JP6709519B2 - Glass and glass substrate - Google Patents

Description

The present invention relates to a glass and a glass substrate, and specifically to a glass and a glass substrate suitable for an organic EL (OLED) display and a liquid crystal display. Further, it relates to a glass and a glass substrate suitable for an oxide TFT, a low temperature p-Si.TFT (LTPS) driven display.

Conventionally, glass substrates have been widely used as substrates for flat panel displays such as liquid crystal displays, hard disks, filters, and sensors. In recent years, in addition to conventional liquid crystal displays, OLED displays have been actively developed due to their self-luminous properties, high color reproducibility, high viewing angle, high-speed response, high definition, etc. Has been done. In addition, since the display of mobile devices such as smartphones is required to display a lot of information while having a small area, an ultra-high-definition screen is required. You will need it.

For such applications, an OLED display or a liquid crystal display driven by LTPS is suitable. An OLED display emits light when a current flows through an OLED element that constitutes a pixel. Therefore, a material having low resistance and high electron mobility is used for the driving TFT element. As this material, in addition to LTPS described above, attention is paid to an oxide TFT represented by IGZO (indium, gallium, zinc oxide). The oxide TFT has low resistance and high mobility, and can be formed at a relatively low temperature. Conventional p-Si TFTs, especially LTPS, form elements on a large-area glass substrate due to the instability of an excimer laser used when polycrystallizing an amorphous Si (a-Si) film. At this time, the TFT characteristics are likely to vary, and display unevenness on the screen is likely to occur in TV applications and the like. On the other hand, oxide TFTs are attracting attention as a powerful TFT forming material because they have excellent uniformity of TFT characteristics when forming elements on a large-area glass substrate, and some have already been put to practical use.

A glass substrate used for a high-definition display has many required characteristics. In particular, the following characteristics (1) to (5) are required.

(1) When the glass contains a large amount of alkali components, alkali ions diffuse during the heat treatment into the deposited semiconductor material, resulting in deterioration of the characteristics of the film. Therefore, the content of the alkali component (particularly, the Li component and the Na component) should be small, or should not be substantially contained.
(2) In the photolithography etching step, various chemicals such as acids and alkalis are used. Therefore, it has excellent chemical resistance.
(3) The glass substrate is heat-treated at several 100° C. in steps such as film formation and annealing. When the glass substrate is heat-shrunk during the heat treatment, pattern shift or the like is likely to occur. Therefore, it is difficult for heat shrinkage, especially high strain point.
(4) The coefficient of thermal expansion is close to that of a member (for example, a-Si, p-Si) formed on the glass substrate. For example, the coefficient of thermal expansion is 30 to 40×10 ⁻⁷ /° C. In addition, when the coefficient of thermal expansion is 40×10 ⁻⁷ /° C. or less, thermal shock resistance is also improved.
(5) The Young's modulus (or specific Young's modulus) is high in order to suppress defects caused by bending of the glass substrate.

Further, from the viewpoint of manufacturing a glass substrate, glass is required to have the following characteristics (6) and (7).
(6) It has excellent meltability in order to prevent melting defects such as bubbles, lumps, and striae.
(7) It has excellent devitrification resistance to avoid the generation of foreign matter in the glass substrate.

The present invention has been made in view of the above circumstances, and its technical problem is to satisfy the above-mentioned required characteristics (1) to (7), and a glass suitable for an LTPS, an OLED display driven by an oxide TFT element, and a liquid crystal display. And to create a glass substrate. Specifically, it is to devise a glass and a glass substrate having a low alkali component, a low density and a low thermal expansion coefficient, a high strain point and a high Young's modulus, and excellent devitrification resistance, meltability, moldability and the like. ..

As a result of repeating various experiments, the present inventors have found that the above technical problems can be solved by controlling the glass composition within a predetermined range, and propose as the present invention. That is, the glass of the present invention has a glass composition of, in terms of mass%, SiO ₂ 58 to 70%, Al ₂ O ₃ 16 to 25%, B ₂ O _{3 3 to} 8%, MgO 0 to 5%, CaO 3 to. 13%, SrO 0 to 6%, BaO 0 to 6%, ZnO 0 to 5%, ZrO ₂ 0 to 5%, TiO ₂ 0 to 5%, and P ₂ O ₅ 0 to 5%. To do.

As a glass satisfying the above-mentioned required characteristics (1) to (7), the present inventors have made SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ -RO (RO: alkaline earth metal oxide, MgO+CaO+SrO+BaO) based glass. If the content of SiO ₂ is 58% or more, the content of Al ₂ O ₃ is 16 to 25%, and the content of B ₂ O ₃ is 3 to 8%, the high strain point and good resistance It was found that both chemical properties can be compatible. It was also found that the Young's modulus, devitrification resistance, etc. are improved by optimizing the contents of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , and RO. Further, it was found that if the contents of B ₂ O ₃ , MgO, and CaO are optimized, the meltability, moldability, devitrification resistance, etc. are improved.

