WO2014091967A1

WO2014091967A1 - Float glass production device and float glass production method

Info

Publication number: WO2014091967A1
Application number: PCT/JP2013/082492
Authority: WO
Inventors: 誓也田中; 要介稲井
Original assignee: 旭硝子株式会社
Priority date: 2012-12-11
Filing date: 2013-12-03
Publication date: 2014-06-19
Also published as: JPWO2014091967A1; KR102120201B1; KR20150095662A; CN104837780A; TW201422540A

Abstract

The present invention provides a float glass production device and a float glass production method that suppress the dropping of tin fixed to a top roll surface on to a glass ribbon or inside a molten tin bath during production, and suppress variation in glass ribbon plate thickness. The present invention pertains to a float glass production device comprising a float bath (230) wherein a molten glass ribbon (240) is carried, and a top roll (300) used to suppress the expansion/contraction of the molten glass ribbon (240). The float glass production device (200) is characterized by: the top roll (300) having a rotatable tip section (320) that comes in contact with the molten glass ribbon (240); the tip section (320) having a hollow structure having an internal tip section space (322), and having a flow channel that provides cooling water to the tip section space (322); and the fluctuation margin for the cooling water temperature being controlled to within 4°C per day, by a temperature control device (265) comprising a temperature measurement device that measures the cooling water temperature and is arranged on the outside of the float bath, and a cooling device that cools the cooling water having had the temperature thereof increased by heat exchange inside the float bath.

Description

Float glass manufacturing apparatus and float glass manufacturing method

The present invention relates to a float glass manufacturing apparatus and a float glass manufacturing method.

A float method is known as one method for producing a glass plate. In this float process, a plate glass is roughly manufactured through the following steps.

(1) The molten glass is introduced onto the surface of the molten tin accommodated in the float bath.

(2) On the molten tin, the molten glass is continuously conveyed from the upstream side to the downstream side to form a glass ribbon.

(3) Slightly hold the side edges of the glass ribbon to suppress shrinkage in the width direction of the glass ribbon.

(4) A sheet glass is produced by slowly cooling the glass ribbon and pulling it out of the float bath by roll conveyance.

Here, in the step (3), an apparatus called a top roll is used. This top roll controls the width and thickness of the glass ribbon of the molten glass that has flowed into the float bath and advances the glass ribbon to the upstream area of the float bath (the side on which the molten glass flows into the float bath). A plurality of edge rolls arranged on both edge portions of the glass ribbon in the region (1). The top roll is provided with a rotating member at the tip. Therefore, the rotating member is brought into contact with the surfaces of the edge portions on both sides of the glass ribbon, the glass ribbon is pressed and the rotating member is rotated, thereby suppressing the shrinkage of the glass ribbon and having a predetermined width and thickness. Can be transported. In the following description, the term “shrinkage of the glass ribbon” means shrinkage in the width direction of the glass ribbon.

In addition, since the tip part of the top roll is in direct contact with the high temperature glass ribbon, the temperature may rise significantly during use in an uncooled state. For this reason, the top end portion of the top roll is usually cooled by circulating cooling water through a flow passage formed inside the top roll (for example, Patent Documents 1 and 2).

溶融 Molten tin adheres to the top roll in the molten tin bath over time. This is because the top roll is water-cooled and is a relatively low temperature member in the molten tin bath, so that the volatilized tin etc. in the molten tin bath condenses on the top roll surface, This is probably because molten tin adheres directly for some reason. When tin adhering to the contact portion between the top roll and the glass ribbon increases, the pressure of pressing the glass ribbon with the top roll fluctuates due to the thickness of the tin, or the tin tends to adhere to the glass ribbon, It may be difficult to separate the glass ribbon from the top roll. As a result, the thickness of the glass ribbon fluctuates, and there is a problem that it is difficult to manufacture a plate glass having a uniform thickness.

The top roll can be intermittently vibrated or an inert gas can be sprayed onto the top roll to prevent an increase in the amount of tin adhering to it. I can't get it. Further, since the adhesion between tin and the top roll becomes stronger with time, it is necessary to replace the top roll after a certain period of time, and there is a problem that productivity is impaired.

Therefore, by the float method characterized in that adhesion of foreign matters such as molten tin to the surface of the top roll used in the molten tin bath for the production of plate glass by the float method is reduced by a thin film provided on the top roll surface. The invention regarding the manufacturing method of plate glass, and the top roll which reduces adhesion of foreign materials, such as the said molten tin suitable for this method, was provided (patent document 1).

Japanese Unexamined Patent Publication No. 2008-189516 International Publication No. 2010/147189

However, even if the measures according to the invention are taken, it is not possible to completely suppress the adhesion of tin to the top roll surface, and tin stuck to the top roll surface falls on the glass ribbon during production, The pressure to hold the glass ribbon with the top roll fluctuated, and the fluctuation of the glass ribbon width could not be suppressed.

In addition, when tin adhered to the top roll surface falls into the molten tin bath during production, bubbles are generated, and a concave bubble defect occurs on the bottom surface of the glass ribbon, affecting the productivity of the plate glass. It was.

Here, the temperature of the cooling water of the top roll fluctuates according to the fluctuation of the outside air temperature. That is, the temperature of the cooling water is high during the day and low at night. Therefore, depending on fluctuations in the outside air temperature, tin adhered to the top roll may fall on the glass ribbon or into the molten tin bath during production due to the difference in thermal expansion from the top roll surface.

Further, the temperature fluctuation of the glass ribbon in contact with the top roll was caused by the temperature fluctuation of the cooling water of the top roll, the pressure for pressing the glass ribbon with the top roll was fluctuated, and the fluctuation of the glass ribbon width could not be suppressed.

The present invention has been made in view of such circumstances, and it is possible to suppress that the tin adhered to the surface of the top roll falls on the glass ribbon or in the molten tin bath during production, and the fluctuation of the plate width of the glass ribbon. Another object of the present invention is to provide a float glass manufacturing apparatus and a float glass manufacturing method that suppress a concave bubble defect on the bottom surface of a glass ribbon.

In this invention, it is a float glass manufacturing apparatus provided with the float bath in which a molten glass ribbon is conveyed, and the top roll used for suppression of shrinkage | contraction of the said molten glass ribbon, Comprising: The said top roll is the said molten glass ribbon. The tip has a hollow structure having a tip space inside, and has a flow passage for supplying cooling water to the tip space, The temperature control device comprising a temperature measuring device installed outside the float bath for measuring the temperature of the cooling water, and a cooling device for cooling the cooling water whose temperature has risen due to heat exchange in the float bath, the temperature control device comprising: The float glass manufacturing apparatus is characterized in that the fluctuation range of the temperature is controlled within 4 ° C. per day.

Preferably, the fluctuation range is controlled within 3 ° C. per hour.

Preferably, the cooling device includes a cooling tower of a water circulation system and a cooling fan whose rotation speed is controlled manually or by an inverter.

Furthermore, preferably, the upper limit temperature of the cooling water measured by the temperature measuring device is 40 ° C. or less.

In the present invention, the step of introducing the molten glass into the float bath, the step of transporting the molten glass from the upstream side to the downstream side of the float bath, forming a glass ribbon, and the top end portion of the top roll as the glass A step of suppressing shrinkage of the glass ribbon by rotating while pressing against the upper surfaces of both sides of a predetermined region in the ribbon traveling direction, wherein the top roll has a rotatable tip The tip portion has a hollow structure having a tip portion space inside, and has a flow passage for supplying cooling water to the tip portion space, and the temperature of the cooling water is adjusted outside the float bath. And a temperature control means having cooling means for cooling the cooling water whose temperature has risen due to heat exchange in the float bath. , In the tip space and the flow passage, a float glass manufacturing method characterized in that the fluctuation range of the temperature of the cooling water is controlled within 4 ° C. on a daily basis is provided.

Preferably, the fluctuation range is controlled within 3 ° C. per hour.

Preferably, the cooling means includes a cooling tower of a water circulation system and a cooling fan whose rotation speed is controlled manually or by an inverter.

Furthermore, preferably, the upper limit temperature of the cooling water measured outside the float bath is set to 40 ° C. or less.

