EP0482230B1 - High power radiation device - Google Patents

Description

The invention relates to a high-power radiator, in particular for ultraviolet light, with a discharge space filled with filling gas emitting radiation under discharge conditions, with electrodes which are connected in pairs to one or more high-voltage sources, dielectric material lying between two electrodes at different potential adjoins the discharge space.
The invention relates to a state of the art, such as that derived from EP-A-0 363 832 or EP-A-0 385 205.

Technological background and state of the art

The industrial use of photochemical processes depends heavily on the availability of suitable UV sources. The classic UV lamps deliver low to medium UV intensities at some discrete wavelengths, such as the mercury low-pressure lamps at 185 nm and especially at 254 nm. Really high UV powers can only be obtained from high-pressure lamps (Xe, Hg), which then but distribute their radiation over a larger wavelength range. The new excimer lasers have provided some new wavelengths for basic photochemical experiments. These are currently for cost reasons for an industrial process probably only suitable in exceptional cases.

In the EP patent application mentioned at the beginning or in the conference paper "New UV and VUV excimer emitters" by U.Kogelschatz and B.Eliasson, distributed at the 10th lecture conference of the Society of German Chemists, Photochemistry Group, in Würzburg (FRG) 18 - November 20, 1987, a new excimer emitter is described. This new type of emitter is based on the fact that excimer radiation can also be generated in silent electrical discharges, a type of discharge that is used on a large scale in ozone generation. In the current filaments of this discharge, which exist only for a short time (<1 microsecond), noble gas atoms are excited by electron surges, which react further to excited molecular complexes (excimers). These excimers only live for a few 100 nanoseconds and release their binding energy in the form of radiation upon decay, the wavelength range of which, depending on the composition of the filler gas, can be in UV-A, UV-B, UV-C or in the visible spectral range.

In the recent past, the demand for such high-performance lamps has increased because the special properties of the lamps have opened up many new fields of application in chemical and physical process engineering, in the graphics industry, for coatings, etc. There is therefore a great need for economical, operationally reliable UV lamps that are constructed as modularly as possible.

Presentation of the invention

On the basis of the prior art, the object of the invention is to create a high-performance radiator, in particular for UV or VUV light, which, owing to its modular structure, can be produced economically and also enables the construction of very large area radiators.

To achieve this object in a high-power radiator of the type mentioned at the outset, it is provided according to the invention that the discharge space is bounded on the outside by a tube which is transparent to the radiation generated and in which tube spaced apart from one another and from the transparent tube are arranged with dielectric electrodes with internal electrodes.

When a sufficiently high AC voltage is present, a large number of partial discharges form from one electrode through the dielectric and the adjacent discharge space and back into the dielectric to the adjacent electrode. These discharges emit the usable UV light, which then penetrates through the tube wall or tube walls. In contrast to the known configurations, the entire expansion of the discharge channels is used to generate radiation.

The manufacture of the high-power radiator according to the invention is simplified and less expensive than in the known radiators. For example, you can use standard quartz tube profiles that are available in many dimensions. Also for the limiting glass / quartz material, there are no very high demands, since the limiting walls only have to be transparent to the useful radiation and are not stressed by the discharge. This leads to a longer lamp life. The gap width and its tolerances are also far less critical. In particular, because of the lower requirements with regard to tolerances, very large area radiators can now be realized, which can be made very thin. Because practically the entire length of the discharge space contributes to emission, the UV yield is very high. There are no transmission losses from an electrode grid or a partially permeable layer.

In contrast to the known, in the arrangement according to the invention the dielectrics can be optimized for the UV radiation to be generated because they do not have to be transparent to the UV light, which means that particularly high efficiencies can be expected for special applications. Such applications with growing economic importance include e.g. use as a strong UV lamp for pre-ionization purposes of other discharges, e.g. Lasers, treatment of surfaces with UV exposure, chemical processes such as the preparation of new chemicals or surfaces and coating processes such as UV-assisted CVD or plasma CVD (Chemical Vapor Deposition), Photo-CVD, in which a substrate to be treated with a suitable filling gas is as dense as possible is brought to a UV light source.

The invention is explained in more detail below on the basis of exemplary embodiments.

