| 摘要 |
<p>Covering element having selective optical properties, suited as a protective screen for refrigerating devices by radiation, consisting of at least one film or sheet of a material, transparent to infrared radiation comprised between 8 and 13 mu m, and selected among polyethylene and ethylene copolymers, additioned with coloring materials selected among pigments and dyes so as to make this film reflecting in a prevailingly diffusive way (white) on the face to be turned to the direct solar radiation and absorbent, that is dark, for wave lengths below 3 mu m on the opposite face, said film thus additioned showing a mean weighted reflectance in the solar spectrum greater than 0.6 on the upper face exposed to the sun and less than 0.3 mu m on the opposite face, as well as a mean weighted transmittance in the solar spectrum not exceeding about 0.1.</p> |
