Glass article manufacturing method and glass melting device

Abstract

The invention provides a method for manufacturing a glass article and a glass melting device, which can prevent platinum foreign matters as defects in the glass article as much as possible when the glass article is manufactured by using the glass melting device. The method for manufacturing a glass article includes: a supply step of supplying a glass raw material to a melting tank of a glass melting device; a melting step of heating the glass raw material while electrically heating the molten glass in the melting tank to melt the glass raw material; a molding step for molding a glass plate from the molten glass; and an inspection step for inspecting defects of the glass plate, in which the glass melting device is provided with a ground electrode made of molybdenum that comes into contact with the molten glass, an outflow duct that comes into contact with the molten glass, and the like. The method for manufacturing the glass article further comprises a confirmation step of confirming the generation of electric leakage between the outflow pipe and the ground electrode via the molten glass when the platinum foreign matter is detected in the glass plate by the inspection step.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing glass products such as glass plates and a glass melting device for melting glass raw materials to generate molten glass. Background Art

[0002] Glass products such as glass sheets, glass tubes, and glass fibers are manufactured by forming molten glass, which is produced by melting glass raw materials, into a predetermined shape. Molten glass is sometimes produced using a glass melting device (a glass melting furnace in this document) that electrically heats the molten glass, as disclosed in Patent Document 1.

[0003] In this device, glass raw material is supplied to a melting tank, and the molten glass contained in the melting tank is heated by applying electricity to the glass raw material, thereby melting the glass raw material. It should be noted that in this device, in addition to the above-mentioned electrical heating, the glass raw material is also heated by a burner. The melting tank is provided with a power electrode for electrically heating the molten glass while it is immersed in the molten glass, and a ground electrode immersed in the molten glass and grounded. Furthermore, the melting tank is provided with a take-off portion for allowing the molten glass generated in the tank to flow out of the tank.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-31355 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] Patent Document 1 does not describe the materials used for the ground electrode and the extraction portion. However, a molybdenum electrode, for example, can be used as the ground electrode. Furthermore, a platinum or platinum alloy pipe can be used as the extraction portion. When using a glass melting apparatus with the present configuration, platinum foreign matter containing platinum (e.g., a platinum-molybdenum alloy) can sometimes form as a defect in glass articles formed from the molten glass. This can lead to problems with the production of the glass articles.

[0009] In view of the above circumstances, a problem to be solved is to prevent platinum foreign matter, which is a defect, from being generated in glass articles as much as possible when glass articles are manufactured using a glass-melting apparatus.

[0010] Solutions to Problems

[0011] The inventors, through extensive research, have discovered that when glass articles are manufactured using a glass-melting apparatus that electrically heats molten glass, the flow of current between a molybdenum member and a platinum or platinum alloy member through the molten glass can result in the formation of platinum foreign matter within the glass article. It should be noted that the molybdenum member serves as the anode, and the platinum or platinum alloy member serves as the cathode.

[0012] Based on the above insights, a first method for manufacturing glass articles for solving the above-mentioned problems includes: a supplying process of supplying glass raw materials to a melting tank provided in a glass melting device; a melting process of heating the glass raw materials supplied to the melting tank while heating the molten glass contained in the melting tank by applying electricity to the melting tank to melt the glass raw materials; a forming process of forming a glass article from the molten glass flowing out of the melting tank; and an inspection process of inspecting defects in the glass article. The method for manufacturing the glass article is characterized in that the glass melting device further includes a molybdenum component in contact with the molten glass and a platinum component in contact with the molten glass. The method for manufacturing the glass article further includes a confirmation process of confirming the occurrence of leakage current between the platinum component and the molybdenum component through the molten glass when a platinum foreign body containing a platinum component is detected in the glass article by the inspection process.

[0013] Here, the term "molybdenum member" means a member made of molybdenum. Also, the term "platinum member" means a member made of platinum (including reinforced platinum) or a platinum alloy (including reinforced platinum alloy).

[0014] In the first glass article manufacturing method, if platinum foreign matter is detected in the glass article during the inspection step, a confirmation step is performed to confirm the occurrence of leakage current between the platinum component and the molybdenum component through the molten glass. Therefore, even if current accidentally flows between the platinum component and the molybdenum component through the molten glass, the condition can be repaired after the confirmation step. Furthermore, after the repair, the flow of current between the platinum component and the molybdenum component through the molten glass can be avoided, thereby minimizing the occurrence of platinum foreign matter in the glass article caused by leakage current.

