JP5549674B2 - Molten glass production apparatus, molten glass production method, and plate glass production method using them - Google Patents

Description

  The present invention relates to a molten glass manufacturing apparatus, a molten glass manufacturing method, and a manufacturing method of plate glass using them. More specifically, the present invention relates to a molten glass manufacturing apparatus, a molten glass manufacturing method, and a plate glass manufacturing method using them for producing high-quality alkali-free glass with high homogeneity.

  For the production of a glass substrate for a flat panel display (FPD), it is preferable to use an alkali-free glass that does not substantially contain alkali metal ions in order to increase the insulating properties of the glass substrate. In addition, alkali-free glass is preferable for the production of a glass substrate for FPD because it has a small coefficient of thermal expansion.

  In manufacturing a glass substrate for FPD, there is a demand for further improvement in quality, that is, manufacturing a high-quality glass substrate with high homogeneity. For this reason, in the melting tank (melting furnace) which melts a glass raw material and obtains molten glass, various ideas are made in order to improve the homogeneity of molten glass.

  In the melting furnace described in Patent Document 1, the melting furnace is divided into an upstream zone and a downstream zone by a transverse sill, and a molten glass circulation flow (upstream circulation flow, downstream circulation flow) is formed in each zone. , Melting raw materials and homogenizing molten glass. More specifically, the glass raw material is melted by forming an upstream circulation flow in the upstream zone, and the molten glass is homogenized by forming a downstream circulation flow in the downstream zone. In the melting furnace described in Patent Document 1, a bubbler is provided on the upstream side of the crossing sill in order to control the upstream circulation flow and the downstream circulation flow.

  The melting furnace (melting tank) described in Patent Document 2 does not have a structure corresponding to the transverse sill in the melting furnace described in Patent Document 1, but includes at least one row of bubblers and at least two opposite burners. It describes using glass to melt and clarify.

Japanese Unexamined Patent Publication No. 9-124323 Japanese Unexamined Patent Publication No. 7-144923

However, the melting furnaces described in Patent Documents 1 and 2 are not necessarily suitable for producing high-quality alkali-free glass.
As an index of the melting temperature of glass, T _η , that is, a temperature at which the glass viscosity η becomes 10 ² [dPa · S] is used, but non-alkali glass has a T _η of 1500 to 1760 ° C. Compared with alkali-containing glass such as lime glass, T _η is 100 ° C. or higher, and homogenization is difficult. For this reason, it cannot be sufficiently homogenized in a melting furnace having a layout for general mass production such as soda lime glass described in Patent Documents 1 and 2, and glass products (for FPDs) that require particularly high homogeneity. It was not necessarily suitable for the production of glass substrates and the like.

Further, as described above, the alkali-free glass has a higher T _η than the alkali-containing glass such as soda lime glass, and therefore the temperature of the molten glass in the melting furnace inevitably increases. If the temperature of the molten glass is high, the erosion action of the molten glass on the in-furnace structure is enhanced accordingly. Therefore, in the case of non-alkali glass, there is a step that affects the flow of the molten glass at the bottom of the melting furnace, such as a crossing threshold in the melting furnace described in Patent Document 1 and a fining table in the melting furnace described in Patent Document 2. Then, the erosion of the level | step difference by molten glass and generation | occurrence | production of the impurity by it become a problem.

  In the case of non-alkali glass, the temperature of the molten glass in the melting furnace is inevitably high. Therefore, when a structure having a long downstream zone as in Patent Document 1 or a large melting furnace as in Patent Document 2, It is disadvantageous in terms of energy efficiency because the range of heating using a burner is widened. Further, erosion by the molten glass, generation of impurities due thereto, and change in the flow rate of the molten glass are also problematic.

  In order to solve the above-described problems of the prior art, the present invention provides a molten glass manufacturing apparatus, a molten glass manufacturing method, and a plate glass using them, which are suitable for producing high-quality non-alkali glass with high homogeneity. An object is to provide a manufacturing method.

  As a result of intensive investigations to achieve the above-mentioned purpose, in order to produce high-quality non-alkali glass with high homogeneity, the flow rate of the upstream circulation flow in the melting tank for melting the glass raw material and the downstream circulation flow The inventor of the present application has found that it is necessary to control the flow rate of the gas so as to have a certain relationship.

