Glass molding apparatus and mold cleaning method

Abstract

To provide a glass molding apparatus capable of cleaning a mold without stopping an apparatus even in a case of repeating molding, and a mold cleaning method.SOLUTION: A glass molding apparatus includes: a molding room; an upper die (stationary mold) and a lower die (movable mold) that are arranged facing in a vertical direction in the molding room; an infrared lamp (heating means) for heating the upper die, the lower die, and a glass raw material arranged between them; a jack (pressure molding means) for pressure molding the glass raw material by moving the lower die in a direction so as to press against the upper die; and a high-voltage pulse power source (cleaning means) that generates a plasma in a space between a metal plate (an electrode) inserted between the upper die and the lower die and the upper die and a space between the metal plate and the lower die by applying such a high-voltage pulse that the metal plate has a higher potential than that of the upper die and the lower die in a state where an inert gas is supplied inside the molding room when the glass raw material is not molded, and cleans the upper die and the lower die using the plasma.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[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. [Background technology]

[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). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-306693 Summary of the Invention [Problem to be solved by the invention]

[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 Figure 2 for details). When this 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 shutting down the device.

[0005] The present invention has been made in view 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 after repeated molding. [Means for solving the problem]

[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 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 pressurizes the glass material with the movable mold and the fixed mold by moving the movable shaft in a direction that presses the movable mold against the fixed mold; and cleaning means that, when the glass material is not being formed, generates plasma by applying a high-voltage pulse to a space between the fixed mold and the movable mold and an electrode inserted between the separated fixed mold and the movable mold, and to the space between the electrode and the movable mold, while supplying an inert gas inside the forming chamber, and then cleans the fixed mold and the movable mold with 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 apparatus comprising: a molding chamber; a fixed mold and a movable mold arranged opposite each other inside the molding 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 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 pressurizing the glass material placed between the movable mold and the fixed mold at a predetermined pressure for a predetermined time, the mold cleaning method being characterized in that an inert gas is supplied into the molding chamber, and a high-voltage pulse is applied to the space between the fixed mold and an electrode inserted between the separated fixed mold and the movable mold, and to the space between the electrode and the movable mold, so that the electrode has a higher potential than the fixed mold and the movable mold, thereby generating plasma, and the fixed mold and the movable mold are cleaned by the plasma. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of a mold structure used in molding a glass material. [Figure 2] FIG. 2 is a diagram illustrating the mechanism by which fusion occurs between the mold and the glass material. [Figure 3] FIG. 3 is a diagram showing an example of a schematic structure for realizing the glass forming function of the glass forming device. [Figure 4] FIG. 4 is a diagram showing an example of an installation structure of a lower mold provided in a glass forming apparatus. [Figure 5] FIG. 5 is a diagram showing an example of a schematic structure for realizing a mold cleaning function provided in a glass molding device. [Figure 6]FIG. 6 is a diagram showing an example of the configuration of an exhaust system provided in a glass forming apparatus. [Figure 7] FIG. 7 is a diagram showing an example of an equivalent circuit of a plasma generating circuit included in the glass forming apparatus of the embodiment. [Figure 8] FIG. 8 is a diagram showing an example of a voltage waveform and a current waveform applied between the upper mold and the lower mold and the metal plate. [Figure 9] FIG. 9 is a diagram showing an example of the state between the electrodes when plasma is generated. [Figure 10] FIG. 10 is a diagram showing an example of an equivalent circuit between electrodes when plasma is generated. [Figure 11] FIG. 11 is a diagram showing an example of a circuit in which an ammeter, a voltmeter, and a control device are connected to an equivalent circuit of a plasma generating circuit provided in the glass forming apparatus of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

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

[0012] (Mold deterioration process) The mechanism by which fusion occurs between a mold 12 (also called a core) used in a glass molding apparatus 10 and a glass material will be described using 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 diagram explaining 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 formed on the surface of a superhard material 12a.

[0014] Molding of glass materials is carried out at higher temperatures than injection molding, for example, up to 750°C for ordinary optical glass and 1500°C for quartz glass. Furthermore, the mold is pressed at a pressure of 200 (N / cm 2 )~220(N / cm 2 ) high pressure is applied. Therefore, a super-hard material 12a with high mechanical strength at high temperatures is used for the mold base material. The super-hard material 12a is an alloy with extremely high hardness and less loss of hardness at high temperatures compared to other metals. The super-hard material 12a is produced, 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 intermediate layer 12b has a thermal expansion coefficient approximately intermediate between that of the super-hard material 12a and the release film 12c.

[0016] The 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 does not react with glass, and 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 release film 12c is heat-resistant and has low reactivity with glass materials, making it a material that is unlikely to fuse with glass materials (having excellent 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 releasability deteriorates, 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. 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 release film 12c, diffuse to the surface of the release film 12c, and become exposed. Similarly, chromium (Cr), a component of the intermediate layer 12b, may cross the release film 12c and diffuse to the surface of the release film 12c. The exposed tungsten, chromium, etc. then promote fusion between the glass material and the mold 12.

