JP5353963B2 - Sheet glass and method for forming the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high quality glass sheet excluding the problems of significant increase of warpage generation and the difficulty of the decrease of productivity associated with the increase of the thickness and the increase of the size of the glass sheet. <P>SOLUTION: A rectangular glass sheet 1 having both unpolished surfaces has a thickness of 0.7 mm or less, the length of short side is 1,000 mm or more, the length of long side is 1,200 mm or more, and warpage rate is 0.03% or less. The glass sheet 1 is molded by providing a cooling roller 5 that holds both width directional ends of the glass sheet G between a molded body 3 having a wedge-like cross-sectional shape and a tension roller 4, and the distance from the lower end 3b of the body 3 to the center axis of the cooling roller 5 is set from 30 to 200 mm. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a substrate for various electronic devices, specifically, a flat panel display such as a liquid crystal display, an electroluminescence display, a plasma display, and a field emission display, a sensor substrate, and a semiconductor package cover such as a solid-state imaging device and a laser diode. The present invention relates to a plate glass that can be used as glass and a molding method thereof.

In recent years, with the development of the electronic equipment industry, various electronic equipment, especially as flat glass display substrates such as liquid crystal displays, electroluminescence displays and plasma displays, or as cover glass for solid-state image sensors, etc., have a thickness of 0.3 to 3 A large amount of .0 mm plate glass has been used. These plate glasses are actually formed by various methods represented by the overflow downdraw method, the slot downdraw method and the float method. Among these, the overflow downdraw method is particularly swelled on the surface. It is known as a molding method capable of obtaining a sheet glass having a small roughness and excellent surface quality.

  More specifically, the overflow downdraw method is a method in which molten glass continuously supplied to a molded body having a wedge-shaped cross-sectional shape is caused to flow down along the both sides from the top of the molded body. This is a method of forming a sheet glass that has been finally solidified by fusing at a portion to form a single sheet, and pulling the sheet glass in this form downward while being held by a pulling roller. In this case, since the pulling roller usually holds only both end portions in the width direction of the plate-like glass, anything can be touched except for a slight holding portion (a portion deviating from the effective surface). It is possible to form a sheet glass having an unfinished surface, whereby a sheet glass having excellent surface quality can be obtained. Therefore, this molding method eliminates the need for a polishing process that causes high costs. On the other hand, when molding a large and thin plate glass used for a liquid crystal display or the like, warping is large. Tend to be.

  In accordance with this trend, if the glass substrate for a liquid crystal display has a large warp, when forming a thin film electrical circuit on it, the exposure distance will not be as designed, or two sheets of glass sandwiching the liquid crystal There arises a problem that unevenness occurs in the gap between the (substrates) and the display performance is impaired. In particular, in the case of a liquid crystal display for a television, a thin film electric circuit is complicated and a high display performance is required, so that the demand for warping of the substrate becomes very severe. Although it is possible to improve the warpage by forming a plate glass and then performing a heat treatment in a state where it is placed on a surface plate, adding a heat treatment step is not preferable because it increases costs.

  From such a background, various techniques for forming a sheet glass with a small warp by the overflow downdraw method have been proposed (see, for example, Patent Documents 1 and 2).

JP-A-5-163032 JP-A-10-291826

  By the way, according to the apparatus for producing sheet glass by the overflow downdraw method disclosed in the above-mentioned Patent Document 1, by providing a hollow blocking plate approaching from both the front and back sides to the sheet glass immediately after fusion under the molded body, Means have been taken to reduce warpage and thickness unevenness of the plate glass.

  However, in such a means, since the sheet glass that is separated downward from the molded body is pulled out only by the pulling force of the pulling roller, when forming a thin and large sheet glass, the lateral direction (width) of the sheet glass Direction) and the longitudinal direction are not sufficiently tensioned, and warping is likely to occur.

  Moreover, in recent years, in addition to the thin and large plate glass, productivity has been emphasized, so even if a hollow blocking plate is interposed between the molded body and the pulling roller as described above, If the plate glass has passed between the hollow blocking plates in a short time, the effect of arranging the hollow blocking plates cannot be sufficiently obtained, and the equipment is wasted.

  On the other hand, according to the apparatus for producing sheet glass by the overflow downdraw method disclosed in Patent Document 2, a pair of cooling rollers that sandwich both ends of the sheet glass are provided below the molded body, and the peripheral speed of the cooling roller is provided. A means for improving the warpage of the plate glass is adopted by making the diameter smaller than the peripheral speed of the pulling roller. According to this means, it becomes possible to apply tension in the horizontal direction and the vertical direction of the sheet glass by the interaction between the cooling roller and the pulling roller, and a reduction in warpage can be expected.

  However, even with the means disclosed in Patent Document 2, in recent years, with the thin and large plate glass, the occurrence of warpage has become prominent, and it has become difficult to improve productivity. Considering this point, there are still problems to be solved.

