JP4239579B2 - Short arc type high pressure mercury lamp - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultra high pressure mercury lamp, and more particularly to a short arc type ultra high pressure mercury lamp used as a backlight of a projector apparatus such as a liquid crystal display device or a DLP (digital light processor) using a DMD (digital mirror device).
[0002]
[Prior art]
Projection-type projector devices are required to illuminate an image with a uniform and sufficient color rendering property on a rectangular screen. For this reason, a metal halide lamp in which mercury or a metal halide is enclosed as a light source Short arc discharge lamps such as xenon lamps or mercury lamps are used.
Since the liquid crystal projector according to the technical field is not so popular that it can be installed in each conference room, it is often carried around, and reduction in size and weight is an important issue. For this reason, liquid crystal panels for liquid crystal projectors have been miniaturized year by year, and accordingly, further miniaturization of the light source is required in order to efficiently focus light on the miniaturized liquid crystal panel. Yes.
To achieve miniaturization of the light source, shortening the distance between the electrodes (hereinafter simply referred to as the arc length) is the most optically effective means. The voltage drops. If a predetermined lamp power is to be turned on when the lamp voltage is low, the lamp current must be increased. However, since the lighting device becomes large in order to increase the lamp current, it deviates from the concept of downsizing the liquid crystal projector device. Further, the increase in lamp current leads to expeditious electrode consumption, leading to early blackening of the tube wall. As a result, the lamp life is shortened and the demand from the market cannot be satisfied. For these reasons, simply shortening the arc length cannot sufficiently meet market needs.
[0003]
Therefore, in order to shorten the arc length without reducing the lamp voltage, means for increasing the arc impedance, in other words, increasing the pressure of the discharge medium during lighting, has been adopted. According to this, it is said that the color rendering properties can be improved while improving the illuminance maintenance factor. Recently, a high-pressure mercury lamp in which a large amount of mercury is enclosed so that the pressure during operation becomes 15 MPa or more. It has been suitably used.
[0004]
By the way, since the pressure in the discharge vessel becomes extremely high when the above-described high-pressure mercury lamp is lit, quartz glass having a high strength is suitably employed as the material of the discharge vessel. In the sealing tube portion extending on both sides of the arc tube portion, it is necessary to sufficiently and firmly adhere the quartz glass and the electrode rod constituting the sealing tube portion. In the state, a so-called shrink seal method, in which the adhesion of the sealing tube portion is improved by gradually shrinking the thick quartz glass, is preferably adopted as realizing high pressure resistance.
[0005]
Thus, when the electrode rod and the quartz glass of the sealing tube portion are in direct contact with each other, the quartz glass constituting the electrode rod and the sealing tube portion at the time of the above-described shrink sealing process or lighting operation after forming the lamp. May cause cracks in the quartz glass of the sealing tube portion, resulting in a decrease in pressure resistance performance inside the discharge vessel. In view of such a problem, for example, according to the technique described in Japanese Patent No. 3204189, a short arc type ultra-high pressure mercury lamp in which a coil is wound in a portion embedded in a sealing portion of an electrode rod is used. Thus, sufficient thermal processing can be realized without generating a crack between the electrode and the quartz glass. Furthermore, by not exposing the coil inside the arc tube, it is possible to prevent undesired discharge immediately after the start of lighting even if the electrode distance is minimal, and as a result, a short arc type high pressure mercury lamp having high pressure resistance is provided. it can.
[0006]
Further, as a short arc type discharge lamp in which a coil is wound around an electrode rod, in addition to the one described in the above publication, for example, JP-A-3-163744, US Pat. No. 5,387,839, etc. The ones described are known. In these publications, a coil is wound around the base end portion of the electrode to prevent the electrode from being decentered when forming the hermetic seal portion, and to further facilitate manufacture.
[0007]
[Patent Document 1]
Japanese Patent No. 3204189 [Patent Document 2]
Japanese Patent Laid-Open No. 3-163744 [Patent Document 3]
US Pat. No. 5,387,839 Publication
[Problems to be solved by the invention]
As described above, a lamp having a structure in which a coil-shaped metal member is inserted into an electrode rod and embedded in a discharge vessel sealing tube portion is conventionally known, and such a structure is preferably employed. In mercury lamps, a higher lighting pressure has recently been required, and sometimes the pressure inside the discharge vessel becomes a high lighting pressure of 16 MPa or higher. It turned out that the probability that a part will be damaged becomes high.
[0009]
This is a portion where the glass constituting the sealing tube portion and the metal member are in contact with each other in a high temperature state (about 1300 K) when the lamp is lit, and the impure metal component contained in the metal member causes the sealing tube portion to It is presumed that the silica glass melts in the state of being ionized into the constituent quartz glass, and the quartz glass is crystallized and weakened with the metal ions as nuclei. In particular, when a coiled metal member is interposed between the electrode rod and the sealing tube part, the surface area of the metal member is large, so there is a large amount of impure metal. Even if the lamp is easily fragile and the lighting time of the lamp is relatively short, the pressure resistance of the sealed tube portion is lowered. When the mercury vapor pressure in the arc tube portion is 16 MPa or more, sometimes the sealing tube portion is damaged.
[0010]
The present invention solves the above-mentioned problem that the pressure resistance decreases as the lamp lighting time increases, and a short arc type high-pressure mercury lamp capable of maintaining a high pressure resistance and realizing a long service life. It is to provide.
[0011]
[Means for Solving the Problems]
The present invention comprises a discharge vessel made of quartz glass and having an arc tube portion and a sealing tube portion connected to the arc tube portion, and a pair of electrodes are disposed oppositely in the arc tube portion, In a short arc type high-pressure mercury lamp in which 0.15 mg / mm ³ or more of mercury is enclosed with respect to the internal volume of the discharge vessel, the proximal end portion of at least one of the electrodes is not exposed in the arc tube portion. The coil is inserted into a coil welded to the sealing tube, and the coil is made of tungsten having a purity of 99.99 mass% or more, and the concentration of potassium (K) is 10 mass ppm or less. And
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the short arc type high pressure mercury lamp of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory cross-sectional view showing an example of the configuration of a short arc type high-pressure mercury lamp (hereinafter also simply referred to as “lamp”) of the present invention. This short arc type high-pressure mercury lamp is of a direct current lighting type, and its discharge vessel 10 is made of quartz glass and extends outwardly from both ends of the arc tube portion 11 and the arc tube portion 11. It has the rod-shaped sealing pipe parts 12 and 13 provided in series.
[0013]
In the arc tube portion 11, on the tube axis of the discharge vessel 10, a cathode 14 and an anode 15 are disposed facing each other with the distance between the electrodes being, for example, 3.0 mm or less, and an electrode having the cathode 14 at the tip. A rod 16 (hereinafter referred to as a “cathode rod”) extends in one sealing tube portion 12 and is attached to the external lead rod 19 via a metal foil 18 that is airtightly embedded at the outer end portion of the sealing tube portion 12. Connected to form an airtight seal. The anode 15 has the same configuration. In the figure, reference numeral 17 denotes an anode bar. Hereinafter, the cathode bar (16) and the anode bar (17) are collectively referred to as an “electrode bar” in the subsequent stage.
The arc tube 11 is filled with a sealing gas made of, for example, 0.15 mg / mm ³ or more of mercury and a rare gas such as argon. Thereby, a continuous spectrum of visible light having a wavelength of 380 to 780 nm can be emitted, and can be suitably used as a light source of a liquid crystal projector, for example.
[0014]
The coils 20 and 21 made of a refractory metal are welded integrally to the inner peripheral surfaces of the sealing tube portions 12 and 13 on the inner peripheral surfaces of the sealing tube portions 12 and 13, respectively. , 21 are respectively inserted into the base end portions 16A and 17A, and the electrode rods 16 and 17 are fixed with respect to the movement of the discharge vessel in the tube axis cross-sectional direction and substantially movable with respect to the movement in the axial direction. Is held in. Accordingly, the electrode can be arranged at a predetermined position with high positional accuracy, and can be freely expanded and contracted even if it is heated to a high temperature and thermally expanded during lamp operation.
[0015]
The coils 20 and 21 are not exposed in the discharge vessel, but are entirely embedded in the sealed tube portion. As a result, an undesired phenomenon in which an arc is generated between the electrodes 14 and 15 and the coil at a position facing the electrodes 14 and 15 does not occur.
[0016]
The materials of the coils 20 and 21 are made of a high-purity metal made of tungsten or molybdenum as a main component and containing such a metal component in a proportion of 99.99% by mass or more. Typical impurities contained in tungsten and molybdenum other than substances are metal elements such as potassium, magnesium, calcium, strontium, barium, iron, aluminum, and copper. In the coil according to the present invention, these substances are used. The total sum of impurities including other substances is less than 100 ppm by mass.
[0017]
Among the impurities described above, potassium is intercalated in the quartz glass in an ionized state, and tends to be a nucleus for crystallization.
According to the short arc type high-pressure mercury lamp according to the present invention, the coil fused to the quartz glass of the sealing tube portion is made of high-purity tungsten or high-purity molybdenum of 99.99% by mass or more. Even if the temperature of the sealing tube portion becomes high during the lighting operation, the absolute amount of impurities contained in the coil is small, so that the absolute amount of impurities eluted into the quartz glass constituting the sealing tube portion also decreases. Therefore, the existence probability of alkali metal ions and alkaline earth metal ions intervening in the quartz glass constituting the sealed tube portion becomes extremely small, and as a result, the promotion of crystallization of the quartz glass is suppressed, and the quartz glass The mechanical strength of the glass can be maintained at the same level as that at the beginning of lamp operation, and the sealing tube portion can be prevented from becoming weak. Accordingly, it is possible to prevent a decrease in the pressure strength of the sealed tube portion and to prolong the service life of the lamp.
Among these, potassium is preferably 10 ppm by mass or less, and particularly preferably less than 10 ppm by mass . When potassium exceeds 10 mass ppm , the quartz glass intervening in the vicinity of the metal foil crystallizes and becomes brittle, so that a phenomenon called “foil floating” is likely to occur, and this foil floating phenomenon occurs. In combination with this, the pressure-resistant strength of the sealed tube portion is significantly reduced.
[0018]
【Example】
The short arc type high pressure mercury lamp according to the present invention a number made in accordance with the configuration and the following specification of Figure 1, was carried out further cold withstand pressure test (and life test).
The specifications of the lamp according to the example used in this experimental example will be described below.
The discharge vessel (10) has a substantially oval shape made of quartz glass, has an inner volume of 116 mm ³ , and contains 11.3 kPa of argon gas and 0.20 mg / mm ^{3 of} mercury in the discharge space.
The outer diameter of the arc tube portion (11) is 11.5 mm, the inner diameter of the arc tube portion (11) is 5.0 mm, the length of the sealing tube portions (12) and (13) is 20 mm, and a metal foil made of molybdenum ( 18) is 15 mm long. The material of the used cathode (14) and the material of the anode (15) is tungsten, and the distance between the electrodes is 1.3 mm. The lamp has a lamp voltage of 82V and a rated power of 200W.
The total length of the coils (20) and (21) embedded in the sealing tube portion is 3.0 mm, and the wire diameter of the metal wires constituting the coils (20) and (21) is 0.1 mm.
[0019]
The material of the coils (20) and (21) was high-purity tungsten of 99.99% by mass or more, specifically 99.990% by mass to 99.999% by mass. It should be noted that potassium having the largest content ratio among the impurity substances contained in the high-purity tungsten was potassium, and the maximum value of the ratio was 10 ppm by mass. Moreover, the sum total of the content rate of an impurity including other impurities (for example, Fe, Al, Si, Ni etc.) was less than 100 mass ppm.
[0020]
<Comparative Example 1>
A number of short arc high-pressure mercury lamps according to conventional products having the same lamp specifications as those in the above examples were manufactured except that the purity of tungsten constituting the coil was not made 99.99 mass% or more. Tungsten at this time had an impurity ratio of 100 mass ppm or more and 1000 mass ppm or less, and its purity was specifically 99.96 mass% to 99.98 mass%.
[0021]
The 27 lamps according to the example and the 25 lamps according to the comparative example thus manufactured were continuously lit at a rated power of 200 W by horizontal lighting, and a cold pressure strength test was performed according to the following procedure to evaluate the pressure strength. Went.
[0022]
<Evaluation of pressure resistance>
About the lamp | ramp which concerns on the lamp | ramp which concerns on the Example mentioned above, and the comparative example, the discharge vessel (10) was cut | disconnected using the low speed cutter, and the sample piece was produced.
In addition, about the lamp | ramp which concerns on an Example, the lamp whose lighting time is 5 hours, 4 lamps whose lighting time is 250 hours, 4 lamps whose lighting time is 380 hours, and whose lighting time is 530 hours 6 lamps, 4 lamps with a lighting time of 770 hours, and 4 lamps with a lighting time of 1120 hours were prepared. As for the lamp according to the comparative example, 5 lamps with a lighting time of 1 hour, 5 lamps with a lighting time of 210 hours, 6 lamps with a lighting time of 350 hours, and a lamp with a lighting time of 530 hours 4 lamps and 5 lamps with a lighting time of 1060 hours were prepared.
A test piece was prepared by the above-described method using each of the lamps according to the above examples and comparative examples.
[0023]
As shown in FIG. 2, with respect to the prepared test piece, one end of the stainless steel tube 30 is inserted into the opening of the arc tube portion (11), and the outer periphery of the stainless steel tube 30 is filled with the epoxy adhesive 31. As a result, an airtight space S corresponding to the arc tube (11) of the discharge lamp was formed. In the figure, 32 is an alcohol tank, 33 is a pressure pump, 34 is a pressure gauge, 35 is a rotary pump, and 36 is a connection joint.
[0024]
Then, the alcohol vapor supplied from the alcohol tank 32 is injected from the other end of the stainless steel tube 30, and the pressure in the airtight space S is gradually increased at a rate of about 0.2 MPa / sec. The pressure when the manufactured discharge vessel was destroyed (hereinafter referred to as “cold pressure strength”) was measured with a pressure gauge 34.
Since the unlit lamp has no thermal distortion due to turning on and off, the destruction location is limited to the sealed tube portion, so the cold pressure strength of the location can be measured relatively easily. . Thus, since the lamp after lighting is thermally distorted in the arc tube portion, the broken portion is not limited to the sealed tube portion and is often broken at the arc tube portion. For this reason, valid data may not be acquired.
Therefore, the lamp after lighting was subjected to the distortion removal treatment at 1150 ° C. for 30 minutes in the atmosphere to eliminate the thermal distortion of the arc tube portion.
By this method, the broken portion could be limited to the sealed tube portion without breaking at the arc tube portion.
[0025]
FIG. 3 is a curve diagram showing the relationship between the lamp lighting time and the cold pressure strength by the above method. The horizontal axis is the lamp operating time (h), and the vertical axis is the cold pressure strength (MPa). In the figure, the cold pressure strength when the lamp is lit at each lighting time is indicated by a white circle for the example and a diamond for the comparative example. The curve is an approximate curve representing the relationship between the lamp lighting time and the example withstand voltage strength according to the example or the comparative example. The example is indicated by a solid line, and the comparative example is indicated by a one-dot broken line.
As shown in the figure, in the lamp according to the example, the cold pressure strength was higher than that of the lamp according to the comparative example, and it was confirmed that the difference increased as the lighting time increased. In the lamp according to the comparative example, when the lighting time exceeds 1000 hours, the cold pressure strength decreases to about 18 MPa. However, in the lamp according to the embodiment, the decrease in the cold pressure strength with the passage of the lighting time is smaller than that. Even lamps that were turned on for more than 1100 hours had an average cold pressure strength of 20 MPa or more, and it was confirmed that the cold pressure strength was improved by 150% compared to the conventional product.
[0026]
As a result of the above-mentioned cold pressure strength test, in the example according to the embodiment, the decrease in the cold pressure strength with the lapse of lighting time is slower than the lamp according to the comparative example, and the mechanical properties of the sealed tube portion from the initial stage of lamp lighting It is understood that the strength can be maintained more. Although the above-mentioned cold withstand pressure strength does not necessarily coincide with the withstand pressure strength at the time of lamp lighting operation, it can be suppressed that the cold withstand pressure strength of the sealing tube portion is reduced, that is, the sealing tube at the initial stage of lamp lighting. In other words, it is obvious that the pressure strength of the sealed tube portion during lamp operation can be improved.
[0027]
<Lamp lighting test>
Twenty lamps having the same specifications as in the above example were produced and lit continuously according to a rated input of 200 W with horizontal lighting. In addition, the purity of tungsten was 99.990 mass%-99.999 mass%, and all were 99.99 mass% or more. About these lamps, even if the lighting time exceeds 2000 hours, the sealed tube portion is not damaged, and the “floating foil” occurs because the quartz glass of the sealed tube portion peels off from the metal foil. The so-called phenomenon did not occur.
[0028]
In addition, 20 lamps having the same specifications as in the comparative example were produced and lit by the same method as in the lamp lighting test described above. In addition, the purity of tungsten was specifically 99.96 mass% to 99.98 mass%, and was less than 99.99 mass%. As a result of the test of the lamp according to the comparative example, in a certain lamp, when the lighting time is 1000 hours, a crack is generated in the sealed tube portion, and the discharge vessel is ruptured. For some lamps, the lighting time is 1300 hours. A leak occurred from the stop tube and it was not lit. Further, with respect to the other lamps, “foil floating” was confirmed after lighting for 1500 hours, and none of the lamps had sufficient reliability.
[0029]
【The invention's effect】
According to the short arc type high-pressure mercury lamp of the present invention, since the coil welded without being exposed in the arc tube portion is composed of high-purity tungsten of 99.99 mass% or more, the electrode rod becomes hot. In this case, the absolute amount of impurities eluted from the coil into the quartz glass constituting the sealed tube portion can be reduced, and the crystallization of the quartz glass can be prevented from being accelerated. The mechanical strength of the quartz glass is prevented from lowering, and the sealed tube portion can have a sufficient pressure resistance.
As a result, it is possible to suppress a decrease in pressure resistance due to the lighting time of the lamp, and it is possible to provide a short arc type high-pressure mercury lamp that can maintain a high pressure resistance and realize a long service life. .
In addition , since the coil is made of tungsten having a potassium (K) concentration of 10 mass ppm or less , crystallization of quartz glass can be avoided, and the so-called foil floating phenomenon of the metal foil embedded in the sealing tube portion can be avoided. It can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is an explanatory sectional view showing an example of a configuration of a short arc type high-pressure mercury lamp according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a method for measuring cold withstand pressure strength of examples and comparative examples of the discharge lamp of the present invention.
FIG. 3 is a diagram showing the relationship between lamp lighting time and cold pressure strength.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Discharge vessel 11 Arc tube part 12, 13 Sealing tube part 14 Cathode 15 Anode 16 Electrode rod (cathode rod)
16A Base end part (cathode)
17 Anode rod 17A Base end part (anode)
18 Metal foil 19 External lead rods 20 and 21 Coil 30 Stainless steel pipe 31 Adhesive 32 Alcohol tank 33 Pressure pump 34 Pressure gauge 35 Rotary pump 36 Connection joint

Claims (1)

A discharge vessel made of quartz glass and having a light emitting tube portion and a sealing tube portion connected to the light emitting tube portion, a pair of electrodes are arranged oppositely in the light emitting tube portion, and the discharge vessel internal volume In a short arc type high-pressure mercury lamp in which 0.15 mg / mm ³ or more of mercury is enclosed,
A base end side portion of at least one electrode is inserted into a coil welded to the sealing tube portion without being exposed in the arc tube portion,
The short arc type high-pressure mercury lamp , wherein the coil is made of tungsten having a purity of 99.99 mass% or more, and the concentration of potassium (K) is 10 mass ppm or less .

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