Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
1998-08-19
2001-03-13
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
Reexamination Certificate
active
06201345
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to cathode-ray tubes used in television receivers, computer-displays or the like.
BACKGROUND OF THE INVENTION
A conventional cathode-ray tube comprises a glass bulb having phosphors for red, green and blue inside and an electron gun that emits electron beams inside the glass bulb. This electron gun comprises cathodes, a first control electrode, a second control electrode, and a third control electrode. The cathodes emit a plurality of electron beams having an inline alignment in the horizontal direction. The first control electrode has first electron-beam through holes opposing the respective cathodes. The second control electrode has second electron-beam through holes provided at positions opposing the respective first electron-beam through holes. The third control electrode has third electron-beam through holes provided at positions opposing the respective second electron-beam through holes.
In cathode-ray tubes, the important factors for determining the image quality are the spot diameter of electron beams striking phosphors and the current value of the electron beams in general. That is to say, the smaller the spot diameter of the electron beams is, the more the resolution is improved. The higher the current value of the electron beams is, the higher the brightness of phosphors becomes. Consequently, bright and clear image pictures can be obtained.
However, in the conventional cathode-ray tube described above, when making the spot diameter of the electron beams small and setting the current value of the electron beams high at the same time, the current density of the current obtained from cathodes becomes high. Consequently, the electron emission from the cathodes becomes difficult, thus limiting the picture image to have high brightness. In addition, the driving voltage of the cathodes becomes high, thus causing problems such as a great burden on a driving circuit. On the contrary, when controlling the current density of the current obtained from the cathodes to a predetermined level or less and increasing the current value of the electron beams, the spot diameter of the electron beams becomes larger, thus causing such problems that the high resolution of image pictures is difficult to obtain.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the above-mentioned problems in the conventional technique and to provide a cathode-ray tube with a high image quality in which an electron beam with a current density higher than the electron-emitting ability of a cathode is formed and the driving voltage of the cathode can be decreased.
In order to attain the object mentioned above, a cathode-ray tube of the present invention comprises: a face-panel having a phosphor screen surface on its inner surface; a funnel connected to the rear part of the face-panel; and an electron gun that is contained in a neck portion of the funnel and emits electron beams. The cathode-ray tube is provided with means for superimposing a plurality of electron beams on a predetermined phosphor on the phosphor screen surface. According to this configuration of the cathode-ray tube, the plurality of electron beams are superimposed and emitted on the predetermined phosphor on the phosphor screen surface. Therefore, while the spot diameter of the electron beams is kept small, the brightness of the phosphor can be improved greatly. As a result, a cathode-ray tube with high brightness and high resolution can be obtained.
In the configuration of the cathode-ray tube of the present invention, it is preferable that the means for superimposing the electron beams is provided between the phosphor screen surface and the cathodes in the electron gun.
In the configuration of the cathode-ray tube of the present invention, it is preferable that the plurality of electron beams are obtained from one cathode in the electron gun. According to this preferable example, electron beams superimposed with a higher current density than the electron-emitting ability in one cathode can be formed without increasing the driving voltage of the one cathode. As a result, the burden on the driving circuit of the cathode can be reduced.
In the configuration of the cathode-ray tube of the present invention, it is preferable that the electron gun is provided with a means for superimposing electron beams. In this case, it is preferable that the electron gun comprises cathodes, a first control electrode, a second control electrode, and a third control electrode. The cathodes emit electron beams. The first control electrode has a plurality of first electron-beam through holes provided at the positions opposing the respective cathodes and are aligned in the perpendicular direction with respect to the horizontal scanning line direction of the electron beams. The second control electrode has second electron-beam through holes provided at the positions opposing the respective first electron-beam through holes. The third control electrode has third electron-beam through holes provided at the positions opposing the respective second electron-beam through holes. According to this preferable example, a cathode-ray tube with high resolution and high brightness can be obtained using the same number of parts as in a conventional one. In this case, it is further preferable that the cathode has a plurality of electron emitting parts opposing the respective first electron-beam through holes aligned in the perpendicular direction with respect to the horizontal scanning line of the electron beams.
Furthermore, in this example, it is preferable that the pitch of the plurality of third electron-beam through holes aligned in the perpendicular direction with respect to the horizontal scanning line of the electron beams of the third control electrode is set to be narrower than that of the plurality of second electron-beam through holes aligned in the perpendicular direction with respect to the horizontal scanning line of the electron beams of the second control electrode. According to this preferable example, an electron lens can be formed of the second control electrode and the third control electrode.
Further, in this case, it is preferable that three electron-beam through holes are aligned in the perpendicular direction with respect to the horizontal scanning line direction of the electron beams of each control electrode. Moreover, it is preferable that the diameters of the electron-beam through holes located at the upper and lower sides are set to be smaller than that of the electron-beam through hole located in the middle. According to this preferable example, the aberration of the electron beams passing through the electron-beam through holes located at the upper and lower sides can be decreased.
In this case, it is further preferable that the electron gun comprises a plurality of cathodes, a first control electrode, a second control electrode, and a third control electrode. The plurality of cathodes for emitting electron beams have an inline alignment in the horizontal direction. The first control electrode has a plurality of first electron-beam through holes opposing the respective plurality of cathodes and being aligned in the perpendicular direction with respect to the horizontal scanning line direction of the electron beams. The second control electrode has second electron-beam through holes provided at the positions opposing the respective first electron-beam through holes. The third control electrode has third electron-beam through holes provided at the positions opposing the respective second electron-beam through holes. According to this preferable example, a cathode-ray tube with high resolution and high brightness can be obtained using the same number of parts as in a conventional one.
In this case, it is further preferable that the pitch of the plurality of third electron-beam through holes aligned in the perpendicular direction with respect to the horizontal scanning line of the electron beams of the third control electrode is set to be narrower than that of the plurality o
Nakagawa Satoru
Yamamoto Yoji
Matsushita Electronics Corporation
Merchant & Gould P.C.
Patel Ashok
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