U.S. patent application number 10/489222 was filed with the patent office on 2005-02-10 for radiation curable precious metal preparation, transfers containing same and method for decoration.
Invention is credited to Debus, Klaus, Schulz, Andreas, Walter, Frank.
Application Number | 20050028895 10/489222 |
Document ID | / |
Family ID | 8178550 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050028895 |
Kind Code |
A1 |
Walter, Frank ; et
al. |
February 10, 2005 |
Radiation curable precious metal preparation, transfers containing
same and method for decoration
Abstract
The invention relates to a precious metal preparation capable of
radiation curing, in particular a gold preparation for the
production of decorations on substrates capable of decoration
firing, containing a precious metal and a medium capable of
radiation curing. The printing medium according to the invention
contains one or more organic compounds in particle form, which are
insoluble and incapable of swelling in the printing medium and burn
away substantially completely in decoration firing, as means of
increasing the pigment volume concentration (PVC), whereby
decoration quality is improved. Preferred means of increasing the
PVC are organic pigments and organic polymers, used in particular
in combination. Transfers according to the invention contain the
precious metal preparation in radiation-cured form.
Inventors: |
Walter, Frank; (Russelsheim,
DE) ; Schulz, Andreas; (Blumenstr., DE) ;
Debus, Klaus; (Eckenheimer Landstr., DE) |
Correspondence
Address: |
RANKIN, HILL, PORTER & CLARK, LLP
925 EUCLID AVENUE, SUITE 700
CLEVELAND
OH
44115-1405
US
|
Family ID: |
8178550 |
Appl. No.: |
10/489222 |
Filed: |
September 17, 2004 |
PCT Filed: |
August 21, 2002 |
PCT NO: |
PCT/EP02/09360 |
Current U.S.
Class: |
148/430 |
Current CPC
Class: |
C04B 41/5188 20130101;
C03C 2217/255 20130101; C03C 2217/72 20130101; C04B 41/009
20130101; C04B 41/009 20130101; C04B 41/5188 20130101; C04B 41/009
20130101; C03C 17/06 20130101; C04B 41/5116 20130101; C04B 41/0045
20130101; C04B 33/00 20130101; C04B 41/5024 20130101; C04B 41/5022
20130101; C04B 33/24 20130101; C04B 41/4511 20130101; B44C 1/1716
20130101; C04B 41/88 20130101 |
Class at
Publication: |
148/430 |
International
Class: |
C22C 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2001 |
EP |
01121227.1 |
Claims
1-8. (canceled)
9. A precious metal preparation capable of radiation curing,
comprising: a. one or more precious metals from among gold, silver,
platinum and palladium in elementary and/or alloyed form and/or in
the form of a compound, b. one or more fluxes from among compounds
of Mg, Al, K, Na, Ca, Bi, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,
Zr, Rh, Ru, Sn, In, Sb, Pb and Bi, c. a printing medium capable of
radiation curing, and d. at least one organic compound in particle
form which is insoluble and incapable of swelling in the printing
medium and burns substantially completely in decoration firing, e.
wherein the at least one organic compound is a medium for
increasing the pigment volume concentration.
10. The precious metal preparation of claim 9, wherein the medium
for increasing the pigment volume concentration is selected from
the group consisting of organic pigments, organic polymers, and
blends thereof.
11. The precious metal preparation of claim 10 wherein medium for
increasing the pigment volume concentration is selected from the
group consisting of cross linked organic polymers and blends of an
organic polymers and inorganic compounds.
12. The precious metal preparation of claim 11 wherein the medium
for increasing the pigment volume concentration further comprises
highly disperse silicic acid.
13. The precious metal preparation of claim 9 comprising up to 15%
by weight of the medium for increasing the pigment volume
concentration.
14. The precious metal preparation of claim 12 comprising from
about 1 to about 10% by weight of the medium for increasing the
pigment volume concentration.
15. The precious metal preparation of claim 14 wherein the medium
for increasing the pigment volume concentration comprises 0.5 to 5%
by weight of an organic pigment and 0.5 to 7% by weight of an
uncrosslinked or crosslinked organic polymer.
