JPH0367455A - Electric discharge tube device - Google Patents

Abstract

PURPOSE: To stably carry out electric discharge and provide a practical light source by applying a radio frequency electric field to a part of a wall of a discharge tube and exciting sealed substances and generating visible light. CONSTITUTION: An electric discharge tube 20 is made of a light transmissive dielectric material and substances 24 are sealed in the tube. A launcher 22 is formed as a coaxial structure consisting of an inner tube 26 and an outer tube 28. When a radio frequency electric power generator 34 is turned on, a vibrating electric field with frequency within a range, for example, 1MHz-1GHz is parallel to an axis in the longitudinal direction of the tube 20 in gaps 32, 33 and a launcher 22 to which sufficient electric power is supplied generates electric discharge in the sealed substances 24 and keeps the electric discharge. Consequently, the electric discharge apparatus can be used as a light source. In this case, the sealed substances 24 consist of compounds, selected from groups of metal halides and metal oxyhalides, and rare gases such as argon.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge tube device, and more particularly to a device used as a light source.

BACKGROUND OF THE INVENTION It is known to use electromagnetic surface waves to create and maintain low pressure electrical discharges in gases, as disclosed for example in European Patent No. 0225753A2 (University of California). The surface waves do not extend the entire length of the discharge tube containing the gas, but are applied to a power supply device (also known as a launcher) located around the outside of the discharge tube.
caused by

In such a device, there is no need to provide electrodes inside the discharge tube. The power for generating electromagnetic waves is obtained from a radio frequency power generator.

It has been proposed to use such devices as visible or ultraviolet light sources. To provide a visible light source, the discharge tube is filled with a mixture of an inert gas and a mercury vapor phase (e.g., argon gas and mercury vapor phase), and a 254-nm light beam is placed on the inner surface of the discharge tube.
It may be a common fluorescent lamp discharge tube coated with phosphor which converts ultraviolet radiation into visible light. To use as an ultraviolet light source, the discharge tube must be a typical germicidal or curing lamp discharge tube made of quartz glass and filled with a mixture of inert gas and mercury vapor, but not coated with phosphorus. It's good to have one.

However, there are disadvantages to using fluorescent lamp type discharge tube devices to obtain visible light. As mentioned above, discharge tubes containing a mixture of inert gas and mercury vapor primarily produce ultraviolet light, and phosphorus must be used to convert the ultraviolet light into visible light. Approximately half of the energy of the UV quanta is lost during this process.

In theory, it is possible to use volatile metal halides to obtain low-pressure discharges that emit visible light. Although such metal halides are highly reactive, their use in certain types of electrodeless discharge vessel devices has been investigated.

In E-discharge (also known as inductively coupled discharge) devices, the discharge occurs as a single loop forming the secondary of the transformer, the secondary being formed by a coil with a core of high magnetic permeability. . It has been found that low pressure metal halide discharges operated in this manner produce extensive instabilities and are therefore impractical as light sources.

In E-discharge devices, the discharge tube is placed between capacitor plates excited with a high frequency source. However, the current that sustains the discharge must flow as a displacement current through the glass or silica walls of the discharge vessel, making it difficult to produce a discharge with sufficient power. The excitation frequency increases the current and therefore the dielectric losses through the glass or silica walls, resulting in significant power losses through the walls of the discharge vessel.

Another type of electrodeless discharge is known as a "very high frequency" discharge. In such discharges, the wavelength of the excitation source is shorter than or comparable to the discharge dimension.

Research on such discharges has been carried out for many years, but problems with the means of power generation and shape have prevented it from becoming a commercially viable light source.

It has been found that discharges operating in the three prior art embodiments using low pressure metal halide encapsulation tend to form tentacles that adhere to the walls of the discharge vessel under adverse conditions. This creates strong localized hot spots and thus spoils the light source. Also, the generated discharge is unstable and presents a fluctuating load on the generator, creating matching difficulties.

Furthermore, during use of the discharge device, the structure that excites and sustains the discharge itself darkens the discharge and thus reduces the amount of light for the observer.

[Problems to be Solved by the Invention] An object of the present invention is to provide a discharge tube used as a light source that avoids at least the various problems described above.

[Means for Solving the Problems] A first feature of the present invention is a method of generating visible light from a discharge tube having a wall made of a light-transmitting dielectric material, the discharge tube comprising a metal halide and a metal oxide. encapsulating an enclosure consisting of at least one compound selected from the group consisting of halides, wherein the method comprises applying power over a portion of the wall of the discharge vessel with sufficient power to excite surface waves in the enclosure; radio frequency (r,
1. ) Applying an electric field, which excites the inclusion to emit visible light.

The inventors have discovered that it is possible to achieve a stable and well-functioning low-pressure metal halide discharge by exciting the discharge using surface waves in an electrodeless discharge vessel. Metal halides are at least partially dissociated and light is emitted in the visible range from both the separated atoms and molecules. Metal oxyhalides are thought to behave similarly to metal halides.

A second feature of the present invention is a discharge tube device that emits visible light, the device comprising a discharge tube having walls made of a light-transmitting dielectric material, the discharge tube being made of metal halides and metal oxyhalides. an enclosure comprising at least one compound selected from the group consisting of: the device further transmitting radio frequency waves across a portion of the wall of the discharge vessel with sufficient power to excite surface waves in the enclosure; It includes means for applying an (r,f,) electric field, which in use excites the inclusion to emit visible light.

A discharge tube device according to this feature of the invention can be used to emit visible light in a method according to the above first feature of the invention.

Preferably, the means for applying a radio frequency electric field comprises a radio frequency power generator and a launcher. This application means can therefore be arranged so as not to substantially darken the discharge, and the discharge itself can also vary in length from centimeters to meters and from millimeters to centimeters, depending on the power used. It has a diameter of

Embodiments Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings.

As shown in FIG. 1, the discharge tube device consists of a discharge tube 20 mounted on a launcher 22. The discharge tube 20 is formed of a transparent dielectric material such as glass and encloses an enclosure 24 .

Launcher 22 is made of a conductive material such as brass and is formed as a coaxial structure consisting of an inner tube 26 and an outer tube 28. A first plate 30 at one end of the outer tube forms the first end wall of the launcher structure. A second plate 31 located at the other end of the outer tube 28 and integral with the outer tube forms a second end wall. The inner tube 26 is shorter than the outer tube 28 and is positioned within the outer tube 28 so as to form a first annular gap 32 and a second annular gap 33 . Each of the first plate 30 and the second plate 31 has an opening for receiving the discharge tube 20. The outer tube 28, the first plate 30, and the second plate 31 form a continuous conductive corridor path but do not make electrical contact with the inner tube 26 to create a radio frequency shielding structure around it. .

Suitable dimensions for the launcher of FIG. 1 are as follows.

Launcher length: 7 to 20 mm Launcher diameter: 25 to 35 mm5 (diameter of outer tube 28) However, it depends on the size of the discharge tube 2o.

Length of inner tube 26: 3 to 18 mm Diameter of inner tube 26
13mm5 However, it depends on the size of the discharge tube 20.

Length of launch gap (first gap 32 of 0.!+-3 mm) Length of second gap 33 1-10 mm The thickness of the conductive material may be millimeters or less depending on the construction method used.

A radio frequency power generator 34 (schematically shown) is electrically connected to the inner tube 26 of the launcher 22 by a coaxial cable 35 and an impedance matching network 36 (schematically shown consisting of a capacitor 37 and an inductor 38). There is. Radio frequency power generator 34, impedance matching network 36, coaxial cable 35, and launcher 2
2 constitutes a radio frequency power excitation device, and supplies electricity to the enclosure to generate discharge.

The body 40 of dielectric material inside the launcher 22 is provided as a structural element to maintain the size of the gaps 32, 33 and to hold the inner tube 26 in position. This body 40 also serves to shape the electric field within the gap 32, 33 to facilitate launcher activation or other purposes. Suitable dielectric materials that provide low loss at radio frequencies include glass, quartz, and polytetrafluoroethylene (PTF).
E). Alternatively, the launcher may be partially or completely air-filled, provided that means are provided to support the inner tube.

When the radio frequency power generator 34 is turned on, typically I
An oscillating electric field with a frequency in the MHz to IGHz range is set up inside the launcher 22. This electric field is
parallel to the longitudinal axis of the discharge vessel 20 in the gaps 32,33. When sufficient power is applied, the resulting electric field in the enclosure 24 is sufficient to cause an electrical discharge, which causes the European Patent No. 02257
Electromagnetic surface waves are propagated in a manner similar to the device of No. 53A2.

The launcher 22 powered by the radio frequency power generator 34 thus creates and maintains a discharge in the enclosure, the length and brightness of the discharge depending, inter alia, on the size of the discharge tube 20 and the radio frequency power generator 34. depends on the power applied at

Such a discharge tube device can therefore be used as a light source.

In order to obtain a discharge tube that emits visible light, the enclosure 24 is
It shall consist of a compound selected from the group consisting of metal halides and metal oxyhalides, and a rare gas such as argon. Mercury is also added.

The inventors have tried fills containing aluminum chloride (AIICl 3 ) and a noble gas, argon (Ar). This inclusion was found to produce a stable discharge that emits visible light when excited by surface waves.

The use of halides of metals from the transition series of the periodic table, such as titanium, iron or niobium, is advantageous. These halides are sufficiently volatile to generate vapor pressures capable of producing a discharge at the operating temperature of the walls of the discharge vessel. These are dissociated by electron bombardment. As a result, the excited atoms, ions and molecules emit radiation; metal atoms have many relatively low energy levels that cause radiation throughout the visible range.

Neodymium (Nd) and other rare earth metal halides also produce radiation throughout the visible light range when excited. These are relatively non-volatile but can form complexes with other metal halides (known as complexing agents). The vapor pressure of the complex formed is a factor of 10' greater than that of the rare earth metal halide. The complex should have a total vapor pressure of greater than about 1 O-3 Torr, for example, at lamp operating temperatures up to 250<0>C. Examples of complexing agents include the following halides (i.e. chlorides,
Bromide or iodide, and X is Cj! , Br or I). Namely, aluminum (AIXi), indium (InX), gallium (GaX3), tin (SnX4),
), titanium (TiX4) and ferric chloride (m) (
There is a Fe 2 C1b) compound.

As a complex, Na AJ C16 (Na C13 and A
complex of lc13) and NaAlCl4 (NaC
1 and AJ C13).

The inventor believed that a stable discharge could be generated by surface waves from an enclosure containing the following mixture.

Tin(II) iodide (Sn I2) Sodium decaiodide (
NaI)+AlC13+Ar; Aj! B+, +Sn C12+niobium chloride (V)
(Nb CJ5) + Ar: Indium (I) bromide (In Br) + AI
C13+Ar; Thallium iodide (Tj' I) +AA'C13+Ar
;Sn CA! , +AJBr, +Ar
;Iron(II) iodide (Fe I2) +AA'
Br 3+Ar; TI I+Na I+Fe 12
+Aj! C13+Ar;Na I+AA'B
r, +A+; TI I+Na I+Fe I2
+AI Br 3 +Ar ;In I+AA' B
+3° Argon is used to increase the overall vapor pressure and can be replaced by other noble gases such as neon, helium, or krypton.

Additionally, certain metal oxide halides (i.e.
oxychloride, oxybromide or oxyiodide, where X is CI, B+ or ■). That is, chromium oxide halide (Cr 02 X2), vanadium oxide halide (VOX2 and vOX3), molybdenum oxide halide (MO02
i), and tungsten oxide halide (WO
2X2 and WOX4), these can be used for inclusions that emit visible light when excited.

[Brief explanation of drawings]

The accompanying drawing is a cross-sectional side view of an exemplary discharge tube device according to the present invention. 20...Discharge tube 22...Launcher-24...
Inclusions 26... Inner tube 28... Outer tube 30...
・First plate 31... Second plate 32. 33... Annular gap 35... Coaxial cable 36... Impedance matching network 3.7... Capacitor 38...
・Inductor 40...Body

Claims (8)

[Claims] (1) A method for emitting visible light from a discharge tube having a wall made of a light-transmitting dielectric material, the discharge tube comprising at least one compound selected from the group consisting of metal halides and metal oxyhalides. encapsulating an enclosure, the method comprising the step of applying a radio frequency electric field across a portion of the wall of the discharge vessel with sufficient power to excite surface waves in the enclosure, thereby exciting the enclosure; A method for emitting visible light from a discharge tube, characterized in that the discharge tube emits visible light. (2) A discharge tube device that emits visible light, the device comprising a discharge tube having a wall made of a light-transmitting dielectric material, the discharge tube being selected from the group consisting of metal halides and metal oxyhalides. enclosing an enclosure comprising at least one compound, and the apparatus further applying a radio frequency electric field across a portion of the wall of the discharge vessel with sufficient power to excite surface waves in the enclosure; A discharge tube device for emitting visible light, characterized in that it comprises means for exciting said enclosure to emit visible light in use. (3) The device according to claim 2, wherein the means for applying the radio frequency electric field comprises a radio frequency power generator and a launcher. (4) The device according to claim 2 or 3, wherein the enclosure is made of an aluminum halide. (5) The device according to claim (4), characterized in that the fill material consists of aluminum chloride. (6) The device according to any one of claims (2) to (5), characterized in that the fill material is made of a transition metal halide. (7) The device according to any one of claims (2) to (6), characterized in that the enclosure is made of a metal halide complex. (8) The device according to claim (2) or (3), wherein the enclosure is made of a metal oxyhalide.