Electric lamp and discharge devices – With gas or vapor – Having electrode lead-in or electrode support sealed to...
Reexamination Certificate
2001-02-28
2003-03-18
Royer, William J. (Department: 2852)
Electric lamp and discharge devices
With gas or vapor
Having electrode lead-in or electrode support sealed to...
C313S625000
Reexamination Certificate
active
06534917
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a discharge lamp that is preferably used as a light source for exposure in the manufacture of a liquid crystal display element, a color filter, a printed circuit board or a semiconductor element.
2. Description of the Related Art
In the case of a manufacturing process of a liquid crystal display element, a color filter, a printed circuit board and a semiconductor element and the like, a photolithography process is utilized for performing exposure of micro-images, and a short-arc type discharge lamp is used as a light source for exposure. Such a short-arc type discharge lamp is made such that there is provided a bulb having bulb-sealing sections jointly connected to both ends of a light emitting tube which encloses a light emitting space, and both an anode and a cathode are arranged opposite to each other within the light emitting tube of this bulb, and both inert gas and mercury or the like, for example, are hermetically filled therein.
In
FIG. 3
, a practical example of a conventional short-arc type discharge lamp will be described as follows, wherein a bulb
50
of the discharge lamp is made such that outward extending cylindrical sealing tubes
52
are jointly arranged at both ends of an elliptical spherical light emitting tube
51
enclosing a light emitting space S, and narrowed sections
52
a
provided such that the diameter of the formed sealing tube
52
is reduced at locations near the light emitting tube
51
of the sealing tubes
52
following the light emitting tube
51
.
Within the light emitting tube
51
an anode
53
and a cathode
54
are arranged opposite, each of these electrodes is fixed to and supported by an electrode rod
55
extending from the sealing tube
52
to the light emitting tube
51
along an axis of the bulb. Within the sealing tubes
52
are arranged electrode rod holding cylinders
56
having cylindrical holes adapted to the outer diameters of the electrode rods
55
in a state in which the base ends of the electrode rods
55
are inserted therein, the outer circumferential surface of the electrode rod holding cylinder
56
adheres and is hermetically sealed to the inner surface of the narrowed section
52
a
. Each of sealing glass members
57
is comprised of an inner frustro-conical end
57
a
, the diameter of which is enlarged in the direction of the outer end, and a cylindrical barrel
57
b
following the inner end is arranged at an outer end of the electrode rod holding cylinder
56
. The sealing glass member
57
is formed with a hole
57
c
having a bottom part extending from its outer end surface along an axial direction, and an outer lead rod
58
having an outer diameter adapted to its inner diameter is inserted into the hole
57
c
having the bottom part.
A plurality of belt-like metallic foils
60
are spaced apart from each other in a circumferential direction of the sealing glass member
57
and arranged at the outer circumferential surface of the sealing glass member
57
so as to extend from the inner end to the outer end of the sealing glass member
57
, the inner end of each of the metallic foils
60
extends along the inner end surface of the sealing glass member
57
and is connected to the electrode rod
55
, an outer end of each of the metallic foils
60
extends along the outer end surface of the sealing glass member
57
and is connected to the outer lead rod
58
. In addition, the outer circumferential surface of the sealing glass member
57
adheres and is hermetically sealed to the inner surface of the sealing tube
52
through the metallic foils
60
. At an outer end of the sealing glass member
57
is arranged a lead rod holding cylinder
59
having a cylindrical hole adapted to an outer diameter of the outer lead rod
58
in a state in which the outer lead rod
58
is being inserted, and the outer circumferential surface of the lead rod holding cylinder
59
adheres and is hermetically fixed to the inner surface of the sealing tube
52
.
Such a discharge lamp as described above is normally lit in a vertical lighting process, i.e., the anode
53
and the cathode
54
are facing oppositely in a vertical direction in order to maintain a stable state of the arc formed between the anode
53
and the cathode
54
during lighting of the discharge lamp. However, in the case in which the discharge lamp is lit in such a way that the cathode
54
is positioned above the anode
53
in such a vertical lighting system, the direction in which mercury vapor flows from convection between the anode
53
and the cathode
54
, and the direction in which thermo-ionic electrons discharged from the cathode
54
move towards the anode
53
are opposite from each other so that the motion of the thermo-ionic electrons is influenced by the convection of the mercury vapor with the result that there is a possibility of arc fluctuation.
Furthermore, in the case in which the discharge lamp is lit such that the anode
53
is positioned above the cathode
54
, the direction in which the mercury vapor flows in a convection between the anode
53
and the cathode
54
and the direction in which the thermo-ionic electrons discharged from the cathode
54
move toward the anode
53
are made to be the same so that the motion of the thermo-ionic electrons is not influenced by the convection of the mercury vapor with the result that the state of the arc can be kept in a more stable condition. However, in the case in which the discharge lamp is lit such that the anode
53
is positioned above the cathode
54
, there occurs numerous problems. For example, in a state in which the discharge lamp is not lit, almost all of the mercury hermetically filled within the light emitting space S of the bulb
50
is present in a state in which the mercury is condensed at the end part of the cathode
54
in the light emitting space S (on the inner end surface of the electrode rod holding cylinder
56
). Then, when the discharge lamp is lit in such a state, since the temperature of heat generated at the cathode
54
is substantially low as compared with the temperature of heat generated at the anode
53
, it is not possible to evaporate the mercury condensed at the end part of the cathode
54
in the light emitting space S within a short period of time after starting lighting of the discharge lamp resulting in that it requires a rather long period of time until the light emitting intensity of the radiated light becomes stable.
In particular, in recent years it has been required to provide a discharge lamp having a high light emitting intensity of radiation light, and in correspondence with this requirement there is a tendency that the amount of mercury filled in the bulb
50
is increased. Although in the case that such a discharge lamp is lit such that the anode
53
is positioned above the cathode
54
it becomes hard to completely evaporate the encapsulated mercury resulting in that radiated light having a desired light emitting intensity cannot be attained.
SUMMARY OF THE INVENTION
The present invention has been made with respect to the aforesaid circumstances, and it is an object of the present invention to provide a discharge lamp in which the state of the arc can be stably maintained and the light emitting intensity of the radiated light can be stabilized within a short period of time after starting the lighting operation.
The discharge lamp of the present invention includes a bulb having a light emitting tube enclosing a light emitting space and sealing tube sections arranged at both ends of the light emitting tube; an anode and a cathode oppositely arranged to face each other within the light emitting space of the bulb; and electrode rods bearing the anode and, respectively, cathode at their extreme ends extending from the sealing tube sections of the bulb toward the light emitting tube, and mercury being hermetically filled in the light emitting space of the bulb, characterized in that a thermal conductor plate is arranged at the end part of the cathode in the light emitt
Nixon & Peabody LLP
Royer William J.
Safran David S.
Ysguidebju Jabysguju Jausga
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