JPH0222980B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a completely new low-pressure discharge lamp that has high brightness and provides a large luminous flux.

(Background Art) High-pressure metal vapor discharge lamps such as mercury lamps have been realized and put into practical use as discharge lamps that can provide high luminance and large luminous flux.

However, this type of discharge lamp is designed to operate at high pressure and high temperature during steady lighting. It requires a warm-up time (time from 0 to _t1 in the figure), and if you try to turn off the light and then immediately turn it on again, the inside of the tube will be at high temperature and pressure. Unable to restart, it takes several minutes after the lights go out until restart is possible (from t ₂ to
The disadvantage is that it requires t ₃ ). Furthermore, even if you try to obtain the desired light color and color temperature, the number of practically usable discharge (light-emitting) substances is limited to a few types or less, so the light color and color temperature will be specific, making it difficult to design freely. There is also a drawback. Furthermore, due to the high temperature, general soft glass cannot be used, and expensive quartz glass, polycrystalline alumina tubes, etc. are required, and processing is also expensive.

(Object of the Invention) The present invention has been made in view of the above drawbacks, and its object is based on a completely different principle from that of conventional discharge lamps. Operates at low pressure even during steady lighting,
To provide a low-pressure discharge lamp that is compact, can be turned on instantly, has high brightness, and has a large luminous flux.

(Disclosure of the Invention) The basic configuration of the present invention is shown in FIG. The low pressure discharge lamp according to the present invention includes a cylindrical outer tube 1 forming an airtight space, and a concentric cylindrical inner tube 2 disposed approximately at the center of the outer tube 1. is open at both ends, and a pair of electrodes 3, 3 are disposed in both openings, the inside of the inner tube 2 is defined as a discharge space A, and the other space inside the outer tube 1 is defined as a non-discharge space B. The outer surface area forming the discharge space A, that is, the outer surface area Sa of the inner tube 2, and the outer surface area forming the non-discharge space B, that is, the outer surface area Sb of the outer tube 1, is set to Sb≧5・Sa, and the discharge inside the discharge space A is The average positive column potential gradient E during maintenance is E≧1.5V/cm, the main discharge (luminescence) substance is metal vapor, the inner tube 2 is made of an ultraviolet transmitting material, and the inner surface of the outer tube 1 is coated with a phosphor (Fig. (not shown).

Note that the shapes of the outer tube 1 and the inner tube 2 do not have to be cylindrical as described above, and the outer tube 1 may have the shape of a current mercury lamp, for example, and the inner tube 2 may be bent. The opening does not need to be limited to the above-mentioned configuration, and may be provided so that the outer tube 1 and the inner tube 2 have the same airtightness.

Next, the operating principle and effects of this discharge lamp will be explained. First of all, since the discharge lamp according to the present invention is a low-pressure metal vapor discharge as mentioned above, its operating principle is essentially the same as that of a fluorescent lamp. can be done immediately. In addition, the non-discharge space B is extremely wide (Sb≧5・Sa) compared to the discharge space A, and each discharge space A, B
Since the metal vapor is airtight, the lowest temperature of the metal vapor is sufficiently lower than the temperature inside the discharge space, and highly efficient radiation can be maintained. In other words, changing the ratio of non-discharge space B to discharge space A (referred to as B/A) will, of course, depend on the outer surface areas Sa, Sb and envelope shapes of discharge space A and non-discharge space B, but these By fixing this as a typical shape, the characteristics shown in FIG. 3 can be obtained. In addition, in the same figure, Ta is the discharge space A
Tb is the surface temperature of non-discharge space B,
Tc indicates the ambient temperature.

Therefore, although the temperature of the discharge space is higher than that of a single-tube discharge lamp consisting only of the discharge space A, the coldest temperature is regulated by the non-discharge space B, so it is lower. The difference becomes larger as the above B/A becomes larger. This becomes very effective when increasing the lamp input and aiming for high brightness and large luminous flux.

Now, if we consider mercury as an example of a metal vapor,
The energy level diagram of mercury is shown in Figure 4, and in the case of a fluorescent lamp, 254 nm ultraviolet radiation is converted into visible light by a phosphor. In this case, the efficiency is determined by the UV radiation efficiency at 254 nm if the phosphor is fixed. As shown in FIG. 5, it is well known that the 254 nm ultraviolet radiation efficiency reaches its maximum at a mercury temperature of approximately 40° C. (the corresponding mercury vapor pressure is approximately several mmTorr). Therefore, as the lamp input is increased, the coldest temperature of mercury generally becomes higher and higher than 40°C and moves out of the coldest range.

Therefore, when trying to emit a large luminous flux in a compact discharge space as in the present invention, a large input must be input into the narrow discharge space, which causes the coldest temperature of mercury to rise extremely. In the case of a single tube, the vapor pressure also increases at the same time, resulting in a significant drop in efficiency and deterioration in starting and restarting due to the increased vapor pressure.However, the discharge lamp according to the present invention has a relatively large area around the discharge space A. Since the non-discharge space B is provided, the coldest temperature of mercury can be reduced, the temperature can be designed and maintained near the optimum coldest temperature of mercury, and the ultraviolet radiation efficiency can be made sufficiently high.

Next, the basis for the above-mentioned numerical limitation of Sb≧5·Sa will be explained. The temperature of the outer surface of the heating element is approximately correlated to the outer surface area of the heating element if the amount of heat generated (substantially the discharge power in the invention) in the heat generating portion (discharge space A in the invention) is constant. , the outer surface temperature of non-discharge space B is Tb, and the outer surface area is
If Sb is Sb and the known temperature is Tc, then non-discharge space B
If it approaches a vacuum, the temperature rise ΔTb on the outer surface of the non-discharge space B becomes approximately ΔTb=Tb−Tc∝1/Sb. Therefore, if the outer surface area Sb of the non-discharge space B is large, , the outer surface temperature of non-discharge space B
Tb approaches the ambient temperature Tc.

Also, since the relationship between discharge space A and non-discharge space B is based on the assumption that the outer surface of non-discharge space B is the new ambient temperature, if the temperature rise in a single tube consisting of only discharge space A is ΔTao, then In this case, the temperature increase ΔTa is approximately ΔTa≒ΔTao+ΔTb. That is, the outer surface area Sb of the non-discharge space B
The larger the temperature, the outer surface temperature of the discharge space A.
Ta approaches the outer surface temperature of a single tube consisting only of discharge space A.

In this way, the larger the outer surface area of the non-discharge space B with respect to the discharge space A (the larger B/A in Figure 3), the larger the outer surface temperature Tb of the non-discharge space B becomes. At temperature Tc, the outer surface temperature Ta of discharge space A approaches the outer surface temperature of a single tube made up of only discharge space A, and (outer surface area Sb of non-discharge space B) ≒ (outer surface area Sa of discharge space A) ), that is, when B/A is 1 in Fig. 3, the opposite limit is reached, and the outer surface temperature Tb of non-discharge space B approaches the outer surface temperature of a single tube made up of only discharge space A, and The outer surface temperature Ta is equal to the outer surface temperature of the single tube plus the temperature difference between the outer surface temperature Tb of the non-discharge space B and the ambient temperature Tc.
When Sb≧5·Sa, the temperature rise due to the discharge space A alone becomes about 1/5 or less of the temperature rise in a single tube. However, when trying to obtain a compact, high-intensity, and high-output lamp, the temperature of discharge space A is generally estimated to be 100 to
Although this is an extremely high value of several hundred degrees Celsius, by setting Sb≧5・Sa as described above, the outer surface temperature Tb of non-discharge space B can be reduced to the tube temperature when a single tube is normally designed and used. This means that it is close to .

Next, the average positive column potential gradient E during discharge maintenance in the discharge space A will be described. A high positive column potential gradient E means that the electron temperature during discharge, that is, the electron energy is high. However, as is well known, in current fluorescent lamps, the positive column potential gradient E is approximately 0.9 to 1.1 V/cm, so the fourth
In the energy level diagram shown in the figure, the lowest energy level (6 ³ P ₁ ) is most excited, and the design is such that the emission from the 254 nm ultraviolet radiation from that excited level to the ground level is the strongest. It's summery.
However, when the positive column potential gradient E is increased to 1.5 V/cm or more, the degree of excitation to higher levels (7 ³ S, 6 ³ D, etc.) increases, and along with the increase in ultraviolet radiation at 254 nm and 185 nm, the ultraviolet radiation at 546 nm, 436nm, 405nm, 577~
Visible luminescence due to radiation such as 579 nm also increases rapidly. This results in relatively low efficiency for fluorescent lamps that effectively utilize only 254 nm radiation, but
By using a phosphor that uses both 254 nm and 185 nm ultraviolet rays as excitation sources and by directly utilizing the visible light spectrum line, it is possible to provide a discharge lamp with higher overall efficiency. Further, as another example, the same effect can be obtained when cadmium is used as a metal vapor. That is, in the energy level diagram shown in Figure 6, when performing normal low-pressure discharge, if the positive column potential gradient E is about 0.8 to 1 V/cm, the energy level will be 326 nm and 229 nm from the 5P excited level.
It is well known that the ultraviolet radiation efficiency of However, if the positive column potential gradient E is 1.5V/cm
By doing the above, like the mercury discharge described above,
Excitation to higher levels than 6S increases rapidly and can be accompanied by effective light emission.

