Maxichem UK Limited v Honeywell International Inc.

The recent Court of Appeal judgment in Mexichem UK Ltd v Honeywell International Inc [2020] EWCA Civ 473 has upheld the first instance decision of Hacon J refusing to strike out Mexichem's requests for Arrow declarations in relation to Honeywell's patents and patent applications.

An Arrow declaration is a negative declaration made by the Court that a product or process was old or obvious at a particular date. As such, any patent claims with a priority date after that date cannot both cover the product or process in question and be valid. The aim of such declaratory relief is to protect against future infringement allegations related to granted or yet-to-be-granted, and potentially unknown, patents. Arrow declarations take their name from the case of Arrow v Merck [2007] EWHC 1900 (Pat), the first case in which such relief was sought, with subsequent cases seeking to define the boundaries of this form of relief. The recent Court of Appeal decision is the latest such case.

The present action relates to Honeywell's patent portfolio of ten granted and pending patents for the use of two particular refrigerants ("ze" and "yf") in mobile air-conditioning systems. Mexichem sought to revoke the six granted patents and obtain Arrow declarations with respect to the four pending divisional patents. In response, Honeywell sought to strike out the declarations.

At first instance Hacon J dismissed Honeywell's contention that an Arrow declaration had to be sought in relation to a specific product or process. Declarations framed in more general terms, he held, could still have utility because "they are aimed at providing a finding of obviousness which can serve as an unchallenged foundation for argument on the inventive step of inventions claimed in patents which may be granted to the defendant in the future".

Honeywell appealed, arguing that a declaration framed in such broad general terms lacked any real utility because no resolution could be achieved until after a second round of contested proceedings. Further, the judge had been wrong to treat the question of inventive step as something which can be sliced up into a series of steps and dealt with in turn. In relation to the latter, Honeywell argued that such a stepwise approach would have "distorted the exercise which the court was later required to perform", which is to decide whether the invention as a whole is inventive.

In dealing with the clarity point, Floyd LJ referred to the Court of Appeal...