1. Field of the Invention
This invention relates to a tinted, green colored soda-lime-silica glass having a low luminous transmittance that makes it desirable for use as a privacy glazing in vehicles, such as the side and rear windows in vans. As used herein, the term "green colored" is meant to include glasses that have a dominant wavelength of about 480 to 510 nanometers (nm) and may also be characterized as green blue, green yellow, or green gray in color. In addition, the glass should exhibit lower infrared and ultraviolet radiation transmittance when compared to typical green glasses used in automotive applications and be compatible with float glass manufacturing methods.
2. Technical Considerations and Prior Art
Various dark tinted, infrared and ultraviolet radiation absorbing glass compositions are known in the art. The primary colorant in typical dark tinted automotive privacy glasses is iron, which is usually present in both the Fe.sub.2 O.sub.3 and FeO forms. Some glasses use cobalt, selenium and, optionally, nickel in combination with iron to further control infrared and ultraviolet radiation and color, for example as disclosed in U.S. Pat. No. 4,873,206 to Jones; U.S. Pat. No. 5,278,108 to Cheng, et al.; U.S. Pat. No. 5,308,805 to Baker, et al.; U.S. Pat. No. 5,393,593 to Gulotta, et al.; U.S. Pat. No. 5,545,596 and U.S. Pat. No. 5,582,455 to Casariego, et al.; and European Patent application no. 0 705 800. Others also include chromium with this combination of colorants as disclosed in U.S. Pat. No. 4,104,076 to Pons; U.S. Pat. No. 4,339,541 to Dela Ruye; U.S. Pat. No. 5,023,210 to Krumwiede, et al; and U.S. Pat. No. 5,352,640 to Combes, et al.; European Patent application no. 0 536 049; French Patent 2,331,527 and Canadian Patent 2,148,954. Still, other glasses may include additional materials, such as disclosed in WO 96/00194, which teaches the inclusion of fluorine, zirconium, zinc, cerium, titanium and copper in the glass composition and requires that the sum of the alkaline earth oxides be less than 10 wt. % of the glass.
In producing infrared and ultraviolet radiation absorbing glasses, the relative amounts of iron and other additives must be closely monitored and controlled within an operating range to provide the desired color and spectral properties. It would be desirable to have a dark tinted green colored glass that may be used as a privacy glazing for vehicles to complement the green colored glasses typically used in automobiles and vans that exhibits superior solar performance properties and is compatible with commercial float glass manufacturing techniques.