JP2007051028A - Method of forming plate glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming high quality plate glass by avoiding problems of occurrence of warpage and difficulty of the improvement of productivity arising accompanied with the plate glass made thin/large-sized. <P>SOLUTION: In the forming method, the plate glass 8 is formed by providing a plurality of cooling rollers 4, 5 for clamping both width directional end parts of the plate glass G and cooling the plate glass in a vertical direction between a foamed body 2 having a wedge-like cross-sectional shape and a tension roller 3 and giving rotary drive force only to the uppermost cooling roller 4. The distance between the cooling rollers 4, 5 adjacent to each other in a vertical direction in the plurality of the cooling rollers is preferably ≤300 mm and the ratio B/A of the peripheral velocity B of the tension roller 3 to the the peripheral velocity A of the uppermost cooling roller 4 is preferably 3.5-20. <P>COPYRIGHT: (C)2007,JPO&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 method for forming plate glass that can be used as glass.

  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, in order to respond to a request to reduce the thickness of the sheet glass by the overflow down draw method, in addition to having to increase the peripheral speed of the pulling roller, it is also possible to meet the request to increase the productivity of the sheet glass. The peripheral speed of the pulling roller must be increased while increasing the amount of molten glass supplied to the body.

  Nevertheless, Patent Document 2 discloses that when the tension roller is increased in peripheral speed, slip occurs between the glass sheet and the cooling roller. Specifically, the peripheral speed of the cooling roller is equal to the peripheral speed of the tension roller. There is a description that slipping occurs when it is less than 30%. However, when such a slip occurs, the moving speed of the sheet glass becomes unstable, and the shrinkage occurs in the horizontal direction, or sufficient tension is not applied in the vertical and horizontal directions, and warping is likely to occur. However, it becomes difficult to form high-quality plate glass while appropriately responding to recent demands for thin and large plate glass and productivity improvement.

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

  As a result of intensive research, the inventor of the present invention has succeeded in efficiently producing thin and large plate glass, for example, plate glass having a thickness of 0.7 mm or less and an effective width of 1200 mm or more by an overflow down draw method. In order to suppress the shrinkage of the sheet glass in the width direction and reduce the warp while increasing the peripheral speed, it has been found that it is necessary to improve the arrangement state of the cooling roller and the driving form thereof.

  The present invention has been completed based on such knowledge, and by letting molten glass flow down along the both sides from the top of the molded body having a wedge-shaped cross-sectional shape, In a method for forming a sheet glass that is pulled out downward while sandwiching a sheet glass that has been fused into a sheet shape, both ends in the width direction of the sheet glass are sandwiched between the molded body and the tension roller. The gist of the invention is to provide a plurality of cooling rollers for cooling in the vertical direction and to apply a rotational driving force only to the uppermost cooling roller.

  According to such a forming method, both end portions in the width direction of the glass sheet are cooled by being sandwiched by the cooling rollers at two or more locations in the vertical direction, so that contraction in the width direction of the glass sheet is minimized. It is done. More specifically, when a sheet glass is formed by the overflow downdraw method, the sheet glass that is separated from the formed body tends to shrink gradually as it is pulled downward. If the both ends in the width direction of the glass sheet that has just been separated from the molded body and is still easily softened and deformed are sandwiched between the uppermost cooling rollers (main cooling rollers), Shrinkage can be suppressed. In addition, even after the glass sheet is cooled by being sandwiched by the main cooling roller, it tends to shrink further in the width direction below the glass sheet. Since the cooling roller (auxiliary cooling roller) sandwiches both ends in the width direction of the sheet glass, the contraction in the width direction after the sheet glass leaves the main cooling roller can be suppressed. In addition, since this auxiliary cooling roller is a non-driving roller to which no rotational driving force is applied, the auxiliary cooling roller rotates in a state that matches the moving speed (flowing speed) of the sheet glass. Slip is less likely to occur between them. Therefore, even if the peripheral speed of the pulling roller is increased for the purpose of efficiently producing thin-walled and large-sized plate glass, the plate-like shape does not cause an undue slip between the plate-like glass and the cooling roller. It is possible to stably cool both ends of the glass in the width direction and suppress shrinkage in the width direction. In this state, the flat glass is pulled downward and solidifies in a state where tension is applied in the horizontal direction (width direction) and the vertical direction. It becomes possible to mold into. As the number of cooling rollers increases in the vertical direction, the effect of suppressing the shrinkage in the width direction of the sheet glass increases. However, in consideration of manufacturing conditions and costs, 2-5 ( It is appropriate to provide a cooling roller).

  In this case, it is preferable that the distance between the cooling rollers that are adjacent to each other in the plurality of cooling rollers is 300 mm or less.

  That is, among the plurality of cooling rollers, the auxiliary cooling rollers other than the uppermost main cooling roller do not require a driving means for applying a rotational driving force, and therefore, between all the cooling rollers adjacent to each other in the vertical direction. Even if the distance (distance between the central axes) is shortened to 300 mm or less as described above, a plurality of cooling rollers can be properly arranged without causing a problem in the mounting space. In this case, for example, if the distance between the uppermost main cooling roller and the auxiliary cooling roller directly below it exceeds 300 mm, there is a problem that the effect of suppressing the shrinkage of the sheet glass described above is reduced. If the distance between each other is 300 mm or less, it is possible to sufficiently suppress the shrinkage of the sheet glass. Considering these matters comprehensively, the distance between the cooling rollers can be preferably 250 mm or less, more preferably 200 mm or less.

  The ratio B / A between the peripheral speed A of the uppermost cooling roller and the peripheral speed B of the pulling roller is preferably 3.5 to 20.

  In other words, when forming sheet glass by the overflow down draw method, it is necessary to increase the peripheral speed of the pulling roller in order to efficiently produce a thin and large sheet glass. In order to properly cool the cooling roller, it is necessary to reduce the peripheral speed of the cooling roller, particularly the uppermost main cooling roller. In that case, if the difference between the peripheral speed A of the main 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 productivity. Not only is it difficult to increase the conditions, but it is also difficult to ensure that a stable movement speed of the glass sheet is secured after the glass sheet is properly cooled by the main cooling roller. 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 peripheral speed A of the main cooling roller and the peripheral speed B of the pulling roller are set to be sufficiently different from each other, specifically, the ratio B / A is set to 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.

  Further, the plurality of cooling rollers are hollow inside, and a gas or a liquid can be used as the refrigerant flowing through the hollow portion.

  According to the above forming method, the plate glass is solidified on the downstream side of the pulling roller, whereby a 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 obtained. Further, a plate glass having a warpage rate of 0.03% or less can be obtained. 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.

  Moreover, the plate glass shape | molded by the above shaping | molding method is suitable for a display substrate, and is especially suitable as a liquid crystal display substrate.

  That is, both surfaces formed by the overflow down draw method are non-polished surfaces, the thickness is 0.7 mm or less, the short side length is 1000 mm or more, the long side length is 1200 mm or more, and the warp rate is 0. When a glass sheet of less than 03% is used as a substrate for a liquid crystal display in particular, when forming a thin film electric circuit on the substrate, the exposure distance is not as designed, or between two glass plates (substrates) sandwiching the liquid crystal It is possible to solve problems such as unevenness in the gap and display performance being impaired.

  As described above, according to the present invention, in order to efficiently produce a thin and large plate glass, even if the peripheral speed of the pulling roller is increased, an inappropriate slip between the plate glass and the cooling roller. In addition to being able to stably cool both ends in the width direction of the sheet glass without causing any shrinkage and to suppress shrinkage in the width direction, the sheet glass is pulled downward in this state. Since it is solidified in a state where tension is applied in the lateral direction (width direction) and the longitudinal direction, it is possible to easily form a thin, large and small warped plate glass.

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

  FIG. 1 is a schematic side view showing an implementation status of a method for forming a sheet glass, and FIG. 2 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. 1 and 2. The basic configuration of the molding apparatus 1 is that a molded body 2 having a wedge-shaped longitudinal cross-section and an overflow groove 2a formed at the top, and a molten glass Y overflowing from the top of the molded body 2 is formed into a sheet glass G. And the upper main cooling roller 4 and the lower auxiliary cooling roller 5 arranged in the middle of the glass forming path from the lower end 2b of the molded body 2 to the pulling roller 3. Each of these components 2, 3, 4, 5 is surrounded by a furnace wall 6 made of refractory bricks. Further, the glass (molten glass) flowing down the side surface 2c of the molded body 2 can be zone-heated in the vertical and horizontal directions around the side surface 2c of the molded body 2, in this embodiment, on the inner surface of the side wall portion of the furnace wall 6. A plurality of heaters 7 are respectively disposed on both sides of the molded body 2.

  The pulling rollers 3 sandwich only both ends in the width direction of the plate glass G, and a total of four pulling rollers 3 are provided at each end. The two pulling rollers 3 existing on the front side of the glass sheet G are connected by a shaft member 3a so as to be integrally rotatable, and the two pulling rollers 3 existing on the back side are also connected by a shaft member 3a. These pulling rollers 3 are provided with a rotational driving force. Further, the main cooling roller 4 also sandwiches both ends in the width direction of the plate glass G, and a total of four pieces are provided at each end portion, but there are two on the front side of the plate glass G. The main cooling rollers 4 are separated so that they can rotate independently, and the two main cooling rollers 4 on the back side of the main cooling rollers 4 are also separated so that they can rotate independently (auxiliary The same applies to the cooling roller 5). The main cooling roller 4 is a driving roller to which a rotational driving force is applied, whereas the auxiliary cooling roller 5 is a non-driving roller that rotates idly without being applied with a rotational driving force.

  The pulling roller 3, the main cooling roller 4, and the auxiliary cooling roller 5 are made of stainless steel, heat resistant steel, ceramics, or the like. Further, these rollers 4 and 5 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.

The main cooling roller 4 is immediately after the molten glass Y flows down from the top of the molded body 2 along both side surfaces 2c and is fused at the lower end 2b of the molded body 2 to form a single plate. It arrange | positions in the position which can clamp and cool the plate glass G of this. More specifically, the main cooling roller 4 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, at both ends in the width direction of the glass sheet G. 10 ^6.0 to 10 ^7.0 dPa · s), the both end portions are held in a sandwiched position. And in order to satisfy | fill such conditions, the distance a from the lower end part 2b of the molded object 2 to the central axis of the main cooling roller 4 is set to 30-200 mm, More preferably, it is 30-100 mm. In this case, the distance b between the main cooling roller 4 and the auxiliary cooling roller 5, that is, the distance b between the central axis of the main cooling roller 4 and the central axis of the auxiliary cooling roller 5, is 300 mm or less, preferably 250 mm or less. It is preferably set to 200 mm or less, and in any case, the lower limit is preferably 50 mm.

  The ratio between the peripheral speed of the main cooling roller 4 and the peripheral speed of the pulling roller 3 is set to 1: 3.5 to 1:20, more preferably 1: 4 to 1:15. In addition, the peripheral speed of the auxiliary cooling roller 5 is provided at a position that is less than 80% of the peripheral speed of the pulling roller 3 within a range equal to or higher than the peripheral speed of the main cooling roller 4. This is because when the peripheral speed of the auxiliary cooling roller 5 exceeds 80% of the peripheral speed of the pulling roller 3, the cooling action on the sheet glass G is remarkably reduced, and it is difficult to efficiently suppress the shrinkage in the width direction. It comes from that. From such a viewpoint, it is more preferable that the peripheral speed of the auxiliary cooling roller 5 is provided at a position that is less than 70% of the peripheral speed of the pulling roller 3.

