Doctrine of Equivalents in Japan
On February 24, 1998, Japan's Supreme Court handed down its 1st decision on doctrine of equivalents; and made it clear that said doctrine isrecognized in Japan on the following 5 conditions (The so-called "Ball SplineCase"; THK vs. Tsubaki Nakashima) :
1. The literal difference does not relate to the essential element of the patented invention;
2. Functional equivalency between the patented invention and the alleged infringement;
3. Substitution is obvious for those skilled in the art;
4. The alleged infringement does not belong to the public domain; and
5. No estoppel is applicable to the patentholder.
We were involved in this important case as the defendant's attorney; and eventually won the litigation.