Lithium-free alkali aluminosilicate glass as well as preparation method and application thereof

Abstract

The invention relates to the field of glass, in particular to lithium-free alkali aluminosilicate glass as well as a preparation method and application thereof. According to the glass, SiO2, Al2O3, Na2O, K2O, MgO and ZrO2 serve as main components, the content of Li2O is lower than 100 ppm, a nitrate-sulfate-carbon powder composite clarifying agent is adopted, the number of bubbles and the content of residual sulfur are effectively reduced, and use of a toxic or ultraviolet absorption type clarifying agent is avoided. ZrO2 is obtained by calcining a zirconium-based metal-organic framework material and is good in dispersity, and the devitrification resistance is improved. During float forming, through micro-positive pressure, high-purity protective atmosphere and four-zone gradient temperature control, the tin penetration depth is controlled within 15 microns, and the surface tin content is smaller than or equal to 4 micrograms / cm < 2 >. The obtained glass has high light transmittance, high hardness and excellent chemical strengthening performance, and is suitable for the high-end fields of electronic display cover plates, vehicle-mounted screens, touch panels, photovoltaic substrates and the like.

Description

Technical Field

[0001] This invention relates to the field of glass, and more particularly to a lithium-free alkali aluminosilicate glass, its preparation method, and its applications. Background Technology

[0002] With the increasing trend towards larger and more curved screens in automotive displays and the ever-increasing demands for impact resistance, surface hardness, and optical performance in consumer electronics, high-alumina silicate glass has become the mainstream choice for high-end cover glass due to its high elastic modulus, high impact strength, and excellent scratch resistance. However, the high viscosity of high-alumina silicate glass significantly increases the difficulty of melting and refining, easily leading to low-melting quality defects such as stones, crystallization, and bubbles during the production process, which seriously affects yield and product reliability.

[0003] In the design of alkali aluminosilicate glass, lithium oxide effectively reduces the viscosity of the glass melt and improves melting performance. In chemically strengthened electronic glass, it facilitates the exchange of sodium and lithium ions (secondary strengthening), further enhancing the exchange of potassium and sodium ions (primary chemical strengthening). With a daily drawing volume exceeding 50 tons for float electronic glass, the market demand for lithium-containing secondary strengthened glass is far lower than that for lithium-free primary strengthened glass. Therefore, float high-alumina electronic glass manufacturers typically switch products directly on a single production line, resulting in residual lithium and affecting the stability of the chemical strengthening performance for downstream customers.

[0004] The high alumina content of lithium-free alkali aluminosilicate glasses leads to high melt viscosity at high temperatures, making bubble removal difficult. Therefore, the selection and combination of refining agents are key technologies in the preparation of high-alumina silicate glasses. While the traditional refining system cerium oxide has a good bubble-eliminating effect, Ce... 3+ / Ce 4+ It exhibits strong absorption in the ultraviolet region, severely impacting the ultraviolet transmittance of glass, making it unsuitable for automotive and electronic display products requiring UV-cured adhesive bonding or those with ultraviolet sensing capabilities. Arsenic trioxide, as a traditional high-efficiency clarifying agent, is subject to strict restrictions under EU RoHS and other regulations due to arsenic's extreme toxicity and environmental pollution, contradicting green manufacturing trends. Other methods, such as using nitrates, sulfates, or toners alone, all have drawbacks. Nitrates have a low decomposition temperature, resulting in insufficient bubble removal in later stages; sulfates used alone are prone to leaving residual sulfate bubbles; and the excessive reducing power of toner may affect the glass's oxidation state.

[0005] During the float glass process, the molten glass ribbon comes into direct contact with the molten tin, and at high temperatures, tin readily reacts as Sn. 2+ or Sn 4+The tin diffusion process spreads to the glass surface, forming a tin-infiltrated layer. For high-aluminosilicate glass, the tin diffusion problem is particularly pronounced due to its higher forming temperature and longer leveling time. An excessively deep tin-infiltrated layer (typically greater than 20μm) can lead to optical inhomogeneity on the glass surface, abnormal chemical strengthening response, and severely affect the adhesion and uniformity of subsequent coatings, failing to meet the stringent requirements for surface cleanliness and interface stability in high-end applications such as automotive curved screens and OLED substrates.

[0006] Although patent CN107673602B proposes high-alkali aluminosilicate glass without alkaline earth metals, its lithium-containing design is difficult to adapt to continuous float glass production, and it lacks effective solutions to key process problems such as high-alumina glass melting and clarification and tin infiltration control, resulting in low actual yield and limited application. Summary of the Invention

[0007] (a) Technical problems to be solved In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a lithium-free alkali aluminosilicate glass, its preparation method and application, which solves the technical problems of high aluminosilicate glass being difficult to melt and clarify under lithium-free conditions, having severe tin infiltration, low ultraviolet transmittance, and being unable to meet the surface quality and chemical strengthening stability requirements of high-end electronic and automotive display devices.

[0008] (II) Technical Solution To achieve the above objectives, the main technical solutions adopted by the present invention include: A lithium-free alkali aluminosilicate glass, wherein the raw material composition of the alkali aluminosilicate glass, in terms of oxide mass parts, is: SiO2: 61-73 parts, Al2O3: 7-12 parts, Na2O: 9-13 parts, K2O: 2-5 parts, MgO: 4-12 parts and ZrO2: 0.2-1.0 parts.

[0009] This invention provides an alkali aluminosilicate glass composition with lithium content strictly controlled below 100 ppm, fundamentally avoiding lithium erosion of corundum bricks and the resulting stone and crystallization defects. Under controlled lithium content, through the synergistic design of other alkali metal oxides and network oxides, suitable melting temperature, forming viscosity, and high mechanical strength are maintained, meeting the performance requirements of automotive and consumer electronics cover glass. Specifically, it maintains good melting performance and forming viscosity in the 1550–1650℃ range while ensuring high mechanical strength and chemical strengthening potential. The low impurity content of this composition provides a good foundation for efficient defoaming using composite clarifying agents (nitrate-sulfate-carbon powder). The reasonable alkali metal ratio also helps to effectively suppress the diffusion of molten tin into the glass in a micro-positive pressure, gradient temperature controlled tin bath environment, thereby controlling the tin penetration depth to within 15 μm.

[0010] In some embodiments, during the preparation of alkali aluminosilicate glass from glass raw materials, a composite clarifying agent is added. The composite clarifying agent includes nitrate, sulfate and carbon powder. The amount of sulfate is 0.20-0.40% of the total mass of the glass raw material mixture, the amount of carbon powder is 20-35% of the amount of sulfate, and the amount of nitrate is 2.5-3.5% of the amount of the raw material mixture.

[0011] The chemical composition of the glass raw material mixture refers to the following molar fractions: SiO2: 61-73 parts, Al2O3: 7-12 parts, Na2O: 9-13 parts, K2O: 2-5 parts, MgO: 4-12 parts, and ZrO2: 0.2-1.0 parts. Based on 600 grams of the glass raw material mixture, the sulfate content is 1.2g-2.4g, with the rest calculated similarly. This means that the glass raw material does not include the amount of composite clarifying agent.

[0012] Composite clarifying agents effectively overcome the shortcomings of single clarifying agents in lithium-free alkali aluminosilicate glass, and are suitable for clarifying the high-temperature and high-viscosity characteristics of high-aluminosilicate glass. Sulfates decompose at high temperatures, typically above 1300℃, releasing SO2 and O2, which absorb and consume carbon dioxide and nitrogen in the molten glass, eliminating residual microbubbles in the high-viscosity melt. Carbon powder, as a reducing agent, can lower the decomposition temperature of sulfate and enhance its clarifying efficiency when added in appropriate amounts. This is because as the decomposition temperature decreases, the use of sulfate and carbon powder can easily cause bubbles in the molten glass to be contaminated with sodium sulfate particles, creating sodium sulfate bubbles. Therefore, the dosage must be strictly controlled. Carbon powder also reduces the reductive properties of the batch, causing iron ions in the molten glass to be reduced to Fe, which is more easily colored. 2+ Nitrates decompose at relatively low temperatures, approximately 500-800℃, producing oxygen, which promotes the initial bubble discharge and maintains the oxidizing properties of the melt, while inhibiting Fe... 2+ The formulation ensures glass whiteness; after optimization of the ratio of the three components, the number of bubbles can be significantly reduced and residual sulfur can be controlled to <400ppm without using As2O3 or CeO2, while maintaining high ultraviolet transmittance, meeting the optical and process requirements of high-end display glass.

[0013] Sodium sulfate is preferred for sulfates, sodium nitrate is preferred for nitrates, and coke is preferred for carbon powder.

[0014] In some embodiments, the ZrO2 is obtained by calcining zirconium-based metal-organic framework materials in air at 550°C to 700°C for 2 to 4 hours.

[0015] Zr-MOF, obtained from commercially available UiO-66, utilizes the highly ordered porous structure and atomically dispersed zirconium nodes of Zr-MOF to generate fine, uniformly distributed nano-ZrO2 particles in situ during pyrolysis. Compared to traditional oxides or nano-ZrO2, this MOF-derived ZrO2 has a higher specific surface area and reactivity, allowing for more uniform integration into the glass network. This effectively suppresses crystallization during high-temperature melting, enhancing the glass's chemical stability and devitrification resistance. The uniformly dispersed ZrO2 strengthens the glass network, increasing hardness and elastic modulus without significantly increasing melt viscosity. After calcination, the ZrO2 nanoparticles have an average particle size of 15-50 nm and a specific surface area of ​​25-60 m² / s. 2 / g, with a pore size distribution concentrated in the range of 3-10nm, and the zirconium element exists in a highly dispersed state without obvious agglomeration. It can dissolve quickly and uniformly in the early stage of batch melting, avoiding local unmelted material or crystal nuclei caused by ZrO2 particle agglomeration or refractory, thereby reducing microbubble retention or secondary nucleation caused by heterogeneous interfaces.

[0016] In some embodiments, Li2O is not actively added to the alkali aluminosilicate glass, and the Li2O content is less than 100 ppm; In the finished alkali aluminosilicate glass, the Fe2O3 content is less than 100ppm, the total content of other coloring or tinting metal elements is less than 5ppm, and the other coloring or tinting metal elements are selected from at least one of Cr, Ni, Co, Cu, Mn, and Se. The use of composite clarifying agents affects the valence state of iron ions in the glass, especially when the iron oxide content in the glass is greater than 100 ppm. Therefore, in order to control the consistent and stable appearance color of the glass, the iron oxide content in the glass is controlled at 100 ppm, and the content of metal ions in physical decolorization is controlled below 5 ppm, so as to control production costs and optical performance stability to the greatest extent possible.

[0017] The residual sulfur content in the finished glass product is less than 400 ppm.

[0018] Secondly, this application provides a method for preparing the above-mentioned alkali aluminosilicate glass, comprising the following steps: Step 1: Weigh the glass raw materials according to the target composition; Step 2: Add the composite clarifying agent and mix evenly to obtain the batch material; Step 3: Put the batch into the melting furnace and melt it at 1550-1650℃ for 6-11 hours. After clarification and homogenization, it is introduced into the tin bath for float forming. Step 4: The formed glass ribbon is annealed in an annealing furnace at 590-630℃ for more than 2 hours, and then naturally cooled before being cut to obtain the finished product.

[0019] Step 3 involves high-temperature melting at 1550-1650℃ for 6-11 hours to ensure full melting and homogenization of the high-alumina batch. Simultaneously, the composite clarifying agent works synergistically within this temperature range to efficiently remove air bubbles. Subsequently, the glass is introduced into a tin bath for float forming, utilizing the natural flattening properties of the molten glass on the tin surface to achieve a highly flat surface. Step 4 involves annealing at 590-630℃ for ≥2 hours to effectively eliminate internal thermal stress in the glass ribbon, prevent warping or microcracks, ensure dimensional stability and mechanical reliability, and provide a high-quality substrate for subsequent chemical strengthening and deep processing.

[0020] In some embodiments, in step 3, the method is used to control the physical erosion and chemical tin infiltration of the glass during the float glass forming process due to contact with the tin bath, so that the tin infiltration depth of the resulting glass tin surface does not exceed 15 μm and the surface tin content does not exceed 4 μg / cm³. 2 ; During the float forming process in step 3, a slightly positive pressure environment is maintained in the tin bath, with the pressure controlled between +5Pa and +30Pa; and a protective atmosphere of mixed high-purity nitrogen and hydrogen is introduced, wherein the volume fraction of H2 is 3%-10%, the dew point of the atmosphere is ≤-40℃, and the oxygen content is <10ppm, in order to inhibit the oxidation of molten tin and reduce the shaking of the glass ribbon and physical corrosion caused by airflow disturbance.

[0021] In some embodiments, the inlet temperature of the tin bath is 1080±10℃, the outlet temperature is ≤600℃, and a gradient cooling system is adopted to avoid sudden changes in the glass-tin interface tension caused by temperature fluctuations, thereby reducing interface disturbances and local physical erosion caused by thermal stress.

[0022] The outlet temperature refers to the surface temperature of the glass ribbon when it leaves the tin bath and enters the annealing furnace, and its upper limit is 600℃. This temperature is located at the end of the outlet transition zone, and the temperature range of this zone is 700-600℃. A smooth transition is achieved through slow cooling.

