JPH0218540B2 - - 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 electrode constituting a main lens.

FIG. 1 is a sectional view of a color picture tube included in a conventional electron gun. A phosphor screen 3 is supported on the inner wall of a face plate portion 2 of a glass envelope 1 and is coated with phosphors of three colors alternately in stripes. The central axes 15, 16, 17 of the cathodes 6, 7, 8 are connected to the G1 electrode 9, the G2 electrode 10, the G3 electrode 11 constituting the main lens, and the openings corresponding to the respective cathodes of the shielding cup 13, as well as the G3 electrode. The inner cylinders 20, 21, and 22 are arranged substantially parallel to each other on a common plane and coincide with the central axes of the inner cylinders 20, 21, and 22 connected to the openings of the inner cylinders. This is the other electrode that makes up the main lens.
The central aperture of the G4 electrode 12 and the central axis of the inner cylinder 24 connected thereto coincide with the central axis 16, but both the outer apertures and the inner cylinders 23 and 25 connected thereto coincide with the central axis 16. Central axis 18, 19
do not coincide with the corresponding central axes 15 and 17, but are slightly displaced outward. The inner diameter of each inner cylinder matches the diameter of the corresponding aperture. Three electron beams emitted from each cathode have central axes 15, 1
The light enters the main lens along lines 6 and 17. The G3 electrode 11 is set to a lower potential than the G4 electrode 12,
The high potential G4 electrode 12 is at the same potential as the shielding cup 13 and the conductive film 5 provided on the inner wall of the glass envelope 1. The opening in the center of both G3 and G4 electrodes and the inner cylinders 21 and 24 are coaxial, and since the inner cylinder cancels out the influence from the non-axisymmetric electrode outer periphery, the main body formed in the center The lenses are axially symmetrical, and the central beam travels straight along a trajectory along the axis after being focused by the main lens. On the other hand, the openings on the outside of both electrodes and the inner cylinders 20, 22 and 23,
Since the axes of the lens elements 25 are shifted from each other, a non-axisymmetric main lens is formed on the outside. Therefore, the outer beam passes through a part of the main lens area that is deviated from the lens center axis in the direction of the center beam in the diverging lens area formed on the G4 electrode side, and at the same time as the main lens focuses, the outer beam Gain concentration in a direction. In this way, the three electron beams form an image on the shadow mask 4 and at the same time are concentrated so as to overlap each other. In this way, the operation of concentrating each beam is called static convergence (hereinafter referred to as
(abbreviated as STC). Furthermore, each electron beam is
The colors are sorted by the shadow mask 4, and only the components that excite the phosphor of the color corresponding to each beam to emit light pass through the apertures of the shadow mask 4 and pass through the phosphor screen 3.
reach. Further, an external magnetic deflection yoke 14 is provided to scan the electron beam on the fluorescent screen.

Factors that greatly affect the focus characteristics of a picture tube include the lens magnification and aberration of the main lens, which strongly depend on the strength of the lens focusing action.
In a picture tube, the distance from the main lens to the image plane is determined by determining the scanning area of the electron beam and the maximum deflection angle. Under the condition that the distance to the image plane is constant, weakening the lens focusing effect will result in a decrease in lens magnification, and in addition, to prevent an increase in deflection aberration, the beam spreading within the main lens will be reduced. Adding the condition of keeping it to a constant value will reduce the beam incidence angle to the main lens.
When the beam incidence angle is α _i , the diameter of the circle of least confusion due to spherical aberration, which is the most dominant among the aberrations of the main lens, is δ
is expressed as δ=1/2MC _sp α _i ³ , and by lowering the beam incidence angle, the spherical aberration can be reduced. Here, M is the lens magnification and C _sp is the spherical aberration coefficient.

In this way, in a picture tube, weakening the lens focusing effect of the main lens reduces lens magnification and spherical aberration, and improves focus characteristics. One way to weaken this focusing effect is to use G3, which forms the main lens,
The diameter of the opening of the G4 electrode as well as the corresponding inner cylinder is enlarged. (Hereafter, to simplify the explanation, when we refer to the aperture diameter, we will also include the diameter of the corresponding inner cylinder.) However, in an in-line electron gun like the one shown in Figure 1, , rim, and the main lenses corresponding to each of the three blue colors are arranged in a row on the same plane.
The diameter of the opening must be 1/3 or less of the inner diameter of the neck portion of the glass envelope 1 that accommodates the electron gun. If the thickness of the electrode is taken into consideration, as well as problems in electrode processing, the limit value becomes even smaller. In order to raise this limit value, increasing the inner diameter of the neck portion increases the deflection power, and generally speaking, increasing the aperture diameter increases the eccentric distance of the aperture, which worsens the convergence characteristics. A problem arises. Taking these points into consideration, the diameter of the opening is usually made as large as possible, so it is extremely difficult to enlarge it any further.

In Japanese Patent Application Laid-Open No. 55-17963, the above-mentioned hole diameter is
One method of expanding beyond the above limit is disclosed. In this method, the diameter of the aperture is set larger than the eccentric distance between adjacent apertures, so that the overlapping portions of the apertures are communicated, and a partition plate is installed in the communication area for potential correction. is provided.

However, even with this method, there is a certain limit to the diameter of the opening. Assuming that the diameter of the outer periphery of the G3 electrode in the horizontal direction (the direction in which the three apertures pass through the electron beam) is h, and the eccentric distance of the aperture is S, the limit value L of the aperture diameter is: L=h-2×S...(1). In reality, this limit value becomes even smaller due to problems in electrode processing.

In the present invention, even when the diameter of the electron gun is restricted by the inner diameter of the neck tube, the diameter of the opening can be adjusted to
It is an object of the present invention to provide an electron gun for a color picture tube that can effectively increase the value more than the value constrained by equation (1) and further improve the focus characteristics.

In order to achieve the above object, the present invention uses a G3 electrode and
It is characterized in that only the electrode plates forming the facing surfaces of the G4 electrode are moved back from each other and these electrode plates are arranged inside the outer peripheral electrode. In this way, the high potential of the G4 electrode penetrates into the G3 electrode, and the low potential of the G3 electrode penetrates deeper into the G4 electrode. Furthermore, the inner cylinders 20 to 25 as in the conventional example are removed, allowing the potential to penetrate deeper. Such potential penetration has substantially the same effect as enlarging the diameter of the aperture on the opposing surface. That is, the effective diameter increases. However, the cross section of the outer peripheral electrode excluding the facing surfaces of the G3 electrode and the G4 electrode is non-circular, and the diameter in the horizontal direction is larger than the diameter in the vertical direction. Therefore, the potential penetration is significant in the horizontal direction, and the effective diameter in the horizontal direction becomes larger than the effective diameter in the vertical direction. For this reason, the lens focusing effect in the horizontal direction is weaker than in the vertical direction, so astigmatism appears when focusing the electron beam. Therefore, in the present invention, the shape of the opening formed in the counter electrode plate is made non-circular, and the diameter in the horizontal direction is made smaller than the diameter in the vertical direction. In this way, if we suppress the invasion of horizontal potential,
The horizontal and vertical lens focusing effects can be made equal, and astigmatism can be eliminated.

According to the present invention, by appropriately selecting the amount of retraction of the counter electrode plate and the shape of the aperture formed in the counter electrode plate, substantially the same effect as increasing the diameter of the aperture is produced; Lens focusing effect is weakened and focus characteristics are improved.

Furthermore, as a secondary effect, a concentration force is generated inward in the outer electron beam, and even if the central axis of the G3 electrode side aperture and the central axis of the G4 electrode side aperture are aligned without deviation. , you can take STC. This is because the potential inside the G3 electrode is low near the outer periphery and higher in the center where the high potential on the G4 side penetrates deeply, so an electric field is generated inward from the outer periphery.

Furthermore, the electron gun of the present invention has no communicating part in the aperture through which the electron beam passes, and also does not require a partition plate for potential correction.
This is completely different from the electrode structure shown in 17963.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view of a main part of an embodiment of the electron gun of the present invention, and is a sectional view in the horizontal direction and the vertical direction of the G3 and G4 electrodes forming the bipotential main lens. In the figure, 111 is the outer periphery of the G3 electrode, 121 is the outer periphery of the G4 electrode, and 13 is the cup electrode. 112 is the outer peripheral part 111 of the G3 electrode
A polar plate for astigmatism correction provided inside the
Reference numeral 22 denotes a polar plate for astigmatism correction provided inside the outer peripheral portion 121 of the G4 electrode. The electrode plate 112 has an aperture 114 through which the central beam passes and apertures 113 and 113' through which the outer beams pass.
An aperture 124 through which the central beam passes and apertures 123 and 123' through which the outer beams pass are provided in a row. In this embodiment, the openings 113, 11
3', 114, 123, 123', and 124 are elliptical, and the shapes and dimensions of the corresponding openings on the G3 side and G4 side are the same. Outer opening 11
3, 113', 123, 123' and central opening 11
4 and 124 have the same shape and size, the lens focusing effect in the horizontal direction of the main lens formed on the outside becomes stronger, so the horizontal diameter of the outer aperture is set to be larger than the horizontal diameter of the central aperture. Increase the strength of the focusing action in both the horizontal and vertical directions.

