JP2011008935A - Ceramic metal halide lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a high color rendering property and a high luminous efficiency of a metal halide lamp and moreover shorten a re-starting time.SOLUTION: An arc tube (1) with capillaries (3A, 3B) continuously formed on both end sides of an almost oval-shaped surface light emitting part (2) is arranged and housed inside a translucent outer tube (10); an average thickness of the light emitting part is made to be 0.85-1.1 mm, a thickness distribution of the light emitting part is made to be within +/-20% of the average thickness, and an inner side dimension of the light emitting part is made to be 1.8≤L/D≤2.2 (L: an effective length, D: an effective inner diameter). The light emitting part is formed to be in a size in which the coldest temperature at lighting up may become 800°C or higher and the highest temperature 1200°C or lower, and at least thulium iodide, thallium iodide, sodium iodide and calcium iodide are enclosed in the light emitting part, sodium iodide and calcium iodide are enclosed at a molar ratio of 40-80 and less than 30% respectively against a total halide metal, and an inert gas is enclosed in the translucent outer tube at a pressure of 5.3-7.6x10Pa.

Description

  The present invention relates to a ceramic metal halide lamp used as general lighting in an office or a store, and in particular, high color rendering properties with a correlated color temperature of 3000 to 4500 K, an average color rendering index Ra ≧ 80, and luminous efficiency η ≧ 100 (lm / W). It is suitable for use when high efficiency and restartability in a short time are required.

The metal halide lamp emits light that is closest to natural light compared to a high-pressure sodium lamp or a mercury lamp, and therefore has excellent color rendering properties, and is also used as a base lighting in offices and stores.
In general, an average color rendering index Ra = 80 or higher, which is ISO 8995 color rendering category 1B or higher, and a high color rendering in which the correlated color temperature is in the range of 3000 to 4500K, and a light source in a range from warm to white is used. From the viewpoint of energy saving, a lamp with higher luminous efficiency is demanded.
However, high color rendering and high efficiency are contradictory effects. If the color rendering is improved, the luminous efficiency is lowered, and if the luminous efficiency is increased, the color rendering is lowered.
For this reason, the conventional metal halide lamps are classified into either an efficiency-oriented type or a color rendering property-oriented type even if high efficiency and high color rendering are desired.
In this case, generally, if the average color rendering index Ra ≧ 80, it is evaluated as high color rendering (ISO 8995 color rendering category 1B or higher), and if the luminous efficiency η ≧ 100, it is evaluated as high efficiency.

  For example, the highest data of the Dy-Ho-Tm metal halide lamp disclosed in Patent Document 1 is excellent with an average color rendering index Ra = 87, but is slightly inferior with luminous efficiency η = 93 (lm / W). It can be said that it is an important type.

  The Na—Ce-based metal halide lamp disclosed in Patent Document 2 is excellent with an average luminous efficiency η = 123 (lm / W) due to intense green light emission of Ce, but is slightly inferior with an average color rendering index Ra = 60. It can be said that it is an efficiency-oriented type (see Patent Document 2 [0049]).

  Further, Patent Document 2 [0082] states that “in addition to NaI, dysprosium (Dy), thulium (Tm), holmium (Ho), thallium (Tl), etc. are appropriately used depending on the desired lamp characteristics. However, even if these substances are added to adjust the ratio of the luminescent encapsulating substance of the Na—Ce metal halide lamp, the intense green light emission of Ce is suppressed and Ra = Not only is it difficult to make it 70 or more, but when Dy, Tm, Ho, and Tl are added as light emitting substances, the lamp characteristics of Patent Document 1 are approached and the light emission efficiency is lowered.

  On the other hand, conventional high color rendering ceramic metal halide lamps achieve high color rendering and high luminous efficiency by increasing the heat insulation effect of the arc tube by evacuating the translucent outer tube that houses the arc tube. Since the arc tube is difficult to be cooled when the lamp is turned off, it takes about 25 to 30 minutes to restart the lamp after it is turned off, and it is desired to reduce this to about 15 minutes.

Although it is possible to shorten the restart time by increasing the starting pulse voltage, when a pulse voltage that can be restarted within 15 minutes was measured in a prototype lamp with a vacuum inside the translucent outer tube, a high voltage pulse of 3 kV or higher I found that it was necessary.
In the recent usage environment that emphasizes safety and security, it is considered that a starting voltage of about 1 to 1.5 kV is appropriate. In a general lighting lamp of a low starting voltage type that is lit by a mercury lamp ballast, it is desirable to avoid generating a high voltage pulse of 3 kV in terms of safety.

JP 2003-187744 A JP 2003-086130 A

  Therefore, the present invention achieves both high color rendering properties and high efficiency, which are contradictory effects in a metal halide lamp. Specifically, while maintaining high color rendering properties with an average color rendering index Ra ≧ 80, luminous efficiency η ≧ 100 ( It is a technical problem to achieve a high efficiency (lm / W) and to shorten the restart time with a start pulse voltage comparable to that of a conventional lamp.

In order to achieve this object, the present invention provides a light-emitting portion in which a metal halide, mercury, and a starting rare gas are sealed, and capillaries through which a pair of electrode assemblies arranged at both ends thereof are inserted with a translucent ceramic. In the ceramic metal halide lamp in which the arc tube formed is housed in a translucent outer tube,
In the arc tube, the capillary is continuously formed on both ends in the major axis direction of the light emitting portion formed in a substantially elliptical shape through transition curved surfaces having no corners, and the average thickness of the light emitting portion is 0. And the thickness distribution of the light emitting part is formed within ± 20% of the average thickness,
The inner dimension of the light emitting part is designed to be 1.8 ≦ L / D ≦ 2.2 when the effective length is L and the effective inner diameter is D, and the light emitting part coldest temperature during lighting is It is formed in a size that is 800 ° C. or higher and the light emitting portion maximum temperature is 1200 ° C. or lower,
As the metal halide, at least thulium iodide, thallium iodide, sodium iodide and calcium iodide are encapsulated, and sodium iodide and calcium iodide are 40 to 80% of the total metal halide, respectively. Enclosed at a molar ratio of less than 30%,
The translucent outer tube is filled with an inert gas at a sealed pressure of 5.3 × 10 ^{4 to} 7.6 × 10 ⁴ (Pa) at room temperature when the lamp is not turned on.

According to the metal halide lamp of the present invention, at least four kinds of metal halides of thulium iodide, thallium iodide, sodium iodide and calcium iodide are enclosed in the arc tube.
Among metal halides, a Tm-Tl-Na ceramic metal halide lamp encapsulating thulium iodide (TmI ₃ ), thallium iodide (TlI) and sodium iodide (NaI) generally has a green emission color. The TmI ₃ and TlI exhibited have improved luminous efficiency, and the NaI exhibiting a yellow luminescent color has improved color rendering, but the overall is an efficiency-oriented metal halide lamp with excellent luminous efficiency.
In the present invention, NaI is made 40 to 80% in molar ratio, and at the same time, calcium iodide (CaI ₂ ) is added.
By adding CaI ₂ , light emission in the red region increases, and thus the light emission efficiency tends to decrease, but the color rendering property is improved. According to the inventor's experiment, it was found that if the encapsulation ratio of CaI ₂ is less than 30%, the luminous efficiency is only slightly lowered and the effect of improving the color rendering property is large.
Therefore, high color rendering properties could be realized by adding CaI ₂ in a molar ratio with an upper limit of 30%.

In addition, the arc tube has a mechanical strength because a pair of capillaries are continuously formed on both ends in the major axis direction of the light emitting portion formed in a substantially elliptical shape through a transition curved surface having no corners. The overall wall thickness can be made relatively thin and uniform without lowering the thickness of the light emitting part. Therefore, unlike the three-piece type or the five-piece type in which the thick part is partially formed, the temperature distribution of the light emitting part is It becomes relatively uniform and the coldest temperature can be kept high, so there is no need to increase the wall load.
In addition, the temperature difference in the light emitting portion is smaller than that in the prior art, and as a result, the chemical reaction rate between the metal halide and the material constituting the inner wall surface of the light emitting portion can be kept low, and the lamp life can be extended.

Further, the inner dimension of the light emitting part is designed to be 1.8 ≦ L / D ≦ 2.2 when the effective length is L and the effective inner diameter is D, and the light emitting part coldest temperature at the time of lighting is designed. Is 800 ° C. or more and the light emitting part maximum temperature is 1200 ° C. or less.
According to the inventor's experiment, it has been found that even if the light emitting portion is formed in an elliptical spherical shape, the aspect ratio and size have some influence on the light emission efficiency and the color rendering properties, and 1.8 ≦ L / D ≦ 2.2
If the light emitting part coldest temperature during lighting is 800 ° C. or more and the light emitting part maximum temperature is 1200 ° C. or less, the average color rendering index regardless of the rated power of the metal halide lamp. Ra ≧ 80 and luminous efficiency η = 100 (lm / W) could be achieved.