[0015] The second method for manufacturing a glass article is based on the above-mentioned first method and is set as follows: the molybdenum component is a grounding electrode immersed in the molten glass in the melting tank and grounded, and the method for manufacturing the glass article also includes a measuring step of measuring the current flowing in the grounding electrode. When platinum foreign matter is detected in the glass article by the inspection step and the current measured by the measuring step increases, a confirmation step is performed.

[0016] As described in the second glass article manufacturing method, if the current measured in the measurement step (current flowing through the ground electrode) increases after the measurement step, the likelihood that leakage current between the platinum member and the molybdenum member through the molten glass is the cause of the platinum foreign matter increases. Therefore, if the confirmation step is performed when platinum foreign matter is detected in the glass article in the inspection step and the current measured in the measurement step increases, it is possible to minimize the waste of performing the confirmation step even when no leakage current has actually occurred.

[0017] The third method for manufacturing a glass article is based on the second manufacturing method described above and is configured as follows: an electrically heated area having an electrically powered electrode configured to electrically heat the molten glass is provided in the melting tank; the glass melting device is further provided with a transfer device for transferring the molten glass flowing out of the melting tank; and a grounding electrode is configured at a position downstream of the electrically heated area and upstream of the transfer device in the flow direction of the molten glass.

[0018] In the third method for manufacturing a glass article, a ground electrode is disposed between the electrically heated area and the transfer device in the direction of flow of the molten glass. This prevents current from flowing from the molten glass in the melting tank to the molten glass in the transfer device, or vice versa.

[0019] The fourth method for manufacturing a glass article is based on any one of the first to third manufacturing methods described above, wherein the molybdenum component is a ground electrode immersed in the molten glass in the melting tank and grounded, and a capacitor is provided on the current path connecting the molybdenum component and the ground wire.

[0020] The inventors' intensive research has led to the discovery that when the current flowing between the molybdenum component and the platinum component via molten glass is DC rather than AC, platinum foreign matter can form in the glass article due to leakage. Based on this discovery, the fourth method for manufacturing a glass article is highly advantageous in preventing the formation of platinum foreign matter due to leakage. This is because the provision of a capacitor blocks DC current in the current path connecting the molybdenum component to the ground, thereby preventing DC current from flowing between the molybdenum component and the platinum component via the molten glass.

[0021] A fifth method for producing a glass article is the method according to any one of the first to fourth methods, wherein the glass raw material is an alkali-free glass raw material.

[0022] A sixth method for producing a glass article is a method according to any one of the first to fifth methods described above, wherein the glass article is a glass substrate for a display.

[0023] In glass substrates for displays, the presence of minute platinum foreign matter may prevent the substrate from being used as a product. Therefore, as described in the sixth method for manufacturing a glass article, when the glass article is a glass substrate for a display, the benefits of performing the aforementioned confirmation step can be appropriately achieved.

[0024] Based on the above insights, the first glass melting device for solving the above problems comprises: a melting tank, which receives the supply of glass raw materials and accommodates molten glass formed by melting the glass raw materials; and a power-carrying electrode, which heats the molten glass by power while it is immersed in the molten glass in the melting tank. The first glass melting device is characterized in that it also comprises: a molybdenum grounding electrode, which is immersed in the molten glass in the melting tank and is grounded; a platinum component, which is in contact with the molten glass; and an ammeter, which measures the current flowing in the grounding electrode.

[0025] The first glass-melting device can more reliably detect leakage between the platinum member and the ground electrode through the molten glass based on the increase in current measured by the ammeter, and can correct the leakage after confirming its occurrence. Therefore, the formation of platinum foreign matter in glass products caused by leakage can be minimized.

[0026] Based on the above insights, a second glass melting device for solving the above-mentioned problems comprises: a melting tank, which receives the supply of glass raw materials and accommodates molten glass formed by melting the glass raw materials; and a power-carrying electrode, which heats the molten glass by applying electricity while the molten glass is immersed in the molten glass in the melting tank. The second glass melting device is characterized in that it also comprises: a grounding electrode made of molybdenum, which is immersed in the molten glass in the melting tank and is grounded; a platinum component, which is in contact with the molten glass; and a capacitor, which is arranged on the path of the current connecting the grounding electrode and the ground wire.

