JP6721311B2 - Glass substrate manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a glass substrate used for a flat panel display such as a liquid crystal display and a plasma display.

As a glass substrate used for a flat panel display (hereinafter referred to as “FPD”) such as a liquid crystal display or a plasma display, a thin glass plate having a thickness of, for example, 0.5 to 0.7 mm is used. The glass substrate for FPD has a size of, for example, 300×400 mm in the first generation, but has a size of 2850×3050 mm in the tenth generation.

Such a thin and large-sized glass substrate for FPD is manufactured by, for example, an overflow down draw method by transferring molten glass in which glass raw materials are melted to a forming furnace. A method of manufacturing a glass substrate using the overflow downdraw method is disclosed in Patent Document 1, for example.

Further, the transfer pipe for transferring the above-mentioned molten glass needs to heat the molten glass in the pipe to a predetermined temperature, and in order to perform this heating efficiently, the transfer pipe is provided with a heating device for heating it. There is. For example, Patent Document 2 discloses a method in which a transfer tube made of platinum or a platinum alloy is used, a flange electrode for energization is provided in the transfer tube, and the transfer tube is electrically heated.

International Publication No. 2012/132425 JP, 2009-298671, A Special table 2011-513173 gazette

By the way, in order to manufacture a glass substrate for FPD, it is necessary to raise the temperature of the molten glass to, for example, about one thousand and several hundred degrees. When the transfer tube is heated to raise the temperature of the molten glass inside the tube to about one thousand and several hundred degrees, the flange electrode itself for energizing the transfer tube also rises, and the flange electrode generally made of platinum or platinum alloy volatilizes. As a result, the flange electrode may be damaged. In addition, when manufacturing is continuously performed for a long period of time, not only the flange electrode but also the transfer tube is greatly damaged, and there is a risk of damage.

Therefore, conventionally, the flange electrode is prevented from being damaged by cooling the flange electrode with water, for example. For example, Patent Document 3 discloses that a flange-shaped electrode is provided with a water cooling tube for cooling.

However, in the method of arranging a water cooling pipe and cooling by water cooling, the temperature is locally lowered, and it is difficult to obtain a stable cooling effect.
A method of applying air from a fan to the flange electrode or the transfer pipe to cool it by air cooling is also conceivable, but it is difficult to efficiently cool the flange electrode or the transfer pipe at a temperature of, for example, 1000° C. or higher. ..

In recent years, in the field of FPDs, the quality requirements for glass substrates for FPDs have become more and more stringent with the progress of higher definition, and it is required to mold the glass substrates at a higher temperature than ever before. When the temperature of the molten glass becomes higher than that of the conventional one, the flange electrode and the transfer tube also have higher temperatures than those of the related art, so that the above-mentioned problem of breakage of the flange electrode and the transfer tube becomes more serious. Further, in glass substrate manufacturing, a melting tank for obtaining molten glass by melting glass raw materials, a fining tank for defoaming bubbles of gas components contained in the molten glass, and a stirring tank for stirring defoamed molten glass. Also, the same problems as those of the above-mentioned transfer pipe and the like occur with respect to the electrodes of these processing tanks.

Therefore, the present invention can cool the processing tank, the transfer pipe, and the electrode by a method that can obtain a stable cooling effect at a low cost with high cooling efficiency, and thus can manufacture a high-quality glass substrate. An object is to provide a method of manufacturing a glass substrate that can be used.

As a result of earnest studies to solve the conventional problems, the present inventor has completed the invention having the following constitution.
(Invention of Structure 1)
That is, the present invention is a glass substrate manufacturing method for manufacturing a glass substrate by transferring a molten glass in which a glass raw material is melted to a forming furnace, wherein the molten glass is flown from an upstream side to a downstream side, or a transfer tank. A pipe, and at least a pair of electrodes provided in the treatment tank or the transfer pipe, respectively, for heating the molten glass in the treatment tank or the transfer pipe by applying an electric current to the treatment tank or the transfer pipe to heat the molten glass. Cooling means for cooling at least one of the processing tank, the transfer pipe and the electrode by air cooling, the cooling means includes the processing tank, the transfer pipe or the electrode and an air layer around them. After the first wind pressure is applied to the boundary layer so that the thickness of the boundary layer formed between and is less than or equal to a predetermined reference thickness, a second wind pressure weaker than the first wind pressure is applied. The method is a method for manufacturing a glass substrate, characterized in that at least one of the processing tank, the transfer pipe, and the electrode is air-cooled.

In the present invention, the cooling means applies a first wind pressure from the horizontal direction to the boundary layer so as to suppress the buffering of the wind pressure applied to the boundary layer, and then the thickness of the boundary layer is It is preferable to apply a second wind pressure from the same direction as the horizontal direction so as to maintain the thickness equal to or less than the reference thickness, and alternately cool the first wind pressure and the second wind pressure.

Further, in the present invention, the reference thickness is preferably 20 mm.

Further, in the present invention, it is preferable that the first wind pressure applied to the boundary layer is 100 kPa or more.

Further, in the present invention, the cooling means may specifically include, for example, a compressor that discharges high-pressure air and a fan that discharges low-pressure air.

According to the present invention, with the above configuration, it is possible to cool the processing tank, the transfer pipe, and the electrode by a method that has a low cooling efficiency, a high cooling efficiency, and a stable cooling effect. Therefore, it is possible to manufacture a high quality glass substrate.

It is a figure which shows an example of the flow of the manufacturing method of the glass substrate which concerns on this invention. It is a figure which shows typically an example of the apparatus which performs the melting process or the cutting process in the manufacturing method of the glass substrate which concerns on this invention. It is a schematic side view of a molding apparatus. It is a perspective view showing the composition of the neighborhood of the transfer pipe for explaining the 1st embodiment of the present invention. It is sectional drawing of the nozzle used as a cooling means. It is a schematic diagram for demonstrating the cooling method in this invention. It is a figure which shows an example of the cooling pattern in the cooling method of this invention. It is a perspective view which shows the structure of the transfer pipe vicinity for describing the 2nd Embodiment of this invention. It is a perspective view which shows the structure of the melting tank vicinity for describing the 3rd Embodiment of this invention. It is sectional drawing of the wall surface of the melting tank for demonstrating the modification of the 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
(Overview of glass substrate manufacturing method)
First, an overall outline of the glass substrate manufacturing method according to the present invention will be described. An example of the outline of the manufacturing process of the glass substrate in which the overflow down draw method is adopted can be shown in FIG. 1, for example.
FIG. 1 is a diagram showing an example of a flow of a method for manufacturing a glass substrate according to the present invention.

In this glass substrate manufacturing process, a melting process (ST1), a fining process (ST2), a stirring (homogenizing) process (ST3), a supplying process (ST4), a molding process (ST5), and a cooling (gradual) process. The cooling step (ST6) and the cutting step (ST7) are included, and the downdraw method is adopted in the molding step (ST5) and the cooling (gradual cooling) step (ST6). In the molding step, for example, As shown in FIG. 3, it is molded by an apparatus including a wedge-shaped molded body 210.

FIG. 2 is a diagram schematically showing an example of an apparatus that performs the melting step (ST1) to the cutting step (ST7). As shown in FIG. 2, the device mainly includes a melting device 100, a molding device 200, and a cutting device 300. The dissolution apparatus 100 has a dissolution tank 101, a fining tank 102, a stirring tank 103, a first transfer pipe 104, a second transfer pipe 105, and a third transfer pipe 106.

In the melting step (ST1), the glass raw material supplied into the melting tank 101 is melted by electric heating using a flame and/or an electrode to obtain a molten glass MG. Molten glass MG is supplied from the melting tank 101 to the refining tank 102 through the first transfer pipe 104.

In the refining step (ST2), the temperature of the molten glass MG supplied to the refining tank 102 is raised, whereby bubbles containing gas components such as O ₂ , CO _{2 and} SO ₂ contained in the molten glass MG are generated. , SnO _2, etc. absorbs O ₂ generated by the reduction reaction of the fining agent, grows, floats on the liquid surface of the molten glass MG, and is released into the air above the fining tank 102 and into an atmosphere containing nitrogen gas or the like. Are removed. Then, the internal pressure of the gas component in the bubbles decreases due to the decrease in the temperature of the molten glass MG, and the reduced fining agent (for example, SnO) undergoes an oxidation reaction due to the decrease in the temperature of the molten glass MG, so that the molten glass Gas components such as O ₂ in the bubbles remaining in the MG are reabsorbed to eliminate the bubbles.
The molten glass MG defoamed in the above refining step is supplied from the refining tank 102 to the stirring tank 103 through the second transfer pipe 105.

In the stirring (homogenization) step (ST3), the molten glass MG degassed in the refining step is supplied, and the molten glass MG in the stirring tank 103 is stirred using a stirring means (for example, a stirrer 103a shown in the drawing). By stirring, the glass components are homogenized.

