JPWO2004060821A1 - Glass plate and method for producing the same - Google Patents

Abstract

A glass plate having a concave portion that is finer than conventional and has a uniform size is efficiently produced. A glass plate obtained by suspending molten glass on molten tin, wherein four or more concave portions having a diameter of 0.05 to 90 μm are formed on the surface in contact with the molten tin.

Description

  The present invention relates to a glass plate obtained by a float method in which molten glass is cast on molten tin and formed into a glass ribbon, and a recess is formed on the surface in contact with the molten tin, and a method for producing the same.

Glass plates having irregularities on the surface are used for various applications such as solar cell panels and window glass by utilizing an antireflection effect, an antiglare effect, an opaqueness effect, and the like.
2. Description of the Related Art Conventionally, as a method for producing a glass plate having a concave portion on the surface, a method for producing a smooth surface of a glass plate by processing using a physical or chemical technique is generally performed. As a physical method for processing the surface of the glass plate, a sand blast method or the like is known, and as a chemical method, etching using hydrofluoric acid or the like is known (see, for example, JP 2000-223724 A). . However, since these processes are performed on a production line provided separately from the glass plate production line such as the float method (offline processing), there are problems in equipment cost, production cost, and production efficiency.
In addition, a method of rolling and forming molten glass with a pair of upper and lower rolls is also widely used as a manufacturing method for architectural template glass and meshed plate glass. In this method, since the pattern engraved on one roll is continuously transferred to the mold pattern (surface recess) of the template glass, it is possible to simultaneously form the glass plate and form the recess on the surface. (For example, refer to Japanese Patent Publication No. 57-17851). However, there is a limitation on the thickness of the glass plate that can be manufactured, and the surface is rolled and formed by a roll, so it is difficult to form a recess on the other surface while maintaining a surface with excellent smoothness. There is a problem.
From such a background, when manufacturing a glass plate by the float process, a bubble is generated in the molten tin, and a concave portion is formed by applying the bubble to the surface of the glass ribbon that is cast on the molten tin and contacting the molten tin. There has also been proposed a method of forming (see, for example, Japanese Patent Application Laid-Open No. 2000-335925). However, in this method, since the molten tin has a high surface tension, the bubbles generated against this need to be quite large spheres, and the formed recesses are correspondingly large. Moreover, it is difficult to control the size of the bubbles, and there are many variations in the size of the recesses.
This invention is made | formed in view of such a condition, and makes it the 1st objective to provide the glass plate which has a recessed part which was finer than before and the size was equal. The second object of the present invention is to provide a method capable of efficiently producing the glass plate and applicable to a float method, which is a general-purpose plate glass production method.

