JPH0117230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a low pressure discharge lamp device using a flat low pressure discharge lamp with a flat tube cross section.

(Background Art) Discharge lamps are widely used as light sources for illumination, such as fluorescent lamps, because of their high radiation efficiency. However, in terms of discharge physical properties, the electrical characteristics are negative resistance in the general design range, so a ballast must be inserted in series to suppress the current. For this reason, it is unavoidable that the lighting device as a whole becomes larger, heavier, and more expensive, which can be a major drawback depending on the usage situation.

Here, negative resistance means that once the discharge current starts to increase due to some reason, ionization is further promoted and the discharge impedance decreases, so the discharge sustaining voltage decreases, the current further increases, and the voltage decreases. It refers to the tendency to decline more and more. To explain why this happens in terms of discharge physics, an increase in current means an increase in electrons, and as the number of electrons increases, the probability of ionization collision with the gas increases, resulting in an increase in the generation of ions and electrons, which increases the number of electrons. This is due to the catastrophic process in which electrons are accelerated by an electric field and ionize the gas. To prevent these problems, it is necessary to increase the loss of electrons, that is, to ensure that more electrons are lost than they are produced due to diffusion, bonding, etc.

(Objective of the Invention) The present invention was made in view of the above-mentioned drawbacks, and its purpose is to provide a low-voltage battery that does not require a ballast and has good starting performance by making the discharge characteristics practically positive. To provide discharge lamp devices.

(Disclosure of the Invention) The present invention will be described below based on Examples. 1st
The figure shows an embodiment of a low-pressure discharge lamp according to the present invention. Inside a thin lamp bulb 1 whose upper and lower surfaces are approximately disk-shaped, a pair of electrodes 2 and 3 are arranged with a circular cross section as shown in figure b. A small amount (several tens of milligrams) of mercury and several Torr of an inert gas such as argon are sealed inside the lamp bulb 1 .

The lower and side surfaces of the lamp bulb 1 are formed of a transparent glass globe 1a, the upper surface is formed of a substrate 1b made of glass or ceramic, and the opening edge of the glass globe 1a and the periphery of the substrate 1b are made of glass frit. It is hermetically sealed. The pair of electrodes 2 and 3 are supported via an encapsulated wire provided on the substrate 1b, one electrode 2 is an anode plate made of nickel, etc., and the other electrode 3 is oxidized on a tungsten coil. It is a cathode filament coated with a thermoelectron emitting substance such as barium, and a phosphor 4 such as calcium halophosphate that converts ultraviolet rays from mercury into visible light is coated on the inner surface of the globe 1a, and titanium oxide, etc. is coated on the inner surface of the substrate 1b. A reflective film 5 that reflects visible light and ultraviolet light is applied, and its surface is coated with the phosphor 4 described above. A permanent magnet 6 having a north pole at the bottom is attached to the upper surface of the substrate 1b.

A lamp with such a configuration has a circuit configuration as shown in FIG. 2, that is, a DC power source 7 is connected between the anode 2 and the cathode 3, and a filament heating power source 8 is connected to the cathode filament constituting the cathode 3 to heat the cathode. Then, a discharge occurs between the electrodes 2 and 3 (point a in FIG. 3), and the discharge voltage between the electrodes 2 and 3 tends to decrease due to rapid ionization. However, since the magnetic field B is applied in a direction perpendicular to the discharge current (or electric field), a Lorentz force f is generated in the direction shown by the arrow in Figure 4, causing the discharge plasma to diffuse to the right in the figure. shall be. Furthermore, since the plasma has a thin space, electrons adhere to and recombine to the wall surfaces (the inner surface of the globe 1a and the inner surface of the substrate 1b) during the diffusion process to a large extent, resulting in an increase in so-called charge loss.

Since the magnetic field gradient and cross-sectional shape are designed in advance so that this charge loss is greater than the degree of charge generation due to promotion of ionization, the plasma acts in the direction of increasing the discharge voltage to further promote ionization. As a result, it exhibits a so-called positive characteristic (as the discharge voltage increases as the current increases), and is stably balanced by the externally applied voltage (from the DC power supply 7) (point b in FIG. 3). Of course, if there is no magnetic field B, the lamp will show a negative characteristic as shown by the dotted line in FIG. 3, and unless current limitation is applied externally, the current will increase catastrophically, leading to destruction of the lamp. In addition, in FIG. 3, straight line c indicates the rated power supply voltage.

Figure 4 schematically shows how discharge is diffused depending on the external voltage. The shaded area in the figure is the discharge area, and the power supply voltage is low for a, medium for b,
c is large. Since the Lorentz force f, which is the driving force for diffusion, is proportional to the current and magnetic field strength, the higher the current, the greater the diffusion, which exerts a self-limiting effect such that the loss of electrons due to recombination increases. Therefore, this shows the positive property.

In this way, it exhibits positive characteristics by applying a magnetic field,
In addition, since the Lorentz suppression force acts immediately in response to instantaneous changes in current, it is possible to stably have an operating point that corresponds to the power supply voltage even without a ballast. In addition, as in the above embodiment, in the case of a DC power source, the thin permanent magnet 6 can be closely attached, so it is possible to provide an extremely clean lamp without substantially impairing the external shape of the lamp. Since both electrodes are close to each other, no special starting means is required for starting, and the light can be lit with a simple lighting device.

Next, a specific example will be described with reference to FIG. The lamp bulb 1 is a thin flat plate with rectangular upper and lower surfaces, and is formed by hermetically sealing plate glass with a glass frit. An anode 2 and a cathode 3 are disposed facing each other through an encapsulation line near one of the short sides thereof, and the distance between the anode 2 and the cathode 3 is 10 mm. Also, a small amount (several tens of
mg) of mercury and several Torr of argon gas are sealed. A sheet-shaped permanent magnet 6 is attached to the upper surface of the bulb 1, with the north pole at the bottom.

A lamp with such a configuration is configured with a circuit as shown in FIG.
Apply a DC voltage of
When the magnetic field strength was maintained at about 50 to 100 G, the discharge was diffused and stable lighting was achieved using only the DC power source 7 (discharge starts at about 20 V). The discharge current at that time is approximately
It was 0.5A.

It goes without saying that the present invention is not limited to the above embodiments. For example, the shape of the lamp bulb 1, that is, the shape of the discharge space,
The spread is large in the plane direction perpendicular to the direction of magnetic field application,
Any shape may be used as long as the thickness in the direction of application of the magnetic field is small, the gas to be filled is not particularly limited, and there is no need to adhere a phosphor to the lamp, so long as it is a lamp that produces low-pressure discharge. In addition, it is desirable to arrange the electrodes close to the end of the lamp bulb 1 (close enough to enable direct starting without providing any additional starting means) as shown in Figure 1. The level is rough and the degree of freedom is large. Although it is desirable that the magnetic field B be applied to the entire flat plate surface, the present invention can be implemented as long as it is applied at least near the electrodes 2 and 3. Furthermore, it is not necessary to limit the DC power supply 7 to an AC power supply, and in such a case, the magnetic field applying means may be divided and arranged small electromagnets synchronized with the frequency of the AC power supply on the substrate 1b, and such a configuration is similar to the above embodiment. Although it is somewhat larger and more complex than a lighting device using a normal ballast, it is much more convenient in terms of size, shape, weight, etc. With this structure, the magnetic field strength increases or decreases in accordance with the increase or decrease of the current, and a further positive characteristic effect can be achieved. Furthermore, it goes without saying that the magnetic field applying means does not need to be provided integrally with the lamp, and may be provided, for example, in the main body of the lighting device to which the lamp is mounted.

(Effects of the Invention) As described above, the present invention includes disposing a pair of electrodes close to the side edges of a lamp bulb whose cross section is flat and whose upper and lower surfaces are substantially flat, and at the same time disposing a discharge body within the bulb. A low-pressure discharge lamp device comprising a sealed low-pressure discharge lamp that is lit by applying an electric field between the two electrodes and applying a magnetic field substantially perpendicular to the flat plate surface of the bulb, wherein the applied electric field and the applied magnetic field are is applied so that the Lorentz force is always perpendicular to the distance between the two electrodes and acts in the direction of the center of the bulb, so that it is possible to practically make the discharge characteristics positive, Therefore, it is possible to provide a low-pressure electric lamp device that does not require a ballast like conventional low-pressure discharge lamp devices and that can be started easily.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the low-pressure discharge lamp according to the present invention, in which a is a sectional view, b is a bottom view, and FIG.
The figure is a diagram showing an example of a circuit configuration according to the present invention.
The figure is a voltage/current characteristic diagram of a low-pressure discharge lamp.
Figures a to c are diagrams schematically showing discharge diffusion in a low-pressure discharge lamp according to the present invention, and Figure 5 is a partially cutaway perspective view showing a specific embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. A low-pressure discharge lamp comprising a lamp bulb having a flat cross section and a substantially flat upper and lower surface, a pair of electrodes being disposed close to the side edges thereof, and a discharge body being sealed within the bulb. A low-pressure discharge lamp device in which a lamp is lit by applying an electric field between the two electrodes and a magnetic field substantially perpendicular to the flat plate surface of the bulb, wherein the directions of the applied electric field and the applied magnetic field are determined by the Lorentz force. A low-pressure discharge lamp device characterized in that the voltage is always applied perpendicularly to the gap between the two electrodes and acts in the direction toward the center of the bulb. 2. The low-pressure discharge lamp device according to claim 1, in which a phosphor is coated on the inner surface of the lamp bulb to provide mercury discharge. 3. The low pressure discharge lamp device according to claim 1 or 2, wherein the applied electric field is a DC electric field and the applied magnetic field is a DC magnetic field.