JP2015124111A - Manufacturing method for glass substrate, and glass substrate manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a glass substrate and a glass substrate manufacturing method, which suppress the volatilization of a platinum group metal from molding equipment thereby to prevent a foreign substance of a volatilized platinum group metal from contaminating a sheet glass.SOLUTION: A manufacturing method comprises: a melting step of melting a glass material into molten glass; and a molding step of molding the molten glass into sheet glass in a molding furnace by using molding equipment made at least partially of a platinum group metal by a down-draw method. The manufacturing method is characterized in that a spray deposit film of a refractory material is formed in at least such a portion of the area to contact with the vapor phase space in said molding furnace as belongs to the portion of a platinum group metal of said molding equipment.

Description

  The present invention relates to a glass substrate manufacturing method and a glass substrate manufacturing method.

In the method of manufacturing a glass substrate using the downdraw method, a forming step of forming molten glass into sheet glass is performed. In the molding process, molten glass is supplied to a molding machine arranged in the molding furnace, and then flows down from the molded body of the molding apparatus, and is drawn into a sheet glass by pulling it with a roller arranged on the downstream side of the molding furnace. (For example, Patent Document 1).
Some conventional molding apparatuses are made of platinum or a platinum alloy in order to increase heat resistance. For example, a molding apparatus is known that is mounted on a molded body and includes a guide made of platinum or a platinum alloy. The guide has a function of restricting the spread of the molten glass flowing out of the molded body in the width direction (direction perpendicular to the flowing direction of the molten glass) by being attached to both ends in the longitudinal direction of the molded body.

JP 2010-189220 A

  It turned out that a foreign material may mix in the shape | molded sheet glass.

  An object of the present invention is to provide a glass substrate manufacturing method and a glass substrate manufacturing method that suppress volatilization of platinum group metal from a molding apparatus and prevent foreign substances of the volatilized platinum group metal from being mixed into sheet glass. To do.

  The inventor has repeatedly investigated the cause of foreign matter mixing into the surface of the sheet glass, and as a result, the portion made of a platinum group metal in the forming apparatus is oxidized by being exposed to a high-temperature atmosphere in the forming furnace. It has been clarified that the volatilized platinum group metal is agglomerated in the forming furnace and dropped onto the molten glass to adhere to the glass surface and be mixed into the sheet glass.

One embodiment of the present invention is a method for manufacturing a glass substrate.
[1] The manufacturing method includes a melting step of melting a glass raw material to produce a molten glass,
Forming a molten glass in a forming furnace, and forming the sheet glass into a sheet glass by a down draw method using a forming device at least part of which is made of a platinum group metal,
A sprayed film of a refractory compound is provided in at least a part of a region in contact with the gas phase space in the molding furnace in a portion made of a platinum group metal of the molding apparatus.

[2] The sprayed film is provided so as to be in contact with the gas phase space in the molding furnace and include a region where the temperature is highest among the portions made of platinum group metal of the molding apparatus. ] The manufacturing method of the glass substrate of description.

[3] The molding apparatus includes: a molded body having a shape extending in one direction; and a platinum group metal cap member fitted to both ends of the molded body in a longitudinal direction so as to cover an outer peripheral wall surface of the molded body. Have
The said cap member is a manufacturing method of the glass substrate as described in [1] or [2] in which the said sprayed film is provided in at least one part of the area | region which contact | connects the gaseous-phase space in the said molding furnace.

[4] The method for manufacturing a glass substrate according to any one of [1] to [3], wherein the sprayed film is formed in all regions of the cap member except a region where the molten glass contacts.

Another embodiment of the present invention is a glass substrate manufacturing apparatus.
[5] The glass substrate manufacturing apparatus includes a melting apparatus that melts a glass raw material to produce a molten glass;
A molding device for molding molten glass into sheet glass in a molding furnace, comprising at least a molding device made of a platinum group metal,
A sprayed film of a refractory compound is provided in at least a part of a region in contact with the gas phase space in the molding furnace in a portion made of a platinum group metal of the molding apparatus.

  According to the glass substrate manufacturing method and the glass substrate manufacturing method of the above-described aspect, it is possible to suppress the volatilization of the platinum group metal from the molding apparatus and to prevent the volatilized platinum group metal from being mixed into the sheet glass. .

It is a figure which shows an example of the process of the manufacturing method of the glass substrate of this embodiment. It is a figure which shows typically an example of the apparatus which performs the melting process-cutting process in this embodiment. (A) is the figure which decomposed | disassembled the shaping | molding apparatus used by this embodiment, and was seen from the side. (B) is the figure which looked at the shaping | molding apparatus from the side. It is an external appearance perspective view which shows one cap member of a shaping | molding apparatus. It is the BB sectional view taken on the line of FIG. It is the sectional view on the AA line of FIG.

Hereinafter, the glass substrate manufacturing method and glass substrate manufacturing apparatus of the present embodiment will be described. Drawing 1 is a figure showing an example of a process of a manufacturing method of a glass substrate of this embodiment.
Platinum or a platinum alloy described below is a platinum group metal, and includes platinum, ruthenium, rhodium, palladium, osmium, iridium, and an alloy of two or more metals selected from these.

  The glass substrate manufacturing method includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a molding step (ST4), a slow cooling step (ST5), and a cutting step (ST6). , Mainly.

  The melting step (ST1) is performed by a melting apparatus. In the melting step, molten glass is made by introducing a glass raw material to the liquid surface of the molten glass stored in the melting apparatus. In addition, it is preferable that a clarifier is added to the glass raw material. As the fining agent, tin oxide is preferably used from the viewpoint of reducing the environmental load.

  The clarification step (ST2) is performed by a clarification device to clarify the molten glass. Specifically, the gas component contained in the molten glass is released from the molten glass, or the gas component is absorbed into the molten glass.

  In the homogenization step (ST3), the molten glass in the stirring device supplied through the pipe extending from the refining device is stirred using a stirrer to homogenize the molten glass.

The forming step (ST4) and the slow cooling step (ST5) are performed in a forming unit including a forming apparatus.
In the forming step (ST4), the molten glass is formed into a sheet glass to make a flow of the sheet glass. For forming, a known method such as a downdraw method, a float method, or a rollout method can be used. In the molding process described below, a case where molding is performed using an overflow downdraw method as an example of the downdraw method will be described.
In the slow cooling step (ST5), the sheet glass that has been formed and flowed is cooled to a desired thickness so that internal distortion does not occur and warpage does not occur.

  In a cutting process (ST6), a plate-shaped glass plate is obtained by cutting the sheet glass supplied from the forming device into a predetermined length in the cutting device. The cut glass plate is further cut into a predetermined size to produce a glass substrate of a target size.

  FIG. 2 is a diagram schematically illustrating an example of an apparatus that performs the melting step (ST1) to the cutting step (ST6) in the present embodiment. As shown in FIG. 2, the apparatus mainly includes a molten glass production unit 100, a molding unit 200, and a cutting unit 300. The molten glass production unit 100 includes a melting device 101, a clarification device 102, a stirring device 103, and glass supply tubes 104, 105, and 106. The molding unit 200 has a molding device 210.

The melting apparatus 101 of the example shown in FIG. 2 melts a glass raw material, and makes a molten glass.
The clarification apparatus 102 performs at least defoaming treatment by passing an electric current between the electrode plates while passing the molten glass MG in a clarification tube made of platinum or a platinum alloy or the like, for example, by energizing and heating the clarification tube.
The agitator 103 agitates the molten glass MG with a stirrer 103a and homogenizes it.
The forming unit 200 forms the molten glass MG processed by the refining device 102 and the stirring device 103 by the overflow down draw method using the forming device 210 in the forming furnace 250 to obtain a sheet glass SG. In FIG. 2, the forming apparatus 210 is shown in a simplified manner. Furthermore, in the slow cooling furnace 260, the sheet glass SG is gradually cooled so that plate thickness deviation, distortion, and warpage do not occur in the sheet glass SG. The forming furnace 250 and the slow cooling furnace 260 are provided adjacent to each other in the direction in which the sheet glass SG flows.
The cutting device 300 cuts the slowly cooled sheet glass SG to form a glass substrate.

(Molding process and molding equipment)
3A and 3B show a molding apparatus 210. FIG.
The molding apparatus 210 includes a molded body 220 and cap members 230 and 240 attached to the molded body 220. 3A is an exploded view of the molded body 220 with the cap members 230 and 240 removed, and FIG. 3B shows a state in which the cap members 230 and 240 are attached to the molded body 220 and assembled. FIG. In FIG. 3, a thermal spray film to be described later is not shown.

As shown in FIG. 3, the molded body 220 is a long structure having a lower end 220a extending in a direction parallel to the width direction of the sheet glass (horizontal direction) and an upper surface 211 inclined with respect to the lower end 220a. is there. The molded body 220 has a wedge-shaped cross section cut in a direction perpendicular to the longitudinal direction (left-right direction in FIG. 3). In addition to the upper surface 211, the molded body 220 has end surfaces 212 and 213 and side surfaces 214 and 215 connected to the upper surface 211. The upper surface 211 is inclined so that the height position in the molding furnace 250 gradually decreases in the direction from the end surface 212 to the end surface 213. On the upper surface 211, a groove 211a that opens upward is formed. The groove 211a opens in the end surface 212. In the groove 211a, the height position of the groove bottom gradually increases in the direction from the end surface 212 to the end surface 213, and the groove depth gradually decreases. The side surfaces 214 and 215 are connected at the lower ends to form the lower end 220a of the molded body 220.
The compact 220 is made of, for example, a fired refractory such as a zirconia refractory or a high alumina refractory, or a non-fired refractory such as a graphite brick. Among them, it is preferably made of a zirconia refractory in terms of excellent heat resistance.

  The cap members 230 and 240 are members that are fitted to both ends of the molded body 220 in the longitudinal direction (the direction in which the lower end 220a extends) so as to cover the outer peripheral wall surface of the molded body 220. Among these, the cap member 230 includes an end surface cover portion 231 and a side surface cover portion 232 as shown in FIG. 4. FIG. 4 is an external perspective view of the cap member 230.

The end surface cover portion 231 is a flat portion facing the end surface 212 of the molded body 220. A glass supply pipe 106 is connected to the end surface cover portion 231, and a hole 231 a through which the molten glass supplied from the glass supply pipe 106 passes is provided. Note that the portion of the glass supply pipe 106 that extends in the molding furnace 250 constitutes the molding apparatus 210 together with the molded body 220 and the cap members 230 and 240. 3, 4, and FIGS. 5 and 6 to be referred to later, the glass supply tube 106 as the forming apparatus 210 is shown only in a portion connected to the end surface cover portion 231. The molten glass supplied from the glass supply pipe 106 is supplied into the groove 211 a of the molded body 220 through the end surface cover portion 231.
The side cover portion 232 is a portion that faces the upper surface 211 and the side surfaces 214 and 215 of the molded body 220 and has a shape that covers the outer peripheral wall surface of the molded body 220. The side cover part 232 is formed with an edge part 233 extending from the end of the side cover part 232 in the direction away from the glass supply pipe 106 in the direction away from the molded body 220. In FIG. 3, the edge portion 233 is not shown. The edge portion 233 restricts the spread in the width direction of the molten glass that overflows from the upper surface 211 of the molded body 220 and flows along the wall surfaces of the side surfaces 214 and 215 in the molding step. In addition, in this specification, the glass after flowing along the wall surfaces 214 and 215 of the molded body 220 and joining at the lower end 220a is referred to as sheet glass, and the glass before joining at the lower end 220a is referred to as molten glass.

The cap member 240 is configured in substantially the same manner as the cap member 230 except that the glass supply pipe 106 is not connected and a hole through which molten glass passes is not provided, and has an end face cover portion and a side cover portion. doing. The side cover portion of the cap member 240 has an edge portion.
The cap members 230 and 240 and the glass supply pipe 106 are made of platinum or a platinum alloy.

(Sprayed film)
On the surfaces of the cap members 230 and 240 and the glass supply pipe 106, a spray coating of a refractory compound is provided. Among these, the sprayed film 320 provided on the cap member 230 is provided on at least a part of the surface of the cap member 230 in contact with the gas phase space in the molding furnace 250. A sprayed film 330 is provided on the surface of the glass supply pipe 106. 5 and 6 show a cap member 230 provided with a sprayed film 320 and a glass supply pipe 106 provided with a sprayed film 330. 5 is a cross-sectional view taken along line BB in FIG. 6 is a cross-sectional view taken along line AA in FIG. 4 to 6, the thickness of the sprayed film 320 with respect to the plate thickness of the cap member 230 and the thickness of the sprayed film 330 with respect to the glass supply pipe 106 are exaggerated for convenience.

Since the sprayed film 320 is provided in at least a part of the region in contact with the gas phase space of the molding furnace 250, platinum or a platinum alloy from the cap member 230 in the molding process is compared with the case where the sprayed film 320 is not provided. The volatilization of etc. is suppressed. The gas phase space is a space surrounded by a partition wall 255 (see FIG. 2) for spatially partitioning the inside of the forming furnace 250 and the slow cooling furnace 260 and the inner wall of the forming furnace 250, and the forming apparatus 210 and the molten glass. In contact with the sheet glass. In the molding step, the temperature in the molding furnace 250 is, for example, 1100 to 1350 ° C. When a cap member made of platinum or a platinum alloy is exposed to such a high temperature atmosphere, the cap member is easily oxidized and volatilized by oxygen in the atmosphere. In this embodiment, the cap member 230 is thermally sprayed with a refractory compound. Since the film 320 is provided, the cap member 230 is not exposed to a high temperature atmosphere in the region where the sprayed film 320 is provided, and volatilization of platinum or a platinum alloy from the region is suppressed.
The cap member 240 and the glass supply pipe 106 are also provided with a thermal spray film in at least a part of the region in contact with the gas phase space of the molding furnace 250, so that the platinum from the cap member 240 and the glass supply pipe 106 in the molding process. Or volatilization of platinum alloy or the like is suppressed. The sprayed film 330 provided on the glass supply pipe 106 is provided in all regions in contact with the gas phase space of the molding furnace 250. The sprayed film 330 provided on the glass supply pipe 106 is provided so as to be connected to the sprayed film 320.

  The sprayed film 320 includes a region of the surface of the cap member 230 that is in contact with the gas phase space in the molding furnace 250 and has the highest temperature among the portions of the molding apparatus 210 made of platinum or a platinum alloy. It is preferable to be provided. Specifically, such a region is a portion 232a (see FIG. 6) of the side cover portion 232 that faces the upper surface 211 of the molded body 210, and a peripheral region thereof. In the molding furnace 250, a heater (not shown) for heating the molten glass supplied to the molded body 220 from above is disposed so as to face the upper surface 211 of the molded body 220. During the molding process, Since these regions receive a lot of heat from the heater, the temperature becomes the highest. In the present embodiment, by providing the sprayed film 320 in such a region, volatilization of platinum or a platinum alloy from the cap member 230 can be effectively suppressed. The region where the temperature of the cap member 230 is highest can be specified as a region where the difference from the maximum temperature is within 10 ° C., for example. In the case where the thermal spray film 320 is provided only in the region where the temperature of the cap member 230 is the highest, the thermal spray film 320 is not provided in any other region, thereby effectively reducing the volatilization of platinum or a platinum alloy or the like while suppressing costs. Can be suppressed.

  The sprayed film is provided so as to include at least a region that is in contact with the gas phase space in the molding furnace 250 and has the highest temperature in the entire molding apparatus 210 among the portions of the molding apparatus 210 made of platinum, platinum alloy, or the like. The thermal spray film may be provided only in the part where the temperature is highest in each of the cap member 230, the cap member 240, and the glass supply pipe 106. Like the thermal spray film 320 provided on the cap member 230, the thermal spray film of the cap member 240 has the highest temperature at the portion of the side cover portion that faces the upper surface 211 of the molded body 210. Although it is preferable to be provided so as to include a region, the surface (inner surface) facing the upper surface 211 of the molded body 210 among the portions may not be provided because molten glass contacts in the molding process. preferable.

  It is preferable that the thermal spray film 320 is formed in all the areas | regions except the area | region where molten glass contacts among the cap members 230. FIG. Thereby, in almost all areas of the surface of the cap member 230 exposed to the gas phase space in the molding process, volatilization of platinum or platinum metal or the like can be suppressed, and the molten glass is in contact with the sprayed film 320. It is possible to avoid the sprayed film 320 from being melted and mixed into the molten glass. In addition, in the area | region where molten glass contacts, in addition to the area | region where molten glass always contacts in a formation process, the area | region which does not always contact but may contact, for example, the end surface cover part 231 among the surfaces of the edge part 233 A lower region including the vicinity of the lower end 220a of the molded body 220 on the surface facing the side is also included.

The refractory compound is not particularly limited as long as it can withstand high temperatures and does not easily volatilize. For example, oxides such as ceramics, nitrides, silicides, carbides, and combinations thereof can be used. From the viewpoint of reducing volatilization of platinum or a platinum alloy in a molding apparatus for producing a glass substrate for a flat panel display, a refractory oxide is preferable. For example, it is preferably stabilized with a Zr, Al, Mg and / or Y compound.
The method of thermal spraying is not particularly limited, but flame spraying and plasma spraying can be used. In order to effectively suppress the volatilization of platinum or a platinum alloy, it is preferable to use plasma spraying.
In order to effectively suppress volatilization of platinum or a platinum alloy while suppressing cost, the sprayed film is preferably formed to a thickness of 50 μm to 800 μm, and more preferably 100 μm to 500 μm.

  According to the present embodiment, the sprayed film of the refractory compound is provided on at least a part of the region of the molding apparatus 210 that is made of platinum or a platinum alloy or the like and in contact with the gas phase space in the molding furnace 250. Thus, in the molding process, the volatilization of platinum or a platinum alloy from the region is suppressed. Thereby, it is possible to suppress volatilized platinum or a platinum alloy or the like from being aggregated in the molding furnace 250, for example, in a region having a low temperature, and falling on the molten glass to be mixed into the molten glass. In addition, adhering to the surface of molten glass is also included when mixing with molten glass.

  The molding apparatus used in the present embodiment is not limited as long as at least a part thereof is composed of platinum or a platinum alloy, and any part of the molding apparatus may be composed of platinum or a platinum alloy. For example, the molded body 220 and other members included in the molding apparatus 210 may include a portion made of platinum or a platinum alloy. Although not shown in the drawings, the other member is, for example, a block shape that supports the molded body 220 from below and clamps the molded body 220 so as to be pressed from both sides in the longitudinal direction via the cap member 230 and the cap member 240. These support members can be mentioned.

(Glass composition)
The present invention is suitable when it is necessary to keep the inside of the molding furnace at a high temperature. Specifically, it is suitable when the inside of the molding furnace is 1000 ° C. or higher, more suitable when it is 1200 ° C. or higher, and particularly suitable when it is 1300 ° C. or higher.
When manufacturing a glass substrate using a glass having a high devitrification temperature, it is necessary to keep the inside of the molding furnace at a high temperature. Therefore, the present invention can be used when manufacturing a glass substrate using a glass having a high devitrification temperature. Is suitable. Specifically, the present invention is suitable for manufacturing a glass substrate having a devitrification temperature of 1000 ° C. or higher, and more preferable for manufacturing a glass substrate having 1160 ° C. or higher.

In addition, since alkali-free glass or glass containing a trace amount of alkali metal has a high devitrification temperature, the present invention is suitable for manufacturing a glass substrate composed of alkali-free glass or glass containing a trace amount of alkali. Yes. As an example of the alkali-free glass, a glass substrate having the following composition range is shown by mass%.
SiO _2: 50~70%,
Al ₂ O _3: 0~25%,
B ₂ O ₃ : 1 to 15%,
MgO: 0 to 10%,
CaO: 0 to 20%,
SrO: 0 to 20%,
BaO: 0 to 10%,
RO: 5 to 30% (where R is the total amount of Mg, Ca, Sr and Ba),
Alkali-free glass containing
As described above, the glass substrate may be a glass containing a trace amount of alkali metal containing a trace amount of alkali metal. When an alkali metal is contained, the total of R ′ ₂ O is 0.10% or more and 0.5% or less, preferably 0.20% or more and 0.5% or less (where R ′ is selected from Li, Na, and K) It is preferable that the glass substrate contains at least one kind. Of course, the total of R ′ ₂ O may be less than 0.10%. That is, the present invention is suitable for manufacturing a flat panel display using an alkali-free glass or a glass substrate with a small amount of alkali.
The present invention is suitably used for, for example, a glass substrate for liquid crystal display, a glass substrate for organic EL display, and a cover glass. In addition, the present invention can also be used as a display for a portable terminal device, a cover glass for a casing, a touch panel plate, a glass substrate of a solar cell, or a cover glass. Further, the present invention is suitable for a glass substrate for a liquid crystal display using a polysilicon TFT.

