JPH09139178A - Gas discharge type display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas discharge type display panel which has a low discharge maintaining voltage and which does not cause a discharge concentration but enhances luminous efficiency and luminance by forming a cathode exposed to discharge space of a mixture of a rare earth element and an oxide. SOLUTION: A backing electrode 2 is buried into a groove part formed in a rear glass substrate 1 and baked and after that, thereon, a mixture of metal and the oxide of a rare earth element, when needed, a high polymer organic binder is applied and baked to form a cathode. After the rear glass substrate 1 and a front glass substrate 6 in which an anode 4 and a phosphor body 8 are formed are laid to overlap each other through a partition wall 5, the circumference is sealed by glass frit to form discharge space 7, and a discharge gas is enclosed into the discharge space 4 by evacuating it while heating it and sufficiently degassing it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas discharge type display panel for displaying characters and figures using gas discharge, and more particularly to a DC (direct current) type plasma display panel (PD).
P) in the cathode (cathode) material.

[0002]

2. Description of the Related Art Generally, in a DC type PDP, cathodes (cathodes) and anodes (anodes) are arranged in a matrix on the inner surfaces of two flat glass plates facing each other, and each electrode is exposed in a discharge space. .

The interior of the panel is partitioned by ribs (partition walls) so that crosstalk of light does not occur, and color PD
In the case of P, a phosphor is applied to the inner surface of the rib, and a mixed gas of a rare gas such as He, Ne, Kr and Xe is filled as a discharge gas at a pressure of several hundred torr.

Between the cathode and the anode, 200 to 35
When a voltage of 0 V is applied, a discharge is generated, and this discharge generates light in a wide band from ultraviolet rays to infrared rays.

In the case of monochrome, light in the visible region is used as it is, but in the case of color, ultraviolet rays are applied to the phosphor to obtain red, green and blue light emission.

Since such a gas discharge panel has a fast response speed and a self-luminous type, it has a wide viewing angle, is bright and easy to see, and can realize a thin and large-screen display panel for displaying OA equipment. It has been developed as a device and a large wall-mounted TV.

In the conventional monochrome PDP, the discharge gas is Ne-
A mixed gas of Ar was used and Ni was mainly used for the cathode, but Ni is susceptible to sputtering due to ion bombardment due to discharge and cannot be used as it is. Therefore, mercury is sealed inside the panel to prevent sputtering. It is used while being suppressed.

However, mercury is very sensitive to temperature, and if there is temperature unevenness, it tends to have a non-uniform distribution, and the portion lacking mercury will deteriorate immediately.

In particular, it is difficult to keep the entire panel at a uniform temperature in the case of a large panel, and it is difficult to put a large panel using mercury into practical use.

Therefore, in place of the Ni cathode, an oxide conductor cathode having a perovskite type crystal structure has been newly developed as a cathode which does not require mercury and has high sputter resistance.

For example, Japanese Patent Application No. 2-87919 discloses an oxide conductor cathode having a perovskite type crystal structure.

[0012] These oxide conductor cathodes are superior in sputter resistance to metal cathodes, have a sufficiently long life without using mercury, and have a low discharge sustaining voltage. The connection is very effective.

On the other hand, in the DC type color PDP, a pulse memory drive system having a memory function has been developed in order to achieve high brightness, and is a mainstream DC type technique.

Since the cathode material is adapted to increase in size, a cathode having a line resistance as low as possible is desired.
Al having high conductivity is used in place of i.

Al, like Ni, is a metal that is susceptible to sputtering, but is used under the condition that the gas pressure of the discharge gas is high in order to prevent sputtering as much as possible.

However, when the gas pressure becomes high, there are some adverse effects, one of which is that the impedance of the gas space becomes too low, and an electric current flows too much, which may easily cause an arc discharge state leading to electrode destruction. To prevent this, a current limiting resistor is attached to each cell to extend the life.

From the above, in the DC type PDP, the AC type PD
Unlike P, it has a structure in which the electrodes are exposed in the discharge space, and in particular, the cathode material is one of the important items that have a great influence on the drive voltage and the prolongation of the life of the panel.

[0018]

However, the above-mentioned Al
Since the cathode has a relatively high discharge sustaining voltage, a driver IC for driving the panel needs a special high withstand voltage IC, which causes a problem that the cost of the circuit becomes too high.

Since each cell is provided with the above current limiting resistor, it consumes reactive power, resulting in a very large power consumption panel, and many panels are used to increase the brightness. When power is applied, the panel temperature rises due to Joule heat generated from the resistance, and in extreme cases, the panel may crack.

On the other hand, the oxide conductor cathode having a perovskite type crystal structure has a low luminous efficiency even though it has a low discharge sustaining voltage even in the case of a Xe gas system for a color PDP.

Although the reason for this is not clear, when the discharge state was observed, it was observed that the light was emitted from the entire surface of the cathode at the beginning of discharge, but the light emitting region gradually became smaller with the discharge time and the discharge was concentrated. It

The present invention has been made in view of the above problems, and an object of the present invention is to provide a cathode material having a low discharge sustaining voltage and a high luminous efficiency in which discharge concentration does not occur.

[0023]

The present invention is not limited to Al and Ni.
Which metal, Y, which is an oxide of a rare earth element_TwoO_Three, La _Two
O_Three, CeO_Two, Er_TwoO_Three, Lu_TwoO_ThreeMix one of
A combined oxide mixed metal cathode is used.

With this structure, it is possible to obtain a gas discharge type display panel having a cathode with a low discharge sustaining voltage and a high luminous efficiency in which discharge concentration does not occur.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 is a gas discharge type display panel in which the cathode exposed to the discharge space is formed by mixing a metal with an oxide of a rare earth element.

Here, as described in claim 2, the metal is
Al or Ni is suitable. And, as described in claim 3, the oxide is Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ ,
At least one of Er ₂ O ₃ and Lu ₂ O ₃ is suitable.

With such a structure, it is possible to drive at a lower voltage than the conventional metal-only cathode. Therefore, it is possible to use an inexpensive driver IC having a low breakdown voltage, which is very effective in terms of cost.

In the DC type PDP, the electrodes are exposed in the discharge space and electrons are directly emitted from the cathode surface.
For that, the cathode material needs to be at least a conductive material.

The conductive perovskite type oxide conductor has conductivity even though it is an oxide by itself, and therefore, it is possible to continuously emit electrons. However, in the oxide mixed metal cathode of the present invention, The mixed oxide is a perfect insulator by nature, and it is not considered that electrons are continuously emitted from the insulator. In fact, even if an oxide such as Al ₂ O ₃ or ZrO ₂ is mixed with Al or Ni, no particular improvement in discharge characteristics is observed.

However, among the oxides, Y, which has been mentioned in the present invention,
_TwoO_Three, La_TwoO_Three, CeO_Two, Er_TwoO _Three, Lu_TwoRare such as O
A metal oxide mixed with a special oxide called an oxide of an earth element.
In the sword, the discharge start voltage and discharge
Low sustaining voltage and luminous efficiency per unit power
Was found to be higher than for metal alone.
Was.

Further, the discharge concentration observed in the conventional oxide conductor cathode having the perovskite type crystal structure is relatively small in the cathode of the present invention.

The reason why the luminous efficiency is lowered when the discharge is concentrated is considered as follows.

By the discharge, the electrons emitted from the cathode surface collide with a rare gas such as Xe and generate excited atoms such as positive ions and metastable atoms. The excited atoms release energy when returning to the original ground state, and are accompanied by a luminescence phenomenon.

On the other hand, the ionized Xe is attracted to the cathode by the electric field, and by the action of γ, electrons are emitted again from the cathode, and the discharge is maintained. Luminous efficiency is considered to be how efficiently electrons emitted from the cathode collide with Xe atoms or metastable atoms to generate a large number of excited atoms. However, when discharge concentration occurs, before colliding with atoms contributing to light emission. In addition, since it collides with Xe ions that do not directly contribute to light emission, or because the excited atoms collide with the excited atoms and ionize before they fall to the ground state, the density of excited atoms that contribute to light emission decreases. Can be considered.

