JPH01264145A - Electron gun for color picture tube - Google Patents

Abstract

PURPOSE:To shrink the diameter of a screen spot and improve resolution by shortening the gap g2-3 between electrodes G2 and G3 in an electron gun using a main lens formed with noncircular facing surfaces of electrodes and having an effectively expanded diameter to reduce aberration. CONSTITUTION:An electron gun is constituted of three electrodes consisting of a cathode 7, a G1 electrode 9, and a G2 electrode 10 and a main lens section consisting of a G3 electrode 101, a G4 electrode 102, a G5 electrode 103, and a G6 electrode 104. The diameter D1 of the G1 electrode 9 and the gap g2-3 between the G2 electrode 10 and the G3 electrode 101 have the following relationship: 0.9<g2-3/D1<1.4. The electrode opening shape is noncircular on facing surfaces of at least a pair of electrodes constituting the main lens. The effect to reduce the aberration of a prefocusing lens can be exerted, the diameter of a screen spot is shrunk, the resolution can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrode structure of an electron gun for a color picture tube. [Prior Art] FIG. 2 is a plan view of a color picture tube equipped with an electron gun of a conventional structure. 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 the G1 electrodes 9
．． G2 electrode 10. 63 electrons forming the main lens 1.
and shielding cups 13, which coincide with the central axes of the openings corresponding to the respective cathodes, and are arranged substantially parallel to each other on a common plane. The central axis of the central aperture of the G 4 t'lt pole 12, which is the other electrode constituting the main lens, coincides with the central axis 16, but the central axis of both outer apertures is 18°. 19 is the corresponding central axis 15.1
7 and is slightly displaced outward. The three electron beams emitted from each cathode have a central axis of 15°16.1
7 and enters the main lens. G3 electric wAll is G
The potential is set lower than that of the four electrodes 12.

The high potential electrode 12 is connected to the shielding cup 13. It has the same potential as the conductive film 5 provided inside the glass envelope. G3,
04 Since the openings at the center of both electrodes are coaxial, the main lens formed in the center is axially symmetrical, and the central beam is focused by the main lens and then travels straight along a trajectory along the axis. Since the outer blooms of the one-sided electrode are off-axis with respect to each other, a non-axisymmetric main lens is formed on the outer side. 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 central beam in the diverging lens area formed on the 64th electrode side.

At the same time as the focusing effect of the main lens, it receives a concentrated force in the direction of the central beam. In this way, the three electron beams form images on the shadow mask 4 and at the same time are concentrated so as to overlap each other. The operation of concentrating each beam in this manner is called static convergence (hereinafter abbreviated as STC).

Furthermore, each electron beam is color-selected by a shadow mask, and only the phosphor of the color corresponding to each beam is excited to emit light, thereby forming a screen spot. Further, an external magnetic deflection yoke 14 is provided to scan the electron beam on the fluorescent screen.

To improve the resolution of color cathode ray tubes.

The screen spot diameter on the phosphor screen 3 must be made small.

The electron beam is transmitted through a cathode lens composed of cathodes 6, 7, 8, a G1 electrode 9° and a G2 electrode 10, a 02 electrode 10, and a G3 electrode.
The light is focused by three types of lenses, a pre-focus lens formed in the middle of the electrode 11 and a main lens, to form a spora 1-. Therefore, in order to reduce the screen spot diameter, it is necessary to reduce each of the above lens aberrations.

Of these, G2 is recommended for reducing aberrations of brifocus lenses.
JP-A-55-19728 shows that shortening the distance g2-a between the electrode 10 and the G3 electrode 11 is effective.

In addition, increasing the diameter of the main lens electrode is effective in reducing aberrations of the main lens, but the three electron beam central axes 15, 16
．． In an in-line electron gun in which 17 is arranged on one plane, when a conventional ordinary cylindrical lens is used, its diameter is approximately 25 mm of the inner diameter of the neck portion of the glass envelope 1 that houses the electron gun.
It was kept within %. Therefore, in order to overcome this limit, it is possible to consider a method of making the electrode opening shape non-circular. In the method disclosed in Japanese Patent Application Laid-Open No. 58-103752, the lens aperture is effectively enlarged to about 35% of the inner diameter of the neck portion.

[Problem to be solved by the invention]

The above-described conventional technology for reducing prefocus lens aberrations has a problem in that it does not lead to a reduction in screen spot diameter when combined with a normal cylindrical lens.

An object of the present invention is to provide conditions under which the effects of the above-mentioned conventional techniques can be fully exhibited.

[Means to solve the problem]

This is an electron gun that uses a main lens that reduces aberrations by making the surface facing the electrode non-circular and effectively enlarging the aperture.
When the 2,03 electrode interval g2-8 is shortened, the screen spot diameter is reduced.

[Effect]

Figure 3 shows the screen spot diameter increase Dsp due to the spherical aberration of the main lens, the screen spot diameter increase Dst due to the silent velocity dispersion and space charge effect, and the combined spot diameter value Dt of these values, which were determined by analysis. An example is shown. The analysis conditions are as follows.

・Main lens-shadow mask distance: 340nn・G4
Electrode 11 potential: 25kV-G3 electrode 12
Potential Near kV/Beam current
:4mA・Main lens aperture
: φ5.5m and φ8m The main lens aperture φ5.5on is approximately the upper limit value of the normal cylindrical lens aperture for a color cathode ray tube with an outer diameter of 29 m (inner diameter 23 mm) at the neck portion of the glass envelope 1. The main lens with a diameter of φ5.5m has a large spherical aberration, so it has a diameter of φ8nwn.
1 composite spot diameter 1 compared to when using a main lens of
) The value of c is large. At this time, in order to obtain the screen spot diameter, the influence of aberrations of the cathode lens and the brisfocal lens should also be considered, but they are not taken into consideration here. It can be seen that for a main lens with an aperture of φ5.5 mm, when the main lens exit beam diameter becomes 1.5 nn or more, the influence of the main lens spherical aberration becomes stronger and the combined spot diameter Dt gradually increases.

On the other hand, in the case of a main lens with a diameter of φ8+na+, Dt starts to increase when the main lens exit beam diameter becomes 2 m or more.

This main lens with an aperture of 8 m cannot be realized using a cylindrical lens for color cathode ray tubes in countries where the outside diameter of the neck portion is 29 m, and it is necessary to use a main lens with a non-circular electrode aperture shape. Although it is possible to achieve an aperture diameter of φ8 m even with a cylindrical lens by enlarging the diameter of the neck portion, this is not preferable since it causes an increase in the deflection power.

〔Example〕

FIG. 1 schematically shows an embodiment using a main lens having a non-circular aperture shape as disclosed in Japanese Patent Laid-Open No. 58-103752. Here, the main lens has 63 electrodes 101°G4 electrodes 102. G5 electrode 103. G61 is constituted by pole 104. G3 electrode 101. The G5 electric FA 103 has a common medium potential Vi, and the G4 electrode 102 has the G2 electrode 9.
A common low potential Vow and a high potential Eb are applied to the G6 electrode. G3. G4. A unipotential lens is formed by the G5 electrodes 101, 102, 103, and a pi potential lens is formed by the G5, 06 electrodes 103, 104, so this main lens is called a unipotential lens which is a combination of two types of lenses. .

A main lens that is composed of two or more types of lenses in this way is called a multistage main lens.

A single horizontally long non-circular aperture is provided on the electrode-opposing surface of the pi-potential lens portion, and further G5 electrodes 103 and G6 electrodes are provided.
Electrode plate 1 with an elliptical aperture inside the electrode 104
05, 106 are provided. This pi-potential lens section, which is designed to be accommodated in a neck section with an aperture of approximately 8 m, an outer diameter of 29 IIn, and an inner diameter of 23 IlIII, has characteristics equivalent to those of a cylindrical lens.

FIG. 4 shows the results of analyzing changes in the screen spot diameter with respect to the main lens exit beam diameter by varying the length of each electrode of the main lens in this example. Here, the spot diameter is analyzed by computer simulation, and in addition to the various factors considered in Figure 3, a prefocus lens is used.

Aberrations of the cathode lens are also taken into account. The analysis conditions are the same as those for FIG. 3, and the main lens aperture is 8 m.

Figure 4 shows that the screen spot diameter can be reduced by increasing the main lens exit beam diameter. This results in an enlargement of the screen spot diameter. However, from Figure 4, we also see that G
It can be seen that reducing the distance g2-3 between the poles 10.101 reduces the screen spot diameter for the same main lens exit beam diameter. In other words, the resolution of the entire screen can be improved without increasing the non-uniformity of resolution between the periphery and the center of one screen.

However, from FIG. 4, it can be seen that this screen spot diameter reduction effect is limited to cases where the main lens exit beam diameter is 1.61 or more, and is not effective for values smaller than that.

When a cylindrical lens with an aperture of 5.5- is used, if the main lens exit beam diameter is set to 1.6 mo+ or more, the main lens aberration increases, and the screen spot diameter increases on the contrary. Therefore, even if g2-3 is shortened, the diameter is φ5.5.
The ns* cylindrical lens does not have the effect of reducing the screen spot diameter.

FIG. 5 shows the results of similar analysis performed for various gx and -s values to determine the screen spot diameter when the main lens exit beam diameter is 1.9 m+.

