Does using of shortened (minus 2 last letters) version of registered trademark infringe the Copyright Law?
Trademarks and copyrights are two different things. Potentially your use of a registered trademark (albeit with 2 letters missing) could be classed as a trademark violation. It would depend on a number of things though such as using the same design, if the word is obviously recognisable as the original trademark etc etc. If it is done in a way in which potential customers would be “confused” etc.