High strain point low shrinkage alkali-free substrate glass and method for producing the same

Abstract

The application belongs to the technical field of glass, and particularly relates to high-strain-point low-shrinkage alkali-free substrate glass and a preparation method thereof. The high-strain-point low-shrinkage alkali-free substrate glass comprises the following components in terms of mole percentage: SiO2 63.2-69.8%, Al2O3 8.5-16.9%, B2O3 3.50-14.5%, MgO 1.5-3.3%, CaO 4.0-11.5%, SrO 0.35-4.5%, ZnO 0.01-1.5%, TiO2 0.01-2.5%, ZrO2 0.05-1.2%, SnO2 0.06-0.32%, and REO 0-4%. The REO is rare earth oxide. The mole percentage of each component satisfies the limitation of a synergy index CPI, and the final CPI value is 4.6-10.8. The prepared glass product has high strain point, low thermal shrinkage, high modulus and the like in terms of performance, has suitable high-temperature resistivity, low liquidus temperature and the like in terms of formability, has environmental friendliness of no heavy metal, simultaneously meets the harsh performance requirements of high-end display processes on the glass product and the feasibility and economy of industrial production, and is suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of glass technology, and in particular relates to a high strain point, low shrinkage, alkali-free substrate glass and its preparation method. Background Technology

[0002] As display technology advances towards higher resolution, larger size, and greater flexibility, LTPS (Low Temperature Polycrystalline Silicon) and IGZO (Indium Tin Oxide Semiconductor) technologies have become core technologies for high-end display devices. These technologies involve multiple high-temperature annealing and rapid thermal annealing processes, placing extremely high demands on the heat resistance and dimensional stability of the substrate glass. If the strain point of the substrate glass is insufficient, irreversible thermal shrinkage will occur during high-temperature processing, leading to misalignment of the TFT (Thin Film Transistor) circuit layer and severely impacting product yield. Simultaneously, the electro-melting / electro-flushing processes used in glass manufacturing also impose strict requirements on the high-temperature resistivity of the molten glass; excessively high or low resistivity will affect melting efficiency and product quality.

[0003] In existing technologies, the development of high-strain-point alkali-free glass often focuses on optimizing a single performance, making it difficult to achieve synergistic improvement of multiple key properties. Chinese invention patent application CN119330583A discloses a low-reheat shrinkage alkali-free glass and its preparation method. On the one hand, it increases the strain point of the glass by increasing the SiO2 content while reducing the reheat shrinkage rate; on the other hand, it introduces BaO to control the glass density and increase the strain point temperature. While the above technical solution increases the glass density by introducing BaO, it does not conform to environmental protection trends. Chinese invention patent application CN121517103A discloses a rare-earth co-doped alkali-free aluminum borosilicate glass and its application. By controlling the co-doping ratio of rare-earth oxides La2O3 and Y2O3, the glass possesses a high strain point, low melting temperature, low coefficient of thermal expansion, and high elastic modulus. However, improper rare-earth element ratios in the above technical solutions can lead to crystallization risks or reduced ultraviolet transmittance. Chinese invention patent application CN121449330A discloses a titanium-rare earth synergistic ultra-high strain point high resistance alkali-free glass and its preparation method. By constructing a unique "titanium-rare earth synergistic reinforcement network" and defining two key control parameters for the first time—high temperature performance index (HTPI) and resistance synergy factor (RCF)—the strain point of the glass product is ultimately improved. However, the above technical solution does not limit the upper limit of rare earth addition. If the rare earth content is too high, not only will the manufacturing cost increase, but the glass density will also increase significantly. At the same time, the melting difficulty and liquidus temperature will increase, affecting glass forming.

[0004] In alkali-free substrate glass systems, the functions of each component do not exist independently, but rather are jointly determined by physicochemical interactions, leading to the glass's melting, forming, and final performance. While the aforementioned technical solutions have achieved optimization of single or a few properties by adjusting the content of some components, they still lack methods for synergistic optimization of multiple components and multiple properties.

[0005] Therefore, there is an urgent need to develop a method for synergistic optimization of multiple components and properties in alkali-free substrate glass to obtain alkali-free substrate glass that has high strain point, low reheat shrinkage rate, suitable high temperature resistivity, low expansion coefficient, high mechanical strength, suitable density and low crystallization risk, and is also cost-controllable, environmentally friendly and easily fusible. Summary of the Invention

[0006] The purpose of this invention is to provide a high strain point, low shrinkage alkali-free substrate glass and its preparation method, so as to solve the problem that the composition optimization of alkali-free substrate glass in the prior art is limited to some components, single or a few properties.

[0007] To achieve the above objectives, the first aspect of the present invention provides a high strain point, low shrinkage, alkali-free substrate glass, wherein the high strain point, low shrinkage, alkali-free substrate glass comprises the following molar percentage components: SiO2 63.2–69.8%, Al2O3 8.5–16.9%, B2O3 3.50–14.5%, MgO 1.5–3.3%, CaO 4.0–11.5%, SrO 0.35–4.5%, ZnO 0.01–1.5%, TiO2 0.01–2.5%, ZrO2 0.05–1.2%, SnO2 0.06–0.32%, REO 0–4%, where REO is a rare earth oxide; The synergy index is calculated according to Formula 1. The synergy index is called CPI (Cooperative Performance Index).

[0008] Wherein, [Al2O3], [SiO2], [TiO2], [ZrO2], [B2O3], [SrO], [CaO], [ZnO], and [MgO] represent the molar percentages of the corresponding components in the low-shrinkage alkali-free substrate glass at high strain points; R is calculated according to Formula 2: R=k1×[RE1O]+k2×[RE2O]+k3×[RE3O]+…+k n ×[RE n Formula 2, Where n≥1, [RE1O], [RE2O], [RE3O], [RE n[O] represents the molar percentages of the first, second, third, and nth rare earth oxides in the high-strain-point, low-shrinkage alkali-free substrate glass, respectively, k1, k2, k3, and k n These are the weighting coefficients for the first, second, third, and nth rare earth oxides, respectively. k is calculated according to formula 3. n : k n =10.0×(CFS) n / 2.82) Formula 3, Where, k n CFS is the weighting coefficient for the nth rare earth oxide. n denoted as ionic strength of rare earth ions in the nth rare earth oxide, 10.0 is the weighting coefficient for lanthanum oxide, and 2.82 is the ionic strength of lanthanum ions. CFS is calculated according to Formula 4. n : CFS n =Z / r 2 Formula 4, Among them, CFS n Let Z be the ionic strength of the rare earth ion in the nth rare earth oxide, Z be the charge of the rare earth ion, and r be the effective ionic radius of the rare earth ion. The R value is 0.005 to 0.44, and the CPI value is 4.6 to 10.8.

[0009] By employing the above technical solution, the composition of the alkali-free substrate glass was designed, with each component having a specific function. The function and content of each component are limited as follows: SiO2: The core framework of the glass network, providing chemical stability and mechanical strength. When the content is below 63.2%, the network structure is incomplete and the thermal stability decreases; when it is above 69.8%, the glass melt viscosity increases sharply, making homogenization difficult. Therefore, the content is limited to 63.2%–69.8%.

[0010] Al2O3: A network intermediate that forms Al-O bonds to strengthen the network structure, significantly increasing the strain point and elastic modulus. When the content is below 8%, the strengthening effect is insufficient; when it is above 16.9%, the liquidus temperature increases, increasing the risk of crystallization. Therefore, the content is limited to 8.5–16.9%.

[0011] B2O3: A flux that reduces viscosity at high temperatures and improves melting performance, while simultaneously forming boron-oxygen tetrahedra at low temperatures to enhance structural density. When the content is below 3%, the fluxing effect is poor; when it is above 14.5%, it significantly lowers the strain point, therefore the range is limited to 3.50–14.5%.

[0012] MgO: Adjusts the viscosity-temperature curve and improves molding performance. The effect is not significant when the content is below 1.5%; above 3.3%, it reduces high-temperature resistivity, therefore the range is limited to 1.5–3.3%.

[0013] CaO: Works synergistically with SrO to lower the liquidus temperature and improve molding stability. The CaO content should be controlled between 4.0% and 11.5%; too high a content will increase the coefficient of thermal expansion.

[0014] SrO: An environmentally friendly alkaline earth metal oxide that replaces BaO, improving chemical stability and network density. Based on the optimized MgO / SrO molar ratio, it is limited to 0.35–4.5% to ensure a balance between high-temperature resistivity and viscosity.

[0015] ZnO: Improves melt uniformity and surface quality, and acts as an amphoteric oxide to regulate network structure. The ZnO content should be 0.01–1.5%; excessive amounts will lower the strain point and increase the risk of crystallization.

[0016] TiO2: It forms a synergistic enhancement effect with rare earth oxides, constructs a stable network structure, and improves strain point and resistivity. The content of TiO2 is 0.01-2.5%, avoiding excessive amounts that may cause discoloration.

[0017] Rare earth oxides (REO): These strengthen the network through the accumulation effect of high-field-strength ions, synergistically improving strain point, elastic modulus, and resistivity. The total content of rare earth oxides is <4% to avoid the risk of crystallization. If the rare earth content is too high, the liquidus temperature increases, approaching the molding temperature of the overflow method, which can easily lead to crystallization during plate pulling and plate breakage.

[0018] ZrO2: It forms a synergistic reinforcing effect with rare earth oxides, further improving the elastic modulus and chemical durability. The ZrO2 content is 0.01% to 1.2%, avoiding excessive content that would increase glass density and melting difficulty.

[0019] SnO2: A highly efficient clarifying agent that releases oxygen at high temperatures to eliminate bubbles. Its content is 0.06% to 0.32%, balancing clarification effect with the avoidance of secondary bubbles.

[0020] In addition to limiting the content of the aforementioned components, this invention proposes a core parameter for precisely controlling the glass network structure and overall performance: the Co-synergy Index (CPI). The CPI is defined as the ratio of the weighted sum of the network-forming components and the synergistic reinforcement components to the weighted sum of the network modifier components. It quantifies the degree of synergy between the titanium-rare earth-zirconium ternary synergistic reinforcement network and the network modifier components, directly related to key properties of the glass such as strain point, reheat shrinkage, and Young's modulus. The network-forming components are SiO2 and Al2O3, the synergistic reinforcement components are rare earth oxides ZEO, TiO2, and ZrO2, and the network modifier components are B2O3, SrO, CaO, ZnO, and MgO. This invention precisely controls the overall performance of the glass by quantifying the balance between high-temperature reinforcing components and flow-promoting components. The weighting coefficient of rare earth oxide REO in the CPI is positively correlated with the ionic strength of the corresponding rare earth ions, and the ionic strength CFS... n The calculation formula is CFS n =Z / r 2 Where Z is the charge of the rare earth ion, and r is the effective ionic radius of the rare earth ion. High ionic strength implies higher charge density, which can generate stronger polarization and accumulation on the Si-O and Al-O bonds in the glass network, forming a denser local structure. Rare earth ions La 3+ The ionic strength (2.82) is relatively low, so its weighting factor is defined as 10.0. The ionic strength (CFS) of rare earth ions in rare earth oxides is... n ) and its weighting coefficient (k) n The relationship between k and k is linear, and the relationship satisfies k. n =k La ×(CFS) n / CFS La =10.0 × (CFS) n / 2.82), where k n k represents the weighting coefficient for rare earth oxides. La The weighting coefficients for lanthanum oxide are CFS. n The ionic strength of rare earth ions, CFS La The ionic strength is denoted as lanthanum ion.

[0021] Based on the linear relationship between the ionic strength of rare earth ions and their weighting coefficients in rare earth oxides, except for lanthanum oxide, whose weighting coefficient is defined as 10.0, the weighting coefficients of the corresponding oxides of other rare earth ions can be calculated according to the above linear relationship based on the ionic strength of their rare earth ions. Here are some examples of the weighting coefficients of the corresponding oxides of typical rare earth ions: Yb₂O₃ has a weighting coefficient of 14.1, Er₂O₃ has a weighting coefficient of 13.4, Y₂O₃ has a weighting coefficient of 13.1, and Gd₂O₃ has a weighting coefficient of 12.1.

[0022] Except for rare earth oxides, the weighting coefficients of the other components are set according to their functions: the weighting coefficient of network forging body Al2O3 is 1.2, and the weighting coefficient of SiO2 is 1.0; the weighting coefficient of synergistic reinforcement TiO2 is 0.9, and the weighting coefficient of ZrO2 is 0.8; the weighting coefficient of network modifier B2O3 is 1.0, the weighting coefficient of SrO is 0.6, the weighting coefficient of CaO is 0.5, the weighting coefficient of ZnO is 0.4, and the weighting coefficient of MgO is 0.3.