In the supply step (ST4), the homogenized molten glass MG is supplied from the stirring tank 103 to the molding apparatus 200 through the third transfer pipe 106. An example of the molding apparatus 200 is shown in FIG. FIG. 3 is a schematic side view of the molding apparatus.

In FIG. 3, the molding apparatus 200 includes a molding furnace 240 and a slow cooling furnace 250. In the molding apparatus 200, the molding step (ST5) and the cooling (slow cooling) step (ST6) are sequentially performed.

In the forming step (ST5), the molten glass MG is formed into a sheet glass SG, and a flow of the sheet glass SG is created. In this embodiment, the overflow down draw method using the molded body 210 is used. In this case, the flow direction of the sheet glass SG is vertically downward.

More specifically, as shown in FIGS. 2 and 3, the molded body 210 molds the molten glass MG flowing from the melting device 100 through the third transfer pipe 106 into a sheet glass SG. As a result, a flow of the sheet glass SG vertically below is created in the forming device 200. The molded body 210 is an elongated structure made of refractory brick or the like, and has a wedge-shaped cross section as shown in FIG. A supply groove 212 that serves as a flow path for guiding the molten glass MG is provided in the upper portion of the molded body 210. The supply groove 212 is connected to the third transfer pipe 106 at the supply port provided in the molded body 210, and the molten glass MG flowing through the third transfer pipe 106 flows along the supply groove 212. The depth of the supply groove 212 becomes shallower in the downstream of the flow of the molten glass MG, so that the molten glass MG overflows vertically downward from the supply groove 212.

The molten glass MG overflowing from the supply groove 212 flows down along the side walls on both sides of the molded body 210. The molten glass MG that has flowed through the side wall joins at the lower end portion 213 (shown in FIG. 3) of the molded body 210, and one sheet glass SG is molded. The sheet glass SG flows vertically downward, which is the flow-down direction of the sheet glass SG shown in FIG. The temperature of the sheet glass SG just below the lower end portion 213 of the molded body 210 is a temperature corresponding to a viscosity of 10 ^4.3 to 10 ⁶ poise (for example, 1000 to 1250° C.). Further, it may be 1150°C to 1250°C.

An atmosphere partition member 220 is provided near the lower end 213 of the molded body 210. The atmosphere partition member 220 is a pair of plate-shaped heat insulating members provided so as to sandwich the sheet glass SG from both sides in the thickness direction. The atmosphere partitioning member 220 including this heat insulating member is provided to partition the lower space from the molding furnace 240 that is the upper space in which the molded body 210 is housed.

A cooling roller (conveying roller having a function as a cooling roller) 230 is provided below the atmosphere partition member 220. As shown in FIG. 3, the cooling rollers 230 are provided on both sides of the sheet glass SG in the thickness direction so as to sandwich the sheet glass SG from both sides of the thickness direction.

Further, in a region below the cooling roller 230, a plurality of transport rollers including further transport rollers 250a to 250d and a temperature adjusting device (not shown) are provided along the flow direction of the sheet glass SG. The individual transport rollers are provided on both sides of the sheet glass SG in the thickness direction, and sandwich both ends of the sheet glass SG in pairs. That is, it constitutes a pair of roller conveying means.

In the cooling (slow cooling) step (ST6) described above, the sheet glass SG formed and flowing has a desired thickness in the process of being nipped and conveyed by the cooling roller 230 and the conveyance rollers 250a to 250d, and is cooled. It is cooled (gradual cooling) so as to prevent warpage and internal strain caused by it.

In the cutting step (ST7), in the cutting device 300, the sheet glass SG supplied from the molding device 200 is cut into a predetermined length to obtain a plate-shaped glass plate.
The glass plate cut into a plate shape is further cut into a predetermined size to produce a glass substrate of a target size. After this, the end surface of the glass substrate is ground, polished, and the glass substrate is cleaned, and after the presence or absence of defects such as bubbles and striae is inspected, the glass substrate that has passed the inspection is packaged as the final product. It

