JP2000251748A - Gas discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combination of electrode material effective for improving the service life of a gas discharge device with the kind of gas. SOLUTION: In this gas discharge device equipped with a pair of substrates 3, 8 joined mutually through a prescribed interval for forming a sealed space, ionizable gas filled in the space, and electrodes K formed at least on one substrate 8, for ionizing gas and generating discharge in the space, the gas is mainly composed of xenon, and at least the surface parts of the electrodes K are made of material mainly composed of carbon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas discharge device used for a flat display or the like. More specifically, it relates to an electrode structure and a gas composition of a gas discharge device.

[0002]

2. Description of the Related Art A gas discharge device used for a flat display or the like is composed of a pair of substrates joined to each other through a predetermined gap to form a sealed space, an ionizable gas filled in the space, and at least An electrode formed on one of the substrates and ionizing the gas to generate a discharge in a space between the pair of substrates.

[0003]

In a gas discharge device, there is a problem of electrode abrasion due to sputtering of discharge gas molecules. When electrode sputtering occurs, the characteristics of the electrode itself are deteriorated, and for example, uniformity of discharge is impaired. or,
A problem may be caused by the sputtered electrode material adhering to other parts. For example, in the case of a flat display, the sputtered electrode material adheres to the glass substrate, causing a deterioration in transmittance or a deterioration in characteristics of a phosphor or the like.

[0004] The main factors affecting electrode sputtering are the electrode material and the type of discharge gas. Generally, characteristics required for an electrode material of a gas discharge device are high sputter resistance and low work function. The work function is an index indicating secondary electron emission characteristics. The lower the work function is, the larger the amount of emitted secondary electrons is, and the more stable the plasma discharge can be maintained. As a discharge gas species, an inert gas such as helium, neon, argon, or xenon, or a mixture thereof has been frequently used. The amount of wear of the electrode varies depending on the combination of the electrode material and gas type and the discharge conditions.

[0005] Specific examples of the gas discharge device include a fluorescent lamp, a neon tube, and a flat display. In a fluorescent lamp, a material having excellent sputter resistance and a low work function, such as a W + Ba compound, is used as an electrode material. The discharge gas uses an inert element such as argon, neon, or krypton, to which a small amount of mercury is added. Mercury is used not only for the purpose of emitting ultraviolet light having the light emitting function of the phosphor, but also for protecting the cathode (cathode) of the discharge electrode which is particularly strongly affected by sputtering. In addition to fluorescent lamps, in other gas discharge devices, mercury vapor is widely added to reduce electrode wear.

[0006] In particular, a flat display utilizing gas discharge is called a PDP.
They are roughly divided into types. The structure of the AC type is shown in FIG. Partition wall 10
The pair of substrates 3 and 8 are joined to each other via. A portion surrounded by the partition wall 10 forms a discharge space 12P, and is filled with an ionizable gas. A pair of electrodes 9 is formed on the inner surface of one substrate 3. These electrodes are composed of a dielectric 31 and magnesium oxide (MgO) 3
2 coated. An address electrode 9X is formed on the inner surface of the other substrate 8, and its surface is also covered with a dielectric 31. Further, the inside of the discharge space 12P is covered with the phosphor 33. In the AC type, an AC voltage is applied between the pair of electrodes 9 to make the dielectric 31 and the MgO 3
Gas discharge is carried out through the circuit 2. Dielectric 31 and Mg
O32 is an insulator. A small amount of Mg due to gas discharge
O32 is sputtered, but since it is a transparent insulator, short-circuiting between the electrodes and deterioration of transmittance do not occur. On the other hand, a DC type structure is shown in FIG. Partition wall 1
The pair of substrates 3 and 8 are joined to each other via 0.
The portion surrounded by the partition wall 10 forms the discharge space 12P. An electrode 9A functioning as an anode is formed on the inner surface of one substrate 3, and an electrode 9K functioning as a cathode is formed on the inner surface of the other substrate 8. A DC voltage is applied between the two electrodes to ionize the gas filled in the discharge space 12P and generate a plasma discharge. As the electrode material, various conductive oxides and borides are used in addition to metals such as Ni and Al. Further, in order to extend the life of the electrode, it has been attempted to add mercury vapor to the gas. However, it is currently difficult to suppress the electrode sputtering and extend the life to a practical level, and this is a problem to be solved.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the prior art, the present invention mainly provides a combination of an electrode material and a gas type effective for improving the life of a DC type gas discharge device. With the goal. However, the present invention can be used not only for the DC type but also for the AC type. The following measures were taken to achieve the object of the present invention. That is, according to the present invention, a pair of substrates that are bonded to each other through a predetermined gap to form a sealed space, an ionizable gas filled in the space, and the gas formed on at least one substrate are ionized. And a gas discharge device provided with an electrode for generating a discharge in the space, wherein the gas is mainly made of xenon, and the electrode is made of a material mainly made of carbon at least on its surface. Preferably, the gas is filled in the space at a pressure in the range of 1 Torr to 500 Torr. Preferably, the electrode has a laminated structure in which a material mainly composed of carbon is coated on a metal material. Further, the present invention includes a display device as an application example of the gas discharge device. This display device has a flat panel structure including a display cell and a plasma cell that are overlapped with each other via an intermediate substrate. The display cell includes an upper substrate bonded to the intermediate substrate through a predetermined gap, an electro-optical material held in the gap, and a signal electrode formed in a row on the upper substrate and to which an image signal is applied. Have. The plasma cell is joined to the intermediate substrate through a predetermined gap to form a sealed space, a lower substrate, an ionizable gas filled in the space, and a row formed in the lower substrate. A scanning electrode for ionizing gas to generate a discharge in the space. The display device having such a configuration sequentially scans the scanning electrodes and writes an image signal applied to the signal electrodes on the electro-optical material. As a characteristic matter, the gas is mainly composed of xenon,
At least the surface of the scanning electrode is made of a material mainly composed of carbon.

