Etching solution for self-cleaning glass and surface roughness control method

Abstract

The invention relates to the technical field of special glass surface treatment, in particular to a self-cleaning glass etching solution and a surface roughness control method, and the self-cleaning glass etching solution is composed of the following components by weight: 3-8% of ammonium fluoride (NH4F); ammonium sulfate ((NH4) 2SO4): 1-4%; 0.5 to 3 percent of citric acid (C6H8O7); 0.01 to 0.1 percent of sodium dodecyl sulfate (SDS); according to the etching solution for the self-cleaning glass and the surface roughness control method, the stability and the safety of the etching solution are remarkably superior to those of hydrofluoric acid while the etching capability is guaranteed, the safety risk of operators is greatly reduced, and the optical performance and the mechanical strength of the glass are guaranteed to the maximum extent while an ideal self-cleaning micro-nano structure is obtained; the harsh requirements on the performance of the self-cleaning glass in the high-end fields of buildings, automobiles, electronic display and the like are met, and the production efficiency and the product quality stability of the self-cleaning glass are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of special glass surface treatment technology, specifically to an etching solution for self-cleaning glass and a method for controlling surface roughness, applicable to building curtain walls, photovoltaic cover plates and other fields. Background Technology

[0002] In numerous fields such as construction, automobile manufacturing, and electronic displays, self-cleaning glass has become a highly sought-after functional material due to its excellent anti-fouling and easy-to-clean properties. Self-cleaning glass primarily achieves its dual effect of self-cleaning through rainwater washing and photocatalytic decomposition of organic matter by constructing a micro-rough structure on the glass surface and combining it with a low surface energy coating. Among these, the precise etching of the glass surface microstructure is a key step in endowing it with self-cleaning properties, and the etching solution formulation and etching process directly determine the quality of the glass surface microstructure and the degree of self-cleaning performance.

[0003] Traditional glass etching solutions primarily use hydrofluoric acid as their main component. While hydrofluoric acid is highly corrosive and effectively etches glass, it poses serious safety hazards and environmental pollution problems. Hydrofluoric acid is highly toxic and volatile; contact with it can easily cause severe burns to operators. Furthermore, the treatment of the discharged fluoride-containing wastewater is difficult and costly, making it difficult to meet increasingly stringent environmental regulations. At the same time, the etching rate and selectivity of a single hydrofluoric acid etching solution are difficult to precisely control, easily leading to over-etching or uneven etching of the glass surface, affecting the glass's light transmittance and mechanical strength, and thus reducing the overall performance of self-cleaning glass.

[0004] In terms of etching technology, most existing glass etching processes rely on single temperature conditions or simple mechanical stirring, making it difficult to achieve precise control over the microstructure of the glass surface. The lack of coordinated optimization of parameters such as temperature, time, and auxiliary methods during etching results in inaccurate control of glass surface roughness, hindering the formation of ideal self-cleaning micro / nano structures. Furthermore, traditional processes often depend on experience to determine the etching endpoint, lacking real-time and accurate online monitoring methods. This easily leads to under-etching or over-etching, making it difficult to achieve the expected light transmittance and self-cleaning effect, thus failing to meet the stringent requirements of high-end applications for self-cleaning glass performance.

[0005] like

[0006] Therefore, developing an environmentally friendly and safe self-cleaning glass etching solution with controllable etching effects and its matching precision etching process to achieve precise construction of the microstructure on the glass surface and improve the performance and production efficiency of self-cleaning glass has become a pressing technical challenge in this field. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention discloses a self-cleaning glass etching solution, the technical solution of which is composed of the following components by weight percentage:

[0008] Ammonium fluoride (NH4F): 3-8%;

[0009] Ammonium sulfate ((NH4)2SO4): 1-4%;

[0010] Citric acid (C6H8O7): 0.5-3%;

[0011] Sodium dodecyl sulfonate (SDS): 0.01-0.1%;

[0012] The remainder is deionized water.

[0013] This invention also discloses an application method based on the above-mentioned self-cleaning glass etching solution, comprising the following steps:

[0014] (1) Immerse the glass substrate in the etching solution described in claim 1;

[0015] (2) Implement temperature gradient control:

[0016] Phase 1 (0-10 minutes): Maintain temperature at 40±2℃;

[0017] Second stage (10-25 minutes): The temperature drops to 25±2℃;

[0018] (3) Apply ultrasonic assistance synchronously: frequency 40kHz, power 50-100W, using intermittent mode (working for 2 seconds / pausing for 1 second);

[0019] (4) Real-time roughness control:

[0020] The scattering intensity of the glass surface is monitored online using a laser scattering sensor;

[0021] Based on the pre-calibrated scattering intensity-Ra value correspondence curve (Ra=K×I) β (K = 0.02-0.05);

[0022] Etching will automatically terminate when the Ra value reaches a preset threshold.

[0023] (5) After the etching is terminated, the glass is removed, rinsed with deionized water and dried with nitrogen.

[0024] As a preferred embodiment of the present invention, the preset threshold is 0.3-0.8μm, and the light transmittance of the glass after etching is terminated is ≥88%.

[0025] As a preferred embodiment of the present invention, the glass substrate is sodium-calcium silicate glass, and its composition satisfies: SiO2 ≥ 72wt%, CaO 8-12wt%, Na2O 12-15wt%.

[0026] The beneficial effects of this invention are:

[0027] 1. In terms of etching solution formulation, we abandon the traditional highly toxic and polluting system with hydrofluoric acid as the main component, and adopt a specific combination of ammonium fluoride, ammonium sulfate, citric acid, sodium dodecyl sulfate, and deionized water. Ammonium fluoride, as the main etching agent, ensures etching capability while its stability and safety are significantly better than hydrofluoric acid, greatly reducing the safety risks to operators; ammonium sulfate can adjust the ionic strength and pH of the etching solution, working synergistically with ammonium fluoride to achieve a mild and controllable etching process; citric acid, as a chelating agent, can complex with metal ions generated during glass etching, preventing precipitation and ensuring the stability of the etching solution; sodium dodecyl sulfate, as a surfactant, can reduce the surface tension of the liquid, promote etching uniformity, and all components are relatively environmentally friendly, effectively reducing the pressure of fluoride-containing wastewater treatment and meeting the requirements of green and environmentally friendly production.

[0028] 2. In terms of etching process, a precise etching strategy combining temperature gradient control, ultrasonic assistance, and real-time roughness control is implemented. The first stage uses a higher temperature (40±2℃) to accelerate the initial etching rate, while the second stage cools to 25±2℃ to slow the etching rate, achieving step-by-step fine control of the glass surface microstructure. Ultrasonic assistance at a frequency of 40kHz, with specific power and intermittent mode, effectively promotes the diffusion and mass transfer of etched products, avoiding uneven local etching and further improving etching uniformity. A laser scattering sensor monitors the scattering intensity of the glass surface online, and the etching endpoint is controlled in real-time based on a pre-calibrated scattering intensity-Ra value curve. Compared to traditional experience-based judgment, the glass surface roughness Ra can be precisely controlled within a preset threshold of 0.3-0.8μm, ensuring a light transmittance of ≥88%. While obtaining an ideal self-cleaning micro / nano structure, this approach maximizes the optical performance and mechanical strength of the glass, meeting the stringent requirements of high-end fields such as construction, automotive, and electronic displays for self-cleaning glass performance, significantly improving the production efficiency and product quality stability of self-cleaning glass. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the application of the self-cleaning glass etching solution of the present invention. Detailed Implementation

[0030] Example 1

[0031] This invention discloses a self-cleaning glass etching solution, which is composed of the following components by weight percentage:

[0032] Ammonium fluoride (NH4F): 8%;

[0033] Ammonium sulfate ((NH4)2SO4): 3%;

[0034] Citric acid (C6H8O7): 2%;

[0035] Sodium dodecyl sulfonate (SDS): 0.05%;

[0036] The remainder is deionized water.

