JP2015171957A - Production method of glass sheet, and glass sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a glass sheet having excellent quality of a principal surface having a contact with a reduction atmosphere in a bath.SOLUTION: In a production method of a glass sheet having a step for molding molten glass by fluidizing on molten tin, the molten glass supplied continuously onto the molten tin in a float bath, the molten glass just before being supplied into the float bath has a total content of impurities of Au, Cu and Ag of 0.5 mass ppm or lower.

Description

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

  A float method is widely used as a method for forming a glass plate. In the float process, molten glass continuously supplied onto molten tin in a float bath (hereinafter also simply referred to as “bath”) is flowed over molten tin and formed into a strip shape (for example, Patent Document 1). reference). The atmosphere in the bath is a reducing atmosphere containing hydrogen gas in order to prevent oxidation of molten tin. Hydrogen gas reacts with oxygen gas mixed from the outside to prevent oxidation of molten tin.

JP 2010-053032 A

  When molding molten glass in a bath, particles in a reducing atmosphere aggregate and fall on the upper surface of the molten glass, which may cause defects.

  This invention is made | formed in view of the said subject, Comprising: It aims at provision of the manufacturing method of a glass plate with favorable quality of the main surface which contacted the reducing atmosphere in a bus | bath, and a glass plate.

In order to solve the above object, a method for producing a glass plate according to the aspect (1) of the present invention comprises:
In the method for producing a glass plate, including a step of forming molten glass that is continuously supplied onto molten tin in a float bath and flowing on the molten tin,
The molten glass immediately before being supplied into the float bath is characterized in that the total content of impurities Au, Cu, and Ag is 0.5 mass ppm or less.

Moreover, the manufacturing method of the glass plate by aspect (2) of this invention is the following.
In the method for producing a glass plate, including a step of forming molten glass that is continuously supplied onto molten tin in a float bath and flowing on the molten tin,
The molten glass immediately before being supplied into the float bath is characterized in that the total content of impurities F, Cl, Br and I is 200 ppm by mass or less.

Moreover, the glass plate by aspect (3) of this invention is
In a glass plate formed by flowing molten glass continuously supplied on molten tin in a float bath on the molten tin,
The total content of impurities Au, Cu, and Ag is 0.5 mass ppm or less.

Moreover, the glass plate by aspect (4) of this invention is
In a glass plate formed by flowing molten glass continuously supplied on molten tin in a float bath on the molten tin,
The total content of impurities F, Cl, Br and I is 200 mass ppm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the glass plate with the favorable quality of the main surface which contacted the reducing atmosphere in a bus | bath, and a glass plate are provided.

Explanatory drawing (1) of the manufacturing apparatus of the glass plate by one Embodiment of this invention. Explanatory drawing (2) of the manufacturing apparatus of the glass plate by one Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof is omitted.

  The manufacturing method of the glass plate by this embodiment has a melt | dissolution process, a formation process, a slow cooling process, and a cutting process, for example, and also has a grinding | polishing process as needed. A grinding | polishing process is performed according to the use of a glass plate.

  In the melting step, a glass raw material prepared by mixing a plurality of types of raw materials is melted to obtain a molten glass. After the glass raw material is put into the melting furnace, it is melted by the radiant heat of the flame injected from the burner to become molten glass.

  In the forming step, the molten glass obtained in the melting step is continuously supplied onto the molten tin in the bath, and the molten glass is flowed on the molten tin and molded to obtain a plate-like glass (so-called glass ribbon). This forming method is called a float method. The atmosphere in the bath is a reducing atmosphere containing hydrogen gas in order to prevent oxidation of molten tin. The glass sheet is cooled while flowing in a predetermined direction, and is pulled up from the molten tin in the vicinity of the exit of the bath.

In the slow cooling step, the sheet glass obtained in the forming step is slowly cooled in a slow cooling furnace. The plate glass is gradually cooled while being transported horizontally on the roll from the inlet to the outlet of the slow cooling furnace. Sulfurous acid (SO ₂ ) gas or the like is sprayed on the surface of the sheet glass near the inside of the inlet of the slow cooling furnace, and a scratch-proof film is formed on the surface layer of the sheet glass. Since the outlet of the slow cooling furnace is open to the atmosphere, the atmosphere in the slow cooling furnace is an air atmosphere.

