JPH0569260B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a low-pressure rare gas discharge lamp having an electrode in which at least one electrode acts as a hot cathode during operation.

[Conventional technology]

In discharge lamps used as light sources for OA equipment, it is strongly required that the brightness be uniform over the entire length of the discharge lamp. In order to improve this brightness distribution, for example, as described in Japanese Patent Application Laid-open No. 11465/1983, the electrode filament coil is made incandescent, and this light emission compensates for the brightness at the end of the discharge lamp, which is particularly susceptible to a decrease in brightness. It is suggested that something be done.

[Problem to be solved by the invention]

However, according to the above method, it is necessary to heat the electrode filament to a color temperature of 2,600〓 to 3,200〓, so in order to prevent the lifetime of the electrode filament, in addition to the electrode for maintaining discharge, an additional pair of electrodes is used to compensate for the reduced brightness at the end. filament coil must be provided,
The problem was that the structure was extremely complicated.

This invention prevents short lifespan while
The purpose of the present invention is to provide a thermal electrode type low-pressure discharge lamp that has a normal electrode structure, that is, a luminance distribution over almost the entire length of the discharge lamp that does not pose a practical problem as a light source for OA equipment, without complicating the structure. shall be.

[Means to solve the problem]

The hot cathode low-pressure rare gas discharge lamp according to the present invention maintains at least the temperature of the electrodes during lighting.
The temperature is 800℃ or higher and 1200℃ or higher.

[Effect]

In this invention, in a hot cathode type low pressure rare gas discharge lamp, the temperature of at least one electrode is controlled.
Because the lamp is heated to 800°C or higher, unlike general discharge lamps filled with mercury, the data confirms that the discharge state between the electrodes is favorable and the brightness distribution is significantly improved. Furthermore, since the upper limit of the heating temperature is set to 1200°C or less, short life can be suppressed.

〔Example〕

FIG. 1 is a partially cutaway front view showing an embodiment of a hot cathode low pressure rare gas discharge lamp having an aperture opening according to the present invention.
1 is a glass bulb with an outer diameter of 15.4 mm and a wall thickness of 0.7 mm, 2
3 is a reflective film formed on the inner surface of the glass bulb 1, and 3 is a phosphor layer formed on the reflective film 2, which is made of GP ₁ G ₁ green phosphor manufactured by Kasei Optonics. An aperture opening 8 with a width of 2 mm, to which the phosphor layer 3 and the reflective film 2 are not coated, is formed at a common location along the longitudinal direction of the glass bulb 1 between the phosphor layer 3 and the reflective film 2. It is formed so that it is exposed on one side. 4 is an electrode, and a stem 5 hermetically closes the end of the glass bulb 1.
It is composed of a pair of lead wires 6 implanted in the wire and a tungsten filament coil 7 connected to the lead wires 6. Furthermore, this filament coil 7 is a so-called triple coil wound three times, and an electron radioactive material is coated on the filament coil 7. And the distance between the electrodes is
It is set to 260mm. Further, a mixed gas of 10% Xe and 90% Ne is sealed in the glass bulb 1 at a pressure of 3 Torr. Note that 9 is a getter that adsorbs pure gas during its life. When lighting the lamp, a 40KHz sine wave power source was used and the lamp was hot cathode started.

Next, the lamp of the embodiment of the invention described above,
This lamp was also made with a lamp filled with mercury and compared. FIG. 2 shows the luminance distribution of a lamp filled with mercury. The brightness values shown in this figure are shown as relative values with the center brightness being 100. As is clear from FIG. 2, the brightness of the electrode 4 in which mercury is sealed decreases rapidly from the vicinity of the center of the glass bulb 1 toward the end of the glass bulb; A uniform brightness distribution is formed over the entire area. Although this tendency is not particularly shown, the filament of electrode 4
There was no difference even if the temperature was heated to 800°C or higher or not heated at all. Figure 3 shows the brightness distribution of a lamp without mercury, and the brightness values are expressed as relative values, with the center brightness being 100 as in Figure 2. In the figure, the brightness distribution of the filament heated to 800°C is shown by a solid line, the filament heated to 540°C is shown by a dotted line, and the filament not heated at all is shown by a dashed line. These brightness distributions show the same tendency as that in FIG. 2 in that the brightness decreases rapidly from the electrode 4 toward the end of the glass bulb 1, but Towards the center of the glass bulb 1, the maximum wave height is set near the electrode 4,
It shows a wavy distribution that gradually attenuates toward the center, which is very different from the one shown in Figure 2, in which mercury is sealed. In this wavy brightness distribution, as the filament temperature increases, the difference in wave height becomes smaller.
Here, including the center part, the brightness of the center part is 20
If the width of the section where the % brightness decreases is called the effective width, the effective width when the filament temperature is 800° C. or higher will extend further to the ends of both tubes than both filaments. On the other hand, the filament temperature
If the temperature is lower than 800°C, the effective width is smaller than the distance between the electrodes, which poses a practical problem.