Figure 5 also shows the results of a similar analysis performed on a cylindrical lens with an aperture of φ5.5 threshold. It can be seen that the screen spot diameter is rapidly reduced when the normalized value g2-s/L)l becomes 2 or less, and approaches a constant value from 0.9 or less.

75% of screen spot diameter reduction when g x-s/D 1 changes from 2.5 to 0.7
gz-3/Di is 1 to reduce the spot diameter to
．． Must be 4 or less. Further, it is not preferable to shorten gz-8 because sparks are likely to occur between the G2 electrode 10 and the G3 electrode 101.

Therefore, this is the range in which the effect of reducing the screen spot diameter disappears. Reducing gz-3 to gx-s/φOf<0.9 is not only ineffective, but also causes performance deterioration.

From the above, the optimal range of g2-s/D1 is 0.9
< gz-s/ D 1 < 1.4.

It can also be seen from FIG. 5 that in the case of a lens with a diameter of φ5.5, shortening gz-8 has no effect on reducing the screen spot diameter.

Furthermore, in order to set the main lens exit beam diameter to an optimum value in this way, it is best to find the optimum combination of the electrode lengths of the multi-stage main lens as shown in FIG. Shortening gz-8 increases the main lens exit beam diameter. Also, if a main lens with a large effective aperture is used, the lens strength will be weak, so
FIG. 2: In order to focus the electron beam on the shadow mask 4 at a predetermined position within a predetermined Vn value range using a pi-potential lens such as the conventional example, the 03 electrode 11
It is necessary to lengthen the G1 electrode, which also leads to an increase in the main lens exit beam diameter.

A technique has been used to suppress the main lens exit beam diameter by changing the electrode dimensions of the G2 electrodes 9 and 10, but this tends to increase aberrations and also has a narrow variable range.

Therefore, if the main lens exit beam diameter becomes larger than the optimum value, in order to suppress this, it is recommended to change the length of each electrode of the multi-stage main lens, without causing an increase in aberrations, and to spread the main lens exit beam diameter over a wide range. This is preferable because the diameter can be controlled.

FIG. 6 shows the results of analyzing the relationship between the screen spot diameter and the G3 inter-electrode hole diameter Dδ when the main lens exit beam diameter is 2.0 on. The conditions for analysis are as described in Section 4 above.
Same conditions as for the figure, gz-3/Di is 1.2
It is.

As can be seen from FIG. 6, when the value of D3/DI exceeds 3, the spot diameter increases rapidly. therefore.

L) 3 / D 1 < 3 It is necessary to do so.

〔Effect of the invention〕

According to the present invention, since the effect of reducing prefocus lens aberration can be exhibited, the screen spot diameter can be reduced and resolution can be improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view and a cross-sectional view taken along line A-A of the main part of an electron gun according to an embodiment of the present invention, FIG. 2 is a horizontal cross-sectional view of a color cathode ray tube equipped with a conventional electron gun, and FIG. Single spherical aberration, silent velocity dispersion, and space charge effect when using various cylindrical lenses as the main lens. And a graph that analytically determined the relationship between each spot diameter and the main lens exit beam diameter by combining these. FIGS. 4, 5, and 6 are graphs showing the results of determining the screen spot diameter by computer simulation for the embodiment shown in FIG. 1, respectively. 1...Glass envelope, 2...Face plate, 3
... Fluorescent screen, 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, 15.17...outer beam central axis, 16...
Central beam center axis, 18.19...G4 electrode outer perforation center axis, 101...G3 electrode, 102...G4 electrode, 103...G5 electrode, Figure 1 AA 100° view broom 3fZ 】Noi Main>Screen output)Bee width 1min (*7Q)Cow 4 Figure: Kozuki Ono, 5
2 2',j
ll-en spa and lobby beam diameter (h 夙)

Claims (1)

[Scope of Claims] 1. Consisting of a three-pole section composed of a cathode, a G1 electrode, and a G2 electrode, and a main lens section composed of at least a pair of electrodes, a G3 electrode and a G4 electrode. There is a relationship of 0.9<g_2_-_3<D1<1.4 between the G1 electrode hole diameter D1 and the G2 electrode G3 electrode spacing g_2_-_3, and furthermore, the opposing surfaces of at least one pair of electrodes constituting the main lens An electron gun for a color picture tube, characterized in that the shape of the electrode opening is non-circular. 2. The electron gun for a color picture tube according to claim 1, wherein the main lens portion is a multistage main lens constituted by at least two or more pairs of electrodes. 3. The color picture tube according to claim 1, wherein there is a relationship of D3/D1<3 between the G2 electrode side electrode aperture diameter D3 of the G3 electrode and the G1 electrode aperture diameter D1. electron gun.