Knowing when to quit

Abstract

This paper discusses the case filed by Kao, a large Japanese cosmetic manufacturer, versus Unilever. Kao filed the first of a long series of patent applications on an improved approach for removing blackheads. Kao scientists discovered that pore strips used in removing blackheads worked better when the adhesive used on the strips was a copolymer of vinyl methyl ether with maleic acid, known to chemists as PVM/MA copolymer. After years of prosecution, Kao finally obtained a basic patent, '382 patent, on the use of its copolymer. It introduced the product to the market under the tradename Biore Deep Cleansing Pore Strips. Prior to the issuance of the '382 patent, Unilever, introduced a competing product under the tradename Pond's Clear Solutions Clear Pore Strips. The Pond's product also used the PVM/MA copolymer but in addition included aminomethyl propanol (AMP) in the product as a plasticizer to make the strips less brittle. The AMP reacted with a small fraction of the maleic acid of the PVM/MA copolymer to form a salt, a fact that turned out to be central to the ultimate decision in the Kao. v. Unilever litigation. Prior to the issuance of the '382 patent, Kao filed a continuation application for a second patent which specifically claimed salts of PVM/MA copolymers. This fact also turned out to be important to the Kao v. Unilever case. The case revolved on the question whether it is proper for a court to limit the scope of the claims of one patent by looking at the claims of a subsequent patent obtained by the same company