GB1580011A

GB1580011A - Television picture tubes

Info

Publication number: GB1580011A
Application number: GB522/78A
Authority: GB
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1977-01-17
Filing date: 1978-01-06
Publication date: 1980-11-26
Also published as: DE2801916C2; FR2377700B1; JPS5389360A; FR2377700A1; NL186413B; SE7800502L; SE435881B; NL7800552A; NL186413C; AU501297B1; DE2801916A1; BR7800242A

Description

(54) TELEVISION PICTURE TUBES (71) We, SONY CORPORATION, a corporation organised and existing under the laws of Japan, of 7-35 Kitashinagawa-6, Shinagawa-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to television picture tubes.

In a conventional colour television picture tube, a high voltage of 25 to 30 KV is applied to a last accelerating electrode of an electron gun unit and a picture screen through an anode button mounted at the funnel portion of a picture tube. At the same time, a voltage of 0 to 5KV is applied to a focussing electrode forming a focussing electron lens positioned near the last accelerating electrode, through a terminal pin provided at the end of a neck portion of the picture tube.

In order to make a small beam spot on the picture screen, which results in a more precise and clear picture, it is desirable to reduce the aberration of the focussing lens as much as possible. To do this, it is necessary to decrease the voltage gradient between the electrodes. To achieve this, there are such methods as increasing the distance between the electrodes and/or applying similar voltages to the electrodes.

In the case of applying similar voltages to the electrodes, it is necessary to apply a high voltage of more than 10 KV to the focussing electrode next to the last accelerating electrode. Such a high voltage cannot be applied through a terminal pin provided at the end of the neck portion of the picture tube, because an electric discharge occurs in the form of a spark between the terminal pin and the other terminal pins which supply voltages to other electrodes of the electron gun unit, for example, heaters. It can be supplied through another button provided at the funnel portion, but this complicates the assembly substantially increases the cost.

In the case of a "Trinitron" (our Registered Trade Mark) picture tube, three electron beams are focussed by passing through the centre of a single electron lens of large diameter. The three focussed electron beams are deflected to hit the same position of an aperture grille provided in front of the picture screen, by four convergence electrodes provided at the downstream end of the electron gun unit and which provide respective passages therebetween for each of the electron beams. Two inner convergence electrodes are supplied with the same potential as the anode potential. Two outer convergence electrodes are supplied with a lower voltage than the anode potential by 0.4 to 1.5KV, so that the electron beams which pass through the convergence electrodes are deflected to the side of the centre beam.

At one time, the voltages were applied through another button provided at the funnel portion and an electrically shielded cable connected to the button and the outer electrodes.

Now, a co-axial anode button which has two cylindrical electrodes electrically insulated from each other, is used to provide an anode voltage through an outer electrode of the anode button, and a convergence voltage through an inner electrode of the anode button and an electrically shielded cable connecting the inner electrode and the convergence electrodes. With the above coaxial anode button, it is not necessary to provide two buttons at the funnel portion of the picture tube. However, it is still troublesome to connect the inner electrode of the anode button to the outer convergence electrodes by the electrically shielded cable.

Other specific disclosures of possible interest are our Japanese Publication No.

40987/72, our US Patent No. 3 514 663 and US Patent No. 3 932 786.

According to the present invention there is provided a television picture tube including an electron beam generating system arranged in the neck portion of the bulb of the tube and comprising a plurality of electrodes which are aligned along the axis of said neck portion and serve for focussing and accelerating the electron beam generated by a cathode, and a resistor including an insulating substrate and a resistive path formed thereon and which extends along said electrodes, one end of the resistor being supplied in use with the same voltage supplied to the screen of the picture tube and the other end of the resistor being supplied with a substantially lower voltage, the resistor having resistor taps from which voltages of differing values can be derived for supply to said electrodes, and wherein said other end of said resistor is conductively connected to a terminal pin which extends through the closed end of said neck portion and to which in use a voltage is supplied which is low enough to avoid electric discharges between said electrodes and said terminal pin.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an electron gun unit of an embodiment of television picture tube according to the invention; Figure 2 is a schematic drawing to show the connection between electrodes and a resistor of the unit of Figure 1; Figure 3 is a schematic side elevation to show the unit of Figure 1 sealed in a neck portion of the picture tube; Figure 4 is a cross-sectional view taken on the line IV-IV in Figure 3; Figure 5 is a schematic side elevation to show the electron gun unit of another embodiment of television picture tube according to the invention sealed in a neck portion of the picture tube; Figure 6 is a cross-sectional view taken on the line VI-VI in Figure 5; and Figure 7 is a diagrammatic plan view of a colour picture tube having an electron gun of the type illustrated in Figure 1, but not showing the resistor thereof.

