European Patent Office backs Borealis in POE encapsulation dispute

The European Patent Office has ruled that Borealis AG can continue producing polyolefin encapsulation (POE) material for solar applications, rejecting a patent challenge by Japan’s Mitsui Chemicals.

Austrian chemical company Borealis AG may continue producing POE material for the solar industry, following a July 2 ruling by the European Patent Office.

Japanese chemical producer Mitsui Chemicals, which holds a patent for the POE material “Engage 8400,” filed the case. Borealis argued that the polymer used in the material was already available on the market before Mitsui Chemicals filed its patent application, making the product “state of the art” under European patent law and therefore not patentable.

Mitsui Chemicals argued that the exact chemical structure of the material could not have been reproduced by a trained expert without excessive effort, an argument referred to in patent law as the “undue burden by a skilled person.”

The European Patent Office considered whether a product can lose its “state of the art” status if reproducibility requires considerable effort. The office ruled that it cannot. Any product marketed before a patent filing qualifies as “state of the art,” even if its exact chemical structure is not readily known. The office also stated that public technical documentation, such as brochures, qualifies as prior art.

The ruling rejected Mitsui’s argument and sided with Borealis.

The decision may have broader implications for European patent law, particularly around whether ease of reproducibility is required for prior art classification.