JP3480453B2 - Short arc type ultra-high pressure discharge lamp - Google Patents

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 ultra-high pressure discharge lamp which has a mercury vapor pressure of 150 atm or more when lit, and particularly to a liquid crystal display device and a DMD
The present invention relates to a short arc type ultra high pressure discharge lamp used as a backlight of a projector device such as a DLP (digital light processor) using a (digital mirror device).

[0002]

2. Description of the Related Art A projection type projector device is required to illuminate an image uniformly and with sufficient color rendering on a rectangular screen. Therefore, as a light source, mercury or metal halide is used. The enclosed metal halide lamp is used. In addition, such a metal halide lamp has recently been further miniaturized and made into a point light source, and a lamp having an extremely small distance between electrodes has been put into practical use.

Under such a background, recently, a lamp having a mercury vapor pressure which has never been present, for example, 150 atm has been proposed in place of the metal halide lamp. This is to increase the mercury vapor pressure to suppress (narrow down) the spread of the arc and to further improve the light output. Such an ultra-high pressure discharge lamp is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 2-145861 and 6-52830.

By the way, in such an ultra-high pressure discharge lamp, the pressure inside the arc tube becomes extremely high at the time of lighting. Therefore, in the side tube parts extending on both sides of the arc tube part, the quartz glass forming the side tube part is It is necessary to firmly and firmly adhere the electrode and the metal foil for power supply. This is because if the adhesion is poor, the filled gas may escape or cracks may occur. Therefore, in the step of sealing the side tube portion, for example,
The quartz glass is heated at a temperature as high as 2000 ° C., and in that state, the thick quartz glass is gradually shrunk or the quartz glass is pinch-sealed to improve the adhesion of the side tube portion.

However, if the quartz glass is baked at an excessively high temperature, the adhesion between the quartz glass and the electrode or the metal foil is improved, but the side tube portion is easily damaged after the discharge lamp is completed. This problem is due to the fact that the temperature of the side pipe part after the heat treatment gradually decreases,
The relative expansion and contraction amount differs depending on the difference in the expansion coefficient between the material that constitutes the electrode (tungsten) and the material that constitutes the side tube (quartz glass), and this causes cracks to occur at the contact area between the two. it is conceivable that. Although this crack is very small, it is considered that the crack grows in combination with the super high pressure state during lamp lighting, which causes damage to the discharge lamp.

In order to solve such a problem, the structure shown in FIG. 6 has been proposed. This figure is an enlarged view of a part of the discharge lamp. The side tube portion 11 is connected to the arc tube portion 10, and the electrode 2 is joined to the metal foil 3 in the side tube portion 11. The coil member 5 is wound around the electrode 2 embedded in the side tube portion 11. In this structure, the coil member 5 wound around the electrode 2 relaxes the stress on the silica glass due to the thermal expansion of the electrode 2, and is described in, for example, Japanese Patent Application Laid-Open No. 11-176385.

However, even if the thermal expansion of the electrode 2 is alleviated by such a structure, in reality, the crack K remains around the electrode 2 and the coil member 5.
Although the cracks K are extremely small, sometimes the side tube portion 11 is damaged when the mercury vapor pressure of the arc tube portion 10 is about 150 atm. Further, in recent years, a very high mercury vapor pressure of 200 atm or even 300 atm has been required. At such a high mercury vapor pressure, the growth of cracks K is promoted during the lighting of the lamp, and as a result, There is a problem that the side tube portion 11 is significantly damaged. In other words, even if the cracks K are initially small, they grow gradually larger when the lamp is lit at a high mercury vapor pressure. It can be said that this is a new technical problem that never exists in a mercury lamp having a vapor pressure during lighting of about 50 to 100 atm.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and has a sufficiently high pressure resistance in an ultra-high pressure mercury lamp which is operated at an extremely high mercury vapor pressure. Providing a structure having.

[0009]

In order to solve the above-mentioned problems, a short arc type ultra high pressure discharge lamp of the present invention has a pair of electrodes facing each other inside, and 0.15 mg / m 2.
m ³ or more mercury-sealed arc tube portion, and a side tube portion that extends on both sides thereof and seals a part of the electrode, and the side surface and end surface of the electrode are inside the side tube portion. It is characterized in that a minute gap is formed between the tube glass and quartz glass, which is a constituent material, and the electrode section is provided with irregularities. Further, the minute space has a degree that the electrode can freely expand and contract without being constrained in the axial direction due to a difference in expansion coefficient between the material forming the electrode and the material forming the side tube portion. It is characterized by being a thing. Further, the unevenness has a depth of 1.0 to 100 μm.

