Cathode-ray tube with improved indirected heated cathode structure

Abstract

A cathode ray tube has a phosphor screen and an electron gun including an indirectly heated cathode structure and a plurality of electrodes for projecting an electron beam toward the phosphor screen, and a deflection yoke for scanning the electron beam on the phosphor screen. The indirectly heated cathode structure includes: a base metal having an electron emissive material coating on an outer top surface thereof; a metal sleeve having the base metal attached to an end of the metal sleeve; a heater housed partly within the metal sleeve which includes a major heating portion and leg portions; an insulating film covering the major heating portion and a portion of each of the leg portions; and a black coating film covering a portion of the insulating film extending from the major heating portion toward each of the leg portions, the whole of the black coating film being housed within the metal sleeve.

Description

technical field [0001] The present invention relates to a cathode ray tube with an electron gun using an indirect heated cathode, and more particularly, to a highly reliable long-term method for preventing the occurrence of leakage current by improving the insulation characteristics between the cathode cylinder and the heater of the indirect heated cathode life of a cathode ray tube. Background technique [0002] Cathode ray tubes for color television receivers, display monitors, etc. are widely used in various fields as display devices because of their ability to reproduce high-resolution images. [0003] This type of cathode ray tube includes: a vacuum glass envelope formed by a glass screen part, a tube neck part, and a funnel part connecting the glass screen part and the tube neck part; a phosphor screen formed by a phosphor covering the inner surface of the glass screen ; an electron gun installed in the neck portion of the tube, which includes a plurality of electrode...

AI Technical Summary

Problems solved by technology

Therefore, there is a problem that if the predetermined value of the cathode current in the color television receiver and the display monitor is not large enough compared with the leakage current between the heater and the cathode, the automatic cut-off voltage control circuit cannot control red, green and blue. The cut-off voltage of the electron beam for three colors, the balance between the three colors is out of balance, so that the white balance cannot be obtained, the automatic cut-off voltage control circuit cannot work, and the receiver and monitor become difficult to control

As a result, there are various problems, and the heater sometimes breaks due to a further increase in the leakage current, so it is important to prevent the leakage current between the heater and the cathode from the viewpoint of securing the reliability of the cathode ray tube

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