JP6955522B2 - Glass and glass substrate - Google Patents

Description

The present invention relates to glass and glass substrates, and specifically to glass and glass substrates suitable for organic EL (OLED) displays and liquid crystal displays. Further, the present invention 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, sensors, and the like. In recent years, in addition to conventional liquid crystal displays, OLED displays have been actively developed for reasons such as self-luminous, high color reproducibility, high viewing angle, high-speed response, and high definition, and some have already been put into practical use. Has been done. In addition, since the display of mobile devices such as smartphones is required to display a large amount of information even though it has a small area, an ultra-high-definition screen is required, and a moving image is also displayed, so that high-speed response is also possible. You will need it.

For such applications, an OLED display or a liquid crystal display driven by LTPS is suitable. The OLED display emits light when a current flows through the OLED elements constituting the pixels. Therefore, a material having low resistance and high electron mobility is used as the drive TFT element. As this material, in addition to the above LTPS, oxide TFTs typified by IGZO (indium, gallium, zinc oxide) are attracting attention. The oxide TFT has low resistance, 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 that time, the TFT characteristics were liable to vary, and in TV applications and the like, screen display unevenness was liable to occur. On the other hand, oxide TFTs are attracting attention as a promising TFT forming material because they are excellent in homogeneity of TFT characteristics when forming an element on a glass substrate having a large area, and some of them have already been put into practical use.

Glass substrates used in high-definition displays have many required characteristics. In particular, the following characteristics (1) to (5) are required.

(1) If the amount of alkaline components in the glass is large, alkaline ions diffuse into the semiconductor material on which the alkali ions are formed during the heat treatment, which causes deterioration of the characteristics of the film. Therefore, the content of the alkaline component (particularly the Li component and the Na component) is low or substantially not contained.
(2) In the photolithography etching process, various chemical solutions such as acids and alkalis are used. Therefore, it has excellent chemical resistance.
(3) The glass substrate is heat-treated to several hundreds of degrees Celsius in steps such as film formation and annealing. If the glass substrate is thermally shrunk during the heat treatment, pattern misalignment or the like is likely to occur. Therefore, it is difficult to shrink due to heat, and the strain point is particularly high.
(4) The coefficient of thermal expansion is close to that of the member (for example, a-Si, p-Si) formed on the glass substrate. For example, the coefficient of thermal expansion is 30-40 × ^10-7 / ° C. When the coefficient of thermal expansion is 40 × 10 ^-7 / ° C. or less, the thermal impact resistance is also improved.
(5) 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, the glass is required to have the following characteristics (6) and (7).
(6) Excellent meltability in order to prevent melting defects such as bubbles, bumps, and veins.
(7) 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 glass suitable for OLED displays and liquid crystal displays driven by LTPS and oxide TFT elements, satisfying the above required characteristics (1) to (7). And to create a glass substrate. Specifically, it is to create a glass and a glass substrate having a small amount of alkaline components, a low density and a coefficient of thermal expansion, a high strain point and 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 restricting the glass composition within a predetermined range, and propose it as the present invention. That is, the glass of the present invention has a glass composition, in _{mass%, SiO 2 58~70%, Al} 2 O 3 16~25%, B 2 O 3 3~8%, 0~5% MgO, CaO 3~ _{13%, SrO 0~6%, BaO} 0~6%, 0~5% ZnO, ZrO 2 0~5%, TiO 2 0~5%, and characterized in that it contains _P 2 O 5 _0~5% do.

The present inventors have, as a glass satisfying the above required characteristics _{(1) ~ (7),} SiO 2 -Al 2 O 3 -B 2 O 3 -RO (RO: alkaline earth metal oxides, MgO + CaO + SrO + BaO ) -based glass Focusing on, if _{the content of SiO 2} is regulated to 58% or more, _{the content of Al 2} O ₃ is regulated to 16 to 25%, and the content of B ₂ O ₃ is regulated to 3 to 8%, a high strain point and good resistance to strain are obtained. It was found that both chemical properties can be achieved. It was also _{found that if the contents of SiO 2} , Al ₂ O ₃ , B ₂ O ₃ , and RO are optimized, Young's modulus, devitrification resistance, and the like are improved. Furthermore, _{it has been found that if the contents of B 2} O ₃ , MgO, and CaO are optimized, the meltability, moldability, devitrification resistance, and the like are improved.