  According to the molding apparatus 1 having the above-described configuration, the molten glass Y that is supplied to the molded body 2 and flows down from the top along the side surface 2 c is adjusted in viscosity by the heater 7, while the viscosity of the molded body 2 is adjusted. The sheet is fused at the lower end 2b to form a single sheet, and the sheet glass G is sandwiched between the pulling rollers 3 and drawn downward. In the initial stage where the pulling by the pulling roller 3 is performed, the main cooling roller 4 sandwiches both ends in the width direction of the sheet glass G that is still in a state of being easily softened and deformed immediately after leaving the molded body 2. By this clamping, contraction in the width direction of the glass sheet G at the position where the main cooling roller 4 is disposed is suppressed. Further, even after the glass sheet G is sandwiched by the main cooling roller 4 and cooled, if it is assumed that the auxiliary cooling roller 5 does not exist in order to further shrink in the width direction below, As shown by the chain line (reference numeral X) in FIG. 2, the sheet glass G shrinks in the width direction, and it becomes impossible to finally obtain a wide sheet glass. However, the auxiliary cooling roller 5 is used as in this embodiment. If it arrange | positions, the shrinkage | contraction of the width direction of the sheet glass G can be suppressed appropriately. Considering this, the auxiliary cooling roller 5 may be arranged in a plurality of stages (for example, 2 to 4 stages) between the uppermost main cooling roller 4 and the lowermost pulling roller 3. preferable.

  On the other hand, the main cooling roller 4 is in contact with both end portions in the width direction of the plate glass G, and appropriately cools the periphery of the contact portion, but the viscosity of the contact portion with the main cooling roller 4 in the plate glass G is: Since it is moderately low as described above, even if the peripheral speed of the pulling roller 3 is increased in order to increase productivity, slip is unlikely to occur between the glass sheet G and the main cooling roller 4. Moreover, since the distance from the lower end 2b of the molded body 2 to the central axis of the main cooling roller 4 is appropriately shortened as described above, the viscosity of the contact portion of the sheet glass G with the main cooling roller 4 is low. Can be effectively reduced. Further, since the peripheral speed of the pulling roller 3 is appropriately increased as described above compared to the peripheral speed of the main cooling roller 4, the productivity of the sheet glass G is prevented from being hindered. Can be greatly increased.

  In this way, while the sheet glass G is being drawn downward, both ends in the width direction of the sheet glass G are also sandwiched by the auxiliary cooling roller 5 to perform auxiliary cooling. Since the roller 5 rotates in accordance with the moving speed (flowing speed) of the sheet glass G, slip is unlikely to occur between the auxiliary cooling roller 5 and the sheet glass G. For this reason, even if the peripheral speed of the pulling roller 3 is increased for the purpose of efficiently producing a thin and large plate glass, no undue slip occurs between the plate glass G and the cooling rollers 4 and 5, It is possible to accurately suppress shrinkage in the width direction while stably cooling both ends in the width direction of the glass sheet G. Moreover, since the glass sheet G is pulled downward in such a state and solidifies in a state where tension is applied in the horizontal direction and the vertical direction, it is easy to form a thin glass sheet having a large size and a low warpage rate. It becomes possible to mold.

  According to the above forming method, even when a thin and large plate glass is manufactured, a plate glass with extremely small warpage can be formed. FIG. 3 is a schematic cross-sectional view exaggeratingly showing the plate glass finally obtained by using the above-described forming method. As shown in the figure, the glass plate 8 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 8 in the direction along the long side (the amount of warpage). ) The warp ratio {(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 8 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 8 is placed on the upper surface J of the precision surface plate with the surface facing upward. And the highest value among the four warpage rates of the long side and the short side when the plate glass 8 is placed on the upper surface J of the precision surface plate with the surface facing downward. This means that a large warpage ratio is 0.03% or less (the same applies to “0.02% or less” and “0.01% or less” below).

  In this case, the warpage rate of the plate glass 8 can be 0.02% or less, and further 0.01% or less. Further, by increasing the effective width of the plate glass 8, both the short side length L1 and the long side length L2 can be 1500 mm or more, and further 2000 mm or more. Furthermore, the thickness t of the plate glass 8 can be 0.65 mm or less, and further 0.60 mm or less. However, if the thickness t of the plate glass 8 is too thin, the strength is remarkably lowered and the formability is lowered. Therefore, the thickness t is preferably 0.03 mm or more, and more preferably at least 0.1 mm or more.

The plate glass 8 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 preferably ^5.8 dPa · s or more and excellent in chemical resistance (buffered hydrofluoric acid resistance and hydrochloric acid resistance). The plate glass 8 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.

Further, the composition of the plate glass 8 is, by mass%, SiO ₂ 55 to 70%, Al ₂ O ₃ 12 to 22%, B ₂ O _{3 3 to} 15%, alkaline earth metal oxide 2 to 20%. 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 8 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 8 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.

As Example 1 of the present invention, by using an apparatus having the same basic configuration as that of the molding apparatus 1 shown in FIGS. 1 and 2, in terms of mass%, SiO ₂ 60%, Al ₂ O ₃ 15%, B ₂ O ₃ A plate glass (OA-10 manufactured by Nippon Electric Glass Co., Ltd.) having a composition of 10%, CaO 6%, SrO 6%, BaO 2%, and refining agent 1% was molded. The length in the width direction of the molded body 2 in this apparatus is 2500 mm, the distance a from the lower end 2b of the molded body 2 to the central axis of the main cooling roller 4 is 100 mm, and the distance between the main cooling roller 4 and the auxiliary cooling roller 5 is The distance b is 200 mm. The refrigerant of the main cooling roller 4 and the auxiliary cooling roller 5 is air. In this molding, the heater 7 heats the molten glass Y flowing down along the both side surfaces 2c of the molded body 2 and the sheet glass G between the lower end 2b of the molded body 2 and the main cooling roller 4, 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 main cooling rollers 4. The peripheral speed of the pulling roller 3 was 200 cm / min, the peripheral speed of the main cooling roller 4 was 40 cm / min, and the peripheral speed of the auxiliary cooling roller 5 was 140 cm / min.

The plate glass formed under such conditions has a plate width of 2200 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 1900 mm. That was all. The plate glass was cut to have a short side of 1870 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 Example 2 of the present invention, all the above except that the peripheral speed of the tension roller 3 was 220 cm / min, the peripheral speed of the main cooling roller 4 was 33 cm / min, and the peripheral speed of the auxiliary cooling roller 5 was 155 cm / min. A plate glass was produced in the same manner as in Example 1.

  The plate glass thus obtained has a plate width of 2250 mm, a thickness in the center in the width direction of 0.63 mm, and an effective width within a range of 0.63 mm ± 0.05 mm is 1950 mm or more. It was. When this flat glass was cut to have a short side of 1950 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. .

  As Example 3 of the present invention, the length in the width direction of the compact 2 is 2000 mm, the peripheral speed of the pulling roller 3 is 500 cm / min, the peripheral speed of the main cooling roller 4 is 40 cm / min, and the peripheral speed of the auxiliary cooling roller 5 A plate glass was produced in the same manner as in Example 1 except that the thickness was 300 cm / min.

  The plate glass thus obtained 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 the range of 0.2 mm ± 0.05 mm is 1200 mm or more. there were. 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.

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

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molding apparatus 2 Molded body 2b Lower end 2c of molded body Side surface 3 of molded body 3 Pulling roller 4 Cooling roller 5 Auxiliary cooling roller 7 Heater 8 Sheet glass Y Molten glass G Sheet glass a Center of cooling roller from lower end of molded body Distance to shaft b Distance between multiple cooling rollers

Claims (8)

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 molding method of the plate glass that is pulled out downward,
A plurality of cooling rollers are provided in the vertical direction between the molded body and the pulling rollers to cool both ends of the sheet glass in the width direction, and a rotational driving force is applied only to the uppermost cooling roller. A method for forming a glass sheet, comprising:   The method for forming a sheet glass according to claim 1, wherein a distance between cooling rollers adjacent to each other in the upper and lower sides of the plurality of cooling rollers is 300 mm or less.   3. The sheet glass molding according to claim 1, wherein a ratio B / A between a peripheral speed A of the uppermost cooling roller and a peripheral speed B of the pulling roller is set to 3.5 to 20. 5. Method.   The method for forming a plate glass according to any one of claims 1 to 3, wherein the plurality of cooling rollers are hollow inside, and the refrigerant flowing through the hollow portion is a gas.   The method for forming a sheet glass according to any one of claims 1 to 4, 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 method for forming a plate glass according to any one of claims 1 to 5, wherein a warp rate of the plate glass solidified downstream of the pulling roller is 0.03% or less.   The glass sheet forming method according to any one of claims 1 to 6, wherein a glass sheet used as a display substrate is formed.   The method for forming a glass sheet according to claim 7, wherein the display substrate is a liquid crystal display substrate.

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