In the first embodiment, an electron gun unit with a uni-potential electron lens is applied to a "Trinitron" (RTM) colour television picture cathode ray tube.

As seen in Figures 1,2 and 7, the picture tube includes a neck portion 23 and a funnel portion 30. A picture screen P closes the end of the funnel portion 30 and has an aperture grille AG in front of the screen P. An electron gun 1 (Figure 1) is mounted in the neck portion 23. The electron gun l includes three cathodes KR, KG and Ke aligned in a horizontal plane. The three cathodes KR. KG and KB are positioned behind a control grid G, which is followed by prefocussing grids G2 and G3.

Next in line is the main focussing lens which is formed by a grid G4. The grids G3, G4 and Gs are accelerating grids. Thereafter, there are formed plate-like convergence electrodes 8 and 9, and 11 and 12. In passing to the screen P, the electron beam from the cathode KR passes through associated apertures in the grid Gl and the grid G2, respectively, then through the grids G3, G4 and Gs, and finally between the convergence electrodes 9 and 12. The electron beam from the cathode KG passes straight through the electron gun 1 and out between the convergence electrodes 8 and 9 before reaching the aperture grille AG.The electron beam from the cathode KB passes through associated apertures in the grid GL and the grid G2, then through the grids G3, G4 and Gs, and finally between the convergence electrodes 8 and 11 before reaching the aperture grille AG.

A deflection yoke DY surrounds the neck portion 23 at the junction with the funnel portion 30.

A conductive carbon coating 24 is formed over the inner surface of the funnel portion 30 of the picture tube, and the carbon coating 24 also extends over the inner surface of the neck portion 23 of the picture tube back to the area of the convergence electrodes 8, 9, 11 and 12. A high voltage anode contact button 31 extends through the wall of the funnel portion 30 for applying a high voltage Eb to the carbon coating 24, to the screen P and the the aperture grille AG.

Figure 1 shows the electron gun unit which is sealed in the neck portion 23 of the picture tube, and Figure 2 shows a circuit diagram for the electrodes of the electron gun 1 and a resistor 15. There is provided a stem 2 made of glass, an evacuation pipe 3 integrally formed with the stem 2, and terminal pins 4 mounted on the step 2. The terminal pins 4 are connected to the various electrodes and to heaters for the cathodes KR, KG and KB.

The grids Gi, G2 G3 G4 and Gs are each of cylindrical shape and are arranged coaxially, being supported by a pair of supports 5 and 6 made of bead glass. The convergence electrodes 8 and 9 are attached to a flange portion 10 of the grid Gs, and the convergence electrodes 11 and 12 are supported by the supports 5 and 6 through a support 13.

A connecting member 14 is also integrally provided with the flange portion 10. As explained later, the connecting member 14 contacts the carbon coating 24 on the inner wall of the funnel portion 30, through which a desired high voltage Eb, which is the same as the voltage applied to the picture screen P (that is, the anode voltage), is supplied to the grid G5. A resistor 15 extends adjacent to the grids Gl to Gs supported at one end by a metal support 16, and at the other end by a lead 22.

The resistor 15 is formed by a printed resistive path 17 on one surface of a substrate made of an insulating material, for example, a ceramic substrate. The resistive path 17 is covered with a glass layer. The dimensions of the resistor 15 are, for example, 10 mm in width, 50 mm in length and 1.5 mm in thickness. An edge of the resistive path 17 and the grid Gs are electrically connected by the support 16, and the grid Gs and the grid Os are electrically connected by a lead 19. A tap b which is remote by a predetermined length from one end of the resistive path 17 and the grid G4 are electrically connected by a lead 20, and another tap a which is remote by a predetermined length from one end of the resistive path 17 is electrically connected to the convergence electrodes 11 and 12 by a lead 21.The other end of the resistive path 17 is electrically connected to a terminal pin 4a by a lead 22. The convergence electrodes 11 and 12 are electrically connected to each other.

The electron gun unit is sealed in the neck portion 23 of the picture tube, as shown in Figures 3 and 4. The carbon coating 24 is electrically connected to the anode button 31 provided on the funnel portion 30 of the picture tube, through which a high voltage of, for example, 30 KV is applied from externally. By the above construction, the high voltage applied to the carbon coating 24 is applied to the convergence electrodes 8 and 9 and the fifth grid Gs through the connecting member, and the same voltage is applied to the third grid G3 through the lead 19 and one end of the resistive path 17 through the support 16. Thus, the convergence electrodes 8 and 9 and the grids G3 and Gs are supplied with the same potential.The high voltage supplied from the anode button 31 is also applied to the screen P.

