JP2008195602A - Method for manufacturing tempered glass substrate and tempered glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a tempered glass substrate, by which the treating time can be shortened and the productivity can be improved when cover glass used for a solid-state imaging device is subjected to ion exchange; and to provide the tempered glass substrate manufactured by the method. <P>SOLUTION: The tempered glass substrate is manufactured through: a process for preparing a raw material so that glass containing alkali metal oxides and having a coefficient of thermal expansion within a temperature range of 30-380°C of 30-100×10<SP>-7</SP>/°C is obtained; a process for melting the prepared raw material in a melting vessel and forming the resulting melt into a plate form by an overflow-down-draw method; and a process for forming a compressive stress layer in the surface of the formed plate-like glass by subjecting the plate-like glass to ion exchange. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention particularly relates to a tempered glass substrate suitable as a substrate used for a solid-state imaging device, a mobile phone, a digital camera, a PDA (portable terminal), a solar cell, a touch panel display, and the like, and a method for manufacturing the same.

  In recent years, devices such as mobile phones, digital cameras, PDAs, and touch panel displays have been widely used, and glass substrates are used for these devices. For example, in a solid-state imaging device mounted on a mobile phone, a solid-state imaging device such as a CCD or CMOS is housed in a ceramic package such as alumina and hermetically sealed with a glass substrate (cover glass) in order to guarantee stabilization of the device. It has the structure. In other words, since the solid-state imaging device needs to take an optical signal into the element, a cover glass as a window glass is always sealed to the package using an ultraviolet curable resin or the like. Therefore, the cover glass is required to have a thermal expansion coefficient approximate to that of the sealing resin and peripheral members so that cracking, warping, distortion, and the like do not occur after sealing with the package.

  In addition, the light transmitted through the cover glass of the solid-state imaging device needs to reach the solid-state imaging element without distortion. For this reason, this type of cover glass is also required to have excellent meltability and moldability and to be free from defects such as heterogeneous parts called striae, bubbles, blisters, dirt, and devitrified substances. It is also required to be excellent in weather resistance and water resistance so that the surface does not deteriorate by use over a wide range.

Under such circumstances, a glass substrate made of borosilicate glass that satisfies the above requirements is mainly used as the cover glass of the solid-state imaging device. (Patent Documents 1 and 2)
In CCD solid-state image sensors, when alpha rays generated from peripheral materials such as packages, sealing materials, and cover glasses are incident on the elements, holes and electron pairs are induced by the energy of the alpha rays. In particular, a so-called soft error that causes bright spots and white spots in the image occurs. Therefore, at present, a glass substrate made of borosilicate glass with a small amount of α-ray emission is mainly used as a cover glass of a CCD. (Patent Documents 3 and 4)
JP 62-65954 A JP-A-1-320236 JP-A-5-279074 Japanese Patent Application Laid-Open No. 6-121539

  By the way, the cover glass used for a digital camera, a solar battery, and the like, including a cover glass for a solid-state imaging device of a mobile phone, has been made thinner, and currently, a cover glass having a thickness of 0.5 mm or less has become mainstream. It's getting on. Therefore, when producing a cover glass for a solid-state imaging device, first, molten glass is cast and formed, and after the obtained glass molded body is cut into a plate shape, the surface (both sides) is polished to obtain a predetermined thickness. A method for producing a cover glass is employed.

  However, as the thickness of the cover glass is reduced, the strength of the cover glass is reduced, and the cover glass is often damaged in the manufacturing process and the device assembly process.

  Attempts have been made to reinforce the cover glass under such circumstances. Conventionally, an ion exchange method is widely known as a method for strengthening glass. However, when the ion exchange of the cover glass for a solid-state imaging device takes time, the process takes time. Therefore, when a large amount of glass is ion exchanged, there is a problem that the productivity is easily lowered.

  An object of the present invention is to provide a tempered glass substrate capable of improving productivity because the processing time can be shortened when ion-exchanging a cover glass used in a solid-state imaging device, and a manufacturing method thereof. To do.

The manufacturing method of the tempered glass substrate of this invention prepares a raw material so that it may become a glass containing an alkali metal oxide and having a thermal expansion coefficient of 30 to 100 × 10 ⁻⁷ / ° C. in a temperature range of 30 to 380 ° C. A step of melting the raw material in a melting vessel and then forming it into a plate shape by an overflow downdraw method, and forming a compression stress layer on the surface of the formed glass plate by ion exchange. It is characterized by that.

  The present inventor formed a plate by the overflow down draw method, and did not perform polishing on the surface of the plate glass, and when the ion exchange treatment was performed in a so-called non-polished surface state, the surface was polished as before. It has been found that the ion exchange time can be shortened as compared with plate glass.

