Yasufumi Iimura

Synthesis of a Novel Organic-Solvent-Soluble Polyimide and Its Application to Alignment Film for Liquid Crystal Displays

We have synthesized a novel organic-solvent-soluble polyimide to be used as alignment films for liquid crystal displays. The polyimide has an aliphatic structure and can be cured at temperatures below 200° C. The novel polyimide also shows better alignment properties judging from its birefringence and dichroic ratio than conventional polyimides derived from the precursor polyamic acids. The alignment of a nematic liquid crystal on the novel polyimide shows a good texture without irregular liquid crystal domains.

Properties of Voltage Holding Ratios of Liquid Crystal Cells Using Organic-Solvent-Soluble Polyimide Alignment Films

We have synthesized organic-solvent-soluble polyimides containing various diamine moieties. The voltage holding ratios of liquid crystal (LC) cells using these polyimides as alignment films have been investigated. The results show that the structures of polyimides considerably affect the characteristics of the voltage holding ratios of LC cells. It is shown that the large polarization in polyimides, which is evaluated from the calculation of partial atomic charges of diamines and the capacitance-voltage measurement of LC cells, gives rise to lower voltage holding ratios of LC cells.

PRETILT ANGLES OF LIQUID CRYSTAL ON ORGANIC-SOLVENT-SOLUBLE POLYIMIDE ALIGNMENT FILMS

The increase of pretilt angle of liquid crystal in an active matrix (AM) liquid crystal display (LCD) is one of the most important issues to achieve high-contrast and defect-free AM LCDs. We have developed a new generation method of the pretilt angle by using newly synthesized organic-solvent-soluble polyimides containing two types of diamine. The maximum pretilt angle of 2.8° for a nematic liquid crystal is obtained using new polyimides.