Preparation method of high-scratch-resistant microcrystalline touch screen glass substrate

Abstract

This application relates to the field of glass manufacturing technology and discloses a method for preparing a high-scratch-resistant microcrystalline touchscreen glass substrate. The method involves mixing raw materials containing silicon dioxide, aluminum oxide, zinc oxide, aluminum phosphate, zirconium dioxide, and a specific ratio of yttrium oxide, cerium oxide, tin dioxide, and alkali metal carbonates; the mixture is then smelted and subjected to a dual clarification process of high-temperature oxygen release and medium-temperature absorption to obtain a glass melt; an amorphous substrate is formed using an overflow-downward method; subsequently, gradient nucleation, intermediate stress tempering, and crystal growth treatments are performed sequentially; finally, the substrate is chemically strengthened with potassium nitrate molten salt to obtain the final product. This invention utilizes the synergistic effect of the cerium-tin system and yttrium ions to eliminate microbubbles and quench iron ion absorption bands, inhibiting substrate yellowing; the intermediate stress tempering treatment effectively releases phase transformation stress, avoiding macroscopic warping and refining grains; the spatial support effect of yttrium ions maintains deep diffusion channels for potassium ions, significantly improving the compressive stress layer depth and scratch resistance of the microcrystalline glass.

Description

Technical Field

[0001] This invention relates to the field of glass manufacturing technology, specifically to a method for preparing a high scratch-resistant microcrystalline touchscreen glass substrate. Background Technology

[0002] As the application scenarios of smart electronic devices expand, touch screen glass substrates require higher impact resistance and scratch resistance. Microcrystalline glass, due to the large amount of nanoscale crystalline phases precipitated within it, possesses higher intrinsic mechanical strength compared to traditional amorphous high-alumina-silicon glass, and is gradually becoming the preferred material for high-end touch display panels.

[0003] During high-temperature chemical strengthening (such as potassium nitrate molten salt ion exchange) of existing microcrystalline glass, the high crystallinity of the material and the limited amount of residual glass phase result in significant resistance to the diffusion of large-radius potassium ions into the deeper layers of the matrix. Simultaneously, during alkali metal ion replacement, the network structure of the base glass is highly susceptible to the mixed alkali effect, leading to localized shrinkage and densification. This microstructural shrinkage obstructs ion migration channels, causing a large accumulation of replaced potassium ions in the shallow surface region. This prevents the construction of a sufficiently deep residual compressive stress layer, thus failing to provide the mechanical protection required against deep scratches and drops from heights.

[0004] On the other hand, the optical quality of glass-ceramic substrates is significantly constrained by the purity of raw materials and the melting process. It is usually difficult to completely remove trace iron impurities from the basic mineral raw materials. These trace iron impurities easily form characteristic absorption bands (photo-induced color centers) in the glass network, leading to overall yellowing of the material and reducing visible light transmittance. Simultaneously, during the melting process of conventional high-alumina silicate glass-ceramics, due to the high viscosity of the melt, the microbubbles generated inside are often difficult to effectively eliminate through a single mechanism. The interfacial light scattering caused by a large number of retained microbubbles, combined with the color-enhancing effect of iron impurities, degrades the display brightness and color reproduction of the screen.

[0005] Furthermore, in the heat treatment and forming process of glass-ceramics, how to coordinate the control of macroscopic flatness and microscopic crystal size is also a technical challenge. Phase separation and the large-scale precipitation of the main crystalline phase are accompanied by drastic rearrangement of the glass network structure and local volume shrinkage. If the stress generated by this internal density change is not sufficiently relaxed, it can easily evolve into irreversible warping deformation of the substrate on a macroscopic scale. At the same time, during the heat crystallization process, if nucleation and crystal growth rate are not properly controlled, abnormal coarsening of grains in local areas is likely to occur. Once the size of the internally precipitated crystals approaches the scattering limit of visible light, strong light scattering will occur inside the material, causing the glass-ceramics to lose its original optical transparency and fail to meet the dual requirements of high light transmittance and high flatness in the touch display field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing a high-scratch-resistant microcrystalline touchscreen glass substrate. This method solves the problems of insufficient ion exchange depth, optical yellowing and transmittance reduction caused by trace iron impurities and microbubble residues during the chemical strengthening process of existing microcrystalline glass, as well as macroscopic warping and abnormal grain coarsening caused by uneven release of internal stress during the heat treatment forming stage.

[0007] To achieve the above objectives, the present invention provides a method for preparing a high scratch-resistant microcrystalline touchscreen glass substrate, comprising the following steps:

[0008] Step (1) Ingredient Mixing: Weigh the raw materials according to the weight ratio, place them in a mixer and mix, controlling the moisture content of the compound to ≤0.1wt%;

[0009] Step (2), Melting and Clarification: The complex obtained in step (1) is put into a furnace and heated to melt. Then, high-temperature oxygen release clarification and medium-temperature absorption clarification are carried out in sequence to obtain high-transparency glass melt.

[0010] Step (3), controlled molding: The glass melt obtained in step (2) is molded by overflow and annealed to obtain an amorphous glass substrate;

[0011] Step (4) Microcrystallization heat treatment: The amorphous glass substrate obtained in step (3) is placed in a crystallization furnace and subjected to gradient nucleation, intermediate stress tempering and ultra-fine crystal growth treatment in sequence. After cooling to room temperature, a microcrystallized substrate is obtained.

[0012] Step (5), chemical strengthening: The microcrystalline substrate obtained in step (4) is immersed in a high-temperature potassium nitrate molten salt bath for ion exchange treatment. After cleaning and drying, the glass substrate is obtained.

[0013] Preferably, the raw materials comprise the following components by weight: 550.0–612.3 parts silicon dioxide; 180.0–220.0 parts aluminum oxide; 100.0–150.0 parts zinc oxide; 35.0–50.0 parts aluminum phosphate; 22.0–30.0 parts zirconium dioxide; 5.2–29.5 parts yttrium oxide; 1.5–5.0 parts cerium oxide; 1.0–3.0 parts tin dioxide; 22.1–35.0 parts sodium carbonate; and 10.0–15.0 parts potassium carbonate.

[0014] By adopting the above technical solution, specific addition ranges for each material component are defined, which mainly provides a basis for subsequent microcrystalline phase transformation, stress relaxation and ion exchange processes, while also ensuring that the viscosity-temperature characteristics of the overall system can match the process temperature set by this invention.

[0015] Preferably, in step (2), the heating melting temperature is 1630-1650℃; the conditions for high-temperature oxygen release clarification are: constant temperature residence at 1640-1650℃ for 4 hours; the conditions for medium-temperature absorption clarification are: cooling down to 1560-1580℃ and constant temperature residence for 2 hours.

[0016] By adopting the above technical solution, specific temperature and time parameters were set, with the aim of enabling the cerium-tin redox clarification system to reach appropriate kinetic equilibrium in the oxygen release and oxygen absorption stages, thereby ensuring the homogenization quality of the glass melt.

