Deep coloured green-to-blue shade soda-lime glass

Details Deep coloured green-to-blue shade soda-lime glass Deep coloured green-to-blue shade soda-lime glass

2001-03-26

2004-10-05

Group, Karl (Department: 1755)

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

C501S070000, C501S904000, C501S905000

Reexamination Certificate

active

06800575

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a deep-colored soda-lime glass of green-to-blue shade, composed of glass-forming principal constituents and of coloring agents.
The expression “soda-lime glass” is used here in a wide sense and relates to any glass which contains the following constituents (in percentages by weight):
Na
2
O
10 to 20%
CaO
 0 to 16%
SiO
2
60 to 75%
K
2
O
 0 to 10%
MgO
 0 to 10%
Al
2
O
3
0 to 5%
BaO
0 to 2%
BaO + CaO + MgO
10 to 20%
K
2
O + Na
2
O
 10 to 20%.
This type of glass is very widely used in the field of glazing for buildings or automobiles, for example. It is usually manufactured in the form of a ribbon by the drawing or float process. Such a ribbon can be cut into sheets which can then be bent or can undergo a treatment to improve the mechanical properties, for example a thermal toughening step.
When referring to the optical properties of a glass sheet, it is generally necessary to relate these properties to a standard illuminant. In the present description, two standard illuminants are used, namely illuminant C and illuminant A defined by the Commission Internationale de l'Eclairage (C.I.E.). Illuminant C represents average daylight having a color temperature of 6700 K. This illuminant is especially useful for evaluating the optical properties of glazing intended for buildings. Illuminant A represents the radiation of a Planck radiator with a temperature of about 2856 K. This illuminant describes the light emitted by car headlights and is essentially intended to evaluate the optical properties of windows intended for automobiles. The Commission Internationale de l'Eclairage has also published a document entitled “Colorimétrie, Recommandations Officielles de la C.I.E. [Colorimetry and Official Recommendations of the C.I.E.]” (May 1970) which describes a theory in which the calorimetric coordinates for light of each wavelength of the visible spectrum are defined so as to be able to be represented on a diagram having orthogonal axes x and y, called the C.I.E. trichromatic diagram. This trichromatic diagram shows the location representative of light of each wavelength (expressed in nanometers) of the visible spectrum. This location is called the “spectrum locus” and light whose coordinates lie on this spectrum locus is said to have 100% excitation purity for the appropriate wavelength. The spectrum locus is closed by a line called the purple boundary which connects the points of the spectrum locus whose coordinates correspond to wavelengths of 380 nm (violet) and 780 nm (red). The area lying between the spectrum locus and the purple boundary is that available for the trichromatic coordinates of any visible light. The coordinates of the light emitted by illuminant C, for example, correspond to x=0.3101 and y=0.3162.This point C is regarded as representing white light and consequently has an excitation purity equal to zero for any wavelength. Lines may be drawn from the point C to the spectrum locus at any desired wavelength and any point lying on these lines may be defined not only by its x and y coordinates but also as a function of the wavelength corresponding to the line on which it lies and on its distance from the point C relative to the total length of the wavelength line. Consequently, the color of the light transmitted by a colored glass sheet may be described by its dominant wavelength and its excitation purity expressed as a percentage.
In fact, the C.I.E. coordinates of light transmitted by a colored glass sheet will depend not only on the composition of the glass but also on its thickness. In the present description, and in the claims, all the values of the excitation purity P, of the dominant wavelength &lgr;
D
of the transmitted light, and of the light transmission factor of the glass (TLC5) are calculated from the spectral specific internal transmissions (SIT
&lgr;
) of a glass sheet 5 mm in thickness. The spectral specific internal transmission of a glass sheet is governed solely by the absorption of the glass and can be expressed by the Beer-Lambert law:
SIT
&lgr;
=e
−E.A&lgr;
where A
&lgr;
is the absorption coefficient (in cm
−1
) of the glass at the wavelength in question and E is the thickness (in cm) of the glass. To a first approximation, SIT
&lgr;
may also be represented by the formula:
(I
3&lgr;
+R
2&lgr;
)/(I
1&lgr;
−R
1&lgr;
)
where I
1&lgr;
is the intensity of the visible light incident on a first face of the glass sheet, R
1&lgr;
is the intensity of the visible light reflected by this face, I
3&lgr;
is the intensity of the visible light transmitted from the second face of the glass sheet and R
2&lgr;
is the intensity of the visible light reflected by this second face toward the interior of the sheet.
In the description which follows and in the claims, the following are also used:
for illuminant A, the total light transmission (TLA) measured for a thickness of 4 mm (TLA4). This total transmission is the result of the integration between the 380 and 780 nm wavelengths of the expression: &Sgr;T
&lgr;
.E
&lgr;
.S
&lgr;
/&Sgr; E
&lgr;
.S
&lgr;
in which T
&lgr;
is the transmission at the wavelength &lgr;, E
&lgr;
is the spectral distribution of illuminant A and S
&lgr;
is the sensitivity of the normal human eye as a function of the wavelength &lgr;;
the total energy transmission (TE) measured for a thickness of 4 mm (TE4). This total transmission is the result of the integration between the 300 and 2150 nm wavelengths of the expression: &Sgr;T
&lgr;
.E
&lgr;
/&Sgr;E
&lgr;
in which E
&lgr;
is the spectral energy distribution of the sun at 30° above the horizon;
the selectivity (SE) measured as the ratio of the total light transmission for illuminant A to the total energy transmission (TLA/TE);
the total transmission in the ultraviolet, measured for a thickness of 4 mm (TUV4). This total transmission is the result of the integration between 280 and 380 nm of the expression: &Sgr;T
&lgr;
.U
&lgr;
/&Sgr;U
&lgr;
in which U
&lgr;
is the spectral distribution of the ultraviolet radiation that has passed through the atmosphere, defined in the DIN 67507 standard.
SUMMARY OF THE INVENTION
The present invention relates in particular to dark-colored glasses of green-to-blue shade. These glasses are generally chosen for their protective properties with respect to solar radiation and their use in buildings is known. They are used in architecture and for partially glazing certain vehicles or railroad compartments.
The present invention relates to a highly selective dark glass of green-to-blue shade which is especially appropriate for use in the make-up of car windows and in particular as rear side windows and as rear window. This is because it is important in the automobile field for the windows of vehicles to provide sufficient light transmission while having as low as possible an energy transmission so as to prevent any overheating of the passenger space in sunny weather. Such glazing may be laminated and may then comprise one or more sheets of glass according to the invention.
The invention provides a colored soda-lime glass composed of glass-forming principal constituents and of coloring agents, which contains from 0.40 to 0.52% by weight of FeO and has, under illuminant A and for a glass thickness of 4 mm, a light transmission (TLA4) of less than 70%, a selectivity (SE4) of greater than 1.65 and an ultraviolet radiation transmission (TUV4) of less than 8%.
The combination of these optical properties is particularly advantageous in that it offers, while ensuring light transmission through the glass sufficient for the uses for which it is intended, a high selectivity value and a low transmission value in the ultraviolet. This makes it possible to avoid both the internal heating of the volumes bounded by windows according to the invention, thereby saving energy when air-conditioning systems are used in said volumes, and the esthetically unattractive discoloration of objects placed inside these volumes, du

Affiliated with

Also associated with

Rating

Deep coloured green-to-blue shade soda-lime glass does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Deep coloured green-to-blue shade soda-lime glass, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Deep coloured green-to-blue shade soda-lime glass will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3271677