Method for producing glass article

Abstract

To provide a method for producing a glass article that prevents a decrease in the efficiency of producing the glass article by enabling efficient degassing after a starting step, without requiring tilting of a molded body.SOLUTION: A method for producing a glass article comprises a heating step S1, a starting step S2, and a molding step S4. A molding furnace comprises a ceiling wall located above a molded body. The temperature of the ceiling wall of the molding furnace in the starting step S2 is lower than that of the ceiling wall of the molding furnace in the molding step S4. This allows the flow velocity of molten glass over the molded body to be reduced. Therefore, the molten glass can be uniformly flowed over a wider area of the molded body, enabling efficient degassing after the starting step without requiring tilting of the molded body as in conventional cases.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a glass article. [Background technology]

[0002] The overflow downdraw method is sometimes used as a method for manufacturing glass articles such as glass sheets. The forming apparatus used in this method is equipped with a roughly wedge-shaped forming body. Molten glass supplied to the forming body overflows in two directions from grooves formed at the top of the forming body, then flows down both outer surfaces of the forming body and meets at the bottom end.

[0003] In this way, a band-shaped glass ribbon is continuously formed from the molten glass. This manufacturing method has the advantage that the front and back surfaces of the formed glass ribbon do not come into contact with the forming body during the forming process, and therefore a smooth glass ribbon without scratches or the like on the front and back surfaces can be formed.

[0004] Patent Document 1 discloses a method for manufacturing a glass article, which includes a degassing step for a forming body (isopipe) before forming a glass ribbon from molten glass. In this method, the degassing step involves bringing molten glass into contact with the forming body, and removing gas contained in the interior and surface of the forming body by transferring it to the molten glass (see paragraph 0023 of the same document).

[0005] Furthermore, in the degassing process, in order to promote contact of the molten glass with the forming body, the forming body is tilted at a predetermined tilt angle θ from its normal posture in which the molten glass can be formed (see claim 5 and paragraph 0012 of the same document). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-120845 Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional manufacturing method of a glass article as described above, the degassing step requires the complex operation of tilting the formed body, which reduces the manufacturing efficiency of the glass article.

[0008] The present invention has been made in view of the above circumstances, and has as its technical object to efficiently perform the degassing step. [Means for solving the problem]

[0009] (1) The present invention is intended to solve the above-mentioned problems, and is a method for manufacturing a glass article, comprising: a heating step of heating a forming body contained in a forming furnace; an initiation step of starting to supply molten glass to the forming body that has undergone the heating step; and a forming step of forming a glass ribbon from the molten glass by an overflow method using the forming body that has undergone the initiation step, wherein the forming furnace has a ceiling wall located above the forming body, and the temperature of the ceiling wall of the forming furnace in the initiation step is lower than the temperature of the ceiling wall of the forming furnace in the forming step.

[0010] According to this configuration, the temperature of the ceiling wall of the forming furnace in the starting step is set lower than the temperature of the ceiling wall of the forming furnace in the forming step. This reduces the speed of the molten glass flowing over the forming body. Therefore, the molten glass can be made to flow uniformly over a wider area of ​​the forming body. This makes it possible to efficiently perform the degassing step after the starting step without the need to tilt the forming body as in the conventional method.

[0011] (2) In the method for manufacturing a glass article having the configuration described in (1) above, a degassing step may be provided between the starting step and the forming step, in which the molten glass is continuously supplied to the formed body to degas the formed body.

[0012] According to this configuration, in the degassing step, molten glass is continuously supplied to the formed body, thereby ensuring degassing of the formed body.

[0013] (3) In the method for manufacturing a glass article described in (2) above, the forming body has a groove portion into which the molten glass is supplied, an upper portion through which the molten glass overflowing from two directions of the groove portion flows down, and a lower portion through which the molten glass flowing down the upper portion is joined to form the glass ribbon, and the forming furnace may include a heater for heating the lower portion of the forming body, and the temperature of the heater in the degassing process may be higher than the temperature of the heater in the forming process.

[0014] According to this configuration, by setting the temperature of the heater that heats the lower part of the forming body in the degassing step higher than the temperature of the heater in the forming step, it is possible to prevent the chunks of molten glass that fall from the lower part of the forming body from becoming large, which makes it easier to process the molten glass that falls from the forming body and prevents damage to the equipment.

