JPH11268922A - Forming of glass plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the flatness of a glass plate by relatively sliding a support introducing a specific vapor film-forming agent into a support of a material or structure, capable of containing liquid in the interior and passing liquid and glass through a thin layer of vapor film-forming agent. SOLUTION: Melted glass heated in a glass-melting tank is make to have a viscosity suitable for forming by controlling the temperature and is passed through plural rolls and formed into ribbon-like shape to provide glass plate. The glass is heated to glass transition point or above and then, a support containing 5-300 wt.% vapor film-forming agent which is a liquid at a temp. of 20 deg.C±5 deg.C in a carbon substrate in which maximum diameter of passage capable of containing liquid, through which a liquid can be passed is <=1,000 μm is slid through a thin film of vapor film-forming agent to provide the objective glass plate in which flatness of the surfaces close to each other through the thin film of the vapor film-forming agent which exists as gas to glass is <=1 mm per unit surface area of 10 cm×10 cm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method in which a support capable of containing a liquid therein and glass at a temperature equal to or higher than the glass transition point are provided through a thin layer of vapor generated by vaporization of a vapor film forming agent. The present invention relates to a method for forming a glass sheet including a step of relatively sliding the glass sheet.

[0002]

2. Description of the Related Art At present, the most widely used method for manufacturing a glass sheet is to melt a predetermined raw material in a melting furnace and then melt the molten metal in a reducing atmosphere at a temperature at which the viscosity of the glass becomes about 10,000 poise. Introduced onto a tin bath, spread and moved in the vertical and horizontal directions using mechanical external force, gradually cooled to near the glass transition point, and made into a flat glass with a smooth surface, the so-called tin bath float method is there. In this method, the smoothness of the product is remarkably improved as compared with the conventional roll-out method or the like.

However, the tin bath float method has the following problems. In other words, the tin bath float method uses a large amount of tin, so there is concern about depletion of tin resources, which cannot be said to be abundant, and it is necessary to maintain a reducing atmosphere using hydrogen gas to prevent oxidation of metal tin. The fining agents that can be used are limited, and the burden on costs and safety is increased. Tin penetrates into the interior from the surface that comes in contact with tin, affecting the quality of the product. The reason is that it takes a long time to recover production after an earthquake, the equipment becomes large and the investment becomes huge, and a large amount of energy is used for heating and keeping the glass.

[0004] On the other hand, production methods such as the so-called fusion method have been proposed, but they have not been satisfactory in terms of surface smoothness of products, stable productivity and quality, dimensions of obtained products, and the like. There is also a proposal (Japanese Patent Publication No. 50-36445) in which a gas such as air is supplied from pores on the surface of a support, and molten glass is spread thereon to form a glass plate. An enormous amount of gas is required for continuous supply. In addition, it is very difficult to balance and control the pressure required for passing through the pores, the stable flow rate, and the temperature. Therefore, this method is not practical.

[0005] In order to solve these problems, the present inventors have proposed a method of continuously forming glass into a plate shape. The method uses a material or structure capable of containing a liquid therein and through which the liquid can pass. A step of introducing a vapor film forming agent which is in a gas state at a temperature equal to or higher than the glass transition point of the glass into the support, and converting the support and glass at a temperature equal to or higher than the glass transition point into a gas. A method of forming a glass sheet including a step of relatively sliding through a thin layer of a vapor film forming agent has been previously proposed (JP-A-9-295819).

The vapor film forming agent mentioned here has a melting point of 40 ° C. or less, a boiling point of 50 to 500 ° C. under atmospheric pressure, and a temperature of 200 ° C. or less from the viewpoint of operability such as supply to a support. It is said that a stable non-combustible substance that does not decompose is preferable.

[0007]

However, the method disclosed in Japanese Patent Application Laid-Open No.
The -295819 molding method had a problem that the flatness of the glass plate had to be improved. An object of the present invention is to solve the above problems.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for continuously forming glass into a plate-like shape, comprising a support made of a material or a structure capable of containing a liquid therein and allowing the liquid to pass therethrough. Introducing a vapor film forming agent which is gaseous at or above the glass transition point of the glass; and And a step of relatively sliding through a thin layer of a glass substrate, wherein a carbon substrate capable of containing a vapor film forming agent in an amount of 5 to 300% by weight based on the carbon substrate is used as the support. Provided is a method for forming a glass plate.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS There are various embodiments of the invention corresponding to the embodiments described in the above-mentioned Japanese Patent Application Laid-Open No. 9-295819. Here, one of them will be described, but the present invention is not limited to this.

As the liquid contained in the support, a vapor film forming agent in a liquid state is preferably used. The vapor film forming agent is preferably a liquid at around normal temperature.
At a temperature of 5 ° C. ± 5 ° C., a liquid is preferable. The vapor film forming agent preferably has a freezing point of 10 ° C. or less. The vaporized vapor of the vapor film forming agent is preferably a non-flammable vapor which does not chemically react with glass to the extent that glass quality is impaired, has low toxicity, and is stable at the temperature of the atmosphere in which it is used. As a vapor film forming agent satisfying such requirements, a liquid containing water as a main component is preferable. Hereinafter, a case will be described in which water is used as the vapor film forming agent and the vapor is steam.

After the molten glass heated in the glass melting furnace is adjusted to a temperature suitable for forming by adjusting the temperature, the molten glass is passed through a plurality of rolls and formed into a ribbon shape. Next, glass shaped into a ribbon (hereinafter referred to as a glass ribbon)
Is made to flow down onto a belt conveyor which is arranged at regular intervals and has a plate-like carbon substrate which can contain water in the range of 5 to 300% by weight and through which water or steam or a mixture thereof can be passed, and which is placed in a substantially horizontal state. . A tensile force is applied to the glass ribbon flowing down on the belt conveyor in the same direction as the traveling direction of the belt, and the glass ribbon is moved to a slow cooling zone which is a cooling step. In addition to the tensile force, a mechanical external force may be applied in the width direction of the glass ribbon perpendicular to the traveling direction of the belt to extend the glass ribbon.

The traveling speed of the belt on the belt conveyor is set to be different from the moving speed of the glass ribbon flowing down on the belt conveyor, so that the belt and the glass ribbon relatively move (slide). The supply of water to the support is possible at any part of the support except for the surface of the support which is in close proximity to the glass via a thin layer of water vapor.
For example, it is carried out by bringing a wet roll containing water into contact with a belt surface (carbon plate surface) facing vertically downward on the back side (return portion of the belt) of the belt conveyor that does not slide with the glass.

The carbon substrate used as the support must be able to contain water in the range of 5 to 300% by weight of water. If the water content is less than 5%, the amount of water that escapes from the support due to the generation of water vapor exceeds the amount of water supplied to the support, making it difficult to form a thin water vapor layer constantly. .
If it is more than 300%, bumping of water occurs, and the glass undergoes unnecessary deformation, and the flatness of the glass plate may be deteriorated. The amount of water that can be contained in the carbon substrate is determined by calculating the difference between the weight of the carbon substrate before and after impregnation by impregnating the carbon substrate with water, and calculating the ratio of the difference between the weight of the carbon substrate and the weight before impregnation. It is a representation.

The carbon substrate used as a support includes
There is a passage through which water passes, a passage through which water vapor generated by evaporation of water, or a passage through which a mixture of water and water vapor passes. The maximum diameter of this passage is preferably 1000 μm or less. If it is larger than 1000 μm, bumping of water occurs and the glass undergoes unnecessary deformation, and the flatness of the formed glass plate deteriorates. The maximum diameter of the passage is measured by an optical microscope or the like.

The volume occupied by the passages in the carbon substrate used as the support is preferably at least 5% of the volume of the carbon substrate. If it is less than 5%, the amount of water that escapes from the carbon substrate due to the generation of water vapor exceeds the amount of water supplied to the carbon substrate, making it difficult to form a water vapor thin layer constantly. The volume occupied by the passage in the carbon substrate is obtained by calculating the difference between the apparent specific gravity and the true specific gravity of the carbon substrate, calculating the ratio of this to the apparent specific gravity, and expressing the result in%.

The unevenness of the surface of the carbon substrate adjacent to the glass ribbon via the thin water vapor layer is preferably 1 mm or less in a range of 10 cm × 10 cm. If it is larger than 1 mm, problems such as damage to the glass ribbon at the convex portion, deterioration of the flatness of the glass plate due to unnecessary deformation of the glass ribbon, and the like occur. Since a steep convex part deteriorates the flatness of a glass plate more than a gentle concave part,
More preferably, there is no sharp projection. The surface irregularities are measured by a stylus method. There are various types of irregularities on the surface of the carbon substrate referred to here, but irregularities of any shape including steps, dents, and the like.

Further, it is preferable that the carbon substrate is provided with a steam discharge portion of 1 cm ² or more per 1000 cm ^{2 of} the surface adjacent to the glass ribbon via the thin steam layer. Without such a steam discharge part, in the carbon substrate,
Alternatively, water vapor generated between the glass ribbon and the carbon substrate cannot be discharged smoothly. As a result, a high pressure portion is locally generated in the thin steam layer, and the glass ribbon is subjected to unnecessary deformation, thereby deteriorating the flatness of the glass plate.

