Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
1999-06-01
2001-09-11
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C315S382000, C315S382100
Reexamination Certificate
active
06288482
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is concerned with the color cathode-ray tube. Especially, the present invention relates to the color cathode-ray tube with the electron gun that discharges 3 electron beams at parallel in the common plane in the direction of the fluorescent face.
The color cathode-ray tube is used for television and for the monitor of the information terminal.
The color cathode-ray tube includes the following components.
(1) Electron gun at which several (3 usual) electron beams are discharged that is provided in the inside of one end of the vacuum envelope
(2) Fluorescent face where several (ordinary 3 colors) fluorescent body picture elements were arranged like the mosaic applied to the inside of the other end of the vacuum envelope
(3) Shadow mask that is the color selection electrode that stood and installed close to the fluorescent face
(4) Deflection yoke installed in the outside of the above vacuum envelope to deflect several electron beams discharged from the above electron gun
By scanning the electron beam to two dimensions by the magnetic field that is generated in the deflection yoke, the color cathode-ray tube displays the required image.
FIG. 3
is a perpendicular section that explains outline structure diagram of the color cathode-ray tube.
The color cathode-ray tube has the following components:
panel
1
, funnel
2
, neck
3
, fluorescent body film
4
, internal conduction film
5
, shadow mask
6
, mask frame
6
A, mask suspension mechanism
6
B, getter
7
and magnetic shield
8
.
In addition, the color cathode-ray tube has the following components:
deflection yoke
9
, magnet
10
for the adjustment of color purity and the convergence, electron gun
11
of the in-line type, reinforcement metal fitting
12
and stem pin
13
.
FIG. 4
is the schematic cross-sectional view that explains the structure of the electron gun of the in-line type that is used for the color cathode-ray tube of this seed. The electron gun shown in
FIG. 4
has heater
20
, cathode
21
, the first electrode
22
, the second electrode
23
, the third electrode
24
, the fourth electrode
25
of the anode, shield cup
26
and contact spring
27
,
28
is the thing point (cross OVER). The same code as
FIG. 3
corresponds to the same part.
FIG. 5
is the schematic cross-sectional view that explains the structure of the electron beam generation part of the electron gun shown in FIG.
4
. The electron beam generation part shown in
FIG. 5
has electron beam pass hole
22
A of the first electrode
22
, electron beam pass hole
23
A of the second electrode
23
and electron beam pass hole
24
A of the third electrode
24
.
30
is the drive circuit. The same code as
FIG. 4
corresponds to the same part.
The electron gun of the in-line type mounted in neck
3
in the same diagram discharges 3 electron beams EB (center beam EBc and side beam EBs×2) on the common plane (horizontal face). The intensity of this electron beam is modulated according to the image signal (red Sr, green Sg and blue Sb) that is applied from drive circuit
30
of the outside through stem pin
13
. And then, the electron beam is deflected by the deflection magnetic field of the horizontal direction and the vertical direction that are generated in deflection yoke
9
. And then, the electron beam is two-dimensionally scanned on fluorescent body film
4
, and the image is regenerated.
The electron emitted from cathode
21
heated by heater
20
by 400~1000 V positive electric potential applied to the second electrode
23
in FIG.
4
and
FIG. 5
is accelerated to the first electrode
22
side, and 3 electron beams are formed. And then, these 3 electron beams pass electron beam pass hole
22
A of the first electrode
22
and pass electron beam pass hole
23
A of the second electrode
23
. The high voltage of 5-10 kV is applied to the third electrode
24
. And then, 3 electron beams receive the focusing action a little through the pre-focus lens that is formed between the second electrode
23
and the third electrode
24
. The high voltage of 20-35 kV is applied to the fourth electrode (anode)
25
. And then, accelerating by the third electrode
24
, 3 electron beams inject into the main lens that is formed between the third electrode
24
and the fourth electrode (anode)
25
.
The electrostatic field is formed out of the electric potential difference between the third electrode
24
and the fourth electrode
25
that compose the main lens of this place. Therefore, the above electrostatic field changes the orbit of 3 electron beams EB supplied to the main lens. Therefore, 3 electron beams adjust the focus on fluorescent body film
4
respectively and form the beam spot.
By the magnetic field that is generated in deflection yoke
9
installed in the transition area of funnel
2
and neck
3
of the color cathode-ray tube, this beam spot is two-dimensionally scanned on the whole screen that is composed of the fluorescent body film. And, this beam spot is sorted for each color in the hole opening of shadow mask
6
. And then, this beam spot reaches the fluorescent body of the corresponding color, and the required color image is formed.
And, in the actual operation of the color cathode-ray tube like above, the specified voltage is applied to above each electrode. It is simultaneously necessary to control the chromaticity and the brightness of the screen to display the image. By changing the drive voltage that is applied to the cathode that corresponded to each of the fluorescent body of 3 colors as it was shown in
FIG. 4
, the quantity of the electron beam that is emitted from each cathode is controlled synchronizing with the deflection. And, the cathodic voltage just before emitting the electron beam from the cathode is called the cathodic cutoff voltage. That is, as for this, the brightness of the screen is the voltage as of 0 levels (dark state).
In the cathode-ray tube that is generally used for color television, the diameter of the electron beam pass hole of the first electrode of the electron gun is an ordinary about 0.6 mm. And, in the cathode-ray tube that is used for the display monitor for information processing terminals such as the computer, the drive voltage is almost 50 V. And then, the electric current quantity that is emitted from the cathode at this time is an about 0.3 mA. This is equivalent to the electric current value when the screen of the above cathoderay tube is shown in recommendation brightness. This recommendation brightness is almost 100 cd/m
2
.
And, about the prior art of this seed, it is disclosed to the Japanese patent publication No. 53-18866 official gazette.
It is most important that in the display image of the color cathode-ray tube like above, brightness, resolution and the contrast are high. Therefore, the reduction of the beam spot diameter in the high brightness is requested, in the cathode-ray tube for the display monitor for information processing terminals such as computer from which these characteristics are required especially. And, high resolution of the fluorescent body dot pitch of each color that constitutes the fluorescent body film is required, and the increase of the number of display picture elements by expansion of the display screen is requested further.
The reduction of the diameter of the thing point that is projected and the increase of the electric current density in the cathode are valid by reducing the measure of the electron beam pass hole of the first electrode and the circumference electrode to reduce the beam spot diameter.
But generally, by the rise of Joule heat, the increase of the cathodic electric current density accelerates evaporation of electron emission materials such as the barium that constitutes the relevant cathode. Therefore, following the declination of cathodic ability, the life of the cathode-ray tube shortens it.
In addition, high resolution of the fluorescent body dot pitch and the increase of the number of display picture elements by screen expansion are connected with reduction of the beam transmission rat
Kato Shin-ichi
Shirai Syoji
Watanabe Ken'ichi
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
Patel Vip
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