Alkali-free glass substrate for surface nanocrystallization TFT (Thin Film Transistor) and preparation method thereof

Abstract

The invention discloses an alkali-free glass substrate for a surface nanocrystallization TFT (thin film transistor) and a preparation method of the alkali-free glass substrate, the surface nanocrystallization of the glass substrate is induced by a specific ion beam, the grain size of surface microcrystals can be accurately controlled to be less than 50nm, and the performance of the surface of the alkali-free glass substrate is improved; through a magnetic field assisted heat treatment process, directional migration of internal atoms is promoted, and uniform distribution of internal nanocrystals is realized, so that the overall performance of the alkali-free glass substrate, such as mechanical strength and heat stability, is improved. Finally, according to the preparation method of the alkali-free glass substrate for the surface nanocrystallization TFT, the mechanical strength, the thermal stability, the chemical stability, the optical performance, the coating bonding strength and the like of the alkali-free glass substrate are greatly improved.

Description

Technical Field

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

[0002] TFT (Thin Film Transistor) display technology, as one of the cores in the modern display field, has been widely applied in multiple fields such as liquid crystal displays (LCDs) and organic light-emitting diode displays (OLEDs). Its advantages of high response speed, high contrast ratio, wide viewing angle, etc. provide excellent visual experiences for various display devices.

[0003] In TFT display technology, the alkali-free glass substrate plays a crucial role. As an important carrier of TFT, the performance of the alkali-free glass substrate directly determines the display quality and production efficiency of TFT. A high-quality alkali-free glass substrate can ensure the stability and reliability of the TFT circuit, thereby improving the performance of the entire display.

[0004] However, after forming, traditional alkali-free glass substrates often face a series of problems:

[0005] 1) Uneven internal stress distribution: leading to easy deformation of the substrate and affecting the display accuracy.

[0006] 2) Poor film layer adhesion: making the TFT circuit layer easy to peel off and reducing the service life of the display.

[0007] 3) Low bending strength: easily causing the substrate to crack and increasing the loss in production.

[0008] 4) Poor acid corrosion resistance: being easily corroded during subsequent processing and affecting the product quality.

[0009] These problems severely limit the further development of TFT display technology and become difficult problems that the industry urgently needs to solve. Summary of the Invention

[0010] The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art and provide an alkali-free glass substrate for surface nanocrystallization TFT and a preparation method thereof, which greatly improve the performance of the alkali-free glass substrate in terms of mechanical strength, thermal stability, chemical stability, optical properties, coating bonding strength, etc.

[0011] The technical solution of the present invention is as follows:

[0012] On the one hand, the present invention provides a method for preparing an alkali-free glass substrate for surface nanocrystallized TFT. The alkali-free glass substrate for surface nanocrystallized TFT comprises the following components in mass percentage: SiO2 55-65%, Al2O3 12-18%, B2O3 8-12%, MgO 3-7%, CaO 2-6%, SnO2 0.1-0.5%, SrO 1-3%, ZrO2 0.5-2%, TiO2 0.1-1%; the method for preparing the alkali-free glass substrate for surface nanocrystallized TFT comprises the following steps:

[0013] S1 Glass substrate forming: After fully mixing each component, melting and forming are carried out to make an alkali-free glass substrate;

[0014] S2 Ion beam-induced surface nanocrystallization: Using a focused ion beam or a broad beam ion source to scan and bombard the surface of the alkali-free glass substrate;

[0015] S3 Magnetic field-assisted heat treatment: Placing the alkali-free glass substrate treated in step S2 in a magnetic field and keeping it warm, then the alkali-free glass substrate for surface nanocrystallized TFT is obtained.

[0016] In the alkali-free glass substrate for surface nanocrystallized TFT of the present invention, SiO2 is the framework component of the glass, providing the basic structure and chemical stability of the glass; Al2O3 can improve the mechanical strength and chemical stability of the glass, and at the same time reduce the thermal expansion coefficient of the glass; B2O3 helps to reduce the melting temperature of the glass and improve the thermal stability of the glass; alkaline earth metal oxides such as MgO, CaO, SrO can adjust the physical properties of the glass, such as density, thermal expansion coefficient, etc.; SnO2 is used as a glass melt clarifier to accelerate the clarification of the glass melt; ZrO2 and TiO2 are used as nucleating agents to promote the formation of subsequent nanocrystals.

[0017] The action of the mixed ion beam on the glass surface: In the mixed ion beam, the argon ion has a relatively large mass. When bombarding the glass surface, it can collide violently with the glass atoms by virtue of its large momentum. This collision will enable the glass surface atoms to obtain sufficient energy to leave their original lattice positions, thus generating a large number of lattice defects. These lattice defects provide rich potential sites for the formation of subsequent crystal nuclei. The helium ion has a small radius and high activity, and can quickly penetrate the glass surface layer in the ion beam and penetrate into the glass interior to a certain depth. Due to its high activity, the helium ion can interact with the atoms in the glass, break some of the chemical bonds between atoms, promote the diffusion movement of atoms, and make it easier for atoms to migrate and rearrange inside the glass.