Therefore, it is important to prevent discharge concentration as much as possible in order to increase the luminous efficiency. In this respect, since the cathode of the present invention is an insulator, it works to disperse the discharge, also helps prevent discharge concentration, and improves the luminous efficiency.

Each embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a sectional view showing the basic structure of a DC PDP of this embodiment.

In FIG. 1, a groove portion is formed in the rear glass substrate 1, and a base electrode 2 and a cathode 3 thereon are formed in the groove portion. The back glass substrate 1 and the front glass substrate 6 are superposed on each other with a partition wall 5 interposed therebetween.

The cathode 3 will be described in the case where Al paste is used as a metal and Y ₂ O ₃ is used as an oxide.

The cathode 3 in which an oxide is mixed with this Al paste has a too high resistance, so the underlying electrode 2 having a high conductivity is provided in the lower layer.

At this time, the base electrode 2 is replaced by the cathode 3 in the upper layer.
A structure was adopted in which the electrode was embedded in the groove so as not to protrude further.

Ribs are provided on the front glass substrate 6, the transparent anode 4 is arranged between the ribs, and the phosphor 8 is arranged on the anode 4.

A mixed gas of, for example, He, Ne, Kr, Xe, etc. is enclosed as a discharge gas inside the panel.

The structure shown in the figure is called a transmission type because the ultraviolet rays emitted by the discharge gas excite the phosphor and the light transmitted through the phosphor is observed. The basic principle of PDP is the same even in a so-called reflective type in which a phosphor is provided on the rear glass substrate side.

The method for manufacturing the DC type PDP of this embodiment will be described below. First, Al paste and Y ₂ O ₃ powder are weighed in a weight ratio of 2: 1 and sufficiently pulverized and mixed in an automatic mortar.

Here, although the viscosity of the paste increases when powder is mixed with the paste, an appropriate amount of vehicle (polymer organic binder) is added to adjust the viscosity so that printing is easy.

Then, a groove having a width of 150 μm and a depth of 50 μm is formed on the rear glass substrate 1 with a diamond cutter.

Next, Ag paste to be the base electrode 2 is applied to the rear substrate 1 having the groove formed therein, and the Ag paste is dropped and embedded in the groove.

After drying, unnecessary Ag attached to the glass surface
The paste is removed with a knife so that the Ag paste remains only in the grooves, and the paste is baked at 550 ° C. for 1 hour.

After firing, the Ag paste contracts and the surface becomes concave. Therefore, the above-mentioned mixed metal cathode paste of Al paste and yttrium oxide is applied to the concave portion, and unnecessary cathodes protruding from the groove are removed in the same manner. After that, it is baked at 580 ° C. for 1 hour.

Further, in order to make it easier to compare the characteristics later, a cathode portion made of Al alone with no oxide mixed was also formed on the same substrate.

Next, a method of manufacturing the front glass substrate 6 will be described. First, after forming a transparent ITO film on the glass substrate 6 and etching it into a stripe shape, a width of 30 μm,
A rib having a height of 100 μm is formed.

Thereafter, a ZnO; Zn phosphor is deposited on the ITO electrode by electroplating. Where ZnO; Z
The n phosphor is a phosphor used in a fluorescent display tube and is adopted because it can be formed relatively easily by an electroplating method.

The back glass substrate 1 thus produced and the above-mentioned back glass substrate 1 are overlapped with each other with the partition wall 5 interposed therebetween, the periphery is sealed with frit glass, and then vacuum evacuation is performed while heating to sufficiently degas. After that, a mixed gas of He and Xe was introduced to form a panel.

Next, the characteristics of the panel thus formed will be described. FIG. 2 shows the cathode of the present embodiment,
It is a current and discharge sustaining voltage characteristic at the time of using a usual Al cathode.

The discharge conditions at this time are as follows. Discharge gas is He 90% Xe 10%, gas pressure 350 Tor
The distance between r, the anode and the cathode is 100 μm.

The panel is 100 μA in advance.
It is data after aging treatment for 1000 minutes.

As is apparent from the figure, the discharge sustaining voltage rises when the current is increased together, but when the discharge sustaining voltages are compared at the same current value, the yttrium oxide mixed cathode of the present embodiment is significantly lower. .

For example, at a current of 50 μA, the discharge sustaining voltage of normal Al is about 180 V, whereas that of the yttrium oxide mixed cathode is about 120 V, which is about 60 V lower.

Then, when the emission brightness is converted per applied electric power and compared, the cathode of the present embodiment is about 26%.
It turned out to be high.

(Embodiment 2) In the following embodiment,
Al paste is used as the metal, and the oxide is classified into alkaline earth oxides, rare earth oxides, and other relatively common oxides, and a paste obtained by mixing the Al paste and the oxide as in the first embodiment is used. Then, the discharge sustaining voltage was examined for the panel having each cathode.

As a result, the discharge sustaining voltage of the so-called rare earth oxide from La of element number 57 to Lu of 71 is as follows.

La ₂ O ₃ is 120 V, CeO ₂ is 130 V
V, Pr ₆ O ₁₁ is 140 V, Nd ₂ O ₃ is 150 V, Pm ₂
O ₃ is 165V, Sm ₂ O ₃ is 185V, Eu ₂ O ₃ is 19V.
0V, 145V for Gd ₂ O ₃ , 150V for Tb ₂ O ₃ , Dy
₂ O ₃ is 160 V, Ho ₂ O ₃ is 140 V, Er ₂ O ₃ is 13 V
0 V, Tm ₂ O ₃ 150 V, Yb ₂ O ₃ 150 V, Lu
₂ O ₃ is 130V.

As described above, it was found that the rare earth oxides generally tend to have a low voltage, but among them, the oxides which are lower than the discharge starting voltage of the cathode of Al alone by 60 V or more are Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Er ₂ O ₃ , Lu ₂
It was O ₃ and was found to be particularly effective. The oxides of Mg, Ca, and Sr, which are so-called alkaline earths, are as follows, with 210 V for MgO and 1 for CaO.
85V and SrO were 230V. Thus, no significant difference from the discharge start voltage of the usual Al cathode was found.

In addition, among other general oxides, no oxide was found in which the discharge sustaining voltage was lowered. For example, Al ₂ O ₃ is 230 V, SiO ₂ is 220 V, Ti
O ₂ is 210 V, ZrO ₂ is 180 V, Nb ₂ O ₃ is 170 V
V.

From the above, rare earth elements are used as oxides.
Elemental oxides are preferred, especially Y _TwoO_Three, La_TwoO_Three, C
eO_Two, Er_TwoO_Three, Lu_TwoO_ThreeSpecially lower the voltage
It was found to be a material that exhibits the effect of

(Embodiment 3) In this embodiment below, a Ni paste was used as the metal and Y ₂ O ₃ was used as the oxide, and a panel was prepared and evaluated in the same manner as in the first embodiment.

As a result, the cathode mixed with Y ₂ O ₃ was N
Discharge sustaining voltage is 60 compared to normal Ni cathode with i only
It was found that V was lowered.

Furthermore, when other rare earth oxides were evaluated, it was confirmed that the discharge sustaining voltage tended to decrease.

When the metals used as cathode materials for other PDPs were also confirmed, the same tendency was obtained.

[0070]

As described above, according to the present invention, since the discharge sustaining voltage becomes low, an IC having a relatively low withstand voltage can be used as an IC for driving the panel, and the cost of the circuit can be reduced. it can.

Further, since the luminous efficiency is high, the heat generation of the panel can be suppressed and a high-brightness panel can be obtained.
The effect of the present invention is very large.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a DC PDP according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the same current and the discharge sustaining voltage.

[Explanation of symbols]

 1 Rear Glass Substrate 2 Base Electrode 3 Cathode 4 Anode 5 Partition 6 Front Glass Substrate 7 Discharge Space 8 Phosphor

Claims (3)

[Claims] 1. A gas discharge display panel in which a cathode exposed to a discharge space is formed by mixing a metal with an oxide of a rare earth element. 2. The gas discharge type display panel according to claim 1, wherein the metal is Al or Ni. 3. The oxide is Y ₂ O ₃ , La ₂ O ₃ , Ce.
The gas discharge display panel according to claim 1 or 2, which is at least one of O ₂ , Er ₂ O ₃ , and Lu ₂ O _3.