Uvc/Vuv Dielectric Barrier Discharge Lamp with Reflector

Abstract

The subject of the present invention relates to a high efficiently dielectric barrier discharge (DBD) -lamp for generating and/or emitting a radiation of ultraviolet (UV)-light comprising: a discharge gap (1) being at least partly formed and/or surrounded by at least an inner wall (2) and an at least partly transparent (3), each with an inner surface (2a, 3a), facing the discharge gap (1) and an outer surface (2b, 3b) arranged opposite of and directed away from the corresponding inner surface (2a, 3a), a filling located inside the discharge gap (1), at least two electrical contacting means (4), a first electrical contacting means (4a) at the inner wall (2) and a second electrical contacting means (4b) at the outer wall (3), and at least one luminescent coating layer (5) arranged at/on and at least partly covering at least a part of the respective wall's inner surface (3a), arranged such, that at least a part of the generated UV-light of a certain wavelength range can pass the luminescent coating layer (5) from the discharge gap (1) to the outside of the DBD-lamp, whereby at least one of both walls (2, 3) is at least partly arranged with directing means (6), so that the diffusive radiation is directed in direction through the transparent part of the outer wall (3) with reduced losses due to absorption effects and the like.

Description

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

FIG. 1 a shows in a longitudinal sectional view an inner part of a DBD-lamp with a reflective coating layer inside the discharge gap instead of a second luminescent coating layer at the inner surface of the inner wall.

FIG. 1 b shows in a cross sectional view the inner part of FIG. 1a.

FIG. 2 shows in detail and in a longitudinal sectional view the layer structure of a coaxial DBD-lamp with a discharge gap formed by an inner and an outer quartz tube according to the layer structure according to FIG. 1a and FIG. 1b with a second luminescent layer on the inside of the inner tube and a reflective layer sandwiched between the inner wall and the luminescent layer.

FIG. 3 shows in a schematic way a coaxial DBD-lamp according to the present invention, where the inner quartz tube is replaced by a reflective metallic tube, which serves simultaneously as the inner wall, as a reflector and as one of the electric contacting means.

FIG. 4 shows schematically different ways of reflecting the radiation in a well defined direction.

FIG. 1 a and 1b show a coaxial DBD-lamp with an annular shaped discharge gap 1. FIG. 1a shows in a longitudinal sectional view an inner part of a DBD-lamp. FIG. 1b shows the same DBD-lamp or the same inner part of the DBD-lamp in a cross-sectional view without the corresponding electrodes. The discharge gap 1 of the DBD-lamp is formed by a dielectric inner wall 2 and a dielectric outer wall 3. In this fig. the discharge gap 1 is formed by an inner lamp tube having a circumferential wall, functioning as the inner wall 2 and an outer lamp tube having a circumferential wall, functioning as the outer wall 3. The lamp tubes are made of quartz glass, which is a dielectric material. The inner wall 2 has an inner surface 2a and an outer surface 2b.The inner surface 2a faces the discharge gap 1 and the outer surface 2b is directed in opposite direction. The thickness of the inner wall 2 is defined by the shortest distance between the inner and the outer surface 2a, 2b. The outer wall 3 has an inner surface 3a and an outer surface 3b analogue. The inner surface 3a corresponds to the inner surface 2a of the inner wall 2 and faces the discharge gap 1. The outer surface 3b is directed in opposite direction to the inner surface 3b. The thickness of the outer wall 3 is defined by the shortest distance between inner surface 3a und outer surface 3b. The DBD-lamp has two corresponding electrodes 4 arranged at the outer and the inner wall 2, 3. The first electrode is arranged at the outer surface 2b of the inner wall 2 and the second electrode 4b, shaped as a grid, is arranged at the outer surface 3b of the outer wall 3. At the inner surface 3a of the inner wall a luminescent coating layer 5 is arranged and/or located. The inner surface 2a of the inner wall 2 has no such luminescent coating layer. Instead of this a directing means 6 in form of a reflective coating layer 6a is arranged at the inner surface 2a of the inner wall 2. In this case the adhesion coating layer is made of ultra fine particles of MgO and functions as a reflecting or directing means 6. Alternatively the reflective coating layer can be replaced by a layer made of ultra fine particles such as SiO₂ or Al₂O₃. The diameter of the grains, forming that layer is chosen such, that an optimal reflection of the wavelength-range of the generated UV-radiation is realised. Here the filling of the DBD-lamp is a Xe-filling with filling pressures in between 100 mbar and 800 mbar. In this case the wavelength range of the xenon-radiation is about λ=172 nm. This reflected wavelength-range reaches the luminescent coating layer on the inner side 3a of the outer wall 3. The materials for that coating layer, that is diverse oxides, are commonly known, and can be purchased as powder.

