EP1422741A2 - Dielectric barrier discharge lamp and use thereof for viewing x-rays image - Google Patents

Abstract

Dielectric barrier discharge lamp (1) comprises a discharge vessel containing a discharge medium, a set of electrodes (8-11) for producing dielectrically hindered discharges in the discharge medium, and a luminescent mixture applied on part of the wall of the vessel and consisting of R: (Y, Gd)BO3: Eu, G: LaPO4: (Tb or LaPO4 (Ce, Tb)) and B: BaMgAl10O17: Eu (where R = 0.05-0.15; G = 0.50-0.70; B = 0.20-0.40; and R + G + B = 1).

Description

Technical field

The invention is based on a dielectric barrier discharge lamp with a fluorescent layer.

The term “dielectric barrier discharge lamp” encompasses sources electromagnetic radiation based on dielectrically disabled Gas discharges.

By definition, a dielectric barrier discharge lamp sets at least a so-called dielectric barrier electrode ahead. A dielectric disabled electrode is opposite the inside of the discharge vessel or separated from the discharge medium by means of a dielectric. This Dielectric - the dielectric barrier - can, for example, act as the electrode covering dielectric layer, or is through the discharge vessel of the lamp itself is formed, namely when the electrode is arranged on the outside of the wall of the discharge vessel. at Lamps that determine whether the electrodes are cathodes or anodes work, i.e. for operation with unipolar voltage pulses, at least the anodes are dielectrically separated from the discharge medium (see EP 0 733 266 B1).

The ionizable discharge medium usually consists of a noble gas, for example xenon or a gas mixture. So-called excimers are formed during the gas discharge, which is preferably operated by means of a pulsed operating method described in EP 0 733 266 B1. Excimers are excited molecules, such as Xe ₂ *, which emit electromagnetic radiation when they return to their normally unbound basic state. In the case of Xe ₂ *, the maximum of the molecular band radiation is approximately 172 nm, in the area of VUV radiation.

However, the present invention relates to a variant in which additionally a phosphor layer to convert the VUV radiation into Radiation with longer wavelengths, especially visible radiation (Light) is provided.

State of the art

A dielectric barrier discharge lamp with a phosphor layer for general lighting is known from EP 0 733 266 B1 already cited. The phosphor layer consists of a three-band phosphor with the red phosphor component (R) gadolinium yttrium borate ((Gd, Y) BO ₃ : Eu), the green phosphor component (G), lanthanum phosphate (LaPO ₄ : (Ce, Tb)) and the blue phosphor component (B) barium magnesium aluminum aluminate (BaM ) ₁₀ O ₁₇ : Eu). A color temperature of 4000 K and a color location with the coordinates x = 0.38 and y = 0.377 are specified for this lamp in accordance with the CIE color standard table.

US 6 034 470 shows a flat dielectric barrier discharge lamp, which is also provided with the aforementioned three-band phosphor. This Flat lamp is especially for the backlighting of liquid crystal screens intended.

EP 0 7 38 311 B1 describes a dielectric barrier discharge lamp for the general lighting with a fluorescent coating reveals which also includes the aforementioned RGB components. The claimed Ranges for the weight fractions of the mixture are 0.2 <R <0.5, 0.4 <G <0.7 and 0.05 <B <0.15 with R + G + B = 1.

Presentation of the invention

The object of the present invention is the application possibilities of dielectric barrier discharge lamps.

This task is accomplished with a dielectric barrier discharge lamp the features of the preamble of claim 1 by the features of characterizing part of claim 1 solved. Particularly advantageous configurations can be found in the dependent claims.

It also provides protection for the use of the dielectric according to the invention Barrier discharge lamp for viewing x-rays claimed, in particular also in connection with an inventive dielectric barrier discharge lamp in flat design for diffuse backlighting.

R: Europium aktiviertes Yttriumgadoliniumborat ([Y, Gd]BO₃:Eu),

G: Terbium aktiviertes Lanthanphosphat (LaPO₄:[Tb]) oder Cer und Terbium aktiviertes Lanthanphosphat (LaPO₄:[Ce, Tb]) und

B: Europium aktiviertes Bariummagnesiumaluminat (BaMgAl₁₀O₁₇:Eu).

The invention proposes a dielectric barrier discharge lamp with a phosphor mixture, the phosphor mixture consisting of the following phosphor components:

R: Europium activated yttrium gadolinium borate ([Y, Gd] BO ₃ : Eu),

G: terbium activated lanthanum phosphate (LaPO ₄ : [Tb]) or cerium and terbium activated lanthanum phosphate (LaPO ₄ : [Ce, Tb]) and

B: Europium activated barium magnesium aluminate (BaMgAl ₁₀ O ₁₇ : Eu).

The following applies to the proportions by weight of the mixture: 0,05≤ R ≤0.15, 0.50≤ G ≤0.70, 0.20≤ B ≤0.40 and R + G + B = 1, better 0.06 ≤ R ≤ 0.12, 0.58 ≤ G ≤ 0.66, 0.25 ≤ B ≤ 0.35 and R + G + B = 1.

The above ranges for the weight fractions of the respective component among other things, the phosphor mixture always carries that in practice inaccuracies and tolerances that occur, e.g. the typically slightly different quantum efficiencies different Fluorescent batches due to small manufacturing fluctuations etc.

In addition, the focus of fine-tuning the phosphor mix, especially the color temperature, depending on the specific application be stored differently. However, all of this is with some fitting fewer, fine-tuned mix variations within these ranges manageable.

For specific information on the weight ratios of the individual phosphor components R, G, B one especially for viewing X-ray images particularly suitable dielectric barrier discharge lamp reference is made to the description of the exemplary embodiment.

In a preferred embodiment, the dielectric barrier discharge lamp according to the invention filled with xenon, typically with a filling pressure in the range from 50 to 200 mbar, preferably between 100 and 150 mbar. Thereby the dielectric barrier discharge produces xenon excimer band radiation with a maximum at about 172 nm, which is the Stimulates phosphors. Both when choosing the fluorescent components as well as for their mixing ratios, the quantum efficiency is the Phosphors for this exciting radiation to be considered to ensure the highest possible luminous efficiency. Another aspect is that Maintenance of the fluorescent components with permanent excitation with them Radiation. The lowest possible number for each phosphor component Decrease in the intensity of the converted radiation over the lifetime of dielectric barrier discharge lamps of typically at least Aimed for 20,000 hours to maintain a constant color locus to ensure the lifespan. This is especially true when looking at it of X-ray images is important to ensure good reproducibility ensure the visual impression when viewing the X-ray image, whereby the backlighting of the X-ray images with the dielectric according to the invention Barrier discharge lamp takes place.

It has been shown that it is advantageous if the for viewing X-ray images, dielectric used especially in mammography Barrier discharge lamp has a color temperature of 10,000 K or more. The color temperature is preferably more than 20,000 K, particularly preferably more than 30,000 K, very particularly preferably more than 40,000 K. Without any purpose with the following interpretation these experimental findings currently with the following facts connected. X-ray films are currently used in general, their transmission maximum in the blue spectral range of light lies. If now for the backlighting of the developed X-ray films Light source is used, which mainly contains blue spectral components (high Color temperature), there is a correspondingly higher proportion of the lamp luminous flux available for transmitted light viewing. Furthermore, Subjectively, "blue light" is perceived as much brighter than "reddish light" (lower Color temperature). This will result in the backlighting of x-rays the contrast with the dielectric barrier discharge lamp mentioned above and thus also the ability to differentiate when considering the X-ray image better. It has been shown that from a color temperature of approximately 10,000 K a significant improvement in the contrast compared to warmer light colors ("reddish light"), for example with a Color temperature of 4000 K, as usual for general lighting, can be determined is. By further increasing the color temperature, for example above 20,000 K, 30,000 K or even 40,000 K can be used for X-ray imaging improve even further.

In a particularly advantageous embodiment, the dielectric according to the invention is Barrier discharge lamp designed as a so-called flat lamp. In contrast to the light sources used today for X-ray film viewing with their extreme luminance, which is a significant one Dazzle effect on the viewer, the invention is characterized Flat lamp by a high and above all on the essentially plane Radiation area extremely homogeneous luminance, which is practically glare-free Backlighting enabled. This will make a reliable diagnosis for the doctor is considerably relieved, in critical cases, especially in mammography, improved. Find details about the flat lamp according to the invention yourself in the embodiment.

In principle, the dielectric barrier discharge lamp according to the invention also be tubular. For backlighting purposes the light from this lamp is usually in the narrow side a light guide plate, e.g. a plexiglass plate, coupled (so-called Edge Light technique). The light from the lamp is then on a broadside of the The light guide plate is largely diffusely coupled and thus also serves as flat light source for backlighting. This technique is known in principle and here only marginally of interest and should therefore not be explained in more detail here become.

In addition to being used for backlighting X-ray images the dielectric barrier discharge lamp according to the invention is also suitable for other areas of application for which a high color temperature is required or is at least desirable, e.g. for the backlighting of liquid crystal screens (LCD) for special applications, especially for monochrome LCD.

Brief description of the drawings

Fig. 1a

eine schematische Draufsicht einer erfindungsgemäßen dielektrischen Barriere-Entladungslampe,

Fig. 1b

eine schematische Seitenansicht der Lampe aus Figur 1a,

Fig. 2

die prinzipiellen Verhältnisse der Elektrodenstruktur für eine vorzugsweise mit unipolaren Spannungspulsen zu betreibende erfindungsgemäßen Flachlampe mit einer Diagonale von 6,8".

The invention is to be explained in more detail below using an exemplary embodiment. Show it:

Fig. 1a

2 shows a schematic plan view of a dielectric barrier discharge lamp according to the invention,

Fig. 1b

2 shows a schematic side view of the lamp from FIG. 1a,

Fig. 2

the basic relationships of the electrode structure for a flat lamp according to the invention, preferably to be operated with unipolar voltage pulses, with a diagonal of 6.8 ".

Preferred embodiment of the invention

In Figures 1a, 1b is a schematic plan view and side view of a dielectric barrier discharge lamp 1 according to the invention schematically shown. It is a flat dielectric barrier discharge lamp for the backlighting of x-rays, in particular in mammography. Is only for performance reasons a lamp with relatively few electrode strips and consequently relatively less Lamp diagonal shown. This aspect is related below explained in more detail with FIG. From their basic mechanical and electrical structure corresponds to this flat lamp in any case essentially that lamp disclosed in the already cited US 6 034 470 is. The main difference is the phosphor layer. Before this in Details will first be given with reference to FIGS Structure of the lamp 1 according to the invention are outlined.

The flat lamp 1 consists of a flat discharge vessel with a rectangular one Base area and an electrode set, which is inside the discharge vessel is arranged. The discharge vessel in turn consists of a Back plate 2, a front plate 3 and a frame 4, each made of glass manufactured. Back plate 2 and front plate 3 are each with glass solder 5 with connected to the frame 4 in a gas-tight manner such that the interior of the discharge vessel is cuboid. The inside of the discharge vessel is filled with xenon with a pressure of approx. 130 mbar. The back plate 2 is larger than the front plate 3 such that the discharge vessel has a rotating one has a free-standing edge. On this edge there are two track-like ones Supply lines 6, 7 applied for the electrode set.

The inner surface of the front plate 3 is coated with a three-band phosphor mixture (not visible in the illustration), which converts the UV / VUV radiation generated by the discharge into visible light. These are the red phosphor component (Y, Gd) BO ₃ : Eu (NP 360-03 from Nichia), the green phosphor component La-PO ₄ : (Ce, Tb) (2213 CCSX from OSRAM Sylvania Inc.) , and the blue phosphor component BaMgAl ₁₀ O ₁₇ : Eu (NP 107-44 from Nichia) with the associated weight fractions 8%, 62% and 30%. The lamp therefore has a color temperature of approx. 50,000 K and a color location with the coordinates x = 0.236 and y = 0.240 according to the CIE color standard table.

For reasons of better representability, the one shown in Fig. 1 a, 1 b Lamp a representative layout of an electrode set for a lamp diagonal of 6.8 "is shown schematically in Fig. 2. With a lamp with a larger diagonal changes the basic layout of the electrode set nothing, they are just more and longer electrode strips required. The electrode set consists of a conductor track-like one Structure with strip-like metallic cathodes 8 and anodes 9, 10, 11, which are arranged alternately and in parallel on the inner surface of the back plate 2 are. The cathode strips 8 specifically have spatially preferred starting points for the individual discharges occurring in pulsed operation (see EP 0 733 266 B1 already cited), which is characterized by nose-like, The extensions 12 facing the respective adjacent anode strip are realized are. They cause locally limited amplifications of the electrical field and consequently that the delta-shaped individual discharges (not shown) ignite only at these points 12. Except for the two outer ones Anodes 10, 11 have the other anodes 9 a double structure 9a, 9b on. All anodes 9-11 are with a dielectric layer made of glass solder (not shown) covered. The anodes 9-11 and cathodes 8 are each on one end extended and on the back plate 2 from the inside of the Discharge vessel led outwards on both sides such that the associated anodic or cathodic bushings on opposite to each other Sides of the back plate 2 are arranged. On the edge of the Back plate 2, the electrode strips 8-11 each go into those already mentioned 6 on the cathode side or 7 on the anode side. The supply lines 6, 7 serve as contacts for connection to preferably an electrical one Pulse voltage source 13. For a flat lamp (not shown) with e.g. 15 "diagonal is a (not shown) electrode set with twelve cathode strips and eleven double anode strips and two outer ones Single anodes provided. Each anode strip points along each of the Thirteen extensions on each of the long sides for igniting the individual discharges on.

Although the invention is based on the example of a flat dielectric Barrier discharge lamp has been explained in detail, it is not on this Lamp shape limited. Rather, their beneficial effects arise also for lamps with other tube shapes, e.g. for tubular lamps. In the latter case, the electrode set consists of two or more elongated ones Electrodes parallel to the lamp's longitudinal axis on the wall of the tubular Discharge vessel are arranged.

Claims (12)

Dielectric barrier discharge lamp (1) with, a discharge vessel, the wall of which encloses a discharge medium, an electrode set (8-11) for generating dielectrically impeded discharges in the discharge medium, at least part of the electrode set (8-11) being dielectrically impeded, a phosphor mixture which is applied to at least part of the wall of the discharge vessel, a phosphor mixture from the following phosphor components: R: (Y, Gd) B0 ₃ : Eu, G: LaPO ₄ : (Tb or LaPO ₄ : (Ce, Tb), B: BaMgAl ₁₀ O ₁₇ : Eu, characterized in that the following applies to the weight fractions of the phosphor components R, G, B of the mixture: 0.05 ≤ R ≤ 0.15, 0.50 ≤ G ≤ 0.70, 0.20 ≤ B ≤ 0.40 and R + G + B = 1. Dielectric barrier discharge lamp according to claim 1, wherein the following applies to the weight fractions of the mixture: 0,06≤ R ≤0.12, 0.58≤ G ≤0.66, 0.25≤ B ≤0.35 and R + G + B = 1. A dielectric barrier discharge lamp as claimed in claim 1 or 2, wherein the discharge vessel contains xenon as the discharge medium. A dielectric barrier discharge lamp as claimed in claim 3, wherein the Filling pressure of the xenon is in the range between 50 and 200 mbar. A dielectric barrier discharge lamp as claimed in claim 3, wherein the Filling pressure of the xenon is in the range between 100 and 150 mbar. Dielectric barrier discharge lamp according to one of the preceding Claims, wherein the discharge vessel is shaped flat and a Back plate (2) and a front plate (3) for the light emission, at least is partially translucent. Dielectric barrier discharge lamp according to one of claims 1 to 5, wherein the discharge vessel is tubular. Dielectric barrier discharge lamp according to claim 6 or 7 with a dielectric layer between at least part of the electrode set and the discharge medium. Dielectric barrier discharge lamp according to one of the preceding Claims, at least according to claim 8, wherein the electrode set from consists of two or more elongated electrodes that are on the wall of the Discharge vessel are arranged. Using a dielectric barrier discharge lamp with a Color temperature of 10,000 K or more for viewing X-ray images. Use according to claim 10, wherein the color temperature is more than 20,000 K, preferably more than 30,000 K, particularly preferably more than Is 40,000 K. Use according to claim 10, wherein the dielectric barrier discharge lamp the features according to one of claims 1 to 9 having.

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