A high-generation TFT-LCD glass substrate preparation process

Abstract

The application discloses a kind of microdefects, high-quality, high generation TFT-LCD glass substrate float process.Compared with ordinary float process, the present application is aimed at TFT-LCD glass substrate particularity, and the raw material formula based on optimization design is used in batching process, and the uniformity of component is improved by using injection, vibration means auxiliary feeding;Melting process adopts three-dimensional gas-electric composite heating to realize sufficient melting;Clarification process specially adopts platinum channel clarification and forced flow disturbance homogenization to complete efficient clarification and homogenization;Forming process improves the quality of thinning by fine control of heating unit and micro edge trimmer;Annealing process realizes fine annealing by independent partition precision annealing control;Grinding process uses specially designed chamfer grinding disc and grinding pad, and grinding pad with optimized hardness for grinding, to achieve excellent processing effect.Through the optimization design and innovation combination of the above process, a new high-generation TFT-LCD glass substrate float production process is developed.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of glass substrate manufacturing, and in particular to a high-generation TFT-LCD glass substrate float process. BACKGROUND

[0002] The electronic information display industry is an important pillar industry of China's national economy. China is the world's largest producer of liquid crystal panels, accounting for 70% of global total capacity. High-generation TFT-LCD glass substrates are core materials and key strategic materials for the electronic information display industry and the semiconductor industry. China needs more than 300 million square meters of high-generation TFT-LCD glass substrates per year.

[0003] The quality and performance of high-generation TFT-LCD glass substrates have a crucial impact on display panel resolution, light transmittance, refresh rate, and viewing angle. Therefore, there are very high requirements for the quality of the substrate interior and surface. Bubbles, stones, tin adhesion, drips, and scratches are strictly controlled indicators in the glass substrate manufacturing process. Therefore, high-generation TFT-LCD glass substrate production technology is complex, production control precision is comparable to the semiconductor industry, and represents the highest level of global modern glass mass production.

[0004] High-generation TFT-LCD glass substrates are mainly formed by float and overflow processes. The float forming process has the advantages of wide forming plate and low production cost, but also has the problems of large mutual influence between multiple processes, many control parameters, high difficulty of regulation and control, and difficult stable control of production state. In addition, in the float forming process, the glass liquid is thinned on the surface of the tin liquid, and the contact surface of the glass liquid and the tin liquid will have small tin adhesion points, scratches, and other microscopic defects. This contact surface is also the processing process surface of downstream liquid crystal panel manufacturers. How to prepare a high-quality, high-generation TFT-LCD glass substrate with excellent mechanical strength, thermal stability, thermal shrinkage, and few surface and internal defects through the float process is an important technical problem that needs to be solved. SUMMARY

[0005] In order to solve the technical problems in the prior art, the applicant's research personnel have made technical innovations on multiple processes of the display glass substrate production process through long-period, large-team, collaborative cooperation and persistent efforts, and have excavated and utilized the advantages of each process, and have made combined innovation research between processes, and finally have realized a breakthrough in the float process of high-generation TFT-LCD glass substrates, and have formed a display glass substrate production process with full resource utilization, complementary advantages and organic unified production line. The high-generation TFT-LCD glass substrate prepared by using the process has excellent control indexes and performance indexes such as bubbles, stones, tin adhesion, drips and scratches, effectively reduces or eliminates the defects of the glass substrate, greatly improves the quality of the glass substrate, and provides a solution for preparing micro-defect, high-quality and high-generation display glass substrates.

[0006] The application provides a glass substrate preparation process, which comprises the processes of batching, melting, fining and homogenizing, forming, annealing, grinding, cleaning, packaging and the like.

[0007] In the batching process, as preferred, by selecting SiO2, Al2O3, B2O3, MgO, CaO, SrO, ZrO2 and P2O5 batch materials meeting specific proportional relationships, the boron evaporation rate in the glass forming process can be effectively reduced, and the composition unevenness problem caused by boron evaporation can be eliminated, and the aluminosilicate glass substrate prepared by using the same has the characteristics of high strain point, high Young's modulus, high hardness, appropriate thermal expansion coefficient, low thermal shrinkage rate, low defect and the like, and meets the special requirements of high-generation TFT-LCD glass substrates.

[0008] As preferred, an electronic scale feeding system combining air nozzle blowing and air hammer vibration is used for the raw material batching mode, after the electronic scale hopper weighs various raw materials, the air feeding valve is opened at the same time, the air nozzle sweeps the inner wall of the electronic scale hopper, and the air hammer knocks and vibrates the electronic scale hopper, so that the raw materials remaining in the inner wall of the electronic scale hopper are synchronously discharged, the components of each batch material are kept constant in the batching process, and the quality stability of the glass substrate is ensured.