Second, the glass of the present invention has a glass composition, in _{mass%, SiO 2 58~70%, Al} 2 O 3 16~25%, B 2 O 3 3~8%, 0~5% MgO, CaO _{3~13%, SrO 0~6%, BaO} 0~6%, 0~5% ZnO, containing _{ZrO 2 0~5%, TiO 2 0~5} %, the _P 2 O 5 _0~5%, substantially It is characterized in that it does not contain a Li component and a Na component, has a density of 2.43 to 2.52 g / cm ³ , and has a strain point of 680 ° C. or higher. Here, "substantially free" refers to the case where the content of the explicit component is 0.1% or less (preferably 0.05% or less), for example, "substantially free of Li component". "" Refers to the case where the content of the Li component 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 ASTM C336 method.

Third, 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 has a coefficient of thermal expansion of 30 to 40 × ^10-7 / ° C. Young ratio 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 by, for example, a dilatometer. “Young's modulus” refers to a value measured by a dynamic elastic modulus measurement method (resonance method) based on JIS R1602. The " ^{temperature at 10 5.0} dPa · s" can be measured by, for example, the platinum ball pulling method. The " ^{temperature at 10 2.5} dPa · s" can be measured by, for example, the platinum ball pulling method. The "liquid phase viscosity" refers to the viscosity of glass at the liquid phase temperature (liquid phase line temperature), and can be measured by, for example, the platinum ball pulling method. For the "liquid phase temperature", the glass powder that has passed through a standard sieve of 30 mesh (500 μm) and remains in 50 mesh (300 μm) is placed in a platinum boat, held in a temperature gradient furnace for 24 hours, and then the platinum boat is taken out. The temperature is such that devitrification (crystal foreign matter) is observed in the glass.

Fourth, the glass of the present invention has a glass composition of SiO ₂ 59 to 67%, Al ₂ O ₃ 17 to 22%, B ₂ O ₃ 4 to 7%, MgO 0 to 4%, CaO in terms of glass composition. _{3~12%, SrO 0~5%, BaO} 0.1~5%, 0~5% ZnO, 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 substantially no Li component or Na component is contained.

Fifth, the glass of the present invention has a glass composition of SiO ₂ 60 to 65%, Al ₂ O ₃ 17 to 20%, B ₂ O ₃ 4 to 7%, MgO 0 to 3%, CaO in terms of glass composition. _{4~10%, 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 It is preferable that the content is 0.01 to 1% and substantially no Li component or Na component.

Sixth, the glass substrate of the present invention is characterized by including any 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 an oxide TFT-driven display.

It is the schematic for demonstrating the method of measuring a heat shrinkage value.

As described above, the reason for restricting the content of each component will be described below. In the description of each component, the following% indication indicates mass%.

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

If _{the content of Al 2} O ₃ is too small, the strain point is lowered, the heat shrinkage value is increased, the Young's modulus is lowered, and the glass substrate is easily bent. On the other hand, if _{the content of Al 2} O ₃ is too large, the BHF (buffered hydrofluoric acid) resistance tends to decrease, the glass surface tends to become cloudy, and the crack resistance tends to decrease. Further, devitrification of mullite or anorthite is likely to occur in the glass. The preferred upper limit content of Al ₂ O ₃ is 25%, 23%, 22%, 21%, particularly 20%, and the preferred lower limit content is 17%, 17.5%, particularly 18%. The most preferable content range is 18 to 20%.

B ₂ O ₃ is a component that acts as a flux to reduce viscosity and improve 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 BHF resistance and crack resistance tend to decrease. In addition, the liquidus temperature tends to rise. On the other hand, if _{the content of B 2} O ₃ is too large, the strain point, heat resistance, and acid resistance tend to decrease. In particular, 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 tends to decrease and the amount of bending of the glass substrate tends to increase.

Considering the balance between strain point and 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, especially 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 lowering the density most in RO, but if it is introduced excessively, 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 adhere to the glass substrate to make the element or the glass substrate 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%.

