Manufacturing method of glass article

Abstract

To suppress generation of a foreign object from a compact even in a case of flowing a molten glass with a less content of Mg along the compact, the foreign object being a possible defect of a glass article.SOLUTION: A manufacturing method of a glass article includes a molding step of molding a glass ribbon Gr from a molten glass Gm1 by flowing the molten glass Gm1 along a compact 3. In the molding step, the compact 3 has a Neferrite layer N on a surface layer.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

[0002] A method for producing a glass article such as a glass sheet or a glass roll, for example, when using an overflow downdraw method, includes a forming step of flowing molten glass along a forming body to form a glass ribbon. The formed glass ribbon is cooled to about room temperature while being transported downstream, and then cut into predetermined lengths to obtain a glass sheet, or wound into a roll to obtain a glass roll (see, for example, Patent Document 1).

[0003] In this type of molding process, for example, a molded body having a spinel layer containing spinel (MgAl2O4) as a main component formed on its surface may be used in order to suppress the occurrence of defects in the glass article that are due to the constituent components of the molded body (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-062433 A [Patent Document 2] International Publication No. 2021 / 124892 Summary of the Invention [Problem to be solved by the invention]

[0005] When a molded body having a spinel layer on the surface is used in a molding process, a problem may occur in that the spinel layer peels off when molten glass with a low Mg content is flowed along the molded body. If the spinel layer peels off in this way, the peeled off material may be mixed into the molten glass, causing defects in the manufactured glass article.

[0006] An object of the present invention is to suppress the generation of foreign matter that may cause defects in a glass article from a formed body, even when molten glass with a low Mg content is caused to flow along the formed body. [Means for solving the problem]

[0007] (1) The present invention, which has been invented to solve the above problems, is a method for manufacturing a glass article, which includes a forming step of forming a glass ribbon from a first molten glass by flowing the first molten glass along a forming body, and is characterized in that in the forming step, the forming body has a nephelite layer on its surface.

[0008] In this way, even if the first molten glass has a low MgO content, the nephelite layer can suppress the generation of foreign matter (eg, peeled matter) from the formed body that could cause defects in the glass article.

[0009] (2) In the above configuration (1), it is preferable to provide a nepherite layer forming step, which is a step preceding the forming step, of forming a nepherite layer on the surface of the molded body by flowing a second molten glass containing Na2O and KO along the molded body.

[0010] In this way, a molded body having a nephelite layer formed on its surface can be used reliably in the molding step.

[0011] (3) In the above configuration (2), a spinel layer forming step may be provided as a preceding step to the nepherite layer forming step, in which a third molten glass containing MgO is caused to flow along the molded body to form a spinel layer on the surface layer of the molded body.

[0012] In this way, the neferite layer can be easily formed in the neferite layer forming step.

[0013] (4) In the above configuration (3), the molded body is preferably made of an alumina-based refractory material.

[0014] In this way, the spinel layer can be easily formed in the spinel layer forming step, and as a result, the neferrite layer can be easily formed in the neferrite layer forming step.

[0015] (5) In the above structures (1) to (4), the nepherite layer preferably contains K2O.

[0016] In this way, the nephelite layer can be stably maintained on the surface layer of the compact. Effect of the Invention

[0017] According to the present invention, even when molten glass with a low Mg content is caused to flow along a formed body, it is possible to suppress the generation of foreign matter that could cause defects in a glass article from the formed body. [Brief description of the drawings]

[0018] [Figure 1] 1 is a side view of a glass sheet manufacturing apparatus according to a first embodiment of the present invention. FIG. [Diagram 2] FIG. 2 is a front view of the glass plate manufacturing apparatus of FIG. [Diagram 3] FIG. 2 is an enlarged view of the periphery of a molded body for explaining a problem that occurs when molten glass with a low MgO content is poured into a molded body having a spinel layer. [Figure 4] FIG. 4 is an enlarged view of the R1 region in FIG. [Diagram 5] 2 is an enlarged view of the periphery of a formed body in the glass plate manufacturing apparatus of FIG. 1. [Figure 6] FIG. 6 is an enlarged view of the R2 region in FIG. 5. [Figure 7] FIG. 11 is an enlarged view of the periphery of a molded body for illustrating a spinel layer forming step included in a method for manufacturing a glass article according to a second embodiment. [Figure 8] FIG. 11 is an enlarged view of the periphery of a molded body for illustrating a nephelite-forming step included in a method for producing a glass article according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. 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. In addition, a direction corresponding to the width direction of the glass ribbon Gr to be molded is called the width direction X, and a direction corresponding to the thickness direction of the glass ribbon Gr to be molded is called the thickness direction Y.