[0019] More specifically, the oxidation and evaporation of the Ir in the Pt-Ir surface layer results in a shortage of Ir in the film. The Pt-Ir, which is originally in a solid solution state with a uniform structure (uniform density), polycrystallizes and separates into dense Pt-rich crystal grains and the low-density grain boundaries between them. Because the density of these grain boundaries is low, the chromium constituting the intermediate layer 12b in Figure 2 and the tungsten constituting the carbide material 12a in Figure 2 diffuse along the grain boundaries and appear on the surface of the mold release film 12c. These are then oxidized by the moisture 13c (H2O) remaining inside the molding chamber. As a result, chromium oxide 13a and tungsten oxide 13b are produced, as shown in the right diagram of Figure 2. Because the produced chromium oxide 13a and tungsten oxide 13b have good wettability with the glass material, the glass fuses to the chromium oxide 13a and tungsten oxide 13b 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 10 of this embodiment has the function of removing these exposed materials without removing the mold from the molding apparatus, i.e., without stopping the apparatus, while the density of the tungsten and chromium exposed to the mold release film 12c is still low.

[0022] (Schematic structure of glass forming device) The schematic structure of the glass forming apparatus 10 of the embodiment will be described with reference to Figures 3 and 4. Figure 3 is a diagram showing an example of a schematic structure for realizing the glass forming function of the glass forming apparatus. Figure 4 is a diagram showing an example of an installation structure of a lower mold of the glass forming apparatus.

[0023] 3, a glass material 5 (e.g., quartz glass) that is the object to be molded is placed on a lower mold 14. An upper mold 15 is disposed above the lower mold 14 at 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.

[0024] 4, the lower mold 14 is fixed to a lower joint 16 that is movable in the vertical direction (Z-axis direction in FIG. 3) via a mold die 17 and a die plate 18, with the release film 12c facing upward. The lower mold 14 is an example of a movable mold in the present disclosure.

[0025] The bottom joint 16 is made of ceramics such as SiN, which has high mechanical strength even at high temperatures, and is connected to a jack 21 that can move up and down by the rotational force of a servo motor 20 via a lower shaft 19 shown in FIG. 3. This allows the bottom joint 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.

[0026] 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 10 further includes a mechanism for detecting the vertical position of the lower shaft 19.

[0027] As shown in Fig. 4, the lower mold 14 on which the glass material 5 is placed is assembled into a mold die 17 with an accuracy of several micrometers. The mold die 17 is then fastened to a die plate 18 with screws 17a. Although only one screw 17a is shown in Fig. 4, the mold die 17 is screwed to the die plate 18 at multiple positions surrounding the lower mold 14.

[0028] 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. 4, the die plate 18 is actually fastened to the bottom joint 16 by the screw at a plurality of positions.

[0029] Returning to Fig. 3, upper mold 15 has a structure similar to the fixing structure of lower mold 14 shown in Fig. 4. That is, upper mold 15, with release film 12c facing downward, is fixed to a ceramic upper joint 23 via a mold die and die plate (not shown). Upper joint 23 is then fixed to an apparatus column 25 constituting the outer housing of glass molding apparatus 10 via an upper shaft 24, which is a fixed shaft. Note that upper mold 15 is an example of a fixed mold in the present disclosure.

[0030] Glass forming apparatus 10 moves lower mold 14 upward, thereby sandwiching and pressurizing glass material 5 placed on lower mold 14 between it and fixed upper mold 15. This causes glass material 5 to be formed into a shape that conforms to the mold surfaces of lower mold 14 and upper mold 15. Glass forming apparatus 10 is also called a fixed mold type forming apparatus.

[0031] 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 the glass molding device 10, O-rings 27 are installed at various sliding parts and joints to maintain airtightness.

[0032] A plurality of ring-shaped infrared lamps 28 are arranged on the outside of the quartz tube 26. A reflecting mirror 29 is arranged behind the infrared lamps 28. The light emitted from the infrared lamps 28 and the light reflected from the reflecting mirror 29 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.

[0033] Furthermore, 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 .

[0034] Because the heat emitted by the infrared lamps 28 causes the reflecting mirror 29 to become hot, the reflecting mirror 29 is cooled by cooling water flowing through a cooling water passage 32 and room temperature nitrogen gas (N2) supplied through an air intake 33 and sprayed toward the outer surface of the quartz tube 26. The cooled cooling water is discharged through a water passage (not shown). The cooled air is exhausted through an exhaust port 34. Each part of the glass forming apparatus 10 is also appropriately cooled by cooling water flowing through a cooling water passage 35.

[0035] When forming the glass material 5 using the glass forming apparatus 10, an inert gas such as nitrogen gas is supplied to the interior of the quartz tube 26 (i.e., the forming chamber 26a) through the gas supply port 36. 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 material 5. 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 according to a preset program, thereby forming the glass material 5 into a predetermined shape. If a more precise transfer of the mold shape is required, the forming chamber is evacuated. Thereafter, the control device supplies a predetermined flow rate of inert gas to the molding chamber 26a while applying a predetermined pressing force to the lower shaft 19, thereby cooling the lower mold 14, the upper mold 15, and the molded glass product to a predetermined temperature, thereby completing the molding. The inert gas supplied to the molding chamber 26a is exhausted from the gas exhaust port 37.

[0036] 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.

[0037] To solve these problems, the glass forming apparatus 10 of this embodiment has a cleaning function for removing tungsten oxide and chromium oxide fused to the mold release film 12c of the lower mold 14 and the upper mold 15. The cleaning function will be described in detail later (see FIG. 5).

[0038] (Cleaning function for glass forming equipment) The mold cleaning function provided in the glass forming apparatus 10 of the embodiment will be described with reference to Fig. 5. Fig. 5 is a diagram showing an example of a schematic structure for realizing the mold cleaning function provided in the glass forming apparatus.

[0039] In addition to the structure shown in FIG. 3, the glass forming apparatus 10 further includes a high-voltage pulse power supply 40, a metal plate 45, and an electromagnetic wave shield 50 shown in FIG.

[0040] High-voltage pulse power supply 40 is connected to lower mold 14 by high-voltage coaxial cable 41a and to upper mold 15 by similarly high-voltage coaxial cable 41b. Glass molding apparatus 10 simultaneously applies a high voltage of about -1 kV to lower mold 14 and upper mold 15 with a pulse width of several nanoseconds to several milliseconds while lower mold 14 and upper mold 15 are spaced apart. High-voltage pulse power supply 40 is an example of the cleaning means of the present disclosure.

[0041] When a high voltage is applied to the lower mold 14 and the upper mold 15, a metal plate 45 held at ground potential is inserted between the lower mold 14 and the upper mold 15. That is, the metal plate 45 is held at GND potential. The metal plate 45 is an example of an electrode in the present disclosure. An insulating lower insulator 52 is installed below the lower mold 14. The lower insulator 52 electrically insulates the lower mold 14 to prevent abnormal discharge. An insulating upper insulator 53 is installed above the upper mold 15. The upper insulator 53 electrically insulates the upper mold 15 to prevent abnormal discharge. The surface areas of the lower insulator 52 and the upper insulator 53 are formed as large as possible to improve insulation.

[0042] The reason for using coaxial cables 41a and 41b to connect the high-voltage pulse power supply 40 and the mold is that the pulses generated by the high-voltage pulse power supply 40 can be applied to the mold with high responsiveness. Furthermore, the use of coaxial cables 41a and 41b provides noise countermeasures, preventing malfunction of the device itself or adjacent devices. The lengths of the coaxial cables 41a and 41b are set equal and as short as possible. This prevents differences in the change over time (amount of current) in the voltage applied to the lower mold 14 and the upper mold 15. Furthermore, since even coaxial cables have a certain amount of impedance, shortening the length minimizes the impedance, improving responsiveness to the applied pulse waveform.

[0043] The metal plate 45 is made of, for example, stainless steel, copper, or aluminum, and has a shape larger than the outer diameters of the lower mold 14 and the upper mold 15. As will be described later, the metal plate 45 is movable in the up and down direction in the drawing, and its height is adjusted so that the distance dd to the lower mold 14 and the distance du to the upper mold 15 are equal.

[0044] One end of the metal plate 45 is fastened to a plate support shaft 46. The plate support shaft 46 can rotate the metal plate 45 around the fastening point with the plate support shaft 46 in response to the rotation of an electrode opening / closing motor 47 driven by instructions from a control device (not shown). Furthermore, the electrode opening / closing motor 47, the plate support shaft 46, and the metal plate 45 are configured to be movable in the vertical direction in the figure. That is, in FIG. 5, the metal plate 45 can be rotated and moved along the XY plane and also in the Z-axis direction. This allows the position of the metal plate 45 to be switched between two positions, position 45a and position 45b, and the distance du between the metal plate 45 and the upper mold 15 and the distance dd between the metal plate 45 and the lower mold 14 can also be adjusted by a drive mechanism (not shown).

[0045] The metal plate 45, the plate support shaft 46, and the electrode opening / closing motor 47 are all electrically grounded via a high-frequency GND line. Other metal parts (such as the device column 25, the lower shaft 19, the upper shaft 24, and the reflecting mirror 29) are also electrically grounded in a similar manner.

[0046] The corners of the lower mold 14 and the upper mold 15 are rounded to prevent abnormal discharge when a high voltage pulse is applied from the high voltage pulse power supply 40 .

[0047] After the glass forming apparatus 10 finishes forming the glass material 5 and removes the formed product, it evacuates the interior of the forming chamber 26a to a desired vacuum level using various pumps (see FIG. 6 ), which will be described later. The vacuum level is measured by a vacuum gauge 51. The glass forming apparatus 10 then switches the position of the metal plate 45 to position 45a and supplies argon (Ar) gas, an example of an inert gas, into the forming chamber 26a to a pressure of, for example, 5 Pa. Nitrogen gas is typically used as the inert gas. Although argon gas is more expensive than nitrogen gas, it has a lower electronegativity and is less reactive even at high temperatures, such as plasma. Therefore, in the glass forming apparatus 10 of this embodiment, argon gas is preferably used as the plasma gas rather than nitrogen gas. A predetermined amount of argon gas is supplied into the forming chamber 26a via a mass flow controller (MFC) 54, which measures the flow rate. The exhaust rate is adjusted to be equal to the supply rate, maintaining a constant pressure inside the forming chamber 26a. Thereafter, the glass forming apparatus 10 simultaneously applies a high voltage pulse of about −1 kV (e.g., −700 V) for a short time to the lower mold 14 and the upper mold 15 from the high voltage pulse power supply 40. This generates plasma in the space between the metal plate 45 and the lower mold 14 and in the space between the metal plate 45 and the upper mold 15.

[0048] At this time, the potential of the lower mold 14 and the upper mold 15 is lower than the potential of the grounded metal plate 45, so that the argon ions (Ar + ) is accelerated toward both molds and collides with the lower mold 14 and the upper mold 15. As a result, the tungsten oxide (WxOy) and chromium oxide (CrxOy) exposed on the mold release film 12c are removed.

[0049] At the moment when a high-voltage pulse is applied to the lower mold 14 and the upper mold 15, and at the moment when the high-voltage pulse is cut off, electromagnetic waves are emitted from the space between the metal plate 45 and the lower mold 14 and the space between the metal plate 45 and the upper mold 15 toward the outside of the molding chamber 26a. These electromagnetic waves penetrate the quartz tube 26 and may cause malfunctions of the infrared lamp 28, other control panels, and adjacent devices. Although the impact is minimal if the infrared lamp 28 and the reflective mirror 29 are at ground potential, to further reduce the impact of the electromagnetic waves, a metal electromagnetic shield 50 is provided to surround the space between the metal plate 45 and the lower mold 14 and the space between the metal plate 45 and the upper mold 15. The electromagnetic shield 50 has an electrically grounded cylindrical shape. During molding of the glass material 5, it is retracted by a sliding mechanism (not shown) to a position where it is not irradiated by the infrared lamp 28 (e.g., the −Z direction in FIG. 5 ).

[0050] In this way, the glass forming apparatus 10 of this embodiment can remove ions (Ar + ) can remove tungsten and chromium exposed on the surfaces of both molds. This allows the molds to be cleaned in a short time without stopping the glass molding apparatus 10, and makes it possible to maintain the performance of the mold release film 12c for a long period of time.

[0051] (Outline of exhaust system structure) An exhaust system 60 provided in the glass forming apparatus 10 of the embodiment will be described with reference to Fig. 6. Fig. 6 is a diagram showing an example of the configuration of an exhaust system provided in the glass forming apparatus.

[0052] The glass forming apparatus 10 is equipped with an exhaust system 60 that exhausts the nitrogen gas supplied to the forming chamber 26a when forming the glass material 5, the argon gas supplied to the forming chamber 26a when generating plasma, and the gas generated by cleaning the mold.

[0053] 6, 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 together as needed, either directly or via valves 66a, 66b, 66c, 66d, and 66e or a butterfly valve 67. Furthermore, the glass forming apparatus 10 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.

[0054] The cryopump 61 is a type of adsorption pump, and has a higher H2O exhaust capacity than, for example, the turbomolecular pump 62. Therefore, by performing exhaust via the cryopump 61, the partial pressure of H2O remaining inside the molding chamber 26a can be further reduced.

[0055] In the glass molding device 10, the molding chamber 26a is opened to the atmosphere each time molding of the glass material 5 is completed, allowing the molded product to be removed and a new glass material 5 to be set. Therefore, H2O adheres to the inner walls of the open molding chamber 26a. The adhered H2O evaporates 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 superhard material 12a, blackening the mold. As a result, the absorption rate of near-infrared light from the infrared lamp 28 increases. OH also oxidizes the chromium on the surface of the mold release film 12c, significantly reducing mold release performance.

[0056] Furthermore, the H2O adsorbed by the cryopump 61 is exhausted at a predetermined timing (for example, at the end of work for the day).

[0057] The turbo molecular pump 62, like a jet engine, uses a combination of high-speed rotating turbine blades and stationary blades to exhaust, compress and discharge gas molecules.

[0058] The mechanical booster pump 63, when used in combination with other pumps, increases the pumping speed in pressure regions where the pumping speed of the other pumps drops.

[0059] The dry pump 64 is a mechanical vacuum pump that does not use oil or liquid inside the vacuum chamber, and because it does not use oil or liquid, it can perform clean evacuation.

[0060] The opening of the butterfly valve 67 is controlled so that the exhaust speed is the same as the above-mentioned argon supply amount.

[0061] The QMASS 65 is a type of mass spectrometer that controls the HO partial pressure when the ultimate vacuum is reached and determines whether the plasma cleaning process is complete. Specifically, the glass molding apparatus 10 terminates the cleaning process when the QMASS 65 detects platinum (Pt) or iridium (Ir) that constitutes the mold release film 12c. This is because if platinum or iridium is detected in the gas generated inside the molding chamber 26a, it is believed that the mold release film 12c itself is being eroded by the cleaning process, which is known as oversputtering.

[0062] (Schematic configuration of plasma generation circuit) 7 and 8, the schematic configuration of the plasma generating circuit (not shown in Fig. 5) provided in the glass forming apparatus 10 of the embodiment will be described. Fig. 7 is a diagram showing an example of an equivalent circuit of the plasma generating circuit provided in the glass forming apparatus of the embodiment. Fig. 8 is a diagram showing an example of a voltage waveform and a current waveform applied between the upper mold and the lower mold and the metal plate.

[0063] Because the thickness of the tungsten or chromium exposed on the release film 12c is on the order of nanometers, it is necessary to control the magnitude and duration of the applied pulse voltage with high precision. In other words, the transient state at the moment the voltage is applied and when it is released is extremely important.

[0064] More specifically, if the pulse width applied to the lower mold 14 and the upper mold 15 to generate plasma for cleaning the mold is too long, the mold release film 12c may also be removed, and the surface roughness of the lower mold 14 and the upper mold 15 may be deteriorated. Therefore, the glass molding apparatus 10 minimizes the pulse width applied to the lower mold 14 and the upper mold 15, and adjusts the amount of fused tungsten and chromium removed by adjusting the number of pulse applications, i.e., the number of times plasma is generated. Therefore, the high-voltage pulse power supply 40 is capable of controlling the pulse width generated on the order of milliseconds. Furthermore, it is desirable that the high-voltage pulse power supply 40 be able to control the pulse shape of the generated pulse (especially the pulse rise shape dV / dt).

