JPH0552020B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electron gun for a cathode ray tube, and more particularly to an electrostatic lens structure for an electron gun for focusing at least one, preferably more, electron beams. .

[Technical background and problems of the invention]

A cathode ray tube is equipped with at least one electron gun, which forms an electron beam spot on a predetermined target. One of the extremely important factors that determines the performance of the cathode ray tube in this electron gun is the spot diameter of the electron beam on the target. It goes without saying that a smaller spot diameter on the target is more desirable, but this spot diameter is determined by the performance of the electron gun. Generally, an electron gun consists of a part that generates an electron beam and a main lens part that accelerates and focuses the electron beam.One effective means of improving the performance of an electron gun is to improve the performance of the main lens part.

Most of the main lens parts are electrostatic lenses, which are formed by arranging a plurality of electrodes having openings coaxially and applying a predetermined potential. There are several types of such electrostatic lenses depending on the electrode configuration, but basically, the electrode aperture diameter is increased to form a large-diameter lens, or the distance between the electrodes is increased to create a gradual potential change. By forming a long focal length lens, lens performance can be improved.

However, since electron guns for cathode ray tubes are generally used enclosed in a thin glass cylinder, firstly the aperture of the electrodes, that is, the lens diameter, is physically limited, and then the focused electric field formed between the electrodes is The distance between the electrodes is limited in order to avoid being influenced by undesired electric fields. Particularly when multiple electron guns are used in a line, such as in a color picture tube, the smaller the electron gun spacing Sg, the easier it is to concentrate multiple electron beams on one point over the entire screen, and the more advantageous it is in terms of deflection power. be. Therefore, the electron gun spacing
In order to reduce Sg, the electrode openings have to be made even smaller.

In the above situation of electron guns for cathode ray tubes,
In order to further improve lens performance, the distance between the electrodes is kept small while forming a long focal length lens that is equivalent to increasing the distance between the electrodes.
USP3863091 specification, USP3895253 specification,
USP3995194 specification, USP3932786 specification,
Specifications such as USP4124810 have been proposed.

However, USP 3863091 and USP 3895253
The electron lenses shown in the specification both have a voltage of 25 to 30 K.V at the first electrode G ₃ (third grid) of the main lens part.
Since a high voltage is applied to the anode, discharge is likely to occur between it and the low voltage electrode of the electron beam generating section, making it impractical.

In addition, in the lenses of USP 3995194 and USP 4124810, three electrodes having the same diameter of the cylinder are sequentially set to low potential, middle potential, and high potential to form a gradual change in potential. Lens performance is achieved when the length of the medium potential electrode is substantially equal to the radius of the electrode aperture;
Lens performance cannot be improved beyond this point.

Therefore, to further improve lens performance
A multi-element bipotential lens has been proposed in USP 3,932,786, but in such an electron gun, the resistors placed near the multiple electrodes are too small, so there are no suitable ones for practical use. Manufacturing is extremely difficult because the potential has to be taken out from the body at even smaller intervals. Also, because the electrode intervals are small, leakage current easily flows between the electrodes, and undesired currents due to this leakage current and beam impact on the electrodes. There are problems such as the lens performance deteriorates if the electrode potential changes due to the influence, and furthermore, the structure is complicated, making it difficult to manufacture and putting it into practical use extremely difficult.

[Purpose of the invention]

An object of the present invention is to improve the lens performance of the main lens section of an electron gun for a cathode ray tube by a highly practical method, and to further reduce the diameter of a spot focused on a predetermined target.

[Summary of the invention]

In the cathode ray tube electron gun of the present invention, the main lens portion includes at least two electrodes each having an electron beam passing hole, and an opening at least partially located between these electrodes and larger than the electron beam passing hole of these electrodes. at least one auxiliary electrode having a hole, a relatively low potential and a relatively high potential are applied to the two opposing electrodes, and a relatively medium potential is applied to the auxiliary electrode. By adopting this structure, a long focal length lens with a substantially long inter-electrode distance can be formed and the lens performance can be improved.

[Embodiments of the Invention] The present invention will be described in detail below with reference to the drawings. FIG. 1 shows an example of an electron gun for a color picture tube embodying the present invention, FIG. 2 a is a Y-Z axis sectional view of FIG. 1, and FIG. 2 b is an X-Z axis sectional view of FIG. be. In FIG. 1, FIG. 2a, and FIG. 2b, an electron gun 1 has a plurality of electrodes, which will be described later, and a plurality of insulating supports 2 that support these electrodes. The plurality of electrodes are three electrodes for generating three electron beams 3a, 3b, and 3c that impinge on the red, green, and blue phosphor layers (not shown) of the phosphor surface as targets. A first cathode having an integrated structure includes cathodes 9a, 9b, 9c arranged in a row containing heaters 6a, 6b, 6c, and predetermined electron beam passage holes protruding from positions relative to these three cathodes. grid 1
1, 2nd grid 12, 3rd grid 13, 4th grid
It consists of a grid 14, a convergence electrode 15, and an auxiliary electrode 16 located between the third grid 13 and the fourth grid 14 and having one large opening, and is implanted and fixedly supported on the insulating support 2. . The first grid 11 and the second grid 12 are flat electrodes arranged close together, and the third grid 13
is the second grid 12 disposed close to and joined to the second grid 12.
It consists of four cup-shaped electrodes 23a and 23b.
The grid 14 consists of two cup-shaped electrodes 24a and 24b which are arranged at a predetermined distance from the third grid 13 and are connected to each other, and the convergence electrode 1
5 consists of one cup-shaped electrode 25a fixed to the fourth grid 14 by welding. Three circular electron beam passage holes aligned with each electron beam are provided on the bottom surface of the cup-shaped electrode and the plate-shaped electrode of each of the grid electrodes and the convergence electrode, respectively. The electron beam passage holes of the first grid 11 and the second grid 12 are relatively small, and the electron beam passage holes 33a, 33b, 33c of the third grid 13 facing the second grid 12 are larger. 13th 4th Grid 1
Electron beam passing holes 43a, 43 on the side facing 4
b, 43c and the electron beam passing holes 34a, 34b, 34c, 44a, 44b of the fourth grid 14,
44c has the same diameter and a relatively large diameter, and has the same diameter as the electron beam passing holes 35a, 35 of the convergence electrode 15.
b and 35c are smaller than that. The auxiliary electrode 16
consists of two cup-shaped electrodes 26a and 26b,
One large track field-like aperture 36, 46 is provided in its bottom surface.

One of the cup-shaped electrodes of the auxiliary electrode 16 is shown in FIG.
The cup-shaped electrode 23b of the third grid 13 is shown in FIG. 6b. As shown in FIG. 6, the diameter DX in the X direction and the diameter DY in the Y direction of the auxiliary electrode are set larger than the diameter dx in the X direction and the diameter dy in the Y direction, respectively, including the three beam passage holes of the third grid. That is, DX＞
dx, DY>dy. The convergence electrode 1
Approximately 25K is applied to the anode terminal (not shown) in 5.
A valve spacer 17 is attached to apply a high voltage of V. Such an electron gun is enclosed within a narrow glass cylinder neck 18, and a stem pin 19 is arranged at the bottom of the neck. This stem pin 19 supports and fixes the electron gun 1, and also allows each grid potential other than the coherence electrode 15 and the fourth grid 14 to be supplied from the outside through the stem pin 19.

