TW201410622A - Method for producing glass plate, and glass plate - Google Patents

Abstract

The present invention provides a method for producing a glass plate wherein a main surface, which has been in contact with a reducing atmosphere within a bath, has good quality. The present invention relates to a method for producing a glass plate which comprises a step wherein molten glass continuously supplied on molten tin within a float bath is molded by being flowed on the molten tin. This method for producing a glass plate is characterized in that molten glass right before being supplied into the float bath has a total content of Au, Cu and Ag, which are impurities, of 0.5 ppm or less.

Description

Glass plate manufacturing method and glass plate

The present invention relates to a method of producing a glass sheet and a glass sheet.

As a method of forming a glass sheet, a floating method is widely used. In the floating method, the molten glass which is continuously supplied to the molten tin in the floating kiln (hereinafter also referred to as "kiln") is flowed on the molten tin to form a strip shape (for example, see Patent Document 1). In order to prevent oxidation of the molten tin, the environment in the kiln is set to a reducing environment containing hydrogen. Hydrogen prevents oxidation of molten tin by reacting with oxygen mixed from the outside.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open Publication No. 2010-053032

When the molten glass is molded in the kiln, the particles in the reducing environment are aggregated and fall on the upper surface of the molten glass to adhere to the defect.

The present invention has been made in view of the above problems, and an object thereof is to provide a method for producing a glass sheet having a good quality in a main surface in contact with a reducing environment in a kiln, and a glass sheet.

In order to achieve the above object, a method for producing a glass sheet according to aspect (1) of the present invention includes a step of forming a molten glass continuously supplied to molten tin in a float bath on the molten tin to form a step; It is characterized by: The content of the total amount of Au, Cu, and Ag as impurities in the molten glass to be supplied to the floating kiln is 0.5 mass ppm or less.

Further, the method for producing a glass sheet according to aspect (2) of the present invention includes a step of forming a molten glass continuously supplied to molten tin in a float bath on the molten tin to form a step; and The content of the total of F, Cl, Br, and I as impurities is 200 ppm by mass or less in the molten glass immediately before the inside of the floating kiln.

Further, in the glass plate of the aspect (3) of the present invention, the molten glass continuously supplied to the molten tin in the float bath is formed by flowing on the molten tin; and characterized in that Au as an impurity The total content of Cu and Ag is 0.5 ppm by mass or less.

Further, in the glass plate of the aspect (4) of the present invention, the molten glass continuously supplied to the molten tin in the float bath is formed by flowing on the molten tin; and it is characterized in that F as an impurity The total content of Cl, Br, and I is 200 ppm by mass or less.

According to the present invention, it is possible to provide a method for producing a glass sheet having good quality in a main surface in contact with a reducing environment in a kiln, and a glass sheet.

10‧‧‧ Kiln

12‧‧‧The entrance to the kiln

14‧‧‧Export of the kiln

20‧‧‧Fused tin

30‧‧‧Solid glass

40‧‧‧Return environment

50‧‧‧Flower exit lip

60‧‧‧heater

70‧‧‧ gas supply pathway

80‧‧‧Exhaust passage

Fig. 1 is an explanatory view (1) of a manufacturing apparatus for a glass sheet according to an embodiment of the present invention.

Fig. 2 is an explanatory view (2) of a manufacturing apparatus for a glass sheet according to an embodiment of the present invention.

Hereinafter, the form for carrying out the invention will be described with reference to the drawings. In the following drawings, the same or corresponding components are designated by the same or corresponding characters, and the description is omitted.

The method for producing a glass sheet according to the present embodiment includes, for example, a melting step, a molding step, a slow cooling step, and a cutting step, and further has a polishing step as needed. The grinding step is carried out depending on the use of the glass plate.

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

In the molding step, the molten glass obtained in the melting step is continuously supplied to the molten tin in the kiln, and the molten glass is flowed on the molten tin to form a sheet glass (so-called glass ribbon). This forming method is called a floating method. In order to prevent oxidation of the molten tin, the environment in the kiln is set to a reducing environment containing hydrogen. The plate glass is cooled while flowing in a specific direction, and is pulled up from the molten tin near the exit of the kiln.

The slow cooling step is to slowly cool the sheet glass obtained in the forming step in a slow cooling furnace. The sheet glass is gently cooled while being horizontally conveyed from the inlet of the slow cooling furnace toward the outlet on the roller. The surface of the plate glass is blown with sulfurous acid (SO ₂ ) gas near the inner side of the inlet of the slow cooling furnace to form a damage prevention film on the surface of the plate glass. Since the outlet of the slow cooling furnace is open to the atmosphere, the environment inside the slow cooling furnace is an atmospheric environment.

The cutting step is to cut the slow-cooled sheet glass in the slow cooling step into a specific size by a cutter. In the cutting step, both end portions (so-called ears) in the width direction of the sheet glass are cut. This is because both ends in the width direction of the sheet glass become thick due to the influence of surface tension or the like.

The grinding step is the main surface of the glass sheet obtained in the grinding step. In the polishing step, the main surface (hereinafter referred to as "bottom surface") in contact with the molten tin in the kiln is polished depending on the use of the glass plate. The main surface (hereinafter referred to as "top surface") which is in contact with the reducing environment in the kiln on the opposite side to the bottom surface is not polished.

Thus, a glass plate as a product can be obtained. The glass plate can be used, for example, as a window glass for a vehicle, a window glass for a building, a substrate for a display, a cover glass for a display, or a substrate for a photomask. "Display" includes flat panel displays (FPD, Flat) such as liquid crystal display (LCD), plasma display (PDP), organic EL (electroluminescence) display Panel Display). The thickness of the substrate for the display is exemplified by 1 mm or less. Moreover, the thickness of the glass plate used for the flexible liquid crystal panel, such as a tablet terminal, is preferably 0.3 mm or less.

The type of glass of the glass plate is selected depending on the use of the glass plate. For example, in the case of a glass substrate for LCD, an alkali-free glass is used. Further, 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. For the case of covering glass for displays, chemically strengthened soda lime glass is mainly used. In the case of a substrate for a photomask, quartz glass having a low coefficient of thermal expansion is mainly used.

The alkali-free glass can be expressed, for example, by mass% of the oxide, and contains SiO ₂ : 50 to 66%, Al ₂ O ₃ : 10.5 to 24%, B ₂ O ₃ : 0 to 12%, MgO: 0 to 8%, and CaO. : 0~14.5%, SrO: 0~24%, BaO: 0~13.5%, ZrO ₂ : 0~5%, SnO: 0~3%, MgO+CaO+SrO+BaO: 9~29.5%, and alkali The combined amount of the metal oxide is 0.1% or less.

The alkali-free glass is preferably expressed by mass% based on oxides, and contains SiO ₂ : 58 to 66%, Al ₂ O ₃ : 15 to 22%, B ₂ O ₃ : 5 to 12%, and MgO: 0 to 8%. , CaO: 0~9%, SrO: 3~12.5%, BaO: 0~2%, SnO: 0~1%, MgO+CaO+SrO+BaO: 9~18%, and the content of alkali metal oxide The combined amount is 0.1% or less.

The soda lime glass is represented, for example, by mass % of oxide, and contains SiO ₂ : 65 to 75%, Al ₂ O ₃ : 0 to 3%, CaO: 5 to 15%, MgO: 0 to 15%, and 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 to 5%, SrO: 0 to 5%, B ₂ O ₃ : 0 to 5%, ZnO: 0 to 5%, ZrO ₂ : 0 to 5%, SnO ₂ : 0 to 3%, SO ₃ : 0 ~0.5%.

Next, details of the forming steps of the above glass sheet will be described based on FIGS. 1 and 2.

Fig. 1 and Fig. 2 are explanatory views of a manufacturing apparatus of a glass sheet according to an embodiment of the present invention. Figure 1 is a top cross-sectional view of the kiln, and Figure 2 is a side cross-sectional view of the kiln.

In the molding step, the molten glass 30 is cooled while flowing on the molten tin 20 in the kiln 10 to be formed into a strip shape. In order to prevent oxidation of the molten tin 20, the upper space in the kiln 10 is filled with a reducing environment 40 containing hydrogen. In order to prevent intrusion of external air, the upper space in the kiln 10 is maintained at a positive pressure higher than atmospheric pressure. The kiln 10 is provided with a flow outlet lip (Spout Lip) 50, a heater 60, an air supply passage 70, an exhaust passage 80, and the like.

The flow path exit lip 50 supplies the molten glass 30 to the supply passage in the kiln 10, and is provided at the inlet 12 of the kiln 10. The flow path exit lip 50 is connected to a melting furnace for making the molten glass 30.

The heater 60 is heated in the kiln 10, for example, as shown in Fig. 2, hanging from the top of the kiln 10. The heater 60 is provided in plural, for example, in a flow direction (X direction) and a width direction (Y direction) of the molten glass 30, and is 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 in such a manner that the temperature of the molten glass 30 gradually becomes lower from the inlet 12 of the kiln 10 toward the outlet 14. Further, the output of the heater 60 is controlled such that the thickness of the molten glass 30 becomes uniform in the width direction (Y direction).