Brief description of the drawings

Fig. 1

Ein erstes Ausführungsbeispiel eines Flächenstrahlers mit einseitiger Abstrahlung im Querschnitt;

Fig. 2

einen Längsschnitt durch den Flächenstrahler nach Fig.1 längs deren Linie AA mit einer schematischen Darstellung der elektrischen Anspeisung;

Fig. 3

eine erste Abwandlung des Flächenstrahlers nach Fig.1 und 2 mit Aussenelektroden, die auf den Schmalseiten des äusseren Rohres angeordnet sind, und einer elektrischen Speisung mit einseitig geerdeter Spannungsquelle;

Fig. 4

eine zweite Abwandlung des Flächenstrahlers nach Fig.1 und 2 mit Aussenelektroden, die auf den Schmalseiten des äusseren Rohres angeordnet sind, und einer erdsymmetrischen elektrischen Speisung;

Fig. 5

einen Flächenstrahler gemäss Fig.1 und 2 mit externer Kühlung;

Fig.6

eine Möglichkeit zur Abstützung der Dielektrikumsrohre bei langgestreckten Strahlern;

Fig.7

eine Alternative zu den bisherigen Konfigurationen mit mehr als einer Lage Dielektrikumsrohre im Innern eines Quarzrohrs;

Fig.8

ein Ausführungsbeispiel der Erfindung in Form eines Zylinderstrahlers, zum Teil im Querschnitt, zum Teil in Stirnansicht;

Fig.9

eine Abwandlung der Ausführungsform gemäss Fig.5 mit mehreren Strahlern in einem gemeinsamen Kühlelement;

Fig.10

eine Abwandlung der Ausführungsform gemäss FIg.9 mit mehrerer Strahlern auf der Innenseite eines gekrümmten Kühlelements.

In the drawing, embodiments of the invention are shown schematically; in it shows

Fig. 1

A first embodiment of a surface radiator with one-sided radiation in cross section;

Fig. 2

a longitudinal section through the surface radiator according to Figure 1 along the line AA with a schematic representation of the electrical feed;

Fig. 3

a first modification of the surface radiator according to Fig. 1 and 2 with outer electrodes, which are arranged on the narrow sides of the outer tube, and an electrical supply with a voltage source grounded at one end;

Fig. 4

a second modification of the surface radiator according to Figures 1 and 2 with outer electrodes, which are arranged on the narrow sides of the outer tube, and an earth-symmetrical electrical supply;

Fig. 5

a surface heater according to Figures 1 and 2 with external cooling;

Fig. 6

a possibility of supporting the dielectric tubes in the case of elongated radiators;

Fig. 7

an alternative to the previous configurations with more than one layer of dielectric tubes inside a quartz tube;

Fig. 8

an embodiment of the invention in the form of a cylinder radiator, partly in cross section, partly in end view;

Fig. 9

a modification of the embodiment according to Figure 5 with several radiators in a common cooling element;

Fig. 10

a modification of the embodiment according to FIg.9 with several radiators on the inside of a curved cooling element.

Detailed description of the invention

1 and 2, dielectric tubes 6 with internal electrodes 7 are arranged in a quartz tube 1 with the broad sides 2, 3 and the narrow sides 4, 5. The dielectric tubes 6 are from each other and also from the Walls of the quartz tube 1 spaced. The dielectric tubes 6 are, for example, quartz tubes, the inner end 8 of which is melted, ie closed (see FIG. 2). The inner electrode 7 is a metal rod which is inserted into the quartz tube. Instead, a metal rod or metal wire covered with dielectric material can also be used.
The two narrow sides 4, 5 and one of the broad sides 3 of the quartz tube 1 are each provided with an aluminum layer 9 on the outside. The three coatings can - but need not - be electrically insulated from one another. The aluminum layer 9 is preferably vapor-deposited, flame-sprayed, plasma-sprayed or sputtered and serves as a reflector.

As can be seen from FIG. 2, the quartz tube 1 is closed on both ends by plates 10, 11 made of insulating material. These plates are glued to the end faces, for example, or, in the case of quartz or glass plates, are fused to said end walls. The plates 10, 11 are provided with openings 12, in which the dielectric tubes 6 are alternately inserted from both sides of the quartz tube 1 and fastened and sealed therein. The dielectric tubes are melted or glued at the ends opposite the installation points. In the case of elongated radiators, the dielectric tubes 6 are held at the free end 8 in tubular support elements 13 into which these ends 8 are immersed. Optionally, additional supports 14 can also be provided in the center of the tube (see FIG. 6). The interior of the quartz tube 1 can be evacuated via a filler neck 15 and then filled with a filler gas.

As can be seen from FIG. 2, the radiator is electrically supplied from an alternating current source 16 in such a way that adjacent inner electrodes 7 are connected to the alternating current source 16 in alternation. As later (based on 9) is explained in more detail, several AC sources can also be used. The discharges 17 then form in the space between two adjacent dielectric tubes 6.

The AC power source 16 basically corresponds to those used for feeding ozone generators. Typically, it delivers an adjustable AC voltage in the order of magnitude of several 100 volts to 20,000 volts at frequencies in the range of technical alternating current up to a few MHz - depending on the electrode geometry, pressure in the discharge space and composition of the filling gas.

The inside of the quartz tube 1 is filled with a filling gas which emits radiation under discharge conditions, e.g. Mercury, noble gas, noble gas-metal vapor mixture, noble gas-halogen mixture, optionally using an additional further noble gas, preferably Ar, He, Ne, as a buffer gas.

Depending on the desired spectral composition of the radiation, a substance / substance mixture according to the following table can be used:

• Ein Edelgas (Ar, He, Kr, Ne, Xe) oder Hg mit einem Gas bzw. Dampf aus F₂, J₂, Br₂, Cl₂ oder eine Verbindung, die in der Entladung ein oder mehrere Atome F, J, Br oder Cl abspaltet;
• ein Edelgas (Ar, He, Kr, Nr, Xe) oder Hg mit O₂ oder einer Verbindung, die in der Entladung ein oder mehrere O-Atome abspaltet;
• ein Edelgas (Ar, He, Kr, Ne, Xe) mit Hg.

In addition, a whole series of other filling gases are possible:

• A noble gas (Ar, He, Kr, Ne, Xe) or Hg with a gas or vapor from F₂, J₂, Br₂, Cl₂ or a compound that splits off one or more atoms F, J, Br or Cl in the discharge;
• a noble gas (Ar, He, Kr, Nr, Xe) or Hg with O₂ or a compound that releases one or more O atoms in the discharge;
• an inert gas (Ar, He, Kr, Ne, Xe) with Hg.

In the electrical partial discharge (micro discharge) that is formed, the electron energy distribution can be optimally adjusted by the wall thickness of the dielectric tubes 6 and their dielectric properties, distance between the dielectric tubes 6, pressure and / or temperature of the filling gas.

When a voltage is applied between two adjacent electrodes 7, a plurality of discharge channels 17 are formed, which emit the UV light, which then penetrates outward through the transparent broad side 2 of the quartz tube 1.
Broad sides 2, 3.

As illustrated in FIG. 3, the metallic reflector layers 9 can be on the narrow sides of the quartz tube 1 can also be used as external electrodes. The electrical contact can be made using stranded strips 18 or resilient contact strips. In this case, it is expedient to provide an odd number of dielectric tubes 6 so that both outer electrodes come to the same potential, in the example case to ground potential. Then discharges 17a also form between the outermost dielectric tubes 6 and the narrow sides 4, 5 of the quartz tube 1.

Because the insulation stresses of the components used in the case of power supply devices with an earth-symmetrical output are lower than those with one-sided supply, such devices are more economical. 4 shows the feeding of a radiator according to FIG. 3 with a power supply device with a balanced output. The full output voltage of the alternating current source 16 lies between adjacent inner electrodes 7, while half the output voltage lies between the inner electrodes 7 of the outer dielectric tubes 6 and the outer electrodes 9. Accordingly, the distance between the dielectric tubes 6 is also larger than the distance between the two outer dielectric tubes 6 from the narrow sides 4, 5 of the quartz tube 1.

High-performance lamps of the type described can be cooled very easily due to their new geometry. As illustrated in FIG. 5, the quartz tube 1 can be converted into a correspondingly dimensioned metal profile 19 with a U-shaped cross section, for example made of aluminum or copper, with, e.g. Coolant bores 20 extending in the longitudinal direction of the profile are inserted.

A resilient metallic contact strip 21 is inserted between the legs of the U-profile and the narrow sides 4, 5 of the quartz tube 1 and extends over the entire length of the tube. In addition to electrical contacting, it is used the layer 9 also for fixing the quartz tube 1 in the space between the legs of the metal profile 19. If necessary, an intermediate layer of thermally conductive paste 30 can be provided between the profile base and the quartz tube 1 in order to improve the heat transfer. The electrical feed takes place analogously to FIG. 4, ie the metal profile 19 is at earth potential. Of course, the electrical feed can also take place as illustrated in FIG. 2 or 3.