16. The precious metal preparation of 9 containing: a. 10 to 50% by
weight of gold in elementary form, b. 0.1 to 20% by weight of flux,
c. 1 to 10% by weight of medium for increasing the pigment volume
concentration, and d. 30 to 80% by weight of a medium capable of
radiation curing, wherein the medium capable of radiation curing
comprises a polymer dissolved in a photo-polymerizable monomer and
a photo-initiator in an amount of 0.1 to 20% by weight, based on
the weight of the medium capable of radiation curing.
17. The precious metal preparation of claim 16, containing: a. 16
to 40% by weight of gold in elementary form, b. 1 to 8% by weight
flux, c. 1 to 10% by weight of medium for increasing the pigment
volume concentration, d. 30 to 80% by weight of a medium capable of
radiation curing, wherein the medium capable of radiation curing
comprises a polymer dissolved in a photo-polymerizable monomer and
a photo-initiator in an amount of 1 to 10% by weight, based on the
weight of the medium capable of radiation curing.
18. The precious metal preparation of 9 containing: a. 10 to 50% by
weight of a precious metal selected from the group consisting of
silver, platinum and palladium, alloys thereof, and compounds
thereof, b. 0.1 to 20% by weight of flux, c. 1 to 10% by weight of
medium for increasing the pigment volume concentration, and d. 30
to 80% by weight of a medium capable of radiation curing, wherein
the medium capable of radiation curing comprises a polymer
dissolved in a photo-polymerizable monomer and a photo-initiator in
an amount of 0.1 to 20% by weight, based on the weight of the
medium capable of radiation curing.
19. A transfer for the production of precious metal decorations,
comprising: a. a transfer carrier, b. an image coating and c. a
film coating, d. wherein the image coating is obtained through
application of a precious metal preparation capable of radiation
curing, wherein the precious metal preparation comprises: i. one or
more precious metals from among gold, silver, platinum and
palladium in elementary and/or alloyed form and/or in the form of a
compound, ii. one or more fluxes from among compounds of Mg, Al, K,
Na, Ca, Bi, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Rh, Ru, Sn,
In, Sb, Pb and Bi, iii. a printing medium capable of radiation
curing, and iv. at least one organic compound in particle form
which is insoluble and incapable of swelling in the printing medium
and burns substantially completely in decoration firing, v. wherein
the at least one organic compound is a medium for increasing the
pigment volume concentration.
20. The transfer of claim 19 wherein the transfer carrier further
comprises a base layer.
21. The transfer of claim 19 wherein precious metal is gold.
22. A method of producing a precious metal decoration on a
substrate capable of decoration firing, comprising a. providing a
substrate capable of decoration firing, b. providing the precious
metal preparation of claim 9, c. applying the precious metal
preparation to the substrate, and d. curing the precious metal
preparation by irradiation using radiation having a wavelength of
about 420 nm or less.
23. A method of producing a precious metal decoration on a
substrate capable of decoration firing, comprising: a. providing a
substrate capable of decoration firing, b. providing the precious
metal preparation of claim 16, c. applying the precious metal
preparation to the substrate, and d. curing the precious metal
preparation by irradiation using radiation having a wavelength of
about 420 nm or less.
24. A method of producing a precious metal decoration on a
substrate capable of decoration firing, comprising a. providing a
substrate capable of decoration firing, b. providing the precious
metal preparation of claim 17, c. applying the precious metal
preparation to the substrate, and d. curing the precious metal
preparation by irradiation using radiation having a wavelength of
about 420 nm or less.
25. The method of producing a precious metal decoration according
to claim 23 wherein the radiation has a wavelength of about 300 to
about 400 nm.
26. The method of claim 22 wherein the precious metal preparation
comprises gold, and wherein the precious metal decoration is
burnished gold.
27. The method of claim 23 wherein the precious metal preparation
comprises gold, and wherein the precious metal decoration is
burnished gold.
28. The method of claim 24 wherein the precious metal preparation
comprises gold, and wherein the precious metal decoration is
burnished gold.
Description
[0001] The invention relates to a precious metal preparation
capable of radiation curing, in particular a burnished gold
preparation which contains, in addition to a precious metal, in
particular elementary gold, and a flux, a printing medium capable
of radiation curing, in particular UV-curable. The invention also
relates to transfers containing the precious metal preparation and
to a method for the decoration of substrates capable of decoration
firing by direct and indirect printing.
