JPS6220651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing low-pressure discharge lamps having oxide-coated electrodes, such as fluorescent lamps and low-pressure sodium lamps.

The conventional method for manufacturing a low pressure discharge lamp was as follows. That is, while heating the tube wall, air, water vapor, etc. inside the lamp are evacuated through an exhaust pipe provided at one end of the discharge lamp. When the interior of the lamp reaches a sufficiently high vacuum, a pair of electrodes provided at both ends of the lamp are heated with electricity to thermally decompose the alkaline earth metal composite carbonate on the electrodes, creating an oxide-coated electrode. Further, after impurity gas such as carbon dioxide gas generated by the decomposition of the composite carbonate is sufficiently exhausted, an ionizing medium such as mercury or a rare gas is sealed. Generally, the diameter of the exhaust pipe of a low-pressure discharge lamp is about 4 mm at most.
It takes a long time to create a good vacuum inside the lamp through such a narrow exhaust pipe. Therefore, the conventional method of manufacturing a low-pressure discharge lamp as described above has the disadvantage that it takes a long time to manufacture the lamp, and the price of the lamp increases. Therefore, a method was devised to install exhaust pipes at both ends of the lamp and exhaust the air from both sides. However, it is obvious that simply exhausting from both sides can only reduce the exhaust time by half at most. In addition, in the conventional low-pressure discharge lamp manufacturing method described above, if the lamp manufacturing time is shortened at the expense of the degree of vacuum inside the lamp, the lamp life will be shortened, tube edge blackening will become significant, and discharge will become unstable. The characteristics of the low-pressure discharge lamp deteriorated.

Therefore, an object of the present invention is to provide a method for manufacturing a low-pressure discharge lamp in a short time, which has performance equivalent to or better than that of low-pressure discharge lamps manufactured by conventional methods.

In order to achieve the above object, the present invention provides a method for manufacturing a low-pressure discharge lamp having a pair of oxide-coated electrodes at both ends and a pair of exhaust pipes, in which air within the lamp is discharged from both of the pair of exhaust pipes. A first step of evacuating impure gas, a second step of injecting rare gas from one of the pair of exhaust pipes and evacuating from the other exhaust pipe, and the second step. a third step of evacuating the injected rare gas from the exhaust pipes at both ends; and a step of removing impurity gas within the lamp by alternately performing the step of evacuating the injected rare gas from the exhaust pipes at both ends; It is characterized in that the heating field of the salt is started during the first step. That is, the present inventors conducted an experimental study on a method of removing impure gas within the lamp in a short time using a low-pressure discharge lamp having a pair of exhaust pipes at both ends. As a result, if you perform vacuum evacuation through one exhaust pipe and inject rare gas from the other end, the impurity gas in the lamp will be pushed out by the rare gas, so simply exhaust from the exhaust pipes on both sides. It was found that the impurity gas could be removed in a much shorter time than using conventional methods.

The inventors conducted a more detailed study on the above evacuation method and found that since the rare gas is injected through an exhaust pipe with a diameter of about 4 mm, the flow velocity of the rare gas is quite high near the injection port. It was found that stagnation occurred at the end of the tube on the rare gas injection side of the lamp, resulting in some impure gas remaining. Therefore,
When we repeated the process of injecting rare gas from one exhaust pipe while evacuating from the other exhaust pipe, and after the above process, exhausting the rare gas from the exhaust pipes at both ends, the inside of the lamp It was found that impure gas could be removed in a shorter time.

The present inventors conducted a more detailed study on the above evacuation method using a fluorescent lamp and argon gas. As a result, the impurity gas removal effect did not change much depending on the number of repetitions of argon gas injection and evacuation from both sides if the total time of the evacuation process was constant, but it did change depending on the argon injection flow rate. . Characteristic curve 1 in FIG. 1 shows the relationship between the argon flow rate per injection and the discharge starting voltage. When the flow rate of argon per injection number becomes less than 2 Torr/s, the effect of pushing out and diluting impurity gas by argon gas becomes smaller, the amount of remaining impurity gas increases, and the firing voltage becomes higher. Furthermore, when the flow rate of argon exceeds 30 Torr/s, the phosphor coated on the tube wall is peeled off by the high-speed argon flow, as shown by characteristic curve 2 in Figure 1. A peeling phenomenon occurs.