Next, the structural features of the method for manufacturing a glass substrate according to the present invention will be described.
The method for manufacturing a glass substrate according to the present invention is the method for manufacturing a glass substrate according to the invention of Structure 1 above, in which the molten glass in which the glass raw material is melted is transferred to a forming furnace to manufacture the glass substrate. A processing tank or a transfer pipe for flowing glass from the upstream side to the downstream side, and the processing tank or the transfer pipe, which is provided in the processing tank or the transfer pipe, respectively, and current is passed through the processing tank or the transfer pipe to heat the treatment tank or the heating tank. At least a pair of electrodes for heating the molten glass in the transfer pipe, and a cooling means for cooling at least one of the processing tank, the transfer tube and the electrode by air cooling, the cooling means, the processing tank , A first wind pressure is applied to the boundary layer so that the thickness of the boundary layer formed between the transfer pipe or the electrode and the air layer around them is equal to or less than a predetermined reference thickness. Then, a second wind pressure, which is weaker than the first wind pressure, is applied to cool at least one of the processing tank, the transfer pipe, and the electrode.
Hereinafter, the first embodiment of the method for manufacturing a glass substrate according to the present invention having such a structural feature will be described.

(First embodiment)
FIG. 4 is a perspective view showing a configuration in the vicinity of a transfer pipe for explaining the first embodiment of the present invention.
As shown in FIG. 4, in the present embodiment, a transfer pipe 10 that transfers the molten glass MG while flowing it from the upstream side to the downstream side, and is provided on the upstream side and the downstream side of the transfer pipe 10, respectively. , A pair of electrodes 20, 20 for heating the molten glass MG in the transfer tube 10 by applying an electric current to the transfer tube 10 to heat the transfer tube 10 and/or the electrodes 20, 20 by air cooling Cooling means 30 for cooling by.

Here, the transfer pipe 10 is, for example, as shown in FIG. 2 described above, connects the respective processes (processing tanks), and transfers the molten glass MG while flowing the molten glass MG from the upstream side to the downstream side. The first transfer pipe 104, the second transfer pipe 105, and the third transfer pipe 106 are used. Therefore, the configuration of the present embodiment is applied to at least one of the first transfer pipe 104, the second transfer pipe 105, and the third transfer pipe 106.
In addition, although this embodiment demonstrates using the transfer pipe 10, each melting|dissolution tank 101 which obtains the molten glass MG by melting a glass raw material, each processing layer of the following clarification tank 102, and stirring tank 103, and each The present invention can be applied to any of the dissolution apparatuses 100 having the first transfer pipe 104, the second transfer pipe 105, and the third transfer pipe 106 that connect the processing tanks.

The transfer tube 10 is a cylindrical member made of, for example, a platinum group metal because the extremely high temperature molten glass MG flows through the tube. The platinum group metal is a metal composed of a single platinum group element (platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), iridium (Ir)), or a platinum group element. It is an alloy of metals consisting of. Although these platinum group metals are expensive, they have high melting points and are excellent in corrosion resistance against the molten glass MG. In the present embodiment, the transfer pipe 10 is formed of, for example, platinum (Pt) or a platinum alloy, and has a thickness of, for example, about 0.5 mm to 1.5 mm. The inner diameter of the transfer tube 10 is, for example, about 100 mm to 500 mm.

The pair of electrodes 20, 20 are made of a conductive metal material, and are used for supplying an electric current to the transfer tube 10 to heat it electrically. Then, the temperature of the molten glass MG flowing inside the transfer tube 10 is adjusted by heating the transfer tube 10. The electrodes 20 and 20 are attached to the outer peripheral surface of the transfer tube 10, and each electrode 20 is formed in a flange shape made of an annular conductor.

Further, each electrode 20 has a power supply terminal 21 connected to a power source (not shown). Electric power is supplied from the power supply through the power supply terminal 21, current flows through the electrodes 20 and 20, and the transfer tube 10 is electrically heated. Therefore, by controlling the current flowing through the pair of electrodes 20, 20, the temperature of the molten glass MG flowing inside the transfer tube 10 can be adjusted.

The number and positions of the electrodes 20 attached to the transfer tube 10 may be appropriately determined according to the material, inner diameter, length, installation position, etc. of the transfer tube 10, and are therefore limited to the embodiment of FIG. No need. In addition, in the present embodiment, the pair of electrodes 20, 20 are arranged on the upper side of the transfer tube 10, but the present invention is not limited to this.

The cooling means 30 is used to cool the transfer pipe 10 and/or the electrodes 20, 20 by air cooling.
The cooling means 30 will be described in more detail.

As shown in FIG. 4, in the present embodiment, the cooling means 30 is arranged at a position where air is discharged near the outer peripheral surface of the transfer pipe 10.

