JP2004055438A - Short arc type ultra-high pressure discharge lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure for a short arc type ultra-high pressure discharge lamp using extremely high mercury vapor pressure when lighting with substantially high pressure resistance. <P>SOLUTION: The short arc type ultra-high pressure discharge lamp comprises a light emitting part in which a pair of electrodes are located and side tubes extending from both sides of the light emitting part in which metal foil connected to the electrodes respectively is sealed. The electrodes are located so that side/end surfaces of the electrodes form microgaps between materials used for the side tubes and the side/end surfaces of the electrodes in the side tubes. The electrode has a linear portion connected to the metal foil and at least a taper portion continued from the linear portion. The taper portion has a diameter diminishing from the side for maintaining arc discharge to the side connected with the metal foil. <P>COPYRIGHT: (C)2004,JPO

Description

【００３３】
この実験の結果、従来の電極構造のランプは、１００本のうち７０本のランプがクラックを発生したのに対し、本発明の電極構造のランプは、１００本のうちクラックを発生したランプが１本も存在しないことが確認された。
【００３４】
以上説明したように、本発明のショートアーク型超高圧放電ランプは、電極にテーパー部を設けることにより、製造工程において、空隙を電極の側面と側管部の内表面との間に十分に形成することができなくても、ランプ点灯時において、このような空隙を新たに形成することができる。この新たに形成された空隙により、電極と側管部が接触しないので、両者の接触部へクラックが発生することを確実に防止できる。
【００３５】
【発明の効果】
本発明の電極構造を用いれば、ランプ点灯時において、電極の端面および側面と側管部との間に微小空隙が確実に存在し、電極と側管部が接触しないので、側管部にクラックが発生しない。これにより、発光管部が１５０気圧を超える高い水銀蒸気圧になっても側管部の破損を防止することができる。
【図面の簡単な説明】
【図１】ショートアーク型超高圧放電ランプの全体図である。
【図２】本発明のショートアーク型超高圧放電ランプの部分図である。
【図３】図２におけるＡ−Ａ´断面図である。
【図４】本発明の電極の構造を示す図である。
【図５】本発明のショートアーク型超高圧放電ランプの製造方法の説明図である。
【図６】本発明のショートアーク型超高圧放電ランプの部分図である。
【図７】本発明を説明するためのショートアーク型超高圧水銀ランプの部分図を示す。
【符号の説明】
１　　　　発光部
２　　　　側管部
３　　　　電極
４　　　　金属箔
５　　　　外部リード
ｄ　　　　空隙[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a short arc type ultra-high pressure discharge lamp in which mercury is sealed so that a mercury vapor pressure at the time of lighting becomes, for example, 150 atm or more, and particularly to a short arc type ultra high pressure discharge lamp used as a backlight of a liquid crystal display device or the like.
[0002]
[Prior art]
A liquid crystal display device is required to illuminate an image with uniform and sufficient color rendering properties on a screen. For this reason, a metal halide lamp in which mercury or a metal halide is sealed is used as a light source. In recent years, such metal halide lamps have been further reduced in size and made into point light sources.
[0003]
However, in a metal halide lamp, it is known that a relatively large amount of halogen present as a halide causes corrosion of an electrode and blackening of a tube wall.
[0004]
From such a background, recently, instead of the metal halide lamp, a lamp having a small amount of enclosed halogen and having a high mercury vapor pressure, for example, 150 atm or more has been proposed. By increasing the vapor pressure of mercury, the spread of the arc is suppressed and the light output is improved.
[0005]
In such an ultra-high pressure discharge lamp, since the inside of the light emitting portion becomes as high as 150 atm or more during lighting, for example, a material constituting the side tube portion, for example, quartz, in the side tube portion extending on both sides of the light emitting portion It is necessary that the glass, the electrode and the metal foil are sufficiently adhered and sealed.
[0006]
Usually, in the step of sealing the side tube portion of such an ultra-high pressure discharge lamp, the quartz glass is heated at a high temperature of, for example, 2000 ° C., and the quartz glass is gradually shrunk or the quartz glass is pinch-sealed.
