In recent years, Some Chinese companies have made breakthroughs in polyimide/PI slurry and polyimide/PI film.
The material used to manufacture foldable displays is called polyimide paste (PI paste), and the polyimide film (PI film) made with it has been used in photoelectric displays such as WHTM Microelectronics, WHHX Optoelectronics, etc. Leading companies applied it in batches and used it to make bendable and foldable mobile phone screens.
R&D: The "gold film" of flexible display has built a "patent wall"
HBDL Electronic Materials Technology Corporation has a national key laboratory for photoelectrochemical materials and devices.
"Flexible displays were first applied to high-end mobile phones, and in the future, they will be widely used in wearable electronic products." Professor Liu Jiyan, CTO of HBDL, introduced flexible display materials to the Hay Think team. The current mobile phone screens cannot be bent because of it. The substrate of the flexible display is made of glass; the substrate of the flexible display is a plastic board, and a layer of polyimide film ("PI film" for short) is laid on the plastic board, and the circuit, evaporation, and light-emitting layer are all built on it.
In the field of optoelectronic display materials, PI film is regarded as "shen film" and "gold film". It is as thin as a cicada wing, with a thickness of only 15-20 microns, but it can withstand a strength of 200 MPa. The screen of a mobile phone made of PI film can be folded and bent like paper.
"The polymer material used to prepare the PI film is PI slurry, which is the basic material for the manufacture of flexible display screens." Professor Liu Jiyan introduced that there are multiple processes for manufacturing flexible display screens. The PI slurry is applied to the bottom layer and covers the glass plate. Thin film transistor (TFT) light-emitting materials are superimposed on it, and after high-temperature evaporation, deposition, annealing and other processes are processed, the laser peels into a thin film.
Display panel manufacturing companies such as BOE, WHHX Optoelectronics, and WHTM Microelectronics have built dozens of flexible display production lines in China, and only manufacture foldable mobile phone screens, which require nearly 5,000 tons of PI slurry each year.
In 2012, the Collaborative Innovation Center for Flexible Display Materials and Technology was established in China, led by the HBDL Key Laboratory of Photoelectrochemical Materials and Devices, WHHZ University of Science and Technology, WHTM Microelectronics, Huashuo Technology Co., Ltd. And display screens, downstream mobile phones, computers, etc. to carry out collaborative innovation across the entire industry chain. This project is supported by many projects such as the National 863 Program and National Key R&D Projects.
In five years of scientific and technological innovation and technological research, the HBDL R&D team has successfully developed and prepared two types of substrate materials for flexible display and solved key technical problems in industrialization. It has applied for and obtained more than 30 domestic and foreign patents, "Building up" Patent Wall'".
In July 2019, HBDL formed an annual production capacity of 1,000 tons of PI slurry.
As the first company in China to realize the industrialization of PI slurry, HBDL has built China’s first PI slurry production line, PI slurry coating film formation verification laboratory, and research and development of colorless PI slurry required for panels and covers. Breakthrough progress has been made.
At the end of 2020, the yellow high temperature resistant PI products prepared by HBDL won the first batch of ton orders, achieving a zero breakthrough.
At present, the HBDL PI slurry production line with an annual output of 1,000 tons has been put into production, and has a continuous and stable supply capacity.
In November 2021, the PI membrane project with an annual output of 5,000 tons successfully started commercial production.