EP1069594A2 - DC arc Lamp - Google Patents

Abstract

A new metal halide direct current arc lamp contains a new filling system, in particular with cadmium and / or zinc, and has an improved bulb geometry. Protection for a corresponding projection device is also claimed.

Description

Technical field

The present invention relates to a DC arc lamp according to the Preamble of claim 1.

Recently there has been an increasing interest in improving such arc lamps, especially for projection applications. For projection applications are above all the locally concentrated light generation on the one hand and on the other the homogeneity of light generation in this local area of interest. The so-called color separation effect plays an important role here. With This term is a local separation of the focus of light generation for different spectral ranges or colors of the generated light, what leads to a deterioration in the quality of light for projection applications which manifests itself in color fringes at border or edge areas of projected images.

The color separation effect is caused by the anode between the lamps and cathode of the direct current arc lamp causes direct electrical field. The DC electrical field influences the concentration distribution of the light-generating Metal ions between anode and cathode. This will make the spatial Distribution of the metal ions between the anode and cathode is usually inhomogeneous. In addition, different concentration distributions arise for different types of metal ions on. Because different types of metal ions have different spectral Contributing to the total luminous flux of the lamp ultimately results in the unwanted Color separation effect.

Furthermore, the invention relates to a DC arc lamp with a halogen filling. As a result, there are metal halides during lamp operation inside the discharge vessel. Metal halides have a higher one Vapor pressure as the corresponding elemental metals. Generate also the high specific arc powers of typically approx. 80 W per mm arc length and more also high vapor pressures of the light-generating metal halides. Thereby on the one hand a high luminous flux of the lamp is ensured. On the other hand, reinforce the high vapor pressures in general also the color separation effect.

Another essential quality criterion - not only in the area of projection - are sufficient proportions of the primary colors blue, green and red for good color rendering and the desired color temperature.

With regard to the prior art, reference is made to EP 0 714 118 A1, the one DC short arc metal halide lamp showing the preamble of the claim 1 is based.

No. 2,965,790 also shows an arc lamp with an asymmetrically shaped one Piston in which the inner wall of the piston around the anode is wider than around the cathode.

Presentation of the invention

The invention is based on the technical problem of a DC arc lamp with improved operating properties, especially with regard to projection applications, and to provide an improved projection device.

According to the invention, this problem is solved by a DC arc lamp a filling of at least the following components: an ignition gas, mercury and a halogen, characterized by the additional component: zinc and in that the total concentration for zinc, including optionally present The total cadmium is in the following range: 0.05 to 3.0 µmol per ml of the lamp vessel or a projection device with such a projection lamp.

It has turned out to be critical for a sufficient amount of red in the light ensure, on the one hand, in favor of good red color rendering and, furthermore, one desired color temperature, preferably between 5,000 and 8,000 Kelvin, preferably 6,000 and 7,000 Kelvin.

The proportion of red in the light generated can be due to lithium in the filling of the invention DC arc lamp are amplified. However, it is found that lithium predominantly shows a very long-wave emission, i.e. to a very deep red part leads. For all applications that have some kind of visual effect lead, for example in projection or lighting, but are not only pure to take into account physical spectral power shares, but also beyond the physiological sensitivity of the human eye with the so-called V (λ) - or brightness sensitivity curve is shown. The spectral sensitivity of the human eye decreases significantly at the long-wave edge. Therefore, as far as the red component is based on the lithium emission, a corresponding one increased spectral power can be generated to the desired - and ultimately of interest - to generate luminous flux.

It has also been found that the addition of lithium to the lamp fill enhances the color separation effect mentioned above.

Because the filling of a metal halide direct current arc lamp is necessary in addition to an ignition gas, e.g. Argon, and a halogen, e.g. Bromine or iodine, too It must contain mercury to build up the necessary burning voltage green color of mercury. That through the mercury content The specified green component must be red when setting the color temperature be compensated, which exacerbates the problem outlined above.

If zinc is used in the lamp filling according to the invention, this will not only increases the red component, but also the color separation effect decreased. The addition of zinc allows compared to the (sole) Adding lithium for the red component significantly improves the color separation problem and, with the same performance, an improved luminous flux.

Mercury is in the context of this invention as an alternative to the 2B element Zinc is not suitable because it is also to a certain extent the color separation is reduced, but it increases the amount of green in the light excessively.

Zinc offers versus cadmium, which can also be included optionally, and Mercury also has the benefit of better environmental performance. Cadmium on the other hand can be beneficial for certain applications because of the red rendering is even better. According to the invention, the zinc and cadmium quantities are therefore measured in individual cases the possibility to choose between optimal lamp data and environmental considerations.

According to the invention, the following preferred concentrations come in particular for Cd and Zn considered: 0.05 to 3.0 pmol per ml of vessel volume.

For various electrical lamp powers in projectors, the following concentration ranges for Cd and Zn have proven particularly useful: Power consumption of the lamp Concentration in µmol / ml Field of application up to 170 W. 0.3 to 3.0 Home or consumer market 170 to 300 W. 0.2 to 2.0 Business area 300 to 3000 W. 0.05 to 1.0 Professional large screen projection

All stated values are to be understood as approximate values. The concentration information refer to the sum of the individual concentrations of Cd or Zn, where the concentration of one of the two individual components can also be zero.

As a further embodiment of the invention, the component additionally shows yttrium just together with the basic composition according to the invention explained special advantages. The first is an improvement in the luminous flux. Secondly, there is a longer lamp life and thirdly a smaller decrease in lamp luminous flux with lamp operating age (so-called maintenance). Yttrium is therefore used to achieve the above basic effects of the invention are not necessary, but has proven to be in in terms of luminous flux, service life and maintenance surprisingly more effective optional addition highlighted.

Various chemical elements are conceivable as further optional additives, in particular for setting the color temperature and enhancing the basic colors. In front the above explanation of the disadvantages of lithium should not be understood to that effect be that lithium would be excluded according to the invention. Lithium can be present in certain quantities as a "red element" by the inventive Use of cadmium or zinc is the required amount however less.

The preferred application in most cases requires a high one Blue content in the spectrum. A “blue element” preferred according to the invention is indium.

Other optional additives, especially to increase the luminous flux, are the rare earth metals, especially dysprosium, as well as thallium.

As halogen for the setting of desired vapor pressures through the formation of metal halide compounds iodine and / or bromine are preferred.

Aspects of the invention that go beyond the filling system relate to the geometric Design of the lamp.

Plays in many areas of application, especially in projection devices the best possible localization of light generation is an important role, why the invention is based on short-arc lamps. Only with the lowest possible Arc length, a point light source can be approximated sufficiently well thus good optical quality for projection or other applications which the light emitted by the lamp is sent through an optical system to reach.

In addition to that, it has changed in terms of uniformity of light generation their local expansion, even with good localization such as short-arc lamps, according to the invention also found to be crucial for a Temperature distribution as uniform as possible in the lamp, especially on the Inner wall of the piston. This mainly affects temperature gradients along the distance between cathode and anode in the lamp. These temperature gradients can be significantly reduced if the geometric shape of the fill containing lamp bulb is chosen appropriately. For this purpose, it is according to the invention asymmetrical to reflect the asymmetry of the temperature distribution of the electrodes of a DC arc lamp to be adapted.

In the case of direct current arc lamps, the anode is in principle a much stronger one exposed to thermal stress than the cathode and becomes accordingly hotter. So that it can withstand this thermal load, the anode is at DC arc lamps are generally much more solid than the cathode. In particular, it generally has a larger diameter.

It has proven disadvantageous that the higher anode temperature on the one hand and the larger anode diameter due to the shorter distance to the inside wall of the piston and the larger heat-conducting and heat-radiating surface on the other hand with symmetrical design of the lamp bulb to much higher Temperatures of the lamp on the anode side, especially also on the inside wall of the bulb to lead. This has an influence on the physical parameters of discharge and light generation. The aim is to keep the temperature difference as small as possible between the hottest and coldest point in the flask. At uniform temperature distribution, on the one hand, the light emission is homogeneous, on the other hand the temperature can be set to an optimal value that both the requirements for the luminous efficacy as well as those for the service life and maintenance is enough.

