JPS6086736A - In-line type electron gun structure - Google Patents

Abstract

PURPOSE:To remove asymmetric aberration due to coma of scanned picture formed by the central and both outside electron beams by locally/cutting off the cylinder side portion in the direction vertical to the line direction of three in-line arrangement openings drilled on the bottom face of a cylindrically concentrated magnetic pole made of non-magnetic material. CONSTITUTION:In a concentrated magnetic pole 20 formed by non-magnetic metal, a pair of magnetism reinforced elements 15, 16 oppositely arranged in such a way as interposing therebetween a central electron beam penetrating opening 22 drilled on the bottom, on the vertical axis Y-Y, and annular magnetism screening elements 17, 18 surrounding both outside electron beam penetrating openings 23, 24 provided on the horizontal axis X-X are arranged. The cylinder side portions 25 having height of h1 are in the direction Y-Y vertical to the line direction X-X of three in-line arrangement openings drilled on the bottom. These portions are cut off in rectangular shape having width w which is the distance between both outside electron beam openings 23, 24 or more and having height h2 from the upper edge of the concentrated magnetic pole 20 to form notches 25. Then eddy current loss in horizontal magnetic field passing through the cylinder side can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power-2 cathode ray tube, in which a center and a pair of inner and outer electron beams emitted from an in-line electron gun form a sister on a fluorescent surface due to a common deflection magnetic field. This is a self-convergence type in-line electron gun that can make the horizontal deflection frequency the same regardless of the horizontal deflection frequency.

FIG. 1 is a longitudinal cross-sectional view of a color cathode ray tube using a so-called self-convergence type in-line electron gun, rather than a conventional dynamic convergence type IL.

A central electron beam Bl emitted from the in-line electron gun 1 and located in the same plane and a pair of inner and 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 Figure 2. As shown, a pair of inner and outer electron beams B2. Fluorescent surface 4 eliminates coma aberration of B3
A scanning screen 6t'' is formed that coincides with the top. In this case, the scanning screen 7 of the central electron beam Bl is generally smaller in horizontal and vertical directions than the scanning screen 6 formed by the outer electron beams B2 and B3.

This misalignment of the scanning screen is due to the coma aberration of the deflection device 50, and in order to remove the coma aberration and match each scanning screen, a deflection device 50 is attached to the tip of the electron gun l, which is exposed to the leakage magnetic field at 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 10 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, with the vertical axis Y passing through the central electron beam transmission aperture 12 formed in the bottom surface 11 of the concentrated magnetic pole io with the short axis of the fluorescent surface 4.
A pair of disc-shaped magnetic enhancement elements 15 and 16 placed opposite each other on -Y, and an inner and outer electron beam transmission aperture 13 bored on the horizontal axis XX, which is the long axis of the fluorescent surface 4. , 14 are arranged to surround the annular magnetic shielding elements 17, 18. The magnetic enhancement elements 15, 16 adjust 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. With respect to B3, the deflection sensitivities of the horizontal and vertical deflection magnetic fields PH and FV of the deflection device 5 are lowered than those of the central electron beam Bl, and the deflection sensitivities of the vertical deflection magnetic field F■ with respect to the central electron beam Bl are lowered to the inner and outer electron beams. It has the effect of increasing the amount.

Therefore, the scanning screen 7 of the central electron beam Bl is horizontal due to the magnetic field control elements 15, 16 and 17, 18.

Both the vertical direction is expanded, and conversely, the inner and outer electron beams B2゜B3
The scanning field 6 is reduced and coma due to the deflection field is eliminated, making it possible to perfectly match the scanning fields 6,7.

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.

