Security articles having diffractive surfaces and color shifting backgrounds

1. A security article comprising:

a light transmissive substrate having a first surface and an opposing second surface and having a predetermined thickness, the first surface having a diffraction grating pattern or a holographic image pattern and the second surface being substantially planar, wherein the diffraction grating pattern or holographic image pattern has a depth that is substantially less than the predetermined thickness of the light transmissive substrate; and

a color shifting optical coating on the second surface of the substrate , said optical coating including a polymeric medium and a plurality of color shifting multilayer optical interference flakes dispersed in the polymeric medium, wherein the flakes comprise an absorber layer, a dielectric layer and a reflector layer, wherein the optical film provides an observable discrete color shift such that the article has a first background color at a first angle of incident light or viewing and a second background color different from the first background color at a second angle of incident light or viewing, the article exhibiting an optical diffraction grating pattern effect or a holographic image pattern effect in addition to the first and second background colors.

2. A security article as defined in claim 1 wherein the polymeric medium includes at least a pigment vehicle for use in ink or paint.