TFT acid-resistant alkali-free glass substrate and preparation method thereof

Abstract

The invention discloses a TFT (Thin Film Transistor) acid-resistant alkali-free glass substrate and a preparation method thereof, the TFT acid-resistant alkali-free glass substrate comprises the following components in percentage by mass: 56-65% of SiO2, 14-16% of Al2O3, 3-4% of CaO, 1.5-2.5% of SrO, 0.5-0.8% of SnO2, 2.0-3.5% of ZrP2O7, MgB4O7, B4C, ZnSiO3 and Mg2SiO4, the sum of the mass percentages of MgB4O7 and B4C is 6.8-8%, and the mass ratio of MgB4O7 to B4C is (0.5-1.2): 1; the sum of the mass percent of ZnSiO3 and the mass percent of Mg2SiO4 is 5-7%, and the molar ratio of ZnSiO3 to Mg2SiO4 is 1: (0.8-1.2). The problems that a traditional TFT alkali-free glass substrate is serious in B2O3 volatilization and poor in thermal stability are effectively solved, and the comprehensive performance of the glass substrate is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of glass, and particularly relates to a TFT acid-resistant alkali-free glass substrate and a preparation method thereof. Background Art

[0002] In TFT (Thin Film Transistor) liquid crystal display technology, as a key supporting material, the performance of the glass substrate plays a decisive role in the display effect and device stability. There are many limitations in the composition system of traditional TFT alkali-free glass substrates, making it difficult to meet the rapid development of current high-resolution, high-refresh-rate, and low-power consumption display requirements.

[0003] In terms of the composition system, B2O3, as an important component in the glass composition, its volatilization problem has always been a difficult problem in the industry. During the production process of traditional glass substrates, the volatilization rate of B2O3 is as high as 12 - 15%, which not only leads to a large deviation in the glass composition, affecting the chemical and thermal stability of the glass, but also increases the production cost. At the same time, the effect of a single rare earth oxide as a stabilizer is limited, and it cannot effectively inhibit the deterioration of the glass network structure at high temperatures, resulting in a relatively high thermal shrinkage rate of the glass, and it is difficult to achieve an ideal matching state between the strain point and the coefficient of thermal expansion. These parameters limit the performance stability of TFT devices in high-temperature environments.

[0004] In summary, in view of the deficiencies in the composition system of existing TFT alkali-free glass substrates, there is an urgent need for an innovative technical solution to achieve breakthroughs in key performance indicators to meet the growing display technology requirements. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art, and provide a TFT acid-resistant alkali-free glass substrate and a preparation method thereof. Through innovative design of the glass composition system, the problems of serious B2O3 volatilization and poor thermal stability existing in traditional TFT alkali-free glass substrates are effectively solved, and the comprehensive performance of the glass substrate is significantly improved.

[0006] The technical solution of the present invention is as follows:

[0007] On the one hand, the present invention provides a TFT acid-resistant alkali-free glass substrate, comprising components in the following mass percentages: SiO2: 56 - 65%, Al2O3: 14 - 16%, CaO: 3 - 4%, SrO: 1.5 - 2.5%, SnO2: 0.5 - 0.8%, ZrP2O7: 2.0 - 3.5%, MgB4O7, B4C, ZnSiO3 and Mg2SiO4, wherein the sum of the mass percentages of MgB4O7 and B4C is 6.8 - 8%, and the mass ratio of MgB4O7 to B4C is (0.5 - 1.2):1; the sum of the mass percentages of ZnSiO3 and Mg2SiO4 is 5 - 7%, and the molar ratio of ZnSiO3 to Mg2SiO4 is 1:

[0008] (0.8 - 1.2).

[0009] SiO2: As the glass network framework, silicon-oxygen tetrahedrons (SiO4) are interconnected to form a stable three-dimensional network structure. When the temperature changes, its structural stability can effectively inhibit the volume change of the glass. The tightness and orderliness of the SiO4 network determine the glass's ability to resist thermal expansion. A reasonable SiO2 content enables the glass to maintain stable physical properties in different temperature environments, playing a key role in controlling the coefficient of thermal expansion.

