JP2022098453A - Float glass production device, float glass production method, and float glass - Google Patents

Abstract

To provide a technology for obtaining a float glass which has a large plane view size with reduced warping.SOLUTION: A float glass production device includes; a bath, a plurality of top rolls, a ceiling, a plurality of heaters, and a plurality of controllers. The bath has a narrow part, a middle part, and a wide part from a lower stream edge to an upper stream side in this order. The narrow part has a deep bottom part, a shallow bottom part, and a pocket part from the low stream edge to the upper stream side in this order. In each division formed by dividing the ceiling into a flowing direction and a width direction of a glass ribbon, there are provided the plurality of heaters collectively controlled by one of the controllers selected for each division. An interval in the flowing direction between a first division line which divides two neighboring rows in the flowing direction, and which is the nearest to the lower stream edge of the pocket part, and the lower stream edge of the pocket part is 0% to 15% of a length in the flowing direction of the pocket part.SELECTED DRAWING: Figure 7

Description

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

The float glass manufacturing apparatus continuously supplies the molten glass onto the molten metal in the bathtub, causes the molten glass to flow on the molten metal, and forms the molten glass into a strip-shaped glass ribbon. After the glass ribbon is slowly cooled, both ends of the glass ribbon in the width direction are cut off to obtain a float glass. Float glass is used for a glass substrate of a flat panel display (FPD) or the like.

Patent Document 1 proposes a method of actively cooling a glass ribbon between a float bath and a slow cooling furnace to optimize the temperature distribution in the transport direction of the glass ribbon as a method of reducing the warp of the float glass. ing.

International Publication No. 2012/066889

With the increase in the screen size of FPDs, float glass having a large plan view size is desired. However, as the plan view size of the float glass increases, the planar distortion of the float glass tends to increase, and the warp of the float glass tends to increase.

One aspect of the present disclosure provides a technique for obtaining a float glass having a large plan view size and a small warp.

The float glass manufacturing apparatus according to one aspect of the present disclosure includes a bathtub for accommodating the molten metal, a plurality of top rolls for pressing the widthwise end of the strip-shaped glass ribbon on the liquid surface of the molten metal, and the glass ribbon. It is provided with a ceiling provided above the ceiling, a plurality of heaters suspended from the ceiling, and a plurality of controllers for controlling the plurality of heaters. The bathtub has a narrow region where the widthwise dimension of the liquid level is constant, an intermediate region where the widthwise dimension of the liquid level gradually increases, and a widthwise dimension of the liquid level from the downstream end to the upstream side. Has a wider region that is larger and constant than the narrow region, in this order. The narrow region includes a deep bottom portion, a shallow bottom portion where the depth of the molten metal is shallower than the deep bottom portion, and a pocket portion where the depth of the molten metal is deeper than the shallow bottom portion from the downstream end to the upstream side. And, in this order. The ceiling is divided into a plurality of rows in the flow direction of the glass ribbon, and each of the rows is divided in the width direction of the glass ribbon. In each section, one controller selected for each section is used. A plurality of the heaters that are collectively controlled are provided. The distance in the flow direction between the first dividing line, which is the first dividing line that divides the two rows adjacent to each other in the flow direction and is closest to the downstream end of the pocket portion, and the downstream end of the pocket portion is , 0% to 15% of the length of the pocket portion in the flow direction.

The float glass according to one aspect of the present disclosure is a rectangular float glass having a vertical dimension of 2900 mm or more, a horizontal dimension of 3200 mm or more, and an average plate thickness of 0.75 mm or less, and has a strain point of 650 ° C. or more. This is non-alkali glass, and the residual stress in the plane direction parallel to the main surface is 2.0 MPa or less on the entire main surface.

According to one aspect of the present disclosure, the temperature distribution of the glass ribbon can be appropriately controlled on the molten metal, and a float glass having a large plan view size and a small warp can be obtained.

FIG. 1 is a cross-sectional view of a float glass manufacturing apparatus according to an embodiment. FIG. 2 is a diagram showing the flow of the glass ribbon and the depth distribution of the molten metal in the flow direction of the glass ribbon. FIG. 3 is a plan view showing an example of a ceiling section. FIG. 4 is a cross-sectional view showing an example of the most downstream section in the flow direction of the glass ribbon. FIG. 5 is a diagram showing an example of the relationship between the coefficient of linear expansion of glass and the temperature. FIG. 6A is a plan view showing an example of stress generated in the glass ribbon in the process of increasing the linear expansion coefficient of the glass, and FIG. 6B is a plan view showing the stress generated in the glass ribbon in the process of decreasing the linear expansion coefficient of the glass. It is a top view which shows an example of stress. FIG. 7A is a cross-sectional view showing an example of the structure of the narrow region of the bathtub and the section of the heater, and FIG. 7B is a diagram showing an example of the temperature change of the glass ribbon in the narrow region. FIG. 8 is a schematic diagram of a floating glass plate according to an embodiment. FIG. 9 is a plan view of the float glass according to the embodiment.

Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding configurations may be designated by the same reference numerals and description thereof may be omitted. In each drawing, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other, the X-axis direction and the Y-axis direction are horizontal directions, and the Z-axis direction is a vertical direction. The X-axis direction is the flow direction of the glass ribbon GR, and the Y-axis direction is the width direction of the glass ribbon GR. In the specification, "-" indicating a numerical range means that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.