[0007]
As described above, when the quartz glass is baked and shrunk at a high temperature, or when pinch sealing is performed, the adhesion between the side tube, the electrode, and the metal foil is improved. However, after the end of the sealing step, cracks occur in the contact portions between the side tubes at a stage where the temperature of the side tube portion decreases. The reason for this is that the relative amount of expansion and contraction differs due to the difference in the thermal expansion coefficient between tungsten forming the electrode and quartz glass forming the side tube portion. Due to this crack, there is a problem that the side tube portion is frequently damaged when the lamp is turned on.
[0008]
Such a problem is solved, for example, by the technique described in JP-A-2001-351576. In this technique, the above-mentioned cracks are eliminated by cooling the side tube portion and then reheating it. Further, by creating a gap around the electrode axis, it is possible to prevent the occurrence of cracks when the lamp is turned on.
Specifically, as shown in FIG. 7, a minute gap d is formed between the electrode 3 and the inner surface of the side tube 2. The gap d absorbs the expansion of the electrode when the lamp is turned on, thereby preventing the occurrence of cracks at the contact portion between the electrode and the side tube.
[0009]
This gap is formed by applying vibrations to the electrode in some form in the manufacturing process of the side tube portion and forcibly moving the electrode with respect to the quartz glass. However, this forced vibration may allow some gaps to be formed at the end faces of the electrodes, but not enough at the side faces of the electrodes. If the formation of the gap is insufficient, the side surfaces of the electrode and the quartz glass are in contact with each other due to the expansion of the electrode when the lamp is turned on, and cracks are generated in the contact portion between the two as described above. . If the mercury vapor pressure of the light emitting section 1 is as high as 150 atm or more, crack growth is promoted during operation of the lamp, leading to a problem that the side tube is damaged.
[0010]
[Problems to be solved by the invention]
It is an object of the present invention to form a structure having a sufficiently high pressure resistance in a short arc type ultra-high pressure discharge lamp having an extremely high mercury vapor pressure during operation.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in a short arc type ultra-high pressure discharge lamp of the present invention, a pair of electrodes are arranged opposite to each other in a light emitting unit, and a metal foil connected to the electrodes extends on both sides of the light emitting unit. The electrode is sealed with a side tube portion, and the side surface and the end surface of the electrode are arranged in the side tube portion so as to form a minute gap with a material constituting the side tube portion, and It has a straight portion joined to the metal foil and at least one tapered portion following the straight portion, and the tapered portion has a diameter from the side holding the arc discharge to the side connected to the metal foil. It is characterized by decreasing.
[0012]
[Action]
The present invention has a configuration in which the electrode has a tapered portion in the shaft portion. As a result, even if a gap is not sufficiently formed between the side surface of the electrode and the inner surface of the side tube portion in the manufacturing process, the gap is newly formed due to the presence of the tapered portion and the expansion of the electrode during lamp operation. Can be formed. Then, the electrode and the side tube portion do not come into contact with each other due to the newly formed void, so that a problem that a crack occurs at a contact portion between the electrode and the side tube portion can be surely prevented.
[0013]
Here, the fact that the electrode structure of the present invention can newly form a gap between the side surface of the electrode and the inner surface of the side tube portion when the lamp is turned on will be described.
When the lamp is turned on, the electrodes expand in the radial direction, and also expand in the electrode axis direction mainly in the direction of the light emitting portion. Due to this expansion, the electrode extends toward the light emitting portion. On the other hand, the inner surface of the side tube portion hardly expands as compared with the electrode due to the fact that the expansion coefficient of quartz glass is much smaller than that of tungsten constituting the electrode, and its shape is maintained.
As will be described later, when the lamp is turned on, the electrode having the tapered portion extends in the direction of the light emitting portion, and the portion where the large diameter portion of the tapered portion faces the inner surface of the side tube portion has a small diameter portion of the tapered portion. Will be located. Thereby, a new gap can be formed between the side surface of the electrode and the inner surface of the side tube portion by an interval corresponding to the difference between the radius of the large diameter portion and the radius of the small diameter portion of the tapered portion.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the overall structure of the short arc type ultra-high pressure discharge lamp of the present invention will be described with reference to FIG. Side tube portions 2 are formed so as to extend on both sides of the light emitting portion 1. A pair of electrodes 3 are arranged in the light emitting portion to face each other, and metal foils 4 connected to the electrodes 3 are sealed by the side tube portions 2 respectively. The external lead bar 5 is welded to the metal foil 4. Although the electrode 3 in FIG. 1 has a tapered portion, the tapered portion is omitted here for convenience of description of the drawings.
