Important progress of UVLED exposure equipment for ink curing

UV curing ink has been widely used in the printing industry because of its advantages of anti-pollution, anti-wear, rapid curing, high production efficiency, and good printing adaptability. Irradiated by ultraviolet light, the curable chemical substance in the ink undergo cross-linking polymerization, which let the ink convert from liquid to solid state in a very short time. In this process, the photoinitiator is the key to initiate the curing of the ink. The UV absorption band of photoinitiator is 250 nm-400 nm. At present, the mercury lamp, with the spectrum covering almost all ultraviolet band of 200 nm-400 nm, is used as the source of ink curing machine. However, mercury lamps have many downsides. It has pollution to the environment, short life, low efficiency of effective ultraviolet light, high price and large power consumption. As an emerging ultraviolet light source, UVLED has many advantages, such as high luminous efficiency, long life, environmentfriendliness and so on. It will replace the mercury lamp in the future. However, as a narrow-band light source (±5nm), UVLEDs can hardly have a spectrum that is fully compatible with the photoinitiator of ultraviolet ink.  How to uniformly mix UV light from UVLEDs with various wavelengths is the key to achieve high-efficiency ink curing by UVLED.

    The research team of Yin Shaoyun, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, is dedicated to the research of UVLED lithography and light source system of ink curing. They applied "LED Precise Light Distribution Technology with Micro-Optic Multi-Freeform Surface" to the ultraviolet optical system and broke through many key technologies, such as "LED’s étendue calculation and beam angle transformation theory", "batch processing and measurement technology of micro-optics / free-form optical components" and so on. The team has developed many kinds of UVLED parallel light exposure devices for PCB/touch screen/LCD panel manufacturing, and 4-12 inches UVLED exposure modules for mask alignment lithography device and multi-wavelength UVLED exposure module for DMD-based projection lithography machine, and UVLED source module for ink curing of mobile phone with curved screen, which have been successfully applied in many listed companies and institutes. Compared with the mercury lamp, the developed products not only considerably improved its processing capacity and stability, but also effectively avoided the pollution of mercury to the environment. The life of the light source was increased by more than 20 times, and the power consumption was reduced to 1/10, which saved many production costs for users. 8 related articles have been published and 12 patents have been applied for. The study effectively promoted the application of UVLED in lithography, ink curing, and other fields. It is of great significance to make the manufacturing and production of related industries meet the Minamata Convention on Mercury by replacing mercury lamp.
    


Figure Photos of some UVLED exposure and curing products developed by the research team, (a) 4-inch UVLED parallel light exposure module for mask alignment lithography device; (b) UVLED source module to replace the 5 kW / 8 kW mercury lamp used in the parallel light exposure device; (c) UVLED source module for ink curing of curved screen of mobile phone.

About team
The Integrated Optoelectronic Technology Research Center of Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences is mainly engaged in the research of micro-nano optics and freeform optics. Currently, the center has four researchers who are awarded senior professional titles and several middle and junior researchers, whose major fields include optics, mechanics, and electronics. Research areas include LED lighting and applications, lithography devices and processes, lightweight optical systems and biomedical equipment. The center undertook several college-enterprise cooperation, national and provincial-ministerial projects. At present, more than 100 articles and 40 patents have been published.

Article

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