TW201345848A - Glass plate manufacturing device and manufacturing method - Google Patents

Abstract

The purpose of the present invention is to provide a technique capable of manufacturing a glass ribbon by a float process without causing a locally deformed portion called a straw. The present invention relates to a glass plate manufacturing device provided with a float bath provided with a molten metal constituting a movement path of a glass ribbon, and a plurality of pairs of top rolls, the top roll is provided with a rotating shaft individually extended horizontally on both sides in the width direction of the movement path, and a barrel head pressed against an end in the width direction of a glass ribbon conveyed along the movement path, and a plurality of barrel heads that are pressed against the glass ribbon and cause outward pull force to act on the glass ribbon have nip margins indicating the distances between the pressing positions of the barrel heads against the glass ribbon and the end edge of the glass ribbon and becoming smaller from the upstream side to the downstream side in a midstream region.

Description

Glass plate manufacturing device and manufacturing method

The present invention relates to an apparatus and a method of manufacturing a thin glass sheet in accordance with a float bath method.

In recent years, glass substrates for flat panel displays such as liquid crystal displays and plasma displays have been increasing in size and thickness.

As an example of the method for producing such a glass substrate, a floating kiln in which molten metal such as metal tin is stored is used, and a molten glass in which the molten glass is elongated in the horizontal direction in the horizontal direction is formed. According to the floating method, the required thickness of the corresponding target is ensured by suspending the molten glass on the molten metal of the floating kiln, and the glass ribbon can be formed by pulling the molten glass horizontally. . A glass substrate of a target size can be obtained by cutting the glass ribbon to a desired size.

In order to manufacture a glass substrate which is increasing in size and thickness as described above, according to the floating method, a method of providing both ends in the width direction of the glass ribbon to the outside of the molten metal of the floating kiln is employed. The forming device called the top roll stretches and thins the glass ribbon toward both end sides in the width direction. The thin glass ribbon is pulled to be slowly cooled, cut to a desired size, and polished and cleaned, whereby a target glass substrate can be obtained. According to this floating method, a large-sized and thin glass substrate can be mass-produced, and a large-sized glass substrate having a thickness of about 0.7 mm and a length and a width of several m can be produced as a glass substrate.

And, more recently, a large number of portable information terminal machines have been manufactured as An example of a liquid crystal panel of the portable information terminal device is provided with a liquid crystal panel having a glass substrate on which a liquid crystal panel is manufactured using a glass substrate having a thickness of about 0.7 mm, and one side of the glass substrate is used. It is thinned to a thickness of about 0.3 mm by a method such as wet etching.

Fig. 8 shows an example of a floating kiln for a floating method comprising a bottom bath 102 having molten metal 101 such as molten tin therein, and the molten glass 103 flows from the furnace to the inlet of the bottom bath 102 before the melting furnace side. The molten glass 103 is elongated on the molten metal 101 by a plurality of top rolls 105 to a target width, and is gradually cooled to form a glass ribbon 106 of a desired width and thickness.

As an example of the top roll 105 applied to the floating kiln 100, a cylinder cover having a disk shape as shown in FIG. 9 and having a two-stage saw blade-shaped outer peripheral blade 105a is known ( Barrelhead) Top roller of 105A. (Refer to Patent Document 1)

The cylinder cover 105A shown in Fig. 9 allows the outer peripheral blades 105a, 105a to enter the edge portion 103a of the molten glass 103 and exert an outward tensile force on the edge portion 103a, and adjust the width of the molten glass 103, thereby adjusting the glass. The width and thickness of the belt 106.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent Laid-Open No. Hei 11-236231

According to the above-described background, the glass substrate tends to be thinner, and a glass substrate having a thickness of about 0.3 mm has been studied as a glass substrate for a panel of a portable information terminal device. Moreover, in the glass substrate for flat panel displays, further thinning is also required.

Previously, the molten glass 103 which flowed into the floating kiln 100 and expanded shortly was liquid at a high temperature, so that it could not be simply stretched, but the molten glass 103 was upstream from the floating kiln 100. Since the region moves to the downstream region and is slowly cooled, the viscosity gradually becomes higher, so that the molten glass 103 having a higher viscosity can be stretched by the can lid 105A.

However, since the molten glass 103 which has a tensile force acting in the flow direction has a property of shrinking, the more it is desired to thin the molten glass 103, the more it is necessary to press the glass with a stronger force, so that a strong tensile force acts. .

As a result, there is a problem in that the edge portion of the can lid 105A is pierced deeper than the state shown in Fig. 9 to the edge portion 103a of the molten glass 103, and the molten glass 103 is largely deformed in the vicinity of the edge portion thereof.

FIG. 10 is a view for explaining a state in which the cylinder cover 105A is pressed from above with a strong force with respect to the edge portion 103a of the molten glass 103.

When the cylinder cover 105A is strongly pressed as shown in FIG. 10(b) with respect to the edge portion 103a of the molten glass 103 shown in FIG. 10(a), the edge portion 103a is deeply proportional to the pressing force of the cylinder cover 105A. The ground sinks and deforms into a U-shaped bag. It is assumed that if the glass which is deformed while maintaining the state of the bag becomes hard, there is a problem that a partial deformation portion 110 called a straw is formed in a T-shaped cross section as shown in FIG.

When the cylinder cover 105A is strongly pressed against the edge portion 103a of the molten glass 103 as shown in Fig. 10(b), the cross section is deformed into an S shape as shown in Fig. 10(c). When this state is maintained and the glass is hardened, there is a problem that a partial deformation portion 111 called a straw is deformed so that the deformed portion is overlapped with the pocket portion 111a in the upper direction and the pocket portion 111b in the lower direction as shown in FIG. When the S-shaped partial deformation portion 111 is formed, the molten metal is wound into the inner side of the glass as indicated by an arrow a and an arrow b in Fig. 10(c), and as a result, there is a subsequent The problem of glass breakage in the slow cooling step. For example, since the metal tin and the glass plate have different thermal expansion coefficients, the stress acts on the glass plate in which the metal tin is caught, and the crack occurs after the heat shrinks during the slow cooling.

When the glass ribbon is cut in the cutting step in the state in which the partial deformation portions 110 and 111 are provided, the glass sheet is cut into a target size, and in this case, The position or direction in which the cutting position or direction is different causes cracking, so there is a hindrance to the stable production of the glass sheet. The case where the local deformation portions 110 and 111 are formed is remarkable in a thin glass plate, and particularly in the case where a glass plate having a thickness of 1 mm or less is produced by a floating method as in the case of the above-described glass substrate for a display device.