The gas supply passage 70 is a passage for supplying a reducing gas into the kiln 10, and is provided at the top of the kiln 10, for example, as shown in Fig. 2 . The plurality of supply passages 70 are provided at intervals in a specific direction (X direction).

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

The exhaust passage 80 is a passage for exhausting the reducing environment 40, and is provided on the side wall of the kiln 10, for example, as shown in Fig. 2 . The exhaust passages 80 are provided in plural in a specific direction (X direction).

As shown in Fig. 2, the molten glass 30 is formed into a plate-like plate glass (so-called glass ribbon) which is pulled up from the molten tin 20 in the vicinity of the outlet 14 of the kiln 10. Thereafter, the plate glass becomes a glass plate of the product via a slow cooling step, a cutting step, or the like.

However, the reducing environment 40 in the kiln 10 contains components derived from the molten tin 20 or the molten glass 30 in addition to the reducing gas supplied from the gas supply passage 70. Among the components (including elemental substances and compounds) which are volatilized from the molten tin 20 or the molten glass 30 to the reducing environment 40, the component having a low vapor pressure is not easily volatilized and is small, so that it is not a problem. On the other hand, since the component having a high vapor pressure is discharged as a gas to the outside of the kiln 10, it is usually not a problem. However, if a component having a low vapor pressure is a specific compound (for example, a halide), the vapor pressure becomes high and may be volatilized, but after being temporarily volatilized, it is immediately reduced by hydrogen in the reducing environment 40, and as a result, it is in the environment. The case is restored to the original component with a lower vapor pressure. In this case, since the component having a low vapor pressure is less likely to be present as a gas, it may become agglomerated in the reducing environment 40 and may fall on the molten glass 30 to become a defect. The element which is low in vapor pressure as a simple substance and which is likely to be a halide is, for example, a group 11 element such as Au, Cu or Ag. The Group 11 element has a structure of the same valence electrons as the alkali metal element, is likely to be a monovalent ion, and is likely to be a halide. Therefore, it is easily volatilized from the molten tin 20 or the molten glass 30 to the reducing atmosphere 40 as a halide. Further, when Au, Cu, and Ag are monovalent ions, they are easily diffused in the molten tin 20 or the molten glass 30, and are easily transferred to the interface with the reducing environment 40, so that they are easily diffused into the reducing atmosphere 40. When the gold halide, the copper halide, and the silver halide in the reducing atmosphere 40 are reduced by hydrogen, Au, Cu, and Ag having a low vapor pressure are generated. Further, since Au, Cu, and Ag are not easily present as a gas as a simple substance, they become aggregates in the reducing environment 40. The aggregate may further contain at least one of Au, Cu, and Ag, and further contains elements other than Au, Cu, and Ag.

In the present embodiment, the total amount of Au, Cu, and Ag (hereinafter collectively referred to as "Au or the like") as impurities is 0.5 ppm by mass or less in the molten glass 30 before being supplied to the kiln 10. When the total content of Au or the like is 0.5 ppm by mass or less, the molten glass 30 is volatilized from the molten glass 30 into the reducing atmosphere 40, and the components which become aggregates are less. Therefore, the aggregates are not easily grown in the reducing environment 40, and the aggregates become less likely to fall into the molten glass. 30 above the surface. Therefore, the quality of the top surface of the glass sheet becomes good. More preferably, the range is 0.3 ppm by mass or less, and further preferably 0.1 ppm by mass or less.

The total amount of Au or the like in the molten glass 30 immediately before being supplied into the kiln 10 is slightly smaller than the total amount of Au or the like which is supplied to the glass raw material of the melting furnace. The reason is that Au is equal to the volatilization from the glass to the outside in the melting step.

Therefore, the total content of Au or the like in the glass raw material is preferably 1.0 ppm by mass or less in order to make the total amount of Au or the like in the molten glass 30 immediately before the kiln 10 to be 0.5 ppm by mass or less. More preferably, the range is 0.5 ppm by mass or less, and further preferably 0.3 ppm by mass or less.

In the present embodiment, the total amount of F, Cl, Br, and I (hereinafter collectively referred to as "F or the like") as impurities is 200 ppm by mass or less in the molten glass 30 before being supplied to the kiln 10. As a simple substance, F or the like has a boiling point lower than the forming temperature of the glass, and promotes the volatilization of Au or the like.

