JP2009298665A - Apparatus for manufacturing sheet glass and method of manufacturing sheet glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus for manufacturing sheet glass by which a manufacturing yield can be enhanced. <P>SOLUTION: The apparatus for manufacturing sheet glass includes: a forming device 5 which overflows fused glass to both sides from a groove 51, allows the fused glass to flow down along a wall surface 52 and fuses the glass into one; a clarifying tank 3 for clarifying the fused glass; and a transfer pipe 4 which guides the fused glass clarified in the clarifying tank 3 to the forming device 5 while adjusting the temperature. The transfer pipe 4 is curved to a lateral side while falling from one end 4a of the clarifying tank 3 side toward the other end 4b of the forming device 5 side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  In flat glass used for a glass substrate of a flat panel display (hereinafter referred to as “FPD”) such as a liquid crystal display or a plasma display, high flatness is required on the glass surface. In recent years, the required quality for the flatness of the glass surface has been increasing.

  Such FPD glass substrate glass is often manufactured by the overflow down draw method. In the overflow down draw method, a glass ribbon is continuously formed by supplying molten glass to a forming apparatus. At that time, the glass ribbon is pulled downward, and the thickness is adjusted by the pulling speed. Then, a glass ribbon is cut | disconnected by predetermined length, and plate glass is manufactured.

  By the way, since the plate glass for TFT liquid crystal displays, for example, requires high thermal stability, a glass raw material prepared so as to realize the plate glass is used. Since such glass raw materials are usually poorly soluble, striae (parts having different components from the surrounding parts) are likely to occur in the molten glass. And when striae exist in the molten glass, when the glass ribbon formed by the molding apparatus is pulled down, the stretched state differs depending on the difference in viscosity between the surrounding portion and the striae. The degree will get worse.

For example, Patent Literature 1 discloses a technique for suppressing the occurrence of striae by using a silica raw material having an average particle diameter of 30 to 60 μm.
JP 2004-67408 A

  However, even if the technique disclosed in Patent Document 1 is used, the striae cannot be completely eliminated, and the manufactured plate glass may not be used as a product without satisfying the required quality for the flatness of the glass surface. . Therefore, it is desired to improve the yield when manufacturing plate glass.

  An object of this invention is to provide the plate glass manufacturing apparatus and plate glass manufacturing method which can improve a yield in view of such a situation.

  In order to achieve the above object, the inventors of the present invention have focused on the fact that the required quality with respect to the flatness of the glass surface differs between the one side and the other side of the plate glass. For example, in flat glass for liquid crystal displays, high flatness is required on the main surface (use surface) on which electrodes and alignment films are stacked, but on the opposite back surface (non-use surface), the flatness is so high. Is not required. Therefore, the inventor considered that if the striae can be concentrated on the back side, a plate glass of satisfactory quality can be manufactured with a high yield. The peak height refers to the maximum of the distances from the average line of the undulation curve to the peak of the mountain or the bottom of the valley in a certain reference length.

  The present invention has been made from such a viewpoint, a molding apparatus for flowing and fusing the molten glass overflowed from the groove on both sides along the wall surface, a clarification tank for refining the molten glass, A transfer pipe for guiding the molten glass clarified in a clarification tank to the molding apparatus, and the transfer pipe is bent sideways while descending from one end on the clarification tank side toward the other end on the molding apparatus side. A flat glass manufacturing apparatus is provided.

  The present invention also relates to a method for producing a sheet glass comprising a step of forming a glass ribbon by overflowing molten glass from both sides of a groove of a molding apparatus, and a transfer pipe that bends sideward while descending from one end to the other end. A method for producing a sheet glass is provided in which molten glass is supplied to the molding apparatus while rotating the molten glass.

  According to the present invention, striae can flow out relatively more to one side of the plate glass. If this surface is used as the back surface, the peak height of the main surface can be kept small, and the required quality for flatness can be satisfied on both the main surface and the back surface. That is, according to this invention, the ratio of the plate glass which can be used as a product can be increased, and a yield can be improved.

  The best mode for carrying out the present invention will be described below with reference to the drawings. The following description relates to an example of the present invention, and the present invention is not limited to these.

  As shown in FIGS. 1-3, the plate glass manufacturing apparatus which concerns on one Embodiment of this invention is from the melting tank 1 for producing | generating a molten glass, the clarification tank 3 for clarifying a molten glass, and a molten glass. And a molding device 5 for molding a belt-shaped glass ribbon. 1 to 3, two orthogonal directions on the horizontal plane are shown as an X direction and a Y direction, and a vertical direction is shown as a Z direction.