Secondly, the glass of the present invention has, as a glass composition, by mass% SiO ₂ 58 to 70%, Al ₂ O ₃ 16 to 25%, B ₂ O _{3 3 to} 8%, MgO 0 to 5%, CaO. 3 to 13%, SrO 0 to 6%, BaO 0 to 6%, ZnO 0 to 5%, ZrO ₂ 0 to 5%, TiO ₂ 0 to 5%, P ₂ O ₅ 0 to 5%, and substantially. It is characterized in that it does not contain Li and Na components, has a density of 2.43 to 2.52 g/cm ³ , and a strain point of 680° C. or higher. Here, "substantially does not contain" refers to a case where the content of the explicit component is 0.1% or less (preferably 0.05% or less), for example, "substantially does not contain a Li component". The term “” means that the Li component content is 0.1% or less (preferably 0.05% or less). "Density" can be measured by the well-known Archimedes method. “Strain point” refers to a value measured based on the method of ASTM C336.

Thirdly, the glass of the present invention contains substantially no Li component or Na component, has a density of 2.43 to 2.52 g/cm ³ , and a thermal expansion coefficient of 30 to 40×10 ⁻⁷ /° C., Young's modulus is 75 GPa or more, strain point is 680° C. or more and less than 740° C., temperature at 10 ^5.0 dPa·s is 1250° C. or less, temperature at 10 ^2.5 dPa·s is 1650° C. or less, liquid phase viscosity (liquid phase The linear viscosity) is 10 ^5.0 dPa·s or more. Here, the “coefficient of thermal expansion” refers to the average coefficient of thermal expansion measured in the temperature range of 30 to 380° C., and can be measured with a dilatometer, for example. “Young's modulus” refers to a value measured by a dynamic elastic modulus measuring method (resonance method) based on JIS R1602. The “temperature at 10 ^5.0 dPa·s” can be measured by, for example, a platinum ball pulling method. The “temperature at 10 ^2.5 dPa·s” can be measured by, for example, a platinum ball pulling method. "Liquid phase viscosity" refers to the viscosity of glass at a liquidus temperature (liquidus temperature) and can be measured by, for example, a platinum ball pulling method. "Liquid phase temperature" means that the glass powder passing through a standard sieve 30 mesh (500 μm) and remaining on 50 mesh (300 μm) was put into a platinum boat and kept in a temperature gradient furnace for 24 hours, and then the platinum boat was taken out, The temperature is the temperature at which devitrification (crystal foreign matter) is recognized in the glass.

Fourthly, the glass of the present invention has a glass composition of, in mass %, SiO ₂ 59 to 67%, Al ₂ O ₃ 17 to 22%, B ₂ O ₃ 4 to 7%, MgO 0 to 4%, CaO. 3-12%, SrO 0-5%, BaO 0.1-5%, ZnO 0-5%, ZrO ₂ 0-5%, TiO ₂ 0-5%, P ₂ O ₅ 0-5%, SnO ₂ It is preferable that the content is 0 to 5% and the Li component and the Na component are not substantially contained.

Fifthly, the glass of the present invention has a glass composition of, by mass %, SiO ₂ 60 to 65%, Al ₂ O ₃ 17 to 20%, B ₂ O ₃ 4 to 7%, MgO 0 to 3%, CaO. 4 to 10%, SrO 0 to 5%, BaO 0.1 to 5%, ZnO 0 to 1%, ZrO ₂ 0 to 1%, TiO ₂ 0 to 1%, P ₂ O ₅ 0 to 3%, SnO ₂ It is preferable to contain 0.01 to 1% and substantially not to contain Li component and Na component.

Sixth, the glass substrate of the present invention comprises any one of the above glasses.

Seventh, the glass substrate of the present invention is preferably used for an OLED display. Eighth, the glass substrate of the present invention is preferably used for a liquid crystal display.

Ninth, the glass substrate of the present invention is preferably used for a display driven by an oxide TFT.

It is a schematic diagram for explaining a measuring method of a heat shrinkage value.

The reason why the content of each component is regulated as described above will be described below. In the description of each component, the following% indication indicates mass%.

When the content of SiO ₂ is too small, chemical resistance, particularly acid resistance is lowered, the strain point is lowered, and it is difficult to reduce the density. On the other hand, when the content of SiO ₂ is too large, the high temperature viscosity becomes high, the meltability is likely to decrease, and devitrification of cristobalite is likely to occur, so that defects of devitrification foreign matter are likely to occur in the glass. The preferred upper limit content of SiO ₂ is 70%, 68%, 66%, 65%, especially 64%, and the preferred lower limit content is 58%, 59%, 60%, especially 61%. The most preferable content range is 61 to 64%.