[0023] The R-value of this invention is limited to 0.005–0.44. If the R-value is too low, a synergistic effect cannot be achieved, resulting in insufficient strengthening performance. If the R-value is too high, it can easily lead to an overly dense glass network, increased glass density, increased melting difficulty, and easy crystallization. This range can balance the glass's heat resistance, dimensional stability, and formability. The CPI value is limited to 4.6–10.8. If CPI < 4.6, the synergistic enhancement is insufficient, and the performance does not meet the standards. If CPI > 10.8, the formability deteriorates, and crystallization is easy. This range can achieve synergistic optimization of multiple glass properties. The synergistic index CPI in this invention can balance the improvement of the overall performance of the finished glass and the glass's formability.

[0024] The rare earth oxides in this invention are not limited to the five types: La2O3, Y2O3, Gd2O3, Er2O3, and Yb2O3. Any rare earth element other than Nd2O3 and Ce2O3 that does not contain heavy metals can be used as a substitute, as long as the weighting coefficient is positively correlated with its ionic strength and the R value is in the range of 0.005 to 0.44.

[0025] Preferably, REO is at least one of La2O3, Y2O3, Gd2O3, Er2O3, and Yb2O3.

[0026] Preferably, n=2~3, and the rare earth elements preferred here are La2O3, Y2O3, and Gd2O3.

[0027] Preferably, the high strain point, low shrinkage, alkali-free substrate glass comprises the following molar percentage components: SiO2 64.0–68.0%, Al2O3 11.5–14.5%, B2O3 6.5–9.5%, MgO 1.8–2.8%, CaO 4.8–8.1%, SrO 0.45–3.5%, ZnO 0.05–0.8%, TiO2 0.4–1.8%, La2O3 0–1.8%, Y2O3 0–1.4%, Gd2O3 0–1.5%, ZrO2 0.01–0.9%, and SnO2 0.08–0.25%.

[0028] Preferably, the high strain point, low shrinkage, alkali-free substrate glass comprises the following molar percentage components: SiO2 64.0–68.0%, Al2O3 11.5–14.5%, B2O3 6.5–9.5%, MgO 1.8–2.8%, CaO 4.8–8.1%, SrO 0.45–3.5%, ZnO 0.05–0.8%, TiO2 0.4–1.8%, La2O3 0–1.8%, Er2O3 0–1.2%, Yb2O3 0–1.1%, ZrO2 0.01–0.9%, and SnO2 0.08–0.25%.

[0029] Preferably, [La2O3] / [Y2O3] = 0.6~1.4, [MgO] / [SrO] = 0.8~5.6, [CaO] / ([MgO]+[CaO]+[SrO]) = 0.52~0.85, and [B2O3] / ([SiO2]+[Al2O3]) ≤ 0.125; [La2O3], [Y2O3], [MgO], [SrO], [CaO], [B2O3], [SiO2], and [Al2O3] represent the molar percentages of the corresponding components in alkali-free substrate glass with low shrinkage at high strain points.

[0030] By adopting the above technical solution, the composition of the high strain point, low shrinkage, alkali-free substrate glass was further optimized, and the ratio between each component was limited. The ratio of [La2O3] / [Y2O3] was used to ensure the synergistic effect of the two rare earth oxides and improve the network density; the ratio of [MgO] / [SrO] was used to optimize the glass forming fluidity and dimensional stability; the ratio of [CaO] / ([MgO]+[CaO]+[SrO]) was used to control the glass thermal expansion coefficient and adapt it to silicon materials; the ratio of [B2O3] / ([SiO2]+[Al2O3]) could avoid the glass strain point being reduced due to excessive B2O3 content.

[0031] Preferably, [RE1O], [RE2O], and [RE3O] are [La2O3], [Y2O3], and [Gd2O3], respectively, k1 is 10.0, k2 is 13.1, k3 is 12.1, R is 0.01 to 0.38, and CPI is 5.2 to 10.2.

[0032] Through the above technical solutions, the R-value and CPI value have been further optimized. Optimizing the CPI value can further improve the synergy of multiple glass properties and ensure that core performance consistently meets standards. Optimizing the R-value can further reduce the risk of crystallization in the glass.

