Metal halide discharge lamp

Lamps were fabricated in accordance with the second embodiment to have arc tubes which were made of quartz and dimensioned to have a maximum inside diameter of 18 mm, and a distance of 48 mm between the electrodes. The arc tubes were filled mainly with sodium iodide and scandium iodide, and with cesium iodide or mercury in listed amounts as shown in Table 1 below. The lamps were configured to have the regulator means defined by the envelope in combination with at least one of the envelope, sleeve, heat insulator layers, reduction-in-diameter sections, and the sealed ends, as shown in Table 1. For a comparative purposes, Comparative Example 2 was prepared which is identical to Example 10 except that the regulator means was not included.

In order to evaluate the lamp characteristics for the Examples 1 to 11 and Comparative Examples 1 and 2, measurements were made to obtain a coldest spot temperature (CST) (°C.) at operating at 100% of rated lamp power and reduced lamp power as listed, as well as to obtain a variation (ΔT (K)) in color temperature when the voltage supplied to the lamp, i.e., the input source voltage to the magnetic ballast varies.

In Examples 2 to 5, 7 to 9, and 11, cesium iodide was added in an amount of 1.25×10 −5 mol/ml. In Examples 6, 10, and 11, mercury was added in an amount of 2.50×10 −5 mol/ml. In Examples 11, mercury was added in an amount of 1.53×10 −5 mol/ml.

As to the column ‘envelope’ in Table 1, ‘Yes’ denotes the use of the envelope. As to the column ‘envelope evacuated’, ‘Yes’ denotes that the envelope is evacuated. Further, Examples 6 and 11 utilize the envelopes each coated on its inner surface with a phosphor coating, while Examples 4, 7, and 11 utilized the envelopes each coated on its inner surface with a coating capable of reflecting infrared radiation. Examples 2 to 4, 7, and 11 utilized the heat insulator layer made of zirconium oxide, while Examples 5, 6, 8, and 10 utilized the heat insulator layer of metal such as platinum or gold capable of reflecting infrared radiation to a large extent than zirconium oxide. In Examples 8 to 11, the reduced-in-diameter sections were formed on opposite ends of the arc tube. In Examples 10 and 11, the sealed ends of the arc tube were made to have a smaller diameter than the arc tube as shown in FIG. 6 . Arc bent was seen in Example 2.

As is seen from Table 1, Comparative Examples 1 and 2 show decreased coldest spot temperatures of 459° C. and 500° C., respectively when the lamp power (Wla) is reduced to 63% of the rated power, and large color temperature variation widths (ΔT) of 442K and 658K when the input source voltage varies by ±10%. On the other hand, all the Examples show the color temperature variation width (ΔT) of 120K or less in response to ±10% variation of the input source voltage to the ballast. This means that Examples are capable of reducing color change even subjected to source voltage variations.

FIG. 12 show curves plotting the coldest color temperatures (CST) changing with varying the lamp power for Examples 1 to 12, and Comparative Examples 1 and 2. The right end plot and the second one from the right of each curve was obtained when operating the lamp at 110%, and 100% of the rated power, respectively, while left and plots of curves for Examples 1 to 11 and Comparative Example 2 were obtained when operating the lamp at 50% of the rated lamp power. The curve for Comparative Example 1 has the left end plot which was obtained when operating the lamp at 63% of the rated lamp power.

EXAMPLES 12 to 17

Lamps were fabricated in accordance with the first embodiment to have arc tubes of quartz which were dimensioned to have an inside diameter of 8 mm, and a distance of 80 mm between the electrodes. The arc tubes were filled with sodium iodide and scandium iodide at varying molar ratio therebetween as listed in Table 2 below. Also, about 27000 Pa of xenon and 1.25×10 −5 mol/ml of cesium iodide were filled in the tube. For example lamp, the arc tube was contained in the evacuated envelope and is coated with the heat insulator layer of zirconium oxide. No sleeve was provided. Measurements were made to obtain the coldest spot temperature (CST) of each arc tube when operating the lamp at 100% and 50% of rated lamp power, respectively, and to obtain a width of color temperature change ΔT in response to ±10% variation in the source voltage.

It is confirmed from Table 2 that the color temperature change (ΔT) can be reduced while the molar ratio of sodium iodide to scandium iodide varies from 2.8 to 17.0. FIG. 13 show luminous efficiency, color rendering index, and color temperature measured for Examples 12 to 17. As seen form FIG. 13, it is known that Examples 12 to 17 show almost constant color rendering index of around 60, and efficiency of around 80 (lm/W), while showing varying color temperature as the molar ratio of sodium iodide to scandium iodide varies. With this result, it is found that a desired color can be chosen, yet reducing the color temperature variation ΔT against the variation in the source voltage.

