Will a patent for a bug repellent that uses a mix of substances become invalid when it is proven that there is prior art for one of those substances?

Question

Lets imagine that I have invented a new kind of bug repellent that targets one specific bug. This repellent uses a group of active ingredients to repel said bug. Each active ingredient does so in its own unique way.

Lets suppose i could not find any prior art concerning any of these ingredients and filed for a patent. The patent is granted and I start looking for license deals. But then suddenly another party determines that there is prior art for one of these ingredients and wants to start using this ingredient as a base for making a competing and cheaper repellent. The evidence for this prior art is rock solid. I had simply overlooked it.

Would this cause the entire patent to become invalid? Would it give others the right to make my repellent without permission even though there exists no prior art for any of the other active ingredients in my repellent?

Answer 1

This is based on the claims. Each independent claim stands on its own. Thus, if you get a claim allowed which is the combination of five active ingredients, then finding prior art for only one of the ingredients will still leave the claim valid. If you have five independent claims, one for each of the five ingredients, then the one with prior art ingredient might be invalidated, but the other four should be fine. Of course a single claim which requires all five ingredients would be pretty narrow. Someone could avoid infringement by leaving out just one of the ingredients. This is why it is prudent to work with a qualified patent attorney or agent when drafting a patent application. What you want isn't just a patent, but a patent with strong, broad claims.