WO2013105667A1

WO2013105667A1 - Manufacturing device and molding device for glass substrate

Info

Publication number: WO2013105667A1
Application number: PCT/JP2013/050489
Authority: WO
Inventors: 伸広前田
Original assignee: ＡｖａｎＳｔｒａｔｅ株式会社
Priority date: 2012-01-13
Filing date: 2013-01-11
Publication date: 2013-07-18
Also published as: CN104024169A; CN104024169B; JP5752787B2; JPWO2013105667A1

Abstract

In the manufacture of a glass substrate, continuous sheet glass is molded by causing molten glass to overflow from a molding body to thereby create the flow of the sheet glass. When the sheet glass is cooled, annealing in which while the distribution of heat supplied by a heat source provided along the width direction of the sheet glass is eased, the sheet glass is cooled by giving a temperature distribution thereto along the width direction of the sheet glass by means of the heat source in order to reduce the warpage and strain of the glass substrate is performed. This annealing is performed in a region in the flow direction of the sheet glass between an annealing point position in the flow direction of the sheet glass corresponding to the annealing point of the sheet glass and a strain point position in the flow direction of the sheet glass corresponding to the strain point of the sheet glass.

Description

Glass substrate manufacturing method and molding apparatus

The present invention relates to a glass substrate manufacturing method and a molding apparatus for manufacturing a glass substrate.

A thin glass plate having a thickness of, for example, 0.5 to 0.7 mm is used for a glass substrate used in a flat panel display (hereinafter referred to as “FPD”) such as a liquid crystal display or a plasma display. For example, the FPD glass substrate has a size of 300 × 400 mm in the first generation, but has a size of 2850 × 3050 mm in the tenth generation.

The overflow down draw method is often used to manufacture such a large size glass substrate for FPD. The overflow down-draw method includes forming a sheet glass (plate glass) below the molded body by causing the molten glass to overflow from the upper part of the molded body in a molding furnace, and a cooling process of gradually cooling the sheet glass in a slow cooling furnace. including. The slow cooling furnace draws the sheet glass between the pair of rollers and stretches it to a desired thickness, and then slowly cools the sheet glass. Thereafter, the sheet glass is cut into a predetermined size to form a glass plate, which is laminated and stored on another glass plate. Or a glass plate is conveyed by the following process.

As a method for manufacturing a glass substrate using such an overflow downdraw method, a method capable of suppressing the occurrence of distortion in the width direction of the glass substrate is known (Patent Document 1).
This production method is a method for producing a glass substrate by forming molten glass into a sheet shape by a downdraw method, and gradually cooling the obtained sheet glass, in the width direction of the sheet glass. The distortion reduction process for reducing the distortion of the sheet glass generated due to the temperature difference between the (peripheral part) and the central part (surface part) is performed using a plurality of heaters during slow cooling. In the strain reduction process, the temperature of the sheet glass is controlled so that the temperature of the sheet glass is equalized in the width direction in the vicinity of the strain point of the glass.

Japanese Patent No. 3586142

However, in the above-described known glass substrate manufacturing method (Patent Document 1), a glass having a warp amount and a strain amount that satisfies the requirements of customers such as a film forming company that forms a thin film on the glass substrate using the glass substrate. The substrate could not be produced.

Accordingly, the present invention controls the temperature distribution in the width direction of the sheet glass during the cooling process in order to reduce warpage and distortion in the glass substrate, and the glass substrate has a warpage amount and a strain amount that satisfy customer requirements. It aims at providing the manufacturing method and shaping | molding apparatus of a glass plate which can produce this.

In general, in a glass substrate, for example, a glass substrate for FPD, a glass substrate having a small thickness deviation and high flatness is desired. That is, it is preferable to cool the sheet glass that is the base of the glass substrate so that the thickness deviation, warpage, and distortion of the glass substrate are reduced.
In the known overflow downdraw method of forming a sheet glass from molten glass using a molded body (cell), in order to reduce the thickness deviation, warpage and distortion of the glass substrate, it is preferable to cool as follows. .
1. Cooling to reduce thickness deviation First, it is preferable to quench the glass both ends of the sheet glass immediately after being overflowed and formed from the formed body (hereinafter also referred to as a cell). The molten glass that has flowed down both side walls of the cell is formed into a sheet glass leaving the lower end of the cell. The sheet glass immediately after molding tries to reduce its surface area by its own surface tension, but by increasing the glass viscosity at both ends of the sheet glass as quickly as possible, its action is hindered and the width can be kept wide. it can. Moreover, the center part of the width direction of sheet glass can produce a glass substrate with few thickness deviations by making temperature distribution uniform. The cooling for reducing the thickness deviation is preferably performed when the central portion in the width direction of the sheet glass is a viscous flow region (in this specification, approximately equal to or higher than the softening point).
2. Cooling to reduce warpage and strain After cooling to reduce the wall thickness deviation in the viscous flow region, the sheet glass is strained from between the plastic deformation region (approximately between the softening point and the annealing point in this specification). In order to prevent warping and distortion during the period up to the point). In order to cool the sheet glass so as not to warp, it is cooled so that a tensile stress always acts on the central part in the width direction of the flat sheet glass cooled to reduce the thickness deviation, and the flatness is maintained. It is preferable to do. In order to cool so as not to cause distortion, it is preferable to cool so that the temperature is uniform in the vicinity of the strain point as described above. Therefore, first, a temperature distribution in a mountain shape is imparted to the sheet glass so that the temperature of the sheet glass decreases from the center in the width direction of the sheet glass toward both ends in the width direction. This temperature distribution is preferably given immediately after being cooled to a temperature range (for example, a temperature range lower than the softening point) that does not affect the thickness deviation of the sheet glass. Then, as the temperature is cooled, the gradient of the temperature distribution is reduced, and the sheet glass is cooled so that the temperature distribution in a mountain shape is substantially flat near the strain point, that is, the temperature is uniform. In other words, since the cooling amount (volume shrinkage) at the center in the width direction of the sheet glass is the largest and is cooled so as to decrease toward both ends, a tensile stress always acts on the center in the width direction of the sheet glass. Become. Also, in the case of a temperature distribution in which the temperature of the sheet glass is not uniform near the strain point, residual stress occurs when the temperature reaches room temperature, so by cooling the sheet glass so that the temperature is uniform near the strain point , Distortion can be reduced.

In consideration of the above contents, the present inventor has studied the reason why a glass substrate having a warpage amount and a strain amount that satisfies customer requirements cannot be produced in the manufacture of a known glass substrate. It was discovered that the temperature distribution in the width direction of the sheet glass is formed stepwise, or that the temperature distribution in the width direction of the sheet glass falls locally and does not become a smooth distribution. . Further, in the cooling of the sheet glass in the plastic deformation region, the smooth mountain shape gradually decreases while the temperature distribution of the sheet glass maintains a smooth mountain shape, and the mountain shape becomes flat near the strain point. Thus, it has been found that it is desirable to adjust the temperature of the sheet glass, and the inventors have come up with the invention of the following aspect.

One embodiment of the present invention is a method for manufacturing a glass substrate. The manufacturing method is
Forming a continuous sheet glass by overflowing the molten glass from the molded body, and forming a flow of the sheet glass;
In order to reduce the warp and distortion of the glass substrate, the sheet glass is used for the sheet glass by using the heat source while relaxing the heat distribution supplied by the heat source provided along the width direction of the sheet glass. And a cooling step including a slow cooling process in which the temperature distribution is given along the width direction of the cooling.
The slow cooling treatment is performed between a slow cooling point position in the flow direction of the sheet glass corresponding to a slow cooling point of the sheet glass and a strain point position in the flow direction of the sheet glass corresponding to a strain point of the sheet glass. In the region of the sheet glass in the flow direction.