[0027] According to the second glass-melting device, the effects described above with respect to the fourth method for producing a glass article can be obtained in the same manner.

[0028] Effects of the Invention

[0029] According to the method for manufacturing a glass article and the glass-melting device of the present invention, when a glass article is manufactured using the glass-melting device, it is possible to prevent platinum foreign matter from being generated in the glass article due to leakage as much as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a partial cross-sectional view showing a method for manufacturing a glass article and a glass-melting device.

[0031] Figure 2 This is a perspective view showing a method for manufacturing a glass article.

[0032] Figure 3 It is a partial cross-sectional view showing a method for manufacturing a glass article and a glass-melting device.

[0033] Figure 4 It is a cross-sectional view showing a test for confirming the generation of platinum foreign matter.

[0034] Description of Reference Numerals

[0035] 2 Glass raw materials

[0036] 3 Molten Glass

[0037] 4 Glass melting device

[0038] 5 Glass ribbon

[0039] 7 Glass Panes

[0040] 9 Melting Tank

[0041] 11 Powered Electrode

[0042] 12 Grounding Electrode

[0043] 13 Ammeter

[0044] 14 Outflow pipe

[0045] 15 Transfer device

[0046] 35 capacitors

[0047] E. Components of the transfer device

[0048] P1 Supply process

[0049] P2 Melting Process

[0050] P3 measurement process

[0051] P4 forming process

[0052] P5 Inspection Process

[0053] P6 Confirmation Process

[0054] S Energizes the heating zone. DETAILED DESCRIPTION

[0055] Embodiments of a method for manufacturing a glass article and a glass-melting apparatus are described below with reference to the accompanying drawings. The embodiments described below illustrate the case of manufacturing a glass substrate for a display as one type of glass article. It should be noted that the X, Y, and Z directions shown in some of the drawings referenced in the description of the embodiments are orthogonal to each other.

[0056] <First embodiment>

[0057] First, a production apparatus used to implement the method for producing a glass article will be described.

[0058] like Figure 1 as well as Figure 2 As shown, the manufacturing apparatus 1 includes: a glass melting device 4 for melting glass raw material 2 to produce molten glass 3; a forming device 6 for continuously forming a glass ribbon 5 (a glass sheet elongated in one direction) from the molten glass 3; a cutting device (not shown) for cutting a glass sheet 7, which becomes a raw material of a glass substrate, from the glass ribbon 5; and an inspection device 8 for inspecting the glass sheet 7 for the presence or absence of defects.

[0059] like Figure 1 As shown, the glass melting device 4 includes: a melting tank 9, which accommodates the molten glass 3 generated from the glass raw material 2; a feeder 10, which supplies the glass raw material 2 onto the molten glass 3 in the melting tank 9; a plurality of powered electrodes 11, which electrically heat the molten glass 3 in a state of being immersed in the molten glass 3 in the melting tank 9; a molybdenum grounding electrode 12, which is immersed in the molten glass 3 in the melting tank 9 and is grounded and does not receive power supply; an ammeter 13, which measures the current flowing in the grounding electrode 12; an outflow pipe 14 made of platinum alloy, which allows the molten glass 3 to flow out of the melting tank 9 and is electrically insulated from the ground wire; and a transfer device 15, which transfers the molten glass 3 flowing out of the melting tank 9 to the forming device 6.

[0060] Here, the ground electrode 12 described above corresponds to a molybdenum member in contact with the molten glass, and the outflow pipe 14 described above corresponds to a platinum member in contact with the molten glass.

[0061] The wall 19 of the melting tank 9 includes a bottom wall 16, side walls 17, and a top wall 18. The portion of the wall 19 that contacts the molten glass 3 is made of refractory materials such as zirconia bricks or zircon bricks. The outer surface of the wall 19 (the outer surface of the wall 19) that contacts the molten glass 3 is sufficiently cooled as needed by air that contacts the outer surface or by cooling gas blown onto the outer surface. This ensures the insulation properties of the wall 19 of the melting tank 9.

[0062] The feeder 10 is disposed on a side wall 17 of the wall portion 19 of the melting tank 9, located at the upstream end in the flow direction (X direction) of the molten glass 3. As the feeder 10, for example, a screw feeder for feeding the glass raw material 2 into the melting tank 9 or a pusher for pushing the glass raw material 2 into the melting tank 9 is used.