According to the present invention, the gas discharge device can minimize the abrasion of the cathode by combining the electrode mainly composed of carbon with the gas mainly composed of xenon.
By using carbon, which is a very light element with an atomic number of 6, as an electrode material, and using xenon, which is an extremely heavy element with an atomic number of 54, as a discharge gas, electrode interaction can prevent electrode wear.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the gas discharge device according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing a display device incorporating a gas discharge device according to the present invention. The present display device is a plasma address display device in which a plasma cell 2 composed of a gas discharge device is used for addressing a display cell 1 typified by a liquid crystal cell. However, the present invention is not limited to this, and it goes without saying that the present invention is also applicable to a PDP using a plasma cell having a flat panel structure alone. As shown, the plasma addressed display device has a flat panel structure including a display cell 1, a plasma cell 2, and a common intermediate substrate 3 interposed therebetween. The plasma cell 2 is composed of a lower substrate 8 bonded to the intermediate substrate 3, and a gap between the two is filled with an ionizable gas. In the present invention, xenon is mainly used as a gas species. Pure xenon may be used, and in some cases, a gas in which xenon is mixed with helium or neon may be used. Inert elements include helium, neon, argon, krypton, xenon, and radon, in ascending order of atomic number. The first feature of the present invention is that xenon, which is the heaviest inert element except for radon, is selected as a gas species from a practical viewpoint. On the inner surface of the lower substrate 8, a striped discharge electrode 9 is formed. Since the discharge electrode 9 is printed and baked on the flat substrate 8 by a screen printing method or the like, it is excellent in productivity and workability and can be miniaturized. In some cases, the discharge electrode 9 may be formed by sputtering or vacuum deposition using nickel or the like as a material instead of the printing method. That is, in the present invention, either a thick-film electrode formed by printing or the like or a thin-film electrode formed by sputtering or vacuum deposition can be used. Here, the plurality of discharge electrodes 9 are separated from each other by a partition wall 10. Partition wall 1
Numeral 0 divides the space in which the ionizable gas is sealed to form the discharge channel 12. The partition 10 can also be printed and baked by a screen printing method or the like, and the top portion is the intermediate substrate 3.
Is in contact with the lower surface side of. A pair of discharge electrodes 9 surrounded by partition walls 10 adjacent to each other function as an anode A and a cathode K, and generate a plasma discharge between the two. The intermediate substrate 3 and the lower substrate 8 are joined to each other by a sealing material 11 such as a glass frit.

On the other hand, the display cell 1 is constituted by using a transparent upper substrate 4. The upper substrate 4 is attached to the intermediate substrate 3 with a predetermined gap with an adhesive 6 or the like.
The gap is filled with an electro-optical material 7 such as a liquid crystal.
The signal electrode 5 is formed on the inner surface of the upper substrate 4.
This signal electrode 5 is orthogonal to the stripe-shaped discharge electrode 9. Pixels in a matrix are defined at intersections between the signal electrodes 5 and the discharge channels 12.

