U.S. patent application number 09/791064 was filed with the patent office on 2001-07-05 for grey glass composition and method of making same.
This patent application is currently assigned to Guardian Industries Corporation. Invention is credited to Cochran, Gary Seldon, Landa, Ksenia Alexander, Landa, Leonid Mendel, Longobardo, Anthony Vincent.
Application Number | 20010006927 09/791064 |
Document ID | / |
Family ID | 23062194 |
Filed Date | 2001-07-05 |
United States Patent
Application |
20010006927 |
Kind Code |
A1 |
Cochran, Gary Seldon ; et
al. |
July 5, 2001 |
Grey glass composition and method of making same
Abstract
A high LTa, low UV and IR transmittance grey glass employing as
its colorant portion iron (Fe.sub.2O.sub.3/FeO), erbium
(Er.sub.2O.sub.3) and, optionally, titanium (TiO.sub.2). Enhanced
effects are achieved by forming separate prebatch mixes, one of
which includes rouge, metallic Si (optional), SiO and sand, the
other including the remainder of ingredients, which after separate
formation are then admixed to form the final, overall batch.
Inventors: |
Cochran, Gary Seldon;
(Eighty-Four, PA) ; Longobardo, Anthony Vincent;
(Mt. Pleasant, PA) ; Landa, Ksenia Alexander;
(Jeannette, PA) ; Landa, Leonid Mendel;
(Jeannette, PA) |
Correspondence
Address: |
Nixon & Vanderhye P.C.
8th Floor
1100 N. Glebe Rd.
Arlington
VA
22201
US
|
Assignee: |
Guardian Industries
Corporation
|
Family ID: |
23062194 |
Appl. No.: |
09/791064 |
Filed: |
February 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09791064 |
Feb 23, 2001 |
|
|
|
09277749 |
Mar 29, 1999 |
|
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Current U.S.
Class: |
501/70 ;
501/64 |
Current CPC
Class: |
C03C 4/085 20130101;
C03C 4/082 20130101; C03C 3/095 20130101; C03C 4/02 20130101 |
Class at
Publication: |
501/70 ;
501/64 |
International
Class: |
C03C 003/087; C03C
003/095 |
Claims
We claim:
1. A glass comprised of a colorant portion consisting essentially
of, by weight percent:
10 Fe.sub.2O.sub.3 (total iron) about 0.5-0.8% FeO about 0.1-0.25%
Er.sub.2O.sub.3 about 0.5-3.0% TiO.sub.2 about 0.0-1.0%
wherein said glass when measured at a nominal thickness of about 1
mm-6 mm has a dominant wavelength of from about 435 nm to less than
about 570 nm and an excitation purity of less than about 4.5%.
2. A glass according to claim 1 wherein said glass is a
soda-lime-silica glass.
3. A glass according to claim 2 wherein said dominant wavelength
and excitation purity are measured at a nominal thickness of said
glass of about 3 mm-4 mm.
4. A glass according to claim 1, 2 or 3 wherein said glass is
substantially free of selenium.
5. A glass according to claim 4 wherein said glass is substantially
free of cerium.
6. A glass according to claim 5 wherein said glass is substantially
free of nickel.
7. A glass according to claim 6 wherein said glass is substantially
free of cobalt.
8. A glass according to claim 1 wherein said glass further includes
by weight percent about 0.1-1.0% TiO.sub.2.
9. A glass according to claim 1 wherein said glass further includes
by weight percent about 0.25-1.0% B.sub.2O.sub.3.
10. A glass according to claim 1 wherein said glass includes by
weight percent:
11 Fe.sub.2O.sub.3 (total iron) about 0.6-0.8% FeO about 0.16-0.25%
Er.sub.2O.sub.3 about 1.0-2.0%.
11. A glass according to claim 1 or 9 wherein said glass has the
following characteristics when measured at a nominal thickness of 4
mm: LTa: greater than or equal to about 70% UV: less than about 42%
IR: less than about 37%.
12. A glass according to claim 11 wherein said: LTa is equal to or
greater than about 70% UV is less than about 39% IR is less than
about 28%, and T.sub.s is less than about 47%.
13. A glass according to claim 12, wherein said glass when measured
at a nominal thickness of 3 mm-4 mm has a purity of about 0.2-4.5%
and a dominant wavelength of 480 nm-550 nm.
14. A glass according to claim 1 wherein when measured at a nominal
thickness of 4 mm, said glass has the following characteristics
according to Ill. C, 2.degree. observer, CIE: L* about 86-91 a*
about -2.4 to +1.6 b* about -5.0 to +2.0.
15. A glass according to claim 14 wherein said characteristic
according to Ill. C, 2.degree. observer, CIE is: L* about 87-89 a*
about -0.5 to +1.0 b* about -3.0 to -1.0.
16. A glass composition comprising by weight percent:
12 Ingredient Wt. % SiO.sub.2 about 65-75 Na.sub.2O about 10-15 CaO
about 1.5-15 MgO about 0-10 Al.sub.2O.sub.3 about 0-3 K.sub.2O
about 0.1-1 SO.sub.3 about 0.1-0.3 TiO.sub.2 about 0-1.0
Fe.sub.2O.sub.3 about 0.50-0.80 FeO about 0.10-0.25 Er.sub.2O.sub.3
about 0.50-3.0 B.sub.2O.sub.3 about 0-12.0
17. A glass composition according to claim 16, wherein, by weight
percent:
13 Ingredient Wt. % TiO.sub.2 0.1-0.50 Fe.sub.2O.sub.3 0.55-0.80
(total iron) FeO 0.16-0.25 Er.sub.2O.sub.3 1.0-2.0
18. A glass composition according to claim 17 wherein said
composition includes about 0.25-1.0% by weight B.sub.2O.sub.3.
19. A glass article formed of the composition of claim 17 wherein
said glass article when measured at a nominal thickness of about 1
mm-6 mm, has a dominant wavelength of from about 435 nm to less
than about 570 nm and an excitation purity of less than about
4.5%.
20. A glass article formed of the composition of claim 18 wherein
said glass article when measured at a nominal thickness of about 1
mm-6 mm, has a dominant wavelength of 480-550 nm and an excitation
purity of 0.2-4.5.
21. A glass article according to claim 17, 18, 19 or 20 wherein
said glass article is a component of an automotive window.
22. A glass article according to claim 17, 18, 19, 20 or 21 wherein
said glass article is a lens of an eyeglass or an architectural
window.
23. A method of making the glass of claim 1 comprising the steps
of: a) forming at least two separate prebatch mixes which when
mixed together form an overall batch mixture comprising: Ingredient
sand iron oxide erbium oxide SiO wherein said first prebatch mix
comprises: Ingredient iron oxide SiO sand and wherein any remaining
prebatch mix or mixes include the remaining ingredients in said
overall batch mixture, b) mixing said first prebatch ingredients
together separately from said remaining batch ingredients to form
said first prebatch mix, c) mixing said remaining ingredients so as
to form at least one other separate prebatch mix, d) mixing said
prebatch mixes together to form said overall batch mixture, e)
melting said overall batch mixture to form a glass therefrom, and
thereafter f) forming said glass into said glass article.
24. A method according to claim 23 which includes the steps of: a)
forming at least three separate prebatch mixes, b) separately
mixing together the ingredients in each said prebatch mix and,
thereafter c) mixing said at least three separate pre-mixed
prebatch mixes to form said overall batch mixture, wherein one of
said prebatch mixes comprises: Ingredient sand dolomite limestone
boric acid salt cake and wherein another of said prebatch mixes
comprises: Ingredient soda ash titania erbium
25. A method according to claim 23 wherein said glass is a grey
glass automotive window which when measured at a nominal thickness
of about 1 mm-6 mm, has a dominant wavelength of from about 435 nm
to less than about 570 nm, an excitation purity of less than about
4.5%, an LTa equal to or greater than about 70%, an IR
transmittance less than about 28%, and a UV transmittance less than
42%.
26. A method according to claim 25 wherein said glass when said
glass is measured at a nominal thickness of about 3 mm-4 mm the
glass has a dominant wavelength of from about 480 mm to 550 mm, an
excitation purity of about 0.2-4.3%, an Lta of greater than about
70%, a UV less than about 38%, an IR less than about 28%, and a
T.sub.s less than about 47%.
27. A method according to claim 23 wherein said overall batch
mixture further includes: Ingredient soda ash dolomite limestone
boric acid salt cake.
28. A method according to claim 27 wherein said first prebatch mix
consists essentially of: Ingredient iron oxide as rouge metallic Si
SiO sand.
29. A method according to claim 27 wherein said overall batch
mixture further includes titania.
30. A batch mixture capable of forming the glass of claims 1, 10,
and 12 wherein said batch mixture includes about 0.01-0.3 wt. % SiO
and about 0-0.12 wt. % metallic silicon.
Description
FIELD OF THE INVENTION
[0001] This invention relates to grey glass compositions and
methods of making same. More particularly, this invention relates
to erbium-containing grey glass compositions having low light
transmittance in the UV and IR range while, at the same time,
having high light transmittance in the visible range, thus making
such glasses suitable for use as windows and windshields in the
automotive industry and architectural field, as well as, in certain
embodiments, as eyeglass lenses.
BACKGROUND OF THE INVENTION
[0002] The automotive industry, for a number of years, has centered
on the color grey, sometimes referred to as "neutral grey", as the
aesthetic color of choice for automotive windows. At the same time,
this industry, as well as the eyeglass art, have demanded that
transmission in the UV and IR range of the light spectrum be
minimized. This is also desirable at certain times in the
architectural field. Governmental regulations in the automotive
industry, moreover, simultaneously insist that the visible light
transmittance be at least 70% or greater in certain, if not all,
vehicular windows when provided by the original equipment
manufacturer of the vehicle (e.g. GM, Ford, Chrysler etc., in the
U.S.A.). A need is thereby created in these diverse industries for
a glass which achieves these properties.
[0003] A glass window, windshield or other glass article is said to
have the desirable color "grey", sometimes referred to as "neutral
grey", if it manifests a dominant wavelength from about 435 nm, and
preferably from about 470 nm, to less than about 570 nm, in
combination with an excitation purity of less than about 4.5%.
This, then, defines the meaning of the term "grey" as used herein.
A still more preferred range of dominant wavelength, thus defining
a more preferred "grey" as used herein, is about 480 nm-550 nm, and
in like manner, a more preferred range of purity is about 0.2-4.5%.
The appearance of such glass, thus defined, has been found to be of
a truly "grey" color, rather than wandering into an objectionable
hew of bronze, green or purple, or some other color. This "grey"
color, as aforesaid, has found a unique demand in the automotive
market, but it also has potential utility in the architectural and
eyeglass markets as well.
[0004] At the same time that a true "grey" color is to be achieved,
there is the usually required need to achieve rather strict levels
of light transmission defined conventionally by:
[0005] LTa as visible light transmission,
[0006] UV as ultraviolet light transmission,
[0007] IR as infrared light transmission, and
[0008] T.sub.s as total solar transmission.
[0009] In order to specify the parameters of these characteristics,
it is generally necessary to specify the thickness of the glass
which is the subject of the measurement. As used herein, in this
respect, the term "a nominal thickness of about 1 mm-6 mm," and in
certain embodiments, "about 3 mm-4 mm" means that the
characteristics of the glass are those experienced when the
thickness of the actual glass under investigation is adjusted for
that nominal thickness range. Such thickness ranges, in this
respect, are generally recognized as conventional thicknesses for
glass sheets made by the float glass process, as well as a
recognized thickness range for the automotive industry.
