WO2013005409A1

WO2013005409A1 - Method for manufacturing glass sheet

Info

Publication number: WO2013005409A1
Application number: PCT/JP2012/004262
Authority: WO
Inventors: 浩幸苅谷
Original assignee: ＡｖａｎＳｔｒａｔｅ株式会社
Priority date: 2011-07-01
Filing date: 2012-06-29
Publication date: 2013-01-10
Also published as: JPWO2013005409A1; JP5452724B2; TWI429602B; KR101372609B1; CN103140447B; TW201309605A; KR20130024881A; CN103140447A

Abstract

A glass ribbon is formed from molten glass in such a manner that the molten glass is caused to overflow a supply groove in the upper part of a forming body, the molten glass is allowed to flow down along the wall surfaces on both sides of the lower part of the forming body while the flow of the molten glass is restricted by a pair of guides protruding from the wall surfaces of the forming body, the molten glass is conducted to the lowermost end of the forming body, and the streams of the molten glass flowing along the wall surfaces on both sides are merged at the lowermost end. The wall surfaces of the forming body along which the molten glass flows include: vertical wall surfaces along which the molten glass flows down in the vertical direction; and sloped wall surfaces for conducting the molten glass, which has flowed down along the vertical wall surfaces, to the lowermost end of the forming body. In the entire region in which the guides protrude from the sloped wall surfaces, the height of the pair of guides from the wall surfaces is set to be less than the thickness of the molten glass.

Description

Manufacturing method of glass plate

The present invention relates to a method for producing a glass plate by a downdraw method.

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 most often used to manufacture such a large FPD glass substrate. The overflow down draw method includes a step of forming a glass ribbon below the formed body by causing the molten glass to overflow from the upper part of the formed body in a forming furnace, and a step of gradually cooling the glass ribbon in a slow cooling furnace. The slow cooling furnace draws the glass ribbon between the pair of rollers and stretches it to a desired thickness, and then slowly cools the glass ribbon. Thereafter, the glass ribbon is cut to a predetermined size to form a glass plate, which is laminated on another glass plate and stored. Or a glass plate is conveyed by the following process. About the downdraw method, it describes in the following patent document 1, for example.

In such an overflow down draw method, glass ribbon can be formed with a stable shape at both ends (ear portions) of the glass ribbon to be formed even when the viscosity of the molten glass is relatively high. An apparatus is known (Patent Document 2).
In the glass forming apparatus, the upper surface on which a supply groove for supplying molten glass is formed, and the molten glass that overflows on both sides of the supply groove from the supply groove along the upper surface and flows down from both ends of the upper surface is guided and fused. And a pair of guides that oppose each other and regulate the width of the molten glass flowing down along the pair of wall surfaces. Each of the pair of guides has a downwardly sharp outline with the point on the ridge line formed by the lower ends of the pair of wall surfaces intersecting each other when viewed from the opposite direction.

JP 10-291826 A JP 2010-189220 A

However, when the above glass forming apparatus is used, the shape of both ends of the glass ribbon may not be sufficiently stabilized. In the overflow down draw method, the glass ribbon formed by the glass forming apparatus is stably maintained at a constant thickness at the ears that are both ends in the width direction of the glass ribbon, as shown in FIG. It is preferable.

However, in the glass forming apparatus described in Patent Document 2, the molten glass that has flowed through the walls on both sides of the formed body is joined and bonded together at the lowermost end of the formed body. As shown in FIG. 9B, the molten glass ears may open in a bifurcated shape while undulating in the longitudinal direction of the glass ribbon. Such a shape of the ear portion may cause the glass ribbon to break, and the glass ribbon may not be continuously operated.

Therefore, an object of the present invention is to provide a method for producing a glass plate, in which the shape of the ear portion of the glass ribbon can be made more stable than before, and the glass ribbon can be formed.

One embodiment of the present invention is a method for producing a glass plate by a downdraw method. The manufacturing method is
A melting step of melting glass raw material to obtain molten glass;
The molten glass is supplied to a supply groove provided in the upper part of the molded body, thereby overflowing the molten glass from the upper part of the supply groove, and melted by a pair of guides protruding from the wall surface of the molded body. While restricting the flow width of the glass, the molten glass is caused to flow down along the respective wall surfaces on both sides of the lower part of the molded body, and the molten glass flowing down is guided to the lowermost end portion of the molded body, Forming a glass ribbon by joining the molten glass flowing through each of the wall surfaces;
A slow cooling step for cooling the glass ribbon flowing in the slow cooling furnace;
A cutting step of cutting the cooled glass ribbon.
The wall surface of the molded body includes a vertical wall surface in which the molten glass overflowing from the supply groove flows down in the vertical direction, and the vertical wall surface that guides the molten glass that has flowed down the vertical wall surface to the lowest end portion of the molded body. Connected inclined wall surfaces.
In the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the inclined wall surface is a thickness of the molten glass flowing through the inclined wall surface in such a range that the molten glass does not get over the pair of guides. It is set low compared to.

At this time, in the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the inclined wall surface is preferably lower at a position below the molded body.

In the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the inclined wall surface decreases continuously or stepwise as it goes downward of the molded body. preferable.

It is preferable that the lowermost end portion of the molded body is a linear ridgeline in which the inclined wall surfaces on both sides are connected, and the lowermost end portions of the pair of guides are located on the ridgeline.

In the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the inclined wall surface may be, for example, 10 mm to 20 mm lower than the thickness of the molten glass flowing through the inclined wall surface. it can.

The viscosity of the molten glass flowing down the wall surface can be set to 3000 to 60000 [Pa · sec].