At that time, the heat distribution of the heat source is relaxed by using one soaking plate provided between the sheet glass and the heat source, and the soaking plate relaxes the heat distribution of the heat source. It is preferable to supply heat to the sheet glass.

The soaking plate is preferably a stainless metal plate having an oxide film formed on the surface by oxidation treatment.

Further, the cooling step is performed using at least a pair of temperature adjusting devices provided on both sides of the sheet glass, and each of the at least one pair of temperature adjusting devices uses the heat source and the heat equalizing plate. It is preferable to supply heat to the sheet glass.

It is preferable that the heat distribution is a distribution of a heat generation amount (heating amount) of the heat source.

The temperature distribution is preferably a mountain-shaped distribution that is maximum at the center in the width direction or a uniform distribution.

The heat distribution is preferably a mountain-shaped distribution that is maximum at the center in the width direction or a uniform distribution.

The heat source includes a plurality of heat source elements provided in the width direction,
It is preferable that the heat distribution of the heat source includes a distribution in which heat supplied at positions corresponding to the ends in the width direction of the heat source elements decreases.

Moreover, the other aspect of this invention is also a manufacturing method of a glass substrate,
A molding step of overflowing the molten glass from the molded body and molding the sheet glass;
A pair of heat sources provided along the width direction of the sheet glass gives a slow cooling process for cooling the sheet glass by providing a temperature distribution along the width direction of the sheet glass on both surfaces of the sheet glass. Including a cooling step.
In the slow cooling treatment, the sheet glass is gradually cooled between a pair of plate members disposed between the pair of heat sources and the sheet glass.

The plate material is a soaking plate that relaxes heat distribution supplied by a heat source provided along the width direction of the sheet glass, and the cooling furnace corresponds to the annealing point of the sheet glass. In the region in the flow direction of the sheet glass, between the annealing point position in the flow direction of the sheet glass and the strain point position in the flow direction of the sheet glass corresponding to the strain point of the sheet glass, It is preferable to use a soaking plate.

At this time, the heat source is a heater that radiates heat toward both sides of the sheet glass, and the plate material is disposed so as to block the entire surface of the heater facing the sheet glass. preferable.

Another embodiment of the present invention is a glass substrate forming apparatus. The molding device is
Forming a continuous sheet glass by overflowing the molten glass from the molded body, and forming a flow of the sheet glass;
A pair of heat sources provided along the width direction of the sheet glass gives a slow cooling process for cooling the sheet glass by providing a temperature distribution along the width direction of the sheet glass on both surfaces of the sheet glass. And a cooling furnace for performing.
In the slow cooling treatment, the sheet glass is gradually cooled between a pair of plate members disposed between the pair of heat sources and the sheet glass.

The cooling furnace, as the slow cooling process, reduces the heat distribution supplied by the heat source provided along the width direction of the sheet glass in order to reduce warpage and distortion of the glass substrate, Use to cool the sheet glass by giving a temperature distribution along the width direction of the sheet glass,
The cooling furnace is configured to perform the slow cooling treatment in the flow direction of the sheet glass corresponding to the slow cooling point position in the flow direction of the sheet glass corresponding to the slow cooling point of the sheet glass and the strain point of the sheet glass. It is performed in a region in the flow direction of the sheet glass between the point positions.

The heat source is a heater that radiates heat toward both surfaces of the sheet glass,
The plate material is preferably arranged so as to block the entire surface of the heater facing the sheet glass.

One embodiment of the present invention is a glass substrate forming apparatus. The molding device is
Forming a continuous sheet glass by overflowing the molten glass from the molded body, and forming a flow of the sheet glass;
In order to reduce the warp and distortion of the glass substrate, the sheet glass is used for the sheet glass by using the heat source while relaxing the heat distribution supplied by the heat source provided along the width direction of the sheet glass. And a cooling furnace that performs a slow cooling process in which a temperature distribution is given along the width direction of the cooling.
The cooling furnace is configured to perform the slow cooling treatment in the flow direction of the sheet glass corresponding to the slow cooling point position in the flow direction of the sheet glass corresponding to the slow cooling point of the sheet glass and the strain point of the sheet glass. It is performed in a region in the flow direction of the sheet glass between the point positions.

In the method and apparatus for producing a glass substrate of the above aspect, the temperature distribution in the width direction applied to the sheet glass during the cooling process can be smoothed, for example, a smooth distribution with a single mountain shape or a uniform distribution without steps. And warpage and distortion in the glass substrate can be reduced. As a result, it is possible to produce a glass substrate having a warpage amount and a strain amount that satisfies customer requirements. Further, in the slow cooling process, the sheet glass is gradually cooled between the pair of plate materials arranged between the pair of heat sources and the sheet glass, so that scattered matter from the heat source is applied to the sheet glass during the slow cooling process. It can prevent adhesion. Furthermore, even if the sheet glass is broken and glass fragments are scattered on the heat source, the heat source can be protected by the plate material.

It is a figure which shows an example of the flow of the manufacturing method of the glass substrate which is this embodiment. It is a figure which shows typically an example of the apparatus which performs the melting process-cutting process of this embodiment. FIG. 3 is a schematic side view of the molding apparatus shown in FIG. 2. FIG. 3 is a schematic front view of a part of the molding apparatus shown in FIG. 2. It is a figure explaining the soaking plate and heater unit used for this embodiment. It is a figure explaining the several temperature distribution of this embodiment. It is a figure explaining the example of the temperature distribution of the sheet glass of this embodiment, and the temperature distribution of the conventional sheet glass. It is a figure which shows the example of the temperature distribution of the sheet glass by the presence or absence of a soaking plate.

Hereinafter, a method for manufacturing a glass substrate and a forming apparatus of the present embodiment will be described.

(Overall overview of glass substrate manufacturing method)
FIG. 1 is a diagram illustrating a flow of a glass substrate manufacturing method according to the present embodiment.
The glass plate manufacturing method includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a forming step (ST5), a cooling step (ST6), Cutting step (ST7). Moreover, the manufacturing method of a glass plate has other processes, such as a grinding process, a grinding | polishing process, a washing | cleaning process, an inspection process, and a packing process. The plurality of glass plates stacked in the packing process are transported to a supplier (customer) as a delivery destination.

FIG. 2 is a diagram schematically showing an apparatus for performing the melting step (ST1) to the cutting step (ST7). As shown in FIG. 2, the apparatus mainly includes a melting apparatus 100, a forming apparatus 200, and a cutting apparatus 300. The melting apparatus 100 includes a melting tank 101, a clarification tank 102, a stirring tank 103, a first pipe 104, a second pipe 105, and a third pipe 106. The molding apparatus 200 will be described later.

In the melting step (ST1), molten glass MG is obtained by melting the glass raw material supplied into the melting tank 101 by heating with a flame and an electric heater (not shown).
The clarification step (ST2) is performed in the clarification tank 102, and oxygen contained in the molten glass MG is heated by heating the molten glass MG in the clarification tank 102 supplied from the melting tank 101 through the first pipe 104. Or SO ₂ bubbles grow by the oxidation-reduction reaction of the clarifying agent and float on the liquid surface and are released, or gas components in the bubbles are absorbed into the molten glass MG, and the bubbles disappear.
In the homogenization step (ST3), the glass component is homogenized by stirring the molten glass MG in the stirring tank 103 supplied from the clarification tank 102 through the second pipe 105 using the stirrer 103a.
In the supply step (ST4), the molten glass MG is supplied from the stirring vessel 103 to the molding apparatus 200 through the third pipe 106.

