558 JOURNAL OF COSMETIC SCIENCE COMPLEX EFFECT PIGMENTS: TECHNOLOGY IN SUPPORT OF BEAUTY & f ASHION INTRODUCTION Leila S. Song, Ph.D. and Gabriel E. Uzunian BASF Corporation There are new fashion trends and new design influences every year. New materials and formulations are developed to support these new trends and influences. New trend colors no longer match the traditional descriptions such as yellow, red, blue, or green, but instead require more sophisticated visual language, such as sunrise gold, baby pink, sheer indigo, or emerald green, which reflect unique combinations of colors and effects. New color also no longer has only a one-dimensional monotone flat appearance, but rather multi-dimensional, multi-color and changing-color shades with depth. More than merely reflecting light, complex effect pigments actually manipulate light to create a visual impression and can dramatically improve cosmetic and personal care products to meet the beauty and fashion trend. In the past decade the technology to produce a variety of effects has been improved dramatically. The early single-oxide-coated mica pigment has simple structure. As new pigments evolve, their structure becomes much more complex. This has led to a proliferation of new effects: appearances from satiny sheen to metallic luster to sparkling and colors from simple white and iridescent interference to optically variable shifting color. Today's formulators have unlimited options to enhance the aesthetic value and performance of their products. DISCUSSION Typically an effect pigment is based on thin, translucent platelets of low refractive index material, coated with a high refractive index material. Effect pigments are optical filters that reflect and transmit light that falls upon them. The basic laws of optics apply to all effect pigments. The fundamental theory of interference pigments is the principle of light interference and the angular dependence of the reflected or refracted lights. Light striking the surface of pigments is refracted, reflected and scattered by the layers that make up the pigment. A changing play of color is created through interference of the reflected rays of light, with the most intense color seen at specular angle. (1,2) Color effect and coating Colors and effects of pigments can be formed in several different ways as described below: Depending on the coating thickness of high refractive index material, interference colors of gold, red, blue, or green can be generated for the simple structured single-oxide-coated interference pigments. Combining absorption and interference colors can create a variety of single- or dual-color effects. The presence of an absorption pigment, either coated onto the interference pigment or used in conjunction with it, produces intense specular reflection colors that give away to the color of the absorption pigment at non­ specular angles. There is also a transmission color that combines the effects. (1,2) Adding layers of both low and high refractive index materials onto the mono-layer pigment, the resulting multi-layer coated effect pigment intensifies the color reflectivity. This is because the pigment has more surfaces to reflect, thus there are more chances for the light to be intensified. Further improvement of the multi-layer coatings by applying non-quarter wavelength multi-layered coating technology can result in a complex effect pigment that not only enhances the intensity and chromaticity of the reflected light but also creates goniochromatic color travel effects. (3)

2007 ANNUAL SCIENTIFIC SEMINAR 559 Color effect and substrate The most widely used substrate is mica. In recent years, a variety of platy materials having a smoother and cleaner surface than mica have been proposed and developed for use as a substrate for complex effect pigments. For example, new levels of shimmer and shine can be produced through the use of a very smooth and transparent borosilicate glass base. Borosilicate-based pigments, which are designed with excellent color purity, brightness, transparency and reflectivity can create a brilliant sparkle effect with a strong feeling of depth. Blending borosilicate-based pigments will generate true multicolored polychrome effects. (4) Color effect and particle size Different coloring effects can be achieved by the right choice of pigments depending on their particle size. Small particles create a smooth silky and satiny luster. They enhance the hiding power of formulations and provide a high coverage as well. Large particles provide high luster effects of sparkling or glittering. Furthermore, interference colors on large flakes are particularly interesting in formulations because they deliver a dramatic overtone that stands out, but without masking the continuous masstone. Large particles of borosilicate-based pigments will give the product deep intensive sparkling highlights with a 3- dimensional appearance. Formulation with effect pigment The following formulations allow formulators to create different colors and appearances to meet the current beauty and fashion trends: • Formulation of interference pigment (10 microns) mixed with organic-colors/interference pigment (30 microns) will create a subtle and luminous calm effect with soft and neutral look. • Formulation of intense absorption-interference pigment (30 microns) mixed with highly smooth interference pigment ( 40 microns) will create a lustrous and shimmering narration effect with distinctive two-color look for the narration theme. • Formulation oflarge smooth interference pigment (60 microns) mixed with large size intense smooth black absorption-interference pigment (60 microns) will create a vibrant sparkling and iridescent resonance effect with intense accents. • Formulation of non-quarter wavelength multi-layer color changing interference pigment will create a goniochromatic polychrome color travel effect. CONCLUSION The unique optical characteristics of complex effect pigments can provide eye-catching appearances. The pigments have helped capture the appearance of the fashion trends and convert them into color cosmetics and personal care products. REFERENCES 1. L. M. Greenstein, Pigment Handbook, New York, John Wiley & Sons (1988). 2. L. Armanini, "Basic Optics and Pearlescent Pigments", Paint and Coatings Industry, 5 (8) (1989). 3. C. J. Zimmermann and D. S. Fuller, "Multi-layer effect Pigment'', US Patent 6,875,264 (2005). 4. G. E. Uzunian and L. S. Song, " The Borosilicate Platform'' Personal Care Ingredients Asia, 53 (2004).