JPH01274338A - Dc type electric discharge display tube and its manufacture - Google Patents

Abstract

PURPOSE:To uniform emission and improve brightness with the operation voltage of a DC type electric discharge display tube lowered, by joining between particles of the electron radioactive substance for a cathode material with a conductive particle of easy degree of sintering. CONSTITUTION:An electron radioactive substance 31 is selected from at least one kind of LaB6, CeB6, BeB6, NbB2, TaB2, TiB2, ZrB2, TiC, ZrC, TiN, and ZrN. A conductive particle 32 is selected from at least one kind of Ni3B, Au, Ni, and Al. A paste is made by mixing a vehicle 10-30 capacity part into a mixture 100 capacity part composed of an electron radioactive substance 80-20 capacity % and a conductive particle 20-80 capacity %. The paste is completed by baking at 500-700 deg.C after printed on a substrate electrode 30. This constitution makes an action voltage reduction and high brightness obtainable, and a large area and capacity display tube also obtainable by printing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC discharge display tube and a method for manufacturing the same, and more specifically, it relates to a direct current discharge display tube and a method for manufacturing the same. The present invention relates to a DC type discharge display tube which is combined and used as a discharge cathode, and a method for manufacturing the same.

[Prior Art] In general, DC type discharge display tubes (plasma display panels, hereinafter simply referred to as rPDPJs) can be classified into two types: DC type FDPs whose electrodes are exposed to a discharge space and operated by applying a DC voltage; They are broadly classified into AC type FDPs whose surfaces are coated with a dielectric material and are operated by applying an AC voltage.

DC type FDPs have the drawbacks of low luminous efficiency and high operating voltage (approximately 150 to 200 V) compared to other display elements such as fluorescent display tubes, liquid crystals, and light emitting diodes.

Various proposals have been made regarding cathode materials for DC type PDPs, but none have yet been found to be satisfactory.

The following conditions are required for the cathode material for DC type FDP.

■Low work function and high secondary electron radiation efficiency; ■Resistance to ion bombardment and resistance to scattering; ■Electrical conductivity; ■Easy to manufacture; ■Structure not complicated. etc.

LaB6 (lanthanum boride), for example, has recently attracted particular attention as a cathode material that satisfies the above-mentioned conditions. This LaB6 has a fairly low work function of 2.66 eV and excellent spatter resistance, so it has been put into practical use by electron beam evaporation and plasma spraying. It is difficult to

In addition, with regard to the printing method, various studies have been made to commercialize DC type FDPs using LaB6, but due to the difficulty of sintering, products with satisfactory characteristics have not been obtained, and it is difficult to achieve practical use. Not yet reached.

Problems when this LaB6 is formed by a printing method include the following points.

(2) Since LaB6 is difficult to sinter, when a pattern is formed by a printing method, mechanical and electrical bonding strength cannot be obtained at a firing temperature of about 60 eV.

(2) When a binder such as frit glass is added to obtain mechanical bonding strength, the glass binder fills the space between the La86 particles, making it difficult to form a conductive path.

■ In order to obtain bonding strength between LaB6 particles, after the final sealing process, a voltage is applied between the anode and cathode, and activation treatment is performed using high current gas discharge to melt the La86 particle surface.
A method of creating a mutually connected state has been proposed (Japanese Unexamined Patent Publications No. 80-221926 and No. 60-221926).

However, this method has fatal flaws as shown below.

a) In order to melt and connect the La86 particles, it is necessary to apply an extremely high current of 2 to 5 A/cm2, and the extremely high temperature is concentrated, causing distortion in the glass and scattering of components. I do things.

b) It is difficult to make the bond between the base electrode and the La86 particles uniform over the entire surface.

In this case, at the initial stage of activation, electrons are emitted from the entire cathode surface, but soon electrons begin to flow selectively through the portion with the lowest electrical resistance. At this time, only the part where electricity is flowing generates heat and becomes high temperature, so thermionic emission from the La86 surface becomes active, and furthermore, electricity flows intensively, the surface of the La86 particle melts, and the La86 particle surface melts.
The bond between the B6 particles becomes stronger, the electrical resistance of that part further decreases, and the current flowing locally increases.

As a result, there is a clear separation between areas where current flows and areas where no current flows, and when the light-emitting areas on the cathode surface become patchy, no electricity flows to areas with high electrical resistance, so activity in those areas is lost. I won't be able to do it.

Therefore, if the repulsion light surface becomes uneven, there is no way to recover it.

C) The bonding between the base electrode and the LaB6 layer is insufficient, and it easily peels off (Television Society Technical Report, p. 61. No. 7)
．． VOI 12.1988), etc.

[Problems to be Solved by the Invention] The present invention solves the problems of the prior art described above, and improves the mechanical and electrical coupling between the base electrode, the electron radioactive material, and the particles of the electron radioactive material in a DC type FDP. The purpose of this invention is to reduce operating voltage, make light emission uniform, and increase brightness.

[Means and effects for solving the problem] As a result of intensive studies to solve the problems of the prior art described above, the present inventors have developed an electron radioactive material with a small work function used as a cathode material (discharge cathode). By bonding the particles with easily sinterable conductive particles, the present invention has been completed, which not only reduces the operating voltage of a DC type FDP, but also makes light emission uniform and increases brightness.

That is, the present invention is a DC type discharge display tube characterized in that a discharge cathode is an electron-emitting substance whose particles are bonded together by conductive particles.

Hereinafter, the DC type FDP of the present invention will be explained in more detail.

As the electron emissive substance used as the cathode material of the DC type PDP of the present invention, LaB6, C, which have a small work function,
eB6, BaB6, NbB2, TaB2, Ti
B2, ZrB2, TicSZrC.

Metal borides, carbides, and nitrides such as TiN5ZrN are preferably used. Since these compounds have a small work function, the discharge starting voltage can be lowered. Moreover, it is preferable to use these compounds as raw materials with a particle size of 0.2 to 5 μm.

This is for uniform sintering and uniform light emission of the resulting discharge display tube.

Next, in the DC type FDP of the present invention, mechanical
To improve the electrical bond, easily sinterable conductive particles are added as a binder.

The easily sinterable conductive particles used in the present invention include N
i3B5Au, Ni, Afi, etc. are preferred. These conductive particles preferably have a particle size of 0.2 to 5 μm as a starting material.

Further, the ratio of the electron radioactive substance to the conductive particles is 80 to 20% by volume of the electron radioactive substance and 20 to 8% by volume of the conductive particles. Within this mixing ratio range, the discharge starting voltage of the DC type FDP can be reduced and a good light emission state can be obtained.

Next, a preferred method of manufacturing the DC discharge display tube of the present invention will be described.

80 to 20 volume % of electron emissive particles having an average particle size of 0.5 to 5 μm and an easily sinterable conductive material having an average particle size of 0.2 to 5 μ are mixed within a range of 20 to 80 volume %.

Next, for 100 parts by volume of this mixture, 10 parts by volume of vehicle
A printing paste is prepared by kneading ~30 parts by volume. Also, if necessary, use this printing paste lo.

Add 1 to 10 parts by volume of frit glass per part by volume.

Next, this printing paste is laminated and printed on the base electrode (Ni paste) to a thickness of 3 to 50 μm, and fired at 500 to 700°C in the air to form the cathode of the panel and the discharge tube. Create. In this case, Ni is used as the conductive particle.
Alternatively, when Afi is added, firing is performed in nitrogen gas or a reducing atmosphere to prevent oxidation of these metals.

Hereinafter, the DC type FDP of the present invention will be explained in detail based on the drawings.

FIG. 1 is a structural diagram showing an example of a DC type FDP, and FIG. 2 is a longitudinal sectional view thereof. Further, FIG. 3 is a diagram showing the state of the electron radioactive substance and the conductive particles before firing, and FIG. 4 is a diagram showing the state after firing.

In Figures 1 to 4, 1 is the front glass, 2 is the anode,
3 is a cathode, 4 is a partition, 5 is a back glass, 30 is a base electrode, 31 is an electron emitting substance, and 32 is a conductive particle.