[0015] (4) In the method for manufacturing a glass article described in (2) or (3) above, the forming furnace may include a pressing member that presses the formed body, and the pressing force applied to the formed body by the pressing member in the degassing step may be smaller than the pressing force applied to the formed body by the pressing member in the forming step.

[0016] In the molding process, a pressing force is applied to the molded body by a pressing member to prevent creep deformation of the molded body. During the heating process and degassing process, the molded body expands as a result of heating. Therefore, applying the same pressing force by a pressing member as during the molding process could result in cracking of the molded body due to expansion. In this method, by making the pressing force during the degassing process smaller than that during the molding process, it is possible to promote the expansion of the molded body during the degassing process and prevent cracking of the molded body.

[0017] (5) In the method for producing a glass article according to any one of (2) to (4) above, the temperature of the ceiling wall of the forming furnace in the degassing step may be higher than the temperature of the ceiling wall of the forming furnace in the starting step.

[0018] According to this configuration, by making the temperature of the ceiling wall of the forming furnace in the degassing process higher than the temperature in the starting process, it is possible to accelerate the degassing process of the formed body. Also, by making the temperature of the ceiling wall in the degassing process closer to the temperature of the ceiling wall in the forming process, it is possible to smoothly start the forming process after the degassing process.

[0019] (6) In the method for manufacturing a glass article described in any one of (1) to (5) above, the forming body has a groove portion into which the molten glass is supplied, an upper portion through which the molten glass overflowing from two directions of the groove portion flows down, and a lower portion through which the molten glass flowing down the upper portion is joined to form the glass ribbon, and the forming furnace may include a heater for heating the lower portion of the forming body, and the temperature of the heater in the starting step may be higher than the temperature of the heater in the forming step.

[0020] According to this configuration, the molten glass supplied to the forming body in the starting step does not become a glass ribbon but falls from the forming body in the form of a lump. In this method, by setting the temperature of the heater that heats the lower part of the forming body in the starting step higher than the temperature of the heater in the forming step, it is possible to prevent the lump of molten glass falling from the lower part of the forming body from becoming large. This makes it easier to process the molten glass that has fallen from the forming body and prevents damage to the equipment. [Effects of the Invention]

[0021] According to the present invention, the degassing step can be carried out efficiently. [Brief explanation of the drawings]

[0022] [Figure 1]FIG. 1 is a side view showing a glass article manufacturing apparatus. [Figure 2] FIG. 1 is a front view showing a glass article manufacturing apparatus. [Figure 3] FIG. 2 is a side view of the forming furnace. [Figure 4] FIG. [Figure 5] 1 is a flowchart showing a method for manufacturing a glass article. [Figure 6] FIG. 10 is a side view of the forming furnace during a temperature increasing step. [Figure 7] FIG. 2 is a front view of the forming furnace during a temperature increasing step. [Figure 8] FIG. 10 is a side view of the forming furnace in the starting step. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figures 1 to 8 show one embodiment of a method for manufacturing a glass article according to the present invention. In the Cartesian coordinate system consisting of XYZ shown in the drawings, the X and Y directions are horizontal directions, and the Z direction is vertical. The direction corresponding to the width direction of the glass ribbon to be formed is called the width direction X, and the direction corresponding to the thickness direction of the glass ribbon to be formed is called the thickness direction Y.

[0024] 1 and 2 show a glass article manufacturing apparatus for carrying out the present method. The manufacturing apparatus 1 includes a forming furnace 2, an annealing furnace 3 located below the forming furnace 2, a cooling chamber 4 located below the annealing furnace 3, and a cutting chamber 5 located below the cooling chamber 4. The forming furnace 2 and the annealing furnace 3, the annealing furnace 3 and the cooling chamber 4, and the cooling chamber 4 and the cutting chamber 5 are separated by partition members (e.g., building floors) F1, F2, and F3, respectively, each having an opening (e.g., a slit) through which the glass ribbon Gr passes.

