JP2001192221A - Improvement of method for continuous production of sheet glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain sheet glass particularly having excellent flatness with high productivity. SOLUTION: The surface on the glass ribbon GL side of a supporting body 12 in forming the glass ribbon GL to sheet glass while sliding the glass ribbon GL and a supporting body 12 via a thin layer 18 of a vapor film is provided with grooves 12B or holes having an area of 1 to 500 cm2 per 1,000 cm2 of the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved continuous production method for sheet glass, and more particularly to an improved method for forming a glass sheet while sliding a glass ribbon through a thin layer of a vapor film.

[0002]

2. Description of the Related Art As a method of forming a sheet glass, a lifting method,
A downdraw method, a rollout method, a fusion method, a tin float method, and the like are known, and a tin glass method which is most widely used at present is a sheet glass forming method. In this method, a molten glass in which a predetermined raw material is melted in a melting furnace is introduced into a molten tin bath in a reducing atmosphere, and is spread and moved in the vertical and horizontal directions using a mechanical external force. It gradually cools to near the point temperature to form a flat glass plate with a smooth surface.Since the smoothness of the product is significantly improved compared to the conventional pulling method, the polishing process is unnecessary. did.

[0003] However, the tin float method is concerned with the depletion of tin resources, the need to maintain a reducing atmosphere using hydrogen gas in order to prevent oxidation of metallic tin,
Tin penetrates into the glass from the surface in contact with tin and adversely affects the quality of the product, is vulnerable to shaking such as earthquakes, takes time to recover production after an earthquake, and consumes a large amount of energy for heating and keeping the glass Problems.

[0004] In addition, in forming a sheet glass by a roll-out method or a tin float method, since a high-temperature molten glass comes into contact with a base material (metal roll) or a medium (tin) having high thermal conductivity, the heat flow between the molten glass and the molten glass is high. The bundle is large and the molten glass is greatly affected by the temperature of the substrate and the medium. Therefore, there is a problem that the temperature control of the substrate and the medium is very important and difficult.

Further, in the roll-out method, since the glass surface is rapidly cooled by contact with the metal roll, it is unavoidable that contact marks with the roll, wrinkles and irregularities remain on the formed sheet glass surface. The quality of the product deteriorates. On the other hand, in the tin float method, it is necessary to perform slow cooling in which the temperature of the tin bath is gradually brought close to the temperature of the glass so as not to generate a temperature distribution on the surface or inside of the glass during cooling, and the molding time is long. Therefore, there is a problem in terms of production efficiency.

In the pulling method, the downdraw method, and the fusion method, both surfaces of the molten glass are brought into contact with air, which is a medium having smaller thermal conductivity than glass, but are caused by gravity due to vertical molding. It is difficult to control the tension on the molten glass, and in any case, the largest stress acts on the uppermost part, making it difficult to control the thickness of the sheet glass and complicating the temperature control of the medium to reduce it. Problem.

Further, as another manufacturing method, a proposal has been made 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 (Japanese Patent Publication No. Sho 50-36445).
However, it is extremely difficult to directly and continuously supply a gas and stably maintain a molten or fluid high-temperature glass.

[0008] As described above, the conventional sheet glass manufacturing methods involve problems of the base material and medium to be used, quality problems such as homogeneity, thickness uniformity, and surface smoothness of the sheet glass, and problems in forming. However, none of the production methods was satisfactory.

[0009] From such a background, the present applicant has proposed a basic technique relating to a sheet glass forming method in which molten glass is formed into a plate shape by using a thin layer of a vapor film obtained by vaporizing a vapor film forming agent (Japanese Patent Laid-Open No. Hei 10 (1994)). 9-295819). According to the manufacturing method of the sheet glass, effects such as resource saving, energy saving, high quality of the sheet glass, reduction of equipment and operation cost, easy job change, various correspondences from small-scale production to large-scale production, and the like are exhibited. be able to.

[0010]

However, a method of forming a molten glass into a plate using a thin layer of a vapor film obtained by vaporizing a vapor film forming agent is a novel molding method that goes beyond the conventional idea. Therefore, it is necessary to improve the quality and process by examining the optimum conditions at the time of molding. In particular, the optimization of the grooves or holes formed in the support that slides relatively with the glass ribbon through the thin layer of the vapor film is extremely important for obtaining high quality sheet glass with high productivity.

