JPH021337B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the shape of an electron beam spot of an in-line electron gun used in a color cathode ray tube.

First, in order to facilitate understanding of the present invention, a conventionally used in-line color cathode ray tube will be explained. FIG. 1 is a longitudinal sectional view of a color cathode ray tube equipped with an in-line electron gun assembly 1 that emits three electron beams. The three electron beams emitted from the in-line electron gun assembly 1 are aligned in a straight line and lie in the same plane, and are deflected horizontally by the deflection coil 5 disposed in the funnel-shaped part of the evacuated glass envelope 2. and is vertically deflected to form a scanning screen on a phosphor screen 3 on which a plurality of phosphor elements emitting red, green and blue light, for example, are deposited on the inside of the front part of the glass envelope 2. A color selection mechanism consisting of a perforated mask 4 is arranged within this tube adjacent to the phosphor screen 3, so that each scanning electron beam stimulates only the phosphor elements of the color corresponding to the respective electron beam. On the other hand, the three electron beams emitted along the parallel paths of the in-line electron gun structure 1 intersect at one point at the center of the perforated mask 4, so that both outer electron beam passage holes of the final electrode of the main electron lens are aligned with the parallel paths. On the other hand, both outer electron beams B _R and B _B are set in advance so as to be tilted with respect to the central electron beam _BG .

A static concentrator 6 is disposed on the deflection yoke 5 side of the electron gun assembly 1 sealed in the glass neck following the funnel-shaped part of the glass envelope 2. The concentration error of the three electron beams at the center and both outer sides at the center of the four surfaces of the hole mask is corrected, so that the three electron beams can be correctly focused on one point. That is, as shown in FIGS. 4 and 5, the static concentration device 6 includes a pair of quadrupole magnets 6A magnetized to four poles on an annular substrate, and a pair of six-pole magnets 6A magnetized to six poles.
It is composed of B. The quadrupole magnet 6A generates the same amount of magnetic flux in opposite directions for both outer electron beams B _R and B _B , moves both outer electron beams B _R and B _B by the same amount in opposite directions, and at the opening angle of the two sheets. The amount of correction is made so that both outer electron beams coincide with each other by rotating the two sheets simultaneously and changing the direction of correction. Also, the hexapole magnet 6B has the function of generating the same amount of magnetic flux in the same direction for both outer electron beams B _R and B _B , and aligning both outer electron beams B _R and B _B with the central electron beam B _G. . Furthermore, a color purification device 7 is arranged adjacent to the static concentrator 6, which can adjust the three electron beams so that they correctly stimulate the phosphor elements of the respective colors.

In a commonly used in-line color cathode ray tube, the horizontal deflection magnetic field formed by the deflection coil 5 is distorted into a barrel shape on the glass neck side where the in-line electron gun structure 1 is sealed, and on the phosphor screen 3 side. By setting the vertical deflection magnetic field to a pincushion distortion on the glass neck side and a barrel distortion on the phosphor screen 3 side, the concentration deviation of the three electron beams can be reduced to the fluorescence. A so-called self-convergence method is realized in which correction is performed over the entire surface 3 and good convergence characteristics are obtained without using a dynamic concentration correction circuit.

However, in this case, the three in-line electron beams pass through the above-mentioned asymmetric magnetic field, so that the beam spot cross section B _C on the phosphor screen 3 is a perfect circle at the center of the screen as shown in Figure 2. However, the edges of the screen are distorted into a horizontally elongated oval shape. That is, since the horizontal deflection magnetic field has a strong pincushion distortion, as the beam spot is deflected in the horizontal direction, the beam spot is distorted, particularly around the screen, and becomes a horizontally elongated oval shape. In addition, when receiving a high-brightness image, a large current is extracted from the electron gun, and especially in the peripheral area of the screen where the deflection angle is large, the above-mentioned deflection distortion causes a thin halo B _H to shine around the high-brightness beam spot nucleus B _C. occurs.

As a result, the focus characteristic deteriorates due to horizontal collapse of the beam spot and a halo around the screen due to deflection distortion of the deflection magnetic field, resulting in a significant decrease in resolution.

In order to compensate for the horizontal distortion of the beam spot due to the deflection distortion, as shown in FIG.
H _R , H _G , and H _B are formed into vertically elongated oval shapes with their major axes in the direction of the vertical deflection axis. This makes the focusing in the long axis direction of the electron beam passage hole weaker and the focusing in the shorter axis direction stronger, making the beam spot at the center of the screen vertically elongated, and reducing the horizontal distortion of the deflected beam at the periphery of the screen. Compensated statically.