[0017] Preferably, in step (3), the controlled molding process parameters are: real-time monitoring of the melt liquidus temperature, controlling the molding channel temperature to the liquidus temperature plus 65°C, controlling the liquidus viscosity of the melt at the molding point to be stable at 4.5~5.2dPa·s, and the molding thickness to be 0.5~0.8mm.

[0018] By adopting the above technical solution, the molding viscosity is locked within the specific range to prevent premature crystallization of the melt on the surface of the overflow brick, thereby ensuring the surface flatness of the original glass.

[0019] Preferably, in step (4), the specific parameters of the microcrystallization heat treatment are as follows: first, the temperature is raised to 700-720℃ and held for 2 hours to perform gradient nucleation; then the temperature is adjusted to the glass transition temperature plus 15℃, and held at a constant temperature for 28-61 minutes to perform intermediate stress tempering treatment to induce yttrium ions to segregate to the interface between the residual glass phase and the nanocrystals; then the temperature is raised to 870-890℃ and held for 1 hour to perform ultra-fine crystal growth, and then cooled to room temperature.

[0020] By employing the above technical solution, the temperature of the intermediate stress tempering treatment is precisely controlled at the glass transition temperature plus 15°C, and the time is limited to 28 to 61 minutes. This combination of parameters allows the internal stress relaxation rate and the crystal nucleus growth rate to work together, thereby controlling the macroscopic deformation within a small range.

[0021] Preferably, in step (5), the specific process parameters of the chemical strengthening treatment are: immersion temperature of 420-435℃, and ion exchange treatment for 7-8 hours.

[0022] By adopting the above technical solution, the setting of immersion temperature and time provides a suitable diffusion activation energy for potassium and sodium ion replacement, which is conducive to successfully completing the construction of ion exchange depth.

[0023] Preferably, the silicon dioxide contains ferric oxide with a mass fraction ≤80ppm and a median particle size D50 of 40μm to 60μm; the alumina is α-type calcined alumina with a purity ≥99.9% and a median particle size D50 of 12μm to 18μm; the zirconium dioxide is monoclinic zirconium dioxide with a purity ≥99.5% and a median particle size D50 of 1.5μm to 2.5μm; and the yttrium oxide has a purity ≥99.99% and a median particle size D50 of 2μm to 4μm.

[0024] By adopting the above technical solution, the total amount of iron impurities introduced is directly limited from the raw material end, further reducing the background base of photochromic centers; at the same time, the crystal phase and median particle size of each key powder are limited, ensuring the uniformity of solid-phase mixing and the reaction rate during the high-temperature melting stage.

[0025] This invention provides a method for preparing a highly scratch-resistant microcrystalline touchscreen glass substrate. It offers the following advantages:

[0026] 1. This invention introduces a specific amount of yttrium oxide into the glass formulation and controls the mass ratio of sodium carbonate to potassium carbonate. By utilizing the spatial support and electrostatic field effect formed by high-field-strength yttrium ions in the silicon-oxygen network pores, it slows down the amorphous phase network shrinkage caused by mixed alkali replacement during the high-temperature ion exchange stage of the microcrystalline glass. This effectively maintains the free volume channels for the continuous diffusion of large-radius potassium ions from the outside into the matrix, thereby increasing the depth of the compressive stress layer after chemical strengthening and improving the drop resistance and scratch resistance of the touch screen glass substrate.

[0027] 2. This invention, by adding cerium oxide and tin dioxide to the raw materials, not only establishes a high-temperature, two-stage oxygen release and absorption mechanism during the smelting stage, effectively reducing the microbubble density inside the substrate; but also, in conjunction with the high electrostatic field environment created by yttrium oxide, it causes a red shift in the charge transfer band of cerium ions, absorbing and quenching photoinduced electronic transitions caused by trace iron impurities. This multi-component synergistic effect eliminates light scattering sources and photoinduced color centers at the source, effectively suppressing the yellowing phenomenon of the material and ensuring excellent and long-term optical transmittance of the glass substrate.

[0028] 3. This invention, through specially designed stress tempering in the microcrystalline heat treatment and isothermal treatment for a specific time, not only releases the microscopic phase transformation volume shrinkage stress accumulated in the early nucleation stage, preventing macroscopic warping deformation of the substrate after cooling, but also promotes the segregation of some yttrium ions to the interface between the residual glass phase and the crystalline phase. The solute resistance generated by this process limits abnormal grain growth in subsequent stages. This intervention in the heat treatment process ensures that the final crystal size is strictly controlled at the nanometer level, thereby improving the material's hardness while ensuring excellent macroscopic transparency of the microcrystalline glass substrate. Attached Figure Description

[0029] Figure 1 The figures show the optical quality and residual microbubble density distribution of various embodiments and comparative examples of the present invention. Figure (a) shows the scatter plot of the b-value and transmittance, and Figure (b) is a bar chart of microbubble density.

[0030] Figure 2 This is a comparison diagram of the warpage test results of the various embodiments of the present invention and the comparative example substrates;

[0031] Figure 3 The figures show a comparison of the chemical strengthening performance tests of the various embodiments of the present invention and the comparative example substrates. In the figure, (a) is a bar chart of the strengthening layer depth and (b) is a scatter plot of the surface compressive stress.

[0032] Figure 4 Figure 1 shows a comparison of the scratch resistance and brittleness resistance of the various embodiments and comparative substrates of the present invention. Figure 2 shows a schematic diagram of the residual scratch depth and Figure 3 shows a schematic diagram of the critical load for scratch fracture.

[0033] Figure 5 The diagram shows the Vickers hardness distribution of the substrates in the various embodiments and comparative examples of the present invention.

[0034] Figure 6 Figure 1 shows a comparison of the overall optical performance degradation of the various embodiments of the present invention and the comparative substrates. Figure 2 shows a schematic diagram of the yellowing increment and Figure 3 shows a schematic diagram of the transmittance attenuation.

[0035] Figure 7 This is a gradient distribution diagram of the potassium ion concentration diffusion cross section of the present invention. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0038] Silica (CAS No.: 14808-60-7), alumina (CAS No.: 1344-28-1), and zinc oxide (CAS No.: 1314-13-2) are all selected from electronic-grade high-purity specifications. The mass fraction of ferric oxide in silica is ≤80ppm, and the median particle size (D50) is controlled between 40μm and 60μm. Alumina is selected from α-type calcined alumina with a purity ≥99.9% and a D50 of 12μm to 18μm. Zinc oxide has a purity ≥99.7%.

[0039] Aluminum phosphate (CAS No.: 7784-30-7) is an anhydrous powder with a purity ≥99.0%; zirconium dioxide (CAS No.: 1314-23-4) is made from monoclinic high-purity zirconium powder with a purity ≥99.5% and a D50 of 1.5μm to 2.5μm.

[0040] Yttrium oxide (CAS No.: 1314-36-9) has a purity of ≥99.99% and a median particle size of 2μm to 4μm; cerium oxide (CAS No.: 1306-38-3) has a purity of ≥99.9%; and tin dioxide (CAS No.: 18282-10-5) has a purity of ≥99.5%.