The present invention has been made in view of such circumstances, and when molten glass is formed into a plate shape using a thin layer of a vapor film forming agent, grooves or holes formed in a support are formed. It is an object of the present invention to provide an improved continuous production method of a sheet glass capable of obtaining a high quality sheet glass with high productivity by optimizing the method.

[0012]

In order to achieve the above object, the present invention provides a method for continuously forming a molten glass ribbon supplied on a support into sheet glass, wherein a liquid is contained inside. Introducing a vapor film forming agent, which is not a gas at least around normal temperature but a gas at or above the glass transition point of the glass, in a liquid state into the support made of a material or a structure which can be used. Sliding the glass at a temperature equal to or higher than the transition point with each other through a thin layer of a vapor film formed by vaporizing the vapor film forming agent, wherein at least the glass ribbon of the support has a surface. In the area to be covered, 100% of the entire surface facing the glass ribbon
Wherein the 0 cm ² per 1 cm ² or more 500 cm ² or less of an area consisting of a plurality having grooves or holes are formed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a side view schematically showing a sheet glass forming apparatus for carrying out the present invention.

The molding apparatus 10 mainly includes supports 12, 12,... Formed so as to contain a vapor film forming agent therein.
A liquid supply device 16 for supplying a vapor film forming agent to the support 12;
A belt conveyor 20 that relatively slides the support 12 and the glass ribbon GL via a thin layer 18 of a vapor film in which a vapor film forming agent is vaporized, and a tension applying device 22 that applies tension to the glass ribbon GL. Be composed. On the front side of the molding apparatus 10, a glass melt G in which a glass raw material is dissolved is placed on a support 1.
A glass melting furnace 14 for supplying the glass melt 2 onto the support 2 is provided. The glass melt G is supplied onto the support 12 and then formed as a glass ribbon GL.

The glass melting furnace 14 melts a predetermined raw material to be a sheet glass and controls a melting temperature to prepare a glass melt G having a viscosity range and a temperature range suitable for molding. Since the viscosity of the glass melt G is controlled by the temperature, the viscosity is simultaneously controlled by controlling the temperature. In the case of molding a sheet glass, the dissolution depends on the glass composition.
In a temperature range of about 00 ° C., the reaction is carried out for a sufficient time so as to eliminate the glass bubble defect, the composition variation, and other defects.

The glass melt G whose temperature and viscosity have been adjusted by the glass melting furnace 14 is supplied to an outlet hole 14A of the glass melting furnace 14.
Is supplied onto the support 12 in the form of a ribbon. The glass melt G can be supplied from the glass melting furnace 14 by any method as long as the glass melt G can be supplied without excessive distribution in viscosity and temperature. That is,
It may be supplied directly from the orifice, lip, or slit onto the support 12 or may be preformed by a roll or the like (not shown) if excessive cooling can be prevented.

The support 12 may be a continuous unit or a combination of unit units of a predetermined length. Further, the support 12 may be a belt processed one, a unit roll continuously arranged, or the like. However, in the present embodiment, an example will be described in which a plurality of supports 12, 12,... Are arranged and fixed so as to be adjacent to the surface of the endless belt 20A of the belt conveyor 20. Then, a groove 12B that is not parallel to the moving direction of the glass ribbon GL is formed on the surface of the support 12 thus formed on the glass ribbon GL side.
Is formed. The groove 12B is effective for efficiently releasing excess vapor from the interface between the support 12 and the thin layer 18 of the vapor film. The groove 12B may be formed by opening a gap between the adjacent supports 12, and the support 1
It may be formed by engraving on the glass ribbon GL side of 2 itself. Further, a plurality of partial pieces constituting the support 12 may be formed by sticking to the surface of the endless belt 20A, and any method may be used.

Endless belt 20 for moving support 12
A is stretched between a pair of rolls composed of a drive roll 20C and a driven roll 20D, and is driven by rotation of a drive roll 20C that can rotate forward and reverse. Thereby, the endless belt 20A can make a circular movement in the forward direction (solid arrow 26 in FIG. 1) or the reverse direction (dashed arrow 28 in FIG. 1). Further, the moving speed of the endless belt 20 </ b> A is set to be different from the moving speed of the glass ribbon GL on the support 12. Thus, the support 12 and the glass ribbon GL
Is relatively sliding through the thin layer 18 of the vapor film.
Further, the belt conveyor 20 is provided with a guide plate 21 for guiding the upper movement path of the endless belt 20A, and the upper surface of the endless belt 20A moves stably by being guided by the guide plate 21.