Further, in the present embodiment, the cooling means 30 specifically includes a compressor (not shown) that discharges high pressure air and a fan (not shown) that discharges low pressure air. Further, FIG. 5 is a sectional view of a nozzle used as a cooling means. As shown in FIG. 5, in the present embodiment, the tip nozzle 31, which is an air discharge port from the cooling means 30, includes a compressor nozzle 31c and a fan nozzle 31f. The compressor nozzle 31c and the fan nozzle 31f are integrally fixed by adhesion or the like.

Generally, a compressor has a discharge pressure of 100 kPa or more. On the other hand, a fan generally has a discharge pressure of 10 kPa or less. Therefore, in the present embodiment, for example, high-pressure air having a discharge pressure of 100 kPa or higher is discharged from the compressor nozzle 31c, and low-pressure air having a discharge pressure of 10 kPa or lower is discharged from the fan nozzle 31f.

Further, in the present embodiment, the cooling means 30 is arranged so that the air from the tip nozzle 31 is discharged toward the longitudinal direction (direction of arrow A in FIG. 4) of the outer peripheral surface of the transfer tube 10. Has been done.

As described above, the structural feature of the present invention is that the thickness of the boundary layer formed between the transfer pipe 10 and the air layer around the transfer pipe 10 is set to be equal to or less than a predetermined reference thickness by the cooling unit 30. As described above, after the wind pressure is applied to the boundary layer, the transfer pipe 10 is air-cooled.

Here, the cooling method in the present invention will be described.
FIG. 6 is a schematic diagram for explaining the cooling method in the present invention. The solid line in the figure is the temperature curve. In the figure, t ₁ (° C.) is the boundary temperature between the air layer and the boundary layer, and t ₂ (° C.) is the surface temperature of the transfer pipe 10 (the boundary temperature between the transfer pipe 10 and the boundary layer). Yes, t ₂ >t ₁ .

As shown in FIG. 3A, a boundary layer having a predetermined thickness (L ₀ ) is formed between the transfer pipe 10 in which the molten glass MG flows and the air layer around the transfer pipe 10. The thickness L ₀ of this boundary layer is considered to be, for example, about 50 to 200 mm. If the thickness of the boundary layer is reduced to L ₁ (L ₁ <L ₀ ) as shown in FIG. 7B, the cooling efficiency can be improved.

In the present embodiment, by the cooling means 30, for example, the thickness of the boundary layer formed between the transfer pipe 10 and the air layer around the transfer tube 10 is set to a predetermined reference thickness or less, with respect to the boundary layer. Then, after the air pressure is applied by the high pressure air discharged from the compressor nozzle 31c, the transfer pipe 10 is cooled by the low pressure air discharged from the fan nozzle 31f. From the viewpoint of improving the cooling efficiency, the reference thickness here is preferably, for example, about 10 to 20 mm, and most preferably about 20 mm. The cooling effect is highest when the thickness of the boundary layer is 0 mm, but the cooling effect by air cooling can be enhanced by setting the thickness of the boundary layer to 10 to 20 mm.

Further, in order to reduce the thickness of the boundary layer as described above, it is desirable to suppress the buffering of the wind pressure applied to the boundary layer. Therefore, after the cooling means 30 applies a predetermined wind pressure of high-pressure air from the horizontal direction to the boundary layer formed between the transfer pipe 10 and the air layer around the transfer tube 10, for example, the boundary layer is cooled. It is preferable to cool the transfer pipe 10 with low pressure air from the same direction as the horizontal direction so that the thickness is maintained below the reference thickness. In the present embodiment, as described above, in the cooling means 30, the air from the tip nozzle 31 is discharged toward the longitudinal direction (the arrow A direction in FIG. 4) of the outer peripheral surface of the transfer tube 10. The boundary layer can be thinned to a predetermined reference thickness or less without being buffered by the wind pressure applied to the boundary layer.

Further, in order to reduce the thickness of the boundary layer to the reference thickness or less, it is preferable that the wind speed applied to the boundary layer is, for example, 15 m/sec to 30 m/sec. The wind pressure applied to the boundary layer is preferably 100 kPa or more.

FIG. 7: is a figure which shows an example of the cooling pattern in the cooling method of this embodiment. In the figure, reference numeral "C" means that high pressure air is applied by the compressor, and reference numeral "F" means that low pressure air is applied by the fan.

