DE102004055328B3 - Plasma light source has flat plate of insulating material with attached flat electrode and has electrode with roughened surface structure for formation of plasma space - Google Patents

Abstract

The plasma light source has a flat plate of insulating material (2) and an electrically-conducting structured electrode (3). There is a gas space (4) above the electrode in which a plasma may be formed. The structure on the electrode may consist of a series of hemispherical protuberances. A flat electrically-conducting second electrode (1) is fastened to the flat insulating plate.

Description

The The invention relates to a device for generating radiation for applications in the field of gas discharge light sources and plasma display devices with gas fillings without mercury. In particular, a special arrangement of a dielectrically impeded discharge provided. Such radiation sources are, depending on the spectrum of the emitted radiation, suitable for the general and emergency lighting, backlighting of displays, for warning signs and promotional purposes and the field of UV technologies.

In front the background of many efforts for the reduction of environmental pollution and the economical use of Energy is intensifying efforts in the area to replace Mercury in gas fillings and economical energy consumption. This global Concern is also devoted to the present invention.

Out The prior art includes various types of gas discharge light sources and plasma light displays known. They are especially after differ from the physical parameters. A rough classification can according to the pressure range and the type of gas filling, the excitation form and the amplitude of the operating voltage and the design taken become.

The More particularly, the narrower scope of the present disclosure is particularly applicable Solutions, a dielectrically impeded discharge to generate suitable plasmas for the Exploiting radiation generation, in particular those, the body in the discharge space exhibit.

The phenomenon dielectrically impeded discharge, often as a silent discharge, Glow discharge at normal pressure or alternating voltage discharge between Insulated electrodes referred to, has long been known. This discharge form is characterized by the fact that they are in a wide pressure range, which ranges from a few 10 mbar to a few bar can. The electrode spacing is usually between tenths of a millimeter to to a few mm. conventional constructed dielectrically impeded discharges are characterized in that at least one of the conductive ones Electrodes are provided with a dielectric, which is then an isolated Electrode forms, or that this dielectric between the conductive electrodes is arranged in the gas space. The shape of dielectrically handicapped Discharge arrangements can be varied. Depending on this form and the other parameters are then often to the desired process adapted specific properties of the dielectric barrier Discharge reached.

As a general rule can the dielectrically impeded discharge with sinusoidal or rectangular alternating voltages be operated in the range of several Hz up to several 100 kHz. Limited by the insulation and the charge carriers deposited on the dielectric the discharge after the breakthrough itself and the discharge time is in many cases only fractions of the half-period duration of the applied maintenance voltage. There is no big one Gas heating. From the discharge form forth are various embodiments of dielectrically impeded discharge in the gas space, the discharge space forms, known. Often are used for large electrodes mostly statistically distributed numerous small to a few tenths mm thick discharge filaments, also called filaments, formed in the gas space. The filaments point in the transition area to the isolated electrodes expansions, which are common in surface discharges with numerous other thin ones Go over discharge channels.

Such Gleitentladungsphänomene can in special arrangements, so-called coplanar or surface discharge arrangements, be dominant. It is also known that in particular in gas fillings with noble gases or their mixtures homogeneous, not filamentated Discharge structures can be formed in the discharge space. Besides are different combinations and transitional forms of discharge formations possible. Partially In the literature such special arrangements are also made with specific ones Designations to emphasize special discharge characteristics. Examples of this are surface discharge arrangements, Sliding discharges, surface sliding discharges or coplanar discharge arrangements. As electrode distance is then meant the resulting in the gas discharge path. Here The term dielectrically impeded discharge should also include such special ones Include arrangements or characteristic discharge characteristics. Independent of the respective training form is the term dielectrically impeded discharge here as a generic term for used the different forms of training.

In dielectrically impeded discharge, a gas discharge is operated to generate electromagnetic radiation with alternating voltages of different shape, frequency and amplitude. An arrangement for generating UV / VUV light is eg in EP 0312 732 A1 described. An improved method with pulse control is WO 94/23442 A1 ( DE 43 11 197 A1 ) at; Studies with very short pulse widths of 150 ns are given in: RP Mildren and RJ Carman, Enhanced Performance of a dielectric barrier discharge lamp using short-pulsed excitation, J. Phys. D: Appl. Phys. 34 (2001) L1-L6.

