JP2019094222A - Float glass production device, float glass production method and float glass - Google Patents

Abstract

To provide a float glass production device capable of reducing plate thickness deviation in the whole face of float glass, and reducing abrupt change of the plate thickness in a narrow range of the float glass.SOLUTION: In the float glass production device with a bath tub for accommodating molten metal, which molds molten glass to a glass ribbon while flowing it on the molten metal, the bath tub has a box type metal casing and a plurality of bottom bricks disposed on the bottom face of the metal casing, and contacting a bottom face of the molten metal, a joint is formed between the bottom bricks neighboring each other in a width direction of the glass ribbon, a bottom brick line is composed with the plurality of bottom bricks lining in a row in the width direction of the glass ribbon, a border line is formed between the bottom brick line neighboring each other in a flow direction of the glass ribbon, and the joint of the bottom brick line in an upper stream and the joint of the bottom brick line of a lower stream are not continued in one or more points, in at least one of the border line.SELECTED DRAWING: Figure 1

Description

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

  The thickness deviation over the entire surface of the glass substrate for flat panel display (FPD) affects the defocus of the exposure machine in the photolithography process. Glass substrates for FPDs, in particular glass substrates for liquid crystal displays (LCDs), have strict requirements for thickness deviation, and are required to be, for example, 20 μm or less in the range of 1500 mm. The thickness deviation is the difference between the maximum thickness and the minimum thickness.

  As a method of reducing thickness deviation, Patent Document 1 divides the heater area of the float bath in the flow direction and width direction of the glass ribbon, provides a plurality of heaters in each section, and controls the plurality of heaters for each section Technology has been proposed.

JP 2012-1398 A

  In recent years, the demand for plate thickness deviation has become more severe as the definition of LCDs has become higher. In particular, in mobile applications, there have been cases in which the focus of the exposure machine has occurred even if the conventional plate thickness standard is satisfied. It has been found that this problem occurs when the plate thickness changes rapidly in a narrow range.

  The present invention has been made in view of the above problems, and it is a float that reduces the thickness deviation in the entire surface of the float glass and suppresses the rapid variation of the thickness in a narrow range of the float glass. Main purpose is to provide glass manufacturing equipment.

According to one aspect of the invention:
What is claimed is: 1. A float glass manufacturing apparatus comprising a bath for containing molten metal, and forming molten glass continuously supplied onto the molten metal in the bath while flowing on the molten metal to form a glass ribbon.
The bath has a box-like metal casing, and a plurality of bottom bricks placed on the bottom of the metal casing and in contact with the lower surface of the molten metal.
A joint is formed between the bottom bricks adjacent in the width direction of the glass ribbon, and a bottom brick row is constituted by a plurality of the bottom bricks arranged in a line in the width direction of the glass ribbon,
A boundary is formed between the bottom brick rows adjacent in the flow direction of the glass ribbon,
The float glass manufacturing apparatus is characterized in that the joint of the bottom brick row on the upstream side and the joint of the bottom brick row on the downstream side are discontinuous at one or more places in at least one of the boundary lines. Provided.

  According to one aspect of the present invention, a float glass manufacturing apparatus is provided that reduces the thickness deviation across the entire surface of the float glass and suppresses abrupt fluctuations in the thickness of the float glass within a narrow range. .

FIG. 1 is a cross-sectional view of a float glass manufacturing apparatus according to one embodiment. FIG. 2 is a cross-sectional view of the float glass manufacturing apparatus taken along line II-II of FIG. FIG. 3 is a plan view of a bath, a glass ribbon and a top roll according to one embodiment. FIG. 4 is a plan view showing the arrangement of bottom bricks and side bricks constituting the bathtub according to the first embodiment. FIG. 5 is a plan view showing the arrangement of the heater control section according to the first embodiment. FIG. 6 is a view showing a plate thickness distribution in the Y direction of float glass having a lateral dimension of 1000 mm according to Example 1 and Comparative Example 1. FIG. 7 is a view showing a plate thickness distribution in the Y direction of float glass having a lateral dimension of 2000 mm according to Example 1 and Comparative Example 1. FIG. 8 is a plan view showing the arrangement of the bottom bricks and the side bricks of the bathtub according to Comparative Example 1.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and the description thereof will be omitted.