[0002] DE patent specification 22 08 915 teaches burnished or
powdered gold preparations for the production of on-glaze gold
decorations. The preparation contains gold powder, a flux, and a
printing medium, the latter involving resins and/or inorganic
solvents. To adjust the colour, the preparation may include besides
gold, other precious metals such as platinum, palladium, rhodium,
iridium and silver. To enhance firing stability, the preparation
may also contain additional compounds such as purple of Cassius,
tin oxide or aluminium oxide. It is expedient, before application
of the gold preparation, to apply to the siliceous base layer a
high-melting intermediate layer comprised of zirconium oxide,
zirconium silicate, tin oxide, silicon oxide or aluminium oxide, or
a mixture of at least two of these compounds. This intermediate
layer may also contain colouring substances, such as inorganic
pigments so that, in the creation of the decoration, its colour
stands out better from the siliceous base layer. To produce the
on-glaze decoration, the gold preparation is applied by means of a
screen printing process to a transfer carrier which may be provided
with the intermediate layer beforehand. After drying of the image
coating, the latter is provided, in a known manner, with an enamel
coating. The transfer thus obtained is transferred to the siliceous
base layer and then fired on at 1100 to 1400.degree. C. The
disadvantages of these precious metal preparations are the long
drying times of the image coating, and the associated ecological
problems due to evaporation of organic solvents.
[0003] Also the screen printing paste for gold decorations
according to DE-OS 21 11 729 contains a commercially available
screen printing oil, such as solutions of polymethyl methacrylate
or ethyl cellulose in high-boiling solvents such as ethyl glycol
acetate, butyl acetate or test benzine.
[0004] The gold preparation according to DE patent 24 35 859
contains, besides gold, one or more non-precious metals such as
titanium, iron and nickel, and if required also an adhesive oxide
or a glass flux. By means of screen printing, this preparation may
be printed without a special base layer directly on to the
substrate to be decorated or on to a transfer carrier. Two typical
gold preparations contain additionally 2.5% by weight of a red
pigment, but its function is nowhere disclosed. It is assumed that
the red pigment serves to make the print image more clearly
recognisable. This gold preparation too contains a conventional
screen printing medium with the drawbacks described above.
[0005] In efforts to minimise the aforementioned drawbacks,
attempts have been made to replace the purely organic printing
medium by one containing or capable of dilution with water--see DE
35 44 339 C1 and DE-OS 38 07 290. The disadvantages of such
preparations are their unsatisfactory drying properties and to some
extent inadequate decoration quality.
[0006] To avoid the problems attached to conventional organic
printing media, i.e. the long drying times and ecological problems
due to evaporation of solvents, radiation-curing media, in
particular UV-curing media have been developed, which can be used
in bright precious metal preparations or in burnished gold
preparations. DE patent specification 30 48 823 teaches accordingly
a resinous substance which may be cured by UV radiation, comprised
of a special saturated copolymer, a polymerisable component with
one, together with such a component with two or more polymerisable
groups, a photosensitiser and where applicable other synthetic
resins, pigments, slip additives, flow-control agents and
thixotropic agents for the purpose of adjusting the printing
properties, and inhibitors of the thermal polymerisation.
[0007] Depending on the intended purpose of the UV-curable resinous
substance according to DE 30 48 823 C2, it may contain known
inorganic pigments such as are generally used for the decoration of
siliceous substrates. Alternatively the UV-curable resinous
substance may also contain organic pigments, but such systems are
decorating preparations for the decoration of substrates which will
not be subjected to decoration firing. No indication may be gained
from this document to suggest that a UV-curable burnished gold
preparation could also contain an organic pigment and/or a polymer
which is insoluble/non-swelling in the binder system.