However, it is necessary to fabricate the electron beam passage holes of the control electrode G1 and the shield electrode G2 described above into elliptical shapes with high precision and uniformity, and to configure the electron gun structure with electrodes having these elliptical beam passage holes. It is much more difficult to assemble an electron gun assembly while maintaining the relative position of the electrode with high accuracy than when using a conventional electrode with a circular beam passage hole. Therefore, the electron beam cutoff voltage determined by the relative positions of the cathode, control electrode, and shielding electrode in the beam forming region may vary among the three electron beams, and the optical characteristics of the electron beam bundle forming region may be deteriorated.

Furthermore, by making the electron beam passage holes of the control electrode and the shielding electrode oval, the horizontal distortion caused by the deflection strain that the electron beam spot receives from the deflection coil magnetic field can be reduced, but the high-intensity electron beam spot nucleus B _C
The surrounding halo component B _H cannot be removed,
The improvement in image quality of high-brightness images was still insufficient.

In addition, in the conventional method in which both outer electron beam passing holes of the main electron lens electrode are shifted outward and concentrated,
There was a drawback that convergence shifted due to fluctuations in the concentrated voltage due to focus adjustment on the screen.

The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide an in-line electron gun assembly which has an extremely simple structure and which significantly improves the resolution of an in-line color cathode ray tube.

That is, at least two electron beams emitted within the same plane are focused by electron lenses formed substantially individually in each beam path by a plurality of electrodes arranged at predetermined intervals along parallel paths, and In an in-line electron gun structure, both outer electron beam passage holes of the final stage electrode of the electron lens are eccentrically outward from the electron beam path to concentrate the electron beam near the screen of the cathode ray tube. In order to concentrate at a point outside the cathode ray tube at the center of the screen, an underconcentration state is created in which the concentration angle ratio (θ - θ ₀ )/θ ₀ is -36 to -73%, and the concentration is corrected using the quadrupole magnetic field of the static concentration device. This invention relates to an in-line electron gun assembly that forms an electron beam spot vertically in the center of the screen. Here, θ represents the angle at which both outer electron beams at the exit of the electron gun reach the concentration point, and θ ₀ represents the concentration angle at which the residual concentration at the center of the screen is zero.

By using this in-line electron gun structure, each beam spot at the center of the screen is shaped into an ellipse with its long axis aligned with the vertical deflection axis due to the magnetic lens effect of the quadrupole magnetic field accompanying the concentration correction action of both outer beams. In addition to shaping, the halo is reduced and the horizontal collapse of the beam spot around the screen due to the deflection distortion of the deflection coil is compensated for, thereby improving the resolution of the color cathode ray tube uniformly on the screen.

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

FIG. 6 is a longitudinal sectional view of a color cathode ray tube equipped with an in-line electron gun assembly 10 that emits three electron beams according to an embodiment of the present invention. Three electron beams B _R emitted from the in-line electron gun structure 10 and aligned on a straight line and in the same plane;
B _G and B _B never intersect at a single point at the center of the perforated mask 4 and the phosphor screen 3 constituting the screen, but are located at a point outside the phosphor screen 3 approximately on the cervical canal axis 8 of the glass envelope 2. Both outer electron beams B _R and B _B are set to be inclined with respect to the central electron beam B _G so that they intersect at . That is, both outer electron beams B _B and B _R are underconcentrated on the phosphor screen with respect to the central electron beam B _G ,
The distance between the outer electron beams on the phosphor screen 3 is set to be d.

FIG. 7 is a longitudinal cross-sectional view showing an example of the in-line type electron gun assembly 10 in detail. That is, the in-line electron gun electrode assembly 10 has three cathode assemblies 10R, 10G, and 10B that are insulated from each other and lined up in a line with equidistant off-axis distances S in the same plane, and facing the electron beam. Control electrode 1 integrally formed with three beam holes sequentially arranged in the traveling direction
1. Consists of a shielding electrode 12, a focusing electrode 13, an anode electrode 14 as the final electrode, and a bottomed cylindrical magnetic pole 15. Each electrode except the magnetic pole 15 is connected to two insulator support rods 16 via an electrode supporter. The electrodes are embedded and fixed so as to be sandwiched between the electrodes to maintain a predetermined distance between the electrodes.
Each electron beam passing aperture 11 through which each electron beam of the control electrode 11, shielding electrode 12, and focusing electrode 13 passes.
R, 11G, 11B; 12R, 12G, 12B;
13R ₁ , 13G ₁ , 13B ₁ ; 13R ₂ , 13G ₂ , 1
_3B2 are also aligned in a line with equal distances S, and the electron beam bundles B _R , B G , B _B emitted from the three cathodes 10R, _10G , and 10B are the axes of the three electron guns. It is accelerated and focused so as to travel on parallel paths 18R, 18G, and 18B. Anode electrode 14
The distance between the apertures _S1 is somewhat larger than the above-mentioned S by ΔS, and therefore both outer apertures 14R and 14B of the anode electrode 14 are offset ΔS outward from the axes 18R and 18B of the electron gun. , a so-called equivalent tilt lens is formed by an asymmetric electric field in both outer openings of the main electron lens formed in each corresponding electron beam opening gap between the focusing electrode 13 and the anode electrode 14, and the phosphor screen 3 of the cathode ray tube is The two outer electron beams B _R and B _B traveling in parallel at the center are electrostatically concentrated on the central electron beam B _G side.

Here, the concentrated electrode 13 and the anode electrode 14 have cross sections perpendicular to the electron gun axes 18R, 18G, and 18B in the direction of arrangement of the central and both outer electron beam apertures, which are aligned and bored in a straight line within the closed end surface. It is a closed cylindrical _body that is long and has a substantially rectangular or elliptical shape that _is short in the direction perpendicular _to the arrangement direction. A closed cylindrical portion having holes 13R ₂ , 13G ₂ , and 13B ₂ is overlapped at the mouth edge.

When operating this color cathode ray tube, since the distance between the outer electron beams on the phosphor screen 3 is d at the center of the screen made up of the phosphor screen, the electron beams are placed outside the glass neck on the electron gun assembly 10 as in the conventional case. The 4-pole magnet 6A of the static concentrator 6 placed there concentrates the under-concentrated outer electron beams B _R and B _B into one point at the center of the screen, and the 6-pole magnet 6B focuses this concentration point into the center electron beam B _G Concentration correction is performed by moving to .

In this case, the effect of the magnetic flux generated by the quadrupole magnet 6A on each electron beam will be examined in detail with reference to FIG. As is clear from the figure, by correcting the concentration of both outer electron beams B _R and B _B , which are in an underconcentrated state, toward the central electron beam B _G , each electron beam has a magnetic field in the horizontal axis direction as shown by the arrow in the figure. It receives a pressing force in the horizontal direction from the axial direction, and an attractive force outward in the vertical direction in the vertical axis direction. Since the vertical attractive force of each electron beam is equal, the electron beam does not move vertically, but on the horizontal axis, both outer electron beams B _R and B _B receive forces toward the central electron beam B _G and interact with each other. The central electron beam B moves to _{the G} side. However, the horizontal pressing force of the central electron beam B _G is equal, and no movement of the beam occurs.

Furthermore, as the electron beams on both sides move in a concentrated manner, each electron beam receives the above-mentioned vertical and horizontal forces from the magnetic field, so that the electron beam spot at the center of the screen is distorted vertically. FIG. 9 shows the shape of the beam spot at the center and periphery of the screen 3 in this case.

However, in the conventional electron gun structure, the three electron beams are set to be concentrated almost at one point in the center of the screen, and residual concentration errors, which are insufficient or overconcentrated amounts that deviate from the settings due to manufacturing errors, etc. is corrected by a static concentrator 6, and the residual concentration error is extremely small, usually about 3 to 4 mm (the distance between the outer electron beams at the center of the screen) at the maximum. In other words, the concentration angle θ, which is the angle at which both outer electron beams are emitted from the electron gun and extend to the concentration point, is within ±30% at maximum of the concentration angle θ ₀ at which the residual concentration error becomes zero at the center of the screen. . Therefore, with this level of concentrated correction by the quadrupole magnetic field, the longitudinal distortion of each electron beam was so small that it could be ignored.

In general, the concentration angle θ is proportional to the eccentricity ΔS and the ratio E _b /E _F of the eccentric electrode potential E _b to the opposing non-eccentric electrode potential E _F .

That is, θ∝ΔS/D・E _b /E _F (1) However, D indicates the diameter of the non-eccentric electrode facing the eccentric electrode.

Therefore, if the potential ratio between the electrodes is constant, the concentration angle θ is proportional to the eccentricity ΔS/D.

For example, a 20-inch 90-degree in-line electron gun with an electron beam off-axis distance S = 6.6 mm, main electron lens aperture D = 5.5 mm, and a focusing voltage ratio of 26 to 30% (typically 28%) to anode voltage. Eccentricity ΔS/ when operating a polarized color cathode ray tube at an anode voltage of 25kV
The concentration correction amount d for D and the concentration angle ratio (θ−
The relationship θ ₀ )/θ ₀ ×100% is shown in FIG. Here, d, θ, and θ ₀ are the residual concentration at the center of the screen, the angle at which the electron beams on both sides extend to the concentration point at the exit of the electron gun, and the residual concentration is zero, as shown in Figure 11. The concentration angles are shown respectively. Also, d, (θ−
A negative value of θ ₀ )/θ ₀ means underconcentration, and a positive value means overconcentration.

Furthermore, when this insufficient concentration is corrected using a quadrupole magnet, the ratio R of the vertical diameter and horizontal diameter of the electron beam spot to the concentration angle ratio (θ - θ ₀ )/θ ₀ ×100 (%)
(R=vertical diameter/horizontal diameter) relationship and concentrated correction amount 0mm
FIG. 12 shows the relationship between the halo generation area ratio S _H and the concentration angle ratio, assuming that the area of the halo component B _H generated around the beam spot nucleus B _c at 100% is 100%.

From Figure 12, (θ-θ ₀ )/θ ₀ =-36% (d=-
4.8), R=1.1, (θ−θ ₀ )/θ ₀ =−73% (d=
−9.6), R=2.0, and the underconcentration angle ratio (θ
When the absolute value of -θ ₀ )/θ ₀ becomes 36% or more, the beam spot clearly shows a vertical tendency, and at the same time, the amount of halo generation also depends on the horizontal pressing force and vertical attractive force that each electron beam receives from the quadrupole magnetic field. It has been shown that the effect of lenses can be rapidly reduced. Also, from FIG. 10, the eccentricities ΔS/D corresponding to (θ−θ ₀ )/θ ₀ =−36% and −73% are 0.0225 and 0.0125, respectively.

Generally, to correct the horizontal distortion of the beam spot around the screen due to non-uniform magnetic fields, the ratio of the vertical diameter to the horizontal diameter of the stationary beam spot at the center of the screen is set to 1.0.
It is sufficient if the length is longer than that. As shown in Fig. 9, the larger the vertical length, the more circular the beam spot at the periphery of the screen becomes, and the peripheral resolution is improved.
At the center of the screen, the beam spot becomes excessively elongated, and the resolution at the center deteriorates. Further, if the ratio is smaller than 1.1, almost no effect on improving the horizontally elongated and crushed spots in the peripheral area will be observed. Experiments have shown that in order to improve the resolution at the periphery of the screen without impairing the resolution at the center of the screen, setting the ratio of the vertical diameter to the horizontal diameter of the beam spot at the center of the screen to 1.1 to 2.0 will improve the screen resolution. It was confirmed that the focus characteristic was such that uniform high resolution could be obtained over the entire surface.

From the above, the 20
In an inch 90 degree deflection color cathode ray tube, both outer electron beams traveling in parallel have an eccentricity ΔS/D=0.0125 to 0.0225.
Both outer electron beam passing holes of the eccentric electrode are shifted outward so that the underconcentration angle ratio (θ−
If the absolute value of θ ₀ )/θ ₀ ×100% is 36 to 37% and the concentration is corrected using the quadrupole magnetic field of the static concentration device 6, then the electron beam deflection received from the deflection magnetic field of the self-convergence method can be reduced. By compensating for distortion and reducing the amount of halo generation, the resolution of the scanned image on the screen can be significantly improved over the entire surface.

Furthermore, in the past, the eccentricity was selected so that both outer beams were concentrated at almost one point at the center of the screen, and the value was around ΔS/D = 0.0325 from Figure 10, whereas the underconcentration setting of the present application The value is from 40 to this value
It is equivalent to 70% and is small. Therefore, as can be seen from equation (1) above, since the eccentricity is smaller than before, even if there is a fluctuation in the focusing voltage due to focus adjustment on the screen, the fluctuation in the focusing angle θ is smaller than before, and the focusing The concentration deviation of the three electron beams on the screen due to voltage fluctuations is also reduced to a negligible extent.

