Land's patent no. 2,669,516

http://www.box.net/shared/static/22ln0zhdab.pdf

Above is a link to the Land patent that does not seem to say too much about the preparation of the receiver layer.   Rott's complete description of the kinetics and chemistry in his book, mentioned below, may seem to have possibly obviated the need, or perhaps the desire, for Land et al to publish a follow-on book that would have had to teach what Polaroid might have considered trade secret information, to be complete.