JPH0345505B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a vacuum-tight container having a fluorescent layer and filled with a gas containing mercury and a rare gas.
a container formed using an elongated tube capable of transmitting radiation, and means for maintaining a positive column discharge in the gas fill, wherein the power consumed by the positive column discharge during operation is Unit surface area of fluorescent layer
It concerns low-pressure mercury vapor discharge lamps with a power of at least 500 W per m ² . In the present specification, a low-pressure mercury vapor discharge lamp (so-called fluorescent lamp) with a compact shape is defined as having relatively small dimensions compared to the known conventional fluorescent tubes at a given input. It is defined as a fluorescent lamp with a volume. All features and characteristics of a normal fluorescent lamp (i.e. in terms of luminous output and service life)
Such a compact fluorescent lamp with high efficiencies but condensed into a small volume offers significant advantages. For example, such lamps are highly suitable for use in many places where ordinary incandescent lamps are used. As a result of the compact shape, the tube wall load of this compact fluorescent lamp is relatively high, ie at least 500 W/m ² . Such compact-shaped lamps consist of a container constructed using an elongated tube. The tube may be straight, but in order to be small in all dimensions, the tube (for example, having a length 10 times or more greater than the cross-sectional area dimension) may be curved or short straight tubes. It can also be formed from subdivided parts. Low-pressure mercury vapor discharge lamps are a widely used radiation source for general lighting and special applications (eg powering photochemical processes). The reason is,
This is because low pressure mercury vapor discharge lamps convert supplied electrical power into radiation very efficiently. These lamps generally consist of a tubular container, which can be straight or curved, for example circular or U-shaped. This vessel is filled with a gas mixture containing mercury and one or more rare gases, in which a positive column discharge occurs. This positive column discharge is typically maintained by supplying electrical energy to the gas mixture via two electrodes. This discharge primarily produces ultraviolet radiation, and a relatively small portion of this ultraviolet radiation is approximately
It has a wavelength of 185 nm, most of which has a wavelength of about 254 nm. This ultraviolet radiation is converted by a phosphor layer provided on the inner wall of the lamp vessel into radiation having a spectral distribution in the near ultraviolet or visible part of the spectrum and a long wavelength, depending on the phosphor material used. One of the most common types of low-pressure mercury vapor discharge lamps is the so-called lamp, which consists of a straight tube with a length of about 1.20 m and an internal diameter of about 37 mm, consuming about 40 W of power.
It is a 40W/T12 lamp. Generally, this lamp is
It operates with a lamp current of approximately 400 mA and a positive column electric field strength of approximately 80 V/m. The temperature at the coldest point of the envelope of such a lamp is approximately 40° C. in such an environment, and at this temperature there is a mercury vapor pressure within the lamp of approximately 6×10 ⁻³ Torr. This condition was found to be quite optimal for the generation of ultraviolet light. Other commonly used lamp types have lamp currents, electric field strengths, and mercury vapor pressures during operation that are the same as, or not significantly different from, the aforementioned values. The tube wall load (wall) of these lamps
load), i.e. the input power of the positive column per unit surface area of the fluorescent layer, is approximately
It is 300W/ ^m2 . Low-pressure mercury vapor discharge lamps have already been produced in which relatively high tube wall loads, i.e. 500 W/m ² , are supplied and therefore the input power per unit volume of the lamp is quite large. This was done primarily for the purpose of obtaining a compact lamp. For example, DE 21 09 898 A1 discloses compact lamps with wall loads of up to approximately 2500 W/m ² . The electric field strength of these lamps is greater than in ordinary lamps, for example on the order of 600 V/m. Secondly, high current densities (0.5-25 A/cm ² ) made it possible to create lamps in which the tube wall was very heavily loaded. These lamps are disclosed, for example, in US Pat. Nos. 3,778,662 and 3,679,928. Accordingly, tube wall loads of the order of 25000 W/m ² can occur with these lamps. A major drawback of prior art lamps with relatively high wall loads is lamp efficiency. That is, the radiant flux or luminous flux of the effective radiation emitted by the fluorescent layer (the output of effective radiation per unit power supplied to the lamp) is of small value. In particular, this efficiency is significantly lower than that of ordinary lamps (eg 40W/T12 lamps). This drawback is particularly apparent for compact lamps and is one of the reasons why such lamps have not yet been provided, which would offer great advantages in practical applications, for example as a replacement for ordinary incandescent lamps. It has not been understood why it has been impossible to produce lamps with high power input per unit volume and with efficiencies comparable to those of ordinary lamps. Optimum mercury vapor pressure (high for high-load lamps, e.g. at the lamp's coldest point temperature of 120°C)
Known knowledge regarding mercury vapor pressure (0.75 Torr) and means of controlling mercury vapor pressure (such as amalgam) have not yielded the desired results. It was therefore believed that manufacturing a compact lamp, for example by reducing the diameter, while retaining the power supplied, would necessarily be achieved by reducing efficiency. The object of the invention is a low-pressure mercury vapor discharge lamp which has a high density power consumption and a high radiant efficiency during operation, on the one hand a compact lamp with an efficiency approximately equal to that of ordinary low-pressure mercury vapor discharge lamps. On the other hand, the object is to provide a lighting lamp with a high current density and improved radiation efficiency. The present invention provides a vacuum-tight container having a fluorescent layer and filled with a gas containing mercury and a rare gas.
