Fluorescent display tube having provision for preventing short-circuit therein, and method of manufacturing the same

A fluorescent display tube comprising:

• a substrate having a display surface;
• anodes formed on said display surface of said substrate, and spaced apart from each other;
• cathodes capable of generating electrons;
• fluorescent layers each of which is fixed to a corresponding one of said anodes, said fluorescent layers being formed by printing a fluorescent paste onto each of said anodes;
• a rib formed on said display surface of said substrate, and extending continuously along respective boundaries each of which is located between a corresponding pair of said anodes which are adjacent to each other, so as to surround a periphery of each said fluorescent layers;
• and
• a control electrode fixed to an upper end face of said rib;
• wherein said fluorescent layers are selectively activated by said control so as to be struck by said electrons generated by said cathodes, for emitting light,
• wherein said rib includes a lower portion and an upper portion which is superposed on said lower portion and which provides said upper end face,
• wherein said rib has a plurality of slots opening in said upper end face, such that said upper portion is divided into a plurality of sections by said slots, and such that said control electrode fixed to said upper end face is divided into a plurality of sections by said slots,
• wherein said lower portion includes paste-flow preventing portions each of which is located below a corresponding one of said plurality of slots and each of which extends between a corresponding pair of said sections of said upper portion adjacent to each other and spaced apart from each other, and
• wherein each of said paste-flow preventing portions of said lower portion of said rib has a height equal to or not smaller than a height of each of said fluorescent layers, said height of each of said paste-flow preventing portions corresponding to a distance measured from said display surface, and said height of each of said fluorescent layers corresponding to a distance measured from said display surface.