JPH11176378A - High pressure discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high pressure discharge lamp, capable of restricting shell-shaped cracking at a metal foil sealing portion even when light-on and light-off are repeated. SOLUTION: A lamp 10 has a pair of electrodes 14, 15 arranged in a silica glass luminous tube 12, an electrode rod 18 welded to a metal foil 20 in a metal foil sealing portion 17 and mercury and rare gas filled therein. The filling amount M of mercury, the temperature T of the electrode rod 18 on the metal foil 20 in stable operation, the diameter ϕ of the electrode rod 18 and the thickness (t) of the metal foil sealing portion 17 are satisfied with conditions 1-3, more preferably with conditions 4, 5: the condition 1; 70 (mg/cc)<=M<=150(mg/cc), the condition 2; (1.67×M+700) degrees C<=T<=1100 degrees C, the condition 3; ϕ/t<=0.15, the condition 4; L×ϕ/1 (mm<2> /A)>=0.05 (mm<2> /A) and the condition 5; L×ϕ (mm<2> )<=1 (mm<2> ), where the overlapping length of the electrode rod 18 is L.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short arc type high pressure discharge lamp such as a metal halide lamp or a high pressure mercury lamp having an airtight sealing structure in which a metal foil is embedded at the end of an arc tube.

[0002]

2. Description of the Related Art In recent years, a metal halide lamp, which is a short arc type high pressure discharge lamp having good color rendering properties, is often used as a projection light source mounted on a presentation device such as a projector or an overhead projector. An example of a DC lighting type metal halide lamp will be described with reference to FIGS. 1 and 2. A metal halide lamp 10 includes a substantially spherical arc tube 12 made of quartz glass, and a cathode 14 and an anode 15 are provided in the arc tube 12. Are arranged to face each other. Further, a metal foil sealing portion 17 is formed at each end of the arc tube 12, and a metal foil 20 usually made of molybdenum is embedded in the metal foil sealing portion 17 by a pinch seal. The base end of the electrode rod 18 having the tip of each of the anode 14 and the anode 15 is welded and electrically connected to one end of the metal foil 20 in a state of being disposed on the end.

However, in such a metal halide lamp, if it is used in a mode in which lighting and extinguishing are repeated,
In the metal foil sealing portion 17, a shell-like crack like a shell pattern is generated in a glass portion around a portion where the electrode rod 18 of the metal foil 20 is welded, and a phenomenon of gradually growing occurs.

[0004] When the high-pressure discharge lamp is repeatedly turned on and off, the shell-shaped cracks expand and contract in the metal foil sealing portion 17 due to repetition of heating and cooling. Since the glass forming the sealing portion 17 is different from the metal foil 20 embedded in the sealing portion 17 and the electrode rod 18 welded thereto, thermal strain is gradually accumulated in the glass portion forming the interface with the metal. As a result, the gap 25 between the glass and the metal foil 20 gradually increases, so-called "foil floating" occurs. Further, the gap 25 grows outward at every expansion and contraction, and It is thought that it is formed so as to extend from the outer edge of 20 to the outside.

When the shell-like crack grows and reaches the outer surface of the glass of the metal foil sealing portion 17, the hermetic sealing of the metal foil sealing portion 17 is broken, and the function as a high-pressure discharge lamp is lost. The occurrence of such shell-like cracks is remarkable in a DC lighting type high-pressure discharge lamp, particularly in the metal foil sealing portion on the anode 15 side, because the temperature of the anode 15 becomes higher than that of the cathode 14 during lighting. Because.

The occurrence of shell-like cracks in such a high-pressure discharge lamp is described in Japanese Patent Application Laid-Open No. 9-185953. And, in the invention of the publication,
In order to prevent the occurrence of shell-like cracks, the temperature of the surface of the metal foil sealing portion during operation is regulated, and the shape of the metal foil and the embedding depth of the metal foil are specified. However, such a conventional technique has a problem that the occurrence of shell-like cracks cannot always be sufficiently prevented.

