Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
2001-06-21
2003-02-25
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C501S070000, C501S071000, C501S904000, C501S905000
Reexamination Certificate
active
06524713
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to an ultraviolet/infrared absorbent low transmittance glass. More particularly, it relates to an ultraviolet/infrared absorbent low transmittance glass which has an almost neutral color such as greenish gray shade and which has low visible light transmittance, low solar energy transmittance, and low ultraviolet transmittance, so that it is useful for windows of vehicles or buildings particularly for a privacy protecting glass in a rear window of a vehicle.
Recently, a variety of glasses with ultraviolet/infrared absorptivity to be used as a vehicle windshield have been proposed with the view of preventing degradation of luxurious interior materials and reducing cooling load of the vehicle. In view of privacy protection, glass with relatively low visible light transmittance is preferably used for a rear window glass of a vehicle. Such kinds of glass include the followings.
For example, a dark gray colored infrared absorbent glass disclosed in Japanese Patent H7-29813B consists of soda-lime-silica glass including colorants consisting of 1.00 to 1.7 weight percent Fe
2
O
3
(total iron), at least 0.27 weight percent FeO, 0.002 to 0.005 weight percent Se, and 0.01 to 0.02 weight percent CoO. The glass exhibits luminous transmittance less than 32 percent and total solar infrared transmittance less than 15 percent at 3.9 mm thickness.
A dark gray colored glass disclosed in Japanese Patent H8-157232A consists of soda-lime-silica glass including colorants consisting of 0.8 to 1.4 weight percent Fe
2
O
3
(total iron), less than 0.21 weight percent FeO, 0.05 to 1.0 weight percent TiO
2
, 0.02 to 0.05 weight percent CoO, and 0.0005 to 0.015 weight percent Se.
A neutral gray colored glass disclosed in claim 25 of U.S. Pat. No. 5,393,593 consists of soda-lime-silica glass including colorants consisting of 1.00 to 2.2 weight percent Fe
2
O
3
(total iron), at least 0.20 weight percent FeO, 0.0005 to 0.005 weight percent Se, and 0.010 to 0.030 weight percent CoO. The glass exhibits luminous transmittance less than 35 percent and total solar infrared transmittance less than 20 percent at 3.9 mm thickness.
A glass disclosed in PCT (Japanese phase) H7-508971 consists of soda-lime-silica glass including colorants consisting of 1.3 to 2.0 weight percent of Fe
2
O
3
(total iron), about 0.01 to 0.05 weight percent of NiO, about 0.02 to 0.04 weight percent of Co
3
O
4
, about 0.0002 to 0.003 weight percent of Se and having a ferrous iron value of 18 to 30 weight percent and less than 0.53 of a light and shade coefficient.
In both the dark gray colored infrared absorbent glass disclosed in Japanese Patent H7-29813B and the neutral gray colored glass disclosed in U.S. Pat. No. 5,393,593, a great quantity of Se is used for providing a desirable color. Such a great quantity of Se is unpreferable for the environment because Se has toxicity and is easy to vaporize. The above dark gray glass disclosed in Japanese Patent H8-157232A including 0.05 to 1.0 weight percent TiO
2
as an essential component is unpreferable because TiO
2
is expensive to increase the batch cost.
The aforementioned glass includes selenium in high concentration to provide optical properties, without essentially including nickel.
The glass disclosed in PCT (Japanese phase) H7-508971 is prepared from standard soda-lime-silica glass to which iron oxide, cobalt oxide, nickel oxide and selenium are added in a specific ratio. However, the glass composition disclosed therein has a great content of selenium and small amount of nickel oxide.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ultraviolet/infrared absorbent low transmittance glass which has an almost neutral color such as greenish gray and which has low visible light transmittance, low solar energy transmittance and low ultraviolet transmittance so that it is useful for a window of a vehicle or a building particularly for a privacy protecting glass of a rear window of a vehicle.
The ultraviolet/infrared absorbent low transmittance glass of the present invention consists of a base glass, that is, the major constituents comprising:
65 to 80 wt. % SiO
2
;
0 to 5 wt. % Al
2
O
3
;
0 to 10 wt. % MgO;
5 to 15 wt. % CaO wherein a total amount of MgO and CaO is between 5 and 15 wt. %;
10 to 18 wt. % Na
2
O;
0 to 5 wt. % K
2
O wherein a total amount of Na
2
O and K
2
O is between 10 and 20 wt. %; and
0 to 5 wt. % B
2
O
3
, and a colorant including:
1.25 to 1.5 wt. % total iron oxide (T—Fe
2
O
3
) expressed as Fe
2
O
3
;
0.01 to 0.019 wt. % CoO;
more than 0.0008 wt. % and equal to or less than 0.003 wt. % Se; and
0.055 to 0.1 wt. % NiO.
When it is measured by using C.I.E. standard illuminant “A”, the glass with a thickness between 2 and 5 mm has a visible light transmittance (YA) in a range from 10 to 25%, a solar energy transmittance (TG) in a range from 5 to 20% and an ultraviolet transmittance (Tuv) of less than 15%.
In the present invention, the desired color shade can be obtained with a smaller amount of Se, which is desired to be decreased in content because of its toxicity and volatility, and with a greater amount of NiO than the amount conventionally required. It has been understood conventionally that adding nickel to glass is unpreferable because of formation of nickel sulfide stones. However, the formation of nickel sulfide stones is more strongly dependent on the size of nickel grains added in the batch or redox of the glass than the concentration of NiO. When the concentration of NiO in the glass is too high, there is a possibility that NiO coagulates to form the nickel sulfide stones. However, when NiO is in a range defined by this invention, the desired color can be obtained without producing the nickel sulfide stones.
PREFERRED EMBODIMENTS
The description will be made as regard to an ultraviolet/infrared absorbent low transmittance glass composition. It should be noted that components will be represented with percentage by weight.
SiO
2
(silica) is a principal component for forming skeleton of glass. Less than 65% SiO
2
lowers the durability of the glass and more than 80% SiO
2
raises the melting temperature of the glass so high.
Al
2
O
3
is a component for improving the durability of the glass. More than 5% Al
2
O
3
raises the melting temperature of the glass so high. The preferable range of Al
2
O
3
is between 0.1% and 2%.
MgO and CaO improve the durability of the glass and adjust a devitrification temperature and viscosity of the glass during molding. More than 10% MgO raises the devitrification temperature. Less than 5% or more than 15% CaO raises the devitrification temperature of the glass. The durability of the glass is lowered when the total amount of MgO and CaO is less than 5%, while the devitrification temperature is increased when the total exceeds 15%.
Na
2
O and K
2
O prompt the glass to melt. The efficiency of promotion of melting becomes poor when Na
2
O is less than 10% or the total of Na
2
O and K
2
O is less than 10%, while the durability of the glass is lowered when Na
2
O exceeds 18% or the total of Na
2
O and K
2
O exceeds 20%. K
2
O is preferable not to exceed 5% because of its expensive cost.
B
2
O
3
is a component for improving the durability of the glass, prompting to melt, and yet enhancing the ultraviolet absorption. B
2
O
3
should be less than 5%, since difficulties during molding are caused due to the vaporization of B
2
O
3
when B
2
O
3
exceeds 5%.
Iron oxide is present in the form of Fe
2
O
3
and the form of FeO in the glass. Fe
2
O
3
is a component for improving the ultraviolet absorptivity and FeO is a component for improving the heat rays absorptivity.
When the total amount of iron oxide (T—Fe
2
O
3
) expressed as Fe
2
O
3
is less than 1.25%, the efficiency of ultraviolet and infrared absorptivity becomes small so as not to provide desired optical properties. On the other hand, when T—Fe
2
O
3
exceeds 1.5%, there is an unpreferable possibility that the temperature around a crown of a glass melting fu
Nagashima Yukihito
Seto Hiromitsu
Yoshii Shigekazu
Jones Deborah
Kanesaka & Takeuchi
McNeil Jennifer
Nippon Sheet Glass Co. Ltd.
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