[0063] The glass feedstock 2 continuously supplied by the feeder 10 is a raw material for alkali-free glass. "Alkali-free glass" herein refers to glass that is substantially free of alkali components (alkali metal oxides). Specifically, it refers to glass having an alkali content of 3000 ppm by weight or less. The alkali content is preferably 1000 ppm by weight or less, more preferably 500 ppm by weight or less, and most preferably 300 ppm by weight or less.

[0064] The plurality of powered electrodes 11 are arranged in the X and Y directions, spaced apart from each other. The plurality of powered electrodes 11 include multiple groups of two paired electrodes. When the melting tank 9 is viewed from above (in the Z direction), the electrically heated region S where the plurality of powered electrodes 11 are arranged corresponds to the region in the X and Y directions where the plurality of powered electrodes 11 are arranged. Each powered electrode 11 is made, for example, of molybdenum, platinum, or a platinum alloy. Each powered electrode 11 is inserted into the melting tank 9 from the bottom wall 16 while being electrically insulated from the bottom wall 16. The power supply (not shown) that supplies power to the powered electrodes 11 in this embodiment is an AC power supply. When the molten glass 3 is electrically heated by the plurality of powered electrodes 11, the glass feedstock 2 on the molten glass 3 is heated and melted.

[0065] The ground electrode 12 is positioned downstream of the electrically heated area S and upstream of the outflow pipe 14 in the direction of flow (X) of the molten glass 3. The ground electrode 12 is inserted into the melting tank 9 through the bottom wall 16. Unlike the powered electrode 11 described above, the ground electrode 12 does not receive intended power from a power source or the like, and is in a state where no power is supplied from outside the melting tank 9. The ground electrode 12 minimizes the potential of the molten glass 3 in the vicinity of the electrode relative to ground (approximately 0V). This minimizes the flow of undesired current from components within the melting tank 9 (e.g., the powered electrode 11) to components within the transfer device 15 via the molten glass 3, and vice versa. Consequently, damage to components within the melting tank 9 and the transfer device 15 due to undesired current can be prevented.

[0066] Amperemeter 13 is placed on the path of current connecting ground electrode 12 to the ground wire. Amperemeter 13 can be used for direct current (DC), alternating current (AC), or both. From the perspective of detecting leakage current caused by platinum foreign matter, it is preferable to include amperemeter 13 for DC.

[0067] The outflow pipe 14 is arranged to penetrate the downstream sidewall 17 of the wall portion 19 of the melting tank 9, which is located in the flow direction (X direction) of the molten glass 3. In this embodiment, the outflow pipe 14 uses a platinum-rhodium alloy as the platinum alloy, but it can also be made of a platinum alloy other than the platinum-rhodium alloy, or it can be made of platinum (pure platinum). The outflow pipe 14 is ensured to be non-contacting with other conductors. The outflow pipe 14 may be equipped with a device for electrically heating the pipe, and the pipe may be electrically heated.

[0068] The transfer device 15 includes, in order from the upstream side in the flow direction of the molten glass 3, a clarification tank 20 for clarifying the molten glass 3 (removing bubbles from the molten glass 3), stirring tanks 21 (installed at two locations in the illustrated example) for stirring and homogenizing the molten glass 3 using a stirrer (not shown), and a state adjustment tank 22 for adjusting the temperature (viscosity) and flow rate of the molten glass 3 to a level suitable for forming the glass ribbon 5. The transfer device 15 also includes pipes 23 to 28 for connecting the above-mentioned devices 20 and 22. In the following description, the devices 20 and 22 and the pipes 23 to 28 may each be referred to as component E of the transfer device 15.

[0069] The plurality of components E (devices 20 to 22 and pipes 23 to 28) included in the transfer device 15 are each made of platinum or a platinum alloy (here, a platinum-rhodium alloy), and at least a portion of the plurality of components E is provided with a device for electrically heating the component. Figure 1 The illustrated boundaries B1, B2, and B3 define multiple (three in the example) units U1 to U3. Adjacent units are electrically isolated from each other by an insulator interposed between them. Furthermore, among the units U1 to U3, unit U1 is electrically isolated from the outflow pipe 14 by an insulator interposed between the unit and the outflow pipe 14.