[0008] The bright precious metal preparation for the decoration of
glass, ceramics and porcelain according to DE-PS 38 19 414 contains
a soluble organic precious metal compound and a UV-curable organic
carrier based on isobornyl acrylate and dicyclopentadienyl acrylate
and a photo-initiator dissolved therein. The preparation may also
contain one or more oligomers with acrylate and/or methyl acrylate
groups. Organic solvents, natural and synthetic resins, means for
adjusting and modifying viscosity, and pigments may also be
included. It is also disclosed that, by adding gold powder and/or a
slightly soluble gold compound to the bright gold preparation,
curable burnished gold may be obtained through
photo-polymerisation. Not disclosed in this document is the type of
pigments involved, and in what quantity and for what purpose these
are used--here too evidently the colouring matter is used to make
the print image more clearly recognisable.
[0009] The inventors of the present application have found that the
transfer quality and decoration quality of burnished gold
preparations containing as medium a conventional UV-curable medium
are unsatisfactory. Evidently on account of the poor flow
properties of such preparations, printing results in an uneven and
in particular grained surface. To improve the flow of the printing
paste, conventional flow-control agents have also been added to
such systems. Such flow-control agents are generally silicone-based
products with a low interfacial tension. While the use of such
products does indeed improve flow properties, at the same time
there is a further problem, namely a lack of capacity for
overprinting, as a result of poor wettability. The use of such a
flow-control agent in a gold preparation means that it is no longer
possible to produce accurately matching multi-colour print
images.
[0010] The problem of the present invention therefore is to find a
way of overcoming the problems described above. The precious metal
preparations, in particular burnished gold preparations to be
prepared according to the invention, should therefore flow
perfectly without the use of flow-control agents so that, when used
in direct or indirect printing, i.e. using the transfer method,
aesthetically pleasing decorations with high surface quality are
obtained.
[0011] It has been found that the aforementioned problems and other
problems revealed in the description which follows may be solved by
a significant increase in the pigment volume concentration (PVK) of
the preparation through the addition of organic substances which
are insoluble in the paste. It is assumed that one of the causes of
the poor flow of burnished gold preparations capable of radiation
curing is the low pigment volume concentration of the paste to be
printed. Even when, by adopting the measure according to the
invention, namely increasing the pigment volume concentration, the
flow is significantly improved, it is not possible to rule out that
the improved quality of the preparations according to the invention
and of the decorations produced from them may also be due to other
causes.
[0012] The subject of the invention is therefore a precious metal
preparation capable of radiation curing, in particular a burnished
gold preparation, containing one or more precious metals from among
gold, silver, platinum and palladium in elementary and/or alloyed
form and/or in the form of a compound, one or more fluxes from
among compounds of Mg, Al, B, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,
Zn, Zr, Rh, Ru, Sn, Sb, Pb and Bi, and a printing medium capable of
radiation curing, characterised in that it contains at least one
organic compound in particle form which is insoluble and incapable
of swelling in the printing medium and burns substantially
completely in decoration firing, as a means of increasing the
pigment volume concentration (PVC). The subsidiary claims are
directed towards preferred embodiments of the precious metal
preparation capable of radiation curing.
[0013] The preparations according to the invention contain as
precious metal one or more metals from among gold, silver, platinum
and palladium, in elementary and/or alloyed form; usually the
amount of gold used exceeds that of the other precious metals,
which are used mainly to modify the colour shade. The preparations
according to the invention may also contain precious metals in the
form of compounds which are soluble or insoluble in the medium. The
use of organic compounds of one or more precious metals in
combination with elementary precious metal is suitable for
adjusting the desired colour. The soluble precious metal compounds
are in particular so-called precious metal resinates and
sulpho-resinates, also mercaptides from organic compounds
containing one or more mercapto groups. Insoluble precious metal
compounds are for example gold sulphide, gold cyanide, gold oxide,
and cyano- and sulphito gold complexes.
[0014] The amount of precious metals used in preparations according
to the invention is usually in the range of 5 to 50% by weight
containing preferably more than 8% by weight of burnished gold
preparation, preferably with 16 to 40% by weight of gold. In
addition to gold, one or more precious metals from among platinum,
palladium, silver, rhodium, copper, ruthenium and osmium may be
present.
