A melt-molded polyvinylidene fluoride or polymonochlorotrifluoroethylene sheet having a thickness of about 20 .mu. to 2 mm and a spherulite size of less than about 10 .mu., whereby the sheet transmits more than about 40% of the dorno rays in a wavelength region of about 2,800 to 3,300 A, and a sun room using as a light admitting plate a sheet or plate of the polyvinylidene fluoride or the polymonochlorotrifluoroethylene permitting transmission of the physiologically active rays in sunlight.