JP2011116590A - Method for manufacturing mold, method for producing glass gob, and method for producing glass molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a mold excellent in durability in which remaining of an air reservoir trace is satisfactorily prevented and peeling off of a cover layer is suppressed, and to provide a method for producing a glass gob and a glass molded article by which the glass gob and the glass molded article with no air reservoir trace is stably produced inexpensively. <P>SOLUTION: The method for manufacturing the mold comprises the steps of: forming a molding surface having a predetermined shape on a base material of the mold; and depositing the cover layer on the molding surface by a sputtering method. The deposition of the cover layer is conducted in a state in which a bias voltage, selected so as to make arithmetic average roughness (Ra) of the molding surface more increased than that before deposition due to collision of a portion of ions of a process gas with the molding surface during deposition, is applied to the base material. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

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

  As a method for producing such a glass molded body, a molten glass droplet having a temperature higher than that of the lower mold is dropped on a lower mold heated to a predetermined temperature, and the dropped molten glass droplet is pressure-molded by the lower mold and the upper mold. A method for obtaining a glass molded body (hereinafter also referred to as “droplet forming method”) has been proposed. Since this method can produce a glass molded body directly from molten glass droplets, it has been attracting attention because the time required for one molding can be extremely shortened.

  Moreover, the molten glass droplet dripped at the lower mold is cooled and solidified as it is to produce a glass gob (glass lump), and the glass gob is heated and pressure-molded together with the mold to produce a glass molded body. (Reheat press method) is also known.

  However, in these methods, when the dropped molten glass droplet collides with the lower mold, an air pool is generated near the center of the lower surface (contact surface with the lower mold) of the molten glass droplet, and the lower surface of the glass molded body is formed. There exists a problem that a fine recessed part (air accumulation mark) will remain.

  In order to solve such a problem, after forming a coating layer on the substrate, use a lower mold whose surface is roughened to secure a flow path for air that has entered the air reservoir. A method for preventing the air accumulation trace from remaining is proposed (see Patent Document 1). Patent Document 1 describes wet etching using an acidic solution or an alkaline solution and dry etching using plasma as methods for roughening the coating layer.

International Publication No. 2009/016993

  However, as described in Patent Document 1, when the coating layer is roughened by wet etching or dry etching, the coating layer deteriorates with the progress of the roughening, and the adhesion to the substrate is reduced. . Therefore, there exists a problem that peeling of a coating layer tends to generate | occur | produce during manufacture of a glass gob or a glass molded object.

  In addition, when the molten glass droplet dropped on the lower mold is pressure-formed between the lower mold and the upper mold, an air pool is generated at the contact portion between the upper mold and the molten glass droplet, and the upper surface of the glass molded body (with the upper mold) There are cases where air accumulation marks remain on the contact surface), which is a problem.

  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 remaining of air accumulation marks and to suppress the peeling of the coating layer, and is excellent in durability. It is to provide a method for manufacturing a mold. Another object of the present invention is to provide a glass gob and a method for producing a glass molded body, which can stably produce a glass gob and a glass molded body free from air accumulation marks at low cost.

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

1. A manufacturing method of a mold for manufacturing a glass gob or a glass molded body from a dropped molten glass drop,
Forming a molding surface having a predetermined shape on the base of the molding die;
Forming a coating layer on the molding surface by a sputtering method,
The film formation of the coating layer is selected so that the arithmetic average roughness (Ra) of the molding surface is increased as compared to that before the film formation due to a part of process gas ions colliding with the molding surface during the film formation. A method for producing a mold, which is performed in a state where the bias voltage applied is applied to the substrate.

  2. 2. The method for producing a molding die according to 1 above, wherein the molding surface after forming the coating layer has an arithmetic average roughness (Ra) of 0.01 μm to 0.2 μm.

  3. 3. The method for producing a molding die according to 2, wherein the molding surface after the coating layer is formed has an average length (RSm) of roughness curve elements of 0.5 μm or less.

