Composite clarifying agent for alkali-free glass and manufacturing method of alkali-free glass substrate

Abstract

The invention discloses a composite clarifying agent for alkali-free glass and a manufacturing method of an alkali-free glass substrate, and relates to the technical field of glass manufacturing, the composite clarifying agent for alkali-free glass comprises the following components by mass: 12-30% of ammonium chloride, 48-73% of sulfate, and 11-25% of calcium fluoride; the preparation method comprises the following steps: adding a composite clarifying agent accounting for 0.2-1.2% of the total weight of the glass raw material into the glass raw material, uniformly mixing to form a batch, and carrying out melting, molding, spraying, annealing, cutting, alkali cleaning and other processes on the batch to finally prepare the glass substrate. The prepared composite clarifying agent does not contain toxic substances such as arsenic oxide and antimony oxide, the glass substrate produced by using the clarifying agent not only has an excellent clarifying effect, but also can recycle SO2 and NH3 gas generated in the melting process, can effectively solve the quality problems such as micro-flaws on the surface of the glass substrate in the production process, and has a good application prospect. And the production cost can be reduced and the product quality can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of glass manufacturing, and in particular to a composite clarifier for alkali-free glass and a method for manufacturing an alkali-free glass substrate. Background Art

[0002] With the rapid development of display technology and 5G communication technology, the mainstream size of home and commercial display terminals has gradually upgraded from 55 inches to 65 inches and 75 inches, and continues to evolve towards larger sizes. As the core base material of display devices, the manufacturing technology of glass substrates has also achieved great progress. Its product specifications have been continuously upgraded from the early third generation (G3) to the fifth generation (G5), sixth generation (G6), eighth and fifth generation (G8.5), tenth and fifth generation (G10.5), and even eleventh generation (G11).

[0003] Alkali-free glass, defined as aluminoborosilicate glass with an extremely low content of alkali metal oxides (Na2O, K2O) (typically <0.1wt%), is widely used in liquid crystal display (LCD) and organic light-emitting diode (OLED) panels, as glass substrates, solar cell covers, and high-end optical devices due to its excellent chemical stability, low thermal expansion coefficient, high mechanical strength, and electrical insulation properties. In the display industry, the development of high-resolution, flexible displays, and miniaturization technologies has placed higher demands on the flatness, thermal stability, and purity of glass substrates.

[0004] However, the manufacturing process of glass substrates requires the use of a variety of raw materials, which are melted at high temperatures, cooled, and then drawn into shape. During high-temperature melting, various raw materials introduce air. Carbonate and nitrate raw materials release large amounts of gas after high-temperature chemical reactions. If these gases remain within the glass, they can cause serious defects, affecting the appearance and performance of the glass substrate product. Therefore, during the manufacturing process, clarifiers are generally used to expel most of the bubbles from the glass interior. Traditional clarifiers are mostly arsenic oxides, typically comprising 0.3-0.8wt% of the glass. Although arsenic has a good clarification effect, its toxicity imposes a significant economic burden on production and processing. Antimony, a subsequent arsenic substitute, has achieved certain clarification purposes with reduced toxicity, but it is still harmful and expensive, making it unsuitable for production processes. Currently, the most commonly used clarifier is tin oxide, but the clarification capacity of a single clarifier is limited, and excessive tin oxide can cause tin defects in the glass substrate. Summary of the Invention

[0005] The present invention aims to provide a composite clarifier for alkali-free glass and a method for manufacturing an alkali-free glass substrate, so as to solve the problems of high toxicity, limited clarification ability and minor surface defects in the glass substrate manufacturing process existing in traditional clarifiers.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A composite clarifier for alkali-free glass, comprising the following components by mass percentage: 12-30% ammonium chloride; 48-73% sulfate; 11-25% calcium fluoride;

[0008] Furthermore, the decomposition temperature of the sulfate is above 1200°C;

[0009] Furthermore, the sulfate is one of calcium sulfate, barium sulfate and strontium sulfate.

