Silky-White Multilayer Coating with Non-Platelet TiO2
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Solution Overview
Problem
Current automotive coatings with titanium dioxide pigments often result in a coarse texture and rainbow interference effects, failing to maintain a bright, pure white color and fine, silky appearance due to large particle size distribution and platelet-shaped pigments.
Innovation Solution
A multilayer coating comprising a ground coat layer with non-platelet-shaped titanium dioxide pigment, a midcoat layer with platelet-shaped titanium oxide pigments such as hydrogen titanium oxide, titanium dioxide coated fluorinated mica, or titanium dioxide coated aluminum, and a clearcoat layer, optimized for lightness and reduced graininess across various viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If platelet-shaped effect pigments are used to create metallic or pearlescent white effects, then the coating displays a multicolored rainbow interference, but the texture becomes coarse and the silky effect is difficult to obtain
Solution Approach 1:
The patent applies parameter changes by carefully controlling the thickness of the transparent coating layer on the platelet-shaped pigments to be between 0.5-5 μm, and by selecting specific refractive index combinations between the pigment core, coating layer, and surrounding medium. This optimizes the optical interference effects to produce silky white appearance while minimizing coarse texture and excessive rainbow interference.
2Illumination intensity
If a large particle size distribution is used in effect pigments, then light scattering along the edges increases, but this arises in an apparent coarse look
Solution Approach 1:
The patent controls the particle size parameters of the platelet-shaped effect pigments within specific ranges (diameter 2-50 μm, thickness 0.5-5 μm, aspect ratio 4:1 to 50:1) to optimize light scattering for brightness while minimizing edge scattering that causes coarse appearance. The uniform size distribution further prevents apparent coarseness.
Solution Approach 2:
The patent uses composite structure with a core material (metal, mica, glass, or metal oxide) coated with a transparent layer having different refractive index, creating a composite pigment that provides both the desired light scattering for brightness and controlled optical effects for smooth appearance.
3Illumination intensity
If titanium dioxide pigments are used to provide white color, then brightness is maintained, but the pure white look is reduced by characteristic interference rainbow effect
Solution Approach 1:
The patent combines titanium dioxide pigment (for brightness and white color) with platelet-shaped effect pigments having controlled transparent coating layers. The composite pigment system maintains the brightness from titanium dioxide while the carefully engineered platelet structure minimizes excessive rainbow interference to preserve pure white appearance.
Solution Approach 2:
The patent optimizes the refractive index parameters of the transparent coating layer (1.4-2.0) and its thickness (0.5-5 μm) to control the optical interference effects, reducing characteristic rainbow interference while maintaining the brightness enhancement provided by titanium dioxide.
4Ease of manufacture
If coated platelets with metal oxide layers are used to produce silky white effects, then white color is achieved, but the texture appears coarse and rainbow interference is evident
Solution Approach 1:
The patent precisely controls the transparent coating layer thickness (0.5-5 μm) and refractive index (1.4-2.0) to optimize optical interference for silky appearance while minimizing coarse texture. The controlled particle size parameters (diameter 2-50 μm, thickness 0.5-5 μm) further ensure fine texture without excessive coarseness.
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 solution achieves a bright, pure white color with a fine, silky texture and reduced graininess, maintaining excellent lightness and metallic appearance without excessive coarseness, as demonstrated by specific L* values and graininess metrics.
Implementation Method 1
A large particle size distribution increases the light scattering along the edges of such flaky pigments, arising in an apparent coarse look
Implementation Method 2
it is usual to discern a multicolored rainbow interference arising from the coated platelets
Data Source
AI summary
Disclosed herein is a multilayer coating including at least one ground coat layer, the at least one ground coat layer including at least one non-platelet-shaped titanium dioxide pigment (T); at least one midcoat layer on top of the at least one ground coat layer, and at least one clearcoat layer on top of the at least one midcoat layer; and having a lightness L* according to CIELab in the viewing angle range from −15° to +45° of at least 80; in the viewing angle range from +75° to +110° of at least 70, if a metal effect pigment is contained in the midcoat layer; in the viewing angle range from +75° to +110° of at least 75, if no metal effect pigment is contained in the midcoat layer. Further disclosed herein are a method for producing such multilayer coating and a multilayer coated substrate.