As shown in FIG. 2, a plurality of anodes 2 and cathodes 3 are formed in a container composed of a front glass 1 and a back glass 5. After sealing the periphery of the container with frit glass and creating a high vacuum through the exhaust pipe, apply Penning gas at 50 to 300 T.
Enclose about orr. 150-300 between anode and cathode
When a voltage of about V is applied, a discharge occurs and the enclosed Penning gas is excited to emit light.

Approximately 200% Ne-Ar (0.5%) as Penning gas
When enclosed in Torr, it emits neon orange light and is usually used for monochrome displays. Also, He-Xe (2
%) is sealed at about 200 Torr, it emits ultraviolet light.

If a phosphor is coated on the inner surface of the front glass, the phosphor will be excited by ultraviolet light and emit light.
) By combining gas and phosphor, multi-color and full-color displays can be realized.

The anode formed on the inner surface of the front glass obstructs visibility, so 5n02 and 5n02-In02 (IT
Either use a transparent electrode such as O film, or use a thin wire that does not get in the way.

Since the cathode and anode are perpendicular to each other and form a dot matrix, characters and figures can be displayed as desired.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Examples 1 to 18 and Comparative Examples 1 to 2 As electron emissive particles, LaBe with an average particle size of 1.3μ
A printing paste was prepared using N15B (specific gravity 4.78) and an easily sinterable conductive material having an average particle size of 2.0 microns (specific gravity 8.1), a low melting point glass frit, and an ethyl cellulose vehicle. In this case, LaB6,
Ni3B and glass frit were mixed in the composition ratio shown in Table 1, and 15 to 20 parts by volume of an ethyl cellulose vehicle was added and kneaded to prepare a printing paste. Here, in order to make the calculation easier to understand, an additional 5 parts by volume of glass frit was added to 100 parts by volume of the mixture of LaB6 and Ni3B.

This paste was printed on a glass plate to a thickness of about 25 μm,
Thereafter, it was fired in an air atmosphere at 600°C. The sheet resistance at that time is shown in Table 1. Note that the sheet resistance is determined by increasing the film thickness by 2
The values are shown in terms of 5 μm.

Next, this paste was laminated and printed to a thickness of 20 μm on a base electrode (Nt paste), and similarly fired at 600° C. to form a cathode of a panel and produce a discharge tube.

The discharge starting voltage and light emitting state of the discharge tube thus produced were tested under the following test conditions.

Test conditions Filled gas Ne-Ar (0.5%) 150T
orr Distance between electrodes 0.511 Discharge pulse width 200 μSee AI l/1B Limiting resistance 20 KΩ The results of the examples obtained from these tests are summarized in Table 1.

Reference Example 1 Metallic nickel and low-melting glass frit were mixed in a ratio of 95=5, and 20 parts of an ethyl cellulose vehicle was added to 100 parts of the resulting mixture and kneaded to prepare a printing paste.

A discharge tube was produced using the obtained printing paste, and the discharge starting voltage and light emitting state of the discharge tube were tested under exactly the same test conditions as in Example 1. However, in order to prevent surface oxidation of the nickel, it was fired in a nitrogen gas atmosphere.

The obtained results are summarized in the first example together with the results of the examples and comparative examples.
Shown in the table.

Table 1 As is clear from the results in Table 1, LaB6 is 50 v
When o1% or more (Examples 5 to 9, Examples 14 to 18, and Comparative Examples 1 to 2), the sheet resistance became 20 MΩ or more, but as soon as discharge started, LaB6 and Ni were effectively combined. It became. Here, Ni3B is 600℃
When fired in an atmospheric atmosphere, it reacts with oxygen in the air and becomes metallic nickel as 2Ni3 B+30→6Ni+B2O3, and this metallic nickel becomes a binder between the La86 particles and between the La86 particles and the base electrode.

Moreover, when low melting point glass was added (Examples 10 to 18 and Comparative Example 2), the sheet resistance became lower than when it was not added (Examples 1 to 9 and Comparative Example 1). This means that
In this system, the frit glass functions to improve sinterability, but it does not serve as an insulating layer between the particles.

When LaB6 is 10 vol% or less (Examples 1 and 10), the light emission state is good, but the discharge starting voltage does not decrease much and the effect of LaB6 is not very effective.

