Preparation process for high-generation TFT-LCD glass substrate

Abstract

A float process for a high-generation TFT-LCD glass substrate. In a batching procedure, on the basis of an optimally designed raw material formula, the means of blowing and vibrating are used to assist in batching, thereby improving the uniformity and stability of the components. In a melting procedure, sufficient melting is achieved by means of three-dimensional pneumatic-electric composite heating. In a clarification procedure, efficient clarification and homogenization are completed by performing clarification by means of platinum channels and performing forced homogenization by means of turbulent flows. In a forming procedure, the thinning quality is improved by means of the fine regulation and control of heating units and micro edge rollers. In an annealing procedure, fine annealing is achieved by means of independently zoned precise annealing control. In a grinding procedure, a good machining effect is achieved by performing grinding by means of a specially designed grinding disk having a chamfer and a specially designed grinding pads having a chamfer and a specific hardness.

Description

A high-generation TFT-LCD glass substrate fabrication process Technical Field

[0001] This application relates to the field of glass substrate manufacturing, and more particularly to a float glass substrate preparation process for high-generation TFT-LCDs. Background Technology

[0002] The electronic information display industry is an important pillar industry of my country's national economy. China is the world's largest producer of LCD panels, accounting for 70% of the global total production capacity. High-generation TFT-LCD glass substrates are core and key strategic materials for the electronic information display industry and the broader semiconductor industry. my country's annual demand for high-generation TFT-LCD glass substrates exceeds 300 million square meters.

[0003] The quality and performance of high-generation TFT-LCD glass substrates have a crucial impact on the resolution, light transmittance, refresh rate, and viewing angle of display panels. Therefore, extremely high requirements are placed on the quality of both the internal structure and surface of the substrate. Bubbles, inclusions, solder adhesion, drips, and scratches are strictly controlled indicators during the glass substrate manufacturing process. Consequently, the production technology for high-generation TFT-LCD glass substrates is complex, with production control precision comparable to the semiconductor industry, representing the highest level of modern large-scale glass manufacturing globally.

[0004] High-generation TFT-LCD glass substrates are mainly formed using two processes: float glass and overflow glass. The float glass process offers advantages such as large formed plates and low production costs, but it also suffers from significant inter-process interference, numerous control parameters, high control difficulty, and challenges in maintaining stable production conditions. Furthermore, in the float glass process, the molten glass is thinned on the surface of molten tin, resulting in microscopic defects such as tiny solder spots and scratches at the contact surface. This contact surface is also the processing surface for downstream LCD panel manufacturers. Therefore, how to produce high-quality, high-generation TFT-LCD glass substrates with excellent mechanical strength, thermal stability, and thermal shrinkage, as well as fewer surface and internal defects, using the float glass process is a crucial technical problem that urgently needs to be solved.

[0005] Summary of the Invention

[0006] To address the technical problems existing in the current technology, the applicant's researchers, through long-term, large-team, collaborative, and persistent efforts, have innovated multiple processes in the production of display glass substrates. They have explored and utilized the advantages of each process, conducting combined innovative research between processes. Ultimately, a breakthrough was achieved in the float glass process for high-generation TFT-LCD glass substrates, forming a display glass substrate production process that fully utilizes resources, complements complementary advantages, and organically unifies the production line. This process can produce high-generation TFT-LCD glass substrates with superior control and performance indicators, including fewer bubbles, stones, solder adhesion, drips, and scratches. It effectively reduces or eliminates defects in the glass substrates, significantly improving their quality and providing a solution for producing micro-defect, high-quality, high-generation display glass substrates.

[0007] This invention provides a glass substrate preparation process, which includes steps such as batching, melting, clarification and homogenization, forming, annealing, grinding, cleaning, and packaging.

[0008] In the batching process, as a preferred method, selecting SiO2, Al2O3, B2O3, MgO, CaO, SrO, ZrO2, and P2O5 in specific proportions can effectively reduce the boron volatilization rate during glass forming and eliminate problems such as uneven composition caused by boron volatilization. The aluminosilicate glass substrate prepared using this method has characteristics such as high strain point, high Young's modulus, high hardness, suitable coefficient of thermal expansion, low thermal shrinkage rate, and low defects, which meet the special requirements of high-generation TFT-LCD glass substrates.

[0009] For the raw material batching method, the preferred method is to use an electronic scale feeding system that combines air nozzle blowing and air hammer vibration. After the electronic scale hopper has weighed all the raw materials, the materials are fed in. At the same time as the pneumatic feeding valve is opened, the air nozzle blows through the inner wall of the electronic scale hopper, and the air hammer strikes and vibrates the electronic scale hopper, so that the raw materials stuck in the inner wall of the electronic scale hopper are discharged synchronously, ensuring that the composition of each batch of materials is constant during the batching process, and ensuring the quality stability of the glass substrate.

[0010] In the melting process, a heating method combining electric flux and oxy-fuel combustion is preferred. Electric heating can be achieved using molybdenum or tin oxide electrodes, which can be installed on the furnace wall and / or bottom. The burner can be installed on the furnace roof and / or breast wall. Preferably, the furnace is equipped with a bubbling device and a furnace sill to perform primary debubbling and clarification of the molten glass, removing bubbles with a diameter greater than 0.2 mm. This setup promotes synchronous heating of the raw materials within the furnace, ensuring thorough and efficient melting of the glass. The primary debubbling and clarification effectively removes bubbles with a diameter greater than 0.2 mm in the furnace section, resulting in a final molten glass volume of ≤0.1 bubbles with a diameter greater than 0.2 mm in the molten glass. Subsequent precision clarification through a platinum channel further removes bubbles with a diameter less than 0.2 mm, ultimately achieving thorough debubbling and clarification of the glass substrate and obtaining high-quality molten glass.