EXAMPLES 18 to 21

Lamps were fabricated in accordance with the second embodiment to have arc tubes of quartz which were dimensioned to have a maximum inside diameter of 18 mm, an average inside diameter of 14 mm, and a distance of 48 mm between the electrodes. The arc tubes were filled with sodium iodide and scandium iodide at varying molar ratio therebetween as listed in Table 3 below. Also, about 6700 Pa of argon and 1.53×10 −5 mol/ml of mercury were filled in the tube. For each lamp, the arc tube was contained in the evacuated envelope and is coated with the heat insulator layer of zirconium oxide. No sleeve was provided. Measurements were made to obtain the coldest spot temperature (CST) of each arc tube when operating the lamp at 100% and 50% of rated lamp power, respectively, and to obtain a width of color temperature change ΔT in response to ±10% variation in the source voltage.

It is also confirmed from Table 3 that the color temperature change (ΔT) can be reduced while the molar ratio of sodium iodide to scandium iodide varies from 5.7 to 22.7.

Lamps were fabricated in accordance with the first embodiment to have arc tubes of quartz which were dimensioned to have an inside diameter of 8 mm, and a distance of 80 mm between the electrodes. The arc tubes were filled with scandium iodide at a varying mount between 1.02×10 −8 mol/ml and 4.59×10 −8 mol/ml and with sodium iodide at a varying molar ratio relative to scandium iodide from 0.0 to 19.8, as listed in Table 4 below. Also, about 27000 Pa of xenon was filled in the tube. For each lamp, the arc tube was contained in the evacuated envelope and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 550° C. or more when operating the lamp at 50% of its rated lamp power. No sleeve was provided. Three samples were prepared for each lamp. Observation was made to see whether an arc bent occurred or not for three samples of identical lamp configuration. The results are shown in Table 4 in which mark ‘◯’ denotes no arc bent occurred in any of the three samples, mark ‘Δ’ denotes arc bent occurred in only one or two of the three samples, and mark ‘X’ denotes arc bent occurred in all of the three samples.

Also, measurements were made to obtain a width of color temperature change ΔT in response to ±10% variation in the source voltage. The condition range encircled by double-lines in Table 4 are found effective to reduce the color temperature change ΔT. Thus, it is known that the color temperature change in kept at a reduced level even when the arc bent occurs. Taking this into consideration, it is found possible to stabilize the arc and at the same time to reduce the color temperature change by suitably selecting the filling amount of the scandium iodide and the molar ratio of the sodium iodide to scandium iodide.

Lamps were fabricated in accordance with the second embodiment to have arc tubes of quartz which were dimensioned to have a maximum inside diameter of 18 mm, an average inside diameter of 14 mm, and a distance of 48 mm between the electrodes. In order to further investigate the relation between the arc bent and the filling amount of scandium iodide, the arc tubes were filled with scandium iodide at a varying mount between 1.15×10 −8 mol/ml and 5.73×10 −6 mol/ml and with sodium iodide at a varying molar ratio relative to scandium iodide from 0.0 to 28.4, as listed in Table 5 below. Also, the arc tube was filled with about 2.15×10 −6 mol/ml of mercury and about 6700 Pa of argon was filled in the tube. For example lamp, the arc tube was contained in the evacuated envelope and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 550° C. or more when operating the lamp at 50% of its rated lamp power. No sleeve was provided. Three samples were prepared for each lamp. Observation was made to see whether an arc bent occurred or not for three samples of identical lamp configuration. The results are shown in Table 5 in which the same marks as in Table 4 are utilized for evaluation of the occurrence of the arc bent.

Also, measurements were made to obtain a width of color temperature change ΔT in response to ±10% variation in the source voltage. The condition range encircled by double-lines in Table 5 are found effective to reduce the color temperature change ΔT. Thus, it is known that the color temperature change is kept at a reduced level even when the arc bent occurs. Taking this into consideration, it is found possible to stabilize the arc and at the same time to reduce the color temperature change by suitably selecting the filling amount of the scandium iodide and the molar ratio of the sodium iodide to scandium iodide.

A lamp was fabricated in accordance with the first embodiment to have the arc tube of quartz which was dimensioned to have an inside diameter of 8 mm, and a distance of 80 mm between the electrodes. The arc tube was filled with 2.32×10 −8 mol/ml of sodium iodide, 2.04×10 −8 mol/ml of scandium iodide (molar ratio of sodium iodide to scandium iodide is about 11.4), 1.02×10 −5 mol/ml of cesium iodide, and about 27000 Pa of xenon. The arc tube was contained in the evacuated envelope and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 586° C. when operating the lamp at 50% of its rated lamp power. No sleeve was provided.

A lamp was fabricated in accordance with the first embodiment to have the arc tube of quartz which was dimensioned to have an inside diameter of 8 mm, and a distance of 80 mm between the electrodes. The arc tube was filled with 2.32×10 −5 mol/ml of sodium iodide, 2.04×10 −8 mol/ml of scandium iodide (molar ratio of sodium iodide to scandium iodide is about 11.4), 2.50×10 −5 mol/ml of mercury, and about 6700 Pa of argon. The arc tube was contained in the evacuated envelope and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 569° C. when operating the lamp at 50% of its rated lamp power. No sleeve was provided, and the envelope was coated with a phosphor.

A lamp was fabricated in accordance with the second embodiment to have the arc tube of quartz which was dimensioned to have a maximum inside diameter of 18 mm, an average inside diameter of 14 mm and a distance of 48 mm between the electrodes. The arc tube was filled with 1.35×10 −5 mol/ml of sodium iodide, 1.15×10 −6 mol/ml of scandium iodide, 2.14×10 −5 mol/ml of mercury, and about 6700 Pa of argon. The arc tube was contained in the evacuated envelope and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 552° C. when operating the lamp at 50% of its rated lamp power. No sleeve was provided.

A lamp was fabricated in accordance with the second embodiment to have the arc tube of quartz which was dimensioned to have a maximum inside diameter of 18 mm, an average inside diameter of 14 mm and a distance of 48 mm between the electrodes. The arc tube was filled with 1.35×10 −5 mol/ml of sodium iodide, 1.15×10 −6 mol/ml of scandium iodide, 1.53×10 −5 mol/ml of mercury, and about 6700 Pa of argon. The arc tube was contained in the envelope filled with about 47000 Pa of nitrogen and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 551° C. when operating the lamp at 50% of its rated lamp power. No sleeve was provided.

For the lamps of Examples 24 to 27, measurements were made to obtain a width of color temperature change ΔT in response to ±10% variation in the source voltage. The results are shown in Table 6 below.

As seen in Table 6, the lamps of Examples 24 to 27 are found to show only reduced color temperature change ΔT. Particularly, the lamp of Examples 24 and 25 show a remarkably reduced color temperature change.

A lamp was fabricated in accordance with the first embodiment to have the arc tube of quartz which was dimensioned to have an inside diameter of 8 mm, and a distance of 80 mm between the electrodes. The arc tube was filled with 2.32×10 −5 mol/ml of sodium iodide, 2.04×10 −6 mol/ml of scandium iodide (molar radio of sodium iodide to scandium iodide is about 11.4), 1.20×10 −5 mol/ml of cesium iodide, and about 27000 Pa of xenon. The arc tube was contained in the evacuated envelope and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 550° C. or more when operating the lamp of 50% of its rated lamp power. No sleeve was provided.

A lamp was fabricated in accordance with the first embodiment to have the arc tube of quartz which was dimensioned to have an inside diameter of 8 mm, and a distance of 80 mm between the electrodes. The arc tube was filled with 2.32×10 −5 mol/ml of sodium iodide, 2.04×10 −6 mol/ml of scandium iodide (molar ratio of sodium iodide to scandium iodide is about 11.4), 2.50×10 −5 mol/ml of mercury, and about 6700 Pa of argon. The arc tube was contained in the evacuated envelope and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 550° C. or more when operating the lamp at 50% of its rated lamp power. No sleeve was provided.

A lamp was fabricated in accordance with the first embodiment to have the arc tube of quartz which was dimensioned to have an inside diameter of 8 mm, and a distance of 80 mm between the electrodes. The arc tube was filled with 2.32×10 −5 mol/ml of sodium iodide, 2.04×10 −8 mol/ml of scandium iodide (molar ratio of sodium iodide to scandium iodide is about 11.4), and about 27000 Pa of xenon. The arc tube was contained in the evacuated envelope and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 550° C. or more when operating the lamp at 50% of its rated lamp power. No sleeve was provided.

For the lamps of Examples 28 to 30, measurements were made to obtain luminous flux (lm), luminous efficiency (lm/W), color temperature (Tc (K)), cooler temperature change (ΔT), cooler rendering index (Ra), coldest spot temperature (CST). The results are shown in Table 7 below, in which source voltage ratio (%) is a ratio of the source voltage relative to the voltage for operating the lamp at 100% of the rated lamp power, and the luminous flux ratio (%) is a ratio of the luminous flux to that obtained at 100% rated lamp power. The color temperature change (ΔT) denotes a value relative to the color temperature obtained at 100% rated lamp power.