[0025] 1 and 2, the forming furnace 2 is a region for forming a glass ribbon Gr from molten glass Gm by the overflow downdraw method. The forming furnace 2 includes therein a forming body 6 that forms a glass ribbon Gr from the molten glass Gm, pressing members 7a and 7b that press the forming body 6, and first conveying rollers 8 that cool both ends in the width direction X of the glass ribbon Gr formed by the forming body 6. The forming furnace 2 also has side walls 2a located on the sides of the forming body 6 and a ceiling wall 2b located above the forming body 6.

[0026] The forming body 6 is formed of a refractory material that is long along the width direction X. Examples of the refractory material include zircon, zirconia, alumina, magnesia, and xenotime. The forming body 6 has an upper portion 6a to which the molten glass Gm is supplied, and a lower portion 6b for shaping the molten glass supplied to the upper portion 6a.

[0027] The formed body 6 has a groove (overflow groove) 8 formed in its upper portion 6a along the width direction X. A supply pipe 10 is connected to one end 9a of the groove 9 in the width direction X. Hereinafter, the end 9a of the groove 9 to which the supply pipe 10 is connected will be referred to as a first end, and the end 9b located opposite the first end 9a in the width direction X will be referred to as a second end.

[0028] The molten glass Gm is supplied into the groove 9 through the supply pipe 10. The method of supplying the molten glass Gm is not limited to this. For example, the molten glass Gm may be supplied from both the first end 9a and the second end 9b of the groove 9, or the molten glass Gm may be supplied from above the groove 9.

[0029] The molded body 6 has a symmetrical shape in the thickness direction Y. Each of the outer surfaces 11 of the molded body 6 in the thickness direction Y includes a vertical surface portion 12 that is flat along the vertical direction and an inclined surface portion 13 that is connected to the lower part of the vertical surface portion 12 and is flat and inclined with respect to the vertical direction. The vertical surface portion 12 is located in the upper part 6a of the molded body 6, and the inclined surface portion 13 is located in the lower part 6b of the molded body 6. The vertical surface portions 12 are parallel to each other. The inclined surface portions 13 are inclined so as to approach each other in the thickness direction Y as they extend downward. In other words, the molded body 6 has a wedge shape that tapers downward when viewed from the width direction X due to the formation of the inclined surface portions 13, and the corner where the inclined surface portions 13 intersect forms the lower end portion 6b1 of the molded body 6. The vertical surface portions 12 may be modified to have an inclined surface or a curved surface, or may be omitted.

[0030] The pressing members 7a, 7b are intended to suppress creep deformation of the compact 6 and press the lower portion 6b of the compact 6. The pressing members 7a, 7b are made of, for example, firebrick. The pressing members 7a, 7b include a first pressing member 7a that presses one end of the compact 6 in the width direction X and a second pressing member 7b that presses the other end of the compact 6. The first pressing member 7a and the second pressing member 7b are arranged to face each other in the width direction X, and by sandwiching the lower portion 6b of the compact 6 between them, a force (pressing force) can be applied to the compact 6 to press the lower portion 6b of the compact 6 in the width direction X.

[0031] 1 to 4, the first conveyor rollers 8 are configured as a pair of rollers that sandwich each end of the glass ribbon Gr in the width direction X in the thickness direction Y directly below the forming body 6. The first conveyor rollers 8 are cantilever rollers and have a cooling mechanism therein. The first conveyor rollers 8 are also called cooling rollers or edge rollers.

[0032] 4, in a state in which the glass ribbon Gr can be formed, the first conveyor rollers 8 of the forming furnace 2 are inserted into the furnace from outside the forming furnace 2 through an opening 2c formed in a side wall 2a of the forming furnace 2. The gap between the opening 2c and the shaft portions 8a of the first conveyor rollers 8 is sealed with a first sealing member 2d made of, for example, refractory fiber. One end of the shaft portion 8a is held by a bearing (not shown) arranged outside the forming furnace 2.

[0033] 3 and 4, a first outer heater 14 for heating the upper part 6a of the compact 6 and a second outer heater 15 for heating the lower part 6b of the compact 6 are provided on the side wall 2a of the forming furnace 2. A third outer heater 16 for heating the upper part 6a of the compact 6 is provided on the ceiling wall 2b of the forming furnace 2.

[0034] 3 and 4, the first external heater 14 is disposed at a position corresponding to the upper part of the side wall 2a of the forming furnace 2 in order to heat the upper part 6a of the compact 6. The second external heater 15 is disposed at a position corresponding to the lower part of the side wall 2a of the forming furnace 2 in order to heat the lower part 6b of the compact 6. The third external heater 16 is disposed at a position corresponding to the ceiling wall 2b of the forming furnace 2 in order to heat the upper part 6a of the compact 6, particularly the upper surface and groove portion 9.

[0035] Further, the side wall 2a is provided with a first outer furnace thermometer 17 for measuring the temperature of the side wall 2a at a position corresponding to the first outer furnace heater 14, and a second outer furnace thermometer 18 for measuring the temperature of the side wall 2a at a position corresponding to the second outer furnace heater 15. The ceiling wall 2b is provided with a third outer furnace thermometer 19 for measuring the temperature of the ceiling wall 2b at a position corresponding to the third outer furnace heater 16. The outer furnace heaters 14 to 16 may be divided into a plurality of sections in the width direction X and configured as a plurality of partial heaters. In this case, the outer furnace thermometers 17 to 19 may be provided for each partial heater.

[0036] As shown in FIGS. 1 and 2 , the annealing furnace 3 is a region for reducing warpage and internal strain of the glass ribbon Gr. Second conveying rollers 20 are arranged inside the annealing furnace 3. The second conveying rollers 20 are also referred to as annealer rollers. The second conveying rollers 20 are configured as a pair of rollers that sandwich each end of the glass ribbon Gr in the width direction X in the thickness direction Y. The second conveying rollers 20 may be double-supported rollers arranged to span the entire width direction X of the glass ribbon Gr, but in this embodiment, they are cantilevered rollers. The second conveying rollers 20 are provided in multiple stages in the vertical direction Z.

[0037] As shown in FIGS. 1 and 2 , the cooling chamber 4 is a region for cooling the glass ribbon Gr to near room temperature. Third conveying rollers 21 are arranged inside the cooling chamber 4. The third conveying rollers 21 are configured as a pair of rollers that sandwich each end of the glass ribbon Gr in the width direction X in the thickness direction Y. The third conveying rollers 21 may be double-supported rollers arranged to span the entire area of ​​the glass ribbon Gr in the width direction X, but in this embodiment, they are cantilevered rollers. The third conveying rollers 21 are provided in multiple stages in the vertical direction Z.

[0038] In this embodiment, both end portions in the width direction X of the glass ribbon Gr obtained by the manufacturing apparatus 1 include ear portions that are thicker than the central portion in the width direction X due to the influence of shrinkage during the molding process, etc.

[0039] As shown in Figures 1 and 2, the cutting chamber 5 is an area for cutting the glass ribbon Gr to a predetermined size to obtain a glass sheet G as a glass article. A cutting device (not shown) for cutting the glass ribbon Gr is arranged inside the cutting chamber 5. In this embodiment, the method for cutting the glass ribbon Gr by the cutting device is scribe cutting, in which a scribe line is formed in the glass ribbon Gr and then the glass ribbon Gr is bent and broken along the scribe line, but is not limited to this. The cutting method by the cutting device may also be, for example, laser cleaving or laser fusing.

[0040] The glass plate G is a glass substrate (mother glass plate) from which one or more product glass plates are obtained. The thickness of the product glass plate is, for example, 0.2 mm to 10 mm, and the size of the product glass plate is, for example, 700 mm × 700 mm to 3500 mm × 3500 mm. The product glass plate is used, for example, as a substrate or cover glass for a display.

[0041] Hereinafter, a method for manufacturing a glass ribbon Gr and a glass sheet G as glass articles using the manufacturing apparatus 1 having the above-described configuration will be described. As shown in Fig. 5, this method includes a heating step S1, a starting step S2, and a degassing step S3 as preparatory steps, and a forming step S4, a slow-cooling step S5, a cooling step S6, and a cutting step S7 as production steps.

[0042] The temperature-raising step S1 is a step of raising the temperature of the compact 6 accommodated in the forming furnace 2 prior to the forming step S4. As shown in Fig. 6 and Fig. 7, in the temperature-raising step S1, an in-furnace heater 22 for heating the lower part 6b (lower end 6b1) of the compact 6 and an in-furnace thermometer 23 for measuring the temperature of the lower part 6b (lower end 6b1) of the compact 6 are arranged inside the forming furnace 2.