[0010] When measured at the specified nominal thickness (e.g. 3.2
mm or 4 mm) the important characteristic of color achieved by this
invention may be reported by the conventional CIE LAB technique
(see U.S. Pat. No. 5,308,805). Such a technique is reported in CIE
Publication 15.2 (1986) and ASTM: E 308-90 [Ill. C 2.degree.
observer].
[0011] "Luminous transmittance" (LTa) [2.degree. observer] is a
characteristic and term well understood in the art, and is used
herein in accordance with its well known meaning [see U.S. Pat. No.
5,308,805]. This term is also known as Ill. A visible transmittance
(380-780 nanometers inclusive), and its measurement is made in
accordance with CIE Publication 15.2 (1986) and ANSI test method
Z26.1.
[0012] "Total solar energy transmittance" (T.sub.s) (300-2100 nm
inclusive, integrated using Simpson's Rule at 50 nm intervals using
Parry Moon Air Mass=2) is another term well understood in the art
[see U.S. Pat. No. 5,308,805]. It is used herein according to this
well known meaning. Its measurement is conventional and well
known.
[0013] The terms, and characteristics, of "ultraviolet light
transmittance" (% UV), "infrared energy transmittance" (% IR),
"dominant wavelength" (DW) and "excitation purity" (i.e. %
"purity", or Pe) are also well understood terms in the art, as are
their measurement techniques. Such terms are used herein, in
accordance with their well known meaning [see U.S. Pat. No.
5,308,805].
[0014] "Ultraviolet transmittance" (% UV) is measured herein using
Parry Moon Air Mass 2=(300-400 nm inclusive, integrated using
Simpson's Rule at 10 nm intervals). Such a measurement is well
known in the art.
[0015] "Infrared transmittance" (% IR) is conventionally measured
using Simpson's Rule and Parry Moon Air Mass=2 over the wavelength
range 800-2100 nm inclusive at 50 nm intervals. Such a measurement
is well known in the art.
[0016] "Dominant wavelength" (DW) is calculated and measured
conventionally in accord with the aforesaid CIE Publication 15.2
(1986) and ASTM: E 308-90. Its calculation and measurement are also
well known in the art. As used herein, therefore, the term
"dominant wavelength" includes both the actual measured wavelength
and, where applicable, its calculated complement.
[0017] "Excitation purity" (Pe or % "purity") is measured
conventionally in accord with CIE Publication 15.2 (1986) and ASTM:
E 308-90.
[0018] For automotive windows (including windshields) it is
desirable that the glass have the following characteristics (when
measured at a nominal thickness of about 3 mm-4 mm and preferably
at about either 3.2 mm or 4 mm as the particular situation may
require), and often in the ultimate product as well:
[0019] LTa, greater than about 70%
[0020] UV, less than about 42%, preferably less than about 38%
[0021] IR, less than about 37%, preferably less than about 28%
[0022] T.sub.s, less than about 47%.
[0023] Generally speaking, the prior art has at times been able to
meet these automotive requirements, including the achievement of
the necessary, aesthetic "grey" color by using as the essential
ingredients of the colorant portion in an otherwise conventional
silicate glass composition (e.g. a typical soda-lime-silica float
glass composition), a combination of cobalt admixed with one or
more of selenium, nickel, and cerium, along with an essential
amount of iron. In many instances this combination was thought
critical to achieving both a grey color and the requisite light
transmission properties, or at least a "neutral bronze color." See,
for example, U.S. Pat. Nos. 4,101,705; 5,061,659; 5,264,400;
5,318,931; 5,380,685; and Japanese Patent JP4-280834.
[0024] Unfortunately, these prior art combinations often had
various problems associated with them. For example, cerium, being a
well known UV absorber when present in glass in its reduced form,
Ce.sup.3+, should be avoided for the following reason. Iron is
conventionally introduced into glass in the form of
Fe.sub.2O.sub.3, part of which should be reduced to FeO to achieve
the requisite low IR transmittance value. Cerium, which is
introduced into glass in the form of CeO.sub.2, is known to oxidize
divalent iron to trivalent iron either directly or by competition
with any reducing agent present in the glass melt. Therefore,
coexistence of iron oxide and cerium oxide will inevitably lead to
a decrease in the concentration of FeO in the glass and thus will
reduce its IR absorbing power.
[0025] The use of nickel in these prior art compositions presented
the problem of nickel sulfide stones forming in the ultimate
product. Selenium, furthermore, is difficult to retain in the glass
during glass making. The loss of selenium created a difficulty in
controlling the redox ratio in the glass, which ultimately
adversely affected transmittance values. Without some, or all, of
these aforesaid key ingredients, cobalt used by itself with the
iron as the colorant portion of the glass composition, could not
achieve the requisite combination of Lta and grey color as defined
above.
[0026] Several attempts in the past have been made to employ the
rare earth element erbium (reported conventionally as
Er.sub.2O.sub.3, and used herein according to this conventional
practice) as a colorant in automotive windows and other glass
articles. For example, the aforesaid U.S. Pat. No. 5,264,400
reports the use of such an ingredient in glasses of both bronze and
grey tinted colors. However, as reported therein, the use of cerium
oxide is an essential ingredient in the composition.
[0027] As another example, the aforesaid Japanese Patent No. 280834
employs Er.sub.2O.sub.3 in a glass composition which is then said
to have a "low thermal expansion coefficient." The glass employs
from 10-20% B.sub.2O.sub.3 and thus is properly referred to as a
borosilicate glass, rather than the more conventional
soda-lime-silica glasses used in automotive windows. While stating,
in effect, that cobalt and nickel are optional, and no use of Se or
Ce is reported, the dominant wavelength reported is accordingly
rather high, i.e. from 570-610 nm, or tending toward an
objectionable bronze color, even at the lower wavelengths achieved,
rather than achieving a true "grey" color as defined above.
