Introduction and Commercial Application of Optical Film (1)
1. High reflective film
Both high-reflective film and anti-reflective film are common optical film applications, and can be divided into metal film, metal dielectric reflective film, and dielectric reflective film according to the film material.
- Metal reflective film：The plating cost is relatively low, but the film layer has absorption, so the reflectivity cannot be very high. Commonly used metal reflective film materials and their application bands are as follows:
- UV light: Aluminum
- Visible light: aluminum, silver
- Infrared light: gold, silver, copper, chromium platinum (special film)
- Metal dielectric reflective film：A dielectric film can be added to the metal film to increase the reflectivity, but the wave range of high reflection will be narrowed due to interference effects.
- Dielectric reflective film：The technical requirements of the plated dielectric reflective film are relatively high, but the advantage lies in the controllability of the high reflection wave domain and the selection of special wavebands, and because the film layer has a low absorption value, it can be used in the mirror of the laser system.
Automotive components (car lights, mirrors), lighting, laser application equipment (red and blue LED applications, barcode scanning, rangefinder level, sensors), optical inspection equipment... etc.
2. Anti-reflection film
According to the Fresnel equation, about 4% of the light on each uncoated glass interface will be reflected. This feature can cause harm in optical systems, especially multi-lens systems, such as camera ghosting, glasses or panels. Glare and back reflection cause the instability of the laser system...etc.
In order to improve the occurrence of this phenomenon, a moth-eye structure film layer (sub-wavelength structure) can be used. Its structural refractive index is equivalent to a multi-layer film with a graded refractive index, which can not only effectively reduce the reflectivity, but also solve the problem of coating a multilayer anti-reflection film. The only disadvantages between the manufacturing process problems and the selection of reflective film materials are that the microstructure is not easy to maintain and it is not suitable for long-term touch products.
Another improvement method is to plate a multilayer film to use the destructive interference of light to increase the transmittance of the required wavelength band, so as to reduce the generation and influence of Fresnel reflection. This method can also be used with a transparent hard film to achieve resistance at the same time. With the effect of reflection and enhanced hardness, this thin film technology has become the most widely used optical film.
Anti-reflective film has a wide range of uses, such as lenses, glasses, various types of display panels, solar panels/batteries... etc.