JPS62117251A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To optimize the temperature of the coldest area located at the rear part of the electrode and minimize the initial color variation so as to enhance efficiency by making one end periphery of the first thermally insulating film almost coincide with the end surface of the electrode and restricting the region where the first thermal insulating film is applied. CONSTITUTION:One end periphery of a first thermal insulating film almost coincides with the end surface of the electrode. The distance (a) between the end surface of the electrode on the central axis of the light-emitting tube and the inner end of the press seal section and the distance (b) between one end periphery of the first thermal insulating film and its other end periphery are adjusted according to the formula 0.6<=b/1<=0.9 in order to restrict at least the region where the first thermal insulating film is applied. Since the electrode- encircling area of the light-emitting tube located at the rear part of the electrode is free from the first thermal insulating film, the temperature of the coldest area located at the rear part of the electrode is optimized and the vapor pressure of the metal halide is prevented from being excessively high and is optimized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a metal halide lamp having a heat insulating film coated on the outer surface of the arc tube.

A conventional metal halide lamp is constructed by completely filling a metal halide, mercury, and argon or a mixed starting gas of neon and argon in an arc tube with electrodes press-sealed at both ends. When this metal halide lamp is lit, the metal halide evaporates within the arc tube, and the evaporated metal halide dissociates in the high-pressure mercury arc generated between the electrodes and emits light. It is well known that halogenides significantly improve lamp luminous efficiency and color rendering.

However, since metals and compounds have relatively low vapor pressure and are easily carbonized, they remain in the coldest part of the arc tube, that is, near the electrode sealing part at the inner end of the arc tube. As a result, gold (4) luminescence in the mercury arc is small, and sufficient characteristics cannot be exhibited. Therefore, conventionally, the outer surface of the arc tube is coated with an electrode, and a heat-resistant heat-insulating film such as zirmanium oxide or carbon is coated on the outer surface of the arc tube. By applying the metal halide in two layers, the inner end of the arc tube is kept warm and the metal halide is prevented from condensing.

Problems to be Solved by the Invention With such a conventional configuration, in a high-wattage metal halide lamp, when only one layer of heat-insulating film is applied, the temperature at the coldest point at the rear of the electrode and the sealing at the press seal part may increase. The temperature of the electrode part did not rise sufficiently, and the metal halide condensed at the light emitting end, resulting in a significant drop in the vapor pressure of the metal halide, making it impossible to obtain sufficient characteristics in both efficiency and color rendering. Furthermore, when two layers of heat-retaining films are applied, the temperature at the coldest point becomes too high to reach an appropriate temperature, and the vapor pressure of the metal halide is high, resulting in significant color variations between the layers. Furthermore, the temperature of the electrode rod sealed to the press seal part is too high, and the quartz glass in the press seal part around the electrode rod becomes devitrified during its life, and eventually wrinkles, lees, and clouds appear and disappear. It had reached this point. As described above, the conventional heat-retaining film adhesion structure has the disadvantage that proper heat-retaining and peeling cannot be obtained, and the desired objective cannot be achieved.

Means for Solving the Problem In order to solve this problem, the metal halide lamp of the present invention is a light-emitting lamp with electrodes sealed at both ends of a press seal and a metal halide, mercury, and rare gas sealed inside. a first-layer heat-retaining film made of a heat absorber and a second-layer heat-retaining film made of a heat reflector are sequentially applied to at least one outer surface of an electrode surrounding portion surrounding at least the electrode of the arc tube; In a metal halide lamp with a rung power of 700 W or more, one edge of the first layer heat-retaining film is substantially aligned with the tip surface of the electrode. The length to the inner edge of the seal part is a (mm), and the length from one edge of the first layer heat insulation film to the other edge of this heat insulation film is b (
, v*), the coating range of at least the first layer of heat insulating film is defined so that Qll is within the range of 0.6≦−≦0.9.