(Outline of float glass manufacturing equipment)
FIG. 1 is a cross-sectional view of a float glass manufacturing apparatus according to one embodiment. FIG. 2 is a cross-sectional view of the float glass manufacturing apparatus taken along line II-II of FIG. In FIG. 1 and FIG. 2, the top roll 60 shown in FIG. 3 is not shown. FIG. 3 is a plan view of a bath, a glass ribbon and a top roll according to one embodiment. In each drawing, the X direction is the flow direction of the glass ribbon 6, the Y direction is the width direction of the glass ribbon 6, and the Z direction is the vertical direction. The X direction, the Y direction and the Z direction are directions perpendicular to each other.

  The float glass manufacturing apparatus 10 has a bath 20 for containing the molten metal 2 on which the molten glass 4 floats. Typically, molten tin or a molten tin alloy is used as the molten metal 2. The molten glass 4 is continuously supplied onto the molten metal 2 contained in the bath 20 and is formed into a plate-like glass ribbon 6 while flowing from the upstream side to the downstream side on the molten metal 2. The glass ribbon 6 gradually cools and hardens while flowing in the direction of arrow A above the liquid surface of the molten metal 2. The glass ribbon 6 is pulled up from the molten metal 2 in the downstream area of the bath 20 and sent to the lehr. A glass plate (float glass) is manufactured by cut | disconnecting the glass ribbon 6 annealed by the lehr to a predetermined | prescribed dimension.

  The float glass manufacturing apparatus 10 has a ceiling 30 provided above the bathtub 20, a plurality of heaters 40 suspended from the ceiling 30, and a plurality of controllers 50 for controlling the plurality of heaters 40. The plurality of heaters 40 heat the glass ribbon 6 passing below under the control of the plurality of controllers 50. For each heater 40, for example, an electric heater that is energized and heated is used. The shape of each heater 40 is not particularly limited, but may be, for example, a rod shape. By controlling the amount of heat generation of each heater 40, the temperature distribution of the glass ribbon 6 is controlled. The plurality of controllers 50 are devices that control the amount of heat generation of the plurality of heaters 40. Each controller 50 is configured by a microcomputer or the like.

  The float glass manufacturing apparatus 10 is provided with a plurality of pairs of top rolls 60 (see FIG. 3) which are spaced along the flow direction of the glass ribbon 6 and support both widthwise ends of the glass ribbon 6. The plurality of pairs of top rolls 60 support both widthwise end portions of the glass ribbon 6 to suppress narrowing of the width of the glass ribbon 6 due to surface tension. Each top roll 60 is formed of a disk-shaped top roll main body 61 supporting an end in the width direction of the glass ribbon 6 and a rotation shaft 62 connected to the top roll main body 61. The disk-shaped top roll main body 61 and the rotating shaft 62 are provided coaxially. When the rotation shaft 62 is rotationally driven by a driving device such as an electric motor, the top roll main body 61 rotates and feeds the glass ribbon 6 to the downstream side.

(Tub)
As shown in FIG. 3, the bathtub 20 has a narrow area A1 in which the widthwise dimension of the bathtub 20 is constant from the downstream end to the upstream side, an intermediate area A2 in which the widthwise dimension of the bathtub 20 gradually increases, a bathtub In this order, the wide area A3 has a width direction dimension of 20 larger and constant than the narrow area A1. The X-direction dimension X1 of the wide area A3 is, for example, 30% or more and 80% or less of the X-direction dimension X0 of the molten metal 2 accommodated in the bath 20.

The plurality of pairs of top rolls 60 support both widthwise ends of the glass ribbon 6 in the wide area A3. The region from the contact position of the pair of top rolls 60 on the most upstream side with the glass ribbon 6 to the contact position of the pair of top rolls 60 on the most downstream side with the glass ribbon 6 is also referred to as a forming area A4. In the forming area A4, the viscosity at the center in the width direction (the center in the Y direction) of the glass ribbon 6 is, for example, 10 ^4.5 dPa · s or more and 10 ^7.5 dPa · s or less.

  As shown in FIG. 2, the bathtub 20 is placed on a box-shaped metal casing 21, a plurality of side bricks 22 placed on the bottom of the metal casing 21 and in contact with the side of the molten metal 2, and a bottom of the metal casing 21. And a plurality of bottom bricks 23 in contact with the lower surface of the molten metal 2. The plurality of side bricks 22 are arranged close to the side of the metal casing 21, and the plurality of bottom bricks 23 are arranged inside the plurality of side bricks 22 in the X direction and the Y direction.

  A joint 24 is formed between the bottom bricks 23 adjacent in the Y direction. The joint 24 is a gap. It is difficult to prevent the flow of the molten metal 2 into the joint 24. The molten metal 2 flowing into the joint 24 reaches the bottom of the metal casing 21.

  In order to suppress the reaction between the metal casing 21 and the molten metal 2, a cooling nozzle 25 for blowing a cooling gas such as air on the lower surface of the metal casing 21 is provided below the metal casing 21. The cooling nozzle 25 injects a cooling gas in the direction of arrow B (upward). Thereby, the temperature of the metal casing 21 can be reduced to the melting point or less of the molten metal 2, and the reaction between the molten metal 2 and the metal casing 21 can be suppressed.

  FIG. 4 is a plan view showing the arrangement of bottom bricks and side bricks constituting the bathtub according to the first embodiment. A plurality of bottom bricks 23 are disposed in the X direction and the Y direction. A bottom brick row 26 is constituted by a plurality of bottom bricks 23 aligned in the Y direction. A plurality of bottom brick rows 26 are arranged in the X direction, and boundaries 27 are formed between the bottom brick rows 26 adjacent in the X direction. The number of bottom brick rows 26 is not limited to that shown in FIG. Further, the number of bottom bricks 23 in each bottom brick row 26 is not limited to that shown in FIG.

  By the way, the molten metal 2 flows into the joint 24, and the molten metal 2 has a higher thermal conductivity than the bottom brick 23. Therefore, the joint 24 tends to be cooled easily by the cooling nozzle 25 and to have a lower temperature than the bottom brick 23. Since the joints 24 and the bottom bricks 23 are alternately arranged in the Y direction, temperature unevenness is formed in the Y direction.

  Therefore, in the present embodiment, the joint 24 of the bottom brick row 26 on the upstream side and the joint 24 of the bottom brick row 26 on the downstream side are discontinuous at one or more places in at least one boundary line 27. It deviates by the place or more. For example, in the k-th boundary line 27-k from the upstream side (left side in FIG. 4), the joint 24 of the k-th bottom brick row 26-k from the upstream side and the k + 1 bottom brick row 26-k + 1 from the upstream The joint 24 is discontinuous at one or more points and deviates at one or more points. Here, k is at least one natural number of 1 or more, and is, for example, any natural number of 1 or more and 11 or less in FIG. 4.

  The part of the glass ribbon 6 which has passed above the low temperature joint 24 in the kth bottom brick row 26-k passes above the high temperature bottom brick 23 in the subsequent k + 1 bottom brick row 26-k + 1. In the glass ribbon 6, the portion of the k-th bottom brick row 26-k passing above the high-temperature bottom brick 23 passes above the low-temperature joint 24 in the subsequent k + 1-th bottom brick row 26-k + 1. Do. Therefore, the temperature nonuniformity in the Y direction of the glass ribbon 6 can be suppressed, and the plate thickness nonuniformity in the Y direction of the glass ribbon 6 can be reduced.

  If the thickness unevenness in the Y direction of the glass ribbon 6 can be reduced, the thickness unevenness in the X direction of the glass ribbon 6 does not occur, so the thickness unevenness in the entire glass ribbon 6 can be reduced. Here, unlike the plate thickness unevenness in the Y direction in which the tensile force by the top roll 60 is dominant, the tensile force by the transport roll in the slow cooling furnace is dominant in the plate thickness unevenness in the X direction of the glass ribbon 6. Therefore, if the conveyance speed of the glass ribbon 6 in a slow cooling furnace is constant, the tensile force by a conveyance roll will become constant, and the plate thickness nonuniformity of the X direction of the glass ribbon 6 will not arise.

  As a result, it is a float glass having a longitudinal dimension of 950 mm or more, a transverse dimension of 1000 mm or more, and an average plate thickness of 0.75 mm or less in a rectangular shape in plan view, and the maximum and minimum values of the plate thickness over the entire surface. The difference between the maximum value and the minimum value of the plate thickness is 4.0 μm or less in the range of a square having an in-plane difference of 20 μm or less, an arbitrary point in the plane as the central point, and longitudinal and lateral dimensions of 150 mm. Float glass is obtained. Here, the longitudinal dimension is the dimension in the short side direction of the float glass having a rectangular shape in plan view, and the lateral dimension is the dimension in the longitudinal direction of the float glass having a rectangular shape in plan view. The plan view means viewing in the Z direction in FIG. 4 and the like.

  In the present embodiment, at least one boundary line 27 in the wide area A3, the joint 24 of the upstream bottom brick row 26 and the joint 24 of the downstream bottom brick row 26 are discontinuous at one or more locations. And be offset at one or more points. The wide area A3 is at a higher temperature than the middle area A2 and the narrow area A1, and adjustment of the size and shape of the glass ribbon 6 is performed in the wide area A3. In the middle area A2 and the narrow area A1, since the viscosity of the glass ribbon 6 is high, it is difficult to adjust the size and the shape of the glass ribbon 6.

  In the present embodiment, at least one boundary line 27 in the forming area A4, the joint 24 of the upstream bottom brick row 26 and the joint 24 of the downstream bottom brick row 26 are discontinuous at one or more locations. And be offset at one or more points. It is because adjustment of the dimension and shape of the glass ribbon 6 is performed using the top roll 60 in the forming area A4 among the wide area A3.

  In this embodiment, at least one boundary line 27 in the area A5 where the X-direction distance from the upstream end of the molten metal 2 is 0.1 × X0 or more and 0.5 × X0 or less, the bottom brick row 26 on the upstream side The joint 24 and the joint 24 of the bottom brick row 26 on the downstream side are discontinuous at one or more places and shifted at one or more places.

  In each bottom brick row 26, the plurality of joints 24 may be provided in line symmetry about the Y-direction center line 20L of the bathtub 20. Thereby, the temperature distribution of the molten metal 2 and hence the temperature distribution of the glass ribbon 6 can be made line symmetrical about the Y-direction center line 20L of the bath 20. As a result, control of the thickness distribution of the glass ribbon 6 is easy.

(heater)
FIG. 5 is a plan view showing the arrangement of the heater control section according to the first embodiment. FIG. 5 illustrates the arrangement of the heater control sections in the wide area A3, and the illustration of the arrangement of the heater control sections in the intermediate area A2 and the narrow area A1 is omitted. The heater 40 may be provided not only in the wide area A3 but also in the middle area A2 and the narrow area A1.

  As shown in FIG. 5, the heater area in which the plurality of heaters 40 are provided is divided into a plurality of heater control rows 41 in the X direction. Each heater control column 41 is divided into a plurality of heater control sections 42 in the Y direction. The number of heater control rows 41 is not limited to that shown in FIG. Further, the number of heater control sections 42 in each heater control row 41 is not limited to that shown in FIG.

  Each heater control section 42 is provided with a plurality of heaters 40 and collectively controlled by one corresponding controller 50 (see FIG. 1). Thereby, the number of controllers 50 can be reduced. The plurality of heaters 40 provided in one heater control section 42 are collectively controlled by a corresponding one controller 50 so that their calorific values are substantially the same.

  Two heater control rows 41 adjacent in the X direction are divided by one dividing line 45. The dividing line 45 is located approximately at the center between the actual heaters 40 adjacent in the X direction. On the other hand, two heater control sections 42 adjacent to each other in the Y direction are divided by one section line 46. The dividing line 46 is located approximately at the center between the actual heaters 40 adjacent in the Y direction.

  By the way, if the calorific value per unit area is different between two heater control sections 42 adjacent to each other in the Y direction in one heater control row 41, a rapid temperature change occurs in the Y direction in the vicinity of the section line 46.

  Therefore, in the present embodiment, in at least one dividing line 45, the dividing line 46 of the heater control line 41 on the upstream side and the dividing line 46 of the heater control line 41 on the downstream side are discontinuous at one or more points. , Offset at one or more points. For example, in the mth dividing line 45-m from the upstream side (left side in FIG. 5), the dividing line 46 of the mth heater control column 41-m from the upstream side and the m + 1th heater control column 41- from the upstream side The m + 1 dividing line 46 is discontinuous at one or more points and deviates at one or more points. Here, m is at least one natural number of 1 or more, and is, for example, any natural number of 1 or more and 6 or less in FIG. 5.

