Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to glazing ~aterial bearing a pyroiyticall~
for~ed, light transmitti~g, solar radiation screening, metal oxide
coating.
-~ 5 The u3e of window glas~ bearing a ~oLar radiation .screening
coating i5 w~ll known ~or glazing building~ in order to reduc~ the
solar heat gain o~ the building, e~peclally during hot sunny weather,
in order that ~he temperature within the bullding may easily be
maintained at a l~Yel which for example is comor~able for occupants o~
the building and can be tolerated by Bny computers or other temperature
sensitive ele~tronic equipment which may be housed within the building.
3y way of example, it is known rom European Patent Spacification
No. EP O 075 516 Al to provide glass with a solar radiation screening
coati~g o~ titanium dioxide ~eposited in an ~mount o~ the order o
140mg~m2, whlch corr~sponds to a thickness of about 35nm. Rnown
windo~ glass with a coating o~ titanium dioxide 35 to 40 nm thick
provide~ an effective screen for solar radiation and gives a metallic
tint in reflection due to int~rference effects. Commercially, it is
extremely important that such a coating should giYe rise to a tint in
rerlection which is neut~al or otherwise aesthetically acceptable.
Unfortunately, known coatings o~ titanium dioxide up to 40nm thick us~d
for this purpos~ are too thin to have adequate abrasion ~sistance so
that the produ~t ha~ an insuf~icient use~ul llfe. It would be po~sible
to impart additional abrasion resistance to the coating by ~aking it
thicker. For example it has been ~ound that ti~anium dioxide coatings
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having a thicknes~ in the range 50nm to 60nm c~n have a satisfactory
abrasion re~istance for the purposes in view~ However increasing the
thickness of such a coating will have the effect o~ altering its tint
in reflection, and a 50 nm to 60 nm titanium dioxide coating gives an
S unpleasant yellowish colour in reflection.
~ t i~ an object of the pre~ent invention to provide gl~zing
ma~erial bearing a pyrolytically ~ormed, light transmitting, solar
radiation screening, metal oxide coating such that the colour o~ the
coatins, when viewed in reflection, can be varied in a manner which is
10 not wholly dependent on the thickness o~ the coating.
AGcording to the present invention, there i8 provided glazing
material bearing a pyroly~ically ~ormed, light trans~itting, solar
radiation screening, metal .oxide coating, characterised in that at
least 95% by w~ight o~ the metal ions in the coating consist of tin and
titanium and in that the relative proportionC o~ tin and t-tanium ions
in the coating are such as to impart to the coating a refractive inde~
which i~ not greater than 2.2~
The refractive index a~ a thin pyrolytically formed titanium oxide
coating is ~bout 2.3. By the adoption o~ the present invention, the
re~ractive index of the coating a a whole is reduced by the addition
o~ 3ufficient tin ion~, and accordingly, a coating acco~ding to the
invention can be made to the same op~ical thickness as, but to a
great0r actual thickness than a coating of substantially pure titanium
dioxide. It will be appreciated that the abra~ion resistance of such a
coating is dependent on the nature and actual thickness of the coating,
whereas any interference effects due to the coating will depend on its
optical tbickness. The optical thickness of a coating which governs
its reflectlve properties is given by t~ice its actual thickness
multiplied by its refractive index. Accordingly the present`inYention
provides a means o~ enhancing the abra~ion resistance of a said coating
while controlling its colour in re~lection so that the resulting
coating has better aging propertles~ Abrasion reslstanc~ o~ a coating
ac~ording to the invention is enhanced as compared with a titanium
dioxide coating of the ~ame optical thickness, because the coating
according to the invention has a greater actual thi~knes~, and also
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because the addition of tin ions modifies the nature o~ the coating in
a way which is beneficial for promoting abraslon resistance. Thus it
is possible to simulate a thin titanium dioxide coatin~, but with
better aging psoperties~
The refractive index of a said coating can be measured by a
classical ellipsometry technique as described in "Thin Film Phenomenan,
g.L. Chcpra, McGraw Hill, 1969, page~ 738 to 741~ and r~erences in
this specification to specific values of refrac~ive ind~x are
re~erences to values measu~ed by that technique~ the measurement bein~
e~fected using sodium D llght.
~o te~t the abrasion resistance of a qaid coating9 us~ can be mad~
of an annula~ reciprocating rubbing member having an internal dia~eter
of 2cm and an externa} diameter of 6cm to give a rubbing sur~ace area
o~ 25cm and formed by a felt pad on a~ annulac metal member. The
rubbing ~ember is set in a welghted tube (weight o~ assembly; 1.7kg~
sLiding vertically in a supportO Constant contact is thereby ensured
between th~ rubbing member and the sample. The hole th~ough the
annular m~tal m2mber forms a r~servoir for a~ aqueous suspen~ion of
crushed sand having a mean grain diameter of O.lm~ which is allowed to
flow out between the felt pad and the coated glazing material being
tested. ~he support carrying ~he rubbing member i recipcocated by a
crank system, with an amplitude of 3cm a~ a frequency o~ l~z. After a
certain time, a pattern of wear is obtained Formed by scratches very
close together, with undestroyed coating left between them, ~ollowed
2S ~ventually by complete or substantially complete removal of ~he
coating. Specific or comparative references in this specification to
abr~sion resistance, are references to abra ion resistance as measured
by that test.
In the most peeferred embodiments of the present invention, the
ralative proportions of tin and ti~anium ions in the coating are such
as to impar~ to the coating a refrac~ive inde~ which is at least 1.9.
This ensuses that there will be a hlgh degree of visible light
reflection at thc coating.
Advantageously, the relative proportions of tin and titanium ions
in the coatinq are such as ~o impart to the coating a refractive index
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which is not greater than 2015. ~'his allow4 a corre3pondingly greater
actual thickness for a given optical thickness of the coating.
Preferably, said coating comprises at least 30~ tin and at ~eas~
30~ titanium calculated as weight per cent o~ the respective dioxide in
the coating. It ha~ been ~ound that this gives the be~t compromise
betwqqn the qolar radiatlon ~creening properties of the coating (which
are largely due to the presence o~ titanium) and reduction in
re~ractive indeæ and increase in abrasion resistance (which is
attributable to th~ preSence of tin). To ~chieve the best abrasion
re~i tance, it is prefe~red that said coating comprises at least 40
tin calculated as weight per cent of tin dioxide in the coating.
~ n the ~o t pse~esred embodiments o~ the invention, the thickness
of ~he coating and the relative proportions of tin and titanium ions in
the coating are such as to give inter~erence enhancement of visible
light reflection within the wavelength range less than 500nm~ In this
way, the qlazing material will exhibit a metallic tint whe~ viewed by
ordinary daylight in re~lection ~rom the coated side.
Advantageously, the coating i~ borne by sheet glass.
Such glass ~ay be clear glass, os it may be opaqu~ glass, for
example for use as exte~nal cladding panels for buildings at floor
levels~ Embcdiments o~ the invention in which the sheet glass i3
tin~ed glass, foc e~ample, bronze glass, have advantageous light
absorbing propertie~.
Various preferred embodiments of the invention will now be
described in greater detail in the following ~xamples.
TEST SAMP~E
A titanium dioxide coating 45n~ thick can be formed on glass as
described in Example 1 of British Patent Specification No 1 397 741 by
pyrolysis of titanyl acetylacetonate. It has been found that when
formed in that way, the titanium dioxide coating has a cefractive index
of 2O3r and thus an optical thickneYs in re1ection of 207nm. When the
abrasion resistance of thiq coating waR tested, it wa~ found that over
at least the central region of the abraded area, the coating was
~ubstantially completely removed within S ~inutes.
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EXA~PLE 1
~n oxid~ coating c~mprising 40~ tin and 60% titanium calculated as
~eight per cent c~ the sespective dioxide in the coatiny was formed by
pyrolysis on a hot glass substrate of a solu~ion containing titanyl
acetylacetonate and tin dibutyldiacetate. The resulting coatlng had a
refractive index of 1.9, and was formed to a thicknes-~ of 55nm! so that
it had the same optical thickness as th~ coating of the Test Sample.
When the abrasion resistanca of this coating was tested, after abrasion
~or 30 minutes, it wa~ found that a few scratches were apparent in the
coating-when the coating was inspected through a microscope.
The coating exbibited a metallic tint in reflection.
In a variant of this Example the coating wa~ formed on tin~ed
glass to give a reduction in luminous transmission.
~XA~P~E 2
A 6mm thick ribbon of freshly ~ormed hot clear float glass was
conveyed through a coatinq station at a speed of 8.5 metres per
minute. The atmospheee in the coating station had a mean temperature
of absut 300C, and the rib~on enterin~ that st~tion had a mean
temperature of about 600C.
A coating precursor solution was made up as follo~:
Tin dibutyldiacetate 6.7 kg
Titanium diacetylacetonatediisopropylate 12.5 kg
Dimethylformamlde to 100 ~
This solution was sprayed at a rate o~ 120 litres per hour to form
a ~oating 42nm thick on the glass ribbon.
The calculated composition of the coating by weight was 47~ tin
dioxide and 53~ titanium dioxide, and the coating had a reEractive
index or 1.~.
With light incid~nt on the coated Eace of a sheet cut from this
ribbon, the luminous tr~nsmissio~ of the sheet was 74.2~ and the
reflectivity of light ~rom the coated face was 22.5~. The coating
exhibited a metallic tint in reflection, and Lts abrasion resiRtance
was similar to that specified in Example l.
In a variant of this Example, the coating was ~ormed on tinted
glass to give a reduction in luminous transmission~
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EXA~rLE 3
An 8mm thick ribbon of clear float glass was coated while hot by
pyrolysis of a coating precur~or ~olution made up as foll~ws:
Tin dibutyldiac:etate 9.3 kg
S Titanium diacetylacetonatediisopropylate 27.8 kg
Dimethylformamide to 100 L
The solution was discharged against the ribbon at a rate of 87
litres per hour ~o for~ a coating 53n~ thick containing 40% tin dioxide
by w~ight~ The ~fractive index of the coating was 2.1.
With light incident on the c~ated face o~ a sheet cut from this
rib~on, ~he luminous transmission of the sheet was 6Ç~ and the
re flectivity of light from ~he coated ace was 28~. The coating
exhibit~d a metallic tint ln reflection, and its abrasion resistance
was si~ilar to that ~pecified in Example 1.
In a ~ariant or this Example the coating was formed on tintad
glass to qive a reduction in luminous transmission.
EX~MæLE 4
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A 6m~ thick ribbon o~ freshly formed hot b~onze float qlass was
conveyed through a coating station.
A coating precursor solution was made up as foLlows:
Tin dibutyldia~etate 13.2 k~
Titanlum diacetylacetonatedii opropylate 27.8 kg
Dimeth~l~or~amide to lOa L
This solution was sprayed at a rate of 82 litres per hour to orm
a c~ating SOnm thick on the glass ribbon.
The calculated composition of the coating by weight was 42~ tin
dioxide and 58~ titanium dioxide ! and the coating had a refractive
index of 2.1.
With llght inoident on the coated face of a sheet cut ~rom this
ribbon, the luminous transmission of the sheet was 39% and the
re~lectivity o light rom the coated face was 24~. The coating
exhibited a metalll~ tint in refl~ction, and its abrasion resistance
was ~imilar to that speoiied in Example L.
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~ n a variant of any of the foregoing Examples, the coating
precursor solution used contained additional Lngredients so as to form
in the coating a doping agent con~tituting up to 5% by weight of the
metal ions in the coatinq, the relative proportions of tin and titanium
dioxides remaining as specified.
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