The float glass manufacturing apparatus 1 according to the present embodiment will be described with reference to FIG. The float glass manufacturing apparatus 1 includes a molding apparatus 2 for molding molten glass G into a strip-shaped glass ribbon GR, a slow cooling apparatus 3 for slowly cooling the glass ribbon GR molded by the molding apparatus 2, and a molding apparatus 2 and a gradual cooling apparatus 1. A connection device 4 for connecting to the cooling device 3 is provided. The connecting device 4 includes a dross box 41 and a plurality of lift-out rollers 42 arranged inside the dross box 41. The glass ribbon GR is conveyed diagonally upward on a plurality of lift-out rollers 42. The slow cooling device 3 includes a slow cooling furnace 31 and a plurality of transfer rollers 32 arranged inside the slow cooling furnace 31. The glass ribbon GR is horizontally transported on a plurality of transport rollers 32. After passing through the slow cooling furnace 31, the glass ribbon GR is cut to a desired size by a processing device (not shown). As a result, a product, float glass, is obtained.

When the use of the float glass is a glass substrate for FPD, which will be described later, the float glass is further subjected to a cutting / folding process, a chamfering process, and a polishing process in this order. In the polishing process, at least one of both main surfaces of the float glass is polished to remove minute irregularities and waviness existing on the main surface of the float glass. The glass substrate obtained by polishing is so-called mother glass, which is further divided in the middle of the FPD manufacturing process.

Examples of the type of float glass include non-alkali glass, aluminosilicate glass, borosilicate glass and soda lime glass. The non-alkali glass means a glass that does not substantially contain alkali metal oxides such as Na ₂ O and K ₂ O. Here, the fact that the alkali metal oxide is substantially not contained means that the total content of the alkali metal oxide is 0.1% by mass or less.

The use of the float glass is not particularly limited, but is, for example, a flat panel display (FPD) such as a liquid crystal display (LCD) or an organic EL display, and is, for example, a glass substrate for FPD. When the use of the float glass is a glass substrate for FPD, the type of the glass of the float glass is non-alkali glass.

For non-alkali glass, for example, in terms of mass% based on oxide, SiO ₂ : 54% to 68%, Al ₂ O ₃ : 10% to 23%, B ₂ O ₃ : 0% to 12%, MgO: 0. % To 12%, CaO: 0% to 15%, SrO: 0% to 16%, BaO: 0% to 15%, MgO + CaO + SrO + BaO: 8% to 26%. In order to obtain a high strain point, the non-alkali glass preferably has a _B2O3 content of ₅ % or less in terms of mass% based on the oxide.

The strain point of the non-alkali glass is, for example, 650 ° C. or higher in order to obtain a low heat shrinkage rate. The strain point is a temperature corresponding to a viscosity of 10 ^14.5 dPa · s, and is measured in accordance with Japanese Industrial Standards JIS R3103-02: 2001. The strain point of the non-alkali glass is preferably 670 ° C. or higher, more preferably 690 ° C. or higher, and further preferably 700 ° C. or higher. Further, the strain point of the non-alkali glass is preferably 750 ° C. or lower so that the temperature inside the molding apparatus 2 does not become too high.

Next, the molding apparatus 2 according to the present embodiment will be described with reference to FIGS. 1 to 4. As shown in FIG. 1, the molding apparatus 2 includes a bathtub 20. The bathtub 20 accommodates the molten metal M. As the molten metal M, for example, molten tin is used. In addition to molten tin, a molten tin alloy or the like can also be used, and the molten metal M may have a higher density than the molten glass G. The bathtub 20 includes a box-shaped bottom casing 20a opened upward, a side brick 20b that protects the side wall of the bottom casing 20a from the molten metal M, and a bottom brick 20c installed on the bottom wall of the bottom casing 20a. , Have.

The molding apparatus 2 includes a spout trip 21 and a twill 22. The spout trip 21 continuously supplies the molten glass G onto the molten metal M in the bathtub 20. The twill 22 is movable up and down with respect to the spout trip 21, and adjusts the flow rate of the molten glass G flowing over the spout trip 21. The narrower the distance between the twill 22 and the spout trip 21, the smaller the flow rate of the molten glass G flowing over the spout trip 21. The twill 22 is made of a refractory material. The twill 22 may be formed with a protective film that prevents the twill 22 from coming into contact with the molten glass G. The protective film is formed of, for example, platinum or a platinum alloy.

As shown in FIG. 2, the bathtub 20 has a narrow region X1, an intermediate region X2, and a wide region X3 in this order from the downstream end to the upstream side. The narrow region X1 is a region in which the widthwise dimension of the liquid surface of the molten metal M is constant. The intermediate region X2 is a region in which the widthwise dimension of the liquid surface gradually increases from the narrow region X1 to the wide region X3. The wide region X3 is a region in which the widthwise dimension of the liquid surface is larger and constant than the narrow region X1.

The molding apparatus 2 includes a top roll 23. The top roll 23 is provided in the wide range X3. The top roll 23 rotates while pressing the widthwise end of the glass ribbon GR on the liquid surface of the molten metal M, and sends out the glass ribbon GR in the X-axis direction. The glass ribbon GR is gradually cooled and hardened while moving in the X-axis direction.