[0015] As is generally known among experts, the precious metal
preparations according to the invention also contain one or more
fluxes. These fluxes involve organic or inorganic compounds of
non-precious metals, also rhodium and ruthenium, which are
preferably dissolved in the medium. Preferred fluxes contain as
metal magnesium, sodium, potassium, calcium, boron, aluminium,
silicon, titanium, vanadium, chromium, manganese, iron, cobalt,
nickel, copper, zinc, zirconium, tin, indium, antimony, lead and
bismuth, together with rhodium and ruthenium. With the aim of
obtaining optimal flow and good adhesion of the preparation to the
substrate to be decorated, generally several fluxes are used, for
example combinations of compounds of: bismuth and boron; bismuth
and vanadium and/or silicon; bismuth, vanadium and rhodium, and
also if required additionally chromium, silicon, copper and/or
zirconium; chromium and cobalt and if required one or more
compounds of in particular Ti, In, B, Si, Zr and Rh, or Ru (see DE
194 10 20 A1). The non-precious metal compounds used as fluxes
involve inorganic and/or organic compounds such as resinates,
sulfo-resinates, alkanoates, naphthenates, salts of carboxylic
acids, such as acetate. The flux elements may also be used in the
form of their oxides, salts, borates and glasses, as for example
alkali borosilicate.
[0016] The amount of flux elements required may lie within wide
ranges. Usually fluxes can be present in a total amount of up to
around 20% by weight, calculated in the form of compounds and based
on the preparation. Preferably the preparation contains 0.1 to 15%
by weight of flux, in particular 0.1 to 8% by weight. The person
skilled in the art will easily determine the optimal amount
required and the flux constituents to be chosen through orientation
tests.
[0017] The feature of the precious metal preparation which is
important for the invention is the presence of an organic medium
described below as a "means of increasing the PVC", which is in
particle form, will not dissolve or swell in the printing medium
under the usual application temperatures, i.e. in particular below
around 60.degree. C., and burns substantially completely in
decoration firing. The "means of increasing the PVC" according to
the invention is used in the form of a single compound or of
several different compounds, and specifically in an overall amount
of up to 20% by weight, preferably up to 15% by weight and in
particular 1 to 10% by weight, based on the preparation. By the use
of the "means of increasing the PVC" according to the invention the
pigment volume concentration of the precious metal preparation,
which is very low owing to the high density of the precious metal,
is significantly increased. An increase in the pigment volume
concentration of 30 to 300% leads to significantly improved flow of
the preparation and thus to high-quality decorations. The means of
increasing the PVC thus acts as an organic filler.
[0018] The means of increasing the volume concentration (PVC)
according to the invention involve at least one but in many cases
several organic compounds in particle form, which substantially
burn away completely in decoration firing. The expression
"substantially completely" indicates that the organic constituents
of such compounds burn away completely, but metal atoms--for
example of metal complexes--which are present become part of the
flux.
[0019] It has been found that organic pigments are very suitable
for increasing the PVC of the precious metal preparations according
to the invention, thereby improving flow properties and decoration
quality in an effective manner. An advantage of the organic
pigments is that they generally already have a particle
distribution such as is used in the production of non-ceramic
printing pastes. Precious metal preparations according to the
invention generally contain up to 10% by weight of one or more
means of increasing the PVC. Especially preferred means contain 0.5
to 5% by weight of an organic pigment.
[0020] In principle, organic pigments of the most widely varying
chemical constitution may be used. Preference is given to those
pigments with the lowest possible UV absorption and which do not
tend to graphitisation under the conditions of ceramic decoration
firing. Organic pigments which may be used are assigned for example
to the following classes of substance: yellow and red mono- and
disazo pigments, naphthol-AS pigments, benzimidazolone pigments,
yellow disazo condensation pigments, metal complex pigments based
on azo compounds, azomethines and isoindolinones, phthalocyanine
pigments, thioindigo pigments. Although quinacridone pigments,
perinone and perylene pigments, also anthraquinone pigments and
pyranthrone pigments are suitable for increasing the PVC, they tend
towards graphitisation. A certain disadvantage of many organic
pigments lies in the fact that they absorb UV light to a greater or
lesser extent, after which curing time is extended.