  In the cutting step, the glass sheet that has been gradually cooled in the slow cooling step is cut into a predetermined size with a cutting machine. In the cutting step, both edges (so-called ears) in the width direction of the sheet glass are cut off. This is because both edges in the width direction of the plate-like glass become thick due to the influence of surface tension and the like.

  In the polishing step, the main surface of the glass plate obtained in the cutting step is polished. In the polishing step, the main surface (hereinafter referred to as “bottom surface”) in contact with the molten tin in the bath is polished according to the use of the glass plate. The main surface opposite to the bottom surface and in contact with the reducing atmosphere in the bus (hereinafter referred to as “top surface”) is not polished.

  In this way, a product glass plate is obtained. A glass plate is used as a window glass for vehicles, a window glass for buildings, a substrate for display, a cover glass for display, or a substrate for photomask, for example. The “display” includes a flat panel display (FPD) such as a liquid crystal display (LCD), a plasma display (PDP), and an organic EL display. The thickness of the substrate for display is exemplified by 1 mm or less. Moreover, it is preferable that the thickness of the glass plate used for flexible liquid crystal panels, such as a tablet terminal, is 0.3 mm or less.

  The kind of glass of a glass plate is selected according to the use of a glass plate. For example, in the case of a glass substrate for LCD, alkali-free glass is used. In the case of a window glass for a vehicle, a window glass for a building, and a glass substrate for a PDP, soda lime glass is used. In the case of a cover glass for display, soda lime glass that can be chemically strengthened is mainly used. In the case of a substrate for a photomask, quartz glass having a low thermal expansion coefficient is mainly used.

Alkali-free glass, for example, represented by mass% based on _{oxide, SiO 2: 50~66%, Al} 2 O 3: 10.5~24%, B 2 O 3: 0~12%, MgO: 0~ 8%, CaO: 0 to 14.5%, SrO: 0 to 24%, BaO: 0 to 13.5%, ZrO ₂ : 0 to 5%, SnO: 0 to 3%, MgO + CaO + SrO + BaO: 9 to 29.5%, and the total content of alkali metal oxides may be 0.1% or less.

The alkali-free glass is preferably expressed in terms of mass% based on oxide, SiO ₂ : 58 to 66%, Al ₂ O ₃ : 15 to 22%, B ₂ O ₃ : 5 to 12%, MgO: 0 to 8 %, CaO: 0 to 9%, SrO: 3 to 12.5%, BaO: 0 to 2%, SnO: 0 to 1%, MgO + CaO + SrO + BaO: 9 to 18%, The total content is 0.1% or less.

Soda lime glass, for example, represented by mass% based on _{oxide, SiO 2: 65~75%, Al} 2 O 3: 0~3%, CaO: 5~15%, MgO: 0~15%, Na 2 _{O: 10~20%, K 2 O} : 0~3%, Li 2 O: 0~5%, Fe 2 O 3: 0~3%, TiO 2: 0~5%, CeO 2: 0~3% _{, BaO: 0~5%, SrO:} 0~5%, B 2 O 3: 0~5%, ZnO: 0~5%, ZrO 2: 0~5%, SnO 2: 0~3%, SO 3 : Contains 0 to 0.5%.

  Next, based on FIG.1 and FIG.2, the detail of the formation process of the said glass plate is demonstrated.

  FIG.1 and FIG.2 is explanatory drawing of the manufacturing apparatus of the glass plate by one Embodiment of this invention. FIG. 1 is a plan sectional view of the bus, and FIG. 2 is a side sectional view of the bus.

  In the forming step, the molten glass 30 is cooled while flowing on the molten tin 20 in the bath 10 and formed into a strip shape. In order to prevent the molten tin 20 from being oxidized, the upper space in the bath 10 is filled with a reducing atmosphere 40 containing hydrogen gas. In order to prevent intrusion of outside air, the upper space in the bus 10 is maintained at a positive pressure higher than the atmospheric pressure. The bus 10 is provided with a spout trip 50, a heater 60, an air supply path 70, an exhaust path 80, and the like.