In the DE 41 40 497 C2 the gap width of the discharge space and / or the effective dielectric capacity is varied in order to influence the emission characteristic.

By using phosphor mounted on at least one electrode insulation, short-wave UV or VUV radiation is also transformed into the visible spectral range for illumination purposes. Such an arrangement and method are for example in DE 197 29 175 A1 and WO 94/23442 A1. It is in the arrangement according to DE 197 29 175 A1 and DE 199 19 363 A1 In addition, a light-reflecting layer on the inner wall of the bottom plate attached.

It also spacers are used in flat radiators, which may be additionally occupied with phosphor (see, eg DE 199 19 363 A1 ). In DE 198 17 478 B4 In particular, the problem of the vessel seal and support points in the discharge space is the subject of the invention. The problem of supporting elements are also devoted DE 100 48 186 A1 and DE 100 48 187 A1 , Spacers or support elements always mean an increased technological effort in the vessel manufacturing process.

To the Rationale of a dielectric barrier discharge include how set forth, including designs in which at least two electrodes are arranged side by side on a substrate, wherein at least one is covered with a dielectric, and those with a further vessel wall before These electrodes, a gas space is formed (coplanar arrangement). It will then be on the surface of the the electrode-carrying substrate discharges, so-called surface discharges, generated. Fields of application of such discharge forms are plasma displays and plasma chemical conversion (see, e.g., G. J. Pietsch and M. Haacke, Some characteristics of different types of dielectric barrier discharges for ozone production, Int. Sympos. on High Pressure Low Temperature Plasma Chem., Greifswald / Germ., Sep. 10-13, 2000, Contributed Papers Vol. 2, pp. 299-303).

Examples of the use of various such forms for lighting purposes are the DE 196 51 552 A1 . DE 197 11 892 A1 DE 198 17 480 B4 . DE 198 44 721 A1 . EP 1 455 381 A2 and DE 198 44 720 A1 , In DE 198 44 721 A1 . DE 198 44 720 A1 meandering or sinusoidally shaped with monotonically varying discharge spacing electrodes are used. The latter also serves for dimming by exploiting this to control the power of the discharge lamp. EP 1 455 381 A2 uses discharges with so-called overhanging discharge electrode sections.

in the Case of display applications is usually a variety of discharge points individually controllable arranged in the form of arrays. In color display devices, e.g. Television screens are suitable phosphors on a substrate for the transformation of short-wave UVA / UV radiation in the desired visible spectral range attached. A compilation to Plasma displays are given for example in A. Rutscher: Wissensspeicher Plasma technology, 1st edition, book publisher, Leipzig 1983, p 211 et seq.

As mentioned, can be provided in the present case, various applications. In addition to the application for Lighting purposes are e.g. Advertising lights or effect lighting known.

In the US 5,281,898 and US 5,383,295 Embodiments are described with bodies in the discharge space for channel-like distribution of the discharge in a flash-like form between the electrodes.

These Discharge configuration is because of the long discharge distances between the bodies located in the gas space and the electrode arrangement and -form for Lighting purposes not suitable. This is also true for plasma display purposes to. Because of the electrode arrangement and the various located in the gas space body the discharge path is not clearly defined and the discharge is looking for each have different breakthrough channels. This is also no Control of defined pixels or areas possible.

The as far as listed known devices for generating a gas discharge, which after the Principle of dielectrically impeded discharge are constructed, have for the Use as light sources and for the visual display has a number of disadvantages. In the prior art with systems based on the principle of dielectrically impeded discharge In the field of gas discharge light sources, in particular for many applications reached a low light output. Furthermore, by the relatively high Operating voltages the control consuming and expensive. At expensive filling gases how Xe should be the capacity preferably be minimized to reduce costs. In the prior art with Systems according to the principle of dielectrically impeded discharge for visual display purposes the problems are similar. In particular, there is always a trade-off between operating voltage, filling pressure, Gas space thickness and optimal radiation transformation to search.