A pair of top rolls 23 are provided on both sides of the glass ribbon GR in the width direction to suppress shrinkage of the glass ribbon GR in the width direction. The plate thickness of the glass ribbon GR can be made thinner than the equilibrium thickness. The equilibrium thickness is the thickness that naturally reaches the balance between gravity and surface tension. A plurality of the pair of top rolls 23 are provided at intervals in the flow direction of the glass ribbon GR.

The top roll 23 has a rotating member 23a and a rotating shaft 23b. The rotating member 23a has, for example, a disk shape, and the end portion in the width direction of the glass ribbon GR is pressed at the outer periphery thereof, and the glass ribbon GR is sent out in the flow direction of the glass ribbon GR. The glass ribbon GR is gradually cooled and hardened while moving in the X-axis direction. The rotary shaft 23b is rotationally driven by a drive device (not shown) to rotate the rotary member 23a.

As shown in FIG. 4, the glass ribbon GR has a flat portion GR1 from which float glass is cut out at a central portion in the width direction, and has ear portions GR2 thicker than the flat portion GR1 at both ends in the width direction. The selvage GR2 is formed in the process of reducing the plate thickness of the glass ribbon GR using a plurality of pairs of top rolls 23. After passing through the slow cooling furnace 31, the glass ribbon GR is cut to a desired size by a processing device (not shown). The processing device excises the selvage GR2 of the glass ribbon GR. As a result, float glass having a uniform plate thickness can be obtained.

As shown in FIG. 1, the molding apparatus 2 includes a ceiling 24 provided above the glass ribbon GR. The ceiling 24 forms the upper surface of the space S above the bathtub 20. The upper space S is filled with a reducing gas in order to prevent oxidation of the molten metal M. The reducing gas is, for example, a mixed gas of nitrogen gas and hydrogen gas, and contains 85% by volume to 98.5% by volume of nitrogen gas and 1.5% by volume to 15% by volume of hydrogen gas. The reducing gas is supplied from the space on the ceiling 24 to the upper space S through the joints between the bricks of the ceiling 24 and the insertion holes of the heater 25 provided in the ceiling 24.

The molding apparatus 2 includes a heater 25. The heater 25 is suspended from the ceiling 24 and heats the glass ribbon GR passing below. The heater 25 is an electric heater and is energized and heated. The heater 25 is, for example, a SiC heater. A plurality of heaters 25 are arranged in a matrix in the flow direction and the width direction of the glass ribbon GR.

By controlling the outputs of the plurality of heaters 25, the temperature distribution of the glass ribbon GR can be controlled, and the plate thickness distribution of the glass ribbon GR can be controlled. The output of the heater 25 means the amount of heat per unit time (unit: kW). The output of the plurality of heaters 25 is controlled for each section. One controller 26 is used for each compartment.

Next, an example of the section of the ceiling 24 will be described with reference to FIGS. 3 and 4. Although FIG. 3 shows only a section that overlaps the narrow region X1 in a plan view, there may be a section that overlaps the intermediate region X2 or the wide region X3 in a plan view. In FIG. 3, the white arrow indicates the flow direction of the glass ribbon GR.

As shown in FIG. 3, the ceiling 24 is divided into a plurality of rows A and B in the flow direction of the glass ribbon GR. Each row A and B is divided into a plurality of sections A1 to A7 and B1 to B3 in the width direction of the glass ribbon GR. It is preferable that the rows A and B are symmetrically divided about the center line CL in the width direction of the glass ribbon GR. The temperature distribution of the glass ribbon GR can be controlled symmetrically.

In each of the compartments A1 to A7 and B1 to B3, a plurality of heaters 25 collectively controlled by one controller 26 selected for each of the compartments A1 to A7 and B1 to B3 are provided. Controlling all at once includes controlling to the same output. The number of controllers 26 can be reduced by collectively controlling a plurality of heaters 25 with one controller 26. The controller 26 is, for example, a microcomputer.

The boundary line D1 of the two rows A and B adjacent to each other in the flow direction of the glass ribbon GR is also referred to as a first dividing line D1. Further, the boundary line D2 of two sections adjacent to each other in the width direction of the glass ribbon GR is also referred to as a second dividing line D2. It is preferable that the second dividing line D2 is displaced in the width direction of the glass ribbon GR between the row A and the row B with the first dividing line D1 interposed therebetween.

For example, the boundary line D2 between the section B1 and the section B2 and the boundary line D2 between the section A2 and the section A3 are displaced in the width direction of the glass ribbon GR with the first dividing line D1 interposed therebetween. Therefore, the portion of the glass ribbon GR that has passed below the boundary line D2 between the compartment B1 and the compartment B2 in the upstream row B will pass below the compartment A3 in the downstream row A.

In the upstream row B, if the output (unit: kW / m ² ) of the heater 25 per unit area differs between the compartment B1 and the compartment B2, a temperature difference occurs between the compartment B1 and the compartment B2. This temperature difference also occurs at the portion of the glass ribbon GR that passes below the boundary line D2 between the compartment B1 and the compartment B2. The site passes below the compartment A3 in the downstream row A, at which time the temperature difference is alleviated.

The ceiling 24 that overlaps with the narrow region X1 in a plan view is divided into two rows (rows A and B) in the present embodiment, but may be divided into three or more rows.

Next, the planar strain of the float glass will be described. The plane strain is a residual stress generated by the thermal history of the glass substrate, and is a residual stress in the plane direction parallel to the main surface of the glass substrate. Planar distortion can be estimated by measuring optical birefringence, that is, measuring the optical path difference between two orthogonal linearly polarized waves. The optical axis of each linearly polarized wave is perpendicular to the main surface of the glass substrate.

