Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
2001-11-01
2003-04-15
Sample, David (Department: 1755)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S064000, C501S071000
Reexamination Certificate
active
06548434
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a light-colored high-transmittance glass having a light blue, neutral gray or bronze tint and high transmittance, that is suitable as a building glass or interior glass, and to a method for manufacturing such a glass at low cost.
BACKGROUND ART
Recently, so-called crystal clear glass that is substantially colorless has been favored for exterior or interior use in buildings. But there are also cases in which light blue, gray or bronze glass is preferred in order to provide balance with the tints of the surrounding interior and exterior.
For this purpose, glass of light color and high transmittance is used, which is obtained by using raw materials of high purity, in which the iron content has been reduced considerably compared to that in regular soda-lime-based glass composition, or by adding small amounts of coloring agents to the glass.
For example, the edge colored (high transmittance) glass disclosed in JP H04-228450A is a soda-lime glass containing (in weight percent) less than 0.02% total iron oxide in terms of Fe
2
O
3
as a coloring agent, and the ratio of the ferrous iron (FeO) to the total iron oxide is at least 0.4, whereby a luminous transmittance (when measured with the CIE Standard illuminant C) of at least 87% is attained at a thickness of 5.66 mm, yielding a glass with slight color and high transmittance.
This glass composition is characterized in that, in order to attain the above properties, it has a small SO
3
content, a manufacturing method is used in which the melting includes separate liquefying and refining steps, and a batch material is used that does not contain limestone or dolomite, so as to lower the iron content in the glass.
In the edge-colored high transmittance glass disclosed in JP H04-228451A, trace amounts of Se and CoO are added to a glass composition containing about the same amount of iron oxide, so as to obtain a glass sheet with a dominant wavelength in transmission of 570 to 590 nm, in which the edge color (of the glass) harmonizes with wood colors.
On the other hand, methods have been proposed, in which the coloring of soda-lime glass containing a normal amount of iron oxide impurities is reduced by changing the basic composition of the glass.
For example, in accordance with the transparent glass composition for manufacturing window glass disclosed in JP H08-40742A, a soda-lime-silica glass in which the total amount of iron oxide in terms of ferric oxide accounts for 0.02 to 0.2 wt % includes as a basic composition, in weight percent, 69 to 75% SiO
2
, 0 to 3% Al
2
O, 0 to 5% B
2
O
2
, 2 to 10% CaO, less than 2% MgO, 9 to 17% Na
2
O, 0 to 8% K
2
O, arbitrary amounts of fluorine, zinc oxide, zirconium oxide, less than 4 wt % of barium oxide and not more than 10 wt % of the alkaline earth metal oxides. According to this composition, the FeO absorption band can be shifted to longer wavelengths, or the gradient of the FeO absorption band at the edge of the visible spectrum near infrared can be made steeper. This makes it possible to manufacture a window glass with superior infrared absorption and with less coloring than soda-lime-silica glasses having a normal basic composition.
However, in the edge-colored high transmittance glasses disclosed in JP H04-228450A and JP H04-228451A, it is a precondition that limestone and dolomite, which contain relatively large amounts of iron oxide impurities, cannot be used, so as to control the total iron oxide in terms of Fe
2
O
3
included as the coloring agent to less than 0.02 wt %. Therefore, it is necessary to use special raw materials such as calcium carbonate minerals or hydrated aluminum containing less iron oxide, which makes the resulting glass more expensive.
In the edge-colored high transmittance glass disclosed in JP H04-228450A, to obtain a desired pure bright azure edge color, it is necessary to make the ratio of ferrous iron (FeO) to the total iron oxide at least 0.4.
Therefore, it is desirable to apply a special manufacturing method, in which the method includes separate melting and refining steps, and to suppress the SO
3
content to a low level, which makes the resulting glass more expensive.
If, in the glasses disclosed in these publications, the raw materials for the glass contain Ni ions as impurities, then the Ni ions tend to bond with sulfide ions, forming NiS, which could cause spontaneous breakage. This is because the amount of Fe ions, which bond more easily with sulfide ions than Ni ions, is suppressed so as to attain a light tint.
In the transparent glass composition for manufacturing window glass disclosed in JP H08-40742A, the transmittance of soda-lime glass containing a normal amount of iron oxide is increased by changing the basic composition of the glass.
However, the effect of the method disclosed in this publication, that is, the degree that the FeO absorption is shifted to longer wavelengths, is insufficient for building or interior glass, for which a light tint is desired.
Moreover, in the composition disclosed in this publication, the amounts of MgO and MgO+CaO are less, and to compensate the adverse effect this has on the melting, the amount of Na
2
O is increased to more than the normal amount, so that this composition is not suitable for mass production due to the high liquidus temperature and the high costs.
The effect disclosed in this publication can be enhanced by adding such components as F or BaO, but adding these components is not desirable, as it increases the costs, and the volatility of the F shortens the furnace lifetime and leads to emission of hazardous substances into the atmosphere.
DISCLOSURE OF THE INVENTION
In view of the problems of the related art, it is an object of the present invention to provide a light-colored high-transmittance glass, in particular a glass having high transmittance and a tint of light blue, neutral gray or bronze that is suitable as building glass or interior glass, as well as a method for manufacturing such a glass at low cost.
According to one aspect of the present invention, a light-colored high-transmittance glass sheet containing silica as a main component is characterized in that
the glass sheet includes, as coloring components, in weight percent:
less than 0.06% total iron oxide (referred to as “T—Fe
2
O
3
” in the following) in terms of Fe
2
O
3
;
0.5 to 5 ppm CoO;
0 to 0.45% cerium oxide;
wherein the ratio of FeO in terms of Fe
2
O
3
to T—Fe
2
O
3
(referred to as “FeO ratio” in the following) is less than 40%; and
wherein the glass has a light blue tint with a dominant wavelength of 470 to 495 nm when measured with the CIE Standard illuminant C at a glass sheet thickness of 10 mm.
It is preferable that the light-colored high-transmittance glass sheet with light blue tint in accordance with the present invention includes, in weight percent, less than 2 ppm CoO and at least 0.02% T—Fe_O
3
.
It is preferable that the dominant wavelength of a light-colored high-transmittance glass sheet with light blue tint in accordance with the present invention is 480 to 490 nm.
According to another aspect of the present invention, a light-colored high-transmittance glass sheet containing silica as a main component is characterized in that the glass sheet includes, as coloring components, in weight percent:
at least 0.02% and less than 0.06% T—Fe
2
O
3
;
0.25 to 3 ppm Se;
0 to 3 ppm CoO;
0 to 0.45% cerium oxide;
wherein the FeO ratio is less than 40%; and
wherein the glass has a light neutral gray or bronze tint with a dominant wavelength of 560 to 585 nm when measured with the CIE Standard illuminant C at a glass sheet thickness of 10 mm.
It is preferable that the light-colored high-transmittance glass sheet with light neutral gray or bronze tint in accordance with the present invention includes, in weight percent, 0.5 to 2 ppm Se, and 0.5 to 1 ppm CoO.
It is preferable that the dominant wavelength of a light-colored high-transmittance glass sheet with light neutral gray and bronze tint in accordance with the present invention is 565 to 580 nm.
It is preferable that in th
Merchant & Gould P.C.
Nippon Sheet Glass Co. Ltd.
Sample David
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