JPS63198241A - Color cathode tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a color cathode ray tube with an electron gun having three electron lenses, and more particularly to a color cathode ray tube having an asymmetrically shaped beam with a substantially constant current density. This invention relates to a three-lens electron gun that can form a three-lens electron gun.

[Background of the invention]

FIG. 1 shows a conventional rectangular color picture tube 10 having a glass envelope 11 including a rectangular faceplate panel 12 and a tubular neck 14 joined by a rectangular funnel 16. There is.

Panel 12 has a viewing faceplate 18 and a peripheral flange or sidewall 2o sealed to funnel 16 by a frit seal 21. A mosaic three-color phosphor screen 2 is provided on the inner surface of the face plate 18.
2 is provided. Preferably, the screen 22 is a line screen with lines of phosphor extending substantially perpendicular to the direction of high frequency mask line scanning of the picture tube (ie, perpendicular to the plane of the page of FIG. 1). Dot screens can also be used. A porous color selection electrode, or shadow mask 24, is mounted at a predetermined distance from the screen 22 by conventional means. An in-line electron gun (shown schematically in dotted lines in FIG. 1) 26 is centered within the neck 14 and generates three electron beams 28 which are directed through the mask 24 and onto the screen 22. The beam is projected onto a beam path that is initially located in the same plane. One type of conventional electron gun was published by Morre in the October 28, 1986 issue shown in Figure 2.
ll) U.S. Patent No. 4.620.133 issued to Mr. et al.
It is a four-grid pi-potential electron gun as described in the issue.

The picture tube in Figure 1 has an external magnetic deflection yoke, for example, a 30% yoke placed at the junction of the funnel and the neck.
designed to be used with. When energized, yoke 30 causes three electron beams 28 to be influenced by a magnetic field. This magnetic field works so that the electron beam 28 scans the screen 22 horizontally and vertically by drawing a rectangular mask. The initial deflection surface (the surface at the zero deflection point) is shown in FIG.
It is shown in Because of the fringe field, the deflection area of the picture tube extends axially from the yoke 30 into the area of the gun 26. To simplify the illustration, the actual curvature of the path of the deflected beam in the deflection region is not shown in FIG. The yoke 3o has a strong pincushion-shaped vertical deflection magnetic field and a strong barrel-shaped horizontal deflection magnetic field, and provides a non-uniform magnetic field that concentrates the electron beam at the periphery of the screen 22. When an electron beam passes through such a non-uniform magnetic field, the beam is distorted and becomes defocused. As a result, the shape of the electron beam spot is greatly distorted at the periphery of the screen 22. FIG. 3 shows the electron beam spot for one beam.

This beam is circular in the center of the screen 22 and is subjected to various types of distortions at the periphery of the screen.

As shown in FIG. 3, the beam spot is spread out horizontally when it is deflected along the horizontal axis. A beam spot on a square of the screen was formed by a combination of a horizontally long part and a vertically long part. It is an elliptical spot with a halo-like extension in its area. As the deflection of the electron beam increases, the resolution decreases and problems arise due to non-negligible non-uniform focusing.

The above-mentioned U.S. Pat. No. 4,620,133 deals with this beam focusing problem and includes a deflection yoke, a first grid Gl, a second grid G2 and a third grid Gl.
an improved beam forming region having a grid G4 of;
The screen 22 cooperates with the yoke and the beam forming area.
An improved color image display device is provided that includes an electron gun having an improved main focus lens G3-G4 that serves to form an improved beam spot thereon. FIG. 4a shows the electron beam current density contour at the center of the screen 22 for the electron beam generated by the beam forming region and main focus lens of the conventional electron gun shown in FIG. . The beam current of the electron gun is 4 mA. The electron beam current density contour of FIG. 4a has a relatively large central portion with a substantially constant beam current of about 50% of the average beam current;
It includes a peripheral region where the beam current is reduced to about 5% of the average beam current, and further reduced to about 1%. The beam has an oval shape along the vertical axis, and the yoke prevents overfocus when the beam is deflected.
decrease. FIG. 4b shows the beam-flow density contours in Wang Shinzu L2 between the 03 and G4 electrodes of FIG. At this location, the electron beam extends horizontally. However, the 50% beam current density section is contained within a small elliptical section in the center of the beam, which is surrounded by a larger elliptical section representing the 5% and 1% beam current density contours. I'm here. FIG. 4c is an electron beam current density contour for an electron beam deflected to the upper right corner of the screen. Above and below the central part of the beam.

