Electric lamp and discharge devices – With gas or vapor – Envelope with particular structure
Reexamination Certificate
1998-08-17
2001-05-15
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Envelope with particular structure
C313S641000, C313S571000, C313S631000
Reexamination Certificate
active
06232720
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a high-pressure mercury vapor discharge lamp used for the back light of an optical instrument such as a liquid crystal projector or an overhead projector.
BACKGROUND OF THE INVENTION
Recently, as the back light of an optical instrument such as a liquid crystal projector or an overhead projector, a projection light source that uses a high-pressure mercury vapor discharge lamp, whose continuous emission in the visible range is increased by increasing the vapor pressure of mercury during lighting to the range of 20 to 35 MPa, combined with a reflecting mirror is known (see Japanese Patent Application (Tokkai Hei) No. 2-148561).
The first requirement for the back light used for a liquid crystal projector or the like is a high luminance. For example, in a high-pressure mercury vapor discharge lamp, the luminance requirement can be satisfied by setting the load input per the unit length of the discharge arc (X/L) to 88 or more, in which X (W) is the lamp power during lighting and L (mm) is the distance between the electrodes. In such a lamp, the lighting life is about 4,000 hours at most. Recently, however, a longer life, that is, a life of 4,000 hours or more, is desired.
In conventional high-pressure mercury vapor discharge lamps, as X is higher and L is shorter, the load input per the unit length of the discharge arc (X/L) increases, in which X (W) is the lamp power during lighting and L (mm) is the distance between the electrodes. Thus, the arc temperature increases. For example, when the lamp is designed with a X/L of 88 or more, the tube wall temperature of the arc tube increases during the lighting life because the arc temperature increases excessively. Also, the arc tube gradually expands during the lighting life because the lighting operation pressure is as high as 10 to 35 MPa. Thus, difficulties are caused. For example, the optical characteristics of the lamp change, and the lamp is damaged by the expansion of the arc tube. Therefore, it is difficult to achieve the life of 4,000 hours or more.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a high-pressure mercury vapor discharge lamp that has a high luminance, can reduce the expansion of the arc tube and occurrence of damage caused by this expansion, and can achieve a life of 4,000 hours or more.
In order to achieve the above object, the present invention provides a high-pressure mercury vapor discharge lamp comprising an arc tube in which a pair of electrodes are provided and in which a rare gas as a starting gas, a material from which a free halogen is to be produced during a lighting operation, and mercury are enclosed. The arc tube satisfies X/L≧88, in which X(W) is a lighting operation power and L (mm) is a distance between the electrodes. The high-pressure mercury vapor discharge lamp satisfies the following expression:
1.2≦&phgr;/(X×10
−2
+3.2)≦1.6
in which &phgr; (mm) is the maximum inner diameter of the arc tube.
It is preferable that the material from which free halogen is produced is at least one material selected from the group consisting of CH
2
Cl
2
, CH
2
Br
2
, CH
2
I
2
, CH
3
Cl, CH
3
Br, CH
3
I, CHCl
3
, CHBr
3
and CHI
3
.
It is preferable that the free halogen is present in the arc tube in the range of 10
−10
to 10
−3
mol/cm
3
during a lighting operation.
It is preferable that the free halogen is present in the arc tube in the range of 10
−7
to 10
−5
mol/cm
3
during a lighting operation.
It is preferable that the free halogen is at least one free halogen selected from the group consisting of Cl, Br and I.
It is preferable that the free halogen is Br.
It is preferable that the rare gas is argon.
It is preferable that the amount of the enclosed mercury is in the range of 100 to 350 mg/cm
3
based on the volume of the arc tube.
It is preferable that the vapor pressure of the mercury during lighting is in the range of 10 to 35 MPa.
In the high-pressure mercury vapor discharge lamp of the present invention, the arc tube does not expand at a lighting power of 150 W for up to 4,000 hours.
In the high-pressure mercury vapor discharge lamp of the present invention, damage due to expansion of the arc tube does not occur at a lighting power of 150 W for up to 6,000 hours.
Therefore, the mercury vapor pressure during lighting can be set to 10 to 35 MPa, and an emission spectrum in which red, green and blue components are balanced can be obtained. Also, a high luminance can be achieved by satisfying X/L≧88, in which L is the distance between the electrodes, and X is the lighting power. Furthermore, even if the are temperature increases excessively, the increase of the tube wall temperature of the arc tube can be prevented, and the expansion and damage of the arc tube during the lighting life can be prevented. In addition, the upper limit of X/L is about 300.
As described above, the high-pressure mercury vapor discharge lamp of the present invention has a high luminance and can achieve a lighting life of 4,000 hours or more.
REFERENCES:
patent: 4340844 (1982-07-01), Tsuchihashi et al.
patent: 4686419 (1987-08-01), Block et al.
patent: 4891555 (1990-01-01), Ahlgren et al.
patent: 4988918 (1991-01-01), Mori et al.
patent: 5107178 (1992-04-01), Ohyama et al.
patent: 5109181 (1992-04-01), Fischer et al.
patent: 5239232 (1993-08-01), Heider et al.
patent: 0 576 071 A1 (1993-12-01), None
Kitahara Yoshiki
Takeuti Nobuyosi
Tsutsumi Takeharu
Matsushita Electronics Corporation
Merchant & Gould P.C.
Patel Nimeshkumar D.
Williams Joseph
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