Kyoto University Develops Transparent Paper for OLED Substrate

According Tech-On.com, Kyoto University’s professor Hiroyuki Yano, has added resin, etc to paper or its material (pulp) to make transparent paper. This breakthrough was announced at the New Technology Presentation Meetings, which the university organized Aug 24, 2012, in Tokyo.

Yano expects that the new technologies will be applied to transparent OLED substrates, substrates of organic thin-film photovoltaic (PV) cells, electronic paper, materials for car windows, packaging containers, etc.

Cellulose nanofibers, which constitute pulp, have a width of 10-20nm and a length of 1μm or longer. It is seven to eight times stronger than steel but as light as 1.5g/cm3, Yano said. So, he considered that a transparent sheet having a low expansion coefficient can be made by adding resin to cellulose nanofibers.

Specifically, an improvement was made for preventing cellulose nanofibers from clumping together in the process of dehydrating pulp. And the fibers were impregnated with acrylate resin to make the pulp transparent.

The transparent sheet has a thickness of 100μm, a light transmittance of 87.8% and a coefficient of linear thermal expansion of 8.30ppm/K with a temperature range of 20-150°C. The coefficient of linear thermal expansion is about 1/3 that of a PET sheet and close to glass'.

The coefficient of linear thermal expansion of a transparent sheet that was made by adding cellulose nanofibers obtained by decomposing pulp to resin was 12.1ppm/K, Yano said. The new paper's coefficient of linear thermal expansion is smaller because pulp is made transparent without being decomposed and the orientations of its fibers are more uniform, he said.

Dehydrated pulp was impregnated with acrylate resin because the refraction index of acrylate resin is 1.52-1.60, which is close to the refraction index of cellulose (1.57). Materials other than acrylate resin can be used as long as their refraction indexes are close to that of cellulose, Yano said.

In general, the refraction indexes of resins change depending on temperature. But the light transmission of the new paper does not change much even at a temperature of 90°C because the pulp prevents the thermal expansion of the resin, Yano said.

In November 2011, Yano announced that he developed a technology to make a transparent sheet by using a material made by making a crab shell transparent.

Disclaimers of Warranties
1. The website does not warrant the following:
1.1 The services from the website meets your requirement;
1.2 The accuracy, completeness, or timeliness of the service;
1.3 The accuracy, reliability of conclusions drawn from using the service;
1.4 The accuracy, completeness, or timeliness, or security of any information that you download from the website
2. The services provided by the website is intended for your reference only. The website shall be not be responsible for investment decisions, damages, or other losses resulting from use of the website or the information contained therein<
Proprietary Rights
You may not reproduce, modify, create derivative works from, display, perform, publish, distribute, disseminate, broadcast or circulate to any third party, any materials contained on the services without the express prior written consent of the website or its legal owner.

Tokushima, Japan - 6 March 2024: Nichia, the world's largest LED manufacturer and inventor of the high-brightness blue and white LED, has started mass production of the new UV-B (308nm) and UV-A (330nm) LEDs in its popular 434 Series packa... READ MORE

New XLamp® S Line LEDs enhance growth, last longer, lower energy costs Horticulture and other forms of agricultural lighting require application-tuned ratios of spectral content, high efficacy and long lifetimes. Whether you are interested... READ MORE