Mitsui Chemicals, Inc.

Koji Yokosawa

Tadahiro Sunaga

Shizuo Tokito

Jun Okabe

Provided are an expandable or bendable circuit board having good body-contact feel, strong against bending and folding, and an electronic device made therefrom. The bendable circuit board includes: a film comprising a polyurethane synthesized by reacting a long-chain polyol with polyisocyanate and having a storage modulus at 25&#xb0; C. of 20 to 200 MPa, a tensile strength of 20 to 80 MPa, and an elongation at break of 500 to 900%, and the temperature of which the storage elastic modulus reaches to 1 MPa is at 155&#xb0; C. or higher; and circuit wiring formed in contact with a surface of the film. Alternatively, an expandable circuit board having the ratio &#x3c1;/&#x3c1;of the specific electrical resistance &#x3c1; of the circuit wiring when the circuit wiring is expanded to the specific electrical resistance (&#x3a9;&#xb7;cm) &#x3c1;of the circuit wiring before the circuit wiring is expanded is within a range of 1.05 to 10.0.

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Yonezawa, Japan

Koji Yokosawa