Let's see, what you are asking is that your printer puts out a transparency with the traces in black, and you are trying to make the transparency with the traces as clear.(posted 8783 days ago)If so, then you want a contact printer (basically a hinged piece of glass on a board) and some lith film and developer. Also stop and fix. You sandwich the lith film under the printer output and expose to room light. You can work under red safelight with lith film. Lith developer is two part, which you mix together just before using. You will get only black or white, nothing in between.
Using this method you probably don't even need to print onto transparency material, white paper will do as well.
Another way, can your software invert the image? This would print the traces clear in the first place.