Further, the average thickness of the light emitting portion of the arc tube is formed to be relatively thin as 0.85 to 1.1 mm, and the thickness distribution of the light emitting portion is uniformly formed within ± 20% of the average thickness. Therefore, when the lamp is turned off, the heat inside the arc tube can easily escape to the outside, and in the translucent outer tube that accommodates the arc tube, the sealed pressure is 5.3 × 10 ⁴ (Pa) or more at room temperature when the lamp is not turned on. Since the inert gas is filled, the cooling of the arc tube is promoted and the restart time can be shortened within 15 minutes.
In addition, since the inert gas leads to breakage of the translucent outer tube if the filling amount is too large, the sealed pressure at normal temperature is 7.6 × 10 ⁴ (Pa) so as not to greatly exceed 1 atm at the time of light emission. ).
Thereby, restart time can be shortened, without reducing a color rendering evaluation number and luminous efficiency.

Explanatory drawing which shows the arc tube used for the metal halide lamp which concerns on this invention. 1 is an overall external view of a metal halide lamp A. FIG. 1 is an overall external view of a metal halide lamp B. FIG. The graph which shows the relationship between luminous efficiency (eta) and L / D. The graph which shows the relationship between average color rendering index Ra and L / D. The graph which shows the restart time and luminous efficiency with respect to inert gas enclosure pressure. Explanatory drawing which shows other embodiment of an arc tube.

The present invention realizes a high efficiency of light emission efficiency η ≧ 100 (lm / W) while maintaining a high color rendering property of average color rendering index Ra ≧ 80, and further reduces the restart time. A light emitting tube in which the capillary is continuously formed on both ends in the major axis direction of the light emitting portion formed in a shape through a transition curved surface having no corners is accommodated in the translucent outer tube, and the light emitting portion The average wall thickness of 0.85 to 1.1 mm is formed, and the wall thickness distribution of the light emitting part is formed within ± 20% of the average wall thickness,
The light emitting part is designed to satisfy 1.8 ≦ L / D ≦ 2.2 when the effective length of the inner dimension is L and the effective inner diameter is D, and the light emitting part coldest temperature during lighting is 800 ° C. The size is such that the light emitting part maximum temperature is 1200 ° C. or lower,
In the light emitting part, at least thulium iodide, thallium iodide, sodium iodide and calcium iodide are encapsulated as a metal halide, and sodium iodide and calcium iodide are 40 to 80% of the total metal halide, respectively. And an inert gas was sealed in the translucent outer tube at a pressure of 5.3 × 10 ^{4 to} 7.6 × 10 ⁴ (Pa).
And about each of the two types of metal halide lamps A and B shown below, it experimented by changing the molar ratio of a rated power or an enclosure.

<About arc tube>
A common arc tube 1 shown in FIG. 1 is used for each metal halide lamp A and B.
The arc tube 1 has a transition in which a pair of capillaries 3A and 3B have no corners at both ends in the long axis direction of the light emitting unit 2 formed in a substantially elliptical shape that is rotated about the long axis of the ellipse. It is formed continuously via the curved surface 4, and the light emitting portion 2 is filled with a metal halide, mercury and a starting rare gas.
The arc tube 1 of this example uses a so-called one-piece type in which the light emitting part 2 and the capillaries 3A and 3B are integrally molded by molding a powdered compact of translucent alumina.

  A pair of electrode assemblies 6A and 6B having electrodes 5 and 5 are inserted into the capillaries 3A and 3B formed at both ends of the light emitting section 2, and both ends of the capillaries 3A and 3B are electrically insulated frit. At the same time as being hermetically sealed by a sealing material such as glass, the electrode assemblies 6A and 6B are fixed at fixed positions in the capillaries 3A and 3B by the sealing material.

The inner dimension of the light emitting portion 2 is designed to be 1.8 ≦ L / D ≦ 2.2, where L is the effective length and D is the effective inner diameter.
The effective length L is defined by the distance between the portions 2A and 2B where the inner diameters of the straight tubular capillaries 3A and 3B are shifted to the transition curved surface 4 continuous with the light emitting portion 2 and start to expand, and the effective inner diameter D is In the case of a one-piece type arc tube, it is defined by the maximum inner diameter at the center between the electrodes.