[0010] Al2O3: Can enhance the mechanical strength and chemical stability of the glass. Al 3+ can replace part of Si 4+ in the glass network to form aluminum-oxygen tetrahedrons (AlO4), enhancing the network connectivity and improving the overall strength of the glass. In terms of chemical stability, Al2O3 can reduce the active sites on the glass surface, reduce the reaction between external chemical substances and the glass, making it more resistant to chemical erosion and meeting the complex environmental requirements during the manufacturing and use of the TFT glass substrate.

[0011] Gradient boron source: A gradient boron source system composed of MgB4O7 and B4C nanoparticles. MgB4O7 decomposes and releases B2O3 in the medium-temperature stage (800 - 1000 °C), avoiding the concentrated volatilization of boron in the high-temperature zone and providing a stable boron source supplement for the formation of the glass network structure. The particle size of the B4C nanoparticles is 20 - 50 nm, and active boron is slowly released through a surface oxidation reaction in the high-temperature stage (>1200 °C). This way of releasing boron elements in stages can better control the distribution of boron during the glass formation process, improve the uniformity and stability of the glass composition, reduce the compositional deviation caused by boron volatilization, and thus enhance the comprehensive performance of the glass.

[0012] Composite stabilizer (ZnSiO3 and Mg2SiO4): Zn 2+ and Mg 2+After entering the glass network, they interact with the silicon-oxygen structure to form a dual-stable mechanism. On the one hand, they can fill the gaps in the glass network and enhance the network density; on the other hand, they can inhibit the thermal vibration activity of boron-oxygen triangles (BO3). BO3 has high activity at high temperatures, which will affect the thermal stability of the glass. The action of the composite stabilizer makes the glass network structure more stable, improving the thermal stability and chemical stability of the glass.

[0013] Other additives: CaO and SrO mainly adjust the melting point and viscosity of the glass. Ca 2+ and Sr 2+ can destroy the glass network structure, lower the melting point of the glass, and at the same time change the viscosity of the glass melt, making it have better fluidity during the preparation process for easy forming and processing.

[0014] SnO2: It has an improving effect on the optical properties and chemical stability of the glass. It can adjust the refractive index of the glass, improve the transparency of the glass, and can also enhance the antioxidant ability of the glass to a certain extent, improving the chemical stability.

[0015] ZrP2O7: It improves the acid resistance of the glass. Its special structure and chemical properties can form an acid-resistant barrier on the glass surface to prevent acidic substances from eroding the glass, meeting the requirements for acid resistance in specific application scenarios.

[0016] On the other hand, the present invention provides a method for preparing the above-mentioned acid-resistant alkali-free glass substrate for TFTs, comprising the following steps:

[0017] S1 Raw material pretreatment: Grind all raw materials so that their particle sizes are less than 100 μm;

[0018] S2 Melting and clarification: Add the ground raw materials into an electric melting furnace, first melt at 1400 - 1450 °C for 2 - 3 h, then raise the temperature to 1550 - 1600 °C and keep it warm for 1 - 1.5 h to promote the homogenization and clarification of the glass melt;

[0019] S3 Forming: The clarified glass melt flows into an overflow tank. The temperature of the overflow tank is 1100 - 1150 °C. The glass melt evenly overflows on both sides of the overflow tank, flows downward along the overflow bricks and converges at the bottom, and is pulled down into shape by a pulling device. During the pulling process, a protective gas is introduced into the overflow tank and the forming area;

[0020] S4 Annealing: The formed glass substrate enters an annealing furnace. The annealing temperature is 650 - 700 °C and the annealing time is 3 - 5 h.

[0021] Preferably, in step S1, a ball mill is used to grind the raw materials, and the grinding time is 4 - 6 h.

[0022] Preferably, in step S2, the current density is controlled by an electrode to be 5 - 8 A / cm2 。

[0023] Preferably, the electrode is a graphite electrode.

[0024] Preferably, in step S3, the drawing speed of the drawing device for downward forming is 0.5 - 0.8 m / min.

[0025] Preferably, in step S3, the thickness of the formed glass is 0.5 - 1 mm.

[0026] Preferably, in step S3, the protective gas is a mixed gas of N2 and H2, and the volume percentage of H2 is 3 - 5%.

[0027] Preferably, in step S4, during the annealing process, the temperature is decreased at a rate of 1 - 2 °C / min.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] Through the design of the composite stabilizer (ZnSiO3 and Mg2SiO4) and the gradient boron source (MgB4O7 and B4C), the present invention greatly reduces the B2O3 volatilization amount compared with the traditional process, and the composition deviation is <0.3 wt.%. This advantage ensures the composition stability of the glass substrate during the production process, improves the product consistency and the yield rate. At the same time, through the Zn-Mg synergistic effect of the composite stabilizer, the glass network polymerization degree (Q 3 / Q 2 ratio) is increased to 3.9 at most, and the thermal shrinkage rate decreases significantly. The optimization of the glass network structure enhances the thermal stability of the glass, enabling it to better meet the working requirements of TFT devices in different temperature environments. Specific Embodiments

[0030] In order to enable those skilled in the art of the present technology to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention.

[0031] Embodiment 1

[0032] The TFT acid-resistant and alkali-free glass substrate of this embodiment includes the following components in mass percentage: SiO2: 61.4%, Al2O3: 16%, CaO: 3.5%, SrO: 2%, SnO2: 0.6%, ZrP2O7: 3%, MgB4O7: 3.5%, B4C: 4%, ZnSiO3 and Mg2SiO4, wherein the sum of the mass percentages of ZnSiO3 and Mg2SiO4 is 6%, and the molar ratio of ZnSiO3 and Mg2SiO4 is 1:1.

[0033] The preparation method of the TFT acid-resistant and alkali-free glass substrate of this embodiment includes the following steps:

[0034] S1 Raw material pretreatment: All raw materials are ground in a ball mill for 5 h to make their particle sizes less than 100 μm, ensuring the uniformity of raw material mixing.

[0035] S2 Melting and clarification: Using the electro-assisted melting process, the ground raw materials are added to an electric melting furnace. First, they are melted at 1425 °C for 2.5 h to achieve preliminary melting; then the temperature is raised to 1575 °C and held for 1.25 h to promote homogenization and clarification of the glass melt. At this stage, the current density is controlled at 6.5 A / cm 2 , ensuring uniform heating of the glass melt and reducing the generation of bubbles and impurities.

[0036] S3 Forming (overflow down-drawing method): The clarified glass melt flows into the overflow trough. The temperature of the overflow trough is 1125 °C to ensure appropriate fluidity of the glass melt. The glass melt overflows evenly on both sides of the overflow trough, flows down along the overflow bricks and converges at the bottom, and is drawn down at a speed of 0.65 m / min by a drawing device to form a glass with a thickness of 0.7 mm; during the drawing process, a protective gas (a mixed gas of N2 and H2, with the volume percentage of H2 being 4%) is introduced into the overflow trough and the forming area to prevent secondary oxidation of the glass melt.

[0037] S4 Annealing: The formed glass substrate enters the annealing furnace. The annealing temperature is 675 °C and the annealing time is 4 h. During the annealing process, the temperature is slowly decreased at a rate of 1.5 °C / min to eliminate internal stress in the glass and improve the flatness and mechanical properties of the glass.

[0038] Performance testing is carried out on the TFT acid-resistant non-alkali glass substrate prepared in this example: The B2O3 volatilization amount is 4.5 wt.%, and the composition deviation is 0.2 wt.%; the glass network polymerization degree (Q 3 / Q 2 ratio) reaches 3.8, and the thermal shrinkage rate (500 °C, 2 h) is 11 ppm; in the acid resistance test, it is soaked in a hydrochloric acid solution with pH = 2 for 24 h, and the weight loss rate is 0.15%.

[0039] Example 2

[0040] The TFT acid-resistant non-alkali glass substrate of this example includes the following components in mass percentage: SiO2: 62%, Al2O3: 15%, CaO: 3.7%, SrO: 2.2%, SnO2: 0.7%, ZrP2O7: 2.7%, MgB4O7: 3.2%, B4C: 4%, ZnSiO3 and Mg2SiO4, where the sum of the mass percentages of ZnSiO3 and Mg2SiO4 is 6.5%, and the molar ratio of ZnSiO3 to Mg2SiO4 is 1:0.9.

[0041] The preparation method of the TFT acid-resistant alkali-free glass substrate in this embodiment includes the following steps:

[0042] S1 Raw material pretreatment: Grind all raw materials through a ball mill for 4 h to make their particle sizes less than 100 μm, ensuring the uniformity of raw material mixing.

[0043] S2 Melting and clarification: Adopt the electro-assisted melting process. Add the ground raw materials into the electric melting furnace. First, melt at 1400 °C for 3 h to preliminarily melt the raw materials; then raise the temperature to 1550 °C and keep it warm for 1.5 h to promote the homogenization and clarification of the glass liquid. At this stage, control the current density to be 5 A / cm 2 through the graphite electrode to ensure uniform heating of the glass liquid and reduce the generation of bubbles and impurities.

[0044] S3 Forming (overflow down-drawing method): The clarified glass liquid flows into the overflow tank. The temperature of the overflow tank is 1100 °C to ensure appropriate fluidity of the glass liquid. The glass liquid overflows evenly on both sides of the overflow tank, flows down along the overflow bricks and converges at the bottom, and is drawn down at a speed of 0.5 m / min by the drawing device to form a glass with a thickness of 1 mm; during the drawing process, introduce a protective gas (a mixed gas of N2 and H2, where the volume percentage of H2 is 3%) into the overflow tank and the forming area to prevent secondary oxidation of the glass liquid.

[0045] S4 Annealing: The formed glass substrate enters the annealing furnace. The annealing temperature is 650 °C and the annealing time is 5 h. During the annealing process, slowly cool down at a rate of 1 °C / min to eliminate the internal stress of the glass and improve the flatness and mechanical properties of the glass.

[0046] Perform performance tests on the TFT acid-resistant alkali-free glass substrate prepared in this embodiment: The volatilization amount of B2O3 is 5 wt.%, and the composition deviation is 0.25 wt.%; the glass network polymerization degree (Q 3 / Q 2 ratio) reaches 3.7, and the thermal shrinkage rate (500 °C, 2 h) is 12 ppm; in the acid resistance test, soak in a hydrochloric acid solution with pH = 2 for 24 h, and the weight loss rate is 0.18%.

[0047] Example 3

[0048] The TFT acid-resistant alkali-free glass substrate in this embodiment includes the following components by mass percentage: SiO2: 61.8%, Al2O3: 15.5%, CaO: 3.8%, SrO: 1.8%, SnO2: 0.6%, ZrP2O7: 3.2%, MgB4O7: 4%, B4C: 3.8%, ZnSiO3 and Mg2SiO4, where the sum of the mass percentages of ZnSiO3 and Mg2SiO4 is 5.5%, and the molar ratio of ZnSiO3 and Mg2SiO4 is 1:1.1.

[0049] The preparation method of the acid-resistant and alkali-free glass substrate for TFT in this embodiment includes the following steps:

[0050] S1 Raw material pretreatment: Grind all raw materials through a ball mill for 6 h to make their particle sizes less than 100 μm, ensuring the uniformity of raw material mixing.

[0051] S2 Melting and clarification: Adopt the electro-assisted melting process. Add the ground raw materials into the electric melting furnace. First, melt at 1450 °C for 2 h to preliminarily melt the raw materials; then raise the temperature to 1600 °C and keep it warm for 1 h to promote the homogenization and clarification of the glass liquid. At this stage, control the current density to 8 A / cm 2 through the graphite electrode to ensure uniform heating of the glass liquid and reduce the generation of bubbles and impurities.

