Background
Laser marking on plastics can be broadly divided into two categories: black laser marking and colored laser marking. While black marking remains the most widely adopted approach, colored laser marking is increasingly required for functional identification, branding, and regulatory differentiation.
Understanding the physical and chemical mechanisms behind these two marking strategies is essential for selecting the appropriate laser-responsive additive and process window.
Mechanisms of Black Laser Marking
Black laser marking typically relies on strong laser absorption followed by localized carbonization or decomposition of the polymer matrix.
Common mechanisms include:
Photothermal degradation of polymer chains
Carbonization of the surface layer
Formation of light-absorbing carbon-rich residues
Carbon black and other broadband absorbers are frequently used because they efficiently convert laser energy into heat.
Key characteristics of black laser marking:
High contrast on light-colored substrates
Wide process window
Relatively low additive cost
However, excessive absorption often leads to uncontrolled heat diffusion, edge burning, and unintended electrical conductivity.
In antimony-free systems, materials such asBasic Copper Hydroxyl Phosphateare evaluated as laser-responsive inorganic additives where surface-localized energy absorption and controlled thermally driven contrast formation are required.
In practical laser marking formulations, this chemistry is implemented throughLaserMark-C™ Laser Marking Additive for Dark Markings, which is designed to generate stable dark contrast under infrared laser irradiation without relying on antimony-based compounds.
Mechanisms of Colored Laser Marking
Colored laser marking does not rely on carbonization. Instead, it is achieved through controlled physicochemical transformations triggered by laser irradiation.
Typical mechanisms include:
Laser-induced phase transitions
Redox reactions of inorganic components
Microstructural surface modification affecting light scattering
Selective decomposition of color-forming precursors
Unlike black marking, colored marking requires precise energy control. Excessive heat often destroys chromatic contrast rather than enhancing it.
Process Sensitivity and Control Requirements
Black laser marking systems are generally tolerant of laser power fluctuations, scan speed variation, and material heterogeneity.
In contrast, colored laser marking systems are highly sensitive to:
Laser wavelength and pulse duration
Energy density and focus accuracy
Polymer–additive compatibility
This sensitivity makes colored marking more demanding in both formulation design and laser parameter optimization.
Performance Trade-offs
| Aspect | Black Laser Marking | Colored Laser Marking |
|---|---|---|
| Contrast | High (black / dark gray) | Moderate to high (color-dependent) |
| Process window | Wide | Narrow |
| Additive behavior | Broadband absorption | Selective laser response |
| Electrical impact | Often conductive | Typically non-conductive |
| Design flexibility | Limited to dark marks | Supports color coding and branding |
Application-Driven Selection Logic
Black laser marking remains suitable for applications prioritizing speed, robustness, and cost efficiency.
Colored laser marking becomes essential when applications require:
Multi-color identification systems
Aesthetic or branding elements
Functional differentiation without conductivity
High-purity or regulated polymer systems
The choice is not binary. Many advanced systems combine black and colored marking strategies depending on part geometry and functional zones.
Key Takeaway
Black laser marking prioritizes robustness and simplicity, while colored laser marking prioritizes control and functionality. Selecting between the two requires understanding not only visual outcomes, but also the underlying laser–material interaction mechanisms and their downstream implications.
Key Variables and Reference Data
Typical laser wavelengths: 1064 nm, 532 nm, 355 nm
Black marking: carbonization and thermal degradation
Colored marking: phase transition, redox reaction, surface optical modulation
FAQ
Q: What is the main difference between black and colored laser marking?
A: Black laser marking relies on carbonization and thermal degradation, while colored laser marking depends on controlled physicochemical transformations.
Q: Why is colored laser marking more difficult to control?
A: Because colored marking requires precise energy input; excessive heat often destroys chromatic contrast.
Q: Is black laser marking always conductive?
A: Not always, but common black absorbers such as carbon black frequently introduce unintended conductivity.
In conventional black laser marking systems, this role is often fulfilled bycarbon-based or broadband laser marking additives, which emphasize high absorption efficiency and rapid heat generation to produce dark contrast through surface carbonization.