(Experimental example)
In order to confirm the effect of the present embodiment, a molding apparatus including a portion made of a platinum group metal was used to perform a molding process using an overflow downdraw method, and molten glass was molded. As the molding apparatus, a molded body made of zirconia refractory, a cap member made of platinum alloy, and a glass supply pipe made of platinum alloy were used. As shown in FIGS. 4 to 6, a sprayed coating was provided on the surface of the cap member and the glass supply tube. The sprayed film was provided by plasma spraying using Zr oxide. The glass composition of the molten glass was the composition of the alkali-free glass. The molding step was performed at a temperature in the molding furnace of 1200 to 1300 ° C. The temperature of the molten glass in the forming step was 1200 to 1350 ° C. After the molding process, the glass substrate is slowly cooled and cut to produce a plurality of glass substrates measuring 2270 mm in length and 2000 mm in width, and the number of foreign matters mixed on the surface of the glass substrate using a laser microscope is measured for 100 randomly extracted ones. The number was counted and the average value was determined (Example).
On the other hand, except that the thermal spray film was not provided on the cap member and the glass supply pipe, the molding process was performed in the same manner as in the example, and the number of foreign matters was counted (comparative example).
As a result, the number of foreign matters per unit area of the glass substrate is reduced in the example compared with the comparative example, and the spraying film is provided on the cap member and the glass supply pipe, so that the platinum is formed in the molding furnace. It was confirmed that the volatilization of was suppressed.

  The glass substrate manufacturing method and glass substrate manufacturing apparatus of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the gist of the present invention. Of course.

DESCRIPTION OF SYMBOLS 101 Melting apparatus 106 Glass supply pipe 210 Molding apparatus 220 Molded body 230, 240 Cap member 250 Molding furnace 320 Thermal spray film

Claims (5)

A melting process for melting glass raw material to produce molten glass;
Forming a molten glass in a forming furnace, and forming the sheet glass into a sheet glass by a down draw method using a forming device at least part of which is made of a platinum group metal,
A method for producing a glass substrate, wherein a sprayed film of a refractory compound is provided in at least a part of a region in contact with a gas phase space in the molding furnace in a portion made of a platinum group metal of the molding apparatus.   2. The sprayed film according to claim 1, wherein the sprayed film is provided so as to be in contact with a gas phase space in the molding furnace and include a region where the temperature is highest in a portion made of a platinum group metal of the molding apparatus. Glass substrate manufacturing method. The molding apparatus includes a molded body having a shape extending in one direction, and a platinum group metal cap member fitted to cover both outer circumferential wall surfaces of the molded body at both ends in the longitudinal direction of the molded body.
The said cap member is a manufacturing method of the glass substrate of Claim 1 or 2 with which the said sprayed film is provided in at least one part of the area | region which contact | connects the gaseous-phase space in the said molding furnace.   The said thermal spray film is a manufacturing method of the glass substrate in any one of Claim 1 to 3 currently formed in all the area | regions except the area | region where molten glass contacts among the said cap members. A melting device that melts glass raw materials to produce molten glass;
A molding device for molding molten glass into sheet glass in a molding furnace, comprising at least a molding device made of a platinum group metal,
An apparatus for producing a glass substrate, wherein a sprayed film of a refractory compound is provided in at least a part of a region in contact with a gas phase space in the molding furnace in a portion made of a platinum group metal of the molding device.

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