When the filament was heated above 800°C, the brightness distribution improved slightly, but when the temperature exceeded 1200°C, the evaporation of the electron emitting material became significant and the lifetime was shortened.

Figure 4 shows the relationship between filament temperature and life. The filament is constantly heated, ON for 1 min,
The lamp was turned on in a 2-minute flashing cycle with 1-minute OFF, and its lifespan was determined by the actual lighting time until it failed. The figure shows relative values with the lifespan at a filament temperature of 800°C as 100. As is clear from the figure, when the temperature of the filament exceeds 1200°C, the problem arises that the lifespan is shortened, which is not preferable.

Now, in the above embodiment, the luminance distribution was described when AC lighting was performed at 40 KHz, but the present inventors have confirmed that the same effect is achieved even when DC lighting is performed. Figure 5 shows the tube voltage
The results of the luminance distribution are shown when the lamp of the above example is used in a DC circuit with a voltage of 80V.
That is, short-circuiting both ends of the electrode filament on one side,
It was used as an anode without heating. Further, the other electrode filament was used as a cathode, which was heated and the brightness distribution was measured at 540°C and 800°C as in the above example.

As can be seen from this result, even in the case of DC lighting, the disturbance in the luminance distribution at the end of the tube during lamp operation depends on the electrode temperature, and when the electrode is operating as a cathode, the difference between the electrode and the positive column This corresponds to multiple dark areas that occur between the two.

In addition, instead of using a filament as an anode, we can use tungsten rods, which are commonly used for cold cathodes, etc.
The phenomenon was similar even when a simple electron receiving means without heating means was used.

In addition, the filament temperature is 800℃ while the lamp is on.
By doing the above, the effect of improving the brightness distribution is recognized, so by heating the filament temperature to 800° C. or higher before starting the lamp, it is possible to obtain an improved brightness distribution immediately after starting the lamp. Furthermore, the purpose of this invention is to obtain a discharge lamp suitable as a light source for OA equipment, and from the viewpoint of brightness distribution characteristics, the mercury-containing re-lamp shown in FIG. 2 can also be said to be effective. However, due to the inclusion of mercury, there are other problems such as slow startup (starting) and susceptibility to the influence of ambient temperature, so this method is excluded from this invention.

Furthermore, in the above embodiment, a filament coil was used as the electrode 4, but the same effect can be expected with an indirectly heated type or sintered type electrode that does not use a filament coil.

〔Effect of the invention〕

As explained above, in this invention, the electrode temperature is heated within the range of 800° C. to 1200° C. during lamp lighting, so that the brightness distribution can be improved with a simple structure without impairing the life characteristics.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view of an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the brightness distribution of a mercury-containing lamp, and FIG. 3 is a characteristic diagram showing the brightness distribution of the lamp according to the present invention. , FIG. 4 is a characteristic diagram showing the relationship between filament temperature and lamp life, and FIG. 5 is a characteristic diagram showing the luminance distribution of the lamp when lit with direct current. In the figure, 1 is a glass bulb, 4 is an electrode, and 7
is a filament coil. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] 1. At least one of the electrodes provided at both ends of the glass bulb is an electrode that operates as a hot cathode during operation, and a rare gas is sealed inside the glass bulb, and the light emitted by this rare gas is utilized,
Alternatively, in a hot cathode low-pressure rare gas discharge lamp that converts the light emitted by this rare gas into the desired visible light using a phosphor, the electrode that operates as the hot cathode at least during lighting is heated to a temperature of 800°C or higher.
A hot cathode low pressure rare gas discharge lamp that is heated to a temperature of 1200°C or less.