TWI389862B - Glass manufacturing apparatus and manufacturing method thereof - Google Patents

Description

Glass manufacturing device and manufacturing method

The present invention relates to a glass manufacturing apparatus and a glass manufacturing method using the same.

As a constituent material of the glass manufacturing apparatus (melting tank, clarification tank, stirring tank, and the like), platinum, or platinum and other precious metal elements, for example, rhodium (Rh), gold (Au), or iridium (Ir) are used. Or an alloy of ruthenium (Ru) (hereinafter, in the present specification, platinum and a platinum alloy are collectively referred to as a platinum material). As a platinum material which can be used as a constituent material of the material, the platinum material has a high melting point, and does not deteriorate due to the formation of an oxide layer in the atmosphere, and is not easily deformed or damaged except for the operation of the device, and chemical stability. It is also excellent, and it is not easy to contaminate the molten glass.

The device temperature of the glass manufacturing step varies depending on the processing content, and is in a high temperature environment of about 900 ° C or higher. Due to the above characteristics, the platinum material does not contaminate the molten glass inside the device even in such a high temperature environment, and can maintain sufficient durability for a long period of time.

However, in a glass manufacturing apparatus using a platinum material, there is a problem that air bubbles due to moisture in the molten glass are generated at the interface of the platinum material at the time of glass production. This is because hydrogen contained in the molten glass is dissociated by contact with the platinum material, and hydrogen and oxygen are generated. It is considered that hydrogen is released to the outside through the platinum material, and oxygen cannot pass through the platinum material. When the oxygen concentration remaining in the molten glass exceeds the solubility limit, bubbles are generated at the interface of the platinum material (Patent Documents 1 to 4 for reference). . When the bubbles generated in this way remain in the glass product to be produced, the quality of the glass product is lowered.

In particular, in the case of an alkali-free glass substrate which does not substantially contain an alkali metal oxide used for a liquid crystal display (LCD), an organic electroluminescence, an OLED, an inorganic electroluminescence, a display, or the like, the alkali-free glass is high. The melting point is highly viscous compared to the alkali-containing glass, so that bubbles in the molten glass are hard to float, and it is difficult to suppress the bubbles.

In order to solve this problem, it is proposed to provide a dense hydrogen-impermeable film on the outer surface of the platinum material (see Patent Documents 1 to 4 for reference). Examples of the material of the dense hydrogen-impermeable coating film include glass, ceramics, and metal.

[Patent Document 1] Japanese Patent Publication No. 2004-523449

[Patent Document 2] International Publication No. WO2006/030738

[Patent Document 3] International Publication No. WO2005/063634

[Patent Document 4] Special Table 2006-522001

In the dense film of hydrogen impermeability proposed in the prior art, a dense film is formed by coating a hydrogen impermeable material with a molecular diameter or an ion diameter, and a hydrogen-impermeable material is passed through the film to prevent hydrogen from being released to the outside. However, in the manufacture of glass, the generation of bubbles cannot be sufficiently reduced. It is considered that the film provided on the outer surface of the platinum material may not be able to be a desired dense film or a film used in a high-temperature environment, or the film may be peeled off due to a difference in thermal expansion coefficient between the platinum material and the film. Released to the outside through the membrane .

In order to solve the above problems, the present invention has an object of providing a glass manufacturing apparatus and a glass manufacturing method which are effective in preventing the generation of bubbles during the production of glass and preventing the remaining bubbles of the glass product to be produced.

In order to achieve the above object, the present invention is a glass manufacturing apparatus having a member made of platinum or a platinum alloy in contact with molten glass, provided on the back side of the surface of the member in contact with the molten glass, formed with oxidation relative to oxidation The total amount of the aluminum-based ceramic particles contains Fe in an amount of 0.2 to 5% by mass in terms of Fe ₂ O ₃ , and has a change point of Fe redox (Fe ²⁺ /Fe ²⁺ +Fe ³⁺ ) in the molten glass temperature range. The layer of alumina-based ceramic particles is a glass manufacturing apparatus characterized by the following.