In the present embodiment, by the cooling means 30, for example, the thickness of the boundary layer formed between the transfer pipe 10 and the air layer around it is equal to or less than a predetermined reference thickness (Ls), After the wind pressure is applied to the boundary layer by the high pressure air discharged from the compressor nozzle 31c, the transfer pipe 10 is cooled by the low pressure air discharged from the fan nozzle 31f. However, when the fan is continuously used, the thickness of the boundary layer gradually increases, the cooling efficiency also decreases, and the temperature of the outer peripheral surface of the transfer pipe 10 gradually increases. The compressor is used again to apply high-pressure air to the boundary layer so as to maintain the reference thickness Ls or less, and then the transfer pipe 10 is appropriately cooled by low-pressure air by a fan. It is suitable.

When air-cooled with only low-pressure air from a fan, the thickness of the boundary layer is about 100 mm, and the thickness of the boundary layer does not fall below the reference thickness Ls, so the cooling effect by air cooling cannot be enhanced. However, by applying high-pressure air from the compressor, the thickness of the boundary layer becomes 10 mm to 20 mm, which is Ls or less. Continuing to flow the molten glass MG into the transfer tube 10 with the boundary layer having a thickness of about 100 mm causes the transfer tube 10 to break in about 3 years (the life of the transfer tube 10 is about 3 years). By maintaining the thickness of the boundary layer to be 10 mm to 20 mm, which is equal to or less than Ls, the life of the transfer pipe 10 becomes 6 years or longer. By reducing the thickness of the boundary layer from 100 mm to 10 mm to 20 mm, the temperature of the transfer tube 10 can be reduced by about 30%, and thus the life of the transfer tube 10 can be extended.

Although it may be difficult to measure the thickness of the boundary layer accurately, for example, the temperature of the outer peripheral surface of the transfer tube 10 or the temperature at a predetermined distance from the outer peripheral surface of the transfer tube 10 may be measured. By measuring, it is possible to grasp the thickness of the boundary layer.

Further, the arrangement position and the number of the cooling means 30 may be appropriately determined depending on, for example, the material, the inner diameter, the length, the installation position and the like of the transfer tube 10, or the arrangement and the installation position of the electrode 20. It need not be limited to the embodiment of FIG. Further, the transfer tube 10 and the electrode 20 may be cooled by a single cooling means, or the transfer tube 10 and the electrode 20 may be cooled simultaneously or individually by separate cooling means.

As described above, in the present embodiment, the high-pressure compressor is limited to, for example, limiting the boundary layer formed between the transfer pipe 10 and the air layer around it to a predetermined reference thickness or less. After the use and thinning of the boundary layer, the transfer pipe 10 is air-cooled by the low pressure air of the fan, which is advantageous in terms of cost. According to the present invention, with the above configuration, it is possible to cool the transfer tube and the electrode by a method that has a low cost, a high cooling efficiency, and a stable cooling effect. Therefore, it is possible to manufacture a high quality glass substrate.

(Second embodiment)
FIG. 8 is a perspective view showing a configuration in the vicinity of a transfer pipe for explaining the second embodiment of the present invention.
As shown in FIG. 8, in the present embodiment, the transfer tube 10, the support member 40, and the heat radiation amount adjustment member 50 are provided. The present embodiment is an embodiment in which the transfer tube 10 is supported by a supporting member 40, and a heat radiation amount adjusting member 50 is arranged around the supporting member 40. Although the electrodes are not shown in FIG. 8, the electrodes may be arranged as in the first embodiment. In that case, the support member 40 and the heat radiation amount adjusting member 50 are separated at the position where the electrode is attached to the transfer tube 10.

Since the transfer pipe 10 has already been described, the duplicate description is omitted here.
The support member 40 is provided to support the transfer tube 10. The support member 40 is provided so as to contact the outer peripheral surface of the transfer tube 10. The support member 40 has a substantially prismatic shape, and the cross-sectional shape of the support member 40 in the cross-sectional direction is a substantially quadrangle. The support member 40 is molded from cement formed by casting or sintering.

The heat radiation amount adjusting member 50 is provided to adjust the heat radiation amount of the molten glass MG flowing inside the transfer tube 10. In the present embodiment, the heat radiation amount adjusting member 50 is provided so as to contact at least a part of the outer peripheral surface of the support member 40. The heat radiation amount adjusting member 50 is formed of, for example, refractory brick, and the size thereof is determined by the material of the member, the temperature of the molten glass MG flowing in the transfer pipe 10, and the like.

In the present embodiment, not the outer peripheral surface of the transfer tube 10 or the like, but the periphery of the support member 40 supporting the transfer tube 10 and the periphery of the heat radiation amount adjusting member 50 arranged on the outer periphery thereof are cooled. do it. The cooling means 30 described in the first embodiment can also be applied to this embodiment.