[0070] Regarding each of the plurality of units U1 to U3, Figure 1 The area enclosed by the dashed line is equipped with a refractory covering the component E of the transfer device 15 (e.g., zirconia bricks, zircon bricks, alumina bricks, cast moldings, etc.), arranged in contact with the component E. The outer surface of the refractory is sufficiently cooled as needed by air in contact with the outer surface or by cooling gas blown onto the outer surface. This ensures the insulation properties of the refractory and prevents electrical leakage through the refractory. Furthermore, each component E of the transfer device 15 is kept away from other conductors.

[0071] As described above, the components E of the outflow pipe 14 and the transfer device 15 are generally kept out of contact with other conductors. However, as an exception, a thermocouple (thermometer) may be attached to the outer surface of the components E of the outflow pipe 14 and / or the transfer device 15 to measure the temperature of the outflow pipe 14 and / or the components E. This thermocouple consists of a conductor (platinum or a platinum alloy, etc.) but is located inside a closed-end protective tube. Therefore, in principle, it does not come into direct contact with the outflow pipe 14 or the components E, but rather contacts them through the protective tube. The protective tube is made of an insulator (e.g., alumina).

[0072] Here, each component E of the transfer device 15 (each of the devices 20 to 22 and the pipes 23 to 28 ) corresponds to a platinum member that comes into contact with the molten glass.

[0073] like Figure 1 As shown, the forming apparatus 6 includes a forming body 29 into which the molten glass 3 flowing from the state adjustment tank 22 flows. The forming body 29 in this embodiment is a forming body for the overflow down-draw method. Alternatively, the forming body 29 may be a forming body for the slot down-draw method. The glass ribbon 5 formed by the forming body 29 is formed into an elongated strip along one direction (the Z direction), with ears formed at each end of the glass ribbon in the width direction (the X direction) having a greater thickness than the other portions.

[0074] Around the formed body 29 (at Figure 1 A refractory is arranged in a manner surrounding the formed body 29 (in the area surrounded by the single-dot chain line).

[0075] The cutting device (not shown) includes a first cutting device for cutting the glass ribbon 5 in the width direction (X direction) to cut out a glass sheet with an ear portion from the glass ribbon 5 ; and a second cutting device for cutting and removing the ear portion from the glass sheet with an ear portion to obtain a glass sheet 7 .

[0076] like Figure 2 As shown, the inspection device 8 includes a conveying device 30 that conveys the glass plate 7 while maintaining the glass plate 7 in a vertical position, and a defect detection device 31 that is disposed on a conveying path of the glass plate 7 and detects defects in the glass plate 7 .

[0077] The defect detection device 31 includes a light source 32 that emits a longitudinally long line of light, and a line sensor 34 formed by a plurality of cameras 33 arranged longitudinally. In this defect detection device 31, light emitted from the light source 32 toward the glass sheet 7 being conveyed is received by the line sensor 34 on the opposite side of the glass sheet 7. The presence or absence of defects is detected based on changes in the amount of received light.

[0078] Hereinafter, a method for producing a glass article using the above-described production apparatus 1 will be described.

[0079] The manufacturing method includes Figure 1 The supply process P1, the melting process P2, the measuring process P3 and the forming process P4 shown, the cutting process and the Figure 2 Inspection step P5 shown.

[0080] In the supply step P1, glass feedstock 2 is continuously supplied from a feeder 10 to the melting tank 9 of the glass-melting device 4. In the melting step P2, the molten glass 3 contained in the melting tank 9 is heated by a plurality of current-carrying electrodes 11, while simultaneously being electrically heated. The glass feedstock 2 supplied to the melting tank 9 is also heated and melted. In the measurement step P3, the current flowing through the ground electrode 12 is measured by an ammeter 13. In the forming step P4, after flowing out of the melting tank 9, the molten glass 3, clarified, stirred, and conditioned in the clarification tank 20, stirring tank 21, and conditioning tank 22, is formed into a glass ribbon 5. In the cutting step, a glass sheet 7 is obtained from the glass ribbon 5 using cutting devices (first and second cutting devices). In the inspection step P5, the glass sheet 7 is inspected for defects using the inspection device 8 (the conveying device 30 and the defect detection device 31). More specifically, in inspection step P5, defects in the glass sheet 7 are detected and their locations are determined using the inspection device 8 (the transport device 30 and the defect detection device 31). The detected defects are then observed using a microscope or chemically analyzed using an analyzer to determine their type (e.g., bubbles, platinum foreign matter, etc.).