Further, the arc tube 1 is formed in such a size that the light emitting portion coldest temperature during lighting is 800 ° C. or higher and the light emitting portion maximum temperature is 1200 ° C. or lower.
The temperature of each part of the light emitting part is determined by the wall load of the light emitting tube, the gas pressure in the translucent outer tube, the material of the light emitting tube and the dimensional ratio (L / D) of the light emitting part.
Here, a value obtained by dividing the lamp power P _L (W) by the total inner area S (cm ² ) of the light emitting unit 2 is defined as “wall load”.

The thickness distribution of the light emitting portion 2 is formed within ± 20% of the average thickness.
In this example,
Average wall thickness t _av = 0.85mm
Whereas
Minimum thickness t _min = 0.78mm
Maximum wall thickness _tmax = 0.98mm
And
Allowable minimum wall thickness t _av -20% = 0.68mm
Maximum allowable wall thickness t _av + 20% = 1.02 mm
Therefore, it is formed within an allowable thickness dimension of an average thickness ± 20%.

In the arc tube 1, a pair of capillaries 3A and 3B are continuously formed on both ends in the major axis direction of the light emitting portion 2 formed in a substantially elliptical shape via a transition curved surface 4 having no corners. In this way, the wall thickness distribution can be uniformly formed in the range of the average wall thickness ± 20%, and the wall load necessary for maintaining the coldest temperature in the arc tube light emitting section 3 at 800 ° C. or higher. Can be small.
Therefore, the temperature difference in the light emitting portion 2 can be made smaller than before, and as a result, the chemical reaction rate between the rare earth metal iodide and the material constituting the inner wall surface of the light emitting portion can be suppressed and the lamp life can be extended. .

  That is, the arc tube of the type in which the light emitting portion and the capillary portion are processed by dividing them into 3 or 5 piece parts and assembled by shrink fitting by shrinkage during arc tube sintering is a machine for shrink fitting parts. In order to ensure the appropriate strength, the end of the light emitting part is generally 1.5 times thicker than the center of the light emitting part.

In this case, since the thick portion is separated from the discharge portion generated between the electrodes, the temperature of the thick portion is difficult to rise, and the wall surface is required to maintain the temperature of this portion (light emitting portion coldest temperature) at 800 ° C. or higher. The load must be set higher, and as a result, the temperature difference in the light emitting section becomes larger.
On the other hand, by setting the wall load higher, the maximum temperature of the light emitting part exceeds 1200 ° C. As a result, the chemical reaction rate between the metal halide and the material constituting the inner wall of the arc tube is increased at the high temperature part, There is a problem that the erosion of the inner wall surface of the arc tube is accelerated and the lamp life is shortened.
In the ceramic metal halide lamp of the present invention, since the wall surface load can be reduced, high efficiency and high color rendering can be realized without sacrificing lamp life.

Further, the light emitting portion 2, a metal halide, at least iodide thulium _(TmI 3), thallium iodide (TlI), along with sodium iodide (NaI) and calcium iodide (CaI ₂₎ is enclosed, iodine Sodium iodide (NaI) and calcium iodide (CaI ₂ ) are encapsulated in molar ratios of 40-80% and less than 30%, respectively, with respect to the total metal halide.
If necessary, dysprosium iodide (DyI ₃ ) is enclosed in a molar ratio of 3% or less with respect to the total metal halide, and cerium iodide (CeI ₃ ) is 5 with respect to the total metal halide. Enclosed at a molar ratio of less than%.

<Metal halide lamp A>
In the metal halide lamp A, as shown in FIG. 2, the above-described arc tube 1 is housed and disposed in a translucent outer tube 10 having a base 11 formed at one end, and a starting voltage is applied between the electrodes 5 and 5. The starter 12 including a non-linear ceramic capacitor to be supplied is disposed.
Support stems 16 and 16 are attached to the support column 15 on the stem 13 of the base 11, and the capillaries 3 </ b> A and 3 </ b> B are inserted into insertion holes formed in the center of the support tube 16 and 16. Is attached and supported, and a translucent sleeve 17 is fixed to the discs 16 and 16 so as to surround the light emitting portion 2.
In addition, the power supply leads 7 and 7 protruding from the ends of the capillaries 3A and 3B are electrically connected to the base 11 by welding directly to the respective support columns 14 and 15 or by welding via the nickel ribbon wires 18. In addition, the starter 12 is electrically connected to the power supply leads 7 and 7.