[0020] First embodiment 1 and 2 are diagrams showing a manufacturing apparatus 1 for realizing a manufacturing method of a glass article according to a first embodiment. As shown in the drawings, the manufacturing apparatus 1 is an apparatus for manufacturing a glass sheet G as a glass article by an overflow downdraw method, and includes, from top to bottom, a forming furnace 2, an annealing furnace 4, a cooling chamber 5, and a cutting chamber 6. The forming furnace 2 and the annealing furnace 4, the annealing furnace 4 and the cooling chamber 5, and the cooling chamber 5 and the cutting chamber 6 are separated by partition members (e.g., floors of a building) F1, F2, and F3 each having an opening (e.g., a slit) through which the glass ribbon Gr passes.

[0021] The forming furnace 2 is a region for forming the glass ribbon Gr from the molten glass Gm1 by the overflow downdraw method. In the forming furnace 2, a forming body 3 for forming the glass ribbon Gr from the molten glass Gm1 and first conveying rollers 7 for cooling both ends in the width direction X of the glass ribbon Gr formed by the forming body 3 are arranged.

[0022] The molded body 3 is formed of a refractory material that is long along the width direction X. For example, an alumina-based refractory material can be used as the refractory material. The alumina-based refractory material preferably has an alumina (Al2O3) content of 90 to 98 mass %. In order to ensure mechanical strength, the alumina-based refractory material preferably contains an yttrium-containing oxide (for example, Y3A, which is a composite oxide of yttrium and aluminum). l5 O 12 The content of the yttrium-containing oxide is preferably 1 mass % or more, and more preferably 2 to 10 mass %. The yttrium-containing oxide may not be contained.

[0023] A groove (overflow groove) 8 formed along the width direction X is provided at the top of the formed body 3. A supply pipe 9 is connected to one end side of the groove 8 in the width direction X. Molten glass Gm1 is supplied into the groove 8 through this supply pipe 9. The method of supplying the molten glass Gm1 is not limited to this. For example, the molten glass Gm1 may be supplied from both ends of the groove 8 in the width direction X, or the molten glass Gm1 may be supplied from above the groove 8.

[0024] The molded body 3 has a symmetrical shape in the thickness direction Y. Both side surfaces 10 of the molded body 3 in the thickness direction Y each have a vertical surface portion 11 that is a plane along the vertical direction, and an inclined surface portion 12 that is connected to the lower side of the vertical surface portion 11 and is a plane inclined with respect to the vertical direction. The vertical surface portions 11 are planes parallel to each other. The inclined surface portions 12 are planes that are inclined so as to approach each other in the thickness direction Y as they go downward. In other words, the molded body 3 has a wedge shape that tapers downward when viewed from the width direction X due to the formation of the inclined surface portions 12, and the corner where the inclined surface portions 12 intersect forms the lower end portion 3a of the molded body 3. The vertical surface portion 11 may be changed in shape to an inclined surface, a curved surface, or the like, or may be omitted.

[0025] The first conveyor rollers 7 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 3. The first conveyor rollers 7 are cantilever type rollers, and are constantly internally cooled in the forming process. The first conveyor rollers 7 are also called cooling rollers or edge rollers.

[0026] The annealing furnace 4 is a region for reducing warpage and internal distortion of the glass ribbon Gr. The internal space of the annealing furnace 4 has a predetermined temperature gradient downward. The temperature gradient of the internal space of the annealing furnace 4 can be adjusted by, for example, a heating device such as a heater disposed on the inner wall of the annealing furnace 4.

[0027] Second conveying rollers 13 are arranged in the annealing furnace 4. The second conveying rollers 13 are also referred to as annealer rollers. The second conveying rollers 13 are configured as a pair of rollers that pinch each end of the glass ribbon Gr in the width direction X in the thickness direction Y. In the present embodiment, the second conveying rollers 13 are provided in a plurality of stages in the vertical direction Z, but the number of stages of the second conveying rollers 13 may be one stage, or the second conveying rollers 13 may be omitted.