The present invention has been made on the basis of the above findings by the inventors of the present application, and is used for producing a molten glass having a temperature T _η of 1500 to 1760 ° C. at which the glass viscosity η is 10 ² [dPa · S]. It is a glass manufacturing apparatus, the molten glass manufacturing apparatus has a melting tank for melting the glass raw material,
A plurality of first bubblers and a plurality of second bubblers over the width direction of the molten glass flow path in the vicinity of the bottom surface of the melting tank;
The first bubbler is provided on the upstream side of the molten glass flow path from the second bubbler,
The dissolution tank has a burner for heating the upper space of the dissolution tank,
When the length of molten glass flow path of the melting tank and L _F, the distance from the upstream end of the molten glass flow path to the row of the first bubbler is 0.4L _F ~0.5L _F, the molten distance from the downstream end of glass flow path to the row of the second bubbler is 0.45L _F ~0.55L _F, the distance of the columns of the first bubbler and said second bubbler row L _P is 500 to 1000 mm,
The distance L _B1 between the row of the first bubblers and the burner closest to the upstream side of the row in the flow direction of the molten glass in the melting tank is 0 to 2000 mm,
The distance L _B2 between the second bubbler row and the burner closest to the downstream side of the row in the flow direction of the molten glass in the melting tank is 800 to 2500 mm,
And the molten glass manufacturing apparatus characterized by it being _LB2 > _LB1 is provided.

The present invention is also a method for producing molten glass using the above-described molten glass production apparatus, wherein the average flow rate of the gas supplied from the first bubbler is V ₁ [liter / minute], and the first The average flow rate of the gas supplied from the second bubbler is V ₂ [liter / min], the ambient temperature above the first bubbler is T ₁ [° C.], and the ambient temperature above the second bubbler is Provided is a molten glass production method for producing molten glass under the conditions of V ₁ > V ₂ and T ₁ > T ₂ when T ₂ [° C.] is satisfied.

  Moreover, this invention provides the plate glass manufacturing method which shape | molds the molten glass obtained by the above-mentioned molten glass manufacturing method of this invention to plate glass.

The molten glass manufacturing apparatus and molten glass manufacturing method of the present invention are suitable for the production of high-quality alkali-free glass with high homogeneity.
Since the plate glass manufacturing method of this invention can manufacture plate glass with high homogeneity and high transparency, it is suitable for manufacture of the board | substrate for FPD.

FIG. 1 is a cross-sectional view of an embodiment of a melting tank in the molten glass production apparatus of the present invention. FIG. 2 is a plan view of the dissolution tank 10 shown in FIG. However, the upper wall surface of the dissolution tank 10 is omitted.

  The present invention will be described below with reference to the drawings.

As described above, T _η is used as an index of the melting temperature of glass. The glass targeted by the present invention is difficult to homogenize molten glass because T _η is 1500 to 1760 ° C., which is 100 ° C. higher than T _η of alkali-containing glass such as general soda lime glass. The molten glass manufacturing apparatus and the molten glass manufacturing method of the present invention are suitable for homogenizing such molten glass. In addition, as a specific example of the glass in which T _η is 1500 to 1760 ° C., alkali-free glass is particularly applicable.
From this point, the molten glass manufacturing apparatus and the molten glass manufacturing method of the present invention produce a predetermined amount (20 to 100 tons / day) of glass products with strict quality requirements such as a glass substrate for FPD. Suitable for

FIG. 1 is a cross-sectional view of one embodiment of a melting tank in the molten glass production apparatus of the present invention, and FIG. 2 is a plan view of the melting tank shown in FIG. However, the upper wall surface of the dissolution tank 10 is omitted for easy understanding.
A glass raw material inlet 11 is provided at the upstream end of the melting tank 10. The glass raw material charged from the charging port 11 is melted by heating by the burner 15 to become molten glass G, and is held in the melting tank 10. A discharge port 12 for discharging the molten glass G to the next process is provided at the downstream end of the melting tank 10. The discharge port 12 communicates with the downstream conduit 20.