a container formed using an elongated tube capable of transmitting radiation, and means for maintaining a positive column discharge in the gas fill, wherein the power consumed by the positive column discharge during operation is Unit surface area of fluorescent layer
In a low-pressure mercury vapor discharge lamp of at least 500 W per m ² , the fluorescent layer contains a fluorescent material, the fluorescent material having a wavelength predominantly of 185 nm.
and 254nm, with a radiation density of 330W/ ^m2 , and a ratio of 185nm output to 254nm output.
After exposing the phosphor for 15 minutes to ultraviolet radiation having a wavelength of 0.30, the luminous flux at 254 nm is at most 5% lower than the initial luminous flux of the phosphor at 254 nm excitation measured under the same environment before this irradiation. The present invention provides a low-pressure mercury vapor discharge lamp, characterized in that the cation bond in the fluorescent substance has a maximum electronegativity of 1.4 and is compact in shape. . Research into the present invention has shown that efficient conversion of electrical power to ultraviolet light is possible in high-load lamps. Surprisingly, it has been found that the efficiency of this conversion can be made approximately equal to that of a common 40W/T12 lamp.
It has been found that it is necessary that the temperature of the electrons in a high-load lamp be no lower, but preferably higher, than that of a normal lamp. Various means are possible to achieve this.
For example, starting with a common lamp, keeping the power supplied to the lamp approximately constant and reducing the diameter of the discharge vessel maintains the required high electron temperature. Compared to ordinary lamps, the electric field strength is large in this case, the lamp current is small and the tube wall loading is greater than in ordinary lamps. Various experiments have shown that the above-mentioned high efficiency of conversion into ultraviolet light can be obtained with a very small diameter of the discharge tube (1 to several mm). Low-pressure mercury vapor discharge lamps provide efficient and compact fluorescent lamps with cylindrical discharge space diameters starting from 3 mm.
Actually possible if chosen in the 15mm range. 3
For diameters smaller than mm the lamp voltage is too high for practical purposes. Moreover, a diameter of 15 mm or more is not suitable for downsizing. Another means of making it possible to maintain high electron temperatures is to reduce the noble gas pressure in the lamp while increasing the power supply. In this case, compared to an ordinary lamp, the lamp current will be much larger, and the electric field strength will be approximately the same or somewhat smaller. The tube wall loads of these lamps are of course high. Moreover, by effectively generating UV radiation in high-load lamps, not only the UV density is large at the tube wall, but also the proportion of radiation with a wavelength of 185 nm is relatively large compared to ordinary lamps. It was discovered that The unexpectedly large ratio between the radiation at 185 nm to 254 nm with the increased density of the total UV radiation generated results in a fairly large 185 nm loading of the tube wall of such a compact lamp. The present invention shows that the failure of prior art lamps with high tube wall loads is due to the phosphor material used, rather than to low efficiency of conversion to ultraviolet light, as has been commonly thought. It is based on recognition. The present invention provides suitable fluorescent materials as a means of obtaining efficient high-load lamps. The invention therefore opens the way to a completely new class of lamps, namely compact low-pressure mercury vapor discharge lamps, which can replace the common incandescent lamps in great numbers. Since the efficiency of low-pressure mercury vapor discharge lamps is approximately five times that of incandescent lamps, considerable savings in energy are possible. In the lamp according to the invention, on the one hand
Quite resistant to 185nm radiation, i.e. (on excitation by 254nm radiation) 185nm
On the other hand, fluorescent materials are used which have a very small reduction in the luminous flux due to irradiation and, on the other hand, have high mercury resistance. It is known that exposing a fluorescent material to 185 nm radiation, even after a very short time, generally has a detrimental effect on the luminous flux of the fluorescent material.