[0052] S3 Forming (overflow down-drawing method): The clarified glass liquid flows into the overflow tank, and the temperature of the overflow tank is 1150 °C to ensure appropriate fluidity of the glass liquid. The glass liquid overflows evenly on both sides of the overflow tank, flows down along the overflow bricks and converges at the bottom, and is drawn down at a speed of 0.8 m / min through the drawing device to form. The thickness of the formed glass is controlled to 0.5 mm; during the drawing process, introduce a protective gas (a mixed gas of N2 and H2, with the volume percentage of H2 being 5%) into the overflow tank and the forming area to prevent secondary oxidation of the glass liquid.

[0053] S4 Annealing: The formed glass substrate enters the annealing furnace. The annealing temperature is 700 °C, and the annealing time is 3 h. During the annealing process, cool down slowly at a rate of 2 °C / min to eliminate the internal stress of the glass and improve the flatness and mechanical properties of the glass.

[0054] Perform performance tests on the acid-resistant and alkali-free glass substrate for TFT prepared in this embodiment: The B2O3 volatilization amount is 4.2 wt.%, and the composition deviation is 0.18 wt.%; the glass network polymerization degree (Q 3 / Q 2 ratio) reaches 3.9, and the thermal shrinkage rate (500 °C, 2 h) is 10 ppm; in the acid resistance test, soak in a hydrochloric acid solution with pH = 2 for 24 h, and the weight loss rate is 0.12%.

[0055] Comparative Example 1

[0056] The acid-free glass substrate for TFT in Comparative Example 1 includes the following components in mass percentage: SiO2: 62%, Al2O3: 16%, CaO: 4%, SrO: 2.5%, SnO2: 0.5%, B2O3: 10%, La2O3: 5%.

[0057] The preparation method of the acid-free glass substrate for TFT in Comparative Example 1 is the same as that in Example 2.

[0058] Perform performance tests on the TFT alkali-free glass substrate prepared in Comparative Example 1: The volatilization amount of B2O3 is 13 wt.%, and the composition deviation is 1.2 wt.%; the glass network polymerization degree (Q 3 / Q 2 ratio) is 2.5, and the thermal shrinkage rate (500 °C, 2 h) is 20 ppm; in the acid resistance test, soak it in a hydrochloric acid solution with pH = 2 for 24 h, and the weight loss rate is 0.3%.

[0059] By comparing Example 2 with Comparative Example 1, it can be seen that in the traditional composition system of the TFT alkali-free glass substrate, the single boron source B2O3 is volatile, resulting in a large composition deviation; the single stabilizer La2O3 cannot effectively stabilize the glass network structure, and the thermal stability is poor; and due to the absence of ZrP2O7, its acid resistance is also poor.

[0060] Comparative Example 2

[0061] The TFT alkali-free glass substrate of Comparative Example 2 includes the following components in mass percentage: SiO2: 64.7%, Al2O3: 15%, CaO: 3.7%, SrO: 2.2%, SnO2: 0.7%, MgB4O7: 3.2%, B4C: 4%, ZnSiO3 and Mg2SiO4, wherein the sum of the mass percentages of ZnSiO3 and Mg2SiO4 is 6.5%, and the molar ratio of ZnSiO3 to Mg2SiO4 is 1:0.9.

[0062] The preparation method of the TFT alkali-free glass substrate of Comparative Example 2 is the same as that of Example 2.

[0063] Perform performance tests on the TFT alkali-free glass substrate prepared in Comparative Example 2: The volatilization amount of B2O3 is 5 wt.%, and the composition deviation is 0.25 wt.%; the glass network polymerization degree (Q 3 / Q 2 ratio) is 3.7, and the thermal shrinkage rate (500 °C, 2 h) is 12 ppm; in the acid resistance test, soak it in a hydrochloric acid solution with pH = 2 for 24 h, and the weight loss rate is 0.25%.

