I have a question about those small sheets of ribbed plastic you find
as a gadget in cereal and such.
the back side of this little sheets of platic is printed on.
If you look from different angles at the plastic you see different
prints. This technique makes it possible to add animation of a few
frames or add 3d-effect.

My question is twofold:
1) What is the name of this print-technique?
2) Where can I find a printer in Belgium (or abroad, but willing to
ship to belgium) that makes these?

Hello fons_from_be-ga,

Thank-you for your question.

The name of images produced using this technique are lenticular
pictures.  They are also sometimes known as auto stereograms.

"The term Lenticular is often confused as a printed image that shows
depth or motion as the viewing angle changes. But in general
Lenticular is a term for the lens effect that creates a convex
perspective of multiple images or light sources, but not necessarily a
physical printed image. This lenticular technology can be used to
create a lenticular image through the process of Lenticular printing. 
Examples of Lenticular printing include flip and animation effects
such as the winking eyes that were given as the prize in Cracker Jack
snack boxes to modern airport advertising graphics that change their
message depending on the viewing angle. This technology was created in
the 1940s but has evolved in recent years to show more motion and
increased depth. Originally used mostly in novelty items, lenticular
prints are now being used as a marketing tool to show products in
motion."
http://en.wikipedia.org/wiki/Lenticular

There is an excellent description of the whole process here:
http://www.lpc-europe.com/lenticular_process.shtml

There are a number of commercial printers of these products and most
would be willing to produce a design of your own should the quantity
be large enough.  I have listed a few from Europe below:

Think 3D:
http://www.3dp.be/

Convergence Point:
http://www.convergencepoint.be

The Lenticular Plastic Company Of Europe:
http://www.lpc-europe.com/profiles/lpc_profiles_europe.shtml

3DZ:
http://www.lenticular.biz
http://www.3dz.co.uk/contact.html

Edmonds:
http://www.edmonds.co.uk/edmonds-contact.html

Digi-Art:
http://www.lenticularsoftware.de/

If you require any further assistance on this subject please ask for clarification.

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