JP2019077611A - Glass and glass substrate - Google Patents

Abstract

To provide glass and a glass substrate which are low in the content of alkaline components, low in density and thermal expansion coefficient, high in strain point and Young's modulus, and excellent in devitrification resistance, meltability, and formability.SOLUTION: This glass has a glass composition comprising, in terms of mass%, 58-70% SiO, 16-25% AlO, 3-8% BO, 0-5% MgO, 3-13% CaO, 0-6% SrO, 0-6% BaO, 0-5% ZnO, 0-5% ZrO, 0-5% TiO, and 0-5% PO.SELECTED DRAWING: Figure 1

Description

  The present invention relates to glasses and glass substrates, and in particular to glasses and glass substrates suitable for organic EL (OLED) displays, liquid crystal displays. Furthermore, it relates to a glass and glass substrate suitable for oxide TFT, low temperature p-Si TFT (LTPS) driven display.

  BACKGROUND ART Conventionally, glass substrates are 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 of self-emission, high color reproducibility, high viewing angle, high-speed response, high definition, etc. It is done. In addition, since displays of mobile devices such as smartphones are required to display a large amount of information while having a small area, an ultra-high-definition screen is required, and a moving image is also displayed. It will be necessary.

  For such applications, OLED displays or liquid crystal displays driven by LTPS are preferred. An OLED display emits light when a current flows in an OLED element constituting a pixel. Therefore, a material with low resistance and high electron mobility is used as the drive TFT element. As this material, in addition to the above-mentioned LTPS, an oxide TFT represented by IGZO (indium, gallium, zinc oxide) is noted. Oxide TFTs have low resistance, high mobility, and can be formed at relatively low temperatures. Conventional p-Si TFTs, especially LTPS, form elements on a large-area glass substrate due to the instability of the excimer laser used when polycrystallizing a film of amorphous Si (a-Si) At the time, the TFT characteristics tended to be uneven, and in the case of a TV application etc., the display unevenness of the screen was apt to occur. On the other hand, when forming an element on a glass substrate with a large area, oxide TFTs are attracting attention as potent TFT-forming materials because they are excellent in the uniformity of the TFT characteristics, and some of them have already been put to practical use.

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

(1) If the alkali component in the glass is large, alkali ions diffuse into the formed semiconductor substance during heat treatment, resulting in deterioration of the film characteristics. Therefore, the content of the alkali component (in particular, the Li component and the Na component) is low or substantially not contained.
(2) In the photolithography etching process, various chemicals such as acids and alkalis are used. Therefore, it should be excellent in chemical resistance.
(3) In the steps of film formation, annealing, etc., the glass substrate is heat-treated to several hundred degrees centigrade. During the heat treatment, when the glass substrate is thermally shrunk, pattern displacement or the like is likely to occur. Therefore, it is difficult to thermally shrink, and in particular, the strain point is high.
(4) The thermal expansion coefficient is close to a member (for example, a-Si or p-Si) to be deposited on a glass substrate. For example, the thermal expansion coefficient is 30 to 40 × 10 ⁻⁷ / ° C. The thermal shock resistance is also improved when the thermal expansion coefficient is 40 × 10 ⁻⁷ / ° C. or less.
(5) A high Young's modulus (or a specific Young's modulus) in order to suppress a defect due to the bending of the glass substrate.

Furthermore, from the viewpoint of producing a glass substrate, the glass is required to have the following characteristics (6) and (7).
(6) It has excellent meltability to prevent melt defects such as bubbles, bumps and cords.
(7) To have excellent devitrification resistance in order to avoid the generation of foreign matter in the glass substrate.

  The present invention was made in view of the above-mentioned circumstances, and the technical subject satisfies the above-mentioned required characteristics (1)-(7), and is a glass suitable for 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 create 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 being excellent in devitrification resistance, meltability, formability, etc. .