[0041] Sodium carbonate (CAS No.: 497-19-8) and potassium carbonate (CAS No.: 584-08-7) are both industrial-grade high-purity products with a purity of ≥99.2%; potassium nitrate (CAS No.: 7757-79-1) has a purity of ≥99.5%.

[0042] Example 1:

[0043] This embodiment provides a method for preparing a highly scratch-resistant microcrystalline touchscreen glass substrate, including the following steps:

[0044] (1) Ingredient mixing: Weigh the following raw materials in parts by weight: 612.3 parts silicon dioxide, 180.0 parts alumina, 100.0 parts zinc oxide, 35.0 parts aluminum phosphate, 25.0 parts zirconium dioxide, 5.2 parts yttrium oxide, 1.5 parts cerium oxide, 1.0 part tin dioxide, 28.0 parts sodium carbonate, and 12.0 parts potassium carbonate. Put all raw materials into a mixer and mix for 45 minutes at a speed of 30 rpm, controlling the moisture content of the complex to be ≤0.1 wt%.

[0045] (2) Smelting and clarification: The complex is put into a continuous furnace and heated to 1630°C to melt. The melt enters the clarification tank and is held at 1640°C for 4 hours for high-temperature oxygen release clarification, and then cooled to 1560°C for 2 hours for medium-temperature absorption clarification.

[0046] (3) Controlled molding: The overflow downward drawing method is used for molding. The liquidus temperature of the melt is monitored in real time. The temperature of the molding channel is controlled to be the liquidus temperature plus 65°C to ensure that the liquidus viscosity of the melt at the molding point is stable at 5.0 dPa·s. The molding thickness is 0.8 mm. Then it is sent to the annealing furnace for annealing. The highest temperature zone of the annealing furnace is set to 650°C. The temperature is kept constant for 20 min to eliminate the thermal stress on the plate surface. Then it is cooled to room temperature at a rate of 3°C / min to obtain an amorphous glass substrate.

[0047] (4) Microcrystallization heat treatment: The glass substrate is placed in a roller crystallization furnace and heated to 700℃ at a rate of 4℃ / min and held for 2 hours for gradient nucleation; then the temperature is adjusted to the glass transition temperature plus 15℃ and held at a constant temperature for 28 minutes for intermediate stress tempering treatment; then the temperature is increased to 870℃ at a rate of 12℃ / min and held for 1 hour for ultra-fine crystal growth, and then cooled to room temperature at a rate of 8℃ / min.

[0048] (5) Chemical strengthening: The microcrystallized substrate is immersed in a molten salt bath of 99.5wt% high-purity potassium nitrate at 430℃ for 7 hours of ion exchange treatment. After the treatment, it is ultrasonically cleaned with multi-stage deionized water and dried.

[0049] Example 2:

[0050] This embodiment provides a method for preparing a highly scratch-resistant microcrystalline touchscreen glass substrate, including the following steps:

[0051] (1) Ingredient mixing: Weigh the following raw materials in parts by weight: 550.0 parts silicon dioxide, 220.0 parts alumina, 150.0 parts zinc oxide, 50.0 parts aluminum phosphate, 30.0 parts zirconium dioxide, 29.5 parts yttrium oxide, 5.0 parts cerium oxide, 3.0 parts tin dioxide, 35.0 parts sodium carbonate, and 15.0 parts potassium carbonate. Put them into a mixer and mix for 45 minutes at a speed of 30 rpm, controlling the moisture content to ≤0.1 wt%.

[0052] (2) Melting and clarification: The melt is placed in a continuous tank furnace and heated to 1650°C for melting. The melt is held at 1650°C for 4 hours for clarification, and then cooled to 1580°C for 2 hours.

[0053] (3) Controlled molding: The overflow downward method is used for molding. The temperature of the molding channel is controlled to be the liquidus temperature plus 65°C, the liquidus viscosity is stabilized at 4.5 dPa·s, the molding thickness is 0.5 mm, and an amorphous glass substrate is obtained after annealing. The highest temperature zone of the annealing furnace is set to 650°C, and the temperature is kept constant for 20 min to eliminate thermal stress on the plate surface. Then, the temperature is reduced to room temperature at a rate of 3°C / min.

[0054] (4) Microcrystallization heat treatment: Place it in a roller crystallizer and heat it to 720°C at 4°C / min and hold it for 2 hours to nucleate; adjust the temperature to the glass transition temperature plus 15°C and hold it at a constant temperature for 61 minutes for stress tempering; heat it to 890°C at 12°C / min and hold it for 1 hour, and then cool it to room temperature.

[0055] (5) Chemical enhancement: Immerse in a molten salt bath of 99.5wt% high-purity potassium nitrate at 435℃ for ion exchange for 8 hours, then clean and dry.

[0056] Example 3:

[0057] This embodiment provides a method for preparing a highly scratch-resistant microcrystalline touchscreen glass substrate, including the following steps:

[0058] (1) Ingredient mixing: Weigh the following raw materials in parts by weight: 600.0 parts silicon dioxide, 185.0 parts alumina, 115.0 parts zinc oxide, 35.0 parts aluminum phosphate, 22.0 parts zirconium dioxide, 18.0 parts yttrium oxide, 4.0 parts cerium oxide, 2.0 parts tin dioxide, 24.0 parts sodium carbonate, and 10.0 parts potassium carbonate. Put them into a mixer and mix for 45 minutes at a speed of 30 rpm, controlling the moisture content to ≤0.1 wt%.

[0059] (2) Melting and clarifying: Heat to 1635℃ to melt. Clarify at 1645℃ for 4 hours, then cool to 1570℃ and remain for 2 hours.

[0060] (3) Controlled molding: The overflow downward method is used for molding. The temperature of the molding channel is controlled to be the liquidus temperature plus 65°C, the liquidus viscosity is stabilized at 5.2 dPa·s, the molding thickness is 0.8 mm, and the amorphous substrate is obtained by annealing. The highest temperature zone of the annealing furnace is set to 650°C and kept at a constant temperature for 20 min to eliminate thermal stress on the board surface. Then, the temperature is reduced to room temperature at a rate of 3°C / min.

[0061] (4) Microcrystallization heat treatment: Heat to 710℃ at 4℃ / min and hold for 2 hours to nucleate; adjust to glass transition temperature plus 15℃, hold at constant temperature for 47 minutes for stress tempering; heat to 880℃ at 12℃ / min and hold for 1 hour, then cool to room temperature.

[0062] (5) Chemical strengthening: Immerse in molten potassium nitrate at 430°C with a concentration of 99.5wt% for ion exchange for 7 hours, then clean and dry.

[0063] Example 4:

[0064] This embodiment provides a method for preparing a highly scratch-resistant microcrystalline touchscreen glass substrate, including the following steps:

[0065] (1) Ingredient mixing: Weigh the following raw materials in parts by weight: 592.0 parts silicon dioxide, 185.0 parts aluminum oxide, 115.0 parts zinc oxide, 35.0 parts aluminum phosphate, 22.0 parts zirconium dioxide, 25.0 parts yttrium oxide, 5.0 parts cerium oxide, 2.0 parts tin dioxide, 24.0 parts sodium carbonate, and 10.0 parts potassium carbonate. Put them into a mixer and mix for 45 minutes at a speed of 30 rpm.

[0066] (2) Melting and clarification: The process parameters are the same as in Example 3.

[0067] (3) Controlled molding: The process parameters are the same as in Example 3.

[0068] (4) Microcrystallization heat treatment: Nucleation is achieved by heating to 710℃ at 4℃ / min and holding for 2 hours; the temperature is adjusted to glass transition temperature plus 15℃ and held at constant temperature for 57 minutes for stress tempering treatment; subsequently, the temperature is increased to 880℃ at 12℃ / min and held for 1 hour, and then cooled to room temperature.

[0069] (5) Chemical enhancement: The process parameters are the same as in Example 3.

[0070] Example 5:

[0071] This embodiment provides a method for preparing a highly scratch-resistant microcrystalline touchscreen glass substrate, including the following steps:

[0072] (1) Mixing of ingredients: Weigh the following raw materials in parts by weight: 600.0 parts silicon dioxide, 185.0 parts aluminum oxide, 115.0 parts zinc oxide, 35.0 parts aluminum phosphate, 22.0 parts zirconium dioxide, 18.0 parts yttrium oxide, 4.0 parts cerium oxide, 2.0 parts tin dioxide, 22.1 parts sodium carbonate, and 11.9 parts potassium carbonate. Mix for 45 min.

[0073] (2) Melting and clarification: The process parameters are the same as in Example 3.

[0074] (3) Controlled molding: The process parameters are the same as in Example 3.

[0075] (4) Microcrystallization heat treatment: process parameters are the same as in Example 3.

[0076] (5) Chemical strengthening: The substrate is immersed in molten potassium nitrate with a concentration of 99.5wt% at 420℃ for 7 hours for ion exchange treatment, then cleaned and dried.

[0077] Comparative Example 1: Compared with Example 3, the difference is that yttrium oxide is not added to the ingredients, and the missing amount is made up with an equal part by weight of silicon dioxide. At the same time, the intermediate stress tempering process is eliminated in the microcrystallization heat treatment step, and the temperature is directly increased to 880°C at 12°C / min after nucleation. All other aspects are the same.

[0078] Comparative Example 2: Compared with Example 3, the difference is that the intermediate stress tempering process was omitted in the microcrystallization heat treatment step. That is, after nucleation at 710°C for 2 hours, the temperature was directly increased to 880°C at a rate of 12°C / min and held for 1 hour for crystal growth. All other steps are the same.

[0079] Comparative Example 3: Compared with Example 3, the difference is that cerium oxide and tin dioxide are not added to the ingredients, and the missing parts are made up with an equal weight of silicon dioxide, while the rest are the same.

[0080] Comparative Example 4: Compared with Example 3, the difference is that the ratio of mixed alkali was adjusted, and 17.0 parts of sodium carbonate and 17.0 parts of potassium carbonate were weighed, while the rest were the same.

[0081] Comparative Example 5: Compared with Example 1, the difference is that the ratio of mixed alkali was adjusted, and 26.0 parts of sodium carbonate and 14.0 parts of potassium carbonate were weighed, while the rest were the same.

[0082] Test Example 1:

[0083] 1. Sample setup: The chemically strengthened microcrystalline glass substrates prepared in Examples 1-5 and Comparative Examples 1-5 were selected as test objects. All samples were ultrasonically cleaned with anhydrous ethanol and dried with nitrogen before testing to ensure that there were no external contaminants remaining on the surface.

[0084] 2. Test steps:

[0085] 2.1 Place each group of samples on the sample stage of the spectrophotometer, select the D65 standard light source and measure the color space parameters at a 10° field of view. Record the b value of each sample to reflect the degree of yellowness of the material. Each group of samples was measured five times in different areas and the average value was taken.

[0086] 2.2 The transmittance of the sample was characterized using a UV-Vis spectrophotometer. The scanning wavelength range was set from 380 nm to 780 nm, with air as the reference optical path. The average visible light transmittance of the sample in this wavelength range was measured and recorded.

[0087] 2.3 The sample was placed under an optical microscope equipped with a side-mounted high-contrast illumination source. Defects inside the substrate were observed in dark-field mode. A randomly selected observation field of 1cm × 1cm was used, and the volume was calculated based on the substrate thickness. The number of residual microbubbles with a diameter ≥ 10μm inside the substrate was counted and recorded, and converted into bubble density per unit volume. The results are shown in Table 1.

[0088] Table 1: Test data on optical quality and clarification effect of each embodiment and comparative example

[0089]

[0090] According to Table 1 and Figure 1 The data shows that the optical performance of the glass substrate is directly related to the establishment of the internal redox balance. In the conventional high-alumina silicate microcrystalline glass melting process, even trace amounts of iron impurities can form color centers in the network, causing overall yellowing. However, in this study, Examples 1 to 5, by introducing a specific ratio of yttrium oxide and cerium oxide system, exhibited excellent high transmittance and low yellowing performance. This improvement in colorimetry is due to the high field strength environment created by yttrium ions in the glass network. This environment forces the charge transfer band of cerium ions to undergo the expected redshift, and the specific orbital overlap formed by cerium ions absorbs and quenches the impurity absorption peaks caused by iron ions, achieving a macroscopic transmittance of over 91.5%.

[0091] When cerium oxide and tin dioxide, which are the core clarifying and decolorizing components, were removed from Comparative Example 3, the entire molten pool lost its medium-to-high temperature two-step oxygen release and absorption buffering mechanism. As a result, free microbubbles in the melt could not be effectively removed or dissolved, and the bubble density increased to 42 bubbles / cm³. 3 Extensive interface scattering combined with the unobstructed color development of iron ions increased the b-value of this comparative example to 2.84, while reducing the transmittance to 86.5%, confirming the crucial role of the dual redox system of cerium oxide and tin dioxide in eliminating bubbles and reducing light attenuation. Comparative Example 1, while retaining the tin-cerium component, removed yttrium oxide, and its yellow index increased to 1.25. This was due to the lack of electrostatic field induction from yttrium ions, which prevented the effective activation of the electron transfer quenching effect of cerium ions, further confirming the synergistic effect of the yttrium-cerium component in the optical modulation mechanism. Observation of the data from Comparative Example 2 revealed that even if the formulation fully met the requirements, omitting the crucial intermediate stress tempering process resulted in the accumulation of microscopic internal stress within the substrate due to phase separation and excessively rapid crystallization. This unrelaxed volume shrinkage led to localized refractive index fluctuations, causing overall transmittance degradation accompanied by slight bubble retention. This indicates that intermediate stress tempering plays a vital role in ensuring the optical quality of the product.