In the glass manufacturing apparatus of the present invention, it is preferable that the member made of platinum or a platinum alloy is a container for accommodating molten glass.

In the glass manufacturing apparatus of the present invention, the molten glass temperature range is preferably from 1,250 to 1,650 °C.

In the glass manufacturing apparatus of the present invention, the alumina-based ceramic particles preferably contain 10% by mass or more of mullite.

Further, the present invention provides a glass manufacturing method using the glass manufacturing apparatus of the present invention.

In the glass production method of the present invention, the glass produced is represented by mass percentage based on the oxide (the total of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, SrO, and BaO is 100%) To contain: SiO ₂ 50~70%, Al ₂ O ₃ 5~25%, B ₂ O ₃ 1~20%, MgO 0~10%, CaO 0~17%, SrO 0~17%, BaO 0~ 20%, MgO + CaO + SrO + BaO 8 ~ 30% of alkali-free glass is preferred.

According to the glass manufacturing apparatus and the glass manufacturing method of the present invention, generation of bubbles at the platinum interface or the platinum alloy interface in contact with the molten glass can be effectively and stably prevented during the production of the glass. As a result, it is possible to produce a glass of good quality in which bubble residue is suppressed.

In particular, the alkali-free glass produced by the glass manufacturing apparatus and the glass manufacturing method of the present invention is suitable for substrate glass for flat panel display, in particular, liquid crystal display (LCD), organic electroluminescence, display (OLED), and Substrate glass for flat panel displays such as electroluminescence and display.

[Best Mode for Carrying Out the Invention]

Hereinafter, a glass manufacturing apparatus according to the present invention will be described.

Fig. 1 is a schematic view showing an example of the configuration of a glass manufacturing apparatus. Figure 1 shows The glass manufacturing apparatus 1 has a melting tank 2, a clarification tank 3 provided on the downstream side of the melting tank 2, a stirring tank 4 provided on the downstream side of the clarification tank 3, and a forming device 5 provided on the downstream side of the stirring tank 4, and a melting tank 2. The clarification tank 3, the agitation tank 4, and the forming apparatus 5 are connected via conduits (contact passages) 6, 7 and 8 which are common to the flow of the molten glass.

The melting tank 2 is provided with a burner, an electrode, etc., and the glass raw material can be melted. On the downstream side of the melting tank 2, an outlet of molten glass is formed, and the melting tank 2 and the clarification tank 3 are connected via a conduit 6 having the outlet end as an upstream end.

The clarification tank 3 is a portion where the glass is mainly clarified, and the fine bubbles contained in the molten glass are floated by the clarified gas discharged from the clarifying agent, and are removed by the molten glass. An outlet of molten glass is formed on the downstream side of the clarification tank 3, and the clarification tank 3 and the stirring tank 4 are connected via the duct 7 which is the upstream end of this outlet.

The agitation tank 4 is a portion where the molten glass is mainly stirred and homogenized via a stirrer or the like. An outflow port is formed on the downstream side of the agitation vessel 4, and the agitation vessel 4 and the forming device 5 are connected via a conduit 8 that makes the outlet port an upstream end.

The molding device 5 is a portion that mainly shapes the glass into a desired shape, and is appropriately selected in accordance with the shape of the glass product to be produced. For example, when the glass product is a glass substrate for a flat panel display, a float forming apparatus, a pull-down forming apparatus, or the like is used.

In the glass manufacturing apparatus 1 shown in Fig. 1, the contact with the molten glass of the melting tank 2 to the conduit 8 is required to have a heat resistance to a high temperature environment and corrosion resistance to molten glass, and a platinum material (i.e., platinum) is used. Or platinum alloy) is preferred.

The glass manufacturing apparatus of the present invention has a member made of platinum or a platinum alloy which is in contact with the molten glass, and is formed on the back side of the surface of the member which is in contact with the molten glass, and contains a total amount with respect to the alumina-based ceramic particles. a layer of alumina-based ceramic particles having a Fe ₂ O ₃ conversion of 0.2 to 5% by mass of Fe and having a point of change in Fe redox (Fe ²⁺ /Fe ²⁺ +Fe ³⁺ ) in the molten glass temperature range It is characterized by it.