High-density display requires two factors: the cathode ray tube must have 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 resolution of the display screen. In order to increase the number of scanning lines, it is essential 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, the horizontal deflection frequency fh is increased to more than 15.734 KHz of the current standard color TV system. In this case, horizontal deflection frequency fh = 15.734
The scanning screen e, t formed by the out-of-plane and central electron beams due to the horizontal deflection magnetic field, which had no problems at around KHz.
, 7/ of the coma aberration occurs, and as shown in FIG. 4, the scanning screen 6' of the inner and outer electron beams is slightly expanded in the horizontal direction with respect to the scanning screen 7' of the central electron beam, and the rate of expansion is as low as 7'. The left and right sides of the optical surface 4 are different, and an asymmetry occurs in which the enlarged dimension cti on the left side is larger than the enlarged dimension d2 on the right side. This shift in the scanning screen results in a convergence error depending on the horizontal deflection frequency, which significantly deteriorates the quality of the image received on the fluorescent surface. For example, 20 inches 90 degree deflection force 2-
In cathode ray tube, horizontal deflection frequency fh=15.73KH
When z is doubled, f h = 31.5 KHz, the above-mentioned deviation dl, dl becomes dl = near the outermost periphery of the effective phosphor screen.
07mm, dl-0.3mm. The reason why the scanning screens 6/, 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
The magnetic flux of the horizontal deflection magnetic field penetrating the cylinder side part 19 in the -Y direction generates an eddy current in the magnetic flux passing surface, which generates a magnetic flux that obstructs the change in the magnetic flux of the horizontal deflection magnetic field, attenuates the magnetic flux, and and inner and outer electron beams B1m B2s B
3 to reduce its horizontal deflection amplitude, the reduction in magnetic flux reduces the magnetic shielding effect of the annular magnetic shielding element 17, 18. The loss of magnetic flux due to this eddy current could be completely ignored at the conventional horizontal deflection frequency fh = 15.73 KHz, but as the frequency increases, the loss of magnetic flux due to eddy current becomes impossible to ignore, as shown in Figure 4. In this case, the scanning screen 6' of the inner and outer electron beams is expanded in the horizontal direction with respect to the scanning screen 7' of the central electron beam.

On the other hand, the current waveform applied to the horizontal deflection coil of the VC steel device 5 to perform horizontal scanning is a sawtooth wave as shown in Fig. 5, and the time from point a to point b in the figure [1 is the horizontal return The line time is the line time, and the time t2 from point b to point C is the horizontal retrace time,
Normally, t2 is set to about 115 of tl. Point a or point 0 corresponds to the left end of the horizontal scanning screen, and point b corresponds to the right end position. That is, the left end position of the horizontal scanning screen corresponds to the end of the horizontal retrace time t2, and the right end position corresponds to the end of the horizontal retrace time t1.
corresponds to the end of the horizontal scanning period t during the horizontal retrace period t2.
A magnetic field is generated by the current that changes at about 5 times the speed of the magnetic shielding element 17.18, and the magnetic flux decreases due to the eddy current loss due to the harmonic component magnetic field. is thicker on the left side of the phosphor screen than on the right side, and as shown in Figure 4, the horizontal expansion width of the child beam scanning screen 6' with respect to the central electron beam scanning screen 7' is d on the left side.
l becomes larger than d2 on the right side, causing asymmetry in coma aberration in the horizontal direction. Conventional standard color TV system (NT
fh = 15.7341G used in SC method)
In I, tl = 51-53pw, t2 = 10-12μE
Therefore, the eddy current loss caused by this can be completely ignored, and the above-mentioned coma aberration and its asymmetry were not found substantially, but as fh increases, the difference between tl and t2, and furthermore, the effective blue time t1 increases. In order to do this, the retrace time t2 is set to be as short as possible, and the asymmetry in the horizontal deflection magnetic flux reduction becomes significant due to eddy current loss, and the above phenomenon becomes remarkable.

The present invention has been made in view of the above-mentioned drawbacks, and the present invention has been made in view of the above-mentioned drawbacks. This is to prevent displacement due to coma aberration from occurring on the screen.

That is, the three in-line array holes bored in the bottom surface of the bottomed cylindrical concentrated magnetic pole made of non-magnetic material attached to the tip of the electron beam exit side of the in-line electron gun and the vertical tube side part are locally It is a notch. This configuration prevents the eddy current loss of the horizontal deflection magnetic field penetrating the side of the concentrated 1ila11IA tube, and prevents the asymmetry caused by coma aberration of the scanning screen formed by the central and both outer electron beams, regardless of the increase in the horizontal deflection frequency. The deviation can be eliminated, and the in-line electron gun can be made into an electron gun assembly capable of displaying high-density video information.

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

FIG. 6 is a perspective view of a concentrated magnetic pole 20 according to an embodiment of the present invention.

The concentrated magnetic pole 20 has a cylindrical shape made of non-magnetic gold leaf with a bottom surface 21 and a cylindrical side portion 29, and has a vertical axis that extends through a central electron beam transmission aperture 22 formed in the bottom surface 21 with a short axis of the fluorescent surface. Y-
A pair of magnetic enhancement elements 15 arranged oppositely on Y.
16, and annular magnetic shielding elements 17 and 18 are disposed surrounding both outer electron beam transmission apertures 23 and 24 formed on the horizontal axis XX, which is the long axis of the fluorescent surface. The cylinder side part 25 having a height hl is located in the Y-Y direction perpendicular to the X-X direction of the three in-line array openings bored in the bottom surface,
A notch 25 is formed in a rectangular shape with a width W having a length equal to or longer than the distance between the inner and outer electron beam apertures 23 and 24, and a distance bze from the top of the concentrated magnetic pole 20. That is, the cylindrical side part of the concentrated magnetic pole 20 through which the three in-line array holes in the Y-Y direction can be seen is cut away leaving a height of (hl h2), and a valve spacer (not shown) is attached to this part. The electron gun assembly is fixed in the neck of the cathode tube, and has the function of supplying high voltage to the Yt electron gun assembly from the funnel-shaped part of the cathode ray tube through an internal S electrical coating applied to the inner wall of the neck.
Alternatively, a getter support holding a getter container necessary to maintain a high vacuum inside the cathode ray tube is attached.

With the concentrated magnetic pole 20 having the above-described configuration, the vertical axis of the screen Y-Y
Since the magnetic flux of the horizontal deflection magnetic field penetrating the cylinder side part 19 in the direction passes through the notch 25, an eddy current is generated in the magnetic flux passing surface as in the conventional case, thereby generating a magnetic flux that obstructs the change of the magnetic flux of the horizontal deflection magnetic field. is prevented. , Therefore, the horizontal deflection magnetic field number fh increases from 15.75 KHz to 31.5 KH.
z, or 64IG, which has been put into practical use in recent years (even if the frequency is made higher than z, it will not reduce the polarization sensitivity or the magnetic field control action of the magnetic field control element disposed in the concentrated magnetic pole 20, and the internal The scanning screen of the outer electron beam will no longer deviate from the scanning screen of the central electron beam, which means that the convergence error between the two can be reduced to a minimum of 0.1 mm or less, and as the amount of error is reduced, the convergence error will be shifted to the left and right of the screen. Even if there is asymmetry at the edges, it can be ignored.

As described above, according to the embodiment of the present invention, even if the horizontal deflection frequency is increased from 15.75 KHz to 64 KHz or higher, the convergence error of the inner and outer electron beams and the center electron beam at the left and right edges of the screen is ignored. It can be made as small as possible, and even if the horizontal deflection frequency of the cathode ray tube is increased to perform high-density display, the image quality will not deteriorate due to color shift. Furthermore, since the dependence of the convergence error on the horizontal deflection frequency is eliminated, the same magnetic field control element can be used for all the magnetic field control elements installed in the concentrated magnetic pole without having to be optimized for each horizontal deflection frequency. It also has the advantage of simplifying the cathode ray tube manufacturing process, and its practical industrial value is extremely high.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view of a 2-power cathode ray tube using a conventional self-convergence type 2-in m electron gun, and Figure 2 is a longitudinal cross-sectional view of a color cathode ray tube with central and inner sections on the fluorescent surface. The scanning screen formed by the electron beam of the outer electron gun is
Figure 3 shows the magnetic field control element that corrects the coma aberration of the scanning screen and its effect on the horizontal and vertical deflection fields, and Figure 4 shows the center and A diagram illustrating the deviation of the scanning screen formed by the electron beams of the inner and outer electron guns, FIG. 5 shows the current waveform flowing through the horizontal deflection coil, and FIG. 6 shows a perspective view of the concentrated magnetic pole showing an embodiment of the present invention. Show each. 1...2-in type electron gun, 2...Glass envelope. 4... Fluorescent surface, -5... Deflection device,
6, 6'... Scanning screen formed by inner and outer electron beams, 7.7'... Scanning screen formed by central electron beam, 10.20... Concentrated magnetic pole , 12.
22...Central electron beam transmission aperture. 13.14, 23.24... Inner and outer electron beam transmission apertures. 19.29・・・・・・ part side, l 5, 16・old・
・Magnetic enhancement element. 17.18...Annular magnetic shielding element ell...
...Horizontal scanning time, t2...Horizontal retrace time,
25...Notch. Power 4 flash 5 flash

Claims (1)

[Claims] Three in-line array holes are drilled in the bottom of the bottomed cylindrical concentrated magnetic pole made of a non-magnetic metal material attached to the tip of the electron beam exit side of the electron gun, and the vertical cylinder side is opened from the upper edge. An in-line electron gun structure characterized by a notch.