Glass composition, alkali-free glass substrate with high strain point and preparation method thereof

Abstract

The present disclosure provides a glass composition, an alkali-free glass substrate with a high strain point, and a preparation method thereof. The glass composition comprises 66-73 mol% SiO2, 10-15 mol% Al2O3, 5-10 mol% CaO, 2-6 mol% MgO, 2-5 mol% B2O3, 1-2.5 mol% Pr2O3, 0-4 mol% SrO, 0-4 mol% BaO, and 0-0.5 mol% SnO2. The alkali-free glass substrate with a high strain point prepared using the glass composition can, by adding an appropriate amount of rare earth oxide Pr2O3 to the glass substrate, reduce the melting temperature during production of the glass substrate, thereby balancing the adverse effects of a lower β-OH value that easily leads to an increase in melting temperature. Furthermore, the introduction of Pr2O3 can also appropriately increase the strain point temperature of the glass substrate. Furthermore, the introduction of Pr2O3 can also impart a blue light filtering effect to the glass substrate.

Description

Technical Field

[0001] The present disclosure relates to the technical field of glass manufacturing, and in particular to a glass composition, an alkali-free glass substrate with a high strain point, and a preparation method thereof. Background Art

[0002] In the field of liquid crystal display applications, polycrystalline silicon thin-film transistors (p-Si-TFTs) are the current mainstream preferred technology. This is mainly based on the fact that (p-Si-TFT) devices have higher electron mobility than traditional amorphous silicon transistors (a-Si), so they can transmit electrons more efficiently and have greater performance advantages in the field of preparing smaller and faster transistors.

[0003] However, p-Si transistors present a significant challenge during fabrication: they require higher heat treatment temperatures (approximately 450-600°C) than a-Si (amorphous silicon) transistors. The typical maximum temperature required during a-Si transistor fabrication is approximately 350°C. Within this temperature range, most AMLCD glass substrates undergo irreversible dimensional changes, also known as shrinkage.

[0004] The degree of shrinkage depends primarily on the manufacturing process used for the glass substrate and the viscoelastic properties of the glass itself. For example, if a glass substrate is produced using the float glass process, the glass substrate cools gradually from a molten state to a solidified state at a relatively slow rate, "freezing" relatively low-temperature structures into the glass substrate during this process, resulting in a lower "fictive temperature." In contrast, using the fusion down-draw process, the glass substrate rapidly cools from a molten state to a solidified state, "freezing" relatively high-temperature structures into the glass substrate, resulting in a higher "fictive temperature." The driving force for shrinkage is determined by the temperature difference between the glass substrate's fictive temperature and the temperature at which it undergoes the shrinkage process. The greater the temperature difference, the greater the driving force for shrinkage. Therefore, for the same glass composition, glass substrates produced using the fusion down-draw process exhibit a relatively higher degree of shrinkage.

[0005] Considering that the glass substrates manufactured by the fusion down-draw method do not need to undergo subsequent grinding and polishing processes, it has more advantages in reducing the production cost of the glass substrates and improving product performance. Therefore, it is hoped that the degree of shrinkage of the glass substrates manufactured by the fusion down-draw method when undergoing high-temperature heat treatment can be reduced as much as possible. At present, the following methods are generally used to improve it: (1) By preheating the glass substrate in advance and placing it at a temperature close to the heat treatment temperature it will undergo, the degree of shrinkage of the glass substrate when it undergoes subsequent high-temperature heat treatment can be effectively reduced. However, the use of pretreatment will increase production costs and reduce production efficiency on the one hand; on the other hand, since different high-temperature heat treatment temperatures will be experienced during the manufacture of p-Si-TFTs, it means that preheating treatments at different temperatures must be performed in the early stage, which will also increase production costs and the complexity of actual operations. (2) By increasing the strain point temperature of the glass substrate to make it significantly higher than the highest temperature at which the glass substrate needs to undergo high-temperature heat treatment in the later stage, the degree of shrinkage of the glass substrate can be effectively reduced. However, in general, the higher the strain point temperature of the glass, the higher the melting temperature required, which will lead to an increase in melting energy consumption and performance requirements for refractory materials.

[0006] In current technology, some have proposed increasing the strain point of a glass substrate by reducing the moisture content (β-OH value) in the glass substrate or by introducing rare earth oxides such as Y2O3 and / or La2O3 into conventional alkali-free glass substrate components. However, in actual applications, these technical solutions all have certain adverse effects on other properties of the glass substrate. For example, if the strain point temperature of a glass substrate is increased by controlling and reducing the moisture content (β-OH value) in the glass substrate, the β-OH value needs to be reduced to a sufficiently low value to achieve a higher glass strain point temperature. However, an excessively low β-OH value can easily increase the melting temperature of the glass, thereby deteriorating the glass's solubility. On the other hand, it can increase the process difficulty and significantly increase the cost. If a higher glass strain point temperature is achieved by introducing rare earth oxides such as Y2O3 and / or La2O3 alone, it can easily increase the overall density of the glass substrate and increase the thermal expansion coefficient, which hinders the lightweighting of the glass substrate. At the same time, considering the relatively high price and cost of rare earth oxides themselves, adding too much rare earth oxides can significantly increase the production cost of the glass.

[0007] Therefore, it is very meaningful to develop a method for preparing a glass substrate that can effectively increase the strain point temperature of the glass substrate without adversely affecting other properties of the glass substrate. Summary of the Invention

[0008] A technical problem to be solved by the present disclosure is: how to effectively increase the strain point temperature of a glass substrate without adversely affecting other properties of the glass substrate.

[0009] To solve the above technical problems, in a first aspect, embodiments of the present disclosure provide a glass composition comprising the following components in molar percentages:

[0010]

[0011]

[0012] In the glass composition disclosed herein, SiO2 is a glass network former and an essential component. Controlling the SiO2 content between 66 and 73 mol% can increase the strain point temperature and Young's modulus of the glass substrate and reduce its density. If the SiO2 content is less than 66 mol%, the glass substrate exhibits poor chemical resistance (particularly acid resistance). If the SiO2 content is greater than 73 mol%, the high-temperature viscosity of the glass substrate increases significantly, impairing the meltability of the glass components.

[0013] Al2O3 can increase the strain point temperature and Young's modulus of the glass substrate. It is more appropriate to control its content above 10 mol%. However, if the Al2O3 content is higher than 15 mol%, it will easily lead to increased viscosity of the glass and prominent crystallization problems.

[0014] CaO can reduce the high-temperature viscosity of glass, improve its meltability, and ensure that the strain point of the glass substrate is not lowered. However, excessive CaO can reduce the chemical resistance and flexural strength of the glass, while also increasing the liquidus temperature of the glass, making it difficult to process overflow down-draw molding. Therefore, it is best to control the CaO content to 5-10 mol%.

[0015] Like CaO, MgO can reduce the high-temperature viscosity of glass and improve its meltability. Furthermore, among alkaline earth metal oxides, MgO is the most effective component in reducing glass density. However, excessive MgO in the glass composition can react with BHF-buffered hydrofluoric acid, resulting in a cloudy appearance on the glass substrate surface. Therefore, the MgO content should be controlled between 2 and 6 mol%.

[0016] B2O3 is a good glass melting flux, improving glass meltability and reducing glass melting costs. However, if its content is too high, it can easily lead to reduced acid resistance in the glass, which can affect subsequent processing of the glass substrate. Therefore, the B2O3 content is preferably controlled within 2-5 mol%.

[0017] Pr2O3, a rare earth oxide, can be added to glass compositions to reduce their high-temperature viscosity, thereby improving their meltability. This can effectively offset the adverse effects of increasing the glass's melting temperature due to a reduction in the β-OH value of the water content in the glass. Furthermore, Pr2O3 can modestly increase the strain point temperature of the glass. Furthermore, the introduction of Pr2O3 can impart a higher blue light filtering capability to the glass (430-480nm band), effectively reducing the damage to the human eye caused by blue light. However, if the amount of Pr2O3 added is too high, it can increase raw material costs and significantly increase the glass density. Therefore, it is advisable to control the Pr2O3 content within the range of 1-2.5 mol%.

