[author: Chunqiao Wang]

In filing cross-border patent applications, it is a general practice for foreign patent applicant to claim “right of priority” of the prior foreign patent application at the time of filing a Chinese patent application so as to enjoy the prior filing date thereof and to obtain a certain degree of flexibility in terms of filing strategy.

However, since the special rule of “conflicting application” in the Chinese patent system is applicable to applications filed by any organization or individual, applications filed by the same applicant may also constitute “conflicting applications” against each other. If a patent application filed in China claims multiple priorities with different priority dates and divisional application(s) will be derived from it, there may be a novelty issue between the divisional application(s) and the parent application. This issue arises from the improper arrangement of the claims in the divisional application(s) and/or the parent application, which is often referred to as a “poisonous” divisional application.

Hereby, we would explain the situation of “poisonous” divisional application through a simplified example as follows.

For instance, we could assume a scenario referring to the figure cited below:

Two foreign applications B1 and B2 from the same applicant could have different filing days, wherein the filing day f2 of B2 is later than the filing day f1 of B1, while the scope of the inferior technical solution s1 recited in B1 is smaller than the scope of the superior technical solution s2 recited in B2.

For entry into China, a Chinese application A3 could be filed by claiming the priorities of both B1 and B2, wherein the application document of A3 includes the inferior technical solution s1 and also the superior technical solution s2. After that, a Chinese divisional application A4 could be further filed on the basis of the Chinese application A3, wherein one claim of A4 seeks protection of the superior technical solution s2. In case that the claim of A4 in principle could enjoy only the priority of B2, the claim of A4 actually enjoys the priority date of f2.

The inferior technical solution s1 recorded in A3 enjoys the priority date f1, which is before the priority date f2 enjoyed by the claim of A4. When the public date p3 of A3 is after f2 and the scope of solution s1 in A3 is smaller than the scope of solution s2 sought by the claim of A4, the Chinese application A3 can constitute a “conflicting application” against the Chinese divisional application A4 and therefore challenge novelty of the divisional application A4.

It can be understood that, as a variation of the above example, if one claim of the parent application A3 seeks protection of solution s2 while the application document of the divisional application A4 includes technical solution s1, the divisional application A4 can challenge novelty of the parent application A3 because A4 constitutes “conflicting application” against the parent application A3.

Thus, in practice, applicants should have the sense for the possibility of the formation of such “poisonous” divisional application and strategically design their patent applications to avoid the “poisonous” trap.

For example, in theory, the applicant could consider firstly submitting an application B2 with superior technical solution s2 (having a broader scope) and thereafter submitting an application B1 with inferior technical solution s1 (having a narrower scope), thereby avoiding the possibility of subsequent “poisonous” division in the priority formation stage. However, sometimes a superior technical solution s2 may appear later than an inferior technical solution s1 with the changes in the development progress or market needs, making the above ideal submitting strategy harder to be implemented.

For another example, in which the foreign application B1 related to the inferior technical solution s1 has been firstly submitted and a feature Tn not appearing in technical solution s1 is recorded in the application document of the foreign application B2 subsequently submitted along with the superior technical solution s2 (i.e., the technical solution s2 + Tn is recorded). By seeking the protection technical solution s2 + Tn in the claims of the divisional application A4, the novelty of the technical solution s2 + Tn claimed in the claims of the divisional application A4 is prevented from being challenged by the technical solution s1 recorded in the parent application A3.

For a further example, in the case that the foreign application B1 related to the inferior technical solution s1 has been submitted prior to the foreign application B2 related to the superior technical solution s2, if the foreign applications B1 and B2 are not disclosed yet, the application A3 for entering China may be filed by not claiming the right of priority of B1 and B2. Since B1 and B2 are foreign applications and do not belong to Chinese applications, the principle of “conflicting application” is not applicable and thus no conflicting application against A3 or its divisional application A4 will be constituted.

Although we have talked about the exemplary situation where Chinese applications claiming multiple foreign priorities with different priority dates may generate “poisonous” divisional application, in the practice of the patent, the situation will inevitably be different, and the most appropriate response strategy should be made based on the case-by-case study.