JPH01200548A - Cold cathode low pressure discharge lamp - Google Patents

Abstract

PURPOSE:To prevent attachment of material of an auxiliary electrode for starting to a bulb tube wall in case its sputtering occurs in providing cold electrodes at both ends of a light emitting tube bulb and providing the auxiliary electrode close to one cold electrode by putting this auxiliary electrode to protrude inside the bulb to be positioned behind the cold cathode. CONSTITUTION:Each end of a light emitting tube bulb 1 having fluorescent coating 2 formed on the inner side is sealed by a button stem 3, and cold cathodes 4a, 4b are installed at the stems 3. The electrode is composed of an electrode shaft 5 of W or the like and an electrode plate 6 of Mo or the like attached at the forward end of it, and the electrode plate 6 carrying electron emitting material is bent like a roof. Next, for installing an auxiliary electrode 7 for starting of wire of W or the like at one stem 3, the electrode 7 is installed at a position behind the roof-formed electrode 6. If W composing the electrode 7 is vaporized, an inner wall of the bulb 1 is not contaminated, and discharge between the electrodes 7, 6 is less likely to occur after starting.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a cold cathode low pressure discharge lamp in which a cold cathode is provided at both ends of an arc tube bulb, and a lighting device thereof.

(Prior Art) Recently, cold cathode low pressure discharge lamps that generate little heat during lighting, such as cold cathode fluorescent lamps, have been used as light sources for office automation equipment and backlights for liquid crystals.

A conventional cold cathode fluorescent lamp is constructed by providing a cold cathode at both ends of an arc tube bulb.The circuit device for lighting this cold cathode fluorescent lamp is such that the secondary transformer of an inverter transformer connected to an AC power source connects the cold cathode to both ends of an arc tube bulb. It was configured to be connected to the cathode.

Such cold cathode fluorescent lamps emit electrons from the cold cathode to accelerate the ions and start discharging when started, so unlike hot cathode fluorescent lamps, they do not emit thermoelectrons. Therefore, starting performance tends to be poor.

For this reason, at startup, it is necessary to apply a high voltage of about 0.5 to IK v between the cold cathodes via the secondary transformer of the inverter transformer described in 2 above, which makes the inverter transformer expensive. There are drawbacks.

In order to solve this problem, it is conceivable to provide the cold cathode fluorescent lamp with an auxiliary starting electrode, which has been widely used in high-pressure metal vapor discharge lamps.

That is, in this device, an auxiliary starting electrode is provided in the arc tube bulb near at least one cold cathode, and at the time of starting, discharge is started between this auxiliary electrode and the cold cathode (main electrode) adjacent thereto. This starting discharge is transferred to the main discharge between the cold cathodes at both ends of the arc tube bulb.

This has advantages such as improving the starting performance of the cold cathode fluorescent lamp, eliminating the need to apply a high voltage, and reducing the cost of the inverter transformer.

(Problem to be solved by the invention) By the way, when the starting auxiliary electrode is provided as described above,
During startup, an auxiliary discharge will occur between this auxiliary electrode and the nearby cold cathode, but in this case, the material that makes up the auxiliary electrode, such as tungsten, will sputter and sputter onto the inner surface of the arc tube bulb. There is a concern that it may adhere and cause the bulb to become dirty or black.

On the other hand, when the above-mentioned auxiliary electrode for starting is provided, at the time of starting, this auxiliary electrode must have the opposite polarity to the cold cathode adjacent to it, that is, the same polarity as the cold cathode facing far away. However, if the auxiliary electrode is in the same voltage state as before the start, even after the start, discharge will occur between the auxiliary electrode and the cold electrode adjacent thereto, inhibiting the main discharge.

The present invention aims to provide a cold cathode low pressure discharge lamp in which staining and blackening of the tube wall are prevented by sputtering of the auxiliary electrode.