Alternatively, since the eccentricity is smaller than before, the difference in electron beam passing aperture diameter between the eccentric electrode and the non-eccentric electrode becomes smaller, which eliminates the optimum focusing voltage difference due to the difference in electron beam passing aperture diameter between both outer electron beam paths and the central electron beam path. There is also.

Incidentally, the greatest feature of the present invention is that the electron beams on both sides are underconcentrated so that they have an excessive concentration angle ratio at the center of the screen. In an overconcentrated state where the beams intersect, the correction is completely opposite to that shown in Fig. 8, and the electron beam spot is conversely collapsed into a horizontally long position.
In addition, due to the aberration of the magnetic lens, halos are generated more than before correction, and the resolution is significantly degraded.

In the above explanation, the case where the static concentrator is installed outside the glass neck has been cited, but it is not necessarily limited to this, and it may be installed in advance on a part of the electron gun structure, or even after the cathode ray tube is manufactured. It may also be formed by magnetizing it from outside the tube.

Also, for convenience of explanation, this study was conducted on a three-electron beam in-line type electron gun structure having a central and outer electron beams spaced at equal intervals within the same plane.
It goes without saying that the present invention can also be applied to a two-electron beam in-line type electron gun assembly having only both outer electron beams.

As described above, according to the present invention, both outer electron beams are excessively and underconcentrated at the center of the screen in the in-line electron gun assembly, and then the concentration is corrected using the quadrupole magnetic field of a commonly used static concentrator. By doing so, the shape of the beam spot at the center of the screen is made vertically long with its long axis in the direction of the vertical deflection axis, which reduces horizontal collapse caused by deflection distortion of the electron beam spot at the periphery of the screen, and prevents the occurrence of halos. This makes it extremely easy to increase the resolution of the received image across the entire screen.
It can be significantly improved.

[Brief explanation of drawings]

Figure 1 is a vertical cross-sectional view of a conventional color cathode ray tube equipped with an in-line electron gun structure that emits three electron beams. 4 and 5 are diagrams of the operating principle of the 4-pole magnetic field and the 6-pole magnetic field of the static concentrator, and FIG. 6 is a diagram of the present invention. A vertical cross-sectional view of a color cathode ray tube equipped with an in-line electron gun structure that emits three electron beams based on one embodiment, FIG. 7 is a detailed vertical cross-sectional view of the in-line electron gun structure, and FIG. 8 is a static view. FIG. 9 is a diagram illustrating the effect that each of the electron beams in an underconcentrated state receives from the quadrupole magnetic field of the device. The figure shows the relationship between the eccentricity ΔS/D, the concentration angle ratio (θ - θ ₀ )/θ ₀ , and the residual concentration amount d. Figure 11 shows the definition of concentration angles θ and θ ₀ . Figure 12 is a 20-inch 90 degree deflection color cathode ray tube equipped with an in-line electron gun with an electron beam off-axis distance S = 6.6 mm, main electron lens aperture D = 5.5 mm, and a focusing voltage ratio of 26 to 30% to the anode voltage, with an anode voltage of 25 kV. The ratio of the vertical diameter to the horizontal diameter of the beam spot on the screen relative to the concentration angle ratio when both outer beams are operated with concentration correction by a quadrupole magnetic field (R = vertical diameter / horizontal diameter), and the residual concentration amount is 0. FIG. 3 is a diagram showing the relationship between the halo generation rate S _H when the amount of halo generation at the time of 100%.

Claims (1)

[Claims] 1. At least two electron beams emitted within the same plane are formed substantially individually in each electron beam path by a plurality of electrodes arranged at predetermined intervals along parallel paths. In an in-line electron gun structure, the electron beam is focused by an electron lens, and the electron beam passing holes on both outer sides of the final stage electrode of the main electron lens are eccentrically outward from the electron beam path to concentrate near the screen of the cathode ray tube. , the concentration angle ratio (θ−
θ ₀ )/θ ₀ (where θ is the angle at which both outer electron beams at the exit of the electron gun reach the concentration point, and θ ₀ is the concentration angle when the residual concentration at the center of the screen is 0) is −
By creating an underconcentration state of 36 to -73% and correcting this concentration using the quadrupole magnetic field of the static concentrator, the electron beam spot is made vertically elongated at the center of the screen with its long axis in the direction of the vertical deflection axis. Inline type electron gun structure. 2 Eccentricity △S/D, which is the ratio of the eccentricity △S of the eccentric electrode to the diameter D of the non-eccentric electrode opposite thereto.
The in-line electron gun assembly according to claim 1, characterized in that the range is 0.0125 to 0.0225.