[0009] In the melting process, the electric melting and full oxygen combustion are preferably combined, the electric heating can use molybdenum electrode or tin oxide electrode to realize heating, which can be arranged on the pool wall and / or pool bottom of the melting furnace, and the burner can be arranged on the roof and / or breast wall of the melting furnace. The melting furnace is preferably provided with bubbling device and kiln ridge to perform primary bubble discharge and clarification of the molten glass liquid, and discharge the bubbles with a diameter of more than 0.2 mm in the molten glass liquid. Through the above arrangement, the raw materials in the melting furnace are promoted to be synchronously heated, and the glass liquid is fully and efficiently melted; the primary bubble discharge and clarification of the melting furnace can promote the discharge of bubbles with a diameter of more than 0.2 mm in the melting furnace section, and the number of bubbles with a diameter of more than 0.2 mm in the molten glass liquid after the bubble discharge is less than or equal to 0.1 per kg. And the bubbles with a diameter of less than 0.2 mm are removed through the subsequent platinum channel precise clarification, so that the glass substrate is fully discharged and clarified, and the high-quality glass liquid is obtained.

[0010] In the clarification and homogenization process, the platinum channel clarification formed by combining 2 or more high-temperature section platinum channels and 1 low-temperature section platinum channel is preferably adopted, and the optimized stirring and flow disturbance method is adopted for forced homogenization. Compared with a single platinum channel, the reduced platinum channel diameter reduces the temperature difference of the glass liquid at the same cross section of the channel, the improved flow disturbance process improves the homogenization efficiency, promotes the full uniformity of the glass liquid flow temperature and composition, and the reduction of the glass liquid level reduces the bubble floating distance, and cooperates with the optimized raw material formula to improve the bubble discharge efficiency of small bubbles. Through the special design of the above clarification and homogenization process, the generation of bubbles, stripes and other defects on the glass plate is avoided, the bubbles in the molten glass liquid are efficiently removed, and the number of bubbles with a diameter of more than 0.05 mm in the molten glass liquid is not more than 0.15 per kg.

[0011] In the forming process, the grid heating unit is preferably arranged at the top of the tin bath, and a plurality of micro edge rollers are arranged in the forming and thinning area. The heating unit and the edge roller are cooperatively controlled, the output power of each heating unit in the transverse direction is adjusted to adjust the transverse temperature difference of the tin bath, so as to realize different viscosities at different positions of the glass ribbon in the transverse direction. Under the action of the optimized combination of the plurality of micro edge rollers and the precise adjustment of the thinning force, and the traction force of the appropriate main drive, the high-generation liquid crystal glass plate is precisely thinned under the multi-acting force. The prepared high-generation TFT-LCD glass substrate has a whole plate thickness difference of less than or equal to 0.015 mm.

[0012] In the annealing process, the three-dimensional grid temperature precise control annealing furnace structure is preferably adopted, the non-turbulent cooling air pipe cooling, low heat conduction ceramic roller transmission, curtain partition isolation, annealing furnace insulation differential design and other methods are used to avoid airflow disturbance, reduce temperature field fluctuation, reduce the transverse temperature difference of the glass substrate, meet the requirements of transverse temperature consistency of the large-size ultra-thin glass substrate and precise matching of the temperature of each zone of the annealing furnace and the annealing curve of the glass substrate, realize perfect matching of the temperature field and the annealing curve, and fully eliminate the stress of the glass substrate.

[0013] In the polishing process, the glass substrate is polished by using three kinds of polishing pads with hardness ratio of 90HD-100HD:60HD-70HD:35HD-40HD in turn, the ratio of the polishing surface at the non-edge to the width of the polishing groove is optimized, chamfers are arranged at the positions of the polishing disc periphery and the position of the polishing pad far away from the polishing disc, and the chamfer angle of the polishing disc is greater than or equal to the chamfer angle of the polishing pad, so that the polishing quality is improved, the scratch during polishing is reduced, and the polishing effect is improved.

[0014] The high-generation TFT-LCD glass substrate float production process controls the preparation process in detail, and realizes the organic cooperation of each production process link.

