Closest prior art for invalidation proceedings

According to China’s local practice, there are three steps to follow when determining whether a claimed invention is obvious when compared to the prior art:

• determining the closest prior art;
• distinguishing the features of the invention and the technical problem that it actually solves; and
• determining whether the claimed invention is obvious to a person skilled in the art.

The closest prior art is the logical starting point for any inventiveness assessment. It is therefore important to accurately identify the closest prior art to be cited in the inventiveness assessment. With reference to a case study based on China’s Patent Examination Guidelines, this chapter briefly discusses the factors that should be considered when selecting the closest prior art in patent practice.

Patent Examination Guidelines

The Patent Examination Guidelines provide for the determination of the closest prior art. The ‘closest prior art’ refers to a technical solution in the prior art that is the most closely related to the claimed invention and that should be the basis for determining whether the claimed invention has prominent substantive features. The closest prior art may, for example, be:

• an existing technology in the same technical field as the claimed invention, where the technical problem to be solved, the technical effects or intended use are the closest to the claimed invention, and that has disclosed the greatest number of the claimed invention’s technical features; and
• an existing technology that, despite being in a different technical field from the claimed invention, can perform the invention’s function, and that has disclosed the greatest number of the invention’s technical features.

When determining the closest prior art, prior art in the same or similar technical fields should be considered first.

In practice, other factors should also be considered in the determination of the closest prior art. A comprehensive grasp and thorough understanding of these factors contributes to developing a proper strategy for invalidation proceedings.

Case study

A recent case (selected from the Annual Report on Intellectual Property Cases of the Supreme People’s Court (2019) and published by the Supreme People’s Court) concerns a patent relating to a shark-fin antenna, Claim 1 of which announced that:

a shark-fin antenna, characterised as comprising an antenna shell, a radio receiving antenna being provided on an inner upper portion of the antenna shell:

• the radio receiving antenna being provided at one end with an antenna signal output end which is connected to an antenna amplifier signal input end via an antenna connecting element or is directly connected to and matches with a coaxial cable, and a mounting base plate being attached to a bottom of the antenna shell, the radio receiving antenna being mounted on the inner upper portion of the antenna shell by injection-moulding embedment or fixed engagement;
• the radio receiving antenna being provided on an inner upper portion of the antenna shell, the radio receiving antenna using a spiral spring antenna or a metal antenna which increases the effective length of the radio signal received by the antenna, thereby achieving 360-degree omnidirectional signal reception;
• the radio receiving antenna being an AM/FM common antenna.

The closest prior art used by the petitioner (D1) also relates to a shark-fin antenna and discloses most of the technical features of Claim 1. Claim 1 has the following distinguishing features:

• feature a – an antenna signal output end that is connected to an antenna amplifier signal input end via a connecting element or that is directly connected to and matches with a coaxial cable;
• feature b – the radio receiving antenna being mounted on the inner upper portion of the antenna shell by injection-moulding embedment or fixed engagement; and
• feature c – the radio receiving antenna being an AM/FM common antenna.

All three of these distinguishing features are disclosed by other prior art documents and are common knowledge.

In a conventional sense, D1 is appropriate as the closest prior art because it pertains to the same technical field as the concerned patent and discloses most of the technical features. However, the Re-examination Board held that Claim 1 was inventive on the following grounds:

Regarding distinguishing technical feature c, the technical solution of D1 realises the antenna arrangement which overcomes the defects mentioned in the description of the background art and achieves good signal reception performance by adopting the very technical solution of forming two individual antennas respectively designed as an AM antenna and an FM antenna. The use of multiple antennas has been considered as defective technical means in the patent concerned. If the technical solution disclosed by D1 is combined with the technical solution using a common antenna for AM/FM, it will be impossible to solve the existing technical problem. That is, D1 provides contrary technical teaching and prevents a person skilled in the art from arriving at the technical solution to the technical problem the patent concerned intends to solve. A person skilled in the art will not have been taught by the disclosure of D1 to combine D1 with a technical solution of the prior art about a common antenna for AM/FM.

Both the first and second-instance court supported the Re-examination Board’s opinion.

At the retrial stage, the Supreme People’s Court opined that there was no alleged contrary technical teaching. It held that as an initial matter, in determining whether claims are inventive, consideration should be given to whether the prior art as a whole offers technical teaching so that a person skilled in the art, when faced with the technical problem to be solved by the claims, may arrive at the proposed technical claim as a solution, after being motivated to combine the closest prior art with common knowledge in the art or other prior art in order to improve the closest prior art.

Further, with respect to the ‘contrary technical teaching’ identified in the decision, the term is usually used in contrast with ‘technical teaching’. Determining whether there is contrary technical teaching in a prior art should be based on analysis of the prior art as a whole in view of the knowledge level and cognitive ability of a person skilled in the art. The technical defects recorded in the specification of a patent document serving as the prior art regarding its background art are essentially subjective perceptions expressed by the patent applicant when drafting the application.