[0028] Reference to the examples presented in this Japanese Patent
'834, moreover, demonstrates that to achieve the lower range of
wavelengths (e.g. the lowest reported in 578 nm) the total iron
content had to be kept at a very low 0.25% and the excitation
purity was a very high 14.2%. This leads to the conclusion that
this patent does not achieve, nor does it teach how to achieve, a
true "grey" glass which, through the use of a high level of iron in
the colorant portion (rather than the low level of iron used), also
simultaneously achieves low UV and IR and high LTa transmittances,
along with a true "grey" color. Indeed, in those examples which do
not use cerium or some other UV absorber, and with the low levels
of iron employed in those examples achieving lower dominant
wavelengths, it is to be presumed that unacceptably high IR and UV
transmittance values are the result.
[0029] In view of the above, it is apparent that there exists a
need in the art for a new glass composition which overcomes the
above problems while achieving the requisite grey color and meets
the other solar management requirements of the particular industry
in which it is to be used. It is a purpose of this invention to
fulfill this and other needs in the art which will become more
apparent to the skilled artisan once given the following
disclosure.
SUMMARY OF THE INVENTION
[0030] Generally speaking, this invention fulfills the
above-described needs in the art by providing a unique glass
composition, glass articles made therefrom, and a unique method of
making the glass. In this respect, the unique glass compositions
are comprised of a colorant portion consisting essentially of, by
weight percent:
1 Ingredient Approximate Wt. % Fe.sub.2O.sub.3 (total iron) about
0.5-0.8% FeO about 0.1-0.25% Er.sub.2O.sub.3 about 0.5-3.0%
TiO.sub.2 about 0-1.0%
[0031] wherein the glass when measured at a nominal thickness of
about 1 mm-6 mm, and preferably about 3 mm-4 mm (e.g. at 3.2 mm and
4 mm) has a dominant wavelength of from about 435 nm to less than
about 570 nm and an excitation purity of less than about 4.5%.
[0032] In achieving (making) the above-described glasses having the
aforesaid unique colorant portion it is preferred to include within
the batch ingredients, and thus during glass formation, a reducing
agent of one or more ingredients. In the practice of certain
embodiments herein the reducing agent is comprised of (by weight of
the batch) about 0.01-0.3 wt. % of silicon monoxide (SiO) and about
0-0.12 wt. % of metallic silicon (Si). In other embodiments the
reducing agent may be selected from one or more conventional glass
melt reducers such as sucrose, tin, carbon, or the like.
[0033] In this respect, it was heretofore known, as reported in
U.S. Pat. No. 5,569,630 (issued to two of the inventors hereto) to
use SiO as a reducing agent for the purpose of reducing cerium and
obtaining a colorless UV absorbing glass which was free of iron. In
the present invention, the combination of two lower valency forms
of silicon; namely, one agent (optional) in the form of metallic
silicon (Si.degree.) powder, and the other, (Si.sup.2+) in the form
of silicon monoxide (SiO), is utilized for the purpose of reducing
the ferric ion to the ferrous ion, thereby obtaining a true "grey"
glass with the requisite low IR transmittance as well as low UV and
high visible transmittances, but without the necessity of the use
of cerium. Indeed, the preferred glasses of this invention are free
of any cerium (except perhaps for an inadvertent trace amount in
some instances). A distinct advantage of this combination of Si/SiO
as the reducing agent is that during glass melting both agents are
converted into SiO.sub.2, i.e. the main component in the preferred
silicate glass matrices employed herein, without the need to add
any dopant or other residue to the glass.
[0034] In this respect, certain unique glass compositions as
contemplated by this invention comprise by weight percent:
2 Ingredient Wt. % SiO.sub.2 about 65-75 Na.sub.2O about 10-15 CaO
about 1.5-15 MgO about 0-10 Al.sub.2O.sub.3 about 0-3 K.sub.2O
about 0.1-1 SO.sub.3 about 0.1-0.3 TiO.sub.2 about 0-1.0
Fe.sub.2O.sub.3 about 0.50-0.80 FeO about 0.10-0.25 Er.sub.2O.sub.3
about 0.50-3.0 B.sub.2O.sub.3 about 0-12.0
[0035] In such compositions, it is preferred that they be
substantially free of one or more of Ce, Co, Se and Ni. Most
preferably the compositions are substantially free of all of these
elements. By the term "substantially free" is meant that such an
element does not exist in an amount greater than a "trace amount"
(i.e.usually as an impurity) and is not purposely added to the mix.
For the purposes of this invention the approximate upper limit for
each element is as follows and below which the element is generally
considered to be present only in a "trace amount". Most preferably,
of course, the glass is entirely free of any measurable amount of
such elements:
3 Element Wt. of Glass ("trace amount") cerium less than about
0.0020% cobalt less than about 0.0003% nickel less than about
0.0005% selenium less than about 0.0003%
[0036] In such instances, where these limits are not exceeded, it
may be said that such an element has no significant affect upon the
relevant solar management properties of the glass, which,
therefore, may be considered the true meaning of the term "trace
amount" as used herein.
[0037] The term "consisting essentially of" is used herein, in its
conventional way, to define the essential ingredients while
eliminating from use above a trace amount, other colorants as
described above (e.g. Co, Se, Ce, Ni) which would significantly
affect the solar management properties of the glass if present.
[0038] While not essential to the practice of this invention, in
theory this invention may be said to achieve its true "grey" color
by recognizing (and utilizing) the known principle of color
formation that an achromatic (grey) glass can be obtained by the
interference of only two colors, blue and pink, which if properly
done, is more appealing aesthetically (as a true "grey" color) than
the so-called "grey" colors heretofore achieved with combinations
of colorants such as Se, Co, and Ni in combination with the
background of blue color given by the ferrous ion in the glass. In
the present invention, the very pure hue of light blue (needed for
the creation of true "grey") is obtained in the glass by the
appropriate reduction of Fe.sub.2O.sub.3 to FeO (the IR absorber).
This is accomplished by a properly balanced combination or amount
of Si (optional) and SiO followed by the achromatization (i.e.
"physical bleaching") to a true grey color as defined herein,
brought about by the use of erbium oxide which provides the true
pink color to create the requisite interference, resulting in the
aesthetically pleasing grey color of the glass.
[0039] Further slight color correction and, if desired, further UV
absorption may be achieved by the addition of titania. As noted
above, TiO.sub.2 is an optional colorant and thus its amount of
about 0.0%-1.0% is included in this term to demonstrate that
TiO.sub.2 is contemplated as an affirmative colorant which
optionally may be used above a trace amount.
[0040] The preferred glasses according to this invention generally
exhibit, in combination, the following characteristics as measured
at their intended nominal thickness:
[0041] a) a true "grey" color as defined above;
[0042] b) a high transmittance of visible light, with an Lta
usually equal to or greater than about 70%;
[0043] c) a low IR transmittance less than about 37% and preferably
less than about 28%;
[0044] d) a low UV transmittance less than about 42% and preferably
less than about 38%; and
[0045] e) a low total solar transmittance less than about 47%.
[0046] In the aforesaid U.S. Pat. No. 5,569,630 there is
additionally disclosed the technique of using a multiple prebatch
approach which employs the matrix components in one prebatch mix
and a separate prebatch mix of CeO.sub.2 and the reducing agent. In
yet another aspect of this invention, a unique method of making the
glasses of this invention has been discovered which draws upon the
teachings in U.S. Pat. No. 5,569,630 to help achieve enhancement of
such characteristics as reproducibility, optimized color, and
further improved UV and IR transmittances. For example, by the use
of such a method it has been found that the reproducible nature of
the solar management properties achieved are optimized over
ordinary techniques of mixing all ingredients together in a single
batch and, thereafter, simply melting the batch to form a glass.
Generally speaking, these unique methods for making the glasses of
this invention, as above-described, comprise the steps of:
[0047] a) forming at least two separate prebatch mixes which when
mixed together form an overall batch mixture comprising:
[0048] Ingredient
[0049] sand
[0050] iron oxide
[0051] erbium oxide
[0052] metallic Si
[0053] SiO (silicon monoxide)
[0054] wherein the first prebatch mix comprises (and preferably
consists essentially of):
[0055] Ingredient
[0056] iron oxide
[0057] metallic Si
[0058] SiO (silicon monoxide)
[0059] sand
[0060] and wherein any remaining prebatch mix or mixes include the
remaining ingredients in the overall batch mixture,
[0061] b) mixing the first prebatch mix ingredients together
separately from said remaining prebatch mix ingredients to form the
first prebatch mix,
[0062] c) mixing the remaining ingredients so as to form at least
one other separate prebatch mix, thereafter,
[0063] d) mixing the prebatch mixes together to form the overall
batch mixture,
[0064] e) melting the overall batch mixture to form a glass
therefrom, and thereafter,
[0065] f) forming the glass into the glass article.
[0066] This invention will now be described with respect to certain
embodiments thereof, wherein:
IN THE DRAWINGS
[0067] FIG. 1 is a side plan view of an automobile having windows
and a windshield employing the glasses of this invention.
[0068] FIG. 2 is a front plan view of a dwelling having an
architectural window made of the glasses of this invention.
[0069] FIG. 3 is a perspective view of eyeglasses employing glass
lenses according to this invention.
DETAILED DESCRIPTION
[0070] With reference to FIGS. 1-3 and as stated above, while the
glasses of this invention find unique application in the automotive
industry, they may also be used as flat glass for the architectural
market for both single sheet windows and dual pane windows known as
I.G. units. They may also be used as eyeglass lenses. Thus, in FIG.
1, windshield W, front side windows F and rear side windows R are
illustrated for areas of use for the glasses of this invention.
Rear windows (sometimes called "backlights") are also applicable,
but are not shown for convenience. In FIG. 2 a typical house H is
schematically shown with a conventional window P having a glass
sheet or sheets (when an I.G. unit) formed of a glass according to
this invention. In FIG. 3, eyeglasses E are provided with a pair of
lenses L made of a glass according to this invention. In general,
then, the glasses of this invention find utility wherever truly
"grey" glasses having low UV and IR transmittances, as usually high
LTa's, are desired or required.
[0071] The preferred glasses for use in this invention employ
conventional soda-lime-silica flat glass as their base composition,
to which is then added certain ingredients to make up a unique
colorant portion. Of particular utility, in this respect, are the
various soda-lime-silica glasses used in making glass sheets by the
float process and generally represented, conventionally, on a
weight percent basis, as comprised of the following basic
ingredients:
4 Ingredient Wt. % SiO.sub.2 68-75 Na.sub.2O 10-18 CaO 5-15 MgO 0-5
Al.sub.2O.sub.3 0-5 K.sub.2O 0-5
[0072] Other minor ingredients, including various conventional and
refining aids, such as SO.sub.3, may also be included. In the past,
furthermore, it has been known to optionally include small amounts
of BaO and B.sub.2O.sub.3. Preferably, the glasses herein include
by weight about 10-15% Na.sub.2O and 6-12% CaO.
[0073] Prior to this invention one of the inventors hereto
discovered and put into commercial practice the finding that by
using a unique amount of B.sub.20.sub.3 in combination with iron as
a principal constituent in a colorant portion of a glass,
B.sub.2O.sub.3 synergistically modified the absorption power of the
ferrous and ferric iron, thereby achieving lower levels of UV,
T.sub.s and IR transmittances than would otherwise be expected from
such a relatively low amount of iron. This synergism is employed in
certain embodiments of this invention as an enhancing factor to UV,
IR and T.sub.s transmittances in order to minimize these
transmittances without the use of cerium oxide or other known UV or
IR absorbers. In certain other embodiments, small amounts of
TiO.sub.2 are optionally employed to further limit UV
absorption.
