Nippon Telegraph and Telephone Corporation

Nippon Shokubai Co., Ltd.

Ntt Advanced Technology Corporation

Hitachi-Johnson Controls Air Conditioning, Inc.

Noriyoshi Yamada

Toru Yamada

Yasunori Okumura

Juichi Noda

Nobuo Tomita

Taisuke Oguchi

Kozo Tajiri

Shiro Nishi

Hiroaki Hanafusa

Yuta Hashimoto

Tohru Matsuura

Masayoshi Kuwabara

Tetsuya Kozai

A polyimide excelling in heat resistance, chemical resistance, water repellency, dielectric characteristics, electrical characteristics, and optical characteristics and a polyamide acid useful as the raw material therefor are provided. Specifically, a polyamide acid containing a chlorine atom and a fluorine atom and comprising a repeating unit represented by the following formula (1):(wherein X and X' independently denote a divalent organic group; Y and Y&#x2032; independently denote a chlorine, bromine, or iodine atom; p and p&#x2032; denote independently denote the number of fluorine atom {F in the formula (1)} bonded to the relevant benzene ring, representing an integer of 0-3; q and q&#x2032; independently denote an integer of 0-3; and p+q total 3, and p&#x2032;+q&#x2032; total 3).

Polyamide acid and polyimide, and optical material

A dielectric multilayer filter applicable to optical communication systems is disclosed, as is a fabrication method therefor, and an optical element incorporating the same. The disclosed dielectric multilayer filter includes a fluorinated polyimide base layer with a dielectric multilayer formed thereover. According to the disclosed fabrication method, a fluorinated polyimide layer is formed by applying liquid fluorinated polyimide material over a smooth surface to a predetermined thickness followed by drying and hardening, after which a dielectric multilayer is formed over the fluorinated polyimide layer by an ion assist vapor deposition method, and then stripping the fluorinated polyimide layer away from the underlying smooth surface. The disclosed dielectric multilayer filter can be easily and economically produced at a suitably small thickness with no need for grinding, exhibits highly uniform physical and optical properties, and is exceedingly durable and resistant to curling and warping.

Dielectric multilayer, filter, manufacturing method therefor, and

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Tokyo, Japan

Noriyoshi Yamada