Method for manufacturing glass articles

Abstract

A method for producing a glass article includes a base material switching step of switching the product type of a molten glass to be produced continuously in a glass melting furnace from a first product type to a second product type. The base material switching step includes: a first flow-out step of flowing out a molten glass from the glass melting furnace; and a second flow-out step of flowing out a molten glass subsequent to the first flow-out step. The flow amount of the molten glass in the first flow-out step is smaller than that in the second flow-out step.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a glass article by changing the base of molten glass. [Background technology]

[0002] In a glass melting furnace, glass raw materials are fed into a glass melting furnace (melting tank) from a raw material supply section (feed port) and heated by heating devices such as burners and electrodes to produce molten glass. The produced molten glass is discharged from the glass melting furnace and formed into a glass article by a forming device or the like.

[0003] When changing the type of glass article, the molten glass is changed. Known methods for changing the type of glass article include a type-punching method and an extrusion method (see, for example, Patent Document 1). For example, in the extrusion method, a first type of molten glass that has been produced in a glass melting furnace is pushed downstream by a second type of molten glass that is produced later, and then the production of a glass article using the second type of molten glass is started. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-157316 Summary of the Invention [Problem to be solved by the invention]

[0005] When the molten glass in a glass melting furnace is reworked by the extrusion method, the molten glass of the first type is extruded from the glass melting furnace by the molten glass of the second type, but not all of it is discharged from the glass melting furnace, and some of it may remain in the glass melting furnace. Specifically, the molten glass that reaches a stagnant layer present above the molten glass in the glass melting furnace may remain in the glass melting furnace. The molten glass in the stagnant layer is likely to be altered to become a different type of glass due to the volatilization of some components or the inclusion of foreign matter.

[0006] In this case, if the molten glass of the first variety remaining in the stagnant layer in the glass melting furnace is mixed with the molten glass of the second variety after the base material change is completed, bubble defects and the like may occur in the glass product, which may result in a decrease in quality.

[0007] The present invention has been made in view of the above circumstances, and has as its technical object to prevent deterioration in the quality of glass articles manufactured after substrate replacement. [Means for solving the problem]

[0008] The present invention is intended to solve the above-mentioned problems, and provides a method for manufacturing a glass article, which includes a base material changing step of changing molten glass continuously produced in a glass melting furnace from a first type to a second type, wherein the base material changing step includes a first outflow step of causing the molten glass to flow out of the glass melting furnace, and a second outflow step of causing the molten glass to flow out after the first outflow step, and wherein a flow rate of the molten glass in the first outflow step is lower than a flow rate of the molten glass in the second outflow step.

[0009] According to this configuration, by making the flow rate of the molten glass in the first outflow step lower than the flow rate of the molten glass in the second outflow step, it is possible to promote mixing by thermal convection of the molten glass related to the first type and the molten glass related to the second type remaining in the glass melting furnace.

[0010] As a result, in the second outflow step, the molten glass in which the molten glass related to the first variety and the molten glass related to the second variety are sufficiently mixed is caused to flow out of the glass melting furnace, so that the molten glass related to the first variety can be caused to flow out without remaining in the glass melting furnace.

[0011] Therefore, after the base material changing step is completed, it is possible to prevent the molten glass of the first type from mixing with the molten glass of the second type, and it is possible to prevent a deterioration in the quality of the glass article of the second type. Furthermore, by making the flow rate of the molten glass in the second outflow step higher than the flow rate of the molten glass in the first outflow step, the time required for the base material changing step is not prolonged.

[0012] In addition, in the first outflowing step, the amount of glass raw material supplied to the glass melting furnace and the amount of molten glass produced can be reduced, making it possible to suppress costs associated with the base material changing step.

[0013] In this method, when the flow rate of the molten glass in the first out-flowing step is Q1 and the flow rate of the molten glass in the second out-flowing step is Q2, the condition Q1≦0.5Q2 may be satisfied, thereby making it possible to suitably mix the molten glass of the first variety and the molten glass of the second variety in the first out-flowing step.