[0043] The in-furnace heaters 22 are arranged in pairs to sandwich the passage portion of the glass ribbon Gr below the lower end portion 6b1 of the forming body 6 from both sides in the thickness direction Y. In the present embodiment, the in-furnace heaters 22 are configured by a pair of rod-shaped heaters (e.g., sheathed heaters) extending along the width direction X and facing each other in the thickness direction Y.

[0044] The in-furnace heater 22 traverses the interior of the forming furnace 2 in the width direction X, and both ends thereof penetrate the side walls 2a of the forming furnace 2 and are held outside the forming furnace 2. Note that a plurality of pairs of in-furnace heaters 22 may be arranged vertically.

[0045] In the temperature increasing step S1, the first conveying rollers 8 are not disposed in the forming furnace 2, and an in-furnace heater 22 is disposed in place of the first conveying rollers 8. That is, the in-furnace heater 22 is disposed from the outside of the forming furnace 2 to the inside of the furnace through an opening 2c in the side wall 2a of the forming furnace 2. The gap between the opening 2c and the in-furnace heater 22 is sealed with a second sealing member 2e made of, for example, refractory fiber. One end of the in-furnace heater 22 and one end of the in-furnace thermometer 23 are held by a member disposed outside the forming furnace 2.

[0046] 6, in a side view, the furnace heater 22 is preferably disposed within a circle C centered on the lower end 6b1 of the compact 6. The diameter D of the circle C is preferably 50 mm to 300 mm, and more preferably 100 mm to 200 mm. In this way, the lower portion 6b of the compact 6, including the lower end 6b1, can be efficiently heated.

[0047] 7, a width direction dimension W1 of the in-furnace heater 22 in the forming furnace 2 is larger than a width direction dimension W2 of the lower end portion 6b1 of the formed body 6. As a result, the entire width of the lower end portion 6b1 of the formed body 6 is heated by the in-furnace heater 22.

[0048] The furnace thermometer 23 (e.g., a thermocouple) is disposed immediately below the lower end 6b1 of the forming body 6, that is, at the portion through which the glass ribbon Gr passes. The location of the furnace thermometer 23 is not particularly limited as long as it can measure the temperature of the lower portion 6b of the forming body 6. For example, the furnace thermometer 23 may be disposed so as to be in contact with the lower portion 6b of the forming body 6, or multiple furnace thermometers 23 may be disposed.

[0049] 6 and 7, in the temperature-raising step S1, the lower portion 6b of the compact 6 is heated by the in-furnace heater 22 arranged in the forming furnace 2. As a result, even if an ascending air current or the like occurs in the forming furnace 2, the in-furnace heater 22 arranged near the lower portion 6b of the compact 6 can stabilize the temperature of the lower portion 6b of the compact 6, thereby reducing damage such as cracking of the compact 6 due to thermal shock.

[0050] In the temperature increasing step S1 in this embodiment, the formed body 6 is also heated by the external heaters 14 to 16 arranged outside the forming furnace 2. This makes it possible to appropriately adjust the temperature distribution inside the forming furnace 2.

[0051] The heating temperatures by the in-furnace heater 22 and / or the outer furnace heaters 14 to 16 are adjusted based on the temperatures measured by the in-furnace thermometer 23 and / or the outer furnace thermometers 17 to 19. For example, it is desirable that the heating temperatures by the second outer furnace heater 15 and the in-furnace heater 22 be set higher than the heating temperatures by the first outer furnace heater 14 and the third outer furnace heater 16. The temperature distribution in the forming furnace 2 is not limited to that in this embodiment.

[0052] In the temperature-raising step S1, the pressing force applied to the compact 6 by the pressing members 7a and 7b is desirably set smaller than the pressing force applied to the compact 6 by the pressing members 7a and 7b in the molding step S4. In the temperature-raising step S1, the compact 6 expands as it is heated. By setting the pressing force small in the temperature-raising step S1, the expansion of the compact 6 can be suitably promoted. The ratio (FP1 / FP4) of the pressing force FP1 (N) in the temperature-raising step S1 to the pressing force FP4 (N) in the molding step S4 can be set to, for example, 0.01 to 0.40, and preferably 0.05 to 0.20.

[0053] When the molded body 6 is heated to a predetermined temperature in the temperature-raising step S1, the process shifts from the temperature-raising step S1 to the start step S2. When shifting from the temperature-raising step S1 to the start step S2, the furnace thermometer 23 is removed from the furnace while the heating of the molded body 6 by the furnace heater 22 and the outer furnace heaters 14 to 16 continues.

[0054] The starting step S2 is a step of starting to supply molten glass Gm to the formed body 6 that has undergone the temperature-raising step S1. In the starting step S2, the flow path for the molten glass Gm, which had been closed by, for example, a plunger or a gate, is opened, and the molten glass Gm is supplied to the groove portion 9 through the supply pipe 10. The molten glass Gm supplied to the groove portion 9 overflows from the groove portion 9 in two directions and flows downward along the pair of outer surfaces 11. Thereafter, the molten glass Gm falls downward from the lower end portion 6b1 of the formed body 6, as shown in FIG.

[0055] The flow rate of the molten glass Gm supplied to the forming body 6 is lower at the beginning of the starting step S2 than the flow rate during the forming step S4, and gradually increases to a predetermined flow rate as the starting step S2 progresses. In this case, the molten glass Gm does not flow out of the grooves 9 uniformly, and the flow is unstable. In particular, the molten glass Gm is likely to overflow from the second ends 9b of the grooves 9. For this reason, in the starting step S2, a process is carried out to allow the molten glass Gm to flow out uniformly over the entire longitudinal range of the grooves 9.

[0056] Specifically, it is desirable that the temperature of the ceiling wall 2b of the forming furnace 2 in the starting step S2 be set lower than the temperature of the ceiling wall 2b of the forming furnace 2 in the forming step S4. That is, in the starting step S2, the heating temperature by the third external heater 16 is adjusted to be lower than the temperature during execution of the forming step S4. The difference between the heating temperature of the third external heater 16 in the forming step S4 and the heating temperature of the third external heater 16 in the starting step S2 can be, for example, 10°C to 80°C, and is preferably 15°C to 60°C.

[0057] This allows the temperature for heating the grooves 9 in the upper part 6a of the formed body 6 to be lower than that during the forming step S4. That is, by lowering the flow rate of the molten glass Gm flowing out of the grooves 9 than that during the forming step S4, it is possible to adjust the molten glass Gm so that it flows out uniformly from the entire range of the grooves 9. The molten glass Gm that flows out of the grooves 9 and down the upper part 6a and lower part 6b of the formed body 6 in the start step S2 falls from the lower end 6b1 of the formed body 6 as a lump without forming a glass ribbon.

[0058] In the initiation step S2, the heating temperature by the second external heater 15 and / or the in-furnace heater 22 is desirably set higher than the heating temperature by the second external heater 15 in the forming step S4. That is, in the initiation step S2, the temperature of the molten glass Gm flowing down the lower part 6b of the formed body 6 is desirably adjusted to be higher than the temperature of the molten glass Gm flowing down the lower part 6b of the formed body 6 in the forming step S4. This makes it possible to prevent the molten glass Gm dropping from the lower end 6b1 of the formed body 6 in the initiation step S2 from becoming large. The difference between the heating temperature of the second external heater 15 and / or the in-furnace heater 22 in the initiation step S2 and the heating temperature of the second external heater 15 in the forming step S4 can be, for example, 20°C to 200°C, and preferably 40°C to 150°C.

[0059] Under the temperature control as described above, the molten glass Gm supplied to the groove portion 9 of the forming body 6 overflows evenly from the first end 9a to the second end 9b of the groove portion 9, and falls from the lower end 6b1 of the forming body 6 while covering the outer surface 11 of the forming body 6 with a constant width.

[0060] As in the temperature-raising step S1, in the initiation step S2, the pressing force applied to the compact 6 by the pressing members 7a, 7b is desirably set to be smaller than the pressing force applied to the compact 6 in the compacting step S4. The ratio (FP2 / FP4) of the pressing force FP2 (N) in the initiation step S2 to the pressing force FP4 (N) in the compacting step S4 can be set to, for example, 0.01 to 0.40, and preferably 0.05 to 0.20.