[0074] The glasses of this invention, as stated above, achieve a
true grey (or "neutral grey") color, as opposed to manifesting an
objectionable "bronze", "blue grey" or "green grey" color. Such a
true "grey" color is best defined, as aforesaid, by referring to
the two characteristics of: (1) "dominant wavelength", and (2)
"excitation purity." Also complementing this definition is
reference to the aforesaid CIE LAB coordinates [Ill. C 2.degree.
observer] . According, then, to this invention, the glasses herein
are true "grey" glasses because they have a dominant wavelength of
from about 435 nm to less than about 570 nm, and most preferably
between about 480 nm-550 nm; coupled with an excitation purity less
than about 4.5% and preferably from about 0.2% to about 4.5%. Such
glasses then will preferably also include the following CIE LAB
color coordinates [Ill. C 2.degree. observer] when measured at a
nominal thickness of from about 1 mm-6 mm (and preferably for most
uses, at about 3 mm-4 mm):
[0075] L* about 86-91
[0076] a* about -2.4 to +1.6
[0077] b* about -5.0 to +2.0.
[0078] Most preferably the CIE LAB color coordinates [Ill. C
2.degree. observer] as measured at a nominal thickness of 3 mm-4 mm
are:
[0079] L* about 87-89
[0080] a* about -0.5 to +1.0
[0081] b* about -3.0 to -1.0.
[0082] When used in the automotive market for windows and/or
windshields that must conform to certain minimal visible light
transmission properties (i.e. as measure as aforesaid as "Lta") ,
the glass articles of this invention will normally have an Lta at
least equal to and preferably greater than about 70% and, in
certain embodiments, greater than about 72%, and in still further
instances, greater than 73%.
[0083] The glasses of this invention achieve the above unique
characteristics, particularly, for example, in silicate glasses,
and more particularly in glasses of the soda-lime-silica type as
defined above, as well as in borosilicate glasses, by the use of a
unique colorant portion which includes a relatively high amount of
iron in combination with erbium oxide (Er.sub.2O.sub.3) and only,
optionally, a small amount of TiO.sub.2, to the exclusion of
anything but, at most, trace amounts of Ce, Se, Co and Ni. As such,
the colorant portions contemplated by this invention consist
essentially of, by weight percent (of the total glass
composition):
5 Ingredient Wt. % Fe.sub.2O.sub.3 (as total iron) about 0.5-0.8%
FeO about 0.1-0.25% Er.sub.2O.sub.3 about 0.5-3.0% TiO.sub.2 about
0.0-1.0%
[0084] In certain preferred embodiments, the colorant portion of
the glasses contemplated herein consist essentially of, by weight
percent (of the total glass composition):
6 Ingredient Wt. % Fe.sub.2O.sub.3 (as total iron) about 0.6-0.8%
FeO about 0.16-0.25% Er.sub.2O.sub.3 about 1.0-2.0%
[0085] Most preferably such a colorant portion also includes
0.1-0.5% TiO.sub.2. Moreover, while perhaps not classifiable as a
"colorant," nevertheless, in certain preferred embodiments the
glasses will also include about 0.25-2.0 weight % B.sub.2O.sub.3,
and preferably about 0.25-1.0% weight % B.sub.2O.sub.3, thereby
achieving the heretofore known synergistic enhancing effect
discussed above, but without adversely affecting color.
[0086] Certain preferred glass compositions of this invention are
generally classifiable as soda-lime-silica glasses, and in certain
preferred embodiments include by weight percent about 10-15%
Na.sub.2O and about 6-12% CaO. Still further embodiments include
high levels of B.sub.2O.sub.3 up to about 12% by weight, and such
glasses are then properly referred to as being in the borosilicate
family of glasses.
[0087] Still further preferred glass compositions of this invention
generally consist essentially of, by weight percent:
7 Ingredient Weight % SiO.sub.2 about 65-75 Na.sub.2O about 10-15
CaO about 1.5-15 MgO about 0-10 Al.sub.2O.sub.3 about 0-3 K.sub.2O
about 0.1-1 SO.sub.3 about 0.15-0.25 TiO.sub.2 about 0-1.0
Fe.sub.2O.sub.3 about 0.50-0.80 FeO about 0.10-0.25 Er.sub.2O.sub.3
about 0.50-3.0 B.sub.2O.sub.3 about 0-12.0
[0088] The glasses of this invention may be made from standard
batch ingredients using well known glass melting and refining
techniques once given the above final glass analysis. For example,
if a single, conventional batch technique for melting is to be
used, a typical batch example would be as follows, based upon a
total of 100 parts by weight:
8 Batch Ingredient Parts by Wt. sand about 70-73 soda ash about
20-25 dolomite about 16-19 limestone about 5.5-6.8 boric acid about
0.5-21 salt cake about 0.2-0.7 rouge (Fe.sub.2O.sub.3) about
0.5-0.8 erbium oxide about 0.5-3.0 Si (metal) about 0.01-0.12 SiO
about 0.02-0.3
[0089] As discussed briefly above, while conventional single batch
melting techniques may be employed here, it is a unique finding,
and thus an additional part of this invention, drawing upon the
teachings in U.S. Pat. No. 5,569,630, that if certain multiple,
prebatch mixing of selected ingredients is accomplished to make up
separate "prebatch mixes", followed thereafter by admixing together
these prebatch mixes to make up the final "overall batch mixture,"
certain quality enhancing characteristics in the final glass are
achieved, principally in the ability to more precisely obtain in
repeatable batches the optimal end result (characteristics) sought
to be achieved, as well as enhanced solar management properties. In
short, by this prebatch mix technique employing at least two
prebatches of selected ingredients, reproducibility of optimized
(i.e. maximized, or more precise) color, UV, IR, and LTa
characteristics are achieved.
