JPH07254376A - Electron gun for color cathode-ray tube - Google Patents

Abstract

PURPOSE:To stably supply a beam current immediately after turning on of a power source by locating a main surface to be fixed to a first grid electrode, a welding point at the main surface, and an embedded surface press-fitted to bead glass in approximately the same position in the tube axial direction. CONSTITUTION:A welding point at a main surface fixed to a side wall surface of a first grid G1 electrode 2 of a bead support 8 is located in approximately the same position in the tube axial direction as an embedded surface to be press-fitted into bead glass. Consequently, since there is almost no distance in the pipe axial direction between the welding point and the embedded surface, the distance therebetween in the tube axial direction is not nearly varied even if the support 8 is thermally expanded due to an increase in temperature. As a result, positional fluctuation at the G1 electrode 2 is not nearly generated even If the support 8 is thermally expanded, thus substantially preventing a change in beam current value. Namely, image display can be performed in suitable luminance except for a short period of 10sec. after turning-on of a power source, and it is possible to prevent generation of a defective phenomenon such as emphasis of a black level and darkening in low luminance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color cathode ray line in which fluctuations in current value during the transition period after the power is turned on until the beam current stabilizes are small, and the reproducibility of brightness and color tone of the screen during that period is improved. Related to electron guns for tubes.

[0002]

2. Description of the Related Art FIG. 2 is a sectional side view of a part of an in-line type electron gun currently used in almost all color cathode ray tubes. In FIG. 2, 1 is a cathode, 2 is a first grid electrode (hereinafter abbreviated as G1 electrode, and the like), 3 is G
2 electrodes, 4 G3 electrodes, 5 G4 electrodes, 6 G5 electrodes,
7 is a G6 electrode, 8 is a bead support, and 9 is bead glass. In this way, the electrodes forming the electron gun are supported by the bead glass 9 so as to be insulated from each other and separated from each other by a predetermined distance in the tube axis direction, and the electron gun as a whole is G6 on the fluorescent surface side. It is supported by the neck tube wall via an elastic piece (not shown) attached to the electrodes, and on the stem side, it is supported by the stem sealed at the end of the neck tube via the lead wires leading to each electrode. As shown in FIG. 2, each of the three cathodes 1 dedicated to a specific primary color has one bottomed cylindrical G
They are arranged on one plane within one electrode 2. That is, three cathodes are arranged in a plane orthogonal to the plane of FIG. 2, and three cathodes are overlapped in this figure. The electron beam passage hole is formed in the bottom surface of the G1 electrode 2 (hereinafter referred to as the G1 electrode surface), which is the fluorescent surface side when in use.

When the power source is turned on during use, the cathode 1 is heated and its temperature is raised, and the radiant heat also heats the G1 electrode 2 to raise its temperature and expand. When more time passes, G1
The bead support 8 fixed to the electrode 2 by welding also expands.

When power is turned on and the heater (not shown) starts to heat up, the cathode sleeve closest to the heater first expands and extends to the G1 electrode surface side. Is supported by a cylindrical support,
When this support expands, the support position of the cathode sleeve is G1.
It moves away from the electrode surface and acts to cancel the influence of the expansion of the cathode sleeve. The G1 electrode 2 heats up and expands due to the heat generated by the contained cathode 1. The degree of temperature rise depends on the distance from the cathode, which is the heat source, and the G1 electrode surface, which is very close to the cathode, has a cylindrical surface. As a result, the G1 electrode surface expands to a higher degree than the above, and the G1 electrode surface bulges toward the fluorescent surface side, that is, the G2 electrode 3 side as shown by the broken line in FIG.

Further, the bead support 8 which is relatively far from the cathode 1 expands much later than the above-mentioned parts, but the embedding surface press-fitted into the bead glass 9 and the welding point of the G1 electrode 2 are in the tube axis direction. If the distance is above, this distance will increase due to thermal expansion, so the G1 supported by the bead support 8
The position of the electrode surface of the electrode 2 will change with respect to the embedding surface of the bead support 8 in the bead glass 9, that is, the position supported by the bead glass 9.

[0006]

The expansion of the cathode sleeve and its cylindrical support is completed in about 10 seconds after the power is turned on. This period overlaps with the temperature rise of the electron emission surface itself of the cathode 1 and the rising timing of the electron emission function, and it does not pose a problem in practical use. The doming of the first grid electrode 2 starts near the end of the above period, and brings the electrode surface of the G1 electrode 2 closer to the G2 electrode 3. A positive potential of several hundreds of volts is applied to the G2 electrode 3 with respect to the G1 electrode 2, accelerating the electrons emitted from the cathode 1 to the fluorescent surface side and increasing the beam current value. The cathode of the electron gun dedicated to each primary color is controlled by the circuit of the television receiver with respect to the grounded G1 electrode 2 so that an appropriate beam current value corresponding to the brightness of the screen to be displayed can be obtained. The applied positive potential is applied, and the higher the positive potential, the lower the beam current value is controlled. When the electrode surface controlling the beam current value of the G1 electrode 2 approaches the G2 electrode 3 which is the electron beam accelerating electrode,
The current values of the three electron beams all increase. Although the doming of the G1 electrode 2 is completed in about 3 minutes, if the degree of increase of each beam current during this period is great, the brightness of the screen is greatly increased, the black level is raised, and the black level is destroyed.

The bead support 8 is fixed to the G1 electrode 2 by welding at a specific position on the main surface along the tube axis direction, and the end of the embedding surface perpendicular to the main surface is embedded in the bead glass 9. If there is a distance in the tube axis direction between the welding point on the main surface of the bead support 8 with the G1 electrode 2 and the surface of the bead support 8 embedded in the bead glass 9, the bead support 8 is formed.
Expands, the distance in the tube axis direction also becomes longer, and G1
The position of the electrode surface of the electrode 2 in the tube axis direction is changed. That is, the position of the welding point for fixing the main surface of the bead support 8 to the side surface of the G1 electrode 2 is an embedding surface that connects the bead support 8 to the bead glass 9 and is perpendicular to the main surface (this embedding position is the electrode support. Position), depending on whether the distance is larger or smaller in the pipe axis direction, above or below.
The situation of fluctuation of the position of the electrode surface of the G1 electrode 2 in the tube axis direction changes. As described above, the influence of the expansion of the bead support 8 is relatively slow after the power is turned on, it starts to appear after 1 minute or more has passed, and usually it may take 10 minutes or more and nearly 30 minutes to finish.

Conventionally, the bead support 8 has a shape in which a metal piece is bent in a U-shape (the same shape as the bead support supporting the G6 electrode 7 in FIG. 2), and the middle portion is used as a main surface to form a G1.
In many cases, a bead glass was welded and fixed to the side surface of the electrode, and two surfaces orthogonal to the main surface were embedded in the bead glass. If such a bead support is used, a distance in the tube axis direction is apt to be generated between the welding position between the bead support and the G1 electrode and the surface embedded in the bead glass, and when the bead support expands, the G1 electrode surface is pushed down. The beam current value was lowered by acting so as to (remove from the fluorescent surface, that is, away from the G2 electrode). This state is shown in FIG. In FIG. 3, the current when the positive potential (beam current control potential) with respect to the G1 electrode of the cathode is kept constant by setting the elapsed time after power-on in minutes on the horizontal axis and the beam current value on the vertical axis in μA. The state of fluctuation is shown. In FIG. 3, (1) is the period during which the cathode is being heated and expanded, and (2) is the period when the G1 electrode is being heated and expanded.
(3) is the period during which the bead support is expanding by heating.

Under the above-mentioned conditions, as a television receiver user, a predetermined beam current corresponding to the control on the television receiver circuit side continues to flow during the period of use from the time when the image starts to appear. Is desirable. Since the beam current is finally stabilized when the bead support is completely expanded, as shown in FIG. 3, the beam is supplied for 2 to 3 minutes after about 10 to 30 seconds have passed since the power was turned on. If we overlook the period when the current is high as an unavoidable transition period (because the circuit adjustment of the television receiver must be done in consideration of the period when the current value is stable for many hours). The screen brightness during this period is much higher than the brightness during the current stabilization period, and it becomes necessary to endure problems such as blackout.

The present invention solves the above-mentioned conventional inconveniences and excludes a constant beam current control potential applied to the cathode except for a period of several seconds to several tens of seconds after the power is turned on. An object of the present invention is to provide an electron gun for a color cathode ray tube in which an electric current is stably supplied.

[0011]

In order to solve the above-mentioned problems, in the present invention, a main surface fixed to the G1 electrode and an embedding surface whose end portion is perpendicular to the main surface into which the bead glass is press-fitted are provided. The welding point on the main surface of the bead support that was fixed to the side wall surface of the G1 electrode and the embedding surface that was press-fitted into the bead glass existed at substantially the same position in the tube axis direction.

As a material for the bead support and the G1 electrode, an iron-nickel alloy containing about 42% nickel and having an expansion coefficient similar to that of glass was used.

[0013]

The welding point on the main surface of the bead support fixed to the side wall surface of the G1 electrode and the embedding surface press-fitted into the bead glass are present at substantially the same position in the axial direction of the tube. Since there is almost no distance in the tube axis direction between the two, even if the bead support thermally expands due to temperature rise, the distance in the tube axis direction between the two is almost unchanged. Therefore, even if the bead support thermally expands, the position of the G1 electrode surface hardly changes, and the beam current value hardly changes. Actually, other than the above-mentioned items as the beam current variation factors, there may be more minute variation factors.
The best results were obtained when the welding position on the electrode was in the tube axis direction and slightly on the G1 electrode surface side with respect to the embedding surface.

[0014]

EXAMPLE FIG. 1 (a) is a view showing a state in which a bead support 8 is welded (welded points are X marks) and fixed to a long side surface of a G1 electrode 2, and FIG. 1 (b) is a side surface perpendicular thereto. FIG. As shown in the figure, the welding point of the bead support 8 to the G1 electrode 2 is slightly shifted to the G1 electrode surface side from the surface embedded in the bead glass. By supporting the G1 electrode 2 by the bead support 8 on the bead glass 9 as described above, after the power is turned on, except for a period of at most ten and several seconds,
The image was displayed with moderate brightness, and no blackening occurred.

The reason why the iron-nickel alloy containing about 42% nickel is used for the material of the bead support is that it has a surface to be embedded in the bead glass, and since this alloy does not contain cobalt. , An iron-nickel-cobalt-based alloy is less expensive, has no problem in workability, has a relatively low expansion coefficient as a metal material, and can be easily welded to a bead support made of the same material, so an electron gun such as a G1 electrode Used for each electrode.

[0016]

As described above, according to the present invention, the position variation of the G1 electrode due to the thermal expansion of the bead support does not occur, and the image display is moderate except for a period of about 10 seconds after the power is turned on. It was carried out at the luminance, and the inconvenient phenomena such as the rise of the black level at the low luminance and the crushed black disappeared.

[Brief description of drawings]

FIG. 1A shows a bead support is welded to a long side surface of a G1 electrode of an electron gun for a color cathode ray tube of the present invention at a position almost the same as an embedding surface in a tube axial direction (welding point × mark)
The figure which shows the state which made it adhere, and figure (b) is a figure which shows the side surface orthogonal to it.

FIG. 2 is a side view in which a part of an electron gun of an in-line type color cathode ray tube is shown in section.

FIG. 3 is a diagram showing the relationship between the beam current value and the elapsed time after the power is turned on in the conventional in-line type color cathode ray tube, showing a stable current value after a high current value for a while after the power was turned on. It shows that.

[Explanation of symbols]

1 ... Cathode, 2 ... G1 electrode, 3 ... G2 electrode, 4 ... G
3 electrodes, 5 ... G4 electrode, 6 ... G5 electrode, 7 ... G6
Electrodes, 8 ... Bead support, 9 ... Bead glass.

Claims (2)

[Claims] 1. Three for specific primary colors arranged on one plane.
The electron gun of this book contained three cathodes inserted from the opening on the side opposite to the fluorescent surface when in use, and provided an electron beam passage hole on the bottom surface that became the fluorescent surface during use. A cylindrical first grid electrode having a bottom, a bead support having a main surface welded and fixed to a side wall surface of the first grid electrode, and a bead support having each electrode including the first grid electrode fixed thereto. In an electron gun for an in-line type color cathode ray tube equipped with a bead glass which is insulated from each other and supported at a predetermined position by press-fitting and embedding the end portion of the bead support into the bead glass in a semi-melted and softened state via A main surface fixed to the side wall surface of the first grid electrode of a bead support having a main surface fixed to the first grid electrode and an embedded surface having an end portion perpendicular to the main surface press-fitted into the bead glass With the upper welding point The embedding surface press-fitted into the bead glass is located at substantially the same position in the pipe axis direction, or the welding point is located slightly closer to the first grid electrode surface than the embedding surface. An electron gun for a color cathode ray tube characterized in that 2. The electron gun for a color cathode ray tube according to claim 1, wherein the materials of the first grid electrode and the bead support are both made of an iron-nickel alloy whose expansion coefficient is close to that of glass.