• Es können handelsübliche, in vielen Dimensionen erhältliche Quarzprofile für die Quarzrohre 1 eingesetzt werden, welche sich durch hohe mechanische Belastbarkeit auszeichnen;
• einfache Erweiterung bestehender Bestrahlungseinrichtungen durch die mit der Erfindung mögliche modulare Bauweise;
• die (auf Hochspannungspotential liegenden) Elektroden samt ihrer Anschlussarmaturen lassen sich mit einfachen Mitteln berührungssicher gestalten;
• der Einsatz von Stromversorgungseinrichtungen mit erdsymmetrischer Ausgangsspannung ermöglicht wirtschaftliche Speisung;
• der Einsatz meherer voneinander unabhängiger Stromversorgungseinheiten ist möglich;
• ein Drahtnetz, Drahtgitter oder eine transparente äussere Elektrode entfällt, wodurch die Reinigung des Strahlers, z.B. beim Einsatz im grafischen Gewerbe, erleichtert ist;
• die Quarzpartien des Strahlers, welche für die Transmission des UV-Lichts verantwortlich sind, werden nicht durch den Entladungsangriff belastet;
• die Aluminiumbedampfung macht einen Grossteil der entstehenden Strahlung nutzbar;
• die ganze Einrichtung einschliesslich Kühlung kann extrem flach und in ihrer Flächenausdehnung nahezu beliebig gross gestaltet werden und ist daher für sehr viele technische Anwendungen geeignet.

The embodiments of the invention described above have a number of advantages, which are summarized below:

• Commercial quartz profiles which are available in many dimensions can be used for the quartz tubes 1 and are distinguished by high mechanical strength;
• simple expansion of existing radiation devices through the modular construction possible with the invention;
• the electrodes (which are at high voltage potential) and their connection fittings can be designed so that they are safe to touch with simple means;
• the use of power supply devices with earth-symmetrical output voltage enables economical supply;
• the use of several independent power supply units is possible;
• a wire mesh, wire mesh or a transparent outer electrode is omitted, which makes cleaning the spotlight easier, for example when used in the graphic arts industry;
• the quartz parts of the radiator, which are responsible for the transmission of UV light, are not burdened by the discharge attack;
• Aluminum vapor deposition makes most of the radiation available usable;
• the entire facility, including cooling, can be designed to be extremely flat and almost any size in terms of its surface area and is therefore suitable for a large number of technical applications.

Without departing from the scope of the invention, a multitude of modifications of the UV high-power lamp described above are possible, which will be discussed below.

Instead of an odd number of quartz tubes 1, even numbered variants can also be provided for configurations according to FIGS. 2, 3 and 4.
Instead of only a single layer of dielectric tubes 6 in a quartz tube 1, two or more layers can be provided, as is illustrated in FIG. The dielectric tubes 6 of one layer are offset from the dielectric tubes of the adjacent layer by half a tube spacing. The dielectric tubes 6 of each layer are connected in parallel and connected to the two poles of the AC power source 16. The discharge channels run obliquely through the discharge space from one position to the next.

Furthermore, the invention offers the possibility of embedding several individual radiators, for example according to FIG. 1 or FIG. 3, in a common cooling element, as is illustrated in FIG. 9. There, an aluminum or copper profile 19a is provided with, in the example case 3, channels with a U-shaped cross section running in the longitudinal direction of the profile. 5, quartz tubes 1 are inserted into these channels, the structure of which was described in detail in connection with FIGS. 1, 3 or 5. The electrical feed can take place analogously to the previous exemplary embodiments. Deviating from this, it is illustrated in FIG. 9 that the individual radiators are connected to separate AC sources 16a, 16b, 16c a are connected. This measure will be necessary if a single source is not sufficient to supply a plurality of radiators.

The previous embodiments of the invention all relate to quartz tubes with a rectangular cross section. It is within the scope of the invention to arrange the dielectric tubes 6 in the intermediate space 22 between two quartz tubes 23, 24 arranged coaxially one inside the other. The internal electrodes 7 are alternately connected to the two connections of the alternating current source 16 analogously to FIG. 2 or 3, analogously to FIG. 1 the internal electrodes 7 of the first group of internal electrodes 7 are connected to one another on one end face, the internal electrodes 7 of the other group to the other end face of the tubes 23, 24 are brought together. Analogously to FIG. 2, the interior 22 is closed on both end faces of the quartz tubes 23, 24 with an annular cover 25, which is also a holder for the dielectric tubes 6.

Depending on whether the device is designed as an external or internal radiator, an aluminum layer 9 serving as a reflector must be provided on the inner surface of the inner quartz tube 23 or on the outer surface of the outer quartz tube 24. 5, there is also the possibility of forced cooling of the radiator in the case of an omnidirectional radiator according to FIG. 8, for example by passing coolant through the interior 26 of the inner quartz tube 23, or by filling this interior 26 with a heat sink (not shown). . In the case of an internal radiator, coolant can either be flushed around the outer jacket of the outer quartz tube 24, or an independent heat sink can be placed over the outer quartz tube 24. An arrangement such as that illustrated in FIG. 10 using the example of an irradiation device for ban-shaped materials such as film or paper webs is advantageous. The one to be irradiated Material 31 is guided over a drum 32. The cooling element 19b made of a good heat-conducting metal, for example copper or aluminum, consists of a tube section adapted to the drum 32 with cooling bores 20 running in the longitudinal direction of the tube. The inner wall of the tube section has open channels 33 with a rectangular cross section, into which quartz profiles according to FIG Fig.3 are inserted and fastened therein. The electrical feed takes place analogously to the previous exemplary embodiments.

Instead of round dielectric tubes 6 and internal electrodes 7, electrodes with almost any cross section can also be used in all embodiments. To improve the heat dissipation from the dielectric 6, it is also possible to design the inner electrodes 7 as hollow electrodes.

Claims (10)

1. A high power emitter, in particular for ultraviolet light, with a discharge chamber, filled with a filling gas emitting radiation under discharge conditions, with electrodes (7) which are connected in pairs to one or more high voltage sources (16), in which dielectric material (6) lies between two electrodes (7) lying at different potential, which material adjoins the discharge chamber, characterised in that the discharge chamber is delimited by a tube (1;23;24) which is transparent, at least in sections, for the radiation which is produced, in which tube (1;23;24) dielectric tubes (6) with internal electrodes (7) are arranged, which dielectric tubes (6) are spaced apart from each other and from the transparent tube (1;23;24), and the silent electric discharge (17) is formed in the free space of the tube (1;23;24).
2. A high power emitter according to Claim 1, characterised in that the tube is a quartz tube (1) with a rectangular cross-section and the internal electrodes (7) are arranged in a position in which adjacent internal electrodes (7) are connected in each case to the two poles of the high voltage source (16).
3. A high power emitter according to Claim 1, characterised in that the tube is a quartz tube (1) with a rectangular cross-section and the internal electrodes (7) are arranged in several layers, in which all the internal electrodes (7) of each layer are connected in parallel and are connected in layers to the two poles of the high voltage source (16).
4. A high power emitter according to Claim 1, characterised in that the discharge chamber is delimited by two tubes (23,24) lying coaxially one inside the other, and the dielectric tubes (6) are arranged in the annular space (25) between the said tubes.
5. A high power emitter according to Claim 2 or 3, characterised in that the tube (1) or the tubes (23,24) are closed at both ends by means of plates (10,11) or covers (25), which plates or covers serve as carriers for the dielectric tubes (6).
6. A high power emitter according to one of Claims 1 to 5, characterised in that the free ends (8) of the dielectric tubes (6) are supported on the plate (10,11;25) lying opposite the mounting by means of support elements (13) and/or are supported in the central tube section by means of additional supports (14).
7. A high power emitter according to one of Claims 1 to 3 or 5 or 6, characterised in that three of the four tube walls (3,4,5) of the tube (1) are provided with an outer reflecting layer (9), preferably an aluminium layer deposited by evaporation.
8. A high power emitter according to Claim 4, characterised in that either the inner surface of the inner tube (23) or the outer surface of the outer tube (24) is provided with an outer reflecting layer (9), preferably an aluminium layer deposited by evaporation.
9. A high power emitter according to one of Claims 1 to 8, characterised in that for cooling, the tube (1) is partially surrounded by a cooling element (19;19a;19b) or is arranged in the latter.
10. A high power emitter according to Claim 9, characterised in that in the case of a tube with a rectangular cross-section, in the cooling element (19;19a;19b) one or more open channels (33) are provided, into which the tube or tubes (1) are placed and are held therein.

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