JPH1055767A - Color image receiving tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable convergence drift to be eliminated for a short time by providing an insulation member at least one part of an electrode positioned on a phosphor screen side and restraining lowering of potential on an inner face of a neck when a power switch is turned OFF. SOLUTION: When a convergence cap C is provided with an insulation layer 25, an inner face of a neck 3 is charged by a high-pressure electric field extending from an end of the neck 3 of an inner face guide electric film 11 together with ON of a power switch, and the insulation layer 25 is charged in a substantially same potential by anode high voltage applied to the convergence cap C. As a result, by voltage fall when the power switch is OFF, a repulsion electron from a phosphor screen 8 side is attracted to the insulation layer 25 positioned on the phosphor screen 8 side than the neck inner face on the neck 3 end side and captured by this insulation layer 25, and lowering of a potential of the inner face of the neck 3 is restrained. Consequently, when the power switch is ON, convergence drift can be eliminated for a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color picture tube, and more particularly, to a color picture tube in which convergence is prevented from occurring when power is turned off.

[0002]

2. Description of the Related Art Generally, a color picture tube has a vacuum envelope composed of a glass panel 1 and a glass funnel-shaped funnel 2, as shown in FIG. The three electron beams 5B, 5G, and 5R emitted from the electron gun 4 are deflected by a deflecting device 6 mounted outside the funnel 2 and, via a shadow mask 7,
The phosphor screen 8 formed of a three-color phosphor layer formed on the inner surface of the panel 1 is horizontally and vertically scanned to display a color image.

In such a color picture tube, an electron gun which emits three electron beams 5B, 5G, 5R arranged in a line consisting of a center beam 5G and a pair of side beams 5B, 5R passing through the electron gun 4 on the same plane. In-line type color picture tubes are widely used.

FIG. 4 shows a structure of a neck portion 3 provided with the electron gun 4. The electron gun 4 includes three cathodes K and a plurality of electrodes sequentially arranged in the direction of the phosphor screen from the cathode K, in the illustrated example, six electrodes G1 to G.
The convergence cup C is attached to the final acceleration electrode G6 located on the phosphor screen side. The final acceleration electrode G6 has an inner conductive film 11 applied from the inner surface of the large-diameter portion 10 of the funnel 2 to the inner surface of the adjacent portion of the neck 3, and a convergence cup C
Through a valve spacer 12 and a convergence cup C which are attached to
Anode terminal 13 provided on funnel 2 (shown in FIG. 3)
Is supplied to the anode. Further, in this color picture tube, a neck 3 near the third grit G3 is provided.
On the inner surface, the potential of the inner surface of the neck 3 extending in the direction of the cathode K from the end of the inner surface conductive film 11 in the direction of the cathode K is relaxed, so that discharge between the inner surface of the neck 3 and the low-voltage electrode located on the cathode K side is prevented. A conductive film 14 made of graphite or the like to be suppressed is provided.

In the color picture tube having such a structure, the electric potential of the inner surface of the neck 3 from the end of the inner conductive film 11 to the conductive film 14 from the end of the inner conductive film 11 changes with the start of the operation of the color picture tube. That is, as shown in FIG.
At the initial stage of the operation of the color picture tube when the power switch is turned on, although it is relatively low as indicated by the dashed line 15a, the secondary electrons generated by the collision of the primary electrons from the phosphor screen side and the primary electrons from the electrodes described later. It gradually rises with the emission of electrons, changes after one hour as shown by a broken line 15b, and finally reaches a stable state shown by a solid line 15c.
When the operation of the color picture tube is stopped,
As shown in the figure, the state changes from the stable state shown by the solid line 15c to the state shown by the broken line 15b immediately after the power switch is turned off, and falls several hours later as shown by the dashed line 15a.

In particular, as shown in FIG. 6, the decrease in the potential of the inner surface of the neck when the power switch is turned off is caused by the electron beam that has collided with the phosphor screen under normal operating conditions. The primary cause is that repulsive electrons 17 from the phosphor screen side collide with the inner surface of the neck 3 and the resulting secondary electrons are emitted less than the repulsive electrons 17 that collide.

When the potential on the inner surface of the neck 3 changes, an electric field lens formed between the final acceleration electrode G6 and the electrode G5 adjacent to the final acceleration electrode G6 changes with the change in the potential on the inner surface of the neck 3. In an in-line type color picture tube which emits distortion, particularly three electron beams arranged in a line, a so-called convergence drift occurs in which a pair of side beams passing through a position closer to the inner surface of the neck 3 is deviated from the center beam.

As shown in FIG. 4, the convergence drift becomes more conspicuous as the distance d2 between the inner surface of the neck 3 and the electrode is smaller. For example, in order to improve the focus characteristics, it is effective to increase the diameter d1 of the final acceleration electrode G6 and increase the diameter of the electric field lens formed between the electrode G5 and the adjacent electrode G5. If the diameter d1 of the electrode G6 is too large, the distance d2 between the electrode G6 and the inner surface of the neck 3 becomes narrow, and the convergence drift increases.
Therefore, an appropriate gap is required between the inner surface of the neck and the electrode.

By the way, a maker who assembles a display device by incorporating a color picture tube, such as a TV receiver, carries out aging necessary to confirm the operation state of the display device. Since the potential is adjusted in a stable state, no particular problem occurs. However, when the user purchases the display device and turns on the power switch at the start of use, the potential on the inner surface of the neck becomes, for example, as shown in FIG.
From the state of the dashed line 15a shown in (b) to the state of the dashed line 15a shown in FIG. 5 (a) and further to the state of the dashed line 15b, it takes time for the potential on the inner surface of the neck to stabilize.
Meanwhile, the convergence in which the potential of the inner surface of the neck is adjusted in a stable state shifts. Moreover, there is a problem that such a convergence shift occurs every time the use is started.

The convergence deviation is a unique problem when the power switch is turned off, and the anode high voltage applied to the final accelerating electrode or the phosphor screen is reduced to 20.
Even while the voltage drops from several kV to several tens of kV to 0 kV, electron emission due to a time lag from the cathode continues (about several seconds), and the emitted primary electrons collide with the inner surface of the neck at high speed. In this case, Since the emission of secondary electrons is smaller than the colliding primary electrons, the colliding portion of the primary electrons is negatively charged, and the potential on the inner surface of the neck decreases. The degree is proportional to the amount of emitted electrons, that is, the cathode current.

[0011]

As described above, in the color picture tube, the electric field lens formed between the electrodes of the electron gun disposed in the neck is distorted due to the change in the potential on the inner surface of the neck. In an in-line type color picture tube which emits three electron beams arranged in a line, a convergence drift occurs in which a pair of side beams is deviated in concentration. In particular, the potential on the inner surface of the neck changes as the power switch is turned on and off, and once the potential on the inner surface of the neck decreases due to the turning off of the power switch, after that, even if the power switch is turned on, the potential on the inner surface of the neck becomes stable. Takes a long time, and during that time, there is a problem that the convergence of the three electron beams is shifted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and suppresses a decrease in the potential of the inner surface of the neck when the power switch is turned off. -It aims to construct a high-quality color picture tube that can eliminate drift.

[0013]

An electron gun comprising a cathode and a plurality of electrodes for focusing a plurality of beams emitted from the cathode onto a phosphor screen is disposed in a neck of a glass funnel funnel, and In a color picture tube in which a high voltage is applied to the electrode located on the phosphor screen side of the electron gun via a conductive film provided on the inner surface of the funnel, at least a part of the electrode located on the phosphor screen side is insulated. A member was provided.

Further, the insulating member is provided on the outer surface of the electrode facing the inner surface of the neck.

The insulating member is formed of a material having a dielectric constant substantially equal to that of the neck.

[0016]

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

FIG. 1 shows a configuration of an in-line type color picture tube which is one embodiment of the present invention. This color picture tube has a vacuum envelope composed of a glass panel 1 and a glass funnel-shaped funnel 2, and has a fluorescent material composed of a three-color phosphor layer emitting blue, green and red light on the inner surface of the panel 1. A body screen 8 is provided, and a shadow mask 7 is arranged inside and opposite to the phosphor screen 8.

On the other hand, in the neck 3 of the funnel 2, the three electron beams 5B, 5 are arranged in a line and consist of a center beam 5G and a pair of side beams 5B, 5R passing on the same plane.
An electron gun 20 for emitting G, 5R is provided. The electron gun 20 includes three cathodes K arranged in a row in the horizontal direction (X-axis direction) and a plurality of electrodes arranged in the direction of the phosphor screen 8 sequentially from the cathode K, in the illustrated example, six cathodes. Electrodes G1 to G6, and a convergence electrode is applied to the final accelerating electrode G6 located on the phosphor screen 8 side.
Cup C is attached. The final accelerating electrode G6 has an anode terminal, an inner conductive film, and a convergence
The anode high voltage supplied to the anode terminal is applied via the valve spacer 12 and the convergence cup C which are attached to the cup C and press-contact the inner conductive film, and other electrodes than the cathode K and the final acceleration electrode G6 are applied. G1 to G
6 is applied with a predetermined voltage via a stem pin 22 that penetrates a stem 21 at the end of the neck 3.

An anode terminal 13 is provided on the large diameter portion 10 of the funnel 2. Further, an inner conductive film 11 is applied and formed from the inner surface of the large diameter portion 10 of the funnel 2 to the inner surface of the adjacent portion of the neck 3. The end of the neck 3 of the inner conductive film 11 is located at a position facing the side surface of the convergence cup C of the electron gun 20. The electron gun 20
On the inner surface of the neck 3 near the third grit G3
Graphite or the like, which alleviates the potential on the inner surface of the neck 3 extending in the direction of the cathode K from the end of the neck 3 of the inner conductive film 11 to suppress discharge between the inner surface of the neck 3 and a low-voltage electrode located on the cathode K side. Is formed.

Further, in this color picture tube, an insulating layer 25 (on the side surface of the convergence cup C of the electron gun 20, preferably on the outer surface closer to the phosphor screen 8 than the end 3 of the neck 3 of the inner conductive film 13). The insulating member is provided in an annular shape. This insulating layer 25 is made of a material having substantially the same dielectric constant as the neck 3.

In this color picture tube, the three electron beams 5B, 5G, 5R in one row emitted from the electron gun 20 are arranged.
Is deflected by a horizontal and vertical deflection magnetic field generated by a deflection device 6 mounted outside the funnel 2, and a shadow mask 7 is formed.
In this case, a color image is displayed by horizontally and vertically scanning the phosphor screen 8 through the device. In this case, in order to improve the quality of the image drawn on the phosphor screen 8, three electrons are displayed over the entire screen. The beams 5B, 5G, and 5R need to be correctly focused (convergence), and a pair of side beams 5B and 5R emitted from the cathode K are tilted in advance, or an electron lens formed between some electrodes of the electron gun 20 is used. It is tilted to concentrate at one point on the center of the screen (static convergence). In particular, in a self-convergence in-line type color picture tube, the deflecting magnetic field generated by the deflecting device 6 is regarded as a non-uniform magnetic field. Horizontal,
The three electron beams 5B, 5G, and 5R arranged in a line are concentrated over the entire screen by the vertical deflection magnetic field.

By the way, as in the conventional case, the convergence
In a color picture tube in which an insulating layer is not formed on the cup, the inner surface of the neck 3 is charged by a high-voltage electric field extending from the neck end of the inner conductive film, and the inner surface of the neck near the third grit from the neck end of the inner conductive film due to the charging. The potential of the inner surface of the neck over the conductive film provided changes with the turning on and off of the power switch for driving the color picture tube, and the turning off of the power switch lowers the potential of the inner surface of the neck.
After turning on the power switch, it takes time to reach a stable potential, during which time there is a problem that the convergence of the three electron beams is shifted.

However, as in the color picture tube of this embodiment, the outer surface of the convergence cup C closer to the phosphor screen 9 than the end 3 of the neck 3 of the inner conductive film 13 is provided.
Insulating layer 2 made of a material having substantially the same dielectric constant as neck 3
When the power switch 5 is provided, the potential change on the inner surface of the neck 3 becomes slow even when the power switch is turned off, and the potential on the inner surface of the neck 3 becomes stable in a short time when the power switch is turned on. Therefore, it is possible to provide a high-quality color picture tube which can eliminate deterioration of image quality due to convergence deviation when the power switch is turned on in a short time.

That is, the main cause of the decrease in the potential on the inner surface of the neck when the power switch in the conventional color picture tube is turned off is that repulsive electrons from the phosphor screen side are caused by the voltage drop when the power switch is turned off. If the insulating layer 25 is provided on the convergence cup C as in the color picture tube of this embodiment, the end of the neck 3 of the inner conductive film 11 is turned on when the power switch is turned on. Neck 3
The inner surface is charged, and the insulating layer 25 is also charged to substantially the same potential by the high anode voltage applied to the convergence cup C. As a result, as shown in FIG. 2, due to the voltage drop when the power switch is turned off, the repulsive electrons 17 from the phosphor screen 8 side cause the neck 3
The insulating layer 25 located closer to the phosphor screen 8 than the inner surface of the neck 3 on the end side is attracted to and captured by the insulating layer 25, and the collision of the repulsive electrons 17 with the inner surface of the neck 3 is greatly suppressed. You. Although the potential of the insulating layer 25 decreases in accordance with the degree of capture of the repulsive electrons 17, the repulsive electrons 17 have already disappeared by the time the insulating layer 25 stops capturing the repelled electrons 17 due to the decrease in the potential. , Neck 3
Collision of electrons to the inner surface is avoided, and the change in potential on the inner surface of the neck 3 after the power switch is turned off can be slowed.

In the above embodiment, an in-line type color picture tube has been described. However, the present invention can be applied to a color picture tube other than the in-line type color picture tube, and the same effect can be obtained.

[0026]

According to the present invention, an electron gun including a cathode and a plurality of electrodes for focusing a plurality of beams emitted from the cathode on a phosphor screen is provided in a neck of a glass funnel funnel. In a color picture tube in which a high voltage is applied to an electrode located on the phosphor screen side via a conductive film provided on the inner surface of the funnel,
If an insulating member is provided on at least a part of the electrode located on the phosphor screen side, even when the power switch is turned off, the potential change on the inner surface of the neck becomes slow, and when the power switch is turned on, the potential on the inner surface of the neck becomes lower. A stable state can be achieved in a short time, and a high-quality color picture tube can be provided in which deterioration of image quality due to convergence deviation when the power switch is turned on is eliminated in a short time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an in-line type color picture tube according to an embodiment of the present invention.

FIG. 2 is a view of an electron gun shown for explaining the operation of the color picture tube.

FIG. 3 is a diagram showing a configuration of a conventional color picture tube.

FIG. 4 is a diagram showing a configuration of a main part of the conventional color picture tube.

FIG. 5A is a diagram showing a change in potential on the inner surface of the neck of the conventional color picture tube when the power switch is turned on, and FIG. 5B is a diagram showing the inner surface of the neck when the power switch is turned off. FIG. 6 is a diagram showing a change in the potential of the semiconductor device.

FIG. 6 is a view of an electron gun for illustrating the operation of the conventional color picture tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Panel 2 ... Funnel 3 ... Neck 8 ... Phosphor screen 14 ... Conductive film 20 ... Electron gun 25 ... Insulating member C ... Convergence cup G1-G6 ... Electrode K ... Cathode

Claims (3)

[Claims] 1. An electron gun comprising a cathode and a plurality of electrodes for focusing a plurality of beams emitted from the cathode on a phosphor screen are provided in a neck of a glass funnel-shaped funnel. In a color picture tube in which a high voltage is applied to an electrode located on the phosphor screen side via a conductive film provided on the inner surface of the funnel, at least a part of the electrode located on the phosphor screen side is an insulating member. A color picture tube characterized by being constituted. 2. The color picture tube according to claim 1, wherein the insulating member is provided on an outer surface of the electrode facing the inner surface of the neck. 3. The color picture tube according to claim 1, wherein the insulating member is made of a material having substantially the same dielectric constant as the neck.