JPH0364076B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a cathode, an anode disposed opposite to the cathode, a control electrode provided between the cathode and the anode, and an anode and a cathode located on the inner surface of the container. The present invention relates to a fluorescent display tube comprising shielding electrodes arranged to face each other, and particularly relates to a fluorescent display tube having a functional voltage generating means for changing the potential of the shielding electrode with respect to the cathode.

Conventionally, a fluorescent display tube consists of an anode formed into a desired character or figure and having a phosphor layer adhered to its surface, a filament-shaped cathode placed opposite the anode, and both electrodes. A grid-shaped control electrode interposed between the electrodes is enclosed in a vacuum container made of a transparent material, and electrons emitted from the cathode are selectively projected onto a phosphor layer deposited on a desired anode. In addition, devices that display desired characters, figures, etc. by emitting light were often used.

In addition, the above-mentioned fluorescent display tubes normally operate at an anode voltage in the range of several volts to several tens of volts, and are easily affected by external electric fields. A shielding electrode for blocking an external electrostatic field is provided on the inner surface of the container, and the same potential as the cathode potential or a predetermined positive potential is applied to the shielding electrode.

However, when the fluorescent display tube based on the above-mentioned conventional technology is actually operated, the difference between the cathodes or the anode part directly below the cathode may occur due to the electrode structure, high/low anode voltage, fluctuations in the potential of the shield electrode, etc. A part with different brightness compared to the part (this part often occurs in a line along the direction in which the cathode is stretched,
A part with higher brightness than other parts is called a bright line,
This has the disadvantage that dark lines (areas where the brightness is lower than other areas) occur, and this impairs the display quality of the fluorescent display tube.

(1) Furthermore, since the positions where such bright lines and dark lines occur are difficult to predict from the standpoint of circuit design and structural design, it has been extremely difficult to eliminate them using conventional techniques.

(2) In addition, in recent years, the display mode of fluorescent display tubes has gone from simply displaying numbers to being used as display devices that can also display larger figures, and the light emitting area (anode area) is increasing. Since then, the display quality of fluorescent display tubes has come to be greatly influenced by the occurrence of such bright lines and dark lines.

Therefore, for the reasons (1) and (2) above, the above-mentioned drawbacks have become even more serious.

In view of the problem of display quality deterioration due to the generation of bright lines and dark lines resulting from the structure of the fluorescent display tube based on the above-mentioned prior art, an object of the present invention is to change the potential of the shielding electrode with respect to the cathode to change the position where the bright lines and dark lines occur. Focusing on the fact that It is an object of the present invention to provide an excellent fluorescent display tube that can make the occurrence of bright lines and dark lines virtually imperceptible to an observer and can maintain good display quality.

The structure of the present invention in accordance with the above object is such that an alternating voltage such as a triangular wave or a sawtooth wave is applied between a shielding electrode, which has been conventionally provided on the inner surface of the container of a fluorescent display tube, and a filament-shaped cathode, which is disposed opposite to the shielding electrode. is supplied from a functional voltage generating means, thereby periodically moving the positions of the bright lines and dark lines according to changes in the alternating voltage, thereby making the bright lines and dark lines visually indistinguishable. That is.

Next, embodiments of the present invention will be described below based on the drawings.

In FIGS. 1 and 2, a plurality of display bodies 2 are formed on a substrate 1 made of a glass material or the like, and each display body is made up of a plurality of segments 3. 7 is a glass cover. The anode A in each display body 2 has a phosphor layer 8 adhered to the surface of the anode conductor 10 facing the cathode 5 and the control electrode G, and each segment 3 has a It is led to the external terminal 6 via the wiring conductor 11. In addition, the segment 3 provided on the substrate 1
A non-transparent insulating layer 9 is provided around the . The control electrode G controls the flow of electrons emitted from the cathode 5, and for example, as shown in FIG.
A support member 1 is interposed between the cathode 5 and the anode A.
Supported by 2. The inner surface of the glass cover 7 which forms the main body of the fluorescent display tube together with the substrate 1 on which the anode A, the filament-shaped cathode 5, and the grid-shaped control electrode G are attached, and the anode A, the cathode 5, and the control electrode G A shielding electrode 13 is provided on the surface facing the
is provided.

In the above configuration, while a positive potential with respect to the potential of the cathode 5 is being applied to an arbitrary segment 3 as an anode A in each display body 2, a segment 3 corresponding to a selected digit of the display body 2 is applied. When a positive potential is applied to the control electrode G, the segment 3 serving as the anode A emits light. On the other hand, when a negative potential with respect to the cathode potential is applied to the control electrode G corresponding to the anode A to which a positive potential has been applied, electrons that are about to hit the anode A from the cathode 5 are cut off, and the anode A
emission of light is prevented.

Furthermore, even if a positive potential is applied to the control electrode G, if a negative potential is applied to the anode A, the electrons will be cut off by the negative electric field created by the anode A in the same way as above. Light emission from anode A is blocked.
That is, the anode A emits light only when a positive potential is simultaneously applied to the anode A and the control electrode G. The above is an operation for the anode A to emit light and function as a fluorescent display tube.

FIG. 3 shows an example of a fluorescent display tube that displays numbers and has a structure in which three cathodes 5 are strung together. As shown by D ₁ and D ₂ , dark lines with lower brightness and bright lines with higher brightness than other parts are generated. Further, if the structure of the electrodes is different, a bright line or a dark line may occur directly under the cathode 5 or in the vicinity thereof. The occurrence of such bright lines and dark lines is thought to be essentially due to the fact that the cathode 5 is a filament-like thin wire, and the area of the anode A that one cathode should cover is spread out. .

That is, as shown in FIG. 4, the cathode 5
Electrons emitted from the cathode 5 travel across it at right angles, but if the distance between the cathodes 5 changes or
When the potential of the shielding electrode 13 changes with respect to the potential of the cathode 5, the flow of electrons reaching the anode A becomes uneven, resulting in bright lines and dark lines.

Incidentally, when the change in relative brightness when the potential of the shielding electrode 13 relative to the potential of the cathode 5 is changed from a predetermined positive potential to a predetermined negative potential is measured in relation to the arrangement position of the cathode 5, Fifth
Data on relative brightness changes as shown in the figure was obtained. Figure 5A shows the case where the potential of the shielding electrode 13 is set to a predetermined positive potential with respect to the cathode potential, Figure 5B shows the case where the potential is set to a predetermined medium positive potential, and Figure 5C shows the case where the potential is zero. In this case, the relative brightness at each position between the cathodes 5 is shown in FIG. This shows the approximate changes in the distribution. For these reasons, even if the structure of each electrode and the anode voltage are determined according to the design requirements of the fluorescent display tube, the relative potential of the shielding electrode 13 with respect to the cathode potential cannot be changed from positive to negative or from negative to positive. It can be seen that by changing this, the positions where bright lines and dark lines occur, or their degree, can be changed considerably.

That is, if a triangular wave as shown in FIG. 6 is applied between the shielding electrode 13 and the filament cathode 5, the beginning of the positive region of the triangular wave (FIG. 6a) When the
An emission line is generated directly under the filament cathodes 5, 5 (Fig. 5A, a), and a bright line is generated in the center of the positive region of the triangular wave (6th line).
5) is applied, a thin dark line directly below the filament cathodes 5, 5 and a thin bright line sandwiching it (Fig. 5 B, b, b') are generated, and the zero crossing part of the triangular wave is (Fig. 6 c), a thick dark line is generated directly under the filament cathodes 5, 5 (Fig. 5 C, c), and the central part of the negative region of the triangular wave (Fig. 6 d) When the voltage is applied, a thick dark line is generated from just below the filament cathodes 5 toward the middle position between the two cathodes (Fig. 5D, d), and the terminal part of the negative region of the triangular wave ( Figure 6 e)
is applied, a thick dark line is generated at the intermediate position between the two filament-shaped cathodes 5, 5 (Fig. 5E, e), and thus the positions of the bright line and the dark line are different from the shielding electrode 13 and the filament-shaped cathode 5. It moves periodically from moment to moment in response to the triangular wave applied during the period.

FIG. 7 is a diagram showing an example of a circuit configuration for changing the potential of the shield electrode. In FIG. 7A, the output voltage of an oscillator 14 that oscillates alternating functional voltages is applied between one end of the cathode 5 and the shield electrode 13. E _A is a power supply for the filament of the cathode 5, E _C is a power supply for cut-off bias, E _B , E _G , E are terminals for anode voltage power supply, control voltage power supply terminals,
The ground terminal is shown, and R ₁ and R ₂ are both bleeder resistors. The circuit configuration shown in FIG. 7A is
The filament of the cathode 5 is driven by a DC power source E _A , and the circuit configuration shown in FIG. 7B is as follows.
The filament is driven by an alternating current voltage taken out by the filament driving winding 15a of the cathode 5 provided on the secondary side of the transformer 15, and at the same time, the shielding electrode 13 is also provided on the secondary side of the transformer 15. An alternating current voltage is applied through the shield electrode winding 15b. In this case, the polarity of the filament drive winding 15a and the shielding electrode winding 15b may be in the same phase or in opposite phases, but if they are in opposite phases, it is effective in reducing bright lines and dark lines even if the voltage to be handled is lower. can be substantially secured. Further, compared to the circuit configuration shown in FIG. 7A, this circuit configuration has the advantage that it does not require an oscillator and only requires adding the shield electrode winding 15b to the conventional transformer. Note that the alternating function voltage waveform from the oscillator 14 in the above-described exemplary circuit configuration may be, for example, a sine wave, a triangular wave, a sawtooth wave, or the like. If the frequency of such a functional voltage waveform is set to an appropriate value, for example, about 200Hz, the positions where the bright lines and dark lines occur will move fairly quickly, so that the bright lines can be virtually discerned visually without flickering.・Dark lines can be removed.

As described above, according to the present invention, there is provided a cathode, an anode disposed opposite to the cathode, a control electrode provided between the cathode and the anode, and a control electrode disposed between the anode and the cathode on the inner surface of the container. In a fluorescent display tube consisting of a shielding electrode arranged to face the cathode, a functional voltage generating means for changing the potential of the shielding electrode with respect to the cathode is added.
The so-called bright lines and dark lines that occur when conventional fluorescent display tubes are operated are apparently completely removed, thereby providing an excellent effect of significantly improving the display quality of the fluorescent display tube.

In particular, the bright lines and dark lines that are noticeable in fluorescent display tubes with large anodes can be visually completely removed, making it possible to further expand the anode area and making it possible to clearly see large and diverse figures. It is accompanied by tremendous practical benefits as it can be displayed on the screen.

In addition, the electrodes inside the vacuum vessel can be used as they are without any processing, and it is sufficient to simply attach a functional voltage generating means outside the vacuum vessel, which is not a problem compared to conventional methods. This has the advantage that subsequent modifications to the fluorescent display tube are extremely easy.

Furthermore, it has been used for a long time because it originally has the role of blocking the influence of electrostatic fields from outside the vacuum chamber and uniformly scattering electrons emitted from the filament-shaped cathode toward the planar anode. Since the conventional shielding electrode is also used for the fluctuation of bright lines and dark lines, there is an advantage that the structure is very simple.

[Brief explanation of drawings]

Figure 1 is a perspective view of a fluorescent display tube, Figure 2 is a sectional view to explain the structure of a fluorescent display tube, Figure 3 is a front view of a fluorescent display tube as a numeric display tube, and Figure 4 is a view from the cathode. An explanatory diagram showing the flow of emitted electrons, Fig. 5 is an explanatory diagram showing the interrelationship between changes in the potential of the shielding electrode and changes in relative brightness of the anode, and Fig. 6 is an explanatory diagram showing the relationship between the change in the potential of the shielding electrode and the relative brightness of the anode. FIG. 7 is a circuit diagram showing a circuit configuration for changing the potential of the shield electrode. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Display body, 3... Segment, 5... Cathode, 7... Glass cover (container part),
13... Shield electrode, 14... Oscillator (function voltage generating means), A... Anode, G... Control electrode.

Claims (1)

[Claims] 1. An anode disposed on a substrate and forming a display body by a plurality of segments to which a phosphor layer is attached, a cathode stretched across the anode, and accommodating each of the electrodes; A fluorescent display tube comprising: a container portion sealed to a peripheral edge of the substrate; and a shielding electrode made of a conductive material and disposed on the inner surface of the container portion so as to face the cathode and the anode. . A fluorescent display tube, further comprising function voltage generating means for changing the potential of the shielding electrode with respect to the cathode.