EP1705688A2 - Metal halide lamp - Google Patents

Abstract

The lamp has a ceramic discharge vessel (10) with an inner contour provided with rounded ends, where the inner contour is convex-shaped. The discharge vessel is filled with a noble gas, mercury and metal halides. The metal halides include two groups in which one group is made up of emitters and the other group is made up of wetters. The latter group comprises one halide (at least 15 mol.%) selected from magnesium and ytterbium, with calcium halide as an additional constituent such that a proportion of the latter group amounts to 55 mol percent of the metal halides.

Description

Technical area

The invention is based on a metal halide lamp according to the preamble of claim 1. These are, in particular, high-pressure discharge lamps with a ceramic discharge vessel for a neutral white light color.

State of the art

From the US Pat. No. 6,218,789 Already a metal halide lamp is known. There, a halide of the Yb is used to generate molecular radiation. The discharge vessel is made of quartz glass.

From the DE 198 57 585 For example, a mercury-free metal halide lamp is known which uses Mg-iodide as a filling in a ceramic discharge vessel.

Presentation of the invention

It is an object of the present invention to reduce color scattering in bulbous geometry metal halide lamps of the discharge vessel, particularly in fillings for neutral white light colors.

This object is solved by the characterizing features of claim 1. Particularly advantageous embodiments can be found in the dependent claims.

The color scattering in metal halide lamps has long been the focus of the effort to improve quality. This problem seemed to be solved in itself, since in cylindrical geometry of the discharge vessel, a corresponding filling composition is known. Certain conditions of the surface must also be taken into account.

Surprisingly, however, it has been found that these established approaches fail if the more isothermal bulbous geometry is used instead of cylindrical geometry. This is understood to mean a discharge vessel with rounded corners which has either a straight central part or an elliptically shaped volume. The rounding may be circular, elliptical or otherwise shaped. This problem is particularly pronounced in fillings for neutral white light color, ie for a color temperature of about 4000 to 4900 K.

According to the invention, therefore, the inner contour is bulged with rounded ends, wherein the discharge vessel contains a filling, the starting gas, preferably as noble gas, mercury and metal halides, wherein the metal halides comprises two groups, namely the first group of emitters and the second group of wetting, and wherein the second group consists of at least one of the halides of Mg and Yb, the proportion of these components of the second group being at least 15 mol%, with the option that Ca halide may be an additional constituent of the second group, the proportion the total second group is at most 55 mol% of the metal halides.

Particularly preferred is the addition of halide of Yb, in particular in a proportion of 10 to 60 mol%, preferably 15 to 45 mol%. In particular, a fraction of the Yb, preferably up to 50%, may be replaced by halides of the Mg. As the halogen is preferably iodine, but also bromine may be suitable, especially as a fraction that replaces iodine, preferably up to 30%.

The operation can be done on electronic ballasts or conventional ballasts.

Metallic halide lamps with bulbous ceramic burners require a relatively high proportion of SE-iodide in the metal halide melt, especially for the adjustment of neutral white light color (NDL, typically 4000 to 4900 K). SE stands for rare earth metals. Burner means discharge vessel.

As a result of the burning time and lamp life, there is an increase in the re-ignition peak voltage Ul and the crest factor (Uls / Ulrms), which can lead to critical lamp conditions and premature failure by extinguishing the lamp.

The remedy for this is usually the addition of Cal ₂ known per se for cylindrical discharge vessels. However, it has been found that the wetting ability of the metal halide melt from typical Cal ₂ concentrations of at least 20 mol%, in particular 25 mol%, significantly changed since the wetting angle of the melt is increased on the lamp components in the operating state.

For lamps with increased power densities, a relatively high copy control of the desired color temperature is produced by fluctuating expansion of the filling wetting on the inner wall of the discharge vessel due to the changed filling wetting. The power density p is understood as the power P of the lamp in W per area S in mm ² , differentiated between the inner and outer power density P _in = P / S _in and p _out = P / S _out (where S is the inner surface in each case (in) or out (out) at the discharge vessel and typical surface conditions of the inner and outer surfaces eo_back in the electrode backspace (eo_back: = total space or burner expansion inside and outside behind the electrode tip, whereby the capillary is included, as far as the neck area is concerned is) to the total surface of the discharge vessel (S inter_deo / Si_tot; So, back_deo / Si_tot) as is the case with bulbous lamps with hemispherical end shapes.

Typical ratios are illustrated for both forms in the following Table 1: parameter cyl. EC. bulbous EC. nominal power Pnom / W 150.00 150.00 Eo-distance eo_d / mm 9.00 9.20 inner surface Sin / mm2 500.00 685.00 outer surface Sout / mm2 900.00 798.00 Relationship of it Sout / Sin 1.80 1.16 Sin, inter_d_eo / mm2 257.00 404.00 Sin, back_eo / mm2 243.00 281.00 Sin, back / Sin, inter 0.95 0.70 Sout_inter_deo / mm2 324.00 451.00 Sout_back_deo / mm2 576.00 347.00 Sout_back / Sout, inter 1.78 0.77 P / Sin [W / cm2] 30.00 21,90 P / Sout [W / cm2] 16.67 18,80

Due to the different surface ratio, which are mainly responsible for the distribution of the transported by radiation transport and heat conduction power on the inner wall and the outer wall of the discharge vessel to the environment, forms at bulbous discharge vessels a very homogeneous temperature distribution.

Thus, the ratio of outer surface to inner surface is typically 1.6 to 2.0 for cylindrical geometry (here in Table 1 it is 1.8), for bulbous geometry it is only typically 1.0 to 1.35 (here in Tab 1 is 1.16). The difference between comparable performance levels is typically 50% (here in Tab. 1 it is 55%). Furthermore, the ratio of the inner surface that lies behind the electrode tips to the inner surface that lies between the electrodes is 0.95 for cylindrical geometry, only 0.7 for bulbous ones, i. 35% larger with cylindrical geometry. The ratio of outer surface Sback lying behind the electrodes to the outer surface Seo lying between the electrodes is 1.78 in cylindrical geometry, but only 0.77 in bulbous geometry, i. 131% larger with cylindrical geometry.

This leads to u.U. when a certain wetting angle of the metal halide filling is exceeded, an increased distribution of the filling into the interior of the burner occurs. This leads to an increased specimen scattering at the color temperature and thus to a corresponding dispersion of the electrical parameters.

The specimen scattering of the color temperature is now reduced by a modified filling compositions, so that a defined expansion of the filling wetting on the inner wall of the discharge vessel in the electrode back space is formed. At the same time, the electrical lamp data such as re-ignition peak and crest factor are comparable to fillings with a high Cal ₂ content (low activity of the SE-iodides).

A typical target value of the color temperature is for example 4000 to 4400 K. The novel filling reduces both the scattering of the color temperature with only a small deviation from the Planckian curve in the CIE diagram and with a low crest factor.

An acceptable variation width δ at 100 h burning time is for the color temperature Tn and the crest factor Cr $$\mathrm{\delta }\mathrm{T}\mathrm{n}\le \pm 75\mathrm{K}.\mathrm{}\mathrm{C}\mathrm{r}=\mathrm{U}{\mathrm{I}}_{\mathrm{s}}/\mathrm{U}{\mathrm{I}}_{\mathrm{rms}}<1.9;$$

The addition of Cal ₂ in metal halide melts to adjust NDL color temperatures is typically 40-50 mole% and thereby reduces the activity of the 3-valent SE iodides, which over the firing time and lifetime reduces the reaction rates of the SE Halides with the lamp components leads and thus to a limitation of the formation of free iodine. This in turn limits the increase in re-ignition peak voltage and crest factor.

In order to achieve a comparable effect in bulbous discharge vessels, according to the invention metal halide additives are exchanged for amounts of Cal ₂ in the filling without the substantial proportion of the SE halide concentration and thus its chemical activity changing. Thus, a change in the degree of wetting is achieved through which a defined charge distribution in the back electrode of the lamps is formed, with a small copy control occurs when setting the color temperature.

It can be seen that the divalent metal halide components of Yb and possibly Mg, preferably Mgl ₂ and Ybl ₂ , are suitable for fulfilling the role of Cal _{2 in} full or in part, but at least 20 mol% in the total charge and thus 20 / 45 of the molar amount of Cal ₂ , to take over.

Preferably, an amount of 20-25 mol% of Ybl ₂ while retaining 20 to 25 mol% of Cal ₂ or the simultaneous use of halides of Mg and Yb such that, in particular using the iodides Mgl ₂ and Ybl ₂ , the Total amount of Ybl2 + Mgl2 a proportion of at least 20 mol%, in particular 20 to 35 mol% of which form metal halides and with Cal ₂ together form a total proportion of 40-50 mol% of the total charge of metal halides.

Brief description of the drawings

Figur 1

ein Entladungsgefäß einer Hochdrucklampe, schematisiert;

Figur 2

ein besonders geeignetes bauchiges Entladungsgefäß;

Figur 3

die innere und äußere Oberfläche bei einem bauchigen Entladungsgefäß;

Figur 4

die innere und äußere Oberfläche bei einem zylindrischen Entladungsgefäß.

In the following the invention will be explained in more detail with reference to several embodiments. Show it:

FIG. 1

a discharge vessel of a high-pressure lamp, schematized;

FIG. 2

a particularly suitable bulbous discharge vessel;

FIG. 3

the inner and outer surfaces of a bulbous discharge vessel;

FIG. 4

the inner and outer surfaces of a cylindrical discharge vessel.

Preferred embodiment of the invention

FIG. 1 shows a metal halide lamp with an outer bulb 1 made of hard glass or quartz glass, which has a longitudinal axis and is closed on one side by a plate melt 2. At the plate smelting 2, two power supply lines are led outwards (not visible). They end in a base 5. In the outer bulb is a two-sided sealed ceramic bulbous discharge vessel 10 made of Al ₂ O ₃ with a filling of metal halides used axially.

• die Kontur besitzt ein im wesentlichen gerades zylindrisches Mittelteil 6 der Länge L und dem Innenradius R sowie zwei im wesentlichen halbkugelförmige Endstücke 7 mit demselben Radius R,
• die Länge des zylindrischen Mittelteils ist kleiner oder gleich seinem Innenradius: $$\mathrm{L}\le \mathrm{R},$$
  
• die Innenlänge des Entladungsgefäßes ist mindestens 10 % größer als der Elektrodenabstand EA: $$2\mathrm{R}+\mathrm{L}\ge 1.1\mathrm{E}\mathrm{A},$$
  
• der Durchmesser (2R) des Entladungsgefäßes entspricht mindestens 80 % des Elektrodenabstands EA; gleichzeitig darf er höchstens eine Länge von 150 % des Elektrodenabstands EA besitzen: $$1.5\mathrm{E}\mathrm{A}\ge 2\mathrm{R}\ge 0.8\mathrm{E}\mathrm{A}.$$
  
  Konkret ist hier beispielsweise Lzyl = 1 mm, L = 15 mm und R = 7 mm.

In particular, the discharge vessel 10 may be spherical or elliptical on the inside or may be a deviation from the sphere geometry through a short cylindrical center piece between the spherical half shells. It has in particular the dimensions according to Figure 2, as shown in EP-A 841,687 are described. The contour of the inner wall is as follows:

• the contour has a substantially straight cylindrical central part 6 of length L and the inner radius R and two substantially hemispherical end pieces 7 with the same radius R,
• the length of the cylindrical middle part is less than or equal to its inner radius: $$\mathrm{L}\le \mathrm{R}.$$
  
• the inside length of the discharge vessel is at least 10% larger than the electrode spacing EA: $$2\mathrm{R}+\mathrm{L}\ge 1.1\mathrm{e}\mathrm{A}.$$
  
• the diameter (2R) of the discharge vessel corresponds to at least 80% of the electrode spacing EA; at the same time, it may not exceed 150% of the electrode spacing EA: $$1.5\mathrm{e}\mathrm{A}\ge 2\mathrm{R}\ge 0.8\mathrm{e}\mathrm{A},$$
  
  Specifically, for example, Lzyl = 1 mm, L = 15 mm and R = 7 mm.

The ratio of outer to inner radius is Ra / Ri = 7.8 / 7 = 1.11. The ratio inner radius / cylinder length is Ri / Lzyl = 7/1 = 7. The electrode distance is 9.2 mm.

Electrodes 3 protrude into the discharge vessel. The electrode spacing EA and the length L of the discharge vessel scale in a ratio EA / L = 9.2 / 15 = 0.61.

There is an ignitable gas from the group of noble gases in the discharge vessel under a cold filling pressure of 300 mbar. Furthermore, mercury and a mixture of metal halides consisting of the following molar compositions (mol%) are present in the discharge vessel according to the following Table 2: Nal TIJ TmI 3 DyI 3 HoJ3 CaJ2 MgJ2 Ybj2 Reference filling (Ref): 15.7 15.5 7.3 7.3 7.3 46.9 0.0 0.0 1st embodiment AB1: 15.7 15.5 7.3 7.3 7.3 31.3 0.0 15.6 2nd embodiment AB2: 15.7 15.5 7.3 7.3 7.3 15.7 0.0 31.2 3rd embodiment AB3: 15.7 15.5 7.3 7.3 7.3 0.0 0.0 46.9 4th embodiment AB4: 15.7 15.5 7.3 7.3 7.3 15.6 15.6 15.6

The power absorbed is in a range of 140 to 150 W. If the power is related to the outer surface of the discharge vessel, the wall load is typically in a ratio of 17.2 to 18.45 W / cm ² .

Placing the power in relation to the inner surface of the discharge vessel, the wall load is typically in a ratio of 21.2 to 22.75 W / cm ² .

The color temperature for these lamps is about 4200K each.

In the embodiments, there is a significant reduction in the dispersion of the color temperature and the crest factor. The evaluation after 100 hours burn time shows the following result: Tab. 3 Filling / burning position Mean value Cr St. Dev. Cr Mean value Tn (K) St. Dev. Tn Ref. Vert 1.741 0.057 4161 128 Ref. Hor 1,787 0,045 4052 44 AB1 vert 1,819 0,036 3958 122 AB1 hor 1,868 0.077 4034 54 AB2 vert 1,770 0.048 4195 60 AB2 Hor 1,856 0,040 4107 45 AB3 vert 1,723 0.056 4378 99 AB3 hor 1.822 0,035 4276 81 AB4 vert 1,903 0.032 4089 93 AB4 Hor 1,983 0,029 4055 44

In this case, the mean value and the standard deviation are shown for the crest factor Cr and the color temperature Tn.

The lowest scattering of the color temperature with a simultaneously acceptable crest factor is found in Example 2 with replacement of 66% of the Cal ₂ mole fraction for Ybl ₂ (a total of 31.2 mol% in the overall mixture).

A similar behavior of reducing color temperature scattering can be obtained by partially replacing Cal ₂ with Mgl ₂ . The effectiveness of the admixture to reduce the scattering of the color temperature results from the reduction of the wetting angle of the molten metal halide melt on the alumina ceramic. The effectiveness with respect to the reduction of the scattering of the color temperature is clear for both Mgl ₂ and Ybl ₂ from an admixture of at least 15 mol%, preferably 20-35 mol% in the molten metal halide. The proportion should not exceed 55 mol%.

This is linked to the replacement of the red ratio-enhancing Cal ₂ , which may typically be present in the range of about 40-45 mole% as an ingredient in MH fillings for a color temperature of 4000K.

The replacement of the Cal ₂ can be carried out completely or partially by the substances Ybl ₂ or Mgl ₂ individually or together, preferably to about 50-70% of the Ca-iodide. This means that optimum conditions are achieved in fillings with typical contents of 15-25 mol%, formed from at least one of the metal halides Dyl ₃ , Hol ₃ , Tml ₃ , and that the moieties from the group of wetting agents of Mgl ₂ and Ybl ₂ in the range of 15 to 55 mol%, possibly including Cal ₂ , and should preferably be in the range of 15-35 mol% in the total mixture.

Figures 3 and 4 show a comparison between a bulbous (11) and a cylindrical (12) discharge vessel with respect to the inner and outer surface. Pulled on the outside and dashed means inside. The representation of the course of the inner and outer surface is based on a symmetrical integration from the center of the lamp (x-position 0) to the capillary ends (x-position 23) (top picture in each case). Respectively in the lower picture exemplary inner and outer contours for bulbous and cylindrical geometries of the discharge vessel are shown.

It turns out that the bulbous discharge vessel has a smooth relationship between the integrated inner (i) and outer (a) surfaces, both of which are closely related. In the cylindrical discharge vessel, the relationship is erratic, not continuously differentiable and the relation changes. In particular, in the meantime, the inner surface may even become larger than the outer surface.

Claims (15)

A metal halide lamp, comprising a ceramic discharge vessel whose inner contour is bulbous with rounded ends, the discharge vessel containing a filling comprising starting gas, preferably as noble gas, mercury and metal halides, the metal halide comprising two groups, namely the first group of emitters and second group of wetting agents, characterized in that the second group consists of at least one of the halides of Mg and Yb, the proportion of these constituents of the second group being at least 15 mol%, with the option that Ca halide is an additional constituent of the second Group may be, wherein the proportion of the entire second group is at most 55 mol% of the metal halides. Metal halide lamp according to claim 1, characterized in that the first group comprises at least halides of the rare earth metals. Metallhalogenidlampe according to claim 2, characterized in that the first group comprises as an additive halides of Na and / or thallium. Metal halide lamp according to claim 1, characterized in that the color temperature is between 4000 and 4900 K. Metal halide lamp according to claim 2, characterized in that as rare earth metals at least one of the elements Dy, Ho, Tm is used. Metal halide lamp according to Claim 1, characterized in that the proportion of rare earth metals in the metal halides is at most 25 mol%, in particular at least 15 mol%. Metal halide lamp according to Claim 1, characterized in that the proportion of additives is not more than 34 mol% of the metal halides, in particular in a mixture of 1: 2 to 2: 1 between Na and Tl. Metal halide lamp according to claim 1, characterized in that Yb is introduced as Ybl ₂ with preferably 15 to 45 mol% proportion of the metal halides. Metal halide lamp according to claim 1, characterized in that Ca is introduced as Cal ₂ with preferably 0.1 to 30 mol% proportion of the metal halides. Metal halide lamp according to claim 1, characterized in that Mg is introduced as Mgl ₂ with preferably 0.1 to 15 mol% proportion of the metal halides. Metal halide lamp according to claim 1, characterized in that the discharge vessel has the following dimensions: the inner contour has a substantially straight cylindrical middle part of length L and the inner radius R and two substantially hemispherical end pieces with the same radius R, • the length of the cylindrical middle section is less than or equal to its inner radius: $$\mathrm{L}\le \mathrm{R}.$$

• the inside length of the discharge vessel is at least 10% larger than the electrode distance EA: $$2\mathrm{R}+\mathrm{L}\ge 1.1\mathrm{e}\mathrm{A}.$$

The diameter (2R) of the discharge vessel corresponds to at least 80% of the electrode spacing EA; at the same time, it may not exceed 150% of the electrode spacing EA: $$1.5\mathrm{e}\mathrm{A}\ge 2\mathrm{R}\ge 0.8\mathrm{e}\mathrm{A},$$

Metallhalogenidlampe according to claim 11, characterized in that the ratio of lamp power to the surface assumes the following values: outer surface: 16-19 W / cm ² , inner surface 20-23W / cm ² . Metal halide lamp according to claim 11, characterized in that Sin / Sout <1.3. Metal halide lamp according to claim 11, characterized in that Sin, back_eod / Sin, inter_eod <= 0.85 applies. Metallhalogenidlampe according to claim 11, characterized in that Sout, back_eod / Sout, inter_eod <= 1.4 applies.

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