What the graphic overlay is?

Graphic overlays, also known as front panels, are an element of masking controllers or other electronic devices. The front panel consists of two layers: 

1. Graphic foil – transparent foil made of polyester PET or polycarbonate PC, printed on the underside with graphical inks
2. Special adhesive layer – adhesive layer fastening the product to the device, keypad or panel. 

Properties of the graphic overlays

Foil fronts thanks to their properties are a great solution for HMI devices, therefore they are the most commonly used decorative layer of membrane, Cu-flex, PCB or silicone keypads

The production technology of graphic overlays is also used to produce:

• Nameplates – plates usually made of composite material. The base of ABS or acrylic, front of foil which could be cut or engraved by laser or milling process
• Descriptions or labels – description elements printed with different techniques from the front side. On back side adhesive layer

The most important advantages of decorative foils include:

• exceptional film durability for damage, scratches and external factors such as humidity or changes in the ambient temperature
• graphics resistance to printing abrasion, cleaning with detergents and the influence of chemicals
• unlimited design possibilities – what kind of film or what printing technology and color palette or pattern you choose, it’s only up to you. Because of laser cutting the shape of the film matches perfectly to the device
• good adhesion to all kinds of metal or plastic surfaces as well as lacquered or rough surfaces.
• easy adjustment of the foil to the parameters and needs of the device.

Print on graphic overlays, nameplates or labels

The printing gives character and functionality of the foil. Two techniques are used – screen printing and digital printing. The choice of colors is virtually unlimited, we can use a full basic RAL or Pantone palette, and gives us unlimited graphic possibilities.

The graphics are placed on the inside of the foil, which makes the print even more durable.

The surface finish of foil fronts

The surface of the graphic film can have various types of finishes:

•  gloss, antiglare, hard coated
• by the structuring lacquer, we can give semi-matte or any other finish.

Construction of foil fronts

The embossing of the graphic overlay is possible in the following shapes:

• spherically,
• flat
• or along the contour.

Exemplary constructions of graphic overlays

graphic overlay for micro switch

Remarks for the design of graphic overlays

Above description is only general information about keypads and foils and does not run out all possible construction and technological solutions.

The final draft of the keypad or foil is made according to our best skills, knowledge and experience. Therefore, we save the right to propose the optimal solution for a given project. Any proposal would be available for improvement only after approval of the buyer

ADDITIONAL REMARKS

Detailed work conditions should be settled before constructing the process for proper keypad functionality. The most important are: environmental, climate, chemical substances contact, mechanical, electrical (isolation, EMI/RFI protection), enclosure or panel.

Guidelines for graphic foil designing may be passed as a drawing or a e-files (CDR, JPG).

Designing keypads or foils we do not recommend:

1. Contour lines of gauge or key
2. Letters with shade elements
3. Spot combining of three colours
4. Thin lines separating the colours
5. Low contrast between the background and description colours
6. Lines of thickness lower than 0,3 mm
7. Colour transparent filters neighbouring to bright background

Guidelines before production of graphic overlays

The choice of film type, surface treatment or selection of paints and graphics depends on the customer and his needs. That’s why the conditions of the device’s operation, as well as the user’s needs, are always agreed before starting the production. So our designers create your foil and take all the guidelines and needs into account.

BASIC GUIDELINES OF MEMBRANE KEYPAD AND FRONT FOIL DIMENSIONING

As an attachment for  keypad/foil description sheet we politely ask for sketch according to data of pictorial drawing.