The high voltage applied to the end of the resistive path 17 is divided at the intermediate tape a by the voltage drop caused by the resistive path 17 between the high voltage end and the intermediate tape a, and the derived voltage is applied to the convergence electrodes 11 and 12 through the lead 21. It is also divided at the tap b to derive a lower voltage than the anode voltage by the voltage drop between the high voltage end and the tap b. and the derived voltage is applied to the grid G4 through the lead 20. There are provided claws on the leads 21 and 20 to be fixed to the intermediate taps a and b. Thus, the potential applied to the convergence electrodes 11 and 12 is a little lower than the potential applied to the convergence electrodes 8 and 9, and the potential of the fourth grid G4 is still lower than that.The other end of the resistive path 17 is electrically connected to the terminal pin 4a mounted in the stem 2 through the lead 22. The terminal pin 4a is connected to ground potential through a variable resistor 25. The variable resistor 25 is provided for fine control of the potential applied to the convergence electrodes 11 and 12 and the grid G4. The grids Oi and G2 are supplied with a predetermined voltage through predetermined terminal pins 4 from externally.

The resistive path 17 is made, for example, by printing and baking a mixture of binder, glass powder and resistive material, for example, metal oxide powder, on a substrate of a thin ceramic plate. An example follows.

A paste of 10 parts by weight of ruthenium oxide powder, 60 parts by weight of glass powder, and 30 parts by weight of binder of ethyl-cellulose is printed in a zig-zag pattern as shown in Figures 1 and 2, on a ceramic substrate. The printed substrate is then baked and the coating glass is applied on the resistive path 17. The resistance of the resistive path 17 is 500 megohms or more between the ends. In using the resistor to supply the required voltage, there is a tendency to increase the current loss, so it is desirable to suppress the current value to less than about 50 microamps.It is convenient electrically to connect and support the end of the resistive path 17 which is supplied with high voltage by the metal support 16 which is welded to the grid Os. The lead 22 welded to the terminal pin 4a is supporting the substrate and also electrically connecting the low voltage end of the resistive path 17. So, there are provided claws on the support 16 and the lead 22 to fix them to the substrate.

In this example, the length of the substrate is substantially the same as the length of the electron gun 1. Thus, it is possible to make the length of the resistive path 17 satisfactorily long, and accordingly, a satisfactorily large voltage drop can be achieved along the resistive path 17. Moreover, the voltage at the terminal pin 4a, that is the low voltage side, can be made close to ground potential and not exceeding 2 KV. Thus, the voltage control for the convergence electrodes 11 and 12 and the grid G4 can be achieved easily and safely. Of course, it is not necessary to provide the variable resistor 25 when the low voltage side is directly connected to ground or directly connected to a terminal of a predetermined potential.In this example, the convergence electrodes 8 and 9, the grid Gs and the grid G3 are supplied with 30 KV, the convergence electrodes 11 and 12 are supplied with about 29 KV, and the grid G4 is supplied with 12 KV. Thus, the positions of the intermediate taps a and b are selected to achieve suitable voltage drops.

The substrate with the resistive path 17 thereon is provided along the electron gun 1 and is supported so that the resistive path 17 does not contact the other electrodes. The respective voltage divider terminals (the high voltage end and the intermediate taps a and b) are supplying voltages to the grids Gs and G3, to the convergence electrodes 11 and 12, and to the grid G4. So, even if the voltage of the terminal 4a is controlled, there is no influence on the electron beam modulating system comprising a cathode KR, KG and KBN the grid G,, and the grid G2. As shown in Figures 1 and 4, the resistor 17 is provided on the opposite side to the bead glass support 5 and 6. So, it is not necessary to reduce the diameter of the electrodes or to widen the diameter of the neck portion 23.In the above example, both the convergence voltage and the focussing voltage are obtained by dividing the anode voltage using the resistor 15.

Of course, it it possible to arrange to obtain only the convergence voltage or only the focussing voltage. In the case when only the convergence voltage is obtained by dividing the anode voltage a low convergence voltage of 0 to 5 KV can be supplied through a terminal pin 4.