In the plasma addressed display device having such a configuration, a row-shaped discharge channel 12 in which plasma discharge is performed is switched in a line-sequential manner, and an image is displayed on the column-shaped signal electrode 5 on the display cell 1 side in synchronization with the scanning. Display driving is performed by applying a signal. When a plasma discharge occurs in the discharge channel 12, the inside becomes the anode D almost uniformly, and pixel selection is performed for each row. That is, the discharge channel 12 functions as a sampling switch. When an image signal is applied to each pixel while the plasma sampling switch is turned on, sampling is performed and lighting or extinguishing of the pixel can be controlled. Even after the plasma sampling switch is turned off, the image signal is held in the pixel as it is. In this embodiment, a DC is used in which one of the discharge electrodes 9 assigned to one discharge channel 12 is an anode A and the other is a cathode K.
The present invention is not limited to this
Applicable to molds.

As a second feature of the present invention, at least one of the discharge electrodes 9 which is to be the cathode K is a carbon film 15.
Covered by In other words, at least the surface of the discharge electrode 9 is made of a material mainly composed of carbon. Specifically, the discharge electrode 9 has a laminated structure in which a material mainly composed of carbon is coated with a metal material such as nickel. In the stacked structure, the lower nickel functions as a so-called bus electrode and forms a current path. On the other hand, the upper carbon layer has sputter resistance necessary to protect the bus electrode from the impact of gas ionized in the discharge channel 12 and has at least secondary electron emission characteristics enabling plasma discharge. Carbon has an atomic number of 6 and belongs to the lightest class as a conductive element. Xenon, a discharge gas combined with this, has an atomic number of 5
4, which is the heaviest of the inert elements except for radon, which is not practical. As described above, by combining the electrode material composed of a light element and the gas species composed of a heavy element, wear of the discharge electrode can be effectively suppressed. Even if carbon is scattered from the electrode surface by the impact of xenon, it is considered that there is a high probability that the carbon is hindered by the xenon cloud and returns to the electrode surface again without adhering to other parts.

As described above, the present invention uses an electrode material mainly composed of carbon in a device utilizing gas discharge, particularly DC discharge. The carbon electrode may be formed as a coating on a bus electrode such as nickel, or the discharge electrode may be formed only of a carbon material without using the bus electrode. The carbon electrode is formed by a printing method, an electrodeposition method, a sputtering / evaporation method, a thermal spraying method, a dipping method, or the like. Among them, the thermal spraying method is a method in which a raw material gas containing carbon is turned into plasma, and carbon melted with high heat is sprayed on a substrate to be processed into an electrode. In the dipping method, a wire serving as a core of an electrode is immersed in a carbon-containing liquid to coat the surface of the wire with carbon. This wire is fixed to a substrate to form a discharge electrode. The gas combined with the carbon electrode is mainly composed of xenon, and may be a mixture of pure xenon, helium and xenon, or neon and xenon. Gas pressure is 1 Torr to 5
It is preferable to set in the range of 00 Torr. When the gas pressure exceeds 500 Torr, the spread of the discharge in the discharge channel becomes insufficient, and the discharge state becomes unstable.
If the gas pressure is less than 1 Torr, a discharge voltage exceeding about 500 V is required to generate an appropriate plasma discharge in the discharge channel, and a new problem such as a withstand voltage of the driving IC occurs.

In the embodiment shown in FIG. 1, the interior space is evacuated through an exhaust pipe 25 opened in the lower substrate 8 and a glass chip pipe 26 communicating with the exhaust pipe 25, and then filled with a gas that can be ionized. The tip tube 26 is completely sealed. A getter is placed inside the glass chip tube 26 to absorb unnecessary outgases other than the ionizable gas by heating the getter. Conventionally, a small amount of mercury is placed inside the glass chip tube 26 in addition to the getter 27, and the mercury vapor is filled in the plasma cell 2 by heating. Generally, mercury vapor is introduced to prevent deterioration of the discharge electrode 9 due to sputtering. In the case of the present invention, since the electrode sputtering can be effectively suppressed by combining carbon as the electrode material and xenon as the gas species, it is often unnecessary to introduce mercury vapor.