[0061] In the start step S2, the flow rate of the molten glass Gm supplied to the forming body 6 gradually increases to a predetermined flow rate, and when the molten glass Gm begins to flow stably and uniformly, the in-furnace heater 22 is retracted from the position where it heats the lower part 6b of the forming body 6, while continuing to heat the forming body 6 with the out-furnace heaters 14 to 16. In this embodiment, the in-furnace heater 22 is removed to the outside of the furnace through the opening 2c of the forming furnace 2. Thereafter, the degassing step S3 is carried out.

[0062] The degassing step S3 is a step of degassing the formed body 6 by continuing to supply molten glass Gm at a predetermined flow rate to the formed body 6 that has undergone the starting step S2. The gas contained inside and on the surface of the formed body 6 is removed by the molten glass Gm that comes into contact with the formed body 6.

[0063] In the degassing step S3, the heating temperature by the second extrafurnace heater 15 is desirably set higher than the heating temperature by the second extrafurnace heater 15 in the forming step S4. That is, in the degassing step S3, the temperature of the molten glass Gm flowing down the lower part 6b of the formed body 6 is desirably adjusted to be higher than the temperature of the molten glass Gm flowing down the lower part 6b of the formed body 6 in the forming step S4. This makes it possible to prevent the molten glass Gm dropping from the lower end part 6b1 of the formed body 6 in the degassing step S3 from becoming large. The difference between the heating temperature of the second extrafurnace heater 15 in the degassing step S3 and the heating temperature of the second extrafurnace heater 15 in the forming step S4 can be, for example, 20°C to 200°C, and preferably 40°C to 150°C.

[0064] The temperature of the ceiling wall 2b of the forming furnace 2 in the degassing step S3 may be set lower or higher than the temperature of the ceiling wall 2b of the forming furnace 2 in the forming step S4, or may be set to approximately the same as the temperature of the ceiling wall 2b of the forming furnace 2 in the forming step S4.

[0065] As in the temperature-raising step S1 and the initiation step S2, in the degassing step S3, the pressing force applied to the compact 6 by the pressing members 7a, 7b is desirably set to be smaller than the pressing force applied to the compact 6 in the molding step S4. The ratio (FP3 / FP4) of the pressing force FP3 (N) in the degassing step S3 to the pressing force FP4 (N) in the molding step S4 can be set to, for example, 0.01 to 0.40, and preferably 0.05 to 0.20.

[0066] The average temperature of the molten glass Gm in the degassing step S3 may be the same as the average temperature of the molten glass Gm in the forming step S4, or may be higher or lower than the average temperature in the forming step S4. The average temperature of the molten glass Gm here is the average value of the temperature of the ceiling wall 2b of the forming furnace 2 (the temperature measured by the third outer furnace thermometer 19) and the temperature of the lower part of the side wall 2a (the temperature measured by the second outer furnace thermometer 18).

[0067] The ratio QS3 / QS4 of the flow rate QS3 of the molten glass Gm in the degassing step S3 to the flow rate QS4 of the molten glass in the forming step S4 is preferably more than 0.8 and not more than 1.2, more preferably 0.85 or more and 1.15 or less, and even more preferably 0.9 or more and 1.1 or less.

[0068] The forming step S4 is a step of forming a glass ribbon Gr from the molten glass Gm using the formed body 6 that has undergone the degassing step S3. The forming step S4 is started to produce a glass sheet G as a product at a stage when predetermined preparations have been completed, such as arranging the first conveyor roller 8 at a predetermined position in the furnace through the opening 2c of the forming furnace 2. In the forming step S4, the pressing force of the pressing members 7a and 7b on the formed body 6 is increased compared to when the degassing step S3 was performed.

[0069] In the forming step S4 as well, the temperature distribution in the forming furnace 2 is controlled by the outer heaters 14 to 16. In the forming step S4, the heating temperature by the second outer heater 15 is desirably set lower than the heating temperature by the third outer heater 16. In addition, the heating temperature by the second outer heater 15 is desirably set lower than the heating temperature by the first outer heater 14.

[0070] 1 and 2, in the forming step S4, in the forming furnace 2, molten glass Gm is supplied to the grooves 9 in the upper part 6a of the forming body 6, and the molten glass Gm overflowing in two directions from the grooves 9 flows down along the vertical surface parts 12 and the inclined surface parts 13 and meets again at the lower end part 6b1. In this way, a belt-shaped glass ribbon Gr is continuously formed from the molten glass Gm. The first conveyor rollers 8 convey the glass ribbon Gr downward while clamping the ends of the glass ribbon GR in the width direction X so that the glass ribbon Gr maintains a constant width.