Based on the above-mentioned background, the inventors of the present invention conducted various studies on a technique of producing a thin glass ribbon of 1 mm or less by forming a molten glass by a floating method, and as a result, it was found that when a thin glass ribbon was formed by applying tension to the edge portion of the molten glass. By investigating the position at which the tension is applied to the canopy, the occurrence of a local deformation portion called a straw can be suppressed, and the present invention is completed.

An object of the present invention is to provide a manufacturing apparatus and a manufacturing method which can produce a glass ribbon without causing a local deformation portion when a thin glass ribbon is formed by a floating method, and contribute to stable production of the glass sheet.

The present invention relates to a glass sheet manufacturing apparatus comprising: a floating kiln that accumulates molten metal, forms a moving path of the molten glass on the molten metal, and moves the molten glass from an upstream region of the moving path to a downstream region; And the plurality of top rollers are disposed on both sides of the width direction of the moving path from the upstream region to the downstream region of the moving path in the floating kiln; the top roller has a rotating shaft and is melted a glass cover extending in a horizontal direction on both sides in a width direction; and a cylinder cover attached to a front end side of the rotating shaft and pressed against a glass ribbon conveyed from the upstream region to the downstream region via the moving region along the moving path An end portion in the width direction; a plurality of cylinder covers that are pressed against the glass ribbon to apply an outward tensile force to the end portion of the glass ribbon in the width direction, and the cylinder cover is opposite to the glass ribbon The width of the clamping margin of the pressing position and the distance from the immediately adjacent end edge of the glass ribbon is smaller on the downstream side than the upstream side.

The invention relates to a manufacturing device for a glass plate, wherein the logarithm of the viscosity of the glass ribbon is 5.29~6.37dPa. The area of s is set as the middle area, and is set in the middle area. The relationship between the widths of the clamping margins of the plurality of cylinder covers of the domain satisfies the above relationship.

The present invention relates to a manufacturing apparatus for a glass sheet, wherein a position of a line mark formed by a cylinder cover on a more upstream side of a specific cylinder cover is formed as a line formed by pressing the glass ribbon by the specific cylinder cover. The position of the mark is further on the inner side of the above glass ribbon.

The present invention relates to a glass sheet manufacturing apparatus, wherein the glass ribbon formed by the floating kiln has a thickness of 1 mm or less.

The present invention relates to a glass sheet manufacturing apparatus in which, as the molten glass, an alkali-free glass having a composition of SiO ₂ : 50 to 73% and Al ₂ O ₃ : 10.5 by mass percentage based on an oxide is used. 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 ~29.5%, ZrO ₂ : 0~5%.

The present invention relates to a glass sheet manufacturing apparatus, wherein as the molten glass, an alkali-free glass having a composition of SiO ₂ : 58 to 66%, Al ₂ O ₃ : 15~ is represented by a mass percentage based on an oxide. 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 ~18%, ZrO ₂ : 0~5%.

The present invention relates to a device for producing a glass sheet, wherein as the molten glass, an alkali-free glass having a composition of the following is used as a mass percentage based on an oxide: SiO ₂ : 54 to 73%

Al ₂ O ₃ : 10.5~22.5%

B ₂ O ₃ : 0~5.5%

MgO: 0~8%

CaO: 0~9%

SrO: 0~16%

BaO: 0~2.5%

MgO+CaO+SrO+BaO: 8~26%

The present invention relates to a method for producing a glass sheet which is formed by moving a molten glass along a moving path of molten glass provided on a molten metal to form a glass ribbon by using an upstream region from the moving path to the downstream When a plurality of glass sheets having a thickness of 1 mm or less are applied to the both ends of the glass ribbon at the opposite ends of the width direction of the moving path, the top roller is provided with the pair of moving paths along the moving path. a cylinder cover that acts on the outward tensile force from the end portion in the width direction of the glass ribbon conveyed from the upstream region to the downstream region; and the plurality of cylinder covers disposed in the middle of the movement path to indicate that the cylinder cover is opposite to the glass ribbon The width of the clamping margin of the distance between the pressing position and the edge of the glass ribbon is smaller than the upstream side on the downstream side to apply a tensile force to both end portions of the glass ribbon.

The invention relates to a method for manufacturing a glass plate, wherein the logarithm of the viscosity of the glass ribbon is 5.29~6.37dPa. The area of s is set as the midstream area, and the relationship of the magnitude of the width of the clamping margin of the plurality of cylinder covers provided in the midstream area is set as the above relationship.

The present invention relates to a method of manufacturing a glass sheet, wherein a position of a line mark formed by a cylinder cover on a more upstream side of a specific cylinder cover is formed as a line formed by pressing the glass ribbon by the specific cylinder cover. The position of the mark is further on the inner side of the above glass ribbon.

The present invention relates to a method for producing a glass sheet, wherein, as the molten glass, an alkali-free glass having a composition of SiO ₂ : 50 to 73% and Al ₂ O ₃ : 10.5 by mass percentage based on an oxide is used. 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 ~29.5%, ZrO ₂ : 0~5%.

The present invention relates to a method for producing a glass sheet, wherein as the molten glass, an alkali-free glass having a composition of SiO ₂ : 58 to 66% or Al ₂ O ₃ : 15 is represented by a mass percentage based on an oxide. 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 ~18%, ZrO ₂ : 0~5%.

The present invention relates to a method for producing a glass sheet, wherein as the molten glass, an alkali-free glass having a composition of the following is expressed by mass percentage based on an oxide: SiO ₂ : 54 to 73%

Al ₂ O ₃ : 10.5~22.5%

B ₂ O ₃ : 0~5.5%

MgO: 0~8%

CaO: 0~9%

SrO: 0~16%

BaO: 0~2.5%

MgO+CaO+SrO+BaO: 8~26%

According to the manufacturing apparatus and the manufacturing method of the present invention, in the middle of the moving path of the floating kiln, when the end edge portion of the glass ribbon is elongated and formed by the cylinder cover, the sleeve of the cylinder cover disposed in the midstream region is clamped The width of the holding margin is formed by sequentially decreasing from the upstream side to the downstream side of the midstream region, so that the position of the glass ribbon pressed by the downstream side cylinder cover can be positioned closer to the glass ribbon pressed by the upstream side cylinder cover. Closer to the end edge of the glass ribbon, the end of the glass ribbon elongated by the upstream side of the cylinder cover is elongated by the downstream side of the cylinder cover closer to the end edge. Thereby, even when the glass cover is strongly pressed by the upstream side cover to deform and exert a strong tensile force, the downstream side cover will be more laterally outward than the deformed portion of the glass ribbon. Stretching, it is also possible to correct the deformed portion of the glass ribbon and form the glass ribbon.