One embodiment of the present invention is also a method for manufacturing a glass plate by a downdraw method. The method is
A melting step of melting glass raw material to obtain molten glass;
The molten glass is supplied to a supply groove provided in the upper part of the molded body, thereby overflowing the molten glass from the upper part of the supply groove, and melted by a pair of guides protruding from the wall surface of the molded body. While restricting the flow width of the glass, the molten glass is caused to flow down along the respective wall surfaces on both sides of the lower part of the molded body, and the molten glass flowing down is guided to the lowermost end portion of the molded body, Forming a glass ribbon by joining the molten glass flowing through each of the wall surfaces;
A slow cooling step for cooling the glass ribbon flowing in the slow cooling furnace;
A cutting step of cutting the cooled glass ribbon.
The wall surface of the molded body includes a vertical wall surface in which the molten glass overflowing from the supply groove flows down in the vertical direction, and the vertical wall surface that guides the molten glass that has flowed down the vertical wall surface to the lowest end portion of the molded body. Connected inclined wall surfaces.
At this time, the pair of guides has a shape along the outer shape of the cross section of the molded body, and has a lowermost portion at the lowermost end portion of the molded body, and the guide from the inclined wall surface. The height from the wall surface of the pair of guides is provided lower than the thickness of the molten glass flowing through the wall surface in the entire region from which the molten glass flows, so that the both ends at the ends when the molten glass merges are provided. Reduce the thickness of the molten glass.

At this time, in the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the wall surface is preferably lower at a position below the molded body.

In the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the wall surface is preferably reduced continuously or stepwise as it goes downward of the molded body. .

In the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the wall surface can be, for example, 10 mm to 20 mm lower than the thickness of the molten glass flowing through the wall surface.

The method for producing a glass ribbon according to the above aspect can form a glass ribbon while making the shape of the ear portion of the glass ribbon more stable than the conventional one.

It is process drawing of the manufacturing method of the glass plate of this embodiment. It is a figure which shows typically the apparatus which performs the melting process-cutting process of this embodiment. It is a figure which mainly shows the structure of the shaping | molding apparatus which performs the shaping | molding process and slow cooling process of this embodiment. It is a figure explaining the forming process of this embodiment in detail. It is a figure explaining the guide plate and molten glass used for this embodiment. It is a figure explaining the guide plate and molten glass used for the manufacturing method of the conventional glass plate. (A), (b) is a figure explaining a mode that the molten glass in the past merges, and a mode that the molten glass in this embodiment merges. It is a figure which shows the form different from the guide plate used for this embodiment. (A) is sectional drawing which shows the ear | edge part of the normal shape of a glass ribbon, (b) is sectional drawing which shows the ear | edge part of the shape defect of a glass ribbon.

Hereinafter, the manufacturing method of the glass plate of this embodiment is demonstrated.

(Overall overview of glass plate manufacturing method)
FIG. 1 is a process diagram of a method for producing a glass plate.
The glass plate manufacturing method includes a melting step (ST1), a refining step (ST2), a homogenizing step (ST3), a supplying step (ST4), a forming step (ST5), and a slow cooling step (ST6). And a cutting step (ST7). In addition, a plurality of glass plates that have a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like and are stacked in the packing process are conveyed to a supplier.

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 200, a forming apparatus 300, and a cutting apparatus 400. The melting apparatus 200 includes a melting tank 201, a clarification tank 202, a stirring tank 203, a first pipe 204, and a second pipe 205. The molding apparatus 300 will be described later.

In the melting step (ST1), the glass raw material supplied into the melting tank 201 is heated and melted with a flame and an electric heater (not shown) to obtain molten glass.
The clarification step (ST2) is performed in the clarification tank 202, and by heating the molten glass in the clarification tank 202, bubbles contained in the molten glass grow by the oxidation-reduction reaction of the clarifier and float on the liquid surface. The gas component in the bubble is released or the gas component in the bubble is absorbed into the molten glass, and the bubble disappears.
In the homogenization step (ST3), the molten glass in the stirring tank 203 supplied through the first pipe 204 is stirred using a stirrer to homogenize the glass components.
In the supplying step (ST4), the molten glass is supplied to the forming apparatus 300 through the second pipe 205.

In the molding apparatus 300, a molding process (ST5) and a slow cooling process (ST6) are performed.
In the forming step (ST5), the molten glass is formed into a glass ribbon G (see FIG. 3) to make a flow of the glass ribbon G. In this embodiment, an overflow down draw method using a molded body 310 described later is used. In the slow cooling step (ST6), the glass ribbon G that has been formed and flows has a desired thickness and is cooled.
In the cutting step (ST7), the cutting device 400 cuts the glass ribbon G supplied from the forming device 300 into a predetermined length, thereby obtaining a plate-like glass plate G1 (see FIG. 3). The cut glass plate G1 is further cut into a predetermined size to produce a glass plate G1 having a target size. Thereafter, grinding, polishing, and cleaning of the glass end surface are performed, and after the presence of abnormal defects such as bubbles and striae is inspected, the glass plate G1 that has passed the inspection is packed as a final product.

(Description of molding process and slow cooling process)
FIG. 3 is a diagram mainly showing a configuration of a molding apparatus 300 that performs the molding process and the slow cooling process.
The glass plate molded by the molding apparatus 300 is preferably used for, for example, a glass substrate for liquid crystal display, a glass substrate for organic EL display, and a cover glass. In addition, it can be used as a display for a portable terminal device, a cover glass for a casing, a touch panel plate, a glass substrate of a solar cell, or a cover glass.

The forming furnace 40 that performs the forming step (ST5) and the slow cooling furnace 50 that performs the slow cooling step (ST6) are surrounded by a furnace wall made of refractory bricks. The molding furnace 40 is provided vertically above the slow cooling furnace 50. The forming furnace 40 and the slow cooling furnace 50 are collectively referred to as a furnace 30. In the furnace inner space surrounded by the furnace wall of the furnace 30, a molded body 310, a cooling roller 330, and conveying rollers 350a to 350c are provided.
The molded body 310 forms the molten glass flowing from the melting device 200 through the second pipe 205 shown in FIG. Thereby, the flow of the glass ribbon G of the vertically lower direction is made in the forming apparatus 300. The molded body 310 is a long and narrow structure made of refractory brick or the like, and has a wedge-shaped cross section as shown in FIG. A supply groove 312 serving as a flow path for guiding the molten glass is provided in the upper part of the molded body 310. The supply groove 312 is connected to the second pipe 205 at a supply port provided in the molding apparatus 300, and the molten glass flowing through the second pipe 205 flows along the supply groove 312. The depth of the supply groove 312 is shallower toward the downstream side of the flow of the molten glass, so that the molten glass overflows vertically downward from the groove 312.
The molten glass overflowing from the supply groove 312 flows down along the vertical wall surface and the inclined wall surface of the side wall on both sides of the molded body 310. The molten glass that has flowed through the side walls merges at the lower end 313 of the molded body 310 shown in FIG. 3 to form one glass ribbon G. The molding process will be described in detail later.

