In patent infringement litigation, it often appears that the patentee gives up a technical solution in order to obtain authorization or maintain the validity of patent at the stage of patent authorization or invalidation, but in the stage of infringement, in order to expand the protection scope of the claim and support their own claims, they declare that the above abandoned technical solution is included in the scope of the claim.
In this regard, the Supreme People's Court provides in article 6 of the Interpretation of the Supreme People's Court on Several Issues concerning the Application of Law in hearing Disputes over Patent Infringement :”Where, in the process of patent authorization or invalidation, a patent applicant or patentee abandons a technical solution by modifying the claim, specification or statement of opinion, and the right holder incorporates it into the scope of patent protection in the case of dispute over patent infringement, the people's court shall not support it” .In this regulation, the principle of "estoppel" is put forward as the restriction of the identification of equivalent infringement.
In order to further refine the principle of estoppel, the Supreme People's Court issued the Interpretations of the Supreme People's Court on Several Issues concerning the Application of Law in the Trial of Patent Infringement Dispute Cases (II) in 2016. Article 13 stipulates that "where the right holder proves that the limited modification or statement made by the patent applicant or patentee to the claim, specification and appended drawings in the procedure of patent authorization and confirmation is explicitly denied, the people's court shall determine that the modification or statement does not result in the abandonment of the technical solution." It provides for exceptions to estoppel.
In 2020, it promulgated the Provisions of the Supreme People's Court on Several Issues concerning the Application of Law to Administrative Cases concerning Patent Authorization and Confirmation (I) . Article 3 stipulates that "when defining the terms of claims in administrative cases of patent right determination, the people's court may refer to the relevant statements of the patentee which has been adopted by effective judgments in civil cases of patent infringement." It stipulates that the disclaimer in the stage of infringement will also affect the stage of patent confirmation, that is, it stipulates the application of estoppel principle from the stage of patent infringement to the stage of patent confirmation.
The establishment of the principle of estoppel is to prevent the patent holder from contracting the scope of claim in the stage of patent authorization or confirmation, and expanding the scope of claim in the stage of patent infringement, thus benefiting from both sides. Its legal basis is the principle of good faith in civil law.
The author analyzes the system based on the following classic case：
Civil Award for retrial Examination and Trial Supervision of Cao Guilan and Hu Meiling's Infringement of patent right for Invention:
In this case, the original patent contains technical features A and B. In this regard, the examiner considers that technical features A and B are common knowledge in the notice of review opinion. When the patentee replies to the notice of examination opinion, it makes limited statements on A and B and adds technical feature C. The examiner maintains that technical features A and B are common knowledge and does not accept the limited representations made by the patentee. However, the patentability of technical feature C is accepted and thus the patent is authorized. In the invalidation phase, the review Board's opinion is the same as that of the examiner. The patentee has made the same limited statement regarding technical characteristics A and B, but the Review Board has also not accepted such statement. But due to the existence of technical feature C, the validity of the patent right is maintained. In the stage of infringement lawsuit, there is a dispute about whether the limited statement of the patentee to the technical characteristics A and B is applicable to the estoppel principle.
In this regard, the Supreme Court holds that when the judge explicitly denies or disapproves the statement of opinion made by the right holder, the technical scheme will not be abandoned and the principle of estoppel is not applicable.
As for the principle of estoppel, patent lawyers need to combine the basic legislative spirit of the principle of good faith in handling cases, investigate and apply it from several specific aspects, such as the applicable conditions and whether to give up technical features explicitly, so as to ensure the interests of the client.
