TWI386381B - Alkali-free glass and alkali-free glass substrate - Google Patents

Description

Alkali-free glass and alkali-free glass substrate

The present invention relates to a flat panel display substrate such as a liquid crystal display (hereinafter referred to as LCD) or an electroluminescence (EL) display, a charge coupled device (CCD) or an equal magnification type. A solid-state imaging device (such as a contact image sensor (CIS)), such as a glass cover for an image sensor, and an alkali-free glass and an alkali-free glass substrate for a substrate for a solar cell.

Electronic components such as thin-film transistor-LCD (hereinafter referred to as TFT-LCD) are thinner and consume less power, so they are car navigation systems and cameras. It has been used in various applications such as screens and televisions for personal computers in recent years.

Currently, glass is widely used as a flat panel display substrate such as an LCD or an EL display. Further, it is known that a TFT-LCD panel manufacturer fabricates a plurality of components on a glass substrate (primary panel) formed by a glass manufacturer, and then cuts and cuts each component to form a product, thereby achieving improvement in productivity and cost.

In recent years, screen sizes of displays such as screens and televisions of personal computers have tended to increase in size, and in order to perform chamfering of the above components a plurality of times, a large-sized glass substrate of 2200 × 2400 mm is required. In particular, in the display for television use, the size of the screen is required to be large, and the technique for stably manufacturing a large glass substrate is important. In addition, an amorphous silicon (a-Si) TFT-LCD (hereinafter referred to as a-Si. TFT-LCD) is generally used for television use (see Japanese Patent Laid-Open No. Hei 7-277762). .

a-Si. The glass substrate used for a TFT-LCD or the like needs to have the following characteristics.

(1) If an alkali metal oxide is contained in the glass, the alkali ions are diffused into the film-formed semiconductor material during the heat treatment, resulting in deterioration of the film properties, and therefore, the glass does not substantially contain an alkali metal oxide.

(2) It has chemical resistance, that is, it does not deteriorate due to various chemicals such as acids and bases used in the photolithography step.

(3) It does not shrink during heat treatment such as film formation or annealing. For this purpose, the glass needs to have a higher strain point (StTain Point).

Further, in consideration of meltability and formability, such a glass substrate also needs to have the following characteristics.

(4) The meltability is excellent so that a poor melting defect as a glass substrate does not occur in the glass. In particular, there are no bubble defects.

(5) The opacity-resistant character is excellent so that foreign matter generated during melting and molding does not exist in the glass.

For the following reasons, (6) a glass having a thermal expansion coefficient of 40 to 50 × 10 ^-7 / ° C is required. Since the heat treatment step is large in the manufacturing process of the TFT-LCD, the glass substrate is rapidly heated and rapidly cooled, so that the thermal shock applied to the glass substrate becomes large. Further, when the glass substrate is increased in size, not only the temperature distribution is likely to occur in the glass substrate, but also the probability of occurrence of minute scratches and cracks on the end surface is increased, and the probability of damage of the glass substrate in the heat treatment step is also increased. In order to solve this problem, it is most effective to reduce the thermal stress caused by the difference in thermal expansion coefficient, so that the smaller the thermal expansion coefficient of the glass substrate, the smaller the thermal stress generated in the heat treatment step becomes. On the other hand, when the coefficient of thermal expansion is made small, the meltability of the glass material and the formability tend to be impaired. Therefore, it is not preferable to excessively improve the expansion. Therefore, it can be said that it is necessary to control the thermal expansion coefficient of the glass substrate within an appropriate range. Further, integration of the glass substrate used in the TFT-LCD with the thermal expansion coefficient of various film materials formed on the glass substrate is also important. If the thermal expansion coefficient of the film does not match, the glass substrate may be warped, and the glass substrate may be damaged. Since the film formed on the glass substrate has various films of a low expansion oxide film such as SiNx and a high expansion metal film such as Al or Mo, it is necessary to set the thermal expansion coefficient of the glass substrate in consideration of the thermal expansion coefficient of the film. In consideration of the above aspects, the coefficient of thermal expansion of the glass is preferably 40 to 50 × 10 ^-7 /°C.

Further, for the following reasons, it is necessary to (7) the viscosity characteristic is suitable for stably producing a glass of a thin plate or a large glass substrate. In a portable device such as a mobile phone or a notebook personal computer, the weight of the device is required in consideration of convenience in carrying, and the glass substrate is required to be light in weight. In order to lighten the glass substrate, it is effective to make the glass substrate thin. At present, the standard thickness of the glass substrate for TFT-LCD is about 0.7 mm and is very thin. On the other hand, the thinner the glass substrate is, the more difficult it is to manufacture. However, in the case of glass which rapidly increases in viscosity during cooling, it is easy to form a thin-plate type glass substrate in a flat manner, which is advantageous. Especially in the case of down draw molding, the furnace distance for slow cooling is limited in equipment design, so the slow cooling time of the glass substrate is also limited, for example, from the forming temperature to the room temperature. Cool for a few minutes. Therefore, it is advantageous to form a glass which is rapidly increased in viscosity during cooling down forming.

As described above, in the LCD, in order to remove a plurality of faces of the display, a large glass substrate is required. The larger the glass substrate, the more difficult it is to manufacture. However, in the case of glass which rapidly increases in viscosity during cooling, it is advantageous in that it is easy to form a large glass substrate flatly. Especially in the case of pull-down forming, the furnace distance for slow cooling is limited in equipment design, and the slow cooling time of the glass substrate is also limited, for example, it must be cooled for several minutes from the forming temperature to room temperature. Therefore, it is more advantageous to form a glass which is rapidly increased in viscosity during cooling down forming. Further, when the glass substrate has temperature unevenness in the sheet width direction, warpage or warpage occurs in the sheet width direction, so that it is difficult to form the glass substrate flatly. In order to solve the temperature unevenness, it is important to strictly control the temperature during the formation of the glass substrate. However, in the case where the glass whose viscosity is gradually increased during cooling is a flat glass substrate, it takes a long time to cool the glass until it is cured, so that it is difficult to strictly control the temperature. In particular, glass having a width of 2000 mm or more must have a strict temperature control in the longitudinal direction, so that it becomes more difficult to manufacture a flat glass. Therefore, the industry is expected to rapidly increase the viscosity during cooling and to form a glass into a glass substrate shape.

However, since the conventional alkali-free glass has a viscosity curve in which the viscosity gradually rises during cooling, it is difficult to determine the thickness of the glass and the warpage or the curved shape in the width direction, and it is difficult to form a large-sized, thin glass substrate flatly.

Therefore, the technical object of the present invention is to obtain a glass which satisfies the above-mentioned required characteristics (1) to (5), and (6) has a thermal expansion coefficient of 40 to 50 × 10 ^-7 /° C., and (7) The viscosity characteristics are suitable for the stable manufacture of thin plates and large glass substrates, and thus are suitable for TFT-LCDs, especially a-Si. TFT-LCD.

As a result of active efforts by the present inventors, it was found that the glass composition was controlled in terms of weight percent (wt%), the content of SiO ₂ was 45 to 65%, the ratio of Al ₂ O ₃ was 12 to 17%, and B ₂ O ₃ was 7.5~15%, MgO is 0~3%, CaO is 5.5~15%, SrO is 0~5%, BaO is 5~15%, ZnO is 0~5%, MgO+CaO+SrO+BaO+ZnO is 15~23%, ZrO ₂ is 0 to 5%, TiO ₂ is 0 to 5%, and P ₂ O ₅ is in the range of 0 to 5%, substantially free of alkali metal oxide, and (CaO+BaO-MgO)/SiO by weight fraction The present invention has been made by controlling the value of ₂ to 0.25 to 0.4 and controlling the average thermal expansion coefficient in the temperature range of 30 to 380 ° C to 40 to 50 × 10 ^-7 / ° C. In the present invention, the term "substantially no alkali metal oxide" means a case where the content of the alkali metal oxide in the glass composition is 1000 ppm or less. In the present invention, the "average thermal expansion coefficient in the temperature range of 30 to 380 ° C" means a value measured using a dilatometer.

When the glass composition is controlled within the above range, viscosity characteristics suitable for pull-down forming, in particular, overflow down draw forming, can be obtained. In addition, when the glass composition is controlled within the above range, glass having excellent opacity resistance can be obtained, and overflow draw-down molding can be stably performed. Therefore, the alkali-free glass of the present invention can be said to be a glass suitable for overflow down-drawing. Further, when the glass composition is controlled within the above range, glass satisfying the above-described demand characteristics (1) to (7) can be easily obtained. Further, the present invention does not exclude a forming method other than overflow down draw forming. Even in the molding method other than the overflow down-draw molding, in the glass production step, the glass opaque resistance is improved, and the production efficiency of the glass substrate is improved. Therefore, the alkali-free glass of the present invention is undoubtedly applicable to other methods. Forming method.

When the glass composition is controlled within the above range, it is possible to obtain a glass which is rapidly increased in viscosity during cooling and which can be rapidly formed into a glass substrate shape. Therefore, since the alkali-free glass of the present invention is a glass whose viscosity is rapidly increased during cooling, it is easy to form a thin-plate type glass substrate flatly, which is advantageous. Moreover, since the alkali-free glass of the present invention is a glass whose viscosity is rapidly increased during cooling, it is easy to form a large glass substrate flatly, which is advantageous. In addition, in the down-draw molding, the furnace distance for slow cooling is limited in equipment design, and the slow cooling time of the glass substrate is also limited, for example, it must be cooled for several minutes from the forming temperature to room temperature. Therefore, it is more advantageous to use a glass which is rapidly increased in viscosity during cooling down forming.

The glass composition of the alkali-free glass of the present invention does not substantially contain an alkali metal oxide (Na ₂ O, K ₂ O, LiO ₂ ). Therefore, in the TFT manufacturing step of the present invention, there is no possibility that the alkali ions diffuse into the film-formed semiconductor material during the heat treatment to cause deterioration of the film characteristics, thereby not impairing the reliability of the TFT-LCD. .

In the alkali-free glass of the present invention, the value of (CaO+BaO-MgO)/SiO ₂ based on the weight fraction is controlled to 0.25 to 0.4. If the value of (CaO+BaO-MgO)/SiO ₂ in terms of weight fraction is controlled within the above range, the opacity resistance is not lowered, and specifically, 105.4 dPa or more can be achieved. The liquid viscosity of s, and the high temperature viscosity can be lowered, so that the viscosity characteristics suitable for pull-down forming can be obtained. In order to lower the high temperature viscosity, increase the alkaline earth metal oxide, SiO ₂ content reduction is effective, but if increasing the alkaline earth metal oxide, SiO ₂ content reduction, the strain point decreases. When the value of (CaO+BaO-MgO)/SiO ₂ by weight fraction is controlled within the above range, even if the alkaline earth metal oxide is increased and the SiO ₂ content is decreased, the strain point can be lowered without lowering the high temperature viscosity. . Moreover, the anti-opacity is not deteriorated. Therefore, if the value of (CaO+BaO-MgO)/SiO ₂ by weight fraction is controlled within the above range, the disadvantage of increasing the alkaline earth metal oxide and reducing the SiO ₂ content can be eliminated. Further, as described below, if a large amount of MgO is contained, the opacity resistance is impaired.

In the alkali-free glass of the present invention, the average thermal expansion coefficient in the temperature range of 30 to 380 ° C is controlled to 40 to 50 × 10 ^-7 / ° C. If the coefficient of thermal expansion of the glass is controlled within the above range, integration with the thermal expansion coefficient of the peripheral material (especially organic material or metal) can be achieved, thereby reducing a-Si. The probability of damage of the glass substrate in the manufacturing process of the TFT-LCD. Further, when the thermal expansion coefficient of the glass is controlled within the above range, the thermal stress due to the difference in thermal expansion can be reduced, and the probability of breakage of the glass substrate in the heat treatment step can be reduced, and as a result, the following state can be effectively avoided, that is, When the glass substrate is broken, the production efficiency of the production line is lowered, or the fine glass powder generated at the time of breakage adheres to the glass substrate, and the disconnection is poor or the pattern is defective.

Second, the alkali-free glass of the present invention is characterized in that the value of (MgO + CaO + SrO + BaO + ZnO) / SiO ₂ is 0.3 to 0.4 in terms of a weight fraction.

Third, the alkali-free glass of the present invention is characterized in that it does not substantially contain As ₂ O ₃ and the content of Sb ₂ O ₃ +SnO ₂ +Cl is 0 to 3% in terms of wt% in terms of the above oxide. In the present invention, the phrase "substantially does not contain As ₂ O ₃ " means that the content of As ₂ O ₃ is 1000 ppm or less.

Fourth, the alkali-free glass of the present invention is characterized in that it does not substantially contain As ₂ O ₃ or Sb ₂ O ₃ , and the content of SbO ₂ is 0 to 1% in terms of wt% in terms of the above oxide. In the present invention, the phrase "substantially does not contain Sb ₂ O ₃ " means that the content of Sb ₂ O ₃ is 0.05 wt% or less.

Fifth, the alkali-free glass of the present invention is characterized in that the liquidus temperature is 1150 ° C or less and / or the liquid viscosity is 10 ^5.4 dPa or more. s. The "liquidus temperature" as used in the present invention means that the glass is pulverized, and the glass powder remaining in the 50 mesh (300 μm) through the standard sieve 30 mesh (500 μm) is placed in a platinum boat at a temperature. After maintaining in a gradient furnace for 24 hours, the temperature of the crystals precipitated into the glass. In addition, the "liquid phase viscosity" as used in the present invention means the glass viscosity at the liquidus temperature, and the glass viscosity means a value measured by a well-known fiber elongation method or a platinum ball pull-up method.

Sixth, the alkali-free glass of the present invention is that the content of SnO ₂ in the glass composition in terms of wt% of the oxide basis, of 0 ~ 0.5wt%, and when added up to 0.5 wt% SnO ₂ to SnO _2, The liquid phase temperature of the obtained glass is 1150 ° C or less. According to the present invention, "adding SnO ₂ SnO ₂ is up to 0.5 wt%, the obtained glass liquidus temperature" refers to a temperature, i.e., SnO ₂ is added to a raw material feeding amount of time until the glass In the composition, SnO ₂ is 0.5 wt% (to make the glass composition total 100 wt%), the glass is melted and formed, and thereafter the obtained glass sample is passed through a standard sieve 30 mesh (500 μm) and remains in 50 mesh (300). The temperature at which the glass powder of μm) was placed in a platinum boat and kept in a temperature gradient furnace for one week to crystallize.

Seventh, the alkali-free glass of the present invention is characterized in that when 1 wt% of ZrO ₂ is added to the glass composition, the liquid phase temperature of the obtained glass is 1150 ° C or less. In the present invention, "the liquid phase temperature of the glass obtained when 1 wt% of ZrO ₂ is added to the glass composition" means a temperature at which a glass equivalent to a raw material required for one operation is added. After ZrO _{2 in} an amount of 1 wt% in the composition (the glass composition is apparently a total of 101 wt%), the glass is melted and formed, and thereafter the obtained glass sample is pulverized and passed through a standard sieve 30 mesh. The temperature at which the 50 mesh glass powder was placed in a platinum boat and kept in a temperature gradient furnace for one week to crystallize.

Eighth, the alkali-free glass of the present invention is characterized in that the strain point is 630 ° C or more. In the present invention, the "strain point" means a value measured by a method based on ASTM C336.

9. The alkali-free glass of the present invention is characterized in that the high temperature viscosity is 10 ^2.5 dPa. The temperature at s is less than or equal to 1535 °C. In addition, the "temperature at a high temperature viscosity of 10 ^2.5 dPa.s" as used in the present invention means a value measured by a well-known platinum ball pull-up method.

Tenth, the alkali-free glass of the present invention is characterized in that the high temperature viscosity is 10 ^2.5 dPa. When the temperature at s is T ₁ (° C.) and the strain point is T ₂ (° C.), the relationship of T _{1 -} T ₂ ≦ 880 ° C is satisfied.

Eleventh, the alkali-free glass of the present invention is characterized in that the high temperature viscosity is 10 ⁴ dPa. When the temperature at s is T ₃ (° C.) and the softening point is T ₄ (° C.), the relationship of T _{3 -} T ₄ ≦ 330 ° C is satisfied. In the present invention, the "temperature at a high temperature viscosity of 10 ⁴ dPa·s" means a value measured by a well-known platinum ball pull-up method, and the "softening point" means a method based on ASTM C338. Value.

Twelfth, the alkali-free glass of the present invention is characterized in that the amount of erosion after immersion in a 10% aqueous solution of HCL at 80 ° C for 24 hours is 5 μm or less. The "erosion amount after immersion in a 10% HCL aqueous solution at 80 ° C for 24 hours" as described in the present invention means that both surfaces of the glass sample are optically polished first, and then a part of the glass sample is masked and adjusted to a concentration of 10% HCL aqueous solution. After immersing in the 80 ° C chemical solution for 24 hours, the mask was removed, and the value of the step difference between the mask portion and the eroded portion was measured by a surface roughness meter. Further, the measurement was carried out by optically polishing both surfaces of each glass sample, and then performing a chemical treatment under the above conditions to remove the mask.

