JPH05190122A - Fluorescent character display tube - Google Patents

Abstract

PURPOSE:To obtain the uniform high luminance by installing a conductive layer which acts as rear grid on the inner surface of a basic body on the opposite side to an anode side grid, nipping a thermal cathode filament between a pair of flat plate shaped substrates. CONSTITUTION:A light transmissive conductive layer 9A is formed on the inner surface of a front surface glass plate 8 on the opposite side, nipping a thermal cathode filament 7 with a back surface plate 1 having an anode 4 formed. The layer 9A is connected with an anode grid 6 by a bonding wire 10A, and applies a positive potential for the filament 7, and acts as rear grid, and the anode electric current can be supplied more than only by with only the grid 6, and high luminance is secured. Further, since the layer 9A is formed in substitution for a common charge preventing conductive film, the need of the specific process is obviated. Accordingly, the uniform high luminance can be obtained, and the cut-off voltage can be made shallow, and drive is facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent display tube.

[0002]

2. Description of the Related Art In recent fluorescent display tubes, in order to be thin, a spacer is sandwiched between a front glass plate and a back plate, and a frit glass is airtightly fixed to form a vacuum container. Holes for exhaust are provided on the spacer part or the back plate, and connect the exhaust pipe to this to tip off,
It is designed to be sealed with a seal lid. This type of fluorescent display tube includes a hot cathode filament and an anode having a phosphor coated on the surface thereof, but it is common to use a control grid to form a triode vacuum tube structure. These hot cathode filaments, anodes and control grids are usually formed on a single substrate because of their ease of manufacture. The substrate therefor is a front glass plate or a back plate. Also, when there are many display elements, a matrix is composed of a plurality of anodes and a control grid, and time-division driving is performed.

In the fluorescent display tube having such a structure,
Although thermions fly out from the hot cathode filament toward the anode, they are also emitted in the opposite direction. Therefore, when the substrate portion on the side opposite to the anode is an insulator, electrons are charged therein, and the amount of emitted electrons becomes unstable due to the influence of the electric field due to this amount of charges. In order to prevent this, the inner surface of the substrate portion on the opposite side is subjected to a conductive treatment so that it has the same potential as the hot cathode filament.

An example of a general fluorescent display tube of this type is shown in a schematic partial sectional view in FIG. 3 of the accompanying drawings. As shown in FIG. 3, the anode wiring 2 and the insulating layer 3 are formed on the back plate 1.
Are formed. Anodes 4 are formed through through holes provided in the insulating layer 3, and phosphors 5 are deposited on the surfaces of these anodes 4 by printing. The control grid 6 is installed at a predetermined height above the phosphor 5. The hot cathode filament 7 is suspended above the control grid 6, and a transparent conductive film 9 is provided on the inner surface of the front glass plate 8. Then, this conductive film 9 is connected to the hot cathode filament 7 by a connection 10 so as to have the same potential as the hot cathode filament 7 in order to prevent charging of emitted electrons to the inner surface of the front glass plate 8. ..

In the fluorescent display tube shown in FIG. 3, the anode 2 is the back plate 1.
However, there is also a fluorescent display tube having an opposite structure in which the anode 2 is formed on the front glass plate 8.

As can be seen from FIG. 3, the formation of the control grid 6 is complicated. Therefore, it has been proposed to form the control grid 6 by a film on the insulating layer. The film formation is known as a thin film or thick film technique, and it is convenient that a plurality of grids can be collectively formed.
An example of a fluorescent display tube having such a structure is shown in FIG. 4 in a schematic partial sectional view similar to FIG. 4, the same components as those of FIG. 3 are designated by the same reference numerals as those of FIG.

[0007]

The control grid 6 in the conventional fluorescent display tube as described above is usually formed of a metal thin plate in the shape of a mesh, and can extract thermoelectrons sufficiently and uniformly, and time division. It is said that when the drive is not selected, it has the effect of suppressing thermoelectrons.
At this time, if the mesh is made finer, power consumption increases, and in the reflection type in which the light emitting surface is directly viewed, the amount of transmitted light decreases. When the eyes are rough, the distribution of emitted electrons becomes worse,
The obtained current also decreased, and uneven brightness and insufficient brightness had occurred.

Further, in the case of time-division driving, a voltage is also applied to the anode in the non-selected grid, so that this anode part is not turned on.
Alternatively, a negative voltage (cutoff voltage) is applied. Of course, the grid voltage when selected is positive. In the configuration of FIG. 3, it is easy to suppress electron emission by the grid, and the cutoff voltage may be 0 V or a slight negative value with respect to the normal cathode. However, in the configuration of FIG. 4, the suppression of the grid is weaker than that of the configuration of FIG. 3, and a large negative value is required as the cutoff voltage. Therefore, the driving voltage width of the grid is increased, and the load on the driving element is increased. For this reason, the conventional configuration of FIG. 4 can be applied only to a fluorescent display tube having one grid or a few grids and a small driving load.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a fluorescent display tube having uniform brightness, high brightness, and easy driving.

[0010]

According to the present invention, there is provided a pair of flat plate base portions extending in parallel and opposite to each other at a predetermined interval so as to provide a predetermined vacuum space. In the fluorescent display tube, an anode, an anode side grid and a hot cathode filament provided on one flat plate base portion of the pair of flat plate base portions and located in the vacuum space are provided, and A phosphor is provided on the surface of the anode, the hot cathode filament is suspended above the anode and the grid on the anode side, and
A conductive layer acting as a rear grid is provided on the inner surface of the pair of flat plate-shaped base portions on the side opposite to the anode side grid with the hot cathode filament interposed therebetween.

[0011]

The invention will now be described in more detail with reference to the accompanying drawings, in particular with reference to FIGS. 1 and 2.

FIG. 1 is a schematic partial sectional view of a fluorescent display tube as an embodiment of the present invention. As is clear from a comparison of FIGS. 1 and 3, the structure schematically shown in the fluorescent display tube of FIG. 1 is similar to the structure of the conventional fluorescent display tube described with reference to FIG. The fluorescent display tube of the embodiment of the present invention shown in FIG. 1 is different from the conventional fluorescent display tube shown in FIG. 3 in that the conductive layer 9A provided on the inner surface of the front glass plate 8 acts as a rear grid. That is, it is connected to the anode side grid 6 by the connection 10A.

FIG. 2 is a schematic partial sectional view of a fluorescent display tube as another embodiment of the present invention. As is clear from a comparison of FIGS. 2 and 4, the structure of the fluorescent display tube shown in FIG. 2 is similar to that of the conventional fluorescent display tube described with reference to FIG. The fluorescent display tube of the embodiment of the present invention shown in FIG. 2 is different from the conventional fluorescent display tube shown in FIG. 4 in that the conductive layer 9A provided on the inner surface of the front glass plate 8 acts as a rear grid. That is, it is connected to the anode side grid 6 by the connection 10A.

Next, the conductive layer 9A provided as a rear grid according to the present invention will be specifically described.

The conductive layer 9A is applied to the inner surface of the substrate opposite to the substrate on which the anode 4 is formed and the hot cathode filament 7, and a positive potential is applied to the hot cathode filament 7. It acts as a rear grid. In the embodiment of FIG. 1, the conductive layer 9A is provided on the inner surface of the front glass plate 8, but in the fluorescent display tube having the opposite structure, the conductive layer is provided on the inner surface of the back plate.

When applied to the inner surface of the front glass plate 8, the conductive layer 9A is required to have translucency as well as conductivity.
In this case, a mesh-shaped thin metal plate is attached, or a mesh-shaped conductive film or a translucent conductive film is applied. Examples of the translucent conductive film are thin films of indium-tin oxide (ITO), tin oxide doped with antimony, zinc oxide doped with aluminum, and the like. In the case of using a mesh-shaped thin metal plate, the mesh shape may be devised so that it also serves as a light-shielding layer that blocks light in a specific direction. The conductive layer 9A does not need to be translucent when applied to the inner surface of the back plate 1, which is easier.

The conductive layer 9A as the rear grid preferably has a film shape rather than a mesh shape. It is clear from the geometrical arrangement that the film-shaped rear grid is superior in uniformity and controllability of electron emission. Therefore, even in the fluorescent display tube having the configuration of FIG. 2, it is not necessary to increase the negative potential of the cutoff voltage, and therefore the driving is easy. Further, the degree of fine processing is small and the formation is easy.

Since the rear grid 9A also controls electrons, it is convenient to have the same positional relationship as the anode grid 6 formed on the anode side. Since the operation timing may be the same for both, grids having the same positional relationship may be commonly connected. By doing so, compared with the case of only the anode side grid, a large amount of anode current can be taken and high brightness can be achieved. The common connection can be provided inside or outside the fluorescent display tube. Internal connection is preferable because the number of terminals is small. At this time,
Since both are formed on different bases, it is necessary to devise them. One method is to use a metal spring or the like to bring them into contact with each other, and another method is to form a conductor circuit on the side surface of a spacer that separates them.

Of course, the rear grid and the anode side grid can be driven separately. In order to change the potentials of both with one power source, different resistors may be inserted in each. The resistors may be designed individually, or may be formed by each material or shape design.

