JP2002373623A - Short arc type ultra-high pressure discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure having sufficiently high pressure resistance in an ultra-high pressure mercury lamp lighted at a very high mercury vapor pressure. SOLUTION: The short arc type ultra-high pressure mercury lamp 1 comprises an arc tube part 10 arranged with a pair of electrodes 2, facing each other in an interior and sealing mercury of >=0.15 mg/mm<3> , and side tube parts 11 extended on both sides of the arc tube part 10 and sealing metal foils 3 connected to the electrodes 2. In the side faces and end faces of the electrodes 2, minute voids B are formed and arranged in the side tube parts 11 in spaces with quartz glass used as a component of the side tube parts 11, acute-angle structures are formed by the end faces of the electrodes 2 and the metal foils 3, and the quartz glass is arranged even in the acute-angle structures between the electrodes 2 and the metal foils 3.

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 having a mercury vapor pressure of 150 atm or more when turned on, 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 a sufficient color rendering property on a rectangular screen. Therefore, mercury or a metal halide is used as a light source. An enclosed metal halide lamp is used. In addition, recently, such a metal halide lamp has been further downsized and a point light source has been promoted, and a lamp having an extremely short distance between electrodes has been put to practical use.

[0003] Against this background, recently, instead of metal halide lamps, lamps having an unprecedented high mercury vapor pressure, for example, 150 atm, have been proposed. This means that by increasing the mercury vapor pressure, the spread of the arc is suppressed (narrowed down) and the light output is further improved. Such an ultra-high pressure discharge lamp is disclosed in, for example, JP-A-2-148561 and JP-A-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, so that the side tube portion extending on both sides of the arc tube portion is made of quartz glass constituting the side tube portion. It is necessary to sufficiently and firmly adhere the electrodes and the metal foil for power supply. This is because if the adhesion is poor, the sealing gas may escape or cracks may occur. For this reason, 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 this state, the thick quartz glass is gradually contracted or the quartz glass is pinch-sealed to increase 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 metal foil is improved, but the problem still remains that the side tube portion is easily damaged after the completion of the discharge lamp. Occurred.
This problem is caused by the relative expansion and contraction due to the difference in the 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. It is considered that the amounts differ, and this causes cracks to occur in the contact portions between the two. This crack is very small at first,
It is considered that, together with the ultra-high pressure state during lamp operation, crack growth is induced, which leads to breakage of 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 11 is connected to the arc tube 10, and the electrode 2 is joined to the metal foil 3 in the side tube 11. The coil member 5 is wound around the electrode 2 embedded in the side tube portion 11. In this structure, the stress on the quartz glass caused by the thermal expansion of the electrode 2 is relaxed by the coil member 5 wound around the electrode 2, and is described in, for example, JP-A-11-176385.

However, even if the thermal expansion of the electrode 2 is reduced by such a structure, the crack K actually remains around the electrode 2 and the coil member 5.
Although this crack K is very small, when the mercury vapor pressure of the arc tube part 10 is about 150 atm, the side tube part 11 may sometimes be damaged. 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 crack K is promoted during lamp operation, and as a result, There is a problem that breakage of the side tube portion 11 occurs remarkably. That is, even if the presence of the crack K is very small at first, the crack K grows gradually and more when the lamp is operated at a high mercury vapor pressure. This can be said to be a new technical problem which does not exist in a mercury lamp having a vapor pressure during operation of about 50 to 100 atm.

[0008]

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

[0009]

Means for Solving the Problems To solve the above problems, a short arc type ultra-high pressure discharge lamp according to the present invention has a pair of electrodes disposed inside and a 0.15 mg / l
In a short arc type ultra-high pressure discharge lamp comprising a light emitting tube portion enclosing mercury of at least ³ mm and a side tube portion extending on both sides thereof and sealing a metal foil connected to the electrode, the side surfaces of the electrode and The end face is arranged so as to form a minute gap between the side tube part and quartz glass which is a constituent material of the side tube part, 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 the acute angle structure. Also,
The acute angle structure has an angle of 70 ° or less.