[0015]
Mercury, a rare gas, and a halogen gas are sealed in the light emitting unit 1. Mercury is sealed in order to obtain a visible light wavelength, for example, radiation light having a wavelength in the range of 360 to 780 nm, and a quantity calculated so that the mercury vapor pressure at the time of lighting exceeds 150 atm. The rare gas is sealed to improve the lighting startability, and the halogen gas is sealed to prevent clouding of the arc tube.
[0016]
FIG. 2 is an enlarged view of a boundary portion between the light emitting section 1 and the side tube section 2, and FIG. 3 is a sectional view taken along line AA 'of FIG. Here, in the present invention, an electrode that includes all of the straight portion 3a, the tapered portion 3b, and the discharge holding portion 3c exposed in the arc tube is referred to as an electrode 3.
The straight portion 3a is provided at the distal end of the side tube portion and has the same diameter, that is, a columnar shape, and is a portion to be welded to a metal foil. The tapered portion 3b is formed following the straight portion 3a, and has a shape in which a minute gap d is formed around the tapered portion 3a as described later and the size gradually decreases from the light emitting portion side toward the metal foil. The discharge holding portion 3c is a portion for holding an arc discharge, and has a large diameter for heat dissipation and the like. The gap d in FIGS. 2 and 3 is actually extremely small, but is exaggerated for convenience of explanation of the drawings.
[0017]
Here, the gap d is formed due to the difference in expansion coefficient between the material forming the tapered portion and the material forming the side tube portion. In the case where the tapered portion is made of tungsten and the side tube portion is made of quartz glass as in the present invention, the gap has a width of 5 to 20 μm and exists in the length direction of the electrode at 1 to 20 mm.
[0018]
Here, the operation of the tapered portion will be described with reference to FIG. Note that the solid lines in the figure indicate the electrodes that have been moved when the lamp is turned on, and the hatched portions indicate the electrodes before the movement.
The electrode 3 expands in the axial direction of the electrode mainly in the direction of the light emitting portion 1 by the length indicated by x in the figure due to the heat energy generated when the lamp is turned on. That is, the tapered portion 3b also extends x in the direction of the light emitting portion 1 due to the expansion of the electrode. Here, the inner surface of the side tube portion 2 facing the tapered portion 3b has almost no expansion coefficient compared to the tapered portion 3b because the expansion coefficient of quartz glass is much smaller than that of tungsten. It does not expand and its shape remains maintained. Therefore, when the lamp is turned on, the tapered portion 3b expands toward the light emitting portion, and the tapered small diameter portion is located where the large diameter portion of the taper faces the inner surface of the side tube portion 2. . That is, between the electrode 3 and the inner surface of the side tube part 2, in addition to the gap d formed in the manufacturing process, a gap indicated by d 'in the figure is newly formed. This gap corresponds to the difference between the radius of the large diameter portion and the radius of the small diameter portion.
Theoretically, it is also considered that the gas expands in the radial direction and the space is closed by the expansion. However, since the expansion in the radial direction is much smaller than the gap d 'formed when the lamp is turned on, the gap is not closed.
[0019]
Here, numerical examples relating to the electrodes of the short arc type ultra-high pressure discharge lamp of the present invention will be introduced.
The straight portion 3a has a diameter in the range of 0.2 to 1.0 mm, for example, 0.4 mm, and a length in the range of 0.5 to 20.0 mm, for example, 2.5 mm. The tapered portion 3b has a diameter on the small diameter side in the range of 0.2 to 1.0 mm, for example, 0.4 mm, and a diameter on the large diameter side in the range of 0.21 to 4.0 mm, for example, 0.7 mm. Yes, the length is in the range of 0.5 to 20 mm, for example 2.5 mm. The discharge holding portion 3c has a diameter on the small diameter side in a range of 0.21 to 4.0 mm, for example, 0.7 mm, and a diameter on the large diameter side in a range of 0.21 to 4.0 mm, for example, 1.8 mm. And the length is in the range of 1.0 to 30.0 mm, for example, 5.0 mm.
[0020]
FIG. 4 shows another structure of the electrode. The shape of the tapered portion of the electrode is not limited to the structure shown in FIG. 2, and may be such that it draws a curve from the straight portion toward the discharge holding portion as shown in FIG. The shape may be a step shape toward the part, or may be another shape. Further, the shape of the tip of the discharge holding portion exposed in the arc tube may be a curved shape as shown in FIGS. 3A and 3B, or may be another shape such as a flat shape.
[0021]
Next, a method for manufacturing the short arc type ultra-high pressure discharge lamp of the present invention will be described.
5A to 5D show a series of manufacturing steps, wherein FIG. 5A shows a sealing step, FIG. 5B shows a cooling step, FIG. 5C shows a heating step, and FIG. Although the electrode 3 has a tapered portion, it is omitted here for convenience of description of the drawings.
[0022]
First, the sealing step of FIG.
An electrode assembly in which the electrode 3, the metal foil 4, and the external lead bar 5 are integrally formed is inserted into one side tube 2 a of the side tube 2 extending on both sides of the light emitting unit 1. Then, the tip of the electrode 3 is exposed to the light emitting unit 1 and the part of the electrode 3 and the metal foil 4 are arranged so as to face the inner surface of the side tube 2a. Thereafter, as shown by A in the figure, the side tube portion 2a surrounding the electrode 3 and the metal foil 4 is heated. The material constituting the side tube portion 2a is quartz glass, which has a softening point temperature of about 1680 ° C., and is heated by a gas burner at about 2000 ° C. which is higher than the softening point temperature.
[0023]
In this sealing step, since the end of the side tube 2a is already closed, the pressure inside the glass bulb is reduced to, for example, 100 Torr through the open end of the other side tube 2b. Therefore, when the side tube 2a is heated, the diameter of the side tube 2a is reduced, and the electrode 3 and the metal foil 4 are sealed. In addition to this method, after the side tube portion 2a is heated, it can be sealed with a pincher.
[0024]
Next, the cooling step of FIG.
After the sealing step is completed, the side tube portion 2a is cooled by forced cooling or natural cooling. This cooling is performed until the temperature reaches, for example, 1200 ° C., so that the electrode 3 and the metal foil 4 are sealed and fixed to the side tube portion 2a.
[0025]
In this cooling step, a part of the electrode 3 is welded to the side tube 2a, but the entire surface of the electrode 3 is not welded to the side tube 2a. The reason for this is that since the tungsten constituting the electrode and the quartz glass constituting the side tube have different expansion coefficients, the welded portion between the electrode 3 and the side tube 2a is partially peeled off. This peeling causes cracks on the inner surface of the side tube portion 2a.
[0026]
Next, the heating step of FIG.
After the completion of the cooling step, as shown by B in the figure, the side tube portion in which the electrode 3 is sealed is reheated. This heating is performed using, for example, a gas burner until the quartz glass constituting the side tube portion 2a is in a viscous flow state and comes into contact with the electrode 3 again so that the electrode 3 and the quartz glass can relatively move. .
This heating step reheats only the portion indicated by B in the drawing of the side tube portion 2a and does not heat the portion where the metal foil 4 is already sealed and fixed. It does not affect the airtightness of the side tube portion 2a.
By performing such reheating, minute cracks existing on the inner surface of the side tube 2a around the electrode 3 can be eliminated.
[0027]
Next, the vibration step of FIG.
After the heating step, when the quartz glass forming the side tube 2a is in a viscous flow state and the electrode 3 and the quartz glass can move relatively, the side tube 2a in FIG. Vibration is applied in the direction of the arrow. Specifically, when the temperature of the portion B in the drawing of the side tube portion 2a is equal to or lower than the softening point (about 1680 ° C.) of the quartz glass and equal to or higher than the cooling point (about 1280 ° C.), in the direction of the arrow in the drawing. Apply vibration.
The vibration is performed, for example, 1 to 10 times, whereby the electrode 3 moves 0.1 to 1.0 mm toward the light emitting unit.
[0028]
As a method for applying the vibration, as shown in FIG. 5 (d), a method in which the holding member 6 holding the side tube portion 2 is connected to a motor or the like and the motor is driven to generate vibration in the direction of the arrow. No. Due to this vibration, the electrode 3 and the side tube 2a are forcibly and relatively displaced, and a gap should be generated between the electrode 3 and the side tube 2a. However, some gaps may be formed at the end face of the electrode 3, but not sufficiently formed at the side face of the electrode.