  It is speculated that the reason why the ion exchange time can be shortened by forming the glass by the overflow down draw method and subjecting the unpolished plate-like glass to the ion exchange time is as follows.

  In the overflow down draw method, as shown in FIG. 1, the molten glass 12 is poured into the recess of the bowl-shaped refractory 11, and the molten glass 12 overflowing from both sides of the bowl-shaped refractory 11 is In this method, the sheet glass 13 is manufactured by drawing downward while being merged. According to such a method, since the surfaces (both sides) to be the surface of the glass substrate are not in contact with the bowl-shaped refractory and are molded in a free surface state, the glass substrate is excellent in surface quality while being unpolished. Can be manufactured. What is necessary is just to determine suitably the structure and material of a bowl-like refractory according to the dimension and surface accuracy of the glass substrate to obtain. Further, the method of performing the downward stretching molding may be appropriately determined according to the glass substrate. For example, a heat-resistant roll having a width dimension larger than the width dimension of the glass substrate may be stretched by contacting the sheet glass and rotating, or a plurality of pairs of heat-resistant rolls may be used. You may employ | adopt the method of extending | stretch-molding by making it contact the both ends vicinity of plate glass, and rotating.

When the alkali-containing borosilicate glass is formed by the overflow downdraw method, when the free surface of the glass melt is obtained, the alkali component in the glass is volatilized by the heat from the surrounding heat source, and the silica component is formed on the surface. A rich silica-rich layer is formed. As a result, a layer (silica-rich layer) having a high SiO ₂ component of about 20 nm is formed on the surface of the molded glass substrate. Since ion exchange is performed by the concentration difference between the alkali component in the glass and the alkali component in the molten salt, when a silica-rich layer is formed on the surface of the glass substrate, the alkali component in the molten salt is converted to silica. It becomes easy to penetrate into the glass through the rich layer. As a result, the ion exchange is promoted and the processing time is shortened as compared with a glass substrate having no silica-rich layer.

  Moreover, the manufacturing method of the tempered glass board | substrate of this invention prepares a raw material so that the liquidus temperature of glass may be 1100 degrees C or less.

The method of manufacturing a tempered glass substrate of the present invention is characterized by preparing a raw material as the liquidus viscosity of the glass is 10 ^4.0 dPa · s or more.

Moreover, the manufacturing method of the tempered glass board | substrate of this invention prepares a raw material so that it may become the glass whose alpha ray emission amount is 10000x10 < ^-4 > C / cm < ² > / h or less.

The method of manufacturing a tempered glass substrate of the present invention, in mass%, characterized by preparing a raw material Na ₂ O to be 1% or more of the glass.

  Moreover, the manufacturing method of the tempered glass board | substrate of this invention prepares a raw material so that it may become a glass of SrO + BaO 0 to 3% by the mass%.

The method of manufacturing a tempered glass substrate of the present invention, in _{mass%, SiO 2 50~80%, Al} 2 O 3 2~20%, B 2 O 3 0~15%, Na 2 O 1~20%, SrO + BaO A raw material is prepared so that it may become glass containing a composition of 0 to 3%.

The method of manufacturing a tempered glass substrate of the present invention, in _{mass%, SiO 2 50~80%, Al} 2 O 3 2~20%, B 2 O 3 0~15%, Na 2 O 1~20%, Li _{2 O 0~10%, K 2 O} 0~10%, MgO + CaO + SrO + BaO 0~5%, SrO + BaO 0~3%, containing a composition of _{ZrO 2 + TiO 2 0~5%,} (Li 2 O + K 2 O) / Na _The raw material is prepared so as to be a glass having a ₂ O ratio of 0 to 0.5.

  Moreover, the manufacturing method of the tempered glass board | substrate of this invention is ion-exchanged by being immersed in 380-600 degreeC molten salt for 1 to 30 hours.

  The method for producing a tempered glass substrate of the present invention is characterized in that the compressive stress of the compressive stress layer formed on the surface of the sheet glass is 100 MPa or more and the thickness of the compressive stress value is 1 μm or more.

  Moreover, the manufacturing method of the tempered glass board | substrate of this invention is manufactured by one of said methods, It is characterized by the above-mentioned.

Further, the tempered glass substrate of the present invention, in _{mass%, SiO 2 50~80%, Al} 2 O 3 2~20%, B 2 O 3 0~15%, Na 2 O 1~20%, Li 2 O 0 10%, K ₂ O 0-10%, MgO + CaO + SrO + BaO 0-5%, SrO + BaO 0-3%, ZrO ₂ + TiO ₂ 0-5% composition, (Li ₂ O + K ₂ O) / Na ₂ O It consists of glass with a ratio of 0-0.5.

  The tempered glass substrate of the present invention is characterized in that a compressive stress layer is formed on the surface.

  The tempered glass substrate of the present invention is characterized in that the compressive stress of the compressive stress layer is 100 MPa or more and the thickness is 1 μm or more.

  The tempered glass substrate of the present invention is characterized in that the surface is an unpolished surface and the surface roughness (Ra) is 10 mm or less.

  According to the production method of the present invention, after forming the plate glass by the overflow downdraw method, the ion exchange treatment is performed. Therefore, compared to the plate glass whose surface is polished as in the past, the alkali component during the ion exchange is reduced. The exchange is easily promoted, and a tempered glass substrate having a desired strength can be obtained in a short time.

  For this reason, the tempered glass substrate obtained by the production method of the present invention is suitable for a touch panel display, a cover glass for a solar cell, a cover glass for a mobile phone, etc., as well as a cover glass for a thin and easily damaged solid-state imaging device.

In the present invention, first, a raw material is prepared so as to be a glass containing an alkali metal oxide and having a thermal expansion coefficient of 30 to 100 × 10 ⁻⁷ / ° C. in a temperature range of 30 to 380 ° C. When an alkali metal oxide is contained in the glass, ion exchange can be performed in a later step. Moreover, if the thermal expansion coefficient of glass is the said range, it will be easy to match with the thermal expansion coefficient of peripheral materials, such as a metal and an organic type adhesive agent, and peeling of a peripheral material can be prevented. The thermal expansion coefficient of glass is preferably 50 to 100 × 10 ⁻⁷ / ° C., 60 to 80 × 10 ⁻⁷ / ° C., 60 to 75 × 10 ⁻⁷ / ° C., or 60 to 70 × 10 ⁻⁷ / ° C.

  Next, the glass raw material is put in a melting container, melted at a predetermined temperature (for example, 1500 to 1600 ° C.), and then homogenized by clarification. As the melting container, a refractory material such as alumina, zirconia, or silica or a heat-resistant container made of platinum may be used.

  Next, the molten and homogenized glass is formed into a plate shape by an overflow down draw method. However, since the silica-rich layer formed on the surface is removed when the surface of the formed plate glass is polished, the polishing should not be performed. Further, polishing the surface of the glass substrate is not preferable because scratches are generated. In other words, the theoretical strength of glass is inherently very high, but breakage often occurs even at a stress much lower than the theoretical strength. This is because a small defect called Griffith flow occurs on the surface of the glass substrate in a process after molding the glass, for example, a polishing process. Therefore, if the surface of the glass substrate is not polished, the mechanical strength inherent to the glass substrate is not impaired, and breakage can be suppressed. The presence or absence and amount of scratches on the glass substrate can be grasped by measuring the surface roughness. Therefore, the smaller the surface roughness of the glass substrate, the shallower and fewer scratches. The surface roughness (Ra) of the glass substrate is desirably 10 mm or less, 8 mm or less, 5 mm or less, 3 mm or less, 2 mm or less. Further, by omitting the glass substrate polishing step, it is possible to prevent the radioisotope contained in the polishing agent from adhering to the surface of the glass substrate, and to greatly reduce the production cost.

Next, ion exchange is performed on the formed sheet glass. In this ion exchange, the glass substrate may be immersed in the KNO ₃ molten salt. As a result, K ions in the molten salt are exchanged for Na ions and Li ions in the glass substrate, and the mechanical strength of the glass substrate is improved. The ion exchange conditions are preferably immersed in a molten salt at 380 to 600 ° C. for 1 to 30 hours. Note that the longer the ion exchange time, the greater the thickness of the compressive stress layer on the glass surface. However, exceeding 30 hours is not preferable because productivity and compressive stress are reduced. The ion exchange time and temperature may be appropriately determined according to the strength required of the glass. For example, in the case of a cover glass for a solid-state imaging device for a mobile phone, the ion exchange time is within 3 hours. It is also possible to obtain the desired strength.

  The compressive stress of the surface stress layer formed on the glass substrate by ion exchange is preferably 100 MPa or more. Since the mechanical strength of the glass substrate increases as the compressive stress increases, it is preferably 300 MPa or more, 400 MPa or more, 500 MPa or more, 600 MPa or more, or 700 MPa or more. However, when an extremely large compressive stress is formed on the surface of the glass substrate, microcracks are generated on the surface and the strength is lowered. Therefore, the compressive stress of the compressive stress layer is desirably 2000 MPa or less.

  The thickness of the compressive stress layer is preferably 1 μm or more. The greater the thickness of the compressive stress layer, the more difficult it is to break even if the surface of the glass substrate is scratched. Therefore, the thickness of the compressive stress layer is desirably 3 μm or more, 5 μm or more, 10 μm or more, or 15 μm or more. However, if the thickness of the compressive stress layer becomes extremely large, it becomes difficult to cut the glass substrate. Therefore, the thickness is preferably 500 μm or less.