As a measure of resistance to 185 nm radiation, the so-called short term decrease is used. In the present invention, this short-term decrease is defined as:
After the fluorescent material was irradiated for 15 minutes with radiation having mainly wavelengths of 185nm and 254nm, a radiation density of 330W/ ^m2 , and a ratio of the power of 185nm to 254nm of 0.3, (254nm This means the value of the reduction ratio (%) at which the luminous flux when excited (by radiation of Measurement methods for determining this short-term reduction and the values of short-term reduction for certain fluorophores are described in “llluminating”
Engineering" 59 (1964), pages 59 to 66. Such a measurement method will be explained in detail below. In the lamp of the present invention, high-density
Due to the 185 nm radiation, high requirements are placed on the short-term reduction of the fluorophore. This short-term decrease is 5
Must not be greater than %. For values larger than this, the lamp was found to have an unacceptably low luminous flux after the few minutes of operation required for a stably operating lamp. In fact, a short-term reduction has already occurred when the luminous flux of the lamp is measured at 0 hours. In the lamp according to the invention, the fluorescent substance used not only meets the requirements regarding short-term reduction, but also
The requirement for a high degree of mercury resistance must also be met. It has thus been found that the fluorescent layer in high-load lamps is exposed to a much greater number of bombardments by excited mercury atoms and ions than in ordinary lamps.
Energetic mercury atoms and ions can absorb and/or react with fluorescent substances at the surface of the fluorescent layer. As a result, a blackening of the fluorescent layer occurs, which considerably reduces the luminous flux of the lamp. A measure of the mercury resistance of a fluorescent material is the electronegativity of the fluorescent material's cations (electro-negativity, e.g.
n.). In the claims and detailed description of the invention, cations are referred to in the “Handbook of Chemistry and Physics”.
shall be understood to mean the metals of columns 1A, 1B, 2A, 2B, 3A of the Periodic Table of the Elements as shown in Cleveland (Ohio). Other elements are here considered to be anions or anion-producing elements. The en value of an element is “The Nature of the
Chemical Bond” by L. Pauling, New York
(1945). If these elements are arranged based on increasing values of en, a so-called electromotive series of elements is obtained. In principle, an element can be replaced by all elements of equal or greater electronegativity in the electromotive series in a given composition. Mercury (has an en of 1.9), but the cation has en≧1.9
(these cations are as noble as or even more noble than mercury). It has been found that the cations of the phosphors suitable for the lamps of the invention must be relatively small, ie, have an en value of 1.4 or less. This can be explained by the fact that the energy of mercury in the discharge plasma is greater than that of neutral mercury, and the impact of mercury on the fluorescent layer is higher. For example, it has been shown that phosphors containing zinc (en = 1.6) as a cation (which in ordinary lamps shows some mercury attack only after a fairly long period of operation) cannot be reliably used in high-load lamps. I found it. The reason is that after the lamp has been lit for a few minutes to several hours, the fluorescent layer is already significantly blackened. If the fluorescent substance contains several cations, for example if the element used as activator is a cation, this bond of these cations must have an en of 1.4 or less. That is, the weighted average of en of these cations must be 1.4 or less. In this case, a small fraction of the cations in the fluorophore are themselves larger than 1.4 en
