EP0869537A1 - DC arc lamp - Google Patents

Abstract

A novel d.c. arc lamp has a filling which contains cadmium and/or zinc in addition to an ignition gas, mercury and a halogen. Preferably, the total concentration of Cd and/or Zn is 0.05-3.0 mu mol per ml volume of lamp vessel, the lamp power consumption being up to 170 W at 0.3-3.0 mu mol/ml concentration, 170-300 W at 0.2-2.0 mu mol/ml concentration and 300-3000 W at 0.05-1.0 mu mol/ml concentration. The filling may also contain one or more of Li, In, rare earth metal (especially Dy) and Tl. Also claimed is a projection system with a projection lamp as described above.

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, in particular for projection applications. For projection applications are above all the locally concentrated light generation on the one hand and on the other hand the homogeneity of the light generation in this local area of interest. The so-called color separation effect plays here an essential role. With this term, a local Separation of the focus of light generation for different spectral ranges or colors of the generated light, causing deterioration the quality of light for projection applications expressed in color fringes at border or edge areas of projected images.

The color separation effect is during the lamp operation by the between Anode and cathode of the direct current arc lamp electrical DC field caused. The DC electrical field influences the concentration distribution of the light-generating metal ions between the anode and Cathode. As a result, the spatial distribution of the metal ions between Anode and cathode usually inhomogeneous. Also stand for different types Metal ions different concentration distributions. Since different types of metal ions have different spectral contributions to If the total luminous flux of the lamp is achieved, the undesirable result Color separation effect.

Furthermore, the invention relates to a DC arc lamp with a halogen-containing filling. This means that during the Lamp operation metal halides within the discharge vessel. Metal halides have a higher vapor pressure than the corresponding elementary ones Metals. In addition, the high specific bow outputs generate of typically approx. 80 W per mm arc length and more also high Vapor pressures of the light-generating metal halides. This is one hand a high luminous flux of the lamp is ensured. On the other hand, 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.

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 on projection applications, and an improved projection device specify.

According to the invention, this problem is solved by a DC arc lamp with a filling of at least the following components: one Ignition gas, mercury and a halogen, characterized by the additional Ingredient: Cadmium and / or zinc or a projection device with such a projection lamp.

It turned out to be critical for a sufficient red component in the To provide light, on the one hand in favor of good red color rendering and further, to a desired color temperature, about 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. One finds however, that lithium mainly shows a very long-wave emission, so leads to a very deep red portion. For all applications that lead to one lead to any kind of visual effect, for example when projecting or of lighting, but are not just the purely physical spectral Performance components to be considered, but also 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 takes on the long-wave edge significantly. Therefore, as far as the red component relates to the lithium emission supports, a correspondingly increased spectral power to be generated to generate the desired - and ultimately interesting - 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, must also contain mercury to the necessary burning voltage the green color of mercury has to be taken into account. The green component specified by the mercury content must when adjusting the color temperature with red, what the The problems outlined above are exacerbated.

If according to the invention cadmium or zinc is used in the lamp filling is surprisingly not only the red component amplified, but also reduces the color separation effect. The addition of cadmium or zinc allows compared to (Sole) addition of lithium for the red portion a significant improvement the color separation problem and, with the same performance, an improved one Luminous flux.

Mercury is an alternative to that in the context of this invention other two 2B elements cadmium and zinc are therefore unsuitable, because, to some extent, it also reduces color separation, however, excessively amplifies the green portion of the light.

Zinc also has the advantage of the better over cadmium and mercury Environmental compatibility. Cadmium, on the other hand, can be used for certain Applications can be advantageous because the red rendering is even better. According to the invention So in individual cases the possibility of making a decision remains between optimal lamp data and environmental aspects.

According to the invention, the following are particularly preferred for Cd and Zn Concentrations into consideration: 0.05 to 3.0 µmol per ml 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, the concentration of one of the two individual components also Can be zero.

As a further embodiment of the invention, the component also shows Yttrium together with the basic composition according to the invention explained special advantages. The first is an improvement of the luminous flux. Secondly, there is also a longer one Lamp life and thirdly a lower decrease in lamp luminous flux with the operating age of the lamp (so-called maintenance). Yttrium is therefore essential to achieve the above Effects of the invention are not necessary, but have been found to be related to Luminous flux, service life and maintenance are surprisingly more effective optional addition highlighted.

Rotelement" vorhanden sein, durch die erfindungsgemäße Verwendung von Cadmium bzw. Zink sind die erforderlichen Mengen jedoch geringer.Various chemical elements are conceivable as further optional additives, in particular for adjusting the color temperature and enhancing the primary colors. Above all, the above explanation of the disadvantages of lithium should not be understood to mean that lithium would be excluded according to the invention. Lithium can certainly be used in certain quantities

Rotelement "to be present, but the amounts required are lower due to the use of cadmium or zinc according to the invention.

The preferred application in most cases requires a high blue component in the spectrum. A preferred according to the invention Blue element "is indium.

Other optional additives, especially for increasing the luminous flux, are the rare earth metals, especially dysprosium, and thallium.

As halogen for setting desired vapor pressures through formation metal halide compounds are preferably iodine and / or bromine into consideration.

Aspects of the invention that go beyond the filling system the geometric design of the lamp.

In many areas of application, especially in projection devices, The best possible localization of light generation plays an important role Role, why the invention is based on short-arc lamps. Only with A point light source can be made with the smallest possible arc length sufficiently close and thus good optical quality at the Projection or other applications where the lamp emits Light is sent through an optical system.

In addition to that, it has changed in terms of uniformity of light generation in their local extent, even with good localization as with short-arc lamps, continue to be decisive according to the invention emphasized for a temperature distribution in the Lamp, especially on the inside wall of the bulb. This affects before temperature gradient along the path between cathode and anode in the lamp. These temperature gradients can be significantly reduced if the geometric shape of the lamp bulb containing the filling is chosen appropriately. According to the invention, it is asymmetrical for this purpose, to the asymmetry of the temperature distribution of the electrodes to be adapted to a DC arc lamp.

With DC arc lamps, the anode is in principle one exposed to much greater thermal stress than the cathode accordingly hotter. So that they can withstand this thermal load can, the anode is generally very large in DC arc lamps more massive than the cathode. In particular, it has in general 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 inner wall of the piston and the larger heat-conducting and heat-radiating ones Surface on the other hand with symmetrical execution of the Lamp bulb at much higher temperatures on the lamp Lead on the anode side, especially on the inside wall of the piston. Out of it there is an influence on the physical parameters of the 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 on the one hand, the light emission is homogeneous, on the other hand, the temperature can be set to an optimal value be that of the requirements for the luminous efficacy as well as those to the lifespan and maintenance is sufficient.

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

Especially with regard to the projection applications mentioned are how already mentioned to strive for the shortest possible arc lengths. It says Arc length in connection with the lamp power. According to the invention Short-arc lamps with an arc length reference are particularly preferred specific performances of more than 80, 100, 120 or best 150 W / mm. A reference to the piston size makes little sense, because the Piston size determined by the thermal load capacity of the piston material and consequently in future material improvements (ceramics instead of quartz glass) can decrease significantly.

Let quantitatively preferred ranges for the asymmetry of the piston shapes describe themselves by the ratio of anode-soapy to cathode-side Longitudinal half-surface. Thus, as in the exemplary embodiment illustrates surfaces meant that in longitudinal section on either side of the Dividing the inner length of the bulb in the middle and perpendicular to the longitudinal axis of the lamp Lie flat, the lamp longitudinal axis to one half of the inner length of the bulb included and otherwise limited by the inner wall of the piston are. This ratio is preferably over 1.1 and more preferred under 1.5.

Shapes in lamp bulb molding machines are often simplified Mold production for the sake of internal surfaces corresponding to the piston shape provided, which are described in longitudinal section by radii of curvature to let. In particular, the anode-side and the cathode-side can often be End of the piston through a longitudinal section radius of curvature (as illustrated in the embodiment in the figure), where It is 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 becomes on the anode side Piston shape reached. It should be noted that the longitudinal cut centers of curvature the curvature above and below the lamp's longitudinal axis do not have to coincide and on the anode and cathode side can lie differently, because otherwise the smaller radius of curvature a narrower piston shape would result.

The intention pursued according to the invention, temperature gradients in the lamp can alternatively be degraded by a suitable reflective and / or absorbent heat build-up on the cathode-side piston end can be achieved. In principle, this measure also applies the piston asymmetry according to the invention in question.

With the asymmetry, however, you can completely rely on such a heat accumulation layer dispense. The advantage is that the lamp can be manufactured by at least one step is simplified. The piston asymmetry leaves namely by appropriate shaping of the corresponding molds in a lamp bulb molding machine without this the conventional functional sequence would be changed otherwise. Another The advantage is that shadowing is avoided.

Description of the drawings

In the figure is a specific embodiment for an inventive Lamp shown. The description of this embodiment Features disclosed can also be used individually or in other combinations be essential to the invention.

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

The figure clearly shows that the piston is 1st with respect to this central plane is asymmetrically shaped. Specifically, the anode side differ Longitudinal section half surface and the cathode side longitudinal section half surface, each of which is to the left or right of the central plane in the figure Corresponds to the longitudinal sectional area within the piston inner wall 3.

The figure also shows that the anode-side curvature of the piston in the Longitudinal section describing radius of curvature 8 significantly smaller than that is the corresponding radius of curvature 9 on the cathode side. Preferably is the radius of curvature 8 50% - 80% of the radius of curvature 9. You can see further that the corresponding longitudinal curvature centers not coincide above and below the lamp longitudinal axis 2 and are different on the anode side and cathode side. However, it is Lamp rotationally symmetrical about the lamp longitudinal axis 2.

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

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 (CdJ ₂ ) - corresponding to approx.0.43 µmol Cd per ml flask volume, 0.42 mg mercury bromide (HgBr ₂ ), 0.12 mg mercury iodide (HgJ ₂ ), 0.05 mg indium iodide (InJ ₂ ), 0.05 mg lithium iodide (LiJ 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: Cadmium and / or zinc. 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. Lamp according to one of the preceding claims, wherein the halogen is in the form of iodine and / or bromine. A lamp as claimed in any preceding claim, wherein the total concentration for Cd or Zn is in the following range: 0.05 to 3.0 µmol per ml volume of the lamp vessel. The lamp as claimed in claim 8, the following concentration ranges 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 one-sided Heat accumulation. Lamp according to one of the preceding claims with a reference Planes (1) perpendicular to a lamp longitudinal axis (2) are asymmetrical shaped piston that the piston inner wall (3) around the anode (4) is wider than around the cathode (5). Lamp according to one of the preceding claims as a short arc lamp. A lamp as claimed in claim 12, wherein one is related to the arc length (6) specific power is greater than 80 W / mm. A lamp as claimed in any one of claims 11-13, wherein the ratio between an anode side longitudinal section half surface and a cathode side Longitudinal half-area is greater than 1.1. The lamp of claim 14, wherein the ratio is less than 1.5. A lamp as claimed in any one of claims 11-15, wherein an anode side Longitudinal section radius of curvature (8) smaller than a cathode side Longitudinal section radius of curvature (9). The lamp of claim 16, 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 with a horizontally extending Longitudinal lamp axis (2). Projection device with a projection lamp according to one of the preceding claims.

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