[0064] Since ZrP2O7 is not added in Comparative Example 2, the acid resistance of the glass decreases significantly, and other properties are similar to those of Example 2, which indicates that ZrP2O7 mainly affects the acid resistance of the glass and has little effect on boron volatilization and thermal stability.

[0065] Comparative Example 3

[0066] The TFT alkali-free glass substrate of Comparative Example 3 comprises the following components in mass percentages: SiO2: 62%, Al2O3: 15%, CaO: 3.7%, SrO: 2.2%, SnO2: 0.7%, ZrP2O7: 2.7%, MgB4O7: 3.2%, B4C: 4%, ZnSiO3 and Mg2SiO4, wherein the sum of the mass percentages of ZnSiO3 and Mg2SiO4 is 6.5%, and the molar ratio of ZnSiO3 to Mg2SiO4 is 1:0.5.

[0067] The preparation method of the TFT alkali-free glass substrate of Comparative Example 3 is the same as that of Example 2.

[0068] Perform performance tests on the TFT alkali-free glass substrate prepared in Comparative Example 3: the B2O3 volatilization amount is 5.5 wt.%, and the composition deviation is 0.3 wt.%; the glass network polymerization degree (Q 3 / Q 2 ratio) is 3.5, and the thermal shrinkage rate (500 °C, 2 h) is 14 ppm; in the acid resistance test, soak in a hydrochloric acid solution with pH = 2 for 24 h, and the weight loss rate is 0.18%.

[0069] Comparative Example 4

[0070] The TFT alkali-free glass substrate of Comparative Example 4 comprises the following components in mass percentages: SiO2: 62%, Al2O3: 15%, CaO: 3.7%, SrO: 2.2%, SnO2: 0.7%, ZrP2O7: 2.7%, MgB4O7: 3.2%, B4C: 4%, ZnSiO3 and Mg2SiO4, wherein the sum of the mass percentages of ZnSiO3 and Mg2SiO4 is 6.5%, and the molar ratio of ZnSiO3 to Mg2SiO4 is 1:1.5.

[0071] The preparation method of the TFT alkali-free glass substrate of Comparative Example 4 is the same as that of Example 2.

[0072] Perform performance tests on the TFT alkali-free glass substrate prepared in Comparative Example 4: the B2O3 volatilization amount is 5.3 wt.%, and the composition deviation is 0.28 wt.%; the glass network polymerization degree (Q 3 / Q 2 ratio) is 3.6, and the thermal shrinkage rate (500 °C, 2 h) is 13 ppm; in the acid resistance test, soak in a hydrochloric acid solution with pH = 2 for 24 h, and the weight loss rate is 0.17%.

[0073] Due to the imbalance in the addition ratio of ZnSiO3 and Mg2SiO4 in the composite stabilizer in Comparative Examples 3-4, the ability to synergistically stabilize the glass network structure is reduced, the thermal stability is lowered, the boron volatilization amount increases slightly, and the acid resistance is less affected.

[0074] Comparative Example 5

[0075] The alkali-free glass substrate for TFT of Comparative Example 5 comprises components in the following mass percentages: SiO2: 62%, Al2O3: 15%, CaO: 3.7%, SrO: 2.2%, SnO2: 0.7%, ZrP2O7: 2.7%, MgB4O7: 7.2%, ZnSiO3 and Mg2SiO4, wherein the sum of the mass percentages of ZnSiO3 and Mg2SiO4 is 6.5%, and the molar ratio of ZnSiO3 to Mg2SiO4 is 1:0.9.

[0076] The preparation method of the alkali-free glass substrate for TFT of Comparative Example 5 is the same as that of Example 2.

[0077] Performance tests were carried out on the alkali-free glass substrate for TFT prepared in Comparative Example 5: the B2O3 volatilization amount was 6.5 wt.%, and the composition deviation was 0.35 wt.%; the glass network polymerization degree (Q 3 / Q 2 ratio) was 3.6, and the thermal shrinkage rate (500 °C, 2 h) was 13 ppm; in the acid resistance test, it was immersed in a hydrochloric acid solution with pH = 2 for 24 h, and the weight loss rate was 0.18%.