[0018] The roles of ZrO2 and TiO2 as nucleating agents: ZrO2 and TiO2 act as nucleating agents in the glass. In the microstructure of the glass, ZrO2 and TiO2 exist in the form of tiny particles or ionic clusters in the glass, which can reduce the nucleation barrier. From the perspective of crystal structure, their atomic arrangement is different from the disordered structure of the glass matrix and has a certain regularity. This regularity makes it easier for the glass atoms around them to aggregate in a specific arrangement, thereby reducing the energy required to form nuclei. Taking ZrO2 as an example, the lattice framework formed by oxygen ions and zirconium ions in its crystal structure provides an arrangement pattern for other ions in the glass to "imitate". When glass atoms aggregate around ZrO2, it is easier to overcome the energy barrier of nucleation, making it easier for nuclei to form and greatly increasing the probability of nucleation.

[0019] Ionic radius matching and lattice distortion: Zr 4+ and Ti 4+ The ionic radii of Zr and Ti are different from those of some main ions in the glass network. In the glass system, this difference in ionic radius will cause local lattice distortion. When ZrO2 and TiO2 are added to the glass, Zr 4+ and Ti 4+ enter the glass network. Due to the mismatch of their ionic radii with the surrounding ions, the surrounding glass network structure will be distorted and deformed. This lattice distortion increases the local energy of the glass system, making the glass atoms more inclined to rearrange to form a more stable structure, that is, nuclei. At the same time, the lattice distortion area also provides more channels for atomic diffusion, which is conducive to the migration and aggregation of atoms, further promoting the formation and growth of nuclei.

[0020] Changing the local chemical environment of the glass: ZrO2 and TiO2 have high chemical activity and will interact with the surrounding glass components in the glass, changing the local chemical environment. For example, the oxygen ions in ZrO2 and TiO2 can form chemical bonds with other cations in the glass network, thereby changing the chemical bond energy and the interaction between atoms in the local area. This change in the chemical environment makes the glass atoms near ZrO2 and TiO2 have different energy states, and the activity of some atoms is enhanced, making it easier to aggregate to form nuclei. Moreover, this change in the local chemical environment can also affect the diffusion rate and direction of atoms, making it easier for atoms to diffuse to the areas favorable for nucleation, promoting the growth of nanocrystals.

[0021] Synergistic Promotion of Nucleation by Mixed Ion Beams and Nucleating Agents: When a mixed ion beam acts on a glass containing ZrO2 and TiO2, a synergistic effect occurs between the two. The large number of lattice defects generated by argon ions provide more attachment sites for the nuclei induced by ZrO2 and TiO2. The nuclei induced by ZrO2 and TiO2 can preferentially grow at these lattice defects because the atomic arrangement at the lattice defects is irregular and has higher energy, which is more conducive to the stable formation of nuclei. At the same time, the atomic diffusion promoted by helium ions enables the atoms in the glass to migrate more rapidly around the nuclei induced by ZrO2 and TiO2, accelerating the growth process of the nuclei. Under this synergistic effect, the number of formed nuclei increases significantly and the distribution becomes more uniform.

[0022] Strengthening Effect of Magnetic Field on the Synergistic Process: After ion beam treatment, magnetic field-assisted treatment is carried out. The presence of the magnetic field will generate a Lorentz force on the charged particles in the glass (such as ions generated by ion beam treatment, some ionized atoms in the glass, etc.). Under the action of the Lorentz force, these charged particles will move along a specific direction, thereby driving the surrounding atoms to move together. This causes the atomic arrangement of the nanocrystals induced by ZrO2 and TiO2 to be affected by the magnetic field during the growth process and gradually align along the magnetic field direction. This alignment method makes the orientation of the nanocrystals more consistent and the distribution more uniform. The magnetic field can also inhibit the abnormal growth of nanocrystals during the growth process, ensure the consistency of the nanocrystal size, and further optimize the structure of the nanocrystals. Through the action of the magnetic field, the structure of the nanocrystals formed by the synergism of the mixed ion beam and ZrO2 and TiO2 is further strengthened, thereby significantly improving the mechanical strength, thermal stability and other properties of the glass substrate.

[0023] Preferably, in step S1, the melting temperature is 1500 - 1650 °C and the time is 4 - 8 h.

[0024] Preferably, in step S1, overflow down-draw method or float method is used for forming.

[0025] Preferably, in step S1, the thickness of the produced alkali-free glass substrate is 0.3 - 0.8 mm.

[0026] Preferably, in step S2, a mixed ion beam of argon ions and helium ions is used to scan and bombard the surface of the alkali-free glass substrate. The ion energy is 50 - 150 keV, the beam current density is 0.2 - 0.8 mA / cm 2 , the scanning speed is 15 - 40 mm / s, and the treatment depth is 150 - 350 nm.

[0027] Preferably, the molar ratio of argon ions to helium ions is (2 - 3):1.

[0028] Preferably, in step S3, the magnetic field strength is 0.3 - 0.7 T, and the magnetic field direction is alternately changed at 0.5 Hz.

[0029] Preferably, in step S3, the heat preservation temperature is 600 - 650 °C, and the heat preservation time is 2 - 4 h.

[0030] On the other hand, the present invention provides an alkali-free glass substrate for surface nanocrystallized TFT prepared by the above preparation method.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The preparation method of the alkali-free glass substrate for surface nanocrystallized TFT of the present invention can precisely control the grain size of the surface microcrystals <50 nm by inducing surface nanocrystallization of the glass substrate through a specific ion beam, improving the surface performance of the alkali-free glass substrate; through the magnetic field-assisted heat treatment process, it promotes the directional migration of internal atoms and realizes the uniform distribution of internal nanocrystals, thereby improving the overall performance of the alkali-free glass substrate, such as mechanical strength, thermal stability, etc. Finally, the preparation method of the alkali-free glass substrate for surface nanocrystallized TFT of the present invention greatly improves the performance of the alkali-free glass substrate in terms of mechanical strength, thermal stability, chemical stability, optical properties, coating bonding strength, etc.