[0015] The application has the advantages that: the application fully excavates and utilizes the advantages of multiple processes of the high-generation TFT-LCD glass substrate float production process, and carries out combination innovation research between processes, so that the display glass substrate production process is organically unified, the advantages are prominent, and the production process is complementary. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a whole flow chart of the glass substrate preparation process;

[0017] Figure 2 It is a feeding system schematic diagram of the batching process;

[0018] Figure 3 It is a front view cross-sectional schematic diagram of the melting furnace of the glass raw material melting process;

[0019] Figure 4 It is a top view schematic diagram of the fining and homogenizing system of the fining and homogenizing process;

[0020] Figure 5 It is a transverse cross-sectional schematic diagram of the tin bath of the forming process;

[0021] Figure 6 It is a top view schematic diagram of the forming and thinning area of the tin bath of the forming process;

[0022] Figure 7 It is a top view schematic diagram of the annealing furnace of the annealing process;

[0023] Figure 8 It is a front view cross-sectional schematic diagram of the annealing furnace of the annealing process;

[0024] Figure 9 It is a schematic diagram of the polishing process;

[0025] Figure 10 It is a schematic diagram of the glass substrate surface before and after polishing of the polishing process;

[0026] Figure 11 Schematic diagram of the structure of a polishing pad for a polishing process;

[0027] Figure 12 Schematic diagram of the surface of a polishing pad for a polishing process;

[0028] Figure 13 Schematic diagram of the structure of a polishing device for a polishing process;

[0029] Figure 14 Schematic diagram of the structure of a polishing device for a polishing process; Figure 13 Enlarged view of A in FIG. 7;

[0030] Figure 15 Schematic diagram of the chamfer of a polishing disc for a polishing process;

[0031] Figure 16 Schematic diagram of the chamfer of a polishing pad for a polishing process. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application. It can be understood that the drawings are provided only for reference and illustration, and are not used to limit the present application.

[0033] Specifically, the embodiments of the present application provide a high-generation TFT-LCD glass substrate float preparation process, as shown in FIG. 1, which mainly includes the following processes: Figure 1

[0034] Batching process: selecting appropriate raw materials, weighing and mixing each raw material to form a glass batch;

[0035] Melting process: heating and melting the mixed and uniform glass batch to form a molten glass liquid;

[0036] Clarification and homogenization process: passing the molten glass liquid through a clarification channel to remove bubbles and homogenize;

[0037] Forming process: flattening and thinning the molten glass liquid on the surface of a metal tin liquid to form a glass substrate;

[0038] Annealing process: annealing the glass substrate to eliminate internal stress in the glass substrate;

[0039] Polishing process: cutting the glass substrate to the required size and performing polishing processing;

[0040] Cleaning process: cleaning the glass substrate; ​

[0041] Packaging process: the cleaned and qualified glass substrate is packaged.

[0042] Next, each process technology is described one by one.

[0043] Batching process:

[0044] High-generation TFT-LCD glass substrate requires the following characteristics: low density, high strain point, suitable thermal expansion coefficient, high Young's modulus, chemical corrosion resistance, low thermal shrinkage, and low micro-defects. Therefore, the raw material components need to be carefully designed.

[0045] As preferred, the following weight fraction of materials is used: 60-72% of SiO2, 13-18% of Al2O3, 8.5-10% of B2O3, 1-4.5% of MgO, 3-8% of CaO, 1-5% of SrO, 0.5-2% of ZrO2, 1-5% of P2O5, 0.1-0.5% of SnO2; wherein SiO2+Al2O3 is 76-85%; (MgO+CaO+SrO) / Al2O3 is 0.4-0.7%; total amount of alkaline earth metal oxides is 5-11.5%; B2O3 / (B2O3+ZrO2+P2O5) is 0.6-0.9%; (ZrO2+P2O5) / (MgO+CaO+SrO) is 0.15-0.8%.

[0046] The above glass material can effectively reduce the boron evaporation rate during glass forming, control the problem of uneven glass liquid composition caused by boron evaporation during glass substrate preparation, and promote glass liquid bubble removal and clarification. The aluminosilicate glass substrate prepared by using the raw material has the characteristics of high strain point, high Young's modulus, high hardness, suitable thermal expansion coefficient, low thermal shrinkage, and low micro-defects, wherein the β-OH value is less than 0.5%, the boron evaporation rate is less than 11%, the thermal expansion coefficient in the range of 50-350℃ is less than 39.5×10 -7 / ℃, the Young's modulus is higher than 78GPa, the strain point is higher than 690℃, the melting temperature is lower than 1690℃, and the thermal shrinkage is lower than 11.5ppm.

[0047] At the same time, the quality requirements of high-generation TFT-LCD glass substrate are much higher than other types of glass, which requires that the components of high-generation TFT-LCD glass substrate batching maintain very high uniformity, and there cannot be obvious differences in components, thereby having strict requirements on the purity, weighing accuracy, and mixing uniformity of various raw materials in the batching.

[0048] As preferred, the following control glass batching component stable electronic scale weighing system can be used.

[0049] For example, Figure 2As shown, the system includes an electronic weighing hopper 101, with a pneumatic feeding valve 102 at the bottom. An air hammer 103 is provided 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.

[0050] 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.

[0051] Melting process:

[0052] After the above batching process is completed, the glass raw materials are melted through a melting process.

[0053] As a preferred option, the following melting process can be used.

[0054] like Figure 3As shown, the electrodes 202 are symmetrically or staggeredly arranged on the inner walls and / or the bottom of the melting furnace 201, and the full-oxygen combustion torches 203 are arranged on the roof and / or the breast wall of the melting furnace 201. When arranged on the roof, the full-oxygen combustion torches are vertically distributed, the flame injection ports are vertically downward, and the flames can contact the liquid surface of the glass liquid in the melting furnace 201. When arranged on the breast wall, the full-oxygen combustion torches are horizontally arranged. Through the direct heating of the electrodes and the radiant heating of the full-oxygen combustion, the melting of the glass raw materials is completely realized. Preferably, the melting furnace is further provided with a bubbling device 204 and a dam 205, so as to preliminarily bubble and clarify the molten glass liquid, and promote the discharge of the larger bubbles in the glass liquid. Through the careful combination of the raw materials, the use of the omnibearing three-dimensional electric-gas full-oxygen combustion composite heating mode, and the action of the bubbling and the dam, the number of bubbles with a diameter of 0.2 mm or more in the molten glass liquid is greatly reduced, and the number of bubbles with a diameter of 0.2 mm or more is ≤0.1 per kg.

[0055] Through the above process, the glass raw materials are heated from the bottom to the top at multiple angles, the raw materials at each position in the melting furnace are uniformly and sufficiently heated, at the same time, the special selection of the glass raw materials promotes the precise clarification coordination of the glass liquid in the primary clarification and clarification homogenization sections of the melting furnace, improves the bubble discharge efficiency of the production line system, and improves the quality of the glass substrate.

[0056] Clarification homogenization process:

[0057] The melted glass raw materials become molten glass liquid, which needs to go through a clarification homogenization process before forming.

[0058] As preferred, the clarification homogenization can be carried out by the following process.

[0059] For example, Figure 4As shown, the platinum channel includes a plurality of high-temperature section platinum channels and a low-temperature section platinum channel (post-flow mixing stirring section, second cooling section, feeding section). The first inlet section (311), the first clarifying section (312), the first cooling section A (313), and the first stirring section (314) are sequentially connected to form a first high-temperature section platinum channel (310), and the second inlet section (321), the second clarifying section (322), the first cooling section B (323), and the second stirring section (324) are sequentially connected to form a second high-temperature section platinum channel (320). The ports of the first inlet section (311) and the second inlet section (321) are connected to the melting furnace (201), and the ports of the first stirring section (314) and the second stirring section (324) are both connected to the post-flow mixing stirring section (340). The post-flow mixing stirring section (340) further has the second cooling section (350) and the feeding section (360) sequentially connected thereto to form a low-temperature section platinum channel, and the feeding section (360) is connected to a tin bath. The first cooling section A (313) and the first cooling section B (323) are used to cool the glass liquid flowing therethrough 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 glass liquid flowing therethrough, and when necessary, the glass liquid flowing therethrough is heated to meet the forming requirements of the glass. The second cooling section (350) has gratings with different installation angles sequentially arranged therein from right to left. The installation angles of adjacent gratings are different, so that the holes on the gratings are staggered to ensure that the glass liquid forms a turbulent flow after passing through the gratings.

[0060] The above multi-platinum channel clarifying and homogenizing process reduces the thermal load of a single platinum channel, avoids the collapse risk of a large-diameter platinum channel caused by long-time high-temperature operation, reduces the temperature difference between the center temperature of the glass liquid on the same cross section of the platinum channel and the temperature of the contact part of the platinum body, improves the stirring and grating turbulent flow process, improves the homogenization efficiency, and improves the homogeneity of the glass liquid. Through the homogenization process, the temperature and composition of the glass liquid can be fully uniform, and the quality of the glass substrate is improved. Due to the reduction of the glass liquid level, the small bubble discharge efficiency is improved, and the number of bubbles with a diameter of ≥0.05 mm in the molten glass liquid is not more than 0.15 per kg. The raw materials, primary clarification of the melting furnace, and precise clarification and homogenization are coordinated to remove bubbles in the glass liquid with high quality.

[0061] Forming process:

[0062] After the above clarifying and homogenizing process is completed, the glass liquid is formed by float thinning.

[0063] As preferred, the float thinning can be performed by the following process.

[0064] As Figure 5 , Figure 6As shown, the molten glass flows into the forming tin bath. The tin bath is divided into a bath pool 401, a breast wall 402 and a top cover 403 from bottom to top; along the direction of the glass flow, the tin bath is divided into a forming and thinning zone 404, a shaping and cooling zone and a temperature homogenization zone.