  In other words, the location and state of the cooling roller, the relationship between the circumferential speed of the cooling roller and the circumferential speed of the pulling roller, etc. can be used when the sheet glass is thin and large, or the molded body is increased in order to increase productivity. When the amount of molten glass to be supplied is increased, it is difficult to obtain a high-quality plate glass as in the conventional case.

  For example, Patent Document 2 discloses that when the peripheral speed of the pulling roller is increased, slip occurs between the glass sheet and the cooling roller. Specifically, the peripheral speed of the cooling roller is more than 30% of the peripheral speed of the pulling roller. There is a description that slipping occurs if it is small. If such a slip occurs, the movement speed of the sheet glass becomes unstable, shrinkage occurs in the horizontal direction, or sufficient tension is not applied in the vertical and horizontal directions, and the fundamental tendency is that warpage is likely to occur. Problems arise. However, if slip has occurred at the ratio of the peripheral speeds of both rollers, it is difficult to appropriately respond to the recent demands for thin and large plate glass and improved productivity.

  The present invention has been made in view of the above circumstances, and provides a high-quality plate glass by avoiding the problems of warpage and the difficulty in improving productivity due to the thinness and size of the plate glass. This is a technical issue.

  As a result of extensive research, the inventor has found that the cause of slippage and the deterioration of productivity between the sheet glass and the cooling roller described above are mainly in relation to the solidified state of the sheet glass. It came to find out that it was because the arrangement | positioning position and arrangement | positioning state of a cooling roller were not appropriate. Depending on the arrangement position and the arrangement state of the cooling roller, slip is not necessarily generated when the circumferential speed of the cooling roller is smaller than 30% of the circumferential speed of the tension roller as described in Patent Document 2. Rather, it has also been found that there is a more appropriate ratio of the peripheral speeds of both rollers including productivity improvement.

  Specifically, in the past, (1) based on the fact that the distance from the lower end of the molded body to the cooling roller was too long, a specific range of numerical values as elements thereof was found. In this connection, (2) the viscosity of the sandwiched portion of the sheet glass by the cooling roller is too high, and (3) the peripheral speed of the cooling roller is relatively high compared to the peripheral speed of the pulling roller. Based on the fact that it has passed, the inventors have found a specific range of numerical values that are the elements of the above (2) and (3).

The present invention has been completed on the basis of such knowledge, and as one corresponding to the above (1), the molten glass is caused to flow down along the both sides from the top of the molded body having a wedge-shaped cross-sectional shape. Accordingly, in the method of forming a sheet glass that is pulled out downward while being sandwiched by a pulling roller, the sheet glass that is fused and formed at the lower end of the formed body is formed between the formed body and the pulling roller. It is characterized in that a cooling roller for cooling by sandwiching both ends in the width direction of the glass is provided, and the distance from the lower end of the formed body to the central axis of the cooling roller is 30 to 200 mm. Secondly, as corresponding to the above (2), when the viscosity of both end portions in the width direction of the sheet glass is 10 ^5.2 to 10 ^8.6 dPa · s, the both ends are characterized by being sandwiched by the cooling roller. Thirdly, as corresponding to the above (3), the ratio B / A between the circumferential speed A of the cooling roller and the circumferential speed B of the pulling roller is characterized by 3.5 to 20.

That is, the present inventor considered that the peripheral speed of the pulling roller is increased in consideration of improvement in productivity when producing a thin and large plate glass having a thickness of 0.7 mm or less and an effective width of 1200 mm or more by the overflow down draw method. It was devised that the distance from the lower end of the molded body to the cooling roller needs to be as short as possible in order to suppress warpage while suppressing shrinkage in the width direction of the sheet glass while increasing the size. And as a concrete means for sandwiching the glass sheet in the high temperature state with the cooling roller, if the distance from the lower end of the molded body to the central axis of the cooling roller is 30 to 200 mm, the space between the glass sheet and the cooling roller is No slip was produced, and the warp rate of the obtained plate glass was 0.03% or less, and it was found that this plate glass is particularly suitable as a substrate for a liquid crystal display. That was completed based on this finding, an invention corresponding to the (1).

In addition, as an invention related to the present invention, in the process of producing a thin and large plate glass in the same manner as described above, the present inventor considered as high a temperature as possible in order to reduce warpage while considering improvement in productivity. It has been devised that it is necessary to sandwich the glass sheet in a state (low viscosity state) with a cooling roller. As a specific means, the viscosity at both ends in the width direction of the glass sheet is 10 ^5.2 to 10 ^8.6 dPa · It was found that if the sheet was sandwiched between the cooling rollers at s, the warp rate of the obtained plate glass was 0.03% or less in the same manner as described above. The invention corresponding to the above (2) has been completed based on this finding.

Further, in the process of producing a thin and large plate glass in the same manner as described above , the present inventor is required to pull in comparison with the peripheral speed of the cooling roller in order to reduce warpage while considering improvement in productivity. It has been devised that it is necessary to significantly increase the peripheral speed of the roller. As a specific means, the ratio B / A between the peripheral speed A of the cooling roller and the peripheral speed B of the pulling roller is set to 3.5-20. As a result, it was found that the warp rate of the obtained plate glass was 0.03% or less in the same manner as described above. The invention corresponding to the above (3) has been completed based on this finding.

  And the invention as plate glass completed based on each said knowledge is a rectangular plate glass whose both surfaces are non-polishing surfaces, and thickness is 0.7 mm or less (preferably 0.03-0.60 mm). The length of the short side is 1000 mm or more, the length of the long side is 1200 mm or more, and the warpage rate is 0.03% or less (preferably 0.01% or less).

  In other words, a plate glass having a non-polished surface formed by the overflow down draw method has been conventionally known as a liquid crystal display substrate. This conventional one has a thickness of 0.7 mm or less and a short side. Even when the length is 1000 mm or more and the length of the long side is 1200 mm or more, the warpage rate exceeds 0.03%, and in this respect, the plate glass according to the present invention is a novel plate glass. When a glass sheet with a very low warpage rate is used as a substrate for a liquid crystal display, when forming a thin film electric circuit on the substrate, the exposure distance is not as designed, or two glass sheets sandwiching the liquid crystal ( It is possible to solve problems such as unevenness in the gap between the substrates) and the deterioration of display performance. From such a viewpoint, the plate glass according to the present invention is suitable as a display substrate for a liquid crystal television or the like. Here, “the warpage rate is 0.03% or less” is a direction along the long side when the glass sheet is placed on the ideal plane (specifically, the upper surface of the precision surface plate) with the surface facing upward. The first warpage rate obtained by dividing the maximum separation distance (warpage amount) between the ideal plane and the back surface of the glass sheet by the total length of the long side, and the ideal plane and the back surface of the glass sheet along the short side The second warp rate obtained by dividing the maximum separation distance (warp amount) by the total length of the short side, and the direction along the long side when the plate glass is placed on the ideal plane with the surface facing downward The third warpage rate obtained by dividing the maximum separation distance (warpage amount) between the ideal plane and the surface of the glass sheet by the total length of the long side, and the ideal plane and the surface of the glass sheet in the direction along the short side A fourth distance obtained by dividing the maximum separation distance (warpage amount) by the total length of the short side. Of the rate Ri, a large warping ratio of most value means that 0.03% or less.

This plate glass has a strain point of 630 ° C. or higher, a coefficient of thermal expansion at 30 to 380 ° C. of 28 to 40 × 10 ⁻⁷ / ° C., a density of 2.60 g / cm ³ or less, and a viscosity at a liquidus temperature of 10 ^5.8 dPa · it can be obtained as those with s or more characteristics, in _{mass%, SiO 2 55~70%, Al} 2 O 3 12~22%, B 2 O 3 3~15%, alkaline earth metal oxides It can also be obtained as a material containing 2 to 20% and having an alkali metal oxide content of 0.1% or less.

  On the other hand, although the plate glass forming method according to the present invention has already been described, in addition, the forming method corresponding to the above (1), that is, the distance from the lower end of the formed body to the central axis of the cooling roller is 30. According to the molding method of ˜200 mm, the following advantages can be enjoyed.

  That is, when the distance from the lower end portion of the molded body to the central axis of the cooling roller is long, both end portions in the width direction of the sheet glass are cooled and the viscosity is already high as in the case described above. When the peripheral speed of the pulling roller is increased to increase productivity in this state, slip occurs between the sheet glass and the cooling roller, and the movement speed of the sheet glass is unstable. The warpage becomes larger. However, in this molding method, when both end portions in the width direction of the sheet glass are still in a state of high viscosity at a high temperature, specifically, at a position where the distance from the lower end of the molded body to the lower side is within 200 mm, Since both ends in the width direction of the sheet glass are sandwiched by the cooling roller, even if the peripheral speed of the pulling roller is increased, the probability of occurrence of slip between the sheet glass and the cooling roller is extremely low. Therefore, even in this molding method, it is possible to easily form a thin, large and small warped plate glass for the same reason as described above, and even if the peripheral speed of the pulling roller is increased, slip is not caused. Since it is difficult to occur, productivity can be improved. In addition, when the glass sheet is sandwiched by the cooling roller when the sheet glass is too soft because the distance from the lower end of the molded body to the central axis of the cooling roller is too short, the glass is wrapped around the cooling roller, etc. Therefore, the distance between the lower end of the molded body and the central axis of the cooling roller needs to be 30 mm or more. Note that a more preferable upper limit value of the separation dimension is 100 mm.

Further, according to the molding method corresponding to the above (2), that is, the molding method in which the cooling rollers sandwich the both ends when the viscosity of both ends in the width direction of the sheet glass is 10 ^5.2 to 10 ^8.6 dPa · s, Benefits shown in

That is, when forming the glass sheet by the overflow down draw method, it is necessary to increase the peripheral speed of the tension roller in order to efficiently produce a thin and large-sized glass sheet. When it is going to cool, it is necessary to reduce the peripheral speed of a cooling roller and to lengthen the contact time between plate glass and a cooling roller. In that case, when both ends of the sheet glass in the width direction are cooled and the viscosity is already high, if the peripheral speed of the pulling roller is increased while the both ends are sandwiched between the cooling rollers, the sheet glass and the cooling roller Slip occurs, and the moving speed of the sheet glass becomes unstable, and warping increases. However, in this molding method, when both end portions in the width direction of the glass sheet are at a high temperature and are still in a low viscosity state, specifically, when the viscosity at the both end portions is 10 ^8.6 dPa · s or less, the glass is sandwiched between cooling rollers. For this reason, even if the peripheral speed of the pulling roller is increased, the probability of occurrence of slip between the sheet glass and the cooling roller becomes extremely low. As a result, both end portions in the width direction of the sheet glass can be stably cooled, and thus shrinkage in the width direction is sufficiently suppressed. In other words, the plate-like glass separated from the lower end of the molded body gradually contracts while being pulled downward, but in this molding method, the plate is still in a state of being easily softened and deformed immediately after being separated from the molded body. Since both end portions in the width direction of the glass sheet can be held between the cooling rollers and the moving speed can be reduced, shrinkage in the width direction can be suppressed. In this state, the sheet glass is pulled downward and solidifies in a state where tension is applied in the lateral direction and the longitudinal direction. Therefore, it is possible to easily form a thin, large and small warped sheet glass. In addition, slipping hardly occurs even when the peripheral speed of the pulling roller is increased, so that productivity can be improved. In this case, if the glass sheet is sandwiched between the cooling rollers when the glass sheet is too soft, the glass tends to wind around the cooling roller or the cooling roller is likely to deteriorate. ^It is necessary to pinch with a cooling roller after ^5.2 dPa · s or more. The lower limit of the viscosity is more preferably 10 ^5.7 dPa · s, the upper limit is more preferably 10 ^7.5 dPa · s, and the lower limit of the viscosity is 10 ^6.0. dPa · s is more preferable, and the upper limit is more preferably 10 ^7.0 dPa · s.

  In addition, according to the molding method corresponding to the above (3), that is, the molding method in which the ratio B / A between the circumferential speed A of the cooling roller and the circumferential speed B of the tension roller is 3.5 to 20, Benefits shown in

  That is, in this case as well, as described above, when forming the glass sheet by the overflow down draw method, it is necessary to increase the peripheral speed of the tension roller in order to efficiently produce a thin and large-sized glass sheet. In order to properly cool both ends in the width direction of the sheet glass, it is necessary to reduce the peripheral speed of the cooling roller. If the difference between the peripheral speed A of the cooling roller and the peripheral speed B of the pulling roller is small, in other words, if the ratio B / A is small, the peripheral speed of the pulling roller is increased to increase the productivity. In this case, since the circumferential speed A of the cooling roller becomes large, it is difficult to properly cool the sheet glass with the cooling roller, and it is difficult to make a condition that can ensure a stable moving speed of the sheet glass. Become. For this reason, when forming a thin and large plate glass, it is extremely difficult to achieve a molding condition that can reduce warpage while enhancing productivity. However, in this molding method, the setting is such that the peripheral speed A of the cooling roller and the peripheral speed B of the pulling roller are sufficiently different, specifically, the ratio B / A is 3.5 or more. Therefore, it is possible to reduce the warpage while improving the productivity of the thin and large plate glass. On the other hand, if the difference between the circumferential speed A of the cooling roller and the circumferential speed B of the pulling roller is unreasonably large (if the ratio B / A is unreasonably large), the molding conditions become unstable, and a plate glass having a desired shape is obtained. It becomes difficult to obtain stably. Therefore, in this molding method, the ratio B / A is set to 20 or less. In consideration of the above matters comprehensively, the lower limit of the ratio B / A is more preferably 4, and the upper limit is more preferably 15.

  In the above molding method, it is preferable to heat the glass by providing a heater near the side surface and / or near the top of the molded body.

  In this way, since the viscosity of the molten glass flowing down from the top of the molded body along the side surface can be adjusted, the viscosity of the sandwiched portion of the sheet glass by the cooling roller described above, from the lower end of the molded body to the cooling roller The ratio between the peripheral speed of the cooling roller and the peripheral speed of the pulling roller can be changed as appropriate, and it is possible to easily set the molding conditions.

  In the molding method described above, it is preferable to provide auxiliary cooling rollers at one location below the cooling roller or at a plurality of locations in the vertical direction below.

  That is, even after the glass sheet is cooled by being sandwiched between the cooling rollers, it tends to shrink further in the width direction below it. If an auxiliary cooling roller is provided below the cooling roller, the auxiliary cooling roller Since both end portions in the width direction of the sheet glass are sandwiched, shrinkage in the width direction of the sheet glass after leaving the cooling roller can be suppressed. As a result, it is possible to obtain a plate glass having a larger effective width. In this case, it is preferable that the peripheral speed of the auxiliary cooling roller be less than 80% of the peripheral speed of the pulling roller. However, if the peripheral speed of the auxiliary cooling roller exceeds 80% of the peripheral speed of the pulling roller, the plate This is because the cooling effect on the glass sheet is remarkably reduced, and it is difficult to efficiently suppress the shrinkage in the width direction. The peripheral speed of the auxiliary cooling roller is more preferably less than 70% of the peripheral speed of the pulling roller. And in order to increase the effect of suppressing the shrinkage in the width direction of the plate glass, it is preferable to provide the auxiliary cooling roller in as many locations as possible in the vertical direction, but considering the manufacturing conditions and cost, the auxiliary cooling roller is It is appropriate to provide in 1 to 4 places in the vertical direction. And even if it is a case where an auxiliary | assistant cooling roller is provided in this way, all the above-mentioned matters regarding the cooling roller existing above it do not become meaningless.

  As described above, according to the present invention, when a thin film electric circuit is formed on a liquid crystal display substrate, the exposure distance is not as designed, or the gap between two plate glasses (substrates) sandwiching the liquid crystal is set. It is possible to provide a thin and large plate glass capable of solving problems such as occurrence of unevenness and impaired display performance.

  In addition, according to the present invention, a thin and large plate glass having a thickness of 0.7 mm or less and an effective width of 1200 mm or more (preferably 1500 mm or more, more preferably 2000 mm or more) is formed by the overflow downdraw method. However, it is possible to provide a molding method capable of improving productivity and reducing warpage.

It is a schematic sectional drawing which exaggerates and shows the plate glass which concerns on embodiment of this invention. It is a schematic side view which shows the principal part of the shaping | molding apparatus used for shaping | molding of the said plate glass. It is a schematic front view which shows the principal part of the shaping | molding apparatus used for shaping | molding of the said plate glass.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic sectional view exaggeratingly showing a plate glass according to an embodiment of the present invention. As shown in the figure, this plate glass 1 has a rectangular shape in which both the front surface and the back surface are non-polished surfaces, the thickness t is 0.7 mm or less, the short side length L1 is 1000 mm or more, and the long side length. (L2) is 1200 mm or more and the warpage rate is 0.03% or less. Here, the warpage rate is the maximum separation distance between the upper surface J of the precision surface plate and the lower surface of the plate glass 1 in the direction along the long side (the amount of warpage). ) The warp rate {(S1 / L1) × 100} on the long side obtained by dividing S1 by the total length L1 of the long side, and the upper surface J of the precision surface plate in the direction along the short side and the lower surface of the plate glass 1 And the warp rate {(S2 / L2) × 100} on the short side obtained by dividing the maximum separation distance (warp amount) S2 by the total length L2 of the short side. The above-mentioned “warp rate is 0.03% or less” means that the warp rate on the long side and the warp on the short side when the plate glass 1 is placed on the upper surface J of the precision surface plate with the surface facing upward. And the largest of the four warp rates of the long side and the short side when the plate glass 1 is placed on the upper surface J of the precision surface plate with the surface facing downward. It means that the warp rate of the value is 0.03% or less (the same applies to “0.02% or less” and “0.01% or less” below).

  In this case, the warp rate of the plate glass 1 is preferably 0.02% or less, and more preferably 0.01% or less. Further, the short side length L1 and the long side length L2 may both be 1500 mm or more, and further 2000 mm or more. Further, the thickness t of the plate glass 1 may be 0.65 mm or less, and further 0.60 mm or less. However, if the thickness t is too thin, the strength is remarkably lowered and formability is lowered. Is preferably 0.03 mm or more, more preferably at least 0.1 mm or more.

Moreover, this plate glass 1 has a strain point of 630 ° C. or higher, a thermal expansion coefficient of 28 to 40 × 10 ⁻⁷ / ° C. at 30 to 380 ° C., a density of 2.60 g / cm ³ or less, and a viscosity at a liquidus temperature of 10 ^{It is 5.8} dPa · s or more and excellent in chemical resistance (buffered hydrofluoric acid resistance and hydrochloric acid resistance). The plate glass 1 having such characteristics is particularly suitable when used as a liquid crystal display substrate. In this case, as long as the viscosity at the liquidus temperature is 10 ^5.8 dPa · s or more as described above, even if the glass sheet is molded at a relatively low temperature, devitrification is not generated in the glass, and the moldability In view of this, it is more preferably 10 ^5.9 dPa · s or more.

Furthermore, the composition of the glass sheet 1, by mass%, containing _{SiO 2 55~70%, Al 2 O} 3 12~22%, B 2 O 3 3~15%, 2-20% alkaline earth metal oxides However, the alkali metal oxide is not substantially contained (in other words, the alkali metal oxide is% by mass and 0.1% or less). When the plate glass 1 has such a composition, it is particularly suitable as a substrate for a liquid crystal display, and within the composition range, the above-described characteristics can be obtained by appropriately combining the content of each component. The provided plate glass 1 is obtained.

The reasons for limiting the glass composition range are as follows. That is, first, if SiO ₂ becomes too small, the chemical resistance of the glass tends to decrease. Conversely, if too much, the melting property of the glass deteriorates and devitrification occurs in the glass. Foreign matter (cristobalite) is likely to occur. Therefore, the content of SiO ₂ is reasonable from 50 to 70%, preferably from 55 to 68%. Secondly, if the Al ₂ O ₃ content becomes too small, the liquidus temperature rises, and devitrified foreign matter (cristobalite) is likely to be generated in the glass, and the strain point of the glass is lowered. When the amount is too large, the buffered hydrofluoric acid resistance of the glass is lowered and the devitrification property is lowered, and mullite and feldspar-based devitrified foreign substances are easily generated in the glass. Therefore, the content of Al ₂ O ₃ is reasonable from 10 to 19%, preferably from 11 to 18%. Third, B ₂ O ₃ is a component that acts as a flux, lowers the high-temperature viscosity of the glass, and improves the meltability. If this B ₂ O ₃ is too small, the function as a flux is ineffective. In addition to this, the buffered hydrofluoric acid resistance of the glass decreases, and conversely, if it increases too much, the strain point of the glass decreases, the heat resistance deteriorates, and the acid resistance deteriorates. Therefore, the content of B ₂ O ₃ is reasonable from 5 to 15%, preferably from 7 to 14%. Fourthly, if the alkaline earth metal oxide (MgO + CaO + SrO + BaO) becomes too small, the meltability of the glass deteriorates or the liquidus temperature tends to rise. On the contrary, if it becomes too much, The density tends to increase. Therefore, the content of the alkaline earth metal oxide is reasonable from 5 to 20%, preferably from 7 to 18%. In addition to the above components, ZnO, P ₂ O ₅ , ZrO ₂ , Y ₂ O ₃ , Nb ₂ O ₃ , La are used for improving the meltability, devitrification resistance, acid resistance and adjusting the thermal expansion coefficient. Components such as ₂ O ₃ and TiO ₂ may be contained at 5% or less, and components such as clarifiers such as As ₂ O ₃ , Sb ₂ O ₃ , Cl, F and SO ₃ are each 2%. You may make it contain. However, if alkali metal oxides (Li ₂ O, Na ₂ O, K ₂ O) are contained in the glass, these components diffuse into the semiconductor element formed on the substrate and adversely affect the semiconductor element. , It is desirable that it does not contain substantially. Therefore, the content of these components should be suppressed to 0.1% or less.

  FIG. 2 is a schematic side view showing the state of implementation of the method for forming a sheet glass, and FIG. 3 is a schematic front view thereof. Here, prior to the description of the sheet glass forming method, the structure of a forming apparatus used for carrying out the sheet glass forming method will be described with reference to FIGS. 2 and 3. The basic configuration of the molding apparatus 2 is that the longitudinal cross-sectional shape is a wedge shape and the molded body 3 in which the overflow groove 3a is formed at the top, and the molten glass Y overflowing from the top of the molded body 3 is formed into a sheet glass G. And an upper cooling roller 5 and a lower auxiliary cooling roller 6 disposed in the middle of the glass forming path from the lower end 3b of the molded body 3 to the pulling roller 4. Each of these components 3, 4, 5, and 6 is surrounded by a furnace wall 7 made of refractory bricks. Further, the glass (molten glass) flowing down the side surface 3c of the molded body 3 can be zone-heated in the vertical and horizontal directions around the side surface 3c of the molded body 3, in this embodiment, on the inner surface of the side wall portion of the furnace wall 7. A plurality of heaters 8 are respectively disposed on both sides of the molded body 3.

  The pulling rollers 4 sandwich only both ends in the width direction of the sheet glass G, and a total of four pulling rollers 4 are provided at each end. The two pulling rollers 4 existing on the front side of the glass sheet G are connected by a shaft member 4a so as to be integrally rotatable, and the two pulling rollers 4 existing on the back side thereof are also connected by the shaft member 4a. These pulling rollers 4 are provided with a rotational driving force. Further, the cooling roller 5 also sandwiches both ends in the width direction of the sheet glass G, and includes a total of four pieces at each end, but two pieces present on the front side of the sheet glass G. The cooling rollers 5 are separated and can be rotated independently of each other, and the two cooling rollers 5 on the back side thereof are also separated so that they can be independently rotated (auxiliary cooling rollers 6). The same). The cooling roller 5 is a driving roller to which a rotational driving force is applied, whereas the auxiliary cooling roller 6 is a non-driving roller that rotates idly without being applied with a rotational driving force.

  The pulling roller 4, the cooling roller 5, and the auxiliary cooling roller 6 are made of stainless steel, heat resistant steel, ceramics, or the like. Furthermore, these rollers 5 and 6 are hollow inside, and the refrigerant can flow through the hollow portion to the vicinity of the tip in the axial direction. In this case, gas or liquid can be used as the refrigerant.