Another object of the present invention is to provide a lighting device for a cold cathode low pressure discharge lamp that prevents discharge from occurring between the auxiliary electrode and the cold cathode adjacent thereto after starting.

[Configuration of the Invention (Means for Solving the Problems) The first aspect of the present invention is a low-pressure discharge lamp in which a cold cathode is provided at both ends of an arc tube bulb, and an auxiliary starting electrode is provided near at least one of the cold cathodes. The electric lamp is characterized in that the auxiliary electrode is surrounded by the cold cathode adjacent to the auxiliary electrode.

The second aspect of the present invention is a device for lighting a low-pressure discharge lamp in which a cold cathode is provided at both ends of an arc tube bulb and an auxiliary starting electrode is provided near at least one cold cathode, in which the auxiliary electrode is connected to a power source. Connected so that it has the same polarity as the other cold cathode, and between this auxiliary electrode and the power supply, there is a current regulation that is lower than the impedance between the cold cathodes at both ends when the lamp is started, and higher than the impedance between the cold cathodes at both ends after the lamp is started. It is characterized by having a means.

(Function) According to the first aspect of the present invention, since the auxiliary electrode is surrounded by the cold cathode close to it, even if sputtering of the auxiliary electrode material occurs, the surrounding cold cathode prevents it from scattering and prevents it from adhering to the tube wall. To prevent.

According to the second aspect of the present invention, a current regulating means is provided between the auxiliary electrode and the power source so that the impedance is lower than the impedance between the cold cathodes at both ends when the lamp is started, but becomes higher than the impedance between the cold cathodes at both ends after the lamp is started. Later on, a discharge between the auxiliary electrode and the cold cathode adjacent thereto is prevented.

(Example) The present invention will be described below with reference to the first example shown in FIGS. 1 and 2.
This will be explained based on an example.

In the figure, ▪ is an arc tube bulb made of a straight glass tube, and a phosphor wave film 2 is formed on the inner surface.

Both ends of the arc tube bulb 1 are each connected to a button stem 3, for example.
, 8, and cold cathodes 4a, 41) are sealed to these stems 3, 3, respectively. These cold cathodes 4a, 4b are composed of an electrode shaft 5 made of tungsten or the like and an electrode plate 6 made of molybdenum or the like bonded to the tip of the electrode shaft 5. The electrode plate C supports an electron emitting material, and the electrode plate 6 of this embodiment has a roof-shaped bend.

As shown in FIG. 2, one of the stems 3 has a starting auxiliary type FFI 7 sealed close to the second cold cathode 4a. The auxiliary electrode 7 is made of wire such as tungsten,
The tip portion is housed inside the roof-shaped electrode plate 6 of the two-legged cold cathode 4a.

Therefore, the auxiliary electrode 7 is surrounded by the roof-shaped electrode plate 6 of the cold cathode 4a.

And, the auxiliary electrode 7 is 0.5 to 0.5 to this cold cathode 4a.
They are separated by a gap of 4.0 mrm.

Note that a predetermined amount of mercury and a starting rare gas are sealed in the arc tube bulb l.

Such a cold cathode fluorescent lamp is connected to an AC power source 10 via a lighting device as described below.

That is, H is an inverter transformer, and the primary transformer Ila of this inverter transformer 11 is connected to the AC power supply 10, and the secondary transformer 111)
are connected to the cold cathodes 4a and 4b of the cold cathode fluorescent lamp, respectively. In this case, a capacitor 12 functioning as a ballast is interposed between the secondary transformer llb and the other cold cathode 4b.

The auxiliary electrode 7 is connected to the capacitor 12, and therefore has the same polarity as the other cold cathode 4b.

Between the auxiliary electrode 7 and the capacitor 12, a current limiting resistor 13 is connected, which corresponds to the current current control means 1111 of the present invention. This current limiting resistor 13 has a lower impedance than the impedance between the inner cold cathodes 4a and 4b when the lamp is started.

It has a high resistance value that is higher than the impedance between 4b and 4b.

The operation of an embodiment with such a configuration will be explained.

When a power switch (not shown) is turned on, the AC power supply IO is boosted by the inverter transformer 11, and this high voltage is applied to the cold cathodes 4a and 4b of the cold cathode fluorescent lamp through the secondary transformer Ilb.

In this case, a voltage of a polarity opposite to this cold cathode 4a, that is, a voltage of the same polarity as the other cold cathode 4b, is also applied to the auxiliary electrode 7 installed close to one cold cathode 4a.

The auxiliary electrode 7 and one cold cathode 4a adjacent thereto are 0.0.
Since they face each other with a small gap of about 5 to 4.0 m+, discharge occurs more easily than between the cold cathodes 4a and 4b, which face each other with a much larger distance. An auxiliary discharge is started between the cold cathode 4a and one cold cathode 4a that is close to the cold cathode 4a.

When such an auxiliary discharge starts, the cold cathode 4a emits a large amount of electrons to grow this auxiliary discharge, and eventually this auxiliary discharge promotes the main discharge between the inner cold cathodes 4a and 4b, and these inner cold cathodes 4a , 4b transitions to the main discharge.

Therefore, according to such starting, a high voltage is not required to generate an auxiliary discharge between the auxiliary electrode 7 and one of the cold cathodes 4a adjacent thereto, and such an auxiliary discharge can be easily generated. Transition to main discharge.

Therefore, the starting voltage may be low, and a large step-up in the inverter transformer 11 is not required. Therefore, the structure of the inverter transformer 11 becomes simple and inexpensive.

Then, when a main discharge occurs between the two cold cathodes 4a and 4b, the impedance between the inner cold cathodes 4a and 4b becomes low, and the lamp voltage between the inner cold cathodes 4a and 4b becomes low.

At such a low voltage, due to the current regulating action of the current limiting resistor 13, the impedance between the auxiliary electrode 7 and one of the cold cathodes 4a adjacent thereto becomes 2.
Since the impedance between the auxiliary electrode 7 and the cold cathode 4a becomes higher than that between the auxiliary electrode 7 and the cold cathode 4a adjacent to the auxiliary electrode 7, generation of electric discharge is prevented.

In the cold cathode fluorescent lamp, since the auxiliary electrode 7 is surrounded by the roof-shaped electrode plate 6 of the cold triple pole 4a, even if the auxiliary electrode 7 is sputtered during the auxiliary discharge, the roof-shaped The electrode plate 6 which forms the structure prevents scattering, thereby reducing the possibility that the substance of the auxiliary electrode 7 adheres to the bulb wall, thereby preventing staining and blackening of the bulb wall.

In addition, in the case of a cold cathode, a predetermined surface area is required to emit a large amount of electrons, and for this reason, an electrode plate 6 is used, and the auxiliary electrode 7 is surrounded by the electrode plate 6 having such a large area. Therefore, there is no need to increase the number of parts in the configuration of the cold cathode.

Furthermore, since the distance between the auxiliary electrode 7 and the cold cathode 4a adjacent thereto is set to 0.1 to 4.0 mm, auxiliary discharge can be reliably generated.

Note that the present invention is not limited to the above embodiments.

In other words, in the first embodiment, the current limiting resistor 13 is used as the current regulating means.
Instead, a bimetallic switch 20 as shown in FIG.
It may be.

This bimetal switch 20 is closed in a relatively low temperature atmosphere before starting the lamp, so that an auxiliary discharge can be generated between the auxiliary electrode 7 and the cold cathode 4a adjacent thereto, and after starting the lamp. When the attitude of the auxiliary electrode 7 becomes high, the switch opens to prevent discharge from occurring between the auxiliary electrode 7 and the cold cathode 4a adjacent thereto.