[0037] This invention also discloses a method for applying a self-cleaning glass etching solution, characterized by comprising the following steps:

[0038] (1) Immerse the glass substrate in the etching solution described in claim 1;

[0039] (2) Implement temperature gradient control:

[0040] Phase 1 (0-10 minutes): Maintain temperature at 40±2℃;

[0041] Second stage (10-25 minutes): The temperature drops to 25±2℃;

[0042] (3) Apply ultrasonic assistance synchronously: frequency 40kHz, power 50-100W, using intermittent mode (working for 2 seconds / pausing for 1 second);

[0043] (4) Real-time roughness control:

[0044] The scattering intensity of the glass surface is monitored online using a laser scattering sensor;

[0045] Based on the pre-calibrated scattering intensity-Ra value correspondence curve (Ra=K×I) β (K = 0.02-0.05);

[0046] Etching will automatically terminate when the Ra value reaches a preset threshold.

[0047] (5) After the etching is terminated, the glass is removed, rinsed with deionized water and dried with nitrogen.

[0048] As a preferred technical solution of the present invention, the preset threshold is 0.3-0.8μm, and the light transmittance of the glass after the etching is terminated is ≥88%.

[0049] As a preferred embodiment of the present invention, the glass substrate is sodium-calcium silicate glass, and its composition satisfies: SiO2 ≥ 72wt%, CaO 8-12wt%, Na2O 12-15wt%.

[0050] Example 2

[0051] I. Preparation of Etching Solution

[0052] Weigh the following components according to their weight percentages: ammonium fluoride 5%, ammonium sulfate 2.5%, citric acid 1.5%, sodium dodecyl sulfonate (SDS) 0.05%, and deionized water 90.95%. Add the weighed components sequentially to a container and stir thoroughly to dissolve, ensuring uniform dispersion. Then, filter the solution using a 0.22 μm filter membrane to remove any impurities, yielding a clear, transparent, homogeneous, and stable self-cleaning glass etching solution.

[0053] II. Etching Process Flow

[0054] (I) Substrate Pretreatment

[0055] Select suitable soda-lime glass with a chemical composition of 73% SiO2, 10% CaO, and 13% Na2O. Cut the glass into 10cm × 10cm glass substrates. The glass substrates are then subjected to acetone ultrasonic cleaning for 15 minutes, rinsed with deionized water, and dried at 120℃ for 20 minutes to remove surface oil, dust, and other impurities, ensuring a clean glass surface and providing a good foundation for the subsequent etching process.

[0056] (II) Etching and Real-time Control

[0057] The pretreated glass substrate is immersed in the prepared etching solution, and the etching process is initiated. The temperature gradient is controlled using a constant-temperature water bath (accuracy ±0.5℃): the temperature is maintained at 40℃ for 0-10 minutes to accelerate the initial etching rate; from 10-25 minutes, the temperature is lowered to 25℃ to slow the etching rate, achieving step-by-step fine control of the glass surface microstructure. Simultaneously, a Branson 2800 ultrasonic device is used, set to a frequency of 40kHz and a power of 80W, operating in an intermittent mode of 2 seconds on, 1 second off (3-second cycle) to assist the etching process, promoting diffusion and mass transfer of the etched products and improving etching uniformity. A Keyence IL-300 laser monitoring device is used, set to a wavelength of 650nm and an incident angle of 60°, to monitor the scattering intensity of the glass surface online. Based on a pre-calibrated scattering intensity-Ra value curve (preset K = 0.034), the etching process automatically terminates when the glass surface roughness Ra reaches a preset threshold of 0.5μm.

[0058] Set up a control group:

[0059] Traditional etching solution formula: 40% hydrofluoric acid (HF) + 10% hydrochloric acid (HCl) + 50% deionized water

[0060] Etching process:

[0061] 1. Isothermal etching: 30℃±2℃ (no gradient)

[0062] 2. Mechanical stirring: 200 rpm (without ultrasonic stirring)

[0063] 3. Termination based on experience: Fixed time 25 minutes (without Ra value monitoring)

[0064] (III) Post-processing

[0065] After etching is completed, the glass substrate is immediately immersed in deionized water for 5 minutes to thoroughly rinse away any residual etching solution on the glass surface. Then, the glass substrate is purged and dried using nitrogen gas at a pressure of 0.2 MPa to obtain a glass product with self-cleaning properties.

[0066] III. Experimental Results

[0067] (I) Performance Comparison

[0068] The performance of glass treated by the etching method of this invention, glass treated without real-time control, and glass treated as a control group were tested through three repeated experiments. The results are shown in the table below:

[0069]

[0070] *Self-cleaning efficiency: Stearic acid residue rate test after 24 hours of UV irradiation (GB / T38141-2019).

[0071] The experimental data obtained by the non-real-time control group is a complete replication of the process of this invention but with the online monitoring device for the scattering intensity of the glass surface turned off.

[0072] Data shows that by controlling the etching process in real time, the present invention can precisely regulate the surface roughness of the glass, resulting in a smaller contact angle, higher light transmittance, and self-cleaning efficiency, which is significantly better than the treatment effect of no real-time control and the control group.

[0073] (II) Environmental Protection Treatment Effect

[0074] The waste liquid generated during the etching process was treated, and the fluoride ion concentration and chemical oxygen demand (COD) at different treatment stages were measured. The results are shown in the table below:

[0075] Processing stage Fluoride ion concentration (mg / L) COD (mg / L) raw waste liquid 1250 320 After neutralization with lime <1.0 85

[0076] Emission standards: Fluoride ion ≤ 10 mg / L (GB8978-2002), COD ≤ 100 mg / L

[0077] As can be seen, after simple lime neutralization treatment, the fluoride ion concentration and COD in the waste liquid can meet the emission standards, demonstrating the excellent performance of the etching solution of this invention in environmental protection.

[0078] IV. Industrial Applications

[0079] (I) Application of Photovoltaic Module Cover Plates

[0080] In the production of photovoltaic module cover plates, after processing with the etching method of this invention, when the surface roughness Ra of the glass is 0.5μm, the power output of the photovoltaic module is increased by 2.1% due to the elimination of reflection loss caused by the lack of a self-cleaning layer, which effectively improves the power generation efficiency of the photovoltaic module.

[0081] (II) Application of Building Curtain Walls

[0082] The self-cleaning glass treated according to this invention was applied to a building curtain wall and subjected to 5000 friction tests according to GB / T9279-2015 standard. The results showed that the contact angle of the glass surface increased by <1°, indicating that the self-cleaning glass has good wear resistance and stable self-cleaning performance and can maintain excellent self-cleaning effect for a long time.

[0083] (III) Cost Advantage

[0084] Cost calculations show that, compared with the traditional etching process using hydrofluoric acid (HF), this invention eliminates the need for a complex waste gas purification system, reducing treatment costs by 32%. While ensuring product performance, it significantly reduces production costs, demonstrating good economic benefits and promising industrial application prospects.

[0085] Components not described in detail in this article are existing technologies.

[0086] While the specific embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and modifications or variations without creative effort are still within the protection scope of the present invention.

Claims

1. A self-cleaning glass etching solution, characterized in that, It consists of the following components by weight percentage: Ammonium fluoride (NH4F): 3-8%; Ammonium sulfate ((NH4)2SO4): 1-4%; Citric acid (C6H8O7): 0.5-3%; Sodium dodecyl sulfonate (SDS): 0.01-0.1%; The remainder is deionized water.

2. A method for applying the self-cleaning glass etching solution according to claim 1, characterized in that, Includes the following steps: (1) Immerse the glass substrate in the etching solution described in claim 1; (2) Implement temperature gradient control: Phase 1 (0-10 minutes): Maintain temperature at 40±2℃; Second stage (10-25 minutes): The temperature drops to 25±2℃; (3) Apply ultrasonic assistance synchronously: frequency 40kHz, power 50-100W, using intermittent mode (working for 2 seconds / pausing for 1 second); (4) Real-time roughness control: The scattering intensity of the glass surface is monitored online using a laser scattering sensor; Based on the pre-calibrated scattering intensity-Ra value correspondence curve (Ra=K×I) β (K = 0.02-0.05); Etching will automatically terminate when the Ra value reaches a preset threshold. (5) After the etching is terminated, the glass is removed, rinsed with deionized water and dried with nitrogen.

3. The application method of the self-cleaning glass etching solution according to claim 2, characterized in that: The preset threshold is 0.3-0.8μm, and the light transmittance of the glass is ≥88% after etching is terminated.

4. The application method of the self-cleaning glass etching solution according to claim 2, characterized in that: The glass substrate is sodium-calcium silicate glass with the following composition: SiO2 ≥ 72wt%, CaO 8-12wt%, Na2O 12-15wt%.

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