[0010]

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

Here, the present applicant has previously filed Japanese Patent Application No.
No. 168798 proposes a structure of a side tube portion having a space in the surface of an electrode as shown in FIG. In the figure, 10 is an arc tube part, 11 is a side tube part, and the electrode 2 is joined to the metal foil 3 in the side tube part 11. The electrode 2 is
On the side surface 2a and the end surface 2b, it is arranged apart from the quartz glass via a minute gap B. However, the structure disclosed in this application is an effective structure in that cracks between the electrode 2 and the quartz glass are effectively prevented, but such a structure has caused a new problem.

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

FIG. 9 is an enlarged view of the gap X. Void X
Is directly connected to the arc tube portion 10 via the gap B, and thus a high pressure (150 atm or more) generated in the arc tube portion 10 is similarly applied. This high pressure,
In the wedge-shaped space X, it is strongly applied in the illustrated arrow directions P3 and P4, which causes the quartz glass and the metal foil 3 to be peeled off. Such a phenomenon,
Ultimately, the separation of the quartz glass and the metal foil will be led, and as a result, the discharge lamp will be damaged. In addition, such a phenomenon has a structure in which the arc tube portion and the electrode end face are connected by a gap, and the internal pressure is 100 atm or more, and higher than 150, 20 as in the present invention.
It can be said that this is a specific technical problem that occurs in a discharge lamp having an extremely high pressure of 0 or more than 300 atm.

According to the present invention, a gap B is provided between an electrode and quartz glass.
In addition, for the purpose of solving the technical problem unique to a discharge lamp having an extremely high internal pressure of the light emitting portion of 150 atm or more, as a result of the inventors' intensive studies, the shape of the end face of the electrode was devised. Things.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A short arc type ultra high pressure mercury lamp according to 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 11 is hermetically sealed with quartz glass.

In the arc tube section 10, a pair of tungsten electrodes 2 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. An 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, which is used to improve lighting startability, and tungsten is wound four to five times.

The arc tube section 10 is filled with mercury as a luminescent substance and a rare gas such as argon or xenon as a lighting starting gas. The amount of mercury sealed is calculated and sealed so that the vapor pressure during stable lighting becomes 150 atm or more, preferably 200 atm or more, more preferably 300 atm or more. For example, when the mercury vapor pressure becomes 150 atm or more, the amount of enclosed mercury is 0.1
5 mg / mm ³ or more.

FIG. 2 is an enlarged view of a boundary portion between the arc tube section 10 and the side tube section 11, and corresponds to FIG. 7 and FIG. As shown in FIG.
The electrode 2 is welded at a welded portion with the metal foil 3, and the other region has a gap B between the electrode 2 and quartz glass constituting the side tube portion 11. Specifically, the electrode 2
The side surface 2a and the sealing-side end surface 2b are not in contact with the quartz glass that is the material of the side tube portion 11. In addition, the metal foil 3
Actually, the gap B and the like are extremely small or thin, but are exaggerated in the drawings for the purpose of explaining the invention. FIG. 3 also shows an end 2b of the electrode, and corresponds to FIG. (A) is an enlarged view of the electrode end, (b) is a C-
FIG. 3C is a cross-sectional view of the C ′ cross section viewed from above (D side),
3A is a cross-sectional view of the DD ′ cross section of FIG.

Here, the gap B is determined from the viewpoint that the electrode can freely expand and contract in the axial direction without being restricted by the difference in the expansion coefficient between the constituent material of the electrode and the material forming the side tube portion. When the electrode is made of tungsten and the side tube is made of quartz glass, the width B of the gap is 6 to 16
It is selected from the range of μm and exists in the length direction of the electrode in the gap B by 3 to 5 mm. Incidentally, the outer diameter of the electrode is, for example,
0.4 to 1.3 mmΦ. By forming such a gap B, the occurrence of cracks due to the relative movement of the electrode and the quartz glass can be favorably prevented. Further, according to the present invention, the shape of the outer end face 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, the technical problem caused by providing the gap B, that is, the generation and growth of an undesired wedge-shaped gap X can be satisfactorily prevented.

FIG. 4 shows an enlarged structure of the electrode end. As shown in the figure, the end 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 gap B formed around the electrode has substantially the same shape. Is formed as The electrode end and the metal foil 2 form an acute angle structure, and quartz glass enters the acute angle structure as shown in FIG. 11A. Here, the “acute angle structure” means an illustration さ れ る formed by the electrode end surface of the gap B and the metal foil 3. And the quartz glass 11a
, A high pressure P from the air gap B is applied in the direction of the arrow shown in the figure.
The quartz glass 11a and the metal foil 3 are brought into close contact with each other by the component force P2. This action can satisfactorily solve the problem of peeling from the portion. That is, in the present invention, the above-described undesired wedge-shaped gap is not generated by devising the end face structure of the electrode 2, and therefore, the problem of peeling of the metal foil generated from the wedge-shaped gap can be solved well. It is possible to do. Further, even if the wedge-shaped void X is generated in the manufacturing stage, the force P2 for bringing the both into close contact acts more strongly than the force P3 for peeling off the quartz glass and the metal foil, so that the occurrence of the problem can be suppressed. .

The structure of the electrode end portion and the sharper structure with the metal foil are not limited to those shown in FIG. FIG. 5 shows another acute angle structure. (A) and (b) show the end of the electrode in a conical shape. 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 の of the point 52 is formed at 30 °. Further, as shown in (c), the columnar electrode may be cut obliquely, and the acute angle の of the point 53 is formed at 45 °. It should be noted that the acute angle structure formed at the electrode end is not limited to that of the embodiment, and other structures can be adopted. Also,
Various angles can also be adopted for 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 the following paragraph 0025. In FIG. 6, the horizontal axis indicates the angle Θ, and data is collected in the range of 20 ° to 90 °. The vertical axis indicates an undesired component force generated in the wedge-shaped gap, that is, P3 in FIGS.
The angle Θ of 90 ° means the conventional electrode end face structure shown in FIG. It can be seen from the relationship shown in FIG. 6 that when the angle Θ falls below 70 °, the undesired component force generated in the wedge-shaped gap is negative. This means that in an acute angle structure defined by the angle Θ, the angle Θ is 7
Below 0 °, the stress P that separates the metal foil from the quartz glass
This 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 decreases. That is, when the angle Θ is less than 70 °, the effect of the present invention is remarkably generated, and the effect becomes larger as the angle becomes smaller at 55 °, 40 °, and 20 °. Even when the angle Θ is larger than 70 °, the stress P
3 cannot be made smaller than the stress P2, but the difference can be reduced as compared with the case where the angle Θ is 90 °.

If the above relationship is strictly interpreted, the relationship varies depending on conditions such as the size of the gap B, the area of the electrode end face, and the internal pressure of the discharge space.
Although it is necessary to consider these conditions also for the numerical value of °, the present inventors have determined from various experiments that if the mercury vapor pressure is 150 atm or more and the gap B is 6 to 16 μm, the angle It has been confirmed that when Θ is 70 °, substantially the same effect is obtained. The manufacturing method of the discharge lamp of the present invention is described in Japanese Patent Application No.
See 0-168798. In particular, a method of forming the gap 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 Overall lamp length: 65.0 mm Side tube length: 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 Mercury sealed amount: 0.15 mg / mm ³ Noble gas: 100 Torr of argon

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 constituting the side tube portion, the occurrence of cracks in this portion is improved. Can be prevented.
In addition, since an acute angle structure is formed between the electrode end face and the metal foil, the generation and growth of wedge-shaped voids in the portion can be favorably suppressed.

[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 the short arc type ultra-high pressure discharge lamp of the present invention.

FIG. 3 is a partial view of the 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 according to the present invention.

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

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

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

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

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

FIG. 10 shows a relationship between an acute angle structure showing the effect of the present invention and stress.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge lamp 10 Arc tube part 11 Side tube part 2 Electrode 3 Metal foil 4 External lead B Void

Claims (2)

[Claims] 1. A pair of electrodes are arranged inside each other, and
In a short arc type ultra-high pressure discharge lamp comprising an arc tube portion containing mercury of 0.15 mg / mm ³ or more and a side tube portion extending on both sides thereof and sealing a metal foil connected to an electrode, The electrode is arranged so that a minute gap is formed between the side surface and the end face thereof 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. A short arc type ultra-high pressure discharge lamp characterized in that quartz glass is also arranged in an acute angle structure. 2. The short arc type ultra-high pressure discharge lamp according to claim 1, wherein said acute angle structure is formed at an angle of 70 ° or less.