Glitter Pigment With Light Scattering Particles For Angle-Dependent Color Stability
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Solution Overview
Problem
Glitter pigments exhibit significant color and brightness variations when observed from different angles due to the optical interference film and fine metal particles, leading to an unnatural appearance, particularly in applications like cosmetics.
Innovation Solution
A glitter pigment comprising a flaky substrate with an optical interference film and fine light scattering particles, where the reflected light is characterized by specific L* and ΔL*(h−s) and Δh(h−s) values to maintain high brightness and reduce angle-dependent variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an optical interference film is designed to present a reflected color close to human skin color in the regular reflection direction, then the brightness in the regular reflection direction is improved, but the color shifts when observed from different directions leading to an unnatural appearance
Solution Approach 1:
The patent applies local quality by creating distinct functional zones within the glitter pigment structure: the optical interference film provides high brightness in the regular reflection direction, while the randomly oriented fine particles provide angle-independent light scattering. This local differentiation of optical properties at different spatial locations and angles resolves the contradiction between directional brightness and angular color stability.
Solution Approach 2:
The patent employs composite materials by combining the optical interference film (providing directional brightness through constructive interference) with fine particles of titanium oxide, zinc oxide, or silicon oxide (providing isotropic light scattering). This composite structure integrates two different optical mechanisms to simultaneously achieve high brightness in the regular reflection direction and color consistency across various observation angles.
2Manufacturing precision
If fine metal particles are attached to enhance the vividness of reflected light, then the color saturation is improved, but the brightness variation depending on observation angle increases
Solution Approach 1:
The patent applies parameter changes by transitioning from using fine metal particles (which provide strong color but high angular variation) to using fine inorganic oxide particles with different optical properties. The inorganic oxide particles have lower refractive indices and provide more isotropic light scattering, changing the optical parameters to reduce brightness variation while maintaining acceptable color vividness through the underlying optical interference film.
3Illumination intensity
If the optical interference film thickness is optimized for regular reflection, then the reflected color in the regular direction is improved, but the color shift to greenish tones when observed from other directions occurs
Solution Approach 1:
The patent introduces fine inorganic oxide particles as an intermediary element between the optical interference film and the observer. These particles scatter light in multiple directions before it reaches the observer, mediating the strongly directional reflected light from the optical interference film and converting it into more isotropic reflected light that maintains color consistency across different observation angles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The glitter pigment maintains high brightness and reduces unnatural color shifts when viewed from different angles, providing a natural appearance by ensuring consistent brightness and hue across various observation directions.
Implementation Method 1
Glitter pigments each including an optical interference film present pearly gloss due to an optical interference effect
Implementation Method 2
fine light scattering particles attached to the optical interference film
Data Source
AI summary
The present invention provides a glitter pigment suitable for imparting high brightness to reflected light toward a regular reflection direction and reducing unnaturalness caused by an observation angle-dependent variation in reflected light. The glitter pigment according to the present invention includes: a flaky substrate; an optical interference film formed on a surface of the flaky substrate; and fine light scattering particles attached to the optical interference film, wherein reflected light is represented by an L*(15) value of more than 100, a ΔL*(h−s) value of less than 30, and a Δh(h−s) value of less than 40° in an L*C*h color system. The L*(15) value is an L* value of the reflected light toward a 15° direction based on an angular representation in which, when an illuminant is disposed so that an incident angle is 45°, an angle at which light is regularly reflected is defined as 0° and a light incident direction is defined as positive. The ΔL*(h−s) value is a difference in L* between a highlight and shade, and the Δh(h−s) value is a difference in h between a highlight and shade. The Δh value expressed in angle is an angular difference. The highlight is an average of values measured at 15° and 25°, and the shade is an average of values measured at 75° and 110°.