As a result, a thin glass ribbon can be obtained without generating a local deformation portion called a straw in the glass ribbon in the midstream region. Further, the glass ribbon in which the local deformation portion is not produced is cut in the subsequent step to form a glass sheet, so that a glass sheet of a target size can be obtained without causing cracks or chipping.

In the case of manufacturing a glass substrate such as a display device, it is thinner than 1 mm, preferably 0.7 mm or less, more preferably 0.5 mm or less, further preferably 0.3 mm or less, and particularly preferably 0.1 mm or less. The glass ribbon in the middle of the kiln is particularly prone to produce a local deformation called a straw, but by using the above-mentioned cylinder cover for the molten glass of the midstream region, a tensile force is applied to the edge near the edge, which can be applied to the glass ribbon. The end side is reduced in the amount of deformation in the thickness direction, and a thin glass ribbon in which no local deformation portion is generated can be obtained. By cutting the glass ribbon, a thin glass sheet having a target size of 1 mm or less, such as no crack or notch, can be obtained.

1‧‧‧Manufactured equipment (floating kiln)

2‧‧‧ bath

3‧‧‧ molten metal

5‧‧‧Entry

6‧‧‧Exports Department

7‧‧‧Transport roller

7A‧‧‧ Slow cooling line

8‧‧‧Moving path

9‧‧‧glass ribbon

9A‧‧‧ recess

10‧‧‧glass ribbon

11‧‧‧ top roller

11A ₀ ~11A ₁₅ ‧‧‧ top roller

13‧‧‧Rotary axis

13a‧‧‧ Hollow

13b‧‧‧Supply tube

13c‧‧‧ Return to the flow path

14‧‧‧Multi-section cover

15‧‧‧Outer knife

16‧‧‧Rotating tube

16a‧‧‧ peripheral wall

16b‧‧‧ Hollow

16c‧‧‧ face wall

16d‧‧‧ face wall

17‧‧‧Rotary axis

17a‧‧‧ Hollow

17b‧‧‧Supply tube

17c‧‧‧ Return to the flow path

18‧‧‧ reference cover

19‧‧‧Outer knife

20‧‧‧Rotating cylinder

20a‧‧‧ peripheral wall

20b‧‧‧ Hollow

20c‧‧‧ face wall

20d‧‧‧ face wall

30‧‧‧Multi-section cover

A‧‧‧width of clamping margin

A ₅ ~A ₈ ‧‧‧Line marks

G‧‧‧ molten glass

T ₅ ~T ₈ ‧‧‧ arrows

Fig. 1 is a schematic view showing an overall configuration of a manufacturing apparatus for a glass sheet according to a first embodiment of the present invention.

Fig. 2 is a configuration diagram showing an example of an arrangement state of a top roll provided in the manufacturing apparatus.

Fig. 3 is a configuration diagram showing a main part of an example of an arrangement state of a top roll provided in the manufacturing apparatus.

Figure 4 is a cross-sectional view showing a top cover for a top roller of the manufacturing apparatus, Figure 4 (a) is a cross-sectional view of the reference cylinder cover, Figure 4 (b) is a front view of the multi-stage cylinder cover, Figure 4 (c) A sectional view of the multi-section cylinder cover.

Figure 5 is a perspective view of a multi-section cartridge cover provided in the manufacturing apparatus.

Fig. 6 is a graph showing a state of viscosity at each temperature as an example of a molten glass supplied to the manufacturing apparatus.

Fig. 7 is a graph showing an example of a compressive stress distribution of an end portion of a glass ribbon supplied to a float bath.

Figure 8 is a plan view showing an example of a floating kiln of a prior top roll.

Fig. 9 is a cross-sectional view showing an example of a state in which a cap provided on a preceding top roll is pressed into an end portion of a glass ribbon.

Figure 10 is a view showing the relationship between the end of the molten glass and the previous can, FIG. 10(a) is a cross-sectional view showing the end of the glass ribbon, and FIG. 10(b) is a view showing the cylinder cover being pressed into the glass ribbon. A cross-sectional view showing an example of the state of the end portion, and Fig. 10 (c) is a cross-sectional view showing an example of a partial deformation portion (sucking pipe) of a cross-sectional S shape formed on the end portion side of the glass ribbon.

Fig. 11 is a cross-sectional view showing an example of a partial deformation portion of a cross-sectional T-shape formed on the end side of the glass ribbon.

Fig. 12 is a cross-sectional view showing an example of a partial deformation portion of a cross-sectional S shape formed on the end side of the glass ribbon.

"First embodiment"

Hereinafter, the first embodiment of the apparatus for manufacturing a glass sheet of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to the embodiments described below.

1 is a schematic configuration of a first embodiment of a manufacturing apparatus for a glass sheet according to the present invention, and a manufacturing apparatus (floating kiln) 1 for a glass sheet according to the present embodiment includes a bath 2 including a substantially rectangular shape in plan view. A refractory furnace; a molten metal 3 such as metal tin, which is housed inside the bath 2; and a top roll 11 which is disposed in the interior of the bath 2 in plural.

The bath 2 includes a bottom structure made of a refractory material, a side wall, and an upper structure. However, in FIG. 1, only the bottom structure is depicted in a plan view. An auxiliary device such as a gas supply pipe or a temperature regulator such as a non-oxidizing gas is disposed on the upper structure side of the bathtub 2, and the environment of the bath 2 can be controlled to a non-oxidizing gas atmosphere, and the temperature of the space portion on the molten metal 3 can be set. Control is the target temperature.

On the left end side of the bath 2 in Fig. 1, an inlet portion 5 for supplying the molten glass G to the molten metal 3 from the furnace before the glass melting furnace provided in the preliminary step is provided. In the bath The outlet portion 6 is formed at an end portion on the opposite side to the side on which the inlet portion 5 is provided, and a plurality of conveying rollers 7 are arranged on the outer side of the outlet portion 6, and a slow cooling line 7A is formed.

The molten metal 3 from the inlet portion 5 to the outlet portion 6 in the bath 2 is partitioned by a rectangular movement path 8 in a plan view in which the molten glass G is formed.

When the molten glass G flows from the inlet portion 5 to the molten metal 3 along the movement path 8, the molten glass G is gradually cooled and discharged to the outlet portion in a state in which the molten glass G is expanded to a desired thickness and width. The 6 side is moved to form a glass ribbon 10 having a width-like uniform strip shape as a final form, and the glass ribbon 10 is discharged from the outlet portion 6 toward the slow cooling line 7A side. In the present embodiment, since the planar shape of the bathtub 2 is formed in a rectangular shape, the movement path 8 which is partitioned on the molten metal 3 inside the bathtub 2 also has a rectangular shape, but the planar shape of the movement path 8 is not limited to the rectangular shape. The shape may be any shape conforming to the planar shape of the bathtub 2.

In the bath 2 of the present embodiment, a plurality of top rollers 11 arranged at a predetermined interval from the upstream region toward the downstream region at both end sides in the width direction of the movement path 8 are disposed between the inlet portion 5 and the outlet portion 6. In the present embodiment, the molten glass G supplied from the inlet portion 5 is elongated in the width direction by the plurality of top rolls 11, and the glass ribbon 9 in the molten state is conveyed toward the downstream region (the outlet portion 6 side). Finally, a ribbon-like glass ribbon 10 of a specific width can be obtained.

As shown in Fig. 2, in the bath 2 of the present embodiment, 16 types of top rollers are arranged at predetermined intervals from the position at which the width of the molten glass G is expanded at the both end sides in the width direction of the movement path 8 11. For the sake of convenience, the symbols of A ₀ to A _{15 are} assigned to the 16 types of top rollers 11 in the following, and the arrangement of each is explained.

Among the top rolls 11, the first stage top roller 11A ₀ to the fifteenth top roll A ₁₅ (that is, the top roll 11A ₁₅ is the 16th if the top roll 11A ₀ starts counting) is set to be provided. The top roller of the reference cylinder cover 18 will be described below. Further, in the present embodiment, the fifth top roller 11A ₅ to the tenth top roller 11A ₁₀ may be provided with a multi-stage cylinder cover 14 as described below instead of the top roller of the reference cylinder cover 18.

The top stage top roller 11A ₀ to the fifteenth top roll A ₁₅ are provided with the rotating shaft 17 shown in Fig. 4 (a) and the reference cylinder cover 18 integrated at the front end portion thereof.

The mechanism for rotationally driving the respective rotary shafts 17 and the mechanism for moving the rotary shaft 17 are omitted in FIGS. 1 and 2, but the rotary shaft 17 extends through the side wall of the bathtub 2 and extends substantially horizontally to the outside of the bathtub 2 in the bathtub. The outer side of the 2 is provided with a rotary drive device and a mobile device. An example of the moving device of the rotating shaft 17 is applicable to a moving device in which a moving carriage that is movably provided on a rail member that is disposed on the outer side of the position where the bathtub 2 is provided is provided with a rotary driving device such as a motor. The rotary driving device or the moving device is the same as the driving device or the moving device provided in the top roller of the conventional floating kiln, and the rotating shaft 17 is moved, for example, in the state of being rotationally driven, at both end sides in the width direction of the moving path 8. The path 8 is movably arranged in the width direction. In FIGS. 1 to 3, the rotation driving device or the moving device is omitted, and only the front end side of the rotating shaft 17 and the reference cylinder cover 18 attached to the front end portion are displayed.

The reference cylinder cover 18 is provided with two (two rows) outer peripheral blades 19 on the outer peripheral wall 20a of the rotary cylinder 20 as shown in Fig. 4(a). Both the rotating shaft 17 and the inside of the reference cylinder cover 18 have a hollow structure, and the hollow portion 17a formed inside the rotating shaft 17 communicates with the hollow portion 20b formed inside the rotating cylinder 20. A supply pipe 17b for cooling water is provided inside the rotary shaft 17, and a return flow path 17c for cooling water is formed in a gap between the supply pipe 17b and the inner peripheral wall of the rotary shaft 17. With such a configuration, the cooling water is supplied from the supply pipe 17b to the hollow portion 20b of the rotary cylinder 20, and the cooling water is recovered via the return flow path 17c, whereby the rotary shaft 17 and the rotary cylinder 20 can be supplied thereto. The inner side is cooled. Further, the cross-sectional shape of the hollow portion 20b can be appropriately changed so that the water flow can be efficiently circulated.

The outer peripheral blade 19 of the reference cylinder cover 18 is formed in a two-stage (two rows) by a plurality of blade tips having a quadrangular pyramid shape as shown in Fig. 4(a) along the outer peripheral wall 20a of the thin cylindrical rotating cylinder 20. Continuous formation. Each of the outer peripheral blades 19 has the same shape and is formed in the circumferential direction of the rotary cylinder 20 at the same distance. Therefore, the outer peripheral blade 19 is formed as one of the circumferences of the rotary cylinder 20 as a whole. 2 lines of 2 sections. In the rotary cylinder 20 of the present embodiment, the end surface wall 20c on the side that is connected to the side of the rotating shaft 17 and the end surface wall 20d on the front end side of the reference cylinder cover 18 are formed in a flat shape. The end face wall 20c may also be inclined obliquely from the center of the canopy toward the outside.

From the top roller 11A ₀ of the first stage, the fourth top roller 11A ₄ is slowly cooled with respect to the molten glass G that has flowed into the molten metal 3 from the inlet portion 5, and the viscosity is increased to become molten. The glass ribbon 9 is disposed in the upstream region of the moving path 8.

From the fifth top roller 11A ₅ described above, the tenth top roller 11A ₁₀ is provided with respect to the intermediate portion of the moving path 8, that is, the region where the viscosity of the glass ribbon 9 is higher than the upstream region.

From the eleventh top roll 11A ₁₁ of the above configuration, the fifteenth top roll 11A ₁₅ is provided with respect to the downstream region of the above-mentioned moving path 8, that is, the region where the viscosity of the glass ribbon 9 is further higher than the midstream region.

In the manufacturing apparatus 1 of the present embodiment, the width of the clamping margin of each of the fifth top roller 11A ₅ to the tenth top roller 11A ₁₀ provided in the midstream region is set as the downstream cylinder cover. The reference cylinder cover 18 on the upstream side is narrower than the width of the clamping margin. The fifth top roller 11A ₅ to the eighth top roller 11A _{8 of the} midstream region are representatively shown in Fig. 3, and the reference cylinder cover 18 from the fifth top roller 11A ₅ is pressed against the upper surface of the glass ribbon 9. The distance to the end edge of the glass ribbon 9 immediately adjacent, in other words from the position of the upper surface of the glass ribbon 9, along the axis of rotation 17 up to the end edge of the glass ribbon 9 is defined as the width of the clamping margin. .

