JPS5823701B2 - Gazouhiyoujisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image display device, and more particularly to a thin image display device having a switching circuit using an electron gun.

An example of the display section of the image display device used in the present invention will first be described with reference to FIGS. 1 and 2. FIG.

FIG. 1 is a structural explanatory diagram of a display section of a thin image display device,
The main parts include a surface cathode 1 for electron emission, a control electrode 2, a row electrode 3, a column electrode 4, and a fluorescent screen anode 5.

These five electrodes are assembled parallel to each other, and at least the front part is enclosed in a vacuum container made of a transparent material such as glass.

In the configuration of such a display section, a heater (not shown)
When ignited, thermionic electrons are uniformly emitted from the surface cathode 1 at ground potential, and these thermionic electrons are directed toward the anode 5 by a grid-like or net-like control electrode to which a voltage of several volts to several tens of volts is applied. accelerated to.

On the other hand, in the row electrodes 3 and column electrodes 4, as shown in FIG. 2, the symbols A1, A2, . . . AN, and B1 . B2,...If we add BM,
For example, if a positive potential of several hundred volts is applied to only the thin wires AI and BJ, and a negative potential of several hundred volts is applied to the other thin wires, then the intersection of the thin wires AI and BJ shown in FIG. The thermoelectrons pass through only the part 6 and illuminate the metal-backed fluorescent screen anode 5, and an image is formed only in this part, while the other parts are cut off by the negative potential of the thin wire group. No image is formed.

However, a positive potential of several thousand volts is applied to the anode 5.

When displaying a television image on the display section of the image display device as described above, the potential of each thin line group of the row electrodes 3 and column electrodes 4 is sequentially set to a positive potential in synchronization with the horizontal and vertical scanning cycles of the television signal. All you have to do is switch it so that

Further, brightness modulation can be performed by changing the potential of the control electrode 2 using a brightness signal.

However, as is clear from the above description, switching of the thin wire groups of the row electrodes 3 and column electrodes 4 is possible at, for example, −300V and +
With a value such as 200■, the switching potential width becomes 500■,
This must be done at high speed in cases such as TV projection.

Conventional switching circuits use ICs or transistors, but it is extremely difficult to perform large electrical switching as described above, and they have the drawback of easily causing dielectric breakdown of the transistors, etc.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the conventional switching circuits as described above and to provide an image display device having a switching device that can switch the electrode electrical equipment quickly and reliably.

The above object is to provide an image display device according to the present invention, in which secondary electron contacts connected to each of row and column electrodes are sequentially scanned by an electron gun, and secondary electrons from the scanned secondary electron contacts are captured. This is achieved by providing a switching device which increases the potential of the secondary electron contact when it is collected by the collector electrode and thus scanned.

Hereinafter, the details of the present invention will be explained with reference to Examples.

FIG. 3 is a diagram showing an embodiment of an electrode potential switching device for an image display device according to the present invention, and shows a switching device for either row electrodes or column electrodes.

In FIG. 3, the secondary electron contact 7 is composed of a secondary electron emitting electrode whose secondary electron emission coefficient K is greater than 1 when irradiated with the electron beam from the electron gun 20. One electrode is connected to each of the thin lines of the row electrode 3 (or column electrode 4, FIG. 1) of the display section of the image display device.

The front surface of the secondary electron contact 7 has a hole through which the electron beam from the electron gun passes, and a secondary electron collecting electrode 8 is provided to collect the generated secondary electrons. ing.

The electron gun 20 is composed of an electron gun cathode 13 for generating an electron beam, a force-lowering electrode 12, a deflection electrode 10 for scanning, and a sawtooth wave power source 11 for generating a scanning voltage.

In the above configuration, the electron beam generated from the electron gun cathode 13 is accelerated by the acceleration electrode, and then deflected by the deflection electrode 10 to scan the secondary electron contact 7.

The scanning speed at this time is determined by the acceleration electric power of the DC power supply 142, the deflection voltage of the sawtooth wave power supply 11, the repetition time, etc. For example, the irradiation time of one secondary electron contact 7 ranges from several hundred nanoseconds to several tens of microseconds. is set to

The operation when the secondary electron contact 7 is irradiated by the electron gun 20 will be described next.

First, when the secondary electron contact 7 is not irradiated, the resistance 1
A negative electric current EVO1, for example, -300 volts, is applied through EVO5.

