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Legend Printing: "Bring It Out Right The First
Time" |
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Legend Types Best Defined Based Upon the Base Material
In presenting this information it seems the base material that the legend information goes on is the best way to categorize the ways in which we identify keys. The four basic types of materials that we print legend information on are membrane switch assemblies (thin plastic sheets), rubber (or elastomerics), injection molded plastic and finally metals. |
Membrane Assemblies: In thinking of membrane keypad legends
it is best to think backwards. The top polycarbonate or polyester
layer of the membrane itself usually acts as the legend protectant.
The numbers, symbols or alphabetical characters are put on from the
back, facing upwards, with outer and background colors layered on
behind the characters in a specific sequence. This is done through
a silk-screening process. Generally speaking the only layer that goes
over the top is the UV protectant – a textured overcoat that
breaks up the reflectivity of light shining on the outer surface.
Depending on the types of colors that are required for the characters
a common background layering might consist of the following: UV velvet
overcoat, several colors for legend information, custom background
colors, a possible “dead front” requirement, a barrier black
back coating and finally a masking layer for adhesion to additional
layers beneath.
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All in all a very intricate process requiring multiple silk-screening sequences and exact layer to layer coordination to inter-relate with key locations, hidden components and embossing criteria.
Embossing is the last way to highlight a legend by raising it slightly from the background, giving it a raised perimeter – in addition to raising the key – to make it more distinctive or employing a more intricate multiple step embossing process for various effects.
Elastomers: The methods of putting characters or backgrounds on elastomers can be done by silk-screening, through special molding requirements and by painting / laser etching. These following methods are defined as follows: |
A.
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Silk-screening: Referenced above in Membrane Assemblies, this is a method where by legend information is transferred to the product by pushing colors through a screen. The screen has been pre-conditioned to allow the passage of the color only in certain areas and also acts as a regulator to allow passage of the ink at a certain rate. |
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B.
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Insert molding or flow molding: This refers to the same process whereby additional cavities are made in the compression mold so that the elastomerics can be formed together into a final two or three part process – or flow molded in one complete step. Usually this applies to the background of a key or the top of a key that requires a separate color from the background carrier color – but could also apply to molding a character out of a separate material and molding around it to achieve varying properties of color or transparency in a specific area. |
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C. |
Painting / laser etching: This defines the process where by the base key is molded a certain color, or painted a specific color, and a final color is put over it all. This final color is then laser etched through in the areas of the specific characters to reveal the colors underneath. The final product has the quality of showing the legends plainly in daytime and backlighting the legend information in the dark. |
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As a final note, the advantage of having the legend or character information behind the protective cover layer of the membrane has to be duplicated in different ways on other materials. A silk-screened, spray on or epoxy finish can be applied over the characters and material for protection. The end result is clear in color, protective in nature and can be varied according to customer requirements to be either a matte (non-glossy), semi-gloss or glossy finish.
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NEWS
e-Bulletins
Legend Printing
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