In the above electrode configuration, each electrode potential is, for example, as follows. The cathode 9 is kept at a cut-off voltage of approximately 150V, to which a modulation signal is respectively applied. Ground potential is applied to the first grid 11, about 700V is applied to the second grid 12, and the third grid 13
about 6.5KV and about 25KV to the fourth grid 14.
An anode high voltage of 16 K.V. is applied to the auxiliary electrode 16, which is approximately an intermediate potential between the third grid 13 potential and the fourth grid 14 potential. In the electron lens part having such an electrode structure in the main lens part, the equipotential distribution is as shown in Figure 3a and Figure 3b.
It will look like this. Figure 3a corresponds to Figure 2a, Figure 3b corresponds to Figure 2b, and equipotential lines 2
0, and a simplified electrode structure is shown in order to explain the main lens portion of this electron gun. As can be seen from Figures 3a and 3b, the potential distribution is almost disordered in the areas approximately equivalent to the openings of the third grid 13 and fourth grid 14 that determine the diameter of the electron lens (inside the dotted line in the figure). First, as shown in FIG. 4, the state is equivalent to the state in which the distance between the two cylindrical electrodes is simply increased and the state is not affected by the surrounding electric field. Therefore, the axial potential distribution becomes quite gentle as shown in FIG. 5, the electro-optical magnification by this electron lens is reduced, and the spherical aberration coefficient is also reduced, so that the lens performance is significantly improved.

Simply increasing the distance between the two electrodes as shown in Figure 4 is not practical because, as mentioned above, the potential distribution will be disturbed by the influence of other electric fields within the network. However, as in the present invention, at least one auxiliary electrode having a diameter considerably larger than the electron lens aperture is disposed between two electrodes, and a potential approximately halfway between the two electrode potentials is applied to this auxiliary electrode. Therefore, other undesired electric fields within the network can be shielded and the necessary electric field of the electron lens section can be prevented from being disturbed. Therefore, as shown in FIG. 4, it is possible to form an electron lens with the same high performance as when the distance between the two electrodes is simply increased. At this time, the hole in the auxiliary electrode only needs to be one large hole, and unlike the other electrodes, three electron beam passing holes are not required, so the three holes are each made larger without changing the center distance. Even if this is not possible, the performance of the electron lens can be improved very easily by increasing the distance between the electrodes.

In the above embodiment, in order to completely eliminate the influence of the auxiliary electrode potential, the larger the electrode spacing between the third and fourth grids, the more the aperture diameter of the auxiliary electrodes can be reduced. It must be made larger than the pore diameter. If the aperture diameter of the auxiliary electrode is not sufficient, the electric field of the electron lens formed between the third and fourth grids will be disturbed, and the beam spot on the target will be distorted. The distortion of this beam spot is caused by the potential of the auxiliary electrode, the shape of the aperture,
It can be corrected by the position of the auxiliary electrode. For example, if the aperture diameter of the auxiliary electrode is track field-shaped and is not large enough, there may be a gap between the third grid with circular apertures and the track field-shaped auxiliary electrode, and similarly between the fourth grid and the auxiliary electrode. A kind of quadrupole lens is formed, and since the directions of lens action of the two quadrupole lenses are opposite, the direction of distortion of the beam spot changes depending on the potential of the auxiliary electrode. That is, when the auxiliary electrode potential is low, the beam spot becomes horizontally long, and when it is high, the beam spot becomes vertically long, so that the beam spot becomes circular when the potential is appropriate. This appropriate potential is a potential slightly lower than the intermediate potential between the third grid potential and the fourth grid potential. This is because even though the two quadrupole lenses have lens effects in opposite directions, the speeds and beam diameters of the beams in the lenses are different, and therefore the lens forces acting on the beams are different. The same effect as adjusting the auxiliary electrode potential can also be achieved by changing the shape of the openings on the third grid side and the fourth grid side of the auxiliary electrode, or by changing the shape of the holes on the third grid side of the auxiliary electrode. This can also be done by adjusting the position, ie, the distance between the third grid and the auxiliary electrode, and the distance between the fourth grid and the auxiliary electrode.
Of course, it is also possible to correct beam distortion using an electron lens section other than the auxiliary electrode. For example, astigmatism may be provided in advance in the electron beam forming section, and this astigmatism may be canceled out by the auxiliary electrode.

In the color picture tube electron gun of the above embodiment, three electron beams must be converged at one point on the shadow mask or screen (target), and several methods are known for this purpose. That is, there are a method of tilting and arranging the electron guns themselves on both sides, a method of tilting and forming the main lenses or other electron lenses on both sides, and a method of forming an asymmetric lens. Although these conventional methods can be used as they are in the present invention, the convergence can also be achieved by the structure of the auxiliary electrode in the present invention. That is, FIG. 7a, FIG. 7b
As shown in Figure 3, by making the X-direction diameter DX4 on the fourth grid side of the auxiliary electrode smaller than the X-direction diameter DX3 on the third grid side, the electron beams on both sides are slightly deflected toward the central electron beam. , to achieve convergence. This is X-
In the Z-axis cross section, the potential of the auxiliary electrode on the fourth grid side penetrates into the electron lens part more than the potential of the auxiliary electrode on the third grid side, and since this potential is lower than the average potential at that position, the electrons on both sides This is because the beams 3a and 3c receive force inward. Alternatively, as shown in FIGS. 8a and 8b, two auxiliary electrodes 16-1 and 16-2 are used, and these auxiliary electrodes are provided with a potential approximately midway between the potential of the third grid 13 and the potential of the fourth grid 14. Although applied, the fourth grid 1
For the same reason, the above convergence can also be achieved by making the potential of the auxiliary electrode 16-2 on the fourth grid side slightly lower than the potential of the auxiliary electrode 16-1 on the third grid side. At this time, the electrode lengths of the two auxiliary electrodes may also be appropriately varied and adjusted. Incidentally, FIGS. 7a and 8a show the Y-Z axis cross section as in FIG. 2, and FIGS. 7b and 8b show the XZ axis cross section, respectively.

In the embodiment described above, the potential of the auxiliary electrode is supplied from the outside through the stem pin, but the present invention is not limited to this, and the potential may be supplied by resistance division. For example, as shown in FIG. 9, a glass coat 53 has a resistive material 51 and a connecting portion 52 arranged on a thin ceramic substrate 50.
A resistor 54 is installed behind the insulating support 2 that supports each electrode of the electron gun 1 as shown in FIG. Connect one end to the stem pin 19 and connect the ground voltage 5 externally.
5 or low voltage source 56 or resistor 57, and connect an appropriate position to an auxiliary electrode. With such a configuration, the electrical configuration is as shown in FIG. 11, and the auxiliary electrode is supplied with a voltage divided by the resistor of the anode high voltage Eb. As such a resistor 54,
It is preferable to use a material mainly composed of palladium or ruthenium-based oxides, and a mixture of ruthenium oxide and glass is particularly preferable. In the embodiment shown in FIG. 10, the resistor is in the form of a single plate and installed behind the insulating support 2, but the present invention is not limited to this. It goes without saying that the scope of the present invention also includes a structure in which a plurality of resistors are used, a resistance material is applied directly behind the insulating support, or a structure in which the insulating support itself is used as a resistor.

Further, in the embodiment shown in FIG. 10, one of the resistors is connected to the stem pin, but the present invention is not limited to this, and the resistor may be connected to other grids such as the third grid, or as shown in FIG. It goes without saying that the third grid potential may also be supplied by resistance division.

As described above, if the auxiliary electrode potential is supplied by resistor division, there is no need to supply a medium-high voltage auxiliary electrode potential at the stem portion, and the withstand voltage reliability around the stem portion is improved, which is highly practical. We can provide cathode ray tubes. Furthermore, if the third grid potential is also supplied by resistor division, the reliability of withstand voltage around the stem part will be further improved, and since the third grid potential can be controlled at a low potential via the stem pin, it will be possible to dynamically control the electron lens. It becomes easy to adjust the focusing state.