In the molding apparatus 200, a molding process (ST5) and a cooling process (ST6) are performed.
In the forming step (ST5), the molten glass MG is formed into a sheet glass SG (see FIG. 3) to make a flow of the sheet glass SG. In the present embodiment, an overflow down draw method using a molded body 210 described later is used. In this case, the flow direction (Z direction in the figure) of the sheet glass SG is vertically downward. In the cooling step (ST6), the sheet glass SG that is formed and flows has a desired thickness, and is cooled so that warpage and distortion due to cooling do not occur.
In the cutting step (ST7), the sheet glass SG supplied from the forming apparatus 200 is cut into a predetermined length in the cutting apparatus 300, whereby a plate-like glass substrate G is obtained.
Then, after grinding and polishing of the end face of the glass substrate G, the glass substrate G is cleaned, and further, the presence or absence of abnormal defects such as bubbles and striae is inspected, and then the glass that has passed the inspection. The substrate G is packed as a final product.

The glass substrate G manufactured in the present embodiment is suitably used for, for example, a glass substrate for liquid crystal display, a glass substrate for organic EL display, and a cover glass. In addition, the glass substrate can also be used as a display for a portable terminal device, a cover glass for a housing, a touch panel plate, a glass substrate for a solar cell, or a cover glass. Particularly, it is suitable for a glass substrate for a liquid crystal display using a polysilicon TFT.
The thickness of the glass substrate G is, for example, 0.1 mm to 1.5 mm. The thickness is preferably 0.1 to 1.2 mm, more preferably 0.3 to 1.0 mm, even more preferably 0.3 to 0.8 mm, and particularly preferably 0.3 to 0.5 mm.
Furthermore, the length in the width direction of the glass substrate G is, for example, 500 mm to 3500 mm, preferably 1000 mm to 3500 mm, and more preferably 2000 mm to 3500 mm. On the other hand, the length of the glass substrate G in the vertical direction is, for example, 500 mm to 3500 mm, preferably 1000 mm to 3500 mm, and more preferably 2000 mm to 3500 mm.

(Composition of glass substrate)
As the glass used for the glass substrate G, for example, borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, soda lime glass, alkali silicate glass, alkali aluminosilicate glass, alkali aluminogermanate glass, or the like can be used. The glass applicable to the present invention is not limited to the above.

The glass composition of the glass substrate G can mention the following, for example.
The content rate display of the composition shown below is mass%.
SiO ₂ : 50 to 70%,
B ₂ O ₃ : 5 to 18%,
Al ₂ O ₃ : 0 to 25%,
MgO: 0 to 10%,
CaO: 0-20%,
SrO: 0 to 20%,
BaO: 0 to 10%,
RO: 5 to 20% (where R is at least one selected from Mg, Ca, Sr and Ba, and the glass plate contains),
It is preferable that it is an alkali free glass containing.

The glass of the glass substrate G can have the following glass composition: SiO ₂ : 50 to 70%,
B ₂ O ₃ : 1-10%,
Al ₂ O ₃ : 0 to 25%,
MgO: 0 to 10%,
CaO: 0-20%,
SrO: 0 to 20%,
BaO: 0 to 10%,
RO: 5-30% (where R is the total amount of Mg, Ca, Sr and Ba),
Similarly, it is also preferable that the glass be an alkali-free glass.

In the present embodiment, alkali-free glass is used, but the glass substrate G may be alkali-containing glass containing a trace amount of alkali metal. When the alkali metal is contained, the total of R ′ ₂ O exceeds 0.20% and 0.5% or less (provided that R ′ is at least one selected from Li, Na and K, and the glass substrate G contains It is preferable to include. In order to facilitate melting of the glass, the content of iron oxide in the glass is more preferably 0.01 to 0.2% from the viewpoint of reducing the specific resistance. Further, the content of tin oxide added as a fining agent is more preferably 0.01 to 0.5%.

(Description of molding equipment)
3 and 4 are diagrams mainly showing the configuration of the molding apparatus 200 for the glass substrate G, FIG. 3 is a schematic side view of the molding apparatus 200, and FIG. 4 is a partially schematic front view of the molding apparatus 200. The figure is shown. The molding apparatus 200 includes a molding furnace 201 that performs a molding process (ST5) and a slow cooling furnace 202 that performs a cooling process (ST6). The slow cooling furnace 202 is a furnace extending from below the atmosphere partition member 220 described later to the cutting device 300.

In the cooling step (ST6) performed in this embodiment, in order to reduce warpage and distortion of the glass substrate G, the width direction of the sheet glass SG formed in the forming step (ST5) (horizontal in the forming apparatus 200 shown in FIG. 2). Using the heater unit provided along the direction), the sheet glass SG is subjected to a slow cooling process for cooling while giving a temperature distribution along the width direction of the sheet glass SG. This slow cooling treatment in the cooling step (ST6) is performed in the flow direction of the sheet glass SG corresponding to the slow cooling point position in the flow direction of the sheet glass SG corresponding to the slow cooling point of the sheet glass SG and the strain point of the sheet glass SG. This is performed in a region in the flow direction of the sheet glass SG between the strain point position. When the sheet glass SG has a temperature distribution, the annealing point position means a position where the maximum temperature of the temperature distribution becomes the annealing point, and similarly, the strain point position indicates that the maximum temperature of the temperature distribution becomes the distortion point. Says the position. Here, the annealing point is a temperature corresponding to the viscosity of 10 ¹³ poise of the sheet glass SG, and the strain point is a temperature corresponding to the viscosity of 10 ^14.5 poise of the sheet glass SG.
In this slow cooling process, the temperature distribution is given to the sheet glass SG by relaxing the heat distribution of the heat generated by the heater unit. In this embodiment, the heat distribution is relaxed by using a soaking plate 260 described later. This will be described in more detail below.

The forming furnace 201 and the slow cooling furnace 202 are configured to be surrounded by a furnace wall made of a refractory material such as a refractory brick, a refractory heat insulating brick, or a fiber-based heat insulating material. The forming furnace 201 is provided vertically above the slow cooling furnace 202. In the furnace internal space surrounded by the furnace walls of the forming furnace 201 and the slow cooling furnace 202, a plurality of transports including a molded body 210, an atmosphere partition member 220, a cooling roller 230, a cooling unit 240, and transport rollers 250a to 250c. A roller and a plurality of temperature adjusting devices are provided.

As shown in FIG. 2, the formed body 210 forms molten glass MG flowing from the melting apparatus 100 through the third pipe 106 into a sheet glass SG. Thereby, the flow of the sheet glass SG in the vertically lower direction is created in the forming apparatus 200. The molded body 210 is a long and narrow structure made of firebrick or the like, and has a wedge-shaped cross section as shown in FIG. A groove 212 serving as a flow path for guiding the molten glass MG is provided in the upper part of the molded body 210. The groove 212 is connected to the third pipe 106 at a supply port 211 (shown in FIG. 4) provided in the molded body 210, and the molten glass MG flowing through the third pipe 106 flows along the groove 212. The depth of the groove 212 is shallower toward the downstream side of the flow of the molten glass MG, so that the molten glass MG overflows vertically downward from the groove 212.
The molten glass MG overflowing from the groove 212 flows down along the side walls on both sides of the molded body 210. The molten glass MG that has flowed through the side walls merges at the lower end 213 (shown in FIG. 3) of the molded body 210 to form one sheet glass SG. The sheet glass SG flows in the Z direction, which is the flow direction of the sheet glass SG shown in FIG. The temperature of the sheet glass SG immediately below the lower end portion 213 of the molded body 210 is a temperature corresponding to a viscosity of 10 ^5.7 to 10 ^7.5 poise (for example, 1000 to 1130 ° C.).