FIG. 2 is a process chart showing a method for manufacturing the display device shown in FIG. First, as shown in FIG. 1A, a discharge electrode 9 serving as an anode A and a cathode K is formed on a cleaned lower substrate 8. The electrodes were formed by a printing method using a nickel paste. In some cases, a sandblasting method is used to increase the aperture ratio. In the sand blasting method, a conductive paste is printed and baked on the entire surface of the lower substrate 8 in advance, and the conductive paste is selectively ground through a precise mask to obtain a stripe-shaped discharge electrode 9. In the case of the printing method, drying is performed after the printing to evaporate the solvent, and further, calcination is performed to remove unnecessary binder resin. Thereafter, in order to fix the nickel powder in the conductive paste, firing for melting the glass particles is performed. The heating temperature at this time ranges from about 500 to 600 ° C. After the discharge electrodes 9 are formed, the partition walls 10 are formed by a glass paste by the same printing method. Further, connection terminal electrodes (not shown) are formed by a printing method. In some cases, the partition wall 10 together with the discharge electrode 9
Alternatively, the terminal electrodes can be fired at once.

Subsequently, as shown in FIG. 1B, a carbon film 15 serving as a surface layer of the discharge electrode 9 is formed so as to completely cover at least the cathode K. Here, electrodeposition is used as a forming method. The electrodeposition solution used for electrodeposition generally uses water, isopropyl alcohol, or the like as a solvent, into which carbon powder to be coated or low-melting glass particles serving as a binder are added, and ions for imparting charge to these powders are added. It is a mixed colloid solution. After drying, the coated carbon film 15 is baked in an inert atmosphere at about 400 ° C. and fixed on the substrate 8.

Subsequently, as shown in FIG. 1C, the intermediate substrate 3 made of thin glass or the like is joined to the lower substrate 8 by the frit 11. The space sandwiched between the lower substrate 8 and the intermediate substrate 3 is partitioned by a partition wall 10 and forms a discharge channel 12. The discharge channel 12 is filled with xenon as an ionizable gas. Thus, the plasma cell 2 is completed.

Finally, as shown in FIG.
And a display cell 1 is assembled thereon to complete a plasma addressed display device. The display cell 1 is assembled using an upper substrate 4, and a signal electrode 5 is formed on an inner surface thereof. The upper substrate 4 is joined to the intermediate substrate 3 by a sealing material 6. Between the upper substrate 4 and the intermediate substrate 3, for example, a liquid crystal is filled as an electro-optical material 7.

FIG. 3 is a schematic sectional view showing an electrodeposition tank used for forming a carbon film. As shown, the electrodeposition tank 10
0 is filled with the electrodeposition liquid 101, and the substrate 8 to be processed and the counter electrode 102 are immersed. In addition, the substrate 8
Is immersed in the electrodeposition tank 100 in a state of being assembled in the jig 104. A power source 103 is connected between the jig 104 and the counter electrode 102, and the substrate 8 is on the negative electrode side, and the counter electrode 102 is on the positive electrode side. On the substrate 8 side, the cathode K
Are commonly connected by a jig 104 and guided to the negative electrode of the power supply 103. The power supply 103 has an output voltage of about several tens of volts, and the distance between the substrate 8 and the counter electrode 102 is maintained at about several to several tens of mm. As the counter electrode 102, for example, stainless steel can be used. With such a configuration of the electrodeposition tank 100, a carbon film of several μm to several tens μm can be deposited on a bus electrode made of nickel or the like by performing electrodeposition for several minutes to several tens of minutes. The electrodeposition liquid 101 is a colloid solution in which a solvent, carbon powder, low-melting glass for a binder, and ions for giving a charge to these powders are mixed. For example, isopropyl alcohol is used as the solvent, lead glass is used as the low-melting glass, and Mg ions are used as ions for imparting electric charge. The substrate 8 is immersed in the electrodeposition liquid 101 having such a composition and connected to the negative electrode of the power supply 103, while the counter electrode 102 made of stainless steel or the like is connected to the positive electrode of the power supply 103, and a voltage is applied between the two. The carbon powder to which a positive charge is provided in the electrodeposition liquid 101 by the electric field is deposited on the electrode. The coating thickness is controlled by the voltage applied between the substrate 8 and the counter electrode 102 and the electrodeposition time.