As seen from Table 7, the lamps of Examples 28 to 30 exhibit reduced color temperature change (ΔT) against the varying lamp power as well as against the varying source voltage. The lamp of Example 28 in which the arc tube additionally contain cesium iodide has a superior effect of reducing the color temperature change as compared to the lamp of Example 30 in which no cesium iodide is contained in the arc tube. From this, it is found that the addition of cesium iodide is responsible for providing a wide range in which the color temperature change is kept reduced, advantageous for dimming the lamp without causing no substantial color change. Also, it is noted that the lamp of Example 29 exhibits the reduced color temperature change against varying lamp power, irrespective of the fact that the arc tube additionally contain mercury. Further, it is confirmed that when the envelope of Example 29 is coated with the phosphor as is made in Example 25, the color temperature change against the varying lamp power can be still reduced.

A lamp was fabricated in accordance with the second embodiment to have the arc tube of quartz which was dimensioned to have a maximum inside diameter of 18 mm, an average inside diameter of 14 mm, and a distance of 48 mm between the electrodes. The arc tube was filled with 1.35×10 −5 mol/ml of sodium iodide, 1.5×10 −6 mol/ml of scandium iodide, 2.14×10 −5 mol/ml of mercury, and about 6700 Pa of argon. The arc tube was contained in the evacuated envelope and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 550° C. or more when operating the lamp at 50% of its rated lamp power. No sleeve was provided.

A lamp was fabricated in accordance with the second embodiment to have the arc tube of quartz which was dimensioned to have a maximum inside diameter of 18 mm, an average inside diameter of 14 mm, and a distance of 48 mm between the electrodes. The arc tube was filled with 1.35×10 −5 mol/ml of sodium iodide, 1.15×10 −6 mol/ml of scandium iodide, 1.53×10 −5 mol/ml of mercury, and about 6700 Pa of argon. The arc tube was contained in the envelope filled with about 47000 Pa of nitrogen, and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 550° C. or more when operating the lamp at 50% of its rated lamp power. No sleeve was provided, and the envelope was coated with the phosphor. The lamp of Example 32 differs from the lamp of Example 31 only in that the envelope was filled with nitrogen and was coated with the phosphor.

A lamp was fabricated in accordance with the second embodiment to have the arc tube of quartz which was dimensioned to have a maximum inside diameter of 18 mm, an average inside diameter of 14 mm, and a distance of 48 mm between the electrodes. The arc tube was filled with 1.35×10 −5 mol/ml of sodium iodide, 1.15×10 −6 mol/ml of scandium iodide, 2.14×10 −5 mol/ml of mercury, and about 6700 Pa of argon. The arc tube was contained in the envelope filled with about 47000 Pa of nitrogen, and was coated with the heat insulator layer of zirconium oxide to give the coldest spot temperature of 550° C. or more than operating the lamp at 50% of its rated lamp power. No sleeve was provided. The lamp of Example 33 differs from the lamp of Example 31 only in the provision of nitrogen filled in the envelope.

For the lamps of Examples 31 to 33, like measurements as made for Examples 28 to 30 were done. The results are shown in Table 8 below in which the source voltage ratio (%) for Example 31 and 32 denotes a ratio of the source voltage relative to 200 V, the source voltage ratio (%) for Example 33 denotes a ratio of the source voltage relative to the voltage for operating the lamp at 100% of the rated lamp power, and the luminous flux ratio (%) is a ratio of the luminous flux to that obtained at 100 V source voltage.

Considering the results of Example 31 in which the envelope is not coated with the phosphor and the results of Example 32 in which the envelope is coated with the phosphor (emitting red light), both Examples show reduced color temperature change responsible for superior dimming characteristics although the phosphor coating can slightly lower the color temperature. Comparing the results of Example 31 having the evacuated envelope with the results of Example 33 having the envelope filled with nitrogen gas, it is confirmed that the lamp of Example 33 is also effective to reduce the color temperature change and is advantageous for making the dimmer control without causing substantial change in color.

As illustrated in FIGS. 14 and 15, the envelope has its inner surface coated with an infrared radiation reflecting layer 14 and 14 A respectively. As illustrated by way of example in FIG. 14, the arc tube is filled with mercury M as the filler F. As shown in FIGS. 15 and 16, the envelope has its inner surface coated with a phosphor layer 12 A and 12 respectively. As shown in FIG. 17, the sleeve 40 has its inner surface coated with an infrared radiation reflecting layer 44 .

Although in the above Examples, metal iodides are utilized as metal halides, the present invention is not limited to the metal iodides and should be equally applicable to metal bromides. Also, either when the lamp is operated at a horizontal position where the electrodes are spaced horizontally or at a vertical position where the electrodes are spaced vertically, the like results were obtained as demonstrated in the above Examples. Further, the like results were obtained to the lamps with the arc tubes having dimensions different from Examples and having rate gases of different filling pressures.