According to this definition, the width of the nip margin is the width of the nip margin of the fifth top roll 11A ₅ , the width of the nip margin of the sixth top roll 11A ₆ , and the seventh top roll 11A. The width of the clamping margin of ₇ and the width of the clamping margin of the eighth top roller 11A ₈ are set in such a manner that the order is gradually reduced. Further, although omitted in Fig. 3, the width of the nip of the ninth top roller 11A ₉ and the width of the nip margin of the tenth top roller 11A _{10 are} similarly followed. Change the mode setting.

Further, in the present embodiment, the width of the nip margin of each of the fifth top roller 11A ₅ to the tenth top roller 11A _{10 in} the midstream region is arranged to be smaller in order, but only In the plurality of top rollers 11 of the midstream region, the width of the clamping margin of any of the top rollers 11 on the downstream side is smaller than any of the top rollers 11 on the upstream side, so that the fifth top roller 11A ₅ to the tenth top In the roll 11A ₁₀ , the width of the nip margin may be made smaller in the top roller 11 of any number of two or more. Therefore, for example, it is also possible to intermittently reduce the width of the nip margin for every one of the top rollers 11 to be small. Alternatively, it is not limited to the midstream region, and may be in a plurality of top rollers 11 disposed from the upstream region to the midstream region, and the width of the clamping margin is from the upstream side to the downstream side in the plurality of top rollers 11 In the plurality of top rolls 11 disposed from the midstream region to the downstream region, the width of the nip margin is sequentially reduced from the upstream side to the downstream side in the plurality of top rolls 11.

Further, in the top roll 11 of the present embodiment, as described above, the fifth top roll 11A ₅ to the tenth top roll 11A _{10 may be} used as shown in FIG. 4(c) on the rotary shaft 13. The multi-stage cylinder cover 14 is integrated with the front end portion instead of the reference cylinder cover 18.

The multi-stage cylinder cover 14 is provided with six (6 rows) outer peripheral blades 15 on the outer peripheral wall 16a of the rotary cylinder 16 as shown in Figs. 4(b), (c) and 5 . Both the rotating shaft 13 and the inside of the multi-stage cylinder cover 14 have a hollow structure, and the hollow portion 13a formed inside the rotating shaft 13 and the hollow portion 16b formed inside the rotating cylinder 16 communicate with each other. A supply pipe 13b for cooling water is provided inside the rotary shaft 13, and a return flow path 13c for cooling water is formed in a gap between the supply pipe 13b and the inner peripheral wall of the rotary shaft 13. With such a configuration, the cooling water is supplied from the supply pipe 13b to the hollow portion 16b of the rotary cylinder 16, and the cooling water is recovered via the return flow path 13c, whereby the rotary shaft 13 and the rotary cylinder 16 can be supplied thereto. The inner side is cooled.

The outer peripheral blade 15 of the multi-stage cylinder cover 14 is divided into six segments by a plurality of blade tips having a quadrangular pyramid shape as shown in Figs. 4(b), (c) and 5, along the outer peripheral wall 16a of the cylindrical rotating cylinder 16. The way (6 lines) is continuously formed. The outer peripheral blades 15 have the same shape and are formed in the circumferential direction of the rotary cylinder 16 at the same distance. Therefore, the outer peripheral blade 15 is formed in a six-segment structure in which the entire outer peripheral blade 15 is formed around the rotary cylinder 16 . In the rotary cylinder 16 of the present embodiment, the end surface wall 16c that is connected to the side of the rotating shaft 13 and the end surface wall 16d of the front end side of the multi-stage cylinder cover 14 are formed flat. Plate shape. Further, the peripheral blade 15 formed on the outer cylinder cover 14 is not limited to a six-stage structure, and may be any number of three stages, four stages, five stages, or seven or more stages. However, if the number of stages is increased to more than necessary, the glass ribbon 9 is cooled more than necessary. Therefore, it is desirable that the number of stages of the glass ribbon 9 is not excessively cooled, and the number of stages of three or more stages, for example, four stages~ 8 or so.

As an example of the viscosity of the glass ribbon 9 in the molten state, FIG. 6 shows that the temperature of the molten glass of the normal alkali-free glass is lowered and the viscosity is changed to become hard until it becomes a glass ribbon.

In the state shown in FIG. 6 indicating the change in viscosity, the area where the common logarithm of the viscosity (η) of the glass ribbon 9 is less than 5.29 can be defined as the upstream region of the moving path 8, and the common logarithm of the viscosity of the glass ribbon 9 is used. The area of 5.29 to 6.37 is defined as the middle area of the moving path 8, and the area where the common logarithm of the viscosity of the glass ribbon 9 exceeds 6.37 is defined as the downstream area of the moving path 8. Furthermore, the viscosity of the glass ribbon 9 is 5.29 to 6.37, and the viscosity (η) of the glass ribbon 9 is 10 ^5.29 ~ 10 ^6.37 dPa. The area of s.

The top rollers 11A ₀ to 11A _{15 are} not oriented in parallel with the width direction of the glass ribbon 9, but have a slight angular inclination. For example, when the moving path 8 is viewed in a plan view, it is assumed that the moving direction of the glass ribbon 9 in the moving path 8 (the direction from the inlet portion 5 toward the outlet portion 6 and the side wall of the bathtub 2) is defined as the Y-axis direction, and the moving path is to be moved. The width direction of 8 is defined as the XY coordinate system in the X-axis direction, and is assumed to include the plane of the peripheral blade 19 of each row of the reference cylinder cover 18 or the plane of the peripheral blade 19 including the rows of the reference cylinder cover 18.

In this case, the plane 19a of the peripheral knives 19, which are arranged in a row in the circumferential direction of the reference cylinder cover 18 shown in Fig. 2, or the plane system of the peripheral knives 19 which are arranged in a row in the circumferential direction of the reference cylinder cover 18 The inclined arrangement is viewed in a plan view with an inclination angle (θ) of about 0 to 16° with respect to the Y axis. Further, any of the outer peripheral blade 19 of the reference cylinder cover 18 or the outer peripheral blade 19 of the reference cylinder cover 18 is pressed substantially perpendicularly from the upper side with respect to the glass ribbon 9. In other words, the respective rotating shafts 13 and 17 of the cartridge covers 14 and 18 are movably provided so as to be vertically movable in a state in which they can be arranged substantially horizontally, and the cylinder covers 14 and 18 are pressed to the end portions of the glass ribbon 9.

As an example of the inclined arrangement, for example, the first top roller 11A ₁ to the fifteenth top roller 11A ₁₅ shown in FIG. 2 are gradually increased from the first top roller 11A ₁ in order. Arranging the respective caps at an angle of a large inclination angle, increasing the inclination angle to the maximum inclination angle of the midstream region, gradually reducing the inclination angle in the reference cylinder cover 18 of the top roller of the downstream region, and the reference cylinder cover of the top roller of the final section In 18, the inclination angle is changed to 0°. The inclined arrangement state of each of the cylinder covers is not limited to the one described here, and may be an arbitrary inclined arrangement having the largest inclination angle in the reference cylinder cover 18 provided in the midstream region.