Since the conductive layer 9A acting as the rear grid is formed in place of the charge prevention conductive film 9 (see FIGS. 3 and 4) formed by a usual fluorescent display tube, the fluorescent display tube of the present invention. The forming process of is less burdensome than in the past. Moreover, no special material or process is required. Further, from the above description, except for the rear grid portion according to the present invention, it may be the same as the conventional fluorescent display tube,
It is obvious that it can be applied to various fluorescent display tubes.

Next, in order to confirm the effect of the rear grid according to the present invention, the results of experiments on the embodiment of the present invention and the comparative example will be described.

First, as Example 1 of the present invention and Comparative Example 1 thereof, the same configurations as those shown in FIGS. 1 and 3 were used. The difference between Example 1 and Comparative Example 1 is that the transparent conductive film made of ITO is different from Comparative Example 1 in that
In the first embodiment, the conductive layer 9A that functions as a rear grid is connected to the control grid 6 that serves as the anode-side grid. The aperture ratio of the mesh-shaped control grid 6 is 92%. When the luminance was measured under the same driving condition, the luminance of Example 1 was uniform and 110 foot-transversal, and Comparative Example 1
The brightness of the sample was uniform and 100 foot lambertian.

Next, as Example 2 and Comparative Example 2 of the present invention, the same as Example 1 and Comparative Example 1 except that the mesh metal control grid 6 was roughened to have an aperture ratio of 97%. I used one. When the luminance was measured under the same driving conditions, the luminance of Example 2 was uniform and 117 foot-transvers, and the luminance of Comparative Example 2 was non-uniform and 105 foot-transvers.

Furthermore, as Example 3 of the present invention and Comparative Example 3 thereof, except that the configurations of FIGS. 2 and 4 are used,
The same ones as in Example 1 and Comparative Example 1 were used. The cut-off voltage for non-emission of the non-selected anode portion was also measured during the time-sharing operation. The luminance of Example 3 was uniform at 122 foot transversal, the cutoff voltage was -1.5V, and the luminance of Comparative Example 3 was uniform at 110 foot transversal and the cutoff voltage was -10V. there were.

[0025]

As is apparent from a comparison of the above examples and comparative examples, according to the present invention, when a similar fluorescent display tube is formed and driven in the same manner, uniform and high brightness can be achieved. Further, since the cutoff voltage can be made shallow, driving is easy. These are static drive with one grid,
It is also good for multiple time division driving. The rear grid forming process of the present invention is not so complicated as compared with the conventional one, and can be applied to fluorescent display tubes having various configurations.

[Brief description of drawings]

FIG. 1 is a schematic partial sectional view showing a fluorescent display tube as one embodiment of the present invention.

FIG. 2 is a schematic partial sectional view showing a fluorescent display tube as another embodiment of the present invention.

FIG. 3 is a schematic partial sectional view showing an example of a conventional fluorescent display tube.

FIG. 4 is a schematic partial sectional view showing another example of a conventional fluorescent display tube.

[Explanation of symbols]

 1 Back Plate 2 Anode Wiring 3 Insulating Layer 4 Anode 5 Fluorescent Material 6 Anode Side Grid 7 Hot Cathode Filament 8 Front Glass Plate 9A Rear Grid 10A Wiring

Claims (6)

[Claims] 1. An extension 1 which is substantially parallel to and opposed to each other at a predetermined interval so as to provide a predetermined vacuum space.
In a fluorescent display tube having a pair of flat plate-shaped substrate portions, an anode and an anode side grid provided on one flat plate-shaped substrate portion of the pair of flat plate-shaped substrate portions and located in the vacuum space. And a hot cathode filament, a phosphor is applied to the surface of the anode, the hot cathode filament is suspended above the anode and the grid on the anode side, and further, the pair of flat plates. Display in which a conductive layer acting as a rear grid is provided on the inner surface of a flat plate-shaped base portion on the side opposite to the anode-side grid of the flat-shaped base portion with the hot cathode filament interposed therebetween. tube. 2. The fluorescent display tube according to claim 1, wherein the conductive layer has a film shape. 3. The fluorescent display tube according to claim 1, wherein the conductive layer has a mesh shape. 4. The fluorescent display tube according to claim 1, wherein the anode-side grid is provided on a surface above the anode. 5. The fluorescent display tube according to claim 1, wherein the anode-side grid is provided on substantially the same surface as the anode. 6. The anode-side grid is divided into a plurality of pieces, and the conductive layer is divided into a plurality of pieces corresponding to the anode-side grid. The fluorescent display tube according to any one of the above.