In the present invention, when the raw material is prepared such that the liquid phase temperature is 1100 ° C. or less and the liquid phase viscosity (viscosity corresponding to the liquid phase temperature) is 10 ^4.0 dPa · s or more, the glass is obtained by the overflow down draw method. It is preferable because devitrification hardly occurs during molding. The liquidus temperature is more preferably 1050 ° C. or less, and most preferably 1000 ° C. or less. The liquid phase viscosity is more preferably 10 ^4.3 dPa · s or more, and most preferably 10 ^4.5 dPa · s or more, 10 ^5.0 dPa · s or more, and 10 ^5.3 dPa · s or more.

Moreover, in this invention, it is preferable to prepare a raw material so that it may become the glass whose alpha ray emission amount is 10000 * 10 < ^-4 > C / cm < ² > / h or less. In order to reduce the amount of α-ray emission, a high-purity material with a low content of radioactive isotopes and a low amount of α-ray emission is used as the glass material. Furthermore, it is preferable to produce the glass so that no radioactive isotopes are mixed into the glass in the glass melting and clarification step. The α-ray emission amount is preferably 1000 × 10 ⁻⁴ C / cm ² or less, more preferably 100 × 10 ⁻⁴ C / cm ² or less, further preferably 50 × 10 ⁻⁴ C / cm ² or less, and 30 × 10 ^−. Most preferably ⁴ C / cm ² or less.

Moreover, since the tempered glass substrate of this invention can aim at weight reduction, so that the density of glass is low, it is preferable. Specifically, it is preferable that the density of the glass is less than 2.6 g / cm ^3, more preferably 2.5 g / cm ³ or less, and most preferably 2.45 g / cm ³ or less.

  Further, the tempered glass substrate of the present invention has a smaller deflection as the Young's modulus of the glass is higher. Therefore, for example, when used as a glass substrate of a device such as a touch panel display, when the display is pressed with a pen or the like, it is possible to solve the problem of causing a display defect by pressing the liquid crystal element inside the device. Specifically, the Young's modulus of the glass is preferably 70 GPa or more, more preferably 71 GPa or more, and most preferably 73 GPa or more.

In the tempered glass substrate of the present invention, the lower the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s of the glass, the easier the melting of the glass improves the bubble quality in the glass and reduces the burden on the glass production equipment. It is possible to improve productivity. Specifically, the temperature corresponding to the high temperature viscosity of 10 ^2.5 dPa · s of the glass is preferably 1600 ° C. or less, more preferably 1500 ° C. or less, further preferably 1450 ° C. or less, and 1400 ° C. Most preferably:

In the present invention, in _{mass%, SiO 2 50~80%, Al} 2 O 3 2~20%, B 2 O 3 0~15%, Na 2 O 1~20%, the composition of SrO + BaO 0 to 3% it is preferable to prepare a raw material so that the glass containing, by _{mass%, SiO 2 50~80%, Al} 2 O 3 2~20%, B 2 O 3 0~15%, Na 2 O 1~20 %, Li ₂ O 0-10%, K ₂ O 0-10%, MgO + CaO + SrO + BaO 0-5%, SrO + BaO 0-3%, ZrO ₂ + TiO ₂ 0-5%, and (Li ₂ O + K ₂ O It is more preferable to prepare the raw material so that the glass has a ratio of 0) / Na ₂ O of 0 to 0.5. Furthermore in _{mass%, SiO 2 50~80%, Al} 2 O 3 3~15%, B 2 O 3 1~14%, Na 2 O 5~15%, Li 2 O 0~5%, K 2 O 0 ~10%, MgO + CaO + SrO + BaO 0~5%, SrO + BaO 0~1%, it is more preferable to prepare a raw material so that the glass containing the composition of ZrO ₂ + TiO ₂ 0~5%, by mass%, SiO ₂ 50 _{~80%, Al 2 O 3 3~15} %, B 2 O 3 1~14%, Na 2 O 7.5~15%, Li 2 O 0~5%, K 2 O 0~5%, MgO + CaO + SrO + BaO 0 The raw material contains a composition of ˜5%, SrO + BaO 0 to 1%, ZrO ₂ + TiO ₂ 0 to 5%, and a ratio of (Li ₂ O + K ₂ O) / Na ₂ O of 0 to 0.5 It is more preferable to prepare In _{mass%, SiO 2 50~80%, Al} 2 O 3 3~9%, B 2 O 3 8~14%, Na 2 O 7.5~13%, Li 2 O 0~5%, K 2 O 0-5%, MgO + CaO + SrO + BaO 0-3%, SrO + BaO 0-1%, ZrO ₂ + TiO ₂ 0-5%, and the ratio of (Li ₂ O + K ₂ O) / Na ₂ O is 0-0. It is most preferable to prepare the raw material so as to be the glass No. 3.

