JPH0568060B2 - - Google Patents

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] Hot cathode tubes, such as so-called fluorescent lamps, which are lit on an AC circuit, have fluorescent substances coated on the inner wall of the glass tube.
Further, tungsten filament coil electrodes are disposed opposite to each other at both ends of the glass tube, and 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.

By passing a current through each of the electrodes of the above discharge tubes,
Discharge is initiated by preheating the electrodes and applying high voltage through both electrode tubes. This discharge generates ultraviolet light, which excites the fluorescent substance on the inner wall of the glass tube to emit visible light. Such discharge tubes are of the single arc discharge type, with negative hot cathode discharge characteristics in which the voltage decreases as the current increases. The disadvantage of this type of discharge tube is that it has a short lifespan.
The duration is short, 3000 to 4000 hours, and the brightness is low, 8000 nt.

The applicant of the present application proposed a composite electrode discharge tube in Japanese Patent Application Laid-Open No. 1-5753, and proposed a new electrode structure, that is, a discharge tube that has the functions of both hot cathode arc discharge and glow discharge, We proposed a discharge tube with high brightness and long life. 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 close to an electrode for arc discharge. In the examples described above, a method for improving the brightness of cold cathode tubes is mainly explained, 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 is an object of the present invention to provide an improved structure that maintains the principle structure of the discharge tube of the above-mentioned Japanese Patent Application Laid-Open No. 2003-100003, and which enables a discharge tube operated by a commercial power source, such as a fluorescent lamp, to have high brightness and a long life.

[Means for Solving the Problem] The 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 source and has both glow discharge and arc discharge functions, and has high brightness and long life. 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.

Figure 1 shows the thin tube of the present invention (with a diameter of approximately 10 mm or less).
An example of a discharge tube is shown below. For example, diameter 6.5mm,
Both ends 1a and 1b of a transparent glass tube 1 with a length of 260 mm
filament coil electrodes 2a, 2b, respectively.
and funnel-shaped sintered electrodes 3a, 3b surrounding this.
is provided. The filament electrode is arranged vertically in the tube axis direction of the glass tube 1, and the terminals at both ends are connected to the stems 1c and 1c at the ends 1a and 1b of the glass tube 1, respectively.
Lead wires 4a, 5a, 4b passing through 1d,
5b, and are supported by these lead wires 4a, 5a, 4b, and 5b so as to be arranged along the central axis of the glass tube 1. The funnel-shaped sintered electrodes 3a, 3b are supported by lead wires 4a, 4b at their bases, and are electrically connected to the lead wires 4a, 4b.
The other end is electrically open. Further, the inner wall of the glass tube 1 is coated with a fluorescent film 6, and a rare gas 7 and a mercury gas 8 are sealed inside the tube. Note that the gas is sealed through an exhaust pipe 9 that is normally closed.

Now, the sintered electrodes 3a and 3b may not have the funnel-like shape as described above, but may have a cylindrical shape or a semi-cylindrical shape, and may also have a spiral shape surrounding the filament coil electrodes 2a and 2b.
It can take any shape as long as it is provided so that particles of the electron emitting substance emitted from a and 2b can be captured. These sintered electrodes 3a, 3b are
In order to facilitate electron emission, it is obtained by, for example, mixing powdered tungsten, zirconium, and nickel with barium carbonate, molding the mixture, and firing the mixture. The diameter of the funnel-shaped opening is about 4.0 mm, and the funnel-shaped sintered electrode has a length of 4 mm, a thickness of 0.3 mm, and a diameter of 1 mm at the part connected to 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 barium hydroxide as an electron emitting substance, for example, and baking it to form a barium carbonate film, and then forming the wire into a coil shape. Alternatively, the same coating may be formed and coated after the tungsten wire is coiled. In this way, the filament electrode 2 with a length of 3 mm and a diameter of 0.5 mm is
a is obtained.

Each filament coil electrode 2a, 2b may be fixedly welded by caulking one end directly to the bottom of the funnel-shaped sintered electrode 3a, 3b.
b 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 example, the pressure of the rare gas (argon gas) sealed in the glass tube 1 is about 5 torr, and the amount of mercury sealed is about 5 mg.

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

The discharge tube includes an oscillation transformer 10 and a high frequency oscillator 1
It is driven by a Kochi lighting circuit 9 consisting of 1. The filament coils 2a, 2b are connected to the lead wires 1a, 1
It is connected to the preheating coil in the oscillation transformer 11 via b. That is, when the lighting circuit 9 is excited, the filament coil electrode 2 is heated by the preheating coil.
A current flows through a and 2b, heating the filament coil electrodes 2a and 2b. As a result, thermoelectrons are emitted from the filament coil electrodes 2a and 2b, and at the same time, a potential difference is applied between both terminals of the respective coils of the filament coil electrodes 2a and 2b. Furthermore, local discharge occurs in 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 3 with a large heat capacity
a, 3b are connected in parallel to the filament coil electrodes 2a, 2b, so the filament electrode 2
a, 2b are not heated to a high temperature, the scattering of evaporated particles is suppressed, and even if the particles are scattered, they are captured by the sintered electrodes 3a, 3b and do not adhere to the inner surface of the glass tube 1, so that the so-called discharge tube The particles of the electron emitting material captured by the sintered electrodes 3a and 3b can be
Since it exerts its effect again, it is possible to extend the life of the discharge tube, which has a short life due to consumption of the electron emitting material.

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 funnel-shaped sintered electrode 3a has a large opening at the bottom, and lead wires 4a and 5a pass through this opening. The lead wire 4a is
Spot welded to sintered electrode. However, the lead wire 5a passes through the opening without contacting the sintered electrode 3a. Filament coil electrode 2
a is the same as in the first embodiment, these lead wires 4a,
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 within the glass tube so that their inner surfaces face each other,
Its cylindrical shaft is arranged in a direction substantially perpendicular to the tube, and its upper end is spot-welded to the lead wires 4a, 4b and fixedly supported, and its lower end is connected to the stems 1c, 1d of the ends 1a, 1b of the glass tube 1. It is supported by anchors 12a and 12b supported by. The filament coil electrodes 20a and 20b are
Lead wires 5a and 5b are provided along the cylindrical axis of the sintered electrode, and have their upper ends fixedly connected to lead wires 4a and 4b, and whose lower ends extend without contacting the sintered electrodes 30a and 30b. Fixedly connected to.

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 suitable for use with thick glass tubes. For example, in a glass tube with a diameter of 25.5 mm and a length of 330 mm, the sintered electrodes 30a,
30b has a diameter of 5 mm, a length of 9 mm, and a curved surface height of 4
mm. Furthermore, the length of the filament coil electrodes 20a, 20b is 5 mm in the coil portion, and the length of each terminal is 3 mm. The diameter of the coil portion is 2 mm. Further, the glass tube 1 is filled with about 10 torr of argon gas and about 20 mg of mercury.

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, thereby preheating the filament coil electrode and emitting thermoelectrons. 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 glow 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 and the discharge is maintained. 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 variant,
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. Similar to the second embodiment, the sintered electrode 30a is supported by the lead wire 4a and the anchor 12a, and the filament coil electrode 20a is supported by the lead wire 4a and the anchor 12a.
A is fixedly connected to the lead wires 4a and 5a, but the lead wire 5a passes through an opening formed in the outer peripheral surface of the sintered electrode 30a in a non-contact state.

FIG. 5 illustrates a third embodiment of the present invention, in which 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 the lead wire 4a at the upper and lower parts.
and anchor 12a, and are supported by spot welding. Filament coil electrode 2
As for 00a, it 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 of the first example was prepared, and a high frequency sinusoidal voltage was applied to the discharge tube under the following conditions.

Conditions: Oscillation frequency: 40kHz Maximum oscillation voltage: 1500V Filament coil voltage: 6.5V Filament coil current: 90mA Filled gas: Argon: 50torr Water Silver 5mg Ambient temperature: Room temperature 20℃ When the oscillation voltage is gradually increased from 0V, it becomes 180V
A discharge current flows, and an arc discharge occurs due to thermionic electrons. Arcing decreases with increasing current,
It showed a negative characteristic of 100V at 20mA.

Glow discharge by sintered electrodes starts at a voltage of 300V, and as the current increases, the discharge voltage increases,
It showed a positive characteristic of 450V at a current of 20mA.

It has been proven that the above arc discharge and glow discharge are maintained during operation of the discharge tube, and that a discharge tube with high brightness and long life can be obtained.

In addition, the filament coil electrode contains barium,
Since active oxides such as strontium are applied to promote the generation of thermoelectrons, these oxides tend to evaporate and peel off due to ion bombardment, adhere to the inner walls of the glass tube, and cause blackening. Yes, but
This blackening phenomenon did not occur because the evaporated particles were captured by the sintered electrode.

Specifically, it has been found that the luminance is 30,000 nt and the lifespan is 10,000 hours.

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

Conditions: Commercial power supply: Voltage: 100V Frequency: 50-60Hz Filled gas: Argon gas 10torr Mercury 20mg Ambient temperature Room temperature 20°C The lighting circuit used a known glow starter method as shown in the figure.

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 discharge tube was continuously lit at a brightness of 8000 nt, a blackening phenomenon occurred on the inner wall of the tube after 100 hours.
After 3000 hours, the brightness decreased to 30% of the initial value, whereas the discharge tube of the present invention shown in Fig. 3 had a low brightness.
Even after 3,000 hours of continuous lighting at 20,000 nt, there was no blackening phenomenon. However, after 10,000 hours, the brightness decreased to 30% of the initial value.

In other words, it has been found that the present invention can provide a discharge tube with 2.5 times the brightness and 3.3 times the lifespan of conventional discharge tubes of the same type.

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

For example, in the above embodiments, the electron emitting material was applied to the filament electrode, but a filament electrode in which the electron emitting material is soaked may also be used. Specifically, an electrode may be used that is manufactured by mixing barium as an electron emitting substance with powdered tungsten, press-molding the mixture, and sintering the mixture.
Further, although a coil-shaped filament electrode has been described, a simply rod-shaped filament electrode may be used.

[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.

2. Because local discharge occurs, a discharge tube that is easy to light and has high responsiveness can be obtained. That is, there is no need to provide an auxiliary electrode on the discharge tube.

3. The ratio phenomenon is unlikely to occur on the inner wall of the glass tube.

4. The glow discharge electrode (layered electrode) does not shift to arc discharge, and the arc discharge electrode (filament current) has its current adjusted by the glow discharge electrode, so the discharge tube can produce a very stable discharge in both phases. can get.

[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 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 showing an electrode portion of a modification of the third embodiment. 1...Glass tube, 2a, 2b, 20a, 20
b, 200a...Filament coil electrode, 3
a, 3b, 30a, 30b, 300a...Sintered electrode, 4a, 4b, 5a, 5b...Lead wire, 6...
...Fluorescent film, 7...Argon gas, 8...Mercury.

Claims (1)

[Claims] 1. In a discharge tube in which arc discharge electrodes with both terminals connected to a lead wire 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 by being connected.