[0007]

SUMMARY OF THE INVENTION The present invention has been made as a result of studying conditions for the occurrence of shell-like cracks in a metal foil sealing portion of a high-pressure discharge lamp.
Even when used in a mode where lighting and extinguishing are repeated,
An object of the present invention is to provide a high-pressure discharge lamp capable of reliably suppressing the occurrence of shell-like cracks in a metal foil sealing portion and having a long service life.

[0008]

A high-pressure discharge lamp according to the present invention has a metal foil sealed in which a pair of electrodes are arranged opposite to each other in an arc tube made of quartz glass, and a metal foil is embedded at an end of the arc tube. Part is formed, a base end of an electrode rod having the electrode at the tip is welded to one end of the metal foil, and at least mercury and a rare gas are sealed in the arc tube. The amount of mercury per unit volume of the arc tube is M (mg / cc), the temperature of the electrode rod on one end of the metal foil during stable operation is T (° C.), and the diameter of the electrode rod is φ.
(Mm), where t (mm) is the thickness of the glass where the metal foil is located in the metal foil sealing portion, all of the following conditions (1) to (3) are satisfied.

Expression (3) Condition (1) 70 (mg / cc) ≦ M ≦ 150 (mg / cc) Condition (2) (1.67 × M + 700) (° C.) ≦ T ≦ 1100 (° C.) Condition (3) φ / t ≦ 0.17 In particular, when the pair of electrodes arranged in the arc tube are an anode and a cathode, it is preferable that the condition (3) is satisfied at least in the metal foil sealing portion related to the anode.

According to the high-pressure discharge lamp which satisfies the above conditions, even when it is used in a mode where lighting and extinguishing are repeated, basically, the occurrence of shell-like cracks in the metal foil sealing portion is sufficiently suppressed. Therefore, a long service life can be obtained.

The high-pressure discharge lamp according to the present invention further has a length L (m)
m ² ), when the lamp current during stable operation is I (A), it is preferable that both of the following conditions (4) and (5) are satisfied.

Condition (4) L × φ / I (mm ² /A)≧0.05 (mm ² / A) Condition (5) L × φ (mm ² ) ≦ 1 (mm ² ) Especially in the arc tube In the case where the pair of electrodes arranged in the above is an anode and a cathode, it is preferable that both of the conditions (4) and (5) are satisfied at least in the metal foil sealing portion related to the anode.

According to the high-pressure discharge lamp satisfying the above conditions, the occurrence of shell-like cracks in the metal foil sealing portion can be more reliably suppressed even when the lamp is used in a mode where lighting and extinguishing are repeated. it can.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The high-pressure discharge lamp of the present invention will be described below in detail. FIG. 1 is a cross-sectional view for explaining an example of the configuration of a DC lighting type metal halide lamp 10 according to the present invention, and FIG. 2 is a cross-sectional view for explaining a metal foil sealing portion of FIG. In the drawing, reference numeral 12 denotes an arc tube having a substantially spherical discharge space portion made of quartz glass, and reference numerals 14 and 15 denote a cathode and an anode, respectively, which oppose each other in the arc tube 12.
Reference numeral 7 denotes a metal foil sealing portion formed at each end of the arc tube 12 by pinch sealing, reference numeral 20 denotes a metal foil usually made of molybdenum embedded in the metal foil sealing portion 17, and includes a cathode 14 and an anode. The base end of the tungsten electrode rod 18 having each of the 15 at the tip is welded in a state where it is arranged so as to overlap the one end of the metal foil 20 to be electrically connected. 22 is at the other end of the metal foil 20;
An external lead rod whose base end is welded and electrically connected. Then, mercury, a rare gas, and other sealed materials are sealed in the arc tube 12 as needed.

The metal halide lamp 1 having such a configuration
0, in the present invention, the following conditions (1) to
It is configured so that all of (3) is satisfied.

Condition (1) 70 (mg / cc) ≦ M ≦ 150 (mg / cc) Condition (2) (1.67 × M + 700) (° C.) ≦ T ≦ 1100 (° C.) Condition (3) φ / t ≦ 0.17 where M is the arc tube 12 sealed in the arc tube 12
(Unit: mg / cc, hereinafter referred to as “mercury filling amount”), T is the temperature of a point P on one end of the metal foil 20 of the electrode rod 18 during stable operation of the lamp (T). Unit: ° C., hereinafter referred to as “electrode bar temperature”), φ is the diameter (unit: mm) of the electrode bar 18, and t is the position of the metal foil 20 in the metal foil sealing portion 17 of the arc tube 12. It is the thickness of glass (unit: mm, hereinafter referred to as “thickness of metal foil sealing portion”).

In practice, the value of the diameter φ of the electrode rod 18 is 0.3 to 0.3.
1.0 mm, the value of the thickness t of the metal foil sealing portion is 3.5 to 6 m
m, the overlap length L of the electrode rod 18 on one end of the metal foil 20 (hereinafter referred to as “overlap length of the electrode rod”) L is 0.5 to 2.0 mm, preferably 0.5 to 1. 5 mm. The rated power of the lamp is 100-400W,
During a stable operation, the lamp voltage is 30 to 100 V, and the lamp current is 1.0 to 10 A.

In the above, the temperature T of the electrode rod 18 is a value measured by a radiation thermometer utilizing the principle that the intensity of radiant energy per unit area of a high-temperature object depends on the temperature of the object. Specifically, of the light radiated from the measured point P of the electrode rod 18 during the stable operation, the light intensity having a wavelength of 1.35 ± 0.05 μm is measured by a germanium sensor, and the loss of the measuring optical system, etc. From the energy intensity obtained by correcting the error due to The light of this measurement wavelength has a high transmittance in quartz glass and a small temperature dependency, and a small temperature dependency in the emissivity of tungsten. In addition, when the thickness t of the metal foil sealing portion 17 is not uniform, the minimum distance between the outer surfaces of the glass in a direction perpendicular to the metal foil 20 in the glass constituting the portion where the metal foil 20 is located is set. A value defined as a value.

Next, the technical contents of the above conditions will be described. Condition (1) 70 (mg / cc) ≦ M ≦ 150 (mg / cc) This condition defines the amount of enclosed mercury M. If the value of the amount of charged mercury M is less than 70 mg / cc, the function of a high-pressure discharge lamp cannot be sufficiently exhibited because the amount of charged mercury is too small, resulting in low luminous efficiency.
On the other hand, if the value of the amount of enclosed mercury M exceeds 150 mg / cc, there is a possibility that the amount of enclosed mercury becomes excessive and a part of the amount of mercury does not evaporate. May cause cracks.
Thus, the condition (1) is a so-called basic condition for a high-pressure discharge lamp.

Condition (2) (1.67 × M + 700) (° C.) ≦ T ≦ 1100 (° C.) This condition is satisfied when the metal foil 2 is in a stable operation of the lamp.
The temperature T of the electrode rod 18 (point P) welded to one end of the zero is defined. If the temperature T is too low, there is a possibility that all of the mercury in the arc tube 12 will not evaporate reliably.
This may cause cracks in the surface. On the other hand, when the temperature T exceeds 1100 ° C., shell-like cracks occur early in the lamp.

FIG. 3 shows that a plurality of sample lamps composed of the metal halide lamps having the configuration shown in FIG. 1 are turned on for 5 minutes while the temperature T during stable operation is changed by changing the lighting power. The relationship between the temperature T and the average number of blinks obtained as a result of performing a blink test in which the light is turned off repeatedly for 5 minutes and examining the average number of blinks until the occurrence of shell-like cracks in the metal foil sealing portion 17 is observed. It is a curve figure.

The sample lamp subjected to the flashing test has a distance d between electrodes of 1.5 mm in a substantially spherical arc tube 12 made of quartz glass having a maximum outer diameter of 13 mm and a thickness of 1.5 mm.
In this state, a cathode 14 and an anode 15 are provided, and the inner volume of the arc tube 12 is 0.36 cc.
6 mg, argon 4 × 10 ⁴ Pa, and appropriate amounts of dysprosium iodide and cesium bromide are enclosed. Further, the diameter φ of the electrode rod 18 is 0.5 mm, the overlap length L of the electrode rod 18 is 1.5 mm, the thickness t of the metal foil sealing portion 17 is 4.9 mm, the rated power is 250 W, and the lamp during stable operation. The voltage is about 55V and the lamp current is about 4.55A. Therefore, in this metal halide lamp, the amount of enclosed mercury M = 100 mg / cc, φ / t = 0.1
0, L × φ / I = 0.16 mm ² / A, L × φ = 0.7
5 mm ² .

As can be understood from the results shown in FIG. 3, when the temperature T is 1100 ° C. or less, an average number of blinks of about 2000 or more is obtained. On the other hand, when the temperature T exceeds 1100 ° C. It is understood that the service life of the lamp is shortened due to the early occurrence of shell-like cracks.

Condition (3) φ / t ≦ 0.17 This condition is the ratio of the diameter φ of the electrode rod 18 to the thickness t of the metal foil sealing portion 17 (φ / t, hereinafter referred to as “electrode rod thickness ratio”).
That. ). When the electrode rod thickness ratio φ / t exceeds 0.17, the electrode rod 18 is formed between the electrode rod 18 and the metal foil 20 because the diameter φ of the electrode rod 18 is relatively large. The gap becomes large, and as a result, large distortion occurs due to repeated expansion and contraction due to turning on and off of the lamp, so that a shell-like crack is easily generated.

FIG. 4 shows the result of the same blinking test using the same sample lamp as that described above except that the electrode rod thickness ratio φ / t was variously changed. FIG. 4 is a curve diagram showing a relationship between / t and the average number of blinks.
In this blinking test, the electric power was adjusted so that the temperature T became 1100 ° C., and the diameter φ of the electrode rod 18 was 0.35 to 0.35.
The thickness t was changed in the range of 1.0 mm, and the thickness t of the metal foil sealing portion 17 was changed in the range of 3.5 to 5.5 mm.

As can be understood from the results shown in FIG. 4, if the thickness ratio φ / t of the electrode rod 18 is in the range of 0.17 or less, the average number of blinks is about 2000 or more.
When it exceeds 17, it is understood that the service life of the lamp is shortened because shell-like cracks occur early.

As will be understood from the above description, according to the present invention, when all of the conditions (1) to (3) are satisfied, even if the number of times of blinking becomes about 2000 or more, the shell-like crack is generated. Does not occur, and thus a high-pressure discharge lamp with a long service life can be obtained.

In the high pressure discharge lamp of the present invention, in addition to the above conditions (1) to (3), the overlapping length L of the electrode rod 18 on one end of the metal foil 20 and the diameter φ of the electrode rod 18 It is preferable that both of the following conditions (4) and (5) are satisfied with respect to the overlapping area (that is, the connection area) of the two represented by the product (L × φ). In this case, it is possible to more reliably obtain a high-pressure discharge lamp in which the occurrence of shell-like cracks in the metal foil sealing portion is suppressed.

Condition (4) L × φ / I (mm ² /A)≧0.05 (mm ² / A) Condition (5) L × φ (mm ² ) ≦ 1 (mm ² )

The condition (4) defines the lower limit of the overlapping area of the electrode rod 18 and the metal foil 20 per unit current value in relation to the rated current value. Because the connection area between the rod 18 and the metal foil 20 is small, it is difficult to bring the lamp into a sufficient operating state, or the temperature T tends to be excessive due to resistance heating at the connection portion. Become.

Condition (5) defines the upper limit of the overlapping area between the electrode rod 18 and the metal foil 20. If the overlapping area is excessive, the expansion and contraction due to the turning on and off of the lamp is repeated. As a result, large distortion is caused, and as a result, shell-like cracks are easily generated.

FIG. 5 shows the result of the same blinking test using the same sample lamp as described above except that the overlapping area between the electrode rod 18 and the metal foil 20 was changed in various ways. FIG. 4 is a curve diagram showing a relationship between (L × φ) and the average number of blinks. In this blinking test, the temperature T is 1
The power is adjusted to 100 ° C.
7 has a thickness t of 5.0 mm, the diameter φ of the electrode rod 18 is changed in the range of 0.35 to 1.0 mm, and
The overlap length L of 8 was changed in the range of 0.5 to 3 mm.

As can be understood from the results shown in FIG. 5, by setting the overlapping area L × φ of the electrode rods to 1 mm ² or less, the average number of flashes of the high-pressure discharge lamp can be reduced to about 20.
It can be more than 00 times, but if not, it is understood that the service life of the lamp is shortened due to the early occurrence of shell-like cracks.

In a DC lighting high pressure discharge lamp in which a pair of electrodes are a cathode and an anode, the condition (2) is particularly applied to the metal foil sealing portion relating to the anode and the electrode rod and metal foil in the metal foil sealing portion. ) To (5) are preferably satisfied. This is because shell-shaped cracks are more remarkably generated and grown in the metal foil sealing portion of the anode than in the metal foil sealing portion of the cathode.

[0031]

According to the high-pressure discharge lamp of the present invention, by satisfying the conditions (1) to (3), even when it is used in a mode in which lighting and extinguishing are repeated, the metal foil is basically sealed. The generation of shell-like cracks in the part can be reliably suppressed, and thus a long service life can be obtained. Further, by further satisfying the conditions (4) and (5),
The occurrence of shell-like cracks in the metal foil sealing portion can be suppressed more reliably.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view showing a configuration of an example of a DC lighting type metal halide lamp according to the present invention.

FIG. 2 is an explanatory sectional view of a metal foil sealing portion of FIG. 1;

FIG. 3 is a curve diagram showing a relationship between a temperature T of an electrode bar on one end of a metal foil and an average number of blinks.

FIG. 4 is a curve diagram showing a relationship between a ratio φ / t of a diameter φ of an electrode rod to a thickness t of a metal foil sealing portion and an average number of blinks.

FIG. 5 shows the overlapping area (L ×
FIG. 4 is a curve diagram showing the relationship between (φ) and the average number of blinks.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Metal halide lamp 12 Arc tube 14 Cathode 15 Anode 17 Metal foil sealing part 18 Electrode rod 20 Metal foil 22 External lead rod 25 Gap

Claims (4)

[Claims] 1. An electrode having a pair of electrodes opposed to each other in an arc tube made of quartz glass, a metal foil sealing portion in which a metal foil is embedded at an end of the arc tube, and an electrode having the electrode at a tip end. A high-pressure discharge lamp in which a base end portion of a rod is welded to one end portion of the metal foil and at least mercury and a rare gas are sealed in the arc tube, wherein the amount of mercury per unit volume of the arc tube is determined. M (mg / c
c) The temperature of the electrode bar on one end of the metal foil during stable operation is T (° C.), the diameter of the electrode bar is φ (mm), and the thickness of the glass at the position where the metal foil is located in the metal foil sealing portion. Where t is (mm), all of the following conditions (1) to (3) are satisfied: Expression (1) Condition (1) 70 (mg / cc) ≦ M ≦ 150 (mg / cc) Condition (2) (1.67 × M + 700) (° C.) ≦ T ≦ 1100 (° C.) Condition (3) φ / t ≦ 0.17 2. When the pair of electrodes arranged in the arc tube are an anode and a cathode, the conditions (2) and (3) are satisfied at least in a metal foil sealing portion related to the anode. The high-pressure discharge lamp according to claim 1, wherein 3. The length of the overlapping portion of the electrode rods in the metal foil is L (mm ² ), and the lamp current during stable operation is I
The high-pressure discharge lamp according to claim 1, wherein when (A) is satisfied, both of the following conditions (4) and (5) are satisfied. Condition (4) L × φ / I (mm ² /A)≧0.05 (mm ² / A) Condition (5) L × φ (mm ² ) ≦ 1 (mm ² ) 4. When a pair of electrodes arranged in an arc tube are an anode and a cathode, at least the conditions (4) and (5) are satisfied at least in the metal foil sealing portion related to the anode. The high-pressure discharge lamp according to claim 3, wherein: