TW201841842A - glass substrate - Google Patents

Abstract

This glass substrate is characterized by containing as the glass composition, in mass%, SiO2 55-65%, Al2O3 15-25%, B2O3 5.4-9%, MgO 0-5%, CaO 5-10%, SrO 0-5%, BaO 0-10%, and P2O5 0.01-10% and having a mass ratio SiO2/B2O3 of 6-11.5 and a molar ratio (MgO + CaO + SrO + BaO)/Al2O3 of 0.8-1.4.

Description

glass substrate

The present invention relates to a glass substrate, and more particularly to a substrate suitable for an organic electroluminescence (EL) (Organic Light-Emitting Diode (OLED)) display, a liquid crystal display. Glass substrate. Further, the present invention relates to a glass substrate suitable for a substrate of an oxide thin film transistor (TFT) or a low temperature poly-Silicon (LTPS) driven display.

Conventionally, a glass substrate has been widely used as a substrate such as a flat panel display such as a liquid crystal display, a hard disk, a filter, or a sensor. In recent years, in addition to the previous liquid crystal displays, OLED displays have been widely developed for reasons such as self-luminescence, high color reproducibility, high viewing angle, high-speed response, high definition, and the like, and some have been put into practical use. In addition, liquid crystal displays and OLED displays of mobile devices such as smart phones require a small area and display a large amount of information, so that an ultra-high-definition picture is required. Further animation is performed, so high-speed response is also required.

An OLED display emits light by causing a current flow on an OLED element constituting a pixel. Therefore, as the driving TFT element, a material having low electric resistance and high electron mobility is used. As the material, in addition to the above-described low temperature polycrystalline silicon (LTPS), an oxide TFT typified by IGZO (indium, gallium, zinc oxide) has been attracting attention. The oxide TFT is low in resistance, high in mobility, and can be formed at a relatively low temperature. In the case of the prior polycrystalline germanium-TFT, particularly LTPS, the instability of the excimer laser used in the polycrystallization of the amorphous germanium (a-antimony) film is easily made on a large-area glass substrate. When the element is formed, the TFT characteristics are deviated, and in a television (TV) use or the like, display unevenness of the screen is likely to occur. On the other hand, when an element is formed on a large-area glass substrate, the oxide TFT has excellent uniformity in TFT characteristics, and thus has been attracting attention as a potent TFT forming material, and some of it has been put into practical use.

A number of characteristics are required for glass substrates used in high definition displays. The following characteristics (1) to (4) are particularly required.

(1) When the amount of the alkaline component in the glass substrate is large, the alkali ions diffuse into the semiconductor material which has been formed during the heat treatment, and the properties of the film are deteriorated. Therefore, the content of the alkaline component (particularly, the Li component and the Na component) needs to be small or substantially not contained. (2) In the steps of film formation, annealing, and the like of the semiconductor element, the glass substrate is heat-treated under several Baidu. When the glass substrate is thermally shrunk during heat treatment, pattern shift or the like is likely to occur. Therefore, heat shrinkage is not easy to occur, especially strain points must be high. (3) The coefficient of thermal expansion must be close to the member formed on the glass substrate (for example, a-矽, polycrystalline germanium). For example, the coefficient of thermal expansion must be 30 x 10 ^-7 / ° C to 45 x 10 ^-7 / ° C. Further, when the coefficient of thermal expansion is 40 × 10 ^-7 / ° C or less, the thermal shock resistance is also improved. (4) In order to suppress a problem caused by bending of the glass substrate, the Young's modulus (or Young's modulus) must be high.

Further, from the viewpoint of producing a glass substrate, the following characteristics (5) and (6) are also required for the glass substrate. (5) In order to prevent melting defects such as bubbles, foreign matter, and streaks, the meltability is excellent. (6) In order to avoid the incorporation of devitrified foreign matter, the devitrification resistance must be excellent. [Prior Art Literature]

[Patent Document] [Patent Document 1] Japanese Patent Laid-Open Publication No. 2016-11256

[Problems to be Solved by the Invention] In general, chemical etching of a glass substrate is used in the case of reducing the thickness of the display. This method is a method of thinning a glass substrate by immersing a display panel in which two glass substrates are bonded together in a hydrofluoric acid (HF)-based chemical solution.

However, since the conventional glass substrate is highly resistant to the HF-based chemical solution, there is a problem that the etching rate is very slow. In order to increase the etching rate and increase the HF concentration in the chemical solution, the amount of insoluble fine particles in the HF-based solution increases, and as a result, the fine particles are likely to adhere to the surface of the glass, and the uniformity of etching is impaired in the surface of the glass substrate.

In order to solve the above problem, Patent Document 1 discloses that the amount obtained by subtracting the content of SiO ₂ from the alkali-free glass by twice the amount of Al ₂ O ₃ is less than 65 mol%. However, the alkali-free glass described in Patent Document 1 has low devitrification resistance (high liquidus temperature), so that devitrification is likely to occur during molding, and it is difficult to form the glass substrate. Therefore, the alkali-free glass described in Patent Document 1 is difficult to achieve both an increase in the etching rate and a high resistance to devitrification.

Therefore, the present invention has been made in view of the above circumstances, and a technical object thereof is to create a glass substrate which is excellent in productivity (particularly resistance to devitrification) and which has a high etching rate with respect to an HF-based chemical solution. [Means for solving the problem]

The present inventors conducted various experiments in turn and found that the technical property can be solved by strictly limiting the glass composition range in SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ -RO (RO is an alkaline earth metal oxide)-based glass. The subject is to present the present invention. That is, the glass substrate of the present invention is characterized in that it contains 55% to 65% of SiO ₂ , 15% to 25% of Al ₂ O ₃ , and 5.4% to 9% of B ₂ O as a glass composition. ₃ , 0% to 5% of MgO, 5% to 10% of CaO, 0% to 5% of SrO, 0% to 10% of BaO, 0.01% to 10% of P ₂ O ₅ , mass ratio of SiO ₂ / B ₂ O ₃ is 6 to 11.5, and the molar ratio (MgO + CaO + SrO + BaO) / Al ₂ O ₃ is 0.8 to 1.4. Here, "MgO+CaO+SrO+BaO" means the total amount of MgO, CaO, SrO, and BaO. "Morbi (MgO + CaO + SrO + BaO) / Al ₂ O ₃ " refers to a value obtained by dividing the molar % of MgO, CaO, SrO, and BaO by the molar % content of Al ₂ O ₃ .

According to the investigation by the present inventors, when the mass ratio SiO ₂ /B ₂ O _{3 is} reduced to 11.5 or less, the etching rate can be increased, and on the other hand, it is difficult to stabilize the glass. Accordingly, the present invention, the glass composition as an essential component, introducing an amount of 5.4 mass% or more of B ₂ O _3, and not more than 0.01% by mass of P ₂ O _5. Thereby, even if the mass is smaller than SiO ₂ /B ₂ O ₃ , the glass can be stabilized.

Further, in the glass substrate of the present invention, the content of Li ₂ O+Na ₂ O+K ₂ O in the glass composition is preferably 0.5% by mass or less. In this case, it is easy to prevent a situation in which the alkali ions are diffused into the film-formed semiconductor film during the heat treatment to deteriorate the characteristics of the semiconductor film. Here, "Li ₂ O+Na ₂ O+K ₂ O" means the total amount of Li ₂ O, Na ₂ O, and K ₂ O.

Further, in the glass substrate of the present invention, the content of Fe ₂ O ₃ +Cr ₂ O ₃ in the glass composition is preferably 0.012% by mass or less. Here, "Fe ₂ O ₃ +Cr ₂ O ₃ " means the total amount of Fe ₂ O ₃ and Cr ₂ O ₃ .

Further, the glass substrate of the present invention preferably has a strain point of 680 ° C or higher. Here, the "strain point" refers to a value measured by a method of the American Society for Testing and Materials (ASTM) C336.

Further, the glass substrate of the present invention preferably has a temperature of 1300 ° C or less at a viscosity of 10 ^4.5 dPa·s. Here, "the temperature at a viscosity of 10 ^4.5 dPa·s" means a value measured by a platinum ball pulling method.

Further, the glass substrate of the present invention preferably has a liquidus viscosity of 10 ^4.8 dPa·s or more. Here, the "liquidus viscosity" means a viscosity at a liquidus temperature, and is a value obtained by a platinum ball pulling method. For the "liquidus temperature", the glass powder remaining on the 50-hole (300 μm) was placed in a platinum boat through a 30-mesh standard sieve (500 μm) and set at a temperature of 1050 ° C to 1300 ° C. After holding in a gradient furnace for 24 hours, the platinum boat was taken out, and the temperature at which devitrification (crystal foreign matter) was found in the glass was set to the liquidus temperature.

Further, the glass substrate of the present invention preferably has an etching depth of 25 μm or more when immersed in a 10% by mass aqueous HF solution at room temperature for 30 minutes.

Further, the glass substrate of the present invention preferably has a Young's modulus of 75 GPa or more. Here, the "Young's modulus" is a value measured by a dynamic elastic coefficient measurement method (resonance method) based on JIS R1602.

Further, the glass substrate of the present invention preferably has a Young's modulus of 30 GPa/(g/cm ³ ) or more. Here, the "specific Young's modulus" means a value obtained by dividing the Young's modulus by the density.

Further, the glass substrate of the present invention is preferably used in a liquid crystal display.

In addition, the glass substrate of the present invention is preferably used in an OLED display.

Further, the glass substrate of the present invention is preferably used in a high definition display for polycrystalline germanium or oxide TFT driving.

The glass substrate of the present invention contains, as a glass composition, 55% to 65% of SiO ₂ , 15% to 25% of Al ₂ O ₃ , and 5.4% to 9% of B ₂ O ₃ , by mass%. 0% to 5% of MgO, 5% to 10% of CaO, 0% to 5% of SrO, 0% to 10% of BaO, 0.01% to 10% of P ₂ O ₅ , mass ratio of SiO ₂ /B ₂ O ₃ is 6 to 11.5, and the molar ratio (MgO + CaO + SrO + BaO) / Al ₂ O ₃ is 0.8 to 1.4. Hereinafter, the reason for limiting the content of each component as described above will be described. In addition, in the description of each component, unless otherwise indicated, the following expression of % means mass%.

When the content of SiO ₂ is too small, chemical resistance, particularly acid resistance, is liable to lower, and the strain point is liable to lower. It is also difficult to achieve low density. Further, as the initial phase, it is difficult to precipitate two or more kinds of crystals. On the other hand, when the content of SiO ₂ is too large, it is difficult to increase the etching rate, and the high-temperature viscosity is high, and the meltability is liable to lower. Further, SiO ₂ -based crystals, in particular, chalk, are precipitated, and the liquidus viscosity is liable to lower. Therefore, the preferred upper limit content of SiO ₂ is 65%, 64.5%, 64%, 63.5%, especially 63%, and the preferred lower limit content is 55%, 55.5%, 56%, 56.5%, especially 57%. . The optimum range is from 57% to 63%.

When the content of Al ₂ O ₃ is too small, the strain point is lowered, the heat shrinkage value is increased, and the Young's modulus is lowered, whereby the glass substrate is easily bent. On the other hand, when the content of Al ₂ O ₃ is too large, Buffered Hydrofluoric Acid (BHF) property is lowered, white turbidity is likely to occur on the surface of the glass, and crack resistance is likely to be lowered. Further, SiO ₂ -Al ₂ O ₃ -based crystals, particularly mullite, are precipitated in the glass, and the liquidus viscosity is liable to lower. Therefore, the preferred upper limit content of Al ₂ O ₃ is 25%, 24%, 23%, 22%, 21%, 20%, especially 19.5%, and the preferred lower limit content is 15%, 15.5%, 16%. 16.5%, 17%, especially 17.5%. The optimum range is from 17.5% to 19.5%.

B ₂ O ₃ is a component that acts as a flux and is a component that lowers high-temperature viscosity and improves meltability. When the content of B ₂ O ₃ is too small, it does not sufficiently act as a flux, and the BHF resistance or crack resistance is likely to be lowered. 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 and acid resistance are liable to lower. Further, the Young's modulus is lowered, and the amount of bending of the glass substrate tends to increase. Therefore, the preferred upper limit content of B ₂ O ₃ is 9%, 8%, 7.5%, 7%, especially 6.5%, and the preferred lower limit content is 5.4%, 5.6%, 5.8%, especially 6%. The optimum range is 6% to 6.5%.

When the mass ratio is smaller than SiO ₂ /B ₂ O ₃ , the etching rate is likely to increase. Therefore, the preferred upper limit of the mass ratio SiO ₂ /B ₂ O ₃ is 11.5, 11.1, 10.8, 10.5, 10.2, especially 10. On the other hand, if the mass becomes larger than SiO ₂ /B ₂ O ₃ , the strain point is liable to lower. Therefore, the preferred lower limit of the mass ratio SiO ₂ /B ₂ O ₃ is 6, 6.5, 7, 7.5, 8, especially 8.5. The optimum range of the mass ratio SiO ₂ /B ₂ O ₃ is 8.5 to 10.

MgO is a component that lowers the viscosity at high temperature without lowering the strain point and improves the meltability. Further, MgO has an effect of maximizing the density in RO, and when it is introduced excessively, SiO ₂ -based crystals, particularly chalk, are precipitated, and the liquidus viscosity is liable to lower. Further, MgO is a component which easily reacts with BHF to form a product. The reaction product may be adhered to an element on the surface of the glass substrate or adhered to the glass substrate to cause whiteness of the element or the glass substrate. Further, impurities such as Fe ₂ O ₃ are mixed with the MgO introduction raw material such as dolomite into the glass to lower the transmittance of the glass substrate. Therefore, the content of MgO is preferably 0% to 5%, 0% to 4.5%, 0% to 4%, 0% to 3.5%, particularly 0.5% to 3.5%.

Like MgO, CaO is a component that lowers the viscosity at high temperature without lowering the strain point and significantly improves the meltability. However, when the content of CaO is too large, SiO ₂ -Al ₂ O ₃ -RO-based crystals, particularly anorthite, are precipitated, the liquidus viscosity is liable to lower, and the BHF resistance is lowered, and the reaction product is fixed on the surface of the glass substrate. The element or the glass substrate is turbid on the element or attached to the glass substrate. Therefore, a preferred upper limit content of CaO is 10%, 9.5%, 9%, 8.5%, especially 8%, and a preferred lower limit content is 5%, 5.5%, 6%, 6.5%, especially 7%. The optimum range is 7% to 8%.

SrO is a component which improves resistance to devitrification and chemical resistance. However, when the ratio of the RO is too high, the meltability is liable to lower, and the density and thermal expansion coefficient are likely to increase. Therefore, the content of SrO is preferably 0% to 5%, 0.5% to 4.5%, 1% to 4%, 1.5% to 3.5%, particularly 2% to 3%.

BaO is a component which improves resistance to devitrification and chemical resistance, and if the content is too large, the density tends to increase. Further, since SiO ₂ -Al ₂ O ₃ -B ₂ O ₃ -RO-based glass is generally not easily melted, it is very important to improve the meltability and reduce the bubble by the viewpoint of inexpensively supplying a high-quality glass substrate in a large amount. The rate of non-performing due to foreign matter. However, BaO lacks the effect of improving the meltability in RO. Therefore, the content of BaO is preferably 0% to 10%, 0.1% to 8%, 1% to 6%, 1.5% to 4%, particularly 2% to 3%.

