Laser Marking Substrates via Controlled Carbonization
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Solution Overview
Problem
Laser marking systems struggle to create durable, high-contrast images on substrates like white copier paper without ablation, as they often vaporize the binder, leading to smudging and poor contrast due to inadequate temperature control for carbonization.
Innovation Solution
A method and system that control the deposition of laser energy to achieve a specific intensity pattern, modulating the power and duration of the laser beam to carbonize the substrate without ablation, using an array of optical devices to manage the thermal heating and ensure the binder is melted rather than vaporized, enhancing the durability and contrast of the mark.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If standard CO2 laser marking system is used to mark white copier paper, then the marking process is simple and requires only sufficient laser energy for ablation, but the mark produced is light brown with poor contrast and is not acceptable to users
Solution Approach 1:
The patent changes the laser parameters from standard ablation mode to controlled carbonization mode by adjusting power density, pulse duration, and scanning speed to fall within the 200-250°C carbonization temperature range, transforming the mark quality from light brown with poor contrast to high-contrast black marks
Solution Approach 2:
The patent replaces the mechanical ablation process with a thermal chemical process (carbonization), where laser energy induces chemical changes in the paper fibers and binder rather than physically removing material, enabling superior mark quality on white paper
2Illumination intensity
If laser power/energy is increased to make the mark lighter, then the mark visibility improves, but the contrast deteriorates and the binder may vaporize causing smudging
Solution Approach 1:
The patent precisely controls laser parameters to maintain power density and pulse duration within the 200-250°C carbonization range, preventing binder vaporization while achieving sufficient carbonization for high-contrast marks without smudging
Solution Approach 2:
The patent converts the potentially harmful effect of laser heating into a beneficial carbonization process by controlling temperature to carbonize fibers and binder without causing vaporization, transforming what could be destructive heat into a useful marking mechanism
3Ease of manufacture
If ablation is used to remove surface material, then the marking process is straightforward, but the only visible indication is from burned fiber ends and yellowed binder, resulting in poor contrast marks
Solution Approach 1:
The patent replaces mechanical ablation with thermal carbonization, where laser energy induces chemical changes that darken the paper surface through carbon formation, providing superior contrast compared to the fiber-end visibility of ablation marks
Solution Approach 2:
The patent utilizes color change through carbonization, where the laser-induced thermal chemical reaction transforms the paper surface from its original color to black carbonized material, creating high-contrast marks unlike the subtle fiber-end visibility of ablation
4Reliability
If the binder is melted without vaporization, then the molten binder encases carbonization and enhances durability, but the temperature control becomes complex and challenging
Solution Approach 1:
The patent uses pulsed laser action with controlled pulse duration and frequency to deliver thermal energy in manageable increments, maintaining temperature within the 200-250°C carbonization range and preventing binder vaporization while achieving durable marks
Solution Approach 2:
The patent employs dynamic control of laser parameters including real-time adjustment of power density, pulse width, and scanning speed to adapt to thermal diffusion and maintain optimal carbonization temperature without binder vaporization
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 effectively creates durable, high-contrast marks on paper substrates by carbonizing the material without vaporizing the binder, improving the longevity and visibility of the image while maintaining the substrate's integrity.
Implementation Method 1
depositing laser energy in such a manner as to raise the substrate to the proper carbonization temperature
Implementation Method 2
Carbonization occurs in a narrow temperature range that is material dependent. Common copier paper will carbonize in the temperature range of 200-250° C.
Implementation Method 3
marking is accomplished by a color change that is induced by a chemical reaction stimulated by the laser energy
Data Source
AI summary
A laser marking system comprises at least one controller to control an array of optical devices, between a laser source and a scan head. The array applies a selected pattern of portions of the received spatial profile of the laser beam to the substrate to achieve a second intensity different from the first intensity of laser beam at a rate of power deposition relative to a rate of thermal diffusion in the substrate for a predetermined time interval to thermally heat locations of the substrate with the selected pattern of the portions. The second intensity effectuates carbonization of materials of the substrate to create a mark without ablation.