[0023] By maintaining a slightly positive pressure of +5 to +30 Pa and a high-purity N2 / H2 protective atmosphere within the tin bath, tin oxidation is effectively suppressed, SnO volatilization and glass ribbon surface contamination are reduced, airflow is stabilized, and vibration and physical corrosion are minimized. Combined with a gradient cooling regime from 1080±10℃ at the inlet to ≤600℃ at the outlet, abrupt changes in glass-tin interface tension are avoided, mitigating interface disturbances and localized erosion caused by thermal stress. This allows the tin penetration depth to be controlled within 15μm, ensuring optical uniformity of the tin surface and adhesion of subsequent coatings.

[0024] In some embodiments, the tin bath is divided into at least four temperature control zones along the glass travel direction, namely, an inlet leveling zone, a polishing and smoothing zone, a curing and shaping zone, and an outlet transition zone. The temperatures in each zone are 1060±10-1020±10℃, 1020±10-900±10℃, 900±10-700±10℃, and 700±10-600±10℃, respectively, with corresponding cooling rates controlled at ≤10℃ / min, 10-20℃ / min, 20-30℃ / min, and ≤15℃ / min.

[0025] The high-temperature zone ensures full flattening and surface polishing, the medium-temperature zone accelerates structural relaxation and inhibits crystallization, and the low-temperature zone rapidly solidifies to limit tin diffusion.

[0026] In the entry leveling zone, the glass is in a low-viscosity state. Slow cooling allows it to naturally level itself using surface tension, preventing ripples or physical erosion caused by sudden changes in interfacial tension due to rapid cooling. Entering the polishing zone, the glass still retains good fluidity. Appropriately accelerating cooling promotes structural relaxation, achieving atomic-level surface polishing, while suppressing crystallization that might be induced by prolonged residence of high-alumina components in the mid-temperature zone. Subsequently, in the curing and shaping zone, the glass viscosity rapidly increases. Rapid cooling significantly shortens its residence time in the tin-sensitive temperature zone, effectively suppressing Sn. 2+ / Sn 4+ Diffusion into the glass significantly reduces the tin penetration depth. Finally, in the exit transition zone, a slow cooling strategy is employed to ensure a smooth transition of the solidified glass ribbon to the annealing furnace, preventing warping or microcracks caused by excessive temperature differences. This zoned gradient temperature control system, combined with processes such as micro-positive pressure and a high-purity protective atmosphere, ensures high flatness and optical uniformity of the glass surface, while also controlling the tin penetration depth to within 15 μm and the surface tin content to below 4 μg / cm³. 2 This meets the stringent requirements of high-end applications such as automotive displays and OLED substrates for interface cleanliness, coating adhesion, and chemically enhanced stability.

[0027] Thirdly, this application provides the application of the above-mentioned alkali aluminosilicate glass in the preparation of cover plates for electronic display devices, touch panel substrates, protective glass for automotive displays or photovoltaic substrates, or high-strength, high-transmittance, and low-defect special glass for aerospace, vehicles, and ships.

[0028] The alkali aluminosilicate glass of this application is a lithium-free glass with low melting quality defects. The tin penetration depth of its tin surface, that is, the surface in contact with molten tin, does not exceed 15 μm, and the surface tin content, calculated as SnO2, is less than 4 μg / cm³. 2 .

[0029] Li2O must be an inactively added oxide, introduced only in trace amounts from raw materials such as alumina, refractory materials, or other sources, and less than 100 ppm, to be considered lithium oxide-free. The tin oxide in lithium-free alkali aluminosilicate glass with low melting quality defects is an inorganic substance that penetrates deeply into the glass during the glass drawing process in the reforming bath due to contact with molten metallic tin and oxides. This structure has a negative effect on the glass itself. Through process control, the tin penetration depth on the glass surface in contact with the tin is controlled to be below 15 μm, and the content is less than 4 μg / cm³. 2 .

