BLUE PROJECTION TYPE CATHODE-RAY TUBE AND DISPLAY DEVICE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a high-brightness projection type television set allowing the usage of a phosphor having conventional composition and particle diameter in a blue projection type cathode-ray tube by improving brightness by nearly one and half times by the use of the single projection type cathode-ray tube without using a secondary adjustment means such as defocusing. SOLUTION: The focus characteristic of an electron gun as a cathode current dependence of an electron beam spot of the projection type cathode-ray tube is so set as to obtain a desired brightness. When it is assumed that the diameters of an electron beam entering into a blue phosphor at cathode currents Ik1 and Ik2 (mA) at two certain points areϕ1 andϕ2 (mm), respectively, the emission brightness of the blue phosphor is so set as to satisfy (ϕ2-ϕ1) to the power of 2∝(Ik2-Ik1) because an output almost proportional to the cathode current can be mostly obtained by keeping the electron beam density constant.