Some halo phenomenon is occurring. Figures 1a to 5c Lt show the paths of electrons exiting the beam forming region of the electron gun of Figure 2 for various beam currents. In Figure 5a, the beam current is adjusted to 4 mA, and the crossover point is approximately 2.8 mA from the cathode located at the origin.
~2.9 mm (110-115 mils). At about 200 mils from the origin, the electrons are concentrated in the central portion of the beam. This distribution of electrons creates the current density contours shown in Figure 4a in the screen. The influence of the beam current on the position of the crossover point and the beam current density contour is shown in Section 5b.
and FIG. 5C. In Figure 5b, the beam current has been reduced to 0.8 mA and the crossover point has been moved to about 45 mils from the cathode. The divergence angle of the electron beam is determined by the operating current of 4
, it is clear that it is somewhat smaller at 0.8 m than at 0 mA (Fig. 5a).

In FIG. 5C, the beam current is 0.2 mA, the crossover point is approximately Q, 5 mm (25 mils) or less from the cathode, and the beam is substantially laminar.

U.S. Patent No. 4,641,058, dated February 3, 1987
In this issue, a four-grid pi-potential electron beam is introduced, in which a prefocus astigmatism lens is formed between the second and third grids, and a principal astigmatism focus lens is formed between the third and fourth grids. A gun is listed. This two-lens structure is superior to the conventional pi-potential structure, as shown in Fig. 2, which uses the first grid to give the electron beam an astigmatic shape. The difference is that the electron gun described in U.S. Pat. No. 4,641,058 uses the second and/or third grid as the first astigmatic lens. This structure If you adopt
It is stated that the astigmatic electron beam formed by the astigmatic lens can be corrected in the main astigmatism focus lens to form a substantially circular beam spot on the phosphor screen of the cathode ray tube. There is. U.S. Patent No. 4,
The structure described in No. 641,058 has also been applied to a compound lens type electron gun having six grids and three separate lenses as shown in FIG. In the six-grid structure described in this patent, a first (prefocus) lens L1 is formed between the second and third grids, and the third... The fourth and fifth grids are sub-lenses (sub-1e
ns) Configure L2, and 5th. The sixth grid constitutes the main lens L3. In this example, the first (prefocus) lens acts as the first astigmatic lens;
The main lens acts as a second astigmatic lens. It is stated that the deflection beam spot of this electron gun is superior to that obtained with conventional electron guns. but.

In such an electron gun structure, the position of the crossover point depends on the beam current of the electron gun. The first asymmetric lens L1 is formed in the region between the second grid G2 and the third grid G3, and depending on the electron beam current, the crossover point may occur before or after the lens L1. do. At a high beam current of about 4 mA, a cross point occurs at a position near the hypothetical 03 electrode of lens L1.

Thus, the asymmetric effect of lens L1 is a function of beam current. Therefore, an electron lens that is not affected by beam current is desired. That is, regardless of the operating beam current of the electron gun, the asymmetric lens must be located closer to the screen than the crossover point. Furthermore, it is desirable to have an electron gun structure that forms a beam with substantially constant current density in both horizontal and vertical directions in the main lens.

[Summary of the invention]

The invention includes an electron gun that generates three electron beams, a central beam and two outer beams, and directs these beams toward a screen along a path initially in the same plane. The aim was to improve the color picture tubes currently available. The electron gun includes a plurality of spaced apart electrodes forming a first lens that includes a beam forming region for providing a substantially symmetrical beam to a second lens. The second lens includes a beam refracting means that refracts the off-axis electron beam coming out of the first lens toward the axis, and an asymmetric beam that supplies a beam with an asymmetric shape to the third lens. and a focusing means. The third lens is a low-aberration main focusing lens that supplies an asymmetrically shaped beam with a substantially constant current density to the screen. As shown in FIG. Electron gun 4o: 1 for 3 beams)
coplanar (coplanar) cathodes 4 arranged at equal intervals of
2 (K), control grid 44 (Gl).

Shielding grid 46 (G2), third electrode 48 (G3).

It includes a fourth electrode 50 (G4), a fifth electrode 52 (G5) and a sixth electrode 56 (G6), where the G5 electrode 52 is the element 5
It has a portion G5' indicated by 4. The electrodes are spaced apart from the cathode in the above order and are attached to a pair of support rods (not shown).

It constitutes the formation area. The other part of the G3 electrode 48,
G4 electrode 50 and G5 electrode 52 constitute a first asymmetric lens. Portion 54 of G5 electrode 52 (G5' electrode) and 0
6 electrodes 56 form the main focusing (ie, second asymmetric) lens.

Each cathode 42 includes a cathode sleeve 58 closed at its front end by a cap 60 having an end-face coating 62 of electron-emissive material, as is known in the art. Each cathode 42 has a sleeve 5
Indirect heating is performed by a heater coil (not shown) disposed within 8.

G1 electrode 44 and G2 electrode 46 are two closely spaced substantially flat plates having three pairs of in-line apertures 64, 66 extending therethrough. Apertures 64 and 66
are centered with the cathode coating 62 and produce three equally spaced coplanar electron beams 28 (FIG. 1) that are directed toward the screen 22. Preferably, the initial electron beam path is parallel to the Si material B', with the central path aligned at -A to the central axis of the electron gun.

G3 electrode 48 has a substantially flat outer plate portion 68 with three in-line apertures 70 aligned with apertures 66, 64 in G2 and G1 electrodes 46,44.

The G3 electrode 48 also has two cup-shaped portions 72 and 74, a first and a second cup-shaped portion.
are joined to each other at their respective open ends.

The first portion 72 has three in-line apertures 76 through the bottom of the cup portion, and these apertures 76 are connected to the plate 68.
It is aligned with the aperture 70 therein. The second portion 74 of the G3 electrode 48 has at its bottom the 3
It has three apertures 78 aligned with three apertures 76 . A protrusion 79 is provided surrounding the opening 78. It should be noted that the plate portion 68 having the in-line apertures 70 may be formed integrally with the first portion 72.

G4 electrode 50 consists of a substantially flat plate having three in-line through-holes 80 aligned with apertures 78 in the G3 electrode.

The G5 electrode 52 is a cup-shaped member formed by deep drawing.

It has three through holes 82 surrounded by protrusions 83 at its bottom. Three apertures 8 aligned with aperture 82
A substantially flat plate member 84 having a diameter of 6 is attached to the open end of the G5 electrode 52 to close it. A first plate portion 88 having a plurality of apertures 90 is attached to the opposite surface of plate member 84 .

The G5' electrode 54 is made of a cup-shaped member formed by deep drawing, and a recess 92 is formed at the bottom end of the cup.

Three in-line holes 94 are formed in the bottom of the recess 92. A protrusion 95 surrounds the aperture 94.

The opposite open end of the G5' electrode 54 is closed by a second plate portion 96 which is aligned with the opening 90 in the first plate portion 88 and has a Three apertures 98 are formed to be energized as shown in FIG.

The G6 electrode 56 is a deep-drawn cup-shaped member having one large opening 100 at one end through which all three electron beams pass, and the open end is closed by being attached to a plate member 102. . The plate member 102 is G5'
31 through-holes 10 aligned with apertures 94 in electrode 54
It has 4. A protrusion 105 is provided around the opening 104.
is formed.

The shape of the recess 92 of the G5' electrode 54 is shown in FIG. The recesses 92 have a uniform vertical width in each electron beam path and are rounded at both ends. This kind of shape is called a "race track (track for track and field events, etc.)"
It's called shape.

The shape of the large opening 100 in the G6 electrode 56 is shown in FIG. The aperture 100 has a larger vertical width in the outer beam path than in the central beam path. This shape is called a "dog bone" or "barbell" shape.

The first plate portion 88 of the G5 electrode 52 is connected to the G5' electrode 54.
is opposed to the second plate portion 96 of. G5 electrode 52
The apertures 90 in the first plate portion 88 have a protrusion from the plate portion that is divided into two segments 106 and 108 for each aperture 90 .

The aperture 98 in the second plate portion 96 of the G5' electrode 54 also
It has a protrusion from the plate portion 96 which is also divided into two segments 110 and 112 for each aperture. As shown in FIG.
08 is interpolated for segments 110 and 112. These segments are.

When different voltages are applied to the G5 electrode 52 and the G5' electrode 54, they are used to form a quadrupole lens in the path of each electron beam. By appropriately applying dynamic voltage changes to either the G5 electrode 52 or the G5' electrode 54, the electron beam can be astigmatized using the quadrupole lens set by segments 106.1081110 and 112. Aberration correction can be added to compensate for astigmatism occurring in the electron gun or in the deflection yoke. Regarding such a quadrupole lens structure,
U.S. Patent Application No. 75, 78 dated July 20, 1987
It is stated in No. 4.

Detailed dimensions of the computer model electron gun for the first preferred embodiment of this invention are shown in Table 2.

Table 1 In the embodiment shown in Table 1, the electron gun is electrically connected as shown in FIG. Typically, the cathode is about 1
Operated at 50V, the Gl electrode is at ground potential, the G2 and G4 electrodes are electrically connected to each other, and the
Operates within the range of oo v. The G3 and 05 electrodes are also connected to each other and operate at about 7KV, and the G6 electrode operates at an anode potential of about 25KV.

Although the electrical parameters of this preferred embodiment are similar to those described in the aforementioned U.S. Pat. No. 4,641,058, this electron gun has superior performance due to its structural differences. I do.

In this electron gun 40, the first lens LL (FIG. 6)
supplies not an asymmetrical electron beam but a symmetrical high-quality electron beam to the second lens L2. This beam has a large divergence angle of about 120 milliradians,
It exhibits an electron distribution as shown in the ray diagram of FIG.

The electron beam crossover, operating at approximately 4 mA, is approximately 2.3 vm (approximately 0.090 inch) from the cathode. The corresponding beam current density contour for one of the three beams is shown in FIG. It can be seen that the beam forming region of this electron gun does not impart any asymmetry to the electron beam that requires any consideration.

In this electron gun 40, the G4 electrode 50 and the G3 electrode 48
and a portion of the G5 electrode 52 adjacent to the G4 electrode constitutes an asymmetric lens that forms an elongated electron beam in the horizontal direction. This electron beam has a beam spot contour line as shown in FIG. 14 within the 3rd percentile, that is, the main focus lens L3.

The substantially rectangular shape of this electron beam corresponds to the G4 electrode 5
is provided by a rectangular aperture 80 provided at 0.

Because the vertical dimension of the aperture 80 is smaller than the horizontal dimension and because the adjacent G3 and G5 electrodes operate at a higher potential than the G4 electrode, the beam is directed to the main lens L3. Before entering, it is subjected to a strong focusing action in the vertical direction. Even if there is some misalignment of the beam forming region apertures 64166 and 70, such as about 0.001 inches, the G4 electrode 50 (
Also, due to the potential of the G2 electrode 46) connected thereto, electrons of the electron beam coming out off-axis from the beam forming region are refracted toward the axis.