When the content of CaO+SrO+BaO is too large, the density increases, and it is difficult to reduce the weight of the glass substrate. Therefore, the content of CaO+SrO+BaO is preferably less than 16%, less than 15%, and particularly less than 14%. Further, "CaO+SrO+BaO" is a total amount of CaO, SrO, and BaO.

When the molar ratio (MgO+CaO+SrO+BaO)/Al ₂ O _{3 is} adjusted to a predetermined range, the liquidus temperature is largely lowered, and crystal foreign matter is less likely to be generated in the glass, and the meltability and moldability are improved. When the molar ratio (MgO+CaO+SrO+BaO)/Al ₂ O ₃ is small, SiO ₂ -Al ₂ O ₃ -based crystals are easily precipitated. On the other hand, when the molar ratio (MgO + CaO + SrO + BaO) / Al ₂ O ₃ becomes large, SiO ₂ -Al ₂ O ₃ -RO-based crystals and SiO ₂ -based crystals are easily precipitated. The preferred upper limit of the molar ratio (MgO + CaO + SrO + BaO) / Al ₂ O ₃ is 1.5, 1.4, 1.35, 1.3, 1.25, especially 1.2, and the preferred lower limit is 0.7, 0.8. 0.9, 0.95, 0.98, 1.0, 1.02, especially 1.05. The optimum range of molar ratio (MgO + CaO + SrO + BaO) / Al ₂ O ₃ is 1.05 - 1.2.

When {2×[SiO ₂ ]—[MgO+CaO+SrO+BaO]} is limited to a predetermined value or less, the etching depth of the HF aqueous solution is increased, and the etching rate is likely to be increased. A preferred upper limit of {2 x [SiO ₂ ]-[MgO+CaO+SrO+BaO]} is 130 mol%, 129 mol%, 128 mol%, 127 mol%, 126 mol% 125.5% by mole, 125% by mole, 124.5% by mole, 124% by mole, 123% by mole, especially 123% by mole. The optimum range is {2 x [SiO ₂ ]-[MgO+CaO+SrO+BaO]}≦123 mol%. Further, "2 × [SiO ₂ ] - [MgO + CaO + SrO + BaO]" means that the molar % of MgO, CaO, SrO, and BaO is subtracted from twice the molar content of SiO ₂ . The value obtained.

It is desirable to introduce two or more (preferably three or more) in the RO. As a result, the liquidus temperature is largely lowered, and crystal foreign matter is less likely to be generated in the glass, and the meltability and moldability are improved.

P ₂ O ₅ is a component which lowers the liquidus temperature of SiO ₂ -Al ₂ O ₃ -CaO-based crystals (especially anorthite) and SiO ₂ -Al ₂ O ₃ -based crystals (especially mullite). Therefore, when P ₂ O ₅ is added, the crystals are hardly precipitated, and two or more crystals are easily precipitated as the initial phase. As a result, the devitrification resistance can be greatly improved. Among them, when P ₂ O ₅ is introduced in a large amount, the glass is easily separated into phases. Therefore, the content of P ₂ O ₅ is preferably 0.01% to 10%, 0.1% to 7%, 0.3% to 6%, 0.5% to 5%, 1% to 4%, particularly preferably 1% to 3%.

When {[Al ₂ O ₃ ]+2×[P ₂ O ₅ ]} is limited to a predetermined value or more, even if the content of SiO ₂ is small, the strain point is likely to be increased. A preferred lower limit value for {[Al ₂ O ₃ ]+2×[P ₂ O ₅ ]} is 10 mol%, 10.5 mol%, 11 mol%, 11.5 mol%, especially 12 mol. %. The optimum range is {[Al ₂ O ₃ ]+2×[P ₂ O ₅ ]}≧12 mol%. Here, "[Al ₂ O ₃ ]+2×[P ₂ O ₅ ]" means the total amount of the molar % content of Al ₂ O _{3 and} the molar % content of twice the P ₂ O ₅ .

In addition to the above components, for example, the following components may be introduced.

ZnO is a component which improves meltability and BHF resistance. When the content is too large, the glass is easily devitrified, or the strain point is lowered, and it is difficult to ensure heat resistance. Therefore, the content of ZnO is preferably 0% to 5%, 0% to 4%, 0% to 3%, 0% to 2%, particularly 0% to 1%.

ZrO ₂ is a component which improves chemical durability, and when the amount of introduction is increased, it is likely to cause devitrified foreign matter of ZrSiO ₄ . A preferred upper limit content of ZrO ₂ is 1%, 0.5%, 0.3%, 0.2%, particularly 0.1%, and from the viewpoint of chemical durability, it is preferably 0.005% or more. The optimum range is from 0.005% to 0.1%. Further, ZrO ₂ may be introduced from the raw material or may be introduced by elution from the refractory.