[0065] 7, an equivalent circuit 70 of the plasma generating circuit provided in the glass forming apparatus 10 includes a high-voltage pulse power supply 40, capacitors Ca and Cb, cable impedances Za and Zb, diodes Da and Db, and a variable capacitance reactance L. Since plasma 100 is generated between the lower mold 14 and the upper mold 15 and the metal plate 45, the equivalent circuit 70 also includes the impedance of the plasma itself (not shown).

[0066] Capacitor Ca is a capacitor formed by the lower mold 14 and the metal plate 45. The capacitance of capacitor Ca is Cd. Capacitor Cb is a capacitor formed by the upper mold 15 and the metal plate 45. The capacitance of capacitor Cb is Cu. As described above, the distance dd between the metal plate 45 and the lower mold 14 is equal to the distance du between the metal plate 45 and the upper mold 15, so the capacitance Cd is equal to the capacitance Cu.

[0067] The operation of the glass forming apparatus 10 described above is equivalent to applying the same high-voltage pulse to the capacitors Ca and Cb at the same time in Fig. 7. Specifically, the high-voltage pulse power supply 40 is turned on to apply a high voltage of, for example, -1 kV to the metal plate 45 of the upper mold 15 and the lower mold 14.

[0068] At this time, the space between the upper mold 15 and the metal plate 45 and the space between the lower mold 14 and the metal plate 45 are filled with an inert gas such as argon adjusted to a predetermined pressure P.

[0069] Incidentally, discharge starts corresponding to the product of pressure P and distance (du, dd), i.e., P×du and P×dd, and plasma 100 (see FIG. 9) is generated in the space between metal plate 45 and upper mold 15 and the space between metal plate 45 and lower mold 14. At this time, distances du and dd are controllable, so the discharge start voltage and plasma characteristics can be controlled.

[0070] FIG. 9 shows an example of the state between electrodes when plasma is generated. Reference numeral 100 in the figure denotes plasma, which is a partially ionized gas. When plasma 100 comes into contact with a solid such as an electrode, a space charge layer called a sheath is formed on the surface of the electrode. Specifically, as shown in FIG. 9, sheath 101 is generated between upper mold 15, lower mold 14, and plasma 100, and sheath 102 is generated between plasma 100 and metal plate 45.

[0071] Taking the sheaths 101 and 102 into consideration, the equivalent circuit 70a of the discharge portion (between the electrodes) when the plasma 100 is generated is as shown in FIG.

[0072] As shown in Figure 10, it is known that a sheath is generally equivalent to a parallel circuit of a resistor and a capacitor. Furthermore, since the plasma 100 in Figure 9 is ionized, it is represented by a resistive element in the equivalent circuit. In Figure 10, the resistance value of resistor 103, which is the equivalent circuit of the plasma body, is set to Rp.

[0073] 9 is replaced with a parallel circuit of a sheath resistor 106 and a sheath capacitor 107, and similarly, the sheath 102 is replaced with a parallel circuit of a sheath resistor 108 and a sheath capacitor 109.

[0074] Here, the resistance value of the sheath resistor 106 is R1, the resistance of the sheath resistor 108 is R2, the electrostatic capacitance of the sheath capacitor 107 is CsA, and the electrostatic capacitance of the sheath capacitor 109 is CsB.

[0075] 10, the sheath 101, plasma 100, and sheath 102 are arranged in series, so that an equal current I flows through each of them. In other words, the voltages applied to each device (voltages VA, VP, and VB in FIG. 10) are adjusted so that this is satisfied.

[0076] As is well known, the current flowing through a capacitor is proportional to the time change (dV / dt) of the applied voltage. Conversely, if there is no time change, no current will flow.

[0077] When a negative high voltage pulse shown in FIG. 8 is applied to such a circuit, theoretically, no current flows through sheath capacitor 107 and sheath capacitor 109 during the time period ta-tc when the voltage v(t) does not change.

[0078] Therefore, the load at this time is only three resistors, that is, the sheath resistor 106, the resistor 103, and the sheath resistor 108.

[0079] However, because the voltage v(t) changes significantly between times ta and tc, at that moment a spike-shaped current i(t) as shown in Fig. 8 flows through sheath capacitor 107 and sheath capacitor 109. In other words, there are a total of five loads: three resistors and two capacitors.

[0080] As mentioned earlier, theoretically, no current flows between time ta and time tc. However, in reality, a current i(t) flows between time ta and time tb, and between time tc and time td, for a period of time corresponding to the attenuation constant (time constant).

[0081] Furthermore, the direction of the spike current flowing at time ta is the I direction shown in Figure 7, but at time tc, the spike current flows in the opposite direction.

[0082] The current flowing in the I direction is the Ar + This means that ions are irradiated onto the upper mold 15 and the lower mold 14, which means that deposits on the mold surfaces are sputtered.

[0083] On the other hand, the reverse flow of current occurs when Ar + This means that ions are irradiated from the plasma 100 onto the metal plate 45, causing the metal plate 45 to be sputtered.

[0084] Naturally, the sputtered material will adhere to the surfaces of the upper mold 15 and the lower mold 14, which will actually worsen the mold releasability. For this reason, diodes Da and Db are provided to prevent backflow, as shown in Figure 7. The withstand voltage of diodes Da and Db is set to several times the voltage that can be applied by the high-voltage pulse power supply 40.

[0085] Furthermore, applying a stepped high voltage as shown in Figure 8 will cause a spike-like overcurrent as described above, which may damage the power supply cable, insulators, or power supply. To avoid this, a variable capacitive reactance L shown in Figure 7 may be inserted to control the voltage rise at time ta to be more gradual.

[0086] However, since this increases the time difference between time tb and time ta and the time difference between time td and time tc in FIG. 8, care must be taken when setting the pulse width of the voltage.

[0087] Because the above-described overcurrent is undesirable for the power supply, the high-voltage pulse power supply 40 is often equipped with a function to prevent this. Therefore, this function may be utilized. Furthermore, because the voltage and current change rapidly as described above, it is desirable to configure an equivalent circuit 70b in which a highly responsive voltmeter 111 and ammeter 110 are additionally installed, as shown in FIG. 11. Furthermore, the voltmeter 111 and ammeter 110 have the function of outputting the measured voltage and current values ​​to the control device 112. Furthermore, the control device 112 not only collects and stores these values, but also has a database function of integrating the collected data over time, particularly for current, and storing the results for a long period of time.

[0088] The time integral value of the current is the Ar flowing into the lower die 14 and the upper die 15. + The total number of ions, i.e., the number of Ar required for a given cleaning + This is the number of ions, and by storing and saving this, it can be used to shorten the time required to optimize the cleaning conditions. For example, if the number of cycles before cleaning is doubled, Ar + The number of ions can be doubled, and if it is halved, it is estimated that it will be 0.5 times as many.

[0089] (Cleaning process performed by glass forming equipment) Next, the cleaning process performed by the glass forming apparatus 10 will be described in more detail.

[0090] After a predetermined number of molding cycles (e.g., several tens of times) have been completed for the glass material 5, and after the molded product has been removed, the glass molding device 10 evacuates the interior of the molding chamber 26a to an ultimate vacuum level using the exhaust system 60 shown in FIG. 6, without any material being set.

[0091] At this time, QMASS 65 confirms that the partial pressures of HO and O remaining inside molding chamber 26a are sufficiently low. Glass molding apparatus 10 then adjusts the position of lower mold 14 so that the distance between upper mold 15 and lower mold 14 is a predetermined distance, adjusts the height of metal plate 45 so that it is exactly midway between upper mold 15 and lower mold 14, and then moves metal plate 45 from position 45b to position 45a. After this operation is completed, electromagnetic wave shield 50 is raised to the position shown in FIG. 5 by a moving mechanism (not shown).

[0092] After confirming that the electromagnetic wave shield 50 has reached the position shown in Fig. 5, the glass forming apparatus 10 opens the valve 66a shown in Fig. 6 and adjusts the flow rate of argon so that the interior of the forming chamber 26a reaches a predetermined pressure. Once the pressure inside the forming chamber 26a has stabilized, the glass forming apparatus 10 applies a pulse voltage of, for example, about -1 kV to each of the lower mold 14 and the upper mold 15 for several hundred milliseconds. The argon pressure in the forming chamber 26a, the voltage applied by the high-voltage pulse power supply 40, the pulse width applied, and the number of pulse applications are all set in advance.

[0093] During the cleaning process, the glass forming apparatus 10 opens the valve 66d shown in FIG. 6 and performs process analysis using the QMASS 65. If the QMASS 65 detects platinum (Pt: (mass number 195)) or iridium (Ir: (mass number 192)), which are elements constituting the release film 12c, during the cleaning process, the glass forming apparatus 10 forcibly terminates the cleaning process even if the set number of pulses has not been reached. This is because it is believed that the cleaning process is causing erosion of the release film 12c. Incidentally, because the atomic weights of Pt and Ir are larger than those of chromium and tungsten, the sputtering rates of the former are overwhelmingly lower and the former are less susceptible to sputtering.

[0094] After the cleaning process is completed and cooling is performed as necessary, the glass forming apparatus 10 moves the metal plate 45 to position 45b and further lowers the electromagnetic wave shield 50. Next, the glass forming apparatus 10 opens the interior of the forming chamber 26a to the atmosphere, sets the glass material 5, and starts the normal forming cycle.

[0095] (Example of cleaning process) Next, a specific cleaning process carried out by the inventors and the results thereof will be described.

[0096] The inventors formed a mold (lower mold 14, upper mold 15) by forming a 20 nm thick Cr intermediate layer and a 600 nm thick Pt-Ir mold release film on an existing flat cemented carbide material.

[0097] Using this mold, glass material 5 (BK-7) was molded 120 times at 650°C, and then the mold was cleaned using the glass molding device 10. The applied pulse voltage was -670 V, the pulse application time was 100 msec, and the pulse was applied 10 times.

[0098] In addition, a process analysis was performed using QMASS65 in parallel with cleaning the mold, but no Pt or Ir was detected. Furthermore, W and Cr were detected every time a pulse was applied.

[0099] Furthermore, by observing the transient state of the voltage and current when the pulse was applied, it was found that the time from when the pulse voltage was input until the plasma was generated was about 15 msec, and a current of about 15 A flowed. From this current value, the ion flux irradiated onto the mold was calculated to be about 9.4 × 10 19 ( / sec).

[0100] Assuming that the sputtering rate of tungsten (W) is 0.5, the removal rate is approximately 4.7 × 10 19 ( / sec). From this result, the partial pressure of tungsten was calculated and found to be in close agreement with the analysis results of QMASS65.

