JP6629920B2 - Glass substrate manufacturing method and glass substrate manufacturing apparatus - Google Patents

Description

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

  A glass substrate is generally manufactured through a process of forming a molten glass from a glass raw material and then forming the molten glass into a glass substrate. The above step includes a step of removing minute air bubbles contained in the molten glass (hereinafter, also referred to as fining). The fining is performed by passing the molten glass containing a fining agent through the fining tube body while heating the main body of the fining tube, and removing bubbles in the molten glass by an oxidation-reduction reaction of the fining agent. More specifically, after raising the temperature of the coarsely-melted molten glass further to make the fining agent function to float and defoam the foam, by lowering the temperature, the relatively small bubbles that could not be completely defoamed remain melted. It is made to absorb in glass. That is, fining includes a process of floating and defoaming bubbles (hereinafter, also referred to as a defoaming process or a defoaming step) and a process of absorbing small bubbles into molten glass (hereinafter, also referred to as an absorbing process or an absorbing step). For this reason, in the fining step, a gas-phase space for floating and defoaming bubbles is formed in the fining tube. The gas phase space is formed by flowing the molten glass into the finer tube so as to be formed between the liquid surface of the molten glass and the inner wall of the finer tube.

  In the fining step, a stirring means may be provided in the fining tube to stir the molten glass in order to increase the homogeneity of the molten glass in the fining tube. For example, as a stirring means, a plate member provided in a fining tube at intervals in the flow direction of the molten glass may be used to partially obstruct the flow of the molten glass (Patent Document 1). .

JP 2017-065973 A

  In the fining step, the velocity of the molten glass passing through the fining tube is higher near the liquid surface than near the inner wall of the fining tube due to wall resistance. On the other hand, in the fining tube, the molten glass containing a large amount of silica or the like having a low specific gravity tends to flow in the upper region near the liquid surface and flow faster than the molten glass flowing in the lower region near the bottom of the fining tube. If the molten glass flows at a different speed between the upper layer region and the lower layer region, even if the molten glass is agitated using the plate member, the molten glass is difficult to be uniformly agitated, and fining may be insufficient. If the fining is insufficient, bubbles may remain in the molten glass and the glass quality may be degraded.

  An object of the present invention is to provide a glass substrate manufacturing method and a glass substrate manufacturing apparatus having a high effect of uniformly stirring molten glass flowing in a fining tube.

The present invention includes a glass substrate manufacturing method and a glass substrate manufacturing apparatus of the following aspects (1) to ( 9 ).

( 1 ) A method for manufacturing a glass substrate,
A melting process of melting glass raw materials to produce molten glass;
A fining step of fining the molten glass in a fining tube,
In the fining step, fining is performed while flowing the molten glass so that a gas phase space is formed above the liquid level of the molten glass in the fining tube,
In the fining tube, using a pair of plate members arranged at intervals in the flow direction of the molten glass, partially obstruct the flow of the molten glass,
The plate member is provided at a different vertical position below the liquid level of the molten glass,
In the pair, a first distance between an upper end of the first plate member disposed closest to the liquid level and the liquid level is disposed closest to the bottom of the inner wall of the fining tube. Shorter than a second distance between the lower end of the second plate member and the bottom,
In the fining step, the molten glass is heated so that a temperature distribution of the molten glass is formed along the flow direction,
At the first flow direction position where the temperature of the molten glass is the first temperature, the temperature of the molten glass is lower than the second flow direction position that is the second temperature lower than the first temperature. A method for manufacturing a glass substrate, wherein the first distance and the second distance are short.

( 2 ) A method for manufacturing a glass substrate,
A melting process of melting glass raw materials to produce molten glass;
A fining step of fining the molten glass in a fining tube,
In the fining step, fining is performed while flowing the molten glass so that a gas phase space is formed above the liquid level of the molten glass in the fining tube,
In the fining tube, using a pair of plate members arranged at intervals in the flow direction of the molten glass, partially obstruct the flow of the molten glass,
The plate member is provided at a different vertical position below the liquid level of the molten glass,
In the pair, a first distance between an upper end of the first plate member disposed closest to the liquid level and the liquid level is disposed closest to the bottom of the inner wall of the fining tube. Shorter than a second distance between the lower end of the second plate member and the bottom,
In the fining step, the molten glass is heated so that a temperature distribution of the molten glass is formed along the flow direction,
The interval between the plate members adjacent in the flow direction is a second temperature lower than the first temperature at a first flow direction position where the temperature of the molten glass is a first temperature. Characterized by being narrower than the position in the flow direction of the glass substrate.

( 3 ) A method for manufacturing a glass substrate,
A melting process of melting glass raw materials to produce molten glass;
A fining step of fining the molten glass in a fining tube,
In the fining step, fining is performed while flowing the molten glass so that a gas phase space is formed above the liquid level of the molten glass in the fining tube,
In the fining tube, using a pair of plate members arranged at intervals in the flow direction of the molten glass, partially obstruct the flow of the molten glass,
The plate member is provided at a different vertical position below the liquid level of the molten glass,
In the pair, a first distance between an upper end of the first plate member disposed closest to the liquid level and the liquid level is disposed closest to the bottom of the inner wall of the fining tube. Shorter than a second distance between the lower end of the second plate member and the bottom,
In the fining step, flowing the molten glass while changing the height of the liquid level,
The method of manufacturing a glass substrate, wherein the second distance is longer than the first distance when the height of the liquid surface is at a highest position.

( 4 ) A method for manufacturing a glass substrate,
A melting process of melting glass raw materials to produce molten glass;
A fining step of fining the molten glass in a fining tube,
In the fining step, fining is performed while flowing the molten glass so that a gas phase space is formed above the liquid level of the molten glass in the fining tube,
In the fining tube, using a pair of plate members arranged at intervals in the flow direction of the molten glass, partially obstruct the flow of the molten glass,
The plate member is provided at a different vertical position below the liquid level of the molten glass,
In the pair, a first distance between an upper end of the first plate member disposed closest to the liquid level and the liquid level is disposed closest to the bottom of the inner wall of the fining tube. Shorter than a second distance between the lower end of the second plate member and the bottom,
A method for manufacturing a glass substrate, wherein a plate member arranged without leaving an interval from the bottom is not provided in the fining tube.

( 5 ) A glass substrate manufacturing apparatus,
A melting device for melting glass raw materials to produce molten glass;
A fining device having a fining tube in which fining of the molten glass is performed,
In the fining tube, fining is performed while the molten glass flows so that a gas phase space is formed above the liquid level of the molten glass,
The fining tube has a plurality of pairs of plate members arranged at intervals in the flow direction of the molten glass, and partially obstructs the flow of the molten glass,
Two plate members forming each said pair are provided vertically different positions of lower than the liquid surface of the molten glass,
In each of the pairs, a first distance between the upper end of the first plate member disposed closest to the liquid surface and the liquid surface is closest to the bottom of the inner wall of the fining tube. the lower end of the arranged second plate member and the second rather short than the distance between the bottom portion,
The fining device heats the molten glass so that a temperature distribution of the molten glass is formed along the flow direction,
At the first flow direction position where the temperature of the molten glass is the first temperature, the temperature of the molten glass is lower than the second flow direction position that is the second temperature lower than the first temperature. An apparatus for manufacturing a glass substrate, wherein the first distance and the second distance are short .
(6) A glass substrate manufacturing apparatus,
A melting device for melting glass raw materials to produce molten glass;
A fining device having a fining tube in which fining of the molten glass is performed,
In the fining tube, fining is performed while the molten glass flows so that a gas phase space is formed above the liquid level of the molten glass,
The fining tube has a plurality of pairs of plate members arranged at intervals in the flow direction of the molten glass, and partially obstructs the flow of the molten glass,
The two plate members forming each of the pairs are provided at different positions in the vertical direction below the liquid surface of the molten glass,
In each of the pairs, a first distance between the upper end of the first plate member disposed closest to the liquid surface and the liquid surface is closest to the bottom of the inner wall of the fining tube. Shorter than a second distance between the lower end of the disposed second plate member and the bottom,
The fining device heats the molten glass so that a temperature distribution of the molten glass is formed along the flow direction,
The interval between the plate members adjacent in the flow direction is a second temperature lower than the first temperature at a first flow direction position where the temperature of the molten glass is a first temperature. A glass substrate manufacturing apparatus, which is narrower than a flow direction position of the glass substrate.
(7) A glass substrate manufacturing apparatus,
A melting device for melting glass raw materials to produce molten glass;
A fining device having a fining tube in which fining of the molten glass is performed,
In the fining tube, fining is performed while the molten glass flows so that a gas phase space is formed above the liquid level of the molten glass,
The fining tube has a plurality of pairs of plate members arranged at intervals in the flow direction of the molten glass, and partially obstructs the flow of the molten glass,
The two plate members forming each of the pairs are provided at different positions in the vertical direction below the liquid surface of the molten glass,
In each of the pairs, a first distance between the upper end of the first plate member disposed closest to the liquid surface and the liquid surface is closest to the bottom of the inner wall of the fining tube. Shorter than a second distance between the lower end of the disposed second plate member and the bottom,
In the fining tube, the molten glass flows while the height of the liquid level fluctuates,
The said 2nd distance is larger than the said 1st distance when the height of the said liquid level is in the highest position, The glass substrate manufacturing apparatus characterized by the above-mentioned.
(8) A glass substrate manufacturing apparatus,
A melting device for melting glass raw materials to produce molten glass;
A fining device having a fining tube in which fining of the molten glass is performed,
In the fining tube, fining is performed while the molten glass flows so that a gas phase space is formed above the liquid level of the molten glass,
The fining tube has a plurality of pairs of plate members arranged at intervals in the flow direction of the molten glass, and partially obstructs the flow of the molten glass,
The two plate members forming each of the pairs are provided at different positions in the vertical direction below the liquid surface of the molten glass,
In each of the pairs, a first distance between the upper end of the first plate member disposed closest to the liquid surface and the liquid surface is closest to the bottom of the inner wall of the fining tube. Shorter than a second distance between the lower end of the disposed second plate member and the bottom,
An apparatus for manufacturing a glass substrate, wherein a plate member arranged without leaving an interval from the bottom is not provided in the fining tube.

  According to the present invention, the effect of uniformly stirring the molten glass flowing in the fining tube is high.

It is a figure showing the flow of the manufacturing method of this embodiment. It is the schematic of a glass substrate manufacturing apparatus. FIG. 3 is a schematic view of a clarification tube shown in FIG. 2. It is a vertical sectional view in the longitudinal direction of a fining tube.

Hereinafter, a glass substrate manufacturing method and a glass substrate manufacturing apparatus of the present invention will be described.
(Overall outline of glass substrate manufacturing method)
FIG. 1 is a diagram illustrating an example of steps of a method for manufacturing a glass substrate of the present embodiment. The manufacturing method of the glass substrate includes a melting step (ST1), a fining step (ST2), a homogenizing step (ST3), a supplying step (ST4), a forming step (ST5), a slow cooling step (ST6), and a cutting step ( ST7). In addition, a grinding step, a polishing step, a cleaning step, an inspection step, a packing step, and the like may be provided. The manufactured glass substrates are laminated as needed in a packing process, and are transported to a delivery destination company.

In the melting step (ST1), a molten glass is produced by heating a glass raw material.
In the refining step (ST2), bubbles containing oxygen, CO ₂ or SO ₂ contained in the molten glass are generated by raising the temperature of the molten glass. These bubbles grow by absorbing oxygen generated by the reduction reaction of the fining agent (such as tin oxide) contained in the molten glass, and float on the liquid surface of the molten glass to be released. Thereafter, in the fining step, the temperature of the molten glass is lowered, so that the reducing substance obtained by the reduction reaction of the fining agent undergoes an oxidation reaction. Thereby, gas components such as oxygen in the bubbles remaining in the molten glass are re-absorbed in the molten glass, and the bubbles disappear. The oxidation reaction and the reduction reaction by the fining agent are performed by controlling the temperature of the molten glass. The fining step (ST2) is performed while flowing the molten glass into the fining tube 120.
In the fining step, a vacuum degassing method in which bubbles existing in the molten glass are grown and degassed in a reduced pressure atmosphere may be used. The vacuum degassing method is effective in that no fining agent is used. However, the vacuum degassing method makes the apparatus complicated and large. Therefore, it is preferable to employ a fining method using a fining agent to raise the temperature of the molten glass.
In the refining step (ST2), the flow of the molten glass is partially hindered by using a pair of plate members described later to stir the molten glass. By lengthening the staying time of the molten glass flowing in the fining tube 120 and sufficiently securing the time for the defoaming of the molten glass, it is possible to improve the glass quality and increase the yield. Further, by performing such stirring, melting of the foreign material mixed in the molten glass into the molten glass and uniformity of the composition unevenness in the molten glass are promoted. The details of the pair of plate members and the fining step (ST2) using the pair of plate members will be described later.

In the homogenization step (ST3), the molten glass is stirred using a stirrer to homogenize the glass components. Thereby, it is possible to reduce the composition unevenness of the glass which is a cause of striae and the like. The homogenization step is performed in a stirring tank described below.
In the supply step (ST4), the stirred molten glass is supplied to the forming apparatus.

The forming step (ST5) and the slow cooling step (ST6) are performed by a forming apparatus.
In the forming step (ST5), the molten glass is formed into a sheet glass to create a flow of the sheet glass. An overflow down draw method is used for molding.
In the slow cooling step (ST6), the formed sheet glass is cooled to have a desired thickness, not to cause internal distortion, and to prevent warpage.
In the cutting step (ST7), the sheet glass after slow cooling is cut into a predetermined length to obtain a plate-like glass substrate. The cut glass substrate is further cut into a predetermined size, and a glass substrate having a target size is produced.

FIG. 2 is a schematic diagram of a glass substrate manufacturing apparatus that performs a melting step (ST1) to a cutting step (ST7) in the present embodiment. As shown in FIG. 2, the glass substrate manufacturing apparatus mainly includes a melting device 100, a forming device 200, and a cutting device 300. The melting apparatus 100 includes a melting tank 101, a fining tube 120, a stirring tank 103, transfer tubes 104 and 105, and a glass supply tube 106.
The melting tank 101 shown in FIG. 2 is provided with a heating means such as a burner (not shown). A glass material to which a fining agent has been added is charged into the melting tank, and a melting step (ST1) is performed. The molten glass melted in the melting tank 101 is supplied to the fining tube 120 via the transfer tube 104 while being maintained at a high temperature (for example, 1300 ° C. or higher). By supplying the molten glass maintained at a high temperature to the fining tube 120, the viscosity of the molten glass can be kept low, and the fluidity of the molten glass flowing in the fining tube 120 can be increased.
In the fining tube 120, the temperature of the molten glass MG is adjusted, and the fining step (ST2) of the molten glass is performed using the oxidation-reduction reaction of the fining agent. Specifically, when the molten glass in the fining tube 120 is heated, the oxygen, CO ₂ or SO ₂ bubbles contained in the molten glass absorb oxygen generated by the reduction reaction of the fining agent. Grows, floats on the liquid surface of the molten glass, and is released into the gas phase space. The gas phase space is formed by flowing the molten glass into the finer tube so as to be formed between the liquid surface of the molten glass and the inner wall of the finer tube. Thereafter, by reducing the temperature of the molten glass, the reducing substance obtained by the reduction reaction of the fining agent undergoes an oxidation reaction. Thereby, gas components such as oxygen in the bubbles remaining in the molten glass are re-absorbed in the molten glass, and the bubbles disappear. The molten glass after fining is supplied to the stirring tank 103 via the transfer pipe 105.
In the stirring tank 103, the molten glass is stirred by the stirrer 103a, and the homogenization step (ST3) is performed. The molten glass homogenized in the stirring tank 103 is supplied to the forming apparatus 200 via the glass supply pipe 106 (supply step ST4).
In the forming apparatus 200, the sheet glass SG is formed from the molten glass by the overflow down draw method (forming step ST5), and is gradually cooled (slow cooling step ST6).
In the cutting device 300, a plate-shaped glass substrate cut out from the sheet glass SG is formed (cutting step ST7).