[0028] The cooling chamber 5 is a region for cooling the glass ribbon Gr to approximately room temperature. A gas (e.g., clean air) at room temperature (e.g., 20°C±15°C) is supplied to the cooling chamber 5, and no heating device such as a heater is provided.

[0029] A third conveying roller 14 is disposed in the cooling chamber 5. The third conveying roller 14 is configured as a roller pair that holds each end of the glass ribbon Gr in the width direction X in the thickness direction Y. In the present embodiment, the third conveying roller 14 is provided in a plurality of stages in the vertical direction Z, but the number of stages of the third conveying roller 14 may be one stage, or the third conveying roller 14 may be omitted.

[0030] Here, the second conveyor rollers 13 and / or the third conveyor rollers 14 may include rollers that do not pinch both ends of the glass ribbon Gr in the width direction X. In other words, the opposing distance between the roller pairs constituting the second conveyor rollers 13 and / or the third conveyor rollers 14 may be made larger than the thickness of both ends of the glass ribbon Gr in the width direction X, so that the glass ribbon Gr passes between the roller pairs. Note that in this embodiment, both ends 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.

[0031] The cutting chamber 6 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 disposed in the cutting chamber 6. In the present embodiment, the method for cutting the glass ribbon Gr by the cutting device is scribe cutting, in which a scribe line is formed on the glass ribbon Gr and then the glass ribbon Gr is bent and broken along the scribe line, but is not limited thereto. The cutting method of the cutting device may be, for example, laser cleaving or laser melting.

[0032] The glass plate G is a glass original plate (mother glass plate) from which one or more product glass plates are obtained. The thickness of the product glass plate is, for example, 0.02 mm to 10 mm, and the size of the product glass plate is, for example, 200 mm×200 mm to 3500 mm×3500 mm. The product glass plate is used, for example, as a substrate or cover glass of a display. Note that the substrate or cover glass of a display is not limited to a flat panel, and may be a curved panel or a foldable panel.

[0033] Next, a method for producing a glass article according to the first embodiment will be described.

[0034] 1 and 2, the present manufacturing method includes a molding step, a slow cooling step, and a cutting step. Each of these steps is performed using the manufacturing apparatus 1 described above.

[0035] In the forming step, in the forming furnace 2, molten glass (first molten glass) Gm1 is supplied to the grooves 8 of the forming body 3, and the molten glass Gm1 overflowing on both sides of the grooves 8 flows down along the vertical surfaces 11 and the inclined surfaces 12 and joins again at the lower end 3a. In this way, a belt-shaped glass ribbon Gr is continuously formed from the molten glass Gm1.

[0036] 3 and 4, if a spinel layer S is formed on the surface layer of the molded body 3 (the portion in direct contact with the molten glass Gm1), and the MgO content of the molten glass Gm1 is low (for example, when the MgO content is 2.5 mass % or less), the spinel layer S may peel off from the molded body 3. When the spinel layer S peels off, the spinel exfoliation product Sx gets mixed into the molten glass Gm1, causing defects originating from the spinel layer S (exfoliation product Sx) to occur in the glass sheet G to be manufactured.

[0037] 5 and 6, the present embodiment uses a neferrite layer N containing neferrite (Na2O-Al2O3-SiO2) as a main component formed on the surface layer of the formed body 3. In detail, the neferrite layer N is formed so as to cover the spinel layer S formed on the formed body 3. In other words, the neferrite layer N is formed on the outer side of the spinel layer S and is in direct contact with the molten glass Gm1 flowing down along the formed body 3.

[0038] In this way, even if the MgO content of the molten glass Gm1 is small, the neferrite layer N can suppress peeling of the spinel layer S from the formed body 3. In other words, peeled matter Sx is less likely to be generated from the spinel layer S. The reason why peeling of the spinel layer S can be suppressed in this way is thought to be that the neferrite layer N suppresses diffusion of Mg ions from the spinel layer S into the molten glass Gm1.

[0039] The thickness of the neferrite layer N is preferably 1 to 30 μm, so that the thickness of the neferrite layer N is sufficient to effectively prevent the spinel layer S from peeling off.

[0040] The neferrite layer N may contain K2O. This makes it easier to maintain the neferrite layer N in a stable state. Of course, the neferrite layer N does not have to contain K2O.

