Finding that particular conduct amounts to “gross negligence” does not justify inference of intent to deceive unless involved conduct, viewed in light of all evidence, including evidence indicative of good faith, indicates sufficient culpability to require finding of deceptive intent, and ultimate question of whether inequitable conduct occurred is equitable in nature and as such is reviewed by appellate court under abuse of discretion standard; final determination that inequitable conduct occurred in relation to one or more claims renders entire patent unenforceable.