The method for forming such a DBD-lamp is mainly described in the following. First the inner and the outer tube are connected one-sided. Afterwards an auxiliary body, for example an auxiliary cylinder is brought between inner wall and outer wall, whereby the diameter of the protective cylinder is slightly larger than the diameter of the inner glass tube. The auxiliary cylinder can be made of any material like metal, glass or quartz. After arranging the auxiliary cylinder, the phosphor coating layer is realised by immersion into another suspension. Finally the protective cylinder is removed. As an alternative to this method it is included in this invention, that both tubes are coated separately before assembling. This second way makes it much easier to apply different coating the tubes. Another embodiment of the invention is shown in FIG. 2.

FIG. 2 shows in detail and in a longitudinal sectional view the layer structure of a coaxial DBD-lamp with a discharge gap 1 formed by an inner and an outer quartz tube according to the layer structure according to FIG. 1a and FIG. 1b with a second luminescent layer on the inside of the inner tube and a reflective layer sandwiched between the inner wall and the luminescent layer. The DBD-lamp is rotation-symmetrical constructed. The dotted-line represents the rotational axis. The layer structure is described from the inside that is from the rotational axis to the outside. The inner layer is the inner wall 2. Arranged at the inner wall 2 is a reflective coating layer 6, which is covered by a first luminescent coating layer 5a, here arranged as a phosphor coating layer. The discharge gap 1 further contains a filling. The second luminescent coating layer 5b also here arranged as a phosphor coating layer, is located at the outer wall 3. A third embodiment is shown in FIG. 3.

FIG. 3 shows in a schematic way the inner part of a DBD-lamp according to the present invention with a reflection or directing means formed as metallic cylinder or metallic tube 7, which serves additionally as one of the walls and one of the means for electrical contacting. In FIG. 3 the inner wall is not made of quartz glass but of a metallic material. In this special case the inner glass tube is replaced by an inner metallic cylinder, which is electrically connected to an external power supply (not shown here). The metallic cylinder has either on its inner surface a reflective coating layer basically made of Al or is completely made of Al with a polished surface facing the discharge gap. To prevent sputtering the surface facing the discharge gap is covered with a protective coating layer, in this case of SiO₂. In this case, the luminescent coating 5 is only deposited on the inside of the outer wall 3.

FIG. 4 a to 4c shows schematically different ways of arranging the directing means 6 to emit the radiation (schematically shown as arrows) in a well defined direction: to the outer surrounding of the lamp (FIG. 4a), to the inner volume of the lamp (FIG. 4b) and to only a certain part of the surrounding of the lamp (FIG. 4c). In all three cases, the luminescent layer (not shown here) can be deposited at/on the inside of the inner wall, at/on the inside of the outer wall, at/on both walls. In the case, that a reflective layer and a luminescent coating are applied to one wall, the reflective coating is sandwiched between the luminescent layer and the wall.