In addition, lowering the anode high voltage to approximately ground voltage through a high resistor can greatly reduce the undesirable spark current generated within the picture tube, and the effect on the picture tube operating circuit can be significantly reduced. Another great advantage is that the tube operating circuit transistors, ICs, etc. can be protected from spark currents within the picture tube.

The electron gun structure of the above embodiment is completely different from the structure shown in the above-mentioned US Pat. No. 3,932,786.

In other words, the resistor can be quite large, it can be easily attached to the electrodes, and it is extremely easy to manufacture.Also, since the distance between the electrodes is wide, it is difficult for leakage current to flow between the electrodes. The structure of the auxiliary electrode makes it easy to adjust the convergence, the focusing power of the beam in the vertical and lateral directions, and the beam shape distortion. Also, as in the electron gun disclosed in USP 3,932,786, multiple electrodes and multiple potentials to be supplied thereto are not required, but as in the electron gun in USP 4,124,810, only one electrode and Depending on the potential, lens performance equivalent to that of the electron gun disclosed in US Pat. No. 3,932,786 can be obtained. Therefore, a resistor-divided voltage is not necessarily necessary, and it has many advantages such as the ability to obtain a single medium-high voltage even through a stem pin. Therefore, the electron gun of the present invention is extremely useful as an electron gun with a high-performance electron lens. Highly practical.

Further, in the above embodiments, the auxiliary electrodes were arranged between the third grid and the fourth grid at predetermined intervals, but the present invention is not limited to this.
Even if the auxiliary electrode covers one or both of the third and fourth grids as shown in FIG. 3, the effects of the present invention will not change. When the auxiliary electrode covers the electrodes on both sides as shown in Figure 13, the influence of undesired electric fields on the inner wall of the network can be completely shielded, thereby eliminating convergence, which is a problem in conventional color picture tubes. It is possible to completely prevent the aging of the inner wall of the network due to electric charges, and provide a color picture tube with excellent performance.

Furthermore, the main lens portion of the above embodiment is basically a bipotential lens consisting of two electrodes, a third grid and a fourth grid, and has an auxiliary electrode having a large aperture arranged between the electrodes. However, the present invention is not limited to this, and may be based on a unipotential lens as shown in FIG. 14a, or may be based on a quadrapotential lens as shown in FIG. As shown in FIG. c, the essence of the present invention does not change even if a periodic potential type lens is used as the basis, or other tripotential type lenses are used as the basis. Note that FIGS. 14a to 14c show schematic configuration diagrams of the main lens part, and the present invention is applied by disposing auxiliary electrodes in all the parts where the electron lens is formed. It goes without saying that the present invention may be applied only to the electronic lens section. In particular, in the lens systems shown in Figures 14b and 14c, the voltage of the third grid _G3 can be set to approximately 8 to 9 K.V., so the quality of the electron beam from the object point forming section can be used in the best possible condition. This will further improve the overall performance of the electron gun.

Furthermore, although the above embodiment has a structure in which three electron guns are integrated in a row in the horizontal direction, the present invention is not limited to this, and the present invention can also be applied to structures in which three electron guns are arranged in an equilateral triangle shape, It goes without saying that the present invention can be applied to a structure in which a large number of electron guns are arranged or a structure in which only one electron gun is arranged.

〔Effect of the invention〕

As described above, according to the present invention, the main lens portion is located at least partially between at least two electrodes each having an electron beam passing hole, and has an opening larger than the electron beam passing hole of these electrodes. at least one auxiliary electrode having a hole, a relatively low potential and a relatively high potential are applied to the two opposing electrodes, and a relatively intermediate potential is applied to the auxiliary electrode. By adopting such a structure, a long focal length lens having a substantially long distance between electrodes can be formed without any practical problems. The electron gun of the present invention has a simple structure and is easy to manufacture. Therefore, it is possible to provide a highly practical and high-performance electron gun for cathode ray tubes.

In addition, in the electron gun of the present invention, a high-performance electron gun can be obtained without increasing the beam spacing between multiple electron beams, that is, the distance between the electron beam passing holes, so that it is possible to obtain a high-performance electron gun without increasing the beam interval between the plurality of electron beams, that is, the distance between the electron beam passing holes. Moreover, it can be used as a high-performance electron gun with good convergence quality.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, and is a side sectional view of an electron gun for a color picture tube, FIGS. 2a and 2b are sectional views along the Y-Z axis and the X-Z axis of FIG. Third
Figure a, Figure 3 b, and Figure 4 are equipotential line distribution diagrams for explaining the present invention, and Figure 3 a and Figure 3 b are cross sections corresponding to Figure 2 a and Figure 2 b, respectively. Figure 4 is a cross-sectional view of the coaxial cylindrical lens, Figure 5 is an axial potential distribution diagram in Figure 4, and Figures 6a and 6b are of the electrodes used in the embodiment of Figure 1. Perspective views, Figure 7a, Figure 7b and Figure 8a, Figure 8
Figure b shows another embodiment of the present invention, and Figure 7a
8a, 7b, and 8b are sectional views along the Y-Z axis and X-Z axis, respectively, FIG. 9 is a sectional view showing a part of the resistor, and FIG. An example of the present invention when using a resistor as shown in FIG. 9, FIG. 11 is an electrical configuration diagram of FIG. 10, FIG. 12 is another example corresponding to FIG. 10, and FIGS. 13 and 14. Figure a, 1st
4b and 14c are side sectional views showing other embodiments of the present invention. 1... Electron gun, 2... Insulating support, 3a, 3
b, 3c...Electron beam, 13...Third grid, 14...Fourth grid, 15...Convergence electrode, 16...Auxiliary electrode, 54...Resistor.

Claims (1)

[Scope of Claims] 1. An electron gun for a cathode ray tube comprising at least an electron beam generating section and a main lens section for focusing the electron beam onto a predetermined target, wherein the main lens sections each have an electron beam passing hole at least opposite to each other. and at least one auxiliary electrode, at least a portion of which is located between these electrodes and has an aperture larger than the electron beam passage aperture of these electrodes; An electron gun for a cathode ray tube, comprising an electrode group to which a relatively low potential and a relatively high potential are applied, and a relatively intermediate potential is applied to the auxiliary electrode. 2. The relatively medium potential applied to the at least one auxiliary electrode is divided from the relatively high potential applied to the main lens part by a resistor disposed near the main lens part. Claim 1 characterized in that the resistor division potential is
Electron gun for cathode ray tube as described in Section 3. 3. Each of the at least two opposing electrodes disposed in the main lens portion has a plurality of openings corresponding to the electron beams in order to allow the plurality of electron beams to pass through each opposing surface, and the auxiliary electrode has a plurality of openings corresponding to the electron beams. 2. The electron gun for a cathode ray tube according to claim 1, wherein the aperture is one aperture that fully encompasses the plurality of apertures. 4. Each of the at least two opposing electrodes disposed in the main lens portion has a plurality of openings corresponding to the electron beams in order to allow the plurality of electron beams to pass through each opposing surface, and the auxiliary electrode has a plurality of holes corresponding to the electron beams. The aperture is an aperture that sufficiently encompasses the plurality of apertures, and the aperture diameter of at least one of the electron beam incident side and electron beam exit side of the aperture of at least one of the auxiliary electrodes is different. Claim 1
Electron gun for cathode ray tube as described in Section 3. 5. Each of the at least two opposing electrodes disposed in the main lens portion has a plurality of openings corresponding to the electron beams in order to allow the plurality of electron beams to pass through each opposing surface, and the auxiliary electrode has a plurality of openings corresponding to the electron beams. The aperture is an aperture that sufficiently encompasses the plurality of apertures, and the shape of the aperture on the electron beam incident side and the electron beam exit side of the aperture of at least one of the auxiliary electrodes is different from each other. An electron gun for a cathode ray tube according to scope 1.