JPH06168668A - Cathode structure for dc type discharge display tube - Google Patents

Abstract

PURPOSE:To eliminate a condition where an electric current is distributed unevenly in a microscopic part, and solve a cathode glow condensing phenomenon by forming a cathode in a three-layer structure sandwiching a resistance layer between a cathode material and a good conductor, and providing resistance in a thickness direction of the cathode. CONSTITUTION:An electrically good conductive layer 3 composed of Ni, Ag, Cu or the like is arranged on a glass substrate 4, and a resistance layer 2 such as RuO2 or C is laid so as to cover all of this surface and a side surface, and a cathode material layer 1 such as Ni is arranged on this so as to surround an exposure surface of the layer 3. Next, such three-layer structure cathode is sealed up in a glass container 12, and an anode 6 arranged on the ceiling of the container 12 is connected to an anode terminal 10, and the layer 3 is connected to a cathode terminal 11, and discharge gas 7 is sealed up in space created between the anode 6 and the layer 1. By constituting in this way, the layer 1 can be regarded as aggregation of microscopic electrodes 8 such as K1-Kn, and since the layer 2 exists between it and the layer 3, a distributive resistance network is created in a thickness direction and a surface direction, so that a similar function when thickness directional impedance of the electrodes 8 is increased can be obtained. Thereby, uneven distribution is not caused in glow discharge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode structure of a DC type discharge display tube.

[0002]

2. Description of the Related Art Conventionally, it has been considered that the cathode of a DC discharge display tube should have as low an impedance as possible on the cathode side in order to enhance the conversion efficiency from electricity to light. It has been considered that a material capable of efficiently converting the above energy into secondary electron radiant energy can be efficiently pursued, and at the same time, the resistance in the thickness direction of the electrode should be lowered as much as possible. Also, there was an idea of stacking an independent resistor for each pixel in the thickness direction on the anode side instead of the cathode, but this is different from the present invention, and this ensures the independence of each pixel and has a memory function. It is something that can be made.

[0003]

The formation of the cathode of a DC type discharge display tube is centered on the thick film printing technique because of its simplicity and the freedom of design. This is a fine powder of a material suitable for a cathode of a discharge tube, such as Ni or LaB6, made into an ink paste together with a solvent or the like using a low melting point glass as a binder, forms a pattern on a glass substrate by a method such as screen printing, and forms about 550 Bake at ~ 600 ° C. Normally, this firing temperature cannot greatly exceed the softening point of the glass, so that the metal powder is not in a sintered state but in a fixed state by the molten low-melting glass.

The cathode of the display discharge tube obtained by the above-described method of forming a cathode by thick film printing has the following basic problems.
There is a problem of so-called glow condensation, in which the cathode glow used for display light emission concentrates on a part of the cathode with the passage of time, which not only seriously impairs the display quality but also shortens the life of the display tube. This phenomenon is a basic problem common to DC type discharge tubes, but it occurs more markedly in the printed cathode formed by mixing foreign substances as described above than in the cathode formed of a uniform material such as a metal plate. It is confirmed to do.

In order to explain the cause of this phenomenon, it is easy to understand the schematic cross-sectional view of the printed cathode of FIG.
That is, the cathode formed by printing is different from the cathode made of one single metal body, and the micro cathode 8 (k1, k
2, ----- kn). In the actual printed cathode after firing, it was thought that the fine particles of the cathode material had a good electrical conductivity while having contact resistance, but the above-mentioned glow condensation phenomenon was mixed as this binder. It was found that the phenomenon of separation of the cathode material by the low melting point glass was caused.

Generally, in the DC type discharge tube, the discharge stabilizing resistor 5 is inserted in series in the circuit system. When one cathode is divided into a plurality of pixels like an XY matrix discharge tube such as a plasma display, one stabilizing resistor 5 is provided for each anode orthogonal to the cathode.

By the way, as is generally well known, as shown in FIG. 4, all the discharges of T1 and --T4 are connected through a single stabilizing resistor 5 by connecting the anode and cathode in common. It is difficult to light the tubes at the same time. that is,
When any one of the discharge tubes discharges first, the voltage drop that occurs in the stabilizing resistor 5 due to the discharge current decreases the potential of the anodes of the other discharge tubes and causes the terminals of the other discharge tubes to drop. This is because the inter-voltage does not reach the discharge start voltage. However, if the discharge current is further increased, the terminal voltage rises beyond the current supply capacity of the cathode of the previously discharged discharge tube, so that discharge also occurs in other discharge tubes. Here, how many discharge tubes are lit subsequent to the previously discharged discharge tube depends on the current supply capacity of the cathode of each discharge tube.