The support 12 needs to have a material capable of containing a liquid therein or a structure capable of containing a liquid therein. For example, a porous body or a fibrous body is used. This porous body or fibrous body is different from the groove 12B described above, and is for supplying the vapor film forming agent toward the surface of the glass ribbon GL. In the case of a porous body, it is preferably a communication hole, and is formed of fine holes having a diameter of 5 mm or less, more preferably 1 mm or less, and still more preferably 100 μm or less. Further, it is preferable that the material has high affinity with the vapor film forming agent.

As a basic material of the support 12, porous hydrophilic carbon is particularly preferred, but other materials such as cellulose, paper, wood, bamboo and other natural materials, thermoplastic resin In addition, synthetic polymer materials such as thermosetting resins and rubbers, and carbon materials can be suitably used. Also iron,
Metal materials such as stainless steel and platinum, aluminum oxide,
Ceramic materials mainly containing metal oxides such as zirconium oxide, silicon carbide and silicon nitride, metal carbides and metal nitrides can also be used. Note that the molding surface of the support 12 may be very smooth except for fine holes or fibrous irregularities, or may have certain irregularities.

The support 12 is supplied with a vapor film forming agent from a liquid supply device 16, and the vapor film forming agent is supplied to the glass ribbon GL.
The thin layer 18 of the vapor film is formed between the plurality of arranged supports 12, 12,... And the glass ribbon GL by instantaneous vaporization with high heat. The thickness of the thin film layer 18 is preferably 10 μm or more and 500 μm or less.

As the vapor film forming agent, various organic and inorganic substances which are liquid at ordinary temperature and gas at or above the glass transition point can be used. From the viewpoint of the operability of supply to the support 12, it is preferable that the melting point is 40 ° C or less and the boiling point under atmospheric pressure is 50 to 500 ° C, more preferably 300 ° C or less. Further, it is preferable that the vaporized vapor film forming agent does not chemically react so as not to adversely affect the glass, has low toxicity, and is nonflammable at the temperature used. Can be used. As described above, as the vapor film forming agent, it is necessary to appropriately select a liquid capable of instantaneously vaporizing due to the high heat of the glass ribbon GL and forming a stable vapor film. Since the thermal conductivity of the thin layer 18 of the vapor film formed by instantaneous vaporization with high heat is significantly smaller than that of a liquid or a solid, an adiabatic environment can be formed for the glass ribbon GL. .

The liquid supply device 16 for supplying the vapor film forming agent to the support 12 is mainly composed of a bath 30 provided below the belt conveyor 20, and the endless belt 20A moves around and a pair of rolls 20C , 20D, the support 12 supported by the endless belt 20A is formed so as to go under the liquid of the vapor film forming agent in the bathtub 30. Thereby, the vapor film forming agent is supplied from the liquid supply device 16 to the support 12. Note that the liquid supply device 16 is not limited to a bathtub type, and may be, for example, a type in which a vapor film forming agent is sprayed on the support 12 or a wet roll (shown in the drawing). ), The wet roll is brought into contact with the support 12 to supply the vapor film forming agent.

The tension applying device 22 is composed of a pair of pinch rollers, and stretches the glass ribbon GL by being pinched and rotated in the pulling direction of the glass ribbon GL at the end portion of the belt conveyor 20 (the drive roll 20C side). For tension. The pinch roller is a pinch roller 22A.
And a pinch roller 22B.
The rotation speeds of A and 22B can be varied. Thus, by changing the tension applied to the glass ribbon GL, the thickness and quality of the formed sheet glass can be adjusted, and the contact time of the glass ribbon GL in contact with the thin layer 18 of the vapor film can be adjusted. Controls the cooling rate.

Sheet glass forming apparatus 1 constructed as described above
0 is used to illustrate the improved continuous production of sheet glass of the present invention. Note that an example of water will be described as a vapor film forming material.