[0065] In the longitudinal direction of the glass flow and the transverse direction perpendicular to the glass flow, the top of the tin bath is divided into a grid of multiple heating units 405, each of which can independently control the heating temperature. Each heating unit includes one or more heating elements, and the TFT-LCD glass substrate has a high forming temperature and volatile components. Therefore, the preferred heating element is a high-density three-phase silicon-carbon rod.

[0066] It is preferred to increase the density of the grid heating units in the forming and thinning zone, thereby more finely controlling the temperature of each region and improving the accuracy and flexibility of temperature control.

[0067] In cooperation with the tin bath heating system, it is preferred to use a precision thinning system for collaborative control in the forming and thinning zone. The TFT-LCD glass has short material properties and a small forming temperature range, so the distance between the edge rollers is reduced and the number of edge rollers is increased. In a limited temperature range, the action range of the thinning system is reduced, and the glass ribbon thinning force can be subdivided to each pair of edge rollers, realizing the ultra-thin and precise forming of the glass substrate. The precision thinning system uses micro edge rollers 406, the body of which is less than 300mm, preferably 200-250mm; the distance between adjacent two edge rollers is less than 1000mm, preferably 500-900mm. A total of 15-25 pairs of edge rollers are provided in the forming and thinning zone, preferably 18-22 pairs.

[0068] It is preferred that at least part of the transverse edge heating units 415 are arranged corresponding to the edge rollers, and one edge heating unit corresponds to 1-4 edge rollers, preferably 2-3 edge rollers.

[0069] The control system uniformly adjusts each heating unit and edge roller. By adjusting the output power of each heating unit in the transverse direction, the transverse temperature difference of the tin bath is adjusted, thereby adjusting the viscosity difference of the glass ribbon at each position in the transverse direction. The thinning force of the edge roller acts on the edge of the glass ribbon and is transmitted to the middle of the glass ribbon. The adjustment of the transverse temperature difference of the tin bath affects the viscosity of the glass, coupled with the adjustment of the thinning force of the edge roller, thereby improving the transverse thinning effect of the glass ribbon, and realizing the thickness difference of the high-generation TFT-LCD glass substrate ≤0.015mm.

[0070] Annealing process:

[0071] After the above float forming is completed, the formed glass substrate needs to be annealed.

[0072] As a preferred, the following glass annealing process can be used.

[0073] For example, Figure 7 , Figure 8As shown, the annealing process adopts a grid control mode, and the annealing zone is divided into multiple sub-zones 501, each of which can be independently controlled in temperature. Each sub-zone includes a temperature detection device 502, a heating device 503, and a cooling device 504, the cooling device adopts a cooling air pipe, the air inlet is outside the kiln body, and the air outlet is provided with a centrifugal fan 505. The temperature of the cooling air pipe is reduced by the flow of air in the cooling air pipe, and the cooling air pipe reduces the temperature of each sub-zone. This mode avoids air disturbance.

[0074] The applicant found that one of the reasons for the poor mechanical properties of the liquid crystal glass substrate is that there is a large internal stress in the same glass substrate in the transverse direction. The reason is that the transverse annealing temperature is not consistent. Since the temperature of the lateral edge of the glass substrate is lower than that of the central part, if the temperature is not differentiated, it is easy to cause different transverse annealing temperatures and generate a large internal stress. Therefore, the temperature of the sub-zone 506 corresponding to the edge of the glass in at least part of the annealing area is higher than the temperature of the sub-zone 507 corresponding to the center of the glass.

[0075] Preferably, a ceramic roller is used as a transmission roller 508. The ceramic roller has excellent heat insulation effect, can prevent heat conduction between the glass substrate and the ceramic roller to the greatest extent, and avoids unintended cooling of the glass substrate. A curtain 509 is provided in the annealing kiln, and the curtain can be controlled to rise and fall. Unlike other float glass, the ultra-thin glass has a faster conveying speed in the annealing kiln. During the conveying process, air flow is easily formed. The use of the curtain avoids the flow of air, which is more beneficial to the independence and precise temperature control of each zone.

[0076] Further preferably, the temperature of the heat preservation layer of the annealing kiln is different from inside to outside, the temperature of the inside is high, and the temperature of the outside is low. By arranging heat preservation materials with different thermal conductivities in the heat transfer direction of the heat preservation layer, the high-temperature layer 510 on the inside uses heat preservation materials with lower thermal conductivity to reduce the overall thermal conductivity. Furthermore, the thermal bridges such as connecting plates and plug holes between the inner and outer walls of the annealing kiln are connected by thermal break bridges to further reduce heat conduction. The temperature difference between the outer wall and the environment is reduced to less than 2 / 3 of the original temperature difference. Through the above means, temperature fluctuations caused by frequent temperature adjustment can be avoided, and the temperature stability in the annealing kiln can be improved.

[0077] The temperature detection device, the heating device, the cooling device, and the curtain lifting device of each sub-zone are connected to the control device, and the automatic intelligent control of the above devices is realized through the control device.

