Preparation method and application of high flatness electronic glass

Abstract

The present application relates to the technical field of glass, and more particularly to a preparation method and application of high flatness electronic glass. The method adopts a float process, melts glass batch of specific composition, and then introduces into a tin bath. The H2 concentration, gas flow rate, drawing speed, transverse tension of edge roller and gate opening height are controlled in the interval of 1185 DEG C to 920 DEG C to directly form a 0.7-1.0 mm thick glass ribbon. Then, the glass ribbon is subjected to gradient cooling and precise annealing treatment to obtain a raw sheet with a micro-ripple degree of less than 0.15 μm / 20 mm and a surface roughness Ra of less than 0.5 μm. The raw sheet is then cut, ground, preheated and ion exchanged to obtain a chemically strengthened glass with high optical transmittance, high bending strength and high fracture toughness. The present application solves the problem of insufficient optical and mechanical properties caused by ripple degree and edge defects in the application of ultra-thin electronic glass in high-end display.

Description

Technical Field

[0001] This invention relates to the field of glass technology, and in particular to a method for preparing high-flatness electronic glass and its application. Background Technology

[0002] With the increasing demands for screen display quality from terminal products such as smartphones, tablets, automotive displays, and high-end medical devices, ultra-thin electronic glass, as a key basic material, not only needs to possess high optical transmittance and excellent mechanical properties, but also faces stringent requirements for surface micro-flatness. Micro-wrinkle, a mid-frequency surface morphology parameter situated between surface roughness and macro-geometric errors, has become one of the core indicators for evaluating the suitability of electronic glass for high-end color LCD or OLED display panels. When the micro-wrinkle of electronic glass exceeds the standard, even after downstream precision polishing, optical interference defects such as rainbow patterns and moiré patterns are easily generated on the display screen, severely affecting the visual experience and product yield. Therefore, controlling the micro-wrinkle of 0.7mm thick electronic glass to below 0.15μm / 20mm has become a technical threshold for entering the high-end display supply chain.

[0003] Currently, the float glass process is the primary method used in industry to manufacture ultra-thin electronic glass. However, during the tin bath forming process of traditional float glass, limitations such as unreasonable glass composition design, insufficient control of molten tin surface tension, low purity of the protective atmosphere, or uneven temperature distribution make it difficult to effectively suppress microscale fluctuations in the glass ribbon during the flattening, polishing, and thinning stages. Especially at thicknesses of 0.7 mm and below, the rigidity of the glass ribbon is significantly reduced, making it more susceptible to airflow disturbances, molten tin fluctuations, and cooling rate gradients, resulting in difficulty in consistently controlling surface waviness.

[0004] To improve the impact and scratch resistance of electronic glass, chemical strengthening treatment is usually required. However, if the substrate glass itself has high waviness or edge defects, it will not only weaken the uniformity of ion exchange, but may also induce microcrack propagation during the strengthening process, resulting in decreased fracture toughness and increased strength dispersion. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for preparing high-flatness electronic glass and its application, which solves the technical problems that the existing float glass process is difficult to stably control the micro-ripple (<0.15μm / 20mm) under the ultra-thin specification of 0.7mm, and that the uneven stress distribution, large strength dispersion and insufficient fracture toughness after chemical strengthening due to defects on the substrate surface and edge lead to the inability to meet the stringent requirements of high-end display devices for both optical performance and mechanical reliability.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0009] In a first aspect, this application provides a method for preparing high-flatness electronic glass, comprising the following float glass forming steps:

[0010] 1. A method for preparing high-flatness electronic glass, comprising the following float glass forming steps:

[0011] Step S1: Melt the glass batch at 1640-1660℃, clarify, stir and homogenize to obtain molten glass;

[0012] Step S2: The molten glass is introduced into a tin bath through a flow channel at a temperature of 1200-1220℃. The tin bath is filled with a protective gas mixture of N2 and H2 with a purity of ≥99.999%. The molten glass floats on the surface of the molten tin in the tin bath at a temperature range of 1175-1195℃ to 910-930℃, and goes through the stages of flattening, polishing, and thinning in sequence. The drawing speed, the lateral tension of the edge-pulling machine, and the opening height of the gate are adjusted to directly form a high-flatness glass strip with a thickness of 0.7 mm or less.