[0078] B4C was not added in Comparative Example 5, and the gradient boron source system was incomplete. The active boron could not be slowly released by B4C to supplement the boron source at the high temperature stage, resulting in a less uniform distribution of boron elements than in Example 2. Furthermore, the B2O3 volatilization amount increased and the composition deviation increased; at the same time, the optimization effect of the glass network structure weakened, and the thermal stability decreased to some extent, but the impact on acid resistance was relatively small.

[0079] Comparative Example 6

[0080] The alkali-free glass substrate for TFT of Comparative Example 6 comprises components in the following mass percentages: SiO2: 62%, Al2O3: 15%, CaO: 3.7%, SrO: 2.2%, SnO2: 0.7%, ZrP2O7: 2.7%, B4C: 7.2%, ZnSiO3 and Mg2SiO4, wherein the sum of the mass percentages of ZnSiO3 and Mg2SiO4 is 6.5%, and the molar ratio of ZnSiO3 to Mg2SiO4 is 1:0.9.

[0081] The preparation method of the alkali-free glass substrate for TFT of Comparative Example 6 is the same as that of Example 2.

[0082] Performance tests were carried out on the alkali-free glass substrate for TFT prepared in Comparative Example 6: the B2O3 volatilization amount was 6.2 wt.%, and the composition deviation was 0.32 wt.%; the glass network polymerization degree (Q 3 / Q 2The ratio is 3.6, and the thermal shrinkage rate (500 °C, 2 h) is 13 ppm; in the acid resistance test, when immersed in a hydrochloric acid solution with pH = 2 for 24 h, the weight loss rate is 0.18%.

[0083] In Comparative Example 6, MgB4O7 was not added, and there was a lack of stable boron source supplementation during the medium-temperature stage, resulting in uneven release of boron elements, increased volatilization of B2O3, and increased composition deviation; due to insufficient optimization of the glass network structure caused by boron source supply problems, the thermal stability was affected to a certain extent, but the impact on acid resistance was relatively small.

[0084] Comparative Example 7

[0085] The TFT alkali-free glass substrate of Comparative Example 7 comprises the following components in mass percentages: SiO2: 62%, Al2O3: 15%, CaO: 3.7%, SrO: 2.2%, SnO2: 0.7%, ZrP2O7: 2.7%, MgB4O7: 3.2%, B4C: 4% and Mg2SiO4: 6.5%.

[0086] The preparation method of the TFT alkali-free glass substrate of Comparative Example 7 is the same as that of Example 2.

[0087] Perform performance tests on the TFT alkali-free glass substrate prepared in Comparative Example 7: the volatilization amount of B2O3 is 5.2 wt.%, and the composition deviation is 0.27 wt.%; the glass network polymerization degree (Q 3 / Q 2 ratio) is 3.6, and the thermal shrinkage rate (500 °C, 2 h) is 16 ppm; in the acid resistance test, when immersed in a hydrochloric acid solution with pH = 2 for 24 h, the weight loss rate is 0.18%.

[0088] Comparative Example 8

[0089] The TFT alkali-free glass substrate of Comparative Example 8 comprises the following components in mass percentages: SiO2: 62%, Al2O3: 15%, CaO: 3.7%, SrO: 2.2%, SnO2: 0.7%, ZrP2O7: 2.7%, MgB4O7: 3.2%, B4C: 4% and ZnSiO3: 6.5%.

[0090] The preparation method of the TFT alkali-free glass substrate of Comparative Example 8 is the same as that of Example 2.

[0091] Perform performance tests on the TFT alkali-free glass substrate prepared in Comparative Example 8: the volatilization amount of B2O3 is 5.2 wt.%, and the composition deviation is 0.27 wt.%; the glass network polymerization degree (Q 3 / Q 2 ratio) is 3.6, and the thermal shrinkage rate (500 °C, 2 h) is 17 ppm; in the acid resistance test, when immersed in a hydrochloric acid solution with pH = 2 for 24 h, the weight loss rate is 0.18%.

[0092] In Comparative Examples 7-8, ZnSiO3 or Mg2SiO4 was not added, the synergistic effect of the composite stabilizer was destroyed, the stability of the glass network structure decreased, the thermal vibration activity of the boron oxygen triangle (BO3) could not be effectively inhibited, the thermal stability decreased, and the thermal shrinkage rate increased; the boron volatilization amount and acid resistance were also affected to a certain extent, but the change was relatively small.

[0093] In summary, in the gradient boron source system of the present invention, MgB4O7 and B4C nanoparticles release boron elements in stages, effectively controlling boron volatilization and ensuring stable composition; the synergistic effect of ZnSiO3 and Mg2SiO4 in the composite stabilizer enhances the density of the glass network and improves the thermal stability; ZrP2O7 improves the acid resistance of the glass.

Claims

1. The acid-resistant and alkali-free glass substrate for TFT, characterized in that, It comprises components with the following mass percentages: SiO2: 56 - 65%, Al2O3: 14 - 16%, CaO: 3 - 4%, SrO: 1.5 - 2.5%, SnO2: 0.5 - 0.8%, ZrP2O7: 2 - 3.5%, MgB4O7, B4C, ZnSiO3 and Mg2SiO4. Among them, the sum of the mass percentages of MgB4O7 and B4C is 6.8 - 8%, and the mass ratio of MgB4O7 to B4C is (0.5 - 1.2):1; the sum of the mass percentages of ZnSiO3 and Mg2SiO4 is 5 - 7%, and the molar ratio of ZnSiO3 to Mg2SiO4 is 1:(0.8 - 1.2).

2. The preparation method of the acid-resistant and alkali-free TFT glass substrate according to claim 1, characterized in that, It comprises the following steps: S1 Raw material pretreatment: Grind all raw materials so that their particle sizes are less than 100 μm; S2 Melting and clarification: Add the ground raw materials into an electric melting furnace, first melt at 1400 - 1450 °C for 2 - 3 h, then raise the temperature to 1550 - 1600 °C and keep it warm for 1 - 1.5 h to promote the homogenization and clarification of the glass melt; S3 Forming: The clarified glass melt flows into an overflow tank. The temperature of the overflow tank is 1100 - 1150 °C. The glass melt overflows evenly on both sides of the overflow tank, flows downward along the overflow bricks and converges at the bottom, and is formed by being pulled down by a pulling device. During the pulling process, a protective gas is introduced into the overflow tank and the forming area; S4 Annealing: The formed glass substrate enters an annealing furnace. The annealing temperature is 650 - 700 °C, and the annealing time is 3 - 5 h.

3. The preparation method of the acid-resistant alkali-free glass substrate for TFT according to claim 2, characterized in that, In step S1, a ball mill is used to grind the raw materials, and the grinding time is 4 - 6 h.

4. The preparation method of the acid-resistant and alkali-free TFT glass substrate according to claim 2, characterized in that, In step S2, the current density is controlled by the electrode to be 5 - 8 A / cm 2 .

5. The preparation method of the acid-resistant and alkali-free TFT glass substrate according to claim 4, characterized in that, The electrode uses a graphite electrode.

6. The preparation method of the acid-resistant and alkali-free glass substrate for TFT according to claim 2, wherein In step S3, the pulling speed of the pulling device for forming is 0.5 - 0.8 m / min.

7. The preparation method of the TFT acid-resistant alkali-free glass substrate according to claim 2, characterized in that, In step S3, the thickness of the formed glass is 0.5 - 1 mm.

8. The preparation method of the acid-resistant and alkali-free TFT glass substrate according to claim 2, characterized in that In step S3, the protective gas is a mixed gas of N2 and H2, and the volume percentage of H2 is 3 - 5%.

9. The preparation method of the acid-resistant and alkali-free TFT glass substrate according to claim 2, wherein, In step S4, during the annealing process, the temperature is decreased at a rate of 1 - 2 °C / min.