JPS6338829B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a metal vapor discharge lamp in which a metal halide is sealed together with mercury and a rare gas in an arc tube, and in particular, a non-alkaline earth metal is coated on electrodes placed opposite to each other at both ends of the arc tube. This relates to oxide electron-emitting materials. In this specification, a non-alkaline earth metal oxide electron emitting material refers to an electron emitting material that does not contain an alkaline earth metal oxide. This type of metal vapor discharge lamp has a structure as shown in Figure 1. In the figure, 1 is an arc tube made of transparent quartz glass, inside of which mercury, starting argon gas, and metal halide are contained. It is enclosed. Reference numerals 2a and 2b denote electrodes disposed opposite to each other at both ends of the arc tube 1, which are connected to external lead-in lines 4a and 4b through molybdenum foils 3a and 3b sealed to both ends of the arc tube 1, respectively. ing. 5,5
is a heat insulating film applied to both ends of the arc tube 1,
Reference numerals 6 and 6 designate holding plates attached to both ends of the arc tube 1, 7 a support frame for holding and fixing the arc tube 1 within the outer tube 9 with the holding plates attached thereto, and 8 a cap.
As shown in FIG. 2, the electrodes 2a and 2b have an electrode core wire 10 made of a heat-resistant metal such as tungsten, and an inner coil 11 and an outer coil 12 wound around the electrode core wire. An electrode component is formed, and an electron emitting material 1 is applied to the surfaces of the inner coil 11 and outer coil 12 of the electrode component and fixed by high-temperature heating.
It is composed of 3. In order to obtain an electrode that operates efficiently with a long life as an electron emitting material, in a mercury discharge lamp in which at least one kind of rare earth metal halide is sealed in the arc tube 11, a rare earth metal sealed as the halide is used. Japanese Patent Publication No. 47-44377 discloses applying the same rare earth metal oxide as the electron emitting material 13 to the electrodes 2a and 2b. Therefore, this publication suggests that it is effective to use scandium oxide as an electron emitting material in a discharge lamp filled with scandium halide. However, because scandium oxide has a high melting point, it has difficulty adhering to the electrode components, and the electron emitting material peels off during lamp lighting, causing the electrodes 2a and 2b to stick to each other.
The electron emission ability of the lamp was reduced, causing blackening of the arc tube 1 of the lamp, resulting in a shortened lifespan. This invention was made in order to improve such conventional drawbacks, and it is possible to use lanthanum oxide (La ₂ O ₃ ), neodymium oxide (Nd ₂ O ₃ ), marium oxide (Sm ₂ O ₃ ), europium oxide (Eu ₂ O ₃ ), gadolinium oxide (Gd ₂ O ₃ ), and at least one of dysprosium oxide (Dy ₂ O ₃ ) 10 to 60 [mol %]
By using an electron-emitting material of a non-alkaline earth metal oxide, the remainder of which is scandium oxide (Sc ₂ O ₃ ), the adhesion of the electron-emitting material to the electrode components is significantly improved, and electron emission during lighting is improved. The object of the present invention is to provide a metal vapor discharge lamp that suppresses peeling of substances and thus exhibits less luminous flux deterioration. An example of the present invention and a conventional example for comparison with this example will be described below. First, as a conventional example, an electrode component was constructed using a tungsten rod with a diameter of 0.9 [mm] as the electrode core wire 10 and a tungsten wire with a diameter of 0.5 [mm] as the inner and outer coils 11 and 12. On the other hand, an electron emitting material consisting only of scandium oxide was placed in butyl acetate together with a nitrocellulose lacquer, and a suspension was prepared by performing a ball mill for 24 hours, and the electrode component was immersed in this suspension. An electron emitting material was applied to the inner coil 11 and outer coil 12, dried, and then heated at 1800° C. for 2 minutes in an argon gas atmosphere to fix the electron emitting material 13 to the surface of the electrode component. Using the electrodes 2a and 2b having the electron emitting material 13 manufactured in this way, an inner diameter of 18 [mm] and a length between the electrodes 2a and 2b with an appropriate amount of mercury, argon gas, and scandium and sodium iodide sealed inside.
A 400W metal vapor discharge lamp equipped with a 44 [mm] arc tube 1 was manufactured. When we conducted a lighting test on this metal vapor discharge lamp, we found that the luminous flux maintenance rate after 6000 hours of lighting was
It was 45%. Next, embodiments of the invention will be described. Scandium oxide and at least one kind of rare earth metal oxide such as lanthanum oxide are selected as the electron emitting material 13,
Various types of electrodes 2a and 2b were prepared by coating and fixing these various electron-emitting substances 13 on electrode constituent members, and various 400W metal vapor discharge lamps were manufactured in the same manner as in the conventional example described above, and lighting tests were conducted. The results of this lighting test are shown in Table 1.

[Table] As shown in Table 1, compared to the metal vapor discharge lamp using the conventional electron emitting material 13 made of scandium oxide, the luminous flux of the metal vapor discharge lamp using the electron emitting material shown in the example is maintained. It can be seen that the rate is significantly better. The reason why the luminous flux maintenance factor of the example is excellent as described above is presumed to be due to the following reason. In other words, since scandium oxide has a high melting point, when it is applied to an electrode component, the adhesion of the electron emitting material 13 made of scandium oxide to the electrode component is weak even after high-temperature heat treatment, resulting in poor discharge lamp performance. During lighting, a phenomenon occurs in which the electron emitting material 13 peels off from the electrode constituent members and falls off, so in conventional devices coated with electron emitting material made only of scandium oxide, when the lamp is turned on for a long period of time, the luminous flux deteriorates significantly. It is. However, in the case of the electron radiation material 13 in which scandium oxide is mixed with at least one of the rare earth metal oxides such as lanthanum oxide as in this embodiment, the scandium oxide and the rare earth metal oxide are composite compounds (e.g. La ₂ O ₃ , Sc ₂ O ₃ ) has a low melting point, and as a result, it wets the electrode component 13 well and improves adhesion, preventing the electron emitting material from peeling off and falling off during lighting of the discharge lamp. It will become less. Furthermore, it was found from Table 1 that desirable results were obtained when the rare earth metal oxide such as lanthanum oxide was mixed in an amount of 10 to 65 [mol %] based on scandium oxide. The above amount is 10
If it is less than mol%, the effect below the melting point is small,
Because the adhesion to the electrode component is insufficient, the luminous flux maintenance rate is less than 60%, and the effect of improving the luminous flux maintenance rate is small.
In addition, if the above amount exceeds 65 [mol%], the electrode 2
Since the amount of scandium oxide coated on a and 2b is relatively reduced, the electron emission ability is lowered, and the effect of improving the luminous flux maintenance factor is also reduced, which is undesirable. Further, in the above embodiments, an electron emitting material made of the rare earth metal oxide such as lanthanum oxide and scandium oxide was used, but a small amount of tungsten or molybdenum powder or both may be added to the mixture. . Further, in the above embodiment, an electron emitting material made of one kind of rare earth metal oxide such as lanthanum oxide and scandium oxide was used, but it is made of one or more kinds of rare earth metal oxide such as lanthanum oxide and scandium oxide. It goes without saying that the same effects as in the above embodiments can be obtained even if an electron emitting substance is used. Further, in the above embodiment, an electrode having the structure shown in FIG. 2 was described, but the electrode is not limited to this structure, and as shown in FIG. an electrode component is formed by winding an outer coil 12 on the outside thereof, and an electron emitting material 13 is filled and fixed in the gap between the electrode components, or
As shown in FIG. 4, an electrode component is formed by winding only the inner coil 11 around the electrode core wire 10, and an electron emitting material 13 is formed on the surface of the electrode component.
It is also possible to apply it to electrodes of various structures, such as those coated and fixed. In addition, although the above embodiment describes a metal vapor discharge lamp filled with scandium iodide and sodium iodide, other metal halides such as dysprosium iodide, thallium iodide, sodium iodide, indium iodide, etc. are also filled. It is also applicable to metal vapor discharge lamps. As described above, the present invention provides a metal vapor discharge lamp in which a metal halide is sealed inside the arc tube. 65
By using an electrode containing an electron-emitting substance of a non-alkaline earth metal oxide with the remainder being scandium oxide, the adhesion of these electron-emitting substances to the electrode constituent members is extremely excellent, even during lighting operation. The electron-emitting material does not peel off, and as a result, the electron-emitting ability is maintained well during its lifetime, resulting in a long-life lamp with little deterioration in luminous flux.

[Brief explanation of the drawing]

Figure 1 is a front view showing a metal vapor discharge lamp, Figure 2
3, and 4 are cross-sectional views showing different configuration examples of electrodes of metal vapor discharge lamps. In the figure, 1 is an arc tube, 2a, 2b are electrodes, 1
0 is an electrode core wire, 11 is an inner coil, 12 is an outer coil, and 13 is an electron emitting material. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a metal vapor discharge lamp in which a metal halide is sealed together with mercury and a rare gas in the arc tube, 10 to 65 mol% of at least one of lanthanum oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, and dysprosium oxide is used. A metal vapor discharge lamp characterized in that electrodes coated with an electron-emitting material of a non-alkaline earth metal oxide, the remainder of which is scandium oxide, are placed opposite to each other at both ends of the arc tube.