Poor render result with »decals«

Hi there,

after applying some high resolution »decal« (tried PNG, JPG and even AI) to a simple object (cylinder) I seem to get poor render results of it in any case. The decal consists of some letter artwork with very sharp and crisp shapes which come out rendered to be very jagged.

What is there to do to get a render result looking as sharp as the original decal artwork?

Thanks –

Klaus