JPH0555973B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to high pressure metal halide lamps. More specifically, the present invention comprises a discharge vessel made of a material with a high melting point and transparent to light, preferably quartz glass, and filled with one or more noble gases as a starting gas, Mercury is included as a buffer gas and also ensures that the additives of dysprosium, holmium, and sodium halides and, in certain cases, thallium and/or cesium and/or lithium halides during the operation period. A metal halide lamp comprising at least two main electrodes sealed at one end or opposite ends of the discharge vessel as described above containing a sufficient amount to keep the discharge saturated. The present invention relates to a high-pressure metal halide lamp having a container housed in a light-transmitting envelope, into which a conductive wire is drawn from one end or both ends of the envelope, and having a low color temperature and good color rendering properties.

[Problems to be solved by conventional technology and invention]

European patent application EP-0049545 not only uses sodium, mercury, and rare gases, but also includes praseodymium, neodymium,
and lutetium, the molar ratio of rare earth metal to sodium is in the range of 1:1 to 1:20, the amount of mercury in the discharge tube is 2 to 100 mg/ ^cm2 , and the above rare earth metal is sodium. A metal halide lamp is described in which the molar ratio of mercury to mercury and the above-mentioned amount of mercury are inversely proportional to the nominal lamp rated output. As stated in Examples 12 and 11 of that specification, the resulting average color rendering index values are:
They were 66 and 71 at color temperatures of 3515K and 3440K, respectively.

According to the specification of West German Patent Application No. 2,519,377, the color temperature of less than 4500K is determined not only by a blue filter but also by rare earth halides,
It is also achieved using alkali halides, alkaline earth halides, and thallium halide additives. As a blue filter, tin iodide is mixed into the filling as an additive.
Alternatively, the blue filter is applied to the discharge vessel as a surface coating or added as an additive to the material of the discharge vessel or outer envelope.
In this case, a major problem arises in that the use of tin is expected to have the effect of restricting arcing within the discharge space. A restricted arc can attack the walls of the discharge vessel, especially after long-term operation, thereby shortening the service life of the lamp. In the lamps described in the above specification, dysprosium, sodium iodide, thallium iodide and tin are used, as well as mercury iodide and bromine, by way of example. During operation, sodium ions diffuse out of the discharge vessel across the quartz wall, leaving excess halogen within the discharge vessel. This results in further arc restriction, which also reduces the lamp's extinction properties. According to this specification, the arc is stabilized by electrodes in order to compensate for the harmful effects of a restricted arc. That is, a small and short discharge tube is used. However, this has the disadvantage of placing greater stress on the walls and, due to faster blackening, the useful life of the lamp is further reduced. Bromine is utilized to offset this effect, but this results in increased corrosion of the electrodes.

A problem of a similar nature arises in West German Patent Application No. 1, which also uses tin and sodium halides to obtain the desired low color temperature.
This can also occur in the case of the high-pressure metal halide lamp described in the specification of Japanese Patent No. 2655167. In the embodiment described in this specification, an average color rendering index Ra=75 is achieved at a correlated color temperature of 3000K.

Lamps containing dysprosium, holmium, thulium, thallium, sodium, mercury, and iodine have been described by Dobrusskin et al.
Wissenschaftliche Abhandlungen der Osram
- Gesellsch ft, Vol. 12, pp. 11-30, 1986).
In this paper, Tobleskin et al. show that a warm white color cannot be obtained with rare earth metal additives, since the higher required load placed on the wall will greatly shorten the lamp's service life. It is concluded that this is because.

Despite the rather pessimistic views found in the technical literature, there is still a real need for metal halide lamps with low color temperature, good color rendering, and a long service life. Plans have been made to develop such a lamp. While researching to find a solution, an independent 3000 to 3000 without using a blue filter or imposing too high a load on the discharge tube wall, and without shortening the service life compared to lamps with higher color temperatures.
It has been recognized that significantly lower correlated color temperatures in the 4000K range can be obtained. As the molar ratio of sodium halide to rare earth metal halide increases, the color temperature becomes lower and the color rendering properties become slightly worse; on the other hand, as the above molar ratio becomes lower, the color temperature becomes higher and It has been found that better color rendering properties can be obtained. By varying the amount of thallium iodide added, the color of the lamp can always be made similar to that of a perfect radiator. With the addition of cesium iodide, the arc suppression effect of rare earth metals is reduced after extended operating times when halide accumulation in the lamp due to sodium loss results in further arc suppression. It was found that even

[Means and effects for solving the problem]

The above recognition was utilized in the metal halide lamp of the present invention. The invention therefore comprises a discharge vessel made of a light-transparent material with a high melting point, preferably quartz glass, and at least two tubes soldered to one end or to opposite ends of the discharge vessel. has two main electrodes, and within this container,
one or more noble gases as starting gas, mercury as buffer gas and halides of dysprosium, holmium, sodium and optionally thallium and/or cesium and/or lithium. The discharge vessel is housed in a light-transmissive envelope into which conductive wires leading to the electrodes are led from one or both ends of the envelope. A high-pressure metal halide lamp with low color temperature and good color rendering properties, in which, according to the present invention, the molar ratio of the sum of dysprosium and holmium halides to sodium halide is from 1:1 to 1:4. The present invention also relates to a discharge tube in which the metal halide filled in the discharge tube is a metal iodide additive.

The invention will now be explained with reference to the accompanying drawings, which show by way of example embodiments of a metal halide lamp particularly suitable for carrying out the invention.

In the embodiment shown in FIG. 1, a quartz glass discharge vessel 1 is housed in a quartz outer envelope 2. In the embodiment shown in FIG. Electrodes 3 and 3' are enclosed in two ends of a discharge vessel 1 made of quartz glass. The electrode material is either pure tungsten or tungsten activated with 1-3% thorium or 1-3% dysprosium + holmium oxide. In the enclosures 4 and 4', an airtight seal is ensured by aluminum foils 5 and 5'. Current is conducted through Mo wires 6 and 6'. Residual gas in the quartz outer envelope 2 is sucked out and the vacuum is maintained by a zirconium-aluminum getter 7.

Enclosures 8 and 8' of the quartz outer envelope 2
Mo foils 9 and 9' are arranged through which a current is introduced by Mo wires 10 and 10'. Ceramic heads 11 and 11' are bonded to the enclosures 8 and 8' with adhesive. Mo wires 10 and 10' are welded to connectors 12 and 12' which securely connect the lamp to the power distribution mains.
The quartz discharge vessel 1 contains mercury, sodium, dysprosium, holmium, thallium, cesium,
and iodine and possibly bromine, but also contains a noble gas, for example argon. In a more precise sense, the invention relates to the composition of this discharge medium. From the point of view of the invention, it is important to note whether the metals listed above, with the exception of sodium, are included in elemental form or whether all of the metals are included as halides and, for example, iodine is added in the form of mercurous iodide. It doesn't matter whether or not. Elemental sodium attacks the quartz cover, so sodium must be added in the form of a halide. Preferably, the discharge medium comprises at most 1 mg of sodium iodide per cm of arc length of the lamp. A heat-reflecting zirconium coating 1 is placed on the end of the quartz glass discharge vessel 1.
4 and 14' apply.

An alternative embodiment is shown in FIG. 2, with the same component numbers used in FIG.

The embodiments shown in FIGS. 1 and 2 are highly preferred from the point of view of the present invention, since the rate of escape of sodium due to migration is low in this type of metal halide lamp. A lamp with a longer expected life can be obtained. Otherwise, the construction of the lamp is not critical from the point of view of the invention, and only one end of the lamp may be provided with an encapsulation, with the only essential feature being the passage of sodium across the quartz wall. The goal is to limit the escape rate.

〔Example〕

Possible embodiments of the invention are illustrated in the examples given below with reference to the drawings.

Example 1 A 250 W metal halide in the form shown in Figure 1 with a quartz glass discharge vessel 1 made from a quartz glass tube with an internal diameter of 13 mm and electrodes 3, 3' spaced apart by 30 mm. I made a lamp.
Zirconium oxide layers 14 and 14' that reflect heat were provided at two ends of the quartz glass discharge vessel 1. Electrodes 3 and 3' were made of two different types of emitting materials. Reduced luminosity of those using thorium oxide coatings (light
reduction) was found to be greater than that with a 50-50% dysprosium-holmium oxide coating. Electrode diameter
It consisted of a double-wound, double-helix tungsten wire made by pulling a 0.7 mm tungsten rod. The quartz glass discharge vessel 1 was charged with 60 mbar of argon, 19 mg of thallium-cesium amalgam, 2 mg of sodium iodide, 50-50%
0.6 mg of dysprosium-holmium foil and 3.1 mg of mercury iodide were added. The value of the molar ratio of sodium iodide to dysprosium-holmium iodide was 3.6. The color temperature of these lamps is
It turns out that they are 3127K and 3245K, and on the other hand,
The color rendering index was 79 and 80, respectively. 10000
After hours of operation, the color temperature changed to 2948K and 3151K, whereas the average color rendering index remained unchanged.

Color temperature 3500K~3600K when changing molar ratio
The color rendering index rose to 83-84.

Example 2 A 150W metal halide lamp was manufactured according to the design shown in Figure 2 using the same additives as in Example 1. The measured color temperature is 3089K and 2993K, and the measured color rendering index is 75 and 79, which are 2000
After hours of operation they changed to 3039K and 2970K and 79 and 83 respectively. That is, the color rendering index was improved without any significant change in color temperature.

Therefore, by applying the present invention, it is possible to simultaneously achieve the desired objectives, namely low color temperature and good color rendering, and to extend the estimated service life. It can be stated that.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a 250 W metal halide lamp according to the invention with a current supply introduced from two ends. Figure 2 is the same as the metal halide lamp in Figure 1, but the rated output is
This is a schematic diagram of a 150W device. In the figure, 1 is the discharge vessel, 2 is the envelope, 3,
3' is an electrode, 6, 6', 10, 10' are conductive wires, 13
is the discharge medium.

Claims (1)

[Claims] 1. Comprising a discharge vessel made of a high melting point, optically transparent material, preferably quartz glass, and having one end or two opposite ends of the discharge vessel. It has at least two main electrodes sealed at the ends, and the container is filled with at least one noble gas as a starting gas, mercury as a buffer gas, and contains dysprosium, holmium,
and metal halide additives such as halides of sodium and, in some cases, halides of thallium and/or cesium and/or lithium, and the amounts of these additives are The discharge vessel is housed in a light-transmitting envelope into which the conductor is led from one or both ends of the envelope. , a high-pressure metal halide lamp with low color temperature and good color rendering properties, wherein the molar ratio of the sum of dysprosium and holmium halides to sodium halide is from 1:1 to 1:
The above-mentioned metal halide lamp is characterized in that it is up to 4. 2. Metal halide lamp according to claim 1, characterized in that it comprises a metal halide additive in the form of metal iodide. 3 Dysprosium and holmium in a ratio of approximately 1:1
2. A metal halide lamp according to claim 1, characterized in that the metal halide lamp comprises the metal halide lamp in an amount giving a molar ratio of . 4. Metal halide lamp according to claim 1, characterized in that at most approximately 1 mg of sodium iodide per cm of arc length is contained in the discharge vessel.