[0092] Test Example 2:

[0093] 1. Sample Setup: Glass substrates from Examples 1 to 5 and Comparative Examples 1 to 5 that had undergone complete microcrystallization heat treatment but had not yet entered the chemical strengthening process were selected as experimental subjects. All samples were uniformly processed into rectangular pieces of 150mm × 75mm using precision cutting equipment, and the edges were lightly chamfered using a diamond grinding wheel to eliminate the interference of microcracks and edge stress concentration caused by mechanical cutting on the macroscopic surface shape data.

[0094] 2. Test steps:

[0095] 2.1 Place the processed test sample in a constant temperature and humidity clean laboratory chamber with an ambient temperature controlled at 23±1℃ and a relative humidity of 50±5% and let it stand freely for 24 hours to ensure that the residual thermal stress inside the sample is fully released and to eliminate the temporary deformation caused by the ambient temperature difference.

[0096] 2.2 A non-contact three-dimensional laser flatness measurement system was used to perform a full-field scan of the substrate's surface morphology. The sample was placed horizontally in its natural state on the measurement stage, supported by a three-point flexible support structure at the bottom to minimize the impact of its own weight on the accuracy of the morphology measurement.

[0097] 2.3 The laser scanning probe was activated, and point cloud data of the surface height was densely acquired along the length and width of the sample using a 2mm grid. The instrument system used the least squares method to fit a theoretical reference plane based on the acquired spatial coordinate data. Then, the highest and lowest points deviating from this reference plane across the entire surface of the sample were extracted, and the absolute value of the vertical height difference between these two points was calculated as the macroscopic warpage data of the sample. Three samples with the same parameters were taken from each group and measured separately. The final result was the arithmetic mean. The results are shown in Table 2:

[0098] Table 2: Macroscopic flatness test data of each embodiment and comparative example

[0099]

[0100] According to Table 2 and Figure 2 Data shows that the macroscopic flatness of the glass substrate has a significant correlation with the heat treatment process during microcrystallization. Phase separation and the large-scale precipitation of the main crystalline phase are accompanied by the rearrangement and volume shrinkage of the network structure. If this microscopic density change is not sufficiently relaxed within a specific viscous flow range, it is prone to forming warping deformation on a macroscopic scale. The deformation in Examples 1 to 5 was controlled within 35 μm, indicating that the intermediate stress tempering stage has a significant effect on releasing nucleation stress. When yttrium oxide is introduced into the formulation system, the larger radius yttrium ions tend to segregate at the interface between the amorphous phase and the crystal nucleus, generating solute resistance. This resistance is beneficial for refining the grain size, but it also prolongs the stress transmission and structural relaxation time. By setting a specific tempering time, the glass network obtains sufficient thermodynamic buffering before undergoing large-scale crystallization, balancing the arrangement of the phase interface and the dissipation of internal phase transformation shrinkage stress.

[0101] Observing the test results of Comparative Example 2, it can be found that, under the premise of the same basic formula, omitting the intermediate stress tempering stage, due to the lack of stress relaxation process, the stress accumulated inside the substrate due to rapid crystallization was not effectively released, resulting in an increase in deformation to 184.2 μm. This confirms that sufficient relaxation time is necessary to eliminate internal stress in yttrium oxide-containing systems. Comparative Example 1, under the condition of simultaneously lacking yttrium oxide and tempering treatment, showed a further increase in warpage to 215.8 μm, indicating that disordered rapid phase transitions are the direct cause of substrate dimensional instability. Furthermore, although Comparative Examples 3 to 5 performed a residence heat treatment procedure, changes in the basic formula (such as the clarifier or alkali metal ratio) altered the overall melt viscosity-temperature characteristics, causing the set tempering time to fail to match the actual stress relaxation rate, resulting in varying degrees of increase in deformation. In summary, the amount of yttrium oxide added must be matched with a specific intermediate stress tempering time and depends on the stability of the basic formula to effectively control the macroscopic warpage of the glass-ceramic substrate.

[0102] Test Example 3:

[0103] 1. Sample setup: Microcrystalline glass substrates from Examples 1 to 5 and Comparative Examples 1 to 5 that underwent complete chemical strengthening processes were selected as test subjects. All test samples were pre-cleaned alternately with anhydrous ethanol and deionized water at a 40 kHz ultrasonic frequency for 15 min, and then dried in a vacuum oven at 80 °C for 2 hours to thoroughly remove residual potassium nitrate salts and organic contaminants from the surface.

[0104] 2. Test steps:

[0105] 2.1 A surface stress meter based on the optical waveguide effect (FSM-6000LE series equipment) was used to perform non-destructive measurements of the surface compressive stress (CS) and stress layer depth (DoL) of the substrate. A refractive index matching liquid (usually a special test oil with a refractive index of about 1.64) was dropped into the test area of ​​the substrate to achieve tight optical coupling between the substrate surface and the test prism of the instrument, eliminating the interference of the interface air layer on the measurement of the critical angle of total internal reflection.

[0106] 2.2 Set the test wavelength to 595 nm (sodium D line) and input the pre-calibrated intrinsic optical constants (including substrate refractive index and photoelastic coefficient) of the glass substrate. Start the measurement program. The system automatically calculates the physicochemical parameters of the ion exchange layer by capturing the order and spacing of the interference fringes generated by birefringence of polarized light in the stress layer. Measurements were performed on each sample at five different locations (center and four corners). After removing abnormal fluctuation values, the average result was calculated. The results are shown in Table 3:

[0107] Table 3: Test data on chemical strengthening performance of each embodiment and comparative example

[0108]

[0109] According to Table 3 and Figure 3 Data shows that the network topology in the residual amorphous phase of the glass directly affects the ion exchange depth. In conventional highly crystalline materials, a large number of precipitated nanocrystals form physical barriers, increasing the tortuosity of the diffusion path of potassium ions into the interior, thus limiting the depth of the reinforcing layer to around 20 μm. In Examples 1 to 5 of this study, by controlling a specific mass ratio of sodium carbonate to potassium carbonate (i.e., defining the source and specific content of sodium and potassium alkali metal ions in the substrate glass network), the depth of the reinforcing layer was increased to over 40 μm without sacrificing the hardness of the matrix. Furthermore, free yttrium ions played a supporting role in the network, and their larger ionic radius expanded the gaps between silicon-oxygen tetrahedral rings in the local microstructure, providing channels for the migration of large-radius potassium ions from the outside.