In the present invention, tin adhered to the surface of the top roll is prevented from falling on the glass ribbon or in the molten tin bath during production, and fluctuations in the plate width of the glass ribbon, or concave bubble defects on the bottom surface of the glass ribbon. It is possible to provide a float glass manufacturing apparatus and a float glass manufacturing method for suppressing the above.

FIG. 1 is a flowchart schematically showing a flow of a method for producing a plate glass by a float process. FIG. 2 is a top view schematically showing an example of the upper surface of the float bath of the float glass manufacturing apparatus. FIG. 3A is a side sectional view schematically showing an example of the relative positional relationship between the top roll and the glass ribbon, and an example of the tip end portion of the top roll. FIG. 3B is a cross-sectional view schematically showing an example of the tip portion of the top roll. FIG. 4 is a schematic view of a water circulation system as an example of the cooling device in the present invention. FIG. 5 is a flowchart schematically showing the flow of the method for manufacturing a glass sheet according to the present invention. FIG. 6 is a graph of changes over time in the temperature of the top roll cooling water and the outside air temperature.

Hereinafter, the features of the present invention will be described in detail.

First, in order to better understand the present invention, a plate glass manufacturing process by the float method will be briefly described with reference to FIG.

FIG. 1 schematically shows a flow chart of a method for producing a plate glass by a float process. The manufacturing method of plate glass by the float process is
(I) a melting step (step S110) for melting the raw materials to produce molten glass;
(II) In the float glass production, a glass ribbon forming step (step S120) for introducing a molten glass into a float bath and forming a glass ribbon;
(III) A slow cooling step (step S130) in which a glass ribbon is obtained by gradually cooling the glass ribbon in a slow cooling furnace;
Have

In the melting step (I), molten glass is manufactured by putting raw materials such as silica sand, limestone, and / or soda ash prepared and mixed in accordance with the composition of the plate glass into a melting furnace. The temperature of the melting furnace varies depending on the composition of the plate glass, but is, for example, about 1400 ° C. to 1600 ° C.

The heating method is not particularly limited. For example, the raw material may be heated by a flame of a burner provided inside the melting furnace. The burner uses, for example, heavy oil or natural gas as fuel. Alternatively, heating may be performed using a general electric melting furnace.

(II) In the glass ribbon forming step, the molten glass obtained in the step (I) is introduced into a float bath containing molten tin to form a glass ribbon. Moreover, the obtained glass ribbon is carried out from the exit of a float bath. This process will be described in detail later.

(III) In the slow cooling step, the glass ribbon drawn out of the float bath is slowly cooled to provide plate glass.

The slow cooling furnace can supply heat from the combustion gas or electric heater to a required position in the slow cooling furnace. Therefore, the glass ribbon introduced into the slow cooling furnace at a relatively high temperature is finally cooled to a temperature range close to normal temperature and discharged from the slow cooling furnace.

A plate glass is manufactured by the above process.

Next, with reference to FIG. 2, the above-described step (II) (step S120) will be described in more detail.

FIG. 2 is a diagram schematically showing an example of a top view of the float bath of the float glass manufacturing apparatus used in the glass ribbon forming step (II) (step S120).

The float glass manufacturing apparatus 200 includes an introduction unit 210, a float bath 230, a transport apparatus 280, and a top roll 300.

The introduction part 210 is a part for introducing the molten glass obtained in the aforementioned step (I) into the float bath 230 having molten tin (including molten tin alloy, hereinafter referred to as molten tin) 220 inside. It is.

The molten glass introduced into the float bath 230 continuously moves from the upstream side 232 to the downstream side 234 of the float bath 230 in a state of floating on the surface of the molten tin 220, whereby the glass ribbon 240 is moved. It is formed.

Note that the glass ribbon 240 tends to reach an equilibrium thickness (for example, around 7 mm) due to the relationship between the surface tension of the molten glass and gravity in an unconstrained state, while the glass ribbon is pulled and conveyed in the traveling direction. In particular, the width (the length in the vertical direction in FIG. 2) tends to shrink toward the central direction. Therefore, the top roll 300 is used to suppress the shrinkage of the glass ribbon 240 and maintain the thickness of the glass ribbon 240 at a predetermined thickness.

The temperature measuring device 260 is a device that measures the temperature of the cooling water of the top roll 300, and is installed outside the float bath 230. For the temperature measuring device 260, for example, a thermocouple is used. By sequentially displaying the measured temperature data on the screen of the temperature display device 261, the monitor can easily grasp the measured temperature data.

Based on the measured temperature measured by the temperature measuring device 260, the fluctuation range is set to 4 ° C. or less per day manually by a monitor or by the cooling fan 263 whose rotation speed is controlled by the inverter 262. The fluctuation range in the present invention means a difference between the maximum temperature and the minimum temperature.

Explain the control of fluctuation range. For example, when the production of float glass is carried out from morning to noon, the outside temperature tends to rise. If the temperature of the cooling water is also increasing and the fluctuation range is likely to be outside the desired range, the number of rotations of the cooling fan 263 is increased.

When the float glass is manufactured from day to night, the outside air temperature is on a downward trend. When the temperature of the cooling water tends to decrease and the fluctuation range is likely to be outside the desired range, the rotational speed of the cooling fan 263 is decreased.

In the above description, the rotational speed of the cooling fan 263 is increased from morning to noon, and the rotational speed of the cooling fan 263 is decreased from day to night. However, the present invention is not limited to this. Even at midnight, when the fluctuation range of the temperature of the cooling water is likely to be outside the desired range, the rotational speed of the cooling fan 263 is increased or decreased.

In addition, the inverter 262 once converts AC power supplied as a driving power source for the cooling fan 263 into DC power, and converts it back to AC power having a frequency different from that of the AC power. Since the rotation speed of the cooling fan 263 depends on the frequency of the AC power converted again, the rotation speed of the cooling fan 263 can be finely adjusted by changing the frequency of the AC power. Therefore, the temperature of the cooling water can be kept within a desired fluctuation range.

When the temperature of the cooling water rises and is likely to be outside the range of the desired fluctuation range, the inverter 262 converts the drive power frequency of the cooling fan 263 to a high frequency and increases the rotational speed of the cooling fan 263. In addition, when the temperature of the cooling water is likely to fall and fall outside the desired fluctuation range, the inverter 262 converts the driving power frequency of the cooling fan 263 to a low frequency and reduces the rotational speed of the cooling fan 263. Let

The control means of the inverter 262 sends a command for adjusting the rotational speed to the cooling fan 263 that supplies cooling air so that the measured temperature approaches the preset temperature by feedback control such as PID control. In this way, by performing temperature measurement, cooling condition setting, and cooling condition change sequentially and continuously, the temperature measured by the temperature measuring device 260 is within the predetermined temperature range from the set temperature. The temperature of the cooling water is controlled.

The PID control includes a proportional element (P), an integral element (I) and a differential element (D), and receives a temperature deviation between the measured temperature and the target temperature. The distribution ratio is calculated according to the proportional gain, integration time, and derivative time, and the driving power frequency of the cooling fan 263 is determined.

FIG. 3 shows the relative positional relationship between the glass ribbon 240 and the tip portion 320 of the top roll 300 when the top roll 300 is used to maintain the thickness of the glass ribbon 240 at a constant thickness.

As shown in FIG. 3, the top roll 300 has a disk-shaped rotating member 325 at the distal end portion 320. In a normal case, the rotating member 325 has a protrusion 326 formed along the circumferential direction around the rotating member 325.

When the rotating member 325 is brought into contact with the surfaces of both side portions along the traveling direction of the glass ribbon 240, both side portions of the glass ribbon 240 are pressed by the rotating member 325, particularly the protrusion 326, and the rotating member 325 is It is rotated. For this reason, the glass ribbon 240 is restrained by the rotating member 325 and cannot contract in a direction perpendicular to the traveling direction. Therefore, the glass ribbon 240 can be maintained at a predetermined thickness by using the top roll 300.

The rotating member 325 has a structure that is rotated with respect to the central axis 328 of the top roll 300.

Since the front end portion 320 of the top roll 300 is in direct contact with the high temperature glass ribbon 240, the temperature may increase significantly during use. Therefore, the front end portion 320 of the top roll 300 is configured to be cooled by circulating cooling water through a front end portion space formed inside the top roll 300. Thereby, the temperature rise of the front-end | tip part 320 of the top roll 300 can be suppressed.

Further, the float glass manufacturing apparatus 200 shown in FIG. 2 includes a transfer device 280 provided in the dross box 281 outside the outlet on the downstream side 234 of the float bath 230.

The transport device 280 is, for example, a lift-out roll device. The glass ribbon 240 is drawn out from the outlet of the float bath 230 by the rotation of the lift-out roll device, and then carried into the slow cooling furnace 285. Thereafter, the glass ribbon 240 is gradually cooled to room temperature (near) in the slow cooling furnace 285.

Next, the top roll will be described in detail with reference to FIG.

FIG. 3A is a side sectional view schematically showing an example of the relative positional relationship between the top roll and the glass ribbon and an example of the top end portion of the top roll. FIG. 3B is a cross-sectional view schematically showing an example of the tip portion of the top roll.

The top roll 300 has a front end portion 320 and a support post portion 350, and the front end portion 320 is installed at one end of the support post portion 350.

The distal end portion 320 is constituted by a substantially disc-shaped rotating member 325, and the rotating member 325 has a hollow structure having a distal end portion space 322 therein. Further, the rotating member 325 has two rows of gear shapes formed along the entire outer periphery of the disk, and thus has a plurality of protrusions 326 on the outer periphery. In the figure, the protrusion 326 has a triangular cross section, but the present invention is not limited to this. That is, the protrusion 326 may have any cross-sectional shape. For example, the cross-section of the protrusion may be rectangular or semicircular. In addition, the rows of the protrusions 326 are not particularly limited, and may be two rows as shown in FIG. 3A or another number (for example, one row or three rows or more).

The support column 350 includes an inner tube 355 and an outer tube 370 that extend along the direction of the same central axis 328. The inner tube 355 and the outer tube 370 are constituted by hollow tubular members. The inner tube 355 has an inner space 360 inside. One end of the outer tube 370 is coupled to the distal end portion 320 via the coupling portion 340, and the inner tube 355 is accommodated therein. An outer space 380 is formed between the inner peripheral surface of the outer tube 370 and the outer peripheral surface of the inner tube 355.

Although not shown in FIG. 3A, the top roll 300 has a speed reduction mechanism such as a gear connected to the outer tube 370 and a drive device such as a motor on the other end side of the support column 350. Therefore, by controlling a speed reduction mechanism such as a gear or a timing belt by the driving device, the rotating member 325 of the distal end portion 320 can be rotated at a predetermined number of rotations via the outer tube 370 of the column portion 350.

As described above, the tip portion 320 of the top roll 300 is cooled by the cooling water. For example, the cooling water passes through the inner space 360 of the inner tube 355, reaches the tip end space 322 of the rotating member 325, and then flows through the outer space 380. Alternatively, the cooling water may flow in the opposite direction. Inside the top roll 300, a cooling water flow path is formed through a path through the inner space 360 of the inner tube 355, the tip end space 322 of the rotating member 325, and the outer space 380.

Here, conventionally, the temperature of the cooling water flowing through the flow path of the top roll 300 fluctuates in accordance with the fluctuation of the outside air temperature, and is in a state of success.

In recent years, production of thin glass plates (for example, thicknesses of 0.1 mm to 1 mm, etc.) for display devices such as liquid crystal panels has been increasing. Moreover, as these glass, an alkali free glass is mainly used. This glass has a high melting point, and the melting point is higher by 100 ° C. or more than ordinary soda lime glass.

In the case of such glass, it is necessary to make the glass ribbon thinner than before when manufacturing the glass, and it is necessary to increase the number of top rolls installed per manufacturing facility more than ever. Moreover, in order to increase the number of top rolls arrange | positioned in the same space, it is necessary to make the dimension of the rotating member installed in the front-end | tip part of a top roll smaller. In recent years, with the reduction in the size of the rotating member, since the flow passage for cooling water tends to be narrowed, it is easily affected by temperature fluctuation of the cooling water.

Therefore, under such a recent situation, in addition to the problem of tin adhesion to the surface of the top roll and the accompanying tin falling, there is a high tendency that a problem that the fluctuation of the plate width of the glass ribbon cannot be suppressed occurs.

In order to suppress the above-mentioned tin dropping, fluctuation of the glass ribbon plate width, or concave bubble defect on the bottom surface of the glass ribbon, cooling water whose temperature fluctuation width is controlled within 4 ° C. is used. In particular, the fluctuation range of the temperature of the cooling water used in the present invention is preferably controlled within 3 ° C, more preferably controlled within 2 ° C, and even more preferably controlled within 1 ° C. .

The fluctuation range of the temperature of the cooling water in the present invention is preferably controlled in units of days (24 hours). Since the outside air temperature fluctuates by several degrees to several tens of degrees per day, by controlling the fluctuation range in units of days, tin falls from the top roll, fluctuations in the width of the glass ribbon, or the bottom of the glass ribbon It is possible to suppress a bubble defect of a concave surface.

Further, it is preferable that the fluctuation range of the temperature of the cooling water in the present invention is controlled even in units of one hour. The outside air temperature may fluctuate close to 10 ° C during one hour, so by controlling the fluctuation range even in units of one hour, the tin falls from the top roll, the fluctuation of the glass ribbon width, or the glass ribbon A concave bubble defect on the bottom surface can be suppressed.

Furthermore, the upper limit temperature of the cooling water measured by the temperature measuring device is preferably 40 ° C. or lower. The temperature of the cooling water is highest in the tip end space 322 of the top roll 300 in contact with the glass ribbon. When the upper limit temperature exceeds 40 ° C., the impurity components contained in the cooling water may be deposited and deposited on the walls constituting the flow path due to the evaporation of the cooling water. Therefore, the flow path of the cooling water is narrowed or the flow path is blocked, and there may arise a problem that the top end portion of the top roll cannot be sufficiently cooled.

When such clogging of cooling water occurs, the temperature at the tip of the top roll rises, the tip of the top roll adheres to the molten glass, or a glass ribbon wraps around the tip, There is a possibility that the gear-shaped rotating member cannot sufficiently rotate. In this case, the top roll cannot operate properly, and there is a possibility that the conveyance of the glass ribbon may be hindered.

In addition, it is a well-known fact that an inert gas is sprayed on the tip portion 320 of the top roll 300 and the fixed tin is dropped during maintenance when the float glass production is temporarily suspended. On the other hand, when the fluctuation range of the temperature of the cooling water exceeds 4 ° C., it is possible to drop tin that is more effectively fixed. Therefore, the productivity of float glass at the time of float glass manufacture can be improved.

In the top roll 300 according to the present invention, the material of the rotating member 325 is not particularly limited. In a normal case, the rotating member 325 is made of a metal such as steel or a heat-resistant alloy. By using the metal rotating member 325, the cooling effect during cooling of the rotating member 325 is enhanced.

Further, the surface of the rotating member 325 may be coated or surface-modified. The coating material preferably has heat resistance, and for example, metal nitride or the like may be used. The surface modification preferably has a property of low affinity and / or low adsorptivity to glass ribbon, molten tin, tin oxide and the like.

Further, the rotating member 325 has a substantially disk shape whose center passes through the central axis 328. The diameter of the disk is not particularly limited, but is preferably in the range of, for example, 100 to 300 mm (about 4 to 12 inches), more preferably in the range of 120 to 250 mm (about 5 to 10 inches), 150 More preferably, it is in the range of ~ 230 mm (about 6-9 inches).

The material of the inner tube 355 and the outer tube 370 is not particularly limited. The inner tube 355 and the outer tube 370 may be made of a metal such as steel (for example, stainless steel) or a heat resistant alloy. Further, the outer tube 370 may have a surface coated or surface modified. The coating material preferably has heat resistance, and for example, metal nitride or the like may be used. The surface modification preferably has a property of low affinity and / or low adsorptivity to glass ribbon, molten tin, tin oxide and the like.

FIG. 4 is a schematic view of a water circulation system as an example of the cooling device in the present invention.

The cooling device 400 includes a cooling tower 410 of a water circulation system and a cooling fan 263 whose rotation speed is controlled manually or by an inverter.

The water tank 450 at the bottom of the cooling tower 410 is connected to the suction port of the pump 420 via a pipe line, and the discharge port of the pump 420 is connected to the inlet of the heat exchanger 430 via the pipe line. The outlet is connected to the upper side surface of the cooling tower 410 via a pipe line.

Cooling fins 440 are installed above the cooling tower 410, and a water treatment material 460 made of resin or metal is installed in a portion of the water tank 450 through which water passes. Although the cooling tower 410 includes a round shape and a square shape, the water treatment material 460 is preferably round and square according to the shape.

Next, a glass manufacturing method according to the present invention will be described with reference to FIG.

The method for producing glass according to the present invention is based on the aforementioned float method,
(1) introducing molten glass into the float bath (step S510);
(2) transporting the molten glass from the upstream side of the float bath to the downstream side to form a glass ribbon (step S520);
(3) By rotating the top roll in the traveling direction of the glass ribbon while pressing the tip of the top roll against a predetermined region in the traveling direction of the glass ribbon, that is, the upper surface of both sides of the glass ribbon in the upstream region of the float bath, A step of suppressing shrinkage of the glass ribbon, wherein the top roll has a tip space at the tip, and the tip space has a temperature fluctuation range of 4 ° C. or less per day. And a step (Step S530) through which water is circulated.

As described above, tin stuck to the surface of the top roll is prevented from falling onto the glass ribbon or into the molten tin bath during production, and fluctuations in the plate width of the glass ribbon, or concave air bubbles on the bottom surface of the glass ribbon. Suppress disadvantages. The present invention is effective for producing a non-alkali glass glass plate having a thin plate (plate thickness: 0.1 mm to 1.0 mm).

Examples for producing non-alkali glass (AN100: Asahi Glass trade name) having a size of 2500 × 2200 × 0.7 mm are shown below.

FIG. 6 is a graph showing daily fluctuations in the cooling water temperature Tb and the outside air temperature Ta under the above conditions. The vertical axis of the graph represents the cooling water temperature Tb and the outside air temperature Ta. The solid line represents the cooling water temperature. The outside air temperature is represented by a broken line, and the value depends on the temperature measuring device installed in the float bath building. In addition, the fluctuation amount on the vertical axis was normalized by setting each minimum temperature to 0 ° C. The normalized cooling water temperature Tb and outside air temperature Ta were set to Tb ′ and Ta ′, respectively.

FIG. 6 shows that although the outside air temperature Ta on the outer surface of the bottom casing varies greatly with the passage of time, the cooling water temperature Tb on the outer surface of the bottom casing does not vary greatly, and the daily fluctuation range is a desired range. It is within.

In Example 1, the fluctuation range of the cooling water temperature was set to 2 ° C. or less per day. In Example 2, the fluctuation range was within 4 ° C. on a daily basis, and within 3 ° C. on an hourly basis. In Example 3, the fluctuation range of the cooling water temperature was within 4 ° C. per day, and was over 3 ° C. per hour.

In Comparative Example 1, since the temperature of the cooling water was determined according to the fluctuation of the outside air temperature, the fluctuation range exceeded 4 ° C. on a daily basis. In Comparative Example 2, the number of rotations of the cooling fan was adjusted so that the upper limit temperature of the cooling water measured outside the float bath exceeded 40 ° C.

The following (1) to (3) were used as evaluation indexes.
(1) Glass ribbon fluctuation occurrence frequency (the fluctuation here is a fluctuation of 4 inches or more)
(2) Tin fall occurrence frequency fixed to top roll (3) Presence / absence of winding of glass ribbon around top end of top roll Table 1 shows the evaluation results and Table 2 shows the definition of the evaluation index. (1) and (3) were confirmed by observing the inside of the float bath from the monitoring camera in the bus or the observation window. Since (2) is difficult to confirm by observing the inside of the float bath from the in-bus monitoring camera or the observation window, it was confirmed by a defect detector after the slow cooling step.

By making the fluctuation range of the temperature of the cooling water within 4 ° C. per day, it was confirmed that (1) the occurrence frequency of fluctuations in the width of the glass ribbon and (2) the occurrence frequency of tin falling fixed to the top roll could be suppressed. . Furthermore, it was confirmed that the frequency of falling can be further suppressed by setting the fluctuation range within 3 ° C. in units of one hour. Moreover, if the upper limit temperature of the cooling water measured outside the float bath was set to 40 ° C. or less, (3) it was confirmed that the glass ribbon was not wound around the top roll tip.

As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to embodiment mentioned above, A various deformation | transformation and substitution are added to embodiment mentioned above, without deviating from the scope of the present invention. be able to.

This application is based on Japanese Patent Application No. 2012-270240 filed on Dec. 11, 2012, the contents of which are incorporated herein by reference.

According to the present invention, tin fixed to the top roll surface can be prevented from falling on the glass ribbon or into the molten tin bath during production, and the fluctuation of the plate width of the glass ribbon can be suppressed. Productivity can be improved. The float glass is useful as a glass substrate for a display such as a liquid crystal display device.

DESCRIPTION OF SYMBOLS 200 ... Float glass manufacturing apparatus, 210 ... Introduction part, 220 ... Molten tin, 230 ... Float bath, 232 ... Upstream side, 234 ... Downstream side, 240 ... Glass ribbon, 250 ... Cooling water circulation path, 260 ... Temperature measuring device, 261 ... Temperature display device, 262 ... Inverter, 263 ... Cooling fan, 264 ... Communication cable, 265 ... Temperature control device, 280 ... Transport device, 281 ... Dross box, 285 ... Slow cooling furnace, 300 ... Top roll, 320 ... Tip, 322 ... tip end space, 325 ... rotating member, 326 ... projection part, 328 ... central axis, 350 ... strut part, 355 ... inner pipe, 360 ... inner space, 370 ... outer pipe, 380 ... outer space, 400 ... cooling device, 410 ... Cooling tower, 420 ... Pump, 430 ... Heat exchanger, 440 ... Cooling fin, 450 ... Water tank part, 460 ... Water treatment Wood

Claims

A float bath in which the molten glass ribbon is conveyed;
A top roll used for suppressing shrinkage of the molten glass ribbon;
A float glass manufacturing apparatus comprising:
The top roll has a rotatable tip that contacts the molten glass ribbon,
The tip has a hollow structure having a tip space inside, and has a flow passage for supplying cooling water to the tip space.
A temperature measuring device installed outside the float bath for measuring the temperature of the cooling water;
A cooling device for cooling the cooling water whose temperature has been increased by heat exchange in the float bath;
With a temperature control device comprising
The float glass manufacturing apparatus, wherein a fluctuation range of the temperature of the cooling water is controlled within 4 ° C. per day.
The float glass manufacturing apparatus according to claim 1, wherein the fluctuation range is controlled within 3 ° C per hour.
The cooling device is
A water cooling tower,
A cooling fan whose rotational speed is controlled manually or by an inverter;
The float glass manufacturing apparatus of Claim 1 or Claim 2 provided with these.
The float glass manufacturing apparatus according to any one of claims 1 to 3, wherein an upper limit temperature of the cooling water measured by the temperature measuring apparatus is 40 ° C or lower.
Introducing molten glass into the float bath;
Transporting the molten glass from the upstream side of the float bath to the downstream side to form a glass ribbon;
Suppressing the shrinkage of the glass ribbon by rotating while pressing the top end of the top roll against the upper surfaces of both sides of the predetermined region in the traveling direction of the glass ribbon;
A float glass manufacturing method comprising:
The top roll has a rotatable tip,
The tip has a hollow structure having a tip space inside, and has a flow passage for supplying cooling water to the tip space.
Temperature measuring means for measuring the temperature of the cooling water outside the float bath; and
Cooling means for cooling the cooling water whose temperature has risen due to heat exchange in the float bath;
By temperature control means having
The float glass manufacturing method, wherein a fluctuation range of the temperature of the cooling water is controlled within 4 ° C. per day in the leading end space and the flow passage.
The method for producing a float glass according to claim 5, wherein the fluctuation range is controlled within 3 ° C in units of one hour.
The cooling means is
A water cooling tower,
A cooling fan whose rotational speed is controlled manually or by an inverter;
The float glass manufacturing method according to claim 5 or 6, comprising:
The float glass manufacturing method according to any one of claims 5 to 7, wherein an upper limit temperature of the cooling water measured outside the float bath is 40 ° C or lower.