A plurality of first bubblers 13 and a plurality of second bubblers 14 are provided in the vicinity of the bottom surface of the dissolution tank 10 shown in FIGS.
The plurality of first bubblers 13 and the plurality of second bubblers 14 have a predetermined interval (pitch) over the width direction of the melting tank 10, more specifically, the width direction of the molten glass flow path of the melting tank 10. ) Is opened.
The first bubbler 13 is provided upstream of the second bubbler 14 in the molten glass flow path, and a predetermined interval is provided between the first bubbler 13 row and the second bubbler 14 row. Is provided.
The preferred range of the pitches of the individual bubblers in the row direction of the first bubbler 13 and the second bubbler 14 and the distance between the row of the first bubblers 13 and the row of the second bubblers 14 is as follows. It will be described later.

  Burners 15 are arranged on both side surfaces of the melting tank 10 shown in FIGS. 1 and 2 so as to be positioned above the molten glass G held in the melting tank 10. The burners 15 are provided at equal intervals over the entire length of the dissolution tank 10 except for an exception part to be described later.

The melting tank 10 in the molten glass manufacturing apparatus of the present invention has Patent Documents 1 and 2 at the bottom of the molten glass channel by arranging the first and second bubblers 13 and 14 and the burner 15 in a specific arrangement described later. Formation of a circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10 without providing a step structure that affects the molten glass flow as described in FIG. Further, the flow rate of the upstream circulating flow 100 and the flow rate of the downstream circulating flow 101 can be controlled to have a predetermined relationship.
The melting tank 10 in the molten glass production apparatus of the present invention is suitable for producing glass having a T _η of 1500 to 1760 ° C. because there is no step structure that causes erosion by the molten glass at the bottom of the molten glass flow path. is there.

The melting tank 10 in the molten glass production apparatus of the present invention is a distance from the upstream end of the molten glass flow path to the first bubbler 13 row when the length of the molten glass flow path of the melting tank 10 is L _F. There is a 0.4L _F ~0.5L _F, the distance from the downstream end of the molten glass flow path to the row of the second bubbler 14 is 0.45L _F ~0.55L _F.
Therefore, compared with the conventional melting tank (melting furnace) as described in Patent Documents 1 and 2, the length of the melting tank 10 is short, and the length of the part forming the downstream circulating flow in the melting tank is also short. .
Although the length L _F of the molten glass flow path of the melting tank 10 of the present invention varies depending on the width of the molten glass flow path, it is preferably 10 to 30 m, more preferably 10 to 25 m, and still more preferably 15 to 22 m.
On the other hand, the width of the molten glass channel is preferably 5 to 10 m, more preferably 5.5 to 9 m, and still more preferably 6.5 to 8 m.

In the melting tank 10 in the molten glass manufacturing apparatus of the present invention, the flow rates of the gases 16 and 17 from the first bubbler 13 and the second bubbler 14 are set to a specific relationship described later, and the burner 15 is set to a specific arrangement described later. By reducing the flow rate per unit time of the molten glass flow (downstream circulating flow 101) in the downstream zone, the flow rate of the upstream circulating flow 100 and the flow rate of the downstream circulating flow 101 have a predetermined relationship. Can be controlled. As a result, when producing molten glass having a T _η of 1500 to 1760 ° C., the forward movement of the heterogeneous layer (scum layer) having a light specific gravity (scum layer) formed by undissolved material in the glass raw material or volatilization on the surface of the molten glass. And the homogenization of the molten glass can be promoted, and a high-quality molten glass with high homogeneity can be obtained.
In addition, the gas 16 and 17 supplied from the first bubbler 13 and the second bubbler 14 should use molten glass G and those that do not adversely affect the components of the melting tank 10 such as the bubblers 13 and 14. Is preferred. Specific examples of such a gas include air, nitrogen, oxygen, helium, and argon. When platinum or a platinum alloy is used as the material of the bubblers 13, 14, it is preferable to use a gas that does not contain oxygen, such as nitrogen, helium, and argon, as the gases 16, 17 supplied from the bubbler 13, the bubbler 14. . Of these, nitrogen is particularly preferred.