[0101] Then, when the release force after mold cleaning was checked using the load cell 22 in Figure 5, it was found to have improved by approximately 80% compared to before the mold was cleaned, confirming the effectiveness of the cleaning process.

[0102] (Effects of the embodiment) As described above, the glass forming apparatus 10 of this embodiment includes the forming chamber 26a, the upper mold 15 (fixed mold) and the lower mold 14 (movable mold) that are arranged opposite each other inside the forming chamber 26a and are formed into a predetermined shape, the lower shaft 19 (movable shaft) that supports the lower mold 14 so that it can move relative to the upper mold 15, the infrared lamps 28 (heating means) that heat the upper mold 15, the lower mold 14, and the glass material 5 placed between the upper mold 15 and the lower mold 14, and the lower shaft 19 is moved in a direction that presses the lower mold 14 against the upper mold 15, thereby pressing the glass material 5 between the lower mold 14 and the upper mold 15. The glass forming apparatus 10 includes a jack 21 (pressure forming means) for forming the glass material 5 by applying a high-voltage pulse to a space between the upper mold 15 and the lower mold 14 and a metal plate 45 (electrode) inserted between the separated upper mold 15 and the lower mold 14, and to a space between the metal plate 45 and the lower mold 14, while supplying an inert gas into the inside of the forming chamber 26a when the glass material 5 is not being formed, so that the metal plate 45 has a higher potential than the upper mold 15 and the lower mold 14, thereby generating plasma, and cleaning the upper mold 15 and the lower mold 14 with the plasma. Therefore, even if forming is repeated, deteriorated molds can be cleaned (regenerated) without completely stopping the glass forming apparatus 10. This prevents a decrease in productivity.

[0103] In addition, in the glass forming apparatus 10 of this embodiment, the high-voltage pulse power supply 40 (cleaning means) applies a high-voltage pulse of negative potential to the upper mold 15 (fixed mold) and the lower mold 14 (movable mold) while the metal plate 45 (electrode) is held at GND potential. Ions in the plasma generated by this collide with the upper mold 15 and the lower mold 14, allowing the molds to be efficiently cleaned.

[0104] In addition, in the glass forming apparatus 10 of this embodiment, when the high-voltage pulse power supply 40 (cleaning means) generates plasma, the amount of inert gas supplied to the inside of the forming chamber 26a, and the voltage, pulse width, and pulse number of the high-voltage pulse are each set to a predetermined value. Therefore, the state of the plasma generated inside the forming chamber 26a can be finely adjusted, and a cleaning process can be achieved that is suited to the state of the mold to be cleaned.

[0105] The glass forming apparatus 10 of this embodiment further includes an ammeter 110 that measures the value of the current flowing in the circuit that applies the high-voltage pulse, and a control device 112 that acquires and stores the current value measured by the ammeter 110. The control device 112 determines the cleaning conditions for cleaning the upper mold 15 (fixed mold) and the lower mold 14 (movable mold) based on the time integral value of the current value. Therefore, the upper mold 15 and the lower mold 14 can be cleaned at an appropriate timing.

[0106] Furthermore, in the glass forming apparatus 10 of this embodiment, the metal plate 45 (electrode) has a shape that completely covers at least the upper mold 15 (fixed mold) and the lower mold 14 (movable mold). Therefore, the molds can be cleaned completely over the entire surface.

[0107] In addition, in the glass forming apparatus 10 of this embodiment, the distance du between the metal plate 45 (electrode) and the upper mold 15 (fixed mold) and the distance dd between the metal plate 45 and the lower mold 14 (movable mold) are adjustable. Therefore, the discharge start voltage and plasma characteristics when generating the plasma 100 can be controlled.

[0108] Furthermore, the glass forming apparatus 10 of this embodiment changes the cleaning conditions for cleaning the upper mold 15 and the lower mold 14 by adjusting the distance du between the metal plate 45 (electrode) and the upper mold 15 (fixed mold) and the distance dd between the metal plate 45 and the lower mold 14 (movable mold). Therefore, the cleaning conditions for the molds can be controlled.

[0109] Furthermore, the glass forming apparatus 10 of this embodiment adjusts the distance du and the distance dd according to the value of the current flowing into the upper mold 15 (fixed mold) and the lower mold 14 (movable mold). Therefore, the timing of cleaning the molds can be appropriately controlled.

[0110] In addition, in the glass forming apparatus 10 of this embodiment, the inert gas supplied to the forming chamber 26a is argon gas. Generally, inexpensive nitrogen gas is used, but nitrogen has a high electronegativity and a certain level of reactivity. This is not a problem at forming temperatures of about 500 to 700°C, but at high temperatures such as plasma, its effects become unignorable. Therefore, although it is expensive, argon gas is preferable.

[0111] The glass molding apparatus 10 of this embodiment also includes an exhaust system 60 (exhaust means) that exhausts the gas inside the molding chamber 26a, monitors whether the gas contains elements that make up the mold release film 12c that forms the surfaces of the lower mold 14 (movable mold) and the upper mold 15 (fixed mold), and terminates the operation of the high-voltage pulse power supply 40 (cleaning means) if any of the elements is detected. This makes it possible to prevent over-sputtering of the mold surfaces during the cleaning process.

[0112] 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 inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0113] 5. Glass material 10 Glass forming equipment 12 Mold 12a Carbide 12b Middle layer 12c Release film 12d WC particles 12e Binder 14 Lower die (moving die) 15 Upper die (fixed die) 16 Bottom Joint 17 Mold Die 17a screw 18 Die Plate 18a screw 19 Lower axis (moving axis) 20 Servo motor 21 Jack (pressure molding means) 22 load cells 23 Upper Joint 24 Upper shaft 25 Equipment Column 26 Quartz tube 26a Molding room 27 O-ring 28 Infrared lamp (heating means) 29 Reflective mirror 30 Thermocouple 31 Reflector 32,35 Cooling waterway 33 Air intake 34 Exhaust port 36 Gas supply port 37 Gas exhaust port 40 High voltage pulse power supply (cleaning means) 41a, 41b coaxial cable 45 Metal plate (electrode) 45a, 45b positions 46 Plate support shaft 47 Electrode opening and closing motor 50 Electromagnetic Shielding 51 Vacuum gauge 52 Bottom insulator 53 Upper insulator 54 MFC 60 Exhaust system (exhaust means) 61 Cryopump 62 Turbomolecular pump 63 Mechanical Booster Pump 64 Dry Pump 65 QMASS 66a, 66b, 66c, 66d, 66e Valves 67 Butterfly valve 70, 70a, 70b Equivalent circuit 100 Plasma 101,102 Sheath 103 Resistance 106,108 Sheath resistance 107,109 Sheathed capacitor 110 Ammeter 111 Voltmeter 112 Control device dd,du distance Ca, Cb capacitors Cd, Cu capacitance Da, Db diode I current L variable capacitance reactance P pressure v(t) voltage Za, Zb cable impedance

Claims

1. a molding chamber; a fixed mold and a movable mold that are arranged vertically opposite each other inside the molding chamber and molded into a predetermined shape; a moving shaft that supports the moving die movably relative to the fixed die; a heating means for heating the fixed mold, the movable mold, and the glass material placed between the fixed mold and the movable mold; a pressure molding means for molding the glass material by pressing it between the movable mold and the fixed mold by moving the moving shaft in a direction that presses the movable mold against the fixed mold; and a cleaning means for generating plasma by applying a high voltage pulse to a space between an electrode inserted between the spaced apart fixed mold and the movable mold and the fixed mold, and to a space between the electrode and the movable mold, while supplying an inert gas into the inside of the molding chamber when the glass material is not being molded, so that the electrode has a higher potential than the fixed mold and the movable mold, and for cleaning the fixed mold and the movable mold with the plasma. Glass forming equipment.

2. The cleaning means is applying a high voltage pulse of negative potential to the fixed mold and the movable mold, respectively, while the electrodes are held at GND potential; The glass forming apparatus according to claim 1 .

3. When the cleaning means generates the plasma, the amount of the inert gas supplied into the molding chamber, and the voltage, pulse width, and number of pulses of the high voltage pulse are set to predetermined values, respectively; The glass forming apparatus according to claim 1 or 2.

4. an ammeter that measures a current value flowing in a circuit to which the high voltage pulse is applied; a control device that acquires and stores the current value measured by the ammeter, the control device determines cleaning conditions for cleaning the fixed mold and the movable mold based on a time integral value of the current value. The glass forming apparatus according to claim 1 or 2.

5. The electrode has a shape that completely covers at least the fixed mold and the movable mold. The glass forming apparatus according to claim 1 or 2.

6. The distance between the electrode and the fixed mold and the distance between the electrode and the movable mold are adjustable. The glass forming apparatus according to claim 1 or 2.

7. changing cleaning conditions for cleaning the stationary mold and the movable mold by adjusting the distance between the electrode and the stationary mold and the distance between the electrode and the movable mold; The glass forming apparatus according to claim 6.

8. The distance is adjusted according to the value of a current flowing into the fixed mold and the movable mold. The glass forming apparatus according to claim 7.

9. The inert gas supplied to the molding chamber is argon gas. The glass forming apparatus according to claim 1 or 2.

10. The glass forming device further includes an exhaust means for exhausting gas from the inside of the forming chamber, monitoring whether the gas contains elements constituting the mold release films that form the surfaces of the movable mold and the fixed mold, and terminating the operation of the cleaning means when the elements are detected. The glass forming apparatus according to claim 1 or 2.

11. a molding chamber; a fixed mold and a movable mold disposed opposite each other inside the molding chamber and molded into a predetermined shape; a moving shaft that supports the moving die movably relative to the fixed die; a heating means for heating the glass material placed between the fixed mold and the movable mold; a pressure molding means for molding a glass material placed between the movable mold and the fixed mold by moving the movable axis in a direction in which the movable mold is pressed against the fixed mold at a predetermined pressure for a predetermined time; A mold cleaning method for cleaning the fixed mold and the movable mold in a glass molding apparatus comprising: an inert gas is supplied into the molding chamber, and a high voltage pulse is applied to a space between the fixed mold and the movable mold, which are spaced apart, and the fixed mold, and to a space between the electrode and the movable mold, so that the electrode has a higher potential than the fixed mold and the movable mold, thereby generating plasma, and the fixed mold and the movable mold are cleaned by the plasma; Mold cleaning method.

12. In the mold cleaning method according to claim 11, when exhausting gas generated when cleaning the fixed mold and the movable mold, monitoring whether the gas contains elements constituting the mold release films that form the surfaces of the movable mold and the fixed mold, and terminating cleaning when the elements are detected; The mold cleaning method according to claim 11.

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