TiO ₂ has an effect of lowering the viscosity at a high temperature, improving the meltability, and improving chemical durability. When the amount of introduction is excessive, the ultraviolet transmittance is liable to lower. The content of TiO ₂ is preferably 3% or less, 1% or less, 0.5% or less, 0.3% or less, 0.2% or less, and particularly preferably 0.1% or less. Further, when TiO ₂ is introduced (for example, 0.001% or more) in a very small amount, an effect of suppressing the coloration of ultraviolet rays can be obtained.

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, or Al, Si, or the like can be used. The content of these is preferably 1% or less in total.

As ₂ O ₃ and Sb ₂ O ₃ are environmentally hazardous chemicals, so it is desirable to use them as little as possible. The contents of As ₂ O ₃ and Sb ₂ O ₃ are preferably less than 0.3%, less than 0.1%, less than 0.09%, less than 0.05%, less than 0.03%, less than 0.01%, less than 0.005%, respectively. Especially less than 0.003%.

SnO ₂ has a function as a clarifying agent for reducing bubbles in the glass, and has an effect of maintaining high ultraviolet transmittance when coexisting with Fe ₂ O ₃ or FeO. On the other hand, when the content of SnO ₂ is too large, devitrified foreign matter of SnO ₂ is likely to be generated in the glass. The preferred upper limit content of SnO ₂ is 0.5%, 0.45%, 0.4%, 0.35%, especially 0.3%, and the preferred lower limit content is 0.01%, 0.02%, 0.03%, 0.04%, especially 0.05%. The optimum range is from 0.05% to 0.3%.

Iron is a component that is mixed as a raw material impurity. If the content of iron is too large, there is a possibility that the ultraviolet transmittance is lowered. When the ultraviolet transmittance is lowered, there is a problem in the photolithography step of producing the TFT or the alignment step of the liquid crystal using ultraviolet rays. Thus, a preferred minimum content of iron in terms of Fe ₂ O ₃ was 0.001%, the upper limit of the preferred content of Fe ₂ O ₃ in terms of 0.012%, 0.011%, particularly 0.01%. The optimum range is from 0.001% to 0.01%.

Cr ₂ O ₃ is a component which is mixed as a raw material impurity. When the content of Cr ₂ O ₃ is too large, when light is incident on the end surface of the glass substrate and foreign matter is inspected inside the glass substrate by the scattered light, light is hardly transmitted through the glass, and the foreign matter is inferior. Especially in the case where 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, or particularly 0.3 mm or less), light incident from the end surface of the glass substrate is reduced, so that the meaning of limiting the content of Cr ₂ O ₃ is large. A preferred upper limit content of Cr ₂ O ₃ is 0.001%, 0.0009%, 0.0008%, 0.0007%, 0.0006%, particularly 0.0005%, and a preferred lower limit content is 0.00001%. The optimum range is from 0.00001% to 0.0005%.

The content of Fe ₂ O ₃ +Cr ₂ O ₃ is preferably 0.02% or less, 0.015% or less, 0.014% or less, 0.013% or less, or particularly 0.012% or less from the viewpoint of improving light transmittance.

When 0.01% to 0.5% of SnO _{2 is} contained, if the content of Rh ₂ O ₃ is too large, the glass is easily colored. Further, Rh ₂ O ₃ may be mixed in from a glass manufacturing container made of platinum. The content of Rh ₂ O ₃ is preferably from 0% to 0.0005%, more preferably from 0.00001% to 0.0001%.

SO ₃ is a component which is mixed from the raw material as an impurity. When the content of SO ₃ is too large, bubbles called reboiling occur during melting or molding, and defects occur in the glass. A preferred upper limit content of SO ₃ is 0.005%, 0.003%, 0.002%, particularly 0.001%, and a preferred lower limit content is 0.0001%. The optimum range is from 0.0001% to 0.001%.

The alkaline component, particularly Li ₂ O or Na ₂ O, deteriorates the characteristics of the semiconductor film. Therefore, the content of Li ₂ O, Na ₂ O and K ₂ O is preferably 0% to 0.5%, 0% to 0.4%, 0% to 0.3%, 0% to 0.2%, particularly 0 in total. %~0.1%. In addition, in the glass substrate, Li ₂ O, Na ₂ O, and K ₂ O are generally mixed as a raw material impurity in a total amount of about 100 ppm by mass to 200 ppm by mass.

In addition to the ingredients, other ingredients may be introduced. The introduction amount is preferably 2% or less, particularly preferably 1% or less.

The glass substrate of the present invention preferably has SiO ₂ -Al ₂ O ₃ -RO crystal, SiO ₂ crystal, SiO ₂ -Al precipitated in a temperature range from liquidus temperature to (liquidus temperature - 50 ° C). The nature of various crystals within the ₂ O ₃ system crystal. Further, when a plurality of crystals are precipitated, it is preferred to precipitate SiO ₂ -Al ₂ O ₃ -RO-based crystals and SiO ₂ -based crystals. In the vicinity of a region where a plurality of crystal phases and a liquid are in equilibrium, the glass is stabilized and the liquidus temperature is largely lowered. The SiO ₂ -Al ₂ O ₃ -RO system crystal is preferably a SiO ₂ -Al ₂ O ₃ -CaO system crystal, and particularly preferably an anorthite. The SiO ₂ -based crystal is preferably chalk. The SiO ₂ -Al ₂ O ₃ system crystal is preferably mullite.

