Any development to make membrane switches more attractive to the user could be a big bonus. Now, Industrial Graphic Technology (IGT) claims to be the first to have a method of printing full four colour onto the graphic overlay of these panels.

The new process gives the manufacturer the chance to put colourful point-of-sale images, photograph quality graphics and other exciting visual effects into the user control panel.

The demand for this kind of graphics originated in the vending industry. In the past, it has only been possible to screen print solid colours only, or to output an image onto a separate graphic layer that is then laminated onto the membrane assembly. But the lamination method has meant that features such as textured finishes, display windows and key embossing cannot be used.

IGT’s process achieves the full range of colour tint density with critical registration, as a litho printer outputting to paper. Using conventional image-processing software the original image has to be optimised to the screen printing process by adjusting the dot gain curve at both the high and low ends of the tint spectrum. This avoids high-tint bleeding into solid and ensures that highlights at low tint values are enhanced.

When the four-colour set is created, the screen angles are selected to avoid generating Moire patterns in the mesh of the printer’s screen. UV-curing inks are essential to avoid colours drying in the screen. Fine quality meshes combined with the use of specialised thickness stencils add colour control and fine image reproduction.

IGT’s technology allows panels to have the full visual impact of a colour halftone image combined with the technical attributes of membrane technology: tactile response, ridge or pillow embossing, backlighting, display windows, selective textured finishes, EMC and ESD protection and secret-until-lit-keys.

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