Note: Descriptions are shown in the official language in which they were submitted.
10749SS
~ .
t
~, .
~ ~ ¦Background of the Invention
;?'
The invention relates generally to the field of precious
metal decorations for ceramics and in particular to a decora-¦
~; tive composition producing the appearance of gold after fir-
ing, but which actually contains no metallic gold.
Decorative compositions for ceramics to achieve a gold
appearance have heretofore contained substantial quantities
of metallic gold, often of the order of 10-15 weight percent j
, with the balance being fluxing agents and vehicle. Such prio~
I art decorations are disclosed in such patents as U.S. Patent
Nos. 2,994,61~ and 3,092,504 which disclose and claim specifi~
.~ , gold compounds and compositions which were found useful for
i decorations having a gold appearance. The maximum gold
I
. . .
Ij 107~955
content is determined primarily by the cost of the gold and
the fact that increasing the gold content does not indefinitel
improve the appearance. The minimum gold content of such
decorations is determined primarily by the poorer adherence
and durability of low gold content films and the deterioration
in their appearance. It will be appreciated that until recent
, ~ years gold, although a precious metal, was less expensive than¦
some of the other precious metals. As the price of gold has
risen, it has become of interest to reduce the quantity of
gold used in decorations since at 4 to 5 times the previous
cost the use of gold in decorating compositions becomes pro-
hibitive, except for the most expensive articles.
~ Palladium has also been used in decorative compositions.
.~ In some compositions, it produces a white metal appearance
when used in combination with gold, and simulates the hereto-
fore more expensive platinum compositions. In other applica-
ions, it has been used to produce a brown color. Examples
ay be found in U. S. patent 3,216,834, which is principally
, l irected to a new compound of palladium for use in decorative
pplications. In one example of the patent, a composition
ontaining 1.5 percent palladium, 3 percent silver, and much
~, maller amounts of rhodium and chromium is shown to produce
'~ chocolate brown color useful for decoration. In other
xamples, bright palladium decorating compositions are shown
o contain large quantities of gold and smaller amounts of
alladium. Other patents disclosing palladium compounds
seful for decorative applications include U. S. Patents Nos.
,718,488 and 770,785.
-2-
,' ,. . . I _,_
1074955
Palladium has also been used with silver in a film
which has the ability to separate gaseous mixtures by
hydrogen diffusion through the film. U.S. Patent No.
3,413,777 discloses such a film which contains an alloy of
5-40 weight percent silver and the remainder palladium,
the alloy being mixed with a glaze in the method of forming ¦
lthe desired film.
;What has been desired since the cost of gold has ,
increased many-fold is a decoration for ceramics which,
while giving the appearance of gold after firing, does not
~,contain substantial quantities of that metal, in order that
the cost may be kept at reasonable levels. This objective
has been accomplished by the composition and the method of
the present invention, in which no metallic gold is used.
Summary of the Invention
,;~
In one aspect, the invention consists of a composition
which, when applied to ceramics and fired, produces a
decoration having a gold appearance. This composition
contains as its principal metallic constituents, minor
amounts of palladium and sufficient silver to produce a gold
appearance in combination with palladium. Typically,
~,~weight ratios of palladium to silver in compositions of the
invention range between about 1:1 and about 12:1, with
preferred ratios between about 2.3:1 and about 9:1. The
total content of palladium and silver for most applications
will be between 1 and 12 weight percent. Within the stated
ranges, a gold color is produced in the fired decoration.
Outside these ranges, the color no longer satisfactorily
simulates gold-containing decorations and in addition, the
_3_
.~
~ !
s
1074955
film has reduced reflectance or adherence. The gold
appearance is particularly enhanced when applied as
relatively narrow lines.
In another aspect, the invention comprises a method for
decorating ceramics to produce a gold appearance using the
composition discussed above. Suitable amounts of palladium
and silver in the form of soluble metallo-organic compounds
and within the described composition ranges are combined
with a flux and vehicles to produce a mixture having an
appropriate viscosity. The usual techniques for applying
decorative compositions, such as screen printing, rolling,
dipping, stamping, spraying, or brushing may be used.
Conditions under which the applied coating is fired for
removing the vehicles and fusing the remaining residue are
determined by the temperature which the substrate will
` accept, generally between 500 and 650C for glass and 650 to
800C for other ceramic materials, such as china.
i Description of the Preferred Embodiments
In the prior art, palladium has been used to produce a ¦
white color in combination with large amounts of gold, as
disclosed in U.S. Patent No, 3,216,834. It also has been
~1 used to produce a brown color when no gold is present.
Silver, when used alone, produces a film having an amber
appearance. It has now been found that a combination of
palladium with a sufficient amount of silver and within
certain narrow ranges of composition produces a decorative
composition having the appearance of metallic gold after
firing. Outside those ranges, the simulation of gold is
unsatisfactory, and the decorative film has reduced
reflectance or poorer adherence. The following table
,i~
.. ..