Further, when LaB6 is 90 vol% or more (Examples 9 and 18), the discharge starting voltage is reduced, but the light emission state becomes sparse and non-uniform, and it cannot be said to be more effective than the conventional technology. Therefore, it was found that a volume ratio of LaB6 to N15B of 80 to 20% by volume to 20 to 80% by volume is effective.

Examples 19 to 24 The composition ratio of electron radioactive substance and easily sinterable conductive particles is 50:5
Printing pastes were prepared in exactly the same manner as in Example 1 for the substances shown in Table 2, with 0% by volume. A discharge tube was produced using the obtained printing paste, and the discharge starting voltage and light emitting state of the discharge tube were tested under exactly the same test conditions as in Example 1. However, when Al powder and Ni powder are used as easily sinterable conductive materials (Example 19).
20) and the case where TiN was used as the electron emissive material (Example 24), firing was performed in a nitrogen gas atmosphere to prevent surface oxidation. All raw materials used had an average particle size of 1
It was ~4μ. Note that no glass frit was added.

These results are summarized in Table 2.

Table 2 As is clear from the results shown in Table 2, the discharge starting voltage could be reduced in all cases, and the light emission state was uniform.

[Effects of the Invention] As explained above, the present invention has the following effects.

■ Since the electrical resistance within the cathode surface becomes uniform, uniform light emission can be obtained within the surface.

■ Strong adhesive strength with base electrode.

■ Realizes lower operating voltage and higher brightness.

■ Since a cathode material with a small work function such as L a B6 can be formed using a thick film printing method, it is possible to create a large-capacity, large-area DC type FD.
P can be obtained easily and at low cost.

- Since the driving voltage of a DC type FDP can be significantly lowered, the driving circuit can be simplified and costs can be reduced.

■ Since the scattering and consumption of cathode material due to ion bombardment is reduced, long life and stable discharge characteristics can be obtained.

■ Since it is not necessary to encapsulate mercury, the panel structure can be simplified and risks to the environment can be prevented.

[Brief explanation of the drawing]

Figure 1 is a structural diagram showing an example of a DC type FDP, Figure 2 is a vertical cross-sectional view of the same, Figure 3 is a diagram showing the state of the electron radioactive material and conductive particles before firing, and Figure 4 is after firing. It is a figure showing a state. 1: Front glass, 2: Anode, 3: Cathode, 4: Partition wall, 5: Back glass, 30: Base electrode, 31: Electron radioactive substance, 32 Biconductive particles. Patent Applicant Noritake Co., Ltd. Agent Patent Attorney Tatsuo Ito Agent Patent Attorney Satoshi Ito Section 4 Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. A DC discharge display tube characterized in that a discharge cathode is an electron radioactive material whose particles are bonded together by conductive particles. 2. The electron radioactive substance is LaB_6, CeB_6,
, BeB_6, NbB_2, TaB_2, TiB_2,
The DC discharge display tube according to claim 1, which is at least one compound selected from ZrB_2, TiC, ZrC, TiN, and ZrN. 3. The DC discharge display tube according to claim 1 or 2, wherein the conductive particles are at least one selected from Ni_3B, Au, Ni, and Al. 4. Mix 10 to 30 parts by volume of vehicle to 100 parts by volume of the mixture consisting of 80 to 20 volume % of the electron radioactive substance and 20 to 80 volume % of conductive particles to make a printing paste, and after printing, bake at 500 to 700 °C. A method for manufacturing a DC discharge display tube, characterized by: 5. The electron radioactive substance is LaB_6, CeB_6,
BeB_6, NbB_2, TaB_2, TiB_2, Z
5. The method for manufacturing a DC discharge display tube according to claim 4, wherein the material is at least one compound selected from rB_2, TiC, ZrC, TiN, and ZrN. 6. The method for manufacturing a DC discharge display tube according to claim 4 or 5, wherein the conductive particles are Ni_3B or Au. 7. The method for manufacturing a DC discharge display tube according to claim 4 or 5, wherein the conductive particles are Ni or Al and are fired in nitrogen or an inert gas. 8. The method for manufacturing a DC discharge display tube according to claim 4, wherein 1 to 10 parts by volume of frit glass is added to 100 parts by volume of the printing paste.