JPH01186540A - Electron gun - Google Patents

Abstract

PURPOSE:To remove the unnecessary portion of the magnetic field adversely affecting on the focusing and concentration of a beam by constituting part or all of electrodes of an electron gun with a superconducting material. CONSTITUTION:A deflecting yoke 6 to deflect an electron beam is installed around a funnel section 8 and forms the deflecting magnetic field 7. A thin film 11 made of a superconducting material is coated or deposited on the inner wall of a neck section so as to surround an electron gun, members 12 made of the superconducting material are fitted to the inner wall of a seal cup 4. These superconducting members 12 are fitted on lines passing nearly the centers between respective beam passing holes in the direction nearly perpendicular to a line connecting a center beam passing hole 15b and side beam passing holes 15a and 15c and the passing direction of the beam. Part of the deflecting magnetic field 7 formed by the deflecting yoke 6 can be prevented from infiltrating into a focusing electrode 3 or an accelerating electrode 4 by the superconducting members 12, and the Lorentz force by the deflecting magnetic field can be prevented from adversely affecting the beam shape during the focusing and acceleration of the beam.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention comprises an electrode and members attached thereto,
The present invention relates to a so-called electron gun that emits an electron beam using a potential difference between electrodes, and particularly to an electron gun suitable for eliminating the adverse effects of a magnetic field.

[Conventional technology]

In conventional color cathode ray tubes, as shown in Figure 2,
It has an electrode system 2 and 3 for focusing and accelerating the three electron beams emitted from the cathode 1.1 The electrodes are supported by a glass support material (not shown), and the entire electron gun is a shield cup 4 which is the last stage electrode. An electron gun 10 is disposed in a neck portion 8 extending substantially perpendicularly to the screen of the cathode ray tube.
It is equipped with Further, as described in Japanese Utility Model Publication No. 55-9163, it is formed by a deflection yoke 6 for deflecting and scanning the electron beam, which is disposed in a funnel section 9 that extends from the neck section 8 to the screen 5 in a substantially trumpet or funnel shape. A part of the deflection magnetic field 7 that is applied extends to the pishield cup. As shown in FIG. 3, magnetic bodies 20a to 20d made of a high-speed magnetic material are provided around electron beam passing holes 15a and 15c provided corresponding to the three beams provided in the shield cup, as shown in FIG. It is controlled so that the strength near the center beam passage hole is stronger than that near the side beam passage hole, and the concentration of the three beams on the screen is achieved.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not take into account the leakage of the deflection magnetic field to the focusing/accelerating electrode, or the influence of eddy currents generated in the shield cup due to the high-speed deflection magnetic field when the screen is enlarged.

For example, the magnetic field leaks into the focusing and accelerating electrodes.

This worsens the focusing of each electron beam and increases the focusing error of the three electron beams. In addition, the eddy current generated in the shield cup generates a magnetic field in a direction that demagnetizes the magnetic field that had been strengthened around the center beam, resulting in problems such as increased beam concentration errors.

An object of the present invention is to reduce or prevent magnetic fields that adversely affect the focusing and concentration of these beams.

(Means for Solving the Problems) The above object is to fix a part of the electrode of an electron gun, a part of the glass support part that supports the electrode, or a part of the glass tube neck, etc.
This is achieved by arranging superconducting materials.

[Effect]

That is, superconducting materials completely shield magnetic fields. This makes it possible to select the necessary and unnecessary parts of the magnetic field, and to create a structure in which the unnecessary parts are shielded. Therefore, the negative influence of the magnetic field on the beam can be removed.

〔Example〕

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

In FIG. 1, an electron gun 10 includes a cathode 1 for emitting three electron beams, a focusing electrode 2 for focusing the emitted beams, an accelerating electrode 3 for accelerating the emitted beams, and a shield cup connected to the cathode 1. 4, the electrodes are supported and fixed by a glass support member (not shown). Further, the shield cup is supported by a neck inner wall 8 made of a glass tube, and supports the entire electron gun 10. Also, the inner wall of the neck part 8
A funnel portion 9 is connected in a trumpet or funnel shape, and a cathode ray tube 13 is constituted by a screen on which the electron beam finally reaches. Further, a deflection yoke 6 for deflecting the electron beam is installed around the funnel portion 8 to form a deflection magnetic field 7. A thin film 11 made of a superconducting material is coated, vapor-deposited, or buried on the inner wall of the neck portion so as to surround the electron gun, and a member made of a superconducting material is provided on the inner wall of the seal cup. is installed.

FIG. 4 shows a front view of the shield cup as seen from the screen side, and the position, shape, etc. of the superconducting member will be explained.

That is, the superconducting member 12 has the center beam passage hole 1
5b and the side beam passage hole, and a line passing approximately at the center between the centers of the respective beam passage holes in a direction substantially perpendicular to the beam passage direction.

According to the present invention, as shown in FIG.
A part of the deflection magnetic field 7 formed by the deflection yoke 6 can be prevented from entering the focusing electrode 3 or the accelerating electrode 4, and the Lorentz force caused by the deflection magnetic field can adversely affect the beam shape during beam focusing and acceleration. can be prevented from happening. In addition, as a result, conventionally the deflection yoke 6 and the electron gun 10 required a certain distance in order to avoid the adverse effect of the deflection magnetic field on the beam shape, but by using the superconducting material coating of the present invention, this distance can be narrowed. This allows the entire electrode system to be shortened and a thin cathode ray tube to be realized. Note that the superconducting material may be present not only on the inner wall of the funnel portion but also on the outer wall.

Next, as shown in FIG. 5, the magnetic field in the opposite direction due to the eddy current that generates the deflection magnetic field is generated by the side beam passing holes 15a and 15c.
It is stronger near the center beam passage hole 15b than in the vicinity,
As a result, the center beam is deflected weaker than the high side beams, causing a beam concentration shift. However, according to the embodiment shown in FIG. 4, magnetic fields can be prevented from entering the vicinity of the center beam passage hole from diagonally above. By equalizing the influence of the magnetic field caused by the eddy current on the three electron beams, it is possible to prevent beam concentration deviation.

Further, FIG. 6 shows a second embodiment of the present invention. In the embodiment of the present invention, two pairs of upper and lower plates or prismatic members are used as members made of superconducting material.

According to this, there is an effect that manufacturing is easier than in the first embodiment.

Furthermore, as a third embodiment, at least a part of the bottom of the shield cup in which the three electron beam passing holes in FIGS. 5 and 6 are provided is made of a superconducting material.
The magnetic field penetrating the bottom of the shield cup focuses the electron beam,
It is possible to prevent it from entering the accelerating electrode area, and good focusing and concentration can be obtained.

〔Effect of the invention〕

According to the present invention, by using a superconducting material,
This has the effect of removing unnecessary parts of the magnetic field that adversely affect beam focusing and concentration.

[Brief explanation of the drawing]

FIG. 1 is a horizontal sectional view of an electron gun showing one embodiment of the present invention;
FIG. 2 is a horizontal sectional view showing an example of a conventional electron gun, FIG. 3 is a front view of a shield cup of a conventional embodiment, and FIG. 4 is a front view of a shield cup of an embodiment of the present invention. FIG. 5 is a front view of eddy currents generated in a conventional shield cup and the resulting magnetic field, and FIG. 6 is a front view of a shield cup showing a second embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Cathode, 2... Focusing electrode, 3... Accelerating electrode, 4... Shield cup, 5... Screen, 6
... Deflection yoke, 7... Deflection magnetic field, 8... Neck part, 9... Funnel part, 10... Electron gun, 11...
...Superconducting coating, 12... Superconducting member, 15... Electron beam passage hole, 15a. C... Side beam passing hole, 15b... Center beam passing hole, 20... High permeability magnetic material, 30...'
Lfk current. 31...Magnetic field formed by eddy current. Agent: Patent Attorney Ogawa Hiroto/'.・ 1z---to the same electric nose l

Claims (1)

[Scope of Claims] 1. Consisting of at least two electrodes and a member electrically connected to the electrodes, a potential difference is applied between the electrodes from an external circuit, and the potential difference causes at least one of the electrodes to be electrically connected to the electrodes. 1. An electron gun that emits an electron beam from an electrode toward another electrode, characterized in that part or all of the electrode is made of a superconducting material. 2. The electron gun according to claim 1, wherein part or all of the member electrically connected to the electrode is made of a superconducting material. 3. The electrodes include a cathode with a relatively low potential that emits an electron beam, at least one grid electrode that has an intermediate potential to focus the emitted electron beam, and a cathode that emits the electron beam. Consists of an accelerating electrode with a relatively high potential for final acceleration, and an electrode (shield cup) that is connected to the accelerating electrode and supported by a member that electrically connects the electron gun to the electrode, and is electrically connected to the electrode. The supporting members include a glass member that supports the electron gun electrode, a glass tube neck portion that is installed around the electron gun, and
It is composed of a funnel part connected to the funnel part and a screen where the electron beam finally reaches, and the electron beam is
In an electron gun configured to be deflected by a deflection device that generates a magnetic field, at least a portion of the inner wall of the glass tube neck has a coating made of a superconducting material. gun. 4. The cathode emits three electron beams, and each focusing electrode, accelerating electrode, and shield cup is provided with three electron beam passing holes for the three electron beams to pass through. In the gun, three of the shield cups
At least one member made of superconducting material is placed between the center beam passage hole and the side beam passage hole so as to be substantially perpendicular to both the direction in which the two electron beam passage holes are lined up and the direction in which the electron beam passes. The electron gun according to claim 3, wherein the electron gun is installed on a line passing approximately through the center. 5. The electron gun according to claim 4, wherein at least a part of the bottom portion of the shield cup provided with the three beam passage holes is made of a superconducting member.