A cooling roller 330 is provided below the molded body 310. The cooling roller 330 is in contact with the surface of the glass ribbon G near both ends in the width direction of the glass ribbon G, pulls the glass ribbon G downward to form the glass ribbon G to a desired thickness, and cools the glass ribbon G. .

Below the cooling roller 330, transport rollers 350a to 350c are provided at predetermined intervals, and the glass ribbon G is pulled downward. A lower space including the cooling roller 330 is a furnace internal space of the slow cooling furnace 50. Each of the transport rollers 350a to 350c has a pair of rollers and is provided at both end portions in the width direction of the glass ribbon G so as to sandwich both sides of the glass ribbon G.
As described above, the forming apparatus 300 forms the glass ribbon G from the molten glass flowing down through the formed body 310. At that time, the molded glass ribbon G changes from a flow that drops vertically on the wall surface of the molded body 310 according to gravity to a flow that is forcibly drawn downward using the cooling roller 330 and the conveying rollers 350a to 350c positioned below. Change.

FIG. 4 is a diagram illustrating the molding process in detail.
The molded body 310 used in the molding process mainly includes a main body portion 314 and a pair of guide plates 316. As shown in FIG. 4, the direction in which the molten glass is supplied is defined as the X direction. This direction is also the width direction of the molten glass flowing on the wall surface of the molded body 310.
The main body 314 is a long member whose cut surface forms a pentagon when cut along a plane perpendicular to the X direction, and is composed of refractory bricks. The pair of guide plates 316 are plate members made of platinum or a platinum alloy, and are provided at both end portions of the main body portion 314 and function as guide portions for molten glass, which will be described later. Each of the guide plates 316 has a substantially pentagonal shape having a larger area than the pentagonal shape of the main body portion 314 by the height of the guide portion described later. Of the pair of guide plates 316, the guide plate 316 on the side connected to the second pipe 205 is provided with a notch for supplying molten glass to the supply groove 312 of the main body 314.

The molding apparatus 300 causes the molten glass to overflow from the upper part of the supply groove 312 by supplying the molten glass to the supply groove 312 provided at the upper part of the molded body 310 via the second pipe 205. At that time, the pair of guide portions protruding from the wall surface of the molded body 310 regulates the width of the flow of the molten glass, and causes the molten glass to flow down along the wall surfaces of the respective side walls on the lower side of the molded body 310. The forming apparatus 300 forms the glass ribbon G by guiding the molten glass flowing down to the lowermost end portion 313 of the molded body 312 and joining the molten glass flowing through the both wall surfaces at the lowermost end portion 313. The formed glass ribbon G is pulled downward by the cooling roller 330.
The wall surface of the molded body 310 includes a vertical wall surface 313a where the molten glass overflowing from the supply groove 312 flows down vertically, and a vertical wall surface 313a that guides the molten glass flowing down the vertical wall surface 313a to the lowest end portion 313 of the molded body 310. And an inclined wall surface 313b connected to the. Therefore, the molten glass overflowing from the supply groove 312 of the molded body 310 travels through the vertical wall surfaces 313a on both sides when the molded body 310 is viewed in the X direction, and then travels along the inclined wall surfaces 313b to reach the lowermost end portion 313. At this time, in the entire area of the vertical wall surface 313a and the entire area where the guide plate 316 protrudes from the inclined wall surface 313b, the height from the wall surface (vertical wall surface 313a, inclined wall surface 313b) of the guide portion of the pair of guide plates 316 is melted. As long as the glass does not pass over the pair of guide plates 316, the glass is provided lower than the thickness of the molten glass flowing through the wall surfaces (vertical wall surface 313a and inclined wall surface 313b). The guide portion is an edge portion of the guide plate 316 and is a portion protruding from the vertical wall surface 313a and the inclined wall surface 313b, and refers to a portion that regulates the position and width of the molten glass flowing along the wall surface.

FIG. 5 is a view for explaining the guide plate 316 and the molten glass viewed from the guide plate 316 on the downstream side in the X direction shown in FIG. 4 in the direction opposite to the X direction. As shown in FIG. 5, the height of the guide portions of the pair of guide plates 316 from the vertical wall surface 313a and the inclined wall surface 313b is within the range where the molten glass does not get over the guide portions of the pair of guide plates 316. It is lower than the thickness of the molten glass G flowing through (the vertical wall surface 313a and the inclined wall surface 313b). On the other hand, the height of the upper guide portion of the guide plate 316 is higher than the thickness of the molten glass flowing through the upper portion. The difference between the thickness of the molten glass and the height from the wall surface of the guide portion of the guide plate 316 in the vertical wall surface 313a and the inclined wall surface 313b, that is, the height at which the molten glass protrudes from the guide portion is, for example, 10 to 20 mm. It is. In this range, the shape of the molten glass can be maintained by the surface tension of the molten glass, and the guide portion is prevented from getting over. That is, in the entire region where the guide portion protrudes from the inclined wall surface 313b, the height of the guide portion from the inclined wall surface 313b is, for example, 10 mm to 20 mm lower than the thickness of the molten glass flowing through the inclined wall surface 313b. The temperature of the molten glass when the molten glass flows through the vertical wall surface 313a and the inclined wall surface 313b is, for example, 1230 ° C. or less and in the range of 1110 ° C. or more, and the viscosity, which is the viscosity characteristic of the molten glass at that time, For example, it is preferably 3000 to 60000 Pa · sec, and more preferably 4000 to 50000 Pa · sec. In this range, the flow of the molten glass can be reliably regulated by the guide portion.
The viscosity of the molten glass exhibits an internal resistance so that the velocity inside the fluid is made uniform when shear is acting in the flow field inside the fluid. Therefore, even if shearing works in the flow field inside the fluid as the molten glass tries to get over the guide portion, the molten glass is more difficult to get over due to internal resistance when the viscosity is large than when the viscosity is small.
As shown in FIG. 4, the lowest end portion 313 of the molded body 310 is a linear ridge line 313c in which the inclined wall surfaces 313b on both sides are connected, and the height of the guide portion of the guide plate 316 on the inclined wall surface is It is substantially zero at the lowermost end 313 (ridge line 313c). That is, the lowermost end portion of the guide portion is located on the ridge line where the two inclined wall surfaces 313b intersect. Further, the guide portion has a lowermost end portion at the lowermost end portion of the molded body 310. Further, when the lowermost end portion of the guide portion is located on the ridge line, or when the guide portion has a lowermost portion at the lowermost end portion of the molded body 310, the lowermost end portion of the guide portion and the molded body 310 The allowable range of displacement in the flow direction of the molten glass with respect to the lowermost end is 10 mm with respect to the upper limit, preferably 8 mm, more preferably 6 mm.

