JP3480454B2 - 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, 2
The quartz glass is heated at a temperature as high as 000 ° 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, when 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 problem that the side tube portion is likely to be damaged after the completion of the discharge lamp is still a problem. Occurred.
This problem is due to the relative expansion and contraction due to the difference in expansion coefficient between the material forming the electrode (tungsten) and the material forming the side tube (quartz glass) when the temperature of the side tube gradually decreases after the heat treatment. The amount is different, and it is considered that this causes cracks to occur in the contact area between the two. This crack is initially very small, but
It is considered that cracks grow in combination with the ultra-high pressure state during lamp operation, which causes damage to the discharge lamp.

In order to solve such a problem, a structure shown in FIG. 10 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 discharge lamp which is ignited with 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 /
A short arc type ultra-high pressure discharge lamp comprising an arc tube portion enclosing mercury of mm ³ or more and side tube portions extending on both sides of the arc tube and sealing a metal foil connected to the electrode. The end face is arranged in the side tube portion with a minute gap formed between the end face of the electrode and the quartz glass which is a constituent material of the side tube portion, and an acute angle structure is formed by the end face of the electrode and the metal foil. The quartz glass is also arranged in this acute angle structure. Also,
The acute angle structure has an angle of 70 ° or less.

[0010]

With the above-mentioned structure, the short arc type ultra-high pressure discharge lamp of the present invention can completely or almost completely suppress the minute cracks generated in the side tube portion.
This is because the electrode (electrode rod) located in the side tube portion has a void on the surface (including the end surface) between it and the quartz glass, so the boundary between the quartz glass and the electrode is not in close contact. Is. With such a structure, since the surface of the electrode is not in contact with the quartz glass, even if the electrode moves relatively to the quartz glass, a crack due to this movement does not naturally occur between them. It will be.

Here, the present applicant has previously filed Japanese Patent Application No. 2000-
No. 168798 proposes a structure of a side tube portion in which a gap is provided on the surface of an electrode as shown in FIG. In the figure, 10 is an arc tube portion, 11 is a side tube portion, and the electrode 2 is joined to the metal foil 3 in the side tube portion 11. The electrode 2 is
The side surface 2a and the end surface 2b are arranged apart from the quartz glass via a minute gap B. However, the structure disclosed in this application is an effective structure in the sense that cracks between the electrode 2 and the quartz glass are well prevented, but such a structure causes new problems.

FIG. 8 shows an enlarged view of portion A in FIG. FIG. 8A is an enlarged view of the portion A of FIG. 7, and FIG.
Shows a cross-sectional view of the CC ′ cross section of (a) seen from above (D side), and (c) shows the DD ′ cross section of (a) on the left side (C side).
The sectional view seen from is shown. As shown in the figure, the void B exists up to the side surface 2a and the end surface 2b of the electrode 2. However, when such a void B is formed, a wedge-shaped void X is undesirably generated in the region surrounded by the quartz glass and the metal foil 3 on the end surface 2b of the electrode 2.

FIG. 9 shows an enlarged view of the gap X. Void X
Is directly connected to the arc tube portion 10 through the void B, so that a high atmospheric pressure (150 atmospheric pressure or more) generated in the arc tube portion 10 is similarly applied. This high pressure
The wedge-shaped void X is strongly applied in the directions P3 and P4 shown in the figure, which causes the quartz glass and the metal foil 3 to be peeled off. Such a phenomenon is
This eventually leads to the peeling of the quartz glass and the metal foil, which in turn leads to damage to the discharge lamp. In addition, such a phenomenon has a structure in which the arc tube portion and the electrode end surface are connected by a gap, and the internal pressure is 100 atm or more, and 150 or 20 is higher as in the present invention.
It can be said that this is a unique technical problem that occurs in a discharge lamp having an extremely high pressure of 0 or even 300 atm or more.

According to the present invention, a space B is provided between the electrode and the quartz glass.
In order to solve the technical problem peculiar to the discharge lamp in which the internal pressure of the light emitting part is 150 atm or more, the inventors of the present invention have made diligent studies, and as a result, devised the shape of the end face of the electrode. It is a thing.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A short arc type ultra high pressure mercury 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, for example, 2.5 mm or less. 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. 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.

