Anti-Reflection 'AR' Films

Microgravure™ COATING APPLICATIONS – Anti-Reflection ‘AR’ Films
(This page is not up-to-date.)

Anti-Reflection ‘AR’ coatings by the ‘liquid’ method, as contrasted to the ‘vacuum sputtering’ method are increasing in popularity. This is so, for the simple reason that liquid coating is a much lower cost production process from both the standpoint of equipment investment and operating costs.

Very high quality AR coatings are routinely manufactured by our exclusive and patented Microgravure™ method of coating. In fact, vacuum sputtering is the ONLY challenge to our Microgravure™ process in terms of product quality.

Anti-reflection surfaces on displays are beneficial for better viewability/readability for two reasons:

1) Specular glare from natural or artificial light sources is dramatically reduced, and

2) Actual image coming out from a display is brighter.

Principle of AR coatings

Light waves partially reflect and partially transmit through boundaries of all non-opaque materials, wherever there is a step change in the refractive index, for instance, at the surface of water.

Our example is between air and PET film (n_air ~ 1.0003, n_PET ~ 1.6). Common AR films use ‘quarter wave’ thickness layers on the surface of PET or TAC films for ‘destructive interference’ to the reflected light, to literally cancel the reflection out.

There are some compromises, as refractive index of most materials is different for different wave lengths, and, the wavelength of the light (and therefore the quarter wave thickness in a coating) changes throughout the ‘visible’ spectrum (most important range of wavelengths for display viewing by humans), and the length the light travels through a coating layer is longer for wider viewing angles….. But, AR coatings can reduce reflections from around 10 % to around 1 %, and are very useful.

Dry coating thickness for these coatings is on the order of 0.06 to 0.12 microns (depending on wavelength and refractive index of materials chosen).

Application by Microgravure™

Typically, AR coatings are applied at a wet thickness of 1 to 3 microns, with solids levels on the order of 5 to 20 pct. With a proper selection of coating materials and solvent(s), and adherence to operating conditions, a Yasui Seiki Microgravure™ coating head can hold variation in thickness to 2 pct or less.