Simple transmittance-measuring instrument

摘要

A simple instrument for measuring the transmittance of a film impregnated with a pyridylazo-2-naphthol or dimethylphenylazo-2-naphthol dye having a continuous absorption spectrum having a plurality of absorption peaks in the wavelength range of from 350 to 800 nm, which comprises a light-emitting diode having a peak of relative emission intensity in the vicinity of a wavelength of 450 nm; a means for allowing the diode to emit a light and adjusting the quantity of the light; a band-pass filter which consists essentially of a resin film or glass plate coated with a coating composition composed essentially of at least one pigment selected from the group consisting of a Phthalocyanine Blue pigment and an organic violet pigment finely dispersed in a binder resin, and which has a peak of transmittance in the range of from 330 to 480 nm, the transmittance at the peak being 40% or more the transmittances at 260 nm or less and 520 nm or more being 1% or less, said band-pass filter being placed in such a position that the light emitted by the above light-emitting diode passes directly through the band-pass filter; a photodiode sensitive to the wavelength of the light which has passed through the band-pass filter which photodiode is placed so as to face the band-pass filter at such a space that a test sample can be inserted into between the band-pass filter and the photodiode.