JP3146061B2 - Cathode ray tube and cathode ray tube image display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube and a cathode ray tube image display device, and more particularly to a countermeasure against a leakage electric field generated from the cathode ray tube and the cathode ray tube image display device.

[0002]

2. Description of the Related Art With the remarkable development of OA equipment in recent years, OA equipment has become familiar even in offices and homes. Under such circumstances, techniques related to leakage electromagnetic field shielding have become important in terms of preventing noise in electronic devices and preventing the effects of electromagnetic fields on the human body. In Northern Europe, in particular, there are concerns about the effect on the human body, and the allowable values of the AC magnetic field and AC electric field are indicated as standards, and the standards are spreading to advanced countries.

[0003] Regarding the AC magnetic field, a method in which a current synchronized with the deflection current of the deflection yoke flows to generate a magnetic field in a direction opposite to the leakage magnetic field, a method in which a magnetically permeable ring is provided on the front surface of the deflection yoke, and the like. Various proposals have been made. However, the focus has recently been on electric fields, and there has been no strong alternative. The frequency bands in question for the AC electric field are ELF (5-2000 Hz), VLF (2
〜400 kHz) band.

[0004] In the case of a cathode ray tube image display device using a cathode ray tube, electromagnetic waves can be suppressed by covering the inside of the cabinet with a metal plate such as stainless steel or a wire net in a direction other than the direction of leakage to the front of the display surface. . However, a transparent electromagnetic wave shield is required for the front surface of the display surface. Conventionally, a method of forming a conductive film on the front surface of a panel of a cathode ray tube by vacuum deposition, spin coating, or the like has been used, but it is not only costly but also insufficient in effect.

[0005]

As described above, a leakage electric field is generated from a cathode ray tube and a cathode ray tube display, and it is necessary to suppress the leakage electric field. In order to suppress the electric field, conventionally, there is a method such as providing a conductive film on the front surface of the display surface, but it is insufficient in cost and effect.

[0006] In view of the above problems, the present invention provides an AC electric field,
In particular, it is an object of the present invention to provide a cathode ray tube and a cathode ray tube display device capable of effectively suppressing a low frequency (ELF) leakage alternating electric field by relatively simple means.

[0007]

According to the present invention, there is provided a cathode ray tube having a metal band or an external conductive film guided to a ground potential, wherein one end is connected to the metal band or the external conductive film. The other end includes a resistor guided to the ground potential, an inverting amplifier circuit for inverting and amplifying a voltage generated on the metal band or the external conductive film side of the resistor, and a compensation electrode connected to an output terminal of the inverting amplifier circuit. It is characterized by doing.

Further, the present invention relates to a cathode ray tube image display device in which a cathode ray tube having a metal band or an external conductive film led to a ground potential is installed in a cabinet.
A resistor connected at one end to the metal band or the external conductive film and the other end guided to the ground potential; an inverting amplifier circuit for inverting and amplifying a voltage generated on the metal band or the external conductive film side of the resistor; A compensating electrode connected to the output terminal of the circuit.

[0009]

Conventionally, no clear study has been made on the leakage electric field, and the inventor has first studied the cause of the AC electric field leaking from the cathode ray tube. as a result,
The leakage electric field does not depend on the potential of the cathode and the vertical deflection voltage, and the current Ib generated in the cathode ray tube when a signal is input.
It turned out to depend on. Therefore, it is considered that the cause of the ELF is not the deflection device mounted on the cathode ray tube but the cathode ray tube itself. It is considered that the supply and relaxation of the electron beam to the inside of the cathode ray tube causes a potential change inside the cathode ray tube, and an AC electric field is formed between the cathode ray tube and the ground potential.

On the other hand, the leakage of the fluctuation voltage due to the cathode current of the anode voltage, which is considered to be one of the causes of the electric field, can be considered by providing a stabilizing circuit on the circuit side.
Although the high-voltage source is generally a DC power supply that is stabilized to some extent, it requires considerable circuit cost to completely suppress the ripple voltage fluctuation due to the cathode current.

