JPH0221095B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron gun for a color picture tube, and more particularly to an electron gun that improves the focus uniformity between the center and the periphery of the screen of a color picture tube.

As shown in FIG. 1, generally a color picture tube 10
reproduces a color image by scanning a plurality of electron beams 13 emitted by an electron gun 12 enclosed in a glass envelope 11 using a deflection yoke 14 and irradiating them onto a screen mainly composed of a phosphor screen 15. are doing. Here, generally three electron beams arranged in a straight line, so-called in-line type electron beams are used. Regarding the deflection yoke magnetic field, the horizontal deflection magnetic field is a strong pincushion-shaped non-uniform magnetic field, and the vertical deflection magnetic field is a strong barrel-shaped non-uniform magnetic field, and a self-concentration method is used in which the three electron beams are made to coincide at the periphery of the screen. When an electron beam passes through such a deflecting magnetic field, it is inevitable that the electron beam will be distorted by the deflecting magnetic field because it has a certain finite cross-sectional shape.
As a result, as shown in FIG. 2, the electron beam reaching the periphery of the screen has a horizontal bright spot 23 at the horizontal axis end 21, a horizontally long diagonal part 22, and a vertically long halo 2.
This results in a complex and severely distorted shape consisting of 4. As a result, the resolution at the periphery of the screen deteriorates, and the uniformity of the focus is impaired.This tendency becomes especially large as the deflection angle increases from 100 degrees to 110 degrees, and becomes a major problem that cannot be ignored. .

As one of the means to solve this problem,
There is a method in which the cross-sectional shape of the electron beam is made elliptical before entering the deflection magnetic field to cancel out the distortion received from the deflection magnetic field. For example, JP-A-54-85666, JP-A-54-85667, and JP-A-55-
Publication No. 18021 discloses that among the electrodes of the electron gun, the opening shape of the first grid electrode is rotationally asymmetric, or in addition to this, an auxiliary electrode is provided between the second grid electrode and the third grid electrode. An example is shown in which a desired electron beam shape is obtained by making the aperture shape of the auxiliary electrode a combination of rotationally symmetric and rotationally non-symmetric aperture shapes. However, in the example disclosed by et. Due to relative complexity, etc., it is difficult to say that this is necessarily an effective means for manufacturing. Furthermore, the first grid electrode has a large influence on the electron emission characteristics, for example, it causes deterioration of the cut-off characteristics, so it cannot necessarily be said to be an effective technique from the viewpoint of characteristics.

Next, the electrostatic lens formed by the main lens section provided after the electron beam radiation source is also a major factor that influences the characteristics of the color picture tube. The larger the diameter of this electrostatic lens, the more advantageous it is in terms of characteristics, but since there is a limit to the diameter that encloses the entire electron gun, it cannot be made larger than a certain limit. For example, FIG. 3 shows a typical example of the electrode constituting the main lens portion, which is formed by drawing a thin plate and has a dish-like shape as a whole. The electron beam passage holes are separated from each other by the protruding portions 31. This is necessary to prevent the electrostatic lens corresponding to the central electron beam and the electrostatic lenses corresponding to the electron beams on both sides from interfering with each other. Furthermore, in order to form this protruding part 31, the width 32 of the bridge part between the beam passage holes cannot be made smaller than a certain value, so the diameter of the electrostatic lens cannot be increased by that amount. . Attempts have been made to reduce the diameter that encloses the entire electron gun in order to reduce the deflection power, but in such cases, the limit on the electrostatic lens diameter poses a major problem.

Incidentally, an example in which the end face in the horizontal axis direction perpendicular to the tube axis is formed into a non-flat shape among the electrodes constituting the main lens part made of electrodes using the thin plate aperture method shown in FIG. 3, for example, US Pat. The end face of the grid electrode facing the third grid electrode, the facing end face of the fifth grid electrode and the sixth grid electrode of U.S. Pat. No. 4,058,753, and the
The opposite end faces of the electrodes to which low voltage and high voltage are applied in No. 47-20255 are for achieving so-called static convergence, which aligns the electron beams on both sides at the center of the screen. It is not intended to adjust the cross-sectional shape of the beam or to enlarge the electrostatic lens system.

The present invention has been made in view of the above points, and includes at least a pair of thick plate-like electrodes on the opposing surfaces in the tube axis direction of the electrodes constituting the main lens portion, and a low potential electrode opposite to a high potential electrode. An electron gun for color picture tubes that adjusts the cross-sectional shape of the electron beam to improve focus uniformity between the center and the periphery by forming the end face of the electrode in a convex shape, and can substantially expand the electrostatic lens system. We aim to provide the following.

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

FIG. 4 is a schematic configuration diagram showing an embodiment of the color picture tube electron gun of the present invention, in which the cathode 40, the first grid electrode 4
1. A second grid electrode 42, a third grid electrode 43, and a fourth grid electrode 44 are sequentially arranged along the tube axis. The cathode 30, the first lattice electrode 40, and the second lattice electrode 41 are referred to as a triode, which emits thermoelectrons and serves as an object point for the third lattice electrode 43 and fourth lattice electrode 44 that constitute the subsequent main lens section. (crossover)
form. The third grating electrode 43 and the fourth grating electrode 44 constituting the main lens part have electron beam emission holes (not shown) aligned in a row in the horizontal axis direction perpendicular to the tube axis, and are composed of a triode part. Make the crossover converge on the screen. The cathode of such an electron gun ~ the fourth
For example, the grid electrode has voltages of about 150V, 0V, about 600V, about
5KV and about 25KV will be applied and operated. Now, in the electron gun of FIG. 4, thick plate-shaped electrodes 431 and 44 are provided on the opposing surfaces of the third grid electrode 43 and the fourth grid electrode 44, which constitute the main lens part.
1 is added. This plate-shaped electrode is formed by punching, and unlike conventional extrusion processing, it is possible to significantly reduce the bridge width.
As a result, the electrostatic lens diameter can be increased. Further, the end face of the opposing surface of the fourth grid electrode 44 of the thick plate-shaped electrode 431 added to the third grid electrode 43 is not flat but is formed in a convex shape in the direction of the fourth grid electrode 44 (Fig. (not shown). Figure 5 shows this third
This shows a thick plate-like electrode added to the grid electrode, and shows the plan view (actually a cross-sectional view in the tube axis direction) of Figure 5a and a side view taken along the X-X' line and the Y-Y' line. are shown respectively. In FIG. 5, two bridge portions 59 between the central electron beam passage hole 54 and the electron beam passage holes 53 and 55 on both sides protrude toward the fourth electrode, and the two bridge portions 59 protrude toward the fourth electrode. is formed to have a convex shape. Since the surface facing the fourth electrode is formed in a convex shape, the electrostatic lens formed by the third grid electrode and the fourth grid electrode can be aligned in the horizontal direction of X-X′ shown in FIG. The convergence effect differs in the vertical direction of Y-Y'. That is, a lens is formed that is relatively strong in the horizontal direction and relatively weak in the vertical direction. In an electron beam focused by such an electrostatic lens, a halo is generated earlier in the horizontal direction than in the vertical direction, and its shape is as shown in FIG. 6. Therefore, since the shape of the electron beam just before it enters the deflection magnetic field is adjusted to the shape shown in Figure 6, the distortion received from the deflection magnetic field can be corrected, and a good beam can be produced over the entire screen. A spot shape is obtained and the focus uniformity is greatly improved.

Next, a specific design example of the thick plate electrode shown in FIG. 5 will be explained. Its specific dimensions are: short diameter 51:6.0mm;
Long diameter 52: 15.5mm, electron beam passage hole (circular) 5
Diameter of 3, 54, 55: 4.5 mm, electron beam passage hole spacing 56: 4.9 mm, bridge width: 0.4 mm, side wall thickness: 0.6 mm, maximum height in the tube axis direction 57: 2.54 mm, minimum height in the tube axis direction Size 58: 2.5mm. That is, the height of the convex portion of the bridge portion is approximately 40 μm. Here, the height of the convex portion of the bridge portion is related to the horizontal and vertical convergence strength of the electrostatic lens of the applied electron gun, but in this example, it is 20 μm to 20 μm.
A range of 60 μm was acceptable, and 40 μm was optimal. In this example, the diameter of the network tube that encloses the entire electron gun is 22.5 mm, which is about 23% smaller than the conventional one, and the deflection power is reduced by about 25%. We were able to improve focus uniformity without any problems. Incidentally, in the conventional electrode structure shown in Figure 3, the lens diameter is approximately 3.7 mm.
While the lens diameter of the present invention is approximately 4.52 mm, which is approximately 20% enlarged, even if the net diameter is reduced by approximately 23%, the lens diameter remains the same as before the reduction. Almost the same amount can be obtained. In general, the magnification component of the electron beam spot diameter on the screen is inversely proportional to the lens diameter, and the spherical aberration component is 3
The electron gun of the present invention improves the spot shape of the electron beam by effectively increasing the lens diameter and forming a convex end face.
Focus uniformity can be improved.

Furthermore, the maximum height of the plate electrode in the tube axis direction has an important effect on interference between electrostatic lenses formed by individual electron beams. In the electron gun of the present invention, mutual interference can be effectively prevented by setting the maximum height of the plate electrode in the tube axis direction to 40% or more of the diameter of the electron beam passage hole.

Although the above embodiments have been described as applied to a bipotential type electron gun, it goes without saying that the present invention is not limited to this and can be applied to other composite type electron guns.

As described above, according to the present invention, it is possible to provide an electron gun for a color picture tube in which the diameter of the electrostatic lens is substantially enlarged and the focus uniformity is improved, and its industrial value is great.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a color picture tube, Figure 2 is a schematic diagram for explaining the shape of the electron beam spot on the screen, Figure 3 is a side sectional view showing the conventional electrode structure, and Figure 4 is the main picture tube. A schematic configuration diagram of an embodiment of the electron gun of the invention, FIGS. 5 a to 5 c are partially enlarged views of the electrodes in FIG. 4, where a is a plan view and b and c are
FIG. 6, a side view taken along the -X' line and the Y-Y' line, is a schematic diagram for explaining the spot shape of the electron gun of the present invention. 40... cathode, 41... first grid electrode, 42...
...Second grid electrode, 43...Third grid electrode, 44...
...Fourth grid electrode, 431,441...Plate electrode,
53, 54, 55...Electron beam passing hole, 59...
...Bridge Department.

Claims (1)

[Scope of Claims] 1. An electron beam radiation source that emits a plurality of electron beams, and a passage hole for the plurality of electron beams that is provided with at least two different potentials for converging the electron beams onto the screen of a picture tube. In an electron gun for a color picture tube, the electron gun has at least a pair of thick plate-shaped electrodes on opposing surfaces in the tube axis direction of the plurality of electrodes constituting the main lens part. An electron gun for a color picture tube, characterized in that a surface of the thick plate-like electrode of the low potential side electrode facing the high potential side electrode is formed in a convex shape in the direction of the high potential side electrode. 2. The electron gun for a color picture tube according to claim 1, wherein the maximum height of the thick plate electrode in the tube axis direction is 40% or more of the diameter of the electron beam passage hole.