Therefore, also in the present embodiment, the above-described configuration makes it possible to cool the transfer pipe and the electrode by a method that has a low cost, good cooling efficiency, and a stable cooling effect, resulting in high quality. It is possible to manufacture the glass substrate of

(Third Embodiment)
FIG. 9 is a perspective view showing the configuration in the vicinity of the dissolution tank for explaining the third embodiment of the present invention.
The present embodiment shows a mode in which the melting tank 101 and the electrodes of the melting tank 101 are cooled.

The melting tank 101 is configured by laminating a plurality of refractory members (fireproof bricks). The melting tank 101 has a wall surface 110 made of a refractory member which is a refractory brick, and has an internal space surrounded by the wall surface 110. The internal space of the melting tank 101 is formed in the upper layer of the molten glass MG and the liquid tank B that holds the molten glass MG formed by melting the glass raw material charged in this space, and the glass raw material is charged. And the upper space A, which is in the vapor phase.

On the wall surface 110 of the upper space A, burners 111 that burn a combustion gas in which fuel, oxygen, and the like are mixed to generate a flame are provided at a plurality of locations. The burner 111 heats the refractory member in the upper space A by the flame to heat the wall surface 110 to a high temperature. The glass raw material is heated and melted by the radiant heat of the wall surface 110 which has become high in temperature and by the vapor phase atmosphere which has become high in temperature.

Further, three pairs of electrodes 112 made of a heat-resistant conductive material such as tin oxide or molybdenum are provided on the wall surfaces 110, 110 of the liquid tank B facing the dissolution tank 101. All the three pairs of electrodes 112 extend toward the inner wall surface of the liquid tank B. Note that the electrode on the back side in the drawing is not shown in each pair of the three pairs of electrodes 112. Each pair of three pairs of electrodes 112 is provided on the facing wall surfaces 110, 110 so as to face each other through the molten glass MG. The electrodes 112 of each pair serve as a positive electrode and a negative electrode, and apply a current to the molten glass MG between the electrodes. The molten glass MG itself generates Joule heat by this energization to heat the molten glass MG. In the melting tank 101, the molten glass MG is heated to, for example, 1500° C. or higher. The heated molten glass MG is sent to the refining tank 102 through the first transfer pipe 104. In FIG. 9, the melting tank 101 is provided with three pairs of electrodes 112, but the present invention is not limited to this, and one pair, two pairs, or four or more pairs of electrodes may be provided.

In the present embodiment, the wall surface 110 of the melting tank 101 and the periphery of the electrode 112 may be cooled. Particularly, the portion around the electrode 112 is most effective. The cooling means 30 described in the first embodiment can also be applied to this embodiment.

Therefore, also in the present embodiment, the above-described configuration makes it possible to cool the melting tank 101 and the electrode 112 thereof by a method that has a low cooling efficiency, a high cooling efficiency, and a stable cooling effect. It is possible to manufacture high quality glass substrates.

(Modification)
FIG. 10: is sectional drawing of the wall surface of the melting tank for demonstrating the modification of the 3rd Embodiment of this invention.
The present modified example shows, as a modified example of the third embodiment, a mode in which wind pressure is applied to the boundary layer in the vertical direction.

As shown in FIG. 10, for example, when cooling the portion around the electrode 112 (B in the drawing), the distance L between the tip nozzle 31 of the cooling means 30 and the dissolution tank 101 is a constant distance (for example, 10 mm to By setting the length to be 300 mm or less, the air emitted from the tip nozzle 31 hits the melting tank 101, then is reversed, and flows avoiding the tip nozzle 31 as shown in the figure. Immediately after the inversion, the inverted air advances in a direction perpendicular to the melting tank 101, but when the speed decreases, the air flows so as to swirl. When the air flowing so as to swirl and the air discharged from the tip nozzle 31 interfere with each other, the effect of reducing the thickness of the boundary layer by the air discharged from the tip nozzle 31 is reduced. Therefore, the cooling effect can be obtained by setting the position of the tip nozzle 31 to a position closer to the melting tank 101 than the position where the reversed air swirls, specifically, the distance L is 10 mm to 300 mm. Thus, even when the wind pressure is applied to the boundary layer in the vertical direction, by setting the distance L between the tip nozzle 31 and the melting tank 101 to be a certain distance or less, Since it is possible to suppress the interference with the air which is turned over after hitting the melting tank 101, the thickness of the boundary layer can be effectively reduced.
Therefore, also in this modification, the cooling efficiency is low, the cooling efficiency is good, and the stable cooling effect is obtained.

The glass substrate manufactured in the above-described embodiment of the present invention is suitably used, for example, as a glass substrate for a liquid crystal display or a glass substrate for an organic EL display. In addition, the glass substrate can also be used as a cover glass for a display or a casing of a mobile terminal device, a touch panel, or a glass substrate or a cover glass for a solar cell. In particular, it is suitable for glass substrates for liquid crystal displays. Among them, it can be suitably used for products requiring a high temperature treatment in the panel manufacturing process, such as LTPS (low temperature polysilicon)/TFT, oxide semiconductor/TFT, etc., which are required to have particularly small heat shrinkage.

Further, the length in the width direction and the length direction of the glass substrate manufactured in the present invention is, for example, 500 mm to 3500 mm, preferably 1000 mm to 3500 mm, and more preferably 2000 mm to 3500 mm.
Moreover, the thickness of the glass substrate manufactured in the present invention is, for example, 0.01 mm to 1.0 mm. Preferably, it is 0.1 mm to 0.7 mm.

(Composition of glass substrate)
As the glass composition of the glass substrate for the above-mentioned use, aluminosilicate glass, boroaluminosilicate glass, non-alkali glass, and slightly alkaline glass, for example, the following can be preferably mentioned. In addition, the content rate display of the composition shown below is mol %.
_{SiO 2 55~75%, Al 2 O} 3 5~20%, B 2 O 3 0~15%, RO 5~20% ( wherein, R is Mg, Ca, among Sr and Ba, contained in the glass substrate all _{elements), R '2 O 0~0.4%} ( provided that, R' is Li, among the Na and K, all the elements contained in the glass substrate).
The strain point of the molten glass used in the present invention may be 650°C or higher, more preferably 680°C or higher.
Further, for example, the liquidus viscosity of the glass substrate is 10 ^4.3 poise to 10 ^6.7 poise.
Of course, in the present invention, the glass composition of the glass substrate is not limited.

Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments and various modifications and changes may be made without departing from the gist of the present invention. ..

10 Transfer Pipe 20 Electrode 21 Power Supply Terminal 30 Cooling Means 31 Tip Nozzle 31c Compressor Nozzle 31f Fan Nozzle 40 Supporting Member 50 Heat Dissipation Amount Adjusting Member 100 Melting Device 101 Melting Tank 102 Clarifying Tank 103 Stirring Tank 104 First Transfer Pipe 105 Second Transfer Pipe 106 Third transfer pipe 110 Melting tank wall surface 112 Electrode 200 Molding device 210 Molded body 212 Supply groove 213 Lower end 220 Atmosphere partition member 230 Cooling roller 240 Molding furnace 250 Gradual cooling furnaces 250a to 250d Conveying roller 300 Cutting device

Claims (4)

A method for manufacturing a glass substrate, which comprises transferring a molten glass obtained by melting a glass raw material to a forming furnace to manufacture a glass substrate,
A processing tank or a transfer pipe for flowing the molten glass from the upstream side to the downstream side,
At least a pair of electrodes provided in the treatment tank or the transfer pipe, respectively, to heat the molten glass in the treatment tank or the transfer pipe by applying an electric current to the treatment tank or the transfer pipe to heat by heating.
Cooling means for cooling at least one of the processing tank, the transfer pipe and the electrode by air cooling,
The cooling means is arranged so that the thickness of the boundary layer formed between the processing tank, the transfer pipe or the electrode and the air layer around them is equal to or less than a predetermined reference thickness with respect to the boundary layer. And apply a first wind pressure, and then apply a second wind pressure weaker than the first wind pressure to cool at least one of the processing tank, the transfer pipe, and the electrode.
The cooling means applies a first wind pressure from the horizontal direction to the boundary layer so as to suppress the buffering of the wind pressure applied to the boundary layer, and then the thickness of the boundary layer is equal to or less than the reference thickness. A method for manufacturing a glass substrate, characterized in that a second wind pressure is applied from the same direction as the horizontal direction so as to maintain the temperature, and the first wind pressure and the second wind pressure are alternately applied for air cooling. The method for manufacturing a glass substrate according to claim 1, wherein the reference thickness is 10 to 20 mm . The method for manufacturing a glass substrate according to claim 1, wherein the first wind pressure applied to the boundary layer is 100 kPa or more. The said cooling means is provided with the compressor which discharges high pressure air, and the fan which discharges low pressure air, The manufacturing method of the glass substrate as described in any one of Claim 1 thru|or 3 characterized by the above-mentioned.

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