JPH0311055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low pressure rare gas discharge lamp that utilizes neon light emission.

Compared to fluorescent lamps, low-pressure neon discharge lamps have features such as less deterioration of luminous flux during their lifetime, less temperature dependence, and less change in luminous flux over time after startup. It is suitable as a light source for facsimile machines and optical character readers.

A conventional example of a low-pressure neon discharge lamp is a neon sign, but because it uses a cold cathode, its firing voltage is much higher than that of a fluorescent lamp. It goes without saying that lowering the discharge starting voltage is advantageous in use, but one way to lower the discharge starting voltage is to improve the electrodes, and by using a preheated cathode, it is possible to achieve a wide discharge start. The voltage can be lowered. Another method that can be expected to have a significant effect is to use the Penning effect. For neon, it is known that adding a small amount of argon or krypton can significantly lower the firing voltage. On the other hand, it is generally known that in a positive column of a mixed gas consisting of two types of rare gases, emission of rare gases with a low ionization voltage can be obtained.
That is, in general, in the case of a mixed gas of neon and argon, only argon will emit light, and in the case of a mixed gas of neon and krypton, only krypton will emit light. For this reason, it has been difficult to use argon or krypton in low-pressure neon discharge lamps that utilize neon light emission.

In view of the above-mentioned drawbacks, the present invention aims to provide a low-pressure neon discharge lamp that contains a trace amount of argon and emits mainly neon light.

The present inventors assumed that a certain amount or a certain mixing ratio or more of argon is mixed in as a condition where argon light emission is the main one in the positive column of the discharge, and calculated the relationship between the pressure and mixing ratio of the mixed gas and the light emission. As a result of research, we found a relationship between the pressure and the mixing ratio of the mixed gas that causes neon to emit mainly in the positive column of the discharge.

The present invention will be explained in more detail with reference to Examples below.

At both ends of a glass tube with an outer diameter of 26 mm and a length of 436 mm,
We fabricated a large number of lamps in which a filament coil electrode supporting a thermionic discharge material was sealed and filled with a mixed gas of 1 Torr to 2 Torr containing 0.01% to 10% argon and the remainder neon, and measured their spectral distribution. . The experiment was conducted using a commercial power supply using a chiyoke coil as a ballast. The discharge electrode was 0.2A to 1.2A, and 3.6V was applied to the electrode. As a result of this experiment,
It was found that the spectral distribution was almost independent of the current, but dependent on the sealing pressure and the mixing ratio. For example, when the pressure of the sealed mixed gas is 5 Torr, when the argon mixture ratio is 1%, argon light emission becomes the main one, at 0.5%, argon and neon light emission coexist, and at 0.1%, neon light emission becomes the main light emission. Become. Also, when the mixing ratio of argon is 0.5%, the pressure is 3 Torr.
At 7 Torrr, the main emission is neon, and at 7 Torrr, the main emission is argon. Figure 1 shows the spectral distribution of a lamp filled only with neon, and the purpose of the present invention is to
The goal is to obtain light emission close to that shown in the figure. FIG. 2 shows the spectral distribution of a lamp filled only with argon. The neon shown in Figure 1 has a maximum spectrum at 640 nm, and the argon shown in Figure 2 has a maximum spectrum at 810 nm. In order to clarify the range in which the object of the present invention is achieved, it is defined that neon light emission is dominant when the spectral intensity of argon at 810 nm is 25% or less of the spectral intensity of neon at 640 nm. When this intensity ratio was 25% or less, the rate of decrease in neon emission was 20% or less compared to a lamp in which only neon was sealed at the same pressure. FIG. 3 shows a spectroscopic diagram of an embodiment of the present invention with a spectral intensity ratio of about 20%. This lamp has a pressure of 7 Torr and an argon mixing ratio of 0.1%. FIG. 4 is a diagram showing the filling pressure and the mixing ratio of argon, and according to the above definition, the circle mark indicates a lamp in which neon light emission is the main one, and the cross mark indicates a lamp in which argon light emission is prominent. From Figure 4, if the sealing pressure is P (Torr) and the partial pressure of argon is P _A (Torr), the mixing ratio of argon, which mainly produces neon light, is A = (P _A /P) x 100 (%). Express it as A≦5P ^-2 (%). If we rewrite this in terms of the partial pressure of argon, we get p _A ≦0.05P ^-1 (Torr).

Next, in order to investigate the effect of pipe diameter,
Pressure near the boundary condition in Figure 4 for a valve of mm
3Torr, argon mixing ratio 0.5%, pressure 7Torr,
As a result of producing lamps filled with gas with a mixing ratio of 0.1% argon, it was found that neon light was the main source of light in each lamp.

In addition, in the above experiments, the sealing pressure was 1 Torr ~
The range of 20 Torr was chosen because the life of the electrode is short at low pressures, and the efficiency tends to decrease as the pressure increases, so we chose a range that was considered to be relatively practical.

However, according to the present invention, since a mixed gas of argon and neon is used, it is possible to lower the discharge starting voltage due to the Penning effect. For example pressure 5Torr
In this case, the discharge starting voltage of the lamp filled with neon alone was about 135V, but the discharge starting voltage of the lamp with an argon mixing ratio of 0.1%, which is an example of the present invention, was about 105V.

As explained above, in this invention, a gas mixture of neon and argon is sealed in a glass tube of a discharge lamp, and the charging pressure and the mixing ratio of argon are configured to satisfy a predetermined relationship. This is a low-pressure rare gas discharge system that provides a low voltage for oxidation and ensures that mainly neon light is emitted in the positive column of the discharge even if the mixed gas filling pressure is selected at any value within the practical range of 1 to 20 (Torr). It provides electric light.

[Brief explanation of the drawing]

FIG. 1 is a spectral distribution diagram of neon, FIG. 2 is a spectral distribution diagram of argon, FIG. 3 is a spectral distribution diagram of one embodiment, and FIG. 4 is a diagram of the relationship between the sealing pressure and the mixing ratio of argon.

Claims (1)

[Scope of Claims] 1. A discharge lamp having a pair of electrodes at both ends of a glass tube and emitting neon sealed in the glass tube in a positive column, in which:
A gas mixture of neon and argon, which is added to the neon to lower the discharge starting voltage, is sealed so that the charging pressure is in the range of 1 to 20 (Torr), and the charging pressure is P (Torr), as described above. When the mixing ratio of argon to neon is A (%), the following relationship is satisfied: A≦5P ^-2 (%), so that neon light is emitted during discharge in the glass tube. Low pressure noble gas discharge lamp.