Serial wins in invalidation and judgment revocation actions over a patent for transparent adhesive sheets used in displays

A Japanese chemical company, M, filed a patent infringement lawsuit against a Korean company, represented by Lee & Ko, asserting three patents. In response, the Korean company initiated invalidation actions against all three of M’s patents. The patents in dispute concerned transparent adhesive sheets used in displays, meaning the case had a direct impact on the supply of materials to display manufacturers. The outcome of the litigation was therefore critical for both parties, as it would determine whether the display materials could continue to be supplied, thereby carrying significant business implications for both companies.

In this case, major law firms represented both parties, and the dispute was fiercely contested. Lee & Ko, representing its client, a Korean company, conducted an extensive search of prior art and filed invalidation actions on the grounds of lack of inventiveness. As a result, Lee & Ko’s arguments were accepted, and both the Intellectual Property Trial and Appeal Board (“IPTAB”) and the IP High Court found the patents in dispute to be invalid.

Although the patents concerned adhesive sheets (i.e., product inventions), they included a limitation stating that “the adhesive sheet is used upon exposure to ultraviolet rays”. Lee & Ko argued that this limitation merely indicated that the adhesive sheet contained a component enabling curing, rather than imparting a substantive distinction. In the chemical field, product claims are often limited by properties, physical characteristics, or methods of use in addition to the actual components. However, in many cases, the claimed invention is essentially identical to prior art. By closely analyzing the patent specification and interpreting the claims accordingly, Lee & Ko demonstrated logically and convincingly that the invention did not differ in substance from known technology, leading to the conclusion that it lacked inventiveness.

Both the IPTAB and the IP High Court agreed with Lee & Ko’s arguments and held that the patents were invalid for lack of inventive step. This case is expected to serve as a valuable precedent for evaluating inventiveness in the field of chemical inventions.