Electric lamp and discharge devices – With gas or vapor – Having electrode lead-in or electrode support sealed to...
Reexamination Certificate
2001-09-20
2004-11-30
Williams, Joseph (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Having electrode lead-in or electrode support sealed to...
Reexamination Certificate
active
06825614
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a short-arc discharge lamp for UV irradiation which, for example, is used in the production of semiconductors and liquid crystals. More particularly, the invention relates to a foil seal arrangement on the cathode side of a large short-arc discharge lamp.
2. Description of Related Art
Among short-arc discharge lamps for semiconductors and liquid crystals, large short-arc discharge lamps with an input electric power of, for example, greater than 1 kW are generally those that use foil sealing to ensure sealing of the discharge space. In short-arc lamps using this foil sealing, it is known that there is a defect in which a gas emerges from the foil sealing areas and destroys the lamps. An explanation for this defect is that the positive ions (i.e., cations) of metallic impurities, and the like, in the quartz glass are attracted by the negative electrical charge on the side of the cathode and in the foil sealing area on the side of the cathode, and that the positive ions concentrated on the cathode side and the foil sealing area detach the metal foil from the quartz tube part surrounding the metal foil. To eliminate this defect, an arrangement of a wire with the same electrical potential, which electrically connects on the outer surface of the quartz tube on the side of the cathode to the cathode, is implemented, as is described in Japanese patent disclosure HEI 4-40828 and its counterpart U.S. Pat. No. 4,673,843, for example, both of which are incorporated herein by reference.
FIG. 6
shows a conventional example of the arrangement of the foil sealing area on the cathode side of a short-arc discharge lamp with an input electrical power of greater than or equal to 1 kW, in which the above described wire with the same electrical potential is located. This lamp consists of the following:
a bulb part
51
which jackets the emission space,
a cathode
52
which is located in this bulb part
51
;
an inner lead pin
53
which is connected to the cathode
52
;
an inner lead pin holding component
54
which holds the inner lead pin
53
securely;
a metal disk
55
which is connected to the end opposite the side of the cathode
52
of the inner lead pin
53
;
a metal foil
56
which is welded to the metal disk
55
;
a sealing quartz component
57
which is in contact with the inside of the metal foil
56
;
a quartz tube part
58
which is in contact with the outside of the metal foil
56
;
an outer lead pin
59
;
a metal disk
60
which connects the outer lead pin
59
and the metal foil
56
to one another;
a foil sealing area
61
which ensures the sealing action of the lamp;
a metal base
62
;
a line
63
;
a terminal part
64
which connects the line
63
to the above described lead pin; and
a wire
65
which provides the same electrical potential between the metal base, which is electrically connected to the cathode
52
, and the outer surface of the quartz tube.
For the metal foil
56
, which is used for the foil sealing area
61
, a strip-like foil with a thickness of a few tenths of a micron is used. The foil is made of a metallic material having a high melting point, such as molybdenum or the like. In the foil sealing area
61
, the sealing action of an emission space is ensured by the metal foil
56
. The sealing quartz component
57
, which is in contact with the inside of the metal foil
56
, and the quartz tube part
58
, which is in contact with the outside of the metal foil
56
, are located directly tightly adjacent to one another. The above-described defect is in the adhesion area, in which the metal foil
56
and the quartz tube part
58
which surrounds the metal foil are located directly tightly adjacent to one another, comes off. Specifically, the defect wherein positive ions of metallic impurities, and the like, in the quartz glass are attracted by the negative electrical charge on the side of the cathode
52
and are concentrated on the foil sealing area
61
on the side of the cathode
52
, such that the positive ions concentrated on the foil sealing area
61
detach the metal foil
56
from the quartz tube part
58
that surrounds the metal foil
56
, which is prevented by the use of a wire
65
which provides the same electrical potential to the outer surface of the quartz tube on the side of the cathode to the cathode by electrically connecting them, as described above.
According to increased market demand, the size and power rating of short-arc discharge lamps are becoming larger and larger. According to the input electrical power of the lamps of, for example, greater than 4 kW, the diameter and a length of the foil sealing area
61
shown in
FIG. 6
are becoming larger and larger. For a lamp of this size, the operating pressure during luminous operation is greater than or equal to 2×10
6
Pa, which creates a new problem, i.e., that the foil floats between the metal foil
56
and the sealing quartz component
57
which is in contact with the inside of the metal foil
56
.
SUMMARY OF THE INVENTION
An object of the invention is, therefore, to prevent the phenomenon of foil floating between the metal foil
56
located in the foil sealing area
61
and the sealing quartz component
57
in contact with the inside of the metal foil
56
in a large lamp with an electrical input power of greater than 4 kW and with an operating pressure during luminous operation of greater than or equal to 2×10
6
Pa.
It is another object of the invention to prevent cracks from forming in the foil sealing area
61
, the leakage of gas from the lamp, and the premature breaking of the lamp during luminous operation.
Thus, in an embodiment of the present invention, there is provided a short-arc discharge lamp which includes:
electrodes which are located in an emission space;
a metal foil which is electrically connected to the electrodes;
a quartz tube part which surrounds the above described metal foil;
a sealing quartz component which is in contact with the inside of the metal foil;
a metallic component which is inserted into the above described sealing quartz component and which is electrically connected to the metal foil; and
a foil sealing area formed by the metal foil, the quartz tube and the sealing quartz component sealed against one another, and by which a sealing action of the above described emission space is ensured. The short-arc lamp has an electric input power greater of than or equal to 4 kW and an operating pressure during luminous operation of greater than or equal to 2×10
6
Pa, and is operated using direct current.
The above-mentioned characteristics of the invention are achieved by the length of the area of the metallic component inserted into the sealing quartz component being greater than or equal to roughly 40% of the total length of the sealing quartz component.
The object characteristics of the lamp of the present invention are furthermore achieved in that at least in one part of the foil sealing area on the cathode side there is an electrically conductive component which is electrically connected to the cathode along the outside surface of the quartz tube part.
Furthermore, it is another object of the invention to provide a short-arc discharge lamp that includes:
electrodes which are located in an emission space;
a metal foil which is electrically connected to the above described electrodes;
a quartz tube part which surrounds the above described metal foil;
a sealing quartz component which is in contact with the inside of the metal foil;
a metallic component which is inserted into the above described sealing quartz component and is electrically connected to the metal foil; and
a foil sealing area formed by which the metal foil, the quartz tube and the sealing quartz component sealed against one another, and by which a sealing action of the above described emission space is ensured. The short-arc lamp has an operating pressure during luminous operation greater than or equal to 2×10
6
Pa, and is operated using direct current.
It is an object of the invention that t
Ikeda Naohisa
Sugihara Masanori
Macchiarolo Peter
Nixon & Peabody LLP
Safran David S.
Ushiodenki Kabushiki Kaisha
Williams Joseph
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