The prior art is also on the document DE 101 33 949 C1 referenced, the one Improvement of the above-mentioned prior art has reached. Accordingly, an arrangement for a gas discharge light source or a plasma gas display device is known, in which at least one layer formed gas chamber, consisting of individual bodies or of contiguous structures of dielectric material, is arranged.

By the layer of bodies of dielectric material is thereby achieved, inter alia, that a plasma distributed in the gas space and enveloping the body, with the advantage of improved radiation efficiency or luminous efficacy across from the state of the art.

OBJECT OF THE INVENTION

The The object of the invention is an improved radiation yield or light output opposite To achieve this known prior art. By the invention should be a simplified manufacturing process and manufacturing be made possible by standard designs in modular design.

The Invention is characterized by the features of claim 1; Further advantageous embodiments are shown in the subclaims.

It has surprisingly been found that a similar result as in DE 101 33 949 C1 can be achieved if at least one layer of coherent, structured bodies or structures made of electrically conductive material is arranged in at least one trained gas space (such as braided or wire-meshed shapes), and if they have the function of an electrode, so that a flat plasma formed can be.

The inventive device according to the principle of dielectrically impeded discharge for radiation generation is characterized in that a structured gas space, in a plasma is generated through a structured electrode a layer of coherent, structured bodies or structures formed of electrically conductive material becomes. On the conductive structured Electrode is at least one insulating plate mounted so that the structural surveys of the conductive structured electrode act as a spacer. Between the conductive one structured electrode and at least one insulating plate a gas space is formed to produce a plasma.

In an embodiment forms the conductive structured Electrode itself a vessel part by creating walls on the edges the conductive one structured electrode are present. The structured on the conductive Electrode lying insulating material is connected to the walls. Thus, a vessel for the gas intake educated.

For universal or changing applications, a module is presented that at least from a conductive structured electrode and an insulating material consists or from a sequence of insulating material, conductive structured electrode and insulating board. Several modules can be used to design a character or picture.

to Transformation of UV / VUV radiation into visible light is the conductive structured electrode with phosphor or at least one den Gas space bounding area provided with a phosphor layer.

to Improvement of the gas purity and / or increase of the secondary electron emission is the conductive one structured electrode and / or insulating plate with tempering layers Mistake.

When an embodiment has the conductive structured Electrode braided or wire mesh shaped. character characters like letters, numbers or symbols are made by the external design in the form of the device or by the design in the mold formed of the electrode.

With the device according to the invention As a major advantage, this results in a greatly simplified one Construction, whereby the product can be produced cheaper.

The coherent, structured body or take structures of electrically conductive material Here are two essential functions. On the one hand, they are used as a conductive electrode On the other hand, they also act as spacers to at least one substrate which is transparent to them and transparent to light, on which there is another transparent electrode. The transparent substrate with transparent electrode thus forms the electrode isolated from the gas or discharge space.

The simple construction also allows a simplified manufacturing process, since in one embodiment practically only a sandwich structure of insulator plate, conductive structured electrode and insulator plate, in another sequence conductive patterned electrode-insulator plate, must be made. The rest can be customized with simple means. The inventive Execution thus enables a production of standard designs as a modular design with variable applications.

One Another advantage is that now simple versions without separate contact protection are possible.

Compared to the It is also apparent from prior art that, irrespective of the size of the structural elements the structured electrode corresponding to the respective filling gas pressure always the minimum ignition voltage according to the breakthrough curves for the respective gas. Thus, you can in all cases low operating voltages are used. The simplified and cheapens the energy supply.

By the arrangement according to the invention comes it to an intensified Inclusion of the surfaces in the plasma education. This will transform the transformation of UV / VUV radiation in visible light in the case of the structured electrode and / or the insulator plate are provided with phosphor, more effective.

Further So is the decoupling of directly generated in the discharge visible radiation, for example in ne fill applications for advertising or hint purposes.

The following embodiments are intended clarify the basic principle.

It demonstrate:

1 a perspective view of an arrangement with a conductive patterned electrode of a plate and worked out hemisphere shapes,

2 an exploded view of an arrangement with interwoven or interwoven structures.

3 a perspective view of an arrangement with a conductive patterned electrode of contiguous spherical shapes and schematically indicated power supply.

