JPH0142111B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving the convergence characteristics of an automatic convergence type in-line electron gun cathode ray tube.

In a color television receiver using an in-line electron gun type cathode ray tube, as shown in Fig. 1, by changing the horizontal deflection magnetic field 1 to a pink tension magnetic field and the vertical deflection magnetic field 2 to a barrel magnetic field, both side beams can be transmitted. This reduces the color misregistration between the two, and the convergence correction circuit can be omitted. As mentioned above, since a nonuniform magnetic field is used, there is a drawback that the deflection sensitivity for the center beam 4 is worse than the deflection sensitivity for the side beams 3 and 5, and a pattern as shown in Figure 2 is obtained on the screen. It will be done. In the figure, 6 is a rectangular pattern formed by the side beams 3 and 5, and 7 is a rectangular pattern formed by the central beam 4.

Such a central beam 4 and side beams 3, 5
Conventionally, the third
A magnetic control element as shown in the figure is provided directly behind the electron beam emitting hole of the electron gun, that is, at a position where the leakage magnetic field of the deflection yoke reaches. In the figure, two washers 8 and 9 are called shants,
It works to weaken both the horizontal and vertical deflection magnetic fields near the side beam holes 12 and 14 and strengthen the vertical deflection magnetic field near the center beam hole 13. The two disks 10 and 11 are called enhancers and work to strengthen the horizontal deflection magnetic field near the central beam hole 13. As a result, the deflection sensitivity for the side beams 3 and 5 is worse than that for the center beam 4, and by making the deflection magnetic field a non-uniform magnetic field, the deterioration in the deflection sensitivity of the center beam is corrected, and as shown in Figure 4 on the screen. The rectangular patterns 6' and 7' of the side beams 3, 5 and the central beam 4 can be matched.

By the way, in recent years color television receivers have become
In addition to displaying images, character displays are now being used to display characters and graphs. A receiver for such a character display is required to have a higher resolution than a receiver for TV images. In order to meet such demands, it goes without saying that the color cathode ray tube must be designed with high resolution, but it is also often attempted to increase the horizontal deflection frequency of the receiver. The horizontal deflection frequency is determined by the application and receiver and can be selected arbitrarily, but generally it is 15.75KHz.
Or it is selected around 31.5KHz.

By the way, when the horizontal deflection frequency is 15.75KHz and the rectangular patterns of the side beams 3 and 5 and the center beam 4 are matched as shown in Figure 4, when the horizontal deflection frequency is set to 31.5KHz, the side beams 3 and 5 are
It has been observed that the rectangular patterns of the central beam 4 and the central beam 4 become inconsistent as shown in FIG. This is because the deflection sensitivity of the center beam 4 is inferior to that of the side beams 3 and 5 by changing the frequency.

In such a case, by changing the sizes of shunts 8, 9 and enhancers 10, 11, side beams 3,
5 and the center beam 4 can be matched as shown in Fig. 4. However, if the horizontal deflection frequency is set to 15.75 KHz, the rectangular pattern 6'' of the side beams 3 and 5 and the center beam 4 can be made to match as shown in Fig. 5. and 7″ mismatch occurs.

On the other hand, the shape of the deflection yoke can be changed to change the strength of the leakage magnetic field to the electron gun to correct the inconsistency in the rectangular pattern, but if the horizontal deflection frequency is changed, the inconsistency in the rectangular pattern also occurs.

In short, the conventional combination of a color cathode ray tube and a deflection yoke has the disadvantage that a convergence shift occurs unless a dedicated color cathode ray tube or deflection yoke is prepared each time the horizontal deflection frequency is changed. This causes a big problem in terms of production control of color cathode ray tubes or deflection yokes.

The object of the present invention is to provide a novel color cathode ray tube which improves the above-mentioned drawbacks and eliminates frequency dependence.

In order to achieve this object, the present invention improves the frequency characteristics by forming the magnetic control element of the in-line electron gun by molding magnetic material powder, and improves the frequency characteristics to at least 15.75KHz and 31.5KHz.
It is characterized by matching rectangular patterns at two frequencies.

The details of the present invention will be explained below. It has been confirmed that the mismatch, ie, convergence shift, in the rectangular patterns of the side beams 3, 5 and the center beam 4 due to changes in the horizontal deflection frequency is mainly due to the frequency dependence of the magnetic properties of the magnetic control device of the electron gun.

Generally, permalloy is used as material for electron gun shunts and enhancers, and the plate thickness is 0.25t or more.

The relationship between the permalloy's magnetic permeability and frequency is shown in Figure 6, where the permalloy has a plate thickness of 0.25t and the permeability drops rapidly around 20KHz. When operating a receiver with the horizontal deflection frequency fixed at 15.75 KHz as in the past, even if the permalloy's permeability changes with the frequency, the permeability to shunts 8 and 9 and enhancers 10 and 11 will be reduced. It is sufficient to simply adjust the size and achieve convergence while keeping the plate thickness fixed without considering the frequency characteristics of magnetic property. However, the horizontal deflection frequency
In the case of a new application where a device that has been adjusted to converge at 15.75KHz is raised to 31.75KHz, the magnetic permeability of shunts 8 and 9 and enhancers 10 and 11 will decrease, so their magnetic The control function deteriorates, the deflection sensitivity of the side beams 3 and 5 increases, and the deflection sensitivity of the center beam 4 relatively decreases, causing a convergence shift.

Currently, the horizontal deflection frequency cannot be increased above around 31.5KHz, so the convergence shift caused by changing the frequency is at least
This can be eliminated by improving the material or structure of the shunts 8, 9 and enhancers 10, 11 at 15.75 KHz and 31.5 KHz.

Eliminating the convergence shift here does not mean that the three beams completely converge at one point, but rather that the three beams converge within a practically acceptable range. The range varies depending on the application, but for example, TV
1.5mm for images, 0.5mm for character displays
It is.

FIG. 7 shows an embodiment of the shunt 8',
The material of 9' and the enhancer (not shown) was changed from permalloy to ferrite to improve the frequency characteristics of magnetic permeability. The shunts 8', 9' and enhancer made of ferrite are molded into a shape that allows the three beams to converge, and are inserted into a hole made in the cup electrode 15 of the electron gun, and are held in place by the holding plate 16. It is firmly fixed at 15.

As mentioned above, the frequency dependence of the deflection yoke is very small, so by improving the frequency characteristics of the magnetic permeability of the magnetic control device of the color cathode ray tube electron gun, it is possible to create a combination of a color cathode ray tube and a deflection yoke. In a cathode ray tube device, three beams can be converged regardless of the horizontal deflection frequency, and the effect is remarkable.

[Brief explanation of drawings]

Figure 1 is a diagram showing a deflection magnetic field used in an in-line color television receiver, Figure 2 is a convergence pattern when no magnetic control element is used, and Figure 3 is a diagram showing a deflection magnetic field used in an in-line color television receiver.
The figure is a front view showing a magnetic control element, Figure 4 is a convergence pattern using a magnetic control element, Figure 5 is an overconvergence pattern using a magnetic control element, and Figure 6 is the frequency characteristic of permalloy's magnetic permeability. , FIG. 7 is a sectional view of a cup electrode to which a ferrite magnetic control element is attached. 8, 9, 8', 9'... shant, 10, 11...
...enhancer.

Claims (1)

[Claims] 1 The magnetic control element of the automatic convergence type in-line electron gun is composed of a molded magnetic material powder, and the deflection frequency of the magnetic control element is
An in-line color cathode ray tube characterized by matching magnetic permeability at 15.75KHz and 31.75KHz.