Like MgO, CaO is a component that lowers the high-temperature viscosity without lowering the strain point and remarkably improves the meltability. If the CaO content is too high, devitrification is likely to occur, and the BHF resistance is lowered, so that the reaction product adheres to the element on the surface of the glass substrate or adheres to the glass substrate. And the glass substrate may become cloudy. The preferred upper limit content of CaO is 12%, 11%, 10.5%, particularly 10%, and the preferred 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 of SrO is too high in RO, the meltability tends to decrease and the density and coefficient of thermal expansion tend to increase. Therefore, the content of SrO 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 the content is too large, the density tends to increase. In addition, BaO has a poor effect of increasing 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 improved from the viewpoint of supplying a high-quality glass substrate in a large amount at low cost. Therefore, it is very important to reduce the defective rate due to bubbles, foreign substances, etc. 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 tends to decrease, and the density and the coefficient of thermal expansion tend to increase.

MgO, SrO, and BaO have the property of increasing crack resistance as compared with CaO. Therefore, the content of MgO + SrO + BaO (the total amount 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 coefficient of thermal expansion 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, crystalline foreign substances are less likely to be generated in the glass, and meltability and moldability are improved. However, if the RO content is too high, the density increases, making it difficult to reduce the weight of the glass substrate. Therefore, the RO content is preferably less than 15%, less than 14%, especially less than 2-13%.

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 meltability and BHF resistance, but if the content is too large, the glass tends to be devitrified and the strain point is lowered, making it difficult to secure heat resistance. .. Therefore, the ZnO content is preferably 0 to 5%, particularly 0 to 1%.

ZrO ₂ is a component that enhances chemical durability, but if the amount introduced is large, devitrification of _{ZrSiO 4 is 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 to 0.1%. ZrO ₂ may be introduced from the raw material or by elution from the refractory.

TiO ₂ has the effect of lowering the high-temperature viscosity, increasing the meltability, and increasing the chemical durability, but when the amount 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. When a very _{small amount of TiO 2} is introduced (for example, 0.001% or more), the effect of suppressing coloration due to ultraviolet rays can be obtained.

P ₂ O ₅ is a component that enhances the strain point and is a component that can suppress the precipitation of devitrified crystals of alkaline earth aluminosilicate type such as anorthite. However, if a _{large amount of P 2} O ₅ is contained, the glass tends to be phase-separated. 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 clarifying agent, _{metal powders such as As 2} O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , Fe ₂ O ₃ , CeO ₂ , F ₂ , Cl ₂ , C, Al, and 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%, and less than 0.01%, respectively. , Less than 0.005%, particularly preferably less than 0.003%.

SnO ₂ has a function as a clarifying agent for reducing bubbles in glass, and also has an effect of maintaining a relatively high ultraviolet transmittance when coexisting _{with Fe 2} O _{3 or Fe O.} On the other hand, if the content of _{SnO 2 is too large, devitrification of SnO 2} is likely to occur in the glass. The preferred upper limit content of SnO ₂ is 0.5%, 0.4%, particularly 0.3%, and the preferred 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 Fe ₂ O _{3 amount regardless of the valence.}

When SnO ₂ is contained in an amount of 0.01 to 0.5%, if _{the content of Rh 2} O ₃ is too large, the glass is easily colored. Rh ₂ O ₃ may be mixed 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 mixed from the raw material as an impurity, but if _{the content of SO 3} is too large, bubbles called riboyl may be generated during melting or molding, which may cause defects in the glass. be. The preferred upper limit content of SO ₃ is 0.005%, 0.003%, 0.002%, particularly 0.001%, and the preferred lower limit content is 0.0001%. The most preferable content range is 0.0001% to 0.001%.