This means that a person skilled in the art does not necessarily consider such technical defects as objective knowledge. It also means that a person skilled in the art will not necessarily be constrained by the content related to the technical defects and cannot, therefore, obtain the corresponding technical teaching from the prior art. Moreover, even if the prior art records technical defects, further consideration must still be given to whether the technical defects are related to the technical problem actually solved by the distinguishing technical features and the determination of technical teachings.

In addition, one important factor contributing to the continuous development and progress of society lies in continuous scientific and technological innovation and the persistent research and improvement of science and technology. But all technology is bound to have both merits and defects. Regarding prior art with both merits and defects, when looking for technical teachings, a person skilled in the art will look at the actual technical problem to be solved and consider all relevant factors to make the corresponding analysis, trade-offs and determination to determine that the prior art overall offers the corresponding technical teaching or the contrary technical teaching.

Based on the common knowledge in the art and the disclosure of D1, a person skilled in the art can recognise that AM and FM functions may share one common antenna, or that the AM antenna and the FM antenna may be designed as two separate antennas. According to D1, a person skilled in the art will not conclude that the technology of a shared antenna for AM and FM functions is technically defective, nor would a person skilled in the art conclude that separating AM and FM functions from each other requires additional creative work.

On the contrary, in order to solve the technical problem that “conventional antennas have a single function, which means that more antennas are required when there are… more electronic devices, making it extremely inconvenient in a vehicle or a vessel with limited space [to install] multiple antennas thereon” – which corresponds to the distinguishing technical feature of the radio-receiving antenna being an AM/FM common antenna – a person skilled in the art is able to arrive at the obvious technical solution of the radio-receiving antenna being an AM/FM common antenna by combining the disclosure of D1 with the common knowledge in this field based on analysis and trade-offs of the pros and cons.

Considerations for selection

Using the shark-fin antenna case as an example, selection of the closest prior art can be controversial. The Re-examination Board determined that D1 employs technical means that are opposite to distinguishing feature c (the radio receiving antenna being an AM/FM common antenna) as a significant point of technical improvement. The board also held that a person skilled in the art had no motive to defeat the inventive purpose of D1. Although this view was eventually rejected at retrial, similar disputes continue to occur in other cases.

Referring to the Patent Examination Guidelines and the shark-fin antenna case, both positive and negative factors should be considered to affirm or negate the selection of the prior art document as the closest prior art.

The positive factors include:

• pertaining to the same or a proximate technical field;
• disclosing more technical features of the patent concerned; and
• having the closest technical problem to be solved, the closest technical effect or the closest use.

The negative factors include the following:

• Not being concerned with the technical problem actually solved by the patent:
  • In the three-step approach, the purpose of improving the closest prior art is to solve the technical problem that exists in the closest prior art (ie, the technical problem actually solved by the patent concerned). If the closest prior art does not relate to the technical problem actually solved by the patent owing to the application scenario or another reason, a person skilled in the art will have no motive to improve the closest prior art and will, therefore, not arrive at the claimed technical solution from the closest prior art.
• Not being able to solve the corresponding technical problem as reasonably expected by a person skilled in the art by incorporating the distinguishing features into the closest prior art:
  • This factor is more frequently considered in technical fields with poor predictability (eg, the chemical field). Since the purpose of combining the closest prior art with the distinguishing technical features is to solve the existing technical problem, where a person skilled in the art cannot foresee that the combination is capable of solving the technical problem that exists in the closest prior art, it will be deemed that a person skilled in the art will have no motive to perform the combination and will, therefore, not arrive at the claimed technical solution from the closest prior art.
• Causing technical difficulty in incorporating the distinguishing features into the closest prior art to the extent that a person skilled in the art may be unable to implement such a combined technical solution:
  • It is presumed that a person skilled in the art does not have the capability of making a creative effort. Therefore, if combining the closest prior art with the distinguishing technical features requires an effort to overcome technical difficulties that makes it difficult to implement such a combination, it will remain impossible to obtain the claimed technical solution.
• Causing impossibility to implement the technical solution of the closest prior art or violation of the original object of invention of the closest prior art by incorporating the distinguishing features to the closest prior art:
  • The purpose of combining the closest prior art with the distinguishing technical features is to improve its technical solution. Accordingly, in a case where the combination makes it impossible to implement the technical solution of the closest prior art or goes against the original object of invention of the closest prior art, it can be considered that a person skilled in the art will have no motive to perform such combination and cannot therefore arrive at the claimed technical solution from the closest prior art to some extent. In the shark-fin antenna case, the patentee mainly made a defence that the prior art contains this negative factor.

These negative factors are not expressly specified in the Patent Examination Guidelines but have been concluded from hands-on experience as a result of following the provisions of the guidelines. Disputes over these negative factors frequently occur in China’s local practice. To be more convincing, both the patentee and the petitioner should prepare statements considering the negative factors.

Comment

The closest prior art should be selected based on a comprehensive judgement considering both positive and negative factors. The selected closest prior art should avoid negative factors to the greatest extent possible. Nevertheless, using a closest prior art with negative factors does not necessarily mean that the invalidation petition will fail.

With sufficient preparation the adverse effects of the negative factors can be reduced and the success rate increased. The success rate of the invalidation proceedings can also be improved by using various evidential materials in combination.