[0021] A further class of suitable means of increasing the pigment
volume concentration of precious metal preparations according to
the invention is that of polymers, also including copolymers, which
under the normal conditions of use are insoluble and incapable of
swelling in the printing medium. The polymers and copolymers may be
assigned to different classes of substance, the only important
factor being that they are insoluble and incapable of swelling in
the precious metal preparation, and will burn away completely under
the conditions of decoration firing. The polymers may for example
include polyolefins, vinyl, acryl or methacryl polymers,
polyesters, polyamides or phenol formaldehyde resins, polymethylene
ureas or polyethers, with the proviso that the degree of
polymerisation is sufficiently high or the polymer is crosslinked,
so as to rule out any solubility or swelling capacity in the
printing medium. The amount required of this class of means for
increasing PVC is usually in the range of up to 10% by weight, in
particular in the range from 0.5 to 7% by weight.
[0022] An advantage of the last-mentioned class of means for
increasing pigment volume concentration lies in the fact that their
UV absorption is significantly less than that of organic pigments.
This minimises any negative effect on the curing behaviour of the
printing medium which is capable of radiation curing.
[0023] A problem of the polymer means of increasing PVC lies in the
fact that they are in some cases not available in the optimal
particle distribution. While means with an average particle size of
around or over 10 .mu.m do give good flow of the precious metal
preparation, decoration faults may occur during decoration firing
on account of the coarse particles. Decoration faults may be
avoided using a polymer medium of lower average grain size, for
example around or below 5 .mu.m, but a high level of use may lead
to a sharp rise in viscosity, a reduction in flow and also to
flatting. It has been found that compositions based on polymers
insoluble in the UV-curable medium, such as polymethyl urea with
finely dispersed silicic acid, as obtainable commercially, also
provide the desired effect very satisfactorily, on the strength of
findings to date.
[0024] In accordance with a preferred embodiment, both organic
pigments and also additionally one or more organic fillers are used
as means of increasing the pigment volume concentration. The
combination of the two classes of substance leads to optimal
matching of both flow properties and also rheological properties.
Expediently a precious metal preparation according to the invention
therefore contains 0.5 to 5% by weight of an organic pigment and
0.5 to 7% by weight of a polymer organic filler, preferably
involving a crosslinked organic polymer. Especially preferred
precious metal preparations contain as means of increasing the
pigment volume concentration around 1 to 3% by weight of one or
more organic pigments and around 2 to 6% by weight of one or more
polymer organic fillers. Such a combination has an outstanding
property profile both in respect of flow, leading to a perfect
decoration surface, and also with regard to trouble-free and rapid
full curing of a decoration coating applied to a substrate to be
decorated or to a transfer carrier.
[0025] The printing medium which is capable of radiation curing
generally involves a multi-component system containing at least one
monomer and/or oligomer compound capable of polymerization by
radiation, together with a photo-initiator and if necessary a resin
dissolved in the monomer or oligomer. With regard to the monomer
and oligomer polymerisable substances to be chosen, reference is
made to the teaching of DE patent specifications 30 48 823 and 38
19 414. According to DE-PS 30 48 823, the printing medium contains
a saturated copolyester dissolved in a polymerisable component. The
polymerisable component involves a combination of a polymerisable
component and a polymerisable double bond, and in addition a
compound with two or more polymerisable double bonds in the
molecule. Examples of suitable photo-polymerisable compounds with a
polymerisable double bond in the molecule are: (i) styrene,
.alpha.-methyl styrene; (ii) alkyl acrylates and methacrylates,
wherein alkyl stands in particular for methyl, ethyl, isopropyl,
n-propyl, n-, sec.- and t-butyl, 2-ethylhexyl, lauryl, stearyl,
cyclohexyl, methoxyethyl, ethoxyethyl, butoxyethyl, hydroxyethyl,
poly(ethyleneoxy)ethyl, (iii) monoacrylates and -methacrylates from
adducts of bisphenol A and alkylene oxides, such as ethyl oxide or
propylene oxide, (iv) urethane-modified monoacrylates and
methacrylates containing an acryloyloxy- or methacryloyloxy group
in the molecule, (v) epoxy-group-modified acrylates and
methacrylates, oligoestermono-acrylate- s and -methacrylates. The
amount of photo-initiator required in the printing medium usually
lies in the range from 0.1 to 20% by weight but mostly in the range
from 1 to 10% by weight.
[0026] Suitable photomerisable compounds with two or more double
bonds are for example: alkylene glycol diacrylate or dimethyl
acrylate, wherein alkylene stands for ethylene, propylene,
1,4-butylene, neopentyl- and hexamethylene; diethylene glycol- and
triethylene glycol diacrylate or -methacrylate; trimethylol propane
trimethacrylate.
[0027] In accordance with an especially preferred embodiment, the
printing medium capable of radiation curing contains a so-called
solid resin dissolved in a monomer acrylate or if applicable
methacrylate, which may be in particular a polymethyl-methacrylate
copolymer, for example a copolymer based on
polymethyl-methacrylate/polybutyl-methacrylate. Preferably such a
printing medium is comprised of around 20 to 40% by weight of one
or more dissolved solid resins, 45 to 70% by weight of one or more
acrylic and/or methacrylic monomers, and 1 to 10% by weight, in
particular 2 to 6% by weight of one or more photo-initiators and
where necessary other auxiliaries such as thixotropic agents,
inhibitors of thermal polymerisation, such as hydroquinone,
hydroquinone methyl ether and tertiary-butylated phenols, and amine
synergists, in an amount of altogether up to 10% by weight, in each
case related to the printing medium.
[0028] Suitable as photo-initiators are: benzoins, e.g. benzoin
methyl ether, benzoin ethyl ether, benzoin isopropyl ether,
benzoin, .alpha.-methyl benzoin; anthraquinones, such as
2-chloro-anthraquinone; benzophenones, such as benzophenone,
p-chloro-benzophenone, p-dimethylamino benzophenone; sulphur
compounds such as diphenyl disulphide, tetramethyl thiuram
disulphide; xanthones and thioxanthones such as 2- or 3-methyl
xanthone, 2- or 3-ethyl xanthone, 3-ethyloxy xanthone,
2,7-dichloroxanthone, 2-nitroxanthone and analogous derivatives of
thioxanthone; aryl-alky-phosphine oxide.
[0029] To enhance the effect of the photo-initiators, they may be
used together with synergists from the range of amines, such as
triethanolamine, N,N-diethyl aminoethylacrylate.
[0030] The radiation curing is effected by means of
radiation-induced polymerisation, involving short-wave radiation,
in particular radiation in the range close to visible light
(.alpha. around 420 nm) and in the entire UV range, in particular
.alpha. 300-400 nm.
[0031] An especially preferred burnished gold preparation according
to the invention contains 10 to 45% by weight of gold in elementary
form, 0.1 to 20% by weight, in particular 0.1 to 5% by weight of
flux, 30 to 80% by weight, in particular 45 to 65% by weight of
radiation curing medium, and 1 to 10% by weight, in particular 3 to
8% by weight of means of increasing the pigment volume
concentration according to the invention. Expediently the
preparation for increasing the pigment volume concentration
contains both an organic pigment and also a polymer organic filler.
The radiation curing medium comprises preferably a polymer
dissolved in a photo-polymerisable monomer, in particular an acryl-
or methacryl monomer, and a photo-initiator, wherein the amount of
photo-initiator required lies in the range of 1 to 20% by weight,
in particular 0.1 to 10% by weight, relative to the printing
medium.
[0032] The precious metal preparation according to the invention is
made in a similar fashion to that used in the production of known
precious metal preparations: the precious metals in powder form,
the flux and the means of increasing the pigment volume
concentration according to the invention are pasted into a printing
medium capable of radiation curing using common pasting equipment,
for example a multiroll mill. The photo-initiator may either be
already present in the medium or else added to the paste at the
end. To the extent necessary, other aids such as thixotropic agents
and further polymerisable solvents for the purpose of adjusting
print viscosity are incorporated in the paste.
[0033] A further subject of the invention is directed to a transfer
for the production of precious metal decorations, in particular
burnished gold decorations. The production of transfers is in
principle known to the experts in this field: a transfer carrier
with a water-soluble or thermally activable interlayer is printed
by means of a printing process, in particular a screen printing
process using a radiation-curing precious metal preparation
according to the invention, to produce an image coating. The image
coating is irradiated from a suitable radiation source, in
particular a radiation source for UV light, by which the image
coating is cured. After curing the image coating is filmed over
with a conventional lacquer film, generally an acrylic or
methacrylic resin film.