[0078] The annealing process of the present application can better meet the precise matching requirements of the temperature field and the annealing curve of the high-generation TFT-LCD glass substrate, reduce the transverse temperature difference of the glass substrate, avoid temperature field fluctuations and disorder, effectively eliminate the internal stress of the glass substrate, and realize the differentiated, refined, automated, and intelligent control of annealing.

[0079] Grinding process:

[0080] After annealing, the glass substrate needs to be ground. Grinding refers to grinding the uneven parts and microscopic defects such as tin sticking and scratches on the surface of the glass. By adding abrasives, additives and other chemical components, the glass surface can be made smooth and flat to achieve the effect of grinding.

[0081] Polishing is a further smoothing of the glass surface after preliminary grinding to improve its flatness.

[0082] As shown in Figure 9 , the grinding process of the embodiment is mainly carried out in the following way:

[0083] The glass substrate is cleaned and dusted;

[0084] The glass substrate is coarsely ground by a coarse grinding pad in cooperation with a grinding liquid;

[0085] The glass substrate after coarse grinding is finely ground by a fine grinding pad in cooperation with a grinding liquid;

[0086] The glass substrate after fine grinding is polished by a polishing pad in cooperation with a grinding liquid;

[0087] The polished glass substrate is cleaned.

[0088] Wherein, when the glass is not ground, the glass surface presents a shape as shown in Figure 10 ①, the glass surface presents many irregular shapes and structures, which will cause the glass transmittance to decrease and the image to deform.

[0089] Before grinding, the glass needs to be cleaned and dusted.

[0090] During grinding, the coarse grinding pad provided on the grinding member is ground together with the grinding liquid to grind the glass substrate from the shape in Figure 10 ① to the shape in Figure 10 ②, eliminating the uneven areas of the glass substrate.

[0091] After completing the coarse grinding, the fine grinding pad provided on the grinding member is ground together with the grinding liquid to grind the glass substrate, removing the extremely fine scratches on the glass substrate, and the glass substrate is ground from the shape in Figure 10 ② to the shape in Figure 10 ③.

[0092] After completing the fine grinding, the polishing pad provided on the grinding member is ground together with the grinding liquid to grind the glass substrate more deeply. After the glass substrate is ground by the polishing pad, the defects invisible to the naked eye on the glass substrate can be polished and eliminated, and the glass substrate is ground from the shape in Figure 10 ③ to the shape in Figure 10The form of the embodiment IV meets the high quality requirement of TFT-LCD glass substrate.

[0093] The grinding device used in the grinding process, such as Figures 11-14 As shown in the figure, the grinding device includes a grinding disc 620 and a grinding pad 610, the grinding pad 610 is assembled on the grinding disc 620, the side of the grinding pad 610 away from the grinding disc 620 grinds the glass, and the 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 not the same.

[0094] For the hardness range, the coarse grinding pad: the fine grinding pad: the polishing grinding pad is preferably controlled to be 90HD-100HD: 60HD-70HD: 35HD-40HD, further preferably 90HD-95HD: 60HD-70HD:

[0095] 35HD-40HD, and still further preferably 90HD-95HD: 65HD-70HD: 35HD-40HD. In the above, HD is the Shore hardness index. As shown in the figure, Figure 11 and Figure 12 In order to improve the grinding effect, a grinding groove 611 is opened on the grinding pad 610, and a plurality of grinding grooves 611 are communicated with each other to facilitate the flow of the grinding liquid. A plurality of grinding surfaces 612 are formed on the grinding pad 610, and the grinding surfaces are preferably square except for the grinding surfaces at the edges. The grinding surface 612 grinds the surface of the glass substrate.

[0096] The ratio of the grinding surface to the width of the grinding groove is preferably 1:1-3:1, and further preferably 1.7:1-2.3:1.

[0097] In the embodiment of the application, the matching relationship between the grinding pad 610 and the grinding disc 620 can also affect the grinding effect of the glass substrate, and the main influence is that the working surface of the edge part of the grinding pad 610 and the processing surface of the glass substrate are not in a completely parallel state during the grinding process.

[0098] In the existing technology, the edge of the grinding pad and the processing surface are basically in a vertical state. In this structure, the edge part of the grinding pad will rub against the glass substrate to a certain extent during the grinding process, which will cause scratches on the glass.