And as for the cooling roller 5, the molten glass Y flows down from the top part of the molded object 3 along the both side surfaces 3c, and fuse | melts by the lower end part 3b of the molded object 3, immediately after it became one plate shape. It arrange | positions in the position which can pinch glass G and can cool it. More specifically, the cooling roller 5 has a viscosity of 10 ^5.2 to 10 ^8.6 dPa · s, more preferably 10 ^5.7 to 10 ^7.5 dPa · s (more preferably 10). ^6.0 to 10 ^7.0 dPa · s), the both ends are held in a sandwiched position. And in order to satisfy | fill such conditions, the distance a from the lower end part 3b of the molded object 3 to the central axis of the cooling roller 5 is set to 30-200 mm, More preferably, it is 30-100 mm. In this case, the distance b between the central axis of the cooling roller 5 and the central axis of the auxiliary cooling roller 6 is set to 50 to 300 mm, more preferably 100 to 200 mm.

The ratio of the peripheral speed of the cooling roller 5 to the peripheral speed of the pulling roller 4 is set to 1: 3.5 to 1:20, more preferably 1: 4 to 1:15. The speed is set to be less than 80%, more preferably less than 70% of the peripheral speed of the pulling roller 4 within a range equal to or higher than the peripheral speed of the cooling roller 5.

  According to the molding apparatus 2 having the above-described configuration, the molten glass Y that is supplied to the molded body 3 and flows down from the top along the side surface 3c is adjusted in viscosity by the heater 8 while the molded glass 3 is adjusted. The sheet is fused at the lower end 3b to form a single sheet, and the sheet glass G is sandwiched between the pulling rollers 4 and drawn downward. In the initial stage where the pulling by the pulling roller 4 is performed, the cooling roller 5 comes into contact with both end portions in the width direction of the sheet glass G and appropriately cools the periphery of the contact portion. Since the viscosity of the contact portion with 5 is moderately low as described above, even if the peripheral speed of the pulling roller 4 is increased to increase the productivity, the slip is not generated between the glass sheet G and the cooling roller 5. It becomes difficult to occur.

  And since the distance from the lower end part 3b of the molded object 3 to the center axis | shaft of the cooling roller 5 is moderately shortened as stated above, the viscosity of the contact part with the cooling roller 5 in the sheet glass G is effective. Can be lowered. Further, since the peripheral speed of the pulling roller 4 is appropriately increased as described above compared to the peripheral speed of the cooling roller 5, the productivity is reduced after preventing the movement of the sheet glass G. It becomes possible to greatly increase.

  In this way, while the sheet glass G is being pulled out downward, both ends of the sheet glass G in the width direction are also sandwiched by the auxiliary cooling roller 6 and cooling is performed supplementarily. In this case, if the auxiliary cooling roller 6 does not exist, the glass sheet G contracts in the width direction as shown by a chain line (reference numeral X) in FIG. 3 to finally obtain a wide glass sheet. However, if the auxiliary cooling roller 6 is provided as in this embodiment, the shrinkage in the width direction of the sheet glass G can be suppressed, which is advantageous in reducing the thickness and size of the sheet glass. Become. In consideration of this, the auxiliary cooling roller 6 is preferably arranged in a plurality of stages (for example, 2 to 4 stages) between the uppermost cooling roller 5 and the lowermost pulling roller 4. .

As Example 1 of the present invention, using a device having the same basic configuration as the molding device 2 shown in FIGS. 2 and 3 and not provided with the auxiliary cooling roller 6, mass%, SiO ₂ 60%, _{al 2 O 3 15%, B} 2 O 3 10%, CaO 6%, SrO 6%, BaO 2%, was molded plate glass (Nippon Electric Glass Co., Ltd. OA-10) having a composition of 1% fining agent. In this apparatus, the length of the molded body 3 in the width direction is 2500 mm, and the distance from the lower end 3b of the molded body 3 to the central axis of the cooling roller 5 is 100 mm. The refrigerant of the cooling roller 5 is air. In this molding, the heater 8 heats the molten glass Y flowing down along the both side surfaces 3c of the molded body 3 and the plate glass G between the lower end portion 3b of the molded body 3 and the cooling roller 5, thereby When the viscosity of both end portions in the width direction of the glass sheet G is 10 ^6.9 dPa · s, the end portions are held between the cooling rollers 5. The peripheral speed of the pulling roller 4 was 200 cm / min, and the peripheral speed of the cooling roller 5 was 40 cm / min.

The plate glass formed under such conditions has a plate width of 2100 mm, a thickness in the center in the width direction of 0.7 mm, and an effective width within a range of 0.7 mm ± 0.05 mm is 1800 mm. That was all. The plate glass was cut to have a short side of 1800 mm and a long side of 2200 mm, and the warpage rate was calculated. Both the short side and the long side were 0.01% or less. . In addition, this plate glass has a strain point of 660 ° C., a thermal expansion coefficient of 37 × 10 ⁻⁷ / ° C. at 30 to 380 ° C., a density of 2.49 g / cm ³ , and a viscosity at a liquidus temperature of 10 ⁶ dPa · s or more. It was also excellent in buffered hydrofluoric acid resistance and hydrochloric acid resistance. The strain point was measured based on the method of ASTM C336-71, the thermal expansion coefficient was measured by a push rod type thermal expansion measuring device, and the density was measured based on the well-known Archimedes method. The viscosity of the plate glass at the liquidus temperature is the highest temperature at which crystals are first crushed to a particle size of 300 to 500 μm in a platinum boat, held in a temperature gradient furnace for 8 hours, and crystals are precipitated inside using a microscope. The temperature was determined as the liquidus temperature, and the viscosity corresponding to the liquidus temperature was measured by a well-known platinum ball pulling method. Buffered hydrofluoric acid resistance is obtained by optically polishing a glass surface and then immersing in a buffered hydrofluoric acid solution composed of 38.7% by mass ammonium fluoride and 1.6% by mass hydrofluoric acid maintained at 20 ° C. for 30 minutes. The surface resistance is evaluated by observing the surface state, and the hydrochloric acid resistance is optically polished on the glass surface, immersed in a 10% by mass hydrochloric acid aqueous solution maintained at 80 ° C. for 24 hours, and then the surface state is observed. Was evaluated by The above plate glass was excellent in chemical resistance with no change in the surface.

