In the method for producing a glass gob having a step of dripping molten glass droplets on a lower die and a step of cooling and solidifying the dropped molten glass droplets on the lower die, the lower die is any one of 1 to 4 above A method for producing a glass gob, which is the lower mold according to claim 1.

  6). In a method for producing a glass molded body, comprising: a step of dropping molten glass droplets on a lower mold; and a step of pressure-forming the dropped molten glass droplets with an upper mold facing the lower mold and the lower mold. The said lower mold is a lower mold of any one of said 1 thru | or 4, The manufacturing method of the glass forming body characterized by the above-mentioned.

  The lower mold of the present invention has a buffer space for letting air that has entered the concave portion of the molten glass droplet escape from the concave portion at the center of the receiving surface, so there is no need to roughen the surface of the lower mold. Further, the lower mold is not deteriorated by etching. Therefore, it is possible to satisfactorily prevent the occurrence of air accumulation without narrowing the choice of lower mold material, and it is excellent in durability. In addition, by using the lower mold of the present invention, it is possible to stably produce a glass gob or a glass molded body without air accumulation.

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

(Lower mold)
FIG. 1 is a diagram schematically showing the lower mold 10 of this embodiment and the state of a molten glass droplet 50 dropped on the lower mold 10. 1A shows a state at the moment when the molten glass droplet 50 collides with the lower mold 10, and FIG. 1B shows a state in which the molten glass droplet 50 is deformed in a round shape by the surface tension thereafter.

  A lower mold 10 shown in FIG. 1 has a receiving surface 11 for receiving a molten glass droplet dripping from above, and a hole 12 is provided at the center of the receiving surface 11. The hole 12 functions as a buffer space for allowing air that has entered the recess 51 of the molten glass droplet 50 formed by the collision with the receiving surface 11 to escape from the recess 51.

  As shown in FIG. 1A, a minute concave portion 51 is once generated in the molten glass droplet 50 at the moment of collision with the receiving surface 11, and air enters the concave portion 51. However, as shown in FIG. 1B, when the molten glass droplet 50 is deformed round by the action of surface tension, the air that has entered the recess 51 escapes to the hole 12 and the recess 51 disappears.

  The position of the hole 12 does not necessarily need to be the exact center of the receiving surface 11 and may be a position where air that has entered the recess 51 of the molten glass droplet 50 formed at the time of collision can be released.

  The cross-sectional shape of the hole 12 is not particularly limited, but it is usually preferable to have a circular cross-sectional shape because it is easy to process. In this case, if the diameter of the hole 12 is too small, the air that has entered the recess 51 is difficult to escape and an air pocket may remain. Moreover, it becomes difficult to process the holes 12. On the other hand, if the diameter is too large, the shape error of the transfer surface becomes large, and the performance of the produced glass molded body or the like is deteriorated. Therefore, the diameter of the hole 12 is preferably 10 μm to 100 μm.

  The hole 12 can be formed by a known processing means such as laser processing.

  FIG. 2 is a view showing a modification of the lower mold 10 having the hole 12 in the central portion of the receiving surface 11. The lower mold 10 shown in FIG. 2A has a hole 12 that penetrates to the bottom surface 13. As described above, the hole 12 as the buffer space may be a bottomed hole or a through hole, but is preferably a through hole from the viewpoint of facilitating the inflow of air that has entered the recess 51. From the same viewpoint, it is also preferable to provide an opening 15 on the side surface 14 like the hole 12 of the lower mold 10 shown in FIG. Furthermore, you may have the some hole 12 like the lower mold | type 10 shown in FIG.2 (c).

  FIG. 3 is a view showing a lower mold 20 of another embodiment of the present invention. 3A is a cross-sectional view of the lower mold 20, and FIG. 3B is a view of the lower mold 20 viewed from the direction of the arrow in FIG. 3A. The lower mold 20 includes a concave groove 22 in the receiving surface 21 instead of the hole 12. The concave groove 22 functions as a buffer space for allowing air that has entered the concave portion 51 of the molten glass droplet 50 to escape from the concave portion 51.

