JPH04220929A - Manufacture of dc type electric discharge display tube - Google Patents

Abstract

PURPOSE:To reduce the manufacturing cost of a display tube with excellent characteristics by generating electric discharge between an anode and a non- metal electroconductive powder layer which is put as covering the substratum prior to assembly of the display tube. CONSTITUTION:Ag paste is printed in stripes on the surface of a back face substratum 1 and subjected to a baking process to form a wiring 3. Further thereover is formed a pattern of a cathode 2 as covering the wiring 3 by the use of a paste prepared by kneading a powder of a certain cathode material having a small work function. A front plate forms an anode by attaching ITO onto a substratum 4, and this is put mating with the cathode 2 with a spacer 7 interposed, and the periphery is sealed with glass to form an envelope. A discharge gas in encapsulated in this envelope, and a certain voltage is impressed to generate electric discharge. Thereby the initial stage aging is performed, and the material powder layer of the cathode 2 is sintered. This allows reduction of the manufacturing costs for a display tube having excellent characteristics.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC type discharge display tube, and more particularly to a method for manufacturing a DC type discharge display tube using a non-metallic conductive powder layer for its cathode.

0002

[Prior Art] Generally, discharge display tubes (plasma display panels: hereinafter abbreviated as PDP) are classified as follows:
DC-type PDPs whose electrodes are exposed to a discharge space and are operated by applying a DC (direct current) voltage; and AC-type display tubes whose electrode surfaces are covered with a dielectric material and which are operated by applying an AC (alternating current) voltage. It is broadly divided into.

Among these, DC type PDPs have low luminous efficiency and have a higher operating voltage (approximately 150 to 200 V) than other display elements such as fluorescent display tubes, liquid crystals, and light emitting diodes.
There is a drawback. This is because the cathode materials conventionally used are metals mainly composed of Ni, which have a large work function, and because Hg is encapsulated to prevent spatter of this metal, the metal Hg amalgam formed on the surface has a large work function. by.

Attempts have been made to reduce the operating voltage by reducing the work function of this cathode material. For example, rare earth borides (JP-A-60-221926 to 60-22192
8, etc.) or a conductive oxide containing at least one element selected from Groups Ia, IIa, and IIIa of the Periodic Table of Elements (Japanese Patent Application No. 2-218947), etc., as the cathode material. These have achieved a reduction in operating voltage. However, it has been found that forming a cathode using these cathode materials has the following drawbacks.

[0005] In recent PDPs, in order to make the panel flat, two substrates are stacked with an appropriate distance between them.
The mainstream type is one in which the envelope is sealed with a sealing glass and gas is filled in, so below we will discuss PDs with this configuration.
I will explain along P. Of the two substrates, the front side needs to be a transparent glass plate for display purposes, and the back plate is also made of the same type of glass plate because it is inexpensive. There are limits to the temperature that can be used to form a cathode on this glass substrate. Normally, the maximum temperature that can be used for glass plates, such as soft or hard glass plates, is 60°C to avoid thermal deformation.
The temperature is below 0°C. In addition, the cathode to be formed is adhered to the substrate in a layer or film form to obtain a fine pattern, and a material with a high melting point is selected to provide sputter resistance. 60
Sputtering and vapor deposition are generally used to form a film of a high melting point material at a substrate temperature of 0° C. or lower, but these devices are often expensive and cannot be said to be suitable for mass production. The same applies to the method of patterning the formed film by etching or the like. If the film thickness is increased to lower the resistance, the cost will become even higher.

[0006] Therefore, a method has been proposed in which a printing paste is created using a cathode material in the form of powder and a thick film technique is utilized. According to this method, a patterned cathode material powder layer can be deposited on the substrate at low cost. However, the firing temperature used in this method is limited by the heat resistance of the substrate; for example, if firing below 600°C, sintering or fusion of the cathode material powders will hardly be achieved.
Achievement of stabilization of discharge characteristics is also not sufficient. Therefore, conventionally P
After creating the DP, an aging process is essential to stabilize the discharge characteristics, and the aging conditions are more complicated than those for metal cathodes.

The first disadvantage of this method is as follows.

Aging is accomplished by discharging at a voltage considerably higher than the normal operating voltage. For metal cathodes, the main effect of aging is surface cleaning, which is easily accomplished, but the situation is different for nonmetallic conductor powders. As mentioned above, the non-metallic conductive powder in the formed cathode layer usually has a melting point higher than the firing temperature.
Electrical connections are maintained mainly by contact only. When a discharge is caused in this state, the powder can be sintered or fused by discharge energy, ie, ion bombardment, Joule heating by discharge current, etc., without damaging the base. However, the electrical resistance of the sintered or fused parts decreases, and although it is not certain, the work function also decreases, making it easier for discharge to concentrate in one part. This means that if the cathode has a large area or if one cathode has a large number of display cells, uniform aging cannot be achieved. To solve this problem, the cathode can be divided into minute parts and each part can be discharged independently. However, this method requires a complicated aging drive circuit, and if the discharge is performed in time division and the circuit is simplified, the aging time becomes longer. Furthermore, in the case of a high-definition PDP that has a large number of terminals, a considerable amount of effort is required just to connect the drive circuit and the panel.

The second disadvantage of this method is that aging is performed on finished panels.

At the initial stage of aging, a voltage considerably higher than the operating voltage is required, and in order to perform aging sufficiently and in a short time, a larger amount of current than usual is passed, so naturally the amount of spatter increases proportionally. If this sputtered material adheres to the front glass plate, it will cause a decrease in light transmittance, and if a phosphor is applied, it will contaminate the phosphor. If the sputtered material is electrically conductive, short circuits between circuits also become a problem.

[0011] Therefore, in the conventional DC type PDP using a non-metal conductive powder layer as a cathode, a complicated aging process is unavoidable, and it is difficult to prevent characteristic deterioration due to spatter generated during aging. It was the current situation.

0012

[Problems to be Solved by the Invention] The present invention has been made in view of these problems of the prior art, and is simple and superior in that it eliminates the complicated aging process and eliminates characteristic deterioration caused by aging. An object of the present invention is to provide a method for manufacturing a DC type PDP.

[0013]

[Means for Solving the Problems] As a result of intensive studies to solve the above-mentioned problems of the prior art, the inventors of the present invention have developed a method for combining a non-metallic conductive powder layer adhered to a substrate and an anode before panel assembly. The present inventors have discovered that the above object can be achieved by causing discharge between the two, and have completed the present invention.

That is, the method for manufacturing a DC-type PDP of the present invention is such that, in a DC-type PDP that uses a non-metallic conductive powder layer adhered to a substrate as a cathode, the powder layer is removed before the display tube is assembled. The powder layer is characterized in that a discharge is generated between the powder layer and the anode to stabilize the discharge characteristics of the powder layer.

The method for manufacturing a DC type PDP of the present invention will be explained in more detail below.

As the non-metallic conductive powder used as the cathode in the present invention, it is preferable to select a material that has a small work function and a high secondary electron emission efficiency because the operating voltage can be reduced. for example,
Rare earth borides and periodic table of elements Ia, IIa, III
Many suitable examples include conductive oxides containing at least one element selected from group a. The above-mentioned oxide exhibits favorable characteristics such as a particularly low operating voltage, little discharge gas occlusion, resistance to sputtering, and the ability to use an air atmosphere in forming the powder layer.

This cathode is patterned to match the display pattern, but if a printing paste is prepared using powder, a simple thick film technique can be applied and a cathode powder layer can be formed. Thick film technology is well known, and in addition to non-metallic conductive powder, a tacking component or a metal component that supplements conductivity can be mixed in the cathode powder layer, and these can also be used in the present invention. It is included in non-metallic conductor powder. It is desirable that the amount of metal components to be mixed is small from the viewpoint of reducing operating voltage and sputtering resistance. The cathode powder layer is fired at 600℃ due to the heat resistance of the base glass.
Since the non-metallic conductive powder is not sintered or melted, the cathode film tends to have high resistance. For example, when a plurality of discharge cells are connected by a common cathode, if the resistance value of the cathode is high, there will be a difference in discharge characteristics and aging characteristics at both ends, which is inconvenient. In such a case, it is preferable to select a conductive oxide with low specific resistance or to increase the thickness of the cathode.

Furthermore, when the resistance value of the cathode is high, it is also effective in the present invention to form a metal film under the cathode. Since the discharge characteristics are mainly determined by the surface, any underlying metal can be selected, and since the metal has a sufficiently low resistance, the resistance of the conductive oxide placed on top of it can be determined by considering only the thickness direction. Get better. Therefore, the specific resistance is 100Ω・c
Even a conductive oxide having a temperature of about 300°K (300°K) can be used. Another advantage of this method is that when connecting the cathode to an external circuit, if a metal film is used and a part of it is exposed, the circuit can be formed without problems with normal soldering, bonding, plating, etc. It's about becoming easier.

