| 摘要 |
<p>In a low pressure mercury vapour fluorescent lamp having the inner surface of its envelope coated with two superimposed luminescent layers, of which the first-next to the envelope-includes manganese - activated magnesium germanate or arsenate, and the second consists mainly of a mixture of a blue luminescent substance and a red luminescent substance, which red luminescent substance has a wide emission spectrum with a maximum between 6000 and 6500 </>rA and an additional emission in the ultra-violet between 3000 and 4000 </>rA. The first layer also includes a substance which efficiently absorbs ultra-violet radiation but is highly permeable to radiation with wavelengths greater than 4000 </>rA-e.g. titanium dioxide or zinc oxide-whereby to absorb any ultra-violet light emitted by the material of the second layer. The blue luminescent substance of the second layer may be antimony-activated ca'cium halophosphate, and the red luminescent substance tin-activated strontium magnesium orthophosphate.</p> |
