Japanese Intellectual Property, Patent and Trademark Law Firm in Japan

Claim interpretation in Japan

1. Doctrine of Equivalents

There are two methods to protect equivalents of claimed invention.

(a) Doctrine of Equivalents

The doctrine of equivalents is a legal rule to hold for patent infringement though the allegedly infringing subject matter is outside the literal scope of a patent claim, but is equivalent to the claimed invention. This method is used in Japan, US, and Germany.

Japanese Supreme Court declared the Doctrine of Equivalents and the Prosecution History Estoppel in THK Co. v. Tsubakimoto Seiko Co. decided 24 February, 1998, the "Ball Spline Bearing" case.

See AIPPI Q175 – Japan report for more detail

See AIPPI Q175 – US report for more detail

See AIPPI Q175 – German report for summary in English (p.4 to p.5)

(b) Purposive construction

The purposive construction is a legal rule to hold for patent infringement with a flexible literal scope of a patent claim in a purposive manner. This method is used in UK and Canada. UK House of Lords or Supreme Court declared that this approach complies with EPC article 69 protocol of EPC2000 in Kirin Amgen case.

See UK House of Lords site for more detail

See AIPPI Q175 – Canada report for more detail

2. Prosecution History Estoppel employed?

(1) Yes

The above mentioned Japanese Supreme Court also stated followings.

(i) If the applicant intentionally excluded the accused device from the claims during the prosecution of the patent application, or (ii) the patentee acknowledged that the accused device was not within the scope of the claims, or (iii) conducted itself as if it acquiesced in such an interpretation but then later asserted the claims in a manner contrary to what was acknowledged earlier, such a contrary assertion should not be permitted in light of file wrapper estoppel.

Japanese district court held that the allegedly infringing products or “Square rice cake” are out of the literal scope of patent claim on Nov. 30^th, 2010. In this decision, the literal scope was interpreted or limited with the arguments in the patent prosecution for obtaining the patent before JPO.

Prosecution History Estoppel is employed in Japan and US.

See AIPPI Q175 – Japan report for more detail

See AIPPI Q175 – US report for more detail

(2) No

Prosecution History Estoppel is not employed in Germany, UK, and Canada.

See AIPPI Q175 – German report for summary in English (p.4 to p.5)

See UK House of Lords site for more detail

See AIPPI Q175 – Canada report for more detail

3. Practice guideline

Beware of Prosecution History Estoppel in the process of patent prosecution. Please practice the patent prosecution before Japan Patent Office as if before USPTO.

End of report