HK1070345B - Method and device for producing thin glass panes - Google Patents

Description

Method and apparatus for manufacturing thin glass sheets

Technical Field

The invention relates to a method for producing glass sheets, in particular glass sheets having a thickness of less than 3mm, by vertically drawing down a continuous thin glass ribbon, wherein a glass melt is fed from a melting point of a tank furnace through an inlet into a run-up channel, which has a nozzle system with at least one slotted channel brick or nozzle brick. The invention also relates to an apparatus for making thin glass sheets using a tank furnace melting section, a homogenizing system, an inlet and a draw tank.

Background

Such thin glass plates are used as glass substrates in electronic devices, such as digital mass storage for displays (portable phones, flat screens, etc.) and computers. Therefore, stringent requirements are placed on the internal quality of the glass, which is determined primarily by bubbles and inclusions, the smoothness, the quality of the surface geometry, which is determined primarily by the shape of the dense waves (waviness) and the deviations from flatness (warpage), and also the resistance to cracking and perhaps light weight.

When used as a glass substrate for a display, the customer subjects the glass to a thermal processing operation near the glass transition temperature. Here, the shape stability of the glass substrate must be always maintained. Therefore, special glasses or glass ceramics with higher glass transition temperatures are used, which mostly have higher crystallization energies and temperature-dependent atypical viscosity profiles. Therefore, these glasses require higher processing temperatures than ordinary glasses.

Since this application relates to mass production, glass sheets must be produced as inexpensively as possible. That is, short equipment and downtime, high throughput, and low scrap to process stability are sought, where the scrap is caused by glass defects and occurs in the glass sheet edge area. In addition, costly subsequent processing steps such as grinding and polishing cannot be eliminated or reduced to the extent possible to meet the customer requirements for surface finish and surface geometry quality.

In the cited processes known to date, the above requirements with regard to product quality and economy are only partially met.

For the production method, one distinguishes the method of guiding with the aid of channel bricks and the method of guiding without channel bricks.

In the introduction method without the use of channel blocks, as described in US 3,338,696, a channel is used into which the glass melt is introduced. The glass melt overflows the upper edge of the trough wall and flows down the outer surface of the wedge trough. At the highest point, the glass film thus formed meets and is pulled downward. The ceramic pot was lined with platinum to inhibit corrosion.

In this method, the total flow rate is essentially determined by the inlet between the melting section and the trough. The so-called linear throughput (which is the throughput per unit length in the transverse direction to the direction of the continuous glass ribbon guidance) is adjusted by the glass flow in the trough, the glass state in the area of the overflow edge of the trough, the geometry of the overflow edge and the glass viscosity. Very precise temperature control is required, which must be below 0.1 ℃.

A change in specification or a change in throughput requires a corresponding adjustment of the geometry of the lead-up channel, in particular for the glass flow in the channel. Because a new pilot channel is sufficient to operate for a week or more, only limited production flexibility is available.

Erosion of the trough edges cannot be compensated for by flipping or stretching the trough. The magazine must be replaced and the process restarted.

In order to adjust a continuous glass ribbon with narrow edges, the continuous glass ribbon must be stretched transversely to the direction of the continuous glass ribbon by so-called edge rolls in the edge regions. Edge rolls make the machining operation more complicated.

The approach of using slotted channel bricks is divided into those with and without flow guides or drains.

In the method using flow-conductor-free slotted channel bricks, as described for example in SU 617,390, the glass flows out from both sides of the tank furnace work or homogenization section through the opposite walls of an overflow opening made of refractory material. The two glass films thus formed are joined in a channel block and subsequently drawn out downwards. The throughput adjustment is done by the glass state value on the overflow edge. This can be done by changing the glass state in the working section or by burying the overflow bricks deeply.

The method of using slotted channel bricks without flow conductors cannot meet the strict requirements for surface quality and in particular for tight waviness (waviness). Since the glass is temporarily retained in the region of the root and since the glass is very viscous, it is not possible to compensate for the unevenness.

Certain processing temperatures should not be exceeded because of the gradual increase in instability in the root region below the critical viscosity of the glass melt. Therefore, special glasses having high crystallization energy cannot be manufactured by the known up-draw method without a current carrier.

The above-mentioned drawbacks are partly avoided by using slotted channel bricks with internal flow conductors.

In US 1,759,229, a drawing-up method for producing sheet glass is described, the glass flowing through a slotted channel block mounted on the floor of a tank or homogenizing unit onto a drainage fluid having a circular cross section and being drawn downwards through the drainage fluid. The drainage body is inserted into a cavity which is widened downwards below the slot-type groove brick. The depth of the glass pool in the working part or the homogenizing part gradually increases towards the two ends of the gap type groove brick. The groove bricks and the drainage fluid can be provided with sharp outlines. It is important here that the slot brick is widened toward the edge and that the usable drainage fluid, which can be aligned in one direction, can be bent upward in the center.

The wedge-shaped lower part of the drainage body has a recess in which a heating or cooling element arranged transversely to the drainage direction can be located. The temperature of the fluid to be discharged can be regulated by means of a thermostatic medium flow.