In 1 is the basic principle of the device according to the invention for generating radiation in a perspective view schematically illustrated. It consists of a conductive structured electrode 3 , an insulating material thereon 2 with an electrode in turn on this 1 and a gas space formed in this way 4 which is structured by it. For practical applications, the conductive patterned electrode 3 flat and formed with at least three structural elements. Not shown in detail are lateral closure elements for the gas space 4 and filler neck for gas filling.

In the filled and sealed vessel, the coherent, structured body made of electrically conductive material assumes the function of a structured electrode conductive with respect to the gas space 3 and at the same time the function of the spacers to the insulating material plate mounted thereon 2 , The insulating plate 2 forms a substrate transparent to light, on which then a transparent electrode 1 located. The electrode 1 and the insulating plate 2 are designed so that the respectively desired electromagnetic radiation can be coupled out, that is, they are transparent or partially transparent for this radiation.

To the conductive patterned electrode 3 and the electrode 1 appropriate AC voltages are applied so that it is in the gas space 4 comes to corresponding gas discharges. As a result, an electromagnetic radiation is generated. The discharges in the gas space 4 In the present case, all discharges or discharge parts in the volume as well as on the surfaces of the conductive structured electrode are included 3 and the surface of the insulating material 2 ,

An advantage of this type of arrangement is that in comparison to the prior art, in particular to DE 101 33 949 C1 , the discharge gap between the conductive patterned electrode 3 and the insulated electrode (formed from 1 and 2 ) is further effectively shortened, since only one dielectric (Isolierstoffplatte 2 ) is between the conductive parts of the electrodes, and that while the conductive patterned electrode 3 already the insulating plate 2 touched.

Independently of the size of the structural elements, the minimum ignition voltage corresponding to the respective filling gas pressure can thus always be set in accordance with the breakthrough curves for the respective gas, so that even coarse structures with larger dimensions of a few mm of the structural elements of the conductive structured electrode 3 can be operated optimally. This voltage value depends practically only on the thickness and the material of the insulating material 2 and is independent of the dimensions of the conductive patterned electrode 3 ,

In the course of the discharge development, more and more become the free surfaces of the insulating plate 2 covered by the plasma. Thus both an effective transformation of plasma generated UV / VUV radiation into visible light in the Ge Fäß attached phosphors possible as well as an increase in the visible radiation component over otherwise conventional arrangements. In particular, higher illuminance levels are observed because of the larger areas on the structural elements in the direction of the vascular normal.

For the outer shaping can planar, cylindrical or spherical Arrangements selected become. It is also possible Character characters such as letters, numbers or symbols in the desired Shape form by the external design.

In another embodiment, at least the conductive patterned electrode 3 or the electrode 1 be formed in the form of a desired character character.

For many applications, it is particularly advantageous to build a module consisting of a sandwich structure (see 2 ). In this case, the conductive structured electrode 3 on another insulating plate (eg 5 ) lie, said insulating plate and the insulating plate 2 are provided with a sealing frame, so that a vessel with internal conductive structured electrode 3 is formed. This system forms a module in a desired area dimension. The display of character characters is now individually the electrode 1 formed. The shaped electrode 1 For example, it may be a film or a glass substrate with an ITO layer. The ITO layer is preferably located directly on the insulating plate 2 ,

In another favorable variant has the conductive structured electrode 3 on the sides of walls, the height of which corresponds approximately to that of the structure surveys, and are polished upwards plan. Then it is the insulating plate 2 together. Thus, the conductive patterned electrode takes over 3 another function by becoming the vessel part itself. The wall of the structured electrode part for receiving and attaching the insulating plate 2 can be configured differently. For example, a recess for receiving and positioning the insulating plate 2 advantageous.

The Modules are universally applicable in this way and can do so be individually adapted with simple means.

Further allows the modular design is an industrial mass production, which is just what Character Characteristics significantly increase productivity.

The Material selection depends i.a. after the application and further In particular, the specific task of the component comes to Wear.

So it is e.g. Cheap, on the radiating side of the vessel transparent ITO layers for decoupling of visible radiation, while in applications for decoupling wire mesh electrodes used by UV or VUV radiation become.

Furthermore, from the material side, conventional means for improving the gas purity and / or increasing the secondary electron emission by means of tempering layers to the gas space can also be used 4 be provided adjacent sowing elements.

In the case of an embodiment with a conductive structured electrode lying inside the vessel 3 , this serves as a high voltage electrode, results in a further advantage that no contact protection is required. This also applies to an embodiment in which the conductive patterned electrode 3 Part of the vessel is thereby grounded, and wherein the high voltage electrode is a vapor deposited on a glass substrate ITO layer. The ITO layer then forms the electrode 1 and is to the insulating plate 2 arranged while the glass substrate forms the outside.

In the present embodiment, has the conductive patterned electrode 3 numerous hemispherical structures. This form can be advantageously modified.

The 2 shows an exploded view of an arrangement with interwoven structures. In this embodiment, the conductive patterned electrode 3 formed from a wire mesh layer. This is very cheap.

Opposite the 1 Here is also an insulating board 5 indicated, together with the insulating material 2 forms the vessel with a sealing frame not shown in detail. The other elements are as shown 1 ,

In 3 is a perspective view of an arrangement with a conductive patterned electrode 3 represented by contiguous spherical shapes and schematically indicated power supply. This arrangement shows the possibility of two-sided radiation. For this purpose, the vessel is made of transparent Isolierstoffplatten 2a and 2 B formed, on which are the transparent electrodes 1a and 1b , The conductive structured electrode 3 is here formed by a symmetrical to both sides ball structure, which acts as a high voltage electrode. The outer electrodes 1a and 1b are then grounded.

The shape of the structure is not on the here ku limited gel-type and can be chosen otherwise.

Next the designs described with reference to drawings other variants are possible, which but the basic principle of the invention is not changed. In particular, cylindrical or tubular vessel shapes chosen become.

Claims (10)

Device according to the principle of a dielectrically impeded discharge for generating radiation, characterized in that a structured gas space ( 4 ), in which a plasma is generated, by a structured electrode ( 3 ) is formed of a layer of coherent, structured bodies or structures of electrically conductive material. Device according to claim 1, characterized in that on the conductive structured electrode ( 3 ) at least one insulating plate ( 2 ) is mounted so that the structure elevations of the conductive structured electrode ( 3 ) act as a spacer, and that between the conductive patterned electrode ( 3 ) and at least one insulating plate ( 2 ) a gas space ( 4 ), which in turn is patterned, is formed to produce a plasma. Device according to claim 1 or 2, characterized in that the conductive patterned electrode ( 3 ) itself forms a vessel part by walls at the edges of the conductive structured electrode ( 3 ) are present, so that the on the conductive patterned electrode ( 3 ) lying insulating material plate ( 2 ) is connected to the walls and these together form a vessel for the gas intake. Device according to one of claims 1 to 3, characterized in that for universal or alternating applications, a module, at least consisting of a conductive structured electrode ( 3 ) and an insulating plate ( 2 ), or that the module consists of a sequence of insulating material ( 5 ; 2 B ), conductive structured electrode ( 3 ) and insulating plate ( 2 ; 2a ) consists. Device according to claim 4, characterized in that that several modules for designing a character character or Picture are summarized. Device according to one of claims 1 to 5, characterized in that the conductive structured electrode ( 3 ) is provided for the transformation of UV / VUV radiation into visible light with phosphor, or that at least one of the gas space ( 4 ) limiting surface is provided with a phosphor layer. Device according to one of claims 1 to 6, characterized in that the conductive structured electrode ( 3 ) and / or insulating material ( 2 ; 5 ) 2a ; 2 B ) are provided with tempering layers for improving the gas purity and / or increasing the secondary electron emission. Device according to one of claims 1 to 7, characterized in that the conductive structured electrode ( 3 ) has braided or wire mesh-shaped structures. Device according to one of claims 1 to 8, characterized that characters such as letters, numbers or symbols through the outer design be formed in the form of the device. Device according to one of claims 1 to 8, characterized in that character characters such as letters, numbers or symbols by the design in the form of the electrode ( 1 ; 1a ; 1b ) be formed.