Damp rod construction for CRT grid structures

A mask structure for a color picture tube including a phosphor screen, the mask structure comprising:

• a frame comprising a pair of opposed parallel rigid supports and a pair of braces resiliently supporting the rigid supports and separating the rigid supports from each other by a predetermined distance,
• a number of grid wires stretched between the opposed parallel rigid supports, the grid wires parallel to and separated from one another, and
• at least one damp wire stretched between the pair of braces, over and in contact with the grid wires, and traversing the grid wires on the side of the grid wires toward the phosphor screen,
• the damp wire being formed of a conductive metal core wire coated with a semiconductor material layer.

A shadow mask structure of a color picture tube including

• a frame having a pair of opposed parallel rigid supports and a pair of braces resiliently supporting the rigid supports separated from each other by a predetermined distance,
• a number of grid wires stretched between the opposed parallel rigid supports in the same direction and separated from one another, and
• at least one damp wire stretched between the pair of braces over and in contact with the number of grid wires in a direction traversing the stretched direction of the number of grid wires,
• the damp wire being formed of a tungsten core wire coated with a secondary emission semiconductor material layer that has a secondary emission ratio greater than 1,
• the damp wire being located only at a phosphor screen side of the grid wires so that:
• a potential difference is induced between each of the grid wires and the tungsten core wire of the damp wire, so as to form an asymmetrical converging electron lens at the phosphor screen side of the grid wires,
• and the secondary emission semiconductor material layer of the damp wire is hit by only an electron beam which has passed through a spacing between each pair of adjacent grid wires so that the secondary electrons are emitted from the secondary emission semiconductor material layer of the damp wire toward a phosphor screen and no spurious electron is emitted in a time other than when the electron beam passes through the spacing between each pair of adjacent grid wires,
• whereby a black line, which would otherwise be formed because an electron beam emitted toward the phosphor screen is blocked by the damp wire, is prevented from appearing in the phosphor screen.

A shadow mask structure of a color picture tube including

• a frame having a pair of opposed parallel rigid supports and a pair of braces resiliently supporting the rigid supports separated from each other by a predetermined distance,
• a number of grid wires stretched between the opposed parallel rigid supports in the same direction and separated from one another, and
• at least one damp wire stretched between the pair of braces over and in contact with the number of grid wires in a direction traversing the stretched direction of the number of grid wires,
• the damp wire being formed of a tungsten core wire coated with a Cs.sub.2 O layer having a secondary electron emission property,
• the damp wire being located only at a phosphor screen side of the grid wires so that a potential difference is induced between each of the grid wires and the tungsten core wire of the damp wire, so as to form an asymmetrical converging electron lens at the phosphor screen side of the grid wires, and the Cs.sub.2 O layer of the damp wire is hit by only an electron beam which has passed through a spacing between each pair of adjacent grid wires so that the secondary electrons are emitted from the Cs.sub.2 O layer of the damp wire toward a phosphor screen and no spurious electron is emitted in a time other than when the electron beam passes through the spacing between each pair of adjacent grid wires,
• whereby a black line, which would otherwise be formed because an electron beam emitted toward the phosphor screen is blocked by the damp wire, is prevented from appearing in the phosphor screen.