[0013] Step S3: Control the temperature from 790-810℃ to 590-610℃ to cool and shape, then enter the annealing furnace;

[0014] Step S4: In an annealing furnace, hold at 550-570℃ and then cool to 500-510℃ to complete the annealing process; then rapidly cool to 200℃ or below and allow to cool naturally to room temperature to obtain electronic glass substrates with micro-ripples <0.15μm / 20mm and surface roughness Ra <0.5μm.

[0015] Step S5: Cut the electronic glass sheet to the target size and grind the edges;

[0016] Step S6: Preheat the ground glass at 370-390℃ for 0.5-1 hour;

[0017] Step S7: Immerse the preheated glass in KNO3 molten salt and perform ion exchange treatment at 400-420℃ for 180-200 minutes to obtain chemically strengthened glass.

[0018] Step S8: Remove the product and clean the surface to remove any remaining molten salt, and you will get the finished product.

[0019] In some embodiments, in step S1, the glass batch material comprises, by mass percentage: SiO2: 60-78%, Al2O3: 3-13%, Na2O: 5-18%, K2O: 0-1%, MgO: 0-8%, and CaO: 0-5%.

[0020] This basic component system falls within the scope of our company's sodium-calcium-aluminum-silicate electronic glass formulation. By systematically matching and optimizing this existing component system with unique float glass process parameters and post-processing procedures, we have achieved breakthroughs in surface flatness and mechanical properties based on this conventional composition. Without changing the mainstream raw material system, we have solved the flatness and reliability issues of high-end display glass.

[0021] In some embodiments, the tin bath is filled with a protective gas mixture of N2 and H2, and is divided into a flattening zone, a polishing zone, and a thinning zone along the drawing direction. The volume fraction of H2 in each zone is 8-10%, 5-7%, and 1-3%, respectively, and the flow rate of the protective gas is controlled to be ≤0.15m / s, ≤0.15m / s, and 0.15-0.25m / s, respectively.

[0022] In the leveling zone, the molten glass has just entered the molten tin surface. At this stage, the temperature is high, the viscosity is low, and the fluidity is strong. A higher H2 concentration of 8-10% effectively reduces any potential SnO2 formation, preventing tin oxide inclusions. Simultaneously, a low gas flow rate (≤0.15 m / s) avoids airflow disturbance to the still-stabilized glass ribbon, allowing it to naturally level itself using surface tension. In the polishing zone, the glass ribbon is in a high-temperature, slow-cooling phase. Microbubble escape and surface defect healing are crucial. Appropriately reducing the H2 concentration to 5-7% maintains a reducing atmosphere to inhibit tin oxidation. A low flow rate continues to ensure thermal stability, reduce surface fluctuations, and promote the formation of a smooth mirror surface. In the thinning zone, the glass viscosity increases, requiring longitudinal stretching to achieve the target thickness of 0.7 mm. At this point, the H2 concentration is further reduced to 1-3%, sufficient to prevent localized oxidation and avoid excessive hydrogen in the low-temperature zone causing unnecessary molten tin bubbling or hydrogen erosion on the lower surface of the glass. Simultaneously, the gas flow rate is increased to 0.15-0.25 m / s. The flow rate of H2 (m / s) helps to remove heat, enhances cooling rate control, and stabilizes the atmosphere boundary layer at the tin bath outlet, preventing air backflow. In summary, this zoned control of H2 concentration and flow rate suppresses the three major waviness-inducing factors—oxidation defects, airflow disturbance, and uneven thermal field—at the source, providing a key process guarantee for achieving micro-waviness <0.15 μm / 20 mm.

[0023] In the float glass forming process, there is a transition zone called the inlet zone before the leveling zone. In this zone, the molten glass flows out of the ladle and first contacts the surface of the molten tin. The temperature of the molten glass at the ladle outlet is 1210±10℃. After entering the tin bath, due to contact with the lower-temperature molten tin, radiating heat to the protective atmosphere, and the lack of active heating compensation, it naturally cools down within a few seconds, dropping to approximately 1185±10℃, which is the initial temperature of the leveling zone. This temperature drop is a crucial aspect of the process design. It prevents the molten glass from flowing excessively due to high temperature, causing ripples due to airflow disturbances, and also prevents a sudden increase in viscosity due to rapid cooling, resulting in insufficient surface tension for natural leveling. It can be considered a pre-conditioning step to provide ideal viscosity and surface tension conditions for the leveling stage, ensuring that the glass ribbon can smoothly widen using its own surface tension and initially eliminate thickness unevenness. This lays the foundation for achieving high flatness with a micro-wrinkle degree of <0.15μm / 20mm in subsequent stages.

[0024] In some embodiments, the drawing speed is controlled to be 15-25 m / min throughout the tin bath forming process;

[0025] During the leveling stage, the glass strip is kept in the leveling zone at 1185±10℃ for 25-40 seconds, allowing it to naturally level out by relying on surface tension.

[0026] During the polishing stage, the temperature is kept stable or slowly cooled at a rate not exceeding 5℃ / min in the polishing zone at 1130±10℃ to promote the escape of microbubbles and the healing of surface defects.

[0027] During the thinning stage, from 1080℃±10℃ to 920℃±10℃, the longitudinal stretching of the glass strip is adjusted using the drawing speed to achieve a target thickness of 0.7mm.

[0028] During the thinning and forming stage, the edge pulling machine is started and its speed is controlled at 80-250 rpm to apply lateral tension to the edge of the glass strip, suppressing widening and improving edge flatness.

[0029] Furthermore, before introducing the molten glass into the tin bath, the cross-section of the glass liquid flow is adjusted by a gate, and the gate opening height is controlled at 8-12mm.

[0030] The overall drawing speed is controlled at 15-25 m / min, ensuring both production efficiency and providing sufficient thermodynamic response time for each forming stage. During the leveling stage, the glass strip is held at a high temperature and low viscosity of 1185±10°C for 25-40 seconds, allowing sufficient time for surface tension to spontaneously eliminate thickness fluctuations and reach a balanced thickness, achieving macroscopic leveling. In the polishing stage, the temperature is maintained at 1130±10°C or cooled at an extremely slow rate not exceeding 5°C / min, effectively extending the time window for the glass to remain in a high-fluidity state. This promotes the escape of residual microbubbles and allows minor surface irregularities to heal through viscous flow, resulting in a mirror-like smooth surface. Subsequently, in the thinning stage, the glass viscosity gradually increases. At this point, by matching the drawing speed... By controlling the speed and longitudinal tensile stress, the glass is controllably thinned from its naturally flattened, relatively thick state to the target thickness of 0.7mm, avoiding stress concentration or uneven thickness caused by sudden changes in pulling speed. The edge-pulling machine is started and its speed is controlled at 80-250rpm, applying appropriate lateral tension to both sides of the glass strip, effectively suppressing edge widening caused by the Poisson effect and improving the uniformity of the board width and the straightness of the edges. Before the molten glass is introduced into the tin bath, the flow cross-sectional height is precisely limited to 8-12mm by the gate, which not only controls the initial volume flow rate of the glass strip, but also optimizes its spreading pattern on the molten tin surface, providing uniform and stable starting conditions for subsequent flattening.

[0031] In some embodiments, during step S3, the protective gas velocity is controlled between 0.15 and 0.25 m / s during the cooling and shaping stage, and a protective gas with a concentration of 1-3% H2 starts from the thinning zone and continues to the tin bath outlet.

[0032] This setup maintains a weak reducing atmosphere to prevent molten tin from oxidizing or tin from adhering to the lower surface of the glass at low temperatures. It also enhances uniform cooling through moderate airflow to avoid stress or warping caused by local temperature differences, thus helping to stabilize the glass ribbon morphology and ensure surface flatness.

[0033] In step S3, uniform cooling is achieved by adjusting the water cooling intensity of the tin bath sidewall and controlling the flow rate of the N2 and H2 mixed protective gas at 0.15-0.25 m / s, with an H2 volume fraction of 1-3%, to prevent thermal stress accumulation and suppress hydrogen evolution and tin penetration in the low-temperature zone. Subsequently, the glass ribbon detaches from the molten tin surface at approximately 700°C, is supported by ceramic rollers, and enters the transition roller table, where it continues to cool to 600°C via natural radiation and convection. The temperature is stabilized at 560°C at the inlet section of the annealing furnace, and then held at 560°C for annealing treatment with a cooling curve slope deviation ≤0.5°C / min.

[0034] The annealing furnace is divided into independent temperature-controlled sections, each equipped with upper and lower heating elements. The heating elements are preferably silicon carbide rods, with side-wall water or air cooling devices, and a high-precision non-contact infrared temperature measurement system that performs high-frequency temperature scans on the glass strip surface, typically dozens of times per second. The control system employs a feedforward-feedback composite algorithm. The feedforward part pre-calculates the required heat power for each temperature zone based on process parameters such as drawing speed and glass thickness; the feedback part compares the measured temperature with the theoretical annealing curve in real time, dynamically adjusting the heating intensity or cooling airflow. For example, if the system detects that the actual cooling rate at a certain time period is 3.8℃ / min, while the set value is 3.2℃ / min, the deviation reaches 0.6℃ / min, exceeding the allowable range. It will immediately fine-tune the fan speed or local heating power to bring the rate back within the tolerance range. We also reconstruct the two-dimensional temperature field of the entire glass sheet through multi-point infrared imaging to compensate for the cooling difference between the edge and center, ensuring consistent cooling across the entire width. Through this control mechanism, the industrial site can stably achieve a cooling rate accuracy within ±0.5℃ / min, thereby ensuring that 0.7mm electronic glass meets the high-end quality requirements of micro-ripple <0.15μm / 20mm and low surface roughness.

[0035] In some embodiments, in step S4, the annealing process includes: holding at 560°C for 10-20 minutes;

[0036] It was then cooled to 500°C at an average rate of 2.5–4.0°C / min;

[0037] After annealing, rapidly cool to 200°C or below at a rate of 10-25°C / min, and then allow to cool naturally to room temperature.

[0038] The formed glass strip is held at 560℃ for 10-20 minutes to bring it close to the glass transition temperature, effectively releasing the structural stress accumulated during the float glass process. Then, it is cooled to 500℃ at a controlled slow cooling rate of 2.5-4.0℃ / min to avoid introducing new thermal stress due to excessively rapid cooling. After annealing, it is rapidly cooled to below 200℃ at 10-25℃ / min, which can suppress the diffusion and segregation of Na ions in the mid-temperature region and prevent the evolution of micro-defects. Finally, it is allowed to cool naturally to room temperature.

[0039] In some embodiments, step S5, the edge grinding process includes:

[0040] Two rough grinding operations: using a 500-mesh grinding wheel, a rotation speed of 37,000-38,000 r / min, a feed rate of 580-600 mm / min, and a single-sided removal amount of 0.15 mm;

[0041] Fine grinding in one pass: using a 1200-mesh grinding wheel, a rotation speed of 37,000-38,000 r / min, a feed rate of 550-570 mm / min, and a single-sided removal amount of 0.1 mm.

[0042] Such edge grinding effectively eliminates stress concentration sources, significantly improves edge strength and chemical strengthening uniformity, and lays the foundation for subsequent high-reliability strengthening.

[0043] In some embodiments, the glass has a thickness of 0.7 mm and an optical transmittance of more than 90.5% at a wavelength of 550 nm; after chemical strengthening, its bending strength is not less than 400 MPa, its fracture toughness is not less than 3.0 MPa•m1 / 2, and its surface center compressive stress is 670-720 MPa, with a stress layer depth of 8.9-12 μm.

[0044] In some embodiments, the chemical strengthening process includes preheating the glass substrate at 380°C for 0.5 h, and then immersing it in 100 wt% KNO3 molten salt at 410°C for ion exchange for 180 min.

[0045] Preheating reduces thermal shock during salt introduction and prevents the initiation of microcracks; the temperature of 410℃ balances the Na+ content. + / K + The exchange rate is crucial for glass structural stability, and a processing time of 180 minutes is sufficient to form a reinforced layer of moderate depth and high compressive stress. Without sacrificing optical transmittance, we have improved the glass's bending strength and fracture toughness, meeting the stringent requirements of high-end cover glass applications.

[0046] Secondly, this application provides an electronic display device comprising a cover plate of high-flatness electronic glass prepared by the method described above.

[0047] (III) Beneficial Effects

[0048] The method for preparing high-flatness electronic glass provided in this invention significantly improves the surface quality and mechanical properties of 0.7mm ultrathin electronic glass. In step S1, a specific glass batch is used to lay the compositional foundation for subsequent high-flatness forming and efficient ion exchange. In step S2, the tin bath is divided into a flattening zone, a polishing zone, and a thinning zone along the drawing direction. The H2 volume fraction and protective gas flow rate in each zone are controlled, and the drawing speed, edge-pulling machine speed, and gate opening height are adjusted to allow the glass strip to complete natural flattening, defect healing, and stable thinning sequentially within the temperature range of 1185±10℃ to 920±10℃, effectively suppressing microscale fluctuations. In steps S3 and S4, a gradient cooling and precise annealing process is adopted to further eliminate internal stress and lock in a high-flatness surface morphology, ultimately obtaining a high-quality raw sheet with micro-waviness <0.15μm / 20mm and surface roughness Ra <0.5μm. Subsequently, through standardized edge grinding, i.e., coarse grinding + fine grinding, preheating, and KNO3 molten salt ion exchange strengthening, the finished glass has high optical transmittance, high bending strength, high fracture toughness, and an ideal compressive stress layer. Attached Figure Description

[0049] 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.

[0050] Figure 1 This is a flowchart of a method for preparing high-flatness electronic glass according to the present invention. Detailed Implementation

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] All parameters not specifically mentioned in this application are based on conventional process conditions; all materials used are commercially available products; unless otherwise stated, percentages or parts mentioned herein refer to mass fractions, and gas ratios refer to volume percentages.

[0056] Example 1

[0057] The glass batch was mixed according to the following mass percentages: SiO2: 60%, Al2O3: 12%, Na2O: 17%, K2O: 1%, MgO: 6%, CaO: 4%. After melting and homogenizing at 1650℃, the mixture was introduced into a tin bath at 1210℃ via a flow channel. The tin bath was filled with a mixture of N2 and H2 gas with a purity ≥99.999%, with H2 content of 10% and flow rate of 0.15 m / s in the leveling zone, 7% and flow rate of 0.15 m / s in the polishing zone, and 1% and flow rate of 0.25 m / s in the thinning zone. The drawing speed was controlled at 15 m / min, and the glass ribbon was held in the leveling zone at 1185℃ for 40 seconds; it was slowly cooled at 5℃ / min in the polishing zone at 1130℃; the thinning stage was from 1080℃ to 920℃, the edge-pulling machine speed was 80 rpm, and the gate opening height was 12 mm. During the cooling and shaping stage, an H2 concentration of 1% and a gas flow rate of 0.25 m / s were used to directly form a high-flatness glass ribbon with a thickness of 0.7 mm. Annealing treatment involved holding at 560℃ for 20 minutes, cooling to 500℃ at 4.0℃ / min, then rapidly cooling to 200℃ at 25℃ / min, and finally allowing it to cool naturally to room temperature. After cutting, the edges were ground twice: coarse grinding at 500 mesh, 38000 r / min, and 600 mm / min, removing 0.15 mm from one edge; and fine grinding once at 1200 mesh, 38000 r / min, and 550 mm / min, removing 0.1 mm from one edge. Subsequently, the ribbon was preheated at 380℃ for 0.5 h, immersed in 100 wt% KNO3 molten salt at 410℃ for ion exchange for 180 min, and cleaned to obtain the finished product.

[0058] Example 2

[0059] The glass batch composition is: SiO2 69%, Al2O3 8%, Na2O 15%, K2O 1%, MgO 5%, CaO 2%. After melting at 1640℃, it is introduced into the tin bath at 1215℃. The H2 concentrations in the three zones of the tin bath—leveling, polishing, and thinning—are 9%, 6%, and 2%, respectively. The gas flow rates are 0.15 m / s in the leveling and polishing zones and 0.20 m / s in the thinning zone. The drawing speed is set to 20 m / min. The leveling zone is held at 1185℃ for 30 seconds; the polishing zone is kept at a constant temperature of 1130℃; the thinning stage is cooled from 1080℃ to 920℃, the edge-pulling machine speed is 160 rpm, and the gate opening height is 10 mm. The H2 concentration in the cooling stage is 2%, and the flow rate is 0.20 m / s. The glass was directly formed into a high-flatness glass strip with a thickness of 0.7 mm. Annealing treatment: held at 560℃ for 15 minutes, cooled to 500℃ at 3.2℃ / min, and then rapidly cooled to below 195℃ at 18℃ / min. Edge grinding parameters were the same as in Example 1. Chemical strengthening: preheated at 390℃ for 0.5 h, and exchanged in KNO3 at 410℃ for 190 min. After removal, the surface was cleaned of residual molten salt to obtain the finished product.