In order to manufacture the glass ribbon 10 using the glass manufacturing apparatus (floating kiln) 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, and is expanded, and a plurality of set reference cylinders are used. The lid 18 is pressed against the glass ribbon 9 in a molten state, and a tensile force is applied to the outer side of the glass ribbon 9 in the width direction, and the width and thickness of the glass ribbon 9 are adjusted to finally obtain the glass ribbon 10 of the target width. Further, the glass ribbon can be obtained by cutting the glass ribbon 10 to a target size in the cutting step of the subsequent step of the slow cooling line 7A.

In the manufacturing apparatus 1 of the present embodiment, the top roller 11A ₀ to the top roller 11A _{15 are provided} with the reference cylinder cover 18, so that the outer peripheral blade 19 of the two-stage structure is pressed against the end portion of the glass ribbon 9 in the width direction and rotated. By the reference cylinder cover 18 of the top rollers, the glass ribbon 9 can be expanded with respect to the tensile forces required to act outwardly on both ends of the glass ribbon 9 in the upstream region, the midstream region and the downstream region, respectively. .

In the manufacturing apparatus 1 of the present embodiment, the width of the clamping margin of each of the fifth top roller 11A ₅ to the tenth top roller 11A ₁₀ is the reference of the downstream side of the reference cylinder cover 18 from the upstream side. The sleeve 18 is then reduced in size to the width of the gripping margin. 3 shows the fifth top roller 11A ₅ to the eighth top roller 11A _{8 of the} midstream region, but each of the top rollers 11A ₅ to 11A ₈ is directed to the respective rotating shafts 17 toward the arrows T ₅ to T _{8 of} FIG. The direction is moved to apply a tensile force of a target size to the end of the glass ribbon 9, and the width of the glass ribbon 9 is expanded.

Thereby, as shown in FIG. 3, the trajectory of the line mark drawn on the surface of the glass cover 9 on the downstream side of the reference cylinder cover 18 on the downstream side is smaller than the trajectory of the line mark on the upper surface of the glass cover 9 on the upstream side. (The track of the line mark imprinted on the upper surface of the glass ribbon 9 by the rotation of the reference cylinder cover 18 in a state where the tip of the outer peripheral blade 19 is pressed against the upper surface of the glass ribbon 9) at the end of the glass ribbon 9 The location of the edge is depicted. That is, as shown in FIG, 11A ₆ depicts a top roll of the first six lines of marks than 5 A ₆ rolls 11A ₅ depicts a top of the line mark A ₅ to the position of the end edge of the belt 9 against the glass for drawing, 7 ₇ depicts a top roll. 11A depicts the line A marks the sixth ₇ than the top roll 11A ₆ A ₆ line mark at a position on the edge 9 of the glass ribbon drawing. Thus, the line marks A ₅ to A ₁₀ are intermittently formed at intervals in order to approach the end edges of the glass ribbon 9 in order.

Here, the fifth top roller 11A ₅ on the upstream side is pressed against the end of the glass ribbon 9 to stretch the pressing portion outward, and the sixth top roller 11A ₆ on the downstream side is pressed against the glass ribbon. The cross section of the state in which the pressing portion is stretched outward is compared with the end portion of 9 and is shown in the region surrounded by the 2-point chain line in Fig. 3 . As shown in Fig. 3, the end portion of the glass ribbon 9 is deformed downward into a convex shape with respect to the fifth top roller 11A ₅ on the upstream side in the midstream region, and the tensile force is applied to the outside, and the sixth side on the downstream side. The position at which the top roller 11A ₆ applies a tensile force to the outside of the end portion of the glass ribbon 9 becomes the outer side position of the glass ribbon 9, so that even if the fifth top roller 11A ₅ on the upstream side forms the deep recessed portion 9A in the glass ribbon 9, The sixth top roller 11A ₆ on the downstream side can also apply a tensile force to the outside of the end portion of the glass ribbon 9, and if so, the tensile force acts on the direction in which the concave portion 9A is stretched and disappears. The recess 9A is eliminated or reduced.

Further, since the top rollers 11A ₇ to 11A _{10 which are} disposed on the downstream side also have the same function, if the top rollers 11A ₅ to 11A _{10 are} arranged in the present embodiment, they can be sequentially arranged on the midstream region. The glass ribbon 9 is formed while eliminating the recess 9A which is to be produced at the end of the glass ribbon 9.

Therefore, even when it is desired to manufacture a glass ribbon 9 which is extremely thin as in the case of 1 mm or less, a partial deformation called a straw is not generated on the end side in the width direction of the molten glass G. .

The molten glass G, which is pulled by the top roll 11A ₁ to the top roll 11A ₁₅ to be thin, gradually increases in hardness as it moves from the upstream region of the moving path 8 to the downstream region, and becomes a fixed width and thickness in the downstream region of the moving path 8 The glass ribbon 10 reaches the outlet portion 6 and is conveyed to the side of the slow cooling line 7A of the subsequent step. According to the apparatus 1 for manufacturing a glass sheet of the present embodiment, the local deformation portion is not generated in the glass ribbon 10 which is conveyed to the slow cooling line 7A in a state in which the partial deformation portion previously called a straw is formed, so that it is not slow The rupture of the glass ribbon 10 on the cold wire 7A.

Further, since the cutting line (not shown) is provided in the subsequent step of the slow cooling line 7A, the glass ribbon of the target size can be obtained by cutting the glass ribbon 10 after the slow cooling to a desired size. Since the local deformation portion is not formed in the glass ribbon 10 sent to the cutting line, there is no occurrence of a defective portion at the time of cutting the cutting, which contributes to an improvement in productivity.

Further, in the case where the fifth top roller 11A ₅ to the tenth top roller 11A _{10 are provided} with a multi-stage cylinder cover 14 having a wide width of six stages, even with respect to the glass ribbon 9 in the midstream region, it is stronger. The force of pressing the multi-stage cylinder cover 14 to exert a strong tensile force, and the pressing margin of the glass ribbon 9 (the amount by which the molten glass G is deformed in the thickness direction thereof) may be compared with the reference cylinder cover 18 of the two-stage configuration. The situation is shallower.

