Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.


  1. Advanced Patent Search
Publication numberUSRE34760 E
Publication typeGrant
Application numberUS 08/173,841
Publication dateOct 18, 1994
Filing dateDec 27, 1993
Priority dateDec 12, 1990
Fee statusPaid
Also published asCA2052990A1, EP0490494A2, EP0490494A3, US5070048
Publication number08173841, 173841, US RE34760 E, US RE34760E, US-E-RE34760, USRE34760 E, USRE34760E
InventorsEdward N. Boulos, Mark F. Best, Roman Surowiec
Original AssigneeFord Motor Company
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Blue glass compositions
US RE34760 E
A blue glass composition comprises conventional soda-lime-silica glass ingredients and specific amounts of Fe2 O3, Co3 O4, NiO, and optionally Se, resulting in an Illuminant C transmittance of 54%±3% at one quarter inch thickness, a dominant wavelength of 482 nm±1 nm, and a color purity of 13%±1%.
Previous page
Next page
We claim:
1. A blue-colored glass having an Illuminant C transmittance of 54%±3% at a glass thickness of one quarter inch, a dominant wavelength of 482 nm±1 nm, and a color purity of 13%±1%, consisting essentially of:
A. 68% to 75% by weight SiO2 ;
B. up to 5% by weight Al2 O3 ;
C. 5% to 15% by weight CaO;
D. up to 10% by weight MgO, wherein CaO+MgO is 6% to 15% by weight;
E. 10% to 18% by weight Na2 O;
F. up to 5% by weight K2 O, wherein Na2 O+K2 O is 10% to 20% by weight; and
G. colorant selected from the group consisting of:
i. 0.290% by weight Fe2 O3, 0.0055% by weight .[.Co3 O4 .]. .Iadd.Co.Iaddend., and 0.0072% by weight .[.NiO.]. .Iadd.Ni.Iaddend.; and
ii. 0.430% by weight Fe2 O3, 0.0054% by weight .[.Co3 O4 .]. .Iadd.Co.Iaddend., 0.0035% by weight .[.NiO.]. .Iadd.Ni.Iaddend., and 0.00015% by weight senelium.
2. A glazing for automotive or architectural use prepared from the blue-colored glass of claim 1.

This invention relates generally to blue glass compositions, and more particularly, to blue glass compositions having an Illuminant C transmittance of 54%±3%, a dominant wavelength of 482 nm±1 nm, and a color purity of 13%±1%, at a glass thickness of one quarter inch.


Glass compositions having various colors are used, for example, by architects in glazing buildings. Normally, the color selected by the architect serves several functions. A first function of the color is to make the glass aesthetically pleasing when viewed from the exterior of the building. Aesthetics will determine the acceptability of a desired particular glass color and, in part, the desired intensity of the color. A second function is to reduce the amount of heat absorbed from the exterior of the building to the interior of the building, so that the air conditioning load in the building is reduced. Generally, more color added to glass results in greater heat absorption. In addition, while color may readily be added to glass to serve these functions, that glass when colored still must have an appropriate visible light transmittance value.

Those skilled in the art of formulating glass compositions are familiar with various suitable glass colorants. Thus, a small amount of cobalt oxide is known to produce a cold blue color widely considered unattractive and undesirable for architectural and certain other uses. A high concentration of nickel is known to produce black glass. Selenium can produce pink or red, and ferrous oxide can produce green glass and contribute to advantageous solar load control properties. The glass color produced by a mixture of colorants will vary with both the amount and relative proportions used. As noted above, varying the choice and amount of colorants also affects the light transmittance value of the glass. As discussed further below, however, the effect on glass color and transmittance of mixing multiple colorants and/or varying the amount of relative proportions of the colorants is not reliably predictable.

In the following discussion, certain terms well known to those skilled of the art are used to describe color in glass. One method of specifying color is by the use of dominant wavelength and color purity. These are derived from tristimulus coefficients that have been defined by the CIE (Commission Internationale de l'Eclairage). Numerical values for a given glass color can be determined by calculating the trichromatic values X, Y, and Z. From the tristimulus values for that glass color, trichromatic coefficients x, y and z are then calculated and plotted on a chromaticity diagram. The 1931 Standard Observer response diagram defines the amount of each of three primary colors (x is amber, y is green, and z is blue) required to produce energy of each wavelength from 3,800 Angstroms to 7,500 Angstroms, wherein the green curve is the standard luminosity curve for the human eye. The dominant wavelength and color purity is then numerically determined with respect to the coordinates of Illuminant C, an established light source.