(Structure of fining tube and fining process)
Next, the configuration of the fining tube 120 will be described with reference to FIGS. FIG. 3 is a schematic perspective view showing the configuration of the fining tube 120 of the present embodiment, and FIG. 4 is a vertical sectional view of the fining tube 120 in the longitudinal direction.
As shown in FIGS. 3 and 4, electrodes 121 a, 121 b, and 121 c are provided on both ends in the longitudinal direction of the fining tube 120 and on the outer peripheral surface at a position therebetween, and the gas phase space 120 a ( An exhaust pipe (not shown) is provided on a wall in contact with (see FIG. 4).

The main body of the fining tube 120, the electrodes 121a, 121b, 121c, and the exhaust pipe are made of a platinum group metal. In this specification, “platinum group metal” means a metal composed of a platinum group element, and is used as a term including not only a metal composed of a single platinum group element but also an alloy of a platinum group element. Here, the platinum group element refers to six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), and iridium (Ir). Although platinum group metals are expensive, they have a high melting point and excellent corrosion resistance to molten glass.
In this embodiment, the case where the fining tube 120 is made of a platinum group metal will be described as a specific example. However, a part of the fining tube 120 may be made of a refractory or another metal. .

The electrodes 121a, 121b, 121c are connected to a power supply device 122. When a voltage is applied between the electrodes 121a and 121b and between the electrodes 121b and 121c, a current flows through the fining tube 120 between the electrodes 121a and 121b and between the electrodes 121b and 121c. Then, the fining tube 120 is electrically heated.
The space between the electrodes 121a and 121b is heated to a temperature at which the defoaming process is promoted. Specifically, the maximum temperature of the main body of the fining tube 120 is, for example, 1600 ° C. to 1750 ° C., more preferably 1630 ° C. to 1750 ° C., and the maximum temperature of the molten glass supplied from the transfer tube 104 is And heated to a temperature suitable for defoaming, for example, 1600 ° C to 1720 ° C, more preferably 1620 ° C to 1720 ° C.
The electrodes 121b and 121c are heated to a temperature at which the absorption process is promoted. Specifically, heating is performed so that the maximum temperature of the fining tube 102 is, for example, 1590 ° C. to 1670 ° C., more preferably 1620 ° C. to 1670 ° C., and the maximum temperature of the molten glass flowing in the fining tube 102 is suitable for absorption. The temperature is raised to 1590C to 1640C, more preferably 1610C to 1640C.
In addition, by controlling the temperature of the molten glass by applying electric current, the viscosity of the molten glass can be adjusted, and thereby the flow rate of the molten glass passing through the fining tube 120 can be adjusted.

The electrodes 121a, 121b, and 121c may be provided with a temperature measuring device (a thermocouple or the like) not shown. The temperature measurement device measures the temperatures of the electrodes 121a, 121b, and 121c, and outputs the measurement result to the control device 123.
The control device 123 controls the amount of current that the power supply device 122 applies to the fining tube 120, thereby controlling the temperature and the flow rate of the molten glass passing through the fining tube 120. The control device 123 is a computer including a CPU, a memory, and the like.

  The exhaust pipe is provided above the gas phase space 120a. The exhaust pipe communicates the gas phase space 120a (see FIG. 4) with the external space of the fining tube 120. The exhaust pipe is preferably provided at a position between the electrodes 121a and 121b or between the electrodes 121b and 121c in the flow direction of the molten glass in the fining tube 120.

In the fining tube 120, as shown in FIG. 4, a pair 126 of plate members composed of a first plate member 124 and a second plate member 125 has a flow direction of molten glass (a direction from left to right in FIG. 4). That is, they are arranged at intervals in the fining tube 120 shown in FIG. The plate members 126 are provided at different positions in the vertical direction below the liquid surface. As long as at least one pair of plate members 126 is disposed in the fining tube 120, in the example shown in FIG. 4, a plurality of pairs are disposed, and all of the plate members disposed in the fining tube 120 are disposed. , And a pair 126 of plate members. In the example shown in FIG. 4, the first plate members 124 and the second plate members 125 are alternately arranged so as to be adjacent to each other in the flow direction of the molten glass. The plate member pair 126 is provided for each section having a length of 10 to 40% of the length of the fining tube 120 from the viewpoint of ensuring the effect of uniformly stirring the molten glass described below regardless of the length of the fining tube 102. Preferably, a pair is arranged. Further, the number of plate members 126 arranged in the fining tube 120 is not particularly limited, but is, for example, 4 to 10 pairs. The first plate member 124 and the second plate member 125 are made of, for example, a platinum group metal.
The arrangement range of the first plate member 124 along the depth direction of the molten glass is different from the arrangement range of the second plate member 125 along the depth direction. Specifically, the first plate member 124 is arranged closest to the liquid surface S of the molten glass. The second plate member 125 is disposed closest to the bottom of the inner wall of the fining tube 120 (the lowermost portion of the inner wall of the fining tube 120). In the example shown in FIG. 4, the length of the first plate member 124 along the depth direction of the molten glass is shorter than the length of the second plate member 125, for example, 0.5 times the length of the second plate member. Less than 1 time.
The first plate member 124 and the second plate member 125 preferably extend in a direction perpendicular to the length direction of the fining tube 120 as in the example shown in FIG.