The glass flow is influenced by the geometry of the channel bricks and the drainage fluid and by the temperature level and distribution at the operation or homogenization section of the tank and the position of the drainage fluid relative to the channel bricks. The drainage fluid also has the task of homogenizing the glass temperature in the transverse direction of the drawing direction in order to produce a sheet glass of predetermined dimensions and the same appearance.

DE-AS 1596484 discloses a device comprising a homogenization vessel which is connected to a draw-up furnace via a closed and heatable tank. The furnace is equipped with a channel brick made of platinum and having a bottom slot. A flow guide body in a vertical plate form is arranged below the groove brick. The glass melt flowing from the channel bricks flows down the sides of the flow conductor and merges at the bottom end into a continuous glass ribbon.

For the purpose of dissipating heat from the inside to the outside, a plurality of bores are provided in the flow conductor, through which bores a cooling medium can be supplied. In addition, an outer cooling body is arranged on the bottom of the flow guide body. The height of the flow conductor can be adjusted by means of the adjusting bolt.

In JP 2-217,327, an apparatus for manufacturing a sheet glass is described, the glass being drawn downward through a slit provided on the bottom surface of a feeder or tank furnace section. The slotted channel brick can be indirectly heated. The glass supply is interrupted by means of a plug located above the gap. In order to stabilize the continuous glass ribbon, a plate-like inner flow conductor which is fixed to the side and is adjustable in position is arranged in the channel brick, the upper part of the inner flow conductor protrudes into the channel brick, and the lower part of the inner flow conductor is covered.

US 1,829,639 describes a method and an apparatus in which the total and linear flow fluxes are adjusted solely by the geometry of the nozzle system, the viscosity of the glass melt in the region of the channel bricks and the pressure of the glass melt on the channel bricks. There is only a small overpressure when the glass melt flows out at the channel brick, because the storage system is open and thus the glass filling level is low. A significant disadvantage of such an apparatus or method is that the total and line fluxes are correlated.

With the known method of slotted channel bricks and flow conductors, outstanding surface qualities cannot be achieved as in the known approach of guiding without slotted channel bricks. Especially in the case of high throughputs and high processing temperatures, the residence time of the glass film on the flow conductor is not sufficient to compensate for the surface waviness which is caused by the use of channel bricks there in the region of the contour edges.

In the known methods of their slotted channel brick belts or of their use without flow carriers, the total flux regulation and the linear flux regulation (thickness distribution laterally over the carriers) are correlated.

The channel brick geometry and temperature control in the channel brick zones are readjusted empirically when changing specifications or throughputs. The start-up procedure is time-consuming and only allows the required production flexibility to be achieved to a limited extent.

In order to set a thickness profile that meets specifications, a defined temperature profile is set in the region of the channel bricks in the upward-directed transverse direction. The temperature profile applied to the continuous glass ribbon can only be partially balanced before reaching the precision cooling zone. This may result in unacceptable deformation (warping) of the continuous glass ribbon when cooled to room temperature.

Disclosure of Invention

The object of the invention is to provide a method by means of which glass or glass ceramics having a strong tendency to crystallize can be processed, wherein the quality of the thin glass plate can be improved and the throughput can be increased. The object of the invention is also to provide a device for carrying out the method.

To this end, the invention provides a method for producing thin glass sheets by vertically drawing down a continuous thin glass ribbon, wherein a glass melt is fed from a melting point of a tank furnace through an inlet into a lead-up trough having a nozzle system with at least one slotted channel sub-brick, characterized in that the total flow is adjusted depending on the viscosity of the glass melt in the vertical inlet by means of the longitudinal and cross sections of the vertical inlet and by means of heating and cooling by the vertical inlet, so that the glass melt pressure resulting from the difference in height of the free surface of the glass melt and the height of the nozzle system is substantially reduced in the vertical inlet, and the flow within a single length in the transverse direction of the continuous thin glass ribbon, i.e. the linear flow, is adjusted depending on the viscosity of the glass melt in the nozzle system by means of the geometry of the nozzle system and by means of the heating and cooling of the lead-up trough section and the slotted channel sub-brick, so that the glass melt does not wet the bottom surface of the slotted trough brick in the contour edge region when it leaves the nozzle system.

In the above method, the thickness of the glass sheet is preferably less than 1 mm. The temperature of the glass melt in the vertical inlet is adjusted to T_ZL1＝Tg+670K-T_ZL2Tg + 590K. The temperature of the glass melt in the lead-up channel can be adjusted to T_ZT1＝Tg+590K-T_ZT2Tg + 570K. Furthermore, the temperature T of the glass melt in the region of the slotted channel block_SDIs adjusted to T_SD1＝Tg+570K-T_SD2Tg + 550K. Here, the temperature difference Δ T of the glass melt along the slotted trough brick is_SDIs adjusted to delta T_SDIs less than or equal to 20K. In addition, the glass melt is divided during the flow through the slot-type channel brick by means of at least one flow conductor, flows on both sides under the flow conductor in the form of a glass film and merges at the bottom end of the flow conductor into the continuous thin glass strip. The residence time and the viscosity of the glass film on the flow conductor are adjusted in such a way that deviations from the ideal surface shape can be almost completely compensated for. The glass film is selectively heated and/or cooled on the current carrier. The glass film can be guided laterally on its side edges. The continuous ribbon of glass can be selectively cooled in the root region thereof. At least a portion of the weight of the continuous ribbon of glass is compensated for when pulled up. In addition, the thickness of the continuous ribbon of glass can be measured continuously, and the draw-up speed can be controlled by measuring the thickness value. The continuous ribbon of glass is stretched in the visco-elastic region transverse to the ribbon direction. The continuous thin glass strip is selectively heated and/or cooled in a roll furnace and/or a lead-up furnace in the direction of the strip and in the direction transverse to the direction of the strip.