[0010] A method for manufacturing a glass substrate using the composite clarifier, the process layout is as follows Figure 1 As shown, the specific steps include:

[0011] S1. Preparation of batch material: Weighing glass raw materials and composite clarifiers according to the batch ratio, adding the composite clarifier to the glass raw materials and mixing evenly, wherein the composition of the glass raw materials is 56-65wt% SiO2, 13-22wt% Al2O3, 0.05-12wt% B2O3, 9-24wt% alkaline earth metal oxides;

[0012] Furthermore, the composition of the alkaline earth metal oxide is 3-6 wt% MgO, 3-10 wt% CaO, 3-6 wt% SrO and 0-2 wt% BaO;

[0013] Furthermore, the addition amount of the composite clarifier is 0.2-1.2 wt% of the glass raw material;

[0014] S2. Melting: The batch material is poured into a furnace pot. When the furnace temperature reaches 1280-1380°C, the furnace pot is placed in the furnace. The temperature is raised to 1540-1580°C over 2 hours. After holding the temperature for 2 hours, the temperature is raised to 1640-1680°C over 1 hour. After holding the temperature for 4-7 hours, the temperature is lowered to 1600-1610°C over 30 minutes to obtain clarified glass liquid.

[0015] Furthermore, the clarification time is 2-5h;

[0016] S3. Tin Bath Forming: The molten glass flows from the melting furnace into the tin bath, where it spreads and flattens on the surface of the tin bath, forming a glass ribbon with smooth upper and lower surfaces. Under the traction of traction rollers, the glass ribbon is drawn into glass sheets of corresponding dimensions.

[0017] S4. Spraying: The SO2 gas collected from the furnace branch pipe is evenly sprayed onto the glass surface through the steam spray equipment;

[0018] Furthermore, the pressure of the spraying equipment is 0.2-0.8 MPa;

[0019] S5. Annealing: The glass sheet is conveyed to the annealing lehr by a roller conveyor process;

[0020] Furthermore, the annealing furnace is a tunnel roller, and the annealing furnace process parameters are: high temperature zone: 700℃-600℃, keep for 5 minutes; medium temperature zone: 600℃-400℃, keep for 3 minutes; low temperature zone: 400℃-200℃, keep for 30 seconds;

[0021] S6. Cutting: Use a cutting machine to cut according to size requirements;

[0022] S7. Alkali cleaning: The NH3 gas collected from the furnace branch pipe is passed through a neutral detergent, the pH is adjusted to 10.5-12, and the glass surface is cleaned with a cleaning roller brush;

[0023] Furthermore, the neutral cleaning agent is an organic amine ester TPP non-foaming surfactant;

[0024] S8. Quality inspection: The glass substrate is inspected online. Unqualified substrates are discarded through an automatic drop-off procedure, while qualified substrates are transported to semi-finished product packaging via a conveyor belt.

[0025] Beneficial effects of the present invention:

[0026] 1. The present invention proposes a composite clarifier for alkali-free glass. The composite clarifier does not contain toxic substances such as arsenic oxide and antimony oxide, can avoid the leaching of harmful substances during storage, and is an environmentally friendly formula.

[0027] 2. The composite clarifier proposed in this invention has excellent clarification effects, resolving the issues of high melting temperature, high viscosity, high surface tension, and difficulty in clarification of alkali-free glass. It primarily utilizes the synergistic effect of a "cascade relay" process. The specific clarification mechanism is as follows: (i) Above 350°C, NH4Cl decomposes: NH4Cl = NH3 + HCl, simultaneously generating products such as CaCl2 and BaCl2. (ii) At 1200-1600°C, sulfates, such as calcium sulfate, barium sulfate, and strontium sulfate, decompose. For example, the decomposition of calcium sulfate yields 2CaSO4 = 2CaO + 2SO2 + O2, releasing SO2 and O2, causing visible bubbles to grow and escape. Furthermore, CaF2 provides a fluxing effect, promoting the dissolution of refractory materials such as quartz sand. (iii) Above 1600°C, products such as calcium chloride remaining in the molten glass vaporize and volatilize. At high temperatures, CaF2 and CaCl2 not only reduce the viscosity of the molten glass but also lower its surface tension, further eliminating any remaining bubbles and ultimately completing the clarification process.

