Glass molding device and die cleaning method

Abstract

This glass molding device (10a) comprises: a molding chamber; an upper die (15) and a lower die (14) that are disposed facing each other in the interior of the molding chamber (26a) and that are molded into a predetermined shape; a lower shaft (19) that supports the lower die to be movable with respect to the upper die; an infrared lamp (28) that heats the upper die, the lower die, and molding glass; a jack (21) that moves the lower die in the direction in which the lower die is pressed against the upper die, thereby pressurizing and molding the molding glass by means of the lower die and the upper die; and an RF power supply (40) that applies a high-frequency pulse between the upper die and the lower die in a state in which a halogen-based gas has been supplied to the interior of the molding chamber when molding is not being performed, thereby generating plasma in the space between the upper die and the lower die and cleaning the upper die and the lower die by means of the plasma.

Description

Glass molding device and mold cleaning method

[0001] The present invention relates to a glass molding apparatus and mold cleaning method for molding glass products having complex shapes such as aspherical glass lenses by pressing a glass material with opposing molds.

[0002] Conventionally, a glass forming device is known in which a glass material is placed between molds installed at the ends of a fixed shaft and a moving shaft arranged opposite each other, the glass material is heated, and the moving shaft is pressed in the direction of the fixed shaft, thereby forcing the glass material against the molds and forming it into a predetermined shape (for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2005-306693

[0004] In such conventional glass molding devices, the mold surface becomes contaminated with each molding cycle, reducing mold releasability and sometimes causing fusion between the glass material and the mold (see FIG. 2 for details). When such fusion occurs on a large scale, the quality of the molded product cannot be maintained, and the mold must be replaced. Furthermore, when replacing the mold, the glass molding device must be stopped, and when mass production is resumed, the glass molding device must be operated in dummy mode until it reaches the appropriate temperature, resulting in reduced productivity. For these reasons, there has been a demand for a glass molding device that can remove the contaminants without stopping the device.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a glass molding apparatus and a mold cleaning method that are capable of cleaning a mold without stopping the apparatus even when molding is repeated.

[0006] In order to solve the above-mentioned problems and achieve the object, the glass forming device of the present invention is characterized by comprising: a forming chamber; a fixed mold and a movable mold arranged opposite each other inside the forming chamber and formed into a predetermined shape; a movable shaft that supports the movable mold so that it can move relative to the fixed mold; heating means that heats the fixed mold, the movable mold, and a glass material placed between the fixed mold and the movable mold; pressure forming means that moves the movable shaft in a direction that presses the movable mold against the fixed mold, thereby forming the glass material by pressurizing it with the movable mold and the fixed mold; and cleaning means that, when the glass material is not being formed, supplies a halogen-based gas inside the forming chamber and applies a high-frequency pulse between the fixed mold and the movable mold to generate plasma in the space between the fixed mold and the movable mold, and cleans the fixed mold and the movable mold with halogen radicals generated from the halogen-based gas by the plasma.

[0007] Furthermore, the present invention provides a mold cleaning method for cleaning the fixed mold and the movable mold in a glass molding device comprising: a molding chamber; a fixed mold and a movable mold arranged opposite each other above and below inside the molding chamber and molded into a predetermined shape; a movable shaft that supports the movable mold so that it can move relative to the fixed mold; heating means that heats the fixed mold, the movable mold, and a glass material placed between the fixed mold and the movable mold; and pressure molding means that moves the movable shaft in a direction that presses the movable mold against the fixed mold, thereby molding the glass material by pressurizing it with the movable mold and the fixed mold.The mold cleaning method is characterized in that, when the glass material is not being molded, a halogen-based gas is supplied into the molding chamber, and a high-frequency pulse is applied between the fixed mold and the movable mold to generate plasma in the space between the fixed mold and the movable mold, and the fixed mold and the movable mold are cleaned with halogen radicals generated from the halogen-based gas by the plasma.

[0008] The glass forming device according to the present invention has the effect of being able to regenerate a deteriorated mold that has been repeatedly used for forming with minimal downtime.

[0009] FIG. 1 is a diagram showing an example of a mold structure used in molding a glass material. FIG. 2 is a first diagram illustrating a mechanism by which fusion occurs between a mold and a glass material. FIG. 3 is a diagram showing the molecular structure of glass. FIG. 4 is a diagram showing an example of the molecular structure of molding glass. FIG. 5 is a second diagram illustrating a mechanism by which fusion occurs between a mold and a glass material. FIG. 6 is a diagram showing an example of a schematic structure for realizing a glass molding function provided in a glass molding apparatus. FIG. 7 is a diagram showing an example of an installation structure of a lower mold provided in a glass molding apparatus. FIG. 8 is a diagram showing an example of a schematic structure for realizing a mold cleaning function provided in the glass molding apparatus of the first embodiment. FIG. 9 is a diagram showing an example of the configuration of an exhaust system provided in a glass molding apparatus. FIG. 10 is a diagram showing an example of plasma generation conditions when argon is used. FIG. 11 is a diagram showing the plasma generation conditions for fluorine radicals (F ＊ 12 is a diagram illustrating an example of a schematic structure for realizing a mold cleaning function provided in the glass forming apparatus of the second embodiment. FIG. 13 is a diagram illustrating an example of a schematic structure for realizing a mold cleaning function provided in the glass forming apparatus of the third embodiment. FIG. 14 is a diagram illustrating an example of a structure of a plasma generating unit provided in the glass forming apparatus of the third embodiment. FIG. 15 is a diagram illustrating an example of a structure of a plasma generating unit provided in the glass forming apparatus of a modified example of the third embodiment.

[0010] Hereinafter, embodiments of a molding apparatus according to the present disclosure will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are replaceable and easily conceivable by those skilled in the art, or those that are substantially the same.

[0011] First Embodiment A first embodiment of the present disclosure relates to a glass molding device 10a that uses a superhard mold used to mold optical elements having complex surface shapes, such as aspherical glass lenses.

[0012] (Mold Deterioration Process (1)) First, a first mechanism by which fusion occurs between a mold 12 (also called a core) used in a glass molding apparatus 10a and a glass material will be described with reference to Figures 1 and 2. Figure 1 is a diagram showing an example of the structure of a mold used in molding a glass material. Figure 2 is a first diagram illustrating the mechanism by which fusion occurs between a mold and a glass material.

[0013] As shown in FIG. 1, the mold 12 has a structure in which an intermediate layer 12b and a mold release film 12c are laminated on the surface of a superhard material 12a.

[0014] Molding of glass materials is carried out at higher temperatures than injection molding, for example, at a maximum of 750°C for ordinary optical glass and 1500°C for quartz glass. Furthermore, during pressing, the mold is subjected to a pressure of 200 (N / cm ２ ) ~ 220 (N / cm ２ ) is applied. Therefore, a super-hard material 12a having high mechanical strength at high temperatures is used for the mold base material. The super-hard material 12a is an alloy that has very high hardness and loses less hardness at high temperatures than other metals. The super-hard material 12a is manufactured, for example, by sintering WC particles 12d (tungsten carbide), which are super-hard particles, with a metal such as Ni, Ti, Cr, or Co as a binder 12e.

