Patent Number: 046833790
Section: summary

CROSS-REFERENCE TO RELATED CASES A sunlamp which emits radiation primarily in the UVA band of the ultraviolet range and in the visible range of the spectrum is disclosed in the commonly owned copending patent application Ser. No. 752,251 filed July 3, 1985. Reference should also be had to commonly owned U.S. Pat. Nos. 4,095,113, 4,106,083, 4,177,384, 4,194,125, 4,196,354, 4,287,554, 4,309,616 and 4,316,094. BACKGROUND OF THE INVENTION The invention relates to improvements in lamps, especially sunlamps, which emit radiation in the visible and ultraviolet ranges of the spectrum. It is already known to fill the envelope of a sunlamp with a mixture of radiation emitting substances which ensure that the lamp can emit radiation in the visible as well as in the UVA band of the ultraviolet range of the spectrum. The effect of such lamps strongly resembles that of sunlight except that the lamps cannot radiate the same amount of heat energy. However, the addition of a substance which causes the lamp to radiate in the UVA band affects a pronounced reduction of radiation in the visible range, i.e., the brightness of such lamps is less than satisfactory. It is also known to confine in the envelope of a lamp a substance which has pronounced radiation peaks in the red, blue and green portions of the visible range, i.e., in those portions of the visible range in which the human eye is particularly sensitive so that the lamp can be categorized as a "bright" lamp. OBJECTS AND SUMMARY OF THE INVENTION An object of the invention is to provide a lamp, particularly a sunlamp, whose brightness is highly satisfactory even though it is capable of emitting radiation in the visible as well as in the ultraviolet range of the spectrum. Another object of the invention is to provide a lamp whose photobiological effect in the ultraviolet range is highly satisfactory in spite of the fact that it can be categorized as a "bright" lamp. A further object of the invention is to provide a sunlamp which can be utilized for long periods of time without any adverse effects upon the person whose body is exposed to its radiation. An additional object of the invention is to provide a novel and improved combination of radiation-emitting substances which can be utilized in a lamp of the above outlined character. Another object of the invention is to provide novel and improved substances which can be utilized in the above outlined lamp to ensure the emission of beneficial radiation in the UVA and UVB bands of the ultraviolet range of the spectrum. A further object of the invention is to provide a novel and improved ratio of radiation emitting substances which can be used in the above outlined lamp. The invention is embodied in a lamp which emits radiation in the red, blue and green bands of the visible range as well as in the long-wave and short-wave portions of the UVA range of the spectrum. The energy maximum of radiation in the long-wave portion of the UVA range is less pronounced than the energy maxima in the red, blue and green bands of the visible range, and the energy maximum of radiation in the short-wave portion of the UVA range is substantially less pronounced than in the long-wave portion of the UVA range and extends into the UVB range to terminate in the region of approximately 300 nm. The energy maximum of radiation in the long-wave portion of the UVA range is preferably between 370 and 390 nm. The lamp comprises an envelope and a mixture (e.g., an internal layer) of radiation emitting substances in the envelope. The mixture includes a first substance which emits radiation in the visible range, a second substance which emits radiation in the longwave portion of the UVA range, and a third substance which emits radiation between 300 and at least 320 nm. The second substance can emit radiation between approximately 350 and 400 nm, and the third substance is preferably selected to emit radiation up to approximately and at least slightly above 350 nm. The percentage of the first substance is preferably at least 80 percent of the sum of the first, second and third substances; the percentage of the second substance preferably exceeds the percentage of the third substance and the second substance preferably contains europium-activated strontium fluoroborate; the third substance preferably contains cerium-strontium-magnesium aluminate; the second substance preferably constitutes between 5 and 10 percent of the sum of the first, second and third substances; and the third substance preferably constitutes between 1 and 4 percent of the sum of the first, second and third substances. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved lamp itself, however, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.