FR2539555A1 - DISCHARGE LAMP IN LOW PRESSURE MERCURY STEAM - Google Patents

Abstract

MERCURY VAPOR DISCHARGE LAMP PRESENTING A TUBULAR DISCHARGE ENCLOSURE 1 TIGHTLY CLOSED ON THE INNER WALL TO WHICH A LUMINESCENT LAYER 4 IS APPLIED EMITTING ULTRAVIOLET RADIATION AT LARGE LENGTH OF ELECTRICAL AND REFLECTING LIGHT BETWEEN 5 LIGHT LENGTH, A COAT 5 AND THE INTERIOR WALL OF THE ENCLOSURE HAS DISCHARGED AND EXTENDS THE ENTIRE LENGTH OF THE ENCLOSURE A DISCHARGE ON PART OF THE PERIPHERY. IN ACCORDANCE WITH THE INVENTION, THE LUMINESCENT LAYER CONTAINS A LUMINESCENT SUBSTANCE BASED ON STRONTIUM TETRABORATE ACTIVE WITH BIVALENT EUROPE AND THE REFLECTOR LAYER CONTAINS ALUMINUM OXIDE.

Description

-1 - "Discharge lamp in mercury vapor at low pressure"

  The invention relates to a vapor discharge lamp

  of low pressure mercury having a tubular discharge chamber

  hermetically sealed on an inner wall of which is

  applied a luminescent layer emitting ultraviolet radiation

  let with a long wavelength, a reflective layer being present

  between this layer and the inner wall and extends over the entire

  length of the discharge vessel on a part of the periphery.

  Such a lamp is known from the patent of the United States of America

3.987 331.

  These lamps, which emit ultraviolet radiation with a long wavelength preferably in the range between 320 and 400 nm (UV-A radiation), are frequently used for photochemical or photobiological purposes, for example for solar beds. and solar devices for direct pigmentation

  skin (tanning without erythema formation) or for phototherapy.

treatment of skin diseases.

  The lamp described in said patent includes an enclosure for

  discharge in which is present a light layer present

  as a phosphor emitting UV-A radiation, for example lead-activated barium mesosilicate. Moreover, it comprises a reflective layer which preferably extends over more than 1800 of the periphery and which is constituted by zirconium dioxide The advantages of using zirconium dioxide compared to many other known reflective materials that are

  frequently used in combination with luminescent

  visible light emitting resides, according to the patent, in the advantageous reflective properties concerning in particular

  said ultraviolet radiation with a long wavelength.

  However, tests have shown that the yield of

  The powders emitting UV-A radiation in general and in particular that of the said lamps provided with a reflective layer are already decreasing.

  strongly after a relatively small number of hours of operation.

  This is a disadvantage because the lamps have to be replaced frequently but it can also be disadvantageous that

  the dose after a relatively small number of hours of operation.

  This is a disadvantage because the lamps need to be replaced frequently but it can also be disadvantageous that the radiation dose per unit of time during the

  Lamp operation decreases sharply.

  The aim of the invention is to provide a discharge lamp in the

  mercury vapor at low pressure designed for the emission of

  long-wave ultraviolet light, avoiding the above-mentioned

disadvantages.

  According to the invention, a discharge lamp in the

  low pressure mercury vapor of the type mentioned in the preamble

  bule is characterized in that the luminescent layer contains a luminescent substance based on strontium tetraborate activated with bivalent europium and that the reflective layer contains

aluminum oxide.

  Surprisingly, it has been found that lamp performance

  according to the invention having the above-mentioned combination of a

  luminescent scent containing a strontium tetraborate and a layer

  reflective material containing aluminum oxide for a long time

  operating time is remarkably high and constant Therefore, the use of these lamps is particularly advantageous

  because they have to be replaced significantly less frequently

  lamps, which makes it possible to achieve considerable cost savings and because, during the operation of the lamps, a more constant value of the radiation dose is obtained per unit of time. In order to attain the above-mentioned advantages, a reflective layer of aluminum oxide must be used in combination with a phosphoric acid-based strontium tetraborate phosphor

  with the aid of bivalent europium Such luminescent substance may

  to form a basic network of the formula Sr B 407, in which part of the Sr, for example from 0.3 to 20 mol%, is replaced by bivalent europium This strontium tetraborate

  is known for example from the German Offenlegungsschrift 26 52 480.

  In addition, it is possible to adapt modifications based on said tetraborate. Thus, part of the strontium (up to about% in moles) can be replaced by barium, magnesium and / or calcium (see FIG. aforesaid Offenlegungs schrift and Japanese Patent Application Publication 74/67892). Furthermore, fluorine-containing stretral tetraborate can be used, as is known from US Pat. No. 3,431,215. strontium have an emission in a narrow band, the

  maximum is at 370 nm and half a width of about 20 nm.

  U.S. Patent 3,225,241 discloses lamps having a reflective layer which may consist of suitable substances such as titanium dioxide or aluminum oxide. However, these layers are applied only by

  combination with a luminescent layer emitting light

  In addition, it is disclosed that aluminum oxide reflects mercury resonance radiation having a wavelength.

  However, no mention is made of the problems

  the reduction in the yield of long-lasting UV radiation

  in the ambient range of 370 nm.

  It is preferred to use a lamp according to the invention which

  is characterized in that the luminescent layer contains a tetra-

  strontium borate having the formula Sr 1 p Eup B 407, wherein 0.003 p 0.20, preferably 0.01 tp 4 0.005 and wherein up to 25 mole% of Sr may be replaced by Ba, Ca and / or Mg Indeed, these tetraborates result in the highest relative radiation currents and can be obtained more

  easily as tetraborate containing fluorine.

  In a special embodiment of a lamp according to

  In addition to the invention, the luminescent layer contains another substance

  luminescent (for example up to 10% by weight of the

  cent total) which emits light in the range of lengths

  between 580 and 650 nm. Such a substance is preferably

  ferment of activated yttrium oxide using trivalent europium.

  The lamp then has a warmer color.

  Very good results were obtained with a lamp in accordance with

  to the invention in which the greatness of most of the

  reflective layer in aluminum oxide was

between 0.1 and 20 microns.

  The following description, with reference to the drawings

  nexés, all given as a non-limitative example, will make a good

  take how the invention can be realized.

  Figure 1 schematically represents a form of reali-

  a discharge lamp in low pressure mercury vapor according to the invention; and FIG. 2 is a cross-section of the

  discharge of the lamp according to Figure 1.

  The lamp according to FIG. 1 comprises a discharge chamber

  hermetically closed tubular section 1, in which two electrodes 2, 3 are disposed between which a discharge is maintained between

  during the operation of the lamp On the inner wall of the

  1 is applied to a luminescent layer 4 emitting long-wave ultraviolet radiation (radiation

  UV-A). The layer contains a phosphor based on

  strontium traborate activated with bivalent europium Between the luminescent layer and the glass wall of the discharge vessel is a reflective layer 5 (see FIG. 2) which extends over the entire length of the Discharge chamber up to about 200 ° from the periphery. This reflective layer contains aluminum oxide.

  In a form of practical réâlisation, the enclosure to de-

  The charge of the aforesaid lamp had a length of approximately 1 80 m and an external diameter of approximately 38 mm. The power consumed was approximately 100 W. The luminescent layer 4 contained strontium tetraborate corresponding to the formula Sr 97 Eu 03 84070 This substance had an emission located in a narrow band at

  370 minutes and half a width of 20 nm.

  The layer of A 1203 (up to about 5 mg / cm 2)

  was about 200 of the periphery The average grain size was about 5 microns The radiation yield of

  this lamp was 23 watt UV-A after 100 hours of operation

  After 2000 hours of operation, the radiation yield

was 20 watts UV-A.

  In the aforesaid lamp, the luminescent layer extends over

  the entire periphery of the discharge chamber.

  alternatively, the luminescent lamp is only present on the reflective layer so that a window free of

  luminescent material and reflector.

-6-

Claims (3)

  1 Discharge lamp in low pressure mercury vapor   having a hermetically sealed tubular discharge chamber   a light-emitting layer emitting long-wave ultraviolet radiation is applied to an inner wall, a reflective layer being present between this layer and the inner wall and extending over the entire length of the discharge vessel on a periphery part, characterized in that the luminescent layer contains a luminescent substance based on strontium tetraborate activated with bivalent europium and the   reflective layer contains aluminum oxide.   2 Discharge lamp in mercury vapor at low pressure   according to claim 1, characterized in that the layer   minescente contains a strontium tetraborate corresponding to the   mule Sr 1 Eu B 407, wherein 0.003 z p 0.20 and preferably 0.01 4 Pp 0.05 and wherein up to 25 mol%   Sr can be replaced by Ba, Ca and / or Mg.   3 Discharge lamp in low pressure mercury vapor   according to claim 1 or 2, characterized in that   aluminum oxide particles are between 0, let 20 micron (s).