The invention also provides an apparatus for manufacturing thin glass sheets using a melting section of a tank furnace, a homogenizing system, an inlet and a run-on trough, said run-on trough having a nozzle system with at least one slotted channel brick, characterized in that said inlet, said run-on trough and said nozzle system constitute a complete system, said inlet having a vertically arranged tube with segmented tube sections, said tube having a length of 2 to 5m and a diameter of 50 to 80mm, the tube being circular in cross-section, the inlet having a segmented heating device and a segmented cooling device, said run-on trough having a heating system segmented in the vertical direction and in the lateral direction.

In the apparatus of the present invention, the glass sheet is preferably less than 1 mm thick. The slotted channel brick has a heating device. At least one flow guide body is vertically arranged in the gap type groove brick. The flow conductor is a plate which tapers in a downward pointed manner and is made of a platinum alloy. In addition, the current carrier may protrude upward onto the slotted trough tile. The current carrier has a side interface. The current carrier may be adjustable in X, Y and the Z direction. Further, the current carrier may be elongated by applying a tensile force in the X-direction. The flow conductor has a heating device and/or a cooling device. A nozzle furnace with a segmented heating device and a segmented cooling device is connected below the slot-type trough brick. Below the slotted trough brick, a nozzle furnace with a segmented heating and cooling device is connected, which has a beam plate on the surface opposite the flow conductor. The nozzle furnace has at least one movable screen below the beam plate. The nozzle furnace may also have means for opening in the transverse direction of the strip. Below the nozzle furnace, a roller furnace with a roller shaft having heating devices and cooling devices which are segmented in the X-direction and in the Z-direction can be connected. At least one pair of winding rollers and/or one pair of upper guide rollers are arranged in the roller distribution vertical cylinder. In addition, the roller furnace can have means for opening transversely to the strip direction. The drawing speed of the drawing roller can be adjusted according to the thickness of the online common continuous glass thin strip. An upper kiln arranged below the roller kiln can be moved away or closer downwards or sideways.

The above-mentioned requirements regarding product quality and economy are met by the process of the invention.

This method combines the advantages of the approach of using channel bricks with the advantages of the approach of not using channel bricks. This means that, with a good thickness distribution in the lateral and upward direction, glass thicknesses of 20 μm to 3000 μm can be adjusted with thickness fluctuations < 20 μm and small overall widths, and, in addition, outstanding surface qualities are obtained, i.e. waviness < 20 nm. In addition, warpage is minimal. High processing temperature and Low processing viscosity (5X 103)^-3×10⁴d) Can also be used for manufacturing glass or glass ceramics which are easy to crystallize. In addition, the specification change can also be very flexible, and the width of the product can be adjusted between 300mm and 2000 mm. In addition, very high line fluxes (mass > 5g/(mmxmin) per unit time and per unit bandwidth) can be achieved with high job stability. Thus, the disadvantages of the approach of using and not using channel bricks are avoided to the greatest extent.

Preferably, the inlet, the lead-up channel and the nozzle system constitute a complete system. The total flow rate is set by the longitudinal and cross-sectional area of the inlet and by the viscosity of the glass melt at the inlet. On the other hand, the throughput per unit length in the cross direction of the continuous glass ribbon, i.e. the linear throughput, is adjusted according to the geometry of the nozzle system and the viscosity of the glass melt along the channel block in order to adjust the thickness as specified. The pressure of the glass melt due to the head between the height of the free surface of the glass melt and the height of the nozzle system is substantially reduced at the inlet. The pressure drop in the area of the nozzle system is so small that the glass spreads out only insignificantly when leaving the nozzle system. The wetting of the channel bricks in the edge regions of the profile is suppressed. As a result of the suppression of wetting of the slotted groove bricks in the contour edge region, a higher surface quality is achieved than with the known approach by means of groove bricks.

According to the invention, the total flux adjustment is as far as possible decoupled from the line flux. The total flow rate is regulated by the defined heating and cooling of the inlet. The linear flow and thus the thickness distribution in the transverse direction of the strip are adjusted by introducing the channel sections, the slotted channel bricks and the flow carriers by heating and cooling as required. This means that pressure drop variations in the riser channel zone and the channel brick zone and caused, for example, by temperature fluctuations in this zone, only do not significantly affect the total flow flux. Thus, the total flow flux and thus the stability of the continuous glass ribbon thickness distribution in the Z-direction (see the coordinate system of fig. 1) is improved. The process control is simplified since the different steps are decoupled from one another. The time to start-up the process is shortened and the production flexibility, i.e. varying the total flow rate or varying the thickness of the continuous glass ribbon, is improved compared to the known approach by enlarging the working window. The apparatus does not have to be adapted to changing continuous glass ribbon geometries or changing process parameters.