It is possible to have Particularly suitable according to the invention are low-pressure mercury vapor discharge lamps which are equipped with a fluorescent material which has the property of giving a luminous flux at most 3% less than the initial luminous flux after 15 minutes of the above-mentioned UV irradiation. A phosphor with such a small short-term reduction results in a lamp with a very high luminous flux and also with a very high tube wall load. In a very advantageous embodiment of such a compact-shaped fluorescent lamp, the container constituted by a tubular element has a substantially circular cross-section perpendicular to the tube axis and an internal diameter of between 3 and 15 mm. In practice, it has been found that within this range of internal diameters a very efficient lamp can be obtained with a luminous flux approximately equal to that of a conventional lamp (having an internal diameter of approximately 36 mm). It has been found that it is possible to use inner diameters smaller than 3 mm, but for some inputs this very small diameter tube becomes too long and requires too much or too much effort to obtain a compact lamp. The manufacturing process (such as connecting curved or segmented parts) must be carried out. Similarly, it is quite possible to use an inner diameter larger than 15 mm, but in this case, considering the cross-sectional dimensions, the significance of miniaturizing the lamp diminishes, so larger dimensions are not desirable for many applications. . It can therefore be seen that a low-pressure mercury vapor discharge lamp with a vessel formed by a cylindrical tube with an internal diameter of 3 to 15 mm is most suitable for the purpose of obtaining a lamp of compact shape. Moreover, such lamps have been found to be extremely simple and easy to make without compromising the excellent phosphor properties. In the lamp according to the invention, an electric field strength of 150 to 1000 V/m is preferably maintained in the positive column discharge during operation. This fairly high field strength can be obtained by using a glass tube with a relatively small diameter. In this case, a compact, high-load lamp with a high luminous flux is obtained with a relatively low lamp current. In another embodiment of the lamp according to the invention, the current maintained in the positive column discharge during operation has a current density of at least 0.5 A/cm ² . These relatively high current densities provide lamps with high luminous flux. Due to the small short-term attenuation and the good mercury resistance of the phosphors used, the luminous flux of these lamps is even greater than that of conventional lamps with large current densities. In a further embodiment of the invention, the lamp contains as the fluorescent material a red fluorescent trivalent europium-activated rare earth metal oxide having a composition of the chemical formula Ln ₂ O ₃ :pEu ³⁺ . Here, Ln represents at least one of the elements Y, Gd, and Lu, and satisfies 0.01≦p≦0.20. According to the invention, these fluorescent oxides, especially known as fluorescent substances themselves, have a very small short-term decay and exhibit a high mercury resistance, so that these fluorescent oxides can be used in the lamp very easily. It can be used with many advantages. Other embodiments according to the invention include phosphorescent aluminates activated with Ce or Ce and Tb and having a hexagonal crystal structure related to the structure of magnetoplumbite. This aluminate has a composition represented by the chemical formula (Ce _1-pq La _p Tb _q ) ₂ O ₃ .xMgO.yAl ₂ O ₃ . Here, up to 25 mol% of Al ₂ O ₃ can be replaced by Ga ₂ O ₃ and or Sc ₂ O 3 and 0≦x≦2 10≦y≦16 0 _≦ p≦0.50 0≦q≦0.60 p+q ≦0.90. This group of phosphors itself is covered by a British patent no.
