JPH02186551A - Discharge tube - Google Patents

Abstract

PURPOSE:To improve brightness by a method wherein an electrode for glow discharge and an electrode for arc discharge are both provided on each of opposite electrode apparatuses. CONSTITUTION:In a discharge tube having a pair of electrode apparatuses provided oppositely with a discharge space in-between wherein at least a part forms a glass wall and gas 5 is sealed, the electrode apparatus is constituted by placing a sintered metallic electrode 2 which can emit electrons and a filament electrode 3 to which oxide, capable of emitting thermions is applied closely to each other and connecting them electrically in parallel to each other. This enables highly bright arc discharge and glow discharge to be obtained at the same time stably, thereby permitting high brightness to be obtained by their synergistic effects and permitting stable glow discharge to be obtained even if current increases.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a discharge tube, and particularly to a discharge tube of a type that uses a combination of the positive characteristics of glow discharge and the negative characteristics of arc discharge in which thermoelectrons are emitted.

[Prior Art] As discharge tubes, cold cathode tubes, hot cathode tubes, and half-boiled cathode tubes have been conventionally used.

Cold cathode tubes as mentioned above have positive discharge characteristics and have the advantages of long life, low power consumption, easy turning on and off, and low heat generation, but they have low brightness. This is a drawback. Hot cathode tubes, so-called fluorescent lamps, have negative thermionic discharge characteristics and are high in brightness, but have short lifespans, high power consumption and heat generation, and disadvantages such as being unable to turn on and off on their own. There is. Since the filament electrode of the semi-heated tube is not energized by an external circuit, it takes a considerable amount of time to obtain the desired brightness, and its lifespan and brightness are impractical.

In Japanese Patent Application No. 63-172761, the present applicant proposed a discharge tube having characteristics that combine the negative characteristics of a cold cathode tube and the positive characteristics of a hot cathode tube. In other words, in the discharge tube, a pair of electrode devices provided facing each other in a discharge space is composed of a cup-shaped electrode for glow discharge and a filament electrode for arc discharge provided within the cup-shaped electrode. This aims to maintain long life with glow discharge and obtain ultra-high brightness with arc discharge. However, this discharge tube required an automatic control circuit to control the discharge current in order to maintain a stable discharge state.

In other words, in the discharge tube, the temperature of the cup-shaped electrode for glow discharge increases several hours after lighting due to thermionic radiation, and as the glow discharge transitions to arc discharge, snaking and flickering phenomena occur, making the discharge unstable. Become. For this purpose, an electronic control circuit is used to control the discharge current, but this control circuit makes the discharge tube expensive, and even with this control circuit, short flickers can still be completely eliminated. It was difficult.

[Problems to be Solved by the Invention] The object of the present invention is to provide a discharge tube that solves the above-mentioned drawbacks.

A specific object of the present invention is to provide a high-brightness device that has both arc discharge and glow discharge functions, and prevents the glow discharge electrode from changing from glow discharge to arc discharge due to temperature rise. It is an object of the present invention to provide a discharge tube with a long life.

[Means for Solving the Invention] In order to achieve the above object, the present invention provides a pair of electrode devices that are provided facing each other in a discharge space at least partially defined by a glass wall and filled with gas. In the discharge tube, the electrode device has a sintered metal electrode capable of emitting electrons and a filament electrode coated with an oxide capable of emitting thermoelectrons, which are arranged close to each other and electrically parallel to each other. The present invention provides a discharge tube characterized in that the discharge tube is connected.

[Operation] Each of the opposing electrode devices installed at both ends of the discharge space has an electrode for glow discharge and an electrode for arc discharge, so if voltage is applied to each from the same high-frequency power source, the discharge space In this method, ultra-high-intensity arc discharge and glow discharge can be stably obtained at the same time, and the synergistic effect of these three
Super high brightness of 5,00 ONt or more can be obtained. To explain specifically, if a metal such as nickel is used for the glow discharge electrode, stable glow discharge can be obtained up to about 3 mmA, but when it exceeds 4 mmA, the glow discharge becomes unstable as it shifts to the arc discharge region. become. However, with the above configuration according to the present invention, a stable glow discharge can be obtained even when the current increases, and the glow discharge alone can reach 10,000 Nt.
is obtained.

[Explanation of Examples] The invention will now be explained in the form of an exemplary embodiment with reference to the accompanying drawings, in which: FIG.