[0018] SrO can improve the devitrification resistance of glass, reduce high-temperature viscosity, and improve the chemical resistance of glass. However, too high an SrO content can easily lead to an increase in the density and thermal expansion coefficient of the glass, and the cost of SrO raw materials is high. Therefore, it is appropriate to control the SrO content within the range of 0 to 4 mol%.

[0019] The role of BaO is similar to that of SrO, but from an environmentally friendly perspective, the Ba content in the glass should be kept as low as possible. Therefore, it is appropriate to control its content within the range of 0 to 4 mol%.

[0020] SnO2 is mainly used as a clarifier to improve the meltability of glass; however, if the SnO2 content is too high, it will easily lead to poor devitrification resistance of the glass. Therefore, it is advisable to control its content within 0 to 0.5 mol%.

[0021] In some embodiments, the glass composition further includes at least one of F, Cl, and Br, and the mole percentage of the at least one of F, Cl, and Br in the glass composition is 0 to 0.5 mol%.

[0022] In the glass composition disclosed herein, the addition of F, Cl, and Br can promote glass melting, reduce glass melting costs, and extend the life of manufacturing equipment. However, excessive F, Cl, and Br content can lower the strain point temperature of the glass. Therefore, it is best to control the F+Cl+Br content within the range of 0 to 0.5 mol%. Furthermore, Cl can act as a desiccant and can be used as a component to reduce the β-OH value in the glass substrate.

[0023] In some embodiments, M is defined as ([CaO] + [SrO] + [BaO] + 1.5 [Pr2O3]) / [Al2O3], so that M satisfies 0.7≤M≤1.1; wherein [CaO], [SrO], [BaO], [Pr2O3], and [Al2O3] represent the molar percentages of CaO, SrO, BaO, Pr2O3, and Al2O3 in the glass composition, respectively.

[0024] In the present disclosure, by making M satisfy 0.7≤M≤1.1, the devitrification resistance of the glass can be significantly improved, which is more conducive to forming the glass substrate by the overflow down-draw method.

[0025] In some embodiments, N is defined as [CaO] / ([MgO]+[BaO]+[SrO]), where [CaO], [MgO], [BaO], and [SrO] represent the mole percentages of CaO, MgO, BaO, and SrO, respectively, such that N satisfies 0.8≤N≤1.6.

[0026] In the present disclosure, if N is less than 0.8, it will increase the difficulty of melting the glass composition and increase the melting cost of the glass; if N is greater than 1.6, it will easily lead to an increase in the liquidus temperature of the glass composition, increase the load of the molding equipment of the glass composition during the molding process, and require higher high-temperature resistance of the refractory materials in the molding equipment, which will indirectly increase production costs.

[0027] In a second aspect, an embodiment of the present disclosure provides a method for preparing an alkali-free glass substrate having a high strain point from the glass composition of the first aspect, comprising: mixing and melting the components, and preparing the alkali-free glass substrate having a high strain point by an overflow down-draw process.

[0028] In some embodiments, the melting temperature is 1580-1660° C., and the temperature is maintained for 4-8 hours after melting.

[0029] In a third aspect, an embodiment of the present disclosure provides an alkali-free glass substrate with a high strain point, which is prepared using the method of the second aspect.

[0030] In some embodiments, the strain point temperature of the glass substrate is above 780°C.

[0031] In some embodiments, the amount of moisture in the glass substrate is β-OH ≤ 0.3 / mm.

[0032] In the present disclosure, by controlling the moisture content in the glass substrate to a β-OH value ≤ 0.3 / mm, the strain point temperature of the glass substrate can be effectively increased. Generally speaking, the moisture content in the glass substrate can be reduced by one or more of the following methods: ① Selecting raw materials with low water content (for example, minimizing the use of raw materials containing hydroxides); ② Appropriately increasing the Cl content in the glass composition; ③ Conducting the glass substrate preparation process under a circulating dry protective gas to avoid the introduction of moisture during the preparation process; ④ Increasing the flow rate of the molten glass to reduce the residence time of the retained molten glass; ⑤ Using an electric melting method.