10749S~
illustrates the sensitivity of the film color, reflectance,
and adherence to the relative proportions of palladium and
s silver.
Characteristics of the decorations after firing onto
' 5 the ceramic surface are not typically measured by a test
method standardized within the industry, but are related by
experience with what color, reflectance, and adherence are
acceptable to purchasers of such decorative compositions.
s It should be understood that,in particular,evaluation of
i 10 color and reflectance, although somewhat subjective, can be
made when comparing side-by-side samples of various
`} decorations and that those experienced in the art would be
expected to concur in such evaluations. Adherence is a more !
objective quality and is usually judged by rubbing the
~, 15 decoration with a rubber eraser containing abrasive since
it is known from experience that such a test correlates
well with actual service life.
s All of the compositions shown were identical (and
similar to the example given hereinafter) except for the
20 adjustment of the ratio of palladium to silver. Each
composition contained a total of 5 weight percent palladium
.' and silver since this amount gives particularly good
i results with a minimum use of these expensive metals. Each ¦
was applied by roller topping to the rim of a translucent
25 opal glass saucer and fired at 600C before comparison of
s the film properties was made. It can be seen from the table
~ that palladium alone, without silver, produces a brown
:J' '. colored film with poor adherence. The addition of small
quanti.ties of silver are insufficient to change the brown
30 ~ ~ color to gol but at the composition of 4.5 weight percent ¦
.,
'~,
~,
1074955
.
h h ~a. ~ ~ 'a ~a ~ ~ 'a ~ ~
h O O -i 0 0 0 0 0 0 0 0 0 0
a) oo~)ooooooooo o
,
'~:- a~
c ~ ~o ~ ~ ~ ~o ~ ~a h h ~ ~1 ~
~: ,1 ~ O O O O O O O O ~r~ O O ~
~ O O O O O O O O O d O 0 5
','.. ~ . Q~ ~
.,. P K ~: h ~I h
, ~ ~ ~1 3 ~ ~ A
O h Ll O ~ h
., ~ ~ 0 3 A A t~ a) h
~: m r, ,, o ~ . h ~
. . u~ O h ~ ~ ~ O O O O 1~ ~ ~ O tJl ~i
~: . E~ l . A --I -1 ~ ~ ~ ~ ~ Q. ~ --I ~ (I)
1 O
, ~ ~ ~
, ~ ~ ,1
.. ~ .. . . .. .. . . .. . . .
~ N ~ ~ ~r ~ ~ l0 0 0
. .
~ ¢
.. ~ d~ ~ ~ ~ Ul O U~
r 3 O O O O O ~ ~~~1 t~l ~I t~
~'
., ~1 ~D In O
¦ ~ l N ~ O
-6-
` I !
`. I
l 10749S5
palladium and 0.5 weight percent silver, a strong gold
color film is produced with good reflectance and adherence.
This effect also occurs with a composition containing 4
weight percent palladium and 1 weight percent sllver. The
color is weakened toward amber when the ratio of palladium
to silver is reduced to about 1.5:1, although the
reflectance and adherence are still good. At a 1:1 ratio
of palladium to silver, the gold appearance has been
; weakened and the reflectance has been significantly reduced.
A- ~atio of 1 weight percent palladium to 4 weight percent
silver produces a green-gray color which is dull and no
longer reflective. Also, tarnishing of the film may limit
the amount of silver which can be used. Thus, it can be seen
that only over a narrow range of compositions can the desire~
gold appearance be obtained. For a total palladium and
silver content of 5 weight percent this range may be more
~` broadly expressed as including compositions between 2.5 and
~- 4.6 weight percent palladium and 0.5 to 2 weight percent
silver. The preferred ranges are 3.5 to 4.5 weight percent
palladium and 0.5 to 1.5 weight percent silver. Expressed as
weight ratios of palladium to silver the broad range is
about 1:1 to about 12:1 and the preferred range about 2.3:1
to about 9:1.
Although a total of 5 weight percent palladium plus
silver is preferred for rolling application, it has been
found that a satisfactory golden appearance can be achieved
using both higher and lower total metal contents. Although
compositions containing larger metal contents would be more
expensive to produce, if such are desired, a golden appearanc~
-7-
~' I I .
.
."' , i ll
1074955
can be obtained by uslng palladium/silver weight ratios
between 1:1 and 12:1. Metal contents below five percent
total of palladium and silver can also be used for roller
applications, although a metal content of 4 weight percent
i5 is a practical minimum, as limited by reduced abrasion
resistance and weakening of the reflective gold appearance.