Therefore, even if the multi-stage cylinder cover 14 is subjected to a strong tensile force with respect to the width direction end portion of the glass ribbon 9 with a strong tensile force, the multi-stage cylinder cover 14 causes the end portion of the glass ribbon 9 in the width direction thereof. The amount of deformation in the thickness direction (pressing margin) can also be reduced. Therefore, compared with the prior art in which the mid-stream region has a stronger tensile force with respect to the glass ribbon 9 than the two-stage structure, even if the thin glass ribbon 9 is to be manufactured, it is not in the molten glass G. A side deformation portion called a straw is produced on the end side in the width direction.

Furthermore, the viscosity of the glass ribbon 9 in the upstream region is low, and it is difficult to apply a strong tensile force. Therefore, the reference cylinder cover 18 can be used, and the glass ribbon 9 in the downstream region has a high viscosity and is close to a hard state, so even if it is based on the reference When the cylinder cover 18 is pressed, the amount of deformation in the thickness direction is also small.

Therefore, in the present embodiment, the arrangement relationship of the reference cylinder cover 18 in the midstream region is specifically arranged as shown in FIG. 3, but the required number of the cylinder cover provided in the midstream region may be used as a multi-stage cylinder. The cover 14 is partially connected to the reference cylinder cover 18 set to the configuration shown in FIG. Replace and share.

In view of this point, the glass ribbon 9 is subjected to a strong tensile force in the midstream region to elongate the glass ribbon 9, so that the configuration of the reference cylinder cover 18 shown in Fig. 3 is employed in the midstream region, and the multi-stage cylinder cover 14 can also be provided. By providing such an arrangement, it is possible to more effectively prevent a local deformation portion called a straw from being generated.

Further, the number of the multi-stage caps 14 provided in the mid-stream region is not particularly limited in the present embodiment, and the number of the glass ribbons 10 required for the final thickness of the target can be set.

Further, the number of the reference cylinder covers 18 provided in the entire region from the upstream region to the downstream region is not limited to the example of the embodiment, and the number of the glass ribbons 10 required to be the thickness of the forming target can be set. .

The composition of the molten glass G to be produced in the glass manufacturing apparatus 1 of the present embodiment is not particularly limited.

Therefore, it may be any of alkali-free glass, soda lime glass, mixed alkali glass, or borosilicate glass, or other glass. Moreover, the use of the manufactured glass product is not limited to flat panel display, construction, or vehicle, and various other uses are mentioned. In particular, an alkali-free glass for a flat panel display of high quality can be preferably used.

Further, as the glass suitable for the molten glass G, an alkali-free glass having the following composition in terms of mass percentage based on the oxide can be used.

SiO ₂ : 50 to 73% is 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 : 0~24%, BaO: 0~13.5%, MgO+CaO+SrO+BaO: 9~29.5%, ZrO ₂ : 0~5%.

As the glass suitable for the molten glass G, when the strain point is high and the meltability is considered, the alkali-free glass having the following composition can be expressed by mass percentage based on the oxide.

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 : 0~2%, MgO+CaO+SrO+BaO: 9~18%, ZrO ₂ : 0~5%.

As the glass suitable for the above-described molten glass G, in particular, in the case of a high strain point, an alkali-free glass having the following composition in terms of a mass percentage based on an oxide can be used.

SiO ₂ : 54 to 73%, Al ₂ O ₃ : 10.5 to 22.5%, B ₂ O ₃ : 0 to 5.5%, MgO: 0 to 8%, CaO: 0 to 9%, SrO: 0 to 16%, BaO : 0~2.5%, MgO+CaO+SrO+BaO: 8~26%.

Example

Fig. 6 is a graph showing an example of the relationship between the temperature and the viscosity of the alkali-free glass, and in the case of forming a glass ribbon, molding a molten glass of about 1110 ° C to 1120 ° C and gradually lowering the temperature at each temperature. The relationship between viscosity.

As shown in Fig. 6, the common logarithm of the viscosity (η) of the glass ribbon 9 can be 5.29 dPa. The area near the area of s is divided into the upstream area, and the common logarithm of the viscosity of the glass ribbon 9 is 5.29~6.37dPa. The area of s is divided into the middle area, and the common logarithm of the viscosity of the glass ribbon 9 exceeds 6.37 dPa. Since the area of s is divided into the downstream area, the reference cylinder cover 18 can be provided in the upstream area and the downstream area as described in the above embodiment, and the multi-stage cylinder cover 14 can be provided in the midstream area.

The molten glass having the viscosity characteristics shown in Fig. 6 was applied to a molding apparatus provided with 16 kinds of reference cylinder caps as shown in Figs. 1 and 2, and the width was about 80 inches (about 2.28 m) to a width of about 110 inches ( A glass ribbon of about 3.05 m) and a thickness of 0.3 mm.

The seventh top roller to the ninth top roller are set to have the following width of the clamping margin.

It is set as the top stage top roll L-0, the 1st top roll L-1 - the 15th top roll L-15.

Regarding the inclination angle θ of each of the top rolls, the inclination angle condition is set such that the cylinder cover of the top roll of L-0 to L-3 is inclined stepwise from 0° to 15°, and L-4~ The cover of the top roller of L-8 gives a tilt of 12~15°, and the cover of the top roller of L-9~L-13 is gradually reduced in inclination, and the top roller of L-11 is set to 0°. .

Width of the clamping margin of the 7th top roller: 155mm

The width of the clamping margin of the 8th top roller: 140mm

Width of the clamping margin of the ninth top roller: 120mm

By using the above conditions to produce a glass ribbon having a thickness of 0.3 mm for 24 hours, the production of the glass ribbon can be performed without causing a local deformation portion called a straw, and the glass ribbon can be slowly cooled and cut to produce a thickness of 0.3 mm. glass plate.

For comparison, the width of the clamping margin of the 7th top roll: 125mm

The width of the clamping margin of the 8th top roller: 140mm

Width of the clamping margin of the ninth top roller: 155mm

The glass ribbon having a thickness of 0.3 mm was produced by increasing the width of the nip margin to the level of the top roller on the downstream side as in the above conditions, and as a result, a local deformation portion called a straw was continuously produced.

From the above comparison, it is found that the width of the nip margin of the plurality of top rollers disposed in the midstream region is reduced to the extent of the width of the nip margin on the downstream side.

Fig. 7 is a view showing a reference cylinder cover provided on all of the top rollers previously shown, and in the case where the glass ribbon is formed as the arrangement of the above comparative example, the pressing position of each of the cylinder caps at the end portions of the glass ribbon is simulated by stress analysis. A graph showing the results of the stress distribution state.

As is clear from the results shown in FIG. 7 , the top rollers of No. 4 (L-4) to No. 11 (L-11) analyze the state of the stress distribution of the glass ribbon at each position, and the results are relative to the present invention. It is assumed that a boundary value R represented by a chain line, which is called a local deformation portion of a straw, is generated, and a significant stress distribution is obtained at positions of No. 5 (L-5) to No. 10 (L-10). Since the simulation As a result, it is effective to adjust the clamping margin for the top roller of the midstream region.

The present application is based on Japanese Patent Application No. 2012-093883, filed on Apr.

[Industrial availability]

The technology of the present invention can be widely applied to an apparatus and method for producing a glass plate for glass for display devices, glass for optical use, medical glass, glass for construction, glass for vehicles, and other conventional glass products.

9‧‧‧glass ribbon

9A‧‧‧ recess

11A ₅ ~11A ₈ ‧‧‧ top roller

17‧‧‧Rotary axis

18‧‧‧ reference cover

19‧‧‧Outer knife

A‧‧‧width of clamping margin

A ₅ ~A ₈ ‧‧‧Line marks

T ₅ ~T ₈ ‧‧‧ arrows

Claims (13)

A glass plate manufacturing apparatus comprising: a floating kiln that accumulates molten metal, forms a moving path of molten glass on the molten metal, and moves the molten glass from an upstream region of the moving path to a downstream region for forming glass And a plurality of counter top rollers disposed on both sides of the moving path from an upstream region to a downstream region of the moving path in the floating kiln; the top roller having: a rotating shaft, the moving path of the molten glass The two sides in the width direction respectively extend in the horizontal direction; and the cylinder cover is attached to the front end side of the rotating shaft, and is pressed against the width direction end of the glass ribbon which is conveyed from the upstream region to the downstream region through the intermediate region along the moving path a plurality of cylinder covers that are pressed against the glass ribbon and that exert an outward tensile force on the width direction end of the glass ribbon, and indicate a pressing position of the cylinder cover relative to the glass ribbon and the glass The width of the clamping margin of the distance from the end edge of the belt is smaller than the upstream side on the downstream side. The manufacturing apparatus of the glass plate of claim 1, wherein the logarithm of the viscosity of the glass ribbon is 5.29~6.37dPa. The area of s is set as the midstream area, and the magnitude relationship of the width of the clamping margin of the plurality of cylinder covers provided in the midstream area satisfies the above relationship. The apparatus for manufacturing a glass sheet according to claim 1 or 2, wherein a position of a line mark formed by a cylinder cover of a more upstream side of the specific cylinder cover is formed to press the glass ribbon to be pressed by the specific cylinder cover The position of the line marks is further on the inner side of the above glass ribbon. The apparatus for manufacturing a glass sheet according to any one of claims 1 to 3, wherein the glass ribbon formed by the above-mentioned floating kiln has a thickness of 1 mm or less. The apparatus for producing a glass sheet according to any one of claims 1 to 4, wherein the molten glass is an alkali-free glass having a composition of SiO ₂ : 50 to 73% by mass percentage based on an oxide. Al ₂ O ₃ : 10.5~24%, B ₂ O ₃ : 0~12%, MgO: 0~8%, CaO: 0~14.5%, SrO: 0~24%, BaO: 0~13.5%, MgO+ CaO+SrO+BaO: 9 to 29.5%, and ZrO ₂ : 0 to 5%. The apparatus for producing a glass sheet according to any one of claims 1 to 4, wherein, as the molten glass, an alkali-free glass having a composition of SiO ₂ : 58 to 66% is used as a mass percentage based on an oxide. 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: 9~18%, and ZrO ₂ : 0~5%. The apparatus for producing a glass sheet according to any one of claims 1 to 4, wherein, as the molten glass, an alkali-free glass having a composition of SiO ₂ : 54 to 73% is used as a mass percentage based on an oxide. Al ₂ O ₃ : 10.5 to 22.5%, B ₂ O ₃ : 0 to 5.5%, MgO: 0 to 8%, CaO: 0 to 9%, SrO: 0 to 16%, BaO: 0 to 2.5%, and MgO +CaO+SrO+BaO: 8~26%. A method for producing a glass sheet, which is formed by moving a molten glass along a moving path of molten glass provided on a molten metal to form a glass ribbon; and is disposed on the downstream region from the upstream to the downstream region of the moving path When a plurality of glass ribbons having a thickness of 1 mm or less are applied to the opposite ends of the glass sheet by the plurality of top rollers on the both end sides in the width direction of the moving path, the top roller is provided to transport from the upstream region along the moving path. a cylinder cover that acts to the outward tensile force at the end portion in the width direction of the glass ribbon in the downstream region; and a plurality of cylinder covers disposed in the middle of the movement path to indicate the pressing position of the cylinder cover relative to the glass ribbon and the glass The width of the clamping margin of the distance between the straight edges of the belt is smaller than the upstream side on the downstream side to exert a tensile force on both ends of the glass ribbon. The method for producing a glass plate according to claim 8, wherein the logarithm of the viscosity of the glass ribbon is 5.29~6.37dPa. The area of s is set as the midstream area, and the relationship of the magnitude of the width of the clamping margin of the plurality of cylinder covers provided in the midstream area is set as the above relationship. The method of manufacturing a glass sheet according to claim 8 or 9, wherein a position of a line mark formed by a cylinder cover on a more upstream side of the specific cylinder cover is formed to be formed by pressing the glass ribbon than the specific cylinder cover The position of the line marks is further on the inner side of the above glass ribbon. The method for producing a glass sheet according to any one of claims 8 to 10, wherein the molten glass is an alkali-free glass having a composition of the following composition by mass percentage based on oxide: SiO ₂ : 50 to 73%, Al ₂ O ₃ : 10.5~24%, B ₂ O ₃ : 0~12%, MgO: 0~8%, CaO: 0~14.5%, SrO: 0~24%, BaO: 0~13.5%, MgO+ CaO+SrO+BaO: 9 to 29.5%, and ZrO ₂ : 0 to 5%. The method for producing a glass sheet according to any one of claims 8 to 10, wherein, as the molten glass, an alkali-free glass having a composition of the following composition is used: 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: 9~18%, and ZrO ₂ : 0~5%. The method for producing a glass sheet according to any one of claims 8 to 10, wherein the molten glass is an alkali-free glass having a composition of the following composition by mass percentage based on an oxide: SiO ₂ : 54 to 73%, Al ₂ O ₃ : 10.5 to 22.5%, B ₂ O ₃ : 0 to 5.5%, MgO: 0 to 8%, CaO: 0 to 9%, SrO: 0 to 16%, BaO: 0 to 2.5%, and MgO +CaO+SrO+BaO: 8~26%.