  The spout trip 50 is a supply path for supplying the molten glass 30 into the bath 10, and is installed at the inlet 12 of the bus 10. The spout trip 50 is connected to a melting furnace for producing the molten glass 30.

  The heater 60 heats the inside of the bus 10, and is suspended from the ceiling of the bus 10, for example, as shown in FIG. For example, a plurality of heaters 60 are provided at intervals in the flow direction (X direction) and the width direction (Y direction) of the molten glass 30 and are arranged in a matrix. The X direction and the Y direction are horizontal directions orthogonal to each other.

  The output of the heater 60 is controlled so that the temperature of the molten glass 30 decreases as it goes from the inlet 12 to the outlet 14 of the bus 10. The output of the heater 60 is controlled so that the thickness of the molten glass 30 is uniform in the width direction (Y direction).

  The air supply path 70 is a passage for supplying reducing gas into the bus 10, and is installed on the ceiling of the bus 10 as shown in FIG. 2, for example. A plurality of air supply paths 70 are provided at intervals in a predetermined direction (X direction).

  The reducing gas may be a mixed gas of hydrogen gas and nitrogen gas. The proportion of hydrogen gas in the reducing gas is, for example, 0.1 to 15% by volume.

  The exhaust path 80 is a passage for exhausting the reducing atmosphere 40, and is installed on the side wall of the bus 10 as shown in FIG. A plurality of exhaust passages 80 are provided at intervals in a predetermined direction (X direction).

  As shown in FIG. 2, a plate glass (so-called glass ribbon) obtained by forming the molten glass 30 into a strip shape is pulled up from the molten tin 20 in the vicinity of the outlet 14 of the bus 10. Thereafter, the plate-like glass becomes a product glass plate through a slow cooling step, a cutting step, and the like.

  By the way, the reducing atmosphere 40 in the bus 10 contains components volatilized from the molten tin 20 and the molten glass 30 in addition to the reducing gas supplied from the air supply passage 70. Of the components (including simple substances and compounds) volatilized from the molten tin 20 or the molten glass 30 to the reducing atmosphere 40, components having a low vapor pressure are inherently difficult to volatilize and are not a problem. On the other hand, since the component with high vapor pressure is discharged out of the bath 10 as gas, there is usually no problem. However, a component having a low vapor pressure has a higher vapor pressure and can be volatilized if it becomes a specific compound (for example, a halide), but once volatilized, it is immediately reduced by hydrogen gas in the reducing atmosphere 40, As a result, it may return to the original low vapor pressure component in the atmosphere. Then, since a component having a low vapor pressure is unlikely to exist as a gas, it becomes an agglomerate in the reducing atmosphere 40 and falls on the molten glass 30, which may be a defect. Examples of the element having a low vapor pressure as a simple substance and easily becoming a halide include Group 11 elements such as Au, Cu, and Ag. The Group 11 element has the same valence electron structure as the alkali metal element, and easily becomes a monovalent ion and easily becomes a halide. Therefore, as a halide, the group 11 element is changed from the molten tin 20 or the molten glass 30 to the reducing atmosphere 40. Easy to strip. Further, when Au, Cu, and Ag become monovalent ions, they easily diffuse in the molten tin 20 and the molten glass 30 and easily move to the interface with the reducing atmosphere 40, so that they easily volatilize in the reducing atmosphere 40. . When the gold halide, copper halide, and silver halide in the reducing atmosphere 40 are reduced by hydrogen gas, Au, Cu, and Ag with low original vapor pressure are generated. Since Au, Cu, and Ag hardly exist as a gas as a simple substance, they become aggregates in the reducing atmosphere 40. The aggregate includes at least one element of Au, Cu, and Ag, and may further include an element other than Au, Cu, and Ag.

  In the present embodiment, the molten glass 30 immediately before being supplied into the bath 10 has a total content of impurities Au, Cu, and Ag (hereinafter collectively referred to as “Au etc.”) of 0.5 mass ppm. It is as follows. When the total content of Au or the like is 0.5 mass ppm or less, there are few components in the molten glass 30 that volatilize from the molten glass 30 to the reducing atmosphere 40 and become aggregates. Therefore, the aggregate is difficult to grow in the reducing atmosphere 40 and the aggregate is difficult to fall on the upper surface of the molten glass 30. Therefore, the quality of the top surface of the glass plate is improved. A more preferable range is 0.3 mass ppm or less, and a still more preferable range is 0.1 mass ppm or less.

  The total content of Au and the like in the molten glass 30 immediately before being supplied into the bath 10 is slightly smaller than the total content of Au and the like in the glass raw material charged into the melting furnace. This is because Au and the like gradually evaporate from the glass to the outside in the melting step.

  Therefore, the total content of Au and the like in the glass raw material is 1.0 mass so that the total content of Au and the like in the molten glass 30 immediately before being supplied into the bath 10 is 0.5 mass ppm or less. It is preferably at most ppm. A more preferable range is 0.5 mass ppm or less, and a further preferable range is 0.3 mass ppm or less.

In the present embodiment, the molten glass 30 immediately before being supplied into the bath 10 has a total content of impurities F, Cl, Br, and I (hereinafter collectively referred to as “F etc.”) of 200 mass. p
pm or less. F or the like as a simple substance has a boiling point lower than the glass forming temperature, and promotes volatilization of Au or the like.

  When the total content of F and the like in the molten glass 30 immediately before being supplied into the bath 10 is 200 mass ppm or less, Au or the like in the molten glass 30 is difficult to be volatilized in the reducing atmosphere 40, and thus the reducing atmosphere 40. Aggregates are difficult to grow and aggregates are difficult to fall. Therefore, the quality of the top surface of the glass plate is improved. A more preferable range is 100 mass ppm or less, and a further preferable range is 50 mass ppm or less.

  The total content of F and the like in the molten glass 30 immediately before being supplied into the bath 10 is slightly smaller than the total content of F and the like in the glass raw material charged into the melting furnace. This is because F and the like gradually evaporate from the glass to the outside in the melting step.

  Therefore, the total content of F and the like in the glass raw material is 500 mass ppm or less so that the total content of F and the like in the molten glass 30 immediately before being supplied into the bath 10 is 200 mass ppm or less. It is preferable. A more preferable range is 300 mass ppm or less, and a further preferable range is 200 mass ppm or less.

  The molten tin 20 in the bus 10 has a total content of impurities such as Au of 10 mass ppm or less and a total content of F or the like of 100 mass ppm or less in order to improve the quality of the top surface. It may be. For example, tin is used as a raw material of the molten tin 20 in the bath 10.

  Next, the glass plate obtained by the said manufacturing method is demonstrated.

  The glass plate has a total content of Au or the like of 0.5 mass ppm or less. Au or the like is volatilized from the glass to the outside in the molding step and the slow cooling step, but the volatilization amount is small compared to the total amount. The glass composition of a glass plate and the glass composition of the molten glass 30 in a formation process are substantially the same. When the total content of Au and the like in the glass plate is 0.5 mass ppm or less, the total content of Au and the like in the molten glass 30 in the molding process is small, and the molten glass 30 has the There are few components which volatilize in the reducing atmosphere 40 and become the core of the aggregate. Therefore, the aggregate is difficult to grow and the aggregate is difficult to fall on the upper surface of the molten glass 30. Therefore, the quality of the top surface of the glass plate is improved.

  The glass plate has a total content of F and the like of 200 mass ppm or less. F and the like are volatilized from the glass to the outside in the molding step and the slow cooling step, but the volatilization amount is slight compared to the total amount. The glass composition of a glass plate and the glass composition of the molten glass 30 in a formation process are substantially the same. When the content of F or the like in the glass plate is 200 mass ppm or less, the content of F or the like in the molten glass 30 in the molding process is small, and Au or the like in the molten glass 30 is difficult to volatilize in the reducing atmosphere 40. In the reducing atmosphere 40, the aggregates are difficult to grow and the aggregates are difficult to fall. Therefore, the quality of the top surface of the glass plate is improved.

  Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. Various modifications and substitutions can be made to the above-described embodiment without departing from the scope of the present invention.

  For example, the molten glass 30 of the above embodiment has a total content of (1) Au or the like of 0.5 mass ppm or less and (2) a total content of F or the like immediately before being supplied into the bath 10. However, it may satisfy only (1) or (2). This is because the deposit on the top surface occurs when there are too many impurities such as Au and impurities such as F. The same applies to the impurities of the molten tin 20 in the bath 10.

  Further, the glass plate of the above embodiment has (1) the total content of Au and the like is 0.5 mass ppm or less, and (2) the total content of F and the like is 200 mass ppm or less. Only 1) or (2) may be satisfied.

  EXAMPLES The present invention will be specifically described below with reference to examples and the like, but the present invention is not limited to these examples.

[Example 1]
In Example 1, a glass plate made of alkali-free glass was produced by the method shown in FIGS. Tin was used as a raw material for molten tin in the bath. The alkali-free glass is expressed in terms of mass% based on oxide, SiO ₂ : 59.5%, Al ₂ O ₃ : 17%, B ₂ O ₃ : 8%, MgO: 3.3%, CaO: 4%, Containing SrO: 7.6%, BaO: 0.1%, ZrO2: 0.1%, MgO + CaO + SrO + BaO: 15%, the balance being inevitable impurities, the total content of alkali metal oxide content Was 0.1% or less.

  The content (mass%) of each element (including Au, F, etc.) contained in the glass raw material, the molten glass immediately before being supplied into the bath, and the glass plate was measured by wet analysis. In the wet analysis, analysis was performed by dissolving a sample such as a glass raw material in an acid. The molten glass sample immediately before being supplied into the bath was prepared by pumping the molten glass near the entrance of the bath with a sufficiently cooled iron handle and then rapidly cooling it.

The average density (pieces / m ² ) of deposits on the top surface of the glass plate was measured by visually observing 40 glass plates having a top surface of 1.0 m × 1.0 m.

  Table 1 shows the measurement results of the total content of Au and the like, the total content of F and the like, and the average density of the deposits.

[Examples 2 to 6]
In Examples 2 to 6, glass plates were produced in the same manner as in Example 1 except that equimolar amounts of trace amounts of CuO and Ag ₂ S were added to the glass raw material. Examples 1 to 4 are examples, and examples 5 to 6 are comparative examples.

  The total content of Au and the like, the total content of F and the like, and the average density of the deposits were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

表１から、バス内に供給する直前の溶融ガラスやガラス板において、Ａｕ等の合計の含有量が０．５質量ｐｐｍ以下であれば、付着物の欠点が有意に少ないことがわかる。

From Table 1, it can be seen that in the molten glass or glass plate immediately before being supplied into the bath, if the total content of Au or the like is 0.5 mass ppm or less, the defects of the deposits are significantly reduced.

[Example 7]
In Example 7, the glass plate which consists of an alkali free glass was manufactured like Example 1 except having changed the glass raw material. The alkali-free glass is expressed in terms of mass% based on oxide, SiO ₂ : 59.5%, Al ₂ O ₃ : 17%, B ₂ O ₃ : 8%, MgO: 3.3%, CaO: 4%, Containing SrO: 7.6%, BaO: 0.1%, ZrO2: 0.1%, MgO + CaO + SrO + BaO: 15%, the balance being inevitable impurities, the total content of alkali metal oxide content Was 0.1% or less.

  The total content of Au and the like, the total content of F and the like, and the average density of the deposits were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[Examples 8 to 12]
In Examples 8 to 12, glass plates were produced in the same manner as in Example 7, except that a small amount of CaF ₂ was added to the glass raw material. Examples 7 to 10 are examples, and examples 11 to 12 are comparative examples.

  The total content of Au and the like, the total content of F and the like, and the average density of the deposits were measured in the same manner as in Example 1. The measurement results are shown in Table 2.

表２から、バス内に供給する直前の溶融ガラスやガラス板において、Ｆ等の合計の含有量が２００質量ｐｐｍ以下であれば、付着物の欠点が有意に少ないことがわかる。

From Table 2, it can be seen that if the total content of F or the like in the molten glass or glass plate immediately before being supplied into the bath is 200 mass ppm or less, the defects of the deposits are significantly reduced.

  From Table 1 and Table 2, in the molten glass or glass plate immediately before being supplied into the bus, the total content of Au and the like is 0.5 mass ppm or less, and the total content of F and the like is 200. It can be seen that if the mass is less than or equal to ppm, the defects of the deposits are sufficiently reduced.

DESCRIPTION OF SYMBOLS 10 Float bath 12 Float bath inlet 14 Float bath outlet 20 Molten tin 30 Molten glass 40 Reducing atmosphere 50 Spaw trip 60 Heater 70 Air supply path 80 Exhaust path

Claims (11)

In the method for producing a glass plate, including a step of forming molten glass that is continuously supplied onto molten tin in a float bath and flowing on the molten tin,
The method for producing a glass plate, wherein the molten glass immediately before being supplied into the float bath has a total content of impurities Au, Cu, and Ag of 0.5 mass ppm or less.   The method for producing a glass plate according to claim 1, wherein the molten glass immediately before being supplied into the float bath has a total content of impurities F, Cl, Br, and I of 200 ppm by mass or less. In the method for producing a glass plate, including a step of forming molten glass that is continuously supplied onto molten tin in a float bath and flowing on the molten tin,
The method for producing a glass plate, wherein the molten glass immediately before being supplied into the float bath has a total content of impurities F, Cl, Br and I of 200 ppm by mass or less. In a glass plate formed by flowing molten glass continuously supplied on molten tin in a float bath on the molten tin,
A glass plate, wherein the total content of impurities Au, Cu, and Ag is 0.5 ppm by mass or less.   The glass plate according to claim 4, wherein the total content of impurities F, Cl, Br and I is 200 ppm by mass or less. In a glass plate formed by flowing molten glass continuously supplied on molten tin in a float bath on the molten tin,
A glass plate, wherein the total content of impurities F, Cl, Br and I is 200 mass ppm or less. The glass plate is represented by mass% based on _{oxide, SiO 2: 65~75%, Al} 2 O 3: 0~3%, CaO: 5~15%, MgO: 0~15%, Na 2 O: _{10~20%, K 2 O: 0~3} %, Li 2 O: 0~5%, Fe 2 O 3: 0~3%, TiO 2: 0~5%, CeO 2: 0~3%, BaO _{: 0~5%, SrO: 0~5%} , B 2 O 3: 0~5%, ZnO: 0~5%, ZrO 2: 0~5%, SnO 2: 0~3%, SO 3: 0 It is a soda-lime glass containing -0.5%, The glass plate of any one of Claims 4-6.   The said glass plate is a glass substrate for a display, The glass plate of any one of Claims 4-6.   The glass plate according to claim 8, wherein the glass plate has a thickness of 1 mm or less. The glass plate is represented by mass% based on _{oxide, SiO 2: 50~66%, Al} 2 O 3: 10.5~24%, B 2 O 3: 0~12%, MgO: 0~8% , CaO: 0~14.5%, SrO: 0~24%, BaO: 0~13.5%, ZrO 2: 0~5%, SnO: containing 0~3%, MgO + CaO + SrO + BaO: 9~29. The glass plate according to any one of claims 4 to 6, which is an alkali-free glass having a content of 5% and a total content of alkali metal oxides of 0.1% or less. The glass plate is represented by mass% based on _{oxide, SiO 2: 58~66%, Al} 2 O 3: 15~22%, B 2 O 3: 5~12%, MgO: 0~8%, CaO : 0 to 9%, SrO: 3 to 12.5%, BaO: 0 to 2%, SnO: 0 to 1%, MgO + CaO + SrO + BaO: 9 to 18%, the content of the alkali metal oxide The glass plate according to any one of claims 4 to 6, which is an alkali-free glass having a total amount of 0.1% or less.

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