JPH0628779Y2 - High pressure discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a high pressure discharge lamp such as a high pressure sodium lamp or a metal halide lamp.

[Prior Art] As shown in FIG. 4, the structure of a metal halide lamp, which is an example of a high-pressure discharge lamp, is such that a cermet closing body 12 is inserted into both open ends of an arc tube 11 made of translucent alumina ceramics. And sealed with a glass frit 15, and an electrode 13 made of tungsten is provided inside the closing body 12.
The lead wires 14 made of tungsten or molybdenum were fixed to the outside. Further, mercury and a metal halide are enclosed inside the arc tube 11, and these compounds are separated into a metal atom and a halogen by arc discharge between the two electrodes 13, and the metal atom emits a unique spectrum. It was supposed to do.

The closing body 12 is made of cermet,
This is because the electrode 13 and the lead-in wire 14 are electrically connected and the corrosion resistance is excellent. (JP-A-61-118934, 6
In addition to this, the one in which the blocking resistance 12 is formed of alumina ceramics and the surface of the blocking body 12 is coated with tungsten as a conductive layer in order to electrically connect the electrode 13 and the lead-in wire 14 is also possible. Was used.

[Problems of conventional technology]

However, in the conventional high-pressure discharge lamp, an arc did not come out from the tip of the electrode 13 at the time of discharge, and a back arc phenomenon occurred from the inner surface portion 12a of the closing body 12 was likely to occur. When the back arc phenomenon occurs, cracks occur in the closing body 12,
There is a problem that the metal component of the cermet material that has evaporated and scattered adheres to the inner wall of the arc tube 11 and does not turn black.

Further, the one in which the closing body 12 is made of cermet has a coefficient of thermal expansion slightly different from that of the light emitting tube 11 made of translucent alumina ceramics, and thus the sealing property is apt to be deteriorated with a change in temperature.

[Means for Solving the Problems]

In view of the above, the present invention forms a conductive layer on the surface of a substrate made of alumina ceramic so as to electrically connect an electrode fixed to the inner side of an arc tube and an electrode lead-out portion formed on the outer side, and A high-pressure discharge lamp is configured by sealing the open end of the arc tube with a closing body formed by covering at least the surface of the conductive layer inside the arc tube with an insulating layer.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

The high-pressure discharge lamp shown in FIG. 1 comprises a light emitting tube 1 made of translucent alumina ceramics, in which mercury, metal halide, etc. are sealed, and both end openings are sealed with a closure H. An electrode 3 is fixed to the inside of the arc tube 1 of the base body 2 made of alumina ceramics constituting the closing body H, and a lead-in wire 4 is fixed to the outside thereof as an electrode lead-out portion, respectively, and these electrodes 3 and 4 are electrically connected. To this end, a conductive layer 5 made of tungsten is deposited on the surface of the base 2. Further, an insulating layer 6 made of alumina or the like is formed so as to cover the conductive layer 5, and such a closing body H is fixed to the arc tube 1 with a glass frit 7 so as to keep airtightness.

The translucent alumina ceramics forming the arc tube 1 is obtained, for example, by firing high-purity alumina ceramics having an Al ₂ O ₃ content of 99.5% at 1950 ° C. in a vacuum atmosphere. In addition to having excellent corrosion resistance. The conductive layer 5 is formed by a general metallizing method, and if tungsten is used, it has excellent corrosion resistance. Further, the insulating layer 6 is formed by the CVD method, the PVD method or another method, and the base 2
It is suitable to use the same alumina ceramics as above because they have the same thermal expansion coefficient.

Further, the back arc phenomenon described above can be prevented by forming the insulating layer 6 in this way. In particular, the insulating layer 6 is also formed on the joint portion of the closing body H with the arc tube 1, and the back arc phenomenon from this portion can also be prevented, so that the dimensional accuracy of the closing body H and the arc tube 1 can be strictly controlled. You don't have to. Further, since the base body 2 and the arc tube 1 which form the closing body H are made of the same alumina ceramics, the coefficients of thermal expansion coincide with each other, and the sealing performance does not deteriorate due to temperature change.

Next, another embodiment of the present invention will be described. As shown in FIG. 2 (a), which is a cross-sectional view of only the block H, the introduction line 4 of the base 2
The side end may be provided with the collar 8 made of alumina ceramics. In this case, since the collar 8 is locked to the end of the arc tube 1, the positioning becomes easy and the airtightness can be improved.

Also, as shown in FIG. 2 (b), an alumina ceramic tape 6a is wound around the conductive layer 5 on the side surface of the base 2 and an alumina coating layer 6b is formed at the end to form the insulating layer 6. Is. With such a structure in which the loop 6a is wound around the side surface portion, the manufacturing is easy, and the thickness of the insulating layer 6 can be easily adjusted.

Further, in the one shown in FIG. 2 (c), the tape 6a is wound around the side surface of the substrate 2, the lead-in wire 4 is not fixed, and the electrode lead-out portion 4'exposes the conductive layer 5. An electrode extraction member (not shown) is pressure-bonded to the.

Further, in the above embodiment, the arc tube 1 and the closing body H are separately formed and bonded by the glass frit 7, but at one opening end, the closing body H is attached to the arc tube 1. It may be integrally sintered with. For example, as shown in FIG. 3, alumina slurry 9 is applied to the gap between the arc tube 1 in the green or calcined state and the base body 2 on which the conductive layer 5 is formed and the inner surface of the base body 2. By firing, the arc tube 1 and the closing body H are integrally sintered and can be made completely airtight. At this time, the alumina slurry 9 forms the insulating layer 6 after firing.

Further, in the above embodiments, the insulating layer 6 does not have to be formed on the entire surface of the substrate 2, and as shown in FIGS. 2 (c) and 3, the inner side including at least the joint portion with the light emitting layer 1 is formed. If the thickness is 0.5 mm or more, the effect of preventing the back arc phenomenon was excellent.

[Effect of device]

As described above, according to the present invention, a conductive layer is formed on the surface of the base body so as to electrically connect the electrode fixed to the inner side of the arc tube of the base body made of alumina ceramics and the electrode lead-out portion formed on the outer side. In addition, the back arc phenomenon occurs because the high-pressure discharge lamp is configured by sealing the open end of the arc tube with a closing body formed by covering at least the surface of the conductive layer inside the arc tube with an insulating layer. As a result, damage to the closing body and blackening of the arc tube can be prevented, and since the coefficient of thermal expansion of the closing body and the arc tube are the same, the sealing property does not deteriorate with temperature change.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a high pressure discharge lamp according to an embodiment of the present invention, and FIGS. 2 (a) (b) (c) and FIG. FIG. FIG. 4 is a longitudinal sectional view showing a conventional high pressure discharge lamp. 1 ... Arc tube 2 ... Substrate 3 ... Electrode 4 ... Introduction wire 5 ... Conductive layer 6 ... Insulating layer 7 ... Glass frit 8 ... Tsuba H ... Closure body

Claims (2)

[Scope of utility model registration request] 1. A conductive layer is formed on the surface of a base made of alumina ceramics so as to electrically connect an electrode fixed to the inner side of the arc tube to an electrode lead-out portion formed on the outer side, and at least an arc tube. A high pressure discharge lamp characterized in that an open end of an arc tube is sealed by a closing body formed by covering the surface of the conductive layer inside with an insulating layer. 2. The high pressure discharge lamp according to claim 1, wherein the closing body is fixed to one opening end of the arc tube by integral firing.