Glass manufacturing – Processes – With chemically reactive treatment of glass preform
Reexamination Certificate
2001-02-26
2003-09-02
Colaianni, Michael (Department: 1731)
Glass manufacturing
Processes
With chemically reactive treatment of glass preform
C065S033200, C065S111000, C501S069000, C501S070000, C501S071000, C501S064000, C501S904000
Reexamination Certificate
active
06612133
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for shifting the absorption peak wavelength of an infrared radiation absorbing glass. More particularly, the invention relates to a method for shifting the absorption peak wavelength in the wavelength range 900-1200 nm of an infrared radiation absorbing glass from less than 1100 nm to 1100 nm or longer without changing a visible light transmission of the glass.
BACKGROUND OF THE INVENTION
From the standpoint in reduction of the load of air conditioning in automobiles, a glass having infrared absorbing power has recently been proposed as window panes of automobiles.
For example, greenish blue-tinted glass having a relatively high Fe
2
O
3
content to exhibit improved infrared absorbing power has been developed for use in automobiles. A typical example of such a greenish blue-tinted infrared absorbing glass has a composition comprising, in % by weight: 71% SiO
2
, 1.5% Al
2
O
3
, 4% MgO, 8.6 t % CaO, 13.5% Na
2
O, 0.7% K
2
O, 0.55% total iron oxides in terms of Fe
2
O
3
, and 0.17 FeO in terms of Fe
2
O
3
. The glass having this composition with a thickness of 4 mm has a visible light transmission of 78% as measured with the CIE standard illuminant A and a solar energy transmission of 54%.
Glass having a bronze tint, on the other hand, contains Fe
2
O
3
in an amount smaller than that in the greenish blue-tinted glass so as to have fair infrared absorbing power while maintaining visible light transmission. A typical example of infrared radiation absorbing glass having a bronze tint has a composition of, in % by weight: 72% of SiO
2
, 1.5% Al
2
O
3
, 4% MgO, 8% CaO, 13.5% Na
2
O, 0.7% K
2
O, 0.24% total iron oxides in terms of Fe
2
O
3
, 0.054% of FeO in terms of Fe
2
O
3
, 0.001% CoO, and 0.001 wt % of Se. The glass having this composition with a thickness of 4 mm has a visible light transmission of 78% as measured with the CIE standard illuminant A and a solar energy transmission of 70%.
In the above-described conventional infrared radiation absorbing glass, its infrared absorbing power is imparted by Fe
2+
(FeO). However, if the FeO concentration in a greenish blue-tinted glass is increased in order to obtain higher infrared absorbing power, the absorption of FeO in the visible region increases, and as a result, there is particularly a problem that the visible light transmission required of windowpanes of vehicles cannot be obtained. In a glass which forms a color utilizing absorption of Se in the visible region, such as bronze type glass, there is the problem that greater restriction is imposed on the FeO concentration, and a high infrared absorbing power is not obtained.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described problems involved in the prior art.
An object of the present invention is to provide a method for producing a glass having a high infrared absorbing power and a high visible light transmission.
According to one embodiment of the present invention, there is provided a method for shifting the absorption peak wavelength in the wavelength range 900-1600 nm of an infrared radiation absorbing glass from less than 1100 nm to 1100 nm or longer without substantially changing the tint of the glass, comprising the step of irradiating the glass which comprises, in % by weight:
65 to 80% SiO
2
,
0 to 5% Al
2
O
3
,
0 to 10% MgO,
5 to 15% CaO,
10 to 18% Na
2
O,
0 to 5% K
2
O,
5 to 15% MgO+CaO,
10 to 20% Na
2
O+K
2
O, and
0 to 5% B
2
O
3
;
0.02% or more total iron oxide (T-Fe
2
O
3
) in terms of Fe
2
O
3
,
0 to 2.0% CeO
2
,
0 to 1.0% TiO
2
,
0 to 0.005% CoO, and
0 to 0.005% Se,
with ultraviolet light of 400 nm or shorter at an energy density of 1.0×10
6
J/m
2
/hr pr more to increase the content of FeO in the irradiated glass by reducing Fe(III) to Fe(II), the ultraviolet light irradiated glass thereby comprising 0.02 wt. % or more FeO in terms of Fe
2
O
3
.
Preferably, the infrared radiation absorbing glass comprises, in % by weight:
0.05% or more T-Fe
2
O
3
in terms of Fe
2
O
3
.
Preferably, the infrared radiation absorbing glass comprises, in % by weight:
0.05 to 1.0% T-Fe
2
O
3
in terms of Fe
2
O
3
, and
0.02 to 0.5% FeO in terms of Fe
2
O
3
.
Preferably, the infrared radiation absorbing glass comprises, in % by weight:
0.02 to 0.6% T-Fe
2
O
3
in terms of Fe
2
O
3
;
0.02 to 0.3 FeO in terms of Fe
2
O
3
;
0.2 to 2.0% CeO
2
; and
0.0005 to 0.005% Se,
wherein the relationship between the transmission at 1,050 nm (T
1050
) and the transmission at 1,200 nm (T
1200
) is T
1050
>T
1200
.
According to another embodiment of the present invention, there is provided a method for shifting the absorption peak wavelength in the wavelength range 900-1600 nm of an infrared radiation absorbing glass from less than 1100 nm to 1100 nm or longer without substantially changing the tint of the glass, comprising the step of irradiating the glass which comprises, in % by weight:
65 to 80% SiO
2
,
0 to 5% Al
2
O
3
,
0 to 10% MgO,
5 to 15% CaO,
10 to 18% Na
2
O,
0 to 5% K
2
O,
5 to 15% MgO+CaO,
10 to 20% Na
2
O+K
20
, and
0 to 5% B
2
O
3
;
0.05% or more total iron oxide (T-Fe
2
O
3
) in terms of Fe
2
O
3
,
0.5 to 3% total of one or more components selected from CeO
2
, Sb
2
O
3
, As
2
O
3
, SnO and Cu
2
O,
0 to 1.0% TiO
2
,
0 to 0.005% CoO, and
0 to 0.005% Se,
with ultraviolet light of 400 nm or shorter at an energy density of 1.0×10
6
J/m
2
/hr or more to increase the content of FeO in the irradiated glass by reducing Fe(III) to Fe(II), the ultraviolet light irradiated glass thereby comprising 0.02 wt. % or more FeO in terms of Fe
2
O
3
.
The infrared radiation absorbing glasses according to the present invention preferably have a visible light transmission of 70% or more as measured with the CIE standard illuminant A and a total solar energy transmission of less than 70% as measured in the wavelength region of from 300 to 2,100 nm, when the thickness of the glass is 4 mm.
It is also preferred that the infrared radiation absorbing glasses according to the present invention have a dominant wavelength of 574 to 580 nm as measured with the CIE standard illuminant C and a total sunlight UV transmission of less than 12% as measured in a wavelength region of 297.5 to 377.5 nm according to ISO 9050, when the thickness of the glasses is 4 mm.
It is further preferred that the infrared radiation absorbing glasses according to the present invention have an ultraviolet transmission of less than 34% at a wavelength of 370 nm, when the thickness of the glasses is 4 mm.
DETAILED DESCRIPTION OF THE INVENTION
The reasons for limitation of the glass compositions of the infrared radiation absorbing glass used in the method according to the present invention are explained below. Hereinafter, unless otherwise indicated, all the percents are by weight.
Iron oxide is present in glass in the form of Fe
2
O
3
(Fe
3+
) and FeO (Fe
2+
). Fe
2
O
3
is a component serving to increase an infrared absorbing power, while FeO is a component serving to increase an ultraviolet absorbing power together with CeO
2
and TiO
2
.
In general soda lime silica glass composition used as window glass of buildings and vehicles, Fe
2+
shows its absorption peak at about 1,050 nm and also has an absorption in the visible light region of from 400 to 780 nm. Therefore, if the FeO content is increased, the infrared absorbing power is increased, but a visible light transmission is simultaneously decreased. The gist of the present invention resides in shifting the absorption peak wavelength of Fe
2+
to a longer wavelength side to minimize the decrease in visible light transmission, thereby achieving both a high infrared absorbing power and a high visible light transmission at a time.
The absorption peak wavelength of Fe
2+
is shifted to the longer wavelength side by irradiating the glass with ultraviolet light at around room temperature.
The inventors of the present invention have found that ultraviolet irradiation of appropriate glass containing Fe
2
O
3
under appropri
Nagashima Yukihito
Sakaguchi Koichi
Seto Hiromitsu
Colaianni Michael
Nippon Sheet Glass Co. Ltd.
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