WO2013154140A1 - Method and device for manufacturing glass plate - Google Patents

Abstract

The purpose of the present invention is to provide a technique that enables a glass ribbon to be manufactured by a float method without generating localized deformations known as straw marks. The present invention comprises applying an outward tensile force to both end parts of a glass ribbon using a plurality of pairs of top rollers provided to both widthwise edge sides of the travel pathway from the upstream region to the downstream region of the travel pathway, and manufacturing a glass ribbon having a thickness equal to or less than 1 mm. The process uses top rollers provided with barrel heads for outwardly pulling the widthwise edges of the glass ribbon transported from the upstream region to the downstream region along the travel pathway. Among the barrel heads provided to the upstream, midstream, and downstream regions of the travel pathway and caused apply an outward tensile force to the widthwise edges of the glass ribbon, a multistage barrel head provided with three or more rows of outer peripheral blades is used as the barrel head provided to the midstream region, and standard barrel heads provided with one or two rows of outer peripheral blades are used as the barrel heads provided to the upstream and downstream regions.

Description

Glass plate manufacturing method and manufacturing apparatus

The present invention relates to a method and an apparatus for manufacturing a thin glass plate according to the float bath method.

In recent years, glass substrates for flat panel displays such as liquid crystal displays and plasma displays have been increased in size and thickness.
As an example of a method for manufacturing this type of glass substrate, a float method is known in which a float bath in which a molten metal such as metallic tin is stored is used and a molten glass is thinly stretched in the horizontal direction on the molten metal. According to this float method, a molten glass is floated on the molten metal of the float bath to ensure a necessary thickness according to the purpose, and a strip-shaped glass ribbon can be formed by drawing the molten glass in the horizontal direction. A glass substrate having a desired size can be obtained by cutting the glass ribbon into a required size.
According to this float method, in order to manufacture a glass substrate that has been increased in size and thickness as described above, a top roll (T / T) that pulls both ends in the width direction of the glass ribbon outward on the molten metal of the float bath. A forming apparatus called R) is provided, and a method is adopted in which the glass ribbon is stretched to both ends in the width direction to reduce the thickness. A thin glass ribbon is slowly cooled and then cut into a required size, followed by polishing and washing, whereby a target glass substrate can be obtained. In accordance with this float method, large and thin glass substrates are produced in large quantities, and large glass substrates having a thickness of about 0.7 mm and a length and width of several meters are produced as glass substrates.

In recent years, a large amount of portable information terminal devices have been manufactured. As an example of a liquid crystal panel applied to the portable information terminal device, a liquid crystal panel using a glass substrate having a thickness of about 0.7 mm is used. There has been provided a liquid crystal panel including a glass substrate that has been thinned to a thickness of about 0.3 mm by scraping one surface of the glass substrate by a technique such as wet etching after manufacturing.

FIG. 11 shows an example of a float bath used in the float process. The float bath 100 includes a bottom bath 102 having a molten metal 101 such as molten tin inside, and a molten bath is formed on the inlet side of the bottom bath 102. Molten glass 103 flows in from the furnace hearth. The molten glass 103 is stretched to a target width on the molten metal 101 by a plurality of top rolls 105 and gradually cooled to form a glass ribbon 106 having a required width and thickness.
As an example of a top roll 105 applied to this type of float bath 100, a barrel head 105A formed in a disk shape as shown in FIG. 12 and provided with two stages of saw blade-shaped outer peripheral blades 105a on the outer periphery thereof is provided. The provided top roll is known. (See Patent Document 1)
The barrel head 105A shown in FIG. 12 adjusts the width of the molten glass 103 by applying an outward tensile force to the edge portion 103a while the outer peripheral blades 105a and 105a are biting into the edge portion 103a of the molten glass 103. The width and thickness of the ribbon 106 can be adjusted.

Japanese Unexamined Patent Publication No. 11-236231

From the background as described above, glass substrates tend to be made thinner and the use of a glass substrate having a thickness of about 0.3 mm as a glass substrate for a panel of a portable information terminal device has been studied from the beginning. Yes. Further, there is a demand for further thinning of glass substrates for flat panel displays.
Conventionally, the molten glass 103 immediately after being poured into the float bath 100 and being expanded cannot be easily pulled because it is liquid at high temperature, but the molten glass 103 moves from the upstream region to the downstream region of the float bath 100. As it is gradually cooled and the viscosity gradually increases, the molten glass 103 having increased viscosity can be pulled and expanded by the barrel head 105A.
However, since the molten glass 103 to which the tensile force is applied has the property of being shrunk, the thinner the molten glass 103 is, the more strongly the glass needs to be pressed down to exert a strong tensile force. is there.

As a result, the edge portion of the barrel head 105A is pierced deeper than the state shown in FIG. 12 into the edge portion 103a of the molten glass 103, and there is a problem that the molten glass 103 is greatly deformed in the vicinity of the edge portion.
FIG. 13 is a diagram for explaining a state in which the barrel head 105A is pressed from above with a strong force against the edge portion 103a of the molten glass 103. FIG.
When the barrel head 105A is strongly pressed against the edge portion 103a of the molten glass 103 shown in FIG. 13A as shown in FIG. 13B, the edge portion 103a sinks deeply in proportion to the pressing force of the barrel head 105A. It is transformed into a U-shaped bag shape. If the deformed glass is solidified in this bag state, there is a problem that a locally deformed portion 110 called a straw having a T-shaped cross section is generated as shown in FIG.

Further, when the barrel head 105A is strongly pressed against the edge 103a of the molten glass 103 as shown in FIG. 13B, the cross section may be deformed into an S shape as shown in FIG. When the glass is solidified in this state, as shown in FIG. 15, a locally deformed portion 111 called a straw is generated that is deformed so that the deformed portion overlaps the upper bag portion 111a and the lower bag portion 111b. There is a problem. When this S-shaped local deformation part 111 is generated, molten metal may be caught inside the glass as indicated by arrows a and b in FIG. There is a problem that causes the glass to break in the cooling process. For example, since metallic tin and a glass plate have different thermal expansion coefficients, there is a possibility that stress acts on the glass plate in the portion where the metallic tin is entrained and causes cracking in accordance with thermal contraction during slow cooling.
When the glass ribbon is cut in the cutting process while having the local deformation portions 110 and 111, when the glass ribbon is cut and folded into a glass plate of a target size, a crack is induced at a position or direction different from the target cutting position or direction. Therefore, there is a risk of inhibiting the stable production of the glass plate. The generation of the locally deformed portions 110 and 111 is conspicuous in a thin glass plate, particularly when a glass plate having a thickness of 1 mm or less is manufactured by the float method like the glass substrate for a display device described above. There is a problem to do.

Based on these backgrounds, the present inventor has made various studies on a technique for producing a thin glass ribbon of 1 mm or less by forming molten glass by a float process. When forming a ribbon, the inventors have found that the occurrence of a locally deformed portion called a straw can be suppressed by devising the position of applying a tension and the barrel head of the top roll used therefor, and have reached the present invention.
It is an object of the present invention to provide a manufacturing method and a manufacturing apparatus that can manufacture a glass ribbon without causing local deformation when forming a thin glass ribbon by a float process, and contribute to stable production of a glass plate. To do.

The present invention relates to a method of manufacturing a glass plate in which a glass ribbon is manufactured by moving a molten glass along a moving path of a molten glass provided on the molten metal, from an upstream area to a downstream area of the moving path. When producing a glass ribbon having a thickness of 1 mm or less by applying an outward tensile force to both ends of the glass ribbon by a plurality of pairs of top rolls disposed at both ends in the width direction of the movement path, the top roll, Using a top roll with a barrel head that pulls the widthwise end of the glass ribbon conveyed from the upstream area to the downstream area along the movement path,
Out of the barrel heads that are provided in the upstream, middle and downstream areas of the moving path and apply an outward tensile force to the widthwise ends of the glass ribbon, three or more outer circumferences as barrel heads provided in the middle stream The present invention relates to a glass plate manufacturing method using a multistage barrel head provided with blades and using a reference barrel head provided with one or two rows of outer peripheral blades as barrel heads provided in an upstream region and a downstream region.

The present invention relates to a method for producing a glass plate in which the multistage barrel head is installed with the logarithm of the viscosity of the glass ribbon as a midstream region in the range of 5.29 to 6.37 dPa · s.
The present invention provides a plurality of upstream reference barrel heads, intermediate flow multistage barrel heads and downstream reference barrel heads for each region, and is formed along the circumferential direction of the outer peripheral surface of each barrel head. The direction of the surface formed by the outer peripheral blades of each row is substantially perpendicular to the glass ribbon and parallel or inclined to the glass ribbon transport direction. The present invention relates to a method of manufacturing a glass plate in which each barrel head is arranged so that the inclination angle gradually decreases from a multistage barrel head in the middle basin to a reference barrel head in the downstream area so that the inclination angle gradually increases toward the multistage barrel head in the basin.
The present invention provides a barrel head provided with an outer peripheral blade in a row in which an outer diameter of one side end portion of the barrel head provided with a row of outer peripheral blades close to the edge in the width direction of the moving path is close to the center in the width direction of the moving path. It is related with the manufacturing method of the glass plate using the multistage barrel head made smaller than the outer diameter of the other side edge part.

This invention relates to the manufacturing method of the glass plate which uses the alkali free glass which has the following compositions in the mass percentage display of an oxide basis as said molten glass.
SiO ₂ : 50 to 73%, Al ₂ O ₃ : 10.5 to 24%, B ₂ O ₃ : 0 to 12%, MgO: 0 to 8%, CaO: 0 to 14.5%, SrO: 0 to 24%, BaO: 0 to 13.5%, MgO + CaO + SrO + BaO: 9 to 29.5%, ZrO ₂ : 0 to 5%.
This invention relates to the manufacturing method of the glass plate which uses the alkali free glass which has the following compositions in the mass percentage display of an oxide basis as said molten glass.
SiO ₂ : 58 to 66%, Al ₂ O ₃ : 15 to 22%, B ₂ O ₃ : 5 to 12%, MgO: 0 to 8%, CaO: 0 to 9%, SrO: 3 to 12.5% BaO: 0 to 2%, MgO + CaO + SrO + BaO: 9 to 18%, ZrO ₂ : 0 to 5%.
This invention relates to the manufacturing method of the glass plate which uses the alkali free glass which has the following compositions in the mass percentage display of an oxide basis as said molten glass.
SiO ₂ : 54 to 73%
Al ₂ O ₃ : 10.5 to 22.5%
B ₂ O ₃ : 0 to 5.5%
MgO: 0-8%
CaO: 0-9%
SrO: 0 to 16%
BaO: 0 to 2.5%
MgO + CaO + SrO + BaO: 8-26%

The present invention includes a float bath for storing molten metal, forming a glass ribbon by moving a molten glass from an upstream area to a downstream area of the molten path, wherein a molten glass moving path is formed on the molten metal. A plurality of pairs of top rolls disposed on both sides in the width direction of the movement path from the upstream area to the downstream area of the movement path in the float bath, the top rolls on both sides in the width direction of the movement path of the molten glass. Rotating shafts that extend individually in the horizontal direction, and outer peripheral blades that are attached to the tip end side of the rotating shaft and pressed against the widthwise end of the glass ribbon that is transported from the upstream region to the downstream region along the movement path A multistage barrel head that has three or more rows of outer peripheral blades and pulls the end of the glass ribbon in the width direction is provided in the middle flow area of the movement path. The basin and downstream region of, has an outer peripheral edge of one or two rows, apparatus for producing a glass plate reference barrel head is provided to pull the end portion in the width direction of the glass ribbon on the outside.

In the glass plate manufacturing apparatus of the present invention, a configuration in which the multistage barrel head is disposed in a region where the logarithmic value of the viscosity of the glass ribbon is 5.29 to 6.37 dPa · s can be employed.
The glass plate manufacturing apparatus of the present invention can be applied when the thickness of the glass ribbon formed by the float bath is 1 mm or less.

The glass plate manufacturing apparatus of the present invention includes a plurality of upstream reference barrel heads, a middle multi-stage barrel head, and a downstream reference barrel head for each region, and a peripheral surface of each barrel head. The direction of the surface formed by the outer peripheral blades of each row formed along the direction is arranged substantially perpendicular to the glass ribbon and parallel to or inclined with respect to the conveying direction of the glass ribbon. Each barrel head is arranged so that the inclination angle gradually increases from the reference barrel head of the middle basin to the multi-stage barrel head in the middle basin, and gradually decreases from the multi-stage barrel head in the middle basin to the reference barrel head in the downstream area. Configuration can be adopted.
In the glass plate manufacturing apparatus of the present invention, the outer diameter of one side end of the barrel head provided with the outer peripheral edge of the row close to the width direction edge of the moving path is in the row close to the width direction center of the moving path. The structure made smaller than the outer diameter of the other side edge part of the barrel head which provided the outer periphery blade is employable.

This invention relates to the manufacturing apparatus of the glass plate to which the alkali free glass which has the following compositions is applied as said molten glass in the mass percentage display of an oxide basis.
SiO ₂ : 50 to 73%, Al ₂ O ₃ : 10.5 to 24%, B ₂ O ₃ : 0 to 12%, MgO: 0 to 8%, CaO: 0 to 14.5%, SrO: 0 to 24%, BaO: 0 to 13.5%, MgO + CaO + SrO + BaO: 9 to 29.5%, ZrO ₂ : 0 to 5%.
This invention relates to the manufacturing apparatus of the glass plate to which the alkali free glass which has the following compositions is applied as said molten glass in the mass percentage display of an oxide basis.
SiO ₂ : 58 to 66%, Al ₂ O ₃ : 15 to 22%, B ₂ O ₃ : 5 to 12%, MgO: 0 to 8%, CaO: 0 to 9%, SrO: 3 to 12.5% BaO: 0 to 2%, MgO + CaO + SrO + BaO: 9 to 18%, ZrO ₂ : 0 to 5%.
This invention relates to the manufacturing apparatus of the glass plate to which the alkali free glass which has the following compositions is applied as said molten glass in the mass percentage display of an oxide basis.
SiO ₂ : 54 to 73%
Al ₂ O ₃ : 10.5 to 22.5%
B ₂ O ₃ : 0 to 5.5%
MgO: 0-8%
CaO: 0-9%
SrO: 0 to 16%
BaO: 0 to 2.5%
MgO + CaO + SrO + BaO: 8-26%

According to the manufacturing method and the manufacturing apparatus of the present invention, a glass ribbon is formed by applying an outward tensile force to the end of the molten glass while pressing the end of the molten glass in the width direction of the moving path of the float bath by the multistage barrel head. As the multi-stage barrel head presses against the end of the glass ribbon and applies a strong tensile force, the amount of deformation in the thickness direction on the end side of the glass ribbon is higher than that of the conventional barrel head. In other words, the holding cost by the barrel head can be reduced.
As a result, a thin glass ribbon can be obtained without causing a local deformation portion called a straw in the glass ribbon in the midstream region. And since the glass ribbon which has not produced the local deformation | transformation part is cut | disconnected in a post process and it is set as a glass plate, the glass plate of the target dimension can be obtained, without producing a crack, a chip | tip, etc.
A glass plate having a thickness of less than 1 mm, preferably 0.7 mm or less, more preferably 0.5 mm or less, still more preferably 0.3 mm or less, particularly preferably 0.1 mm or less, such as a glass substrate for a display device. In this case, the glass ribbon in the midstream area of the float bath tends to cause a local deformation part called a straw, but by using a multistage barrel head on the molten glass in the midstream area and applying a tensile force, The amount of deformation in the thickness direction can be reduced on the end side, and a thin glass ribbon with no locally deformed portion can be obtained. By cutting this glass ribbon, there are no desired dimensions such as cracking or chipping. A thin glass plate of 1 mm or less can be obtained.

FIG. 1 is a schematic diagram showing the overall configuration of the glass plate manufacturing apparatus according to the first embodiment of the present invention. FIG. 2 is a configuration diagram illustrating an example of an arrangement state of top rolls provided in the manufacturing apparatus. 3 shows a barrel head applied to a top roll provided in the manufacturing apparatus, FIG. 3 (a) is a front view of the multi-stage barrel head, FIG. 3 (b) is a cross-sectional view of the multi-stage barrel head, FIG. 3C is a cross-sectional view of the reference barrel head. FIG. 4 is a perspective view of a multistage barrel head provided in the manufacturing apparatus. FIG. 5: is a side view which shows the state which is making the pushing force and the tensile force act on the edge part of a molten glass using the other example of the multistage barrel head provided in the manufacturing apparatus. FIG. 6 is a plan view showing a state in which a tensile force is applied to the end portion of the molten glass using another example of the multistage barrel head provided in the manufacturing apparatus. FIG. 7 is a graph showing the state of viscosity at each temperature for an example of molten glass supplied to the production apparatus. FIG. 8 is a graph showing an example of a state of occurrence of a glass ribbon straw in a conventional float bath. FIG. 9 is a graph showing the results obtained by comparing the width of the glass ribbon when the multi-stage barrel head is provided in the float bath and when the conventional barrel head is provided. FIG. 10 is a graph showing an example of compressive stress distribution at the end of a glass ribbon supplied to a conventional float bath. FIG. 11 is a schematic plan view showing an example of a float bath provided with a conventional top roll. FIG. 12 is a cross-sectional view showing an example of a state in which a barrel head provided on a conventional top roll is pushed into an end portion of a glass ribbon. FIG. 13 shows the relationship between the end of the molten glass and the conventional barrel head. FIG. 13 (a) is a sectional view showing the end of the glass ribbon, and FIG. 13 (b) is the barrel at the end of the glass ribbon. FIG. 13C is a cross-sectional view showing an example of an S-shaped local deformation portion (straw) formed on the end side of the glass ribbon. FIG. 14 is a cross-sectional view showing an example of a T-shaped local deformation portion formed on the end side of the glass ribbon. FIG. 15 is a cross-sectional view showing an example of a locally deformed portion having an S-shaped cross section formed on the end side of the glass ribbon.

"First embodiment"
Hereinafter, a glass plate manufacturing apparatus according to a first embodiment of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to the embodiment described below.
FIG. 1 shows a schematic configuration of a glass plate manufacturing apparatus according to a first embodiment of the present invention. A glass plate manufacturing apparatus (float bath) 1 according to the present embodiment is a refractory furnace having a substantially rectangular shape in plan view. A bathtub 2, a molten metal 3 such as metal tin accommodated in the bathtub 2, and a plurality of top rolls 11 disposed in the bathtub 2.
The bathtub 2 is composed of a refractory bottom structure, side walls, and an upper structure. In FIG. 1, only the bottom structure is illustrated in a plan view. The upper structure side of the bathtub 2 is provided with accessory equipment such as a gas supply pipe such as a non-oxidizing gas and a temperature controller, and the atmosphere of the bathtub 2 can be controlled to a non-oxidizing gas atmosphere. The temperature of the space portion can be controlled to a target temperature.

In FIG. 1, on the left end side of the bathtub 2, an inlet portion 5 for supplying the molten glass G onto the molten metal 3 from the forehearth of the glass melting furnace provided in the previous step is provided. An outlet 6 is formed at the end of the bathtub 2 opposite to the side where the inlet 5 is provided, and a plurality of transport rolls 7 are arranged outside the outlet 6 to form a slow cooling line 7A. Yes.
In the bathtub 2, a moving path 8 having a rectangular shape in plan view for forming the molten glass G is defined on the molten metal 3 from the inlet portion 5 to the outlet portion 6.
When the molten glass G flows from the inlet portion 5 onto the molten metal 3 along the movement path 8, the molten glass G is expanded to the required thickness and width to form a molten glass ribbon 9. It is gradually cooled and moved to the outlet portion 6 side to form a glass ribbon 10 as a band-like final form having a uniform width, and this glass ribbon 10 is discharged from the outlet portion 6 to the slow cooling line 7A side. . In this embodiment, since the planar shape of the bathtub 2 is formed in a rectangular shape, the movement path 8 partitioned on the molten metal 3 in the bathtub 2 is also rectangular, but the plane of the movement path 8 is The shape is not limited to a rectangular shape, and any shape that matches the planar shape of the bathtub 2 is possible.

In the bathtub 2 of the present embodiment, a plurality of top rolls 11 arranged between the inlet portion 5 and the outlet portion 6 along the width direction both ends of the moving path 8 from the upstream area toward the downstream area at predetermined intervals. Has been placed. In the present embodiment, the molten glass G supplied from the inlet portion 5 is stretched in the width direction by the above-described plurality of top rolls 11 to form the above-described molten glass ribbon 9 in the downstream region (the outlet portion 6). The belt-shaped glass ribbon 10 having a predetermined width is finally obtained.

As shown in FIG. 2, in the bathtub 2 of the present embodiment, 16 top rolls 11 are arranged at predetermined intervals from positions for starting to expand the width of the molten glass G on both ends in the width direction of the movement path 8. It is arranged with a gap. These 16 top rolls 11 will be distinguished by attaching symbols A ₀ to A _{15 for} the sake of convenience, and individual arrangements will be described.
Among these top rolls 11, the first-stage top roll 11A ₀ and the first top roll 11A ₁ to the fourth top roll 11A ₄ are the top rolls provided with a reference barrel head 18 to be described later. The tenth top roll 11A ₅ to the tenth top roll 11A ₁₀ are top rolls equipped with a multistage barrel head 14 to be described later, and the eleventh top roll 11A ₁₁ to the fifteenth top roll 11A ₁₅ are The top roll is provided with a reference barrel head 18 to be described later.

As shown in FIG. 3B, the _fifth top roll 11A ₅ to the tenth top roll 11A ₁₀ include a rotary shaft 13 and a multi-stage barrel head 14 integrated at the tip of the rotary shaft 13. I have.
The mechanism for rotationally driving the rotating shaft 13 and the mechanism for moving the rotating shaft 13 are omitted in FIGS. 1 and 2, but the rotating shaft 13 penetrates the side wall of the bathtub 2 to the outside of the bathtub 2. Extending substantially horizontally, a rotary drive device and a moving device are provided outside the bathtub 2. As an example of the moving device for the rotary shaft 13, a moving device provided with a rotary driving device such as a motor is applied to a movable carriage that is movably provided along a rail member laid outside the position where the bathtub 2 is installed. it can. These rotational driving devices and moving devices are the same as top roll driving devices and moving devices provided in a general float bath, and the rotary shaft 13 is driven to rotate at, for example, both ends in the width direction of the moving path 8. It is arranged to be movable in the width direction of the movement path 8 on the side. In FIG. 1 and FIG. 2, these rotary drive devices and moving devices are omitted, and only the tip end side of the rotary shaft 13 and the multistage barrel head 14 attached thereto are shown.

The multistage barrel head 14 is provided with six stages (six rows) of outer peripheral blades 15 on the outer peripheral wall 16a of the rotary drum 16 as shown in FIGS. Both the rotary shaft 13 and the multistage barrel head 14 have a hollow structure, and a hollow portion 13a formed inside the rotary shaft 13 and a hollow portion 16b formed inside the rotary drum 16 are communicated with each other. ing. A cooling water supply pipe 13 b is provided inside the rotary shaft 13, and a cooling water return flow path 13 c is formed in a gap between the supply pipe 13 b and the inner peripheral wall of the rotary shaft 13. With these configurations, the cooling water is supplied from the supply pipe 13b to the hollow portion 16b of the rotating drum 16, and the cooling water is recovered through the return flow path 13c, whereby the rotating shaft 13 and the rotating drum 16 are connected from the inside thereof. It is configured to be cooled.

The outer peripheral blade 15 of the multi-stage barrel head 14 has a plurality of quadrangular pyramid-shaped cutting edges having six stages (see FIGS. 3A, 3B, and 4) along the outer peripheral wall 16a of the cylindrical rotary drum 16. (6 rows). Since these outer peripheral blades 15 are formed in the circumferential direction of the rotating drum 16 with the same pitch with each blade edge having the same shape, six rows of outer peripheral blades 15 that make one row around the rotating drum 16 are formed in total. It is structured. In the rotary drum 16 of this embodiment, the end face wall 16c on the side connected and integrated to the rotary shaft 13 side and the end face wall 16d located on the front end side of the multistage barrel head 14 are both formed in a flat plate shape. In addition, the outer peripheral blade 15 formed in the multistage barrel head 14 is not limited to a six-stage structure, and may have any number of stages of three stages, four stages, five stages, or seven stages or more. However, if the number of stages is increased more than necessary, the glass ribbon 9 is unnecessarily cooled. Therefore, it is desirable that the number of stages is such that the glass ribbon 9 is not overcooled, and the number of stages is 3 or more, for example, about 4 to 8. *

The first top roll 11A ₀ to the fourth top roll 11A ₄ (that is, the top roll 11A ₄ is the fifth when counted from the first top roll 11Ao), and the eleventh top roll 11A ₁₁ to the fifteenth The top roll 11A ₁₅ is composed of a rotating shaft 17 and a reference barrel head 18 integrated at the tip thereof. The rotation drive device and the movement device of the rotation shaft 17 are provided with devices similar to the rotation drive device and the movement mechanism connected to the rotation shaft 13 of the previous top rolls 11A ₅ to 11A _10. Is configured to be movable in the width direction of the movement path 8 while being driven to rotate, but is omitted in FIGS. 1 and 2.

As shown in FIG. 3C, the reference barrel head 18 includes a two-stage outer peripheral blade 19 on the outer peripheral wall 20 a of the rotary drum 20. Both the rotary shaft 17 and the rotary drum 20 have a hollow structure, and a hollow portion 17a formed inside the rotary shaft 17 and a hollow portion 20b formed inside the rotary drum 20 are communicated with each other. Yes. The rotating shaft 17 and the rotating drum 20 can be cooled from the inside by flowing a coolant such as cooling water through the hollow portion 17a and the hollow portion 20b.
A cooling water supply pipe 17 b is provided inside the rotary shaft 17, and a cooling water return flow path 17 c is formed in a gap between the supply pipe 17 b and the inner peripheral wall of the rotary shaft 17. With these configurations, the cooling water is supplied from the supply pipe 17b to the hollow portion 20b of the rotary drum 20, and the cooling water is recovered through the return flow path 17c, whereby the rotary shaft 17 and the rotary drum 20 are connected from the inside thereof. It is configured to be cooled. In addition, you may change suitably the cross-sectional shape of the hollow part 20b so that a water flow may circulate efficiently.

The outer peripheral blade 19 of the reference barrel head 18 has a number of quadrangular pyramid-shaped cutting edges in two stages (two rows) along the outer peripheral wall 20a of the thin cylindrical rotating drum 20 as shown in FIG. Is formed continuously. Since these outer peripheral blades 19 are formed in the circumferential direction of the rotary drum 20 with the same pitch with each blade edge having the same shape, a two-stage in which one row of outer peripheral blades 19 that make a round of the rotary drum 20 is formed as a whole. It is structured. In the rotary drum 20 of the present embodiment, the end face wall 20c on the side connected and integrated with the rotary shaft 17 side and the end face wall 20d located on the front end side of the reference barrel head 18 are both formed in a flat plate shape. . The end wall 20c may be inclined obliquely outward from the center of the barrel head.

From the first-stage top roll 11A ₀ , the fourth top roll 11A ₄ gradually cools the molten glass G flowing from the inlet portion 5 into the moving path 8 on the molten metal 3 and the viscosity starts to rise and is in a molten state. The glass ribbon 9 is installed in the upstream area.
From the fifth top roll 11A _{5 having} the above structure, the tenth top roll 11A ₁₀ is installed in the middle region of the moving path 8, that is, the region where the glass ribbon 9 has a higher viscosity than the upstream region. ing.
From the eleventh top roll 11A ₁₁ of the structure to the fifteenth top roll 11A ₁₅ are installed in the downstream area of the moving path 8, that is, in the area where the viscosity of the glass ribbon 9 is higher than the middle flow area. ing.

