JPS63138635A - Fluorescent character display tube - Google Patents

Abstract

PURPOSE:To uniformize the light emitting luminance of a phosphor, by installing a current control electrode which controls emission and diffusion of an electric current being emitted out of a filament, in and around this filament, in case of a fluorescent character display tube to be constituted of sealing the filament and an anode in a transparent vacuum vessel. CONSTITUTION:A current control electrode 12, using a pure tungsten wire, is placed between a filament 7 and cover glass 8 at the point midway in a setup pitch of the filament 7, and it impresses such electric potential that makes a radiant electron out of the filament 7 incident into an anode 4 with uniform density upon adjusting a resistor 13. Since the current control electrode 12 is situated in and around the filament 7, it is able to control the emission and diffusion of an electric current of the filament 7 with a small potential difference to the potential of the filament 7. It is merely good enough that potential lower as much as 1-5V than the filament potential is impressed on the current control electrode 12. With this constitution, the light emitting luminance of a phosphor is uniformizable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluorescent display tube, and particularly to its electrode structure.

[Conventional technology and its problems]

Conventionally, the electrode structure of a fluorescent display tube has an anode 4. as shown in FIG. Lattice 6. It consisted of a filament 7 and a transparent conductive film 9 on the inner surface of a cover glass 8. The emitted electrons from the filament 7 are accelerated and diffused by the potential of the lattice 6 and enter the anode 4 . Transparent conductive M9 is ordinary filament 7
It is provided to make the potential equal to the potential of With such an electrode structure, it is difficult to make the luminance of the phosphor 5 completely uniform. This non-uniformity in brightness is called display unevenness, and often occurs in a direction perpendicular to the stretching direction of the filament 7, and is particularly noticeable in the vicinity directly below the filament and in areas outside of it. The main reason for this is that current flows into the flat anode 4 from the plurality of linear filaments 7. In addition, in order to increase the brightness of the phosphor 5, the number of filaments 7 is increased and the spacing between the filaments 7 becomes smaller, and the spacing between the filament 7 and the transparent conductive film 9 is smaller than the spacing between the anode 4 and the filament 7. is 1.5 times or more, the diffusion of electrons from filament 7 is
This is also due to the fact that the voltage is restricted to the potential of 9.

Conventionally, in order to solve this problem, a method has been adopted in which the potential of the transparent conductive fi9 is set to a lattice potential. However, in this method, unless the distance between the anode 4 and the filament 7 is approximately equal to the distance between the filament 7 and the transparent conductive film 9, the current flowing from the filament 7 to the grid 6 and the anode 4 and the current flowing toward the transparent conductive film 9 Because the distribution is different, no fundamental solution has been reached.

In this way, in conventional fluorescent display tubes, the current density incident on the anode is determined when the electrode positions of the anode, filament, and cover glass and the electrode potential are determined, and the current density distribution at the anode depends on the tension of the filament. This has the drawback that differences tend to occur in the vertical direction and the luminance of the phosphor on the anode becomes non-uniform.

[Means for solving problems]

The present invention provides a fluorescent display tube constructed by enclosing a filament and an anode in a vacuum container with at least one side transparent, in which a current control electrode is provided near the filament to control the radiation and diffusion of the current emitted from the filament. It is characterized by

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view of an electrode structure according to an embodiment of the present invention. A wiring layer 2 is formed on the substrate glass 1 by thin film printing or thick film printing. Insulating layer 3. and an anode 4 are formed, and the anode 4 is coated with a phosphor 5. The wiring layer 2 has an anode 4. Lattice 6
．． There is a connection part for filament 7 (not shown),
From there, each tip is pulled out of the tube and connected to an external circuit through a lead terminal 11. The filament 7 is a directly heated filament cathode made of pure tungsten wire coated with oxide, and is heated to around 650°C by applying a voltage to emit thermionic electrons.
A current control electrode 12 that controls the current from the filament 7
is provided. The lattice 6 accelerates and diffuses the electrons emitted from the filament 7. The electrons passing through the lattice 6 and entering the anode 4 stimulate the phosphor 5 to emit light on the way. These elements are sealed in a vacuum container in which a substrate glass 1 and a cover glass 8 are sealed with a frit glass 10.

FIG. 2 shows a driving circuit diagram of the fluorescent display tube of the above embodiment. The current control electrode 12 is made of pure tungsten wire and is connected to the filament 7 at the middle of the pitch of the filament 7.
and a cover glass 8, and a resistor 13 is placed between the resistor 13 and the cover glass 8, and a resistor 13 is placed between the
Adjust and apply. The current control electrode 12 can control the current emission and diffusion of the filament 1-7 with a small potential difference with respect to the potential of the slick filament 1-7 near the filament 7. A potential that is 1 to 5 cm lower than the filament potential may be applied to the current control electrode 12.

In this embodiment, the current control electrode 12 was placed between the filament 7 and the cover glass 8 at the middle of the pitch between the filaments 7, but this position may be placed at any position depending on the shape of the phosphor and the characteristics of display brightness. It is also possible to arrange the filament 7 in a direction other than parallel to the filament 7. Further, the shape of the current control electrode 12 is not limited to a linear shape, and can be operated in any shape.

FIG. 3 is another driving circuit diagram of the fluorescent display tube of the present invention.

In this case, an AC power source 14 is used for the current control electrode 12. By applying the voltage of the AC power source 14 to the current control electrode 12, it is possible to dynamically control the diffusion of emitted electrons from the filament 7. At this time, the current density on the anode 4 also changes depending on the frequency of the AC power source 14, but if the frequency is set to 100 Hz or more, the brightness of the phosphor 5 will appear uniform, especially in the direction in which the filament 7 is stretched. This is effective in eliminating uneven brightness that occurs in the vertical direction. Even in the case of this alternating current application, the current can be sufficiently controlled by lowering the potential of the current control electrode 12 by about 1 to 5 V from the potential of the filament 7.

In the above embodiment, a grating 6 was provided to uniformly diffuse the electrons emitted from the filament 7, but the operation is possible even without the grating 6.

〔Effect of the invention〕

As explained above, the fluorescent display tube according to the present invention is equipped with a current control electrode, and the potential of the electrode is set to 1 with respect to the filament I.
A low value of ~5■ has the effect of making the luminance of the phosphor uniform.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention, FIG. 2 is a drive circuit diagram of a fluorescent display tube of the present invention, and FIG. 3 is another drive circuit diagram.
FIG. 4 is a longitudinal sectional view of a conventional fluorescent display tube. DESCRIPTION OF SYMBOLS 1... Substrate glass, 2... Wiring layer, 3... Insulating layer, 4... Anode, 5... Phosphor, 6... Grid, 7...
... Filament, 8 ... Cover glass, 9 ... Transparent conductive film, 10 ... Frit glass, 11 ... Lead terminal, 12 ... Current control electrode, 13 ... Resistor, 1
4...AC power supply.

Claims (1)

[Claims] A fluorescent display tube having a filament and an anode in a vacuum container with at least one transparent surface, characterized in that a current control electrode for controlling radiation and diffusion of current emitted from the filament is disposed near the filament. .