[0028] 3. The present invention provides a method for manufacturing an alkali-free glass substrate. By diverting and collecting the NH3 and SO2 generated during the melting process and applying them to the spraying and alkali cleaning processes of producing the glass substrate, it can not only effectively reduce scratches on the glass plate surface and realize the resource utilization of waste gas, but also effectively solve quality problems such as micro-defects on the glass substrate surface, which helps to improve product quality and reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Layout for glass substrate manufacturing process. DETAILED DESCRIPTION

[0030] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0031] Unless otherwise specified, the experimental methods in the following examples are conventional methods and were performed according to the techniques or conditions described in literature in the field or according to product specifications. The materials and reagents used in the following examples were all commercially available unless otherwise specified. For example, the types and sources of the raw materials used in the preparations, examples, and comparative examples are shown in Table 1.

[0032] Table 1

[0033]

[0034]

[0035] Preparation Example

[0036] Preparation of composite clarifiers: According to the formula in Table 2, weigh the corresponding masses of raw materials, mix them evenly, and obtain composite clarifiers of Formula 1, Formula 2, Formula 3, and Formula 4.

[0037] Table 2

[0038] raw material Recipe 1 Recipe 2 Recipe 3 Recipe 4 <![CDATA[NH4Cl(kg)]]> 12.5 20.4 22.3 30.0 <![CDATA[CaF2(kg)]]> 14.9 11.3 24.6 21.3 <![CDATA[CaSO4(kg)]]> 72.6 68.3 53.1 48.7

[0039] Example 1

[0040] S1. Preparation of batch material: Weigh 996kg of glass raw materials and 4kg of the composite clarifier of Formula 1, and add the composite clarifier to the glass raw materials and mix evenly, wherein the composition of the glass raw materials is 60.00wt% SiO2, 16.50wt% Al2O3, 5.90wt% B2O3, 3.10wt% MgO, 8.00wt% CaO, 5.00wt% SrO and 1.50wt% BaO;

[0041] S2. Melting: The batch material was poured into a platinum crucible, and the crucible containing the batch material was placed in a silicon molybdenum rod lifting furnace. When the lifting furnace temperature reached 1350°C, the platinum crucible was placed in the crucible. The temperature was raised to 1560°C at a constant rate over 2 hours. After maintaining the temperature at 1560°C for 2 hours, the temperature was raised to 1640°C over 1 hour. After maintaining the temperature at 1640°C for 5 hours, the temperature was lowered to 1610°C over 30 minutes. The glass liquid was clarified at 1610°C for 4 hours.

[0042] S3. Tin Bath Forming: The molten glass flows from the melting furnace into the tin bath, where it spreads and flattens on the surface of the tin bath, forming a glass ribbon with smooth upper and lower surfaces. Under the traction of traction rollers, the glass ribbon is drawn into glass sheets of corresponding dimensions.

[0043] S4. Spraying: The SO2 gas collected from the furnace branch pipe is evenly sprayed onto the glass surface through a steam spraying device at a spraying pressure of 0.6 MPa;

[0044] S5, Annealing: The glass sheet is conveyed to a tunnel roller annealing lehr under the action of a roller process. The annealing lehr process parameters are as follows: high temperature zone: 700℃-600℃, hold for 5 minutes; medium temperature zone: 600℃-400℃, hold for 3 minutes; low temperature zone: 400℃-200℃, hold for 30 seconds;

[0045] S6. Cutting: Using an online cutting machine, cut the glass substrate into a size of 2580mm*2280mm;

[0046] S7 alkaline cleaning: The NH3 gas collected by the kiln branch pipe is passed into the organic amine ester TPP foam-free surfactant, the pH is adjusted to 11.3, and the glass plate surface is cleaned with a cleaning roller brush;

[0047] S8. Quality inspection: The glass is inspected online. Unqualified glass will be discarded through the automatic plate-dropping program, while qualified glass will be transported to semi-finished product packaging via a conveyor belt.

[0048] Example 2

[0049] S1. Preparation of batch material: Weigh 992kg of glass raw materials and 8kg of the composite clarifier of Formula 1, and add the composite clarifier to the glass raw materials and mix them evenly, wherein the composition of the glass raw materials is 60.00wt% Si O2, 16.50wt% Al2O3, 5.90wt% B2O3, 3.10wt% MgO, 8.00wt% CaO, 5.00wt% SrO and 1.50wt% BaO;

[0050] S2. Melting: The batch material was poured into a platinum crucible, and the crucible containing the batch material was placed in a silicon molybdenum rod lifting furnace. When the lifting furnace temperature reached 1350°C, the platinum crucible was placed in the crucible. The temperature was raised to 1560°C at a constant rate over 2 hours. After maintaining the temperature at 1560°C for 2 hours, the temperature was raised to 1640°C over 1 hour. After maintaining the temperature at 1640°C for 5 hours, the temperature was lowered to 1610°C over 30 minutes. The glass liquid was clarified at 1610°C for 4 hours.