The viscosity of the molten glass flowing through the molded body 310 can be obtained by converting from the temperature of the molten glass using a temperature-viscosity curve diagram prepared in advance. The above temperature-viscosity curve diagram is obtained by plotting the measurement results at this time by measuring a plurality of viscosities of molten glass having a predetermined glass composition under different temperature conditions. The viscosity at each position of the molded body 310 is specifically calculated by measuring the temperature of the molten glass flowing through the molded body 310 at each position and using the temperature-viscosity curve from the measured temperature. The temperature of the molten glass is obtained by using a method of converting the atmospheric temperature value at each position of the molded body 310 detected using a thermocouple into a molten glass temperature obtained in advance, or melting with a radiation thermometer. It is obtained by measuring the surface temperature of the glass. The viscosity used for creating the temperature-viscosity curve diagram is measured by a well-known ball pulling method. The ball pulling method is a method in which molten glass is used as a Newtonian fluid and the resistance is measured using a balance to determine the viscosity. Specifically, the platinum ball is immersed in the molten glass and the platinum ball is pulled up at a constant speed. In this method, the resistance force of the platinum sphere is measured, and the viscosity is obtained by applying the measurement result to the well-known Stokes law.

At this time, when the height of the guide portion (the position of the top portion in the height direction) decreases linearly as it goes downward of the molded body 310 and becomes 0 at the lowermost end portion 313, the top portions of the guide portions shown in FIG. Is less than 180 degrees, preferably 120 degrees or less, more preferably 90 degrees or less. Therefore, it can be said that the guide portion has a shape along the outer shape of the cross section of the inclined wall surface 313b. In this case, “the shape along the outer shape of the cross-section of the inclined wall surface 313b” means that the edge of the guide portion is inclined substantially the same as the inclination of the inclined wall surface 313b. It means that it inclines to the same side as the inclination with respect to the horizontal surface in the inclined wall surface 313b. In this case, the inclination may be a constant ratio or an inclination that changes the inclination angle stepwise or continuously. Further, in the case of an inclination that changes the inclination angle stepwise or continuously, the edge of the guide portion may be inclined at a constant inclination angle so as to be directed to the vicinity of the lowermost end portion 313 of the molded body 310. Inclination may be performed while changing the inclination angle continuously or continuously. Here, the vicinity of the lowermost end portion 313 refers to a region within 10 mm from the position of the lowermost end portion 313 in the flow direction of the molten glass.
In addition, the height of the guide part of the guide plate 316 in the inclined wall surface 313b is lower as the position is lower than the molded body 310. The height of such a guide portion may be such that the height decreases linearly at a constant ratio (gradient), or the ratio (gradient) at which the height decreases may vary discontinuously, It may change continuously. In the embodiment shown in FIG. 5, the ratio (gradient) at which the height of the guide portion is lowered changes discontinuously. Further, as described above, the height of the guide portion protruding from the inclined wall surface 313b continuously decreases toward the lower side of the molded body 310 in the entire protruding region. Good.
As described above, the height of the guide portion can be lowered as it approaches the position of the lowermost end portion 313 of the molded body 310. The viscosity of the molten glass gradually increases, and the cooling roller 330 and the conveying rollers 350a to 350a- This is because the thickness of the molten glass gradually decreases toward the target thickness by pulling 350c.
By determining the height of the guide portion of the guide plate 316 as described above, it is possible to suppress the molten glass from moving away from the wall surface along the guide portion and vertically downward. That is, after the molten glass passes through the lowermost end portion 313 of the molded body 310, the lamination with the molten glass flowing down the other wall surface is stabilized, and a bifurcated ear portion as shown in FIG. 9B is generated. The glass ribbon G having the shape as shown in FIG. 9A can be stably flowed.
In addition, the viscosity of the molten glass that passes through the lowermost end 313 is, for example, 20000 to 50000 Pa · second, in that the shape of the ear portion of the glass ribbon is stably formed as shown in FIG. preferable.
The viscosity of the molten glass when it flows through the wall surface of the molded body 310 and the viscosity of the molten glass that passes through the lowermost end 313 are controlled by a heating device such as a heater (not shown) provided in the molding furnace 40. By adjusting, it can set in the said range.

FIG. 6 is a view for explaining a conventional guide plate 316 ′ and molten glass flowing through the molded body 310 ′. FIGS. 7A and 7B are views for explaining a state in which the conventional molten glass is merged and a state in which the molten glass in the present embodiment is merged.

The conventional molded body 310 ′ has the same size, the same shape, and the same configuration as the molded body 310 in the above embodiment. The guide plate 316 ′ is larger than the guide plate 316 of the above embodiment, and as shown in FIG. 6, the guide portion protruding from the wall surface of the side wall of the molded body 310 ′ is higher than the guide portion in the above embodiment. Is high. Therefore, as shown in FIG. 6, the whole edge part of the molten glass width direction contacts a guide part. Since the guide plate 316 ′ having the guide portion uses platinum having a good wettability with the molten glass, the guide portion also has a high wettability with the end portion of the molten glass. For this reason, the molten glass wetted with the guide portion tends to flow vertically downward as indicated by an arrow shown in FIG. For this reason, the molten glass located in the vicinity of the ear | edge part which contacts a guide part to the vicinity of the lowest end part 313 has a big component which tends to flow through a guide part to the perpendicular downward direction. For this reason, the width w ′ in the thickness direction of the two molten glasses that merge at the lowermost end portion 313 ′ is wider than the width of the central portion in the width direction of the molten glass, and the bifurcated shape as shown in FIG. Shaped ears are likely to occur. That is, molten glass may not merge at the end.