In the vicinity of the lower end 213 of the molded body 210, an atmosphere partition member 220 is provided. The atmosphere partition member 220 is a pair of plate-like heat insulating members, and is provided on both sides in the thickness direction of the sheet glass SG so as to sandwich the sheet glass SG from both sides in the thickness direction (X direction in the drawing). Yes. A gap is provided between the sheet glass SG and the atmosphere partition member 220 to such an extent that the atmosphere partition member 220 does not contact the sheet glass SG. The atmosphere partition member 220 partitions the internal space of the molding furnace 201, thereby blocking heat transfer between the furnace internal space above the atmosphere partition member 220 and the furnace internal space below.

An air-cooled cooling roller 230 is provided below the atmosphere partition member 220. As shown in FIG. 3, the cooling roller 230 is provided on both sides in the thickness direction of the sheet glass SG so as to sandwich the sheet glass SG from both sides in the thickness direction. Further, as shown in FIG. 4, the cooling roller 230 contacts the surface of the sheet glass SG at both ends in the width direction (Y direction in the drawing) of the sheet glass SG to cool the sheet glass SG. The cooling roller 230, until the decrease in temperature (for example 900 ° C. or less) the temperature of the widthwise end portions of the sheet glass SG is equivalent to about ¹⁰ 9.0 poise or more viscosity, it is preferable to cool. Further, a pair of end cooling units 244 (see FIG. 4) is provided as one of the cooling units 240 described later below the cooling roller 230 on each side of the sheet glass SG. The edge part cooling unit 244 is comprised from the water cooling plate which is not shown in figure, and has opposed the both ends of the sheet glass SG. Thereby, both ends of the sheet glass SG are efficiently cooled.

A cooling unit 240 is provided below the atmosphere partition member 220. The cooling unit 240 includes a central cooling unit 242 and the end cooling unit 244 described above. In the central cooling unit 242, the entire casing is cooled by cooling air sent from a cooling pipe provided in the casing (not shown). The outer surface of this housing is opposed to the central portion in the width direction of the sheet glass SG. The central cooling unit 242 is provided in at least three stages downward from the same position in the Z direction (flowing direction of the sheet glass SG) as the cooling roller 230. Thereby, the center part of the sheet glass SG is cooled efficiently. As shown in FIG. 3, the central cooling unit 242 is provided on both sides in the thickness direction of the sheet glass SG so as to sandwich the sheet glass SG from both sides in the thickness direction above the top plate 202 a of the slow cooling furnace 202. Yes. The uppermost center cooling unit 242 cools the sheet glass SG until the maximum temperature (temperature at the center) of the sheet glass SG decreases to a temperature near the softening point. At this time, the cooling action of the central cooling unit 242 is adjusted and cooled so that the temperature distribution in the central portion in the width direction of the sheet glass SG becomes a substantially uniform temperature distribution. Here, the softening point refers to the glass temperature corresponding to a viscosity of about 10 ^7.6 poise.
Further, the center cooling unit 242 and the end cooling unit 244 in the second and subsequent stages change the sheet from a uniform temperature distribution in the center in the width direction to a temperature distribution in a mountain shape having a smooth temperature gradient. The glass SG is cooled. The central cooling unit 242 and the end cooling unit 244 in the third and subsequent stages are gradually cooled while the maximum temperature of the sheet glass SG (the temperature of the central part) is maintained while maintaining a temperature distribution with a smooth temperature gradient. The sheet glass SG is cooled until it falls to a temperature near the point.
Thus, between the atmosphere partition member 220 and the top plate 202a, both ends in the width direction of the sheet glass SG are cooled by the cooling roller 230, the end cooling unit 244, and the multi-stage central cooling unit 242. .

A temperature adjusting device is provided in a region sandwiched between the top plate 202a and the top plate 202b below the top plate 202a. In this region, conveyance rollers 250a are provided on both sides in the thickness direction of the sheet glass SG. Further, in this region, a soaking plate 260 and a heater unit 270 as a heat source are provided as temperature adjusting devices on both sides in the thickness direction of the sheet glass SG. The heat equalizing plate 260 is a single stainless steel plate that is provided in parallel to both sides of the sheet glass SG and extends in the width direction so as to correspond to the width in the width direction of the sheet glass SG. The heater unit 270 includes a plurality of heaters provided along the width direction of the sheet glass so that a mountain-shaped temperature distribution is formed in the sheet glass SG along the width direction of the sheet glass SG. Each heater can adjust the amount of heat generated. The soaking plate 260 is a single plate-like member provided between the sheet glass SG and the heater unit 270 that is a heat source. The soaking plate 260 has a function of soaking heat distribution of the heat generated by the heater unit 270 that is a heat source and supplying heat to the sheet glass SG (soaking effect). Specifically, the soaking plate 260 diffuses the heat received from the heater unit 270 with a different calorific value to form a smooth temperature distribution, and supplies heat to the sheet glass SG according to the smooth temperature distribution. Thereby, the temperature distribution along the width direction of the sheet glass SG becomes a smooth mountain shape. The soaking plate 260 and the heater unit 270 will be described later.

In a region sandwiched between a top plate (not shown) adjacent to the bottom of the top plate 202b and the top plate 202b, a temperature adjusting device using another heat equalizing plate 260 and a heater unit 270 is further provided. .
The cooling rate (° C./second) of the sheet glass SG between the

top plates

202a and 202b and the adjacent top plate on the downstream side (Z direction side) of the sheet glass SG, that is, adjacent to the top plate 202a and the top plate 202b. Among the top plates, the temperature of the sheet glass SG when the sheet glass SG passes through the top plate located below from the temperature of the sheet glass SG when the sheet glass SG passes through the top plate located at the upper side. The value when dividing by the time to pass between the top plates to be performed is smaller than the cooling rate (° C./second) of the sheet glass SG between the atmosphere partition member 220 and the top plate 202a. Therefore, the cooling of the sheet glass SG between the atmosphere partition member 220 and the top plate 202a is the first cooling, and the cooling of the sheet glass SG between the adjacent top plates below the top plate 202a in the Z direction is the second cooling. At this time, the cooling rate of the sheet glass SG in the second cooling is smaller than the cooling rate of the sheet glass SG in the first cooling. Therefore, the second cooling is also called slow cooling. That is, in the present embodiment, soaking is performed so that the sheet glass SG has a temperature distribution corresponding to a predetermined temperature distribution in the slow cooling process performed on the downstream side in the flow direction of the sheet glass SG from the top plate 202a. The sheet glass SG is gradually cooled by a temperature adjusting device using the plate 260 and the heater unit 270. This cooling is performed through temperature control of a control device (not shown).