[0034] Through the use of precious metal preparations according to
the invention, containing one or more means according to the
invention for increasing the pigment volume concentration, it is
possible to obtain high-quality transfer carriers which have a
perfect surface and also give a decoration of high quality after
decoration firing. In accordance with an especially preferred
embodiment of the transfers according to the invention, the image
coating contains a precious metal preparation, the printing medium
of which contains a monoacrylate or monomethacrylate, but not a
multi-functional acrylate or methacrylate. By dispensing with
multi-functional acrylates or methacrylates in the printing medium,
transfers with greater flexibility and therefore a lower tendency
to cracking of the image coating are made accessible.
[0035] The precious metal preparations according to the invention
may be used to produce a precious metal decoration, in particular a
burnished gold decoration, on a substrate capable of decoration
firing, wherein the precious metal preparation may be applied by
direct or indirect printing (transfer method) on the substrate to
be printed. Decoration firing is effected in an intrinsically known
manner at a temperature geared to the substrate which for porcelain
and ceramics lies in the range from 700 to 1400.degree. C., in
particular 800 to 1250.degree. C. To produce burnished gold
decorations, the fired-on decoration is polished in a known
manner.
[0036] If desired, the precious metal preparation according to the
invention may contain additional substances for enhancing firing
stability, such as are known from the prior art.
[0037] In similar fashion, a base layer known from the prior art
may also be provided beneath an image coating, according to the
invention, of a transfer carrier, to improve adhesion and/or
resistance to scratching.
[0038] A further subject of the invention is directed towards the
production of a precious metal decoration, in particular a
burnished gold decoration, on a substrate capable of decoration
firing, such as glass, ceramics and porcelain. This involves
printing the preparation according to the invention on to the
substrate in a known manner, undertaking radiation curing to the
extent still necessary, and finally firing under conditions of
decoration firing.
[0039] It was not foreseeable that, through the use of means
according to the invention of increasing the pigment volume
concentration, the flow and thereby the decoration quality of the
precious metal preparation could be significantly improved. Equally
it was not foreseeable that, through the combination of an organic
pigment with a polymer organic filler, the flow properties of the
preparation and thereby the decoration qualities of the resultant
decoration could be improved while maintaining good, i.e. rapid,
radiation curing.
EXAMPLE
[0040]
1 Gold powder 32 g Zirconium silicate 0.2 g Alkaline earth/alkali
borosilicate 1.8 g Tin oxide 3.5 g 1-((2,4
dinitrophenyl)azo)-2-naphtol 2 g (= paint pigment) Compound based
on polymethylene urea and 4 g highly disperse silicic acid
(Deuteron .RTM. MM 659, Deuteron GmbH, Achim (DE)) Medium 56.5 g
The medium is comprised of: Isobornyl acrylate 57% Oligoglycol
acrylate 9% Phthalate plasticiser 4% MMA-n-BuMA copolymer 20%
Benzyldimethylketal 1% Triphenyl phosphine oxide 6% N,N-dimethyl
aminobenzole 2% Castor oil derivative 1%
[0041] The contents are thoroughly homogenised in a ball mill and
then pasted to form the medium.
[0042] The printing of the screen printing paste is effected with a
300 mesh/inch steel screen on Trucal brand transfer paper on a PLC
printing machine. Curing takes place in a downstream UV drier,
followed by overfilming with a commercially available film solution
(product no. 83450 of the company dmc.sup.2 AG) and a 27
filament/cm polyester screen. The transfers are transferred to
porcelain and fired in 90 min (cold to cold) at 1230.degree. C. The
decorations are then polished. The polished decorations, made with
the paste of the example, have a beautiful yellow burnt-out shade
of colour with silk matt gloss.
COMPARATIVE EXAMPLE
[0043]
2 Gold powder 32 g Zirconium silicate 0.2 g Alkaline earth/alkali
borosilicate 1.8 g Tin oxide 3.5 g Medium (identical to that of the
example) 62.5 g
[0044] In contrast to the example according to the invention, the
transfer carriers produced using the paste of the comparative
example showed craters even in the unfired state. This fault is
also visible subsequently in the fired-on transfer carrier.
* * * * *