FIG. 1 shows a first embodiment of the present invention, in which a rod-shaped sintered electrode 2 and a filament coil electrode 3 are placed in parallel proximity to both ends of a transparent glass tube 1 with a diameter of about 6 mm and a length of 260 mm. Thus, the discharge tubes are shown arranged in a non-contact manner. The rod-shaped sintered electrode 2 has a diameter of 2 mm and a length of 6 mm by adding barium carbonate to powdered tungsten, zirconium, and nickel, solidifying with a press, and post-sintering. The filament coil electrode 3 is made by applying a barium hydroxide solution to the circumferential surface of a tungsten wire and firing it to provide a barium carbonate outer sheath, which is then formed into a coil shape to provide good electron emission. . These picture electrodes 2 and 3 are held within the glass tube 1 by a tungsten wire or its rod 7, and are further connected via the tungsten rod 7 to a lead wire 8 penetrating the end wall of the glass. There is. A fluorescent film 4 is coated on the inner surface of the glass tube 1, and argon gas 5 is sealed inside at 30 torr.
mmg of mercury 6 is sealed. The outer surface of the glass tube 1 is coated with a trigger paint 9 extending in its length direction. A lead wire 10 is also drawn out from the trigger paint 9 and connected to a lead wire 8 drawn out from one end of the glass tube 1. AC power supply 1 is connected to both lead wires 8.
1 is connected.

FIG. 2 shows a discharge tube in a modified form of the first embodiment shown in FIG. In FIG. 2, parts similar to those in FIG. 1 are designated with the same reference numerals. The difference in this modification is that the filament coil electrode 3a is arranged so as to surround the rod-shaped sintered electrode 2a in a non-contact state.

When a sine wave with an oscillation frequency of 40 KHz and an effective voltage of 1500 V is applied to the lead wires 8 at both ends of the discharge tube, an extremely stable discharge is obtained with a discharge current of 20 mA and a brightness of 35,000 Nt. Furthermore, the temperature of the tube wall of the discharge tube surrounding the electrode device is about 15 degrees higher than room temperature, so the amount of heat generated can be reduced, and power consumption can therefore be kept low. Furthermore, since there is no need to provide a control circuit for obtaining stable discharge, the discharge tube drive circuit can be made compact.

FIG. 3 shows another modification of the first embodiment, and only the different electrode device is shown.

In this variant, the filament coil electrode 3b is
Similar to the case shown in the figure, the coil ring wires surround the rod-shaped sintered electrode 2b, but the difference is that the coil ring wires are in contact with each other and tightly wound into a cup-like shape.

FIG. 4 shows still another modification of the first embodiment, and only the different part, the electrode device, is shown in detail. In this device, a sintered metal electrode 2c for glow discharge is formed into a cup shape, and a filament coil electrode 3c for arc discharge extends linearly along the axis of the cup. The cup-shaped electrode 2 may be formed into a hollow cylindrical shape with a bottom.

The glass tube diameter of the discharge tube of the first embodiment is suitably about 4 mm to 10 mm.

[Test Example 1] A sinusoidal oscillation voltage was applied to the discharge tube shown in FIG. 2 under the following conditions.

Filled gas: Argon gas 50 torr and mercury 5 mm
Mixed gas oscillation frequency with addition of The result was as shown in .

As is clear from FIG. 5, glow discharge started between the sintered electrodes at 400 rmsV, and discharge at the filament coil electrodes started at about 500 rmsV. 500 rms
Even when the voltage was increased to more than sV, positive characteristics were obtained between the sintered electrodes. That is, it was proven that glow discharge was maintained even at 500 rmsV. However, 50
It was proved that a negative characteristic was obtained between the filament coil electrodes at 0 rmsV or more, and that arc discharge was maintained due to this.

As mentioned above, since two types of discharge, glow discharge and arc discharge, are maintained in one discharge tube, ultra-high brightness can be obtained, and since the filament coil electrode is heated by glow discharge, arc discharge can be relatively reduced. Can be generated at low voltage. Since the two types of electrodes are arranged in a non-contact manner,
The sintered metal electrodes are not heated by the heat generated by the filament coil, and therefore the latter do not undergo thermal runaway, so that arc discharge does not occur, and glow discharge is maintained extremely stably between the electrodes.

The filament coil electrodes are coated with active oxides such as barium and strontium to promote the generation of thermionic electrons, so particles scattered due to ion bombardment or evaporated and peeled off during heating can hit the tube wall of the discharge tube. This results in a blackening phenomenon. However, if the cup-shaped sintered metal electrode is used as shown in FIG. Since it is possible to reduce adhesion to the tube wall between discharges and prevent blackening, the life of the discharge tube can be extended. A life test was conducted on the electrode with this configuration, and almost no blackening phenomenon was observed after about 10,000 hours.

FIG. 6 shows a second embodiment of the present invention, in which the discharge tube is an example of a flat discharge plate in the form of a thin box.

This discharge plate has a glass frame spacer 11 sandwiched between an upper glass plate 1a and a lower glass plate 1b, each of which has a fluorescent film coated on its inner surface, and these are joined with glass solder to form a discharge space. ing. In the discharge space, there are several tens of
A discharge gas containing torr of argon gas 5 and several milligrams of mercury 4 is sealed. At both ends of the discharge space, a rod-shaped sintered metal electrode 2d and a filament coil electrode 3d are arranged in parallel and close to each other. The filament coil electrode 3d is a tungsten wire coated with a metal oxide that emits electrons and tightly coiled to form a rod shape.A conductive plate 9a for triggering or a film is attached to the outer surface of the lower glass plate 2a. is pasted.