The following temperature zones for the inlet (ZL), lead-in groove (ZT) and slotted groove brick (SD) have proven advantageous for alkali-free borate glasses having a Tg2 of about 700 ℃ and a Tg of about 5g/cm³Density of about 37X 10^-7Thermal expansion rate of/K, i.e.

T_ZL1＝Tg+670K-T_ZL2＝Tg+590K

T_ZT1＝Tg+590K-T_ZT2＝Tg+570K

T_SD＝Tg+570K-Tg+550K

Here, Tg represents a glass transition temperature.

Although the method without a current carrier also provides good results with respect to surface quality, such results may be improved by using a current carrier. The glass melt is divided by means of a flow guide as it flows through the slotted channel block. The glass melt flows down on both sides of the flow conductor. The two layers of glass films are merged into a continuous glass ribbon at the bottom end of the flow guide body.

The residence time and the viscosity of the glass film on the flow conductor are preferably adjusted in such a way that deviations from the ideal surface shape are almost completely compensated for. To achieve this, the glass film is preferably selectively cooled and/or heated on the current carrier.

By allowing the two glass films to remain on the current carrier for a long time with a low glass viscosity, deviations from the ideal surface shape due to surface stresses are almost completely compensated. A surface quality is achieved which is comparable to that of the non-grooved brick approach (waviness < 20 mm).

Furthermore, the following temperatures are preferably set on the current carrier (LK):

T_LK＝Tg+560K-Tg+540K

this corresponds to 1 × 10⁴Glass viscosity of dPas.

The gap width between the slotted trough tile and the flow conductor may be, for example, 10mm each. The thickness of the two glass films is, for example, 8mm each. That is, the two glass films did not wet the slotted channel brick from below.

The quality requirements for the geometry of the contour edge of the slotted channel tile are lower than with the known approach of guiding up by means of channel tiles. It is therefore also possible to reuse the channel bricks several times after a stop, unlike the known introduction method. Therefore, the production cost is reduced.

Since the glass film is stabilized by the flow conductor and is cooled rapidly after melting in the root zone, it is possible to select a processing temperature (up to 100K) which is much higher than that of the approach with grooved bricks without flow conductor and is thus comparable to that of the approach without grooved bricks. The provision of the processing temperature makes it possible to produce special glasses or glass ceramics having a strong tendency to crystallize.

It is preferred to selectively cool the continuous glass ribbon in the region of the root.

The glass mass in the region of the root is small, since the glass film is stabilized by means of the flow conductor and the glass is cooled rapidly in the region of the root. Thus, a line flux of up to 5g/(mmxmin) can be set with high process stability. In the above temperature regulation, for example, a line flux of 3.5g/(mmxmin) is obtained. In this way, the throughput is significantly improved.

Temperature difference DeltaT of glass melt along slit-type channel brick_SDIs preferably adjusted to Δ T_SDIs less than or equal to 20K. In contrast to the known approach with the aid of channel bricks, the temperature in the region of the channel bricks becomes significantly more uniform. Thus, the speed of contraction of the continuous glass ribbon during cooling is more uniform in the lead-up direction along the transverse direction of the continuous glass ribbon than heretofore known lead-up methods via channel bricks. In this way, the deformation (warp) of the continuous glass ribbon upon cooling to room temperature is significantly reduced. Thus, thin glass sheets are produced which have stringent requirements for flatness.

The glass film is preferably guided on its side edges. By laterally delimiting the flow conductor and controlling the temperature in the region of the cooling system of the nozzle furnace, the process can be controlled so that the edge width and thus the glass loss is sufficiently small. The uneven temperature control in the channel brick zone and on the edge rollers in order to set the desired width can be dispensed with. By improving the effect, the throughput is improved.

In the nozzle furnace, the glass in the region of the plate root is cooled, for example, to approximately Tg +290K by means of a main cooling device.

Less uniformity in the linear flux may result in small thickness fluctuations in the transverse direction of the continuous glass ribbon lead-up direction. According to the invention, the thickness distribution is corrected by a cooling system of the nozzle furnace below the main cooling device, which cooling system is segmented in the X direction. To this end, if desired, different regions of the continuous glass ribbon are cooled slightly differently, so that the continuous glass ribbon elongation in the Z-direction is greater for the hot glass zone than for the cold glass zone. Thus, as the continuous glass ribbon lengthens, the thickness reduction of the cooler regions is suitably reduced compared to the thickness reduction of the hotter regions. In the nozzle furnace, therefore, a predetermined temperature distribution in the strip direction and transversely thereto can be set by means of the segmented heating and cooling elements. Thus, the thickness distribution improves the effect of the quality feature.