In order to achieve the first object, the present invention is a glass plate obtained by suspending molten glass on molten tin, and is a surface in contact with molten tin (hereinafter also referred to as “bottom surface”). ) to provide a glass plate, characterized in that it is formed concave having a diameter 0.05~90μm four / mm ² or more. In the present invention, the diameter of the concave portion is a value obtained from an electron micrograph of the bottom surface of the glass plate, and the depth of the concave portion is obtained from the reflected light by irradiating the bottom surface with laser light. Value.
Further, in order to achieve the second object, the present invention floats a plate-like molten glass on the molten tin and directly generates a gas at the interface between the molten tin and the molten glass. on the side of the surface in contact with, to provide a method of manufacturing a glass plate and forming a recess having a diameter 0.05～90Myuemu 4 pieces / mm ² or more. Specifically, the following first to fourth manufacturing methods are provided.
(1) A method for producing a glass plate in which a plate-like molten glass is floated on molten tin, and a recess is formed on the surface of the plate-like molten glass on the side in contact with the molten tin, wherein the dew point is −30 ° C. or less and hydrogen. In an atmosphere composed of a mixed gas with nitrogen, the viscosity of the plate-like molten glass is maintained at a liquid surface temperature of 10 ³ to 10 ⁶ poise, and on the molten tin in which 200 ppm or more of oxygen is dissolved in the liquid surface layer, A first manufacturing method characterized by floating a molten glass.
(2) A method for producing a glass plate in which molten glass is cast on molten tin to form a glass ribbon, and a recess is formed on the surface of the glass ribbon in contact with the molten tin, the dew point being −30 On the molten tin in which the viscosity of the molten glass is maintained at a liquid surface temperature of 10 ³ to 10 ⁶ poises in an atmosphere composed of a mixed gas of hydrogen and nitrogen at a temperature of ≦ ° C. and oxygen is dissolved in the liquid surface layer by 200 ppm or more. Second, the second manufacturing method is characterized by casting molten glass.
(3) A method for producing a glass plate in which a plate-like molten glass is floated on molten tin, and a recess is formed on the surface of the plate-like molten glass on the side in contact with the molten tin, with a dew point of −30 ° C. or less and hydrogen. In an atmosphere composed of a mixed gas with nitrogen, the molten tin was floated on the molten tin maintained at a liquid surface temperature at which the viscosity of the molten molten glass was 10 ³ to 10 ⁶ poise. A third production method is characterized in that the anode is energized with a plate-shaped molten glass as a cathode.
(4) A method for producing a glass plate in which molten glass is cast on molten tin to form a glass ribbon, and a recess is formed on the surface of the glass ribbon in contact with the molten tin, the dew point being −30 On the molten tin maintained at a liquid surface temperature at which the viscosity of the molten glass is 10 ³ to 10 ⁶ poise in an atmosphere composed of a mixed gas of hydrogen and nitrogen at a temperature of ℃ or lower, the molten tin is used as an anode, A fourth production method characterized by casting molten glass while energizing as a cathode.
In the first and second production methods, in order to dissolve 200 ppm or more of oxygen in the molten tin liquid surface layer, oxygen gas or oxygen-containing gas is introduced from the molten tin liquid surface, or tin oxide is added to the molten tin. It is preferable to throw in the powder.
In the said 1st and 2nd manufacturing method, the mechanism in which a recessed part is formed in the bottom face of a glass plate is estimated as follows. That is, by introducing oxygen gas or oxygen-containing gas from the molten tin liquid surface, or introducing tin oxide powder into the molten tin, a depth of typically 10 mm from the molten tin liquid surface (typically 10 mm In the liquid surface layer, oxygen is dissolved, and particularly in the very vicinity of the liquid surface, the amount of dissolved oxygen is extremely high and is supersaturated. And when such a region and the bottom surface of the glass in the molten state come into contact with each other, the oxygen concentration is reduced to a saturated state at the interface between them, and at that time, excess oxygen becomes SnO (gas) and the molten tin It is estimated that this gas is released from the surface, this gas accumulates between the bottom surface and the molten tin, gradually deforms the bottom surface to form vacancies, and these vacancies eventually remain as recesses. The
In the third and fourth methods, the mechanism for forming the recesses on the bottom surface of the glass is estimated as follows. That is, by supplying electricity with the molten tin side as the anode and the molten glass side as the cathode, the alkali metal ions move in the glass and the charges move, and accordingly, the oxygen ions in the glass are charged on the bottom surface. It is presumed that oxygen is released as oxygen gas from the bottom surface, and this released portion remains as a recess.

FIG. 1 is a schematic view showing the main part of an apparatus for carrying out the first manufacturing method of the present invention.
FIG. 2 is a schematic view showing a main part of an apparatus for carrying out the third manufacturing method of the present invention.

Explanation of symbols

1: Furnace 2: Molten tin bath 3: Plate-shaped molten glass 4: Molten tin liquid surface 5: Airtight container 6: Gas introduction path 7: Gas exhaust path 8: Observation hole 9: Anode (carbon electrode)
10: Cathode (platinum electrode)
20: Molten tin 30: Hole