Here, as a specific example of the member made of platinum or a platinum alloy which is in contact with the molten glass, a container made of platinum or a platinum alloy containing the molten glass may be mentioned. However, the present invention is not limited thereto, and includes a member made of platinum or a platinum alloy which is in contact with the molten glass when the glass manufacturing apparatus is used. In the present specification, a specific example of a member made of platinum or a platinum alloy that is in contact with the molten glass is exemplified by a container made of platinum or a platinum alloy in which molten glass is housed, and the container containing the molten glass is used. The member made of a platinum or platinum alloy is described as a member made of a platinum or platinum alloy.

The container for accommodating the molten glass is a container that temporarily holds or stores the molten glass in the glass manufacturing step. One configuration example of the glass manufacturing apparatus 1 shown in FIG. 1 is a melting tank 2, a clarification tank 3, a stirring tank 4, and Catheters 6, 7, 8.

Further, in the glass manufacturing apparatus of the present invention, at least one of the containers for accommodating the molten glass is made of a platinum material, and the back side of the surface of the container made of the platinum material in contact with the molten glass, that is, the glass shown in Fig. 1 is used. In one configuration example of the apparatus, the above-described alumina-based ceramic particle layer is formed on the outside of the container wall surface made of a platinum material.

In the past, focusing on the molecular diameter or ion diameter of hydrogen, it is considered that a dense film is formed by coating or the like with a material that does not permeate hydrogen. However, the inventors of the present invention have diligently studied the results and found that the dense film formed by the material which does not permeate hydrogen, and the change in the valence of Fe (Fe ³⁺ →Fe ²⁺ ) contained in the alumina-based ceramic particles to the bubble residue The inhibition is effective.

The change in the valence of Fe is caused by an increase in the temperature of the platinum material due to an increase in the temperature of the molten glass (assuming that the temperature outside the container made of platinum material is almost the same as the temperature of the molten glass), and it is considered that the valence of Fe is changed, and then While the temperature of the platinum material is maintained constant, the residual effect of suppressing the bubbles is almost constant.

In the present invention, the alumina-based ceramic particle layer needs to contain a sufficient amount of Fe in order to exhibit the residual effect of suppressing the bubbles. Specifically, the alumina-based ceramic particles are preferably contained in an amount of 0.2 to 5% by mass in terms of Fe ₂ O ₃ based on the total amount of the alumina-based ceramic particles, and more preferably 0.5% by mass or more. However, when the amount of Fe is large, it does not mix into the crystal structure of the alumina-based ceramics, and the Fe ₂ O ₃ remains in hematite, so that the change point of the Fe redox increase described later is lowered. Therefore, the content of Fe is preferably 5% by mass or less in terms of Fe ₂ O ₃ .

Further, when Fe is contained in the alumina-based ceramic particles, it is necessary to easily change the valence from Fe ³⁺ to Fe ²⁺ when a glass manufacturing apparatus is used. Therefore, Fe contained in the alumina-based ceramic particles needs to have a change point of Fe redox (Fe ²⁺ /Fe ²⁺ +Fe ³⁺ ) rise in the molten glass temperature range. Temperature as the horizontal axis, Fe redox ^{(Fe 2+ / Fe 2+ + Fe} 3+) is plotted against the vertical axis, at a specific temperature, Fe redox ^{(Fe 2+ / Fe 2+ + Fe} 3+) abruptly rise. In this specification, this temperature is referred to as a point of change in Fe redox (Fe ²⁺ /Fe ²⁺ +Fe ³⁺ ) rise. More specifically, the point at which the first differential value of the approximate curve of the above graph starts to increase with an increase in temperature is referred to as a change point.

Further, Fe redox (Fe ²⁺ /Fe ²⁺ + Fe ³⁺ ) of the alumina-based ceramic particles can be obtained by a redox titration method. Specifically, the sample of the alumina-based ceramic particles is heated to a specific temperature at a rate of 300 ° C per hour, and maintained at a specific temperature for 1 hour, and then cooled to room temperature, and Fe ² is added to the solution in which the sample is dissolved in hydrofluoric acid. ⁺ indicator, the amount of Fe ²⁺ was determined by spectrometry. Further, after the measurement sample is dissolved in hydrofluoric acid, the Fe ³⁺ in the solution is reduced to Fe ²⁺ , and the amount of Fe ²⁺ is measured in the same manner as the above method to obtain Fe ³⁺ +Fe ^{2+ .} the amount.

When the change in the Fe redox (Fe ²⁺ /Fe ²⁺ +Fe ³⁺ ) rise is in the molten glass temperature range, when a glass manufacturing apparatus is used, more specifically, the wall made of platinum material in the container for accommodating the molten glass In the state of being in contact with the molten glass, the valence change (Fe ³⁺ → Fe ²⁺ ) of Fe contained in the alumina-based ceramic particles is likely to occur.

The molten glass temperature domain refers to the temperature domain experienced by the molten glass in the glass manufacturing step from melting to forming. The glass manufacturing apparatus 1 shown in Fig. 1 refers to a temperature range experienced by the molten glass from the melting tank 2 to the duct 8. The molten glass temperature range varies depending on the type of glass or the components of the glass manufacturing apparatus, but in the case of alkali-free glass, it is usually 1250 to 1650 °C. It is preferable to form the molten glass temperature range of each of the glass manufacturing apparatus containers mentioned later.

The alumina-based ceramic particles used in the present invention are heated in molten glass The degree range has a change point of Fe redox increase, and when the molten glass temperature range is 1250 to 1650 ° C, it is preferable to contain 10% by mass or more of mullite. The mullite content is more preferably 20% by mass or more, more preferably 30% by mass or more, and particularly preferably 40% by mass or more.

The alumina-based ceramic particles may be a crystal phase containing only mullite. However, when the mullite content satisfies the above range, the crystal phase may contain other crystal phases, and specifically, it may contain oblique zircon and steel jade. Further, as other components, zircon, sillimanite or the like may be contained.

The content of the glass phase in the alumina-based ceramic particles is preferably 50% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, and particularly preferably 10% by mass or less. When the content of the glass phase exceeds 50% by mass, the surface of the mullite phase is covered with a glass phase, and there is a tendency that the residual effect of suppressing the bubbles due to the change in the valence of Fe is not exhibited.

In the glass manufacturing apparatus of the present invention, the alumina side is formed on the back side of the surface of the container made of platinum material in contact with the molten glass, that is, on the outer side of the wall surface of the container (for example, the side surface and the bottom surface in the case of a crucible container). In the case of the ceramic particle layer, alumina-based ceramic particles are filled to a desired thickness on the outer side of the wall surface of the container. The thickness measurement exerts a residual suppression effect of the bubbles, preferably 1 mm or more, more preferably 2 mm or more. Further, if it is too thick, it is necessary to use ceramic particles more than necessary, and therefore it is preferably 40 mm or less. Specifically, a fire-resistant block is provided on the outer side of the wall surface of the container at a predetermined interval from the container, and alumina ceramic particles are filled in the gap between the container and the fire-resistant block. The fire-resistant block is fire-resistant and can retain alumina-based ceramic particles, and is not particularly limited, and is, for example, a fired refractory, specifically, such as alumina zircon, zircon, and tantalum. Stone, burned powder, alumina, magnesia, etc. However, alumina smelting is preferred from the viewpoints of ease of production (formability, processability, etc.) and cost of the refractory block.

Further, in the present invention, alumina-based ceramics using particles are easily filled on the outer side of the wall surface of a container made of a platinum material. Further, it can be pulverized to a particle diameter of about 2 mm or less, and does not mean that it can be adjusted to a specific particle size distribution.

The particle size in the present invention means the size of particles which can be sieved through the size. For example, when the particle diameter is 2 mm or less, it means a particle which passes through a sieve having a diameter of 2 mm. However, the shape of the ceramic particles may be spherical, square, amorphous, or the like. It is preferable to have a sufficient contact point with the periphery of the container to fill the ceramic particles, and it is preferable that the particle diameter is 2 mm or less. Further, it is preferable to prevent the splash at the time of filling, and it is preferable that the particle diameter is 10 μm or more.

In the present invention, the alumina-based ceramic particles filled on the outer side of the wall surface of the container made of a platinum material can be appropriately selected depending on the temperature of the molten glass accommodated in the container. The molten glass temperature of the glass manufacturing apparatus differs depending on the container made of each platinum material, that is, the constituent elements of the glass manufacturing apparatus made of each platinum material (the container in which the molten glass is accommodated). For example, in the case of the alkali-free glass, in the glass manufacturing apparatus 1 shown in FIG. 1, the molten glass temperature in the melting tank 2 is about 1400 to 1650 ° C, and the molten glass temperature in the clarification tank 3 is about 1300 to 1550 ° C, and the stirring tank 4 is used. The temperature of the molten glass is about 1250~1400 °C, the temperature of the molten glass in the duct 6 is about 1400~1600 °C, the temperature of the molten glass in the duct 7 is about 1300~1500 °C, and the temperature of the molten glass in the duct 8 is about 1250~1350 °C.

Further, according to the present invention, the outer surface of the wall of the container made of the platinum material constituting the glass manufacturing apparatus is filled with the Fe redox (Fe ²⁺ /Fe ²⁺ +Fe ³⁺ ) in the temperature range of the molten glass accommodated in the container. Alumina ceramic particles with changing points.

The method for producing the glass of the present invention is the same as the conventional method except that the glass manufacturing apparatus of the present invention described above is used. Further, the melting tank 2 of the glass manufacturing apparatus shown in Fig. 1 is put into a raw material which is adjusted to have a desired glass composition, and the molten glass obtained by heating and melting is sequentially passed through the conduit 6, the clarification tank 3, the conduit 7, and the stirring tank 4. The conduit 8 and the forming device 5 obtain a glass product of a desired shape.

According to the present invention, various glasses can be produced. An example of the alkali-free glass in the production of a suitable glass of the present invention is shown below. The alkali-free glass shown below is suitable as a substrate glass for a liquid crystal display (LCD).

The alkali-free glass is represented by mass percentage based on oxides, and contains: SiO ₂ 50 to 70%, Al ₂ O ₃ 5 to 25%, B ₂ O ₃ 1 to 20%, MgO 0 to 10%, and CaO. 0~17%, SrO 0~17%, BaO 0~20%, MgO+CaO+SrO+BaO 8~30%.

Further, the above mass percentage is represented by a total of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, SrO and BaO of 100%.

SiO ₂ is an essential component, and when it exceeds 70%, the meltability of glass is lowered, or it becomes easy to devitrify. It is preferably 64% or less. If it is less than 50%, the specific gravity increases, the strain point decreases, the coefficient of thermal expansion increases, and the chemical resistance decreases. It is preferably 55% or more.

Al ₂ O ₃ is necessary to suppress the phase separation of the glass or to increase the composition of the strain point (Strain Point). When it exceeds 25%, it becomes easy to devitrify, causing a decrease in chemical resistance. It is preferably 22% or less. Below 5%, the glass becomes easy to phase, or the strain point (Strain Point) decreases. It is preferably 10% or more.

B ₂ O ₃ is a component which makes the specific gravity small, improves the meltability of the glass, and makes it difficult to devitrify. When it exceeds 20%, the strain point (Strain Point) is lowered, the chemical resistance is lowered, or the volatilization is remarkable when the glass is melted, and the glass heterogeneity is increased. It is preferably 12% or less. When it is less than 1%, the specific gravity increases, and the meltability of the glass is lowered, and it becomes easy to devitrify. It is preferably 6% or more.

MgO is a component which has a small specific gravity and improves the meltability of the glass. When it exceeds 10%, the glass becomes easy to separate, and it becomes easy to devitrify or the chemical resistance is lowered. It is preferably 7% or less. MgO is preferably contained in an amount of 1% or more.

CaO is used to increase the meltability of the glass, and it is difficult to devitrify to 17%. When it exceeds 17%, the specific gravity increases, and the coefficient of thermal expansion becomes large, and on the contrary, it becomes easy to devitrify. It is preferably 14% or less. CaO is preferably 2% or more.

In order to suppress the phase separation of the glass, SrO can be contained up to 17%. When it exceeds 17%, the specific gravity increases, and the coefficient of thermal expansion becomes large, and on the contrary, it becomes easy to devitrify. It is preferably 14% or less. SrO is preferably 3% or more.

BaO may be contained up to 20% in order to suppress phase separation of the glass and to prevent devitrification. When it exceeds 20%, the specific gravity increases and the coefficient of thermal expansion becomes large. It is preferably 1% or less, and is substantially not contained.

When the total amount of the alkaline earth metal oxide (RO), that is, (MgO + CaO + SrO + BaO) is too small, the melting of the glass is difficult, so it is 8% or more. On the other hand, if the amount is too large, the density of the glass becomes large, so it is 30% or less. It is preferably 10 to 30%.

On the other hand, the alkali-free glass is expressed by mass percentage based on oxides, and contains: SiO ₂ 55 to 64%, Al ₂ O ₃ 10 to 22%, B ₂ O ₃ 6 to 12%, and MgO 1 to 7%. CaO 2~14%, SrO 3~14%, BaO 0~1%, and MgO+CaO+SrO+BaO 10~30% are more preferable.

Further, the above-mentioned mass percentage means that the total of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, SrO and BaO is 100%.

In addition, in order to further suppress the bubbles in the molten glass, F, Cl, SO ₃ , SnO ₂ , Fe ₂ O ₃ or the like as a clarifying agent with respect to 100% by mass of the glass raw material and a total amount of 5% by mass or less may be added.

[Examples]

Hereinafter, the present invention will be further described by way of examples, but the invention is not limited thereto.

In the present embodiment, a crucible made of a platinum alloy (platinum-rhenium alloy, ruthenium 10% by mass) shown in Fig. 2(a) (based on JIS H6201 (1986.11.1)) and shown in Fig. 2(b) are used. The zirconia-made base (fire-resistant block) evaluates the generation of bubbles at the platinum alloy interface. The dimensions of the crucible shown in Fig. 2(a) and the base shown in Fig. 2(b) are as follows.

Shabu-shabu

Height: 27mm

Upper diameter: 25mm

Bottom diameter: 15mm

Capacity: 10cc

Quality: 8.0g

Abutment

External dimensions: 48mm × 48mm × 48mm

Concave depth: 26mm

Concave diameter: 35mm

Further, the alumina-based ceramic particles used in the examples are shown in Table 1. The particle diameter is 10 μm to 2 mm. In Table 1, the ratio of the crystal phase to the glass phase (% by mass) in the alumina-based ceramic particles was determined by measuring the ratio of each crystal phase by a powder X-ray diffraction (XRD) method. Specifically, the ratio of the crystal phase is determined from the ratio of the XRD intensity of the pure substance (oblique zircon, zircon, mullite, steel jade, etc.) of each crystal phase to the sample, and the difference between the ratio of the sample and each crystal phase Find the ratio of the glass phase. Moreover, the composition ratio (mass % basis) of the alumina-based ceramic particles was determined by fluorescent X-ray analysis. Further, the composition ratio RO _x is a total of oxidized impurities other than Al ₂ O ₃ , SiO ₂ , ZrO ₂ , and Fe ₂ O ₃ , and R is a metal element, O is oxygen, and x is a stoichiometric ratio.

The graphs showing the relationship between the oxidation of Fe and the temperature of the alumina-based ceramic particles of Examples 1, 3 and 5 are shown in Fig. 3 .

The crucible of Fig. 2(a) is placed in the concave portion of the base of Fig. 2(b), and the gap (the gap between the abutment recess and the bottom surface of the crucible is 3~5 mm) is filled as shown in Fig. 2(c) as shown in Table 1. The alumina-based ceramic particles shown are placed in a heating furnace and heated up to 1400 °C. Next, the alkali-free glass was placed in the crucible of Fig. 2 while maintaining the temperature at 1400 ° C to melt. The composition of the alkali-free glass is represented by mass percentage, and is SiO ₂ 59.4%, Al ₂ O ₃ 17.6%, B ₂ O ₃ 7.9%, MgO 3.3%, CaO 3.8%, SrO 8.0%, MgO+. CaO+SrO 15.1%.

After the alkali-free glass was melted, it was further maintained at 1400 ° C for 1 hour, and the generation of bubbles at the platinum alloy interface, that is, the wall surface of the crucible was observed. The results are shown in Table 1. In Table 1, Examples 1 to 4 are Examples, and Examples 5 to 7 are Comparative Examples. In Table 1, the bubble occupancy ratio is the ratio of the area occupied by the bubble in the bottom surface of the crucible of Fig. 2(a), and 0% is below the measurement limit.

As is clear from the results of Table 1, the alumina-based ceramic particles of Examples 1 to 4 were effective and stable in suppressing the remaining of the bubbles. Further, it is considered that the alumina-based ceramic particles of Examples 5 and 6 have a redox change point of 950 ° C, and in the molten glass temperature (1400 ° C) of the example, the valence change of Fe is not ^exhibited (Fe ³⁺ →Fe ^{2 +} ) The residual suppression effect of the resulting bubbles. In addition, it is considered that the alumina-based ceramic particles of Example 7 have a redox change point of 1,350 ° C, and the Fe ₂ O ₃ content is less than 0.2% by mass, so that the valence of Fe cannot be sufficiently exhibited (Fe ³⁺ →Fe ^{2+ )} The resulting residual suppression effect of the bubbles.

[Industrial use]

The alkali-free glass produced by the glass manufacturing apparatus and the glass manufacturing method of the present invention is suitable as a substrate glass for a flat panel display, in particular, a liquid crystal display (LCD), an organic electroluminescence, an OLED, and an inorganic electroluminescence. Substrate glass for flat panel display such as display

1‧‧‧Glass manufacturing equipment

2‧‧‧melting tank

3‧‧‧Clarification tank

4‧‧‧Stirring tank

5‧‧‧Forming device

6,7,8‧‧‧ catheter

Fig. 1 is a schematic view showing a configuration example of a glass manufacturing apparatus.

Fig. 2 (a) is a view showing a crucible made of a platinum alloy used in the embodiment, Fig. 2 (b) is a view showing a base of a zirconia smelting system used in the embodiment, and Fig. 2 (c) is a view Fig. 2(a) is a view showing a state in which the crucible is placed in the concave portion of the base of Fig. 2(b).

Fig. 3 is a graph showing the relationship between redox oxidation and temperature for alumina-based ceramic particles of Examples 1, 3 and 5.

Claims (4)

A glass manufacturing apparatus comprising a member made of platinum or a platinum alloy in contact with molten glass, characterized in that a back surface side of a surface of the member in contact with the molten glass is formed to be contained with respect to the alumina-based ceramic particles. Alumina ceramics containing Fe in an amount of 0.2 to 5% by mass in terms of Fe ₂ O ₃ and having a change point of Fe redox (Fe ²⁺ /Fe ²⁺ +Fe ³⁺ ) in the molten glass temperature range In the layer of the particles, the alumina-based ceramic particles contain 10% by mass or more of mullite, and the molten glass temperature range is 1,250 ° C to 1,650 ° C. The glass manufacturing apparatus of claim 1, wherein the member made of platinum or platinum alloy is a container for containing molten glass. A glass manufacturing method characterized by using the glass manufacturing apparatus of claim 1 or 2. The glass manufacturing method of claim 3, wherein the glass produced is expressed by mass percentage based on oxides (the total of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, SrO, and BaO). 100%) contains: SiO ₂ 50~70%, Al ₂ O ₃ 5~25%, B ₂ O ₃ 1~20%, MgO 0~10%, CaO 0~17%, SrO 0~17% , BaO 0~20%, MgO+CaO+SrO+BaO 8~30% alkali-free glass.