The distance L1 (first distance) between the upper end of the first plate member 124 and the liquid surface S is shorter than the distance L2 (second distance) between the lower end of the second plate member 125 and the bottom. In the fining tube, the molten glass generally flows faster in the upper region near the liquid level in the depth region of the molten glass, while the molten glass flows slowly in the lower region near the bottom of the fining tube due to wall resistance. For this reason, there is a difference in the flow rate of the molten glass between the upper layer region and the lower layer region, and it is difficult for the molten glass to be uniformly stirred, and the fining may be insufficient. In the present embodiment, the first plate member 124 and the second plate member 125 are arranged so that the distance L1 and the distance L2 satisfy the above relationship, so that the difference in the flow rate of the molten glass between the upper layer region and the lower layer region is reduced. It can be made smaller and stirred so that the molten glass becomes homogeneous. Thereby, the fining of the molten glass is sufficiently performed, and the deterioration of the glass quality is suppressed.
If the distance L1 is equal to or longer than the distance L2, it is difficult to reduce the flow velocity of the molten glass flowing in the upper layer region, and it is difficult to reduce the difference in speed between the molten glass in the upper layer region and the lower glass region. If the distance L2 is shorter than the distance L1, for example, a component having a large specific gravity, including a large amount of zirconia eluted from the melting tank, tends to accumulate at the bottom of the fining tube 120, thereby causing striae on the glass substrate. May occur.
Note that the distance L1 is longer than 0 mm. If the distance L1 is 0 mm, that is, if the upper end of the first plate member 124 is arranged at the same height as the liquid surface S or beyond the liquid surface S, the platinum group metal at the upper end is oxidized. Thus, there is a tendency that a problem that the vaporized platinum group metal is reduced and precipitated, and the precipitate is mixed in the molten glass. Therefore, when the liquid level of the molten glass fluctuates as described later, the distance L1 is set to be longer than 0 mm when the liquid level is at the lowest position.

  The ratio L1 / L2 of the distance L1 and the distance L2 is preferably 0.2 to 0.8 from the viewpoint of enhancing the effect of reducing the speed difference between the molten glass in the upper layer region and the lower layer region. Further, from the viewpoint of reducing the flow rate of the molten glass in the upper layer region, the distance L1 is larger than the length corresponding to the region of the uppermost layer 20% in the depth direction region of the molten glass forming the liquid phase in the fining tube 120. Preferably it is short. The distance L2 is preferably longer than the length corresponding to the region of the lowermost layer 20% of the depth region of the molten glass from the viewpoint of increasing the flow rate of the molten glass flowing through the lower region, and the entire molten glass is uniformly stirred. Therefore, it is preferable that the length be shorter than the length corresponding to the region of the lowermost layer 40%. Note that the upper layer region means, for example, a region of 40% of the depth of the molten glass in the depth direction of the molten glass from the liquid surface. The lower layer region means, for example, a region of 40% of the depth of the molten glass from the bottom of the fining tube 120 in the depth direction of the molten glass.

  In the fining step (ST2), when the main body of the fining tube 120 is heated to different temperatures between the electrodes 121a and 121b and between the electrodes 121b and 121c, a temperature distribution of the molten glass is formed along the flow direction. Is done. In this case, at the first flow direction position where the temperature of the molten glass is the first temperature, the temperature of the molten glass is longer than the second flow direction position where the temperature is the second temperature lower than the first temperature. It is preferable that L1 and distance L2 are short. In other words, at a position along the flow direction of the molten glass, it is preferable that the higher the temperature of the molten glass is, the shorter the distance L1 and the distance L2 are. For example, the distance L1 and the distance L2 between the electrodes 121a and 121b are preferably shorter than those between the electrodes 121b and 121c. At a position in the flow direction where the temperature of the molten glass is high, since the viscosity of the molten glass is low, the speed difference between the molten glass in the upper layer region and the lower layer region is large, and it is difficult to stir the molten glass uniformly. For this reason, at a position in the flow direction where the temperature of the molten glass is high, the distance L1 is shorter than the distance L2, and the distance L1 and the distance L2 are shortened to reduce the speed difference between the molten glass in the upper layer region and the lower layer region. The size can be reduced, and the molten glass can be uniformly stirred.

Further, in the fining step (ST2), when the temperature distribution of the molten glass is formed along the flow direction, the interval D between the adjacent plate members along the flow direction is determined at a position where the temperature of the molten glass is high (first position). In the (flow direction position), it is preferable that the temperature of the molten glass is narrower than in a low position (second flow direction position). At a position in the flow direction where the temperature of the molten glass is high, the viscosity of the molten glass is small and the flow velocity is large. For this reason, by reducing the interval D between the adjacent plate members and increasing the frequency at which the molten glass hits the plate member, the effect of reducing the speed difference between the molten glass in the upper layer region and the lower layer region is increased, and in the fining tube. The residence time of the molten glass can be lengthened, and the time for the defoaming of the molten glass can be sufficiently ensured.
In addition, if the interval D is too long, the effect of reducing the speed difference between the upper layer region and the lower layer region is reduced. Therefore, the interval D is, for example, 1/3, preferably 1/5 or less of the length of the fining tube 120. Is set to the length of The interval D is, for example, 100 to 400 mm.

  It is preferable that the height position of the bottom end (lower end) of the first plate member 124 is lower than the height position of the liquid surface side end (upper end) of the second plate member 125. Accordingly, the flow of the molten glass that passes straight through the depth region (middle layer region) between the first plate member 124 and the second plate member 125 in the flow direction is prevented, and the molten glass is uniformly stirred. Can be avoided.

  In the fining step (ST2), the molten glass may be flown while changing the height of the liquid surface S. For example, during operation, the height of the liquid level S fluctuates as the glass raw material is charged into the melting tank. In this case, the distance L2 is preferably larger than the distance L1 when the height of the liquid surface S is at the highest position. Thereby, the speed difference of the molten glass between the upper region and the lower region of the molten glass in the fining tube 120 can be stably kept small.

It is preferable that no plate member is provided in the fining tube 120 without leaving a space from the bottom. That is, it is preferable that all the members provided in the fining tube 120 are arranged at an interval from the bottom. If a plate member arranged without a gap from the bottom is provided in the fining tube 120, the flow of the molten glass in the lower region is hindered, and the effect of reducing the speed difference with the upper region is impaired. .
On the other hand, since such a plate member is not provided in the fining tube 120, the flow rate of the molten glass flowing through the lower layer area becomes too fast with respect to the flow rate of the molten glass flowing through the upper layer area. There is a case where the speed difference in the area is rather large. For this reason, it is preferable that the distance L2 is shorter than the length corresponding to the region of the lowermost layer 40% in the depth region of the molten glass. In this case, the distance L2 is preferably shorter than the distance between the second plate members 125 adjacent in the flow direction, and more preferably shorter than the distance D. The ratio of the distance L2 to the distance D (L2 / D) is, for example, 0.1 to 0.7.

  According to the present embodiment, since the first plate member 124 and the second plate member 125 are arranged so that the distance L1 and the distance L2 satisfy the above relationship, the flow rate of the molten glass in the upper region and the lower region is reduced. The difference can be reduced and the molten glass can be stirred to be homogeneous. Thereby, the fining of the molten glass is sufficiently performed, and the deterioration of the glass quality is suppressed.

(Glass substrate)
Although the size of the glass substrate manufactured in the present embodiment is not particularly limited, for example, each of the vertical dimension and the horizontal dimension is 500 mm to 3500 mm, 1500 mm to 3500 mm, 1800 to 3500 mm, 2000 mm to 3500 mm, and 2000 mm to 3500 mm. It is preferable that
The thickness of the glass substrate is, for example, 0.1 to 1.1 mm, more preferably an extremely thin rectangular plate of 0.75 mm or less, for example, 0.55 mm or less, and further preferably 0.45 mm or less. The thickness is more preferred. The lower limit of the thickness of the glass substrate is preferably 0.15 mm, more preferably 0.25 mm.

<Glass composition>
As such a glass substrate, a glass substrate having the following glass composition is exemplified. That is, the raw materials of the molten glass are prepared so as to produce a glass substrate having the following glass composition.
55 to 80 mol% of SiO ₂ ,
Al ₂ O ₃ 8~20 mol%,
B ₂ O ₃ 0 to 12 mol%,
RO 0 to 17 mol% (RO is the total amount of MgO, CaO, SrO and BaO).

SiO ₂ is preferably from 60 to 75 mol%, more preferably from 63 to 72 mol%, from the viewpoint of reducing the heat shrinkage.
Of the RO, it is preferable that MgO is 0 to 10 mol%, CaO is 0 to 15 mol%, SrO is 0 to 10%, and BaO is 0 to 10%.

It contains at least SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ and RO, and the molar ratio is ((2 × SiO ₂ ) + Al ₂ O ₃ ) / ((2 × B ₂ O ₃ ) + RO). The glass may be five or more. Further, it is preferable that at least one of MgO, CaO, SrO, and BaO is contained, and the molar ratio (BaO + SrO) / RO is 0.1 or more.

The total of twice the content of B ₂ O ₃ expressed in mol% and the content of RO expressed in mol% is preferably 30 mol% or less, more preferably 10 to 30 mol%.
The content of the alkali metal oxide in the glass substrate having the above glass composition may be 0 mol% or more and 0.4 mol% or less.
In addition, a metal oxide (tin oxide, iron oxide) whose valence varies in the glass is contained in a total of 0.05 to 1.5 mol%, and As ₂ O ₃ , Sb ₂ O ₃ and PbO are substantially contained. The absence is not mandatory and optional.

Further, it is preferable that non-alkali boroaluminosilicate glass or glass containing a small amount of alkali is used for the glass substrate manufactured according to the present embodiment.
The glass substrate manufactured according to the present embodiment is preferably made of, for example, non-alkali glass having the following composition.
Examples of the glass composition of the glass substrate manufactured according to the present embodiment include the following (in mass%).
SiO ₂ : 50 to 70% (preferably 57 to 64%), Al ₂ O ₃ : 5 to 25% (preferably 12 to 18%), B ₂ O ₃ : 0 to 15% (preferably 6%) -13%), and may optionally further contain the composition shown below. As optional components, MgO: 0 to 10% (preferably 0.5 to 4%), CaO: 0 to 20% (preferably 3 to 7%), SrO: 0 to 20% (preferably, 0.5 to 8%, more preferably 3~7%), BaO: 0~10% ( preferably 0-3%, more preferably _{0~1%), ZrO 2: 0~10} % ( preferably , 0 to 4%, more preferably 0 to 1%). Further, it is more preferable that R ′ ₂ O: more than 0.10% and not more than 2.0% (where R ′ is at least one selected from Li, Na and K).

