Slater plastics are manufacturers of optical filters, contrast enhancement filters, RFI / EMC shielded windows, instrumentation and display fascia panels, we also offer a design and consultation service.

RFI / EMC Filter Windows

Shielded filter windows are designed for use with electronic displays and give a high level of shielding from both internally and externally generated electromagnetic emissions. These windows can be designed to incorporate any of the filter characteristics described in the Optical Filters and Fascia Panels data page.

RFI / EMC shielded windows can be manufactured in allyl carbonate or CR39 ^TM, acrylic, polycarbonate or glass. The shielding element is either a cast in micro - fine mesh (allyl carbonate or CR39 ^TM only ), laminated micro - fine mesh or ITO deposition.

Cast allyl carbonate or CR39 ^TM embedded mesh windows.

These shielded windows offer the superb screening performance of micro - fine mesh, combined with the outstanding characteristics of allyl carbonate or CR39 ^TM
( see Optical Filters and Fascia Panels for details on allyl carbonate or CR39 ^TM ).
The general properties of cast windows are:

• Micro - fine mesh is cast in to a one piece sheet, therefore no delamination problems and higher temperature specification than laminated parts.
• They can be machined to any desired profile, with or without rebates.
• Extremely good abrasion, solvent, impact and heat resistance.
• Light weight.
• Different meshes available to suit the application and mesh is blackened to reduce reflections.
• None reflective surfaces can be cast in.
• Mesh can be set at any desired angle.
• Silver loaded bus - bar termination.

Laminated Mesh Windows.

These shielded windows again offer the superb screening performance of micro - fine mesh, which in this version can be left flying for direct termination to the equipment screen. Material and characteristics for the filter can be selected from the full range,
( see Optical Filters and Fascia Panels for details of the filter range ).

The general properties of laminated windows are:

• Micro - fine mesh is laminated in between your selected filter medium.
• Plastic versions can be machined to any desired profile, and glass versions can be constructed with or without rebates.
• Different meshes available to suit the application and mesh is blackened to reduce reflections.
• None reflective surfaces can be included.
• Mesh can be set at any desired angle.
• Various termination methods are available including ; tape edge, mesh over gasket, flying mesh, silver bus - bar.

Mesh Performance.

The performance of any RFI / EMC window is dependent on how well it is bonded to the equipment screen. The following table shows the screening capability of the mesh, where the mesh itself is clamped to the screen with no gaskets in between. The size of the test window was 300 x 300 mm and the shielding performance will improve as the window size reduces, due to the performance characteristics of the aperture. Mesh selection should be based on required performance and with the way that it interacts with your chosen display.

ITO Deposition Windows.

Indium Tin Oxide ( ITO ), is a transparent semiconductor which can be coated onto optical filter materials. ITO benefits over metal depositions because it is more transparent and less reflective, for a given impedance level. A good ITO coating will have optical transmission levels of greater than 75 %.

The ITO coating can be sputtered onto glass or plastic and has good chemical and mechanical durability, it will also not oxidise when exposed to air.

The oxygen content of the coating is adjusted to a compromise point, giving good optical transparency and low impedance, normally between 10 - 40 Ohms / square for shielding.

The shielding effect of thin film coatings is due to reflection of the electromagnetic wave. This means that the coatings are only effective when the wave impedance is greater than the coating impedance. This in turn means that the coatings have no effect in the magnetic, or H - Field, and are not suitable for all applications. There can also be some optical limitations to ITO coated windows and these should be fully discussed before selection is made.

Performance of an ITO window will depend on its impedance and the field impedance, but generally will produce between 80 and 120 dB attenuation in the E - Field, and around 20 dB for Plane waves.

Who are Slater Plastics?, Slater Plastics was established by Andrew Tognola, to manufacture optical filters, and RFI / EMC shielded windows, Geoff Eccleshall joined Slater Plastics as a design consultant and to promote sales. Together Andrew and Geoff have over 30 year experience in the design and manufacture of optical filters and fascia panels. This team can provide full technical and design support, together with top quality custom made products, and a friendly, efficient service