The arc tube 10 is filled with mercury as a light emitting substance and a rare gas such as argon or xenon 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 corresponds to FIGS. 7 and 10. As shown in the figure, in the side pipe portion 11,
The electrode 2 is welded to the metal foil 3 at the welded portion, and has a void B between the electrode 2 and the quartz glass forming the side tube portion 11 in the other region. Specifically, the electrode 2 is
The side surface 2a and the end surface 2b on the sealing side are not in contact with the quartz glass which is the material of the side tube portion 11. In addition, metal foil 3
Although the voids and the voids B are actually extremely small or thin, they are exaggerated in the drawings for the purpose of explaining the invention. Further, FIG. 3 also shows the end portion 2b of the electrode and corresponds to FIG. (A) is an enlarged view of the electrode end, (b) is C- of (a)
A cross-sectional view of the C ′ cross section viewed from above (D side) is shown (c)
Shows a cross-sectional view of the DD ′ cross section of (a) viewed from the left side (C side).

Here, the void B is determined from the viewpoint that the electrode can freely expand and contract in the axial direction without being constrained by the difference in expansion coefficient between the material forming the electrode and the material forming the side tube. When the electrode is made of tungsten and the side tube is made of quartz glass, the width B of the void is 6 to 16
It is selected from the range of μm and exists in the gap B in the length direction of the electrode of 3 to 5 mm. By the way, the outer diameter of the electrode is, for example,
It is 0.4 to 1.3 mmΦ. By forming such a void B, it is possible to favorably prevent the occurrence of cracks due to the relative movement of the electrode and the quartz glass. Further, according to the present invention, the shape of the end face on the outer side of the electrode 2 is not a flat end as shown in FIG. 7, but an acute angle structure is formed by the end face of the electrode and the metal foil.
With such a structure, it is possible to favorably prevent the technical problem caused by providing the void B, that is, the generation of the wedge-shaped undesired void X and its growth.

FIG. 4 shows an enlarged structure of the electrode end portion. As shown in the figure, the end portion of the electrode is not a flat end surface (a plane perpendicular to the longitudinal direction of the electrode) but a spherical surface or a curved surface, so that the void B formed around the electrode has substantially the same shape. Formed as. Then, the electrode end portion and the metal foil 2 form an acute angle structure, and the quartz glass also enters the acute angle structure as shown in FIG. 11a. Here, the “acute angle structure” means the illustrated Θ formed by the electrode end surface of the void B and the metal foil 3. And quartz glass 11a
On the other hand, a high pressure P from the air gap B is applied in the direction of the arrow in the figure, and this pressure P is divided by the angle Θ into the component force P1 and the component force P.
It is divided into two and the component force P2 acts so as to bring the quartz glass 11a and the metal foil 3 into close contact with each other. This action can satisfactorily solve the problem of peeling from the portion. That is, in the present invention, the wedge-shaped undesired void is not generated by devising the end face structure of the electrode 2, and therefore, the problem of peeling the metal foil caused by the wedge-shaped void is satisfactorily solved. It becomes possible to do. Further, even if the wedge-shaped void X is generated in the manufacturing stage, the force P2 for adhering the quartz glass and the metal foil to each other is stronger than the force P3 for peeling the quartz glass and the metal foil, so that the problem can be suppressed. .

The structure of the electrode end and the more acute angle structure with the metal foil are not limited to those shown in FIG. FIG. 5 shows another acute angle structure. (A) and (b) are the ones in which the ends of the electrodes are conical, and the acute angle at the contact point with the metal foil is (a) the acute angle Θ of the point 51 is 45 °,
In (b), the acute angle Θ of the point 52 is formed to be 30 °. Further, as shown in (c), a cylindrical electrode may be cut obliquely, and the acute angle Θ of the point 53 is formed at 45 °. The acute-angled structure formed at the end of the electrode is not limited to that of this embodiment, and other structures can be adopted. Also,
Various angles can be adopted as the angle formed by the acute angle structure.