  4). 4. The method for producing a molding die according to 2 or 3, wherein the molding surface before forming the coating layer has an arithmetic average roughness (Ra) of 0.005 μm or less.

  5. 5. The method for producing a mold according to any one of 1 to 4, wherein the outermost surface layer of the coating layer is a metal layer made of at least one of chromium, aluminum, and titanium.

  6). 6. The method for manufacturing a mold according to any one of 1 to 5, wherein the process gas includes an argon gas.

7). Dropping molten glass droplets into the first mold,
Cooling the dripped molten glass droplets on the first mold, and a method for producing a glass gob,
The method for producing a glass gob, wherein the first mold is a mold manufactured by the method for manufacturing a mold according to any one of 1 to 6.

8). Dropping molten glass droplets into the first mold,
A step of pressure-molding the dropped molten glass droplets with a first mold and a second mold facing the first mold, and a method for producing a glass molded body,
At least one of the first mold and the second mold is a mold manufactured by the method for manufacturing a mold according to any one of 1 to 6 above. Manufacturing method of a molded object.

  In the present invention, when the coating layer is formed on the molding surface by the sputtering method, the bias selected so that the arithmetic average roughness (Ra) of the molding surface is increased as compared with that before the film formation due to collision of ions of the process gas. Film formation is performed with a voltage applied to the substrate. Therefore, the arithmetic average roughness (Ra) of the molding surface can be increased without reducing the adhesion to the substrate due to the deterioration of the coating layer as in the conventional method. Therefore, it is possible to satisfactorily prevent the remaining of air accumulation marks, suppress peeling of the coating layer, and manufacture a mold having excellent durability. In addition, by using the mold manufactured by the above method, it is possible to improve the life of an expensive mold, and to stably manufacture a glass gob and a glass molded body having no air accumulation trace at low cost. it can.

It is sectional drawing which shows the state of the shaping | molding die in each process. It is a schematic diagram which shows the sputtering device used by this embodiment. It is a graph which shows typically the relationship between the absolute value of the bias voltage applied to a board | substrate, and the arithmetic mean roughness (Ra) of a film-forming surface. It is a flowchart which shows the manufacturing method of a glass molded object. It is a schematic diagram (state in process S103) which shows the manufacturing apparatus of the glass forming body used by this embodiment. It is a schematic diagram (state in process S105) which shows the manufacturing apparatus of the glass forming body used by this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 6, but the present invention is not limited to the embodiments.

(Manufacturing method of mold)
First, the manufacturing method of a shaping | molding die is demonstrated using FIGS. 1-3. FIG. 1 is a cross-sectional view showing a state of a molding die in each step, and FIG. 2 is a schematic view showing a sputtering apparatus used in this embodiment. FIG. 3 is a graph schematically showing the relationship between the absolute value of the bias voltage applied to the substrate and the arithmetic average roughness (Ra) of the film formation surface.

  First, a molding surface 15 having a predetermined shape is formed on a base material 11 serving as a base of a mold 10 to be manufactured (see FIG. 1A). There is no restriction | limiting in the shape of the shaping | molding surface 15, What is necessary is just to process into various shapes according to the shape of the glass gob to manufacture or a glass molded object. The processing method may be appropriately selected from known methods such as cutting, grinding, and polishing according to the material of the base material 11 and the like. In addition, the shaping | molding surface 15 means the surface for shape | molding (deforming) a molten glass drop in contact with a molten glass drop here, and press-molding a molten glass drop in order to manufacture a glass molded object. In addition to the surface for the purpose, it also includes a surface for receiving and deforming molten glass droplets dropped to produce a glass gob.

  The molding surface 15 has an arithmetic average roughness (Ra) of 0.005 μm or less in order to reliably remove defects such as tool marks and improve the adhesion and coverage of the coating layer 12. Is more preferable, and 0.003 μm or less is more preferable.