  In the m-th heater control row 41-m of the glass ribbon 6, the portion passing below the dividing line 46 where the temperature change is rapid is heater control where the temperature change is gradual in the m + 1st heater control row 41-m + 1 Pass under the compartment 42. Therefore, the temperature nonuniformity in the Y direction of the glass ribbon 6 can be suppressed, and the plate thickness nonuniformity in the Y direction of the glass ribbon 6 can be reduced.

  In the present embodiment, the dividing line 46 of the heater control line 41 on the upstream side and the dividing line 46 of the heater control line 41 on the downstream side are at least one dividing line 45 in the wide area A3 in the Z direction. It is discontinuous at one or more locations and deviates at one or more locations. The wide area A3 is at a higher temperature than the middle area A2 and the narrow area A1, and adjustment of the size and shape of the glass ribbon 6 is performed in the wide area A3. In the middle area A2 and the narrow area A1, since the viscosity of the glass ribbon 6 is high, it is difficult to adjust the size and the shape of the glass ribbon 6.

  In the present embodiment, the dividing line 46 of the heater control row 41 on the upstream side and the dividing line 46 of the heater control row 41 on the downstream side are at least one dividing line 45 in the forming area A4 in the Z direction. It is discontinuous at one or more locations and deviates at one or more locations. It is because adjustment of the dimension and shape of the glass ribbon 6 is performed using the top roll 60 in the forming area A4 among the wide area A3.

  In the present embodiment, at least one of the dividing lines 45 in the area A5 where the X-direction distance from the upstream end of the molten metal 2 is 0.1 × X0 or more and 0.5 × X0 or less, The dividing line 46 and the dividing line 46 of the heater control row 41 on the downstream side are discontinuous at one or more places and shifted at one or more places.

  In each heater control column 41, the plurality of dividing lines 46 may be provided in line symmetry about the Y-direction center line 20L of the bathtub 20. Thereby, the temperature distribution of the molten metal 2 and hence the temperature distribution of the glass ribbon 6 can be made line symmetrical about the Y-direction center line 20L of the bath 20. As a result, control of the thickness distribution of the glass ribbon 6 is easy.

(Float glass)
The float glass has a rectangular shape in plan view, a longitudinal dimension of 950 mm or more, a transverse dimension of 1000 mm or more, and an average plate thickness of 0.75 mm or less. The difference between the maximum value and the minimum value of the plate thickness over the entire surface of the float glass is 20 μm or less. The difference between the maximum value and the minimum value of the plate thickness is 4.0 μm or less in a square area having 150 mm in the longitudinal direction and the lateral direction with an arbitrary point in the plane of the float glass as the central point. When this float glass is used as a glass substrate for FPD, the thickness deviation in the whole surface of the glass substrate for FPD can be reduced, and the rapid fluctuation of the thickness in a narrow range of the glass substrate for FPD can be suppressed. The defocus of the exposure apparatus can be suppressed. The float glass having a rectangular shape in plan view includes float glass whose corner portion is ground by a grindstone for corner cut. This grinding portion is called a corner cut portion, and the size of the corner cut portion is, for example, several mm.

  The difference between the maximum value and the minimum value of the plate thickness over the entire surface of the float glass is preferably 10 μm or less.

  The average thickness of the float glass is preferably 0.45 mm or less.

  The float glass preferably has a longitudinal dimension of 1700 mm or more and a lateral dimension of 2000 mm or more.

The float glass is, for example, SiO ₂ : 54 to 66%, Al ₂ O ₃ : 10 to 23%, B ₂ O ₃ : 0 to 12%, MgO: 0 to 12% in terms of mass% on an oxide basis. It is comprised with non-alkali glass containing CaO: 0-15%, SrO: 0-16%, BaO: 0-15%, MgO + CaO + SrO + BaO: 8-26%. Here, “MgO + CaO + SrO + BaO” means the total content of MgO, CaO, SrO and BaO. Further, “alkali-free glass” means that the total content of alkali metal oxides such as Li ₂ O, Na ₂ O and K ₂ O is less than 0.1% by mass. Preferably, the alkali-free glass has a content of B ₂ O ₃ of 5% or less in mass% display based on the oxide.

  Hereinafter, the present invention will be further described using examples and comparative examples. The present invention is not limited to these descriptions. In Example 1 and Comparative Example 1, the vertical direction corresponds to the X direction, and the horizontal direction corresponds to the Y direction.

Example 1
In Example 1, a glass ribbon is manufactured using a float glass manufacturing apparatus having the arrangement of the bottom brick shown in FIG. 4 and the arrangement of the heater control section shown in FIG. 5, and a float glass having a lateral dimension of 1000 mm from the manufactured glass ribbon. And float glass with a lateral dimension of 2000 mm was cut out. Float glass is SiO ₂ : 60%, Al ₂ O ₃ : 17%, B ₂ O ₃ : 8%, MgO: 3%, CaO: 4%, SrO: 8% in terms of mass% on an oxide basis. It comprised by the alkali free glass containing BaO: 0% and MgO + CaO + SrO + BaO: 15%.

  The float glass having a lateral dimension of 1000 mm was cut out from the area Y1 shown in FIGS. The plate thickness distribution of the obtained float glass is shown in FIG. In FIG. 6, the vertical axis is the plate thickness, and the horizontal axis is the distance from the widthwise center line 6L of the glass ribbon 6. The distance is represented as negative on the lower side in FIG. 3 and positive on the upper side in FIG.

  As shown in FIG. 6, the float glass having a lateral dimension of 1000 mm obtained in Example 1 has an average thickness of 0.50 mm, a thickness deviation of 3.3 μm as a whole, and an arbitrary 150 mm. Thickness deviation in the range of 4.0 μm or less. The thickness deviation in the range from the Y direction position 0 mm to the Y direction position 150 mm was 1.0 μm.

  In addition, float glass with a lateral dimension of 2000 mm was cut out from the area Y2 shown in FIGS. The plate thickness distribution of the obtained float glass is shown in FIG. In FIG. 7, the vertical axis is the plate thickness, and the horizontal axis is the distance from the width direction center line 6L of the glass ribbon 6. The distance is represented as negative on the lower side in FIG. 3 and positive on the upper side in FIG.

  As shown in FIG. 7, the float glass having a lateral dimension of 2000 mm obtained in Example 1 has an average thickness of 0.50 mm, a thickness deviation of 3.3 μm as a whole, and an arbitrary 150 mm. Thickness deviation in the range of 4.0 μm or less. The thickness deviation in the range from the Y direction position 0 mm to the Y direction position 150 mm was 3.3 μm.

Comparative Example 1
FIG. 8 is a plan view showing the arrangement of the bottom bricks and the side bricks of the bathtub according to Comparative Example 1. In Comparative Example 1, instead of the arrangement of the bottom bricks shown in FIG. 4, the arrangement of the bottom bricks shown in FIG. 8 was used. A float glass with a lateral dimension of 1000 mm and a float glass with a lateral dimension of 2000 mm were manufactured under the same conditions as Example 1 except for this.

  The float glass having a lateral dimension of 1000 mm was cut out from the area Y1 shown in FIG. 3, FIG. 5, and FIG. The plate thickness distribution of the obtained float glass is shown in FIG.

  As shown in FIG. 6, the float glass having a lateral dimension of 1000 mm obtained in Comparative Example 1 has an average thickness of 0.51 mm, a thickness deviation of 5.2 μm as a whole, and a Y-direction position. The thickness deviation in the range from 0 mm to the Y-direction position 150 mm was 4.6 μm.

  In addition, float glass having a lateral dimension of 2000 mm was cut out from a region Y2 shown in FIG. 3, FIG. 5, and FIG. The plate thickness distribution of the obtained float glass is shown in FIG.

  As shown in FIG. 7, the float glass having a lateral dimension of 2000 mm obtained in Comparative Example 1 has an average thickness of 0.51 mm, a thickness deviation of 11 μm as a whole, and a Y-direction position of 0 mm The thickness deviation in the range of 150 mm in the Y direction was 4.6 μm.

[Summary]
In Example 1 which adopted the arrangement of the bottom bricks shown in FIG. 4, compared with Comparative Example 1 which adopted the arrangement of the bottom bricks shown in FIG. 8, the thickness deviation in the whole was small, and in arbitrary 150 mm of range. Thickness deviation was small. The joint 24 of the bottom brick row 26 on the upstream side and the joint 24 of the bottom brick row 26 on the downstream side are discontinuous at one or more places and deviated at one or more places at at least one boundary line 27 The temperature unevenness in the Y direction of the glass ribbon 6 can be suppressed, and the thickness unevenness in the Y direction of the glass ribbon 6 can be reduced.

  Although the embodiments of the float glass manufacturing apparatus, the float glass manufacturing method, and the float glass and the like have been described above, the present invention is not limited to the above embodiments and the like, and the scope of the present invention is described in the claims. In the inside, various modifications and improvements are possible.

DESCRIPTION OF SYMBOLS 10 float glass manufacturing apparatus 20 bathtub 21 metal casing 22 side brick 23 bottom brick 24 joint 25 cooling nozzle 26 bottom brick row 27 boundary line 30 ceiling 40 heater 41 heater control row 42 heater control section 45 division line 46 division line 50 controller 60 Top roll

Claims (11)

What is claimed is: 1. A float glass manufacturing apparatus comprising a bath for containing molten metal, and forming molten glass continuously supplied onto the molten metal in the bath while flowing on the molten metal to form a glass ribbon.
The bath has a box-like metal casing, and a plurality of bottom bricks placed on the bottom of the metal casing and in contact with the lower surface of the molten metal.
A joint is formed between the bottom bricks adjacent in the width direction of the glass ribbon, and a bottom brick row is constituted by a plurality of the bottom bricks arranged in a line in the width direction of the glass ribbon,
A boundary is formed between the bottom brick rows adjacent in the flow direction of the glass ribbon,
The float glass manufacturing apparatus characterized in that the joint of the bottom brick row on the upstream side and the joint of the bottom brick row on the downstream side are discontinuous at one or more places in at least one of the boundary lines. The tub is a narrow area in which the width dimension of the bath is constant, the middle area in which the width dimension of the bath gradually increases, from the downstream end of the flow direction of the glass ribbon to the upstream side; Having in this order a wide area whose widthwise dimension is larger and constant than the narrow area,
In the wide area, in at least one of the boundaries, the joint of the bottom brick row upstream and the joint of the bottom brick row downstream are discontinuous at one or more locations. The float glass manufacturing apparatus as described. A plurality of pairs of top rolls provided at intervals along the flow direction of the glass ribbon and supporting both widthwise ends of the glass ribbon,
In the forming area from the contact position between the pair of top rolls on the upstream and the glass ribbon to the contact position between the pair of top rolls on the downstream and the glass ribbon, the bottom on the upstream side at at least one of the boundaries The float glass manufacturing apparatus according to claim 1, wherein the joint of the brick row and the joint of the bottom brick row downstream are discontinuous at one or more places.   The heater region provided with a plurality of heaters provided above the molten metal and a plurality of controllers, and provided with a plurality of the heaters is divided into a plurality of rows in the flow direction of the glass ribbon, and each row is the glass ribbon The float according to any one of claims 1 to 3, wherein a plurality of the heaters are respectively provided in each section divided in the width direction of the block, and collectively controlled by one corresponding one of the controllers. Glass manufacturing equipment. The molten glass is formed into the glass ribbon using the float glass manufacturing apparatus according to any one of claims 1 to 4,
The float glass manufacturing method which cuts out a glass plate from the said glass ribbon. A float glass having a longitudinal dimension of 950 mm or more, a transverse dimension of 1000 mm or more, and an average plate thickness of 0.75 mm or less, which is rectangular in plan view,
The difference between the maximum value and the minimum value of the plate thickness in the entire plane is 20 μm or less,
The difference between the maximum value and the minimum value of the plate thickness is 4.0 μm or less in the range of a square having an arbitrary point in the plane as the central point and the dimensions in the longitudinal direction and the lateral direction being 150 mm. Float glass.   The float glass according to claim 6, wherein the difference between the maximum value and the minimum value of the plate thickness in the entire surface is 10 μm or less.   The float glass according to claim 6 or 7, wherein the average plate thickness is 0.45 mm or less.   The float glass according to any one of claims 6 to 8, wherein the longitudinal dimension is 1700 mm or more and the transverse dimension is 2000 mm or more. In mass% display of oxide standard,
SiO ₂ : 54 to 66%,
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%
The float glass as described in any one of Claims 6-9 comprised with the alkali free glass containing. The float glass according to claim 10, wherein the alkali-free glass has a content of B ₂ O ₃ of 5% or less in terms of mass% on the basis of an oxide.

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