[0071] Next, in the annealing step S5, the glass ribbon Gr is annealed while being transported by the second transport rollers 20 in the annealing furnace 3. In the subsequent cooling step S6, the glass ribbon Gr is cooled to near room temperature while being transported by the third transport rollers 21 in the cooling chamber 4. Then, in the cutting step S7, the glass ribbon Gr is cut in the cutting chamber 5 to obtain a glass sheet G. The cutting step S7 includes a first cutting step of cutting the glass ribbon Gr in the width direction X at predetermined lengths to obtain a glass sheet G, and a second cutting step of cutting and removing edge portions at both ends of the glass sheet G in the width direction X. Note that the process subsequent to the forming step S4 is not particularly limited. For example, the present method may further include a cleaning step, an inspection step, a packaging step, etc.

[0072] According to the method for manufacturing a glass article according to the present embodiment described above, in the starting step S2, the temperature of the ceiling wall 2b of the forming furnace 2 is set lower than the temperature of the ceiling wall 2b of the forming furnace 2 in the forming step S4, thereby allowing the molten glass Gm to flow uniformly from the entire range of the grooves 9 of the formed body 6. This makes it possible to efficiently perform the degassing step S3 after the starting step S2 without performing the conventional operation of tilting the formed body 6.

[0073] 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.

[0074] In the temperature-raising step S1, an example has been shown in which the in-furnace heater 22 for heating the lower end 6b1 of the compact 6 is arranged in the forming furnace 2, but the present invention is not limited to this configuration. In the temperature-raising step S1, the lower part 6b (lower end 6b1) of the compact 6 may be heated only by the second external heater 15 without arranging the in-furnace heater 22. [Explanation of symbols]

[0075] 2 Molding furnace 2b Ceiling wall of the molding furnace 6. Molded body 6a Upper part of the molded body 6b Lower part of the molded body 7a First pressing member 7b Second pressing member 15 Second outer furnace heater Gm molten glass S1 Temperature rising process S2 start process S3 Gas removal process S4 Molding process

Claims

1. a temperature raising step of raising the temperature of the compact housed in the forming furnace; a starting step of starting to supply molten glass to the forming body that has undergone the temperature increasing step; a forming step of forming a glass ribbon from the molten glass by an overflow method using the forming body that has undergone the starting step, the forming furnace includes a ceiling wall located above the formed body, A method for manufacturing a glass article, wherein the temperature of the ceiling wall of the forming furnace in the starting step is lower than the temperature of the ceiling wall of the forming furnace in the forming step.

2. The method for manufacturing a glass article according to claim 1 , further comprising a degassing step of degassing the formed body by continuing to supply the molten glass to the formed body between the starting step and the forming step.

3. the forming body includes a groove portion to which the molten glass is supplied, an upper portion through which the molten glass overflowing from two directions of the groove portion flows down, and a lower portion through which the molten glass flowing down the upper portions is joined to form the glass ribbon, the forming furnace includes a heater for heating the lower portion of the formed body, The method for manufacturing a glass article according to claim 2, wherein the temperature of the heater in the degassing step is higher than the temperature of the heater in the forming step.

4. the forming furnace includes a pressing member that presses the formed body, 4. The method for manufacturing a glass article according to claim 2, wherein the pressing force applied to the formed body by the pressing member in the degassing step is smaller than the pressing force applied to the formed body by the pressing member in the forming step.

5. The method for manufacturing a glass article according to claim 2 or 3, wherein the temperature of the ceiling wall of the forming furnace in the degassing step is higher than the temperature of the ceiling wall of the forming furnace in the starting step.

6. the forming body includes a groove portion to which the molten glass is supplied, an upper portion through which the molten glass overflowing from two directions of the groove portion flows down, and a lower portion through which the molten glass flowing down the upper portions is joined to form the glass ribbon, the forming furnace includes a heater for heating the lower portion of the formed body, The method for manufacturing a glass article according to claim 1 or 2, wherein the temperature of the heater in the starting step is higher than the temperature of the heater in the forming step.

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