When the content of Al ₂ O ₃ is too small, the strain point decreases, the heat shrinkage value increases, the Young's modulus decreases, and the glass substrate easily bends. On the other hand, when the content of Al ₂ O ₃ is too large, the BHF (buffered hydrofluoric acid) resistance is lowered, white turbidity is likely to occur on the glass surface, and the crack resistance is apt to be lowered. Further, devitrification of mullite or anorthite easily occurs in the glass. The preferred upper limit content of Al ₂ O ₃ is 25%, 23%, 22%, 21%, especially 20%, and the preferred lower limit content is 17%, 17.5%, especially 18%. The most preferable content range is 18 to 20%.

B ₂ O ₃ is a component that acts as a fluxing agent and reduces the viscosity to improve the meltability. The content of B ₂ O ₃ is preferably 3 to 8%, 3 to 7%, and particularly 4 to 7%. If the content of B ₂ O ₃ is too small, it does not act sufficiently as a flux, and the BHF resistance and crack resistance are likely to decrease. In addition, the liquidus temperature easily rises. On the other hand, if the content of B ₂ O ₃ is too large, the strain point, heat resistance, and acid resistance are likely to decrease. Especially, when the content of B ₂ O ₃ is 7% or more, the tendency becomes remarkable. Further, if the content of B ₂ O ₃ is too large, the Young's modulus is lowered, and the amount of bending of the glass substrate tends to be large.

Considering the balance between the strain point and the meltability, the mass ratio Al ₂ O ₃ /B ₂ O ₃ is preferably 1 to 5, 1.5 to 4.5, _{2 to} 4, and particularly 2.5 to 3.5. Is.

MgO is a component that lowers the high temperature viscosity without lowering the strain point and improves the meltability. Further, MgO has the effect of reducing the density most in RO, but if introduced in excess, the liquidus temperature tends to rise. Further, MgO is a component that easily reacts with BHF or hydrofluoric acid to form a product. This reaction product may adhere to the element on the surface of the glass substrate or may adhere to the glass substrate to cause the element and the glass substrate to become cloudy. Therefore, the content of MgO is preferably 0 to 5%, more preferably 0 to 4%, further preferably 0 to 3%, and most preferably 0 to 2.5%.

CaO is a component that, like MgO, lowers the high temperature viscosity without lowering the strain point and remarkably improves the meltability. When the content of CaO is too large, devitrification is likely to occur, the BHF resistance is lowered, and the reaction product adheres to the element on the surface of the glass substrate or adheres to the glass substrate. And may cause the glass substrate to become cloudy. The preferable upper limit content of CaO is 12%, 11%, 10.5%, particularly 10%, and the preferable lower limit content is 3%, 3.5%, particularly 4%. The most preferable content range is 4 to 10%.

SrO is a component that enhances chemical resistance and devitrification resistance, but if the proportion thereof in RO is too high, the meltability tends to decrease and the density and thermal expansion coefficient tend to increase. Therefore, the SrO content is preferably 0 to 6%, 0 to 5%, and particularly 0 to 4.5%.

BaO is a component that enhances chemical resistance and devitrification resistance, but if its content is too large, the density tends to increase. In addition, BaO has a poor effect of enhancing the meltability in RO. Since the SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —RO glass according to the present invention is generally difficult to melt, the meltability is increased from the viewpoint of supplying a high quality glass substrate inexpensively and in a large amount. Therefore, it is very important to reduce the defective rate due to bubbles, foreign substances, and the like. Therefore, the content of BaO is preferably 0 to 6%, 0.1 to 5%, and particularly 0.5 to 4%. In the SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —RO glass according to the present invention, when the content of SiO ₂ is reduced, the meltability is effectively improved, but the content of SiO ₂ is reduced. Then, the acid resistance is likely to decrease, and the density and the thermal expansion coefficient are likely to increase.

MgO, SrO, and BaO have a property of improving crack resistance as compared with CaO. Therefore, the content of MgO+SrO+BaO (the total content of MgO, SrO and BaO) is preferably 2% or more, 3% or more, and particularly more than 3%. However, if the content of MgO+SrO+BaO is too large, the density and the thermal expansion coefficient tend to increase. Therefore, the content of MgO+SrO+BaO is preferably 9% or less and 8% or less.

When RO is mixed and introduced, the liquidus temperature is significantly lowered, and it becomes difficult for crystalline foreign matter to occur in the glass, and the meltability and moldability are improved. However, if the RO content is too high, the density increases and it becomes difficult to reduce the weight of the glass substrate. Therefore, the content of RO is preferably less than 15%, less than 14%, and particularly less than 2 to 13%.

In order to optimize the mixing ratio of RO, the mass ratio CaO/(MgO+SrO+BaO) is preferably 0.7 or more, 0.8 or more, 0.9 or more, particularly 1 or more, and the mass ratio CaO/MgO is It is preferably 2 or more, 3 or more, 4 or more, and particularly 5 or more.

ZnO is a component that improves the meltability and BHF resistance, but if its content is too large, the glass tends to devitrify or the strain point decreases, making it difficult to ensure heat resistance. .. Therefore, the content of ZnO is preferably 0 to 5%, particularly 0 to 1%.

ZrO ₂ is a component that enhances chemical durability, but when the amount of ZrO ₂ introduced is large, devitrification pits of ZrSiO ₄ are likely to occur. The preferable lower limit content of ZrO ₂ is 1%, 0.5%, 0.3%, 0.2%, particularly 0.1%, and 0.005% or more may be introduced from the viewpoint of chemical durability. preferable. The most preferable content range is 0.005-0.1%. ZrO ₂ may be introduced from the raw material or may be introduced by elution from the refractory.

TiO ₂ has the effect of lowering the viscosity at high temperature to enhance the meltability and chemical durability, but if the amount of TiO ₂ introduced is excessive, the ultraviolet transmittance tends to decrease. The content of TiO ₂ is preferably 3% or less, 1% or less, 0.5% or less, 0.1% or less, 0.05% or less, and particularly 0.03% or less. If a very small amount of TiO ₂ is introduced (for example, 0.001% or more), the effect of suppressing coloring due to ultraviolet rays can be obtained.

P ₂ O ₅ is a component that raises the strain point and is also a component that can suppress the precipitation of devitrification crystals of alkaline earth aluminosilicates such as anorthite. However, when P ₂ O ₅ is contained in a large amount, the glass is likely to undergo phase separation. The content of P ₂ O ₅ is preferably 0 to 5%, 0 to 3%, 0 to 2%, 0 to 1%, and particularly 0 to 0.5%.

As the fining agent, As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , Fe ₂ O ₃ , CeO ₂ , F ₂ , Cl ₂ , C, or a metal powder such as Al or Si can be used. .. The total content of these is preferably 3% or less.

Since As ₂ O ₃ and Sb ₂ O ₃ are environmentally hazardous chemical substances, it is desirable not to use them as much as possible. The contents of As ₂ O ₃ and Sb ₂ O ₃ are less than 0.3%, less than 0.1%, less than 0.09%, less than 0.05%, less than 0.03%, less than 0.01%, respectively. , Less than 0.005%, particularly preferably less than 0.003%.

SnO ₂ has a function as a fining agent for reducing bubbles in glass, and has an effect of maintaining a relatively high ultraviolet transmittance when coexisting with Fe ₂ O ₃ or FeO. On the other hand, if the content of SnO ₂ is too large, devitrification spots of SnO ₂ are likely to occur in the glass. The preferable upper limit content of SnO ₂ is 0.5%, 0.4%, particularly 0.3%, and the preferable lower limit content is 0.01%, 0.05%, particularly 0.1%. The most preferable content range is 0.1 to 0.4%. Further, with respect to the content of _Fe 2 _{O 3} or FeO in terms _{of Fe} 2 _{O 3} is 0.01 to 0.05%, is introduced to SnO ₂ 0.01 to 0.5% foam quality and UV transmittance The rate can be increased. Here, “Fe ₂ O ₃ conversion” refers to a value obtained by converting the total Fe amount into the Fe ₂ O ₃ amount regardless of the valence.

When SnO ₂ is included in an amount of 0.01 to 0.5%, the glass tends to be colored when the content of Rh ₂ O ₃ is too large. Note that Rh ₂ O ₃ may be mixed in from the platinum manufacturing container. The content of Rh ₂ O ₃ is preferably 0 to 0.0005%, more preferably 0.00001 to 0.0001%.

SO ₃ is a component that is mixed as an impurity from the raw material, but if the content of SO ₃ is too large, bubbles called reboil may be generated during melting or molding, which may cause defects in the glass. is there. The preferable upper limit content of SO ₃ is 0.005%, 0.003%, 0.002%, particularly 0.001%, and the preferable lower limit content is 0.0001%. The most preferable content range is 0.0001% to 0.001%.

Iron is a component that is mixed as an impurity from the raw material, but if the content of iron is too large, the ultraviolet transmittance may decrease. When the ultraviolet ray transmittance is lowered, problems may occur in a photolithography step for manufacturing a TFT or a liquid crystal aligning step by ultraviolet rays. Therefore, the preferable upper limit content of iron is 0.001% in terms of Fe ₂ O ₃ , and the preferable lower limit content is 0.05% or 0.04% in terms of Fe ₂ O _3. , 0.03%, especially 0.02%. The most preferable content range is 0.001% to 0.02%.

Cr ₂ O ₃ is a component mixed as an impurity from the raw material, but when the content of Cr ₂ O ₃ is too large, light is incident from the end surface of the glass substrate and scattered light is used to inspect foreign substances inside the glass substrate. When it is performed, it becomes difficult for light to pass therethrough, which may cause a problem in the foreign matter inspection. Particularly, when the substrate size is 730 mm×920 mm or more, this problem is likely to occur. Moreover, when the plate thickness of the glass substrate is small (for example, 0.5 mm or less, 0.4 mm or less, particularly 0.3 mm or less), the amount of light incident from the end surface of the glass substrate decreases, so the Cr ₂ O ₃ content is restricted. The significance of doing this will increase. The preferable upper limit content of Cr ₂ O ₃ is 0.001%, 0.0008%, 0.0006%, 0.0005%, particularly 0.0003%, and the preferable lower limit content is 0.00001%. The most preferable content range is 0.00001 to 0.0003%.

Alkali components, especially Li components and Na components (for example, Li ₂ O and Na ₂ O) deteriorate the characteristics of various films and semiconductor elements formed on the glass substrate, and therefore their contents are preferably reduced. However, it is desirable that they are not substantially contained.

A preferable glass composition range can be obtained by combining the preferable content ranges of the respective components. Among them, particularly preferable glass composition ranges are as follows.
(1) As a glass composition, by mass %, SiO ₂ 59 to 67%, Al ₂ O ₃ 17 to 22%, B ₂ O ₃ 4 to 7%, MgO 0 to 4%, CaO 3 to 10%, SrO 0. -5%, BaO 0.1-5%, ZnO 0-5%, ZrO ₂ 0-5%, TiO ₂ 0-5%, P ₂ O ₅ 0-5%, SnO ₂ 0-5%, Substantially no Li component or Na component is contained.
(2) As a glass composition, by mass %, SiO ₂ 60 to 65%, Al ₂ O ₃ 17 to 20%, B ₂ O ₃ 4 to 7%, MgO 0 to 3%, CaO 4 to 10%, SrO 0. _{~5%, BaO 0.1~5%, 0~1} % ZnO, ZrO 2 0~1%, TiO 2 0~1%, P 2 O 5 0~3%, SnO 2 0.01~1% content However, it does not substantially contain a Li component and a Na component.

In recent years, demands for weight reduction have been increasing in mobile flat panel displays such as OLED displays and liquid crystal displays, and glass substrates have also been required to reduce weight. In order to satisfy this requirement, it is desirable to reduce the weight of the glass substrate by reducing the density. The density is preferably 2.52 g/cm ³ or less, 2.51 g/cm ³ or less, 2.50 g/cm ³ or less, 2.49 g/cm ³ or less, and particularly 2.48/cm ³ or less. On the other hand, if the density is too low, the melting temperature is likely to increase and the liquidus viscosity is likely to decrease, so that the productivity of the glass substrate is likely to decrease. In addition, the strain point also tends to decrease. Therefore, the density is preferably 2.43 g / cm ³ or more, 2.44 g / cm ³ or more, in particular 2.45 g / cm ³ or more.

In the glass and glass substrate of the present invention, the coefficient of thermal expansion is preferably 30 to 40×10 ⁻⁷ /° C., 32 to 39×10 ⁻⁷ /° C., 33 to 38×10 ⁻⁷ /° C., and particularly 34 to 37. ×10 ⁻⁷ /°C. This makes it easier to match the coefficient of thermal expansion of the member (eg, a-Si, p-Si) formed on the glass substrate.

In an OLED display or a liquid crystal display, a large-area glass substrate (for example, 730×920 mm or more, 1100×1250 mm or more, particularly 1500×1500 mm or more) is used, and a thin glass substrate (for example, a plate thickness of 0.5 mm is used. Hereinafter, 0.4 mm or less, particularly 0.3 mm or less) tends to be used. When the glass substrate has a large area and a thin wall, bending due to its own weight becomes a serious problem. In order to reduce the bending of the glass substrate, it is necessary to increase the specific Young's modulus of the glass substrate. The specific Young's modulus is preferably 30.0 GPa/g·cm ⁻³ or more, 30.5 GPa/g·cm ⁻³ or more, 31.0 GPa/g·cm ⁻³ or more, and particularly 31.5 GPa/g·cm ^−3. That is all. Further, when the glass substrate has a large area and a thin wall, the warpage of the glass substrate becomes a problem after a heat treatment process on a surface plate or a film formation process of various metal films, oxide films, semiconductor films, organic films, and the like. Become. In order to reduce the warp of the glass substrate, it is effective to increase the Young's modulus of the glass substrate. Young's modulus is preferably 75 GPa or more, and particularly 76 GPa or more.

Currently, in LTPS used for ultra-high definition mobile displays, the process temperature is about 400 to 600°C. In order to suppress heat shrinkage at this process temperature, the strain point is preferably 680°C or higher, 690°C or higher, and particularly 700°C or higher.

Recently, OLED displays are also used in mobile and TV applications. As the driving TFT element for this application, an oxide TFT is drawing attention in addition to the above LTPS. Until now, oxide TFTs have been manufactured by a temperature process of 300 to 400° C., which is equivalent to that of a-Si, but more stable element characteristics can be obtained by annealing at a heat treatment temperature higher than conventional ones. I understand. The heat treatment temperature is about 400 to 600° C., and a glass substrate with low heat shrinkage is required even in this application.

In the glass and glass substrate of the present invention, when the temperature is raised from room temperature (25° C.) to 500° C. at a rate of 10° C./minute, held at 500° C. for 1 hour, and then lowered to room temperature at a rate of 10° C./minute. The heat shrinkage value is preferably 30 ppm or less, 25 ppm or less, 23 ppm or less, 22 ppm or less, and particularly 21 ppm or less. With this configuration, even if the heat treatment is performed in the LTPS manufacturing process, a problem such as pixel pitch deviation is less likely to occur. If the heat shrinkage value is too small, the productivity of glass tends to decrease. Therefore, the heat shrinkage value is preferably 5 ppm or more, particularly 8 ppm or more. In addition to increasing the strain point, the heat shrinkage value can be reduced by lowering the cooling rate during molding.

In the overflow down draw method, molten glass flows down the surface of a wedge-shaped refractory (or a refractory coated with a platinum group metal) and joins at the lower end of the wedge to form a plate. In the slot down draw method, for example, a ribbon-shaped molten glass is made to flow down from a platinum group metal pipe having a slit-shaped opening, cooled, and shaped into a plate. If the temperature of the molten glass in contact with the molding apparatus is too high, the molding apparatus will be deteriorated and the productivity of the glass substrate will be likely to decrease. Therefore, the temperature at a high temperature viscosity of 10 ^5.0 dPa·s is preferably 1300° C. or lower, 1280° C. or lower, 1270° C. or lower, 1260° C. or lower, 1250° C. or lower, 1240° C. or lower, particularly 1230° C. or lower. The temperature at a high temperature viscosity of 10 ^5.0 dPa·s corresponds to the temperature of the molten glass during molding.

_{SiO 2 -Al 2 O 3 -B 2} O 3 -RO based glass according to the present invention are generally difficult to melt. Therefore, improvement of meltability becomes a problem. When the meltability is increased, the defective rate due to bubbles, foreign matters, etc. is reduced, so that a large amount of high-quality glass substrates can be supplied at low cost. On the other hand, when the viscosity of the glass in the high temperature range is too high, it becomes difficult to promote defoaming in the melting step. Therefore, the temperature at a high temperature viscosity of 10 ^2.5 dPa·s is preferably 1650° C. or lower, 1640° C. or lower, 1630° C. or lower, 1620° C. or lower, and particularly 1610° C. or lower. The temperature at a high temperature viscosity of 10 ^2.5 dPa·s corresponds to the melting temperature, and the lower the temperature, the better the melting property.

When molding by the down draw method or the like, devitrification resistance is important. Considering the molding temperature of the SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —RO glass according to the present invention, the liquidus temperature is preferably 1250° C. or lower, 1230° C. or lower, 1220° C. or lower, 1210° C. or lower, The temperature is 1200°C or lower, particularly 1190°C or lower. The liquidus viscosity is preferably 10 ^5.0 dPa·s or more, 10 ^5.2 dPa·s or more, 10 ^5.3 dPa·s or more, 10 ^5.4 dPa·s or more, 10 ^5.5 dPa·s or more. -S or more, especially 10 ^5.6 dPa-s or more.

A transparent conductive film, an insulating film, a semiconductor film, a metal film, and the like are formed on a glass substrate used for a high-definition display. Further, various circuits and patterns are formed by a photolithography etching process. In these film forming step and photolithography etching step, the glass substrate is subjected to various chemical treatments. For example, in a TFT type active matrix liquid crystal display, an insulating film or a transparent conductive film is formed on a glass substrate, and a large number of TFTs (thin film transistors) of amorphous silicon or polycrystalline silicon are formed on the glass substrate by a photolithography etching process. It In such a process, various chemical liquid treatments such as sulfuric acid, hydrochloric acid, an alkaline solution, hydrofluoric acid and BHF are applied. In particular, BHF is widely used for etching an insulating film, but BHF easily corrodes the glass substrate and makes the surface of the glass substrate cloudy, and the reaction product thereof clogs the filter during the manufacturing process. , There is a risk of adhesion on the glass substrate. From the above circumstances, it is important to enhance the chemical resistance of the glass substrate.

The glass and glass substrate of the present invention are preferably formed by the overflow down draw method. The overflow down draw method is a method of forming a glass substrate by causing molten glass to overflow from both sides of a wedge-shaped refractory material, and allowing the overflowed molten glass to join at the lower ends of the wedge-shaped materials while drawing downward. In the overflow down draw method, the surface to be the surface of the glass substrate does not come into contact with the refractory material, and is molded in a free surface state. Therefore, an unpolished glass substrate having a good surface quality can be manufactured at low cost, and it is easy to increase the area and reduce the thickness. The refractory material used in the overflow downdraw method is not particularly limited as long as it can achieve desired dimensions and surface accuracy. Further, the method of applying a force when performing the downward stretch molding is not particularly limited. For example, a method of rotating and stretching a heat-resistant roll having a sufficiently large width in contact with the glass may be adopted, or a plurality of pairs of heat-resistant rolls may be contacted only in the vicinity of the end face of the glass. You may employ|adopt the method of making it extend.

In addition to the overflow down draw method, the glass substrate can be formed by, for example, a down draw method (slot down method, redraw method, etc.), a float method, or the like.

In the glass and glass substrate of the present invention, the plate thickness (wall thickness) is not particularly limited, but is preferably 0.5 mm or less, 0.4 mm or less, 0.35 mm or less, and particularly 0.3 mm or less. The smaller the plate thickness, the easier it is to reduce the weight of the device. On the other hand, the smaller the plate thickness, the more easily the glass substrate bends. However, since the glass and glass substrate of the present invention have a high Young's modulus and a specific Young's modulus, defects due to the bending hardly occur. The plate thickness can be adjusted by the flow rate during glass production, the plate drawing speed, and the like.

In the glass and glass substrate of the present invention, the strain point can be increased by decreasing the β-OH value. The β-OH value is preferably 0.5/mm or less, 0.45/mm or less, 0.4/mm or less, and particularly 0.35/mm or less. If the β-OH value is too large, the strain point tends to decrease. Note that if the β-OH value is too small, the meltability tends to decrease. Therefore, the β-OH value is preferably 0.01/mm or more, particularly 0.05/mm or more.

The following method is mentioned as a method of lowering the β-OH value. (1) Select a raw material having a low water content. (2) Add components (Cl, SO _3, etc.) that reduce the amount of water in the glass. (3) The water content in the furnace atmosphere is reduced. (4) N ₂ bubbling is performed in the molten glass. (5) Adopt a small melting furnace. (6) Increase the flow rate of the molten glass. (7) The electric melting method is adopted.

Here, “β-OH value” refers to a value obtained by measuring the transmittance of glass using FT-IR and using the following formula.
β-OH value=(1/X)log(T ₁ /T ₂ ).
X: Glass wall thickness (mm)
T ₁ : transmittance (%) at reference wavelength 3846 cm ^-1
T _2: minimum transmittance in the vicinity of the hydroxyl group absorption wavelength 3600 cm ^-1 (%)

The glass and glass substrate of the present invention are preferably used for an OLED display. Although OLEDs are generally on the market, cost reduction by mass production is strongly desired. The glass and glass substrate of the present invention are excellent in productivity and can be easily made large in area and thinned, so that such requirements can be appropriately satisfied.

Hereinafter, the present invention will be described in detail based on examples. The following embodiments are merely examples. The present invention is not limited to the following examples.

Tables 1 to 3 show Examples of the present invention (Sample Nos. 1 to 30).

Each sample was prepared as follows. First, a glass batch prepared by mixing glass raw materials so as to have the glass composition shown in the table was put into a platinum crucible and melted at 1600° C. for 24 hours. Upon melting the glass batch, it was homogenized by stirring with a platinum stirrer. Next, the molten glass was cast onto a carbon plate and formed into a plate shape. For each of the obtained samples, the density, thermal expansion coefficient, Young's modulus, specific Young's modulus, strain point, softening point, temperature at high temperature viscosity 10 ^5.0 dPa·s, temperature at high temperature viscosity 10 ^2.5 dPa·s, The liquidus temperature, liquidus viscosity log ηTL, and chemical resistance were evaluated.

The density is a value measured by the well-known Archimedes method.

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

Young's modulus refers to a value measured by a dynamic elastic modulus measurement method (resonance method) based on JIS R1602, and specific Young's modulus is a value obtained by dividing Young's modulus by density.

The strain point and the softening point are values measured based on the method of ASTM C336.

The temperature at a high temperature viscosity of 10 ^5.0 dPa·s and 10 ^2.5 dPa·s is a value measured by a platinum ball pulling method.

Next, each sample was crushed, passed through a standard sieve 30 mesh (500 μm), and the glass powder remaining on 50 mesh (300 μm) was put in a platinum boat and kept in a temperature gradient furnace for 24 hours, and then the platinum boat was placed The liquid phase temperature was determined as the temperature at which devitrification (crystal foreign matter) was observed in the glass. Further, the viscosity of the glass at the liquidus temperature was measured by the platinum ball pull-up method, and this was taken as the liquidus viscosity.

Moreover, after chemically polishing both surfaces of each sample, and immersing it in a chemical solution set to a predetermined concentration at a predetermined temperature for a predetermined time, observing the surface of the obtained sample, chemical resistance Was evaluated. Specifically, after the chemical treatment, the glass surface becomes cloudy or has cracks, "x", weak cloudiness or roughness is seen as "△", and no change at all is marked as "○". did. As conditions for chemical treatment, acid resistance was evaluated by treatment with 10% hydrochloric acid at 80° C. for 3 hours, and BHF resistance was evaluated by treatment with a well-known 130BHF solution at 20° C. for 30 minutes.

Further, the sample No. With respect to 12, 20, 23, and 24, a glass substrate having a plate thickness of 0.5 mm was prototyped by the overflow downdraw method, and the heat shrinkage value thereof was measured. First, a sample of 30 mm×160 mm×0.5 mm was cut out from a glass substrate, and the heat shrinkage value of each sample was measured in the following manner. As shown in FIG. 1A, two linear marks M1 and M2 are written at predetermined intervals on a predetermined portion of the glass substrate 25, and then, as shown in FIG. By cutting the glass substrate 25 in different directions, glass plate pieces 25a and glass plate pieces 25b were obtained. Then, only the glass plate piece 25a was heated from room temperature to 500° C. at a rate of 10° C./minute, held at 500° C. for 1 hour, and then cooled to room temperature at a rate of 10° C./minute. After that, as shown in FIG. 1C, the glass plate piece 25a that has been heat-treated and the glass plate piece 25b that has not been heat-treated are aligned and fixed with the adhesive tape T, and the mark M1 of the glass plate piece 25a is fixed. , M2 and the marks M1 and M2 of the glass plate piece 25b were measured, and the heat shrinkage value was calculated based on the following mathematical formula 1.

In Formula 1, l ₀ is the distance between the marks M on the glass substrate 25, l ₁ is the distance between the mark M1 on the glass plate piece 25a and the mark M1 on the glass plate piece 25b, and l ₂ is the glass plate piece It is the distance between the mark M2 of 25a and the mark M2 of the glass plate piece 25b.

Sample No. Each of 1 to 30 has a density of 2.43 to 2.52 g/cm ³ and can reduce the weight of the glass substrate. Further, the coefficient of thermal expansion is 30 to 40×10 ⁻⁷ /° C., the strain point is 680° C. or higher and lower than 740° C., and the thermal shrinkage value is also small. Further, the Young's modulus is 75 GPa or more, and the specific Young's modulus is 30 GPa/(g/cm ³ ) or more, so that bending and deformation hardly occur. Further, the temperature at high temperature viscosity 10 ^5.0 dPa·s is 1250° C. or lower, the temperature at 10 ^2.5 dPa·s is 1650° C. or lower, the liquidus temperature is 1300° C. or lower, and the liquidus viscosity is 10 ^5.0. Since it is dPa·s or more, it has excellent meltability and moldability and is suitable for mass production. Furthermore, it has excellent chemical resistance.

INDUSTRIAL APPLICABILITY The glass and glass substrate of the present invention are low in alkali components, low in density and coefficient of thermal expansion, high in strain point and Young's modulus, and excellent in devitrification resistance, meltability, moldability and the like. Therefore, the glass and glass substrate of the present invention are suitable for displays such as OLED displays and liquid crystal displays, and are suitable for displays driven by LTPS and oxide TFTs.

Claims (9)

As a glass composition, SiO ₂ 58 to 70%, Al ₂ O ₃ 19.1 to 25%, B ₂ O _{3 3 to} 8%, MgO 0 to 5%, CaO 3 to 13%, SrO 0 to 0% by mass. _{6%, BaO 0~6%, 0~1} % ZnO, ZrO 2 0~5%, TiO 2 0.001~0.1%, glass, characterized in that it contains P ₂ O 5 0~5% .. The glass according to claim 1, which does not substantially contain Li and Na components, has a density of 2.43 to 2.52 g/cm ³ and a strain point of 680° C. or higher. The thermal expansion coefficient is 30 to 40×10 ⁻⁷ /° C., the Young's modulus is 75 GPa or more, the strain point is 680° C. or more and less than 740° C., and the temperature at 10 ^5.0 dPa·s is 1250° C. or less, 10 ^2.5 dPa·s. The glass according to claim 1 or 2, wherein the temperature at s is 1650°C or lower, and the liquidus viscosity is 10 ^5.0 dPa·s or higher. As a glass composition, by mass %, SiO ₂ 59-67%, Al ₂ O ₃ 19.1-22%, B ₂ O ₃ 4-7%, MgO 0-4%, CaO 3-10%, SrO 0- _{5%, BaO 0.1~5%, 0~1} % ZnO, ZrO 2 0~5%, TiO 2 0.005~0.05%, P 2 O 5 0~5%, SnO 2 0~5% The glass according to any one of claims 1 to 3, wherein the glass contains and does not substantially contain a Li component and a Na component. As a glass composition, by mass %, SiO ₂ 60 to 65%, Al ₂ O ₃ 19.1 to 20%, B ₂ O ₃ 4 to 7%, MgO 0 to 3%, CaO 4 to 10%, SrO 0 to 0%. _{5%, BaO 0.1~5%, 0~1} % ZnO, ZrO 2 0~1%, TiO 2 0.01~0.03%, P 2 O 5 0~3%, SnO 2 0.01~ The glass according to any one of claims 1 to 4, wherein the glass contains 1% and does not substantially contain a Li component and a Na component. A glass substrate comprising the glass according to any one of claims 1 to 5. The glass substrate according to claim 6, which is used for an OLED display. The glass substrate according to claim 6, which is used for a liquid crystal display. The heat shrinkage value is 30 ppm or less when the temperature is raised from room temperature (25° C.) to 500° C. at a rate of 10° C./min, held at 500° C. for 1 hour and then cooled to room temperature at a rate of 10° C./min. The glass substrate according to claim 6, wherein the glass substrate is a glass substrate.