[0029]
Incidentally, regarding the sealing of the electrode in the side tube portion 2b, after the vibration step is completed, after the mercury, rare gas and halogen gas necessary for the light emitting portion 1 are sealed, the same sealing, cooling, heating and vibration are performed. The process will be performed.
[0030]
Next, numerical examples of the short arc type ultra-high pressure discharge lamp of the present invention will be introduced.
Outer diameter of cathode: 1mm
Cathode length: 10mm
Outer diameter of anode: 2mm
Anode length: 10mm
Outer diameter of side tube: 6mm
Side tube length: 20mm
Lamp length: 50mm
Inner volume of arc tube: 0.1cc
Distance between electrodes: 1 mm
Rated lighting voltage: 100V
Rated lighting current: 2A
The amount of enclosed mercury: 30mg
Noble gas: 100 Torr of argon
[0031]
Next, an experiment showing the effect of the present invention will be described. In conducting the experiment, the present inventors carried out a lamp (the lamp shown in FIG. 2) manufactured by using the electrode having the tapered portion of the present invention and an electrode having no tapered portion through the above manufacturing steps. 100 lamps (lamps shown in FIG. 7) manufactured by using the same were prepared. Specifically, as shown in Table 1, a trial of turning on the lamp for 2 minutes, turning off the lamp, and allowing the lamp to stand for 1 minute was repeated seven times for a total of 200 lamps. Next, the light was turned on for 5 minutes, then turned off, and left for 5 minutes. Finally, after turning on the light for 30 minutes, the light is turned off, the lamp is allowed to reach a room temperature, and the lamp is visually checked for cracks in the side tube portion.
[0032]
[Table 1]

[0033]
As a result of this experiment, 70 lamps out of 100 lamps had cracks in the conventional electrode structure, whereas 1 lamp out of 100 lamps had cracks in the electrode structure of the present invention. It was confirmed that there was no book.
[0034]
As described above, in the short arc type ultra-high pressure discharge lamp of the present invention, the gap is sufficiently formed between the side surface of the electrode and the inner surface of the side tube portion in the manufacturing process by providing the electrode with the tapered portion. Even if it is not possible, such a gap can be newly formed when the lamp is turned on. Since the newly formed void does not allow the electrode and the side tube portion to come into contact with each other, it is possible to reliably prevent the occurrence of cracks at the contact portion between the two.
[0035]
【The invention's effect】
With the use of the electrode structure of the present invention, when the lamp is turned on, a minute gap surely exists between the end surface and side surface of the electrode and the side tube portion, and the electrode and the side tube portion do not come into contact with each other. Does not occur. Thereby, even if the arc tube part has a high mercury vapor pressure exceeding 150 atm, it is possible to prevent the side tube part from being damaged.
[Brief description of the drawings]
FIG. 1 is an overall view of a short arc type ultra-high pressure discharge lamp.
FIG. 2 is a partial view of a short arc type ultra-high pressure discharge lamp according to the present invention.
FIG. 3 is a sectional view taken along line AA ′ in FIG. 2;
FIG. 4 is a diagram showing a structure of an electrode of the present invention.
FIG. 5 is an explanatory view of a method for manufacturing a short arc type ultra-high pressure discharge lamp according to the present invention.
FIG. 6 is a partial view of the short arc type ultra-high pressure discharge lamp of the present invention.
FIG. 7 is a partial view of a short arc type ultra-high pressure mercury lamp for explaining the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Light emitting part 2 Side tube part 3 Electrode 4 Metal foil 5 External lead d Void

Claims (1)

In a short arc type ultra-high pressure discharge lamp in which a pair of electrodes are disposed opposite to each other in the light emitting unit and the metal foil connected to the electrodes is sealed with side tubes extending on both sides of the light emitting unit,
The electrode, the side surface and the end surface, in the side tube portion, forming a minute gap between the material constituting the side tube portion, is arranged,
And it has a straight portion joined to the metal foil and at least one tapered portion following the straight portion, and the tapered portion is directed from the side holding the arc discharge to the side connected to the metal foil. And a short arc type ultra-high pressure discharge lamp having a reduced diameter.

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