JP3158955B2 - Short arc type mercury discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short arc type mercury discharge lamp in which mercury contributes to light emission.
The present invention relates to a small-sized short-arc type mercury discharge lamp used as a light source for a fiberscope or a microscope, for example.

[0002]

2. Description of the Related Art A mercury discharge lamp which generates ultraviolet rays has been widely used as a light source for a fiberscope or a light source for a microscope. A mercury discharge lamp is suitable as a light source for a microscope that utilizes fluorescence emission of a sample by ultraviolet rays, particularly in the field of biochemistry. The light source for a microscope is required to be small in size due to its configuration, and a mercury rare gas discharge lamp without an exhaust pipe for vacuum evacuation when a lamp is usually manufactured is adopted. This is because it is possible to sufficiently adapt to the demand for miniaturization of the light source, and it is possible to exclude an adverse effect on the microscope optical system due to the exhaust pipe.

With reference to FIGS. 3, 4, 5 and 6, a process for manufacturing a general short arc discharge lamp without an exhaust pipe (chip) will be described. First, a pair of external lead rods 9, a pair of conductive foils, an anode 7 and a cathode 6 are mounted on a sealing body (bulb) 4 made of, for example, quartz glass having one end A sealed, as shown in FIG. After mounting, the inside of the envelope is exhausted from the other open end B.

After evacuation, a predetermined amount of a rare gas such as Ar or mercury 3 is sealed therein, and the open end B is sealed as shown in FIG. Next, the anode 7 side is sealed as shown in FIG. 5, and the cathode 6 side is further sealed as shown in FIG. Finally, as shown in FIG. 7, a heat insulating film 5 is applied to the surface of the valve 4 and is dried in, for example, a furnace 10 having an internal temperature of 750 ° C. As described above, the short arc discharge lamp having the chipless bulb 4 in which the rare gas such as Ar or the mercury 3 shown in FIG. 1 is sealed and the anode 7 and the cathode 6 are disposed therein is manufactured. . Here, the step of attaching the base 1 and the like is omitted.

In general, at the time of sealing at a high temperature, gases such as oxygen and hydrogen are released from electrodes, glass and the like.
These gases react with the mercury 3 and the electrode material tungsten when the lamp is turned on, or promote the reaction between the mercury 3 and the electrode material tungsten. These reaction products adhere to the inner surface of the bulb by sputtering or the like, and as a result, the inner surface of the bulb 4 is blackened, which adversely affects the operating life of the lamp. In particular, in the case of a chipless valve, the exhaust gas ends before sealing, so that the above-mentioned impurity gas stays. Therefore, normally, as shown in FIG. 1, a getter 8 for absorbing these impurity gases is provided in the valve 4.

As the material of the getter 8, zirconium or tantalum is used. Zirconium is stable at room temperature and has a low vapor pressure. Therefore, in the case of a small lamp having a small electric input and a small temperature rise during lighting, the getter 8
Zirconium is often used as a material for the above.

[0007]

However, such a small-sized short arc type mercury discharge lamp has a problem that the illuminance tends to deteriorate quickly due to blackening of the inner surface of the bulb 4. This is affected by the shape of the electrode, the conditions for enclosing the rare gas and mercury 3, and the like. The inventor has further found the following facts as conditions for illuminance degradation due to blackening of the inner surface of the bulb 4.

A lighting test of a chipless short arc type mercury discharge lamp having an electric input of 100 W, a material of the getter 8 of zirconium, and different shapes of the bulb 4 was performed, and found that the inner surface of the bulb 4 was blackened. The degree was different. As a result of the investigation, the getter 8
It has been found that a lamp having a shape that makes contact with mercury 3 has a higher blackening speed than a lamp that does not make contact.

Although it is not always clear what mechanism causes the difference in the degree of blackening, it is considered as follows. (A) Investigation of substances contributing to blackening Generally, in a short arc type mercury discharge lamp,
The blackening of the inner surface of the bulb 4 is due to the sputtering of tungsten as an electrode material. When the blackened portion of each lamp used in the above-mentioned lighting test was examined, there were some lamps in which mercury 3 and zirconium as a material of the getter 8 were detected. These were more remarkable in a lamp in which the inner surface of the bulb 4 was blackened faster. Therefore, it was found that zirconium contributed to the difference in blackening speed.

Further, the influence of the manufacturing process of the short arc type mercury discharge lamp was examined. As a result, it was found that a lamp having a chip that exhausts after sealing the anode 7 and the cathode 6 has a lower blackening speed of the inner surface of the bulb than a chipless lamp. That is, it was found that the amount of impurity gas such as oxygen or hydrogen generated at the time of sealing affects the difference in blackening speed.