Furthermore, a timer 25 as shown in FIG. 4 may be used in place of the current limiting resistor 13 and the bimetal switch 20. This timer 25 is closed when the power is turned on, so that an auxiliary discharge can be generated between the auxiliary electrode 7 and the cold cathode 4a adjacent thereto, and when a predetermined time (within a few seconds) has elapsed after the power is turned on, the timer 25 is closed. This prevents discharge from occurring between the auxiliary electrode 7 and the cold cathode 4a adjacent thereto.

Further, in the first embodiment, the auxiliary electrode 7 is surrounded by the roof-shaped electrode plate B, but as in the fourth embodiment shown in FIG. 5, the electrode plate 30 is configured in a ring shape. The auxiliary electrode 7 may be placed approximately at the center of the ring to surround it.

Furthermore, when implementing the lighting device of the second invention of the present invention, the auxiliary electrode 7 is not limited to being surrounded by the electrode plate 6 or 30, but as shown in FIG. Board 3
It may be set outside of 0.

Furthermore, the present invention is not limited to cold cathode fluorescent lamps, but instead of sealing mercury inside the arc tube bulb 1, a so-called cold cathode fluorescent lamp is used, in which a rare gas such as xenon, argon, neon, etc. is sealed inside the arc tube bulb 1. Similar effects can be expected when applied to gas discharge lamps.

[Effects of the Invention] As explained above, according to the first aspect of the present invention, since the auxiliary electrode is surrounded by the cold cathode adjacent to it, scattering of the auxiliary electrode material even if sputtering occurs can be prevented. Prevent adhesion to. Therefore, staining and blackening of the tube wall are prevented and the lifespan is extended.

According to the second aspect of the present invention, a current regulating means is provided between the auxiliary electrode and the power source so that the impedance is lower than the impedance between the cold cathodes at both ends when the lamp is started, but becomes higher than the impedance between the cold cathodes at both ends after the lamp is started. Discharge between the auxiliary electrode and the adjacent cold cathode is prevented after startup.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention, FIG. 1 is a configuration diagram showing a cold cathode fluorescent lamp and lighting device, FIG. 2 is a perspective view showing one end of the lamp, and FIG. FIG. 3 is a block diagram showing a cold cathode fluorescent lamp and lighting device according to a second embodiment of the present invention, and FIG. 4 shows a cold cathode fluorescent lamp and lighting device according to a third embodiment of the present invention. FIG. 5 is a perspective view showing one end of a lamp showing a fourth embodiment of the present invention, and FIG. 6 is a perspective view showing one end of a lamp showing a fifth embodiment of the present invention. . ■... Arc tube bulb, 3... Stem, 4a, 4b
... cold cathode, 5 ... electrode shaft, 6 ... electrode plate, 7.
... Auxiliary electrode, 10... Power source, 11... Inverter transformer, 12... Capacitor, f3... Current limiting resistor, 20... Bimetal switch, 25... Timer. Applicant's agent Patent attorney Takehiko Suzue

Claims (2)

[Claims] (1) In a low-pressure discharge lamp in which cold cathodes are provided at both ends of an arc tube bulb and an auxiliary starting electrode is provided near at least one of the cold cathodes, the auxiliary starting electrode is surrounded by the cold cathode adjacent to the starting auxiliary electrode. A cold cathode low pressure discharge lamp characterized by: (2) In a device for lighting a low-pressure discharge lamp in which a cold cathode is provided at both ends of an arc tube bulb and an auxiliary starting electrode is provided near at least one of the cold cathodes, the auxiliary starting electrode is connected to the power source at the other end. Connected so that the polarity is the same as that of the cold cathode, and between this auxiliary electrode and the power supply, a current regulating means is provided between the auxiliary electrode and the power source so that the impedance is lower than the impedance between the cold cathodes at both ends when the lamp is started, and is higher than the impedance between the cold cathodes at both ends after the lamp is started. A lighting device for a cold cathode low pressure discharge lamp, characterized in that: