Design of arrayed multi-wavelength UVLED ink curing system

Chen Zhongyu; Jiang Haibo; Sun Xiuhui; Yang Ruofu; Wu Peng; Du Chunlei; Yin Shaoyun

doi:10.12086/oee.2019.180252

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Chen Zhongyu, Jiang Haibo, Sun Xiuhui, et al. Design of arrayed multi-wavelength UVLED ink curing system[J]. Opto-Electronic Engineering, 2019, 46(2): 180252. doi: 10.12086/oee.2019.180252

Citation:

Chen Zhongyu, Jiang Haibo, Sun Xiuhui, et al. Design of arrayed multi-wavelength UVLED ink curing system[J]. Opto-Electronic Engineering, 2019, 46(2): 180252. doi: 10.12086/oee.2019.180252

Design of arrayed multi-wavelength UVLED ink curing system

1.
Integrated Optoelectronic Technology Center, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China
2.
University of Chinese Academy of Sciences, Beijing 100049, China

Fund Project: Supported by National Natural Science Foundation of China (61475199) and Chongqing Science and Technology Bureau (cstc2015zdcy-ztzx70006)

More Information

Corresponding author: Yin Shaoyun, E-mail:ysy@cigit.ac.cn

Received Date 25 July 2018

Revised Date 18 October 2018

Published Date 18 February 2019

Abstract

Abstract

Compared with mercury-vapor lamp, ultraviolet (UV) LED suffers from the disadvantage of having a single wavelength, which is not fully compatible with the existing photoinitiator of ultraviolet ink. It is difficult using UVLEDs to achieve the curing effect comparable to what mercury-vapor lamp can do. This article presents a design of UVLED ink curing system that provides evenly mixed light with multiple wavelengths. We put a UVLED array with three wavelengths on a cambered surface and achieved uniform illumination in ink curing area by using optical freeform surface. By adding the adjusting of the tilt angle, we solved the dilemma of uniform wavelength mixing and uniform illumination. The ray tracing simulation results show that an illumination spot with uniform wavelength mixing, an average illumination of 110.7 mW/cm², and an illuminance uniformity of 0.82 is obtained on a target surface 600 mm away from the light source. This design is expected to simulate the multi-spectral illumination effect of mercury-vapor lamps, which can promote the application of UVLEDs in ink curing.
- optical design /
- LED array /
- ink curing /
- mercury lamp /
- uniformity

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References

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Overview

Overview

Overview: Ultraviolet light emitting diode (UV-LED) with the advantages of small volume, high luminous efficiency and long life, shows a good prospect in replacing the traditional mercury lamp for the ink curing. At present, there have been many researches on UV-LED light source array, which mainly focus on how to improve the uniformity and illuminance of the spot formed by LED array on the target surface, and use secondary light distribution design to optimize. However, these researches are all aimed at UV-LED of single wavelength, and obtain curing spot that meets demand by theoretically calculating the arrangement spacing and number of LEDs. The ink for traditional UV curing is all matched with the spectrum of mercury lamp, but the curing effect of UV-LED with single wavelength and narrow spectrum is often different from mercury lamp, so the curing effect is unsatisfactory, which block the spread of UV-LED in ink curing. In present, the central wavelength of commercial UV-LED covers the main UV spectra of mercury lamp. The wavelength range is from 250 nm to 435 nm, and the absorption bandwidth of the photoinitiator is large. In theory, combining UV-LEDs of multiple wavelengths is a feasible way to solve the problem of unsatisfactory single-wavelength UV-LED curing effect. Based on this idea, this paper presents a design method of arrayed multi-wavelength UV LED ink curing system and applies it to the design of three-wavelength UV LED ink curing system. A freeform lens is used to even the light of the LED, and the technical problems of uniform wavelength mixing and uniform illumination are solved by the design of freeform lens and its tilt. The designing steps are as follows: firstly, a freeform lens should be designed to form uniform illuminance distribution for single LED, and then the total number of demanded LEDs is determined according to the required illuminance. Finally, each LED and its homogenization lens are arrayed on the curved substrate. The final entity is shown in the figure. The ray tracing simulation results show that an average illuminance of 110.7 mW/cm² and an illuminance uniformity of 0.82 are obtained on a target surface 600 mm away from the light source. This method is not limited to the use of three wavelengths and is expected to solve the problem that UV-LED in ink curing cannot be fully compatible with existing photoinitiators of UV inks. It is also expected to promote the application of UVLEDs in ink curing by this study.