JPS63308861A - ceramic discharge lamp - Google Patents

Abstract

PURPOSE:To prevent leakage and breakage in a tube sealed part from occurring by sealing an opening part of an alumina tube specific in its thickness by the use of an enclosing matter made of ceramics of two specific materials specified in their thicknesses and diameters and the like. CONSTITUTION:An opening of an alumina tube 1 of 0.6mm to 1.2mm in its thickness, for use in forming a ceramic discharge lamp, is sealed by an enclosing matter 2. This enclosure 2 is made 5mm to 20mm in its thickness and 10mm<y<35mm in its diameter y, and it is composed of a central part of a conductive ceramics part 2a, where an electrode 3 and an external introduction matter 4 are buried and fixed, and an peripheral part of an alumina ceramics part 2b. The ceramics part 2a is made of a sintered material formed by mixing 10wt.% to 20wt.% of tungsten with alumina as a remaining part. A diameter d of this part 2a is made to be a value which satisfies a condition shown in an equation when d/y is assumed to be x%. Tensile strength applied to the ceramics part 2a from the tube 1, caused by a difference of thermal expansion coefficients accompanying a rise in temperature at the start of the lighting of a discharge lamp, is made small. Consequently leakage and breakage in the sealed part of the tube can be prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Field of Industrial Application) The present invention relates to a ceramic discharge lamp using an alumina tube as the arc tube pulp.

(Prior art) Conventionally, in ceramic discharge lamps that use a translucent ceramic tube (1), usually an alumina tube, as the arc tube pulp, the opening is heated and softened to crush and seal it, as in the case of quartz glass arc tube bulbs (2). Since it is difficult to do so, the opening is hermetically sealed using a sealing material such as glass solder using a ceramic closure.

In recent years, for example, Japanese Patent Application Laid-Open No. 52-71695
The publication describes the use of conductive ceramics as the material for the closure body.

The conductive ceramic closure body itself also serves as an electricity introduction body, similar to the case of conventional non-conductive ceramic closure bodies.

There is no need to pass the electricity introduction body to the electrode protruding into the arc tube airtightly through the closing body through glass solder, and the proximal end of the electrode is placed on the inner surface side of the conductive ceramic closing body (inside the arc tube). On the other hand, since it is only necessary to fix the introduction bodies to the outer surface, there is no need for glass solder for airtight penetration of the introduction bodies. Therefore, the glass solder is used in the arc tube sealing part between the closure body and the arc tube bulb. It's just a club,
It is possible to reduce leakage caused by glass solder.

Furthermore, Japanese Patent Application Laid-Open No. 61-61338 describes a method of directly sealing a conductive ceramic closure to an alumina tube, which is an arc tube bulb, by solid phase bonding without using glass solder. According to this method, since no glass solder is used, leakage defects caused by glass solder can be completely prevented. However, because the thermal expansion coefficients of conductive ceramics (for example, alumina-tungsten) mixed sintered bodies and alumina ceramics are different, the sealing part formed by solid-phase bonding between the closing body and the alumina tube gradually deteriorates during the life of the lamp. Defects such as cracks, leaks, and breakage of the alumina tube, which has a thin inner thickness of typically 0.75 mm, are likely to occur. This drawback is especially true when using thick alumina pipes with diameters exceeding 10 m.

In other words, in lamps where the diameter of the occluder exceeds 10 mm, this phenomenon occurs significantly.

(Problems to be Solved by the Invention) As described above, when a thick alumina tube with a diameter of more than 10 mm is directly sealed with a conductive ceramic closure by solid phase bonding without using glass solder.

Disadvantages such as leakage from the sealing part and easy breakage of the alumina tube, which is one arc tube bulb, were apparent. Therefore, the present invention solves the above-mentioned drawbacks, and is a ceramic discharge lamp that does not cause leakage or damage to the sealed part of the alumina tube, which is an arc tube bulb with a diameter of more than 10 m, even when a conductive ceramic closure is used. The purpose is to provide

[Structure of the invention]

(Means for Solving the Problems) In the ceramic discharge lamp of the present invention, a disk-shaped closing body that airtightly seals the opening of the alumina tube by solid phase bonding is provided.
The center part is made of conductive ceramic that supports the electrode, and the outer peripheral part is made of alumina ceramic, and its thickness is 5n to 20 rxx.

The diameter y is Low<y≦35m, and the ratio of the diameter of the conductive ceramic portion to the diameter y of the closure body is d/
When y is X (%).

y<--xmo40 It is configured so that

(Function) The damage to the sealing part of the alumina tube described above is due to the difference in thermal expansion coefficient α between the conductive ceramic that forms the disk-shaped closure and the alumina tube that forms the arc tube bulb. Since the α of the ceramic closure is smaller than that of the alumina tube, when 9 is turned on (when the temperature of the sealing part rises), a pulling force acts on the alumina tube in the sealing part in the radial direction of the closure, that is, inward, and this If the force is too strong, it will break. The force that pulls the alumina tube inward increases as the area of contact with the conductive ceramic agricultural enclosure, that is, the thickness of the closure increases, and as the diameter of the closure increases.

However, according to the configuration of the present invention, only the central part of the closing body is made of conductive ceramics, and the outer periphery, that is, the part where it joins to the alumina tube, is made of the same alumina ceramics, so that when the temperature rises, the sealing part of the alumina tube is made of conductive ceramics. The inward pulling force exerted on the alumina can be reduced as if using a small (small diameter) closure entirely made of conductive ceramics, and therefore Even in the case of a pipe, damage to the sealing part can be prevented.

(Example) The present invention will be described in detail below based on the example and test results shown in one drawing.

FIG. 1 shows a vertical cross-sectional view of the sealing portion at one end of a metal halide lamp arc tube, which is an embodiment of the ceramic discharge lamp of the present invention. The alumina tube (2) forming the valve is a closing body that airtightly seals the opening of the alumina tube (1) by solid phase bonding, and has a thickness of 10 fl and a diameter y of 15 m1. The center of the closure body (2) includes the electrode (3) and the external introduction body (
4) is a conductive ceramic part (2a) that embeds and fixes each end of the part, and the outer periphery thereof is made of an alumina ceramic part (2b), and the conductive ceramic part (2a) has a weight ratio of Tungsten (average particle size 0.
5μm), and the remainder is alumina (center particle size: 50μm).
), the conductive ceramic part (2a
) is 5fl, so the ratio X (%) of this diameter d (mm) to the diameter y of the entire obturator (2) is
) is d(5n)7. <□5. ) was 33%.

Note that a predetermined amount of a starting rare gas such as argon gas, mercury, and metal halides such as dysprosium, thallium, and sodium iodide are sealed inside the arc tube. The lamp is housed in an outer tube (not shown) filled with inert gas.

For example, when a metal halide lamp with such a configuration is lit at a room temperature of 20°C with a tube wall load of 30 W/-, the temperature at the end of the two arc tubes rises to about 800°C.
As a result of conducting a flashing test with a cycle of (lights on for 5.5 hours - lights off for 0.5 hours), no leakage or damage occurred in the sealed portion of the alumina tube (1) even after hours i and ooo.

Next, the inner diameter D (am) of the alumina tube (1), whose inner diameter exceeds 10 m and which easily causes damage to the sealed portion, was varied.

Solid-phase bonding is performed in combination with a closed body dense having a diameter y (zm) corresponding to each variety, and the diameter y of the closed body (2) is
The ratio of the diameter d of the conductive ceramic part (2a) to that, d (n)/, (,) = x (%)
The table below shows the results of tests on the occurrence of cracks in the sealed portion of the alumina tube (1) when various changes were made.

The relationship between the inner diameter of the alumina tube and the diameter y of the closure body is D
= 1, and the wall thickness of the alumina tube was 0.75 nm, and the thickness of the closing body was constant at 10 nm. Furthermore, the test conditions were the same as above (lights on for 5.5 hours - lights off for 0.5 hours), and a flashing test was conducted for 1,000 hours.
) The lamps with cracks in the sealing part and defective lamps are marked with an x, and the lamps with good quality are marked with an O.

Using an alumina tube (1) with a large inner diameter from the front, a closed body that inevitably seals the opening (even if the diameter y of the voice becomes larger than 10 mm, the center of the closing body (2) If the diameter d of the conductive ceramic part (2a) that occupies the entire area is made smaller, that is, d/y=x (%), the alumina tube (1
) It can be seen that cracks can be prevented from occurring in the sealed portion.

Figure 2 shows the results of the above table as a graph.If y and X are selected so that the vertical axis is D and the horizontal axis is x (=d/y), the crack It is possible to obtain an arc tube without the occurrence of .

However, since the conductive ceramic part (2a) at the center of the closure body is embedded and fixed at least at the end of the electrode (3), its diameter d must be at least 2fi, and curve B is the limit that takes this into account. It shows a line. Therefore, the preferred area on the graph is the shaded area.

In addition, in the above test, the wall thickness of the alumina tube was 0.75 m,
Thickness of p blocker: 10 Fle tungsten content: 20
% of conductive ceramics was used, but the wall thickness of the alumina tube was 0.6 to 1.211! The thickness of the II obturator is 5-20
Similar effects can be obtained when the iwe tungsten content is within the range of 10 to 20%, and it can also be applied to other ceramic discharge lamps using alumina tubes.

〔Effect of the invention〕

As described above, according to the configuration of the present invention, there is provided a disk-shaped closing body for sealing the opening of an alumina tube.

The center part is made of conductive ceramics, and the outer periphery is made of alumina ceramics, and the ratio of the diameter of the conductive ceramic part to the diameter of the entire closure body is regulated, so even if the inner diameter exceeds 10 mm, Even if an alumina tube is used, it is possible to obtain a ceramic discharge lamp in which no double cracks occur at the sealing portion.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of the sealed portion at one end of the arc tube of an embodiment of the ceramic discharge lamp of the present invention, and FIG. It is a graph showing the relationship between the ratio X (%) occupied by the diameter d and the occurrence of cracks in the alumina tube. (1)・・・Alumina tube. (2)...Occluded body. (2a)... Conductive ceramic portion of the closure body. (2b)...Alumina ceramic part of the closure body. (3)... Electrode.

Claims (1)

[Scope of Claims] An opening in an alumina tube with a wall thickness of 0.6 mm to 1.2 mm is formed by a disk-shaped closing body whose center part is a conductive ceramic part that supports an electrode and whose outer periphery is an alumina ceramic part. The closure body has a thickness of 5 mm to 20 mm and a diameter y of 10 mm<y≦35.
mm, and the conductive ceramic part is made of a mixed sintered body of 10 to 20% tungsten and the remainder alumina by weight, and the ratio of the diameter d of the conductive ceramic part to the diameter y of the above-mentioned closure body. A ceramic discharge lamp characterized in that, when d/y is x (%), y<-(3/8)x+40 is satisfied.