Flat picture display device

A method of manufacturing shape retention structure for retaining filament electrodes of a flat picture display device in a predetermined curved shape, said method comprising the steps of:

• placing a shape retention plate on a concave outer surface of a mold, the concave surface having a predetermined curvature;
• forcing said shape retention plate under pressure into contact with the concave outer surface of the mold so as to conform to the predetermined curvature thereof;
• securing a plurality of rows of equal numbers of fixtures to a surface of the shape retention plate, opposite the surface thereof which contacts the concave outer surface of the mold in said step of forcing, in such a manner that the fixtures of each said row are spaced from one another in a first direction corresponding to the direction in which the outer concave surface of the mold is curved and in such a manner that the rows of fixtures are spaced from another in a second direction perpendicular to said first direction;
• while the shape retention plate is conformed to the predetermined curvature of the outer surface of the mold, connecting first elongate reinforcement plates, equal in number to the number of said rows of fixtures, to the shape retention plate via said fixtures in such a manner that said first elongate reinforcement plates extend in said first direction;
• while the shape retention plate is conformed to the predetermined curvature of the outer surface of the mold, connecting second elongate reinforcement plates, equal in number to said number of fixtures in each row thereof, to said shape retention plate in such a manner that said second elongate reinforcement plates extend across said first elongate reinforcing plates in said second direction without being rigidly connected to said first elongate reinforcement plates at those locations where the reinforcing plates cross, whereby the reinforcing plates constitute a grid-like structure secured to the shape retention plate;
• and
• subsequently removing the shape retention plate and the grid-like structure secured thereto from the mold.