Optical device having low visual light transmission and low visual light reflection

A solar control film having low visible light transmittance and low visible light reflectance comprising

• a first sheet of transparent substrate material bearing thereon a thin transparent layer of a material of high refractive index and a thin, transparent, incoherent coating of metal overlying the material of high refractive index, the metal film being effective to partially block visible light transmittance through the coated substrate and having a preselected low visible light reflectance,
• a second sheet of transparent substrate material bearing thereon a thin transparent layer of a material of high refractive index and a thin, transparent, incoherent coating of metal overlying the material of high refractive index, the metal film being effective to partially block visible light transmittance through the coated substrate and having a preselected low visible light reflectance, and
• a layer of adhesive bonding said first and second sheets to one another with the films of metal facing one another and optically decoupled and separated from one another,
• the bonded sheets forming a composite film having a combined visible light transmittance blocking effect equal approximately to the sum of the blocking effects of the incoherent films and low visible light reflectance substantially equal to the visible light reflectance of just one of the incoherent films, the visible light reflectance of each incoherent film being such that the visible light reflectance of the composite film does not exceed about 20% when visible light transmittance is no greater than about 25%, does not exceed about 15% when visible light transmittance is no greater than about 35% and does not exceed about 12% when visible light transmittance is up to about 50%.

A method of making solar control films having low visible light transmittance and low visible light reflectance comprising the steps of

• depositing onto a transparent substrate a thin, incoherent, transparent coating of metal that is effective to partially block visible light transmittance through the coated substrate and that is sufficiently thin and incoherent as to have a preselected low visible light reflectance,
• assembling into a composite film a plurality of the coated substrates such that the incoherent metal coatings face one another internally of the composite film and are separated and optically decoupled from one another and such that the metal coatings together provide a combined visible light blocking effect sufficient to provide a preselected low level of visible light transmittance through the composite film, and
• laminating the coated substrates to one another to provide a composite film having a combined visible light transmittance blocking effect equal approximately to the sum of the blocking effects of the incoherent metal coatings and low visible light reflectance substantially equal to the visible light reflectance of just one of the incoherent metal coatings, the visible light reflectance of each incoherent metal coating being such that the visible light reflectance of the composite film does not exceed about 20% when visible light transmittance is no greater than about 25%, does not exceed about 15% when visible light transmittance is no greater than about 35% and does not exceed about 12% when visible light. transmittance is up to about 50%.