(B) Mechanism of Blackening From the above investigation, it was found that the blackening of the inner surface of the bulb 4
It has been found that zirconium and mercury 3, which are the materials of the above, and impurity gases such as oxygen or hydrogen staying in the bulb during lamp production contribute. According to literatures, zirconium and mercury 3 do not react. However, zirconium and mercury were detected from the blackened portion on the inner surface of the bulb 4. This was particularly noticeable below the inner surface of the bulb 4. Normally, short arc type mercury discharge lamps are
Since the anode 7 is installed with the anode 7 side down, the lower side of the inner surface of the bulb 4 here means near the anode 7 where the getter 8 is installed. Therefore, the mechanism of blackening of the inner surface of the bulb 4 is considered as follows. (1) First, the impure gas adsorbed on the getter 8 reacts with zirconium, and the resulting reaction product, for example, zirconium oxide or zirconium hydride forms amalgam with mercury 3. (2) Next, the amalgam flows on the mercury surface without evaporating in, for example, a drying process of the heat retaining film (750 ° C. in a furnace). (3) When the lamp is turned off, the solidified mercury collects on the lower side of the bulb 4, and when the mercury 3 in contact with the inner surface of the bulb 4 is also in contact with the getter 8, the amalgam flows on the surface of the mercury 3. By doing so, the inner surface of the valve 4 is reached. As a result, the inner surface of the bulb 4 is blackened.

Of course, zirconium detected from the inner surface of the bulb 4 may be sputtered from the body of the getter 8, but the blackening generated by the sputter mainly occurs on the upper side of the bulb inner surface (the cathode 6). Side)
Considering the mechanism as described above, zirconium and mercury are remarkably detected from the blackened portion below the inner surface of the bulb 4, and a lamp in which the getter 8 and the mercury 3 come into contact with each other in the bulb at the time of installation is obtained. It can be explained that the blackening speed of the inner surface of the bulb 4 was faster than that of the non-contacting lamp.

In a small lamp, the bulb 4 is designed by design.
In many cases, the getter 8 and the mercury 3 must be in contact with each other, so that there is a problem that the illuminance is quickly deteriorated by the above mechanism. For this reason, the following countermeasures were taken, but none of them could provide satisfactory results.

(First Countermeasure and Result) Mercury 3 and Getter 8
The getter 8 was placed closer to the tip of the anode 7 in order to prevent the contact. However, since the getter 8 is located closer to the distal end, the temperature of the getter 8 becomes higher, the temperature is out of the optimum temperature range as the getter, and the adsorption action of the impurity gas is almost eliminated. Was.

(Second Countermeasure and Result) The position of the anode 7 on which the getter 8 is installed is changed. However,
Naturally, the position of the arc discharge changed, and in some cases, the product specifications could not be satisfied. Further, the temperature balance inside the bulb 4 changed, and the non-evaporation of mercury occurred in some cases.

(Third Countermeasure and Results) The thermal power of the burner used in the sealing step shown in FIGS. 5 and 6 is adjusted to suppress the generation of impurity gas, and to perform a pretreatment such as heating each part in advance. The adsorbed impurity gas was removed to reduce the amount of the impurity gas mixed into the valve 4 during the sealing process. However, blackening of the inner surface of the bulb 4 could not be suppressed.

(Fourth Countermeasure and Result) Further, the internal volume of the valve 4 was increased to reduce the impurity gas concentration. Although the blackening of the inner surface of the bulb 4 could be suppressed to some extent, the demand for miniaturization of the lamp could not be satisfied naturally. Further, as a result of the investigation by the inventor, it has been found that when the internal volume of the bulb 4 becomes larger than 0.005 cc / W per unit electric input, the non-evaporation of mercury in the bulb 4 occurs.

The present invention has been made under the circumstances described above, and its object is to solve the problem of the blackening mechanism of the inner surface of the valve discovered by the inventor, in accordance with the getter position, the anode position, and the burner position. An object of the present invention is to provide a small, short-arc type mercury discharge lamp having a long service life by suppressing blackening of the inner surface of a bulb without adjusting the heating power or changing the bulb shape.

[0019]

[Means for Solving the Problems] To solve the problems,
According to the present invention, a cathode and an anode to which a getter is attached are sealed in a bulb, mercury and a rare gas are sealed in the bulb , and oxygen or hydrogen is present as an impure gas, and the bulb is a chip. Valve.
The inner volume of the lube is 0.005cc / W per electric input
In a short arc type mercury discharge lamp in which the getter and the mercury contact each other when the anode is held at room temperature (standard at 25 ° C.) at room temperature (25 ° C. standard), the material of the getter is Substances that do not react with getter and mercury, or that do not react with getter and mercury and oxygen or getter with mercury and hydrogen .
Is selected.

[0020]

[0021]

As described above, based on the fact discovered by the inventor, it is considered that the blackening of the inner surface of the valve is caused by the amalgam formed by the getter material with the intervening impurity gas. That is, it is a phenomenon that cannot be avoided as long as the getter comes in contact with mercury. In the present invention, the inner volume of the bulb is set to 0.005 cc / W or less per unit electric input, and the material of the getter is changed to a two-body reaction between the getter and mercury when the lamp is turned on.
Alternatively, since a substance that does not react with the three-body reaction between getter and mercury and oxygen or between getter mercury and hydrogen is selected, amalgam contributing to blackening of the inner surface of the bulb is not formed. Therefore, blackening of the inner surface of the bulb by the amalgam is suppressed. That is, the invention of claim 1 can solve the problem first discovered by the inventor.

In the present invention, tantalum is selected as the substance used for the getter. According to the inventors' investigation, when tantalum was selected as the getter material, tungsten as an electrode material was detected from the blackened substance on the inner surface of the bulb, but tantalum was not detected.

In the present invention, since the bulb is a chipless bulb, blackening of the inner surface of the bulb due to the amalgam can be suppressed, and the demand for downsizing the lamp can be realized.

In the present invention, the internal volume of the valve is set to 0.005 cc / W or less per unit electric input.
Blackening of the inner surface of the bulb by the amalgam can be suppressed, and problems such as non-evaporation of mercury can be avoided.

[0025]

EXAMPLE In a chipless short arc type mercury discharge lamp as shown in FIG. 1, tantalum and zirconium were selected as getter materials, and the degree of blackening of the inner surface of the bulb 4 was compared. The specifications of the lamp used are as follows.・ Type Ultra-high pressure mercury lamp ・ Electric input 100W ・ Bulb inner volume 0.3cc (excluding electrode volume) ・ Mercury filling amount 1.5mcc ・ Distance between electrodes 0.5mm ・ Bulb (per unit electric input) inner volume 0 .003cc / W

FIG. 2 shows a temporal transition of relative illuminance in a blackened portion when a tantalum getter and a zirconium getter are used and an ultra-high pressure mercury lamp of the above specification is turned on at an electric input of 100 W. . Here, the relative illuminance in the blackened part is A,
When the illuminance of the blackened portion is B, (B / A) · 100
(%). In addition, lighting was performed in a state where the anode 7 was installed so as to face down. In addition, before each lamp is turned on, the mercury 3 and the getter 8 are configured to be in contact with each other when the anode is held at a room temperature (25 ° C. standard) so that the anode is located below. As a result, when lit for 300 hours, the relative illuminance was maintained at about 75% when tantalum getter was used. On the other hand, when the zirconium getter was used, the relative illuminance was reduced to about 55%. Therefore, it has been found that it is advantageous to select a material such as tantalum, which hardly reacts with the mercury 3 through the impurity gas, as the material of the getter 8.

Further, the inner volume of the valve is 0.003 cc /
Since it was W, no problem such as the non-evaporation of mercury occurred. Further, since the bulb is chipless, it is suitable as a light source for a microscope.

[0028]

As described above, in the short arc type mercury discharge lamp of the present invention, the inner volume of the bulb is 0.005 cc / W per unit of electric input, and the material of the getter is two bodies of getter and mercury. Since a substance that does not react or cause a three-body reaction between getter and mercury and oxygen or between getter and mercury and hydrogen is selected, amalgam contributing to blackening of the inner surface of the valve is not formed, and the inner surface of the valve is formed by the amalgam. Blackening can be suppressed. That is, it is possible to deal with a problem first discovered by the inventor.

Further, if the bulb is a chipless bulb, it is possible to meet the demand for downsizing of the lamp, and if the lamp is incorporated in an apparatus, it has no effect on the optical system. It becomes suitable.

Further, when the surface area of the valve is set to 0.005 cc / W or less per unit electric input, it is possible to avoid a problem such as non-evaporation of mercury.

[Brief description of the drawings]

FIG. 1 shows a configuration of a chipless short arc type mercury discharge lamp.

FIG. 2 shows a temporal transition of relative illuminance in a blackened portion.

FIG. 3 shows a main evacuation step when a chipless short arc type mercury discharge lamp is manufactured.

FIG. 4 shows the completion of evacuation when a chipless short arc type mercury discharge lamp is manufactured.

FIG. 5 shows an anode-side sealing step in manufacturing a chipless short arc type mercury discharge lamp.

FIG. 6 shows a cathode-side sealing step in manufacturing a chipless short arc type mercury discharge lamp.

FIG. 7 shows a protective film drying step in manufacturing a chipless short arc type mercury discharge lamp.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 Cap 2 Conductive foil 3 Mercury 4 Bulb 5 Heat insulation film 6 Cathode 7 Anode 8 Getter 9 External lead rod 10 Furnace A end B end

────────────────────────────────────────────────── ─── Continuing from the front page Examiner Shinichi Omori (56) References JP-A-2-5358 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 61/26 H01J 61 / 12 H01J 61/20 H01J 61/88

Claims (1)

(57) [Claims] 1. A cathode and an anode to which a getter is attached are sealed in a bulb, mercury and a rare gas are sealed in the bulb , and oxygen or hydrogen is present as an impure gas. A chipless valve having an inner volume of 0.005 cc per unit electric input.
/ W or less, in a short arc type mercury discharge lamp in which the getter and the mercury contact each other when the anode is held at a lower temperature at room temperature (25 ° C. standard), tantalum during lighting, two-body reaction of the getter and mercury, or a material not to three-body reaction of the getter and mercury and oxygen or getter and mercury and hydrogen
Short arc mercury discharge lamp, characterized in that the selected Le.