[0110] In Comparative Example 4, when the mass ratio of sodium carbonate to potassium carbonate was adjusted to 1:1, the sodium-potassium mixed alkali effect within the matrix shifted, causing local closure of the migration channels through which external potassium ions replaced internal sodium ions. Test data showed that although the surface compressive stress increased to 884.2 MPa, this was due to stress accumulation caused by a large number of potassium ions clogging the shallow surface layer, and its DoL value decreased to 18.6 μm. Furthermore, Comparative Example 5, although containing yttrium oxide, adjusted the ratio of sodium carbonate to potassium carbonate (i.e., the alkali metal component), leading to structural densification of the network structure in the high-temperature molten salt. The ion migration channels were compressed in the early stages of diffusion, resulting in a final depth of only 22.1 μm. Comparative Example 1, completely lacking yttrium oxide, not only struggled to maintain deep penetration, but the overall stress network also became loose due to reduced interfacial bonding, with the CS value decreasing to 678.9 MPa. This further confirms the role of synergistic network optimization of yttrium oxide with a specific sodium-potassium alkali metal ratio in the mechanical strengthening process. This deep compressive stress field and internal crystalline phase design constitute the mechanical basis for preventing cracks from extending downwards when scratched by sharp external objects.

[0111] Test Example 4:

[0112] 1. Sample Setup: Glass substrates from Examples 1 to 5 and Comparative Examples 1 to 5, which underwent complete microcrystallization heat treatment and chemical strengthening processes, were selected as test samples. All samples were cut to a standard size of 50mm × 50mm, and their surfaces were wiped with isopropyl alcohol in a cleanroom environment to ensure that the test area was free of dust particles or organic oil film.

[0113] 2. Test steps:

[0114] 2.1 The sample was fixed on the precision moving platform of the nano-scratcher, which is equipped with a standard spherical diamond indenter with a radius of curvature of 2 μm. The test program was set to constant load mode, with a normal load of 500 mN, a scratch length of 3 mm, and a scratching speed of 1 mm / min. After the probe completed scratching, the cross-sectional profile of the middle section of the scratch was scanned in situ using the instrument's built-in three-dimensional topography scanning module. The residual scratch depth on the substrate surface was extracted and recorded. Each sample was tested in parallel five times in different areas to obtain average data.

[0115] 2.2 Adjust the test program of the nano-scratch tester to the gradual load mode to evaluate the brittle fracture resistance of the material. Set the initial normal load to 0 mN, and linearly increase it to 15 N at a constant loading rate over a scratch distance of 5 mm.

[0116] 2.3 During the test, the acoustic emission sensor and tangential force monitoring module were simultaneously activated. By observing the scratch morphology under a microscope and combining it with the first abrupt change point of the tangential force curve, the instant when lateral microcracks were generated on both sides of the scratch or when transverse edge chipping (brittle spalling) occurred was accurately determined, and the corresponding normal applied force at this time was recorded as the critical load for scratch fracture. The results are shown in Table 4:

[0117] Table 4: Scratch resistance and brittleness resistance test data for each embodiment and comparative example

[0118]

[0119] According to Table 4 and Figure 4 Data shows that when high-strength glass-ceramics are subjected to concentrated shear stress from sharp objects, material failure typically originates from the propagation of microcracks at the phase interface. In conventional scratch tests, simply increasing surface hardness cannot completely prevent lateral peeling of the glass surface. Examples 1 to 5 exhibited excellent scratch resistance in the tests, with residual scratch depths all suppressed to within 270 nm, and the critical fracture load exceeding 7.0 N. This data reflects the effect of specific grain boundary structure optimization. Due to the large radius of yttrium ions, they are difficult to enter the main crystalline phase lattice. During intermediate stress tempering, these high-field-strength ions segregated and accumulated at the interface between the remaining glass phase and nanocrystals. This yttrium-rich phase boundary layer significantly enhances the shear resistance of the phase interface, resulting in higher grain boundary resistance encountered by the indenter during cutting. This allows more mechanical energy to be dissipated through local densification, reducing crack formation.

[0120] Comparative Example 1 data validates the role of this mechanism. After the complete removal of yttrium oxide, the matrix loses this grain boundary resistance, and the spinel grains are only connected to the glass phase by weak structural bonds. Under a low load of only 3.1 N, the indenter induces rapid deflection and penetration of microcracks along the grain boundaries, resulting in an increase in scratch depth to 392.6 nm accompanied by severe brittle spalling. Comparative Example 2 illustrates the impact of heat treatment on strength. Even with the presence of yttrium oxide in the system, once the critical intermediate tempering stage is eliminated and the temperature is rapidly increased directly, the crystals coarsen. These coarse crystal particles form discrete stress concentration sources in the stress field, and the yttrium ions originally used to strengthen the interface do not have time to distribute evenly and fail to effectively distribute at the phase interface, resulting in a decrease in the critical load of the substrate to 4.2 N. In Comparative Examples 4 and 5, due to the change in the mixed alkali ratio, the gradient of compressive stress inside the chemically strengthened layer is not fully established. The disconnect between the high surface stress and the internal support network causes premature brittle fracture during deep scratching. In summary, the specific amount of yttrium oxide added, combined with intermediate stress tempering treatment, promotes the enrichment of yttrium ions at the phase interface, which is the key to improving the scratch resistance and fracture resistance of glass-ceramics.

[0121] Test Example 5:

[0122] 1. Sample Setup: Glass substrates from Examples 1 to 5 and Comparative Examples 1 to 5, which underwent both microcrystallization heat treatment and chemical strengthening, were selected as hardness test samples. The substrates were cut into 20mm × 20mm test cubes, placed in an ultrasonic cleaning tank, and cleaned with anhydrous ethanol for 10 minutes to remove surface deposits. After removal, they were allowed to air dry at room temperature.

[0123] 2. Test steps:

[0124] 2.1 Fix the processed test block horizontally on the test stage of the micro Vickers hardness tester, adjust the light source and focus of the device to make the substrate surface clearly imaged in the microscope field of view, and select test points while avoiding areas with possible micro-scratches or particle contamination on the surface.

[0125] 2.2 Set the normal load of the hardness tester's indenter to 200 gf and the holding time to 15 seconds. Start the loading program, and the diamond square pyramid indenter is pressed into the substrate surface at a constant rate. After reaching the predetermined load, it remains stationary, and then the indenter is automatically unloaded and lifted.

[0126] 2.3 The residual indentation morphology on the substrate surface was observed using a high-magnification objective lens with micrometer graduations on a hardness tester. The crosshairs were aligned with the endpoints of the two diagonals of the indentation, and the system read and recorded the lengths of the two diagonals. The hardness value of each test point was calculated using the standard Vickers hardness formula. Ten non-overlapping test points were randomly selected from different areas of each sample to obtain data. After discarding invalid data with significant bias, the arithmetic mean was calculated as the macroscopic Vickers hardness of the sample. The results are shown in Table 5.

[0127] Table 5: Surface Vickers hardness test data for each embodiment and comparative example

[0128]

[0129] According to Table 5 and Figure 5 The data shows that the test results of Examples 1 to 5 indicate that combining the addition of specific rare earth elements with stress relaxation heat treatment stabilizes the Vickers hardness of the substrate in the high range of 792 Hv to 821 Hv. This high hardness is achieved because the solute resistance effect generated by yttrium oxide during the microcrystallization heat treatment stage inhibits the abnormal growth of nascent nanocrystals, leading to a significant increase in the number of grain boundaries per unit volume. This dense grain boundary network acts as a rigid support framework during indentation, rapidly dissipating the concentrated load applied externally into the surrounding matrix.