Thirteenth, the alkali-free glass of the present invention is characterized by the amount of erosion after immersion in a 130-buffered hydrofluoric acid solution (NH ₄ HF ₂ : 4.6 wt%, NH ₄ F: 36 wt%) at 20 ° C for 30 minutes. Less than or equal to 2 μm. The "amount of erosion after immersion in a 130-buffer hydrofluoric acid solution at 20 ° C for 30 minutes" as described in the present invention means a value measured under a treatment condition of 30 minutes using a 130-buffer hydrofluoric acid solution at 20 ° C. In addition, first, optical polishing was performed on both sides of each glass sample, and then a part of the glass sample was covered, and after immersing for 30 minutes in a chemical solution of 20 ° C adjusted to the above concentration, the mask was removed, and the mask portion was measured by a surface roughness meter. The value of the step of the erosion part. Further, the measurement was carried out by optically polishing both surfaces of the glass sample, and then performing a chemical treatment under the above conditions to remove the mask.

Fourteenth, the alkali-free glass of the present invention is characterized in that after immersing in a 10% HCL aqueous solution at 80 ° C for 3 hours, no white turbidity or wrinkles were observed by visual observation.

Fifteenth, the alkali-free glass of the present invention is characterized in that surface observation by visual observation after immersion in a 63 buffered hydrofluoric acid solution (HF: 6 wt%, NHF ₄ : 30 wt%) at 20 ° C for 30 minutes It is cloudy and wrinkled.

Sixteenth, the alkali-free glass of the present invention is characterized in that the Young's modulus is 27 GPa/(g.cm ^-3 ) or more. In addition, the "specific Young's modulus" as used in the present invention means a value calculated by dividing the Young's modulus by the density, and "Young's modulus" means a value measured by a resonance method.

Seventeenth, the alkali-free glass substrate of the present invention is characterized by comprising the alkali-free glass according to any one of the above.

Eighteenth, the alkali-free glass substrate of the present invention is characterized in that it is formed by drawing down.

Nineteenth, the alkali-free glass substrate of the present invention is characterized in that it is formed by overflow down-drawing.

Twentyth, the alkali-free glass substrate of the present invention is characterized by being used for a display.

Twenty-first, the alkali-free glass substrate of the present invention is characterized in that it is used for an LCD.

Twenty-second, the alkali-free glass substrate of the present invention is characterized in that it is used for a-Si. TFT-LCD.

Twenty-third, the alkali-free glass substrate of the present invention is characterized in that the substrate size is 32 Å or more.

The reason for limiting the glass composition range as described above will be described in detail. Further, the following % means that, except for a specific case, it means weight percentage (wt%).

SiO ₂ is a component forming a glass network, and its content is 45 to 65%, preferably 48 to 62%, more preferably 50 to 60%, and most preferably 52 to 58%. When the content of SiO ₂ is less than 45%, chemical resistance, particularly acid resistance, is deteriorated, and density is increased. On the other hand, when the content of SiO ₂ is more than 65%, the high-temperature viscosity is high and the meltability is deteriorated, and opaque foreign matter (cristobalite) is likely to be generated in the glass.

Al ₂ O ₃ is a component effective for increasing the strain point of the glass and increasing the Young's modulus, and the content thereof is 12 to 17%, preferably 14 to 16.5%, more preferably 15 to 16%. If the content of Al ₂ O ₃ is less than 12%, the effect of increasing the strain point is deteriorated. Further, when the content of Al ₂ O ₃ is less than 12%, the Young's modulus tends to decrease. On the other hand, when the content of Al ₂ O ₃ is more than 17%, the liquidus temperature becomes high and it is easy to become opaque.

B ₂ O ₃ acts as a melting agent and is a component which is effective for lowering the viscosity of the glass and improving the meltability and lowering the liquidus temperature, and the content thereof is 7.5 to 15%, preferably 7.7 to 13%, more preferably It is 8~12%. When the content of B ₂ O ₃ is less than 7.5%, the effect as a melt is insufficient, and buffered HF (hereinafter referred to as BHF resistance) is deteriorated. Further, when the content of B ₂ O ₃ is less than 7.5%, it tends to be opaque, so that the liquidus temperature tends to increase. Further, when the content of B ₂ O ₃ is more than 15%, the strain point of the glass may be lowered to lower the heat resistance, and the acid resistance may be deteriorated. Further, when the content of B ₂ O ₃ is more than 15%, the Young's modulus is lowered to lower the Young's modulus.

MgO is a component that increases the Young's modulus of the glass, lowers the high-temperature viscosity, and improves the meltability, and is the component that most effectively reduces the density among the alkaline earth metal oxides. However, when the content of MgO is large, in addition to a decrease in strain point and opacity, there is a possibility that MgO reacts with BHF to form a product which is fixed or adhered to the surface of the glass substrate. On the element, the glass substrate is white turbid, so the content of MgO is limited. Therefore, the content of MgO is 0 to 3%, preferably 0 to 1%, more preferably 0 to 0.5%, further preferably 0 to 0.3%, and most preferably 0 to 0.2%, ideally In other words, it is best not to contain MgO. Here, "substantially no MgO is contained" means a case where the content of MgO is 0.05% or less.

CaO is a component which does not lower the strain point of the glass and lowers the viscosity of the high temperature, and is a component which improves the opacity resistance, and the content thereof is 5.5 to 15%, preferably 6 to 14%, more preferably 6.5 to 14%. Further better is 7~12%. Since the glass composition of the present invention is difficult to melt and bubbles easily remain in the glass, bubbles are often generated in the glass substrate. In order to reduce bubble defects, it is important to increase the meltability of the glass. In the glass composition system of the present invention, when the amount of SiO ₂ is decreased, the meltability is improved, but the acid resistance is extremely lowered, and the density and the thermal expansion coefficient are increased. Therefore, in the alkali-free glass of the present invention, in order to improve the meltability of the glass, CaO is contained in an amount of 5.5% or more. On the other hand, when the content of CaO is more than 15%, the BHF resistance of the glass is deteriorated, and the surface of the glass substrate is easily corroded. In addition, the reaction product may adhere to the surface of the glass substrate. The glass substrate is cloudy. Further, if the content of CaO is more than 15%, the density or coefficient of thermal expansion becomes too high.

SrO is a component which improves the chemical resistance of the glass, reduces the strain point, lowers the high temperature viscosity, and improves the meltability, and the content thereof is 0 to 5%, preferably 0 to 4%, more preferably 0 to 3.5. %, further better is 0~3%. If the content of SrO is more than 5%, the density or coefficient of thermal expansion increases, or it tends to become opaque.

BaO is a component which improves the chemical resistance and opacity of the glass to improve the meltability, and the content thereof is 5 to 15%, preferably 7 to 14%, more preferably 8 to 13%, and even more preferably 10~13%. When the content of BaO is more than 15%, the opacity resistance is deteriorated, and the density or the coefficient of thermal expansion tends to increase. On the other hand, when the content of BaO is less than 5%, the liquidus viscosity is lowered and it is likely to become opaque. As described above, the introduction of CaO is effective for improving the opacity resistance. If it contains a large amount of CaO, it can enjoy the advantages of improving the meltability and prolonging the life of the melting kiln, but it has the following disadvantages: high temperature viscosity. Significantly, the viscosity of the liquid phase is lowered, so that it is difficult to form into a glass substrate. Therefore, if an appropriate amount of BaO is contained instead of CaO, the decrease in high-temperature viscosity can be suppressed, and the liquidus viscosity can be improved.

ZnO is a component which improves the BHF resistance of the glass and improves the meltability. However, when the content of ZnO is large, it tends to be opaque or the strain point is easily lowered. 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%.

In order to obtain a viscosity characteristic suitable for pull-down forming, it is effective to increase the content of the alkaline earth metal oxide which lowers the high-temperature viscosity and to reduce the content of SiO ₂ . However, if the alkaline earth metal oxide is increased and the content of SiO ₂ is decreased, the strain point is lowered. In order not to deteriorate the anti-opacity, specifically to achieve a liquid viscosity of 10 ^5.4 dPa. s or 10 ^5.4 dPa. s or more, and in order to lower the high temperature viscosity, the value of (CaO+BaO-MgO)/SiO ₂ by weight fraction is 0.25 to 0.40, preferably 0.26 to 0.39, more preferably 0.27 to 0.38, preferably It is 0.30~0.36. That is, by limiting the value of (CaO+BaO-MgO)/SiO ₂ to 0.25 to 0.40, the high temperature viscosity can be lowered without lowering the strain point, and the opacity resistance is not deteriorated. When the value of (CaO+BaO-MgO)/SiO ₂ is less than 0.25, the high-temperature viscosity becomes high or it tends to become opaque. On the other hand, when the value of (CaO+BaO-MgO)/SiO ₂ is more than 0.40, the density tends to be high and the thermal expansion coefficient tends to be high.

When two or more components are mixed in the respective components of MgO, CaO, SrO, BaO, and ZnO, the liquidus temperature of the glass is lowered, and crystal foreign matter is less likely to be generated in the glass, and as a result, the meltability and formability can be improved. . The total amount of the above components (MgO + CaO + SrO + BaO + ZnO) is 15 to 23%, preferably 17 to 22%, more preferably 18 to 21%. When the total amount is less than 15%, the effect as a melt is insufficient, and the meltability is likely to be deteriorated. On the other hand, when the total amount is more than 23%, the density and the coefficient of thermal expansion increase, and the Young's modulus decreases, which tends to become opaque.

ZrO ₂ is a component which improves the chemical resistance of the glass, particularly acid resistance, and increases the Young's modulus, and the content thereof is 0 to 5%, preferably 0 to 3%, more preferably 0 to 1%. If the content of ZrO ₂ is more than 5%, the liquidus temperature rises, so that an opaque foreign matter such as zircon is likely to occur.

TiO ₂ is a component which improves the chemical resistance of the glass, particularly acid resistance, and lowers the high temperature viscosity to improve the meltability, and the content thereof is 0 to 5%, preferably 0 to 3%, more preferably 0 to 1%. Further better is 0~ less than 0.5%, and the best is 0~0.3%. When the content of TiO ₂ is more than 5%, the glass is colored and the transmittance thereof is lowered, so that it is difficult to use for display.

P ₂ O ₅ is a component for improving the opacity resistance of the glass, and the content thereof is 0 to 5%, preferably 0 to 3%, more preferably 0 to 1%, further preferably 0 to less than 0.5. %, the best is 0~0.3%. When the content of P ₂ O ₅ is more than 5%, phase separation and milkiness occur in the glass, and the acid resistance is remarkably deteriorated.

As described above, when the content of both SnO ₂ and ZrO ₂ is large, the glass is likely to be opaque. However, if it is to be used in terms of weight fraction (MgO+CaO+Sr The value of +BaO+ZnO)/SiO ₂ is preferably 0.3 to 0.4, more preferably 0.32 to 0.39, and most preferably 0.34 to 0.38, to suppress opacity of SnO ₂ or ZrO ₂ .

In the alkali-free glass of the present invention, various components may be added in addition to the above components, and for example, up to 5% of Y ₂ O ₃ , Nb ₂ O ₅ , and La ₂ O ₃ may be contained. The above components are used to increase the strain point and Young's modulus of the glass. However, if the content is more than 5%, the density tends to increase.

When the glass composition system of the present invention is melted, As ₂ O ₃ which functions as a clarifying agent at a high temperature has been used in the past. However, in the interest of environmental concerns in recent years, it is preferable to use As ₂ O _{3 as} environmentally hazardous chemicals as much as possible. SnO _{2 is the} same as As ₂ O ₃ and has a clearing force at a high temperature, and is very effective as a clarifying agent for melting the alkali-free glass of the present invention. Therefore, in the alkali-free glass of the present invention, the content of SnO ₂ is preferably 0 to 5%, more preferably 0 to 2%, further preferably 0 to 0.5%, and most preferably 0 to 0.35%. . If the content of SnO ₂ is more than 5%, it is easily opaque. Further, since the alkali-free glass of the present invention is excellent in meltability, even if As ₂ O _{3 is} not added as a clarifying agent, a glass substrate having no bubble defects can be efficiently produced by adding a clarifying agent such as SnO ₂ .

Cl has an effect of promoting the melting of the alkali-free glass, and has the effect of melting the glass at a low temperature and allowing the clarifying agent to function more effectively, and is a component that reduces the melting cost of the glass and can extend the life of the manufacturing equipment. The content is preferably 0 to 3%. If the Cl content is more than 3%, the strain point may decrease. Further, a chloride such as an alkaline earth metal oxide such as cerium chloride or a raw material such as aluminum chloride can be used as a raw material of the Cl component.

As the clarifying agent for the alkali-free glass of the present invention, Sb ₂ O _{3 is} also effective. However, in general, the alkali-free glass has a higher melting temperature, so that the effect of Sb ₂ O ₃ as a clarifying agent is smaller than that of As ₂ O ₃ . Therefore, when Sb ₂ O _{3 is} used as the clarifying agent, it is preferred to increase the amount of addition or to lower the melting temperature by a combination with a component which promotes meltability such as Cl. However, when the content of Sb ₂ O ₃ is 5% or more, the density tends to increase, and the amount of addition is preferably 0 to 2%, more preferably 0 to 1.5%. Further, Sb ₂ O ₅ may be used for some or all of the Sb ₂ O _{3 in the} glass raw material.

Further, in the alkali-free glass of the present invention, when As ₂ O _{3 is} not used as the clarifying agent, one, two or more kinds selected from the group consisting of Sb ₂ O ₃ , SnO ₂ and Cl are preferably used. The content is 0 to 3%, and particularly preferably, the content ratio of Sb ₂ O ₃ is 0 to 2%, SnO ₂ is 0.01 to 1%, and Cl is 0 to 1%.

Sb ₂ O ₃ is less toxic than As ₂ O ₃ , but since it is a substance that causes a load on the environment, it is preferable that Sb ₂ O ₃ does not substantially contain Sb ₂ O _{3 from the} viewpoint of the environment. Further, since a halogen such as Cl is toxic to a volatile substance generated when the glass is melted, it is preferred from the viewpoint of the environment that the halogen is not substantially contained. Here, the term "substantially does not contain a halogen such as Cl" means a case where the content of halogen in the glass composition is 0.05% or less. From the viewpoint of the above-mentioned environmental concerns, it is preferable that substantially no As ₂ O ₃ or Sb ₂ O ₃ (preferably not containing As ₂ O ₃ , Sb ₂ O ₃ , Cl), and the following It is contained in an amount of 0% by weight (preferably 0.01 to 1%) of Sn ₂ O in terms of wt% of oxides as a clarifying agent.

Further, the alkali-free glass of the present invention may contain, as a clarifying agent, F, SO ₃ , C or the like of 3% or less as long as the properties are not impaired. Further, a metal powder such as Al or Si of 3% or less may be contained as a clarifying agent. Further, CeO ₂ , Fe ₂ O ₃ or the like of 5% or less may be contained as a clarifying agent.

In the above glass composition range, it is of course possible to arbitrarily combine the preferred ranges of the respective components, thereby selecting a preferred glass composition range, wherein the alkali-free glass may exemplify a glass having a better glass composition range, that is, in wt. The content of SiO ₂ is 50 to 60%, Al ₂ O ₃ is 14 to 16.5%, B ₂ O ₃ is 7.7 to 13%, MgO is 0 to 0.5%, CaO is 6 to 14%, and SrO is 0. ~3.5%, BaO is 7~14%, ZnO is 0~3%, MgO+CaO+SrO+BaO+ZnO is 17~22%, ZrO ₂ is 0~1%, TiO ₂ is 0~3%, P ₂ O ₅ is 0~3% It does not substantially contain an alkali metal oxide, and has a weight fraction (CaO+BaO-MgO)/SiO ₂ of 0.25 to 0.4, and an average thermal expansion coefficient of 42 to 48×10 in a temperature range of 30 to 380 ° C. ^-7 / °C. When the composition range of the glass is limited to the above range, the opacity resistance can be greatly improved, and the viscosity characteristics necessary for the overflow down-draw formation can be surely ensured.

A more preferable aspect of the alkali-free glass is a glass having a content of SiO ₂ of 52 to 58% by weight %, 15 to 16% of Al ₂ O ₃ , and 8 to 12% of B ₂ O ₃ . , MgO is 0~0.5%, CaO is 7~12%, SrO is 0~3%, BaO is 10~13%, ZnO is 0~0.5%, MgO+CaO+SrO+BaO+ZnO is 18~21%, ZrO ₂ is 0~1% TiO ₂ is 0-0.5%, P ₂ O ₅ is 0-0.5%, and substantially does not contain an alkali metal oxide, and the value of (CaO+BaO-MgO)/SiO ₂ is 0.25-0.4 by weight fraction, and The average thermal expansion coefficient in the temperature range of 30 to 380 ° C is 44 to 47 × 10 ^-7 / ° C. When the composition range of the glass is limited to the above range, the opacity resistance can be remarkably improved, and the viscosity characteristics necessary for the overflow down-draw formation can be reliably ensured.

The alkali-free glass of the present invention has an average thermal expansion coefficient in the temperature range of 30 to 380 ° C of 40 to 50 × 10 ^-7 / ° C, preferably 42 to 49 × 10 ^-7 / ° C, more preferably 43 ~48×10 ^-7 /°C, further preferably 44~47×10 ^-7 /°C. If the average coefficient of thermal expansion is less than 40 × 10 ^-7 / ° C, integration with the thermal expansion coefficient of the peripheral material (especially organic material or metal) may not be obtained. On the other hand, if the average thermal expansion coefficient is more than 50 × 10 ^-7 / ° C, the probability of breakage of the glass substrate in the manufacturing process of the TFT-LCD becomes high. In addition, in LCD applications, the thermal shock resistance of glass substrates is also an important requirement. Even if the end surface of the glass substrate is subjected to chamfering, there are fine flaws or cracks, and if the tensile stress caused by heat is concentrated on the flaw or crack, the glass substrate may be broken. When the glass substrate is damaged, there is a possibility that the production efficiency of the production line is lowered, and the fine glass frit which is generated at the time of breakage adheres to the glass substrate to cause a disconnection failure or a patterning failure. In the manufacturing steps of a TFT-LCD, in particular, a polysilicon TFT-LCD (p-Si. TFT-LCD), since the heat treatment step is large, the glass substrate is repeatedly subjected to rapid heating and rapid cooling, so that the glass substrate is The thermal shock becomes even bigger. Further, as described above, the glass substrate tends to increase in size, and the large-sized glass substrate is likely to have a temperature difference in the heat treatment step, and the probability of occurrence of minute scratches and cracks on the end surface is also high, and the probability of breakage of the glass substrate in the heat treatment step is changed. high. The most fundamental and effective method for solving this problem is to reduce the thermal stress caused by the difference in thermal expansion. Therefore, a glass having a low coefficient of thermal expansion is required, and specifically, a glass having a coefficient of thermal expansion of 50 × 10 ^-7 /° C or less is required.

In the alkali-free glass of the present invention, the liquidus temperature is preferably 1150 ° C or less, more preferably 1080 ° C or less, still more preferably 1050 ° C or less, and most preferably 1030 ° C or less. In general, in the pull-down forming, particularly in the overflow down-draw molding, the viscosity at the time of glass forming is higher than the other forming methods. Therefore, if the opaque resistance of the glass is poor, an opaque substance is generated during the forming process, and it is difficult to form the glass substrate. Specifically, if the liquidus temperature is higher than 1150 ° C, the overflow down-draw molding becomes difficult, and it is necessary to employ a molding method such as float forming, and in order to obtain a glass substrate having a good surface quality, it is necessary to additionally process. step. Therefore, if the liquidus temperature is higher than 1150 ° C, the method of forming the alkali-free glass is unduly restricted, and the glass having the desired surface quality cannot be formed. Furthermore, the lower the liquidus temperature, the better the opacity resistance of the glass.

In the alkali-free glass of the present invention, the liquid phase viscosity is preferably 10 ^5.4 dPa or more. s, better is greater than or equal to 10 ^5.6 dPa. s, further better is greater than or equal to 10 ^5.8 dPa. s, the best is greater than or equal to 10 ^6.0 dPa. s. In general, in the pull-down forming, especially in the overflow down-draw forming, the viscosity at the time of glass forming is higher than other forming methods, so if the opaque resistance of the glass is evil, opaque matter is generated during the forming process, and it is difficult to form a glass substrate. . Specifically, if the liquid viscosity is lower than 10 ^5.4 dPa. In other cases, it is difficult to form an overflow down-draw, and it is necessary to use a molding method such as a floating method, and in order to obtain a glass substrate having a good surface quality, a processing step must be additionally added. Therefore, if the liquid viscosity is lower than 10 ^5.4 dPa. s, the method of forming the alkali-free glass is unduly restricted, and it is impossible to form a glass having a desired surface quality. In addition, the greater the viscosity of the liquid phase, the better the opacity of the glass.

When alkali-free glass of the present invention, the following terms of an oxide and contains, wt% 0 ~ 0.5 wt% of SnO _2, and the glass composition is added until the SnO ₂ SnO ₂ of 0.5 wt%, the obtained glass The liquidus temperature is preferably 1150 ° C or less, more preferably 1100 ° C or less. If an internal defect such as a bubble is present in the glass, the light is prevented from being transmitted, which is a fatal defect in the glass substrate for a display. Generally, the glass substrate is enlarged. The probability of remaining bubbles is increased, so that the probability of bubbles becoming defective defects is increased, and the productivity of the glass substrate is lowered. Therefore, the technique of reducing bubbles in the glass becomes important. A method of reducing bubbles contained in the glass, a method using a clarifying agent, and a method of lowering the viscosity at a high temperature. In the former method, the alkali-free glass as a fining agent, the most effective is As ₂ O _3, As ₂ O ₃ but is environmental chemical load, it must reduce the use of As ₂ O _3. Therefore, from the viewpoint of the environment, it has been studied to introduce SnO ₂ as a substitute clarifying agent for As ₂ O ₃ , but SnO ₂ tends to be a crystalline foreign matter (opaque), which may become an internal defect of the glass substrate. Therefore, when it is difficult to produce opaque glass with respect to SnO ₂ , even if SnO ₂ is introduced as a clarifying agent, opacity due to SnO _{2 is} less likely to occur, so that the glass substrate manufacturing efficiency and environmental concerns can be achieved together, and it is considered to be very effective. . Further, in the manufacturing step of the glass substrate, it is also assumed that the Sn electrode is segregated in the glass to some extent, so that it is more advantageous to produce opaque glass with respect to SnO ₂ . In this respect, according to the alkali-free glass of the present invention, even if the SnO ₂ content in the glass composition is increased to 0.5%, the liquid phase temperature of the obtained glass can be made 1150 ° C or less, so that the above-mentioned maximum enjoyment can be enjoyed. effect. On the other hand, when the content of SnO ₂ in the glass composition is 0.5%, if the liquidus temperature of the obtained glass is higher than 115 ° C, it is difficult to enjoy the above effects.

In the alkali-free glass of the present invention, when 1% of ZrO ₂ is added to the glass composition, the liquid phase temperature of the obtained glass is preferably 1150 ° C or less, more preferably 1100 ° C or less. In addition to reducing internal defects such as bubbles and foreign matter, it is effective to reduce the manufacturing cost of the glass substrate by prolonging the life of the melting kiln and reducing the frequency of repairing the melting kiln. For this reason, it is preferable to use a Zr-based refractory material which is hard to erode the molten glass. However, as the Zr-based refractory is used, the Zr-based crystalline foreign matter (opaque) is likely to be generated, which may become the inside of the glass substrate. defect. Therefore, in the case where it is difficult to produce opaque glass with respect to ZrO ₂ , even if a Zr-based refractory is used as the refractory of the melting kiln, opacity caused by the refractory is hard to occur, and the manufacturing cost of the glass substrate can be reduced, which is considered to be very effective. In this respect, according to the alkali-free glass of the present invention, even if 1% of ZrO ₂ is added to the glass composition, the liquid phase temperature of the obtained glass can be made 1150 ° C or less, so that the above-mentioned maximum enjoyment can be enjoyed. effect. On the other hand, when 1% of ZrO ₂ is added to the glass composition, if the liquidus temperature of the obtained glass is higher than 1150 ° C, it is difficult to enjoy the above effects.

In the alkali-free glass of the invention, the high temperature viscosity is 10 ^2.5 dPa. The temperature at s is preferably 1535 ° C or less, more preferably 1530 ° C or less, further preferably 1520 ° C or less, particularly preferably 1510 ° C or less, and most preferably 1500 ° C or less. As described above, when the glass is melted at a high temperature for a long period of time, internal defects such as bubbles or foreign matter in the glass can be reduced, but the melting in the high temperature region increases the load on the glass melting furnace. For example, a refractory such as alumina or zirconia used in a melting kiln is violently eroded by molten glass as the temperature is higher, and the life cycle of the melting kiln is also shortened. Further, the running cost for maintaining the high temperature inside the kiln is higher than that of the glass which is melted at a low temperature, and the melting in the high temperature region is disadvantageous for manufacturing the glass substrate. Therefore, it is required that the alkali-free glass can be melted at a low temperature. In this respect, the alkali-free glass according to the present invention can have a high temperature viscosity of 10 ^2.5 dPa. The temperature at s is less than or equal to 1,535 ° C, so that the above effects can be surely obtained. On the other hand, if the high temperature viscosity is 10 ^2.5 dPa. When the temperature at s is higher than 1535 ° C, it is difficult to enjoy the above effects. In addition, the high temperature viscosity is 10 ^2.5 dPa. The temperature of the molten glass at s corresponds to the melting temperature.

The strain point of the alkali-free glass of the present invention is preferably 630 ° C or more, more preferably 635 ° C or more, still more preferably 640 ° C or more, and most preferably 645 ° C or more. Further, the glass substrate is supplied to the high-temperature heat treatment in the manufacturing process of the TFT-LCD. If the heat resistance of the glass substrate is low, for example, when the glass substrate is exposed to a high temperature of 400 to 600 ° C, a small size shrinkage called heat shrinkage may occur, which may cause the pixel pitch of the TFT to shift to become a display. Bad cause. Further, if the heat resistance of the glass substrate is lower, the glass substrate may be deformed, warped, or the like. Further, in order to prevent heat shrinkage of the glass substrate in the manufacturing process of the TFT-LCD such as the film forming step without causing pattern shift, a glass excellent in heat resistance is also required. In this respect, according to the alkali-free glass of the present invention, the strain point can be made 630 ° C or more, so that the above problem is difficult to occur. On the other hand, if the strain point is less than 630 ° C, the above problem becomes serious. Also, with a-Si. Compared to TFT-LCD, p-Si. In the manufacturing process of the TFT-LCD, the heat treatment temperature is high, so the glass substrate with a high strain point is suitable for p-Si. TFT-LCD.

The alkali-free glass of the invention will have 10 ^2.5 dPa. When the temperature at s is T ₁ (°C) and the strain point is T ₂ (°C), it is preferable to satisfy the relationship of T ₁ -T ₂ ≦880 °C. T ₁ corresponds to the melting temperature and corresponds to the temperature at which the glass is fused in the kiln. T ₂ is an index of heat resistance, and the higher the T ₂ , the more excellent the heat resistance. In general, when T ₁ is lowered, T _{2 is} also lowered, and if T ₂ is increased, T _{1 is} increased. However, in order to allow the glass to be melted at a relatively low temperature and excellent in heat resistance, it is preferred to make T _{1 -} T ₂ is 880 ° C or less, more preferably 870 ° C or less, further preferably 860 ° C or less, and most preferably 850 ° C or less. When T ₁ -T _{2 is} higher than 880 ° C, it is difficult to achieve low-temperature melting and heat resistance together.

The alkali-free glass of the invention will be 10 ⁴ dPa. When the temperature at s is T ₃ (°C) and the softening point is T ₄ (°C), it is preferable to satisfy the relationship of T ₃ -T ₄ ≦330 °C. The thickness of the glass substrate, the warpage or the curved shape in the sheet width direction are substantially determined in the process from the temperature of the molten glass reaching the softening point. Therefore, if T ₃ -T _{4 is} decreased, specifically, it is preferable to make T ₃ -T ₄ equal to or lower than 330 ° C, more preferably 325 ° C or less, and most preferably 320 ° C or less, then control The thickness of the glass substrate and the warpage or the curved shape in the sheet width direction become easy. Further, when T _{3 -} T ₄ ≦ 330 ° C is controlled, the viscosity rapidly rises during cooling, and the shape can be quickly formed into a glass substrate. That is, when T ₃ -T ₄ is made 330 ° C or less, it becomes easy to form a thin glass substrate flatly. Further, when T ₃ -T _{4 is} less than or equal to 330 ° C, it is easy to form a large glass substrate flatly. In addition, in the down-draw molding, the furnace distance for slow cooling has a design limitation, and the slow cooling time of the glass substrate is also limited. For example, it is necessary to cool for several minutes from the molding temperature to room temperature. Therefore, the above viscosity characteristics are very advantageous. On the other hand, when T ₃ -T _{4 is} higher than 330 ° C, it is necessary to control the thickness of the glass substrate and the warpage or the curved shape in the sheet width direction. Further, T ₃ corresponds to the forming temperature.

The density of the alkali-free glass of the present invention is preferably 2.80 g/cm ³ or less, more preferably 2.70 g/cm ³ or less, further preferably 2.68 g/cm ³ or less, and most preferably less than or equal to 2.68 g/cm ³ . Is equal to 2.65 g/cm ³ . The lower the density of the glass, the more lightweight the glass can be, and as a result, the weight of the TFT-LCD can be reduced. On the other hand, in the alkali-free glass system, when the density of the glass is lowered, the viscosity of the glass is increased, the meltability is deteriorated, and the opacity tends to increase, and the moldability is also deteriorated. For example, quartz glass has a low density of 2.2 g/cm ³ but must be melted at a very high temperature and has poor opacity resistance, so that it is impossible to perform overflow down-draw formation, and it is difficult to melt a large glass substrate without defects. . Therefore, from the viewpoint of coexistence of density and meltability, density and formability, the objective is to make the density 2.50 g/cm ³ or more (more desirably 2.60 g/cm ^{3 or more} ).

Preferably, the alkali-free glass of the present invention is immersed in a 10% aqueous solution of HCL at 80 ° C for 24 hours, and the amount of erosion is less than or equal to 5 μm, and/or immersed in a 10% aqueous solution of HCL at 80 ° C for 3 hours and visually observed. No turbidity or wrinkles were observed on the surface. Further, it is preferred that the alkali-free glass of the present invention is immersed in a 130 BHF solution at 20 ° C for 30 minutes or less after etching for 2 minutes, and/or immersed in a 63 BHF solution at 20 ° C for 30 minutes, and then visually observed for surface observation. No turbidity or wrinkles were found. A transparent conductive film, an insulating film, a semiconductor film, a metal film, or the like is formed on the surface of the glass substrate for TFT-LCD, and various circuits are formed by photolithography etching (photoetching) Or pattern. Further, in the film formation and photolithography steps described above, various heat treatments or chemical treatments are applied to the glass substrate. Generally, in the TFT array process, a series of processes such as a film forming step → a photoresist pattern formation → an etching step → a photoresist stripping step are repeatedly performed. In this case, the etching of the Al and Mo films is performed using a phosphoric acid solution as an etching solution, and the etching of ITO (indium tin oxide) film is performed using a solution of aqua regia (HCL+HNO ₃ ) as an etching solution for SiNx, In the etching of the SiO ₂ film or the like, various kinds of chemical liquids such as a BHF solution are used as the etching liquid, and the etching liquid is not disposable, but is a circulating liquid flow. If the chemical resistance of the glass substrate is low, the following problems may occur during etching, that is, the reaction product of the chemical liquid and the glass substrate blocks the filter of the circulating liquid stream, or the glass is inhomogeneously etched. The surface of the substrate is white turbid, or the etching rate becomes unstable due to a change in the composition of the etching liquid. In particular, a fluoric acid-based chemical liquid represented by BHF is likely to cause the above problems due to strong erosion of the glass substrate, and the glass substrate is required to have excellent BHF resistance. That is, from the viewpoint of preventing contamination of the chemical solution or reaction product and blocking the filter in the etching step, the chemical resistance of the glass is very important. Further, the chemical resistance of the glass substrate is important not only in that the amount of erosion on the surface of the glass substrate is small, but also in that the appearance is not changed. In the chemical liquid treatment, the appearance of the glass is not changed by white turbidity or wrinkles, and it is an indispensable property of a glass substrate for display such as a TFT-LCD which is important in light transmittance. The evaluation result of the amount of erosion and the change in appearance does not necessarily coincide with the BHF resistance. For example, even if the glass shows the same amount of erosion, the appearance change or the appearance change does not occur after the treatment of the medicine due to the difference in the glass composition. In this respect, the alkali-free glass according to the present invention, after being immersed in a 10% aqueous solution of HCL at 80 ° C for 24 hours, may have an erosion amount of 5 μm or less and immersed in a 10% aqueous solution of HCL at 80 ° C for 3 hours. After the surface observation by visual observation, it was found that no white turbidity or wrinkles were generated, so that the above problems can be reliably solved. In particular, the alkali-free glass according to the present invention can be etched in a 130 BHF solution at 20 ° C for 30 minutes, and the amount of etching can be 2 μm or less, and even if it is immersed in a 63 BHF solution at 20 ° C for 30 minutes, the surface observation is visually observed. No turbidity or wrinkles can be found, so the above problems can be reliably solved.

The alkali-free glass of the present invention preferably has a Young's modulus (a value obtained by dividing the Young's modulus by the density) of 27 GPa/g or more. Cm ^-3 , more preferably greater than or equal to 28 Gpa / g. Cm ^-3 , the best is greater than or equal to 29 Gpa / g. Cm ^-3 . If the specific Young's modulus is greater than or equal to 27 Gpa / g. With cm ^-3 , even a large-sized and thin glass substrate can suppress the amount of warpage to the extent that no problem occurs.

The alkali-free glass substrate of the present invention can be produced by continuously feeding a glass raw material to achieve a desired glass composition, and continuously feeding it into a melting furnace, followed by heating and melting, defoaming, and then supplying to the forming. The apparatus further forms the molten glass into a plate shape, followed by gentle cooling.

