JPS6129049A - Cathode-ray tube of electrostatic deflection type - Google Patents

Abstract

PURPOSE:To heighten sensitivity and definition, by providing anti-charging electroconductive coating films on at least the portions of electrically-insulating support bars which face Y-direction deflecting electrodes, to prevent the charging of the support bars to preclude aberration and bright line bending. CONSTITUTION:Electroconductive coating film 20 are provided on the main and side surfaces of the portions of electrically-insulating support bars 19 which face Y-directiondeflecting electrodes 16 and surround the planted portions 161, 162 thereof. One end 201 of each coating film 20 is located near the planted portion of a second anode 15, within such an area that a voltage applied to the second anode and that applied to the Y-direction deflecting electrodes 16 are not hindered. The other end 202 of each coating film 20 is likewise located near the planted portion 171 of an osilation electrode 17. As a result, the form of an electron beam spot hardly undergoes aberration even if there are floating electrons. Furtheremore, the support bars 19 are kept from being electrically charged to distort a converged electron beam. Sensitivity and definition are thus heightened.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an electrostatic deflection type cathode ray tube.

[Technical background of the invention and its problems]

Electrostatic deflection cathode ray tubes (hereinafter referred to as CRTs) used in oscilloscope devices and the like are required to have as high brightness, high sensitivity, and a wide practical frequency band as possible.

For this purpose, a structure is known that can obtain high deflection sensitivity without increasing the final acceleration voltage or increasing the overall length, such as a deflection amplification type CRT.

As a structure aimed at high deflection sensitivity, "double other vehicles"
Even in acceleration type CRTs, a structure in which the length of the deflection electrode along the electron beam is made longer is also simple and common.

Next, an electron gun used in an example of a conventional CRT will be explained with reference to FIG.

That is, the electron gun (1) includes a first grid electrode (2) having a cathode inside, a second grid electrode (3), a first anode (4), and a second grid electrode (3).
Consisting of an anode (5), a Y deflection electrode (6), an isolation electrode (7) and an Accelerated by the positive electric field of the two grid electrodes (3), the second grid electrode (13), the first anode (4) and the second anode (5)
The electrons enter the main electron lens, which is made up of It is designed to depict.

However, in order to achieve the highest possible sensitivity and practical frequency band with this structure, by increasing the length of the deflection electrode along the electron beam, the electron beam spot on the phosphor screen becomes a perfect circle. It has been found that when the angle does not change, that is, aberrations often occur. After conducting various experiments to ascertain the cause of this, it was found that the cause was the accumulation of charge on the insulated support rod (9) that supports the electron gun.

That is, in the electron gun (1) as shown in FIG. 3, the electron beam is focused by the main electron lens, and is focused by the second anode (
After passing through the restriction hole (not shown) in 5), the Y deflection electrode (6)
The isolation electrode (
Pass through 7) and submit the transfer.

Furthermore, each of these electrodes is supported by a plurality of insulating support rods (9), and the surface potential of these insulating support rods (9) is close to the potential of each electrode near the part where each electrode is installed. As the distance increases, the potential tends to stabilize at a level determined by the relationship between adjacent electrode voltage and distance. However, although it depends on the material of the insulating support rod (9), in general, the potential on the surface of a highly insulating material tends to become extremely unstable due to dirt, scratches, internal impurities, etc. This tendency becomes stronger as the distance from the implantation site increases, and the greater the potential difference between adjacent electrodes, the greater the tendency.
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Therefore, in order to obtain high deflection sensitivity, if the Y deflection electrode -3= (6) is lengthened, the insulator exposed part (6a ) can be done.

It is quite conceivable that the scattered electrons of the electron beam will enter this insulator exposed part (6a) and be charged, and as a result, from the second anode (5) to the Y deflection electrode (6), the isolation electrode (
7) An undesired electric field is added to the electron beam that is focused while passing through the phosphor screen, causing the spot of the electron beam that reaches the phosphor screen to have a distorted shape, that is, a shape that is not a perfect circle and has aberrations, or a scanning bright line. This is thought to be the cause of the curved and distorted arcuate emission line.

[Purpose of the invention]

The present invention has been made based on the above-mentioned idea, and an object of the present invention is to provide a high-sensitivity, high-quality CRT that prevents charging of an insulating support rod and is free from aberrations and curved bright lines.

[Summary of the invention]

That is, in the present invention, a cathode, a first grid electrode, and a second grid electrode are disposed within the neck of an envelope consisting of a face plate having a phosphor screen adhered to the inner surface and a neck connected to the face plate via a funnel. In an electrostatic deflection type cathode ray tube, an electron gun is attached, in which a grid electrode, a first anode, a second anode, a Y deflection electrode, an isolation electrode, and an X deflection electrode are implanted in order on an insulated support rod. An electrostatic deflection type cathode ray tube characterized in that a conductive coating capable of preventing charging of the insulated support rod is provided at least at a position opposite to the Y deflection electrode of the insulated support rod along the region, The conductive film must be at the same potential as the second anode, the Y deflection electrode, or the isolation electrode. If the conductive film is at the same potential as the Y deflection electrode, it must be conductive at two or more places with the Y deflection electrode. An embodiment of the invention is that they are in contact with each other.

[Embodiments of the invention]

Next, one embodiment of the present invention will be described with reference to FIGS. 1 and 2.

That is, the electron gun (11) includes a first grid electrode (12) having a cathode inside, a second grid electrode (13), and a first anode (4).
), second anode (15), Y deflection electrode (16), isolation electrode (17) and ing. Up to this point, the structure is almost the same as that of the conventional electron gun, but in this embodiment, the X deflection electrode (16) includes the implanted part (+61) (1, 62), and the X of the insulating support rod (19).
A conductive coating (2
0) is provided. One end (20+) of this conductive coating (20) is connected to the second electrode (15).
The second anode (15) is provided close to the implanted portion of the second anode (15) within a range that does not interfere with the voltage applied to the electrode and the X deflection electrode (16). Further, the other end (202) is similarly provided close to the implanted part (171) of the isolation electrode (17).

This electron gun (11) is mounted in a neck (24) that is joined via a funnel (23) to a face plate on which a phosphor screen (21) is adhered.

In this structure (RT), electrons emitted from the cathode are accelerated by the positive electric field of the second grid electrode (13) from the electron beam passage hole of the first grid electrode (I2), The electron beam enters the main lens consisting of the first anode (14) and the second anode (15), is focused into a small diameter, and is sent from the electron beam passage hole (15+) to the X deflection electrode (16),
Isolation electrode (17) and X deflection electrode (18)
Various phenomena are depicted on a phosphor screen (21) through the phosphor screen (21).

By structuring the electron gun in this way, the second anode (15) which gives an aberration to the electron beam and the X deflection electrode (16)
Between and X deflection electrode (16) and isolation electrode (1
7) Even if there are floating electrons from between the surfaces of the insulating support rod (19) opposite to the Since the electron beam spot is uniform from the vicinity to the isolation electrode (17), aberrations in the shape of the electron beam spot are extremely reduced.

In this case, the X deflection electrode (16) has a certain width.

In addition, the entrance gap between the pair of X-deflection electrodes (16) is as narrow as possible considering the utilization rate of the electron beam, and in order to reduce the capacitance between the X-deflection electrodes (16),
16) The width on the inlet side is made as narrow as possible. By doing this, it becomes easier for undesired external electric fields to enter between the second anode (15) and the vicinity of the entrance of the X-deflection electrode (16). When a charging phenomenon occurs on the insulating support rod (19), this charging phenomenon gives distortion to the focused electron beam, but this distortion is prevented by the conductive coating (20).

This conductive film (20) can be formed by applying a conductive paint mixed with carbon, silver, or other metal powder after assembling the electron gun, or by depositing molybdenum or the like on an insulating support rod in advance by vapor deposition or sintering. Use a metalized one.

Further, this conductive coating (20) is attached to the implanted portion (161) (1
6□) Making electrical connections to everything is effective in stabilizing the potential. This is because when the surface resistance of the conductive film (20) is high, the discharge time constant for the charge of scattered electrons becomes longer due to the resistance, and during that time, aberrations may appear temporarily. To prevent this, the implanted part (16
+)(1,6□) to reduce the resistance. From a different point of view, =8= Connecting the implanted portion (16,) (16□) with the conductive coating (20) causes a connection failure at the uneven portion of the implanted portion (161) (162). Even if there is a problem, the conductive film (20) will not be in an open state at all, which will also help improve reliability.

In addition, although the conductive coating (20) is difficult to manufacture, it is possible to connect it to the isolation electrode (17) and the second anode (15), and the (+
62) may be provided in such a way that it escapes, or an isolation electrode may be formed from the implanted part (15+) of the second anode (15) using a conductive coating with a high resistance within a range that does not interfere with the function of the electron gun (11). (17) may be provided up to the implanted portion (17+), or may be set to the same potential as either the second anode (15) or the isolation electrode (17).

In the above-mentioned embodiment, a single-acceleration type CRT with one pair of insulating support rods was shown, but the present invention is not limited to this. X
It can be applied as is to a CRT in which a shield mesh electrode or the like is arranged on the phosphor screen side of the deflection electrode (18), or by further increasing the implanted part of the X deflection electrode (16) ) It is also possible to measure the average of the potentials.

[Brief explanation of drawings]

1 and 2 are views showing one embodiment of the RT of the present invention, in which FIG. 1 is a partially cutaway side view, FIG. 2 is a perspective view showing the main parts of the electron gun, and FIG. FIG. 3 is an explanatory side view of an electron gun used in a conventional CRT.

Claims (3)

[Claims] (1) A cathode, a first lattice electrode, and a second lattice are placed in the neck of an envelope consisting of a face plate with a phosphor screen adhered to the inner surface and a neck connected to the face plate via a funnel. In an electrostatic deflection cathode ray tube, the electrostatic deflection cathode ray tube is equipped with at least an electron gun in which an electrode, a first anode, a second anode, a Y deflection electrode, an isolation electrode, and an X deflection electrode are implanted in order on an insulated support rod. A conductive coating capable of preventing charging of the insulating support rod is provided at least at a position opposite to the Y deflection electrode of the insulating support rod along the electron beam passing region of the electrode. Electrode deflection type cathode ray tube. (2) The electrostatic deflection type cathode ray tube according to claim 1, wherein the conductive film is at the same potential as any of the second anode, the Y deflection electrode, and the isolation electrode. (3) The electrostatic deflection type cathode ray tube according to claim 1, wherein the conductive coating has the same potential as the Y deflection electrode and is electrically connected to the Y deflection electrode at two or more locations.