The principle of inkjet printing and its application

FIGURE 1

image: fig. 1 Line division obtained by inkjet printing of different solutions
vision Lake

Credit: OEA

A new publication from Optoelectronic Advances† DOI 10.29026/oea.2022.210123 discusses inkjet printing and its applications on AR/VR microdisplays.

With the rapid development of artificial intelligence, image recognition and 5G communication technology, augmented reality (AR) and virtual reality (VR) technologies are developing at an alarming rate. Against the backdrop of the COVID-19, the remote office and consumption interaction are increasing. The market is refocusing on AR/VR and increasing its investment in technology applications. One of the main reasons for the market breakout is the breakthrough of new display technology with excellent performance. As a basic element of AR/VR, display devices must have an ultra-high pixel density and a high refresh rate, in addition to a low weight and small volume. At present, liquid crystal display (LCD) and organic light-emitting diode (OLED), two common display technologies, have been applied to near-eye displays (NEDs) and head-mounted displays (HMDs). However, due to the low conversion efficiency and color saturation, rapid aging and short lifespan, the development of new display technology has accelerated. Micro LED has excellent optical performance and long life, which is considered the next generation and ultimate display technology. The minimum pixel size reaches tens of microns and the high pixel density makes it suitable for AR/VR. In addition to high pixel density, full color is also the most important element to realize Micro-LED in AR/VR and the color conversion scheme is an effective method. Quantum dots were deposited on blue or ultraviolet micro-LED chips through inkjet printing technology to achieve tricolor luminescence while avoiding mass transfer technology. In recent years, inkjet printing technology shows great potential in microfabrication due to the advantages of digitization, patterning, additive manufacturing, low material waste and large area printing. In particular, the emergence of super inkjet (SIJ) printing technology can achieve ultra-high-resolution printing, where the minimum line width of printing falls into the sub-micrometer range. It sheds light on the fabrication of a high-resolution color conversion layer for micro-LED to realize a color display, and in particular for the augmented/virtual reality (AR/VR).

The authors of this article provide an overview of the principle of inkjet printing technology and its application to microdisplay for AR/VR. This review first introduces the advancement of AR/VR technologies, followed by a discussion of the adaptability of micro-LED display technology in AR/VR and the benefit of printing a color conversion layer for micro-LED using inkjet printing technology. The energy transfer mechanism without radiation and the influence of the thickness of the color conversion layer on the efficiency of the color conversion are discussed. The advantages of SIJ over other printing technologies in resolution are introduced. In the second part, the printing principle of different inkjet printing technologies were introduced, as well as two important issues – the optimization of ink rheological parameters and the reduction of coffee ring effects. The rheological parameters of ink suitable for each printing technology and the influence of rheological parameters on the printing effect were introduced. Two solutions for the caffeine ring effect and specific enhancement methods were evaluated. Finally, some potential problems associated with the color conversion layer are highlighted, including light crosstalk, blue light absorption, and self-absorption effect. This review article serves as a reference for those about to access the areas of inkjet printing technologies, micro-LED full colourization and its application in AR/VR.

This work is supported by the National Natural Science Foundation of China (11904302), the Fundamental Research Funds for the Central Universities (Grant No. 20720190005) and the Major Science and Technology Project of Xiamen in China (3502Z20191015).

Authors thank Prof. Kei May Lau in the Hong Kong University of Science and Technology, Prof. Bin Liu of Nanjing University and Prof. Zhaojun Liu at Southern University of Science and Technology, for their valuable advice and discussion.

Item reference: Yang X, Lin Y, Wu TZ, Yan ZJ, Chen Z et al. An overview of the principle of inkjet printing technology and its application in microdisplays for augmented/virtual reality. Optoelectron Adv 5, 210123 (2022). bye: 10.29026/oea.2022.210123

keywords: micro-LED / quantum dots / augmented reality / virtual reality / inkjet printing

Established in 2006, the solid state laboratory (SSLAB) of Xiamen University ECE mainly focuses on micro-LED display technology and quantum dot fluorescent materials. Under the supervision of Prof. Rong Zhang and Prof. Zhong Chen, SSLAB members have published several high-profile papers and awards in recent years. Taking advantage of the geometric advantages of the Taiwan Strait, we collaborate in several ways with universities on the other side of the Strait. Prof. dr. Yue Lin and Prof. Tingzhu Wu have worked in depth with Prof. HC Kuo in NCTU, which has produced several works that are easily applicable in the industry.

https://ssl.xmu.edu.cn/

Optoelectronic Advances (OEA) is a high-impact, open access, peer-reviewed monthly SCI journal with an impact factor of 9.682 (Journals Citation Reports for IF 2020). Since its launch in March 2018, OEA has been indexed over time in SCI, EI, DOAJ, Scopus, CA and ICI databases and has expanded its editorial board to 36 members from 17 countries and regions (average h-index 49).

The journal is published by The Institute of Optics and Electronics, Chinese Academy of Sciences, with the aim of providing a platform for researchers, academics, professionals, practitioners and students to transfer and share knowledge in the form of high-quality empirical and theoretical research papers on the topics of optics, photonics and optoelectronics.

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