FIG. 5 is a view for explaining the soaking plate 260 and the heater unit 270. In FIG. 5, the conveyance roller 250a is not shown.
The heater unit 270 is divided into five heaters 270a to 270e along the width direction of the sheet glass SG, and each of the heaters 270a to 270e generates heat. Although the heaters 270a to 270e shown in FIG. 5 are arranged adjacent to each other without a gap in the width direction of the sheet glass SG, they may be arranged with a certain gap in the width direction of the sheet glass SG. Good. The heaters 270a to 270e include a heat source such as a chromium-based heating wire, for example. The respective calorific values of the five heaters 270a to 270e can be individually adjusted. In order to create a temperature distribution in the sheet glass SG, the heaters 270a to 270e are adjacent to each other between the annealing point and the strain point, as will be described later, in order to give the sheet glass SG a temperature distribution having a mountain shape. Control is made so that the amount of heat generated differs between the heaters. That is, the heater unit 270 supplies heat toward the sheet glass SG with a heat distribution along the Y direction.
Here, the heat distribution of the heat generated by the heater unit 270 is the distribution of the amount of heat generated by the heaters 270a to 270e. This heat distribution is, for example, a distribution that becomes maximum at the center position in the width direction of the sheet glass SG.
The soaking plate 260 is a single plate member provided corresponding to the entire width of the heater unit 270 including the heaters 270a to 270e.
Each of the heaters 270a to 270e supplies heat toward the soaking plate 260, and the soaking plate 260 is heated by the supplied heat, and the temperature is increased in the Y direction (width direction of the sheet glass SG) shown in FIG. Form a distribution. On the surface of the heat equalizing plate 260 facing the heaters 270a to 270e, a temperature distribution having a step corresponding to the amount of heat generated by the heaters 270a to 270e is formed by the heat from the heaters 270a to 270e. Each temperature is diffused and transmitted in the Y direction by heat conduction of the soaking plate 260 and further in the thickness direction of the soaking plate 260 by heat conduction. Therefore, the temperature distribution with a step is relaxed and becomes gradually smoother. However, when the plate thickness of the soaking plate 260 is sufficiently smaller than the width of the soaking plate 260 in the Y direction, the temperature distribution on the surface of the soaking plate 260 on the side facing the sheet glass SG is not uniform and smooth. It becomes a temperature distribution with a single mountain shape. Therefore, the soaking plate 260 radiates heat with a temperature distribution in which the stepped temperature distribution is relaxed and becomes a smooth mountain shape with respect to the sheet glass SG. Thereby, the sheet glass SG can have a temperature distribution having a smooth mountain shape.

If the heat flux in the heat conduction in the plane direction of the soaking plate 260 is excessively large in the soaking plate 260, the temperature difference of the temperature distribution of the sheet glass SG to be realized by the heater divided in the width direction (Y direction) is increased. The harmful effect of being reduced occurs. On the other hand, if the heat flux is too small, the soaking effect expected is not fully exhibited, and the stepwise heat radiation distribution (calorific value distribution) emitted from the heater can be converted into a gentle temperature gradient on the glass surface. Can not. For this reason, it is necessary to select a material having an appropriate thermal conductivity and to select a thickness (plate thickness) according to the selected material.
For the soaking plate 260, for example, a stainless metal plate is preferably used. The thermal conductivity of the soaking plate 260 is preferably 10 W / (m · K) or more from the viewpoint of thermally radiating the sheet glass SG with a temperature distribution having a smooth mountain shape. The thermal conductivity of the soaking plate 260 is more preferably 15 W / (m · K) or more. The thermal conductivity of the soaking plate 260 is preferably 90 W / (m · K) or less, and more preferably 80 W / (m · K) or less. If the thermal conductivity of the soaking plate 260 is less than 10 W / (m · K), the plate thickness of the soaking plate 260 becomes excessively large in order to obtain the above-described appropriate heat flux, and the heater as a heat source When the heat exchange rate between 270a to 270e and the sheet glass SG is deteriorated and the thermal conductivity of the soaking plate 260 exceeds 90 W / (m · K), the above-mentioned appropriate heat flux is obtained. Further, the plate thickness of the soaking plate 260 becomes excessively small, and the strength of the soaking plate 260 decreases.
Specifically, the plate thickness of the soaking plate 260 should be about 1.5 to 8 mm when using stainless steel with a thermal conductivity of around 16 W / (m · K). It is preferable from the viewpoint of thermally radiating the sheet glass SG with the temperature distribution obtained, and more preferably 1.5 to 3 mm. Further, the soaking plate 260 is coated with a ceramic paint to improve the emissivity and increase the heat exchange efficiency between the heaters 270a to 270e and the sheet glass SG and to improve the emissivity of the surface. Alternatively, an oxide film obtained by subjecting the surface to oxidation treatment, for example, a passive film (super black treatment film) may be formed. In particular, it is preferable that a passive film (super black treatment film) having a film thickness of about 1 μm is formed in terms of preventing unnecessary particles, dust, and the like from adhering to the surface of the sheet glass SG. When the ceramic paint is used, there is an increased risk that particles and dust generated by partial peeling of the ceramic paint adhere to the sheet glass.

The soaking plate 260 is also a plate material for preventing scattered matter from the heater heating element from adhering to the sheet glass SG. The soaking plate 260 is also a plate material that protects the heating element of the heater from glass fragments even if the sheet glass SG is broken. For example, when the heat source is a chromium-based heating wire, chromium and the like are gradually peeled off from the surface due to oxidation and become scattered matter, but the soaking plate 260 prevents the scattered matter from adhering to the sheet glass SG. be able to.
In addition, when using a board | plate material in order to prevent the scattered material from the heating element of a heater adhering to the sheet glass SG, or in order to protect the heating element of a heater from glass fragments, the said board | plate material is heat-resistant. However, the material is not limited to a material having a high thermal conductivity such as a stainless metal plate such as the soaking plate 260. That is, when the plate material is the soaking plate 260, the above-described soaking effect can be obtained.
The heater unit 270 is a heater that radiates heat toward both sides of the sheet glass SG, and the soaking plate 260 is disposed so as to block the entire surface of the heaters 270a to 270e facing the sheet glass SG. It is preferable.
Thus, in this embodiment, a pair of soaking plates 260 disposed between the pair of heater units 270 and the sheet glass SG are used as a pair of plates, and the sheet glass SG is gradually passed between the pair of plates. Cool down.

Also, the surface of the soaking plate 260 is preferably a diffuse reflection surface, particularly when the emissivity is low (that is, the reflectivity is high), from the viewpoint that the temperature distribution of the sheet glass SG can be controlled effectively. When the surface of the soaking plate 260 is a specular reflection surface, the heat rays (heat radiation) radiated from the sheet glass SG are specularly reflected by the surface of the soaking plate 260 and recurs to the sheet glass SG. The risk of deteriorating the temperature distribution of the sheet glass SG by the reflection state according to the surface shape of 260 increases. The diffuse reflection surface refers to a light reflection surface having a rough or uneven surface, and refers to a surface on which incident light does not reflect only in one specific direction but reflects at various angles.

In this embodiment, the heaters 270a to 270e are provided as the heat source elements along the width direction of the sheet glass SG. However, the heaters 270a to 270e do not emit heat at the ends in the width direction, or the generated heat is low. When the entire heater unit 270 is used as a heat source, the heat distribution of the heat provided by the heater unit 260 may have a distribution in which the heat decreases at positions corresponding to the widthwise ends of the heaters 270a to 270e. Even in such a case, it is possible to provide the sheet glass SG with a smooth mountain-shaped temperature distribution relaxed by using the heat equalizing plate 260 or a constant temperature distribution.

FIG. 6 is a diagram for explaining a plurality of temperature distributions used as a reference used for temperature adjustment of the sheet glass SG. Such temperature distribution is memorize | stored in the control apparatus which is not shown in figure, and is used for control of temperature distribution of the sheet glass SG as target temperature distribution. In the example of the present embodiment, the first temperature distribution P1, the second temperature distribution P2, the third temperature distribution P3, and the fourth temperature distribution P4 are set along the flow direction of the sheet glass SG. Has been. These temperature distributions are targets of the furnace atmosphere temperature distribution measured by a plurality of temperature sensors provided in each of the regions (a plurality of regions sandwiched between the top plates) for adjusting the temperature distribution of the sheet glass SG. Temperature distribution. The actual temperature of the sheet glass SG is considered to be several tens of degrees lower than this temperature distribution.
The second temperature distribution P2 is set on the downstream side in the flow direction of the sheet glass SG with respect to the first temperature distribution P1, and the third temperature distribution P3 is in the flow direction of the sheet glass SG with respect to the second temperature distribution P2. Set on the downstream side. Similarly, the 4th temperature distribution P4 is each set in the flow direction downstream of the sheet glass SG rather than the 3rd temperature distribution P3.