[0033] A second aspect of the present invention provides a method for preparing alkali-free substrate glass with high strain point and low shrinkage, comprising the following steps: (1) Weigh each raw material according to the proportion and mix them evenly to obtain a mixture; (2) Place the mixture in a crucible and heat to remove volatiles; (3) Continue heating to melt the glass to obtain molten glass; (4) Pour the molten glass into a preheated mold to form the base glass; (5) Anneal the base glass and then cool it to room temperature to obtain a high strain point, low shrinkage, alkali-free substrate glass, which is the finished glass.

[0034] The raw materials used in this invention can be the corresponding oxides or the corresponding salts. For example, CaO can be replaced by calcium carbonate, which has more stable physicochemical properties, and SrO can be replaced by strontium nitrate or strontium carbonate, which have more stable physicochemical properties.

[0035] Preferably, in step (2), the heating temperature is 800℃~850℃ and the holding time is 20~24h.

[0036] Preferably, in step (3), the temperature is further increased to 1650℃~1700℃ for melting, and the temperature is maintained for 40~50h. While maintaining the temperature, the mixture is stirred at a speed of 25rpm~35rpm.

[0037] Preferably, in step (5), the annealing temperature is 800℃~820℃, the annealing time is 24~48h, and the cooling rate is 0.3~0.5℃ / min.

[0038] Therefore, the present invention employs the above-mentioned high strain point, low shrinkage, alkali-free substrate glass and its preparation method, which has the following beneficial effects: (1) This invention constructs a titanium-rare earth-zirconium synergistic reinforcement network by precisely controlling the oxide content of titanium, rare earth elements, and zirconium, thereby achieving synergistic optimization of ultra-high strain point and low reheat shrinkage rate. This invention also proposes a synergistic index CPI, which limits the R value in the CPI formula to 0.005–0.44 to avoid crystallization problems caused by excessive rare earth elements, while simultaneously satisfying a strain point higher than 715℃, a reheat shrinkage rate less than 20ppm, and a density less than 2.65g / cm³. 3 It combines a low coefficient of thermal expansion, high Young's modulus, and excellent ultraviolet transmittance, effectively solving problems such as irreversible shrinkage of substrate glass and misalignment of TFT circuits caused by multiple high-temperature annealing in high-end display manufacturing processes, and significantly improving product yield.

[0039] (2) By precisely controlling the proportion of each oxide and combining it with the quantitative control of the synergistic index CPI, the present invention stabilizes the melt resistivity of the glass at 1620℃ at 60-120Ω. m is perfectly suited for electro-melting / electro-assisted melting production processes, improving the melting efficiency and homogenization of molten glass, reducing production energy consumption, and making it suitable for large-scale industrial production.

[0040] (3) The glass composition of the present invention does not contain any harmful heavy metals such as BaO and PbO, which is in line with the trend of environmental protection and lightweight development; at the same time, the liquidus temperature is ≤1250℃, which is compatible with mainstream molding processes such as overflow pull-down method, and can prepare large-size, high-precision substrate glass to meet the molding requirements of high-end display panels.

[0041] The technical solution of the present invention will be further described in detail below through embodiments. Detailed Implementation

[0042] The technical solution of the present invention will be clearly and completely described below. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the technical solution of the present invention are within the scope of protection of the present invention.

[0043] The glass compositions of Examples 1-5 are shown in Table 1.

[0044] Table 1. Glass composition (mol%) of Examples 1-5

[0045] In Table 1, the weighting coefficient for La2O3 is defined as 10.0, according to Formula 4 (CFS). n =Z / r 2 =3 / (1.078Å) 2 The ionic strength of La₂O₃ was calculated to be 2.58, and the ionic strength of Y₂O₃ was calculated to be 3.69 (CFS) using Formula 4. n =Z / r 2 =3 / (0.902Å) 2 The ionic strength of Gd₂O₃ is 3.41 (CFS). n =Z / r 2 =3 / (0.938Å) 2 ).

[0046] The weighting coefficient of Y₂O₃ calculated according to Formula 3 is 13.1 (k n =10.0×(CFS) n / 2.82) = 10.0 × (3.69 / 2.82)), and the weighting coefficient of Gd2O3 is 12.1 (k n =10.0×(CFS) n / 2.82)=10.0×(3.41 / 2.82)), therefore R=k1×[RE1O]+k2×[RE2O]+k3×[RE3O]=10.0×[La2O3]+13.1×[Y2O3]+12.1×[Gd2O3]. By directly substituting the molar percentages of La2O3, Y2O3, and Gd2O3 in Examples 1 to 5 into the above formula, the corresponding R values ​​can be obtained. Taking Example 1 as an example, R=10.0×0.0007+13.1×0.0009+12.1×0.00=0.02.

[0047] The glass compositions of Examples 6-7 and Comparative Examples 1-2 are shown in Table 2.

[0048] Table 2. Glass composition (mol%) of Examples 6-7 and Comparative Examples 1-2

[0049] In Table 2, the weighting coefficient for La2O3 is defined as 10.0, according to Formula 4 (CFS). n =Z / r 2 =3 / (1.078Å) 2 The ionic strength of La₂O₃ was calculated to be 2.58, and the ionic strength of Er₂O₃ was calculated to be 3.78 (CFS) using Equation 4. n =Z / r 2 =3 / (0.891Å) 2 The ionic strength of Yb₂O₃ is 3.98 (CFS). n =Z / r 2 =3 / (0.868Å) 2 ).

[0050] The weighting coefficient for Er₂O₃, calculated according to Formula 3, is 13.4 (k). n =10.0×(CFS) n / 2.82) = 10.0 × (3.78 / 2.82)), and the weighting coefficient of Yb2O3 is 14.1 (k n =10.0×(CFS) n / 2.82) = 10.0 × (3.98 / 2.82)), therefore R = k1 × [RE1O] + k2 × [RE2O] + k3 × [RE3O] = 10.0 × [La2O3] + 13.4 × [Er2O3] + 14.1 × [Yb2O3]. By directly substituting the molar percentages of La2O3, Er2O3, and Yb2O3 in Examples 6-7 and Comparative Examples 1-2 into the above formula, the corresponding R values ​​can be obtained. Taking Example 6 as an example, R = 10.0 × 0.0038 + 13.1 × 0.0067 + 14.1 × 0.0034 = 0.18.

[0051] The preparation methods of the alkali-free substrate glass in the above embodiments and comparative examples are as follows: (1) Weigh each raw material according to the molar percentage of its oxide. Among them, calcium carbonate with more stable physical and chemical properties is used to replace CaO, and strontium nitrate with more stable physical and chemical properties is used to replace SrO. After mixing each raw material evenly, a mixture is obtained. Ensure raw material purity ≥ 99% and total alkali metal oxide impurity content < 0.05 mol%; (2) Place the mixture in a platinum crucible and keep it at 800°C for 23 hours to remove volatiles; (3) Continue heating to 1680℃ and hold for 46 hours, during which time mechanical stirring is performed at 30 rpm to ensure homogenization of the molten liquid, and finally obtain glass melt; (4) Pour the molten glass into a flat mold preheated to 800°C and form it. The molten glass flows by itself to form a flat surface. After cooling and solidification, the base glass is obtained. (5) Anneal the base glass at 810℃ for 34 hours to eliminate internal stress, and then slowly cool it to room temperature at 0.4℃ / min to obtain the finished glass.

[0052] Test case The finished glass samples of the examples and comparative examples were subjected to performance tests, and the test methods are as follows: Strain point: The strain point of the glass was determined using the fiber elongation method according to ASTM C336 standard; Reheat shrinkage rate: The reheat shrinkage rate of glass under the condition of 600℃ / 1h was determined according to GB / T 37991-2019 standard. High-temperature resistivity: The resistivity of the glass melt at 1620℃ was determined according to GB / T 41708-2022 standard; Coefficient of thermal expansion: The coefficient of thermal expansion of glass in the range of 30 to 380℃ was determined by a horizontal dilatometer in accordance with GB / T 16920-2015 standard. Young's modulus: The Young's modulus of glass was determined by ultrasonic pulse-echo method according to GB / T 7962.6-2010 standard; Density: The density of glass was determined using the buoyancy method according to GB / T 5432 standard; Ultraviolet transmittance: The ultraviolet transmittance of glass (0.5 mm thick sample) at a wavelength of 308 nm was determined using an ultraviolet-visible spectrophotometer in accordance with GB / T 2680-2021 standard. Liquidus temperature: According to GB / T 44753-2024 standard, after holding at a gradient furnace for 24 hours, observe the crystallization and determine the liquidus temperature of the glass.

[0053] The test results are shown in Tables 3 and 4.

[0054] Table 3 Performance test results of finished glass products from Examples 1 to 5

[0055] Table 4 Performance test results of glass products from Examples 6-7 and Comparative Examples 1-2

[0056] As can be seen from Tables 3 and 4, the finished glass products of Examples 1 to 5 of this invention have all achieved the expected performance targets, including strain point: all ≥715℃, reheat shrinkage rate: all <20ppm, and expansion coefficient: all <37×10. -7 / ℃, High Young's modulus: all ≥80GPa, UV transmittance: all ≥70%, Density: all <2.65g / cm³ 3 Furthermore, as seen in Examples 1-5, with the gradual increase of CPI and R value, the glass strain point, Young's modulus, and resistivity at 1620℃ increase simultaneously, while the reheat shrinkage rate and coefficient of thermal expansion gradually decrease. A comparison between Example 1 and Comparative Example 1 shows that adding rare earth elements can rapidly increase the CPI value and improve the glass strain point, reduce the glass shrinkage rate, and increase Young's modulus. Compared to Examples 1 and 2, Example 3 has more reasonable CPI and R values, with a strain point ≥745℃, a reheat shrinkage rate <18ppm, a Young's modulus ≥92GPa, and a resistivity stable between 90 and 110Ω. m, which is superior to other examples in the same group. Examples 4 and 5 have higher CPI values ​​and densities close to 2.65 g / cm³ due to the higher proportion of rare earth oxides. 3 As the liquidus temperature rises, the moldability decreases slightly. In summary, Example 3 is the optimal choice, exhibiting a high strain point, low shrinkage, high modulus, UV transmittance at 308nm ≥76%, and density <2.60 g / cm³. 3 With a low risk of crystallization, it is the most suitable high-end display substrate for LTPS / OLED.

[0057] Comparing Examples 3 and 6, with other components remaining similar, replacing Er₂O₃ and Yb₂O₃, rare earth elements with higher ionic field strengths, resulted in slight improvements in properties such as the strain point and Young's modulus of the glass. Due to the higher molecular weight of the rare earth element oxides, its density also increased. In Example 7, increasing the proportion of Yb₂O₃ further increased its density to 2.64 g / cm³. 3 Approximately 2.65 g / cm³ 3In Comparative Example 1, no TiO2, ZrO2, or any rare earth oxides (REO) were added, and both the R value and CPI value were below the range defined in this invention. The strain point of the glass product decreased, the reheat shrinkage rate increased, and the heat resistance decreased. Simultaneously, the high-temperature resistivity was also lower, resulting in decreased electrical properties. This demonstrates that the addition of TiO2, ZrO2, and all rare earth oxides in this invention is crucial for the overall improvement of the glass product's performance. In Comparative Example 2, the total amount of rare earth oxides was slightly higher than the range defined in this invention, and the R value and CPI value were also higher than the range defined in this invention. Due to the further increase in the proportion of rare earth oxides, although the strain point and Young's modulus of the glass were further improved, the glass density was greater than 2.65 g / cm³. 3 Furthermore, when the liquidus temperature exceeds 1250℃, the forming performance deteriorates further, and the risk of crystallization increases significantly. The R-value in this invention prevents excessive density and crystallization caused by excessive rare earth elements, while the CPI value balances network reinforcement and melt forming properties. These two are crucial for synergistic and controllable performance; excessive rare earth elements and synergistic reinforcements disrupt the balance between multiple properties. This invention optimizes the content of each component and limits the content of each component to within the range specified by the CPI value, resulting in glass that balances both finished product performance and formability.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high strain point, low shrinkage, alkali-free substrate glass, characterized in that: The high strain point, low shrinkage, alkali-free substrate glass comprises the following molar percentages: SiO2 63.2–69.8%, Al2O3 8.5–16.9%, B2O3 3.50–14.5%, MgO 1.5–3.3%, CaO 4.0–11.5%, SrO 0.35–4.5%, ZnO 0.01–1.5%, TiO2 0.01–2.5%, ZrO2 0.05–1.2%, SnO2 0.06–0.32%, REO 0–4%; REO is a rare earth oxide. The synergy index is calculated using Formula 1, and the synergy index is the CPI. Wherein, [Al2O3], [SiO2], [TiO2], [ZrO2], [B2O3], [SrO], [CaO], [ZnO], and [MgO] represent the molar percentages of the corresponding components in the low-shrinkage alkali-free substrate glass at high strain points; R is calculated according to Formula 2: R=k1×[RE1O]+k2×[RE2O]+k3×[RE3O]+…+k n ×[RE n Formula 2, Where n≥1, [RE1O], [RE2O], [RE3O], [RE n [O] represents the molar percentages of the first, second, third, and nth rare earth oxides in the high-strain-point, low-shrinkage alkali-free substrate glass, respectively, k1, k2, k3, and k n These are the weighting coefficients for the first, second, third, and nth rare earth oxides, respectively. k is calculated according to formula 3. n : k n =10.0×(CFS) n / 2.82) Formula 3, Where, k n CFS is the weighting coefficient for the nth rare earth oxide. n denoted as ionic strength of rare earth ions in the nth rare earth oxide, 10.0 is the weighting coefficient for lanthanum oxide, and 2.82 is the ionic strength of lanthanum ions. CFS is calculated according to Formula 4. n : CFS n =Z / r 2 Formula 4, Among them, CFS n Let Z be the ionic strength of the rare earth ion in the nth rare earth oxide, Z be the charge of the rare earth ion, and r be the effective ionic radius of the rare earth ion. The R value is 0.005 to 0.44, and the CPI value is 4.6 to 10.

8.

2. The high strain point, low shrinkage, alkali-free substrate glass according to claim 1, characterized in that: REO is at least one of La2O3, Y2O3, Gd2O3, Yb2O3, and Er2O3.

3. The high strain point, low shrinkage, alkali-free substrate glass according to claim 1, characterized in that: n=2~3。 4. The high strain point, low shrinkage, alkali-free substrate glass according to claim 2, characterized in that: The high strain point, low shrinkage, alkali-free substrate glass comprises the following molar percentage components: SiO2 64.0–68.0%, Al2O3 11.5–14.5%, B2O3 6.5–9.5%, MgO 1.8–2.8%, CaO 4.8–8.1%, SrO 0.45–3.5%, ZnO 0.05–0.8%, TiO2 0.4–1.8%, La2O3 0–1.8%, Y2O3 0–1.4%, Gd2O3 0–1.5%, ZrO2 0.01–0.9%, and SnO2 0.08–0.25%.

5. The high strain point, low shrinkage, alkali-free substrate glass according to claim 4, characterized in that: [La2O3] / [Y2O3]=0.6~1.4, [MgO] / [SrO]=0.8~5.6, [CaO] / ([MgO]+[CaO]+[SrO])=0.52~0.85, [B2O3] / ([SiO2]+[Al2O3])≤0.125; [La2O3], [Y2O3], [MgO], [SrO], [CaO], [B2O3], [SiO2], and [Al2O3] represent the molar percentages of the corresponding components in alkali-free substrate glass with low shrinkage at high strain points.

6. The high strain point, low shrinkage, alkali-free substrate glass according to claim 5, characterized in that: [RE1O], [RE2O], and [RE3O] are [La2O3], [Y2O3], and [Gd2O3], respectively. k1 is 10.0, k2 is 13.1, k3 is 12.1, R is 0.01 to 0.38, and CPI is 5.2 to 10.

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7. A method for preparing a high strain point, low shrinkage, alkali-free substrate glass according to any one of claims 1 to 6, characterized in that: Includes the following steps: (1) Weigh each raw material according to the proportion and mix them evenly to obtain a mixture; (2) Place the mixture in a crucible and heat to remove volatiles; (3) Continue heating to melt the glass to obtain molten glass; (4) Pour the molten glass into a preheated mold to form the base glass; (5) Anneal the base glass and then cool it to room temperature to obtain a high strain point, low shrinkage, alkali-free substrate glass.

8. The method for preparing a high strain point, low shrinkage, alkali-free substrate glass according to claim 7, characterized in that: In step (2), the heating temperature is 800-850℃ and the holding time is 20-24h.

9. The method for preparing a high strain point, low shrinkage, alkali-free substrate glass according to claim 7, characterized in that: In step (3), the temperature is raised to 1650-1700℃ for melting, and the temperature is maintained for 40-50 hours. While maintaining the temperature, the mixture is stirred at a speed of 25-35 rpm.

10. The method for preparing a high strain point, low shrinkage, alkali-free substrate glass according to claim 7, characterized in that: In step (5), the annealing temperature is 800-820℃, the annealing time is 24-48h, and the cooling rate is 0.3-0.5℃ / min.

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