The translucent outer tube 10 is filled with nitrogen gas as an inert gas.
The higher the inert gas pressure, the higher the cooling efficiency and the shorter the restart time. However, when the temperature exceeds 5.3 × 10 ⁴ (Pa) at room temperature when the lamp is not turned on, it will not be shortened any longer and remain almost constant. It becomes. The luminous efficiency also decreases as the sealing pressure increases, but becomes substantially constant when the sealing pressure exceeds 5.3 × 10 ⁴ (Pa).
On the other hand, if the sealing pressure is too high, the translucent outer tube is easily damaged even by a slight scratch or impact.
Therefore, the inert gas sealing pressure at room temperature (300 K) when the lamp is not turned on is set to 5.3 × 10 ⁴ (Pa) or more in consideration of the restart time and the luminous efficiency, and the arc tube due to excessive internal pressure. In order to prevent damage to the light, it was set to 7.6 × 10 ⁴ (Pa) or less so as not to greatly exceed 1 atm during light emission.
That is, assuming that the average temperature (operating temperature) in the translucent outer tube 10 at the time of stable lighting is 400K and the inner pressure reaches 1 atm (10.1 × 10 ⁴ Pa), the lamp is not turned on. The enclosure pressure at normal temperature (300 K) is 7.6 × 10 ⁴ (Pa).
Further, in the case of this example, the wall surface load is 15 to 25 (W / cm ² ), and it is lit by being arranged in the vertical direction (direction of FIG. 2).

<Metal halide lamp B>
As shown in FIG. 3, the metal halide lamp B is common to the metal halide lamp A in the basic structure in which the arc tube 2 and the starter 12 are housed in the translucent outer tube 10, and there is no translucent sleeve 16. Only different. Portions common to the metal halide lamp A are denoted by the same reference numerals, and detailed description thereof is omitted.
In addition, wall surface load is 20-25 (W / cm < ² >), and is a type which arrange | positions and lights up in a horizontal direction (direction of FIG. 3) fundamentally.
Also in this example, the filling pressure of the inert gas (nitrogen gas) at room temperature when the lamp is not turned on is 5.3 × 10 ⁴ (Pa) or more so that it does not significantly exceed 1 atm even during light emission. And 7.6 × 10 ⁴ (Pa) or less.

<Experimental result>
In each metal halide lamp A and B, when L / D = 2, the composition ratio of the metal halide encapsulated in the light emitting part 2 was changed, and the average color rendering index Ra and the luminous efficiency η were measured. 1.
Thus, in any case, the average color rendering index Ra ≧ 80, and the luminous efficiency η = 100 (lm / W) could be achieved while maintaining the color rendering category 1B or higher of ISO 8895.

  FIGS. 5 and 6 show L / D, average color rendering index Ra, and luminous efficiency when metal halide lamp A is filled with a metal halide at a predetermined molar ratio in arc tube 1 having different L / D. 5 is a graph showing the relationship between η and L / D, and FIG. The measurement results when encapsulated at a molar ratio of 1 are shown in FIG. The measurement results when encapsulated at a molar ratio of 3 are shown.

From these graphs, the average color rendering index Ra ≧ 80 and the luminous efficiency η ≧ 100 (lm / W) at least in the range of 1.8 ≦ L / D ≦ 2.2. Although the graphs are omitted, similar results were obtained with other lamps that were lit with the built-in ballast.
Since the recent curves are all in the vicinity of L / D = 2, in order to maintain both the average color rendering index Ra and the luminous efficiency η at a high level when taking measurement errors into consideration. Is preferably an arc tube 1 with L / D = 2.

Further, FIG. 7 is a graph showing the start time and luminous efficiency with respect to the nitrogen gas filling pressure of the translucent outer tube 10 for the type of the metal halide lamp A.
From this, when the sealed pressure of the inert gas (nitrogen gas) at room temperature when the lamp is not turned on is set to 5.3 × 10 ^{4 to} 7.6 × 10 ⁴ (Pa), the restart time is up to 15 minutes. It can be seen that the luminous efficiency is reduced and the luminous efficiency is maintained at about 125 (lm / W).
Even if sealed at the maximum pressure, the inside of the translucent outer tube 10 does not significantly exceed 1 atm during light emission, so that the translucent outer tube 10 is not damaged due to excessive internal pressure.
Similar results were obtained with the metal halide lamp B and other lamps that were lit with a built-in ballast.