Thus, a glass color may be specified either by its trichromatic coefficients x and y or by its dominant wavelength and purity values. The lower the color purity, the closer the color is to the Illuminant C standard and the closer it is to being a neutral color.

An understanding of the foregoing terms and definitions thereof may be had by reforming to the Handbook of Colorimetry prepared by the staff of the Color Measurement Laboratory, Massachusetts Institute of Technology. This book was printed in 1936 by the Technology Press, Massachusetts Institute of Technology, Cambridge, Mass. Also, a good explanation and list of definitions is given in Color in Business, Science and Industry, (3 Ed.) John Wiley & Sons (especially pages 170-172, 377-378). Useful also is An Introduction to Color, John Wiley & Sons (especially pages 105-106).

Those skilled in the art know that adding or substituting one colorant for another and/or changing the amount or relative proportion of colorants in a glass composition affects not only the color of the glass, i.e., its dominant wavelength and its color purity, but also affects the light transmittance of the glass and its structural qualities. Furthermore, there is in many cases substantial complexity and unpredictability in these effects. Thus, for example, even if the proper alteration in the composition of a particular color glass were determined for achieving a desired color shift, the same alteration, unfortunately, would also alter (for example, unacceptably reduce) the light transmittance of the glass. It may, of course, also undesirably alter the color purity of the glass. In short, all these factors--dominant wavelength, purity, and light transmittance--are variable, and may vary unpredictably with each other. Developing a new glass composition, therefore, having a particular color and appropriate light transmittance value, is in some cases like searching for a needle in a haystack. An experimental change in the amount or relative proportion of one or more colorants in a glass composition intended to bring one of these numerical values closer to a target value causes one or both of the other values simultaneously to drift off target (or further off target).

The difficulty of this task, finding the correct glass composition for a colored glass having the desired dominant wavelength, color purity, and light transmittance, is discussed in U.S. Pat. No. 3,296,004 to Duncan, wherein a neutral brown heat absorbing glass is disclosed. Duncan expressly noted that the development of the particular color requires a careful consideration of the transmittance characteristics of the glass and that the amounts of the colorants must be carefully controlled to achieve the desired color (dominant wavelength and color purity), transmittance, and heat-absorbing characteristic. Thus, for example, Duncan pointed out that if his glass contained more cobalt oxide than be specified, the color would be more blue than desired. Considering the glass composition of the present invention for a moment, however, the great unpredictability of this area is well demonstrated by the fact that it employs cobalt oxide in an amount well within the range used by Duncan, yet achieves a blue, not a brown color. That is, the amount of cobalt oxide used by Duncan to produce brown surprisingly yields the attractive blue color in combination with the other components of the glass composition of the present invention, notwithstanding the fact that such other components are not normally associated with producing blue coloration.

This inherent unpredictability in achieving specific purity, dominant wavelength, and light transmittance values simultaneously in a glass composition had to be overcome in discovering the glass composition of the present invention. A series of blue glass compositions was fabricated for aesthetic evaluation for automotive and architectural uses, and the like. From amongst the many samples, one was chosen having a very attractive blue color--the color of the glass composition of the present invention. In particular, it was a blue having a dominant wavelength of 482 nm±1 nm and a purity of 13%±1%. These values correspond to the color coordinates of the glass, i.e., trichromatic coefficients, of about x=0.2799 and y=0.2947.

The task then was to develop a blue glass composition including appropriate colorants which yielded the same dominant wavelength and color purity, but with a desired Illuminant C transmittance value of 54%±3%. As explained above, however, altering the various colorants, the amounts, and relative proportions in which they were used, for purposes of achieving the correct light transmittance value simultaneously caused the color, that is the dominant wavelength and purity, to drift off target.

The visible light transmittance value of the blue glass of the present invention is dictated by an important commercial consideration. Specifically, glass of the same composition has to be suitable for both motor vehicle glazing and architectural glazing applications. That is, in order to achieve significant manufacturing cost savings, glass for both architectural glazing and automotive glazing applications had to be producible together on the same float glass production line. To use the same glass in both of these applications, it must have an Illuminant A transmittance at least high enough to meet applicable government standards for motor vehicle glazings, and yet low enough to provide heat load reduction to meet architectural glazing specifications. Thus, an Illuminant C transmittance value of 54%±3% was determined for the glass, at one quarter inch thickness. This meets various applicable architectural standards and, when used as one of the 0.090 inch thick glass panels (the other 0.090 inch thick glass panel being clear) in a laminated safety glass windshield, yields the desired blue of the invention with an Illuminant A visible light transmittance of at least 70% to meet current U.S. government standards for motor vehicle windshields.

Dozens of experimental glass compositions were tried without success. The numerous variables affecting color in a glass composition, e.g., selection of colorant(s), their amounts, relative amounts, etc., and the unpredictability of the type or degree of change effected by varying one or more of them led to failure after failure. The search continued and dozens of additional experimental glass compositions were tried. Those skilled in the practical aspects of this art will understand the very considerable effort and expense involved in a research and development program of this nature. Still the glass compositions which provided the necessary light transmittance together with the selected dominant wavelength and the selected purity were undiscovered. More time, money, and effort were expended to produce and test dozens of additional experimental glass compositions. All of these were also unsuccessful.

Finally a glass composition was produced and tested and found to have the needed Illuminant C transmittance of 54%±3% in conjunction with the desired blue color having a dominant wavelength equal to 482 nm±1 nm and a color purity equal to 13%±1%. Furthermore, as disclosed below, this was achieved using four colorants, each readily commercially available at resonable cost and each used in a practical, easily measured quantity.

A blue glass having approximately the same transmittance, dominant wavelength, and excitation purity values, but containing only three colorants, is disclosed in U.S. Pat. No. 4,866,010 to Boulos et al. However, the patent does not suggest that a fourth colorant may be added, and the proportions of the original three colorants modified, to achieve virtually the same values for transmittance, dominant wavelength, and color purity as for the present inventive glass composition. Specifically, the patent does not suggest, and in fact teaches away from, the use of nickel, which typically imparts a reddish-brown color to glass, as a component of the present inventive blue glass composition.

U.S. Pat. No. 2,938,808, subsequently reissued as U.S. Pat. No. Re. 25,312, discloses as a new article of manufacture a neutral color sheet of glass having a thickness in the range of 1/8-1/4 inch. The glass is suitable for glazing purposes and has a substantially uniform transmittance for light in the portion of the spectrum between 440 and 660 millimicrons, a color purity below 7%, a total solar energy transmittance between 40% and 48%, and a total luminous transmittance between 35% and 45%, at a thickness of 1/4 inch. The disclosed glass composition consists essentially of base ingredients in percentages by weight as follows: 60-75% SiO2, 11-20% Na2 O, 0-10% K2 O, the sum of the Na2 O and the K2 O being 11-21%, 6-16% CaO, and 0-10% MgO, the sum of the CaO and MgO being 6-18%, together with 0.4% Fe2 O3, 0.0076-0.008% Co3 O4, 0.009-0.126% NiO, and 0.005-0.0056% Se. The patent teaches that the amounts of the colorants Fe2 O3, Co3 O4 , NiO, and Se are greater when the thickness of the sheet is less than 1/4 inch, and is approximately twice the above listed amounts for each colorant when the thickness of the sheet is 1/8 inch.

U.S. Pat. No. 3,723,142 discloses a neutral gray colored heat absorbing glass having a low color purity. The glass is defined as consisting essentially of the following base components in percentages by weight: 68-75% SiO2, 0-5% Al2 O3, 5-15% CaO, 0-10% MgO, the sum of the CaO and the MgO being 6-15%, 10-18% Na2 O, and 0-5% K2 O, the sum of the Na2 O and the K2 O being 10-20%, together with coloring components of 0.1-0.5% Fe2 O3, 0.003-0.02% Co3 O4, 0.0005-0.001% Se, and negligible NiO. The patent states that the quantity of NiO should be less than about 0.002% and preferably less than 0.0004%.

U.S. Pat. No. 3,498,806 discloses various specific compositions for glasses of "generally blue" coloration, along with compositions for clear glass and glasses of green or other coloring. None of these compositions, however, is the same or even similar to the composition of the glass of the present invention. They differ most notably in both the selection of colorants (using certain colorants not used in the present invention and others which are used) and the amounts and relative proportions of the colorants. Specifically, the patent does not disclose the use of nickel in the glass composition.

Finally, U.S. Pat. No. 4,101,705 discloses neutral bronze glazings having a dominant wavelength in the range of 570 nm to 580 nm and a color purity from 2% to 6%. the weight percentages of Co3 O4 and NiO are lower, and the weight percentage of Se is higher, than the allowable ranges for these colorants in the present invention.

It must be noted that the prior art referred to hereinabove has been collected and examined only in light of the present invention as a guide. It is not to be inferred that such diverse art would otherwise be assembled absent the motivation provided by the present invention, nor that the cited prior art when considered in combination suggests the present invention absent the teachings herein.


Accordant with the present invention, a blue glass composition having an Illuminant C transmittance of 54%±3% at a glass thickness of one quarter inch, a dominant wavelength of 482 nm±1 nm, and a color purity of 13%±1%, has surprisingly been discovered. The glass consists essentially of 68% to 75% by weight SiO2 ; up to 5% by weight Al2 O3 ; 5% to 15% by weight CaO; up to 10% by weight MgO, wherein CaO+MgO is 6% to 15% by weight; 10% to 18% by weight Na2 O; up to 5% by weight K2 O, wherein Na2 O+K2 O is 10% to 20% by weight; 0.189% to 0.478% by weight Fe2 O3 ; 0.0048% to 0.0080% by weight Co3 O4 ; and additional colorant selected from the group consisting of: a mixture of 0.00005% to 0.0153 % by weight NiO and 0.00005% to 0.0003% by weight Se; and 0.0048% to 0.0153% by weight NiO.

The present invention also includes a method for coloring a basic soda-lime-silica glass batch to produce precise color and transmittance properties by admixing into the batch specific quantities of Fe2 O, Co3 O4, NiO, and optionally Se.

The glass compositions of the present invention are particularly suited for the manufacture of blue-colored automotive and architectural glazings.


The glass of the Present invention generally comprises a base soda-lime-silica glass composition having specific colorants in specific quantities therein.

The basic soda-lime-silica glass comprises 68% to 75% by weight SiO2, up to 5% by weight Al2 O, 5% to 15% by weight CaO, up to 10% by weight MgO, with the proviso that CaO+MgO is 6% to 15% by weight of the glass, 10% to 18% by weight Na2 O, and up to 5% by weight K2 O, with the proviso that Na2 O+K2 O is 10% to 20% by weight of the glass. Silica forms the glass matrix. Alumina regulates the viscosity of the glass, and prevents devitrification. Calcium oxide, magnesium oxide, sodium oxide, and potassium oxide act as fluxes to reduce the melting temperature of the glass. Furthermore, the alumina calcium oxide, and magnesium oxide act together to improve the durability of the glass.

Colorants are admixed into the molten batch of basic soda-lime-silica glass (which is otherwise clear), according to the present invention, to impart a blue color and achieve specific transmittance and chromatic characteristics. By "admixing into the molten batch" is also contemplated the addition of the colorants along with the basic glass batch ingredients simlutaneously into the melting tank. Ferric oxide (Fe2 O3) is present in an amount from 0.189% to 0.478% by weight of the glass. Additionally, cobalto-cobaltic oxide (Co2 O4) is present in an amount from 0.004% by 0.0080% by weight of the glass. Further, nickel oxide (NiO) is present, either alone or in combination with selenium (Se), as follows: 0.0048% to 0.0153% by weight NiO; or a mixture of 0.00005% to 0.0153% by weight NiO and 0.00005% to 0.0003% by weight Se.

Glass compositions according to the present invention are blue in reflection and transmission and have an Illuminant C transmittance of 54%±3% at a glass thickness of one quarter inch, a dominant wavelength of 482 nm±1 nm, and a color purity of 13%±1%. The tristimulus coefficients are approximately x=0.2799 and y=0.2947.


Various quantities of sand, soda ash, dolomite, limestone, salt cake, sodium nitrate, rouge, cobalto-cobaltic oxide, and selenium metal and/or nickel oxide are combined as set forth in Table I.

              TABLE I______________________________________Glass Batch Ingredients (Grams)Ingredient     Example 1 Example 2______________________________________Sand           1000.0    1000.0Soda Ash       311.1     311.3Dolomite       260.8     261.2Limestone      70.4      70.1Salt Cake      10.9      11.0Sodium Nitrate 10.4      10.4Rouge          3.430     5.301Co3 O4          0.1107    0.1118NiO            0.1345    0.0660Selenium Metal 0.0       0.0147______________________________________

The aforementioned glass batch ingredients are melted together to form glass compositions as set forth in Table II.

              TABLE II______________________________________Glass Compositions (wt %)Component      Example 1 Example 2______________________________________SiO2      73.93     72.62Na2 O     12.63     13.70CaO            8.56      8.67MgO            4.10      4.09Al2 O3          0.12      0.11SO3       0.28      0.30TiO2      0.01      0.01K2 O      0.06      0.04Fe2 O3          0.290     0.430.[.Co3 O4 .]. .Iadd.Co.Iaddend.          0.0055    0.0054.[.NiO.]. .Iadd.Ni.Iaddend.          0.0072    0.0035Se Metal       0.0       0.00015______________________________________

The properties of the resultant glass compositions, at a thickness of 1/4 inch, are set forth in Table III.

              TABLE III______________________________________Optical Properties (at 1/4 inch)        Example 1                Example 2______________________________________Illuminant C   53.4%     51.4%TransmittanceDominant       481.4 nm  481.5 nmWavelengthColor Purity   13.9%     13.9%______________________________________

These examples may be repeated with similar success by substituting the generically or specifically described reactants and/or reactant conditions recited herein for those actually used in the preceding example.

From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from its spirit and scope, can make various changes and modifications in the invention to adapt it to various usages and conditions.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3296004 *Aug 12, 1963Jan 3, 1967Pittsburgh Plate Glass CoNeutral brown heat absorbing glass composition
US3498806 *Sep 7, 1965Mar 3, 1970Owens Illinois IncGlass compositions and process
US3723142 *Dec 11, 1970Mar 27, 1973Asahi Glass Co LtdNeutral gray glass
US4101705 *Dec 2, 1975Jul 18, 1978Saint-Gobain IndustriesNeutral bronze glazings
US4866010 *Feb 17, 1989Sep 12, 1989Ford Motor CompanyNickel ion-free blue glass composition
US4873206 *Jul 5, 1988Oct 10, 1989Ppg Industries, Inc.Dark, neutral, gray, nickel-free glass composition
USRE25312 *Feb 25, 1957Jan 1, 1963 Glass composition
DE1141417B *Jun 13, 1955Dec 20, 1962Pittsburgh Plate Glass CoGezogenes Tafelglas
JPS38923B1 * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5558942 *Nov 10, 1994Sep 24, 1996Asahi Glass Company Ltd.Ultraviolet ray absorbent colored glass
US5807417 *Jul 11, 1997Sep 15, 1998Ford Motor CompanyNitrate-free method for manufacturing a blue glass composition
US5851940 *Jul 11, 1997Dec 22, 1998Ford Motor CompanyBlue glass with improved UV and IR absorption
US5897956Apr 21, 1997Apr 27, 1999Asahi Glass Company Ltd.Glass having low solar radiation and ultraviolet ray transmittance
US6313053Apr 9, 1998Nov 6, 2001Ppg Industries Ohio, Inc.Infrared and ultraviolet radiation absorbing blue glass composition
US6548434 *Mar 2, 2001Apr 15, 2003Nippon Sheet Glass Co., Ltd.Palely colored glass having high transmittance and method for producing the same
US6673730Dec 10, 1999Jan 6, 2004Ppg Industries Ohio, Inc.Infrared and ultraviolet radiation absorbing glass article and method
US6995102Jul 16, 2003Feb 7, 2006Visteon Global Technologies, Inc.Infrared absorbing blue glass composition
US7625830Feb 10, 2005Dec 1, 2009Ppg Industries Ohio, Inc.Blue glass composition
US20040077479 *Mar 28, 2001Apr 22, 2004Dominique CosterColoured soda-lime glass of high light transmission
US20050014627 *Jul 16, 2003Jan 20, 2005Visteon Global Technologies, Inc.Infrared absorbing blue glass composition
U.S. Classification501/71
International ClassificationC03C4/02, C03C3/087
Cooperative ClassificationC03C3/087, C03C4/02
European ClassificationC03C3/087, C03C4/02
Legal Events
May 3, 1999FPAYFee payment
Year of fee payment: 8
Jun 20, 2000ASAssignment
Effective date: 20000615
Jul 7, 2003FPAYFee payment
Year of fee payment: 12
Jul 7, 2003SULPSurcharge for late payment
Year of fee payment: 11
Dec 7, 2005ASAssignment
Effective date: 20051129
May 9, 2008ASAssignment
Effective date: 20080414