[0011] In the clarification and homogenization process, a platinum channel clarification system, consisting of two or more high-temperature platinum channels and one low-temperature platinum channel, is preferred, with optimized stirring and turbulence methods for forced homogenization. Compared to a single platinum channel, the reduced channel diameter decreases the temperature difference of the molten glass on the same cross-section. The improved turbulence process enhances homogenization efficiency and promotes full uniformity of temperature and composition in the molten glass. The lowered molten glass level reduces the distance bubbles need to rise, and combined with optimized raw material formulation, this improves the efficiency of small bubble removal. Through this special design of the clarification and homogenization process, defects such as bubbles and streaks on the glass plate are avoided, and bubbles in the molten glass are efficiently removed, with the number of bubbles with a diameter ≥0.05mm in the molten glass not exceeding 0.15 per kg.

[0012] In the forming process, a gridded heating unit is preferably set at the top of the tin bath, and multiple micro-edge pulling machines are set in the forming and thinning zone. The heating units and edge pulling machines are controlled in tandem. By adjusting the output power of each heating unit in the lateral direction, the lateral temperature difference of the tin bath is adjusted, thereby achieving different viscosities at different points in the lateral direction of the glass strip. Under the optimized combination and precise adjustment of the thinning force by multiple micro-edge pulling machines, and with the appropriate traction force of the main drive, precise thinning of the high-generation LCD glass panel under multiple forces is achieved. The thickness difference of the prepared high-generation TFT-LCD glass substrate is ≤0.015mm.

[0013] In the annealing process, a three-dimensional grid-based annealing furnace structure with precise temperature control is preferred. By utilizing non-turbulent cooling ducts, low-thermal-conductivity ceramic rollers for transport, baffle partitions for zoned isolation, and differentiated insulation design of the annealing furnace, airflow turbulence is avoided, temperature field fluctuations are reduced, and the lateral temperature difference of the glass substrate is decreased. This meets the requirements of constant lateral temperature for large-size ultra-thin glass substrates and precise matching of the temperature of each zone of the annealing furnace with the annealing curve of the substrate, achieving a perfect match between the temperature field and the annealing curve, and fully eliminating stress on the glass substrate.

[0014] In the grinding process, three types of grinding pads with hardness ratios of 90HD-100HD:60HD-70HD:35HD-40HD are used to grind and polish the glass substrate in sequence. The ratio of the grinding surface to the width of the grinding groove at non-edge areas is optimized. Chamfers are set around the grinding pad and at the outermost edge of the grinding pad away from the grinding pad. The chamfer angle on the grinding pad is greater than or equal to the chamfer angle on the grinding pad. This improves the grinding quality, reduces scratches during grinding, and enhances the grinding effect.

[0015] The aforementioned float glass substrate manufacturing process for high-generation TFT-LCDs features precise control over the fabrication process, achieving organic synergy among various production stages. This process has enabled the pioneering industrial-scale, stable mass production of micro-defect, high-quality, high-generation float electronic glass substrates.

[0016] The beneficial effects of this invention are as follows: This invention fully explores and utilizes the advantages of multiple processes in the float glass production process of high-generation TFT-LCD glass substrates, and conducts combined innovative research between processes to form a display glass substrate production process that is organically unified, has prominent advantages, and is synergistically complementary. Attached Figure Description

[0017] Figure 1 is a schematic diagram of the overall process of glass substrate fabrication.

[0018] Figure 2 is a schematic diagram of the feeding system for the batching process;

[0019] Figure 3 is a frontal cross-sectional view of the melting furnace in the glass raw material melting process;

[0020] Figure 4 is a top view of the clarification and homogenization system in the clarification and homogenization process;

[0021] Figure 5 is a schematic cross-sectional view of the tin bath in the molding process;

[0022] Figure 6 is a top view of the tin bath forming and thinning zone in the forming process;

[0023] Figure 7 is a top view of the annealing furnace for the annealing process;

[0024] Figure 8 is a front view cross-sectional view of the annealing furnace in the annealing process;

[0025] Figure 9 is a schematic diagram of the grinding process;

[0026] Figure 10 shows a schematic diagram of the glass substrate surface before and after the grinding process;

[0027] Figure 11 is a schematic diagram of the grinding pad structure in the grinding process;

[0028] Figure 12 is a schematic diagram of the grinding surface in the grinding process;

[0029] Figure 13 is a schematic diagram of the grinding device structure in the grinding process;

[0030] Figure 14 is an enlarged view of point A in Figure 11;

[0031] Figure 15 is a schematic diagram of the chamfering of the grinding disc in the grinding process;

[0032] Figure 16 is a schematic diagram of the chamfering of the grinding pad in the grinding process. Detailed Implementation

[0033] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this application. It is understood that the accompanying drawings are provided for reference and illustration only, and are not intended to limit this application.

[0034] Specifically, this application provides a float glass substrate fabrication process for high-generation TFT-LCDs, as shown in Figure 1. This glass substrate fabrication process mainly includes the following steps:

[0035] Ingredient preparation process: Select appropriate raw materials, weigh and mix each raw material to form glass batch material;

[0036] Melting process: The uniformly mixed glass batch is heated and melted to form molten glass;

[0037] Clarification and homogenization process: The molten glass is passed through a clarification channel to remove air bubbles and homogenize it;

[0038] Forming process: The molten glass is spread and thinned on the surface of the molten tin to form a glass substrate;

[0039] Annealing process: Annealing the glass substrate to eliminate internal stress in the glass substrate;

[0040] Grinding process: Cut the glass substrate to the required size and then grind it.

[0041] Cleaning process: The glass substrate is cleaned.

[0042] Packaging process: Pack the cleaned and qualified glass substrates.

[0043] The technology for each process will be explained in detail below.

[0044] Ingredient preparation process:

[0045] High-generation TFT-LCD glass substrates require the following characteristics: low density, high strain point, suitable coefficient of thermal expansion, high Young's modulus, resistance to chemical corrosion, low thermal shrinkage, and low micro-defects. Therefore, careful design of the raw material composition is necessary.

[0046] Preferably, the materials used have the following weight fractions: 60-72% SiO2, 13-18% Al2O3, 8.5-10% B2O3, 1-4.5% MgO, 3-8% CaO, 1-5% SrO, 0.5-2% ZrO2, 1-5% P2O5, and 0.1-0.5% SnO2; wherein SiO2+Al2O3 accounts for 76-85%; (MgO+CaO+SrO) / Al2O3 accounts for 0.4-0.7%; the total amount of alkaline earth metal oxides accounts for 5-11.5%; B2O3 / (B2O3+ZrO2+P2O5) accounts for 0.6-0.9%; and (ZrO2+P2O5) / (MgO+CaO+SrO) accounts for 0.15-0.8%.

[0047] The aforementioned glass feedstock can effectively reduce boron volatilization during glass forming and control problems such as uneven glass composition caused by boron volatilization during glass substrate preparation. Furthermore, this feedstock can promote bubble removal and clarification of the glass melt. Aluminosilicate glass substrates prepared using this feedstock exhibit characteristics such as high strain point, high Young's modulus, high hardness, suitable coefficient of thermal expansion, low thermal shrinkage, and low micro-defects. Specifically, the β-OH value is less than 0.5%, the boron volatilization rate is less than 11%, and the coefficient of thermal expansion in the 50-350℃ range is less than 39.5 × 10⁻⁶. -7 / ℃, Young's modulus higher than 78GPa, strain point higher than 690℃, melting temperature lower than 1690℃, and thermal shrinkage rate lower than 11.5ppm.

[0048] At the same time, the quality requirements for high-generation TFT-LCD glass substrates are much higher than those for other types of glass. This requires that the composition of the high-generation TFT-LCD glass substrate formulation maintain a very high degree of uniformity and that there be no significant differences in composition. Therefore, there are strict requirements for the purity, weighing accuracy, and mixing uniformity of various raw materials in the formulation.

[0049] As a preferred option, an electronic weighing system for controlling the stability of glass batch composition can be used.

[0050] As shown in Figure 2, the system includes an electronic weighing hopper 101, a pneumatic feeding valve 102 at the bottom of the electronic weighing hopper, and an air hammer 103 on the outer wall of the electronic weighing hopper 101. The pneumatic feeding valve 102 is controlled to open and close by an opening solenoid valve 104 and a closing solenoid valve 105. The opening solenoid valve 104 is also connected to the air hammer 103. The opening solenoid valve 104 is connected to a first air pipe 106 and a second air pipe 107. The first air pipe 106 is connected to the pneumatic feeding valve 102, and the second air pipe 107 is connected to the air hammer 103. The closing solenoid valve 105 is provided with a third air pipe 108, which is connected to the pneumatic feeding valve 102. An air nozzle 109 is provided on the upper part of the inner wall of the electronic weighing hopper 101. The air nozzle 109 is connected to a fourth air pipe 110 extending out of the electronic weighing hopper 101. The fourth air pipe 110 is connected to the first air pipe 106. Air nozzles 109 can be installed in areas prone to material accumulation, depending on actual needs. Multiple air nozzles 109 can be installed in areas with multiple accumulation points. This system ensures a stable proportion of each component in the glass raw material batching process. Specifically, when the electronic weighing hopper 101 weighs all the glass raw materials and begins feeding, the pneumatic feeding valve 102 opens while the air nozzles 109 blow air into the inner wall of the electronic weighing hopper 101. The air hammer 103 then strikes the electronic weighing hopper 101, causing the raw materials retained on the inner wall of the electronic weighing hopper 101 to be discharged simultaneously. This ensures the stability of the components in each batch during the liquid crystal glass batching process, guaranteeing the quality of the glass substrate.

[0051] By adopting the above-mentioned batching process, the quality and performance of the glass substrate are improved from the source, and the accuracy and stability of the batching are guaranteed.

[0052] Melting process:

[0053] After the above batching process is completed, the glass raw materials are melted through a melting process.

[0054] As a preferred option, the following melting process can be used.

[0055] As shown in Figure 3, electrodes 202 are symmetrically or staggeredly arranged on the inner walls and / or bottom of the melting furnace 201 on both sides. Oxygen lances 203 are installed on the top and / or breast wall of the melting furnace 201. When installed on the top, the lances are vertically distributed with the flame nozzles pointing vertically downwards, and the flames can contact the surface of the molten glass inside the melting furnace 201. When installed on the breast wall, the lances are horizontally arranged. Complete melting of the glass raw materials is achieved through direct heating of the electrodes and radiant heating of the oxygen combustion. Preferably, the melting furnace also includes a bubbling device 204 and a furnace sill 205 to perform primary debubbling and clarification of the molten glass, promoting the removal of larger bubbles. Through careful combination of raw materials, the use of a comprehensive three-dimensional electric-oxygen combustion composite heating method, and the effects of bubbling and the furnace sill, the number of bubbles with a diameter greater than 0.2 mm in the molten glass is significantly reduced, with the number of bubbles with a diameter greater than 0.2 mm ≤ 0.1 per kg.

[0056] Using the above process, the glass raw material is heated from the bottom to the top at multiple angles, ensuring that the raw material is heated evenly and fully in all positions in the melting furnace. At the same time, the special selection of glass raw material promotes the precise clarification and coordination of the glass melt in the primary clarification and clarification homogenization stages of the melting furnace, improving the defoaming efficiency of the production line system and enhancing the quality of the glass substrate.

[0057] Clarification and homogenization process:

[0058] The melted glass raw material becomes molten glass, which needs to undergo a clarification and homogenization process before being formed.

[0059] As a preferred method, the following process can be used for clarification and homogenization.

[0060] As shown in Figure 4, the platinum channel includes multiple high-temperature platinum channels and one low-temperature platinum channel (combined stirring section, second cooling section, and feeding section). A first high-temperature platinum channel (310) is formed by sequentially connecting a first inlet section (311), a first clarification section (312), a first cooling section A (313), and a first stirring section (314). A second high-temperature platinum channel (320) is formed by sequentially connecting a second inlet section (321), a second clarification section (322), a first cooling section B (323), and a second stirring section (324). The ports of the first inlet section (311) and the second inlet section (321) are connected to the furnace (201), and the ports of the first stirring section (314) and the second stirring section (324) are both connected to the combined stirring section (340). The stirring section (340) after the confluence is also connected in sequence to a low-temperature platinum channel consisting of a second cooling section (350) and a feeding section (360). The feeding section (360) is connected to the tin bath. The first cooling section A (313) and the first cooling section B (323) are used to cool the flowing glass liquid and control the cooling rate to achieve the process temperature required by the stirring section. The second cooling section (350) is also used to cool the flowing glass liquid and heat it when needed to meet the glass forming requirements. The second cooling section (350) has grids with different installation angles arranged from right to left inside. The installation angles of adjacent grids are different, so that the holes on the grids are misaligned to ensure that the glass liquid forms turbulence after passing through the grids.

[0061] The aforementioned multi-platinum channel clarification and homogenization process reduces the thermal load on individual platinum channels, avoiding the risk of collapse caused by prolonged high-temperature operation of large-diameter platinum channels. The reduced diameter of the platinum channels decreases the temperature difference between the center of the molten glass and the contact area with the platinum body on the same cross-section. Improved stirring and grid turbulence processes enhance homogenization efficiency and improve the homogeneity of the molten glass. This homogenization process achieves sufficient uniformity in the temperature and composition of the molten glass, improving the quality of the glass substrate. The lowered molten glass level improves the efficiency of small bubble removal, ensuring that the number of bubbles with a diameter ≥0.05mm in the molten glass does not exceed 0.15 per kg. The coordinated selection of raw materials, primary clarification in the melting furnace, and fine clarification and homogenization effectively remove bubbles from the molten glass with high quality.

[0062] Molding process:

[0063] After completing the above clarification and homogenization process, the molten glass is thinned and formed by float glass.

[0064] As a preferred option, the following process can be used for float glass thinning.

[0065] As shown in Figures 5 and 6, molten glass flows into the forming tin bath. The tin bath is divided into a pool 401, a breast wall 402, and a top cover 403 from bottom to top; along the direction of glass flow, the tin bath is divided into a forming and thinning zone 404, a shaping and cooling zone, and a temperature homogenization zone.

[0066] With the glass melt flow direction as the longitudinal direction and the direction perpendicular to the glass melt flow direction as the transverse direction, the top of the tin bath is divided into multiple grid-like heating units 405, and the heating temperature of each heating unit can be independently controlled. Each heating unit includes one or more heating elements. TFT-LCD glass substrates have the characteristics of high forming temperature and easy volatility of components, so high-density three-phase silicon carbide rods are preferred as heating elements.

[0067] In the forming and thinning zone, it is preferable to increase the density of the gridded heating units, thereby controlling the temperature of each area more precisely and improving the accuracy and flexibility of temperature control.

[0068] In conjunction with the tin bath heating system, a precision thinning system is preferably used for coordinated control in the forming and thinning zone. TFT-LCD glass has a short melt flow period and a narrow forming temperature range; therefore, reducing the spacing between the edge-pulling machines and increasing the number of edge-pulling machines narrows the effective range of the thinning system within the limited temperature range and allows for the distribution of glass strip thinning force to each pair of edge-pulling machines, achieving ultra-thin precision forming of the glass substrate. The precision thinning system uses a miniature edge-pulling machine 406, with a machine body less than 300mm, preferably 200-250mm; the spacing between two adjacent edge-pulling machines is less than 1000mm, preferably 500-900mm. A total of 15-25 pairs of edge-pulling machines are set in the forming and thinning zone, preferably 18-22 pairs.

[0069] Preferably, at least some of the transverse edge heating units 415 are configured to correspond to the edge pulling machine, with one edge heating unit corresponding to 1 to 4 edge pulling machines, preferably 2 to 3.