The glass substrate of the present invention preferably has the following characteristics.

In recent years, in the display for mobile use, the demand for weight reduction has been increased, and the glass substrate has been required to be lighter. In order to satisfy this requirement, it is desirable to reduce the density of the glass substrate. The density is preferably 2.6 g/cm ³ or less, 2.57 g/cm ³ or less, 2.56 g/cm ³ or less, 2.55 g/cm ³ or less, 2.54 g/cm ³ or less, or particularly 2.53 g/cm ³ or less. On the other hand, if the density is too low, the balance of the composition of the glass composition is impaired. As a result, an increase in the melting temperature and a decrease in the viscosity of the liquidus are liable to occur, and the productivity of the glass substrate is liable to lower. In addition, the strain point is also easy to drop. Therefore, the density is preferably 2.4 g/cm ³ or more, 2.41 g/cm ³ or more, 2.42 g/cm ³ or more, 2.43 g/cm ³ or more, 2.44 g/cm ³ or more, and particularly 2.45 g/cm ³ or more.

The coefficient of thermal expansion is preferably 28 × 10 ^-7 / ° C to 45 × 10 ^-7 / ° C, 30 × 10 ^-7 / ° C ~ 43 × 10 ^-7 / ° C, 32 × 10 ^-7 / ° C ~ 42 × 10 ^-7 / ° C, 34 × 10 ^-7 / ° C ~ 41 × 10 ^-7 / ° C, especially 35 × 10 ^-7 / ° C ~ 40 × 10 ^-7 / ° C. If so, it is easy to match the thermal expansion coefficient of the member (for example, a-矽, polysilicon) formed on the glass substrate. Here, the "thermal expansion coefficient" means an average thermal expansion coefficient measured in a temperature range of 30 ° C to 380 ° C, and can be measured, for example, by a dilatometer.

In OLED displays, liquid crystal displays, etc., large-area glass substrates are preferred (for example, 730 mm × 920 mm or more, 1100 mm × 1250 mm or more, particularly 1500 mm × 1500 mm or more), and tend to use thin walls. The glass substrate (for example, the plate thickness is 0.5 mm or less, 0.4 mm or less, particularly 0.3 mm or less). When the glass substrate is made larger in size and thinner, the bending due to its own weight becomes a big problem. In order to reduce the bending of the glass substrate, the specific Young's modulus of the glass substrate must be increased. The specific Young's modulus is preferably 28 GPa/g·cm ^-3 or more, 28.5 GPa/g·cm ^-3 or more, 29 GPa/g·cm ^-3 or more, 29.5 GPa/g·cm ^-3 or more, and 30 GPa. /g·cm ^-3 or more, 30.5 GPa/g·cm ^-3 or more, 31 GPa/g·cm ^-3 or more, 31.5 GPa/g·cm ^-3 or more, and particularly 32 GPa/g·cm ^-3 to 40 GPa/g·cm ^-3 . In addition, when the glass substrate is increased in size and thickness, warpage of the glass substrate becomes a problem after the heat treatment step on the platen or the film formation steps of various metal films, oxide films, semiconductor films, and organic films. 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, 76 GPa or more, 77 GPa or more, 78 GPa or more, and particularly 79 GPa to 100 GPa.

The strain point is preferably 680 ° C or higher, 690 ° C or higher, 695 ° C or higher, 700 ° C or higher, 705 ° C or higher, particularly 710 ° C to 800 ° C. Thereby, it is difficult for the glass substrate to thermally shrink in the formation process of the semiconductor element.

The glass substrate of the present invention is heated from room temperature (25 ° C) at a rate of 5 ° C / min to 500 ° C, held at 500 ° C for 1 hour, and then cooled to room temperature at a rate of 5 ° C / min, the heat shrinkage value It is preferably 30 ppm or less, 25 ppm or less, 22 ppm or less, 20 ppm or less, 18 ppm or less, or particularly 15 ppm or less. In this case, even if the heat treatment is performed in the formation process of the semiconductor element, it is less likely to cause a problem such as a pixel shift. Further, if the heat shrinkage value is too small, the productivity of the glass is liable to lower. Therefore, the heat shrinkage value is preferably 5 ppm or more, 8 ppm or more, and particularly 10 ppm or more. Further, in addition to lowering the heat shrinkage value by increasing the strain point, the heat shrinkage value can be lowered by lowering the cooling rate during molding.

In the overflow downdraw method, the molten glass is flowed down on the surface of the refractory having a substantially wedge-shaped cross section, joined at the lower end of the wedge, and formed into a plate shape. In the slot down draw method, for example, a ribbon-shaped molten glass is poured into a plate-like shape by flowing down from a platinum group metal container having a slit-like opening. If the temperature of the molten glass contacting the forming apparatus is too high, the forming apparatus is likely to deteriorate, and the productivity of the glass substrate is lowered. Therefore, the temperature at a viscosity of 10 ^4.5 dPa·s is preferably 1350 ° C or lower, 1340 ° C or lower, 1330 ° C or lower, 1320 ° C or lower, 1310 ° C or lower, 1300 ° C or lower, particularly 1100 ° C to 1290 ° C. Further, the temperature at a viscosity of 10 ^4.5 dPa·s corresponds to the temperature of the molten glass at the time of molding.

In general, since low-alkali glass or alkali-free glass has low meltability, improvement in meltability is a problem. When the meltability is improved, the defect rate due to bubbles, foreign matter, and the like can be reduced, so that a high-quality glass substrate can be supplied in a large amount and at low cost. On the other hand, if the viscosity of the glass in the high temperature region is too high, it is difficult to promote the exhaust in the melting step. Therefore, the temperature at a viscosity of 10 ^{2 .5} dPa·s is preferably 1700 ° C or lower, 1690 ° C or lower, 1680 ° C or lower, 1670 ° C or lower, 1660 ° C or lower, or particularly 1650 ° C or lower. Here, "the temperature at a viscosity of 10 ^2.5 dPa·s" can be measured by a platinum ball pulling method. Further, the temperature at a high temperature viscosity of 10 ^2.5 dPa·s corresponds to the melting temperature, and the lower the temperature, the more excellent the meltability.

In the case of forming by a down-draw method or the like, the devitrification resistance becomes important. When the molding temperature of the glass containing SiO ₂ , Al ₂ O ₃ , B ₂ O _{3 ,} and RO in the glass composition is considered, the liquidus temperature is preferably less than 1300 ° C, 1280 ° C or less, 1270 ° C or less, and 1260. °C or less, 1250 ° C or less, 1240 ° C or less, 1230 ° C or less, 1220 ° C or less, particularly 900 ° C to 1210 ° C. Further, the liquidus viscosity is preferably 10 ^4.3 dPa · s or more, 10 ^{4. 4} dPa · s or more, 10 ^4.5 dPa · s or more, 10 ^4.6 dPa · s or more, 10 ^4.7 dPa · s or more, 10 ^4.8 dPa · s or more, 10 ^4.9 dPa·s or more, particularly 10 ^5.0 dPa·s to 10 ^7.0 dPa·s.

The etching depth when immersed in a 10% by mass aqueous HF solution at room temperature (20 ° C) for 30 minutes is preferably 25 μm or more, 27 μm or more, 28 μm or more, 29 μm to 50 μm, and particularly preferably 30 μm to 40 μm. Mm. This etch depth is an indicator of the etch rate. That is, if the etching depth is large, the etching rate is increased, and if the etching depth is small, the etching rate is slow.

The β-OH value is preferably 0.35/mm or less, 0.3/mm or less, 0.25/mm or less, 0.2/mm or less, and particularly preferably 0.15/mm or less. If the β-OH value is too large, the strain point is liable to decrease. On the other hand, if the β-OH value is too small, the meltability is liable to lower. Therefore, the β-OH value is preferably 0.01/mm or more, particularly 0.03/mm or more.

Here, the "β-OH value" refers to a value obtained by measuring the transmittance of glass using Fourier transform infrared spectroscopy (FT-IR) and using the following formula.

[Number 1] 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 : hydroxyl group Minimum transmittance (%) near the absorption wavelength of 3600 cm ^-1

As a method of lowering the β-OH value, there are the following methods (1) to (7), and among them, the methods (1) to (4) are effective. (1) Select a raw material with a low moisture content. (2) Adding a desiccant such as Cl or SO ₃ to the glass batch. (3) Conductive heating by heating the electrode. (4) A small melting furnace is used. (5) Decreasing the amount of water in the furnace environment. (6) N ₂ foaming was carried out in molten glass. (7) Increase the flow rate of the molten glass.

The glass substrate of the present invention preferably has a molded merging surface at a central portion in the thickness direction, that is, it is formed by an overflow down-draw method. The overflow down-draw method is a method in which molten glass is allowed to overflow from both sides of a wedge-shaped refractory, and the overflowed molten glass is joined at the lower end of the wedge shape, and is formed by extending downward and forming into a plate shape. 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 a state of a free surface. Thereby, a glass substrate which is excellent in surface quality even if it is not polished can be manufactured at low cost. Further, it is also easy to increase the area or thickness of the glass substrate.

In addition to the overflow down-draw method, the glass substrate may be formed by, for example, a down-draw method (a flow-down method, a re-drawing method, or the like), a float method, or the like.

In the glass substrate of the present invention, the 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 0.05 mm to 0.3 mm. The smaller the plate thickness, the easier it is to make the device lighter. On the other hand, when the thickness of the sheet is too small, the glass substrate is easily bent. Since the Young's modulus or the Young's modulus of the glass substrate of the present invention is high, it is difficult to cause a problem due to bending. Further, the thickness of the sheet can be adjusted in accordance with the flow rate at the time of glass production, the plate drawing speed, and the like. [Examples]

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

Table 1 shows examples (sample No. 1 to sample No. 18) of the present invention.

