When I joined Polychrome in 1965, Polychrome was involved in a bitter lawsuit perhaps for survival with mighty 3M. As I understood then 3M sued a Polychrome plate user and a dealer claiming Polychrome infringed in their technology； the interelayer treatment called silicating. Apparently Polychrome used the silicate technology in early production days but soon changed to use Zirconium interlayer but felt continued pressure from 3M and later filed civil suit for anti-trust law violation. The following is an extract from the interesting file 1966 Polychrome vs 3M
1955 3M received patent on silicate treatment
1958 3M sue a Polychrome's customer and a dealer claiming Polychrome infringed their patent,
1960 Polychrome patent on Zriconium compound issued.
1961 Indictment against 3M regarding antitrust action
1962 Polychrome and 3M agree to end law suit and Polychrome receives license on silicate
1966 Jan, a sentence was imposed on 3M (see above 1961 indictment), 3M claimed no contest
1966 Apr. Polychrome file civil suit
1966 Apr. (2 days later) Government start civil action against 3M for Sherman Act (antitrust) violation
1966 Oct. Judge denies move by 3M to move the court venue from NY to Chicago
In 1966 as the suit continued, Polychrome needed to show that the Zirconium technology is not infringing on 3M patent and a court supervised experiment was conducted in Polychrome lab with the presence of 3M chemists and a court appointed referee Dr. Henry Linford of Columbia University.
The suit was abruptly terminated when both party agreed on a settlement. The details are not known but it was rumored that the Polychrome received $1m from 3M and paid our lawyers more than $1m!