No. 1393040 and No. 1452083, where it is described in detail with regard to composition and fluorescence properties. These aluminates were found to have small short term decay and good mercury resistance. Other embodiments of the lamp according to the invention are activated with divalent europium, or with divalent europium and divalent manganese, or with trivalent cerium, and have a hexagonal crystal structure related to the structure of β-alumina. Contains phosphorescent aluminate with This aluminate has the chemical formula MeO・xMgO・yAl ₂ O ₃ :pEuO・qMnO・
It has a composition represented by rCe ₂ O ₃ . Here, Me represents barium and or strontium,
Up to 25 mol% of Al ₂ O ₃ with Ga ₂ O ₃ and or
It can be replaced with Sc ₂ O ₃ and 0≦x≦2 5≦y≦8 0.01≦p≦0.50 0≦q≦1.0 0≦r≦0.50. When x=0, Me is barium. This group of phosphors itself is described in British Patent No. 1190520,
No. 1384683 and No. 1452083, which describe the composition and fluorescence properties in detail. These fluorescent aluminates are particularly suitable for use in lamps according to the invention due to their very low short-term decay and good mercury resistance. The fluorescent layer of the lamp according to the invention consists of divalent europium activated strontium tetraborate, lead activated barium disilicate, divalent europium activated chlorophosphate with a apatite crystal structure, strontium cerium and Terbium activated gadolinium metaborate, trivalent bismuth and trivalent europium can contain fluorescent substances selected from the group consisting of activated gadolinium borate. As discussed below, these phosphors have excellent short term decay. Also, since these mercury resistors are highly preferred, these materials can be used advantageously in lamps according to the invention. Some embodiments according to the invention are illustrated by the examples and figures shown below. FIG. 1 is a schematic longitudinal cross-sectional view of a low-pressure mercury vapor discharge lamp according to the invention, with the central part of the discharge lamp cut away. The glass discharge tube 1 of the lamp according to the invention shown in FIG. 1 has an inner diameter of 10.3 mm and a length of 30 cm. Electrodes 2, 3 are provided at both ends of the lamp. During operation of the lamp, a discharge occurs between these electrodes. Electrode 2
The distance between and 3 is 26 cm. This lamp has 3 Torr at room temperature to act as starting gas.
of argon and a small amount of mercury. A fluorescent layer 4 is provided inside the tube 1. According to the invention, this fluorescent layer 4 contains a fluorescent material with a small short-term decay and a large mercury resistance. This fluorescent substance can be applied to the tube 1 in the usual manner, for example by suspension. FIG. 2 is a schematic cross-sectional side view of an apparatus suitable for measuring short-term decline of fluorescent substances. The device comprises a table 21 on which a bell-shaped enclosure 22 is arranged in a vacuum-tight manner. A disk-shaped holder 23 having an inner diameter of 45 mm is provided inside the enclosure 27. A layer 24 of the fluorescent powder to be tested is provided on the holder 23. This holder 23 is supported by the hollow tube 5. This hollow tube is provided with a hole at a location located within the enclosure 22.
Furthermore, a UV source 6 is provided inside said enclosure 22. The radiation source 6 is a low-pressure mercury vapor discharge lamp consisting of a quartz glass tube 7 with an internal diameter of approximately 9.5 mm. The glass tube 7 has a flat helical shape with approximately 2.5 turns, so a flat disk-shaped radiation source with a diameter of approximately 70 mm is used. The ends 8 and 9 of the tube 7 are perpendicular to the plane of the helical part of the radiation source and are each provided with an electrode. The spacing between the electrodes measured along the discharge path is approximately 33 cm. Furthermore, the tube 7 is filled with rare gas and a large amount of mercury. The distance from the radiation source 6 to the fluorescent layer is
It is 45nm. The conductors 10, 11 ensure the necessary power supply to the radiation source 6 and exit from the bell enclosure 22 via a hollow tube 12. During operation of the radiation source 6, the positive column discharge is about 65V and the lamp current is about
It is 500mA. Most of the ultraviolet radiation generated by the radiation source 6 passes through the quartz tube 7. During the measurement, nitrogen is admitted from 13 to enclosure 22. This nitrogen flow is 14
released from. The nitrogen atmosphere thus formed absorbs almost no short wavelength ultraviolet light.
During radiation, the density of ultraviolet radiation (185 nm and 254 nm) in the fluorescent layer 24 is 330 W/m ² .
The ratio between the 185nm output and 254nm output is 0.30. The value of this ratio is important. The reason is that when a fluorescent material is used in a low-pressure mercury vapor discharge lamp, the fluorescent material
This is because they are simultaneously irradiated by 254 nm radiation. In other words, it has become clear that the effect of 185 nm radiation on fluorescent substances is influenced by the simultaneously existing 254 nm radiation. Reproducible measurements are obtained with a value of said ratio of 0.3. For short-term reduction measurements of fluorophore, the fluorophore sample is irradiated for 15 minutes in the apparatus shown in FIG.