[0060] Example 3

[0061] The glass composition used is: 78% SiO2, 38% Al2O3, 11% Na2O, 1% K2O, 1% MgO, and 1% CaO. It is melted at 1645℃, clarified, and homogenized by stirring to obtain molten glass; this is then introduced into a tin bath at 1200℃. The tin bath atmosphere is as follows: 8% H2 in the leveling zone, flow rate 0.12 m / s; 5% H2 in the polishing zone, flow rate 0.12 m / s; and 3% H2 in the thinning zone, flow rate 0.15 m / s. The drawing speed is 25 m / min, with a 25-second dwell time in the leveling zone. The temperature in the leveling zone is 1185℃, and the polishing zone temperature is maintained at a stable 1130℃. During the thinning stage, the temperature is reduced from 1080℃ to 920℃. During the thinning stage, the edge-drawing machine is started at 250 rpm, and the gate opening height is 8 mm. Cooling and shaping are performed using 3% H2 at a flow rate of 0.15 m / s. Annealing: Hold at 560℃ for 10 minutes, cool to 500℃ at 2.5℃ / min, then rapidly cool to 200℃ at 10℃ / min. Edge grinding is the same as in Example 1, with strengthening conditions of preheating at 390℃ for 1 hour and ion exchange in KNO3 molten salt at 420℃ for 200 minutes. After removal, clean the surface to remove residual molten salt to obtain the finished product.

[0062] Comparative Example 1

[0063] Comparative Example 1 used the exact same glass batch composition and all process parameters as Example 1, except for the control of the protective atmosphere in the tin bath. The difference was that a N2 / H2 mixed protective gas with an H2 volume fraction of 8% was continuously introduced into the tin bath, and the gas flow rate was uniformly maintained at 0.15 m / s. That is, the glass ribbon was exposed to a highly reducing atmosphere throughout the entire process of flattening, polishing, and thinning.

[0064] Comparative Example 2

[0065] The difference between Comparative Example 2 and Example 1 is that the drawing speed in the tin bath was set to 30 m / min, significantly higher than the 15-25 m / min range specified in this invention. Due to the increased drawing speed, the actual residence time of the glass ribbon in the flattening zone at 1185±10℃ was shortened to approximately 20 seconds. The rest was the same as in Example 1.

[0066] Comparative Example 3

[0067] The difference between Comparative Example 3 and Example 1 is that, during the annealing stage, the average cooling rate of the glass ribbon from 560°C to 500°C was set to 5.5°C / min. The rest was the same as in Example 1.

[0068] Comparative Example 4

[0069] The difference between Comparative Example 4 and Example 1 is that after the glass sheet is cut, only one rough grinding process is performed, that is, a 500-grit grinding wheel is used, the rotation speed is 38,000 r / min, the feed rate is 600 mm / min, and the single-sided removal amount is 0.15 mm. No fine grinding process is performed. The rest is the same as Example 1.

[0070] Comparative Example 5

[0071] The difference between Comparative Example 5 and Example 1 is that the gate opening height is set to 15 mm before the tin bath is introduced, while the rest is the same as Example 1.

[0072] Comparative Example 6

[0073] The difference between Comparative Example 6 and Example 1 is that the temperature when the molten glass is introduced into the tin bath is set to 1300°C, the temperature of the flattening zone is set to 1200°C, the temperature of the polishing zone is set to 1100°C and rapidly cooled at a rate of about 8°C / min, and the starting temperature of the thinning and forming stage is 1020°C. The rest is the same as Example 1.

[0074] Comparative Example 7

[0075] The difference between Comparative Example 7 and Example 1 is that the annealing temperature is set to 520°C, while the rest is the same as Example 1.

[0076] Comparative Example 8

[0077] The difference between Comparative Example 8 and Example 1 is that the chemical strengthening treatment temperature was set to 450°C, while the rest was the same as Example 1.

[0078] Data detection:

[0079] The transmittance at wavelengths of 520 nm and 550 nm was measured using a UV-Vis spectrophotometer (Shimadzu UV-2600i); the surface compressive stress and stress layer depth were measured using a surface stress meter (Orihara FSM-6000X); 4PB was measured and fracture toughness was tested using a Beidou Precision PT-605BS; Vickers hardness was measured using a Vickers hardness tester (Laizhou Zhijin CHQS-10AT) with a load of 100 gf and a holding time of 15 s.

[0080] Surface roughness Ra was measured using a white light interferometer (ZYGO NewView 9000) with a cutoff wavelength of 0.8 mm and an evaluation length of 4.8 mm. Microscopic waviness was measured using the same white light interferometer with bandpass filtering λs = 0.08 mm and λc = 2.5 mm, within a 20 mm evaluation length.

[0081] The test samples for micro-wrinkle and surface roughness Ra were taken from the electronic glass sheet after annealing in step S4 and cooling to room temperature. They were not cut, edged, or chemically strengthened. All other parameters were measured on the final chemically strengthened product.

[0082] The test results are shown in the table below.

[0083]

[0084] Comparative Example 1, lacking zoned control of the tin bath protective atmosphere, maintained a high-reducing atmosphere throughout. This could lead to bubbling due to excessive reduction of the molten tin, or hydrogen etching of the glass's lower surface, directly increasing the micro-waviness of the original sheet. It also affects the uniformity of the glass substrate, resulting in significant dispersion of surface compressive stress and stress layer depth between samples after chemical strengthening, thus reducing overall mechanical properties. Comparative Example 2, with its excessively fast drawing speed and insufficient flattening time, suffered from significantly deteriorated waviness and roughness. Comparative Example 3, due to its excessively rapid cooling rate from 560°C to 500°C during the annealing stage, experienced uneven cooling near the strain point, failing to fully release the thermal stress generated during structural relaxation. This unbalanced cooling not only caused uneven distribution of residual stress within the substrate and slightly disturbed the already formed high-flatness surface, manifesting as increased micro-waviness, but also resulted in internal stress concentration becoming a potential source of cracks, leading to fracture toughness and bending strength lower than the levels of the examples. The lower fracture toughness and flexural strength of Comparative Example 4 reflect the negative impact of edge defects on the final mechanical properties, further illustrating the importance of the fine grinding process in improving strengthening uniformity and edge strength. In Comparative Example 5, the excessively large gate opening resulted in an excessively thick initial flow stream, increasing the difficulty of controlling the thinning process. This manifested as increased waviness, reduced DOL (Density of Lift), and fracture toughness approaching the critical value, making it inferior to the overall example. In Comparative Example 6, the excessively high introduction temperature and rapid cooling of the polishing zone caused severe thermal shock, reflecting an increase in surface and bulk defects. In Comparative Example 7, the annealing holding temperature was reduced to 520°C, below the glass transition temperature, preventing effective relaxation of internal stress during annealing. This left some residual thermal stress in the glass substrate, affecting the stability of the surface morphology, increasing micro-waviness, and weakening the material's resistance to crack propagation. In Comparative Example 8, the excessively high strengthening temperature led to a decrease in compressive stress, reduced transmittance, and weakened fracture toughness, indicating that an excessively deep stress layer, if accompanied by insufficient stress peaks, actually weakens overall reliability.

[0085] 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.

