JP5131147B2 - Method for producing mold, method for producing glass gob, and method for producing glass molded body - Google Patents

Description

  The present invention relates to a mold manufacturing method for manufacturing a glass gob or a glass molded body, a glass gob manufacturing method using the mold manufactured by the manufacturing method, 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 pressure molding a glass material with a molding die is widely used.

  As one method 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 and molded together with a molding die (hereinafter referred to as “reheat”). Also known as “pressing method”). Conventionally, glass preforms used in such a reheat press method have been manufactured by machining such as grinding and polishing. However, there is a problem that production of glass preforms by machining requires a great deal of labor and time. It was. For this reason, studies are being made on a method of receiving a molten glass droplet dropped from a dropping nozzle or the like with a lower mold to produce a glass gob (glass lump) and directly using it as a glass preform (gob preform).

  On the other hand, as another method for producing a glass molded body, a dropped glass melt is received by a lower mold, and the received molten glass droplet is pressure-formed by a lower mold and an upper mold to obtain a glass molded body (hereinafter referred to as a glass molded body). , Also referred to as “droplet forming method”). 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 glass gob is manufactured or a glass molded body is manufactured by a droplet forming method, when the dropped molten glass droplet is received by the lower mold, the lower surface of the manufactured glass gob or glass molded body (contact surface with the lower mold) In addition, there is a problem that air pockets remain. This problem will be described with reference to FIG. FIG. 17 is a schematic diagram showing a state of molten glass droplet 50 received by lower mold 10 by a conventional method. FIG. 17A shows a state at the moment when the molten glass droplet 50 collides with the lower mold 10, and FIG. 17B shows a state after the molten glass droplet 50 is deformed by the surface tension thereafter. Yes.

  As shown in FIG. 17A, 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 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 lower mold 10). The mechanism by which such a recess 51 is generated is not necessarily clear, but according to an analysis using simulation or the like, when the molten glass droplet 50 collides with the lower mold 10, the glass in the portion that first collides with the lower mold 10. It is thought that this is caused by a recoil that bounces upward. Thereafter, the molten glass droplet 50 is deformed into a round shape by the action of the surface tension, as shown in FIG. At this time, the lower surface of the molten glass droplet 50 and the surface of the lower mold 10 are in close contact with each other, and there is no escape route for the air accumulated in the recess 51, so that the recess 51 remains as an air reservoir without disappearing.

In order to cope with this problem, a method has been proposed in which the surface of the lower mold is roughened to secure a flow path of air that has entered the concave portion of the molten glass droplet, thereby preventing air from remaining. For example, see Patent Document 1). Further, a lower mold has been proposed in which a covering layer including a dissolved layer is formed on a roughened base surface to prevent air accumulation and facilitate regeneration (for example, see 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 perform roughening 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 of the molding die for molding glass, it is difficult to react with glass at high temperatures, a mirror surface can be obtained, workability is good, it is hard, it is not brittle, etc. Need to satisfy many conditions. The materials that satisfy these conditions are very limited. For example, cemented carbide 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 preferable properties as a molding die so that the surface has a predetermined surface roughness. Also, roughing by etching is possible, such as super hard material mainly composed of tungsten carbide, but the roughened surface becomes very brittle and the durability is remarkably 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 may not be implemented, or even if it can be performed, the lower mold has poor durability and is stable. As a result, there is a problem that a glass molded body cannot be manufactured.

  In addition, when pressure-molding molten glass droplets between the lower mold and the upper mold, the surrounding gas is confined between the glass material and the upper mold in the process of deforming the glass material along the molding surface of the upper mold. In other words, defects such as dents and wrinkles may exist in the glass molded body, which has been a problem.

  This invention is made | formed in view of the above technical subjects, The objective of this invention is the metal mold | die which can prevent that defects, such as an air pocket and a dent, generate | occur | produce in the glass gob and glass molding to manufacture. It is to provide a manufacturing method. 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 from defects such as air accumulation. It is providing the manufacturing method of the glass forming body which can do.

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

1. In the method for producing a mold for producing a glass gob or glass molded body,
A film forming step of forming a coating layer on the substrate;
A roughening step of roughening the surface of the coating layer,
Wherein the roughening step, the reflectivity or lightness of the surface of the coating layer, the production process of the mold tool, which comprises carrying out the roughening until reduced to a value within a predetermined range by roughening.

2. In the roughening step, roughening is performed while measuring the reflectance or brightness of the surface of the coating layer, and the roughening is terminated when the measured reflectance or brightness reaches a predetermined value. 2. The method for producing a mold according to 1 above.

3 . 3. The mold manufacturing method according to 1 or 2 , wherein the coating layer contains at least one element of chromium, aluminum, and titanium.

4 . The coating layer includes elemental chromium;
4. The method for producing a mold according to 3 above, wherein the surface is roughened by wet etching using an acidic solution containing ceric ammonium nitrate.

5 . The coating layer includes elemental chromium;
4. The method for producing a mold as described in 3 above, wherein the surface is roughened by wet etching using an alkaline solution containing potassium ferricyanide and potassium hydroxide.

6 . The coating layer includes elemental chromium;
4. The method for producing a mold according to 3 above, wherein the surface is roughened by dry etching using a gas containing halogen.

7 . In the predetermined range, the surface of the roughened coating layer has an arithmetic average roughness (Ra) of 0.01 μm or more and an average length (RSm) of roughness curve elements of 0.5 μm or less. 2. The method for manufacturing a mold according to 1 above, characterized in that the mold is defined as follows.

8 . The predetermined range, the surface of the roughened the coating layer, the arithmetic average roughness (Ra) according to the 7, characterized in that the defined so that 0.2μm or less Mold manufacturing method.

9 . 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 lower die, the glass gob production method which is characterized in that which has been produced by the method for producing a mold according to any one of the 1-8.

10 . 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,
At least one of the lower mold or the upper mold is manufactured by the mold manufacturing method according to any one of the above 1 to 8 , wherein the glass molded body is manufactured.

  According to the present invention, a coating layer is formed on a substrate, and the surface of the coating layer is roughened so that the reflectance of the surface is in a predetermined range. Can be uniformly roughened, and the base material is not deteriorated. Therefore, it is possible to manufacture a mold that can prevent the occurrence of defects such as air traps in the glass gob or glass molded body to be manufactured. In addition, by using the mold manufactured by the mold manufacturing method of the present invention, it is possible to stably manufacture glass gobs and glass molded bodies that are free from defects such as air pockets generated by the surrounding gas being confined. Can do.

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

  First, the manufacturing method of the lower mold | type (metal mold | die) in this embodiment is demonstrated using FIGS. FIG. 1 is a cross-sectional view showing the state of the lower mold in each step, and FIG. 2 is a schematic diagram for explaining the meaning of the etching rate. FIG. 3 is a cross-sectional view showing a wet etching method, FIG. 4 is a cross-sectional view showing an etching method using a mask, and FIG. 5 is a schematic view showing an example of a parallel plate type dry etching apparatus. FIG. 6 is a graph showing the relationship between the etching processing time and the reflectance of the surface of the coating layer, and FIG. 7 is a schematic diagram and graph showing a method of roughening while measuring the reflectance. FIG. 8 is a schematic diagram illustrating an example of a reflectance measurement method when the lower mold has a curvature.

(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. 1A). In the present embodiment, 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 the coating layer 14 is formed. . Therefore, the material of the base material 11 is selected from among materials known as lower mold materials for receiving molten glass droplets without considering the ease of roughening and the durability when roughened. These can be appropriately selected according to the conditions. Examples of materials that can be preferably used include various heat-resistant alloys (such as stainless steel), super hard materials mainly composed of tungsten carbide, various ceramics (such as silicon carbide and silicon nitride), and composite materials including carbon. . Further, a dense processed layer such as a CVD silicon carbide film may be formed on the surface of these materials.

(Film formation process)
Next, the coating layer 14 is formed on the base material 11 (film formation step: FIG. 1B). The material of the coating layer 14 is not particularly limited, and 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, etc.) can be used. Especially, it is preferable that the coating layer 14 contains at least 1 element among chromium, aluminum, and titanium. For example, in addition to metal chromium, metal aluminum, and metal titanium, these oxides and nitrides, or mixtures thereof are suitable.

  Any of these films can be easily formed and roughened by a method described later. Further, when the coating layer 14 contains at least one element of chromium, aluminum, and titanium, these elements are oxidized by heating in the atmosphere, and a stable oxide layer is formed on the surface. There is a common feature. These oxides have the great advantage that they do not react easily even when they come into contact with hot molten glass droplets because they have a small standard free energy (standard Gibbs energy) and are very stable. . Among these, chromium oxide is particularly stable, and thus it is more preferable to provide the coating layer 14 containing chromium element.

  The thickness of the coating layer 14 is sufficient if it has a thickness sufficient to form minute irregularities by roughening by etching or the like, and is usually preferably 0.05 μm or more. Conversely, if the coating layer 14 is too thick, defects such as film peeling may easily occur. Therefore, the thickness of the coating layer 14 is preferably 0.05 μm to 5 μm, particularly preferably 0.1 μm to 1 μm.

  The coating layer 14 may be a single layer or may have a plurality of layers having different components and film qualities. For example, the coating layer 14 is divided into two layers (lower layer and surface layer) having different etching rates, a layer having a lower etching rate is formed on the substrate 11 as a lower layer, and then the surface layer having a higher etching rate than the lower layer. It is also preferable to form a film. With such a configuration, since the surface layer on the outermost surface of the coating layer 14 has a high etching rate, minute irregularities can be easily formed by etching, and uniform roughening can be achieved. Further, the presence of a lower layer having a low etching rate under the surface layer improves the adhesion of the coating layer 14 and can more reliably prevent the etching effect from reaching the base material 11. The lower mold 10 having excellent durability can be manufactured.

  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. 2 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.

  There is no restriction | limiting in the film-forming method of the coating layer 14, 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 preferable because a film with high adhesion can be easily formed.

  When the coating layer 14 is formed by sputtering, 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. Thereby, a lower layer and a surface layer can be formed. According to this method, it is possible to continuously form a lower layer having a low etching rate and a surface layer having a high etching rate only by changing the film forming conditions without changing the material and equipment of the target. The reason why the coating layer 14 has such a two-layer structure is that even if the surface layer is etched, the presence of the lower layer can prevent the influence of the etching from reaching the substrate 11, and the lower layer This is because the adhesion between the base material 11 and the coating layer 14 can be improved by the high energy film formation.

  In order to reduce the energy of the sputtered particles that reach the film formation surface, for example, the pressure of the sputtering gas during film formation is increased, the distance between the target and the film formation surface is increased, and the sputtering electrode is applied. For example, a method of reducing electric power can be used. Conversely, in order to increase the energy of sputtered particles that reach the film formation surface, for example, the sputtering gas pressure during film formation is reduced, the distance between the target and the film formation surface is shortened, The method of enlarging the electric power applied to the method is mentioned.

(Roughening process)
Next, the surface of the coating layer 14 is roughened (roughening step: FIG. 1C). In this embodiment, since the surface roughness of the coating layer 14 is roughened so that the reflectance R or a parameter calculated based on the reflectance R falls within a predetermined range, regardless of the material of the base material 11, The surface of the coating layer 14 can be uniformly roughened. Although there is no restriction | limiting in particular in the method of roughening, From a viewpoint that a uniform unevenness | corrugation can be formed easily, it is preferable to carry out by wet etching or dry etching.

  The wet etching is a method in which a predetermined etching solution 30 is reacted with the coating layer 14 to roughen the surface. The entire lower mold 10 may be immersed in the etching solution 30 stored in the etching solution tank 31 as shown in FIG. 3A, or the coating layer 14 is immersed in the etching solution 30 as shown in FIG. You may let them. Further, as shown in FIG. 3 (c), a predetermined amount of the etching solution 30 may be supplied onto the coating layer 14, or the etching solution 30 is sprayed from the spray nozzle 32 as shown in FIG. 3 (d). The method of spraying and spraying on the coating layer 14 may be used. According to wet etching, expensive and large equipment is not required, and processing with excellent uniformity can be performed efficiently and at low cost. In order to perform a stable process, it is preferable to maintain constant conditions such as the atmospheric temperature and illuminance of the process chamber, the temperature of the lower mold, the number of processes, the temperature, amount, and concentration of the etching solution. Conversely, by changing these conditions, the depth and period of the irregularities formed can be adjusted as appropriate.

  Dry etching is a method in which an etching gas is introduced into a vacuum chamber, plasma is generated by a high frequency or the like, and the coating layer 14 is roughened by ions or radicals generated by the plasma. Sometimes called plasma etching or reactive ion etching (RIE). This is a preferable method because the waste liquid is not generated, the environmental load is small, the surface is less contaminated with foreign matter, and the reproducibility of the treatment is excellent.

The dry etching apparatus may be appropriately selected from known apparatuses such as a parallel plate type, a barrel (cylindrical) type, a magnetron type, and an ECR type, and is not particularly limited. Here, a parallel plate type dry etching apparatus will be described as an example. A parallel plate type dry etching apparatus 40 shown in FIG. 5 has two electrodes 42 and 43 arranged in parallel to each other in a vacuum chamber 41, and one electrode 42 is connected to a high frequency power supply 44. Has been. After the lower mold 10 to be processed is disposed on the electrode 42, the valve 45 is opened, and the vacuum chamber 41 is brought into a high vacuum state of 10 ⁻³ Pa by the exhaust pump 46. Thereafter, plasma is generated between the two electrodes 42 and 43 by introducing an etching gas from the gas cylinder 48 through the flow rate adjusting valve 47 and applying a high frequency to the electrode 42. Fine irregularities are formed on the surface of the coating layer 14 by the ions and radicals generated by the plasma, and the surface is roughened. The etching action by dry etching includes a physical action by collision with ions and a chemical action by reaction with radicals. In the present invention, the coating layer 14 is formed by at least one of the actions. It is sufficient that the surface is roughened, and both actions may work simultaneously. The etching gas may be an inert gas such as Ar, or a highly reactive gas containing a halogen such as F, Cl, or Br.

  In either wet etching or dry etching, the entire surface of the coating layer 14 does not necessarily have to be roughened, and at least a region in contact with the molten glass droplet has only to be roughened. It is also preferable to use a mask 33 as shown in FIGS. 4 (a) and 4 (b) in order to prevent deterioration of the substrate 11 and the like due to etching and process only a desired region.

  Furthermore, when the coating layer 14 contains a chromium element, the surface can be roughened more uniformly by etching by any one of the following methods (1) to (3).

(1) Wet etching using an acidic solution containing ceric ammonium nitrate By using an acidic solution containing ceric ammonium nitrate (Ce (NH ₄ ) ₂ (NO ₃ ) ₆ ) as an etching solution, elemental chromium Fine irregularities can be formed more uniformly and in a short time on the surface of the coating layer 14 containing the. As long as ceric ammonium nitrate is contained, a solution containing a plurality of acids such as nitric acid and perchloric acid may be used. What is necessary is just to select the density | concentration of ceric ammonium nitrate suitably so that a desired process rate may be obtained, and 5 mass%-50 mass% are preferable normally.

(2) Wet etching using an alkaline solution containing potassium ferricyanide and potassium hydroxide As an etchant, an alkaline solution containing potassium ferricyanide and potassium hydroxide is used to form fine particles on the surface of the coating layer 14 containing chromium element. Unevenness can be formed more uniformly and in a short time. As the alkaline solution containing potassium ferricyanide and potassium hydroxide, for example, a mixed solution of potassium ferricyanide, potassium hydroxide, and pure water can be used. The etching solution may further contain other components. The ratio of potassium ferricyanide and potassium hydroxide is preferably 0.2 to 5 parts by mass of potassium hydroxide with respect to 1 part by mass of potassium ferricyanide. The amount of pure water to be mixed is not particularly limited, and may be adjusted as appropriate so as to obtain a desired processing speed.
(3) Dry etching using a gas containing halogen Gas containing halogen such as F, Cl, Br (for example, CF ₄ , SF ₆ , CHF ₃ , Cl ₂ , BCl ₃ , HBr, etc.) contains a chromium element. Since the reactivity with the coating layer 14 is high, roughening can be performed in a shorter time by using these gases as an etching gas. It is also effective to use a mixed gas of a gas containing halogen and another gas (for example, O ₂ , N _2, etc.).

  Regardless of which method is used to roughen the surface, it is necessary to appropriately manage the progress of the roughening of the coating layer 14 in order to satisfactorily prevent the occurrence of air accumulation. In the present embodiment, the reflectance R of the surface of the coating layer 14 is measured, and roughening is performed so that the measured reflectance R or a parameter calculated based on the reflectance R falls within a predetermined range. The degree of progress of the roughening of the coating layer 14 is managed.

  Other methods for managing the degree of progress of roughening include a method for visual control, a method for management by surface roughness measured with a stylus roughness meter, and a surface measured by an atomic force microscope (AFM). A method of management based on roughness, a method of management based on images observed with a scanning electron microscope (SEM), a method of management based on surface roughness measured with a laser microscope, and the like are conceivable. However, these methods have the following problems, respectively, and it is difficult to appropriately manage the progress of roughening. That is, in the method of visually managing the degree of progress of roughening, there is a problem that there is a large variation due to individual differences in judgment. Moreover, in the method managed by the surface roughness measured with the stylus type roughness meter, the coating layer 14 may be scratched by the measurement, and there is a problem that the measurement while performing the surface roughening treatment is difficult. . Furthermore, since the tip R of the stylus is small and about 2 μm, there is a problem that accurate evaluation cannot be performed when the period of the unevenness of the coating layer 14 is small. In the method of managing by the surface roughness measured with an atomic force microscope (AFM), there is a problem that measurement cannot be performed when the molding surface 15 has a curvature, and measurement while performing the roughening treatment is difficult. . In the method of managing by an image observed with a scanning electron microscope (SEM), there are problems that the time required for the measurement is long and it is difficult to perform the measurement while performing the roughening treatment. Furthermore, in order to quantify the progress of the roughening, there is a problem that expensive dedicated equipment and software are required. In the method managed by the surface roughness measured with the laser microscope, the surface periodic structure below the wavelength of the laser cannot be evaluated, so there is a problem that the resolution is insufficient, and the measurement while performing the roughening treatment is difficult. There's a problem.

  On the other hand, in the present embodiment, the reflectance R of the surface of the coating layer 14 is measured, and the measured reflectance R or a parameter calculated based on the reflectance R is roughened so as to fall within a predetermined range. By performing the above, the progress of the roughening of the coating layer 14 is managed. According to this method, there is no problem as described above, and the progress of the roughening can be appropriately managed. Further, even when the molding surface 15 has a curvature, it can be handled without any problem, and it has a great merit that it is easy to perform measurement while performing the roughening treatment.

There is no particular limitation on the wavelength of light used for the measurement of the reflectance, and it may be ultraviolet light, infrared light, or the like in addition to visible light, or may be managed using the reflectance of light having a plurality of wavelengths. Further, the measured reflectance may be managed so as to fall within a predetermined range, or the parameter calculated based on the reflectance may be managed so as to fall within the predetermined range. Examples of the parameters calculated based on the reflectance include lightness and saturation in various color systems. Among them, the brightness can be preferably used because it has the advantages that the change due to the progress of the roughening is large and the reproducibility of the measured value is high. There is no restriction on the color system for calculating the lightness, and various color systems such as Munsell color system, L ^* a ^* b ^* color system, Hunter Lab color system, XYZ color system, etc. may be used. it can. In addition, what is necessary is just to measure a reflectance, a brightness, etc. with well-known various reflectance measuring machines, a spectrophotometer, a colorimeter.

  FIG. 6A is a graph showing an example of the relationship between the etching processing time and the reflectance of the surface of the coating layer 14. Here, an example is shown in which the coating layer 14 made of metallic chromium is roughened by wet etching using an acidic solution containing ceric ammonium nitrate. The measurement wavelength of the reflectance is 700 nm.

  Range A in the graph (the processing time is less than 7 minutes) is a region where the progress of roughening is insufficient and an air pocket tends to remain in the glass molded body or the like. The reflectivity before the etching process is about 53%, but the reflectivity decreases as the process proceeds. This is thought to be due to an increase in the amount of loss due to light scattering due to an increase in the depth of the concave portion of the concave-convex structure formed by etching, resulting in a decrease in reflectance. Range B (processing time: 7 to 12 minutes) in the graph is a region where the roughening of the coating layer 14 proceeds appropriately and the occurrence of air pockets can be sufficiently prevented. In this region, the coating layer 14 is not peeled off. At this time, the reflectance gradually decreases from 22% (processing time 7 minutes) to 2% (processing time 12 minutes). A range C (processing time exceeds 12 minutes) in the graph is a region where the etching proceeds excessively and peeling occurs on a part or the entire surface of the coating layer 14. When peeling occurs in the coating layer 14, defects are likely to occur in the glass molded body to be manufactured, and therefore, it is not suitable for use.

  In this way, the reflectance of the surface of the coating layer 14 is measured, and the surface is roughened so that the measured reflectance is within a predetermined range (22% to 2% in the case of FIG. 6A). By performing the above, it is possible to appropriately manage the progress of the roughening of the coating layer 14, and it is possible to manufacture a lower mold that can favorably prevent the occurrence of air pockets.

FIG. 6B shows an example in which the same sample as that evaluated in FIG. 6A is evaluated using the lightness L ^* in the L ^* a ^* b ^* color system instead of the reflectance. It is a graph which shows. It can be seen that the lightness L ^* changes with the same tendency as the reflectance as the processing time elapses. Therefore, the degree of progress of the roughening of the coating layer 14 is appropriately adjusted by roughening so that the lightness L ^* is within a predetermined range (in the case of FIG. 6B, a range of 53 to 15). Can be managed. The values of the reflectance and brightness L ^* shown in FIGS. 6A and 6B and the range (range B) in which the occurrence of air pockets can be satisfactorily prevented are merely examples, and the shape of the molding surface 15 The material varies depending on various conditions such as the material of the coating layer 14, the type of glass, the shape and size of the glass gob to be produced and the glass molded body.

  Furthermore, from the viewpoint of suppressing the variation in the degree of progress of the roughening and managing the roughening with higher accuracy, the roughening is performed while measuring the reflectance of the surface of the coating layer 14, and the measured reflection is measured. It is also preferable to finish the roughening when the ratio or the parameter calculated based on the reflectance reaches a predetermined value. FIG. 7A schematically shows a method of etching two lower molds 10x and 10y processed in the same manner while measuring the reflectance of the coating layer 14. Moreover, the graph of FIG.7 (b) has each shown the relationship between processing time and a reflectance about two lower mold | types 10x and 10y. The lower molds 10x and 10y have slightly different surface states due to slight differences in processing conditions, and the lower mold 10x has a smaller surface roughness than the lower mold 10y, so the lower mold 10x is less than the lower mold 10y. The reflectivity is high. Therefore, if the processing times of the two lower molds 10x and 10y are the same, a difference remains in the surface roughness after the processing. However, as shown in FIG. 7, roughening is performed while measuring the reflectance of the coating layer 14, and the roughening is finished when the measured reflectance reaches a predetermined value (for example, 30%). By performing (for example, the processing time of the lower mold 10x is 7 minutes and the processing time of the lower mold 10y is 6 minutes), the difference in surface roughness after the processing can be reduced. Therefore, variation in the degree of progress of the roughening of the two lower molds 10x and 10y can be reduced, and the roughening can be managed with higher accuracy.

  Further, when the molding surface 15 has a curvature, the degree of progress of roughening may vary depending on the position in the molding surface 15 (center, middle band, end, etc.). In this case, as shown in FIG. 8A, the reflectance at a desired position can be measured by changing the positional relationship between the light source 24 and the light receiving unit 25 for measuring the reflectance. The progress of surfaceization can be managed more appropriately. In order to measure the reflectance at a desired position, the inclination of the lower mold 10 may be changed without changing the positional relationship between the light source 24 and the light receiving unit 25 as shown in FIG. The degree of progress of the surface roughening depends on the reflectance at a desired position, such as the central part, the middle band part, and the edge part of the molding surface 15 according to the quality and manufacturing conditions required for the glass molded body to be produced. Just manage. Further, it may be managed by the maximum value, minimum value, average value, etc. of the reflectance at a plurality of positions.

  As described above, in this embodiment, the reflectance of the surface of the coating layer 14 is measured, and the degree of progress of roughening is managed so that the measured reflectance or the like falls within a predetermined range. The management width (predetermined range) such as the rate is such that the surface of the roughened coating layer 14 has an arithmetic average roughness (Ra) of 0.01 μm or more, and the average length (RSm) of the roughness curve elements ) Is preferably set to 0.5 μm or less. By setting the arithmetic average roughness (Ra) of the surface of the coating layer 14 and the average length (RSm) of the roughness curve elements in such a range, it is more likely that air pools are generated in the manufactured glass gob or glass molded body. It can be effectively prevented. The arithmetic average roughness (Ra) and the average length of the roughness curve element (RSm) are roughness parameters defined in JIS B 0601: 2001. These parameters are preferably measured using a measuring machine having a spatial resolution of 0.1 μm or less, such as AFM (Atomic Force Microscope).

  Here, the reason why an air pocket can be prevented from occurring in the glass gob or the glass molded body by roughening the coating layer 14 will be described in detail with reference to FIGS. FIG. 9 is a view showing a state of the molten glass droplet 50 dropped on the lower mold 10. FIG. 9A shows a state at the moment when the molten glass droplet 50 collides with the lower mold 10, and FIG. 9B shows a state after the molten glass droplet 50 is deformed round by surface tension. .

  As shown in FIG. 9A, the molten glass droplet 50 at the moment of collision with the lower mold 10 has a diameter of several tens to several hundreds of μm near the center of the lower surface (the surface in contact with the coating layer 14). A very small concave portion 51 is generated. However, since the surface of the coating layer 14 is roughened by a predetermined method, a gap remains between the lower surface of the molten glass droplet 50 and the coating layer 14, and as shown in FIG. When the droplet 50 is deformed round by the action of surface tension, the air accumulated in the recess 51 through the gap escapes and 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. 10 is a schematic diagram showing details of the C portion of FIG. 9B. As shown to Fig.10 (a), the unevenness | corrugation is formed in the surface of the coating layer 14 by the roughening process. 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. 10B 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, the surface of the coating layer 14 preferably has an arithmetic average roughness (Ra) of 0.01 μm or more, and more preferably 0.01 μm or more and 0.2 μm or less.

  In addition, the period of unevenness affects the occurrence of air accumulation. FIG. 10C shows a case where the height of the irregularities on the surface of the coating layer 14 is the same as that in FIG. In this way, even if the height of the unevenness is the same, if the period is long, the glass easily enters the bottom of the uneven valley, 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.

  The covering layer 14 may have a multilayer structure composed of two or more layers. For example, an intermediate layer for improving the adhesion between the substrate 11 and the coating layer 14 may be provided, or a protective layer for protecting the surface may be provided on the coating layer 14 on which irregularities are formed by roughening. Further, it may be provided. Thus, when the coating layer 14 consists of two or more layers, the arithmetic average roughness (Ra) of the outermost surface that contacts the molten glass droplet and the average length (RSm) of the roughness curve element are within the predetermined range. Preferably it is.

  In the above description, the case of manufacturing the lower mold has been described as an example. However, the present invention is similarly applied to the case of manufacturing the upper mold that press-molds molten glass droplets together with the lower mold. Can do.

(Glass gob manufacturing method)
The manufacturing method of the glass gob which is an example of embodiment of this invention is demonstrated referring FIGS. 11-13. FIG. 11 is a flowchart illustrating an example of a glass gob manufacturing method. 12 and 13 are schematic views of a glass gob manufacturing apparatus used in the present embodiment. FIG. 12 shows the state in the step (S22) of dropping the molten glass droplet on the lower mold, and FIG. 13 shows the state in the step (S23) of cooling and solidifying the dropped molten glass droplet on the lower mold. Yes.

  The lower mold 10 is manufactured by the above-described manufacturing method. That is, after the coating layer 14 is provided on the substrate 11, the surface is roughened so that the reflectance of the surface falls within a predetermined range. 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 are likely to be generated 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 set higher than necessary, fusion between the glass and the lower mold 10 is likely to occur, and the life of the molding die may be shortened. By doing so, an air pocket may remain in the glass gob. Actually, since the appropriate temperature varies depending on various conditions such as the type, shape, size, material of the molding die, and size of the glass, it is preferable to obtain an appropriate temperature experimentally. Usually, when the glass transition temperature of the glass to be used is Tg, it is preferably set to a temperature of about Tg-100 ° C. to Tg + 100 ° C.

  Next, the molten glass droplet 50 is dropped from the dropping nozzle 63 (step S22) (see FIG. 12). The dropping of the molten glass droplet 50 is performed by heating the dropping nozzle 63 connected to the melting tank 62 storing the molten glass 61 to a predetermined temperature. When the dropping nozzle 63 is heated to a predetermined temperature, the molten glass 61 stored in the melting tank 62 is supplied to the front end portion of the dropping nozzle 63 by its own weight, and is accumulated in a droplet shape by the surface tension. When the molten glass collected at the tip of the dropping nozzle 63 reaches a certain mass, it is naturally separated from the dropping nozzle 63 by gravity and becomes a molten glass drop 50 and falls downward.

  The mass of the molten glass droplet 50 dropped from the dropping nozzle 63 can be adjusted by the outer diameter of the tip of the dropping nozzle 63 and the like, and depending on the type of glass, the molten glass droplet of about 0.1 to 2 g is dropped. be able to. Further, the molten glass droplet 50 dropped from the dropping nozzle 63 is once collided with a member having a through-hole, and a part of the collided molten glass droplet is allowed to pass through the through-hole, thereby miniaturizing the molten glass droplet. May be dropped onto the lower mold 10. By using such a method, it is possible to obtain a minute molten glass droplet of, for example, 0.001 g. Therefore, a smaller glass gob than the case where the molten glass droplet 50 dropped from the dropping nozzle 63 is directly received by the lower mold 10 is used. Can be manufactured. The interval at which the molten glass droplet 50 is dropped from the dropping nozzle 63 can be finely adjusted by the inner diameter, length, heating temperature, etc. of the dropping nozzle 63.

  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.

  Next, the dropped molten glass droplet 50 is cooled and solidified on the lower mold 10 (step S23) (see FIG. 13). 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 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 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 as a glass preform used for manufacturing various optical elements by the reheat press method.

(Manufacturing method of glass molding)
The manufacturing method of the glass forming body which is another example of embodiment of this invention is demonstrated referring FIGS. 14-16. FIG. 14 is a flowchart showing an example of a method for producing a glass molded body. FIGS. 15 and 16 are schematic views of a glass molded body manufacturing apparatus used in this embodiment. FIG. 15 shows the state in the step (S33) of dropping the molten glass droplet on the lower die (die), and FIG. 16 shows the step of pressurizing the dropped molten glass droplet with the lower die and the upper die (die) (S35). ) Shows the respective states. In the following description, the case where a roughened mold manufactured by the method of the present invention is used as a lower mold is taken as an example in order to prevent air accumulation on the contact surface with the lower mold. In order to prevent the occurrence of defects such as dents on the contact surface with the upper mold, a roughened mold manufactured by the method of the present invention may be used as the upper mold. .

  The glass molded body manufacturing apparatus shown in FIGS. 15 and 16 includes, in addition to the configuration of the glass gob manufacturing apparatus shown in FIGS. 12 and 13, an upper mold for press-molding molten glass droplets 50 together with the lower mold 10. 60. Similar to the lower mold 10, the upper mold 60 is configured to be heated to a predetermined temperature by a heating unit (not shown). It is preferable that the temperature of the lower mold 10 and the upper mold 60 can be controlled independently. In addition, the material of the upper mold 60 can be appropriately selected from the same materials as the lower mold 10. The material of the lower mold 10 and the upper mold 60 may be the same or different. The lower mold 10 has a position (dropping position P1) for receiving the molten glass droplet 50 by a driving means (not shown) and a position (pressure position P2) for performing pressure molding opposite to the upper mold 60. It is configured to be movable along the guide 65. Further, the upper mold 60 is configured to be movable in a direction in which the molten glass droplet 50 is pressurized (vertical direction in the drawing) by a driving unit (not shown).

  Hereinafter, each step will be described in order according to the flowchart shown in FIG. In addition, detailed description is abbreviate | omitted about the process similar to the manufacturing method of the above-mentioned glass gob.

  First, the lower mold 10 and the upper mold 60 are heated to a predetermined temperature (step S31). What is necessary is just to select suitably the temperature which can form a favorable transfer surface on a glass molded object by pressure molding with predetermined temperature. 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 dripping nozzle 63 (process S33) (refer FIG. 15). 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 pressure position P2 (step S34), the upper mold 60 is moved downward, and the molten glass droplet 50 is pressure-molded by the lower mold 10 and the upper mold 60 (process S35). (See FIG. 16). The molten glass droplet 50 received by the lower mold 10 is cooled by heat radiation from the contact surface with the lower mold 10 and the upper mold 60 while being pressed and solidified to become a glass molded body 55. When the glass molded body 55 is cooled to a predetermined temperature, the upper mold 60 is moved upward to release the pressure. Depending on the type of glass, the size and shape of the glass molded body 55, the required accuracy, etc., it is usually preferable to release the pressure after cooling to a temperature near the 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 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 this embodiment 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, it can also be used as a glass preform used for manufacturing various optical elements by the reheat press method.

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 sectional drawing which shows the method of wet etching. It is sectional drawing which shows the method of the etching using a mask. It is a schematic diagram which shows the example of a parallel plate type dry etching apparatus. It is a graph which shows the relationship between processing time, the reflectance of the surface of a coating layer, etc. It is the schematic diagram and graph which show the method of roughening, measuring a reflectance. It is a schematic diagram which shows the example of the measuring method of a reflectance in case a lower mold | type has a curvature. It is a figure which shows the state of the molten glass droplet dripped at the lower mold | type. It is the schematic diagram which showed the detail of the C section of FIG.9 (b). It is a flowchart which shows an example of the manufacturing method of a glass gob. It is a schematic diagram (state in process S22) of the manufacturing apparatus of a glass gob. It is a schematic diagram (state in process S23) of the manufacturing apparatus of a glass gob. It is a flowchart which shows an example of the manufacturing method of a glass forming body. It is a schematic diagram (state in process S33) of the manufacturing apparatus of a glass molded object. It is a schematic diagram (state in process S35) of the manufacturing apparatus of a glass molded object. It is a schematic diagram which shows the state of the molten glass droplet received with the lower mold | type by the conventional method.

Explanation of symbols

10, 10x, 10y Lower mold (mold)
DESCRIPTION OF SYMBOLS 11 Base material 14 Covering layer 15 Molding surface 24 Light source 25 Light-receiving part 30 Etching liquid 31 Etching liquid tank 32 Injection nozzle 33 Mask 40 Dry etching apparatus 41 Vacuum chamber 42, 43 Electrode 44 High frequency power supply 45 Valve 46 Exhaust pump 47 Flow control valve 48 Gas cylinder 50 Molten glass droplet 51 Recessed portion 52 Lower surface 53 Gap 54 Glass gob 55 Glass molded body 60 Upper mold (mold)
61 Molten glass 62 Melting tank 63 Dropping nozzle 65 Guide P1 Dropping position P2 Pressure position

Claims (10)

In the method for producing a mold for producing a glass gob or glass molded body,
A film forming step of forming a coating layer on the substrate;
A roughening step of roughening the surface of the coating layer,
Wherein the roughening step, the reflectivity or lightness of the surface of the coating layer, the production process of the mold tool, which comprises carrying out the roughening until reduced to a value within a predetermined range by roughening. In the roughening step, roughening is performed while measuring the reflectance or brightness of the surface of the coating layer, and the roughening is terminated when the measured reflectance or brightness reaches a predetermined value. The manufacturing method of the metal mold | die of Claim 1 characterized by these. The coating layer is chromium, mold manufacturing method according to claim 1 or 2, characterized in that it comprises at least one element selected from aluminum and titanium. The coating layer includes elemental chromium;
4. The method for producing a mold according to claim 3 , wherein the surface is roughened by wet etching using an acidic solution containing ceric ammonium nitrate. The coating layer includes elemental chromium;
4. The method for producing a mold according to claim 3 , wherein the surface is roughened by wet etching using an alkaline solution containing potassium ferricyanide and potassium hydroxide. The coating layer includes elemental chromium;
4. The method of manufacturing a mold according to claim 3 , wherein the surface is roughened by dry etching using a gas containing halogen.   In the predetermined range, the surface of the roughened coating layer has an arithmetic average roughness (Ra) of 0.01 μm or more and an average length (RSm) of roughness curve elements of 0.5 μm or less. 2. The method for manufacturing a mold according to claim 1, wherein the mold is defined as follows. The predetermined range, the surface of the roughened the coating layer, according to claim 7 in which the arithmetic mean roughness (Ra) is characterized in that the defined so that 0.2μm or less Mold manufacturing method. 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 lower die, the glass gob production method, characterized in that claim 1 are those prepared by the method of manufacturing a mold according to any one of the eight. 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,
At least one of the lower mold or the upper mold is manufactured by the mold manufacturing method according to any one of claims 1 to 8 , wherein the glass molded body is manufactured. .

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