Of the first temperature distribution P1, the first distribution P1a shown in FIG. 6 corresponds to the temperature distribution at the center in the width direction of the sheet glass SG, and the second distribution P1b is at both ends in the width direction of the sheet glass SG. Corresponds to the temperature distribution. The first temperature distribution P1 has a uniform temperature in the center of the Y direction (the width direction of the sheet glass SG) at the same position in the flow direction of the sheet glass SG, and the temperature at both ends in the Y direction is the center in the Y direction. It is set to be lower than the temperature of the part. As described above, the thickness deviation of the glass substrate G can be reduced by setting the temperature of the central portion in the Y direction of the sheet glass SG to be uniform. In the first temperature distribution P1, the difference between the temperature at the center in the Y direction (average temperature) and the temperatures at both ends in the Y direction is set to the first temperature difference T1.

The cooling roller 230 and the uppermost central cooling unit 242 cool the sheet glass SG based on the set first temperature distribution P1. More specifically, the cooling roller 230 is based on the second distribution P1b of the first temperature distribution P1 until the temperature at both ends in the Y-direction decreases to a temperature corresponding to a viscosity of about 10 ^9.0 poise or more. , Quench both ends in the Y direction. The rapid cooling of both ends in the Y direction prevents the surface area of the sheet glass SG immediately below the formed body 210 from being reduced by the surface tension of the sheet glass SG by rapidly increasing the viscosity at both ends in the Y direction, and thus the sheet. This is to keep the width of the glass SG constant.
Further, the uppermost center cooling unit 242 has a temperature in the Y direction center that is higher than the temperatures in both ends in the Y direction based on the first distribution P1a of the first temperature distribution P1, and the center in the Y direction. The amount of cooling is adjusted in accordance with the ambient temperature measured by a temperature sensor (not shown) so that the temperature of the sheet glass SG becomes substantially uniform in the Y direction, and the Y direction center portion of the sheet glass SG is cooled.
Thereby, the temperature distribution corresponding to 1st temperature distribution P1 is provided to the sheet glass SG.

The second temperature distribution P2 is set so that the temperature of the sheet glass SG is lower at any position than the first distribution P1. The second temperature distribution P2 has a first distribution P2a and a second distribution P2b, and has a mountain shape. The first distribution P2a corresponds to the temperature distribution at the center in the Y direction, and the second distribution P2b corresponds to the temperature distribution at both ends in the Y direction. The second temperature distribution P2 is such that, at the same position in the flow direction of the sheet glass SG, the temperature in the center in the Y direction decreases from the center in the Y direction toward both ends in the width direction, and at both ends in the Y direction. The temperature is set to be lower than the temperature at the center in the Y direction. In the second temperature distribution P2, the difference between the temperature at the center in the width direction of the sheet glass SG and the temperature at both ends in the width direction of the sheet glass SG is set to be the second temperature difference T2. .
Among the cooling units 240, the second-stage central cooling unit 242 and the pair of end cooling units 244 have a mountain-shaped second temperature distribution according to the furnace atmosphere temperature measured by a temperature sensor (not shown). The sheet glass SG is cooled by controlling the cooling amount based on P2. Thereby, the temperature distribution corresponding to 2nd temperature distribution P2 is provided to the sheet glass SG.
Similarly, the third and subsequent central cooling units 242 and the pair of end cooling units 244 in the cooling unit 240 are formed in a predetermined mountain shape according to the furnace atmosphere temperature measured by a temperature sensor (not shown). The sheet glass SG is cooled by controlling the cooling amount based on the temperature distribution. The temperature distribution set in this case becomes lower as it goes downstream in the flow direction of the sheet glass SG, the mountain shape of the temperature distribution becomes gentler, and the temperature gradient in the width direction becomes smaller.

The third temperature distribution P3 is set so that the temperature of the sheet glass SG is lower at any position than the second distribution P2. The third temperature distribution P3 is such that, at the same position in the flow direction of the sheet glass SG, the temperature in the center in the Y direction decreases smoothly from the center in the Y direction toward both ends in the Y direction, and both ends in the Y direction. The temperature of the part is set to be lower than the temperature of the central part in the Y direction. In the third temperature distribution P3, the difference between the temperature at the center in the Y direction and the temperature at both ends in the Y direction is set to be the third temperature difference T3. Here, the third temperature difference T3 is smaller than the second temperature difference T2.
The heater unit 270 and the soaking plate 260 cool the sheet glass SG while controlling the amount of heat generated by the heater unit 270 based on the third temperature distribution P3 according to the ambient temperature measured by a temperature sensor (not shown). . This cooling is performed using a heater unit 270 and a soaking plate 260 provided between the top plate 202a and the top plate 202b. Thereby, the smooth temperature distribution of the mountain shape corresponding to 3rd temperature distribution P3 is provided to the sheet glass SG. In the region surrounded by the top plate 202a and the top plate 202b, cooling is performed so that the maximum temperature of the sheet glass SG passes through the annealing point, which is the glass temperature corresponding to a viscosity of about 10 ¹³ poise. It has been broken.

The fourth temperature distribution P4 is substantially uniform along the width direction of the sheet glass SG. The reason for making the temperature distribution uniform in this way is to make the residual strain in the glass substrate as the final product as small as possible. When the temperature distribution in the width direction of the sheet glass SG is not uniform in the vicinity of the strain point, which is the glass temperature corresponding to the viscosity of about 10 ^14.5 poise, the residual strain in the glass substrate that is the final product is As a result, the temperature distribution in the width direction of the sheet glass SG is made uniform in the vicinity of the strain point. For this reason, the 4th temperature distribution P4 is used in the area used as the strain point of the sheet glass SG. The control based on the temperature distribution is performed using a heater unit 270 and a soaking plate 260 provided below the top plate 202b. Therefore, in the cooling (second cooling) of the sheet glass SG performed on the downstream side of the flow of the sheet glass SG from the top plate 202a, not only the temperature of the sheet glass SG, that is, the temperature of the center portion, The sheet glass SG is cooled so as to simultaneously pass through the vicinity of the strain point of the glass SG. Thereby, a certain temperature distribution without a step corresponding to the fourth temperature distribution P4 is given to the sheet glass SG.
Thus, in this embodiment, while controlling the temperature distribution of the sheet glass SG using the soaking plate 260 and the heater unit 270, the maximum temperature of the sheet glass SG (the temperature at the center) is the annealing point and the strain point. The sheet glass SG is cooled so as to pass through.
Note that at least one temperature distribution may be set between the third temperature distribution P3 and the fourth temperature distribution, and the sheet glass SG may be cooled based on the temperature distribution. In this case, the cooling of the sheet glass SG using this temperature distribution is performed by using the heater unit 270 and the soaking plate 260 for cooling the sheet glass SG based on the third temperature distribution, and the sheet based on the fourth temperature distribution. The heating is performed using the heater unit 270 and the soaking plate 260 provided in the area between the heater unit 270 and the soaking plate 260 for cooling the glass SG. The temperature distribution set in this case is, of course, a distribution in which the mountain shape is gentler than the third temperature distribution P3.

In the present embodiment, the region downstream of the top plate 202a in the flow direction of the sheet glass SG is a temperature region in which the sheet glass SG passes through the annealing point to the strain point. That is, since this temperature region is a temperature region in which the sheet glass SG is plastically deformed, this embodiment gives a smooth temperature distribution to the sheet glass SG so as to reduce the amount of warpage of the sheet glass SG in the temperature region. Cool down. In the present embodiment, the sheet glass SG is cooled so that the cooling amount (volume shrinkage amount) at the center of the sheet glass SG is larger than the cooling amount (volume shrinkage amount) at both ends in the above temperature region. A tensile stress is always generated in the flow direction and the width direction of the sheet glass SG at the center portion in the Y direction of the SG to prevent the glass substrate from warping. Therefore, this embodiment can reduce the curvature amount of the glass substrate G. FIG.
In addition, when the temperature distribution of the sheet glass SG is not uniform at the strain point of the sheet glass SG, residual strain occurs in the glass substrate G. In this embodiment, the temperature distribution of the sheet glass SG is at the strain point of the sheet glass SG. Since it becomes substantially uniform, residual strain in the glass substrate G can also be reduced. Furthermore, since the temperature distribution of the sheet glass SG is controlled based on the first temperature distribution P1, the thickness deviation in the glass substrate can also be reduced.

That is, in the present embodiment, in the second cooling (slow cooling) performed in the region between the annealing point position and the strain point position of the sheet glass, in order to reduce the warp and distortion of the glass substrate, The heater unit 270 provided along the width direction is used as a heat source for cooling while controlling the temperature distribution. At this time, the heat distribution of the heater unit 270, which is a heat source, is relaxed by using the heat equalizing plate 260, so that a smooth temperature distribution without a step, for example, a smooth mountain-shaped temperature distribution or a smooth uniform temperature distribution can be obtained. Give to glass SG. Thereby, the glass substrate G which has the curvature amount and distortion amount which satisfy a customer's request | requirement is producible.

Further, the heat distribution of the heater unit 270 that is a heat source is reduced because the single heat equalizing plate 260 provided between the sheet glass SG and the heater unit 270 reduces the heat distribution of the heater unit 270. Even if there is a step in the heat distribution generated by the above, it is possible to provide a relaxed and smooth temperature distribution (a temperature distribution in a mountain shape or a uniform temperature distribution) over the entire width of the sheet glass SG. For this reason, the curvature amount and distortion amount in the glass substrate G can be further reduced.

Since the soaking plate 260 of the present embodiment is a stainless metal plate having an oxide film formed on the surface by oxidation treatment, the emissivity of heat radiated from the soaking plate 260 to the sheet glass SG is increased. Therefore, the heat distribution generated by the heater unit 270 can be effectively relaxed by the soaking plate 260.

In the present embodiment, at least a pair of temperature adjusting devices are provided on both sides of the sheet glass SG, and each of the pair of temperature adjusting devices uses the heater unit 270 and the soaking plate 260 to heat the sheet glass SG. Therefore, the temperature distribution of the sheet glass SG can be controlled from both sides of the sheet glass SG. For this reason, the curvature amount and distortion amount in the glass substrate G can be reduced.

Furthermore, in the present embodiment, the heater unit 270 supplies heat to the heat equalizing plate 260 according to the distribution of the amount of heat generated by the heater unit 270, so the temperature of the sheet glass SG is easily controlled by the amount of heat generated by the heaters 270a to 270e. be able to. At this time, the distribution of the calorific value is a single mountain-shaped distribution that is maximized at the center in the width direction of the sheet glass SG, and therefore, a single temperature that is a preferable temperature distribution that can reduce the amount of warpage in the glass substrate G. The temperature distribution of the shape can be efficiently given to the sheet glass SG. Further, since the distribution of the calorific value is a uniform distribution, it is possible to efficiently give the sheet glass SG a uniform temperature distribution without a step, which is a preferable temperature distribution capable of reducing the amount of distortion in the glass substrate G. it can.

A distribution in which the heat distribution of the heat supplied by the heater unit 270 toward the sheet glass SG includes a distribution that decreases at positions corresponding to the widthwise ends of the sheet glass SG of the respective heaters 270a to 270e, and as a result includes a step. Even so, the soaking plate 260 can provide the sheet glass SG with a smooth, uniform temperature distribution or a uniform temperature distribution by relaxing the heat distribution of the heat generated by the heater unit 270.

FIG. 7 is a schematic diagram comparing the temperature distribution A of the sheet glass SG when there is no soaking plate 260 and the temperature distribution B of the sheet glass SG formed corresponding to the above-described third temperature distribution P3. is there. As shown in FIG. 7, when there is no soaking plate 260, the temperature distribution A of the sheet glass SG has a level difference depending on the amount of heat generated by the heaters 270a to 270e. However, by providing the soaking plate 260 between the sheet glass SG and the heaters 270a to 270e, a smooth mountain shape like the temperature distribution B is obtained. For this reason, it can suppress that the sheet glass SG and by extension the glass substrate G originate in the level | step difference of the temperature distribution of the sheet glass SG. Although not shown, when there is no soaking plate 260, the heaters 270a to 270e are arranged in the width direction with a gap therebetween, so that the temperature distribution of the sheet glass SG is locally corresponding to the gap. Even in the case of a distribution that falls, by providing the soaking plate 260 between the sheet glass SG and the heaters 270a to 270e, a smooth mountain shape like the temperature distribution B is obtained. For this reason, it can suppress that the sheet glass SG and by extension the glass substrate G originate in the level | step difference of the temperature distribution of the sheet glass SG.

FIG. 8 is an actual measurement diagram showing how the measured temperature of the surface of the sheet glass SG changes depending on the presence or absence of the soaking plate 260. The measured temperature is measured using an infrared radiation thermometer directly under the soaking plate. The heater unit 270 is provided with seven heaters in the width direction, the central heater 1 is the longest in the width direction, and is changed according to the total width of the sheet glass SG, and six heaters ( In FIG. 8, only heaters 2 to 4 are shown. Of the heaters 2 to 4, the heaters 3 and 4 have a constant length regardless of the total width of the sheet glass SG, and the heater 2 adjacent to the central heater is approximately 1.5 times longer than the heaters 3 and 4. Thus, a profile is realized in which the temperature gradient is very gentle near the center of the sheet glass SG and gradually increases toward the end near the end.
FIG. 8 shows the temperature distribution on one side from the center of the sheet glass SG. Since there is no soaking plate 260, the heat of the heater is directly transferred, so the temperature of the sheet glass SG is higher than when there is a soaking plate, but the temperature drops locally in the region X and decreases. ing. This decrease in temperature is about 1.5 degrees. Such a region X in which the temperature decreases corresponds to a gap between the heater 1 and the heater 2, between the heater 2 and the heater 3, and between the heater 3 and the heater 4. It is thought that this is because the On the other hand, when there is the soaking plate 260, a local temperature decrease as in the region X is not observed, and it can be seen that the temperature distribution of the sheet glass SG is a one-sided temperature distribution. In FIG. 8, when the soaking plate 260 is present, the glass temperature is lowered from several degrees C. to several tens of degrees C. compared to the case where the soaking plate 260 is not present. The degree of reduction depends on the emissivity of the soaking plate 260, and the degree of reduction becomes smaller as the emissivity approaches 1.0. Therefore, keeping the emissivity of the soaking plate 260 high is important for improving the heat exchange efficiency between the heaters 1 to 4 and the sheet glass SG.

