Conductive Interference Pigments via Graphene Coating
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Solution Overview
Problem
Existing electrically conductive pigments either have good color properties with indeterminate electrical properties or satisfactory conductivity with achromatic coloration, failing to achieve both high electrical conductivity and attractive coloration necessary for reliable shielding or antistatic applications, and often require additional colorants that increase electrical resistance.
Innovation Solution
Development of electrically conductive, colored interference pigments with a platelet-shaped carrier coated by an outermost layer consisting of at least 95% crystalline carbon in the form of graphite and/or graphene, which enhances electrical conductivity and provides high hiding power without the need for additional colorants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon black or graphite is used as conductive filler, then electrical conductivity is improved, but the materials darken which is perceived as a disadvantage
Solution Approach 1:
The patent uses a composite structure with a transparent substrate (mica or silica) coated with a thin layer of crystalline carbon (graphite or graphene). This composite approach combines the transparency of the substrate with the conductivity of the carbon layer, achieving both optical clarity and electrical functionality without the severe darkening effect of bulk carbon black.
Solution Approach 2:
Instead of using carbon throughout the entire pigment volume, the patent applies carbon only as a thin outermost layer (a few nanometers to micrometers thick) on the surface of transparent substrate particles. This localized application provides sufficient conductivity at the surface while maintaining the transparency of the bulk material.
2Illumination intensity
If transparent substrates with conductive coatings are used, then transparency and light color are improved, but inherent color is achromatic or light gray requiring additional colorants
Solution Approach 1:
The patent utilizes interference effects through precise control of layer thicknesses in the multilayer coating structure. By adjusting the optical thickness of dielectric layers and the carbon layer, specific wavelengths of light are enhanced or suppressed, producing vibrant interference colors without requiring organic colorants. This optical interference mechanism generates color directly from the structural properties of the coating.
3Ease of manufacture
If colorants are added to achieve colorful conductive media, then color properties are improved, but electrical resistance increases significantly
Solution Approach 1:
The patent replaces organic colorants with optical interference effects generated by the multilayer coating structure. The interference colors arise from the constructive and destructive interference of light waves reflected from different interfaces within the coating, providing vibrant colors that do not interfere with electrical conductivity since no additional non-conductive colorant materials are introduced.
Solution Approach 2:
The multilayer composite structure (substrate + dielectric layers + carbon layer) generates color optically rather than through pigment absorption. This allows the conductive carbon component to remain the primary coloring agent, maintaining conductivity while achieving colorful appearance through the optical properties of the layered structure.
4Quantity of substance
If pigment concentration is increased to compensate for reduced conductivity, then color intensity is improved, but processing problems occur due to technical limits
Solution Approach 1:
The patent changes the fundamental parameters of the conductive component by using crystalline carbon (graphite or graphene) with superior electrical properties compared to amorphous carbon black. This parameter change in carbon structure allows achieving the same or better conductivity at lower pigment concentrations, avoiding processing issues associated with high pigment loading while maintaining or enhancing color intensity.
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 pigments achieve specific powder resistances of no more than 1x10^6 ohm*cm, enabling reliable electrical properties while displaying attractive colors, and can be used to create coatings with high gloss, chroma, and hiding power on both white and black substrates.
Implementation Method 1
electrically conductive pigments which have an outermost layer containing crystalline carbon in the form of graphite and/or graphene
Implementation Method 2
colored interference pigments... optically variable behavior... high gloss, chroma, and hiding power
Implementation Method 3
by pyrolytic decomposition of the carbon-containing compound
Data Source
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AI summary
The present invention relates to electrically conductive, colored interference pigments, in particular platelet-type interference pigments, which have an outermost layer that contains crystalline carbon in the form of graphite and/or graphene. The invention also relates to a method for producing such pigments and the use of the thus produced pigments.