Assuming that the optical path difference between two orthogonal linearly polarized waves is R (nm), the planar strain F (MPa) is
F = R / (C × D)
It is expressed as. D is the distance (cm) through which the linearly polarized wave has passed, and is the thickness of the glass substrate. C is a proportional constant determined by the chemical composition of the glass substrate and is called a photoelastic constant. C is usually 20 to 40 (nm / cm) / (MPa).

If the planar stress on the glass substrate is zero or isotropic, the two orthogonal linearly polarized waves pass through the glass substrate at the same velocity. On the other hand, when the stress applied to the glass substrate in the planar direction is anisotropic, the linearly polarized wave passes quickly in the compressive stress direction and slowly passes in the tensile stress direction. That is, an optical path difference occurs in two orthogonal linear polarized waves. The anisotropy of stress (direction and magnitude) can be measured by measuring the direction in which the optical path difference is maximum and its magnitude.

The plane strain F is an index showing the anisotropy of stress, and is obtained as the direction in which the stress difference is maximum in the plane perpendicular to the optical axis and the stress difference thereof. The value of the plane strain F in the case where the compressive stress remains in a certain direction (for example, the X-axis direction) and the case where the tensile stress of the same magnitude remains in the direction perpendicular to it (for example, the Y-axis direction). Will be the same. Further, when the same amount of compressive stress or tensile stress remains in the orthogonal biaxial directions (for example, the X-axis direction and the Y-axis direction), the value of the plane strain F becomes zero.

As described above, the plane strain F is a stress difference in two directions orthogonal to each other in a plane perpendicular to the optical axis. Since the glass is broken on each side in the vicinity of each side of the rectangular glass substrate in a plan view, stress does not remain in the direction perpendicular to each side, and stress is applied only in the direction parallel to each side. Remains. Therefore, the planar strain in the vicinity of each side is almost equal to the residual stress. On the other hand, in the vicinity of the center of the rectangular glass substrate in a plan view, stress is applied from all directions in the plane and the stresses cancel each other out, so that the plane strain becomes a small value.

The plane strain F is measured using, for example, an ABR-10A birefringence measuring instrument manufactured by Uniopt. The ABR-10A birefringence measuring instrument is a device that measures the birefringence optical path difference and the principal axis orientation by irradiating a horizontal Zeeman laser beam and detecting the phase difference of orthogonal linear polarized waves. As the resolution, it has an accuracy of an optical path difference of 0.01 nm and a principal axis direction of 0.1 degree. Unlike the case where the Senalmon method is used as the measuring method, it is possible to measure a planar strain of about 0.1 MPa to 5 MPa. The planar strain is measured at a plurality of points arranged in a matrix at intervals of, for example, 50 mm in the vertical and horizontal directions on the entire main surface of the glass substrate. The maximum value of planar strain at all measurement points is also called maximum planar strain. The plane strain is measured without annealing after excision of the selvage GR2 of the glass ribbon GR.

Next, the cause of the plane strain of the float glass will be described with reference to FIGS. 5 and 6. As shown in FIG. 5, the coefficient of linear expansion of glass generally has a peak at high temperatures. During its cooling process, the glass ribbon GR passes through the peak of the coefficient of linear expansion of the glass, as shown by the arrow in FIG. The place where the peak is passed is near the outlet 2a (see FIG. 1) of the molding apparatus 2. The temperature of the glass ribbon GR near the outlet 2a is a temperature near the glass transition point.

In the process of cooling the glass ribbon GR inside the molding apparatus 2, the coefficient of linear expansion of the glass gradually increases toward the peak. In the process, as shown by the arrow in FIG. 6A, tensile stress acts on the selvage GR2 of the glass ribbon GR. The selvage portion GR2 of the glass ribbon GR is thicker than the flat portion GR1, and a large tensile stress acts on the selvage portion GR2.

On the other hand, in the process of cooling the glass ribbon GR inside the connecting device 4 or the slow cooling device 3, the coefficient of linear expansion of the glass gradually decreases from the peak. In the process, as shown by the arrow in FIG. 6B, compressive stress acts on the selvage GR2 of the glass ribbon GR. The selvage portion GR2 of the glass ribbon GR is thicker than the flat portion GR1, and a large compressive stress acts on the selvage portion GR2.

The plane strain of the float glass is mainly the magnitude of the tensile stress indicated by the arrow in FIG. 6 (A), the time during which the tensile stress acts, and the magnitude of the compressive stress indicated by the arrow in FIG. 6 (B). It is determined by the time that the compressive stress acts. The longer the tensile stress acts, the easier it is for the tensile stress to remain. Further, the longer the compressive stress acts, the more likely the compressive stress remains.

Compressive stress usually remains in the selvage GR2 of the glass ribbon GR. Therefore, in the present embodiment, in order to reduce the compressive stress remaining on the selvage GR2 of the glass ribbon GR, the time during which the tensile stress acts on the selvage GR2 of the glass ribbon GR is lengthened. Specifically, the structure of the narrow region X1 of the bathtub 20 as shown in FIG. 7A and the section of the heater 25 are adopted.

First, the structure of the narrow region X1 of the bathtub 20 will be described with reference to FIG. 7 (A). As shown in FIG. 7A, the narrow region X1 of the bathtub 20 has a deep bottom portion X1a and a shallow bottom portion X1b in which the depth of the molten metal M is shallower than that of the deep bottom portion X1a from the downstream end to the upstream side. The pocket portion X1c, which has a deeper depth of the molten metal M than the shallow bottom portion X1b, is provided in this order. If the entire pocket portion X1c is provided in the narrow region X1 and the pocket portion X1c does not extend to the wide region X3, the top roll 23 can sufficiently grip the glass ribbon GR even in the downstream region of the wide region X3. The temperature of the ribbon GR is high, and the formability of the glass ribbon GR is good.
In the present embodiment, the entire pocket portion X1c is provided in the narrow region X1, but a part of the pocket portion X1c may be provided in the intermediate region X2 and the rest may be provided in the narrow region X1. The bathtub 20 of the present embodiment has a narrow region X1, an intermediate region X2, and a wide region X3, but the technique of the present disclosure is not limited to this. For example, the bathtub 20 does not have to have an intermediate region X2 between the narrow region X1 and the wide region X3, and even if the widthwise dimension of the liquid surface changes discontinuously between the narrow region X1 and the wide region X3. good. The number of regions in which the widthwise dimension of the liquid surface is constant is not limited to two, and may be one or three or more. The widthwise dimension of the liquid level may continue to change from the upstream end to the downstream end of the bathtub 20.

The deep bottom portion X1a has, for example, a horizontal bottom surface and two vertical stepped surfaces. The stepped surface of the deep bottom portion X1a rises vertically from the bottom surface, but may be inclined. The pocket portion X1c also has, for example, a horizontal bottom surface and two vertical stepped surfaces. The stepped surface of the pocket portion X1c rises vertically from the bottom surface, but may be inclined. The shallow bottom portion X1b has a horizontal top surface higher than the bottom surface of the deep bottom portion X1a and the bottom surface of the pocket portion X1c.

The depth Dc of the molten metal M in the pocket portion X1c is deep, the heat capacity of the molten metal M is large, and the molten metal M easily absorbs the heat of the glass ribbon GR. Therefore, as shown in FIG. 7B, the cooling rate of the glass ribbon GR in the pocket portion X1c can be increased. As a result, the cooling rate of the glass ribbon GR in the deep bottom portion X1a can be reduced while maintaining the length L in the flow direction of the narrow region X1. As a result, the glass ribbon GR can be gently cooled immediately before the outlet 2a of the molding apparatus 2, the time for the tensile stress to act on the selvage GR2 of the glass ribbon GR can be lengthened, and the planar strain of the float glass can be reduced.

The average cooling rate of the widthwise center line CL of the glass ribbon GR when passing through the pocket portion X1c is, for example, 60 ° C./min to 120 ° C./min, preferably 70 ° C./min to 110 ° C./min. , More preferably 80 ° C./min to 100 ° C./min, and even more preferably 88 ° C./min to 100 ° C./min. When the average cooling rate is 60 ° C./min to 120 ° C./min, the transport speed of the glass ribbon GR can be increased, the productivity of the float glass can be increased, and the cooling rate of the glass ribbon GR in the deep bottom portion X1a can be reduced. The plane distortion of the float glass can be reduced.

The depth Db of the molten metal M in the shallow bottom portion X1b is shallower than both the depth Dc of the molten metal M in the pocket portion X1c and the depth Da of the molten metal M in the deep bottom portion X1a. That is, the relationship between "Db <Dc" and "Db <Da" is established. As shown in FIG. 7B, the shallow bottom portion X1b serves to make a difference in the cooling rate of the glass ribbon GR between the pocket portion X1c and the deep bottom portion X1a. In the pocket portion X1c, the cooling rate of the glass ribbon GR is higher than that in the deep bottom portion X1a.

The depth Da of the molten metal M in the deep bottom portion X1a is deeper than the depth Db of the molten metal M in the shallow bottom portion X1b. That is, the relationship of "Da> Db" is established. Therefore, the heat capacity of the molten metal M is large, and the temperature change of the glass ribbon GR due to the output fluctuation of the heater 25 can be suppressed.

The depth Dc of the molten metal M in the pocket portion X1c may be deeper than the depth Da of the molten metal M in the deep bottom portion X1a. That is, the relationship of "Dc> Da> Db" may be established. Compared with the case where Dc is smaller than Da, the heat capacity of the molten metal M in the pocket portion X1c is large, and the molten metal M easily absorbs the heat of the glass ribbon GR. Therefore, the cooling rate of the glass ribbon GR in the pocket portion X1c can be increased. As a result, the cooling rate of the glass ribbon GR in the deep bottom portion X1a can be reduced while maintaining the length L in the flow direction of the narrow region X1.

The depth Dc of the molten metal M in the pocket portion X1c is, for example, 1.5 to 2.5 times the depth Db of the molten metal M in the shallow bottom portion X1b. That is, Dc / Db is 1.5 to 2.5. Dc / Db is preferably 1.5 to 2.0, and more preferably 1.7 to 1.8.

The depth Da of the molten metal M in the deep bottom portion X1a is, for example, 1.5 to 2.5 times the depth Db of the molten metal M in the shallow bottom portion X1b. That is, Da / Db is 1.5 to 2.5. Da / Db is preferably 1.5 to 2.0, and more preferably 1.7 to 1.8.

The length Lc of the pocket portion X1c in the flow direction is, for example, 15% to 35% of the length L of the narrow region X1 in the flow direction. Lc is preferably 20% to 30% of L. When the length Lc is 15% to 35% of the length L, the cooling rate of the glass ribbon GR in the pocket portion X1c can be increased.

The length La of the deep bottom portion X1a in the flow direction is 40% to 60% of the length L of the narrow region X1 in the flow direction. La is preferably 49% to 56%. When the length La is 40% to 60% of the length L, the cooling rate of the glass ribbon GR in the deep bottom portion X1a can be reduced.

Next, in addition to FIG. 7A, the section of the heater 25 will be described with reference to FIGS. 3 and 4. As shown in FIG. 7A, the first dividing line D1 that divides the two rows A and B adjacent to each other in the flow direction and is closest to the downstream end X1d of the pocket portion X1c, and the pocket. The distance E in the flow direction of the portion X1c from the downstream end X1d is 0% to 15% of the length Lc of the pocket portion X1c in the flow direction.

When the interval E is 0% to 15% of the length Lc, the first dividing line D1 substantially coincides with the downstream end X1d of the pocket portion X1c in a plan view. Therefore, it is easy to make a difference in the cooling rate of the glass ribbon GR between the pocket portion X1c and the deep bottom portion X1a.
The molding apparatus 2 quenches the glass ribbon GR in the pocket portion X1c on the upstream side and slowly cools the glass ribbon GR in the deep bottom portion X1a on the downstream side. Increase the output of. If the interval E is outside the range of 0% to 15% of the length Lc, the heating amount of the glass ribbon GR in the upstream pocket portion X1c by the downstream heater 25 is large, and the pocket portion X1c and the deep bottom portion X1a are heated. , It is difficult to make a difference in the cooling rate of the glass ribbon GR.
The interval E is preferably 0% to 10% of the length Lc, and more preferably 0% to 5% of the length Lc.

The smaller the interval E, the more preferable. The interval E is, for example, 0 mm to 500 mm, preferably 0 mm to 250 mm, and more preferably 0 mm to 125 mm.

In the present embodiment, the first dividing line D1 is provided on the upstream side of the downstream end X1d of the pocket portion X1c, but may be provided on the downstream side of the downstream end X1d of the pocket portion X1c.

As shown in FIG. 3, the most downstream row A in the flow direction includes 5 or more (for example, 7) compartments A1 to A7 in the width direction. When the number of compartments included in the row A is 5 or more, it is easy to make a temperature difference in the width direction of the glass ribbon GR immediately before the outlet 2a of the molding apparatus 2. The number of compartments included in column A is preferably 7 or more. Further, the number of compartments included in the column A is preferably 11 or less from the viewpoint of the number of controllers 26.

In a plan view, the second dividing line D2 that divides the two adjacent sections in the width direction in the most downstream row A overlaps the selvage GR2 of the glass ribbon GR. Immediately before the outlet 2a of the molding apparatus 2, it is easy to make a temperature difference between the selvage GR2 and the flat portion GR1 of the glass ribbon GR, and the flat portion GR1 can be cooled to a temperature lower than that of the selvage GR2.

As a result, the flat portion GR1 can be hardened immediately before the outlet 2a of the molding apparatus 2. Further, the selvage GR2 can be cooled gently, the time for the tensile stress to act on the selvage GR2 can be lengthened, and the planar strain of the float glass can be reduced.

As shown in FIG. 8, the float glass manufacturing apparatus and the float glass manufacturing method according to the present disclosure include two float glasses having a substrate size of 11th generation (G11) or larger from the glass ribbon GR in the width direction of the glass ribbon GR. (Site L and R) Suitable for sampling. In this case, the widthwise dimension of the glass ribbon GR in the narrow region X1 is 6 m or more, and it is not easy to reduce the planar distortion of the float glass.

The board size of the 11th generation (G11) is 2792 mm in length (short side) and 3404 mm in width (long side) before cutting and folding, and 2940 mm in length (short side) and 2940 mm in width (long side) after cutting and folding. Side) 3370 mm. The substrate size of the 6th generation (G6) is 1524 mm in length (short side) and 1880 mm in width (long side) before cutting and folding.

Next, the float glass 10 according to the present embodiment will be described with reference to FIG. The float glass 10 is manufactured by using the float glass manufacturing apparatus 1 described above. The float glass 10 is a so-called mother glass, and is cut into two pieces in the middle of the manufacturing process of the FPD, for example, at the position shown by the broken line in FIG. The float glass 10 may be cut into four or more pieces in the middle of the manufacturing process of the FPD, or may be cut into a plurality of pieces. The production efficiency of FPD can be improved.

The float glass 10 has a rectangular shape in a plan view. The rectangle is a rectangle in which the length of one set of two sides is different from the length of another set of two sides, but it may be a square having the same length of four sides. Further, the rectangle includes a rectangle with chamfered corners on four sides.

The float glass 10 has a vertical dimension T1 of 2900 mm or more, a horizontal dimension T2 of 3200 mm or more, and an average plate thickness of 0.75 mm or less. The vertical dimension T1 and the horizontal dimension T2 represent the plan view size. The vertical dimension T1 is preferably 3000 mm or more. The vertical dimension T1 is preferably 4500 mm or less. The horizontal dimension T2 is preferably 3300 mm or more. The horizontal dimension T2 is preferably 5000 mm or less. The average plate thickness is preferably 0.55 mm or less, and may be 0.45 mm or less. The average plate thickness is preferably 0.05 mm or more.