[Example]
In order to investigate the effect of this embodiment, the glass substrate was manufactured using the manufacturing method of a glass substrate. In addition, the glass raw material was prepared so that it might become the following compositions.
SiO ₂ 61%,
Al ₂ O ₃ 17%,
B ₂ O ₃ 11%,
CaO 6%,
SrO 3%,
BaO 1%

For each of the produced glass substrates, one piece (8 pieces / day) was sampled every 3 hours over one week, and the flatness and strain were measured for each 56 pieces of samples, and the average value of each was calculated. did.
As a result, the flatness of the glass substrate produced by the glass substrate molding apparatus having the soaking plate 260 of the present embodiment is equal to the glass substrate produced by the conventional glass substrate molding apparatus not having the soaking plate 260. The flatness was reduced by 5%. The amount of strain of the glass substrate manufactured by the glass substrate molding apparatus having the soaking plate 260 of the present embodiment was reduced by 5% from the amount of strain of the glass substrate manufactured by the conventional glass substrate molding apparatus.
In addition, about flatness, it measured using the laser displacement meter. In addition, the birefringence amount is measured at a plurality of predetermined measurement positions using a birefringence measuring instrument ABR-10A manufactured by UNIOPT, and the maximum value of the measured birefringence amounts is used as the distortion amount. Adopted.
From this, the effect of the manufacturing method of the glass substrate of this embodiment is clear.

In the cooling process of the present embodiment, at least a pair of temperature adjusting devices including the heater unit 270 and the heat equalizing plate 260 are provided on both sides of the sheet glass SG to perform cooling, but the temperature adjusting device is the sheet glass SG. You may cool by the structure provided only in the surface of one side. However, in order to further reduce warpage and distortion in the glass substrate, it is preferable that the temperature adjusting device is provided on both surfaces of the sheet glass SG.
In the present embodiment, a heater unit including a plurality of heaters is used as a heat source. However, the heat source is not limited to a heater that is a heat source that radiates heat, and a high-temperature air blowing device that provides hot air toward the sheet glass SG is used as a sheet. A plurality of glass SGs may be provided in the width direction.

As mentioned above, although the manufacturing method and shaping | molding apparatus of the glass substrate of this invention were demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, even if various improvement and a change are carried out. Of course it is good.

DESCRIPTION OF SYMBOLS 100 Melting apparatus 101 Melting tank 102 Clarification tank 103 Stirring tank 104 1st piping 105 2nd piping 106 3rd piping 200 Molding apparatus 201 Molding furnace 202

Slow cooling furnace

202a, 202b Top plate 210 Molded body 212 Groove 213 Lower end 220 Atmosphere partition member 230 Cooling roller 240 Cooling unit 242 Central cooling unit 242 Cooling amount adjustment unit 244 End cooling unit 250a to 250c Conveying roller 260 Heat equalizing plate 270 Heater unit 270a to 270e Heater 300 Cutting device

Claims

A method of manufacturing a glass substrate,
Forming a continuous sheet glass by overflowing the molten glass from the molded body, and forming a flow of the sheet glass;
In order to reduce the warp and distortion of the glass substrate, the sheet glass is used for the sheet glass by using the heat source while relaxing the heat distribution supplied by the heat source provided along the width direction of the sheet glass. And a cooling step including a slow cooling process for cooling by giving a temperature distribution along the width direction of
The slow cooling treatment is performed between a slow cooling point position in the flow direction of the sheet glass corresponding to a slow cooling point of the sheet glass and a strain point position in the flow direction of the sheet glass corresponding to a strain point of the sheet glass. It is performed in the area | region of the flow direction of the said sheet glass, The manufacturing method of the glass substrate characterized by the above-mentioned.
The heat distribution of the heat source is relaxed by using one soaking plate provided between the sheet glass and the heat source, the soaking plate relaxes the heat distribution of the heat source, and The manufacturing method of the glass substrate of Claim 1 which supplies heat to sheet glass.
The method for producing a glass substrate according to claim 2, wherein the soaking plate is a stainless metal plate having an oxide film formed on the surface by oxidation treatment.
The cooling step is performed using at least a pair of temperature adjusting devices provided on both sides of the sheet glass, and each of the at least one pair of temperature adjusting devices uses the heat source and the heat equalizing plate. The method for producing a glass substrate according to any one of claims 1 to 3, wherein heat is supplied to the sheet glass.
The method for manufacturing a glass substrate according to any one of claims 1 to 4, wherein the heat distribution is a distribution of a calorific value of the heat source.
The method for manufacturing a glass substrate according to any one of claims 1 to 5, wherein the temperature distribution is a single-peak distribution that is maximum at the center in the width direction or a uniform distribution.
The heat source includes a plurality of heat source elements provided in the width direction,
The production of a glass substrate according to any one of claims 1 to 6, wherein the heat distribution of the heat source includes a distribution in which heat supplied at a position corresponding to the end in the width direction of each of the heat source elements decreases. Method.
A method of manufacturing a glass substrate,
A molding step of overflowing the molten glass from the molded body and molding the sheet glass;
A pair of heat sources provided along the width direction of the sheet glass gives a slow cooling process for cooling the sheet glass by providing a temperature distribution along the width direction of the sheet glass on both surfaces of the sheet glass. Including a cooling step,
In the slow cooling treatment, the glass substrate is slowly cooled through the sheet glass between a pair of plate members arranged between the pair of heat sources and the sheet glass.
The plate material is a soaking plate that relaxes the heat distribution supplied by the heat source provided along the width direction of the sheet glass,
The slow cooling treatment is performed between a slow cooling point position in the flow direction of the sheet glass corresponding to a slow cooling point of the sheet glass and a strain point position in the flow direction of the sheet glass corresponding to a strain point of the sheet glass. The method for producing a glass substrate according to claim 8, wherein the heat soaking plate is used in a region in the flow direction of the sheet glass.
The method for producing a glass substrate according to claim 9, wherein the heat soaking plate has a thermal conductivity of 10 W / (m · K) or more.
A glass substrate molding apparatus,
A molding furnace for overflowing the molten glass from the molded body and molding the sheet glass;
A pair of heat sources provided along the width direction of the sheet glass gives a slow cooling process for cooling the sheet glass by providing a temperature distribution along the width direction of the sheet glass on both surfaces of the sheet glass. A cooling furnace to perform,
In the slow cooling process, the glass substrate forming apparatus is characterized in that the sheet glass is gradually cooled between a pair of plate members disposed between the pair of heat sources and the sheet glass.
The plate material is a soaking plate that relaxes the heat distribution supplied by the heat source provided along the width direction of the sheet glass,
The cooling furnace is configured to perform the slow cooling treatment in the flow direction of the sheet glass corresponding to the slow cooling point position in the flow direction of the sheet glass corresponding to the slow cooling point of the sheet glass and the strain point of the sheet glass. The apparatus for forming a glass substrate according to claim 11, which is performed using the heat-uniforming plate in a region in the flow direction of the sheet glass between the point positions.
The heat source is a heater that radiates heat toward both surfaces of the sheet glass,
The said board | plate material is a glass substrate shaping | molding apparatus of Claim 11 or 12 arrange | positioned so that the whole surface facing the said sheet glass of the said heater may be interrupted | blocked.
A glass substrate molding apparatus,
Forming a continuous sheet glass by overflowing the molten glass from the molded body, and forming a flow of the sheet glass;
In order to reduce the warp and distortion of the glass substrate, the sheet glass is used for the sheet glass by using the heat source while relaxing the heat distribution supplied by the heat source provided along the width direction of the sheet glass. And a cooling furnace that performs a slow cooling process that cools by giving a temperature distribution along the width direction of
The cooling furnace is configured to perform the slow cooling treatment in the flow direction of the sheet glass corresponding to the slow cooling point position in the flow direction of the sheet glass corresponding to the slow cooling point of the sheet glass and the strain point of the sheet glass. An apparatus for forming a glass substrate, which is performed in a region in the flow direction of the sheet glass between the point positions.