[0014] The base material changing step may include a bubbling step of introducing bubbles into the molten glass in the glass melting furnace. The movement of bubbles in the molten glass promotes the flow of the molten glass, enabling the molten glass of the first variety and the molten glass of the second variety to be mixed more efficiently.

[0015] In the method, the density of the molten glass of the second variety may be greater than the density of the molten glass of the first variety, thereby facilitating mixing of the molten glass of the first variety and the molten glass of the second variety, and enabling the mixed molten glass to efficiently flow out of the glass melting furnace. [Effects of the Invention]

[0016] According to the present invention, it is possible to prevent deterioration in the quality of glass articles produced after substrate replacement. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a side view showing a glass article manufacturing apparatus. [Figure 2] FIG. 2 is a cross-sectional view showing a glass melting furnace during normal operation. [Figure 3] 1 is a flowchart showing a method for manufacturing a glass article. [Figure 4] 10 is a flowchart showing a substrate changing process. [Figure 5] FIG. 2 is a cross-sectional view showing a glass melting furnace during a substrate replacement process. [Figure 6] FIG. 1 is a cross-sectional view of a glass melting furnace when a conventional glass substrate changing process is carried out. [Figure 7] 1 is a graph showing the relationship between the period, the concentration of glass components involved in the base material replacement, and the cumulative flow rate of molten glass when a conventional base material replacement process is carried out. [Figure 8] 1 is a graph showing the relationship between the period, the concentration of glass components involved in the base material replacement, and the cumulative flow rate of molten glass when the base material replacement step according to the present invention is carried out. DETAILED DESCRIPTION OF THE INVENTION

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figures 1 to 5 show an embodiment of the method for manufacturing a glass article according to the present invention.

[0019] 1 shows an apparatus for manufacturing a glass article. This manufacturing apparatus comprises, in order from the upstream side, a glass melting furnace 1, a fining tank 2, a homogenization tank (stirring tank) 3, a pot 4, a forming body 5, and glass supply paths 6a-6d connecting these components 1-5. In addition, the manufacturing apparatus also comprises an annealing furnace (not shown) for annealing the sheet glass GR (glass article) formed by the forming body 5, and a cutting device (not shown) for cutting the sheet glass GR after annealing.

[0020] The glass melting furnace 1 is a vessel for carrying out a melting step in which charged glass raw materials are melted to obtain molten glass GM. The glass melting furnace 1 is connected to a fining vat 2 by a glass supply line 6a.

[0021] The glass melting furnace 1 is made of, for example, a refractory material, such as a firebrick (for example, a zirconia-based electrocast brick, an alumina-based electrocast brick, an alumina-zirconia-based electrocast brick, an AZS (Al-Zr-Si)-based electrocast brick, or a dense-fired brick).

[0022] As shown in FIG. 2, the glass melting furnace 1 mainly includes a raw material supply unit 7 for supplying glass raw materials, a heating device (not shown) such as a burner or an electrode for heating the glass raw materials and the molten glass GM, an outlet 8 for discharging the molten glass GM, and a gas supply unit 9 for supplying gas to the molten glass GM.

[0023] The raw material supply unit 7 is provided on a side wall at one end (upstream side) of the glass melting furnace 1. The raw material supply unit 7 is equipped with an extrusion device including a screw. The raw material supply unit 7 can adjust the supply amount of glass raw materials by changing the rotation speed of the screw.

[0024] The discharge outlet 8 is provided in the side wall at the other end (downstream side) of the glass melting furnace 1. The discharge outlet 8 is connected to the glass supply path 6a. The discharge outlet 8 is provided at a position lower than the raw material supply part 7 (at the bottom of the side wall).

[0025] The gas supply unit 9 is provided at the bottom of the glass melting furnace 1. The gas supply unit 9 is composed of a nozzle fixed to the bottom of the glass melting furnace 1, piping for transporting gas, etc. The gas supply unit 9 generates bubbles B in the molten glass GM in the glass melting furnace 1 by discharging gas from the nozzle.

[0026] 2, the molten glass GM produced by the glass melting furnace 1 has a liquid surface FS. Here, the "liquid surface" refers to the surface of the molten glass GM that comes into contact with the gas phase (the interface with the gas phase).

[0027] The fining tank 2 is a container for carrying out a fining step in which the molten glass GM is transported and degassed by the action of a fining agent, etc. The fining tank 2 is connected to the homogenizing tank 3 by a glass supply path 6b.

[0028] The homogenization vessel 3 is a tubular vessel with a bottom for carrying out a process of stirring and homogenizing the refined molten glass GM (homogenization process). The homogenization vessel 3 is equipped with a stirrer 3a having stirring blades. The homogenization vessel 3 is connected to the pot 4 by a glass supply path 6c.

[0029] The pot 4 is a container for performing a condition adjusting step of adjusting the molten glass GM to a state suitable for forming. The pot 4 is exemplified as a volume portion for adjusting the viscosity and flow rate of the molten glass GM. The pot 4 is connected to the forming body 5 by a glass supply path 6d.

[0030] Molten glass GM is formed into a plate shape by an overflow downdraw method to form forming body 5. Specifically, forming body 5 has a substantially wedge-shaped cross section (cross section perpendicular to the paper surface of FIG. 1), and an overflow groove (not shown) is formed in the upper part of forming body 5.

[0031] The forming body 5 causes the molten glass GM to overflow from the overflow groove and flow down along both side wall surfaces of the forming body 5 (side surfaces located on the front and back sides of the paper in FIG. 1). The forming body 5 fuses the flowing molten glass GM at the lower end of the side wall surfaces. This allows a belt-shaped sheet glass GR (glass ribbon) to be continuously formed. After passing through an annealing furnace, the belt-shaped sheet glass GR is cut by a cutting device to form sheet glass of the desired size.

[0032] The thus obtained plate glass has a thickness of, for example, 0.01 to 10 mm, and is used as a substrate or protective cover for panel displays such as liquid crystal displays and organic EL displays, organic EL lighting, solar cells, and the like.

[0033] The forming body 5 may be one that implements other downdraw methods such as the slot downdraw method, and a forming device that uses the float method may be used instead of the forming body 5. The glass article manufactured by the manufacturing device is not limited to sheet glass GR, but also includes glass tubes, glass fibers, and other articles having various shapes. For example, when forming a glass tube, a forming device that uses the Danner method is installed instead of the forming body 5.

[0034] A method for manufacturing a glass article (plate glass GR) using the manufacturing apparatus configured as described above will be described below.

[0035] As shown in FIG. 3, the method includes a melting step S1, a fining step S2, a homogenizing step S3, a conditioning step S4, a forming step S5, a slow cooling step S6, and a cutting step S7.

[0036] In the melting step S1, glass frits are continuously fed into the glass melting furnace 1 from the raw material supply unit 7. The fed glass frits are heated by a heating device. As a result, the glass frits are melted in the glass melting furnace 1, and molten glass GM is produced.

[0037] In the melting step S1, gas is introduced into the molten glass GM in the glass melting furnace 1 by the gas supply unit 9. As shown in Fig. 2, the gas becomes bubbles B and moves from the bottom of the glass melting furnace 1 to the liquid surface FS of the molten glass GM. The molten glass GM flows in accordance with the movement of the bubbles B.

[0038] The molten glass GM flows continuously from the outlet 8 of the glass melting furnace 1 and is transferred to the fining tank 2 through the glass supply path 6a. A fining agent is blended into the glass raw materials, and gas (bubbles) are generated in the molten glass GM due to the action of this fining agent. In the fining step S2, the molten glass GM is circulated through the fining tank 2 to remove this gas.