According to the present invention, one end of the resistor is connected to a metal band or an external conductive film, and the other end is led to the ground potential, so that the fluctuating potential of the cathode ray tube is taken out to the metal band or the external conductive film side of the resistor. The fluctuating potential is obtained by the inverting amplifier circuit to obtain a potential of the opposite polarity, and the potential of the opposite polarity is applied to the compensation electrode. Accordingly, a fluctuating electric field having a polarity opposite to that of the fluctuating electric field generated by the cathode ray tube is generated from the compensating electrode, so that the leakage ac electric field can be compensated without using an expensive circuit.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. (Example 1)

FIG. 1 is a perspective view showing an embodiment of a cathode ray tube according to the present invention. The cathode ray tube 10 has the same structure as the conventional one, and mainly includes a substantially rectangular panel 11 and this panel 11.
A glass envelope consisting of a funnel 12 connected to the phosphor screen, a phosphor screen formed on the inner surface of the panel 11, and a phosphor screen opposed to the phosphor screen and inserted into the neck 13 of the funnel 12 to excite the phosphor screen to emit light. And an electron gun (not shown) that emits an electron beam. An internal conductive film (not shown) is formed inside the funnel 12, and an external conductive film is formed outside.
14 is formed. Furthermore, on the side wall of panel 11,
A metal band 15 is wound to prevent implosion of the cathode ray tube 10. Further, the cathode ray tube 10 is provided with a compensating electrode 20 for compensating for a leakage AC electric field and an inverting amplifier circuit 21 for supplying a compensating potential to the compensating electrode. The connection state of the compensation electrode 20 and the inverting amplifier circuit 21 is shown in FIG.
This will be described with reference to FIG.

Normally, an anode voltage is applied to the cathode ray tube 10 on the phosphor screen side in order to cause an electron beam to strike the phosphor screen. This anode voltage is
It is obtained by rectifying AC voltage to DC by a rectifier circuit. Therefore, although the anode voltage is a DC power supply that is stabilized to some extent, the ripple voltage fluctuation due to the cathode current cannot be completely suppressed. Therefore, a method of providing a stabilizing circuit on the circuit side is conceivable, but considerable circuit cost is required to completely suppress the ripple voltage fluctuation.

From the measurement results by the inventor, it has been found that the fluctuation waveform of the low-frequency AC electric field generated when the anode current is supplied to the cathode ray tube 10 substantially coincides with the anode voltage waveform. It is considered that the AC electric field around the tube image display device is formed by the fluctuation of the anode voltage. Furthermore, the waveform of the anode voltage is
From the measurement results, the waveform almost coincides with the waveform of the anode current.
Further, the change in the anode current changes the charge amount of the external conductive film and the internal conductive film. In other words, since the external conductive film and the internal conductive film play the role of a capacitor for stabilizing the potential in the tube, when the anode current increases, electrons in the internal conductive film increase, and the internal conductive film and the external conductive film increase. As a result, a potential drop occurs between the internal conductive film and the external conductive film. At that moment, the electrons move toward the ground direction on the ground line connected to the external conductive film, so that the current flows in the opposite direction. When the anode current decreases, the opposite phenomenon occurs. At this time, it is considered that the waveform of the current flowing between the resistors matches the waveform of the anode voltage and the waveform of the AC electric field. Therefore, the external conductive film 14 and the metal band 15 are originally grounded by a ground wire, but as shown in FIG. 2, a resistor R having one end connected to the metal band 15 or the external conductive film 14 and the other end grounded. , It is possible to obtain a voltage proportional to the above-described current. Therefore,
It is possible to obtain an anode voltage based on the ground potential or a voltage v synchronized with the anode current.

Since the voltage v obtained in this manner is synchronized with the AC electric field leaking from the cathode ray tube, this potential is applied to the compensating electrode, and a compensating electric field of the opposite polarity is generated from the compensating electrode in synchronization with the leaking electric field. By doing so, the leakage electric field can be compensated. FIG. 3 schematically shows a connection state of the configuration shown in FIG. 1. A voltage obtained between both ends of the resistor R is connected to an input terminal of the inverting amplifier circuit 21 to reverse the polarity of the voltage. By amplifying and connecting the compensation electrode 20 to the output terminal, a compensation electric field can be generated from the cathode ray tube 10.

FIG. 4 is a diagram showing an example in which an operational amplifier is used as an example of the inverting amplifier circuit. Reference numeral 22 denotes an input terminal for obtaining a voltage between the above-described resistors, reference numeral 23 denotes a capacitor for removing a DC component, and reference numeral 24 denotes a capacitor. An operational amplifier, 25 is a resistor for adjusting the amplification factor, 26 is a transformer for further amplifying the voltage, 27
Is an output terminal for connecting to the compensation electrode.

Next, the leakage electric field compensation operation by the compensation electric field will be described with reference to FIGS. FIG. 5 schematically shows an electric field at a certain time in an AC electric field generated from a cathode ray tube. This is because the electric field generated by the cathode ray tube is simply approximated and represented by a potential distribution formed between the ground (ground potential). In the example shown in FIG. 5, the equipotential lines 30a radially spread from the center of the cathode ray tube 31, the potential decreases as the distance from the center increases, and the electric force lines 32a are directed in the radial direction from the center. FIG. 6 schematically shows an electric field at a certain time in the AC electric field generated by the pair of upper and lower compensating electrodes 33. In the case of FIG. 6, the equipotential line 30b extends around the pair of upper and lower compensating electrodes 33, and a voltage having the opposite polarity to the voltage generated in the cathode ray tube is applied to the compensating electrode 33. The direction of the force line 32b is directed to the direction of the compensation electrode 33 above and below the cathode ray tube, and is directed to the screen direction on the front surface of the screen. FIG. 7 shows a composite of the leakage electric field shown in FIG. 5 and the compensation electric field shown in FIG. As shown in FIG. 7, by arranging the compensating electrode 33, it is understood that the leakage electric field spreading around the cathode ray tube, particularly on the front surface of the screen can be suppressed. FIG. 8 shows AA ′ and B in FIGS. 5 to 7.
It shows the potential in the -B 'and CC' cross sections. The electric field can be calculated as the slope of the potential. FIG. 7 also shows that the electric field generated from the cathode ray is suppressed.

Next, modified examples of the compensation electrode according to the present invention are shown in FIGS. In the example shown in FIG. 9, the compensation electrode 40 is arranged over the entire circumference of the side wall of the panel 11 of the cathode ray tube 10. In the example shown in FIG. 10, a pair of compensation electrodes 41 are arranged on the left and right sides of the cathode ray tube 10 on the panel 11 side. FIG.
In the example shown in FIG. 1, compensation electrodes are provided at the four corners of the panel 11 of the cathode ray tube 10.
42 is arranged.

As described above, the leakage electric field generated in the cathode ray tube can be easily suppressed by arranging the compensating electrode. Therefore, it is not necessary to provide a special electromagnetic wave shielding means on the front surface of the screen, which is advantageous in cost. is there.

In the present invention, any structure may be used as long as the leakage electric field is suppressed by a compensating electrode to which a voltage opposite to the voltage generated in the cathode ray tube is applied. The size may be appropriately determined in consideration of the size of the cathode ray tube to which the present invention is applied, the distribution of the leakage electric field, the level of suppression, and the like. (Example 2)

Next, a cathode ray tube image display device according to the present invention will be described. FIG. 12 is a partially cutaway perspective view of a cathode ray tube image display device according to the present invention. The cathode ray image display device has a structure in which a cathode ray tube 51 is disposed inside a cabinet 50. Then, the compensation electrode 53 is arranged on the side wall of the panel 52 of the cathode ray tube 51 in the cabinet 50,
An electric potential is supplied to 53 from the output terminal of the inverting amplifier circuit 54. The configuration and operation of the compensation electrode 53 and the inverting amplifier circuit 54 are the same as those in the above embodiment.