As the steam discharging portion, for example, one or more grooves (hereinafter, referred to as steam discharging grooves), one or more holes (hereinafter, referred to as steam discharging grooves).
It is called a steam exhaust hole. ) Or combinations thereof.

As the vapor discharge groove, a gap between carbon substrates arranged as a support can be used. In this case, the water vapor generated between the glass ribbon and the carbon substrate is discharged from a portion where the groove is not covered by the glass ribbon or the like. Further, a groove may be provided on the surface of the carbon substrate as a vapor discharge groove.

As the vapor discharge hole, a hole penetrating a carbon substrate can be used. In this case, the water vapor generated between the glass ribbon and the carbon substrate is discharged from the side where the holes are not covered by the glass ribbon or the like.

[0021]

EXAMPLE Soda lime silica glass (SiO ₂ : 70)
Wt%, Al ₂ O _3: 1.8 wt%, CaO: 9.8 wt%, MgO: 4.2 wt%, Na ₂ O: 13.0 wt%, K ₂ O: 0.7 wt%) Is melted in a platinum crucible at 1500 ° C. for 30 minutes, and then poured down into a 10 cm square iron frame laid on a carbon plate and placed horizontally on a moving floor at 5 cm per second. The carbon plate has a size of 20 cm × 5 cm × 5 mm in thickness, and contains 18% of water in terms of% by weight.

The supply of water to the carbon plate is performed by supplying water to a hydrophilic nonwoven fabric (20 cm in width) that comes into contact with the carbon plate. The average diameter of the passage through which water or steam passes through the carbon plate is 20 μm, and the maximum diameter is 100 μm.
m, and the volume of the passage is 30% of the volume of the carbon plate. The unevenness of the surface of the carbon plate in a range of 10 cm × 10 cm is 50 μm or less.

[0023] Between each carbon plate of the moving bed,
An open groove (steam discharge groove) of 2 mm is provided as a steam discharge part. This is 40 per 1000 cm ² of carbon plate
Corresponds to a cm ² vapor outlet. The horizontal flatness of the moving bed is set so that the level difference between the surfaces of the respective carbon plates is ± 40 μm or less.

The temperature of the glass when flowing is about 1200 ° C. The temperature of the glass is about 7 in 50 seconds after flowing down on the carbon plate.
The temperature is lowered to 00 ° C., at which point the glass plate is taken out of the moving bed, placed in a lehr set at 500 ° C., and cooled to room temperature over 24 hours. The surface of the obtained 10 cm square glass plate close to the carbon plate had a flatness of ± 50 μm within the 8 cm square of the central portion, and a glass plate having the same flatness as the fired surface was obtained.

[0025]

According to the present invention, it is possible to provide a method for forming a glass plate having good flatness.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutomu Koyama 1150 Hazawa-machi, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Asahi Glass Co., Ltd. 72) Inventor Toru Shimoyama 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa

Claims (5)

[Claims] 1. A method for continuously forming glass into a plate-like shape, wherein a glass transition point of the glass is provided in a support made of a material or structure capable of containing a liquid therein and through which the liquid can pass. In the above, a step of introducing a vapor film forming agent which is gaseous, and the support and glass at a temperature equal to or higher than the glass transition point,
A step of relatively sliding through a thin layer of a gaseous film-forming agent in the form of a gas, comprising the steps of:
A method for forming a glass sheet using a carbon substrate which may contain from 300 to 300% by weight. 2. The support, wherein the maximum diameter of a passage through which the vapor film forming agent passes through the support is 1000 μm or less, and the volume of the passage in the support is 5% of the volume of the support.
The method for forming a glass sheet according to claim 1, wherein the above-mentioned carbon substrate is used. 3. The support according to claim 1, wherein said support has a thin film of a vapor film forming agent, and a surface of 10c which is close to glass.
1 m per unit surface area of mx 10 cm
3. The method for forming a glass sheet according to claim 1, wherein a carbon substrate having a diameter of not more than m is used. 4. The support according to claim 1, wherein said support has a thin film of a vapor film-forming agent, and has a surface close to said glass.
claim 1, 2 or 3 forming method for a glass plate according using carbon substrate having a cm ² per 1 cm ² or more steam discharge portion. 5. The method for forming a glass sheet according to claim 1, wherein the vapor film forming agent comprises a liquid containing water as a main component.