[0051] S3. Tin Bath Forming: The molten glass flows from the melting furnace into the tin bath, where it spreads and flattens on the surface of the tin bath, forming a glass ribbon with smooth upper and lower surfaces. Under the traction of traction rollers, the glass ribbon is drawn into glass sheets of corresponding dimensions.

[0052] S4. Spraying: The SO2 gas collected from the furnace branch pipe is evenly sprayed onto the glass surface through a steam spraying device at a spraying pressure of 0.6 MPa;

[0053] S5, Annealing: The glass sheet is conveyed to a tunnel roller annealing lehr under the action of a roller process. The annealing lehr process parameters are as follows: high temperature zone: 700℃-600℃, hold for 5 minutes; medium temperature zone: 600℃-400℃, hold for 3 minutes; low temperature zone: 400℃-200℃, hold for 30 seconds;

[0054] S6. Cutting: Using an online cutting machine, cut the glass substrate into a size of 2580mm*2280mm;

[0055] S7 alkaline cleaning: The NH3 gas collected by the kiln branch pipe is passed into the organic amine ester TPP foam-free surfactant, the pH is adjusted to 11.3, and the glass plate surface is cleaned with a cleaning roller brush;

[0056] S8. Quality inspection: The glass is inspected online. Unqualified glass will be discarded through the automatic plate-dropping program, while qualified glass will be transported to semi-finished product packaging via a conveyor belt.

[0057] Example 3

[0058] S1. Preparation of batch material: Weigh 990kg of glass raw materials and 10kg of the composite clarifier of Formula 1, and add the composite clarifier to the glass raw materials and mix evenly, wherein the composition of the glass raw materials is 60.00wt% SiO2, 16.50wt% Al2O3, 5.90wt% B2O3, 3.10wt% MgO, 8.00wt% CaO, 5.00wt% SrO and 1.50wt% BaO;

[0059] S2. Melting: The batch material was poured into a platinum crucible, and the crucible containing the batch material was placed in a silicon molybdenum rod lifting furnace. When the lifting furnace temperature reached 1350°C, the platinum crucible was placed in the crucible. The temperature was raised to 1560°C at a constant rate over 2 hours. After maintaining the temperature at 1560°C for 2 hours, the temperature was raised to 1640°C over 1 hour. After maintaining the temperature at 1640°C for 5 hours, the temperature was lowered to 1610°C over 30 minutes. The glass liquid was clarified at 1610°C for 4 hours.

[0060] S3. Tin Bath Forming: The molten glass flows from the melting furnace into the tin bath, where it spreads and flattens on the surface of the tin bath, forming a glass ribbon with smooth upper and lower surfaces. Under the traction of traction rollers, the glass ribbon is drawn into glass sheets of corresponding dimensions.

[0061] S4. Spraying: The SO2 gas collected from the furnace branch pipe is evenly sprayed onto the glass surface through a steam spraying device at a spraying pressure of 0.6 MPa;

[0062] S5, Annealing: The glass sheet is conveyed to a tunnel roller annealing lehr under the action of a roller process. The annealing lehr process parameters are as follows: high temperature zone: 700℃-600℃, hold for 5 minutes; medium temperature zone: 600℃-400℃, hold for 3 minutes; low temperature zone: 400℃-200℃, hold for 30 seconds;

[0063] S6. Cutting: Using an online cutting machine, cut the glass substrate into a size of 2580mm*2280mm;

[0064] S7 alkaline cleaning: The NH3 gas collected by the kiln branch pipe is passed into the organic amine ester TPP foam-free surfactant, the pH is adjusted to 11.3, and the glass plate surface is cleaned with a cleaning roller brush;

[0065] S8. Quality inspection: The glass is inspected online. Unqualified glass will be discarded through the automatic plate-dropping program, while qualified glass will be transported to semi-finished product packaging via a conveyor belt.

[0066] Example 4

[0067] Compared with Example 1, the only difference is that the composite clarifier of Formula 1 is replaced by the composite clarifier of Formula 2 of equal mass, and other conditions remain the same, and finally a glass substrate is prepared.

[0068] Example 5

[0069] Compared with Example 2, the only difference is that the composite clarifier of Formula 1 is replaced by the composite clarifier of Formula 2 of equal mass, and other conditions remain the same, and finally a glass substrate is prepared.

[0070] Example 6

[0071] Compared with Example 3, the only difference is that the composite clarifier of Formula 1 is replaced by the composite clarifier of Formula 2 of equal mass, and other conditions remain the same, and finally a glass substrate is prepared.

[0072] Example 7

[0073] Compared with Example 1, the only difference is that the composite clarifier of Formula 1 is replaced by the composite clarifier of Formula 3 of equal mass, and other conditions remain the same, and finally a glass substrate is prepared.

[0074] Example 8

[0075] Compared with Example 2, the only difference is that the composite clarifier of Formula 1 is replaced by the composite clarifier of Formula 3 of equal mass, and other conditions remain the same, and finally a glass substrate is prepared.

[0076] Example 9

[0077] Compared with Example 3, the only difference is that the composite clarifier of Formula 1 is replaced by the composite clarifier of Formula 3 of equal mass, and other conditions remain the same, and finally a glass substrate is prepared.

[0078] Example 10

[0079] Compared with Example 1, the only difference is that the composite clarifier of Formula 1 is replaced by the composite clarifier of Formula 4 of equal mass, and other conditions remain the same, and finally a glass substrate is prepared.

[0080] Example 11

[0081] Compared with Example 2, the only difference is that the composite clarifier of Formula 1 is replaced by the composite clarifier of Formula 4 of equal mass, and other conditions remain the same, and finally a glass substrate is prepared.

[0082] Example 12

[0083] Compared with Example 3, the only difference is that the composite clarifier of Formula 1 is replaced by the composite clarifier of Formula 4 of equal mass, and other conditions remain the same, and finally a glass substrate is prepared.

[0084] Comparative Example 1

[0085] Compared with Example 2, the only difference is that the composite clarifier is replaced with CaSO4 of equal mass, and other conditions remain the same, and finally a glass substrate is produced.

[0086] Comparative Example 2

[0087] Compared with Example 2, the only difference is that the composite clarifier is replaced with CaCl2 of equal mass, and other conditions remain the same, and finally a glass substrate is produced.

[0088] Comparative Example 3

[0089] Compared with Example 2, the only difference is that the composite clarifier is replaced with NH4Cl of equal mass, and other conditions remain the same, and finally a glass substrate is prepared.

[0090] Comparative Example 4

[0091] Compared with Example 2, the only difference is that the composite clarifier is replaced with CaF2 of equal mass, and other conditions remain the same, and finally a glass substrate is produced.

[0092] In order to more intuitively and clearly demonstrate the differences between the embodiments of the present invention and the comparative examples in terms of various key performance indicators, and to facilitate understanding of the significant advantages of the technical solution of the present invention, the formulas of key materials and experimental results of Examples 1-12 and Comparative Examples 1-4 are listed in Table 3. The specific test method is:

[0093] Bubble counting method: Use a grid to mark a transparent glass plate. The same person uses a microscope to confirm the total number of bubbles (n). Then weigh the glass block (m (kg)). The final unit bubble number = n / m;

[0094] The criteria for judging the quality of glass melting: if there is no unmelted matter and no crystallization nodules on the surface, and the number of bubbles is less than 5 / kg, it is excellent; if there is no unmelted matter and no crystallization nodules, and the number of bubbles is 5 / kg≤≤30 / kg, it is fair; if there is no unmelted matter and no crystallization nodules, and the number of bubbles is greater than 30 / kg, it is poor; if there is unmelted matter or crystallization nodules, it is poor.