[0030] (III) Beneficial Effects In terms of glass composition, by precisely controlling the ratio of SiO2, Al2O3, Na2O, K2O, MgO, and ZrO2, high chemical stability, high hardness, and strengthenability of the glass are achieved without introducing Li2O (the content is controlled below 100ppm). The ZrO2 is obtained by calcining zirconium-based metal-organic framework materials, which not only improves its dispersion uniformity in the glass network but also enhances its resistance to crystallization. To address the high viscosity and difficulty in removing bubbles caused by high alumina, a composite clarification system of nitrates, sulfates, and carbon powder is used to achieve full-process coverage from low-temperature pre-clarification to high-temperature deep clarification, reducing the number of bubbles and avoiding the toxicity or UV absorption problems associated with traditional clarifiers such as As2O3 or CeO2. In the float glass forming stage, a micro-positive pressure, high-purity protective atmosphere, and gradient temperature control zones are established to suppress the physical erosion and chemical tin penetration of the molten tin onto the glass, controlling the tin penetration depth to within 15μm and the surface tin content to below 4μg / cm³. 2 This ensures the optical uniformity of the glass tin surface and the adhesion of subsequent coatings. The resulting glass has high light transmittance, excellent ultraviolet transmittance, and low impurity content (Fe2O3 < 100 ppm, total coloring metal < 5 ppm), making it suitable for direct application in high-end fields such as automotive curved displays, OLED substrates, touch panels, and photovoltaic cover plates. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a physical diagram of Embodiment 1 of the present invention; Figure 2 To clarify the defective bubble diagram; Figure 3 This is a physical drawing of Comparative Example 1 of the present invention; Figure 4 A photograph of the alkali aluminosilicate glass prepared in Comparative Example 5; Figure 5 This is a photograph of the lithium-free alkali aluminosilicate glass prepared in Example 6. Detailed Implementation

[0033] The embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application. This application can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0034] These embodiments are provided to make the application thorough and complete, and to fully express the scope of the application to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​illustrated in these embodiments should be interpreted as merely exemplary and not as limiting.

[0035] It should be noted that, in the description of this application, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationship, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0036] Furthermore, the terms "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the permissible margin of error. "Parallel" is not strictly parallel, but within the permissible margin of error. Terms such as "including" or "contains" mean that the element preceding the word encompasses the element listed after it, and do not exclude the possibility of encompassing other elements as well.

[0037] It should also be noted that, in the description of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0038] All terms used in this application have the same meaning as understood by one of ordinary skill in the art to which this application pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0039] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0040] Example 1 Step 1: Weigh the raw materials according to the proportions in the table below. The raw materials include high-purity quartz sand, alumina, sodium carbonate, potassium carbonate, magnesium oxide, and ZrO2 nanoparticles obtained by calcination. Step 2: Add the compound clarifying agent listed in the table below to the raw materials and mix thoroughly to obtain the batching material; Step 3: The batch material is fed into the melting furnace and melted at 1550℃ for 11 hours. After thorough clarification and homogenization, it is introduced into a tin bath for float glass forming. The tin bath, along the glass ribbon's travel direction, has four independent temperature-controlled sections from upstream to downstream: an inlet leveling zone, a polishing and leveling zone, a solidification and shaping zone, and an outlet transition zone. Each temperature-controlled section is controlled by independent heating and cooling devices and thermocouples. A slight positive pressure of +10Pa is maintained inside the tin bath, with a protective atmosphere of N2 / H2 (H2 volume fraction 5%) and a dew point of... 40℃, O25ppm; the tin bath is divided into four temperature control zones. The inlet leveling zone is located at the upstream end of the tin bath, controlling the glass ribbon's inlet temperature at 1060℃ and its outlet surface temperature at 1020℃. The polishing and leveling zone controls the glass ribbon's surface temperature to steadily decrease from the inlet temperature of 1020℃ to the outlet temperature of 900℃. The curing and shaping zone controls the glass ribbon's surface temperature to decrease from the inlet temperature of 900℃ to the outlet temperature of 700℃. The outlet transition zone is located at the downstream end of the tin bath, close to the transition roller table, controlling the glass ribbon's surface temperature at the outlet temperature to drop to 600℃, corresponding to cooling rates of 8℃ / min, 15℃ / min, 25℃ / min, and 12℃ / min, respectively. Step 4: The formed glass ribbon enters the annealing furnace through the slag box and is annealed from about 600°C. It passes through the critical annealing zone, rapid cooling zone, and natural cooling zone of conventional methods to 50°C. After being cut, the finished product is brought to the ambient temperature. Specifically, the critical annealing zone is held at 590°C for 1 hour to fully relax the internal thermal stress; then it is cooled to 500°C at a rate of 10°C / min in the rapid cooling zone, and then naturally cooled to 50°C in the slow cooling zone, and finally cut to obtain the finished product.

