Use of phosphorescent pigment is known. For instance, U.S. Pat. Nos. 5,472,737 and 5,874,491 incorporate phosphorescent pigment into phosphorescent paint compositions that are used as highway or roadway paint compositions. Use of phosphorescent pigment in automotive and other coating systems is also known in the art. For instance, U.S. Pat. No. 6,242,056 incorporates phosphorescent pigment, specifically phosphorescent-coated beads, into reflective, heat-cured paint coating systems to enhance the light emission of the paint coating system.
The conventional use of phosphorescent pigment in conventional coating systems is inadequate for various reasons. Many compositions that are used to form the coating systems with the phosphorescent pigment are not cross-linkable. Examples of compositions that are not cross-linkable are disclosed in the '737 and '491 patents. Due to the lack of cross-linking, these compositions are not suitable for automotive coating systems where durability and the physical integrity of the coating system, relative to weathering and exposure, is paramount. Furthermore, many coating systems, such as the coating system disclosed in U.S. Pat. No. 5,998,525, do not provide for multiple film layers for making-up the coating system. Unlike the coating system of the '525 patent, the present invention provides a method for wet-on-wet application of multiple film layers, such as a clearcoat film layer, to achieve excellent gloss and DOI. For these reasons, the prior art compositions are not suitable for automotive coating systems where multiple film layers are required that provide acceptable appearance, as measured by gloss and DOI. In fact, some DOI measurements for the prior art compositions do not even register on typical DOI meters.
The conventional use of phosphorescent pigment in conventional coating systems is also inadequate because the phosphorescent pigment in some conventional coating systems must be completely encapsulated within a particular film layer to be able to produce the desired light emission of the coating system. An example of such a conventional coating system is disclosed in the '056 patent. These conventional coating systems of the prior art typically require cures, or bakes, between each film layer of the coating system to achieve complete encapsulation of the phosphorescent pigment within the particular film layer and to achieve suitable gloss and DOI. These coating systems are inadequate because they do not allow for wet-on-wet application of the various film layers that make up the coating system. It is widely known in the art that any method requiring cures for each film layer of a coating system is time consuming and expensive because ovens must be used for each cure. Finally, certain phosphorescent coating systems of the prior art strictly rely on conventional phosphorescent pigments such as zinc sulfide, or radioactive substances such as radioisotopes, and reliance on such conventional phosphorescent pigments is not always desirable.
In sum, the coating systems and compositions of the prior art, primarily the uses of the phosphorescent pigment in these coating systems and compositions, are characterized by one or more inadequacy. As a result, it is desirable to implement a method of providing a phosphorescent coating system that is cross-linkable and includes phosphorescent pigment for wet-on-wet application of the coating system to a substrate, such as an automotive body panel.