[0033] 2. The preparation method of the alkali-free glass substrate for surface nanocrystallized TFT of the present invention is improved on the basis of the existing glass forming process, does not require complex equipment and processes, and has good operability and industrial application prospects. Detailed Embodiments

[0034] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0035] Example 1

[0036] The alkali-free glass substrate for surface nanocrystallized TFT in this example comprises the following components in mass percentages: SiO2 55%, Al2O3 18%, B2O3 12%, MgO 7%, CaO 4%, SnO2 0.5%, SrO 1%, ZrO2 2%, TiO2 0.5%.

[0037] The preparation method of the alkali-free glass substrate for surface nanocrystallized TFT in this example comprises the following steps:

[0038] S1 Glass Substrate Forming: Place the raw materials in a high-speed blender and mix them thoroughly at a rotation speed of 1500 r / min for 30 min to ensure uniform mixing. Subsequently, put the mixed raw materials into a high-temperature furnace at 1550 °C and melt them for 6 h. After the raw materials are completely melted, use the overflow down-draw method to form an alkali-free glass substrate with a thickness of 0.5 mm.

[0039] S2 Ion Beam Induced Surface Nanocrystallization: Select a focused ion beam, and the ion source is a mixed ion beam of argon ions and helium ions with a molar ratio of 2:1. Set the ion energy to 100 keV and the beam current density to 0.5 mA / cm 2 , and the scanning speed is 25 mm / s. Scan and bombard the surface of the glass substrate, and control the processing depth within 250 nm.

[0040] S3 Magnetic Field Assisted Heat Treatment: Place the alkali-free glass substrate processed in step S2 in a magnetic field environment with a magnetic field strength of 0.5 T, where the magnetic field direction is perpendicular to the ion beam scanning direction, and alternately change the magnetic field direction at a frequency of 0.5 Hz. Keep it at a temperature of 620 °C for 3 h to obtain an alkali-free glass substrate for surface nanocrystallized TFT.

[0041] Perform performance tests on the alkali-free glass substrate for surface nanocrystallized TFT prepared in this example, and the test results are as follows:

[0042] Grain Size and Distribution: Observed by transmission electron microscope (TEM), the grain size of the surface microcrystalline layer is between 35 - 40 nm, the average size of the internal nanocrystals is 20 nm, and the size deviation is within the range of ±5 nm.

[0043] Thermal Stability: The strain point reaches 680 °C, and the thermal expansion coefficient is 3.8×10 -6 / °C.

[0044] Mechanical Strength: Through the three-point bending strength test, the result is 190 MPa.

[0045] Surface Hardness: The Vickers hardness of the microcrystalline layer is measured to be 700 HV.

[0046] Chemical Stability: Immerse the glass substrate in a HCl solution with pH = 1 for 24 h, and the mass loss rate is 0.05%; test it in a high-temperature and high-humidity (85 °C / 85% RH) environment, and the surface precipitation of Na + concentration decreases by 80%.

[0047] Optical Properties: The transmittance in the visible light band (400 - 700 nm) is 92%, and the absorption rate of ultraviolet light (<300 nm) is above 95%.

[0048] Coating bonding strength: During the subsequent ITO film coating process, taking the film layer bonding strength of Comparative Example 9 as the reference value, the film layer bonding strength of Example 1 was increased by 35%.

[0049] Example 2

[0050] The alkali-free glass substrate for surface nanocrystallized TFT in this example comprises the following components in mass percentage: SiO2 60%, Al2O3 16%, B2O3 10%, MgO 5%, CaO 4%, SnO2 0.5%, SrO 2%, ZrO2 1.5%, TiO2 1%.

[0051] The preparation method of the alkali-free glass substrate for surface nanocrystallized TFT in this example comprises the following steps:

[0052] S1 Glass substrate forming: Place the raw materials in a high-speed mixer, mix them thoroughly at a rotation speed of 1500 r / min for 45 min to ensure uniform mixing; subsequently, put the mixed raw materials into a high-temperature furnace at 1600 °C and melt for 5 h; after the raw materials are completely melted, use the float method to form an alkali-free glass substrate with a thickness of 0.6 mm;

[0053] S2 Ion beam-induced surface nanocrystallization: Select a focused ion beam, the ion source is a mixed ion beam of argon ions and helium ions with a molar ratio of 2.5:1, set the ion energy to 120 keV, the beam current density to 0.6 mA / cm 2 , the scanning speed to 30 mm / s, scan and bombard the surface of the glass substrate, and control the treatment depth within 300 nm;

[0054] S3 Magnetic field-assisted heat treatment: Place the alkali-free glass substrate treated in step S2 in a magnetic field environment with a magnetic field strength of 0.6 T, the magnetic field direction is perpendicular to the ion beam scanning direction, and alternately change the magnetic field direction at a frequency of 0.5 Hz; keep it at a temperature of 630 °C for 3.5 h to obtain the alkali-free glass substrate for surface nanocrystallized TFT.

[0055] Perform performance tests on the alkali-free glass substrate for surface nanocrystallized TFT prepared in this example, and the test results are as follows:

[0056] Grain size and distribution: Observed by transmission electron microscope (TEM), the grain size of the surface microcrystalline layer is between 38 - 42 nm, the average size of the internal nanocrystals is 22 nm, and the size deviation is within ±5 nm.

[0057] Thermal stability: The strain point reaches 685 °C, and the thermal expansion coefficient is 3.7×10 -6 / °C.

[0058] Mechanical strength: Through the three-point bending strength test, the result is 195 MPa.

[0059] Surface hardness: The Vickers hardness of the microcrystalline layer is measured to be 750 HV.

[0060] Chemical stability: The glass substrate is immersed in an HCl solution with pH = 1 for 24 h, and the mass loss rate is 0.04%; tested in a high-temperature and high-humidity (85 °C / 85% RH) environment, the surface precipitation of Na + The concentration decreases by 85%.

[0061] Optical properties: The light transmittance in the visible light band (400 - 700 nm) is 93%, and the absorption rate of ultraviolet light (< 300 nm) is above 96%.

[0062] Coating bonding strength: In the subsequent process of depositing ITO film, taking the film layer bonding strength of Comparative Example 9 as the reference value, the film layer bonding strength of Example 2 is increased by 40%.

[0063] Example 3

[0064] The alkali-free glass substrate for surface-nanocrystallized TFT in this example comprises the following components in mass percentages: SiO2 65%, Al2O3 12%, B2O3 9%, MgO 3%, CaO 6%, SnO2 0.1%, SrO 3%, ZrO2 1%, TiO2 0.9%.

[0065] The preparation method of the alkali-free glass substrate for surface-nanocrystallized TFT in this example comprises the following steps:

[0066] S1 Glass substrate forming: The raw materials are placed in a high-speed mixer and fully mixed at a rotation speed of 1500 r / min for 60 min to ensure uniform mixing; subsequently, the mixed raw materials are put into a high-temperature furnace at 1650 °C and melted for 4 h; after the raw materials are completely melted, they are formed by the overflow down-draw method to make an alkali-free glass substrate with a thickness of 0.7 mm;

[0067] S2 Ion beam-induced surface nanocrystallization: A focused ion beam is selected, and the ion source is a mixed ion beam of argon ions and helium ions with a molar ratio of 3:1. The ion energy is set to 150 keV, the beam current density is 0.8 mA / cm 2 , and the scanning speed is 40 mm / s. The surface of the glass substrate is scanned and bombarded, and the treatment depth is controlled within 350 nm;

[0068] S3 Magnetic field-assisted heat treatment: The alkali-free glass substrate treated in step S2 is placed in a magnetic field environment with a magnetic field strength of 0.7 T, the magnetic field direction is perpendicular to the ion beam scanning direction, and the magnetic field direction is alternately changed at a frequency of 0.5 Hz; it is kept warm at a temperature of 650 °C for 4 h to obtain the alkali-free glass substrate for surface-nanocrystallized TFT.

[0069] The performance of the alkali-free glass substrate for surface nanocrystallized TFT prepared in this embodiment was tested, and the test results are as follows:

[0070] Grain size and distribution: Observed by transmission electron microscope (TEM), the grain size of the surface microcrystalline layer is between 40 - 45 nm, the average size of the internal nanocrystals is 25 nm, and the size deviation is within the range of ±5 nm.

[0071] Thermal stability: The strain point reaches 690 °C, and the coefficient of thermal expansion is 3.6×10 -6 / °C.

[0072] Mechanical strength: Through the three-point bending strength test, the result is 200 MPa.

[0073] Surface hardness: The Vickers hardness of the microcrystalline layer is measured to be 800 HV.

[0074] Chemical stability: The glass substrate was immersed in HCl solution with pH = 1 for 24 h, and the mass loss rate was 0.03%; tested in a high-temperature and high-humidity (85 °C / 85% RH) environment, the surface precipitation of Na + concentration decreased by 90%.

[0075] Optical properties: The light transmittance in the visible light band (400 - 700 nm) is 93%, and the absorption rate of ultraviolet light (<300 nm) is above 97%.

[0076] Film coating bonding strength: In the subsequent process of coating ITO film, taking the film layer bonding strength of Comparative Example 9 as the reference value, the film layer bonding strength of Example 3 increased by 45%.

[0077] Comparative Example 1

[0078] The difference from Example 1 is that Comparative Example 1 does not perform Step S2 and Step S3.

[0079] The performance of the alkali-free glass substrate prepared in Comparative Example 1 was tested, and the test results are as follows:

[0080] Grain size and distribution: Observed by transmission electron microscope (TEM), there are no obvious nanocrystals inside the glass, and the grain size is in the thick state of traditional glass.

[0081] Thermal stability: The strain point reaches 650 °C, and the coefficient of thermal expansion is 4×10 -6 / °C.

[0082] Mechanical strength: Through the three-point bending strength test, the result is 130 MPa.

[0083] Surface hardness: The Vickers hardness of the microcrystalline layer is measured to be 500 HV.

[0084] Chemical stability: The glass substrate was immersed in a HCl solution with pH = 1 for 24 h, and the mass loss rate was 0.2%; tested in a high temperature and high humidity (85 °C / 85% RH) environment, Na was precipitated on the surface. + The concentration did not decrease significantly.

[0085] Optical properties: The light transmittance in the visible light band (400 - 700 nm) was 90%, and the absorption rate of ultraviolet light (<300 nm) was 26%.

[0086] Coating bonding strength: During the subsequent ITO film coating process, the film layer bonding strength was comparable to the reference value of Comparative Example 9.