When the electron beam current ■ is irradiated for a time T, the charges of K, ■, T at the secondary electron emitting group JK of the secondary electron contact are captured by the secondary electron collecting electrode 8, and therefore the secondary electron contact This is equivalent to a positive charge (K-1)·■·T flowing into 7.

Therefore, the capacitance between the secondary electronic contact 7 and the ground is C
If so, the potential ■ of the secondary electron contact 7 will be V at the time of no irradiation.
O to V=VO+(K-1)・■・T/C・・・・・・(1)
The potential changes to a value determined by .

Note that the potential VC of the secondary electron collecting electrode 8 is sufficiently higher than the potential of the secondary electron contact 7.

As mentioned above, the secondary electron emission coefficient K of the secondary electron contact 7 is 1.
If it is a dog, as is clear from equation (1), the potential ■ of the secondary electron contact 7 irradiated by the electron beam increases from ■0 by (K-1)・■・T/C volts. become.

For example, = 2, l-100 (μA) T = 10 (μS
], C=2 (PF), and VO=-300 (V), then V=200 (V) from equation (1).

In this way, the potential of the secondary electron contact 7 can be switched, but in order to keep the voltage constant after switching, the potential VC of the secondary electron collecting electrode 8 must be set as It is sufficient to set it to a certain degree.

In this case, the potential of the secondary electron contact 7 increases with time during irradiation, and when it approaches the potential VC of the electrode 8, the secondary electrons emitted from the secondary electron contact 7 are not captured by the collection electrode 8 and return to the contact. Returning to T, there exists a potential ■S at the contact point 7 such that the apparent emission coefficient K becomes 1.

Such an equilibrium state is independent of the initial potential (2)0, and if the value of (2)·T is above a certain level, the potential of the contact 7 will always become (2) S and will be in equilibrium.

Moreover, the time required to reach such an equilibrium potential ■S is extremely short, so that ■S can be set to a required value, for example +20.
If set to 0 volts, reliable switching is always possible.

Next, the potential of the secondary electron contact 7, which has increased in potential as described above, is transferred to the resistor 15 when the irradiation with the electron beam is completed.
Then, the potential drops with a time constant determined by the capacitor 16.

Therefore, when displaying images on television, the time constant may be determined to provide an appropriate afterimage time until the next scan is performed.

Further, the resistor 15 and capacitor 16 do not necessarily need to be inserted, and may be constructed using an insulator or stray capacitance having an appropriate resistance value.

Although the secondary electron collecting electrode 8 has a plate-like configuration with holes in the embodiment shown in FIG. 3, it is clear that the same effect can be obtained even if it is configured with a mesh-like or lattice-like electrode. .

As is clear from the above description, in the image display device according to the present invention, it is possible to reliably switch the row and column electrodes for determining the display selection point, and it is possible to prevent the occurrence of failures. be.

[Brief explanation of drawings]

1 and 2 are configuration explanatory diagrams showing a display section of an image display device used in the present invention, and FIG. 3 is a diagram showing an embodiment of a switching device for an image display device according to the present invention. In FIGS. 1 to 3, the same reference numerals indicate the same or corresponding members, 1 is a surface cathode, 2 is a control electrode, 3 is a row electrode, 4 is a column electrode, 5 is an anode, 6 is a selection point, 7 is a secondary electron contact, 8 is a secondary electron collection electrode, 10 is a deflection electrode, 1
1 is a sawtooth wave power supply, 12 is an accelerating electrode, 13 is an electron gun cathode, 140°141.142 and 143 are DC power supplies, 1
5 is a resistor, 16 is a capacitor, A1,...A
N, and B1, . . . BM are grid thin lines.

Claims (1)

[Claims] 1. A plane cathode for generating a plane electron beam, first and second groups of thin wires that are perpendicular to each other, and one thin wire of each of the first and second groups of wires at a high positive potential. In an image display device comprising a switching device for allowing the surface electron flow to pass only at the intersections of the thin wires set at a high potential, and a phosphor screen for projecting an image by the passed electron flow. ; a secondary connected to each of the thin wires of the first and second thin wire groups and having a secondary electron emission coefficient greater than 1 and connected to a negative potential through a parallel circuit of a resistive element and a capacitor element; an electron contact, an electron gun for sequentially scanning and irradiating each of the secondary electron contacts in accordance with image information and emitting secondary electrons from the irradiated secondary electron contacts; The switching device is a switching device comprising a secondary electron collecting electrode for collecting the emitted secondary electrons, and the irradiated secondary electron contact is set at a positive high potential. An image display device characterized by: