Conductive Antireflection (AR) technology For EMI Shielding & Heating in Display

Brinell K-AR conductive antireflection technology 

for EMI shielding & heating.

High quality electronic displays are now becoming a standard requirement for many vehicles and aircraft and they need to operate well in demanding environments. High ambient light readability and electromagnetic compatibility (EMC) can be achieved only by modifying commercial 'off-the-shelf' display screens.  

To provide electromagnetic shielding components need to be surrounded by a conductive enclosure which will attenuate any unwanted electrical fields. Unfortunately this proves more of a challenge on the display area where there is a requirement for good optical transmission. A common technique for adding conductive properties to an optical substrate involve integration of fine wire meshes within a lamination of two planes of glass or plastic. These generally create moiré patterns and can seriously hinder display readability in certain conditions especially if the mesh interferes with active-matrix display.

Example of Moire' patterns 

A far better solution is the deposition of electrically conductive, thin optically transparent conductive oxide films onto the display screen. Specially selected and processed conductive films will transmit up to 80% of the visible spectrum (from 400 nm to 700 nm). The problem with both techniques is that both provide unwanted reflections which can create problems in high ambient light conditions such as aircraft cockpit or vehicle display. 

Destructive optical interference coatings

By incorporating other optical materials with different refractive indexes into a multi-layer optical design it is possible to reduce reflections and improve both transmission and clarity of a transparent conductive oxide (TCO). Reflections from the higher index TCO are cancelled out by creating corresponding reflections which are 180 degrees out of phase. This is the same method used for multi-layer AR eyeglass coatings however the challenge is the ability to control the optical thickness of the TCO to within 10nm. (10 millionths of a millimetre).

Brinell heater glass panels and EMI shielding plates are designed optically to give outstanding transmission and low spectral reflection for challenging applications by use of a complex multi-layer thin film to optically match the transparent conductive oxide. 

The resulting transmission is also extremely high and can be used in demanding applications such as vehicle display and cock-pit environments where ambient light would cause high levels of reflection.

Brinell K-AR has been tested to ensure compliance with DEF STAN 59-411, MIL-STD 461E and MIL-C-48497. Below illustrates one example of a COTS (commercial display) before modification and after modification. The top red line shows the maximum limit for electrical/electromagnetic interference allowed. In case 1 the measured signal breaches the required standard and is well above the desired value. 

                               1. Standard commercial display 

In case 2 the standard display unit is fitted with a front cover glass coated with Brinell K-AR-550-16. In this case the noise signal is suppressed well below the required standard MIL-STD 461E and also meets the lower desired level.

                               2. Standard commercial display with Brinell K-AR front plate 

Brinell BV-K-AR technology

• Resistivity from 4 Ohm/Sqr to 100 Ohm/sq

• High Clarity EMI Shielding to MIL-STD 461E

• Efficient alternative to mesh filters with outstanding optical transmission

• Optically matched for low loss lamination or air interface

• DEF STAN 59-411 and MIL-C-48497 compliant

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