JPH01194260A - Discharge lamp for growing plant - Google Patents

Abstract

PURPOSE:To have good light emitting characteristic when used for plant growing and provide long lifetime and improved starting voltage by encapsulating rare gas as start aid in a light emitting tube together with specified amounts of lithium iodide and mercury. CONSTITUTION:Together with lithium iodide and mercury, a rare gas as start aid is encapsulated in a light emitting tube, in which the end of a light permeable alumina tubing is sealed with a conductive thermet cap. The amount of encapsulated lithium iodide shall range 0.02-4.2mg per cm<2> internal volume of light, emitting tube, while the mercury range 5.0-20mg. Rare gas such as argon gas etc., is encapsulated as the start aid gas. Thereby the spectral distribution characteristic can be approximated to the light synthesis curve, which leads to improvement of the life characteristic and drop of the start voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an improvement in a discharge lamp for growing plants using an arc tube made of a translucent alumina tube, and more particularly to an improvement in the filling inside the arc tube.

[Conventional technology] Traditionally, three-wavelength fluorescent lamps,
High-wave color type high-pressure sodium lamps or metal halide lamps are known.

Among these, metal halide lamps in which metal halides are sealed in quartz arc tubes are
As disclosed in Japanese Patent Publication No. 16397 or Japanese Patent Publication No. 46-19394, it is possible to obtain radiation whose emission radiation spectrum is concentrated in the red and blue regions, and to achieve excellent growth effects for the growth of various plants. It has been known.

And as an enclosure for the arc tube of this kind of lamp.

Lamp containing indium iodide and lithium iodide,
Alternatively, lamps containing indium iodide, lithium iodide, and potassium iodide are known.

The emission spectrum of the lamp containing indium and lithium iodide is 610% of lithium.
nm, 670 nm and indium 410 nm, 451
Luminescence of nm wavelength can be obtained. Therefore, it has strong luminescence lines in the blue and red parts, making it ideal for growing plants, especially leafy vegetables.

Furthermore, it is known that near-infrared light emission with a wavelength of 800 nm or less can provide good growth effects on leafy vegetables.

[Problems to be Solved by the Invention] However, when lithium iodide, which has a strong emission spectrum at 61 hm and 670 nm, is sealed in order to enhance the luminescence in the red region as in the above-mentioned lamp, lithium ions pass through the quartz of the arc tube material. However, lithium luminescence disappears in a short period of time, changing the luminescent characteristics, and quartz and lithium easily react, eventually causing arc tube leakage, which is a practical problem.

Therefore, a metal halide lamp using a translucent alumina tube used in high-pressure sodium lamps as an arc tube instead of a quartz tube is described in Japanese Patent Application Laid-Open No. 76563/1983.

When manufacturing the arc tube, this lamp cannot be heated and exhausted as thoroughly as quartz lamps due to limitations in the material and structure of the arc tube, and even though the gas inside the arc tube is perfect, Normally, this will result in a high starting voltage.

Furthermore, in lamps that do not have an exhaust pipe and have a structure in which exhaust is performed at the same time as the arc tube is sealed, such as an arc tube according to an embodiment of the present invention described later, impurity gas generated during sealing may enter the arc tube. There is a possibility of containment and the starting voltage will rise significantly.

[Manual preparation for solving the problem] The present invention was made in view of the above points, and a predetermined amount of lithium iodide is placed inside an arc tube in which a conductive cermet cap is sealed at the end of a translucent alumina tube. By enclosing the discharge lamp and mercury, the spectral distribution characteristics of this discharge lamp match the photosynthesis curve of the plant, increasing the growth effect, improving the starting voltage, and providing a long life without the risk of arc tube leakage. The purpose of this invention is to provide a discharge lamp for growing plants.

[Function] The discharge lamp according to the present invention contains a certain amount of lithium iodide and mercury sealed in the arc tube so that the appropriate amount turns into vapor when the discharge lamp is lit, and further prevents corrosion of the sealed portion of the arc tube by lithium. Excess lithium is encapsulated to ensure thermodynamic stability.

In this way, not only the life characteristics of the discharge lamp can be significantly improved, but also the starting voltage can be lowered, and a discharge lamp with excellent practicality can be obtained.

It has also been found that by selecting the ratio of lithium iodide to mercury, it is possible to obtain a discharge lamp with spectral distribution characteristics that approximate the photosynthesis curve of plants.

Therefore, the discharge lamp according to the present invention contains 0.02 mg to 4.2 μg of lithium iodide per 1 cm3 of the internal volume of the arc tube, and the same <5
．． A rare gas such as argon gas as a starting auxiliary gas which can be ionized together with mg to 20 μg of mercury is sealed.

[Example] An embodiment of the present invention will be described below with reference to FIG.

In the figure, 1 is an arc tube in which a conductive cermet cap 3 made of alumina and tungsten is hermetically sealed at the end of a translucent alumina tube 2 via a sealing material 4. An electrode core 5 made of tungsten and having a tungsten coil wound around its tip is buried and fixed in the center, and a lead rod 6 made of tungsten, molybdenum, etc. is buried and fixed in the outer surface of the cap.

A predetermined amount of lithium iodide and mercury are sealed in the arc tube, and a predetermined amount of argon gas is also sealed as a starting rare gas.

Here, the amount of lithium iodide (LiI)
The amount is 0.02 rN per cm3 of the internal volume of the arc tube! : As is clear from the Lil-starting voltage characteristic diagram shown in Figure 2, the starting voltage is 4,000 V or less with a pulse voltage of 50 ns width once every half cycle, which is a practically good voltage. In addition, the starting voltage may rise suddenly. Furthermore, the light emission in the red region is significantly reduced, resulting in a marked difference from the photosynthesis curve of plants, and the effect of growing plants is reduced.

In addition, if it exceeds <4.2 mgti', the arc tube becomes chemically unstable, that is, the reaction with the alumina tube, the sealing material, and the cermet cap, which are the constituent materials of the arc tube, becomes excessive, making it impossible to maintain the desired lifespan and causing the arc tube to deteriorate. Not only will leakage occur and the lifespan will be shortened, but the balance with the luminescence intensity of the blue portion will be lost, and the effect of growing plants will be reduced as described above.

Next, when the amount of mercury is less than 5 cm per cm3 of the internal volume of the arc tube, the luminescence intensity in the blue region decreases.

Not only is there no effect on growing plants, but there may be a reaction between the arc tube constituent materials and lithium during its life.

Moreover, if the amount exceeds 20 mg, the balance with the luminescence intensity of the red part will be poor and the plant growth effect will be lost as described above.

In this way, by keeping the amount of lithium iodide and mercury within a predetermined range and keeping the luminescence intensity in the red and blue regions well-balanced and approximating the photosynthesis curve of plants, we have achieved optimal luminescence characteristics for growing plants. In addition to maintaining stable chemical equilibrium with the alumina tube, sealing material, and cermet cap that are the constituent materials of the arc tube, it is also possible to reduce the starting voltage within the practically optimum range. can.

Next, specific examples according to the present invention will be described.

Arc tube dimensions: tube inner diameter 10mm+, arc length 20II
I11 with an internal volume of lt) 2, 0.9ffIg of lithium iodide and 0 lithium metal in the arc tube of Occ.
．． 60 too much argon gas with 1■ and 15■ mercury
The spectral distribution characteristics of the sealed discharge lamp when it was turned on at a tube input of 250 W were as shown in FIG.

This discharge lamp had characteristics such as an initial luminous flux of 13,000 Q m, a color temperature of 2,400 K, and a starting voltage of 3,000 V with a 5 ounce width pulse once every half cycle. Further, there was little change in spectral distribution characteristics after lighting for s, ooo hours, and the luminous flux maintenance rate was 86%.

In particular, it was found to be effective in growing leafy vegetables such as lettuce and saladana.

Next, a comparative example will be explained.

0.0% lithium iodide was placed inside the arc tube constructed in the same manner as above.
1. Input a discharge lamp containing 60 tor of argon gas with 0.1 g of lithium metal and 15 tg of mercury into the tube input 25.
Although it was lit at 0W, the initial luminous flux of this discharge lamp was 12.50W.
Although the color temperature was over 4,800 at 0 Q m, the starting voltage was as high as 5,300 V, requiring a special starting device. Furthermore, after the lighting time elapsed, the luminescence intensity in the blue part was strong, and the leaves of leafy vegetables such as lettuce and Chinese cabbage became hard and discolored, causing them to lose their commercial value.

Furthermore, as a comparative example, 5.6 m of lithium iodide was added as above.
g, lithium metal 0. A discharge lamp containing 60 toor of argon gas with IN and 10 μm of mercury has a tube input of 250 W.
When turned on, the initial luminous flux of this discharge lamp was 9,300
Q tn, color temperature was 2 mg 100 K, and starting voltage was 2,500 V. Although the luminous flux maintenance rate after lighting for s, ooo hours was 76%, the color characteristics changed significantly throughout the lighting period, and the growth rate of leafy vegetables was slow, which was a practical problem.

[Effects of the Invention] As is clear from the above description, the discharge lamp for growing plants according to the present invention has excellent light emitting characteristics for growing plants by enclosing a predetermined amount of lithium iodide and mercury. In addition, it is possible to obtain a discharge lamp using an arc tube made of a translucent alumina tube and a conductive cermet cap, which has a long life and improved starting voltage, and is particularly useful in the field of plant cultivation, which has been attracting attention in recent years. Edible vegetables have great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a partially longitudinal side view showing an arc tube of a discharge lamp according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the relationship between the amount of lithium iodide enclosed and the starting voltage, and FIG. FIG. 3 is a diagram showing a spectral distribution of a discharge lamp according to the present invention.

Claims (1)

[Claims] (1) Inside the arc tube with the end of the translucent alumina tube sealed with a conductive cermet cap, 0.02 mg to 4.2 mg of lithium iodide and 5 mg to 20 mg of mercury per cm^3 of the inner volume of the arc tube are placed. A discharge lamp for growing plants filled with a rare gas for starting aid.