polyva brings you an introduction to coating process technology-technical knowledge

Polyva brings you the introduction of coating technology. Source: Protective film factory direct sales Release time: 2019-05-06 Hits: 1592 Different from ordinary protective film or tape, the optical film must be uniform in thickness, and the surface must be free of dust and less crystal points. , This puts forward higher requirements on coating technology, requiring a more uniform film thickness. Therefore, the precision coating process has gradually developed and been continuously improved. Optical film coatings are traditionally prepared by vacuum evaporation, chemical deposition, plasma polymerization and other methods. These methods are difficult to achieve large-scale production of roll film substrates. In modern coating processes, the commonly used coating methods include dip coating, Roll coating, gradient extrusion coating, curtain coating, etc. These coating methods are suitable for materials with different properties and coating thickness, and have their own advantages and disadvantages. For example, the coating amount of dip coating is not easy to control, which is greatly affected by the characteristics and temperature of the material; the thickness of the coating layer coated by roller coating is easy to control, the coating amount is easier to control, and the uniformity is better, but it is more affected by the characteristics of the material. Large, suitable for a narrow range of material viscosity; although gradient extrusion coating is easy to control the coating amount, it is suitable for a narrow range of material viscosity, and the coating amount is too small to be easy to coat, and it cannot be coated to the edge, resulting in a waste of substrate ; Curtain drop coating is a predictive coating method, it is easy to operate, the longitudinal and transverse coating thickness is very uniform, the coating has no scratches, streaks, orange peel, but the drop curtain is easily affected by factors such as vehicle speed Therefore, the stability of the curtain falling is a big problem. The thickness of the coatings currently used varies widely, and some coatings are very thin, and the surface is required to be uniform and smooth. In order to improve production capacity, the coating speed must be high, so some research institutions began to study micro-gravure roll coating and slot coating. Micro-gravure roll coating has the advantages of easy operation, wide coating range, saving substrate, wide adaptation range of substrate thickness, good coating appearance, smooth and shiny surface. Slot coating is a predictive coating method with uniform coating, which can realize large-scale coating and ultra-thin coating. These two coating methods are new precision coating technology developed after precision coating technology such as multi-layer slope extrusion coating and falling curtain coating. They are gradually used in flat panel displays, optoelectronic products, and lithium batteries And other related products. The micro-gravure coating method was first proposed by Japan's Fuji Company, which mainly coats high-end functional films. The micro-gravure coating method has been used in its anti-reflective film preparation process. Others such as Konica Minolta and Hitachi Maxell Companies and others have also adopted micro-gravure coating equipment in related products. The slit coating method is also the earliest development and application of Fuji Company in Japan. Fuji Company has prepared an anti-reflection film with a 4-layer structure, namely substrate/hard layer/medium refractive index layer/high refractive index layer/low refractive index layer, preferably in a slit coating method. Huang Shanghong once studied the cavity design of the slit coating nozzle, discussed the role of each component of the slit coating nozzle, and pointed out that the structure of the distribution cavity should make the pressure distribution reasonable, reduce the vortex, and fit the slit. It is necessary to set up the auxiliary cavity, so that the residence time of the material in the coating nozzle is the same, and other key factors in the design and manufacture of the slit coating nozzle. Micro-gravure coating system and slit coating system are precision coating systems involving elastic fluid dynamics. They need to be coated in an environment with high requirements for coating cleanliness. Any dust and impurities are important for coating. As a result, it is necessary to build new factories in accordance with ISO cleanliness standards and strictly implement cleanliness rules and regulations.