[0086] 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 method for preparing high-flatness electronic glass, characterized in that, The float forming process includes the following steps: Step S1: Melt the glass batch at 1640-1660℃, clarify, stir and homogenize to obtain molten glass; Step S2: The molten glass is introduced into a tin bath through a flow channel at a temperature of 1200-1220℃. The tin bath is filled with a protective gas mixture of N2 and H2. The molten glass floats on the surface of the molten tin in the tin bath at a temperature range of 1175-1195℃ to 910-930℃, and goes through the flattening, polishing and thinning stages in sequence. The drawing speed, the lateral tension of the edge-pulling machine and the opening height of the gate are adjusted to directly form a high-flatness glass strip with a thickness of 0.7 mm or less. Throughout the entire tin bath forming process, the drawing speed is controlled at 15-25 m / min; During the leveling stage, the glass strip is kept in the leveling zone at 1185±10℃ for 25-40 seconds. During the polishing stage, the temperature is kept stable or slowly cooled at a rate not exceeding 5℃ / min within the polishing zone at 1130±10℃. During the thinning stage, from 1080℃±10℃ to 920℃±10℃, the longitudinal stretching of the glass strip is adjusted using the drawing speed to achieve a target thickness of 0.7mm. During the thinning and forming stage, the edge pulling machine is started and its speed is controlled at 80-250 rpm to apply lateral tension to the edge of the glass strip, suppressing widening and improving edge flatness. Furthermore, before introducing the molten glass into the tin bath, the cross-section of the glass liquid flow is adjusted by a gate, and the gate opening height is controlled at 8-12mm. Step S3: Control the temperature from 790-810℃ to 590-610℃ to cool and shape, then enter the annealing furnace; Step S4: In an annealing furnace, after holding at 550-570℃, cool to 500-510℃ at an average rate of 2.5-4.0℃ / min to complete the annealing process; then rapidly cool to 200℃ or below and allow to cool naturally to room temperature to obtain an electronic glass substrate with micro-wrinkle <0.15μm / 20mm and surface roughness Ra <0.5μm. Step S5: Cut the electronic glass sheet to the target size and grind the edges; The edge grinding process includes: Two rough grinding operations: using a 500-mesh grinding wheel, a rotation speed of 37,000-38,000 r / min, a feed rate of 580-600 mm / min, and a single-sided removal amount of 0.15 mm; Fine grinding in one pass: using a 1200-mesh grinding wheel, a rotation speed of 37,000-38,000 r / min, a feed rate of 550-570 mm / min, and a single-sided removal amount of 0.1 mm; Step S6: Preheat the ground glass at 370-390℃ for 0.5-1 hour; Step S7: Immerse the preheated glass in KNO3 molten salt and perform ion exchange treatment at 400-420℃ for 180-200 minutes to obtain chemically strengthened glass. Step S8: Remove the product and clean the surface to remove any remaining molten salt, and you will get the finished product.

2. The preparation method according to claim 1, characterized in that, In step S1, the glass batch material comprises, by mass percentage: SiO2: 60-78%, Al2O3: 3-13%, Na2O: 5-18%, K2O: 0-1%, MgO: 0-8%, and CaO: 0-5%.

3. The preparation method according to claim 1, characterized in that, The tin bath is filled with a protective gas mixture of N2 and H2, and is divided into a flattening zone, a polishing zone, and a thinning zone along the drawing direction. The volume fraction of H2 in each zone is 8-10%, 5-7%, and 1-3%, respectively, and the flow rates of the protective gas are controlled to be ≤0.15m / s, ≤0.15m / s, and 0.15-0.25m / s, respectively.

4. The preparation method according to claim 1, characterized in that, During the thinning and forming stage, the edge-pulling machine is started and its speed is controlled at 80-250 rpm to apply lateral tension to the edge of the glass strip, suppressing widening and improving edge flatness.

5. The preparation method according to claim 1, characterized in that, In step S3, during the cooling and shaping stage, the protective gas velocity is controlled between 0.15-0.25 m / s, and the protective gas with a concentration of 1-3% H2 starts from the thinning zone and continues to the tin bath outlet.

6. The preparation method according to claim 1, characterized in that, In step S4, the annealing process includes: holding at 560°C for 10-20 minutes; After annealing, rapidly cool to 200°C or below at a rate of 10-25°C / min, and then allow to cool naturally to room temperature.

7. The preparation method according to claim 1, characterized in that, The chemical strengthening process involves preheating the glass substrate at 380℃ for 0.5 hours, followed by immersion in 100wt% KNO3 molten salt at 410℃ for ion exchange for 180 minutes.

8. The preparation method according to claim 1, characterized in that, The glass has a thickness of 0.7 mm and an optical transmittance of greater than 90.5% at a wavelength of 550 nm; after chemical strengthening, its flexural strength is not less than 400 MPa and its fracture toughness is not less than 3.0 MPa•m. 1 / 2 The surface center compressive stress is 670-720 MPa, and the stress layer depth is 8.9-12 μm.

9. An electronic display device, characterized in that, The cover plate contains high-flatness electronic glass prepared by the method described in any one of claims 1-8.

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