The maximum planar strain of the float glass 10 is, for example, 2.0 MPa or less. If the maximum planar strain is 2.0 MPa or less, the plan view size is large and the average plate thickness is small, even before and after cutting. Deformation of glass can be suppressed. Therefore, it is possible to prevent the pattern of the color filter or the thin film transistor (TFT) from shifting due to cutting of the glass substrate.

The maximum planar strain of the float glass 10 is preferably 1.5 MPa or less. When the maximum planar strain is 1.5 MPa or less, the size in plan view is large and the warp of the float glass 10 is small even when the average plate thickness is small. Therefore, in the manufacturing process of the FPD, the vacuum adsorption failure of the float glass 10 (glass substrate) can be suppressed.

The present inventor investigated the cause of the vacuum adsorption failure of the mother glass in the manufacturing process of the FPD. As a result, the present inventor has a case where the vertical dimension T1 is 2900 mm or more, the horizontal dimension T2 is 3200 mm or more, and the maximum planar strain of the mother glass having an average plate thickness of 0.75 mm or less exceeds 1.5 MPa. In addition, it was found that the warp of the mother glass is large and vacuum adsorption failure occurs. Then, by using the float glass manufacturing apparatus 1 described above, the maximum planar strain of the mother glass could be reduced.

The maximum planar strain of the float glass 10 is more preferably 1.0 MPa or less. The maximum planar strain of the float glass 10 is preferably 0.1 MPa or more.

The experimental data will be described below. In Examples 1 to 3, the float glass manufacturing apparatus 1 according to the above embodiment is used, and the vertical dimension is 2972 mm, the horizontal dimension is 3404 mm, and the average plate thickness is 0 under the same conditions except for the “cooling rate” shown in Table 1. A float glass having a rectangular shape in a plan view of 5.5 mm was manufactured. Float glass is non-alkali glass with a strain point of 670 ° C., and is expressed in terms of mass% based on oxides, SiO ₂ : 60%, Al ₂ O ₃ : 17%, B ₂ O ₃ : 8%, MgO: 3 %, CaO: 4%, SrO: 8%.

In Examples 1 to 3, the distance E in the flow direction between the first dividing line D1 closest to the downstream end X1d of the pocket portion X1c and the downstream end X1d of the pocket portion X1c is the length Lc in the flow direction of the pocket portion X1c. It was 0% of (see FIG. 7 (A)). Examples 1 to 3 are all examples. Table 1 shows the experimental conditions and the experimental results.

表１において、「冷却速度」は、ポケット部Ｘ１ｃを通過する際の、ガラスリボンＧＲの幅方向中心線ＣＬの平均冷却速度である。また、表１において、「η１」はドロスボックス４１の下流域におけるガラスリボンＧＲの幅方向中心線ＣＬの粘度（[ｄＰａ・ｓ]）であり、「η２」は徐冷炉３１の最上流端から下流側に向けて３ｍ離れた位置におけるガラスリボンＧＲの幅方向中心線ＣＬの粘度（[ｄＰａ・ｓ]）である。

In Table 1, the "cooling rate" is the average cooling rate of the widthwise center line CL of the glass ribbon GR when passing through the pocket portion X1c. Further, in Table 1, "η1" is the viscosity ([dPa · s]) of the widthwise center line CL of the glass ribbon GR in the downstream region of the dross box 41, and “η2” is downstream from the most upstream end of the slow cooling furnace 31. It is the viscosity ([dPa · s]) of the center line CL in the width direction of the glass ribbon GR at a position 3 m away from the side.

As is clear from Table 1, in Examples 1 to 3, float glass having a maximum planar strain of 2.0 MPa or less was obtained.

Further, in Examples 2 to 3, the cooling rate of the glass ribbon GR in the pocket portion X1c was higher and the cooling rate of the glass ribbon GR in the deep bottom portion X1a was lower than in Example 1. As a result, the glass ribbon GR can be cooled gently immediately before the outlet 2a of the molding apparatus 2, the time for the tensile stress to act on the ear portion GR2 of the glass ribbon GR can be lengthened, and the maximum planar strain can be 1. Float glass of 5 MPa or less was obtained.

The float glass manufacturing apparatus, the float glass manufacturing method, and the float glass according to the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiment and the like. Various changes, modifications, replacements, additions, deletions, and combinations are possible within the scope of the claims. Of course, they also belong to the technical scope of the present disclosure.

1 Float glass manufacturing equipment 20 Bathtub 23 Top roll 24 Ceiling 25 Heater 26 Controller M Molten metal G Molten glass GR Glass ribbon

Claims (19)

A bathtub for accommodating the molten metal, a plurality of top rolls for holding the widthwise end of the strip-shaped glass ribbon on the liquid surface of the molten metal, a ceiling provided above the glass ribbon, and hanging from the ceiling. A float glass manufacturing apparatus comprising a plurality of heaters and a plurality of controllers for controlling the plurality of heaters.
The bathtub has a narrow region where the widthwise dimension of the liquid level is constant, an intermediate region where the widthwise dimension of the liquid level gradually increases, and a widthwise dimension of the liquid level from the downstream end to the upstream side. Has a wider range that is larger and constant than the narrow range, in this order.
The narrow region includes a deep bottom portion, a shallow bottom portion where the depth of the molten metal is shallower than the deep bottom portion, and a pocket portion where the depth of the molten metal is deeper than the shallow bottom portion from the downstream end to the upstream side. And, in this order,
The ceiling is divided into a plurality of rows in the flow direction of the glass ribbon, and each of the rows is divided in the width direction of the glass ribbon. In each section, one controller selected for each section is used. A plurality of the heaters that are collectively controlled are provided, and the heaters are provided.
The distance in the flow direction between the first dividing line, which is the first dividing line that divides the two rows adjacent to each other in the flow direction and is closest to the downstream end of the pocket portion, and the downstream end of the pocket portion is , A float glass manufacturing apparatus, which is 0% to 15% of the length of the pocket portion in the flow direction. The float glass manufacturing apparatus according to claim 1, wherein the depth of the molten metal in the pocket portion is deeper than the depth of the molten metal in the deep bottom portion. The float glass manufacturing apparatus according to claim 1 or 2, wherein the depth of the molten metal in the pocket portion is 1.5 to 2.5 times the depth of the molten metal in the shallow bottom portion. The float glass manufacturing apparatus according to any one of claims 1 to 3, wherein the length of the pocket portion in the flow direction is 15% to 35% of the length of the narrow region in the flow direction. The float glass according to any one of claims 1 to 4, wherein the depth of the molten metal in the deep bottom portion is 1.5 to 2.5 times the depth of the molten metal in the shallow bottom portion. manufacturing device. The float glass manufacturing apparatus according to any one of claims 1 to 5, wherein the length of the deep bottom portion in the flow direction is 40% to 60% of the length of the narrow region in the flow direction. The glass ribbon has a flat portion in which the float glass is cut out at a central portion in the width direction, and has ears thicker than the flat portion at both ends in the width direction.
The row most downstream in the flow direction comprises five or more said compartments in the width direction.
One of claims 1 to 6, wherein the second dividing line that divides the two adjacent sections in the width direction in the most downstream row overlaps the selvage portion of the glass ribbon in a plan view. Float glass manufacturing equipment according to. The float glass manufacturing apparatus according to any one of claims 1 to 7, wherein the first dividing line is provided on the upstream side of the downstream end of the pocket portion. The float glass manufacturing apparatus according to any one of claims 1 to 7, wherein the first dividing line is provided on the downstream side of the downstream end of the pocket portion. The float glass manufacturing apparatus according to any one of claims 1 to 9, wherein the pocket portion is entirely installed in the narrow area. A bathtub for accommodating the molten metal, a plurality of top rolls for pressing the widthwise ends of the strip-shaped glass ribbon on the liquid surface of the molten metal, a ceiling provided above the glass ribbon, and hanging from the ceiling. A float glass manufacturing apparatus comprising a plurality of heaters and a plurality of controllers for controlling the plurality of heaters.
The bathtub has a deep bottom portion, a shallow bottom portion where the depth of the molten metal is shallower than the deep bottom portion, and a pocket portion where the depth of the molten metal is deeper than the shallow bottom portion from the downstream end to the upstream side. , In this order,
The ceiling is divided into a plurality of rows in the flow direction of the glass ribbon, and each of the rows is divided in the width direction of the glass ribbon. In each section, one controller selected for each section is used. A plurality of the heaters that are collectively controlled are provided, and the heaters are provided.
The distance in the flow direction between the first dividing line, which is the first dividing line that divides the two rows adjacent to each other in the flow direction and is closest to the downstream end of the pocket portion, and the downstream end of the pocket portion is , A float glass manufacturing apparatus, which is 0% to 15% of the length of the pocket portion in the flow direction. A float glass manufacturing method using the float glass manufacturing apparatus according to any one of claims 1 to 11.
Forming the glass ribbon in the shape of a strip on the molten metal,
Using the heater to heat the glass ribbon passing under the heater,
Float glass manufacturing method having. The float glass manufacturing method according to claim 12, wherein the average cooling rate of the widthwise center line of the glass ribbon when passing through the pocket portion is 60 ° C./min to 120 ° C./min. Float glass having a rectangular shape in a plan view having a vertical dimension of 2900 mm or more, a horizontal dimension of 3200 mm or more, and an average plate thickness of 0.75 mm or less.
Non-alkali glass with a strain point of 650 ° C or higher,
Float glass in which the residual stress in the plane direction parallel to the main surface is 2.0 MPa or less on the entire main surface. The float glass according to claim 14, wherein the residual stress in the plane direction parallel to the main surface is 1.5 MPa or less on the entire main surface. The float glass according to claim 14 or 15, wherein the average plate thickness is 0.55 mm or less. The non-alkali glass is displayed in terms of mass% based on oxides.
SiO ₂ : 54% to 68%
Al ₂ O ₃ : 10% to 23%
B ₂ O ₃ : 0% to 12%
MgO: 0% to 12%
CaO: 0% to 15%
SrO: 0% to 16%
BaO: 0% to 15%
MgO + CaO + SrO + BaO: 8% -26%
The float glass according to any one of claims 14 to 16, which comprises. The float glass according to claim 17, wherein the non-alkali glass has a _B2O3 content of ₅ % or less in terms of mass% based on an oxide. Float glass produced by the float glass manufacturing method according to claim 12 or 13.

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