JPS5822856B2 - metal halide lamp - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in metal halide lamps.

Metal halide lamps are known in which a metal halide is added together with mercury into the arc tube to prevent arc discharge.

Such metal halide lamps have excellent features of high efficiency and high color rendering properties.

However, some lamps of this kind, especially those containing sodium halides, may cause the lamp light color to change during operation, or may exhibit sudden and irregular fluctuations in lamp light color, especially during vertical lighting. A repeating light may occur.

The former phenomenon occurs because the sodium halide added to the arc tube is set to operate in a temperature range where it remains mostly liquid during lighting, so as the arc tube wall blackens during operation, The temperature of the coldest part where liquid sodium halide exists also gradually rises, and the vapor pressure of the sodium halide rises accordingly.

Therefore, as a result of the excited emission of sodium increasing compared to the emission of other elements, the color of the lamp light gradually changes during the operation.
This is due to a decrease in the color temperature of the lamp.

In addition, in the latter phenomenon, as mentioned above, the temperature of liquid sodium halide gradually increases during the six-stroke cycle, but along with this, the viscosity of liquid sodium halide decreases, and the lower electrode This is because droplets distributed in the form of drops on the upper tube wall fall due to vibration etc. 1 and touch the high temperature lower electrode, temporarily increasing the vapor pressure of the sodium halide.

The present invention was completed as a result of various studies in order to eliminate these disadvantages, and it is possible to solve the problem by using a mixture in which a part of thorium oxide, which is an electron radioactive substance contained in the electrode, is replaced with yttrium oxide. The objectives of the period have been achieved.

Yttrium oxide has a work function of about 23 eV, which is larger than thorium oxide's work function of about 20 eV, so its electron emissivity is inferior to thorium oxide, and since it does not emit radiation like thorium oxide, a time lag phenomenon occurs when starting. However, when yttrium oxide is contained in the electrode, yttrium halide is generated during the operation of the lamp due to reaction with free halogen generated in the arc tube or halogen dissociated in the arc. Ru.

This yttrium halide forms a sodium halide complex compound, and the vapor pressure of yttrium, which has a low vapor pressure on its own, increases due to the formation of a complex compound1, while sodium halide, which has a high vapor pressure. On the contrary, the vapor pressure of

To explain the iodide of the halide in more detail, Y2O3 contained in the electrode reacts with iodine during the movement to gradually generate Y23.

This Y13 and NaI form a composite compound (NaYI4).

The vapor pressure of NaYI4 increases more than the vapor pressure of Y3 alone, and decreases more than the vapor pressure of NaI alone.

That is, the vapor pressure of NaYI is intermediate between that of NaI and Y13.

As a result, in the presence of Y■3, the vapor pressure of NaI is
■Decreased compared to the case alone.

Therefore, the vapor pressure of NaI, which increases due to the rise in the temperature of the coldest part of the tube wall due to the blackening of the tube wall during the stroke, is suppressed by the generation of NaYI4, so the luminescence of Na increases significantly during the stroke, and the lamp This prevents light color changes from occurring.

The light emission from Y13 is still very weak in the visible range, so
Even if YI3 is present, it has the advantage of not affecting the lamp characteristics.

Another effect of the present invention is that it is possible to prevent sudden changes in light color during lighting that occur during movement.

That is, when the electrode contains only thorium oxide, most of the NaI during lighting exists in liquid form, but this tends to form droplets, whereas ThO2 and Y2O
When a mixture of 3 and 3 is contained in the electrode, NaI gradually comes to exist in the form of a film during the movement, and therefore, as mentioned above, NaI in liquid form may fall to the lower electrode due to vibration, etc. This prevents sudden changes in light color.

In lamps using a mixture of ThO2 and Y2O3, liquid NaI adheres to the tube wall in the form of a film rather than in the form of drops, which is thought to be due to the decrease in surface tension due to the formation of Y13. However, the details are unknown.

As understood from the above explanation, the present invention contains a mixture of thorium oxide and yttrium oxide in the electrode portion in a molar ratio of more than 1 mole of yttrium oxide to 2 moles of thorium oxide per mole of thorium oxide. This has the effect of reducing light color changes during the movement of a metal halide lamp containing sodium halide and preventing sudden light color changes.

Here, the mixing ratio of ThO□ and Y2O3 is expressed as a molar ratio of ThO
The reason why Y2O3 is more than 1 mole and up to 2 moles per 21 moles of 7 is because when the molar ratio of Y2O3 to ThO2 is less than 1, the production of Y13 is small, and the vapor pressure of NaI increases during the movement. This is because the red component ratio increases relatively greatly during the movement, resulting in a large change in lamp light color.
This is because if the mixture ratio is greater than 2, the starting voltage will be high and a time lag phenomenon during starting will likely occur.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows the results of an experiment using a 400W metal halide lamp having the structure shown in FIG.

Curve A shows the electrode containing only ThO2, Curve B shows the electrode with a molar ratio of 1:1.2, and Curve C shows the red component ratio during the movement of the electrode with a molar ratio of 1:2. This is a clear sign.

As the vapor pressure of NaI increases, the radiation due to broadening of the 589 nm line of Na and wavelengths longer than this increases, so the red component ratio, which indicates the ratio of the luminous flux of 600 nm or more to the total luminous flux, increases.

In curve A of FIG. 1, the increase in the red component ratio is large, and the change in lamp light color during the movement is large.

On the other hand, in curves B and C, the increase in the red component ratio is small, and therefore the lamp light color changes little.

FIG. 2 shows the change in starting voltage during the stroke, and is the result of an experiment using a lamp having the structure shown in FIG. 3, which will be explained in Examples.

Curve A in Figure 2. B and C are the same as in Figure 1, Th0
2 shows a lamp with a mixed molar ratio of 2 and Y2O3.

As can be seen from FIG. 2, the starting voltage tends to increase as the ratio of Th02 decreases.

The lamp used in this experiment contained 0.5% Ne and 0.5% Ne in the arc tube.
This is the case when a mixed gas with Ar gas is used, but this tendency becomes even more remarkable when Ar gas alone is used.

Next, an example will be described.

As shown in FIG. 3, the metal halide lamp of this embodiment is made of a quartz arc tube 1 with an inner diameter of 185 rrrra and a distance between electrodes of 42 m, in which Nat T1% In iodide is added together with mercury, and Ne is used as a starting gas. and 0.5
A mixed gas of 40mHf with %Ar is sealed, and this is
It is held in an outer tube 2 made of 20mm hard glass.

Inside the outer tube 2, 35% of a mixed gas of Ne and 40% N2 is charged.
0mynH'iI' was included.

This lamp can be operated with a rated power of 400W.

A main electrode 3 is sealed to both ends of the arc tube 1, and an auxiliary electrode 4 is further sealed to one end.

The auxiliary electrode 4 is connected to the opposite potential through a resistor 5,
In addition, a bimetal switch 6 is connected to electrically short-circuit the adjacent main electrode 3 after the lamp is turned on.

In addition, for the purpose of suppressing the rise in starting voltage during the stroke, ZrA
A getter material made of a single alloy is fixed to the sealing portion.

The structure of the main electrode of such a lamp is as shown in FIG.
An outer coil 8 made of a tungsten wire with a diameter of 0.6 mrn and an inner coil 9 made of a two-layer coil containing ThO2 and Y2O3 are fixed to an electrode rod 10.

ThO2 and Y2O3 are applied only to the inner coil 9, and are not contained in the outer coil.

When a mixture of ThO2 and Y2O3 in a molar ratio of 1:1.2 was coated, the coating amount was about 45w1.

When a metal ride lamp with the above structure was lit and tested, the initial characteristics were that the total luminous flux was 33,500 lumens, white light with a red component ratio of 10% was obtained, and the color temperature was approximately 470 lumens.
It was at 0°.

The changes in the red component ratio and starting voltage during the stroke are the first
The characteristics were as shown in the curve B of FIG. 2 and FIG.

As explained above, the metal halide lamp of the present invention has little light color change during movement, can still improve sudden color fluctuations, and can maintain the starting voltage below 200V, so it is inexpensive and lightweight. It can be operated with a ballast for general high-pressure mercury lamps, and is extremely useful.

[Brief explanation of the drawing]

Figure 1 shows how the red component ratio changes during the movement when the mixing ratio of ThO2 and Y2O3 is changed, and Figure 2 shows the behavior when the mixing ratio of ThO2 and Y2O3 is changed. FIG. 3 is a structural diagram showing a metal halide lamp according to an embodiment of the present invention, and FIG. 4 is an enlarged sectional view showing the electrodes of the metal halide lamp. 1... Arc tube, 2... Outer tube, 3... Main electrode, 4...
・Auxiliary electrode.

Claims (1)

[Claims] 1. A mixture of thorium oxide and yttrium oxide is contained in the electrode part of an arc tube in which a sodium halide is sealed inside, in a molar ratio of more than 1 mole of yttrium oxide to 2 moles of yttrium oxide per mole of thorium oxide. A metal halide lamp characterized by: