JPS60262336A - Inline type electron gun - Google Patents

Abstract

PURPOSE:To prevent generation of dislocation caused by coma-aberration on a scanning screen formed by both outside electron beams by forming a magnetic field control device by machining a magnetic material so that it is this as a whole but thick partially. CONSTITUTION:A concentrated magnetic pole 10 which is made of non-magnetic material and formed in a cylinder with bottom is installed at the tip of electron beam emission side of an electron gun. Circular magnet shielding devices 20 and 21 are arranged so as to surround outside electron beam transmission holes 13 and 14. The circular magnet shielding device 20 is formed by a magnetic material such as permalloy having a thickness of 0.1mm. or less as a whole except for a plurality of thicker parts 24 which are partially thick in a radial direction. By this construction, a desired magnetic field control function can be obtained without increase in outer diameter. To fix the concentrated magnetic pole 10 to a specified position, the thicker part 24 is spot-welded to the magnetic pole 10. Therefore, welding process is made easy.

Description

[Detailed Description of the Invention] <Technical Field of the Invention> The present invention relates to a color cathode ray tube, in which a central and a pair of outer electron beams emitted from an in-line electron gun are formed on a fluorescent surface by a common deflection magnetic field. This invention relates to an in-line type electron gun using a sesph convergence method, which can make the size of the sister to be the same regardless of the horizontal deflection frequency.

<Prior Art> FIG. 1 is a longitudinal sectional view of a color cathode ray tube using a so-called self-convergence type in-line electron gun that does not require dynamic convergence correction, which is conventionally used.

A central electron beam B1 emitted from the in-line electron gun 1 and located in the same plane, and a pair of outer electron beams B2.
B3 is deflected horizontally and vertically by a deflection device 5 disposed in the funnel-shaped part of the evacuated glass envelope 2, and is located on the top surface of the glass envelope 20, and has a plurality of fireflies emitting light in three colors inside. A scanning screen is formed on the phosphor surface 4 on which the light body pixels are deposited through a shadow mask 3 placed opposite thereto. In order to make this color cathode ray tube a self-convergence system that does not require dynamic convergence correction, the horizontal deflection magnetic field of the deflection device 5 is made to have a strong pincushion distortion, and the vertical deflection magnetic field is made to have a strong barrel distortion, as shown in Fig. 2. As shown, a pair of inner and outer electron beams B2. By eliminating the comatic aberration of B3, the fluorescent surface 4
A scanning screen 6 corresponding to the top is formed. In this case, the scanning screen 7 of the central electron beam B1 is generally horizontal and vertical, with the inner and outer electron beams B2, . It is smaller than the scanning screen 6 formed by B3. This misalignment of the scanning screen is due to the coma aberration of the deflection device 50, and in order to eliminate the coma aberration and match each scanning screen, a deflection device 50 is installed at the tip of the electron gun 1, which is exposed to the leakage magnetic field from the rear of the deflection device 5. A magnetic field control element made of a magnetic material with high magnetic permeability is disposed on the bottom surface 11 of the concentrated magnetic pole 1o formed of a non-magnetic material in the shape of a cylinder with a bottom. FIG. 3 shows an example of a magnetic field control element, in which a central electron beam transmission aperture 12 formed in the bottom surface 11 of a concentrated magnetic pole 10 is arranged so as to be sandwiched on the vertical axis YY, which is the short axis of the fluorescent surface 4. A pair of disc-shaped magnetic enhancement elements 15 and 16 are provided, and the electron beam transmission apertures 13 and 14 on both sides are bored on the horizontal axis XX, which is the long sleeve of the fluorescent surface 4. An annular magnetic shielding element 17 arranged in
．． It consists of 18. The magnetic enhancement elements 15, 16 increase the deflection sensitivity of the horizontal deflection magnetic field FH of the deflection device 5 to the inner and outer electron beams B2, . B3, the annular magnetic shielding elements 17 and 18 are arranged to prevent the inner and outer electron beams B2. B3, the deflection sensitivities of the horizontal and vertical deflection magnetic fields FH and Fv of the deflection device 5 are lowered than that of the central electron beam B1, and the vertical deflection magnetic field Fv is lower than that of the central electron beam B1.
It has the function of increasing the deflection sensitivity of the inner and outer electron beams.

Therefore, the scanning screen 7 of the central electron beam B1 is enlarged both horizontally and vertically by the magnetic field control elements 1,5,16 and 17,18, and conversely, the scanning screen 7 of the central electron beam B1 is enlarged in both the horizontal and vertical directions. The B3 scanning screen 6 is reduced, comatic aberration due to the deflection magnetic field is removed, and the scanning screens 6 and 7 can be made to coincide completely.

<Problems with the prior art> On the other hand, recently, so-called display color cathode ray tubes, which are color cathode ray tubes with high resolution characteristics, have been used to display various types of information.
Kanji, charts, etc. are displayed in high density.

In order to perform high-density display, the color 118-pole ray tube must have a high resolution and uniform focus characteristics, the video circuit must have a wide frequency band to increase the horizontal resolution of the display screen, and the vertical direction of the display screen must be wide. In order to achieve high resolution, it is necessary to have a large number of scanning lines.

Normally, in order to increase the number of scanning lines as a means of high-density display, it is common practice to increase the horizontal deflection frequency fh to more than 15.734 kHz of the current standard TV system. In this case, horizontal deflection frequency fh=15.73
Scanning screen 6 formed by the inner, outer, and center electron beams due to the horizontal deflection magnetic field, which had no problems at around 4 kHz.
Comatic aberrations of / and 7/ occur, and as shown in FIG. The ratio is different on the left and right sides of the fluorescent surface 4, and the enlarged size on the left side is smaller than the enlarged size on the right side d! A larger asymmetry results.

This shift in the scanning screen results in a convergence error that depends on the horizontal deflection frequency, which significantly deteriorates the quality of the image received on the fluorescent surface. For example 20 inch 90 degree polarized color cathode #
In the II tube, the horizontal deflection frequency fh = 15.73
If fh = 31.5 kHz, which is twice as high as k↓2, then the above-mentioned deviation c+,, d, becomes d1 = 0.7 mm, d2 = 0.3 m + n near the outermost part of the effective fluorescent surface1, The reason why the scanning screens 6' and 7' formed by the inner and outer electron beams and the center electron beam are shifted in the horizontal direction due to coma aberration as the horizontal deflection frequency fh increases is as follows.

First of all, the screen vertical axis Y of the bottomed cylindrical concentrated magnetic pole 10
- Due to the horizontal deflection magnetic flux penetrating the tube measuring section in the Y direction, an overcurrent is generated on this magnetic flux passing surface, and this generates a magnetic flux that prevents the change in the magnetic flux of the horizontal deflection magnetic field, thereby attenuating the magnetic flux.
Central and inner and outer electron beams B,, B2. Lowering the deflection sensitivity of Li2 reduces its horizontal deflection amplitude, and the reduction in magnetic flux reduces the magnetic shielding effect of the annular magnetic shielding elements 17,18.

The loss of magnetic flux due to this eddy current is due to the conventional horizontal deflection frequency f
It could be completely ignored at around h = 15.73 kHz, but
As the frequency increases, magnetic flux loss due to eddy currents cannot be ignored, and as shown in FIG. 4, the scanning screen 6' of the outer electron beam expands in the horizontal direction with respect to the scanning screen 7' of the central electron beam. K becomes.

On the other hand, the current waveform applied to the horizontal deflection coil of the deflection device 5 to perform horizontal scanning is a sawtooth wave shown in FIG. 5, and the time t from point a to point b in the figure is the horizontal scanning time. The time t2 from point B to point C is the horizontal retrace time, and normally t and l are set to about 1.15. a
The point or 0 point corresponds to the left edge IC on the screen of the horizontal scanning section, and the point b corresponds to the right edge position (7).In other words, the left edge position of the horizontal scanning time corresponds to the end of the horizontal scanning interval t, and the corresponds to the end of the horizontal scanning time t1, and during the horizontal retrace period t2, a magnetic field is generated due to the current that changes about five times as fast as during the horizontal scanning period t, and therefore its harmonic component magnetic field ((The reduction of magnetic flux due to eddy current loss due to the annular magnetic shielding element 1.7.1
The loss of magnetic shielding effect of 8 is 1.2 mm higher on the left side of the fluorescent surface than on the right side.
1,' As shown in Fig. 4, the expansion width of the outer electron beam scanning screen 6' in the horizontal direction with respect to the central electron beam scanning screen 7' is as follows: d on the left side is wider than d on the right side, Asymmetry occurs in coma aberration in the horizontal direction.

At fh = 15.734 kHz, which is used in the conventional standard color TV system (NTSC system), t, =
51-531tsec.

t, = io ~ 12 μsec, the eddy current loss due to this can be completely ignored, and the above-mentioned coma aberration and its asymmetry were not found substantially, but as f++ increases, the difference between 11 and t2, and even more effective In order to increase the scanning time t, the retrace time t2 is set to be as small as possible, and the slight asymmetry in the horizontal deflection magnetic flux due to eddy current loss becomes a phenomenon that cannot be ignored.1. becomes noticeable.

<Object of the invention and shield 8. The present invention has been made in view of the above-mentioned drawbacks, and is aimed at increasing the horizontal deflection frequency of a color electron beam tube equipped with an in-line electron gun. An object of the present invention is to provide a magnetic field control element that does not cause deviation due to coma aberration.

The present invention is directed to a magnetic field that is arranged so as to surround the electron beam A area on both sides of an in-line electron gun arranged in a line on the horizontal axis, and that corrects the coma aberration of the scanning screen formed by the deflection magnetic field. In a color cathode ray tube equipped with a control element, the above object was achieved by processing the magnetic material of the magnetic field control cape element so as to have locally thicker parts and to have a thinner and baser structure as a whole. It is something.

〈Embodiments of the invention〉 Hereinafter, the implementation sequence of ``Let's make one shot'' will be explained in detail with reference to the drawings.

No. 6Nd is a bottom view of the concentrated magnetic pole 10 according to the present example J (n example), and FIG. 7 is a perspective view of the annular magnetic shielding element 20.
Not shown. At the tip of the electron beam emission side of the electron gun, a concentrated magnetic pole 1 ( ) formed in a cylindrical shape at the top and made of a non-magnetic material is attached as in the past, and a central magnetic pole 1 ( ) formed in the center of the bottom surface 11 is installed.
The aperture 12 is placed between the apertures 12 on the vertical 1itill Y-Y, which is the short axis of the phosphor surface 4 passing through the center of the beam transmission aperture 12 (10(
A pair of disc-shaped magnetic value increasing elements 15 and 16 are arranged facing each other,
A ring-shaped magnetic shielding element 20.
21 will be installed. As shown in FIG. 7, the annular magnetic shielding element 20 is an annular body having an aperture 22 that is almost the same as the electron beam transmission apertures 13 and 14 on both sides, and an outer circle 23 having a larger diameter than the conventional one. The overall thickness is 0.2 mm, except for a plurality of thick wall sections 24 that are locally thickened in the radial direction. It is made of a magnetic material such as permalloy with a thickness of less than im. The thick part and the thin part are formed by punching out an annular body from a magnetic material having the same thickness as the deep part, leaving the thick part locally, and then applying 5VC chemical etching to obtain a predetermined thickness. What is necessary is to form a thin wall portion.

The actions of these magnetic field control elements 15, 16, 20, and 21 on the deflection magnetic field are completely the same as in the prior art example described above.

In general, the eddy current loss that generates magnetic flux that impedes the applied magnetic flux change is proportional to the multiplicative product of the square of the magnetic flux change rate and the square of the material plate thickness to which the magnetic flux is applied, so if the magnetic flux change rate is constant, the eddy current loss K that minimizes current loss can be achieved by reducing the thickness of the material plate. Therefore, in order to make the magnetic field control characteristics of the annular magnetic shielding elements 20, 21 independent of the frequency of the deflection magnetic field, the thickness of the material should be made as thin as possible. However, if the plate thickness of the annular magnetic shielding element 20 and 21 is simply made thinner, for the same magnetic field strength, the thickness of the magnetic field j[il], i.e., '1':0), will be reduced by the outer diameter. Although it is necessary to make a big deal, the center 1 drilled in the bottom of the concentrated magnetic hole 10 has a small diameter hole 15 with an over-open hole 12 and an outer open hole 13.1.
The distance between 4 and 4 is the outer diameter of the annular shielding element 20 and 2, and the distance between
functions will no longer be available. Furthermore, as the thickness of the plate becomes thinner, it becomes difficult to fix the concentrated magnetic pole 10 in a predetermined position by spot welding, and in an emergency, 1C welding process results in 6N contamination.In the present invention, a thin annular magnetic shield is used. Since a plurality of thick portions 2ji are locally left on the elements 20 and 21, a predetermined magnetic field control function can be obtained without increasing the external shape too much, and the concentrated magnetic pole 10 can be fixed at a predetermined position. In order to do this, it is sufficient to weld the thick portion 24 to the concentrated magnetic pole 10 through the grooves 7, and the welding operation 1 can be easily performed as in the conventional case.

As mentioned above, even if the horizontal deflection magnet Fyy is guided to the bottom surface 21 of the concentrated magnetic pole 20 and penetrates the annular magnetic shielding element 20.21, the plate thickness is very thin as a whole, so the vortex Current generation is very small and can be ignored.

Therefore, the annular magnetic shielding element 20.21 is caused by the eddy current.
The generation of magnetic flux that interferes with magnetic flux changes becomes extremely small,
Even if the horizontal deflection frequency is higher than fh = 15.73 kHz used in the current standard color TV system,
Regardless of its frequency, its magnetic shielding effect no longer decreases. As a result, the horizontal deflection frequency f
Even if h becomes high, the scanning screen of both outer electron beams may be enlarged with respect to the scanning screen of the central electron beam, or the enlargement ratio may become asymmetrical due to the difference in the ratio of horizontal scanning time to horizontal retrace time. It disappears.

FIG. 8 is a perspective view of an annular magnetic shielding element 30 according to another embodiment of the present invention. 3
Thin wall portions 32 having the required plate thickness are formed by chemical etching from both sides, except for 1. The thin wall portions 32 can be formed relatively easily from one side.

<Effects of the Invention> According to the present invention, the comatic aberration of the scanning screen formed by the deflection magnetic field, which is disposed at the tip of the self-convergence type in-line electron gun so as to surround both outer electron beam passing regions, can be reduced. In a magnetic field control element that corrects
The dependence of the magnetic field control action on the horizontal deflection frequency of the magnetic field control element and the difference in action due to the difference between the horizontal scanning time and the horizontal retrace time can be eliminated. As a result, regardless of the increase in the horizontal deflection frequency, it is possible to eliminate asymmetric shifts based on coma in the scanning screen formed by the central and both outer electron beams, and the in-line electron gun has extremely high resolution characteristics that enable high-density display. It can be made into an excellent electron gun.

Furthermore, due to the presence of the thick part, the necessary magnetic field control function can be provided without significantly increasing the external shape of the magnetic field control element.Furthermore, when it is installed at a predetermined position on the bottom surface of the shielding pole at the tip of the electron gun, it is possible to Installation by welding becomes easier.

Furthermore, if the present invention is applied to a random scanning method in which the scanning speed is indeterminate, rather than the above-mentioned Rask scanning method in which the scanning speed is constant during the effective scanning period in line sequential order, coma aberration will not occur in this case as well. , its effectiveness becomes even more remarkable.

[Brief explanation of drawings]

Figure 1 is a longitudinal cross-sectional view of a color cathode ray tube using a conventional self-co/vergence type in-line electron gun, and Figure 2 shows the center and both outer sides of the fluorescent surface of this color cathode ray tube. Figure 3 shows the scanning screen formed by the electron gun, the magnetic field control element that corrects the coma aberration of the scanning screen and its effect on the horizontal and vertical deflection magnetic fields, and Figure 4 shows the flashing when the horizontal deflection frequency increases. A diagram explaining the deviation of the scanning screen formed by the electron beams of the central and both outer electron guns appearing on the optical surface, and Figure 5 shows the current waveform flowing through the horizontal deflection coil.
FIG. 6 is a plan view showing a magnetic field control element according to an embodiment of the present invention disposed on the bottom surface of a concentrated magnetic pole; FIG. 7 is a perspective view of an annular magnetic shielding element according to an embodiment of the present invention; FIG. 8 shows perspective views of annular magnetic shielding elements according to other embodiments of the present invention. 1,...-1 infin type electron gun, 2.・・・・・・
...Round envelope, 4, ... Fluorescent surface, 5. ...
... Deflection device, 6, 6'... Scanning screen formed by the inner and outer electronic beams, 7+7'... Scanning screen formed by the medium-fired electron beam, 10... ...Central magnetic pole, 12...Central electron beam transmission aperture on the bottom of the concentrated magnetic pole, 13.14...1 outer electron beam transmission aperture on the bottom of the concentrated magnetic pole, 15.16... ... Magnetic enhancement element, 17.18, 20.21.30 ... Annular magnetic shielding element, 24.31 ... Thick part, 25.
32... Thin wall part. Figure 62 64-■

Claims (1)

[Claims] The device is equipped with a magnetic field control element that is arranged to surround both outer electron beam passing areas of the in-line electron guns arranged in a row on the horizontal axis, and corrects the coma aberration of the scanning screen formed by the deflection magnetic field. 1. An in-line electron gun in a color cathode ray tube, wherein the magnetic field control element has a structure in which a magnetic material is processed so as to have a locally thick portion and a thin plate overall.