CRT having an improved internal conductive coating and making the same

A color cathode ray tube comprising:

• an evacuated envelope comprising a generally rectangular panel portion, a narrow neck portion having a circular cross-section and a funnel portion tapering down from a panel-portion side thereof toward a neck-portion side thereof for connecting said panel portion and said neck portion;
• said funnel portion being provided with a yoke-mounting portion of generally truncated quadrilateral-pyramidal shape for mounting a beam deflection yoke therearound on said neck-portion side of said funnel portion;
• a three-color phosphor screen formed on an inner surface of said panel portion;
• an electron gun housed in said neck portion;
• and
• an internal conductive film extending from an inner wall of said neck portion to an inner wall of said funnel portion,
• said internal conductive film comprising a first part and a second part,
• said first part being formed of graphite, metallic oxide and potassium silicate,
• said second part being formed of graphite and potassium silicate,
• wherein said first part extends from said neck portion in the vicinity of a forward end of said electron gun to a position in said yoke-mounting portion spaced a distance in a range of 60 mm to 150 mm from a splice line between said neck portion and said funnel portion, and said second part overlaps with said first part at opposing ends thereof and extends to a vicinity of a seal line between said funnel portion and said panel portion, and
• wherein said first part is divided into a first subpart disposed on a panel-portion side of said first part and a second subpart disposed on a neck-portion side of said first part, a boundary between said first and second subparts being in the vicinity of said splice line,
• said first subpart is comprised principally of
• 15 to 25 weight % graphite,
• 45 to 70 weight % titanium oxide and
• 35 to 60 weight % potassium silicate,
• said second subpart is comprised principally of
• 15 to 25 weight % graphite,
• 15 to 25 weight % titanium oxide and
• 45 to 70 weight % potassium silicate, and
• said second part is comprised principally of
• 60 to 70 weight % graphite and
• 35 to 45 weight % potassium silicate.