[0087] In Comparative Example 1, since ion beam-induced surface nanocrystallization was not carried out, no nanocrystals were formed on the glass surface and inside, and nucleating agents such as ZrO2 and TiO2 could not play an effective role, and the microstructure of the glass was not optimized. At the same time, Comparative Example 1 did not perform magnetic field-assisted heat treatment, which could not promote the directional migration of atoms and the arrangement of nanocrystals, resulting in poor performance of the glass substrate in terms of mechanical strength, thermal stability, chemical stability, optical properties, and coating bonding strength.

[0088] Comparative Example 2

[0089] The difference from Example 1 is that Comparative Example 1 does not perform step S3.

[0090] Performance tests were carried out on the alkali-free glass substrate for surface nanocrystallized TFT prepared in Comparative Example 2, and the test results are as follows:

[0091] Grain size and distribution: Observed by transmission electron microscopy (TEM), the grain size of the surface microcrystalline layer was between 35 - 40 nm, but the internal nanocrystals were unevenly distributed and the size deviation was large.

[0092] Thermal stability: The strain point reached 660 °C, and the thermal expansion coefficient was 3.9×10 -6 / °C.

[0093] Mechanical strength: Through the three-point bending strength test, the result was 160 MPa.

[0094] Surface hardness: The Vickers hardness of the microcrystalline layer was measured to be 600 HV.

[0095] Chemical stability: The glass substrate was immersed in a HCl solution with pH = 1 for 24 h, and the mass loss rate was 0.1%; tested in a high temperature and high humidity (85 °C / 85% RH) environment, the Na + concentration decreased by 53%.

[0096] Optical properties: The light transmittance in the visible light band (400 - 700 nm) is 90%, and the absorption rate of ultraviolet light (<300 nm) is 87%.

[0097] Coating bonding strength: During the subsequent ITO film coating process, taking the film layer bonding strength of Comparative Example 9 as the reference value, the film layer bonding strength of Comparative Example 2 was increased by 20%.

[0098] In Comparative Example 2, ion beam-induced surface nanocrystallization formed nanocrystals on the glass surface, improving some properties. However, due to the lack of magnetic field-assisted heat treatment, there was no driving force for the directional arrangement of nanocrystals during growth, resulting in uneven distribution of internal nanocrystals and affecting the improvement of the overall performance of the glass substrate. The absence of a magnetic field prevented the directional movement of charged particles and ions, unable to effectively promote the uniform distribution and consistent orientation of nanocrystals, so the improvement effects in terms of mechanical strength, thermal stability, chemical stability, and coating bonding strength were not as good as those of the examples.

[0099] Comparative Example 3

[0100] The difference from Example 1 is that Comparative Example 1 does not perform step S2.

[0101] Performance tests were carried out on the alkali-free glass substrate with surface nanocrystallization for TFT prepared in Comparative Example 3, and the test results are as follows:

[0102] Grain size and distribution: Observation by transmission electron microscopy (TEM) found that no obvious nanocrystals were formed inside and on the surface of the glass, and the grain size was similar to that of traditional glass.

[0103] Thermal stability: The strain point reached 653 °C, and the thermal expansion coefficient was 3.95×10 -6 / °C.

[0104] Mechanical strength: Through the three-point bending strength test, the result was 137 MPa.

[0105] Surface hardness: The Vickers hardness of the microcrystalline layer was measured to be 503 HV.

[0106] Chemical stability: The glass substrate was immersed in a HCl solution with pH = 1 for 24 h, and the mass loss rate was 0.19%; tested in a high-temperature and high-humidity (85 °C / 85% RH) environment, the surface precipitation of Na + concentration did not decrease significantly.

[0107] Optical properties: The light transmittance in the visible light band (400 - 700 nm) is 90.5%, and the absorption rate of ultraviolet light (<300 nm) is 15%.

[0108] Coating bonding strength: During the subsequent ITO film coating process, the film layer bonding strength was equivalent to the reference value of Comparative Example 9.

[0109] In Comparative Example 3, only magnetic field-assisted heat treatment was carried out, and no lattice defects were induced by ion beams and atomic diffusion was promoted. Nucleating agents such as ZrO2 and TiO2 were difficult to play a role, and a large number of nanocrystals could not be formed. Although the magnetic field could have a certain influence on the ions in the glass, the lack of the basis for nanocrystal formation led to a very limited improvement effect on the performance of the glass substrate, far lower than that of the glass substrate in the examples that had been subjected to ion beam-induced surface nanocrystallization and magnetic field-assisted heat treatment.

[0110] Comparative Example 4

[0111] The alkali-free glass substrate of Comparative Example 4 comprises the following components in mass percentage: 54% of SiO2, 18% of Al2O3, 12% of B2O3, 7% of MgO, 4% of CaO, 0.5% of SnO2, 1% of SrO, 3% of ZrO2, and 0.5% of TiO2.

[0112] Performance tests were carried out on the alkali-free glass substrate for surface nanocrystallized TFT prepared in Comparative Example 4, and the test results are as follows:

[0113] Grain size and distribution: Observed by transmission electron microscope (TEM), the grain size of the surface microcrystalline layer is between 40 - 45 nm, the average size of the internal nanocrystals is 30 nm, and the size deviation is within the range of ±8 nm.

[0114] Thermal stability: The strain point reaches 670 °C, and the coefficient of thermal expansion is 3.85×10 -6 / °C.

[0115] Mechanical strength: Tested by three-point bending strength, the result is 170 MPa.

[0116] Surface hardness: The Vickers hardness of the microcrystalline layer is measured to be 650 HV.

[0117] Chemical stability: The glass substrate was immersed in an HCl solution with pH = 1 for 24 h, and the mass loss rate was 0.08%; tested in a high-temperature and high-humidity (85 °C / 85% RH) environment, the surface precipitation of Na + The concentration decreased by 70%.

[0118] Optical properties: The light transmittance in the visible light band (400 - 700 nm) is 91%, and the absorption rate for ultraviolet light (<300 nm) is 94%.

[0119] Film coating bonding strength: In the process of subsequent ITO film coating, taking the film coating bonding strength of Comparative Example 9 as the reference value, the film coating bonding strength of Comparative Example 4 was increased by 25%.

[0120] In comparative example 4, excessive addition of ZrO2 will result in an excessive number of crystal nuclei in the glass and uneven distribution, and the crystal nuclei in local areas are too dense, which is easy to agglomerate during the growth of the crystal nuclei, destroying the uniformity of the glass structure; although the probability of crystal nuclei formation may be increased to a certain extent, too much crystal nuclei compete for resources, which deteriorates the growth environment of nanocrystals and affects their normal development. At the same time, the lattice distortion caused by excessive ZrO2 is too serious, which increases the stress concentration inside the glass, making the glass more prone to crack expansion and other problems when used for a long time or subjected to external effects, thereby affecting the comprehensive performance of the glass.

[0121] Comparative Example 5

[0122] The alkali-free glass substrate of Comparative Example 5 includes the following components in mass percentage: SiO2 54%, Al2O3 18%, B2O3 12%, MgO 7%, CaO 4%, SnO2 0.5%, SrO 1%, ZrO2 2%, and TiO2 1.5%.

[0123] The performance of the alkali-free glass substrate for the surface nanocrystallized TFT prepared in Comparative Example 5 was tested, and the test results are as follows:

[0124] Grain size and distribution: Using transmission electron microscopy (TEM) observation, the grain size of the surface microcrystalline layer is between 42-52nm, the average size of the internal nanocrystals is 28nm, and the size deviation is within the range of ±7nm.

[0125] Thermal stability: strain point reaches 675℃, thermal expansion coefficient is 3.82×10 -6 / ℃.

[0126] Mechanical strength: Passed the three-point bending strength test, the result is 175MPa.

[0127] Surface hardness: The Vickers hardness of the microcrystalline layer was measured to be 680HV.

[0128] Chemical stability: The glass substrate was immersed in a pH = 1 HCl solution for 24 hours, and the mass loss rate was 0.07%; under high temperature and high humidity (85℃ / 85%RH) environment, Na + Concentration reduced by 75%.

[0129] Optical properties: The transmittance in the visible light band (400-700nm) is 91.5%, and the absorption rate of ultraviolet light (<300nm) is 95%.

[0130] Coating bonding strength: In the subsequent ITO film coating process, the film bonding strength of Comparative Example 9 was used as a reference value, and the film bonding strength of Comparative Example 5 was increased by 30%.

[0131] In Comparative Example 5, excessive addition of TiO2 would cause abnormalities in the process of crystal nucleus formation and growth inside the glass. The excessive TiO2 provided a large number of crystal nucleus formation sites, resulting in a sharp increase in the number of crystal nuclei. During the growth process, the mutual competition and interference among the crystal grains intensified, making it difficult to form a uniform and dense nanocrystalline structure. At the same time, the interaction between TiO2 and other components in the glass was enhanced, changing the local chemical environment and chemical bond state of the glass, increasing the internal stress of the glass, and thus reducing the comprehensive performance of the glass. For example, in terms of optics, excessive TiO2 might lead to an increase in light scattering, affecting the light transmission uniformity of the glass; in terms of mechanical properties, the increase in internal stress made the glass more likely to break when stressed.

[0132] Comparative Example 6

[0133] The alkali-free glass substrate of Comparative Example 6 comprises the following components in mass percentages: SiO2 57.5%, Al2O3 18%, B2O3 12%, MgO 7%, CaO 4%, SnO2 0.5%, SrO 1%.

[0134] Performance tests were carried out on the alkali-free glass substrate for surface nanocrystallization TFT prepared in Comparative Example 6, and the test results are as follows:

[0135] Grain size and distribution: Observed by transmission electron microscope (TEM), the grain size of the surface microcrystalline layer is in the traditional glass state (no obvious nanocrystals), the average size of the internal nanocrystals is none (nanocrystals are not formed), and the size deviation is none.

[0136] Thermal stability: The strain point reaches 655 °C, and the thermal expansion coefficient is 4.1×10 -6 / °C.

[0137] Mechanical strength: Tested by three-point bending strength, the result is 125 MPa.

[0138] Surface hardness: The Vickers hardness of the microcrystalline layer, measured to be 480 HV.

[0139] Chemical stability: The glass substrate was immersed in HCl solution with pH = 1 for 24 h, and the mass loss rate was 0.25%; tested in a high-temperature and high-humidity (85 °C / 85% RH) environment, the surface precipitation of Na + The concentration did not decrease significantly.

[0140] Optical properties: The light transmittance in the visible light band (400 - 700 nm) is 88%, and the absorption rate for ultraviolet light (<300 nm) is 20%.

