JPH0422057A - Discharge tube - Google Patents

Abstract

PURPOSE:To achieve high luminance and long life of a discharge tube by providing a glow discharge electrode around each arc discharge electrode, and electrically connecting the glow discharge electrode to the terminal of one arc discharge electrode. CONSTITUTION:A transparent glass tube 1 is provided at both end portions 1a, 1b with filament coil electrodes 2a, 2b and funnel-shaped sintered electrodes 3a, 3b in such a manner that the sintered electrodes 3a, 3b surround the respective filament coil electrodes 2a, 2b. Each of the sintered electrodes 3a, 3b is supported at its root portion by lead wire 4a, 4b and is electrically connected at one end thereto but is electrically released at the other end. The sintered electrodes 3a, 3b with large thermal capacity are connected in parallel to the respective filament electrodes 2a, 2b. Therefore the filament electrodes 2a, 2b are not heated to high temperature and evaporated particles are restrained from scattering and are captured by the sintered electrodes 3a, 3b even when scattering and are not attached to the inner surface of the glass tube 1 and particles of electron-emitting material captured by the sintered electrodes 3a, 3b exhibit their effects again. High luminance and long life of the discharge tube are thus obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in discharge tubes, and particularly to improvements in hot cathode discharge tubes.

[Description of prior art 1 Hot cathode tubes, such as so-called fluorescent lamps, which are lit in an AC circuit, have a fluorescent material coated on the inner wall of the glass tube, and tungsten filament coil electrodes are placed facing each other at both ends of the glass tube. These electrodes are coated with an electron emitting material. Furthermore, argon gas and mercury gas are sealed inside the tube at a pressure of several Torr.

When a current is applied to each of the electrodes of the discharge tube to preheat the electrodes, and a voltage is applied through both electrode tubes, a discharge is started. This discharge generates ultraviolet light, which excites the fluorescent substance on the inner wall of the glass tube to emit visible light. Such a discharge tube is of the single arc discharge type and has a negative hot cathode discharge characteristic in which the voltage decreases as the 'ri current increases. The disadvantages of this type of discharge tube are:
The lifespan is short, 3000 to 4000 hours, and the brightness is 8
It is as low as 000 nt.

The applicant of the present application proposed a composite electrode discharge tube in JP-A-1-5753, and proposed a new electrode structure, that is, a discharge tube that has the functions of both hot cathode arc discharge and electric discharge. proposed a high-brightness, long-life discharge tube. As described in the claims of the patent application, a discharge tube with high brightness and long life is obtained by arranging a sintered electrode in close proximity to an electrode for arc discharge. In this embodiment, the explanation is mainly about improving the brightness of cold cathode tubes, and there is no specific explanation about hot cathode tubes such as so-called fluorescent lamps that operate on commercial power.

[Problems to be Solved by the Invention] The present invention has been made in view of the above, that is, it maintains the principle structure of the discharge tube of the above-mentioned Japanese Patent Application Laid-Open No. 2002-120010, but operates on a commercial power source such as a fluorescent lamp. The purpose of this invention is to provide an improved structure of a discharge tube with high brightness and long life.

[Means for Solving the Problem 1] A discharge tube of the present invention that achieves the above objects is a discharge tube in which arc discharge electrodes, both terminals of which are connected to lead wires, are arranged facing each other, and a glow discharge is generated around each arc discharge electrode. The present invention is characterized in that an electrode is provided and the glow discharge electrode is electrically connected to one terminal of the arc discharge electrode.

[Function] The above configuration of the present invention provides a discharge tube that operates on a commercial power supply and has both glow discharge and arc discharge functions, has high brightness and a long life, and is further suitable for arc discharge. In addition to preventing the temperature rise of the electrodes, the dispersion and evaporation of electron emitting substances and electrode particles due to ion bombardment and evaporation peeling can be prevented, and the phenomenon of blackening of the inner wall of the discharge tube can be extremely reduced.

[Description of Embodiments] The present invention will be described in detail in the form of embodiments with reference to the accompanying drawings.

FIG. 1 shows an embodiment of a discharge tube for thin tubes (diameter 10 mm or less) according to the present invention. For example, diameter 6.5 rin, quality 260
(2) Both ends 1a of the transparent glass tube 1.

A filament coil electrode 2a is provided on each of the electrodes 1b.

2b, and a funnel-shaped sintered electrode 3a surrounding it.