[0081] Furthermore, in this manufacturing method, if platinum foreign matter containing platinum (e.g., a platinum-molybdenum alloy) is detected in the glass sheet 7 during inspection step P5 and the current measured in measurement step P3 increases compared to a reference value, confirmation step P6 is executed. In confirmation step P6, the occurrence of leakage current between the platinum member and the molybdenum member through the molten glass is confirmed. For example, the electrical insulation between the outflow pipe 14 and other conductors, the electrical insulation between the component E of the transfer device 15 and other conductors, and the electrical insulation between the ground electrode 12 and other conductors is confirmed. In other words, the platinum member and the molybdenum member are confirmed to have insulation defects. If insulation is ensured, it can be confirmed that the leakage current has not occurred. If insulation is not ensured, there is a possibility that the leakage current has occurred. If insulation is not ensured, a repair step is executed to restore insulation.

[0082] As described above, if platinum foreign matter is detected in inspection step P5 and the current measured in measurement step P3 increases compared to the reference value, there is a high probability that the outflow pipe 14 or component E of the transfer device 15 has accidentally come into contact with another conductor, resulting in the current flowing in that conductor leaking to the platinum member and then flowing from the platinum member to the molybdenum member via the molten glass. The reason for this is as follows. The inventors' extensive research has determined that if another conductor (e.g., a thermocouple) through which current flows accidentally comes into direct contact with the platinum alloy outflow pipe 14 due to wear and tear of the protective tube, current flows between the molybdenum ground electrode 12 and the platinum alloy outflow pipe 14 via the molten glass 3, potentially leading to the formation of platinum foreign matter on the glass sheet 7. Therefore, performing the above-mentioned confirmation step P6 is effective.

[0083] The reference value of the current in the measurement step P3 is set to be larger than the maximum value (for example, 0.1 A) of the current (current measured by the ammeter 13 ) that may flow through the ground electrode 12 when the above-mentioned leakage does not occur.

[0084] As a specific example of the situation where the above-mentioned insulation failure occurs, in addition to the above-mentioned loss of the thermocouple protection tube, there is also the situation where a portion of the outflow pipe 14 is damaged and the molten glass 3 leaking from the damaged portion comes into contact with other conductors. When insulation failure is confirmed in the confirmation step P6 as in this example, work is performed in the repair step to eliminate the cause of the insulation failure.

[0085] <Second embodiment>

[0086] Below, refer to Figure 3 The second embodiment will be described. It should be noted that the second embodiment will be described only with respect to the differences from the first embodiment described above.

[0087] The second embodiment differs from the first embodiment described above in that a capacitor 35 is disposed on the path of the current connecting the ground electrode 12 to the ground. In this embodiment, capacitor 35 is disposed closer to the ground than ammeter 13. However, capacitor 35 may be disposed closer to the ground electrode 12 than ammeter 13. In the latter case, ammeter 13 is preferably an AC ammeter.

[0088] The provision of the capacitor 35 blocks direct current from flowing through the current path connecting the ground electrode 12 to the ground. This prevents direct current from flowing between the molybdenum ground electrode 12 and the platinum alloy outflow pipe 14, and between the molybdenum ground electrode 12 and the platinum alloy component E, via the molten glass 3.

[0089] Below, refer to Figure 4A test for confirming the generation of platinum foreign matter will be described.

[0090] This test confirmed that insulation failure occurred in the outflow pipe 14, the platinum member such as the component E, and / or the molybdenum member such as the ground electrode 12, and current flowed between the platinum members through the molten glass 3, which may cause platinum foreign matter to be generated.

[0091] The equipment used in this experiment consisted of a crucible 36 containing molten glass 3, a pair of molybdenum electrodes 37 (anode), and platinum-rhodium alloy electrodes 38 (cathode). Molten glass 3 was molten glass for alkali-free glass substrates (product name: OA-11) manufactured by Nippon Electric Glass Co., Ltd. Crucible 36 was made of refractory (dense zircon). Electrodes 37 and 38 were connected to a DC power supply (1V) and inserted into crucible 36 so as to be immersed in molten glass 3.

[0092] In this test, current flows between electrodes 37 and 38 via molten glass 3. This state reproduces the state in which current flows between the platinum member and the molybdenum member via molten glass 3 due to insulation failure between the platinum member and the molybdenum member.