The discharge plate configured as described above also exhibits the same characteristics as the discharge tube shown in Figure 2, in other words, glow discharge and arc discharge coexist, and ultra-high brightness, long life, and low power consumption can be expected. Moreover, it is easy to turn off the light, generates little heat, and provides an extremely stable surface light source.

FIG. 7 shows a modification of the second embodiment shown in FIG. 6, and only the different parts of the electrode device are shown. In this electrode device, a rod-shaped sintered electrode 2e for glow discharge is surrounded by a filament coil electrode 3e for arc discharge in a non-contact state.

FIG. 8 shows a modified electrode device of the second embodiment, in which a rod-shaped tungsten wire electrode 3f for arc discharge is provided along the vertical axis of a semi-cylindrical sintered electrode 2f. There is. This modification provides the same effect as the discharge tube shown in FIG.

FIG. 9 shows a discharge plate according to a third embodiment of the present invention.

The main difference from the embodiment shown in FIG. 2 is that ribs 12a and 12b are provided on the inner surfaces of the upper and lower glass plates 1c and 1d, respectively. In the case of the second embodiment, a surface light source the size of a postcard can be obtained when the thickness of the glass plate is approximately 4 mm, but if the thickness is increased beyond this, the thickness of the glass plate becomes even more impractical.

However, as in the second embodiment, the ribs 12a, 12b
By providing a glass plate 1c on the upper and lower surfaces, considerable strength is achieved.
M, a lightweight and fairly large-sized surface light source can be obtained.

Furthermore, if the gaps A and B between the tips of the ribs 12a and 12b and the inner surface of the opposing glass plate are approximately 0.5 to 0.1 mm, then
The discharge impedance of this gap increases, and the discharge space becomes
It is substantially divided into a plurality of small discharge spaces x, y, and z, and electrode devices E similar to those shown in FIG. A discharge plate is obtained. With this configuration, arc discharge can be reliably obtained in each small discharge space, and the phenomenon of arc discharge concentrating on one opposing electrode (which tends to occur mainly at low temperatures of 5° C. or lower) can be prevented. Furthermore, since a fluorescent film is applied to the inner surface of the glass plate including the ribs 12a and 12b, the glass plate surface at the rib portions will not become dark. Furthermore, since the ribs increase the number of fluorescent screens, the overall brightness as a surface light source increases. Reference numeral 13 indicates a glass end plate, through which the lead wires 8 pass and hold the electrode devices E, respectively.

In FIG. 10, the ribs 12c and 12d are closely arranged on the glass plate 1e,
This is a modification of the third embodiment in which it is provided at 1d. In this case, an electrode device Ea similar to the electrode device shown in FIG. 8 is provided to avoid providing a large number of pairs of electrode devices in each small discharge space. The end plate is also groove-shaped to accommodate the electrode device Ea.

Even in such a configuration, discharge characteristics similar to those of the discharge plate shown in FIG. 9 can be obtained.

Although sintered metal is used as the glow discharge electrode, it is also possible to use nickel, although the brightness decreases to some extent.

[Effects of the Present Invention] Since the filament coil for arc discharge is heated by glow discharge, thermionic emission is promoted, so rapid lighting is possible (several tens of seconds).

Since the active oxide can be reused and the blackening phenomenon can be suppressed, a long life of about 20,000 hours can be achieved.

Since both glow discharge and arc discharge coexist, 35,
Ultra-high brightness of about 000 Nt can be achieved.

Arc discharge electrodes can be heated by the electrode device itself, so
There is no need to take the trouble to provide an external preheating device, and power consumption can be kept considerably low. Also, the amount of heat generated can be reduced.

The electrode for glow discharge does not shift to an arc discharge state, and stable discharge can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a first embodiment of the present invention. FIGS. 2 to 4 are schematic diagrams each showing a modification of the first embodiment of the present invention, and FIGS. 3 and 4 partially show only the modified portion. FIG. 5 is a graph showing the effects of the present invention. FIG. 6 is a schematic perspective view showing a second embodiment of the present invention. 7 to 8 are partial perspective views showing a modification of the second embodiment of the present invention. FIG. 9 is a perspective view showing a third embodiment of the present invention. FIG. 10 is a perspective view showing only the different parts of a modification of the third embodiment of the present invention. 1... Glass tube, 2... Sintered metal for glow discharge, 3
... Filament electrode for arc discharge, 4 ... Fluorescent film, 5, 6 ... Discharge gas, 7 ... Tungsten wire, 8
, 10...Leader line, 9...Trigger paint, 11
...Discharge power supply.

Claims (1)

[Claims] (1) In a discharge tube having a pair of electrode devices provided opposite to a gas-filled discharge space at least partially defined by a glass wall, the electrode device is made of a sintered material capable of emitting electrons. A discharge tube characterized in that a metal electrode and a filament electrode coated with an oxide capable of emitting thermoelectrons are arranged in close proximity and are electrically connected in parallel to each other.