When the total content of F or the like in the molten glass 30 before being supplied to the kiln 10 is 200 ppm by mass or less, Au or the like in the molten glass 30 is less likely to be volatilized into the reducing environment 40, so that the aggregate is not easily reduced to the environment 40. Growing up, the agglomerates become less likely to fall. Therefore, the quality of the top surface of the glass sheet becomes good. More preferably, the range is 100 ppm by mass or less, and further preferably 50 ppm by mass or less.

The total amount of F or the like in the molten glass 30 immediately before being supplied into the kiln 10 is slightly smaller than the total content of F or the like which is supplied to the glass raw material of the melting furnace. The reason for this is that F is equal to diffusing from the glass to the outside in the melting step.

Therefore, the total content of F or the like in the glass raw material is preferably 500 ppm by mass or less in order to make the total content of F or the like in the molten glass 30 immediately before being supplied into the kiln 10 to be 200 ppm by mass or less. A more preferable range is 300 ppm by mass or less, and a further preferred range is 200 ppm by mass or less.

In order to improve the quality of the top surface, Au or the like as an impurity in the molten tin 20 in the kiln 10 The total content may be 10 ppm by mass or less, and the total content of F or the like may be 100 ppm by mass or less. As a raw material of the molten tin 20 in the kiln 10, for example, tin is used.

Next, the glass plate obtained in the above production method will be described.

The total content of Au or the like in the glass plate is 0.5 mass ppm or less. Although Au or the like is volatilized from the glass to the outside in the forming step and the slow cooling step, the amount of volatilization is a trace amount as compared with the entire amount. The glass composition of the glass plate is substantially the same as the glass composition of the molten glass 30 in the forming step. When the total content of Au or the like in the glass plate is 0.5 ppm by mass or less, the total content of Au or the like in the molten glass 30 in the molding step is small, and the molten glass 30 is volatilized from the molten glass 30 to the reducing environment. In 40, there are fewer components that become the core of the condensate. Therefore, the aggregate does not easily grow, and the aggregate becomes less likely to fall on the upper surface of the molten glass 30. Therefore, the quality of the top surface of the glass sheet becomes good.

Moreover, the total content of F or the like in the glass plate is 200 ppm by mass or less. Although F or the like is volatilized from the glass to the outside in the forming step and the slow cooling step, the amount of volatilization is a trace amount as compared with the entire amount. The glass composition of the glass plate is substantially the same as the glass composition of the molten glass 30 in the forming step. When the content of F or the like in the glass plate is 200 ppm by mass or less, the content of F or the like in the molten glass 30 in the molding step is small, and Au or the like in the molten glass 30 is not easily volatilized to the reducing atmosphere 40, so that the agglomerates are not easily formed. Growing in the reducing environment 40, the agglomerates become less likely to fall. Therefore, the quality of the top surface of the glass sheet becomes good.

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

For example, before the molten glass 30 of the above-described embodiment is supplied to the kiln 10, the total content of (1) Au or the like is 0.5 ppm by mass or less, and the total content of (2) F or the like is 200 ppm by mass or less. It can also only satisfy (1) or (2). The reason for this is that the deposit on the top surface is generated when there are too many impurities such as Au and impurities such as F. The impurities of the molten tin 20 in the kiln 10 are also the same.

Further, in the glass plate of the above-described embodiment, the total content of (1) Au or the like is 0.5 ppm by mass or less, and the total content of (2) F or the like is 200 ppm by mass or less, but may satisfy only (1) or (2).

Example

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

[example 1]

In Example 1, a glass plate containing an alkali-free glass was produced by the method shown in Figs. 1 and 2. Tin is used as a raw material for molten tin in the kiln. The alkali-free glass is represented by mass % of oxide, and contains SiO ₂ : 59.5%, Al ₂ O ₃ : 17%, B ₂ O ₃ : 8%, MgO: 3.3%, CaO: 4%, and SrO: 7.6%. BaO: 0.1%, ZrO ₂ : 0.1%, MgO + CaO + SrO + BaO: 15%, the remainder is an unavoidable impurity, and the total amount of the alkali metal oxide is 0.1% or less.

The content (% by mass) of each element (including Au, F, etc.) contained in the glass raw material, the molten glass immediately before being supplied to the kiln, and the glass plate is measured by wet analysis. In the wet analysis, a sample such as a glass raw material was dissolved in an acid to be analyzed. Further, a sample of the molten glass to be supplied to the kiln was produced by rapidly cooling the molten glass near the inlet of the kiln by a well-cooled iron ladle.

The average density (number/m ² ) of the adhering matter 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.

The measurement results of the total content of Au and the like, the total content of F, and the average density of the attached matter are shown in Table 1.

[Example 2 to Example 6]

A glass plate was produced in the same manner as in Example 1 except that a molar amount of CuO or Ag ₂ S was added to the glass raw material in Examples 2 to 6. Examples 1 to 4 are examples, and examples 5 to 6 are comparative examples.

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

As can be seen from Table 1, when the total content of Au or the like is 0.5 mass ppm or less in the molten glass or the glass plate immediately before being supplied to the kiln, the defects of the deposits can be remarkably reduced.

[Example 7]

A glass plate containing an alkali-free glass was produced in the same manner as in Example 1 except that the glass raw material was changed in Example 7. The alkali-free glass is represented by mass % of oxide, and contains SiO ₂ : 59.5%, Al ₂ O ₃ : 17%, B ₂ O ₃ : 8%, MgO: 3.3%, CaO: 4%, and SrO: 7.6%. BaO: 0.1%, ZrO ₂ : 0.1%, MgO + CaO + SrO + BaO: 15%, the remainder is an unavoidable impurity, and the total amount of the alkali metal oxide is 0.1% or less.

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

[Example 8 to Example 12]

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

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

As can be seen from Table 2, when the total content of F or the like is 200 ppm by mass or less in the molten glass or the glass plate immediately before being supplied to the kiln, the defects of the deposits can be remarkably reduced.

According to Tables 1 and 2, when the total content of Au or the like is 0.5 ppm by mass or less, and the total content of F or the like is 200 ppm by mass or less, in the molten glass or the glass plate immediately before being supplied to the kiln, The defects of the attached matter are sufficiently reduced.

The present application is based on Japanese Patent Application No. 2012-159048, filed on Jan.

10‧‧‧ Kiln

12‧‧‧The entrance to the kiln

14‧‧‧Export of the kiln

20‧‧‧Fused tin

30‧‧‧Solid glass

50‧‧‧Flower exit lip

Claims (11)

A method for producing a glass sheet, which comprises a step of forming a molten glass continuously supplied to molten tin in a float bath to be formed by flowing on the molten tin; and is characterized in that it is supplied to the float bath In the molten glass in the front, the total content of Au, Cu, and Ag as impurities is 0.5 ppm by mass or less. The method for producing a glass sheet according to claim 1, wherein the content of the F, Cl, Br, and I as impurities is 200 ppm by mass or less in the molten glass immediately before the inside of the floating kiln. A method for producing a glass sheet, which comprises a step of forming a molten glass continuously supplied to molten tin in a float bath to be formed by flowing on the molten tin; and is characterized in that it is supplied to the float bath In the molten glass in the front, the total content of F, Cl, Br, and I as impurities is 200 ppm by mass or less. A glass plate in which molten glass continuously supplied to molten tin in a float bath is formed by flowing on the molten tin; and characterized in that the total content of Au, Cu, and Ag as impurities is 0.5 mass ppm or less. The glass plate of claim 4, wherein the total content of F, Cl, Br, and I as impurities is 200 ppm by mass or less. A glass plate which is formed by continuously flowing molten glass which is supplied onto molten tin in a float bath to the molten tin; and is characterized by a total of F, Cl, Br and I as impurities The content is 200 ppm by mass or less. The glass plate according to any one of claims 4 to 6, wherein the glass plate is represented by mass % of oxide, containing SiO ₂ : 65 to 75%, Al ₂ O ₃ : 0 to 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 to 3%, SO ₃ : 0 to 0.5% soda lime glass. The glass plate according to any one of claims 4 to 6, wherein the glass plate is a glass substrate for a display. The glass plate of claim 8, wherein the glass plate has a thickness of 1 mm or less. The glass plate according to any one of claims 4 to 6, wherein the glass plate is represented by mass % of oxide, containing SiO ₂ : 50 to 66%, Al ₂ O ₃ : 10.5 to 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: 0~3%, MgO+CaO+SrO+BaO: 9 to 29.5%, and the total amount of the alkali metal oxide is 0.1% or less of alkali-free glass. The glass plate according to any one of claims 4 to 6, wherein the glass plate is represented by mass % of oxide, containing SiO ₂ : 58 to 66%, Al ₂ O ₃ : 15 to 22%, B ₂ O ₃ : 5~12%, MgO: 0~8%, CaO: 0~9%, SrO: 3~12.5%, BaO: 0~2%, SnO: 0~1%, MgO+CaO+SrO+BaO: An alkali-free glass having a total amount of the alkali metal oxide of 9 to 18% and an amount of 0.1% or less.