  In this embodiment, the dissolution tank 1 and the clarification tank 3 are arranged in the X direction, and the molding device 5 is disposed obliquely downward from the dissolution tank 1 in the −Y direction. And the melting tank 1 and the clarification tank 3 are connected by the linear 1st transfer pipe 2 extended in a X direction, and the clarification tank 3 and the shaping | molding apparatus 5 are the 2nd transfer pipes which curve in a X direction from a Y direction by planar view. 4 are connected.

In the melting tank 1, the glass raw material thrown into the said melting tank 1 is melt | dissolved, and a molten glass is produced | generated. For example, when manufacturing a glass plate for TFT, the glass raw material charged into the melting tank 1 is expressed in mol%, SiO ₂ : 50 to 70%, B ₂ O ₃ : 5 to 15%, Al ₂ O. _{3: 5~15%, MgO: 0~3} %, CaO: 3~10%, SrO: 1~3%, BaO: 0~5%, Na 2 O: 0~1%, K 2 O: 0~ 1%, as ₂ O _3: is prepared containing 0 to 1%. In addition to the above components, the glass raw material may contain Sb ₂ O ₃ , Fe ₂ O ₃ , SnO ₂ , ZrO ₂ , Cl, etc., preferably in a range of 2 mol% or less.

  The molten glass generated in the melting tank 1 is sent to the clarification tank 3 through the first transfer pipe 2. In the clarification tank 3, the molten glass is maintained at a predetermined temperature (for example, 1500 ° C. or more in the case of glass having the above composition) for a certain period of time, and clarification (removal of bubbles from the molten glass, etc.) is performed.

  The second transfer pipe 4 is a molding apparatus 5 while adjusting (cooling) the temperature so that the molten glass clarified in the clarification tank 3 has a temperature suitable for molding (for example, about 1200 ° C. in the case of glass having the above composition). It leads to. Details of the second transfer pipe 4 will be described later.

  The forming device 5 has a pentagonal wedge shape (narrow home base shape) that is pointed downward and extends in the X direction. A groove 51 that gradually decreases in depth toward the −X direction is formed on the upper surface thereof. Is formed. In the groove 51, molten glass is supplied from the second transfer pipe 4 toward the −X direction. When molten glass is supplied into the groove 51, as shown in FIG. 4, the molten glass 6 overflows from the groove 51 to both sides on the + Y direction side and the −Y direction side. The overflowing molten glass 6 flows down along the wall surface 52, thereby fusing below the ridgeline where the lower end portions of the wall surface 52 intersect. Thereby, the strip-shaped glass ribbon 60 is continuously formed. In addition, although illustration is abbreviate | omitted, in the shaping | molding apparatus 5, the guide which regulates the width | variety of the molten glass 6 which flows down along the wall surface 52 is provided. Further, the glass ribbon 60 formed by the forming device 5 is pulled down by a pulling device (not shown).

  Next, the second transfer pipe 4 will be described in detail. The second transfer pipe 4 has a circular cross section, one end 4 a is connected to the −Y direction side surface of the clarification tank 3, and the other end 4 b is connected to the + X direction side end surface of the molding device 5. . The second transfer pipe 4 is bent by approximately 90 ° in the direction of the molding apparatus while descending from the one end 4a toward the other end 4b.

  More specifically, the second transfer pipe 4 is straight from the side surface of the clarification tank 3 to the upstream linear portion 41 that goes straight down in the −Y direction, and straight to the end surface on the + X direction side of the molding device 5 in the −X direction. And a bent portion 42 having a semicircular arc shape that connects these 41 and 43.

  1 to 3, the second transfer pipe 4 is drawn as a single pipe for simplification, but the actual second transfer pipe 4 is divided into a plurality of blocks with a predetermined length in the axial direction. Has been. Each block is a short tube made of platinum or a platinum alloy and having a wall thickness of about 0.7 to 0.8 mm, and flanges to which electrodes are connected are provided at both ends thereof. Each block keeps the molten glass at an appropriate temperature by generating Joule heat by energizing the short tube. Each block is surrounded by fire bricks on the outside.

  The gradient of the second transfer pipe 4 may be constant (for example, 9 °) over the entire length. In this case, the center line of the bent portion 42 is located on an inclined surface that intersects with the X axis and the Y axis at 9 °, that is, inclined in a direction in which the + X direction is swung by 45 ° in the −Y direction.

  In the present embodiment, the bent portion 42 has an arc shape that overlaps with a perfect circle in plan view. That is, the bent part 42 overlaps the ellipse on the inclined surface. The radius when the center line of the bent portion 42 is projected on the horizontal plane is, for example, 2.5 m. However, the bent portion 42 may have an arc shape that overlaps with a perfect circle on the inclined surface. Alternatively, the bent portion 42 only needs to be bent in a substantially arc shape, and the center line is configured by a plurality of straight lines, for example, by connecting the linear blocks with an angle. May be.

  The second transfer pipe 4 may have a constant diameter over the entire length. For example, the second transfer pipe 4 has a tapered shape in which the whole or a part of the upstream linear portion 41 is increased in diameter toward the downstream side, and the downstream linear portion 43. You may make the whole or one part into the taper shape which diameter-reduces toward downstream. As a specific example, the diameter of the bent portion 42 is set to φ210 mm, a tapered portion that is expanded from φ130 mm to φ210 mm is provided in the middle of the upstream linear portion 41, and the diameter is reduced from φ210 to φ145 mm in the middle of the downstream linear portion 43. A tapered portion is provided.

  Next, the operation of the plate glass forming apparatus described above will be described.

If heterogeneous glass containing a large amount of SiO ₂ component generated by melting segregation in the clarification tank 3 from the dissolution tank 1 is generated, it causes striae. Since this heterogeneous glass containing a large amount of SiO ₂ has a slightly lower specific gravity than the surrounding molten glass, it flows more into the upper part of the second transfer pipe 4 that leads to the molding device 5. Moreover, in the clarification tank 3 from the dissolution tank 1, B ₂ O _{3 and the} like are volatilized, so that the molten glass of the surface (upper) layer has a high SiO ₂ concentration, and it flows into the second transfer pipe 4 as it is. Become. For this reason, in the molten glass 6 immediately after flowing into the 2nd transfer pipe 4 from the clarification tank 3, as shown to Fig.5 (a), striae is relative to the 90 degree 1st angle area A of upper side. And there is not much striae in the lower third angle region C of 90 °. In the second angle region B and the fourth angle region D in the meantime, there is a striae of an intermediate amount between the precipitation amount in the first angle region A and the precipitation amount in the third angle region C.

  And since the 2nd transfer pipe 4 of this embodiment is bent rightward while going down, the molten glass 6 which flows through the 2nd transfer pipe 4 has the resistance which receives from the 2nd transfer pipe 4 by the viscosity and dead weight, Due to the difference in the path length between the inner side and the outer side in the bent portion 42, the upper molten glass having a small resistance force received from the second transfer pipe 4 passes through the bent portion 42 so as to be pushed outward. That is, the molten glass 6 flows through the second transfer pipe 4 so as to be twisted to the left, and as a result, at the other end 4b of the second transfer pipe 4, as shown in FIG. The first angle region A that rotates around and has a large amount of striae is biased in the −Y direction, and the third angle region C that has a small amount of striae is biased in the + Y direction. In other words, the molten glass 6 is supplied to the molding apparatus 5 while being rotated clockwise as viewed from the traveling direction (as viewed in the direction of arrows VA and VB in FIG. 1) by flowing through the second transfer pipe 4. The

  Therefore, as shown in FIG. 4, striae is reduced in the molten glass 6A on the side (+ Y direction side) that overflows from the groove 51 of the forming device 5 to the bending direction side of the second transfer pipe 4. Striae increases in the molten glass 6B on the side (−Y direction side) that overflows from the groove 51 to the side opposite to the direction in which the second transfer pipe 4 is bent. That is, if plate glass is manufactured using the plate glass manufacturing apparatus of this embodiment, striae can flow out relatively more to one surface side of the plate glass. And if this surface is used as a back surface where high flatness is not required, the peak height of the main surface where high flatness is required can be kept small, and the required quality for flatness can be achieved on both the main surface and the back surface. To be satisfied. Thus, according to the plate glass manufacturing apparatus of this embodiment, the ratio of the plate glass which can be used as a product can be increased, and a yield can be improved.

  Next, a simulation performed to confirm that the molten glass 6 flowing through the second transfer pipe 4 rotates as described above will be described.

In the model of the second transfer pipe 4 created by the simulation, the dimensions exemplified in the above embodiment are adopted, and the lengths of the upstream linear portion 41 and the downstream linear portion 43 are each about 2 m. The flow rate of the molten glass flowing through the second transfer pipe 4 was 28.9 cm ³ / s, and the temperature was a constant 1490 ° C. (viscosity 67.6 Pa · s).

  As a result of the simulation, the molten glass 6 was rotated about 18 ° clockwise by flowing through the second transfer pipe 4.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not restrict | limited to these Examples at all.

  In the Example, plate glass was manufactured using the plate glass manufacturing apparatus of the said embodiment. The plate glass to be manufactured was 1300 mm in width (width in the X direction), 1100 in length (length in the Y direction), and 0.7 mm in thickness.

Glass raw material to be introduced into the dissolution tank 1 is displayed in _{mol%, SiO 2: 64.7%,} B 2 O 3: 10.9%, Al 2 O 3: 11.4%, MgO: 2.7 %, CaO: 5.7%, SrO: 1.9%, BaO: 2.3%, As ₂ O ₃ : 0.4% were used.

  Various conditions in the plate glass manufacturing apparatus were the same as those in the simulation.

  A total of 336 plate glasses were produced. As a result of optically inspecting these, 14 sheets were determined to be unsatisfactory.

  About 14 plate glass determined to be unsatisfactory, since the optical surface cannot distinguish between the main surface and the back surface, the peak heights of both surfaces of the plate glass were measured. For this measurement, a surface roughness measuring machine (Surfcom 1400-D) manufactured by Tokyo Seimitsu Co., Ltd. was used.

  When the measured peak height is compared with a certain reference height for each of a relatively small surface (main surface) and a relatively large surface (rear surface), the average value is 0.8 on the main surface. The maximum value was 1.1 and the minimum value was 0.7. On the rear surface, the comparison values were 1.2 on average, 1.6 on the maximum, and 1.1 on the minimum.

  From this result, it can be seen that a relatively large amount of striae can flow out to the back side, and the flatness of the main surface can be improved.

(Modification)
In the embodiment, the angle at which the second transfer pipe 4 is bent is approximately 90 °, but the angle at which the second transfer pipe 4 is bent is not limited to this, and may be variously selected, for example, 180 °. In this case, the amount of rotation of the molten glass 6 flowing through the second transfer pipe 4 can be further increased. However, if the angle at which the second transfer pipe 4 is bent is approximately 90 °, the molten glass 6 flowing in the second transfer pipe 4 can be rotated by an appropriate amount while suppressing the length of the second transfer pipe 4. it can.

  In addition, the bending direction of the bent portion 42 may be lateral, and may be rightward or leftward.

  Furthermore, the one end 4a of the second transfer pipe 4 is not necessarily connected to the side surface on the −Y direction side of the clarification tank 3, and may be connected to the side surface on the + X direction side, for example.

  Further, it is possible to bend the second transfer pipe 4 over the entire length by omitting the upstream linear portion 41 and the downstream linear portion 43.

  The present invention is particularly suitable for a manufacturing apparatus and a manufacturing method for manufacturing a plate glass for an FPD glass substrate.

It is a perspective view which shows roughly the plate glass manufacturing apparatus which concerns on one Embodiment of this invention. It is a front view of the plate glass manufacturing apparatus shown in FIG. It is a side view of the plate glass manufacturing apparatus shown in FIG. It is sectional drawing of the shaping | molding apparatus corresponding to the IV-IV line of FIG. (A) is sectional drawing of the end of the transfer pipe corresponding to the VA-VA line of FIG. 1, (b) is sectional drawing of the other end of the transfer pipe corresponding to the VB-VB line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dissolution tank 2 1st transfer pipe 3 Clarification tank 4 2nd transfer pipe 4a One end 4b The other end 42 Bending part 5 Molding apparatus

Claims (4)

A molding device that melts and melts molten glass that has overflowed to both sides from the groove along the wall surface;
A refining tank for refining molten glass;
A transfer pipe for guiding the molten glass clarified in the clarification tank to the molding apparatus,
The said transfer pipe | tube is a plate glass manufacturing apparatus bent to the side, descending toward the other end by the side of the said shaping | molding apparatus from the one end by the side of the said clarification tank.   The plate glass manufacturing apparatus according to claim 1, wherein the transfer pipe guides the molten glass while adjusting a temperature.   The plate glass manufacturing apparatus according to claim 1, wherein an angle at which the transfer pipe is bent is approximately 90 °. A method for producing a sheet glass comprising a step of forming a glass ribbon by overflowing molten glass from both sides of a groove of a molding apparatus,
A plate glass manufacturing method in which molten glass is supplied to the forming apparatus while rotating the molten glass by flowing the molten glass through a transfer tube that bends from one end to the other while bending downward.

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