Don't ignore old documents in a prior-art search

Our team at ExpertLancing was assigned to work on an invalidation case related to the field of pulp and paper technology and the objective from the client was to find novelty-destroying prior-art, or at least art that can challenge the inventive step for a European subject patent. The patent was focused on a method of pulp production and comprised of 4 key steps. Before starting with the search, the understanding of an invention plays a crucial role in identifying relevant results. Our team started with understanding the invention and the claimed matter of the subject patent. This was followed by an in-depth analysis of the prosecution history of the invention.

As our team went through the prosecution history, we also noticed that the subject patent had “third party observation”, where our client had cited a few references in opposition of the subject patent. However, the cited references were not able to destroy the novelty of the invention. As explained by the applicant, this was due to the fact that the cited references had a different “technical effect”. A different technical effect means that the problem and solution to the problem discussed in the prior-art references are different from those in the subject patent. In EP patents, the motivation for a patent, i.e., the problem solved by an invention is considered an important criterion for checking the relevancy of a prior-art against a patent.

Therefore, based on our insights of the prosecution history, we determined the novel feature of the invention, as well as found out that a relevant prior-art reference will have to satisfy the technical effect as disclosed in the subject patent. Enlightened with these inputs, our team started the invalidation search.

Our analysis started with a general search, followed by a citation-search using various databases. An effective citation-search can help in not just identifying the closest prior-art to the subject patent, but also forming a list of keywords and classes that we might have missed.

This was followed by a thorough keyword-based search on various patent databases. Beyond a simple analysis for relevant patents, we also saw key trends of patents during the analysis. A majority of patents published in the field and related to our search were published in Sweden. This particular insight was also very useful in our search and analysis, as we also ran dedicated queries in Swedish on various databases to capture all the relevant results. Although, our primary goal was to search a prior art covering all the aspects (or all the steps) of the invention to attack the validity, but with no availability of such results, our focus shifted on analysis of a combination art that covered maximum aspects of the invention. Our analysis also covered class-based searches, apart from keyword-based search. We used all the relevant IPC, CPC, US classes, and F-term classifications (Japanese classification system). This was followed by assignee-based searches and inventor-based searches.

Based on our analysis, we found a Japanese patent literature published in 1993 which seemed to cover a majority of our aspects, however not all. At first, our team did a thorough analysis of the patent to check if all the elements were actually disclosed as needed. Considering the publishing date of the patent was 30 years prior to our cut-off date, our team did a detailed analysis if the patent could even be considered relevant. To our amazement, our analysis revealed that the literature was quite relevant. Still, the novel feature of the patent was not clearly identified. Even though a few patent references broadly disclosed the novel aspect or element of the subject patent, explicit disclosure of the aspect was still not evident in the analyzed results.

A prior art for a subject patent basically discloses that the invention was either already known, or does not involve any inventive step, i.e., are obvious to a person skilled in the art. Thus, the reference used for destroying the novelty does not necessarily have to be a patent reference. Our next step in analysis was searching for non-patent literature including research papers, blogs, thesis, articles, or any such written documents uploaded online. However, like the patent analysis, our non-patent analysis could also not substantially destroy the novelty. We did come across a few references including research papers disclosing a majority of the aspects of the subject invention which were shared with our client.

After sharing our results with the client, we asked for their input for cracking the invalidation based on the relevant prior art results we analyzed. On subsequent discussions, our client explained how none of our provided results seemed eligible for a good combination-based case.

Based on the discussion, our team made another strategy for analysis, which included search and analysis of the broadest concepts, solely dedicated to the novel aspect of the subject patent to find literature in which the novel aspect is very explicitly disclosed, even if other aspects are not mentioned. For such a search, we only used the keywords for the basic technology, i.e., pulp and paper manufacturing, and the novel aspect. Finally, we found a French patent reference disclosing the key novel aspect of the invention, although the other aspects of the subject disclosure were not clearly mentioned. However, using this reference in combination with the earlier JP patent prior-art, a strong case could be formed for invalidation against the subject patent. Also, the French prior art reference had a publication date of 1987!

We shared both the references with the client and our team received good feedback from the client for the case and the client agreed that the references together can be used as a combination art for the EP invalidation case.


Every case we work on can yield a new learning, not only by emphasizing the techniques for searching and analysis, but also key insights of a domain and/or technology. One of the key observations our team made while working on the case was the timestamp of the relevant prior-art references. Both the patent prior-art references, which were shared with the client for making the combination art were published more than 20 years prior to the subject patent’s cut-off date. Thus, a common misconception that relevant prior art will only be restricted to a particular timeline (such as only a few years ago since it must be novel in the field) can lead to missing out on certain good references. Specially, in certain fields such as pulp & paper processes, industrial designs, metallurgical processes, older references may disclose relevant features you may be looking for.

Note: At Expertlancing, we always strive for excellence and continuous development – we keep refining our prior-art search processes with new learning so that we can always provide brilliant results for our clients. Please feel free to reach out to us for more information.

Food for thought

Delve deeper and savor a treasure trove of more such insightful reads

The future of telecom is here – 6G

In the world of telecommunications, it is all about 5G right now but just around the corner is the revolutionizing 6G standard which is currently being developed.

How analysis of a provisional application led us to a killer prior art for a 5G technology patent?

As we undertake challenging projects related to 5G and telecom SEPs, we often come across certain scenarios that leave an indelible impression.

Chess’s Knight forces a Checkmate and Leads to a Strong Prior-Art

As prior-art searchers, we perform complex prior-art searches everyday. But at times we stumble upon some cases that result in truly amazing experiences and takeaways.

Searching the complex world of standards – Finding a needle in a haystack

When we talk about standard searching, the first question that comes to our mind is...

Want to explore more?

Take a look at who we are and what we have to offer.