PET polyester film refers to a film made of biaxially stretched polyethylene terephthalate polymer in the polyester family. Optical grade PET polyester film has high light transmittance, low haze, high brightness, no yellowing, good adhesion, good flatness, no light and dark lines, high temperature resistance and ultraviolet radiation resistance, good stiffness, anti-burn cracking, and not easy to Damage and other characteristics.
The coating technology of PET optical film is the key technology of optical film. According to Coating Online, coatings can be divided into three categories according to their functions, namely protective coatings, decorative coatings and functional coatings. By coating different coatings on PET polyester film, films with different functions can be produced. For example, the surface of PET polyester film is coated with an anti-scratch and antistatic (106~108Ω) coating to make a screen protective film, which is used to protect the surface of mobile phone or computer screens; on the PET polyester film, coating containing The coating of optical particles or glass beads can be made into an optical diffusion film, which can be used in the LCD panel backlight module to effectively eliminate the interlacing of light and dark or dot phenomena, improve the brightness of the light, and soften the light emitted from the light guide plate. The LCD panel provides a uniform surface light source; coating the surface of the PET polyester film with a resin system with particle components can make an anti-glare film, which can be used in LCD screens to utilize the scattering of reflected light and is made of hard-coated resin and Internal scattering caused by the difference in refractive index of particles prevents screen smearing, etc. Technologies related to coatings mainly include coating formulation technology, coating curing technology and coating process technology, etc.
PET optical film coatings used in the LCD field are divided according to the main resin used, mainly including silicone coatings, polyurethane coatings and acrylate coatings or their modified derivatives.
The preparation and curing methods of optical films can be divided into thermal curing and UV curing. Thermal curing is the more traditional and common curing method. Generally speaking, thermal curing is not prone to serious volume shrinkage due to curling, which will produce shrinkage stress and affect the strength of the coating. However, thermal curing requires a long time period and is labor-intensive. Solvent-based coating fluids are also prone to environmental pollution problems. UV curing is summarized as having the "5E" characteristics, which are efficient, adaptable, economical, energy saving, environmentally friendly, etc. The disadvantages of UV curing are: the curing process of free radical photo-curing coatings is easily inhibited by oxygen, and the surface curing is poor; different UV light bands have different irradiation depths, which will cause the interior of the coating to be incompletely cured, thereby causing the coating to Insufficient bonding strength at the interface with the substrate.
(1) With the increasing demand for functional and environmentally friendly coatings for liquid crystal displays, PET optical film coatings will develop towards high-performance, multi-functional and environmentally friendly coatings. This is the reason why a variety of high-performance optical coatings have been developed. important basis for thin films.
(2) The curing method of coatings for PET optical films is developing from the original single curing method to dual curing methods, such as light-thermal curing, heat-light curing, light-moisture curing, light-oxygen curing and other curing methods. Being studied and applied, hybrid photocuring systems such as free radicals and cations also have research value.
(3) Develop new optical PET film surface treatment technology to improve the PET film/coating interface bonding performance.
(4) Continuing to seek new precision coating technology and adapting to the market competition model of low-cost, high-quality, and large-scale production are inevitable requirements for future research and development.