[0039] Thereafter, the molten glass GM that has been subjected to the fining treatment (degassing treatment) is transferred through the glass supply path 6b to the homogenization vessel 3. In the homogenization step S3, the stirrer 3a is rotated in the homogenization vessel 3, whereby the molten glass GM is stirred (homogenized).

[0040] The homogenized molten glass GM is transferred through the glass supply path 6c to the pot 4. In the condition adjusting step S4, the viscosity and flow rate of the molten glass GM are adjusted through this pot 4.

[0041] The molten glass GM that has passed through the pot 4 flows into the overflow groove of the forming body 5 through the glass supply path 6d. In the forming step S5, the molten glass GM overflows from the overflow groove and flows down along the side wall surface of the forming body 5. The forming body 5 fuses the flowing molten glass GM at its lower top to form a belt-shaped plate glass GR.

[0042] The belt-shaped sheet glass GR is then subjected to an annealing process S6 in an annealing furnace. In a cutting process S7 using a cutting device, sheet glass of the desired size is cut out from the belt-shaped sheet glass GR that has undergone the annealing process S6. In the cutting process S7, after the sheet glass GR has been cut, the edge portions of the sheet glass are removed. If necessary, a re-cutting process, an edge processing process, and a cleaning process may be provided. In the re-cutting process, the sheet glass is cut to the desired size, in the edge processing process, the edge of the sheet glass is ground and polished to remove microcracks, and in the cleaning process, dirt adhering mainly to the surface of the sheet glass is removed. The sheet glass obtained in this manner is suitable, for example, for use as a glass substrate or cover glass for displays.

[0043] In the cutting step S7, the cutting method is not limited to the above, and both widthwise ends of the sheet glass GR may be cut and removed. In this case, the strip-shaped sheet glass GR from which both widthwise ends have been removed may be wound up in a roll (winding step).

[0044] In the above-described method for manufacturing a glass article, when a glass article having a composition different from that of the glass article currently being manufactured is to be manufactured, a base material changing step is carried out. In the base material changing step, the type of molten glass GM produced in the glass melting furnace 1 is changed from a first type to a second type by an extrusion method while the operation of the manufacturing apparatus is continued.

[0045] Hereinafter, the molten glass relating to the first type of glass article will be referred to as first molten glass GM1, and the molten glass relating to the second type of glass article will be referred to as second molten glass GM2.

[0046] In the base material changing step, glass frits of the second variety are fed from a raw material supply unit 7 into the glass melting furnace 1 while maintaining the flow of the first molten glass GM1 from the glass melting furnace 1 to the forming body 5. Thereafter, the glass frits are heated to produce a second molten glass GM2, which pushes out the first molten glass GM1 remaining in the glass melting furnace 1 from an outlet 8. This allows the variety to be changed while continuously producing the molten glasses GM1 and GM2.

[0047] As shown in Fig. 4, the first molten glass GM1 and the second molten glass GM2 are mixed in the glass melting furnace 1. In the base material changing process, bubbles B are introduced from a gas supply unit 9 into the molten glasses GM1 and GM2 in the glass melting furnace 1 (bubbling process). The movement of the bubbles B and the thermal convection of the molten glasses GM1 and GM2 cause the first molten glass GM1 and the second molten glass GM2 to mix. Hereinafter, the molten glass obtained by mixing the first molten glass GM1 and the second molten glass GM2 will be referred to as "mixed molten glass," and the first molten glass GM1, the second molten glass GM2, and the mixed molten glass will be collectively referred to simply as "molten glass."

[0048] The density ρ2 of the second molten glass GM2 is preferably larger than the density ρ1 of the first molten glass GM1 (ρ2>ρ1). The difference ρ2-ρ1 between the density ρ1 of the first molten glass GM1 and the density ρ2 of the second molten glass GM2 is 0.5 kg / m 3 More than 1kg / m is preferable. 3 The above is more preferable.