LIST OF REFERENCE NUMBERS

• 1 discharge gap
• 2 inner wall
• 2 a inner surface (of the inner wall)
• 2 b outer surface (of the inner wall)
• 3 outer wall
• 3 a inner surface (of the outer wall)
• 3 b outer surface (of the outer wall)
• 4 electrical contacting mean(s)
• 4 a first electrical contacting mean(s)
• 4 b second electrical contacting mean(s)
• 5 luminescent coating layer
• 5 a first luminescent coating layer
• 5 b second luminescent coating layer
• 6 directing/reflecting means
• 6 a reflective coating layer
• 7 metallic tube (serving as inner wall, reflector and electrode)

Claims

1. Highly efficient dielectric barrier discharge (DBD) lamp for generating and emitting an ultraviolet radiation comprising: a discharge gap (1) being at least partly formed and/or surrounded byat least an inner wall (2) andan outer wall (3),each with an inner surface (2a, 3a), facing the discharge gap (1) andan outer surface (2b, 3b) arranged opposite of and directed away from the corresponding inner surface (2a, 3a), whereby at least one of the walls is a dielectric wall and/or one of the walls (2, 3) has an at least partly transparent part,a filling located inside the discharge gap (1),at least two electrical contacting means (4),a first electrical contacting means (4a) associated with the outer wall (3) and

2. High efficiently DBD-lamp according to claim 1, whereby the directing means (6) are arranged as at least one reflecting coating layer (6a), as a reflective, metallic wall, as a reflective, metallic cylinder (7), as a reflective, metallic coating, as a reflective, non-metallic and the like arranged at least partly at the inner wall (2) and/or at the outer wall (3).

3. High efficiently DBD-lamp according to claim 1, whereby the reflecting coating layer (6a) is arranged at/on the inner surface (2a) of the inner wall (2), at/on the inner surface (3a) of the outer wall (3), at least partly at/on the inner surface (2a) of the inner wall (2) and at least partly at/on the inner surface (3a) of the outer wall (3).

4. High efficiently DBD-lamp according to claim 3, whereby the reflecting coating layer (6a) is of a reflective material preferably selected from the group comprising metallic coatings such as Al or Al-alloy or highly reflective ultra fine oxide particle coatings such as SiO2, MgO, Al2O3 or the like.

5. High efficiently DBD-lamp according to claim 3, whereby the reflecting coating layer (6a) is coated by a protective oxide layer (6b).

6. High efficiently DBD-lamp according to claim 1, whereby the reflecting means (6) is arranged at/on the outer surface of the inner wall (2), at/on the outer surface of the outer wall (3), at least partly at/on the outer surface of the inner wall (2) and/or at least partly at/on the outer surface of the outer wall (3).

7. High efficiently DBD-lamp according to claim 1, whereby the lamp geometry is selected from the group comprising a flat lamp geometry, a coaxial lamp geometry, a dome lamp geometry, a planar lamp geometry and the like.

8. High efficiently DBD-lamp according to claim 1, whereby the metallic directing means is arranged as an electrical contacting means for simultaneously reflecting radiation and providing electricity.

9. High efficiently DBD-lamp according to claim 1, whereby the DBD-lamp comprises only one luminescent coating layer (5) at least partly arranged at/on the inner surface of one of the walls (2, 3) and one reflective coating layer at least partly arranged at/on the inner surface of the opposite wall (3, 2).

10. Method for producing a high efficiently DBD-lamp according to claim 1, comprising steps for arranging all parts together.

11. A system incorporating a lamp according to claim 1 and being used in one or more of the following applications: fluid and/or surface treatment of hard and/or soft surfaces, preferably cleaning, disinfection and/or purification;liquid disinfection and/or purification,beverage disinfection and/or purification,water disinfection and/or purification,wastewater disinfection and/or purification,drinking water disinfection and/or purification,tap water disinfection and/or purification,production of ultra pure water,gas disinfection and/or purification,air disinfection and/or purification,exhaust gases disinfection and/or purification,cracking and/or removing of components, preferably anorganic and/or organic compoundscleaning of semiconductor surfaces,cracking and/or removing of components from semiconductor surfaces,cleaning and/or disinfection of food,cleaning and/or disinfection of food supplements,cleaning and/or disinfection of pharmaceuticals.