JPWO2009060718A1 - Lower mold manufacturing method, lower mold, glass gob manufacturing method, and glass molded body manufacturing method - Google Patents

Abstract

In a lower mold manufacturing method for receiving molten glass droplets dropped from above, a film forming step of forming a coating layer including a blocking layer and a surface layer formed on the blocking layer on a substrate; A roughening step of roughening the surface of the coating layer by etching, and the surface layer has a higher etching rate in the roughening step than the blocking layer. Thus, it is possible to satisfactorily prevent the occurrence of air accumulation without narrowing the choice of lower mold material, and to provide a lower mold manufacturing method with excellent durability.

Description

  The present invention relates to a lower mold manufacturing method for receiving molten glass droplets dropped from above, a lower mold manufactured by the manufacturing method, a glass gob manufacturing method using the lower mold, and a glass molded body manufacturing method.

  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 mechanical processing such as grinding and polishing, but there is a problem that the production of glass preforms by mechanical processing 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 molten glass droplets on 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 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 a glass molded body, the bottom of the molten glass droplet (contact surface with the lower mold) is finely formed near the center due to collision with the lower mold. Recesses are formed. The air that has entered the recess has no escape, and the molten glass droplet is confined until it cools and solidifies, leaving a recess (air reservoir) on the lower surface of the manufactured glass preform or glass molded body. There was a problem that.

  In order to address this problem, the surface of the lower mold is roughened (Rmax is 0.05 μm to 0.2 μm) to prevent air from remaining by securing a flow path for air 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 pressure molding glass, it is difficult to react with glass at high temperatures, a mirror surface can be obtained, workability is good, it is hard, and it is brittle. It is necessary to satisfy many conditions such as not being. 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 for these materials having properties preferable as a molding die to be uniformly roughened so that the surface has a predetermined surface roughness by general wet etching or dry etching. 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 lower mold has poor durability and is stable. There was a problem that it could not be manufactured.

  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 to be excellent in durability. It is to provide a lower mold and a manufacturing method thereof. Another object of the present invention is to provide a glass gob production method capable of stably producing a glass gob without an air pool, and to stably produce a glass molded body without an air pool. 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. In a lower mold manufacturing method for receiving molten glass droplets dropped from above, a film forming step of forming a covering layer including a blocking layer and a surface layer formed on the blocking layer on a substrate; And a roughening step of roughening the surface of the coating layer by etching, wherein the surface layer has a higher etching rate in the roughening step than the blocking layer. Lower mold manufacturing method.

  2. 2. The method for manufacturing a lower mold according to 1 above, wherein, in the roughening step, the etching rate of the surface layer is 1.5 times or more and 10 times or less of the etching rate of the blocking layer.

  3. The film formation step is a step of forming the coating layer by a sputtering method, and the film formation condition when forming the surface layer is more than the film formation condition when forming the blocking layer. 3. The method for manufacturing a lower mold according to 1 or 2 above, wherein the energy of the sputtered particles reaching the film forming surface is reduced.

  4). 4. The lower die manufacturing method according to 3 above, wherein a film forming condition for forming the surface layer is higher in sputtering gas pressure than a film forming condition for forming the blocking layer. .

  5. 5. The lower mold manufacturing method according to claim 1, wherein the blocking layer and the surface layer include at least one element of chromium, aluminum, and titanium.

  6). 6. The method for manufacturing a lower mold according to any one of 1 to 5, wherein the blocking layer and the surface layer are made of the same constituent element.

  7. 7. The lower mold manufacturing method according to 6, wherein the blocking layer and the surface layer are continuously formed while continuously changing the film forming conditions.

  8). The roughening step is a step of setting the arithmetic average roughness (Ra) of the surface of the coating layer to 0.01 μm to 0.2 μm, and setting the average length (RSm) of the roughness curve elements to 0.5 μm or less. The method for manufacturing a lower mold according to any one of the above 1 to 7, wherein the method is provided.

  9. In the manufacturing method of the glass gob which has the process of dripping a molten glass drop to a lower mold, and the process of cooling and solidifying the dropped molten glass drop on the lower mold, the lower mold is the above 1-8 A method for producing a glass gob, wherein the glass gob is produced by the method for producing a lower die according to any one of the above.

  10. 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 | type is a lower mold | type manufactured by the manufacturing method of the lower mold | type of any one of said 1-8, The manufacturing method of the glass forming body characterized by the above-mentioned.

  11 A lower mold for receiving a molten glass droplet dripped from above, wherein the lower mold is manufactured by the method for manufacturing a lower mold described in any one of 1 to 8 above.

  According to the present invention, the surface of the coating layer provided on the lower mold substrate is roughened, so that the surface is uniformly roughened so that the surface has a predetermined surface roughness regardless of the material of the substrate. can do. In addition, since it has a blocking layer with a low etching rate during the roughening treatment under the surface layer, the adhesion between the coating layer and the substrate is strong, and the etching treatment may adversely affect the substrate. Nor. Therefore, it is possible to satisfactorily prevent the occurrence of air accumulation without narrowing the choice of lower mold material, and it is possible to manufacture a lower mold excellent in durability. Moreover, by using the lower mold manufactured by the lower mold manufacturing method of the present invention, it is possible to stably manufacture a glass gob or a glass molded body free from air accumulation.

It is a flowchart which shows an example of the manufacturing method of a lower mold | type. It is sectional drawing which shows the state of the lower mold | type in each process. It is a schematic diagram for demonstrating the meaning of an etching rate. It is a figure which shows an example of a structure of the sputtering device used by this embodiment. It is a schematic diagram which shows the arrangement | positioning state of the lower mold | type in a sputtering device, and the state of film thickness distribution. It is a figure which shows the state of the molten glass droplet 50 dripped at the lower mold | type 10. FIG. It is the schematic diagram which showed the detail of the C section of FIG.6 (b). 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Lower mold | type 11 Base material 12 Blocking layer 13 Surface layer 14 Covering layer 15 Molding surface 30 Sputtering device 31 Vacuum chamber 32 Sputtering electrode 33 Target 34 Shutter 35 Rotating shaft 36 Base material holder 37 Heater 50 Molten glass droplet 51 Recessed part 52 Lower surface 53 Gap 54 Glass Gob 55 Glass Molded Body 60 Upper Mold 63 Nozzle

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

  First, the manufacturing method of the lower mold | type in this embodiment is demonstrated using FIGS. FIG. 1 is a flowchart showing a method for manufacturing a lower mold in the present embodiment, and FIG. 2 is a cross-sectional view showing a state of the lower mold in each process. FIG. 3 is a schematic diagram for explaining the meaning of the etching rate. FIG. 4 is a diagram showing an example of the configuration of the sputtering apparatus used in the present embodiment, and FIG. 5 is a schematic diagram showing the arrangement state of the lower mold and the film thickness distribution in the sputtering apparatus.

(Base material)
In the lower mold base 11, a molding surface 15 having a predetermined shape corresponding to a glass molded body to be manufactured is processed in advance (FIG. 2A). In the present invention, since the roughening treatment is performed on the coating layer 14 formed on the base material 11, it is not necessary to roughen the base material 11 before forming the coating layer 14. Therefore, the material of the base material 11 can be selected without considering the ease of roughening and the durability when roughened.

  Therefore, the material of the base material 11 can be appropriately selected from materials known as lower mold materials for receiving molten glass droplets according to conditions. Examples of materials that can be preferably used include various heat-resistant alloys (such as stainless steel), cemented carbide materials mainly composed of tungsten carbide, various ceramics (such as silicon carbide and silicon nitride), and composite materials containing carbon. .

(Film formation process)
Next, the coating layer 14 is formed on the substrate 11 (film formation step). The coating layer 14 includes a blocking layer 12 and a surface layer 13. After forming the blocking layer 12 on the substrate 11 (S 11: FIG. 2B), the surface layer 13 is further formed on the blocking layer 12. A film is formed (S12: FIG. 2C).

  In general, when a surface roughening process is performed on a layer formed on a substrate by etching, the etching rate is relatively low in order to uniformly roughen the surface to have a predetermined surface roughness. It is necessary to be a large layer in which minute irregularities are easily formed by etching. However, when etching is performed by providing a layer having a high etching rate directly on the substrate, the durability of the roughened layer is very poor, and peeling occurs easily. This is because the layer with a high etching rate often does not have sufficient adhesion between the substrate and the effect of etching reaches the substrate, further reducing the adhesion. Conceivable.

  Therefore, in the present invention, the coating layer 14 is divided into two layers having different etching rates, a layer having a low etching rate is formed on the substrate 11 as the blocking layer 12, and then the etching rate is higher than that of the blocking layer 12. A large surface layer 13 is formed.

  With such a configuration, since the etching rate of the surface layer 13 is high, minute unevenness can be easily formed by etching, and uniform roughening is possible. In addition, the blocking layer 12 having a low etching rate originally has high adhesion to the base material, and the presence of the blocking layer 12 can prevent the influence of etching from reaching the base material 11, so that it has excellent durability. The lower mold 10 can be manufactured.

  As for the degree of the etching rate difference between the surface layer 13 and the blocking layer 12, the etching rate of the surface layer 13 is particularly preferably 1.5 times or more and 10 times or less than the etching rate of the blocking layer 12. Outside this range, it becomes difficult to balance the etching of the surface layer 13 and the etching of the blocking layer 12, and the influence of the etching may reach the base material 11, and the unevenness due to the etching is maintained at an optimum roughness. It becomes difficult to do.

  Here, the meaning of the etching rate in this specification will be described with reference to FIG. The diagram on the left side of FIG. 3 shows an initial state before etching, and a film 22 is formed on the substrate 21. The diagram on the right side shows a state after etching is performed for the processing time t. At this time, the etching rate is obtained by dividing the etching amount A (the reduction amount of the thickness of the film 22) by the processing time t. Note that fine irregularities are formed on the surface of the film 22 by etching, but an average line 23 of irregularities is used for calculating the etching rate.

  Various materials can be used for the blocking layer 12 and the surface layer 13. For example, various metals (such as chromium, aluminum, and titanium), nitrides (such as chromium nitride, aluminum nitride, titanium nitride, and boron nitride), oxides (such as chromium oxide, aluminum oxide, and titanium oxide) can be used. .

  Among these, it is particularly preferable that at least one element of chromium, aluminum, and titanium is included. Films containing these elements are not only advantageous in that they can be easily formed and can be easily roughened by etching, but the surface is oxidized by heating in the atmosphere, resulting in 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.

  Moreover, it is particularly preferable that the blocking layer 12 and the surface layer 13 are made of the same constituent elements. By doing so, not only film formation becomes easy, but also the adhesion between the blocking layer 12 and the surface layer 13 can be made extremely strong, and a lower mold having excellent durability can be manufactured.

  There is no restriction | limiting in the film-forming method of the blocking layer 12 and the surface layer 13, What is necessary is just to select suitably from well-known film-forming methods, and to use. For example, a vacuum deposition method, a sputtering method, a CVD method, and the like can be given. Among these, the sputtering method is a particularly preferable method because it is easy to continuously form the blocking layer 12 having a low etching rate and the surface layer 13 having a high etching rate by changing the film forming conditions. .

  FIG. 4 is a diagram showing an example of the configuration of the sputtering apparatus used in the present embodiment, and shows the configuration of a parallel plate type sputtering apparatus 30.

  The base material 11 is held by the base material holder 36 at the top of the vacuum chamber 31 with the film formation surface facing downward. Further, a target 33 which is a material of the blocking layer 12 and the surface layer 13 is attached to the sputter electrode 32 connected to the power source 38, and the inside of the vacuum chamber 31 is exhausted by the exhaust pump 42 connected to the vacuum chamber 31 via the valve 41. Is exhausted to a predetermined degree of vacuum. At this time, the substrate 11 is heated to a predetermined temperature by the heater 37 provided in the substrate holder 36. After the inside of the vacuum chamber 31 is evacuated to a predetermined degree of vacuum, a sputtering gas is introduced from the gas cylinder 44 through the flow rate adjusting valve 43 to set the inside of the vacuum chamber 31 to a predetermined pressure, and the power source 38 applies a predetermined pressure to the sputter electrode 32. A voltage is applied to generate plasma near the upper surface of the target 33. Thereby, ions of the sputtering gas collide with the target 33, and the constituent elements of the target are repelled as sputtered particles. Then, when the rotating shaft 35 is rotated and the shutter 34 is retracted from above the target 33, the sputtered particles repelled by the collision of ions reach the upper substrate 11 and deposit, and a film is formed on the film formation surface. It is formed.

  It is also possible to use an apparatus that includes a plurality of sputter electrodes 32 and targets 33 and can form films of different types in order or simultaneously.

  The inventor has found that the etching rate of the formed film varies depending on the energy level of the sputtered particles reaching the film formation surface. That is, the etching rate increases as the energy of the sputtered particles reaching the film formation surface decreases, and the etching rate decreases as the energy of the sputtered particles increases. Accordingly, in the film forming process, first, after forming the film under the condition that the energy of the sputtered particles reaching the film forming surface is large, the film forming condition is changed, and the film is formed under the condition of the low energy of the sputtered particle. Thus, the blocking layer 12 and the surface layer 13 can be formed. According to this method, it is possible to form the blocking layer 12 having a low etching rate and the surface layer 13 having a high etching rate only by changing the film forming conditions without changing materials and equipment.

  Examples of film formation conditions that affect the energy of sputtered particles that reach the film formation surface include the pressure of the sputtering gas during film formation, the distance between the target 33 and the film formation surface, and the power applied to the sputter electrode 32. It is done.

  When the pressure P of the sputtering gas increases, the mean free path of the sputtered particles becomes shorter, and the average number of times the sputtered particles collide with the sputtered gas particles before reaching the film forming surface increases. Has less energy. Therefore, the etching rate of the formed film is increased. On the other hand, when the pressure P of the sputtering gas decreases, the energy of the sputtered particles that reach the film formation surface increases and the etching rate of the formed film decreases. The pressure P of the sputtering gas when forming the surface layer 13 is preferably 0.5 Pa or more, and more preferably 1 Pa or more.

  When the distance between the target 33 and the film formation surface (D in FIG. 4) is increased, the average number of times the sputtered particles collide with the sputter gas particles before reaching the film formation surface increases, and thus the film formation surface is reached. The energy possessed by the sputtered particles is reduced. Therefore, the etching rate of the formed film is increased. Conversely, when the distance (D) between the target 33 and the film formation surface is shortened, the energy of the sputtered particles that reach the film formation surface increases, and the etching rate of the formed film decreases.

  In general, a film having better adhesion can be obtained when the distance (D) between the target 33 and the film formation surface is short. However, if the distance D is too short, the film thickness distribution on the film formation surface becomes large. Come. For this reason, the distance (D) between the target 33 and the film formation surface is preferably 50 mm to 200 mm.

  When the power applied to the sputter electrode 32 is reduced, the energy of ions that collide with the target 33 is reduced, so that the energy of sputtered particles that are repelled by the collision is also reduced. Therefore, the etching rate of the formed film is increased. Conversely, when the power applied to the sputter electrode 32 increases, the energy of the sputtered particles increases and the etching rate of the formed film decreases.

  Among these film forming conditions, the method of changing the sputtering gas pressure is particularly preferable because the conditions can be easily changed and the effect of differentiating the etching rate is great.

  Further, it is more preferable that the blocking layer 12 and the surface layer 13 are continuously formed while continuously changing the film forming conditions. As a result, the lower die 10 having a particularly strong adhesion between the blocking layer 12 and the surface layer 13 and having excellent durability can be manufactured.

  The thickness of the surface layer 13 only needs to be large enough to form minute irregularities by etching, and is usually preferably 0.05 μm or more. The thickness of the blocking layer 12 is preferably 0.05 μm or more in order to effectively prevent the influence of etching from reaching the substrate. Conversely, if the blocking layer 12 or the surface layer 13 is too thick, defects such as film peeling may easily occur. Therefore, the overall thickness of the coating layer 14 is preferably 0.05 μm to 5 μm, and particularly preferably 0.1 μm to 1 μm.

  When a plurality of base materials 11 are arranged on the base material holder 36 and are simultaneously formed, the film thickness distribution of the coating layer 14 may be a problem. For example, when the base materials 11a, 11b, and 11c are disposed as shown in FIG. 5A, the film thickness distribution of the coating layer 14 formed on the base material 11a disposed vertically above the center of the target 33. There is no problem. However, the coating layer 14 formed on the base materials 11b and 11c disposed at a position deviated from the vertically upper portion of the center of the target 33 is biased, and the shape of the precisely processed molding surface 15 is lost. There is a risk of it.

In order to prevent such an uneven thickness of the coating layer 14, when the base materials 11 b and 11 c are arranged at a position deviated from the vertically upper portion of the center portion of the target 33, as shown in FIG. It is preferable that the target 33 is disposed so as to be inclined toward the central portion. When the distance between the target 33 and the film formation surface is D and the amount of horizontal displacement of the base material 11b from the center of the target 33 is B, the inclination angle θ of the base material 11b is tan ⁻¹ (B / D) is particularly preferred.

  Furthermore, in the present embodiment, the case where the coating layer 14 is composed of only two layers of the blocking layer 12 and the surface layer 13 has been described as an example. However, the coating layer 14 has a multilayer structure composed of three or more layers. You may do it. For example, in order to improve the adhesion of the coating layer 14, another layer (underlayer) may be provided under the blocking layer 12, or on the coating layer 14 on which irregularities are formed by the roughening treatment, A protective layer for protecting the surface may be further provided.

(Roughening process)
Next, the surface of the coating layer 14 is roughened by etching (roughening step S13) (FIG. 2D). As described above, in the present invention, since the blocking layer 12 with a low etching rate is provided under the surface layer 13 with a high etching rate, minute irregularities can be easily formed by etching, and the influence of etching is based. It can prevent reaching to the material 11.

  Etching may be wet etching using a liquid or dry etching using a reactive gas or the like. Among these, wet etching using a liquid is preferable because it does not require expensive equipment and can easily form uniform unevenness.

  Wet etching is a method in which a reactive etching solution is brought into contact with the coating layer 14 to react to form irregularities. The coating layer 14 may be immersed in the stored etching solution, or a predetermined amount of etching solution may be supplied onto the coating layer 14. Moreover, the method of spraying etching liquid in the spray form may be used.

  As the etchant, a known etchant corresponding to the material of the coating layer 14 may be selected as appropriate. When the coating layer 14 is aluminum, the etching liquid which can be preferably used for aluminum, such as various acidic solutions, is marketed. Even when the coating layer 14 is titanium, an etchant that can be preferably used for titanium is commercially available. For example, an etching solution mainly containing a reducing acid such as hydrochloric acid or sulfuric acid can be used.

  Similarly, when the coating layer 14 is chromium, an etching solution that can be preferably used for chromium is commercially available. For example, an acidic solution containing ceric ammonium nitrate can be used. An alkaline solution containing potassium ferricyanide and potassium hydroxide can also be used.

  The etching is preferably performed so that the arithmetic average roughness (Ra) of the surface of the coating layer 14 is 0.01 μm to 0.2 μm, and the average length (RSm) of the roughness curve elements is 0.5 μm or less. . By making the arithmetic average roughness (Ra) and the average length of the roughness curve element (RSm) in such a range, it is possible to more effectively prevent the occurrence of air accumulation in the manufactured glass gob or glass molded body. Can do.

  The arithmetic average roughness (Ra) and the average length of the roughness curve element (RSm) are roughness parameters defined in JIS B 0601: 2001. In the present invention, these parameters are measured using a measuring instrument having a spatial resolution of 0.1 μm or less, such as an AFM (Atomic Force Microscope). A general stylus type roughness measuring machine is not preferable because the radius of curvature of the stylus tip is as large as several μm or more.

  Here, the reason why it is possible to prevent the occurrence of air accumulation in the glass gob or the glass molded body by roughening the coating layer 14 by etching will be described with reference to FIGS.

  FIG. 6 is a view showing a state of the molten glass droplet 50 dropped on the lower mold 10. FIG. 6A shows a state at the moment when the molten glass droplet 50 collides with the lower mold 10, and FIG. 6B shows a state where the molten glass droplet 50 is rounded by the surface tension thereafter.

  As shown in FIG. 6A, the molten glass droplet 50 at the moment of collision with the lower mold 10 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 generated near the center of the lower surface (the surface in contact with the coating layer 14). 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 10, the glass of the portion that first collides with the lower mold 10 is rebounded. It is thought that the concave portion 51 is generated by rebounding upward.

  The molten glass droplet 50 is then deformed into a round shape by the action of surface tension, as shown in FIG. At this time, if the coating layer 14 is not roughened, the lower surface of the molten glass droplet 50 and the coating layer 14 are in close contact with each other, and there is no escape route for the air accumulated in the recess 51. The recess 51 remains as an air pool without disappearing.

  However, the coating layer 14 of the lower mold 10 in this embodiment is roughened by etching after the coating layer 14 is formed. Therefore, a gap remains between the lower surface of the molten glass droplet 50 and the coating layer 14, and when the molten glass droplet 50 is deformed round by the action of surface tension, air accumulated in the recess 51 escapes through the gap. Thus, the recess 51 disappears.

  The state of the gap generated between the lower surface of the molten glass droplet 50 and the coating layer 14 will be described in more detail with reference to FIG. FIG. 7 is a schematic diagram showing details of the part C in FIG. As shown in FIG. 7A, unevenness is formed on the surface of the coating layer 14 by etching. The lower surface 52 of the dropped molten glass droplet 50 does not completely enter the concave and convex valleys on the surface of the coating layer 14 due to the action of surface tension, and a gap 53 remains. The gap 53 becomes an escape path for the air accumulated in the recess 51, and the recess 51 disappears.

  FIG. 7B shows a case where the unevenness period of the coating layer 14 is the same, but the height of the unevenness is higher than that in FIG. When the unevenness is high in this manner, a sufficiently large gap 53 is formed and the recess 51 easily disappears, but large unevenness is also formed on the lower surface 52 of the molten glass droplet 50, and the obtained glass gob or glass molded body is obtained. The surface roughness of the film may become too large. On the other hand, if the height of the unevenness of the coating layer 14 is too low, the glass enters a considerable portion of the valley of the unevenness, and the recess 51 is completely disappeared without forming a sufficiently large gap 53. May remain. Therefore, it is preferable that the surface of the coating layer 14 has an arithmetic average roughness (Ra) of 0.01 μm to 0.2 μm.

  In addition, the period of unevenness affects the occurrence of air accumulation. FIG. 7C shows a case where the height of the unevenness on the surface of the coating layer 14 is the same as that in FIG. Thus, even if the height of the unevenness is the same, the glass enters the bottom of the uneven valley when the period is long, so that a sufficiently large gap 53 is not formed, and the recess 51 is completely formed. May remain without disappearing. Therefore, the average length (RSm) of the roughness curve element on the surface of the coating layer 14 is preferably 0.5 μm or less.

  Note that the entire surface of the coating layer 14 does not need to be roughened by etching, and at least a region in contact with the molten glass droplet 50 may be roughened.

(Glass gob manufacturing method)
The manufacturing method of the glass gob of this invention is demonstrated referring FIGS. 8-10. FIG. 8 is a flowchart showing an example of a glass gob manufacturing method. 9 and 10 are schematic views for explaining the glass gob manufacturing method according to this embodiment. FIG. 9 shows the state in the step (S22) of dropping the molten glass droplet on the lower mold, and FIG. 10 shows the state in the step (S23) of cooling and solidifying the dropped molten glass droplet on the lower mold. Yes.

  As described above, the lower mold 10 is provided with the covering layer 14 including the blocking layer 12 and the surface layer 13 on the substrate 11, and the surface of the covering layer 14 is roughened by etching.

  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 that is used by being embedded inside the member to be heated, a sheet heater that is used while being in contact with the outside of the member to be heated, 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 pool may remain in the glass gob. Actually, the appropriate temperature varies depending on various conditions such as glass type, shape, size, mold material, size, heater and temperature sensor position, 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. 9).

  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 a micro droplet. Alternatively, it may be dropped through the through mold through the through-hole. 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. 10). 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 surface of the coating layer 14 of the lower mold 10 has been subjected to a predetermined roughening treatment, no air accumulation occurs in the solidified glass gob 54.

  Thereafter, the solidified glass gob 54 is recovered (step S24), and the glass gob manufacturing is completed. The glass gob 54 can be collected using, for example, a known collection device using vacuum suction. 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 for manufacture of various precision optical elements by the reheat press method.

(Manufacturing method of glass molding)
The manufacturing method of the glass forming body of this invention is demonstrated referring FIGS. 11-13. FIG. 11 is a flowchart showing an example of a method for producing a glass molded body. FIG. 12 and FIG. 13 are schematic views for explaining a method for producing a glass molded body in the present embodiment. FIG. 12 shows the state in the step (S33) of dropping the molten glass droplet on the lower mold, and FIG. 13 shows the state in the step (S35) of pressing the dropped molten glass droplet with the lower mold and the upper mold. Yes.

  The lower mold 10 is the same as that described in FIGS. The upper mold 60 is made of the same material as the base 11 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 a coating layer on the molding surface 64 and perform the roughening treatment.

  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. 12). 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) ( (See FIG. 13).

  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 the pressure is released, the pressure is released after cooling to a temperature at which the shape of the transfer surface formed on the glass molded body does not collapse. 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 the glass Tg.

  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 surface of the coating layer 14 of the lower mold 10 has been subjected to a predetermined roughening treatment, no air accumulation occurs in the obtained glass molded body. Thereafter, when the glass molded body is subsequently manufactured, the lower mold 10 is moved again to the dropping position P1 (step S32), 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 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.

  Hereinafter, although the Example performed in order to confirm the effect of this invention is described, this invention is not limited to these.

(Lower mold: Example 1)
The lower mold was manufactured according to the flowchart shown in FIG. The material of the base material 11 was silicon carbide (SiC), and the material of the blocking layer 12 and the surface layer 13 was chromium (Cr). The blocking layer 12 and the surface layer 13 were formed by sputtering. The sputtering apparatus used was a parallel plate type sputtering apparatus shown in FIG. The target 33 was a chromium target having a diameter of 152 mm (6 inches), and the distance (D) between the target 33 and the film formation surface was 65 mm.

The base material 11 was set in the base material holder 36, and the vacuum chamber 31 was evacuated to a high vacuum of 10 ⁻³ Pa while the base material was heated to 350 ° C. by the heater 37. Thereafter, argon gas was introduced as a sputtering gas to 0.33 Pa, and a high frequency power of 500 W was applied to form a 0.35 μm chromium film (blocking layer 12). The argon gas pressure was gradually changed from 0.33 Pa to 0.99 Pa over about 1 minute with the high frequency power applied, and then a 0.35 μm chromium film (surface layer 13) was formed.

  Next, the surface of the coating layer 14 was immersed in an etching solution to perform a roughening treatment. As the etching solution, a commercially available chromium etching solution (ECR-2 manufactured by Nacalai Tesque, Inc.) containing ceric ammonium nitrate was used. The arithmetic average roughness (Ra) of the surface of the coating layer 14 after etching was 0.01 μm, and the average length (RSm) of the roughness curve elements was 0.03 μm. The arithmetic average roughness (Ra) and the average length of the roughness curve element (RSm) were measured by AFM (D3100 manufactured by Digital Instruments).

  Moreover, the etching rate of the chromium film produced on the film-forming conditions of the said blocking layer 12 and the chromium film produced on the film-forming conditions of the said surface layer 13 was measured. The etching rate of the chromium film produced under the film formation conditions of the blocking layer 12 was 1 nm / min, and the etching rate of the chromium film produced under the film formation conditions of the surface layer 13 was 7.5 nm / min.

(Lower mold: Comparative example 1)
Using the same substrate as in Example 1, a chromium film was formed under the same conditions. However, the film forming conditions were not changed during the film formation of the chromium film, and the high pressure power of 500 W was applied while the argon gas pressure was fixed at 0.33 Pa to form a 0.7 μm chromium film. did.