The alkali-free glass substrate of the present invention is preferably a down-draw molding, in particular, an overflow down-draw molding, from the viewpoint of producing a glass substrate having a good surface quality. The reason for this is that when the overflow down-draw is formed, the surface of the surface of the glass substrate is not in contact with the launder-like refractory, but is formed in a state of a free surface, whereby the surface quality can be formed without grinding. Good glass substrate. Here, the overflow down-draw molding refers to a method in which molten glass overflows from both sides of the heat-resistant flow-like structure, and then the overflowed molten glass merges at the lower end of the flow-like structure and downward The glass substrate is manufactured by extension molding. The structure or material of the flow channel structure is not particularly limited as long as the size and surface quality of the glass substrate are in a desired state, and the quality of the glass substrate for TFT-LCD can be achieved. Further, in order to perform the stretching forming below, the glass substrate can be biased by any method. For example, a method in which a heat-resistant roller having a sufficiently large width is rotated and extended in contact with a glass substrate, or a method in which a plurality of pairs of heat-resistant rollers are brought into contact with only the vicinity of the end surface of the glass substrate may be employed. Since the alkali-free glass of the present invention is excellent in opaque resistance and is suitable for molding in viscosity characteristics, it can be subjected to overflow down-drawing molding with high precision.

In the method for producing an alkali-free glass substrate of the present invention, various methods can be employed in addition to the overflow down-draw molding. For example, various molding methods such as float molding, slot down draw molding, redraw molding, and rollout molding can be employed. Further, from the viewpoint of inexpensively producing a glass substrate, it is preferred to form a floating method.

The alkali-free glass of the present invention is preferably used as a glass substrate. The alkali-free glass of the present invention can be formed by various molding methods. However, the alkali-free glass of the present invention is excellent in opacity resistance and has appropriate viscosity characteristics, and can be suitably formed into a glass substrate, and the method can be suitably formed. The glass substrate can be applied to displays such as LCDs.

As described above, the glass substrate tends to be large. However, when the substrate size is increased, the probability of occurrence of opaque substances in the substrate is increased, and the yield is drastically lowered. Therefore, according to the alkali-free glass substrate of the present invention which is excellent in opacity resistance, it is advantageous in producing a large-sized glass substrate. For example, the substrate size is greater than or equal to 0.1 m ² (specifically, the size is greater than or equal to 320 mm × 420 mm), especially greater than or equal to 0.5 m ² (specifically, the size is greater than or equal to 630 mm × 830 mm), greater than or equal to 1.0 m ² (specifically, the size is greater than or equal to 950 mm × 1150 mm), further greater than or equal to 2.3 m ² (specifically, the size is greater than or equal to 1400 mm × 1700 mm), greater than or equal to 3.5 m ² (specifically, the size is greater than Equal to 1750 mm × 2050 mm), 4.8 m ^{2 or more} (specifically, the size is 2100 mm × 2300 mm or more), and the larger the substrate size as described above, the more advantageous it is. In terms of the screen size of the display, the substrate size is preferably 32 Å or more, more preferably 36 Å or more, and still more preferably 40 Å or more. Further, according to the alkali-free glass substrate of the present invention, low density and high specific Young's modulus can be obtained, and in addition to the above, the thin glass substrate can be formed with high precision. For example, if the wall thickness is made 0.8 mm or less (preferably 0.7 mm or less, more preferably 0.5 mm or less, further preferably 0.4 mm or less), the advantages of the present invention can be effectively enjoyed. Further, the alkali-free glass substrate of the present invention can reduce the amount of warpage of the glass substrate by reducing the thickness of the glass substrate as compared with the conventional glass substrate, so that it is easy to prevent the glass substrate from being placed in a cassette. Or breakage when taking out from the cassette holder.

The alkali-free glass substrate of the present invention is preferably used for displays such as LCDs, especially a-Si. TFT-LCD. The alkali-free glass substrate of the present invention is suitable for the above-mentioned use because it satisfies the above-described characteristics (1) to (7) required for a glass substrate for LCD. In addition, the alkali-free glass of the present invention is excellent in opaque resistance and has a viscosity characteristic suitable for overflow down-drawing, so that a large-sized and/or thin-plate glass substrate can be efficiently manufactured, so that the glass substrate can be reliably satisfied (especially for a television set). The size of the glass substrate) is required. In addition, the alkali-free glass substrate of the present invention is also suitable for p-Si. A glass substrate for a TFT-LCD.

[Examples]

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

Tables 1 to 7 show glass (sample Nos. 1 to 38) and comparative examples (sample Nos. A and B) of the examples of the present invention.

Each of the glass samples in the table was made in the following manner.

First, the glass raw material was blended to obtain a single-feed amount of the composition in the table, and it was put into a platinum crucible, melted at 1550 ° C for 24 hours, and then discharged to a carbon plate to be formed into a plate shape. For the glass samples obtained in this way, the density, thermal expansion coefficient, strain point, slow cooling point, softening point, high temperature viscosity, Young's modulus, specific Young's modulus, anti-opacity (liquidus temperature, liquid phase) were measured. Various properties of viscosity, chemical resistance (BHF resistance, HCl resistance) are shown in the table.

Density is determined using the well-known Archimedes method.

The coefficient of thermal expansion is an average value within a temperature range of 30 to 380 ° C measured using a dilatometer.

The strain point and the slow cooling point were measured by a method based on ASTMC336. The higher the value of the strain point and the slow cooling point, the higher the heat resistance of the glass.

The softening point is determined by the method based on ASTMC338.

The high temperature viscosity is 10 ^4.0 dPa. s, 10 ^3.0 dPa. s, 10 ^2.5 dPa. Each temperature at s is measured by a well-known platinum ball pull-up method.

Young's modulus is determined by resonance. The specific Young's modulus is calculated by dividing the Young's modulus by the density.

The liquid phase temperature means that each glass sample is pulverized, and the glass powder remaining in 50 mesh (300 μm) through a standard sieve 30 mesh (500 μm) is placed in a platinum boat and kept in a temperature gradient furnace for 24 hours to determine crystallization. The temperature that precipitates into the glass.

Added with a liquidus temperature of SnO ₂ (Table opacity anti SnO ₂₎ refers, SnO ₂ is added to a raw material feeding amount of time until the SnO ₂ in the glass composition is 0.5%, the same as described above in The glass was melted and formed under the conditions. Thereafter, the glass sample was pulverized, and the glass powder remaining in 50 mesh (300 μm) through a standard sieve 30 mesh (500 μm) was placed in a platinum boat and kept in a temperature gradient furnace for one week. The temperature at which the crystals were precipitated was measured. Next, the case where no opacity was observed at 1150 ° C was recorded as "○", and the case where opacity was found at 1150 ° C was recorded as "X". In addition, the clarity of the glass was evaluated at the same time as this evaluation, and when SnO _{2 was} added until SnO ₂ was 0.5%, no bubble defects were observed in the glass.

The liquidus temperature when ZrO ₂ is added (in the table, the anti-ZrO ₂ opacity) means that 1% of ZrO ₂ corresponding to the glass composition is added to the primary charge of the raw material under the same conditions as above. The glass was melted and formed, and thereafter, the glass sample was pulverized, and the glass powder remaining in 50 mesh (300 μm) through a standard sieve 30 mesh (500 μm) was placed in a platinum boat and kept in a temperature gradient furnace for one week. The temperature at which the crystals were precipitated was measured. Next, the case where opacity was found at 1150 ° C was recorded as "X", and the case where opacity was not observed at 1150 ° C was recorded as "○".

The liquid viscosity refers to the glass viscosity at the liquidus temperature. Glass viscosity is measured by the well-known platinum ball pull-up method. Further, the lower the liquidus temperature and the higher the liquid phase viscosity, the more excellent the opacity resistance and the excellent moldability.

BHF resistance and HCl resistance were evaluated by the following methods. First, after optically grinding both sides of each glass sample, a part of the glass sample is masked, and immersed in a chemical solution adjusted to a predetermined concentration at a predetermined temperature for a predetermined time. After the chemical treatment, the mask was removed, and the step difference between the mask portion and the eroded portion was measured by a surface roughness meter, and the step difference value was recorded as the erosion amount. Further, each measurement was carried out by optically polishing both surfaces of each glass sample, and then performing a chemical liquid treatment under the following conditions to remove the mask. In terms of the chemical solution and the treatment conditions, the amount of BHF resistance was measured using a 130 BHF solution (NH ₄ HF ₂ : 4.6 wt%, NH ₄ F: 36 wt%) at 20 ° C for 30 minutes. . For BHF resistance, if the amount of erosion is less than 1 μm, it is marked as "◎", and if it is 1 to 2 μm, it is marked as "○". The amount of HCl-resistant erosion was measured using a 10 wt% aqueous hydrochloric acid solution at 80 ° C for 24 hours. If the HCl resistance was less than 2.5 μm, it was recorded as "◎", and if it was 2.5 to 5 μm. It is recorded as "○", and if it is larger than 5 μm, it is recorded as "X".

For the evaluation of the appearance of the liquid and the treatment conditions, the BHF resistance was carried out using a 63 BHF solution (HF: 6 wt%, NH ₄ F: 30 wt%) at 20 ° C for 30 minutes under treatment conditions, HCl resistant The properties were carried out using a 10 wt% aqueous hydrochloric acid solution at 80 ° C for 3 hours. The surface of the glass was visually observed, and the case where no turbidity, wrinkles, and cracks were observed on the surface of the glass was observed as "○", and the case where white turbidity, wrinkles, or cracks were formed on the surface of the glass was referred to as "x".

In the examples, the glass samples of Nos. 1 to 38 did not contain an alkali metal oxide, and had a density of 2.67 g/cm ³ or less, a thermal expansion coefficient of 43 to 48 × 10 ^-7 /° C., and a strain point of 637 ° C or more. In addition, the specific Young's modulus is greater than or equal to 29 GPa/g. Cm ^-3 . In addition, the high temperature viscosity of each of the above samples was 10 ^2.5 dPa. The temperature at s is less than or equal to 1532 ° C, so it is easy to melt, and the liquidus temperature is less than or equal to 1070 ° C, and the liquid viscosity is greater than or equal to 10 ^5.4 dPa. s, so it is excellent in anti-opacity. Therefore, it was judged that the glass substrate productivity of each sample of the Example was also excellent. Further, each sample of the examples was excellent in BHF resistance and HCl resistance, and the appearance evaluation was also good. In consideration of the above, each sample of the examples can be considered to be suitable as a glass substrate for a TFT-LCD.

On the other hand, the glass sample A of the comparative example had a value of (CaO+BaO-MgO)/SiO ₂ of 0.05 and a high temperature viscosity of 10 ^2.5 dPa. The temperature at s is higher at 1542 °C. Further, in the glass sample B of the comparative example, the value of (CaO+BaO-MgO)/SiO ₂ was 0.43, and the strain point was 626 ° C and was low.

Further, the glass of Example No. 17 was melted in a test melting furnace and subjected to overflow down-draw molding to thereby form a glass substrate for a display having a substrate size of 900 mm × 1100 mm and a thickness of 0.5 mm. The warpage of the substrate is less than or equal to 0.05%, the curved center (WCA) is less than or equal to 0.1 μm, and the surface roughness (Ry) is less than or equal to 50. (Through λc: 9 μm), the surface quality is excellent, and it is suitable as a glass substrate for LCD. Further, in the overflow down-draw molding, by appropriately adjusting the speed of the stretching roll, the speed of the cooling roll, the temperature distribution of the heating device, the temperature of the molten glass, the flow rate of the glass, the speed of the pulling plate, the number of rotations of the agitator, and the like, Adjust the surface quality of the glass substrate. Further, "warping" was carried out by placing a glass substrate on an optical plate and using a clearance gauge described in JIS B-7524. "Bending" is a value obtained by measuring the WCA (filter center line bending) described in JIS B-0610 using a stylus type surface shape measuring device, and the measurement is performed by using SEMI STD D15-1296 "the surface of the FPD glass substrate is bent. The measurement method was measured according to the method, and the measurement was performed at a measurement of 0.8 to 8 mm, and a length of 300 mm was measured in a direction perpendicular to the extraction direction of the glass substrate. The "average surface roughness (Ry)" is a value measured by a method based on SEMI D7-94 "Method for Measuring Surface Roughness of FPD Glass Substrate".

[Industrial availability]

Therefore, the alkali-free glass of the present invention is suitable for a flat panel display substrate such as an LCD or an EL display, a glass cover for an image sensor such as a charge coupled device (CCD) or a similarly-sized solid-state imaging device (CIS), and a substrate for a solar cell. .

Claims (23)

An alkali-free glass characterized in that the glass composition of the alkali-free glass is SiO ₂ content of 45 to 65%, Al ₂ O ₃ of 12 to 17%, and B ₂ O by weight percentage (wt%). ₃ is 7.5~15%, MgO is 0~3%, CaO is 5.5~15%, SrO is 0~5%, BaO is 5~15%, ZnO is 0~5%, MgO+CaO+SrO+BaO+ZnO is 15~23%, ZrO ₂ is 0 to 5%, TiO ₂ is 0 to 5%, and P ₂ O ₅ is 0 to 5%; the alkali-free glass is substantially free of alkali metal oxide; (CaO+BaO-MgO)/ by weight fraction The value of SiO ₂ is 0.25 to 0.4; and in the temperature range of 30 to 380 ° C, the average thermal expansion coefficient of the alkali-free glass is 40 to 50 × 10 ^-7 /°C. The alkali-free glass according to claim 1, wherein the value of (MgO+CaO+SrO+BaO+ZnO)/SiO ₂ is 0.3 to 0.4 by weight fraction. The alkali-free glass according to claim 1 or 2, which substantially does not contain As ₂ O ₃ , and the content of Sb ₂ O ₃ +SnO ₂ +Cl is 0% in terms of wt% of the oxide in terms of the oxide. 3%. The alkali-free glass according to claim 1 or 2, which substantially does not contain As ₂ O ₃ and Sb ₂ O ₃ , and the content of SnO ₂ is 0% in terms of wt% of the oxide. 1%. For example, in the alkali-free glass described in the first or second aspect of the patent application, the liquidus temperature is less than or equal to 1150 ° C and / or the liquid viscosity is greater than or equal to 10 ^5.4 dPa. s. The alkali-free glass according to claim 1 or 2, wherein the content of SnO ₂ in the glass composition is 0 to 0.5 wt% in terms of wt% of the above oxide, and SnO _{2 is} added until SnO ₂ When the content is 0.5 wt%, the liquid phase temperature of the obtained glass is 1150 ° C or less. The alkali-free glass according to claim 1 or 2, wherein when the glass composition is added with 1 wt% of ZrO ₂ , the liquid phase temperature of the obtained glass is 1150 ° C or less. The scope of the patent application to item 1 or 2 of the alkali-free _glass, its strain point not less than 630 ℃. 1. The alkali-free glass as described in claim 1 or 2, wherein the high temperature viscosity is 10 ^2.5 dPa. The temperature at s is less than or equal to 1535 °C. For example, in the non-alkali glass mentioned in Item 1 or 2 of the patent application, the high temperature viscosity is 10 ^2.5 dPa. The temperature at s is T ₁ (° C.), and when the strain point is T ₂ (° C.), the relationship of T ₁ -T ₂ ≦880 ° C is satisfied. For example, in the alkali-free glass mentioned in Item 1 or 2 of the patent application, the high temperature viscosity is 10 ⁴ dPa. The temperature at s is T ₃ (° C.), and when the softening point is T ₄ (° C.), the relationship of T ₃ -T ₄ ≦330 ° C is satisfied. The alkali-free glass according to claim 1 or 2, wherein the amount of erosion after immersion in a 10% aqueous HCl solution at 80 ° C for 24 hours is 5 μm or less. The alkali-free glass according to claim 1 or 2, wherein the amount of erosion after immersion in a 130-buffered hydrofluoric acid solution at 20 ° C for 30 minutes is 2 μm or less. The alkali-free glass according to claim 1 or 2, wherein after immersing in a 10% aqueous HCl solution at 80 ° C for 3 hours, the surface was visually observed, and no white turbidity or wrinkles were observed. The alkali-free glass according to claim 1 or 2, wherein the surface was observed by visual observation after immersing in a 63 buffered hydrofluoric acid solution at 20 ° C for 30 minutes, and no white turbidity or wrinkles were observed. The alkali-free glass according to claim 1 or 2, wherein the specific Young's modulus is 27 GPa/(g.cm ^-3 ) or more. An alkali-free glass substrate comprising the alkali-free glass according to any one of claims 1 to 16. The alkali-free glass substrate according to claim 17, wherein the alkali-free glass is formed by down-draw molding. The alkali-free glass substrate according to claim 18, wherein the pull-down is formed into an overflow down-draw. The alkali-free glass substrate according to any one of claims 17 to 19, wherein the alkali-free glass substrate is used for a display. The alkali-free glass substrate according to claim 20, wherein the display is a liquid crystal display. The alkali-free glass substrate according to claim 21, wherein the display is an amorphous germanium TFT liquid crystal display. The alkali-free glass substrate according to claim 17, wherein the alkali-free glass substrate has a size of 32 Å or more.