Iron is a component mixed from raw materials as an impurity, but if the iron content is too large, the ultraviolet transmittance may decrease. If the ultraviolet transmittance is lowered, a problem may occur in the photolithography process for manufacturing the TFT and the liquid crystal alignment process 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% and 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 from the raw material as an impurity, but if _{the content of Cr 2} O ₃ is too large, light is incident from the end face of the glass substrate and scattered light is used to inspect the inside of the glass substrate for foreign matter. When this is done, light transmission is less likely to occur, and there is a risk of problems in foreign matter inspection. In particular, when the substrate size is 730 mm × 920 mm or more, this problem is likely to occur. Further, if the 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 face of the glass substrate is reduced, so that the content of _{Cr 2} O _{3 is regulated.} The significance of doing this increases. The preferred upper limit content of Cr ₂ O ₃ is 0.001%, 0.0008%, 0.0006%, 0.0005%, particularly 0.0003%, and the preferred lower limit content is 0.00001%. The most preferable content range is 0.00001 to 0.0003%.

Since the alkaline component, particularly the Li component and the Na component (for example, Li ₂ O and Na ₂ O) deteriorates the characteristics of various films and semiconductor elements formed on the glass substrate, it is preferable to reduce the content thereof. , It is desirable that it is not substantially contained.

A preferable content range of each component can be combined to obtain a preferable glass composition range. Among them, the particularly preferable glass composition range is as follows.
(1) As the glass composition, 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 in mass%. _{~5%, BaO 0.1~5%, 0~5} % ZnO, ZrO 2 0~5%, TiO 2 0~5%, P 2 O 5 0~5%, contains SnO 2 0 to 5%, It contains substantially no Li component or Na component.
(2) As the glass composition, in _{terms of 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 Li component and Na component.

In recent years, there has been an increasing demand for weight reduction in flat panel displays for mobile applications such as OLED displays and liquid crystal displays, and there is also a demand for weight reduction in glass substrates. In order to meet 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 tends to rise and the liquidus viscosity tends to decrease, and the productivity of the glass substrate tends to decrease. In addition, the distortion point 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 the 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. In this way, it becomes easy to match the coefficient of thermal expansion of the member (for example, 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 or more) 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 big 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 Young's modulus is preferably 30.0 GPa / g · cm ^-3 or higher, 30.5 GPa / g · cm ^-3 or higher, 31.0 GPa / g · cm ^-3 or higher, and particularly 31.5 GPa / g · cm ^-3. That is all. In addition, when the glass substrate has a large area and a thin wall, warpage of the glass substrate becomes a problem after a heat treatment step on a surface plate or a film forming step of various metal films, oxide films, semiconductor films, organic films, etc. 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, particularly 76 GPa or more.

Currently, LTPS used in ultra-high-definition mobile displays has a process temperature of 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 applications such as mobile and TV. In addition to the above LTPS, oxide TFTs are attracting attention as drive TFT elements for this application. Conventionally, 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 the conventional one. I understand. The heat treatment temperature is about 400 to 600 ° C., and a glass substrate having low heat shrinkage is also required for 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./min, held at 500 ° C. for 1 hour, and then lowered to room temperature at a rate of 10 ° C./min. 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. In this way, even if heat treatment is performed in the LTPS manufacturing process, problems such as pixel pitch deviation are less likely to occur. If the heat shrinkage value is too small, the productivity of the glass tends to decrease. Therefore, the heat shrinkage value is preferably 5 ppm or more, particularly 8 ppm or more. The heat shrinkage value can be reduced not only by increasing the strain point but also by decreasing the cooling rate at the time of 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 formed into a plate shape. If the temperature of the molten glass in contact with the molding apparatus is too high, the molding apparatus is aged and the productivity of the glass substrate tends 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, and 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 at the time of molding.

_{The SiO 2-} Al ₂ O _3- B ₂ O _3- RO based glass according to the present invention is generally difficult to melt. Therefore, improvement of meltability becomes an issue. When the meltability is increased, the defect rate due to bubbles, foreign substances, etc. is reduced, so that a large amount of high-quality glass substrate can be supplied at low cost. On the other hand, if 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, It is 1200 ° C. or lower, especially 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, and 10 ^5.5 dPa.・ S or more, especially ^105.6 dPa ・ s or more.