In terms of the apparatus, the continuous glass ribbon is extended in a visco-elastic state by rollers or drums, as required, below the nozzle furnace in a transverse direction to the ribbon direction, so that the continuous glass ribbon is conveyed flat and stress-free to a cooling device in a draw-up lehr. In this way, deviations in flatness caused in the thermoformed area can be corrected. In addition, the penetration of deformation from the elastic zone in the thermoforming zone is reduced by means of rollers or drums. The rolls or drums are located in a roll furnace or draw-up kiln, in which a defined temperature distribution in the strip direction and transversely to the strip direction can be set by means of segmented heating and cooling elements. In this way, the benefits with respect to quality characteristics are improved.

According to the invention, the continuous glass ribbon is drawn vertically down by means of a drawing roll below the nozzle furnace. Here, the continuous glass ribbon is extended by the upper drawing roll at a speed of, for example, 1.6m/min, so that a continuous glass ribbon with a net thickness of 0.7mm is obtained with a linear flux of 3.5g (minxmm) and a total width of about 800 mm. The thickness of the continuous wave band is preferably measured continuously, wherein the drawing speed is controlled by means of the thickness value measured.

Perhaps, the pull-up speed can be controlled based on prior thickness measurements taken after the glass has cooled. Thus, the benefits associated with medium-thick quality features are improved.

If the strip is thick, i.e. the strip has a high weight and a low pull-up force, the pull-up force required to adjust the desired thickness is less than the strip weight, and the pull-up roller can compensate for a part of the strip weight. Thus, the upper guide roller is preferably arranged in a guide kiln or roller furnace.

According to another embodiment, the continuous glass ribbon is selectively cooled and/or heated in the roll furnace and/or the draw-up furnace in the direction of the ribbon and in the direction transverse to the direction of the ribbon.

In the first rapid cooling zone, the continuous ribbon is preferably cooled to Tg +50K, while in the fine cooling zone for adjusting the stress of the cooling body, it is fine cooled to Tg-50K and rapidly cooled in the rapid zone to, for example, 450K.

The preferred application of the glass plate made according to the method is a glass substrate in an electronic instrument, such as a glass substrate for a display (cell phone, flat screen, etc.) or a mass memory of a computer.

In the present invention, the inlet, the lead-up tank and the nozzle system constitute one complete system. The inlet may be constructed of a platinum alloy or of ff material (refractory) and have segmented, directly or indirectly cooled and heated tube sections. The tube or tubing system has a length of 2m-5m and has a circular cross-section with a diameter of 50mm-80 mm.

The tubes are preferably arranged vertically.

In the tube, the desired glass viscosity is adjusted by a combination of cooling and heating. At the inlet end, the glass is fed into the lead-up trough.

In the draw-up channel, the glass melt is distributed uniformly transversely to the draw-up direction. The lead-up channel is a container, preferably made of platinum alloy, in which the required change in viscosity of the glass can be adjusted by a combination of heating and cooling. The glass is fed to the nozzle system below the lead-up trough.

The nozzle system preferably has one or two slotted channel bricks and possibly a flow conductor from a platinum alloy process. The slotted channel block preferably has a heating device. The current carrier may be a platinum alloy plate which is tapered downwardly and preferably has a heating device and a cooling mechanism as required. The regulation of the uniform linear flow is carried out by the defined heating and cooling of the guide channels, the slotted channel bricks and the flow conductor.

The flow conductor is arranged vertically in the slotted trough brick and preferably projects into the upper trough through the slot of the slotted trough brick. The glass flow has been diverted in the Y direction (see coordinate system of fig. 1) in the lead-up channel by means of a flow conductor. In this way, the same glass film thickness is also ensured by an external regulating system, by means of which the flow conductor is calibrated in the direction X, Y and, if necessary, also in the Z direction with respect to the groove brickwork joint position. It is essential to ensure a small degree of warpage after as uniform a glass film as possible.

Furthermore, the straightness of the flow conductor can be ensured by applying a pulling force in the X-direction, especially for large bandwidths and long machining times. Therefore, a large bandwidth can be manufactured for a long processing time, which in turn significantly improves productivity.

A nozzle furnace is connected below the slit type groove bricks. The flow conductor preferably extends into the nozzle furnace. The nozzle furnace preferably has a heating device and two cooling systems.

In order to regulate the residence time of the glass film on the current carrier as specified, the current carrier may be directly heated and cooled. For this purpose, the flow conductor has a preferably heating and/or cooling device. Furthermore, the glass film can be heated on both sides by means of a segmented heating device of a nozzle furnace.

The nozzle furnace has preferably opposite beam plates in the region of the flow guide.

According to another embodiment, the nozzle furnace has at least one wall below the beam plate, which wall can be moved into the furnace space.

By forming a smaller plate root, the glass is directly cooled under the flow conductor by two cooling systems, a main cooling device and a segment cooling device under the main cooling device. The main cooling device dissipates a large part of the heat. The precisely segmented cooling in the X-direction ensures correction of small thickness fluctuations caused by the nozzle system.

The continuous ribbon of glass extends vertically downward and perhaps laterally in the direction of the ribbon. The upper guide roller and the winding roller required for this purpose are located below the nozzle furnace, possibly in a roller furnace, an upper guide kiln or a guide machine.

The upper guide roller is used for adjusting the thickness. The required flatness of the continuous glass ribbon and subsequent glass sheets is ensured by the winding rollers.

The continuous glass ribbon is preferably drawn during startup by means of a pull-up roller below the nozzle furnace. In this way, the start-up time is significantly reduced.

The nozzle furnace can be opened transversely to the strip direction in order to simplify the start-up process. Therefore, the burden of the starting process is reduced.

The roll furnace can also be opened transversely to the direction of the strip to simplify the start-up process.

The lead-up kiln can be moved away downwards or sideways to simplify the start-up process. During production, the roll kiln is connected from below to the drawing kiln. Thus, the start-up procedure is also simplified.

Drawings

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The attached drawings are as follows:

FIG. 1 is a vertical cross-sectional view of the device;

fig. 2 shows a vertical section of the slotted channel brick zone in an enlarged manner.

Detailed Description

Fig. 1 and 2 show a coordinate system for determining spatial directions. Here, the X direction represents the width direction of the continuous glass ribbon, the Y direction represents the direction perpendicular to the ideal ribbon surface (continuous glass ribbon thickness), and Z represents the pull-up direction.

In fig. 1, a vertical section of the apparatus is schematically shown, having the parts inlet 1, lead-up channel 6, nozzle furnace 18, roller furnace 25, lead-up kiln 32.

Through the inlet 1, the glass melt is fed from a homogenizing system, not shown, into the upper trough 6. The inlet 1 comprises a tube 2 arranged in a vertical direction. The tube 2 consists of a platinum alloy or ff material, which has symmetrically directly or indirectly heated or cooled tube sections 2a, b, c and is divided. Corresponding to the pipe sections 2a, b, c, a correspondingly segmented heating device 3 and a segmented cooling device 4 are provided, which are insulated from the outside by an insulating material 5. The heating device 3 operates in a direct or indirect electrical heating mode. The cooling device 4 consists of cooling tubes through which a cooling medium flows. The cooling pipes act around the pipe sections and are connected to suitable cooling equipment.

The lead-up channel 6, which is connected to the inlet 1 in the downward direction, has a distributor 7 made of platinum alloy, which is turned vertically downward into a glass conveying channel 8, which is also made of platinum alloy. The glass distributor 7 is used to distribute the glass melt throughout the length of the slotted trough block 11, which is described in more detail below. The uptake shaft 6 has a heating system 9 which is also segmented in the vertical and transverse directions. The heating can be carried out directly or indirectly by means of electrical heating. In addition, the lead-up groove 6 is surrounded by an insulating material 10.

On the bottom surface of the lead-up channel 6 there is a nozzle system comprising a slotted channel brick 11, seals 12, 13 and a flow conductor 16. The slotted channel tile 11 is pressed from below onto the lead-up channel 6 by the channel tile carrier plate 14. The seal 12 and the flexible seal 13 ensure a force-fit and a form-fit.

The slotted channel tile 11 is electrically heated, directly or indirectly, by means of heating means 15 mounted in the channel tile carrier plate 14. In order to optimize the glass flow, a further slotted channel block (not shown) made of a platinum alloy can be arranged above slotted channel block 11, if necessary.

In the slotted trough tile 11, as shown in fig. 2, a flow conductor 16 made of a platinum alloy is provided, which is formed by a plate-shaped part that tapers at its lower end. The current carrier 16 may have side interfaces 17 and is arranged to be adjustable in the X-direction, Y-direction and Z-direction, which are not shown in fig. 1, 2. Current carrier 16 also has a direct electrical heating device and perhaps a cooling mechanism.

The two glass films flowing out of the slotted channel block 11 and flowing downward on the outer surface of the flow conductor 16 merge into a common continuous glass ribbon at the bottom end which is constricted to a pointed shape. The glass film, the web and the extended region of the continuous glass ribbon on the flow conductor are located between beam plates 19 of a nozzle furnace 18 which has an electrical heating device 20 in the upper part and cooling systems 23, 24 in the lower part. The beam plate 19 shields the heating device to improve the temperature equalization effect.

The heat dissipation of the continuous glass strand by the cooling system 23, 24 can be adjusted by means of the wall 22 which is movable in the Y direction at the level of the plate base. Below the screen 22 there are main cooler elements 23 for regulating the temperature of the continuous glass ribbon in the region of the root. A cooling system 24 segmented in the X direction is used to adjust the thickness profile across the continuous glass ribbon. The nozzle furnace 18 is insulated from the outside by an insulating material 21. To simplify the start-up operation, the nozzle furnace may be opened in the Y direction.

Below the channel bricks 11 there is a roller oven 25 with a roller shaft 26. The roller furnace 25 has an electric heating device 27 segmented in the X-direction and the Z-direction and a cooling device 28 segmented in the X-direction and the Z-direction. To improve the temperature equalization, the vertical roller cylinders 26 isolate the heating device from the continuous glass ribbon. In the roll furnace 25, there are winding rolls 29 which extend the continuous glass ribbon in the X direction by an oblique arrangement or a special shape in order to adjust the desired flatness. Also within the roll furnace 25 are one or more pairs of upper rollers 30 which cause the continuous glass ribbon to extend in the Z-direction as specified to adjust the desired thickness. The roller furnace 25 is insulated from the outside by an insulating material 31. To simplify the start-up operation, the roller oven may be opened in the Y-direction.

Below the roller kiln 25 is a lead-up kiln 32. The uptake shaft 32 has an electric heating device 35 segmented in the X and Z directions and a cooling device 36 segmented in the X and Z directions. To improve temperature uniformity, the beam kiln walls 33 insulate the heating device 35 from the continuous glass ribbon. In order to suppress undefined convection, a screen 34 is provided which can be moved in the beam kiln wall. Stabilizing rollers 37 may be provided in the pull-up lehr 32 to stabilize the position of the continuous ribbon in the Y direction. The upper kiln 32 is insulated from the outside (insulating material 38).

To simplify the start-up operation, the kiln 32 is pulled up or allowed to open in the Y direction, or a door provided on the end side can be opened. In addition, the upper kiln 32 is directed downwardly away to simplify the equipment process. For production, the lead-up kiln 32 is attached to the roller kiln 25 from the underside.

The roll furnace 25 may also be omitted. In the absence of a roller kiln, the winding roller 29 or the upper guide roller 30 may be located in the upper guide kiln 32. In the short draw-up kiln 32, the upper draw roller 30 and the stabilizing roller 37 can be dispensed with when the wall thickness is small, i.e. when the belt weight is small and the draw force is small. Further, the upper guide roller 30 is located below the upper guide kiln 32.

All heating systems may be electrically operated. The cooling system is cooled by means of a circulating liquid or gas.

Hereinafter, an example for manufacturing a glass substrate for a TFT display is described.

Glass:

alkali-free borate glasses having a Tg of > 700 ℃ and a density of < 2,5g/cm³And a thermal expansion coefficient of < 37X 10^-7/K。

Quality features with respect to geometry:

quality features related to geometry:

length 670mm

Width 590mm

Thickness of 0.7mm

Thickness distribution is less than 0.025mm

Warpage of less than 0.5mm

Waviness < 50mm

Controlling the working process:

Tg+670KTg+590K2,8kg/min

an inlet:

the glass temperature at the inlet was set to Tg +670K-Tg +590K (single drop along the inlet). The total flux was 2.8 kg/min.

Draw up the trough, the heating device of nozzle system and nozzle stove:

the glass temperature in the lead-up channel 6 is set to Tg +590K-Tg +570K, the glass temperature at the slot-type channel brick 11 is set to Tg +570K-Tg +550K, and the glass temperature on the current carrier 16 is set to Tg +560K-Tg + 540K. Thus, a uniform linear flux of 3.5g/(minxmm) was obtained in the transverse direction of the continuous glass ribbon. The thickness of the glass film on current carrier 16 is always 8 mm. When the gap width (the distance between the gap-type groove brick 11 and the current carrier 16) is 10mm, the glass film on the current carrier 16 does not wet the bottom surface of the gap-type groove brick 11.

Cooling in nozzle and roller furnaces:

the main cooling device 23 (water as cooling medium) cools the glass in the root region to Tg + 290K. Here, the glass is elongated by means of a drawing roll 30 of a roll furnace 25 at a speed of 1.6m/min, so as to form a continuous glass ribbon having a total width of 800mm and a thickness of 0.7 mm. The sectional cooling devices 23, 24 (cooling medium water/air) are adjusted in such a way that the desired thickness distribution is reliably achieved. The continuous glass ribbon is uniformly cooled to Tg +140K by the staged heating and cooling of the roll furnace 25.

Guiding to a kiln:

by staged heating and cooling by induction of the furnace 32, the continuous glass ribbon is cooled to Tg +50K in a first rapid cooling zone, then cooled to Tg-50K in a precision cooling zone to accommodate permanent cooling body stresses, and then rapidly cooled to 450K in a second rapid cooling zone B. Within the pull-up kiln 32 and below the pull-up kiln are other rollers that stabilize the position of the continuous glass ribbon within and below the pull-up kiln 32. After isothermal quenching and cutting to length, the requirement for warping is met.

Claims (34)

1. A method for producing thin glass sheets by vertically downdrawing a continuous thin glass ribbon, wherein a glass melt is fed from a melting section of a tank furnace through an inlet into a lead-up trough having a nozzle system with at least one slotted channel sub-brick, characterized in that the total flow is adjusted depending on the viscosity of the glass melt in the vertical inlet by means of the longitudinal and cross-sections of the vertical inlet and the heating and cooling by means of the vertical inlet, so that the glass melt pressure resulting from the difference in height of the free surface of the glass melt and the height of the nozzle system is substantially reduced in the vertical inlet, and the flow within a single-bit length in the transverse direction of the continuous thin glass ribbon, i.e. the linear flow, is adjusted depending on the viscosity of the glass melt in the nozzle system by means of the geometry of the nozzle system and by means of the heating and cooling of the lead-up trough section and the slotted channel sub-brick, so that the glass melt does not wet the bottom surface of the slotted trough brick in the profiled edge region when it leaves the nozzle system.

2. The method of claim 1, wherein the temperature of the glass melt in the vertical inlet is adjusted to T_ZL1＝Tg+670K-T_ZL2＝Tg+590K。

3. The method of claim 1, wherein the temperature of the glass melt in the pull-up channel is adjusted to T_ZT1＝Tg+590K-T_ZT2＝Tg+570K。

4. The method according to one of claims 1 to 3, characterized in that the temperature T of the glass melt in the region of the slotted channel block_SDIs adjusted to T_SD1＝Tg+570K-T_SD2＝Tg+550K。

5. The method of claim 4, wherein the temperature differential Δ T of the glass melt along the slotted trough tile_SDIs adjusted to delta T_SD≤20K。

6. The method according to one of claims 1 to 3, characterized in that the glass melt is split as it flows through the slit channel brick by means of at least one flow conductor, the glass melt flowing as a glass film on both sides under the flow conductor and merging into the continuous thin glass strip on the bottom end of the flow conductor.

7. The method of claim 6, wherein the residence time and viscosity of the glass film on the flow conductor are adjusted in such a way that deviations from the ideal surface shape are almost completely compensated for.

8. The method of claim 6, wherein the glass film is selectively heated and/or cooled on the current carrier.

9. The method of claim 6, wherein the glass film is side guided on its side edges.

10. The method of claim 6, wherein the continuous ribbon of glass is selectively cooled in a root region thereof.

11. The method of any of claims 1 to 3, wherein at least a portion of the weight of the continuous ribbon of glass is compensated for when drawn.

12. The method according to one of claims 1 to 3, characterized in that the thickness of the continuous glass ribbon is measured continuously and the pulling-up speed is controlled by means of the measured thickness value.

13. The method of any of claims 1 to 3, wherein the continuous ribbon of glass is stretched in the visco-elastic region in a direction transverse to the ribbon direction.

14. The method according to one of claims 1 to 3, wherein the continuous thin glass ribbon is selectively heated and/or cooled in a roll furnace and/or a draw-up furnace in the direction of the ribbon and in the direction transverse to the direction of the ribbon.

15. The method of any of claims 1 to 3, wherein the thin glass sheet has a thickness of less than 1 mm.

16. Apparatus for manufacturing thin glass sheets using a tank furnace melting section, a homogenizing system, an inlet and a lead-up trough, said lead-up trough having a nozzle system with at least one slotted channel brick, characterized in that said inlet (1), said lead-up trough (6) and said nozzle system constitute a complete system, said inlet having a vertically arranged tube (2) with segmented tube sections (2a, b, c), said tube (2) having a length of 2 to 5m and a diameter of 50 to 80mm and being circular in cross-section, the inlet (1) having a segmented heating device (3) and a segmented cooling device (4), said lead-up trough (6) having a heating system (9) segmented in the vertical and in the transverse direction.

17. Device according to claim 16, characterized in that the slotted channel brick (11) is provided with heating means (15).

18. Device according to claim 16 or 17, characterized in that in the slotted channel brick (11) at least one flow conductor (16) is arranged vertically.

19. The device as claimed in claim 18, characterized in that the flow conductor (16) is a downwardly tapering plate made of a platinum alloy.

20. The device as claimed in claim 18, characterized in that the flow conductor (16) projects upwards onto the slotted trough tile (11).

21. The arrangement as claimed in claim 18, characterized in that the flow conductor (16) has a side interface (17).

22. The device as claimed in claim 18, characterized in that the flow conductor (16) is adjustable in X, Y and in the Z direction.

23. The arrangement as recited in claim 18, characterized in that the flow conductor (16) is extendable by applying a pulling force in the X-direction.

24. The device as claimed in claim 18, characterized in that the flow conductor (16) has a heating device and/or a cooling device.

25. The apparatus as claimed in claim 16 or 17, characterized in that below the slotted channel brick (11) there is connected a nozzle furnace (18) with a segmented heating device (20) and a segmented cooling device (23, 24).

26. The apparatus as claimed in claim 18, characterized in that below the slotted channel brick (11) there is connected a nozzle furnace (18) with segmented heating (20) and cooling (23, 24) devices, the nozzle furnace (18) having a beam plate (19) on the surface opposite the flow conductor (16).

27. The apparatus according to claim 26, wherein the nozzle furnace (18) has at least one movable screen (22) below the beam plate (19).

28. The apparatus according to claim 25, characterized in that the nozzle furnace (18) has means for opening in the transverse direction of the strip.

29. The apparatus as claimed in claim 25, characterized in that a roller furnace (25) with a roller shaft (26) having heating devices (27) and cooling devices (28) which are segmented in the X-direction and in the Z-direction is connected downstream of the nozzle furnace (18).

30. Device according to claim 29, characterized in that at least one pair of winding rollers (29) and/or a pair of upper guide rollers (30) is provided in the roller-distribution shaft of the roller furnace.

31. An apparatus according to claim 29 or 30, characterized in that the roller oven (25) has means for opening transversely to the strip direction.

32. The apparatus according to claim 30, wherein the speed of the upper roll (30) is adjustable according to the thickness of the common continuous thin glass ribbon on-line.

33. An apparatus according to claim 29, characterized in that an upper run (32) arranged below the roller kiln (25) can be moved away or closer downwards or sideways.

34. The apparatus of claim 16 or 17, wherein the thin glass sheet has a thickness of less than 1 mm.