[0093] Using the above-described apparatus, current was flowed between electrodes 37 and 38 for 24 hours while the temperature of molten glass 3 was at 1550°C. Platinum foreign matter (formed from an alloy of platinum and molybdenum) was observed to form around electrode 38 (the cathode). However, no platinum foreign matter was observed when the anode and cathode were swapped, with electrode 37 made of a platinum-rhodium alloy serving as the anode and electrode 38 made of molybdenum serving as the cathode; when both the anode and cathode were made of a platinum-rhodium alloy; and when an AC power source was used instead of a DC power source.

[0094] The results of this test revealed that when an electric current flows between a platinum member and a molybdenum member via molten glass, platinum foreign matter may be generated.

[0095] Here, the following modified examples can also be applied to the above-mentioned embodiment.

[0096] In the above embodiment, confirmation step P6 is executed when a platinum foreign particle is detected in inspection step P5 and the current measured in measurement step P3 increases above a reference value. However, this is not limiting, and confirmation step P6 may be executed without regard to the current measured in measurement step P3. In other words, confirmation step P6 may be executed only when a platinum foreign particle is detected in inspection step P5.

[0097] In the above embodiment, the case where the component E of the outflow pipe 14 or transfer device 15 accidentally contacts another conductor is cited as an example, but the present invention is not limited to this. For example, a layer made of platinum or a platinum alloy may be formed on the inner surface of the wall portion 19 of the melting tank 9 in a region that contacts the molten glass 3, and this layer may accidentally contact another conductor. The method for manufacturing a glass article of the present invention may also be applied by using a platinum member as the layer. It should be noted that the layer made of platinum or a platinum alloy may be formed, for example, by a spray coating or a plate material.

Claims

1. A method for manufacturing a glass article, comprising: A supplying step of supplying glass raw materials to a melting tank provided in a glass melting device; a melting step of heating the molten glass contained in the melting tank by applying electricity and simultaneously heating the glass raw materials supplied to the melting tank to melt the glass raw materials; a forming step of forming a glass article from the molten glass flowing out of the melting tank; and An inspection process to inspect the glass article for defects, The method for manufacturing the glass article is characterized in that: The glass-melting device further includes a molybdenum member in contact with the molten glass and a platinum member in contact with the molten glass. The method for manufacturing the glass article further includes a confirmation step of confirming occurrence of leakage current between the platinum member and the molybdenum member via the molten glass when platinum foreign matter containing a platinum component is detected in the glass article in the inspection step.

2. The method for manufacturing a glass article according to claim 1, wherein: The molybdenum member is a ground electrode immersed in the molten glass in the melting tank and grounded. The method for manufacturing a glass article further includes a measuring step of measuring the current flowing through the ground electrode. The confirmation step is performed when platinum foreign matter is detected in the glass article in the inspection step and the current measured in the measurement step increases.

3. The method for manufacturing a glass article according to claim 2, wherein: The melting tank is provided with an electric heating area where electric electrodes are arranged for electrically heating the molten glass. The glass-melting device further includes a transfer device for transferring the molten glass flowing out of the melting tank. The ground electrode is arranged at a position downstream of the electrically heated region and upstream of the transfer device in a flow direction of the molten glass.

4. The method for manufacturing a glass article according to claim 1, wherein: The molybdenum member is a ground electrode immersed in the molten glass in the melting tank and grounded. A capacitor is provided on a current path connecting the molybdenum member and the ground.

5. The method for producing a glass article according to any one of claims 1 to 4, wherein: The glass raw material is a raw material of alkali-free glass.

6. The method for producing a glass article according to any one of claims 1 to 4, wherein: The glass article is a glass substrate for a display.

7. A glass melting device comprising: a melting tank that receives supply of glass raw materials and accommodates molten glass formed by melting the glass raw materials; and a power electrode for heating the molten glass by applying electricity while the molten glass is immersed in the melting tank; The glass-melting device is characterized by further comprising: a molybdenum ground electrode immersed in the molten glass in the melting tank and grounded; a platinum member in contact with the molten glass; and An ammeter measures the current flowing through the ground electrode.

8. A glass melting device comprising: a melting tank that receives supply of glass raw materials and accommodates molten glass formed by melting the glass raw materials; and a power electrode for heating the molten glass by applying electricity while the molten glass is immersed in the melting tank; The glass-melting device is characterized by further comprising: a molybdenum ground electrode immersed in the molten glass in the melting tank and grounded; a platinum member in contact with the molten glass; and A capacitor is provided on a current path connecting the ground electrode and the ground line.

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