It was found that irradiation for 15 minutes at a radiation density of 330 W/m ² provides reproducibility. After 15 minutes of irradiation, the luminous flux of the sample is measured in the usual way. The measurements are carried out in such a way that no ultraviolet or visible radiation reaches the sample during this time. The luminous flux measured in this manner is compared with the luminous flux of a non-irradiated sample measured in the same manner. In the manner described above, short-term reductions in a number of fluorescent substances are measured. The table shows measurement results for a number of fluorescent materials suitable for use in lamps according to the invention. In addition to the chemical formula of the substance, the table shows for each sample in the column "en" the electronegativity values of the bonds of the cations within the substance. Column "STD" shows the short term reduction in %. Examples a and b are outside the scope of the invention, but are shown for comparison. These examples are often used for ordinary lamps, but
It concerns materials that are unsuitable for use in the lamp of the invention because their STD is too high. Example c (zinc silicate) is also shown for comparison.
This material, which is often used in ordinary lamps, is an excellent
STD, but because the material's resistance to erosion by mercury (mercury resistance) is very low,
It is not suitable for use in the lamp of the present invention. This is evidenced by a value of en greater than 1.4.
In high-load lamps, this material is already sufficiently eroded after a short period of time (after stabilizing the lamp on the test bench to measure the so-called 0-time value) and therefore has a very small value for the luminous flux. is obtained. The materials listed in the table were applied to a lamp having a discharge vessel with an internal diameter of 10.3 mm as described in connection with FIG.
These lamps have a lamp current of 175mA and
It was operated at an electric field strength of 196 V/m (tube wall load 750 W/m ² ). The measurement of the positive column efficiency (after stabilizing the lamp) at time 0, i.e. the efficiency of the conversion of the electrical power input of the discharge positive column into useful radiation, is defined as “L0 0
For comparison, the values of the positive column efficiency of these materials when used in an ordinary lamp with an internal diameter of 36 mm (tube wall load 300 W/m ² ) are , in the column "L0 0 hours, φ36". It is clear that reducing the diameter in accordance with the present invention (resulting in a high-load lamp) is not accompanied by a loss in positive column efficiency.

[Table] Examples 11, 12, 13 The three lamps were shaped as explained in relation to Figure 1, but with different inner diameters of 7, 8, 10.3, and 10.3, respectively.
It was set to 14.5mm. Lamp with inner diameter of 7.8mm is 100mA
It was operated with a lamp current of 286 V/m and an electric field strength of 286 V/m. As a result, the tube wall load was approximately 780W/ ^m2 . For a lamp with an internal diameter of 10.3 mm, these values are 175 mA, 196 V/m, and 750 W/ ^m2 , respectively, and for a lamp with an internal diameter of 14.5 mm, respectively.
250mA, 150V/m, 595W/ ^m2 . These three lamps have the chemical formula BaMgAl ₁₀ O ₁₇ :Eu ²⁺
A blue phosphor material was provided having the composition shown by. The table shows measurements of the positive column efficiency, ie, the luminous flux in lumens per watt of power input to the positive column, at various times during the lamp's operation over the lifetime of these lamps. The table is 100
Positive column efficiency LOP100 hours after hours is expressed in lm/W. Results at 0 and 500 hours are expressed as % of the value at 100 hours.

[Table] Examples 14, 15, 16 The same procedure as described above for Examples 11, 12, and 13 was used. However, the three lamps have a chemical formula
A red fluorescent material was provided having the composition indicated by Y ₂ O ₃ :Eu ³⁺ . The table is 0,100,500,
Measurement of positive column efficiency at 1000 hours is shown.

[Table] Example 17 The lamp shown in Figure 1 with an inner diameter of 7.8 mm has a chemical formula
A green phosphorescent aluminate having the composition shown as Ce _0.67 Tb _0.33 MgAl ₁₁ O ₁₉ was provided. 100mA,
The lamp, operated at 286 V/m (load 790 W/m ² ), obtained a positive column efficiency of 122.5 lm/W in 100 hours. At 0, 500, and 1000 hours, the positive column efficiency was 103, 96, and 96% of the 100 hours, respectively. Example 18, 19, 20 The three lamps shown in Figure 1, all having a length of 45 mm and an inner diameter of 7.8 mm (same as Examples 11 and 14), have a color of approximately 3000 K. two types of fluorescent substances in such amounts as to have a temperature;
That is, a mixture of Y ₂ O ₃ :Eu ³⁺ and Ce _0.67 Tb _0.33 MgAl ₁₁ O ₁₉ was provided. The tube wall load of these discharge lamps was 1090 W/m ² . In this case the lamp is
It was operated with a current of 200 mA and an electric field strength of 200 V/m. The measurement results of the positive column efficiency are shown in the table. The table also shows measurements for three lamps (e, f, g) equipped with a fluorescent calcium halide phosphor activated by antimony and manganese with a color temperature of approximately 3000 K. ing. Lamps e, f, g, which are identical in all other respects (as well as with respect to electric field strength) to lamps 18, 19, 21, are not based on the invention and are shown for comparison only. be. It is clear that a high positive column efficiency can be obtained with the lamp according to the invention and that this efficiency is maintained very well over the life of the lamp.

[Table] Examples 21 to 26 Three lamps No. 21, 22, and 23, which are the same as lamps 18, 19, and 20, have a voltage of 286 V/m at 100 mA.
It was operated with an electric field strength of . In this case, the discharge lamp tube wall load of these lamps was 780 W/m ² .
Three same lamps No.24, 25, 26 are 300mA
It was operated at an electric field strength of 160 V/m. In this case, the tube wall load of these discharge lamps was 1300 W/m ² . The measurement results of the positive column efficiency are shown in the table.

[Table] Examples 27, 28 Two lamps as shown in Figure 1 contain 54% by weight of Y ₂ O ₃ :Eu ³⁺ and 36.5% by weight of Ce _0.67 Tb _0.33
A mixture of three phosphors was provided consisting of MgAl ₁₁ O ₁₉ and 9.5% by weight BaMgAl ₁₀ O ₁₇ :Eu ²⁺ . The radiation emitted by these lamps is approximately 4400K
It had a color temperature of The first lamp (Example 27) is
Operating at a current of 175mA (tube wall load 750W/ ^m2 ,
It had a positive column efficiency of 99lm/W. The second lamp (Example 28) has a current of 250 mA (tube wall load 893 W/m ² )
It operated at 93 lm/W and had a positive column efficiency of 93 lm/W. It is clear that the examples described above serve to explain the invention. Based on the requirements set forth in this description regarding short-term decay and mercury resistance, and according to the methods described above for determining these properties, one skilled in the art will be able to use any phosphor material in a lamp according to the invention. You can easily check whether it is suitable. Furthermore, fluorescent substances which do not satisfy the above-mentioned requirements, eg imposed on short-term reduction, can be made suitable, eg by optimizing the preparation of this substance. By coating the fluorescent material with a protective layer, sufficient resistance of the fluorescent material to attack by mercury can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal cross-sectional view of a low-pressure mercury vapor discharge lamp according to the invention, and FIG. 2 is a schematic side cross-sectional view of an apparatus suitable for measuring the short-term depletion of fluorescent substances. DESCRIPTION OF SYMBOLS 1... Glass discharge tube, 2, 3... Electrode, 4... Fluorescent layer, 5, 12... Hollow tube, 6... Ultraviolet source, 7... Quartz glass tube, 10, 11... Conductive wire, 21... Table,
22...enclosure, 23...holder, 24...layer of fluorescent powder.

Claims (1)

[Claims] 1 A vessel formed using a vacuum-tight, radiation-transparent elongated tube having a fluorescent layer and filled with a filler gas containing mercury and noble gases, and a positive column in the filler gas. and in which the power consumed by the positive column discharge during operation is at least 500 W per m ² of surface area of the phosphor layer, said phosphor layer comprising: , contains a fluorescent material, and this fluorescent material has a wavelength of mainly 185 nm and
It consists of 254nm and has a radiation density of 330W/ ^m2 ,
Furthermore, the phosphor was exposed to ultraviolet radiation having a ratio of 185 nm power to 254 nm power of 0.30 for 15 minutes and was measured under the same environment before this irradiation.
having the property of having a luminous flux at 254 nm excitation that is at most 5% smaller than the initial luminous flux of the fluorescent material at 254 nm excitation, and the bonding of cations in the fluorescent material having an electronegativity of at most 1.4; A low-pressure mercury vapor discharge lamp characterized by its compact size.