JP7174360B2 - Glass article manufacturing method, melting furnace and glass article manufacturing apparatus - Google Patents

Description

The present invention relates to a method for manufacturing glass articles, a melting furnace for melting glass, and an apparatus for manufacturing glass articles.

As is well known, plate glass is used for flat panel displays such as liquid crystal displays and organic EL displays.

As disclosed in Patent Literature 1, sheet glass is formed into a thin plate through steps such as a melting step, a clarification step, a homogenization (stirring) step, and a forming step. In the method for manufacturing sheet glass disclosed in the document, in the melting step, frit is placed in a melting tank body made of a refractory material, and the frit is heated by an electrode pair and a burner.

JP 2017-14055 A

In the method of manufacturing sheet glass as described above, when the electric resistivity of the molten glass is high, the difference in electric resistivity from the refractory (refractory bricks) constituting the melting tank body is small. may flow. If the refractory is energized in this manner, the melting of the raw material for frit is inhibited, or the power consumption increases, which may lead to an increase in the manufacturing cost of the glass article.

The present invention has been made in view of such circumstances, and a technical object thereof is to prevent energization of a refractory material when molten glass is produced by energization heating.

The present invention is intended to solve the above problems, and includes a melting step of heating and melting frit in a melting furnace equipped with a plurality of electrodes at the bottom, A method for manufacturing a glass article, has first bricks surrounding the electrode and second bricks arranged between the first bricks, the first bricks having a higher corrosion resistance than the second bricks, and the The second brick is characterized by having a higher electrical resistivity than the first brick.

According to such a configuration, the second bricks arranged between the first bricks can prevent energization (short circuit) between the first bricks. The first brick surrounding the electrode can exhibit high corrosion resistance against the convection of high-temperature molten glass that occurs in the vicinity of the electrode. In addition, since the second brick is arranged at a position separated from the electrode via the first brick, it comes into contact with molten glass of relatively low temperature and less convection. Therefore, according to the present invention, the melting furnace can be used for a long period of time while preventing energization between the first bricks, and the manufacturing cost of the glass article can be reduced as much as possible.

In the above method, the first brick is preferably an electroformed brick. Also, the second brick is preferably a dense zircon fired brick. Since electroformed bricks are superior in corrosion resistance to dense zircon fired bricks, erosion due to convection of high temperature molten glass in the vicinity of the electrodes can be reliably reduced. Dense zircon fired bricks also have significantly higher electrical resistivity than electroformed bricks. Therefore, it is possible to reliably prevent energization between the electroformed bricks.

Moreover, in the melting step, it is preferable that the glass raw material is electrically heated only by the plurality of electrodes. Compared to the combined use of a burner and multiple electrodes, when the raw materials for frit are heated and melted only by multiple electrodes without using a burner, it is necessary to greatly increase the energization of the molten glass. The energization of objects also tends to increase. Therefore, if the present invention is applied to the case of heating and melting glass raw materials only with a plurality of electrodes without using a burner, the effect of preventing the refractory from being electrified becomes more remarkable.

Moreover, it is desirable that the glass article is made of alkali-free glass. In the present invention, the alkali-free glass is a glass that does not substantially contain an alkali component (alkali metal oxide), and specifically refers to a glass in which the weight ratio of the alkali component is 3000 ppm or less. Alkali-free glass has a high electric resistivity, and in molten glass, the difference in electric resistivity from that of the first brick (for example, an electroformed brick) becomes small. Therefore, the energization of the first brick also tends to increase. If the present invention is applied to a glass article made of such an alkali-free glass, the effect of preventing current flow through the refractory becomes more pronounced.

The present invention is intended to solve the above problems, and is a melting furnace provided with a plurality of electrodes on a bottom, wherein the bottom includes first bricks surrounding the electrodes and a gap between the first bricks. and a second brick arranged in the second brick, wherein the first brick has a higher corrosion resistance than the second brick, and the second brick has a higher electrical resistivity than the first brick and A manufacturing apparatus for glass articles according to the present invention is characterized by comprising the melting furnace configured as described above and a forming apparatus for forming the molten glass produced by the melting furnace.

ADVANTAGE OF THE INVENTION According to this invention, when producing|generating a molten glass by electric heating, electricity supply of a refractory can be prevented.

It is a side view which shows the manufacturing apparatus of a glass article. It is a side sectional view of a melting furnace. It is a plane sectional view of a melting furnace. FIG. 4 is a sectional view taken along line IV-IV of FIG. 3; It is a flow chart which shows a manufacturing method of a glass article. FIG. 3 is a cross-sectional plan view showing another embodiment of a melting furnace; FIG. 7 is a cross-sectional view taken along line VII-VII of FIG. 6; FIG. 3 is a cross-sectional view showing another embodiment of a melting furnace; FIG. 3 is a cross-sectional view showing another embodiment of a melting furnace;

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated, referring drawings. 1 to 4 show an embodiment of the method and apparatus for manufacturing a glass article according to the present invention.

As shown in FIG. 1, the apparatus for manufacturing glass articles according to the present embodiment includes, in order from the upstream side, a melting furnace 1, a clarification tank 2, a homogenization tank (stirring tank) 3, a pot 4, and a molded body. 5 and glass supply paths 6a-6d connecting these components 1-5. In addition, the manufacturing apparatus includes a slow cooling furnace (not shown) for slowly cooling the band-shaped sheet glass GR (glass article) formed by the molded body 5, and a cutting device ( not shown).

The melting furnace 1 is a container for performing a melting step of melting the supplied frit GRM to obtain molten glass GM. The melting furnace 1 is connected to a fining tank 2 by a glass feed line 6a.

The clarification tank 2 is a container for performing a clarification step of defoaming the molten glass GM supplied from the melting furnace 1 by the action of a clarifier or the like. The fining tank 2 is connected to the homogenizing tank 3 by a glass feed line 6b.

The homogenization tank 3 is a container for performing a process of stirring and homogenizing the clarified molten glass GM (homogenization process). The homogenization tank 3 is provided with a stirrer 3a having stirring blades. The homogenization vessel 3 is connected to the pot 4 by a glass feed channel 6c.

The pot 4 is a container for performing a conditioning step of conditioning the molten glass GM to a state suitable for molding. Pot 4 is exemplified as a volume for viscosity adjustment and flow rate adjustment of molten glass GM. The pot 4 is connected to the molding 5 by a glass feed channel 6d.

Each glass supply path 6a to 6d is constructed by connecting a plurality of glass supply pipes made of platinum or platinum alloy. The outer peripheral surface of each glass supply path 6a-6d is held by a refractory material.

In this embodiment, the molding 5 constitutes a molding apparatus for molding the molten glass GM into a desired shape. The formed body 5 is formed by forming the molten glass GM into a plate shape by the overflow downdraw method. Specifically, the molded body 5 has a substantially wedge-shaped cross-sectional shape (a cross-sectional shape perpendicular to the paper surface of FIG. 1), and an overflow groove (not shown) is formed in the upper part of the molded body 5. It is

The molded body 5 causes the molten glass GM to overflow from the overflow groove and flow down along both side wall surfaces of the molded body 5 (side surfaces located on the front and back sides of the paper surface). The formed body 5 is formed into a plate shape by fusing the flowing molten glass GM at the lower top portion of the side wall surface.

The molded plate glass GR has a thickness of 0.01 to 10 mm, for example, and is used for substrates and protective covers for flat panel displays such as liquid crystal displays and organic EL displays, organic EL lighting, solar cells and the like. In addition, the molding apparatus is not limited to the molded article 5, and may perform other down-draw methods such as the slot down-draw method. The glass article according to the present invention is not limited to plate glass GR, and includes glass tubes and other various shapes. For example, when forming a glass tube, instead of the formed body 5, a forming apparatus using the Danner method is provided.

As the material of the plate glass GR, silicate glass and silica glass are used, preferably borosilicate glass, soda lime glass, aluminosilicate glass and chemically strengthened glass are used, and alkali-free glass is most preferably used. Here, the alkali-free glass is a glass that does not substantially contain an alkali component (alkali metal oxide), and specifically, a glass in which the weight ratio of the alkali component is 3000 ppm or less. be. The weight ratio of the alkali component in the present invention is preferably 1000 ppm or less, more preferably 500 ppm or less, and most preferably 300 ppm or less.

A specific configuration of the melting furnace 1 will be described below with reference to FIGS. 2 to 4. FIG.

