The Korea Institute of Production Technology (KITECH) has successfully developed an optical film based on fluoropolyimide, which solves the problem of wrinkles in foldable displays.
According to Korean media Newsis, Dr. Seong-woo Hong's research team at the KITECH Environmental fusion Materials Research Department said on August 10 that the research team has developed a high-strength transparent flexible optical film with bending reliability while maintaining the optical properties of the existing glass substrate materials.
When the display is folded, the inside side produces compressive force and the outside side produces tensile force. Therefore, repeated folding of the display can lead to surface fragmentation, cracks and wrinkles.
One of the representative new optical materials that can solve these problems is the plastic-based "flexible optical film."
The flexible optical film used in foldable display should be engineering plastics with excellent physical properties and characteristics compared with general plastics.
Polyimide is a representative engineering plastic, which forms a unique structure called Charge Transfer Complex (CTC). Compared with general plastics and common engineering plastics, polyimide has excellent mechanical and physical properties.
In addition, polyimide materials have good resilience and impact resistance. Through continuous film making process, it can be made into thin film form to achieve thin and flexible display.
On the contrary, because of the structural properties of CTCS, which are easy to absorb light in low wavelength bands, it has a fatal disadvantage, that is, the film is yellow.
This phenomenon, known as the Trade-Off between polyimide mechanical and optical properties, is the biggest problem in the flexible (Flaxible) product line, which includes laptops, TVS and foldable smartphones.
Through CTC control, Dr. Hong's research team overcame this tradeoff and successfully developed a new type of fluorinated polyimides with world-class properties.
First, the research team introduced a large volume of carbonized fluorine into the polyimide to ensure the optical properties by reducing the distance between the chains of the polyimide, which is strongly bound by CTC.
At the same time, the Trade-Off phenomenon was overcome by increasing the probability of hydrogen and metal ion bonds between the polyimide chains to amplify the CTC interaction forces in order to solve the problem of mechanical mass reduction proportional to the control physical distance.
As a result, the team developed an optical film with an elastic coefficient of more than 8GPa, an overall transmittance of 90%, a yellow index of less than 3, and more than 200,000 repeated folds, with flexibility and bending reliability, without any fragmentation, cracks, and folds.
In particular, the transparent polyimide introduced into the carbonized fluorine group contains fluorine atoms, so it is classified as fluorinated polyimide. Fluorinated polyimide is one of the three export controlled varieties from Korea to Japan, and is a key material for the development of next-generation displays.
Dr HongChengYu led the research, said: "as the core of the development of new generation of display materials, is also a material of South Korea's localization is imminent, so attention to fluorinated polyimide", saying that "based on the results, will be committed to the development and application in wearable, scalable, etc. The development of flexible display materials. "
In addition, the research results were published in Advanced Functional Materials, an international academic journal in the field of materials, and were selected as the cover issue of this May.
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Gestant Display Technology Co.,LTD was founded in 2012 in Shenzhen China. Even, the founder of the company, has more than 15 years of rich experience in LCD display industry. He has been engaging in the basic research of LCD display technology in Japan since his graduate school and has been working in the flat panel display industry after graduation.
Proficient in the manufacturing process and technology development of LCD / OLED / polarizer, Even was also one of the members of China liquid crystal Association who has a senior industry background and supply chain resources. In the past three years, he assisted his shareholders in building factories, purchasing equipment，establishing production lines, and successfully obtaining ISO9001 and ISO14001 system certificates.
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