As a second embodiment of the present invention, a molding apparatus provided with a single stage auxiliary cooling roller 6 in addition to the cooling roller 5, that is, a component similar to that shown in FIGS. A plate glass having the same composition as in Example 1 was formed by using a molding apparatus that was different from the molding apparatus used in Example 1 only in that the auxiliary cooling roller 6 was provided. In this molding apparatus, the distance between the center axis of the cooling roller 5 and the center axis of the auxiliary cooling roller 6 is set to 200 mm, and the viscosity at both ends in the width direction of the sheet glass G is 10 ^6.9 dPa · s. The end portion was sandwiched between the cooling rollers 5, the peripheral speed of the pulling roller 4 was 220 cm / min, the peripheral speed of the cooling roller 5 was 33 cm / min, and the peripheral speed of the auxiliary cooling roller 6 was 155 cm / min. Note that the refrigerant of the cooling roller 5 and the auxiliary cooling roller 6 is air.

  The plate glass molded under such conditions has a plate width of 2250 mm, a thickness in the center in the width direction of 0.63 mm, and an effective width that falls within the range of 0.63 mm ± 0.05 mm. It was 1950 mm or more. And when this flat glass was cut and processed so that the short side had a dimension of 1950 mm and the long side was 2200 mm, and the warpage rate was calculated, both the short side and the long side were 0.01% or less. there were.

  As Example 3 of the present invention, a sheet glass having the same composition as that of Example 1 was molded using a molding apparatus having the same components as those used in Example 2 above. The molding apparatus used in Example 3 differs from the molding apparatus in Example 2 described above in that the length in the width direction of the molded body 3 is 2000 mm and the peripheral speed of the tension roller 4 is 500 cm / min. The peripheral speed of the cooling roller 5 is 40 cm / min, and the peripheral speed of the auxiliary cooling roller 6 is 300 cm / min.

  The plate glass molded under such conditions has a plate width of 1600 mm, a thickness in the center in the width direction of 0.2 mm, and an effective width that falls within a range of 0.2 mm ± 0.05 mm. It was 1200 mm or more. And when this flat glass was cut and processed so that the short side had a dimension of 1200 mm and the long side was 1400 mm, and the warpage rate was calculated, both the short side and the long side were 0.02% or less. there were.

DESCRIPTION OF SYMBOLS 1 Sheet glass 2 Molding apparatus 3 Molded body 3b Lower end 3c of molded body Side surface 4 of molded body Tension roller 5 Cooling roller 6 Auxiliary cooling roller 8 Heater Y Molten glass G Sheet glass a Center of cooling roller from lower end of molded body Distance to axis

Claims (7)

By letting the molten glass flow down along the both sides from the top of the molded body having a wedge-shaped cross-sectional shape, the glass sheet fused into a plate shape at the lower end of the molded body is sandwiched between tension rollers. In the method for forming the sheet glass that is drawn downward, a cooling roller is provided between the formed body and the pulling roller to sandwich and cool both ends in the width direction of the sheet glass, and from the lower end of the formed body The distance to the central axis of the cooling roller is 30 to 200 mm, and the ratio B / A between the circumferential speed A of the cooling roller and the circumferential speed B of the pulling roller is 3.5 to 20. A method for forming sheet glass. The method for forming a glass sheet according to claim 1 , wherein the glass is heated by providing a heater near the side surface and / or near the top of the molded body. Forming method of the glass sheet according to claim 1 or 2, characterized in that an auxiliary cooling roller at a plurality of positions in the vertical direction in one place or lower in the lower of the cooling roller. The method for forming a sheet glass according to any one of claims 1 to 3 , wherein the thickness of the sheet glass solidified downstream of the pulling roller is 0.7 mm or less and the effective width is 1200 mm or more. The plate glass forming method according to claim 4 , wherein the thickness of the plate glass solidified downstream of the pulling roller is 0.03 to 0.60 mm. The method for forming a sheet glass according to any one of claims 1 to 5 , wherein a warp rate of the sheet glass solidified downstream of the pulling roller is 0.03% or less. The method for forming a glass sheet according to claim 6 , wherein a warpage rate of the glass sheet solidified downstream of the pulling roller is 0.01% or less.

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