Regarding the viscosity of the glass ribbon 9 in the molten state, as an example, FIG. 7 shows a state in which, in a general alkali-free glass production process, the molten glass becomes hard due to a change in viscosity as the temperature decreases. Indicates. This is the result of computer simulation analyzed with our own solver.
In the state showing the change in viscosity shown in FIG. 7, the region where the common logarithm of the viscosity (η) of the glass ribbon 9 is less than 5.29 dPa · s is the upstream region of the movement path 8, and the common logarithm of the viscosity of the glass ribbon 9 is 5 The region of .29 to 6.37 dPa · s can be defined as the midstream region of the moving path 8 and the region where the common logarithm of the viscosity of the glass ribbon 9 exceeds 6.37 dPa · s can be defined as the downstream region of the moving path 8. The region where the logarithm of the viscosity of the glass ribbon 9 is ^5.29 to ^6.37 dPa · s corresponds to the region where the viscosity (η) of the glass ribbon 9 is 10 ^5.29 to 10 ^6.37 dPa · s. ing.

The top rolls 11A ₀ to 11A ₁₅ are not directed parallel to the width direction of the glass ribbon 9, but are inclined with a slight angle. For example, when the moving path 8 is viewed in plan, the moving direction of the glass ribbon 9 in the moving path 8 (the direction parallel to the side wall of the bathtub 2 from the inlet portion 5 toward the outlet portion 6) is the Y-axis direction, and the moving path 8 Assuming an XY coordinate system in which the width direction is defined as the X-axis direction, a plane including the outer peripheral edge 19 of each row of the reference barrel head 18 or a plane including the outer peripheral edge 15 of each row of the multistage barrel head 14 is assumed. .
In this case, the plane 14a including the outer peripheral blades 15 aligned in the circumferential direction of the multistage barrel head 14 shown in FIG. 2 or the plane including the outer peripheral blades 19 aligned in the circumferential direction of the reference barrel head 18 is the Y axis. On the other hand, it is inclined in plan view so as to have an inclination angle (θ) of about 0 to 16 °. Further, the outer peripheral blade 15 of the multistage barrel head 14 or the outer peripheral blade 19 of the reference barrel head 18 is pressed almost vertically against the glass ribbon 9 from above. In other words, the rotary shafts 13 and 17 of the barrel heads 14 and 18 are movable so that the barrel heads 14 and 18 can be pressed against the end of the glass ribbon 9 by moving up and down while being arranged almost horizontally. Is provided.

As an example of the inclined arrangement, for example, in the first top roll 11A ₁ to the fifteenth top roll 11A ₁₅ shown in FIG. 2, the inclination angle is gradually increased from the _first top roll 11A ₁ to each gradually increasing angle. The barrel head is arranged, the inclination angle is increased to the maximum inclination angle in the middle basin, and the inclination angle is gradually decreased in the reference barrel head 18 of the top roll in the downstream area. Is an example in which the tilt angle is set to 0 °. The inclined arrangement state of each barrel head is not limited to the example described here, and any inclined arrangement having the maximum inclination angle may be employed in the multistage barrel head 14 provided in the midstream region.

In order to manufacture the glass ribbon 10 using the glass manufacturing apparatus (float bath) 1 of the present embodiment, the molten glass G is supplied from the inlet portion 5 to the moving path 8 on the molten metal 3 to be spread and provided in plural. The barrel heads 14 and 18 are used to apply a tensile force to both ends in the width direction of the molten glass ribbon 9 to adjust the width and thickness of the glass ribbon 9, and finally the glass ribbon having the target width. 10 can be obtained. Moreover, a glass plate can be obtained by cutting this glass ribbon 10 to a target size in a subsequent cutting step of the slow cooling line 7A.

In the manufacturing apparatus 1 of the present embodiment, the top roll 11A ₀ to top roll 11A ₄ and the top roll 11A ₁₁ to top roll 11A ₁₅ are provided with the reference barrel head 18, so that the outer peripheral blade 19 having a two-stage structure is made of glass. While pressing against the end of the ribbon 9 in the width direction, the reference barrel head 18 of each of the top rolls applies a necessary tensile force to the both ends in the width direction of the glass ribbon 9 in the upstream region and the downstream region. be able to.
Further, since the fifth top roll 11A ₅ from the 10 th top roll 11A ₁₀ it is provided with a wide multi-stage barrel head 14 width of 6-stage structure, to the glass ribbon 9 medium basin, multistage with a strong force Even when the barrel head 14 is pressed and a strong tensile force is applied, the press margin of the glass ribbon 9 (the amount by which the molten glass G is deformed in the thickness direction) is used when the reference barrel head 18 having a two-stage structure is used. Can be shallower.

For this reason, even if a strong tensile force is applied to the end of the glass ribbon 9 in the width direction with a strong tensile force using the multi-stage barrel head 14, the multi-stage barrel head 14 has the width direction end of the glass ribbon 9. The amount of deformation in the thickness direction (pressing margin) is reduced. Therefore, compared with the conventional apparatus in which a strong tensile force is applied to the glass ribbon 9 with a two-stage outer peripheral blade in the middle stream region, the molten glass G The local deformation part called a straw does not arise in the width direction edge part side of this.
The glass ribbon 9 in the upstream region has a low viscosity and it is difficult to apply a strong tensile force from the beginning, so the reference barrel head 18 may be used. The glass ribbon 9 in the downstream region has a high viscosity and is almost in a hard state. Even if it is pressed, the amount of deformation in the thickness direction is small. In view of this point, since the glass ribbon 9 is stretched by applying a strong tensile force to the glass ribbon 9 in the midstream region, it is desirable to provide the multistage barrel head 14 in the midstream region.

Note that the number of the multistage barrel heads 14 provided in the middle stream is not particularly defined in the present embodiment, and a necessary number of the glass ribbons 10 having a final thickness can be provided. For example, it is not necessary to use all the barrel heads in the middle basin as the multistage barrel heads 14, and some barrel heads may be the multistage barrel heads 14, and the remaining barrel heads may be the reference barrel heads 18. What is necessary is just to install a required number so that the local deformation part called a straw may not be produced in order to shape | mold the glass ribbon 10 of the target thickness.
Further, the total number of barrel heads 14 and 18 provided in the entire region from the upstream region to the downstream region is not limited by the example of the present embodiment, and the number necessary for forming the glass ribbon 10 having a desired thickness. Should be installed.

The molten glass G thinly stretched using the top rolls 11A ₁ to 11A ₁₅ is gradually cooled as it moves from the upstream area to the downstream area of the movement path 8 to increase its hardness. It becomes the glass ribbon 10 of a fixed width and thickness, reaches the outlet 6 and is conveyed to the slow cooling line 7A side in the subsequent process. According to the glass plate manufacturing apparatus 1 of the present embodiment, a local deformation portion is not generated in the glass ribbon 10 that has been conventionally transported to the slow cooling line 7A while a local deformation portion called a straw is formed. Therefore, there is no possibility that the glass ribbon 10 breaks in the slow cooling line 7A.
In addition, since a cutting line (not shown) is installed in the subsequent process of the slow cooling line 7A, a glass plate having a desired size is obtained by cutting and folding the glass ribbon 10 after the slow cooling to a required size. be able to. Since the local deformation | transformation part is not produced | generated in the glass ribbon 10 sent to this cutting line, there is no possibility of producing a cutting | disconnection defect location in the case of cutting cut and fold, and it contributes to improvement in productivity.

There is no restriction | limiting in particular in the composition of the molten glass G which it is going to manufacture in the glass manufacturing apparatus 1 of this embodiment.
Therefore, any of non-alkali glass, soda lime glass, mixed alkali glass, borosilicate glass, or other glass may be used. Moreover, the use of the manufactured glass product is not limited to flat panel display use, architectural use, and vehicle use, and includes various other uses. In particular, alkali-free glass for flat panel displays that requires high quality is preferred.

In addition, as a glass suitable for the molten glass G, an alkali-free glass having the following composition in the oxide-based mass percentage display can be used.
SiO ₂ : 50 to 73%, preferably 50 to 66%, Al ₂ O ₃ : 10.5 to 24%, B ₂ O ₃ : 0 to 12%, MgO: 0 to 8%, CaO: 0 to 14.5 %, SrO: 0 to 24%, BaO: 0 to 13.5%, MgO + CaO + SrO + BaO: 9 to 29.5%, ZrO ₂ : 0 to 5%.
As a glass suitable for the molten glass G, when the strain point is high and solubility is considered, an alkali-free glass having the following composition can be used in the oxide-based mass percentage display.
SiO ₂ : 58 to 66%, Al ₂ O ₃ : 15 to 22%, B ₂ O ₃ : 5 to 12%, MgO: 0 to 8%, CaO: 0 to 9%, SrO: 3 to 12.5% BaO: 0 to 2%, MgO + CaO + SrO + BaO: 9 to 18%, ZrO ₂ : 0 to 5%.
As a glass suitable for the molten glass G, when considering a high strain point in particular, an alkali-free glass having the following composition can be used in the oxide-based mass percentage display.
SiO ₂ : 54-73%
Al ₂ O ₃ : 10.5 to 22.5%,
B ₂ O ₃ : 0 to 5.5%,
MgO: 0-8%,
CaO: 0-9%,
SrO: 0 to 16%,
BaO: 0 to 2.5%,
MgO + CaO + SrO + BaO: 8-26%.

FIG. 5 shows a second example of the multi-stage barrel head applied to the glass plate manufacturing apparatus according to the present invention, and the multi-stage barrel head 30 of this second example was provided in the previous embodiment. Instead of the multistage barrel head 14, it is integrally attached to the tip of the rotating shaft 13.
The multi-stage barrel head 30 of this example has six stages of serrated outer peripheral blades, but from the side close to the rotary shaft 13, the first outer peripheral blade 30a ₁ , the second outer peripheral blade 30a ₂ , and the third stage. The outer diameters are sequentially increased in the order of the outer peripheral blade 30a ₃ , the fourth outer peripheral blade 30a ₄ , the fifth outer peripheral blade 30a ₅ , and the sixth outer peripheral blade 30a ₆ .
That is, the rotary drum 31 provided with the outer peripheral blades 30a ₁ to 30a ₆ has a small outer diameter on the rotating shaft 13 side and a large outer diameter on the opposite side. In other words, the outer diameter of one end of the rotating drum 31 near the width direction end 9 a of the glass ribbon 9 is smaller than the outer diameter of the other end of the rotating drum 31 near the center of the glass ribbon 9 in the width direction. Is formed. In the present embodiment, the outer peripheral blades 30a ₁ to 30a ₆ are formed larger in this order.

The multistage barrel head 30 having the configuration shown in FIG. 5 is configured so that the rotary shaft 13 is inclined so as to be substantially horizontal when viewed from the side and as shown in the plan view of FIG. The outer peripheral blades 30a ₁ to 30a ₆ are used by pressing from the top near the end portion 9a in the width direction of the glass ribbon 9.
With this arrangement, the circumferential lengths of the outer peripheral blades 30a ₁ to 30a ₆ are different from each other, so that the outer peripheral blade 30a ₆ bites into the glass ribbon 9 deeper than the outer peripheral blade 30a ₁ as shown in FIG. As shown by the size of the arrows c and d shown, a peripheral speed difference is generated between the outer peripheral blade 30a ₆ and the outer peripheral blade 30a ₁ , and a tensile force is applied to the width direction end portion 9a of the glass ribbon 9 toward the outer side. Can act. When the outer peripheral edge 30a ₁ as shown in FIG. 5 is the position e and the outer peripheral edge 30a ₆ in contact with the molten glass G contrasting position f in contact with the molten glass G, slower peripheral speed of the peripheral cutting edge 30a _1, the outer peripheral edge 30a ₆ Since the peripheral speed of the glass ribbon 9 is increased, a target tensile force can be applied to the width direction end portion 9a of the glass ribbon 9 in the outward direction.

According to the multi-stage barrel head 30 of this example, a tensile force can be applied in a direction that naturally expands the width of the molten glass G by pressing the outer peripheral blades 30a ₁ to 30a ₆ having different diameters against the ends of the glass ribbon 9. Therefore, it is advantageous when the glass ribbon 9 is formed thin, and the thin glass ribbon 10 can be manufactured.
Further, the multi-stage barrel head 30 has a structure having six stages (six rows) of outer peripheral blades 30a ₁ to 30a ₆ and can effectively generate a force for pulling the glass ribbon 9 to the outside, so that a large tensile force acts. However, compared to a conventional barrel head having a two-stage outer peripheral blade, the glass ribbon 9 is less likely to be greatly deformed in its thickness direction. Does not occur.

FIG. 7 is a graph showing the relationship between the temperature and viscosity of a general alkali-free glass. When a glass ribbon is formed, a molten glass of about 1110 ° C. to 1120 ° C. is formed and the temperature is gradually lowered. The relationship of the viscosity at each temperature is shown.
As shown in FIG. 7, the region in front of the region where the common logarithm of the viscosity (η) of the glass ribbon 9 is 5.29 dPa · s is the upstream region, and the common logarithm of the viscosity of the glass ribbon 9 is 5.29 to 6.37 dPa. Since the region of s can be divided into the middle flow region, and the region where the common logarithm of the viscosity of the glass ribbon 9 exceeds 6.37 dPa · s can be distinguished from the downstream region, the upstream region and the downstream region as described in the above embodiment It is possible to provide the reference barrel head 18 and the multistage barrel head 14 in the middle stream area.