FIG. 3 shows, in the embodiment shown in FIG.
4 vertical diameter a ₁ = outer opening 113, 113',
Vertical diameter a ₂ of 123, 123' = 8.4 mm, plate 1
Retraction amount d ₁ of electrode plate 122 = Retraction amount d ₂ of electrode plate 122 = 1.5 mm,
When the eccentric distance S = 6.6 mm, the central opening 114,
The ratio of the focus distance in both the horizontal and vertical directions to the horizontal diameter b ₁ of 124 was determined by computer simulation.

Here, the horizontal or vertical focus distance means that the electron beam that is emitted from one point on the central axis at a certain emission angle and passes through the horizontal or vertical axis of symmetry of the central aperture is focused by the main lens. , the distance from the end face of the G3 electrode on the G4 electrode side to the point where it crosses the central axis again is measured. The distance from the same end face to the fluorescent screen is 3.40mm,
The emission angle is set to a constant value, the emission points whose horizontal and vertical focus distances match this value of 340 mm are found, and the electron beam is then emitted from the middle of these emission points at the same emission angle. FIG. 3 shows the ratio of focus distances in both the horizontal and vertical directions at this time. As can be seen from the figure, if the horizontal diameter of the central hole is b ₁ 5.5 mm,
Vertical and horizontal focus distances match,
Since the intensity of the focusing action in both directions becomes equal, astigmatism can be eliminated.

Further, in this case, the lens focusing action has a strength equivalent to that of bipotential lenses of 8 mm diameter cylinders that are aligned at an interval of 1 mm. This is h=
When 20.0 mm and S = 6.6 mm, this value is larger than the limit value of 6.8 mm for the electrode opening restricted by equation (1).

FIG. 4 shows the outer openings 113, 113',
The relationship between the value of the horizontal diameter _b2 of 123 and 123' and the horizontal spot movement distance of the outer electron beam on the fluorescent surface was determined by computer simulation. 7kV for G3 electrode, 7kV for G4 electrode
25 kV was applied, and the distance from the end of the G3 electrode on the G4 electrode side to the fluorescent surface was set to 340 mm. an outer electron beam;
The central electron beam is 6.6 mm apart in the horizontal direction, so the spot movement distance required to take STC is 6.6 mm, but in reality it is 6.1 mm in order to leave freedom in color purity adjustment. It is often designed to a certain degree. In order to secure this moving distance, the value of b ₂ is 5.8 mm.

FIG. 5 is a sectional view of a main part of another embodiment of the electron gun of the present invention, and is a view showing a vertical cross section of the G3 electrode. Openings 41 and 4 provided in the electrode plate 112
1' and 42 have a shape in which the end points of two circular arcs are connected by two parallel straight lines. Although the shape of the spot on the fluorescent surface is worse than when the aperture is elliptical, it has the advantage that it can be machined easily and with high precision because the aperture consists of circular arcs and straight lines. In this embodiment as well, the horizontal diameter of the opening is smaller than the vertical diameter.

FIG. 6 and FIG. 7 are main part sectional views of still another embodiment of the electron gun of the present invention, respectively.
FIG. 3 is a diagram showing a vertical cross section of the G4 electrode. The central apertures 52, 62 have a vertical axis of symmetry, but the outer apertures 51, 51', 61, 61' do not have a vertical axis of symmetry. Outer openings 51, 51', 52,
52' is a combination of two ellipses with the same major axis and different minor axes, and the outer openings 51, 51' of the G3 electrode are such that the minor axis of the ellipse combined on the outside is the same as the ellipse combined on the inside. It is smaller than the short axis of. When the outer aperture of the G3 electrode is shaped like this, the force for concentrating the electron beam toward the center becomes stronger than when the aperture is a single ellipse like 113 and 113' in Fig. 2. STC can be obtained even if the horizontal diameter is made smaller.

On the other hand, in the G4 electrode, if the outer aperture is constructed by combining two ellipses, the inner ellipse's minor axis being smaller than the outer ellipse's minor axis, as shown at 61 and 61' in Figure 7, the electron beam The force that concentrates the energy toward the center becomes stronger.

In this way, by making the outer aperture asymmetrical with respect to the vertical direction, the concentration of the electron beam increases,
STC becomes easier to take. Furthermore, if the concentration is too strong, the concentration can be weakened by using the aperture shown in FIG. 6 on the G4 electrode side and the aperture shown in FIG. 7 on the G3 electrode side.

FIG. 8 is a sectional view of a main part of still another embodiment of the present invention, and is an embodiment in which the electrode plates 112 and 122 are not retracted but are arranged on the same plane as the facing surface of the electrode outer enclosure. Oval openings 113, 113', 114,
123, 123', and 124 correct astigmatism.

In this embodiment, since the electrode plate is not retracted, the counter electrode potential does not penetrate as deeply into the electrode as in the embodiments shown in FIGS. 2, 5, 6, and 7. However, since the inner cylinder as in the conventional example is removed, the counter electrode potential penetrates deeper than in the conventional electrode structure shown in Figure 1, so the same effect as increasing the aperture diameter can be obtained to some extent. obtained, and the focus characteristics are improved.

The embodiment shown in FIG. 8 has the advantage that the outer circumferential portion of the electrode and the electrode plate can be simultaneously molded by press working, and manufacturing is easy.

According to the present invention, cylindrical electrodes with the largest diameter possible when arranging the main lenses corresponding to the three colors of red, edge, and blue on the same horizontal plane are brought together within the constraints of the outer shape of the electron gun. Since it is possible to configure a main lens with a weaker focusing effect than in the case of the present invention, it is possible to significantly improve the focus characteristics of a color cathode ray tube.

Furthermore, the amount of retraction of the electrode plate and the shape of the aperture formed in the electrode plate are appropriately selected without deviating the central axis of the outer aperture formed in the G3 and G4 electrodes that make up the main lens. As a result, since the STC can be taken, jigs with the same diameter and the same axis can be used for the G3 electrode and the G4 electrode during assembly, and assembly accuracy can be improved.

Note that the present invention is of course applicable not only to the bipotential type main lens exemplified in the above description but also to a unipotential type or other type main lens. Further, in the above description, an example was described in which the present invention is applied to both of a pair of electrodes that constitute the main lens, but the same effect can be obtained even if the present invention is applied to only one of the electrodes.

[Brief explanation of drawings]

FIG. 1 is a sectional view schematically showing a conventional in-line color picture tube, FIG. 2 is a sectional view of a main part of an embodiment of an electron gun of the present invention, and FIG. 3 is a sectional view of a central main lens of an electron gun of the present invention. A diagram showing an example of the relationship between the focus distance in the horizontal and vertical directions and the minor diameter of the aperture. Figure 4 shows the minor diameter of the aperture of the outer main lens and the horizontal spot movement distance on the fluorescent surface. A diagram showing an example of the relationship between
5 to 8 are sectional views of main parts of other embodiments of the electron gun of the present invention. 1... Glass envelope, 2... Face plate, 3... Fluorescent surface, 4... Shadow mask, 5...
...Conductive film, 6,7,8...Cathode, 9...G1 electrode,
10...G2 electrode, 11...G3 electrode, 12...G4
Electrode, 13... Shielding cup, 14... External magnetic deflection yoke, 121... G3 side astigmatism correction pole plate,
122...G4 side astigmatism correction polar plate, 113,
114, 123, 124, 41, 42, 51, 5
2, 61, 62...Apertures for beam passage.

Claims (1)

[Scope of Claims] 1. Electron beam generating means that generates three electron beams toward the phosphor screen, and a main lens that focuses the three electron beams on the phosphor screen, which are provided at a distance from each other. In addition, two outer peripheral electrodes surrounding the three electron beams, and three openings arranged at opposing ends of the outer peripheral electrodes, through which the three electron beams pass, are arranged along one direction. In a color picture tube electron gun having two electrode plates, at least one of the two electrode plates is retracted and disposed inside the outer peripheral electrode, and the retracted electrode plate is disposed inside the outer peripheral electrode. An electron gun for a color picture tube, characterized in that the diameter of each opening in the electrode plate in one direction is smaller than the diameter in the vertical direction. 2. The electron gun for a color picture tube according to claim 1, wherein the aperture of the retracted electrode plate is elliptical. 3. Claim 1, characterized in that the opening in the retracted electrode plate is formed in a shape surrounded by two straight lines perpendicular to the one direction and two circular arcs. electron gun for color picture tubes. 4 Among the apertures of the retracted electrode plate, the central aperture has an axis of symmetry perpendicular to the one direction, and the outer apertures do not have an axis of symmetry parallel to the axis of symmetry, and 2. The electron gun for a color picture tube according to claim 1, wherein the two outer apertures are formed to be symmetrical with respect to the axis of symmetry of the central aperture. 5. The electron gun for a color picture tube according to claim 1, wherein the two electrode plates are both set back the same distance and placed inside each of the electrode plates. 6. A color picture tube according to claim 1, wherein the vertical diameter of the central aperture of the electrode plate is approximately the same as the vertical diameter of the outer apertures. electron gun. 7. The electron gun for a color picture tube according to claim 1, wherein the diameter of the central opening of the electrode plate in the one direction is smaller than the diameter of the outer opening in the one direction. 8. The color image receiving device according to claim 1, wherein the shapes of the three openings in the one electrode plate are the same as the shapes of the three corresponding openings in the other electrode plate. Tube electron gun.