  Thereafter, etching was performed under the same conditions as in Example 1. However, since the etching rate of the chromium film is small, it is not possible to form a sufficiently high unevenness, the arithmetic average roughness (Ra) is 0.002 μm, and the average length (RSm) of the roughness curve element is 1 μm. there were.

(Lower mold: Comparative example 2)
Using the same base material as in Example 1, a 0.7 μm chromium film was formed in the same manner as in Comparative Example 1. However, the pressure of argon gas was fixed at 0.99 Pa. Thereafter, etching was performed under the same conditions as in Example 1. The arithmetic average roughness (Ra) was 0.01 μm, and the average length (RSm) of the roughness curve elements was 0.03 μm.

(Lower mold: Example 2)
As in Example 1, the lower mold was manufactured according to the flowchart shown in FIG. The material of the base material 11 was tungsten carbide (WC), and the material of the blocking layer 12 and the surface layer 13 was chromium (Cr). In addition, a titanium nitride (TiN) film was formed as a base layer between the base material 11 and the blocking layer 12 to improve the adhesion of the coating layer 14. As the sputtering apparatus, an apparatus that includes two sputtering electrodes 32 and two targets 33 each and can perform two-way simultaneous sputtering was used. One target 33 was a titanium nitride target having a diameter of 152 mm (6 inches), and the other target 33 was a chromium target having a diameter of 152 mm (6 inches). The distance (D) between the target 33 and the film formation surface was 100 mm.

The base material 11 was set in the base material holder 36, and the vacuum chamber 31 was evacuated to a high vacuum of the order of 10 ⁻³ Pa while the base material was heated to 300 ° C. by the heater 37. Thereafter, Ar gas was introduced as a sputtering gas up to 0.33 Pa, and a high frequency power of 500 W was applied to the titanium nitride target to form a 0.2 μm titanium nitride film (underlayer). Thereafter, switching to the chromium target and applying high frequency power of 500 W, a 0.2 μm chromium film (blocking layer 12) was formed. The sputtering gas pressure was gradually changed from 0.33 Pa to 2.4 Pa over about 1 minute with the high frequency power applied, and then a 0.5 μm chromium film (surface layer 13) was further formed.

  Next, the surface of the coating layer 14 was immersed in an etching solution to perform a roughening treatment. As an etching solution, an alkaline solution containing potassium ferricyanide and potassium hydroxide was used. The arithmetic average roughness (Ra) of the surface of the coating layer 14 after the etching was 0.2 μm, and the average length (RSm) of the roughness curve elements was 0.5 μm.

  Moreover, the etching rate of the chromium film produced on the film-forming conditions of the said blocking layer 12 and the chromium film produced on the film-forming conditions of the said surface layer 13 was measured. The etching rate of the chromium film produced under the film formation conditions of the blocking layer 12 was 24 nm / min, and the etching rate of the chromium film produced under the film formation conditions of the surface layer 13 was 80 nm / min.

(Lower mold: Example 3)
As in Examples 1 and 2, the lower mold was manufactured according to the flowchart shown in FIG. The material of the base material 11 was tungsten carbide (WC), and the material of the blocking layer 12 and the surface layer 13 was chromium (Cr). In addition, a titanium (Ti) film was formed as a base layer between the base material 11 and the blocking layer 12 to improve the adhesion of the coating layer 14. As the sputtering apparatus, an apparatus capable of performing two-way simultaneous sputtering with two each of the electrode 32 and the target 33 was used. One target 33 was a titanium target having a diameter of 152 mm (6 inches), and the other target 33 was a chromium target having a diameter of 152 mm (6 inches). The distance (D) between the target 33 and the film formation surface was 165 mm.

The base material 11 was set in the base material holder 36, and the vacuum chamber 31 was evacuated to a high vacuum of 10 ⁻³ Pa while the base material was heated to 350 ° C. by the heater 37. Thereafter, Ar gas was introduced as a sputtering gas up to 0.06 Pa, high frequency power of 800 W was applied to the titanium target, and a 0.2 μm titanium film (underlayer) was formed. Immediately before the completion of the titanium film formation, 2.15 kW DC power was applied to the chromium target to start discharging, the shutter 34 was opened, and titanium and chromium were simultaneously sputtered for 10 seconds. Thereafter, the shutter 34 on the titanium target side was closed, and a 0.25 μm chromium film (blocking layer 12) was formed. After the formation of the blocking layer 12, the sputtering gas pressure is gradually changed from 0.06 Pa to 0.5 Pa and the DC power is gradually changed from 2.15 kW to 1.5 kW over about 1 minute, and then further changed to 0. A 5 μm chromium film (surface layer 13) was formed.

  Next, the surface of the coating layer 14 was immersed in an etching solution to perform a roughening treatment. As an etching solution, an alkaline solution containing potassium ferricyanide and potassium hydroxide was used. The arithmetic average roughness (Ra) of the surface of the coating layer 14 after etching was 0.1 μm, and the average length (RSm) of the roughness curve elements was 0.25 μm.

  Moreover, the etching rate of the chromium film produced on the film-forming conditions of the said blocking layer 12 and the chromium film produced on the film-forming conditions of the said surface layer 13 was measured. The etching rate of the chromium film produced under the film formation conditions of the blocking layer 12 was 15 nm / min, and the etching rate of the chromium film produced under the film formation conditions of the surface layer 13 was 40 nm / min.

(Lower mold: Example 4)
As in Example 1, the lower mold was manufactured according to the flowchart shown in FIG. The material of the base material 11 was tungsten carbide (WC), and the material of the blocking layer 12 and the surface layer 13 was chromium (Cr). In addition, a titanium nitride (TiN) film was formed as a base layer between the base material 11 and the blocking layer 12 to improve the adhesion of the coating layer 14. As the sputtering apparatus, an apparatus that includes two sputtering electrodes 32 and two targets 33 each and can perform two-way simultaneous sputtering was used. One target 33 was a titanium nitride target having a diameter of 152 mm (6 inches), and the other target 33 was a chromium target having a diameter of 152 mm (6 inches). The distance (D) between the target 33 and the film formation surface was 100 mm.

The base material 11 was set in the base material holder 36, and the vacuum chamber 31 was evacuated to a high vacuum of the order of 10 ⁻³ Pa while the base material was heated to 300 ° C. by the heater 37. Thereafter, Ar gas was introduced as a sputtering gas up to 0.33 Pa, and a high frequency power of 500 W was applied to the titanium nitride target to form a 0.2 μm titanium nitride film (underlayer). Thereafter, switching to the chromium target and applying high frequency power of 500 W, a 0.2 μm chromium film (blocking layer 12) was formed. The sputtering gas pressure was gradually changed from 0.33 Pa to 0.5 Pa over about 1 minute with the high frequency power applied, and then a 0.5 μm chromium film (surface layer 13) was formed.

  Next, the surface of the coating layer 14 was immersed in an etching solution to perform a roughening treatment. As an etching solution, an alkaline solution containing potassium ferricyanide and potassium hydroxide was used. The arithmetic average roughness (Ra) of the surface of the coating layer 14 after etching was 0.1 μm, and the average length (RSm) of the roughness curve elements was 0.2 μm.

  Moreover, the etching rate of the chromium film produced on the film-forming conditions of the said blocking layer 12 and the chromium film produced on the film-forming conditions of the said surface layer 13 was measured. The etching rate of the chromium film produced under the film forming conditions of the blocking layer 12 was 24 nm / min, and the etching rate of the chromium film produced under the film forming conditions of the surface layer 13 was 32 nm / min.

(Lower mold: Example 5)
As in Example 1, the lower mold was manufactured according to the flowchart shown in FIG. The material of the base material 11 was tungsten carbide (WC), and the material of the blocking layer 12 and the surface layer 13 was chromium (Cr). In addition, a titanium nitride (TiN) film was formed as a base layer between the base material 11 and the blocking layer 12 to improve the adhesion of the coating layer 14. As the sputtering apparatus, an apparatus that includes two sputtering electrodes 32 and two targets 33 each and can perform two-way simultaneous sputtering was used. One target 33 was a titanium nitride target having a diameter of 152 mm (6 inches), and the other target 33 was a chromium target having a diameter of 152 mm (6 inches). The distance (D) between the target 33 and the film formation surface was 100 mm.

The base material 11 was set in the base material holder 36, and the vacuum chamber 31 was evacuated to a high vacuum of the order of 10 ⁻³ Pa while the base material was heated to 300 ° C. by the heater 37. Thereafter, Ar gas was introduced as a sputtering gas up to 0.05 Pa, and a high frequency power of 500 W was applied to the titanium nitride target to form a 0.2 μm titanium nitride film (underlayer). Thereafter, switching to the chromium target and applying high frequency power of 500 W, a 0.2 μm chromium film (blocking layer 12) was formed. The sputtering gas pressure was gradually changed from 0.05 Pa to 3 Pa over about 1 minute with the high frequency power applied, and then a 0.5 μm chromium film (surface layer 13) was formed.

  Next, the surface of the coating layer 14 was immersed in an etching solution to perform a roughening treatment. As an etching solution, an alkaline solution containing potassium ferricyanide and potassium hydroxide was used. The arithmetic average roughness (Ra) of the surface of the coating layer 14 after the etching was 0.2 μm, and the average length (RSm) of the roughness curve elements was 0.5 μm.

  Moreover, the etching rate of the chromium film produced on the film-forming conditions of the said blocking layer 12 and the chromium film produced on the film-forming conditions of the said surface layer 13 was measured. The etching rate of the chromium film produced under the film formation conditions of the blocking layer 12 was 10 nm / min, and the etching rate of the chromium film produced under the film formation conditions of the surface layer 13 was 120 nm / min.

(Lower mold: Comparative example 3)
Using the same base material (WC) as in Examples 2 to 5, a lower mold was manufactured. However, the base layer surface was directly etched without forming the underlayer, blocking layer, and surface layer. However, the etching rate could not be appropriately controlled, and the arithmetic average roughness (Ra) of the rough surface was 0.4 μm, and the average length (RSm) of the roughness curve element was 0.6 μm.

(Lower mold: Comparative example 4)
Using the same base material as in Comparative Example 3, a chromium film was formed. A chromium target having a diameter of 152 mm (6 inches) was used as the target 33 of the sputtering apparatus. The distance (D) between the target 33 and the film formation surface was 65 mm.

The base material 11 was set in the base material holder 36, and the vacuum chamber 31 was evacuated to a high vacuum of 10 ⁻³ Pa while the base material was heated to 350 ° C. by the heater 37. Thereafter, Ar gas was introduced as a sputtering gas up to 0.5 Pa, and a high frequency power of 500 W was applied to the chromium target to form a 0.5 μm chromium film (blocking layer 12). The sputtering gas pressure was gradually changed from 0.5 Pa to 0.33 Pa over about 1 minute while high frequency power was applied, and then a 0.7 μm chromium film (surface layer 13) was formed.

  Next, the surface of the coating layer 14 was immersed in an etching solution to perform a roughening treatment. As an etching solution, an alkaline solution containing potassium ferricyanide and potassium hydroxide was used. By the time the etching process is finished and the desired unevenness is obtained, film peeling occurs from the blocking layer, and the arithmetic average roughness (Ra) of the surface of the coating layer 14 and the average length (RSm) of the roughness curve element can be measured. There wasn't.

  Moreover, the etching rate of the chromium film produced on the film-forming conditions of the said blocking layer 12 and the chromium film produced on the film-forming conditions of the said surface layer 13 was measured. The etching rate of the chromium film produced under the film forming conditions of the blocking layer 12 was 32 nm / min, and the etching rate of the chromium film produced under the film forming conditions of the surface layer 13 was 24 nm / min.

  The production conditions and measurement results of Examples 1 to 5 are summarized in Table 1, and the production conditions and measurement results of Comparative Examples 1 to 4 are summarized in Table 2.

(Manufacture of glass moldings)
A glass molded body was manufactured according to the flowchart shown in FIG. 11 using the lower mold 10 manufactured under the conditions of the above Examples 1 to 5 and Comparative Examples 1 to 3 in total. As the glass material, phosphoric acid glass having a Tg of 480 ° C. was used. The heating temperature in step S31 was 500 ° C for the lower mold 10 and 450 ° C for the upper mold 60. The temperature near the tip of the nozzle 63 was set to 1000 ° C., and about 190 mg of the molten glass droplet 50 was set to drop. The load at the time of pressurization was 1800N.

  About the glass molded object manufactured with each lower mold | type, the presence or absence of an air pool was evaluated by microscope observation. Evaluation was performed using samples manufactured at the 1000th, 5000th, and 10000th shots. When no air accumulation was observed in all the samples, it was excellent (◎), and the first shot where air accumulation was observed was 10000 shots. The case of the eye was particularly good (◯), the case of the 5000th shot was good (Δ), and the case of the 1000th shot was impossible (×).

  Moreover, the arithmetic mean roughness (Ra) of the surface was measured about the glass molded object manufactured with each lower mold | type similarly to the surface roughness measurement of the lower mold | type coating layer mentioned above. The evaluation is excellent when the measured value of arithmetic average roughness (Ra) of the surface is 0.01 μm or less (（), particularly good when it is 0.05 μm or less (◯), The case of 2 μm or less was judged as good (Δ), and the case of exceeding 0.2 μm was judged as impossible (×).

  Tables 1 and 2 show the evaluation results of the air reservoir and the arithmetic average roughness (Ra) of the molded product.

  In any of Examples 1 to 5, the occurrence of air accumulation in the glass molded body and the arithmetic average roughness (Ra) are good (Δ) or more, and it is confirmed that the effects of the present invention are exhibited. It was done. However, since the lower mold of Comparative Example 1 does not have sufficient unevenness on the surface, the arithmetic average roughness (Ra) of the molded product was excellent (◎), but the air pool was not possible (×). there were. On the contrary, the lower mold of Comparative Example 2 was too uneven, and the air accumulation was good (Δ), but the arithmetic average roughness (Ra) of the molded product was not possible (×).

  In the lower mold of Comparative Example 3, since the base material was etched without providing the coating layer, the unevenness could not be adjusted appropriately, and became too large, and the arithmetic average roughness (Ra) of the molded product became impossible (x). Yes. In the lower mold of Comparative Example 4, the surface layer has an etching rate larger than that of the blocking layer, and the blocking layer does not function as the blocking layer, and the coating layer is peeled off during processing, which is not possible.

  In the lower mold of Example 4, the etching rate of the surface layer is about 1.3 times the etching rate of the blocking layer. In the lower mold of Example 5, the etching rate of the surface layer is about 12 times the etching rate of the blocking layer. In any case, the occurrence of air accumulation in the glass molded body and the arithmetic average roughness (Ra) were good (Δ) or more, and it was confirmed that the effects of the present invention were exhibited. However, in any of the lower molds, it becomes difficult to balance the etching of the surface layer and the blocking layer, and it is difficult to maintain the unevenness at an optimum roughness in a range where the influence of etching does not reach the base material. Compared with, the evaluation of air accumulation remains good (Δ).

Claims (11)

In the lower mold manufacturing method for receiving molten glass droplets dripped from above,
A film forming step of forming a coating layer including a blocking layer and a surface layer formed on the blocking layer on the substrate;
A roughening step of roughening the surface of the coating layer by etching,
The manufacturing method of the lower mold | type characterized by the said surface layer having a larger etching rate in the said roughening process than the said blocking layer.   2. The lower die manufacturing method according to claim 1, wherein, in the roughening step, the etching rate of the surface layer is 1.5 to 10 times the etching rate of the blocking layer. Method. The film forming step is a step of forming the coating layer by sputtering.
The film formation condition when forming the surface layer is characterized in that the energy of the sputtered particles reaching the film formation surface is smaller than the film formation condition when forming the blocking layer. A method for manufacturing a lower mold according to claim 1 or claim 2.   The film forming condition for forming the surface layer is lower than the film forming condition for forming the blocking layer, wherein the sputtering gas pressure is higher. Mold manufacturing method.   The underlayer according to any one of claims 1 to 4, wherein the blocking layer and the surface layer contain at least one element of chromium, aluminum, and titanium. Mold manufacturing method.   The method for manufacturing a lower mold according to any one of claims 1 to 5, wherein the blocking layer and the surface layer are made of the same constituent elements.   7. The lower mold manufacturing method according to claim 6, wherein the blocking layer and the surface layer are continuously formed while continuously changing the film forming conditions.   The roughening step is a step of setting the arithmetic average roughness (Ra) of the surface of the coating layer to 0.01 μm to 0.2 μm, and setting the average length (RSm) of the roughness curve elements to 0.5 μm or less. The method for manufacturing a lower mold according to any one of claims 1 to 7, wherein the method is provided. 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 producing a glass gob, wherein the lower die is a lower die produced by the method for producing a lower die according to any one of claims 1 to 8. 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 die is a lower die produced by the method for producing a lower die according to any one of claims 1 to 8. In the lower mold for receiving molten glass droplets dripped from above,
A lower mold manufactured by the method for manufacturing a lower mold according to any one of claims 1 to 8.