Colorless nano high transmittance and anti reflection AR glass and its preparation method

Abstract
This paper focuses on colorless nano high transmittance and anti reflection AR glass, systematically explaining its optical principles, performance advantages, application fields, and innovative preparation methods. By studying the design of nanoscale materials and multilayer film structures, the low reflection and high transmission characteristics of glass in the visible light band can be achieved, effectively solving the problems of high reflectivity and insufficient transmittance of traditional glass. In this paper, the preparation processes such as magnetron sputtering method and sol gel method are introduced in detail, and the influence of process parameters of each method on the film performance is analyzed, which provides theoretical and practical basis for the research and development and industrial application of colorless nano AR glass with high transmittance and antireflection.

1. Introduction
1.1 Research Background
In the field of modern optics and numerous industrial applications, glass is an important optical material, and its optical properties are crucial to product functionality and user experience. Due to the difference in refractive index between the surface and air, ordinary glass has a high reflectivity, usually around 4%. This not only causes energy loss of light, but also produces glare, affecting the visual effect. For example, in application scenarios such as display screens, building curtain walls, and optical instruments, the reflected light on the surface of glass can interfere with image clarity, reduce lighting effects, and limit the application efficiency of glass. With the rapid development of display technology, building energy efficiency, solar energy utilization and other fields, higher requirements have been put forward for the optical performance of glass. Developing anti reflective (AR) glass with low reflection and high transparency characteristics has become an urgent need in the industry. Colorless nano high transmittance and anti reflection AR glass can effectively reduce reflectivity and improve transmittance, demonstrating outstanding performance in reducing light loss and enhancing visual clarity, making it a hot research direction in optical materials.

1.2 Research significance
The research and application of colorless nano high transmittance and anti reflection AR glass have important scientific significance and broad market prospects. At the level of scientific research, its preparation involves interdisciplinary fields such as nanomaterial science, optical thin film technology, and surface engineering, promoting theoretical and technological innovation in related fields. From a practical application perspective, in the field of electronic displays, AR glass can improve the image quality of display screens, reduce visual interference caused by ambient light reflection, and enhance user experience; In the field of architecture, it can reduce building energy consumption, improve indoor lighting effect, and achieve green energy conservation; In the field of solar photovoltaics, it helps to improve the absorption efficiency of photovoltaic modules towards sunlight and enhance power generation efficiency. Therefore, studying colorless nano high transmittance and anti reflection AR glass and its preparation methods plays a key role in promoting the technological upgrading of related industries and meeting the market demand for high-performance optical materials.

2、 The principle and characteristics of colorless nano high transmittance and anti reflection AR glass
2.1 Principle of anti reflection
Light undergoes reflection and refraction when propagating at interfaces between different media, and the reflectivity is related to the difference in refractive index between the two media. According to the Fresnel formula, when light is vertically incident from air (refractive index n0 \ approx1) onto the surface of ordinary glass (refractive index n2 \ approx1.52), the reflectance R=\ left (\ frac {n2- n0} {n2+n0} \ right) ^ 2 \ approx4 \%. Colorless nano high transmittance and anti reflection AR glass reduces reflectivity by coating multiple thin films with specific refractive indices and thicknesses on the glass surface, utilizing the principle of light interference. In an ideal situation, when the thickness of the thin film is one-quarter of the wavelength of light in the medium (d=\ frac {\ lambda} {4n}, where d is the thickness of the thin film, \ lambda is the wavelength of light, and n is the refractive index of the thin film), and the refractive index of the thin film n1 satisfies n1=\ sqrt {n0n_2}, the phases of the light reflected from the upper and lower surfaces of the thin film are opposite, interfering and canceling each other out, thereby reducing the intensity of reflected light and increasing the intensity of transmitted light. In practical applications, multi-layer film structures are often used to achieve low reflection effects over a wider spectral range by combining thin films with different refractive indices.

2.2 Characteristics
1. High transmittance: Colorless nano high transmittance and anti reflection AR glass has a transmittance of over 98% in the visible light band (400-760nm), which is significantly higher than ordinary glass. It can allow more light to pass through, presenting clearer and brighter images in display devices and providing more abundant natural lighting in building lighting.

2. Low reflectivity: Its reflectivity can be reduced to below 1%, effectively reducing ambient light reflection. In application scenarios such as museum display cabinets and electronic displays, it eliminates the interference of reflection glare on viewing and enhances visual comfort.

3. Colorless Transparency: This glass maintains good colorless transparency characteristics, does not affect the color of light and the original color of objects, ensures the authenticity of visual effects, and is suitable for occasions with high requirements for color reproduction, such as art exhibitions, photography equipment, etc.

4. Stability and durability.

2.3 Application Fields
1. In the field of electronic display, it is widely used in liquid crystal displays (LCD), organic light-emitting diode displays (OLED), touch screens, mobile phone screens, tablet screens, etc., to improve display clarity and contrast, reduce the impact of reflected light on the image, and enhance the user's visual experience.

2. In the field of architecture: used for building doors, windows, curtain walls, skylights, etc., to improve indoor lighting effect, reduce building energy consumption, and reduce light pollution caused by glass reflection; In high-end architecture, it can also enhance the aesthetics and modernity of the building's appearance.

3. In the field of optical instruments, such as camera lenses, telescopes, microscopes, projector lenses, etc., AR glass can reduce light reflection loss, improve imaging quality and optical system efficiency, and help obtain clearer and more accurate images and observation data.

4. In the field of solar energy, it is applied to solar photovoltaic modules to improve the transmittance of sunlight, reduce reflection losses, increase the absorption of light energy by photovoltaic cells, thereby improving the photoelectric conversion efficiency and reducing the cost of photovoltaic power generation.

3、 Preparation method of colorless nano high transmittance and anti reflection AR glass
3.1 Magnetron Sputtering Method
1. Process principle: Magnetron sputtering is a technique that uses a magnetic field to constrain electron motion in a vacuum environment, increasing plasma density and enhancing sputtering efficiency. By bombarding the target material (such as silicon dioxide SiO2, titanium dioxide TiO2 and other coating materials) with high-energy ion beams (such as argon ions), atoms or molecules of the target material are sputtered out and deposited on the surface of the glass substrate to form a thin film.

2. Process: First, the glass substrate is strictly cleaned to remove surface oil stains, dust, and other impurities, and then placed in a vacuum chamber. Install the target material on the sputtering equipment and vacuum it to 10 ^ {-4} -10^ {-6}Pa Introduce working gas (such as argon), adjust the gas flow rate and pressure to achieve the appropriate working pressure (usually 0.1-1Pa) in the vacuum chamber. Applying radio frequency or direct current power to generate plasma, ion beam bombards the target material, and atoms or molecules of the target material are sputtered and deposited on the surface of the glass substrate. By controlling parameters such as sputtering time, power, and gas flow rate, the thickness and composition of the film layer can be accurately controlled. To prepare multilayer film structures, different target materials can be sequentially replaced for sputtering deposition.

3. Impact of process parameters: Sputtering power affects the atomic sputtering rate and film deposition rate. Excessive power may lead to loose film structure and coarse particles; The gas flow rate and pressure affect the plasma state and membrane composition uniformity; The substrate temperature affects the internal stress and adhesion of the film layer. If the temperature is too low, the internal stress of the film layer will be high, which is prone to cracking. If the temperature is too high, it may cause changes in the film structure. For example, when preparing SiO2 film, the sputtering power is controlled at 100-300W, the argon flow rate is 10-30sccm, and the substrate temperature is 200-400 ℃ to obtain a high-quality film layer.

4. Advantages and disadvantages: The advantages include good uniformity of the film layer, strong adhesion, a wide range of materials that can be plated, the ability to coat at lower temperatures, and suitability for industrial large-scale production; The disadvantage is that the equipment is complex, the cost is high, and impurity gases may be introduced during the sputtering process, which affects the purity of the film layer.

3.2 Sol gel method
1. Process principle: The sol gel method takes metal alkoxides or inorganic salts as precursors, forms sol through hydrolysis and polycondensation reaction in solvent, and then coats the sol on glass substrate, converts it into gel after drying and heat treatment, and forms a solid coating layer. Taking the preparation of SiO2 film as an example, tetraethyl orthosilicate (Si (OC2H5) 4) undergoes hydrolysis reaction under the action of water and catalyst (such as hydrochloric acid): Si (OC2H5) 4+4H2O \ rightarrow Si (OH) 4+4C2H5OH. Subsequently, Si (OH) 4 undergoes condensation reaction to form SiO2 sol, which is finally dried and heat-treated to form SiO2 film layer.

2. Process: Firstly, the precursor (such as ethyl orthosilicate, butyl titanate, etc.) is dissolved in an organic solvent (such as ethanol), water and catalyst (such as hydrochloric acid, ammonia) are added, and stirred at a certain temperature to undergo hydrolysis and condensation reactions, forming a uniform and stable sol. The glass substrate is coated with sol by dipping, spin coating or spraying, and then dried at low temperature (such as 60-100 ℃) to remove the solvent and form a gel film. Finally, the gel film is heat treated at high temperature (such as 400-600 ℃) to convert the gel into oxide film.

3. Impact of process parameters: The concentration of precursor determines the thickness and structure of the film layer, and excessive concentration may lead to cracking of the film layer; The catalyst dosage controls the reaction rate, and improper dosage can affect the stability of the sol; The reaction temperature and time affect the hydrolysis and condensation reaction processes, which in turn affect the quality of the film layer; Drying and heat treatment conditions affect the density and optical properties of the film layer, and excessive temperature or rapid heating rate can easily lead to film cracking.

4. Advantages and disadvantages: The advantages are simple process, low cost, operation at room temperature, ability to prepare large-area uniform film layers, and precise adjustment of film composition and structure by controlling sol composition and process parameters; The disadvantage is that cracks are prone to occur during the drying and heat treatment of the film layer, and the adhesion between the film layer and the substrate is relatively weak, resulting in a longer preparation cycle.

3.3 Chemical vapor deposition method
1. Process principle: Chemical vapor deposition (CVD) is the process of using gaseous reactants to undergo chemical reactions on the surface of a heated glass substrate, resulting in the formation of a solid coating layer. According to different reaction conditions, it can be divided into atmospheric pressure chemical vapor deposition (APCVD), low-pressure chemical vapor deposition (LPCVD), and plasma enhanced chemical vapor deposition (PECVD). Taking the preparation of SiO2 film as an example, silane (SiH4) and oxygen (O2) are used as reactants, and the reaction occurs at high temperature: SiH4+O2 \ rightarrow SiO2+2H2.

2. Process: Place the glass substrate into the reaction chamber, introduce gaseous reactants and carrier gas (such as nitrogen), and adjust the gas flow rate and pressure. In APCVD, the reaction is carried out at atmospheric pressure, and the substrate temperature is raised to the required temperature (usually 700-900 ℃) by heating the reaction chamber; LPCVD is carried out at low pressure (usually 1-100Pa), which can reduce collisions between gaseous reactant molecules and improve deposition uniformity; PECVD utilizes plasma enhanced chemical reaction activity to achieve chemical vapor deposition at lower temperatures (usually 200-400 ℃), and excites reaction gases to generate plasma through methods such as radio frequency or microwave.

3. Process parameter influence: Reaction temperature, gas flow ratio, reaction time, pressure (LPCVD and PECVD) and other parameters have a significant impact on the quality of the film layer. The reaction temperature determines the reaction rate and membrane structure; The gas flow rate ratio affects the composition and stoichiometry of the membrane layer; Reaction time controls the thickness of the film layer; Pressure affects plasma state and reaction rate (LPCVD and PECVD).

4. Advantages and disadvantages: The advantages are high film quality, good uniformity, strong step coverage ability, and the ability to prepare thin films with complex components; The disadvantages are high equipment cost, high reaction temperature (APCVD) or relatively slow deposition rate (LPCVD), complex PECVD equipment, and difficulty in controlling plasma parameters.

4、 Research progress and challenges
4.1 Research Progress
In recent years, significant progress has been made in the research of colorless nano high transmittance and anti reflection AR glass. In terms of materials, new nanoscale coating materials have been developed, such as doped metal oxides, organic-inorganic hybrid materials, etc. The optical properties, wear resistance, and corrosion resistance of the film layer are improved through doping modification. In terms of preparation process, magnetron sputtering continuously optimizes equipment and process parameters, improves film deposition rate and quality, and achieves precise control of multilayer films; The sol gel method solves the problems of cracking and adhesion of the film by improving the sol formula and process conditions, and produces a more stable film; Chemical vapor deposition is developing towards lower temperatures, higher efficiency, and more environmentally friendly directions, researching new reaction gases and catalysts to reduce energy consumption and environmental pollution. At the same time, the composite application of a variety of preparation methods has become a trend, such as combining the magnetron sputtering method and the sol gel method to learn from each other to prepare high-performance AR glass.

4.2 Challenges Faced
Despite many achievements, the research and application of colorless nano high transmittance and anti reflection AR glass still face challenges. On the one hand, the key issue is how to further improve the optical performance, stability, and durability of the film layer while reducing costs. At present, some high-performance preparation processes have high costs, which limits the large-scale application of AR glass. On the other hand, for large-scale industrial production, it is necessary to develop efficient, stable, and continuous preparation processes and equipment to improve production efficiency and product consistency. In addition, with the continuous expansion of application fields, the performance requirements of AR glass in special environments (such as high temperature, high pressure, high humidity, strong radiation, etc.) are higher, and targeted research is needed to meet the needs of different scenarios.

5、 Conclusion
Colorless nano high transmittance and anti reflection AR glass, with its excellent optical properties, has shown great potential for applications in electronic displays, construction, optical instruments, solar energy, and other fields. There are various preparation methods, including magnetron sputtering, sol-gel, chemical vapor deposition, and so on. Through continuous optimization of process parameters and material systems, high-performance AR glass can be prepared. Although current research faces challenges such as cost, production processes, and special environmental adaptability, with continuous innovation in materials science and preparation technology, colorless nano high transmittance and anti reflective AR glass is expected to achieve wider applications, promoting technological progress and development in related industries. In the future, we should strengthen the combination of basic research and application development, break through technological bottlenecks, develop more efficient, low-cost, and high-performance preparation methods, expand the application boundaries of AR glass, and inject new impetus into the development of optical materials.