[0015] The intermediate layer 12b is a layer containing Cr, Ni, etc., and has a thickness of about 30 nm, which is formed on the surface of the super-hard material 12a. The intermediate layer 12b is a layer provided to improve the adhesion between the super-hard material 12a and the release film 12c, which have different thermal expansion coefficients. The thermal expansion coefficient of the intermediate layer 12b is approximately intermediate between that of the super-hard material 12a and the release film 12c.

[0016] The mold release film 12c is a layer made of Pt-Ir or the like, with a thickness of, for example, about 600 (nm), to prevent reaction with the glass material. Pt (platinum) is well known as a material that is non-reactive with glass, while Ir (iridium) is highly heat-resistant and durable even at high temperatures, and is used in parts exposed to high temperatures, such as jet engines. In other words, the mold release film 12c is made of a material that is heat-resistant and has low reactivity with the glass material, making it less likely to fuse with the glass material (excellent mold release properties).

[0017] However, it is known that even with such a mold 12, the glass material gradually changes in quality as the molding cycle is repeated, the mold release properties deteriorate, and eventually the glass and the mold fuse together.

[0018] As the molding cycle of the glass material is repeated, the temperature of the mold 12 is repeatedly raised and lowered, and as a result, as shown in the left diagram of Figure 2, tungsten (W), a component of the superhard material 12a, may cross the intermediate layer 12b and the mold release film 12c, diffuse to the surface of the mold release film 12c, and become exposed. Similarly, chromium (Cr), etc., a component of the intermediate layer 12b, may cross the mold release film 12c and diffuse to the surface of the mold release film 12c. The exposed tungsten, chromium, etc. then promotes fusion between the glass material and the mold 12.

[0019] More specifically, the Ir in the Pt-Ir surface layer is oxidized and evaporated, causing a shortage of Ir in the film, and the Pt-Ir, which is originally in a solid solution state and has a uniform structure (uniform density), becomes polycrystallized and separates into high-density Pt-rich crystal grains and low-density grain boundaries between them. Because the density of these grain boundaries is low, the chromium constituting the intermediate layer 12b in FIG. 2 and the tungsten constituting the superhard material 12a in the same figure diffuse along the grain boundaries and appear on the surface of the mold release film 12c, and these are absorbed by the moisture 13c (H ２ O). As a result, chromium oxide 13a and tungsten oxide 13b are produced, as shown in the right diagram of Figure 2. The produced chromium oxide 13a and tungsten oxide 13b have good wettability with the glass material, so the glass is fused to the chromium oxide 13a and tungsten oxide 13b that are adhered to the surface of the mold 12.

[0020] This phenomenon occurs and accumulates with each molding cycle of the glass material, gradually increasing the area of ​​the fusion points and gradually worsening the mold releasability, which may ultimately result in large-scale fusion.

[0021] Since it is difficult to prevent the exposure of tungsten and chromium, the glass molding apparatus 10a of this embodiment has the function of removing these exposed materials from the mold release film 12c while the density of the exposed tungsten and chromium is still low, without removing the mold from the molding apparatus, i.e., without stopping the apparatus.

[0022] (Mold Deterioration Process (2)) Next, a second mechanism by which fusion occurs between the mold 12 used in the glass molding device 10a and the glass material will be described with reference to Figures 3, 4, and 5. Figure 3 is a diagram showing the molecular structure of glass. Figure 4 is a diagram showing an example of the molecular structure of molding glass. Figure 5 is a second diagram explaining the mechanism by which fusion occurs between the mold and the glass material.

[0023] In order to improve productivity by shortening the time required for heating and cooling the glass during molding, molding glasses that can be deformed at low temperatures are commercially available. For example, as shown in Fig. 4, such molding glasses 6 contain alkali metals such as Na, K, and Li, or alkaline earth elements such as Ca, Ba, and Mg.

[0024] In theory, alkali metals and alkaline earth metals have very high electronegativity and a strong ability to attract electrons, which allows them to break the Si-O bonds (see Figure 3) that form glass material 5 and insert into the network. Furthermore, because they are monovalent and divalent elements, they act to break the network, which makes it possible to lower the forming temperature.

[0025] However, alkali metals and alkaline earth metals are highly volatile, and for example, the vapor pressure of Na at 400° C. is 45 (Pa).

[0026] That is, N ２ However, the moment the mold is evacuated to improve transferability, Na evaporates from the molding glass 6 and adheres to the mold surface.

[0027] The Na attached to the surface of the release film 12c in FIG. 1 is immediately converted into H remaining in the molding chamber. ２It reacts with O to form oxides such as sodium hydroxide 6a (NaOH) and potassium hydroxide 6b (KOH) shown in Figure 5. For example, Na is originally contained in glass, so it has a high affinity, and fusion occurs between the molding glass 6 and the release film 12c. Since the density of fusion is low at first, the fused regions are scattered like islands, but they gradually grow and eventually reach a large-scale fusion.

[0028] The glass molding apparatus 10a of this embodiment removes the fused material from the surface of the release film 12c by cleaning the surface of the mold 12 without stopping the apparatus before the fusion that occurs in this manner becomes large-scale.

[0029] (Schematic Structure of Glass Forming Apparatus) The schematic structure of a glass forming apparatus 10a according to an embodiment will be described with reference to Figures 6 and 7. Figure 6 is a diagram showing an example of a schematic structure for realizing the glass forming function of the glass forming apparatus. Figure 7 is a diagram showing an example of an installation structure of a lower mold of the glass forming apparatus.

[0030] In Fig. 6, a molding glass 6, which is an object to be molded, is placed on a lower mold 14. An upper mold 15 is disposed above the lower mold 14 in a position opposite the lower mold 14. Both the lower mold 14 and the upper mold 15 have the same structure as the mold 12 described above.

[0031] 7, the lower mold 14, with the release film 12c facing upward, is fixed to a lower joint 16 that is movable in the vertical direction (the Z-axis direction in FIG. 6) via a mold die 17 and a die plate 18. The lower mold 14 is an example of a movable mold in the present disclosure.

[0032] The bottom fitting 16 is made of a ceramic such as SiN, which has high mechanical strength even at high temperatures, and is connected to a jack 21 that can be moved up and down by the rotational force of a servo motor 20 via a lower shaft 19 shown in FIG. 6. This allows the bottom fitting 16 to move up and down (in the Z-axis direction). The lower shaft 19 is an example of a moving shaft in the present disclosure. The jack 21 is also an example of a pressure molding means in the present disclosure.

[0033] A load cell 22 for detecting the pressing force of the lower mold 14 is installed between the lower shaft 19 and the jack 21. Although not shown, the glass forming apparatus 10a further includes a mechanism for detecting the vertical position of the lower shaft 19.

[0034] The lower mold 14 on which the molding glass 6 is placed is assembled into the mold die 17 with an accuracy of several μm, as shown in Fig. 7. The mold die 17 is then fastened to the die plate 18 with screws 17a. Although only one screw 17a is shown in Fig. 7, the mold die 17 is screwed to the die plate 18 at multiple positions surrounding the lower mold 14.