Effect The adhesion range of the first layer of heat insulation film is set to 0.6≦b/'a≦0.
In other words, the temperature of the coldest point at the rear of the electrode is optimal because the first layer of heat insulating film is not formed in the rear part of the electrode in the electrode surrounding part of the arc tube. The vapor pressure of the metal halide becomes appropriate without becoming too high, and the above problems are solved.

Embodiment FIG. 2 shows a metal halide lamp which is an embodiment of the present invention. In the same figure, a pair of main electrodes 2.3 (the main electrode 3 is hidden and cannot be seen in Fig. 2) and an auxiliary electrode 4 are arranged at both ends of the arc tube 1 in close proximity to the main electrode 2 by press seals. It is sealed, and mercury, rare gas, and metal halide are sealed inside. The main electrodes 2.3 are connected to the row lead holes 17, 8 through molybdenum foils 5°6'lJ:. Further, the auxiliary pole 4 is connected to an external lead wire 1o via a molybdenum foil 9. Said arc tube 1
A first layer of heat insulating film 1 made of a heat absorber is provided on the outer surface of one end.
1 and a second layer of heat insulating film 12 made of a heat reflector are sequentially applied. The two-layer structure is shown enlarged in FIG. The external lead wire 7 is connected to the stem wire 14 via the ribbon connection wire 13, and the external lead wire 8 is connected to the stem wire 15 through the ribbon connection wire 13.
It is connected to the. Also, the external lead wire 1o has a starting resistance of 1
6 and a normally closed bimetal switch 17 to the stem wire 15 .

The arc tube 1 is supported at both ends by support plates 18 and 19 and is connected and fixed to stems 14 and 15.

The arc tube 1 is filled with a predetermined amount of mercury, a metal halide such as thorium iodide, thallium iodide, indium iodide, and scandium iodide, and a starting rare gas such as neon-argon.

Hereinafter, specific examples of the present invention will be described.

In the lamp with the above configuration, the distance between the main electric currents is set to 1
Approximately 260 Mg of mercury, scandium iodide, and sodium iodide are sealed, and approximately 60 (MB) of neon (99.5%)-argon (0.5%) is added as a rare gas.
) In the sealed arc tube, one edge of the first layer heat insulating film is aligned with the tip surface of the electrode, and the length a from the electrode tip surface on the central axis of the arc tube to the inner end of the press seal part is 1
When the temperature is 0H, the position of the other edge of the first layer heat insulation film, the length b (mm) from one edge of the tab to the other edge
) by making various changes to produce various lamps. In addition, the second layer of heat insulating film at this time is applied from a portion slightly protruding from the electrode tip surface to the outer surface of the electrode rod sealed to the shiveless seal portion. Bluffitera was used as the first layer of heat insulation film, and zirconia was used as the second layer of heat insulation film.

The 200oW metal ride lamp created in this way was turned on and off (on for 5.5 hours, off for 0.5 hours), and the color temperature change, luminous efficiency, and pinch seal on the electrode rod were measured at a cumulative lighting time of 4000 hours. The state of devitrification in the area was investigated. The results are shown in the table below.

As is clear from the table above, b/a is 0.6 to 0.9
Within this range, the color variation, efficiency, devitrification state of the pinch seal around the electrode rod, and defect rate are all good. However, when b/a is smaller than 0.6, the color variation, devitrification state, and defect rate are good, but the efficiency from the initial stage becomes extremely poor.

Furthermore, when b/a increases by 0.9 or more, the color variation becomes large (), and although the efficiency becomes high, the variation also occurs. Furthermore, devitrification of quartz on the electrode rod also begins to occur and the defect rate increases.

Note that the application position of the first layer (b/
When a) was similarly varied, the efficiency did not exceed 801 m/W in any case, and the desired characteristics could not be obtained.

The reason why the metal halide lamp of the embodiment of the present invention has such excellent characteristics is considered to be due to the following reason.

In other words, if b/a is less than 0.6, the temperature at the coldest point at the rear of the electrode will not be the optimum temperature to evaporate the metal halide, and the light color will be blue and the efficiency will be low. . If b/a exceeds 0.9, the temperature at the coldest point at the rear of the electrode will become abnormally high, the vapor pressure of the metal halide will increase, and variations among individual lamps will increase.

Furthermore, the temperature of the 'd'fi and electrode rods sealed to the press seal part is too high, and the quartz glass in the press nol part on the electrode rod becomes devitrified in the middle of its life, eventually leading to leakage. , the failure rate will also increase.

On the other hand, when b/a is in the range of 0.6 to 0.9, such problems do not occur and it is possible to improve initial color variation, efficiency, devitrification of quartz, and defect life. It has become.

The above embodiment is an example of a metal halide lamp with a lamp power of 2000W, but based on a preliminary experiment, the present invention has a lamp power of 700W.
, 1000W, 1500W, 3000W, and other high wattage metal halide lamps of 700W or more were found to have similar effects.

Experiments have shown that in high-wattage metal halide lamps with a lamp power of 700 W or more, color rendering can be improved even if one edge of the first layer heat-retaining film is extended forward from the electrode tip surface without nearly matching the electrode tip surface. Compared to a case where the lamp characteristics such as performance are almost the same, there is almost no difference, and on the contrary, light shielding occurs and efficiency decreases, and the problem arises that the heat insulating film material is wasted and the cost increases. This was recognized.

It should be noted that one edge of the first layer heat-retaining film does not need to be completely aligned with the tip surface of the electric tome, but should be at an angle of ±0,
5 All you have to do is fall within the TILM range.

Furthermore, the second layer of heat-retaining film does not necessarily need to be applied to the electrode surrounding portion and the pinch seal portion, and may be applied only to the electrode surrounding portion.

The second layer of heat retaining film may be deposited on at least the entire first layer of heat retaining film.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention provides a first layer of a heat-retaining film made of a heat absorber and a second layer made of a heat reflector on at least one outer surface of the electrode surrounding portion surrounding at least the electrode of the arc tube. In a metal halide lamp having a lamp power of 700 W or more, which is formed by successively depositing heat insulating films, one edge of the first layer heat insulating film is substantially aligned with the tip surface of the electrode, and the edge of the heat insulating film of the first layer is made to substantially coincide with the tip surface of the electrode. The length from the electrode tip surface to the inner edge of the press seal part is -(ff), and the length from one edge of the first layer heat-insulating film to the other edge of this heat-insulating film is b( By regulating at least the coverage area of the first layer heat insulating film so that it is within the range of O06≦−≦0.9, the temperature of the coldest point at the rear of the electrode can be optimized. This makes it possible to reduce initial color variation, increase efficiency, and eliminate devitrification around the electrode rod at the pinch seal portion throughout the life of the product, providing a long-life metal halide dragon. .

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view of a main part of a metal halide lamp according to an embodiment of the present invention, and FIG. 2 is a front view of the metal halide lamp. 1...--- Arc tube, 2, 3... Main electrode, 1
1... First layer heat insulating film, 12... Second layer heat insulating film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (1)

[Scope of Claims] An arc tube is provided with electrodes sealed at both ends by press seals and a metal halide, mercury, and a rare gas are sealed inside, and at least an electrode surrounding portion of the arc tube surrounds at least the electrode. In a metal halide lamp having a lamp power of 700 W or more and having a first layer heat insulating film made of a heat absorber and a second layer heat insulating film made of a heat reflector sequentially applied to one outer surface, the first layer heat insulating film one end edge of the electrode is substantially aligned with the tip surface of the electrode, the length from the electrode tip surface on the central axis of the arc tube to the inner end of the press seal portion is a (mm), and the first layer When the length from one edge of the heat insulating film to the other edge of this heat insulating film is b (mm), at least the above-mentioned A metal halide lamp characterized in that the coverage area of the first layer of heat insulation film is regulated.