Hereinafter, the present invention will be described in detail.
The glass plate of the present invention has four or more concave portions having a diameter of 0.05 to 90 μm per 1 mm ^{2 on the} bottom surface. When using as a solar cell panel or when utilizing the non-permeability effect, it is preferable to use a recess having a diameter of 1 to 90 μm. In addition, the depth of the recess is more preferably 0.2 to 25 μm in order to improve the antireflection efficiency and the like. Furthermore, for use in a wider range of applications, it is preferable that 10 or more recesses are formed per 1 mm ² . Such a glass plate is obtained by the 1st-4th manufacturing method shown below, for example.
(First manufacturing method)
FIG. 1 is a diagram schematically showing an example of an apparatus for carrying out the first manufacturing method of the present invention, and a furnace having a low dew point of −30 ° or less and a 90% N ₂ /10% H ₂ atmosphere. 1 is provided with a molten tin bath 2 made of heat-resistant brick, and a plate-shaped molten glass 3 is floating. The molten tin bath 2 is made of a material having corrosion resistance to the molten tin 20, for example, SiO ₂ , ZrO ₂ , Al ₂ O _3, etc., and a gas introduction pipe 6 and a gas exhaust pipe 7 are connected, and the molten tin side is opened. The sealed container 5 is floated and forms a sealed space with the liquid surface 4 of the molten tin 20. In the recess formation mechanism described above, in order for the recess to be efficiently formed on the bottom surface of the plate-like molten glass 3 by the action of oxygen, it is preferable that the plate-like molten glass 3 is softened to some extent. , plate-shaped molten glass 3 is ¹⁰ 3 to 10 ⁶ poise, which is preferably maintained at a temperature flowing at a viscosity of ¹⁰ 3 to 10 ⁴ poise. Furthermore, for the same reason, the sealed container 5 is preferably as close as possible to the plate-like molten glass 3.
Oxygen gas or oxygen-containing gas is supplied to the sealed container 5 through the gas introduction path 6. Thereby, part of oxygen dissolves from the liquid surface 4 of the molten tin 20 and dissolves in the liquid surface layer at a high concentration of 200 ppm or more, preferably 200 to 2000 ppm, and the remainder is exhausted from the gas exhaust path 7. As the oxygen-containing gas, a mixed gas of oxygen and an inert gas, preferably nitrogen can be used.
In addition, the code | symbol 8 in a figure is an observation hole installed in order to observe the inside of the furnace 1. FIG.
In order to manufacture the glass plate of the present invention using the apparatus configured as described above, the plate-like molten glass 3 is floated on the molten tin 20, and oxygen gas or oxygen-containing gas is supplied to the sealed container 5 through the gas introduction pipe 6. Then, oxygen is dissolved in the liquid surface layer of molten tin 20 to maintain the dissolved amount of oxygen in the liquid surface layer at the above value. When the molten tin 20 in which oxygen is dissolved and the plate-like molten glass 3 come into contact with each other, bubbles are generated at the interface between them and grow gradually and large numbers of fine holes 30 are formed on the entire bottom surface. Then, when the temperature of the molten tin 20 is lowered, the plate-like molten glass 3 is cured, while the pores 30 remain as recesses, and finally a fine recess is formed on the bottom surface.
The dimensions (diameter and depth), shape, and density of the recesses are such that the oxygen concentration (dissolved oxygen concentration) dissolved in the liquid surface layer of the molten tin 20 and the plate-like molten glass 3 are retained on the molten tin 20. The time is adjusted appropriately and controlled. This dissolved oxygen concentration can be easily controlled by the amount of oxygen gas or oxygen-containing gas supplied to the sealed container 5.
(Second manufacturing method)
The second manufacturing method of the present invention is an application of the first manufacturing method to the float method. First, an outline of the float method will be described. The glass plate is manufactured by the float process. The glass raw material is charged into a glass melting furnace and melted. The molten glass overflowing from the glass melting furnace is cast on the molten tin in the molten tin bath and formed into a glass ribbon. The glass ribbon is gradually cooled while adjusting the thickness of the molten tin bath, and the glass ribbon pulled up from the molten tin bath is solidified by cooling in a slow cooling furnace, and then the solidified glass ribbon is cut. Is cut into a predetermined length to produce a glass plate, and is manufactured through a series of steps of taking a glass plate with a plate-taking device.
In order to carry out the second production method of the present invention, the above-described sealed container 5 may be attached to a float furnace (molten tin bath) similar to the conventional one. Provided that time, the glass ribbon is flowing, sealed container 5, a glass ribbon ¹⁰ 3 to 10 ⁶ poise at the liquid surface of the molten tin, preferably in the region flowing at a viscosity of ¹⁰ 3 to 10 ⁴ poise Is done. Furthermore, it is preferable that the sealed container 5 is as close as possible to the glass ribbon in the region. From such a viewpoint, the sealed container 5 is preferably disposed on both sides of the glass ribbon at a point where the molten glass flowing down from the glass melting furnace starts to be cast as a glass ribbon in the molten tin bath. . Moreover, the dissolved oxygen concentration of the liquid surface layer of molten tin is the same as that of the first manufacturing method.