[0141] Coating adhesion strength: During the subsequent ITO coating process, the coating adhesion strength is comparable to the reference value in Comparative Example 9. The coating adhesion strength cannot be improved. The absence of the nanocrystalline structure results in a lack of good binding sites and interactions between the glass surface and the coating, making it impossible to enhance the coating adhesion.

[0142] TiO2 and ZrO2, as nucleating agents, play a key role in the glass nanocrystallization process. In Comparative Example 6, the absence of these two components makes it impossible to effectively form nanocrystalline nuclei during the ion beam treatment and heat treatment of the glass, and thus the strengthening of the glass properties by nanocrystallization cannot be achieved. The interior of the glass maintains the traditional disordered structure, without the effects of dispersion strengthening and grain refinement of nanocrystals, resulting in no improvement or even a significant decrease in the thermal stability, mechanical strength, chemical stability, optical properties, and coating adhesion strength of the glass.

[0143] Comparative Example 7

[0144] The alkali-free glass substrate of Comparative Example 7 comprises the following components in mass percentages: SiO2 55.5%, Al2O3 18%, B2O3 12%, MgO 7%, CaO 4%, SnO2 0.5%, SrO 1%, ZrO2 2%.

[0145] Performance tests were carried out on the alkali-free glass substrate for surface nanocrystallized TFT prepared in Comparative Example 7, and the test results are as follows:

[0146] Grain size and distribution: Observed by transmission electron microscope (TEM), the grain size of the surface microcrystalline layer is between 45 - 50 nm, and the average size of the internal nanocrystals is 24 nm, with a size deviation within the range of ±6 nm.

[0147] Thermal stability: The strain point reaches 665 °C, and the thermal expansion coefficient is 3.9×10 -6 / °C.

[0148] Mechanical strength: Tested by three-point bending strength, the result is 150 MPa.

[0149] Surface hardness: The Vickers hardness of the microcrystalline layer is measured to be 580 HV.

[0150] Chemical stability: The glass substrate is immersed in HCl solution with pH = 1 for 24 h, and the mass loss rate is 0.12%; tested in a high-temperature and high-humidity (85 °C / 85% RH) environment, the surface precipitation of Na + concentration decreases by 60%.

[0151] Optical properties: The light transmittance in the visible light band (400 - 700 nm) is 90%, and the absorption rate of ultraviolet light (<300 nm) is 90%.

[0152] Coating bonding strength: During the subsequent ITO coating process, taking the coating bonding strength of Comparative Example 9 as the reference value, the coating bonding strength of Comparative Example 7 was increased by 22%.

[0153] TiO2, as a nucleating agent, plays an important role in promoting the formation and uniform distribution of nanocrystals. When TiO2 was not added in Comparative Example 7, only ZrO2 was relied on to induce the formation of crystal nuclei, and the number of crystal nuclei was insufficient. Moreover, under the action of ion beams and magnetic fields, the growth and distribution of nanocrystals were affected. This made it impossible to form an ideal nanocrystal structure inside the glass, weakening the enhancement effect of nanocrystals on the glass properties, resulting in varying degrees of decline in the glass's thermal stability, mechanical strength, chemical stability, optical properties, and coating bonding strength.

[0154] Comparative Example 8

[0155] The alkali-free glass substrate of Comparative Example 8 comprises the following components in mass percentages: SiO2 57%, Al2O3 18%, B2O3 12%, MgO 7%, CaO 4%, SnO2 0.5%, SrO 1%, TiO2 0.5%.

[0156] Performance tests were carried out on the alkali-free glass substrate for surface nanocrystallization TFT prepared in Comparative Example 8, and the test results are as follows:

[0157] Grain size and distribution: Observed by transmission electron microscopy (TEM), the grain size of the surface microcrystalline layer is between 38 - 48 nm, the average size of the internal nanocrystals is 23 nm, and the size deviation is within the range of ±6 nm.

[0158] Thermal stability: The strain point reaches 660 °C, and the thermal expansion coefficient is 3.92×10 -6 / °C.

[0159] Mechanical strength: Tested by three-point bending strength, the result is 155 MPa.

[0160] Surface hardness: The Vickers hardness of the microcrystalline layer, measured to be 600 HV.

[0161] Chemical stability: The glass substrate was immersed in HCl solution with pH = 1 for 24 h, and the mass loss rate was 0.13%; tested in a high-temperature and high-humidity (85 °C / 85% RH) environment, the surface precipitation of Na + The concentration decreased by 65%.

[0162] Optical properties: The light transmittance in the visible light band (400 - 700 nm) is 90.5%, and the absorption rate for ultraviolet light (<300 nm) is 92%.

[0163] Coating bonding strength: In the subsequent ITO film coating process, the film bonding strength of Comparative Example 9 was used as a reference value, and the film bonding strength of Comparative Example 8 was increased by 23%.

[0164] In the process of glass nanocrystallization, ZrO2 not only acts as a nucleating agent to reduce the nucleation barrier, but also promotes nucleation and atomic diffusion by causing lattice distortion through ion radius differences. In comparative example 8, ZrO2 was not added, and it was difficult to induce the formation of a sufficient number of uniformly distributed nanocrystals only by TiO2. The nanocrystal structure inside the glass is imperfect, and the nanocrystals cannot effectively improve the performance of the glass, which results in the glass being inferior to the case where ZrO2 is added in various performance indicators.

[0165] Comparative Example 9

[0166] The alkali-free glass substrate of Comparative Example 9 includes the following components in mass percentage: SiO2 57.5%, Al2O3 18%, B2O3 12%, MgO 7%, CaO 4%, SnO2 0.5%, and SrO 1%.

[0167] The preparation method of the surface nanocrystallized TFT alkali-free glass substrate of Comparative Example 9 comprises the following steps:

[0168] S1 Glass substrate molding: The raw materials are placed in a high-speed mixer and fully mixed at a speed of 1500r / min for 45 minutes to ensure uniform mixing; then, the mixed raw materials are put into a high-temperature furnace at 1600℃ and melted for 5 hours; after the raw materials are completely melted, float molding is used to produce an alkali-free glass substrate with a thickness of 0.6mm.

[0169] The performance test of the alkali-free glass substrate prepared in Comparative Example 9 was carried out, and the test results are as follows:

[0170] Grain size and distribution: Using transmission electron microscopy (TEM) observation, the grain size of the surface microcrystalline layer is in the state of traditional glass (no obvious nanocrystals), the average size of the internal nanocrystals is no (no nanocrystals are formed), and the size deviation is no. This is because Comparative Example 9 did not undergo ion beam induced surface nanocrystalization, and did not add TiO2 and ZrO2 as nucleating agents. The glass could not form a nanocrystalline structure during the molding process, so it showed the grain state of traditional glass.

[0171] Thermal stability: strain point 650℃, thermal expansion coefficient 4.2×10 -6 / ℃, since there is no dispersion strengthening and structural optimization of nanocrystals inside the glass, its thermal stability is poor, the strain point is low, and the thermal expansion coefficient is large. Compared with the embodiment, it is more likely to deform when the temperature changes.

[0172] Mechanical strength: Tested by three-point bending strength, the result is 120 MPa. The lack of nanocrystalline structure results in no effective strengthening mechanism inside the glass, so the mechanical strength of the glass is low and it is more likely to break under external force.

[0173] Surface hardness: Measured to be 450 HV. Without the strengthening effect of nanocrystals, the surface hardness of the glass is low and its ability to resist external friction and wear is weak.

[0174] Chemical stability: The glass substrate is immersed in HCl solution with pH = 1 for 24 h, and the mass loss rate is 0.3%; tested in a high-temperature and high-humidity (85 °C / 85% RH) environment, the surface precipitates Na + The concentration does not decrease significantly. The absence of nanocrystals leads to an insufficiently dense structure on the surface and inside of the glass, making it more easily corroded in acidic solutions, with a high mass loss rate, and it is also unable to effectively inhibit the precipitation of sodium ions in a high-temperature and high-humidity environment.

[0175] Optical properties: The light transmittance in the visible light band (400 - 700 nm) is 87%, and the absorption rate of ultraviolet light (<300 nm) is 18%.

Claims

1. A method for preparing an alkali-free glass substrate for a surface nanocrystallized TFT, characterized in that: The surface nano-crystallized TFT alkali-free glass substrate includes the following components in mass percentage: SiO2 55-65%, Al2O3 12-18%, B2O3 8-12%, MgO 3-7%, CaO 2-6%, SnO2 0.1-0.5%, SrO 1-3%, ZrO2 0.5-2%, TiO2 0.1-1%; The method for preparing an alkali-free glass substrate for a surface nanocrystallized TFT comprises the following steps: S1 Glass substrate molding: After fully mixing the components, melting and molding to make an alkali-free glass substrate; S2 ion beam induced surface nanocrystallization: Use a focused ion beam or a broad beam ion source to scan and bombard the surface of the alkali-free glass substrate; S3: Magnetic field assisted heat treatment: placing the alkali-free glass substrate treated in step S2 in a magnetic field and keeping it warm to obtain an alkali-free glass substrate for TFT with surface nanocrystallization.

2. The method for preparing an alkali-free glass substrate for a surface nanocrystallized TFT according to claim 1, characterized in that: In step S1, the melting temperature is 1500-1650°C and the time is 4-8h.

3. The method for preparing an alkali-free glass substrate for a surface nanocrystallized TFT according to claim 1, characterized in that: In step S1, the molding is performed by overflow down-draw method or float molding.

4. The method for preparing an alkali-free glass substrate for a surface nanocrystallized TFT according to claim 1, wherein: In step S1, the thickness of the prepared alkali-free glass substrate is 0.3-0.8 mm.

5. The method for preparing an alkali-free glass substrate for a surface nanocrystallized TFT according to claim 1, wherein: In step S2, a mixed ion beam of argon ions and helium ions is used to scan and bombard the surface of the alkali-free glass substrate, with an ion energy of 50-150 keV and a beam current density of 0.2-0.8 mA / cm 2 , scanning speed is 15-40mm / s, and processing depth is 150-350nm.

6. The method for preparing an alkali-free glass substrate for a surface nanocrystallized TFT according to claim 5, characterized in that: The molar ratio of argon ions to helium ions is (2-3):

1.

7. The method for preparing an alkali-free glass substrate for a surface nanocrystallized TFT according to claim 1, characterized in that: In step S3, the magnetic field strength is 0.3-0.7 T, and the magnetic field direction is changed alternately at 0.5 Hz.

8. The method for preparing an alkali-free glass substrate for a surface nanocrystallized TFT according to claim 1, wherein: In step S3, the insulation temperature is 600-650° C. and the insulation time is 2-4 hours. 9 . An alkali-free glass substrate for TFT with surface nanocrystallization prepared by the preparation method according to claim 1 .