  There is no restriction | limiting in particular in the position, number, direction, etc. of the ditch | groove 22, What is necessary is just to have the volume which can escape the air which entered the recessed part 51 of the molten glass droplet 50 formed in the case of a collision. For example, the plurality of concave grooves 22 may be arranged radially, or may be a spiral groove extending from the center of the receiving surface 21 toward the outer peripheral direction. Moreover, the concave groove 22 does not need to reach the side surface 24, and a plurality of concave grooves 22 can be arranged concentrically. The width and depth of the groove 22 may be appropriately selected in consideration of the ease of air flow and the shape accuracy required of the glass molded body, but when the plurality of grooves 22 are arranged concentrically. The width and depth are preferably such that the optical performance is not adversely affected by the diffraction effect. From such a viewpoint, it is usually preferable that the groove 22 has a width of 10 μm to 30 μm and a depth of 0.1 μm to 10 μm.

  FIG. 4 is a diagram showing a lower mold 30 according to another embodiment of the present invention. The lower mold 30 includes a porous film 32 on a base material 33. The porous film 32 functions as a buffer space for letting air that has entered the recess 51 of the molten glass droplet 50 escape from the recess 51.

  By setting the arithmetic average roughness (Ra) of the surface of the porous film 32 to 1 nm to 100 nm and the porosity to 20% to 50%, the flow of air to the void portion is improved and the air pool remains. While being able to prevent, the influence on performance, such as a glass molded object, can be suppressed to the minimum. Here, the arithmetic average roughness (Ra) is a roughness parameter defined in JIS B 0601: 2001.

  When the arithmetic average roughness (Ra) is smaller than 1 nm, air hardly flows and an air pocket tends to remain. On the other hand, when the arithmetic average roughness (Ra) is larger than 100 nm, the arithmetic average roughness (Ra) of the surface of the obtained glass molded article is increased, which becomes a factor of deteriorating optical performance and the like. On the other hand, if the porosity is less than 20%, the air that has entered the recess 51 cannot escape and the air pocket tends to remain. When the porosity exceeds 50%, the arithmetic average roughness (Ra) of the surface of the obtained glass molded article increases, and the porous film 32 becomes brittle, resulting in a problem in durability.

  The porous film 32 only needs to be able to escape the air that has entered the recess 51, and is not necessarily provided on the entire receiving surface 31. For example, when the inclination of the peripheral portion 34 of the receiving surface 31 is large as in the lower mold 30 shown in FIG. 4, the fusion with the molten glass droplet is likely to occur due to the shear stress at the time of pressure molding. Therefore, it is preferable not to provide the porous film 32 in the peripheral portion 34.

  FIG. 5 is a diagram showing an example of a method for producing the porous film 32. As shown in FIG. 5A, a film 35 is formed on the base material 33 in advance, and a mother die 37 having fine protrusions 36 is pressed against the film 35, so that the fine recesses are transferred to the film 35. A porous film 32 as shown in FIG. 5B is formed (nanoindentation method). In addition to such a method, the porous film 32 can also be produced using a method such as a method of treating a film formed on a substrate with an etching solution, or a film formation by anodic oxidation.

  Thus, since the lower mold | type of this invention is equipped with the buffer space for escaping the air which entered the recessed part 51 of the molten glass droplet 50, it is not necessary to roughen the surface of a lower mold | type by an etching etc. . Therefore, the lower mold material can be selected without considering the ease of roughening and the durability when roughened.

  Therefore, the material for the lower mold is not particularly limited, and 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 receiving surface in order to improve the durability of the lower mold and prevent fusion with molten glass droplets. The material of the coating layer is not particularly limited. For example, various metals (chromium, aluminum, titanium, etc.), nitrides (chromium nitride, aluminum nitride, titanium nitride, boron nitride, etc.), oxides (chromium oxide, aluminum oxide, Titanium oxide or the like) 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.

(Glass gob manufacturing method)
The manufacturing method of the glass gob of this invention is demonstrated referring FIGS. 6-8. FIG. 6 is a flowchart showing an example of a glass gob manufacturing method. 7 and 8 are schematic views for explaining the glass gob manufacturing method in the present embodiment. FIG. 7 shows the state in the step (S22) of dropping the molten glass droplet on the lower die, and FIG. 8 shows the state in the step (S23) of cooling and solidifying the dropped molten glass droplet on the lower die. Yes.

  The lower mold 10 shown in FIGS. 7 and 8 is provided with a hole 12 at the center of the receiving surface 11 as a buffer space for escaping air that has entered the recess of the molten glass droplet 50.

  Moreover, the lower mold | type 10 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 used by being embedded in the lower mold 10, a sheet heater used by being in contact with the outer side of the lower mold 10, an infrared heating device, a high frequency induction heating device, or the like can be used.

  Hereinafter, each step will be described in order according to the flowchart shown in FIG.

  First, the lower mold 10 is heated to a predetermined temperature in advance (step S21). If the temperature of the lower mold 10 is too low, large wrinkles may occur on the lower surface of the glass gob (contact surface with the lower mold 10), and cracks and cans may occur due to rapid cooling. On the other hand, if the temperature is excessively high, fusion between the glass and the lower mold 10 may occur or the life of the molding die may be shortened. By doing so, an air pocket may remain in the glass gob. Actually, the appropriate temperature varies depending on various conditions such as glass type, shape, size, mold material, size, position of heater and 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 molten glass droplet 50 is dropped on the lower mold 10 (step S22). The melting tank 62 provided above the lower mold 10 is heated by a heater (not shown), and a molten glass 61 is stored therein. A nozzle 63 is provided in the lower part of the melting tank 62, and the glass 61 in a molten state passes through a flow path provided in the nozzle 63 by its own weight, and accumulates at the tip portion by surface tension. When a certain amount of molten glass accumulates at the tip of the nozzle 63, it naturally separates from the tip of the nozzle 63, and a certain amount of molten glass droplet 50 is dropped downward (see FIG. 7).

  In general, the mass of the molten glass droplet 50 to be dropped can be adjusted by the outer diameter of the tip of the nozzle 63, and depending on the type of glass, etc., about 0.1 to 2 g of molten glass droplet can be dropped. it can. Moreover, the dropping interval of the glass droplets can be adjusted by the inner diameter, length, heating temperature, and the like of the nozzle 63. 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, instead of dropping the molten glass droplet directly from the nozzle to the lower mold, the molten glass droplet dropped from the nozzle is collided with a member provided with a through-hole, and a part of the collided molten glass droplet is formed as a micro droplet. You may make it pass through a through-hole and it is dripped at a lower mold | type. Thereby, it becomes possible to manufacture a finer glass gob. This method is described in detail in JP-A No. 2002-154834.

  Next, the dropped molten glass droplet 50 is cooled and solidified on the lower mold 10 (step S23) (see FIG. 8). By leaving on the lower mold 10 for a predetermined time, the molten glass droplet 50 is cooled and solidified by heat radiation to the lower mold 10 and surrounding air. Since the hole 12 is provided in the central portion of the receiving surface 11 of the lower mold 10, no air pool is generated in the solidified glass gob 54.

  Thereafter, the solidified glass gob 54 is collected (step S24), and the production of the glass gob is completed. The glass gob 54 can be collected using, for example, a known collection device using vacuum adsorption. Furthermore, what is necessary is just to repeat the process after process S22, when manufacturing a glass gob succeedingly.

  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.

(Manufacturing method of glass molding)
The manufacturing method of the glass forming body of this invention is demonstrated referring FIGS. 9-11. FIG. 9 is a flowchart showing an example of a method for producing a glass molded body. FIG. 10 and FIG. 11 are schematic views for explaining a method for producing a glass molded body in the present embodiment. FIG. 10 shows the state in the step (S33) of dropping the molten glass droplet on the lower mold, and FIG. 11 shows the state in the step (S35) of pressurizing the dropped molten glass droplet with the lower mold and the upper mold. Yes.

  The lower mold 10 is the same as that described with reference to FIGS. The upper mold 60 is made of the same material as that of the lower mold 10 and has a molding surface 64 for pressing the molten glass droplet 50. However, unlike the lower mold 10, it is not necessary to provide holes on the molding surface 64.

  The lower mold 10 has a position (dropping position P1) for receiving the molten glass droplet 50 below the nozzle 63 and a position for pressing the molten glass droplet 50 facing the upper mold 60 (not shown). It is configured to be movable between the pressing position P2). Further, the upper mold 60 is configured to be movable in a direction (a vertical direction in the figure) in which a molten glass droplet is pressed between the upper mold 60 and a lower mold 10 by a driving unit (not shown).

  Hereinafter, each step will be described in order according to the flowchart shown in FIG.

  First, the lower mold 10 and the upper mold 60 are heated in advance to a predetermined temperature (step S31). The lower mold 10 and the upper mold 60 are configured to be heated to a predetermined temperature by a heating unit (not shown). It is preferable that the lower mold 10 and the upper mold 60 be configured to be able to independently control the temperature. The predetermined temperature is the same as that in step S21 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 10 and the upper mold 60 may be the same or different.

  Next, the lower mold | type 10 is moved to the dripping position P1 (process S32), and the molten glass droplet 50 is dripped from the nozzle 63 (process S33) (refer FIG. 10). About the conditions at the time of dripping the molten glass droplet 50, it is the same as that of the case of process S22 in the manufacturing method of the above-mentioned glass gob.

  Next, the lower mold 10 is moved to the pressing position P2 (step S34), the upper mold 60 is moved downward, and the molten glass droplet 50 is pressurized with the lower mold 10 and the upper mold 60 (process S35) ( FIG. 11).

  The molten glass droplet 50 is cooled and solidified by heat radiation from the contact surface with the lower mold 10 and the upper mold 60 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 mold 60 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 60 is moved upward and retracted, the solidified glass molded body 55 is recovered (step S36), and the production of the glass molded body is completed. Since the hole 12 is provided in the central portion of the receiving surface 11 of the lower mold 10, no air pool is generated in the obtained glass molded body 55. Then, when manufacturing a glass molded object succeedingly, the lower mold | type 10 is again moved to the dripping position P1 (process S32), and the subsequent processes should just 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 10 and the upper mold 60 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.

It is a figure which shows typically the state of the molten glass droplet 50 dripped at the lower mold | type 10. FIG. It is a figure which shows the modification of the lower mold | type 10 which has the hole 12. FIG. It is a figure which shows the lower mold | type 20 of another embodiment of this invention. It is a figure which shows the lower mold | type 30 of another embodiment of this invention. 5 is a diagram illustrating an example of a method for producing a porous film 32. FIG. It is a flowchart which shows one example of the manufacturing method of a glass gob. It is a figure which shows the process (S22) to which a molten glass droplet is dripped at a lower mold | type. It is a figure which shows the process (S23) which cools and solidifies the dripped molten glass drop on a lower mold | type. It is a flowchart which shows one example of the manufacturing method of a glass forming body. It is a figure which shows the process (S33) of dripping a molten glass droplet to a lower mold | type. It is a figure which shows the process (S35) which pressurizes the dripped molten glass droplet with a lower mold | type and an upper mold | type. It is a figure which shows typically the state of the molten glass droplet 50 dripped at the conventional lower mold | type 70. As shown in FIG.

Explanation of symbols

10, 20, 30 Lower mold 11, 21, 31 Receiving surface 12 Hole 22 Recessed groove 32 Porous film 50 Molten glass droplet 51 Recessed portion 54 Glass gob 55 Glass molded body 60 Upper mold 63 Nozzle P1 Dropping position P2 Pressure position

Claims (6)

In the lower mold having a receiving surface for receiving molten glass droplets dripping from above,
The lower mold | type provided with the buffer space for releasing the air which entered into the recessed part of the said molten glass droplet formed by the collision with the said receiving surface from this recessed part.   The lower mold according to claim 1, wherein the buffer space is a hole formed in the receiving surface.   The lower mold according to claim 1, wherein the buffer space is a concave groove formed in the receiving surface. The buffer space is a porous film formed on the receiving surface,
The lower mold according to claim 1, wherein the porous film has an arithmetic average roughness (Ra) of 1 nm to 100 nm and a porosity of 20% to 50%. Dropping molten glass droplets on the lower mold; and
A step of cooling and solidifying the molten glass droplet dropped on the lower mold,
The method for manufacturing a glass gob, wherein the lower mold is the lower mold according to any one of claims 1 to 4. Dropping molten glass droplets on the lower mold; and
In the method for producing a glass molded body, the step of pressure-molding the dropped molten glass droplets with the lower mold and the upper mold facing the lower mold,
The method for producing a glass molded body, wherein the lower mold is the lower mold according to any one of claims 1 to 4.

Images