The molten glass having the viscosity characteristics shown in FIG. 7 is applied to a molding apparatus provided with 16 barrel heads shown in FIGS. 1 and 2, and has a width of about 80 inches (about 2.03 m) to a width of about 110 inches (about 2. 79 m), a glass ribbon having a thickness of 0.3 mm was produced.
The following pressing depths were set for the twelfth top roll from the first top roll. The pressing depth of the first to fifth top rolls was set to 25 mm. The pressing depth of the sixth top roll was set to 20 mm, the pressing depth of the seventh to tenth top rolls was set to 10 to 15 mm, and the pressing depth of the eleventh to thirteenth top rolls was set to 5 to 10 mm. . The barrel head speed is 2 to 30% of the transport speed in the upstream area, 30 to 60% of the transport speed in the middle stream area, and 69 to 90% of the transport speed in the downstream area.

The top roll L-0 is the first stage, the first top roll L-1 to the fifteenth top roll L-15.
With respect to the inclination angle θ of each top roll, the barrel heads of the top rolls of L-0 to L-3 are inclined stepwise from 0 ° to 15 °, and the top rolls of L-4 to L-8 are inclined. An inclination angle condition of 12 to 15 ° is given to the barrel head, and the inclination of the top roll barrel heads up to L9-L-13 is gradually reduced to 0 ° for the top rolls after L-11. did.
For comparison, a test for producing glass ribbons using a two-stage reference barrel head for all of the first to fifteenth top rolls was also conducted. The result of this comparative test is shown in FIG.

FIG. 8 shows the test results when all the top rolls L-0 to L-15 in the first stage are used as reference barrel heads. FIG. 8 shows the results of the position where the locally deformed portion called the straw was generated. This is the result of computer simulation analyzed with our own solver.
From the test results shown in FIG. 8, it was found that the local rolls called straws are most likely to occur in the middle roll top roll from L-5 to L-10.

Therefore, a six-stage multi-stage barrel head shown in FIGS. 3 and 4 was provided on six top rolls L-5 to L-10, and a molding test was performed under the same conditions. The results are summarized in FIG.
Fig. 9 shows a case where a standard barrel head is provided for all top rolls and a multi-stage barrel head is provided for six top rolls L-5 to L-10 in order to produce a glass ribbon having a thickness of 0.3 mm. The other top rolls all show the results when the reference top rolls are used. This is the result of computer simulation analyzed with our own solver. In FIG. 9, a region indicated by a white arrow indicates a middle flow region, and a multistage barrel head is provided in the middle flow region.
The position in the width direction of the upper graph in FIG. 9 indicates the position of the edge of the glass ribbon on the left side in the traveling direction of the moving path, and the position in the width direction of the lower graph in FIG. Indicates the position of the edge portion.
The distance between the edge portions on both sides of the upper and lower glass ribbons in FIG. 9 (that is, the distance between the edge portion of the glass ribbon in the upper graph of FIG. 9 and the edge portion of the glass ribbon in the lower graph of FIG. 9) Corresponds to the width of the glass ribbon.

We are trying to manufacture glass ribbons of the same thickness by tilting the barrel heads at the same angle and applying an outward tensile force to the end of the glass ribbon for the same molten glass. It can be seen that the glass ribbon width is clearly wider in the case of the test results.
That is, a reference barrel 1L provided with a reference barrel head over the entire area (indicated by a ◇ in the upper graph of FIG. 9, the left reference barrel when the glass ribbon is viewed in plan) and a reference barrel 1R (lower graph of FIG. 9). The vertical width between the □ mark and the glass ribbon in the plan view of the glass ribbon corresponds to the glass ribbon width of the first test, and the reference barrel 2L (where the reference barrel head is provided over the entire area) The vertical width between the □ mark in the upper graph of FIG. 9 and the reference barrel 2R (the ◯ mark in the lower graph of FIG. 9) corresponds to the glass ribbon width of the second test.
On the other hand, in FIG. 9, the multistage barrel 1L when the multistage barrel head is provided in the middle stream area (Δ mark in the upper graph of FIG. 9) and the multistage barrel 1R when the multistage barrel head is provided in the middle stream area (see FIG. 9). 9 in the lower graph of FIG. 9 corresponds to the glass ribbon width of the first test, and a reference barrel 2L (a cross mark in the upper graph in FIG. 9) provided with a reference barrel head over the entire area. The vertical width between the reference barrels 2R (the crosses in the lower graph of FIG. 9) corresponds to the glass ribbon width of the second test.
The glass ribbon width is wider when the vertical width between the plot positions of the marks in the upper graph of FIG. 9 and the plot positions of the marks in the lower graph of FIG. 9 is larger. The wide width of the glass ribbon means that an outward tensile force can be favorably applied to the end of the glass ribbon.
In addition, when the multistage barrel head is provided and molded, a local deformation portion called a straw does not occur on the glass ribbon.

As can be seen from FIG. 9, the glass ribbon is about 10% wider on both the left and right sides.
FIG. 10 shows the stress distribution simulation obtained by stress analysis simulation at the pressing position of each barrel head at the end of the glass ribbon when the glass ribbon is formed by providing the reference barrel head on all the top rolls shown above. It is a figure which shows the result.
From the results shown in FIG. 10, the inventors analyzed the state of the stress distribution acting on the glass ribbon at each position for each of the top rolls No. 4 (L-4) to No. 11 (L-11). Conspicuous stress at the positions of No. 5 (L-5) to No. 10 (L-10) with respect to the boundary value R indicated by the chain line where the assumed local deformation portion called a straw is expected to occur. From this simulation result, it can be seen that it is effective to apply the barrel head to the middle roll top roll.

This application is based on Japanese Patent Application No. 2012-091094 filed on April 12, 2012, the contents of which are incorporated herein by reference.

The technology of the present invention can be widely applied to apparatuses and methods for producing glass plates used in display glass, optical glass, medical glass, architectural glass, vehicle glass, and other general glass products.

G ... Molten glass, 1 ... Manufacturing apparatus (float bath), 2 ... Bath, 3 ... Molten metal, 5 ... Inlet part, 6 ... Outlet part, 7 ... Conveyance roll, 7A ... Slow cooling line, 8 ... Movement path, 9 Glass ribbon, 10 ... Glass ribbon, 11 ... Top roll, 11A ₀ to 11A ₁₅ ... Top roll, 13 ... Rotating shaft, 14 ... Multi-stage barrel head, 16 ... Rotating drum, 17 ... Rotating shaft, 18 ... Reference barrel head, 20 ... Rotating drum, 30 ... Multistage barrel head,

Claims (15)