[0033] In some embodiments, from the perspective of optimizing cost, the amount of moisture in the glass substrate is 0.1 / mm≤β-OH≤0.2 / mm.

[0034] In some embodiments, the density of the glass substrate is ≤2.45 g / cm 3 .

[0035] In some embodiments, the liquidus viscosity of the glass substrate is ≥ 110 kpoise.

[0036] In some embodiments, the liquidus viscosity of the glass substrate is ≥ 120 kpoise.

[0037] In some embodiments, the liquidus viscosity of the glass substrate is ≥ 150 kpoise.

[0038] In some embodiments, the Young's modulus of the glass substrate is greater than 78 GPa.

[0039] In some embodiments, the thermal expansion coefficient CTE (20-300°C) of the glass substrate is 32×10 -7 ~42×10 -7 / ℃;

[0040] In some embodiments, the glass substrate has a melting temperature (temperature at which the high temperature viscosity is 200 poise) lower than 1660°C.

[0041] In a fourth aspect, an embodiment of the present disclosure provides a use of the alkali-free glass substrate with a high strain point according to the third aspect in preparing a display device.

[0042] Through the above-mentioned technical solution, the alkali-free glass substrate with a high strain point provided by the present disclosure incorporates an appropriate amount of the rare earth oxide Pr2O3 into the glass substrate. This reduces the melting temperature during glass substrate production, thereby balancing the adverse effect of a lower β-OH value that tends to increase the melting temperature. Furthermore, the introduction of Pr2O3 also serves to appropriately increase the strain point temperature of the glass substrate. Furthermore, the introduction of Pr2O3 into the alkali-free glass substrate with a high strain point provided by the present disclosure also imparts a blue light filtering effect to the glass substrate. DETAILED DESCRIPTION

[0043] The embodiments of the present disclosure are further described in detail below with reference to the examples. The detailed description of the following examples is used to illustrate the principles of the present disclosure, but is not intended to limit the scope of the present disclosure. The present disclosure can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions within the scope of the claims.

[0044] The present disclosure provides these embodiments to make the present disclosure thorough and complete, and to fully express the scope of the present disclosure to those skilled in the art. It should be noted that unless otherwise specifically stated, the method steps, material components, numerical expressions and numerical values ​​described in these embodiments should be interpreted as merely exemplary and not as limiting.

[0045] It should be noted that, in the description of this disclosure, unless otherwise specified, the meaning of "a plurality of" is greater than or equal to two. In addition, the use of "include" or "comprise" and similar words in this disclosure means that the elements before the word include the elements listed after the word, and does not exclude the possibility of also including other elements.

[0046] All terms used in this disclosure have the same meaning as understood by one of ordinary skill in the art to which this disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in, for example, common dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and should not be interpreted in an idealized or highly formal sense, unless explicitly defined as such herein.

[0047] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0048] The glass substrate samples of the embodiments and comparative examples were prepared as follows: raw materials were prepared according to the amounts of the components shown in Table 1, and the raw materials were uniformly mixed to obtain a raw material mixture; the raw material mixture was then subjected to a high-temperature melting treatment at 1640° C. and kept warm for 5 hours to obtain a molten glass liquid; and the molten glass liquid was then formed by an overflow down-draw process to obtain a glass substrate.

[0049] The performance indicators of the glass substrate samples prepared in each embodiment and comparative example were tested, and the test results are shown in Table 1.

[0050] The performance indicators tested include:

[0051] (1) High temperature viscosity: A rotary high temperature viscometer (equipment model: RSV1700) was used to test the relationship between the viscosity of the glass liquid and the temperature at different temperatures.

[0052] (2) Liquidus viscosity: The test was performed using a gradient temperature furnace (equipment model: Orton GTF-MD-16 series). The required liquidus viscosity was obtained by the liquidus viscosity curve obtained from the test.

[0053] (3) Young's modulus: obtained by resonance method test based on JIS R1602.

[0054] (4) Density: obtained by the Archimedes method (based on ASTM C693 standard), unit: g / cm 3 .

[0055] (5) Annealing point temperature and strain point temperature: obtained by testing with an annealing point and strain point temperature tester (equipment model: ANS-800).

[0056] (6) Thermal expansion coefficient (20-300°C): obtained by testing with a thermal expansion coefficient tester (equipment model: DIL 402 Expedis Classic).

[0057] (7) Transmittance of short-wave blue light T (430-480 nm): obtained by testing with a UV-visible spectrophotometer (equipment model: Perkin Elmer Lamda950).

[0058] Table 1 Glass component content (mol %) and performance indicators of each embodiment and comparative example

[0059]

[0060]

[0061]

[0062] The above test results show that as the moisture content (β-OH) value in the glass substrate decreases, the strain point temperature of the glass substrate increases, and at the same time, its melting temperature also increases. By introducing an appropriate amount of rare earth oxide (Pr2O3), the problem of increasing the melting temperature due to a decrease in the moisture content (β-OH) value can be effectively solved, while further increasing the strain point temperature of the glass substrate. When the Pr2O3 content is less than 1 mol%, i.e., 0.5 mol% (Comparative Example 1), the effect of improving the meltability of the glass substrate at a relatively low moisture content (β-OH) value is not significant. When the Pr2O3 content is greater than 2.5 mol%, i.e., 3 mol% (Comparative Example 2), a relatively higher strain point temperature is achieved, but the density of the glass substrate increases significantly, which has a negative impact on achieving lightweight glass substrates, especially for the production of large-generation glass substrates. Therefore, the Pr2O3 content should be controlled within the range of 1 to 2.5 mol%.

[0063] Thus far, various embodiments of the present disclosure have been described in detail. To avoid obscuring the concept of the present disclosure, some details known in the art have not been described. Based on the above description, those skilled in the art can fully understand how to implement the technical solutions disclosed herein.

[0064] Although some specific embodiments of the present disclosure have been described in detail through examples, those skilled in the art will understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Those skilled in the art will understand that the above embodiments may be modified or some technical features may be replaced with equivalents without departing from the scope and spirit of the present disclosure. In particular, as long as there are no structural conflicts, the various technical features mentioned in the various embodiments may be combined in any manner.

Claims

1. A glass composition, characterized in that: The following mole percentages of the components are included: SiO2 66~73mol%; Al2O310~15mol%; CaO 5~10mol% MgO 2~6mol%; B2O32~5mol%; Pr2O31~2.5mol%; SrO 0~4mol%; BaO 0~4mol%; SnO20~0.5mol%; Define M = ([CaO] + [SrO] + [BaO] + 1.5 [Pr2O3]) / [Al2O3], so that M satisfies 0.7 ≤ M ≤ 1.1; where [CaO], [SrO], [BaO], [Pr2O3], and [Al2O3] represent the mole percentages of CaO, SrO, BaO, Pr2O3, and Al2O3 in the glass composition, respectively; The method for preparing an alkali-free glass substrate having a high strain point from the glass composition comprises: mixing and melting the components, and preparing the alkali-free glass substrate having a high strain point by an overflow down-draw process; The moisture content in the alkali-free glass substrate is β-OH ≤ 0.3 / mm.

2. The glass composition according to claim 1, wherein The glass composition further includes at least one of F, Cl, and Br, and the mole percentage of the at least one of F, Cl, and Br in the glass composition is greater than 0 and less than or equal to 0.5 mol %.

3. The glass composition according to claim 1 or 2, characterized in that Define N = [CaO] / ([MgO] + [BaO] + [SrO]) so that N satisfies 0.8 ≤ N ≤ 1.6; wherein [CaO], [MgO], [BaO], and [SrO] represent the mole percentages of CaO, MgO, BaO, and SrO in the glass composition, respectively.

4. The glass composition according to claim 3, wherein The strain point temperature of the alkali-free glass substrate is above 780°C.

5. The glass composition according to claim 4, wherein The moisture content in the alkali-free glass substrate is 0.1 / mm≤β-OH≤0.2 / mm. 6 . Use of the glass composition according to claim 1 in preparing an alkali-free glass substrate for a display device.

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