By the way, the model as shown in FIG. 3 shows that the same phenomenon as described above can occur on one pixel. That is, assuming that a discharge is first generated in a minute portion of one pixel, for example, the minute cathode k1, the minute cathode 8
When the current supply capacity of the cathode material is excellent and the impedance in the thickness direction of the cathode is sufficiently low, the potential drop of the stabilizing resistor on the anode side becomes large. Will not spread. This tendency is that the k1 portion is activated over time, and the phenomenon becomes more and more established. This is the main cause of the ubiquitous phenomenon of glow, which is a cause of significantly impairing the display quality and shortening the life of the display tube.

[0009]

In order to solve the above problems, the present invention provides a three-layer cathode structure in which a resistance layer is arranged under the surface layer of the cathode and a good conductive layer is arranged under the resistance layer. It was done. The construction of this new cathode is explained with reference to one of its embodiments, FIG.

FIG. 1 is a sectional view of a three-layer structure cathode. First, on the lowermost layer on the glass substrate 4, there is a good conductive layer 3 that guides a discharge current to an external terminal. A resistance layer 2 is formed thereon, and is sandwiched between the uppermost cathode material layer 1 and the lowermost good conductive layer 3.

[0011]

The function of the cathode of the structure of FIG. 1 is shown in FIG. 2, which is a schematic cross-sectional view in the case where the discharge gas 7 is enclosed in the discharge vessel formed by the glass container 12 and the glass substrate 4 using the cathode of FIG. Explained. The cathode of FIG. 2 is divided into minute cathodes 8 (k1, k2, --kn) as assumed in FIG. 3, but the resistance layer 2 is present between the good conductive layer 3 and It is distributed in the plane direction to form a resistance network. That is, this corresponds to intentionally increasing the impedance (micro resistance 9) in the thickness direction of each micro cathode 8.

Therefore, first, the discharge is k1, k2, --kn.
If any of these occurs, for example, in k1, the anode potential decreases due to the discharge current, but the potential of k1 increases due to the impedance (micro resistance 9) on the side of the microcathode 8 and it becomes difficult for the current to flow. In order to supply more current, glow also occurs in k2 adjacent to k1. That is, the glow easily diffuses and the ubiquitous phenomenon becomes difficult to occur.

[0013]

EXAMPLE In FIG. 1, Ni, Ag, Cu or the like is used as the material of the lowermost good conductive layer 3 on the glass substrate 4, but the forming method is not necessarily thick film printing, and vapor deposition or It can also be formed by sputtering or the like. The resistance layer 2 is formed by printing a resistance material such as ruthenium oxide (RuO2) or carbon (C) so as to cover the good conductive layer 3 and baking the resistance material, but a vapor deposition method or the like may be used. In addition, the uppermost cathode material layer 1 is made of LaB in addition to Ni, which is commonly used.
A material having a higher secondary electron emissivity such as 6 may be used,
It is formed by stacking on the above two layers by thick film printing. Of course, similar to the above two layers, it can be formed by a thin film method such as vapor deposition.

Of the above three layers, the resistance layer 2 and the cathode material layer 1 may be provided only in the pixel portion, but this is difficult in terms of manufacturing. Therefore, the upper two layers are covered so as to cover the lowermost good conductive layer 3 entirely. Even if formed, there is no problem in operation.

[0015]

EFFECTS OF THE INVENTION In the cathode of a discharge lamp for a direct current type display, the problem of so-called glow condensation, which is a problem in display quality and life, is concentrated in a part of the cathode, thereby solving the problem. Generally, a good cathode material has a high secondary electron emissivity and a small work function, and therefore can supply a large current at a low operating voltage.Therefore, a high secondary electron emissivity and a high cathode resistance cannot both be achieved. As a result, the problem that had been an obstacle to improving the performance of the discharge tube for direct current type display was solved, and it became possible to freely apply excellent cathode materials.

[0016]

[Brief description of drawings]

FIG. 1 is a sectional view of a three-layer structure cathode of the present invention.

FIG. 2 is a schematic explanatory view of a discharge tube using the cathode of FIG.

FIG. 3 is a schematic explanatory diagram of a conventional discharge tube using a cathode.

FIG. 4 is an operation explanatory view when the discharge tubes are connected in parallel.

[Explanation of symbols]

 1 Cathode Material Layer 2 Resistance Layer 3 Good Conductive Layer 4 Glass Substrate 5 Discharge Stabilizing Resistance 6 Anode 7 Discharge Gas 8 Micro Cathode (1 Cathode Material Layer) 9 Micro Resistance (2 Resistance Layer) 10 Anode Terminal 11 Cathode Terminal 12 Glass Container

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[Procedure amendment]

[Submission date] November 26, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

Claims (1)

[Claims] 1. A cathode structure of a direct current discharge display tube, comprising a three-layer cathode structure in which a resistance layer is arranged under a surface layer of the cathode which is in contact with a gas space, and a good conductive layer is arranged under the resistance layer.