[0010]

The short arc type ultra-high pressure discharge lamp of the present invention has the above-mentioned structure, and in the sealing step of the electrode and the quartz glass forming the side tube portion, the generation of minute cracks is completely eliminated.
Or it was almost completely suppressed. The reason for this is
This is because the electrode (also referred to as the electrode rod) located in the side tube has a void on its surface and does not adhere to the boundary with the quartz glass, and because there is no quartz glass on the surface of the electrode. As a matter of course, cracks cannot occur.

Here, the present applicant has previously filed Japanese Patent Application No. 2000-
No. 168798 proposes a structure of a side tube portion having a gap on the outer surface of an electrode as shown in FIG. However, the void structure disclosed in this application has no problem if the void structure as shown in the figure can be formed completely accurately, but in reality, it is difficult to form such completely accurate voids. It has been found. Specifically,
It is disclosed that the void is formed by applying vibration to the electrode in the manufacturing process of the side tube portion. However, in reality, the void cannot sufficiently form the void. Then, the present invention invents that unevenness is provided on the surface of the electrode as a structure for forming such a void more easily and surely.

Although the technical explanation that the formation of the uneven shape leads to the reliable formation of the voids is not clear, the applicant of the present invention has considered the following as a result of intensive studies. That is, as disclosed in the above-mentioned prior specification, the manufacturing method for forming the void is
It is to apply an impact to the electrode in the final stage of the sealing process. Then, if unevenness was formed when the shock was applied, the fused silica glass present in the recess would jump out with the shock, and it is speculated that this jump may form a void reliably. There is.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A short arc type ultra high pressure discharge lamp of the present invention will be described. First, referring to FIG.
The overall structure of the discharge lamp will be described. Discharge lamp 1
Has an arc tube portion 10 made of quartz glass substantially at the center and side tube portions 11 at both ends thereof. The side tube portion 11 is hermetically sealed with quartz glass.

In the arc tube portion 10, a pair of electrodes 2 made of tungsten are arranged with a gap of 2.5 mm or less, for example. The metal foil 3 is welded to one end of the electrode 2, and the metal foil 3 and a part of the electrode 2 are embedded in the side tube portion 11 and sealed. The external lead 4 is joined to the other end of the metal foil 3.

Mercury is enclosed in the arc tube portion 10 as a light emitting substance, and a rare gas such as argon or xenon is enclosed as a lighting starting gas. The amount of mercury enclosed is calculated and enclosed so that the vapor pressure during stable lighting is 150 atm or more, preferably 200 atm or more, more preferably 300 atm or more. For example, when the mercury vapor pressure is 150 atm or higher, the amount of mercury enclosed is 0.1
It becomes 5 mg / mm ³ or more.

FIG. 2 is an enlarged view of a boundary portion between the arc tube portion 10 and the side tube portion 11, and FIG. 3 is a sectional view taken along the line AA 'of FIG. Although the void B and the unevenness 20 in FIGS. 2 and 3 are actually extremely small, they are exaggerated in the drawings for convenience of description. In the side tube portion 11, the electrode 2 is welded to the metal foil 3, and the other region has a void B between it and the quartz glass forming the side tube portion 11. Specifically, the side surface 2a of the electrode 2 and the sealing-side end surface 2
In b, it is not in contact with the side tube portion 11 (quartz glass). A coil 21 is wound around the tip of the electrode 2. This improves the lighting startability, and tungsten is wound 4 to 5 times.

Here, the space B is determined from the viewpoint that the electrode can freely expand and contract without being constrained in the axial direction due to the difference in expansion coefficient between the material forming the electrode and the material forming the side tube portion. If the electrode is made of tungsten and the side tube is made of quartz glass, the width B of the void is
Is selected from the range of 6 to 16 μm, and the gap B exists in the length direction of the electrode in the range of 2 to 5 mm. The outer diameter of the side tube portion of the electrode is, for example, 0.3 to 1.5 mmΦ.

FIG. 4 shows a specific structure of the electrode. As shown in (a), those that have the same outer diameter and extend to the tip,
As shown in (b), in some cases, the portion exposed in the light emitting space is formed thicker than the sealed portion, and electrodes of other shapes can also be adopted. Further, the tip of the electrode on the light emitting space side may be flat as shown in (a), may be curved as shown in (b), or may be another shape such as a conical shape. Absent. Concavities and convexities 20 are formed on the electrode 2 at positions corresponding to the side tube portions. The unevenness 20 has a width W and a depth d, and may have a jagged shape as shown in the figure or a square shape as shown in FIG. For example, it may be curved or wavy. Depth of unevenness 20 (d)
Is, for example, 1 to 100 μm.
0 can be formed by lathe processing, cylindrical grinding, or the like.

Next, a method of manufacturing the short arc type ultra high pressure discharge lamp of the present invention will be described. Figure 5 (a) ~
(D) shows a series of manufacturing steps, (a) a sealing step,
(B) shows a cooling process, (C) shows a heating process, and (D) shows a vibration process. It should be noted that although the electrode 2 is formed with the unevenness as described above, the unevenness is omitted in this drawing for convenience of explaining the manufacturing process.

First, the sealing step of FIG. 5A will be described. An electrode assembly in which an electrode 2, a metal foil 3 and an external lead bar 4 are integrally formed is inserted into one side tube portion 11a of a glass bulb in which an arc tube portion 10 and a side tube portion 11 are formed. Then, the tip of the electrode 2 is exposed to the arc tube portion 10, and the base of the electrode 2 and the metal foil 3 are arranged so as to be located in the side tube portion 11. Then, as indicated by C in the figure, the side tube portion 11a surrounding the electrode 2 and the metal foil 3 is heated at a temperature equal to or higher than the softening point of the side tube portion 11a. Specifically, the softening point temperature when the side tube portion is made of quartz glass is 1680.
The heating temperature is about 2,000 ° C., and heating is performed by a gas burner at about 2,000 ° C.

In this sealing step, since the end of the side tube portion 11a has already been closed, the inside of the glass bulb is, for example, 100 Ton through the open end of the other side tube portion 11b.
The pressure is reduced to rr. Therefore, when the side tube portion 11a is heated, the diameter of the portion is reduced, whereby the electrode 2 and the metal foil 3 are sealed. In addition to the method of making the inside of the glass bulb a negative pressure, the side tube portion 11 may be heated and then sealed with a pincher.

Next, the cooling process of FIG. 5B will be described. Following the sealing step, the side tube portion 11a is cooled. This cooling is performed by forced cooling or natural cooling, for example, 1
Cool to 200 ° C.

By this cooling process, the electrode 2 and the side tube portion 11
Although part a is welded, it is not welded to the material forming the side tube portion on the entire surface of the electrode 2. This is because the material forming the electrode, for example, tungsten, and the material forming the side tube portion, for example, quartz glass, have different expansion coefficients, so that the electrode 2 and the side tube portion 11 are welded (welded in the sealing step). This is because a part of (part) is peeled off. When such peeling occurs, the minute cracks K described above occur.

Next, the heating step of FIG. 5C will be described. Subsequent to the cooling step, the portion indicated by D in the figure is heated again. This heating is performed, for example, by a gas burner until the material forming the side tube portion 11, for example, quartz glass is in a viscous flow state and comes into contact with the electrode 2 again, and the material forming the electrode 2 and the side tube portion 11 is It is possible to move relatively. Here, this heating step is performed by the side tube portion 11a.
Of these, only the region indicated by D in the figure is reheated, and therefore the region where the metal foil 3 is already sealed and fixed is not heated. Therefore, the metal foil 3 and the side tube portion 11
There is no effect on the airtight sealing. By performing such reheating, the microscopic cracks existing around the electrode 2 can be eliminated.

Next, the vibration step of FIG. 5D will be described. After completion of the heating step, the temperature of the region D of the side tube portion 11a is vibrated with respect to the side tube portion 11a in a state where the temperature is equal to or lower than the softening point of the side tube portion constituent material and is equal to or higher than the cooling point. Add. This vibration occurs in the direction indicated by the arrow in the figure. This is because the region D of the side tube portion 11 is in a viscous flow state and the electrode 2 and the quartz glass 11 can move relatively. The vibration is performed, for example, 1 to 10 times, and thereby a movement of 0.1 to 1.0 mm is performed. In the last vibration, the distance between the electrodes must be proper, and it can be adjusted by ± 0.0% manually or by using an image processing device.
It is performed with an accuracy of 5 mm.

With respect to this vibration, the holding member 13 holding the side tube portion 11 is connected to a vibration means such as a motor, and vibration in the direction of the arrow is generated in accordance with the driving of this motor. Due to this vibration, the electrode 2 and the side tube portion 11 are forcibly and relatively displaced from each other, and a good gap is generated therebetween. To form this void,
There is also an effect that the fused silica glass located in the recesses of the not-shown concavo-convex 20 is affected by the vibration and satisfactorily pops out.

Regarding the production of the electrodes in the side tube portion 11b, after the above steps are completed, the necessary mercury and rare gas are sealed in the arc tube portion 10, and then the same sealing, cooling, heating and vibration steps are performed. Will be done.

Here, the number of vibrations is affected by the depth of the irregularities formed on the electrodes. As a result of accumulating a number of experiments, the inventors have found that when the depth of the unevenness is 35 to 100 μm, the vibration occurs once or twice (once the side pipe part moves in the arrow direction shown in FIG. 5D). 1 round trip), the depth of the unevenness is 12-25μ
When m, the vibration is 3 to 4 times, and the depth of the unevenness is 1.0 to 6.5.
It has been confirmed that vibration is required 5 to 10 times when the thickness is μm. This result means that the greater the depth of the unevenness, the smaller the number of vibrations required, which is also a reason to support the effect of the void forming action by the unevenness. In addition, if the frequency of vibration increases, the metal foil may be adversely affected. The present inventors have confirmed that a vibration frequency of 10 times or less, preferably 5 times or less is effective in the sense of affecting the metal foil.

The unevenness formed on the electrode is not limited to the structure in which the concave portion and the convex portion are continuously arranged in the extending direction of the electrode as in the above-mentioned embodiment. That is, the structure may be such that the concave portions and the convex portions are continuously arranged in the circumferential direction of the electrode.
In this case, the direction of applying vibration is not from the end of the side tube as described in the manufacturing process but from the side surface of the side tube. The irregularities formed in the circumferential direction of the electrode may not be formed in the entire circumferential direction, but may be formed in part in relation to the direction in which vibration is applied.

Next, numerical examples of the short arc type discharge lamp according to the present invention will be introduced. Outer diameter of cathode: 0.8 mm Outer diameter of anode: 1.8 mm Outer diameter of side tube part: 6.0 mm Total length of lamp: 65.0 mm Length of side tube: 25.0 mm Inner volume of arc tube: 0.08 cc Distance between electrodes: 2.0 mm Rated lighting voltage: 200 w Rated lighting current: 2.5 A Encapsulated mercury amount: 0.15 mg / mm ³ Noble gas: Argon at 100 Torr

As described above, since the short arc type ultra high pressure discharge lamp of the present invention has minute voids on the side surface and the end surface of the electrode, the generation of minute cracks at that portion is completely or almost completely generated. Further, by providing the electrodes with irregularities, it is possible to reliably and accurately form a minute space in the manufacturing process of the discharge lamp.

[Brief description of 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 of the present invention.

3 is a cross-sectional view taken along the line AA in FIG.

FIG. 4 is a diagram showing a structure of an electrode of the present invention.

FIG. 5 is an explanatory view of a method of manufacturing a short arc type ultra-high pressure discharge lamp of the present invention.

FIG. 6 shows a partial view of a conventional short arc type ultra high pressure discharge lamp.

FIG. 7 shows a partial view of a short arc type ultra-high pressure mercury lamp for explaining the present invention.

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Claims (3)

(57) [Claims] 1. A pair of electrodes are arranged to face each other, and
In a short arc type ultra-high pressure discharge lamp comprising an arc tube section containing 0.15 mg / mm ³ or more of mercury and side tube sections extending on both sides of the arc tube and sealing a part of the electrode, the electrode comprises: The side surface and the end surface are arranged in the side tube portion so as to form a minute gap between the side tube portion and the quartz glass which is a constituent material of the side tube portion, and the electrode portion has irregularities. Short arc type ultra high pressure discharge lamp. 2. The micro space can be freely expanded and contracted without being constrained in the axial direction due to a difference in expansion coefficient between a material forming the electrode and a material forming the side tube portion. The short arc type ultra-high pressure discharge lamp according to claim 1, characterized in that 3. The short arc type ultra high pressure discharge lamp according to claim 1, wherein the unevenness has a depth of 1.0 to 100 μm.