Next, the relationship between the acute angle Θ and the component force was examined in the structure shown in FIG. 4, that is, in the acute angle structure formed by the electrode end face and the metal foil. This structure shows the relationship in a discharge lamp having the structure described in paragraph 0025 below. In FIG. 6, the horizontal axis represents the angle Θ, and data is collected in the range of 20 ° to 90 °. The vertical axis represents an undesired component force generated in the wedge-shaped void, that is, P3 in FIGS. 4 and 9.
The angle Θ of 90 ° means the conventional electrode end face structure shown in FIG. From the relationship shown in FIG. 6, it can be seen that the undesired component force generated in the wedge-shaped void becomes negative when the angle Θ falls below 70 °. This means that in an acute angle structure defined by angle Θ, angle Θ is 7
Below 0 °, the stress P that separates the metal foil from the quartz glass
It means that the stress P2 for bringing the two into close contact with each other exceeds 3. And as the angle Θ becomes smaller,
It is clearly shown that the stress P3 is small. That is, it can be seen that when the angle Θ is less than 70 °, the effect of the present invention is remarkably generated, and as the angle θ decreases to 55 °, 40 °, and 20 °, the effect increases. Even if the angle Θ is larger than 70 °, the stress P
Although 3 cannot be made smaller than the stress P2, the difference can be reduced more than when the angle Θ is 90 °.

If the above relation is strictly interpreted, it depends on conditions such as the size of the void B, the area of the electrode end face, and the internal pressure of the discharge space, and the angle Θ is 70.
Although it is necessary to consider these conditions also for the numerical value of °, the present inventors have found from various experiments that the mercury vapor pressure is 150 atm or more and the void B has a diameter of 6 to 16 μm. It has been confirmed that if Θ is 70 °, it has substantially the same effect. Regarding the manufacturing method of the discharge lamp of the present invention, Japanese Patent Application No.
See 0-168798. In particular, the method of forming the void B on the side surface and the end surface of the electrode 2 is described.

The acute angle structure of the electrode and the metal foil of the present invention can be suitably used for both the anode and the cathode of the discharge lamp, and is preferably used for both electrodes.

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, in the short arc type ultra high pressure discharge lamp of the present invention, by providing a minute gap between the electrode and the quartz glass forming the side tube portion, the occurrence of cracks in this portion is good. Can be prevented.
Further, since the acute angle structure is formed between the electrode end surface and the metal foil, the generation and growth of the wedge-shaped voids in that portion can be suppressed well.

[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.

FIG. 3 is a partial view of a short arc type ultra high pressure discharge lamp of the present invention.

FIG. 4 is a partial view of a short arc type ultra-high pressure discharge lamp of the present invention.

FIG. 5 shows another embodiment of the short arc type ultra-high pressure discharge lamp of the present invention.

FIG. 6 shows a partial view of a short arc type ultra high pressure discharge lamp for explaining the present invention.

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

FIG. 8 shows a partial view of a short arc type ultra high pressure discharge lamp for explaining the present invention.

FIG. 9 shows a partial view of a short arc type ultra high pressure mercury lamp for explaining a conventional structure.

FIG. 10 shows the relationship between the acute angle structure and the stress, which shows the effect of the present invention.

[Explanation of symbols]

1 discharge lamp 10 arc tube 11 side pipe 2 electrodes 3 metal foil 4 External lead B void

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01J 61/36 H01J 61/20

Claims (2)

(57) [Claims] 1. A pair of electrodes are arranged to face each other, and
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 to seal a metal foil connected to electrodes. The electrode is arranged on its side surface and end face with a minute gap formed between it and the quartz glass which is the constituent material of the side tube portion, and an acute angle structure is formed by the end face of the electrode and the metal foil, and A short arc type ultra-high pressure discharge lamp characterized in that quartz glass is also arranged in the acute angle structure. 2. The short arc type ultra high pressure discharge lamp according to claim 1, wherein the acute angle structure is formed at an angle of 70 ° or less.