[0070] The control system uniformly adjusts each heating unit and the edge-pulling machine. By adjusting the output power of each heating unit in the lateral direction, the lateral temperature difference of the tin bath is adjusted, thereby regulating the viscosity difference of the glass strip in different lateral directions. The thinning force of the edge-pulling machine acts on the edge of the glass strip and is transmitted towards the center. The effect of controlling the lateral temperature difference of the tin bath on the viscosity of the molten glass is coupled with the control of the thinning force of the edge-pulling machine, thus improving the lateral thinning effect of the glass strip and achieving a thickness difference of ≤0.015mm for the entire high-generation TFT-LCD glass substrate.

[0071] Annealing process:

[0072] After completing the float glass forming process, the formed glass substrate needs to be annealed.

[0073] As a preferred option, the following glass annealing process can be used.

[0074] As shown in Figures 7 and 8, a grid-based control method is adopted in the annealing process, dividing the annealing area into multiple zones 501, each of which can be independently temperature-controlled. Each zone includes a temperature detection device 502, a heating device 503, and a cooling device 504. The cooling device uses cooling ducts with the air inlet located on the outside of the kiln body and a centrifugal fan 505 installed at the air outlet. By allowing air to flow through the cooling ducts, the temperature of the cooling ducts is reduced, thereby lowering the temperature of each zone. This method avoids air disturbance.

[0075] The applicant's research revealed that one reason for the poor mechanical properties of liquid crystal glass substrates is the presence of significant internal stress in the transverse direction of the same glass substrate. This is caused by inconsistent transverse annealing temperatures. Since the temperature at the transverse edges of the glass substrate is lower than that at the center, without differentiated temperature control, inconsistent transverse annealing temperatures can easily lead to significant internal stress. Therefore, it is preferable that at least in some annealing areas, the temperature of partition 506 corresponding to the glass edge is higher than the temperature of partition 507 corresponding to the glass center.

[0076] Ceramic rollers are preferably used as the transfer rollers 508. Ceramic rollers have excellent heat insulation properties, which can minimize heat conduction between the glass substrate and the ceramic roller, and avoid unexpected cooling of the glass substrate. A baffle curtain 509 is installed in the annealing furnace. The baffle curtain can be raised and lowered in a controlled manner. Unlike other float glass, ultra-thin glass is transported at a relatively high speed in the annealing furnace, and airflow is easily formed during the transport process. The use of the baffle curtain prevents airflow, which is more conducive to the independence of each zone and precise temperature control.

[0077] Further optimization involves different temperatures in the insulation layer of the annealing kiln from the inside out, with a higher temperature on the inside and a lower temperature on the outside. This is achieved by using insulation materials with different thermal conductivity in the heat transfer direction of the insulation layer. The inner high-temperature layer 510 uses an insulation material with even lower thermal conductivity, reducing the overall thermal conductivity. Furthermore, thermal breaks are used to connect the thermal bridges such as the connecting plates and plugs between the inner and outer walls of the annealing kiln, further reducing heat conduction. The temperature difference between the outer wall and the environment is reduced to less than 2 / 3 of the original temperature difference. These measures avoid temperature fluctuations caused by frequent temperature adjustments and improve the temperature stability within the annealing kiln.

[0078] Temperature detection devices, heating devices, cooling devices, and curtain lifting devices in each zone are all connected to the control device, which enables automated and intelligent control of these devices.

[0079] The annealing process of this invention can better meet the precise matching requirements of the temperature field and annealing curve of high-generation TFT-LCD glass substrate, reduce the lateral temperature difference of the glass substrate, avoid temperature field fluctuations and disturbances, effectively eliminate the internal stress of the glass substrate, and realize differentiated, refined, automated and intelligent control of annealing.

[0080] Grinding process:

[0081] After annealing, the glass substrate needs to be ground. Grinding refers to removing uneven parts and micro-defects such as tin adhesion and scratches from the glass surface. By adding abrasives, additives, and other chemical components, the glass surface can be made smooth and flat, achieving the grinding effect.

[0082] Polishing is a further process performed after initial grinding to smooth the glass surface and improve its flatness.

[0083] As shown in Figure 9, the grinding process in this embodiment is mainly carried out in the following manner:

[0084] Clean and remove dust from the glass substrate;

[0085] The glass substrate is coarsely ground using a coarse grinding pad and grinding fluid.

[0086] The glass substrate, after coarse grinding, is finely ground using a fine grinding pad and grinding fluid.

[0087] Polishing is performed on a finely ground glass substrate using a polishing pad and polishing fluid.

[0088] The polished glass substrate is then cleaned.

[0089] When the glass is not ground, the glass surface has the shape shown in ① of Figure 10. The glass surface has many irregular shapes and structures, which will lead to reduced light transmittance and image distortion.

[0090] Before grinding, the glass needs to be cleaned and dust removed.

[0091] During grinding, the coarse grinding pad on the grinding workpiece and the grinding fluid grind the glass substrate together, grinding the glass substrate from the shape in ① of Figure 10 to the shape in ② of Figure 10, eliminating the uneven areas of the glass substrate.

[0092] After coarse grinding, the fine grinding pad on the grinding workpiece, together with the grinding fluid, grinds the glass substrate to remove extremely fine scratches on the glass substrate, and the glass substrate is ground from the shape in ② of Figure 10 to the shape in ③ of Figure 10.

[0093] After fine grinding, the polishing pad on the grinding part, together with the grinding fluid, performs a deeper grinding on the glass substrate. After the polishing pad grinds the glass substrate, it can polish and eliminate defects on the glass substrate that are not visible to the naked eye. The glass substrate is ground from the shape in ③ of Figure 10 to the shape in ④ of Figure 10, which meets the high quality requirements of TFT-LCD glass substrate.