On the other hand, the molten glass flowing down the molded body 310 of the present embodiment has a smaller contact area between the molten glass and the guide portion where platinum having good wettability is used, compared to the conventional guide portion. A component that tends to flow vertically downward along the guide portion is small. Therefore, as shown in FIG. 7 (b), the width w in the thickness direction of the two molten glasses that merge at the lowermost end portion 313 is equal to the width of the central portion in the width direction of the molten glass. It is difficult to generate a bifurcated ear as shown in FIG.
In particular, as in this embodiment, in the entire region of the guide portion protruding from the inclined wall surface 313b, the height of the guide portion is set lower than the thickness of the molten glass flowing through the inclined wall surface 313b, and By using a form in which the height of the inclined wall surface 313b is set to 0 at the lowermost end portion 313, the shape of the ear portion of the glass sheet can be made more stable as shown in FIG. That is, in the region immediately before the lowest end portion 313, the height of the guide portion is drastically lowered with respect to the thickness of the molten glass, and compared with the conventional form in which the guide height is 0 at the lowest end portion 313, In the present embodiment, when the molten glass merges at the lowermost end portion 313, a small component that tends to flow vertically downward through the guide portion can be changed to 0 more gently. Therefore, this embodiment can make the shape of the ear | edge part of a glass sheet more stable in the shape as shown to Fig.9 (a).

In this embodiment, the height of the guide portion of the guide plate 316 is lower than the thickness of the molten glass flowing along these surfaces on the vertical wall surface and the inclined wall surface, but at least in the entire region of the inclined wall surface. It is sufficient that the height is lower than the thickness of the molten glass. Unlike the inclined wall surface, the molten glass flowing on the vertical wall surface flows vertically downward, and therefore it is not necessary to reduce the area in contact with the molten glass and suppress the component flowing vertically downward along the guide portion. However, the guide plate 316 may function as a radiation surface that takes the heat of the molten glass and emits it. For this reason, it is preferable to make the height of a guide part lower than the thickness of a molten glass in the vertical wall surface at the point which suppresses the area where the edge part of molten glass contacts a guide part.

The height of the above-described guide portion can be determined so that the molten glass does not get over the guide portion when the glass plate is manufactured.
For example, before manufacturing a glass plate, the amount of molten glass supplied to the molded body 310 and the viscosity of the molten glass when the molten glass flows down the molded body 310 are variously changed. The thickness of the molten glass flowing down 310 is examined in advance. Thereby, the information of the thickness (the thickness of the molten glass which flows through the molded object 310) with respect to the said supply amount and the said viscosity is previously acquired as sample information. When trying to manufacture a glass plate, using the acquired sample information, the molded body 310 is flowed down from the supply amount of the molten glass of the glass plate to be manufactured and the viscosity of the molten glass when the molded body 310 is flowed down. Predict the thickness of the molten glass. Furthermore, the height of the guide portion is determined by subtracting a preset value from the predicted molten glass thickness. The preset value means that when the viscosity of the molten glass of the glass plate to be manufactured and the supply amount of the molten glass are variously changed within the range of the actual manufacturing conditions, the height of the guide portion is the molded body 310. The maximum value of the difference between the thickness of the molten glass and the height of the guide portion so that the molten glass does not get over the guide portion even if it is lower than the thickness of the molten glass when flowing down. This value is in the range of 10 to 20 mm, for example. Although this value is a constant value, in order to determine the height of the guide portion in more detail according to the glass plate to be manufactured, the surface tension determined by the composition of the glass plate and the temperature of the molten glass, and further the molten glass It can be adjusted according to the viscosity. The point that the surface tension depends on the composition and temperature is a well-known matter. For example, “Glass Handbook” (Sakuo Sakuo, Teruo Sakino, Katsuaki Takahashi, Asakura Shoten, November 20, 1985, 8th edition) ) Pages 772 to 778.
In addition, the thickness of the molten glass is predicted using the supply amount of the molten glass and the viscosity of the molten glass. In addition to this, the surface tension of the molten glass is further added to predict the thickness of the molten glass. You can also.
Further, before the glass plate is manufactured, the molten glass is preliminarily supplied to the molded body 310 under the manufacturing conditions when the glass plate is to be manufactured, so that the height of the guide portion is such that the molten glass does not get over the guide portion. May be found.

Since the thickness of the molten glass depends on the supply amount of the molten glass supplied to the molded body 310 and also the viscosity when flowing through the molten glass molded body 310, the glass plate is manufactured at the guide portion of the guide plate 316. It is also possible to finely adjust the supply amount and the viscosity of the molten glass so that the thickness of the molten glass flowing on the wall surface of the molded body 310 increases with respect to the height.
For example, in the supply step (ST5), the supply amount of the molten glass is adjusted using a supply amount adjusting device (not shown) provided in the second pipe 205. For example, the supply amount is adjusted according to the result of the weight of the manufactured glass sheet per unit time. Such adjustment may be performed manually by an operator or automatically by a computer (not shown).

FIGS. 8A to 8C are views showing a guide plate 316 having a shape different from the shape of the guide plate 316 shown in FIG. The guide plate 316 shown in FIGS. 8A to 8C can also be used in the glass manufacturing method of the present invention.
The guide plate 316 shown in FIG. 8A has a constant ratio as the entire guide portion on the inclined wall surface of the molded body 310 approaches the lowermost end portion 313 of the molded body 310 from the connection portion with the guide portion on the vertical wall surface. (Gradient) has a shape in which the height of the guide portion is lowered.
The guide plate 316 shown in FIG. 8B has a guide plate 316 as the entire guide portion on the inclined wall surface of the molded body 310 approaches the lowermost end portion 313 of the molded body 310 from the connection portion with the guide portion on the vertical wall surface. Although it has a shape in which the height gradually decreases, it has a shape in which the ratio (gradient) at which the height of the guide portion decreases becomes larger as it approaches the lowest end portion 313.
The guide plate 316 shown in FIG. 8 (c) has a shape in which the height of the guide portion on the vertical wall surface gradually decreases as it goes downward, in addition to the shape of the guide portion on the inclined wall surface shown in FIG. 8 (b). And the ratio (gradient) at which the height of the guide portion decreases also increases in the downward direction.

(Glass composition)
Examples of the glass used in the present embodiment include borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, soda lime glass, alkali silicate glass, and alkali aluminosilicate glass.
The glass plate manufactured in this embodiment has the following compositions, for example.
(A) SiO ₂ : 50 to 70% by mass,
(B) B ₂ O ₃ : 5 to 18% by mass,
(C) Al ₂ O ₃ : 10 to 25% by mass,
(D) MgO: 0 to 10% by mass,
(E) CaO: 0 to 20% by mass,
(F) SrO: 0 to 20% by mass,
(G) BaO: 0 to 10% by mass,
(H) RO: 5 to 20% by mass (wherein R is at least one selected from Mg, Ca, Sr and Ba, and RO is the total of components contained in MgO, CaO, SrO and BaO),
(I) R ′ ₂ O: more than 0.20% by mass and 2.0% by mass or less (where R ′ is at least one selected from Li, Na and K, and R ′ ₂ O is Li ₂ O, Na ₂ O and the sum of the components contained in K ₂ O),
(J) 0.05 to 1.5 mass% in total of at least one metal oxide selected from tin oxide, iron oxide, cerium oxide, and the like.
The compositions (i) and (j) are not essential, but preferably include the compositions (i) and (j). It is preferable that the glass plate of this embodiment does not substantially contain As ₂ O ₃ , Sb ₂ O ₃ and PbO.
In addition to the components described above, the glass plate of the present embodiment may contain various other oxides to adjust the various physical, melting, fining, and forming properties of the glass. Examples of such other oxides include, but are not limited to, TiO ₂ , MnO, ZnO, Nb ₂ O ₅ , MoO ₃ , Ta ₂ O ₅ , WO ₃ , Y ₂ O ₃ , and La _2. O ₃ is mentioned.
In the present embodiment, tin oxide is a component that makes glass easily devitrified. Therefore, in order to prevent devitrification while enhancing clarity, its content is 0.01 to 0.5% by mass. It is preferably 0.05 to 0.3% by mass, more preferably 0.1 to 0.2% by mass.
When the metal oxide contains iron oxide, the content of the iron oxide is preferably 0.01 to 0.2% by mass, and more preferably 0.01 to 0.15% by mass. More preferably, the content is 0.01 to 0.10% by mass.

Other preferable glass compositions include the following compositions.
(A) SiO ₂ : 50 to 70% by mass,
(B) B ₂ O ₃ : 0 to 10% by mass,
(C) Al ₂ O ₃ : 1 to 20% by mass,
(D) MgO: 0 to 10% by mass,
(E) CaO: 0 to 15% by mass,
(F) SrO: 0 to 10% by mass,
(G) BaO: 0 to 10% by mass,
(H) RO: 0 to 20% by mass (wherein R is at least one selected from Mg, Ca, Sr and Ba, and RO is the total of components contained in MgO, CaO, SrO and BaO),
(I) Li ₂ O: 0 to 10% by mass,
(J) Na ₂ O: 0 to 20% by mass,
(K) K ₂ O: 0 to 10% by mass,
(L) R ′ ₂ O: 10% by mass to 20% by mass or less (where R ′ is at least one selected from Li, Na and K, and R ′ ₂ O is Li ₂ O, Na ₂ O and K ₂ O) Of the total ingredients)
(M) ZrO ₂ : 0 to 10% by mass.

In summary, this specification discloses the following contents.

(Disclosure 1)
A method for producing a glass plate by a downdraw method,
A melting step of melting glass raw material to obtain molten glass;
The molten glass is supplied to a supply groove provided in the upper part of the molded body, thereby overflowing the molten glass from the upper part of the supply groove, and melted by a pair of guides protruding from the wall surface of the molded body. While restricting the flow width of the glass, the molten glass is caused to flow down along the respective wall surfaces on both sides of the lower part of the molded body, and the molten glass flowing down is guided to the lowermost end portion of the molded body, Forming a glass ribbon by joining the molten glass flowing through each of the wall surfaces;
A slow cooling step for cooling the glass ribbon flowing in the slow cooling furnace;
A cutting step of cutting the cooled glass ribbon,
The wall surface of the molded body includes a vertical wall surface in which the molten glass overflowing from the supply groove flows down in the vertical direction, and the vertical wall surface that guides the molten glass that has flowed down the vertical wall surface to the lowest end portion of the molded body. Connected inclined wall surfaces,
In the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the inclined wall surface is a thickness of the molten glass flowing through the inclined wall surface in such a range that the molten glass does not get over the pair of guides. The manufacturing method of the glass plate characterized by being provided low compared with.
In the first disclosure, in the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the inclined wall surface flows in the inclined wall surface so that the molten glass does not get over the pair of guides. Since it is provided lower than the thickness of the molten glass, it is possible to suppress the molten glass from flowing away from the wall surface along the guide portion and vertically downward. That is, after the molten glass has passed through the lowermost end of the molded body, the lamination with the molten glass that has flowed down the other wall surface is stable, and the two-pronged ear portion of the glass ribbon that has been obtained in the past is less likely to occur. Thus, the glass ribbon can be flowed in a stable shape.

(Disclosure 2)
The manufacturing method of the glass plate of Claim 1 with which the height from the said inclined wall surface of the said pair of guides is low as the position below the said molded object in the whole area | region where the said guide protruded from the said inclined wall surface. .
Since the thickness of the molten glass is gradually reduced by pulling the lower glass ribbon as it approaches the position of the lowermost end of the molded body, the molten glass is separated from the wall surface by determining the height of the guide as described above. Therefore, it is possible to suppress the vertical downward flow through the guide portion.

(Disclosure 3)
In the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the inclined wall surface decreases continuously or stepwise as it goes downward of the molded body. The manufacturing method of the glass plate of description.
The height of the pair of guides from the inclined wall surface is lowered continuously or stepwise as it goes downward of the molded body, so that the molten glass moves vertically away from the inclined wall surface along the guide. It can suppress reliably flowing below.

(Disclosure 4)
The lowest end portion of the molded body is a linear ridge line in which the inclined wall surfaces on both sides are connected,
The method for producing a glass sheet according to any one of claims 1 to 3, wherein the lowermost ends of the pair of guides are located on the ridgeline.
Since the lowermost end portions of the pair of guides are located on the ridgeline, the molten glass can be surely separated from the inclined wall surface and flowed vertically downward without being transmitted through the guide.

(Disclosure 5)
In the entire region in which the guide protrudes from the inclined wall surface, the height of the pair of guides from the inclined wall surface is 10 mm to 20 mm lower than the thickness of the molten glass flowing through the inclined wall surface. 5. The method for producing a glass plate according to any one of 1 to 4.
Even if the height from the inclined wall surface is lower by 10 mm to 20 mm than the thickness of the molten glass flowing through the inclined wall surface, the molten glass does not get over the pair of guides. Such a molten glass is used in the molded body.

(Disclosure 6)
The method for producing a glass sheet according to any one of disclosures 1 to 5, wherein the viscosity of the molten glass flowing down the wall surface is 3000 to 60000 [Pa · sec].
By setting the viscosity of the molten glass to 3000 to 60000 [Pa · sec], it is possible to reliably suppress the molten glass from getting over the pair of guides.

(Disclosure 7)
A method for producing a glass plate by a downdraw method,
A melting step of melting glass raw material to obtain molten glass;
The molten glass is supplied to a supply groove provided in the upper part of the molded body, thereby overflowing the molten glass from the upper part of the supply groove, and melted by a pair of guides protruding from the wall surface of the molded body. While restricting the flow width of the glass, the molten glass is caused to flow down along the respective wall surfaces on both sides of the lower part of the molded body, and the molten glass flowing down is guided to the lowermost end portion of the molded body, Forming a glass ribbon by joining the molten glass flowing through each of the wall surfaces;
A slow cooling step for cooling the glass ribbon flowing in the slow cooling furnace;
A cutting step of cutting the cooled glass ribbon,
The wall surface of the molded body includes a vertical wall surface in which the molten glass overflowing from the supply groove flows down in the vertical direction, and the vertical wall surface that guides the molten glass that has flowed down the vertical wall surface to the lowest end portion of the molded body. Connected inclined wall surfaces,
The pair of guides has a shape along the outer shape of the cross section of the molded body, has a lowermost portion at the lowermost end portion of the molded body, and the guide protrudes from the inclined wall surface. In the entire region, the height of the pair of guides from the wall surface is set lower than the thickness of the molten glass flowing through the wall surface, so that the molten glass at both ends when the molten glass merges is provided. A method for producing a glass plate, wherein the thickness is reduced.
Here, “having a portion which becomes the lowermost end in the lowermost end portion of the molded body” means that the positional deviation in the flow direction of the molten glass between the lowermost end portions is 10 mm or less. The “shape along the outer shape of the cross section of the molded body” means that the edge of the guide portion is inclined to the same degree as the inclination of the inclined wall surface, and the edge of the guide portion is a horizontal plane on the inclined wall surface 313b. It is inclined to the same side as the inclination relative to. In this case, the inclination may be a constant ratio, or may be an inclination that changes while changing the inclination angle stepwise or continuously. Further, in this case, the edge of the guide portion may be inclined at a constant inclination angle so as to go to the vicinity of the lowermost end portion of the molded body, or may be inclined while changing the inclination angle stepwise or continuously. May be. Here, the vicinity of the lowermost end portion 313 refers to a region within 10 mm from the position of the lowermost end portion 313 in the flow direction of the molten glass.
The pair of guides has a shape along the outer shape of the cross section of the molded body, has a lowermost portion at the lowermost end portion of the molded body, and the guide protrudes from the inclined wall surface. In the entire region, the height of the pair of guides from the wall surface is set lower than the thickness of the molten glass flowing through the wall surface. Even if the guide having such a configuration is used, the molten glass can be prevented from getting over the pair of guides. At this time, since the pair of guides has a shape along the outer shape of the cross section of the molded body, it is possible to suppress the molten glass from moving away from the inclined wall surface and along the guides to flow vertically downward. Further, since the pair of guides has a lowermost portion at the lowermost end portion of the molded body, the molten glass flowing on the inclined surfaces on both sides can be stably stabilized at the lowermost end portion of the molded body. Can be pasted together. Moreover, since the height from the wall surface of the pair of guides is lower than the thickness of the molten glass flowing through the wall surface, the molten glass is prevented from flowing vertically downward along the guide portion away from the wall surface. it can. That is, after the molten glass has passed through the lowermost end of the molded body, the lamination with the molten glass that has flowed down the other wall surface is stable, and the two-pronged ear portion of the glass ribbon that has been obtained in the past is less likely to occur. Thus, the glass ribbon can be flowed in a stable shape.

(Disclosure 8)
The manufacturing method of the glass plate of Claim 7 with which the height from the said wall surface of the said pair of guide is so low that the position below the said molded object in the whole area | region where the said guide protruded from the said inclined wall surface.
Since the thickness of the molten glass is gradually reduced by pulling the lower glass ribbon as it approaches the position of the lowermost end of the molded body, the molten glass is separated from the wall surface by determining the height of the guide as described above. Therefore, it is possible to suppress the vertical downward flow through the guide portion.

(Disclosure 9)
In the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the wall surface decreases continuously or stepwise as it goes downward of the molded body. The manufacturing method of the glass plate of description.
The height of the pair of guides from the inclined wall surface is lowered continuously or stepwise as it goes downward of the molded body, so that the molten glass moves vertically away from the inclined wall surface along the guide. It can suppress reliably flowing below.

(Disclosure 10)
The lowest end portion of the molded body is a linear ridge line in which the inclined wall surfaces on both sides are connected,
The method for producing a glass plate according to any one of claims 7 to 9, wherein the lowermost ends of the pair of guides are located on the ridgeline.
Since the lowermost end portions of the pair of guides are located on the ridgeline, the molten glass can be surely separated from the inclined wall surface and flowed vertically downward without being transmitted through the guide.

(Disclosure 11)
In the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the wall surface is 10 mm to 20 mm lower than the thickness of the molten glass flowing through the wall surface. The method for producing a glass plate according to any one of 10.
Even if the height from the inclined wall surface is lower by 10 mm to 20 mm than the thickness of the molten glass flowing through the inclined wall surface, the molten glass does not get over the pair of guides. Such a molten glass is used in the molded body.

As mentioned above, although the manufacturing method of the glass plate of this invention was 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, what may be variously improved and changed. Of course.

30 furnace 40 molding furnace 50 slow cooling furnace 200 melting apparatus 201 melting tank 202 clarification tank 203 stirring tank 204 first pipe 205 second pipe 300 molding apparatus 310, 310 'molded body 312 supply groove 313, 313'

lower end

313a, 313a '

Vertical wall surface

313b, 313b ′ Inclined wall surface 313c Ridge line 316 Guide plate 330 Cooling rollers 350a to 350c Conveying roller 400 Cutting device

Claims

A method for producing a glass plate by a downdraw method,
A melting step of melting glass raw material to obtain molten glass;
The molten glass is supplied to a supply groove provided in the upper part of the molded body, thereby overflowing the molten glass from the upper part of the supply groove, and melted by a pair of guides protruding from the wall surface of the molded body. While restricting the flow width of the glass, the molten glass is caused to flow down along the respective wall surfaces on both sides of the lower part of the molded body, and the molten glass flowing down is guided to the lowermost end portion of the molded body, Forming a glass ribbon by joining the molten glass flowing through each of the wall surfaces;
A slow cooling step for cooling the glass ribbon flowing in the slow cooling furnace;
A cutting step of cutting the cooled glass ribbon,
The wall surface of the molded body includes a vertical wall surface in which the molten glass overflowing from the supply groove flows down in the vertical direction, and the vertical wall surface that guides the molten glass that has flowed down the vertical wall surface to the lowest end portion of the molded body. Connected inclined wall surfaces,
In the entire region where the guide protrudes from the inclined wall surface, the height of the pair of guides from the inclined wall surface is a thickness of the molten glass flowing through the inclined wall surface in such a range that the molten glass does not get over the pair of guides. The manufacturing method of the glass plate characterized by being provided low compared with.
The manufacturing of the glass plate according to claim 1, wherein the height of the pair of guides from the inclined wall surface in the entire region where the guide protrudes from the inclined wall surface is lower as the position is lower than the molded body. Method.
The height of the pair of guides from the inclined wall surface in the entire region where the guide protrudes from the inclined wall surface decreases continuously or stepwise as it goes downward of the molded body. The manufacturing method of the glass plate of 2.
The lowest end portion of the molded body is a linear ridge line in which the inclined wall surfaces on both sides are connected,
The method for producing a glass sheet according to any one of claims 1 to 3, wherein the lowermost ends of the pair of guides are located on the ridge line.
The height of the pair of guides from the inclined wall surface in the entire region where the guide protrudes from the inclined wall surface is 10 mm to 20 mm lower than the thickness of the molten glass flowing through the inclined wall surface. Item 5. The method for producing a glass plate according to any one of Items 1 to 4.
6. The method for producing a glass plate according to claim 1, wherein the viscosity of the molten glass flowing down the wall surface is 3000 to 60000 [Pa · sec].
A method for producing a glass plate by a downdraw method,
A melting step of melting glass raw material to obtain molten glass;
The molten glass is supplied to a supply groove provided in the upper part of the molded body, thereby overflowing the molten glass from the upper part of the supply groove, and melted by a pair of guides protruding from the wall surface of the molded body. While restricting the flow width of the glass, the molten glass is caused to flow down along the respective wall surfaces on both sides of the lower part of the molded body, and the molten glass flowing down is guided to the lowermost end portion of the molded body, Forming a glass ribbon by joining the molten glass flowing through each of the wall surfaces;
A slow cooling step for cooling the glass ribbon flowing in the slow cooling furnace;
A cutting step of cutting the cooled glass ribbon,
The wall surface of the molded body includes a vertical wall surface in which the molten glass overflowing from the supply groove flows down in the vertical direction, and the vertical wall surface that guides the molten glass that has flowed down the vertical wall surface to the lowest end portion of the molded body. Connected inclined wall surfaces,
The pair of guides has a shape along the outer shape of the cross section of the molded body, has a lowermost portion at the lowermost end portion of the molded body, and the guide protrudes from the inclined wall surface. In the entire region, the height of the pair of guides from the wall surface is set lower than the thickness of the molten glass flowing through the wall surface, so that the molten glass at both ends when the molten glass merges is provided. A method for producing a glass plate, wherein the thickness is reduced.
The manufacturing method of the glass plate according to claim 7, wherein the height of the pair of guides from the wall surface in the entire region where the guide protrudes from the inclined wall surface is lower as the position is lower than the molded body. .
The height from the wall surface of the pair of guides in the entire region where the guide protrudes from the inclined wall surface decreases continuously or stepwise as it goes downward of the molded body. The manufacturing method of the glass plate of description.
The lowest end portion of the molded body is a linear ridge line in which the inclined wall surfaces on both sides are connected,
The method for producing a glass plate according to any one of claims 7 to 9, wherein the lowermost ends of the pair of guides are located on the ridge line.
The height of the pair of guides from the wall surface in the entire region where the guide protrudes from the inclined wall surface is 10 mm to 20 mm lower than the thickness of the molten glass flowing through the wall surface. The method for producing a glass plate according to any one of 1 to 10.