[0099] The applicant found through many simulations and researches that the special designed double chamfer coupling arrangement can greatly reduce the probability of the grinding pad rubbing against the glass substrate during grinding. The specific method is as follows:

[0100] A circular chamfer is processed at the position around the grinding disc 620. In the embodiment of the application, the circular chamfer is a circular chamfer 621. The preparation method of the circular chamfer is as follows: Figure 15Let the height of the grinding disc's side surface be H. Extend the bottom surface of the grinding disc vertically upwards along the side surface by a distance h to point a. Take the side surface of the grinding disc as one side, point a as the vertex, and draw the other side with a rounded chamfer angle. The intersection of this other side and the bottom surface of the grinding disc is point b. Connect points ab and use this as one side to draw an isosceles triangle. 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.

[0101] Preferably, the grinding pad is tightly attached to the grinding disc 620 with rounded chamfers around its perimeter.

[0102] At the same time, such as Figure 13 and Figure 14 The outermost edge of the polishing pad, away from the polishing disc 620 and facing the glass substrate, also has a chamfer. Preferably, this chamfer is a straight chamfer 615. The straight chamfer 615 further prevents scratching of the glass substrate compared to the rounded chamfer 621. Figure 16 The chamfer is located at position c on the side of the polishing pad, where c is h' from the bottom surface of the polishing pad, and the side thickness of the polishing pad is H'. h' / H' = 4:5-1:2, preferably 4:5-3:5. Regarding the relationship between the chamfer angle of the polishing disc and the chamfer angle of the polishing pad, it is preferable that the chamfer angle of the polishing disc is greater than or equal to the chamfer angle of the polishing pad. More preferably, 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 ≥50°. Even more preferably, 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 ≥60°. Still more preferably, the chamfer angle of the polishing disc is greater than or equal to the chamfer angle of the polishing pad, and 75° ≥ chamfer angle of the polishing disc ≥ 60°.

[0103] 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%.

[0104] In this embodiment of the application, in order to improve the grinding effect, the grinding pressure, grinding temperature and grinding speed can be controlled.

[0105] 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.

[0106] For the grinding temperature, it can be controlled in the range of 20-60℃, preferably between 20-50℃, further preferably between 30-50℃, still further preferably between 30-40℃.

[0107] For the grinding rotation speed, it can be controlled between 5000rmp-7000rmp, preferably between 5200rmp-6500rmp, further preferably between 5500rmp-6300rmp, still further preferably between 5800rmp-6000rmp.

[0108] For the grinding time, it can be controlled between 30 seconds-300 seconds, preferably between 60 seconds-240 seconds, further preferably between 80-150 seconds.

[0109] Cleaning process:

[0110] After the above process is completed, the glass substrate needs to be cleaned, and the cleaning process is mainly to remove the residual grinding liquid and other impurities on the surface of the glass substrate, so as to facilitate the detection of roughness of the glass substrate by the Surtronic S-100 series surface roughness tester in the later period.

[0111] The glass substrate is deeply cleaned by disc brush, roller brush, ultrasonic, two-fluid, etc. to achieve the purpose of cleaning the glass surface.

[0112] Packaging process:

[0113] The glass substrate that passes the inspection after cleaning is packaged to avoid cracks and notches caused by the collision of the glass, which affects the sale of the glass in the market.

[0114] Embodiment:

[0115] The embodiment part of the present application focuses on the grinding process of the present application.

[0116] In the embodiment, the grinding liquid is prepared by mixing cerium oxide as the main component (cerium oxide content 58%) and 0.2 mega ohm (MΩ) pure water, and the concentration range is 4%. In the following grinding process, the composition of the glass grinding liquid is used as the basis for grinding. For the grinding disc, h / H=1:4, h=4mm, for the grinding pad, h' / H'=3 / 4.

[0117] In the embodiment of the present application, the hardness of the coarse grinding pad is in the range of 90HD-100HD, the hardness of the fine grinding pad is in the range of 60HD-70HD, and the hardness of the polishing pad is in the range of 35HD-45HD. The cooperation of the grinding pads 610 with different hardness can produce different effects on the flatness of the glass surface.

[0118] In the embodiment of the application, the grinding pressure is 0.15 MPa, the grinding temperature is 35 DEG C, the grinding speed is 6000 rpm, and the grinding time is 140 seconds.

[0119] The roughness is detected by a Surtronic S-100 series surface roughness tester.

[0120] The grinding effects of the grinding pads of various hardnesses are shown in Table 1.

[0121] Table 1:

[0122]

[0123]

[0124] The flatness refers to the deviation degree between the geometric shape of the glass substrate surface and an ideal plane, and is usually represented by the distance between two points or the radius of curvature. The flatness of a high-generation TFT-LCD glass substrate has a great influence on the strength, optical performance, physical performance and the like of the glass substrate. Therefore, the flatness needs to be strictly controlled and detected 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 after forming and processing are not completely eliminated after grinding. The lower the glass scratch defect rate, the fewer scratches are left on the glass surface after grinding.

[0125] As can be seen from Table 1, when the coarse grinding pad: fine grinding pad: polishing grinding pad is selected as 90HD-100HD: 60HD-70HD: 35HD-40HD, the flatness compliance rate and the scratch defect rate after grinding are both good. When the coarse grinding pad: fine grinding pad: polishing grinding pad is selected as 90HD-95HD: 65HD-70HD: 35HD-40HD, the flatness compliance rate and the scratch defect rate are both better.

[0126] In the embodiment of the application, the ratio of the grinding surface 612 at the non-edge position to the width of the grinding groove 611 is set as a proportional relationship of 1:1-3:1. The grinding pad meeting the proportional relationship can better complete the grinding of the glass substrate. The applicant has found through a large number of experiments and researches that:

[0127] Compared with the optimal scheme, when the ratio of the grinding surface 612 at the non-edge position to the width of the grinding groove 611 is 1:1-1.7:1, the flow guiding effect is good, the flow rate of the grinding liquid is fast, but the grinding contact area is small, and the grinding efficiency is relatively low.

[0128] When the ratio of the grinding surface 612 at the non-edge position to the width of the grinding groove 611 is 1.7:1-2.3:1, the flow guiding effect and the grinding efficiency of the grinding liquid are considered, the grinding efficiency is ensured, and secondary defects are not easily generated.

[0129] Compared with the optimal scheme, when the ratio of the polishing surface 612 at the non-edge to the width of the polishing groove 611 is 2.3:1-3:1, the polishing efficiency is high, but the flow guiding effect is poor, the flowability of the polishing liquid is poor, and secondary defects are prone to occur.

[0130] Therefore, according to the test results, when the ratio of the polishing surface 612 at the non-edge to the width of the polishing groove 611 is 1.7:1-2.3:1, as shown in FIG. 2, Figure 12 As shown in FIG. 2, the flow guiding effect of the polishing liquid and the polishing efficiency are balanced, and the demand for manufacturing high-quality glass substrates can be better met.

[0131] For the selection of the circular chamfer and the straight chamfer, different angles result in changes in the occurrence rate of the grinding marks on the glass, as shown in Table 2:

[0132] Table 2:

[0133]

[0134]

[0135] According to the data in the above table, when 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°, the occurrence rate of the grinding marks is low, and a good polishing effect can be achieved.

[0136] The above examples are only used to illustrate the technical method of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical method of the present application can be modified or replaced equivalently without departing from the spirit and scope of the technical method of the present application.

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 pour into the melting furnace. Spray or vibration is adopted to prevent material stagnation or accumulation during pouring; Melting process: electrode 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 unit in the tin bath can be independently controlled, and the thinning force of the micro edge roller is used to make the glass ribbon thin into a glass substrate; Annealing process: the annealing furnace is divided into multiple zones, and each zone is independently temperature-controlled for annealing the glass substrate; 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 to grind and polish the glass substrate in turn. The grinding pad includes a plurality of grinding surfaces divided by grinding grooves. Except for the grinding surfaces at the edges, the remaining grinding surfaces are square. The width ratio of the grinding surface at the non-edge to the grinding groove is 1:1-3:

1. The grinding pad is assembled on the grinding disc. The four directions of the side of the grinding disc facing the grinding pad form a circular chamfer. The four directions of the side of the grinding pad away from the grinding disc form a straight chamfer. 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 greater than or equal to 60°.

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. The sum of SiO2 and Al2O3 is 76-85%, the sum of (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%, (ZrO2+P2O5) / (MgO+CaO+SrO) is 0.15-0.8%, and the sum of each component is 100%. 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. The material accumulated in the inner wall of the scale is discharged synchronously by the spray of the air nozzle arranged on the inner wall of the scale and the vibration of 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 a bubbling device and a kiln ridge.

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 the adjacent gratings are staggered. The stirring of the stirring device and the flow disturbance of the multiple gratings realize the full homogenization of the molten glass liquid.

5. The process of claim 1, wherein the process is a high generation TFT-LCD glass substrate float process. 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 roller corresponding to the same transverse position of the heating unit is adjusted, so that 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 conveyed by ceramic rollers as transmission rollers, 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 in at least part of the annealing area in the annealing furnace, and the thermal conductivity of the high-temperature layer of the inner side of at least part of the furnace wall is lower than that of the low-temperature layer of the outer side.

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

8. The float glass substrate fabrication process for high-generation TFT-LCDs according to claim 7, characterized in that, In the grinding process, the hardness of the coarse grinding pad, the fine grinding pad and the polishing grinding pad is selected to be 90HD-95HD: 65HD-70HD: 35HD-40HD.

9. The process of claim 7, wherein the process further comprises the step of: The chamfer angle of the grinding disc is greater than or equal to the chamfer angle of the grinding pad, and 60°≤the chamfer angle of the grinding disc≤75°. ​

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