[0090] In this respect, one of the prebatch mixes should be made up
of the iron-containing ingredient (e.g. rouge) along with SiO
(silicon monoxide) and optionally, metallic Si (i.e. the reducing
agents), and preferably some of the sand. In preferred embodiments
the total amount of the iron (e.g. rouge), metallic Si, and SiO are
used in this first prebatch mix with a small amount of sand and are
thoroughly mixed together separately from the remaining batch
ingredients. It is preferred that, for example, on the basis of a
total of 70-73 parts of sand by weight per hundred in the overall
batch, only about 5-13 parts of sand is used in this first prebatch
mix.
[0091] The remaining batch ingredients can then be made up by
admixing them in another separate prebatch mix or into two or more
prebatch mixes before admixing them with the iron and reducing
agent-containing first prebatch mix. In certain embodiments of this
invention the remaining ingredients are formed into two additional
prebatch mixes. The first additional prebatch mix (i.e. the second
prebatch mix) is made up of a portion of the soda ash, and all the
titania (if used) and the erbium oxide. The second additional
prebatch mix (i.e. the third prebatch mix) is then made up of the
remaining ingredients which thus normally includes the rest of the
sand (e.g. 60-65 parts and preferably about 61.5 parts, per
hundred) and soda ash, and all of the dolomite, limestone, boric
acid and salt cake to be used in the final batch.
[0092] After each separate prebatch mix is thoroughly separately
mixed, to form a substantially homogenous powdered admixture, the
two or more prebatch mixes are then thoroughly mixed together to
form the overall (or final) batch mixture. Conventional melting and
refining techniques are then used to form a molten glass from which
flat sheet glass or other articles may be formed.
[0093] It has been found that the use of at least two prebatch
mixes, wherein the iron is isolated with the silicon monoxide (SiO)
and metallic Si (if used), produces glasses of a much more
predictable and often optimized nature as far as their color and
other solar management properties go.
[0094] While not essential to the practice of this invention, it
may be theorized that this multi-prebatch technique procedure of
isolating and thoroughly mixing the iron, silicon monoxide and
silicon metal in a separate prebatch mix leads to the formation of
aggregates, or "clusters" in the batch, which form a
"quasi-ingredient" of the batch. This quasi-ingredient then
comprises all the "participants" (i.e. Fe.sub.2O.sub.3, SiO and Si
"dissolved" in a small amount of sand) of the above-described
reactions of reduction of ferric ion to ferrous ion by the two
lower valence forms of silicon. By making up the quasi-ingredient
from these reactants, the probability of their encounter is
increased, thus increasing the completion of the chemical reactions
in the melt, and resulting in glasses of a more predictable
(reproducible) nature as far as their color and solar management
properties go. The above reactions are also optimized in this
quasi-ingredient (prebatch) approach for the amounts of the
ingredients employed, thus providing a more effective use of SiO
which is relatively expensive.
[0095] The following constitute examples of this invention:
EXAMPLES
[0096] Glass samples having the composition and properties shown in
the TABLE below were formed from the ingredients listed in the
first columns of this table, using the three prebatch mixing
technique as described above. The ingredient listed as
"Fe.sub.2O.sub.3" is total iron and was added as conventional rouge
to the first prebatch which also included metallic silicon (when
used), silicon monoxide, and a portion (5-13 parts per hundred) of
the total sand. The second prebatch then included the erbium oxide,
titania (when used), and about one-third of the total soda ash
employed. The third prebatch included the remainder of the
ingredients as listed. The three prebatch mixes were then mixed
together to form the overall batch mixture.
[0097] The overall batch mixture was then melted in an electric
furnace in a conventional crucible at a temperature in the range
between 1480.degree. and 1520.degree. C. The molten glass was then
cast into molds for measurement sampling (e.g. 2" diameter
buttons), annealed at 620.degree. C. for 1/2hour and cooled to room
temperature. The cooled glass was polished to prepare either 4 mm
or 3.2 mm thick specimens which were then measured using
conventional practices as described above.
9TABLE Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10
Ex. 11 Ex. 12 Sand 71.50 71.50 71.50 71.50 71.50 71.50 71.50 71.50
71.50 71.50 71.50 71.50 Soda ash 23.70 23.70 23.70 23.70 23.70
23.70 23.70 23.70 23.70 23.70 23.70 23.70 Potash 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Alumina 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Dolomite 18.32 18.32
18.32 18.32 18.32 18.32 18.32 18.32 18.32 18.32 18.32 18.32
Limestone 6.10 6.10 6.10 6.10 6.10 6.10 6.10 6.10 6.10 6.10 6.10
6.10 Boric acid 0.89 0.89 0.89 0.89 0.89 0.89 0.89 0.89 0.89 0.89
0.89 0.89 Salt cake 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50
0.50 0.50 0.50 Fe.sub.2O.sub.3 0.50 0.50 0.50 0.60 0.70 0.65 0.80
0.60 0.60 0.60 0.58 0.60 Si met. 0.10 0.12 0.08 0.00 0.00 0.00 0.00
0.00 0.00 0.05 0.12 0.00 SiO 0.01 0.02 0.01 0.20 0.21 0.21 0.20
0.20 0.19 0.10 0.02 0.17 Sucrose 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 Er.sub.2O.sub.3 2.00 2.00 0.50 2.00 1.70
1.75 2.00 1.70 1.50 1.50 1.70 2.00 TiO.sub.2 0.40 1.00 0.10 0.20
0.20 0.25 0.20 0.19 0.40 0.25 0.00 0.00 Thickness 4.1 mm 4.1 mm 4.1
mm 4.1 mm 4.1 mm 4.1 mm 4.1 mm 4.1 mm 4.1 mm 4.1 mm 4.1 mm 4.1 mm %
Lta 73.14 70.75 77.40 71.40 72.14 72.94 67.41 71.88 72.00 71.86
70.97 73.34 % UV 41.24 34.61 49.10 39.37 35.04 39.11 31.32 37.59
35.91 36.81 41.84 39.32 % TS 50.76 46.49 54.15 47.87 49.44 50.17
42.72 49.48 48.45 48.05 46.19 51.89 % IR 31.25 26.49 33.54 27.26
30.37 30.48 22.07 30.35 28.60 27.75 24.07 33.33 wt. % FeO 0.160
0.185 0.149 0.180 0.164 0.163 0.213 0.164 0.173 0.178 0.200 0.150 %
Ltc (Y) 73.30 70.85 78.43 71.77 72.34 73.23 67.81 72.05 72.33 72.29
71.75 73.44 x 0.3077 0.311 0.3023 0.3055 0.3089 0.3074 0.3071
0.3087 0.3082 0.3067 0.3013 0.308 y 0.3111 0.3181 0.3153 0.3104
0.3152 0.3131 0.315 0.3141 0.3161 0.3143 0.3081 0.3107 Dom. Wave.