[0041] Here, the molten glass Gm1 with a low content of MgO preferably contains, for example, in mass %, SiO2 40% to 70%, Al2O3 10% to 30%, B2O3 0% to 3%, Na2O 5% to 25%, K2O 0% to 3.3%, Li2O 0.1% to 10%, MgO 0% to 2.5%, and P2O 52% to 10%. With such a glass composition, it is easy to achieve both ion exchange performance and devitrification resistance at a high level. Therefore, if chemical strengthening treatment is performed, it can be suitably used as a cover glass.

[0042] Alternatively, the molten glass Gm1 having a low MgO content preferably contains, for example, in mass %, SiO2 50% to 75% (preferably 60% to 70%), Al2O3 12% to 25% (preferably 14% to 20%), B2O3 0% to 10% (preferably 0% to 1%), Li2O 1% to 10% (preferably 2% to 6%), Na2O 3% to 15% (preferably 4% to 10%), K2O 0% to 10% (preferably 2% to 6%), MgO 0% to 2.5% (preferably 1% to 2.5%), and P2O 50% to 8% (preferably 0% to 1%). Such a glass composition has excellent chemical stability, and can be suitably used as a cover glass if chemically strengthened.

[0043] The MgO content of the molten glass Gm1 is preferably 2.5 mass % or less, 2.3 mass % or less, or 2.1 mass % or less.

[0044] In the annealing step, the glass ribbon Gr formed in the forming step is annealed in an annealing furnace 4.

[0045] In the cooling step, the glass ribbon Gr that has been slowly cooled in the slow cooling step is cooled to approximately room temperature in the cooling chamber 5.

[0046] In the cutting step, in the cutting chamber 6, the glass ribbon Gr cooled in the cooling step is cut to obtain a glass sheet G. The cutting step 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 the edge portions at both ends of the glass sheet G in the width direction X.

[0047] The steps subsequent to the cutting step are not particularly limited, and may include, for example, a cutting step of cutting a glass plate of a desired size from the glass plate G, an edge processing step, a cleaning step, an inspection step, a packaging step, a chemical strengthening step, etc. In the inspection step, it is preferable to inspect whether the glass plate G contains foreign matter derived from the spinel layer S.

[0048] Second Embodiment The method for producing a glass article according to the second embodiment includes a spinel layer forming step and a nephelite forming step as steps preceding the above-mentioned forming step.

[0049] As shown in FIG. 5, in the spinel layer forming step, a molten glass (third molten glass) Gm3 having a high MgO content is caused to flow along the formed body 3 to form a spinel layer S on the surface layer of the formed body 3. By forming the spinel layer S, it becomes easier to form a neferite layer N in the neferite forming step described below. However, the spinel layer forming step is not an essential step and may be omitted. In the spinel layer forming step, a glass plate may be manufactured by carrying out a forming step of forming a glass ribbon, or the molten glass Gm3 may be processed as cullet without forming a glass ribbon.

[0050] The thickness of the spinel layer S is preferably 100 μm or less, preferably 20 to 100 μm, and even more preferably 50 to 100 μm.

[0051] The molten glass Gm3 with a high MgO content preferably has an MgO content of more than 2.5% by mass. Specifically, the molten glass Gm3 with a high MgO content preferably contains, for example, in mass %, SiO2 50-80%, Al2O3 5-25%, B2O3 0-15%, Na2O 1-20%, K2O 0-10% (preferably 0.1-3%), and more than 2.5-10% MgO as a glass composition. Such a glass composition makes it easier to achieve both ion exchange performance and devitrification resistance at a high level. Therefore, it is possible to manufacture a cover glass made of a glass for chemical strengthening while forming a spinel layer.

[0052] The MgO content of the molten glass Gm3 is preferably more than 2.5 mass %, not less than 2.7 mass %, and not less than 2.9 mass %.

[0053] As shown in Fig. 6, in the neferrite layer forming step, a molten glass (second molten glass) Gm2 containing Na2O and K2O is caused to flow along the formed body 3, thereby forming a neferrite layer N on the surface layer of the formed body 3. In this manner, the neferrite layer N can be reliably formed on the surface layer of the formed body 3 used in the forming step. Note that in the neferrite layer forming step, a glass plate may be manufactured by carrying out a forming step of forming a glass ribbon, or the molten glass Gm2 may be processed into cullet without forming a glass ribbon.

