Transparent Thermoplastic Laser Marking via Absorbing Layer
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Solution Overview
Problem
Current laser marking technologies face challenges in achieving consistent, high-quality marks on thermoplastic compositions, particularly in transparent materials, due to low absorption rates and the difficulty in confining marks to the surface without damaging underlying components, and the need for specialized inks and procedures for generating light-colored or covert marks.
Innovation Solution
A thermoplastic composition with a visible transmission of greater than or equal to 80% and an active component that undergoes chemical rearrangement upon laser exposure, allowing for the creation of light-colored marks and microdots with varying visibility levels, using wavelengths less than or equal to 500 nm, and enabling laser welding of transparent components without surface interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If 1064 nm laser is used to mark transparent thermoplastic compositions, then marking capability is achieved, but absorption is low leading to inhomogeneous interaction and poor mark quality
Solution Approach 1:
The patent introduces an intermediary absorbing layer containing carbon black or other absorbing pigments between the laser beam and the transparent thermoplastic composition. This intermediary layer absorbs the laser energy and converts it to heat, which then conducts to the transparent material to create the mark, solving the low absorption problem without requiring the transparent material itself to absorb the laser wavelength.
Solution Approach 2:
The patent applies local quality by creating a concentrated absorbing layer at the surface or near-surface region of the transparent thermoplastic composition. This localized absorption zone ensures that laser energy is concentrated where marking is needed, improving mark quality and consistency while preventing energy loss throughout the entire material volume.
2Manufacturing precision
If absorbing additives are added to increase mark quality, then marking consistency improves, but visible transmission decreases and haze increases
Solution Approach 1:
The patent segments the thermoplastic composition into multiple layers: a transparent base layer maintaining high visible transmission and an absorbing layer containing carbon black or pigments. This segmentation allows the absorbing layer to provide consistent marking while the transparent layer preserves optical clarity, preventing haze and color shifts.
Solution Approach 2:
The absorbing additives are confined to a localized absorbing layer rather than being distributed throughout the entire transparent composition. This localized placement ensures that absorption occurs only where needed for marking, while the bulk of the material remains transparent and haze-free.
3Manufacturing precision
If laser beam interacts with transparent composition to create mark, then marking is achieved, but laser passes through to damage underlying components
Solution Approach 1:
The absorbing layer acts as an intermediary that intercepts and absorbs the laser energy before it can pass through the transparent composition to underlying components. This intermediary layer converts laser energy to heat locally, creating the mark while preventing harmful laser transmission to sensitive components beneath.
Solution Approach 2:
The patent converts the potentially harmful effect of laser transmission into a beneficial localized heating effect by using the absorbing layer to convert laser energy into controlled heat at the marking location, preventing damage to underlying components while achieving the desired mark.
4Illumination intensity
If carbonization process is used to create dark mark, then mark visibility improves, but mark durability decreases due to easy compression of voids
Solution Approach 1:
The absorbing layer containing carbon black serves as an intermediary that provides both the carbonization effect for visibility and a stable structural foundation. The carbon black particles create a durable, compression-resistant mark while maintaining high visibility, overcoming the durability issues of void-based marks.
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
Enables the generation of customizable, machine-readable light-colored marks and microdots on transparent and opaque thermoplastics with improved durability and visibility control, while allowing for laser welding of transparent components without surface interaction, thus addressing the limitations of existing technologies.
Implementation Method 1
A photochemical interaction between the substrate and the laser light is another reaction mechanism by which identifiers are transferred to thermoplastics compositions. Lower wavelength light lasers such as those at 532 nm and especially with wavelengths lower than 400 nm (e.g., ultraviolet) generate contrast in polymer compositions in such a manner.
Implementation Method 2
opaque thermoplastic compositions can be marked with a 1064 nanometer (nm) laser light and rely on heat build-up in the substrate as the method of interaction between the laser light and the thermoplastic composition
Implementation Method 3
the heat generated either causes a char, i.e., carbonization, to form a dark mark
Implementation Method 4
A vaporization process, or the bleaching of an additive, or a bleaching of the combination of additives, can also achieve light colored marks by exposing the lighter colored, thermally stable materials below the surface.
Implementation Method 5
In order to join two components by LTW one component needs to be essentially laser transparent (e.g., no absorption), while the second component needs to absorb the laser light. The laser light then passes through the first component and heat is generated at the interface through the absorption of the laser light in the second component. The heat is conducted to the first layer, which melts and a weld is created upon re-solidification of both components.
Data Source
AI summary
An article for laser marking can comprising: a thermoplastic composition comprising a thermoplastic polymer, an active component comprising at least one of a polymeric unit and an additive, wherein the thermoplastic polymer has a visible transmission of greater than or equal to 80% according to ASTM D1003-00, Procedure A, using D65 illumination, 10 degrees observer, and thickness of 1 mm; and a mark produced by chemical rearrangement of the active component generated by a laser of a first wavelength; wherein the mark exhibits at least one of: (i) a change in optical properties in the region 400 nm to 700 nm when exposed to light having a wavelength less than or equal to 500 nm; and (ii) a change in optical properties in the region of 400 nm to 700 nm when exposed to light having a wavelength greater than or equal to the first wavelength.