  The material of the base material 11 can be appropriately selected from known materials as a material of a mold for producing a glass molded body according to conditions. Since the substrate 11 is not directly roughened, it can be selected without considering the ease of etching, durability when etched, and the like. 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. . Further, a dense processed layer such as a CVD silicon carbide film may be formed on the surface of these materials.

  Next, the coating layer 12 is formed on the molding surface 15 by a sputtering method in which a target is sputtered by process gas ions (FIG. 1B). The film formation of the coating layer 12 is selected such that the arithmetic average roughness (Ra) of the molding surface 15 increases as compared to that before the film formation due to a part of process gas ions colliding with the molding surface 15 during the film formation. The bias voltage thus applied is applied to the substrate 11. Therefore, the arithmetic average roughness (Ra) of the molding surface 15 can be increased without reducing the adhesion to the substrate 11 due to the deterioration of the coating layer 12. Therefore, it is possible to satisfactorily prevent the air accumulation marks from remaining, to suppress the peeling of the coating layer 12, and to manufacture the mold 10 having excellent durability.

  FIG. 2 shows an example of the sputtering apparatus 20 used in this embodiment. The sputtering apparatus 20 includes a base material holding unit 23 that holds the base material 11 inside the vacuum chamber 21, a sputter target 22 that is a material of the coating layer 12 and is disposed below the base material holding unit, and a sputter target 22. And a sputtering power source 24 for applying a predetermined voltage. The substrate holding unit 23 is connected to a bias power supply 25 for applying a negative bias voltage to the substrate 11. Further, the vacuum chamber 21 is connected to an exhaust pump 28 for exhausting the inside of the vacuum chamber 21 to a predetermined degree of vacuum via a valve 29, and inside the vacuum chamber 21 via a flow rate adjusting valve 27. Are connected to an argon cylinder 26 for introducing an argon gas as a process gas.

When forming the coating layer 12, first, the base material 11 is attached to the base material holding part 23 with the molding surface 15 facing downward. The substrate 11 held by the substrate holder 23 may be one or plural. Next, the valve 29 is opened, and the inside of the vacuum chamber 21 is exhausted to a predetermined degree of vacuum by the exhaust pump 28. Usually, it is preferable to exhaust to a pressure of 1 × 10 ⁻³ Pa or less. It is also preferable to provide a heater in the base material holding part 23 and to heat the base material 11 to a predetermined temperature. After the inside of the vacuum chamber 21 is evacuated to a predetermined degree of vacuum, the flow rate adjusting valve 27 is opened, and argon gas as a process gas is introduced from the argon cylinder 26. Then, while applying a negative bias voltage to the base material 11 (base material holding part 23) by the bias power source 25, a predetermined voltage is applied to the sputter target 22 by the sputter power source 24 to generate plasma near the upper surface of the sputter target 22. generate. Thereby, a part of the argon gas is ionized to be argon ions 31 and collide with the sputter target 22, and the constituent elements of the sputter target 22 are repelled as sputtered particles. The sputtered particles that have been repelled reach the upper substrate 11 and accumulate, and the coating layer 12 is formed on the molding surface 15.

  In general, in the sputtering method, it is known that the film formation surface can be flattened by performing film formation with a negative bias voltage applied to the substrate 11. This is thought to be because the surface diffusion of the sputtered particles reaching the film formation surface is promoted by collision of some of the process gas ions such as argon ions 31 with the film formation surface. FIG. 3 schematically shows the relationship between the absolute value of the bias voltage to be applied and the arithmetic average roughness (Ra) of the film formation surface. When film formation is performed under the conditions of region a in the figure, the arithmetic average roughness (Ra) of the film formation surface becomes the smallest. On the other hand, in this embodiment, the absolute value of the negative bias voltage applied to the substrate 11 is further increased as shown in the region b in the figure, and the energy when the argon ions 31 collide with the molding surface 15 is increased. Thus, the coating layer 12 is formed such that the arithmetic average roughness (Ra) of the molding surface 15 is greater than that before the film formation.

  As the magnitude of the negative bias voltage to be applied, it is necessary to select an appropriate value according to the configuration of the sputtering apparatus 20 to be used, such as the size of the substrate holding unit 23 and the sputtering target 22 and the distance between them. If the absolute value of the bias voltage to be applied is too small, the arithmetic average roughness (Ra) of the molding surface 15 after the coating layer 12 is formed is too small, and the effect of preventing the remaining air trap marks is not sufficient. End up. On the contrary, if the absolute value of the bias voltage to be applied is too large, the film formation rate is reduced and the efficiency is lowered, and if the absolute value of the bias voltage is further increased, the argon ion etching rate is larger than the film formation rate, Film formation hardly progresses. For example, in the case of the sputtering apparatus 20 in which the sputter target 22 has a size of 6 inches, the base material holding portion 23 has a size of 4 inches, and the distance between the sputter target 22 and the film formation surface is 100 mm, film formation is generally performed. For the purpose of flattening the surface, if the effective voltage to the target is 500V, the bias voltage applied to the substrate 11 is about −20V to −100V. On the other hand, in the present embodiment, the bias voltage applied to the substrate 11 when the film is formed such that the arithmetic average roughness (Ra) of the molding surface 15 is larger than that before the film formation is in the range of −150V to −450V. A range of −250V to −400V is more preferable.

  The coating layer 12 is formed from the viewpoint of ensuring a sufficient flow path for the air that has entered the air reservoir, reliably preventing the air reservoir traces from remaining, and preventing the surface roughness of the glass molded body from being deteriorated more than necessary. The molding surface 15 after film formation preferably has an arithmetic average roughness (Ra) of 0.01 μm to 0.2 μm, and more preferably 0.02 μm to 0.15 μm. The arithmetic average roughness (Ra) of the molding surface 15 may be adjusted according to the magnitude of the bias voltage applied to the substrate 11 during film formation. Further, from the viewpoint of ensuring the air flow path that has entered the air reservoir more reliably, the molding surface 15 after forming the coating layer 12 has an average length (RSm) of roughness curve elements of 0.5 μm or less. More preferably. 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 measured using a measuring machine having a spatial resolution of 0.1 μm or less, such as an AFM (Atomic Force Microscope).

  Unlike the method of the present embodiment, film formation is performed without applying a bias voltage to the substrate 11, and then a negative bias voltage is applied to the substrate 11 in a state where the application of the voltage to the sputtering target 22 is stopped. And the method of making the argon ion 31 collide with the coating layer 12 is also considered. However, in such a method, although the film thickness of the coating layer 12 is reduced by the collision of the argon ions 31, it is difficult to appropriately increase the arithmetic average roughness (Ra) of the molding surface 15. In the method of the present embodiment, a bias voltage is applied to the substrate 11 during film formation, and the film formation is performed while the argon ions 31 collide with the molding surface 15, so the film formation is performed by the interaction between the film formation process and the ion collision process. The arithmetic average roughness (Ra) of the subsequent molding surface 15 can be appropriately increased to a value.

  Although there is no restriction | limiting in particular in the material of the coating layer 12, The adjustment of arithmetic mean roughness (Ra) by the above-mentioned film-forming method is easy, and the material with low reactivity with glass is preferable. Especially, the metal layer which consists of at least 1 among chromium, aluminum, and titanium is preferable. All of these films have a common feature that they can be easily formed and the surface is oxidized by heating in the atmosphere to form a stable oxide layer. 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 a metal layer containing chromium is more preferable.

  The covering layer 12 may be constituted by a single layer made of one kind of material, or may be constituted by laminating a plurality of layers made of different materials. When laminating | stacking a some layer, it is preferable that the outermost surface of the coating layer 12 which contacts a molten glass drop is a metal layer which consists of at least 1 among chromium, aluminum, and titanium. It is also preferable that the coating layer 12 be a mixed film of a plurality of materials. Such a mixed film may be formed using a sputter target 22 containing a plurality of materials at a predetermined ratio, or may be formed by composite sputtering using a plurality of sputter targets 22 made of each material. Also good.

  The coating layer 12 only needs to have a thickness that can increase the arithmetic average roughness (Ra) of the molding surface 15 to a predetermined value. Usually, the coating layer preferably has a thickness of 0.05 μm or more. On the other hand, if the coating layer 12 is too thick, defects such as film peeling may easily occur. Therefore, the film thickness of the coating layer 12 is preferably 0.05 μm to 5 μm, and more preferably 0.1 μm to 1 μm.

  Argon gas is preferably used as the process gas introduced into the vacuum chamber 21 during film formation. It is also preferable to add an active gas such as nitrogen gas or oxygen gas to the argon gas. For example, the coating layer 12 made of nitride or oxide may be formed by introducing nitrogen gas or oxygen gas in addition to argon gas and reacting with the constituent elements of the sputtering target 22.

(Manufacturing method of glass molding)
Next, the manufacturing method of a glass forming body is demonstrated, referring FIGS. 4-6. FIG. 4 is a flowchart showing a method for producing a glass molded body. Moreover, FIG.5 and FIG.6 is a schematic diagram of the manufacturing apparatus of the glass forming body used by this embodiment. FIG. 5 shows the state in the step of dropping molten glass droplets on the lower mold (step S103), and FIG. 6 shows the state in the step of pressing the dropped molten glass droplets with the lower mold and the upper die (step S105). Show.

  The glass molded body manufacturing apparatus shown in FIGS. 5 and 6 includes a melting tank 32 that accommodates a molten glass 34, a dropping nozzle 33 that is connected to the lower part of the melting tank 32 and drops the molten glass droplet 30, and a dropping unit. The lower mold 10a for receiving the molten glass droplet 30 and the upper mold 10b for press-molding the molten glass droplet 30 together with the lower mold 10a are provided. The lower mold 10a and the upper mold 10b are the molding mold 10 manufactured by the above-described manufacturing method, and a negative bias voltage is applied so that the base material 11 serving as a base and the arithmetic average roughness (Ra) are increased. And a coating layer 12 formed in a state.

  The mold 10 manufactured by the above-described manufacturing method may be used as the lower mold 10a or the upper mold 10b. When using the shaping | molding die 10 as the lower mold | type 10a, the air accumulation trace produced when receiving the molten glass droplet 30 can be suppressed effectively. Moreover, when using a metal mold | die as the upper mold | type 10b, the air accumulation trace produced when pressurizing the dripped molten glass droplet 30 can be suppressed effectively. Here, the case where the molding die 10 is used for both the lower die 10a and the upper die 10b will be described as an example. However, by using the molding die 10 for at least one of the lower die 10a and the upper die 10b, An effect is obtained.

  The lower mold 10a and the upper mold 10b are configured to be heated to a predetermined temperature by a heating unit (not shown). As the heating means, known heating means can be appropriately selected and used. For example, a cartridge heater that is used while being embedded inside, a sheet heater that is used while being in contact with the outside, an infrared heating device, a high-frequency induction heating device, or the like can be used. It is preferable that the temperature can be controlled independently for the lower mold 10a and the upper mold 10b. The lower mold 10a has a position (dropping position P1) for receiving the molten glass droplet 30 by a driving means (not shown) and a position (pressure position P2) for performing pressure molding opposite to the upper mold 10b. It is configured to be movable between. Moreover, the upper mold | type 10b is comprised so that a movement to the direction (up-down direction of a figure) which presses the molten glass droplet 30 with the drive means which is not shown in figure is comprised.

  Hereinafter, according to the flowchart shown in FIG. 4, each process of the manufacturing method of the glass forming body 35 is demonstrated in order.

  First, the lower mold 10a and the upper mold 10b are heated to a predetermined temperature (step S101). 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 10a and the upper mold 10b may be the same or different. An appropriate temperature is appropriately set according to various conditions such as glass type, shape, size, mold material, size and the like. 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 lower mold 10a is moved to the dropping position P1 (step S102), and the molten glass droplet 30 is dropped from the dropping nozzle 33 (step S103) (see FIG. 5). The dropping of the molten glass droplet 30 is performed by heating the dropping nozzle 33 connected to the melting tank 32 that accommodates the molten glass 34 to a predetermined temperature. When the dropping nozzle 33 is heated to a predetermined temperature, the molten glass 34 accommodated in the melting tank 32 is supplied to the front end portion of the dropping nozzle 33 by its own weight, and accumulates in droplets by surface tension. When the molten glass collected at the tip of the dropping nozzle 33 reaches a certain mass, it is separated from the dropping nozzle 33 by gravity and becomes a molten glass droplet 30 and drops downward.

  The mass of the molten glass droplet 30 dropped from the dropping nozzle 33 can be adjusted by the outer diameter of the tip of the dropping nozzle 33 and the like, and depending on the type of glass, the molten glass droplet 30 of about 0.1 to 2 g is dropped. Can be made. Further, the molten glass droplet 30 dropped from the dropping nozzle 33 is once collided on the through-hole of the member having the through-hole, and a part of the collided molten glass droplet is allowed to pass through the through-hole. The melted molten glass droplet may be dropped on the lower mold 10a. By using such a method, it is possible to obtain a molten glass droplet 30 as small as 0.001 g, for example, so that the molten glass droplet 30 dropped from the dropping nozzle 33 is smaller than when it is directly received by the lower mold 10a. The glass molded body 35 can be manufactured.

  In this embodiment, as the lower mold 10a, the molding mold 10 having the coating layer 12 formed with a negative bias voltage applied so as to increase the arithmetic average roughness (Ra) is used. Air accumulation marks generated when the molten glass droplet 30 is received by the mold 10a can be effectively suppressed, and occurrence of film peeling of the coating layer 12 can be suppressed.

  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 lower mold 10a is moved to the pressing position P2 (step S104), the upper mold 10b is moved downward, and the molten glass droplet 30 is pressurized with the lower mold 10a and the upper mold 10b (process S105) ( (See FIG. 6). Since the molten glass droplet 30 is hotter than the lower mold 10a, the molten glass droplet 30 dropped on the lower mold 10a is cooled by heat radiation from the contact surface with the lower mold 10a and the upper mold 10b while being pressurized. Then, it is solidified to form a glass molded body 35. When the glass molded body 35 is cooled to a predetermined temperature, the upper mold 10b is moved upward to release the pressure. Depending on the type of glass, the size and shape of the glass molded body 35, the required accuracy, etc., it is usually preferable to release the pressure after cooling to a temperature near the Tg of the glass.

  In the present embodiment, since the molding die 10 having the coating layer 12 formed with a negative bias voltage applied so as to increase the arithmetic average roughness (Ra) is used as the upper die 10b, Air accumulation marks generated when the molten glass droplet 30 is pressurized by the mold 10a and the upper mold 10b can be effectively suppressed, and occurrence of film peeling of the coating layer 12 can be suppressed.

  The load applied to press the molten glass droplet 30 may be always constant or may be changed with time. What is necessary is just to set the magnitude | size of a load suitably according to the size etc. of the glass forming body 35 to manufacture. The driving means for moving the upper mold 10b 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 10b is moved upward and retracted, the solidified glass molded body 35 is recovered (step S106), and the production of the glass molded body 35 is completed. Thereafter, when the glass molded body 35 is subsequently manufactured, the lower mold 10a is moved again to the dropping position P1 (step S102), and the subsequent steps may be repeated. In addition, the manufacturing method of the glass forming body of this embodiment may include another process other than having demonstrated here. For example, a step of inspecting the shape of the glass molded body 35 before collecting the glass molded body 35, a step of cleaning the lower mold 10a and the upper mold 10b after collecting the glass molded body 35, and the like may be provided.

  As described above, according to the method for manufacturing a glass molded body of the present embodiment, at least one of the lower mold 10a and the upper mold 10b uses the mold 10 manufactured by the above-described method. As a result, it is possible to satisfactorily prevent the occurrence of air accumulation during receiving 30 or pressure molding, and to suppress the occurrence of film peeling of the coating layer 12. Therefore, the lifetime of an expensive mold can be improved, and a glass molded body having no air accumulation trace can be stably produced at a low cost.

  The glass molded body 35 manufactured by the manufacturing method of the present 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.

(Glass gob manufacturing method)
When using the shaping | molding die 10 as the lower mold | type 10a, the molten glass droplet 30 dripped at the lower mold | type 10a by process S103 is cooled and solidified on the lower mold | type 10a as it is, without pressure-molding, and a glass gob (glass lump) is obtained. It can also be obtained. Even in that case, it is possible to satisfactorily produce a glass gob having no air accumulation at low cost because it can satisfactorily prevent the occurrence of air accumulation marks when receiving the molten glass droplet 30 and suppress the occurrence of film peeling of the coating layer 12. can do. The details of each step are the same as those in the case of manufacturing the above-described glass molded body. The manufactured glass gob can be used as a material glass (glass preform) for manufacturing an optical element or the like 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.

  First, the molding surface 15 was formed on the base material 11 of the molding die 10 used as the lower die 10a and the upper die 10b. The material of the base material 11 was a sintered body of silicon carbide (SiC). The forming surface 15 was a concave spherical surface, and after cutting using a diamond bite, polishing was performed so that the arithmetic average roughness (Ra) was 0.005 μm.

Next, the base material 11 was attached to the base material holding part 23 of the sputtering apparatus 20 shown in FIG. The sputter target 22 was a chromium target having a diameter of 152 mm (6 inches), and the distance between the sputter target 22 and the molding surface 15 was 65 mm. The base material 11 is heated to 200 ° C. while the valve 29 is opened and the inside of the vacuum chamber 21 is evacuated. After the inside of the vacuum chamber 21 reaches a high vacuum of 10 ⁻³ Pa level, the flow rate adjustment valve 27 was opened, and argon gas was introduced from the argon cylinder 26 to 1 Pa. Then, while applying a predetermined negative bias voltage to the base material 11 (base material holding part 23) by the bias power source 25, a high frequency power of 600 W is applied to the sputter target 22 by the sputter power source 24, and the film thickness becomes 0. A 5 μm chromium film (coating layer 12) was formed. At this time, the effective voltage (self-potential bias Vdc) to the target was about 500V. The bias voltages applied to the substrate 11 were 0V (Comparative Example 1), -50V (Comparative Example 2), -200V (Example 1), -300V (Example 2), -400V (Example 3) and-. There were six types of 500V (Comparative Example 3), and two molds 10 were prepared for each. However, under the conditions of Comparative Example 3, the absolute value of the bias voltage to be applied was too large, and the chromium film was hardly formed.

  After the film formation was completed, the mold 10 was taken out from the vacuum chamber 21, and the arithmetic average roughness (Ra) and the average length (RSm) of the roughness curve element of the molding surface 15 on which the chromium film was formed were measured. The measurement results are shown in Table 1. As shown in Table 1, in the molds 10 of Comparative Examples 1 and 2, the arithmetic average roughness (Ra) of the molding surface 15 is almost the same as that before the film formation or smaller than that before the film formation. It was confirmed that in the molds 10 to 3, the arithmetic average roughness (Ra) was higher than that before film formation. The arithmetic average roughness (Ra) and the average length of the roughness curve element (RSm) were measured by AFM (D3100 manufactured by Digital Instruments).

  For each of the five types of molds 10 excluding Comparative Example 3, the produced molds 10 were used as the lower mold 10a and the upper mold 10b, and a glass molded body was manufactured according to the flowchart shown in FIG. Phosphoric acid glass having a Tg of 480 ° C. was used as the glass material. The temperature near the tip of the dropping nozzle 33 was set to 1000 ° C., and about 190 mg of the molten glass droplet 30 was set to drop. The heating temperatures of the lower mold 10a and the upper mold 10b were 500 ° C. for the lower mold 10a and 450 ° C. for the upper mold 10b, and the load during pressure molding was 1800N.

  1000 glass molded bodies are produced for each mold 10, and the upper and lower surfaces of the produced glass molded bodies are observed to check for the presence of air accumulation marks and the presence or absence of peeling of the chromium film (coating layer 12). Evaluated. The results are also shown in Table 1. As shown in Table 1, when the molds 10 of Examples 1 to 3 were used, there were no air accumulation marks on the upper and lower surfaces of the glass molded body, and no peeling of the coating layer 12 was observed. On the other hand, in the case of Comparative Example 1, air accumulation marks were confirmed on the lower surface of the glass molded body, and in the case of Comparative Example 2, air accumulation marks were confirmed on both the upper and lower surfaces of the glass molded body.

  Thus, in Examples 1 to 3, when the chromium film (coating layer 12) is formed on the molding surface 15, the arithmetic average roughness (Ra) of the molding surface 15 is higher than that before the film formation due to the collision of argon ions. Since the film was formed in a state where a negative bias voltage was applied to the base material 11 so as to increase, it is possible to satisfactorily prevent air accumulation marks from remaining and to suppress peeling of the coating layer 12 and to have excellent durability. It was confirmed that

DESCRIPTION OF SYMBOLS 10 Molding die 10a Lower die 10b Upper die 11 Base material 12 Coating layer 15 Molding surface 20 Sputtering device 21 Vacuum chamber 22 Sputter target 23 Base material holding part 24 Sputter power source 25 Bias power source 26 Argon cylinder 27 Flow rate adjustment valve 28 Exhaust pump 29 Valve 30 Molten Glass Drop 31 Argon Ion 32 Melting Tank 33 Dropping Nozzle 34 Molten Glass 35 Glass Molded Body P1 Dropping Position P2 Pressurizing Position

Claims (8)

A manufacturing method of a mold for manufacturing a glass gob or a glass molded body from a dropped molten glass drop,
Forming a molding surface having a predetermined shape on the base of the molding die;
Forming a coating layer on the molding surface by a sputtering method,
The film formation of the coating layer is selected so that the arithmetic average roughness (Ra) of the molding surface is increased as compared to that before the film formation due to a part of process gas ions colliding with the molding surface during the film formation. A method for producing a mold, which is performed in a state where the bias voltage applied is applied to the substrate.   2. The method for producing a molding die according to claim 1, wherein the molding surface after the coating layer is formed has an arithmetic average roughness (Ra) of 0.01 μm to 0.2 μm.   3. The method for manufacturing a mold according to claim 2, wherein an average length (RSm) of roughness curve elements on the molding surface after the coating layer is formed is 0.5 μm or less.   4. The method for manufacturing a molding die according to claim 2, wherein the molding surface before forming the coating layer has an arithmetic average roughness (Ra) of 0.005 μm or less. 5.   The outermost surface layer of the said coating layer is a metal layer which consists of at least 1 among chromium, aluminum, and titanium, The manufacturing method of the shaping | molding die in any one of Claim 1 to 4 characterized by the above-mentioned.   The method for manufacturing a mold according to any one of claims 1 to 5, wherein the process gas includes an argon gas. Dropping molten glass droplets into the first mold,
Cooling the dripped molten glass droplets on the first mold, and a method for producing a glass gob,
The method for manufacturing a glass gob, wherein the first mold is a mold manufactured by the method for manufacturing a mold according to any one of claims 1 to 6. Dropping molten glass droplets into the first mold,
A step of pressure-molding the dropped molten glass droplets with a first mold and a second mold facing the first mold, and a method for producing a glass molded body,
At least one of the first mold and the second mold is a mold manufactured by the mold manufacturing method according to any one of claims 1 to 6. A method for producing a glass molded body.

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