When the glass melt G flows from the glass melting furnace 14 into a ribbon and flows down onto the support 12, the water held on the support 12 is instantaneously vaporized by the high heat of the glass ribbon GL. Thereby, water vapor is continuously generated at the interface between the glass ribbon GL and the support 12, and a thin layer 18 of a vapor film is formed between the glass ribbon GL and the support 12. In addition, air exists on the upper surface of the glass ribbon GL. Therefore, the glass ribbon GL is sandwiched between the thin layer 18 of the vapor film and the air to form an adiabatic environment. Here, the adiabatic environment means that the glass ribbon GL is covered with a medium (a thin layer of a vapor film, a gas) having a significantly lower thermal conductivity than glass.
An environment in which heating through the medium is not received so much that cooling of L is hindered, and there is an advantage that the temperature distribution in the thickness direction of the glass ribbon GL and the direction parallel to the glass ribbon GL surface in the forming process of the sheet glass can be reduced. . Then, the glass ribbon GL is cast on the thin layer 18 of the vapor film, and is formed into a plate-like glass by the tensile force of the tension applying device 22.

What is important in forming such a glass ribbon GL is that a groove 12 B is formed on the surface of the support 12. This groove 12B is caused, in part, by the steam generated from the support 12 pushing up the glass ribbon GL more than necessary, causing undesirable deformation of the glass ribbon GL, for example, a balloon phenomenon in which a part of the glass ribbon GL expands like a balloon. It plays a role as a steam discharge groove to prevent that. The groove 12B also plays a role of contributing to the extension of the glass ribbon GL by providing a light handling effect to the soft glass ribbon GL. Further, in a device that causes the support 12 to operate by a mechanism such as a belt conveyor, the connection portion of the support unit and the interval therebetween are necessary.

The area occupied by the groove 12B with respect to the surface of the support 12 is somewhat related to the temperature and viscosity of the glass ribbon GL to be processed, the relative moving speed of the support 12 and the glass ribbon GL, etc. At least a region of the support 12 facing the glass ribbon GL has a size of 1 cm ² or more and 500 c per 1000 cm ^{2 of the} entire surface facing the glass ribbon GL.
m requires ^two following areas. As a preferable lower limit, an area of 1 cm ² or more per 100 cm ^{2 of the} entire surface of the support 12 facing the glass ribbon GL is required.

Each of the grooves 12B provided in the support 12 preferably has a width of 1 mm or more and 10 mm or less and a depth of 2 mm or more, and the intervals are appropriately set. If the groove width is less than 1 mm, there is a possibility that the effect of discharging the steam may not be sufficiently exerted. Conversely, if the groove width exceeds 10 mm, the glass ribbon GL may not be sufficiently effective.
In a state where the viscosity is low, there is a high possibility that the water will flow down into the groove 12B and be fitted. The depth of the groove 12B is 2 m.
If not more than m, there is a possibility that a sufficient effect of discharging steam cannot be obtained. The width and depth of the groove 12B are not necessarily required to be constant, and various widths and depths may be mixed as long as they are within the above-described range.

It is necessary and desirable that the groove 12B is formed in a direction different from the moving direction 25 of the glass ribbon GL. This is because the groove 12B is formed in the same groove direction as the moving direction 25 of the glass ribbon GL. Is fitted into the groove 12B, and it is difficult to obtain a smooth and flat plate-like glass.
As described above, the direction of the groove 12B is not particularly limited as long as it is different from the moving direction 25 of the glass ribbon GL.
It may be in a direction perpendicular to the moving direction of L or at a certain oblique angle, and various directions may be mixed. Further, one groove 12B does not necessarily have to be straight, but may be curved.

In the present embodiment, the example of the groove 12B has been described as a structure for discharging steam. However, the shape of the steam discharging structure is not limited to the groove shape, and the cross section is circular or elliptical. The hole may have a rectangular shape or the like. Similarly, in the case of a hole, the diameter corresponding to the width is 1 mm or more and 10 mm.
Below, it is desirable that the depth is 2 mm or more. Further, it is also preferable to combine a groove-shaped and a hole-shaped vapor discharge structure as required. Further, in the case of the groove 12B including a gap formed between the supports, the thickness of the support 12 corresponds to the depth of the groove 12B.

Then, these grooves 12B or holes are
At least part of the structure is electrically connected to the outside of the support 12.

In the present invention, the quality of the molding is high because the molding factors such as the thickness of the thin layer of the vapor film, the cooling rate, and the relative sliding between the support 12 and the glass ribbon GL are organically related. It is a method of manufacturing a sheet glass, and it is desirable to control these forming factors by computer control.

[0035]

(Example 1) According to the embodiment of the invention, the support shown in FIG. 1 has a width of 40 mm, a length of 350 mm, and a thickness of 10 m.
m, at a center of the surface of the porous carbon (at a position of 20 mm in the middle of 40 mm in width), a groove having a width of 3 mm and a depth of 5 mm is perpendicular to the moving direction of the glass ribbon. The bottom of the groove is provided with an opening that is open to the outside (in a direction not facing the glass ribbon) over a length of 5 mm at intervals of 20 mm. Further, the distance between the porous carbon and the support having the same shape made of adjacent porous carbon is 3 mm.
The support is placed at a distance of 12 seconds per second in the same direction as the direction of movement of the glass ribbon.
Operate the conveyor to move at a speed of cm. A glass melt of soda lime glass having a normal composition at 1100 ° C. was allowed to flow down from the lip of the glass melting furnace at a flow rate of 270 kg / h on the support, and was drawn through a transport roll at a speed of 6 cm / s.

As a result, the glass ribbon on the support moves on the support via steam in a stable state, and has a width of 25c.
A plate glass having a thickness of 2 m and a thickness of 2 mm was formed. In this case, the groove, the sum of the areas of the gap between the support each other, the area of the support (3 + 3) /40=0.15, i.e., the support area 1000 cm ² per 150 cm ² Correspondingly, 1 cm ² or more per 1000 cm ² of the support area of the present invention.
The range of 00 cm ² or less was satisfied. (Comparative Example 1) The same operation as in Example 1 was performed using a support made of porous carbon having no grooves and with the gap between the supports being substantially zero. As a result, the glass ribbon on the support had large and small bulges, so that stable plate-like glass could not be formed. In this case, the ratio of the groove (including the gap between the supports) to the support area was substantially zero, deviating from the lower limit of the present invention of 1 cm ² or more per 1000 cm ² of the support area. (Comparative Example 2) The same operation as in Example 1 was carried out except that a groove having a width of 5 mm was provided at the center of the porous carbon and at a position of 10 mm (measured at the center) on both sides and a total of three grooves were provided. And the gap between adjacent supports was 6 mm. As a result, the glass ribbon on the support was not able to stably move on the support, and caused many bulges, so that a stable plate glass could not be formed. In this case, the ratio of the groove (including the gap between the supports) to the area of the support is (5 × 3 + 6) / 40 =
0.525, 5 per 1000 cm ^{2 of} support area
25 cm ² , which is the upper limit of the present invention.
000cm was out from ² per 500cm ² or less.

[0037]

As described above, according to the present invention,
High quality sheet glass can be obtained with high productivity.

[Brief description of the drawings]

FIG. 1 is a side view schematically illustrating a sheet glass forming apparatus for carrying out the present invention.

[Explanation of symbols]

10: sheet glass forming device, 12: support, 12B: groove,
14: glass melting furnace, 16: liquid supply device, 18: thin layer of vapor film, 22: tension applying device

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Isamu Kaneko 1150 Hazawa-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Asahi Glass Co., Ltd. (72) Inventor Kenji Oda 1-12-1 Yurakucho, Chiyoda-ku, Tokyo Asahi Glass Co., Ltd. (72) Inventor Shikuni Inoue Asahi Glass Co., Ltd., 1-12-1 Yurakucho, Chiyoda-ku, Tokyo (72) Inventor Gaku Kubo 1-1-1, Suehirocho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Asahi Glass Co., Ltd.

Claims (5)

[Claims] 1. A method for continuously forming a molten glass ribbon supplied on a support into a sheet glass, wherein the support is made of a material or a structure capable of containing a liquid therein. A step of introducing a vapor film forming agent which is not a gas in the vicinity but a gas at or above the glass transition point of the glass in a liquid state; and Sliding each other through a thin layer of a vapor film of a vaporized agent, the method comprising the steps of:
Improved flat glass continuous production method, wherein a groove or hole comprising a plurality having 1000 cm ² per 1 cm ² or more 500 cm ² or less of the area of the entire surface facing the glass ribbon is provided. 2. The method of claim 1 wherein said vapor film forming agent is water. 3. The groove or hole of the support has a width of 1 mm.
3. The improved continuous production method for a sheet glass according to claim 1, wherein the thickness is not less than 10 mm and the depth is not less than 2 mm. 4. The improved continuous production method of a sheet glass according to claim 1, wherein the grooves or holes of said support are formed in a direction different from a moving direction of the glass ribbon. 5. The improved sheet glass as claimed in claim 1, wherein at least a part of said groove or hole of said support is electrically connected to the outside of said support. Continuous manufacturing method.