Finally, the operation of the plasma addressed display device shown in FIG. 1 will be briefly described for reference with reference to FIG. In the figure, only two signal electrodes 51 and 52, one cathode K and one anode A are shown for easy understanding. Each pixel PXL has a signal electrode 5
1, 52, an electro-optical material 7, an intermediate substrate 3, and a discharge channel. The discharge channel is connected substantially to the anode potential during the plasma discharge. When an image signal is applied to the pixel in this state, charges are injected into the electro-optical material 7 and the intermediate substrate 3. On the other hand, when the plasma discharge ends, the discharge channel returns to the insulating state, and becomes a floating potential, and the injected charge is held in each pixel PXL. A so-called sampling hold operation is performed. Since the discharge channels function as individual sampling switch elements provided in the individual pixels PXL, they are schematically shown using switch symbols SW. On the other hand, the electro-optical material 7 and the intermediate substrate 3 sandwiched between the signal electrodes (51, 52) and the discharge channel function as sampling capacitors. When the sampling switch SW is turned on by line-sequential scanning, the image signal is held by the sampling capacitor, and each pixel is turned on or off according to the signal voltage level. Even after the sampling switch SW is turned off, the signal electrode is held by the sampling capacitor and the active matrix operation of the display device is performed.

[0021]

As described above, according to the present invention,
In the gas discharge device, the ionizable gas is mainly composed of xenon, and the discharge electrode is made of a material composed mainly of carbon at least on the surface. With a relatively simple structure combining xenon and carbon, the sputter resistance of the discharge electrode can be improved and the service life can be extended. Further, the spatter resistance of the discharge electrode can be improved without adding mercury vapor, and the life can be similarly extended.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a plasma addressed display device incorporating a gas discharge device according to the present invention.

FIG. 2 is a process chart showing a method for manufacturing the display device shown in FIG.

FIG. 3 is a schematic view showing an electrodeposition tank used in the method of manufacturing the display device shown in FIG.

FIG. 4 is a schematic view for explaining the operation of the display device shown in FIG. 1;

FIG. 5 is a sectional view showing a conventional AC type gas discharge device.

FIG. 6 is a sectional view showing a conventional DC gas discharge device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Display cell, 2 ... Plasma cell, 3 ... Intermediate substrate, 4 ... Upper substrate, 5 ... Signal electrode, 7 ...
・ Electro-optical material, 8 ・ ・ ・ Lower substrate, 9 ・ ・ ・ Discharge electrode, 10 ・ ・ ・ Partition, 15 ・ ・ ・ Carbon film, 100 ・
..Electrodeposition tank, 101 ... Electrodeposition liquid, 102 ... Counter electrode, 103 ... Power supply, 104 ... Jig

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoichi Morita 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Takehiro Tokawa 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Hirohito Komatsu 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo Sony Corporation Inside (72) Inventor Kiyoshi Okano 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka In-company (72) Inventor Atsushi Seki 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo F-term in Sony Corporation (reference) 5C040 FA01 FA02 FA09 GC03 GC18 GC19 GJ02 GJ08 JA07 JA08 JA12 JA17 JA31 JA40 KA20 KB22 MA10

Claims (4)

[Claims] 1. A pair of substrates joined to each other through a predetermined gap to form a sealed space, an ionizable gas filled in the space, and an ionizable gas formed on at least one of the substrates. A gas discharge device comprising: an electrode that generates a discharge in the space; and wherein the gas is mainly made of xenon, and the electrode is made of a material whose at least surface portion is mainly made of carbon. . 2. The gas has a pressure of 1 Torr to 50 Torr.
2. The gas discharge device according to claim 1, wherein the space is filled in a range of 0 Torr. 3. The gas discharge device according to claim 1, wherein the electrode has a laminated structure in which a material mainly composed of carbon is coated on a metal material. 4. A flat panel structure comprising a display cell and a plasma cell which are overlapped with each other via an intermediate substrate, wherein the display cell is joined to the intermediate substrate via a predetermined gap, and And a signal electrode formed in a row on the upper substrate and to which an image signal is applied. The plasma cell is bonded to the intermediate substrate through a predetermined gap and sealed. A lower substrate forming a space, an ionizable gas filled in the space, and a scanning electrode formed in a row on the lower substrate to ionize the gas and generate a discharge in the space; In a display device for sequentially scanning a scanning electrode and writing an image signal applied to the signal electrode to the electro-optical material, the gas is mainly made of xenon, and the scanning electrode is made of a material whose at least surface portion is mainly made of carbon. From Display device according to claim Rukoto.