[0035] Furthermore, the die plate 18 is fastened to the bottom joint 16 by a screw 18a. Although only one screw 18a is shown in Fig. 7, the die plate 18 is actually fastened to the bottom joint 16 by the screw at a plurality of positions.

[0036] Returning to Fig. 6, the upper mold 15 has a structure similar to the fixing structure of the lower mold 14 shown in Fig. 7. That is, the upper mold 15, with the mold release film 12c facing downward, is fixed to a ceramic upper fitting 23 via a mold die and die plate (not shown). The upper fitting 23 is then fixed to an apparatus column 25 constituting the outer housing of the glass molding apparatus 10a via an upper shaft 24, which is a fixed shaft. The upper mold 15 is an example of a fixed mold in the present disclosure.

[0037] The glass forming apparatus 10a moves the lower mold 14 upward, thereby sandwiching and pressurizing the molding glass 6 placed on the lower mold 14 between the lower mold 14 and the fixed upper mold 15. This causes the molding glass 6 to be formed into a shape that conforms to the mold surfaces of the lower mold 14 and the upper mold 15. The glass forming apparatus 10a is also called a fixed mold type molding apparatus.

[0038] The lower mold 14, upper mold 15, lower joint 16, and upper joint 23 are housed inside a quartz tube 26. O-rings 27 are installed at the top and bottom of the quartz tube 26 to maintain airtightness. As a result, a sealed molding chamber 26a is formed inside the quartz tube 26. In addition, O-rings 27a are also installed at various sliding parts and joints in the glass molding device 10a to maintain airtightness.

[0039] A plurality of ring-shaped infrared lamps 28 are arranged on the outside of the quartz tube 26. In addition, a reflecting mirror 29 is arranged on the outer periphery of the infrared lamps 28. The light emitted from the infrared lamps 28 and the light reflected from the reflecting mirror 29 are also used to heat the lower mold 14 and the upper mold 15. The temperatures of the lower mold 14 and the upper mold 15 are measured by a thermocouple 30, and the output of the infrared lamps 28 is controlled so as to obtain a desired temperature rise curve. The infrared lamps 28 are an example of a heating means in the present disclosure.

[0040] In addition, reflectors 31 are installed above and below the infrared lamp 28 to surround the bottom fitting 16 and the top fitting 23 so that the light emitted by the infrared lamp 28 does not heat the O-ring 27 .

[0041] The reflecting mirror 29 becomes hot due to the heat emitted by the infrared lamp 28. Therefore, the reflecting mirror 29 is cooled by the cooling water flowing through the cooling water passage 32 and the room temperature nitrogen gas (N ２ The cooled cooling water is discharged from a water channel (not shown). The cooled air is exhausted from an exhaust port 34. Each part of the glass forming apparatus 10a is also appropriately cooled by the cooling water flowing through the cooling water channel 35.

[0042] When forming the glass 6 using the glass forming apparatus 10a, an inert gas such as nitrogen gas is supplied through the gas supply port 36 into the interior of the quartz tube 26 (i.e., the forming chamber 26a). This inert gas is dried to thoroughly remove moisture. A control device (not shown) then detects the temperatures of the lower mold 14 and the upper mold 15 using a thermocouple 30. The control device also controls the output of the infrared lamp 28 to heat the lower mold 14, the upper mold 15, and the glass 6 to be formed. Once the forming temperature is reached, the control device controls the speed, torque, and rotation amount of the servo motor 20 in relation to the detected temperature, thereby moving the lower shaft 19 at a predetermined speed, torque (pressing force), and position control according to a preset program, thereby forming the glass 6 to a predetermined shape. If a more precise transfer of the mold shape is required, the forming chamber is evacuated and then formed. Dry nitrogen is then supplied through the gas supply port 36 to open the forming chamber to the atmosphere and cool the mold and the formed product. At this time, the control device first applies a predetermined pressing force to the lower shaft 19, and then supplies a predetermined flow rate of inert gas to the molding chamber 26a to slowly cool the lower mold 14, the upper mold 15, and the molded glass product. Then, the molding is completed by rapid cooling. The inert gas supplied to the molding chamber 26a is exhausted from the gas exhaust port 37.

[0043] When glass fusion occurs between the mold and the glass in such a glass molding device, the mass production molding line and the molding operation of the glass molding device must first be stopped, the mold must be cooled with nitrogen gas, and the mold die and die plate must be removed from the joint. The mold must then be removed, the fused glass must be removed, and the mold release film and intermediate layer must be peeled off and re-formed. During this time, the glass molding device is in a stopped state, so a spare mold unit is typically prepared and replaced to shorten downtime. However, during the mold replacement process, the temperature of the vertical shaft and column drops and shrinks. If the column shrinks, the vertical position of the mold changes, resulting in a deterioration in the thickness accuracy of the molded glass product. Therefore, the glass molding device must be idled until the column temperature stabilizes, and production is halted during this time. In particular, for large-diameter lenses, for which fixed mold systems are advantageous, the molds are large and heavy, and therefore have a large heat capacity, which means it takes a long time for the temperature to stabilize. Thus, when glass fusion occurs between the mold and the glass in a fixed mold system, productivity is significantly reduced.

[0044] To solve this problem, the glass molding apparatus 10a of this embodiment has a cleaning function for removing tungsten and chromium fused to the mold release films 12c of the lower mold 14 and the upper mold 15. The cleaning function will be described in detail later (see FIG. 8).

[0045] (Cleaning Function of Glass Forming Apparatus) The mold cleaning function provided in the glass forming apparatus 10a of the first embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram showing an example of a schematic structure for realizing the mold cleaning function provided in the glass forming apparatus of the first embodiment.

[0046] The lower mold 14 is at ground potential via the lower electrical introduction flange 42a and the coaxial cable 41a. The upper mold 15 is connected to the RF power supply 40 via the upper electrical introduction flange 42b and the coaxial cable 41b. The coaxial cables 41a and 41b prevent noise generation, thereby preventing malfunction of the device itself or adjacent devices. Furthermore, since even coaxial cables have a certain degree of impedance, it is desirable for their length to be short.

[0047] The RF power supply 40 applies high-frequency power, such as 13.56 MHz, between the lower mold 14 and the upper mold 15. A matching box 43 is connected between the RF power supply 40 and the upper electrical introduction flange 42b. The matching box 43 is also called a matching box, and is a unit incorporating a circuit made up of a capacitor and a coil that can control the capacitance. The matching box 43 adjusts the impedance of the matching box 43 (performs impedance matching) so that the reflected power from the upper mold 15 toward the RF power supply 40 is minimized.

[0048] The inside of the molding chamber 26a surrounded by the quartz tube 26 is supplied with Ar (argon), NF ３ (nitrogen trifluoride), CF ４ (carbon tetrafluoride), Cl ２ A gas containing a halogen element such as chlorine (hereinafter referred to as a halogen-based gas) is supplied.

[0049] The argon gas supply line is provided with an Ar flow meter 45a. The nitrogen trifluoride supply line is provided with an NF ３ The carbon tetrafluoride supply line is provided with a flow meter 45b. ４ The supply path for chlorine gas is provided with a flow meter 45c. ２ A flow meter 45d is provided. As the flow meter, a well-known mass flow controller (MFC) is used.

[0050] A gas exhaust port 37 is provided at the lower end of the molding chamber 26a, and gas exhausted from the gas exhaust port 37 passes through an exhaust system 60 (see FIG. 9) to be described later and is then exhausted.

[0051] After the glass forming apparatus 10a has repeatedly formed the forming glass 6 a predetermined number of times, the inside of the forming chamber 26a is evacuated to an ultimate vacuum. A vacuum gauge (not shown) is installed inside the forming chamber 26a to measure the vacuum level inside the forming chamber 26a. At this time, the QMASS 65 (see FIG. 9), which will be described later, is operated to evacuate the forming chamber 26a to a vacuum level of water (OH), oxygen (O ２ , O) is sufficiently low.

[0052] After that, with the exhaust system running, Ar / NF ３ / Cl２ The gases are supplied at a flow rate ratio of, for example, 9.5 / 0.4 / 0.1 so that the pressure P inside the molding chamber 26a becomes approximately 50 Pa. The flow rates of the gases are controlled by the flow meters shown in Fig. 8. Note that the blend of the mixed gases is an example, and is optimized in advance depending on the types and ratios of elements adhering to the molds (lower mold 14, upper mold 15).

[0053] Next, the lower shaft 19 (see FIG. 6 ) is moved so that the distance d between the lower mold 14 and the upper mold 15 (hereinafter referred to as the mold-to-mold distance d or the electrode-to-electrode distance d ) is 20 mm. The value of 20 mm is determined based on the pressure P inside the molding chamber 26a, which is set to 50 Pa. If the pressure P inside the molding chamber 26a is set to a different value, the mold-to-mold distance d is set to a different value. The lower mold 14 must be grounded. However, since a ceramic bottom fitting 16 (see FIG. 6 ) is located below the lower mold 14, it is desirable to provide separate wiring to ensure that the bottom fitting 16 is at ground potential. Meanwhile, an RF voltage must be applied to the upper mold 15, and an upper insulator 53 is installed between the upper mold 15 and the top fitting 23 (see FIG. 6 ) to prevent abnormal discharge. It is desirable to maximize the surface area of ​​the upper insulator 53 to enhance insulation. A lower insulator 52 is disposed between the lower mold 14 and the lower joint 16 (see FIG. 6) to improve the insulating properties of the lower mold 14 .

[0054] Glass forming apparatus 10a generates plasma in the space between lower mold 14 and upper mold 15 by applying pulse-modulated high-frequency power (hereinafter referred to as high-frequency pulse) from RF power supply 40. At this time, the ease of discharge (level of discharge inception voltage) depends on the gas type and pressure multiplied by the inter-electrode distance (in this case, inter-mold distance d) (Paschen's law).

[0055] A specific example of plasma generation conditions will now be described with reference to Fig. 10. Fig. 10 is a diagram showing an example of plasma generation conditions when argon is used.

[0056] The vertical axis of Fig. 10 represents the discharge inception voltage V0 (ease of discharge), and the horizontal axis of Fig. 10 represents the product of the pressure P inside the molding chamber 26a and the inter-electrode distance d. From Fig. 10, it can be seen that the discharge inception voltage V0 is at its minimum (easiest discharge) when the product Pd of the pressure P and the inter-electrode distance d is near 1.0. This is an empirical rule known as Paschen's law. Therefore, when the pressure P = 50 Pa and the inter-mold distance d (inter-electrode distance) is set to 20 mm, the discharge inception voltage V0 becomes minimal (approximately 277 V).

[0057] The pressure P is also related to the rate of the reaction described below, so it is desirable to take this into consideration when determining the pressure. Once the pressure P is determined, the mold-to-mold distance d is adjusted according to Figure 10. However, the mold-to-mold distance d also affects the exhaust efficiency of various reaction products, so this must also be taken into consideration.

[0058] Next, the RF power supply 40 provided in the glass forming apparatus 10a is turned on. As a result, plasma 100a is generated in the space between the molds, i.e., between the lower mold 14 and the upper mold 15. A halogen-based gas (e.g., NF ３ The gases are decomposed, excited, or ionized within the plasma 100a.

[0059] The chemical reactions occurring at this time are described by, for example, chemical reaction formulas (1) and (2).

[0060]

[0061]

[0062] e in chemical reaction formula (1) － represents high-energy electrons. Chemical reaction formula (1) shows the reaction between high-energy electrons and NF ３ The chemical reaction formula (2) shows that the generated fluorine atoms collide with high-energy electrons, activating the fluorine to form high-energy fluorine radicals (F ＊ ) is generated.

[0063] The generated F ＊reacts with the glass attached to the surface of the mold (lower mold 14 and upper mold 15) to form silicon tetrafluoride SiF as shown in chemical reaction formula (3). ４ Fluorine radicals (F ＊ ) to remove the glass (SiO ２ 11 shows an example of how the surface of the release film 12c is cleaned in this manner.

[0064] As shown in FIG. 11, fluorine radicals (F ＊ ) 70 reacts with the molding glass 6 attached to the surface of the release film 12c, thereby generating silicon tetrafluoride 71 and oxygen 72. Note that the fluorine radicals 70 are an example of the halogen radicals in the present disclosure.

[0065]

[0066] As shown in chemical reaction formula (3), the generated fluorine radicals react with glass (SiO2) to form SiF ４ is generated. ４ Because of its high vapor pressure, it is vaporized and exhausted. ４ In order to promote evaporation of the glass (SiO ) adhering to the surface of the mold, the mold (lower mold 14 and upper mold 15) may be heated to about 200°C by operating the infrared lamp 28 in FIG. 8. Chemical reaction formula (3) is a process known as reactive etching. The reactive etching process removes the glass (SiO ) adhering to the surface of the mold. ２ ) is removed and cleaned, and the releasability of the release film 12c is restored.

[0067] As is well known, platinum (Pt) constituting the mold release film 12c is not easily corroded by fluorine (F), so the SiO fused to the surface of the mold release film 12c ２ In addition, alkali metal oxides, alkaline earth oxides, tungsten oxide 13b, and chromium oxide 13a other than glass are also removed by the same process (F ＊ ) is removed.

[0068] The key to this process is the fluorine radical (F ＊ ) amount of F ＊ The more SiO ２From the chemical reaction formula (1) and the chemical reaction formula (2), the fluorine radical (F ＊ ) is found to be highly dependent on the electron density of the plasma.

[0069] The plasma 100a generated in this embodiment is called a CCP (Capacitively Coupled Plasma). The electron density of the CCP is, for example, 1×10 １６ ( / m ３ ) and the generated fluorine radicals (F ＊ The amount of electrons is estimated to be about 1 / 10 to 1 / 100 of the electron density of the CCP. Therefore, it is desirable to generate plasma 100a having as high an electron density as possible.

