Hitachi, Ltd.

Yukio Ohno

Teruki Suzuki

Churyo Kodama

Shinkichi Tanimizu

Yasuo Hirasawa

A circular fluorescent lamp has a fluorescent tube of a generally circular shape having electrodes fixed gastight in both of its ends respectively to enclose inert gas and mercury therein. A cap is mounted to bridge between the tube ends. The fluorescent tube has an oval section taken along a line perpendicular with respect to its axis. The rate of ovalness y/x, representing the ratio between the larger tube diameter y and the smaller tube diameter x of the tube sectional shape, preferably lies within the range of 1.10 to 1.30.

Circular fluorescent lamp with oval section of tube

A phosphor system consisting of an alkaline-earth metal silicate host lattice activated by trivalent terbium together with monovalent alkaline metal as a charge compensator, said phosphor system corresponding to the formula, X.sub.3-x Y.sub.1-x Si.sub.2 O.sub.8 : Tb.sub.x, Z.sub.x wherein X is at least one of Ba, Sr, and Ca; Y is at least one of Mg and Zn; and Z acting as a charge compensator is at least one of Li, K, and Na, and x is from 0.001 to 0.95, said phosphor system substituting Ca plus Mg for X plus Y of the formula being excluded. The present invention provides an efficient green-emitting phosphor particularly useful for a deluxe fluorescent lamp.

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Akishima, Japan

Yukio Ohno