UV LED Curing Device with Pinhole Apertures for Ink Matting Control
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Solution Overview
Problem
Existing UV ink drying systems face issues with matting effects and ink quality due to inadequate radiation control, leading to undesirable gloss reduction and increased maintenance needs for printheads.
Innovation Solution
A device with UV LED radiation sources and optical elements, such as perforated panels with pinhole arrays, limits the maximum beam angle to 30 degrees, ensuring that only targeted radiation penetrates the ink layer, reducing matting effects and stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV radiation power is increased to improve pinning effectiveness, then ink curing quality improves, but matting effects occur that reduce gloss and print quality
Solution Approach 1:
The patent applies microlenses with different focal lengths to different regions of the printhead array. Central printheads use microlenses with longer focal lengths to concentrate radiation and reduce stray light, while outer printheads use microlenses with shorter focal lengths. This local differentiation allows effective pinning in central regions while minimizing matting effects in outer regions where stray light would otherwise accumulate.
Solution Approach 2:
The patent changes the focal length parameter of microlenses based on position within the printhead array. By varying this optical parameter spatially, the system optimizes radiation concentration for each location, achieving effective pinning without excessive stray light that causes matting.
2Reliability
If UV radiation power is increased to improve pinning, then ink curing improves, but stray light reaches adjacent printhead nozzles causing ink hardening and requiring frequent cleaning
Solution Approach 1:
The patent implements position-dependent microlens focal lengths that are optimized for each printhead's location. This local optimization ensures that radiation is concentrated where needed while stray light is minimized in directions toward adjacent printheads, reducing ink hardening on nozzle surfaces.
Solution Approach 2:
The microlenses act as intermediary optical elements between the UV LED sources and the substrate. These intermediaries focus the radiation and control its angular distribution, preventing stray light from reaching adjacent printheads while still achieving effective pinning of the ink.
3Reliability
If UV radiation is applied to pin thick white ink layers, then white areas are cured, but strong heating causes substrate wrinkling
Solution Approach 1:
The patent uses position-specific microlens focal lengths that optimize radiation delivery to different areas of the substrate. This localized optimization ensures adequate curing of thick white ink layers while distributing thermal load more evenly, reducing localized overheating and wrinkling.
Solution Approach 2:
The patent employs pulse-width modulation to control UV LED activation. By periodically activating LEDs rather than continuous operation, the system delivers required UV energy for pinning while allowing thermal dissipation between pulses, preventing excessive substrate heating and wrinkling.
4Object-affected harmful factors
If microlenses with narrow beam angle are used to reduce matting, then radiation focus improves, but installation space requirements increase
Solution Approach 1:
The patent varies the focal length parameter of microlenses based on position within the printhead array. This parameter differentiation allows the system to achieve effective radiation focus with reduced stray light (minimizing matting) while maintaining a compact overall configuration that does not require excessive installation space.
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 solution effectively prevents matting, maintains ink quality, reduces maintenance, and allows for closer placement of dryers, optimizing installation space and production efficiency.
Implementation Method 1
a plurality M1 of emitters (12) which are designed as UV LED radiation sources
Implementation Method 2
The curing of printing fluids (more generally: coating fluids) on substrates, especially polymerizable printing inks, varnishes, or inks on paper, cardboard, or plastic film, can be achieved by exposing the applied fluid to electromagnetic radiation, particularly ultraviolet or UV radiation. This polymerizes the fluid, or at least its polymerizable components.
Implementation Method 3
the optical elements (15) are designed as pinhole apertures and form a pinhole aperture array (23) in the second plane (14), wherein the maximum beam angle αmax of the spotlights on the substrate (2) is limited to ≤ 30°
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The invention relates to a device for curing UV ink on a substrate, comprising a plurality M1 of emitters (12) configured as UV LED radiation sources. The device includes a plurality M2 of optical elements (15) configured and arranged such that the respective maximum beam angle αmax of the emitters is limited to αmax ≤ 30°. The invention advantageously enables the reduction or even prevention of undesirable matting effects.