[0070] (Schematic Structure of Exhaust System) The exhaust system 60 provided in the glass forming apparatus 10a of the embodiment will be described with reference to Fig. 9. Fig. 9 is a diagram showing an example of the configuration of the exhaust system provided in the glass forming apparatus.

[0071] The glass forming apparatus 10a is equipped with an exhaust system 60 that exhausts the nitrogen gas supplied to the forming chamber 26a when forming the glass 6 to be formed, the halogen-based gas supplied to the forming chamber 26a when generating plasma, and the gas generated by cleaning the mold.

[0072] 9, the exhaust system 60 includes a cryopump 61, a turbomolecular pump 62, a mechanical booster pump 63, and a dry pump 64. These multiple pumps are connected as appropriate either directly or via valves 66a, 66b, 66c, 66d, 66e, and 66f, a butterfly valve 67, and an orifice 68. Furthermore, the glass forming apparatus 10a includes a QMASS 65, which is a type of mass spectrometer, in the exhaust system. The exhaust system 60 is an example of the exhaust means of the present disclosure.

[0073] The cryopump 61 is a type of adsorption pump, and is H ２ Therefore, by performing evacuation via the cryopump 61, the H remaining inside the molding chamber 26a can be removed. ２The O partial pressure can be reduced.

[0074] In the glass forming apparatus 10a, the forming chamber 26a is opened to the atmosphere every time the forming of the forming glass 6 is completed in order to remove the formed product and set a new forming glass 6. Therefore, the inner wall of the opened forming chamber 26a is exposed to the atmosphere. ２ O adheres. Adhered H ２ O vaporizes during evacuation and decomposes into H and OH when the mold (lower mold 14 and upper mold 15) is heated. The generated active oxygen OH reacts with the cemented carbide material 12a, blackening the mold. As a result, the absorption rate of near-infrared light from the infrared lamp 28 increases. In addition, the active oxygen OH oxidizes the chromium and tungsten on the surface of the mold release film 12c, significantly reducing mold release performance.

[0075] In addition, the cryopump 61 absorbed H ２ The O is exhausted at a predetermined timing (for example, at the end of work for the day).

[0076] The turbo molecular pump 62 is a type of mechanical vacuum pump, and exhausts gas by ejecting gas molecules contained in the gas as a result of the high speed rotation of a rotor, which is a rotating body having metallic turbine blades.

[0077] The mechanical booster pump 63 is used in combination with other pumps to increase the pumping speed in pressure regions where the pumping speed of the other pumps is low.

[0078] The dry pump 64 is a mechanical vacuum pump that does not use oil or liquid inside the vacuum chamber, and because no oil or liquid is used, it can perform clean evacuation.

[0079] QMASS65 is a type of mass spectrometer that measures H when the ultimate vacuum is reached. ２This is a means for managing the O partial pressure and determining the end of the plasma cleaning process. Specifically, the glass forming apparatus 10a forcibly terminates the cleaning process when the QMASS 65 detects platinum (Pt: mass number 195) or iridium (Ir: mass number 192) that constitutes the mold release film 12c. This is because if platinum or iridium is detected in the gas generated inside the forming chamber 26a, it is believed that the mold release film 12c itself is being eroded by the cleaning process, that is, so-called over-etching has occurred.

[0080] The exhaust system 60 also includes a dedicated detoxification device 69 at the downstream of the dry pump 64. The detoxification device 69 is an adsorption unit that detoxifies halogen-based reactive gases such as fluorine by adsorbing them.

[0081] As described above, the glass forming apparatus 10a of the first embodiment comprises the forming chamber 26a, the upper mold 15 (fixed mold) and the lower mold 14 (movable mold) which are arranged vertically opposite each other inside the forming chamber 26a and which are formed into a predetermined shape, the lower shaft 19 (movable shaft) which supports the lower mold 14 so that it can move relative to the upper mold 15, the infrared lamps 28 (heating means) which heat the upper mold 15, the lower mold 14, and the glass to be formed placed between the upper mold 15 and the lower mold 14, and the lower shaft 19 is moved in a direction in which the lower mold 14 is pressed against the upper mold 15, thereby pressing the glass to be formed 6 against the lower mold 14. The apparatus includes a jack 21 (pressure molding means) for molding the glass 6 by applying pressure between the upper mold 15 and the lower mold 14 and the upper mold 15, and an RF power supply 40 (cleaning means) for generating plasma 100a in the space between the upper mold 15 and the lower mold 14 by applying a high-frequency pulse between the upper mold 15 and the lower mold 14 while a halogen-based gas is supplied to the interior of the molding chamber 26a when the molding glass 6 is not being molded, and cleaning the upper mold 15 and the lower mold 14 with fluorine radicals 70 (halogen radicals) generated from the halogen-based gas by the plasma 100a. Therefore, even if molding is repeated, cleaning can be performed with the molds (lower mold 14 and upper mold 15) mounted thereon without stopping the apparatus. Furthermore, by using the lower mold 14 and the upper mold 15 as electrodes, plasma 100a can be generated only in the space between the lower mold 14 and the upper mold 15, thereby enabling the overall apparatus to be made smaller.

[0082] Furthermore, in the glass forming apparatus 10a of the first embodiment, the heating means uses light emitted from infrared lamps 28 to heat the upper mold 15 (fixed mold), the lower mold 14 (movable mold), or the forming glass 6. Therefore, by measuring the temperatures of the lower mold 14 and the upper mold 15 with thermocouples 30 and controlling the output of the infrared lamps 28, the temperatures of the lower mold 14 and the upper mold 15 can be controlled so as to follow a desired temperature rise curve.

[0083] In the glass forming apparatus 10a of the first embodiment, the plasma 100a is a capacitively coupled plasma (CCP), which can be generated by using the molds (lower mold 14 and upper mold 15) themselves as electrodes, thereby enabling the molding chamber 26a to be made smaller.

[0084] In the glass forming apparatus 10a of the first embodiment, the halogen-based gas is at least NF ３ Therefore, plasma-activated NF ３ The fluorine radicals 70 generated from the glass (SiO ２ ), as well as alkali metal oxides and alkaline earth oxides contained in the molding glass 6 can also be washed away.

[0085] Second Embodiment A second embodiment of the present disclosure relates to a glass molding device 10b that uses a superhard mold used to mold optical elements having complex surface shapes, such as aspherical glass lenses.

[0086] The mold cleaning function provided in the glass forming apparatus 10b of the second embodiment will be described with reference to Fig. 12. Fig. 12 is a diagram showing an example of a schematic structure for realizing the mold cleaning function provided in the glass forming apparatus of the second embodiment.

[0087] The glass forming apparatus 10b includes, for example, a three-stage RF coil 80a instead of the infrared lamps 28 (see FIG. 8) included in the glass forming apparatus 10a.

