Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Patent
1997-07-23
2000-06-06
Marcheschi, Michael
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
501904, 501905, C03C 3087, C03C 402
Patent
active
060718404
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a dark green colored glass having low visible light transmittance, low ultraviolet ray transmittance and low solar radiation transmittance, which is suitable for a sunroof or rear window glass of an automobile.
BACKGROUND ART
In recent years, along with a trend for high quality of glasses for vehicles, an optimum glass is required for each application site. For example, for a rear window glass of an automobile, a glass which has, in a thickness of 5 mm, a visible light transmittance (illuminant A) of from 25 to 40% and a solar radiation transmittance of from 10 to 30% is used, and for a sunroof, a glass which has a visible light transmittance (illuminant A) of at most 30% and a solar radiation transmittance of at most 20%, is frequently used. The properties commonly required for these glasses are such that they have low visible light transmittance and low solar radiation transmittance, and preferably low ultraviolet ray transmittance, particularly low light transmittance at a wavelength of 370 nm, is desired.
Meantime, in recent years, a green colored glass which has high visible light transmittance and which at the same time has low solar radiation transmittance and low ultraviolet ray transmittance, has been used for a windshield, and to secure harmony in the color of the vehicle, it is preferred that the rear window glass or the like also has a green type color.
Most of well known heat absorbing glasses having relatively low visible light transmittance contain nickel. However, nickel is not desirable, since it sometimes forms nickel sulfide in glass. Nickel sulfide is almost indistinguishable by naked eyes and presents no adverse effects to glass in a usual state. However, if nickel sulfide is present in glass after toughening treatment by quenching, the volume will expand due to crystal transformation at room temperature, and a thermal stress sufficient to break the glass may sometimes be formed.
JP-A-2-64038 (which corresponds to U.S. Pat. No. 4,873,206) or JP-A-4-275943 (which corresponds to EP-A-482253) discloses a glass which contains no nickel and which has a visible light transmittance of lower than 40%. However, the one disclosed in JP-A-2-64038 has a problem that the solar radiation transmittance tends to be high, since its infrared ray shielding ability is not so high. The one disclosed in JP-A-4-275943 has a large content of iron and thus has a practical problem in its production such that it takes time to change the base material.
Further, JP-A-6-247740 discloses a glass having visible light transmittance reduced by replacing a NiO component by a chromium component. However, this relates to a glass having a relatively long dominant wavelength and low excitation purity by an addition of selenium in an amount of at least 15 ppm, and it is intended to obtain a neutral (gray) color i.e. not a green color.
Still further, U.S. Pat. No. 5,411,922 discloses a glass having low visible light transmittance which contains at least 10 ppm of selenium as an essential component in addition to iron, cobalt and titanium. In a glass melting furnace, Se is most volatile and an expensive material, and among Se put into the furnace, at least 90% will be discharged out of the furnace together with a combustion exhaust gas and will be captured, for example, by an absorbing liquid in an absorption tower for flue gas desulfurization. The major portion of Se in the liquid will be recovered and utilized as a raw material, but in order to carry out treatment to sufficiently reduce Se ions remaining in the liquid after the recovery, large amounts of investment for installation and running costs will be required. In Japan, a regulation relating to Se concentration in an industrial waste water is expected to come into force from 1997.
Further, Examples 11 to 13 in U.S. Pat. No. 5,411,922 describe an influence of an addition of titanium in a certain specific glass containing iron, cobalt and selenium as essential components. According to the description, as the titanium
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patent: 4106076 (1978-08-01), Pons
patent: 5318931 (1994-06-01), Nakaguchi et al.
patent: 5411922 (1995-05-01), Jones
patent: 5545596 (1996-08-01), Alvarez Casariego et al.
patent: 5650365 (1997-07-01), Higby et al.
patent: 5763342 (1998-06-01), Mita et al.
Kijima Takashi
Sasage Mizuki
Tanii Shiro
Asahi Glass Company Ltd.
Marcheschi Michael
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