nm 435.6 569.1 489.2 472.0 478.8 474.6 485.4 466.0 489.6 483.6
478.5 565.5c Ex. Purity 1.69% 0.73% 2.97% 2.38% 0.55% 1.38% 1.23%
0.81% 0.74% 1.46% 4.11% 1.85% L* 88.59 87.41 90.97 87.86 88.13
88.56 85.91 87.99 88.13 88.11 87.85 88.66 a* 1.26 -0.44 -3.43 0.56
-0.11 0.14 -0.85 0.31 -0.90 -0.7 -0.41 1.59 b* -2.16 0.83 -1.58
-2.74 -0.51 -1.51 -0.87 -0.94 -0.32 -1.19 -4.20 -2.25 Ex. 13 Ex. 14
Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex. 19 Ex. 20 Ex. 21 Ex. 22 Ex. 23 Sand
71.50 71.50 71.50 71.50 70.50 71.40 66.50 71.40 71.40 72.00 72.00
Soda ash 23.70 23.70 23.70 23.70 23.20 23.70 23.94 23.70 23.70
23.70 23.70 Potash 0.00 0.00 0.00 0.00 0.00 0.00 1.47 0.00 0.00
0.00 0.00 Alumina 0.00 0.00 0.00 0.00 0.00 0.00 2.00 0.00 0.00 0.00
0.00 Dolomite 18.32 18.32 18.32 18.32 18.32 18.32 0.00 18.32 18.32
18.32 18.32 Limestone 6.10 6.10 6.10 6.10 6.10 6.10 2.68 6.10 6.10
6.10 6.10 Boric acid 0.89 0.89 0.89 0.89 3.54 1.06 21.24 1.06 1.06
0.00 0.00 Salt cake 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50
0.50 0.50 Fe.sub.2O.sub.3 0.60 0.58 0.58 0.65 0.80 0.80 0.80 0.80
0.80 0.80 0.80 Si met. 0.10 0.12 0.12 0.08 0.10 0.00 0.05 0.00 0.00
0.00 0.00 SiO 0.02 0.02 0.02 0.01 0.05 0.00 0.30 0.30 0.30 0.30
0.30 Sucrose 0.00 0.00 0.00 0.00 0.00 0.20 0.00 0.00 0.00 0.00 0.00
Er.sub.2O.sub.3 2.00 1.00 1.40 2.00 2.00 2.00 2.00 2.50 3.00 2.00
2.50 TiO.sub.2 0.00 0.00 0.00 0.00 0.05 0.11 0.05 0.08 0.00 0.00
0.10 Thickness 4.1 mm 4.1 mm 4.1 mm 4.1 mm 3.2 mm 3.2 mm 3.2 mm 3.2
mm 3.2 mm 3.2 mm 3.2 mm % Lta 70.35 72.61 71.57 70.59 70.47 71.23
73.26 70.62 71.21 72.00 71.31 % UV 40.88 39.52 43.44 39.60 37.57
40.35 34.37 38.97 35.67 40.97 38.85 % TS 45.88 48.40 46.30 46.41
45.79 46.90 51.12 46.85 49.26 48.82 48.50 % IR 24.10 27.52 23.62
25.00 24.09 25.41 31.33 25.95 30.56 28.40 28.61 wt. % FeO 0.199
0.179 0.203 0.194 0.250 0.245 0.206 0.240 0.208 0.222 0.221 % Ltc
(Y) 71.00 73.45 72.51 71.14 71.20 71.89 73.40 71.09 71.24 72.51
71.59 x 0.3018 0.3031 0.3004 0.3033 0.3024 0.3033 0.3085 0.3044
0.3083 0.3049 0.3064 y 0.3068 0.314 0.3091 0.3084 0.3099 0.3108
0.313 0.3096 0.3101 0.3117 0.3105 Dom. Wave. nm 474.9 486.9 481.4
474.5 480.2 480.4 443.8 474.4 562.7c 479.4 466.3 Ex. Purity 4.12%
2.80% 4.32% 3.41% 3.52% 3.08% 1.08% 2.86% 2.16% 2.41% 2.11% L*
87.49 88.66 88.21 87.55 87.58 87.92 88.64 87.53 87.6 88.22 87.77 a*
0.47 -2.39 -1.36 0.44 -0.79 -0.74 0.74 0.38 2.04 -0.40 0.88 b*
-4.57 -1.87 -4.03 -3.79 -3.39 -2.95 -1.36 -3.18 -2.38 -2.39
-2.56
[0098] Once given the above disclosure many other features,
modifications and improvements will become apparent to the skilled
artisan. Such features, modifications and improvements are
therefore considered to be a part of this invention, the scope of
which is to be determined by the following claims:
* * * * *