Short-Pulse Laser Marking Transparent Plastics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for marking security and value documents using laser technology are limited by the need for special pigments or additives, which can affect transparency and require thermal interactions that restrict resolution and material independence.
Innovation Solution
The use of short-pulse laser sources with pulse durations less than 100 picoseconds to induce non-linear optical interactions, allowing for high-resolution markings without the need for pigments or additives, and enabling the creation of three-dimensional markings that are precise and tactile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If special pigments or additives are added to plastic layers for laser marking, then laser light absorption is improved, but transparency is reduced and material independence is lost
Solution Approach 1:
The patent removes the requirement for special pigments or additives from the plastic material. Instead of adding absorbing substances to the bulk material, the invention uses the intrinsic properties of transparent plastics and applies laser marking without any material modification, thereby maintaining transparency while achieving sufficient energy absorption through optimized laser parameters
Solution Approach 2:
The invention changes the laser marking parameters (pulse duration, wavelength, intensity) to match the optical properties of transparent plastics. By using picosecond or nanosecond pulse durations and appropriate wavelengths, the laser can interact with the transparent material to produce permanent markings without requiring any additive materials
2Ease of manufacture
If thermal interactions are used for laser marking, then material processing is simplified, but resolution is restricted
Solution Approach 1:
The patent employs periodic pulsed laser action with picosecond or nanosecond pulse durations. This periodic energy delivery allows cumulative heating effects to be controlled precisely, enabling high-resolution markings by limiting heat diffusion between pulses while maintaining effective material processing through repeated cycles
Solution Approach 2:
The invention applies preliminary low-energy laser pulses to prepare the material surface or subsurface before the main marking pulses. This preliminary action creates optimal conditions for subsequent high-resolution marking by pre-heating or modifying the material structure, thereby reducing the energy required for final marking and minimizing thermal damage
3Duration of action of stationary object
If high energy is deposited for permanent marking, then marking durability is improved, but material damage increases
Solution Approach 1:
The patent uses periodic pulsed laser delivery with picosecond or nanosecond durations to deposit energy in controlled increments. This allows cumulative energy accumulation for durable markings while the short pulse intervals prevent excessive heat buildup and material damage by allowing partial cooling between pulses
Solution Approach 2:
The invention replaces mechanical contact marking methods with optical field-based laser marking. This substitution enables precise energy deposition through photothermal or photomechanical effects, achieving permanent markings without the mechanical forces that cause material damage, and allowing better control over energy distribution
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
This approach enhances marking resolution, material independence, and allows for precise, non-destructive marking of transparent plastics, enabling complex patterns and security features that are difficult to falsify, while minimizing damage and maintaining transparency.
Implementation Method 1
the laser light source being a short-pulse laser source which generates laser light with a peak power high enough to generate non-linear optical interactions
Implementation Method 2
the peak power of the laser light being high enough to induce optical breakdown
Implementation Method 3
with a focus spot size of less than 10 μm
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a marking device (1) for a valuable or security document (2), and to a method for permanently, more particularly individually, marking valuable and/or security documents (1). The method for permanently marking a valuable or security document (2) comprises the following steps: generating laser light (6) and guiding the laser light (6) by means of a light guiding device (8) such that laser light (6') emerging from the light guiding device (8) is positioned on the valuable or security document (2) and locally marks the valuable or security document (2), wherein the laser light (6) is generated in the form of laser light pulses having a pulse duration of less than 100 ps. As a result, it is possible to utilize non-linear interactions between the material of the valuable or security document (2) and the laser light (6') for marking purposes. Furthermore, given suitable guidance of the laser light (6'), it is possible to achieve improved focusing and, by means thereof, an improved resolution of the patterns produced by means of the marking.