Molecular Engineering and Application of Highly Fluorescent Liquid Crystalline Materials without Absorption in Visible Light

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02710
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 32020:Functional solid state chemistry-related
• Research Institution: Kyoto Institute of Technology
• Principal Investigator: Sakurai Tsuneaki 京都工芸繊維大学, 分子化学系, 講師 (50632907)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: ESIPT / 液晶 / 蛍光 / ドーパント / 偏光発光 / ASE

Outline of Final Research Achievements

In this research project, the project leader found that excited-state intramolecular proton transfer-type fluorophores (ESIPT) are promising candidates as a fluorescent dopant for liquid crystals, which relies on their colorless, visible emissive, highly miscible, and non-concentration quenching properties. For this achivement, it is needed to overcome the problem of low fluorescent quantum yield (Φ) of ESIPT fluorophores in solutions and liquid crystals (LCs). The project leader developed a molecular design strategy of introducing conjugated substituents to 2-(2-hydroxyphenylbenzothiazole) (HBT), a famous ESIPT core, which is quite effective for increasing Φ values in solutions and LCs. This strategy was rationalized by means of a quantum chemical calculation method. The prepared room-temperature LCs doped with a newly-designed HBT derivative show polarized emission and amplified spontaneous emission, which opens a new door to the possibility of novel LC-based optical devices.

Free Research Field

機能物性化学

Academic Significance and Societal Importance of the Research Achievements

これまでESIPT型蛍光体は固体状態でのみ効率よく発光する材料という認識であったが、研究代表者の今回の取り組みによって、適切な置換基導入を施せば、溶媒中や液晶中でも高い蛍光量子収率を示すことが可能であることが明らかとなった。これにより、非着色・可視域発光する有機材料のレパートリーが大きく増大することが考えられ、有機発光材料の研究分野の広がりを促進する学術的意義があると考えられる。また、非着色・可視域発光という特徴を活かし、環境光下では目立たないが紫外光で照らした際だけ色が見えるような表示素子としての応用が考えられ、将来的にこのような素子の実装の可能性も示すことができたと考えられる。