JPS6017848A - Metal halide lamp - Google Patents

Abstract

PURPOSE:To obtain a metal halide lamp containing scandium halide with a good starting feature and excellent life characteristics by depositing scandium oxide on main electrodes with an electrode axis formed with tungsten containing one or more of Al, K, Si. CONSTITUTION:A luminous tube 1 having a pair of main electrodes 2a, 2b is sealed with metal halide containing mercury and at least scandium halide and (neon-argon) gas or ( a sealed and wired radioactive material and starting rare gas), and this luminous tube 1 is stored in an outer tube 11 together with a pulse generating glow starter 7 so that it can be used as a ballast 12 for a mercury lamp. Main electrodes 2a, 2b of such a metal halide lamp are formed by fitting an electrode coil 5 to an electrode axis 4 made of tungsten containing one or more of Al, K, Si, scandium oxide 6 is deposited on the surface, and the current density of the electrode axis 4 during the normal lighting is made within a range of 7.5-12A/cm<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a metal halide lamp containing scandium norogenide.

[Technical background of the invention and its problems]

A rare starting gas, mercury, and a metal halogenide were sealed in a quartz arc tube equipped with electrodes. So-called metal halide lamps have high efficiency and high color rendering, and are therefore widely used in practice. In particular, lamps containing this type of lamp are particularly prized for their extremely high color rendering properties. However, lamps filled with scandium have the disadvantage that the starting voltage is high and the starting time is also long.

As a means to improve this point, for example, Japanese Patent Application No. 55-1
No. 28328 (4? No. 57-53064) discloses that a radioactive substance such as glometium (147 pm) is dispersed and sealed in a ceramic body, etc. in the arc tube to create a sealed radiation source for handling purposes. A metal halide lamp has been proposed in which the starting voltage is lowered by enclosing the tube together with a pulse-generating lighting tube in an outer bulb so that the lamp can be lit using a mercury lamp ballast.

However, lamps filled with scandium halide have a further problem of poor luminous flux maintenance due to their extremely strong reactivity. That is, in metal halide lamps that use halides such as thorium, thallium, and indium.

Using thorium oxide (Th02) as an electrode emitter, or using tungsten containing ThO2 (thorium tungsten) as an electrode material,
Efforts have been made to improve startability through the emission effect of Th02, but if Th02 is used in a lamp using scandium halide.

3 Th 02 +4. SCI3→2 Sc O3+
3 Th I4... (1) reaction occurs, and when a relatively large amount of Th02 is used as an emitter, T11
Not only is 02 consumed, but also scandium equivalent to ScO becomes an oxide and no longer contributes to luminescence, reducing the luminous flux maintenance factor.

In addition, when thorium tungsten is used as an electrode material, the generated TllI4 affects the thermodynamic transport process of tungsten during lighting, promoting the transport of tungsten to the tip of the electrode and the wall of the arc tube. Tungsten accumulates at the tip, and when the lamp is lit for a long time, the tungsten of the electrode adheres to the wall of the arc tube, causing blackening and significantly reducing the luminous flux maintenance rate.

In addition, scandium halide is used in a quartz arc tube (810
2) also reacts.

4 Sc IB +38i02→ 3 Sr I4 +
3 Sc 03... (2). 5iT4 migrates to the tip of the electrode, reacts with tungsten (5) on the electrode to form a low melting point alloy of W and Si, and is scattered from the tip of the electrode by the arc and adheres to the inner wall of the arc tube, causing blackening. This absorbs visible light and reduces the luminous flux. Moreover, the above W
Due to the reaction and scattering of Si and Si, the shape of the tip of the electrode is eroded and deformed, which also causes instability of the arc bright spot.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances.

An object of the present invention is to provide a metal halide lamp containing scandium halide that has good startability and excellent life characteristics.

[Summary of the invention]

The present invention relates to a metal halide lamp having an arc tube sealed with scandium halide.

To facilitate starting, Bennink gas (sealed radioactive material and rare gas for starting) or (Ne-Ar) is sealed inside the arc tube, and a lighting tube for pulse generation is housed inside the outer tube. At the same time, in order to further prevent deformation and scattering of the electrode tip, the electrode shaft of the main electrode, which has an electrode coil attached to the electrode shaft, is made of aluminum, potassium, and silicon, each containing a small amount (all at least one of them). The main electrode is made of tungsten, and the main electrode is coated with scandium oxide, and the current density of the electrode shaft during steady lighting is 7.5 to 12 A/cm.
2 range, and is unique in that it is lit using a mercury lamp ballast.

[Embodiments of the invention]

The details of the present invention will be explained below with reference to an embodiment shown in the drawings. The figure shows a front view of a 400W metal halide lamp.Inside the arc tube (1) made of quartz glass, there are a pair of main electrodes (2a) and (2b), and a starting aid adjacent to one of the main electrodes (2a). An electrode (3) is provided.

The arc tube (1) has an inner diameter of 20 mm and a distance between electrodes of 42 mm.

Inside is 7Qmg of mercury, 50 torr of argon gas as a starting rare gas, and 5"L of scandium iodide.
Sodium iodide 25mg plus glomethium 14.7
For safety reasons, radioactive substances such as (147Pm) are dispersed in ceramics and sealed in the form of a sealed radiation source). The main electrodes (2.) and (2b) consist of an electrode coil (5) attached to an electrode shaft (4) as shown in Figure 2.

Scandium oxide (6) is deposited on its surface. The electrode shaft (4) has a wire diameter of 0.7 mm and is made of aluminum (
The diameter of the tungsten coil wire of the electrode coil (5) is Q, 5 r.
am, for example, has a two-layer coil, and the electrode axis (4)
The tip of the coil is about 2mmM, and is made to protrude from the polar coil (5).

Scandium oxide (6) is deposited on the surface of the main electrode, such as the protrusion of the electrode shaft (4) and the surface of the electrode coil (5).

(7) constitutes a series circuit with the pulse generator f# and the lighting tube together with the normally closed bimetal switch (8) and the current limiting resistor (9), and this series circuit is as shown in Figure 3. The starting auxiliary resistance (if) is connected to the connection point between the lighting tube (power) and the bimetal switch (8). Such a lighting starting circuit is It is housed in an outer tube (11) together with the arc tube (1), and is connected to a power source α■ via a mercury lamp ballast α2 with a secondary voltage of 200μ and a 40LW mercury lamp ballast α2 for use.

In a metal halide lamp having such a configuration, when the power source a is turned on, the secondary voltage of this ballast is applied to the lamp through the ballast Oz. Then, since the normally closed bimetal switch (8) is closed, the current limiting resistor (9) and the lighting tube (
7) Current flows through. In the lighting tube (7), the contacts of the lighting tube are opened and closed due to the glow current of the lighting tube itself, and the interruption and energization of the IF flow are repeated. Therefore, a pulse voltage is generated in the circuit of the lighting tube (7), current limiting resistor (9), and bimetal switch (8) due to the inductance of the ballast O2, and this pulse voltage is mainly generated between the poles (2a) + (2b). At the same time, an auxiliary electrode for starting (
3) and one of the main electrodes (2a) adjacent thereto. Then, first the main electrode (2a) and the auxiliary electrode (3
) starts a glow discharge between the two.

In this case, the 2 arc tube (1) is filled with 147Pm J:N radioactive material, which emits beta rays, etc., which triggers the initial electron emission.

In other words, it becomes an electron seed and causes a glow discharge to occur quickly, and this glow discharge is immediately transferred to the glow discharge between the main electrodes (2a) and (2b). This glow discharge lasts for several seconds to several tens of seconds, and during this time the lighting tube (7) repeats opening and closing operations, so pulse voltage is also generated repeatedly, which increases the temperature of the main electrodes (2a) and (2b). Then, seven arc spots are formed on the main electrodes (2a) and (2b), and the glow discharge quickly changes to an arc discharge.

When arc discharge starts between the main electrodes (2a) and (2b) in this way, the arc tube current increases and the secondary voltage of the ballast decreases, so the lighting tube (7) no longer operates. Na(
When the temperature of the arc tube (1) gradually rises and reaches a predetermined temperature, the normally closed bimetal switch (8) is opened by the heat of the arc tube (1).

No current flows through the current limiting resistor (9) 2 and the lighting tube (7), and the power to the starting auxiliary electrode (3) is cut off, maintaining stable steady lighting.

During steady lighting, this 400W lamp has a lamp voltage of approximately 1.25V, a lamp current of approximately 3.3A, and a wire diameter of 0.7
The current density of my electrode shaft (4) is 8.6A, /CrIL2
It is.

In addition, the single lamp has less deformation of the main electrode during operation, and less decrease in luminous flux maintenance than conventional lamps.

This is considered to be due to the following reasons. That is, one of the reasons is that the main electrodes (2a) and (2b) have Th 02
Since it does not include the reaction shown in equation (1) of the conventional example, that is.

3 Th02 +4 ScI3-+ 28c203+
Since 3 Th and I4 are not generated, there is no loss due to the formation of oxide of 8C, which is a luminescent metal. Another reason is that the reaction shown in equation (2) above.

4 ScI3+35i02→3 Si I4 + 28
c(,)3 is generated, and even if S+ generated by the decomposition of this product R5II4 in the arc adheres to the tip of the main electrode (2a) (2b), this tip is scandium oxide. (
There is an optimum temperature range for the main electrodes (2a) and (2b) in order to completely coat the main electrodes (2a) and (2b) with scandium oxide (6).
This range corresponds to the current density at the tip of the main electrode, i.e., the electrode axis (4), that is, the lamp current divided by the area of the electrode axis (4), and if this value is 7.5 to 12 A/cm2, then Since the above-mentioned optimum temperature range is maintained and this value is designed to be 8.6 A/m2 in the 9 lamps, the reaction between the above-mentioned S1 and the tungsten W of the main electrode can be prevented. It is possible to prevent the blackening of the wall of the arc tube due to the scattering of tungsten W and the severe decrease in the luminous flux maintenance factor caused by this. Moreover, the electrode shaft (4) is made of tungsten W and aluminum A7. Since potassium contains at least one kind of silicon S+, scattering of W can be further prevented. The reason for this is not clear at present.

Maybe AA! , it is presumed that Si acts as an aggregate of W and firmly grasps W, so that the loss of W is prevented.

Next, using the same 400W lamp as the example lamp described above, only the structure and material of the main electrode were changed, and the lighting conditions were exactly the same as above, that is, the lamp voltage was about 125V and the lamp current was about 3.3A during steady lighting. .

Table 1 below shows the results of the first test when the ballast was lit with a 400W mercury lamp ballast with a secondary voltage of 200V. In Table I, Group A uses tungsten W as the material of the electrode shaft, as in the above embodiment.
Contains about 20 to 10 loppm (-).

Group B is the same material with 1.7% of tungsten W.
The C group contains a certain amount of Th 02, and the C group uses pure tungsten as the same material.

Group D was made of the same material as Group A, but scandium oxide 5c203 was not deposited.

From the results in the margin table (■) below, in a 400W lamp, Group A, that is, tungsten W containing (Al, K, Si) was used as the electrode material, and the main electrode was coated with 5c203, @I electrode axis diameter 06 Those designed to ~0.75 mm, that is, those with a current density of 7.5 to 12 A2 cold 12, had a good luminous flux maintenance rate of over 80% after 3000 hours, but other groups had good luminous flux. No retention rate was obtained.

Table I shows the test results for a 400W lamp, but for lamps of different watts with different secondary inputs, the same main electrode as in Group A was used, but only the electrode shaft diameter, that is, the current intensity during steady lighting, was varied. The tested results are shown in Table H.

Below is a margin table■ From the results shown in Table II, regardless of the lamp input, if the current density of the electrode axis is set to 7.5 to 12 A, /CrrL2, 3
It can be seen that the luminous flux maintenance rate after 000 hours can be improved to 80%.

In the above embodiment, for example, argon gas A, r is used as the rare gas for starting, and 147P is used to facilitate starting.
Although a radioactive substance such as m is sealed in the arc tube, if a Penning gas such as (Ne-Ar) is used as the starting rare gas, the same effect can be obtained without sealing the radioactive substance.

Table 3 relates to a 700W metal halide lamp, in which main electrodes are placed facing each other at both ends of an arc tube made of quartz glass with an inner diameter of 25 mm, separated by a distance of 65 mm.

An auxiliary electrode for starting is provided close to one of the main electrodes, and about 0.01 to 10% of A and r are mixed inside (Ne
An arc tube is formed by enclosing 100 # of -Ar) gas, 75 mg of mercury, 7 mg of scandium iodide, and 35 mg of sodium iodide. The main electrode has an electrode shaft formed of tungsten W containing at least one of (Al, K, and Si) as in the above embodiment, and an electrode coil is attached so that a part of the electrode shaft protrudes. Scandium oxide 5c203 is deposited on this main electrode. Such an arc tube is also housed in the outer bulb together with a starting circuit consisting of a lighting tube, a normally closed bimetal switch, and a series circuit of a current-limiting resistor to form a lamp.
It is connected to a power source via a 700W mercury lamp ballast with a secondary voltage of 200V and used for lighting. At this time, the lamp voltage was approximately 125V and the lamp current was approximately 5.9A.

Table (3) shows the effect on the luminous flux maintenance factor when the current density during steady lighting is varied in various ways by changing the electrode axis diameter of the main electrode.

Margin table below III Based on these results, the current density was set to 7.
5 to 12 AlcTL2, it can be seen that a good luminous flux maintenance factor can be obtained.

The following table TV shows the results of a similar test on the relationship between current density and luminous flux maintenance factor for each lamp with different input watts, in contrast to the test conducted for a 700W lamp in Table 111 above. Similarly to the 700W lamp, the current density of the electrode axis is set to 7.5 to 12A 7cm,
It was confirmed that a good luminous flux maintenance rate could be obtained by setting the value to 2.

Margin table below TV From the above test results, it can be seen that the same effect can be obtained even when (Ne-Ar) Penning gas is sealed in the arc tube instead of filling the rare gas and radioactive substance.

In addition, in the above example, sodium iodide was added as a metal halide in addition to scandium iodide.
The present invention is not limited to this, but the point is that all effects can be obtained in a metal halide lamp containing a small amount of scandium halide.

〔Effect of the invention〕

As described in detail above, according to the present invention, in a metal halide lamp sealed with Scandium halide, a radioactive substance or (Ne-A
r) filled with Penning gas, and.

By housing a pulse-generating lighting tube inside the outer bulb, it is easy to start and can be lit using a mercury lamp ballast, and the main electrode is coated with scandium oxide.

The electrode shaft is made of tungsten W containing at least one of (AI, K, Si), and the current density during steady lighting of the electrode shaft is regulated to a range of 7.5 to 12 A, 7 cm2, so that the main power By preventing deformation and scattering of the shuttle tip, the luminous flux maintenance rate after 300 hours (1 hour) could be improved to over 80%.

[Brief explanation of the drawing]

FIG. 1 is a front view of a 4,00 W metal halide lamp which is an embodiment of the present invention, FIG. 2 is an enlarged front view of the main electrode, and FIG. 3 is a lighting circuit diagram thereof. (1)... Arc tube, (2a), (2b)... Main electrode. (3)... Auxiliary electrode, (4)... Electrode axis, (5)...
...Electrode coil. (6)...Scandium oxide, (7)...Lighting tube. (8)...Normally closed bimetal switch. (9)...Current limiting resistance, (In)...Auxiliary resistance, ol
)...outer tube. (1,21... Ballast for mercury lamps. Agent: Patent attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 10

Claims (1)

[Claims] A gas (neon-argon) or (a sealed radioactive material and a rare gas for starting) is sealed in an arc tube with a pair of main electrodes along with mercury and metal halogenides, including at least scandium halogenide. In a metal halide lamp used in a mercury lamp ballast, the arc tube is housed in an outer bulb together with a pulse-generating lighting tube, and the main electrode contains at least one of (aluminum, potassium, silicon). An electrode coil is attached to an electrode shaft made of tungsten, scandium oxide is deposited on one surface, and the current density of the electrode shaft during steady lighting is set to 7.5 to 12 A/α2. A metal halide lamp featuring