Partial Coloring of Thermoplastic Parts via Laser-Activated Dye Bath
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Solution Overview
Problem
Current methods for colored laser engraving of plastic parts, particularly thermoplastic parts with a layer structure, face challenges in achieving precise partial coloring without the need for complex printing processes or multiple laser sources, often resulting in inadequate bonding and low resolution.
Innovation Solution
A method involving immersion in a coloring bath, optional heating, and irradiation with focused non-ionizing electromagnetic radiation, where the wavelength range allows for light transmittance between 10% to 99%, enabling selective coloring only on irradiated areas due to additives with absorption maxima in the used wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional printing processes are used to create colored images on plastic parts, then color variety is achieved, but process complexity and time consumption increase significantly
Solution Approach 1:
The invention extracts the coloring function from the laser beam itself by introducing a separate coloring bath. The laser only provides energy for heating and activating the coloring agent, while the actual color application is handled by the bath containing coloring agents. This separation allows color variety without requiring the laser to carry multiple colors or complex printing mechanisms.
Solution Approach 2:
The coloring bath acts as an intermediary between the laser and the plastic part. Instead of the laser directly creating colored images through complex multi-color deposition, the laser heats the plastic surface which then activates the coloring agents in the bath. This intermediary approach simplifies the overall process while maintaining color variety.
2Adaptability or versatility
If multiple laser sources are used to achieve full-color laser engraving, then color completeness improves, but device complexity and cost increase
Solution Approach 1:
A single laser source is made multi-functional by using it to heat different areas of the plastic part that contact the coloring bath. The same laser can create different colors by controlling which areas receive heat activation, eliminating the need for multiple specialized laser sources for different colors.
Solution Approach 2:
The invention changes the approach from using multiple lasers with different wavelengths for different colors to using a single laser with parameter control (power, duration, scanning pattern) to activate different coloring agents. By changing thermal parameters rather than optical wavelength parameters, full-color capability is achieved with one laser source.
3Adaptability or versatility
If printing processes are used before laser engraving, then colored images can be created, but resolution and precision are limited by printing capabilities
Solution Approach 1:
The invention replaces the mechanical printing system with a thermal-field-based coloring system. Instead of physically depositing colored materials through printing mechanisms, the laser creates colored images by thermally activating coloring agents in the bath. This substitution enables higher resolution since the laser can precisely control thermal activation at the microscopic level without being constrained by printing head mechanics.
4Use of energy by moving object
If the coloring bath has high light transmittance, then laser energy reaches the plastic surface effectively, but coloring intensity in the bath decreases
Solution Approach 1:
The invention optimizes the balance between light transmittance and coloring intensity by adjusting parameters of the coloring bath (concentration of coloring agents, composition, temperature) and laser parameters (power, scanning speed, pulse duration). This allows finding the optimal point where sufficient laser energy penetrates the bath while enough coloring agents are activated to produce intense colors.
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 method allows for high-resolution, precise partial coloring of thermoplastic parts with minimal coloring in non-irradiated areas, suitable for applications like security documents, without requiring high-precision printing or multiple laser sources, and can achieve intense coloring with medium laser power.
Implementation Method 1
the plastic part comprises at least one additive which has an absorption maximum in the wavelength range of the focused non-ionizing electromagnetic radiation used
Implementation Method 2
the dye migrates into the plastic surface at this point
Implementation Method 3
The laser beam removes the paint layer and at the same time the dye migrates into the plastic surface at this point
Data Source
AI summary
The present invention relates to an improved method for the partial colouring, in particular for the coloured laser engraving, of plastic parts, in particular thermoplastic plastic parts, more particularly thermoplastic plastic parts, comprising a layer structure, and to the resulting partially coloured, preferably coloured and laser engraved, plastic parts, in particular thermoplastic plastic parts.