[0094] The grinding device used in the grinding process is shown in Figures 11-14. The grinding device includes a grinding disc 620 and a grinding pad 610. The grinding pad 610 is mounted on the grinding disc 620. The side of the grinding pad 610 away from the grinding disc 620 is used to grind the glass. Each grinding pad is composed of a grinding substrate 614 and a grinding particle layer 613. The hardness of the grinding particle layer 613 on different grinding pads 610 is different.

[0095] For the hardness range, the preferred ratios for coarse grinding pads, fine grinding pads, and polishing pads are 90HD-100HD: 60HD-70HD: 35HD-40HD, with further preferred ratios of 90HD-95HD: 60HD-70HD.

[0096] The preferred hardness levels are 35HD-40HD, with further optimization towards 90HD-95HD, 65HD-70HD, and 35HD-40HD. Here, HD represents the Shore hardness index. As shown in Figures 11 and 12, to improve the polishing effect, polishing grooves 611 are formed on the polishing pad 610. Multiple polishing grooves 611 are interconnected to facilitate the flow of polishing fluid. Multiple polishing surfaces 612 are formed on the polishing pad 610. Preferably, except for the polishing surfaces at the edges, the remaining polishing surfaces are square. The polishing surfaces 612 polish the surface of the glass substrate.

[0097] The ratio of the width of the grinding surface to the width of the grinding groove at non-edge locations is preferably 1:1-3:1, and more preferably 1.7:1-2.3:1.

[0098] In this embodiment, the mating relationship between the polishing pad 610 and the polishing disk 620 can also affect the polishing effect of the glass substrate. The main effect is that the working surface of the edge of the polishing pad 610 is not completely parallel to the processing surface of the glass substrate during the polishing process.

[0099] In existing technologies, the edge of the polishing pad is basically perpendicular to the processing surface. During the polishing process, the edge of the polishing pad will rub against the glass substrate to a certain extent, which will cause scratches on the glass.

[0100] Through multiple simulations and studies, the applicant discovered that a specially designed double-bevel coupling combination can significantly reduce the likelihood of the polishing pad scratching the glass substrate during polishing. The specific method is as follows:

[0101] A rounded chamfer is applied around the perimeter of the grinding disc 620. In this embodiment, the rounded chamfer is 621. The method for preparing the rounded chamfer is as follows: As shown in Figure 15, with the height of the side surface of the grinding disc as H, extend vertically upwards along the side surface of the grinding disc by a distance h to point a. Using the side surface of the grinding disc as one side and point a as the vertex, draw the other side with the rounded chamfer angle. The intersection of this other side and the bottom surface of the grinding disc is point b. Connect points ab and draw an isosceles triangle using this as one side. The side length of this isosceles triangle is the radius R of the rounded chamfer. Here, h / H = 1:2-1:6, preferably 1:3-1:5, and even more preferably 1:3.5-1:5.

[0102] Preferably, the grinding pad is tightly attached to the grinding disc 620 with rounded chamfers around its perimeter.

[0103] Meanwhile, as shown in Figures 13 and 14, a chamfer is also formed at the outermost edge of the polishing pad, away from the polishing disk 620, i.e., facing the glass substrate. Preferably, this chamfer is a straight chamfer 615. The straight chamfer 615 can further prevent the glass substrate from scratching, based on the rounded chamfer 621. As shown in Figure 16, the position of this straight chamfer is at position c on the side of the polishing pad, where the distance from c to the bottom surface of the polishing pad is h', the thickness of the side of the polishing pad is H', and h' / H' = 4:5-1:2, preferably 4:5-3:5. Regarding the relationship between the chamfer angle of the grinding disc and the chamfer angle of the grinding pad, it is preferable that the chamfer angle of the grinding disc is greater than or equal to the chamfer angle of the grinding pad. Further preferably, the chamfer angle of the grinding disc is greater than or equal to the chamfer angle of the grinding pad and the chamfer angle of the grinding disc is ≥50°. Even further preferably, the chamfer angle of the grinding disc is greater than or equal to the chamfer angle of the grinding pad and the chamfer angle of the grinding disc is ≥60°. Still more preferably, the chamfer angle of the grinding disc is greater than or equal to the chamfer angle of the grinding pad, and 75° ≥ chamfer angle of the grinding disc ≥60°.

[0104] Glass polishing slurry is a crucial material in glass manufacturing and processing. It primarily consists of abrasives, solvents, and other additives, which are suspended in the liquid as particles. The main function of glass polishing slurry is to remove impurities from the glass surface through these abrasive particles, achieving a smooth glass surface. The glass polishing slurry used in this invention preferably comprises cerium oxide, lanthanum oxide, fluorides, praseodymium oxide, silicon oxide, aluminum oxide, calcium oxide, and iron oxide, with a concentration range of 1-10%.

[0105] In this embodiment of the application, in order to improve the grinding effect, the grinding pressure, grinding temperature and grinding speed can be controlled.

[0106] The grinding pressure can be controlled between 0.01-0.3 MPa, preferably 0.01-0.28 MPa, further preferably 0.1-0.25 MPa, even further preferably 0.1-0.2 MPa, and most preferably 0.15-0.2 MPa.

[0107] The grinding temperature can be controlled within the range of 20-60℃, preferably between 20-50℃, further preferably between 30-50℃, and even more preferably between 30-40℃.

[0108] The grinding speed can be controlled between 5000 rpm and 7000 rpm, preferably between 5200 rpm and 6500 rpm, further preferably between 5500 rpm and 6300 rpm, and even more preferably between 5800 rpm and 6000 rpm.

[0109] The grinding time can be controlled between 30 and 300 seconds, preferably between 60 and 240 seconds, and even more preferably between 80 and 150 seconds.

[0110] Cleaning process:

[0111] After completing the above steps, the glass substrate needs to be cleaned. The cleaning process mainly removes residual polishing fluid and other impurities from the surface of the glass substrate, making it easier to test the roughness of the glass substrate using a Surtronic S-100 series surface roughness tester later.

[0112] The glass substrate is subjected to deep composite cleaning using methods such as disc brushes, roller brushes, ultrasound, and two-fluid cleaning to achieve the purpose of cleaning the glass surface.

[0113] Packaging process:

[0114] After cleaning and inspection, the glass substrates that pass the inspection are packaged to prevent the glass from being damaged by impacts, which could cause cracks and chips and affect its sale in the market.

[0115] Example:

[0116] The embodiments section of this application focuses on describing the grinding process of the present invention.

[0117] In this embodiment, the polishing slurry is prepared by mixing polishing powder with cerium oxide as the main component (cerium oxide content 58%) and 0.2 megohms (MΩ) of pure water, with a concentration range of 4%. All polishing processes described below are based on the composition of this glass polishing slurry. For the polishing disc, h / H = 1:4, h = 4 mm; for the polishing pad, h' / H' = 3 / 4.

[0118] In the embodiments of this application, the hardness range of the coarse grinding pad is between 90HD and 100HD, the hardness range of the fine grinding pad is between 60HD and 70HD, and the hardness range of the polishing pad is between 35HD and 45HD. By combining grinding pads 610 with different hardnesses, different effects of glass surface flatness can be produced.

[0119] In this embodiment, the grinding pressure is 0.15 MPa, the grinding temperature is 35°C, the grinding speed is 6000 rpm, and the grinding time is 140 seconds.

[0120] Roughness was measured using a Surtronic S-100 series surface roughness tester.

[0121] The grinding effects of combining various grinding pads with different hardnesses are shown in Table 1 below:

[0122] Table 1:

[0123] Flatness refers to the degree of deviation between the geometry of the glass substrate surface and the ideal plane. It is usually expressed as the distance between two points or the radius of curvature. The flatness of high-generation TFT-LCD glass substrates has a great impact on the strength, optical performance, and physical properties of the glass substrate. Therefore, it is necessary to strictly control and inspect the flatness during the manufacturing process. The glass scratch defect rate mainly refers to the probability that the scratches on the surface of the semi-finished glass substrate during forming and processing are not completely eliminated after grinding. The lower the glass scratch defect rate, the fewer scratches remain on the glass surface after grinding.

[0124] As can be seen from Table 1 above, when selecting 90HD-100HD, 60HD-70HD, and 35HD-40HD for coarse grinding, fine grinding, and polishing, the resulting grinding exhibits good performance in terms of flatness compliance rate and scratch defect rate. Furthermore, selecting 90HD-95HD, 65HD-70HD, and 35HD-40HD results in even better performance in both flatness compliance rate and scratch defect rate.

[0125] In this embodiment, the width ratio of the polishing surface 612 to the polishing groove 611 at non-edge locations is set to a ratio of 1:1 to 3:1. Polishing pads conforming to this ratio can effectively polish the glass substrate. The applicant has discovered through extensive experiments and research that:

[0126] Compared to the optimal solution, when the ratio of the width of the grinding surface 612 at the non-edge to the width of the grinding tank 611 is 1:1-1.7:1, the flow guiding effect is good and the flow rate of the grinding fluid is fast, but the grinding contact area is small and the grinding efficiency is relatively low.

[0127] When the ratio of the width of the grinding surface 612 to the width of the grinding groove 611 at non-edge locations is 1.7:1-2.3:1, the guiding effect of the grinding fluid and the grinding efficiency are both taken into account, ensuring the grinding efficiency while minimizing the generation of secondary defects.

[0128] Compared to the optimal solution, when the ratio of the width of the grinding surface 612 to the width of the grinding groove 611 at the non-edge is 2.3:1-3:1, the grinding efficiency is high, but the flow guiding effect is poor and the fluidity of the grinding liquid is poor, which makes it easier to generate secondary defects.

[0129] Therefore, based on the experimental results, when the ratio of the width of the grinding surface 612 to the width of the grinding groove 611 at the non-edge is 1.7:1-2.3:1, as shown in Figure 12 ②, the guiding effect of the grinding fluid and the grinding efficiency are both taken into account, which can better meet the needs of high-quality glass substrate manufacturing.

[0130] Table 2 shows the changes in the incidence of scratches on the glass due to different angles for choosing between rounded and straight chamfers.

[0131] Table 2:

[0132] According to the data in the table above, when the chamfer angle of the grinding disc is greater than or equal to the chamfer angle of the grinding pad, and the chamfer angle of the grinding disc is ≥60°, the rate of wear marks is low, and a better grinding effect can be achieved.

[0133] The above embodiments are only used to illustrate the technical methods of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical methods of the present invention without departing from the spirit and scope of the technical methods of the present invention.