When molten tin in which oxygen is dissolved and the glass ribbon come into contact with each other, bubbles start to form at the interface between the two, and as the glass ribbon moves, the bubbles grow larger and many fine voids are formed on the entire bottom surface. . Then, the glass ribbon further moves, cools, and cures, leaving voids as concave portions, and finally forming fine concave portions on the bottom surface. The size (diameter and depth), shape, and density of the recess depend on the concentration of oxygen dissolved in the liquid tin layer (dissolved oxygen concentration) and the time for holding the glass ribbon on the molten tin. In general, since the moving speed of the glass ribbon is determined by design, in the second manufacturing method, the dissolved oxygen concentration in the liquid surface layer of molten tin is appropriately adjusted. Thereafter, in the same manner as the ordinary float method, cutting and plate-making are performed after cooling.
In the first and second manufacturing methods, tin oxide (SnO ₂ ) powder is used instead of the above-described method of introducing oxygen gas or oxygen-containing gas in order to dissolve oxygen in the liquid surface layer of molten tin. It may be continuously or periodically put into an appropriate place where the sealed container is disposed. The tin oxide powder is easily dissolved in molten tin, and oxygen ions act on the bottom surface of the plate-like molten glass or glass ribbon in the same manner as described above. For this reason, the tin oxide powder is adjusted in the input amount and the input interval so that the dissolved oxygen amount is maintained at 200 ppm or more in the same manner as described above.
In the first and second production methods, the glass material (composition) is not limited as long as it can be float molded, and can be applied to conventional glass sheet materials that can be float molded.
(Third production method)
FIG. 2 is a view schematically showing an example of an apparatus for carrying out the third manufacturing method of the present invention, and a furnace having a low dew point of −30 ° or less and a 90% N ₂ /10% H ₂ atmosphere. 1 is provided with a molten tin bath 2 made of heat-resistant brick, and a plate-shaped molten glass 3 is floating. The plate-shaped molten glass 3 side is set as the cathode 10 and the molten tin 20 side is set as the anode 9 so as to be energized. The cathode material is not limited as long as it is a material that is not corroded by the plate-like molten glass, but a platinum electrode is preferable. Similarly, the anode material is not limited as long as it is a material that is not attacked by the molten tin 20, but a carbon electrode is suitable. There is no restriction | limiting in the electrode shape of the anode 9 and the cathode 10, It can be set as a rod-shaped electrode or a plate-shaped electrode. For example, as shown, the anode 9 can be a rod-shaped electrode and the cathode 10 can be a plate-shaped electrode. Further, in order to increase the energization efficiency, a plurality of pairs of anodes 9 and cathodes 10 can be used. The power source may be an alternating current, but in this case, the electrodes 9 and 10 are not distinguished from each other as an anode and a cathode.
In the recess formation mechanism described above, in order for the recess to be efficiently formed on the bottom surface of the plate-shaped molten glass 3 by the release of oxygen gas, it is preferable that the plate-shaped molten glass 3 is softened to some extent. similar to the method, molten tin 20 is plate-shaped molten glass 3 is ¹⁰ 3 to 10 ⁶ poise, which is preferably maintained at a temperature flowing at a viscosity of ¹⁰ 3 to 10 ⁴ poise.
In order to manufacture the glass plate of the present invention using the apparatus configured as described above, the anode 9 and the cathode 10 are energized while the plate-like molten glass 3 is floated on the molten tin bath 2. Like the recess formation mechanism described above, this energization causes the movement of alkali metal ions and the movement of charges in the plate-shaped molten glass 3, and the oxygen ions in the glass are released as oxygen gas, and the recesses are formed on the bottom surface. And remains. Since the movement of alkali metal ions and the movement of charges are proportional to the amount of energization, the amount of oxygen gas generated can be controlled by controlling the amount of energization, and as a result, the size, shape, and density of the recess can be controlled. .
The energized state is greatly influenced by the glass composition, particularly the alkali metal oxide content, and the third production method is based on silicate glass containing a total of 0.1 mol% or more of alkali metal oxides. This is a particularly effective method. In this case, when the energization amount is preferably 1.75 A / m ² or more, more preferably 3 A / m ² or more, the movement of alkali metal ions and the movement of charges can be efficiently performed.
(Fourth manufacturing method)
The fourth manufacturing method of the present invention is a method in which the third manufacturing method is applied to the float process, and a normal float process is performed with an energized state between the glass ribbon and the molten tin. At that time, the cathode 10 is provided in the molten glass in the glass melting furnace, the glass ribbon anode 9 ¹⁰ 3 to 10 ⁶ poise, preferably provided in a region flowing at a viscosity of ¹⁰ 3 to 10 ⁴ poise. The energization amount may be the same as in the third manufacturing method.