In the melting tank 10, the distance from the upstream end of the molten glass flow path to the row of the first bubblers 13 is preferably 0.43L _{F to} 0.46L _F , and the second from the downstream end of the molten glass flow path. The distance to the row of bubblers 14 is preferably 0.47L _{F to} 0.54L _F.

In the dissolution tank 10, when the distance between the row of the first bubblers 13 and the row of the second bubblers 14 is L _P , L _P is 500 to 1000 mm. When L _P satisfies the above range, it is excellent in the effect of promoting the formation of a circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10, and upstream. This is preferable in controlling the flow rate of the side circulation flow 100 and the flow rate of the downstream circulation flow 101 so as to have a predetermined relationship.
If L _P is less than 500 mm, the distance between the row of the first bubblers 13 and the row of the second bubblers 14 is too close, so the circulating flow of the molten glass G in the melting tank 10 (upstream circulating flow 100 In addition, the effect of promoting the formation of the downstream circulation flow 101) is poor, and it is difficult to control the flow rate of the upstream circulation flow 100 and the flow rate of the downstream circulation flow 101 to have a predetermined relationship.
Even when L _P is more than 1000 mm, the distance between the row of the first bubblers 13 and the row of the second bubblers 14 is too wide, so the circulating flow of the molten glass G in the melting tank 10 (upstream circulating flow) 100, the effect of promoting the formation of the downstream circulation flow 101) is poor, and it is difficult to control the flow rate of the upstream circulation flow 100 and the flow rate of the downstream circulation flow 101 so as to have a predetermined relationship. .
In the dissolution tank 10, L _P is preferably 600 to 800 mm.

In the first bubbler 13 and the second bubbler 14, the pitch p between the individual bubblers in the row direction of the bubblers, that is, the distance between the individual bubblers in the width direction of the molten glass channel of the melting tank 10 is 400 to It is preferable that it is 700 mm. If the pitch p between the individual bubblers is in the above range, it is excellent in the effect of promoting the formation of a circulating flow (upstream circulating flow 100, downstream circulating flow 101) of the molten glass G in the melting tank 10, and upstream. This is preferable for controlling the flow rate of the side circulation flow 100 and the flow rate of the downstream circulation flow 101 so as to have a predetermined relationship, and is excellent in terms of manufacturing cost.
If the pitch p between the individual bubblers exceeds 700 mm, the distance between the individual bubblers is too wide, so that the molten glass G circulating flow (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10 There is a possibility that the effect of promoting the formation may be insufficient. In particular, in the width direction of the molten glass flow path, the formation of the circulating flow (the upstream circulating flow 100 and the downstream circulating flow 101) of the molten glass G depending on the part. A difference occurs in the acceleration, and the flow rate of the circulating flow may be uneven, which is not preferable from the viewpoint of homogenizing the molten glass G. Further, it may be difficult to control the flow rate of the upstream circulation flow 100 and the flow rate of the downstream circulation flow 101 so as to have a predetermined relationship.
On the other hand, even if the pitch p between individual bubblers is less than 400 mm, it no longer contributes to the promotion of the formation of the circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10. Rather, from the viewpoint of cost effectiveness, the number of the first and second bubblers 13 and 14 provided in the melting tank 10 becomes excessive, which leads to an increase in the manufacturing cost of the molten glass, which is not preferable.

It is preferable that the first bubbler 13 and the second bubbler 14 are arranged so as not to be coaxial with respect to the flow direction of the molten glass in the melting tank 10.
In the dissolution tank 10 shown in FIG. 2, the protruding ports of the first bubbler 13 and the protruding ports of the second bubbler 14 are arranged in a staggered manner, and the protruding port of the first bubbler 13 and the second bubbler 14 are arranged. There is no coexistence with the protruding port.
In such an arrangement, even if one of the protruding ports of the first bubbler 13 stops functioning, due to the presence of the protruding ports of the second bubbler 14 arranged in a staggered manner downstream. In addition, the effect of promoting the formation of the circulating flow of the molten glass G (upstream circulating flow 100, downstream circulating flow 101) in the melting tank 10 is not impaired, and the flow rate and the downstream of the upstream circulating flow 100 are not impaired. The flow rate of the side circulation flow 101 can be controlled to have a predetermined relationship.

Burners 15 are provided at equal intervals over the entire length of the dissolution tank 10 on both sides of the dissolution tank 10 shown in FIGS. However, the burner 15 is not provided above the second bubbler 14.
As will be described in detail later, in the present invention, the average flow rate V ₂ of the gas 17 supplied from the second bubbler 14 is made smaller than the average flow rate V _{1 of the} gas 16 supplied from the first bubbler 13 (control 1). ) And lowering the ambient temperature T ₂ above the second bubbler 14 to be lower than the ambient temperature T ₁ above the first bubbler 13 (control 2), the unit of the downstream circulating flow 101 per unit time It is possible to control the flow rate of the upstream circulating flow 100 and the downstream circulating flow 101 so as to have a predetermined relationship by decreasing the flow rate. Thus, when the T _eta is producing molten glass from 1500 to 1760 ° C., can promote homogenization of molten glass, it is possible to obtain high homogeneity quality molten glass.

In order to achieve the above control 2, as shown in FIG. 2, it is necessary to arrange the row of the second bubblers 14 and the burner 15 nearest to the downstream side of the row to some extent. Therefore, it is necessary to set L _B2 = 800 mm or more.
However, if the row of the second bubblers 14 and the burner 15 closest to the downstream side of the row are separated too much, the ambient temperature above the second bubbler 14 becomes too low and the homogenization of the molten glass is not achieved. The problem of becoming sufficient arises. Moreover, the temperature of the molten glass G discharged | emitted from the discharge port 12 provided in the downstream edge part of the melting tank 10 becomes low, and when depressurization defoaming is performed in a post process, it is difficult to defoam. Arise. For this reason, it is necessary to set L _B2 = 2500 mm or less.
Therefore, L _B2 = 800 to 2500 mm. Incidentally, it is preferable that an L _B2 = 1000 to 2000 mm, and more preferably L _B2 = 1000~1600mm.

Further, in order to achieve the above control 2, in the melting tank 10 shown in FIG. 2, the burner 15 nearest to the row of the first bubblers 13 and the upstream side of the row in the flow direction of the molten glass in the melting bath 10. the distance L _B1 between, the distance L _B2 of the nearest burner 15 on the downstream side of the column and said column of the second bubbler 14, but have a relationship of L _B2> L _B1. That is, the burner 15 is provided above the first bubbler 13, whereas the burner 15 is not provided above the second bubbler 14. In the dissolution tank 10 shown in FIG. 2, with such an arrangement, the atmospheric temperature T ₂ above the second bubbler can be made lower than the atmospheric temperature T ₁ above the first bubbler.
In the present invention, L _B2 −L _B1 ≧ 300 mm is preferable, L _B2 −L _B1 ≧ 500 mm is more preferable, and L _B2 −L _B1 ≧ 800 mm is further preferable.

On the other hand, in the dissolution tank 10 shown in FIG. 2, the burner 15 is provided above the row of the first bubblers 13, but as long as the relationship of L _B2 > L _B1 is satisfied, The nearest burner 15 may be arranged some distance away from the upstream side of the row. However, if the row of the first bubblers 13 and the burner 15 closest to the upstream side of the row are separated too much, the ambient temperature above the first bubbler 13 becomes too low and the upstream side circulation flow 100 becomes weak, and the glass Problems such as insufficient melting of the raw materials and insufficient homogenization of the molten glass G in the downstream region of the melting tank 10 occur. For this reason, it is necessary to set L _B1 = 2000 mm or less.
Therefore, L _B1 = 0 to 2000 mm. Note that L _B1 = 500 to 1500 mm is preferable.
Moreover, although the pitch between the adjacent burners 15 is based also on the kind of burner 15 and the layout of the dissolution tank 10, 600-2600 mm is preferable and 800-2400 mm is more preferable.

  Combustion in the burner 15 can be performed by mixing the fuel with oxygen gas and burning it, or mixing the fuel with oxygen gas and air and burning it. By using these methods, moisture can be contained in the molten glass. In the post-process of the molten glass sent from the melting tank 10 to the downstream conduit 20, when the bubbles in the molten glass are defoamed by vacuum degassing, the molten glass preferably contains moisture. Therefore, the combustion as described above is preferable.

The constituent material of the melting tank 10 in contact with the molten glass G is required to be excellent in heat resistance and corrosion resistance to the molten glass. Therefore, a refractory brick containing ZrO ₂ is used. of the bottom surface of the dissolving tank 10, in a portion of the 0.1L _F ~0.3L _F on the upstream side from the columns of the first bubbler 13, ZrO ₂ is not more than 97% 85% by mass%, the balance being SiO It is preferable to use a glassy hot-melt refractory mainly composed of ₂ . The temperature of the molten glass flowing through the melting tank 10 is higher on the upstream side than on the downstream side, and since the flow rate from the first bubbler 13 is higher than the flow rate from the second bubbler 14, This is because it is easily eroded. In this case, the thickness of each hot-melt refractory is preferably 50 to 120 mm, and preferably two or three hot-melt refractories are laminated. Furthermore, 2-5 layers of other ZrO ₂ -containing refractory bricks can be laminated outside the layer of the hot-melt refractory thus formed. In addition, it is preferable to comprise all the parts which contact | connect the molten glass G of the melting tank 10 with the hot-melt refractory material of the said composition. Moreover, each refractory brick can be laminated | stacked via stamp materials, such as an alumina zircon material.
It is preferable that cooling means by air cooling or water cooling for cooling the refractory brick is provided on the outer side of the refractory brick at the bottom of the melting tank 10 because the life of the refractory brick is improved.

Next, the molten glass manufacturing method of this invention is demonstrated.
In the molten glass manufacturing method of the present invention, the molten glass is manufactured while performing the above controls 1 and 2.
By performing the above controls 1 and 2, the flow rate per unit time of the downstream circulation flow 101 is lowered, and the flow rate of the upstream circulation flow 100 and the flow rate of the downstream circulation flow 101 have a predetermined relationship described later. Can be controlled.

In the molten glass production method of the present invention, V ₁ is preferably 0.5 to 20 liters / minute, more preferably 0.7 to 5 liters / minute, and 0.9 to 3 liters / minute. More preferably, it is particularly preferably 1.8 to 2.6 liters / minute. The V ₂ is preferably 0.3 to 19.8 liters / minute, more preferably 0.4 to 4.8 liters / minute, and 0.5 to 2 liters / minute. Is more preferable, and 0.9 to 2.0 liter / min is particularly preferable.
Further, V ₁ −V ₂ ≧ 0.2 liter / min is preferable, V ₁ −V ₂ ≧ 0.4 liter / min is more preferable, V ₁ −V ₂ ≧ 0.6 liter / min is further preferable, V ₁₋ V ₂ ≧ 1.0 liter / min is particularly preferred.

In the molten glass producing method of the present invention, it is preferable that the T ₁ is a 1590-1710 ° C., and more preferably from 1600 to 1695 ° C.. Further, it is preferable that the T ₂ is 1570-1690 ° C., and more preferably 1580-1675 ° C..
Further, T ₁ -T ₂ is preferably 10~35 ℃, T ₁ -T ₂ is more preferably 15 to 30 ° C., more preferably 19 to 26 ° C..
T ₁ and T ₂ can be measured by the following method.
(Measurement position)
T ₁ : Intermediate position between the burner closest to the upstream side of the first row of bubblers and the latest burner positioned further upstream than the burner.
T ₂ : Intermediate position between the second row of bubblers and the burner closest to the downstream side of the bubblers.
(Measuring method)
From the observation window provided on the side surface of the dissolution tank, the inner wall surface temperature of the facing side surface is measured with a radiation thermometer (for example, CHINO IR-AH3SU (measurement wavelength: 0.65 μm, ε = 1.0)). taking measurement.

