Croconic Acid Derivatives for Invisible Laser Welding of Plastics
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Solution Overview
Problem
Existing laser welding methods for plastics using near-infrared (NIR) lasers face challenges with colored dyes that are chemically unstable, leaving residues and being unsuitable for colorless plastics, and require dyes that are toxic-free and invisible in the visible spectrum.
Innovation Solution
The use of croconic acid derivatives as NIR-absorbing compounds, which are almost colorless in the visible region and efficiently convert NIR light into heat for welding, ensuring minimal energy release through pathways other than heat, thereby providing invisible sealing of transparent plastics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional NIR dyes (carbon black, metallated phthalocyanines, perylenes) are used for laser welding, then the welding process can be performed, but the plastics become colored and the dyes leave residues
Solution Approach 1:
The patent applies the color changes principle by selecting dyes with specific spectral properties - they absorb in the near-infrared region (700-2500 nm) where laser welding operates, but are colorless or nearly colorless in the visible region (380-700 nm). This allows the welding process to function effectively while leaving no visible coloration or residues on the plastic surface.
2Reliability
If conventional dyes are used, then laser welding is achieved, but the dyes are toxic and chemically unstable
Solution Approach 1:
The patent applies parameter changes by carefully selecting and optimizing the chemical structure of dye molecules, specifically their absorption spectra, stability characteristics, and toxicity profiles. The chosen dyes have absorption maxima in the NIR region matching laser wavelengths, demonstrate high chemical stability under welding conditions, and exhibit low or no toxicity, thus resolving the contradiction between welding effectiveness and safety.
3Productivity
If visible-colored dyes are used for NIR absorption, then laser welding can be performed, but the aesthetic appearance of transparent plastics is compromised
Solution Approach 1:
The patent resolves this contradiction by exploiting the difference between visible and near-infrared spectral regions. The selected dyes are designed to be transparent or colorless in the visible spectrum (maintaining aesthetic appearance) while having strong absorption coefficients in the near-infrared spectrum (enabling efficient laser welding). This spectral selectivity allows simultaneous achievement of welding efficiency and visual clarity.
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 efficient, invisible welding of transparent plastics without leaving residues, ensuring the dyes are non-toxic and cost-effective, with croconic acid derivatives effectively transferring heat between plastic materials to achieve strong welds.
Implementation Method 1
providing a first plastic material to be welded comprising a compound capable of absorbing near-infrared light
Implementation Method 2
croconic acid derivatives as NIR-absorbing compounds, which are almost colorless in the visible region and efficiently convert NIR light into heat for welding
Implementation Method 3
activating a laser source emitting a wave length in the near-infrared spectrum
Implementation Method 4
croconic acid derivatives effectively transferring heat between plastic materials to achieve strong welds
Implementation Method 5
exposing the joint region to incident radiation having a wavelength outside the visible range so as to cause melting of the surface of one or both components at the joint region
Data Source
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AI summary
The present invention discloses a method for laser welding of plastics, comprising the steps of providing a first plastic material to be welded comprising a compound capable of absorbing near-infrared light,positioning a second plastic material in intimate contact with the first plastic material, and activating a laser source emitting a wave length in the near-infrared spectrum to obtain attachments of the first and the second plastic material. The compound capable of absorbing near-infrared light is a dye derived from croconic acid.