As described above, only when the flow rate of argon per injection is in the range of 2 Torr/s to 30 Torr/s, impurity gas can be efficiently removed without causing the phosphor film flaking phenomenon.

Furthermore, it can be easily inferred that even when a rare gas other than argon is used, an optimum gas flow rate range as described above exists.

Therefore, we applied the vacuum evacuation method described above to a fluorescent lamp, and tried a method of thermally decomposing the composite carbonate while injecting argon gas from one end and evacuation from the other end.
It was possible to produce a fluorescent lamp with initial characteristics equivalent to those of lamps produced using conventional methods, in less than one-third of the time required for production using conventional lamp production methods. However, when life tests were conducted on these fluorescent lamps, it was found that the tube end blackening performance was considerably inferior to that of fluorescent lamps manufactured using conventional manufacturing methods. This problem could not be improved much even by changing the heating current for thermally decomposing the carbonate.

According to experiments conducted by the present inventors, both the life and blackening performance are best achieved only when the amount of the so-called intermediate layer compound, which is a compound of tungsten and an alkaline earth metal oxide, is within a certain appropriate range. I understand. Therefore, when we investigated the amount of interlayer compounds in the electrodes of fluorescent lamps manufactured using the vacuum evacuation method described above, we found that they were considerably smaller than those in lamps manufactured using conventional manufacturing methods, and that there was almost no change even when the heating current was changed. I found out. this is,
This is due to the fact that carbonates are conventionally thermally decomposed in a vacuum, whereas in the present invention, composite carbonates are thermally decomposed in an argon gas flow as described above. Seem.

Therefore, the present inventors closely observed the state of the electrode during thermal decomposition in argon gas, and found that the phenomenon shown in FIG. 2 occurred. Figure 2 shows the state of the electrodes during thermal decomposition in argon, where 3 and 4 are nickel wires for supporting the tungsten double coil filament 5, and 6 is an alkaline earth metal composite carbonate. be. As the carbonate thermal decomposition current flowing through the nickel wires 3 and 4 is increased, the voltage difference between both ends of the filament coil 5 increases. When this voltage difference exceeds a certain value, ionization of argon gas near the coil occurs, and an arc discharge 7 occurs with both ends of the coil 5 as electrode bright spots. In such arc discharge, the discharge voltage hardly changes even if the discharge current is increased. Therefore, even if the heating current flowing through the nickel wires 3 and 4 is increased in the state where the above-mentioned arc discharge has occurred, almost all of the increased current flows through the arc and the carbonate 6 is coated. Since there is no flow through the coil, the temperature of the carbonate does not increase. Therefore, the amount of the intermediate layer compound cannot be increased, and the tube end blackening performance deteriorates.

It can be easily inferred that the above phenomenon will also occur when rare gases other than argon are used.

As a result of repeated various experiments, the inventors of the present invention found that a lamp with excellent discharge starting voltage and blackening performance can be manufactured by using the following method. That is, thermal decomposition of carbonates is initiated during the first step of exhausting impure gases such as air within the lamp through a pair of exhaust pipes. Since the above-mentioned arc discharge is extremely difficult to occur in nitrogen gas, air, etc., the heating temperature of carbonate can be made sufficiently high by changing the applied current, and the necessary and sufficient amount of carbonate can be heated. Interlayer compounds can be produced. Of course, it is not necessary to complete the decomposition of the carbonate during this step, and the carbonate is completely thermally decomposed during the next step of repeating the injection of rare gas and evacuation from the exhaust pipes on both sides.

As explained above, the thermal decomposition of the alkaline earth metal composite carbonate is started during the first step of exhausting impurity gas such as air from a pair of exhaust pipes, and the rare gas is discharged from one of the exhaust pipes. If the impurity gas inside the lamp is removed by alternately performing the step of evacuating from another exhaust pipe while injecting the rare gas and the step of evacuating the noble gas injected in the above step from the exhaust pipes at both ends. , a low-pressure discharge lamp having performance equivalent to that of a lamp produced by a conventional manufacturing method can be manufactured in a short time.