[Table 1]

Each sample was prepared as follows. First, a glass batch obtained by blending a glass raw material in the form of a glass composition in the table was placed in a platinum crucible and melted at 1600 ° C for 24 hours. When the glass batch is melted, it is stirred and homogenized using a platinum stirrer. Then, the molten glass was discharged to a carbon plate and formed into a plate shape. For each sample obtained, the density, thermal expansion coefficient, Young's modulus, specific Young's modulus, strain point, cold point, softening point, temperature at a viscosity of 10 ^4.5 dPa·s, and 10 ^4.0 dPa were evaluated. The temperature at s viscosity, the temperature at a viscosity of 10 ^3.0 dPa·s, the temperature at a viscosity of 10 ^2.5 dPa·s, the liquidus temperature, the initial phase, the liquidus viscosity logη, the amount of H ₂ O, by The etching depth of the HF aqueous solution.

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

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

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

The strain point, the cold point, and the softening point are values measured based on the methods of ASTM C336 and C338.

10 ^4.5 dPa·s viscosity, temperature at 10 ^4.0 dPa·s, temperature at 10 ^3.0 dPa·s, temperature at 10 ^2.5 dPa·s is a platinum ball pull method The value obtained by the measurement.

The liquidus temperature and the liquidus viscosity were measured as follows. Each sample was pulverized, and the glass powder remaining on 50-hole (300 μm) was placed in a platinum boat through a 30-well standard sieve (500 μm), and maintained in a temperature gradient furnace set at 1050 ° C to 1300 ° C. After the hour, the platinum boat was taken out, and the temperature at which devitrification (crystal foreign matter) was found in the glass was taken as the liquidus temperature. Then, the crystal precipitated from the liquidus temperature to the temperature range of (liquidus temperature - 50 ° C) was evaluated as the initial phase. In the table, "Ano" means albite, "Cri" means chalk, and "Mul" means mullite. Further, the viscosity of the glass at the liquidus temperature was measured by a platinum ball pulling method and used as a liquidus viscosity.

After optical polishing on both surfaces of each sample, a part of the surface of the sample was shielded, and after immersing in a 10 mass% HF aqueous solution at room temperature (20 ° C) for 30 minutes, the surface of the obtained sample was measured. The step between the shield and the etched portion is used to evaluate the etch depth.

The amount of H ₂ O is a value obtained by measuring the β-OH value of the glass by the above method.

The sample No. 1 to sample No. 18 have a coefficient of thermal expansion of 35 × 10 ^-7 / ° C to 40 × 10 ^-7 / ° C, and the strain point is 680 ° C or more, thereby reducing the heat shrinkage value. Further, the Young's modulus is 75 GPa or more, and the Young's modulus is 30 GPa/(g/cm ³ ) or more, and it is less likely to be bent or deformed. In addition, the temperature at a viscosity of 10 ^4.5 dPa·s is 1290 ° C or less, the temperature at a viscosity of 10 ^2.5 dPa·s is 1632 ° C or lower, and the liquidus temperature is 1206 ° C or lower, and the liquidus viscosity is 10 ^4.9 dPa. s or more, it is excellent in meltability, moldability, and devitrification resistance, and is suitable for mass production. Further, since the etching depth is 30 μm or more, the etching rate can be increased. [Industrial availability]

The glass substrate of the present invention can simultaneously achieve high devitrification resistance, high strain point, and high etching rate. Therefore, the glass substrate of the present invention is suitable for a substrate of a display such as an OLED display or a liquid crystal display, and is suitable for a substrate of a display driven by LTPS or an oxide TFT.

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Claims (12)

A glass substrate characterized by containing, as a glass composition, 55% to 65% of SiO ₂ , 15% to 25% of Al ₂ O ₃ , and 5.4% to 9% of B ₂ O ₃ , 0. % to 5% of MgO, 5% to 10% of CaO, 0% to 5% of SrO, 0% to 10% of BaO, 0.01% to 10% of P ₂ O ₅ , mass ratio of SiO ₂ /B ₂ O ₃ is 6 to 11.5, and the molar ratio (MgO + CaO + SrO + BaO) / Al ₂ O ₃ is 0.8 to 1.4. The glass substrate according to claim 1, wherein the content of Li ₂ O+Na ₂ O+K ₂ O in the glass composition is 0.5% by mass or less. The glass substrate according to any one of the items 1 to 2, wherein the content of Fe ₂ O ₃ +Cr ₂ O ₃ in the glass composition is 0.012% by mass or less. The glass substrate according to any one of claims 1 to 3, wherein the glass substrate has a strain point of 680 ° C or higher. The glass substrate according to any one of claims 1 to 4, wherein a temperature at a viscosity of 10 ^4.5 dPa·s is 1300 ° C or lower. The glass substrate according to any one of claims 1 to 5, which has a liquidus viscosity of 10 ^4.8 dPa·s or more. The glass substrate according to any one of claims 1 to 6, which has an etching depth of 25 μm or more when immersed in a 10 mass% hydrofluoric acid aqueous solution at room temperature for 30 minutes. The glass substrate according to any one of claims 1 to 7, which has a Young's modulus of 75 GPa or more. The glass substrate according to any one of claims 1 to 8, which has a Young's modulus of 30 GPa/(g/cm ³ ) or more. The glass substrate according to any one of claims 1 to 9, which is used in a liquid crystal display. The glass substrate according to any one of claims 1 to 10, which is used in an organic light emitting diode display. The glass substrate according to any one of claims 1 to 11, which is used in a high-definition display of polycrystalline germanium or oxide film transistor driving.