The following experiment was conducted to verify the effect of the present invention. Experimental Examples 1 to 4 relate to the first manufacturing method, Experimental Examples 5 to 7 relate to the second manufacturing method, and Experimental Examples 8 to 11 relate to the third manufacturing method.
(Experimental example 1)
In accordance with the apparatus shown in FIG. 1, a molten tin bath 2 made of heat-resistant brick was placed in a furnace 1 having an atmosphere of 90% N ₂ /10% H ₂ , and the bath temperature was maintained at about 1050 ° C. A soda lime glass plate (plate-shaped molten glass 3) having a diameter of 40 mm was floated on the molten tin 20, and a ZrO ₂ sealed container 5 was floated in the vicinity of the soda lime glass plate. Then, oxygen gas was supplied to the sealed container 5 through the gas introduction path 6 at a flow rate of 0.015 Nm ³ / min per 1 m ^{2 of} soda lime glass plate.
When the liquid surface of the molten tin 20 and the state of the soda lime glass plate were observed from the observation hole 8, bubbles started to be generated at the interface between the soda lime glass plate and the molten tin 20 almost at the same time as the supply of oxygen gas. Bubbles spread across the entire interface. After cooling, the soda lime glass plate was taken out, the bottom surface was photographed with an electron microscope, and the diameter of the recess was measured. Further, the depth of the recess was measured by scanning with laser light. As a result, hemispherical concave portions having a depth of about 10 μm and a diameter of about 40 μm and a uniform size were uniformly distributed at intervals of about 300 μm on the bottom surface.
(Experimental example 2)
A glass plate is obtained in the same manner as in Experimental Example 1 except that an oxygen-nitrogen mixed gas (oxygen concentration 21%) is introduced into the sealed container 5. On the bottom surface of the obtained glass plate, hemispherical concave portions having a depth of about 3 μm and a diameter of about 10 μm and uniform sizes are uniformly distributed at intervals of about 100 μm.
(Experimental example 3)
In Experimental Example 1, instead of introducing oxygen gas into the sealed container 5, 5 g of SnO ₂ powder was charged per 1 m ^{2 of} soda lime glass plate at the location where the sealed container 5 was disposed. When the liquid surface of the molten tin 20 and the state of the soda lime glass plate were observed from the observation hole 8, bubbles started to form at the interface between the soda lime glass plate and the molten tin 20 almost simultaneously with the addition of the SnO ₂ powder. The bubbles spread to the whole interface. On the bottom surface of the obtained glass plate, hemispherical concave portions having a depth of about 10 μm and a diameter of about 40 μm and a uniform size were uniformly distributed at intervals of about 300 μm.
(Experimental example 4)
In Experimental Example 1, instead of supplying oxygen gas to the sealed container 5, oxygen gas was sprayed directly onto the liquid surface 4 of the molten tin 20, so that the entire liquid surface of the molten tin 20 was covered with tin oxide (dross). . A soda lime glass plate was floated as it was to obtain a glass plate. On the bottom surface of the obtained glass plate, various concave portions having a depth of 5 to 20 μm and an outer diameter of 30 to 100 μm were scattered at intervals of 100 to 400 μm. The surface of the glass plate was also contaminated with tin oxide.
(Experimental example 5)
A glass plate in which hemispherical concave portions having a depth of about 10 μm and a diameter of about 40 μm and a uniform size are uniformly distributed at intervals of about 300 μm on the bottom surface can be manufactured by the float method, for example, as follows. .
A molten tin bath (float bath) made of heat-resistant brick with an atmosphere of 90% N ₂ /10% H ₂ is arranged, and the bath temperature is maintained at about 1050 ° C. In addition, ZrO ₂ sealed containers are disposed on both sides of the casting region of the glass ribbon at the position where the molten glass of the molten tin bath flows (position where the viscosity of the glass ribbon becomes approximately 10 ³ poise). Then, molten soda lime glass is supplied from a glass melting furnace to a molten tin bath and cast as a glass ribbon having a width of 3000 mm and a thickness of 6 mm at a speed of about 7 m / min. Oxygen gas of 0.015 Nm ³ / min per ² is supplied. Thereafter, the glass ribbon is cooled in a cooling furnace and cut into a glass plate.
(Experimental example 6)
A glass plate is obtained in the same manner as in Experimental Example 5 except that an oxygen-nitrogen mixed gas (oxygen concentration: 21%) is introduced into the sealed container. On the bottom surface of the obtained glass plate, hemispherical concave portions having a depth of about 3 μm and a diameter of about 10 μm and uniform sizes are uniformly distributed at intervals of about 100 μm.
(Experimental example 7)
In Experimental Example 5, instead of introducing oxygen gas into the sealed container, 5 g of SnO ₂ powder is charged per 1 m ^{2 of} the glass ribbon that passes through the location where the sealed container is disposed. On the bottom surface of the obtained glass plate, hemispherical concave portions having a depth of about 10 μm and a diameter of about 40 μm and a uniform size are uniformly distributed at intervals of about 300 μm.
(Experimental example 8)
In accordance with the apparatus shown in FIG. 2, a molten tin bath 2 made of heat-resistant brick and having an inner diameter of 100 mm is placed in a furnace 1 having a 90% N ₂ /10% H ₂ atmosphere, and the bath temperature is maintained at about 1050 ° C. A soda-lime glass plate having a diameter of 40 mm (alkali metal oxide content 13 mol%: plate-like molten glass 3) was floated. Moreover, while inserting the carbon electrode (anode 9) in molten tin, the platinum electrode (cathode 10) was mounted on the soda-lime glass plate, and both electrodes were connected to DC power supply.
And the voltage of 5V was applied for 1 minute, preventing a carbon electrode from contacting a soda-lime glass plate. The current value at this time was 3.5 mA. Thereafter, the soda lime glass plate was rapidly cooled, and the bottom surface of the obtained glass plate was observed in the same manner as in Experimental Example 1. As a result, hemispherical concave portions having a depth of about 10 μm and a diameter of about 40 μm and a uniform size were uniformly distributed at intervals of about 500 μm.
(Experimental example 9)
A glass plate was obtained in the same manner as in Experimental Example 8 except that the applied voltage was 20V. The current value was 7 mA. On the bottom surface of the obtained glass plate, hemispherical concave portions having a depth of about 20 μm and a diameter of about 100 μm and a uniform size were uniformly distributed at intervals of about 500 μm.
(Experimental example 10)
A glass plate was obtained in the same manner as in Experimental Example 8, except that the applied voltage was 100V. At this time, the current value was 35 mA at the beginning of voltage application, but decreased to 1 mA in the middle. On the bottom surface of the obtained glass plate, there were scattered spherical concave portions having a diameter of 500 μm or more and substantially closed openings.
(Experimental example 11)
A glass plate is obtained in the same manner as in Experimental Example 8, except that the voltage application time is 10 minutes. At this time, the current value is about 3.5 mA for 3 minutes after the voltage is applied, and then decreases to 1 mA. On the bottom surface of the obtained glass plate, there are scattered spherical recesses having a diameter of 500 μm or more and substantially closed openings.
From the above experimental examples 1 to 7, it was confirmed that in the first and second production methods, the size, shape, and density of the recesses on the bottom surface of the glass plate can be controlled by the amount of dissolved oxygen in the molten tin. Therefore, it was confirmed that the addition of SnO ₂ powder was also effective as an oxygen dissolving means. Moreover, it is confirmed from Experimental Examples 8 to 11 that the size, shape, and density of the recesses on the bottom surface of the glass plate can be controlled by the energization amount in the third manufacturing method. In addition, from Experimental Examples 8 to 11, in the fourth manufacturing method, it can be sufficiently analogized that the size, shape, and density of the concave portion of the glass plate bottom surface can be controlled by the energization amount, as in the third manufacturing method.