[0054] The molten glass Gm2 containing Na2O and K2O preferably contains, for example, in mass %, SiO2 50% to 75% (preferably 60% to 70%), Al2O3 12% to 25% (preferably 14% to 20%), B2O3 0% to 10% (preferably 0% to 1%), Li2O 1% to 10% (preferably 2% to 6%), Na2O 3% to 15% (preferably 4% to 10%), K2O 1% to 10% (preferably 2% to 6%), MgO 0% to 2.5% (preferably 1% to 2.5%), and P2O 50% to 8% (preferably 0% to 1%). With such a glass composition, a glass for chemical strengthening having excellent chemical stability can be obtained. Therefore, a cover glass can be manufactured while forming a nephelite layer.

[0055] The Na2O content of the molten glass Gm2 is preferably 2 mass% or more, 3 mass% or more, 4 mass% or more, or 5 mass% or more.The K2O content of the molten glass Gm2 is preferably 1 mass% or more, 2 mass% or more, 3 mass% or more, or 4 mass% or more.

[0056] Although a glass article manufacturing apparatus and a method for manufacturing the same according to an embodiment of the present invention have been described, the embodiment of the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

[0057] In the above embodiment, an aluminosilicate glass is exemplified as the first molten glass used in the forming step, but the present invention is also useful for other glasses with a low MgO content.

[0058] In the above embodiment, after forming a nepherite layer on the surface layer of the molded body, if molten glass with a high MgO content is poured along the molded body, a spinel layer is again formed on the surface layer of the molded body. Therefore, in a state in which the spinel layer has been formed again, if it becomes necessary to produce a glass article by pouring molten glass with a low MgO content over the molded body in the molding step, it is preferable to form a nepherite layer again on the surface layer of the molded body.

[0059] In the above embodiment, a spinel layer and a neferrite layer are formed on the surface of the compact in the molding step, but the spinel layer does not have to be formed. In other words, the spinel layer may disappear in the process of forming the neferrite layer, or the neferrite layer may be formed directly on the surface of the compact without the spinel layer.

[0060] In the above embodiment, the case has been described where the glass article is the glass sheet G. However, the glass article may be, for example, a glass roll obtained by winding up a glass ribbon Gr in a roll shape. EXAMPLES

[0061] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0062] Molten glasses having glass compositions A to D shown in Table 1 were prepared.

[0063] [Table 1]

[0064] (Comparative Example) As a comparative example, a first step was carried out in which molten glass having glass composition A was poured along a molded body made of an alumina-based refractory material, and a second step was carried out in which molten glass having glass composition C was poured along the molded body after the first step. As a result, since glass composition A had a high MgO content of 3.0 mass%, a spinel layer was formed on the surface layer of the molded body in the first step. On the other hand, glass composition C had a very low MgO content of 0.2 mass%, so in the second step, the spinel layer peeled off and defects resulting from the spinel layer were generated in the glass sheet.

[0065] Example 1 In Example 1, a first step was performed in which molten glass having glass composition A was poured along a molded body made of an alumina-based refractory, and a second step was performed in which molten glass having glass composition D was poured along the molded body after the first step. As a result, since glass composition A had a high MgO content of 3.0 mass%, a spinel layer was formed on the surface layer of the molded body in the first step. On the other hand, glass composition D had a low MgO content of 2.0 mass%, but a high Na2O and K2O content, so a neferite layer was formed on the spinel layer of the molded body in the second step. Due to the formation of this neferite layer, peeling of the spinel layer was prevented in the second step, and defects due to the spinel layer were not generated in the glass plate. In Example 1, the molten glass having glass composition A corresponds to the third molten glass for forming the spinel layer, and the molten glass having glass composition D serves both the role of the first molten glass for forming a glass ribbon in the forming step and the second molten glass for forming a neferite layer.

[0066] Example 2 In Example 2, a first step was performed in which molten glass having glass composition B was poured along a molded body made of an alumina-based refractory material, and a second step was performed in which molten glass having glass composition D was poured along the molded body after the first step. As a result, since glass composition B had a high MgO content of 3.0 mass%, a spinel layer was formed on the surface layer of the molded body in the first step. On the other hand, glass composition D had a low MgO content of 2.0 mass%, but a high Na2O and K2O content, so a neferite layer was formed on the spinel layer of the molded body in the second step. Due to the formation of this neferite layer, peeling of the spinel layer was prevented in the second step, and defects due to the spinel layer were not generated in the glass plate. In Example 2, the molten glass having glass composition B corresponds to the third molten glass for forming the spinel layer, and the molten glass having glass composition D serves both the role of the first molten glass for forming a glass ribbon in the forming step and the role of the second molten glass for forming a neferite layer.

[0067] Example 3 In Example 3, a first step was carried out in which molten glass having glass composition A was flowed along a molded body made of an alumina-based refractory material, a second step was carried out in which molten glass having glass composition D was flowed along the molded body after the first step, and a third step was carried out in which molten glass having glass composition C was flowed along the molded body after the second step. As a result, since glass composition A had a high MgO content of 3.0 mass%, a spinel layer was formed on the surface layer of the molded body in the first step. On the other hand, glass composition D had a low MgO content of 2.0 mass%, but a high Na2O and K2O content, so a neferite layer was formed on the spinel layer of the molded body in the second step. Therefore, even if molten glass having glass composition C with a very low MgO content of 0.2 mass% was flowed along the molded body in the subsequent third step, the surface layer of the molded body was kept covered with the neferite layer, and peeling of the spinel layer could be prevented. As a result, no defects due to the spinel layer were generated in the glass plate in the third step. In Example 3, the molten glass having the glass composition A corresponds to the third molten glass for forming the spinel layer, the molten glass having the glass composition D corresponds to the second molten glass for forming the nepherite layer, and the molten glass having the glass composition C corresponds to the first molten glass for forming a glass ribbon in the forming step.

[0068] Example 4 In Example 4, a first step was carried out in which molten glass having glass composition B was flowed along a molded body made of an alumina-based refractory material, a second step was carried out in which molten glass having glass composition D was flowed along the molded body after the first step, and a third step was carried out in which molten glass having glass composition C was flowed along the molded body after the second step. As a result, since glass composition B had a high MgO content of 3.0 mass%, a spinel layer was formed on the surface layer of the molded body in the first step. On the other hand, glass composition D had a low MgO content of 2.0 mass%, but a high Na2O and K2O content, so a neferite layer was formed on the spinel layer of the molded body in the second step. Therefore, even if molten glass having glass composition C with a very low MgO content of 0.2 mass% was flowed along the molded body in the subsequent third step, the surface layer of the molded body was kept covered with the neferite layer, and peeling of the spinel layer could be prevented. As a result, no defects due to the spinel layer were generated in the glass plate in the third step. In Example 4, the molten glass having the glass composition B corresponds to the third molten glass for forming the spinel layer, the molten glass having the glass composition D corresponds to the second molten glass for forming the nepherite layer, and the molten glass having the glass composition C corresponds to the first molten glass for forming a glass ribbon in the forming step.

[0069] From the above results, it was confirmed that if a nephelite layer is formed on the surface of a molded body, peeling of the spinel layer is prevented and no defects are generated in the glass plate (glass article) even if molten glass with a low MgO content is then flowed along the molded body. [Explanation of symbols]

[0070] 1. Glass product manufacturing equipment 2 Molding furnace 3. Molded body 3a Bottom end 4 Annealing furnace 5 Cooling room 6 Cutting chamber 7 First conveyor roller 8 Groove 9 Supply Pipe 13 Second conveyor roller 14 Third conveyor roller G Glass plate Gm1 Molten glass (first melting glass) Gm2 molten glass (second molten glass) Gm3 molten glass (third molten glass) Gr Glass ribbon N Nephelite layer S Spinel layer Sx Peeling material

Claims

1. A method for producing a glass article, comprising a forming step of forming a glass ribbon from a first molten glass by flowing the first molten glass along a forming body, The method for producing a glass article, wherein in the molding step, the molded body has a nephelite layer on its surface.

2. As a pre-process of the molding process, Na ２ O and K ２ The method for producing a glass article according to claim 1 , further comprising a nephelite layer forming step of forming the nephelite layer on a surface layer of the formed body by flowing a second molten glass containing O along the formed body.

3. 3. The method for producing a glass article according to claim 2, further comprising, as a preceding step of the nepherite layer forming step, a spinel layer forming step of forming a spinel layer on a surface layer of the formed body by flowing a third molten glass containing MgO along the formed body.

4. The method for producing a glass article according to claim 3, wherein the formed body is made of an alumina-based refractory material.

5. The nephelite layer is ２ The method for producing a glass article according to any one of claims 1 to 4, which contains O.

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