According to the invention, the temperature homogeneity of the lamp is improved by that the inside wall of the piston is wider around the anode than around the cathode. This can, depending on the selected shape of the electrodes and depending on the manufacturing technology Aspects, with different concrete geometric shapes can be achieved, with geometrically simple and therefore easy to manufacture piston shapes are preferred.

Especially with regard to the projection applications mentioned are, as already mentions striving for the shortest possible arc lengths. The arc length is in Connection with the lamp power. Are particularly preferred according to the invention Short arc lamps with specific powers of arc length more than 80, 100, 120 or best 150 W / mm. A reference to the piston size makes little sense, because the piston size due to the thermal load capacity of the piston material is determined and consequently in future material improvements (Ceramic instead of quartz glass) can decrease significantly.

Quantitatively preferred ranges for the asymmetry of the piston shapes can be describe by the ratio of anode-side to cathode-side longitudinal section half-area. As illustrated in the exemplary embodiment, these are surfaces meant that in longitudinal section on both sides of one dividing the inner length of the piston in the middle and lie on the plane perpendicular to the lamp longitudinal axis, the lamp longitudinal axis each contain half of the inside length of the piston and the rest of the inside wall of the piston are limited. This ratio is preferably over 1.1 and further preferably less than 1.5.

Shapes are often used in lamp bulb molding machines for simplified mold production for the sake of internal surfaces corresponding to the shape of the piston have it described in longitudinal section by radii of curvature. In particular let often the anode-side and the cathode-side end of the piston by one Longitudinal section radius of curvature (as illustrated in the exemplary embodiment in the figure) describe, it being preferred according to the invention that the anode-side Longitudinal section radius of curvature is smaller than the cathode side, preferably 50% to 80% of the latter. This means that the piston is stronger on the anode side curved or less flat. So another piston shape becomes on the anode side reached. It should be noted that the longitudinal centers of curvature of the The curvature above and below the lamp's longitudinal axis does not coincide must and can be different on the anode and cathode side, because otherwise the smaller radius of curvature would result in a narrower piston shape.

The intention pursued according to the invention to reduce temperature gradients in the lamp, can alternatively also by a suitable reflecting and / or absorbing Heat accumulation can be reached at the end of the piston on the cathode side. This In principle, the measure also comes in addition to the piston asymmetry according to the invention in question.

In the case of asymmetry, however, such a heat accumulation layer can be dispensed with entirely. The advantage is that the lamp is thus manufactured by at least one working step is simplified. The piston asymmetry can namely by suitable Forming the corresponding molds in a lamp bulb molding machine achieve without the conventional function otherwise would be changed. Another advantage is that shadowing is avoided.

Description of the drawings

In the figure is a specific embodiment for a lamp according to the invention shown. The features disclosed in the description of this embodiment can also be essential to the invention individually or in another combination.

The figure shows in longitudinal section a DC short-arc lamp with a longitudinal axis 2, along which an anode 4 and a cathode 5 lie. In the longitudinal direction in the Middle of the piston interior enclosed by a piston inner wall 3, that is bisecting an inner bulb length 7 is also one on the lamp longitudinal axis 2 perpendicular center plane 1 is drawn.

The figure clearly shows that the piston is asymmetrical with respect to this central plane 1 is shaped. The anode-side longitudinal section half surface differs specifically and the cathode-side longitudinal section half surface, each of which in the Figure left or right of the central plane lying longitudinal section area within the piston inner wall 3 corresponds.

Furthermore, the figure shows that the anode-side curvature of the piston in longitudinal section Descriptive radius of curvature 8 significantly smaller than the corresponding one Radius of curvature 9 on the cathode side. The radius of curvature is preferably 8 50% - 80% of the radius of curvature 9. It can also be seen that the corresponding Longitudinal intersection centers above and below the lamp longitudinal axis 2 do not coincide and are different on the anode side and cathode side lie. However, the lamp is rotationally symmetrical about the lamp longitudinal axis 2.

The corresponding asymmetrical piston design has the consequence that the piston around the anode 4, which is much thicker than the cathode 5, is sufficient Keeps a distance and thus a uniform temperature distribution overall results in the longitudinal direction.

Finally, the figure shows that the distance between the anode 4 and the cathode 5, that is to say the arc length 6, is selected to be very short, in the present case 1.5 mm in comparison to radii of curvature of 4 mm (8) and 6 mm (9) and a lamp power of 270 W (specific power 180 W / mm). In the present case, the inside length of the piston 7 is almost 10 times the length of the arc 6. An operating voltage of 35 V with a luminous flux of 18 klm results from a filling volume of 0.7 ml with a wall load of 65 W / cm ² .

A color temperature of 6,800 K was set with the following filling: 200 mbar argon, 20 mg mercury, 0.11 mg cadmium iodide (Cdl ₂ ) - corresponding to approx.0.43 µmol Cd per ml flask volume -, 0.42 mg mercury bromide (HgBr ₂ ), 0.12 mg mercury iodide (Hgl ₂ ), 0.05 mg indium iodide (Inl ₂ ), 0.05 mg lithium iodide (LiI ₂ ), 0.11 mg dysprosium and 0.05 mg yttrium. Cadmium can be replaced by zinc in a molar equivalent. Thallium iodide can be added up to a value of 0.2 mg / ml.

Claims (19)

DC arc lamp with a filling of at least the following components: an ignition gas, Mercury and a halogen, characterized by the additional component: zinc and in that the total concentration for zinc including any cadmium present is in the following range: 0.05 to 3.0 µmol per ml volume of the lamp vessel. Lamp according to claim 1 with the filling component yttrium. Lamp according to claim 1 or 2 with the filling component lithium. Lamp according to one of the preceding claims with the filling component Indium. Lamp according to one of the preceding claims with a rare earth metal, especially dysprosium, as a filling component. Lamp according to one of the preceding claims with the filling component Thallium. A lamp as claimed in any preceding claim, wherein the halogen is in the form of iodine and / or bromine is present. Lamp according to one of the preceding claims, the following concentration ranges for cadminium and / or zinc as a whole depending on the electrical power consumption: Power consumption of the lamp Concentration in µmol / ml up to 170 W. 0.3 to 3.0 170 to 300 W. 0.2 to 2.0 300 to 3000 W. 0.05 to 1.0 Lamp according to one of the preceding claims with a cathode side Heat accumulation. Lamp according to one of the preceding claims with a plane (1) perpendicular to a lamp longitudinal axis (2) so asymmetrically shaped Piston that the inner wall of the piston (3) is wider around the anode (4) than around the cathode (5). Lamp according to one of the preceding claims as a short arc lamp. A lamp as claimed in claim 11, wherein a specific one is related to the arc length (6) Power is greater than 80 W / mm. A lamp as claimed in any one of claims 10-12, wherein the ratio between one anode side longitudinal section half surface and a cathode side longitudinal section half surface is greater than 1.1, the longitudinal sectional half-surfaces in Longitudinal section through the lamp on both sides of the inside length of a bulb the lamp dividing in the middle and perpendicular to the lamp longitudinal axis (2) lie and the lamp longitudinal axis (2) each to one half of the inner length of the bulb included and otherwise limited by the inner wall of the piston (3) are. The lamp of claim 13, wherein the ratio is less than 1.5. Lamp according to one of claims 10 -14, wherein an anode-side longitudinal section radius of curvature (8) smaller than a radius of curvature on the cathode side (9) is. The lamp of claim 15, wherein the anode-side longitudinal section radius of curvature (8) 50% to 80% of the cathode side longitudinal radius of curvature (9) is. Lamp according to one of the preceding claims as a daylight lamp. Use of a lamp according to one of the preceding claims with horizontal longitudinal lamp axis (2). Projection device with a lamp according to one of the preceding claims 1 - 17 as a projection lamp.

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