[0130] By comparing and analyzing the data from Comparative Example 1 and Comparative Example 2, the role of the hardness control mechanism is as follows. In Comparative Example 1, without yttrium oxide and the stress-tempering section, crystal growth is disordered and uncontrolled, inevitably resulting in coarse crystal particles and associated micro-interfacial cracks. These micro-defects, when subjected to the vertical load applied by the indenter, easily induce phase interface rupture and micro-crack propagation, leading to an abnormally large diagonal size of the indentation and a calculated hardness value reduced to 645.8 Hv. Even if yttrium oxide is retained in the formulation, and the intermediate stress-tempering section is ignored as in Comparative Example 2, the volumetric shrinkage stress caused by the rapid phase transformation cannot be fully released in the viscous flow region and is frozen in the cross-linked network as residual internal stress. This metastable phase interface is prone to brittle fracture under the secondary superposition of external mechanical stress, resulting in a hardness of only 682.1 Hv.

[0131] Besides the intervention of crystallization kinetics, the structural stability of the chemically strengthened channels also left traces on the test surface. Comparative Examples 4 and 5 deviated from the originally optimized alkali metal ratio. The local collapse of the ion exchange channels in the high-temperature molten salt not only hindered the deep penetration of potassium ions but also triggered macroscopic relaxation of the surface glass network density. The surface structure, no longer deeply encased by the high-pressure stress field, exhibited a significant softening tendency when resisting indentation, with the hardness decreasing to the range of 700 Hv to 720 Hv. In summary, the appropriate addition of yttrium oxide, the introduction of intermediate stress tempering treatment, and the setting of a specific alkali metal ratio together constitute the necessary conditions for improving the Vickers hardness of the microcrystalline glass surface of this invention.

[0132] Test Example 6:

[0133] 1. Sample Setup: Microcrystalline glass substrates from Examples 1 to 5 and Comparative Examples 1 to 5 were selected, with the initial optical data measured in Test Example 1 used as the background reference value. To simulate and accelerate the optical degradation process induced by long-term exposure to high-energy photon radiation in real-world applications, the edges of all experimental samples were fixed to a dedicated aluminum sample holder in the UV aging test chamber to ensure that the test surface was completely exposed.

[0134] 2. Test steps:

[0135] 2.1 The excitation source of the UV aging test chamber was set to a broadband high-pressure mercury lamp with a total power of 1000W, whose main emission wavelength covers the high-energy UV characteristic spectral band from 254nm to 365nm. The vertical radiation distance between the lamp tube emitting surface and the sample surface was adjusted to 150mm. The environmental chamber temperature control system was turned on to keep the ambient temperature in the chamber constant at 45±2℃, and all samples were subjected to continuous high-intensity UV irradiation for 168 hours.

[0136] 2.2 After the irradiation aging stage is completed, the light source is turned off and the sample is taken out. The sample is then placed in a light-proof vacuum desiccator at a temperature of 25°C and left to stand for 24 hours to eliminate the interference of transient short-lived color centers generated by high-energy photoexcitation inside the glass network on subsequent measurements.

[0137] 2.3 Using the same spectrophotometer and colorimetric measurement equipment as in Test Example 1, and under the same D65 light source and 10° field of view test conditions, the average visible light transmittance and b-value of each aged sample in the 380nm to 780nm wavelength range were re-measured. The measured data were recorded, and the absolute increase in yellow index (Δb) and transmittance decrease (ΔT%) before and after degradation of each sample were calculated. The results are shown in Table 6:

[0138] Table 6: Test data on the overall optical performance degradation of each embodiment and comparative example

[0139]

[0140] According to Table 6 and Figure 6 The data shows that the optical attenuation characteristics of high-alumina silicate microcrystalline glass after high-energy ultraviolet irradiation reflect the dissipation effect of ultraviolet excitation energy within the matrix. In routine high-temperature melting processes, raw materials from complex sources often inevitably introduce trace amounts of iron impurities into the glass matrix. These free Fe... 3+ with Fe 2+ Ions form potential photo-induced color centers in the amorphous network. Data from Examples 1 to 5 show that after 168 hours of continuous ultraviolet irradiation, the optical transmittance of the samples remained stable, with the transmittance attenuation limited to within 0.5%, and the Δb value, reflecting the degree of yellowing, showed minimal change. When external ultraviolet photons excite electron transitions in the glass network, cerium ions undergo a charge transfer band redshift effect in the high-field environment introduced by yttrium ions. This redshifted absorption band overlaps with the absorption band of iron impurities, quenching the photo-excited state energy that would otherwise induce glass yellowing through non-radiative transitions, thereby effectively suppressing the photo-induced yellowing phenomenon.

[0141] In Comparative Example 3, without the addition of the cerium-tin system to the formulation, the glass network lost its buffering capacity against photogenerated electrons. Trace amounts of iron ions and structural defects within the matrix evolved into deep-level absorption centers under strong ultraviolet radiation. This unsuppressed electronic transition led to an increase in the b-value of the substrate after aging to 6.75, while the transmittance decreased to 80.6%, resulting in a significant decline in UV aging resistance. The degradation rate of Comparative Example 1 was still significantly higher than that of the Example 1 because the removal of yttrium oxide resulted in the absence of a high-field environment around cerium ions that induced their bandgap shift. 4+ The charge transfer band cannot achieve a sufficient redshift to cover the absorption cross-section of the impurities, causing the energy quenching mechanism to fail and photo-induced yellowing to still occur. Furthermore, the elimination of the intermediate stress tempering section in Comparative Example 2 led to microscopic shrinkage cracks at the interface. These unevenly distributed phase separation boundaries acted as light scattering sources, exacerbating the attenuation of transmittance. In summary, the synergistic coupling effect of yttrium oxide and cerium oxide in the microstructure, combined with the process intervention of intermediate stress tempering, is a necessary technical feature to ensure that the microcrystalline glass of this invention maintains excellent optical quality under long-term high-energy photon irradiation.

[0142] Test Example 7:

[0143] 1. Sample Setup: The chemically strengthened microcrystalline glass substrates from Examples 3, 4, and 5 were selected as samples for cross-sectional analysis. The glass samples were vacuum-embedded and cured using cold-mounted epoxy resin, and then cut along the thickness direction of the substrate to expose the complete cross-section.

[0144] 2. Test steps:

[0145] 2.1 The cross-section of the resin-embedded sample was ground step by step using silicon carbide wet sandpaper, and then transferred to a polishing machine equipped with diamond suspension for mechanical polishing until the cross-section reached the optical mirror level without scratches. Ultrasonic cleaning was then used to remove the abrasive residue from the surface.

[0146] 2.2 The polished sample was placed in a small ion sputtering instrument, and a conductive carbon film with a thickness of about 15 nanometers was uniformly deposited on the cross-sectional surface to eliminate the surface charge accumulation effect that may be generated during subsequent electron beam bombardment.

[0147] 2.3 Place the sample in the vacuum sample chamber of the electron probe microanalyzer (EPMA). Set the accelerating voltage to 15 kV and the beam current to 1.0 × 10⁻⁶. -8 A. Start the wavelength dispersive X-ray spectroscopy (WDS). Starting from the reinforced surface of the glass substrate, perform a line scan analysis along the normal direction perpendicular to the surface into the matrix. Record the characteristic X-ray intensity of potassium (K) at fixed intervals. Convert this to the mass percentage concentration of potassium ions using standard sample calibration, and then plot the true diffusion gradient curve of the ion exchange depth. The results are shown in Table 7:

[0148] Table 7: Cross-sectional potassium ion concentration diffusion data for Example 3 and the parameter out-of-bounds comparison example.

[0149]

[0150] According to Table 7 and Figure 7Data shows that the EPMA cross-sectional scanning results of Example 3 indicate that, under specific sodium carbonate to potassium carbonate mass ratios and with the addition of yttrium oxide, the potassium ion mass concentration on the substrate surface is 14.82 wt%, and an effective concentration of 1.96 wt% is still maintained even at a test depth of 40 μm. Combined with microstructure analysis, this specific alkali metal ratio and the electrostatic field effect of free yttrium ions synergistically provide spatial support within the interstices of the silicon-oxygen tetrahedral network, effectively slowing down the densification rate of the glass network under high-temperature salt bath conditions, thereby maintaining channels for the migration of large-radius potassium ions. When the sodium carbonate to potassium carbonate ratio is adjusted to 1:1, as shown in Comparative Example 4, the potassium ion concentration at the test surface reaches 16.51 wt%. However, its concentration gradient decreases significantly after entering a depth of 15 μm, dropping to 3.12 wt%, and essentially decays to the edge of the detection threshold after 25 μm. This phenomenon of high concentration enrichment on the surface and rapid decay of concentration inside is an objective manifestation of localized network contraction caused by the mixed alkali effect deviating from the optimal coordination window. Excess sodium ion vacancies cannot maintain their original coordination geometry during the potassium ion entry stage, and the migration channels close in the early stages of diffusion, leading to a large accumulation of potassium ions in the near-surface region. In practical applications, once this shallow stress distribution layer encounters scratches deeper than 20 μm, the substrate is prone to cracking due to the penetration of the stress layer.

[0151] On the other hand, data from Comparative Example 5 shows that when the mass ratio of sodium carbonate to potassium carbonate is adjusted to 26.0:14.0, although yttrium oxide is present in the system, the change in the alkali metal ratio causes a shift in the network topology. The metastable amorphous phase undergoes thermodynamic densification under high-temperature molten salt replacement conditions. The potassium ion concentration at 20 μm has decreased to 2.51 wt%, indicating that ion diffusion is hindered by the structure after passing through the shallow surface layer. In conclusion, a specific sodium-potassium alkali metal formulation is a necessary prerequisite for ensuring deep diffusion of potassium ions.

[0152] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a highly scratch-resistant microcrystalline touchscreen glass substrate, characterized in that, Includes the following steps: Step (1) Ingredient Mixing: Weigh the raw materials according to the weight ratio, place them in a mixer and mix, controlling the moisture content of the compound to ≤0.1wt%; Step (2), Melting and Clarification: The complex obtained in step (1) is put into a furnace and heated to melt. Then, high-temperature oxygen release clarification and medium-temperature absorption clarification are carried out in sequence to obtain high-transparency glass melt. Step (3), controlled molding: The glass melt obtained in step (2) is molded by overflow and annealed to obtain an amorphous glass substrate; Step (4) Microcrystallization heat treatment: The amorphous glass substrate obtained in step (3) is placed in a crystallization furnace and subjected to gradient nucleation, intermediate stress tempering and ultra-fine crystal growth treatment in sequence. After cooling to room temperature, a microcrystallized substrate is obtained. Step (5), chemical strengthening: The microcrystalline substrate obtained in step (4) is immersed in a high-temperature potassium nitrate molten salt bath for ion exchange treatment. After cleaning and drying, the glass substrate is obtained.

2. The method for preparing a glass substrate according to claim 1, characterized in that, The raw materials comprise the following components by weight: 550.0–612.3 parts silicon dioxide; 180.0–220.0 parts aluminum oxide; 100.0–150.0 parts zinc oxide; 35.0–50.0 parts aluminum phosphate; 22.0–30.0 parts zirconium dioxide; 5.2–29.5 parts yttrium oxide; 1.5–5.0 parts cerium oxide; 1.0–3.0 parts tin dioxide; 22.1–35.0 parts sodium carbonate; and 10.0–15.0 parts potassium carbonate.

3. The method for preparing a glass substrate according to claim 1, characterized in that, In step (2), the heating melting temperature is 1630-1650℃; the conditions for high-temperature oxygen release clarification are: constant temperature residence at 1640-1650℃ for 4 hours; the conditions for medium-temperature absorption clarification are: cooling down to 1560-1580℃ and constant temperature residence for 2 hours.

4. The method for preparing a glass substrate according to claim 1, characterized in that, In step (3), the controlled molding process parameters are: real-time monitoring of the melt liquidus temperature, controlling the molding channel temperature to be the liquidus temperature plus 65°C, controlling the liquidus viscosity of the melt at the molding point to be stable at 4.5~5.2dPa·s, and the molding thickness to be 0.5~0.8mm.

5. The method for preparing a glass substrate according to claim 1, characterized in that, In step (4), the specific parameters of the microcrystallization heat treatment are as follows: First, the temperature is raised to 700-720℃ and held for 2 hours to induce gradient nucleation. The temperature was then adjusted to the glass transition temperature plus 15°C, and the temperature was kept constant for 28–61 min for intermediate stress tempering treatment to induce yttrium ions to segregate at the interface between the residual glass phase and the nanocrystals. The temperature was then raised to 870–890°C and held for 1 hour to grow extremely fine crystals, followed by cooling to room temperature.

6. The method for preparing a glass substrate according to claim 1, characterized in that, In step (5), the specific process parameters for the chemical enhancement treatment are: immersion temperature of 420-435℃, and ion exchange treatment for 7-8 hours.

7. The method for preparing a glass substrate according to claim 2, characterized in that, The silicon dioxide contains ferric oxide with a mass fraction of ≤80ppm and a median particle size D50 of 40μm~60μm.

8. The method for preparing a glass substrate according to claim 2, characterized in that, The alumina is α-type calcined alumina with a purity ≥99.9% and a median particle size D50 of 12μm~18μm.

9. The method for preparing a glass substrate according to claim 2, characterized in that, The zirconium dioxide is monoclinic zirconium dioxide with a purity ≥99.5% and a median particle size D50 of 1.5μm~2.5μm.

10. The method for preparing a glass substrate according to claim 2, characterized in that, The yttrium oxide has a purity of ≥99.99% and a median particle size D50 of 2μm to 4μm.

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