The present invention relates to a diazo imaging process and, more specifically, to a two-component aqueous diazo imaging composition and method of preparing a diazo imaging member.
In reprographic methods for forming a dye image utilizing a light-sensitive diazonium compound, the diazo composition is selectively exposed to actinic radiation, decomposing the diazonium molecules in the light struck areas to produce a relatively colorless area which is inactive during further processing. The light-sensitive diazonium compound remaining in the unexposed areas is subjected to a coupling reaction with a compound referred to as a coupler capable of reacting with the diazonium compound in an alkaline environment to form a dye image selectively in the reprographic material. The two most widely accepted diazo processes are often referred to as the one-component or semi-moist development process, wherein the light-sensitive diazo type material contains the diazo compound in the absence of a coupler, and the development step entails applying a developer solution containing a coupler to the radiation-exposed diazo composition, and a two-component or dry development process wherein the light-sensitive diazo composition contains the diazo compound and the coupling component or components in an acidic environment, which protects against pre-exposure coupling, wherein the development step following actinic radiation exposure entails exposing the diazo-type material to an alkaline atmosphere of ammonia or amine vapors.
Although the two-component or dry development process has certain advantages over the one-component or semi-moist development process, the major advantage being the fact that it is essentially a dry process, there are certain disadvantages associated with the dry process. Heretofore, in the preparation of the diazo imaging member, the diazo composition has been coated onto a pretreated film base from an organic solvent system to produce the diazo copy member to be used in a conventional dry diazo imaging process. The use of organic solvents in the coating of the diazo member, however, has not only proved to be costly but the use of the solvents present safety hazards and have a negative impact upon the environment such that elaborate solvent recovery systems must be utilized taking into consideration serious environmental constraints with respect to waste disposal. Thus, not only is the solvent system expensive, but the solvent itself must be recovered from gases expelled from a dryer present in the system and then must be disposed of by environmentally accepted procedures. The solvents used also require special storage facilities.