UV Curing Process for Ultraviolet Curable Paint Without Yellowing
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Solution Overview
Problem
Ultraviolet curable paints used as luster coating materials face issues with insufficient curing and yellowing due to photopolymerization initiators sensitive to visible light, leading to obscured base colors of objects, especially when high-pressure mercury and metal halide lamps are used, which emit high light intensity in wavelengths beyond 350 nm.
Innovation Solution
A curing process utilizing ultraviolet curable paints sensitive only to light below 380 nm and irradiated with ultraviolet radiation units that peak below 350 nm, such as rare gas fluorescent lamps, to enhance curing efficiency and prevent visible light absorption, maintaining the object's temperature below the glass transition temperature of the cured article.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photopolymerization initiators sensitive to visible light are used in ultraviolet curable paint, then the paint can be cured with conventional ultraviolet radiation units, but the cured paint absorbs visible light causing yellowing and obscuring the base color
Solution Approach 1:
The patent changes the sensitivity wavelength parameter of the photopolymerization initiator from a range including visible light (380-400 nm) to a range exclusively in the ultraviolet region (peak sensitivity below 380 nm). This parameter change eliminates visible light absorption after curing, preventing yellowing while maintaining curing reliability through selective ultraviolet sensitivity.
2Illumination intensity
If high-pressure mercury lamps or metal halide lamps are used for ultraviolet curing, then high light intensity is achieved, but the light intensity in wavelengths above 350 nm causes insufficient selectivity and yellowing
Solution Approach 1:
The patent applies local quality by selecting a photopolymerization initiator with highly localized sensitivity in the ultraviolet region (peak below 380 nm) that does not extend into the visible region. This localized sensitivity profile ensures that only ultraviolet light triggers polymerization, while visible light passes through without causing yellowing, thus resolving the contradiction between curing efficiency and color preservation.
3Reliability
If conventional ultraviolet curable paint formulations are used, then complete curing is achieved, but visible light absorption occurs leading to yellowing
Solution Approach 1:
The patent modifies the chemical composition parameter by selecting photopolymerization initiators whose molecular structure provides sensitivity exclusively in the ultraviolet region (below 380 nm) without visible light sensitivity. This compositional change ensures complete ultraviolet-induced curing while eliminating the harmful visible light absorption that causes yellowing in conventional formulations.
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 allows for rapid and efficient curing of ultraviolet curable paints without yellowing, enabling the visualization of base colors through the paint layer and providing abrasion and weather resistance, even for thick coatings and complex shapes.
Implementation Method 1
If the ultraviolet curable paint is irradiated with ultraviolet rays, the photopolymerization initiator initially absorbs the ultraviolet rays. The photopolymerization initiator is thereby activated to generate radicals or ions. The generated radicals or ions react (cause a polymerization reaction) with the photopolymerizable monomer and the photopolymerizable oligomer for curing.
Implementation Method 2
the ultraviolet radiation unit radiates ultraviolet rays having a peak wavelength within a range of not greater than 350 nm in wavelength
Data Source
AI summary
A curing process of an ultraviolet curable paint by which a paint cured layer can be formed on an object to be processed without needing a long time, and intended color can be obtained of the object to be processed on which the paint cured layer is formed. The curing process of an ultraviolet curable paint is one for curing an ultraviolet curable paint through an ultraviolet irradiation step of irradiating a surface of an object to be processed to which the ultraviolet curable paint is applied with ultraviolet rays from an ultraviolet radiation unit. The ultraviolet curable paint is not sensitive to light of not less than 380 nm in wavelength but sensitive to light of less than 380 nm in wavelength. The ultraviolet radiation unit radiates ultraviolet rays having a peak wavelength within a range of not greater than 350 nm in wavelength.