A transparent conductive film, an insulating film, a semiconductor film, a metal film, or the like is formed on a glass substrate used for a high-definition display. Further, various circuits and patterns are formed by the photolithography etching process. In these film forming steps and photolithography etching steps, the glass substrate undergoes 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 amorphous silicon or polycrystalline silicon TFTs (thin film transistors) are formed on the glass substrate by a photolithographic etching process. NS. In such a step, it is subjected to various chemical treatments such as sulfuric acid, hydrochloric acid, alkaline solution, hydrofluoric acid, and BHF. In particular, BHF is widely used for etching an insulating film, but BHF easily erodes the glass substrate and makes the surface of the glass substrate cloudy, and the reaction product may clog the filter during the manufacturing process. , May adhere to the glass substrate. From the above circumstances, it is important to improve the chemical resistance of the glass substrate.

The glass and the glass substrate of the present invention are preferably molded by the overflow down draw method. The overflow down draw method is a method in which molten glass is overflowed from both sides of a wedge-shaped refractory, and the overflowed molten glass is merged at the lower end of the wedge shape and stretch-molded downward to form a glass substrate. In the overflow down draw method, the surface of the glass substrate that should be the surface does not come into contact with the refractory and is formed in a free surface state. Therefore, it is possible to inexpensively manufacture a glass substrate that is unpolished and has good surface quality, and it is easy to increase the area and reduce the wall thickness. The material of the refractory 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 downward stretching 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 brought into contact with only the vicinity of the end face of the glass. You may adopt the method of letting and stretching.

In addition to the overflow down draw method, it is also possible to form a glass substrate by, for example, a down draw method (slot down method, redraw method, etc.), a float method, or the like.

In the glass and the glass substrate of the present invention, the plate thickness (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 easier it is for the glass substrate to bend. However, since the glass and the glass substrate of the present invention have a high Young's modulus and a specific Young's modulus, problems due to bending are unlikely to occur. The plate thickness can be adjusted by adjusting the flow rate at the time of glass production, the plate pulling speed, and the like.

In the glass and the glass substrate of the present invention, the strain point can be increased by lowering 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 distortion point tends to decrease. 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.

Examples of the method for lowering the β-OH value include the following methods. (1) Select a raw material with a low water content. _{(2) Add components (Cl, SO 3,} etc.) that reduce the amount of water in the glass. (3) Reduce the amount of water in the atmosphere inside the furnace. (4) performing the _{N 2} bubbling in the molten glass. (5) Use a small melting furnace. (6) Increase the flow rate of the molten glass. (7) The electric melting method is adopted.

Here, the "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 a reference wavelength of 3846 cm ^-1
T ₂ : Minimum transmittance (%) near hydroxyl group absorption wavelength 3600 cm ^-1

The glass and the 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. Since the glass and the glass substrate of the present invention are excellent in productivity and can be easily increased in area and thinned, such requirements can be accurately satisfied.

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

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

Each sample was prepared as follows. First, a glass batch prepared with a glass raw material was placed in a platinum crucible so as to have the glass composition shown in the table, and melted at 1600 ° C. for 24 hours. When melting the glass batch, stirring was performed using a platinum stirrer to homogenize the glass batch. Next, the molten glass was poured onto a carbon plate and molded into a plate shape. For each of the obtained samples, density, coefficient of thermal expansion, Young ratio, specific Young ratio, 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 logηTL, and chemical resistance were evaluated.

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

The coefficient of thermal expansion is an average coefficient of thermal expansion measured with 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 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 the platinum ball pulling method.

Next, each sample is crushed, passed through a standard sieve of 30 mesh (500 μm), the glass powder remaining in 50 mesh (300 μm) is placed in a platinum boat, held in a temperature gradient furnace for 24 hours, and then the platinum boat is placed. The temperature at which devitrification (crystal foreign matter) was observed in the glass after taking out was defined as the liquidus temperature. Further, the viscosity of the glass at the liquidus temperature was measured by the platinum ball pulling method, and this was taken as the liquidus viscosity.

Further, chemical resistance is obtained by observing the surface of the obtained sample after optically polishing both sides of each sample and immersing the sample in a chemical solution set to a predetermined concentration at a predetermined temperature for a predetermined time. Was evaluated. Specifically, after the chemical treatment, the glass surface becomes cloudy or cracked as "x", the glass surface becomes weakly cloudy or rough as "△", and the glass surface does not change at all as "○". bottom. As conditions for the chemical treatment, acid resistance was evaluated by treatment at 80 ° C. for 3 hours using 10% hydrochloric acid, and BHF resistance was evaluated by treatment at 20 ° C. for 30 minutes using a well-known 130 BHF solution.

Furthermore, the sample No. in the table. For 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 the glass substrate, and the heat shrinkage value of each sample was measured in the following manner. As shown in FIG. 1 (a), linear marks M1 and M2 are drawn in two places at predetermined intervals on the glass substrate 25, and then perpendicular to the mark M as shown in FIG. 1 (b). By dividing the glass substrate 25 in the above directions, a glass plate piece 25a and a glass plate piece 25b were obtained. Then, only the glass plate piece 25a was heated from room temperature 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. After that, as shown in FIG. 1 (c), the heat-treated glass plate piece 25a and the non-heat-treated glass plate piece 25b are arranged side by side 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 formula 1.

In Equation 1, l ₀ is the distance between the marks M on the glass substrate 25, l ₁ is the distance between the mark M1 of the glass plate piece 25a and the mark M1 of the glass plate piece 25b, and l ₂ is the glass plate piece. It is a 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 the weight of the glass substrate can be reduced. Further, the coefficient of thermal expansion is 30 to 40 × ^10-7 / ° C, the strain point is 680 ° C or more and less than 740 ° C, and the heat 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 or deformation is unlikely to occur. Further, the temperature at a high temperature viscosity of 10 ^5.0 dPa · s is 1250 ° C. or lower, the temperature at 10 ^2.5 dPa · s is 1650 ° C. or lower, the liquid phase temperature is 1300 ° C. or lower, and the liquid phase 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.

The glass and the glass substrate of the present invention have a small amount of alkaline components, low density and coefficient of thermal expansion, high strain points and Young's modulus, and are excellent in devitrification resistance, meltability, moldability, and the like. Therefore, the glass and the 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 the glass composition, in _{terms of mass%, SiO 2} 58 to 70%, Al ₂ O ₃ 19.1 to 25%, B ₂ O ₃ 3 to 5.9 %, MgO 0 to 5%, CaO 3 to 13%, SrO _{0~6%, BaO 1 ~1.9%,} 0~5% ZnO, ZrO 2 0~5%, TiO 2 0~5%, P 2 O 5 0~5%, Sb 2 O 3 0~0. A glass characterized by containing less than 3%. The glass according to claim 1, wherein the glass is substantially free of Li and Na components, has a density of 2.43 to 2.52 g / cm ³ , and has a strain point of 680 ° C. or higher. The coefficient of thermal expansion is 30-40 × ^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 ·. 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 more.} As the glass composition, SiO ₂ 59 to 67%, Al ₂ O ₃ 19.1 to 22%, B ₂ O ₃ 4 to 5.9 %, MgO 0 to 4%, CaO 3 to 10%, SrO in terms of mass%. _{0~5%, BaO 1 ~1.9%,} 0~5% ZnO, ZrO 2 0~5%, TiO 2 0~5%, P 2 O 5 0~5%, SnO 2 0~5%, Sb ₂ The glass according to any one of claims 1 to 3, which contains less than _{30 to} 0.3% of O and substantially does not contain a Li component or a Na component. As the glass composition, SiO ₂ 60 to 65%, Al ₂ O ₃ 19.1 to 20%, B ₂ O ₃ 4 to 5.9 %, MgO 0 to 3%, CaO 4 to 10%, SrO in terms of mass%. _{0~5%, BaO 1 ~1.9%,} 0~1% ZnO, ZrO 2 0~1%, TiO 2 0~1%, P 2 O 5 0~3%, SnO 2 0.01~1% , Sb ₂ O The glass according to any one of claims 1 to 4, which contains less than _{30 to 0.3% and substantially does not contain a Li component or 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, wherein the glass substrate is used for an OLED display. The glass substrate according to claim 6, wherein the glass substrate is used for a liquid crystal display. The heat shrinkage value 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 lowered to room temperature at a rate of 10 ° C./min is 30 ppm or less. The glass substrate according to any one of claims 6 to 8, wherein the glass substrate.

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