The main focus lens L3 formed between the G5' electrode 54 and the G6 electrode 56 is also an asymmetric lens with low aberrations, and is designed to form a vertically long beam spot, that is, an asymmetrical beam spot at the center of the screen. It is something. The resulting beam spot (shown in Figure 15a) has substantial Gaussian current density contours. As shown in Figure 15b, when the beam is deflected to the upper right corner of the screen, the central 50% density region of the beam becomes considerably longer, converting the central region into a low-intensity enlarged region, i.e., a halo-like region. is surrounding.

The potential of the G5 electrode 52 (at zero deflection) is applied to the G5' electrode 54.
By applying to the G5' electrode 54 a dynamically changing focusing voltage that varies from 1 to 1000 V more positive than the voltage at the 05 electrode (at maximum deflection), the current density contour of the deflected electron beam is adjusted to the 15th ctl. It can be improved as shown in

The first embodiment described above can be modified as follows. The rectangular opening 80 of the G4 electrode 50 has a diameter of approximately 4.06 mm.
Replaced with a circular aperture of mm (0,160 inch).

The thickness of the G4 electrode is reduced to approximately 0.64 mm (0.025 inch), and the dimensions of the barbell-shaped opening 100 of the G6 electrode are reduced to approximately 17.86 mm (0.703 inch) in length, with a center beam. Vertical height at part approximately 6.99 mn (0,
275 inches), vertical height at outer beam section approximately 7
．． 37ffl+! (0,290 inches).

Additionally, the total length of the G5 and G5' electrodes is increased to approximately 22.86 mm (0,900 inches). As a result.

The beam spot size depicted by the 5% density contour on the screen is comparable to that of the conventional electron gun shown in FIG.

A second embodiment of the electron gun 4o based on the computer model shown in FIGS. 7 and 8 is shown in Table 2. The beam forming region of the electron gun of this second embodiment is the same as the beam forming region of the first embodiment, and like tube elements are designated using the same reference numerals.

r22) Table ■ In the embodiment shown in Table ■, the electron gun 40 is electrically connected as shown in FIG. Typically, the cathode is at about 150V, the Gl electrode is at ground potential, and the G2 electrode is at about 40V.
Each operates at 0v. The G3 electrode is electrically connected to the G5 electrode and operates at approximately 7 KV. Also, G4
The electrode is electrically connected to the G6 electrode and approximately 25 K
Operates at an anode potential of V.

In the electron gun of this embodiment, the first lenses L, 1
(FIG. 16) supplies a symmetrical and high quality electron beam to the second lens L2. Since the beam forming region of this second embodiment is the same as that of the first embodiment, FIGS. 12 and 13 show the electron distribution and beam current density contours of one of the electron beams from this region. It also represents.

In the second embodiment, the second electron lens L2 has a G4 electrode 40 and a G3 electrode 48 . A portion of the G5 electrode 52 adjacent to the G4 electrode forms an elliptical electron beam elongated in the horizontal direction.

This electron beam is transmitted through the third, ie, main focus lens L.
3, the beam current exhibits density contour lines as shown in FIG. The elliptical shape of this beam is formed by the interaction of the rectangular aperture 80 in the G4 electrode 50 and the voltage gradient in the second lens L2.

FIG. 18 shows the beam current density contours of the electron beam at the center of the screen obtained by this method. In this second embodiment, the horizontal dimension of the aperture 80 is smaller than the vertical dimension, and the potential of the G3 and G5 electrodes adjacent to the G4 electrode is lower than that of the G4 (2 et al.) electrode. Since it operates with electric potential, raw lens L
3, the beam is subjected to weak focusing in the vertical direction as well.

The first and second embodiments of the electron gun 40 shown in Tables ■ and ■ are as follows:
Although the construction and operating voltages are different, the beam contours shown in FIGS. 15a and 18 are similar, indicating that acceptable performance can be obtained using either eave embodiment.

The electrical configuration shown in FIG. 6 is preferred because no anode potential is introduced into the low voltage region of the electron gun.

Examples of the embodiments shown in Table 1 and ■, for example, U.S. Patent Nos. 4 and 6
41, No. 058, is that the first asymmetric lens L2 is located in front of the electron beam crossover. Therefore, the asymmetric effect that lens L2 has on the beam spot size and the current density contour on the screen is relatively independent of the beam current.

When the structure of the present invention is adopted, a horizontal beam (ie, a beam having a substantially constant current density in both directions) can be obtained at the main lens.

The embodiments described herein are merely examples, and the invention is not limited thereto. for example.

Instead of the rectangular aperture of the G4 electrode 50 in the second embodiment, other suitable geometrical apertures can be used to form an asymmetrical second lens.

Furthermore, the intensity of the electron lens within the electron gun may be changed by selecting the focusing voltages of the G3 and G5 electrodes.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing a part of a normal color cathode ray tube in cross section along the axis, Fig. 2 is a schematic sectional view showing the overall structure of a 4-grid pi potential electron gun, and Fig. 3 is a conventional color cathode ray tube. Figure 4a shows the shape of the electron beam spot on the screen of the tube, Figure 4a shows the electron beam current density contour obtained at the center of the screen by the electron gun in Figure 2, Figure 4b shows the shape of the electron beam spot on the main lens. FIG. 4c is a diagram showing the current density contours for an electron beam deflected to the upper right corner of FIG. 3; FIGS. Figure 6 shows the electron beam rays for the beam forming region of the electron gun of Figure 2 operating with beam currents of 0 mA, 0.8 mA and 0.2 mA; Figure 6 shows the second and fourth grids at the first potential; A schematic cross-sectional view of a six-grid electron gun in which the third and fifth grids are operated at a second potential; FIGS. 9, 10 and 11 are cross-sectional views taken along lines 9-9, 10-10 and 11-11 in FIG. 7, respectively. FIG. 12 is a diagram showing electron beam lines related to the beam forming region of the electron gun of the present invention, and FIG. 13 is a diagram showing current density contour lines of the electron beam from the beam forming region (first lens) of the electron gun of the present invention. figure. 14 is a diagram showing the electron beam current density contour lines in the main lens formed by the second lens of the electron gun of the present invention connected as shown in FIG. 6, FIG. 15a and the first
Figure 5b is a diagram showing the beam current density contours at the center and upper right corner of the screen of the electron gun of the present invention connected as shown in Figure 6, and Figure 15c is a diagram showing the contour lines of the main (third) lens.
A diagram showing the beam current density contours at the upper right corner of the screen when dynamic correction voltages are applied to two electrodes,
Figure 16 shows the third and fifth grids at the third potential and the fourth grid at the third potential.
FIG. 17 is a schematic cross-sectional view of a second embodiment of a six-grid electron gun in which the sixth grid is operated at a fourth potential.
FIG. 6 is a diagram showing electron beam current density contour lines in a main lens made by a second embodiment of the electron gun of the present invention connected as shown in the figure; FIG. 18 is a diagram showing electron beam current density contour lines at the center of the screen for a second embodiment of the electron gun of the present invention connected as shown in FIG. 16. DESCRIPTION OF SYMBOLS 11... Envelope, 40... Electron gun, 22... Screen, 44-56... Electrode, Ll, L2. La...
- 11th second and third lenses, G4... Beam refracting means. 80...Asymmetrical beam focusing means.

Claims (1)

[Claims] (1) A color cathode ray tube including an envelope having an in-line electron gun therein, wherein the in-line electron gun generates three in-line electron beams and transmits them into the envelope. The electron beam is initially projected along a coplanar axis on its path toward the screen, and the electron gun also has first and second electron beams for focusing the electron beam.
and a plurality of spaced apart electrodes forming a third lens, the first lens having a beam forming region for providing a substantially symmetrical beam to the second lens. The second lens includes: a beam refracting means for refracting the electron beam emitted from the first lens off the axis toward the axis; asymmetrical beam focusing means of a color cathode ray tube, wherein the third lens is a low aberration main focus lens that provides an asymmetrically shaped beam with a substantially constant current density to the screen.