Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1998-10-20
2001-03-27
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C501S056000, C501S070000, C501S071000, C501S904000
Reexamination Certificate
active
06207284
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to silicate based glass compositions with nitrogen compounds included in the composition as performance modifiers and the methods of making the composition and glass articles formed therefrom. More particularly, the present invention is directed toward the use of metal nitrides in silicate based glasses for the improvement of spectral properties such as the absorption of infrared energy.
2. Summary of Related Art
Performance modifiers and colorants are often added to base glass compositions to impart specific color and energy transmittance properties in the finished glass. The absorption of energy at specific wavelengths is often desirable to enable various uses for the glass compositions. Additionally, certain colors are preferred for various glasses for aesthetic reasons. There are limitations within specific glass compositions that must be balanced or optimized when attempting to achieve desired color and energy transmittance properties. For example, certain ingredients may improve the absorption of near infrared energy while imparting an undesirable color or reducing the light transmittance. Thus, the optimization of a specific color or energy transmittance property often negatively impacts other desirable transmittance properties.
The present invention utilizes metal nitrides in silicate based glass compositions to improve either color or energy transmittance properties of the finished glass. The use of a metal nitride results in the unexpected improvement of color and energy transmittance properties when added to conventional silicate based glass compositions. Different metal nitrides will impact the silicate based glass in different manners. Thus, the selection of a specific metal nitride is dependent upon the silicate based glass composition, the additional colorants in the composition, and the desired color or energy transmittance properties. For example, the inclusion of a metal nitride in a soda-lime-silica glass, containing an iron colorant, exhibits a reduction in the transmittance of near infrared energy over similar non-nitride containing compositions, without adversely affecting the visible light transmittance.
Silicate based glass batch compositions recognized within the art may include nitrogen compounds in the form of nitrates. Sodium nitrate, or niter, is generally utilized to improve the retention of the colorant selenium in the finished glass. The nitrate does not improve the spectral performance of the finished glass.
Also, infrared absorbing, or heat reducing, silicate glasses are known within the art. In general, infrared absorbing silicate glasses involve the addition of specific colorants that impact the color and energy transmittance properties of the glass.
For example, U.S. Pat. No. 4,792,536 discloses a process for producing an infrared energy absorbing glass, containing a low total iron concentration which is highly reduced to FeO. It is further disclosed that the infrared energy absorption can be increased by including greater amounts of total iron in the glass composition, but states that the visible light transmittance would thereby be reduced below levels considered adequate for automotive glazings. The patent teaches that the iron must be at least 35% reduced to FeO.
Another example of an infrared absorbing silicate glass is found in U.S. Pat. No. 5,077,133. The patent discloses a green colored infrared and ultraviolet absorbing silicate glass which includes an amount of ceric oxide, or alternatively ceric oxide and titanium dioxide, and a high concentration of moderately reduced iron. The glass composition exhibits a visible light transmittance of at least 70% and a total solar energy transmittance of less than 46%. Although the glass composition exhibits a low solar energy transmittance, it is desirable to further reduce the total solar energy transmittance, through the absorption of near infrared energy, while maintaining the high visible light transmittance.
It would be an advantage to provide a performance modifier for use in a silicate glass composition that significantly improves color and energy transmittance values without adversely impacting other transmittance properties in the finished glass.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a nitrogen compound suitable for use in a silicate batch glass composition as a performance modifier to impart improved color and energy transmittance properties over conventional silicate glasses. The nitrogen compound is generally a metal nitride which is added to the batch glass composition prior to melting. The present invention also includes a process for melting the glass batch composition and the articles produced therefrom.
The preferred metal nitrides suitable for use in the present invention are selected from the group consisting of aluminum nitride, barium nitride, boron nitride, calcium nitride, chromium nitride, copper nitride, gallium nitride, germanium nitride, hafnium nitride, iron nitride, lithium nitride, magnesium nitride, neodymium nitride, potassium nitride, silicon nitride, sodium nitride, strontium nitride, tantalum nitride, titanium nitride, tungsten nitride, vanadium nitride, zinc nitride, and zirconium nitride. Each of the metal nitrides may impart different characteristics to the finished silicate glass. Therefore, the selection of the metal nitride is dependant upon the desired color and energy transmittance properties of the finished glass as well as the base glass composition and other colorants included in the base glass composition. Additionally, several of the noted performance modifiers may be utilized in combination in the glass batch composition.
The metal nitrides of the present invention are added to the batch glass composition prior to the admixing, heating, and melting of the batch. The metal nitrides are included in the batch glass composition at concentrations from about 0.05% to about 4% by weight. The most preferred compounds included in glass compositions are aluminum nitride, boron nitride, iron nitride, magnesium nitride, silicon nitride, titanium nitride, and zinc nitride.
It is an object of the present invention to provide a performance modifier for use in silicate batch glass compositions that improves color or energy transmittance properties of the finished glass composition. The metal nitrides of the present invention are suitable performance modifiers that are capable of improving the color and energy transmittance properties of the glass over conventional silicate glasses.
It is also an object of the present invention to utilize a metal nitride in a glass composition to improve specific color or energy absorbance properties without adversely affecting other properties, such as the visible light transmittance.
REFERENCES:
patent: 1961603 (1934-06-01), Berger
patent: 3944352 (1976-03-01), Morgan
patent: 4035548 (1977-07-01), Chang et al.
patent: 4713359 (1987-12-01), Lubelski et al.
patent: 4792536 (1988-12-01), Pecoraro et al.
patent: 5077133 (1991-12-01), Cheng
patent: 5508236 (1996-04-01), Chiang et al.
patent: 4042224134A (1992-08-01), None
Higby Paige L.
Varanasi Srikanth
Young Gwendolyn A.
Jones Deborah
Libben-Owens-Ford Co.
Marshall & Melhorn, L.L.C.
Stein Stephen
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