3b is provided. The filament electrodes are arranged vertically in the tube axis direction of the glass tube 1, and terminals at both ends thereof are lead wires 4a, 5a passing through the stems 1c, 1d of the ends 1a, 1b of the glass tube 1.

4b, 5b, respectively, and these leads 14a, 5a, 4b, 5b connect the glass tube 1.
is supported so that it is aligned along the central axis of the The funnel-shaped sintered electrodes 3a, 3b are connected to the lead wire 4 at their bases.
a, 4b, and is electrically connected to them, but the other end is electrically open. Furthermore, a fluorescent film 6 is coated on the inner wall of the glass tube 1, and a rare gas 7 and a mercury gas 8 are contained inside the tube.
is included. Note that the gas is sealed through an exhaust pipe 9 that is normally closed.

Now, the sintered electrode 38.3b is not limited to the funnel shape as described above, but may also be cylindrical, semi-cylindrical, or spiral shaped surrounding the filament coil electrodes 2a, 2b.

It can take any shape as long as it is provided so that particles of the electron emitting substance emitted from 2b can be captured. The sintered electrodes 3a, 3b are obtained by, for example, mixing powdered tungsten, zirconium, and nickel with barium carbonate, molding the mixture, and firing the mixture in order to facilitate electron emission.

The diameter of the funnel-shaped opening is approximately 4.0as+, and the length is 451.
11. A funnel-shaped sintered electrode with a diameter of 0.3 mm and a diameter of 1 am at the joint with the filament coil electrode. Alternatively, nickel metal can be formed into the above shape and used instead of sintered metal. However, in this case, the discharge characteristics are somewhat degraded.

The filament coil electrode 2a is formed by coating a tungsten wire with a solution of, for example, barium hydroxide as an electron emitting material and firing it to form a barium carbonate film, and then forming this into a 2-il shape. Alternatively, the tungsten wire may be coiled and then the field sheathing may be formed and coated. In this way, a filament electrode 2a with a length of 3 m and a diameter of 0.5 MI is obtained.

The ends of each filament coil electrode 2a, 2b may be directly caulked and fixedly welded to the bottom of the funnel-shaped sintered electrode 3a, 3b.

3b along the axis. The other ends of the filament coil electrodes 2a, 2b extend close to the open ends of the funnel-shaped portions of the sintered electrodes 3a, 3b, and are in a non-contact state with the sintered electrodes 3a, 3b.

The filament coil electrodes 2a, 2b and the funnel-shaped sintered electrodes 3a, 3b electrically form a parallel circuit.

In this embodiment, the pressure of the rare gas (argon gas) sealed in the glass tube 1 is about 5 torr, and the amount of mercury filled is about 5J15F.

The operation of the discharge tube of the first embodiment will be explained below.

The discharge tube is driven by a known lighting circuit 9 comprising an oscillation transformer 10 and a high frequency oscillator 11. The filament coils 2a and 2b are lead wires 1a.

It is connected to the preheating coil in the oscillation transformer 11 via 1b. That is, when the lighting circuit 9 is excited, a current flows through the filament coil electrodes 2a, 2b by the preheating coil, and the filament coil electrodes 2a, 2b are heated. As a result, thermoelectrons are emitted from the filament coil electrodes 2a, 2b, and at the same time, the filament coil electrodes 2a, 2
A potential difference is applied between both terminals of each coil of b.

Furthermore, local discharge occurs at each filament coil electrode 2a.

2b and each corresponding sintered electrode 3a, 3b.

A main discharge is easily established by this local discharge, and thereafter arc discharge and glow discharge are maintained within the discharge tube.

Further, the electron emitting material applied to the filament coil electrodes 2a, 2b is evaporated by heating, and the evaporated particles are scattered, but the main discharge is promoted by local discharge, and the sintered electrode 3a has a large heat capacity.

3b is connected in parallel to the filament coil electrodes 2a and 2b, so the filament electrode 2a.

2C) Since it is not heated to $8 temperature, scattering of evaporated particles is suppressed, and even if particles are scattered, the sintered electrode 3a
, 3b, and does not adhere to the inner surface of the glass tube 1, so that the so-called blackening phenomenon that shortens the life of the discharge tube does not occur, and the sintered electrode 3a.

The particles of the electron emitting material captured by the electron emitting material 3b exert their effect again, so that the life of the discharge tube, which has a short life due to consumption of the electron emitting material, can be extended.

FIG. 2 shows a modification of the first embodiment of the present invention, and only the different electrode portions are shown. The other configurations are the same as those in the first embodiment, so they are omitted. The bottom of the funnel-shaped sintered electrode 3a has a large opening, and the lead wires 4a and 5a pass through this opening. The lead wire 4a is spot welded to the sintered electrode. However, the lead wire 5a passes through the opening without contacting the sintered electrode 3a. The filament coil electrode 2a is
These leads 14a are the same as in the first embodiment.

5a.

FIG. 3 shows a second embodiment of the present invention, in which sintered electrodes 30a and 30b have a half-cylindrical shape.

The sintered electrodes 30a and 30b are provided in a glass tube so that their inner sides face each other, and their cylindrical axes are arranged in a direction substantially perpendicular to the tube axis, and their upper ends are spot welded to lead wires 4a and 4b for fixed support. The lower ends of the glass tube 1 are supported by anchors 12a and 12b supported by the stems IG and 1d of the ends 1a and 1b of the glass tube 1, respectively.

The filament coil electrodes 20a, 20b are provided along the cylindrical axis of the sintered electrode, and the upper ends thereof are connected to the lead wire 4.
A lead wire 5a that is fixedly connected to the sintered electrodes 30a and 4b and whose F end extends without contacting the sintered electrodes 30a and 30b.
, 5b.

The rest of the structure of the second embodiment is almost the same as that of the first embodiment, but the discharge tube lighting circuit is different from that shown in FIG. 1, and is of a known glow start type.

This discharge tube is suitably used for thick glass tubes, for example, diameter 25.5JW+.

In a glass tube with a length of 330 am, the sintered electrode 30a
, 30b has a diameter of 5 shoes, a length of 9aw+, and a curved surface height of 4
Shoes are worn. Furthermore, filament coil electrode 20a
, 20b has a coil portion of 5 wires, and each terminal has a length of 3 wires. The diameter of the coil portion is 2'1 m. Further, the glass tube 1 is filled with argon gas of about 10 torr and mercury of about 20 torr.

The operation of the second embodiment is similar to that of the first embodiment, except that driving is started using a known glow start method. That is, when commercial power is applied, a glow discharge occurs between the bimetal electrode and the fixed electrode of the glow starter 13 and heat is generated, so that the bimetal curvature widens and comes into contact with the fixed electrode. Therefore, a current flows from the AC power supply 15 to the filament coil electrode via the ballast 14, so that the filament coil electrode is heated and hot electrons are emitted. Since a potential difference is applied between the filament coil electrodes, this causes a local discharge between the filament coil electrodes and the sintered electrodes. After a few seconds, the temperature inside the claw starter 13 drops, so the bimetal curves sharply and the contact with the fixed electrode is severed. As a result, a back electromotive force is generated in the choke of the ballast 14, and the main discharge of the discharge tube is started.
Maintain discharge. In this case, the main discharge becomes extremely easy due to the local discharge, and an auxiliary discharge electrode such as a trigger coat is not required even in a long discharge tube.

FIG. 4 shows a modification of the second embodiment, and only the electrode portion of the discharge tube is shown. In this modification, a sintered electrode 30a having a half-cylindrical shape with both ends closed is used to further improve the ability to capture evaporated particles of the electron emitting material. Second
Similar to the embodiment, the sintered electrode 30a is supported by the lead 114a and the anchor 12a, and the filament coil electrode 20a is fixedly connected to the lead wires 4a and 5a, but the lead wire 5a is supported by the sintered electrode 30a. It passes through an opening formed in the outer peripheral surface of the tube in a non-contact manner.

FIG. 5 illustrates a third practical embodiment of the present invention,
Only the electrode portion of the discharge tube is shown. In this embodiment, the sintered electrode 300a has a cylindrical shape whose axial direction coincides with the tube axis direction of the glass tube 1, and is spot-welded to the lead 1I4a and the anchor 12a at the upper and lower parts. Each is supported. The filament coil electrode 200a is connected and supported by lead wires 4a and 5a as in the second embodiment.

FIG. 6 shows a modification of the third embodiment, in which a cylindrical sintered electrode 300a is closed by providing a wall at the bottom, and a lead wire 5a is passed through an opening provided in the bottom wall in a non-contact state. I'm letting you do it. This configuration improves the capture of evaporated particles of the electron emitting material.

Example 1 A discharge tube according to the first example was prepared, and a high frequency sinusoidal voltage was applied to the discharge tube under the following conditions.

Conditions: Oscillation frequency 2 Maximum oscillation voltage: Filament coil voltage: Filament coil current: Filled gas: Argon: 50tOrr mercury
5ay Ambient temperature: Normal m 20℃ oscillation voltage QV
If you raise it more gradually, the discharge current will flow at 180V,
Arc discharge occurs due to hot electrons. The arc discharge decreased as the current increased, and showed a negative characteristic of 100 V at 20 A.

Glow discharge by the sintered electrode starts at a voltage of 300V, and the discharge voltage increases as the IL current increases, and the iJ current increases to 20V.
It showed a positive characteristic of 450V at -8.

0kHz 7 500V 6.5v 0eA It was proved that the above arc discharge and glow discharge were maintained during the operation of the discharge tube, and that a discharge tube with high brightness and long life could be obtained.

In addition, active oxides such as barium and strontium are coated on the filament coil electrodes to promote the generation of thermoelectrons, so these oxides evaporate and peel off due to ions such as liiν and adhere to the inner wall of the glass tube. Although there is an axis direction that causes a blackening phenomenon, this blackening phenomenon did not occur because the evaporated particles were captured by the sintered electrode.

Specifically, it has been found that the luminance has a lifetime of 30,000 ntrlOOOO hours.

Test Example 2 A discharge tube similar to the example shown in FIG. 3 was prepared, and a commercial magnetic pressure was applied under the following conditions.

Conditions 2 Commercial power supply: Voltage 100V Frequency 50-60Hz Enclosed gas: Argon gas 10tOrr Mercury 20#j Ambient temperature Normal 20°C The lighting circuit used a known glow starter system as shown.

As a comparative example, a discharge tube shown in FIG. 3 without a sintered electrode was prepared and driven under the same conditions as above.

When the comparative TI tube was continuously lit at Ili degree of 8000 nt, a blackening phenomenon occurred on the inner wall of the tube after 100 hours.
While the brightness decreased to 30% of the initial value after 3000 hours, the discharge tube of the present invention shown in FIG. 3 had a brightness of 20000.
Even after 3000 hours of continuous lighting at nt, no blackening phenomenon occurred. However, after 10,000 hours, the brightness decreased to 30% of the initial value.

In other words, compared to conventional discharge tubes of the same type, the brightness is 2.5
It has been found that a discharge tube with a lifetime 3.3 times longer can be obtained by the present invention.

Although the present invention has been described above in detail in the form of examples, the present invention is not limited to the examples and can be modified in various ways within the scope of the claims.

[Effects of the present invention] With the above configuration of the present invention, 1. A discharge tube with high brightness, long life and low heat generation can be obtained.

Since a 2.8 part discharge occurs, a discharge tube that is easy to stipple and has high responsiveness can be obtained. That is, there is no need to provide an auxiliary electrode on the discharge tube.

3. Blackening phenomenon hardly occurs on the inner wall of the glass tube.

4. The glow discharge electrode (sintered electrode) does not shift to arc discharge, and the arc discharge current (filament current) is adjusted by the glow discharge** electrode, so both of these combine to produce a very stable discharge. A tube is obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a discharge tube according to a first embodiment of the present invention, and the same figure also schematically shows a lighting circuit for driving the discharge tube. FIG. 2 is a perspective view of an electrode portion in a modified form of the first embodiment. FIG. 3 is a perspective view showing a discharge tube according to a second embodiment of the present invention, and the same figure also schematically shows a lighting circuit for driving the discharge tube. FIG. 4 is a perspective view showing an electrode portion in a modified form of the second embodiment. FIG. 5 is a perspective view showing an electrode portion of a third embodiment of the present invention, and FIG. 6 is a perspective view of a modified version of the third embodiment! FIG. 4 is a perspective view showing four electrodes. 1...Glass tube, 2a, 2b, 20a, 20b. 200a...Filament coil electrode, 3a, 3b. 30a, 30b, 300a--Sintered electrode, 4a, 4b
, 5a, 5b-IJ-t'il, 6-It light film, 7.
...Argon gas, 8...Mercury. Procedural amendment (voluntary) February 21, 2008

Claims (1)

[Claims] (1) In a discharge tube in which arc discharge electrodes, both terminals of which are connected to lead wires, are arranged facing each other, a glow discharge electrode is provided around each arc discharge electrode, and the glow discharge electrode is connected to one terminal of the arc discharge electrode. A discharge tube characterized in that it is electrically connected to.