1. In the method of manufacturing a glass plate, which is formed while moving the molten glass along the moving path of the molten glass provided on the molten metal, and manufacturing a glass ribbon,
   A glass ribbon having a thickness of 1 mm or less is formed by applying an outward tensile force to both ends of the glass ribbon by a plurality of pairs of top rolls disposed on both ends in the width direction of the movement path from the upstream area to the downstream area of the movement path. When manufacturing
   As the top roll, using a top roll provided with a barrel head that pulls outward in the width direction end of the glass ribbon conveyed from the upstream area to the downstream area along the movement path,
   Out of the barrel heads that are provided in the upstream, middle and downstream areas of the moving path and apply an outward tensile force to the widthwise ends of the glass ribbon, three or more outer circumferences as barrel heads provided in the middle stream A method for producing a glass plate, which uses a multistage barrel head provided with blades and uses a reference barrel head provided with one or two rows of outer peripheral blades as barrel heads provided in an upstream region and a downstream region.
2. 2. The method for producing a glass plate according to claim 1, wherein the multi-stage barrel head is installed with an area where the logarithm of the viscosity of the glass ribbon is 5.29 to 6.37 dPa · s as a middle flow area.
3. A plurality of the upstream reference barrel head, the middle-stream multistage barrel head, and the downstream reference barrel head are provided for each region, and each row formed along the circumferential direction of the outer peripheral surface of each barrel head. When arranging the direction of the surface formed by the outer peripheral blade substantially perpendicular to the glass ribbon and parallel or inclined with respect to the conveying direction of the glass ribbon, the multistage barrel in the middle stream area from the reference barrel head in the upstream area 3. The glass plate according to claim 1, wherein the barrel heads are arranged so that the inclination angle gradually decreases from the multistage barrel head in the middle stream region to the reference barrel head in the downstream region so that the inclination angle gradually increases toward the head. Production method.
4. The other side of the barrel head provided with the outer peripheral blade of the row close to the center in the width direction of the moving path, the outer diameter of one end of the barrel head provided with the outer peripheral blade of the row close to the width direction edge of the moving path The method for producing a glass plate according to any one of claims 1 to 3, wherein a multistage barrel head having a smaller outer diameter than the end portion is used.
5. The method for producing a glass plate according to any one of claims 1 to 4, wherein the molten glass is an alkali-free glass having the following composition in terms of oxide-based mass percentage:
   SiO ₂ : 50 to 73%,
   Al ₂ O ₃ : 10.5-24%,
   B ₂ O ₃ : 0 to 12%,
   MgO: 0-8%,
   CaO: 0 to 14.5%,
   SrO: 0 to 24%,
   BaO: 0 to 13.5%,
   MgO + CaO + SrO + BaO: 9 to 29.5%, and ZrO ₂ : 0 to 5%.
6. The method for producing a glass plate according to any one of claims 1 to 4, wherein the molten glass is an alkali-free glass having the following composition in terms of oxide-based mass percentage:
   SiO ₂ : 58 to 66%,
   Al ₂ O ₃ : 15-22%,
   B ₂ O ₃ : 5 to 12%,
   MgO: 0-8%,
   CaO: 0-9%,
   SrO: 3 to 12.5%,
   BaO: 0-2%,
   MgO + CaO + SrO + BaO: 9 to 18% and ZrO ₂ : 0 to 5%.
7. The method for producing a glass plate according to any one of claims 1 to 4, wherein the molten glass is an alkali-free glass having the following composition in terms of oxide-based mass percentage:
   SiO ₂ : 54-73%
   Al ₂ O ₃ : 10.5 to 22.5%,
   B ₂ O ₃ : 0 to 5.5%,
   MgO: 0-8%,
   CaO: 0-9%,
   SrO: 0 to 16%,
   BaO: 0 to 2.5%, and MgO + CaO + SrO + BaO: 8 to 26%.
8. A float bath for storing molten metal, a molten glass moving path formed on the molten metal, and moving the molten glass from an upstream area to a downstream area of the moving path to form a glass ribbon, and the float bath A plurality of top rolls disposed on both sides in the width direction of the movement path from the upstream area to the downstream area of the movement path within,
   The top roll is attached to a rotating shaft individually extending horizontally on both sides in the width direction of the moving path of the molten glass, and attached to the front end side of the rotating shaft, from the upstream area to the downstream area along the moving path. A barrel head having an outer peripheral blade pressed against the widthwise end of the glass ribbon being conveyed,
   A multistage barrel head that has three or more rows of outer peripheral blades and pulls the end in the width direction of the glass ribbon outward is provided in the middle flow area of the movement path, and one line or An apparatus for producing a glass plate, which has two rows of outer peripheral blades and is provided with a reference barrel head that pulls the end in the width direction of the glass ribbon outward.
9. The apparatus for producing a glass plate according to claim 8, wherein the multistage barrel head is disposed in a region where the logarithmic value of the viscosity of the glass ribbon is 5.29 to 6.37 dPa · s.
10. The apparatus for producing a glass plate according to claim 8 or 9, wherein the glass ribbon formed by the float bath has a thickness of 1 mm or less.
11. The upstream reference barrel head, the middle-stream multistage barrel head, and the downstream reference barrel head are all provided for each region, and each row is formed along the circumferential direction of the outer peripheral surface of each barrel head. The direction of the surface formed by the outer peripheral blade of the multi-stage barrel is arranged from the upstream reference barrel head to the middle-stream barrel by being arranged so as to be substantially perpendicular to the glass ribbon and parallel or inclined with respect to the glass ribbon transport direction. 11. The barrel heads according to claim 8, wherein the barrel heads are arranged such that the inclination angle gradually decreases from the multistage barrel head in the middle stream area to the reference barrel head in the downstream area so that the inclination angle gradually increases toward the head. The manufacturing apparatus of the glass plate of description.
12. The other side of the barrel head provided with the outer peripheral blade of the row close to the center in the width direction of the moving path, the outer diameter of one end of the barrel head provided with the outer peripheral blade of the row close to the width direction edge of the moving path The apparatus for producing a glass plate according to any one of claims 8 to 11, wherein the apparatus is made smaller than the outer diameter of the end portion.
13. The glass plate manufacturing apparatus according to any one of claims 8 to 12, wherein an alkali-free glass having the following composition in terms of oxide-based mass percentage is applied as the molten glass:
    SiO ₂ : 50 to 73%,
    Al ₂ O ₃ : 10.5-24%,
    B ₂ O ₃ : 0 to 12%,
    MgO: 0-8%,
    CaO: 0 to 14.5%,
    SrO: 0 to 24%,
    BaO: 0 to 13.5%,
    MgO + CaO + SrO + BaO: 9 to 29.5%, and ZrO ₂ : 0 to 5%.
14. The glass plate manufacturing apparatus according to any one of claims 8 to 12, wherein an alkali-free glass having the following composition in terms of oxide-based mass percentage is applied as the molten glass:
    SiO ₂ : 58 to 66%,
    Al ₂ O ₃ : 15-22%,
    B ₂ O ₃ : 5 to 12%,
    MgO: 0-8%,
    CaO: 0-9%,
    SrO: 3 to 12.5%,
    BaO: 0-2%,
    MgO + CaO + SrO + BaO: 9 to 18% and ZrO ₂ : 0 to 5%.
15. The glass plate manufacturing apparatus according to any one of claims 8 to 12, wherein an alkali-free glass having the following composition in terms of oxide-based mass percentage is applied as the molten glass:
    SiO ₂ : 54-73%
    Al ₂ O ₃ : 10.5 to 22.5%,
    B ₂ O ₃ : 0 to 5.5%,
    MgO: 0-8%,
    CaO: 0-9%,
    SrO: 0 to 16%,
    BaO: 0 to 2.5%, and MgO + CaO + SrO + BaO: 8 to 26%.

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