[0041] Step 5: Using the bubble monitoring data from the online inspection machine, confirm that the number of bubbles is below 30 per ton of molten glass. Use an X-ray fluorescence spectrometer to test the amount of tin penetration per square centimeter of the finished glass, and an electron probe microanalysis to test the thickness of the tin penetration layer (µm). The finished product should be examined against a black background using a magnifying glass with a scale. Figure 1 Bubble observation images show the number of bubbles with a diameter >0.1 mm and >0.5 mm in the glass. To accurately assess the clarification effect, bubble detection samples were taken from the central area of ​​the annealed glass strip at the tin bath outlet (i.e., the central area away from the edges and free from interference from the edge-pulling machine). Figure 1 The area between the two tapes (the region between the two tapes) corresponds to the main stream of molten glass after it has been fully homogenized and clarified in the electric melting furnace, and can truly reflect the clarification quality of the glass melt. Suspected bubble defects are further confirmed by optical microscopy for morphology and distribution (e.g., Figure 2 (The clarification of poor bubble defects is shown). Step 6: Crush the sample from Step 5 and grind it into glass powder with a particle size of less than 100 μm (be careful to avoid contamination). (1) Use an X-ray fluorescence spectrometer to test the glass composition to confirm whether it is consistent with the design composition. (2) Digest the glass into a clear solution and use an inductively coupled ion emission spectrometer to test the lithium content, iron content, etc. in the glass. (3) Use a high-frequency carbon-sulfur analyzer to test the residual sulfur content in the glass.

[0042] Step 7: Take another batch of original glass from the same batch, cut the finished glass obtained in Step 4 into the specified size, clean and dry it, and then place it in a pure KNO3 molten salt bath for chemical strengthening. The strengthening conditions are: temperature 420℃, time 6 hours. After strengthening, remove it and clean it thoroughly.

[0043] Optical transmittance was measured at 550 nm using a Shimadzu UV-2600i UV-Vis spectrophotometer; surface compressive stress and compressive stress layer depth after chemical strengthening were measured using an Origen FSM-6000X surface stress meter; bending strength was tested using a Beidou Precision PT-605BS universal testing machine with a four-point bending test (span 40 mm, loading rate 0.5 mm / min). Vickers hardness was measured using a Laizhou Zhijin CHQS-10AT hardness tester with a load of 100 gf and a holding time of 15 s, with 10 points measured per sample and the average taken.

[0044] ICP-OES testing showed that the Fe2O3 content in all the glass samples was below 100 ppm, and the total content of coloring metals such as Cr, Ni, Co, Cu, Mn, and Se was less than 5 ppm, meeting the optical purity requirements for high-end display glass. The preparation methods for Examples 2 to 12 were the same as for Example 1, differing only in the composition of the glass raw materials (per 600g) or the amount of composite clarifying agent added. Specific proportions and corresponding test results are shown in Table 1.

[0045] Table 1: Glass composition, composite clarifying agent ratio and performance test results of Examples 1-6

[0046] Table 2: Glass composition, composite clarifying agent ratio and performance test results of Examples 7-12.

[0047]

[0048] Table 3: Glass composition, composite clarifying agent ratio and performance test results of Comparative Examples 1-8.

[0049]

[0050] The comparative examples are otherwise the same as Example 1, except that: in Comparative Example 1, 2% cerium oxide by mass of the raw material mixture was added as a clarifying agent; in Comparative Example 2, different mass percentages of sulfate were added as clarifying agents; in Comparative Example 3, different mass percentages of nitrate were added as clarifying agents; and in Comparative Example 4, different mass percentages of sulfate and nitrate were added as clarifying agents. Li₂O was added to Comparative Example 3. In Comparative Example 4, the number of bubbles was confirmed to be above 200 per ton of molten glass by online inspection data. Bubbles affected the product yield by 10%, which is far from the target of controlling the bubble defect rate to below 1%.

[0051] The rest of Comparative Example 5 is the same as Example 1, except that it uses commercially available nano ZrO2 powder, which is not obtained by calcining metal-organic framework materials in air. Figure 4The image shows the alkali aluminosilicate glass prepared in Comparative Example 5 of this invention. Obvious milky-white crystallization bands are visible on its surface and edges. This defect stems from the severe agglomeration and low specific surface area of ​​the commercially available nano-ZrO2 particles used. During the high-temperature melting process, these particles failed to dissolve uniformly into the glass network, leading to localized supersaturation and crystal precipitation. Figure 5 The image shows a physical sample of the lithium-free alkali aluminosilicate glass prepared in Example 6 of this invention. The glass surface is smooth and flat, without crystallization, bubbles, or turbidity, exhibiting excellent transparency and uniformity. This result is attributed to the use of highly dispersed nano-ZrO2 obtained by calcining zirconium-based metal-organic framework materials. ZrO2 dissolves rapidly and uniformly during melting, enhancing the glass network connectivity and significantly improving its resistance to crystallization. Simultaneously, the combination of a nitrate-sulfate-carbon powder composite clarifying agent and a four-zone gradient temperature-controlled forming process enables stable production of high-quality glass.

[0052] Comparative Example 6 treats the entire solder bath as a single temperature-controlled zone, linearly cooling from 1060°C at the inlet to 600°C at the outlet, with a constant cooling rate of 20°C / min. Comparative Example 7, while maintaining other process parameters consistent with Example 1, adjusts the temperature control range of the solder bath's curing and shaping zone to 900±10°C to 650±10°C, and reduces the cooling rate in this zone to 8-12°C / min. Comparative Example 8, while maintaining other process parameters consistent with Example 1, weakens the overall cooling intensity of the solder bath, reducing the cooling rate of the polishing and smoothing zone to 5-8°C / min and the curing and shaping zone to 10-15°C / min, and controlling the final temperature of the outlet transition zone at 630°C. This results in a longer residence time of the glass ribbon in the high-temperature section, allowing the solder diffusion driving force to continue operating.

[0053] In the examples, the number of bubbles in all samples was consistently controlled below 30 per ton, with no more than 2 bubbles larger than 0.1 mm in diameter, and no large bubbles exceeding 0.5 mm in diameter, fully demonstrating the effectiveness of the composite clarifying agent. In contrast, Comparative Examples 1-4, due to the use of a single or non-optimized clarifying system, experienced a sharp increase in the number of bubbles, severely impacting product yield. Although Comparative Example 1 used cerium oxide clarifying agent to achieve low residual sulfur, its bubble count reached as high as 87, indicating that while CeO2 can remove bubbles, it is difficult to simultaneously ensure overall melt uniformity and bubble size distribution. Comparative Examples 2-4, on the other hand, exhibited a large number of tiny or large bubbles due to an imbalance in the clarifying agent ratio. The tin penetration depth in all examples was controlled within 10-12 μm, thanks to the multiple processes employed in the float forming stage of this invention: micro-positive pressure, high-purity protective atmosphere, and four-zone gradient temperature control. Comparative Example 5 used commercially available ordinary nano-ZrO2. However, due to issues such as agglomeration, wide particle size distribution, and low specific surface area, commercially available ZrO2 particles were difficult to dissolve uniformly in high-alumina melt, leading to a decrease in the local density of the glass network and exacerbating the diffusion of molten tin into the glass during the tin bath forming process. Test results showed that the data for Comparative Example 5 significantly exceeded the technical indicators defined in this invention. This indicates that the introduction of ZrO2 not only affects the glass's anti-crystallization properties but also indirectly but significantly inhibits tin diffusion by regulating the homogeneity and interfacial stability of the high-temperature melt. In contrast, this invention uses highly dispersed nano-ZrO2 obtained by calcining MOF precursors, which effectively improves the uniformity of the glass structure and assists in the four-zone gradient temperature control process to control the depth of tin diffusion. Comparative Example 6 treated the entire tin bath as a single temperature control zone, resulting in the inability to achieve targeted control of the glass in key temperature ranges: excessively rapid cooling in the high-temperature section affected the leveling effect, while insufficient cooling in the medium- and low-temperature sections prolonged the thermal exposure of the tin diffusion-sensitive temperature zone, ultimately leading to increased tin diffusion depth and surface tin content. Comparative Example 7, by reducing the cooling rate of the curing and shaping zone to 8-12°C / min and lowering the endpoint temperature of this zone to 650°C, weakened the effect of rapid curing to block tin diffusion. This resulted in the glass undergoing a slow cooling process in the 700–900°C range, allowing tin ions to diffuse into the glass interior under more sufficient thermodynamic and kinetic conditions, leading to a further increase in tin penetration depth and surface tin content. Comparative Example 8, on the other hand, weakened the overall cooling intensity of the tin bath, causing the glass ribbon to extend in the high-temperature section, resulting in continuous interfacial reactions and poor tin penetration depth and surface tin content. Comparative Examples 6-8 demonstrate that without employing the zoned independent temperature control and differentiated cooling rate strategy defined in this invention, even with the same composition and clarification process, it is still difficult to effectively suppress tin penetration, failing to meet the stringent requirements of high-end electronic and automotive display glass for tin surface cleanliness, optical uniformity, and subsequent coating reliability.

[0054] Comparative Examples 1, 3, and 4, due to defects in composition or process such as high alkali and high air bubbles, have shallow stress layers, low strength, and reduced hardness. This also demonstrates that the present invention achieves a technological breakthrough in high strength and strengthenability through Na2O / K2O / MgO / ZrO2 without lithium.

[0055] Comparative Example 3, containing a high concentration of Li2O, was placed before Comparative Examples 2 and 4 in the experimental sequence. After melting, the residual lithium-containing components in the system could not be completely removed, resulting in cross-contamination in subsequent batches and a significant increase in the measured Li2O content.

[0056] The embodiments of this application have now been described in detail. To avoid obscuring the concept of this application, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions disclosed herein based on the above description.

[0057] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any manner.

Claims

1. A lithium-free alkali aluminosilicate glass characterized in that, The alkali-aluminosilicate glass raw material composition in terms of mole fraction of oxides is: SiO2: 61-73 parts, Al2O3: 7-12 parts, Na2O: 9-13 parts, K2O: 2-5 parts, MgO: 4-12 parts, and ZrO2: 0.2-1.0 parts.

2. The alkali alumino-silicate glass according to claim 1, wherein, In the process of preparing the alkali-aluminosilicate glass from the glass raw material, a composite clarifying agent is added, the composite clarifying agent includes a nitrate, a sulfate, and carbon powder, the amount of the sulfate is 0.20-0.40% of the total mass of the glass raw material mixture, the amount of the carbon powder is 20-35% of the amount of the sulfate, and the amount of the nitrate is 2.5-3.5% of the amount of the raw material mixture.

3. The alkali alumino-silicate glass according to claim 1, wherein, The ZrO2 is obtained by calcining a zirconium-based metal-organic framework material in an air atmosphere at 550-700°C for 2-4 hours.

4. The alkali alumino-silicate glass according to claim 1, wherein, The alkali-aluminosilicate glass does not actively add Li2O, and the content of Li2O is less than 100 ppm; In the finished alkali-aluminosilicate glass, the content of Fe2O3 is less than 100 ppm, and the total content of other coloring or toning metal elements is less than 5 ppm, the other coloring or toning metal elements being selected from at least one of Cr, Ni, Co, Cu, Mn, and Se; In the glass finished product, the residual sulfur content is less than 400 ppm.

5. A method of making an alkali alumino-silicate glass according to any one of claims 1-4, characterized in that, The method comprises the following steps: Step 1: weighing the glass raw materials according to the target composition; Step 2: adding a composite clarifying agent and mixing uniformly to obtain a mixture; Step 3: putting the mixture into a melting furnace, melting at 1550-1650°C for 6-11 hours, clarifying and homogenizing, and then introducing into a tin bath for float forming; Step 4: annealing the formed glass ribbon in an annealing furnace at 590-630°C for more than 1 hour, naturally cooling, and then cutting to obtain the finished product.

6. The method of making an alkali alumino-silicate glass according to claim 4, wherein, In step 3, the method is used to control the physical erosion and chemical tin infiltration of the glass caused by contact with the tin bath in the float forming process, so that the tin infiltration depth of the obtained glass tin surface is not more than 15 μm, and the surface tin content is not more than 4 μg / cm 2 ; In the float forming process of step 3, a micro-positive pressure environment is maintained in the tin bath, and the pressure is controlled at +5 Pa to +30 Pa; and a mixed protective atmosphere of high-purity nitrogen and hydrogen is introduced, wherein the volume fraction of H2 is 3%-10%, the atmosphere dew point is ≤-40°C, and the oxygen content is <10 ppm, thereby inhibiting the oxidation of the tin liquid and reducing the glass ribbon shaking and physical erosion caused by airflow disturbance.

7. The method of making an alkali alumino-silicate glass according to claim 6, wherein, The inlet temperature of the tin bath is 1080±10°C, and the outlet temperature is ≤600°C, and a gradient cooling system is used.

8. The method for preparing the alkali-aluminosilicate glass according to claim 7, wherein the tin bath is divided into at least four temperature control zones along the glass advancing direction, which are an inlet flattening zone, a polishing flattening zone, a solidification setting zone, and an outlet transition zone. The temperatures of the zones are 1060±10-1020±10°C, 1020±10-900±10°C, 900±10-700±10°C, and 700±10-600±10°C, respectively.

9. The method for preparing the alkali-aluminosilicate glass according to claim 8, wherein the cooling rates of the inlet flattening zone, the polishing flattening zone, the solidification setting zone, and the outlet transition zone are controlled at ≤10°C / min, 10-20°C / min, 20-30°C / min, and ≤15°C / min, respectively. ​ ​ 10. Use of the alkali-aluminosilicate glass according to any one of claims 1 to 4 for the production of a cover plate for an electronic display device, a touch panel substrate, a protective glass for a vehicle display screen, a photovoltaic substrate or a high-strength, high-transparency, low-defect special glass for aerospace, vehicles, ships.

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