In the above manufacturing method, the latter half of the carbonate decomposition process may overlap with the process of injecting a rare gas from one of the exhaust pipes and evacuation from the other exhaust pipe. In this case, the temperature of the electrode on the side where the rare gas is injected decreases, causing a mismatch in the amount of the intermediate layer compound.
The end of the lamp tube may turn black, and its life may be slightly shortened. In this case, if the heating current of the electrode on the side where the rare gas is injected is made larger than the heating current of the electrode on the other end, the performance of the lamp can be greatly improved.

The present invention will be explained in detail below with reference to Examples.
A normal 40 Watt fluorescent lamp was used as the sample low pressure discharge lamp. That is, a glass tube with a diameter of 33 mm and a length of 1180 mm is coated with a phosphor on the inner surface, and an electrode and an exhaust pipe are coated with a ternary carbonate of barium, strontium, and calcium on a double coil of tungsten at both ends. are provided for each. This sample fluorescent lamp was attached to a vacuum evacuation device, and the vacuum was first evacuated from both exhaust pipes. Eight seconds after the start of evacuation, evacuation of one side was stopped, and while argon gas was injected from one side, vacuum evacuation was performed from the other side.

The argon injection flow rate was 10 Torr/s, and the injection time was 3 seconds. At the same time as the injection of argon gas was stopped, vacuum evacuation was performed for 7 seconds from the exhaust pipes on both sides. The above process was repeated three times.
Thermal decomposition of carbonates was carried out using the following two methods. The first method is according to the invention, in which carbonate thermal decomposition was started 3 seconds before the first argon injection. The heating time was 15 seconds. A second method performed for comparison with the present invention started thermal decomposition of carbonate at the same time as the first argon injection was completed. The heating time was 15 seconds. After completing the above evacuation process, 2.6 Torr of argon gas and mercury were filled in and sealed off. The time from the start of exhaust to the completion of seal-off was 38 seconds. Conventional methods require a minimum of 120 seconds.

Note that the number of times of cleaning with cleaning gas, activation time, etc. in the above manufacturing method are not limited to those of this embodiment, and may be modified in various ways within the scope of the present invention.

A 1000 hour lighting life test was conducted on the above fluorescent lamp. As a result, among the fluorescent lamps manufactured by the first method, the discharge starting voltage and the rate of tube end blackening of the lamps thermally decomposed with an appropriate amount of current were significantly reduced compared to the conventional method. Although the length could be shortened, it was still equivalent to the conventional manufacturing method. On the other hand, in the case of lamps manufactured using the second method for comparison with the present invention, the discharge start voltage tended to be slightly lower than that of conventional lamps, but the tube end blackened after 1000 hours of lighting. The incidence of is approximately
It was 30%, which was considerably worse than the conventional 0-3%.

As explained above, according to the method for manufacturing a low-pressure discharge lamp of the present invention, a low-pressure discharge lamp having the same performance as a low-pressure discharge lamp produced by a conventional manufacturing method can be manufactured in less than one third of the time required by the conventional method. This makes it possible to provide an inexpensive low-pressure discharge lamp.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the changes in the discharge starting voltage of the fluorescent lamp and the change in the peeling rate of the phosphor film depending on the flow rate of argon per number of injections, where 1 is the discharge starting voltage and 2 is the fluorescent light. Indicates the rate of baldness of body membranes.
Figure 2 is a diagram showing the state of the electrodes during thermal decomposition in argon, where 3 and 4 are nickel wires for supporting the filament, 5 is a double coil filament,
6 indicates carbonate and 7 indicates arc discharge.

Claims (1)

[Claims] 1. A method for manufacturing a low-pressure discharge lamp having a pair of oxide-coated electrodes at both ends and a pair of exhaust pipes, in which impurity gas such as air within the lamp is evacuated from both of the pair of exhaust pipes. However, there is a first step which is the first step of the exhaust step, a second step in which rare gas is injected from one of the pair of exhaust pipes and vacuum exhaust is performed from the other exhaust pipe, and the second step is a third step of evacuating the rare gas injected in the step from the exhaust pipes at both ends; and a step of removing impurity gas within the lamp by alternately performing the second and third steps. and a method for manufacturing a low-pressure discharge lamp, characterized in that thermal decomposition of the alkaline earth metal composite carbonate on the electrode is started during the first step. 2. The method for manufacturing a low-pressure discharge lamp according to claim 1, wherein the rare gas to be injected is argon, and the injection flow rate is set within a range of 2 Torr/s to 30 Torr/s.