In the present embodiment, the compensation electrode is provided on the panel side wall of the cathode ray tube in the cabinet, but the present invention is not limited to this. That is, the compensating electrode can be arranged on the back side of the entire surface in the cabinet, or can be arranged integrally with the degaussing coil provided in the ordinary cathode ray tube. The compensating electrode may be arranged at an appropriate position where an opposite electric field capable of compensating the leakage electric field can be generated.

As described above, the leakage electric field generated in the cathode ray tube can be easily suppressed by arranging the compensating electrode. Therefore, it is not necessary to provide a special electromagnetic wave shielding means on the front surface of the screen, which is advantageous in cost. is there.

The present invention only needs to have a structure in which a leakage electric field is suppressed by a compensation electrode to which a voltage opposite to the voltage generated in the cathode ray tube is applied. The number, installation position, size, etc. of the compensation electrodes are as follows. The size may be appropriately determined in consideration of the size of the cathode ray tube to which the present invention is applied, the distribution of the leakage electric field, the level of suppression, and the like.

[0026]

According to the present invention, it is possible to compensate for a leakage AC electric field with a simple structure without using an expensive transparent conductive film.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a cathode ray tube according to the present invention.

FIG. 2 is a diagram illustrating a voltage generated in a cathode ray tube.

FIG. 3 is a diagram illustrating a connection state of a compensation electrode shown in FIG.

FIG. 4 is a circuit diagram showing one embodiment of an inverting amplifier circuit.

FIG. 5 is a schematic diagram showing a distribution of an electric field leaking from a cathode ray tube.

FIG. 6 is a schematic diagram showing a distribution of a compensation electric field generated by a compensation electrode of the cathode ray tube according to the present invention.

7 is a diagram for explaining an electric field suppressing action according to the present invention, and is a schematic diagram showing a distribution obtained by combining the electric field shown in FIG. 5 and the electric field shown in FIG. 6;

FIG. 8 is AA ′, BB ′, and CC of FIGS. 5 to 7;
FIG.

FIG. 9 is a perspective view showing another example of a compensation electrode installed in a cathode ray tube according to the present invention.

FIG. 10 is a perspective view showing another example of a compensation electrode in which a cathode ray tube according to the present invention is installed.

FIG. 11 is a perspective view showing another example of a compensation electrode in which a cathode ray tube according to the present invention is installed.

FIG. 12 is a partially cutaway perspective view showing an embodiment of a cathode ray tube image display device according to the present invention.

[Explanation of symbols]

 10 ... Cathode tube 20 ... Compensation electrode 21 ... Inverting amplifier circuit

Claims (2)

(57) [Claims] 1. A cathode ray tube having a metal band or an external conductive film led to a ground potential, one end of which is connected to the metal band or the external conductive film, the other end of which has a resistor guided to a ground potential, and a metal of the resistor. A cathode ray tube comprising: an inverting amplifier circuit for inverting and amplifying a voltage generated in a band or an external conductive film; and a compensation electrode connected to an output terminal of the inverting amplifier circuit. 2. A cathode ray tube image display device comprising a cathode ray tube having a metal band or an external conductive film guided to a ground potential and installed in a cabinet, one end of which is connected to the metal band or the external conductive film, and the other end. Comprises a resistor guided to the ground potential, an inverting amplifier circuit for inverting and amplifying a voltage generated on the metal band or the external conductive film side of the resistor, and a compensation electrode connected to an output terminal of the inverting amplifier circuit. A cathode ray tube image display device characterized by the above-mentioned.