The foregoing data and discussion is based on
compositions suitable for such applications as machine
banding and stamping which require a high viscosity mixture,
which typically will contain a total of between 4 and 12
weight percent palladium and silver. For other applications
,~which require lower viscosity mixtures, as are typically
used for silk screening and brushing, thetotal content of
palladium and silver would be about 2-4 weight percent, and
,15 for spraying about 1-2 weight percent. The ratios of
palladium to silver would be maintained between 1:1 and 12:1
in such other applications as in the principal examples.
If corresponding compositions were to be prepared from
ithe prior art using metallic gold, the gold content of such
compositions would be about 4-5 weight percent for sprayingus~,
about 8-10 weight percent for brushing and silk screening,
12-15 weight percent for machine banding, and 15-20 weight
percent for stamping. Thus, it is clear that in the present
invention the total valuable metal content is distinctly lower
and the cost of the metals used is less than metallic gold in
the present market.
"Another important component of the composition of the
invention is the flux material, which is typically a soluble
`metallo-oxganic compound of a metal as typically used in the
30¦¦prior art to flu palladium and silver. Specifically, such
~!
..~
~ 1074955
metals include bismuth, chromium, lead, cadmium, uranium, tin
copper, cobalt, antimony, and rhenium. Such flux materials
are well known in the prior art. Reference may be made to
U.S. 3,216,834 previously mentioned. Those experienced in th~
art will appreciate that such fluxes are useful to improve
the adherence of the metal film and its abrasion resistance.
~ The fluxes have the property of softening or melting at thefiring temperature which, in general, the metallic components
~! do not. They react with the substrate and create an adhesive
10 vitreous layer for the metallic film and at the same time binc
the metallic particles in the decorative film. All prior art
fluxes, however, are not equally useful in the gold appearing
decoration of the present invention. They may affect the
color, the reflectance, and the adherence of the resultant
15 film and so be more or less useful.
In a preferred embodiment, a metallo-organic bismuth
s~ compound is used. In the typical decorative compositions for
roller topping, the bismuth content is preferably about 0.5
weight percent. Expressed more generally, the weight ratio
20 of bismuth to the combined palladium and sllver would
typically be in the range of about 0.02:1 to 0.2:1, with a
preferred ratio of Bi (Pd + Ag) of about 0.1:1 ~based on
metal content).
A ~ A typical decorative composition of the invention
, 25 formulated for machine roller topping is given in the
¦~following exampl
~''sr~ 1,
,s'
:,
i, ,
1074955
Weight Percent
Resin in essential oil 47.17
Pd neodecanoate in solution 26.42
(15% Pd)
Resin ester (plasticizer) 7.55
Balsam (tackifier) 5.66
Ag neodecanoate in solution 3.77
(25% Ag)
Organic hydrocarbon solvent 7.55
~! 10 (diluent for viscosity
adjustment)
Bi neodecanoate in solution 1.89
(26~ Bi) -100.00
As will be observed, the metallic constituents in compositionC
of the invention are present as soluble metallo-organic
compounds. The neodecanoates shown in the examples were
selected for ease of availability and low cost. Other
. soluble organo-metallic compounds may also be used. For
example, the following: sulfonates, sulfo-resinates,
~ 20 mercaptides, thio-ethers, chelates, and carboxylates can be
.r substituted for neodecanoates.
~ ~ The solvent and resins serve to form a paste or ink- j
; like material and they are added as required to adjust the
viscosity needed for particular applications. Generally,
it is known in the art that compositions in the range of
50-100 poise are suitable for screen printing, machine lining,
rolling, and stamping applications. On the other hand, for
spraying or brushing more dilute solutions are applied.
Typically, these may have a viscosity of the order of 1
centi-poise. The relative proportion of the metallic
constituents remain the same but they are diluted in the
,~ formulation in order to adjust the handling qualities of the
resulting solution.
~,
~:' -10-
I
", ~ I
I1 1074955
After being applied to a ceramic article, they are
: fired at temperatures typical of those of the prior art,
. glass being fired typically between 500 and 650C and china,
between 650 and 800C. During firing, the organic materials
are substantially decomposed and removed, leaving behind a
composition which consists essentially of finely divided
. particles of palladium and silver in a base metal oxide
. binder.
The resulting fired film gives a gold appearance when
. 10 t~e proportions of palladium and silver are properly selected
Owing to its relatively low cost, the decorative composition
of the invention can be applied to many inexpensive
applications where gold decorations using the traditional
high gold content compositions would be too costly.
The gold appearance of films formed according to the
invention is particularly pronounced with narrower lines;
.~ however, the decoration always gives a golden color. The
highly reflectance property of such films appear to enhance
the appearance of bright metallic gold when applied in
~, 20 narrower widths.
.~. The foregoing description of the preferred embodiments
.,~. is for illustration of the invention only and not to limit
7~ the scope of the invention which is defined by the claims
, ¦¦which Eollow.
'~ 1,
;j
~'''
