JPH0312423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cathode ray tube with improved voltage resistance characteristics.

Generally, a color cathode ray tube has a glass bulb 4 consisting of a panel part 1, a funnel part 2, and a neck part 3, as shown in FIG. A conductive film 6 is provided. The internal conductive film 5 extends to the inner surface of the neck portion 3, and the electron gun assembly 9 is housed in the neck portion 3. As shown in FIG. 2, this electron gun assembly 9 includes an anode 11 and a fifth
A grid electrode consisting of a grid 12, a fourth grid 13, a third grid 14, a second grid 15, and a first grid (not shown), a cathode (not shown), a bead glass 18 that holds each electrode together, and a cup-shaped body 19
and a valve spacer 20.

The anode 11 and the fourth grid 13 are connected by a connector 21 as shown in FIG. 3, and the anode terminal 8, internal conductive film 5, and valve spacer 2 shown in FIG.
A high voltage is applied from the outside through 0. The fifth lattice 12 and the third lattice 14 are connected by a connector 22, and an auxiliary high voltage is applied from the outside via a lead wire implanted in a stem (not shown). Similarly, the second lattice 15, the first lattice, and the cathode are also connected by lead wires through separate connectors, and respective voltages are applied from the outside. When operating such a cathode ray tube in a TV set, etc., take the case of a multi-step focus electron gun as an example.
A voltage of 25 KV is applied to the anode 11 and the fourth grid 13, a voltage of 9 KV is applied to the fifth grid 12 and the third grid 14, a voltage of about 600 V is applied to the second grid 15, and a voltage of about -150 V is applied to the first grid.

The voltage difference applied between the fifth grid 12 and the anode 11 is 16KV, but when the TV set is turned off, the capacitance between the outer conductive film 6 and the inner conductive film 5 of the cathode ray tube increases. Since the reverse impedance of the high-voltage power supply is very large, the charges accumulated in the high-voltage power supply are difficult to discharge and remain for a long time.
On the other hand, the voltage applied to the fifth grid 12 is quickly discharged to zero potential due to the low impedance of the grid voltage power source.

Therefore, the potential difference between the fifth grid 12 and the anode 11 is 25 KV, which is 9 KV higher than during operation. Furthermore, since the current flowing through the deflection coil (not shown) also becomes zero, electrons field-emitted from points around the apertures of the fifth lattice 12 pass through the apertures of the anode 11 and reach the phosphor screen (not shown). )
The device collides with the device and emits light in a narrow area, making it easily noticeable, and causing problems such as the screen flashing even when the switch is turned off. Furthermore, when the area around the cathode ray tube is darkened, even a field emission current as small as 0.1 nA causes the screen to emit light, making it very difficult to eliminate these problems.

FIG. 3 is an enlarged view of the cross section near the high voltage electrode of the electron gun structure 9. If the field emission source 25 is located near the aperture of the fifth grating 12, it will be drawn to the electric field perpendicular to the equipotential surface 26 and become unnecessary. Electrons are emitted, pass through the aperture of the cup state 19 as in trajectory 27, and collide with the phosphor screen, causing it to emit light.

FIG. 4 is an enlarged view of the vicinity of the field emission source 25 in FIG. Since the voltage is applied, unnecessary electrons are emitted as shown in orbit 27. On the other hand, a strong electric field parallel to the axial direction of the network portion 3 is applied to the field emission source 28 located at the center of the electrode of the fifth grating 12, so that all unnecessary electrons are attracted to the anode 11 and reach the phosphor screen. Therefore, it does not become a problem until the current becomes large, on the order of several microamperes. The field emission source 29 located at the shoulder portion of the fifth grating 12 near the neck portion 3 includes:
Since an electric field similar to that of the field emission source 25 is applied to the outside, unnecessary electrons are emitted as shown in the trajectory 27, collide with the inner wall of the network part 3, and emit secondary electrons 30, some of which become fluorescent. It reaches the surface and makes it emit light.

Furthermore, conventionally, as shown in FIG.
The aperture diameter D ₁₁ is the aperture diameter of the fifth grid 12.
_D12 , the gap D between the anode 11 and the neck portion 3 is shortened, and the facing area _S11 of the anode 11 with respect to the fifth grating 12 is made larger than the facing area _S12 of the fifth grating 12. ing. According to such a configuration, unnecessary electrons emitted from the field emission source 25 are captured by a part of the anode 11 and do not reach the phosphor screen. Similarly, unnecessary electrons from the field emission source 29 are also captured by a portion of the anode 11 and do not collide with the inner wall of the neck portion 3.

Therefore, it is possible to obtain a cathode ray tube that does not have harmful symptoms such as causing the phosphor screen to emit light and has good withstand voltage characteristics. Note that even if the aperture diameter D ₁₁ of the anode 11 becomes smaller than the aperture diameter D ₁₂ of the fifth grating 12, since the equipotential surface 26 is axially symmetrical, the focus characteristics of the beam current from the cathode passing near its central axis will be affected. No harmful effects. On the other hand, the size A of the protruding portion 31 of the anode 11 with respect to the fifth lattice 12 must be at least 1/4 of the dimension d between the anode 11 and the fifth lattice 12. However, if the size A of the protruding part 31 is made too large, the beam from the cathode will collide with the protruding part 31 of the anode 11, causing red heat of the electrode and gas emission from the surface, which will deteriorate other characteristics. Therefore, the size A of the protruding portion 31 needs to be smaller than the beam diameter from the cathode.

However, when the size A of the protruding portion 31 is reduced as described above, a situation occurs in which unnecessary electrons emitted from the field emission sources 25 and 29 are not captured by the anode 11.

On the other hand, when the opposing area between the anode 11 and the fifth lattice 12 increases, the vacuum discharge phenomenon becomes more active, resulting in an increase in unnecessary electrons from the field emission sources 25 and 29.

This invention was made in order to improve the above-mentioned drawbacks, and it suppresses the emission of unnecessary electrons from the field emission source at the electrode to which a low voltage is applied, and also ensures that the emitted unnecessary electrons are compensated to the electrode to which a high voltage is applied. It is an object of the present invention to provide a cathode ray tube that can prevent the harmful luminescence phenomenon of a phosphor screen from being captured.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 is an enlarged view of the main part of the anode section showing an example of the cathode ray tube according to the present invention. In this figure, the difference from FIG. 5 is that the anode 11 to which a high voltage is applied;
facing the fifth grid 12 to which a low voltage is applied;
This is because the protruding portion 31 protruding from the opposing surface is retreated toward the phosphor screen side.

As described above, by retracting the protruding portion 31 toward the phosphor screen side, the anode 11 and the fifth grating 1
The area facing the field emission sources 25 and 2 is reduced, the vacuum discharge phenomenon is suppressed, and the emission of unnecessary electrons from the field emission sources 25 and 29 is reduced.

Furthermore, because the protruding portion 31 does not have to be made small, unnecessary electrons emitted from the field emission sources 25 and 29 are reliably captured by the anode 11, effectively preventing the harmful light emission phenomenon of the phosphor screen. be able to.

The above description has been made regarding the anode 11 and the fifth lattice 12, but the same holds true for the fourth lattice 13 and the third lattice 14. However, if the axial length of the fifth lattice 12 is long, it becomes difficult for unnecessary electrons emitted from the vicinity of the apertures of the third lattice 14 to pass through the fifth lattice 12, so there is no need to take the above consideration. Further, a high voltage is also applied between the fifth lattice 12 and the fourth lattice 13, but unnecessary electrons are emitted from the fifth lattice 12, which is a low voltage electrode, to the fourth lattice 13, which is a high voltage electrode. Therefore, it moves in the opposite direction to the phosphor screen and does not cause the phosphor screen to emit light, causing no problem.

As explained above, in this invention, the protruding portion of the electrode to which a high voltage is applied that protrudes from the opposing surface of the electrode to which a low voltage is applied in the horizontal scanning direction of the electron beam is retreated toward the phosphor screen. In addition to suppressing the emission of unnecessary electrons from the field emission source at the voltage application electrode, the emitted unnecessary electrons are reliably captured by the high voltage application electrode, thereby preventing harmful light emission phenomena on the phosphor screen. can.

[Brief explanation of drawings]

Figure 1 is a partially cutaway front view of a conventional cathode ray tube, Figure 2 is an enlarged sectional view of the neck portion of the cathode ray tube in Figure 1, and Figure 3 is a high voltage section of the electron gun assembly in a conventional cathode ray tube. 4 is an enlarged view of the main part of FIG. 3; FIG. 5 is an enlarged view of the main part of the anode section in another example of a conventional cathode ray tube; FIG. 6 is an enlarged view of the main part of an anode in an embodiment of the present invention. It is an enlarged view of the main part of the section. 11... Anode, 12... Fifth lattice, 31... Protruding portion. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An electrode placed on the phosphor screen side to which a high voltage is applied and an electrode placed on the cathode side to which a low voltage is applied are made to face each other, and the opposing area of the electrodes to which the high voltage is applied is In a cathode ray tube in which an electron lens is configured by having a larger area facing the electrodes to which a low voltage is applied, the electrodes to which the high voltage is applied are horizontal to the electron beam from the opposite surface to the electrodes to which the low voltage is applied. A cathode ray tube characterized in that a protruding portion protruding in the scanning direction is retreated toward the phosphor screen.