[0088] Because the glass forming apparatus 10b does not have an infrared lamp for heating the glass to be formed 6 placed on the lower mold 14, the forming chamber 26a is an alumina forming chamber 81. Incidentally, the relative dielectric constant εr of quartz glass is 3.4, while the relative dielectric constant εr of alumina is 8.5, which is very high, and therefore the transmittance of radio waves is high.

[0089] An RF power supply 40a for induction heating the molds (lower mold 14 and upper mold 15) and an RF power supply 40b for generating plasma 100b inside the molding chamber 26a are connected to the RF coil 80a. In this embodiment, the frequency of the RF power supply 40a is 100 kHz, and the frequency of the RF power supply 40b is 13.56 MHz. A matcher 43a is connected in series to the RF power supply 40a. A matcher 43b is connected in series to the RF power supply 40b. The matchers 43a and 43b adjust the impedances of the matchers 43a and 43b (perform impedance matching) so that the reflected power from the RF coil 80a toward the RF power supplies 40a and 40b is minimized.

[0090] A switch 44a is connected in series to the RF power supply 40a. When the switch 44a is turned on, the glass forming apparatus 10b supplies 100 kHz high-frequency power to the RF coil 80a. This causes an induced current (eddy current) to flow on the surface of the mold, and the mold is heated by the resulting Joule heat. The RF coil 80a is an example of the heating means in the present disclosure.

[0091] Incidentally, because eddy currents are generated only on the very surface of the mold, the mold temperature rises very quickly. However, because the magnitude of the induced magnetic field is highly dependent on the distance from the RF coil 80a, uniform heating becomes difficult when the mold diameter is large. Therefore, this embodiment is preferably used for molding small-diameter lenses, for example.

[0092] Once the heating of the mold is complete, the glass molding device 10b performs the conventional molding and slow cooling of the molding glass 6. Once these steps are complete, the switch 44a is turned off to rapidly cool the mold, after which the interior of the molding chamber 26a is opened to the atmosphere, and the molded product is removed, completing one molding cycle.

[0093] After the glass molding device 10b has performed a predetermined number of molding cycles, it cleans the molds (the lower mold 14 and the upper mold 15). The process flow will be described below.

[0094] First, the glass forming apparatus 10b evacuates the inside of the forming chamber 26a to the ultimate vacuum. ３ / Cl ２ Gas (halogen-based gas) is supplied in a volume ratio of, for example, 9.5 / 0.4 / 0.1 so that the pressure P inside the molding chamber 26a becomes approximately 50 Pa. At this time, the distance d between the lower mold 14 and the upper mold 15 is adjusted to a predetermined appropriate value.

[0095] Once the pressure P inside the forming chamber 26a has stabilized, the switch 44b connected in series to the RF power supply 40b is turned on, and the glass forming apparatus 10b supplies high frequency power of 13.56 MHz to the RF coil 80a.

[0096] RF coil 80a supplied with high frequency power generates plasma 100b in a region including lower mold 14 and upper mold 15. Plasma 100b is called ICP (Inductively Coupled Plasma).

[0097] The glass forming apparatus 10b performs cleaning to remove fused glass and various oxides fused to the surfaces of the release films 12c of the lower mold 14 and the upper mold 15 by using fluorine radicals 70 generated by a reaction between the generated plasma 100b and a halogen-based gas supplied from the gas supply port 36. That is, the RF coil 80a in this embodiment is an example of the cleaning means in the present disclosure.

[0098] In the glass forming apparatus 10b, the plasma 100b is confined (confined) by the induced magnetic field, so the density of the plasma is about 10 to 100 times higher than that of the glass forming apparatus 10a described in the first embodiment. ＊ It is easy to imagine that the amount of the additives will also increase by 10 to 100 times, and the processing time required to clean the mold can be shortened accordingly.

[0099] As described above, the glass forming apparatus 10b of the second embodiment comprises the forming chamber 26a, the upper mold 15 (fixed mold) and the lower mold 14 (movable mold) which are arranged vertically opposite each other inside the forming chamber 26a and which are formed into a predetermined shape, the lower shaft 19 (movable shaft) which supports the lower mold 14 so that it can move relative to the upper mold 15, the RF coil 80a (heating means) which heats (induction heats) the upper mold 15 and the lower mold 14, and the lower shaft 19 is moved in a direction in which the lower mold 14 is pressed against the upper mold 15, thereby heating the glass to be formed 6 placed between the upper mold 15 and the lower mold 14. The apparatus includes a jack 21 (pressure molding means) for forming the glass 6 by applying pressure with a jack 21a and a jack 15a, and an RF coil 80a (cleaning means) for generating plasma 100b inside the forming chamber 26a by applying high-frequency pulses to an RF coil 80a wound around the forming chamber 26a while a halogen-based gas is supplied into the forming chamber 26a when the forming glass 6 is not being formed. The RF coil 80a generates fluorine radicals 70 (halogen radicals) from the halogen-based gas by the plasma 100b, and cleans the upper mold 15 and the lower mold 14. Therefore, even if molding is repeated, the molds (lower mold 14 and upper mold 15) can be cleaned without stopping the apparatus. Furthermore, generating inductively coupled plasma (ICP) can achieve a higher electron density than capacitively coupled plasma (CCP), thereby increasing the amount of halogen radicals generated. This further improves mold cleaning performance. Furthermore, the improved cleaning performance shortens cleaning time.

[0100] In the glass molding apparatus 10b of the second embodiment, the RF coil 80a (heating means) heats the upper mold 15 (fixed mold) and the lower mold 14 (movable mold) by induction heating. Therefore, the molding chamber 26a can be formed of alumina, for example. Furthermore, the same RF coil 80a can have two functions, namely, as a heating means for heating the molds and as a cleaning means for cleaning the molds.

[0101] In the glass molding apparatus 10b of the second embodiment, the plasma 100a is an inductively coupled plasma (ICP). Therefore, a higher electron density can be achieved compared to a capacitively coupled plasma (CCP), and the amount of halogen radicals generated is also increased. This further improves mold cleaning performance. Furthermore, the improved cleaning performance can shorten cleaning time.

[0102] Third Embodiment A third embodiment of the present disclosure relates to a glass molding apparatus 10c that uses a superhard mold used to mold optical elements having complex surface shapes, such as aspherical glass lenses.

[0103] The mold cleaning function of the glass forming apparatus 10c of the third embodiment will be described with reference to Figures 13 and 14. Figure 13 is a diagram showing an example of a schematic structure for realizing the mold cleaning function of the glass forming apparatus of the third embodiment. Figure 14 is a diagram showing an example of the structure of a plasma generation unit of the glass forming apparatus of the third embodiment.

[0104] When cleaning the molds (lower mold 14 and upper mold 15), glass molding apparatus 10c does not generate plasma inside molding chamber 26a, but generates plasma inside quartz glass cavity 82 located upstream of molding chamber 26a. Glass molding apparatus 10c then introduces fluorine radicals 70 generated by the reaction of a halogen-based gas with the plasma from gas supply port 36 into molding chamber 26a.

[0105] 14, the plasma generation unit 90a provided in the glass forming apparatus 10c includes a silica glass cavity 82 and an RF coil 80b wound around the silica glass cavity 82. High frequency power of, for example, 13.56 MHz is input to the RF coil 80b from an RF power source 40b via a matching box 43b.

[0106] The halogen-based gas supplied from the pipe 91a into the silica glass cavity 82 reacts with plasma 100b (inductively coupled plasma (ICP)) generated by high-frequency power supplied to the RF coil 80b, thereby generating fluorine radicals 70. The generated fluorine radicals 70 are supplied through the pipe 91b and the gas supply port 36 (see FIG. 13) into the molding chamber 26a.

[0107] Generally, the radical lifetime (the distance L at which the radical density in the plasma source becomes 1 / e) is expressed by equation (4).

[0108] L = D / u (4)

[0109] where D is the diffusion coefficient (m ２ / sec), and u is the gas flow velocity (m / sec). The diffusion coefficient D is inversely proportional to the pressure P.

[0110] Therefore, in order to extend the life of the radicals as long as possible, it is desirable to suppress the gas flow velocity u and transport the halogen-based gas at the lowest possible pressure P. Therefore, in glass forming apparatus 10c, the generation pressure of plasma 100b is set to, for example, P = 1 (Pa) or less.

[0111] Furthermore, it is known that radicals are deactivated (their reactivity decreases) when they come into contact with metal. Therefore, the material of the pipe 91b between the plasma generation unit 90a and the forming chamber 26a in the glass forming apparatus 10c is, for example, Teflon (registered trademark). The inner diameter of the pipe 91b is desirably made as large as possible to reduce the number of collisions between the radicals and the inner wall of the pipe 91b.

[0112] For example, in this embodiment, the inner diameter of the pipe 91a on the cylinder side is set to 6 mm, and the inner diameter of the pipe 91b on the molding chamber 26a side is set to 25 mm. Furthermore, in order to reduce the area in the pipe where high pressure occurs midway, the pipe system is designed to have as few bends as possible.

[0113] The glass molding device 10c performs cleaning to remove fused glass and various oxides fused to the surfaces of the release films 12c of the lower mold 14 and the upper mold 15 using fluorine radicals 70 generated by the generated plasma 100b.

[0114] As described above, the glass forming apparatus 10c of the third embodiment comprises the forming chamber 26a, the upper mold 15 (fixed mold) and the lower mold 14 (movable mold) which are arranged vertically opposite each other inside the forming chamber 26a and which are formed into a predetermined shape, the lower shaft 19 (movable shaft) which supports the lower mold 14 so that it can move relative to the upper mold 15, the infrared lamps 28 (heating means) which heat the upper mold 15, the lower mold 14, and the glass to be formed 6 placed between the upper mold 15 and the lower mold 14, and the lower shaft 19 which moves in a direction to press the lower mold 14 against the upper mold 15. The glass molding apparatus 10c includes a jack 21 (pressure molding means) that operates to pressurize the molding glass 6 between the lower mold 14 and the upper mold 15, thereby molding the glass 6 to be molded, and a cleaning means that generates plasma in the supply path that supplies a halogen-based gas to the molding chamber 26a when the molding glass 6 to be molded is not being formed, and supplies fluorine radicals 70 (halogen radicals) generated from the halogen-based gas by the plasma into the molding chamber 26a, thereby cleaning the upper mold 15 and the lower mold 14. Therefore, even when molding is repeated, the molds (lower mold 14 and upper mold 15) can be cleaned without stopping the apparatus. Furthermore, because the plasma generating means is located in the supply path that supplies the halogen-based gas, the molding chamber 26a can be made smaller. Furthermore, the design flexibility of the apparatus layout of the glass molding apparatus 10c can be improved.

[0115] (Modification of the Third Embodiment) A plasma generation unit 90b provided in a glass forming apparatus 10c which is a modification of the third embodiment will be described with reference to Fig. 15. Fig. 15 is a diagram showing an example of the structure of the plasma generation unit provided in the glass forming apparatus of the modification of the third embodiment.

[0116] The plasma generation unit 90b generates the plasma 100b inside the quartz glass cavity 82 by microwaves 9 irradiated to a microwave waveguide 92, instead of generating the plasma 100b by high-frequency pulses applied from an RF power supply 40b to an RF coil 80b. The frequency of the microwaves is, for example, 2.45 GHz.

[0117] 15, microwaves 9 are introduced into microwave waveguide 92 and irradiated onto the halogen-based gas supplied inside quartz glass cavity 82, thereby generating plasma inside quartz glass cavity 82. Fluorine radicals 70 are generated from the halogen-based gas by the plasma generated in this manner. Note that matching adjuster 93 is used to adjust the reflected power of microwaves 9 so as to minimize it.

[0118] The generated fluorine radicals 70 are supplied into the molding chamber 26a as explained in the third embodiment, and clean the surface of the mold.

[0119] It is generally known that the higher the excitation frequency, the higher the plasma density (electron density). Therefore, the plasma generation mechanism using microwaves 9 shown in Fig. 15 can increase the electron density compared to the plasma generation mechanism using the 13.56 MHz RF power supply 40b shown in Fig. 14. This can increase the amount of fluorine radicals 70 generated.

[0120] The configuration of the pipes 91a and 91b in FIG. 15 is the same as that described in the third embodiment.

[0121] Although an example in which the cavity 82 is made of quartz glass is shown in FIGS. 14 and 15, the cavity material may be made of alumina, which has a high relative dielectric constant.

[0122] As described above, in the glass forming apparatus 10c according to the modified example of the third embodiment, plasma is generated by irradiating microwaves 9 onto a halogen-based gas. Therefore, plasma with a higher electron density can be generated, thereby increasing the amount of fluorine radicals 70 (halogen radicals). This further improves mold cleaning performance. Furthermore, the cleaning time required to achieve the same cleaning performance can be shortened.

[0123] Although the example of molding the molding glass 6 has been described here, the glass molding devices 10a, 10b, and 10c can also be used in the same way when molding a glass material 5 that does not contain alkali metals or alkaline earth elements.

[0124] Although the embodiments of the present invention have been described above, the above-described embodiments are presented as examples and are not intended to limit the scope of the present invention. This novel embodiment can be embodied in various other forms. Furthermore, various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Furthermore, this embodiment is included within the scope and spirit of the invention, and is also included in the scope of the invention and its equivalents as defined in the claims.

[0125] 5 Glass material 6 Molding glass 9 Microwave 10a, 10b, 10c Glass molding device 12 Mold 12a Super hard material 12b Intermediate layer 12c Mold release film 12d WC particles 12e Binder 14 Lower mold (movable mold) 15 Upper mold (fixed mold) 16 Lower joint 17 Mold die 17a Screw 18 Die plate 18a Screw 19 Lower shaft (movable shaft) 20 Servo motor 21 Jack (pressure molding means) 22 Load cell 23 Upper joint 24 Upper shaft 25 Device column 26 Quartz tube 26a Molding chamber 27, 27a O-ring 28 Infrared lamp (heating means) 29 Reflecting mirror 30 Thermocouple 31 Reflecting plate 32, 35 Cooling water channel 33 Air intake port 34 Exhaust port 36 Gas supply port 37 Gas exhaust port 40, 40a, 40b RF power source (cleaning means) 41a, 41b Coaxial cable 42a Lower electrical introduction flange 42b Upper electrical introduction flange 43, 43a, 43b Matching box 44a, 44b Switch 45a Ar flow meter 45b NF ３ Flow meter 45c CF ４ Flow meter 45d Cl ２Flow meter 52 Lower insulator 53 Upper insulator 60 Exhaust system (exhaust means) 61 Cryopump 62 Turbomolecular pump 63 Mechanical booster pump 64 Dry pump 65 QMASS 66a, 66b, 66c, 66d, 66e, 66f Valve 67 Butterfly valve 68 Orifice 69 Abatement device 70 Fluorine radical (halogen radical) 71 Silicon tetrafluoride 72 Oxygen 80a RF coil (heating means, cleaning means) 80b RF coil 81 Alumina molding chamber 82 Quartz glass cavity 90a, 90b Plasma generation unit 91a, 91b Piping 92 Microwave waveguide 93 Matching adjuster 100a Plasma (CCP) 100b Plasma (ICP) D Diffusion coefficient d Distance (distance between molds, distance between electrodes) L Distance P Pressure

Claims

1. A glass forming device comprising: a forming chamber; a fixed mold and a movable mold arranged opposite each other above and below inside the forming chamber and formed into a predetermined shape; a movable shaft that supports the movable mold so that it can move relative to the fixed mold; heating means that heats the fixed mold, the movable mold, and a glass material placed between the fixed mold and the movable mold; pressure forming means that moves the movable shaft in a direction that presses the movable mold against the fixed mold, thereby forming the glass material by pressurizing it with the movable mold and the fixed mold; and cleaning means that, when the glass material is not being formed, generates plasma in the space between the fixed mold and the movable mold by applying a high-frequency pulse between the fixed mold and the movable mold while a halogen-based gas is supplied inside the forming chamber, and cleans the fixed mold and the movable mold with halogen radicals generated from the halogen-based gas by the plasma.

2. The glass forming device according to claim 1, wherein the heating means heats the fixed mold, the movable mold, and the glass material by light emitted from an infrared lamp.

3. The glass forming apparatus according to claim 1 or 2, wherein the plasma is a capacitively coupled plasma (CCP).

4. A glass forming device comprising: a forming chamber; a fixed mold and a movable mold arranged opposite each other above and below inside the forming chamber and formed into a predetermined shape; a movable shaft that supports the movable mold so that it can move relative to the fixed mold; heating means for heating the fixed mold and the movable mold; pressure forming means that moves the movable shaft in a direction that presses the movable mold against the fixed mold, thereby forming a glass material placed between the fixed mold and the movable mold by pressurizing it with the movable mold and the fixed mold; and cleaning means that, when the glass material is not being formed, generates plasma inside the forming chamber by applying high-frequency pulses to an RF coil wound around the forming chamber while a halogen-based gas is supplied inside the forming chamber, and cleans the fixed mold and the movable mold with halogen radicals generated from the halogen-based gas by the plasma.

5. The glass forming device according to claim 4, wherein the heating means heats the fixed mold and the movable mold by induction heating.

6. A glass forming device comprising: a forming chamber; a fixed mold and a movable mold arranged opposite each other above and below inside the forming chamber and formed into a predetermined shape; a movable shaft that supports the movable mold so that it can move relative to the fixed mold; heating means that heats the fixed mold, the movable mold, and a glass material placed between the fixed mold and the movable mold; pressure forming means that moves the movable shaft in a direction that presses the movable mold against the fixed mold, thereby forming the glass material by pressurizing it with the movable mold and the fixed mold; and cleaning means that, when the glass material is not being formed, generates plasma midway along a supply path that supplies a halogen-based gas into the forming chamber, and supplies halogen radicals generated from the halogen-based gas by the plasma into the forming chamber, thereby cleaning the fixed mold and the movable mold.

7. The glass forming apparatus according to claim 4 or claim 6, wherein the plasma is an inductively coupled plasma (ICP).

8. The glass forming apparatus according to claim 6, wherein the plasma is generated by irradiating the halogen-based gas with microwaves.

9. The halogen-based gas is at least NF ３ The glass forming apparatus according to claim 1, claim 4 or claim 6, comprising:

10. A mold cleaning method for cleaning the fixed mold and the movable mold in a glass molding device comprising: a molding chamber; a fixed mold and a movable mold arranged opposite each other above and below inside the molding chamber and molded into a predetermined shape; a movable shaft that supports the movable mold so that it can move relative to the fixed mold; a heating means that heats the fixed mold, the movable mold, and a glass material placed between the fixed mold and the movable mold; and a pressure molding means that moves the movable shaft in a direction that presses the movable mold against the fixed mold, thereby molding the glass material by pressurizing it with the movable mold and the fixed mold, the mold cleaning method comprising: when the glass material is not being molded, supplying a halogen-based gas into the molding chamber and applying a high-frequency pulse between the fixed mold and the movable mold to generate plasma in the space between the fixed mold and the movable mold, and then cleaning the fixed mold and the movable mold with halogen radicals generated from the halogen-based gas by the plasma.

11. A mold cleaning method for cleaning the fixed mold and the movable mold in a glass molding device comprising: a molding chamber; a fixed mold and a movable mold arranged opposite each other above and below inside the molding chamber and molded into a predetermined shape; a movable shaft that supports the movable mold so that it can move relative to the fixed mold; a heating means for heating the fixed mold and the movable mold; and a pressure molding means that moves the movable shaft in a direction that presses the movable mold against the fixed mold, thereby molding a glass material placed between the fixed mold and the movable mold by pressurizing it with the movable mold and the fixed mold, the mold cleaning method comprising: when the glass material is not being molded, supplying a halogen-based gas into the interior of the molding chamber and applying a high-frequency pulse to an RF coil wound around the molding chamber to generate plasma inside the molding chamber, and then cleaning the fixed mold and the movable mold using halogen radicals generated from the halogen-based gas by the plasma.

12. A mold cleaning method for cleaning the fixed mold and the movable mold in a glass molding device comprising: a molding chamber; a fixed mold and a movable mold arranged opposite each other above and below inside the molding chamber and molded into a predetermined shape; a movable shaft that supports the movable mold so that it can move relative to the fixed mold; a heating means that heats the fixed mold, the movable mold, and a glass material placed between the fixed mold and the movable mold; and a pressure molding means that moves the movable shaft in a direction that presses the movable mold against the fixed mold, thereby molding the glass material by pressurizing it with the movable mold and the fixed mold, the mold cleaning method comprising: generating plasma midway through a supply path that supplies a halogen-based gas into the molding chamber when the glass material is not being molded; and supplying halogen radicals generated from the halogen-based gas by the plasma into the molding chamber, thereby cleaning the fixed mold and the movable mold.

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