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 to a predetermined range, and are proposed as the present invention. That is, the glass of the present invention is composed of SiO ₂ 58-70%, Al ₂ O ₃ 16-25%, B ₂ O ₃ 3-8%, MgO 0-5%, CaO 3-3 by mass as a glass composition. 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% Do.

The inventors of the present invention have found that SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ -RO (RO: alkaline earth metal oxide, MgO + CaO + SrO + BaO) -based glass as a glass satisfying the above-mentioned required characteristics (1) to (7). If the content of SiO ₂ is controlled to 58% or more, the content of Al ₂ O ₃ is controlled to 16 to 25%, and the content of B ₂ O ₃ to 3 to 8%, high strain point and good resistance It has been found that the drug properties can be compatible. In addition, it has been found that when 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, when the contents of B ₂ O ₃ , MgO and CaO are optimized, the meltability, the formability, the 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 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%, substantially It is characterized in that it does not contain the Li component and the 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, "does not substantially contain" refers to the case where the content of the specified component is 0.1% or less (preferably 0.05% or less), for example, "substantially does not contain the Li component. "Indicates that 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 method of ASTM C336.

Third, the glass of the present invention is substantially free of Li and Na components, and 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 75GPa 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 Linear viscosity) is 10 ^5.0 dPa · s or more. Here, the "thermal expansion coefficient" refers to an average thermal expansion coefficient measured in a temperature range of 30 to 380 ° C, and can be measured, for example, with 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, for example, by a platinum ball pulling method. The “temperature at 10 ^2.5 dPa · s” can be measured, for example, by a platinum ball pulling method. "Liquid viscosity" refers to the viscosity of glass at liquidus temperature (liquidus temperature), and can be measured, for example, by a platinum ball pulling method. The “liquidus temperature” is passed through a standard sieve of 30 mesh (500 μm) and the glass powder remaining on 50 mesh (300 μm) is put in a platinum boat and kept in a temperature gradient furnace for 24 hours. Let the temperature at which devitrification (crystal foreign matter) is recognized in the glass.

Fourthly, the glass of the present invention is composed of SiO ₂ 59-67%, Al ₂ O ₃ 17-22%, B ₂ O ₃ 4-7%, MgO 0-4%, CaO by mass as a glass composition. 3 to 12%, SrO 0 to 5%, BaO 0.1 to 5%, ZnO 0 to 5%, ZrO ₂ 0 to 5%, TiO ₂ 0 to 5%, P ₂ O ₅ 0 to 5%, SnO ₂ It is preferable to contain 0 to 5% and to contain substantially no Li component and Na component.

Fifth, the glass of the present invention is, as a glass composition, by mass, SiO ₂ 60-65%, Al ₂ O ₃ 17-20%, B ₂ O ₃ 4-7%, MgO 0-3%, CaO _{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 to contain 0.01 to 1% and to contain substantially no Li component and Na component.

  Sixth, the glass substrate of the present invention is characterized by comprising any of the above-mentioned 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 drive display.

It is the schematic for demonstrating the measuring method of a thermal contraction value.

  The reason for restricting the content of each component as described above will be described below. In addition, in description of each component, the following% indication points to the mass%.

When the content of SiO ₂ is too small, the chemical resistance, in particular, the 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 and the meltability tends to decrease, and devitrification of cristobalite tends to occur, and defects of devitrified foreign matter are likely to occur in the glass. The preferred upper limit content of SiO ₂ is 70%, 68%, 66%, 65%, in particular 64%, and the preferred lower limit content is 58%, 59%, 60%, in particular 61%. The most preferable content range is 61 to 64%.

When the content of Al ₂ O ₃ is too small, the strain point is lowered, the thermal contraction value is increased, the Young's modulus is decreased, and the glass substrate is easily bent. On the other hand, when the content of Al ₂ O ₃ is too large, resistance to BHF (buffered hydrofluoric acid) is lowered, and white turbidity tends to occur on the glass surface, and crack resistance is easily lowered. Furthermore, devitrification of mullite or anorthite in glass tends to occur. The preferred upper limit content of Al ₂ O ₃ is 25%, 23%, 22%, 21%, in particular 20%, and the preferred lower limit content is 17%, 17.5%, in particular 18%. The most preferable content range is 18 to 20%.

B ₂ O ₃ is a component which acts as a flux and lowers the viscosity to improve the meltability. The content of B ₂ O ₃ is preferably 3 to 8%, 3 to 7%, in particular 4 to 7%. When the content of B ₂ O ₃ is too small, it does not function as a flux sufficiently, and the BHF resistance and the crack resistance easily decrease. Also, the liquidus temperature tends to rise. On the other hand, when the content of B ₂ O ₃ is too large, the strain point, the heat resistance and the acid resistance tend to be lowered. In particular, when the content of B ₂ O ₃ is 7% or more, the tendency becomes remarkable. On the other hand, when 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.

In consideration of 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, particularly preferably 2.5 to 3.5. It is.

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

  Similar to MgO, CaO is a component that significantly reduces the high temperature viscosity without lowering the strain point to significantly improve the meltability. When the content of CaO is too large, devitrification tends to occur and the resistance to BHF is lowered, and 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%, in particular 10%, and the preferred lower limit content is 3%, 3.5%, in particular 4%. The most preferable content range is 4 to 10%.

  SrO is a component that enhances the chemical resistance and the devitrification resistance, but if the ratio is too high in RO, the meltability tends to decrease and the density and the thermal expansion coefficient 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 its content is too large, the density tends to increase. In addition, BaO is less effective in improving 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 enhanced from the viewpoint of supplying a high quality glass substrate inexpensively and in large quantities. It is very important to reduce the defective rate due to bubbles, foreign matter, etc. Therefore, the content of BaO is preferably 0 to 6%, 0.1 to 5%, particularly 0.5 to 4%. In the _{SiO 2 -Al 2 O 3 -B 2} O 3 -RO based glass according to the present invention, when reducing the content of SiO _2, although the melting property is effectively improved, reducing the content of SiO ₂ As a result, the acid resistance is likely to be lowered, and the density and the thermal expansion coefficient are likely to be increased.

  MgO, SrO and BaO have the property of improving the 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 3% or more. However, when 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 reduced, crystal foreign substances are less likely to be generated in the glass, and the meltability and the formability are improved. However, when the content of RO is too large, the density is increased, which makes it difficult to reduce the weight of the glass substrate. Thus, the content of RO is preferably less than 15%, less than 14%, in particular 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 Preferably, it is 2 or more, 3 or more, 4 or more, particularly 5 or more.

  ZnO is a component that improves the meltability and BHF resistance, but if the content is too large, the glass is likely to be devitrified or the strain point is reduced, 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 introduced is increased, devitrification of ZrSiO ₄ tends to occur. The preferable lower limit content of ZrO ₂ is 1%, 0.5%, 0.3%, 0.2%, particularly 0.1%, and it is preferable to introduce 0.005% or more 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 may be introduced by elution from a refractory.

TiO ₂ has the effect of lowering the high temperature viscosity to enhance the meltability and enhancing the chemical durability, but when the introduced amount is excessive, the ultraviolet light 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 the coloring due to ultraviolet light 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 alkali earth aluminosilicate-based devitrified crystals such as anorthite. However, when a large amount of P ₂ O ₅ is contained, the glass is likely to be separated. The content of P ₂ O ₅ is preferably 0 to 5%, 0 to 3%, 0 to 2%, 0 to 1%, particularly 0 to 0.5%.

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

As ₂ O ₃ and Sb ₂ O ₃ are environmentally harmful chemicals, it is desirable not to use them as much as possible. The content of As ₂ O ₃ and Sb ₂ O ₃ is 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 less than 0.003% is preferred.

SnO ₂ works as a fining agent to reduce bubbles in glass, and also has the effect of maintaining a relatively high ultraviolet light transmittance when it coexists with Fe ₂ O ₃ or FeO. On the other hand, when the content of SnO ₂ is too large, devitrification of SnO ₂ easily occurs in the glass. The preferred upper limit content of SnO ₂ is 0.5%, 0.4%, especially 0.3%, and the preferred lower limit content is 0.01%, 0.05%, especially 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 percent, by introducing a 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 amount of Fe into an amount of Fe ₂ O ₃ regardless of the valence number.

In the case of containing 0.01 to 0.5% of SnO ₂ , when the content of Rh ₂ O ₃ is too large, the glass tends to be colored. Incidentally, _Rh 2 _{O 3} is likely to be mixed from the manufacturing vessel platinum. 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, it may generate bubbles called riboyl during melting or molding, which may cause defects in the glass. is there. The preferred upper limit content of SO ₃ is 0.005%, 0.003%, 0.002%, in particular 0.001%, and the preferred lower content is 0.0001%. The most preferable content range is 0.0001% to 0.001%.

Iron is a component mixed from the raw material as an impurity, but if the content of iron is too large, there is a risk that the ultraviolet light transmittance may decrease. If the ultraviolet light transmittance decreases, problems may occur in a photolithography process for manufacturing a TFT or an alignment process of liquid crystal by ultraviolet light. 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%, 0.04% in terms of Fe ₂ O ₃ , 0.03%, in particular 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 made incident from the end surface of the glass substrate, and foreign particles are inspected inside the glass substrate by scattered light. When this is done, the transmission of light is less likely to occur, which may cause a defect in the foreign substance inspection. In particular, when the substrate size is 730 mm × 920 mm or more, this problem is likely to occur. In addition, when 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 surface of the glass substrate is reduced, so the content of Cr ₂ O ₃ is regulated. The significance of 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%.

In order to degrade the characteristics of various films and semiconductor elements formed on a glass substrate, it is preferable to reduce the content of an alkali component, in particular, a Li component and a Na component (for example, Li ₂ O, Na ₂ O) It is desirable not to contain substantially.

The preferable content range of each component can be combined and it can be set as a preferable glass composition range. Among them, the particularly preferable glass composition range is as follows.
(1) As a glass composition, by mass%, SiO ₂ 59-67%, Al ₂ O ₃ 17-22%, B ₂ O ₃ 4-7%, MgO 0-4%, CaO 3-10%, 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%, It contains substantially no Li component and no Na component.
(2) As a glass composition, by mass%, SiO ₂ 60-65%, Al ₂ O ₃ 17-20%, B ₂ O ₃ 4-7%, MgO 0-3%, CaO 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 0.01~1% content And contains substantially no Li component and no Na component.

In recent years, in flat panel displays for mobile applications such as OLED displays and liquid crystal displays, the demand for weight reduction is increasing, and weight reduction is also required for glass substrates. In order to meet this demand, 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, in particular 2.48 / cm ³ or less. On the other hand, if the density is too low, the melting temperature is likely to be increased and the liquid phase viscosity is likely to be reduced, and the productivity of the glass substrate is likely to be reduced. 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 thermal expansion coefficient is preferably 30 to 40 × 10 ⁻⁷ / ° C., 32 to 39 × 10 ⁻⁷ / ° C., 33 to 38 × 10 ⁻⁷ / ° C., particularly 34 to 37. × 10 ^-7 / ° C. This makes it easy to match the thermal expansion coefficient of a member (for example, a-Si or p-Si) to be deposited on a glass substrate.

Large-area glass substrates (for example, 730 × 920 mm or more, 1100 × 1250 mm or more, particularly 1500 × 1500 mm or more) are used in OLED displays or liquid crystal displays, etc., and thin glass substrates (for example, plate thickness 0.5 mm) Below, 0.4 mm or less, especially 0.3 mm or less) tends to be used. When the glass substrate has a large area and a small thickness, bending due to its own weight becomes a serious problem. In order to reduce the deflection 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 It is above. In addition, when the glass substrate is enlarged in area and thinned, warpage of the glass substrate becomes a problem after a heat treatment step on a platen or a film formation step of various metal films, oxide films, semiconductor films, organic films, etc. Become. In order to reduce the warpage of the glass substrate, it is effective to increase the Young's modulus of the glass substrate. The Young's modulus is preferably 75 GPa or more, in particular 76 GPa or more.

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

  Recently, OLED displays are also used in applications such as mobile and TV. In addition to the above-described LTPS, an oxide TFT is focused on as a driving TFT element for this application. In the past, oxide TFTs have been manufactured at a temperature process of 300 to 400 ° C equivalent to a-Si, but when annealing is performed at a heat treatment temperature higher than conventional, more stable device characteristics can be obtained I understand. The heat treatment temperature is about 400 to 600 ° C., and even in this application, a glass substrate with low heat shrinkage is required.

  In the glass and glass substrate of the present invention, 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, particularly 21 ppm or less. In this way, problems such as pixel pitch deviation are less likely to occur even if heat treatment is performed in the LTPS manufacturing process. When the heat shrinkage value is too small, the productivity of glass tends to be reduced. Thus, the heat shrinkage value is preferably 5 ppm or more, in particular 8 ppm or more. The heat shrinkage value can also be reduced by reducing the cooling rate at the time of molding, in addition to increasing the strain point.

In the overflow down draw method, molten glass flows down the surface of a crucible-shaped refractory (or a refractory coated with a platinum group metal), and is joined at the lower end of the crucible to form a plate. In the slot down draw method, for example, a ribbon-like molten glass is made to flow down from a platinum group metal pipe having a slit-like opening, and is cooled and formed into a plate. When the temperature of the molten glass in contact with the forming apparatus is too high, the forming apparatus is deteriorated, and the productivity of the glass substrate is likely to be reduced. Therefore, the temperature at a high temperature viscosity of 10 ^5.0 dPa · s is preferably 1300 ° C. or less, 1280 ° C. or less, 1270 ° C. or less, 1260 ° C. or less, 1250 ° C. or less, 1240 ° C. or less, particularly 1230 ° C. or less. 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 glass according to the present invention is generally difficult to melt. For this reason, improvement of meltability becomes a subject. When the melting property is enhanced, the defective rate due to bubbles, foreign matters, and the like is reduced, so that high-quality glass substrates can be supplied in large quantities and inexpensively. On the other hand, if the viscosity of the glass in the high temperature range is too high, it is difficult to promote degassing in the melting step. Therefore, the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is preferably 1650 ° C. or less, 1640 ° C. or less, 1630 ° C. or less, 1620 ° C. or less, particularly 1610 ° C. or less. 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 forming by the down draw method etc., devitrification resistance becomes important. The liquidus temperature is preferably 1250 ° C. or less, 1230 ° C. or less, 1220 ° C. or less, 1210 ° C. or less, considering the forming temperature of the SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ -RO glass according to the present invention. It is at most 1200 ° C., in particular at most 1190 ° C. The liquid phase 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, in particular 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. Furthermore, various circuits and patterns are formed by a photolithographic etching process. In these film formation processes and photolithography etching processes, the glass substrate is subjected to various chemical treatment. For example, in a TFT 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 photolithography etching process. Ru. In such a process, various chemical treatment such as sulfuric acid, hydrochloric acid, alkali solution, hydrofluoric acid, BHF and the like is performed. In particular, BHF is widely used for etching of insulating films, but BHF corrodes the glass substrate and tends to cloud the surface of the glass substrate, and its reaction product clogs the filter during the manufacturing process. , May adhere on 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 formed by the overflow down draw method. The overflow down draw method is a method of forming a glass substrate by drawing downward while making molten glass overflow from both sides of a crucible-shaped refractory and joining the overflowed molten glass at the lower end of the crucible. In the overflow down draw method, the surface to be the surface of the glass substrate is not in contact with the refractory but is formed in the state of a free surface. For this reason, a glass substrate which is not polished and has a good surface quality can be manufactured at low cost, and it is easy to increase the area and reduce the thickness. The material of the refractory used in the overflow down draw method is not particularly limited as long as it can realize desired dimensions and surface accuracy. In addition, the method of applying a force is not particularly limited when performing the downward stretch forming. For example, a method may be adopted in which a heat-resistant roll having a sufficiently large width is rotated and brought into contact with glass and stretched, or a plurality of paired heat-resistant rolls are brought into contact only near the end face of the glass You may employ | adopt the method of making it extend.

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

  In the glass and 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, 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, but the glass and the glass substrate of the present invention have high Young's modulus and specific Young's modulus, so that problems due to bending hardly occur. The plate thickness can be adjusted by the flow rate at the time of 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 at most 0.5 / mm, at most 0.45 / mm, at most 0.4 / mm, in particular at most 0.35 / mm. When the β-OH value is too large, the strain point tends to be lowered. In addition, when (beta) -OH value is too small, meltability will fall easily. Accordingly, the β-OH value is preferably at least 0.01 / mm, in particular at least 0.05 / mm.

The following method is mentioned as a method of reducing (beta) -OH value. (1) Select a raw material with low water content. (2) Add components (Cl, SO _3, etc.) to reduce the water content in the glass. (3) Decrease the amount of water in the furnace atmosphere. (4) N ₂ bubbling is performed in the molten glass. (5) Adopt a small melting furnace. (6) To increase the flow rate of molten glass. (7) Adopt the electric melting method.

Here, "(beta) -OH value" points out the value calculated | required using the following formula, measuring the transmittance | permeability of glass using FT-IR.
β-OH value = (1 / X) log (T ₁ / T ₂ )
X: Glass thickness (mm)
T ₁ : transmittance at a reference wavelength 3846 cm ⁻¹ (%)
T ₂ : Minimum transmittance in the vicinity of a hydroxyl group absorption wavelength of 3600 cm ⁻¹ (%)

  The glass and glass substrate of the present invention are preferably used in an OLED display. OLEDs are generally becoming commercially available, but cost reduction due to mass production is strongly desired. The glass and the glass substrate of the present invention are excellent in productivity, and are easy to increase in area and thickness, so that such requirements can be met exactly.

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

  Tables 1-3 have shown the Example (sample No. 1-30) of this invention.

Each sample was produced as follows. First, a glass batch prepared from glass materials was placed in a platinum crucible and melted at 1600 ° C. for 24 hours so that the glass composition in the table was obtained. At the time of melting of the glass batch, it was stirred using a platinum stirrer and homogenized. Next, the molten glass was poured onto a carbon plate and formed into a plate shape. For each sample obtained, 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 TLTL, 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 a 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 the 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 is crushed, passed through a standard sieve of 30 mesh (500 μm), and the glass powder remaining on 50 mesh (300 μm) is put in a platinum boat and held in a temperature gradient furnace for 24 hours. The temperature at which devitrification (crystal foreign matter) was observed in the glass was taken as the liquidus temperature. Furthermore, the viscosity of the glass at the liquidus temperature was measured by a platinum ball pulling method, and this was taken as the liquidus viscosity.

  In addition, after optically polishing both surfaces of each sample, after immersing at a predetermined temperature for a predetermined time in a chemical solution set to a predetermined concentration, chemical resistance is obtained by observing the surface of the obtained sample. Was evaluated. Specifically, after chemical treatment, the glass surface becomes clouded or cracked "X", weak clouding or rough can be seen "Δ", the one without any change "○" did. As the chemical treatment conditions, the acid resistance was evaluated by treatment at 80 ° C. for 3 hours using 10% hydrochloric acid, and the BHF resistance was evaluated by treatment using a known 130 BHF solution at 20 ° C. for 30 minutes.

  Furthermore, sample No. 1 in the table. With respect to 12, 20, 23, and 24, a glass substrate with a plate thickness of 0.5 mm was made by trial using the overflow down draw method, and the heat shrinkage value thereof was measured. First, samples of 30 mm × 160 mm × 0.5 mm were cut out from the glass substrate, and the thermal shrinkage value of each sample was measured in the following manner. As shown in FIG. 1 (a), after two linear marks M1 and M2 are written at predetermined intervals on a predetermined portion of the glass substrate 25, as shown in FIG. 1 (b), they are perpendicular to the mark M. The glass substrate 25 was divided in the above direction to obtain a glass plate piece 25a and a glass plate piece 25b. Then, only the glass plate piece 25a was heated from normal temperature to 500 ° C. at a rate of 10 ° C./min, held at 500 ° C. for 1 hour, and then cooled to normal temperature at a rate of 10 ° C./min. Thereafter, as shown in FIG. 1 (c), the mark M1 of the glass plate piece 25a in a state in which the glass plate piece 25a subjected to heat treatment and the glass plate piece 25b not subjected to heat treatment are arranged side by side and fixed with adhesive tape T. The amount of deviation between M2 and the marks M1 and M2 of the glass plate piece 25b was measured, and the thermal contraction value was calculated based on Formula 1 below.

In Equation 1, ₁₀ is the distance between the marks M on the glass substrate 25, ₁₁ is the distance between the mark M1 of the glass plate 25a and the mark M1 of the glass plate 25b, and ₁₂ is the glass plate It is the distance between the mark M2 of 25a and the mark M2 of the glass plate 25b.

Sample No. The density of each of 1 to 30 is 2.43 to 2.52 g / cm ³ , and the weight of the glass substrate can be reduced. The thermal expansion coefficient is 30 to 40 × 10 ^-7 / ° C, the strain point is 680 ° C to less than 740 ° C, and the thermal contraction value is also small. In addition, the Young's modulus is 75 GPa or more, and the specific Young's modulus is 30 GPa / (g / cm ³ ) or more, and deflection and deformation hardly occur. In addition, the temperature at high temperature viscosity of 10 ^5.0 dPa · s is 1250 ° C. or less, the temperature at 10 ^2.5 dPa · s is 1650 ° C. or less, the liquidus temperature is 1300 ° C. or less, and the liquidus viscosity is ^105.0 Since it is dPa · s or more, it is excellent in meltability and formability, and is suitable for mass production. Furthermore, chemical resistance is also excellent.

  The glass and the glass substrate of the present invention have a low alkali component, a low density and a low thermal expansion coefficient, a high strain point and a high Young's modulus, and are 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 suitable for displays driven by LTPS and oxide TFT.

Claims (9)

As a glass composition, by mass%, SiO ₂ 58-70%, Al ₂ O ₃ 16-25%, B ₂ O ₃ 3-8%, MgO 0-5%, CaO 3-13%, SrO 0-6% And 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%. As a glass composition, by mass%, SiO ₂ 58-70%, Al ₂ O ₃ 16-25%, B ₂ O ₃ 3-8%, MgO 0-5%, CaO 3-13%, SrO 0-6% , 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%, substantially containing no Li or Na component A glass having a density of 2.43 to 2.52 g / cm ³ and a strain point of 680 ° C. or higher. Substantially no Li component or Na component, density is 2.43 to 2.52 g / cm ³ , thermal expansion coefficient is 30 to 40 × 10 ^-7 / ° C, Young's modulus is 75 GPa or more, strain point is 680 ° C to 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, and liquid phase viscosity is 10 ^5.0 dPa · s or more Characterized glass. As a glass composition, by mass%, SiO ₂ 59-67%, Al ₂ O ₃ 17-22%, B ₂ O ₃ 4-7%, MgO 0-4%, CaO 3-10%, 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 The glass according to any one of claims 1 to 3, which does not contain a Li component and a Na component. As a glass composition, by mass%, SiO ₂ 60-65%, Al ₂ O ₃ 17-20%, B ₂ O ₃ 4-7%, MgO 0-3%, CaO 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%, contains SnO 2 0.01 to 1%, substantially The glass according to any one of claims 1 to 4, wherein the glass does not 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.   7. The glass substrate according to claim 6, which is used for a display driven by an oxide TFT.