In a conventional picture tube, other than the "Trinitron" (RTM) picture tube, only the focussing voltage is obtained by dividing the anode voltage. Figures 5 and 6 show another embodiment applied to a picture tube which does not have the convergence electrodes 8, 9, 11 and 12 of Figure 1. Figures 5 and 6 show an example of the electron gun unit applied to a so-called unitized inline three beam hi-unipotential type electron gun, in which each grid electrode has a slightly flattened shape, and each grid electrode for three electron beams are formed integrally as one body. In Figures 5 and 6 elements corresponding to those in Figures 1 and 2 are designated by the same reference numerals.

The substrate formed with the resistive layer 17 is mounted on one of the supports 5 and 6 which support the grids G1 to G6 each of which has a, slightly flattened shape. There is provided a connecting member 14 on the grid G6 which contacts the carbon coating 24 of the neck portion 23. The grid G6 is electrically connected to the grid G4 through a lead 26 and is connected to one end of the resistive path 17 through another lead 27.

A voltage applied to the resistive path 17 is divided at the intermediate tap a and applied to the grid Gs through a lead 28. The grid Gs is connected to the grid G3 through a lead 29.

The grids G1 and G2 are connected to predetermined terminal pins 4. Thus, the grids G6 and G4 are supplied with the same high voltage (for example, 30 KV. that is the anode voltage). and the grids Gs and G3 are supplied with lower voltages than the above (for example, 12 KV), Or, the grid G3 iS separated from the grid Gs and connected to a different position of the resistive path 17 to be supplied with a differcnt voltage from that of the grid G5.

As shown in Figure 6, in this embodiment the substrate 15 is mounted on the support 5, because the electrodes are slightly flattened.

A similar supporting method to the first embodiment can be considered, in which the substrate is supported by the leads 27 and 22.

Moreover, the substrate 15 can be meltbonded to the support 5. It might be expected that directly printing and baking the resistive path 17 on the support 5 made of bead glass, would make a simplified structure. However, in this case, there is a problem that the resistance value of the resistive path 17 may change during the heat treatment for softening the bead glass supports 5 and 6. So in practice, the ceramic substrate formed with the resistive path 17 thereon is melt-bonded on the support 5.

Further, the ceramic substrate can be bonded to the bead glass support 5 after the beading operation. In this case, the substrate can be bonded by using low melting temperature glass or frit type ceramics, for example "Sumiseramu" (trade designation of Sumitomo Kagaku Corporation, Japan).

Suitable materials for the resistive layer other than ruthenium oxide include Ni-SiO type oxide, Cr-SiO type oxide, Ni-Cr type alloy, CuMn-type and Cr metal. These can be manufactured as thin films by a sputtering technique.

WHAT WE CLAIM IS: 1. A television picture tube including an electron beam generating system arranged in the neck portion of the bulk of the tube and comprising a plurality of electrodes which are aligned along the axis of said neck portion and serve for focussing and accelerating the electron beam generated by a cathode, and a resistor including an insulating substrate and a resistive path formed thereon and which extends along said electrodes, one end of the resistor being supplied in use with the same voltage as the voltage supplied to the screen of the picture tube and the other end of the resistor being supplied with a substantially lower voltage, the resistor having resistor taps from which voltages of differing values can be derived for supply to said electrodes, and wherein said other end of said resistor is conductively connected to a terminal pin which extends through the closed end of said neck portion and to which in use a voltage is supplied which is low enough to avoid electric discharges between said electrodes and said terminal pin.

2. A picture tube according to claim 1 wherein said resistive material comprises ruthenium oxide.

3. A picture tube according to claim 1 wherein said resistive path is coated with glass.

4. A picture tube according to claim 1 wherein a variable resistor is connected between said terminal pin and ground potential.

5. A picture tube according to claim 1 wherein said one end of said resistive path is

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. G3, to the convergence electrodes 11 and 12, and to the grid G4. So, even if the voltage of the terminal 4a is controlled, there is no influence on the electron beam modulating system comprising a cathode KR, KG and KBN the grid G,, and the grid G2. As shown in Figures 1 and 4, the resistor 17 is provided on the opposite side to the bead glass support 5 and 6. So, it is not necessary to reduce the diameter of the electrodes or to widen the diameter of the neck portion 23. In the above example, both the convergence voltage and the focussing voltage are obtained by dividing the anode voltage using the resistor 15. Of course, it it possible to arrange to obtain only the convergence voltage or only the focussing voltage. In the case when only the convergence voltage is obtained by dividing the anode voltage a low convergence voltage of 0 to 5 KV can be supplied through a terminal pin 4. In a conventional picture tube, other than the "Trinitron" (RTM) picture tube, only the focussing voltage is obtained by dividing the anode voltage. Figures 5 and 6 show another embodiment applied to a picture tube which does not have the convergence electrodes 8, 9, 11 and 12 of Figure 1. Figures 5 and 6 show an example of the electron gun unit applied to a so-called unitized inline three beam hi-unipotential type electron gun, in which each grid electrode has a slightly flattened shape, and each grid electrode for three electron beams are formed integrally as one body. In Figures 5 and 6 elements corresponding to those in Figures 1 and 2 are designated by the same reference numerals. The substrate formed with the resistive layer 17 is mounted on one of the supports 5 and 6 which support the grids G1 to G6 each of which has a, slightly flattened shape. There is provided a connecting member 14 on the grid G6 which contacts the carbon coating 24 of the neck portion 23. The grid G6 is electrically connected to the grid G4 through a lead 26 and is connected to one end of the resistive path 17 through another lead 27. A voltage applied to the resistive path 17 is divided at the intermediate tap a and applied to the grid Gs through a lead 28. The grid Gs is connected to the grid G3 through a lead 29. The grids G1 and G2 are connected to predetermined terminal pins 4. Thus, the grids G6 and G4 are supplied with the same high voltage (for example, 30 KV. that is the anode voltage). and the grids Gs and G3 are supplied with lower voltages than the above (for example, 12 KV), Or, the grid G3 iS separated from the grid Gs and connected to a different position of the resistive path 17 to be supplied with a differcnt voltage from that of the grid G5. As shown in Figure 6, in this embodiment the substrate 15 is mounted on the support 5, because the electrodes are slightly flattened. A similar supporting method to the first embodiment can be considered, in which the substrate is supported by the leads 27 and 22. Moreover, the substrate 15 can be meltbonded to the support 5. It might be expected that directly printing and baking the resistive path 17 on the support 5 made of bead glass, would make a simplified structure. However, in this case, there is a problem that the resistance value of the resistive path 17 may change during the heat treatment for softening the bead glass supports 5 and 6. So in practice, the ceramic substrate formed with the resistive path 17 thereon is melt-bonded on the support 5. Further, the ceramic substrate can be bonded to the bead glass support 5 after the beading operation. In this case, the substrate can be bonded by using low melting temperature glass or frit type ceramics, for example "Sumiseramu" (trade designation of Sumitomo Kagaku Corporation, Japan). Suitable materials for the resistive layer other than ruthenium oxide include Ni-SiO type oxide, Cr-SiO type oxide, Ni-Cr type alloy, CuMn-type and Cr metal. These can be manufactured as thin films by a sputtering technique. WHAT WE CLAIM IS:

1. A television picture tube including an electron beam generating system arranged in the neck portion of the bulk of the tube and comprising a plurality of electrodes which are aligned along the axis of said neck portion and serve for focussing and accelerating the electron beam generated by a cathode, and a resistor including an insulating substrate and a resistive path formed thereon and which extends along said electrodes, one end of the resistor being supplied in use with the same voltage as the voltage supplied to the screen of the picture tube and the other end of the resistor being supplied with a substantially lower voltage, the resistor having resistor taps from which voltages of differing values can be derived for supply to said electrodes, and wherein said other end of said resistor is conductively connected to a terminal pin which extends through the closed end of said neck portion and to which in use a voltage is supplied which is low enough to avoid electric discharges between said electrodes and said terminal pin.

electrically connected to and supported by a last accelerating electrode which in use is supplied with the same voltage as that of the screen of the picture tube.

6. A picture tube according to claim 5 wherein said other end of said resistive path is electrically connected to and supported by a terminal pin.

7. A picture tube according to claim 6 wherein said last accelerating electrode and said terminal pin have a metal claw to be fixed to said substrate of said resistor.

8. A picture tube according to claim 5 wherein in use three electron beams pass through the centre of the focussing electrodes and are deflected by one pair of inner and one pair of outer plate-shaped electrodes, so as to hit the same position of a mask provided in front of said screen, said inner pair of electrodes being supplied with the anode voltage, and said outer pair of electrodes being supplied with a lower voltage than said anode voltage derived from said intermediate tap.

9. A picture tube according to claim 5 wherein said resistor is positioned on one side of said electrode, and supports for said electrodes are positioned on the other side.

10. A picture tube according to claim 5 wherein three generally coplanar electron beams are produced by said system and said resistor is disposed substantially parallel to and out of said plane.

11. A television picture tube substantially as hereinbefore described with reference to Figures 1 to 4 and 7 of the accompanying drawings.

12. A television picture tube substantially as hereinbefore described with reference to Figures 1 to 4 and 7 as modified by Figures 5 and 6 of the accompanying drawings.