As shown in FIGS. 2 and 3, the melting furnace 1 has a long shape, and includes a bottom portion 1a having a rectangular shape in plan view, a side portion 1b surrounding the bottom portion 1a, and a side portion 1b. and a closing ceiling portion 1c. The melting furnace 1 has a supply portion 1d for the frit GRM at one end (side portion 1b) in the longitudinal direction X, and an outflow portion 1e for the molten glass GM at the other end. The bottom portion 1a, the side portions 1b, and the ceiling portion 1c are made of a refractory material (refractory bricks). In addition, in FIG.3 and FIG.4, in order to show the structure of the melting furnace 1 clearly, frit GRM and molten glass GM are not illustrated.

The melting furnace 1 energizes and heats the frit GRM by energizing the electrodes 7A and 7B, and does not have a burner. As shown in FIGS. 2 and 3, a plurality of electrodes 7A and 7B are arranged on the bottom portion 1a. Each of the electrodes 7A and 7B is made of a heat-resistant conductive material such as molybdenum and is formed in a columnar shape, but is not limited to this shape. A plurality of electrodes 7A and 7B are configured as a pair of a first electrode 7A and a second electrode 7B. The pair of electrodes 7A and 7B are spaced apart in the width direction Y of the melting furnace 1, as shown in FIG.

The bottom portion 1a of the melting furnace 1 includes electrocast bricks 9A and 9B (first bricks) surrounding the electrodes 7A and 7B, and a plurality of insulating bricks 10 (second bricks) disposed between the electrocast bricks 9A and 9B. two bricks) and The top surfaces of the electroformed bricks 9A and 9B and the top surface of the insulating brick 10 are in contact with the molten glass GM in the furnace. Refractory bricks are layered on the lower surface side of the electroformed bricks 9A and 9B and the lower surface side of the insulating brick 10 for heat insulation (heat retention). The layered heat-insulating refractory brick may be a single layer or a plurality of layers. Alumina-zircon bricks, mullite bricks, and siliceous bricks, for example, can be used as heat-insulating refractory bricks. The electroformed bricks 9A and 9B include a first electroformed brick 9A surrounding the first electrode 7A and a second electroformed brick 9B surrounding the second electrode 7B.

Zirconia-based refractories, for example, can be used as the electroformed bricks 9A and 9B. The electric resistivity of the electroformed bricks 9A and 9B is, for example, 100 Ω·cm or more and less than 1000 Ω·cm at 1500°C.

As shown in FIG. 4, the electroformed bricks 9A, 9B have holes 9a through which parts of the electrodes 7A, 7B are inserted. Each electroformed brick 9A, 9B surrounds a part of each electrode 7A, 7B by the inner surface of the hole 9a by inserting each electrode 7A, 7B into the hole 9a. The holes 9a of the electroformed bricks 9A, 9B are configured to be larger than the outer diameters of the electrodes 7A, 7B, and gaps are formed between the inner surfaces of the holes 9a and the outer surfaces of the electrodes 7A, 7B. This gap is closed by the molten glass GM flowing into and solidifying.

As shown in FIGS. 2 and 4, each electrode 7A, 7B is supported by an electrode holder 8. As shown in FIG. The electrode holder 8 is internally provided with a cooling pipe (not shown). The electrode holder 8 cools the electrode holder 8 and the electrodes 7A and 7B by circulating a liquid coolant such as water in the cooling pipes.

The insulating brick 10 is a refractory brick having a higher electrical resistivity than the electroformed bricks 9A and 9B. The electrical resistivity of the insulating brick 10 is, for example, 1000Ω·cm or more at 1500°C.

In this embodiment, fired bricks are used as the insulating bricks 10 . As the fired bricks, for example, alumina-based, zircon-based, alumina-zirconium-based, silica-based, mullite-based, and clay-based fired bricks can be used. As the material for the insulating bricks 10, it is most desirable to use dense zircon fired bricks. The electrical resistivity of the dense zircon fired brick is, for example, 1000 Ω·cm or more and 10000 Ω·cm or less at 1500°C. Here, the dense zircon-fired brick is a dense zircon-fired brick having a small porosity, and for example, a zircon-fired brick having a porosity of 5% or less may be used. Dense zircon calcined bricks are often shaped by a rubber press method so as to reduce porosity.

The thickness of the insulating bricks 10 is desirably 50 mm or more and 300 mm or less, but is not limited to this range, and is appropriately set according to the type of glass article to be melted, the temperature of the molten glass GM, and other conditions. The thickness of the insulating bricks 10 is approximately the same as that of the electroformed bricks 9A and 9B, but may differ from the thickness of the electroformed bricks 9A and 9B.

As shown in FIG. 4, the insulating brick 10 is arranged between the first electroformed brick 9A and the second electroformed brick 9B to separate them. It is desirable that this separation distance, that is, the width W of the insulating brick 10 (referring to the length dimension in the separation direction of the pair of electrodes 7A and 7B) is 50 mm or more and 3000 mm or less. The width W of the insulating brick 10 is not limited to this range, and can be appropriately set according to the material and temperature of the glass to be melted. As shown in FIGS. 2 and 4, the upper surface 10a of the insulating brick 10 is a contact surface with respect to the molten glass GM.

Hereinafter, a method for manufacturing a glass article (flat glass GR) using the manufacturing apparatus having the above configuration will be described.

As shown in FIG. 5, the method includes a melting step S1, a clarification step S2, a homogenization step S3, a conditioning step S4, a forming step S5, a slow cooling step S6, and a cutting step S7. . In the melting step S1, frit GRM is continuously introduced into the melting furnace 1 from the supply section 1d. The charged glass raw material GRM is electrically heated by the electrodes 7A and 7B. As a result, the frit GRM is melted in the melting furnace 1 to produce molten glass GM.

In the melting step S1, the temperature of the molten glass GM is relatively high around the electrodes 7A and 7B, and convection (upward flow) of the molten glass GM occurs as indicated by arrows F in FIG. . In this case, since the electroformed bricks 9A, 9B surrounding the electrodes 7A, 7B have higher corrosion resistance than the insulating bricks 10, they exhibit high corrosion resistance against the convection of the high-temperature molten glass GM. On the other hand, the insulating bricks 10 are further away from the respective electrodes 7A, 7B than the electroformed bricks 9A, 9B, and are in contact with the molten glass GM at positions where convection of the molten glass GM is small.

After the melting step S1, the molten glass GM is continuously discharged from the outflow part 1e of the melting furnace 1 and transferred to the clarification tank 2 through the glass supply path 6a. The frit GRM contains a fining agent, and the molten glass GM generates gas (bubbles) due to the action of this fining agent. In the clarification step S2, the molten glass GM is circulated through the clarification tank 2 to remove this gas.

After that, the molten glass GM that has been subjected to the clarification treatment (defoaming treatment) is transferred to the homogenization tank 3 through the glass supply path 6b. In the homogenization step S<b>3 , the molten glass GM is stirred (homogenized) by rotating the stirrer 3 a in the homogenization tank 3 .

The homogenized molten glass GM is transferred to the pot 4 through the glass supply channel 6c. In the condition adjustment step S4, the pot 4 is used to adjust the viscosity and flow rate of the molten glass GM.

The molten glass GM that has passed through the pot 4 flows into the overflow groove of the molding 5 through the glass supply channel 6d. In the forming step S<b>5 , the molten glass GM is overflowed from the overflow groove and flowed down along the side wall surface of the formed body 5 . The formed body 5 forms a belt-like sheet glass GR by fusing the molten glass GM that has flowed down at the lower top.

After that, the band-shaped plate glass GR is subjected to a slow cooling step S6 using a slow cooling furnace. In a cutting step S7 by a cutting device, a plate glass having a desired size is cut out from the band-shaped plate glass GR that has undergone the slow cooling step S6. Alternatively, in the cutting step S7, both widthwise end portions of the plate glass GR may be cut and removed, and then the strip-shaped plate glass GR may be wound into a roll (winding step). A glass article (plate glass GR) is thus completed.

According to the method and apparatus (melting furnace 1) for manufacturing a glass article according to the present embodiment described above, the insulating bricks 10 (second bricks) arranged between the electrocast bricks 9A and 9B (first bricks) Thus, it is possible to prevent energization between the electroformed bricks 9A and 9B during the melting step S1. Furthermore, as described above, by arranging the electroformed bricks 9A and 9B near the electrodes 7A and 7B and arranging the insulating brick 10 at a position away from the electrodes 7A and 7B, convection occurs near the electrodes 7A and 7B. While ensuring the high corrosion resistance with respect to high temperature molten glass GM which carries out, the wear of the insulating brick 10 can be suppressed. Therefore, the melting furnace 1 can be used for a long period of time while preventing energization (short circuit) between the electrocast bricks 9A and 9B, thereby reducing the manufacturing cost of the glass article (flat glass GR) as much as possible.

6 and 7 show another embodiment of a glass article manufacturing apparatus (melting furnace). 1 to 5, the pair of electrodes 7A and 7B are spaced apart in the width direction Y of the melting furnace 1; are spaced apart in the longitudinal direction X (see FIG. 6). Further, as shown in FIG. 7, the electroformed bricks 9A and 9B are configured by vertically stacking a plurality of plate-shaped (layered) electroformed bricks 9A and 9B. The laminated electroformed bricks 9A and 9B may have different materials and different thicknesses. Similarly, the insulating bricks 10 are constructed by stacking a plurality of fired bricks 10 vertically. Each insulating brick 10 having a different thickness may be used.

8 and 9 show another embodiment of a glass article manufacturing apparatus (melting furnace). In the example shown in FIG. 8, at the bottom 1a of the melting furnace 1, a plurality of insulating bricks 10 are arranged between a pair of electrodes 7A and 7B. Electroformed bricks 9</b>C may be arranged between the plurality of insulating bricks 10 . In the example shown in FIG. 9, a concave portion 10b is formed in an insulating brick 10 arranged between a pair of electrodes 7A and 7B in a bottom portion 1a of a melting furnace 1, and an electroformed brick 9C is fitted in the concave portion 10b. there is Without being limited to this configuration, a through hole may be formed in the insulating brick 10 instead of the concave portion 10b, and the electroformed brick 9C may be inserted into the through hole.

In addition, the present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. Various modifications can be made to the present invention without departing from the gist of the present invention.

Although the melting furnace 1 having no burner is exemplified in the manufacturing apparatus of the above embodiment, the configuration is not limited to this. The melting furnace 1 may be equipped with a burner for auxiliary heating of the frit GRM from above in the melting step S1. Further, even when the frit GRM is electrically heated only by a plurality of electrodes without using a burner in the melting step S1, a burner may be used in the start-up step. The start-up step is a step of bringing the melting furnace 1 from a room temperature state to a state filled with the molten glass GM.

In the present invention, the electrical resistivity of the first brick and the second brick shall be measured by the AC four-probe method, and when the glass article is made of alkali-free glass, the measurement temperature shall be 1500°C. In addition, the corrosion resistance of the first brick and the second brick shall be measured by a rotary erosion test, and when the glass article is made of alkali-free glass, the test temperature shall be 1500° C. and the test time shall be 24 hours.

1 Melting Furnace 1a Bottom Part of Melting Furnace 5 Formed Body 7A First Electrode 7B Second Electrode 9A First Electroformed Brick (First Brick)
9B second electroformed brick (first brick)
10 insulating brick (second brick)
GRM Glass raw materials GM Molten glass GR Sheet glass (glass products)

Claims (7)

A method for producing a glass article, comprising a melting step of heating and melting a glass raw material in a melting furnace having a plurality of electrodes at the bottom,
the bottom portion has first bricks surrounding the electrodes and second bricks disposed between the first bricks;
The first bricks are superior in corrosion resistance to the second bricks,
The second brick has a higher electrical resistivity than the first brick,
The electrical resistivity of the first brick is 100 Ω·cm or more and less than 1000 Ω·cm at 1500°C,
A method for producing a glass article, wherein the electrical resistivity of the second brick is 1000Ω·cm or more at 1500°C . The method for manufacturing a glass article according to claim 1, wherein the first brick is an electroformed brick. The method for producing a glass article according to claim 1 or 2, wherein the second brick is a dense zircon fired brick. The method for producing a glass article according to any one of claims 1 to 3, wherein in the melting step, the frit is electrically heated only by the plurality of electrodes. The method for manufacturing a glass article according to any one of claims 1 to 4, wherein the glass article is made of alkali-free glass. A melting furnace equipped with a plurality of electrodes at the bottom for generating molten glass by electric heating ,
the bottom portion has first bricks surrounding the electrodes and second bricks disposed between the first bricks;
The first bricks are superior in corrosion resistance to the second bricks,
The second brick has a higher electrical resistivity than the first brick,
The electrical resistivity of the first brick is 100 Ω·cm or more and less than 1000 Ω·cm at 1500°C,
The melting furnace , wherein the electric resistivity of the second brick is 1000Ω·cm or more at 1500°C . An apparatus for manufacturing glass articles, comprising: the melting furnace according to claim 6; and a forming apparatus for forming the molten glass produced by the melting furnace.

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