1、 Introduction
High reflectivity PET reflective film plays a crucial role in fields such as display, lighting, and solar energy utilization. In LCD displays, high reflectivity PET reflective film can effectively improve the light utilization efficiency of the backlight source, enhance the brightness and contrast of the image; In lighting equipment, it can enhance the light efficiency of lamps and achieve energy conservation and consumption reduction; In solar photovoltaic systems, it helps to improve the light capture efficiency of photovoltaic modules and enhance power generation efficiency. With the continuous improvement of product performance requirements in various industries, the demand for high reflectivity PET reflective films is increasing day by day. Traditional preparation techniques are no longer able to meet the market's requirements for high-performance reflective films. Therefore, the research and development of innovative preparation technologies to achieve breakthroughs in the performance of PET reflective films has become a hot topic and focus of current research.
2、 Limitations of traditional preparation techniques
The traditional methods for preparing PET reflective films mainly include coating and vapor deposition. The coating method is to uniformly coat a coating solution containing reflective pigments (such as titanium dioxide, barium sulfate, etc.) on the surface of a PET base film, and then dry and cure to form a reflective layer. This method has the problems of poor dispersion of reflective pigments and difficult control of coating uniformity, which can easily lead to color difference and graininess on the surface of the reflective film, affecting its optical performance. Meanwhile, the organic solvents used in the coating process are prone to environmental pollution, and the energy consumption during the drying and curing process is relatively high.
The evaporation method involves heating and evaporating metals (such as aluminum) or metal oxides in a high vacuum environment to deposit them on the surface of a PET base film, forming a reflective layer. Although this method can achieve high reflectivity, it requires large equipment investment and low production efficiency. In addition, the deposition uniformity of metals or metal oxides during the evaporation process is poor, and the thickness of the film layer is difficult to accurately control, which can easily lead to quality problems such as pinholes and peeling, limiting the further improvement of product performance.
3、 Innovative preparation technology for high reflectivity PET reflective film
（1） Magnetron sputtering technology
Magnetron sputtering technology uses a magnetic field to control the motion trajectory of charged particles in a vacuum environment, causing atoms or molecules on the surface of the target material (such as aluminum, silver, and other metals or metal oxides) to be sputtered under the bombardment of high-energy particles, and deposited on the surface of the PET substrate to form a reflective layer. This technology has the advantages of fast deposition rate, good film uniformity, and precise control of film thickness. By adjusting parameters such as sputtering power, gas pressure, and the distance between the target material and the base film, reflective films with different structures and properties can be prepared. For example, by adopting a multi-layer film structure design and alternately sputtering different materials, the reflectivity of the reflective film can be effectively improved over a wide spectral range.
（2） Nanocomposite technology
Nanocomposite technology is the process of blending nanoscale reflective materials (such as nano titanium dioxide and nano aluminum oxide) with PET resin, melt blending and granulation through a twin-screw extruder, and then preparing PET reflective films through casting or biaxially stretching molding. The small size effect and surface effect of nanomaterials, when uniformly dispersed in PET matrix, can significantly enhance light scattering and reflection, improve reflectivity and haze. Meanwhile, the addition of nanomaterials can also improve the mechanical properties of PET reflective films, enhancing their tensile and tear resistance. In addition, the preparation process of nanocomposite technology does not use organic solvents, which is more environmentally friendly.
（3） Inkjet printing technology
Inkjet printing technology is the precise spraying of ink containing reflective materials onto the surface of PET base film through a nozzle, forming a reflective layer according to a predetermined pattern. This technology has high flexibility and customization capabilities, enabling the preparation of complex patterns and high-resolution reflective films. Compared with traditional coating methods, inkjet printing technology has a higher ink utilization rate, reduces the use of organic solvents, and is more environmentally friendly. By optimizing the ink formula and printing parameters, such as ink viscosity, nozzle temperature, printing speed, etc., the optical performance and surface quality of the reflective film can be improved.
4、 Performance breakthroughs brought by innovative preparation technology
（1） Breakthrough in optical performance
The PET reflective film prepared by magnetron sputtering technology has a reflectivity of 92% -96% in the visible light range, and the spectral reflection curve is smooth with good color consistency. By designing a multi-layer film structure, the reflective performance of the reflective film in the infrared and ultraviolet bands can be further improved to meet the needs of different application scenarios. The PET reflective film prepared by nanocomposite technology can increase the reflectivity to over 95% and achieve a haze of 80% -90%. It can effectively diffuse light, reduce glare, and improve display and lighting effects. Inkjet printing technology can flexibly adjust the reflectivity and haze of the reflective film by adjusting the ink formula and printing pattern, achieving personalized optical performance design.
（2） Breakthrough in mechanical performance
In nanocomposite technology, a good interface bonding is formed between nanomaterials and PET matrix, significantly enhancing the mechanical properties of PET reflective film. After testing, the tensile strength of the reflective film prepared by this process increased by 20% -30%, the elongation at break increased by 15% -25%, and the tear resistance performance was significantly improved. The reflective film prepared by magnetron sputtering technology has strong adhesion between the film layer and the base film, as well as good mechanical stability, making it less prone to problems such as film detachment during processing and use.
（3） Breakthrough in weather resistance performance
The innovative preparation technology has been improved in material selection and process control, effectively enhancing the weather resistance of PET reflective films. The reflective film prepared by magnetron sputtering technology has good film density, which can block the invasion of external moisture, oxygen, and ultraviolet rays, and prolong the service life of the reflective film. The nanomaterials used in nanocomposite technology have good chemical stability and corrosion resistance, which can improve the aging resistance of reflective films. Inkjet printing technology optimizes the ink formula to provide reflective films with good water resistance and wear resistance.
5、 Experimental verification and result analysis
（1） Experimental Design
To verify the improvement effect of innovative preparation technology on the performance of PET reflective film, a comparative experiment is designed. PET reflective film samples were prepared using magnetron sputtering technology, nanocomposite technology, and inkjet printing technology, and samples prepared by traditional coating and vapor deposition methods were used as controls. Test the optical properties (reflectivity, haze), mechanical properties (tensile strength, elongation at break), and weather resistance (aging resistance test) of the sample, and record the data.
（2） Experimental results
The experimental results show that the sample prepared by magnetron sputtering technology has a reflectivity of 95.3%, a smooth spectral reflection curve, a tensile strength of 83 MPa, and a performance retention rate of over 92% after 500 hours of aging resistance testing; The reflectivity of the nanocomposite technology sample is 96.5%, the haze is 87%, the tensile strength is 86MPa, and the aging resistance is excellent; Inkjet printing technology samples can achieve different optical properties according to design requirements, and their mechanical and weather resistance properties are significantly better than traditional samples.
6、 Conclusion and Prospect
The innovative preparation technologies studied in this article, such as magnetron sputtering, nanocomposite, and inkjet printing, effectively break through the limitations of traditional preparation techniques, significantly improve the optical, mechanical, and weather resistance properties of PET reflective films, and provide strong support for the development of related industries. However, there is still room for improvement in innovative technologies, such as the high cost of magnetron sputtering equipment and the high dispersion cost of nanomaterials in nanocomposite processes. In the future, we should focus on reducing costs, improving production efficiency, exploring the integration and application of innovative technologies, developing multifunctional PET reflective films, and promoting their widespread application in more fields.
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