JPH047530B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a high voltage processing method for suppressing the occurrence of cracks in the neck glass in a cathode ray tube and obtaining good high voltage characteristics.

[Prior art] Generally, when performing high voltage processing on cathode ray tubes,
As shown in FIG. 1, a heater 1, a cathode 2, a first grating 3, a second grating 4, and a focus electrode 5
is set at ground potential, the anode 6 is connected to a high voltage power source 7, and a voltage of 1.5 to 3.5 times the rated voltage of the anode of the cathode ray tube is applied.

When a high voltage as described above is applied to the anode 6, the anode 6 and the focus electrode 5, or the anode 6 and the first,
A discharge occurs between the second grids 3 and 4, and the electrode surface is gradually cleaned. However, if the energy during this discharge is too large, or if the electric charge is charged on the inner surface of the mesh glass 8 and the electrode If a discharge occurs between the two, cracks may occur on the inner surface of the neck glass 8. This crack increases rapidly when the applied voltage is increased, so the voltage cannot be increased above a certain level.

On the other hand, the characteristics of cathode ray tubes improve as the applied voltage increases, but due to the occurrence of cracks in the neck glass 8 as described above, it is not possible to increase the applied voltage, and it is difficult to maintain sufficient voltage resistance characteristics. It was difficult to obtain a cathode ray tube with high quality.

In particular, recently developed cathode ray tubes with a net glass 8 having an outer diameter of 22.5φ are
Since the distance between the inner surface and the focus electrode 5 is narrow, the neck glass 8 is likely to crack, which has been a problem.

[Summary of the Invention] This invention was made to eliminate the above-mentioned conventional drawbacks, and by inserting a discharge circuit between the focus electrode and the ground, the generation of cracks in the neck glass is eliminated and good withstand voltage characteristics are achieved. An object of the present invention is to provide a high-voltage processing method that allows a cathode ray tube to be obtained.

[Embodiments of the Invention] Examples of the invention will be described below with reference to the drawings.

FIG. 3 shows an example of a high voltage processing method attempted prior to the present invention, in which a discharge circuit 9 is interposed between the focus electrode 5 and the ground, and the heater 1, the cathode 2, the first grid 3, and the second grid 4 are is set to earth potential as before. The discharge circuit 9 consists of a pair of sharp discharge electrodes facing each other with an air gap in between.

In such a high voltage processing apparatus, when a high voltage is applied to the anode 6 from the high voltage power supply 7, the high voltage is applied between the focus electrode 5 and the anode 6. At this time, if there is a minute protrusion on the surface of the focus electrode 5, electric field concentration occurs there and field emission occurs. A discharge circuit 9 is inserted between the focus electrode 5 and the ground, but its insulation resistance is quite high, so even if the field emission described above is minute, the voltage applied to the focus electrode 5 becomes high, and the discharge circuit finally closes. 9 starts corona discharge.

When discharging in this state, intraluminal discharge occurs between the focus electrode 5 and the anode 6. The frequency of tube discharge is high at the beginning of high-voltage processing of cathode ray tubes, and gradually decreases. Therefore, at the beginning,
In-tube discharge occurs at the same time as the discharge circuit 9 generates corona discharge, and there is almost no time difference, but as the frequency becomes lower, the time difference between the corona discharge in the discharge circuit 9 and the in-tube discharge becomes large. Become.

Corona discharge generally has a pulsed discharge current, or
Alternatively, since it has a property of constantly changing, the voltage across the discharge circuit 9 becomes higher or lower. Therefore, the voltage applied to the focus electrode 5 and the anode 6 is a voltage that constantly changes depending on the magnitude of corona discharge in the discharge circuit 9, and intraluminal discharge is likely to occur. When an intraluminal discharge occurs, this discharge current flows from the anode 6 through the focus electrode 5 to the discharge circuit 9, so that the discharge energy becomes small. Therefore, Netsuku Glass 8
Cracks are less likely to occur.

In experiments using many cathode ray tubes, when a discharge circuit 9 is inserted between the focus electrode 5 and the arm, the anode applied voltage that causes a crack in the neck glass 8 is lower than when the focus electrode 5 is directly grounded. 50~ of the discharge starting voltage of circuit 9
It will be 80% more expensive. For example, if the discharge starting voltage of the discharge circuit 9 is 10KV, then in the circuit of FIG.
It is possible to increase the voltage to 8KV, and only when this voltage is applied will the rate of occurrence of cracks in the neck glass 8 be the same as before.

On the other hand, there is almost no difference in the withstand voltage characteristics of the cathode ray tube due to the insertion of the discharge voltage path 9, so the characteristics obtained when voltage processing is performed by increasing the anode voltage of the conventional circuit by 5 to 8 KV are This was obtained by using the circuit shown in the figure.

Note that if the discharge electrode of the discharge circuit 9 has a flat tip and is less likely to cause corona discharge, it is possible to increase the anode voltage without causing a crack in the net glass 8, but the withstand voltage characteristics of the cathode ray tube are Since the improvement is not so great, no effect can be seen with such a discharge electrode. That is, a discharge electrode having a relatively sharp tip is desirable.

Also, as shown in Fig. 2, a resistor 10 may be inserted between the focus electrode 5 and the ground, or the focus electrode 5 may be
In a high-voltage processing circuit where the socket is floated from the ground, discharge may occur between the socket pins, causing the same phenomenon as in this invention, but the dielectric strength between the socket pins varies widely, and moreover, recent sockets have a focus electrode of 5. Since the pins are silo type and the dielectric strength exceeds 20KV, it is difficult to obtain the desired characteristics. Note that the appropriate discharge starting voltage of the discharge circuit 9 is 7 to 15 KV.

In FIG. 4, a solid varistor is used instead of the discharge circuit 9.
For example, in this embodiment, a ZNR element manufactured by Matsushita Electronics Co., Ltd. with a current capacity of 1000 to 2000 A is used. When this solid varistor 10 is used, the discharge starting voltage of the solid varistor 10 is 70~
Even when processed at a high voltage by adding 100% of the voltage to the anode voltage, the cracks in the Nekku Glass 8 are the same as when processed using the conventional circuit shown in Figure 1, and the withstand voltage characteristics of the cathode ray tube are In the circuit shown in FIG. 1, characteristics comparable to those obtained when a voltage of 70 to 100% of the discharge starting voltage of the solid-state varistor 10 is added to the anode voltage were obtained.

It is not necessarily clear why using a solid varistor in this way provides better characteristics than using an air gap, but for example,
In the case of a ZNR element, even if a discharge occurs, the terminal voltage of the element does not always drop below several KV, so the discharge energy of the cathode ray tube is limited to a certain limit value.
It can be considered that this reduces the occurrence of cracks in the neck glass 8.

[Effects of the Invention] As described above, according to the present invention, since the solid varistor is interposed between the focus electrode and the ground, the discharge energy is reduced, which has the effect of suppressing the occurrence of cracks in the glass. be.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a conventional high voltage processing method for cathode ray tubes, Fig. 2 is a circuit diagram showing an example of another conventional high voltage processing method, and Fig. 3 is a circuit diagram showing an example of another conventional high voltage processing method. FIG. 4 is a circuit diagram showing an embodiment of the high voltage processing method according to the present invention. DESCRIPTION OF SYMBOLS 1... Heater, 2... Cathode, 3... First grating, 4... Second grating, 5... Focus electrode, 6
...Anode, 7...High voltage power supply, 10...Solid varistor. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A high voltage processing method for a cathode ray tube, characterized in that the heater, cathode, and grid electrode are set to ground potential, a solid varistor is interposed between the focus electrode and the ground, and a high voltage is applied to the anode. .