If you can buy a normal printer that can print this, anyone can.
A "security" measure should be at least expensive to make in a short run. This is if you are a company you could let's say, spend 1000 dollars to print 2000 copies of your "security" paper. It will cost you 50 cents each.
For a random person to try to forge it for one or 10 copies, it will cost 1000 or 100 dollars each, which could dissuade them to do it.
Using a digital printer to print it directly makes you be able to print just one... so it is not a good strategy.
For example, some hologram manufacturers have strict control on who's logo they make a run of stickers, so no one can come and claim they want a random logo made. Making holograms needs expensive and specialized equipment, so only serious companies do it, so it is harder to forge unless it is an organized crime endeavor.
Try at least to print a base of your background on a different system than an inkjet printer. Sheeted offset is the cheapest one, but still one option.
I am going to steal Wolff's comment.
In order to print sharper as your printer can, make the image in vectors and force the colors to print just one color.