[0049] 5, the base material changing process includes a first outflowing process S10 in which molten glass is caused to flow out of the glass melting furnace 1, and a second outflowing process S11 in which the molten glass is caused to flow out after the first outflowing process S10. The flow rate of the molten glass in the first outflowing process S10 is lower than the flow rate of the molten glass in the second outflowing process S11, i.e., a low flow rate. In other words, the flow rate of the molten glass in the second outflowing process S11 is higher than the flow rate of the molten glass in the first outflowing process S10, i.e., a high flow rate. From the discharge port 8 of the melting furnace 1, the first molten glass GM1 flows out at the beginning of the base material changing process, followed by the mixed molten glass, and finally the second molten glass GM2 flows out.

[0050] In the first outflowing step S10, the molten glass is caused to flow out of the outlet 8 of the glass melting furnace 1 at a flow rate lower than the flow rate of the first molten glass GM1 before the base material changing step.

[0051] Examples of methods for reducing the flow rate of molten glass while maintaining the liquid level of the molten glass in the glass melting furnace 1 include a method of reducing the input amount of glass raw materials supplied from the raw material supply unit 7 to the glass melting furnace 1 while reducing the amount of heat generated by the heating devices provided in the glass melting furnace 1 and the glass supply paths 6a to 6d, or a method of arranging flow rate adjusting members such as baffles in the glass supply paths 6a to 6d to reduce the flow rate of molten glass.These methods may be combined as appropriate to reduce the flow rate of molten glass.

[0052] By reducing the input amount of glass raw materials as described above, the amount of newly generated second molten glass GM2 can be reduced. This can reduce the flow rate of molten glass. Furthermore, by reducing the amount of heat generated by the heating device, the time required to heat the molten glass increases, and the flow rate can be reduced.

[0053] From the viewpoint of further promoting the mixing of the molten glass by convection in the first outflowing step S10, the flow rate Q1 (kg / h) of the molten glass in the first outflowing step S10 preferably satisfies Q1≦0.5Q2, and more preferably Q1≦0.4Q2, where Q2 (kg / h) is the flow rate of the molten glass in the second outflowing step S11. On the other hand, from the viewpoint of shortening the period required for the material changing step, the flow rate Q1 of the molten glass in the first outflowing step S10 preferably satisfies 0.2Q2≦Q1.

[0054] The cumulative flow rate (total discharge amount) M1 (kg) in the first outflow step S10 preferably satisfies, for example, 1M≦M1≦3M, where M (kg) is the mass of molten glass held in the glass melting furnace 1 during operation.

[0055] The cumulative flow rate (total discharge amount) M2 (Kg) of the second outflow step S11 preferably satisfies, for example, 1M≦M2≦3M, where M (Kg) is the mass of molten glass held in the glass melting furnace 1 during operation.

[0056] In the first outflowing step S10, it is desirable to check the progress of the base material change by sampling molten glass from the liquid surface FS in the glass melting furnace 1 and measuring its components (measurement step). This measurement step is desirably carried out multiple times at regular intervals. It is also desirably carried out continuously in the second outflowing step S11.

[0057] After a predetermined period of time has elapsed, the base material changing process transitions from the first outflow process S10 to the second outflow process S11. In the second outflow process S11, the flow rate of the molten glass is increased. The flow rate Q2 of the molten glass in the second outflow process S11 is preferably set to be approximately the same as the flow rate Q3 of the second molten glass GM2 after the base material changing process is completed (e.g., 0.75Q3≦Q2≦1.25Q3), and more preferably equal to the flow rate Q3 of the second molten glass GM2 after the base material changing process is completed, so that the second type of glass article can be produced without delay after the base material changing process is completed. However, the flow rate of the molten glass in the second outflow process S11 may be different from the flow rate Q3 of the second molten glass GM2 after the base material changing process is completed.

[0058] In the first outflowing step S10, the flow rate of the molten glass can be increased by, for example, increasing the amount of glass raw material fed from the raw material feed section 7 to the glass melting furnace 1 while increasing the amount of heat generated by the heating devices provided in the glass melting furnace 1 and the glass supply paths 6a to 6d, in contrast to the first outflowing step S10, or by changing the position of or removing fixing members such as baffles provided in the glass supply paths 6a to 6d.

[0059] In the second outflow step S11, a determination step is carried out to determine whether the substrate replacement step has progressed properly. In the determination step, the mass% concentration of the specific glass component related to the substrate replacement measured in the measurement step is compared with a reference value (threshold value). That is, when the mass% concentration of the specific glass component periodically measured in the measurement step exceeds the threshold value, the second outflow step S11 ends.

[0060] In this determination step, it can also be determined whether the second outflow step S11 is proceeding normally. For example, when the mass percent concentration of a specific glass component involved in the substrate replacement is reduced, if a value that significantly deviates from a certain decreasing trend is measured, it can be assumed that an abnormality has occurred in the second outflow step S11.

[0061] After the second outflowing step S11 is completed, the second molten glass GM2 is flowed out of the glass melting furnace 1, and the above-described manufacturing method is carried out, whereby glass articles of the second variety are continuously manufactured.

[0062] As a result of extensive research into the substrate changing process, the inventors have discovered problems with conventional substrate changing processes and have confirmed that the substrate changing process of the present invention is effective in solving these problems.

[0063] The problems with the conventional substrate changing process and the effects of the present invention will be described below with reference to FIGS.

[0064] Fig. 6 shows the glass melting furnace 1 when the conventional base material changing process is carried out. Fig. 7 shows the results of carrying out the measurement process in the conventional base material changing process.

[0065] In the conventional base material changing process, the extrusion method was carried out without changing the flow rate of the molten glass. As the base material changing process progressed, the amount of the first molten glass GM1 remaining in the glass melting furnace 1 gradually decreased, and it sometimes remained in a stagnant layer near the liquid surface FS as shown in Figure 6, becoming a heterogeneous glass. In this state, during the base material changing process or after the base material changing process was completed, the heterogeneous glass (first molten glass GM1) remaining near the liquid surface FS in the glass melting furnace 1 sometimes unexpectedly flowed out from the discharge port 8.

[0066] If this situation occurs during the glass material change process, it will hinder the progress of the glass material change process and hinder its planned operation. Furthermore, if this situation occurs after the glass material change process has been completed, the composition of the second molten glass GM2 will change, resulting in a decrease in the quality of the glass article produced.

[0067] Figure 7 shows the changes in the mass % concentration of glass components and the cumulative flow rate of molten glass during and after a conventional substrate replacement process. In Figure 7, the horizontal axis indicates the period during and after the substrate replacement process. TE on the horizontal axis indicates the end of the substrate replacement process.

[0068] In Fig. 7, the mass% concentration of the specific glass component to be measured is represented by the vertical axis on the left and circular dots. Also in Fig. 7, the cumulative flow rate (kg) of molten glass is represented by the vertical axis on the right and bar graph. Note that Fig. 7 shows an example in which the mass% concentration of the specific glass component involved in the base material change is reduced, and the base material change process is terminated when this concentration exceeds (falls below) a threshold value CTH.

[0069] 7, during the conventional base material changing process, the mass % concentration of the glass component showed a minimum value C1 in a period T1, and then showed a maximum value C2 in a period T2. When the concentration changed drastically like this, it is presumed that the extraneous glass (first molten glass GM1) stagnating near the liquid surface FS in the glass melting furnace 1 was mixed into the molten glass flowing out from the outlet 8.

[0070] In the present invention, the above-mentioned conventional problems are solved by discharging the molten glass at a low flow rate from the glass melting furnace 1 in the first outflow step S10. Fig. 8 is a graph similar to Fig. 7 showing the mass % concentration of specific glass components involved in the base material replacement and the cumulative flow rate of molten glass when the base material replacement step according to the present invention is carried out.

[0071] In FIG. 8, TE1 indicates the end of the first outflowing step S10, and TE2 indicates the end of the second outflowing step S11 (substrate changing step).

[0072] As shown in FIG. 8, in this method, a first outflowing step S10 is performed in which the flow rate of the molten glass is reduced, and then a second outflowing step S11 is performed in which the flow rate of the molten glass is increased. This makes it possible to perform the base material changing step in a planned manner without causing a sudden change in the mass % concentration of the glass component over time.

[0073] Furthermore, even when the first outflow step S10 was performed as in the present invention, the material changing process could be completed within a period of time comparable to that of the conventional method without prolonging the period of the material changing process. Furthermore, when comparing the cumulative flow rates of the molten glass flowing out of the glass melting furnace 1 during the material changing process, the cumulative flow rate CQE2 at the end of the material changing process according to the present invention (see FIG. 8) could be made smaller than the cumulative flow rate CQE1 at the end of the conventional material changing process (see FIG. 7) (CQE2 <CQE1)。

[0074] The above-described effects of the present invention are thought to be due to the fact that the flow rate of the molten glass is reduced in the first outflow process S10, which promotes mixing by thermal convection of the first molten glass GM1 and the second molten glass GM2 remaining in the glass melting furnace 1, making it difficult for the first molten glass GM1 to remain alone in the glass melting furnace 1.

[0075] The present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. The present invention can be modified in various ways without departing from the spirit of the present invention.

[0076] In the above embodiment, the glass article manufacturing apparatus is shown to have one glass melting furnace 1, but the present invention is not limited to this configuration. The manufacturing apparatus may have two or more glass melting furnaces arranged in series or in parallel.

[0077] The base material changing step in the above embodiment is composed of a first outflowing step S10 in which molten glass is caused to flow out of the glass melting furnace 1 and a second outflowing step S11 in which molten glass is caused to flow out. However, if necessary, another outflowing step in which molten glass is caused to flow out of the glass melting furnace 1 may be provided as a step before the first outflowing step S10 or as a step after the second outflowing step S11. Alternatively, another outflowing step in which molten glass is caused to flow out of the glass melting furnace 1 may be provided between the first outflowing step S10 and the second outflowing step S11. In these cases, the flow rate of the another outflowing step is not particularly limited as long as molten glass can be continuously produced. However, to ensure the above-mentioned effects of the present invention, the cumulative flow rate (total discharge amount) M3 (Kg) of the another outflowing step is preferably M≧M3, and more preferably M≧0.5M3, where M (Kg) is the mass of molten glass held in the glass melting furnace 1 during operation. [Explanation of symbols]

[0078] 1. Glass melting furnace B. Air bubbles GM Molten Glass GM1 First Glass Melt GM2 Second Melt Glass GR Plate glass (glass products) S10 First outflow process S11 Second outflow process

Claims

1. A method for manufacturing a glass article, comprising a base material changing step of changing molten glass continuously produced in a glass melting furnace from a first type to a second type, the base material changing step includes a first outflowing step of causing the molten glass to flow out of the glass melting furnace, and a second outflowing step of causing the molten glass to flow out after the first outflowing step, A method for manufacturing a glass article, characterized in that the flow rate of the molten glass in the first outflowing step is lower than the flow rate of the molten glass in the second outflowing step.

2. 2. The method for manufacturing a glass article according to claim 1, wherein when a flow rate of the molten glass in the first outflowing step is Q1 and a flow rate of the molten glass in the second outflowing step is Q2, the condition Q1≦0.5Q2 is satisfied.

3. The method for manufacturing a glass article according to claim 1 or 2, wherein the base material changing step includes a bubbling step of introducing bubbles into the molten glass in the glass melting furnace.

4. The method for manufacturing a glass article according to claim 1 or 2, wherein the density of the molten glass of the second variety is greater than the density of the molten glass of the first variety.

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