FIG. 7 is a simplified diagram showing a different embodiment of the present invention, in which a is a longitudinal sectional view and b is a horizontal sectional view. A configuration different from the basic configuration described above is that the inner tube 2 is made of ultraviolet-transparent glass, both ends where a pair of electrodes 3 are located are closed, an opening 5 is provided in the center of the tube, and the inner surface of the outer tube 1 is closed. In that the phosphor 4 is coated on the phosphor 4, the phosphor 4 is mainly made of a rare phosphor having excellent high-temperature characteristics, such as pink yttrium oxide,
It is preferable to appropriately mix green zinc silicate, magnesium aluminate, blue magnesium/barium aluminate, etc. to obtain the desired light color.
The inner tube 2 is set to 10 mm or less, and the positive column potential gradient E≧1.5 V/cm is a well-known structure that mainly increases the diffusion and recombination of charged particles, such as light rare gases such as neon and helium. It is desirable to achieve this by enclosing a tube, using a thin tube, making the cross section of the inner tube non-circular, etc.

(Effects of the Invention) As described above, the present invention includes an airtight outer tube that forms the non-discharge space B, and an inner tube that is disposed inside the outer tube and has an opening in a part and forms the discharge space A. A low-pressure discharge lamp in which the outer surface area Sb of the non-discharge space B is Sb≧5・Sa with respect to the outer surface area Sa of the discharge space A, and the main discharge substance is metal vapor, The average positive column potential gradient E during discharge maintenance is set to E≧1.5V/cm, the inner tube is made of an ultraviolet transmitting material, and the inner surface of the outer tube is coated with phosphor. Despite being a discharge lamp with high brightness and large luminous flux, it is possible to provide a new low-pressure discharge lamp that is completely different from conventional discharge lamps, as it can be turned on instantly and provides sufficient luminous flux instantly. . Furthermore, since the temperature of the discharge space A is several hundred degrees Celsius at most, there is no need to use expensive quartz glass or polycrystalline alumina as the tube material. Furthermore, since the inner tube is made of an ultraviolet transmitting material and the inner surface of the outer tube is coated with phosphor, deterioration of the phosphor can be reduced and a decrease in luminous flux maintenance factor can be prevented.

[Brief explanation of drawings]

Figure 1 is a lighting characteristic diagram of a high-pressure metal vapor discharge lamp, and Figure 2 is a simplified diagram explaining the basic configuration of the present invention.
is a sectional view, b is a perspective view, FIG. 3 is a temperature characteristic diagram inside the tube of the discharge lamp according to the present invention, FIG. 4 is an energy level diagram of mercury, and FIG. 5 is a characteristic diagram showing ultraviolet radiation efficiency at 254 nm. FIG. 6 is an energy level diagram of cadmium, and FIG. 7 is a simplified diagram showing a different embodiment of the present invention, in which a is a vertical sectional view and b is a horizontal sectional view. 1... Outer tube, 2... Inner tube, 3... Electrode, 4...
phosphor.

Claims (1)

[Scope of Claims] 1. Consisting of an outer tube that is airtight and forms a non-discharge space B, and an inner tube that is disposed within the outer tube and has an opening in a part and forms a discharge space A. Space A
The outer surface area of non-discharge space B with respect to the outer surface area Sa of
A low-pressure discharge lamp in which Sb is Sb≧5・Sa and the main discharge substance is metal vapor, and the average positive column potential gradient E during discharge maintenance in the discharge space A is E≧1.5V/cm. , a low-pressure discharge lamp characterized in that the inner tube is made of an ultraviolet-transmitting material, and the inner surface of the outer tube is coated with a phosphor.