  As described above, since the glass plate of the present invention has a concave portion that is finer than that of the conventional one on the bottom surface, the antireflection effect and the antiglare effect are higher than the conventional one. Moreover, the glass manufacturing line by the float process can also be utilized for the manufacturing method of this invention, and the glass plate which has a recessed part in a bottom surface can be manufactured efficiently.

Claims (10)

Wherein a glass sheet obtained by floating molten glass on molten tin, the surface on the side in contact with molten tin, that is formed recess diameter 0.05~90μm four / mm ² or more A glass plate. The glass plate according to claim 1, wherein the recess has a diameter of 1 to 90 μm. The glass plate according to claim 1 or 2, wherein the recess has a depth of 0.2 to 25 µm. Plate-shaped molten glass is floated on the molten tin, gas is directly generated at the interface between the molten tin and the plate-shaped molten glass, and the surface of the plate-shaped molten glass on the side in contact with the molten tin has a diameter of 0.05 to 90 μm. 4. A method for producing a glass plate, comprising forming at least 4 recesses / mm ² . A method of manufacturing a glass plate in which a plate-like molten glass is floated on molten tin and a recess is formed on the surface of the plate-like molten glass on the side in contact with the molten tin, wherein the dew point is −30 ° C. or less and hydrogen and nitrogen In an atmosphere consisting of a mixed gas, the viscosity of the plate-like molten glass is maintained at a liquid surface temperature of 10 ³ to 10 ⁶ poise, and on the molten tin in which 200 ppm or more of oxygen is dissolved in the liquid surface layer, the plate-like molten glass The manufacturing method of the glass plate characterized by the above-mentioned. A method for producing a glass plate in which molten glass is cast on molten tin and formed into a glass ribbon, and a recess is formed on the surface of the glass ribbon in contact with the molten tin, the dew point being −30 ° C. or less. In an atmosphere consisting of a mixed gas of hydrogen and nitrogen, the molten glass is maintained at a liquid surface temperature at which the viscosity is 10 ³ to 10 ⁶ poise, and melted on molten tin in which 200 ppm or more of oxygen is dissolved in the liquid surface layer. A method for producing a glass plate, characterized by casting glass. The oxygen is dissolved in the liquid surface layer of molten tin by introducing oxygen gas or oxygen-containing gas from the liquid surface of molten tin or by introducing tin oxide powder into the molten tin. Manufacturing method of glass plate. A method of manufacturing a glass plate in which a plate-like molten glass is floated on molten tin and a recess is formed on the surface of the plate-like molten glass on the side in contact with the molten tin, wherein the dew point is −30 ° C. or less and hydrogen and nitrogen In an atmosphere consisting of a mixed gas, the molten tin is used as an anode in a state where the molten glass is floated on the molten tin maintained at a liquid surface temperature at which the viscosity of the molten glass is 10 ³ to 10 ⁶ poise. A method for producing a glass plate, comprising energizing a plate-shaped molten glass as a cathode. A method for producing a glass plate in which molten glass is cast on molten tin and formed into a glass ribbon, and a recess is formed on the surface of the glass ribbon in contact with the molten tin, the dew point being −30 ° C. or less. Using molten tin as an anode and molten glass as a cathode on molten tin maintained at a liquid surface temperature at which the melt viscosity of the molten glass is 10 ³ to 10 ⁶ poise in an atmosphere composed of a mixed gas of hydrogen and nitrogen A method for producing a glass sheet, comprising casting molten glass while energizing. The method for producing a glass plate according to claim 8 or 9, wherein the molten glass is a silicate glass containing a total of 0.1 mol% or more of alkali metal oxides.

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