Printed indicator compositions
A method of revealing exposure of a substrate to an environmental stimulus includes exposing the substrate to the environmental stimulus, where the substrate includes at least one indicia, where each of the at least one indicia includes a plurality of chromatically selective scattering particles having a particle size distribution as measured by (weight average diameter)/(number average diameter) of less than or equal to about 1.1, and a colorant; and the at least one indicia exhibits a change in color in response to the environmental stimulus.
1. A method of revealing exposure of a substrate to an environmental stimulus comprising:
exposing said substrate to said environmental stimulus;
wherein:
said substrate comprises
at least one indicia, wherein each of said at least one indicia comprises:
a plurality of chromatically selective scattering particles having a particle size distribution as measured by (weight average diameter)/(number average diameter) of less than or equal to about 1.1, and
a colorant;
said at least one indicia exhibits a change in color in response to said environmental stimulus;
said chromatically selective scattering particles comprise polymeric particles; and
said polymeric particles have a glass transition temperature from about 20° C. to about 180° C.
2. The method of claim 1 , wherein said environmental stimulus is heat, pressure, liquid, or vapor.
3. The method of claim 1 , wherein said glass transition temperature is from about 40° C. to about 140° C.
4. The method of claim 1 , wherein said colorant is a dye or pigment.
5. The method of claim 1 , wherein said colorant is carbon black.
6. The method of claim 1 , wherein said substrate is paper, paperboard, plastic film, or foil.
7. The method of claim 1 , wherein said at least one indicia is a pattern, a logo, a picture, or text.
8. The method of claim 1 , wherein said at least one indicia is configured to provide information regarding said environmental stimulus.
9. The method of claim 1 , wherein said at least one indicia is at least a first indicia and a second indicia; and said chromatically selective scattering particles in said first indicia have a glass transition temperature that is different from a glass transition temperature of said chromatically selective scattering particles in said second indicia.
10. The method of claim 9 further comprising identifying a thermal history for a product comprising said substrate, based upon said observing a change in color.
11. The method of claim 9 further comprising identifying a counterfeit product comprising said substrate, based upon said observing a change in color.
12. The method of claim 1 , wherein said chromatically selective scattering particles comprise an emulsion polymer or other types of polymer colloid.
13. The method of claim 1 , wherein said weight average diameter of said chromatically selective scattering particles is from about 125 to about 700 nm.
14. The method of claim 1 , wherein said chromatically selective scattering particles comprise polymeric particles polymerized from vinyl aromatic monomers, (meth)acrylic acid monomers, and (meth)acrylate monomers, or mixtures thereof.
15. The method of claim 1 , wherein said chromatically selective scattering particles comprise polymeric particles polymerized from styrene, α-methylstyrene, butadiene, vinyl acetate, (meth)acrylic acid, 2-hydroxyethyl(meth)acrylate, 2-ethylhexyl acrylate or mixtures of any two or more thereof.
16. The method of claim 1 , wherein said chromatically selective scattering particles comprise inorganic particles selected from the group consisting of silica particles, glass particles, and titanium dioxide particles.
17. The method of claim 1 , wherein said chromatically selective scattering particles are a mixture of solid and hollow sphere particles.
18. The method of claim 1 , wherein a ratio of refractive indices of said chromatically selective scattering particles and a surrounding medium is at least about 1.2.