[0095] Table 3

[0096]

[0097] The data in Table 3 show that in Examples 1-12, the glass substrates prepared had no unmelted material or crystallization nodules. Except for the glass substrates prepared in Examples 1, 4, 7, and 10, which had 11-13 bubbles per kilogram and average glass melting quality, the glass substrates prepared in the other Examples all had less than 5 bubbles per kilogram and excellent glass melting quality. This is due to the relatively small amount of composite clarifier added in Examples 1, 4, 7, and 10. In contrast, the glass substrates prepared in Comparative Examples 1-4, which used a single component of the composite clarifier as a clarifier, all had a small amount of unmelted material on the surface, with a minimum of 100 bubbles per kilogram, and poor glass melting quality. In summary, the composite clarifier provided by the present invention has a good clarification effect, and the glass substrates produced using the composite clarifier have excellent melting quality.

[0098] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A composite clarifier for alkali-free glass, characterized in that: Calculated by mass percentage, it includes the following components: Ammonium chloride 12-30%; Sulfate 48-73%; Calcium fluoride 11-25%.

2. The composite clarifier for alkali-free glass according to claim 1, wherein The decomposition temperature of the sulfate is above 1200°C.

3. The composite clarifier for alkali-free glass according to claim 2, wherein The sulfate is any one of calcium sulfate, barium sulfate and strontium sulfate.

4. A method for manufacturing an alkali-free glass substrate, using the composite clarifier for alkali-free glass according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1. Preparation of batch material: Weighing glass raw materials and composite clarifiers according to the batch ratio, adding the composite clarifier to the glass raw materials and mixing evenly, wherein the composition of the glass raw materials is 56-65wt% Si O2, 13-22wt% Al2O3, 0.05-12wt% B2O3, 9-24wt% alkaline earth metal oxides; S2. Melting: The batch material is poured into a furnace pot. When the furnace temperature reaches 1280-1380°C, the furnace pot is placed in the furnace. The temperature is raised to 1540-1580°C over 2 hours. After holding the temperature for 2 hours, the temperature is raised to 1640-1680°C over 1 hour. After holding the temperature for 4-7 hours, the temperature is lowered to 1600-1610°C over 30 minutes to obtain clarified glass liquid. S3. Tin Bath Forming: The molten glass flows from the furnace into the tin bath, where it spreads and flattens on the surface of the tin bath, forming a glass ribbon with smooth top and bottom surfaces. The ribbon is then pulled by traction rollers into a glass substrate of the desired size. S4. Spraying: The SO2 gas collected from the furnace branch pipe is evenly sprayed onto the glass surface through the steam spray equipment; S5. Annealing: The glass substrate is transferred to the annealing lehr under the action of a roller process; S6. Cutting: Use a cutting machine to cut according to size requirements; S7. Alkali cleaning: The NH3 gas collected from the furnace branch pipe is passed through a neutral detergent, the pH is adjusted to 10.5-12, and the glass surface is cleaned with a cleaning roller brush; S8. Quality inspection: The glass substrate is inspected online. Unqualified substrates are discarded through an automatic drop-off procedure, while qualified substrates are transported to semi-finished product packaging via a conveyor belt.

5. The method for manufacturing an alkali-free glass substrate according to claim 4, wherein: In step S1 , the composition of the alkaline earth metal oxide is 3-6 wt % MgO, 3-10 wt % CaO, 3-6 wt % SrO and 0-2 wt % BaO.

6. The method for manufacturing an alkali-free glass substrate according to claim 4, wherein: In step S1, the added amount of the composite clarifier is 0.2-1.2 wt% of the glass raw material.

7. The method for manufacturing an alkali-free glass substrate according to claim 4, wherein: In step S2, the clarification time is 2-5 hours.

8. The method for manufacturing an alkali-free glass substrate according to claim 4, wherein: In step S4, the pressure of the spraying equipment is 0.2MPa-0.8MPa.

9. The method for manufacturing an alkali-free glass substrate according to claim 4, wherein: In step S5, the annealing lehr is a tunnel roller, and the annealing lehr process parameters are: high temperature zone: 700℃-600℃, keep for 5 minutes; medium temperature zone: 600℃-400℃, keep for 3 minutes; low temperature zone: 400℃-200℃, keep for 30 seconds.

10. The method for manufacturing an alkali-free glass substrate according to claim 4, wherein: In step S7, the neutral cleaning agent is an organic amine ester TPP non-foaming surfactant.

Images