Claims

1. A process for the production of high generation TFT-LCD glass substrates by the float process, characterized in that, The process is combined by multiple process systems, including: Batching process: select alkali-free aluminum boro-silicate glass raw material formula, weigh and mix various raw materials, and feed into the melting furnace. Spray or vibration is adopted during feeding to prevent material stagnation or accumulation; Melting process: electrode assisted melting and full oxygen combustion composite heating method is adopted to melt the glass batch into molten glass liquid; Clarification and homogenization process: a plurality of high-temperature platinum channels and one low-temperature platinum channel are combined to clarify and homogenize the molten glass liquid; Forming process: the molten glass liquid floats on the surface of the tin liquid to form a continuous glass ribbon. The heating units in the tin bath can be independently controlled, and the thinning force of the micro edge stretcher is adjusted to make the glass ribbon thin into a glass substrate; Annealing process: the annealing furnace is divided into multiple zones, each zone is independently temperature-controlled, and the glass substrate is annealed; Grinding process: coarse grinding, fine grinding and polishing three kinds of grinding pads with a hardness ratio of 90HD-100HD:60HD-70HD:35HD-40HD are used in turn to grind and polish the glass substrate.

2. The high generation TFT-LCD glass substrate float process of claim 1, wherein, In the batching process, the raw material formula is 60-72% SiO2, 13-18% Al2O3, 8.5-10% B2O3, 1-4.5% MgO, 3-8% CaO, 1-5% SrO, 0.5-2% ZrO2, 1-5% P2O5, and 0.1-0.5% SnO2. Among them, SiO2+Al2O3 is 76-85%, (MgO+CaO+SrO) / Al2O3 is 0.4-0.7%, the total amount of alkaline earth metal oxides is 5-11.5%, B2O3 / (B2O3+ZrO2+P2O5) is 0.6-0.9%, and (ZrO2+P2O5) / (MgO+CaO+SrO) is 0.15-0.8%. The boron evaporation rate of the raw material composition is less than 11%. According to the above raw material formula, the raw materials are weighed, and the material accumulated in the inner wall of the scale is discharged synchronously by spraying through the air nozzle arranged on the inner wall of the scale and vibration through the air hammer arranged on the outer wall of the scale. Multiple air nozzles can be arranged according to the material accumulation.

3. The process of claim 1, wherein the process is a high generation TFT-LCD glass substrate float process. In the melting process, the raw materials are heated and melted by electrodes arranged on the inner wall and / or pool bottom of the melting furnace, and full oxygen combustion guns arranged on the roof and / or breast wall of the melting furnace. The melting furnace is provided with bubbling devices and kiln ridges.

4. The process of claim 1, wherein the process is a high generation TFT-LCD glass substrate float process. The low-temperature platinum channel includes a stirring device and multiple gratings. The installation angles of adjacent gratings are different, so that the holes on adjacent gratings are misaligned. The stirring device and the multiple gratings realize sufficient homogenization of the molten glass liquid.

5. The float glass substrate fabrication process for high-generation TFT-LCDs according to claim 1, characterized in that, In the forming process, the transverse temperature difference of the tin bath is adjusted by controlling the output power of each heating unit in the transverse direction, and the thinning force of the micro edge stretcher corresponding to the same transverse position of the above heating unit is adjusted. The glass ribbon is thinned and formed.

6. The process of claim 1, wherein the process is a high generation TFT-LCD glass substrate float process. In the annealing process, the glass substrate is transported by ceramic rollers as transmission rollers. In at least part of the annealing area in the annealing furnace, the temperature of the partition corresponding to the edge of the glass substrate is higher than that of the partition corresponding to the center of the glass substrate. The thermal conductivity of the high-temperature layer heat preservation material inside at least part of the kiln wall is lower than that of the low-temperature layer heat preservation material outside.

7. The process of claim 1, wherein the process is a high generation TFT-LCD glass substrate float process. In the polishing process, the hardness of the coarse polishing pad, the fine polishing pad and the polishing pad is selected as 90HD-95HD: 60HD-70HD: 35HD-40HD.

8. The process of claim 7, wherein the process further comprises the step of: In the polishing process, the hardness of the coarse polishing pad, the fine polishing pad and the polishing pad is selected as 90HD-95HD: 65HD-70HD: 35HD-40HD.

9. The process of claim 7, wherein the process further comprises the step of: The polishing pad comprises a plurality of polishing surfaces divided by polishing grooves, and the polishing surfaces other than the edge are square, and the ratio of the width of the polishing surface to the width of the polishing groove is 1:1-3:

1. ​ 10. The process of claim 9, wherein the process is a high-generation TFT-LCD glass substrate float process. The polishing pad is assembled on the polishing disc, and the side of the polishing disc facing the polishing pad is chamfered in the peripheral direction, the polishing pad is tightly attached to the polishing disc in the peripheral direction, and the side of the polishing pad away from the polishing disc is chamfered in the peripheral direction.

11. The process of claim 10, wherein the process is a high generation TFT-LCD glass substrate float process. The side of the polishing disc facing the polishing pad is chamfered in the peripheral direction, and the side of the polishing pad away from the polishing disc is straight chamfered in the peripheral direction.

12. The process of claim 11, wherein the process is a high-generation TFT-LCD glass substrate float process. The chamfer angle of the polishing pad is less than or equal to the chamfer angle of the polishing disc.

13. The process of claim 12, wherein the process is a high-generation TFT-LCD glass substrate float process. The chamfer angle of the polishing disc is greater than or equal to the chamfer angle of the polishing pad, and the chamfer angle of the polishing disc is greater than or equal to 60°.

14. The process of claim 13, wherein the process further comprises the step of: The chamfer angle of the polishing disc is greater than or equal to the chamfer angle of the polishing pad, and 60°≤ the chamfer angle of the polishing disc≤75°. ​

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