  The reason for limiting the glass composition in this way is as follows.

SiO ₂ is a component that forms a network of glass, and its content is 50 to 80%. If the amount of SiO ₂ is too large, the meltability and formability of the glass will be reduced, or the thermal expansion coefficient will be too small to match the thermal expansion coefficient of the surrounding materials. On the other hand, if SiO ₂ becomes too small, the thermal expansion coefficient of the glass becomes too large and it becomes difficult to match the thermal expansion coefficient of the surrounding materials. The content of SiO ₂ is preferably 55 to 75%, more preferably 60 to 75%.

Al ₂ O ₃ is a component that enhances the ion exchange performance of glass. In addition, when Al ₂ O ₃ is contained, the strain point of the glass is increased, heat resistance is improved, and the Young's modulus is increased. Therefore, when heating is performed during the manufacturing process or during use, it is desirable to suppress bending of the glass substrate. In some cases, it is an effective ingredient. Therefore, the content of Al ₂ O ₃ is 2 to 20%. When the amount of Al ₂ O ₃ is too large, devitrified substances are likely to be precipitated in the glass, or the thermal expansion coefficient of the glass is too small to match the thermal expansion coefficient of the surrounding materials. Furthermore, the amount of α-ray emission tends to increase as the amount of Al ₂ O ₃ increases. On the other hand, if Al ₂ O ₃ is too small, ion exchange may be hindered. The preferable range of Al ₂ O ₃ is 18% or less, 16% or less, 15% or less, 13% or less, 10% or less, 9% or less, and the lower limit is 3% or more and 4% or more. .

B ₂ O _{3 is} also a component that enhances the ion exchange performance of the glass. Further, when B ₂ O ₃ is contained, the liquidus temperature of the glass is lowered, so that devitrification when forming by the overflow down draw method can be easily suppressed. Further, when B ₂ O ₃ is contained, the high-temperature viscosity is lowered, so that melting is facilitated, and the density of the glass is lowered, so that weight reduction can be achieved. However, too much B ₂ O ₃ is not preferable because, after ion exchange, there is a possibility that discoloration called burnt may occur on the glass surface or the weather resistance and water resistance of the glass may be lowered. Therefore, the content of B ₂ O ₃ is 0 to 15%, 0.1 to 15%, preferably 1 to 14%, more preferably 3 to 14%, and further preferably 8 to 14%.

Na ₂ O is an ion exchange component. Moreover, it is a component which lowers the high temperature viscosity of glass and improves meltability and moldability, and also improves the devitrification resistance of glass, and should be contained at 1% or more. If the amount of Na ₂ O is too large, the thermal expansion coefficient of the glass becomes too large and it becomes difficult to match the thermal expansion coefficient of the surrounding materials. Moreover, the balance of the glass composition is deteriorated, and the devitrification resistance of the glass tends to be deteriorated. On the other hand, if the amount of Na ₂ O is too small, it is difficult to obtain the above action. The content of Na ₂ O is 1 to 20%, preferably 3 to 18%, more preferably 5 to 15%, further preferably 7.5 to 15%, and most preferably 7.5 to 13%.

Li ₂ O is also an ion exchange component. Moreover, while reducing the high temperature viscosity of glass and improving a meltability and a moldability, it is a component which improves the Young's modulus of glass, The content is 0 to 10%. If the amount of Li ₂ O increases too much, the liquid phase viscosity of the glass decreases and the glass tends to devitrify, and the thermal expansion coefficient of the glass becomes too large to match the thermal expansion coefficient of the surrounding materials. . Furthermore, the amount of alpha rays emitted from the glass increases. The content of Li ₂ O is preferably 0 to 5%, more preferably 0 to 1%.

K ₂ O is a component that promotes ion exchange and lowers the high temperature viscosity of glass to improve meltability and moldability. K ₂ O is also a component that improves devitrification resistance, and its content is 0 to 10%. If the amount of K ₂ O is too large, the thermal expansion coefficient of the glass becomes too large and it becomes difficult to match the thermal expansion coefficient of the surrounding materials. Moreover, the balance of the whole glass composition will worsen, and the devitrification resistance of glass tends to fall on the contrary. Furthermore, the amount of alpha rays emitted from the glass increases. The content of K ₂ O is preferably 0 to 5%, more preferably 0 to 2%, and still more preferably 0.1 to 2%.

When the ratio of (Li ₂ O + K ₂ O) / Na ₂ O is adjusted to 0 to 0.5 (preferably 0 to 0.4, more preferably 0 to 0.3), the viscosity and thermal expansion of the glass are increased. It is easy to reduce the amount of α-ray emission while maintaining the coefficient, devitrification, and the like within an appropriate range.

  Further, alkaline earth metal oxides (RO) of MgO, CaO, SrO and BaO are all components that lower the high temperature viscosity of the glass to increase the meltability and formability, and increase the strain point and Young's modulus. However, when the total amount exceeds 5%, the thermal expansion coefficient and density of the glass increase, and the devitrification resistance tends to decrease. In addition, the ion exchange performance is reduced and the amount of α-ray emission is increased. Therefore, RO should be 5% or less, preferably 4% or less, more preferably 3% or less, and still more preferably 1% or less.

  MgO has the above-mentioned action and is a component that has a high effect of improving ion exchange performance in RO. However, if the content is too large, the amount of α-ray emitted from the glass increases or the density increases. And the thermal expansion coefficient becomes high. Moreover, it becomes easy to devitrify glass. Therefore, MgO should be 0 to 5%, more preferably 0 to 3%, and still more preferably 0 to 1%.

  CaO also has the above-mentioned action and is a component that has a high effect of improving ion exchange performance in RO. However, if its content is excessive, the amount of α-ray emitted from the glass increases and the density increases. And the thermal expansion coefficient becomes high. Moreover, it becomes easy to devitrify glass. Therefore, CaO should be 0 to 5%, more preferably 0 to 4%, and still more preferably 0 to 3%.

  SrO also has the above action. However, if its content is too large, the amount of α-ray emitted from the glass increases, and the density and thermal expansion coefficient increase. Moreover, it becomes easy to devitrify glass, and ion exchange performance falls. Therefore, SrO should be 0-3%, more preferably 0-1%, even more preferably 0-0.8%, most preferably 0-0.5%, preferably substantially. It is desirable not to contain. Here, “substantially no SrO” means that the content of SrO in the glass composition is 0.2% or less.

  BaO also has the above-mentioned action, but if its content is too large, the amount of α-ray emitted from the glass increases, and the density and thermal expansion coefficient increase. Moreover, it becomes easy to devitrify glass, and ion exchange performance falls. Therefore, BaO should be 0 to 3%, more preferably 0 to 2%, still more preferably 0 to 1%, and most preferably 0 to 0.5%, preferably substantially contained. It is desirable not to. Here, “substantially free of BaO” means that the content of BaO in the glass composition is 0.2% or less.

  Moreover, it is preferable to regulate the total amount of SrO and BaO from the viewpoint of improving ion exchange performance and reducing the amount of α-ray emission. Specifically, SrO + BaO should be 0 to 3%, preferably 0 to 1%, more preferably 0 to 0.5%, and still more preferably 0 to 0.2%.

ZrO ₂ is a component that improves the strain point and Young's modulus of the glass and improves the ion exchange performance. However, if the amount is too large, the amount of α-ray emitted from the glass increases and the devitrification resistance decreases. . In particular, when glass is formed by the overflow down draw method, crystals due to ZrO ₂ are precipitated at the interface of the glass with the refractory, which may reduce the productivity of the glass substrate during long-term operation. . Therefore, the content of ZrO ₂ is 0 to 5%, more preferably 0 to 3%, 0 to 1%, 0 to 0.8%, 0 to 0.5%, and 0 to 0.3%. Most preferably, it is 0 to 0.1%.

TiO ₂ is a component that enhances the ion exchange performance of the glass. However, if the amount is too large, the α-ray emission amount is increased, the devitrification resistance is lowered, and the glass is further colored, which is not preferable. Therefore, the content of TiO ₂ is 0 to 5%, more preferably 0 to 3%, 0 to 1%, 0 to 0.8%, 0 to 0.5%, and 0 to 0.3%. Most preferably, it is 0 to 0.1%.

In particular, if ZrO ₂ + TiO ₂ is restricted to 0 to 5%, it is preferable because reduction of α-ray emission and improvement of devitrification are easily achieved.

  In the present invention, other glass components can be added as long as the properties of the glass are not significantly impaired.

SO ₃ , Sb ₂ O ₃ and SnO ₂ can be used as fining agents, and one or more of these can be contained in an amount of 0 to 3%.

  ZnO has the effect of reducing the high temperature viscosity of the glass. However, if a large amount of ZnO is contained, it is not preferable because the thermal expansion coefficient of the glass is increased, devitrification resistance and ion exchange performance are decreased, and the amount of α-ray emission is increased. Therefore, the content of ZnO is 0 to 5%, preferably 0 to 3%, more preferably 0 to 1%, and most preferably 0 to 0.5%.

Rare earth oxides such as Nb ₂ O ₅ and La ₂ O ₃ are components that increase the Young's modulus of the glass. However, if the amount is too large, the amount of α-ray emission increases and the devitrification resistance decreases. Moreover, since these raw materials are expensive, production costs increase. Therefore, the rare earth oxide content is 0 to 3%, preferably 0 to 2%, more preferably 0 to 1%, and still more preferably 0 to 0.5%, and it is desirable that the rare earth oxide is not substantially contained. . Here, “substantially no rare earth oxide” means that the rare earth oxide in the glass composition is 0.1% or less.

  Note that transition metal elements such as Co and Ni should be avoided because they strongly color the glass and lower the transmittance of the glass substrate. In particular, in applications where a certain amount of light and visibility are required, such as a solid-state imaging device, a touch panel display, and a cover glass of a mobile phone, coloring of the glass must be avoided. Therefore, it is required to adjust the amount of the glass raw material and cullet used so that the transition metal element is 0.5% or less, 0.1% or less, and 0.05% or less.

  Moreover, since the tempered glass substrate of the present invention is reinforced by ion exchange, it is possible to prevent cracking even if the thickness is reduced for the purpose of reducing the weight. Specifically, the thickness can be 3.0 mm or less, 1.5 mm or less, 0.7 mm or less, 0.5 mm or less, or 0.3 mm or less. In addition, in order to suppress cracking of the glass substrate, ion exchange may be performed after chamfering or chamfering is performed after the glass substrate is cut into a predetermined dimension. In order to reduce the manufacturing cost, the glass substrate may be cut into a predetermined dimension after ion exchange.

  Hereinafter, the present invention will be described in detail based on examples.

  Table 1 shows Example glass (No. 1-4) of this invention.

  Each sample of Table 1 was produced as follows. First, a high-purity glass raw material was prepared so as to have the glass composition shown in Table 1, then placed in a platinum pot and melted at 1570 ° C. for 8 hours.

  Thereafter, the molten glass was poured onto a carbon plate and formed into a plate shape. Various properties of the plate glass thus obtained were evaluated, and the results are shown in Table 1.

As is apparent from Table 1, the glass of the example has a thermal expansion coefficient of 60 to 100 × 10 ⁻⁷ / ° C., an α-ray emission amount of 25 to 40 × 10 ⁻⁴ C / cm ² / h, and a liquidus temperature. Was 950 ° C. or lower, and the liquid phase viscosity was 10 ^4.6 or higher.

  Each characteristic in Table 1 was evaluated as follows.

  The thermal expansion coefficient is obtained by measuring an average thermal expansion coefficient in a temperature range of 30 to 380 ° C. using a dilatometer.

  The α-ray emission amount was measured using a gas flow proportional counter measuring device.

  The density was measured by the well-known Archimedes method.

  The strain point and annealing point were measured based on the method of ASTM C336.

  The softening point was measured based on the method of ASTM C338.

The temperatures corresponding to the glass viscosities of 10 ^4.0 dPa · s, 10 ^3.0 dPa · s and 10 ^2.5 dPa · s were measured by the platinum ball pulling method.

  The liquid phase temperature is obtained by crushing glass, passing through a standard sieve 30 mesh (a sieve opening of 500 μm), putting the glass powder remaining in 50 mesh (a sieve opening of 300 μm) into a platinum boat, and keeping it in a temperature gradient furnace for 24 hours. Then, the temperature at which the crystals are deposited is measured. The liquid phase viscosity is obtained by measuring the viscosity of the glass corresponding to the liquid phase temperature.

  Young's modulus was measured by a resonance method.

Next, no. The raw materials prepared so as to become 1-4 glasses are put into a melting device 14 shown in FIG. 2, melted at 1500 to 1600 ° C., then clarified with a clarification device 15, and further stirred with a stirrer 16 and a supply device 17. Then, the glass sheet was sent to the forming apparatus 18 and formed into a glass sheet using the overflow downdraw apparatus shown in FIG. 1, and then slowly cooled to prepare a glass substrate having a thickness of 0.5 mm. Next, each glass substrate was cut into a length of 35 mm and a width of 35 mm, subjected to chamfering and chamfering, and then reinforced by ion exchange. The ion exchange treatment is No. The glass substrates 1, 2, and 4 were immersed in KNO ₃ molten salt at 490 ° C. for 2 hours. The third glass substrate was immersed in KNO ₃ molten salt at 460 ° C. for 6 hours. Thereafter, the glass substrate was taken out of the molten salt and washed with water.

  For comparison, the same ion exchange treatment was performed for each sample (polished product) obtained by polishing the surface of the glass substrate subjected to the chamfering process and the chamfering process to a thickness of about 100 μm.

  These glass substrates are measured for the number of interference fringes and their spacing using a surface stress meter (FSM-60 manufactured by Toshiba Corporation), and the compression stress value formed on the surface and the thickness of the compression stress layer are calculated. The results are shown in Table 1.

  As is apparent from the table, a compressive stress higher than that of the polished product was formed on the surface of the non-polished glass substrate. From the above, it can be understood that a glass substrate formed by the overflow downdraw method and having a non-polished surface is formed with higher compressive stress by ion exchange than a glass substrate having a polished surface.

  The present invention is a method capable of manufacturing a tempered glass substrate that is thin and requires high mechanical strength. The tempered glass substrate of the present invention is suitable as a glass substrate used for a cover glass of a mobile phone, a digital camera, a PDA or the like, or a touch panel display, etc., and for other applications requiring high strength, such as window glass, magnetic It can also be used as a disk substrate, a flat panel display substrate, or the like.

It is explanatory drawing which shows the method of shape | molding sheet glass by the overflow downdraw method. It is explanatory drawing which shows the apparatus which manufactures the tempered glass substrate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Refractory material 12 Molten glass 13 Sheet glass 14 Melting apparatus 15 Clarification apparatus 16 Stirring apparatus 17 Feeding apparatus 18 Molding apparatus

Claims (15)

A step of preparing a raw material so as to be a glass containing an alkali metal oxide and having a thermal expansion coefficient of 30 to 100 × 10 ⁻⁷ / ° C. in a temperature range of 30 to 380 ° C., and melting the raw material in a melting vessel Thereafter, a method of forming a tempered glass substrate comprising a step of forming into a plate shape by an overflow downdraw method, and a step of forming a compressive stress layer on the surface of the formed plate glass by ion exchange .   The method for producing a tempered glass substrate according to claim 1, wherein the raw material is prepared so that the glass has a liquidus temperature of 1100 ° C. or lower. The method for producing a tempered glass substrate according to claim 1, wherein the raw material is prepared so as to be a glass having a liquidus viscosity of 10 ^4.0 dPa · s or more. The method for producing a tempered glass substrate according to any one of claims 1 to 3, wherein the raw material is prepared so as to be a glass having an α-ray emission amount of 10,000 × 10 ^-4 C / cm ² / h or less. . In mass%, the production method of the tempered glass substrate according to any one of claims 1 to 4, characterized in that the Na ₂ O to prepare a raw material to be 1% or more of the glass.   The method for producing a tempered glass substrate according to any one of claims 1 to 5, wherein the raw material is prepared such that SrO + BaO is 0 to 3% by mass. In mass%, the glass containing _{SiO 2 50~80%, Al 2 O} 3 2~20%, B 2 O 3 0~15%, Na 2 O 1~20%, the composition of SrO + BaO 0 to 3% The method for producing a tempered glass substrate according to claim 1, wherein the raw material is prepared as described above. By _{mass%, SiO 2 50~80%, Al} 2 O 3 2~20%, B 2 O 3 0~15%, Na 2 O 1~20%, Li 2 O 0~10%, K 2 O 0~ Glass having a composition of 10%, MgO + CaO + SrO + BaO 0-5%, SrO + BaO 0-3%, ZrO ₂ + TiO ₂ 0-5%, and a ratio of (Li ₂ O + K ₂ O) / Na ₂ O of 0-0.5 A raw material is prepared so that it becomes. The manufacturing method of the tempered glass substrate in any one of Claims 1-7 characterized by the above-mentioned.   The method for producing a tempered glass substrate according to any one of claims 1 to 8, wherein ion exchange is performed by immersing in a molten salt at 380 to 600 ° C for 1 to 30 hours.   The method for producing a tempered glass substrate according to claim 1, wherein the compressive stress of the compressive stress layer formed on the surface of the sheet glass is 100 MPa or more and the thickness is 1 μm or more.   A tempered glass substrate produced by the method according to claim 1. By _{mass%, SiO 2 50~80%, Al} 2 O 3 2~20%, B 2 O 3 0~15%, Na 2 O 1~20%, Li 2 O 0~10%, K 2 O 0~ Glass having a composition of 10%, MgO + CaO + SrO + BaO 0-5%, SrO + BaO 0-3%, ZrO ₂ + TiO ₂ 0-5%, and a ratio of (Li ₂ O + K ₂ O) / Na ₂ O of 0-0.5 A tempered glass substrate comprising:   The tempered glass substrate according to claim 12, wherein a compressive stress layer is formed on the surface.   The tempered glass substrate according to claim 13, wherein the compressive stress of the compressive stress layer is 100 MPa or more and the thickness is 1 μm or more.   The tempered glass substrate according to any one of claims 12 to 14, wherein the surface is an unpolished surface and the surface roughness (Ra) is 10 mm or less.