_{Alternatively,} SiO 2: _{50~70% (preferably, 55~65%), B 2 O} 3: 0~10% ( _{preferably, 0~5%, 1.3~5%),} Al 2 O 3: 10 to 25% (preferably 16 to 22%), MgO: 0 to 10% (preferably 0.5 to 4%), CaO: 0 to 20% (preferably 2 to 10%, 2 to 6%) %), SrO: 0 to 20% (preferably 0 to 4%, 0.4 to 3%), BaO: 0 to 15% (preferably 4 to 11%), RO: 5 to 20% (preferably) (8 to 20%, 14 to 19%) (R is at least one selected from Mg, Ca, Sr and Ba). Further, it is more preferable that R ′ ₂ O contains more than 0.10% and not more than 2.0% (where R ′ is at least one selected from Li, Na and K).

<Young's modulus>
The Young's modulus of the glass substrate manufactured according to the present embodiment is, for example, preferably 72 GPa or more, more preferably 75 GPa or more, even more preferably 77 GPa or more.

<Strain point>
The strain rate of the glass substrate manufactured according to the present embodiment is, for example, preferably 650 ° C. or higher, more preferably 680 ° C. or higher, even more preferably 700 ° C. or higher and 720 ° C. or higher.

<Heat shrinkage>
The heat shrinkage of the glass substrate manufactured by the present embodiment is, for example, 50 ppm or less, preferably 40 ppm or less, more preferably 30 ppm or less, and even more preferably 20 ppm or less. The range of the heat shrinkage of the glass substrate before the heat shrinkage is reduced is preferably 10 ppm to 40 ppm.

The glass substrate manufactured in the present embodiment is suitable as a glass substrate for a flat panel display, a glass substrate for a display including a glass substrate for a curved panel display, for example, a glass substrate for a liquid crystal display or a glass for an organic EL display. It is suitable as a substrate. Further, the glass substrate manufactured in the present embodiment is a glass substrate for an oxide semiconductor display using an oxide semiconductor such as IGZO (indium, gallium, zinc, oxygen) used for a high definition display, and an LTPS (low It is suitable for a glass substrate for LTPS display using a temperature polysilicon) semiconductor.
Further, the glass substrate manufactured in this embodiment can be applied to a cover glass, a glass for a magnetic disk, a glass substrate for a solar cell, and the like.

As described above, the glass substrate manufacturing apparatus and the glass substrate manufacturing method of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the gist of the present invention. Of course, you can.
The pair of plate members 126 may not be arranged in all the regions in the flow direction of the molten glass in the fining tube 120, and may be arranged in only a part of the region in the flow direction. For example, the plate member pair 126 may be arranged only between the electrodes 121a and 121b.
Further, the first plate members 124 and the second plate members 125 need not be arranged alternately in the flow direction of the molten glass. For example, the fining tube 120 may have a region in which plate members of the same type are arranged in the flow direction of the molten glass.

REFERENCE SIGNS LIST 100 melting device 101 melting tank 102 fining tube 103 stirring tank 103 a stirrer 104, 105 transfer tube 106 glass supply tube 120 fining tube 120 a gas phase space 121 a, 121 b, 121 c electrode 122 power supply device 123 control device 124 first plate member 125 2 plate member 126 plate member pair 200 forming device 300 cutting device MG molten glass SG sheet glass

Claims (8)

A method for manufacturing a glass substrate,
A melting process of melting glass raw materials to produce molten glass;
A fining step of fining the molten glass in a fining tube,
In the fining step, fining is performed while flowing the molten glass so that a gas phase space is formed above the liquid level of the molten glass in the fining tube,
In the fining tube, using a pair of plate members arranged at intervals in the flow direction of the molten glass, partially obstruct the flow of the molten glass,
The plate member is provided at a different vertical position below the liquid level of the molten glass,
In the pair, a first distance between an upper end of the first plate member disposed closest to the liquid level and the liquid level is disposed closest to the bottom of the inner wall of the fining tube. It was rather short than the second distance between the lower end portion and the bottom portion of the second plate member,
In the fining step, the molten glass is heated so that a temperature distribution of the molten glass is formed along the flow direction,
At the first flow direction position where the temperature of the molten glass is the first temperature, the temperature of the molten glass is lower than the second flow direction position that is the second temperature lower than the first temperature. A method for manufacturing a glass substrate, wherein the first distance and the second distance are short. A method for manufacturing a glass substrate,
A melting process of melting glass raw materials to produce molten glass;
A fining step of fining the molten glass in a fining tube,
In the fining step, fining is performed while flowing the molten glass so that a gas phase space is formed above the liquid level of the molten glass in the fining tube,
In the fining tube, using a pair of plate members arranged at intervals in the flow direction of the molten glass, partially obstruct the flow of the molten glass,
The plate member is provided at a different vertical position below the liquid level of the molten glass,
In the pair, a first distance between an upper end of the first plate member disposed closest to the liquid level and the liquid level is disposed closest to the bottom of the inner wall of the fining tube. It was rather short than the second distance between the lower end portion and the bottom portion of the second plate member,
In the fining step, the molten glass is heated so that a temperature distribution of the molten glass is formed along the flow direction,
The interval between the plate members adjacent in the flow direction is a second temperature lower than the first temperature at a first flow direction position where the temperature of the molten glass is a first temperature. Characterized by being narrower than the position in the flow direction of the glass substrate. A method for manufacturing a glass substrate,
A melting process of melting glass raw materials to produce molten glass;
A fining step of fining the molten glass in a fining tube,
In the fining step, fining is performed while flowing the molten glass so that a gas phase space is formed above the liquid level of the molten glass in the fining tube,
In the fining tube, using a pair of plate members arranged at intervals in the flow direction of the molten glass, partially obstruct the flow of the molten glass,
The plate member is provided at a different vertical position below the liquid level of the molten glass,
In the pair, a first distance between an upper end of the first plate member disposed closest to the liquid level and the liquid level is disposed closest to the bottom of the inner wall of the fining tube. It was rather short than the second distance between the lower end portion and the bottom portion of the second plate member,
In the fining step, flowing the molten glass while changing the height of the liquid level,
The method of manufacturing a glass substrate, wherein the second distance is longer than the first distance when the height of the liquid surface is at a highest position. A method for manufacturing a glass substrate,
A melting process of melting glass raw materials to produce molten glass;
A fining step of fining the molten glass in a fining tube,
In the fining step, fining is performed while flowing the molten glass so that a gas phase space is formed above the liquid level of the molten glass in the fining tube,
In the fining tube, using a pair of plate members arranged at intervals in the flow direction of the molten glass, partially obstruct the flow of the molten glass,
The plate member is provided at a different vertical position below the liquid level of the molten glass,
In the pair, a first distance between an upper end of the first plate member disposed closest to the liquid level and the liquid level is disposed closest to the bottom of the inner wall of the fining tube. It was rather short than the second distance between the lower end portion and the bottom portion of the second plate member,
A method for manufacturing a glass substrate, wherein a plate member arranged without leaving an interval from the bottom is not provided in the fining tube. A glass substrate manufacturing apparatus,
A melting device for melting glass raw materials to produce molten glass;
A fining device having a fining tube in which fining of the molten glass is performed,
In the fining tube, fining is performed while the molten glass flows so that a gas phase space is formed above the liquid level of the molten glass,
The fining tube has a plurality of pairs of plate members arranged at intervals in the flow direction of the molten glass, and partially obstructs the flow of the molten glass,
Two plate members forming each said pair are provided vertically different positions of lower than the liquid surface of the molten glass,
In each of the pairs, a first distance between the upper end of the first plate member disposed closest to the liquid surface and the liquid surface is closest to the bottom of the inner wall of the fining tube. the lower end of the arranged second plate member and the second rather short than the distance between the bottom portion,
The fining device heats the molten glass so that a temperature distribution of the molten glass is formed along the flow direction,
At the first flow direction position where the temperature of the molten glass is the first temperature, the temperature of the molten glass is lower than the second flow direction position that is the second temperature lower than the first temperature. An apparatus for manufacturing a glass substrate , wherein the first distance and the second distance are short . A glass substrate manufacturing apparatus,
A melting device for melting glass raw materials to produce molten glass;
A fining device having a fining tube in which fining of the molten glass is performed,
In the fining tube, fining is performed while the molten glass flows so that a gas phase space is formed above the liquid level of the molten glass,
The fining tube has a plurality of pairs of plate members arranged at intervals in the flow direction of the molten glass, and partially obstructs the flow of the molten glass,
The two plate members forming each of the pairs are provided at different positions in the vertical direction below the liquid surface of the molten glass,
In each of the pairs, a first distance between the upper end of the first plate member disposed closest to the liquid surface and the liquid surface is closest to the bottom of the inner wall of the fining tube. Shorter than a second distance between the lower end of the disposed second plate member and the bottom,
The fining device heats the molten glass so that a temperature distribution of the molten glass is formed along the flow direction,
The interval between the plate members adjacent in the flow direction is a second temperature lower than the first temperature at a first flow direction position where the temperature of the molten glass is a first temperature. A glass substrate manufacturing apparatus, which is narrower than a flow direction position of the glass substrate. A glass substrate manufacturing apparatus,
A melting device for melting glass raw materials to produce molten glass;
A fining device having a fining tube in which fining of the molten glass is performed,
In the fining tube, fining is performed while the molten glass flows so that a gas phase space is formed above the liquid level of the molten glass,
The fining tube has a plurality of pairs of plate members arranged at intervals in the flow direction of the molten glass, and partially obstructs the flow of the molten glass,
The two plate members forming each of the pairs are provided at different positions in the vertical direction below the liquid surface of the molten glass,
In each of the pairs, a first distance between the upper end of the first plate member disposed closest to the liquid surface and the liquid surface is closest to the bottom of the inner wall of the fining tube. Shorter than a second distance between the lower end of the disposed second plate member and the bottom,
In the fining tube, the molten glass flows while the height of the liquid level fluctuates,
The said 2nd distance is larger than the said 1st distance when the height of the said liquid level is in the highest position, The glass substrate manufacturing apparatus characterized by the above-mentioned. A glass substrate manufacturing apparatus,
A melting device for melting glass raw materials to produce molten glass;
A fining device having a fining tube in which fining of the molten glass is performed,
In the fining tube, fining is performed while the molten glass flows so that a gas phase space is formed above the liquid level of the molten glass,
The fining tube has a plurality of pairs of plate members arranged at intervals in the flow direction of the molten glass, and partially obstructs the flow of the molten glass,
The two plate members forming each of the pairs are provided at different positions in the vertical direction below the liquid surface of the molten glass,
In each of the pairs, a first distance between the upper end of the first plate member disposed closest to the liquid surface and the liquid surface is closest to the bottom of the inner wall of the fining tube. Shorter than a second distance between the lower end of the disposed second plate member and the bottom,
An apparatus for manufacturing a glass substrate, wherein a plate member arranged without leaving an interval from the bottom is not provided in the fining tube.

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