In the molten glass production method of the present invention, when the average flow velocity of the upstream circulation flow 100 is F ₁ [m / hour] and the average flow velocity of the downstream circulation flow 101 is F ₂ [m / hour], F ₁ = 5 to 20 m / time is preferably controlled such that F ₂ = 0.5~7m / time. Thus, when the T _eta is producing molten glass from 1500 to 1760 ° C., can promote homogenization of molten glass, it is possible to obtain high homogeneity quality molten glass.
It is more preferable to control such that F ₁ = 8 to 15 m / hour and F ₂ = _{1 to 4} m / hour.
F ₁ and F ₂ can be measured by the following method.
(Measurement position)
F _1: distance from the upstream end of the molten glass flow path at 0.30L _F ~0.34L _F, near the center in the width direction of the molten glass flow path.
F _2: distance from the downstream end of the molten glass flow path at 0.22L _F ~0.30L _F, near the center in the width direction of the molten glass flow path.
(Measuring method)
Video of the flow of bubbles on the surface of the molten glass is taken, and the moving time with respect to the moving distance of the bubbles is measured to obtain the flow velocity. Repeat this procedure 2-3 times to determine the average flow rate.

Next, the plate glass manufacturing method of the present invention will be described.
In the plate glass manufacturing method of the present invention, the molten glass obtained by the above-described molten glass manufacturing method of the present invention is formed into a plate glass. As a means for forming molten glass into plate glass, various forming methods such as a float method and a downdraw method can be used. If T _eta is a glass of 1,500 to 1,760 ° C., a float method is particularly preferable.
In the plate glass manufacturing method of the present invention, before the molten glass obtained by the above-described molten glass manufacturing method of the present invention is formed into plate glass, bubbles in the molten glass may be degassed by vacuum degassing.
In the plate glass manufacturing method of the present invention, since the molten glass having high homogeneity obtained by the molten glass manufacturing method of the present invention is formed into a plate glass, a plate glass having high homogeneity and high transparency can be obtained.
The plate glass production apparatus of the present invention can be applied to the production of plate glass for various uses. However, since a plate glass having high homogeneity and high transparency can be obtained, the homogeneity of the glass substrate for FPD can be obtained. It is particularly preferable to apply it to the production of plate glass for applications in which the demands of these are extremely strict.

By introducing glass raw materials so that the desired composition into the slot of the dissolution tank 10 shown in FIG. 1, 2, T _eta is the production of alkali-free glass of 1500 to 1760 ° C.. The dimensions of each part of the dissolution tank 10 shown in FIGS.
Molten glass flow path length L _F : 16 to 25 m
Width of molten glass flow path: 5.5-9m
Distance from the upstream end of the molten glass flow path to the first bubbler 13 row: 0.43L _{F to} 0.46L _F
Distance from the downstream end of the molten glass flow path to the second bubbler 14 row: 0.47 L _{F to} 0.54 L _F
Distance L _p between first bubbler 13 row and second bubbler 14 row: 600 to 800 mm Pitch of individual bubblers 13 and 14 in the row direction of bubblers p: 400 to 700 mm
Distance L _B1 between the row of first bubblers 13 and the burner 15 closest to the upstream side of the row in the flow direction of the molten glass in the melting tank: 500-1500 mm
Distance L _B2 between the row of second bubblers 14 and the burner 15 nearest to the downstream side of the row in the flow direction of the molten glass in the melting tank: 1000 to 2000 mm
L _B2 -L _B1 ≧ 500mm
Distance between individual burners in the flow direction of molten glass in the melting tank: 800 to 2400 mm
The average flow rate V ₁ from the first bubbler 13 and the average flow rate V ₂ from the second bubbler 14 are adjusted to satisfy the following conditions.
V ₁ : 1.8 to 2.6 liters / minute V ₂ : 0.9 to 2.0 liters / minute V ₁ −V ₂ ≧ 0.6 liters / minute By the combustion in the burner 15, the first bubbler 13 The ambient temperature T ₁ above and the ambient temperature T ₂ above the second bubbler 14 are maintained under the following conditions. T ₁ and T ₂ are measured by the method described above.
T ₁ : 1590 to 1710 ° C.
T ₂ : 1580-1675 ° C
T ₁ -T _2: 10~35 ℃
The average flow rate F ₂ in average flow rate F ₁ and the downstream circulation flow 101 of the upstream circulation flow 100 in the dissolution tank 10 is measured by the method described above. The results are as follows.
F ₁ = 8 to 15 m / hour F ₂ = _{1 to 4} m / hour By carrying out under the above conditions, T _η is 1500 to 1760 ° C., and high-quality alkali-free glass with high homogeneity is produced.

Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2009-219347 filed on Sep. 24, 2009, the contents of which are incorporated herein by reference.

  The molten glass manufacturing apparatus and molten glass manufacturing method of the present invention are suitable for the production of high-quality alkali-free glass with high homogeneity. Moreover, since the plate glass manufacturing method of this invention can manufacture plate glass with high homogeneity and transparency, it is suitable for manufacture of the board | substrate for FPD.

10: Dissolution tank 11: Input port 12: Discharge port 13: First bubbler 14: Second bubbler 15: Burner 16: Gas from the first bubbler 17: Gas from the second bubbler 20: Downstream side Conduit 100: Upstream circulating flow 101: Downstream circulating flow

Claims (8)

A molten glass production apparatus for producing a molten glass having a temperature T _η of 1500 to 1760 ° C. at which the glass viscosity η is 10 ² [dPa · S], wherein the molten glass production apparatus dissolves a glass raw material. Have
A plurality of first bubblers and a plurality of second bubblers over the width direction of the molten glass flow path in the vicinity of the bottom surface of the melting tank;
The first bubbler is provided on the upstream side of the molten glass flow path from the second bubbler,
The dissolution tank has a burner for heating the upper space of the dissolution tank,
When the length of molten glass flow path of the melting tank and L _F, the distance from the upstream end of the molten glass flow path to the row of the first bubbler is 0.4L _F ~0.5L _F, The distance from the downstream end of the molten glass flow path to the second bubbler row is 0.45L _{F to} 0.55L _F , and the first bubbler row and the second bubbler row are The distance L _P is 500 to 1000 mm,
The distance L _B1 between the row of the first bubblers and the burner closest to the upstream side of the row in the flow direction of the molten glass in the melting tank is 0 to 2000 mm,
The distance L _B2 between the second bubbler row and the burner closest to the downstream side of the row in the flow direction of the molten glass in the melting tank is 800 to 2500 mm,
And the molten glass manufacturing apparatus characterized by it being L _B2 > L _B1 .   The molten glass manufacturing apparatus of Claim 1 whose pitch p of each bubbler in the row direction of a bubbler is 400-700 mm in a said 1st bubbler and a said 2nd bubbler.   The molten glass according to claim 1 or 2, wherein the first bubbler and the second bubbler are arranged so as not to be coaxial with each other when the flow direction of the molten glass in the melting tank is an axis. manufacturing device. The constituent material of the dissolving tank is a refractory brick of the ZrO ₂ content, of the bottom surface of the melting bath forms a molten glass flow path, 0.1L _F ~0.3L _F on the upstream side from a column of the first bubbler of the portion, ZrO ₂ is not more than 97% 85% by mass%, the balance being according to any one of claims 1 to 3, hot melt refractory vitreous was used consisting mainly of SiO ₂ Molten glass manufacturing equipment.   The first bubbler and the second bubbler are made of platinum or a platinum alloy, and the gas supplied from the first bubbler and the second bubbler is a gas not containing oxygen. The molten glass manufacturing apparatus of any one of these. Using the molten glass manufacturing apparatus according to any one of claims 1 to 5, an average flow rate of gas supplied from the first bubbler is set to V ₁ [liter / minute], and from the second bubbler The average flow rate of the supplied gas is V ₂ [liter / min], the ambient temperature above the first bubbler is T ₁ [° C.], and the ambient temperature above the second bubbler is T ₂ [° C. when _{a], V 1> V 2,} T 1> molten glass producing method of producing molten glass by T ₂ become condition. The average flow velocity of the upstream circulating flow of the molten glass formed upstream of the first bubbler is F ₁ [m / hour], and the downstream of the molten glass formed downstream of the second bubbler. The molten glass is produced under the conditions of F ₁ = 5 to 20 m / hour and F ₂ = 0.5 to 7 m / hour when the average flow velocity of the side circulation flow is F ₂ [m / hour]. The molten glass manufacturing method of description.   The plate glass manufacturing method which shape | molds the molten glass obtained by the molten glass manufacturing method of Claim 6 or 7 to plate glass.

Images