In the above description, the arc tube 1 is of a one-piece type. However, the capillaries pass through transition curved surfaces having no corners at both ends in the major axis direction of the light emitting portion formed in a substantially elliptical shape. As long as it is formed continuously, a two-piece type may be used.
As shown in FIG. 8, the two-piece type arc tube 30 has a funnel-like light emission in which one capillary 33 is continuously formed on the apex side of a substantially semi-elliptical surface 31 via a transition curved surface 32 having no corners. The tube forming half 34 is formed by butt welding.

In this case, the effective length L of the light emitting portion 35 is the same as the light emitting tube 1 of FIG. 1, the portion 35A where the inner diameter of the straight tubular capillary 33 shifts to the transition curved surface 32 continuous to the light emitting portion 35 and starts to expand. It is defined by the distance between 35B.
The effective inner diameter D is defined as the maximum inner diameter of the center portion between the electrodes on the assumed elliptical surface 37 when the butt weld 36 is thick, and there is no bulge on the inside of the weld 36.
The ratio between the effective length L and the effective inner diameter D is set to 1.8 ≦ L / D ≦ 2.2.

  Further, in the two-piece type arc tube 30, the thickness distribution of the light emitting portion 35 is formed within ± 20% of the average thickness calculated excluding the thick portion of the butt weld portion 36, and the thick portion Is 1 to 1.5 times the average wall thickness.

Then, the arc tube 30 of this example is attached to the metal halide lamps A and B in place of the arc tube 1, and an inert gas (nitrogen gas) is supplied to the translucent outer tube 10 at a normal temperature of 5.3 × 10 ⁴ (Pa ) To 7.6 × 10 ⁴ (Pa) at a filling pressure, and a lighting experiment was conducted. As in the above examples, high color rendering properties with an average color rendering index Ra ≧ 80 and η ≧ 100 (lm / W) was able to achieve both high luminous efficiency and the restart time could be shortened to 15 minutes.

  As described above, the present invention can be applied to the use of a ceramic metal halide lamp that requires high color rendering properties and high luminous efficiency and restart in a short time.

A, B Metal halide lamp 1 Light emitting tube 2 Light emitting portion 3A, 3B Capillary 4 Transition curved surface 6A, 6B Electrode assembly L Effective length D Effective inner diameter 10 Translucent outer tube

Claims (5)

An arc tube formed of a translucent ceramic with a light emitting part enclosing a metal halide, mercury, and a rare gas for starting, and a capillary inserted through a pair of electrode assemblies arranged at both ends of the light emitting part is provided in the translucent outer tube. In the stored ceramic metal halide lamp,
In the arc tube, the capillary is continuously formed on both ends in the major axis direction of the light emitting portion formed in a substantially elliptical shape through transition curved surfaces having no corners, and the average thickness of the light emitting portion is 0. And the thickness distribution of the light emitting part is formed within ± 20% of the average thickness,
The inner dimension of the light emitting part is designed to be 1.8 ≦ L / D ≦ 2.2 when the effective length is L and the effective inner diameter is D, and the light emitting part coldest temperature during lighting is It is formed in a size that is 800 ° C. or higher and the light emitting portion maximum temperature is 1200 ° C. or lower,
As the metal halide, at least thulium iodide, thallium iodide, sodium iodide and calcium iodide are encapsulated, and sodium iodide and calcium iodide are 40 to 80% of the total metal halide, respectively. Enclosed at a molar ratio of less than 30%,
A ceramic metal halide, wherein the translucent outer tube is filled with an inert gas at an enclosed pressure of 5.3 × 10 ^{4 to} 7.6 × 10 ⁴ (Pa) at room temperature when no lamp is lit. lamp.   The ceramic metal halide lamp according to claim 1, wherein dysprosium iodide is enclosed as a metal halide in a molar ratio of 3% or less with respect to the total metal halide.   The ceramic metal halide lamp according to claim 1, wherein cerium iodide is sealed as the metal halide in a molar ratio of 5% or less with respect to the total metal halide.   A two-piece type in which the arc tube is formed by butt welding a funnel-shaped arc tube forming half in which one capillary is continuously formed on the apex side of a substantially semi-elliptical surface via a transition curved surface having no corners The average wall thickness is calculated by excluding the wall thickness of the butt weld, and the wall thickness of the butt weld is 1 to 1.5 times the average wall thickness. Ceramic metal halide lamp. The ceramic metal halide lamp according to claim 1, wherein a translucent sleeve is disposed around the arc tube.

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