Furthermore, in the present invention, since the cathode is resistant to ion bombardment, there is no need to include toxic mercury in the gas filled in the tube, and therefore it is preferable to use a gas filled that does not contain mercury.

In the present invention, it is preferable that a pattern of a metal layer is formed on the substrate, and the cathode pattern is formed on this metal pattern. Furthermore, when forming a cathode pattern on this metal pattern, it is effective to cover the entire metal layer with the cathode material on the discharge surface. In this way, there is no need to consider metal sputtering, and any metal such as Ag, Au, Al, Cu, Ni, etc. can be used without adding Hg to the filler gas. For forming the metal pattern, ordinary thick film, thin film technology, etc. can be applied. By configuring as described above, it becomes possible to uniformly cause discharge in a large number of cells.

In the present invention, a discharge is performed to stabilize the discharge characteristics of the nonmetallic conductive powder layer before assembling the PDP (
(Hereafter, this is referred to as initial aging). The purpose of the initial aging is primarily to sinter or fuse the nonmetallic powder layer that serves as the cathode. The discharge voltage required for this is considerably higher than the aging voltage for conventional metal cathodes. Therefore, there is a large amount of spatter due to initial aging, which may adhere to the front glass and reduce light transmittance.If the sputtered material is conductive, it may cause short circuit problems on the circuit, and if the phosphor is deposited, There is a concern that contamination of the phosphor will increase if the phosphor is present. These matters do not pose any problems in the present invention. That is, phosphor deposition can be performed after initial aging without worrying about contamination. Further, the sputtered material can also be removed in a post-process. For example, mechanical, chemical or physical removal methods can be applied. A more convenient method is to prepare an anode for initial aging separately from an anode for the DC type PDP. According to this method, the adverse effects of sputtering during initial aging can be eliminated. In this case, since the anode can be used as a fixing device, there is no need to connect the wires each time the substrate on which the cathode is formed changes, which is particularly convenient for PDPs with a large number of anode wires. Even in a PDP having a large number of discharge cells, only one anode is sufficient for each cathode line or for initial aging of all lighting.

[0022] The discharge gas during initial aging may be in a closed space or an open space. It also generates a gas flow,
The amount of sputtered material deposited on the cathode forming substrate can also be reduced. The discharge gas pressure and distance between electrodes are determined by the manufactured PD.
It may be the same as P, or it may be different. In other words, it can be selected so that initial aging is easy. The discharge gas may be the same as that of the completed PDP, or may be different. The impact of gas ions generated by discharge affects the aging effect, and generally the larger the ion molecular weight, the greater the effect. Therefore, if the gas in the completed PDP is a light element mainly composed of He, a greater effect can be obtained in a shorter time by performing initial aging with other heavy elements such as Ne, Ar, Kr, N2 gas, etc.

As can be seen from this, the initial aging conditions can be set over a wide range of conditions. The simplest gas condition is to use air at atmospheric pressure. To use a specific gas composition or gas pressure, a specific gas container is required, and operations such as replacement are also required. Atmospheric pressure air is convenient without such complications. In this case, there is a risk that the cathode material will be damaged by oxygen components in the air. When the cathode material is a metal or a non-oxide compound, an oxidation reaction occurs, which is not preferable. If a conductive oxide is used as the cathode material, any material with no problems can be selected arbitrarily. Although many conductive oxide materials are known, those containing at least one element selected from Groups Ia, IIa, and IIIa of the Periodic Table of Elements are preferable because they reduce the operating voltage of DC-type PDPs. A detailed example is given in Japanese Patent Application No. 2-218947.

The base on which the cathode that has been initially aged in this way is assembled with another base, the periphery of which is sealed with a sealing glass to form an envelope, into which a discharge gas is sealed. A completed PDP is then manufactured. These steps are no different from those for ordinary PDPs. In these processes, the cathode is made of a non-metallic material and has good sputtering resistance, so the inclusion of toxic Hg can be omitted, and if a conductive oxide is selected as the cathode, gas occlusion is small. Penning gas can be used as the discharge gas. Conventionally, normal panel aging is performed after gas filling, but according to the present invention, this normal panel aging can be omitted, and even if necessary, it can be completed in a short time. .

[0025]

EXAMPLES The present invention will be explained in more detail below based on Examples and Comparative Examples.

Examples 1 to 7 and Comparative Examples 1 to 5 A soda lime glass plate was used as the back substrate, and a commercially available Ag paste (manufactured by DuPont, product No. 7713) was applied to the surface of this plate.
) is printed in a stripe shape and fired to form wiring, and the discharge surface portion is coated with cathode material paste as shown in Table 1 in the same stripe shape and after firing, in order to cover the Ag wiring. A cathode pattern was formed by printing to a thickness of about 10 μm, and after drying, it was fired at 580° C. in air or nitrogen to obtain a cathode made of a non-metal conductive powder layer. A partial perspective view of this is shown in FIG. In the same figure,
Reference numeral 1 indicates the rear substrate, 2 indicates the cathode, and 3 indicates the lower wiring of the cathode. The cathode material paste here was formed as follows. That is, the cathode materials listed in Table 1 were first coated with a thickness of 5 μm.
It was ground to the following particle size and sized to have an average particle size of 1 to 3 μm. Next, SiO2-B2O3-PbO based low melting point glass powder (
Manufactured by Noritake Company Limited, product No. NP-7
A cathode material paste having a viscosity of 100,000 to 200,000 centipoise was prepared by mixing 6 parts by volume of ethyl cellulose (903) with a liquid vehicle in which ethyl cellulose was dissolved in butyl carbitol acetate.

Next, ITO (indium-tin oxide) was deposited in a stripe shape as an anode on the front plate. In order to construct a large number of discharge cells, cathode stripes and anode stripes were faced perpendicularly, and an envelope was formed by sealing the four peripheries with sealing glass via a spacer to obtain an appropriate discharge gap. In addition, Examples 6 to 7
In Comparative Examples 4 to 6, a green phosphor was deposited on the ITO, and in the others, no phosphor was deposited. This cross section is shown in FIG. The same reference numerals as those in FIG. 1 are used, and 4 is a front glass substrate, 5 is an anode, 6 is a phosphor, and 7 is a spacer that also serves as a partition. This discharge gap is 0.
Standardized to 15mm.

Aging was performed for initial aging before assembly of the PDP and for panel aging after assembly; Example 1 was performed only for initial aging, and Example 2 was performed for initial aging only.
In Comparative Examples 1 to 7, both initial aging and panel aging were performed, and in Comparative Examples 1 to 5, only panel aging was performed. These conditions are shown in Table 1.

[0029] These aging processes were carried out specifically as follows. That is, the voltage was once increased until lighting was ensured, and then immediately set to the aging voltage shown in Table 1. The voltage waveform was a square wave with a pulse width of 40 milliseconds and a period of 100 milliseconds, and the total voltage ON state was defined as the aging time. The current value was adjusted using an external resistor so that it was approximately 0.1 A/cm2 per discharge area.

Table 1 shows the discharge sustaining voltage and luminance of the DC type PDP thus obtained. Note that the discharge sustaining voltage was measured as the voltage immediately before the PDP was turned on with direct current after the panel aging was completed, the voltage was gradually lowered, and the light was turned off. In addition, regarding brightness, since almost the same brightness is shown if the discharge current value is the same, each PDP was measured with the same current value, and the one with the highest brightness was set as 100, and the relative value was evaluated.

A schematic sectional view of the apparatus used for this initial aging is shown in FIG. 3, and the details of the initial aging will be explained in further detail.

The container that can be replaced with gas consists of a metal container 8, a glass plate 9 that can be confirmed to be lit, and an O-ring 1 for sealing.
0. The metal container 8 has a hole 11 for gas replacement.
is provided, which includes an exhaust valve 12 and a gas inlet valve 1.
3 as shown in the figure. Back base 1 into this container
is inserted, and a cathode (wiring) 2 is deposited on this base. A stainless steel plate was used as the anode 14, and a hole was provided so that lighting could be confirmed. This stainless steel plate was placed on the back substrate 1 with a spacer 15 having a thickness of 0.15 mm interposed therebetween. Cathode and anode are external lead wires 16, 1
7 and connected to an external power source via an O-ring 10. In this state, the inside of the container was evacuated, and then various pressures were introduced at each composition of the gas filled in the panel shown in Table 1. In addition, for Example 6, the gas composition was changed to Ne-Ar(
0.5%) and the pressure was 250 Torr. Further, since the spacer 15 is not necessary all around the base, it does not interfere with gas exchange.

In this state, the back substrate which had been aged under each of the initial aging conditions described above and shown in Table 1 was taken out of the container. Those that underwent this initial aging (
Examples 1 to 6), non-metal conductive powder layer (cathode) on the substrate
The densification was also achieved in terms of appearance.

Example 8 A DC-type PDP having the characteristics shown in Table 1 was produced in the same manner and under the same conditions as in Example 5, except that the device shown in the schematic cross section shown in FIG. 4 was used for initial aging. I got it.

In the apparatus shown in FIG. 4, a hole 11 for gas replacement is provided in the rear substrate 1, and is connected to an exhaust valve 12 and a gas introduction valve 13 via an O-ring 10. As the anode 14, a glass plate 9 coated with ITO was used. The back substrate 2 and the anode 14 are overlapped with a spacer 15 having a thickness of 0.2 mm interposed therebetween, and a seal ring 18 made of silicone rubber is further inserted around the four peripheries. The gas pressure at this time is 19
It was set to 0 Torr.

Example 9 A stainless steel plate with a hole for confirming the lighting of the discharge was used as an anode on the back plate on which a non-metallic conductive powder layer was adhered as a cathode material, and a 10 μm thick spacer was used as the anode. I placed it. Initial aging was performed by applying 700 V using dry air at atmospheric pressure as the discharge gas space. Densification of the cathode layer was achieved. Hereinafter, a DC type PDP having the characteristics shown in Table 1 was manufactured using the same method and conditions as in Example 5.
I got it.

[0037]

[Table 1]

As is clear from the comparison between the example and the comparative example shown in Table 1, by performing the initial aging, a DC type PDP with sufficiently low discharge sustaining voltage and no reduction in brightness can be produced even when used as a PDP panel. Obtainable. A low discharge sustaining voltage cannot be obtained under panel aging conditions with little brightness reduction without initial aging (Comparative Example 1)
, 4) On the other hand, under panel aging conditions with a low discharge sustaining voltage, the amount of spatter increases, resulting in a decrease in brightness (Comparative Examples 2 to 3 and 5).

That is, if conditions are set so that the discharge sustaining voltage is sufficiently low during initial aging, even if the amount of spatter caused by this is large, the front substrate will not be contaminated.
Or even if it gets dirty, it can be removed, so a PDP with high brightness can be obtained. As described above, in the present invention, although the extra step of initial aging is added, it can be performed in the same manner as normal panel aging, and furthermore, normal panel aging can be omitted or simplified, making the total process less complicated. It rarely happens.

Furthermore, since the gas composition and conditions for initial aging can be changed, aging can be performed for a shorter time than normal panel aging.

The voltage, time, gas composition and pressure, inter-electrode distance, etc. in the initial aging are determined experimentally by confirming that the discharge sustaining voltage has decreased sufficiently.

[0042]

As explained above, according to the method of manufacturing a DC type display discharge tube of the present invention, a PDP with good characteristics can be obtained at a low cost, and furthermore, the following effects are achieved.

(1) Since a non-metal conductive powder with a low work function is used as the cathode, the operating voltage is low, and thick film technology can be applied to patterning the cathode, so mass production is excellent.

(2) By performing initial aging, even if the operating voltage is sufficiently lowered, the adverse effects of spatter during aging can be removed, and the work process and work time can be reduced to the same or less than conventional methods. It is possible.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view showing a cathode layer deposited on a substrate according to the present invention.

FIG. 2 is a schematic partial cross-sectional view showing an example of a DC type PDP manufactured according to the present invention.

FIG. 3 is a schematic cross-sectional view showing an example of an initial aging device used in the present invention.

FIG. 4 is a schematic cross-sectional view showing another example of the initial aging device used in the present invention.

[Explanation of symbols]

1　Back base 2 Cathode 3 Cathode lower wiring base 5,14 Anode

Claims (5)

[Claims] Claim 1: In a DC type discharge display tube that uses a non-metallic conductive powder layer adhered to a substrate as a cathode, a discharge is caused between the powder layer and the anode before the display tube is assembled. D characterized in that the discharge characteristics of the powder layer are stabilized.
A method for manufacturing a C-type discharge display tube. 2. The method for manufacturing a DC type discharge display tube according to claim 1, wherein the anode used for discharge before assembling the display tube is different from the anode used for the display tube. 3. The method for manufacturing a DC type discharge display tube according to claim 1, wherein the discharge gas space before the display tube is assembled is made of air at atmospheric pressure. 4. The method for manufacturing a DC type discharge display tube according to claim 1, wherein the non-metallic conductive powder contains a conductive oxide. 5. The conductive oxide is a member of the periodic table of elements Ia.
5. The method for manufacturing a DC-type discharge display tube according to claim 4, further comprising at least one element selected from Groups , IIa, and IIIa.